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Biomedical subjects

G Szabó

Publications and source records attributed to G Szabó.

At least 19 recordsLinked to original sources
PubMed1992

Inhibition by D-MePhe-Pro-Arg-H (GYKI-14766) of thrombus growth in experimental models of thrombosis.

The antithrombotic action of the highly effective synthetic thrombin inhibitor D-MePhe-Pro-Arg-H (GYKI-14766) was studied in various models of experimental thrombosis. The compound administered to rats and rabbits by i.v. bolus injections, continuous i.v. infusions, subcutaneously and orally, respectively, induced significant decrease in thrombus weight (i) in a quantitative venous thrombosis model with stasis based on vascular lesion in rats, (ii) in an extracorporeal arterio-venous shunt model in rabbits, and (iii) prevented the occlusion of the vessel in arterial thrombosis induced by mechanical damage in rats. By using the arterio-venous shunt model in rabbits the inhibitory effect on thrombus growth could be demonstrated as a function of dose and time in self-controlled experiments. Blood level of the inhibitor determined by a bioassay varied between 0.09-0.67 microgram/ml whole blood when doses of 15 and 20 mg/kg were administered orally. A correlation was found between thrombin time, platelet aggregation induced by thrombin ex vivo and the weight of thrombi formed.

Amino Acid Sequence↗
PubMed1992

[Effect of intra-arterial chemotherapy of head and neck tumors on cerebral blood circulation].

A combination of Cisplatin and Epirubicin was administered through the external carotid artery system according to a standard protocol as preoperative or palliative therapy in 14 oral cancer patients. With the aim of clarifying the subacute side-effects of this chemotherapy on the intracerebral circulation, rCBF SPECT investigations with 99mTc-HMPAO were performed before and after the cytostatic treatment. The interval between SPECT studies was 24 (SD +/- 12) days. In concordance with the neurological condition, visual assessment of the rCBF SPECT reconstructed transversal slices revealed no perfusion abnormalities and no changes on the follow-up. No significant changes were found in the side activity ratios in 22 regions of each hemisphere (unpaired t-test) in the whole group of patients. It was concluded that within the investigated time interval this highly effective combination of cytostatics administered perfectly through the external carotid artery system causes no serious disturbances in the cerebral circulation in oral cancer cases.

Aged↗
PubMed1992

In vivo anticoagulant and antiplatelet effect of D-Phe-Pro-Arg-H and D-MePhe-Pro-Arg-H.

D-Phe-Pro-Arg-H and D-MePhe-Pro-Arg-H synthetized in our institute were administered to mice, rats, rabbits and beagle dogs. The kinetics of the anticoagulant and antiplatelet effect was recorded by measuring various clotting parameters, platelet count and aggregation, and evaluated as proposed by Verstraete and Verwilghen. The minimum effective doses were found to be 0.25-0.5 mg kg-1h-1 by intravenous continuous infusions and 0.5-1.0 mg/kg by single injections. The dose-dependent prolongation of clotting times appeared after application within minutes and returned to baseline values as a function of dose. Blood level of the inhibitors was determined by a bioassay. Unlike heparin, no higher starting dose was required to reach the anticoagulant threshold level, i.e. 0.03-0.1 microgram/ml whole blood. The peptides did not cause significant changes in platelet count and function or in hemodynamic parameters (blood pressure, heart rate and ECG) and in respiration. They blocked platelet aggregation induced by thrombin ex vivo specifically. No rebound effect or bleeding could be demonstrated even after subtoxic doses of the compounds. The onset of the anticoagulant and antithrombotic effect appeared within 60 min after single oral doses and lasted for 3-6 h. In close correlation with the anticoagulant effect a complete or significant inhibition of platelet aggregation induced by thrombin ex vivo could also be recorded by using 5-10 mg/kg doses.

Animals↗
PubMed1992

[Waldenstrm macroglobulinemia presenting in the form of cold urticaria and cold purpura].

