Effects of activin A and somatostatin on intact FSH secretion and intracellular Ca2+ concentration in human FSH-secreting pituitary adenoma cells.

Activin A stimulated synthesis and secretion of intact FSH in dispersed human FSH-secreting adenoma cells. Significant stimulation was observed after 24 hr. Activin A caused an increase in Ca2+ concentration ([Ca2+]i). This response occurred soon after the activin A action. These effects were blocked in Ca(2+)-deficient medium and by nitrendipine (5 microM). Somatostatin inhibited the activin A-induced intact FSH secretion and the [Ca2+]i response. These findings indicated that Ca2+ influx through voltage-gated Ca2+ channel was involved in the activin A induced synthesis and secretion of intact FSH.     

Redox titrations of carbon monoxide dehydrogenase from Clostridium thermoaceticum.

Redox titrations of carbon monoxide dehydrogenase (CODH) from Clostridium thermoaceticum were performed using the reductant CO and the oxidant thionin. Titrations were followed at 420 nm, a wavelength sensitive to redox changes of the iron-sulfur clusters in the enzyme. When CODH was oxidized by just enough thionin to maximize A420, two molecules of CO per mole of CODH dimer (4 equiv/mol) reduced the enzyme fully. Likewise, 4 equiv/mol of thionin oxidized the fully-reduced enzyme to the point where A420 maximized. The four n = 1 redox sites which titrated in this region were designated group I sites. They include at least two iron-sulfur clusters, [Fe/S]A and [Fe/S]B, and two other sites, A' and B'. The [Fe4S4]2+/1+ cluster in CODH is included in this group. [Fe/S]B and B' have reduction potentials (at pH 8) below -480 mV vs NHE; [Fe/S]A and A' have reduction potentials above that value. The reduction potential of either [Fe/S]B or B' is near to the CO/CO2 couple at pH 8 (-622 mV). When CODH was oxidized by more than enough thionin to maximize A420, some of the excess thionin oxidized the so-called group II redox sites. These sites have reduction potentials more positive than group I and do not exhibit changes at 420 nm when titrated. Titration of group II sites required 1-2 equiv/mol. EPR of reduced group II sites exhibited the gav = 1.82 signal. When these sites were oxidized, the only signal present had g values at 2.075, 2.036, and 1.983.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of the Epitopes Recognized by Mouse Monoclonal Antibodies Directed to Yersinia enterocolitica Heat-Shock Protein 60

To determine amino acid sequences of the epitopes recognized by monoclonal antibodies (mAbs) 3C8 and 5C3 directed against Yersinia enterocolitica heat-shock protein (HSP60), a dot blot analysis was perfomed using synthesized peptides of Y. enterocolitica HSP60 such as peptides p316-342, p327-359, p340-366, p316-326, p316-321, p319-323, and p321-326 which represent positions of amino acids in Y. enterocolitica HSP60. The dot blot analysis revealed that 5C3 mAb reacted with p316-342, p316-326 and p321-326, and 3C8 mAb p316-342 and p316-326. These results indicate that the epitopes recognized by the mAbs were associated with eleven amino acids, Asp Leu Gly Gln Ala Lys Arg Val Val Ile Asn, of p316-326. The sequence homology between p316-326 of Y. enterocolitica HSP60 and the rest of the HSP60 family suggests that the five amino acids of Lys, Arg, Val, Ile and Asn, which are highly conserved in the HSP60 family, might be related with the epitope recognized by 3C8. In contrast, it was also demonstrated that three amino acids of Leu, Gly and Val, which are not well conserved in the HSP60 family, might be related to the epitope recognized by 5C3.     

Induction of Light Dependent Pyruvate Transport into Chloroplasts of Mesembryanthemum crystallinum by Salt Stress

Mode of photosynthesis in Mesembryanthemum crystallinum changesfrom C₃ to Crassulacean acid metabolism (CAM) when the plantswere stressed with high salinity. [¹⁴C]Pyruvate uptake for 30s into intact chloroplasts isolated from leaves of the CAM modeof M. crystallinum was enhanced more than 5-fold in the lightcompared with that in the dark. The stromal concentration ofpyruvate in the light reached to more than 2.5 times of themedium. In contrast, little or no pyruvate uptake occurred inchloroplasts from C₃ leaves in either light or dark condition.The initial uptake rate (10 s incubation at 4°C) into theCAM chloroplasts in the light was about 3-fold higher than therate in the dark. K_m and V_max of the initial uptake in the lightwere 0.54 mM and 8.5 µmol (mg Chl)^–1 h^–1 respectively.These suggest that pyruvate was actively incorporated into theCAM chloroplasts against its concentration gradient across theenvelope in the light. When hydroponically grown M. crystallinumwere stressed by 350 mM NaCl, the capacity of chloroplasts forpyruvate uptake was induced in 6 d corresponding to the inductionof the activities of PEP-carboxylase and NAD(P)⁺-malic enzymesin response to salt stress. (Received October 12, 1995; Accepted January 19, 1996)     

The effect of rebamipide on gastric xanthine oxidase activity and type conversion in ethanol-treated rats

Rebamipide, a novel antipeptic ulcer drug, 2-(4-chlorobenzoylamino)-3-[2(1H)-quinolinone-4-yl]-propionic acid, was studied for its inhibitory effect on gastric xanthine oxidase activity and type conversion of the enzyme that has a profound role in free radical generation. Intraperitoneal administration of rebamipide at 60 mg/kg body weight reduced gastric mucosal hemorrhagic lesions and lipid peroxidation, which was proportional to the inhibitory effect of rebamipide on alcohol-induced xanthine oxidase-type conversion and enzyme activity. It was also observed that the activity of xanthine oxidase was significantly inhibited by administration of rebamipide at 60 mg/kg body weight, leading to a significant reduction of lipid peroxide content in alcohol-treated rats. The results suggest that alcohol-induced gastric mucosal lesions might be, in part, due to the increased activity of xanthine oxidase and type conversion rate of the enzyme and the protective effect of rebamipide on gastric mucosal lesions would result from its ability to protect against oxidative stress on gastric mucosal lesions of alcohol-treated rats.     

Plasmid formation and its relation to the formation of spontaneously developing pocks in Streptomyces azureus ATCC 14921

Streptomyces azureus ATCC 14921 harboured a plasmid pSA1 together with its chromosomal integrated sequence (pSA1_int). The att P site on the plasmid was located at ca 170 bp Bam HI- Sph I fragment by site-specific integration. The free form was generated from the integrated sequence during the development of its host mycelia in the solid culture, but not in the liquid culture. The free form seemed to elicit the formation of spontaneously developing pocks on its host mycelia in the solid culture.     

Galacto-oligosaccharide production byβ-galactosidase in hydrophobic organic media

Summary Production of galacto-oligosaccharide (GO), including trisaccharide and tetrasaccharide, was performed using a -galactosidase in water-hydrophobic solvent mixtures. A maximum GO concentration of 45% (w/w) was attained in a 95% cyclohexane/5% water mixture from a 55% (w/w) of lactose at 60°C and pH 6.0, while a maximum of 38% GO in aqueous media. GO production decreased with an increase in surfactant concentration. The optimum water content for GO production showed a broad range from 2.5 to 10% (v/v). Solvent properties, such as log P and the dipole moment, had no relation to GO production.