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  • Drosophila  (203)
  • Calcium
  • Fluoride
  • Springer  (417)
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  • 101
    ISSN: 1432-1939
    Schlagwort(e): Hymenoptera ; Eucoilidae ; Leptopilina heterotoma ; Infochemicals ; Kairomone ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Parasitoids that forage for herbivorous hosts by using infochemicals may have a problem concerning the reliability and detectability of these stimuli: host stimuli are highly reliable but not very detectable at a distance, while stimuli from the host's food are very detectable but generally not very reliable in indicating host presence. One solution to this problem is to learn to link highly detectable stimuli to reliable but not very detectable stimuli. Ample knowledge is available on how associative learning aids foraging parasitoids in the location of suitable microhabitats. However, in this paper we report on another solution to the reliability-detectability problem and present evidence for an essential, but as yet overlooked, aspect of Drosophila parasitoid ecology. For the first time it is shown that a parasitoid of Drosophila larvae spies on the communication system of adult Drosophila flies to locate potential host sites: naive parasitoids strongly respond to a volatile aggregation pheromone that is deposited in the oviposition site by recently mated female flies. Thus, the parasitoids resort to using highly detectable information from a host stage different from the one under attack (i.e. infochemical detour). The function and ecological implications of these findings are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 102
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 15 (1993), S. 153-159 
    ISSN: 1432-0789
    Schlagwort(e): Calcium ; Maize ; Nitrogen ; Brazilian Amazon ; Cation leaching ; Canavalia ensiformes ; Mucuna aterrima
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary This work investigated the effectsof amendments of fertilizer N and lime on subsoil acidity and maize rooting depth in an acid soil of the central Amazon basin. A split-plot designed field experiment was conducted on a clayey Oxisol (Typic Acrudox) during a 16-month period. Main plots received 0 or 4 Mt ha-1 of lime. Subplots were four crop sequences: (1) Maize-green manure (Canavalia ensiformes); (2) maize-green manure (Mucuna aterrima); (3) maize-bare fallow, with the maize receiving 300 kg ha-1 of urea-N; and (4) bare fallow, with an application of 300 kg ha-1 of urea-N at the same time as sequence 3. Plots were periodically sampled to 1.2 m. The experimental site received 4265 mm of precipitation during 16 months; approximately 60%–90% of this rain percolated through the profile. Substantial amounts of Ca were leached from the 0–30 cm horizon during the experimental period, but only limited amounts accumulated in the subsoil. Base saturation below 45 cm was less than 50% at the end of the experiment regardless of lime treatment. Roots of maize were concentrated in the 0–30 cm layers in limed plots and the 0–20 cm layers in unlimed plots. In all treatments less than 5% of the roots was found below 50 cm. An acidity balance indicated that considerable acidity was leached below the plow layer and out of the profile.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 103
    ISSN: 1432-072X
    Schlagwort(e): Calcium ; Nitrogen fixation ; Nodulation ; Periplasmic proteins ; Rhizobium fredii
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Calcium is essential for the growth of rhizobia and the formation of nitrogen-fixing root-nodules on legumes, but its precise role in these processes remains unknown. We have found that Rhizobium fredii USDA208 accumulates a major 38 kDa protein when grown in media supplemented with 0.3–2 μmM CaCl2. We have purified this protein and raised polyclonal antibodies against it. The protein initially is synthesized as a 40 kDa precursor which subsequently undergoes calcium-dependent processing to give rise to the mature polypeptide. Subcellular and immunocytochemical localization studies indicate that the 38 kDa protein accumulates preferentially in the periplasmic space. Its N-terminal sequence, AETIKIGVAGPMTG, shows significant homology to the N-termini of amino acid binding proteins from the periplasm, including leucine-, isoleucine-, and valine-specific binding proteins of Pseudomonas aeruginosa and Escherichia coli and a leucine-specific binding protein of E. coli. The R. fredii protein does not, however, bind [3H]-leucine. The 38 kDa protein is encoded by the bacterial chromosome. It is absent in several rhizobia other than R. fredii, but antigenically related polypeptides are present in Escherichia coli and Erwinia carotovora subsp. carotovora.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 104
    ISSN: 1432-072X
    Schlagwort(e): Methanospirillum ; Morphology ; Flagella ; Archaea ; Growth conditions ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Methanospirillum hungatei strains GP1 and JF1 when cultivated at 37°C in JMA medium grew as motile single cells or short chains of cells (typically 10–30 μm long). When M. hungatei was grown in low Ca2+ concentrations or with the divalent cation chelator EDTA, the organism grew as long non-flagellated filaments (up to 900 μm long). The two strains had different thresholds of calcium concentrations for long filament formation (〈0.25 mM for GP1 and 〈0.15 mM for JF1) as well as different minimal Ca2+ requirements for growth. Both strains produced long, almost straight, filaments at Ca2+ concentrations near the minimum required for growth. At suboptimal growth temperatures the organisms still grew as short filaments but no longer possessed flagella. Western blot analysis indicated that flagellin monomer was present in cultures of long non-flagellated filaments and short non-flagellated cultures grown at suboptimal temperatures. The amount of flagellin present appeared to be equal in both non-flagellated and flagellated cultures. When cells were grown as long non-flagellated filaments and switched to growth conditions inducing short, flagellated forms, flagella were first observed at 2.5 h after this switch.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 105
    Digitale Medien
    Digitale Medien
    Springer
    Behavior genetics 23 (1993), S. 85-90 
    ISSN: 1573-3297
    Schlagwort(e): period gene ; Drosophila ; genetic coupling ; coevolution ; sexual selection ; female preference
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract Mutations at theperiod (per) locus inDrosophila melanogaster alter rhythmic components of the male courtship song. We have examined the mating speed of females homozygous for mutantper alleles when presented with artificial mutant songs. Mutant females retain a preference for wild-type over mutant songs, thus male song and female preference are probably under separate genetic control. In contrast,per-mutant females from an established laboratory stock which had been maintained for nearly two decades appear to have an enhanced response to the corresponding mutant song in that they no longer discriminate against mutant song. These results are discussed in terms of the “genetic coupling” and “coevolution” theories of complementarity between male and female components of communication systems.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 106
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 393-407 
    ISSN: 1573-4927
    Schlagwort(e): alcohol dehydrogenases ; protein evolution ; Drosophila ; Streptomyces
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Polyclonal antibodies raised against purifiedDrosophila alcohol dehydrogenase (ADH) were used in Western blot analyses to search for structurally and/or immunologically related proteins in prokaryotes and eukaryotes. No immunological-reactive protein was detected in a flesh fly, a locust, and butterflies. Immunological similarity with the 50-kDa PQQ-glucose dehydrogenase (GluDH)-B enzyme ofAcinetobacter calcoaceticus was found, but the cross-reactivity apparently is dependent on the high hydrophilic character of this protein. Antibodies against PQQ-GluDH did not recognizeDrosophila ADH. In five of seven species of the gram-positive soil bacteria actinomycetes tested, a protein approximately 28–30 kDa in subunit size was strongly recognized by α-DADH. It is probably not one of the two proteins with known homology toDrosophila ADH,viz., theactIII gene product and 20β-hydroxysteroid dehydrogenase. The protein is present in both the soluble and the pellet-membrane fraction of the cells. The protein has a late temporal expression in surface-grown cultures and, therefore, might be involved in secondary metabolism.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 107
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 61-74 
    ISSN: 1573-4927
    Schlagwort(e): isofemale ; allele frequency estimation ; population structure ; allozyme ; microsatellites ; restriction fragment length polymorphisms ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Isofemale lines are commonly used inDrosophila and other genera for the purpose of assaying genetic variation. Isofemale lines can be kept in the laboratory for many generations before genetic work is carried out, and permit the confirmation of newly discovered alleles. A problem not realized by many workers is that the commonly used estimate of allele frequency from these lines is biased. This estimation bias occurs at all times after the first laboratory generation, regardless of whether single individuals or pooled samples are used in each well of an electrophoretic gel. This bias can potentially affect the estimation of population genetic parameters, and in the case of rare allele analysis it can cause gross overestimates of gene flow. This paper provides a correction for allele frequency estimates derived from isofemale lines for any time after the lines are established in the laboratory. When pooled samples are used, this estimator performs better than the standard estimator at all times after the first generation. The estimator is also insensitive to multiple inseminations. After the lines have drifted oneN e generations, multiple inseminations actually make the new estimator perform better than it does in singly inseminated females. Simulations show that estimates made using either estimator after the lines have drifted to fixation have a much greater error associated with their use than do those estimates made earlier in time using the correction. In general it is better to use corrected estimates of gene frequency soon after lines are established than to use uncorrected estimates made after the first laboratory generation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 108
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 259-278 
    ISSN: 1573-4927
    Schlagwort(e): serine esterase ; substrate interactions ; Drosophila ; acetylcholine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Esterase 6 fromDrosophila melanogaster is a carboxylesterase that belongs to the serine esterase multigene family. It has a basic histidine (His) at residue 187, adjacent to the reactive serine (Ser) at residue 188, whereas most other characterized members of the family have an acidic glutamate (Glu) in the equivalent position. We have used site-directedin vitro mutagenesis to replace the His codon of the esterase 6 gene with either Gln or Glu codons. The enzymes encoded by these active-site mutants and a wild-type control have been expressed, purified, and characterized. Substitution of Gln for His at position 187 has little effect on the biochemical properties of esterase 6, but the presence of Glu at this position is associated with three major differences. First, the pH optimum is increased from 7 to 9. Second, the mutant enzyme shows decreased activity for β-naphthyl esters andp-nitrophenyl acetate but has gained the ability to hydrolyze acetylthiocholine. Finally, the Gibb's free energy of activation for the enzyme is increased. These results suggest that residue 187 interacts directly with the substrate alkyl group and that this interaction is fully realized in the transition state. We further propose that the presence of His rather than Glu at position 187 in esterase 6 contributes significantly to its functional divergence from the cholinesterases and that this divergence is due to different interactions between residue 187 and the substrate alkyl group.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 109
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 259-278 
    ISSN: 1573-4927
    Schlagwort(e): serine esterase ; substrate interactions ; Drosophila ; acetylcholine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Esterase 6 fromDrosophila melanogaster is a carboxylesterase that belongs to the serine esterase multigene family. It has a basic histidine (His) at residue 187, adjacent to the reactive serine (Ser) at residue 188, whereas most other characterized members of the family have an acidic glutamate (Glu) in the equivalent position. We have used site-directedin vitro mutagenesis to replace the His codon of the esterase 6 gene with either Gln or Glu codons. The enzymes encoded by these active-site mutants and a wild-type control have been expressed, purified, and characterized. Substitution of Gln for His at position 187 has little effect on the biochemical properties of esterase 6, but the presence of Glu at this position is associated with three major differences. First, the pH optimum is increased from 7 to 9. Second, the mutant enzyme shows decreased activity for β-naphthyl esters andp-nitrophenyl acetate but has gained the ability to hydrolyze acetylthiocholine. Finally, the Gibb’s free energy of activation for the enzyme is increased. These results suggest that residue 187 interacts directly with the substrate alkyl group and that this interaction is fully realized in the transition state. We further propose that the presence of His rather than Glu at position 187 in esterase 6 contributes significantly to its functional divergence from the cholinesterases and that this divergence is due to different interactions between residue 187 and the substrate alkyl group.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 110
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 375-391 
    ISSN: 1573-4927
    Schlagwort(e): Drosophila ; sulfite oxidase ; molybdenum ; MoCo
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The relationship between sulfite oxidase (SO) and sulfite sensitivity inDrosophila melanogaster is addressed. Significant improvements to the SO assay have provided an investigative tool which can be applied to further studies of this molybdoenzyme. Using the second-instar larval stage ofD. melanogaster, we have shown a direct relationship between measured levels of sulfite oxidase activity and the organism's ability to withstand a sulfite challenge. Implementation of a sulfite-testing procedure confirmed the documented instability of sulfite in solution and may explain some of the conflicting results reported in the SO literature. Results of the tungstate-addition experiments confirm thatDrosophila SO is a molybdoenzyme and its activity was shown to be governed by three of the four loci known to affect more than one molybdoenzyme. The ability ofD. melanogaster to withstand the application of exogenous sulfites is shown to be dependent on sulfite oxidase activity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 111
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 393-407 
    ISSN: 1573-4927
    Schlagwort(e): alcohol dehydrogenases ; protein evolution ; Drosophila ; Streptomyces
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Polyclonal antibodies raised against purifiedDrosophila alcohol dehydrogenase (ADH) were used in Western blot analyses to search for structurally and/or immunologically related proteins in prokaryotes and eukaryotes. No immunological-reactive protein was detected in a flesh fly, a locust, and butterflies. Immunological similarity with the 50-kDa PQQ-glucose dehydrogenase (GluDH)-B enzyme ofAcinetobacter calcoaceticus was found, but the cross-reactivity apparently is dependent on the high hydrophilic character of this protein. Antibodies against PQQ-GluDH did not recognizeDrosophila ADH. In five of seven species of the gram-positive soil bacteria actinomycetes tested, a protein approximately 28–30 kDa in subunit size was strongly recognized by α-DADH. It is probably not one of the two proteins with known homology toDrosophila ADH,viz., theactIII gene product and 20β-hydroxysteroid dehydrogenase. The protein is present in both the soluble and the pellet-membrane fraction of the cells. The protein has a late temporal expression in surface-grown cultures and, therefore, might be involved in secondary metabolism.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 112
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 375-391 
    ISSN: 1573-4927
    Schlagwort(e): Drosophila ; sulfite oxidase ; molybdenum ; MoCo
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The relationship between sulfite oxidase (SO) and sulfite sensitivity inDrosophila melanogaster is addressed. Significant improvements to the SO assay have provided an investigative tool which can be applied to further studies of this molybdoenzyme. Using the second-instar larval stage ofD. melanogaster, we have shown a direct relationship between measured levels of sulfite oxidase activity and the organism's ability to withstand a sulfite challenge. Implementation of a sulfite-testing procedure confirmed the documented instability of sulfite in solution and may explain some of the conflicting results reported in the SO literature. Results of the tungstate-addition experiments confirm thatDrosophila SO is a molybdoenzyme and its activity was shown to be governed by three of the four loci known to affect more than one molybdoenzyme. The ability ofD. melanogaster to withstand the application of exogenous sulfites is shown to be dependent on sulfite oxidase activity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 113
    Digitale Medien
    Digitale Medien
    Springer
    Planta 189 (1993), S. 491-498 
    ISSN: 1432-2048
    Schlagwort(e): Blue light ; Calcium ; Calcium ionophore ; Chloroplast movement ; Lemna
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The presence of calcium is essential for chloroplast movement induced by blue light in Lemna trisulca L. The regulatory role of calcium was confirmed by the inhibition of chloroplast movement by cytochalasin B and trifluoperazine. The calcium concentration in tissues was modified by ethylene glycol-bis(2-aminoethylether)-N,N,N′, N′-tetraacetic acid (EGTA), the calcium ionophore A23187 and La3+. Only a long period of incubation (12h) in EGTA or La3+ caused distrubances in chloroplast movement. This indicates that calcium influx is not essential for chloroplast movement. Those conditions that dramatically changed the internal calcium concentration, either applications of calcium ionophore A23187 and EGTA, or ionophore and La3+, markedly decreased the amplitude of response to blue-light pulses. This demonstrates that disturbances of chloroplast movement are observable only when internal stores of calcium are affected by Ca2+-antagonists. We suggest that the calcium involved in blue-light-induced chloroplast movement is derived from intracellular stores. The addition of Mg2+ to EGTA buffer counteracted its effect, indicating that Mg2+, as well as Ca2+, might possibly be involved in chloroplast movement.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 114
