PubMed Health⌕ Search

Biomedical subjects

T Stephens

Publications and source records attributed to T Stephens.

At least 19 recordsLinked to original sources
PubMed1991

In vivo studies of cartilage regeneration after damage induced by catabolin/interleukin-1.

The response of the rabbit knee joint to a brief episode of cytokine induced damage is described. After three intra-articular injections of catabolin/interleukin-1 all joint cartilages showed an immediate extensive loss of proteoglycan (glycosaminoglycan), which was gradually replaced over three to four weeks. Glycosaminoglycan biosynthesis (measured by 35SO4 uptake) was initially depressed, but at one week had almost doubled its rate as compared with the normal side. This increased synthetic activity was further maintained throughout the duration of the experiment (28 days), though the rate gradually fell. Histological cartilage metachromasia to toluidine blue mirrored the glycosaminoglycan changes. No disturbance of the articular cartilage collagen network was found. It is considered, therefore, that during treatment for arthritis the indigenous chondrocyte must continue to be capable of carrying out regenerative matrix repair and that antiarthritic agents should first be screened for interference with that process.

Animals↗
PubMed1991

The dimensions of health promotion applied to physical activity.

Health promotion is a complementary array of educational and environmental strategies applied in various settings and targeted at selected populations. The few successful and well-described physical activity projects have applied multiple strategies in multiple settings to specific target groups. There is clear and persuasive evidence that regular physical activity improves health. Over the past 20-25 years participation in leisure-time physical activity has increased in Canada, Finland, the USA, and the German Democratic Republic. Unfortunately, more than half the population in each of these four countries remains inactive during leisure time, and total physical activity probably has decreased because of declining activity on the job and for transportation. National physical activity promotion programs need to include both educational and environmental strategies. Regular surveys of physical activity patterns and continued research into the most effective methods to promote regular physical activity are needed.

Exercise↗
PubMed1990

Effect of intensity of physical activity on body fatness and fat distribution.

To evaluate the effect of intensity of physical activity on body fatness and fat distribution, observations of 1366 women and 1257 men who participated in the 1981 Canada Fitness Survey were analyzed. Subjects were tested for energy expenditure of leisure-time activities and estimated maximal oxygen uptake (VO2max), body fatness was measured by subcutaneous skinfold thicknesses, and anthropometric measurements were made. Subjects of both sexes were categorized into four subgroups on the basis of their participation in leisure-time activities of various intensities. In general, subjects practicing vigorous activities on a regular basis had lower subcutaneous skinfold thicknesses and waist-to-hip ratios (WHRs) than those not performing these activities. These differences remained statistically significant after a covariance analysis was used to remove the effect of total energy expenditure of leisure-time activities on subcutaneous fat and fat distribution. Moreover, the WHR remained significantly lower in subjects performing high-intensity exercise after the effect of subcutaneous fat on fat distribution was adjusted for.

Adipose Tissue↗
PubMed1989

Xanthene-dye-labelled phosphatidylethanolamines as probes of interfacial pH. Studies in phospholipid vesicles.

We have been developing the use of plasma-membrane-bound fluorescent probes to measure the pH values at the surfaces of living chondrocytes. For this purpose, three lipophilic pH indicators were made by covalently binding the xanthene dyes fluorescein, eosin or dichlorofluorescein to the amino group of phosphatidylethanolamine. The probes were incorporated into phospholipid vesicles and the effect of pH on the fluorescence was characterized. Fluorescence was measured at a single emission wavelength during excitation at two wavelengths, and the ratio of the intensities was calculated. The experimentally observed pKobs. values were determined by fitting the fluorescence ratios to the Henderson-Hasselbalch equation. All three probes acted as pH indicators, and the eosinyl-, dichlorofluoresceinyl- and fluoresceinylphosphatidylethanolamines had pKobs. values of 3.5, 6.3 and 7.5 respectively. At physiological salt concentrations, changes in the composition of the vesicle membrane had little effect on these values. We concluded that these probes were promising candidates for the measurement of pH values at cell surfaces.

Cell Membrane↗
PubMed1988

Physical activity and mental health in the United States and Canada: evidence from four population surveys.

Secondary analysis of four surveys was carried out in order to examine the association of physical activity and various aspects of mental health in the household populations of the United States and Canada. Level of physical activity was shown to be positively associated with general well-being, lower levels of anxiety and depression, and positive mood. This relationship is independent of the effects of socioeconomic status and physical health, and described younger and older members of both sexes. The association is particularly strong for women and persons age 40 years and over. The robustness of this conclusion stems from the nature of the data sources: four population samples in two countries over the span of 10 years in which physical activity levels were assessed by four techniques and psychological status was assessed by six distinct scales. Although the surveys are cross-sectional, the most plausible explanation for the results is that physical activity enhances mental health in certain respects. Data on the comparative effects of recreation and housework suggest that quality of time, and not mere energy expenditure, must be taken into account in attempts to explain the psychological benefits of physical activity.

Adult↗
PubMed1988

Adult health practices in the United States and Canada.

The prevalence levels of 12 health practices in the United States and Canada are compared in this study: smoking; drinking status; average daily alcohol consumption; physical activity; eating breakfast; use of seatbelts and child safety restraints; ownership of smoke detectors; recency of blood pressure checks, breast examinations, and Pap tests; and practice of breast self-examination. Data for two additional variables--drinking and driving and blood pressure awareness--are shown for the two countries, but the statistics cannot be strictly compared. Data are presented for four age groups by sex and for three levels of education. Trends in smoking and seatbelt use between 1979 and 1985 are also discussed.

Adolescent↗
PubMed1987

The prevalence of overweight and obesity in Britain, Canada, and United States.

Three nations carried out large surveys of their non-institutionalized populations during the period 1976-81, with essentially similar techniques for measuring height and weight. Using criteria previously published for the British survey, we analyzed the Canadian and United States data and compared the prevalence of excessive weight for ages 20-64 in the three countries. Overweight was defined as a Quetelet index value of 25.1-30, and obesity as a value exceeding 30. Compared to their Canadian and British counterparts, American men are more likely to be overweight or obese, especially at the lower age levels. The proportion of excessively heavy men reaches a plateau around age 50 in all three countries, possibly indicative of a survivor phenomenon. Among women, the US has the highest proportion of excessively heavy individuals at all ages except 20-24; this difference is especially marked at ages 45-54. Unlike men, there is no evidence that the proportion of overweight or obese women reaches a plateau by age 64.

Adult↗
PubMed1975

Galactose metabolism in relation to cataract formation in marsupials.

Erythrocytic galactokinase and/or galactose-1-phosphate uridyl transferase activity were low in many species of marsupials. However, cataract formation was observed only in pouch-young members of these species when reared on cow's milk. The galactose tolerance of young kangaroos was found to be greatly impaired, but improved rapidly and markedly at the stage of which the definitive structure of the ruminant type of stomach as in adults is formed. The combination of high absorption of galactose and low levels of galactokinase and/or transferase thus appears to determine the predisposition of pouch-young marsupials to galactose cataractogenesis.

Adult↗