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Biomedical subjects

K Owen

Publications and source records attributed to K Owen.

At least 37 records · Page 2Linked to original sources
PubMed1994

Spearman's hypothesis and test score differences between whites, Indians, and blacks in South Africa.

Numerous studies in the United States have shown that mean test scores between Blacks and Whites differ by about one standard deviation. It has further been noted that the magnitudes of these differences vary on different tests. This variation can be explained by Spearman's hypothesis, which states that Black-White differences on a set of cognitive tests are positively associated with the tests' g loadings (the general intellectual ability). The present study, conducted among Black, Indian, and White secondary students in South Africa, showed mean Black-White differences of two standard deviations, indicating that the American results of one standard deviation are not universally correct. With regard to Spearman's hypothesis, it was found that, although the mean White-Indian differences were about one standard deviation, these differences did not support the hypothesis. Results pertaining to the Black-White differences were ambiguous; the correlation of .62 (p < .05) between the Black g and the Black-White differences strongly supported the hypothesis. A nonsignificant correlation of .23 was obtained between the White g and the Black-White differences. Possible reasons for this finding are discussed.

Adolescent↗
PubMed1994

Toxicity of a novel HMG-CoA reductase inhibitor in the common marmoset (Callithrix jacchus).

1. GR95030X, a potent inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, was administered daily to marmosets by gavage. In a Maximum Repeatable Dose (MRD) study, doses of up to 30 mg kg-1 day-1 were administered for 49 days. In a chronic study, animals received dosages equivalent to 0, 1, 2.5, 7.5 and 20 mg kg-1 day-1 for 204 or 205 days. Some animals were maintained without treatment for a recovery period of 29 or 30 days. 2. Clinical signs included poor coat condition, weakness with impaired coordination, lethargy and other behavioural changes. There was also alimentary disturbance, and some deaths occurred at doses of 20 mg kg-1 day-1 and above. 3. Adverse effects upon body weight were seen although some recovery was apparent after the cessation of treatment. 4. Serum cholesterol concentrations were reduced. Very large increases in serum ALT, AST and CK activities were recorded with CK-MM isoenzymes accounting for 80% or more of the total CK enzyme activity. 5. Treatment was associated with muscle fibre atrophy and a sarcolemmal response with little evidence of regeneration. Histological examination revealed vascular changes, glial proliferation and cell death in the brain, with no consistent distribution. Alveolar capillary congestion and alveolar proteinosis indicated that there may have been a reduction in cardiac function. 6. HMG-CoA reductase inhibitors have evident potential to cause myopathy in marmosets. This is believed to be the first report of such an effect.

Administration, Oral↗
PubMed1993

Sex differences in primary cognitive abilities among blacks, Indians and whites in South Africa.

Sex differences are reported for samples of approximately 1000 16-year-old blacks, Indians and whites in South Africa on ten tests of cognitive ability. Males obtained significantly higher means on non-verbal reasoning, spatial and mechanical aptitude, and females obtained significantly higher means on perceptual speed and memory for meaning (except among the black sample). In general the sex differences in South Africa are consistent with those typically obtained in the United States.

Adolescent↗
PubMed1992

The growth hormone response to clonidine in acute and remitted depressed male patients.

The growth hormone (GH) response to clonidine was evaluated in 28 acutely depressed male patients, 17 remitted depressed patients, and 26 normal control subjects. The GH response to clonidine was blunted (delta less than 4 ng/ml) in a significantly increased proportion of both acute and remitted patients compared to control subjects. Covarying for age effects, the GH response to clonidine (as area-under-the-curve) was not significantly different between any of the three groups, but was significantly diminished in both the acute and remitted depressed patients who were ever hospitalized for an episode of depression, compared to control subjects. Six patients studied in both the acute and remitted states were blunted in both states. These findings could not be accounted for by other clinical and demographic variables including weight, time off antidepressants, severity of current depressive symptoms, and subtype of depression. These results raise the possibility that the blunted GH response to clonidine may represent a state-independent correlate of some forms of severe depression. Issues regarding the specificity and interpretation of this finding require further clarification.

Acute Disease↗
PubMed1991

Thyroid releasing hormone test in schizophrenic patients with post-psychotic depression.

1. TSH response to TRH was assessed in 25 patients meeting operationalized criteria for the post-psychotic depression syndrome and in an age and sex matched control group of 34 primary depressed patients. 2. A blunted TSH response was observed in 36% of the patients with post-psychotic depression. 3. The rate of blunted TSH response was similar for patients with secondary post-psychotic depression to those patients with primary depressions. 4. Demographic and clinical parameters did not distinguish those post-psychotic depressed patients who had a blunted response from those who did not. 5. A blunted TSH response to TRH did not predict which patients were more likely to have a favorable response when adjunctive imipramine was added to their on-going fluphenazine decanoate and benztropine regimen.

Adult↗
PubMed1990

Prism adaptation and viewing distance.