A Waldenström macroglobulinemia case, manifested in the form of non-specific skin-symptoms (cold urticaria and cold purpura) is described in a 37 years old female patient. As new skin-symptoms progressive telangiectasia and naevi aranei could be observed. Involvement of skin may be explained by macroglobulins with kryoprotein properties, making early diagnosis possible at the same time.

Adult↗
PubMed1992

Critical role of endogenous corticotropin-releasing factor (CRF) in the mediation of the behavioral action of cocaine in rats.

The role of endogenous CRF in the locomotor hyperactivity induced by cocaine was investigated by using the immunoneutralization of endogenous CRF and an antagonist of CRF-receptors (alpha-helical CRF9-41: alpha h-CRF) in rats. Different dilutions of anti-CRF antibody (1:5, 1:20, but not 1:100) injected intracerebroventricularly (i.c.v.) 24 hours before the cocaine treatment blocked the expression of locomotor hyperactivity. Pretreatment with different doses (0.001, 0.01, 0.1, 1.0 micrograms i.c.v.) of alpha h-CRF inhibited the locomotor hyperactivity induced by cocaine dose-dependently. Neither the immunoneutralization nor the receptor blockade for CRF changed the hyperactivity induced by another locomotor stimulant caffeine. These results serve as indirect in vivo evidence of the selective role of endogenous CRF in the cocaine-induced behavioral alterations. The findings have implications as concerns the possible role of CRF in human psychopathological changes induced by cocaine.

Animals↗
PubMed1992

Oxytocin modulates behavioural adaptation to repeated treatment with cocaine in rats.

Behavioural adaptation to and the effects of the neurohypophyseal peptide, oxytocin, on repeated treatment with cocaine were investigated in rats. The content of immunoreactive oxytocin in the plasma, hypothalamus and different limbic structures in the brain were also studied after treatment with cocaine, identical to that used in the behavioural experiment. Repeated administration of cocaine (7.5 mg/kg, s.c.) produced a behavioural tolerance to the stereotyped sniffing-inducing effect of the challenge doses (1.875, 3.75 and 7.5 mg/kg, s.c.) of cocaine on the fifth day, which was demonstrated by parallel shifting of the dose-response and time-effect curves of the test doses of cocaine. The development of tolerance was inhibited by pretreatment with oxytocin (0.05 micrograms, (s.c.), administered before each daily injection of cocaine. A smaller dose of oxytocin (0.005 micrograms, s.c.) had no effect in this model. A decreased amount of immunoreactive oxytocin was detected in the plasma, in the hypothalamus and in the hippocampus, after repeated treatment with cocaine. Replacement of oxytocin by local injection (100 pg) into the ventral hippocampus, before each daily administration of cocaine, prevented the development of tolerance to cocaine. These results suggest that endogenous oxytocin, localized in limbic-forebrain areas, may have an important regulatory role in the development of behavioural changes induced by the repeated administration of cocaine.

Analysis of Variance↗
PubMed1992

Opposite actions of oxytocin and vasopressin in the development of cocaine-induced behavioral sensitization in mice.

Subchronic administration of cocaine induces behavioral sensitization (increasing hypermotility) to a challenge dose of the drug administered 72 h after the cessation of treatment. The effects of repeated administration of the neurohypophyseal hormones oxytocin (OXT) and arginine8-vasopressin (AVP) on the development of behavioral sensitization induced by subchronic treatment with cocaine were investigated in mice. Repeated treatment of OXT and AVP did not modify the locomotor stimulatory effect of the challenge dose of cocaine in cocaine-naive control animals. OXT in a dose of 0.5 microgram (sc) augmented the cocaine-induced behavioral sensitization. In contrast, AVP (0.005-0.5 microgram/mouse, sc) dose dependently attenuated the development of sensitization to the hypermotility-inducing effect of cocaine. The results suggest that the behavioral sensitization induced by cocaine can be modulated in opposite directions by neurohypophyseal hormones.

Animals↗
PubMed1992

Oxytocin blocks the development of heroin-enkephalin cross-tolerance in mice.

