Irreversible inhibition of the human placental NADP-linked 15-hydroxyprostaglandin dehydrogenase/9-ketoprostaglandin reductase by glutathione thiosulfonate

Oxidation of glutathione disulfide by a mixture of performic and hydrochloric acids leads to the formation of several compounds that are stronger inhibitors than glutathione disulfide of the placental enzyme that possess both NADP-linked 15-hydroxyprostaglandin dehydrogenase and 9-ketoprostaglandin reductase activities. The only one of these inhibitors that has been identified is glutathione thiosulfonate. The others are unstable and may include glutathione sulfinyl sulfone and glutathione disulfone. Since the enzyme appears to have a glutathione binding site in close proximity to its active site and glutathione thiosulfonate reacts with free sulfhydryl groups, the effects of this thiosulfonate on the enzyme were examined in more detail. Glutathione thiosulfonate and methyl methanethiosulfonate cause a time-dependent irreversible inhibition of both the hydroxyprostaglandin dehydrogenase and the ketoprostaglandin reductase activities, presumably by reacting with a free sulfhydryl at the prostaglandin binding site. Experiments with PGA1-glutathione show that this sulfhydryl is not necessary for the catalytic activity of the enzyme as long as the substrate can bind at the glutathione site.     

Deactivation ofCandida rugosa lipase

Summary Deactivation ofCandida rugosa lipase was found to be complex. Hydrophobic interaction induced by iso-octane influenced the initial phase of deactivation, and increased the turn-over rate of the intermediate in the transition phase. After urea-treatment the structure of the last phase was not further influenced by thermal treatment, whereas that of initial phase was more sensitive to temperature change. Charge interaction was important in maintaining the structure during the deactivation, and especially anion charge might be a major factor.     

Cleavage of territrems by alkaline hydrogen peroxide: Isolation and characterization of the aromatic moiety of territrems

The chemical reaction of cleavaging territrem B to give 3,4,5-trimethoxy benzoic acid by alkaline hydrogen peroxide was investigated. The method was applied for confirmation of the chemical structure of the aromatic moiety of territrem A, A’, B, and B’. The physicochemical properties of the aromatic cleavage product of territrem Aindicated the structure as 3,4-methylendioxy, 5-methoxy benzoic acid (or 4-methoxy, 6-carboxy, 1, 3-benzodioxole). The experiment also gave the evidences that territrem A and A’, on the other hand territrem B and B’ have the identical aromatic moieties on their structures.     

Human immunodeficiency virus neutralizing antibodies recognize several conserved domains on the envelope glycoproteins.

Serum neutralizing antibodies against the human immunodeficiency virus were frequently detected in infected individuals, and low or absent serum neutralizing titers correlated with poor prognosis. Multiple diverse human immunodeficiency virus isolates were found to exhibit similar susceptibility to neutralization by a panel of human seropositive sera, suggesting that neutralizing antibodies are largely directed against conserved viral domains. Furthermore, utilizing antisera raised against a library of synthetic env peptides, four regions which are important in the neutralization process have been identified within both human immunodeficiency virus envelope glycoproteins (gp41 and gp120). Three of these are in conserved domains and should be considered for inclusion in a candidate vaccine.     

