The role of kinesin, dynein and microtubules in pancreatic secretion

The regulated secretion of pancreatic zymogens depends on a functional cytoskeleton and intracellular vesicle transport. To study the dynamics of tubulin and its motor proteins dynein and kinesin during secretion in pancreatic acinar cells, we infused rats with 0.1 μg/kg/h caerulein. Electron and fluorescence microscopy detected neither dynein nor kinesin at the apical secretory pole, nor on the surface of mature zymogen granules. After 30 min of secretagogue stimulation, kinesin and the Golgi marker protein 58 K were reallocated towards the apical plasma membrane and association of kinesin with tubulin was enhanced. Disruption of acinar cell microtubules had no effect on initial caerulein-induced amylase release but completely blocked secretion during a second stimulus. Our results suggest that mature zymogen granule exocytosis is independent of intact microtubules, kinesin and dynein. However, microtubule-dependent mechanisms seem to be important for the replenishment of secretory vesicles by redistribution of Golgi elements towards the apical cell pole. J. Schnekenburger and I.-A. Weber have contributed equally to this work.     

Thyrotropin-releasing hormone does not inhibit lysine vasopressin-induced growth hormone secretion in normal men

Summary In order to establish whether thyrotropin-releasing hormone (TRH) inhibits lysine-vasopressin (LVP)-induced growth hormone (GH) release, six normal men were tested with LVP alone or in combination with TRH. LVP strikingly increased serum GH levels; this response was not altered by TRH. These results indicated that in man TRH is not involved in the control of GH secretion in response to LVP.     

Thyrotropin-releasing hormone does not inhibit lysine vasopressin-induced growth hormone secretion in normal men

In order to establish whether thyrotropin-releasing hormone (TRH) inhibits lysine-vasopressin (LVP)-induced growth hormone (GH) release, six normal men were tested with LVP alone or in combination with TRH. LVP strikingly increased serum GH levels; this response was not altered by TRH. These results indicate that in man TRH is not involved in the control of GH secretion in response to LVP.     

The role of phosphoenolpyruvate in insulin secretion: the effect of L-phenylalanine

Summary Incubation of rat islets with phenylalanine increased the tissue content of phosophoenolpyruvate, both in the presence and in the absence of glucose. At the same time, L-phenylalanine neither stimulated nor inhibited insulin release. It is unlikely that insulin secretion is tightly coupled to the availability of phosphoenolpyruvate in rat islets.     

Hypophysial feed-back in the hypothalamic regulation of luteinizing hormone secretion

Resumen LH exógeno disminuye LHRF circulante no así estradiol ni estradiol-progesterona, concluyéndose que: eminencia media regula LH siendo su nivel plasmático la señal feed-back.     

The effect of anesthetics on the basal secretion of immunoreactive growth hormone in rats]

The authors investigated basal levels of plasma immunoreactive growth-hormone in the rat (R-GH) after administration of 3 different anesthetic drugs: urethan, chloral hydrate and gamma-hdroxy-butyrate (GHB). Lowest R-GH concentrations (5 +/- 3 ng/ml) are observed after urethan; they are significantly higher (15 +/- 4 ng/ml) after chloral hydrate but this anesthetic also causes hyperglycemia (210 +/- 30 mg/100 ml). Normal blood glucose levels are observed under GHB narco-analgesia which elicits a clear-cut R-GH secretory episode (70 +/- 5 ng/ml); basal values (12 +/- 3 ng/ml) are maintained for several hours thereafter.     

The role of growth hormone and insulin-like growth factors in the immune system

Growth hormone (GH) and insulin-like growth factor I (IGF-I) can modulate the development and function of the immune system. In this chapter, we present data on the expression of receptors for GH and IGFs and the in vitro and in vivo effects of these proteins. We show that expression of GH and IGFs in the immune system opens up the possibility that these proteins are not only involved in endocrine control of the immune system but can also play a role as local growth and differentiation factors (cytokines). Endocrine control of GH could be direct or mediated via endocrine or autocrine/paracrine IGF-I. In addition, GH can act as an autocrine or paracrine factor itself. Furthermore, IGF-I in the immune system has been shown to be regulated by cytokines, such as interleukin-1 and interferon-γ, alluding to a cytokine-like function of IGF-I. In addition to data on the function of GH and IGF-I in the immune system, we present new findings which imply a possible function of IGF-II and IGF-binding proteins.     

