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Biomedical subjects

M Cox

Publications and source records attributed to M Cox.

At least 181 records · Page 10Linked to original sources
PubMed1981

Aldosterone-induced proteins in toad urinary bladders. Identification and characterization using two-dimensional polyacrylamide gel electrophoresis.

Aldosterone-stimulated Na+ transport is mediated by new protein synthesis, but the identification of specific aldosterone-induced proteins (AIPs) has proven difficult and the cellular function of such proteins is unknown. Using high resolution two-dimensional polyacrylamide gel electrophoresis and autoradiography we have identified AIPs of similar isoelectric points (5.8 to 6.4) and molecular weights (70,000 to 80,000) in membrane-rich and cytosolic subcellular fractions of epithelial cells derived from single toad urinary bladders. The ability of actinomycin D to inhibit both AIP synthesis and aldosterone-induced Na+ transport is consistent with a role for these proteins in the natriferic action of aldosterone. In addition, since non-natriferic concentrations of cortisol did not induce similar proteins, AIP synthesis appears to be mineralocorticoid-specific. The relationship of AIP synthesis to Na+ transport was also studied. Since amiloride, which blocks Na+ transport in high resistance epithelia, did not affect the synthesis of these proteins, Na+ transport is not required for their synthesis. In addition, similar proteins were not induced when Na+ transport was stimulated by antidiuretic hormone and theophylline. Consequently, AIP synthesis is not merely a nonspecific consequence of the cellular metabolic changes associated with Na+ transport.

Aldosterone↗
PubMed1981

Subcellular localization of aldosterone-induced proteins in toad urinary bladders.

Paired toad urinary hemibladders were incubated with [35S]methionine in the presence (experimental) or absence (control) of aldosterone. Short-circuit current was used to monitor aldosterone-induced Na+ transport. Protein synthesis in epithelial cell subcellular fractions (cytosolic, microsomal, mitochondrial) was evaluated by gradient polyacrylamide gel electrophoresis and autoradiography. Aldosterone-induced proteins were identified in the cytosolic and microsomal fractions (70 000 and 15 000 daltons, respectively). These results represent the first demonstration of aldosterone-induced proteins in subcellular fractions of epithelial cells derived from single toad urinary hemibladders.

Aldosterone↗
PubMed1981

Ultrastructural studies of a polygonal myofilament network in cultured rat aortic smooth muscle cells.

Cultured rat aortic smooth muscle cells (SMC) were examined by electron microscopy and found to contain polygonal networks of 75 A degrees thin myofilament bundles. The cells also had large bundles of longitudinally aligned thin myofilaments with periodically spaced dense bodies. Abundant plasmalemmal vesicles were present at the cell periphery, and the cells were connected by desmosomes. Intercellular spaces contained sparse amounts of elastic fibers, a material generally present in SMC cultures. Analyses of amino acids by automated column-chromatography showed that isodesmosine and desmosine, two amino acid residues unique for elastin, were present. Accordingly, it was concluded that polygonal networks, previously detected solely in cultured nonmuscle cells, were present in SMC. Other findings suggest 1) a change in myofilament arrangement takes place during cell migration, and 2) rat aortic SMC grown in tissue culture flasks is an important experimental tool in the study of cell motility since such myofilament rearrangements were observed to occur up to fourteen days in first passage.

Animals↗
PubMed1981

Internal potassium balance and the control of the plasma potassium concentration.

The plasma potassium concentration is determined both by external potassium balance and by the distribution of potassium between extracellular and intracellular fluid compartments, i.e., "internal potassium balance." Whenever external potassium balance is altered, the resultant change in the plasma potassium concentration is strongly influenced by concomitant alterations in internal potassium balance. Several factors alter internal potassium balance independently of changes in external balance. Acid-base disturbances produce shifts of potassium into or out of cells, but attempts to quantify these effects are not likely to be clinically useful. Hypertonicity produces a shift of potassium out of cells. Several hormones (insulin, aldosterone, catecholamines, glucagon, and growth hormone) may have roles in internal potassium balance. Digitalis and succinylcholine, by producing efflux of potassium from cells, may cause hyperkalemia. Potassium is released from skeletal muscle during exercise, causing an increase in the plasma potassium concentration. The periodic paralyses are associated with well-defined transient alterations in internal potassium balance.

