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L Macho

Publications and source records attributed to L Macho.

At least 37 records · Page 2Linked to original sources
PubMed1999

Postnatal monosodium glutamate treatment results in attenuation of corticosterone metabolic rate in adult rats.

OBJECTIVE: To study the basal and ACTH stimulated production of corticosterone by adrenal cortex on one hand and the binding and degradation of corticosterone in the liver of adult rats which were treated with monosodium glutamate (MSG) during the neonatal period. METHODS: Male offsprings of Sprague-Dawley rats were injected i.p. with MSG (4 mg/g of b.w. in saline) on alternated days for the first 10 days of life, their littermates being used as controls. On the 21st postnatal day they were weaned and used for the observation at the age of 65-75 days. After sacrifice the level of corticosterone in serum and the release of corticosterone from incubated adrenals under basal and ACTH stimulated conditions (ACTH in 6 concentrations from 1.25 to 80 mU/ml medium) were estimated. In addition, glucocorticoid binding to cytosol receptors in the liver and muscle tissues was determined. Corticosterone degradation rate was measured by decrease of corticosterone concentration added to the medium after the incubation with liver slices. RESULTS: Adult rats neonatally treated with MSG had reduced weight of adrenal glands, while plasma corticosterone levels and its basal production by adrenals in vitro were significantly higher than in controls. In MSG treated rats the stimulation of corticosterone production by ACTH was diminished. Glucocorticoid binding to liver cytosolic receptors was significantly decreased, while that in muscle tissue was only slightly elevated. Moreover, a decreased corticosterone degradation rate in liver slices was observed in rats treated neonatally with MSG. CONCLUSIONS: These results are in agreement with previously observed decrease of corticosterone clearance rate in MSG treated animals and suggest that elevated corticosterone levels in plasma and its prolonged response to stressogenic stimulation are due to elevated corticosterone production in adrenals and lower degradation rate in the liver.

Adrenal Cortex↗
PubMed1999

Changes of insulin binding in rat tissues after exposure to stress.

The effects of various stressors on insulin receptors in adipose, liver and skeletal muscle tissues were studied in rats exposed to acute or repeated stress. Adult male rats were exposed to immobilization (IMO) for 2.5 hours daily for 1, 7 and 42 days, or to hypokinesia (HK) for 1, 7 and 21 days. We determined the values of specific insulin binding (SIB) and insulin receptor binding capacity (IR) of plasma cell membranes from adipose, liver and muscle tissue (IMO groups), or insulin binding to isolated adipocytes and hepatocytes (HK groups). A significant decrease of SIB and IR was observed in rats exposed to acute stress (1x IMO) in muscle, adipose and liver tissues. However, in animals exposed to repeated stress (7x and 42x IMO), SIB and IR were diminished in the muscle tissue, whereas no significant changes were noted in the liver and adipose tissue. When tissue samples were collected 3-24 hours after exposure to IMO stress, no changes of SIB and IR were found in liver and adipose tissue, but insulin binding was lowered in skeletal muscles. In animals exposed to HK for one day, a decrease of SIB and IR was found in isolated adipocytes, but no changes in insulin binding were noted in the liver tissue. In rats exposed to HK for 7 and 21 days, values of IR were similar as in control group. Our results indicate a) the different changes of IR in the liver, fat and muscle tissues after exposure to stress situations, b) a long-term decrease of insulin binding in muscles of rats exposed to repeated IMO stress, and c) the return of reduced SIB and IR (induced by acute stress) to control values in the liver and adipose tissue after a short recovery period.

Adipocytes↗
PubMed1999

Effects of a new hypoglycemic agent A-4166 on glucose metabolism in rat adipocytes and muscle tissues.

