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Biomedical subjects

K W Nowak

Publications and source records attributed to K W Nowak.

At least 37 records · Page 2Linked to original sources
PubMed1994

The possible involvement of galanin in the modulation of the function of rat pituitary-adrenocortical axis under basal and stressful conditions.

The effect of a s.c. bolus injection of 2 micrograms galanin on the hypothalamo-pituitary-adrenocortical (HPA) axis were investigated in both normal and ether-stressed (2 min ether-vapor inhalation) or cold-stressed (20 min at 4 degrees C) rats. Blood concentrations of ACTH, aldosterone (ALDO) and corticosterone (B) were measured by specific RIA, 1, 2 or 4 h after galanin injection. Galanin administration to normal rats resulted in a marked rise in the blood levels of ACTH, ALDO and B at 1h and 2 h, the values returned to the baseline after 4 h. Ether and cold stresses notably raised the blood levels of ACTH, ALDO and B, and these rises lasted unchanged until 4 h. Galanin markedly potentiated ACTH and ALDO responses to ether stress at 1 and 2 h, but B response remained unchanged. ACTH response to cold stress was not affected by galanin; however, galanin magnified ALDO response to cold stress at 4 h, and enhanced at 1 h and depressed at 2 h that of B. In light of these findings the following conclusions can be drawn: (i) galanin exerts a stimulatory effect on HPA axis of rats under basal conditions; (ii) under our experimental conditions, ether stress exerts a stronger stimulation of HPA axis than cold stress; (iii) the galaninergic mechanisms involved in the stimulation of ACTH release do not interfere with ether stress-activated ones controlling ACTH secretion, and are probably similar to those underlying the effect of cold stress; (iv) steroidogenic capacity of adrenal cortex, at least in term of glucocorticoid hormones, is a rate-limiting step in the response of rat HPA axis to severe stresses; and (v) galanin exerts a direct secretory action of the rat adrenal gland, that can manifest itself only in the case of submaximally cold stress-stimulated HPA axis.

Adrenal Cortex↗
PubMed1993

Effects of neuromedin-N on the pituitary-adrenocortical axis of dexamethasone-suppressed rats.

Neuromedin-N (NMN) (6 micrograms/100 g body weight for 2 d) partially reversed the dexamethasone (Dx)-induced inhibition of ACTH release and the consequent adrenal atrophy and decrease in glucocorticoid (corticosterone) plasma concentration in rats. Dx administration did not alter the level of circulating mineralocorticoid (aldosterone), but NMN (2 or 6 micrograms/100 g body weight for 2 d) significantly increased it. These findings suggest that the mechanism underlying the glucocorticoid (but not the mineralocorticoid) secretagogue action of NMN involves the stimulation of hypophyseal ACTH release. The hypothesis is advanced that the potent mineralocorticoid secretagogue effect of NMN may be mediated either by a direct action on zona glomerulosa cells or by the enhanced release of other regulatory peptides exerting aldosterone stimulating effect.

Adrenocorticotropic Hormone↗
PubMed1993

Preliminary investigations of bony fish--tench (Tinca tinca L.)--erythrocyte insulin receptors.

Specific insulin receptors were identified on tench (Tinca tinca L.) erythrocytes. The samples of blood from 3-4 fish per experiment were pooled in summer. Erythrocytes were washed twice with saline solution, then centrifuged and resuspended in the assay buffer. Incubations were carried out in 0.5 ml samples containing 10(9) cells, with addition of 0.03 nmol/l of 125I-pork insulin in the absence or presence of unlabelled pork or salmon insulin (0.05-2000 nmol/l) for 24 h at 4 degrees C. Calculated from seven experiments specific binding of 125I-insulin was 6.2 +/- 0.2% (mean +/- SD). Scatchard analysis of the binding data from insulin radioreceptor assay showed two different binding sites with high (HAIR) and low (LAIR) affinity. KD values were 0.82 +/- 0.17 nmol/l and 2.05 +/- 1.62 mumol/l, and maximal binding capacity (Bmax) 24.9 +/- 1.6 fmol/10(9) cells and 17.5 +/- 12.2 pmol/10(9) cells, respectively (N = 4). If compared with pork insulin, six to seven times more of salmon insulin was required to displace 50% of iodine labelled hormone. Thus, insulin receptors of tench erythrocytes are similar to those described in other species of fish and other lower vertebrates.

Animals↗
PubMed1993

Effect of hypothermia on the insulin--receptor interaction in liver plasma membranes.