Acid-Base Imbalance↗
PubMed1981

Fitness program participation: its effect on worker performance.

The effects of an employee fitness program upon absenteeism and productivity were investigated in a controlled trial involving two large offices. During the six-month experimental program, the test company developed substantial gains of fitness. However self-reports and supervisor evaluations showed small and relatively similar gains of productivity, with reduction of absenteeism at both test and control companies. Further studies on a large scale are warranted. The presently observed changes probably reflect (1) sample attenuation, (2) seasonal trends, and (3) a "Hawthorne" effect. If the last factor is substantiated, employee fitness programs may be of economic interest, despite the nonspecific nature of the resultant gains in productivity.

Adult↗
PubMed1980

Effects of a 6-month industrial fitness programme on serum lipid concentrations.

The serum lipid profile (total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides) has been studied in 98 men and 158 women before and 6 months after introducing an employee fitness programme. Over this period, the sample sorted itself into 4 sub-groups (non-participants, drop-outs, high adherents, and low adherents). The high-adherents attended 2--3 30-min physical activity classes per week over the 6-month study, progressing to 15--17 min of aerobic activity per session, with significant gains of predicted maximum oxygen intake, and reductions of body fat. Nevertheless, there were few "favourable" changes of lipids that could be related to the physical activity sessions. A decrease of total cholesterol (mainly in the women) was unrelated to the changes of maximum oxygen intake, and occurred equally in non-participants and high adherents. High adherent women showed a decrease of LDL cholesterol, but this also was almost matched by changes in non-participants, while the main response of HDL cholesterol was a decrease in non-participants and drop-outs rather than an increase in high-adherents. It is concluded that if data are collected while subjects are in energy balance and persisting with their activity, a programme of the intensity practical in an employee fitness class has little impact upon blood lipids.

Adult↗
PubMed1980

Some factors influencing serum lipid levels in a working population.

Life-style variables (perceived fitness, excess body mass, percent fat, lean mass, predicted maximum oxygen intake, cigarette consumption, alcohol consumption, use of contraceptive medication) have been related to the lipid profile (serum triglycerides, total cholesterol, HDL and LDL cholesterol) in a sizeable volunteer population of Toronto office-workers. Multivariate analysis demonstrates an independent positive association of age with total cholesterol, HDL and LDL cholesterol, and (in women only) a weak negative association with triglycerides. Much of the fitness effect is related to body fat, which is positively correlated with triglycerides and (in the men only) with total and LDL cholesterol, but is negatively related to HDL cholesterol. However, maximum oxygen intake per unit of body mass shows a small independent association with triglycerides, total cholesterol (women only) and LDL cholesterol. Cigarette smoking bears an independent relationship to triglycerides, HDL cholesterol and (in women only) LDL cholesterol. Alcohol consumption is independently related to high values for total and LDL cholesterol, but is also related to high HDL cholesterol readings. While multivariate analysis allows for the inter-relationship of smoking habits, alcohol consumption, and the various fitness measurements, it cannot prove cause and effect. Nevertheless, the potential improvement of lipid profile associated with (i) abstinence from cigarettes, (ii) a 4% reduction of body fat, and (iii) avoidance of contraceptive medication is sufficient to warrant experimental trial of such a change in life-style.

Adult↗
PubMed1980

Physical fitness, respiratory symptoms and lung function.

Lung volumes (FVC1, FEV1.0 and peak flow) were measured in 403 men and 561 women volunteers for fitness testing, using the SRL automated spirometer system. Average scores for this population were 5--10% higher than predicted from age, height and sex using either the formulae inherent in the SRL computer or standards proposed by Anderson et al. [1968] for the Toronto population; existing standards may thus underestimate respiratory potential. Lung function data showed a dose-dependent decrease within the category of cigarette smokers, but there was no significant difference between average results for smokers and non-smokers. Multivariate analysis showed significant contributions of lean mass and obesity to the overall description of lung volumes; however, effects were not large enough to justify incorporation of such variables into routine prediction equations. Positive responses to the respiratory section of the Cornell Medical Index were in several instances associated with below expected lung volumes. The most consistent response was to the question 'do you suffer from asthma?' Although the average effect was significant, the magnitude of response (10--20%) would have been overlooked in individual testing; this suggests that there may be more scope for pulmonary screening through the improvement of questionnaires than through the purchase of expensive electronic spirometers.

