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  • Evolution  (37)
  • gene expression
  • Springer  (59)
  • American Meteorological Society
  • 1995-1999
  • 1990-1994  (59)
  • 1965-1969
  • 1990  (59)
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Verlag/Herausgeber
Erscheinungszeitraum
  • 1995-1999
  • 1990-1994  (59)
  • 1965-1969
Jahr
  • 1
    ISSN: 1420-9071
    Schlagwort(e): Aldehyde dehydrogenase ; developmental changes ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Previous reports suggested that the major cytosolic aldehyde dehydrogenase (ALDH1) was present in fetal and infant livers, but the major mitochondrial isozyme (ALDH2) was absent or severely diminished. Re-examination by means of starch gel electrophoresis followed by enzyme activity staining, and by means of dot blot immuno-hybridization of liver samples with known genotypes of theALDH 2 locus, indicated that bothALDH 1 andALDH 2 genes are expressed in fetal and infant livers. In addition, ALDH4 isozyme was also observed. The results imply that a fetus with the ‘usual’ homozygousALDH 2 1 /ALDH 2 1 genotype, but not one with the atypicalALDH 2 1 /ALDH 2 2 orALDH 2 2 /ALDH 2 2 , is capable of detoxifying acetaldehyde transferred from the mother.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal for general philosophy of science 21 (1990), S. 309-328 
    ISSN: 1572-8587
    Schlagwort(e): Evolution ; evolutionäre Erkenntnistheorie ; Organismus ; Autonomie ; Abbildungskritik
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Philosophie , Wissenschaftskunde und Wissenschaftsorganisation, Hochschul- und Universitätswesen, Museumswissenschaft
    Notizen: Summary The concept of evolutionary epistemology has been critically discussed by philosophers who have mainly pointed to unacceptable philosophical tenets (cf. Vittorio Hösle, this Journal, Vol. 19 (1988), pp. 348–377). However, as most philosophers are extremely reluctant to critically treat the biological theories on which the ideas of evolutionary epistemology are based, the invalid concepts of adaption escaped their critical scrutiny. Therefore the influence of preconceived biological theories on the biological basis of evolutionary epistemology and the distorting consequences on the philosophical level could not be elaborated. The following context sketches a new view of organismic reasoning and its impact on evolutionary aspects of epistemology. The basic theorem of adaptation is shown to be unacceptable and invalid if organisms are conceived as autonomous entities which can only evolve according to their specific internal organismic properties.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 9 (1990), S. 110-118 
    ISSN: 1432-0789
    Schlagwort(e): Kuehneltiella terricola gen. nov., sp. nov. ; Soil ciliates ; Colpodidae ; Systematics ; Evolution ; Australia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The morphology and biology of the colpodid ciliate Kuehneltiella terricola gen. nov., sp. nov. has been investigated using living organisms, various silver impregnation methods, and scanning electron microscopy. The new species has been isolated in soil from central Australia and might be endemic to this continent. The new genus Kuehneltiella differs from its nearest relative, Bresslaua, in having a right oral polykinetid composed of a single row of dikinetids. A reinvestigation of Lynn's slides of Bresslaua insidiatrix showed that, contrary to the statement of Lynn (1979), this species has a typic colpodid right oral polykinetid, i.e., composed of many short, disordered kineties. A brief review of the literature suggests that simple, single-rowed, right oral polykinetids are apomorphic in the colpodids s. str. Further, this special character has obviously evolved independently several times within the class Colpodea and even within the colpodids s. str. An illustrated key to the genera of the family Colpodidae is provided.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 9 (1990), S. 95-100 
    ISSN: 1432-0789
    Schlagwort(e): Assulina-Valkanovia ; Testacea ; Polymorphism ; Genotypes ; Evolution ; Spruce forest ; Sphagnum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The taxonomy and evolution of the Assulina-Valkanovia complex were investigated in a spruce forest soil which included a Sphagnum plot (GDR, Thuringia). In both habitats Assulina muscorum occurred in two colour forms (brown and colourless) and four shapes. A quantified phenospectrum from Assulina muscorum was obtained. The four shapes were distributed differently between the brown and the colourless forms in Sphagnum and soil. The shell measurements showed statistically significant differences between the brown and the colourless forms. Even between the two brown populations there were some significant differences. Each of the four shape types of brown and of colourless Assulina can be kept in clonal cultures for some time. However, without selection, single cultures eventually revert to mixed types. The four shape types show different degrees of stability. These colour and shape forms are genotypes, which can also occur for short periods in the natural habitats. The brown populations in Sphagnum and in the soil were dominated by different shape types during the period of investigation. Valkanovia elegans cannot be distinguished from Assulina muscorum type 4, but Valkanovia can inhabit both upper and lower soil horizons, whereas Assulina and its forms lives exclusively in the upper horizon (litter). Valkanovia from the lower horizon is constant in clonal culture. The conclusion of the present investigation is that there are stable and unstable constellations within a changeable genome, which give asexual groups both a taxonomic structure and a continuum of forms. Selection can increase stability, by polygenic control of features.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Current genetics 17 (1990), S. 223-227 
    ISSN: 1432-0983
    Schlagwort(e): Orotidine-5′-phosphate decarboxylase ; Cephalosporium acremonium ; Recombinant DNA ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have cloned the Cephalosporium acremonium pyr4 gene by cross-hybridization with the equivalent gene from Neurospora crassa, the closest relative from which this gene is available. The C. acremonium pyr4 gene complements an E. coli pyrF mutant lacking orotidine-5′-phosphate decarboxylase (OMPdecase), and most probably does not contain introns. Maxicell analysis in E. coli shows that it encodes a 46 kDa polypeptide. The C. acremonium OMPdecase contains a highly conserved pentadecapeptide characteristic for this category of enzyme. Extensive sequence comparison suggests an important role of this region in enzymatic activity.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-0983
    Schlagwort(e): Trypanosomes ; RNA polymerase ; Transcription ; Evolution ; Phylogeny
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have sequenced the genes encoding te largest subunits of the three classes of DNA-dependent RNA polymerases of Trypanosoma brucei. The nucleotide and deduced amino acid sequences were compared and aligned with the corresponding sequences of other eukaryotes. Phylogenetic relationships were subsequently calculated with a distant matrix, a bootstrapped parsimony and a maximum-likelihood method. These independent calculations resulted in trees with very similar topologies. The analyses show that all the largest subunits of T. brucei are evolutionarily distant members within each of the three RNA polymerase classes. An early separation of the trypanosomal subunits from the eukaryotic lineage might from the fundamental basis for the unusual transcription process of this species. Finally, all dendrograms show a separate ramification for the largest subunit of RNA polymerase I, II and III. RNA polymerase II and/or III form a bifurcation with the archaebacterial lineage. RNA polymerase I, however, arises separately from the eubacterial β′ lineage. This suggests that the three eukaryotic RNA polymerase classes are not simply derived by two gene duplications of an ancestral gene with subsequent differentiation.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-0983
    Schlagwort(e): Cyanophora paradoxa ; Ferredoxin-NADP+-oxidoreductase ; Protein-import ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cyanophora paradoxa is an important model organism for the study of the transition from endocytobiontic cyanobacteria to factual eukaryotic cell organelles. The cyanelles of these organisms possess cyanobacterial, as well as plastidic, characteristics. Although the transfer of cyanellar proteins from cytosolic into cyanellar space has been shown, the process of translocation of a known protein across the peptidoglycan layer and the envelope membranes has not been characterized. In this study we demonstrate that a specific and obligate cyanelle protein —Ferredoxin-NADP+-oxidoreductase (FNR) — is coded on the nuclear genome, synthesized on 80S ribosomes and transported from the eukaryotic cell compartment into the cyanelles of Cyanophora paradoxa, an original intracellular host-guest relation. These results indicate a gene transfer from guest to host genome and support the view that, in spite of their cyanobacterial origin, cyanelles have been evolved to cell organelles comparable to plastids.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 30 (1990), S. 489-492 
