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  • Drosophila  (339)
  • Calcification
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  • Springer  (646)
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  • 2000-2004  (38)
  • 1990-1994  (260)
  • 1980-1984  (329)
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  • 1
    Digitale Medien
    Digitale Medien
    Behavioural induction in Drosophila: timing and specificity (2000)
    Springer
    Entomologia experimentalis et applicata 94 (2000), S. 159-171 
    Details
    ISSN: 1570-7458
    Schlagwort(e): Drosophila ; induction ; habituation ; associative learning ; T-maze olfactometer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Experiments reported in this paper investigate the properties of a change in the responsiveness of adult Drosophila melanogaster induced by exposure to different rearing media. This effect has previously been described as habituation or associative learning. Exposure to food medium containing 0.08% menthol induced a positive response to menthol odour in a T-maze olfactometer. A brief (one hour) exposure to mentholic food just before testing was sufficient to induce a change in responsiveness. The effect did not persist through periods of more than an hour of separation from mentholic medium. Effects induced by exposure to a single compound were not specific to that compound alone. Menthol-reared flies (MRFs) differed from plain reared flies (PRFs) in their responsiveness to the odours of benzaldehyde and ethyl acetate, as well as menthol, and exposure to ethyl acetate induced a change in response to menthol odour. That there was an induced positive response to menthol in MRFs suggests that conventional habituation is insufficient to explain the induced change in responsiveness, but the generalised nature of this behavioural induction in MRFs is hard to explain in terms of associative learning. The mechanism underlying the induction remains elusive.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003998715018
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  • 2
    Digitale Medien
    Digitale Medien
    Lack of Evolutionary Divergence in Courtship Songs of Drosophila pseudoobscura Subspecies (2000)
    Springer
    Journal of insect behavior 13 (2000), S. 255-262 
    Details
    ISSN: 1572-8889
    Schlagwort(e): courtship song ; wingbeat ; sexual isolation ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007744416116
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  • 3
    Digitale Medien
    Digitale Medien
    Copulatory Courtship in Drosophila birchii and D. serrata, Species Recognition and Sexual Selection (2000)
    Springer
    Journal of insect behavior 13 (2000), S. 361-373 
    Details
    ISSN: 1572-8889
    Schlagwort(e): Drosophila ; copulatory courtship ; mate choice ; cryptic female choice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two endemic Australian Drosophila species, D. birchii and D. serrata, have a copulatory courtship, i.e., the males court the female mainly during copulation. In the present study we found the males of both species to mount their prospective mating partners selectively, exhibiting both sex and species recognition. The males began to sing after mounting the female, and they often exhibited also postcopulatory displays typical to copulatory courtship. D. birchii and D. serrata females discriminated against males which did not sing during mounting/copulation, which suggests that the females utilize cryptic female choice. Our findings raise the question of how widespread a phenomenon cryptic female choice is in Drosophila species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007710218609
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  • 4
    Digitale Medien
    Digitale Medien
    Patterning defects in the primary axonal scaffolds caused by the mutations of the extradenticle and homothorax genes in the embryonic Drosophila brain (2000)
    Springer
    Development genes and evolution 210 (2000), S. 289-299 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Key words Brain development ; Axonal scaffold ; Extradenticle ; Homothorax ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  During early brain development in Drosophila a highly stereotyped pattern of axonal scaffolds evolves by precise pioneering and selective fasciculation of neural fibers in the newly formed brain neuromeres. Using an axonal marker, Fasciclin II, we show that the activities of the extradenticle (exd) and homothorax (hth) genes are essential to this axonal patterning in the embryonic brain. Both genes are expressed in the developing brain neurons, including many of the tract founder cluster cells. Consistent with their expression profiles, mutations of exd and hth strongly perturb the primary axonal scaffolds. Furthermore, we show that mutations of exd and hth result in profound patterning defects of the developing brain at the molecular level including stimulation of the orthodenticle gene and suppression of the empty spiracles and cervical homeotic genes. In addition, expression of a Drosophila Pax6 gene, eyeless, is significantly suppressed in the mutants except for the most anterior region. These results reveal that, in addition to their homeotic regulatory functions in trunk development, exd and hth have important roles in patterning the developing brain through coordinately regulating various nuclear regulatory genes, and imply molecular commonalities between the developmental mechanisms of the brain and trunk segments, which were conventionally considered to be largely independent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004270050316
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  • 5
    Digitale Medien
    Digitale Medien
    Analysis of a swallow homologue from Drosophila pseudoobscura (2000)
    Springer
    Development genes and evolution 210 (2000), S. 157-161 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Key words Swallow ; bicoid ; Drosophila ; mRNA localization ; Oogenesis ; Embryogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  We analyzed a functional homologue of the swallow gene from Drosophila pseudoobscura. The swallow gene of D. melanogaster plays an essential role in localizing bicoid mRNA in oocytes, and swallow mutant embryos show anterior pattern defects that result from the lack of localization of the bicoid morphogen. The pseudoobscura homologue rescues the function of swallow mutants when introduced into the genome of D. melanogaster, and its expression is similar to that of the melanogaster gene. The predicted pseudoobscura and melanogaster proteins are 49% identical and 69% conserved. The coiled-coil domain previously identified in the melanogaster swallow protein is strongly conserved in the pseudoobscura homologue, but the weak similarity of the melanogaster swallow protein to the RNP class of RNA-binding proteins is not conserved in the pseudoobscura homologue. These and other observations suggest a structural role for swallow in localizing bicoid mRNA, perhaps as part of the egg cytoskeleton.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004270050023
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  • 6
    Digitale Medien
    Digitale Medien
    Changes in cell shape in the ventral neuroectoderm of Drosophila melanogaster depend on the activity of the achaete-scute complex genes (2000)
    Springer
    Development genes and evolution 210 (2000), S. 190-199 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Key words Ventral neuroectoderm ; Cell shape ; Achaete-scute complex ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  In the embryonic ventral neuroectoderm of Drosophila melanogaster the proneural genes achaete, scute, and lethal of scute are expressed in clusters of cells from which the neuroblasts delaminate in a stereotyped orthogonal array. Analyses of the ventral neuroectoderm before and during delamination of the first two populations of neuroblasts show that cells in all regions of proneural gene activity change their form prior to delamination. Furthermore, the form changes in the neuroectodermal cells of embryos lacking the achaete-scute complex, of embryos mutant for the neurogenic gene Delta, and of embryos overexpressing l’sc suggest that these genes are responsible for most of the morphological alterations observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004270050303
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  • 7
    Digitale Medien
    Digitale Medien
    A polymorphism of the rat T-cell receptor β-chain variable gene 13 (BV13S1) correlates with the frequency of BV13S1-positive CD4 cells (2000)
    Springer
    Immunogenetics 51 (2000), S. 296-305 
    Details
    ISSN: 1432-1211
    Schlagwort(e): Key words Vβ13 ; CD4/CD8 ratio ; Rat ; Tcrb ; Polymorphism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Three rat BV13S1 alleles (T-cell receptor β-chain variable gene 13) were characterized by new BV13S1-allele specific monoclonal antibodies (18B1 and 17D5) and sequence analysis of expressed and genomic BV13S1. Two alleles were functional and designated BV13S1A1 present in strains LEW, BUF, PVG, and BV13S1A2 present in BN and WF. Their products differed by six amino acids, two of them in complementarity-determing region (CDR)1 and one in CDR2. A third nonfunctional allele, BV13S1A3P, was found in strains F344 and DA. Apart from a single nucleotide insertion, it was identical to BV13S1A2. All 12 rat strains tested showed association of TCRBC1 with BV8S2/4 alleles but not with the BV13S1 alleles, which may reflect a different gene order of the rat BV compared to mouse. BV13S1A1-encoded T-cell receptors (TCRs) which bind both monoclonal antibody (mAb) 18B1 and mAb 17D5 are over-represented in the CD4 lymphocyte subset. BV13S1A2-encoded TCRs which are stained by mAb 18B1 but not by mAb 17D5 show a slight CD8-biased expression. Preferential usage of BV13S1A1-positive TCRs by CD4 but not by CD8 cells in (LEW×WF)F1 hybrids and cosegregation of BV13SA1 and increased frequency of BV13S1 TCR-positive CD4 cells in a (LEW×BN)×BN backcross suggest structural differences of the two allelic products as the reason for their contrasting CD4/CD8 subset bias.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002510050623
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  • 8
    Digitale Medien
    Digitale Medien
    Localization of endothelin receptors in bleomycin-induced pulmonary fibrosis in the rat (2000)
    Springer
    Histochemistry and cell biology 122 (2000), S. 507-517 
    Details
    ISSN: 1432-119X
    Schlagwort(e): Endothelin-A receptor ; Endothelin-B receptor ; Rat ; Pulmonary fibrosis ; Immunohistochemistry ; Quantitative PCR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: AbstractPulmonary fibrosis is characterized by excessive extracellular matrix deposition with concomitant loss of gas exchange units, and endothelin-1 (ET-1) has been implicated in its pathogenesis. Increased levels of ET-1 from tissues and bronchoalveolar lavage have been reported in patients with pulmonary fibrosis and in animal models after intratracheal bleomycin. We characterized the cellular distribution of alveolar ET receptors by immunohistochemistry in bleomycin-induced pulmonary fibrosis in the rat and determined the regulation by bleomycin of ET receptor mRNA expression in isolated alveolar macrophages and rat lung fibroblasts. We found significant increases in the numbers of fibroblasts and macrophages at day 7 compared to day 28 and control animals. ETB receptor immunoreactivity was observed on fibroblasts and invading monocytes. Isolated fibroblasts expressed both ETA and ETB receptor mRNA, and ETA receptor mRNA was upregulated by bleomycin. Isolated resident alveolar macrophages expressed neither ETA nor ETB receptor mRNA which were also not induced by bleomycin. We conclude that, while ETB receptor stimulation of fibroblasts and monocytes recruited during bleomycin-induced lung injury exerts antagonistic effects on fibroblast collagen synthesis, the observed increase in the number of fibroblasts in vivo and upregulation of fibroblast ETA receptor mRNA by bleomycin in vitro point to a predominance of the profibrotic effects of ET receptor engagement.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s00418-004-0708-7
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  • 9
    Digitale Medien
    Digitale Medien
    Coexistence of drosophilid flies: Aggregation, patch size diversity and parasitism (2000)
    Springer
    Ecological research 15 (2000), S. 93-100 
    Details
    ISSN: 1440-1703
    Schlagwort(e): aggregation ; coexistence ; Drosophila ; parasitism ; patch size
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: We carried out field experiments to investigate the coexistence of Drosophila species in domestic and forest areas on the basis of the aggregation model. Three cosmopolitan species Drosophila simulans Sturtevant, Drosophila melanogaster Meigen and Drosophila immigrans Sturtevant, and a native species, Drosophila auraria Peng, emerged abundantly from banana placed at the domestic station, while Drosophila immigrans and five native species, Drosophila lutescens Okada, Drosophila rufa Kikkawa and Peng, Drosophila bizonata Kikkawa and Peng, Drosophila sternopleuralis Okada and Kurokawa and Scaptodrosophila coracina (Kikkawa and Peng), were abundant at the forest station. The present analysis suggests that their coexistence was facilitated by the aggregation mechanism. In the cosmopolitan species, the density of individuals that emerged from patches increased with the increase of patch size, but the relationship between fly density and patch size was not clear in the native species. This difference in distribution patterns between the cosmopolitan and native species is likely to be due to the difference in the female visiting behavior. In the present analysis, however, it was not clear whether patch size diversity facilitated their coexistence or not. The effect of patch size diversity may have been masked, because the effect of aggregation was more prominent. The rate of parasitism by wasps was high in October at the domestic station, and in May and June at the forest station. The present result suggests that the rate of parasitism was density-dependent, at least at the domestic station, and therefore parasitism facilitates the coexistence of drosophilid species in domestic areas.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1440-1703.2000.00328.x
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  • 10
    Digitale Medien
    Digitale Medien
    Identification ofDrosophila mutant with memory defects after acquisition of conditioned reflex suppression of courtship (2000)
    Springer
    Neuroscience and behavioral physiology 30 (2000), S. 307-313 
    Details
    ISSN: 1573-899X
    Schlagwort(e): Memory ; suppression of courting ; Drosophila ; mutants ; P insertion mutagenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Four lines were selected from a collection of 33 lines prepared by P insertion mutagenesis using a single-copy P-element system; the males of these four lines showed memory defects after acquisition of conditioned reflex suppression of courting. In two lines (P171 and P95), the dynamics of retention of the conditioned reflex in the repeated impregnated-female courting test were similar to those of known short-term memory mutantsdnc andrut. In line P153, the dynamics were more reminiscent of the memory dynamics in a known medium-term memory mutant,amn. In line P124, the learning index was insignificant immediately after training was completed, which may indicate that this line was unable to acquire conditioned reflex suppression of courting. Determination of the positions of the P elements (P171: 48A-B; P153: 49B-C; P124; 67B–68A; P95: 77C-D) showed no correspondence with previously known mutations producing memory lesions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02471783
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  • 11
    Digitale Medien
    Digitale Medien
    Parental Imprinting in Drosophila (2000)
    Springer
    Genetica 109 (2000), S. 35-44 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; heterochromatin ; imprinting ; parental effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Genetic imprinting is a form of epigenetic silencing. But with a twist. The twist is that while imprinting results in the silencing of genes, chromosome regions or entire chromosome sets, this silencing occurs only after transmission of the imprinted region by one sex of parent. Thus genetic imprinting reflects intertwined levels of epigenetic and developmental modulation of gene expression. Imprinting has been well documented and studied in Drosophila, however, these studies have remained largely unknown due to nothing more significant than differences in terminology. Imprinting in Drosophilais invariably associated with heterochromatin or regions with unusual chromatin structure. The imprint appears to spread from imprinted centers that reside within heterochromatin and these are, seemingly, the only regions that are normally imprinted in Drosophila. This is significant as it implies that while imprinting occurs in Drosophila, it is generally without phenotypic consequence. Hence the evolution of imprinting, at least in Drosophila, is unlikely to be driven by the function of specific imprinted genes. Thus, the study of imprinting in Drosophilahas the potential to illuminate the mechanism and biological function of imprinting, and challenge models based solely on imprinting of mammalian genes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026592318341
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  • 12
    Digitale Medien
    Digitale Medien
    Searching for a Common Centromeric Structural Motif: Drosophila Centromeric Satellite DNAs Show Propensity to form Telomeric-Like Unusual DNA Structures (2000)
    Springer
    Genetica 109 (2000), S. 71-75 
    Details
    ISSN: 1573-6857
    Schlagwort(e): centromere ; heterochromatin ; non B-DNA structures ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The molecular basis of centromere formation in a particular chromosomal region is not yet understood. In higher eukaryotes, no specific DNA sequence is required for the assembly of the kinetochore, but similar centromeric chromatins are formed on different centromere DNA sequences. Although epigenesis has been proposed as the main mechanism for centromere specification, DNA recognition must also play a role. Through the analysis of Drosophilacentromeric DNA sequences, we found that dodeca satellite and 18HT satellite are able to form unusual DNA structures similar to those formed by telomeric sequences. These findings suggest the existence of a common centromeric structural DNA motif which we feel merits further investigation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026546510127
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  • 13
    Digitale Medien
    Digitale Medien
    Genetic and biochemical analysis of brown eye mutation in Drosophila nasuta nasuta and Drosophila nasuta albomicans (2000)
    Springer
    Genetica 109 (2000), S. 235-243 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; brown eye ; eye pigments ; fitness ; gene localization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract By analyzing the progeny of crosses involving brown eye mutants and the wild types in two members of Drosophila nasuta subgroup namely D. n. nasuta and D. n. albomicans we could show that the mutant gene is recessive, located in the chromosome 2 and the alleles of this gene are present at different loci. A study of fitness in the eye color mutants in comparison with the wild types revealed that D. n. nasuta mutant has higher viability at both 25 ± 1°C and ambient temperatures; while D. n. albomicans mutant has faster rate of development only at 25 ± 1°C. Quantitative analysis of eye pigments in the mutants revealed that there is biosynthesis of both pteridines and xanthommatins unlike in bw/bw of D. melanogaster, where only xanthommatins are synthesized. In both the species, the pteridine quantities in mutants are similar; whereas xanthommatin quantity in $$\user1{bw}_n \user1{/bw}_n$$ is 10 times higher than that of $$\user1{bw}_a \user1{/bw}_a$$ . Further, the F1 progeny of intraspecific crosses (wild type X mutant) are found to have high amounts of pteridine, even when compared with parental wild type.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017505400086
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  • 14
    Digitale Medien
    Digitale Medien
    Dnop56, a Drosophila gene homologous to the yeast nucleolar NOP56 gene (2000)
    Springer
    Genetica 109 (2000), S. 275-282 
    Details
    ISSN: 1573-6857
