Effects of photoperiod,temperature and testosterone-treatment on plasma T3 and T4 levels in the Djungarian hamster,Phodopus sungorus

Summary The effects of photoperiod, temperature and testosterone treatment on plasma T₃ and T₄ levels were investigated in the Djungarian hamster. Plasma T₃ level was affected by temperature (25°C<7°C) but not by photoperiod. Plasma T₄ level was affected by photoperiod (short day < long day) at 25°C. Administration of testosterone increased plasma T₄ level under short photoperiod at 25°C. Thus, higher plasma T₄ level under long photoperiod at 25°C might be induced by testosterone.     

New observations on the karyotype of the Djungarian hamster,Phodopus sungorus

Summary In this paper, the C-banding pattern of the karyotype of Phodopus sungorus is presented and polymorphism is taken into consideration.     

Complete cold substitution of noradrenaline-induced thermogenesis in the Djungarian hamster,Phodopus sungorus

Summary The thermogenic response to injections of noradrenaline at thermoneutrality was substituted by thermogenesis at low ambient temperatures. This demonstrates that noradrenaline-induced heat production is equivalent to physiologically induced nonshivering thermogenesis during cold exposure.Supported by the Deutsche Forschungsgemeinschaft (He 990).     

Pinealectomy inhibits stimulation of testicular development by long photoperiods in a hamster (Phodopus sungorus)

Zusammenfassung Beim HamsterPhodopus sungorus verhinderte Pinealektomie die durch lange Photoperioden bewirkte Beschleunigung der Entwicklung von Hoden und Anhangsdrüsen. Die Befunde zeigen, dass die Epiphyse nicht ausschliesslich antigonadotroph wirkt, sondern auch an der progonadotrophen Wirkung langer Photoperioden beteiligt ist.     

Effects of photoperiod and temperature on reproductive diapause inDrosophila testacea

Summary In photoperiodic adult diapause ofDrosophila testacea, the critical daylength fell between 14 and 16 h at 15°C, but between 13 and 14 h at 18°C. None entered diapause at LD 1014 and LL at 23°C. This species quantitatively responded to daylengths around the critical daylength in the process of diapause induction. The length of the sensitive period seems to change with temperature.     

Diurnal variations in serum and liver zinc levels throughout the 4-day estrous cycle of the hamster

Summary Diurnal variations of serum zinc level and liver zinc level of the golden hamster were found throughout the 4-day estrous cycle, and on the different days of the cycle, the patterns of fluctuation differed.     

Effects of thyroxine and exercise on the glandular and plasma levels of corticosterone in the male rat

Summary The results presented here demonstrates that the thyroid gland is essential for normal corticosterone production. They further show that exercise stimulates this production whether the thyroid gland is present or not. The release or metabolism of corticosterone seems dependent upon an intact thyroid gland since plasma levels of corticosterone are decreased during exercise if the thyroid is absent. The administration of thyroxine is not sufficient to renew these levels.     

Photoperiodic effects in the Djungarian hamster: one minute of light during darktime mimics influence of long photoperiods on testicular recrudescence, body weight and pelage colour

In male Djungarian hamsters (Phodopus sungorus) short photoperiods (L/D 8/16) with additional 1- or 5-min light-pulses 8 h after light-off were as effective as long photoperiods (L/D 16/8) in stimulating testicular recrudescence, increase in body weight and moult into summer pelage. The results are discussed with regard to the hypothesis that the pattern of melatonin release from the pineal gland is important in mediating photoperiodic effects in mammals.     

Photoperiodic effects in the Djungarian hamster: one minute of light during darktime mimics influence of long photoperiods on testicular recrudescence,body weight and pelage colour

Summary In male Djungarian hamsters (Phodopus sungorus) short photoperiods (L/D 8/16) with additional 1- or 5-min light-pulses 8 h after light-off were as effective as long photoperiods (L/D 16/8) in stimulating testicular recrudescence, increase in body weight and moult into summer pelage. The results are discussed with regard to the hypothesis that the pattern of melatonin release from the pineal gland is important in mediating photoperiodic effects in mammals.Supported by Deutsche Forschungsgemeinschaft, Schwerpunktprogramm Biologie der Zeitmessung.     

Perinatal changes in plasma carnitine levels in 4 species of mammal

Summary Plasma levels of carnitine, acetylcarnitine, and -hydroxybutyrate rise perinatally in rats, guinea-pigs and sheep but not in rabbits. In the fetus, carnitine levels are high in rabbits and guinea-pigs but not in rats and sheep.     

