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Biomedical subjects

T Torda

Publications and source records attributed to T Torda.

At least 55 records · Page 3Linked to original sources
PubMed1980

Effect of indomethacin on cardiac beta-adrenergic receptors.

Treatment of rats with indomethacin, 1.5 mg/kg per day, for one week, significantly reduced the number of beta-adrenoceptors in the heart without altering their affinity for the specific beta-adrenergic ligand. In indomethacin-treated rats there was a reduction in the cardiac response to epinephrine in vivo as indicated by a shift to the right of the epinephrine dose-heart rate response curve. These results support a possible interference by indomethacin in beta-adrenoceptor-mediated effects.

Animals↗
PubMed1980

Presynaptic noradrenergic regulation during depression and antidepressant drug treatment.

A specific testable hypothesis in which supersensitive alpha-2-adrenoreceptors play an important role in the etiology and maintenance of affective illness is presented based on the following observations: (1) published findings of changes in adrenergic receptors in the periphery and brains of rats in response to antidepressant regimens; (2) new studies of the monoamine oxidase type A-inhibiting antidepressant clorgyline, specifically relating to adaptation in the alpha-adrenergic presynaptic negative feedback system; (3) human peripheral alpha-adrenergic receptor changes from studies of patients with affective illness; and (4) observations from animals and humans experiencing stress and withdrawal from chronic amphetamine and opiate administration, suggesting that the development of supersensitive alpha-2-adrenoreceptors may lead to affective illness in vulnerable individuals. Old and new pharmacologic treatments are then discussed in terms of their capacity to specifically alter adrenergic receptor state.

Animals↗
PubMed1980

The nature of gentamicin-induced neuromuscular block.

Gentamicin in concentrations of 0.05--0.2 mmol litre-1 blocked neuromuscular transmission in the toad sartorius nerve--muscle preparation by decreasing the release of transmitter. In concetnrations of 0.5--1 mmol litre-1 it decreased the amplitude of the miniature end-plate current by a curare-like action, without affecting the mean open channel lifetime.

Animals↗
PubMed1980

Increased brain stem and decreased hypothalamic adrenaline-forming enzyme after acute and repeated immobilization stress in the rat.

The effects of immobilization stress on the activity of the adrenaline-forming enzyme, phenylethanolamine N-methyltransferase (PNMT), have been studied in discrete areas of the rat brain stem and hypothalamus. The changes in brain PNMT activity varied with the duration of the stress, were localized to a few brain areas, and the direction of the change varied with the area considered. PNMT was increased after acute immobilization in several areas of the brain stem: A2 area, the anterior part of the nucleus tractus solitarius, and the locus coeruleus. After 7 days of stress, significantly increased PNMT activity was found only in the A2 area and in the cerebellum. In the anterior hypothalamic nucleus, immobilization stress repeated for seven days resulted in a significant decrease in methyltransferase activity. These results implicate discrete, localized adrenaline-forming neurons in the central regulation of the stress response.

Animals↗
PubMed1979

The stress induced increase of liver phosphorylase A and cyclic AMP in adrenomedullectomized and adrenalectomized rats.

In adult male rats injected with Pentobarbital, 50 mg.kg-1 i.p. and subjected immediately after administration of the anaesthetic to 400 revolutions (lasting of 6 min and 40 s) in rotating Noble-Collip drums the activity of the active form of hepatic phosphorylase was increased at time 0 after injury without respect to previous adrenomedullectomy or adrenalectomy (7 weeks or 10 days before, respectively). Completeness of surgery was checked by plasma catecholamines which were essentially near zero. The level of liver cAMP was increased in intact and adrenomedullectomized animals at time zero. 90 min after injury a recovery of enzyme activity towards basal levels was observed in contrast to cAMP which was increased in all the three groups. A net glycogenolytic response was found in the injured animals irrespective of previous surgery. It is concluded that for the stress induced activation of hepatic phosphorylase the presence of adrenal cortical and medullary tissue is not always indispensable.

Adrenal Medulla↗
PubMed1979

Inhibition of thyroid monoamineoxidase by thyroxine and some specific inhibitors.

