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Biomedical subjects

I Szabó

Publications and source records attributed to I Szabó.

At least 19 recordsLinked to original sources
PubMed1992

A patch-clamp study of Bacillus subtilis.

In patch-clamp experiments on giant protoplasts of the Gram-positive bacterium Bacillus subtilis, membrane stretch resulted in an initial transient collapse of the membrane resistance, after which stretch-activated, voltage modulated, high-conductance channels could be observed. The channel open probability increased exponentially with applied suction and positive voltage, as a result of variations of both the mean open and the mean closed times. The substate structure and other characteristics of the electrical activity suggested the presence of a family of pores exhibiting cooperative behavior. A role in osmotic protection is suggested. In the intact bacteria, the pores may be part of an unidentified envelope apparatus, having other functions as well.

Bacillus subtilis↗
PubMed1992

[Comparative study of preoperative chemotherapy and radiotherapy in squamous cell carcinoma of the oral cavity].

The results of the preoperative Co 60 irradiation and BVMM (bleomycin, vincristine, mitolactol, methotrexate) chemotherapy were compared. Both treatments were used in 50-50 advanced squamous cell cancer of the oral cavity. The general condition, size of lesion and age of the patients were similar. Surgery in the irradiated group was significantly more radical at the primary sites. Local recurrences during a three-year follow-up period were diagnosed in 36% from the radiotherapy group, whilst 8% such recurrences diagnosed in the chemotherapy group. There was no significant difference in the radicality of lymph node surgery. Lymph node recurrences occurred in 8% from the irradiated group, whilst 22% was diagnosed in the chemotherapy group. The main opinion is that BVMM chemotherapy and irradiation can be used to support one another in the interest of better result, like preoperative chemo- and postoperative radiotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1992

Modulation of the mitochondrial megachannel by divalent cations and protons.

In patch-clamp experiments on rat liver mitoplasts, the 1.3 nanosiemens (in 150 mM KCl) mitochondrial megachannel was activated by Ca2+ and competitively inhibited by Mg2+, Mn2+, Ba2+, and Sr2+. Cyclosporin A, which inhibits the megachannel, also showed a competitive behavior versus Ca2+. The pore is regulated by pH in the physiological range; lower pH values cause its closure in a Ca(2+)-reversible manner. The modulating sites involved in these effects are located on the matrix side of the membrane. As illustrated in the companion paper (Bernardi, P., Vassanelli, S., Veronese, P., Colonna, R., Szabó, I., and Zoratti, M. (1992) J. Biol. Chem. 267, 2934-2939), the calcium-induced permeability transition of mitochondria is affected by these various agents in a similar manner. The results support the identification of the megachannel with the pore believed to be involved in the permeabilization process. The kinetic characteristics of the single channel events support the idea that the megachannel is composed of cooperating subunits.

Animals↗
PubMed1992

Modulation of the mitochondrial permeability transition pore. Effect of protons and divalent cations.

We have studied the induction of the mitochondrial cyclosporin A-sensitive permeability transition pore (PTP) by the bifunctional SH group reagent phenylarsine oxide (PhAsO). Addition of nanomolar concentrations of the electroneutral H(+)-K+ ionophore nigericin to nonrespiring mitochondria in sucrose medium determines a dramatic increase of the time required for PTP induction by PhAsO, while no effect of nigericin is apparent in KCl medium. Using mitochondria loaded with the internal pH indicator 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, we show that the effect of nigericin is mediated by the ionophore-induced acidification of matrix pH. Indeed, experimental manipulation of pHi by a number of treatments indicates that PTP induction is directly related to matrix pH, in that the PTP induction process becomes slower as pHi decreases at constant pHo. PTP induction by PhAsO in respiration-inhibited mitochondria is stimulated by Ca2+ and inhibited by a series of divalent cations. Since PhAsO induces the PTP even in the presence of excess EGTA and in the absence of respiration (Lenartowicz, E., Bernardi, P., and Azzone, G.F. (1991) J. Bioenerg. Biomembr. 23, 679-688), we have been able to study the Ca2+ dependence of the induction process. We show that the apparent Km for Ca2+ activation is about 10(-5) M and that Ca2+, cyclosporin A, and inhibitory Me2+ ions behave as if they were competing for the same binding site(s) on the pore. Since similar results are obtained from patch-clamp experiments on the mitochondrial megachannel (Szabó, I., Bernardi, P., and Zoratti, M. (1992) J. Biol. Chem. 267, 2940-2946), we suggest that (i) the PTP and the mitochondrial megachannel are the same molecular structures and (ii) the same factors affect both the process of pore induction and its open-closed orientation.

Arsenicals↗
PubMed1992

Determination of mephenytoin stereoselective oxidative metabolism in urine by chiral liquid chromatography employing beta-cyclodextrin as a mobile phase additive.