    ISSN: 1432-1432
    Schlagwort(e): Actinomyces ; Phosphotransferase ; Aminoglycoside ; Phylogenetic tree ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The protein sequences of seven 3′-aminoglycoside phosphotransferases falling into the six identified types and three 6′-aminoglycoside phosphotransferases were analyzed to give a rooted phylogenetic tree. This tree supports the origin of these groups of enzymes in an ancestor closely related to the actinomycetes, and that horizontal transfer of the resistance genes occurred, possibly via transposons. The implications for genetic engineering of a novel antibiotic are discussed.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1432-1432
    Schlagwort(e): Mitochondrial DNA ; Evolution ; Echinoderms ; Sea stars ; DNA sequence ; Mitochondrial proteins ; Mitochondrial tRNA genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have cloned and sequenced over 9 kb of the mitochondrial genome from the sea starPisaster ochraceus. Within a continuous 8.0-kb fragment are located the genes for NADH dehydrogenase subunits 1, 2, 3, and 4L (ND1, ND2, ND3, and ND4L), cytochrome oxidase subunits I, II, and III (COI, COII, and COIII), and adenosine triphosphatase subunits 6 and 8 (ATPase 6 and ATPase 8). This large fragment also contains a cluster of 13 tRNA genes between ND1 and COI as well as the genes for isoleucine tRNA between ND1 and ND2, arginine tRNA between COI and ND4L, lysine tRNA between COII and ATPase 8, and the serine (UCN) tRNA between COIII and ND3. The genes for the other five tRNAs lie outside this fragment. The gene for phenylalanine tRNA is located between cytochrome b and the 12S ribosomal genes. The genes for tRNAglu and tRNAthr are 3′ to the 12S ribosomal gene. The tRNAs for histidine and serine (AGN) are adjacent to each other and lie between ND4 and ND5. These data confirm the novel gene order in mitochondrial DNA (mtDNA) of sea stars and delineate additional distinctions between the sea star and other mtDNA molecules.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 30 (1990), S. 60-71 
    ISSN: 1432-1432
    Schlagwort(e): Cysteine endopeptidase ; Cysteine proteinase ; Inhibitor ; Cystatin ; Kininogen ; Evolution ; Amino acid sequence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have examined the amino acid sequences of a number of proteins that have been suggested to be related to chicken cystatin, a protein from chicken egg white that inhibits cysteine proteinases. On the basis of statistical analysis, the following proteins were found to be members of the cystatin superfamily: human cystatin A, rat cystatin A(α), human cystatin B, rat cystatin B(β), rice cystatin, human cystatin C, ox colostrum cystatin, human cystatin S, human cystatin SA, human cystatin SN, chicken cystatin, puff adder cystatin, human kininogen, ox kininogen, rat kininogen, rat T-kininogens 1 and 2, human α2HS-glycoprotein, and human histidine-rich glycoprotein. Fibronectin is shown not to be a member of this superfamily, and the c-Ha-ras oncogene protein p21(Val-12) probably is not a member also. It was convenient to divide members of the superfamily into four types on the basis of the presence of one, two, or three copies of cystatin-like segments and the presence or absence of disulfide bonds. Evolutionary dendrograms were calculated by three methods, and from these we have constructed a scheme depicting the sequence of events in the evolution of these proteins. We suggest that about 1000 million years ago a precursor containing disulfide loops appeared, and that all disulfide-containing cystatins are derived from this. We follow the evolution of the proteins of the superfamily along four main lineages, with special attention to the part that duplication of segments has played in the development of the more complex molecules.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 424-431 
    ISSN: 1432-1432
    Schlagwort(e): Drosophila melanogaster ; Evolution ; Hybrid dysgenesis ; I elements ; Transposons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary There are two categories of strains inDrosophila melanogaster with respect to the I-R system of hybrid dysgenesis. The inducer strains contain particular transposable elements named I factors. They are not present in the strains of the other category called reactive (R) strains. Defective I elements are present in the pericentromeric regions of both categories of strains. This last subfamily of I sequences has not yet been described in detail and little is known about its origin. In this paper, we report that the defective I elements display an average of 94% of sequence identity with each other and with the transposable I factor. The results suggest that they cannot be the progenitors of the present day I factors, but that each of these two subfamilies started to evolve independently several million years ago. Furthermore, the sequence comparison of these I elements with an active I factor fromDrosophila teissieri provides useful information about when the deleted I elements became immobilized.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 30 (1990), S. 333-346 
    ISSN: 1432-1432
    Schlagwort(e): Protamine ; Evolution ; Nuclear protein ; DNA condensation ; Sperm proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The availability of the amino acid sequence for nine different mammalian P1 family protamines and the revised amino acid sequence of the chicken protamine galline (Oliva and Dixon 1989) reveals a much close relationship between mammalian and avian protamines than was previously thought (Nakano et al. 1976). Dot matrix analysis of all protamine genes for which genomic DNA or cDNA sequence is available reveals both marked sequence similarities in the mammalian protamine gene family and internal repeated sequences in the chicken protamine gene. The detailed alignments of the cis-acting regulatory DNA sequences shows several consensus sequence patterns, particularly the conservation of a cAMP response element (CRE) in all the protamine genes and of the regions flanking the TATA box, CAP site, N-terminal coding region, and polyadenylation signal. In addition we have found a high frequency of the CA dinucleotide immediately adjacent to the CRE element of both the protamine genes and the testis transition proteins, a feature not present in other genes, which suggests the existence of an extended CRE motif involved in the coordinate expression of protamine and transition protein genes during spermatogenesis. Overall these findings suggest the existence of an avian-mammalian P1 protamine gene line and are discussed in the context of different hypotheses for protamine gene evolution and regulation.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 30 (1990), S. 409-424 
    ISSN: 1432-1432
    Schlagwort(e): Phylogeny ; Tetrapods ; Morphology ; Cladistics ; Divergence ; Evolution ; Amphibians ; Reptiles ; Birds ; Mammals
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The phylogeny of the major groups of tetrapods (amphibians, reptiles, birds, and mammals) has until recently been poorly understood. Cladistic analyses of morphological data are producing new hypotheses concerning the relationships of the major groups, with a focus on the identification of monophyletic groups. Molecular phylogenies support some of these views and dispute others. Geological dates of the major evolutionary branching points are recalculated on the basis of the cladograms and new fossil finds.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 3-9 
    ISSN: 1432-1432
    Schlagwort(e): Caenorhabditis elegans ; Caenorhabditis briggsae ; hsp70 ; grp78 ; Gene comparison ; Evolution ; Regulatory elements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Caenorhabditis elegans andCaenorhabditis briggsae are two closely related nematode species that are nearly identical morphologically. Interspecific cross-hybridizing DNA appears to be restricted primarily to coding regions. We compared portions of thehsp-3 homologs two grp 78-like genes, fromC. elegans andC. briggsae and detected regions of DNA identity in the coding region, the 5′ flanking DNAs, and the introns. Thehsp-3 homologs share approximately 98% and 93% identity at the amino acid and nucleotide levels, respectively. Using the nucleotide substitution rate at the silent third position of the codons, we have estimated a lower limit for the date of divergence betweenC. elegans andC. briggsae to be approximately 23–32 million years ago. The 5′ flanking DNAs and one of the introns contain elements that are highly conserved betweenC. elegans andC. briggsae. Some of the regions of nucleotide identity in the 5′ flanking DNAs correspond to previously detected identities including viral enhancer sequences, a heat shock element, and an element present in the regulatory regions of mammalian grp78 and grp94 genes. We propose that a comparison ofC. elegans andC. briggsae sequences will be useful in the detection of potential regulatory and structural elements.