Adolescent↗
PubMed1980

Some characteristics of participants in an industrial fitness programme.

A controlled study has allowed an investigation of several hypotheses relating to initial recruitment and continued participation in an employee fitness programme. Following initial physiological and psychological testing, attendance records show that the staff of the experimental company sorted themselves into four categories (non-participants, drop-outs, low adherents, and high adherents). Parallel observations were made at a second, comparable company where there was no employee fitness programme. Exercise classes met three times per week for 30 minutes of rhythmic calisthenics and endurance-type activities. Continued participation was favoured by a short stature, but perhaps because of gentle progression of intensity, there was no selective loss of obese subjects. A below average strength in high adherent men was related to their short stature. Participation was favoured by an interest in activity as the release of tension on the scale of Kenyon (women). Negative factors were a low score for personal and social factors on the scale of Holmes & Rahe (men), a recent health change (women), dissatisfaction with pay on the Job Description Index of Smith et al. (male non-participants, female drop-outs), and an interest in activity as Games of Chance (women). In the men, "Type A" score on the questionnaire of Friedman and Rosenman was highest in those with infrequent participation, but not in drop-outs; this possibly reflects a real time conflict among upper executives. Body image (Kenyon and McPherson scales), manifest anxiety (Taylor Scale) and reported health (Cornell Medical Index) were unrelated to participation in the programme. Lessons for future programming include (i) matching of prescribed activity to body build, (ii) gentle progression (to avoid discouragement of the obese), (iii) attention to the desired rewards of the individual, and (iv) flexibility of class schedules to accommodate subjects with real or perceived time conflicts.

Anxiety↗
PubMed1980

Post-coronary rehabilitation and risk factors, with special reference to diet.

Volunteers were randomly allocated to high intensity exercise (HIE, n = 17, added energy expenditure, 254 progressing to 761 kJ . day-1) and light intensity exercise (LIE, n = 13, < 76 kJ . day-1) programs for a period of one year, commencing 3-12 months after myocardial infarction. Dietary behaviour (7-day records), activity levels (diary records of prescribed activity) and body composition (skinfold readings) were noted at the beginning and end of the study. Both subject groups initially had a low level of energy expenditure (approximately 9.4 MJ . day-1) and a diet relatively low in animal fat. The HIE group showed no significant changes of energy intake, body composition, or blood lipids over the year of observation. In contrast, the LIE group reported a decrease in both energy intake (1.45 MJ . day-1, P < 0.05) and the intake of most individual dietary constituents. It also showed a decrease of triglyceride (P < 0.05), but a suggestion of an increase of subcutaneous fat (triceps, P < 0.05). The HIE program does not confer any necessary advantage of body composition or serum lipid levels, but it does allow a larger food intake. It may thus be of particular value for patients who find adherence to low energy or low cholesterol diets irksome.

Body Composition↗
PubMed1979

Effects of tetracyclines on aldosterone- and insulin-mediated Na+ transport in the toad urinary bladder.

The effect of oxytetracycline and demethylchlortetracycline on aldosterone- and insulin-mediated Na+ transport (short-circuit current) were examined in toad urinary bladders mounted in modified Ussing chambers. Oxytetracycline had little or no effect on either basal or aldosterone-mediated Na+ transport. In contrast, demethylchlortetracycline markedly inhibited both basal and aldosterone-mediated Na+ transport. Furthermore, demethylchlortetracycline inhibited the aldosterone response significantly out of proportion to its effects on basal Na+ transport. Neither of the drugs had an effect on insulin-mediated Na+ transport. Consequently, the natriuresis observed in certain patients treated with demethylchlortetracyline may be related to drug-induced renal resistance to the effects of aldosterone.

Aldosterone↗