Formation of artifactual DMPO-OH spin adduct in acid solutions containing nitrite ions

We investigated aqueous solutions containing nitrite ions and DMPO (5,5-dimethyl-1-pyrroline-N-oxide) by electron spin resonance (ESR) in the pH range from 1 to 6. A DMPO-OH signal was observed below pH 3.0 in the presence of nitrite ions, whereas in the absence of nitrite ion, an extremely weak signal was observed below pH 1.5. Addition of methanol, a hydroxyl radical scavenger, to this system did not lead to the appearance of a detectable DMPO-CH₂OH signal. The possibility of this DMPO-OH signal being due to a genuine spin trapping process with hydroxyl radical was, therefore, ruled out. The reactivities of reactive nitrogen species (RNS) in this system with DMPO have also been investigated by density functional theory (DFT) at the IEFPCM (water)/B3LYP/6–311?+?G ** level of theory. On the basis of the pH dependence of the signal intensity and the redox potential E° (versus SHE) calculated by DFT theory, we propose that the origin of this signal is “inverted spin trapping” via one-electron oxidation of DMPO by H₂ONO⁺, followed by the nucleophilic addition of water. Prevention of these false-positive results when detecting hydroxyl radical using ESR spin trapping requires an awareness of both the presence of nitrite ions in the solution and the solution pH.     

Cultured bovine endothelial cells convert big endothelin isopeptides to mature endothelin isopeptides

The incubation of big endothelin-1 (big ET-1), big ET-2 or big ET-3 with cultured bovine endothelial cells (ECs) resulted in their conversions to mature endothelins (ETs). These conversions apparently exhibited Michaelis-Menten kinetics as a function of each big ET isopeptide. The conversions of big ETs were abolished by phosphoramidon. These results indicate that vascular endothelium can convert exogenous big ET-1 to mature ET-1 through a phosphoramidon-sensitive metalloprotease, and that this enzyme has also high affinities for big ET-2 and big ET-3.     

Ribonuclease activity of sialic acid-binding lectin from Rana catesbeiana eggs

Sialic acid-binding lectin (SBL) isolated from Rana catesbeianaeggs is a basic protein which agglutinates a large variety oftumour cells and has an amino acid sequence homologous to thatof human angiogenin and pancreatic ribonuclease (RNase). AlthoughSBL and angiogenin lack the Cys-65-Cys-72 disulphide bond ofpancreatic RNase, the locations of the other three disulphidebonds are similar among the three molecules. SBL was found toexhibit RNase activity, as well as catalytic properties resemblingthose of bovine RNase A in some respects. For example, SBL hydrolysespoly(uridylic acid) and poly(cytidylic acid) as substrates,and prefers the former. RNase A and angiogenin are stronglyinhibited by human placental RNase inhibitor, whereas the RNaseactivity and tumour cell agglutination activity of SBL are notaffected by this inhibitor.     

Bevantolol hydrochloride (nc-1400): Absolute configuration and direct separation of the enantiomers

Synthesis of (?)-bevantolol hydrochloride from 3,4-dimethoxyphenethylamine and (S)-(+)-m-tolyl glycidyl ether derived from (R)-(?)-epichlorohydrin established the absolute configuration of the (+) and (?) enantiomer as R and S, respectively. The purity of the enantiomers was determines using a chiral cellulose column (CHIRALCEL OD®) which allowed direct separation of the enantiomers. A separation factor (α) of 4.20 and a resolution factor (Rs) of 9.21 were obtained. © 1995 Wiley-Liss, Inc.     

Multiple subtypes of endothelin receptors in porcine tissues: characterization by ligand binding, affinity labeling and regional distribution.

To clarify the existence and the distribution of endothelin (ET) receptor subtypes, we have examined the pharmacological properties and the molecular weight (Mr) of 125I-ET-1 and 125I-ET-3 binding sites in various tissues of pigs. ET-1 and ET-2 showed almost identical potencies in displacing the bound 125I-ET-1 in all the tissues examined. ET-3, sarafotoxin S6b (SRT-b) and sarafotoxin S6c (SRT-c) displaced the 125I-ET-1 with the same sensitivity as ET-1 (IC50 = 0.1-1.4 nM) in brain, kidney, liver and adrenal, whereas the three peptides showed very weak competition (IC50 = 40-500 nM) against 125I-ET-1 binding in cardiac atria, aorta, lung, stomach and uterus. The computer analyses of the binding data suggested the presence of high (Kd1 = 0.04-0.29 nM) and low (Kd2 = 60-190 nM) affinity binding sites for ET-3 and SRT-b in lung and stomach. 125I-ET-3 bound to the high affinity sites in lung and stomach was displaced by ET/SRT isopeptides almost equipotently. Two proteins with Mr of 47,000 and 35,000 were affinity-labeled with 125I-ET-1 in cerebellum, while a protein with Mr of 123,000, in addition to the two proteins, was predominantly labeled in lung. The above findings indicated that two distinct subclasses of ET receptors, namely, ET-1-specific and ET/SRT family-common receptors were distributed in various proportions in mammalian tissues, and suggested that their molecular forms are also different.     

Cloning and sequence analysis of a cDNA encoding human non-selective type of endothelin receptor.

A cDNA encoding non-selective type (ETB) of endothelin receptor was isolated from a human liver cDNA library. The cDNA had an open reading frame encoding a protein of 442 amino acid residues with a relative Mr of 49,643. The deduced amino acid sequence of human ETB receptor was 88% and 64% identical to those of rat lung ETB receptor and bovine lung ET-1-specific (ETA) receptor, respectively, and contained a relatively long and proline-rich extracellular N-terminal region in addition to a significant similarity with the G protein-coupled receptor super-family with seven transmembrane segments.     