    Schlagwort(e): DmNop56 ; DsNop56 ; Drosophila ; molecular evolution ; snoRNPs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Small nucleolar RNAs (snoRNAs) are trans‐acting factors involved in maturation of rRNA and have been classified into Box C/D and Box H/ACA families. Most of the snoRNAs occur as ribonucleoprotein complexes with snoRNA‐associated proteins (snoRNPs). All Box C/D snoRNAs in yeast form complexes with Nop1p, Nop56p and Nop58p. Similarly, it has been reported that Box H/ACA‐containing snoRNAs form complexes with yeast Gar1p. Nop56p and Nop58p homologs have been described in several species. Here we report the isolation and molecular characterization of the Dnop56 genes from D. melanogaster and D. subobscura which show a very similar structure. Drosophila Nop56p proteins contain lysine‐rich regions at their carboxy‐terminus, and show a high degree of similarity to other Nop56p proteins from different organisms. Phylogenetic relationships among these proteins and other snoRNPs have been established.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017596312331
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  • 15
    Digitale Medien
    Digitale Medien
    Calmodulin-dependent and -independent apoptosis in cells of a Drosophila neuronal cell line (2000)
    Springer
    Apoptosis 5 (2000), S. 133-140 
    Details
    ISSN: 1573-675X
    Schlagwort(e): Apoptosis ; calmodulin ; caspases ; cell line ; Drosophila ; neuron
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract This study was undertaken to reveal apoptotic pathways in neurons using a Drosophila neuronal cell line derived from larval central nervous system. We could induce apoptotic cell death in the cells by a Ca2+ ionophore (A23187), a protein kinase inhibitor (H-7), an RNA synthesis inhibitor (actinomycin D) and a protein synthesis inhibitor (cycloheximide). All the apoptosis induced by each chemical required Ca2+ ions, although the origin of Ca2+ ions were different: apoptosis induced by A23187 was dependent on extracellular Ca2+ ions whereas those by the other three chemicals utilized intracellular Ca2+ ions. Furthermore, different reactions to W-7, a calmodulin inhibitor, were found: W-7 prevented the cell death by each of the three chemicals but not by A23187. Based on the results, we proposed that the apoptotic pathways are classified into two types in individual cells. One pathway induced by H-7, actinomycin D or cycloheximide is calmodulin-dependent (pathway H), and another induced by A23187 is calmodulin-independent (pathway A).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009676528805
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  • 16
    Digitale Medien
    Digitale Medien
    An episode of accelerated amino acid change in Drosophila esterase-6 associated with a change in physiological function (2000)
    Springer
    Genetica 110 (2000), S. 231-244 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; , esterase-6 ; function ; sequence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In most lineages of the subgenus Sophophora esterase-6 is a homodimeric haemolymph protein. In the melanogaster subgroup of species it has become a monomer which is mainly expressed in the male sperm ejaculatory duct. Our analyses of esterase-6 sequences from three melanogaster subgroup species and two close relatives reveal a brief period of accelerated amino acid sequence change during the transition between the ancestral and derived states. In this period of 2–6Myr the ratio of replacement to silent site substitutions (0.51) is about three times higher than the values in other lineages of the phylogeny. There are about 50 more replacements in this period than would be predicted from the ratios of replacement to silent site substitutions found elsewhere in the phylogeny. Modelling on the known structure of a related acetylcholinesterase suggests that an unusually high proportion of the replacements in the transitional branch are non-conservative changes on the protein surface. Up to half the accelerated replacement rate can be accounted for by clusters of changes to the face of the molecule containing the opening of the active site gorge. This includes changes in and around regions homologous to peripheral substrate binding sites in acetylcholinesterase. There are also three changes in glycosylation status. One region predicted to lie on the protein surface which becomes markedly more hydrophilic is proposed to be the ancestral dimerisation site that is lost in the transitional branch.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1012727814167
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  • 17
    Digitale Medien
    Digitale Medien
    Impact of Multiple Insertions of two Retroelements, ZAM and Idefix at an Euchromatic Locus (2000)
    Springer
    Genetica 109 (2000), S. 53-59 
    Details
    ISSN: 1573-6857
    Schlagwort(e): chromatin structure ; Drosophila ; mutagenic effect ; retroelements ; white
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Transposable elements represent a large fraction of eukaryotic genomes and they are thought to play an important role in chromatin structure. ZAMand Idefixare two LTR-retrotransposons from Drosophila melanogastervery similar in structure to vertebrate retroviruses. In all the strains where their distribution has been studied, ZAMappears to be present exclusively in the intercalary heterochromatin while Idefixcopies are mainly found in the centromeric heterochromatin with very few copies in euchromatin. Their distribution varies in a specific strain called RevI in which the mobilization of ZAMand Idefixis highly induced. In this strain, 15 copies of ZAMand 30 copies of Idefixare found on the chromosomal arms in addition to their usual distribution. Amongst the loci where new copies are detected, a hotspot for their insertion has been detected at the whitelocus where up to four elements occurred within a 3-kb fragment at the 5′ end of this gene. This property of ZAMand Idefixto accumulate at a defined site provides an interesting paradigm to bring insight into the effect exerted by multiple insertions of transposable elements at an euchromatic locus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026534207401
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  • 18
    Digitale Medien
    Digitale Medien
    Variations of male cuticular hydrocarbons with geoclimatic variables: an adaptative mechanism in Drosophila melanogaster? (2000)
    Springer
    Genetica 110 (2000), S. 117-130 
    Details
    ISSN: 1573-6857
    Schlagwort(e): adaptation ; Drosophila ; hydrocarbons ; latitude ; longitude ; natural populations ; polymorphism ; temperaturey ; vapour pressure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract 7-tricosene (7T) and 7-pentacosene (7P) are the major components of cuticular hydrocarbons in Drosophila simulans and D. melanogaster males. A chemical study of 16 isofemale lines of D. melanogaster sampled at the first and eighth generations in laboratory conditions showed the stability of chromatographical profiles. Then a large scale study of male 7T/7P polymorphism was performed with 85 populations of D. melanogaster and 29 of D. simulans collected all over the world. There were significant correlations of the values of the balanced ratio (7T − 7P)/(7T + 7P) with geo-climatic parameters, such as latitude, longitude, mean temperature, temperature range and vapour pressure. Parallel variations were also reported for the homologous linear alkanes (23 and 25 Carbon atoms) but not for the longer branched alkanes (27 and 29 Carbon atoms). No correlation was significant for the D. simulans populations studied. In this species a similar polymorphism of 7T/7P was found but restricted to a few populations from West Equatorial Africa.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017987220814
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  • 19
    Digitale Medien
    Digitale Medien
    Genetic variance in temperature dependent adult size deriving from physiological genetic variation at temperature boundaries (2000)
    Springer
    Genetica 110 (2000), S. 195-207 
    Details
    ISSN: 1573-6857
    Schlagwort(e): biophysics ; body size ; Drosophila ; ectotherm ; genetic variance ; stress ; temperature extreme
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An increase in genetic variation in body size has often been observed under stress; an increase in dominance variance and interaction variance as well as in additive genetic variance has been reported. The increase in genetic variation must be caused by physiological mechanisms that are specific to adverse environments. A model is proposed to explain the occurrence of an increase in genetic variation in body size in Drosophila at extreme temperatures. The model has parameters specific to the low- and high-temperature regions of the viable range. Additive genetic variation in the boundary temperatures leads to a marked increase in additive genetic variation in development rate and body size at extreme temperatures. Additive genetic variation in the temperature sensitivity in the low- and high-temperature regions adds non-additive genetic variation. Development rate shows patterns in additive genetic variation that differ from the patterns of genetic variation in body size; therefore, the genetic correlation between development rate and body size changes sign repeatedly as a function of temperature. The existence of dominance in the genetic variation in the boundary temperatures or in the low- and high-temperature sensitivities leads to a higher total genetic variance due to higher dominance and interaction variance, for both development rate and body size.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017974618477
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  • 20
    Digitale Medien
    Digitale Medien
    Distinct requirements for the AP-3 adaptor complex in pigment granule and synaptic vesicle biogenesis in Drosophila melanogaster (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 1003-1014 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Key words AP-3 ; Biogenesis ; Pigment granule ; Synaptic vesicle ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The AP-3 adaptor protein complex has been implicated in the biogenesis of lysosome-related organelles, such as pigment granules/melanosomes, and synaptic vesicles. Here we compare the relative importance of AP-3 in the biogenesis of these organelles in Drosophila melanogaster. We report that the Drosophila pigmentation mutants orange and ruby carry genetic lesions in the σ3 and β3-adaptin subunits of the AP-3 complex, respectively. Electron microscopy reveals dramatic reductions in the numbers of electron-dense pigment granules in the eyes of these AP-3 mutants. Mutant flies also display greatly reduced levels of pigments housed in these granules. In contrast, electron microscopy of retinula cells reveals numerous synaptic vesicles in both AP-3 mutant and wild-type flies, while behavioral assays show apparently normal locomotor ability of AP-3 mutant larvae. Together, these results demonstrate that Drosophila AP-3 is critical for the biogenesis of pigment granules, but is apparently not essential for formation of a major population of synaptic vesicles in vivo.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00008688
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  • 21
    Digitale Medien
    Digitale Medien
    Modulation of Paired-Pulse Responses in the Dentate Gyrus: Effects of Normal Maturation and Vigilance State (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 128-134 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Hippocampus ; Vigilance states ; Paired-pulse ; Dentate gyrus ; Dentate granule cells ; Evoked response ; Rat ; In vivo studies ; Perforant path ; Maturation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract This study examined the effect of normal development and vigilance state on the modulation of dentate granule cell activity in the freely moving rat at 15, 30, and 90 days of age across three vigilance states: quiet waking, slow-wave sleep, and rapid eye movement sleep. Using paired-pulse stimulation, the paired-pulse index (PPI) was obtained for the dentate evoked field potentials elicited by the stimulation of the medial perforant path. Although significant differences in PPI values were observed during development, no significant vigilance state related changes were obtained. Preweaning infant rats, i.e., 15-day old, exhibited significantly less early (interpulse intervals, IPI= 20–50 ms) and late (IPI = 300–1000 ms) inhibition, and less facilitation (IPI = 50–150 ms) when compared to the 90-day old adult rats during all three vigilance states. PPI values obtained from the 30-day old group fell intermediate between the 15- and 90-day old animals. These changes in PPI values provide a quantitative measure of changes in the modulation of dentate granule cell excitability during normal maturation. They can now can be used to evaluate the impact of various insults, such as prenatal protein malnutrition or neonatal stress, on hippocampal development. © 2000 Biomedical Engineering Society. PAC00: 8717Nn, 8719La, 8719Nn
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1114/1.261
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  • 22
    Digitale Medien
    Digitale Medien
    Left Ventricular Contractility is Impaired Following Myocardial Infarction in the Pig and Rat: Assessment by the End Systolic Pressure–Volume Relation Using a Single-Beat Estimation Technique and Cine Magnetic Resonance Imaging (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 484-494 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Heart ; Left ventricle ; LV contractility ; ESPVR ; Pig ; Rat ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract The end systolic pressure–volume relation (ESPVR) has been shown to be a relatively load independent measure of left ventricular (LV) contractility. Recently, several single-beat ESPVR computation methods have been developed, enabling the quantification of LV contractility without the need to alter vascular loading conditions on the heart. Using a single-beat ESPVR method, which has been validated previously in humans and assumes that normalized elastance is constant between individuals of a species, we studied the effects of myocardial infarction on LV contractility in two species, the rat and the pig. In our studies, LV pressure was acquired invasively and LV volume determined noninvasively with magnetic resonance imaging, at one week postinfarction in pigs and at 12 weeks postinfarction in rats. Normalized systolic elastance curves in both animal species were not statistically different from that of humans. Also, the slope of the ESPVR $$\left( {E_{es} } \right)$$ decreased significantly following infarction in both species, while the volume-axis intercept $$\left( {V_0 } \right)$$ was unaffected. These results indicate that a single-beat ESPVR method can be used to measure the inotropic response of the heart to myocardial infarction, and that the basis for this method (i.e., constant normalized elastance) is applicable to a variety of mammalian species. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8761Lh, 8719Hh, 8719Rr, 8719Ff
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1114/1.289
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  • 23
    Digitale Medien
    Digitale Medien
    Quantifying Coevolution of Nonstationary Biomedical Signals Using Time-Varying Phase Spectra (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 1101-1115 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Time–frequency analysis ; Coherence ; Cross correlation ; Nonstationary persistent signals ; Central pattern generator ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract We present a novel time-varying phase spectrum (TVPS) method to quantify the dynamics of coevolution of two persistent nonstationary coupled signals. Based on the TVPS, an instantaneous intersignal phase shift is defined within the primary frequency range in which the two signals are highly correlated. The TVPS is estimated using a fixed-window method or an adaptive-window method. In the latter method, the window length changes dynamically and automatically as a function of change in frequency of the signals. The effects of altering window types and lengths on the accuracy of the estimation of the primary phase shift is assessed by analyzing synthesized linear chirp signals with decaying amplitude and constant relative phase shift or decaying amplitude and changing relative phase shifts. The methods developed are also used for determining the evolution of the primary phase shift among ventral root activities during fictive locomotion in an in vitro rat spinal cord preparation. The analyses indicate that the TVPS method in conjunction with the determination of the primary frequency range, allows determination of both the evolution of the coupling strength and the evolution of the phase shift between two persistent nonstationary rhythmic signals in the joint time–frequency domain. An adaptive window reduces the estimation bias and the estimation variability. © 2000 Biomedical Engineering Society. PAC00: 0230-f, 8780Tq
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1114/1.1313775
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  • 24
    Digitale Medien
    Digitale Medien
    Control of Telomere Elongation and Telomeric Silencing in Drosophila Melanogaster (2000)
    Springer
    Genetica 109 (2000), S. 61-70 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; heterochromatin ; telomere ; transcription ; transposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Chromosome length in Drosophilais maintained by the targeted transposition of two families of non-LTR retrotransposons, HeT-Aand TART. Although the rate of transposition to telomeres is sufficient to counterbalance loss from the chromosome ends due to incomplete DNA replication, transposition as a mechanism for elongating chromosome ends raises the possibility of damaged or deleted telomeres, because of its stochastic nature. Recent evidence suggests that HeT-Atransposition is controlled at the levels of transcription and reverse transcription. HeT-Atranscription is found primarily in mitotically active cells, and transcription of a w +reporter gene inserted into the 2L telomere increases when the homologous telomere is partially or completely deleted. The terminal HeT-Aarray may be important as a positive regulator of this activity in cis, and the subterminal satellite appears to be an important negative regulator in cis. A third chromosome modifier has been identified that increases the level of reverse transcriptase activity on a HeT-A RNA template and greatly increases the transposition of HeT-A. Thus, the host appears to play a role in transposition of these elements. Taken together, these results suggest that control of HeT-Atransposition is more complex than previously thought.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026548503320
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  • 25
    Digitale Medien
    Digitale Medien
    Molecular organization of the Drosophila melanogaster Adh chromosomal region in D. replete and D. buzzatii, two distantly related species of the Drosophila subgenus (2000)
    Springer
    Chromosome research 8 (2000), S. 375-385 
    Details
    ISSN: 1573-6849
    Schlagwort(e): Adh ; Drosophila ; FISH ; genome evolution ; repleta group
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The molecular organization of a 1.944-Mb chromosomal region of Drosophila melanogaster around the Adh locus has been analyzed in two repleta group species: D. repleta and D. buzzatii. The extensive genetic and molecular information about this region in D. melanogaster makes it a prime choice for comparative studies of genomic organization among distantly related species. A set of 26 P1 phages from D. melanogaster were successfully hybridized using fluorescence in-situ hybridization (FISH) to the salivary gland chromosomes of both repleta group species. The results show that the Adh region is distributed in D. repleta and D. buzzatii over six distant sites of chromosome 3, homologous to chromosomal arm 2L of D. melanogaster (Muller's element B). This observation implies a density of 2.57 fixed breakpoints per Mb in the Adh region and suggests a considerable reorganization of this chromosomal element via the fixation of paracentric inversions. Nevertheless, breakpoint density in the Adh region is three times lower than that estimated for D. repleta chromosome 2, homologous to D. melanogaster 3R (Muller's element E). Differences in the rate of evolution among chromosomal elements are seemingly persistent in the Drosophila genus over long phylogenetic distances.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009206702214
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  • 26
    Digitale Medien
    Digitale Medien
    Distribution of the Transposable Element Minos in the Genus Drosophila (2000)
    Springer
