A resonance Raman study on the interaction of rifampicin with Escherichia coli RNA polymerase

The technique of resonance Raman spectroscopy has been used to investigate the interaction of the antibiotic rifampicin with Escherichia coli RNA polymerase. Spectra were analyzed by generating the first derivative of each recorded spectrum using the Savitsky-Golay algorithm. The only band that shifted significantly in the resonance Raman spectrum of rifampicin upon the formation of the drug-core polymerase complex was the amide III band. It underwent an 8 cm-1 shift from 1306 cm-1 in aqueous solution to 1314 cm-1. A comparable shift was observed for the rifampicin-holoenzyme complex. Thus, the interaction of the sigma subunit with the core polymerase does not significantly alter the manner in which rifampicin interacts with RNA polymerase. The nature of this shift has been analyzed further by recording the resonance Raman spectrum of rifampicin in a variety of solvents with different hydrogen-bonding solvents (benzene and carbon disulfide) the amide III band was observed at approximately 1220 cm-1; in dimethyl sulfoxide, a weak hydrogen-bond acceptor, 1274 cm-1; in water, a strong hydrogen-bonding solvent, 1306 cm-1; and finally, in triethylamine, a stronger hydrogen-bonding solvent than water, it was observed at 1314 cm-1. Thus, as the hydrogen-bonding ability of the solvent increased, the amide III band shifted to higher frequency. Based on these results, the rifampicin binding site in RNA polymerase provides a stronger hydrogen-bonding environment for the amidic proton of rifampicin than is encountered when rifampicin is free in aqueous solution.     

Cross-linking of histone H5 in hen erythrocyte nuclei

Following treatment of hen erythrocyte nuclei with dimethyl 3,3'-dithiobispropionimidate, dimers between histones H1a, H1b, and H5 were extracted with 5% perchloric acid. They resolved electrophoretically into four sub-bands and these were identified by non-reducing/reducing gel electrophoresis. The H5-H5 homodimer species was purified by gel electrophoresis and was treated sequentially with BrCN and dithiothreitol. The pattern of resulting fragments indicates that cross-links were mainly formed between the COOH-terminal portions and at a significantly lower frequency between the COOH-terminal and the NH2-terminal portions.     

Characterization of a substance P-Gly12 amidating enzyme in human cerebrospinal fluid

Enzyme activity capable of converting the glycine-extended substance P precursor, substance P-Gly12, into substance P was purified from human cerebrospinal fluid. The conversion reaction was monitored by radioimmunoassay measurement of substance P formation. The chemical identity of the product was verified by reversed-phase HPLC. The enzyme reaction was stimulated by Cu(II) ion and ascorbic acid and inhibited by the presence of diethyldithiocarbamate. By HPLC molecular sieving, the major enzyme activity appeared as a protein of 26,000 molecular weight.     

Effect of cortisol, its polymeric derivative and adenylate cyclase activators on the content of cyclic AMP in rat thymocytes

In has been shown that cortisol immobilized on polyvinylpyrrolidone (PVP-GC) affects cyclic AMP production stimulated by adenosine and isoproterenol in rat thymocytes. This effect of PVP-GC is specific for cortisol: antiglucocorticoid progesterone (at a concentration of 10(-5) M) inhibited completely the action of PVP-GC on the intracellular cAMP level. It is suggested that cortisol effect on cAMP production is one of the mechanisms of glucocorticoid hormone action in target cells.     

Quantification of human spermatogenesis: germ cell degeneration during spermatocytogenesis and meiosis in testes from younger and older adult men

Germ cell degeneration during spermatocytogenesis and meiosis was investigated to explain the age-related decline in daily sperm production (DSP). Numbers of Types A-dark, A-pale, and B-spermatogonia, potential daily sperm production per g parenchyma (PDSP) based on type B-spermatogonia, early primary spermatocytes, and late primary spermatocytes, and DSP per g based on early spermatids were determined in 15 men aged 20 to 48 yr (mean +/- SEM, 33 +/- 2 yr) and 15 men aged 52 to 90 yr (65 +/- 3 yr). Testes obtained within 15 h of death (largely due to trauma or heart failure) were perfused vascularly with glutaraldehyde. The number of each cell type per g parenchyma was calculated as the product of the percentage of nuclei in the parenchyma times a correction factor for section thickness and nuclear diameter divided by the volume of a single nucleus of that cell type. Paired testicular weight was lower (p less than 0.01) in older men (33 +/- 3 g) than in the younger men (49 +/- 3 g). Younger and older men had similar numbers of A-dark, A-pale, and B-spermatogonia per g parenchyma. PDSP based on late primary spermatocytes and DSP based on early spermatids were lower (p less than 0.01) in older men than in younger men. In younger men, PDSP was similar (p greater than 0.05) between B-spermatogonia and late primary spermatocytes, whereas DSP measured at the spermatid level was abruptly lower than that estimated from younger cell types. Older men showed reduction in PDSP between early and late primary spermatocytes, with further reduction occurring in DSP at the spermatid level.(ABSTRACT TRUNCATED AT 250 WORDS)