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Biomedical subjects

O Földes

Publications and source records attributed to O Földes.

At least 37 records · Page 2Linked to original sources
PubMed1984

Comparison of biliary excretion of iodothyronines after intravenous and intraduodenal administration of various doses of T4 and T3.

Intraduodenal 10 or 40 micrograms thyroxine (T4) and 5 or 10 micrograms triiodothyronine (T3) or i.v. bolus of 2, 4 or 8 micrograms T4 or infusion of 10 micrograms T4 within 2 h were administered to groups of 3 to 5 rats. All experiments were made under pentobarbiturate anesthesia and administration of heparin and changes of several iodothyronine levels in plasma and of their biliary excretion were measured with the aid of specific radioimmunoassay. About 1 to 4 per cent of administered T4 were found in bile within 4 h. From this it was concluded that hepatic clearance of T4 does not increase significantly under nearly physiological levels of this hormone in plasma and that, under such conditions, a majority of absorbed or administered T4 is distributed and utilized within the whole body rather than excreted by bile. In addition, several changes of the level of various iodothyronines in plasma and of their excretion by bile as related to the administered doses of T4 and T3 were described.

Animals↗
PubMed1983

Fasting reduces the response of liver glycogen phosphorylase to physiological levels of epinephrine in rats.

The effect of 24 h fasting on the response of rat liver glycogen phosphorylase activity to an i.v. bolus of 2.75, 5.50 or 22.00 nmol kg-1 of epinephrine was studied. Even the lowest dose increased activity of the a form of the enzyme in the liver of anesthetized, fed rats to approximately 70 - 80% of total enzyme activity two minutes after administration. Further increased epinephrine doses failed to potentiate the enzyme response significantly, but shortened the time necessary for attaining the response, and delayed the return of enzyme activity to control values. No activation of phosphorylase was demonstrable after 2.75 nmol kg-1 of the hormone injected to fasted rats, but after increasing the hormone dose to 5.50 nmol kg-1 the enzyme response was the same as in the corresponding fed group at 2 min, and after administering the highest dose both at 1 and 2 min. According to these results, an increased threshold to epinephrine should be added to the already described effects of fasting, i.e. decreased phosphorylase a and total enzyme activity and shortened response to catecholamines. The efficacy of the i.v. bolus of 5.50 nmol kg-1 of epinephrine in increasing plasma epinephrine level to the theoretical value of 27.5 pmol ml-1 was proven by measuring plasma epinephrine which increased during the first minute after hormone administration to 24.5 + 5.9 pmol ml-1, to decrease during an additional minute with a half life of cca 22.2 seconds.

Animals↗
PubMed1983

Pituitary-thyroid function during acute immobilization stress in rats.

In nine experiments a total of 394 male Wistar rats weighing about 300 g was used. In each experiment, one intact control group was used and several other groups were subjected to immobilization (IMO) for 2 to 240 min in a prone position by inserting their heads through steel wire loops fixed on a board and by fasting their limbs to four metal strips by adhesive tape. All animals were killed by decapitation and the levels of thyrotropin (TSH), thyroxine (T4), 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) in plasma were estimated by radioimmunoassay. In one experiment, significant changes in the level of all hormones measured were found within 2 to 15 min of IMO, e.g. an increase of TSH, T4 and rT3 and a decrease of T3. Later (i.e. between 30 and 240 min) the level of TSH, T4 and T3 was repeatedly found to be significantly decreased almost in all experiments as compared to controls. In contrast, a significant increase of rT3 was found only in one out of 7 experiments, the values in other ones being unchanged. Corresponding changes of hormone levels were observed when IMO for 150 min was repeated daily for 7 or 40 days and the animals were sacrificed immediately after the last stress, while one day of rest after such procedures as well as after a single IMO for 150 min appeared to be sufficient for the levels to return to control values.

Animals↗
PubMed1983

The impairment of osmoregulation in the rat offsprings of hyperadiuretic mothers is probably of renal nature.

