A water channel of the nematode C.elegans and its implications for channel selectivity of MIP proteins

A genome project focusingon the nematode Caenorhabditis elegans has demonstrated thepresence of eight cDNAs belonging to the major intrinsic proteinsuperfamily. We functionally characterized one of these cDNAs namedC01G6.1. Injection of C01G6.1 cRNA increased the osmotic waterpermeability (P_f) of Xenopusoocytes 11-fold and the urea permeability 4.5-fold but failed toincrease the glycerol permeability. It has been speculated that the MIPfamily may be separated into two large subfamilies based on thepresence or absence of two segments of extra amino acid residues (~15amino acids) at the second and third extracellular loops. BecauseC01G6.1 (designated AQP-CE1), AQP3, and glycerol facilitator (GlpF) all have these two segments, we replaced the segments of AQP-CE1 with thoseof AQP3 and GlpF to identify their roles. The functional characteristics of these mutants were principally similar to that ofwild-type AQP-CE1, although the values of P_f andurea permeability were decreased by 39-74% and 28-65%,respectively. These results suggest that the two segments of extraamino acid residues may not contribute to channel selectivity orformation of the route for small solutes.

     

Degradation of thyroxine by microsomal particles from rat liver II. Purification of Fe3+-dependent particles and some of their properties

Particles, which catalyze the deiodination of thyroid hormones in the presence of Fe²⁺, have been purified about 25-fold with respect to the rat liver microsomes. This purification involves deoxycholate treatment, trypsin treatment and density gradient centrifugutions.The purified particles range from 1.019 to 1.063 in density and consist of 21% protein, 60% phospholipid and 19% neutral fat. No hemoprotein moiety is associated with the purified particles. The purified particles degrade not only l-thyroxine but also other iodinated thyronines and their derivatives, such as d-thyroxine, l-3′,3,5- triiodothyronine and tetraiodothyropropionic acid. They are inactive towards monoiodotyrosine and diiodotyrosine.Thyroxine is not metabolized in the drug hydroxylation system which involves cytochrome P-450.     

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.     

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.     

Dysbindin-1, a Schizophrenia-Related Protein,Functionally Interacts with the DNA- Dependent Protein Kinase Complex in an Isoform-Dependent Manner

DTNBP1 has been recognized as a schizophrenia susceptible gene, and its protein product, dysbindin-1, is down-regulated in the brains of schizophrenic patients. However, little is known about the physiological role of dysbindin-1 in the central nervous system. We hypothesized that disruption of dysbindin-1 with unidentified proteins could contribute to pathogenesis and the symptoms of schizophrenia. GST pull-down from human neuroblastoma lysates showed an association of dysbindin-1 with the DNA-dependent protein kinase (DNA-PK) complex. The DNA-PK complex interacts only with splice isoforms A and B, but not with C. We found that isoforms A and B localized in nucleus, where the kinase complex exist, whereas the isoform C was found exclusively in cytosol. Furthermore, results of phosphorylation assay suggest that the DNA-PK complex phosphorylated dysbindin-1 isoforms A and B in cells. These observations suggest that DNA-PK regulates the dysbindin-1 isoforms A and B by phosphorylation in nucleus. Isoform C does not contain exons from 1 to 6. Since schizophrenia-related single nucleotide polymorphisms (SNPs) occur in these introns between exon 1 and exon 6, we suggest that these SNPs might affect splicing of DTNBP1, which leads to impairment of the functional interaction between dysbindin-1 and DNA-PK in schizophrenic patients.     

Relationship between Stereoisomerism and Biological Activity of Pyrethroids

Higher homologous acids of chrysanthemic acid described in the previous papers were esterified with (±)-allethrolone. The toxicity of these esters and the related compounds were evaluated by the topical application method to Musca domestica vicina Macq. The allethronyl homochry-santhemate (entry Nos. 4, 5) was shown to be toxic and the dextrorotatory form was far more toxic than the laevorotatory one. Further elongation of the ester linkage resulted in a loss of toxicity. The cyclobutane carboxylic acid ester (entry No. 10) was shown to be toxic and so, the cyclopropane ring might be replaced to some extent by the cyclobutane ring, provided the other requirements were fulfiled. However, further elongation of the ester linkage also reduced the toxicity. The lactones (entry Nos. 12–16) obtained by the hot sulfuric acid treatment were non-toxic.     

Processing Studies on Canned Corned Beef and Canned Luncheon Meat

Heat penetration data on canned corned beef and luncheon meat are presented. The effects of can size, retort temperature and composition on process requirements and quality are demonstrated and discussed.     

Enzymatic properties of Myxococcus xanthus exopolyphosphatases mxPpx1 and mxPpx2

Myxococcus xanthus possesses two exopolyphosphatases, mxPpx1 and mxPpx2, which belong to the family of Ppx/GppA phosphatases; however, their catalytic properties have not been described. mxPpx1 and mxPpx2 contain 311 and 505 amino acid residues, respectively; mxPpx2 has an additional C-terminal region, which corresponds to the metal-dependent HDc phosphohydrolase domain. mxPpx1 mainly hydrolyzed short-chain polyPs (polyP₃ and polyP₄), whereas mxPpx2 preferred long-chain polyP_60–70 and polyP_700–1000. mxPpx2 was activated by 25–50 mM KCl, but mxPpx1 did not significantly depend on K⁺. In addition, mxPpx1 and mxPpx2 showed weak hydrolysis of ATP and GTP in the absence of K⁺, and mxPpx2 could also hydrolyze guanosine pentaphosphate (pppGpp) in the presence of K⁺. The exopolyphosphatase activity of mxPpx1 toward polyP₃ was inhibited by polyP_700–1000 and that of mxPpx2 toward polyP_60–70 and polyP_700–1000, by pyrophosphate. To clarify the function of the mxPpx2 C-terminal domain, it was fused to mxPpx1 (mxPpx1-2C) and deleted from mxPpx2 (mxPpx2?C). Compared to wild-type mxPpx2, mxPpx2?C had significantly reduced exopolyphosphatase activity toward long-chain polyPs (by 90%), whereas that toward polyP₃ and polyP₄ was much less affected; furthermore, the phosphohydrolase activity toward pppGpp, ATP, and GTP was also decreased (by 30–75%). In contrast, mxPpx1-2C had increased hydrolytic activity compared to mxPpx1. Furthermore, mxPpx2?C lost the requirement for K⁺ characteristic for the wild-type enzyme, whereas mxPpx1-2C acquired it. These results suggest that the C-terminal domain of mxPpx2 is necessary for its maximum hydrolytic activity, especially toward long-chain polyPs, and defines mxPpx2 dependency on K⁺ for activation.