Effects of growth hormone on insulin release in the rat

Summary Growth hormone injected intravenously in the rat elicited a 6-fold spike change in immunoreactive insulin with little variation in glucose. Subcutaneous administration of growth hormone for 4 days augmented by 56% the insulin-secretory response to glucose of isolated islets from hypophysectomised rats but not the response of control rat islets. When islets were cultured in the presence of growth hormone, the glucose-induced insulin release was increased by 35% in batch incubations of islets from both normal and hypophysectomised rats and by 70–110% in perifused islets. Thus the capacity for stimulated release of insulin is limited by hypophysectomy, and growth hormone is capable of directly influencing the secretory function of the - cell.     

Effect of hypophysectomy on somatostatin-14 and somatostatin-28 biosynthesis in the rat hypothalamus

The in vivo incorporation of [³⁵S]cysteine into hypothalamic somatostatin-14 and somatostatin-28 was found to be substantially below normal in hypophysectomized rats. A smaller reduction in label incorporation into arginine vasopressin was also observed, while incorporation into acid-precipitable protein was normal. The diminution in somatostatin biosynthesis presumably reflects the absence of pituitary growth hormone secretion, while that in vasopressin synthesis may reflect the loss or disruption of vasopressin-producing cells.     

Food restriction,pituitary hormones and ageing

Reducing the intake of food in rodents inhibitsbody growth, retards most physiologicalageing processes, delays the onset ofpathology and prolongs life. Food restriction(FR) reduces pituitary hormone secretion andin consequence has been called`functional hypophysectomy'. Direct life-longcomparisons in the rat showedthat hypophysectomy (HYP) (a complete absenceof pituitary hormones) has a greateranti-ageing action than FR (a partial lack ofpituitary hormones) on collagen, kidneyand muscle. This suggests that pituitaryhormones accelerate ageing. Recent Americanresearch on genetic variants of the mouseindicates that pituitary growth hormone (GH)may accelerate ageing and shorten life. Boththe Snell and Ames dwarf mice have adeficiency of pituitary GH and live 50%longer than normal mice. The Snell dwarfmouse has retarded ageing of both collagen andimmune functions. The Ames dwarfmouse has high antioxidant enzyme activitiesin liver and kidney. A transgenic humanGH mouse is short lived, has a low activity ofantioxidant enzymes in liver and kidneyand an early development of disease in theseorgans. It is postulated that FR byreducing the secretion of pituitary hormones,such as GH, diminishes the oxidativedamage of certain tissues, thereby delayingthe development of age-related diseases inthese tissues and by this means extendslife.     

Hypophysectomy disturbs the noradrenergic feeding system of the paraventricular nucleus

Injection of norepinephrine (NE) into the hypothalamic paraventricular nucleus (PVN) of satiated rats is known to stimulate eating behavior. In addition, drinking behavior is potentiated just prior to the onset of eating, followed by a strong inhibition of water intake. To understand the relationship between these PVN noradrenergic phenomena and endocrine processes associated with the PVN, chronically hypophysectomized animals were tested for their behavioral responsiveness to PVN NE injection. Pituitary ablation was found to abolish the NE-elicited eating response and the NE drinking suppressive effect. However, hypophysectomy had no impact on the NE-elicited preprandial drinking response, nor did it affect drinking produced by carbachol, angiotensin, and histamine, or the feeding and drinking responses induced by insulin. These results demonstrate that hypophysectomy disturbs PVN noradrenergic mechanisms in a behaviorally and pharmacologically specific specific manner.     

应激对大鼠中性粒细胞内髓过氧化物酶的影响及其机制的初步分析

大鼠经3小时束缚-浸水应激后,中性粒细胞内髓过氧化物酶(MPO)积分显著增高。摘除垂体后,MPO积分基础值显著降低,但应激后仍显著增高。切除肾上腺或使用利血平后,应激所引起的MPO升高现象不复出现。表明应激后MPO升高可能是通过交感-肾上腺系统实现的。     

Pituitary apoplexy following coronary artery bypass surgery

Pituitary apoplexy is a syndrome with variable clinical manifestations depending on which parasellar structures (such as the optic nerves and chiasm, cavernous and sphenoid sinuses, or the hypothalamus) are compressed when the pituitary undergoes rapid enlargement. Factors associated with cardiopulmonary bypass that may lead to pituitary apoplexy include ischemia, hemorrhage, edema, and positive pressure ventilation. Seven cases of pituitary apoplexy following cardiopulmonary bypass have been reported, including the present case. Transsphenoidal surgical decompression in the present case and those previously reported appears to be safe after cardiac surgery and may be helpful in amelioration of compression of nearby structures. Pituitary apoplexy should be considered as a diagnostic possibility in patients who develop visual disturbances or ophthalmoplegia following open heart surgery.     

Bromocriptine-induced cerebrospinal fluid rhinorrhea

We describe a case of hyperprolactinemia in a patient with sellar enlargement shown radiologically who, after a short course of bromocriptine, developed cerebrospinal fluid (CSF) rhinorrhea. The causal effects and relationship between tumor shrinkage resulting from bromocriptine administration and subsequent CSF rhinorrhea are discussed.     

Transsphenoidal hypophysectomy: A laboratory approach and commentary

A laboratory technique for learning and practicing the transsphenoidal approach to hypophysectomy is described. The procedure utilizes a sphenoid block with the sella turcica at its center taken from a cadaver skull. The laboratory approach simulates the operative technique, including the use of standard instruments designed for transsphenoidal hypophysectomy. Commentary on the historical background and applications of the transsphenoidal approach to the sella turcica is presented.