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Biomedical subjects

B Radnai

Publications and source records attributed to B Radnai.

At least 19 recordsLinked to original sources
PubMed2004

Pivotal role of an endogenous tetrahydroisoquinoline, salsolinol, in stress- and suckling-induced release of prolactin.

In mammals, the role of a prolactin-releasing factor (PRF) in the acute changes of prolactin (PRL) secretion that usually occur after challenges (e.g., suckling stimulus or stress) of homeostasis has been suspected for a long time. We have recently observed that 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, salsolinol (SAL), produced by the hypothalamus and the neuro-intermediate lobe (NIL) of the pituitary gland, can selectively release PRL from the anterior lobe (AL). Moreover, binding sites for SAL have been detected in areas like median eminence, NIL, and AL. It has been proposed that SAL is a putative endogenous PRF. We have also found that a structural analogue of SAL, 1-methyl-3,4-dihydroisoquinoline (1MeDIQ), is able to block dose-dependently SAL-, suckling-, and immobilization (IMO) stress-induced release of PRL without having any influence on alpha-methyl-p-tyrosine (alphaMpT)-induced PRL responses. Neither SAL nor 1MeDIQ has any effect on alpha-melanocyte-stimulating hormone (alphaMSH), adrenocorticotrophic hormone (ACTH), beta-endorphin (beta-END) and arginine-vasopressin (AVP) secretion. Moreover, SAL-induced PRL response was attenuated in male rats pretreated with dexamethasone (DEX). These results strongly suggest that SAL has an important role in the regulation of PRL release induced by physiologic and environmental stimuli; therefore, it can be considered as the strongest candidate for being the PRF in the hypothalamo-hypophysial system. Our findings also indicate that the adrenal steroids may play an inhibitory feedback role in SAL-mediated PRL response.

Animals↗
PubMed2001

Salsolinol is a putative endogenous neuro-intermediate lobe prolactin-releasing factor.

The isolation and identification of a prolactin-releasing factor (PRF) from the neuro-intermediate lobe of the pituitary gland has been pursued for over a decade. Using high-pressure liquid chromatography with electrochemical detection (HPLC-ECD) and gas chromatography/mass spectrometry (GC/MS) (R)-salsolinol (SAL) (a dopamine-related stereo-specific tetrahydroisoquinoline) was found to be present in neuro-intermediate lobe as well as median eminence extracts of male, intact-, and ovariectomized female rats. Moreover, analysis of SAL concentrations in neuro-intermediate lobe revealed parallel increases with plasma prolactin in lactating rats exposed to a brief (10 min) suckling stimulus following 4-h separation. SAL appears to be a selective and potent stimulator of prolactin secretion in vivo and it was without effect on the secretion of other pituitary hormones. We have also found that SAL can elevate prolactin release, although to a lesser extent, in pituitary cell cultures as well as in hypophysectomized rats bearing anterior lobe transplants under the kidney capsule. Lack of interference of SAL with [3H]-spiperone binding to AP homogenates indicates that SAL does not act at the dopamine D2 receptor. Moreover, [3H]-SAL binds specifically to homogenate of AL as well as neuro-intermediate lobe obtained from lactating rats. Taken together, our data clearly suggest that SAL is synthesized in situ and this compound can play a role in the regulation of pituitary prolactin secretion.

Animals↗
PubMed1999

Inhibition of protein phosphatase 2A (PP2A) mimics suckling-induced sensitization of mammotropes: involvement of a pertussis toxin (PTX) sensitive G-protein and the adenylate cyclase (AC).

In lactating rats, suckling renders mammotropes more responsive to prolactin (PRL)-releasing stimuli and less responsive to PRL-inhibiting secretagogues. We have previously shown that a decrease in the activity of protein phosphatase 2A (PP2A) may be responsible for the decrease in responsiveness to the inhibitory secretagogue dopamine (DA). In our present experiments, we have studied the involvement of the adenylate cyclase (AC), stimulatory and inhibitory GTP-binding proteins and also the role of PP2A in the sensitization phenomenon. Pituitary cells obtained from mother rats separated from their pups for 4 h prior to dispersion (non-suckled), suckled for 10 or 30 min after the separation period (suckled) and without separation (continual suckling) were incubated in the presence of different doses of forskolin to activate AC and DA. In a further study, pituitary cells of non-suckled rats were pretreated with cholera toxin (CTX) or pertussis toxin (PTX) and tested for the stimulatory action of forskolin or TRH on PRL release. Ocadaic acid (OA) pretreatment has been used to investigate the involvement of PP2A. Hormone secretion was measured by the reverse hemolytic plaque assay (RHPA). Our results have shown that cells from non-suckled rats were unresponsive to forskolin. A 10-min suckling stimulus sensitizes pituitary mammotropes to respond with a PRL release to a dose-dependent activation of AC by forskolin. This sensitization of AC becomes a permanent feature of the cells when suckling continues for an additional 20 min. We have also found that pituitary mammotropes from non-suckled dams respond to forskolin or TRH with PRL release when they were preincubated with either PTX or the PP2A inhibitor OA. It clearly indicates that the non-responsive pituitary can be shifted to the responsive stage by uncoupling of inhibitory G-protein from its receptor as well as by inhibition of PP2A. This latter finding, consonant with our previous results, suggests that suckling may cause selective changes in the function of G(i) of mammotropes due to a rapid phosphorylation which can remove tonic, GTP-dependent inhibitory function.