    ISSN: 1432-2048
    Schlagwort(e): Auxin ; Calcium ; Cucurbita ; 31P nuclear magnetic resonance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Calcium deficiency in zucchini (Cucurbita pepo L.) is associated with reduced growth and a reduced ability to transport auxin (Allan and Rubery, 1991, Planta 183, 604–612). An investigation of the effects of calcium-deficiency on zucchini hypocotyl cells was made using weak-acid uptake and 31P-nuclear-magneticresonance (31P-NMR) spectroscopy in vivo and in tissue extracts. Calcium-deficient tissue had the same cytoplasmic and vacuolar pHs as normal tissue when extracellular pH was near neutral. At acidic external pH the vacuolar pH was lower in deficient tissue. Adenine nucleotides were present predominantly as ATP in both control and calcium-deficient tissues. Addition of calcium to calcium-deficient tissue, under conditions which cause recovery of auxin transport induced no changes in the 31P-NMR spectra of deficient tissue. The content of mobile, phosphorylated metabolites was reduced in calcium-deficient tissue in comparison to control tissue. However, a substantial increase in the content of phosphorylcholine occurs in calcium-deficient tissues compared with controls; this may reflect changes in lipid turnover in calcium-stressed cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 115
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 136 (1993), S. 9-21 
    ISSN: 1432-1424
    Schlagwort(e): Maxi K+ channel ; Calcium ; pH ; Charybdotoxin ; Rabbit distal colon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract To determine if their properties are consistent with a role in regulation of transepithelial transport, Ca2+-activated K+ channels from the basolateral plasma membrane of the surface cells in the distal colon have been characterized by single channel analysis after fusion of vesicles with planar lipid bilayers. A Ca2+-activated K+ channel with a single channel conductance of 275 pS was predominant. The sensitivity to Ca2+ was strongly dependent on the membrane potential and on the pH. At a neutral pH, the K 0.5 for Ca2+ was raised from 20nm at a potential of 0 mV to 300nm at −40 mV. A decrease in pH at the cytoplasmic face of the K+ channel reduced the Ca2+ sensitivity dramatically. A loss of the high sensitivity to Ca2+ was also observed after incubation with MgCl2, possibly a result of dephosphorylation of the channels by endogenous phosphatases. Modification of the channel protein may thus explain the variation in Ca2+ sensitivity between studies on K+ channels from the same tissue. High affinity inhibition (K 0.5=10nm) by charybdotoxin of the Ca2+-activated K+ channel from the extracellular face could be lifted by an outward flux of K+ through the channel. However, at the ion gradients and potentials found in the intact epithelium, charybdotoxin should be a useful tool for examination of the role of maxi K+ channels. The high sensitivity for Ca2+ and the properties of the activator site are in agreement with an important regulatory role for the high conductance K+ channel in the epithelial cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 116
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 134 (1993), S. 1-13 
    ISSN: 1432-1424
    Schlagwort(e): Endocytosis ; Exocytosis ; Calcium ; Adrenal medulla
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The intracellular requirements for membrane recapture in permeabilized chromaffin cells were compared to the requirements for exocytosis from the same cells. In permeabilized bovine chromaffin cells, calcium-driven exocytosis also triggers, with a short delay, uptake of extracellular horseradish peroxidase (HRP). This internalized HRP remains compartmentalized within the cell and migrates to a low density band on a Percoll gradient which is distinct from the heavier chromaffin granules. The amount of horseradish peroxidase internalized is similar in intact and leaky cells and is approximately equivalent to the volumes secreted. Endocytosis in both preparations is blocked by botulinum toxin, operates in a collapsed membrane potential, and is inhibited by low temperature. In permeabilized cells, exocytosis and coupled endocytosis are activated by the same concentrations of Ca2+ and MgATP. Although secretion requires Ca2+ and MgATP, once exocytosis has occurred the subsequent endocytosis can proceed in the virtual absence of Ca2+ or MgATP, and is largely unaffected by a variety of nucleotide triphosphates (including nonhydrolyzable analogues), and cyclic nucleotides. These data suggest that endocytosis can proceed, once exocytosis has been triggered, under conditions that are quite different from those necessary to support exocytosis, and that the specific requirements for Ca2+ and MgATP in secretion are for the exocytotic limb of the secretory cycle rather than for the associated endocytotic pathway.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 117
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 134 (1993), S. 15-29 
    ISSN: 1432-1424
    Schlagwort(e): Amphibian skin ; Amphibian urinary bladder ; Tight junction ; Paracellular path ; Calcium ; Barium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Selective deposition of BaSO4 in the tight junctions (TJs) of frog skins led to profound and reversible functional alterations of these structures, as revealed by changes of tissue conductance (G), clamping current (I), and fluxes of extracellular markers (sulfate (JSO 4) and sucrose (JSUC)). Experiments were performed with nominally Ca2+ -free simple salt solutions on the apical side (usually KCl) and Na2SO4-Ringer on the inner side of skins. The deposition of BaSO4 in the TJs was obtained by diffusion and/or migration through the paracellular path of Ba2+ from the apical solution and SO 4 2− from the inner solution. A brief presence (2 to 6 min) of apical Ba2+ (Ba2+ pulse) is followed (i.e., when Ba2+ is removed from the apical fluid) by a large increase of G, I, JSO 4 and JSUC, above pre-Ba2+ levels. These attain a steady state within 15 to 30 min (overshoot phase), characterizing a conspicuous increase of the paracellular permeability. During the overshoot phase, a second Ba2+ pulse blocks the paracellular route while apical Ba2+ is present, leading to a new and larger overshoot when the Ba2+ pulse is terminated. Addition of apical Ca2+ triggers the resealing of the TJs, resulting in a full recovery of G, I, JSO 4 and JSUC. This Ca2+ -induced recovery persists when apical Ca2+ is removed. The presence of a normal Ca2+ concentration in the inner bathing Ringer does not induce the recovery process. Tissues remain viable after being submitted to the Ba2+ treatment and the subsequent overshoot. Experiments performed in the urinary bladder of Rana catesbeiana and skins and urinary bladders of Bufo marinus indicate that Ba2+ effect can also be elicited in these tissues. The above results seem to report general properties of the TJs. Incidentally, they warn about the use of Ba2+ as an ion channel blocker in epithelial membranes in association with SO 4 2− -containing solutions on the contralateral side.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 118
    ISSN: 1432-1424
    Schlagwort(e): Drosophila ; per mutants ; pertransgenic ; Lucifer Yellow injections ; Gap junctions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Larval salivary gland cells of Drosophila melanogaster were injected with a fluorescent dye to assess strengths of intercellular communication among such cells, as influenced by mutations at the period locus and by a per transgene. This clock gene had been reported to increase the extent of dye transfer when mutated such that it shortens the period of biological rhythms; the previous study also showed that a per-null mutant decreased the strength of transfer among salivary gland cells. Our re-examination of this feature of larval physiology—in observer-blind analyses, using the per s and per o mutants as well as two per-normal strains—revealed no appreciable differences in extents of dye transfer among these four genotypes. These results are discussed in the context of emerging findings which suggest that the period gene's product controls pacemaker functioning as an intracellularly acting entity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 119
    Digitale Medien
    Digitale Medien
    Springer
    Behavioral ecology and sociobiology 33 (1993), S. 383-391 
    ISSN: 1432-0762
    Schlagwort(e): Operational sex ratio ; Maxim system ; Sperm ; Age of maturity ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Males of the cactophilic fruitfly, Drosophila pachea, produce relatively few but very large sperm, and partition their limited gamete numbers among successive mates. The present study found that males take 10 days longer than females, post-eclosion, to become sexually mature. The pattern of testes development suggests that the need to produce testes long enough to manufacture the giant sperm is the cause of the delayed male maturity. These findings generate the prediction that the operational sex ratio (OSR) of populations will be female-biased. The size, sex ratio, and OSR of natural populations were examined. In general, local populations tended to be small and sex ratios tended to be slightly male-biased. However, as predicted, the OSR of populations, at least in one season, tended to be female-biased, with an average of 2.3 receptive females for each sexually active male. Results of laboratory experiments to determine the relationship between female remating frequency and fitness, and between population OSR and productivity, suggest that natural populations with female-biased OSRs are sperm-limited. The origin and maintenance of sperm gigantism and the unusual sperm-partitioning behavior of males are discussed with respect to population structure.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 120
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 239 (1993), S. 109-114 
    ISSN: 1617-4623
    Schlagwort(e): Drosophila ; melanogaster ; rough ; 97D
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The rough homeobox gene of D. melanogaster is required for the correct patterning of the developing eye. The locus maps to cytological location 97D2-5, a region which has not been extensively characterised. As part of our genetic and molecular characterization of rough we carried out an EMS mutagenesis to generate mutants that map to the surrounding region, 97D2-9 which is deleted in Df(3R)ro-XB3. We have generated 1 visible and 13 lethal mutations which, together with the previously described Toll and ms(3)K10 loci, and other unpublished lethals, define nine complementation groups — four lethal, three semi-lethal, one visible and one male-sterile. In addition to rough, one other locus within this region, 1(3)97De, was shown to be required for formation of the normal pattern of photoreceptor cells in the compound eye.
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  • 121
    Digitale Medien
    Digitale Medien
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    Protoplasma 174 (1993), S. 142-146 
    ISSN: 1615-6102
    Schlagwort(e): Action potential ; Calcium ; Cytoplasmic streaming ; Nitella
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Taking advantage of prolonged action potential under low temperature, we studied temporal relationship among the action potential, increase of cytoplasmic Ca2+ concentration and cessation of cytoplasmic streaming inNitella. The Ca2+ concentration began to increase at a very early stage of the action potential and the cessation of streaming followed that increase.
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  • 122
    ISSN: 1615-6102
    Schlagwort(e): Mechanical stimulation ; Bryonia dioica ; Calcium ; Fluorescent probes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The distribution of membrane-bound calium, activated calmodulin, and callose synthesis was visualized inBryonia dioica internodes before and after mechanical stimulus, using fluorescent probes, respectively, chlorotetracycline, fluphenazine, and aniline blue. Bright chlorotetracycline fluorescence remains localized in the plasma membrane of control cells, 30 s after stimulation calcium left the plasmalemma. A delocalization of activated calmodulin was observed after wounding and deposition of callose, which could not be detected before, appeared in the same times in most cells. The callose formation and the decrease in membrane-associated calcium suggest a rapid influx of calcium in the cytosol and an intervention of this ion in the cascade of the early events underlyingBryonia dioica thigmomorphogenesis.
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  • 123
    ISSN: 1615-6102
    Schlagwort(e): Calcium ; Cyclopiazonic acid ; Endoplasmic reticulum ; Golgi apparatus ; Membrane traffic ; Secretory cell
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary An electron microscopic study of cress (Lepidium sativum L.) roots treated with cyclopiazonic acid (CPA), an inhibitor of the Ca2+-ATPase in the endoplasmic reticulum (ER) has been carried out. Drastic changes in the endomembrane system of the secretory root cap cells were observed. After treatment with CPA dense spherical or elliptoidal aggregates of ER (diameter 2–4 μm) were formed in addition to the randomly distributed ER cisternae characteristic for control cells. The formation of ER aggregates indicates that in spite of an inhibition of the Ca2+ -ATPase in the ER by CPA, membrane synthesis in the ER continued. The ER aggregates are interpreted as a reservoir of ER membrane material newly synthesized during the 2 h CPA-treatment. Hypertrophied Golgi cisternae and secretory vesicles, which are characteristic for secretory cells under control conditions, were completely absent. Additionally the shape of the Golgi stacks was flat and the diameter of the cisternae was shortened by about one third. These phenomena are indicative of an inactive state of the Golgi apparatus. The cellular organization of both other cell types of the root cap, meristematic cells and statocytes, was not visibly affected by CPA, both having a relatively low secretory activity. The formation of ER aggregates as well as the reduction of Golgi compartments are indications for the existence of a unidirectional transport of membrane material from the ER to the Golgi. It is suggested that the membrane traffic from the ER to the Golgi apparatus is regulated by the cytosolic and/or luminal calcium concentration in secretory cells of the root cap.
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  • 124
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 176 (1993), S. 174-177 
    ISSN: 1615-6102
    Schlagwort(e): Cytoplasmic streaming ; Nitellopsis ; Characeae ; Low temperature ; Actin ; Myosin ; Calcium ; pH
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The temperature dependence of cytoplasmic streaming in intact and tonoplast-free cells ofNitellopsis obtusa was studied using a cryomicroscope. The streaming velocity decreases linearly with decrease in the temperature in well-buffered tonoplast-free cells but non-linearly in some intact cells. These results suggest that low temperature causes a disturbance in the homeostasis of calcium and protons, which inhibit cytoplasmic streaming in intact cells.
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  • 125
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 29-50 
    ISSN: 1573-4927
    Schlagwort(e): Drosophila ; peptidase ; activity modifiers ; kinetic parameters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The peptidase system inDrosophila melanogaster (dipeptidase-A, -B, and -C and leucine aminopeptidases G and P) was used as a model to study the effects of modifier genes on activity of enzymes with similar functions. A screen of X, second, and third chromosome substitution isogenic lines revealed the presence of activity modifiers for peptidases on all three chromosomes. Correlation analyses indicated that covariation between some of the peptidase activities is independent of genetic background, while others are associated with variable second chromosomes. Chromosome-specific effects onK m ,V max, and specific activity of partially purified peptidases were also detected. Moreover, a repeatable technique using anion-exchange column chromatography allowed the characterization of possibly two putative peptidic enzymes, glycyl-l-isoleucine-ase andl-leucyl-l-proline-ase, whose kinetic properties differ from the dipeptidases and the leucine aminopeptidases. These findings confirm the existence of activity modifiers for peptidases, much like other enzymes inDrosophila melanogaster.
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  • 126
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 61-74 
    ISSN: 1573-4927
    Schlagwort(e): isofemale ; allele frequency estimation ; population structure ; allozyme ; microsatellites ; restriction fragment length polymorphisms ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Isofemale lines are commonly used inDrosophila and other genera for the purpose of assaying genetic variation. Isofemale lines can be kept in the laboratory for many generations before genetic work is carried out, and permit the confirmation of newly discovered alleles. A problem not realized by many workers is that the commonly used estimate of allele frequency from these lines is biased. This estimation bias occurs at all times after the first laboratory generation, regardless of whether single individuals or pooled samples are used in each well of an electrophoretic gel. This bias can potentially affect the estimation of population genetic parameters, and in the case of rare allele analysis it can cause gross overestimates of gene flow. This paper provides a correction for allele frequency estimates derived from isofemale lines for any time after the lines are established in the laboratory. When pooled samples are used, this estimator performs better than the standard estimator at all times after the first generation. The estimator is also insensitive to multiple inseminations. After the lines have drifted oneN e generations, multiple inseminations actually make the new estimator perform better than it does in singly inseminated females. Simulations show that estimates made using either estimator after the lines have drifted to fixation have a much greater error associated with their use than do those estimates made earlier in time using the correction. In general it is better to use corrected estimates of gene frequency soon after lines are established than to use uncorrected estimates made after the first laboratory generation.
