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Biomedical subjects

A C Wilson

Publications and source records attributed to A C Wilson.

At least 109 records · Page 6Linked to original sources
PubMed1991

Influence of dietary fish oil on the aortic, myocardial, and renal lesions of SHR.

To examine the effects of menhaden oil on the progressive glomerulosclerosis, arteriosclerosis, plasma cholesterol and triglyceride levels, and myocardial damage, spontaneously hypertensive rats (SHR) were fed Purina rat chow supplemented either with 6 g % of menhaden oil or with 6 g % of corn oil. They were sacrificed on the 12th and 18th months, and the kidneys, aorta, and heart were examined by light microscopy. At sacrifice, body weight, plasma creatinine, systolic blood pressure, 24 h' urinary protein output, total plasma cholesterol and triglyceride, glomerular filtration rate (GFR), and glomerulosclerosis index were measured. There was no significant difference between the experimental and control groups in the average body weight, plasma creatinine level, systolic blood pressure, total 24 h urinary protein output, and glomerular filtration rate. Rats with menhaden oil had, however, statistically significant less aortic arteriosclerosis, myocardial damage, plasma cholesterol and triglyceride levels, and renal interstitial fibrosis than those with corn oil. The glomerular damage of the former as expressed by glomerulosclerosis index was numerically less than that of the latter. The data indicated that menhaden oil lessened the hypertensive damage to the renal and cardiovascular systems.

Animals↗
PubMed1991

mtDNA polymorphism in two communities of Jews.

Twenty-one types of mtDNA were found in a survey of 39 Israeli Jews, of whom 18 were Sephardic and 21 Ashkenazic. The survey was made with six restriction enzymes that together recognize an average of 600 bp/genome. The differences among the types appear to be due to base substitution at 19 cleavage sites, one deletion, and one conformational mutation. The numbers of differences imply that these modern Jews stem from a minimum of 21 maternal lineages that were already distinct from one another 4,000-5,000 years ago. In three of the four cases where a type was found in more than one person, it occurred in both Ashkenazic and Sephardic populations. The diversity of types in the combined sample of two Jewish populations is lower than both that in a sample from various parts of Africa and that in a sample from various parts of East Asia. Nevertheless, it is as high as that in a sample from diverse parts of New Guinea, an area much larger than that in Israel to which the Jewish population traces back.

Base Composition↗
PubMed1990

Monophyletic origin of Lake Victoria cichlid fishes suggested by mitochondrial DNA sequences.

Lake Victoria, together with its satellite lakes, harbours roughly 200 endemic forms of cichlid fishes that are classified as 'haplochromines' and yet the lake system is less than a million years old. This 'flock' has attracted attention because of the possibility that it evolved within the lake from one ancestral species and that biologists are thus presented with a case of explosive evolution. Within the past decade, however, morphology has increasingly emphasized the view that the flock may be polyphyletic. We sequenced up to 803 base pairs of mitochondrial DNA from 14 representative Victorian species and 23 additional African species. The flock seems to be monophyletic, and is more akin to that from Lake Malawi than to species from Lake Tanganyika; in addition, it contains less genetic variation than does the human species, and there is virtually no sharing of mitochondrial DNA types among species. These results confirm that the founding event was recent.

Africa, Eastern↗
PubMed1990

Ancestral lysozymes reconstructed, neutrality tested, and thermostability linked to hydrocarbon packing.