    Materialart: Digitale Medien
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  • 15
    ISSN: 1432-1432
    Schlagwort(e): Archaebacteria ; rRNA operons ; Secondary structure ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Several sequences flanking the large rRNA genes of several transcripts from extreme thermophiles, extreme halophiles, and methanogens were aligned and analyzed for the presence of common primary and secondary structural features, which would bear on the concept of monphyletic archaebacteria. Few sequences were common to all the archaebacterial transcripts, and these were confined to short regions generally flanking putative double helices. At a secondary structural level, however, in addition to the previously characterized processing stems of the 16S and 23S RNAs, four helices were detected that were common to the archaebacterial transcripts: two in the 16S RNA leader sequence and two in the 16S-23S RNA spacer. Although all of these helices vary in size and form from organism to organism, three of them contain double helical segments that are strongly supported by compensating base changes among the three archaebacterial groups. Three extreme halophiles exhibited two additional helices in their relatively large spacers and a further helix preceding the 5S RNA, which are also supported by compensating base changes. Ribosomal RNA transcripts from eubateria/chloroplasts and eukaryotes were also examined for secondary structural features with locations and forms corresponding to those of the archaebacteria, but none were detected. The analysis provides support for the monophyletic nature of the archaebacteria and reinforces their differences from eubacteria/chloroplasts and eukaryotes.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 205-210 
    ISSN: 1432-1432
    Schlagwort(e): Isozyme ; Intron ; Phylogenetic tree ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Both the mouse cytosolic malate dehydrogenase gene and its mitochondrial counterpart contain eight introns, of which two are present at identical positions between the isozyme genes. The probability that the two intron positions coincide by chance between the two genes has been shown to be significantly small (=1.3×10−3), suggesting that the conservation of the intron positions has a biological significance. On the basis of a rooted phylogenetic tree inferred from a comparison of these isozymes and lactate dehydrogenases, we have shown that the origins of the conserved introns are very old, possibly going back to a date before the divergence of eubacteria, archaebacteria, and eukaryotes. In the aspartate aminotransferase isozyme genes, five of the introns are at identical places. The origins of the five conserved introns, however, are not obvious at present. It remains possible that some or all of the conserved introns have evolved after the divergence of eubacteria and eukaryotes.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 325-329 
    ISSN: 1432-1432
    Schlagwort(e): PLP-dependent decarboxylase ; Evolution ; Profile analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A database search has revealed significant and extensive sequence similarities among prokaryotic and eukaryotic pyridoxal phosphate (PLP)-dependent decarboxylases, includingDrosophila glutamic acid decarboxylase (GAD) and bacterial histidine decarboxylase (HDC). Based on these findings, the sequences of seven PLP-dependent decarboxylases from five different organisms have been aligned to derive a consensus sequence for this family of enzymes. In addition, quantitative methods have been employed to calculate the relative evolutionary distances between pairs of the decarboxylases comprising this family. The multiple sequence analysis together with the quantitative results strongly suggest an ancient and common origin for all PLP-dependent decarboxylases. This analysis also indicates that prokaryotic and eukaryotic HDC activities evolved independently. Finally, a sensitive search algorithm (PROFILE) was unable to detect additional members of this decarboxylase family in protein sequence databases.
    Materialart: Digitale Medien
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Journal of molecular evolution 31 (1990), S. 485-492 
    ISSN: 1432-1432
    Schlagwort(e): BK virus ; Strains ; Regulatory region ; Late region ; Nucleotide sequence ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Within the genome of human polyomavirus BK (BKV), there exists a noncoding regulatory region toward the late region side of the origin of DNA replication. In most BKV strains isolated by viral culture, this regulatory region contains tandem repeats varying in size. Recently. however, several laboratories isolated new BKV strains (designated as archetypal strains) lacking such repeat sequences. To examine the genetic relationship between archetypal strains, a phylogenetic tree was constructed for seven BKV strains, including three archetypal strains, from DNA sequence data on the late genes, those for leader protein (agnoprotein), and those for structural proteins (VP1, VP2, and VP3). For three strains data previously reported were used, whereas for the others sequences were determined in this study. From total numbers of nucleotide substitutions in each pair of strains, a phylogenetic tree was constructed by the unweighted pair-group method. The phylogenetic tree obtained reveals that BKV strains containing the archetypal regulatory region do not constitute a cluster of closely related strains and that these strains, together with those carrying the major part of the archetypal regulatory region, are widespread in the BKV population. This finding suggests that the basic structure of the archetypal regulatory region has been conserved in the course of BKV evolution.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 46 (1990), S. 530-533 
    ISSN: 1420-9071
    Schlagwort(e): Evolution ; genetics ; heritability ; locomotion ; physiology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Locomotor capacities and their physiological bases are thought to be of considerable selective importance in natural populations. Within this functional complex, organismal performance traits (e.g., speed, stamina) are expected to be of more direct selective importance than their suborganismal determinants (e.g., heart size). Quantitative genetics theory predicts that traits of greater selective importance should generally have lower heritabilities at equilibrium. Contrary to these expectations, we report that organismal performance traits had the highest heritabilities in a natural population of garter snakes.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 167 (1990), S. 71-78 
    ISSN: 1432-1351
    Schlagwort(e): Compound eye ; Optics ; Crustacea ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Compound eyes of the decapod shrimp Gennadas, the hermit crab Dardanus, and the syncarid crustacean Anaspides are studied histologically and with optical experiments. The results demonstrate that these three crustaceans all have refracting superposition eyes. The conclusion is based on the following observations: 1. There is a wide clear-zone, which allows for a superposition image to be formed. 2. Dark-adapted eyes display a large eye-glow, and the ommatidia are not optically isolated. 3. The crystalline cones have the shape typical for refracting superposition eyes, and they contain the required lens-cylinder gradient of refractive index. Euphausiids and mysids were previously thought to be the only crustaceans with refracting superposition eyes, whereas the species investigated here were assumed to have reflecting superposition eyes (decapod shrimps) or apposition eyes (hermit crabs and syncarids). The present findings increase more than twofold the number of crustacean groups that are known to have developed refracting superposition optics. It also provides insight into the evolutionary mechanisms that may have led to the development of this type of imaging optics.
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  • 21
    ISSN: 1432-072X
    Schlagwort(e): Oligotrophic bacteria ; Caulobacter ; “Hyphobacter” ; Hyphomonas ; Hyphomicrobium ; Antibiotic sensitivity ; Evolution ; Fatty acids ; Lipids ; Taxonomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A new approach was developed for the determination of taxonomic and evolutional relationships among four genera of oligotrophic bacteria. The main idea of this approach is the algorithmized integrative analysis of the morphological and physiological specificity of these bacteria, their 5S rRNA sequences, fatty acid and lipid composition of their membranes, as well as their sensitivity to a large variety of antibiotics. It was shown that the genera Caulobacter and Hyphomonas are closely related to each other, but they are both distant from Hyphomicrobium species. The new genus, “Hyphobacter”, is placed between Caulobacter and Hyphomonas. Taxonomic heterogeneity was found to exist within the genera Caulobacter and Hyphomicrobium. Evolutional pathways from Caulobacter to Hyphomicrobium are proposed on the basis of the present data. No correlations were found between the cell morphology of the organisms and their geno-and chemotaxonomy.
