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Biomedical subjects

Z Lengyel

Publications and source records attributed to Z Lengyel.

35 records · Page 2Linked to original sources
PubMed1997

The role of disulfide bond C191-C220 in trypsin and chymotrypsin.

Serine proteases of the chymotrypsin family contain three conserved disulfide bonds: C42-C58, C168-C182, and C191-C220. C191-C220 connects the loops around the substrate binding pocket. Using site directed mutagenesis, cysteines of this disulfide bridge were replaced by alanines in trypsin, in chymotrypsin, and in Tr-->Ch-[S1+L1+L2+Y172W], a mutant trypsin with high chymotrypsin like activity. The functional role of this "active site" disulfide was assessed by comparing the catalytic properties of wild-type and mutant enzymes. Its removal from all three proteases caused a decrease in kcat/KM of two to three orders of magnitude, mainly as a consequence of a dramatic increase in KM. The pH dependence of the activity also changed: the rather wide pH optimum, characteristic of the wild-type enzymes (especially trypsin), narrowed since the pKa in the alkaline region shifted downwards. Results show that C191-C220 is necessary for the high activity of both trypsin and chymotrypsin. By contrast, elimination of this disulfide bridge greatly decreased the specificity of trypsin and of Tr-->Ch-[S1+L1+L2+Y172W], but had no significant change on that of chymotrypsin.

Amino Acid Sequence↗
PubMed1996

Chronic aluminum treatment results in aluminum deposits and affects Ml muscarinic receptors in rat brain.

The effects of chronic aluminum (Al) administration on the deposition of the metal and on the receptor binding characteristics of the Ml muscarinic acetylcholine receptors (MlAChR) were studied in selected rat brain areas. Animals were injected intraperitoneally with an AlCl3 solution of 1.0 mg/ml/100 g of body weight for 5 weeks, 5 days a week. Al accumulation was detected by solochrome azurine histochemistry in the brain, where the metal could be visualized in capillaries, endothelial cells and surrounding brain tissues. Changes in the binding properties of the MlAChR after chronic Al treatment were determined with the use of selective and nonselective muscarinic antagonists. Significantly decreased number of maximal MlAChR binding sites (Bmax) as measured by the equilibrium binding of [3H]pirenzepine, were detected in all of the brain areas examined. While the nonselective antagonist [3H] (-)QNB displayed a generally decreased Bmax, value, it reached the level of significance only in the striatum. These results provide a further indication that chronic Al treatment results in the accumulation of Al in the brain and consequently affects the cholinergic neurotransmission.

Aluminum Chloride↗
PubMed1995

Cholinotoxic effects of beta-amyloid (1-42) peptide on cortical projections of the rat nucleus basalis magnocellularis.

Beta-amyloid(1-42) peptide (betaAP) was injected into the right nucleus basalis magnocellularis (nbm) of rats. After a 14-day survival time, the acetylcholinesterase and choline acetyltransferase activities and the number of muscarinic receptors were found biochemically to be significantly reduced in the ipsilateral frontal cortices. Confirmation of these data with silver staining also revealed degeneration of the projective fibers of the nbm to the frontal cortex. These results demonstrate the cholinotoxicity of betaAP in an in vivo animal model.

Acetylcholinesterase↗
PubMed1986

The effect of adrenalectomy on the proteinuria of spontaneously hypertensive rats and normotensive controls.

Urinary proteins were studied by quantitative and electrophoretic methods in 6-month-old spontaneously hypertensive rats and normotensive controls. Protein analysis was carried out before and after adrenalectomy and during gluco- or mineralocorticoid treatment. Urinary protein excretion was significantly diminished after adrenalectomy both in the hypertensive and control groups. The original level of protein excretion was restored only by glycocorticoid treatment. Normal or pathologic electrophoretic pattern of urinary proteins was not influenced by the experimental procedure. Moderately non-selective glomerular proteinuria persisted in the spontaneously hypertensive rats referring to a definitely damaged glomerular barrier. One protein fraction of about 130,000 dalton molecular weight disappeared from the urine of hypertensive animals after adrenalectomy and reappeared after glucocorticoid treatment only. This fraction probably represents the dimeric form of albumin. Quantitative changes of urinary protein excretion can be explained by haemodynamic factors.

Adrenal Cortex Hormones↗
PubMed1977

[Syringomyelia with severe osteo-articular changes].

Attention was drawn to a patient after admission to the Central Institute of Oncology, and syringomyelia was diagnosed on the basis of X-ray films taken by the author. The deformations were symmetrical and they were localized in the area of innervation of the C VI, VII, D I segment. The radiological diagnosis was proved by the neurological examinations.

Bone Diseases↗
PubMed1977

Synthesis of vitamin B12 by various species of mycobacteria.

The synthesis of Vitamin B12 by five reference strains of species of mycobacteria, the influence of cobalt upton the synthesis and the correlation between the phase of growth and quantitative biosynthesis of Vitamin B12 were studied. Assays were performed on cell extracts and culture filtrates using Lactobacillus leichmannii ATCC7830 (tube method). All five species synthesized Vitamin B12, which could be deomonstrated both in cell extracts and in the culture filtrates. An optimum accumulation of Vitamin B12 by BCG and M. phlei could be observed on the 30th day of cultivation. Addition of cobalt did not influence the growth of BCG and M. phlei, but markedly enhanced the production of Vitamin B12. Cells contained much more Vitamin B12 than culture filtrates did. Vitamin B12 levels in M. smegmatis, M. fortuitum and M. asiaticum were lower than those in BCG and M. phlei.

BCG Vaccine↗
PubMed1976

[Evaluation of lymphography in neurologic complications of neoplastic diseases (author's transl)].

1. By lymphographic examination, first of all, the primary and secondary tumours of the lymphatic system may be revealed and localized. Further on, it makes possible to state the stage of the disease and thus to apply the appropriate treatment. 2. In case of symptoms indicating that nerve-roots of unknown origin have been damaged, the result of lymphographic examination may call the attention to pathomechanism related to some tumour-disease. If the symptoms of the nervous system are caused by compression or infiltration of a tumour, most frequently the presence of pathologic lymph nodes in their surroundings can be revealed. 3. Among the patients of the National Oncological Institute, in 25 Hodgkin and 2 cases pathologic filling of the lymphatic system was observed by lymphographic examination, -- in 4 cases in the surroundings affected by the damage of the spinal cord while in 23 cases in that of nerve-root. If a tumour disease is discovered and localized in time by lymphographic examination, the symptoms caused by it in the nervous system may be reduced, or, seldom, even alleviated, with a treatment of directed irradation combined with cytostatics. The favourable effect on alleviating pains is to be especially emphasised.

Adolescent↗