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Biomedical subjects

T Stephens

Publications and source records attributed to T Stephens.

At least 37 records · Page 2Linked to original sources
PubMed1997

Using pretreatment and posttreatment assessments to enhance and evaluate existing treatment packages.

Pretreatment assessment data were used to enhance an existing treatment package to reduce aggression and to increase positive social interactions between a young boy and his peers. Based on the results of pretreatment assessments, additional reinforcement (differential reinforcement of alternative behavior with adult attention) and punishment (performing a nonpreferred task during time-out) components were added to an existing nonresetting differential reinforcement of other behavior (access to peers unless aggression occurred) plus time-out procedure. A posttreatment component analysis of the additional treatment components indicated that the reinforcement component facilitated positive social interactions and the punishment component suppressed aggression towards peers.

Aggression↗
PubMed1997

The relationship of cigarette prices and no-smoking bylaws to the prevalence of smoking in Canada.

OBJECTIVES: The aim of this study was to analyze the association of cigarette prices and no-smoking bylaws with the prevalence of smoking. METHODS: Data on individual smoking status were taken from two national household surveys in Canada. Current cigarette price, the 1-year and 10-year increase in price, and the extent of local restrictions on public smoking were added to the model. Logistic regression was used to estimate the odds of being a smoker. RESULTS: The odds ratio for being a smoker was 1.21 where no-smoking by-laws were relatively infrequent and 1.26 when cigarettes were relatively inexpensive, after adjusting for individual age, sex, education, and marital status. CONCLUSIONS: Both cigarette prices and no-smoking bylaws are effective in controlling smoking; either alone will likely have less impact than the two measures together.

Adult↗
PubMed1996

Ultradian oscillations of leptin secretion in humans.

We have recently demonstrated the nocturnal increase in leptin secretion in humans. In the present study we have examined the pulsatile pattern of leptin secretion using two different experimental protocols. The first protocol utilized blood samples withdrawn at 30 minute intervals immediately after meals, at 1 hour intervals between meals, and at 2 hour intervals during the night from 4 lean, 11 obese, and 5 obese NIDDM subjects. Analysis of circulating leptin levels by ULTRA algorithmic program and using matched intra-assay coefficient of variations demonstrated 1 to 7 ultradian oscillations with a mean of 3.25 +/- 0.36 (SEM) pulses per 24 hour period (period: 10.0 +/- 1.5 hours; mean relative amplitude: 0.52 +/- 0.06, n = 20). Significant positive correlations were observed for changes in absolute amplitude with body mass index (p < 0.025) and fasting leptin levels (< 0.0001). In the second series of experiments utilizing 15 minute blood sampling from 10 overnight fasted obese subjects (BMI 35.9 +/- 2.0 kg/m2), ultradian oscillations for leptin were more frequent, i.e., 2 to 7 oscillations (4.20 +/- 0.59), over a 12 hour duration (period: 3.44 +/- 0.49; mean relative amplitude: 0.28 +/- 0.03). The number of oscillations over a 12 hour period correlated significantly with BMI (p < 0.001), fasting leptin levels (p < 0.01), and absolute amplitude (p < 0.005) in a 15 minute sampling protocol. In summary, similar to other hormones, ultradian oscillations of leptin are observed in humans, although the physiological significance in relation to obesity or feeding behavior is not yet understood.

Blood Glucose↗
PubMed1994

Summary report of the workshop on data for monitoring tobacco use.

Health Canada convened a workshop in Ottawa in March 1994 in order to consider existing measures of tobacco use in Canada and to develop consensus on a standard set of measures for monitoring tobacco use in the future. The impetus for the workshop was the growing awareness of inconsistencies in definition and approach that have arisen over many years of monitoring, and a concern that future efforts to control tobacco use could be hampered by inadequate data. This report proposes standard definitions of key terms, identifies core topics, briefly discusses major data quality issues and offers a set of survey questions to monitor the elements of tobacco use.

Canada↗
PubMed1993

Social status and health risks in Canadian adults: 1985 and 1991.

Smoking, overweight and physical inactivity are three lifestyle risk factors associated with increased risks of cancer, heart disease and other chronic diseases. Using data from the 1985 and 1991 General Social Surveys, this study examines the prevalence of these risk factors by respondents' education levels, and how the prevalence of these risk factors changed from 1985 to 1991. The prevalence of smoking, overweight and physical inactivity varied widely by respondent's education levels. In 1991, persons with more education had consistently lower rates for all three risk factors than those with lower educational levels. Smoking and sedentary living declined between 1985 and 1991, but the prevalence of overweight increased. However, except for physical activity, little progress was made in narrowing the socio-economic differences for these risks. Declines in the prevalence of health risks varied by educational level and by sex within educational level. This has implications for future patterns of chronic disease morbidity and mortality. Differences in risk factor prevalence between socioeconomic groups may be partly due to differences in how each group acquires and interprets health information, and to differences between groups' exposure to environments that support healthy lifestyles.

Adult↗
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↗