Effects of bilateral lesions of the nuclei habenulae on plasma thyroxine levels in Japanese quail

Summary Electrolytic bilateral lesions of the nuclei habenulae were made in male, adult photostimulated quail. Habenular destruction led to a marked decrease in the plasma thyroxine level (40%), whereas sham operated birds did not differ from controls. This result appears to be somewhat different from those obtained in mammals and the mechanisms of habenular-thyroid interrelationships are unknown.     

Effects of intracerebroventricular injections of angiotensin II on prolactin plasma levels in the Rhesus monkey

Summary Intracerebroventricular injections of angiotensin II (A II) induced a sharp and dose-dependent increase in plasma prolactin (PRL) levels in the awake Rhesus monkey. Our results suggest that in primates, A II may be involved in the mechanisms controlling PRL secretion.Acknowledgments. We thank Mrs. J. Arsaut and D. Verrier for excellent technical assistance. This work was supported by grants from INSERM (CRL No. 78.1.2656), DGRST (77.7.9654) and CNRS (ERA 493).     

Effects of epinephrine on plasma fibrinogen levels in rats submitted to tissue injury

Summary Tissue injury (laparotomy) produces an increase in plasma fibrinogen. This increase is inhibited by the removal of the adrenal medulla, but injection of epinephrine in laparotomized-medullectomized rats returns fibrinogen levels to values similar to those observed in only laparotomized rats. Epinephrine administration to laparotomized rats increases the fibrinogen compared with the group of laparotomized rats without treatment, but epinephrine by itself does not modify plasma fibrinogen levels in uninjured rats. Epinephrine is apparently responsible for the increase of plasma fibrinogen in rats subjected to tissue injury, probably through beta adrenergic stimulation.     

Influence of the carbohydrate moiety on the growth inhibitory activity and adhesiveness of 3T3 cell plasma membranes

Treatment of 3T3 cell plasma membranes with glycosidase enzymes decreased their ability to inhibit cell growth and also decreased their binding to 3T3 cells. This suggests that carbohydrate is required for complete function of inhibitory activity and that inhibition is associated with membrane adhesion.     

Influence of the carbohydrate moiety on the growth inhibitory activity and adhesiveness of 3T3 cell plasma membranes

Summary Treatment of 3T3 cell plasma membranes with glycosidase enzymes decreased their ability to inhibit cell growth and also decreased their binding to 3T3 cells. This suggests that carbohydrate is required for complete function of inhibitory activity and that inhibition is associated with membrane adhesion.     

Effects of bilateral lesions of the nuclei habenulae on plasma thyroxine levels in Japanese quail.

Electrolytic bilateral lesions of th nuclei habenulae were made in male, adult photostimulated quail. Habenular destruction led to a marked decrease in the plasma thyroxine level (40%), whereas sham operated birds did not differ from controls. This result appears to be somewhat different from those obtained in mammals and the mechanisms of habenular-thyroid interrelationships are unknown.     

Effects of bromocriptine on plasma testosterone and gonadotropin levels and testicular lipid fractions in adult rats

Summary Bromocriptine treatment of adult male rats resulted in a decrease in testicular testosterone (T) content and a reduction in plasma T levels. This was accompanied by increase in testicular total lipids and cholesterol and depletion of testicular phospholipids.Acknowledgments. We thank Dr R. L. Elton of Sandoz Pharmaceuticals for provision of CB-154. This work was supported by the Rockefeller Foundation, New York, NY, and by NIH grants HD 12642 and P-30 HD 10202 (Radioimmunoassay Core).     

Effects of stress and adrenocorticotrophin administration on plasma corticosterone levels at different stages of pregnancy in the mouse

Summary Stress or administration of ACTH to pregnant mice gave rise to much higher plasma corticosterone levels in the second half of pregnancy than in the first half, suggesting that there may be increased adrenal sensitivity to ACTH or decreased metabolism of corticosterone during the second half of pregnancy.     

Serotonin levels in fish brain: Effects of hydrostatic pressure and water temperature

Summary The contents of serotonin (5 HT) and its metabolite 5 hydroxy indoleacetic acid (5 HIAA) have been measured (HPLC technique) in the brains of eels exposed to different conditions of hydrostatic pressure and temperature (HP=1 or 101 ATA in winter, Tw=14°C, and in summer, Tw=19°C). It appears that an increase of Tw induces a significant increase of the 5 HT/5 HIAA ratio. In contrast, eels exposed at 101 ATA of HP for 1 h do not exhibit any modification in the 5 HT/5 HIAA brain ratio at a given temperature. The involvement of 5 HT under the conditions studied is discussed.