Adenylate Cyclase Toxin↗
PubMed1996

[Loss of consciousness of unusual etiology in a young patient].

The authors have presented the case of a young woman, who was observed because of repetitive loss of consciousness. The unbalance of the vegetative nervous system (parasympathetic overactivity) was responsible for the syncopic events, which could be prevented by the implantation of pacemaker successfully. The reoccurrence of loss of conciousness after 10 years could be attributed partly to the presence of dysfunction of pacemaker (undersensing+inhibition of myopotential), partly to a passing off the stress situation, with previous status of fever, and the consequent orthostatic hypotension caused by actually inadequat use of nitratvasodilator.

Adult↗
PubMed1994

[The effect of high blood viscosity, caused by secondary polycythemia, on pulmonary circulation and gas exchange in patients with chronic cor pulmonale].

Blood viscosity, pressure of pulmonary artery, pulmonary functions, arterial and mixed venous oxygen content, cardiac output, oxygen transport capacity, oxygen consumption, ejection fraction have been examined at 25 patients with or without hypoxic cor pulmonale with or without secondary polycythaemia. Although secondary polycythaemia occurs in patients with hypoxic cor pulmonale as a compensatory process to increase the oxygen carrying capacity of the blood theoretically but as our findings: 1. The rise of haematocrit causes rise in blood viscosity significantly. 2. Polycythaemia secondary over 0.50 l/l of haematocrit contributes the rise of pressure in pulmonary artery. 3. The systemic oxygen carrying capacity is increasing with the rise of haematocrit up to 0.45 l/l but decreasing over 0.50 l/l. 4. Oxygen consumption is decreasing parallel with the rise of haematocrit. 5. Pulmonary functions, cardiac output do not change by the rise of haematocrit.

Blood Viscosity↗
PubMed1992

[Correlations between radionuclide first passage, hemodynamic and respiratory function parameters in cor pulmonale patients].

37 patients with chronic cor pulmonale have been investigated with radionuclide first passage, microcatheter-technique, respiratory function investigation, furthermore blood gas analysis. Significant positive correlation have been found between the pulmonary circulation time and the pulmonary artery pressure; between the pulmonary mean transit time and the pulmonary artery pressure; furthermore between the pulmonary stagnation index was calculated for the characterization of peripheral pulmonary stagnation and the pulmonary artery pressure. Significant negative correlation have been found between the pulmonary circulation time, the pulmonary mean transit time and the vital capacity, the FEV1, furthermore the O2-saturation values. The authors establish, that on the base of the close correlations between the isotopic circulation parameters and the clinical data, the radionuclide first passage investigation is suitable for the demonstration of the current conditions of cardiopulmonary circulation.

Adult↗
PubMed1987

The effect of droperidol on the ST-T segment of the ECG.

It is generally accepted that droperidol as a dopaminergic blocking agent has some influence on heart function. Therefore, a study was performed to investigate the effect of droperidol on the so-called ischaemic ST-T segment depression in the ECG. Droperidol treatment 0.1 mg/kg b.w. in a single i.m. injection was performed in 30 patients 21 women and 9 men, aged 15-55 years producing marked ST-T depression in at least two conventional leads, at rest. Droperidol had a beneficial effect in the majority of patients, i.e. the ST-T segment inversion had normalized in 23%, and improved in 30%. It is concluded that droperidol abolishes the ST-T alteration produced by dopaminergic mechanism.

Adolescent↗
PubMed1984

Effect of metoprolol in carotid sinus hypersensitive patients.

The reflex effects induced by carotid sinus stimulation were studied in 23 subjects before and after oral administration of 200 mg metoprolol. Eight patients had sustained hypertension, eight had normal blood pressure. All patients had carotid sinus hypersensitivity (CSH). Seven normotensive subjects without carotid sinus hypersensitivity constituted the control group. Two hours after intake of metoprolol the baroreflex induced sinus node inhibition and blood pressure lowering effect proved to be greater, in all groups of subjects, than before taking the drug, however, in the group of carotid sinus hypersensitive patients with high blood pressure only the parameters relating to heart rate showed significant differences. In a comparison of the effects of the metoprolol on the parameters induced by carotid stimulation, significant increases could be seen in both CSH groups compared to the data found in the control group. The reflex induced fall in blood pressure and the time needed for the return to the prestimulating level showed a significantly greater augmentation in the normotensive, than in the hypertensive CSH patients.

Blood Pressure↗
PubMed1983

Effect of an irradiated Escherichia coli endotoxin reparation on the sensitivity to a lymphotropic cytostatic agent in germfree and conventional mice.

