Identification of N-[p-(2-benzimidazolyl)phenyl]maleimide-modified residue participating in dynamic fluorescence changes accompanying Na+,K+-dependent ATP hydrolysis

Na+,K+-ATPase from pig kidney was specifically modified with a sulfhydryl fluorescent reagent, N-[p-(2-benzimidazolyl)phenyl]maleimide (BIPM), by pretreatment of N-ethylmaleimide. The preparation thus obtained retained 100% of initial Na+,K+-ATPase activity and contained 1 BIPM residue/alpha-chain, and it showed almost 2-fold larger fluorescence changes accompanying ATP hydrolysis than the previous preparations which retained 60% of initial activity and contained 3-4 BIPM residues/alpha-chain (Taniguchi, K., Suzuki, K., and Iida, S. (1982) J. Biol. Chem. 257, 10659-10667). Extensive trypsin (Sigma type I) treatment of the new preparation produced mainly two different fluorescent peptide peaks in both ion-exchange and reverse-phase chromatography. Amino acid sequence analysis of both peptides showed that they had the same common sequence, Ser-Tyr-X-Pro-Gly-Met-Gly-Val, except that the larger one contained Ala-Leu next to the Val residue. From the comparison of the amino acid sequence deduced from cDNA from sheep kidney (Shull, G. E., Schwartz, A., and Lingrel, J. B. (1985) Nature 316, 691-695), X was shown to correspond to Cys-964 of the alpha-chain in Na+,K+-ATPase. The data suggest that the microenvironment of the BIPM residue covalently bound to the sulfhydryl group of Cys-964 changes accompanying sequential appearance of reaction intermediates of Na+,K+-ATPase.     

Atrial natriuretic factor increases cyclic GMP and inhibits cyclic AMP in rat renal papillary collecting tubule cells in culture

The present study was undertaken to determine whether human atrial natriuretic factor (hANF) produces guanosine-3', 5'-monophosphate (cGMP) and alters arginine vasopressin (AVP)- and forskolin (F)- induced adenosine-3', 5'-monophosphate (cAMP) production in the cultured rat renal papillary collecting tubule cells. hANF increased cellular cGMP levels in a dose dependent manner. AVP and F, however, did not affect cGMP production. hANF significantly inhibited AVP- and F-stimulated cAMP levels, but hANF by itself did not affect cellular cAMP production. Since F activates adenylate cyclase at a step of catalytic unit and the cellular action of AVP to activate adenylate cyclase is mediated through receptor-catalytic units, the present results indicate that hANF may directly inhibit the AVP- and F-stimulated adenylate cyclase in renal papillary collecting tubules.     

Isolation of porcine follicular fluid inhibin of 32K daltons

Purification of ovarian inhibin from porcine follicular fluid was performed by using an bioassay based upon the suppression of spontaneous FSH release from cultured cells of rat anterior pituitary. The presence in the follicular fluid of four molecular forms of inhibin activity corresponding to Mr 100K, 80K, 55K and 32K was revealed by SDS-gel electrophoresis under non-reducing conditions. The smallest inhibin amongst them, named 32K inhibin, eliciting about 70% of the total activity in the follicular fluid, was separated by gel filtration in the presence of 8 M urea. By subsequent ion-exchange chromatography, followed by RP-HPLC, 32K inhibin was purified to homogeneity with a 8,000 fold purification factor in a yield of 12%. The purified 32K inhibin was found to comprise two polypeptide subunits (Mr 20K and 13K), linked by disulfide bridges and to specifically suppress the secretion of FSH, but not of LH from the pituitary cells.     

Atrial natriuretic polypeptide-like immunoreactivity in the rat pituitary: light and electron microscopic studies

Immunoreactive atrial natriuretic polypeptide (ANP) was investigated in the pituitary of rats by light and electron microscopy using the indirect immunofluorescence and peroxidase-antiperoxidase techniques. ANP-like immunoreactivity was present in 30-35% of anterior pituitary cells. These cells have two types of secretory granules being characteristic of rat gonadotrophin-storing granules, and were usually adjacent to the capillary endothelium. The results of this study suggest the co-occurrence of ANP and gonadotrophins in the anterior pituitary cells.     

Neuromedin K: a novel mammalian tachykinin identified in porcine spinal cord

A new peptide, designated "neuromedin K" has been discovered and isolated from porcine spinal cord by using bioassays for a tachykinin-like effect on the contractility of smooth muscle preparation from guinea-pig ileum. Porcine neuromedin K has been identified by microsequencing as: Asp-Met-His-Asp-Phe-Phe-Val-Gly-Leu-Met-NH2. The sequence thus determined has been confirmed by synthesis. Neuromedin K has been found to have not only a remarkable sequence homology to kassinin and substance P, but also a prompt stimulant activity on guinea-pig ileum in a manner similar to that of substance P, suggesting that neuromedin K may be involved in neural transmission.     

Characterization of a new fetal hemoglobin variant, Hb F Izumi A gamma 6Glu replaced by Gly, by molecular secondary ion mass spectrometry

Molecular secondary ion mass spectrometry has characterized the structure of a new fetal hemoglobin variant, Hb F Izumi, without separation of peptides or amino acid analysis. First, the mass spectrum of a tryptic digest of the abnormal gamma globin revealed a decreased by 72 mass units in the molecular mass of peptide T-1,2, indicating the presence of a Glu leads to Gly substitution. Next, the analysis of the digest produced by the addition of staphylococcal protease, which specifically cleaves glutamyl peptide bonds, determined the site of substitution at 6th glutamic acid residue in peptide T-1,2 which contains two glutamic acid residues. Since this mass spectrometric approach provides digitalized data on peptide analysis, we call it 'digit printing'. The high sensitivity of this technique is especially promising for the analysis of molecular abnormality in various genetic disorders.     

Isolation of Mycoplasma and Ureaplasma species from raccoon dogs (Nyctereutes procyonoides viverrinus)

Mycoplasma spp. were isolated from five wild raccoon dogs (Nyctereutes procyonoides viverrinus). On the basis of biochemical properties and serological tests, nine isolates were identified as Mycoplasma edwardii and four were similar to a possibly new Mycoplasma sp. represented by strain LM2 which is negative for both glucose fermentation and arginine hydrolysis. In addition, ureaplasmas were detected from these animals. Ureaplasmas were compared serologically with ureaplasma strains isolated from human, monkey, cattle, goat, sheep, cat, chicken and dog and cross-reacted with one of four serological groups of canine ureaplasmas.