Conformational analysis of a chain reversal in alpha-chymotrypsin

A complete conformational analysis of the fold (Asp-Lys-Thr-Gly) (residues 35-38), and additional adjacent residues of alpha-chymotrypsin has been performed. A comparison of these findings with those of Lewis et al. (1) is made, and a discussion of the implications of protein-fold models is discussed. This particular residue sequence prefers to bend over maintaining a helical conformation. However, the bend conformation of the tetramer is different from that of the native bend. The native bend conformation is nearly realized when an additional residue of the native primary structure is added to each side of the tetramer. Early and late folding-sequence studies suggests that while the native fold is of low energy, there are fold-points along the primary structure which are more stable. The structural implications of this finding are discussed.     

Digoxin bioavailability: formulations and rates of infusions

22 patients with atheromatous narrowing of the left coronary trunk underwent surgery between 1969 and 1974. Most of these patients had severe and incapacitating angina pectoris. The clinical features are readily explained by the size of the diffuse anatomical lesions, which are to be found on the left coronary trunk as well as on the three coronary vessels themselves. This series has not confirmed the serious risk of surgery in such cases, as there were no operative deaths. Secondary mortality was low (9%), and the 20 survivors (average length of follow-up: 26 months) were mostly (18/20) in an excellent condition functionally. These facts have lead us to advise surgery whenever possible.     

Suppressive role of B cells in chronic colitis of T cell receptor alpha mutant mice

The role of antibodies (Abs) in the development of chronic colitis in T cell receptor (TCR)-alpha-/- mice was explored by creating double mutant mice (TCR-alpha-/- x immunoglobulin (Ig)mu-/-), which lack B cells. TCR-alpha-/- x Ig mu-/- mice spontaneously developed colitis at an earlier age, and the colitis was more severe than in TCR-alpha-/- mice. Colitis was induced in recombination-activating gene-1 (RAG-1-/-) mice by the transfer of mesenteric lymph node (MLN) cells from TCR-alpha-/- x Ig mu-/- mice. When purified B cells from TCR-alpha-/- mice were mixed with MLN cells before cell transfer, colitis did not develop in RAG-1-/- mice. Administration of the purified Ig from TCR-alpha-/- mice and a mixture of monoclonal autoAbs reactive with colonic epithelial cells led to attenuation of colitis in TCR-alpha-/- x Ig mu-/- mice. Apoptotic cells were increased in the colon, MLN, and spleen of TCR-alpha-/- x Ig mu-/- mice as compared to Ig mu-/- mice and TCR-alpha-/- mice. Administration of the purified Ig from TCR-alpha-/- mice into TCR-alpha-/- x Ig mu-/- mice led to decrease in the number of apoptotic cells. These findings suggest that although B cells are not required for the initiation of colitis, B cells and Igs (autoAbs) can suppress colitis, presumably by affecting the clearance of apoptotic cells.     

N-substituted octahydro-4a-(3-hydroxyphenyl)-10a-methyl-benzo[g]isoquinolines are opioid receptor pure antagonists

N-Methyl- and N-phenylethyl-(+/-)-1,2,3,4,4a,5,10,10a- octahydro-4a-(3-hydroxyphenyl)-10a-methyl-benzo[g]isoquinolines (4 and 5, respectively) were found to be pure opioid antagonists. These compounds were shown to share many of the characteristics identified with the N-methyl- and N-phenylethyl trans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine (1 and 2, respectively) including N-substituent mediated potency and a lack of N-substituent mediated antagonism. These data suggest that compounds 4 and 5 and the N-substituted trans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidines (1 and 2) may interact with opioid receptors similarly.     

Comparison of traditional and molecular methods for typing nontoxigenic strains of Corynebacterium diphtheriae

Thirty-eight nontoxigenic strains of Corynebacterium diphtheriae isolated between 1987 and 1992 from clinical specimens of French patients were typed by biotyping, antibiograms, bacteriophage typing, ribotyping, and restriction analysis by pulsed-field gel electrophoresis (PFGE). Excellent correlation occurred between the genotypes defined by PFGE SfiI profiles or by ribotype BstEII profiles. Genotyping revealed seven genotype patterns among the 26 biotype mitis isolates, five among the nine biotype gravis isolates, and three among the three biotype belfanti isolates. Phage typing was nonreactive for nine of the 38 isolates. A combination of all the typing methods led to the identification of 19 different types of Corynebacterium diphtheriae.     

In vivo effects of fumonisin B1-producing and fumonisin B1-nonproducing Fusarium moniliforme isolates are similar: fumonisins B2 and B3 cause hepato- and nephrotoxicity in rats

Orellanine, [2,2'-bipyridine]-3,3',4,4'-tetrol-1,1'-dioxide, is the toxin responsible for the lethal nephrotoxicity of some Cortinarius mushrooms. Our present ESR and spin-trapping studies of the redox properties of the system of non-illuminated orellanine, ferrous iron and dioxygen contribute to understanding the molecular mechanism of its toxicity. UV-visible spectrophotometry, cyclic voltammetry and ESR in frozen medium showed the formation of a wine-red tris complex, Fe(III)Or3. This ferric complex is easily reducible (Ep = -565 mV vs Ag/AgCl/3M KCl at pH 7), involving a one-electron reversible process. Spin-trapping using DMPO is employed to detect the generation of superoxide anion and hydroxyl radicals. The instantaneous one-electron oxidation of ferrous ions in the presence of the toxin under air is concomitant with dioxygen consumption as supported by dioxygen consumption. GSH involves the toxin and ferrous ions under air in a redox cycling process resulting in the production of glutathionyl and oxygen free radicals, observed for the first time with an iron complex of a mushroom toxin. In most cases, EDTA is not able to prevent the Fe(III)Or3 and radical formation. The ortho-dihydroxylated groups borne by the di-N-oxidized bipyridine structure and not the bipyridine structure itself, are responsible for the formation of a stable ferric complex at pH 7, as they are for the generation of an apparently stable ortho-semiquinone anion radical. These one-electron mechanisms may play a major role in some of the known toxic effects of orellanine.     

Salicylic acid induces a cytosolic Ca2+ elevation in yeast

Cytosolic free calcium ion concentration ([Ca2+]cyt) after a salicylic acid (SA)-stimulus was monitored in cells of the yeast Saccharomyces cerevisiae expressing apoaequorin, which constitutes a Ca(2+)-sensitive luminescent protein, aequorin, when combined with coelenterazine. SA induced a transient [Ca2+]cyt elevation that was dependent on the concentration of SA and pH of the SA solution. The SA-induced [Ca2+]cyt elevation was not reduced in Ca(2+)-deficient medium, suggesting that Ca2+ was mobilized from an intracellular Ca2+ store(s). Benzoic acid, butyric acid and sorbic acid did not induced a [Ca2+]cyt elevation.