The aim of the study was to estimate the effect of hypothermia on (125J)-iodoinsulin binding to liver plasma membranes. Rat liver membranes were prepared from control, normothermic rats (Tr = 35.6 +/- 0.3 degrees C) and hypothermic rats (Tr = 26.5 +/- 0.9 degrees C) and purified according to Havrankowa. In addition, serum insulin and glucagon levels by means of RIA and glucose concentration using the glucose oxidase method were measured. Scatchard analysis was used to determine the kinetic parameters of the hormone receptor interaction. The data showed no significant differences in the affinity of the binding sites but indicated a decrease in receptor concentrations in liver plasma membranes from hypothermic rats. In contrast to changes in serum insulin level which was decreased by about 50% in hypothermic rats blood glucose concentrations did not significantly differ between the hypothermic and normothermic ones. Our results show that in hypothermic rats the hormonal adaptation operates on the level of the number of liver receptors whereas the insulin receptor affinity remains unaffected.

Animals↗
PubMed1993

Insulin-secretional effect of exogenic amino acids in rabbits.

D,L-arginine and L-lysine, introduced into the alimentary canal (IAC), caused significant secretion of insulin in rabbits, whereas D,L-methionine or L-phenylalanine evoked only a small effect. Also, intravenous (IV) injection of D,L-arginine caused dose dependent and biphasic insulin output. On the other hand, L-phenylalanine given IV decreased both basal and glucose--stimulated insulin level in blood.

Administration, Oral↗
PubMed1993

Comparative studies on fish and bird insulin receptors.

The comparative studies were performed on insulin receptors of erythrocytes and liver plasma membranes in fish (tench and carp) and bird (duck). The Scatchard plots indicated the presence of two pools of binding sites both in fish and duck. These pools show inter-species differences in binding ability and the number of receptors. Specific binding of insulin and the binding affinity are higher in duck than in fish.

Animals↗
PubMed1992

Dexamethasone-induced adrenal cortex atrophy and recovery of the gland from partial, steroid-induced atrophy.

This study aims to examine the effects of low dexamethasone (DX) doses on cellular and functional changes in the rat adrenal cortex and to observe the recovery of the gland from DX-induced partial atrophy. Within seven days doses of 15, 30 and 60 micrograms DX/100 g/day resulted in a dose dependent decrease in body and adrenal gland weight. Within two weeks the lowest DX dose tested caused further decrease in adrenal weight. DX markedly lowered plasma ACTH and corticosterone (B) level, B content in the gland and B output by adrenal slices. Adrenocortical atrophy induced by 15 micrograms DX was dependent upon the linear decrease in the volume of fasciculata and reticularis zones, in the average volume of the fasciculata cell and in the number of adrenocortical cells in the entire cortex. This dose of DX resulted in a prompt and potent inhibition of proliferative activity of adrenocortical cells as assessed by the counting of metaphases per adrenal section. Partial adrenal atrophy evoked by 7 day DX-treatment was reversible within seven days of the discontinuation of the steroid treatment. Recovery of the gland depended mainly on the increases in the volume of all adrenocortical zones, in the average volume of fasciculata cell and in the number of parenchymal cells in the gland. Seven days after discontinuation of DX administration plasma ACTH was significantly higher than in controls. Plasma B and B secretion by adrenal slices were similar to the control group while B content in the gland was still depressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex↗
PubMed1992

Analysis of the preventive action of ACTH on dexamethasone-induced adrenocortical atrophy in the rat.

Adult female rats were treated for 4 or 6 days consecutively with dexamethasone (Dx; 100 micrograms kg-1 day-1) alone or with ACTH (100 micrograms kg-1 day-1) for 2, 4 or 6 days. After 2 days of ACTH administration, zona fasciculata cells increased in volume, and the blood concentration of corticosterone was raised. Basal corticosterone secretion by adrenal slices appeared to be enhanced by ACTH treatment only when calculating per adrenal pair (and not per unit wt of adrenals). A significant increase in the number of metaphase cells was observed after only 4 days of ACTH administration. It is suggested that (1) the first action of ACTH on Dx-suppressed rats is to induce the hypertrophy of adrenocortical cells; (2) the steroidogenic capacity of adrenocortical cells is directly proportional to their average volume; and (3) the stimulatory effect of ACTH on the proliferative activity of adrenocortical cells is subsequent to the stimulation of their specialized functions.

Adrenal Cortex↗
PubMed1992

Effect of phytooestrogen--coumestrol and oestrone on some aspects of carbohydrate metabolism in ovariectomized female rats.

