Circular dichroism study of NaSCN effect on conformation of poly-L-lysine

Effects of NaSCN, urea and KCl on alpha, beta and random conformations of poly-L-lysine (PLL) in water at room temperature were examined and compared quantitatively on the basis of the rotational strength of maximal peak by means of circular dichroism (CD) measurement. Alpha and beta helical conformational change of PLL was markedly concentration dependent in both the cases of NaSCN and urea, but not KCl. Among these salts, the distortion potency of millimolar concentrations of NaSCN on both alpha and beta conformations was undoubtedly several hundred times stronger than for the other salts, showing a slightly lesser effect on the alpha conformation as compared with that on the beta helical one, while there was no significant effect on random conformations even in maximal salt concentrations. The concentration required to alter the peptide conformation was substantially smaller for urea than for KCl, but both urea and KCl exhibited more effectiveness on alpha than beta conformation in contrast to NaSCN throughout the respective concentrations.     

The Gene Encoding Flavanone 3-Hydroxylase is Expressed Normally in the Pale Yellow Flowers of the Japanese Morning Glory Carrying the speckled Mutation Which Produce Neither Flavonol nor Anthocyanin but Accumulate Chalcone, Aurone and Flavanone

The Japanese morning glory carrying the recessive mutable speckledallele with the dominant speckled-activator bears colorlessflowers with fine and round colored spots distributed over thecorolla whereas the plant without the speckled-activator producespale yellow flowers. Previous chemical analysis has indicatedthat a mutation in the gene for flavanone 3-hydroxylase (F3H)is a likely candidate for the speckled allele. However, theF3HmRNA without sequence alteration accumulates normally inthe pale yellow flowers, indicating that the speckled alleleis neither the F3H gene nor a regulatory gene acting on theF3H gene expression. (Received April 4, 1997; Accepted June 2, 1997)     

Ibaraki Virus,an Agent of Epizootic Disease of Cattle Resembling Bluetongue

Replication of Ibaraki virus was not inhibited by 5-iodo-2′-deoxyuridine, indicating that the virus is an RNA virus. The virus was resistant to ether, chloroform and deoxycholate, sensitive to trypsin, very labile at acidic pH but stable at pH 6.4 or higher, and was resistant to repeated freezing and thawing. The virus was readily inactivated at 56 C or higher, was fairly stable at 37 C, and very stable at 4 C, while it rapidly lost infectivity when stored frozen at —20 C. The virus was readily sedimented by centrifugation at 40 000Xg for 60 min. It readily passed through membrane filters of 200 mμ pore size, passed through 100 μfilters but only with some titer loss and did not through 50 mμ filters. In these tests, the bluetongue virus used as a control behaved in the same manner as Ibaraki virus. These findings provide additional evidence for the similarity of Ibaraki virus to bluetongue virus which had been previously demonstrated on the basis of seasonal incidence, symptomatology and pathology of the diseases caused by these viruses and the behavior of the viruses in cell cultures, embryonated eggs and laboratory animals. The present study, however, provided no evidence for any serological relation between these two viruses. More Information is needed to reach a final decision on the classification of Ibaraki virus, particularly regarding the morphology of the virion, the doublestrandedness of the viral RNA and other basic features.     

Involvement of aquaporin in thromboxane A2 receptor-mediated, G12/13/RhoA/NHE-sensitive cell swelling in 1321N1 human astrocytoma cells

The physiological role of the thromboxane A₂ (TXA₂) receptor expressed on glial cells remains unclear. We previously reported that 1321N1 human astrocytoma cells pretreated with dibutyryl cyclic AMP (dbcAMP) became swollen in response to U46619, a TXA₂ analogue. In the present study, we examined the detailed mechanisms of TXA₂ receptor-mediated cell swelling in 1321N1 cells. The cell swelling caused by U46619 was suppressed by expression of p115-RGS, an inhibitory peptide of Gα_12/13 pathway and C3 toxin, an inhibitory protein for RhoA. The swelling was also inhibited by treatment with Y27632, a Rho kinase inhibitor and 5-(ethyl-N-isopropyl)amiloride (EIPA), a Na⁺/H⁺-exchanger inhibitor. Furthermore, cell swelling was suppressed by the pretreatment with aquaporin inhibitors mercury chloride or phloretin in a concentration-dependent manner, suggesting that aquaporins are involved in U46619-induced 1321N1 cell swelling. In fact, U46619 caused [³H]H₂O influx into the cells, which was inhibited by p115-RGS, C3 toxin, EIPA, mercury chloride and phloretin. This is the first report that the TXA₂ receptor mediates water influx through aquaporins in astrocytoma cells via TXA₂ receptor-mediated activation of Gα_12/13, Rho A, Rho kinase and Na⁺/H⁺-exchanger.     