The effects of the oral administration of a non-sulfonylurea hypoglycemic agent, the phenylalanine derivative A-4166, on serum insulin and glucose levels and glucose metabolism in isolated rat adipocytes and slices of muscle tissues were studied. An increase in serum insulin and a decrease in glucose levels were observed 30 minutes after A-4166 administration to rats fed basal or high fat diet. No changes in basal glucose transport in isolated fat cells were observed after the administration of A-4166. The effect of in vitro added insulin was, however, stronger in rats fed basal diet and treated with A-4166. An elevation of the membrane glucose transporter GLUT 4 was observed in rats treated with A-4166. An increase of basal lipogenesis, measured by incorporation of radiocarbon labeled glucose into lipids, was noted in adipocytes from rats fed high fat diet. The addition of insulin was followed by stimulation of lipogenesis in rats fed basal diet, however, this hormone had no effect in rats fed high fat diet. The administration of A-4166 did not affect the basal or insulin stimulated lipogenesis. Basal glucose oxidation in the diaphragm was not influenced by high fat diet or by A-4166 treatment. In the soleus muscle, basal glucose oxidation was decreased in rats fed high fat diet, and treatment with A-4166 increased the glucose oxidation up to values observed in the control basal diet fed rats. These results indicate that the administration of A-4166 can affect glucose metabolism in muscle tissue and the sensitivity of adipocytes to insulin.

Adipocytes↗
PubMed1998

Four-week ethanol intake decreases food intake and body weight but does not affect plasma leptin, corticosterone, and insulin levels in pubertal rats.

Long-term intake of ethanol decreases food intake and inhibits growth in experimental rats. The aim of this study was to determine the effect of 4-week oral ethanol ingestion on plasma leptin and adrenal function. Male 45-day-old Wistar rats were divided into three groups: absolute control (AC), ethanol (E) administered 10% (wt/vol) ethanol instead of tap water, and pair-fed (PF) given an amount of food corresponding to the food intake of E animals. E rats consumed less pelleted diet (74% cumulative total intake); however, this caloric deficit was compensated by ethanol ingestion. Net water intake in E animals was 76% of that in the control groups. The body growth of both E and PF rats was stunted compared with AC animals, but E rats were heavier than PF rats. The plasma leptin level was similar in E and AC and decreased in PF animals. There were no differences in plasma osmolality or glycemia among the three groups. Plasma insulin was decreased in PF compared with both AC and E rats. Plasma corticosterone was not affected by ethanol, but was increased in the food-restricted (PF) group. Although there were no differences in basal adrenal corticosterone production in vitro, there was a slightly higher response to corticotropin (ACTH) in E rats. We conclude that drinking 10% ethanol decreased the dietary intake and body growth. These changes were not mediated by plasma leptin changes. Although alcohol ingestion and its energy content theoretically normalized the total energy intake and prevented the decrease of plasma leptin, the growth of young rats was inhibited. Drinking 10% ethanol instead of tap water for 4 weeks did not stimulate basal adrenal activity.

Adrenal Glands↗
PubMed1998

[Dynamic changes in the reactivity of the hormonal system regulation with the impact by LBNP sessions in long-term space mission].

Experiment INTERSTITIUM was performed on days 3, 170, 287, and 430 of the long-term MIR mission of the Russian cosmonaut-physician in order to evaluate reactivity of the system of hormonal regulation of homeostasis during LBNP sessions. Data of the experiment displayed different types of reaction of the volume controls to LBNP at the onset (F-3), in the course of and soon after recovery (R-4) from the extended mission which are signs of specific phases of adaptive shifts in the organism of cosmonaut. Exaggerated reactivity of the hormonal systems during LBNP in flight suggests more significant consequences of the test for the cardiovascular system of human in microgravity. The most expressed hormonal reaction to LBNP was documented at the very beginning of the postflight period. Plasma cGMP was materially reduced in the process of the mission and remained quite low on R-4; return of nucleotides to the norm was observed no earlier than on R-90. Complete recovery from the space mission took three months when the hormonal reaction to LBNP was same as prior to launch.

Hormones↗
PubMed1997

Insulin and catecholamines act at different stages of rat liver regeneration.

Insulin and catecholamines are known to exert effects on hepatocyte growth and metabolism. The binding of insulin, the plasma levels of insulin (INS), and the plasma catecholamine levels of epinephrine (EPI) and norepinephrine (NE) were measured during liver regeneration after partial hepatectomy (PH). A significant decrease (p < 0.05) of INS receptor binding capacity was found at 1, 2, and 3 days after operation. A single insulin injection (2.5 IU/kg body weight) at 24 h after sham operation or partial hepatectomy did not affect these changes of INS binding to hepatocytes. The plasma insulin and glucose levels were similar in both hepatectomized and sham-operated rats. Within 20 min after liver resection or sham operation, plasma NE and EPI concentrations increased rapidly. Then, a significant decrease was observed in plasma catecholamine levels at 1 h after laparotomy and PH. In both groups, laparotomized and partially hepatectomized plasma levels of NE at 4 h reached control values and remained unchanged at the 4- and 24-h periods. After PH, the levels of EPI remained elevated at 4 h in comparison with laparotomy. Adrenal tyrosine hydroxylase mRNA levels were significantly elevated at 4 h in both PH and sham-operated groups. These results suggest that signals that are initiated by catecholamines and transduced through second messengers presumably participate in the trigger mechanism of liver regeneration, while insulin (considered as a secondary mitogen) enhances a stimulus for liver regeneration.