The role of parathyroid hormone and calcitonin in magnesium absorption in the rat small intestine

Summary We studied duodenal and ileal magnesium (Mg) absorption in intact, parathyroidectomized (PTX), thyroid-(TX) and thyroparathyroidectomized (TPTX) rats with iodine hormones replaced, and, additionally, in PTX rats receiving bovine parathyroid hormone 1–34 and 1,25-dihydroxyvitamin D₃, respectively. Ma absorption was reduced after PTX and TPTX in the duodenum, but not in the ileum, whereas TX had no influence on duodenal or ileal Mg absorption. Both bovine parathyroid hormone 1–34 and 1,25-dihydroxyvitamin D₃ increased Mg absorption in the duodenum and the ileum in PTX rats.Acknowledgments. We are grateful to B. Schreiber, K. Schwille and I. Goldberg for technical and secretarial help. Supported by Deutsche Forschungsgemeinschaft (Schw 210/3). Reprint requests to P.O.S., University Hospital, Maximiliansplatz, D-8520 Erlangen.     

Effect of adrenaline and adrenergic active drugs on growth hormone secretion in immature cockerels

Summary In immature cockerels adrenaline administration lowered the levels of plasma growth hormone. Both alpha and beta adrenergic receptor agonists also depressed the circulating growth hormone levels. In the presence of beta blockade, the suppressive effect of adrenaline on growth hormone secretion was not observed.     

Free amino-acids in the snailLimnaea and their changes with morphogenesis

Résumé Les auteurs étudient l'état des acides-aminés libres aux différents stades de développement de l'escargot (Gastéropode)Limnéa. Cet état est constant de l'éclosion jusqu'à un stade avancé; ce n'est qu'après celui-ci que l'on trouve de nouveaux acides-aminés libres. Par contre, le modèle-type se maintient inchangé dans les animaux affamés.     

Dysfunctional insulin secretion in type 2 diabetes: role of metabolic abnormalities

Insulin secretion is finely tuned to the requirements of tissues by tight coupling to prevailing blood glucose levels. The normal regulation of insulin secretion is coupled to glucose metabolism in the pancreatic B cell, a major but not exclusive signal for secretion being closure of K⁺ATP (adenosine triphosphate)-dependent channels in the cell membrane through an increase in cytosolic ATP/adenosine diphosphate. Insulin secretion in type 2 diabetes is abnormal in several respects due to genetic causes but also due to the metabolic environment of the pancreatic B cells. This environment may be particularly important for the deterioration of insulin secretion which occurs with increasing duration of diabetes. Factors in the environment with potential importance include overstimulation, a negative effect of hyperglycemia per se (‘glucotoxicity’) as well as adverse effects of elevated fatty acids (‘lipotoxicity’). Elucidating the mechanisms behind these factors as well as their clinical importance will pave the way for treatment which could preserve B-cell function in type 2 diabetic patients. Received 4 October 1999; received after revision 1 November 1999; accepted 3 December 1999     

Effect of adrenaline and adrenergic active drugs on growth hormone secretion in immature cockerels.

In immature cockerels adrenaline administration lowered the levels of plasma growth hormone. Both alpha and beta adrenergic receptor agonists also depressed the circulating growth hormone levels. In the presence of beta blockade, the suppressive effect of adrenaline on growth hormone secretion was not observed.     

Effect of anaesthesia on growth hormone secretion in the domestic fowl (Gallus domesticus)

Summary Chloral hydrate, Equithesin, Althesin, Rompun, Sagatal and ether anaesthesia lowered the concentration of plasma growth hormone in immature cockerels. Handling and serial bleeding of the conscious controls had no effect on the growth hormone concentration.     

Failure to stimulate significant cortisol or growth hormone secretion in man by ether infusion

Zusammenfassung Bei endokrin gesunden Menschen wurde die Wirkung einer intravenösen äther-NaCl-Infusion auf den Gehalt an Cortisol im Plasma untersucht. Es erfolgte keine Stimulation von ACTH, respektive Cortisol oder Wachstumshormon.