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L Macho

Publications and source records attributed to L Macho.

At least 91 records · Page 5Linked to original sources
PubMed1983

Thyroid hormones in milk: physiological approach--a review.

Reported values of the concentration of thyroid hormones in milk vary substantially. There are some doubts on the specificity of methods used for their estimation. We aimed, therefore, to study the effects of mother milk on thyroid function parameters in sucklings as well as at the effect of milk secretion on maternal thyroid. According to Fukuda et al. [1980] the lactation induces a hypothyroid state in the rat (high TSH, low thyroid hormones in maternal plasma). In our study the weaning of 18-day old rats resulted in gradual decrease of T4 in suckling plasma through 24 h followed with a transient thyroid activation. Thyroidectomy of lactating rats resulted in a transient decrease of T4 in sucklings. The difference in mother milk intake achieved by different litter size also affected the thyroid function of sucklings. The pups from small size litters (more milk consumption) had low thyroid secretion rate and low plasma TSH, while the level of T4 in plasma was high under a higher growth rate and accelerated overall maturation. All these results suggest an exogenous intake of thyroid hormones in suckling rat. We found that lactation in women resulted in lower T4 and higher TSH in plasma as compared to women who had interrupted their lactation. In the next part of our study more than 80 infants were longitudinally followed and sampled at birth (cord blood), at 2, 6 and 10 weeks and at 4, 6, 9 and 12 months. Only moderate differences were found at 4 months (high rT3) in breast fed infants and 9 at months (high T3 in plasma of infants weaned during the first week of life) when the data were evaluated according to the type of feeding. Thyroid activity of human milk was tested by feeding thyroidectomized rats with a diet containing human milk. Although plasma TSH was affected by such a diet, we did not detect any T4 and T3 in plasma of thyroidectomized rats which probably refects low calculated intake of hormones with the diet. We conclude that the lactation affects the thyroid economy of maternal organisms. Maternal milk definitely affects thyroid function parameters in the rat, while the effect on infant thyroid is more difficult to demonstrate.

Adolescent↗
PubMed1983

TRH transport to rat milk.

Neonatal rat possess several unique features in relation to TRH. Thus, the hypothalamus does not control pituitary TSH secretion, neonatal plasma does not degrade TRH and a significant quantity of this neurohormone is present in upper part of gastrointestinal tract, contractile response of duodenum to TRH being dependent on suckling. Therefore, a possible role of exogenous TRH from maternal milk was studied. Repeated or single injection of 50 micrograms TRH to lactating rats resulted in an increase of serum TSH and decrease of pituitary TSH content in sucklings. Repeated TRH administration to thyroidectomized lactating rats prevented a decrease of plasma T4 in their pups. After intravenous administration of 3H-TRH the total radioactivity of plasma and milk equalized at 25 min and increased continuously in milk during 2 h study. The presence of unaltered 3H-TRH in rat milk and gastric content of pups was confirmed by paper chromatography, electrophoresis and specific antibody precipitation. TRH degrading activity of rat milk, though qualitatively similar, represents one fifth of plasma activity in vitro. It is concluded that there is one way transport of TRH between plasma and milk and that this neurohormone is transferred to rat milk in a biologically active form.

Animals↗
PubMed1983

Glucocorticoids in human, cow and rat milk.

The concentration of corticosteroids found by a competitive protein binding (CPB) assay in human milk ranged from 20 to 136 ng ml-1, in cow milk 8 to 18 ng ml-1 and rat in milk it averaged 144 ng ml-1. The lower concentration of cortisol in human milk was observed when thin layer chromatography of milk extract was made before CPB assay. Using thin layer and paper chromatography cortisone, cortisol and progesterone were identified in human milk, while in cow milk cortisol and progesterone and in rat milk only corticosterone was found. The presence of these hormones in plasma suggests a possibility of their transport from blood to the milk.

Adrenal Cortex Hormones↗
PubMed1982

Electrophysiological and cyclic AMP responses to beta-adrenergic receptor stimulation and catecholamine levels in cat and rabbit sympathetic ganglion.

