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Biomedical subjects

O Földes

Publications and source records attributed to O Földes.

At least 19 recordsLinked to original sources
PubMed1993

Effect of a low salt diet on blood pressure and vasoactive hormones in the hereditary hypertriglyceridemic rat.

In hereditary HTG rats, basal systolic blood pressure using tail-cuff sphygmomanometry was significantly higher (122.1 +/- 2.1 mm Hg; n = 16) than that in NTG animals (107.1 +/- 1.52; n = 16). A low salt diet did not influence blood pressure in NTG rats during the consecutive 4 weekly periods. However, in the second week blood pressure in HTG rats rose significantly in both the control rats on a normal salt diet and those on a low salt diet (132.5 +/- 1.89, n = 8, and 132.6 +/- 1.93, n = 8). No further changes were registered in the third and fourth week in control HTG rats. On the other hand, blood pressure fell significantly in HTG rats on a low salt diet in the third week in comparison with the second week (119.5 +/- 3.2, n = 8), and it increased again in the fourth week (123.0 +/- 2.35, n = 8). Hormones in plasma were determined at the end of the experiment. Plasma levels of norepinephrine were not influenced by differences in salt intake and were significantly higher by about 45% in HTG than in NTG animals. The lowest concentration of corticosterone in plasma was found in control HTG rats (1.2 +/- 0.2 vs 4.6 +/- 0.8 micrograms/100 ml in control NTG rats). Nevertheless, corticosterone concentration increased in HTG rats on a low salt diet at comparable values found in NTG rats on a low salt diet (3.1 +/- 0.8 vs 4.3 +/- 1.5). Plasma renin activity and plasma aldosterone concentrations were not different in the NTG and HTG groups and were uninfluenced by the diets (Table 1). We conclude that the elevated blood pressure in HTG rats and its variations during the experiment may reflect more pronounced sympathetic activity in HTG rats rather than blood pressure dependency on different salt intake.

Aldosterone↗
PubMed1993

On the role of digoxin-like substances, ANP, and AVP in natriuresis induced by hypertonic saline infusion in dogs.

The increase of sodium concentration in cerebrospinal fluid or in plasma triggers the osmoregulatory mechanism, namely, the enhancement of renal free-water reabsorption and natriuresis. The increase of free-water reabsorption has been recognized for many years as a consequence of the osmotically released vasopressin (AVP). However, the control of renal sodium excretion in the mechanism of osmoregulation has not been clarified It has been suggested to be, at least in part, of hormonal nature, implying the decreased release of aldosterone and the increased release of atrial natriuretic peptide (ANP), digoxin-like substances (DLIS), and AVP. Neither of these factors, however, has been unequivocally linked to the mechanism of immediate natriuresis caused by an acute increase in cerebrospinal fluid or plasma sodium concentration. It was reconfirmed in our present experiments in anesthetized dogs that aldosterone, ANP, and DLIS could hardly play a role in the immediate natriuresis after the i.v. infusion of hypertonic saline (20% NaCl solution infused in 20 min in an amount that was 0.13% of body weight). However, the role of AVP in this type of natriuresis seems more promising as a V1/V2 receptor antagonist applied i.v. before the hypertonic saline loading completely prevented the increase of renal sodium excretion. Natriuresis after the isotonic saline load was not impaired by the same antagonist of vasopressin receptors.

Animals↗
PubMed1992

[Immunochemical determination of gentamicin in serum. III. The competitive ELISA].

The author describes the use of polyclonal antibodies against gentamicin by competitive ELISA. The author used polystyrene microplates as the solid phase for antibodies. Gentamicin was marked by horse radish peroxidase and a known amount of thus labelled gentamicin competed for a bond with an antibody with an unknown amount of gentamicin in serum. The method requires 10 microliters non-diluted serum and the results can be evaluated within one hour. The accuracy of the method according to values of the coefficient of variation (CV) is 9.0-13.2% in different tests and 5.2 to 9.2% within one examination.

Enzyme-Linked Immunosorbent Assay↗
PubMed1991

Failure to demonstrate natriuretic activity in the posterior pituitary after immunoneutralization of the vasopressin content.

The attempt to demonstrate the presence of a natriuretic substance in the posterior pituitary after immunoneutralization of the AVP content failed. Rats infused i.v. AVP-immunoneutralized posterior pituitary extract did not respond by natriuresis to a saline infusion, in contrast to those infused untreated posterior pituitary extract. Thus, vasopressin seems to be the natriuretic substance in the posterior pituitary extract.

