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Biomedical subjects

A C Wilson

Publications and source records attributed to A C Wilson.

At least 199 records · Page 11Linked to original sources
PubMed1983

Effect of high fat and high sucrose feeding on lipogenesis by isolated rat intestinal cells.

Lipid synthesis was studied in intestinal mucosal cells isolated from rats fed a high fat or a high sucrose diet. The cells actively incorporated 14C(1)-labeled free fatty acids into glycerolipids [( 1-14C]acetate was utilized for both fatty acid and cholesterol synthesis), while [14C(U)]glucose label was found in cholesterol and in the glycerol moiety of glycerolipids, but not in fatty acids. Sucrose feeding resulted in increased acetate incorporation into cholesterol, but not into fatty acids while the high fat diet markedly depressed the incorporation of acetate. In contrast, fat feeding increased both glucose and fatty acid incorporation into glycerolipids, as well as glucose incorporation into cholesterol. Using the incorporation of glucose into lipid glycerol as an estimate of the phosphatidic acid pathway, it was found that this pathway was stimulated by both fat and carbohydrate feeding. The results suggest that differences in the regulation of cholesterol and glycerolipid synthesis in the intestine compared with adipose tissue and liver may relate to the role of intestine in synthesizing lipoproteins for lipid transport.

Acetates↗
PubMed1982

Mitochondrial DNA sequences of primates: tempo and mode of evolution.

We cloned and sequenced a segment of mitochondrial DNA from human, chimpanzee, gorilla, orangutan, and gibbon. This segment is 896 bp in length, contains the genes for three transfer RNAs and parts of two proteins, and is homologous in all 5 primates. The 5 sequences differ from one another by base substitutions at 283 positions and by a deletion of one base pair. The sequence differences range from 9 to 19% among species, in agreement with estimates from cleavage map comparisons, thus confirming that the rate of mtDNA evolution in primates is 5 to 10 times higher than in nuclear DNA. The most striking new finding to emerge from these comparisons is that transitions greatly outnumber transversions. Ninety-two percent of the differences among the most closely related species (human, chimpanzee, and gorilla) are transitions. For pairs of species with longer divergence times, the observed percentage of transitions falls until, in the case of comparisons between primates and non-primates, it reaches a value of 45. The time dependence is probably due to obliteration of the record of transitions by multiple substitutions at the same nucleotide site. This finding illustrates the importance of choosing closely related species for analysis of evolutionary process. The remarkable bias toward transitions in mtDNA evolution necessitates the revision of equations that correct for multiple substitutions at the same site. With revised equations, we calculated the incidence of silent and replacement substitutions in the two protein-coding genes. The silent substitution rate is 4 to 6 times higher than the replacement rate, indicating strong functional constraints at replacement sites. Moreover, the silent rate for these two genes is about 10% per million years, a value 10 times higher than the silent rate for the nuclear genes studied so far. In addition, the mean substitution rate in the three mitochondrial tRNA genes is at least 100 times higher than in nuclear tRNA genes. Finally, genealogical analysis of the sequence differences supports the view that the human lineage branched off only slightly before the gorilla and chimpanzee lineages diverged and strengthens the hypothesis that humans are more related to gorillas and chimpanzees than is the orangutan.

Animals↗
PubMed1982

Molecular evolution of Drosophila and higher Diptera. I. Micro-complement fixation studies of a larval hemolymph protein.

LHP is a suitable protein for studying evolution in flies (Diptera). This blood protein, which occurs at high concentration late in larval development, was purified to homogeneity from 5 species of Drosophilidae and one species each of Tephritidae and Calliphoridae. Rabbit antisera to the purified LHPs allowed immunological comparisons to be made with the micro-complement fixation technique. Various indirect tests indicated that immunological distance is a reliable estimator of the degree of amino acid sequence difference between LHPs from different species. An evolutionary tree for the 7 LHPs was constructed from the immunological distances with the method of Fitch and Margoliash (1967) to provide the branching order and the method of Chakraborty (1977) to provide the branch lengths. A modified method of tree construction allowed LHPs from 10 additional species to be attached to this tree. The resulting LHP tree for 17 species agrees approximately in branching order with that based on Throckmorton's study of 60 anatomical traits. However, the ratio of anatomical change to LHP change along branches within the tree varies widely, confirming the independence of organismal and molecular evolution. The LHP tree thus provides a new perspective on evolution within and among the families of higher Diptera.