The purpose of the presented study is a comparison of phytooestrogen--coumestrol and oestrone effects on carbohydrate metabolism in ovariectomized female rats and to examine the participation of pancreatic hormones in changes of this metabolism. Administration of coumestrol diminished muscle glycogen in investigated animals. There were no significant changes in insulin and glucagon blood level but decrease in the specific insulin binding in the muscle membranes was observed. It suggests that coumestrol effects the insulin receptor activity in this tissue and it could be a cause of glycogen deficiency.

Animals↗
PubMed1990

Gestational changes in hamster adrenal cortex: stereologic and functional studies.

Pregnancy in hamsters evoked a prompt increase in adrenal weight, with the highest value at day 5 and a subsequent fall toward the end of gestation. The surface densities of mitochondrial cristae and smooth endoplasmic reticulum did not display significant changes in the course of gestation, while 11 beta-hydroxylase and 3 beta-hydroxysteroid dehydrogenase/isomerase activity (two enzymes located in these two organelles) underwent significant increases at day 5 and day 10 of pregnancy, respectively. Neither the adrenal content of cortisol nor cortisol output by adrenal homogenates changed, but cortisol production measured in adrenal slices gradually rose during the course of pregnancy. Blood cortisol concentration increased about ten-fold toward the end of gestation, whereas the plasma ACTH level remained unchanged and plasma aldosterone concentration was significantly lowered. The conclusion is drawn that the pregnant hamster's adrenal glands possess an enhanced capacity to secrete cortisol, but the factor(s) involved remain unknown.

3-Hydroxysteroid Dehydrogenases↗
PubMed1987

[Use of diazoxide in the studies of the effect of glucagon on the blood serum levels of glucose, free fatty acids and triglycerides in rabbits].

Diazoxide was used to prevent the high insulin secretion after glucagon administration to rabbits. Using of this benzothiadiazine allowed to investigate an effect of glucagon on the blood glucose, free fatty acids and triglycerides without raised insulin. The concentration of serum glucose was increased in all experiments (with or without diazoxide infusion), however both normoinsulinemic and hyperinsulinemic rabbits showed return to the control value in the end of experiments. In the case of FFA the high level of insulin was necessary to return their concentration to the control value. Glucagon alone had no effect on serum TG level.

Animals↗
PubMed1986

Arginine, administrated in various ways, as a stimulator of insulin secretion in the rabbit.

The insulin-secretional effect of arginine administrated to rabbits either intravenously or via alimentary tract was measured. Arginine stimulatory effect on insulin secretion was found after both ways of amino acid introduction, however, the extent of the stimulation depended upon the route of administration, with intravenous route being four times more effective than the oral one. This difference may depend on the small susceptibility to food stimulators of the herbivorous animals.

Animals↗
PubMedDate not supplied

The influence of coumestrol, zearalenone, and genistein administration on insulin receptors and insulin secretion in ovariectomized rats.

The influence of phytoestrogens (genistein and coumestrol) and mycoestrogen (zearalenone) on insulin secretion, liver insulin receptors and some aspects of lipid and carbohydrate metabolism were investigated in this study. Ovariectomized rats were injected s.c. with the above mentioned compounds in the amount of 1 mg for three days. Coumestrol and zearalenone caused a significant increase in uterus weight, similar to the effects observed after estrone action, while this effect was not observed after the genistein injection. Blood insulin level was not changed after phyto- or mycoestrogen treatment. However, coumestrol and genistein significantly decreased the binding capacity of liver insulin receptors. These changes corresponded with alterations in glucose and free fatty acids profiles in blood, as well as with glycogen content in liver. The effects observed after genistein and coumestrol injections differed from those noticed in rats treated with zearalenone or estrone. On the basis of these results we conclude that metabolic effects of high doses of coumestrol and genistein in ovariectomized rats are partly mediated by changes in insulin sensitivity of the liver and that the action of plant estrogens on metabolism is, at least to the some degree, independent of their estrogen activity.

Animals↗
PubMedDate not supplied

Steroidogenic effect of peptide histidine-isoleucine (PHI) in vitro: comparison with VIP.

VIP and PHI originate from the same precursor, and the two peptides share considerable sequence homology. Present studies, however, revealed notable differences in their steroidogenic effect on isolated rat adrenocortical cells. VIP seems to act through the VIP and/or PACAP receptor while PHI acts, directly or by sensitivity increase, through the ACTH receptor.

Adrenal Cortex↗