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Biomedical subjects

R Jackson

Publications and source records attributed to R Jackson.

At least 343 records · Page 19Linked to original sources
PubMed1988

Atrial natriuretic peptide lowers pulmonary arterial pressure in hypoxia-adapted rats.

To test the hypothesis that atrial natriuretic peptide (ANP) has a direct vasodilator effect on the pulmonary vasculature that is enhanced in hypoxia-induced pulmonary hypertension in the rat, we determined the effects of ANP on mean pulmonary (MPAP) and systemic arterial pressure (MSAP) in intact conscious Sprague-Dawley rats exposed to 10% O2 or room air for 4 wk. Catheters were placed in the pulmonary artery through the right jugular vein by means of a closed-chest technique. MPAP and MSAP were monitored before and after intravenous injections of graded doses of ANP. ANP produced dose-related decreases in MPAP that were greater in the hypoxic group than in air controls. There were no significant between-group differences in the systemic depressor responses to ANP or in the ANP-induced reduction in cardiac output. ANP lowered MPAP significantly in isolated perfused lungs from both hypoxia-adapted and air control rats, and this effect was significantly greater in the hypoxic than the air control lungs. These data indicate that ANP lowers pulmonary arterial pressure in rats with hypoxia-induced pulmonary hypertension, mainly by a direct vasodilator effect on the pulmonary vasculature.

Animals↗
PubMed1988

International trends in asthma mortality: 1970 to 1985.

Recent international trends in asthma mortality among people aged five to 34 years were examined as a follow-up to an epidemic of asthma deaths in the late 1970s which appeared to be confined to New Zealand. Mortality rates were compared in 14 countries with suitable statistics; Australia, Canada, England and Wales, Finland, France, Japan, Israel, the Netherlands, New Zealand, Singapore, Sweden, Switzerland, the United States, and West Germany, for the period 1970 to 1984/5. In New Zealand, asthma mortality in this age group more than trebled from 1.3 per 100,000 in 1974 to 4.2 per 100,000 in 1979 and since then has declined substantially to 1.85 per 100,000 in 1985. Asthma death rates vary more than six-fold among the other countries examined, and although the New Zealand experience has not been seen to the same degree elsewhere, a gradual increase in reported asthma mortality has occurred since the mid to late 1970s in the majority of countries studied. The increase and subsequent decline in asthma mortality in New Zealand could not be explained by changes in diagnostic fashions or in the International Classification of Disease coding rules. Similarly, the US data do not suggest there is diagnostic transfer among diseases of airway obstruction. However, part of the differences in asthma mortality among the countries examined and the recent increases in asthma death rates, could be due to changing diagnostic fashions rather than true differences in mortality. International studies on the validity of asthma death statistics and on asthma prevalence are required to clarify these issues.

Adult↗
PubMed1987

Inhibition of gastric H+,K+-ATPase and acid secretion by SCH 28080, a substituted pyridyl(1,2a)imidazole.

A hydrophobic amine, SCH 28080, 2-methyl-8-(phenylmethoxy)imidazo(1,2a)pyridine-3-acetonitrile, previously shown to inhibit gastric acid secretion in vivo and in vitro, was also shown to inhibit basal and stimulated aminopyrine accumulation in isolated gastric glands when histamine, high K+ concentrations, or dibutyryl cAMP were used as secretagogues. Stimulated, but not basal, oxygen consumption was also inhibited. Neutralization of the acid space of the parietal cell by high concentrations of the weak base, imidazole, reduced the potency of the drug, suggesting that SCH 28080 was active when protonated. Studies on the isolated H+,K+-ATPase showed that the compound inhibited the enzyme competitively with K+, whether ATP or p-nitrophenyl phosphate were used as substrates. In contrast, the inhibition was mixed with respect to p-nitrophenyl phosphate and uncompetitive with respect to ATP. The drug reduced the steady state level of the phosphoenzyme but not the observed rate constant for phosphoenzyme formation in the absence of K+ nor the quantity of phosphoenzyme reacting with K+. The drug quenched the fluorescence of fluorescein isothiocyanate-modified enzyme and also inhibited the ATP-independent K+ exchange reaction of the H+,K+-ATPase. Its action on gastric acid secretion can be explained by inhibition of the H+,K+-ATPase by reversible complexation of the enzyme. This class of compound, therefore, acts as a reversible inhibitor of gastric acid secretion.

