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Biomedical subjects

R Stevens

Publications and source records attributed to R Stevens.

At least 163 records · Page 9Linked to original sources
PubMed1985

The effect of chronic estrogen treatment on immunoreactive beta-endorphin levels in intact female rats.

Intact female rats were treated chronically with estradiol benzoate (EB) until a state of constant estrus (CE) was achieved and maintained. When compared to female rats on the day of estrus, estrogen-treated rats in constant estrus demonstrated a 33% decrease in the concentration of immunoreactive beta-endorphin (IR-BE) in the plasma, and a 45-50% decrease in the content and concentration of IR-BE in the anterior pituitary and hypothalamus. The content and concentration of IR-BE in the neurointermediate lobe of the pituitary were similar in each group. Column chromatography revealed that the reduction in IR-BE in the plasma and anterior pituitary of EB-treated CE female rats appeared to be due to a reduction in peptides coeluting with beta-endorphin and beta-lipotropin, whereas the reduction in IR-BE in the hypothalamus represented a decrease in a peptide which coeluted with beta-endorphin. These data suggest that constant estrus, induced by prolonged treatment of intact female rats with estrogen, resulted in a reduction in central and peripheral levels of IR-BE in these animals as compared to female rats on the day of estrus.

Animals↗
PubMed1984

Comparison of supervised and unsupervised exercise training after coronary bypass surgery.

Functional capacity and cardiovascular responses to serial graded treadmill testing ( GXT ) were compared in 180 patients who performed prescribed unsupervised exercise and 24 patients who were referred for supervised exercise after coronary artery bypass surgery (CABS). The groups were men similar in age range, number of bypass grafts, preoperative left ventricular impairment and number of days hospitalized. All patients received similar predischarge exercise monitoring and began a progressive home walking or cycling program. Initial GXT (T1) was performed 44 +/- 9 days postoperatively. Both groups were instructed to continue prescribed exercise at 75 to 85% maximal heart rate (HR) for 30 to 40 minutes 3 days (supervised) or 5 days ( unsupervised ) per week. The second GXT (T2) was performed 115 +/- 27 days after CABS. In each group there were significant (p less than 0.01) increases in exercise capacity and HR from T1 to T2. However, there were no significant differences in maximal exercise capacity and HR between groups at T1 or T2. Improvement in functional capacity was not influenced by therapeutic beta blockade. These findings indicate that prescribed unsupervised exercise can be performed safely and results in similar functional improvements compared with supervised exercise after uncomplicated CABS.

Adrenergic beta-Antagonists↗
PubMed1984

Treatment of canine blastomycosis with amphotericin B and ketoconazole.

The treatment of 62 dogs with blastomycosis was reviewed to identify prognostic factors and response to various treatment regimens. Severity of lung involvement, as determined by radiography, and the number of nonsegmented neutrophils were useful prognostic factors. Females survived treatment better than did males, but females were more prone to relapse. Ketoconazole treatment at a dose of 10 mg/kg daily for 60 days was not as effective as amphotericin B. The most notable adverse effect of amphotericin B treatment was nephrotoxicosis . Treatment with amphotericin B followed by ketoconazole was as effective as amphotericin B alone and resulted in less nephrotoxicosis . Most dogs that had relapses were retreated effectively with amphotericin B and/or ketoconazole. Canine blastomycosis was shown to be a treatable disease, with a cure rate of approximately 75%.

Amphotericin B↗
PubMed1984

Estrogen treatment increases the oral component of apomorphine-induced stereotypy.

Twelve weeks after surgery, sham operated intact and ovariectomized (OVX) female rats were treated for 3 days with either estradiol benzoate (50 micrograms/kg per day) or the oil vehicle. They were then tested for apomorphine-induced stereotypy 24 or 72 h after the last steroid injection. The data was collected and analysed in terms of both stereotypy ratings and individual behavioural responses. Estradiol, in those animals tested 72 h after estrogen, increased the frequency of oral behaviour in intact and in OVX groups. One possible explanation for the results is that estradiol may exert an anti-dopaminergic effect in the nigrostriatal system.

Animals↗
PubMed1984

Effects of stereoisomers of estradiol on food intake, body weight and hoarding behavior in female rats.

The effects of 17-alpha and 17-beta estradiol on food intake, body weight and hoarding behavior in ovariectomised rats were investigated. For five days, ten animals received subcutaneous injections of both isomers (10 micrograms/kg/day) in a counterbalanced design. Hoarding tests were conducted on the last three days of each 5-day injection period. 17-Alpha estradiol significantly reduced food intake but was without effect on body weight. 17-Beta estradiol reduced food intake significantly more than the alpha form and also significantly reduced body weight. These differential effects suggest that stereoisomers of estradiol may be acting on separate regulatory systems. The treatments did not change hoarding activity compared to pre-treatment levels.

Animals↗
PubMed1983

IgG1 is the predominant subclass of in vivo- and in vitro- produced anti-tetanus toxoid antibodies and also serves as the membrane IgG molecule for delivering inhibitory signals to anti-tetanus toxoid antibody-producing B cells.