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  • 127
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 31 (1993), S. 29-50 
    ISSN: 1573-4927
    Schlagwort(e): Drosophila ; peptidase ; activity modifiers ; kinetic parameters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The peptidase system inDrosophila melanogaster (dipeptidase-A, -B, and -C and leucine aminopeptidases G and P) was used as a model to study the effects of modifier genes on activity of enzymes with similar functions. A screen of X, second, and third chromosome substitution isogenic lines revealed the presence of activity modifiers for peptidases on all three chromosomes. Correlation analyses indicated that covariation between some of the peptidase activities is independent of genetic background, while others are associated with variable second chromosomes. Chromosome-specific effects onK m ,V max, and specific activity of partially purified peptidases were also detected. Moreover, a repeatable technique using anion-exchange column chromatography allowed the characterization of possibly two putative peptidic enzymes, glycyl-l-isoleucine-ase andl-leucyl-l-proline-ase, whose kinetic properties differ from the dipeptidases and the leucine aminopeptidases. These findings confirm the existence of activity modifiers for peptidases, much like other enzymes inDrosophila melanogaster.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 128
    Digitale Medien
    Digitale Medien
    Springer
    Evolutionary ecology 7 (1993), S. 103-108 
    ISSN: 1573-8477
    Schlagwort(e): host-parasite interactions ; coevolution ; host specificity ; Drosophila ; Howardula
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In eastern North America, the nematodeHowardula aoronymphium parasitizes four species of mushroom-breedingDrosophila:D. falleni andD. recens of the quinaria species group, andD. putrida andD. testacea of the testacea group. One strain ofH. aoronymphium, designated Mendon-87, was initially capable of infecting all four of these host species. After less than 3 years in laboratory culture usingD. falleni as the sole host, this strain had completely lost the ability to infectD. putrida. Two other nematode strains parasitizedD. falleni andD. putrida at equal rates. These results demonstrate the existence of genetic variation for host specificity within this nematode species. More importantly, they show that host specificity can evolve rapidly when only one host is available for parasitization. Ecological conditions are such that natural populations ofH. aoronymphium may comprise numerous host races, lineages incapable of parasitizing the full range of host species. However, I argue that such host races are probably ephemeral and thus unlikely to persist long enough to undergo speciation.
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  • 129
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 238 (1993), S. 383-389 
    ISSN: 1617-4623
    Schlagwort(e): APRT ; Drosophila ; Nuclear matrix attachment site ; Dosage compensation ; Introns
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Aprt locus of Drosophila encodes the structural gene for the purine salvage enzyme adenine phosphoribosyltransferase. Aprt is autosomal and enzyme activity is gene-dose-dependent in Drosophila melanogaster. However, Aprt is X-linked and dosage compensated in Drosophila pseudoobscura, as shown here. The Aprt genes of both Drosophila species contain a DNA sequence associated with nuclear matrix attachment sites and these Aprt sequences specifically bind to nuclear matrix in vitro. Putative promoter sequences positioned upstream of the predicted transcriptional start site in the two Aprt genes have a similar structure of direct repeats with an overlapping dyad symmetry, but the DNA sequence of these motifs is not conserved between the two species. Biological features in mutants of Aprt as well as natural variants suggest that dosage compensation of this gene in Drosophila pseudoobscura is due to a general control Mechanism on X-linked genes rather than a gene-specific mechanism.
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  • 130
    ISSN: 1617-4623
    Schlagwort(e): I factor ; LINE ; Drosophila ; Hybrid dysgenesis ; Maternal inheritance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract I factor is a functional LINE (long interspersed nucleotidic element) which is mobilized in the germ-line of dysgenic SF females during I-R hybrid dysgenesis. Such females are obtained when an oocyte from a reactive stock, devoid of I factors but characterized by a level of reactivity, i.e. its potential for hybrid dysgenesis, is fertilized by a spermatozoon from an I factor-containing inducer stock. In a previous paper we described the expression of an I factor-lacZ fusion. Expression was detected in the ovaries of reactive and dysgenic flies only. In this paper we show that this transgenic activity can be quantified and depends upon the maternally inherited reactivity. Reactivity is not just a permissive state and modifiers of the reactivity level such as heat treatment and ageing change the level of expression of our transgenic fusion accordingly. Moreover, ageing through generations has the same cumulative and reversible effect on both reactivity and I factor expression. Using our fusion as a test for reactivity we show that the silencing of I factor after its introduction into a reactive genome may not be established in a single generation.
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  • 131
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 238 (1993), S. 437-443 
    ISSN: 1617-4623
    Schlagwort(e): Polytene chromosome ; Transformation ; Interband ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Interband DNA of Drosophila melanogaster polytene chromosomes was studied using a novel approach based on the electron microscopic (EM) analysis of chromosome regions carrying DNA fragements of known molecular genetic composition, inserted by P element-mediated transformation. Insertion of such fragments predominantly into interbands makes it possible to clone interband DNA by constructing genomic libraries from transformed strains and probing them with the insert DNA. The transformed strain P[H-sp70:Adh](61C) has insertion in the 61 C7-8 interband on the left arm of chromosome 3. This DNA consists of part of the hsp70 gene promoter fused to the coding region of the Adh gene, and is flanked on either side by P element sequences. We constructed a genomic library from DNA of this strain and isolated a clone containing the insert and the interband DNA. Subsequently the genomic library of wild-type strain was probed with a subclone composed of interband DNA only. We have thus isolated a clone containing the entire native interband. 1289 by of interband DNA was sequenced and found to be AT-rich (53.4%) with numerous regions of overlapping direct and inverted repeats, regulatory sites, and two overlapping open reading frames (ORFs).
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    Standort Signatur Erwartet Verfügbarkeit
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  • 132
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 241 (1993), S. 42-48 
    ISSN: 1617-4623
    Schlagwort(e): Vg mutant ; Antifolates ; Dihydrofolate reductase ; Drosophila ; Nucleotide metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The vestigal (vg) gene encodes a nuclear protein which plays a major role in the formation of the wing of Drosophila. Resistance or sensitivity to aminopterin, an inhibitor of the dihydrofolate reductase enzyme in D. melanogaster, seems to be associated with a specific alteration in vg gene function. Wild-type and vg mutant strains selected for growth on increasing concentrations of aminopterin display changes in physiological and biochemical parameters such as viability on normal and aminopterin-containing media, duration of development, wing phenotype, dihydrofolate reductase activity, and cross-resistance to fluorodeoxyuridine (FUdR) and to methotrexate. Our results indicate that the mechanisms of resistance differ in the wild-type and mutant strains. The vg 83b27 mutant, in which the major part of intron 2 of the vg gene is deleted, is associated with a high rate of resistance to FUdR, an inhibitor of thymidylate synthetase. Moreover, vg 83b27/vg BGheterozygotes, which are wild type when grown on normal medium, display a strong vg phenotype when grown on aminopterin. Our results indicate a role for the vestigial locus in mediating resistance to inhibitors of dTMP synthesis.
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  • 133
    Digitale Medien
    Digitale Medien
    Springer
    Genetica 90 (1993), S. 201-215 
    ISSN: 1573-6857
    Schlagwort(e): micro-evolution ; Drosophila ; alcohol tolerance ; alcohol dehydrogenase ; ethanol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The population ofDrosophila melanogaster inside the wine cellar of Chateau Tahbilk of Victoria, Australia was found by McKenzie and Parsons (1974) to have undergone microevolution for greater alcohol tolerance when compared to the neighboring population outside the cellar. This triggered additional studies at Tahbilk, and at other wine cellars throughout the world. The contributions and interactions of researchers and the development of ideas on the ecology and genetics of this unique experimental system are traced. Although the ADH-F/ADH-S polymorphism was found to be maintained by selection in the Tahbilk populations, the selection is not significantly associated with alcohol tolerance. The environment inside the Tahbilk wine cellar is not as rich in ethanol as was originally anticipated, and selection that affects the alcohol dehydrogenase polymorphism may be more concerned with the relative efficiency with which ethanol is used as a nutrient byD. melanogaster. The synthesis and modification of lipids, particularly in membranes, appears to be important to alcohol tolerance. The studies of the Tahbilk population are at a crossroad. New experimental approaches promise to provide the keys to the selection that maintains the alcohol dehydrogenase polymorphism, and to factors that are important to alcohol tolerance and stress adaptation. From these research foundations at Tahbilk very significant contributions to our future understanding of the genetic processes of evolution can be made.
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  • 134
    ISSN: 1573-6857
    Schlagwort(e): aging ; extended longevity ; genetics of aging ; Drosophila ; gene-environment interactions ; gene regulation ; antioxidants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 135
    ISSN: 1573-6857
    Schlagwort(e): superoxide dismutase ; aging ; Drosophila ; evolutionary genetics ; senescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effects of superoxide dismutase on aging were tested using two differt experimental approaches. In the first, replicated populations with postponed aging were compared with their controls for frequencies of electrophoretic alleles at the SOD locus. Populations with postponed aging had consistently greater frequencies of the allele coding for more active SOD protein. This allele was not part of a segregating inversion polymorphism. The second experimental approach was the extraction ofSOD alleles from different natural populations followed by the construction of differentSOD genotypes on hybrid genetic backgrounds. This procedure did not uncover any statistical effect ofSOD genotype on hybrid genetic backgrounds. This effects on longevity and fecundity due to the family from which a particularSOD genotype was derived. To detect the effects ofSOD genotypes on longevity with high probability would require a ten-fold increase in the number of families used.
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  • 136
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; esterase 6 ; interspecific sequence comparison ; protein evolution ; regulatory evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Esterase 6 (Est-6/EST6) is the major β-carboxylesterase inD. melanogaster and its siblingsD. simulans andD. mauritiana. It is expressed in several tissues but its major site of expression is the sperm ejaculatory duct of the adult male. Although EST6 activity affects reproductive fitness, there are high levels of electrophoretic and activity polymorphism, at least withinD. melanogaster andD. simulans. Here we present the nucleotide sequences of anEst-6 allele and its flanking regions from each ofD. simulans andD. mauritiana and compare them with the publishedD. melanogaster sequences. As might be expected, replacement sites are significantly less divergent than exon silent sites in all comparisons, suggesting that selection is acting to maintain EST6 structure and function among the three species. Nevertheless, the ratio of the levels of replacement to silent site divergence is still much higher forEst-6 than for seven of ten other genes (including both isozyme-coding loci) for which comparable data have been published for these species. This is consistent with the high levels of EST6 electrophoretic polymorphism withinD. melanogaster andD. simulans and implies that selective constraints against amino acid change are relatively weak for EST6. By contrast, comparisons involving promotor sequences show that the level of divergence in the first 350bp 5′ of the gene is significantly lower than those for four of the six other loci for which comparable data have been published for these species. In particular, there are two perfectly conserved stretches (−1 to −158bp and −219 to −334bp) each over 100bp long included in this 350bp region. Thus the data suggest a relatively low level of selective constraint on the amino acid sequence of EST6 but a relatively high level of constraint on sequences affecting aspects of its expression.
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  • 137
    Digitale Medien
    Digitale Medien
    Springer
    Genetica 90 (1993), S. 157-163 
    ISSN: 1573-6857
    Schlagwort(e): cell cycle, development ; Drosophila ; embryogenesis ; proliferation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The zygotic expression of only a fewDrosophila genes is known to be required for completion of the normal embryonic mitoses. Molecular genetic analyses of these genes reveal that they fall into two classes, those whose mRNA levels are regulated in a stage and/or tissue-specific fashion to control cell cycle events during embryogenesis, and those in which, in the absence of functional zygotic expression, the maternal mRNA contribution does not provide sufficient product to complete the normal embryonic mitoses. Genes that comprise the first class are involved in the developmental control of the cell cycle, while those of the second class identify components of the cell cycle machinery.
    Materialart: Digitale Medien
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  • 138
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; stambh A ; paralysis ; embryonic lethal ; neural hypertrophy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The mutantstambhA 1 (2–56.8) ofDrosophila melanogaster was identified as a reversible temperature sensitive adult and larval paralytic. We have (i) isolated and analysed phenotypes of one new homozygous viable paralytic allele and two recessive unconditional embryonic lethal alleles ofstmA and (ii) studied the interaction of the viable paralytic alleles with ts paralytic mutantsnap ts1 (2–55.2) andpara ts1 (1–53.9). The homozygous viable paralytic allelesstmA 2 andstmA 1 are semi dominant neomorphs. The lethal allelesstmA 12 andstmA 7 appear to be amorphs. Unhatched embryos expressing lethalstmA alleles showed hypotrophy of the anterior dorsal cuticle overlying the brain with a concomitant hypertrophy of the anterior dorsal neurogenic region (the brain). The ventral cuticle was poorly differentiated, and the ventral nerve chord showed mild hypertrophy and poor organisation. The epidermal cells in 12–13 h old embryos did not show the normal palisade layer arrangement. These phenotypes are similar to mutant phenotypes of the neurogenic class of genes whose wild type functions are necessary for intercellular communication. The allelesstmA 1 andstmA 2 do not appear to interact with the paralytic mutantsnap ts1 orpara ts1 in double mutant combinations. On the basis of our results it is proposed thatstmA may belong to the neurogenic class of genes.
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  • 139
    Digitale Medien
    Digitale Medien
    Springer
    Genetica 90 (1993), S. 239-268 
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; esterases ; multigene families ; structure function models
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Over 30 carboxylester hydrolases have been identified inD. melanogaster. Most are classified as acetyl, carboxyl or cholinesterases. Sequence similarities among most of the carboxyl and all the cholinesterases so far characterised fromD. melanogaster and other eukaryotes justify recognition of a carboxyl/cholinesterase multigene family. This family shows minimal sequence similarities with other esterases but crystallographic data for a few non-drosophilid enzymes show that the family shares a distinctive overall structure with some other carboxyl and aryl esterases, so they are all put in one superfamily of /β hydrolases. Fifteen esterase genes have been mapped inD. melanogaster and twelve are clustered at two chromosomal sites. The constitution of each cluster varies acrossDrosophila species but two carboxyl esterases in one cluster are sufficiently conserved that their homologues can be identified among enzymes conferring insecticide resistance in other Diptera. Sequence differences between two other esterases, the EST6 carboxyl esterase and acetylcholinesterase, have been interpreted against the consensus super-secondary structure for the carboxyl/cholinesterase multigene family; their sequence differences are widely dispersed across the structure and include substantial divergence in substrate binding sites and the active site gorge. This also applies when EST6 is compared across species where differences in its expression indicate a difference in function. However, comparisons within and among species where EST6 expression is conserved show that many aspects of the predicted super-secondary structure are tightly conserved. Two notable exceptions are a pair of polymorphisms in the substrate binding site of the enzyme inD. melanogaster. These polymorphisms are associated with differences in substrate interactionsvitro} and demographic data indicate that the alternative forms are not selectively equivalentin vivo.