    Genetica 108 (2000), S. 263-267 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; horizontal transfer ; Minos ; Tc1-like ; Tc1-marinerfamily ; transposable elements ; transposon distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We analyzed 28 species of the genus Drosophilafor the presence of the Tc1-like transposable element Minosusing Southern blot hybridization under high stringency conditions. The Minostransposon was found in members of both the Drosophilaand the Sophophorasubgenus showing a distribution that is wider if compared to other well-studied Drosophilatransposons such as the Pelement, hoboand mariner. The presence of Minos-hybridizing sequences was discontinuous in the Sophophorasubgenus, especially in the melanogasterspecies group. Using the Polymerase Chain Reaction we amplified a portion corresponding to the putative Minostransposase from different Drosophilaspecies. Cloning and sequence analysis of randomly selected Minoscopies from D. mojavensisis, D. saltansand D. willistonisupports the idea that event(s) of horizontal transfer may have contributed to the spreading of this transposon in the Drosophilagenus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004185024017
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  • 27
    Digitale Medien
    Digitale Medien
    Spatial differences in patterns of modification: selection on hairy in Drosophila melanogaster wings (2000)
    Springer
    Genetica 109 (2000), S. 169-181 
    Details
    ISSN: 1573-6857
    Schlagwort(e): artificial selection ; atavistic structures ; Drosophila ; pattern formation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Artificial selection was carried out for over 45 generations to enhance and suppress expression of the mutation hairy on the Drosophila melanogaster wing. Whole chromosome mapping of X‐linked and autosomal modifiers of sense organ number displayed regional differences in magnitude and direction of their effects. Regional specificity of modifier effects was also seen in some interchromosomal interactions. Scanning electron microscopy allowed precise measurement of sense organ size and position along the L3 longitudinal wing vein. Sense organ size varied in a predictable fashion along the proximal–distal axis, and the dorsal pattern differed from the ventral pattern. The high and low selection lines differed most in the proximal portion of the L3 vein. Extra sense organs in the High line were often associated with vein fragments at locations predicted from ancestral vein patterns. Thus, regional specificity of polygenic or quantitative trait locus modifier effects was identified in several different parts of the wing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017531404454
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  • 28
    Digitale Medien
    Digitale Medien
    Genetic analysis of extended lifespan in Drosophila melanogaster III. On the relationship between artificially selected and wild stocks (2000)
    Springer
    Genetica 109 (2000), S. 245-253 
    Details
    ISSN: 1573-6857
    Schlagwort(e): artificial selection ; Drosophila ; lifespan ; mortality ; paraquat ; DDT ; recovery hypothesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Adult lifespans, age‐specific survival, age‐specific mortality, survival times on paraquat, and survival times on DDT were assayed in seven lines of Drosophila melanogaster, including two genetically heterogeneous wild lines recently collected from nature, and three inbred and recombinant inbred lines derived from an artificial selection experiment for increased lifespan. Survival on paraquat is positively correlated with adult lifespan. DDT resistance is uncorrelated with either paraquat resistance or lifespan. The wild lines are unexceptional with respect to average lifespan, paraquat resistance, age‐specific survivorship, and leveling off of mortality rates at advanced ages, but have high levels of DDT resistance. Cluster analysis groups the wild lines with three unselected laboratory stocks in one cluster, while two long‐lived elite recombinant inbred lines form a second cluster. Long‐lived laboratory‐adapted lines are quantitatively differentiated from the wild stocks, both with respect to average adult lifespans and resistance to an oxidizing agent. We reject the ‘recovery’ hypothesis, which proposes that Drosophila artificially selected for long life have phenotypes that merely recover the wild state.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017569318401
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  • 29
    Digitale Medien
    Digitale Medien
    Role of AWD/Nucleoside Diphosphate Kinase in Drosophila Development (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 293-300 
    Details
    ISSN: 1573-6881
    Schlagwort(e): abnormal wing discs ; lethal mutant ; Drosophila ; Killer-of-prune ; prune
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract The abnormal wing discs gene of Drosophila encodes a soluble protein with nucleosidediphosphate kinase activity. This enzymic activity is necessary for the biological function ofthe abnormal wing discs gene product. Complete loss of function, i.e., null, mutations causelethality after the larval stage. Most larval organs in such null mutant larvae appear to benormal, but the imaginal discs are small and incapable of normal differentiation.Killer-of-prune is a neomorphic mutation in the abnormal wing discs gene. It causes dominant lethalityin larvae that lack prune gene activity. The Killer-of-prune mutant protein may have alteredsubstrate specificity. Null mutant larvae have a low level of nucleoside diphosphate kinaseactivity. This suggests that there may be additional Drosophila genes that encode proteinswith nucleoside dipthosphate kinase activity. Candidate genes have been found in theDrosophila genome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005545214937
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  • 30
    Digitale Medien
    Digitale Medien
    Common Mechanisms of Y Chromosome Evolution (2000)
    Springer
    Genetica 109 (2000), S. 105-111 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; evolution ; heterochromatin ; Y chromosome
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Y chromosome evolution is characterized by the expansion of genetic inertness along the Y chromosome and changes in the chromosome structure, especially the tendency of becoming heterochromatic. It is generally assumed that the sex chromosome pair has developed from a pair of homologues. In an evolutionary process the proto-Y-chromosome, with a very short differential segment, develops in its final stage into a completely heterochromatic and to a great extends genetically eroded Y chromosome. The constraints evolving the Y chromosome have been the objects of speculation since the discovery of sex chromosomes. Several models have been suggested. We use the exceptional situation of the in Drosophila mirandato analyze the molecular process in progress involved in Y chromosome evolution. We suggest that the first steps in the switch from a euchromatic proto-Y-chromosome into a completely heterochromatic Y chromosome are driven by the accumulation of transposable elements, especially retrotransposons inserted along the evolving nonrecombining part of the Y chromosome. In this evolutionary process trapping and accumulation of retrotransposons on the proto-Y-chromosome should lead to conformational changes that are responsible for successive silencing of euchromatic genes, both intact or already mutated ones and eventually transform functionally euchromatic domains into genetically inert heterochromatin. Accumulation of further mutations, deletions, and duplications followed by the evolution and expansion of tandem repetitive sequence motifs of high copy number (satellite sequences) together with a few vital genes for male fertility will then represent the final state of the degenerated Y chromosome.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026584016524
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  • 31
    Digitale Medien
    Digitale Medien
    Versatility of Conviction: Heterochromatin as Both a Repressor and an Activator of Transcription (2000)
    Springer
    Genetica 109 (2000), S. 19-24 
    Details
    ISSN: 1573-6857
    Schlagwort(e): chromosomal proteins ; Drosophila ; heterochromatin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026544717126
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  • 32
    Digitale Medien
    Digitale Medien
    Drosophila Telomeric Transgenes Provide Insights on Mechanisms of Gene Silencing (2000)
    Springer
    Genetica 109 (2000), S. 25-33 
    Details
    ISSN: 1573-6857
    Schlagwort(e): chromatin ; Drosophila ; heterochromatin ; position effect variegation ; telomeres
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A significant fraction of most eukaryotic genomes is packaged into chromatin that is not permissive for gene expression. This silent chromatin is typically located near centromeres and telomeres and has fascinated scientists for more than 70 years, yet many questions remain unanswered. Part of the difficulties in studying silent chromatin at the molecular level is the repetitive nature of the DNA sequences in these regions. To overcome this problem, Drosophilastocks carrying in vitrodesigned transgenes inserted within silent chromatin have been generated. Molecular analysis of these transgenes has shed light on the nature of the chromatin structure within these regions and provided insights on the mechanisms of gene silencing. This review will focus on recent studies using telomeric transgenes. The results from these studies suggest that nuclear organization plays a role in gene silencing and that silencing is the result of a block early in the process of transcription initiation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026556705137
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  • 33
    Digitale Medien
    Digitale Medien
    Isolation of True Rbp9 Null Alleles by Imprecise P Element Excisions (2000)
    Springer
    Molecules and cells 10 (2000), S. 61-64 
    Details
    ISSN: 0219-1032
    Schlagwort(e): Drosophila ; Imprecise Excision ; Null Allele ; P Element ; Rbp9
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The P element has been widely used as a mutagen because of its convenience in locating the site of mutagenesis. However, P element-induced mutations often result in varied mutant phenotypes, making it difficult to identify the null phenotype. Previously, three Rbp9 alleles were isolated using P element mutagenesis. Although the coding regions of Rbp9 were disrupted by P elements in all three cases, they showed different degrees of defects. In order to characterize the null phenotype of Rbp9, Rbp9 alleles with chromosomal deletions were created by inducing imprecise excisions of the P elements. All Rbp9 alleles generated from imprecise excisions showed the same mutant phenotype: female flies were sterile and cystocyte differentiation was blocked. This result reveals that the primary function of Rbp9 resides in the regulation of cystocyte differentiation. In addition, this result shows that a P element does not always completely inactivate gene activity, even when it is incorporated into the coding region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s10059-000-0061-1
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  • 34
    Digitale Medien
    Digitale Medien
    Effects of Polycomb Group Mutations on the Expression of Ultrabithorax in the Drosophila Visceral Mesoderm (2000)
    Springer
    Molecules and cells 10 (2000), S. 156-161 
    Details
    ISSN: 0219-1032
    Schlagwort(e): Drosophila ; Polycomb Group Genes ; Ultrabithorax ; Visceral Mesoderm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Polycomb group (PcG) genes encode repressors of many developmental regulatory genes including homeotic genes and are known to act by modifying chromatin structure through complex formation. We describe how Ultrabithorax (Ubx) expression is affected by the PcG mutants in the visceral mesoderm. Mutant embryos of the genes extra sex combs (esc), Polycomb (Pc), additional sex combs (Asx) and pleiohomeotic (pho) were examined. In each mutation, Ubx was ectopically expressed outside of their normal domains along the anterior-posterior axis in the visceral mesoderm, which is consistent with the effect of PcG proteins repressing the homeotic genes in other tissues. All of these four PcG mutations exhibit complete or partial lack of midgut constriction. However, two thirds of esc mutant embryos did not show Ubx expression in parasegment 7 (PS7). Even in the embryos showing ectopic Ubx expression, the level of Ubx expression in the PcG mutations was weaker than that in normal embryos. We suggest that in PcG mutations the ectopic Ubx expression is caused by lack of PcG repressor proteins, while the weaker or lack of Ubx expression is due to the repression of Ubx by Abd-B protein which is ectopically expressed in PcG mutations as well.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s10059-000-0156-8
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  • 35
    Digitale Medien
    Digitale Medien
    Regulation of Mst57Dc Expression in Male Accessory Glands of Dorsophila melanogaster (2000)
    Springer
    Molecules and cells 10 (2000), S. 180-185 
    Details
    ISSN: 0219-1032
    Schlagwort(e): Drosophila ; Gene Expression ; JHRE ; Juvenile Hormone ; Male Accessory Gland ; Mst57Dc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Mst57Dc has been isolated as a male accessory gland transcript of Drosophila melanogaster. Its product is a secretory protein, which is phosphorylated by protein kinase A. In the present study, the expression pattern of Mst57Dc was analyzed. It is preferentially expressed in but not restricted to the male accessory glands. Other than in the accessory glands, it is slightly expressed in other body parts, including the head and female body. In the accessory glands, a high level of expression was detected right after eclosion when the titer of juvenile hormone III (JHIII) reaches a peak. Its accumulation was increased by mating, which has been known to act via JH. In ap56f, a JH-deficient mutant, the level of Mst57Dc transcripts was about 60% of the wild type. Moreover a JH-responsive element like palindromic sequence and several sequence motifs were found in the 5′ and 3′ flanking regions of Mst57Dc. Taken together, JH is proposed as a regulator of Mst57Dc gene expression.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s10059-000-0180-8
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  • 36
    Digitale Medien
    Digitale Medien
    c-Fos Expression by Dopaminergic Receptor Activation in Rat Hippocampal Neurons (2000)
    Springer
    Molecules and cells 10 (2000), S. 546-551 
    Details
    ISSN: 0219-1032
    Schlagwort(e): c-Fos ; Dopamine ; D1 ; Hippocampus ; Rat ; Synaptic Plasticity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract While dopamine is likely to modulate hippocampal synaptic plasticity, there has been little information about how dopamine affects synaptic transmission in the hippocampus. The expression of IEGs including c-fos has been associated with late phase LTP in the CA1 region of the hippocampus. The induction of c-fos by dopaminergic receptor activation in the rat hippocampus was investigated by using semiquantitative RT-PCR and immuno-cytochemistry. The hippocampal slices which were not treated with dopamine showed little expression of c-fos mRNA. However, the induction of c-fos mRNA was detected as early as 5 min after dopamine treatment, peaked at 60 min, and remained elevated 5 h after treatment. Temporal profiles of increases in c-fos mRNA by R(+)-SKF-38393 (50 μM) and forskolin (50 μM) were similar to that of dopamine. An increase in [cAMP] was observed in dopamine-, SKF-, or forskolin-treated hippocampal slices. By immunocytochemical studies, control hippocampal cells showed little expression of c-Fos immunoreactivity. However, when cells were treated with dopamine, an increase in the expression of c-Fos immunoreactivity was observed after treatment for 2 h. The treatment of hippocampal neurons with R(+)-SKF38393 (50 μM) or forskolin (50 μM) also induced a significant increase in c-Fos expression. These results indicate that the dopamine D1 receptor-mediated cAMP dependant pathway is associated with the expression of c-Fos in the hippocampal neurons. These data are consistent with the possible role of endogenous dopamine on synaptic plasticity via the regulation of gene expression. Furthermore, these results imply that dopamine might control the process of memory storage in the hippocampus through gene expression.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s10059-000-0546-y
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  • 37
    Digitale Medien
    Digitale Medien
    Behavioral Characterization and Genetic Analysis of the Drosophila melanogaster Larval Response to Light as Revealed by a Novel Individual Assay (2000)
    Springer
    Behavior genetics 30 (2000), S. 59-69 
    Details
    ISSN: 1573-3297
    Schlagwort(e): Insect ; larval photobehavior ; locomotion ; Drosophila ; behavioral mutants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract A new assay was designed, named checker, that measures the individual response to light in the fruitfly Drosophila melanogaster larva. In this assay the Drosophila larva apparently modulates its pattern of locomotion when faced with a choice between a dark and lit environment by orienting its movement towards the dark environment. We show that, in this assay, a response to light can be measured as an increase in residence time in the dark versus the lit quadrant. Mutations that disrupt phototransduction in the adult Drosophila abolish the larval response to light, demonstrating that this larval visual function is similar to that of the adult fly. Similarly, no response to light was detected in strains where the larval visual system (photoreceptors and target area) was disrupted by a mutation in the homeobox containing gene sine oculis (so) gene. Ablation of photoreceptors by the targeted expression of the cell death gene hid under the control of the photoreceptor-specific transcription factor glass (gl) abolishes this response entirely. Finally, we demonstrate that this response to light can be mediated by rhodopsins other than the blue absorbing Rh1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1002090627601
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  • 38
    Digitale Medien
    Digitale Medien
    Detection and analysis of gastrointestinal sounds in normal and small bowel obstructed rats (2000)
    Springer
    Medical & biological engineering & computing 38 (2000), S. 42-48 
    Details
    ISSN: 1741-0444
    Schlagwort(e): Bowel sounds ; Rat ; Motility ; Body acoustics ; Signal detection ; Signal characterisation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract This study is aimed at detecting gastrointestinal sounds (GIS) and correlating their characteristics with gastrointestinal (GI) conditions. The central hypotheses are that GIS generation depends on the motility patterns and the mechanical properties of the gut, and that changes in those result in measurable differences in GIS. An animal model which included both healthy rats and those with small bowel obstruction (SBO) was developed. The acoustic bursts, of GIS were detected by amplitude thresholding the signal envelope. Three methods of envelope estimation were proposed and evaluated. Envelope estimation using a Hilbert transform was found to produce the best results in the current application. The duration and dominant frequency of each detected GIS event was estimated and clear differences between healthy and diseased rats were discovered. In the control state, GIS events were found to consistently be of relatively short duration (3–65ms). Although the majority of events in the SBO state had similar short duration, infrequent longer events were also detected and appeared to be pathognomonic. Long duration events (〉100 ms) occurred in each of seven obstructed, but in none of 14 non-obstructed, cases (p〈0.001). It is concluded that GIS analysis may prove useful in the non-invasive, rapid, and accurate diagnosis of SBO.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02344687
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  • 39
    Digitale Medien
    Digitale Medien
    Unrewarding experiences and their effect on foraging in the parasitic waspLeptopilina heterotoma (Hymenoptera: Eucoilidae) (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 465-481 
    Details
    ISSN: 1572-8889