A direct high-performance liquid chromatographic assay was developed for the separation and determination of S- and R-mephenytion enantiomers in human urine. Separation was achieved on a Supelcosil LC-8 column with methanol-0.1 M acetate buffer as the mobile phase and beta-cyclodextrin as a mobile phase additive. The urinary S/R enantiomeric ratio of mephenytoin was measured in a 32-h urine sample (as phenotypic traits) for determination of the ability of normal subjects to hydroxylate racemice mephenytoin after oral administration of the drug.

Administration, Oral↗
PubMed1992

The mitochondrial megachannel is the permeability transition pore.

Single-channel electrophysiological recordings from rat liver mitoplast membranes showed that the 1.3-nS mitochondrial megachannel was activated by Ca++ and inhibited by Mg++, Cyclosporin A, and ADP, probably acting at matrix-side sites. These agents are known to modulate the so-called mitochondrial permeability transition pore (Gunter, T. E., and Pfeiffer, D. R. (1990) Am. J. Physiol. 258, C755-C786) in the same manner. Furthermore, the megachannel is unselective, and the minimum pore size calculated from its conductance is in agreement with independent estimates of the minimum size of the permeabilization pore. The results support the tentative identification of the megachannel with the pore believed to be involved in the permeabilization process.

Adenosine Diphosphate↗
PubMed1992

Effect of flumecinol (Zixoryn) on the cytochrome P450 and cytochrome P448 dependent hepatic microsomal monooxygenase activities in male rats.

The effect of three-day oral administration of 50 mg/kg bw. and 100 mg/kg bw. flumecinol (Zixoryn, Gedeon Richter Chemical Works Ltd., Budapest, Hungary) and intraperitoneal administration of 50 mg/kg bw. phenobarbital as well as the single intraperitoneal administration of 20 mg/kg bw. 3-methylcholanthrene on various cytochrome P450 and P448 dependent hepatic microsomal enzyme activities was studied in male albino Wistar rats. 50 mg/kg bw. flumecinol had no significant effect. 100 mg/kg bw. flumecinol had an inducing effect comparable to the one of phenobarbital. The activity of the cytochrome P448 dependent 7-ethoxyresorufin O-deethylase was enhanced by all three substances, but flumecinol's effect was by far behind that of 3-methylcholanthrene, so the carcinogenic promoter effect of flumecinol can be questioned.

Administration, Oral↗
PubMed1992

Improvement of the reproductive performance of sows by treatment with a GnRH superactive analogue.

The effect of a Hungarian-made superactive analogue of GnRH (Ovurelin, D-Phe6-GnRH-EA, Reanal, Hungary) on the postpartal sexual function of sows was monitored. GnRH treatment was carried out on day 19 before weaning. The sows were inseminated at the first oestrus after weaning. GnRH treatment markedly increased litter size at weaning, substantially reduced (to 25 and 50%, respectively) the number of sows failing to come into oestrus after weaning, and increased the number of sows coming into oestrus within one week after weaning by 42.5% and 9%, respectively. These beneficial effects were particularly apparent on the far using closed management technology.

Animals↗
PubMed1992

[Effect of interferon and interferon combined with 3-methylcholanthrene on the mixed function oxidase system in the liver of mice].

The authors have studied the effect of human interferon alpha alone, as well as its effect when co-administered with 3-methylcholanthrene, on the mixed function oxidase system (MFO) of mouse liver. The single interferon alpha treatment did not influence the activities of MFO. However it decreased significantly the enzyme-inducing effect of 3-methylcholanthrene during combined treatment.

Animals↗
PubMed1991

[D-penicillamine does not affect the liver and kidney function in newborn infants nor the in vitro function of phagocytes].

D-penicillamine was introduced to treat neonatal hyperbilirubinaemia in 1973 and to prevent retinopathy of prematurity in 1980. In this study we investigated the renal and liver functions of neonates treated with DPA and the in vitro effect of the drug on superoxide anion generation and beta-glucuronidase release as well as on phagocytic and intracellular killing activation on human peripheral blood granulocytes. Our data concerning the renal and liver functions before and after 3 to 4 days DPA treatment reveal no pathological change during short-term administration in the neonatal period. Furthermore, none of the examined DPA concentrations influenced the phagocytic or killing activity of neutrophils.

Humans↗
PubMed1991

The giant channel of the inner mitochondrial membrane is inhibited by cyclosporin A.

In patch-clamp experiments on rat liver mitoplasts, cyclosporin A inhibited the activity of the recently described (Petronilli, V., Szabó, I., and Zoratti, M. (1989) FEBS Lett. 259, 137-143) 1.3-nanosiemens channel of the inner mitochondrial membrane at concentrations in the 10(-8)-10(-7) M range. The inhibitor acts when present on the matrix side of membrane. The Ca2(+)-dependent "permeability transition channel" of mitochondria is inhibited by cyclosporin A in the same concentration range. The results suggest therefore that the same pore is responsible for the permeabilization of the inner mitochondrial membrane and for the conduction of the high currents observed in electrophysiological experiments.