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  • 140
    Digitale Medien
    Digitale Medien
    Springer
    Genetica 91 (1993), S. 111-125 
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; evolution ; reproduction ; senescence ; sperm competition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Populations ofDrosophila melanogaster that had been subjected to long-term selection favoring either delayed or rapid senescence were compared with respect to age-specific components of male reproductive success involving sperm competition. These components of reproductive success were divided into those related to sperm ‘defense’ (protection of sperm from other males), and into those related to sperm ‘offense’ (ability to mate with previously mated females and to displace the sperm of other males). Males were tested at four ages ranging from 1–2d to 5–6 wk after eclosion. Several aspects of sperm defense capability showed clear evidence of senescent decline. Furthermore, males from populations selected for delayed senescence were superior to males from control (rapid senescence) populations with regard to components of sperm defense. The superiority of males from populations with delayed senescence either increased as a function of male age, or was present at all ages tested. These results indicate that the rate of reproductive senescence in maleD. melanogaster can be altered in predictable directions by artificial selection. There were no differences between selection regimes with regard to sperm offense, and most components of sperm offense did not show clear evidence of senescence. The improved late-age reproductive success of males from populations selected for delayed senescence did not appear to entail any cost or trade-off at early ages with respect to the reproductive traits examined in these experiments.
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  • 141
    Digitale Medien
    Digitale Medien
    Springer
    Genetica 91 (1993), S. 167-182 
    ISSN: 1573-6857
    Schlagwort(e): lifespan ; elongation factor ; Drosophila ; life history evolution ; genetic manipulation ; tradeoffs ; genetic correlations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract This paper summarizes three experiments on the genetic manipulation of fitness components involved in the evolution of lifespan through the introduction of an additional copy of the gene for elongation factor EF-1α into the genome ofDrosophila melanogaster. The first experiment checked a prior claim that enhanced expression of elongation factor increased the lifespan of virgin male fruitfies. It used inbred stocks; three treatment and three control lines were available. The second experiment put one treatment and one control insert into different positions on the third chromosome, then measured the influence of six genetic backgrounds on treatment effects in healthier flies. The third experiment put six treatment and six control inserts into the genetic background whose lifespan was most sensitive to the effects of treatment in the second experiment, then measured the influence of insert positions on treatment effects in healthy flies. The treatment never increased the lifespan of virgin males. It increased the lifespan of mated females in inbred flies reared to eclosion at 25°, reduced it in the positions experiment, and made no difference to lifespan in the backgrounds experiment. When it increased lifespan, it reduced fecundity. In inbred flies and in the positions experiment, the treatment reduced dry weight at eclosion of females. Marginal effects of gene substitutions on tradeoffs were measured directly. The results suggest that enhanced expression of elongation factor makes local changes within the bounds of tradeoffs that are given by a pre-existing physiological structure whose basic nature is not changed by the treatment.
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  • 142
    ISSN: 1573-6857
    Schlagwort(e): aging ; Drosophila ; electrophoresis ; evolution ; longevity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Five populations ofDrosophila melanogaster that had been selected for postponed aging were compared with five control populations using two-dimensional protein gel electrophoresis. The goals of the study were to identify specific proteins associated with postponed aging and to survey the population genetics of the response to selection. A total of 321 proteins were resolvable per population; these proteins were scored according to their intensity. The resulting data were analyzed using resampling, combinatoric, and maximum parsimony methods. The analysis indicated that the populations with postponed aging were different from their controls with respect to specific proteins and with respect to the variation between populations. The populations selected for postponed aging were more heterogeneous between populations than were the control populations. Maximum parsimony trees separate the selected populations, as a group, from their controls, thereby exhibiting a homoplastic pattern.
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  • 143
    Digitale Medien
    Digitale Medien
    Springer
    Genetica 92 (1993), S. 1-22 
    ISSN: 1573-6857
    Schlagwort(e): alcohol dehydrogenase ; Drosophila ; evolution ; gene ; protein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Evolutionary genetics embodies a broad research area that ranges from the DNA level to studies of genetic aspects in populations. In all cases the purpose is to determine the impact of genetic variation on evolutionary change. The broad range of evolutionary genetics requires the involvement of a diverse group of researchers: molecular biologists, (population) geneticists, biochemists, physiologists, ecologists, ethologists and theorists, each of which has its own insights and interests. For example, biochemists are often not concerned with the physiological function of a protein (with respect to pH, substrates, temperature, etc.), while ecologists, in turn, are often not interested in the biochemical-physiological aspects underlying the traits they study. This review deals with several evolutionary aspects of the Drosophila alcohol dehydrogenase gene-enzyme system, and includes my own personal viewpoints. I have tried to condense and integrate the current knowledge in this field as it has developed since the comprehensive review by van Delden (1982). Details on specific issues may be gained from Sofer and Martin (1987), Sullivan, Atkinson and Starmer (1990); Chambers (1988, 1991); Geer, Miller and Heinstra (1991); and Winberg and McKinley-McKee (1992).
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  • 144
    Digitale Medien
    Digitale Medien
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    Genetica 88 (1993), S. 165-173 
    ISSN: 1573-6857
    Schlagwort(e): Drosophila ; meiosis ; recombination ; spermatogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two meiotic genes from natural populations are described. A female meiotic mutation,mei(1)g13, mapped to 17.4 on the X chromosome, causes nondisjunction of all homologs except for the fourth chromosomes. In addition, it reduces recombination by 10% in the homozygotes and causes 18% increased recombination in the heterozygotes. A male meiotic mutation,mei-1223 m144 , is located on the third chromosome. Although this mutation causes nondisjunction of all chromosomes, each chromosome pair exhibits a different nondisjunction frequency. Large variations in the sizes of the premature sperm heads observed in the homozygotes may reflect irregular meiotic pairing and the subsequent abnormal segregation, resulting in aneuploid chromosome complements.
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  • 145
    ISSN: 1573-6857
    Schlagwort(e): alternative splicing ; Drosophila ; dunce ; pleiotropy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The D. melanogaster dunce gene is involved in both the learning and memory processes of the fly. The gene encodes for a cAMP-specific phosphodiesterase, a function playing a central role in the regulation of the intracellular cAMP level. Molecular cloning of dunce has so far not been completely achieved, although it is known that the gene encodes a large set of RNAs and has a complex organization, extending for more than 140 kilobases and containing several genes within its introns. Here wer report the isolation and the characterization of 21/7, a cDNA clone representative of a novel dunce splicing pattern. The nucleotide sequence of this clone led to the identification of a dunce exon included in at least one transcript so far uncharacterized.
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  • 146
    Digitale Medien
    Digitale Medien
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    Genetica 91 (1993), S. 89-98 
    ISSN: 1573-6857
    Schlagwort(e): aging ; senescence ; lifespan ; survival ; Drosophila ; evolution ; fertility
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Evolutionary explanations of aging (or senescence) fall into two classes. First, organisms might have evolved the optimal life history, in which survival and fertility late in life are sacrificed for the sake of early reproduction or high pre-adult survival. Second, the life history might be depressed below this optimal compromise by the influx of deleterious mutations; since selection against late-acting mutations is weaker, deleterious mutations will impose a greater load on late life. We discuss ways in which these theories might be investigated and distinguished, with reference to experimental work withDrosophila. While genetic correlations between life history traits determine the immediate response to selection, they are hard to measure, and may not reflect the fundamental constraints on life history. Long term selection experiments are more likely to be informative. The third approach of using experimental manipulations suffers from some of the same problems as measures of genetic correlations; however, these two approaches may be fruitful when used together. The experimental results so far suggest that aging inDrosophila has evolved in part as a consequence of selection for an optimal life history, and in part as a result of accumulation of predominantly late-acting deleterious mutations. Quantification of these effects presents a major challenge for the future.
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  • 147
    Digitale Medien
    Digitale Medien
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    Journal of comparative physiology 163 (1993), S. 99-106 
    ISSN: 1432-136X
    Schlagwort(e): Prolactin ; Growth hormone ; Calcium ; Pituitary ; Eel, Anguilla japonica
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Effects of changes in environmental Ca2+ on the secretion of prolactin, a possible hypercalcemic hormone, were examined both in vivo and in vitro in the Japanese ecl, Anguilla japonica. Transfer of seawater- or freshwater-adapted fish to fresh water, fresh water containing 10 mmol Ca2+ · 1-1 sea water, Ca2+-free sea water, or deionized water was accompanied by significant changes in plasma Ca2+ levels after 7 days, except for the fish transferred from fresh water to fresh water and from sea water to sea water. Changes in external Ca2+ concentrations did not affect plasma prolactin levels, although plasma prolactin levels as well as pituitary prolactin contents were significantly greater in fish in a hypotonic environment than those in a hypertonic environment, regardless of the external Ca2+ concentration. Hypercalcemia, induced by removal of the corpuscles of Stannius, did not alter plasma prolactin levles. Incubation of the pituitary in the medium with different Ca2+ concentrations (up to 2.9 mmol·l-1) did not affect the basal release of prolactin, except at an extremely low Ca2+ concentration (less than 0.1 mmol·l-1) where prolactin release was inhibited. Addition of Ca2+ ionophore (A23187) to the medium led to a marked and significant increase in prolactin release, indicating that an increase in intracellular Ca2+ stimulates prolactin release. However, the effect was not specific to prolactin cells; a similar increase was seen in growth hormone release. These results indicate that changes in environmental Ca2+ concentration may not be the primary factor influencing prolactin secretion in the eel; changes in environmental osmolality or Na+ levels seem to be more critical for the regulation of prolactin secretion.
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  • 148
    Digitale Medien
    Digitale Medien
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    Behavior genetics 23 (1993), S. 99-104 
    ISSN: 1573-3297
    Schlagwort(e): Anesthesia ; photoresponse ; phototaxis ; relative light values ; behavior ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract Five isofemale strains from each of four sympatric species,Drosophila immigrans, D. repleta, D. melanogaster, andD. affinis, were lightly anesthetized with ether, CO2, Flynap, or cold temperature. The photoresponse of each treatment group was measured in an open field and a Y-tube apparatus. Relative light values were compared with those of the unanesthetized control groups of each species, as well as among the different treatments themselves and among species. Significant differences between species were apparent for all treatments in the Y-tube and for all treatments except ether and CO2 in the open field. Response to anesthesia may differ between species due, in part, to their differing genotypes. Comparing treatment groups within species in the Y-tube design, all species exceptD. melanogaster showed significant differences between treatments. In the open field, onlyD. affinis was significantly affected. Particularly in the Y-tube, anesthetized flies generally differed significantly from the controls, indicating that the use of anesthesia during a behavioral study could cause deviations in behavior from that of normal unanesthetized flies.
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  • 149
    Digitale Medien
    Digitale Medien
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    Journal of solution chemistry 21 (1992), S. 525-532 
    ISSN: 1572-8927
    Schlagwort(e): Calcium ; molybdate ; aqueous ; thermodynamic ; complexation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The solubility of powellite [CaMoO4(c)] was studied in aqueous Na2MoO4, CaCl2 and Ca(NO3)2 solutions ranging in concentrations from 1×10−4M to 1.0M and over equilibration times extending to 36 days. Our experimental data were interpreted using the aqueous ion-interaction model of Pitzer and coworkers. The Ca2+−MoO 4 2− ion-interactions were found to be analogous to Ca2+−SO 4 2− . The use of Ca2+−MoO 4 2− ion-interactions parameters (β(0)=0.2, β(1) = 3.1973 and β(2)) and a logK sp of −7.93 gave excellent predictions of all of the experimental data. Commonion ternary interaction parameters such as MoO 4 2− −Cl− or MoO 4 2− −NO 3 − were not required.
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  • 150
    Digitale Medien
    Digitale Medien
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    Calcified tissue international 50 (1992), S. 391-396 
    ISSN: 1432-0827
    Schlagwort(e): Bone ; Matrix ; Phosphoproteins ; Biomineralization ; Calcium ; Nucleation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Osteopontin, bone sialoprotein, and bone acidic glycoprotein-75 are three acidic phosphoproteins that are isolated from the mineralized phase of bone matrix, are synthesized by osteoblastic cells, and are generally restricted in their distribution to calcified tissues. Although each is a distinct gene product, these proteins share aspartic/glutamic acid contents of 30–36% and each contains multiple phosphoryl and sialyl groups. These properties, plus a strict relationship of acidic macromolecules with cell-controlled mineralization throughout nature, suggest functions in calcium binding and nucleation of calcium hydroxyapatite crystal formation. However, direct proof for such roles is still largely indirect in nature. The purpose of this review is to present two speculative hypotheses regarding acidic phosphoprotein function. The goal was to use new sequence information along with database comparisons to develop a structural rationalization of how these proteins may function in calcium handling by bone. For example, our analysis has identified a conserved polyacidic stretch in all three phosphoproteins which we propose mediates metal binding. Also, conserved motifs were identified that are analogous with those for casein kinase II phosphorylation sites and whose number correlates well with that of phosphoryl groups/protein. A two-state conformational model of calcium binding by bone matrix acidic phosphoproteins is described which incorporates these findings.
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  • 151
    ISSN: 1432-0827
    Schlagwort(e): Calcitonin ; Antibodies ; Calcium ; Osteoporosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary In order to evaluate the potential inhibition of the acute anti-osteoclastic activity of salmon calcitonin (SCT) by specific antibodies (Ab), we compared the SCT-induced hypocalcemic effect in young male rabbits with significant titers of high affinity Ab and in matched animals without Ab. Immunization of rabbits was performed by repetitive s.c. injections of SCT and Freund adjuvant. Ab were present in four-fifths of SCT-treated rabbits (Ab+). Their titer varied from 0.8×10(-9) to 30×10(-9) M/liter and their constant of affinity from 0.97×10(9) to 4.2×10(9) L/M. Intravenous injection of 1 IU/kg SCT to Ab+ rabbits induced a significant decrease (P〈0.01) of ionized serum calcium (Ca2+) after 30 minutes (mean±SD:-9±0.6%) and until the 240th minute of the test (-16.7±4.7%), with a maximum after 120 minutes (-22.6±2%). This was not significantly different from the hypocalcemic effect measured after the same procedure performed in matched animals without Ab (Ab-): significant decrease in Ca2+ (P〈0.01) after 30 minutes (-8.2±2.2%), maximal after 150 minutes (-23.2±4.9%), and lasting until 210 minutes (-14.5±3.7%). We conclude that, in the particular model of the male young rabbit, specific anti-SCT Ab do not block or reduce the acute anti-osteoclastic activity of SCT.
