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Biomedical subjects

S Richardson

Publications and source records attributed to S Richardson.

At least 163 records · Page 9Linked to original sources
PubMed1987

Glycolipid binding of purified and recombinant Escherichia coli produced verotoxin in vitro.

Escherichia coli verotoxin (also known as Shiga-like toxin) has been implicated in the aetiology of the hemolytic uremic syndrome and hemorrhagic colitis. The glycolipid binding specificity of verotoxin purified from E. coli H30 and verotoxin cloned from bacteriophage H19B has been examined. Verotoxin from both sources binds specifically to globotriosyl ceramide containing the carbohydrate sequence galactose alpha 1-4galactose beta 1-4glucose-ceramide. Removal of the terminal galactose or substitution with N-acetylgalactosamine in beta 1-3 linkage deletes toxin binding activity. A ceramide trihexoside species, consistent with a globotriosyl ceramide structure was shown to be the major verotoxin-binding glycolipid of cultured vero cells which are routinely used to measure the cytotoxicity of toxin samples.

Bacterial Toxins↗
PubMed1987

Comparison of relative risks obtained in ecological and individual studies: some methodological considerations.

This paper is concerned with the problem of estimating relative risks from ecological correlation studies. In the first part, some of the biases encountered when analysing aggregated data are discussed and in particular attention is focused on the shape of the dose-response relationship obtained from aggregated and non-aggregated data, on the need for extrapolation and on the scale of aggregation. In the second part some empirical observations are made on these points by means of four examples concerning the relative risk between smoking and different pathologies. The estimates of relative risks derived from French geographical data and from case control or cohort studies are compared. The performance of ecological studies is discussed with respect to the strength of the risk factor considered, the geographical distribution of counfounding factors and the adjustment of different models.

Adult↗
PubMed1987

Implementing contract learning in a senior nursing practicum.

The use of learning contracts with undergraduates and graduate nursing students, as well as in staff inservice and continuing nursing education, has been promoted in North America as a teaching/learning strategy to individualize learning, promote independence, promote habits of lifelong learning and teach nurses how to cope with change. The purpose of this article is to describe the implementation of contract learning in a required clinical nursing course at the undergraduate level in a Canadian university and to describe retrospectively perceived benefits and difficulties. The process of peer consultation and student evaluation used in modifying contract learning is described. Recommendations for nurse educators considering implementing contract learning are presented.

Alberta↗
PubMed1987

Relationship between tuberculous scar and carcinomas of the lung.

Results of a transversal case-control study are reported which shows that there is a statistically significant association between tuberculous scars and carcinoma of the lung. Accordingly the possibility of malignancy has to be kept in mind when radiological or scintigraphic scanning reveal the presence of lung scars.

Cicatrix↗
PubMed1985

Mouse hypothalamic somatostatin release: roles of calcium and calmodulin.

We employed a short term system of dispersed adult mouse hypothalamic cells, as previously described in the rat, to examine the roles of calcium and calmodulin in SRIF release. Incubation studies were performed 24 h after hypothalamic cell dispersion. SRIF release, as determined by RIA was stimulated in a dose-dependent manner by the membrane-depolarizing agents KCl, ouabain, and veratridine as well as by the calcium ionophore A23187. The stimulation of SRIF release induced by depolarizing agents was abolished or diminished by 1) omission of extracellular calcium, 2) chelation of extracellular calcium by EGTA, and 3) the calcium channel blocker verapamil, indicating calcium dependence of this process. Three chemically distinct groups of calmodulin inhibitors were employed to study the role of calmodulin in stimulus-secretion coupling of hypothalamic SRIF. The neuroleptic calmodulin inhibitors trifluperazine (1 microM), chlorpromazine (10 microM), and promethazine (10 microM) as well as the naphthalene sulfonamide calmodulin inhibitor W7 (1 microM) and compound 48/80 (50 micrograms/ml) were all demonstrated to have an inhibitory effect on the stimulation of SRIF release induced by membrane depolarization. No inhibitory effect of the less potent naphthalene sulfonamide agent W5 was observed at 1 microM, although an inhibitory effect was seen at 10 microM. The stimulation of SRIF release induced by A23187 was not inhibited by omission of extracellular calcium or by verapamil, but was inhibited by EGTA and trifluperazine. These data demonstrate the role of calcium in membrane depolarization-induced stimulus-secretion coupling of mouse hypothalamic SRIF. Inhibition of the stimulatory response by low concentrations of three distinct groups of calmodulin inhibitors, i.e. neuroleptics, naphthalenesulfonamide agents and compound 48/80, suggests a role for calmodulin in this process.