A 18 mg/kg dose of dianhydrodulcitol, a lymphotropic cytostatic agent produced the same death rate among germfree as a 12 mg/kg dose did in conventional mice. Pretreatment with the same dose of an irradiated immunomodulatory endotoxin preparation had increased the sensitivity to these dianhydrodulcitol doses in the same degree in germfree as in conventional mice. A study of the lymphoid organs and the intestinal wall indicate that both in germfree and conventional mice the dianhydrodulcitol sensitivity increasing effect of the endotoxin preparation was due to its stimulation of the lymphoid system. The higher resistance of germfree mice to dianhydrodulcitol is ascribed to their lack of a normal intestinal flora.

Animals↗
PubMed1983

The course of lymphocytic choriomeningitis virus infection in germfree mice treated with Bordetella pertussis vaccine.

A single injection of Bordetella pertussis vaccine, applied intraperitoneally one day before intracerebral lymphocytic choriomeningitis virus infection depressed the immune response both in conventional and germfree adult mice, but the rate of the immunosuppressive effect differed. In adult mice with a normal immune system the vaccine only delayed the manifestation of fatal lymphocytic choriomeningitis, while it prevented its development in germfree mice with an underdeveloped lymphoid system, i.e. it inhibited the cellular immune response to the virus infection.

Animals↗
PubMed1983

Human tolerance of flumecinol (Zixoryn, RGH-3332), its regime and dosage in healthy volunteers.

The enzyme inductive effect of flumecinol (Zixoryn, RGH-3332), a new hepatic enzyme inducer, was studied in healthy volunteers. The dosages employed were as follows: 25, 50, 100, 200, 400, 600 and 800 mg single doses; and during a 7-day period single doses of 50 mg daily, and doses of 200, 300 and 400 mg three times daily. The intensity of enzyme induction was measured by the following parameters: antipyrine metabolic clearance, D-glucaric acid excretion, menthol loading, and total serum bilirubin. The minimal and optimal inductive doses of flumecinol were determined. A single dose of 600 mg of flumecinol is recommended at intervals of 7 days. This dosage also induces the first and the second phases of reactions. The induction effect becomes manifest after 24 hours. Its peak is reached between 48 and 96 hours, and the inductive activity ceases between 216 and 408 hours.

Adult↗
PubMed1982

Higher resistance of germfree mice to dianhydrodulcitol, a lymphotropic cytostatic agent.

The same dose of dianhydrodulcitol (DAD) produced a lower mortality rate among germfree mice than among SPF or conventional C3H mice. On the other hand, it caused graver lymphoid atrophy in germfree mice. Their higher resistance, as evidenced by the mortality rate, can be explained on the basis of a histological study of the ileum. It showed milder alterations of the intestinal wall in germfree than in SPF mice. The lymphotropic cytostatic agent had a less direct toxic effect in germfree mice, due to the lacking damaging effect of endotoxin from the normal intestinal flora.

Animals↗
PubMed1979

Clinical aspects of carotid sinus hyperaesthesia.

Carotid sinus hyperaesthesia (CSH) was found in 605 of the clinical cases observed by the authors in a 6-year period. In the patients with CSH, disorders of impulse formation and conduction, both at rest and in response to the carotid compression test, were prevalent. No relationship was demonstrable between the duration of carotid compression and the consequent rhythm disorders. Nor did the vascular state of the CSH patients affect the type, duration or severity of arrhythmia elicited by carotid compression. In 8 cases of CSH unilateral carotid sinus infiltration with lidocain was performed with the objective of pharmacological denervation. Predominance of sympathicotonia induced in this manner was not found to be provocative of arrhythmia. Sensitization of the carotid sinus reflex in response to i.v. administration of 0.5 mg digoxin was confirmed on the evidence of clinical investigations.The results thus obtained are primarily attributed to a decreased sympathetic efferentation.

Adolescent↗
PubMed1979

Stimulation of the cellular immune response to lymphocytic choriomeningitis (LCM) virus infection in suckling mice.

Death occurred earlier and its rate was higher in one-week-old mice treated with phytohaemagglutinin (PHA) and subsequently inoculated intracerebrally with LCM virus than in their virus infected but untreated littermates. Thus PHA treatment contributed to the outcome of LCM virus infection in the form of lethal meningitis. The course of LCM virus infection in 1-week-old PHA treated mice was similar as in the untreated 2-week-old mice. This indicates that PHA treatment accelerated the development of cell mediated immunological capacity in suckling mice.

Animals↗
PubMed1978

Course of lymphocytic choriomeningitis (LCM) virus infection in suckling mice treated with Bordetella pertussis vaccine.

Death occurred earlier and the mortality rate was higher in one and two-week-old mice pretreated with Bordetella pertussis vaccine and infected intracerebrally with LCM virus, than in not pretreated animals of the same litter. Pertussis vaccine treatment contributed to the course of LCM virus infection ending in lethal meningitis in suckling mice, by accelerating the development of their cellular immune response.

Animals↗