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  • 152
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 50 (1992), S. 144-148 
    ISSN: 1432-0827
    Schlagwort(e): Enamel ; Fluoride ; Hydroxyapatite ; Magnesium ; Octacalcium phosphate ; 32Phosphate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Considerable evidence suggests that an acidic calcium phosphate, such as octacalcium phosphate (OCP) or brushite, is involved as a precursor in enamel and other hard tissue formation. Additionally, there is in vitro evidence suggesting that fluoride accelerates and magnesium inhibits the hydrolysis of OCP to hydroxyapatite (OHAp). As the amount of OCP or brushite in enamel cannot be measured directly in the presence of an excess of hydroxyapatite, a procedure was developed that allows for their indirect in vivo quantification as pyrophosphate. This permits study of the effects of fluoride and magnesium ions on enamel mineral synthesis. Rat incisor calcium phosphate was labeled by intraperitoneal injection of NaH2 32PO4. The rats were then subjected to various fluoride and magnesium treatments with subcutaneous implanted osmotic pumps. They were then killed at predetermined intervals; the nascent sections of the incisors were collected, cleaned, and pyrolyzed at 500°C for 48 hours to convert acidic calcium phosphates to calcium pyrophosphate; the pyrophosphate was separated from orthophosphate by anion-exchange chromatography; and the resulting fractions were counted by liquid scintillation spectrometry. The activities of the pyro- and orthophosphate fractions were used to calculate the amount of acidic calcium phosphate present in the nascent mineral. The results demonstrated that the percentage of radioactive pyrophosphate in nascent incisors decreased with time, with increasing serum F- concentration, and with decreasing serum magnesium content. The technique described here should prove to be a powerful new tool for studying the effects of various agents on biological mineral formation.
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  • 153
    ISSN: 1432-0827
    Schlagwort(e): Computed tomography ; Trabecular bone density ; Strontium ; Calcium ; Atomic absorption spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Changes in the average linear attenuation coefficient (LAC) within a fixed measurement volume in the proximal end of the dog tibia, which contains trabecular bone and associated soft tissues (the trabecular bone “space”), were monitored continuously using gamma-ray computed tomography (γ-CT) prior to, during, and following intravenous infusion of strontium (Sr) lactate. An infusion of 1.3–4.7 g of Sr over a period of 110–160 minutes into 20-kg dogs resulted, within 6–8 hours, in an increase of 0.019–0.045 cm-1 (P〈0.002) in the LAC. Calibration of the γ-CT system showed that 0.44 mg/cm3 of Sr produced a change of 0.01 cm-1 in the LAC. Using this conversion factor, the Sr concentration in the trabecular bone space resulting from infusion, as measured by flame atomic absorption spectroscopy, agreed with that predicted by the change observed in the LAC. Sr present in the serum and urine was consistent with the changes observed in the LAC over the study period. Control dogs infused with mineral-free solutions showed no change in LAC. Calcium equivalents required to give the changes observed in the LAC using Sr indicate that variations in skeletal turnover in man can be monitored in the peripheral skeleton using γ-CT.
    Materialart: Digitale Medien
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  • 154
    ISSN: 1432-0827
    Schlagwort(e): Octacalcium phosphate ; Apatite ; Fluoride ; Intergrowth ; Enamel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary In order to study the effect of F- on tooth enamel-like apatite formation, crystal growth experiments were carried out in the presence of 0.1}2 ppm F- at 37°C and at pH 6.5 in a model system of enamel formation where octacalcium phosphate (OCP) was stable. Morphology changed from long and thin ribbons to small needle-like plates, and the product changed from OCP to apatite with an increase in F- concentration. In the presence of 0.1–1 ppm F-, apatite-OCP intergrowth took place, and crystals composed of apatite and OCP lamellas were formed. These crystals showed long and thin plate-like morphology and embedded an OCP lamella in the center of the crystal. The OCP lamella and its (100) planes were parallel to the (100) planes of apatite. The thickness of OCP decreased and that of apatite increased with an increase in F- concentration. Some apatite crystals obtained at 1 ppm F- embedded a central plane instead of the distinct OCP lamella. The result indicates that initially formed, thin, plate-like OCP acted as a template for the subsequent epitaxial overgrowth of apatite and, moreover, F- played an important role in regulating the apatite-OCP intergrowth.
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  • 155
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 51 (1992), S. 42-47 
    ISSN: 1432-0827
    Schlagwort(e): Kidney ; Endoplasmic reticulum ; Calcium ; In vivo
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Calcium uptake by the endoplasmic reticulum (ER) is important for cellular calcium homeostasis, yet its regulation in nonmuscle cells is poorly understood. We reported that Ca2+ uptake by a light fraction of canine renal cortical ER (LER) is stimulated by protein kinase C in vitro. Here we describe conditions in vivo that stimulated renal cortical LER Ca2+ uptake. Thirty minutes after contralateral nephrectomy in the dog, 45Ca2+ uptake into renal cortical LER was increased 42% above control LER. There was no difference in LER Ca2+ uptake 24 hours after uninephrectomy. Acute denervation did not reproduce the increase in LER 45Ca2+ uptake seen at 30 minutes after uninephrectomy, nor did prior thyroparathyroidectomy abolish it. Forty-eight hours after thyroparathyroidectomy, 45Ca2+ uptake activity into renal cortical LER was decreased ≈sevenfold. In a proximal tubular cell line (LLC-PK1), 30-minute incubation with 12-O-tetradecanoylphorbol-13-acetate doubled 45Ca2+ uptake into a nonmitochondrial pool. Pretreatment with epidermal growth factor halved ER Ca2+ uptake, whereas insulin-like growth factor and growth hormone, alone or in combination, had no effect. Our data suggest that Ca2+ uptake into renal cortical ER is stimulated acutely during compensatory renal growth, perhaps through protein kinase C, and is stimulated chronically by parathyroid hormone.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 156
    Digitale Medien
    Digitale Medien
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    Journal of molecular evolution 35 (1992), S. 51-59 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Gart locus ; Chironomus tentans ; Purine nucleotide biosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The Drosophila Gart locus consists of two genes. One gene encodes three enzymes in the de novo purine nucleotide biosynthesis pathway [glycinamide ribonucleotide synthetase (GARS), aminoimidazole ribonucleotide synthetase (AIRS), and glycinamide ribonucleotide transformylase (GART)]. The second gene lies within an intron of the purine gene and encodes a cuticle protein. To investigate the evolution of the Gart locus, the Chironomus tentans homolog was cloned by screening a genomic DNA library with a polymerase chain reaction product. This study shows that the interesting structural features of this locus conserved in two distant Drosophila species are not found in the Chironomus homolog. These features include the cuticle protein gene nested within an intron and the existence of an alternative transcript to yield a monofunctional enzyme. In addition, the extremely rapid divergence of coding sequence seen for members of the tandemly duplicated AIRS domain in Drosophila is found to be much less rapid in Chironomus.
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  • 157
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; per gene ; Threonine-Glycine ; repeat sequence ; melanogaster subgroup phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The Threonine-Glycine (Thr-Gly) region of the period gene (per) in Drosophila was compared in the eight species of the D. melanogaster subgroup. This region can be divided into a diverged variable-length segment which is flanked by more conserved sequences. The number of amino acids encoded in the variable-length region ranges from 40 in D. teissieri to 69 in D. mauritiana. This is similar to the range found within natural populations of D. melanogaster. It was possible to derive a Thr-Gly “allele” of one species from that of another by invoking hypothetical Thr-Gly intermediates. A phylogeny based on the more conserved flanking sequences was produced. The results highlighted some of the problems which are encountered when highly polymorphic genes are used to infer phylogenies of closely related species.
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  • 158
    Digitale Medien
    Digitale Medien
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    Journal of molecular evolution 34 (1992), S. 130-140 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila ; Sophophora ; cDNA-DNA hybridization ; Phylogenetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have performed DNA-DNA hybridization experiments among several species of Drosophila using the evolutionarily conserved portion of the genome representing sequences coding for amino acids of proteins. This was done by using as tracer, radioactively labeled complementary DNA that was reverse transcribed from adult mRNA. We show that this procedure extends phylogenetically the distance over which the technique can be applied to fast-evolving groups such as Drosophila. The major phylogenetic conclusions are (1) the subgenus Sophophora is a monophyletic lineage; (2) within Sophophora the melanogaster subgroup is closer to the obscura group than either group is to the willistoni group; (3) the subgenus Drosophila is complex with most major lineages originating deep in the phylogeny; the subgenus may not be monophyletic; (4) as with most groups classically placed in Drosophila, the Hawaiian Drosophila originate early, supporting the notion that this lineage is older than the extant islands; and (5) the virilis/repleta lineage is monophyletic within Drosophila.
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  • 159
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 170 (1992), S. 311-316 
    ISSN: 1432-1351
    Schlagwort(e): Phototransduction ; Limulus polyphemus ; Inositol trisphosphate ; Calcium ; Latency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The latent period before depolarization of Limulus ventral photoreceptors by light flashes was compared with that following brief, intracellular, pressure-injection of d-myo-inositol 1,4,5 trisphosphate. At temperatures between 18 °C and 22 °C and with an extracellular calcium concentration of 10 mM, the responses of 4 cells to light and to injections of 100 μM inositol trisphosphate displayed average latencies of 71 and 56 ms, respectively. The latencies of responses to InsP3 included an estimated 20 ms dead-time inherent in the injection method. Reducing the temperature lengthened the latency of the response to light (Q10 approximately 3.2 between 7 and 22 °C) more than that to inositol trisphosphate (Q10 approximately 2.3). Bathing the photoreceptors in seawater containing no added calcium and 1 mM of the calcium chelator EGTA greatly increased the latency of the light response at all temperatures, but did not increase the latency of the response to inositol trisphosphate. We conclude that the response to inositol trisphosphate lacks the calcium- and temperature-sensitive latent period which characterizes the response to light. If inositol trisphosphate acts, via the release of stored calcium, to stimulate an intermediate in the visual cascade, then that intermediate would appear to be downstream from the latency-generating mechanism.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 160
    Digitale Medien
    Digitale Medien
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    Journal of comparative physiology 171 (1992), S. 413-419 
    ISSN: 1432-1351
    Schlagwort(e): Calcium ; Cobalt ; Lateral line ; Behavior
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The hypothesis that the blind cave fish (Astyanax hubbsi) adjusts the level of stimulation to its lateral line system (LLS) by varying its own velocity was examined. When the sensitivity of the LLS sense organs was reduced by lowering the Ca2+ concentration in the water or by adding Co2+ the fish compensated for this by swimming at a higher velocity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 161
    ISSN: 1420-9071
    Schlagwort(e): Aromatic plants ; essential oils ; Drosophila ; insecticides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Effects of the essential oils (EOs) extracted from eleven aromatic plants belonging to the Lamiaceae family (common in the Greek flora) were examined upon three different developmental stages ofDrosophila auraria. All of the EOs examined exhibited insecticidal effects, either by preventing egg hatching, or by causing the death of larvae and adult flies. In several cases, malformation and/or prohibition of puparium formation was also observed.
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  • 162
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 201 (1992), S. 221-234 
    ISSN: 1432-041X
    Schlagwort(e): Muscle ; Salivary glands ; Gut ; Programmed cell death ; Steroid hormones ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In holometabolous insects, the steroid molting hormone 20-OH-ecdysone (ecdysterone) orchestrates the diverse developmental events of metamorphosis, in large part by regulating gene expression. In Drosophila, the Broad Complex (BR-C) is one of the first loci to be induced by ecdysterone at the end of larval life, and is essential for translating the hormonal signal into the behavioral and anatomical events which herald the onset of metamorphosis. BR-C products are believed to act by binding to and modifying the transcriptional activities of other hormone-sensitive genes. In addition to abnormalities of the epidermis, BR-C mutants dying during metamorphosis manifest a syndrome of multiple internal tissue defects which represent a failure of the larval-to-adult transition. We have reported features of central nervous system metamorphosis requiring BR-C function, notably morphogenetic movements and optic lobe organization. In this paper we describe defective development of salivary glands, flight muscles, and gut in BR-C mutants, including: persistence of larval salivary glands; failure of the adult salivary glands to extend into the thorax; abnormalities of midgut transition and of proventriculus structure and location; and absence of dorsal-ventral indirect flight muscles. Some of these abnormalities represent defects in programmed cell death. Distinct patterns of phenotypes were seen in mutants of each of the three lethal complementation groups comprising the BR-C. The patterns of phenotypes suggest overlapping but distinct functions encoded by this complex locus.
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  • 163
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; Imaginal discs ; Pattern formation ; rotund
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary InDrosophila imaginal discs, pattern formation requires the activity of three positional information systems, antero-posterior (A/P), dorso-ventral (D/V) and proximo-distal (P/D). Three genes,Decapentaplegic, Distal-less androtund (rn), involved in pattern formation along the P/D axis have been characterized. Thern gene is required in a sub-distal region, localized at a similar position along the P/D axis in all appendages; it encodes two major transcripts, m1.7 and m5.3, both expressed in the central region of all the major imaginal discs. The present study of these transcripts in severalrn mutant favours m5.3 as encodingrn morphogenetic function in the imaginal discs. The fine characterization of its distribution partitions all major imaginal discs in domains along the P/D axis. The ventral and dorsal discs appear to be similarly but not identically organized: two P/D domains are evident in the wing and haltere discs whilst the leg and antenna discs appear to be composed of at least three. We also show that m5.3 is sex-regulated in the genital disc and thatrn function is required for proper development of a sub-distal structure of the female genitalia. This suggests that the primordia of the female genitalia may be organized in a similar way to the other imaginal discs, and strongly supports the hypothesis thatrn function is specific to pattern formation along the P/D axis and that it may be involved in the establishment or maintenance of this pattern.
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  • 164
    Digitale Medien
    Digitale Medien
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    Development genes and evolution 201 (1992), S. 364-375 
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; Tissue culture ; In vitro ; Invertebrate embryogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have devised techniques to culture whole, dissected embryos of Drosophila melanogaster. We examine multiple aspects of the morphological and physiological development of the epidermis, musculature, nervous system, and internal organs in this cultured preparation, and show that in vitro development closely parallels normal embryogenesis. These techniques permit a wide range of experimental manipulations during embryogenesis and allow us to extend observations through late embryonic stages, after cuticle deposition. Applications of this technique are presented.