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  • 22
    ISSN: 1432-072X
    Schlagwort(e): Eubacterium ; Thermophile ; Evolution ; Fervidobacterium ; Lipids ; Thermotoga
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An extremely thermophilic anaerobic fermentative eubacterium growing at temperatures between 50 and 80°C (opt.: 65°C) was isolated from an Icelandic hot spring. The cells were Gram-negative motile rods, about 1.8 μm in length, and 0.6 μm in width occurring singly and in pairs. About 50% of the cells formed large spheroids at one end similar to Fervidobacterium nodosum. The new isolate H 21 differed from Fervidobacterium nodosum by a 6 mol % higher GC-content of its DNA (41 mol %), its ability to grow on cellulose, and insignificant DNA homology. The lipids of isolate H 21 were similar to that of members of “Thermotogales”. 16S rRNA sequencing of isolate H 21 and Fervidobacterium nodosum indicated (a) that isolate H 21 represents a new species of the genus Fervidobacterium which we name Fervidobacterium islandicum and (b) that the genus Fervidobacterium belongs to the “Thermotogales” branch.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 28 (1990), S. 9-20 
    ISSN: 1573-4927
    Schlagwort(e): mutator ; transposable element ; alcohol dehydrogenase ; maize ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract A secondary mutant, derived from an allele of maize alcohol dehydrogenase 1 (Adh1) carrying a Mutator transposable element (Mu1) in its first intron, was reported to exhibit a threefold decrease in ADH enzymatic activity and steady-state RNA levels compared to the original mutant. The original mutant,Adh1-S3034 (abbreviatedS3034), was previously characterized at the molecular level. The derivative, abbreviatedS3034b, has now been cloned; at the DNA sequence level the insertion and surroundingAdh1 sequences are indistinguishable fromS3034. Furthermore, in our lines there is no difference in relative ADH activities between products of the two putative alleles. A comparison of gene expression in heterozygotes obtained by crossing to different tester lines reveals a correlation between the measured decrease in levels of ADH polypeptide produced by the mutant allele and the background in which it is measured; this effect is distinct from any background-related variation in the expression of the progenitor allele. It does not appear to be attributable to alternative patterns of DNA modification. It appears to reflect a background-associated difference in the level of normalAdh1-RNA produced. Thus the previously reported distinction betweenS3034 andS3034b may be due to differences in the extent to which the mutant allele and a given genetic background interact to produce functionalAdh1-RNA.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 28 (1990), S. 337-346 
    ISSN: 1573-4927
    Schlagwort(e): glutamate dehydrogenase ; Drosophila melanogaster ; gene expression ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract We have isolated theDrosophila melanogaster locus coding forl-glutamate dehydrogenase (EC 1.4.1.3) by virtue of its similarity to the corresponding human gene. There is only one copy of this gene in the fruit fly genome, located on the right arm of chromosome 3 (95D1-4). The transcript includes at least one large intron and matures to a ∼2.4-kb-long polyadenylated RNA whose expression is under developmental control.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 28 (1990), S. 337-346 
    ISSN: 1573-4927
    Schlagwort(e): glutamate dehydrogenase ; Drosophila melanogaster ; gene expression ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract We have isolated theDrosophila melanogaster locus coding forl-glutamate dehydrogenase (EC 1.4.1.3) by virtue of its similarity to the corresponding human gene. There is only one copy of this gene in the fruit fly genome, located on the right arm of chromosome 3 (95D1-4). The transcript includes at least one large intron and matures to a ∼2.4-kb-long polyadenylated RNA whose expression is under developmental control.
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 28 (1990), S. 445-457 
    ISSN: 1573-4927
    Schlagwort(e): mouse ; hemoglobin ; embryonic ; adult ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Adult alpha-globin in mice is synthesized in large amounts during development, first in the primitive, nucleated erythrocytes of yolk sac origin and later in the definitive, nonnucleated erythrocytes that differentiate in the fetal liver, spleen, and bone marrow. Isoelectric focusing analysis of hemoglobins of mice with theHba g2 andHba c haplotypes shows that the ratios of alpha chain 1 to chain 5m and alpha chain 1 to chain 4 in adult hemoglobins fromHba g2 andHba c mice, respectively, change between day 11.5 and day 16.5 of gestation in nucleated red cells, while no change occurs in nonnucleated red cells. The percentage ratios of the two different alpha-globin chains are different inHba g2 andHba c mice for EII, EIII, and adult hemoglobin. In nucleated red cells of yolk sac origin, differences and changes in alpha-globin ratios are a composite of changing globin gene transcription and posttranslational competitive affinities among globins to form embryonic and adult hemoglobin tetramers.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 14 (1990), S. 207-216 
    ISSN: 1573-5028
    Schlagwort(e): developmental mutant ; gene expression ; nodule formation ; Pisum sativum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Mutational analysis of Pisum sativum L. was used to search for constitutive proteins that might function in nodule formation. The sym 5 locus is a mutational hot spot, represented by seven independently derived mutant lines with decreased nodulation. Comparison of two-dimensional polyacrylamide gels of in vitro-translated root RNA showed a consistent difference in the migrational pattern of one peptide. In the nodulating parental cultivar ‘Sparkle’, a 66 kDa peptide had a pI of 5.9. In four of the five tested sym 5 mutants, the 66 kDa peptide had a more acidic pI of 5.8. This 66 kDa peptide is found in lateral root, tap root, and shoot. Its expression was independent of rhizobial inoculation, root temperature, or light.
    Materialart: Digitale Medien
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  • 28
    ISSN: 1573-5028
    Schlagwort(e): auxin action ; cDNA clone ; gene expression ; developmental regulation ; strawberry fruit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A complementary DNA (cDNA) library has been constructed in λgt10 from poly(A)+ mRNA isolated from auxin-deprived strawberry receptacles. By differential plaque filter hybridization, a cDNA (λSAR5) to an auxin-repressed mRNA has been isolated. The expression of the auxin-repressed gene is studied at various stages of normal fruit development and in fruits of variant strawberry genotype using λSAR5 as a probe. Northern analyses of RNA isolated from pollinated and unpollinated fruits of various developmental stages revealed that mRNA corresponding to the λSAR5 clone is repressed during normal fruit development, and the level of λSAR5 mRNA is regulated by endogenous auxin. Furthermore, results with both normal and variant genotype strawberry fruit indicate that there is a positive correlation between growth of strawberry fruit and repression of mRNA corresponding to the λSAR5 clone. The λSAR5 cDNA has been sequenced and is 723 nucleotides in length. The deduced protein has 111 amino acid residues with a molecular mass of 12.5 kDa. The putative polypeptide starts at nucleotide position 20 and ends at 352. The molecular weight of the predicted polypeptide is in agreement with the molecular weight of the in vitro translated polypeptide of hybrid selected mRNA. A comparison of the nucleotide and deduced amino acid sequence of λSAR5 with nucleotide and protein sequences in data banks has not revealed any homology to known proteins.
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  • 29
    ISSN: 1573-5028
    Schlagwort(e): auxin action ; cDNA clones ; developmental regulation ; gene expression ; strawberry fruit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract By differential hybridization, two auxin-inducible cDNA clones (λSAR1 and λSAR2) have been isolated from a cDNA library constructed to poly(A)+ mRNA from auxin-treated strawberry receptacles. Both the clones have been used as probes to study the expression of the auxin-induced genes in pollinated and unpollinated fruits of various stages of development and in different organs. A high level of auxin-induced mRNAs is found in pollinated fruits as compared to unpollinated fruits of the same age, suggesting that the expression of the auxin-induced genes is developmentally regulated and the level of auxin-induced mRNAs is regulated by endogenous auxin. Furthermore, our data on the expression of λSAR1 and λSAR2 genes in pollinated and unpollinated fruits revealed a positive correlation between growth of strawberry fruit and the induction of mRNA corresponding to the λSAR1 and λSAR2 clones. Ethylene has no effect on the expression of the auxin-induced mRNAs. λSAR1 mRNA is not detected in other parts of strawberry plants whereas λSAR2 mRNA is present in roots. Furthermore, mRNA corresponding to λSAR1 and λSAR2 is not detected in other auxin-responsive plant systems such as pea epicotyls and bean explants.