Animals↗
PubMed1990

Thyroid volume by ultrasound in boys and girls 6-16 years of age under marginal iodine deficiency as related to the age of puberty.

The results of thyroid volume estimation with the aid of ultrasound in a total of 921 boys and girls 6-16 years of age are reported. The thyroid volume was found to be increasing slowly between the age of 6 and 12 years, but somewhat more remarkable increase occurred at 13 and 14 years of age. However, in both sexes it was nearly doubled at the age of 15-16 years as compared with the values at 13-14 years irrespective of body weight. The thyroid growth rate (as calculated from the least squares analysis of the correlation between thyroid volume and body weight) in girls was significantly higher (P less than 0.001) than in boys. In spite of long-term mandatory iodine prophylaxis the average urinary excretion of iodine as estimated in 69 randomly selected subjects was 78.06 micrograms/g creatinine (geometrical mean). It may be suggested that such intake of iodine, though marginally deficient, may be satisfactory up to the age of about 12-14 years, while it appeared to be inadequate for the adolescents at the age of puberty.

Adolescent↗
PubMed1989

Effect of the glycogenolytic gluconeogenetic hormones, glucagon, vasopressin and angiotensin II, on biliary excretion of iodothyronines in rats is possibly related to the inhibition of 5'-monodeiodination in the liver.

Polyethylene tubes were inserted into the bile duct and femoral vein of rats under pentobarbital anaesthesia and bile was collected for three 2-h periods. After the first (control) period the animals were infused intravenously at a rate of 1.2 ml/h with the following compounds: (1) 0.9% (w/v) NaCl (control group), (2) glucagon (1200 ng/h), (3) vasopressin (1200 ng/h) or (4) angiotensin II (600 ng/h). The concentrations of thyroxine (T4), tri-iodothyronine (T3) and reverse tri-iodothyronine (rT3) in the bile were estimated by radioimmunoassay. No significant differences between groups were found in the biliary excretion of T4 and T3, while the excretion of rT3 after the infusion of all the hormones used was significantly (P less than 0.001 at 2 to 4 h of the infusion) increased, no such increase being found in the controls. It may be concluded therefore that the administration of the above hormones resulted in some changes in iodothyronine metabolism in the liver. These may be explained by an inhibition of iodothyronine 5'-monodeiodination related to the glycogenolytic and gluconeogenetic effects of these hormones.

Angiotensin II↗
PubMed1989

Studies and reevaluations of some aspects on thyroid function after superior cervical sympathetic gangliectomy in rats.

The results of 11 experiments in a total of 571 rats (initial body weight of 150-250 g) are reported and some findings differing from those by others are discussed. It was repeatedly found that the animals after bilateral or even unilateral superior cervical sympathetic gangliectomy (GX) did not gain body weight during the first week after surgery. Though they started to grow later, for several weeks their body weight remained significantly less than that of sham operated controls (SH). Though such phenomenon has not yet been described, it may well explain the increase of thyroid weight (as expressed per body weight) after gangliectomy alone or combined with antithyroid drug treatment or hypophysectomy as described by others. It was suggested that such changes may depend on general metabolic changes resulting in a striking inhibition of body weight gain rather than on some specific effect of GX on the thyroid. This view was supported by evaluating the data on absolute and relative thyroid weight from 4 experiments in a total of 265 animals. The level of thyroxine (T4) and thyrotropic hormone (TSG) was repeatedly found to be significantly decreased after GX for until about 72 h and 24 h after surgery, respectively, which was in agreement with the data reported by others. However, the onset of such decrease was repeatedly found to appear at 6 or 8 h after surgery (in one experiment even at 3 h after surgery) which is also contrasting to the onset of T4 decrease at 14 h after surgery as found by others who suggested a correlation of such thyroid depression with a depletion of noradrenaline from the thyroid and may be even from median eminence. In these experiments, however, a decrease of T4 level was found several hours before the depletion of noradrenaline from the thyroid which appeared at 12 h after surgery and remained at similar level until 40 days, while no remarkable changes of that were found in SH animals (with the excretion of slight increase after 24 h). Between about 4 and 40 days after surgery no significant changes in T4 and TSH levels after GX were found as compared with SH animals is in agreement with others.4+n one experiment the increase of T4 at 2 h after TRH injection, resulting apparently from the effect of endogenous TSH, was significantly inhibited in GX animals at 8 days after surgery, while in other experiments (at 8 and 40 days after surgery) no difference in T4 level increase was found in GX animals as compared with SH ones. In general, it may be suggested that superior cervical sympathetic gangliectomy may result in some temporary and perhaps transient changes in pituitary-thyroid function in rats.