The controversy surrounding the idea that neutral mutations dominate protein evolution is attributable in part to the inadequacy of the tools available to evolutionary investigators. With a few exceptions, most investigations into the force driving protein evolution have relied on indirect criteria for distinguishing neutral and non-neutral variants. To investigate a particular pathway of molecular evolution, we have reconstructed by site-directed mutagenesis likely ancestral variants of the lysozymes of modern game birds (order Galliformes), tested their activity and thermostability and determined their three-dimensional structure. We focused on amino acids at three positions that are occupied in all known game birds either by the triplet Thr 40, Ile 55, Ser 91, or by the triplet Ser 40, Val 55, Thr 91. We have synthesized proteins representing intermediates along the possible three-step evolutionary pathways between these triplets. Although all of these are active and stable, none of these intermediates is found in known lysozymes. A comparison of the structures and thermostabilities of the variants reveals a linear correlation between the side-chain volume of the triplet and the thermostability of the protein. Each pathway connecting the two extant triplet sequences includes a variant with a thermostability outside the range of the extant proteins. This observation is consistent with a non-neutral evolutionary pathway. The existence of variants that are more stable than the extant proteins suggests that selection for maximum thermostability may not have been an important factor in the evolution of this enzyme.

Amino Acid Sequence↗
PubMed1990

Concerted evolution of ruminant stomach lysozymes. Characterization of lysozyme cDNA clones from sheep and deer.

Contradictory evolutionary histories of ruminant lysozymes have been predicted by analysis of genomic blots (Irwin, D.M., Sidow, A., White, R., and Wilson, A.C. (1989) in The Immune Response to Structurally Defined Proteins: The Lysozyme Model (Smith-Gill, S.J., and Sercarz, E.E., eds) pp. 73-85, Adenine Press, Guilderland, NY) and sequences of cow stomach lysozyme cDNAs (Irwin, D.M., and Wilson, A.C. (1989) J. Biol. Chem. 264, 11387-11393). Genomic blots indicate that the amplification of the lysozyme gene family occurred 40-50 million years ago, while the cDNA sequences imply that the stomach genes began diverging from one another after the splitting of the deer and cow lineages, 25 million years ago. To resolve this contradiction, we characterized 111 stomach lysozyme cDNAs from two additional ruminant species: domestic sheep and axis deer. The cDNA sequences of the coding region of mature lysozyme together with the 3'-untranslated region were obtained from abomasum (true stomach) mRNA with the use of the polymerase chain reaction. The two primers for amplifying the cDNA were a lysozyme-specific primer, encoding a conserved sequence at the amino terminus of mature stomach lysozyme, and oligo(dT) as a general mRNA primer. Comparison of the cDNA sequences from these species to one another and to those of the cow revealed that different parts of the ruminant stomach lysozyme genes have had different evolutionary histories. The 3'-untranslated region has evolved in a divergent fashion since the original duplications 40-50 million years ago, supporting the genomic blot interpretation; by contrast, the coding region has evolved in a concerted fashion, that is, the multiple sequences within a species have evolved in unison. The 3'-untranslated portion of the lysozyme genes appears to have escaped from concerted evolution due to inability to initiate concerted evolution, rather than due to reduced sequence similarity. The process of concerted evolution in stomach lysozymes may have had roles both in adapting lysozyme to the stomach environment in early ruminants as well as in retarding amino acid sequence evolution in the well adapted lysozyme of modern ruminants.

Animals↗
PubMed1990

DNA damage promotes jumping between templates during enzymatic amplification.

Pairs of templates and primers were designed so that only recombination events would lead to amplification via the polymerase chain reaction. This approach reveals that lesions such as breaks, apurinic sites, and UV damage in a DNA template can cause the extending primer to jump to another template during the polymerase chain reaction. By comparing sequences of amplification products that were determined directly or via bacterial cloning, it was shown that when the thermostable Thermus aquaticus DNA polymerase encounters the end of a template molecule, it sometimes inserts an adenosine residue; the prematurely terminated product then jumps to another template and polymerization continues, creating an in vitro recombination product. Consequently, amplification products from damaged templates such as archaeological DNA are made up of a high proportion of chimeric molecules. The illegitimate adenosine and thymidine residues in these molecules are detected when cloned molecules are sequenced, but are generally averaged out when the amplification product is sequenced directly. However, if site-specific lesions exist in template DNA or if the amplification is initiated from very few copies, direct sequencing also may yield incorrect sequences. The phenomenon of the "jumping polymerase chain reaction" can be exploited to assess the frequency and location of lesions in nucleic acids.