Rat thyroid monoamine oxidase (MAO) was inhibited by the non-hydrazine derivatives paragyline and tranylcypromine to a higher degree than the hydrazine derivative iproniazide. MAO was also inhibited by monoiodotyrosine and thyroxine. These results indicate that MAO may be an important enzyme in the metabolism of biogenic amines, iodotyrosines and tyronines in the thyroid gland.

Animals↗
PubMed1978

Changes of adrenal catecholamines and their synthesizing enzymes during ontogenesis and aging in rats.

Male Wistar specific-pathogen-free rats aged 2, 7, 17, 30, 60, 120, 200, 360 and 600 days, all killed in experiment on the same day, were examined. The body weight significantly increased until the 200th day, the weight of adrenals until the 120th day and the adrenal protein content until the 30th day of life. The adrenaline content of the adrenals increased continuously during the 600 days studied. Adrenal noradrenaline content increased rapidly over the first 17 days, remained at a stable level until the 120th day, and rose to a higher level after 200 days. The activity of adrenal catecholamine-synthesizing enzymes also increased with age: tyrosine hydroxylase gradually increased until the 360th day, dopamine-beta-hydroxylase and phenylethanolamine-N-methyl transferase until the 200th day. Our results demonstrate that, in the rat, during development there is a gradual increase of adrenal weight, adrenaline content, tyrosine hydroxylase and phenylethanolamine-N-methyl transferase activity until maturation (120th day), whereas the adrenal noradrenaline content reaches the adult values earlier, around the 17th day. During aging, adrenal catecholamines significantly increase when compared to young-adult rats (120-day-old), probably due to the elevated activity of the adrenal catecholamine-synthesizing enzymes. The increased adrenal catecholamine levels in old animals might be connected with a higher incidence of cardiovascular diseases in aged.

Adrenal Glands↗
PubMed1978

Effect of handling and forced immobilization on rat plasma levels of epinephrine, norepinephrine, and dopamine-beta-hydroxylase.

Forced immobilization of rats triggers activation of adrenal-medullary discharge of epinephrine (EPI) and sympathetic neuronal release of norepinephrine (NE). Plasma levels of EPI reach peak values, which are about 40-fold greater than in undisturbed rats, at about 20 min and then decline to about one-third the peak levels. Plasma levels of NE are increased about 6-fold throughout the immobilization interval. Decapitation produces an 80-fold increase in plasma levels of EPI and an 8-fold increase in NE. These striking decapitation-induced increases are potentiated about 3-fold by immobilization, presumably as a consequence of an immobilization-induced alteration in the "set" of responsivity of spinal cord mechanisms controlling sympathoadrenal medullary discharge. Even minor disturbances produce highly significant increases in plasma EPI and NE and special precautions must be observed when studies involving plasma catecholamines or their effects are performed in animals.

Animals↗
PubMed1978

Posterior pituitary dopamine and noradrenaline content: effect of thirst, ethanol and saline load.

Dopamine and noradrenaline content in the posterior pituitary were found to be lower in alcohol-loaded unanesthetized rats than in rats thirsting for 72 h. Dopamine content was also found to be lower in anesthetized saline loaded rats in comparison with hydropenic animals. It is concluded that in situations in which an increase of vasopressin release is expected, the posterior pituitary content of catecholamines will also be increased, and vice versa, which might imply their role in the release of vasopressin.

Animals↗
PubMed1977

Catecholamines in individual hypothalamic nuclei of acutely and repeatedly stressed rats.

Norepinephrine (NE) and dopamine (DA) concentrations in 17 individual hypothalamic nuclei and 3 other brain regions were measured in rats, acutely or repeatedly stressed by immobilization, using a microdissection technique and a radioisotopic-enzymatic assay. Following the first 20 min immobilization (IMO) a significant NE decrease in the ventromedial (NVM) and supraoptic (NSO) nuclei and a DA decrease in the arcuate nucleus (NA) as well as NE and DA increase in the dorsomedial nucleus (NDM) were seen. Repeated IMO (40 times) produced a NE increase in the NVM, NDM, NSO paraventricular nucleus (NPV) and median eminence (ME), and a DA increase in the NDM and NPV. Changes of NE and DA concentration found in some individual hypothalamic nuclei under the influence of stress indicate that catecholamines (CAs), particularly in the medial basal hypothalamus, could be involved in the regulation of some neuroendocrine processes which are being activated during stress, especially ACTH release.

