Showing papers in "European Journal of Endocrinology in 1967"

An analogue computer model for the insulin response to glucose infusion.

Abstract: An analogue computer model has been constructed for the analysis of the interrelationship between blood glucose and plasma insulin concentrations during glucose infusion The model presented gives quantitative information on the effect of plasma insulin on glucose uptake, the total amount of glucose taken up by the tissues at a given time, the effect of blood glucose on the release of stored and newly formed insulin, and the rapidity by which plasma insulin is increased in response to hyperglycaemiaSuch an analogue computer model might be a useful tool in the investigation of the various dynamic factors involved in the glucose- insulin interrelationship

Pituitary-adrenal activation in rats with hereditary hypothalamic diabetes insipidus

Abstract: Pituitary adrenal activation in rats with hereditary hypothalamic diabetes insipidus (DI) and normal control rats (Brattleboro strain) was studied under various conditions. Plasma corticosterone concentration was essentially the same in resting DI and control rats. No significant difference in plasma corticosterone was observed after giving the animals ether, histamine, vasopressin or acetylcholine. Since DI rats lack vasopressin, these findings provide some evidence that vasopressin is unlikely to be the physiological corticotrophin releasing factor (CRF). Epinephrine induced a smaller increase in plasma corticosterone in DI rats than control animals, but the difference was not statistically significant. However, intraperitoneal injection of 0.9% saline resulted in significantly less elevation of plasma corticosterone in DI rats than normal. This suggests certain differences in responses between normal and DI rats depending upon the intensity or nature of the stress. Hypothalamic CRF in control and DI rats was determined using rats treated with chlorpromazine, morphine and Nembutal\\s=r\\.The CRF of hypothalami of DI rats was about half of that of control animals. In the extracts of posterior pituitary lobes, corticotrophin (ACTH) activity was found in almost the same amount in DI and control rats. The posterior pituitary lobe of DI rats lacked CRF This investigation was supported by Public Health Service Research Grants No. AM 09094 and AM 07467. Downloaded from Bioscientifica.com at 11/03/2018 10:57:48PM via free access activity when tested in neurohypophysectomized rats. Histological examination of the adrenals of DI rats revealed normal structure, suggesting normal ACTH secretion at rest. The relationship of corticotrophin releasing factor (CRF) to vasopressin has been extensively studied. McCann Sc Brobeck (1954) were the first to demon¬ strate corticotrophin releasing activity of vasopressin in rats with lesions in the median eminence of the hypothalamus. They reported that rats with diabetes insipidus caused by placing lesions in the hypothalamus failed to release corticotrophin (ACTH) in response to stress and postulated that vasopressin may be the physiological releaser of ACTH. A number of papers have appeared to date to describe corticotrophin releasing activity of vasopressin (McCann Sc Fruit 1957; Jergensen Sc Nielsen 1958; Leeman Sc Munson 1958; Dasentini et al. 1959; Kwaan Sc Bartelstone 1959; Martini et al. 1959; Anderson et al. 1962; Martini Sc Pecile 1962). On the other hand many reports clearly demonstrated the existence of a corticotrophin relasing factor different from vasopressin in the neurohypophysis and the hypothalamus (Saffron et al. 1955; Porter Sc Jones 1956; Guillemin 1957; Royce Sc Sayers I960; Schally et al. 1962). This subject has been reviewed by Nichols (1961), Guillemin Sc Schally (1963) and de Wied et al. (1964). Re¬ cently McCann et al. (in press) reported that in rats with hereditary hypo¬ thalamic diabetes insipidus (DI), plasma corticosterone rose in response to etherization and to the mild stress of restraint. They also reported that the hypothalamic tissue of DI rats contained CRF in almost the same amount as the control rats. We also had an opportunity to study the pituitary adrenal activation in the DI rats of the same strain which were supplied by Dr. H. Valtin. Although we confirmed that DI rats released ACTH in response to various stresses, the data which we obtained was different in some respects from those reported by McCann el al. (in press). The present paper describes this study in detail and debates the relationship between vasopressin and CRF. MATERIALS AND METHODS Animals The animals studied were hereditary hypothalamic DI homozygous rats and normal rats of the Brattlebro strain, kindly supplied by Dr. H. Valtin. Each rat was kept in an individual cage. Determination of stress response ACTH release in 4-5 month old DI and control rats was evaluated by increase in plasma corticosterone 15 minutes after stress. In order to test the responses to various types of stress in the 12 animals in each group at our disposal, several experiments had to be performed using the same animal. These experiments, except for the last one in which the animals were sacrificed in the laboratory, were performed in the Downloaded from Bioscientifica.com at 11/03/2018 10:57:48PM via free access animal room. Each rat was transferred to an anaesthesia jar containing ether vapor. As soon as the rat was anaesthetized, approximately 0.5 ml of blood was collected in a heparinized syringe from the jugular vein. The blood collection was completed within 2 minutes of the beginning of ether inhalation so that the effect of ether itself on the plasma corticosterone was considered to be negligible. Usually an interval of 1 week elapsed between each experiment. In the last experiment, for convenience, the rats were moved from the animal house to the laboratory where they were de¬ capitated by a guillotine without anaesthesia, and blood samples were collected from the trunk into heparinized test tubes. Animals were handled as carefully as possible to avoid unnecessary stimulation. After centrifugation of the blood, 0.2 ml of plasma was used for corticosterone determination done by the method of Silber et al. (1958) as described by Guillemin et al. (1959). The difference in response between the DI and the control groups was tested by Student's t test. In order to make up for the blood loss by repeated blood collections. 2 to 3 ml of heparinized blood from normal intact rats of Sprague-Dawley strain was transfused into the experimental animals every 2 weeks. Measurement of hypothalamic CRF Rat hypothalamic tissue extending from the optic chiasma to the mammillary body was dissected out immediately after the animals were sacrificed by decapitation. Twelve hypothalami of rats of the same group were pooled and homogenized in 2 ml of 0.1 ice cold HC1. The extract was then centrifuged in a refrigerated centrifuge at 15 000 rpm for 5 minutes. The supernatant was diluted with 0.9 °/o saline. Acid extracts of the posterior pituitary lobes were made in a similar way. CRF assays were performed using chlorpromazine-morphine-Nembutal-treated male rats (CPZ-M-N preparations) of Sprague-Dawley strain weighing 240-280 g. The acid extracts of hypothalami or the posterior lobes were injected into the jugular vein. Plasma corticosterone concentration 15 minutes after the injection was used as the index of CRF activity. This assay is superior to morphine-Nembutal or dexamethasone-morphine-Nembutal tests (in preparation for publication). Comparison of CRF activity in the hypothalamic tissue between control and DI rats was made at 2 dose levels and the result was subjected to factorial analysis (Bliss 1952). Determination of CRF activity of neurohypophysial extracts CRF activity in the extracts of the posterior pituitary glands was also tested in neurohypophysectomized male rats from Charles River Breeding Laboratories Inc., Boston, Mass., because these rats were found to be partially refractory to vasopressin (Arimura et al. 1965). The neurohypophysectomized rats were used 1 week after the operation (Arimura et al. 1965). The extracts to be tested were injected into the jugular vein of these rats under Nembutal anaesthesia. Five minutes later, blood was collected from the trunk after decapitation and immediately centrifuged. The separated plasma was stored at -5° C until assayed for ACTH activity. ACTH activity of plasma ACTH activity of the plasma was determined by a micromethod described by Lipscomb Sc Nelson (1959) with our modification which simplified the original tech¬ nique. Assays were performed in male rats 3 to 6 hours after transauricular hypo¬ physectomy (Tanaka 1955). Samples were given into the jugular vein and immediately Downloaded from Bioscientifica.com at 11/03/2018 10:57:48PM via free access followed by 0.1 ml heparin solution (1000 U/ml). Adrenal venous blood collected from the 7th to 10th minute after the injection was transferred into a graduated centrifuge tube which contained approximately 2.5 ml of 0.9 °/o saline. After the blood was gently mixed with saline, the mixture was centrifuged for 30 minutes at 2000 rpm. The volume of clear supernatant usually ranged from 2.7 to 3.2 ml, a volume large enough to be measured with fair accuracy. Thus measuring haematocrit to obtain plasma volume can be omitted. This dilution of blood brought the concentration of the supernatant into a similar range with corticosterone levels in the peripheral plasma, thus enabling us to use the routine determination in measuring corticosterone in the adrenal effluent. Total corticosterone secreted into the adrenal venous blood for a period of 3 minutes was calculated. ACTH activity of the test plasma was expressed in terms of corticosterone secretion rate (ng/min). Using this method, we obtained an excellent linear relationship between log responses and log doses. The following formula of the dose-response curve with the precision index, = 0.112, was obtained with 6 determinations at each dose between 0.02 and 0.18 mU of ACTH USP. y = 3.514 + 1.115 where, y: log response (ng/min)