Peripheral blood leukocytes from individuals immunized with tetanus toxoid can be stimulated by pokeweed mitogen to produce IgG anti-tetanus toxoid antibody (IgG-Tet) in vitro. Previous studies have shown that treatment of these cells with tetanus toxoid or anti-human IgG reagents can inhibit this in vitro antibody synthesis. We have examined the four IgG subclasses on the surface of B cells for their relative contributions in the anti-IgG antibody-induced inhibition of IgG-Tet production. With all donors, the inclusion of anti-IgG1, but not anti-IgG2, -IgG3, or -IgG4, antiserum resulted in the in vitro inhibition of IgG-Tet synthesis. The magnitude of this inhibition was similar to that induced by treatment of the B cells with tetanus toxoid antigen. When the supernatants from normal in vitro cultures were assayed for IgG-Tet of the various IgG subclasses, it was observed that the IgG-Tet were almost exclusively IgG1. Similar results were obtained when serum IgG-Tet were measured. Thus, IgG1 appears to be the major subclass for (1) the in vivo-produced IgG-Tet, (2) the in vitro-produced IgG-Tet, and (3) the membrane receptor which can selectively convey an inhibitory signal to the IgG-Tet B cell.

Antibody Formation↗
PubMed1983

Effects of ovariectomy, estrogen treatment and CI-628 on food intake and body weight in female rats treated neonatally with gonadal hormones.

Body weights and skeletal growth of female rats treated neonatally with low doses of testosterone propionate (TP) or estradiol benzoate (FB) were greater than oil-treated controls. After ovariectomy at 75 days of age EB-treated animals gained less weight than did the oil-treated controls and TP-treated rats which were comparable in weight gain. Neonatal treatment with TP or EB produced decreased sensitivity to the anorexic and weight-limiting effects of estrogen treatment after ovariectomy. However, all groups were equally sensitive to the anorexic effects of a single dose of CI-628. The possible mechanisms by which neonatal treatments with gonadal hormones influence food intake and body weight regulation are discussed.

Animals↗
PubMed1983

Comparative effects of estradiol stereoisomers on pimozide-induced catalepsy, locomotor activity and body-weight in the rat.

The effects of 17-alpha and 17-beta estradiol were compared at three dose levels on locomotor activity, pimozide-induced catalepsy, and changes in body weight. At 10 micrograms/kg/day they increased locomotor activity to a similar degree but at 5 and 1 microgram/kg/day the beta form was mor effective. However the alpha isomer failed to potentiate catalepsy, or reduce body weight, even at the highest dose whereas 17-beta estradiol did both. From these and other results it is suggested that estradiol might act on intracellular receptors and not by changing catecholamine metabolism.

Animals↗
PubMed1983

Acute and chronic effects of estrogen treatment on pimozide-induced catalepsy in the rat.

The effects of acute (3 days) and chronic (3 weeks) estrogen treatment on pimozide-induced catalepsy in ovariectomized female rats is described. Bar and grid tests were used to evaluate the cataleptic response to a 4 mg/kg dose of pimozide. Bar data showed that acute estrogen treatment (10 microgram/kg/day) significantly potentiated catalepsy when rats were tested 24 hours after the hormone but not if a dose-test interval of 48 hours was used. In the chronic phase catalepsy was significantly increased in both hormone treated groups (24 and 48 hours after estrogen). The grid data showed a qualitatively similar trend but did not reach significance in either the acute or chronic test phase. The difference between the two test phases may arise from the operation of independent factors in each case: the acute phase effect resulting from a central action of estrogen while the chronic data might be more typical of a metabolic effect. These, and other, possibilities are discussed.

Animals↗
PubMed1982

The remediation of the student at-risk for failure.

Investigated the efficacy of teaching students at-risk for academic failure to deal more adaptively with school-related stress. Forty-eight beginning high school students previously identified by their grade six teachers as likely to fail in grade seven were assigned randomly to one of three groups: A coping skills training group, a counselor intervention group and a control group. After a 9-week, twice-weekly intervention program, the students given coping skills training showed significantly improved social problem-solving ability and a trend toward heightened self-concept when compared with the group that received standard school counseling and an untreated control group.

Adaptation, Psychological↗
PubMed1982

The identification of the student at-risk for failure.

Investigated the classroom teacher's ability to identify which students are at-risk for future school failure and how students so identified differ from their most able classmates. The intelligence, academic ability, and cognitive and affective competence of 337 Grade Six students, age 11 to 13, were assessed with standard group measures. Two hundred and eighty-four of these students had been identified previously by their teachers as being at-risk for failure to cope with Grade Seven because of a history of problems in school. The remaining 53 had been selected by their teachers as the most able students in their classes. Correlations between the teachers' ratings and standard measures of intelligence, cognitive ability, anxiety, self-concept, and academic achievement were all highly significant, as were correlations between these ratings and grades earned the following year in high school. Discriminant Analysis generated a function that separated the groups with 95.6% accuracy. The at-risk students, although of normal intelligence, were significantly less intellectually, cognitively and academically able, were more anxious, and had lower self-concepts.

Adaptation, Psychological↗