Adenosine↗
PubMed1990

Compositional statistics: an improvement of evolutionary parsimony and its application to deep branches in the tree of life.

We present compositional statistics, a new method of phylogenetic inference, which is an extension of evolutionary parsimony. Compositional statistics takes account of the base composition of the compared sequences by using nucleotide positions that evolutionary parsimony ignores. It shares with evolutionary parsimony the features of rate invariance and the fundamental distinction between transitions and transversions. Of the presently available methods of phylogenetic inference, compositional statistics is based on the fewest and mildest assumptions about the mode of DNA sequence evolution. It is therefore applicable to phylogenetic studies of the most distantly related organisms or molecules. This was illustrated by analyzing conservative positions in the DNA sequences of the large subunit of RNA polymerase from three archaebacterial groups, a eubacterium, a chloroplast, and the three eukaryotic polymerases. Internally consistent results, which are in accord with our knowledge of organelle origin and archaebacterial physiology, were achieved.

Amino Acid Sequence↗
PubMed1990

Amino acid sequences of stomach and nonstomach lysozymes of ruminants.

Complete amino acid sequences are presented for lysozymes c from camel and goat stomachs and compared to sequences of other lysozymes c. Tree analysis suggests that the rate of amino acid replacement went up as soon as lysozyme was recruited for the stomach function in early ruminants. The two lysozymes from goat stomach are the products of a gene duplication that probably took place before the divergence of cow, goat, and deer about 25 million years ago. Partial sequences of three lysozymes from goat tears indicated that (a) the goat tear family of lysozymes may have diverged from the stomach lysozyme family by an ancient duplication and (b) later duplications are probably responsible for the multiple forms of tear and milk lysozymes in ruminants.

Amino Acid Sequence↗
PubMed1990

Origin of tetrapods inferred from their mitochondrial DNA affiliation to lungfish.

This paper shows that questions of an unexpected phylogenetic depth can be addressed by the study of mitochondrial DNA (mtDNA) sequences. For decades, it has been unclear whether coelacanth fishes or lungfishes are the closest living relatives of land vertebrates (Tetrapoda). Segments of mtDNA from a lungfish, the coelacanth, and a ray-finned fish were sequenced and compared to the published sequence of a frog mtDNA. A tree based on inferred amino acid replacements, silent transversions, and ribosomal RNA (rRNA) substitutions showed with statistical confidence that the lungfish mtDNA is more closely related to that of the frog than is the mtDNA of the coelacanth. This result appears to rule out the possibility that the coelacanth lineage gave rise to land vertebrates; hence, morphological characters that link the latter two groups are possibly due to convergent evolution or reversals and not to common descent. Besides supporting the theory that land vertebrates arose from an offshoot of the lineage leading to lungfishes, the molecular tree facilitates an evolutionary interpretation of the morphological differences among the living forms. It would appear that the common ancestor of lungfishes and tetrapods already possessed multiple morphological traits preadapting their locomotion, circulation, and respiration for life on land.

Animals↗
PubMed1990

Spatial and temporal continuity of kangaroo rat populations shown by sequencing mitochondrial DNA from museum specimens.

The advent of direct sequencing via the polymerase chain reaction (PCR) has opened up the possibility of molecular studies on museum specimens. Here we analyze genetic variation in populations over time by applying PCR to DNA extracted from museum specimens sampled from populations of one species over the last 78 years. Included in this study were 43 museum specimens of the Panamint kangaroo rat Dipodomys panamintinus from localities representing each of three geographically distinct subspecies. These specimens were originally collected and prepared as dried skins in 1911, 1917, or 1937. For each specimen, a 225-bp segment of the mitochondrial genome was sequenced. These mitochondrial DNA sequences were compared to those of 63 specimens collected at the same localities in 1988. The three subspecies were nearly completely distinct. Only 2 of the 106 individuals shared mitochondrial types between subspecies. For all three localities, the diversity levels were maintained between the two temporal samples. The concordance observed between the two temporally separate phylogenies supports the use of museum specimens for phylogenetic inference. This study demonstrates the accuracy and routine nature of the use of museum specimens in the analysis of mitochondrial sequence variation in natural populations and, importantly, that a temporal aspect can now be added to such studies.

