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Biomedical subjects

M Ledvina

Publications and source records attributed to M Ledvina.

At least 73 records · Page 4Linked to original sources
PubMed1979

Preparation and isolation of dityrosine.

A new procedure for the isolation of dityrosine has been developed. Tyrosine was oxidized by means of incubation both with hydrogen peroxide and horse-radish peroxidase. The reaction mixture was separated by permeation chromatography on Sephadex G-10 being monitored at 280 and 310 nm spectrophotometrically. The dityrosine fraction was freeze-dried and purified on a cation-exchange column (in acidic citrate buffer). The purified fraction was desalted and freeze-dried. The yield was 96 mg of homogenous dityrosine per 1 g of D,L-tyrosine. Some physico-chemical constants of the preparation were measured (optical characteristics with U.V. and I.R. spectra, fluorescence spectra, chromatography on an amino acid analyzer).

Chromatography, Gel↗
PubMed1979

The content of dityrosine in chick and rabbit aorta proteins.

The possible presence of dityrosine in elastin derived by two different methods and in structural glycoproteins from aortas of 1 day old chicks, adult rabbits and fetal rabbits was determined by a sensitive spectrofluorimetric procedure. Only chick tissues were found to contain dityrosine, 0.3 residues/100,000 total amino acid residues in aortic elastin and 12-15 residues/100,000 residues in the structural glycoproteins. No dityrosine could be detected in any of the fetal or mature rabbit tissues. However, related fluorescent compounds with different excitation-emission maxima and different elution times were obtained by ion exchange chromatography of structural glycoproteins partially hydrolyzed under alkaline conditions.

Aging↗
PubMed1978

A comparative study of two isolation procedures for elastin and contaminating substances in fetal and adult rabbit aortas.

A quantitative study of the individual steps in the isolation of elastin from mature and fetal aortas of rabbits was carried out. The proportions of insoluble residue and acetone- and ether-soluble substances were determined. The yields of elastin and other associated components of connective tissue derived from the aortas by two different isolation procedures were compared, i.e. the classical Lansing treatment with hot alkali and the less drastic procedure described by Rasmussen et al. Results were found to be strongly influenced by the method used. The purity of the elastin preparations was evaluated by means of amino acid analyses for relative contents of desmosines and dicarboxylic amino acids. The possible reasons for the differences found are discussed.

Amino Acids↗
PubMed1978

Influence of D-penicillamine on the formation of elastin and its cross-links.

The amount of insoluble elastin and its content of desmosine cross-links were investigated in aortas of chick embryos, to which D-penicillamine was administered on the 6th or 14th--16th day of incubation. D-Penicillamine was shown to alter the formation and maturation of elastin. Using lower doses (less than 50 mg) the weight of pooled aortic elastin is higher as compared with controls (related to 1 mg of elastin or to total weight of elastin). Increased isodesmosine:desmosine ratio in these samples indicates that this elastin is very young. On the other hand, a high dose of D-penicillamine (100 mg) decreased the content of elastin and also of its desmosine cross-links. The authors explain their findings by counteraction of two factors due to administration of penicillamine: the increased solubility of "insoluble elastin", and the decreased cross-link formation.

Amino Acids↗
PubMed1978

The changes in pharmacokinetics and conjugation of chloramphenicol in irradiated rats.

In the serum and the liver of rats levels of chloramphenicol (CAP) following its i.v. administration (200 mg/kg) in the control groups and in the rats irradiated with whole-body air exposure to 500 R were determined with spectrophotometric methods. The CAP-levels in the serum increased in the group of rats 3 days after irradiation, but only during the 1st hour. At later time intervals the values were lower than in the controls. This decrease at the 60th min is striking even in the groups 6 and 9 days after exposure. Free CAP in the liver of rats irradiated 6 and 9 days before was lower at interval 30 min after CAP-administration, but the group irradiated 9 days before was unaltered. However, 120 min after CAP-administration the values of free CAP decreased at all intervals investigated following the irradiation. The levels of conjugated CAP in the liver of the rats 3 and 6 days after exposure were lower than in controls in both intervals after drug administration; but in rats 9 days after irradiation they increased. Our results indicate that the kinetics of CAP is altered and corresponding changes in its conjugation are effected under the condition of acute radiation syndrome.

Animals↗