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 15 (1990), S. 175-176 
    ISSN: 1573-5028
    Schlagwort(e): Lupinus polyphyllus ; cell culture ; cDNA clone ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Molecular biology reports 14 (1990), S. 1-9 
    ISSN: 1573-4978
    Schlagwort(e): prosomes ; messenger RNP ; intermediate filaments ; heat shock complex ; multicatalytical protease (MCP) ; protein synthesis ; gene expression ; differentiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract PROSOMES are a novel class of small RNP particles of uniform morphology, but of variable RNA (pRNA) and protein composition (about 650 000 MW; 12 nm diameter in the EM). They were discovered as subcomplexes of free mRNP, tightly attached to inactive mRNA in the cytoplasm. The pRNAs hybridize stably to mRNA. Prosomes associate in vitro to mRNA and inhibit cell free protein synthesis inducing an mRNA structure unable to interact with ribosomes. Many types of prosomes were observed. The individual particle is made up by a variable combination of about 20 characteristic proteins and one or several pRNA. Some prosomal proteins are glycosylated, phosphorylated and, possibly, ADP-ribosylated and are highly conserved in evolution whilst others vary with the species and the mRNA population they are associated to. A protease activity was found associated to prosomes. The function(s) of the prosomes is(are) still unknown. The differential inhibition of in vitro protein synthesis points to a capacity to recognize mRNA and to keep it in an inactive state. The observation with the aid of monoclonal antibodies (pMABs) that prosomes and thus mRNP are attached to the intermediate filaments (IF) raises the question if one of the functions of the IF might be in the topological distribution of mRNA within the cell. Similar to the cytokeratin fibers, the prosome networks bridge neighboring cells at specific positions. — The nucleus also contains some prosomal antigens, located on chromosomes and on the nuclear matrix. Their presence and distribution in the cell compartments varies with the cell type and the prosomal antigen probed. Oocytes contain large amounts of prosomes. In embryonic development, the synthesis of individual prosomal proteins starts progressively after the blastula stage and resumes fully in gastrulation only; cleavage and blastula stage prosomes are thus of maternal origin. The nucleo-cytoplasmic distribution of prosomal antigens changes in embryos, with the stage of development and type of differentiation. In human tissues specific patterns of prosomal antigens were found in function of cell type and differentiation. In view of these data, the hypothesis may be formulated that prosomes are a population of mRNA-linked RNP which includes particles of varying individual composition and hence specificity. Attached to IF sub-networks, specific types of prosomes might accompany families of mRNA in function of the physiological state and the specialisation of given differentiated cell types. The cell-type specific organisation of the IF networks might be related to the messenger RNA complement of a given cell, and to its status of gene expression. The prosomes might thus have a function in controlling the transport, distribution and control of activity of specific mRNAs in the cell.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 14 (1990), S. 585-594 
    ISSN: 1573-5028
    Schlagwort(e): cytokinin ; gene expression ; mRNA ; nitrate reductase ; transcriptional regulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract To investigate the molecular mechanism of cytokinin regulation of nitrate reductase (NR) activity, the influence of benzyladenine (BA) on the level of NR transcript was studied in etiolated barley leaves using a barley NR cDNA as a probe. Northern blot analyses of the levels of NR poly (A)+ RNA indicate that the amount present is proportional to the concentration of BA (2×10-8 to 2×10-4 M) applied to the leaves. Enhancement of NR mRNA by 2×10-5 M BA was clearly detected after 15 minutes of exposure of the leaves to light. The enhancement is cytokinin-specific and adenine is ineffective. Brief treatment with the protein synthesis inhibitor, cycloheximide, inhibited BA-enhanced NR activity but did not inhibit BA-enhanced NR transcript level, thus the enhancement was independent of concurrent protein synthesis. Nuclear runoff transcription studies showed that the enhancement of NR mRNA was at least partially due to increased transcription rates.
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  • 33
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; glutamine synthetase ; leghaemoglobin ; nitrogen metabolism ; Phaseolus vulgaris ; root nodules
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In this paper we have examined whether the four glutamine synthetase (gln) genes, expressed in roots and nodules of Phaseolus vulgaris are substrate-inducible by ammonium. Manipulation of the ammonium pool in roots, through addition and removal of exogenous ammonium, did not elicit any changes in the abundances of the four mRNAs thus suggesting that the gln genes in roots of this legume are neither substrate-inducible by ammonium nor derepressed during nitrogen starvation. In nodules the effect of the ammonium supply on expression of the gln genes has been examined by growing nodules under argon/oxygen atmospheres, or with a number of Fix- Rhizobium mutants, and following addition of exogenous ammonium. The results of these experiments suggest that the expression of the gln-γ gene, which is strongly induced during nodule development, is primarily under a developmental control. However nitrogen fixation appears to have a quantitative effect on expression of gln-γ as the abundance of this mRNA is about 2 to 4-fold higher under nitrogen-fixing conditions. This effect could not be mimicked by addition of exogenous ammonium and moreover is not specific to the gln-γ gene as mRNA from a leghaemoglobin gene was similarly affected. Taken together these results have failed to find an effect of ammonium on specifically inducing the expression of glutamine synthetase genes in roots and nodules of P. vulgaris.
    Materialart: Digitale Medien
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  • 34
    ISSN: 1573-5028
    Schlagwort(e): antisense ; gene expression ; plants ; regulation ; RNA ; transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have shown leaf-specific inhibition GUS gene expression in transgenic Nicotiana plants using an antisense RNA with a 41-base homology spanning the translation start codon of the gene. GUS was expressed from the nominally constitutive 35S promoter and the antisense RNA was expressed from the light-regulated ca/b promoter of Arabidopsis thaliana. A range of GUS inhibition from 0 to 100% was obtained by screening a small population of transgenic plants and the specific levels of inhibition observed were stably inherited in two generations. An antiGUS ‘gene’ dosage effect was observed in plants which were homozygous for antiGUS. RNA detection results suggest that duplex formation with the 41 base pair antiGUS RNA destabilized the GUS mRNA and that an excess of antisense. RNA was not required. Our results demonstrate the potential of antisense RNA as a strategy for obtaining plant mutants, especially ‘down mutations’ in essential genes where only a short 5′ sequence of the mRNA is required. They also suggest that the ‘position effect’ on gene expression could be used in conjunction with an antisense RNA strategy to provide a versatile approach for crop improvement.
    Materialart: Digitale Medien
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  • 35
    ISSN: 1573-5028
    Schlagwort(e): Nicotiana tabacum ; fungal disease resistance ; groundnut stilbene synthase ; gene expression ; resveratrol synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A gene from groundnut (Arachis hypogaea) coding for stilbene synthase was transferred together with a chimaeric kanamycin resistance gene. It was found to be rapidly expressed after induction with UV light and elicitor in tobacco cells (Nicotiana tabacum). Comparative studies of stilbene synthase mRNA synthesis in groudnut and transgenic tobacco suspension cultures revealed the same kinetics of gene expression. Stilbene synthase specific mRNA was detectable 30 minutes after elicitor induction and 10 minutes after UV irradiation. The maximum of mRNA accumulation was between 2 and 8 hours post induction. 24 hours after induction stilbene synthase mRNA accumulation ceased. Furthermore, in transgenic tobacco plants, the gene was found to be inducible in sterile roots, stems and leaves. Stilbene synthase was demonstrated in crude protein extracts from transgenic tobacco cell cultures using specific antibodies. Resveratrol, the product of stilbene synthase, was identified by HPLC and antisera raised against resveratrol.
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    Standort Signatur Erwartet Verfügbarkeit
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 14 (1990), S. 1055-1056 
    ISSN: 1573-5028
    Schlagwort(e): Lupinus polyphyllus ; cell culture ; cDNA clone ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 15 (1990), S. 695-705 
    ISSN: 1573-5028
    Schlagwort(e): salt stress ; abscisic acid ; cDNA sequence ; gene expression ; LEA protein sequence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have characterized a new tomato cDNA, TAS14, inducible by salt stress and abscisic acid (ABA). Its nucleotide sequence predicts an open reading frame coding for a highly hydrophilic and glycine-rich (23.8%) protein of 130 amino acids. Southern blot analysis of tomato DNA suggests that there is one TAS14 structural gene per haploid genome. TAS14 mRNA accumulates in tomato seedlings upon treatment with NaCl, ABA or mannitol. It is also induced in roots, stems and leaves of hydroponically grown tomato plants treated with NaCl or ABA. TAS14 mRNA is not induced by other stress conditions such as cold and wounding. The sequence of the predicted TAS14 protein shows four structural domains similar to the rice RAB21, cotton LEA D11 and barley and maize dehydrin genes.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Journal of mathematical biology 28 (1990), S. 237-256 
    ISSN: 1432-1416
    Schlagwort(e): Behavior ; Evolution ; Neural network ; Dynamic optimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract One of the main challenges to the adaptionist program in general and the use of optimization models in behavioral and evolutionary ecology, in particular, is that organisms are so constrained' by ontogeny and phylogeny that they may not be able to attain optimal solutions, however those are defined. This paper responds to the challenge through the comparison of optimality and neural network models for the behavior of an individual polychaete worm. The evolutionary optimization model is used to compute behaviors (movement in and out of a tube) that maximize a measure of Darwinian fitness based on individual survival and reproduction. The neural network involves motor, sensory, energetic reserve and clock neuronal groups. Ontogeny of the neural network is the change of connections of a single individual in response to its experiences in the environment. Evolution of the neural network is the natural selection of initial values of connections between groups and learning rules for changing connections. Taken together, these can be viewed as “design parameters”. The best neural networks have fitnesses between 85% and 99% of the fitness of the evolutionary optimization model. More complicated models for polychaete worms are discussed. Formulation of a neural network model for host acceptance decisions by tephritid fruit flies leads to predictions about the neurobiology of the flies. The general conclusion is that neural networks appear to be sufficiently rich and plastic that even weak evolution of design parameters may be sufficient for organisms to achieve behaviors that give fitnesses close to the evolutionary optimal fitness, particularly if the behaviors are relatively simple.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 79 (1990), S. 397-400 
    ISSN: 1432-2242
    Schlagwort(e): Durum wheat ; C-banding ; Homoeologous pairing ; Chromosome structure ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Meiotic pairing was analyzed at metaphase I in ABRR triticale × rye hybrids to identify the arm homoeology of chromosomes ofTriticum turgidum. Wheat chromosomes were identified using a C-banding technique. Results confirmed that the homoeologous relationships between chromosome arms of the A and B genomes inT. turgidum are the same as inT. aestivum, and that a double translocation involving4AL,5AL, and7BS is present inT. turgidum. It is proposed that a pericentric inversion involving a substantial portion of chromosome4A is present inT. turgidum andT. aestivum.