The development of cross-tolerance to an analgesic effect has been observed between a mu-receptor agonist, heroin, and a delta-receptor agonist, Met2-Pro5-enkephalinamide. Repeated treatments with heroin twice a day for 4 days resulted in a decreased nociceptive effect to enkephalin on day 5. The enkephalin dose-response line was shifted to the right, considered a sign of the development of cross-tolerance. Peripheral treatment with oxytocin blocked the development of heroin-enkephalin cross-tolerance. A similar effect was observed after intracerebroventricular administration of oxytocin, supporting our assumption that oxytocin blocks the development of heroin-enkephalin cross-tolerance via CNS mechanisms.

Analgesics↗
PubMed1992

Effects of atrial natriuretic peptide on acute and chronic effects of morphine.

Atrial natriuretic peptide (ANP) is known to participate in different vegetative functions. The aim of the present study was to investigate the influence of ANP on nociception itself, pain sensitivity to morphine, and the development of acute and chronic tolerance to morphine. Morphine withdrawal signs were also evaluated by injecting naloxone. In adult, male NMRI mice, ANP administered SC or ICV did not affect pain sensitivity itself in a heat-radiant tail-flick test. Peptide treatment, however, depressed the acute nociceptive effect of a single dose of morphine (4 mg/kg, SC) after both SC (20-200 ng/animal) and ICV (5, 10, 20, or 200 ng/animal) ANP administration. ANP given SC and ICV attenuated the development of acute morphine tolerance. Acute morphine tolerance was assessed by giving a bolus injection of morphine (60 mg/kg) 24 h before the pain sensitivity to a challenge dose of morphine (4 mg/kg) was measured. ICV treatment with ANP also blocked the development of chronic morphine tolerance, but did not affect the appearance of naloxone-precipitated withdrawal syndromes. ANP seems to act differently on the development of tolerance to and dependence upon morphine.

Animals↗
PubMed1992

Effects of cocaine on the contents of neurohypophyseal hormones in the plasma and in different brain structures in rats.

The effects of acute and chronic cocaine treatments on the levels of the neurohypophyseal hormones oxytocin (OXT) and vasopressin (AVP) in the plasma and in different brain structures in rats were measured by radioimmunoassay (RIA). Acute cocaine treatment had no effect on the level of OXT in the plasma or in the amygdala, but increased OXT contents were measured in the hypothalamus and in the hippocampus. The OXT levels in the basal forebrain structures (including the septum and the nucleus accumbens) were decreased by a single dose of cocaine. The acute injection of cocaine increased the level of AVP in the plasma, and decreased contents of OXT were measured in the amygdala and in the basal forebrain. Repeated treatment with cocaine decreased the level of OXT in the plasma, hypothalamus and hippocampus. The AVP contents were decreased in all of the brain structures investigated, but no change was caused in the plasma level of AVP by repeated injections of cocaine. These results demonstrate complex, region-specific interactions between cocaine and the neurohypophyseal hormones in the brain and in the periphery underlying the alteration in behavioral and autonomic functions caused by acute and chronic cocaine exposure.

Amygdala↗
PubMed1992

Bacteriorhodopsin: a picosecond optoelectric signal transducer.

This paper summarizes the results found in our laboratory investigating the ultrafast light-induced charge separation in bacteriorhodopsin. A special technique was elaborated for dried oriented samples of long term stability. An upper limit of 21 ps was found by a direct electric method for the early charge separation processes. A permanent electric field on the surface of illuminated samples was demonstrated. The potential application of such samples as ultrafast optoelectric signal transducers is discussed.

Bacteriorhodopsins↗
PubMed1992

Effects of cocaine and pimozide on plasma and brain alpha-melanocyte-stimulating hormone levels in rats.