    Schlagwort(e): host selection ; experience ; learning ; extinction ; reinforcement ; parasitoids ; Drosophila ; Leptopilina heterotoma ; Hymenoptera ; Eucoilidae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The host-foraging behavior of female entomophagous parasitoids is commonly modified by positive associative learning. Typically, a rewarding experience (e.g., successful oviposition in a host) increases a female's foraging effort in a host microhabitat of the type associated with that experience. Less well understood are the effects of unrewarding experiences (i.e., unsuccessful foraging). The influence of unrewarding experience on microhabitat choice and residence time within a microhabitat was examined for the eucoilid parasitoid,Leptopilina heterotoma, in laboratory and greenhouse assays. As determined previously, females which oviposited successfully in either of two microhabitat types (fermenting apple or decaying mushroom) strongly preferred to forage subsequently on that microhabitat type. However, failure to find hosts in the formerly rewarding microhabitat caused females to reverse their preference in favor of a novel microhabitat type. The effect, though striking, was transient: within 1–2 h, the original learned preference was nearly fully restored. Similar effects of unrewarding experiences were observed with respect to the length of time spent foraging in a microhabitat. As determined previously, oviposition experience in a particular microhabitat type increased the time spent foraging in a patch of that microhabitat type. However, failure to find hosts in the patch caused the time a wasp spent in the next unoccupied patch of that type to decrease to almost nothing. In addition, there was a tendency for an unrewarding experience on a formerly rewarding microhabitat type to extend the time spent in a patch of a novel type. The function of the observed effects of unrewarding experiences is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02025444
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  • 40
    Digitale Medien
    Digitale Medien
    Drosophila do not skew offspring sex ratio as predicted by trivers and willard (Diptera: Drosophilidae) (1994)
    Springer
    Journal of insect behavior 8 (1994), S. 231-239 
    Details
    ISSN: 1572-8889
    Schlagwort(e): Drosophila ; sex ratio ; life history ; optimality model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Based on both previously published literature and results reported here, it appears thatDrosophila melanogaster meet the explicit assumptions of the Trivers and Willard offspring sex allocation model. However, contrary to the model's predictions, offspring sex ratio was not significantly affected when we manipulated factors that influence offspring quality. We suggest that contrary to implicit predictions of offspring sex ratio models,Drosophila may lack the genetic plasticity to readily alter sex ratio.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01988907
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  • 41
    Digitale Medien
    Digitale Medien
    Egg-laying experience and acceptance of parasitized hosts by the parasitoid,Leptopilina heterotoma (Hymenoptera: Eucoilidae) (1994)
    Springer
    Journal of insect behavior 8 (1994), S. 331-342 
    Details
    ISSN: 1572-8889
    Schlagwort(e): parasitoid ; superparasitism ; learning ; motivation ; egg load ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The influence of egg-laying experience on the response of females of the eucoilid parasitoid,Leptopilina heterotoma, to parasitized and unparasitizedDrosophila melanogaster host larvae was examined under more controlled conditions than those used in past studies. In laboratory assays, we precisely manipulated both the number of eggs laid by females and the kind of larvae (parasitized versus unparasitized) in which the eggs were laid. We found that the tendency to avoid laying eggs in parasitized hosts depended markedly on whether or not eggs had been laid previously, but depended little on whether those eggs had been laid in parasitized or unparasitized hosts. The observed effect of general egg-laying experience on avoidance of parasitized hosts may reflect responses to either changes in the wasp's internal state (perhaps, changes in egg load) or changes in the wasp's neural representation of the external environment (such as those presumed to occur during learning). In light of these results, we offer a tentative reinterpretation of several earlier studies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01989362
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  • 42
    Digitale Medien
    Digitale Medien
    Courtship success and multivariate analysis of sexual selection on morphometric traits inDrosophila buzzatii (Diptera: Drosophilidae) (1994)
    Springer
    Journal of insect behavior 8 (1994), S. 219-229 
    Details
    ISSN: 1572-8889
    Schlagwort(e): Drosophila ; sexual selection gradients ; courtship success
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Using wild-reared flies, we examined sexual selection on five phenotypic traits (thorax length, wing length, wing width, head width, and face width) inDrosophila buzzatii, by scoring copulatory status in nine mass mating cages. Only male face width was identified as a direct target of sexual selection in an analysis of selection gradient, while indirect selection was present on all other studied traits, as expected from their correlations with face width. In contrast to males, there was no indication of selection in females. Nor was there evidence of assortative mating. The suggested direct selection on face width seems to take place during licking behavior of the courtship and might be related to courtship feeding. This study suggests that courtship success gives rise to indirect selection on body size.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01988906
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  • 43
    Digitale Medien
    Digitale Medien
    Parasitization of embedded and nonembeddedDrosophila melanogaster (Diptera: Drosophilidae) pupae by the parasitoidPachycrepoideus vindemniae (Hymenoptera: Pteromalidae) (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 129-131 
    Details
    ISSN: 1572-8889
    Schlagwort(e): Drosophila ; parasitoid wasp ; behavior ; genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01989833
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  • 44
    Digitale Medien
    Digitale Medien
    The effects of acclimation and rearing conditions on the response of tropical and temperate populations ofDrosophila melanogaster andD. simulans to a temperature gradient (Diptera: Drosophilidae) (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 279-288 
    Details
    ISSN: 1572-8889
    Schlagwort(e): temperature preference ; Drosophila ; acclimation ; compensation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effects of rearing and acclimation on the response of adultDrosophila to temperature were investigated in a gradient.D. melanogaster flies preferred a higher mean temperature and were distributed over a wider range of temperatures thanD. simulans flies. Acclimating adults at different temperatures for a week did not influence the response of either species. Adults reared at 28°C as immatures had a lower mean preference than those reared at cooler temperatures, suggesting that flies compensated for the effects of rearing conditions. Adults from tropical and temperate populations ofD. melanogaster andD. simulans did not differ in the mean temperature they preferred in a gradient, suggesting little genetic divergence for this trait within species. The species differences and environmental responses may be related to changes in optimal physiological conditions for the flies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01989735
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  • 45
    Digitale Medien
    Digitale Medien
    Sensorimotor transformation from light reception to phototactic behavior inDrosophila larvae (Diptera: Drosophilidae) (1994)
    Springer
    Journal of insect behavior 7 (1994), S. 553-567 
    Details
    ISSN: 1572-8889
    Schlagwort(e): review ; Drosophila ; larva ; phototaxis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In this paper we examine theDrosophila melanogaster larval response to light. We survey the morphology of the larval visual and motor systems in relation to larval locomotory behavior and phototaxis. In addition, this paper proposes a model of sensorimotor transformation and examines the reversal in taxis occurring at theD. melanogaster larval wnadering stage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02025449
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  • 46
    Digitale Medien
    Digitale Medien
    Phylogeny of the Drosophila obscura species group deduced from mitochondrial DNA sequences (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 478-488 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Mitochondrial DNA ; Nucleotide sequences ; Drosophila ; Rapid phyletic radiation ; Molecular phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Approximately 2 kb corresponding to different regions of the mtDNA of 14 different species of the obscura group of Drosophila have been sequenced. In spite of the uncertainties arising in the phylogenetic reconstruction due to a restrictive selection toward a high mtDNA A+T content, all the phylogenetic analysis carried out clearly indicate that the obscura group is formed by, at least, four well-defined lineages that would have appeared as the consequence of a rapid phyletic radiation. Two of the lineages correspond to monophyletic subgroups (i.e., afftnis and pseudoobscura), whereas the obscura subgroup remains heterogeneous assemblage that could be reasonably subdivided into at least two complexes (i.e., subobscura and obscura).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00173417
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  • 47
    Digitale Medien
    Digitale Medien
    Aspects of nonrandom turnover involved in the concerted evolution of intergenic spacers within the ribosomal DNA of Drosophila melanogaster (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 151-159 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Concerted evolution ; Molecular drive ; Drosophila ; rDNA spacers ; PCR length polymorphism ; MVR-PCR mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Polymerase chain reaction (PCR)-amplified, sequenced, and digitally typed intergenic spacers (IGSs) of the ribosomal (r)DNA in D. melanogaster reveal unexpected features of the mechanisms of turnover involved with the concerted evolution of the gene family. Characterization of the structure of three isolated IGS length variants reveals breakage “hot spots” within the 330-base-pair (bp) subrepeat array found in the spacers. Internal mapping of variant repeats within the 240-bp subrepeat array using a novel digital DNA typing procedure (minisatellite variant repeat [MVR]-PCR) shows an unexpected pattern of clustering of variant repeats. Each 240-bp subrepeat array consists of essentially two halves with the repeats in each half identified by specific mutations. This bipartite structure, observed in a cloned IGS unit, in the majority of genomic DNA of laboratory and wild flies and in PCR-amplified products, has been widely homogenized yet is not predicted by a model of unequal crossing over with randomly placed recombination breakpoints. Furthermore, wild populations contain large numbers of length variants in contrast to uniformly shared length variants in laboratory stocks. High numbers of length variants coupled to the observation of a homogenized bipartite structure of the 240-bp subrepeat array suggest that the unit of turnover and homogenization is smaller than the IGS and might involve gene conversion. The use of PCR for the structural analysis of members of the rDNA gene family coupled to digital DNA typing provides powerful new inroads into the mechanisms of DNA turnover affecting the course of molecular evolution in this family.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00163804
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  • 48
    Digitale Medien
    Digitale Medien
    Degenerating gypsy retrotransposons in a male fertility gene on the Y chromosome of Drosophila hydei (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 452-465 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Y chromosome ; Male fertility genes ; Lampbrush loops ; Germ line ; Transposable elements ; Gypsy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract During the evolution of the Y chromosome of Drosophila hydei, retrotransposons became incorporated into the lampbrush loop pairs formed by several of the male fertility genes on this chromosome. Although insertions of retrotransposons are involved in many spontaneous mutations, they do not affect the functions of these genes. We have sequenced gypsy elements that are expressed as constituents of male fertility gene Q in the lampbrush loop pair Nooses. We find that these gypsy elements are all truncated and specifically lost those sequences that may interfere with the continuity of lampbrush loop transcription. Only defective coding regions are found within the loop. Gypsy is not transcribed in loops of many other Drosophila species harboring the family. These results suggest that any contribution of gypsy to the function of male fertility gene Q does not depend on a conserved DNA sequence.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00173414
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  • 49
    Digitale Medien
    Digitale Medien
    Visual control of wing beat frequency in Drosophila (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 587-596 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Wing beat frequency ; Optomotor responses ; Landing response ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The present study shows that the wing beat frequency of Drosophila is visually controlled and modulated in response to different optomotor stimuli. Whereas rotational large field stimuli do not appear to modulate wing beat frequency, single rotating vertical stripes increase or decrease wing beat frequency when moving back-to-front or front-to-back, respectively. Maximal modulations occur at lateral stripe positions. Expansion stimuli eliciting the landing response cause a marked increase in wing beat frequency. Parameters of this frequency response depend in a graded fashion on certain stimulus properties, and the frequency response co-habituates with the landing response. Several results indicate that the frequency response is an integral component of the landing response, although it can also occur when the characteristic front leg extension is not observed. The complex spatial input integration underlying the frequency response and other motor components of the landing response cannot easily be explained by a system of large field integration units, but might indicate the existence of local expansion detectors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00199480
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  • 50
    Digitale Medien
    Digitale Medien
    Improved stability of Drosophila larval neuromuscular preparations in haemolymph-like physiological solutions (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 179-191 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Drosophila ; Neuromuscular ; Haemolymph ; Membrane potential ; Synaptic potential
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Neuromuscular preparations from third instar larvae of Drosophila are not well-maintained in commonly used physiological solutions: vacuoles form in the muscle fibers, and membrane potential declines. These problems may result from the Na∶K ratio and total divalent cation content of these physiological solutions being quite different from those of haemolymph. Accordingly haemolymph-like solutions, based upon ion measurements of major cations, were developed and tested. Haemolymph-like solutions maintained the membrane potential at a relatively constant level, and prolonged the physiological life of the preparations. Synaptic transmission was well-maintained in haemolymph-like solutions, but the excitatory synaptic potentials had a slower time course and summated more effectively with repetitive stimulation, than in standard Drosophila solutions. Voltage-clamp experiments suggest that these effects are linked to more pronounced activation of muscle fiber membrane conductances in standard solutions, rather than to differences in passive muscle membrane properties or changes in postsynaptic receptor channel kinetics. Calcium dependence of transmitter release was steep in both standard and haemolymph-like solutions, but higher external calcium concentrations were required for a given level of release in haemolymph-like solutions. Thus, haemolymph-like solutions allow for prolonged, stable recording of synaptic transmission.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00215114
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  • 51
    Digitale Medien
    Digitale Medien
    Altered mechanoreceptor response in Drosophila bang-sensitive mutants (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 267-278 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Drosophila ; Bang sensitivity ; Mechanotransduction ; Adaptation ; Sensory coding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Bang-sensitive mutants of Drosophila melano gaster (bas 1, bssMW1, eas2, tko25t) display seizure followed by paralysis when subjected to mechanical shock. However, no physiological or biochemical defect has been found to be common to all of these mutants. In order to observe the effects of bang-sensitive mutations upon an identified neuron, and to study the nature of mechanically induced paralysis, we examined the response of a mechanosensory neuron in these mutants. In each single mutant and the double mutant bas 1 bssMW1, the frequency of action potentials in response to a bristle displacement was reduced. This is the first demonstration of a physiological defect common to several of the bang-sensitive mutations. Adaptation of spike frequency, cumulative adaptation to repeated stimulation (fatigue) and the time course of recovery from adaptation were also examined. Recovery from adaptation to a conditioning stimulus was examined in two mutants (bas 1 and bss MW1), and initial recovery from adaptation was greater in both mutants. Quantification of receptor potentials was complicated by variability inherent in extracellular recording conditions, but examination of the waveform and range of amplitudes did not indicate clear mutant defects. Therefore the differences observed in the spike response may be due to an alteration of the transfer from receptor potentials to action potential production. DNA sequence analysis of tko and eas has indicated that they encode apparently unrelated biochemical products. Our results suggest that these biochemical lesions lead to a common physiological defect in mechanoreceptors. Although this defect does not provide a straightforward explanation for bang sensitivity, the altered cellular process may lead to bang sensitivity through its action in different parts of the nervous system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00192986
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  • 52
    Digitale Medien
    Digitale Medien
    Speciation in the Artemia genus: Mitochondrial DNA analysis of bisexual and parthenogenetic brine shrimps (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 156-168 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Artemia franciscana ; Artemia salina ; Artemia parthenogenetica ; Mitochondrial DNA evolution ; Cytochrome c oxidase I ; Cytochrome b ; Drosophila ; Arthropods ; Parthenogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract From the cloned mitochondrial DNAs (mtDNAs) isolated from two bisexual species, one Mediterranean, Artemia salina, and one American, Artemia franciscana, and two parthenogenetic (diploid and tetraploid) strains of Artemia parthenogenetica collected in Spain, physical maps have been constructed and compared. They are extremely different among themselves, much more than the differences between Drosophila melanogaster and D. yakuba and in the same range of different mammalian species such as mouse/rat or man/cow. The nucleotide sequences of two regions of mtDNA encoding parts of the cytochrome c oxidase subunit I (COI) and cytochrome b (Cytb) genes have been determined in the two bisexual species and the two parthenogenetic strains. Comparisons of these sequences have revealed a high degree of divergence at the nucleotide level, averaging more than 15%, in agreement with the differences found in the physical maps. The majority of the nucleotide changes are silent and there is a strong bias toward transitions, with the C↔T substitutions being highly predominant. The evolutionary distance between the two Artemia parthenogenetica is high and there is no clear relationship with any of the bisexual species, including the one present nowadays in Spain. Using a combination of molecular (mtDNA) and morphological markers it is possible to conclude that all of these Artemia isolates should be actually considered as belonging to different species, even the two Artemia parthenogenetica diploidica and tetraploidica.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00166162
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  • 53
    Digitale Medien
    Digitale Medien
    Interspecific sequence comparison of the muscle-myosin heavy-chain genes from Drosophila hydei and Drosophila melanogaster (1994)
    Springer