Animals↗
PubMed1990

Geographic variation in human mitochondrial DNA from Papua New Guinea.

High resolution mitochondrial DNA (mtDNA) restriction maps, consisting of an average of 370 sites per mtDNA map, were constructed for 119 people from 25 localities in Papua New Guinea (PNG). Comparison of these PNG restriction maps to published maps from Australian, Caucasian, Asian and African mtDNAs reveals that PNG has the lowest amount of mtDNA variation, and that PNG mtDNA lineages originated from Southeast Asia. The statistical significance of geographic structuring of populations with respect to mtDNA was assessed by comparing observed GST values to a distribution of GST values generated by random resampling of the data. These analyses show that there is significant structuring of mtDNA variation among worldwide populations, between highland and coastal PNG populations, and even between two highland PNG populations located approximately 200 km apart. However, coastal PNG populations are essentially panmictic, despite being spread over several hundred kilometers. Highland PNG populations also have more mtDNA variability and more mtDNA types represented per founding lineage than coastal PNG populations. All of these observations are consistent with a more ancient, restricted origin of highland PNG populations, internal isolation of highland PNG populations from one another and from coastal populations, and more recent and extensive population movements through coastal PNG. An apparent linguistic effect on PNG mtDNA variation disappeared when geography was taken into account. The high resolution technique for examining mtDNA variation, coupled with extensive geographic sampling within a single defined area, leads to an enhanced understanding of the influence of geography on mtDNA variation in human populations.

Australia↗
PubMed1990

Phylogenetically informative length polymorphism and sequence variability in mitochondrial DNA of Australian songbirds (Pomatostomus).

A combination of restriction analysis and direct sequencing via the polymerase chain reaction (PCR) was used to build trees relating mitochondrial DNAs (mtDNAs) from 50 individuals belonging to five species of Australian babblers (Pomatostomus). The trees served as a quantitative framework for analyzing the direction and tempo of evolution of an intraspecific length polymorphism from a third mitochondrial ancestor. The length polymorphism lies between the cytochrome b and 12S rRNA (srRNA) genes. Screening of mtDNAs within and between the five species with restriction enzymes showed that Pomatosomus temporalis was polymorphic for two smaller size classes (M and S) that are completely segregated geographically, whereas mtDNAs from the other four species were exclusively of a third, larger size (L). Inter- and intraspecific phylogenetic trees relating mtDNAs based on restriction maps, cytochrome b sequences obtained via PCR, and the two data sets combined were compared to one another statistically and were broadly similar except for the phylogenetic position of Pomatosomus halli. Both sets of phylogenies imply that only two deletion events can account for the observed intraspecific distribution of the three length types. High levels of base-substitutional divergence were detected within and between northern and southern lineages of P. temporalis, which implies a low level of gene flow between northern and southern regions as well as a low rate of length mutation. These conclusions were confirmed by applying coalescent theory to the statistical framework provided by the phylogenetic analyses.

Animals↗
PubMed1990

Comparative platelet inhibitory effects of human neutrophils and lymphocytes.