Animals↗
PubMed1988

Effect of ethanol and linoleic acid on changes in biliary excretion of iodothyronines possibly related to thyroxine deiodination in rat liver.

Groups of male rats weighing about 350 g were inserted polyethylene tubings into bile duct and femoral vein under pentobarbital anesthesia. Several iodothyronines (i.e. T4, T3, rT3, 3,5-T2, 3,3'-T2 and 3',5'-T2) were estimated in 2-hr portions of bile with the aid of specific radioimmunoassay. After the infusion of ethanol (0.3 ml/hr/rat for 4 hr) an increase of biliary excretion of rT3 and a decrease of 3,5-T2 was found as compared to controls. When 5 mg linoleic acid was added to 1.2 ml ethanol, the increase of rT3 was significantly higher than that after ethanol only and, in addition, significant increase of 3',5'-T2 excretion was found. It was concluded that both ethanol and unsaturated fatty acids may inhibit 5'-monodeiodination in the liver and that unsaturated nonesterified fatty acids may exert such effect even when administered intravenously without underlying metabolic disorders.

Animals↗
PubMed1988

Iodothyronines in human bile.

Bile was collected from 7 patients after cholecystectomy with routine T-tube drainage of bile duct postoperatively. In all patients reported, the total volume of bile collected was more than 500 ml which was considered to be close to the volume of bile excreted by the liver during the 24 h collection period. The excretion of total thyroxine (T4), triiodothyronines (T3 and rT3) and diiodothyronines (3,3'-T2, 3,5-T2 and 3'.5'-T2) was estimated with the aid of specific radioimmunoassay described previously. It was found that the total amount of T4 corresponded to its content in about 100 ml plasma, while corresponding figures for triiodothyronines were about 1000-1500 ml and these for diiodothyronines about 10-15 liters. It was concluded that in man the biliary excretion of iodothyronines appears to be of much less importance for their total body balance than in rats.

Aged↗
PubMed1987

Delayed changes of plasma level and biliary excretion of several iodothyronines after a single administration of low doses of thyroxine in rats.

Male Wistar rats were injected i.p. 2.5 or 5.0 micrograms thyroxine (T4) and the level of several iodothyronines and TSH in plasma or biliary excretion of iodothyronines were estimated by radioimmunoassay in groups of animals in various intervals up to 144 hr after the administration. In general, two peaks in the plasma level and biliary excretion of iodothyronines were found: first one within 24 hr and a delayed second one between about 48 and 72 hr after the administration. It was concluded that the first peak may correspond to the metabolic changes in fast tissue pools, while a second one might reflect some delayed iodothyronine metabolic steps in slow tissue pools after a bolus injection of T4.

Animals↗
PubMed1987

Studies on in-vivo capacity of thyroxine deiodinating system in rat liver: biliary excretion of several iodothyronines after increasing loading doses of thyroxine.

Eighteen male rats were inserted with polyethylene tubings into bile duct and femoral vein and two rats each were injected a series of doses from 5 to 1280 micrograms L-thyroxine into a venous cannula. The bile was collected for three subsequent 2-hr periods and the excretion of total thyroxine (T4), triiodothyronines (T3 and rT3) and all diiodothyronines (3,3'-T2, 3,5-T2 and 3',5'-T2) was estimated as well as that of conjugated T4 and T3. The excretion of all compounds was considerably increased as early as within the first 2-hr period. Almost linear dose-response relationship was found between the dose of T4 and its biliary excretion up to the dose of 640 micrograms, only smaller increase being observed after 1280 micrograms T4. Similar relationship was found also in the excretion of diiodothyronines, while that of triiodothyronines after 1280 micrograms T4 was slightly less than after 640 micrograms T4. The excretion of rT3 was consistently about twice as high as that of T3. The data on diiodothyronine excretion suggested a preferential conversion of rT3 to 3',5'-T2 and that of T3 to 3,5-T2 over that to 3,3'-T2. The ratio of 3,5-T2/T3 after different doses of T4 was about 2--4 times higher than that of 3',5'-T2/rT3 suggesting the higher deiodination rate of T3 than that of rT3.

Animals↗
PubMed1987

Dual dose-related action of peripherally administered morphine on cold-stimulated thyrotropin secretion in male rats.

