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Biomedical subjects

S Stone

Publications and source records attributed to S Stone.

At least 253 records · Page 14Linked to original sources
PubMed1981

Glucoreceptors controlling feeding and blood glucose: location in the hindbrain.

Microinfusion of 5-thioglucose into either the lateral or fourth cerebral ventricle caused increased feeding and hyperglycemia in rats when the cerebral aqueduct was unobstructed. If the aqueduct was obstructed and 5-thioglucose was infused into the fourth ventricle, increased feeding and hyperglycemia persisted, whereas feeding and hyperglycemia in response to lateral ventricle infusion were abolished. Drinking in response to infusion of angiotensin II into the lateral ventricle was not diminished by aqueduct obstruction. These results indicate that glucoreceptors that mediate feeding and hyperglycemia in response to cerebral glucoprivation are located in the caudal hindbrain and not in the hypothalamus where they have previously been sought.

Animals↗
PubMed1981

Simulation of protein evolution by random fixation of allowed codons.

Computer simulation of protein evolution is based on a simple model consisting of random fixation of allowed codons (RFAC). Random replacement of single nucleotides occurs in a DNA sequence. If this results in any of the synonomous codons for allowed amino acids the mutation is fixed, if not, there is no change in the DNA and the cycle is repeated. Multiple fixations at the same nucleotide site, back mutations, degenerate fixations and coincidental identity of amino acids all occur. RFAC simulation begins with a single DNA sequence and follows a phylogeny based on the fossil record. The rate of fixation at the level of DNA is constant. The model upon which RFAC simulation is based is the same as the neutral theory of molecular evolution. The simulation is therefore a test of this theory. The results of simulated and real evolution are compared for fibrinopeptides A in mammals and cytochromes C and hemoglobin alpha and beta chains in vertebrates. In each case the allowed variation at each site has been set equal to that observed, twice that observed and all protein amino acids. Rates of fixation vary from 2.4 X 10(-10) to 10(-8) accepted nucleotide fixations per codon per year. There is some, although never excellent, agreement between real and simulated evolution, the better fits are obtained in the cases of fibrinopeptides A and cytochromes C. The major source of discrepancy between real evolution and simulation is irregularities in the rates of real evolution. RFAC simulation is compared with the random evolutionary hit (REH) model, augmented maximum parsimony and the accepted point mutations (PAM) approach.

Amino Acids↗
PubMed1981

Preradial myxedema in thyroid disease.

Patients with Graves' disease were noted to have thickening of the skin on the extensor surfaces of their forearms. Skin biopsy specimens were obtained from nine consecutive patients with Graves' disease treated with sodium iodide I 131, from three patients with other thyroid disorders, and from one patient with acromegaly. Skin specimens from one patient with scleredema and one patient with scleromyxedema were used as controls for the histologic stains. Hematoxylin-eosin-stained sections of forearm skin from eight of nine patients with Graves' disease showed prominent round-cell (probably lymphocytic) infiltration around dermal capillaries and distortion of collagen fibers. In five of the patients with Graves' disease, staining with Mowry's colloidal iron disclosed dense deposits of mucin in the papillary dermis, with a distribution similar to that reported for pretibial myxedema. Mucopolysaccharide deposition in the skin on the extensor surface of the forearms may be the clinical counterpart of pretibial myxedema.

Acromegaly↗
PubMed1980

Fate of patients with fixed subaortic stenosis after surgical removal.

Thirty-nine consecutive patients, aged 5 to 57 years, were followed for two to 15 years with serial haemodynamic studies after removal of fixed subaortic stenosis, which was never a "membrane". Two late deaths occurred, one sudden and one in congestive failure. Of 37 survivors, 25 were asymptomatic and could be classified as good or excellent if judged by well-being. Seven were symptomatic, two having had reoperation for fixed subaortic stenosis, and four needed long-term pacing. Evaluation, including the effect of isoprenaline, showed important dynamic obstruction in 17, five of whom redeveloped fixed obstruction. Seven had congestive features without outflow gradients, and 14 had neither congestion nor outflow obstruction. Complete assessment therefore confirmed that only 14 (36%) were haemodynamically satisfactory; two of them had permanent pacing, and four had had aortic valve surgery. Fixed subaortic stenosis should be removed early, when diagnosed, and completely before secondary myocardial changes occur. Patients however "well" need regular supervision and early haemodynamic assessment. The aortic valve, whether repaired, replaced, or untouched, remains a site for infective endocarditis for life. The fixed subaortic stenosis removed at operation may not be present in that form at birth, but acquired secondary to other congenital abnormalities which remain in the patient.

Adolescent↗
PubMed1979

Long-term results of pulmonary autograft for aortic valve replacement.

Eighty-five survivors who left hospital after pulmonary autograft replacement for severe aortic regurgitation have been followed critically. Five patients died in the first five years and 80 were followed for six to 11 years. Important aortic regurgitation occurred only early and was always related to technical malpositioning of one autograft cusp. Seven patients with fascial pulmonary valves had problems, requiring removal in four. There was a small (2%) morbidity from the right sided homograft and six were removed five to seven years later for progressive calcification; three of these had been irradiated. Despite a high incidence of trivial diastolic murmurs this valve replacement is still preferred for young patients without dilated aortic roots since the survivors remain well, with excellent, maintained relief of outflow obstruction, without problems from haemolysis and thromboembolism, and without deteriorating autograft function or need for anticoagulants. Histology of five autografts examined up to seven years after operation has shown normal living architecture.

Adolescent↗
PubMed1978

Spatial deficit in familial left-handed children.

This study was designed to evaluate the hypothesis that familial left-handed children who presumably have bilateral representation of language ability should show an impairment in spatial ability. Children, whose average age was 8 yr. and of whom 22 were right-handed, 11 familial left-handed, and 11 non-familial left-handed, were tested on verbal subtests of the Wechsler Intelligence Scale for Children--Revised, i.e., Vocabulary and Similarities and on spatial subtests, i.e., Block Design and Object Assembly. The results did not support the hypothesis that the spatial ability of familial left-handed children would be worse than their verbal ability. However, there was modest support for the hypothesis that familial left-handers were worse in spatial ability than right-handers.

Adolescent↗
PubMed1976

Hormonal dependency in Darier disease.

Variation in the severity of keratosis follicularis relative to states of homonal change was noted in eight women with the disease. Observations included frequent onset near puberty, puberty, exacerbation during menses, and improvement while patients are pregnant or on oral contraceptive agents. It is proposed that states of relative estrogen excess are associated with quiescence of this skin disorder. In support of this hypothesis, three postpubertal women with Darier desease were observed to undergo significant improvement with the use of estrogen-dominant birth control pills.

Adolescent↗