HPLC-studies on nonmercapt-mercapt conversion of human serum albumin

Human mercaptalbumin (HMA) and nonmercaptalbumin (HNA) could be separated by high-performance liquid chromatography (HPLC) at neutral pH. Using HPLC, the present authors found the nonmercapt-mercapt conversion (HNA----HMA) during hemodialysis and the mercapt-nonmercapt conversion (HMA----HNA) after hemodialysis in chronic renal failure, indicating HMA as the covalent carrier protein for sulfur-containing amino acids.     

Distribution and serological specificity of sialidase produced by various groups of streptococci

The occurrence of a streptococcal sialidase (designated St-sialidase) in culture fluids of various streptococci was investigated. St-sialidase was found to occur in strains belonging to groups A, B, C, E, G, H, and L, and the unclassified strains, Streptococcus sanguis and Streptococcus uberis. St-sialidase of group A was confined predominantly to types 4 and 22. St-sialidases, extracted from the culture fluids of some selected strains, were antigenic, eliciting the formation of antibody which effectively neutralized the enzymatic activity of the enzyme. Antisera to the St-sialidases of groups A, B, C, E, G, and L, and Streptococcus sanguis were produced in rabbits. The St-sialidases of groups A, B, and E streptococci were serologically distinct and group-specific. The St-sialidases from groups C, G, and L were serologically homologous, but distinct from St-sialidases of the other groups. Antiserum to the enzyme of strain 10557 (S. sanguis) cross-reacted with the St-sialidase of strain 9927 (S. uberis).     

Sialidase-like Enzymes Produced by Group A, B, C, G, and L Streptococci and by Streptococcus sanguis

A group of enzymes were prepared from the culture fluids of streptococci belonging to groups A, B, C, G, and L, and from a strain of Streptococcus sanguis. These streptococcal enzymes (designated St-sialidases) released a substance shown to belong to the sialic acid group from the specific substrate BSM-St, a sialomucoid prepared from bovine submaxillary gland. They were inactive on N-acetylneuramin lactose prepared from bovine colustrum and on a sialomucoid prepared from bovine submaxillary mucin, whereas these substances are susceptible to sialidases produced by group K streptococci and by Vibrio cholerae. Some of the St-sialidases were markedly activated by divalent cations, but others showed little response. The heat stability of the enzymes produced by the different strains varied. The optimal pH was between 5.5 and 6.5 with acetate buffer and was about 7 with phosphate buffer. K(m) values were determined for the St-sialidases with BSM-St as substrate.     

ET-1-induced bronchoconstriction is mediated via ETB receptor in mice

Nagase, Takahide, Tomoko Aoki, Teruaki Oka, YoshinosukeFukuchi, and Yasuyoshi Ouchi. ET-1-induced bronchoconstriction ismediated via ET_B receptor in mice.J. Appl. Physiol. 83(1): 46-51, 1997.Endothelin (ET)-1 is one of the most potent agonists of airwaysmooth muscle and can act via two different ET receptor subtypes, i.e.,ET_A andET_B. To determine the effects ofET-1 on in vivo pulmonary function and which ET receptors are involved in murine lungs, we investigated 1)the effects of ET and sarafotoxin S6c (S6c), a selectiveET_B agonist, on pulmonary functionand 2) the effects of BQ-123 andBQ-788, specific ET_A- andET_B-receptor antagonists, onET-1-induced bronchoconstriction. ICR mice were anesthetized and mechanically ventilated (frequency = 2.5 Hz, tidalvolume = 8 ml/kg, positive end-expiratory pressure = 3 cmH₂O). Intravenous ET-1, ET-2,and ET-3 increased lung resistance similarly and equipotently, whereasS6c elicited a greater degree of bronchoconstriction. Mice were thenpretreated with saline (Sal), BQ-123 (0.2, 1, and 5 mg/kg), or BQ-788(0.2, 1, and 5 mg/kg) before administration of ET-1(10⁷ mol/kg iv). No dose ofBQ-123 blocked ET-1-induced constriction, whereas pretreatment witheach dose of BQ-788 significantly inhibited ET-1-induced responses.There were significant differences in morphometrically assessed airwayconstriction between Sal and BQ-788 and between BQ-123 and BQ-788,whereas no significant difference was observed between Sal and BQ-123.There were no significant morphometric differences in the airway wallarea among the three groups. These observations suggest that theET_B- but notET_A-receptor subtype may mediatethe changes in murine pulmonary function in response to ET-1. Inaddition, the ET_B-receptorantagonist reduces ET-1-induced airway narrowing by affecting airwaysmooth muscle contraction in mice.

     

Characterization of Methanosarcina mazeii TMA isolated from a paddy field soil

We isolated a methanogenic strain, designated as strain TMA (=DSM 9195), from an enrichment culture inoculated with a Japanese paddy field soil. Strain TMA was Gram positive and strictly anaerobic. Cell shape was pseudosarcina-like, and cells were nonmotile. The strain was able to use methylamines, methanol, H₂–CO₂, and acetate as substrates for methanogenesis, but did not utilize formate. The optimum temperature and optimum pH were 30–37°C and 6.5–7.5 respectively. The G+C content of the DNA was 42.1 mol %. Strain TMA had DNA-DNA hybridization values of more than 80% with Methanosarcina mazeii S-6^T (T = type strain). On the basis of phenotypic and genotypic characteristics, we identified strain TMA as M. mazeii. This is the first methylotrophic methanogen isolated from a paddy field soil and identified to the species level.     

Cell-Free Synthesis of a Putative Precursor of Polygalacturonase in Tomato Fruits

By using a monospecific anti-polygalacturonase-2 antibody, a54K-dalton polypeptide was detected in in vitro translationproducts by a wheat germ cell-free translation system programmedwith polyadenylated RNA from ripe tomato pericarp tissue. Thisputative precursor of polygalacturonase was about 9K daltonslarger in molecular weight than polygalacturonase-2. (Received December 12, 1983; Accepted May 17, 1984)     

Effect of ethylene on DNA synthesis in potato tuber discs

The effect of ethylene on DNA synthesis in potato tuber discsinduced by cutting was examined. Continuous presence of ethylenein the ambient atmosphere of the slices lowered the rate ofinduced DNA synthesis by about 50%, but did not alter the timecourse pattern of development of DNA synthesis. RNA and proteinsyntheses were not affected. The inhibitory effect on DNA synthesiswas observed at as low as 0.01 µl/liter and was due tothe specific action of ethylene, not to a non-specific actionof gaseous hydrocarbons. Ethylene also decreased the numberof cells which could synthesize DNA. The results of ethylenetreatment of various durations at various times after cuttingindicate that a process prerequisite for DNA synthesis and susceptibleto ethylene action starts at about 6 hr after cutting and continuesfor only a limited period. (Received July 5, 1976; )