Cold-induced increase of thyrotropin (TSH) release was found to be inhibited after 10 or 20 mg/kg morphine sulfate (MO) injected intraperitoneally 30 min before the transfer of adult male rats from 30 to 4 degrees C for 60 min (i.e. 90 min before sacrifice). In contrast, lower doses of MO such as 2.5 and 5 mg/kg were found to stimulate the cold-induced TSH release under the same conditions. Such a cold-induced TSH release stimulated by lower doses of MO was found to be inhibited by intraperitoneal injection of 2 or 4 mg/kg naloxone (NX) 30 min before MO injection (i.e. 120 min before sacrifice) in a dose-dependent manner, while the same doses of NX were without effect on the levels of TSH after higher doses of MO. It is suggested that these effects may depend on different sensitivities of various hypothalamic loci involved in mediating either a stimulation or inhibition of TSH release.

Animals↗
PubMed1985

Acute changes of iodothyronine excretion by bile after a single and repeated administration of dexamethasone in rats.

Bile was collected from cannulated bile duct under pentobarbiturate anesthesia and the excretion of several iodothyronines was estimated with the aid of radioimmunoassay as described previously. The excretion of triiodothyronine (T3) was significantly decreased between 4 and 6 h after a single injection of 20 and 40 mg kg-1 dexamethasone (DEX), while no changes in the excretion of thyroxine (T4) and reverse triiodothyronine (rT3) were found. In another experiment a decrease of T3 excretion was observed together with an increase of rT3 excretion and of T4/T3 and rT3/T3 ratio between 9 and 11 h after a single injection of 0.75, 1.5 and 3.0 mg kg-1 DEX, the differences being in most cases significant as compared to controls. In the same experiments a dose related increase of excretion of 3,3'-diiodothyronine (3,3'-T2) and 3,5-diiodothyronine (3,5-T2) was found, while the excretion of 3',5'-diiodothyronine (3',5'-T2) decreased with dose of DEX. Similar results were observed even after the administration of 1.5 and 3.0 mg kg-1 DEX for 5 days. In addition, the level of rT3 in serum was significantly increased at 9 h after a single dose of 3.0 mg kg-1 DEX and after 5 days administration of 1.5 and 3.0 mg kg-1 DEX. The data support a previous view that the changes in biliary excretion of iodothyronines are closely related to deiodinating metabolism of T4 in the liver and are expressed earlier and more remarkably than these in their plasma level.

Animals↗
PubMed1984

Studies on the inhibitory effect of apomorphine and bromocryptine on basal and TRH induced level of TSH and PRL in hypothyroid rats under pentobarbiturate anesthesia.

Groups of male rats were inserted with polyethylene tubings into femoral artery and vein under pentobarbiturate anesthesia and small blood samples were frequently taken for the estimation of TSH and PRL under maintaining isovolemia. After a single injection of apomorphine (12 mg kg-1) or bromocryptine (20 mg kg-1) much more expressed effect of these drugs on a decrease of PRL level in plasma was found than that on a decrease of TSH level and similar observation was made with the use of continuous i.v. infusion of apomorphine (50 micrograms in 20 microliter per min for 180 min). Finally, under the above dose of infused apomorphine, the effect of TRH on the increase of TSH level was depressed at the 30th min as compared to that 0 and 120th min of infusion. In addition, at 120 min of infusion the effect of TRH was significantly higher than that at 0 min. These results suggest that the effect of apomorphine may take place at the pituitary level.

Anesthesia↗
PubMed1984

In vivo effect of amiodarone, thiocyanate, perchlorate and goitrin on thyroxine deiodination in rat liver.

The bile duct of male Wistar rats weighing 350 g was cannulated with polyethylene tubing under pentobarbiturate anesthesia and biliary excretion of thyroxine (T4), triiodothyronine (T3), reverse triiodothyronine (rT3) and 3,3'-,3,5- and 3',5'-diiodothyronine (3,3'-T2, 3,5-T2 and 3',5'-T2, respectively) was estimated in 2 h samples of bile with the aid of specific radioimmunoassay. In each animal the excretion of appropriate compounds for 2 h after intravenous injection of various drugs was expressed as per cent of that during 2 h control period before the injection. The results obtained in individual groups of animals were compared to control group which was injected saline before the second bile collection period. The injection of amiodarone (15 mg kg-1) resulted in significant decrease of T3, rT3, 3,3'-T2 and 3,5-T2 excretion and that of thiocyanate (SCN-; 50 mg kg-1) resulted in significantly increased excretion of T4, while that of T3 and 3,5-T2 was significantly decreased. Goitrin (L-5-vinyl-2-oxazolidinethione; 6 mg kg-1) and perchlorate (ClO4-; 50 mg kg-1) showed only slight effects. It was concluded that amiodarone and thiocyanate in the doses used inhibited the conversion of T4 to T3 in vivo immediately after the administration.

Amiodarone↗