Role of the hypothalamus and pituitary gland in the development of pancreatic islet sensitivity to glucose in fetal rats

Differences in the pattern of the development of three enzymes of the plasma membrane have been established. The activity of Na, K-ATPase progressively increases, that of adenylate cyclase decreases, whereas the activity of 5-nucleotidase undergoes only slight changes during embryogenesis. Differences between these enzymes were also found with respect to the development of their sensitivity to the regulatory effects of catecholamines. Adrenaline reactivity of adenylate cyclase may be detected already in embryogenesis; it is lower than that in definite muscle tissue increasing during further ontogenesis. Catecholamine reactivity was not found in Na, K-ATPase and 5-nucleotidase up to the 17th day of incubation of chick embryos. The effect of adrenalin was observed at later stages of ontogenesis, it may be initiated by exogeneous cAMP and protein kinase. At postembryonic stages, similarity in the behavior of these enzymes was found with respect to the presence and pattern of their reaction to adrenalin (stimulation), as well as with respect to temporal dynamics of the effect. The data obtained indicate the existence of close connections between these enzymes, which are realized in the sequence adrenoreceptor-adenylate cyclase-cAMP-protein kinase-effector proteins.     

雷洛昔酚对大鼠垂体的作用

目的 观察雷洛昔酚是否能诱发出催乳素瘤的动物模型以及对PRL水平的影响,以研究雷洛昔酚对大鼠垂体的作用.方法 雌性Wistar大鼠切除卵巢后,分别在皮下埋植含有雷洛昔酚、雌激素和空白硅胶管,术后8周处死大鼠,检测大鼠体重变化、垂体重量变化、血清催乳素(PRL)水平和垂体组织学变化.结果 雷洛昔酚组与阴性对照组大鼠体重无明显统计学差异,与雌激素组大鼠体重具有统计学差异(P＜0.05);雷洛昔酚组与阴性对照组大鼠垂体重相比无明显差异,与雌激素组大鼠垂体重相比具有统计学差异(P＜0.05);雌激素组大鼠血清PRL水平最高,阴性对照组血清PRL水平最低,雷洛昔酚组介于两者之间,分别与雌激素组、对照组相比较差异均具有统计学意义(P＜0.05);雷洛昔酚组与对照组垂体病理为正常细胞形态,雌激素组垂体病理为PRL瘤表现.结论 雷洛昔酚对大鼠垂体有一定的影响,但不能诱发催乳素瘤.     

Role for glutathione in the hyposensitivity of LPS-pretreated mice to LPS anorexia

To study the role of the redox state regulator glutathione (GSH) in bacterial lipopolysaccharide (LPS)-induced anorexia we measured total reduced GSH (trGSH) in liver, serum and brain in response to intraperitoneal (ip) lipopolysaccharide (LPS, 4 microg/mouse) injection in LPS-na?ve and LPS-pretreated (4 microg/mouse given 3 days earlier) mice. LPS reduced food intake in LPS-na?ve mice and LPS pretreatment attenuated this effect. LPS decreased trGSH at 24 hours after injection in LPS-na?ve mice but 4 days later trGSH levels were upregulated in brain and liver, and this was associated with a significant attenuation of LPS-induced anorexia. In addition, LPS increased mitochondrial GSH levels in brain and liver at 4 days after injection. Pharmacological GSH depletion with diethylmaleate and L-buthionine sulfoximine in LPS-pretreated mice ablated the hyposensitivity to the anorexic effect of LPS. Together, these findings suggest a prominent role for GSH and its intracellular repartition in LPS anorexia.     

Role of the adrenal gland in the thermal response to morphine withdrawal in rats.

Administration of naloxone to morphine-dependent rats results in an elevation of tail skin temperature and a fall in core temperature. Previous studies have demonstrated a role of the adrenal gland in the thermal responses that accompany morphine withdrawal in the rat. In the present study, experiments were designed to determine if the duration of adrenalectomy significantly influenced the thermal response observed in morphine withdrawal. In addition we evaluated the influence of the adrenal medulla and glucocorticoid replacement in adrenalectomized rats in mediating the thermal responses of the morphine-dependent rat. Ovariectomized rats were addicted to morphine and subsequently withdrawn by administration of naloxone. This treatment results in a significant rise in tail skin temperature and subsequent fall in colonic temperature. These thermal responses were not observed in morphine-naive rats. Adrenalectomy resulted in a significant attenuation of the rise in tail skin temperature associated with withdrawal. This reduced tail skin temperature response was not different among animals adrenalectomized for 1, 7, 14, 21, or 28 days. Likewise, the moderate increase in core temperature associated with morphine treatment was not observed in the adrenalectomized rats. Serum corticosteroid determinations confirmed the loss of the adrenal steroids in the adrenalectomized rats. In a subsequent experiment it was determined that adrenal demedullation did not reduce the tail skin temperature response during morphine withdrawal, and corticosteroids restored the naloxone-induced surge in tail skin temperature in morphine-dependent, adrenalectomized rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relation of the pituitary gland to gonadal hormone effects on the adrenocortical 11beta-hydroxylase system in rats.

Studies were conducted to further examine the mechanisms responsible for gonadal hormone effects on the rat adrenocortical 11beta-hydroxylase system. Despite higher concentrations of cytochrome P-450 and larger 11-deoxycorticosterone (DOC)-induced difference spectra in adrenal mitochondria from females than males, no sex difference in 11beta-hydroxylase activity was observed. The pregnenolone-induced difference spectrum, indicative of cholesterol binding to cytochrome P-450, also was similar in males and females. Testosterone administration to castrated males lowered both 11beta-hydroxylase activity and mitochondrial cytochrome P-450 content. Estradiol produced the opposite effects in castrated females. However, when given to ACTH-replaced hypophysectomized rats, neither testosterone nor estradiol affected cytochrome P-450 levels or the rate of 11beta-hydroxylation. These observations, taken with the known effects of estradiol and testosterone on ACTH secretion in rats and the effects of ACTH on 11beta-hydroxylation, indicate that gonadal hormone effects on the 11beta-hydroxylase system are mediated by ACTH.     

Influence of the pineal gland on testicular function in offspring of pinealectomized rats

Female Sprague-Dawley rats exposed to a short (6L:18D) photoperiod from 21 days of age were mated when they reached 55 days of age. On Day 2 of gestation animals were pinealectomized or sham-operated. On Day 5 after birth male pups of the two groups of dams were either pinealectomized or sham-operated. They were killed at 42 and 49 days of age. In offspring born to sham-operated dams and in those born to pinealectomized mothers, neonatal pineal ablation resulted in increased testicular testosterone and androstenedione content. In sham-operated and neonatally pinealectomized rats removal of the maternal pineal gland induced a decrease in testicular testosterone and androstenedione content. In contrast, after maternal pinealectomy there was a decrease in plasma testosterone and dihydrotestosterone values and testicular dihydrotestosterone content in sham-operated rats but not in those neonatally pinealectomized. We conclude that (1) the pineal glands of the mother and offspring are required to maintain normal testicular testosterone and androstenedione content in the rat, and (2) the pineal of the offspring influences the inhibitory effects of maternal pinealectomy on testicular dihydrotestosterone content and on plasma testosterone and dihydrotestosterone concentration in the offspring.