Adenosine Triphosphatases↗
PubMed1987

Inhibition of (H+ + K+)-ATPase by omeprazole in isolated gastric vesicles requires proton transport.

Omeprazole was found to inhibit the (H+ + K+)-ATPase activity in isolated gastric vesicles only when acid was accumulated in the vesicle lumen. The ATPase activity was time- and dose-dependently inhibited in the presence of K+ and valinomycin. Under conditions in which no pH-gradient was generated, i.e., in the presence of K+ alone or NH4+, no effect of omeprazole was found. The degree of inhibition was directly correlated to the amount of inhibitor bound to the preparation. A stoichiometry of 2 mol radiolabelled inhibitor bound per mol phosphoenzyme was found on total inhibition of the K+ plus valinomycin-stimulated activity. This inhibitory action of omeprazole on the ATPase activity could be fully reversed by addition of beta-mercaptoethanol. The inhibition of the proton transport in the (H+ + K+)-ATPase-containing vesicles by omeprazole was also strictly correlated to the amount of bound inhibitor. The stoichiometry of binding at total inhibition of this reaction was found to be 1.4 mol per mol phosphoenzyme. The K+-stimulated p-nitrophenylphosphatase activity was inhibited in parallel with the ATPase activity, whereas the phosphoenzyme levels were affected to a lesser extent by omeprazole. Gel electrophoresis of an omeprazole-inhibited vesicle preparation showed that the radiolabel was mainly found at 94 kDa, the molecular weight of the (H+ + K+)-ATPase catalytic subunit(s).

4-Nitrophenylphosphatase↗
PubMed1987

AI/LEARN: an interactive videodisk system for teaching medical concepts and reasoning.

This paper describes AI/LEARN, an educational videodisk system designed to teach clinical observational skills and reasoning in medicine. The AI/LEARN system uses a learning conditions approach to teaching. To teach visual concepts, we use the principle of exemplar/nonexemplar pairs and immediate feedback. To teach If-Then problem solving we use the format of minicases with delayed feedback. The software to operate the system has been custom developed and is domain independent. The result is a prototype of a new authoring package for videodisk teaching which operates on IBM compatible microcomputers. The medical domain selected for this prototype system was rheumatic diseases; the knowledge used to teach reasoning skills is derived from the knowledge base of an expert system: AI/RHEUM.

Computer Systems↗
PubMed1987

Trends in dietary fat and cigarette smoking and the decline in coronary heart disease in New Zealand.

Coronary heart disease (CHD) mortality declined by approximately 23.5% in New Zealand men aged 35-64 years between 1968 and 1980. The contributions of secular trends in dietary fat and tobacco consumption to this decline were examined using data from national consumption statistics and population based studies of risk factor levels. Per capita saturated fat and dietary cholesterol consumption fell by approximately 12% and 10% respectively during this period while polyunsaturated fat consumption increased by 73%. Per capita tobacco consumption fell by approximately 15%. Using equations developed by Keys and Hegsted it was calculated that the mean serum cholesterol level declined by between 6.6 and 10.3 mg/dl (2.9%-4.4%) during this period. The potential impact of these risk factor changes on CHD mortality was estimated using a Framingham multivariate logistic risk function. Between 38% and 51% of the observed decline in CHD mortality in men aged 35-64 years in New Zealand between 1968 and 1980 could be accounted for by the calculated changes in serum cholesterol and tobacco consumption. If serum cholesterol and cigarette smoking were reduced further to meet current recommendations, it is estimated that CHD mortality would decline by a further 26%-30% from the 1980 level.

Adult↗
PubMed1987

Alcohol and exercise in myocardial infarction and sudden coronary death in men and women.