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 80 (1990), S. 296-304 
    ISSN: 1432-2242
    Schlagwort(e): Sorghum ; Isozyme ; Genetic diversity ; Evolution ; Systematics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A survey of allozyme variation among the spontaneous taxa of Sorghum section Sorghum was undertaken. Eight plants each of 90 accessions representing the diploid S. bicolor (ssp. arundinaceum and drummondii) and the tetraploids S. almum and S. halepense were analyzed for 17 enzyme systems encoded by 30 loci. Low levels of variation were found within and among accessions, although there was more variation than is typical of inbreeding species. We found an average of 3.2 alleles per locus in ssp. arundinaceum, with a mean expected heterozygosity for the accessions of 0.034 and total panmictic heterozygosity of 0.154. An analysis of the apportionment of genetic variation among accessions of ssp. arundinaceum indicated that 26% of the variation occurs within accessions and 74% among accessions. Cultivated sorghum contains far less allozymic variation than ssp. arundinaceum, its presumed progenitor. This is consistent with the prediction that cultivated sorghum experienced a loss of genetic variation during domestication. For the most part, cultivated sorghum contains a subset of the allozymes found in ssp. arundinaceum. Principal component analysis revealed continuous variation among the accessions and geographic regions, with accessions failing to segregate into discrete clusters. However, accessions of race virgatum of ssp. arundinaceum occupied one end of the continuum and were, in that sense, distinguished from the other accessions. Similarly, most accessions of S. halepense and S. almum occupied the central portion of the continuum. The allozymic data presented here are consistent with the hypothesized origin of S. halepense via autopolyploidy or segmental allopolyploidy.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 80 (1990), S. 641-647 
    ISSN: 1432-2242
    Schlagwort(e): Pinus ; Species hybridization ; Chloroplast DNA ; Molecular markers ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Restriction fragment analysis and heterologous hybridization of chloroplast (cp) DNA was used to develop species-specific markers for P. tabulaeformis, P. yunnanensis and P. massoniana. Fragment patterns created by the BclI and DraI restriction enzymes and hybridization patterns to the psbC and psbD probes were distinctive among the three species. No intraspecific variation was detected with respect to any of the cpDNA markers developed in this study. The cpDNA markers obtained were subsequently used to examine the parentage of P. densata, a putative Tertiary hybrid between P. tabulaeformis and P. yunnanensis. The analysis demonstrated for the first time that P. densata populations accommodate chloroplast genomes of P. tabulaeformis and P. yunnanensis, which strongly supports earlier suggestions of the hybrid origin of this species. It appears that P. densata represents a stabilized natural hybrid that has become adapted to high mountain environments where neither of the parental species can normally grow.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 80 (1990), S. 635-640 
    ISSN: 1432-2242
    Schlagwort(e): Pinus ; Species hybridization ; Allozymes ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Allozyme differentiation at 13 loci was studied in populations of Pinus tabulaeformis, P. densata, and P. yunnanensis from China. It was previously suggested that P. densata represents a Tertiary hybrid between P. tabulaeformis and P. yunnanensis. The observed levels of allozyme variation within and among the investigated species were comparable to those of other conifers. P. tabulaeformis differed markedly from P. yunnanensis with respect to allozyme frequencies, while P. densata was intermediate between the two putative parents. There was evidence of homozygote excess in embryos from all investigated species, as compared to Hardy-Weinberg expectations. The observed allozyme composition of P. densata conformed to earlier morphological and molecular evidence indicating hybrid origin of this taxon. It was proposed that fusion of gene pools from P. tabulaeformis and P. yunnanensis has led to adaptive evolution of a new species, P. densata.
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  • 43
    ISSN: 1615-6102
    Schlagwort(e): Basal-body root complex ; Cell division cycle ; Centrosome ; Chlamydomonas ; Evolution ; Monoclonal antibody
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The mammalian centrosome monoclonal antibody MPM-13 recognized component(s) of the well defined MTOC basal-body root complex in the green plantChlamydomonas. The antibody reaction coincided in location with the basal-body root complex and the cruciate nature of the staining pattern corresponded to the configuration of the root microtubules. During mitosis the behaviour of MPM-13 stained material mirrored the duplication, separation and migration to the spindle poles of the basal body-root complex. It is suggested that conserved MTOC components were recognized and that these may have retained a similar, perhaps universal, function in microtubule organization.