Effects of alcohol feeding on androgen receptors in the rat pituitary gland

Specific binding of testosterone-1 beta, 2 beta-3H by cytosol from anterior pituitary gland of alcohol-fed, isocaloric control, and castrated control and alcohol-fed rats with or without testosterone treatment has been investigated by charcoal assay. The number of androgen binding sites was significantly reduced in alcohol-fed rats (8 +/- 1.0 fmoles/mg cytosol protein), when compared to the isocaloric control value (13.2 +/- 2.1 fmoles/mg protein), with no significant change in Kd (0.7 +/- 0.14 nM). Castration significantly increased the number of receptor sites in control rats and when castrated control animals were treated with testosterone the binding sites were decreased to the intact control level. In contrast, castration or testosterone given to castrated alcohol-fed rats did not alter alcohol-induced reduction of the receptor sites. The binding affinity (Kd) is identical in all groups. The concentration of serum luteinizing hormone (LH) was significantly lower in alcohol-fed rats when compared to that of normal controls. An increased serum LH level with a decreased testosterone level was noted in castrated control rats. However, castration of alcohol-fed rats had little or no effects on the concentrations of LH and testosterone. Administration of testosterone suppressed castration-induced high LH in control rats but alcohol-induced reduction of LH level was not altered by this treatment. These findings indicate that alcohol exerts a suppressive effect on the content of androgen receptors and secretory functions of gonadotropins in the pituitary gland.     

The pancreatic glucagon and C-peptide secretion during hyperinsulinemia in euglycemic glucose clamp with or without somatostatin infusion in normal man

6 normal subjects received two times of 2 hr euglycemic glucose clamp studies (insulin infusion rate 40 mU/M2/min) one with and the other without somatostatin (SRIF) infusion (500 microgram/hr). Serum C-peptide and glucagon levels were measured during clamp to study the sensitivity of pancreatic alpha and beta cells to the suppressive effects of exogenous hyperinsulinemia during normoglycemia in normal subjects and to find whether SRIF had any modulative effects on endocrine pancreas secretion at the status of hyperinsulinemia. The results showed that in normal man the degree of suppression of pancreatic glucagon secretion by hyperinsulinemia (approximately 100 uU/ml) during euglycemic glucose clamp without SRIF infusion was less than that of C-peptide with mean value of 62 +/- 4% of basal glucagon remained at the end of clamp study; while only about 30 +/- 2% of basal C-peptide concentrations remained. But during SRIF infused glucose clamp studies (SRIF was infused from 60 to 120 min), 32 +/- 2% of mean basal C-peptide concentrations and 38 +/- 6% of mean basal glucagon concentrations left at the end of 2 hr clamp studies when serum insulin level was about 100 uU/ml. For the glucose infusion rate (M value), it was significantly greater in our normal subjects in response to insulin + SRIF as compared to insulin alone (12.0 + 0.9 vs 8.8 +/- 1.4; P less than 0.01). We concluded: during hyperinsulinemia (100 uU/ml), the sensitivity of pancreatic alpha cells to insulin seems less than that of beta cells in normal man at normoglycemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tn4556, a 6.8-kilobase-pair transposable element of Streptomyces fradiae.

A 6.8-kilobase-pair (kbp) transposable element (Tn4556) was found in a neomycin-producing strain of Streptomyces fradiae. This element was first observed in two 30.3-kbp plasmids (pUC1123 and pUC1124) which arose when a thiostrepton resistance gene (1 kbp) was ligated with the BclI-2 fragment (22.5 kbp) that contains the origin of replication of phage SF1. The Tn4556 segment was deleted when these plasmids were transduced into another S. fradiae host with phage SF1. These deletion plasmids (pUC1210 and pUC1211) had copy numbers of less than 1 per chromosome and were unstable. In contrast, pUC1123 and pUC1124, with copy numbers of 12 to 15 per chromosome, respectively, were relatively stable. When pUC1210 and pUC1211 were reintroduced into S. fradiae by protoplast transformation, the Tn4556 element transposed again to the plasmids at numerous new locations in either of two orientations. A copy of Tn4556 was found in the S. fradiae chromosome by hybridization studies. It appears that Tn4556 originated from the chromosome, transposed into unstable pUC1210 and pUC1211, and made stable plasmids. A temperature-sensitive hybrid plasmid carrying a viomycin resistance derivative of Tn4556 (pMT660::Tn4556::vph) was constructed. When Streptomyces lividans UC8390 containing the hybrid plasmid was grown at 39 degrees C, Tn4556::vph (Tn4560) transposed to random positions in the host chromosome.