Experimental hyperadiuretism in pregnant rats was induced by applying them daily throughout the pregnancy a synthetic analogue of vasopressin--dDAVP (1-deamino-8-D-arginine vasopressin). It brought about a moderate alteration in the ability to produce hypertonic urine in their offsprings. The osmoregulatory function in the offsprings in the course of fetal development could have been suppressed either by a direct or an indirect effect of dDAVP i.e. by the hypotonicity of mothers' internal environment. There is by now some evidence based on the simultaneous determination of urinary vasopressin and osmolality that the impairment of the osmoregulatory function may be, at least partly, on the renal level.

Animals↗
PubMed1983

In vivo study of iodothyronine deiodination in rat liver: effect of salicylate on biliary excretion of several iodothyronines.

Biliary excretion of total (i.e. conjugated plus unconjugated) thyroxine (T4), 3,5,3'-triiodothyronine (T3), 3,3',5'-triiodothyronine (rT3), 3,5-diiodothyronine (3,5-T2), 3,3'-diiodothyronine (3,3'-T2) and 3',5'-diiodothyronine (3',5'-T2) was measured with the aid of specific radioimmunoassay in 17 control rats and in 31 rats injected sodium salicylate i.v. (200 mg kg-1). The animals were anesthetized with pentobarbiturate and the samples of bile were taken in subsequent 2 h periods from a drained bile duct. In controls a gradual decrease of excretion of all compounds measured was found during 10 h observation period. In contrast, after salicylate injection a transient increase of total bile volume and of T4, T3 and 3,5-T2 excretion was observed followed by a remarkable decrease, while a multifold and prolonged increase of the excretion of rT3, 3,3'-T2 and 3',5'-T2 was found. These data suggest an acute and remarkable effect of salicylate on T4 deiodinating pathway in the liver.

Animals↗
PubMed1983

Acute and transient activation of pituitary-thyroid axis during unforced restriction in rats: component of nonshivering thermogenesis in conscious animals?

Groups of 6-8 male Wistar Olac SPF rats weighing about 300 g were subjected to unforced restriction (UR) in small cages with a metallic bottom and a Plexiglas cover for various intervals from 2 min to 72 h. An acute activation of the pituitary-thyroid axis was found which was manifested by an increase of thyrotropin (TSH) and thyroxine (T4) levels at 2-5 min of UR. This was presumably due to the emotional effect of a rapid transfer and to the placing of the animals into restriction cages. Later, between 3 and 6 h of UR, another, and more pronounced period of activation of the pituitary-thyroid axis and of the peripheral thyroid hormone metabolism was repeatedly observed which lasted until about 36-48 h and was manifested by a highly significant increase of TSH, T4, 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) levels. It was concluded that this phenomenon presumably may be a component of nonshivering thermogenesis resulting from a decreased muscular activity and resembling the conditions occurring under cold stress. Such a view was supported by findings of highly increased nonesterified fatty acid levels in plasma in restricted animals, by unchanged levels of TSH and thyroid hormones found in unrestricted animals kept individually in regular group cages and, finally, by a preventive effect of ambient temperature of 32 degrees C on the pituitary-thyroid activation at 6 h of UR. In some experiments, no substantial differences in hormone levels were found between the animals kept in Plexiglas or stainless wire-mesh restriction cages. Finally, a multifold increase of prolactin level in plasma was found as early as 2 min of UR, the peak being observed between 5 and 20 min and a decrease to about the initial level at about 360 min.

Animals↗
PubMed1983

Immediate increase of thyroid hormone release during acute stress in rats: effect of biogenic amines rather than that of TSH?