The effects of cocaine on rat plasma and brain alpha-melanocyte-stimulating hormone (alpha-MSH) levels have been studied by means of a specific radioimmunoassay. The selected brain areas were the hypothalamus, septum-nucleus accumbens and hippocampus. Cocaine given subcutaneously decreased the alpha-MSH levels in the peripheral blood. Pimozide, a dopaminergic antagonist, had an opposite effect: it increased the alpha-MSH levels in the peripheral blood. Combined treatment with cocaine + pimozide resulted in a decrease in the pimozide-induced increase in alpha-MSH levels in the blood. Cocaine and pimozide or the combination of cocaine + pimozide were ineffective on the alpha-MSH levels in the hypothalamus and septum-accumbens brain regions. In the hippocampus, cocaine in the dose applied induced a slight but not significant decrease in the alpha-MSH level. Pimozide caused a significant decrease in the hippocampal alpha-MSH level which disappeared at 60 min. Cocaine prevented the pimozide-induced depletion of alpha-MSH. The data indicate that cocaine may act as a dopaminergic agonist in the mechanism of control of alpha-MSH secretion from the intermediate lobe of the pituitary. The alpha-MSH levels in the brain are controlled by different mechanisms. In some brain areas, the dopaminergic system has no action; in others the mechanisms might be similar to but slightly different from that in the pituitary.

Animals↗
PubMed1992

[Bone transplantation methods].

Author sums on the basis of the literature of this country and of the international literature the more frequently used methods of bone substitution, their mechanical and biological characteristics. On the basis of the practice of their institute and of the international publications it can be stated that beside the usual transplantation of preserved bone the always increasing clinical claim makes the introduction and the knowledge of other methods also necessary. The advantages and disadvantages of the bone grafts of different types are detailed. It is stated that none of the implantates of different characteristics fulfils perfectly the ideal mechanical and biological requirements. To obtain the possibly best result it is recommended to choose, and on individual indication, the bone substitution method that will fulfil in the given case the requirements desired.

Bone Transplantation↗
PubMed1992

[Enhancement of the ossification of decalcified bone].

Authors have proven with previous experiments that the decalcinated bone can be used as transplant. In this paper their experiments to increase the osteogene capacity of this kind of bone for replacement are described. It is stated that with the use of electric after treatment both the speed of the development of new bone after bone replacement both the rebuilding on the recipient bone ends may be advantageously influenced. With their method the bone defect in the rabbit's radius could be healed in four weeks.

Animals↗
PubMed1992

[Use of biomaterials for preventive and restorative purposes].

At the Dept. of Maxillofacial Surgery, Semmelweis University of Medicine many biomaterials have been used in the last 10 year. Author deals with only three materials, such as solid aluminiumoxyde ceramics, titanium screws and HTR Polymers. The Al2O3 ceramics can be used for the reconstruction of the lower jaws, the condyle and the coronoid process of the mandible as well as for dental implants and for the improvement of the facial contour. This material proved to be the most suitable for the reconstruction of the mandible and TM joint. The titanium screw implant (Flexi-root system) has been used in many hundreds of patients with some 90% success rate. The HTR Polymer has been used in the periodontal surgery, in small and medium size cyst operations and sinus lift procedures. The technique of sinus lift has also been discussed.

Biocompatible Materials↗
PubMed1991

[Osteitis pubis].

Lytic degeneration of the pubic symphysis is a relatively rare entity. The present study is dedicated to the fact that the disease causes numerous diagnostic problems. Authors based on their three cases describe the clinical features and review the literature. It is stated that both from the aspect of the diagnosis and the result of the treatment, operative intervention is beneficial. In contraversion to numerous papers it is found that the described disease is often infectious and can be consequence of an infection of the urinary tract.

Adult↗
PubMed1991

[Fetal growth rate and its variations 1988/89].

Considering that the last intrauterine growth standards were constructed more than two decades ago, the authors defined the measure of 5, 10, 25, 50, 75, 90 and 95 percentiles of birth weight on the base of Genetic and Obstetric Computer Register of East-Hungary, birth data having epidemiological value in Szabolcs-Szatmár-Bereg, Hajdú-Bihar and Jász-Nagykun-Szolnok counties in 1988-89. From the 36th week of pregnancy the mean values of birth weights between boys and girls, boys and gipsy boys, girls and gipsy girls as well as singular and twin newborn infants differed from each other significantly. Possessing these standards, the clinical judgement and supplying of the various newborn infants can be more exact.

Analysis of Variance↗