    Journal of molecular evolution 39 (1994), S. 357-368 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Muscle-myosin heavy-chain gene ; Alternative exons ; Synonymous substitutions ; Amino acid substitutions ; Evolution ; Testis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The muscle-myosin heavy-chain (mMHC) gene of Drosophila hydei has been sequenced completely (size 23.3 kb). The sequence comparison with the D. melanogaster mMHC gene revealed that the exonintron pattern is identical. The protein coding regions show a high degree of conservation (97%). The alternatively spliced exons (3a-b, 7a-d, 9a-c, 11a-e, and 15a-b) display more variations in the number of nonsynonymous and synonymous substitutions than the common exons (2, 4, 5, 6, 8, 10, 12, 13, 14, 16, 17, and 19). The base composition at synonymous sites of fourfold degenerate codons (third position) is not biased in the alternative exons. In the common exons there exists a bias for C and against A. These findings imply that the alternative exons of the Drosophila mMHC gene evolve at a different, in several cases higher, rate than the common ones. The 5′ splice junctions and 5′ and 3′ untranslated regions show a high level of similarity, indicating a functional constraint on these sequences. The intron regions vary considerably in length within one species, but the corresponding introns are very similar in length between the two species and all contain stretches of sequence similarity. A particular example is the first intron, which contains multiple regions of similarity. In the conserved regions of intron 12 (head-tail border) sequences were found which have the potential to direct another smaller mMHC transcript.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00160268
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  • 54
    Digitale Medien
    Digitale Medien
    Nucleotide sequence of the genomic region encompassing Adh and Adh-Dup genes of D. lebanonensis (Scaptodrosophila): Gene expression and evolutionary relationships (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 455-467 
    Details
    ISSN: 1432-1432
    Schlagwort(e): Alcohol dehydrogenase ; Drosophila ; Drosophila lebanonensis ; Gene expression ; Codon usage ; Phylogenetic relationships
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The region of the genome of D. lebanonensis that contains the Adh gene and the downstream Adh-dup gene was sequenced. The structure of the two genes is the same as has been described for D. melanogaster. Adh has two promoters and Adh-dup has only one putative promoter. The levels of expression of the two genes in this species are dramatically different. Hybridizing the same Northern blots with a specific probe for Adh-dup, we did not find transcripts for this gene in D. lebanonensis. The level of Adh distal transcript in adults of D. lebanonensis is five times greater than that of D. melanogaster adults. The maximum levels of proximal transcript are attained at different larval stages in the two species, being three times higher in D. melanogaster late-second-instar larvae than in D. lebanonensis first-instar larvae. The level of Adh transcripts allowed us to determine distal and proximal initiation transcription sites, the position of the first intron, the use of two polyadenylation signals, and the heterogeneity of polyadenylation sites. Temporal and spatial expression profiles of the Adh gene of D. lebanonensis show qualitative differences compared with D. melanogaster. Adh and Adh-dup evolve differently as shown by the synonymous and nonsynonymous substitution rates for the coding region of both genes when compared across two species of the melanogaster group, two of the obscura group of the subgenus Sophophora and D. lebanonensis of the victoria group of the subgenus Scaptodrsophila. Synonymous rates for Adh are approximately half those for Adh-dup, while nonsynonymous rates for Adh are generally higher than those for Adh-dup. Adh shows 76.8% identities at the protein level and 70.2% identities at the nucleotide level while Adh-dup shows 83.7% identities at the protein level and 67.5% identities at the nucleotide level. Codon usage for Adh-dup is shown to be less biased than for Adh, which could explain the higher synonymous rates and the generally lower nonsynonymous substitution rates in Adh-dup compared with Adh. Phylogenetic trees reconstructed by distance matrix and parsimony methods show that Sophophora and Scaptodrosophila subgenera diverged shortly after the separation from the Drosophila subgenus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00178845
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  • 55
    Digitale Medien
    Digitale Medien
    Drive-selection equilibrium: Homopolymer evolution in the Drosophila gene mastermind (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 637-641 
    Details
    ISSN: 1432-1432
    Schlagwort(e): mastermind ; Drosophila ; Homopolymer ; Repeat length variation ; Molecular drive ; Natural selection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Interspecific sequence comparison of the highly repetitive Drosophila gene mastermind (mam) reveals extensive length variation in homopolymer domains. The length variation in homopolymers is due to nucleotide misalignment in the underlying triplet repeats, which can lead to slippage mutations during DNA replication or repair. In mam, the length variation in repetitive regions appears to be balanced by natural selection acting to maintain the distance between two highly conserved charge clusters. Here we report a statistical test of the null hypothesis that the similarity in the amino acid distance between the charge clusters of each species arose by chance. The results suggest that at mam there is a juxtaposition of length variability due to molecular drive and length conservation maintained by natural selection. The analysis of mam allows the extension of current theories of drive-selection interaction to encompass homopolymers. Our model of drive-selection equilibrium suggests that the physical flexibility, length variability, and abundance of homopolymer domains provide an important source of genetic variation for natural populations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00175884
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  • 56
    Digitale Medien
    Digitale Medien
    Olfactory physiology in the Drosophila maxillary palp requires the visual system gene rdgB (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 687-693 
    Details
    ISSN: 1432-1351
    Schlagwort(e): rdgB ; Maxillary palp ; Drosophila ; Electrophysiology ; Olfaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract We describe the kinetics of odorant response in the maxillary palp of Drosophila, and show that the rate of recovery from odorant stimulation is affected by mutation of the rdgB (retinal degeneration B) gene. We use immunocytochemistry to confirm that the rdgB gene product is expressed in the maxillary palp. rdgB has recently been shown to encode a protein with Ca2+-binding sites and sequence similarity to rat brain phosphatidylinositol transfer protein; it is located near the rhabdomeric membranes in photoreceptor cells, where it has been suggested to play a role in membrane transport. The delay in recovery kinetics that we observe in olfactory tissue may reflect a defect in membrane restoration at the conclusion of the olfactory transduction cascade. The use of common molecules in the physiology of two olfactory organs, and in both visual and olfactory physiology, is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00191841
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  • 57
    Digitale Medien
    Digitale Medien
    Quantifying relative importance of maxillary palp information on the olfactory behavior of Drosophila melanogaster (1994)
    Springer
    Journal of comparative physiology 175 (1994), S. 761-766 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Olfactory behavior ; Antenna ; Maxillary palp ; Olfaction ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Maxillary palps have been proposed as secondary olfactory organs, after the antennae, in Drosophila melanogaster. Our study tries to establish the quantitative importance of both organs as olfactory information mediators. Dose-response curves for three odorants: ethyl acetate, propionaldehyde and benzaldehyde were carried out for comparing olfaction in either complete animals or flies surgically deprived of antennae. Antennaless flies tested in our behavioral assay showed indifferent, attractant and repellent responses depending on concentration, similarly as normal flies do. However, they clearly displayed less sensitivity than normal flies. The range of concentrations they were able to perceive was correlated to antennal sensitivity approximately by a factor 1∶10 for ethyl acetate and benzaldehyde, and between 1∶10 and 1∶100 at high concentrations of propionaldehyde. A complementary experiment was performed to test changes in olfactory behavior produced by removing maxillary palps in the presence of antennae. At high concentrations of odorant, responses to ethyl acetate and propionaldehyde experienced small changes when both palps were removed. Results are compatible with a summation model of all olfactory information reaching the brain either through antennae or palps.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00191847
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  • 58
    Digitale Medien
    Digitale Medien
    Renal eicosanoids and blood pressure in genetically hypertensive rats of the lyon strain (1994)
    Springer
    Journal of biomedical science 1 (1994), S. 201-203 
    Details
    ISSN: 1423-0127
    Schlagwort(e): Hypertension ; Eicosanoid ; Rat ; Genetics ; Kidney
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The present paper reviews the evidence for a possible involvement of renal eicosanoids in the pathophysiology of high blood pressure in genetically hypertensive rats of the Lyon strain. Both in vivo and in vitro experiments suggest that an increased ability to synthesize the vasoconstrictor prostaglandin H2 and/or thromboxane A2 in renal vessels (1) acts as an autocrine amplifier of pressor agents and (2) may contribute to resetting the pressure natriuresis curve which is a prerequisite for the development and maintenance of hypertension.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02253302
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  • 59
    Digitale Medien
    Digitale Medien
    BrdU incorporation reveals DNA replication in non dividing glial cells in the larval abdominal CNS ofDrosophila (1994)
    Springer
    Development genes and evolution 204 (1994), S. 54-61 
    Details
    ISSN: 1432-041X
    Schlagwort(e): CNS ; Glia ; Drosophila ; BrdU
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Glial cells are of significant importance for central nervous system development and function. In insects, knowledge of the types and development of CNS glia is rather low. This is especially true for postembryonic glial development. Using bromodeoxyuridine incorporation and enhancer trap lines we identified a reproducible spatial and temporal pattern of DNA replicating cells in the abdominal larval CNS (A3-7 neuromeres) ofDrosophila melanogaster. These cells correspond to embryonically established glial cells in that region. Except for a specific subfraction, these cells apparently do not divide during larval life. Similar patterns were found in two otherDrosophila species,D. virilis andD. hydei.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00744873
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  • 60
    Digitale Medien
    Digitale Medien
    Drosophila glial development is regulated by genes involved in the control of neuronal cell fate (1994)
    Springer
    Development genes and evolution 204 (1994), S. 118-125 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; glia ; Proneural ; Neurogenic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Drosophila proneural genes specify neuronal determination among cells within the ectoderm. Here we address the question of whether proneural genes also affect the specification of glia, the most abundant cell type in the nervous system. We provide evidence that the proneural gene daughterless is essential for the formation of two major classes of PNS glia. In contrast, the proneural genes in the achaete-scute complex have no detectable effect on the specification and differentiation of these PNS glia and certain CNS glia. We also show that, as with neuronal development, glial determination is restricted by the neurogenic genes neuralized, Delta, and the genes of the Enhancer of split complex. Finally, we demonstrate that prospero, a gene involved in neuronal differentiation, also affects glial development. These results demonstrate extensive overlap in the genetic control of glial and neuronal development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00361106
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  • 61
    Digitale Medien
    Digitale Medien
    Embryonic origin and differentiation of the Drosophila heart (1994)
    Springer
    Development genes and evolution 203 (1994), S. 266-280 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Heart ; Drosophila ; Morphogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have followed the normal development of the different cell types associated with the Drosophila dorsal vessel, i.e. cardioblasts, pericardial cells, alary muscles, lymph gland and ring gland, by using several tissue-specific markers and transmission electron microscopy. Precursors of pericardial cells and cardioblasts split as two longitudinal rows of cells from the lateral mesoderm of segments T2-A7 (“cardiogenic region”) during stage 12. The lymph gland and dorsal part of the ring gland (corpus allatum) originate from clusters of lateral mesodermal cells located in T3 and T1/dorsal ridge, respectively. Cardioblast precursors are strictly segmentally organized; each of T2-A6 gives rise to six cardioblasts. While moving dorsally during the stages leading up to dorsal closure, cardioblast precursors become flattened, polarized cells aligned in a regular longitudinal row. At dorsal closure, the leading edges of the cardioblast precursors meet their contralateral counterparts. The lumen of the dorsal vessel is formed when the trailing edges of the cardioblast precursors of either side bend around and contact each other. The amnioserosa invaginates during dorsal closure and is transiently attached to the cardioblasts; however, it does not contribute to the cells associated with the dorsal vessel and degenerates during late embryogenesis. We describe ultrastructural characteristics of cardioblast differentiation and discuss similarities between cardioblast development and capillary differentiation in vertebrates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00360522
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  • 62
    Digitale Medien
    Digitale Medien
    Novel tissue units of regional differentiation in the gut epithelium of Drosopbila, as revealed by P-element-mediated detection of enhancer (1994)
    Springer
    Development genes and evolution 203 (1994), S. 243-249 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Gut ; Drosophila ; Compartment ; Regional differentiation ; P-element enhancer detectors
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We analysed spatial patterns of expression of a lacZ reporter gene in the gut of Drosophila larvae that had been transformed with a P-element-lacZ vector to identify regional differences in gene expression. lacZ-positive epithelial cells formed distinct domains with discrete transverse and longitudinal boundaries along the gut tube. Boundaries were often found at sites at which morphological boundaries were not obvious. The gut epithelium was subdivided into 36 compartments by the boundaries. We refer to these novel compartments as “tissue compartments”. The lacZ-positive domain of each strain appeared as a single tissue compartment or as a combination of several tissue compartments. The tissue compartment is considered to be a unit of regional differentiation. The spatial organization of the tissue compartments may represent the “floor plan”, determined by genes that control the regional differentiation of this nonsegmental organ.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00360519
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  • 63
    Digitale Medien
    Digitale Medien
    The function of the proneural genes achaete and scute in the spatio-temporal patterning of the adult labellar bristles of Drosophila melanogaster (1994)
    Springer
    Development genes and evolution 203 (1994), S. 340-350 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; achaete ; scute ; Taste bristles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The sensory precursors for labellar taste bristles develop from the labial disc in three distinct temporal waves occurring at 0 h, 8 h and 14 h of pupal development. In each temporal wave, transcripts for the achaete (ac) and scute (sc) genes are expressed in overlapping patterns in cells of the disc epithelium prior to the appearance of sensory mother cells (SMCs). No bristles form in mutant flies in which the ac and sc genes are absent. When the sc gene alone is deleted, a set of seven bristles fail to form. Pulses of ubiquitous sc + expression during pupal development, in a strain mutant for both ac and sc, can result in flies with all the labellar bristles at their correct positions. sc + pulses at times corresponding to the initiation of each of the waves of SMC specification in the disc was sufficient to restore bristle pattern. Bristles were not induced at ectopic positions and times as a result of the ubiquitous expression of sc +. These results suggest that the proneural genes ac and sc do not themselves set the pattern of the labellar bristles. Instead, they are required for the elaboration of the pattern set by other gene products. We also show that the formation and positioning of the later waves of bristles can take place even in the absence of bristles normally specified earlier.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00457805
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  • 64
    Digitale Medien
    Digitale Medien
    Fate-mapping in the procephalic region of the embryonic Drosopbila head (1994)
    Springer
    Development genes and evolution 203 (1994), S. 367-373 
    Details
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; Embryogenesis ; Morphogenetic movements ; Brain ; HRP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Using intracellular horseradish peroxidase injection we traced the developmental fate of early gastrula cells of the procephalic region in the stage 16/17 embryo. Morphogenetic movements in the developing brain are described in three dimensions. The results are related to head segmentation, and an early gastrula fate map of pregnathal head segments is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00188684
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  • 65
    Digitale Medien
    Digitale Medien
    BrdU incorporation reveals DNA replication in non dividing glial cells in the larval abdominal CNS of Drosophila (1994)
    Springer
    Development genes and evolution 204 (1994), S. 54-61 
    Details
    ISSN: 1432-041X
    Schlagwort(e): CNS ; Glia ; Drosophila ; BrdU
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Glial cells are of significant importance for central nervous system development and function. In insects, knowledge of the types and development of CNS glia is rather low. This is especially true for postembryonic glial development. Using bromodeoxyuridine incorporation and enhancer trap lines we identified a reproducible spatial and temporal pattern of DNA replicating cells in the abdominal larval CNS (A3-7 neuromeres) of Drosophila melanogaster. These cells correspond to embryonically established glial cells in that region. Except for a specific subfraction, these cells apparently do not divide during larval life. Similar patterns were found in two other Drosophila species, D. virilis and D. hydei.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00189068
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  • 66
    Digitale Medien
    Digitale Medien
    Noninvasive loading of the rat ulna in vivo induces a strain-related modeling response uncomplicated by trauma or periostal pressure (1994)
    Springer
    Calcified tissue international 54 (1994), S. 241-247 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Loading ; Strain ; Modeling ; Rat ; Ulna
