Biomedical subjects

A C Wilson

Publications and source records attributed to A C Wilson.

276 records · Page 16Linked to original sources

PubMedDate not supplied

Duplication and remoulding of tRNA genes during the evolutionary rearrangement of mitochondrial genomes.

During the evolution of sea urchins, a transfer RNA gene lost its tRNA function and became part of a protein-coding gene. This functional loss of a tRNA with specificity for one group of leucine codons (CUN, where N is any base) was accompanied by the gain of a new tRNA with that specificity. The new tRNA gene for CUN codons appears to have evolved by duplication and divergence from a tRNA gene specific for another group of leucine codons (UUR, where R is a purine). These proposals account for (1) the strong sequence resemblance between the modern tRNA genes for CUN and UUR codons in Paracentrotus, (2) the altered location of the CUN gene in mitochondrial DNA of this urchin, and (3) the persistence of a 72-base pair sequence containing a trace of the old CUN gene at its original location. The old CUN gene now codes for an extra 24 amino acids at the amino end of subunit 5 in NADH dehydrogenase. Besides giving clues about the mechanisms by which tRNA genes move during mitochondrial DNA evolution, this finding leads us to propose a pathway relating the arrangements of other genes in mitochondrial DNAs from four animal phyla.

Animals↗

PubMedDate not supplied

Adaptive evolution in the stomach lysozymes of foregut fermenters.

The convergent evolution of a fermentative foregut in two groups of mammals offers an opportunity to study adaptive evolution at the protein level. The appearance of this mode of digestion has been accompanied by the recruitment of lysozyme as a bacteriolytic enzyme in the stomach both in the ruminants (for example the cow) and later in the colobine monkeys (for example the langur). The stomach lysozymes of these two groups share some physicochemical and catalytic properties that appear to adapt them for functioning in the stomach fluid. To examine the basis for these shared properties, we sequenced langur stomach lysozyme and compared it to other lysozymes of known sequence. Tree analysis suggest that, after foregut fermentation arose in monkeys, the langur lysozyme gained sequence similarity to cow stomach lysozyme and evolved two times faster than the other primate lysozymes. This rapid evolution, coupled with functional and sequence convergence upon cow stomach lysozyme, could imply that positive darwinian selection has driven about 50% of the evolution of langur stomach lysozyme.

Adaptation, Physiological↗

PubMedDate not supplied

Maternal inheritance of mitochondrial DNA during backcrossing of two species of mice.

As judged by restriction analysis, mitochondrial DNA shows strictly maternal inheritance during 6-8 generations of backcrossing in both directions between Mus domesticus and Mus spretus. The average number of paternal mitochondrial genomes contributed to the next generation is estimated to be no more than one per thousand maternal mitochondrial genomes contributed. Despite the estimated accumulation of over 2000 mutational differences between M. spretus and M. domesticus mtDNAs since their divergence from a common ancestor, each of these mitochondrial DNAs, whether on a M. spretus or a M. domesticus nuclear background, allows mice to develop with seemingly normal viability and fertility.

Animals↗

PubMedDate not supplied

Suppression of aortic atherosclerosis in cholesterol-fed rabbits by purified rabbit interferon.

The effectiveness of rabbit interferon in suppressing atherosclerosis was evaluated in rabbits fed a diet containing 1% cholesterol. Ten male New Zealand White rabbits received intramuscular injections of 1 million units of interferon twice a week, while a control group of 10 rabbits received injections of buffer. Both groups had average serum cholesterol levels of over 2000 mg/dl during the 8-week experimental period. Interferon treatment resulted in no significant hypolipidemic effect or changes in lipoprotein composition. Atherosclerotic lesions in aortas were quantified both macroscopically and microscopically. Interferon treatment decreased the grossly visible lesion area significantly from 25 +/- 4% to 8 +/- 1% (mean +/- SEM, p less than 0.005) compared to the untreated group. Microscopic analysis of serial cross-sections of aortic segments revealed significant (p less than 0.01) reductions in both lesion size and frequency in the interferon-treated group. Electron microscopy also showed that interferon treatment reduced the pathological effects of cholesterol feeding. Tissue analysis showed that total aortic cholesterol was reduced by 28% by interferon treatment, while the aortic phospholipid concentration was increased by 25%. The possibility exists that the interferon preparation used contained other biological response modifiers and that the observed effects may be totally unrelated with interferon. These results suggest that the mechanism of atherosclerosis suppression in these cholesterol-fed rabbits is not related to the lowering of serum cholesterol but may be associated with inhibition of lesion initiation.

Adrenal Glands↗

PubMedDate not supplied

Extracranial carotid arterial disease in patients with familial hypercholesterolemia and coronary artery disease treated with colestipol and nicotinic acid.

Carotid bifurcation atherosclerosis was demonstrated in 34 of 108 patients with familial hypercholesterolemia and coronary artery disease by B-scan, continuous-wave Doppler sonography, and intravenous digital subtraction angiography. An intensive combined therapy of diet, colestipol, and nicotinic acid was mounted to control the hypercholesterolemia of these patients. Their serial sonographies and digital subtraction angiography were evaluated independently by technical specialists who served as coinvestigators. The data obtained suggest that extracranial arterial disease can develop concurrently with coronary artery disease in a significant proportion of patients with familial hypercholesterolemia, and amaurosis fugax, transient ischemic attack, cerebral infarction, and myocardial infarction did not recur during 58-72 months of control of familial hypercholesterolemia in this series of patients.

Adult↗

PubMedDate not supplied

Salivary fluoride concentrations in children with various systemic fluoride exposures.

Parotid ductal saliva fluoride concentrations were determined as an indication of baseline plasma fluoride levels in three groups of children. Group I had been exposed to drinking water containing less than 0.1 ppm F and had not received fluoride supplements. Group II had consumed optimally fluoridated water (1 ppm) since infancy. Group III had consumed water with less than 0.1 ppm F but had received a daily fluoride supplement for at least two years. The mean salivary fluoride concentrations in Groups II and III were significantly higher than Group I, but were not significantly different from each other. The findings suggest that peak plasma fluoride concentrations achieved following a daily fluoride supplement dose are higher than previously thought.

Child↗