An increase of thyroxine (T4; 36% in average) and 3,5,3'-triiodothyronine (T3; 9% in average) levels in plasma was found in rats after 2 min of immobilization stress (IMO), while later (from 5 to 240 min of IMO) the level of both hormones decreased sharply. This increase was prevented by ip injection of phenoxybenzamine (4 or 16 mg kg-1), prazosin (2.5 mg kg-1), yohimbin (4 or 16 mg kg-1) and fluoxetine (10 mg kg-1) at 60 min before IMO, but similar injections of phentolamine (4 or 16 mg kg-1), tolazoline (4 or 16 mg kg-1), methysergide (10 mg kg-1), cyproheptadine (10 mg kg-1) as well as of lower doses of prazosin (0.6 or 1.2 mg kg-1) did not show such an effect. The level of TSH was increased after 2 min IMO too, but this was considered to be a separate phenomenon from the increase of T4 and T3, since in several groups injected with some of the above drugs the level of TSH was decreased together with increased levels of T4 and T3. It is suggested that the acute release of thyroid hormone might be due to the effect of biogenic amines which may be blocked by some alpha-adrenergic blocking agents. Since neither adrenalectomy nor adrenal-medullectomy prevented such a release, it may be concluded that circulating catecholamines of adrenal origin did not play any role in this process.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1982

Direct quantitative estimation of several iodothyronines in rat bile by radioimmunoassay and basal data on their biliary excretion.

A method was developed for the hydrolysis of conjugated iodothyronines in bile with the aid of beta-glucuronidase/arylsulfatase and for subsequent direct estimation of total and free iodothyronines with the aid of specific radioimmunoassay. The amount of conjugated fraction could then be calculated from the difference. Thus, basal biliary excretion of several iodothyronines was measured in 31 normal, fed rats in which the bile duct was drained with polyethylene tubing under pentobarbiturate anesthesia and the bile was collected for 2 h. The free fraction of thyroxine, 3,5,3'-triiodothyronine and 3,3'-diiodothyronine was approx. 30% of total content, while that of 3,3',5'-triiodothyronine and 3,5-diiodothyronine was approx. 20% and that of 3',5'-diiodothyronine was less than 10%. This suggests some considerable differences in the conjugation of individual iodothyronines in the liver. The concentration of T4 in bile was about the same as in plasma, while that of other iodothyronines was about 3-8 times higher than in plasma. This shows close interrelations between the iodothyronine deiodinating pathway in liver cells in vivo and the spectrum of iodothyronine in bile. The average ratio of T3/rT3 as found in bile was about 4.

Animals↗
PubMed1982

Preliminary observations on the absorption of biliary iodothyronines from the intestine in vivo in rats.

From a drained bile duct of the rats injected i. v. with various doses of L-thyroxine (50 to 200 microgram per animal) bile was obtained which was then injected to various parts of intestine in recipient rats. The recipient animals were anesthetized with pentobarbiturate and their bile duct as well as femoral artery and vein were cannulated with polyethylene tubings. The level of thyroxine (T4), 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) in plasma and biliary excretion of these compounds was estimated by specific radioimmunoassay, the samples of plasma and bile being taken up to 4 h after the administration of donor bile. In one experiment also concentration of three different diiodothyronines (e.e. 3,5-T2, 3,3'T2 and 3',5'T2) in recipient bile was measured. A dose dependent increase of T4 excretion was fond in recipient bile. In some experiments also an increase of 3,3'-T2 and 3',5'-T2 excretion was observed and a higher ratio between the excreted and administered amount of rT3 was found than that of T3. An increase of T4 level in plasma was also directly related to the administered dose of this compound, while the increase of T3 and rT3 under the conditions used was observed only in some experiments where relatively higher doses of these substances were administered. It was also observed that the absorption of T4 from the administered bile was higher in fed than in fasted animals.

Animals↗
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

Immediate opposite effect of salicylate on thyroxine and 3,5,3'-triiodothyronine versus 3,3',5'-triiodothyronine level in plasma in rats.