Animals↗
PubMed1982

Mapping the antigenic epitope for a monoclonal antibody against lysozyme.

A monoclonal antibody (HyHEL-5), prepared to chicken lysozyme c by the method of Köhler and Milstein, identified an antigenic site (epitope) that was shared by the lysozymes of seven different species of galliform birds. The lysozymes of two galliform species, bobwhite quail and chachalaca, shared only partial antigenic identity with the epitope defined by this antibody. Duck lysozyme did not react with the antibody at all. Amino acids that determined the epitope structure were tentatively identified by comparing the amino acid sequences of these lysozymes and assuming the antigenic changes produced by evolutionary substitutions are not due to long-range conformational changes. Arg 68 was identified as a determining amino acid. Arg 68 is hydrogen-bonded to Arg 45, and together these two amino acids form a basic cluster that may be a subsite of the epitope. The antibody inhibited lysis of Micrococcus lysodeikticus by chicken lysozyme. Additionally, Biebrich Scarlet, a dye that binds to the catalytic site, inhibited antibody binding to this lysozyme, which indicates that the epitope extends into the cleft region between Arg 45 and Arg 114. The epitope was hypothesized to involve a region measuring at least 13 x 6 x 15 A including the Arg 68-Arg 45 complex that borders the enzymatic catalytic site. Four other monoclonal antibodies to lysozyme have been partially characterized; each had a distinct pattern of binding specificity for various species of bird lysozymes.

Animals↗
PubMed1982

Evolution of human mitochondrial DNA: a preliminary report.

Preliminary mapping of 346 cleavage sites in the mitochondrial genome of 100 human beings gives evidence that the genes for transfer RNA are highly variable, a result that points to the need for testing the accuracy of mitochondrial protein synthesis. In addition, the map comparisons imply that Australia has as much mtDNA diversity as any other area tested in the Old World. Assuming a model of strictly maternal inheritance, it appears possible to follow individual female lineages back hundreds of generations thereby providing human genetics with an important new measure of population heterogeneity. This measure, when compared with those available from protein and morphologic considerations, will help highlight particular groups of people whose mitochondria may increase greatly our understanding of the historical processes leading to the evolution of our own species.

Biological Evolution↗
PubMed1981

The untranslated regions of beta-globin mRNA evolve at a functional rate in higher primates.

We have sequenced the 3' and 5' untranslated regions of beta-globin mRNAs from cebus monkey, rhesus monkey and chimpanzee. A comparison with the corresponding human sequences reveals that the rate of sequence divergence among the higher primates is the same in the 3' and 5' noncoding regions and that this rate is several times lower than the rate for silent substitutions in the coding regions. In addition, the rate of sequence divergence in the 3' untranslated region of the primate beta-globin nRNA is several times lower than the rate calculated for this region from other comparisons. The low rate of sequence divergence in the noncoding 3' end of the primate beta-globin mRNAs may indicate a specialized and significant function for this region in the higher primates.

Animals↗
PubMed1981

Extensive polymorphism in the mitochondrial DNA of apes.