Histometric investigations on the testicular tissue of rats with alloxan diabetes and chinese hamsters with spontaneous diabetes

Abstract: A qualitative as well as quantitative analysis of testicular tissue was made in 15 rats with alloxan diabetes, 11 Chinese hamsters with spontaneous diabetes, and 6 control animals of each species to determine whether morphological changes also occur in the diabetic test animal. Histometric determinations in both test groups showed a marked decrease in germinal epithelium throughout the testicular tissue and an increase in lumen. The interstitial tissue showed no significant quantitative dissimilarity between healthy and diseased animals. In both animal species we found that the more serious the metabolic disorder was during the period of observation, the more marked were the changes in the germinal epithelium and in the lumen. Qualitatively, disorders of various degrees were found, from a reduced number of sperms and spermatids to severe inhibition of spermatogenesis with cessation of spermatogenesis at the stage of primary spermatocytes. In addition, we observed in both animal species, a marked decline in the number of Leydig cells in cases of severe metabolic disorder. In the diabetic animal as well as in the diabetic human male, the changes in the testes can be determined histologically and both are indicative of hypogonadotrophic hypogonadism frequently encountered in diabetes mellitus. During the past six years, we were able to demonstrate that sexual disorders in human males with diabetes are the result of hypogonadotrophic hypo* Supported by the Deutsche Forschungsgemeinschaft, Bad Godesberg. Downloaded from Bioscientifica.com at 11/04/2018 06:04:35PM