Previous studies have shown that subjects with normal binocular vision adapt to prism-induced phorias. However, there are conflicting reports as to the amount of adaptation shown to horizontal prisms. Some investigations found a greater amount of adaptation to base out prisms compared with base in, whilst others found the reverse and one study found no adaptation to base out prism at all. This study investigated the adaptation response to horizontal prisms at distance and near in a larger number of subjects (n = 40). The results confirmed our previous findings and showed that at distance the adaptation responses are asymmetrical, there being a significantly greater amount of adaptation to base out prism compared with base in, whilst at near the responses are virtually symmetrical. Possible reasons for these findings are discussed.

Adaptation, Ocular↗
PubMed1989

Adaptation ability of subjects with different refractive errors.

In previous studies we have shown that subjects with normal binocular vision adapt to prism-induced heterophorias. In this study we have continued the work by investigating the adaptation ability of subjects with different refractive errors to horizontal prisms. The results showed that emmetropes, late-onset myopes (LOM's), and early-onset myopes (EOM's) can adapt to prism-induced phorias at distance and at near. The early-onset myopes demonstrated the greatest amount of adaptation after 3.5 min of binocular viewing in all cases. However, the differences found between the refractive groups in the amount of adaptation after 3.5 min of binocular viewing are not statistically significant.

Adaptation, Ocular↗
PubMed1982

Distribution of mammary gland neoplasms and factors influencing metastases in hybrid mice.

Mammary neoplasms in yellow (C3H x VY-A vy) F-1 virgin female mice with the murine mammary tumor virus were distributed equally between the left and right sides. The ratio of thoracic to inguinal gland involvement was 6.4 to 3.6 indicating that the A vy mutation, which enhances age-specific mammary tumor incidence, apparently does not affect the distribution of mammary tumors. The average tumor size was similar in all mammary glands. Multiple tumors occurred seven times more frequently in the thoracic than in the inguinal glands. Metastases occurred more frequently in moribund mice than in those killed at a scheduled time, and the incidence of pulmonary metastases in both groups was associated with the duration of the mammary tumors, their size, their location, and the number of neoplasms. Adenocarcinomas in the thoracic glands metastasized to the lungs more frequently than those in the inguinal glands.

Animals↗
PubMed1980

Production of prostaglandin E2 by tumor cells in vitro.

Our previous observations on the production of prostaglandin E2 (PGE2) by bladder tumor cell lines in vitro and the enhancement of tumor cell PGE2 production upon exposure to purified peripheral blood lymphocytes from normal human donors prompted us to examine this interaction in an animal model in order to further define conditions that determine the occurrence of this phenomenon. Cell lines derived from carcinogen-induced bladder and mammary tumors and from embryo fibroblasts in Fischer rats were exposed to purified peripheral blood or splenic lymphocytes in the presence or absence of indomethacin (10(-7)M). After varying times at 37 degrees, supernatants were harvested for determination of PGE2 by radioimmunoassay. Time course studies demonstrated rapid PGE2 production with plateau levels appearing at 8 hr. Increased tumor cell PGE2 production occurred in the presence of increased numbers of lymphocytes. Indomethacin partially inhibited PGE2 production. Preincubation studies suggested that the contribution of lymphocytes to overall PGE2 production in the present system was minimal. On the basis of previous observations of PGE2-associated inhibition of lymphocyte cytotoxicity against tumor cells in vitro, the present results suggest that tumor cell PGE2 production may reflect a response of the tumor cells to challenge by effector lymphocytes and may represent a mechanism whereby tumor cells subvert an immune response mounted against them.

Animals↗
PubMed1979

Intracranial pressure in the cat during nitroglycerin-induced hypotension.

Intracranial pressure measurements were made during nitroglycerin-induced hypotension in the cat anesthetized with halothane. A total of 48 individual observations were made in eight animals. The administration of sufficient nitroglycerin to decrease mean arterial pressure from a control value of 87 +/- 7 torr by 12 +/- 4 torr resulted in an increase in mean intracranial pressure from a control value of 7 +/- 2 torr to 12 +/- 2 torr. Larger decreases in mean blood pressure were associated with larger increases in intracranial pressure. The increase in intracranial pressure was similar to that previously reported for nitroprusside, and greater as well as more reproducible than that reported for trimethaphan. Thus, nitroglycerin may produce significant increases in intracranial pressure, and this may be a limiting factor in its clinical use.

Anesthesia, Inhalation↗
PubMed1975

Results of adrenal surgery in patients with hypertension, aldosterone excess, and low plasma renin concentration.

Fifty patients with hypertension, aldosterone excess, and low plasma renin concentration underwent adrenal surgery. There was a highly significant fall in mean systolic and diastolic pressures after the operation. The mean postoperative diastolic pressure fell to strictly normal levels, however, in only 19 out of 38 patients from whom an adrenocortical adenoma was removed and in only two out of 10 non-tumour patients. There was a significant correlation between the fall in blood pressure during spironolactone treatment and after adrenal surgery though levels were generally slightly lower during the former therapy. It is suggested that removal of an aldosterone-producing adenoma is the treatment of choice provided a good preoperative hypotensive response to spironolactone occurs, while the treatment of choice for non-tumour patients is often long-term spironolactone.

Adenoma↗