Ape species are 2-10 times more variable than the human species with respect to the nucleotide sequence of mtDNA, even though ape populations have been smaller than the human population for at least 10,000 years. This finding was made by comparing purified mtDNAs from 27 individuals with the aid of 25 restriction endonucleases; for an additional 59 individuals, comparisons were made with fewer enzymes by using the blot hybridization method. The amount of intraspecific sequence divergence was greatest between orangutans of Borneo and Sumatra. Among common chimpanzees, a large component of the variation is due to two highly distinct forms of mtDNA that may reflect a major geographic subdivision. The least amount of sequence variation occurred among lowland gorillas, which exhibit only twice as much sequence variation as humans. The large intraspecific differences among apes, together with the geological and protein evidence, leads us to propose that each ape species is the remnant of an ancient and widespread population that became subdivided geographically and reduced in size and range, perhaps by hominid competition. The low variation among human mtDNAs is consistent with geological evidence that the human species is young. The distribution of site changes within the mitochondrial genome was also examined. Comparison of closely related mtDNAs shows that the ribosomal RNA genes have diverged more slowly than the rest of the genome.

Animals↗
PubMed1981

Evolutionary tree for apes and humans based on cleavage maps of mitochondrial DNA.

The high rate of evolution of mitochondrial DNA makes this molecule suitable for genealogical research on such closely related species as humans and apes. Because previous approaches failed to establish the branching order of the lineages leading to humans, gorillas, and chimpanzees, we compared human mitochondrial DNA to mitochondrial DNA from five species of ape (common chimpanzee, pygmy chimpanzee, gorilla, orangutan, and gibbon). About 50 restriction endonuclease cleavage sites were mapped in each mitochondrial DNA, and the six maps were aligned with respect to 11 invariant positions. Differences among the maps were evident at 121 positions. Both conserved and variable sites are widely dispersed in the mitochondrial genome. Besides site differences, ascribed to point mutations, there is evidence for one rearrangement: the gorilla map is shorter than the other owing to the deletion of 95 base pairs near the origin of replication. The parsimony method of deriving all six maps from a common ancestor produced a genealogical tree in which the common and pygmy chimpanzee maps are the most closely related pair; the closest relative of this pair is the gorilla map; most closely related to this trio is the human map. This tree is only slightly more parsimonious than some alternative trees. Although this study has given a magnified view of the genetic differences among humans and apes, the possibility of a three-way split among the lineages leading to humans, gorillas, and chimpanzees still deserves serious consideration.

Animals↗
PubMed1980

Mammoth albumin.

Serum albumin was detected immunologically in muscle from a mammoth that died about 40,000 years ago. Rabbits injected with ground mammoth muscle produced antibodies that react strongly with elephant albumin, weakly with sea cow albumin, and still more weakly or not at all with other mammalian albumins. Since elephant albumin elicited antibodies with the same specificity, some of the surviving mammoth albumin molecules evidently have antigenic sites identical to those on native elephant albumin. Much of the mammoth albumin has, however, undergone postmortem change. The small amount of soluble albumin extractable from mammoth muscle is heterogeneous in size, charge, and antigenic properties.

Animals↗
PubMed1980

Rapid duplication and loss of genes coding for the alpha chains of hemoglobin.

Rapid cycles of gene duplication and loss appear to have been going on in the region coding for the alpha chain of adult hemoglobin. This is inferred from restriction endonuclease analysis of the alpha gene region in five species of apes, whose common ancestor lived about 10 million years ago. Because all five species resemble humans in having duplicate alpha genes, the duplicate state of this region is probably at least as old as the common ancestor of all these species. However, the alpha polypeptides within these species are about 10 times more alike than is expected for 10 million years of divergent evolution. Thus, the alpha polypeptides within each species have been evolving in concert. Changes in gene number have also taken place in the apes. Whereas the predominant number of alpha genes per chromosome is two for most species, it is three for chimpanzees. Concerted evolution appears also to have occurred, but far more slowly, in the region coding for the adult beta-like chains of hemoglobin. Consideration of the structural differences between the two regions leads to the hypothesis that the lengths of the noncoding regions are important determinants of the rates at which genes are gained and lost by intergenic recombination.

Adaptation, Biological↗
PubMed1980

Silent delta-globin gene in Old World monkeys.