Animals↗
PubMed1997

The effect of in vivo thyroxine treatment on insulin receptors, glucose transport and GLUT4 in rat adipocytes.

Daily i.p. administration of thyroxine (T4; 50 micrograms/100 g BW) to adult male rats for one week doubled the thyroxinemia and induced significant augmentation of glycemia and insulinemia. Hyperthyroxinemia was also manifested by significant elevation of liver malic enzyme activity and by the presence of smaller fat cells. Adipocytes of T4 treated rats displayed significantly lower density of insulin receptors, decreased insulin stimulatory effect on glucose transport and less glucose transporter (GLUT4) protein in plasma membranes after insulin stimulation as those of controls. These results indicate a deleterious effect of hyperthyroxinemia on insulin controlled glucose metabolism in fat cells.

Adipocytes↗
PubMed1996

Effects of space flight on endocrine system function in experimental animals.

The effects exposing rats to space flights of various lengths in a series of COSMOS satellites are reported based on an evaluation of plasma hormone levels and several enzyme activities in the tissues. The results after space flights are compared with those obtained from rats exposed to acute or repeated stress. Space flight induced selective morphological responses in the corticotrophs and gonadotrophs of the pituitary. Plasma levels of ACTH did not change, but plasma growth hormone and TSH levels decreased after longer space flights (>14 days), while prolactin in the plasma increased after short flights (5-7 days). Plasma corticosterone was higher after all flights. Catecholamine levels in plasma increased only after long space flights. These changes in plasma hormone levels affected the activities of enzymes involved in the amino acid metabolism of the liver and lipolysis in the adipose tissues. Norepinephrine level and catecholamine synthesizing enzyme activity in the hypothalamus did not change in flight rats. The norepinephrine content, however, decreased in several nuclei selected from the hypothalamus of flight rats. Increases in plasma insulin and glucose were noted in rats after space flight. Glucagone values in plasma remained unchanged. Comparing these results from flight rats against rats exposed to acute or repeated stress indicate that long stays in microgravity do not represent intensive stressogenic stimulus of the adrenocortical and sympathetic adrenomedullar systems, and hormone alterations observed after space flight may be due primarily to acute stressor activity resulting from a return to Earth's gravity (gravitational stress).

Adaptation, Physiological↗
PubMed1995

The effect of early weaning on insulin receptors in rat liver.

The effect of early weaning on insulin binding was studied in rat hepatocytes. Early weaned rats were separated from lactating females on the 18th postnatal day, control animals were maintained with dams up to the 30th day. Plasma insulin and glucose levels, insulin binding capacity of isolated hepatocytes were determined at the age of 18, 22, 30 and 120 days. In some age groups a body mass and also insulin degradation by hepatocytes were determined. A decrease of plasma insulin and glucose level was found in 22day old early weaned rats as compared to 18 day old rats and to controls of the same age. A decrease of body mass was found in early weaned rats during the first week after weaning. An increase of insulin binding was observed in hepatocytes from 18 to 30 day-old control rats. However, in early weaned animals a highly significant elevation of insulin binding capacity was found in 22 day-old rats. At the age of 30 and l20 days no significant differences in insulin binding capacity of hepatocytes between early weaned and control rats were noted. A decrease of insulin degradation was observed in 22 day-old early weaned rats. These results showed that early weaning affects the glucose homeostasis and insulin binding capacity of rat hepatocytes.

Journal Article↗
PubMed1995

[The effect of neonatal nutrition on lipolysis and catecholamine binding in rat adipocytes].