In a total of 46 male rats polyethylene tubings were introduced into femoral artery and vein under pentobarbiturate anesthesia. Then heparin (300 U kg-1) was injected at 60-90 min after pentobarbiturate and two control blood samples were subsequently taken. After that sodium salicylate (200 mg kg-1) was injected i.v. and blood samples were taken at 30-420 min later. An immediate decrease of the thyroxine (T4) level in plasma to about 20% of original level and that of 3,5,3'-triiodothyronine (T3) to about 60% of that was found, while the level of 3,3',5'-triiodothyronine (rT3) was increased 20%. It was concluded that the administration of salicylate results in an immediate displacement of T4 and T3 from plasma protein binding and possibly inhibits the conversion of T4 to T3 and of rT3 to 3,3'-diiodothyronine which results in an increase of rT3 level in plasma. This might by partially prevented by an inhibiting effect of salicylate on the binding of rT3 to plasma proteins.

Animals↗
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↗
PubMed1980

Changes in adenylate cyclase activity in rat pituitary after TRH and T3 injection in vivo.

Increased activity of adenylate cyclase in whole anterior pituitary was repeatedly found in groups of 3-6 adult male rats 5 min after iv injection of 10, 100 and 200 nmol of TRH kg-1. After the administration of 100 nmol TRH kg-1 the activity of adenylate cyclase was significantly increased at 2, 5, 10 and 30 min with a peak level at 5 min, while at 60 min the values did not differ from controls. The level of TSH in serum was significantly increased in all TRH injected groups with a peak value at 10 min, while no dose-response relationship was found at 5 min. Finally, the activity of adenylate cyclase was significantly decreased in animals injected with 20 nmol of L-triiodothyronine kg-1 180 min before sacrifice, the decrease being not overcome by 100 nmol TRH kg-1 injected 5 min before sacrifice.

Adenylyl Cyclases↗
PubMed1980

Detection of herpesvirus antigens by solid-phase radioimmunoassay with 125I-antiglobulin and 125I-protein A.

The binding of immune (IS) and non-immune (NS) sera to herpes simplex virus type 1- (HSV-1) infected Vero cells was tested by indirect solid-phase radioimmunoassay (RIA) with radioiodinated swine anti-rabbit IgG (125I-SwAR-IgG) or staphylococcal protein A (125I-SPA). To indicate the binding of non-immune IgG molecules to virus-induced Fc-receptors, the cells were incubated in the presence or absence of the glycosylation inhibitor 2-deoxy-D-glucose (DOG). With 125I-SwAR-IgG, the binding of both IS and NS to untreated cells was higher at all time intervals than their binding to infected cells kept post infection in the presence of DOG. The titre of IS as detected by 125I-SwAR-IgG remained unchanged regardless whether the cells were incubated in the presence or absence of the drug. 125I-SPA gave much higher net binding than 125I-SwAR-IgG but, the end point titre of IS as measured by 125I-SPA was 1-2 dilution steps lower than with 125I-SwAR-IgG.

Animals↗
PubMed1980

In vitro effect of TRH on adenylate cyclase and cAMP in rat anterior pituitary and on TSH and PRL release into incubation medium.

Rat anterior pituitaries were incubated for 20 min with 1, 5 or 20 nmol TRH ml-1 and cAMP was measured in the homogenate of pituitary tissue after incubation, while TSH and PRL release into the medium was estimated with the aid of specific radioimmunoassay. In a similar experiment the activity of adenylate cyclase in pituitary homogenates was measured after the incubation with 0.5, 1.0 or 5.0 nmol TRH ml-1. Significant increase of TSH and PRL in the medium was found after 5 and 20 nmol TRH ml-1, while cAMP was significantly increased after 20 nmol TRH ml-1 only. The activity of adenylate cyclase was significantly increased after all doses of TRH used. In general, these findings are consistent with current views on the effect of hypothalamic hormones via adenylate cyclase - cAMP system and show that the responsiveness and sensitivity of an in vitro system using whole pituitaries appears to be less that of in vivo system.

Adenylyl Cyclases↗