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  • 44
    ISSN: 1573-8221
    Schlagwort(e): plasmid ; transception ; transcipient ; segregation ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Behavior genetics 20 (1990), S. 251-264 
    ISSN: 1573-3297
    Schlagwort(e): egg-laying behavior ; Aplysia ; neuropeptides ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Psychologie
    Notizen: Abstract TheAplysia neuroendocrine system is a particularly advantageous model for cellular and molecular studies because of the relatively small number and large size of its component neurons. In addition, numerous anatomical and physiological studies have resulted in the assignment of behavioral roles to individual identified neurons. Recombinant DNA techniques have been used to isolate the genes that encode the precursors of peptides involved in egg-laying behavior. The comparison of the egg-laying hormone (ELH) gene family within the genusAplysia reveals high homologies in the overall structure of the precursors. A well-conserved tetrabasic residue has been shown to be the first endoproteolytic cleavage site of the precursor, giving rise to two intermediates, which are differentially processed and packaged. Some members of the ELH gene family are expressed specifically in the bag cell clusters or the atrial gland, respectively, providing an opportunity to study control of gene expression at the molecular level.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Evolutionary ecology 4 (1990), S. 130-142 
    ISSN: 1573-8477
    Schlagwort(e): Evolution ; Darwin's finches ; extinction ; Geospizinae ; island biogeography ; ecological isolation ; reproductive isolation ; speciation ; taxon cycle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The Hamilton-Rubinoff model of evolution in the avifauna of the Galapagos Islands suggests that speciation occurs on small outlying islands, and that new species invade the central island region, where ecological differentiation takes place. I present an alternative model in which both speciation and ecological differentiation leading to origin of actively colonizing taxa occur on the large islands, with colonization of small and outlying islands being primarily one way. Although forms on outlying islands may differentiate to the level of new species, their fate is postulated to be extinction rather than re-invasion of central islands. Data on species with expanding, differentiating, fragmenting, and relict distributions support this second model. Polytypy and incompleteness of distributions on the large islands indicate that isolation is adequate for differentiation to occur. Distributions of expanding taxa centre on the large islands, and their distributions show sequences leading from large islands to smaller and more outlying islands. Curves of occupancy of large islands versus total islands also agree with the prediction that expansions begin in the large islands.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 224 (1990), S. 459-468 
    ISSN: 1617-4623
    Schlagwort(e): Flaveria ; C3/C4 plants ; Phosphoenolpyruvate carboxylase ; Gene family ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Phosphoenolpyruvate carboxylase (PEPCase) was shown to be encoded by a multigene family in various Flaveria species analysed. Several clones were isolated from genomic libraries of F. pringlei (C3 species) and F. trinervia (C4 species) and classified into four distinct groups according to their hybridization behaviour to a full-length cDNA clone encoding the PEPCase C4 isozyme of F. trinervia. A detailed cross-hybridization analysis demonstrated that the closest relative of most of the PEPCase genes isolated from F. trinervia and F. pringlei was not found in the same but in the other species. Northern analysis, using stringent conditions, allowed discrimination of class-specific PEPCase transcripts and revealed characteristic organ-specific expression patterns.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 48
    ISSN: 1617-4623
    Schlagwort(e): Aspergillus nidulans ; Gene regulation ; amdS gene ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary In Aspergillus nidulans expression of the acetamidase structural gene, amdS, is under the control of at least four regulatory genes including the trans-acting amdA regulatory gene. A cis-acting mutation (amdI66) consisting of an 18 by duplication in the 5′ region of the amdS gene results in very high levels of acetamidase activity but only in strains carrying semi-dominant mutations in the amdA gene. In selecting for increased amdS expression in an amdI66 amdA – strain, an A. nidulans strain with a mutation in the 5′ region of the amdS gene was isolated. The nucleotide sequence was determined of the region containing the mutation, designated amdI666. The mutant strain carries three tandem copies of the 18 by sequence that is duplicated in the amdI66 mutation. Thus, from a strain carrying a duplication of an apparent regulatory protein binding site with little effect on gene expression, a strain has been derived that carries a triplication of the site with consequent major effects on regulation. The multiple copies of regulatory sites present in many genes may have been generated by a similar mechanism.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 221 (1990), S. 315-321 
    ISSN: 1617-4623
    Schlagwort(e): Small stable RNA ; Signal recognition particle ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The genes encoding the 7S RNAs of the archaebacteria Archaeoglobus fulgidus, Methanosarcina acetivorans, Sulfolobus solfataricus, and Thermococcus celer have been isolated. All four genes occur as single genomic copies and are flanked by sequences containing potential signals for transcriptional promotion and termination. The genes encode RNA molecules approximately 300 nucleotides in length which conform strictly to a model of secondary structure common to all described archaebacterial 7S RNAs. Archaebacterial 7S RNAs exhibit a strong similarity to eukaryotic 7S RNAs in terms of overall secondary structure, while primary sequence conservation is limited to a specific structural domain of the molecule. This domain displays strong primary and secondary structural similarity to features of small eubacterial RNAs, including the small cytoplasmic (sc) RNA of Bacillus subtilis and the 4.5S RNA of Escherichia coli. Conservation of this structural domain among divergent RNA molecules across three kingdoms suggests that these RNAs are the descendants of a unique subcellular structure present before the divergence of the archaebacterial, eubacterial and eukaryotic kingdoms.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Cell biology and toxicology 6 (1990), S. 105-126 
    ISSN: 1573-6822
    Schlagwort(e): DNA damage ; DNA amplification ; ultraviolet light irradiation ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Both naturally occuring and carcinogen-induced tumors display not only point mutations in cellular oncogenes but also more complex changes in cellular oncogenes and other cellular genes. For this and other reasons, it seems likely that DNA damage in mammalian cells can induce alterations in gene expression that may have both short and long term consequences in the target cell. The purpose of this review is to summarize current available information on inducible responses to UV-irradiation and other mediators of DNA damage in mammalian cells, and to provide some working hypotheses. We have divided these responses into three time frames, immediate (0–12 hours), early (12–48) and late (beyond 48 hours). Immediate responses include the action of DNA repair enzymes, some of which are induced as a consequence of DNA damage, and transient inhibition of DNA synthesis. Within the past few years considerable evidence has accumulated that during this immediate period there is increased expression of certain cellular oncogenes, proteases and proteins whose functions remain to be identified. It is of interest that the expression of some of these genes is also induced by certain growth factors, tumor promoters and heat shock. Alterations in gene expression during the subsequent “early” period (12–48 hrs.) have not been studied in detail, but it is during this period that one can detect increased replication of several types of viruses in cells that harbor these viruses. We have examined in detail the induction of asynchronous polyoma DNA replication (APR) in a rat fibroblast cell line carrying integrated copies of this DNA. We have obtained evidence that UV-irradiation of these cells leads to the synthesis of a 40 kd protein, within the first 1–24 hrs after irradiation, that binds to a specific sequence TGACAACA in the regulatory region of polyoma DNA. We suggest that this protein acts together with other proteins to induce APR and that this serves as a useful model for understanding the mechanisms responsible for amplification of cellular genes, a phenomenon often seen in malignant tumors. Finally, we discuss how the events occurring during the immediate and early periods following DNA damage might lead to late effects in the target cell that are stable and contribute to the genotype and phenotype of some of the progeny of these cells that are destined to become tumor cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 51
    ISSN: 1573-6830
    Schlagwort(e): molecular biology of peptidergic neurons ; in situ hybridization ; gene expression ; preproenkephalin ; preprodynorphin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary 1. The working hypothesis that neuropeptide gene expression in a neuron is an indicator of that neuron's physiological activity is discussed. 2. Representative examples from the literature are presented to support the hypothesis. 3. Further, we discuss the regulation of expression of two opioid peptides, preproenkephalin and preprodynorphin, in laminae I and II of the spinal cord and in nucleus caudalis of the trigeminal nuclear complex, where they may play a role in pain modulation. 4. The expression of the opioid peptide genes can be induced by both painful and nonnoxious stimuli in neurons in time-dependent and sensory-specific fashions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular neurobiology 10 (1990), S. 281-289 
    ISSN: 1573-6830
    Schlagwort(e): haloperidol ; gene expression ; DNA polymerases ; brain development ; mesencephalon ; forebrain ; dopamine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary 1. Previous studies have reported a marked reduction in the [3H]thymidine incorporation in forebrain after administration of a dopamine antagonist such as haloperidol. 2. We have investigated the possibility that the expression levels of genes related to DNA metabolism could be altered by haloperidol treatment. 3. By Northern blot analysis, we have studied the steady-state mRNA levels for genes involved in DNA metabolism, in neonate rat mesencephalon and forebrain, after chronic prenatal blockade of dopamine receptors with haloperidol. 4. We found that the expression levels for DNA polymerases alpha and beta were clearly reduced in forebrain by haloperidol treatment. On the contrary, the expression of DNA polymerase beta was increased in mesencephalon. 5. Our results suggest that dopamine receptors occupancy may be a critical factor in controlling cell proliferation during brain development, through a mechanism(s) involving changes in the expression of DNA polymerases.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 53
    ISSN: 1573-6830