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract Adaptive changes in bone modeling in response to noninvasive, cyclic axial loading of the rat ulna were compared with those using 4-point bending of the tibia. Twenty cycles daily of 4-point bending for 10 days were applied to rat tibiae through loading points 23 and 11 mm apart. Control bones received nonbending loads through loading points 11 mm apart. As woven bone was produced in both situations, any strain-related response was confounded by the response to direct periosteal pressure. Four-point bending is not, therefore, an ideal mode of loading for the investigation of strain-related adaptive modeling. The ulna's adaptive response to daily axial loading over 9 days was investigated in 30 rats. Groups 1–3 were loaded for 1200 cycles: Group 1 at 10 Hz and 20 N, Group 2 at 10 Hz and 15 N, and Group 3 at 20 Hz and 15 N. Groups 4 and 5 received 12,000 cycles of 20 N and 15 N at 10 Hz. Groups 1 and 4 showed a similar amount of new bone formation. Group 4 showed the same pattern of response but in reduced amount. The responses in Groups 2 and 3 were either small or absent. Strains were measured with single-element, miniature strain gauges bonded around the circumference of dissected bones. The 20 N loading induced peak strains of 3500–4500 μstrain. The width of the periosteal new bone response was proportional to the longitudinal strain at each point around the bone's circumference. It appears that when a bone is loaded in a normal strain distribution, an osteogenic response occurs when peak physiological strains are exceeded. In this situation the amount of new bone formed at each location is proportional to the local surface strain. Cycle numbers between 1200 and 12,000, and cycle frequencies between 10 and 20 Hz have no effect on the bone's adaptive response.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00301686
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  • 67
    Digitale Medien
    Digitale Medien
    Effect of running exercise on the bone loss induced by orchidectomy in the rat (1994)
    Springer
    Calcified tissue international 55 (1994), S. 33-37 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Osteoporosis ; Rat ; Orchidectomy ; Exercise ; Strength
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract The effect of exercise on castration-induced osteoporosis in 3-month-old male rats weighing 264±4 g at the beginning of the experiment was studied. A testosterone deficiency was induced by orchidectomy (ORC), and the exercise group ran 10 m/minute for 1 hour a day on a treadmill at 0% grade. There were seven groups of eight rats (n=56) randomized into a control group killed at time 0, and sham, ORC and ORC and exercise groups killed at 4 and 8 weeks. ORC reduced body weight gain (with analysis of variance (ANOVA) P〈0.001), and at 4 weeks the body weight was 343±14 g in ORC group and 301±4 g in the ORC and exercise group (P〈0.01). The increase in femoral length was slower in the ORC+exercise groups. The ash weight of the tibia did not decrease significantly after ORC or ORC+ exercise. ORC did not affect 45Ca incorporation, but exercise slightly increased it in the whole tibia 8 weeks after ORC (with ANOVA P=0.057). ORC had significantly lowered the trabecular bone volume in the secondary spongiosa of the distal femur at 4 and 8 weeks, and exercise did not prevent this. This is an opposite finding to our previous study with ovariectomized female rats [12]. ORC also significantly had reduced the osteoblast-lined trabecular bone surface and the number of osteoclasts by 8 weeks after the operation. Exercise increased the osteoblast-lined surface and the number of osteoclasts. The mechanical strength of the femoral neck also was reduced after ORC and this was not prevented by exercise either. In conclusion, ORC reduces bone growth and turnover which leads to osteopenia in growing rats. Moderate treadmill exercise does not reverse the ORC-induced loss of trabecular bone and the reduced mechanical strength of the femoral neck, although it has a positive effect on the osteoblast and osteoclast indices and on calcium incorporation into bone.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00310166
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  • 68
    Digitale Medien
    Digitale Medien
    The in vivo effect of a new, in vitro, extremely potent vitamin D3 analog KH1060 on the suppression of renal allograft rejection in the rat (1994)
    Springer
    Calcified tissue international 54 (1994), S. 150-154 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Vitamin D analog ; KH1060 ; Kidney transplantation ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract KH1060 is a new 20-epi-vitamin D3 analog, which has exerted a considerable immunosuppressive potency in vitro. We have tested in vivo the effect of KH1060 on the suppression of renal allograft rejection in the rat. Allogenic kidney transplantation from DA donor rats to Lewis recipient rats treated intraperitoneally with KH1060 in doses from 0.2 to 6 μg/kg/day, or saline (placebo group), or CyA 10 mg/kg/day for 10 days (positive control group), was performed. Median graft survival time in KH1060-treated groups was 7–9 days, in the placebo group 6 days, whereas CyA led to long-term graft survival, 34 days in 50% of rats and 〉100 days in 50% of rats. In vivo, KH1060 failed to prolong renal allograft survival considerably, and led to development of hypercalcemia. Our results stress the existence of a large discrepancy between the in vitro and in vivo immunoregulatory effects of this vitamin D analog.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00296066
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  • 69
    Digitale Medien
    Digitale Medien
    Effect of ultrafilterable fragments from chondroitinase and protease-treated aggrecan on calcium phosphate precipitation in liposomal suspensions (1994)
    Springer
    Calcified tissue international 55 (1994), S. 176-179 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Calcification ; Calcium phosphates ; Liposomes ; Mineralization ; Proteoglycans
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract A liposome-centered endogenous precipitation method was used to investigate the effect of ultrafilterable fragments from the enzymatic digestion of rat chondrosarcoma aggrecan on the formation of insoluble calcium phosphate salts in buffered solutions at pH 7.4 and 22°C. Unlike the intact aggrecan and its major chondroitin sulfate and core protein components, disaccharide units from chondroitinase degradation of the aggrecan and small (〈3kg/mol molecular weight) fragments from protease digestion of the core structure were found to be only weakly inhibitory toward mineral formation. Corresponding reductions in Ca2+-binding indicate that these fragments were unable to adsorb to active sites on the apatite surface for long enough periods to significantly hinder crystal growth. The data suggest that controlled enzymatic breakdown of aggrecan may be one possible mechanism by which the calcification of growth plate cartilage is allowed to advance in vivo.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00425872
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  • 70
    Digitale Medien
    Digitale Medien
    Stimulation of human osteoblast differentiation and function by ipriflavone and its metabolites (1994)
    Springer
    Calcified tissue international 55 (1994), S. 356-362 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Osteoblasts ; Matrix proteins ; Collagen ; Cell differentiation ; Calcification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract Ipriflavone (IP), an isoflavone derivative, has been shown to interfere with bone remodeling by inhibiting bone resorption and perhaps stimulating bone formation. In this study, we have analyzed the effect of IP and its metabolites on the differentiation and function of human osteoblastic cells. Bone marrow stromal osteoprogenitor cells (BMC) and trabecular bone osteoblasts (HOB) were isolated from human donors. The former can be induced to differentiate by treatment with dexamethasone, whereas the latter represent a more differentiated osteoblast. Incubation of BMC with metabolite III (10-5 M) for 1 week induced modest but significant changes of alkaline phosphatase activity. Though both IP and metabolite III stimulated the expression of bone sialoprotein mRNA, a protein involved in cell attachment to the matrix, only metabolite III increased the steady-state level of decorin mRNA, a collagen fibrillogenesis-regulating proteoglycan. Metabolites III and V, but not the other isoflavones, increased the expression of type I collagen mRNA in HOB, whereas no detectable changes were observed in BMC cells with any of the experimental compounds. In HOB, an increased abundance of osteopontin and bone sialoprotein mRNA were also obtained after 1-week treatment with IP or metabolite V. No appreciable effects of IP or its metabolites were seen on osteocalcin expression and synthesis by either cell type. Finally, IP consistently increased the amount of 45Ca incorporated into the cell layer by BMC, and stimulated mineralization of both BMC and HOB, assessed by von Kossa staining. Thus, IP and its metabolites regulate the differentiation and biosynthetic properties of human bone-forming cells by enhancing the expression of some important matrix proteins and facilitating the mineralization process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00299315
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  • 71
    Digitale Medien
    Digitale Medien
    Effect of 1α-vitamin D3 on bone strength and composition in growing rats with and without corticosteroid treatment (1994)
    Springer
    Calcified tissue international 55 (1994), S. 443-450 
    Details
    ISSN: 1432-0827
    Schlagwort(e): Bone mechanics ; Bone composition ; Vitamin D3 ; Corticosteroid ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Abstract The effects of 1α-vitamin D3 were studied for 6 months in 2-month-old male and female rats on a moderately low calcium diet with or without low-dose prednisolone treatment. Both cortical bone mechanical and biochemical properties were examined. Femoral bone specimens were subjected to torsional loading tests. With age, bone strength and stiffness increased in both sexes, accompanied by an increased degree of mineralization (bone ash and calcium concentrations). During growth, strength and stiffness increased more in male than in female rats. When 1α-vitamin D3 (0.5 μg/kg/day) was given alone, bone mechanical competence improved significantly whereas insulin-like growth factor-I (IGF-I) and calcium concentrations in the bone matrix were significantly reduced. Treatment with low-dose prednisolone (0.5 mg/kg/day) alone did not influence bone mechanical properties compared with intact control rats (without prednisolone) although a significant reduction in calcium concentration and an increased phosphorus concentration were measured. A combined therapy with prednisolone and 1α-vitamin D3 significantly increased bone strength, toughness, and stiffness compared with control bones. Both mineralization degree (ash and calcium concentration) and IGF-I concentration were decreased. We conclude that (1) mechanical properties of rat cortical bones improve relatively more in males compared with agematched females during growth which is related to increased bone mass and size, (2) low-dose prednisolone treatment does not change mechanical properties in males, and altered them only nonsignificantly in females despite a change in mineralization degree in both sexes; (3) treatment with 1α-vitamin D3 results in a consistent increase in mechanical competence of the bone accompanied by a significant decrease in IGF-I concentration in the bone matrix.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00298558
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  • 72
    Digitale Medien
    Digitale Medien
    Comparison of larval and adult P-450 activity levels for alkaloid metabolism in desertDrosophila (1994)
    Springer
    Journal of chemical ecology 20 (1994), S. 1893-1906 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Drosophila ; Diptera ; Drosophilidae ; cytochrome P-450 ; poly-substrate monooxygenase ; cactus ; alkaloids ; resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The cytochrome P-450 monooxygenase system has been implicated in plant utilization by at least three species ofDrosophila (D. nigrospiracula, D. mettleri, andD. mojavensis) that are endemic to the Sonoran Desert of the southwestern United States and northwestern Mexico. Basal and induced levels of total cytochrome P-450 were determined for third-instar and decapitated 2- to 5-day post eclosion adults of the three desert species. Total P-450 levels, both basal and induced for all species assayed, were significantly higher for adults than for larvae by up to 20-fold. On a per organism basis, the levels of in vitro metabolism of the cactus alkaloid, carnegine, and patterns of response to induction by cactus tissue for adult desertDrosophila approximated those of larvae. Induction by phenobarbital, however, resulted in levels of in vitro carnegine metabolism that were up to 5.6-fold higher in adults than in larvae.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02066231
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  • 73
    Digitale Medien
    Digitale Medien
    Alterations in flightin phosphorylation inDrosophila flight muscles are associated with myofibrillar defects engendered by actin and myosin heavy-chain mutant alleles (1994)
    Springer
    Biochemical genetics 32 (1994), S. 301-314 
    Details
    ISSN: 1573-4927
    Schlagwort(e): flightin ; Drosophila ; insect flight muscle ; phosphoprotein ; actin ; myosin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Flightin is a 20-kD myofibrillar protein found in the stretch-activated flight muscles ofDrosophila melanogaster. Nine of the eleven isoelectric variants of flightin are generatedin vivo by multiple phosphorylations. The accumulation of these isoelectric variants is affected differently by mutations that eliminate thick filaments or thin filaments. Mutations in the myosin heavy-chain gene that prevent thick filament assembly block accumulation of all flightin variants except N1, the unphosphorylated precursor, which is present at much reduced levels. Mutations in the flight muscle-specific actin gene that block actin synthesis and prevent thin filament assembly disrupt the temporal regulation of flightin phosphorylation, resulting in premature phosphorylation and premature accumulation of flightin phosphovariants. Cellular fractionation of fibers that are devoid of thin filaments show that flightin remains associated with the thick filamentrich cytomatrix. These results suggest that flightin is a structural component of the thick filaments whose regulated phosphorylation is dependent upon the presence of thin filaments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00555832
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  • 74
    Digitale Medien
    Digitale Medien
    Translational regulation of the heat shock response (1994)
    Springer
    Molecular biology reports 19 (1994), S. 211-220 
    Details
    ISSN: 1573-4978
    Schlagwort(e): Drosophila ; eIF-2 ; eIF-4F ; heat shock ; mRNA translation regulation ; phosphorylation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract All organisms from bacteria to man respond to an exposure to higher than physiological temperatures by reprogramming their gene expression, leading to the increased synthesis of a unique set of proteins termed heat shock proteins (hsps). The hsps function as molecular chaperones in both normal and stressed cells. The rapid and efficient synthesis of hsps is achieved as a result of changes occurring at gene transcription, RNA processing and degradation, and mRNA translation. With regard to the translational regulation, the emerging picture is that the two key steps of polypeptide chain initiation, namely mRNA binding and Met-tRNA i binding to ribosomes, are regulated in heat-shocked mammalian cells. InDrosophila, mRNA binding is regulated by a structural feature of the leader of heat shock mRNAs and by the inactivation of eukaryotic initiation factor- (eIF-) 4F. No clear evidence for changes in Met-tRNA i binding has been obtained yet.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00986963
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  • 75
    Digitale Medien
    Digitale Medien
    Expression of the α-subunit of glycoprotein hormones in the pars tuberalis-specific glandular cells in rat, mouse and guinea-pig (1994)
    Springer
    Cell & tissue research 278 (1994), S. 617-624 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Pituitary ; Pars tuberalis ; α-Subunit ; Immunocytochemistry ; In situ hybridization ; Rat ; Mouse ; Guinea-pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The nature of the hormone(s) secreted by the pars tuberalis (PT) is still unknown. This pituitary lobe is mainly formed by specific glandular cells that differ in their ultrastructural features from the other adenohypophysial cell types. Data from the literature indicate the presence of thyroid-stimulating hormone immunoreactivity in the PT-specific cells of the rat and the Djungarian hamster but not of other species, including the mouse and guinea-pig. The PT also encloses variable numbers of pars distalis cells, essentially gonadotrophs that are mainly dispersed in its caudal area. We studied the expression of the glycoprotein hormone α-subunit in the PT of the rat, mouse and guinea-pig by in situ hybridization and immunocytochemistry. In situ hybridization, using an oligonucleotide probe complementary to rat cDNA sequence 196–237 revealed the expression of the α-subunit gene throughout the PT of the rat and the mouse; in the guinea-pig, the probe labelled no pituitary cells. Light- and electron-microscopic immunocytochemistry demonstrated α-subunit immunoreactivity in the secretory granules of the PT-specific cells in the three species examined. These cells did not react with a specific antibody against the β-subunit of luteinizing hormone, an antibody that labelled scattered gonadotrophs. The present data suggest that hormone(s) produced by the PT-specific glandular cells are, at least partly, related to glycoprotein hormones.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410050253
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  • 76
    Digitale Medien
    Digitale Medien
    Occurrence of osteoblast necroses during ossification of long bone cortices in mouse fetuses (1994)
    Springer
    Cell & tissue research 275 (1994), S. 345-353 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Osteogenesis ; Ossification ; Mineralization ; Calcification ; Cell necroses ; Mouse (NMRI)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Previous investigations concerned with in vitro osteogenesis and mineralization have revealed some indication of a participation of cell necroses in the course of calcification. These observations were confirmed by in vivo investigations on desmoid ossification in fetal mouse calvariae, where abundant necrotic osteoblasts were found at the mineralization border and in the osteoid. In the present study, ossification of long bone cortices from fetal mice was investigated by use of electron microscopy. Specimens obtained from the collection of the Institute of Anatomy, Free University of Berlin (mouse fetuses, forearm; rat fetuses, forearm) were reinvestigated for control purposes. In all cases, mineralization of osteoid was accompanied by cell necroses. Cell degeneration was characterized by swelling of the endoplasmic reticulum and loss of the plasma membrane resulting in freely distributed vesicular structures. Cell debris was incorporated within the mineral. Initially, cell necroses in the perichondrium occurred in the region surrounding the hypertrophic cartilage and the matrix of which showed spots of endochondral mineralization. Necrotic osteoblasts occurred simultaneously with mineralization of the osteoid. During further ossification of the long bone cortices, the number of necrotic cells increased markedly. In addition to necrotic cells, healthy osteoblasts, osteocytes and perichondral tissue were present, indicating that an artifact can be excluded. The importance of cell necroses in the process of mineralization is as yet unclear. Possibly, the cells act as calcium and/or phosphate stores, which are liberated by cell death to increase the amount of mineral constituents at sites of mineralization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00319433
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  • 77
    Digitale Medien
    Digitale Medien
    Expression of the α-subunit of glycoprotein hormones in the pars tuberalis-specific glandular cells in rat, mouse and guinea-pig (1994)
    Springer
