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Biomedical subjects

W Thornton

Publications and source records attributed to W Thornton.

8 recordsLinked to original sources
PubMed1999

Transition through stages of smoking: the effect of gender and self-concept on adolescent smoking behavior.

PURPOSE: To determine whether self-concept, gender, and age are significant factors in an adolescent's transition through stages of smoking to regular smoking. METHODS: A questionnaire composed of 29 items (nine questions pertaining to smoking behavior and 20 to four self-concept variables: physical, family, social, and peer self-concept) was administered to 368 randomly selected high school adolescents (188 males and 180 females) aged 12-17 years during regular contact (roll call) time. RESULTS: Overall, 40.5% of the sample had tried tobacco (excluding chewing tobacco) (42.8% of females and 38.3% of males). Although prevalence of smoking varied according to the stage of smoking, it increased with age. With reference to self-concept, Scheffe post hoc contrasts revealed a statistically significant difference between physical self-concept and the remaining measures of self-concept (peer, family, and social) and at each stage of smoking. The effect for male students was less than for females. CONCLUSION: Programs aimed at prevention and intervention should incorporate strategies which are commensurate with female lifestyles and the more positive aspects that individuals might experience on quitting.

Adolescent↗
PubMed1989

Beta-carotene and aryl hydrocarbon hydroxylase in the rat: an effect of beta-carotene independent of vitamin A activity.

Animal models demonstrate a cancer-protective effect of vitamin A. However, human epidemiologic studies correlate the intake of the precursor, beta-carotene, rather than active vitamin A, to a reduced risk for certain cancers. This suggests that beta-carotene may have cancer-protective properties independent of its vitamin A activity. In the present rat study, effects of beta-carotene or active vitamin A on carcinogen metabolizing enzyme activity were evaluated. The activity of intestinal aryl hydrocarbon hydroxylase (AHH, EC 1.14.14.1) was higher in rats fed a purified diet supplemented with beta-carotene than in rats fed the control diet containing adequate vitamin A as retinyl palmitate (165 +/- 30 vs. 90 +/- 18 pmol/min x mg), P less than (0.05). Supplementing the control diet with retinyl acetate had no effect. This AHH-enhancing effect of beta-carotene on the activity of the intestinal mucosal enzyme was not seen on the hepatic enzyme, which is consistent with the nearly complete conversion of beta-carotene to vitamin A prior to reaching the liver. These results demonstrate an effect of beta-carotene on carcinogen metabolism which is independent of its vitamin A activity. This may help explain human epidemiologic data, and may lead to further work which would allow for prudent dietary recommendations toward a reduction in cancer risk.

Animals↗
PubMed1981

Sources of variation in the column-chromatographic determination of glycohemoglobin (HbA1).

We studied the influence of many variables on the cation-exchange chromatographic determination of glycohemoglobin was minicolumns (HbA1) and with macrocolumns (HbA1a+b and HbA1c). Minicolumns are most sensitive to buffer composition. The best conditions are pH 6.78 and sodium, potassium, and phosphate concentrations of 54.8, and 36 mmol/L, respectively. In fact, there is no clear cut-off point for elution. A cyanide concentration of 1.5 mmol/L has no negative effects. For macrocolumns, the influence of temperature is demonstrated; 20 degrees C is optimal. A higher temperature caused results for HbA1 to be higher. For minicolumns, the temperature effect corresponds to 1% HbA1 per 1 degrees C, necessitating rigorous temperature control. The amount of sample applied also influences the results. Therefore a constant column load, chosen between 1.3 and 2.0 mg of Hb permilliliter of resin, is advised. Heparinized blood can be kept for three days at 4 degrees C; hemolyzed samples are best stored at -70 degrees C.

Chromatography, Ion Exchange↗
PubMed1977

Withdrawal from methadone maintenance. Rate of withdrawal and expectation.

One hundred twenty-seven successfully methadone-hydrochloride-maintained patients were randomly assigned to one of the following four groups and studied for 30 weeks: (1) known maintenance-patients were maintained on methadone under open conditions; (2) blind maintenance-patients were maintained on methadone under double blind conditions; (3) rapid withdrawal-patients were withdrawn under double-blind conditions at a rate of 10% of initial dose per week; (4) gradual withdrawal-patients were withdrawn under double-blind conditions at a rate of 3% of initial dose per week. Differences in dropout rates, illicit drug use, symptoms scores, and requests for study interruption indicate that withdrawal from methadone maintenance should be carried out at approximately 3% of initial dose per week. Better patient preparation also is indicated to reduce the effects of expectation.

Adult↗
PubMedDate not supplied

Physiological mass measurements on Skylab 1/2 and 1/3.

Mass measurements of crewmen and objects were made for the first time in space during Skylab. A description of the new devices designed for such measurements and of the technique of their use is detailed. Results from ground-based chamber simulation tests and from those during Skylab II and III show similar patterns of simple metabolic deficits, of a rapid loss during the first few days of flight followed by a reciprocal gain for the first few postflight days, and other transient changes. It is concluded that two major causes of weight loss are present: (1) a fluid redistribution and loss, and (2) metabolic losses. Added to these are short-term changes from transient stress. Smaller, simpler, and cheaper devices have since been designed which should allow mass measurements on virtually any object in almost any spacecraft.

Adaptation, Physiological↗