Analysis of the mode of antigen presentation required for triggering of T cell proliferation by using various azobenzenearsonate-tyrosine derivatives

Various azobenzenearsonate-tyrosine (ABA-Tyr) derivatives were synthesized by modifying amino and carboxyl groups at the alpha-carbon of tyrosine, with preservation of most of the ABA-Tyr moiety (ABA plus hydroxyphenyl portion of tyrosine). These derivatives were tested for the ability to stimulate ABA-L-Tyr specific T cell lines derived from B10.BR and B10.S mice. ABA-acetyltyramine, ABA-hydroxyphenylpropionic acid (ABA-PPr), and ABA-propylphenol, which lack either the carboxyl or amino group or both, could not induce T cell proliferation. The lack of stimulation by these derivatives was not due to their cytotoxic effects. A similar pattern of proliferation was obtained on stimulating lymph node T cells from B10.BR and B10.S mice primed with ABA-L-Tyr. Some differences were observed, however, between B10.BR and B10.S mice. ABA-L-Tyr-specific T cells from B10.BR mice could not respond well to ABA-D-Tyr in contrast to B10.S T cells. Furthermore, B10.BR mice primed with ABA-acetyltyramine or ABA-PPr in complete Freund's adjuvant could not induce ABA-L-Tyr-reactive T cells, whereas T cells from B10.S mice primed with these derivatives could proliferate in the presence of ABA-L-Tyr. The differences between B10.BR and B10.S mice were further investigated by using (B10.S X B10.BR)F1 mice. T cells from ABA-L-Tyr-immunized F1 mice responded poorly to ABA-D-Tyr when presented with B10.BR antigen-presenting cells (APC), but responded well when presented with B10.S APC. Similarly, T cells from ABA-PPr-primed F1 mice did not proliferate to ABA-L-Tyr in the presence of B10.BR APC, but could proliferate in the presence of B10.S APC. Our results clearly indicate that the presence of charged groups at the alpha-carbon of tyrosine plays a critical role in the triggering of ABA-L-Tyr-specific T cell proliferation. The significance of these results is discussed.     

Diurnal variations in response of rat liver tyrosine aminotransferase activity to food intake

Effects of fasting and refeeding on the hepatic tyrosine aminotransferase activity were examined in rats that had been fed during the night. The tyrosine aminotransferase activity showed clear diurnal variations, with a maximal activity after the feeding time. The tyrosine aminotransferase rhythm persisted even under starvation, though the amplitude decreased remarkably. When the starved rats were refed at night, the tyrosine aminotransferase activity increased rapidly to a high level, but it increased slowly to a rather lower level when they were refed in daytime.     

Characterization of Vibrio cholerae O1 isolates responsible for cholera outbreaks in Kenya between 1975 and 2017

Kenya is endemic for cholera with different waves of outbreaks having been documented since 1971. In recent years, new variants of Vibrio cholerae O1 have emerged and have replaced most of the traditional El Tor biotype globally. These strains also appear to have increased virulence, and it is important to describe and document their phenotypic and genotypic traits. This study characterized 146 V. cholerae O1 isolates from cholera outbreaks that occurred in Kenya between 1975 and 2017. Our study reports that the 1975–1984 strains had typical classical or El Tor biotype characters. New variants of V. cholerae O1 having traits of both classical and El Tor biotypes were observed from 2007 with all strains isolated between 2015 and 2017 being sensitive to polymyxin B and carrying both classical and El Tor type ctxB. All strains were resistant to Phage IV and harbored rstR, rtxC, hlyA, rtxA and tcpA genes specific for El Tor biotype indicating that the strains had an El Tor backbone. Pulsed field gel electrophoresis (PFGE) genotyping differentiated the isolates into 14 pulsotypes. The clustering also corresponded with the year of isolation signifying that the cholera outbreaks occurred as separate waves of different genetic fingerprints exhibiting different genotypic and phenotypic characteristics. The emergence and prevalence of V. cholerae O1 strains carrying El Tor type and classical type ctxB in Kenya are reported. These strains have replaced the typical El Tor biotype in Kenya and are potentially more virulent and easily transmitted within the population.     

Effect of Clostridium perfringens Beta Toxin on Blood Pressure of Rats

Guanethidine treatment or adrenal medullectomy significantly inhibited the elevation in blood pressure induced by Clostridium perfringens beta toxin, and the combination of the two drastically reduced the pressure rise, to less than 19% of that in control rats. When rats were pretreated with tetrodotoxin or hexamethonium, the toxin-evoked rise was significantly inhibited. Elevation in blood pressure induced by the toxin in spinal rats tended to be less than that in control rats. When investigated by a microscopical technique, arteriolar constriction in the mesenteric vasculature was observed after the blood pressure elevation induced by the toxin reached a maximum. Blood flow in the skin decreased with an increase in blood pressure following intravenous injection of the toxin. It is concluded that beta toxin acts on the autonomic nervous system and produces arterial constriction.