    Cell & tissue research 278 (1994), S. 617-624 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Pituitary ; Pars tuberalis ; α-Subunit ; Immunocytochemistry ; In situ hybridization ; Rat ; Mouse ; Guinea-pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The nature of the hormone(s) secreted by the pars tuberalis (PT) is still unknown. This pituitary lobe is mainly formed by specific glandular cells that differ in their ultrastructural features from the other adenohypophysial cell types. Data from the literature indicate the presence of thyroid-stimulating hormone immunoreactivity in the PT-specific cells of the rat and the Djungarian hamster but not of other species, including the mouse and guinea-pig. The PT also encloses variable numbers of pars distalis cells, essentially gonadotrophs that are mainly dispersed in its caudal area. We studied the expression of the glycoprotein hormone α-subunit in the PT of the rat, mouse and guinea-pig by in situ hybridization and immunocytochemistry. In situ hybridization, using an oligonucleotide probe complementary to rat cDNA sequence 196–237 revealed the expression of the α-subunit gene throughout the PT of the rat and the mouse; in the guinea-pig, the probe labelled no pituitary cells. Light-and electron-microscopic immunocytochemistry demonstrated α-subunit immunoreactivity in the secretory granules of the PT-specific cells in the three species examined. These cells did not react with a specific antibody against the β-subunit of luteinizing hormone, an antibody that labelled scattered gonadotrops. The present data suggest that hormone(s) produced by the PT-specific glandular cells are, at least partly, related to glycoprotein hormones.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00331382
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  • 78
    Digitale Medien
    Digitale Medien
    The immunolocalization of small nuclear ribonucleoprotein particles in testicular cells during the cycle of the seminiferous epithelium of the adult rat (1994)
    Springer
    Cell & tissue research 278 (1994), S. 363-378 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: snRNPs ; Testis ; Spermatocytes ; Spermatids ; Immunocytochemistry ; Chromatoid body ; Intermitochondrial nuage ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. The objective of this study was to determine the cellular and subcellular distribution of small nuclear ribonucleoprotein particles (snRNPs) in the adult rat testis in relation to the different cell types at the various stages of the cycle of the seminiferous epithelium. The distribution of snRNPs in the nucleus and cytoplasm of germ cells was quantitated in an attempt to correlate RNA processing with morphological and functional changes occurring during the development of these cells. Light-microscopic immunoperoxidase staining of rat testes with polyclonal anti-Sm and monoclonal anti-Y12 antibodies localized spliceosome snRNPs in the nuclei and cytoplasm of germ cells up to step 10 spermatids. Nuclear staining was intense in Sertoli cells, spermatogonia, spermatocytes, and in the early steps of round spermatid development. Although comparatively weaker, cytoplasmic staining for snRNPs was strongest in mid and late pachytene spermatocytes and early round spermatids. Quantitative electron-microscopic immunogold labeling of Lowicryl embedded testicular sections confirmed the light-microscopic observations but additionally showed that the snRNP content peaked in the cytoplasm of mid-pachytene spermatocytes and in the nuclei of late pachytene spermatocytes. The immunogold label tended to aggregate into distinct loci over the nuclear chromatin. The chromatoid body of spermatids and spermatocytes and the finely granular material in the interstices of mitochondrial aggregates of spermatocytes were found to be additional sites of snRNP localization and were intensely labeled. This colocalization suggests that these dense cytoplasmic structures may be functionally related. Anti-U1 snRNP antibodies applied to frozen sections showed the same LM localization pattern as spliceosome snRNPs. Anti-U3 snRNP antibodies applied to frozen sections stained nucleoli of germ cells where pre-rRNA is spliced.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00414179
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  • 79
    Digitale Medien
    Digitale Medien
    Selective association of nerve fibres immunoreactive for substance P or bombesin with putative cholinergic neurons of the male rat major pelvic ganglion (1994)
    Springer
    Cell & tissue research 278 (1994), S. 589-594 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Autonomic ganglia ; Neuropeptides ; Pelvic plexus ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The male rat major pelvic ganglion contains both sympathetic and parasympathetic neurons that supply the lower urinary and digestive tracts, and the reproductive organs. The aim of this study was to describe the distribution and identify potential targets of sensory and intestinofugal axons in this ganglion. Two putative markers of these projections were chosen, substance P for primary sensory axons and bombesin for myenteric intestinofugal projections. Varicose substance P-immunoreactive axons were associated only with non-noradrenergic (putative cholinergic) somata, and most commonly with those that contained vasoactive intestinal peptide. Immunoreactivity for substance P was also present in a small group of non-noradrenergic somata, many of which were immunoreactive for enkephalins, neuropeptide Y or vasoactive intestinal peptide. Bombesin immunoreactivity was found only in preterminal and terminal (varicose) axons, the latter of which were exclusively associated with non-noradrenergic somata that contain neuropeptide Y-immunoreactivity. Some varicose axons containing either substance P-or bombesin-immunoreactivity were intermingled with clumps of small, intensely fluorescent cells. These studies indicate that substance P-and bombesin-immunoreactive axons are likely to connect with numerically small, but discrete, populations of pelvic neurons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00331378
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  • 80
    Digitale Medien
    Digitale Medien
    Zona glomerulosa of the adrenal gland in a transgenic strain of rat: a morphologic and functional study (1994)
    Springer
    Cell & tissue research 278 (1994), S. 21-28 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words: Adrenal cortex ; Renin-angiotensin system ; Steroidogenesis ; Electron microscopy ; Morphometry ; Rat ; transgenic (mRen2) 27
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Transgenic rats for the murine Ren-2 gene display high blood pressure, low circulating levels of angiotensin II, and high renin content in the adrenal glands. Moreover, transgenic rats possess an increased aldosterone secretion (maximal from 6 to 18 weeks of age), paralleling the development of hypertension. To investigate further the cytophysiology of the adrenal glands of this strain of rats, we performed a combined morphometric and functional study of the zona glomerulosa of 10-week-old female transgenic rats. Morphometry did not reveal notable differences between zona glomerulosa cells of transgenic and age- and sex-matched Sprague-Dawley rats, with the exception of a marked accumulation of lipid droplets, in which cholesterol and cholesterol esters are stored. The volume of the lipid-droplet compartment underwent a significant decrease when transgenic rats were previously injected with angiotensin II or ACTH. Dispersed zona glomerulosa cells of transgenic rats showed a significantly higher basal aldosterone secretion, but their response to angiotensin II and ACTH was similar to that of Sprague-Dawley animals. Angiotensin II-receptor number and affinity were not dissimilar in zona glomerulosa cells of transgenic and Sprague-Dawley rats. These data suggest that the sustained stimulation of the adrenal renin-angiotensin system in transgenic animals causes an increase in the accumulation in zona glomerulosa cells of cholesterol available for steroidogenesis, as indicated by the expanded volume of the lipid-droplet compartment and the elevated basal steroidogenesis. However, the basal hyperfunction of the zona glomerulosa in transgenic animals does not appear to be coupled with an enhanced responsivity to its main secretagogues, at least in terms of aldosterone secretion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00305774
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  • 81
    Digitale Medien
    Digitale Medien
    The immunolocalization of small nuclear ribonucleoprotein particles in testicular cells during the cycle of the seminiferous epithelium of the adult rat (1994)
    Springer
    Cell & tissue research 278 (1994), S. 363-378 
    Details
    ISSN: 1432-0878
    Schlagwort(e): snRNPs ; Testis ; Spermatocytes ; Spermatids ; Immunocytochemistry ; Chromatoid body ; Intermitochondrial nuage ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The objective of this study was to determine the cellular and subcellular distribution of small nuclear ribonucleoprotein particles (snRNPs) in the adult rat testis in relation to the different cell types at the various stages of the cycle of the seminiferous epithelium. The distribution of snRNPs in the nucleus and cytoplasm of germ cells was quantitated in an attempt to correlate RNA processing with morphological and functional changes occurring during the development of these cells. Light-microscopic immunoperoxidase staining of rat testes with polyclonal anti-Sm and monoclonal anti-Y12 antibodies localized spliceosome snRNPs in the nuclei and cytoplasm of germ cells up to step 10 spermatids. Nuclear staining was intense in Sertoli cells, spermatogonia, spermatocytes, and in the early steps of round spermatid development. Although comparatively weaker, cytoplasmic staining for snRNPs was strongest in mid and late pachytene spermatocytes and early round spermatids. Quantitative electron-microscopic immunogold labeling of Lowicryl embedded testicular sections confirmed the light-microscopic observations but additionally showed that the snRNP content peaked in the cytoplasm of midpachytene spermatocytes and in the nuclei of late pachytene spermatocytes. The immunogold label tended to aggregate into distinct loci over the nuclear chromatin. The chromatoid body of spermatids and spermatocytes and the finely granular material in the interstices of mitochondrial aggregates of spermatocytes were found to be additional sites of snRNP localization and were intensely labeled. This colocalization suggests that these dense cytoplasmic structures may be functionally related. Anti-U1 snRNP antibodies applied to frozen sections showed the same LM localization pattern as spliceosome snRNPs. Anti-U3 snRNP antibodies applied to frozen sections stained nucleoli of germ cells where pre-rRNA is spliced.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00414179
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  • 82
    Digitale Medien
    Digitale Medien
    Calcified structures and calcification in protists (1994)
    Springer
    Protoplasma 181 (1994), S. 78-105 
    Details
    ISSN: 1615-6102
    Schlagwort(e): Calcification ; Coccolithophorids ; Coccolithogenesis ; Foraminifera ; Protists ; Taxonomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The diversity of calcified structures found in protists, the mechanisms utilized to form these structures, and the role these structures play in the taxonomy and systematics of the protists are presented. The two most frequently studied orders of protists which produce calcified structures, the coccolithophorids and foraminifera, are featured. However, consideration is given to the less known and least studied organisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01666390
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  • 83
    Digitale Medien
    Digitale Medien
    Recombinant protein expression in aDrosophila cell line: comparison with the baculovirus system (1994)
    Springer
    Cytotechnology 15 (1994), S. 139-144 
    Details
    ISSN: 1573-0778
    Schlagwort(e): Baculovirus ; cell culture ; Drosophila ; gene expression ; insect cell ; metallothionein promoter ; recombinant protein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract In this report, we compare two different expression systems: baculovirus/Sf9 and stable recombinantDrosophila Schneider 2 (S2) cell lines. The construction of a recombinant S2 cell line is simple and quick, and in batch fermentations the cells have a doubling time of 20 hours until reaching a plateau density of 20 million cells/ml. Protein expression is driven by theDrosophila Metallothionein promoter which is tightly regulated. When expressed in S2 cells, the extracellular domain of human VCAM, an adhesion molecule, is indistinguishable from the same protein produced by baculovirus-infected Sf9 cells. Additionally, we present data on the expression of a seven trans-membrane protein, the dopamine D4 receptor, which has been successfully expressed in both systems. The receptor integrates correctly in the S2 membrane, binds [3H]spiperone with high affinity and exhibits pharmacological characteristics identical to that of the receptor expressed in Sf9 and mammalian cells. The general implications for large scale production of recombinant proteins are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00762388
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  • 84
    Digitale Medien
    Digitale Medien
    Molecular heterogeneity of naturally occurringsn-glycerol-3-phosphate dehydrogenase low-activity variants inDrosophila melanogaster (1994)
    Springer
    Biochemical genetics 32 (1994), S. 161-179 
    Details
    ISSN: 1573-4927
    Schlagwort(e): Drosophila ; glycerol-3-phosphate ; dehydrogenase ; low activity ; DNA sequence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Northern analyses of two low-activitysn-glycerol-3-phosphate dehydrogenase(Gpdh) alleles extracted from natural populations ofDrosophila melanogaster showed that one of them,Gpdh ACyg22 , produced wild-type levels of a normal sized (1.7-kb) mRNA but the other,Gpdh AMB5 , had very low levels of a 1.7-kb mRNA together with low levels of a transcript 200 bp larger. The two variant genes were cloned and sequenced. Compared with normal activity alleles, there were two nucleotide differences in the DNA sequence ofGpdh ACyg22 which were in first-codon positions and would be expected to give rise to Asn-13 → Tyr and Arg-272 → Cys substitutions. The second of these changes is most likely to account for the altered properties of the enzyme. In contrast, none of the nucleotide differences inGpdh AMB5 would give rise to amino acid substitutions, but a 76-bp deletion in the 5′ region removed the normal TATA box and there was a 20-bp insertion in the same region. One of the two transcripts was derived from the use of a substitute TATA box sequence in the insertion, but the 1.9-kb transcript had heterogeneous 5′ ends that were not associated with substitute TATA box sequences. The two transcripts either are produced at a lower rate or are less stable than the normal mRNA.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00554620
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  • 85
    Digitale Medien
    Digitale Medien
    Histone H4 acetylated at lysine 16 and proteins of theDrosophila dosage compensation pathway co-localize on the male X chromosome through mitosis (1994)
    Springer
    Chromosome research 2 (1994), S. 398-404 
    Details
    ISSN: 1573-6849
    Schlagwort(e): dosage compensation ; Drosophila ; histone acetylation ; nuclear domains
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In the fruit flyDrosophila, dosage compensation involves several proteins acting in concert to double the transcriptional activity of genes on the single male X chromosome. Three of these proteins, MLE, MSL-1 and histone H4 acetylated at lysine 16 (H4Ac16), have recently been shown to be located almost exclusively on the male X chromosome in interphase (polytene) cells. We show here that in neuroblasts from third instarDrosophila larvae antisera to H4Ac16, MLE and MSL-1 uniquely label the distal, euchromatic region of the male X chromosome through mitosis. The centromere-proximal, heterochromatic region of the male X is not labelled with these antisera, nor are male autosomes or any chromosomes in female cells. That the association of H4Ac16 with the male X chromosome persists, even when the chromosome is maximally compacted and transcriptionally quiescent, argues that this modified histone is an integral component of the dosage compensation pathway. In the nuclei of interphase neuroblasts from male (but never female) larvae, antibodies to H4Ac16 revealed a small, brightly labelled patch against a background of generally weak nuclear staining. In double-labelling experiments, this patch was also labelled, albeit comparatively weakly, with antibodies to MSL-1. These results strongly suggest that the distal, euchromatic region of the X chromosome in male cells occupies a limited and relatively compact nuclear domain.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01552799
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  • 86
    Digitale Medien
    Digitale Medien
    bHLH proteins encoded by theEnhancer of split complex ofDrosophila negatively interfere with transcriptional activation mediated by proneural genes (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 465-473 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Drosophila ; Enhancer of split ; Helix-loop-helix protein ; Neurogenesis ; Transcriptional repressors
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract TheEnhancer of split complex [E(SPL)-C] ofDrosophila participates in the control of cell fate choice by uncommitted neuroectodermal cells in the embryo. It encodes seven proteins that belong to the basic helix-loop-helix (bHLH) family, six of which are expressed in very similar patterns in the neuroectoderm. Here we describe experiments aimed at unravelling the molecular basis of their function. We found that two products of the complex, HLH-M5 andEnhancer of split, are capable of binding as homo-and heterodimers to a sequence in the promoters of theEnhancer of split andachaete genes, called the N-box, which differs slightly from the consensus binding site (the E-box) for other bHLH proteins. In transient expression assays in cell culture, both proteins were found to attenuate the transcriptional activation mediated by the proneural bHLH proteinslethal of scute anddaughterless at theEnhancer of split promoter.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00583897
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  • 87
    Digitale Medien
    Digitale Medien
    Discrimination of related transcribed and non-transcribed repetitive DNA sequences from the Y chromosomes of Drosophila hydei and Drosophila eohydei (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 54-62 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Drosophila ; Y chromosome ; Fertility genes Lampbrush loops ; Repetitive DNA sequences
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The short arm of the Y chromosome of Drosophila hydei carries a single male fertility gene, gene Q, which forms the lampbrush loop pair Nooses. Conflicting observations have been reported concerning the identity of the repetitive DNA sequences that are transcribed in this loop pair. It has been claimed by other investigators that the loop transcripts contain repeats of two distinct, but related families of Y-specific repetitive DNA sequences, ayl and YsI. We reinvestigated this issue, using as probes single ayl and YsI repeats which, under stringent conditions, hybridize only to members of their own family. Under non-stringent conditions, both repeats hybridize in situ to Nooses transcripts. However, if hybridization conditions are stringent, only the ayl probe hybridizes to loop transcripts. Hybridizations to Northern blots of testis RNA confirm these results. Further, YsI repeats are not found the closely related species D. eohydei. We conclude that the YsI repeats are not relevant for the function of fertility gene Q.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00283876
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  • 88
    Digitale Medien
    Digitale Medien
    Drosophila GABAergic systems II. Mutational analysis of chromosomal segment 64AB, a region containing the glutamic acid decarboxylase gene (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 555-564 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Drosophila ; Glutamic acid decarboxylase ; GAD ; GABA ; Lethal mutations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Drosophila melanogaster Gad gene maps to region 64A3-5 of chromosome 3L and encodes glutamic acid decarboxylase (GAD), the rate-limiting enzyme for the synthesis of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). Because this neurotransmitter has been implicated in developmental functions, we have begun to study the role of GABA synthesis during Drosophila embryogenesis. We show that Gad mRNA is expressed in a widespread pattern within the embryonic nervous system. Similarly, GAD-immunoreactive protein is present during embryogenesis. These results prompted us to screen for embryonic lethal mutations that affect GAD activity. The chromosomal region to which Gad maps, however, has not been subjected to an extensive mutational analysis, even though it contains several genes encoding important neurobiological, developmental, or cellular functions. Therefore, we have initially generated both chromosomal rearangements and point mutations that map to the Drosophila 64AB interval. Altogether, a total of 33 rearrangements and putative point mutations were identified within region 64A3-5 to 64B12. Genetic complementation analysis suggests that this cytogenetic interval contains a minimum of 19 essential genes. Within our collection of lethal mutations are several chromosomal rearrangements, two of which are in the vicinity of the Gad locus. One of these rearrangements, Df(3L)C175, is a small deletion that removes the Gad locus and at least two essential genes; the second, T(2;3)F10, is a reciprocal translocation involving the second and third chromosomes with a break within region 64A3-5. Both of these rearrangements are associated with embryonic lethality and decreased GAD enzymatic activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00284204