    Schlagwort(e): neuroblastoma ; differentiation ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary 1. Neuroblastoma (NB) is an unusual neuroectodermal tumor showing a high degree of spontaneous regression. NB cells can be induced to differentiatein vitro by various agents. Cell differentiation results in morphological changes characteristic of the mature neuronal phenotype, including outgrowth of neuritelike structures with several interconnections. 2. Recent experiments indicate that morphological differentiation of NB cells is associated with changes in expression of N-myc, c-myc, and c-myb oncogenes and synthesis of neurofilament proteins. However, little is known about the transcription of neurofilament genes during differentiation. 3. We have analyzed the expression of both the N-myc oncogene and mid-size neurofilament (NF) genes in the LAN-1 human NB cell line, cultured in the presence of retinoic acid (RA). Continuous treatment with RA induced morphological differentiation within 5–6 days. The transcription of N-myc was down-modulated within 24 hr of the initial exposure to RA. The mid-size NF mRNA was increased at this time. The expression of N-myc was not modified in serum-deprived LAN-1 cells, indicating that N-myc transcription is unaffected by the arrest of the cells in the G1 phase. 4. We conclude that new synthesis of mid-size NF mRNA and a decrease in N-myc transcription precedede novo formation of neurite-like processes and morphological cell differentiation of neuroblastoma cells.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 28 (1990), S. 33-75 
    ISSN: 1573-5133
    Schlagwort(e): Sharks ; Rays ; Chimaeras ; Chondrichthyes ; Evolution ; Success ; Diversity ; Ecology ; Ecomorphotypes ; Reproductive modes ; Conservation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Cartilaginous fishes, the sharks, rays and chimaeras (class Chondrichthyes), are a very old and successful group of jawed fishes that currently contains between 900 and 1100 known living species. Chondrichthyians show a high morphological diversity during most of their evolutionary career from the Paleozoic to the present day. They are relatively large predators which have remained a major, competitive element of marine ecosystems despite the varied rivalry of numerous other marine vertebrate groups over at least 400 million years. Although restricted in their ecological roles by morphology, reproduction and other factors, the living cartilaginous fishes are highly diverse and show numerous alternative life-history styles which are multiple answers to exploiting available niches permitted by chondrichthyian limitations. Chondrichthyians living and fossil can be divided into at least eighteen ecomorphotypes, of which the littoral ecomorphotype is perhaps the most primitive and can serve as an evolutionary origin for numerous specialist ecomorphotypes with benthic, high-speed, superpredatory, deep-slope and oceanic components. Reproductive modes in cartilaginous fishes are of six types, ranging from primitive extended oviparity through retained oviparity and yolk-sac viviparity (previously ovoviviparity) to three derived forms of viviparity. Reproductive modes are not strongly correlated with ecomorphotypes and with the phylogeny of living elasmobranchs. The success and importance of cartilaginous fishes is largely underrated by marine biologists and by the public, and requires new and ‘heretical’ emphasis to overcome the present inadequacies of chondrichthyian research and the problems of overexploitation that cartilaginous fishes face.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 28 (1990), S. 87-100 
    ISSN: 1573-5133
    Schlagwort(e): Evolution ; Speciation ; Stabilizing selection ; Mbuna ; Cyrtocara ; Mouthbrooding ; Mate recognition ; Haplochromine ; Tilapiine ; Cuckoo ; Parental care ; Co-operative care
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis About 50% of African cichlid species have been described. Little is known about cichlid ecology, behaviour or about the evolution and interactions of communities. Nevertheless, trends which provide an insight into cichlid life histories, into evolutionary alternatives and into behavioural alternatives which may be followed during the life time of these fishes are emerging. Cichlids which spend their entire life history in a single habitat belong to species flocks that have spectated greatly. In contrast, those groups which live in a variety of habitats during their life history have spectated little. Despite the trophic specializations that have occurred among cichlids, many and perhaps all species, have the ability to feed upon alternative food resources. They do so by switching or by markedly modifying their behaviour and all are particularly opportunistic. The extensive adaptive radiation of cichlids with regard to those attributes of morphology and behaviour that are associated with survival and growth, is apparently not matched by similar radiations in reproductive behaviour. The perceived evolutionary conservatism with regard to reproductive behaviour is attributed to the effects of stabilizing selection, but this still needs to be tested. The constraints of stabilizing selection appear to be lifted with regard to coloration. If colour is an important component of the specific-mate recognition system then it should also be subjected to stabilizing selection so the readiness with which colour variation occurs within and between populations needs explanation. Parental care in cichlids has followed a variety of evolutionary alternatives, all of which are geared to improve the chances of survival of offspring in their specific micro-habitats.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 28 (1990), S. 77-85 
    ISSN: 1573-5133
    Schlagwort(e): Evolution ; Egg production ; Survival ; Iteroparity ; Monte Carlo simulation ; Reproduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Marine fish species with planktonic larval stages experience high and variable pre-adult mortality, and in accordance with general life-history theory have evolved iteroparity to reduce the uncertainty in reproductive success of individuals. In this paper we use a Monte Carlo model to explore the influence of spawning style and adult survival of clupeoids on the spawning success of individual fish during their life span, when early stage survival is determined according to different spectra of environmental variability. In these simulations the variation in reproductive success was governed first by the number of batches of eggs spawned by each adult fish over its lifespan (as determined by its pattern of spawning and the adult survival rate), and secondly by the patterning of environmental variability affecting early stage survival. We consider that the life history styles of the clupeoids are based on co-evolved traits in which the different patterns of iteroparity represent different solutions for coping with the variable nature of early-stage survival. When these life history traits are compared on time scales appropriate to each species, they are therefore unlikely to provide the correlation between brood strength variation and the life span of adults proposed in Murphy's (1968) contribution to this aspect of life history theory.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 28 (1990), S. 273-284 
    ISSN: 1573-5133
    Schlagwort(e): Cichlids ; Epigamic selection ; Courtship behavior ; Species recognition ; Mate choice ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis The cichlid species flocks of the African Great Lakes represent the most extreme case of adaptive radiation among vertebrates. Recently, attention has focused on the potential for sexual selection to drive or accelerate speciation in these fishes. Cichlids as a whole are social in nature and display complex behavior, particularly during courtship and spawning; however, the extent to which changes in species recognition cues may account for species diversity among haplochromine lineages has remained speculative. Our investigations have indicated that oral incubating haplochromines show a reduction in diversity and extent of courtship relative to substrate brooding cichlids, and apparently retain aspects of a primitive specific mate recognition system. Laboratory observations of courtship in the Malawian endemicPseudotropheus zebra suggest that organization of the spawning bout is loose, and lacking in any well defined stimulus-response chain. Interspecific comparisons of in situ courtship behavior among male mbuna, lithophilous haplochromines of Lake Malawi, revealed only one potential example of species-specific behavior, and indicated that mate choice occurred prior to the onset of intense courtship. Courtship display by male mbuna does not appear critical to species recognition and may represent an evolutionary relict. Alternatively, male courtship display may have an indirect effect on successful reproduction or may be maintained through pleiotropic effects. The mbuna display no evidence of behavioral innovation and show limited interspecific differentiation in behavioral expression. More generally, there is no evidence at present to suggest that epigamic sexual selection, acting on courtship behavior, has been a major mechanism in the diversification of the haplochromine species flocks.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 159 (1990), S. 761-769 
    ISSN: 1432-136X
    Schlagwort(e): Crocodile ; Lung ; Morphometry ; Strategy ; Evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The respiratory surface area (SAR) per kilogram body mass (MB), the harmonic mean thickness of the air-blood barrier (τhtR) in the gas exchange tissue, and the anatomical diffusion factor (ADF=SAR/τhtR per MB) were calculated for four juvenile Nile crocodiles. The ADF of three small specimens (mean MB=3.59 kg) was 625 cm2·μm−1·kg−1. The values varied considerably among individuals and were similar to that of a 5.68-kg specimen (593 cm2·μm−1·kg−1). Only 9% of the ADF is located in the anterior third of the lung, which because of its conical shape makes up only 14 percent of the total lung volume. Particularly in the middle third of the lung, the proximal region near the intrapulmonary bronchus displays a greater ratio of respiratory/non-respiratory surface areas than do more distally located sampling sites. The τhtR is also significantly smaller proximally than distally. The cumulative ADF per unit MB is greater than that previously reported for this species on the basis of overall estimates of SAR and τhtR, but is still less than that of lizards and testudinids. The disposition of ADF between distal air storage region and the intrapulmonary bronchus is consistent with a bidirectional cross-current gas exchange model.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Human evolution 5 (1990), S. 471-482 
    ISSN: 1824-310X
    Schlagwort(e): Creationism ; Evolution ; hominid affinity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Using samples of skulls of early and modern hominids and modern pongids we compare the plausibility of Evolutionist and Creationist viewpoints. Multivariate methods are used to assess the corollary of Creationism that all fossil specimens which Evolutionists consider to be hominids are either apes or humans. We conclude that the results of this study cannot easily be accommodated within a Creationist framework, and, therefore, contribute substantial evidence for the Evolutionist viewpoint.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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