Biomedical subjects
Publications and source records attributed to J Nagy.
A mutant of Escherichia coli K-12 carrying a deletion in the aroG-nadA region of the genome requires a high concentration of iron for growth. The strain is chromium sensitive, and in the presence of citrate lower concentrations of iron support cell growth. The deletion mutant lost a gene between aroG and nadA that is responsible for the uptake of iron.
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The dehydrogenase activity of chorismate mutase-prephenate dehydrogenase, the allosteric enzyme of the tyrosine biosynthetic pathway in Escherichia coli, is inhibited by tRNA. The inhibitory effect of tRNA from E. coli is specific, other RNA species or polynucleotides have no inhibitory effect or only slightly influence the activity of the enzyme. While NAD only slightly influences the inhibitory effect of tRNA from E. coli, prephenic acid at high concentrations suppresses the inhibition. In he presence of a fixed concentration of NAD and low concentration or absence of prephenic acid the inhibitory effect of tRNA is time and temperature dependent. It seems that in the presence of tRNA and low concentration of prephenate the enzyme undergoes a time and temperature dependent conformational change. This process is reversible and can be influenced by the concentration of prephenic acid, the first precursor of the tyrosine biosynthetic pathway. The possible regulatory role of allosteric enzyme-tRNA complexes is discussed.
The authors report a case of chronic aggressive hepatitis associated with persisting HBs (Australia) antigenaemic nephrosis. The disease proved to be membranous glomerulonephritis. Immune fluorescence revealed granular type IgG, IgM, C3 and HBs antigen deposits along the glomerular basement membrane. The IgA deposit was partly linear, partly granular. Subepithelial deposits were noted by electron microscopy along the glomerular basement membrane. It is supposed that the deposition in the glomeruli of HBs antigen-antibody immune complex was responsible for the diffuse membraneous glomerulonephritis.
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Rabbit skeletal muscle phosphorylase b was investigated by the dielectric dispersion method in different media. Comparison of calculated and measured relaxation times revealed the effective molecular diameters to be higher than published earlier. Using an estimated value of 4 A for the thickness of the hydration layer of the protein, a good agreement was obtained between the calculated and measured relaxation times. On the basis of these calculations and measurements the molecular dimensions of hydrate phosphorylase b were taken for 118 X 74 X 63 A. Dispersion measurements suggested that the volume of a subunit was smaller than the half volume of the dimeric form.
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One component (rearing) of the stereotyped behavior of the rat was quantitated using erigometer, a new device developed in this laboratory. Intraperitoneal injection of atropine, but not methylatropine, caused dose-related stereotyped behavior in the rat and this effect was antagonized by intracaudate injection of triperidol in a dose-related manner. It is concluded that stereotypy can be evoked also in the case when the striatal dopaminergic tone is normal or even below normal: it is the equilibrium of the striatal cholinergic-dopaminergic systems which must be shifted towards dopamine, which is necessary for the development of this behavioral manifestation.
The chemiluminescence associated with phagocytic and intracellular killing activity of human polymorphonuclear leucocytes and monocytes was investigated. A significant, opsonization-dependent increase in photon emission of polymorphonuclear leucocytes and monocytes was observed induced by engulfment of opsonized, heat-killed and living fungi (Saccharomyces cerevisiae), aggregated gamma globulin, latex and India ink particles. Mononuclear cells displayed only minimal enhancement of photon emission after incubation of various particles. It is suggested that the method can be used in clinical practice as a test of phagocytotic and intracellular killing function.