Underfeeding or overfeeding of rats during the suckling period, realized by the adjustment of the number of sucklings per litter, are followed by important changes in the function of endocrine glands and hormonal stimulation of lipolysis in adipocytes. For explanation of causes of the differences in the stimulation of lipolysis the changes of beta-receptors in adipocytes were studied in animals with different neonatal nutrition. The number of suckling pups in litter was adjusted to 4, 8, 14 on the second postnatal day. After weaning (at the age of 30-500 days) the size of adipocytes, basal and norepinephrine stimulated lipolysis, the binding of 3H-dihydroalprenolol in adipocytes were determined. In neonatally underfed animals, in comparison to overfed, those a decrease in the size of adipocytes, a diminution of basal lipolysis and lower stimulation of lipolysis by norepinephrine were observed. The decrease in binding capacity (at the age of 30-60 days) and of affinity of beta-receptors (at the age of 60 to 360 days) were found in neonatally overfed rats. These results showed that the changes of beta-adrenergic receptors in adipocytes of animals with neonatal nutritions have a role in the alteration of the stimulation of lipolysis in adipocytes. (Tab. 2, Fig. 4, Ref. 29.).

Adipocytes↗
PubMed1995

The role of angiotensin II and its receptors in regulation of adipose tissue metabolism and cellularity.

Angiotensin II exerts its action via at least two distinct receptor subtypes designated AT1 and AT2. AT1 receptors seem to be responsible for most of the known angiotensin II effects while the role of AT2 receptors is not yet clear. Adipocytes of adult rats express exclusively the AT1 subtype. Angiotensin II stimulates prostacyclin release in adult rat adipocytes and in mouse preadipocytes. In the latter prostacyclin release is completely blocked by an AT2 receptor antagonist. Adipocyte angiotensin II receptors seem to be regulated by age and fat mass. Blockade of these receptors by an AT1 antagonist seems to prevent adipose tissue hypertrophy. Moreover, adipose tissue contains all the main components of the renin-angiotensin system such as angiotensinogen, angiotensin converting enzyme, angiotensin II and angiotensin II receptors. Angiotensinogen expression in adipocytes is stimulated by a high fat diet concurrent with enlargement of fat mass, associated with insulin resistance. Angiotensin converting enzyme inhibitors improve insulin sensitivity. Taken together, there is evidence of interaction between insulin and angiotensin II in regulation of adipose tissue metabolism and cellularity. Clarification of these interactions could lead to significant progress in pharmacological treatment of obesity and its comorbidity.

Adipose Tissue↗
PubMed1995

Milk-borne hormones: possible tools of communication between mother and suckling.

Early studies suggested endocrine type mother-pup interaction: 131I administered to suckling rats appeared via the urine of the suckling and mother's milk in the circulation of litter mates who were not injected with iodine; levels of thyroxin in rat milk were influenced by the status of the thyroid gland of the lactating rat. Administration of TRH (thyrotropin releasing hormone) to lactating mothers led to an appearance of unaltered hormones in the milk and stomach content of sucklings. TSH (thyroid stimulating hormone) or ACTH (adrenocorticotropic hormone) when given orogastrically to suckling rats increased thyroid hormones and corticosterone serum levels in suckling rats. Functional effects of gastrointestinal administration of insulin, bombesin (mammalian analog of gastrin-releasing peptide) and epidermal growth factor (EGF) are reviewed in detail (32 references).

Animal Communication↗
PubMed1995

Late effects of early nutritional manipulations.