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  • 165
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 201 (1992), S. 105-112 
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; Genital disc ; tra-2 ts ; Differentiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Diplo-X flies homozygous for the transform-er-2 ts (tra-2 ts) mutation develop into females at 16° C, while they develop into males at 29° C (Belote and Baker 1982). By means of this conditional mutation, we have carried out a detailed analysis of the development of the genital disc. Temperature shifts between 16 and 29° C, in both directions, and temperature pulses at 29° C, have been applied during the larval growth of tra-2 ts homozygous diplo-X flies, and the external derivatives of the genital disc have been analysed. Genital discs shifted from 16 to 29° C rapidly lose their capacity to differentiate female genital structures, while they become able to differentiate male genital structures whose inventory is more complete the earlier in larval development the temperature shift is carried out; moreover, duplicated male genital structures were observed. In the shift from 29 to 16° C, the genital disc loses its capacity to differentiate male genital structures, while it becomes able to differentiate female genital structures. The inventory of male structures is smaller, and the inventory of the female structures is more complete, the earlier in larval development the temperature is shifted. No duplicated female or male genital structures were observed in the downshift experiment. With respect to the analia, the shift from 16 to 29° C resulted in the quick formation of pure male anal plates, while in the opposite shift the formation of pure female anal plates occurred gradually. Moreover, the time course for the dorsal and ventral anal plates to show normal female phenotype was different: when the dorsal anal plates were completely normal, it was still possible to find incomplete ventral anal plates. In the pulse experiment at 29° C, the genital disc is able to differentiate both female and male genital structures, although the inventory of the latter ones was not complete. In addition, the capacity of the genital disc to differentiate male genital structures depended on the duration of the temperature pulse. The anal plates were always female, although they showed a reduction in their size, the ventral female anal plate being more affected than the dorsal one. No male anal plates were observed. The results have revealed that the genital disc follows a sequence in its capacity to differentiate female or male adult structures. We suggest that this sequence reflects the sequence of determination events occurring in the genital disc during its larval growth. In addition, results shown here provide evidence for the existence in the female genital primordium of a set of cells capable of giving rise either to female genital structures (ventral vaginal plates) or to male genital structures (hypandrium and penis apparatus). We also present evidence supporting the previous idea of two primordia for the anal plates.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 166
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; Homeotic gene regulation ; Antennapedia ; Development ; β-galactosidase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In order to study the regulation of spatial and temporal expression of the homeotic gene Antennapedia (Antp) in Drosophila melanogaster, we have constructed fusion genes which contain Antp sequences linked to the reporter gene lac Z of Escherichia coli. In one case of P-element transformation, a fusion gene construct integrated into the endogenous Antp gene close to one of the two promoters (P1). The spatial expression from the reporter gene in this transformant line, as analysed by the detection of β-galactosidase activity, was found to exactly mimic the normal expression from the P1 promoter of the Antp gene. We have used this unique transformant as a tool for studying the expression of the P1 promoter in embryonic, larval and adult development. Parallel lines transformed with the same fusion gene construct did not confer a correct P1 pattern of expression. The position in the genome was, therefore, crucial for the expression pattern of the reporter gene. Experiments aiming at the detection of autoregulatory control of Antp gene expression were designed. The results did not, however, support models of positive or negative autoregulation of P1 expression by Amp protein.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 167
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 201 (1992), S. 120-123 
    ISSN: 1432-041X
    Schlagwort(e): Integrin ; Drosophila ; In vitro ; Imaginal disc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Drosophila imaginal disc cell lines show a characteristic pattern of aggregation in culture, which appears to be due to cell-cell rather than cell-substrate interactions. We have examined the distribution of PS integrins in wing and leg cell lines, and find that these integrin homologues are expressed preferentially in aggregates. Cell sheets, small cell clumps and chains of cells express antigen at points of cell-cell contact only.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 168
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; Pattern formation ; Segment polarity genes ; gooseberry ; Cell interactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Segment polarity genes define the cell states that are required for proper organization of each metameric unit of the Drosophila embryo. Among these, the gooseberry locus has been shown to be composed of two closely related genes which are expressed in an overlapping single-segment periodicity. We have used specific antibodies raised against the protein product of the gooseberry proximal (gsb-p) gene to determine the spatial distribution of this antigen in wild type embryos, and to monitor the effects of segment polarity mutants on the pattern of the gsb-p protein distribution. We find that the gsb-p protein accumulates beneath each posterior axonal commissure in the progeny of neuroblasts deriving from the epidermal compartments of wingless (wg) and engrailed (en) expression. The results of this analysis support the idea that gsb-p has a specific role in the control of cell fates during neurogenesis, and indicate that en and wg provide critical positional cues to define the domain in which gsbp will be activated. Furthermore, these data suggest that, in order to be expressed in the embryonic CNS, gsb-p may preliminarily require activity of the gooseberry-distal gene in the epidermis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 169
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 201 (1992), S. 88-94 
    ISSN: 1432-041X
    Schlagwort(e): Fate map ; Drosophila ; Flight muscle ; Mosaics ; Cell lineage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A blastoderm fate map has been prepared for Drosophila, using mosaics of a temperature-sensitive mutation, shibire (shi). The mutation can cause abnormal flight muscle morphology, inducible only by a short heat pulse in early metamorphosis. Thus muscle lineage and development are unperturbed until the heat pulse in the early pupa. The developmental focus of the shi muscle phenotype maps to the ventral thorax at the expected site of thoracic mesoderm, and probably indicates the blastoderm progenitors of the adult flight muscle. The fate map provides greater detail than previously available for the dorsolongitudinal fibers (DLM) of flight muscle, showing wide separation of the fibers of flight muscle. DLM fibers a and b map close together, and far anterior to fibers e and f, which also map together. On a fate map, common developmental focus indicates a common blastoderm origin. Thus, the observed pattern for DLM fibers suggests that the blastoderm progenitors for each of these syncytial fiber pairs (a, b; e, f) include only one or two cells. It follows that there is usually a single genotype within each fiber pair (a, b; e, f), and that this genotype is directly reflected in the fiber phenotype. In a large number of cases, DLM fibers a and b differ in phenotype from other DLM fibers, in parallel with their other differences (e.g., timing of development in pupa, innervation, motor activity). The separation of fate map locations of the developmental focus for DLM fibers within mesoderm suggests that specific fibers of flight muscle may, in normal development, originate in all three thoracic mesodermal parasegments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 170
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 202 (1992), S. 23-35 
    ISSN: 1432-041X
    Schlagwort(e): Ecdysteroid ; Imaginal disc ; Drosophila ; Cell line
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have investigated the action of the moulting hormone 20-hydroxy ecdysone (20-HOE) on our leg and wing imaginal disc cell lines. At the morphological level, cells stop dividing and there is some cell death. The remaining cells elongate and aggregate, often producing long processes which form connections between different aggregates. 20-HOE acts within the first one or two days of a passage, at an optimum concentration of 10 ng/ml, this being about 1/100 of the optimum for ecdysone. One cloned wing cell line, C9, has been found to be relatively insensitive to the action of 20-HOE. We have been able to select for resistance to 20-HOE by growing cells in gradually increasing concentrations of hormone followed by passages in hormone-free medium. This has enabled us to isolate a wing cell line C1.8R from its parent cloned line C1.8+. This shows no response to 20-HOE, and cell growth continues even at hormone concentrations as high as 150 ng/ml. We have measured chitin synthesis by the incorporation of radioactive glucosamine into a cell fraction resistant to extensive alkali hydrolysis. The residue was incubated with chitinase, which resulted in a 50% reduction in labelled product. Treatment with 10 ng/ml of 20-HOE dramatically increased chitin synthesis in line C1.8+, but had no effect in the line C1.8R, selected for resistance to hormone.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 171
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 202 (1992), S. 49-60 
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; Delta ; Enhancers ; Suppressors ; Neurogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have screened for dominant enhancers and suppressors of the wing phenotype associated with two Delta alleles: Dl 9P39, an amorphic allele, and Dl FE32, an antimorphic allele. The interactions of some of the modifiers with Delta are due to haplo-insufficient expression of the corresponding genes. Although not explicitly shown for the remaining cases, we assume that haploin-sufficiency is also the basis for the relationships of these genes to Delta, since no allele specific interactions were observed. The modifiers found define 22 genes with pleiotropic expression, which can be classified into two groups: genes required for wing vein pattern formation and for neurogenesis, and genes which are not required for neurogenesis. Among the genes of the first group, Hairless and Star were previously known to participate in neural development. One further modifier was found which may correspond to a new neurogenic gene. The second group of genes is larger and includes already known loci, e.g., Plexate, blistered, plexus, etc, as well as other previously unidentified genes, which function during wing morphogenesis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 172
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 201 (1992), S. 1-11 
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; Neurogenesis ; Signals ; Delta ; Notch
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The ectodermal germ layer of Drosophila melanogaster gives rise to two major cell lineages, the neural and the epidermal. Progenitor cells for each of these lineages arise from groups of cells, whose elements must decide between taking on either fate. Commitment of the progenitor cells to one of the developmental fates implies two factors. One is intrinsic to the ectodermal cells and determines a propensity to take on neural fate; this factor is probably represented by the products of the so-called proneural genes, which are differentially distributed throughout the ectoderm. The other factor in the cells' decision to adopt one of the two alternative fates is intercellular communication, which is mediated by the products of the so-called neurogenic genes. Two types of interactions, one inhibiting and the other stimulating neural development, have been inferred. We discuss here the assumed role of various neurogenic genes, in particular Notch and Delta, in these processes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 173
    Digitale Medien
    Digitale Medien
    Springer
    Development genes and evolution 201 (1992), S. 194-220 
    ISSN: 1432-041X
    Schlagwort(e): Drosophila ; Enhancer trap lines ; Embryogenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Embryos of 171 Drosophila lines carrying a P-lacZ insertion on the second or third chromosome were analyzed regarding their pattern of lacZ expression. All lines were selected from a larger screen of about 4000 lines (Bier et al. 1989). Tissue specificity and time of onset of lacZ expression was documented for each line. Thereby, a comprehensive list of markers for the various tissue and cell types of the Drosophila embryo could be assembled. With the help of several P-lacZ lines the development of a number of structures was studied which so far had been described only insufficiently or not at all. In particular, the embryonic origin and early development of the oenocytes, imaginal discs, histoblasts, fat body, dorsal vessel, and perineurial cells was analyzed. Several previously unknown cell types associated with the dorsal vessel, trachea, and epidermis were discovered. By combining data regarding the origin of the different mesodermally derived organs it was possible to generate in some detail a fate map of the mesoderm of the stage 11 Drosophila embryo.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 174
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 48 (1992), S. 623-629 
    ISSN: 1420-9071
    Schlagwort(e): Drosophila ; heat shock ; stress ; heat shock protein ; gene regulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Major alterations in genetic activity have been observed in every organism after exposure to abnormally high temperatures. This phenomenon, called the heat shock response, was discovered in the fruit flyDrosophila. Studies with this organism led to the discovery of the heat shock proteins, whose genes were among the first eukaryotic genes to be cloned. Several of the most important aspects of the regulation of the heat shock response and of the functions of the heat shock proteins have been unraveled inDrosophila.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 175
    ISSN: 1432-0827
    Schlagwort(e): Fluoride ; Bioavailability ; Osteoporosis ; Menopause
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Fluoride (F) increases trabecular bone mass and can be used in the treatment of osteoporosis with crush fractures. As the bioavailability of sodium fluoride (NaF) can be impaired by concomitant absorption of calcium, both drugs have to be ingested separately. However, disodium monofluorophosphate-calcium carbonate (MFP-Ca), another F compound, allows a single administration. In a cross-over randomized study, we compared the bioavailability of both drugs under regular conditions of prescription. Ten postmenopausal women (aged 48–77 years) with glomerular filtration rate (GFR)〉70 ml/minute and without bone disease entered the study. Each received 25 mg of NaF [i.e., 11.3 mg F ion (F-)] fasting and 100 mg of Na2FPO3-1250 mg CaCO3 (i.e., 13.2 mg F-) with breakfast in a single dose separated by an 8-day washout. After dosing, plasma F levels and fractionated and total urinary F collection were determined during a 24-hour period using a specific electrode. Results show a significant shorter lag time absorption (Tmax=1.4±0.2 hour) and a higher maximal concentration (Cmax=260±60 ng/ml) for MFP-Ca than for NaF (Tmax=2.5±0.4 hour; Cmax=200±85 ng/ml). However, areas under curve (AUC) for MFP-Ca (1711±195 μg/liter/hour) and for NaF (1202±147 μg/liter/hour) were not significantly different. The relative bioavailability of both F compounds related to their fluoride content (i.e., 1.22 for AUC ratio) was equivalent, according to the Westlake method. These data provide the first evidence of comparable bioavailability of two F compounds in a population of postmenopausal women. In addition to the higher Cmax achieved with this compound, it could suggest the use MFP-Ca as a simple treatment schedule in osteoporosis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 176
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 51 (1992), S. 35-41 
    ISSN: 1432-0827
    Schlagwort(e): Kidney ; Endoplasmic reticulum ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary A subcellular fraction enriched in cytochrome c reductase (7.9-fold) and relatively de-enriched (0.64-fold) in Na+/K+-ATPase was prepared from canine kidney cortex by sucrose density gradient ultracentrifugation. It was shown by electron microscopy to consist primarily of a light fraction of endoplasmic reticulum (LER). LER vesicles displayed ATP-dependent 45Ca2+ uptake that was insensitive to 10 mM KCN or NaN3, and was promptly released by 20 μM A23187 or ionomycin. Inositol-1,4,5-trisphosphate (IP3) appeared to produce a time-dependent release of 45Ca2+. Vanadate inhibited 45Ca2+ uptake with a Ki≈0.3 mM, further suggesting that the activity resided in the ER rather than the plasma membrane. 45Ca2+ uptake by LER, at 5 μM total [Ca2+], displayed a strong dependence on divalent cations (Mg2+〉Co2+〉Mn2+≫Ba2+≥Cd2+≥Sr2+, present at 2 mM) as well as on monovalent cations (Na+≥K++Na+ 〉K+〉Li+〉choline+), and anions (Cl-〉acetate-≥NO3 -≥F-〉H2PO4 -≫gluconate-≥oxalate=≫SO4 =). It had a fairly narrow pH optimum (7.25–7.50). Preincubation (10 min) of LER vesicles with 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated LER Ca2+ uptake; this effect was enhanced in the presence of renal cytosol [5% (vol/vol)]. However, Ca2+ uptake was not affected by preincubation with dibutyryl cyclic AMP, calmodulin, or 1,25-(OH)2-vitamin D3, either in the absence or presence of renal cytosol. Thus, the Mg2+-ATP dependent 45Ca2+ uptake activity of this canine renal cortical LER fraction displays modulation by IP3, TPA, and pH that appears to be physiologically relevant.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 177
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 51 (1992), S. 143-150 
    ISSN: 1432-0827