Animals↗
PubMed1975

Activity of catecholamines inactivating enzymes in heart muscle during anoxic cardioplegia in cardiosurgical patients.

On the model of anoxic cardioplegia in cardiosurgical patients the influence of anoxia on the activity of monoamine oxidase (MAO) and catechol-O-methyltransferase (COMPT) in right auricular tissue was studied. It was found out that the activity of COMT does not change during anoxia, the activity of MAO considerably increases. With regard to catecholamines stimulating effect upon cardiac metabolism as well as to their calorigenic and oxygen wasting effect the raise of MAO activity may be regarded as favourable phenomenon, because the hastened degradation of released catecholamines at least to a certain degree diminishes the disproportion between oxygen supply and actual oxygen need of the heart and by means of that mitigates the anoxic damage of myocardium.

Cardiac Output, Low↗
PubMed1975

Activity of catecholamine degrading enzymes in rat adrenal medulla and cortex after acute and repeated stress.

The activity of catecholamine degrading enzymes (catechol-O-methyltransferase--COMT and monoamine oxidase--MAO) in separated adrenal cortex and medulla was measured in rats stressed by a singel or repeated immobilization. In controls, the activity of both enzymes was higher in adrenal cortex than in adrenal medulla. After stress, the activity of COMT in adrenal cortex was significantly decreased, while that in adrenal medulla was significantly increased. Moreover, the animals repeatedly immobilized showed lower COMT activity in both parts of adrenals when compared to first time stressed rats. The activity of MAO was not remarkably changed, but was increased only in adrenal medulla when expressed per mg protein, the decrease of which resulted from acute stress. It was concluded that the findings of changed activity of catecholamine degrading enzymes, namely a decreased activity of COMT in both adrenal cortex and medulla in repeatedly stressed rats, might show a possible participation of these enzymes in increased catecholamine content in adrenals of repeatedly stressed animals.

Adrenal Cortex↗
PubMedDate not supplied

Effect of weightlessness on sympathetic-adrenomedullary activity of rats.

Three cosmic experiments were performed in which rats spent 18-20 days in space on board the biosatellites "COSMOS 782", "COSMOS 936" and "COSMOS 1129". The following indicators of the sympathetic-adrenomedullary system (SAS) activity were measured: tissue and plasma catecholamines (CA), CA-synthesizing enzymes--tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), phenylethanolamine-N-methyltransferase (PNMT)--as well as CA-degrading enzymes-monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). Adrenal epinephrine (EPI) and norepinephrine (NE) as well as CA-synthesizing and degrading enzymes were not significantly changed in the animals after flight on COSMOS 782. On the other hand, a significant increase was found in heart CA, the indicator which is usually decreased after stress. 26 days after landing all values were at control levels. The results obtained, compared to our previous stress experiments on Earth, suggest that prolonged weightlessness does not appear to be a pronounced stressful stimulus for the SAS. Heart and plasma CA, mainly NE, were increased both in the group living in the state of weightlessness and the group living in a centrifuge and exposed to artificial gravitation 1 g (COSMOS 936), suggesting again that prolonged weightlessness is not an intensive stressful stimulus for the SAS. The animals exposed after space flight on COSMOS 1129 to repeated immobilization stress on Earth showed a significant decrease of adrenal EPI and an expressive increase of adrenal TH activity compared to stressed animals which were not in space. Thus, the results corroborate that prolonged state of weightlessness during space flight though not representing by itself an intensive stressful stimulus for the sympathetic-adrenomedullary system, was found to potentiate the response of "cosmic rats" to stress exposure after return to Earth.

Adaptation, Physiological↗