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Biomedical subjects

K Barna

Publications and source records attributed to K Barna.

At least 19 recordsLinked to original sources
PubMed2000

Synthesis and conformational studies of poly(L-lysine) based branched polypeptides with Ser and Glu/Leu in the side chains.

In a new group of polypeptides, the branches were composed of DL-Ala oligopeptide, L-serine and L-leucine or L-glutamic acid residues. The synthesis of eight different side-chain combinations is described. In the first group, Ser was attached directly to the epsilon-amino groups of polylysine, and Leu or Glu was situated at the side chain end (poly[Lys(X(i)-DL-Ala(m)-Ser(j))]). Alternatively, Leu or Glu was positioned next to the polylysine backbone (poly[Lys(Ser(j)-DL-Ala(m)-X(i))], where X=L-Leu or L-Glu and m approximately 3-6, i</=1 and j</=1). The second group of polymers was synthesised by grafting oligo(DL-alanine) chains to the epsilon-amino groups of polylysine, followed by coupling of Ser and Leu or Glu consecutively to the chain ends, however, in a different order, resulting in the polymers (poly[Lys(X(i)-Ser(j)-DL-Ala(m))] and poly[Lys(Ser(j)-X(i)-DL-Ala(m))], where X=L-Leu or L-Glu and m approximately 3-6, i</=1 and j</=1). The effect of amino-acid composition and sequence of side chains in branched polypeptides on solution conformation was studied by CD spectroscopy. CD spectra recorded in aqueous solutions of various pH (2-11) and ionic strengths (0.02-2.0 M NaCl) suggest that leucine- and serine-containing polypeptides have more ordered (alpha-helical) structure than the polymers with glutamic acid and serine residues in the same position. The influence of serine residues on ordered structure (helical or beta-sheet) formation depends on its position in the side chain as well as on the nature of amino acid X (Leu or Glu). The incorporation of Ser into the branches resulted in polypeptides possessing prolonged shelf stability and high water-solubility. No toxic effect of this new class of polymers was observed on mouse spleen cells, even after 4 h of incubation.

Animals↗
PubMed1997

Comparison of the lymphoid toxicities of mitobronitol and busulphan in mice: reduced B cell toxicity and improved thymic recovery as possible contributors to the reduced risk for complications following BMT with mitobronitol preconditioning.

It has previously been reported that the use of mitobronitol (dibromomannitol, DBM) instead of busulphan (BU) for myelosuppression is associated with significantly decreased risk for several complications of allogeneic bone marrow transplantation in accelerated chronic granulocytic leukemia. In exploring the pharmacologic basis for this observation, we have compared the acute and subacute cytotoxicities of DBM and BU on the spleen and thymus of mice. While there was comparable early (day 3) weight loss in both organs following these treatments, splenic B cells exhibited significantly less damage, and thymic regeneration (over weeks) was significantly faster following DBM treatment than with BU. These observations raise the possibility that improved post-BMT immune recovery could contribute to the clinical benefits observed with DBM-preconditioning.

Animals↗
PubMed1991

[Peroxidative effects of tetracycline antibiotics].

After six-day administration of rolitetracycline (RTC) in the cardiac mitochondria of old rabbits the rate of oxygen consumption (glutamate-malate as well as 2-oxoglutarate) declines, while the malonic dialdehyde (MDA) rises. This provides evidence of more intense lipoperoxidation due to rolitetracycline. However, the ATP-ase activity increases and therefore this parameter is unsuitable in this experimental set-up (presence of tetracycline antibiotic) as an indicator of impaired integrity of mitochondrial membranes. After administration of RTC the activity of superoxide dismutase (SOD) increases markedly, but in case of concurrent administration of vitamin E it declines which is evidence of the prooxidative action of tetracyclines. Tetracycline itself and its metabolites which are formed during the biotransformation and degradation of epianhydrotetracycline (ETC) do not alter significantly the oxygen consumption nor the ATP-ase activity in cardiac mitochondria of old rabbits in vitro. Of these metabolites only anhydrotetracycline (ATC) and in particular epianhydrotetracycline (EATC) inhibit both parameters. From experiments in vitro ensues the relationship between the action and structure of the antibiotic and its metabolites the structure of cycle C and the nature of the substituents in positions C6 and C1 of this tetracycline cycle, as prerequisites are created for the formation of prooxidative structures.