    Schlagwort(e): Adsorption ; Magnesium ; Calcium ; Apatite crystals ; Enamel ; Dentin ; Bone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Magnesium (Mg) is a conspicuous constituent of hard tissues but its possible role in biomineralization is poorly understood. It is possible that Mg2+ adsorbed onto bioapatites may contribute to the modulation of crystal growth as such inhibitory activity has been reported for synthetic apatites. The present study was undertaken to determine the adsorption isotherms of Mg ions onto synthetic apatites and biominerals in tooth and bone tissues in the presence of other ions of natural occurrence. Synthetic crystals used as adsorbents were hydroxyapatite and, as a better prototype for the biomineral, Mg-containing carbonatoapatite. Human enamel and dentin materials were obtained from extracted, caries-free, permanent teeth. Porcine dentin materials at two developmental stages were obtained from erupted deciduous and unerupted permanent teeth of a 6-month-old slaughtered piglet. Porcine bone was obtained from the cortical portion of the mandible of the same animal. All biomineral samples were pulverized and then treated by plasma ashing (deproteination) at about 60°C. Each of the powdered samples was equilibrated in solutions containing various initial concentrations of Mg2+, Ca2+, and Na+ (or K+) as nitrate salts. Following equilibration, concentrations (and activities) of magnesium and calcium ions in the experimental solution were determined. The pH values of the equilibrium solutions were in the range of 6.2–6.5. Experimental data of the Mg adsorption onto hydroxyapatite were interpreted on the basis of a Langmuir-type model for binary systems assuming competition of Mg2+ and Ca2+ for the same adsorption sites on the crystal surfaces of the apatites. According to this model, the adsorbed Mg is expressed as a function of the ionic activity ratio (Mg2+)/(Ca2+) in the equilibrium solution. The model contains two parameters, the adsorption selectivity constant Ks and the maximum number of adsorption sites N (μmol/g). The numerical values of Ks were similar for all adsorbents used (synthetic and biological) and indicated the preferential adsorption of Ca2+ probably due to spacial restrictions extending to the very surface of the crystals. The initial level of Mg2+ in the surface pool was different in the various biominerals, probably reflecting the composition of fluid in which the biominerals were formed. Whereas the surface pool of Mg of human enamel was marginal, only 5% of the total Mg, significant fractions of the total Mg in human and porcine dentins (about 20–30%), and porcine bone (about 40%) existed on the crystal surfaces. There were significant differences in the total Mg and the value of the parameter N between young (unerupted) and mature (erupted) dentin minerals. It was ascertained that the occupancy of adsorption sites by Mg ions became greater with maturation of the dentin tissues. The overall results suggest that the Mg-mineral interaction in tooth and bone tissues may be a highly tissue-specific process, presumably reflecting differences in fluid composition (particularly Ca and Mg activities) responsible for biomineralization.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 178
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 50 (1992), S. 420-426 
    ISSN: 1432-0827
    Schlagwort(e): Fluoride ; Cortical bone ; Density ; Specific gravity ; Fractionation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary In addition to increasing bone volume, fluoride has been demonstrated to increase ash weight and mineral density. To determine whether newly formed or older bone is most affected by fluoride treatment, bone from chickens receiving fluoridated water was fractionated into lower density (recently formed) and higher density (more mature) specific gravity fractions. Fluoride was administered to the chickens for different lengths of time (4 or 13 weeks) or at varying doses for a 4-week period (0, 4.2, 16.8 mmol/liter drinking water). Fluoride treatment caused a shift in the mineral density profile, showing an increased proportion of mineral distribution in the more mature, higher density fractions. To determine whether this density gradient shift was due to increased maturation rate of bone or decreased resorption and mineralization rates, [3H]proline and 45Ca were injected 5 days and 24 hours prior to sacrifice, respectively. The distributions of both 3H or 45Ca, as percentages of total counts incorporated, were shifted by fluoride treatment into more mature, higher density fractions. Expressing the number of counts as a percent of the bone in each fraction (total hydroxyproline or Ca) revealed an increased incorporation of both 3H and 45Ca into the higher specific gravity fractions 2.0–2.2. These results suggest that fluoride treatment increases bone maturation and the rate of secondary mineralization in the cortical bone. Such changes in the quality of more mature, well-mineralized bone, in humans as well as animals, may have a significant influence on brittleness and strength.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 179
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 51 (1992), S. 340-343 
    ISSN: 1432-0827
    Schlagwort(e): Menopause ; Estrogens ; Bone ; Osteoporosis ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Biochemical parameters reflecting bone resorption [urinary calcium/creatinine (Ca/Cr) and hydroxyproline/ creatinine (OH/Cr)] were related to serum estrogens [estrone (E1) and estradiol (E2)] in 262 healthy women including 158 patients receiving estrogen replacement therapy (ERT) for at least 6 months, 49 eugonadal women, and 55 untreated postmenopausal women. A significant (P〈0.001) correlation exists between serum E2 and Ca/Cr: Ca/Cr (mg/dl)=-0.00044 E2 (pg/ml)+0.129 (n=262; r=-0.37), serum E2 and OH/Cr: (OH/Cr (mg/g)=-0.049 E2 (pg/ml)+18.76 (n=262; r=-0.36), serum E1 and Ca/Cr: Ca/Cr (mg/dl)=-0.0003 E1 (pg/ml)+0.127 (n=261; r=-0.28) but not between serum E1 and OH/Cr. Women with circulating levels of E2 between 60 and 90 pg/ml have a significant (P〈 0.01) reduction of Ca/Cr and OH/Cr when compared with those with lower levels of E2. Higher values of E2 do not provide additional benefit. We conclude that in postmenopausal women receiving an estrogen replacement therapy (ERT), a significant reduction of bone resorption is achieved when circulating levels of estradiol reach a value (60 pg/ml) corresponding to the one measured, in eugonadal women, during the last days of the early follicular phase of the menstrual cycle. We suggest that oral or percutaneous ERT should induce a minimal value of 60 pg/ml to prevent postmenopausal bone loss.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 180
    ISSN: 1432-2048
    Schlagwort(e): Calcium ; Chloride ; Epidermis (leaves) ; Ion compartmentation ; Mesophyll
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The cation and anion distribution between the epidermis and mesophyll of primary leaves of 10-d-old barley (Hordeum vulgare L.) seedlings was studied in relation to growth conditions. A new method was employed to isolate epidermal protoplasts. The following observations were made: (i) Under standard hydroponic growth conditions, K+ was the dominant cation and NO 3 3− the predominant anion, both in epidermal and mesophyll protoplasts. (ii) Levels of Cl− and particularly of Ca2+ were specifically increased in the epidermis when growth conditions stimulated uptake of these ions into the plants. (iii) Epidermal PO 4 3− was maintained at a very low level even in the presence of 50 mM phosphate in the rooting medium, whereas the phosphate concentration in the mesophyll was high, with phosphate being accumulated in the mesophyll vacuoles. (iv) Sulphate and NO 3 − accumulated to a similar degree in the mesophyll and the epidermis when K2SO4 or KNO3 in the rooting medium caused salt stress to the plants. (v) Epidermal protoplasts took up 35SO 4 2− and 36Cl− from the surrounding medium. A comparison of the uptake rates indicates that specific ion deposition into the epidermis may partially be the consequence of differential uptake of ions from the transpiration stream. The results indicate an important function of the epidermis for ion compartmentation in barley leaves.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 181
    Digitale Medien
    Digitale Medien
    Springer
    Planta 188 (1992), S. 279-288 
    ISSN: 1432-2048
    Schlagwort(e): Aplanospore (germination) ; Calcium ; Vaucheria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Germination of aplanospores in Vaucheria longicaulis Hoppaugh var. macounii Blum proceeds through three stages of development. Stage I begins with the initiation of germination and lasts approx. 2 h. During this stage germinating filaments grow at an accelerated rate (266 ± 12 μm · h−1). Stage II is characterized by a sharp decline in the growth rate of germinating filaments (96 ± 4 μm · h−1) and lasts 4 h. This is followed, during the next 4 h, by a recovery in the growth rate (168 ± 8 μm · h−1) of germinating filaments, stage III. Growth rates stabilize and remain unchanged during subsequent development (Oliveira and Fitch, 1988, J. Submicrosc. Cytol. Pathol. 20, 397–406). The Ca2+-influx modulators LaCl3, nifedipine and methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4 (2-trifluoromethylphenyl)-pyridine-5-carboxylate (Bay K-8644), the ionophore calcimycin (A23187), the intracellular Ca2+-release antagonist 8-N-N'-(diethylamino)-octyl-3,4, 5-trimethoxybenzoate (TMB-8), the Ca2+-uptake inhibitor ruthenium red and the phosphoinositide-cycle modulators LiCl and myo-inositol show that the events required for the initiation are distinct from those required for the completion of each stage of germination. These studies in conjunction with microinjection of germinating filaments with inositol 1,4,5-trisphosphate, the natural ligand for Ca2+ release from Ca-storing organelles (endoplasmic reticulum, vacuole), and treatment with chlorotetracycline (CTC), to visualize the distribution of membrane-bound Ca2+ reveal that both the initiation and completion of each stage of germination are controlled by Ca2+ signals which are restricted to well-defined time intervals and are modulated by the origin (source) of Ca2+.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 182
    ISSN: 1432-1939
    Schlagwort(e): Wood mouse ; Bank vole ; Calcium ; Growth ; Body weight
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Calcium intake by wild rodents varies with season and habitat. This may have important ecological consequences; several studies have suggested that calcium availability may limit growth and reproduction. We studied the effect on growth of varying the calcium intake of captive wood mice Apodemus sylvaticus (L.) and bank voles Clethrionomys glareolus (Schreber 1780). To determine whether effects observed in the laboratory could be detected in free-living animals, we also compared the body weights and lengths of free-living animals on calcium-poor gritstone areas with those of rodents on calcium-rich limestone habitats where the dietary calcium concentration was between 2 and 5 times higher. Captive wood mice fed high calcium (0.87%) diet grew at the same rate as mice fed low calcium (0.30%) diet but continued growing for longer, thereby achieving higher asymptotic weights. In contrast, captive bank voles fed the high calcium diet grew more slowly and had lower asymptotic weights than voles fed the low calcium diet. As expected from the laboratory growth study, the higher calcium intake of free-living wood mice on the limestone was associated with greater body size compared with mice on the gritstone. However, bank voles were also larger on the limestone, even though high calcium intake impaired growth in captive animals. The contrast between wood mice and bank voles in the effects of calcium on growth, the reason why impaired growth may not be apparent in bank voles from calcium-rich habitats and the ecological significance of these results are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 183
    Digitale Medien
    Digitale Medien
    Springer
    Oecologia 92 (1992), S. 183-187 
    ISSN: 1432-1939
    Schlagwort(e): Drosophila ; Resource exploitation ; Decaying-herbage breeding ; Host choice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The Drosophila fauna of a deciduous flood plain forest rich in undergrowth near the river Isar, close to Munich, Germany, was surveyed in summer 1990. Decaying herbage baits (decay artificially induced) were set out to study the exploitation of that resource by Drosophila. Sixteen plant species belonging to several families dominant in the collecting area were tested. All attracted and produced drosophilid flies. Ten Drosophila species utilized decaying plant material as breeding sites; at least eight of the ten are polyphagous. Decaying stalks and leaves of Angelica sylvestris (Apiaceae) were examined in detail. In the case of the most frequent species of Drosophila attracted to A. sylvestris, the number of adults collected did not correlate with the number of flies emerging from the substrate. This was particularly true of D. limbata and D. phalerata. When oviposition and larval development of D. limbata and D. phalerata on A. sylvestris was tested in the laboratory, the number of offspring per female was the same in both species. The difference between these two species of the quinaria group in the exploitation of A. sylvestris in the field is therefore not due to differential suitability of the substrate.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 184
    ISSN: 1432-2145
    Schlagwort(e): Calcium ; Calmodulin ; Microsporogenesis ; Pollen germination ; Gasteria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The distribution of membrane calcium and calmodulin (CaM) has been fluorimetrically determined in the anther of Gasteria verrucosa with particular attention to sporogenous cells, meiocytes, microspores, pollen and stages of pollen germination and tube growth using chlortetracycline (CTC) and fluphenazine (FPZ). CTC and FPZ fluorescence in sporogenous cells is relatively higher than in the adjacent tapetal cells, indicating higher membrane calcium and CaM levels in the former cell type. However, during meiosis there is a significant increase in membrane calcium and CaM levels in the meiocytes compared to that found in the young microspores. CTC and FPZ fluorescence in the sporogenous cells, meiocytes and young microspores is punctate and slightly diffused throughout the cytoplasm. In the microspores of the tetrad and the young released microspores CTC fluorescence (CTCf) is polarized and mainly associated with the area opposite the future colporal region. FPZ fluorescence (FPZf) becomes polarized in the young microspore. Subsequently, there is a shift in the polarity, and most of the CTCf and FPZf in the old microspores and pollen is regionalized towards the colporal region, and the fluorescence is more diffused, indicating a change in the organellar-bound calcium and CaM. This final graded distribution of CTCf is maintained during pollen germination in that the growing pollen tubes invariably show a tip to base membrane-calcium gradient. In the tapetal cells a high level of Ca2+ is present during the microspore stage. During the preparation for anthesis the endothecium differentiation is marked by the presence of Ca2+. Post-treatment of labelled cells with a Ca2+ chelator such as EGTA resulted in a substantial decrease in diffuse and punctate CTCf. Alternatively, treatment of cells with non-ionic detergent Nonidet P-40 resulted in the total elimination of CTCf, suggesting that the observed CTC fluorescence was due to membrane-associated calcium. The cytological specification of CTC as a probe for calcium is discussed. From cytofluorometric measurements and atomic absorption, it became clear that the level of Ca2+ in the anther is high during the sporogenous and meiotic phases. An increase in CTCf and FPZf occurred after microspore mitosis. An interaction of Ca2+ transport from tapetum to the young pollen is postulated. These findings suggest that the level of Ca2+ in the anther during meiosis is generally relatively higher than at the sporogenous or young microspore stage. These findings are discussed in the light of available information on the role of Ca2+ and CaM-mediated processes such as cell division, callose synthesis and pollen-tube tip growth.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 185
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 5 (1992), S. 138-145 
    ISSN: 1432-2145
    Schlagwort(e): Pollen germination ; ATPases ; Calcium ; Magnesium ; Potassium ; Agapanthus umbelatus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cytochemical detection of ATPase activity in the pollen grain (PG) and pollen tube (PT) of Agapanthus umbelatus showed that the enzymes concerned presented specific patterns of membrane distribution according to their ionic dependencies and to the timecourse of germination and tube growth. In the pollen tubes Ca2+-ATPases were mainly localized in mitochondria and ER membranes, while Mg2+-ATPases were found especially in the tonoplast and in the membrane of the P-particles. K+-ATPases showed a high activity at the plasma membrane. In the pollen grain similar patterns of ATPase activity were observed. The highest activity of all three types was observed at the plasma membrane of the grain and at the intine and inner exine layers of the cell wall. The activity observed in the pollen grain cell wall decreased with germination time. In vivo germination studies in the presence of specific inhibitors of the ATPases showed patterns of inhibition that could be correlated with the corresponding ATPase putative role. The results are discussed in terms of the ultrastructural organization of the PG and PT, especially those correlated with (1) formation and maintenance of ionic gradients throughout the PT, (2) polarized growth and (3) hydrodynamics of PT elongation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 186
    Digitale Medien
    Digitale Medien
    Springer
    Sexual plant reproduction 5 (1992), S. 151-155 
    ISSN: 1432-2145
    Schlagwort(e): Calcium ; Chlorotetracycline ; Fertilization ; Nicotiana ; Synergid degeneration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Synergid degeneration was examined in the isolated embryo sac and egg apparatus of Nicotiana tabacum using quantitative cytology, fluorochromatic reaction (FCR) and chlorotetracycline (CTC). Most synergid degeneration occurs after pollen tubes (PT) arrive in the ovarian chamber between 42 and 48 h after pollination; synergid degeneration was precluded when PT were prevented from entering the ovary by stylar excision indicating that the signal that triggers synergid degeneration travels only relatively short distances in this plant. There was no evidence for any preferentiality between right or left synergids with regard to cell size or degeneration pattern. FCR staining confirms that synergid degeneration involves the loss of membrane integrity and is a reliable indicator of the onset of degeneration. CTC labeling of the degenerated synergid reveals that a concentrated reserve of membrane-bound calcium is present in the receptive synergid, possibly aiding in the attraction, arrest and discharge of the PT, releasing the sperms into the receptive ES.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 187