The effects of isolated leukocytes (polymorphonuclear leukocytes [PMNLs] or neutrophils and lymphocytes) on platelet aggregation in platelet-rich plasma (PRP) were examined. Both PMNLs and lymphocytes decreased platelet aggregation in a concentration-dependent fashion. PMNL-induced, but not lymphocyte-induced, inhibition of platelet aggregation was more pronounced as the incubation time of PRP with PMNLs was prolonged. The platelet-inhibitory effect of PMNLs was enhanced by superoxide dismutase (SOD) and was attenuated by oxyhemoglobin and methylene blue. These agents, in contrast, had no effect on lymphocyte-mediated inhibition of platelet aggregation. Adenosine deaminase did not modulate the platelet inhibitory effects of either PMNLs or lymphocytes. The incubation of PMNLs with PRP was associated with an increase in cyclic guanine 5' monophosphate (cGMP) levels in PRP. Incubation of lymphocytes, however, did not result in an increase in cGMP levels in PRP. Neither PMNLs nor lymphocytes in PRP caused a reduction in thromboxane B2 (TXB2) or an increase in 6-keto-PGF1 alpha. Thus this study shows potent inhibitory effects of isolated PMNLs mediated by a substance with biologic characteristics of nitric oxide. However, the mechanism of lymphocyte-induced inhibition of platelets appears to be independent of prostaglandins, nitric oxide, or adenosine.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Atherosclerosis and glomerulosclerosis in WHHL rabbits and obese Zucker rats.

The aorta and the kidney of 12 month old hyperlipidemic WHHL and obese Zucker rats, were examined morphologically. The WHHL developed severe and premature atherosclerosis but did not develop glomerulosclerosis. In contrast, the Zucker rats did not manifest atherosclerosis of the aorta, but developed glomerulosclerosis. These two animal models could be useful in understanding the roles of heterogeneous lipoprotein particles, genetic susceptibility, hemodynamic stress, and mesangial interactions with lipoproteins in the development of glomerulosclerosis.

Animals↗
PubMed1990

Serum lipids after gastric bypass surgery for morbid obesity.

Thirty-eight of 151 consecutive patients (25 percent) undergoing bypass surgery for morbid obesity had increased serum levels of total cholesterol (TC), triglycerides (TG) or both preoperatively. Ten patients had isolated TC elevation, six had isolated TG elevation and 22 had both TC and TG elevation. High density lipoprotein-cholesterol (HDL-C) levels were subnormal in 28 of the 38 patients (74 percent). Fasting lipid profiles were determined in the 38 hyperlipidemic patients at 6-month intervals postoperatively. Mean follow-up period was 29 months. By 6 months postop, patients had a greater than or equal to 20 percent mean reduction in TC and greater than or equal to 50 percent mean reduction in TG which were significant in comparison with preop levels and correlated with weight loss (P less than or equal to 0.05). Mean HDL-C levels had increased significantly vs. preop levels by 12 months postop (P less than 0.05). Lipid profiles became normal in 32 of the 38 patients (84 percent). Improvements in lipid profile were sustained in all patients with satisfactory weight loss but regressed after 12 months in patients who did not lose greater than or equal to 50 percent of their excess weight. These results suggest that abnormal serum lipid profiles can be permanently improved with sustained weight loss after gastric restriction surgery for morbid obesity.

Adult↗
PubMed1989

DNA phylogeny of the extinct marsupial wolf.

The phylogenetic affiliation of the extinct marsupial wolf (Thylacinus cynocephalus), which once was widespread in Australia, has been uncertain. On the basis of morphology, some systematists argue that the thylacine was most closely related to an extinct group of South American carnivorous marsupials, the borhyaenids, whereas others consider it to be closer to Australian carnivorous marsupials. Here we use direct sequencing by means of the polymerase chain reaction (PCR) to compare 219 bases of mitochondrial (mt) DNA from museum specimens of the marsupial wolf and representatives of six genera of extant marsupials. In agreement with the results of an antigenic study of albumin, our genetic data suggest that the marsupial wolf was more closely related to other Australian marsupial carnivores than to those of South America. Thus, the marsupial wolf represents an example of convergent morphological evolution to South American carnivorous marsupials as well as to true wolves.

Amino Acid Sequence↗