Aging↗
PubMed1991

[The effect of tetracycline and vitamin E on energy metabolism in cardiac mitochondria of old rabbits pretreated with isoproterenol].

The possibility of eliminating adverse effects of tetracycline and isoproterenol pretreatment on energy generation of myocardial mitochondria by vitamin E administration was investigated in old rabbits. Vitamin E administered in doses of 1.5 mg per kg body weight over 6 days was found to improve energy metabolism in old rabbits whose metabolism had been deranged by isoproterenol pretreatment in the dose of 1.5 mg per kg body weight. Subsequent administration of vitamin E to rabbits pretreated with isoproterenol and tetracycline in doses of 15 mg per kg body weight daily over 6 days also resulted in improvement of energy metabolism parameters studied. Under the given conditions vitamin E was found to exert a protective effect on oxidative phosphorylation of the myocardium damaged by isoproterenol and tetracycline.

Adenine Nucleotides↗
PubMed1985

[Angiosarcoma of the liver following brief arsenic therapy].

Hepatic angiosarcoma developed in a 46-year-old man, who had had 7-months of arsenic therapy 24 years before. The role of arsenic in the etiology of angiosarcoma of the liver is well know, although rarely has it followed such a brief period of arsenic therapy.

Arsenic↗
PubMed1980

Serologic studies of hepatitis viruses for their aetiologic role in chronic liver disease.

Serum samples from 130 patients with chronic (persistent or active) hepatitis, including cirrhosis, and 70 patients with chronic alcoholic disease, all confirmed by biopsy, were examined by counter electrophoresis (CEP) for HBsAg. The patients were residents in the South-Transdanubian region of Hungary. Of the former 25%, of the latter 3%, proved positive. In 138 of the cases, 4 different tests were performed, viz. CEP, complement fixation, reverse passive haemagglutination (RPH) and radioimmunoassay (RIA). The results were positive in 24, 36, 43 and 60%, respectively, in chronic hepatitis and in 4, 6, 8 and 14%, respectively, in cases of alcoholic origin. Serum samples from the same patients were tested for anti-HBs and anti-HBc. Positive anti-HBs was found in 24% of the patients with chronic hepatitis and in 26% of those with alcoholic liver disease. The presence of anti-HBc was demonstrated in 42% and 38%, respectively. Joint evaluation of RPH-positive and anti-HBc positive cases on the one hand and of RIA-positive and anti-HBc positive cases on the other resulted in 68% and 71% HB virus-related positivity, respectively. The present study failed to furnish evidence in support of the presence of hepatitis A virus of its involvement in the aetiology of chronic liver disease.

Adolescent↗
PubMed1980

Levamisole treatment of acute viral hepatitis and HBsAG-positive chronic active hepatitis.

A fundamental role is attributed to the pathological immune response in the development of chronic hepatitis B. By virtue of its non-specific immune modulatory effect, levamisole is capable of improving impaired T-cell function. Hence, studies with treated and control groups were performed in determine the effect of levamisole in acute viral hepatitis and chronic active hepatitis B. In acute hepatitis B, levamisole promoted the normalization of GPT, the elimination of HBsAg; this improvement was preceded by higher GPT values and increased titres of IgG, IgA, and of anti-HBcore. In chronic active hepatitis in the first few months of treatment a moderate increase of the GPT and HBsAg levels occurred, followed later by a decrease of these values. At the same time the phytohaemagglutinin reactivity of lymphocytes increased, and so did the ratio of circulating active T-cells.

Acute Disease↗
PubMed1979

Cellular immune responses and lymphocyte populations in chronic hepatitis.

Cellular immune responsiveness was examined in chronic persistent hepatitis, chronic active hepatitis and alcoholic liver disease by the use of the lymphocyte transformation test in response to PHA and to allogenic liver mitochondria, inhibition of leukocyte migration, delayed-type skin tests and non-immunospecific granulocyte function tests. Lymphocyte markers, E and EAC rosette forming cells were used for the study of lymphocyte populations. The results have confirmed that the T-cell borne cell-mediated immune function is impaired in chronic active hepatitis, as also in a number of cases of chronic persistent hepatitis.

Adolescent↗