Studies on Hemolytic Action of a Hemolysin Produced by Vibrio mimicus

Some properties and mechanism of action of a hemolysin (VMH) produced by an enteropathogenic Vibrio mimicus strain was examined. VMH was heat-labile and inhibited by addition of divalent cations, including Ca²⁺, Mg²⁺ and Mn²⁺. The hemolysis by VMH was inhibited by incubating with gangliosides, suggesting that the ganglioside was the binding site on the erythrocyte membrane for VMH. Existence of a galactose moiety on reducing end of the ganglioside molecule and a sialic acid on the galactose moiety was suggested to be important for the binding of VMH molecule. Colloid osmotic manner of the hemolysis by VMH was demonstrated.     

Identification and expression of boar sperm proteins in the reproductive tract that interact with antibodies in serum from an infertile woman

Serum designated as IS obtained from a young healthy infertile woman induced a head-to-head agglutination of ejaculated boar sperm. The immunoglobulin G (IgG) prepared from IS localized to the acrosomal region of the sperm head obtained from the corpus and cauda epididymis as determined by an indirect immunofluorescent method. The IgG interacted with a boar sperm protein with an estimated molecular weight of 45-kDa, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoretic (SDS-PAGE) immunoblotting technique. However, the IgG did not interact with proteins extracted from sperm obtained from the testis and caput epididymis or from non-gonadal tissues including liver, kidney, spleen, muscle and serum. The IgG interacted with additional proteins of about 75- and 38-kDa present in the corpus and cauda epididymal fluids but not those in the caput epididymal fluid. The staining intensity of the 75-kDa band was reduced and that of the 38-kDa was nullified with ejaculated seminal plasma proteins. The interacting proteins were adsorbed when chromatographed on Concanavalin A Sepharose column, suggesting that they are glycoproteins.     

Etinoic acid (vitamin A acid) induces spermatogenesis in adult mouse cryptorchid testes in vitro

Artificially-induced cryptorchid testes of adult mice were cultured $\text{in}\text{vitro}$ in order to study the effects of retinoic acid, a compound considered to be a biochemically inactive in mammalian reporductive function, on testicular germ cell differentiation, especially that of type A spermatogonia. Retinoic acid activated cell division in type A spermatogonia. and stimulate them to differentiate. It is suggested that retinoic acid might play an essential role in the control of early stages in spermatogenesis.     

A lymphocyte blastogenesis inhibitory factor (LBIF) reversibly arrests a human melanoma cell line, A375, at G1 and G2 phases of cell cycle

A lymphocyte blastogenesis inhibitory factor, LBIF, has been found in the culture supernatant of a human macrophage-like cell line, U937. The factor has been purified by fast protein liquid chromatography. Partial amino acid sequencing analysis showed that LBIF was a novel immunoregulatory factor. Recent study has demonstrated that LBIF possesses a remarkable tumor growth inhibitory activity. In this study, the cell growth inhibitory activity of LBIF was characterized on the proliferation of a human melanoma cell line A375 in vitro. LBIF strongly inhibits the proliferation of A375 cells. The inhibitory activity was cytostatic and reversible by Day 5 although the lethal effect became apparent at Day 7. Cell cycle analysis by flow cytometry showed that LBIF arrested A375 cells at both G₁ and G₂/M phases. Mitotic index analysis indicated that A375 cells were arrested in G₁ and G₂ phases. LBIF function was not attributed to the elevation of intracytoplasmic cyclic-AMP levels. Thus, these results suggest that LBIF plays an important role in controlling cell cycle and there is a similarity between the mechanisms of G₁ and G₂ arrests in eukaryotic cell proliferation. LBIF-induced reversible cell-cycle arrest of A375 cells can be a useful system to analyze the signal transduction for cell proliferation and cell-cycle arrest.     

Molecular Cloning, Water Channel Activity and Tissue Specific Expression of Two Isoforms of Radish Vacuolar Aquaporin1

A major membrane intrinsic protein (VM23) in vacuoles of radish(Raphanus) tap root was investigated. The cDNAs for two isoformsof VM23,      

Protein phosphorylation during 1-methyladenine-induced maturation of Asterias oocytes

Maturation was induced in Asterias oocytes with 1-methyladenine (1-MA) at a final concentration of 2 microM. At 5, 10, and 30 min of treatment, oocytes were homogenized and the cytosolic fraction was prepared. The cytosol was incubated with [gamma-32P]ATP and [gamma-32P]GTP. The phosphorylated proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the radioactivity in the gels was determined by autoradiography. The cytosol prepared from 1-MA-treated oocytes incubated with [gamma-32P]ATP showed a marked increase in the radiolabeling of proteins with estimated molecular weights of 70,000 and 62,000 Da. With [gamma-32P]GTP a 56,000-Da protein showed increased radiolabeling. The present finding suggests that an early biochemical event of 1-MA-induced oocyte maturation in Asterias is the stimulation of phosphorylation of specific proteins.     

An improved method for detecting cytostatic toxin (emetic toxin) of Bacillus cereus and its application to food samples

Abstract We developed an improved HEp-2 cell assay method for the detection of Bacillus cereus toxin, which affects the proliferation of HEp-2 cells. The cytostatic toxin was stable upon exposure to heat, pH 2, pH 11 and trypsin, which suggests it is an emetic. Using the HEp-2 cell assay, we examined the distribution and contamination of B. cereus strains that produced an emetic toxin in various foods. Although there were 228 enterotoxin producers among 310 B. cereus strains obtained from foods, 16 of them produced the cytostatic type (emetic toxin). All of the strains that produced the cytostatic toxin were of the H.1 serotype.