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  • 89
    Digitale Medien
    Digitale Medien
    Transcription of repetitive DNA sequences in the lampbrush loop pair Nooses formed by sterile alleles of fertility gene Q on the Y chromosome of Drosophila hydei (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 653-660 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Drosophila ; Fertility genes ; Y chromosome Lampbrush loops ; Repetitive DNA sequences
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Y chromosomal lampbrush loop-forming male fertility genes of Drosophila consist mainly of repetitive DNA sequences that do not code for proteins. We investigated whether differences in the transcription of these sequences can be detected in male-sterile alleles of male fertility gene Q, which forms the loop pair Nooses. The loop consists, for approximately two-thirds, of repeats of the Y-specific ay1 family of repetitive DNA sequences. Of the remaining one-third, at least one-half is represented by defective retrotransposons of the gypsy family. Both sequence types are interspersed throughout the loop. Using both ay1 and gypsy sequences as probes for transcript in situ hybridization, we show that, at the level of the light microscope, transcription of neither sequence is detectably affected in the loops formed by a male-sterile allele of gene Q. We conclude that the transcription of ay1 and gypsy is required, but not sufficient for the function of gene Q.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00282756
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  • 90
    Digitale Medien
    Digitale Medien
    The lysozyme locus in Drosophila melanogaster: an expanded gene family adapted for expression in the digestive tract (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 152-162 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Antibacterial ; Digestive tract ; Drosophila ; Gene family ; Lysozyme
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Lysozyme has been studied in insects as part of the system of inducible antibacterial defence in the haemolymph. We recently found two Drosophila lysozyme genes that are constitutively expressed in the digestive tract, and are probably involved in the digestion of bacteria in the food. To obtain an overview of the lysozyme genes in this species and their possible roles in immunity and digestion, we have now characterized all six lysozyme genes in the cloned part of the lysozyme locus at 61F, and a seventh gene that maps to the same chromosomal location. The expression of the genes follows four different patterns: firstly, four closely related genes, LysB, C, D and E, are all strongly expressed in the midgut of larvae and adults; secondly, LysP is expressed in the adult salivary gland; thirdly, LysS is expressed mainly in the gastric caecae of larvae; and finally, LysX is primarily expressed in the metamorphosing midgut of late larvae and early pupae. The LysD-like genes and LysS are strongly repressed in artificially infected animals, possibly reflecting a malaise reaction in the digestive tract. None of the genes is expressed in the fat body or haemocytes. Thus rather than being a component of the haemolymph, the Drosophila lysozymes are found mainly in the digestive tract where they are expressed at a high level. Furthermore all genes, except LysP, encode acidic proteins, in contrast to the strongly basic “typical” lysozymes. This is highly reminiscent of the situation in ruminants, where the lysozymes have been recruited for the digestion of symbiotic bacteria in the stomach.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00391008
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  • 91
    Digitale Medien
    Digitale Medien
    Functional relationships between genes of the Shaker gene complex of Drosophila (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 197-204 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Drosophila ; Shaker gene complex Dominant lethality ; K+ channel ; Troponin I
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Different mutations belonging to the HLI and HLII complementation groups of the haplolethal (HL) region of the Shaker complex (ShC) are described. The HLI complementation group includes viable (hdp), recessive lethals [l(1)1614], semidominant lethals [l(1)8384] and dominant lethals [l(1)5051,l(1)9916, l(1)13193], lack-of-function alleles that affect nervous system, cuticle and muscle development. The HLI complementation group encodes troponin I. HLII lack-of-function mutations [l(1)174 and l(l)4058] affect nervous system development. The semidominant lethal HLI mutation 1(1)8384 shows differential complementation with other mutations in the ME and HL regions of ShC. Thus, heterozygous combinations of l(1)8384 with ME mutations l(1)162 and l(1)387 are poorly viable. The same phenomenon is observed for heterozygotes of l(1)8384 with HL mutations l(1)1199, l(1)2288 and l(1)3014. These specific interactions indicate the existence of functional relationships among the genetic elements of ShC. The implications for the understanding of the functional organization of ShC are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00283523
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  • 92
    Digitale Medien
    Digitale Medien
    Functional interactions between the gene tetanic and the Shaker gene complex of Drosophila (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 205-215 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Drosophila ; tetanic ; Shaker gene complex ; Maternal effect ; K+ channel modulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Different phenotypes associated with the tetanic (tta) mutation such as appendage contraction, maternal effect and low viability and fertility are enhanced by one extra dose of the Shaker gene complex (ShC). The tta mutation is lethal with two extra doses of ShC. In addition, tta embryos have a defective nervous system. In this paper, I analyse the interaction between tta and ShC to gain insight into their relationship. Aneuploid analysis suggests that the lethality is due to an interaction of the tta mutation with the maternal effect (ME) region of this gene complex. Mutations in the ME region of ShC partially suppress this interaction. Trans-heterozygous combinations of MEI[l(1)305] and MEIII [l(1)459] mutations causes dominant lethality in a tta background. Trans-heterozygous combinations of an MEII [l(1)1359] mutation with the cited MEI and MEIII mutations are lethal in a tta background. Double mutant combinations and gene dosage experiments, suggest that tta also interacts with the viable (V) region of ShC. These specific genetic interactions indicate that tta and the ME and V regions of ShC are functionally related. These results, together with the previous electrophysiological, molecular and biochemical studies on these mutants suggest an interaction at the protein level. Thus, in the case of the V region, the tta gene product may modulate the activity of the K+ channels encoded in this region. Furthermore, the extreme dosage sensitivity of the interaction between tta and ShC suggests a stoichiometric requirement for the different gene products involved, which might be physically associated and form heteromultimers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00283524
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  • 93
    Digitale Medien
    Digitale Medien
    Drosophila melanogaster acetylcholinesterase: Identification and expression of two mutations responsible for cold- and heat-sensitive phenotypes (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 699-705 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Acetylcholinesterase ; Drosophila ; Thermosensitive mutation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Ace IJ29 and Ac IJ40 are cold- and heat-sensitive variants of the gene coding for acetylcholinesterase in Drosophila melanogaster. In the homozygous condition, these mutations are lethal when animals are raised at restrictive temperatures, i.e., below 23° C for Ace IJ29 or above 25° C for Ace IJ40. The coding regions of the gene in these mutants were sequenced and mutations changing Ser374 to Phe in Ace IJ29 and Pro75 to Leu in Ace IJ40 were found. Acetylcholinesterases bearing these mutations were expressed in Xenopus oocytes and we found that these mutations decrease the secretion rate of the protein most probably by affecting its folding. This phenomenon is exacerbated at restrictive temperatures decreasing the amount of secreted acetylcholinesterase below the lethality threshold. In parallel, the substitution of the conserved Asp248 by an Asn residue completely inhibits the activity of the enzyme and its secretion, preventing the correct folding of the protein in a non-conditional manner.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00279580
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  • 94
    Digitale Medien
    Digitale Medien
    DPhK-γ, a putative Drosophila kinase with homology to vertebrate phosphorylase kinase γ subunits: molecular characterisation of the gene and phenotypic analysis of loss of function mutants (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 588-597 
    Details
    ISSN: 1617-4623
    Schlagwort(e): Phosphorylase kinase γ gene ; Kinase ; Drosophila ; Maternal effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Partial and total loss of function mutant alleles of a putative Drosophila homologue (DPhK-γ) of the vertebrate phosphorylase kinase γ-subunit gene have been isolated. DPhK-γ is required in early embryonic processes, such as gastrulation and mesoderm formation; however, defects in these processes are seen only when both the maternal and zygotic components of DPhK-γ expression are eliminated. Loss of zygotic expression alone does not appear to affect normal embryonic and larval development; some pupal lethality is observed but the majority of mutant animals eclose as adults. Many of these adults show defects in their leg musculature (e.g. missing and degenerating muscles), in addition to exhibiting melanised “tumours” on their leg joints. Loss of only the maternal component has no obvious phenotypic consequences. The DPhKγ gene has been cloned and sequenced. It has an open reading frame (ORF) of 1680 by encoding a 560 amino acid protein. The predicted amino acid sequence of DPhK-γ has two conserved domains, the catalytic kinase and calmodulin-binding domains, separated by a linker sequence. The amino acid sequence of DPhK-γ is homologous to that of mammalian PhK-γ proteins but differs in the length and amino acid composition of its linker sequence. The expression of DPhK-γ mRNA is developmentally regulated. We discuss the implications of these observations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00282221
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  • 95
    Digitale Medien
    Digitale Medien
    DrosophilaP element: Transposition, regulation and evolution (1994)
    Springer
    Genetica 93 (1994), S. 61-78 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; transposable elements ; hybrid dysgenesis ; transcriptional regulation ; horizontal transfer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01435240
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  • 96
    Digitale Medien
    Digitale Medien
    Genome and stresses: Reactions against aggressions, behavior of transposable elements (1994)
    Springer
    Genetica 93 (1994), S. 149-160 
    Details
    ISSN: 1573-6857
    Schlagwort(e): environment ; genome ; stress ; transposable elements ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The action of stresses on the genome can be considered as responses of cells or organisms to external aggressions. Stress factors are of environmental origin (climatic or trophic) or of genomic nature (introduction of foreign genetic material, for example). In both cases, important perturbations can occur and modify hereditary potentialities, creating new combinations compatible with survival; such a situation may increase the variability of the genome, and allow evolutive processes to take place. The behavior of transposable elements under stress conditions is thus of particular interest, since these sequences are sources of mutations and therefore of genetic variability; they may play an important role in population adaptation. The survey of the available experimental results suggests that, although some examples of mutations and transposable elements movements induced by external factors are clearly described, environmental injuries or introduction of foreign material into a genome are not systematically followed by drastic genomic changes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01435247
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  • 97
    Digitale Medien
    Digitale Medien
    Analysis of nucleotide substitutions and amino acid conservation in theDrosophila Adh genomic region (1994)
    Springer
    Genetica 94 (1994), S. 27-36 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Adh ; Adh-dup ; Drosophila ; molecular clock ; nucleotide substitution rates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The homologous genomic region that contains two paralogous genes,Adh andAdh-dup, was compared in severalDrosophila species. Sequences were analyzed as follows: a) At the nucleotide level, Ka and Ks values were determined for each pair of species. Ka-Adh and Ka-Adh-dup are not significantly different. However, Ks-Adh values are significantly lower than Ks-Adh-dup, which are more variable. In agreement with other reports, lower Ks values forAdh correlate with a high level of gene expression and relatively high percentage of G+C content in the third codon position, while the opposite applies toAdh-dup. b) At the protein level, amino acid comparisons reveal conserved regions shared by ADH and ADH-DUP, which have been assigned to known functional domains. Key residues for dehydrogenasic function are also found in ADH-DUP, thus pointing to a dehydrogenase activity for ADH-DUP, albeit very different from that of ADH.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01429217
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  • 98
    Digitale Medien
    Digitale Medien
    Associations of esterase 6 allozyme and activity variation with reproductive fitness inDrosophila melanogaster (1994)
    Springer
    Genetica 94 (1994), S. 43-56 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; esterase 6 ; reproduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Previous studies have shown that the esterase 6 (EST6) enzyme ofD. melanogaster is mainly produced in the sperm ejaculatory duct of the adult male and comparisons of wild-type males with laboratory null mutants have suggested that the enzyme plays a role in reproductive fitness. In this study we have compared 18 field-derived lines each isoallelic forEst6 for differences in five components of male reproductive fitness. No consistent fitness differences were found among lines differing in respect of the two major allozyme classes EST6-F and EST6-S, despite other evidence that these two classes are not selectively equivalent in the field. However, differences in reproductive fitness were found among lines differing in the minor mobility variants that segregate within EST6-F and EST6-S. A failure to distinguish among these minor forms may explain the discrepancies in previous studies on the effects of the major EST6 allozymes on reproductive fitness. The most significant associations we have found between EST6 and reproductive fitness were due to variation in EST6 activity levels. Male EST6 activity levels were found to be positively correlated with their time to first mating, negatively correlated with the numbers of eggs laid and progeny produced by their mates, and negatively correlated with the frequency with which their mates remate. We conclude that some EST6 variants differ in components of male reproductive fitness operative in laboratory cultures. However, the evidence for fitness differences is stronger for variants affecting the amount, rather than the structure of the enzyme, and the direction of the differences varies between some of the fitness components tested.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01429219
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  • 99
    Digitale Medien
    Digitale Medien
    Genetic, molecular and developmental analysis of the glutamine synthetase isozymes ofDrosophila melanogaster (1994)
    Springer
    Genetica 94 (1994), S. 275-281 
    Details
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; glutamine synthetase ; isozyme functional specialization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The glutamine synthetase isozymes ofDrosophila melanogaster offer an attractive model for the study of the molecular genetics and evolution of a small gene family encoding enzymatic isoforms that evolved to assume a variety of specific and sometimes essential biological functions. InDrosophila melanogaster two GS. isozymes have been described which exhibit different cellular localisation and are coded by a two-member gene family. The mitochondrial GS structural gene resides at the 21B region of the second chromosome, the structural gene for the cytosolic isoform at the 10B region of the X chromosome. cDNA clones corresponding to the two genes have been isolated and sequenced. Evolutionary analysis data are in accord with the hypothesis that the twoDrosophila glutamine synthetase genes are derived from a duplication event that occurred near the time of divergence between Insecta and Vertebrata. Both isoforms catalyse all reactions catalysed by other glutamine synthetases, but the different kinetic parameters and the different cellular compartmentalisation suggest strong functional specialisation. In fact, mutations of the mitochondrial GS gene produce embryo-lethal female sterility, defining a function of the gene product essential for the early stages of embryonic development. Preliminary results show strikingly distinct spatial and temporal patterns of expression of the two isoforms at later stages of development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01443441
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  • 100
    Digitale Medien
    Digitale Medien
    The role of extracellular calcium in pregnancy-induced attenuation of phenylephrine contraction in rat aorta with functional endothelium (1994)
    Springer
    Journal of comparative physiology 164 (1994), S. 81-87 
    Details
    ISSN: 1432-136X
    Schlagwort(e): Vascular smooth muscle ; Phenylephrine-induced contraction ; Pregnancy ; Aorta ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The effect of pregnancy on the supply of calcium ions for the contractile responses of rat aortic rings to phenylephrine was investigated. The contractility of intact aortic rings from pregnant rats, compared with that of similar rings from non-pregnant rats, to phenylephrine and potassium chloride was significantly decreased. Contractions of rings from non-pregnant rats, pretreated with phenylephrine or potassium chloride, in response to calcium chloride were greater than those of similarly treated rings from pregnant rats. When the concentration of calcium chloride in the medium bathing the rings was reduced to 0.8 mmol·l-1, the contractile response to phenylephrine was significantly (P〈0.005) inhibited in rings from both pregnant and non-pregnant rats but to a greater extent in rings from non-pregnant rats. Contractions of aortic rings from pregnant rats in response to phenylephrine in calcium-free medium were similar to those of rings from non-pregnant rats, suggesting equal dependence on calcium from intracellular stores. The results suggest that pregnancy decreased the response to calcium influx into the aortic smooth muscle cells through both receptor-and voltage-operated calcium entry pathways. Since de-endothelialisation reversed the pregnancy-induced diminished contraction to phenylephrine, it is likely that pregnancy interferred with contractions induced by activation of receptors with phenylephrine through enhanced production of endothelium-derived relaxing factor(s).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00714575
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