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 158 (1992), S. 85-92 
    ISSN: 1432-072X
    Schlagwort(e): Arthrobacter photogonimos ; lipA Gene ; Photoinduction ; Calcium ; Metals ; Chelation ; Gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Expression of the light-inducible (lipA) gene in Arthrobacter photogonimos is repressed by Ca2+ at a concentration greater than 0.1 μM. Expression of lipA was induced by relatively high concentrations of Zn2+ Ni2+ or Co2+ in cell suspensions, an effect that was blocked by an increase in the concentration of Ca2+ in the medium. Zn2+ and other metals apparently overcame repression by Ca2+ by competing for a cellular binding site. Expression of lipA was also induced when the amount of free Ca2+ was lowered with ethylene-bis (oxyethylenenitrilo)tetraacetic acid (EGTA). Our results show that the lipA gene does not require Zn2+ or other divalent cation for expression and that it is regulated negatively by Ca2+. Accumulation of the mature product of this gene (light-inducible protein, LIP) was minimal in the presence of EGTA. Accumulation increased 10-to 20-fold when divalent cations such as Ca2+, Mn2+, Cu2+ or Zn2+ were added to cell suspensions treated with chelator. These divalent cations, which allowed the protein to achieve a protease-resistant form on the cell surface, could be substituted by protease inhibitors such as antipain, leupeptin or 1,10-phenanthroline. Our data can be explained by a biparous mechanism in which divalent cations regulate both expression of the lipA gene and accumulation of the gene product.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 188
    Digitale Medien
    Digitale Medien
    Springer
    Behavior genetics 22 (1992), S. 469-487 
    ISSN: 1573-3297
    Schlagwort(e): courtship ; pheromones ; Drosophila ; apterous ; juvenile hormone ; reproductive development ; sexual behavior
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract Theapterous (ap) gene ofDrosophila melanogaster exhibits extreme pleiotrophy: its functioning is essential for life, normal wing structure, juvenile hormone production, female fertility, and normal development of female sexual receptivity. Four mutantap alleles (ap 4,ap 56f,ap c, andap blt) were characterized for three additional phenotypes: male mating success, courtship behavior, and immature male sex appeal (the ability of males to stimulate homosexual cortship). Mating success with mature wild-type virgin females is reduced in males mutant for theap gene, the extreme case beingap 4/ap 4 males, which are behaviorally sterile. Inap mutants, nonwing courtship elements are qualitatively like those ofap +/ap + males. However, the mean rate of nonwing courtship directed toward virgin wild-type females (i.e., the mean temporal frequency of these displays) is reduced in males homozygous forap 4,ap 56f, orap c alleles. In contrast, theap blt allele makes for wild-type rates of nonwing courtship. Immature male sex appeal persists for at least 3 days in males homozygous forap c and, to a lesser extent, inap 56f orap 4 homozygotes;ap blt/ap blt and wild-type males lose immature male sex appeal after 1 day. All three male phenotypes map to theap locus, which is therefore essential for the development of normal levels of male courtship and male mating success and for the timely loss of immature male sex appeal. For each phenotype,ap + is dominant toap alleles making for behavioral abnormalities, with a single exception (for rate of nonwing courtship,ap +/ap c was low). For mating success and frequency of nonwing courtship, each allele pair exhibits at least partial complementation, except forap 4 andap 56f, which fail to complement. For immature male sex appeal,ap c,ap 4, andap 56f fall into the same complementation group. Juvenile hormone production is not correlated with effects on male reproductive behavior.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 189
    Digitale Medien
    Digitale Medien
    Springer
    Behavior genetics 22 (1992), S. 557-573 
    ISSN: 1573-3297
    Schlagwort(e): Drosophila ; biometrical analysis ; behavior genetics ; genetic analysis ; ss a ; deletion mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract The homeotic mutationspineless-aristapedia (ss a ) transforms the aristae into second tarsi. Flies with aSS a phenotype also show extremely positive geotaxis as measured in a Hirsch-type geotaxis maze. Other antennal mutants and flies with their aristae amputated do not show such extreme positive geotaxis. Deletion analysis has comapped the geotaxis effect withSS a in band 89C on the third chromosome. Finally, a biometrical analysis has detected additional genes on the X chromosome that also affects geotaxis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 190
    Digitale Medien
    Digitale Medien
    Springer
    Journal of fluorescence 2 (1992), S. 47-62 
    ISSN: 1573-4994
    Schlagwort(e): Calcium ; fluorescence lifetime imaging ; calcium imaging ; fluorescence microscopy ; ratiometric imaging ; long-wavelength probes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We describe imaging of calcium concentrations using the long-wavelength Ca2+ indicators, Calcium Green, Orange, and Crimson. The lifetimes of these probes were measured using the frequency-domain method and were found to increase from 50% to severalfold in response to calcium. The two-dimensional images of the calcium concentration were obtained using a new apparatus for fluorescence lifetime imaging (FLIM). We also describe procedures to correct for the position-dependent frequency response of the gain-modulated image intensifier used in the FLIM apparatus. Importantly, the FLIM method does not require the probe to display shifts in the excitation or emission spectra. Using the FLIM method, calcium imaging is possible using probes which display changes in lifetime in response to calcium. Consequently, calcium imaging is possible with excitation wavelengths ranging from 488 to as long as 620 nm, where autofluorescence and/or photochemical damage is minimal. These probes are also suitable for calcium measurements of single cells using lifetime-based flow cytometry.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 191
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 30 (1992), S. 159-168 
    ISSN: 1573-4927
    Schlagwort(e): Drosophila ; indirect flight muscle ; tropomyosin ; polymorphism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract We describe polymorphism in aDrosophila indirect flight muscle-specific tropomyosin isozyme, named TnH-34. Three variants of this protein differ in their mobilities as determined by 1-D and 2-D SDS-PAGE. Meiotic mapping places the polymorphism close to, if not within, the structural gene encoding this tropomyosin isozyme. The most likely site of the mutations is within a single C-terminal exon. Flight-testing of different genotypes reveals that this variation in TnH-34 does not affect flight ability. These results suggest that some sequence variation may be tolerated in this section of the protein and correlate with the variability of this protein in different insect species.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 192
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 30 (1992), S. 305-315 
    ISSN: 1573-4927
    Schlagwort(e): Drosophila ; diaphorase ; purification ; kinetics ; immunochemical characteristics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Diaphorase-1 and diaphorase-2 were isolated from twoDrosophila species,D. virilis andD. melanogaster, and purified by gel filtration, affinity chromatography, immunoaffinity chromatography, and ion-exchange chromatography. The molecular weights of both enzymes were the same in each species. The molecular weight of diaphorase-1 was the same under both denaturating and nondenaturating conditions, close to 60,000, indicating a monomeric structure. Sodium dodecyl sulfate (SDS) electrophoresis of the purified diaphorase-2 revealed the presence of a single protein band of 55,000 Da, while the molecular weight of the native enzyme was found to be 67,000. The two diaphorases were further characterized by their pH optima, isoelectric points, and kinetic parameters, and antibodies were raised in rabbits against the purified enzymes fromD. virilis. The antibodies showed no cross-reactions but recognized the corresponding diaphorases inD. melanogaster andD. novamexicana as well asD. virilis. The data obtained confirmed the hypothesis of an independent genetic control of diaphorase-1 and diaphorase-2 inDrosophila.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 193
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 30 (1992), S. 305-315 
    ISSN: 1573-4927
    Schlagwort(e): Drosophila ; diaphorase ; purification ; kinetics ; immunochemical characteristics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Diaphorase-1 and diaphorase-2 were isolated from twoDrosophila species,D. virilis andD. melanogaster, and purified by gel filtration, affinity chromatography, immunoaffinity chromatography, and ion-exchange chromatography. The molecular weights of both enzymes were the same in each species. The molecular weight of diaphorase-1 was the same under both denaturating and nondenaturating conditions, close to 60,000, indicating a monomeric structure. Sodium dodecyl sulfate (SDS) electrophoresis of the purified diaphorase-2 revealed the presence of a single protein band of 55,000 Da, while the molecular weight of the native enzyme was found to be 67,000. The two diaphorases were further characterized by their pH optima, isoelectric points, and kinetic parameters, and antibodies were raised in rabbits against the purified enzymes fromD. virilis. The antibodies showed no cross-reactions but recognized the corresponding diaphorases inD. melanogaster andD. novamexicana as well asD. virilis. The data obtained confirmed the hypothesis of an independent genetic control of diaphorase-1 and diaphorase-2 inDrosophila.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 194
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 30 (1992), S. 77-83 
    ISSN: 1573-4927
    Schlagwort(e): acetylcholinesterase ; insecticide ; resistance ; Drosophila
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Selection of field populations originating from several countries allowed us to isolate 13 strains ofDrosophila melanogaster resistant to parathion.In vitro studies of acetylcholinesterase inhibition by paraoxon have been carried out on purified enzymes: most of the resistant strains harbor an altered acetylcholinesterase. Enzymes with higher resistance levels have been characterized with respect to their cross-resistance toward several insecticides. The patterns obtained have permitted us to group them and to delineate four categories. The existence of four distinct types of protein suggests that several mutations of acetylcholinesterase are responsible for insecticide resistance inDrosophila.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 195
    ISSN: 1573-4927
    Schlagwort(e): Drosophila ; glycerol-3-phosphate dehydrogenase ; restriction map ; duplication ; enzyme activity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Restriction site variation in a 25-kb region including thesn-glycerol-3-phosphate dehydrogenase (Gpdh) locus has been assessed in 29 single femaleD. melanogaster lines from the Cardwell (Australia, QLD) population. TheGpdh locus was duplicated in about one-third of the lines, although the duplication was incomplete and lacked exons 1 and 2. There was no restriction site variation in the duplicated region. Three insertions were found in the gene region but only one affected GPDH activity. The lines with the duplication had higher levels of GPDH activity and protein amount than did nonduplicated lines. This effect was also observed in lines extracted from two other Australian populations. The duplication is shown to have a similar structure in each population investigated and is also present in populations from China and Africa. It is suggested that the effect of the duplication on GPDH activity, which might be due to structural factors affecting transcription at theGpdh locus, could account for the worldwide distribution of the duplication.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 196
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 30 (1992), S. 515-527 
    ISSN: 1573-4927
    Schlagwort(e): glutathioneS-transferase ; Drosophila ; cellular detoxification ; pesticide resistance ; insect metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract We have isolated aDrosophila gene,DmGST-2, that encodes glutathioneS-transferase, a homo- or heterodimeric enzyme thought to be involved in detoxification of xenobiotics, including known carcinogens. The encoded protein has a primary sequence that is more similar to mammalian placental and nematode GSTs than that of a previously describedDrosophila GST gene, herein referred to asDmGST-1. We provide a physical map of the gene and show that it specifies at least two mRNAs, measuring 1.9 and 1.6 kb, which differ only in the lengths of their 3′ untranslated regions. Both of the mRNAs are present during all developmental stages.In situ hybridization of theDmGST-2 gene to larval polytene chromosomes places it within the 53F subdivision of chromosome 2, and Southern blotting to chromosomal DNA indicates that the gene has no close relatives within theDrosophila genome. Our results make possible molecular genetic approaches for further elaborating the function of glutathioneS-transferases in insect development and physiology, in the metabolism of plant toxins, and in conferring insecticide resistance.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 197
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 170 (1992), S. 605-613 
    ISSN: 1432-1351
    Schlagwort(e): Phototransduction ; Sensitivity ; Facilitation ; Calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Deeply dark adapted (1 h) photoreceptor cells of the honey bee drone show a light-induced enhancement of sensitivity (facilitation) as an aftereffect of illumination or in the presence of dim backgrounds. The Ca2+-dependency of this effect was studied: Reduction of extracellular Ca2+ to 0.1 mM decreases the sensitivity of a dark adapted cell, and the light-induced increase in sensitivity due to repetitive, dim, 20 ms test flashes is slower than in normal saline. After a sensitizing conditioning light, the sensitivity drops faster in low-calcium saline. The light-induced enhancement of sensitivity is mimicked by pressure injections of low amounts of Ca2+ (Ca2+/EGTA-buffers; 0.15 μM free Ca2+) into a dark adapted cell. Injection of EGTA alone decreases the sensitivity. Injection of a solution containing ca1 mM free Ca2+ sequentially decreases and later increases the sensitivity transiently. These results suggest a model in which a progressive increase in intracellular Ca2+ concentration by light first increases (facilitates), and, at higher concentrations, decreases (light adapts) the sensitivity of the cells. One possible site of action for this positive and negative feedback control of cell sensitivity by Ca2+ is the endoplasmic reticulum.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 198
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 83 (1992), S. 821-826 
    ISSN: 1432-2242
    Schlagwort(e): Drosophila ; Balancers ; Inversions ; Translocations ; Meiosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We used a screen for maternally generated late embryonic lethals as a new method for the isolation of inversions that are suitable for the balancing of mutations in Drosophila hydei. The recovery of several inversions by this method demonstrates that female meiosis in D. hydei apparently differs from meiosis in female D. melanogaster, since in D. hydei the defective chromosomes which are generated by a single crossing-over within a paracentric inversion can be recovered via the egg nucleus. In addition, the classic method of crossingover suppression was used in order to isolate more inversions and to improve the balancing capacities of inversions. We succeeded in constructing chromosomes that allow the balancing of mutations on nearly the whole genome of D. hydei. We discuss here whether or not this method is suited for application to other organisms.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 199
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 167 (1992), S. 19-32 
    ISSN: 1615-6102
    Schlagwort(e): Scales ; Golgi apparatus ; Vacuole ; Calcium ; Vesicle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The unicellular green algal flagellate,Mesostigma viride, is characterized by an extracellular matrix of multiple layers of scales. These scales are processed within the Golgi apparatus (GA). The GA consists of 11–13 closely stacked cisternae. The cis cisternae are highly fenestrated and grow via vesicles from adjacent transition ER. Medial-trans cisternae are plate-like with swollen peripheries. The calcified basket scales are produced in the peripheries of GA cisternae, usually first observable in the medial zone of the cisternal stack. Cisternal membrane closely conforms to the precise architecture of the developing scale. Antimonate labeling reveals that a population of smooth cytoplasmic vacuoles situated near the GA contains a store of calcium, perhaps used for scale processing. Vesicles carry calcium from these vacuoles to the cisternal loci where basket scale ontogenesis is occurring. The smaller scale types are produced within the central areas of the GA. A discussion concerning membrane flow through the GA is provided.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 200
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 168 (1992), S. 141-152 
    ISSN: 1615-6102
    Schlagwort(e): Calcium ; Chara corallina ; Cytoplasmic streaming ; Gravity perception ; Hydrostatic pressure ; Sensory transduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Hydrostatic pressure applied to one end of a horizontalChara cell induces a polarity of cytoplasmic streaming, thus mimicking the effect of gravity. A positive hydrostatic pressure induces a more rapid streaming away from the applied pressure and a slower streaming toward the applied pressure. In contrast, a negative pressure induces a more rapid streaming toward and a slower streaming away from the applied pressure. Both the hydrostatic pressure-induced and gravity-induced polarity of cytoplasmic streaming respond identically to cell ligation, UV microbeam irradiation, external Ca2+ concentrations, osmotic pressure, neutral red, TEA Cl−, and the Ca2+ channel blockers nifedipine and LaCl3. In addition, hydrostatic pressure applied to the bottom of a vertically-oriented cell can abolish and even reverse the gravity-induced polarity of cytoplasmic streaming. These data indicate that both gravity and hydrostatic pressure act at the same point of the signal transduction chain leading to the induction of a polarity of cytoplasmic streaming and support the hypothesis that characean cells respond to gravity by sensing a gravity-induced pressure differential between the cell ends.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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