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Biomedical subjects

Y Amir

Publications and source records attributed to Y Amir.

7 recordsLinked to original sources

Social and academic treatments in mixed-ethnic classes and change in student self-concept.

The efficacy of three pedagogical strategies for the enhancement of student academic and social self-concept in mixed-ethnic classes was examined among 594 Israeli children of varying status levels in their first year of junior high school. One treatment approach involved cooperative learning in small groups; a second approach employed a specially designed social relations programme; and the third approach presented the social relations programme and cooperative learning. A comparison group using traditional pedagogical approaches was also investigated. Status level was defined according to student sociometric standing and academic standing. Results indicated that low-achieving students of Middle Eastern background only in the comparison group sustained a significant negative change in their social and academic self-concepts. All three treatment strategies succeeded in curbing this decline. Findings were in the same direction when status was defined by sociometric standing. These results suggest that under proper pedagogical conditions minority children in mixed-ethnic classes need not suffer any decline in their self-concept.

Child

Sex-role orientation and work adaptation of male nurses.

Three competing hypotheses regarding the influence of sex-role orientation on work-stress (pressure and strain at work) and work-attraction (work centrality and satisfaction) adaptation of 154 male nurses were contrasted. The findings reveal that even in a female-dominated profession, masculine-type male nurses were, on the whole, the best adapted type while the feminine-type male nurses were the least. The androgynous-type nurses, though ranking high in pressure and strain stemming from their work, nevertheless ranked highest in work satisfaction. In contrast, the undifferentiated were not stressed nor pressured at work, but they did not enjoy their work. These analyses were repeated for 54 female nurses. Among the female nurses no significant differences were found between the four sex role orientations, indicating that the differences found among the male nurses stemmed from the special situation in which a male nurse finds himself. It is suggested that change in the nature of the nursing profession into more "masculine" tasks also may partially explain the results.

Adaptation, Psychological

Modulation of adenylate cyclase activity by sulfated glycosaminoglycans. I. Inhibition by heparin of gonadotrophin-stimulated ovarian adenylate cyclase.

Heparin inhibits (I50 = 2 microgram/ml) the activity of luteinizing hormone and human chorionic gonadotropin-stimulated adenylate cyclase in purified rat ovarian plasma membranes. Unstimulated enzyme activity and activity stimulated by NaF, GTP or guanosine 5'-(beta,gamma-imido)triphosphate were inhibited to a lesser extent. Human chorionic gonadotropin binding to this membrane preparation was inhibited by heparin (I50 = 6 microgram/ml). The inhibition with respect to hormone concentration was of a mixed type for hormone binding and adenylate cyclase stimulation. Inhibition by heparin was not eliminated at saturating hormone concentration. The degree of inhibition was unaffected by the order in which enzyme, hormone and heparin were introduced into the assay system. Heparin (3 microgram/ml) did not affect the pH activity relationship of basal and hormone-stimulated adenylate cyclase activity and did not change the dependence of enzyme activity on magnesium ion concentration. The inhibitory action of heparin cannot be solely attributed to interference with either catalysis or hormone binding. The possibility is considered that the highly charged heparin molecule interferes with enzyme receptor coupling, by restricting the mobility of these components or by effecting their conformation.

Adenylyl Cyclases

Modulation of adenylate cyclase activity by sulfated glycosaminoglycans. II. Effects of mucopolysaccharides and dextran sulfate on the activity of adenylate cyclase derived from various tissues.

Heparin was found to be the most potent inhibitor of rat ovarian luteinizing hormone-sensitive adenylate cyclase (I50 = 2 microgram/ml) when compared to other naturally occurring glycosamin oglycans. This inhibition was also apparent when this enzyme was stimulated by follicle-stimulating hormone or prostaglandin E2. Heparin was also found to inhibit glucagon-sensitive rat hepatic adenylate cyclase, and the prostaglandin E1-sensitive enzyme from rat ileum and human platelets. In contrast, heparin stimulated the dopamine sensitive adenylate cyclase from rat caudate nucleus. The sulfated polysugar dextran sulfate exerts similar effects on adenylate cyclase activity of the rat ovary and was shown to inhibit hormone binding to rat ovarian plasma membrane in a manner similar to that exerted by heparin. In contrast to heparin, dextran sulfate inhibited dopamine-sensitive adenylate cyclase from rat caudate nucleus.

Adenylyl Cyclases

Histophysiological studies of prostaglandin F2alpha on isolated organs. I. Effect of prostaglandin F2alpha on the heart.

The physiological and histochemical effects of PGF2alpha on isolated rabbit hearts were examined. The results showed a positive inotropic effect. The coronary flow increased. From the histochemical studies, adenosine triphosphatase (ATP-ase) and succinic dehydrogenase activities were increased while that of alkaline phosphatase was decreased. Glycogen granules were depleted. These findings were discussed on a histophysiological basis.

Adenosine Triphosphatases

Synchronous generation of ovarian hCG binding sites and LH-sensitive adenylate cyclase in immature rats following treatment with pregnant mare serum gonadotropin.

A concomitant increase in the activity of LH-senstive adenylate cyclase and in the number of LH/hCG binding sites was induced in ovaries of immature rats upon administration of pregnant mare serum gonadotropin (PMSG), a hormone preparation known to have predominantly follicle stimulation (FSH-like) activity. When an optimal dose of PMSG (15 i.u./rat) was administered to 25-day-old rats, specific activity of LH-dependent adenylate cyclase and the number of binding sites for LH/hCG per mg protein remained unchanged during the first 24h, but 48h after injection a 2-to 4-fold increase in both parameters was observed. By contrast, there was no change in basal adenylate cyclase activity or in the response of the enzyme to the stimulatory action of guanosine-5'-(beta gamma-imino) triphosphate (Gpp (NH)p), GTP, or NaF. Specific activity of succinate cytochrome c reductase, glucose-6-phosphatase and 5'-nucleotidase were found to be unaffected by the hormonal pretreatment, although total protein determined in these homogenates increased 3-fold in the course of this treatment. It is inferred that during follicular maturation, FSH enhances the responsiveness of ovarian adenylate cyclase to LH by stimulating the insertion of LH/hCG-receptors into the cell membrane.

Adenylyl Cyclases