The relation of alcohol consumption and regular leisure time physical activity with nonfatal myocardial infarction and sudden coronary death in men and women of Auckland, New Zealand, was examined in a large population-based case-control analysis. Within each sex, alcohol drinkers had decreased relative risks of both myocardial infarction and sudden coronary death compared with nondrinkers. Similarly, physical activity was associated with decreased relative risks of myocardial infarction and sudden coronary death in both women and men, but only in those subjects who had been exercising for five or more years. After controlling for hypertension, cigarette smoking, and alcohol consumption, 43% (95 confidence interval (CI) = 26-60) of coronary events could be explained by lack of exposure to physical activity. This compares with the per cent of coronary events in the study population attributable to hypertension (22%; 95% CI = 17-27) or cigarette smoking (31%; 95% CI = 25-38). Although the estimation of the attributable risk for a continuous variable is affected by the cut-point used to define exposure, from a public health viewpoint, regular leisure time physical activity may be as important as the above-mentioned major coronary heart disease risk factors.

Adult↗
PubMed1987

The relationship between the complex of immunoglobulin A and alpha-1-antitrypsin, its constituent components and the acute-phase response as measured by C-reactive protein in rheumatoid arthritis treated with gold or D-penicillamine.

Serum levels of immunoglobulin A (IgA), alpha 1-antitrypsin (AT), their complex (IgA-alpha 1AT) and C-reactive protein (CRP) were measured prior to treatment and at 6 months, in 45 rheumatoid arthritis (RA) patients. Twenty-five patients were treated with D-penicillamine (DPA) and 20 patients with gold (sodium aurothiomalate). The level of circulating complex was reduced by both treatments (p less than 0.001). There was a significant correlation between the circulating levels of IgA-alpha 1AT complex and serum IgA (p less than 0.05). No relationship was observed between the level of circulating complex and CRP. These findings suggest that formation of IgA-alpha 1AT complex in RA is dependent on the level of IgA. The complex is reduced by gold and DPA but it does not reflect an acute phase response as measured by CRP.

Acute-Phase Proteins↗
PubMed1987

Cerebral ventricular enlargement in chronic schizophrenia: consistencies and contradictions.

A study of cerebral ventricular size measured as ventricle to brain ratio (VBR) using computerised tomographic brain scan in chronic schizophrenics provided no support for suggestions that there are significant differences between patients who fall into different clinical subtypes. We found no significant difference in VBR between patients with and without a family history of schizophrenia or between those with or without paranoid symptoms. Applying Crow's classification, contrary to expectations, Type 1 patients had significantly larger ventricles than those with 'mixed' symptomatology (both Type 1 and Type 2 features). We also applied a variety of operational criteria which attempt to define schizophrenia as a whole: of these only Schneider's first-rank symptoms (FRS) yielded conclusive results--FRS-positive patients had significantly larger mean VBR than those without such symptoms. Previously, it has been suggested that ventricular enlargement is more closely associated with 'negative' than with 'positive' symptoms.

Adult↗
PubMed1987

Nevoid basal cell carcinoma syndrome. A 15-year follow-up of cases in Ottawa and the Ottawa Valley.

The nevoid basal cell carcinoma syndrome is an autosomal dominant condition that consists of multiple basal cell carcinomas of the skin, odontogenic keratocysts, pits of the hands and feet (especially the palms and soles), various ectopic calcifications, notably lamellar calcification of the falx cerebri and skeletal anomalies. As well as these major findings, there are many other associated abnormalities. This paper is a 15-year follow-up study on twelve cases from the Ottawa Valley with details on nine new cases discovered during that time. Sixteen were males; 5, females. The number of basal cell cancers requiring removal varied greatly from patient to patient. There was one patient with a horror lesion; none had metastatic disease.

Basal Cell Nevus Syndrome↗
PubMed1986

Cigarette smoking and risk of premature stroke in men and women.

A case-control study was carried out of the relation between cigarette smoking and hypertension and stroke. A total of 132 cases of stroke (79 in men, 53 in women) identified as a part of a population based register were compared with 1586 controls (1017 men, 569 women) from a survey of cardiovascular risk factors conducted in the same population. Cigarette smokers had a threefold increase in the risk of stroke compared with current non-smokers. This association remained significant after adjusting for hypertension. Those who both smoked and had hypertension had an increased risk of stroke of almost 20-fold compared with those who neither smoked nor had hypertension. Overall, in this population roughly 37% of stroke events may be attributed to cigarette smoking and 36% to hypertension.

Adult↗