The delta polypeptide chain is present in the adult hemoglobin of all higher primates except Old World monkeys. Because Old World monkeys have evolved from higher primate ancestors, it can be concluded that the ability to synthesize this polypeptide has been lost relatively recently. It is shown here that the gene for delta globin exists in two of these species, the rhesus monkey (Macaca mulatta) and the baboon (Papio papio). Restriction endonuclease fragments of monkey genomic DNA bearing the delta- and beta-globin genes were detected after hybridization of human globin cDNA probes to filter-bound primate DNAs according to the Southern method. A restriction map prepared for rhesus DNA was identical in overall organization to the map of the human region. This indicates that large deletions or additions of DNA are not responsible for the Old World monkeys' lack of delta globin.

Animals↗
PubMed1980

Evolution in Pseudomonas fluorescens.

The relationships among 93 strains of Pseudomonas fluorescens were investigated by (1) a numerical taxonomic analysis on the results of 150 phenotypic tests, (2) DNA hybridization studies using 16 reference strains, (3) quantitative microcomplement fixation studies using six reference strains with antibodies directed against the protein azurin. In general, the strains fell into distinct clusters. Assignment to these clusters on the basis of azurin immunological similarity showed 98% agreement with assignment based on DNA homology, suggesting that many genes will follow the same pattern. Of the strains that clustered on the basis of genotype (DNA, azurin) 88% also clustered on the basis of phenotype. The occasional noncongruency observed between the genotypic and phenotypic data may be due to the variable rates of phenotypic evolution. These results provide a perspective on the roles of horizontal and vertical transfer of genes in the evolution of this bacterial group.

Azurin↗
PubMed1980

Lipid involvement in oleoyl CoA desaturase activity of Fusarium oxysporum microsomes.

Desaturation of oleoyl CoA by the microsomal fraction of Fusarium oxysporum hyphal cells required O2, NADPH, MgCl2, and the addition of either bovine serum albumin or the 105 000g supernatant fraction. In the absence of reduced nucleotide, [14C]oleoyl CoA was rapidly incorporated into phospholipid and triacylglycerol and hydrolyzed to free fatty acids. After addition of NADPH, oleate was desaturated at the normal rate. Analysis of the distribution of [14C]oleate and [14C]linoleate between different lipid classes revealed that phosphatidylcholine and phosphatidylethanolamine were labeled with [14C]linoleate before any other lipid class. These results are consistent with oleoyl phospholipid being a direct intermediate in the desaturation of oleoyl CoA. The preference of the oleoyl-desaturase for NADPH, the relatively high pH optimum of 8.2, and the sensitivity to thenoyltrifluoroacetone inhibition suggest that some components of the microsomal electron-transport chain are common to both the oleoyl desaturase and stearoyl CoA desaturase systems in this fungus.

Fatty Acid Desaturases↗
PubMed1979

Amino acid sequence of California quail lysozyme. Effect of evolutionary substitutions on the antigenic structure of lysozyme.

To examine the effect of amino acid substitutions in lysozyme on the binding of antibodies to lysozyme, we purified lysozyme from the egg whites of California quail and Gambel quail. Tryptic peptides were isolated from digests of the reduced and carboxymethylated lysozymes and subjected to quantitative analysis of their amino acid compositions. The two proteins were identical by this criterion. Each peptide from the California quail lysozyme was then sequenced by quantitative Edman degradation, and the peptides were ordered by homology with other bird lysozymes. California quail lysozyme is most similar in amino acid sequence to bobwhite quail lysozyme, from which it differs by two substitutions: arginine for lysine at position 68 and histidine for glutamine at position 121. California and bobwhite quail lysozymes were antigenically distinct from each other in quantitative microcomplement fixation tests, indicating that substitutions at one or both of these positions can alter the antigenic structure of lysozyme. Yet neither of these positions is among those claimed to account for the precise and entire antigenic structure of lysozyme [Atassi, M. Z., & Lee, C.-L. (1978) Biochem. J. 171, 429--434]. Two possible explanations for this discrepancy are discussed.

Amino Acid Sequence↗