Effects of early neonatal interventions on metabolic parameters later in life (s.c. late effects) were studied in rats using two models; namely, (a) the effects of premature weaning and (b) the effects of "dietary" manipulations during the suckling period (s.c. small vs. large litters). (a) Premature weaning of rats caused an earlier degeneration of spermiogenesis and elevated plasma cholesterol levels in adult animals when compared to levels found in animals weaned 12 days later (on day 30 after birth). In adult rats, radioiodine uptake in thyroid glands was lower in the group weaned prematurely. Premature weaning was followed by a decrease of corticosterone production in adrenal glands in adult animals; in female adult prematurely weaned rats, an elevated response of adrenal cortex to stressors was observed. Several other studies explored the "immediate" effects of early, premature weaning. (b) Early exposure to high fat diet evoked a hypercholesterolaemic response in adulthood following brief exposure to HF diet. Rats from litters reduced to 3 or 4 pups per mother on postnatal day 3 exhibited 2 days later plasma levels of cholesterol higher than in rats raised in large litters of 8 or 14. The difference between small and large litters was preserved for the whole lifespan of the animals. In adulthood, rats from small litters were fatter and had higher levels of plasma cholesterol and insulin. Other studies suggester that early dietary experience may regulate the pattern of drug metabolism in adult life. An inhibition of diurnal plasma corticosterone variation was found in rats overfed during the neonatal period and an increased stimulation of lipolysis by norepinephrine and lipogenesis by insulin was demonstrated in neonatally underfed rats. Interesting studies were reported in longitudinally studies in children: at the age of 9-12 year breast-fed children (for more than 6 months) had the highest cholesterol levels; on the other hand significantly increased levels of APO B, Apo A1, ATH index and Apo/B Apo A1 quotient (p < 0.05) were found in the nonbreast-fed group (27 references).

Animal Nutritional Physiological Phenomena↗
PubMed1994

New approaches to evaluate sympathoadrenal system activity in experiments on earth and in space.

In previous studies the activity of the sympathoadrenal system (SAS) in cosmonauts during space flights was evaluated by measuring plasma catecholamines (CA) levels and urinary CA and their metabolites concentrations. Plasma CA levels are accepted indicators of SAS activity, however, they are determined by the plasma clearances as well as the rates of CA release (spillover-SO) into the bloodstream. Nowadays methods are available which evaluate not only plasma levels of CA but also their release, spillover, uptake, reuptake, degradation and also CA synthesis in vivo measured by plasma levels of dihydroxyphenylalanine (DOPA). Plasma concentrations of DOPA, the CA noradrenaline (NE), adrenaline (ADR), and dopamine (DA), the deaminated catechol metabolites dihydroxyphenylglycol (DHPG) and dihydroxyphenylacetic acid (DOPAC), and the O-methylated metabolites methoxyhydroxyphenylglycol (MHPG) and homovanillic acid (HVA) were measured during immobilization stress (IMO) in conscious rats. Radiotracer methods were used to measure NE SO. IMO markedly increased arterial NE levels but NE SO was less elevated because the NE clearance was slightly reduced in IMO rats. Simultaneous measurements of plasma CA and their metabolites provide another means to obtain information about SAS function. For instance, dissociation between changes of plasma DHPG and NE levels can indicate changes in neuronal reuptake of NE. We found marked parallel increases in plasma NE and DHPG levels during acute IMO; however after repeated IMO, plasma NE levels were increased but DHPG responses were less pronounced suggesting a reduced NE reuptake. DOPA, the CA precursor, circulates in plasma at a concentration higher than NE. During stress, increased sympathoneural outflow stimulates DOPA synthesis and release into the circulation supporting the view that changes in plasma DOPA levels during stress reflect in vivo changes in the rate of CA synthesis. We propose to measure the new plasma indicators of SAS activity in cosmonauts and/or in animals before, during and after space flights.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Changes of insulin in plasma and receptor for insulin in various tissues after the exposure of rats to space flights and hypokinesia.

The explanation of the mechanism of the response to gravity changes is of great importance for the determination of the capacity of human subjects to adapt to the load of gravitational stress. Therefore several studies were performed to investigate the activity of endocrine system, since the hormones are involved in the regulation of physiological functions and metabolic processes. However the studies of endocrine system activity during altered gravity conditions, especially during the weightlessness are influenced by the several interventions in biomedical observations due to operational program of astronauts, wide variability in individual response and tolerance, use of extensive countermeasures, differences in the type of space missions and in the studies after landing also a hypergravity effect at landing and variability in postflight readaptation process. The significant changes of plasma insulin and glucose levels were observed in astronauts during space flights and in the first days of recovery period. In the first inflight period plasma insulin levels were increased, unchanged or decreased however after 4-5 weeks of exposure to weightlessness a decrease of insulin plasma levels were noted. After space flights an increase of plasma insulin levels were demonstrated in experimental animals and in human subjects. Since plasma insulin level is considered as most important factor involved in the regulation for insulin receptors in target tissues, an investigation of insulin receptors in various tissues was performed in rats exposed to space flight or to hypokinesia (model used for simulation of some effects of microgravity).

Adipose Tissue↗