The effects of beta 1- and beta 2-selective and nonselective adrenergic agonists and antagonists were studied in the cat and rabbit superior cervical ganglion (SCG) in situ and in vitro. In experiments on the cat SCG in situ beta-adrenergic agonists induced an increase in positive afterpotential (PAP) of compound ganglionic action potential evoked by preganglionic stimulation in the following order of potency: isoprenaline (ISO) greater than salbutamol much greater than tazolol. Beta-adrenergic antagonists inhibited the ISO response in the following order of potency: propranolol greater than exaprolol much greater than H 35/25. Practolol did not exhibit beta-adrenergic blocking action; on the contrary, in higher doses it enhanced the response to ISO. In higher doses all beta-adrenergic antagonists tested depressed ganglionic transmission in an approximately similar range of doses. In experiments in vitro, using sucrose-gap technique. ISO induced depolarization of the cat SCG and this effect was inhibited in a dose-dependent manner by propranolol. Beta-adrenergic agonists did not induce depolarization of the rabbit SCG in experiments in situ and in vitro. The level of noradrenaline and dopamine in the cat and rabbit SCG did not differ significantly. Low level of adrenaline was found in the cat SCG; however, no adrenaline was detected in the rabbit SCG. No statistically significant change of cyclic AMP content was observed in the cat and rabbit SCG or in the incubation medium under conditions similar to those in which ISO induced depolarization of the cat SCG. It is concluded that the beta-adrenergic receptors present in the cat SCG resemble the beta 2-subtype and that the presence of an electrophysiologic response to beta-adrenergic agonists appears to be species-dependent. The depolarization of the cat SCG due to beta-adrenergic receptor stimulation is not coupled with cyclic AMP increase.

Action Potentials↗
PubMed1982

Postnatal development of the circadian adrenocortical rhythm in rats with different neonatal nutrition.

The development of diurnal rhythm of plasma and adrenal corticosterone levels was examined in rats overfed, standardfed and underfed during the suckling period (realised by adjustment of the number of suckling pups per litter to 4, 8, and 14). The first presence of circadian rhythm of plasma corticosterone was observed in 18-day-old overfed and standardfed rats, and slight delay in the manifestation of rhythm was noted in neonatally underfed animals (rhythm present in 21-day-old rats). The distinct circadian rhythm was present in 23- to 30-day-old rats. However in adult animals a significant diurnal rhythm of plasma and adrenal corticosterone content was noted in standardfed and underfed rats, whereas the variation of hormone levels was not significant in the neonatally overfed group. In young animals the peak of plasma corticosterone concentration occurred during the dark period while in adult animals it was shifted to the end of the light period. The values of amplitude of plasma corticosterone variation are increasing during the postnatal period. In weaned and adult rats the mesor values were found to be higher in neonatally underfed rats in comparison to the neonatally overfed group.

Adrenal Cortex↗
PubMed1981

Activity of the sympathetic-adrenomedullary system in rats after space flight on the Cosmos biosatellites.

The indicators of adrenomedullary activity (catecholamine content (CA) and the activity of the catecholamine-synthesizing enzymes tyrosine hydrozylase (TH) and dopamine-beta-hydrozylase (DBH) were measured in the adrenal glands of rats living in a state of weightlessness for 18.5-19.5 days on board the biosatellites COSMOS 936 and COSMOS 1129. None of these indicators was significantly changed by space flight, neither in the group living in a state of weightlessness nor in the group living in a centrifuge on board the spacecraft and exposed to artificial gravity of 1 g (COSMOS 936). Animals exposed after space flight to repeated immobilization stress on Earth showed a significant decrease of adrenal adrenaline and an appreciable increase in adrenal TH activity compared to stressed animals which were not in space. These results suggest that a prolonged state of weightlessness during space flight does not by itself represent an intensive stressful stimulus for the adrenomedullary system but potentiates the response of cosmonauts to stress after return to Earth.

Adrenal Medulla↗
PubMed1981

Metabolic changes in rats subjected to space flight for 18.5 days in the biosatellite Cosmos 936.

From an investigation of the activity of six glucocorticoid dependent liver enzymes, the existence of chronic, transient, stress-induced hypercorticosteronaemia during flight is probable. This hypercorticosteronaemia arises from weightlessness and induces gluconeogenesis. Weightlessness also caused substantial increases in liver glycogen level. The increased lipolytic activity and that of lipoprotein lipase in several groups of animals could be interpreted as enhancement of fat mobilization and utilization under the influence of stress. As this latter enhancement was also found in ground-based controls, it may have been due to the stress of handling rather than to space flight per se.

Adipose Tissue↗
PubMed1981

Changes of iodothyronine levels in plasma after acute and long term hypokinesia (unforced restriction) in rats.