Decreased levels of steroid 21-hydroxylase [P450(c21)] and its mRNA in an adrenocortical adenoma associated with 21-hydroxylase deficiency

Adrenocortical adenoma incidentally found in a 37-yr-old female patient, with simple virilizing form of 21-hydroxylase deficiency, was studied. Cultured adenoma cells revealed excessive secretion of 17 alpha-hydroxyprogesterone in response to 10(-8) M ACTH, compared with those of 11-deoxycortisol and cortisol, which indicated impaired activity of the 21-hydroxylase. To elucidate the molecular mechanisms of this defective 21-hydroxylase in the adenoma, we analyzed the gene encoding specific cytochrome P450 (P450c21) for steroid 21-hydroxylation and its expression. DNA and RNA were extracted from the adrenal adenoma and were hybridized with a probe of human P450c21 gene, by Southern and Northern blot analysis. In Southern blot analysis with Taq I, Bgl II or Bam HI, there was no difference between the pattern of restriction fragments in DNA from the adenoma and normal peripheral leucocytes. Northern blot analysis of the adenoma showed the same size of P450c21 mRNA as in the normal adrenal gland, but the amount was low--about a half that of the normal adrenal. In Western blot analysis with polyclonal antibody to P450c21, only a small amount of P450c21 protein was detected in the adenoma, although it was found to be of the same molecular weight as that in the normal adrenal gland. In view of these findings it is conceivable as one of possibilities that a mild and small mutation in the structural or promotor region of the P450c21 gene may cause the decreased 21-hydroxylase activity in this adenoma.     

NovelN-linked oligo-mannose type oligosaccharides containing an α-d-galactofuranosyl linkage found in α-d-galactosidase fromAspergillus niger

Structures of oligosaccharides fromAspergillus niger -d-galactosidase [EC 3.2.1.22] were studied. Purified -d-galactosidase was treated withN-glycosidase F, and six kinds of oligosaccharides were isolated by gel chromatography and anion-exchange chromatography. The structures of the oligosaccharides were determined by¹H-NMR and compositional analysis to be Man₅GlcNAc₂, Man₆GlcNAc₂, Man₉GlcNAc₂, GlcMan₉GlcNAc₂, GalMan₄GlcNAc₂ and GalMan₅GlcNAc₂. From mild acid hydrolysis, methylation analysis and ROESY spectral analysis, it was ascertained that the galactosyl residue in two oligosaccharides was in the furanose form and was bound to mannose at the nonreducing end with an 1–2 linkage (GalfMan₄GlcNAc₂ and GalfMan₅GlcNAc₂).     

A derivative of befunolol, BFE-55, interacts with only the high affinity sites in beta-adrenoceptors

The effect of BFE-55, a derivative of befunolol (a beta-adrenergic partial agonist) on specific [3H]befunolol binding to a microsomal fraction from the guinea pig taenia caecum was tested. A Scatchard plot of specific [3H]befunolol binding in the absence of BFE-55 was concave, suggesting an existence of high and low affinity sites in beta-adrenoceptors. In contrast, the Scatchard plot of data in the presence of BFE-55 (3 X 10(-7) M) was straight. In the presence of BFE-55, the high affinity sites disappeared and the low affinity site was unaffected. In the absence and presence of BFE-55 there was no difference between the pKD values or Bmax values at the low affinity site. These findings indicate that BFE-55 interacts with only the high affinity sites in beta-adrenoceptors.     

Mechanism of dissociation of cortisol and adrenal androgen secretion after removal of adrenocortical adenoma in patients with Cushing's syndrome

We investigated the mechanism of dissociation of cortisol and dehydroepiandrosterone sulfate (DHEA-S) secretion by the adrenal glands after the removal of an adrenal gland containing an adrenocortical adenoma in a patient with Cushing's syndrome. After removal of the adrenocortical adenoma, the serum cortisol rapidly decreased from 24.6 +/- 6.4 micrograms/dl (mean +/- SD, n = 6) to 0.7 +/- 0.5 micrograms/dl. Serum DHEA-S levels were 15 +/- 14 micrograms/dl and 6 +/- 9 micrograms/dl before and after surgery, respectively, and significantly lower than the control values. Serum cortisol levels reverted to normal levels 1.5 to 3 years after the surgery. On the other hand, DHEA-S levels reverted to normal 5 to 7 years after the serum cortisol levels had normalized. Monolayer cultures of normal human adrenal cells obtained at adrenalectomy in patients with advanced breast cancer and atrophic adrenal cells adjacent to the adrenocortical adenoma in patients with Cushing's syndrome were used to study the mechanism of the dissociation of cortisol and DHEA-S secretion. ACTH caused significant increases in the productions of pregnenolone (P5), progesterone (P4), 17-hydroxypregnenolone (17-OH-P5), 17-hydroxyprogesterone (17-OH-P4), DHEA, DHEA-S, androstenedione (delta 4-A), and cortisol. The amounts of 17-OH-P5 and 17-OH-P4 produced by ACTH in atrophic adrenal cells were significantly greater than those in normal adrenal cells. The amounts of DHEA, DHEA-S and delta 4-A produced by ACTH in atrophic adrenal cells were significantly smaller than those of normal adrenal cells. The conversion rate of 17-OH-[3H]P5 to 17-OH-[3H]P4 and 11-deoxy-[3H] cortisol was higher in atrophic adrenal cells than in normal adrenal cells, but the conversion rate to [3H]DHEA, [3H]DHEA-S and [3H]delta 4-A was significantly lower in atrophic adrenal cells than in normal adrenal cells. These results suggest that the dissociation of cortisol from DHEA-S after the removal of adrenocortical adenoma is a probably due to diminished C17,20-lyase activity in the remaining atrophic adrenal gland.