Animals↗
PubMed1991

Modulation of type II Fc gamma receptor expression on activated human B lymphocytes.

We have monitored Fc gamma RII expression during the activation of human B lymphocytes by simultaneous analysis of monoclonal antibody (mAb) binding and EA rosetting. The expression of Fc gamma RII showed a biphasic time course. Initially, a transient increase of Fc gamma RII with no ligand-binding capacity was observed with mAb staining as early as 10 min after stimulation by the F(ab')2 fragment of anti-human IgM or phorbol 12-myristate 13-acetate and then after 3 to 24 h a decrease in the number of Fc gamma RII+ cells was seen. Trypsin-like serine protease activity also appeared in the lysate of activated B cells at this time. On the 2nd day of activation a significant enhancement of Fc gamma RII expression was observed, mainly on enlarged blast cells as monitored by both mAb and by ligand binding (EA rosette). At the same time, soluble fragments of Fc gamma RII with the ability to bind human Fc were detected in the supernatant of activated B cells, probably as a result of proteolytic cleavage. These findings suggest that activated B cells are identical with the population of mononuclear cells which shed Fc gamma R when incubated at 37 degrees C. The ability of activated but not resting B cells to release Fc gamma RII correlates with the expression of early activation markers and with the appearance of a trypsin-like serine protease activity of the same cells; thus, the release of Fc gamma RII occurs in the early G1 phase of cell cycle as a result of proteolysis. Later the release of Fc gamma RII is accompanied by the enhancement of Fc gamma RII expression before the cells reach the S phase. The fragments of cleaved Fc gamma RII had an apparent molecular mass of 33 and 14-18 kDa under nonreducing conditions, and upon reduction fragments of smaller size were observed.

Antigens, CD↗
PubMed1991

Human paraoxonase polymorphism: Hungarian population studies in children and adults.

The paraoxonase phenotype distribution pattern was studied in a Hungarian population of 102 children and 100 adults. All the subjects were of Caucasian origin and are not related. The adult population showed the trimodality in phenotype distribution similar to other European population data. The gene frequencies obtained were statistically not significantly different either. There was no correlation between the activity of serum paraoxonase and activity of cholinesterase, sex, age and body weight. The phenotype distribution was trimodal in the children's population too. There was a significant difference in gene frequency, however, compared to data from adult population.

Adolescent↗
PubMed1991

Effect of treatment with Prolan or with a GnRH superactive analog on the sexual function of sows after weaning.

On a large, closed pig farm using artificial insemination (AI), 29 sows were treated with Prolan S-öl injection (Bayer, FRG) and 31 sows with a GnRH superactive analog (Ovurelin, D-Phe6-GnRH-EA, Reanal, Hungary) 48 h after weaning. The effect of treatment on the sows' sexual function was monitored by serum progesterone radioimmunoassay (RIA). The conception rate in the control group (36 sows) was 69.4%. In the groups treated with Prolan and Ovurelin it was 79.3 and 71%, respectively. The use of Prolan S-öl injection markedly reduced the number of acyclic sows and of those having an irregular oestrous cycle. Treatment with the GnRH analog inhibited the manifestation of weaning-induced heat; subsequently, however, it induced a regular cycle in 30 out of the 31 sows treated.

Animals↗
PubMed1990

ADP-ribosylation of membrane proteins of Streptomyces griseus strain 52-1.

Membranes purified from cells of Streptomyces griseus strain 52-1 possess an ADP-ribosyltransferase activity. The enzyme transfers the ADP-ribose moiety of NAD to one major membrane protein of Mr 32,000 and 2-3 minor proteins of larger molecular weights. The effects of inhibitors on the ADP-ribosyltransferase activity proves that the reaction is enzymatic and suggests that the enzyme ADP-ribosylates the guanidine group of arginine. The kinetics of liberation of ADP-ribose during alkaline hydrolysis of the modified proteins is consistent with the arginine-ADP-ribose bond. This is the first report of ADP-ribosylation of proteins in a Gram-positive bacterium.

Bacterial Proteins↗
PubMed1990

Effect of aminoglycoside antibiotics on the autolytic enzyme of Streptomyces griseus.

The isolated cell wall of Streptomyces griseus 52-1 strain labelled with fluorescein isothiocyanate (FITC) and containing wall-bound autolytic enzyme was lysed as a function of different cations. The autolysis was accelerated by aminoglycoside antibiotics (streptomycin and the structurally closely related neomycin) which have a polycationic character. Since this strain is a streptomycin producer it is suggested that streptomycin may have a regulatory function on autolysis.

Amidohydrolases↗