Groups of 8 rats each were subjected to hypokinesia (unforced restriction) in plexiglass cages for 1, 5 and 9 days in first experiment and groups of 10 rats each were subjected to 1, 5, 14 and 60 days of hypokinesia in a second experiment. In addition, in a second experiment two groups of 10 animals were subjected first to hypokinesia for 60 days and then kept in regular group cages for 7 and 21 days, respectively. In each experiment a control group was used which was not subjected to restriction. Each animal was decapitated at the appropriate interval and the level of thyroxine (T4), 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) was measured with the aid of radioimmunoassay. Most remarkable changes appeared on the first day of hypokinesia when significantly increased levels of TR and T3 were found in both experiments. In a second experiment the level of T4 was significantly decreased in all groups but that restricted for 1 day. No changes of T3 level were found with the exception of the above described increase in the first day, while the levels of rT3 showed irregular and inconsistent changes. A hypothesis was tested whether the increased T4 and T3 levels result from a decreased fecal excretion of these compounds due to presumably increased food intake during the first day of hypokinesia, but it was found that the intake of food and water on the first day was the same as on subsequent days. Thus, the mechanism of the observed changes remains to be further studied.

Animals↗
PubMed1981

Insulin receptors in isolated adipocytes from rats with different neonatal nutrition.

The influence of different neonatal nutrition on the properties of insulin receptor in isolated adipocytes was studied. The changes of neonatal nutrition were achieved by adjustment of the number of sucklings to 4, 8 and 14 per one litter. After weaning (at the age of 30 days) the animals were fed standard pelleted diet ad libitum. The isolated fat cells from male rats neonatally overfed (i.e. 4 per litter), underfed (i.e. 14 per litter) and control group (i.e. 8 per litter) aged 30, 60, 120 and 500 days were prepared and used for insulin binding studies. The results showed that the total number of insulin receptors is the same in small and large adipocytes from neonatally over- or underfed animals, but a negative correlation between insulin binding sites per unit of surface area and fat cell size was found. The smaller adipocytes from neonatally underfed rats apparently showed a higher binding affinity to insulin as compared to larger fat cells from neonatally overfed animals.

Adipose Tissue↗
PubMed1980

Transport of 3H-TRH from plasma to rat milk: accumulation and slow degradation in milk and presence of unaltered hormone in gastric content of pups.

10 microCi 3H-TRH was administered intravenously to lactating rats 14 days after delivery. The total radioactivity of plasma and mild equalized about 25 min after injection and increased continually in milk during the 2-hour study. The percentage of activity bound to specific TRH antibody was the same in extracts of plasma and mild (about 60% of standard binding) throughout the experiment. Besides milk, the radioactivity was also accumulated in pituitary, thyroid, kidney and liver; the tissue:plasma ratio being 2:4 2 h after injection. The presence of 3H-TRH in milk extracts was also confirmed by paper chromatography (butanol-acetic acid-water-ethylacetate, 1:1:1:1) and electrophoresis (in pyridine acetate buffer, pH 5.8). TRH-degrading activity, representing about one fifth of that in plasma, was found in rat milk in vitro by means of paper chromatography and electrophoresis. The gastric contents of suckling pups after injection of 3H-TRH were also analyzed. The total radioactivity increased from 30 to 60 min after the injection. The percentage reacting with the specific TRH antibody in extracts of gastric contents was the same as that in plasma and milk and did not change throughout the 2 h of experiment. Our results show one-way transport of TRH from plasma to milk, low TRH-degrading activity of milk and passage of unaltered neurohormone from plasma to milk and stomach of suckling. The gastric content does not have a deteriorating effect on TRH. We suppose that the presence of accumulated TRH in maternal milk could be some biological significance in suckling, in which the plasma TRH-degrading system is lacking.

Animals↗
PubMed1980

Differences in growth and thyroid activity persisting in adult rats reared in nests of different sizes during suckling period.

The undernutrition or overnutrition during a suckling period achieved by adjusting the number of infants per lactating rat to 4 (overfed-0), 8 (control-C) or 14 (underfed-U) resulted in long lasting differences in body weight. The consumption of the diet in 260-day old males and females was similar in all experimental groups if expressed per unit of body weight, thus suggesting the differences in energy utilization. An increase of thyroid hormone secretion rate was found in U rats aged 30, 120 and 300 days as compared to 0 ones. Serum TSH level was also higher in U rats at the age of 30 days and 1 year. However, serum thyroxine level in U groups was either higher or similar as in controls. Paper chromatography of thyroglobulin hydrolyzate 24 h after 125I injection to 300 days old males showed a decrease of radioactivity in iodide area in U animals and an increase in triiodothyronine area in 0 animals. The analysis of thyroglobulin from 200 days old females on linear sucrose gradient did not reveal any rough change in its iodination. The results indicate an increase of thyroid activity in adult, previously moderately underfed male and female rats. Some changes in feedback sensitivity of hypothalamo-pituitary-thyroid axis may presumably also occur in these animals.

Animals↗