Animals↗
PubMed1985

Presence of neuron-specific enolase and somatostatin in human parathyroid tissues.

The association of parathyroid abnormalities with apudomas prompted us to examine parathyroid tissues for the presence of neuron-specific enolase and somatostatin. Enolase was present in extracts of 29 out of 29 parathyroid specimens; tissue content was significantly higher in adenoma than in hyperplasia tissues (p less than 0.005). Somatostatin was present in 14 of 33 specimens. Immunoreactive somatostatin measured in tissue extracts' fluids coeluted on Sephacryl chromatography along with synthetic somatostatin-14 in studies of two parathyroid carcinoma specimens. Since neuron-specific enolase has been found only in neural and neuroendocrine cells, our results suggest that human parathyroid glands may contain neuroendocrine elements. The differential content of neuron-specific enolase in adenoma versus hyperplasia specimens may be diagnostically useful in selected cases. The significance of the presence of somatostatin in some but not all parathyroid tumors requires further investigation. Taken together with our prior findings of gastrin and pancreatic polypeptide in some human parathyroid glands, we postulate that human parathyroid tumors contain neural crest elements.

Adenoma↗
PubMed1984

[Oral contraceptives and cardiovascular mortality].

Several epidemiological studies have demonstrated at the individual level an elevated risk of cardiovascular death for women who have been using oral contraceptives. Nevertheless, there has been no detectable increase in the number of cardiovascular deaths during the last fifteen years in countries where the use of oral contraceptives has become widespread. In this paper, we have tried to analyse this apparent contradiction and to discuss the causal nature of the relationship linking oral-contraceptives and cardiovascular death. For this purpose, we present a bibliographical summary of the relevant studies as well as an analysis of the trend in cardiovascular deaths among women in France from 1968 to 1975.

Adult↗
PubMed1982

Keeping up-to-date.

Explore the source record for details and available documents.

Abstracting and Indexing↗
PubMed1980

The biomechanical responses to tension in a peripheral nerve.

The biomechanical adjustments rat sciatic nerves make to tension were studied 7 weeks after experimental nerve repair. Nerve tissue adjusts to tension by increasing its compliance if stretched within its physiological limits. Anatomical changes observed in the nerve tissue 7 weeks after stretching apparently accounts for the nerves extensibility, a biomechanical adjustment that helps preserve nerve continuity during the joint extension phase of extremity rehabilitation.

Adaptation, Physiological↗
PubMed1977

Immunobiology of primary intracranial tumors. Part 1: studies of the cellular and humoral general immune competence of brain-tumor patients.

Cellular and humoral immune parameters were evaluated in a series of brain-tumor patients, 42 with glioblastoma multiforme, 17 with other anaplastic gliomas, and 17 with meningiomas. A degree of anergy was found, which seems in the group as a whole to be proportional to the degree of anaplasia. In addition, serial bimonthyl testing in individual cases revealed further reduction in certain immune responses coincident with clinical decline.

Antibodies, Viral↗
PubMed1976

Long-term effects of chondrocyte death on rabbit articular cartilage in vivo.

The effects of freezing localized areas of rabbit articular cartilage in vivo were studied at two to twelve months morphologically (gross and microscopic examination, including scanning electron microscopy), histochemically (toluidine blue and safranin O), and metabolically (35S uptake). Up to six months the frozen cartilage was intact but appeared to be dead, as shown by the absence of stainable chondrocytes, severely decreased acid mucopolysaccharide content, and absence of significant uptake of 35S. At twelve months fibrillation and softening were evident, clusters of new chondrocytes with surrounding acid mucopolysaccharides were visible microscopically, and scanning electron microscopy revealed an irregular pattern of collagen fibers which were larger than normal, of varying thickness, and broken in some areas. These changes resembled those seen in degenerative joint disease.

Animals↗