Structural organization of cholera toxin gene and its expression in an environmental non-pathogenic strain ofVibrio cholerae

Non-pathogenic, environmental strain ofVibrio cholerae, ELTOR Ogawa EW6 carries a copy of the cholera toxin gene in its chromosome. Restriction enzyme digestion followed by Southern blot analysis revealed that the structure of the cholera toxin gene in this organism is different from that found in the virulent strains. The xbaI site which has been found to be conserved in the cholera toxin of the virulent strains examined so far, is absent here. Results of the RNA dot blot analysis indicated that the cholera toxin gene in EW6 is transcribed much less efficiently compared to the cholera toxin gene present in the virulent strainVibrio cholerae classical Inaba 569B.     

Ethanol vapours above lacrimal fluid in the rabbit

Ethanol was administered intravenously to rabbits. The concentration of ethanol, determined by gas chromatographic analysis, in lacrimal fluid was shown to reflect the concentration in plasma. The vapour above lacrimal fluid was analyzed in situ by the use of a small resistivity sensor that measures ethanol vapours. After a dose of approximately 750 mg/kg, the metabolic rates of ethanol determined by gas chromatographic analysis of plasma (226 +/- 13 mg.kg-1.h-1) and by eye ethanol vapour analysis (210 +/- 8 mg.kg-1.h-1) were virtually identical. The data suggest that ethanol eye vapour analysis may be an attractive, noninvasive method for the determination of ethanol in animals.     

Cloning and DNA sequence of plasmid determinant iss, coding for increased serum survival and surface exclusion, which has homology with lambda DNA

Summary Escherichia coli K12 cells carrying a cloned 1.4 kb HindIII fragment from plasmid ColV2-K94, showed increased survival in guinea pig serum. The recombinant plasmid also conferred group II surface exclusion, i.e. the cells were reduced in recipient ability towards the incoming plasmid R538drd in conjugation experiments. Southern blotting suggested homology with bacteriophage lambda DNA and to the insertion element IS2. Determination of the DNA sequence of the fragment demonstrated the presence of a truncated IS2 (165 bp), separated by 250 bp from a 900 bp stretch of homology with lambda DNA, beginning within the Rz gene and continuing in the rightward direction on the lambda map. A 97 amino acid open reading frame (ORF) adjacent to Rz and on the opposite strand, remained intact in iss, with several amino acid changes. The ORF in iss is preceded by sequences resembling prokaryotic ribosome binding sites and promoters.     

Immunocytochemical localization of beta-N-acetyl glucosaminidase in human reproductive organs

Immunocytochemical localization of hexosaminidase activity in human males revealed that the enzyme activity is localized mainly in the Sertoli cells and interstitial tissue of the testis and in the columnar cells of the epididymis. In seminal vesicles, activity was observed around the glandular epithelium in the form of fine granules.     

Evidence that a system similar to the recA system of Escherichia coli exists in Vibrio cholerae

Summary Two lines of evidence suggest that a gene analogous to the recA gene of Escherichia coli exists in Vibrio cholerae and that its product serves a proteolytic function in the SOS response. Firstly, Southern blot hybridization using the recA gene of E. coli as a probe revealed a genomic sequence in V. cholerae which hybridized with the probe. Secondly, the SOS-like response in V. cholerae (as measured by beta phage induction) triggered by DNA damaging agents like Furazolidone could be blocked by Antipain, a protease inhibitor known to inhibit RecA protease action in E. coli. Maximal blocking effect of Antipain on beta phage induction occurred at 1 mM. At this concentration neither the viability of the host bacterium nor the lytic growth of a clear plaque mutant of the phage was affected by Antipain.     

Ultrasonic radiation induced lipid peroxidation in liposomal membrane

Summary Ultrasonic radiation produced a dose dependent linear increase in lipid peroxidation (MDA formation) in the liposomal membrane. The yield of MDA was significantly inhibited by butylated hydroxytoluene (BHT), the antioxidant, sodium formate, the OH radical scavenger, and EDTA, the metal ion chelator. Ascorbic acid at low concentration increased the ultrasonic induced MDA formation while high concentrations inhibited lipid peroxidation. A mechanism of ultrasound induced lipid peroxidation is suggested.     

Symmetrical effect of pre-exposure between alcohol and morphine on conditioned taste aversion

It has previously been reported that pre-exposure to a psychoactive drug can block the conditioned taste aversion associated with that drug. This study was an attempt to investigate alcohol-morphine interactions using this pre-exposure paradigm. After two weeks of adaptation to a schedule of daily 30-minute access to water, rats were pre-exposed to morphine, ethanol, or the respective vehicle control every second day for three days before (Days 1, 3, 5) and after the first conditioning day (Days 8, 10, 12). On conditioning days (Days 7, 14), animals were first presented with a saccharin solution for 30 minutes following which animals that were pre-exposed to morphine were injected with ethanol while those pre-exposed to ethanol were administered with morphine. Saccharin was again presented on three more occasions (Days 21, 28, 35) without drug injection. Using the percent change in saccharin consumed from the first presentation as a measure of aversion, it was found that pre-exposure to morphine blocked ethanol conditioned taste aversion. Similarly, animals pre-exposed to ethanol showed less aversion to the saccharin paired with morphine. This is the first demonstration of a symmetrical relationship between alcohol and the opiates.     

Production by K 562 cells of an inhibitor of adherence-related functions of human neutrophils

Certain tumor cells generate factors that inhibit neutrophil chemotaxis. Our study was designed to explore whether such factors are produced by K 562 malignant cells and whether these have a broader effect in altering neutrophil functions. After 48 h of in vitro culture of K 562 cells, the culture medium and the cells were separated, lyophilized, and extracted with ethanol. These K 562 products, i.e., either the cell or supernatant extract, inhibited both nonstimulated locomotion and locomotion induced either by FMLP or activated serum. Furthermore, K 562 products inhibited neutrophil adherence and oxidative burst induced by opsonized zymosan, whereas oxidative burst induced by PMA or FMLP was not altered. K 562 products had an inhibitory effect on the PMN binding to iC3b-coated particles. They did not modify Mo1 expression of resting cells, did not alter the up-regulation of the receptor induced by FMLP but inhibited the FMLP-induced capping of Mo1 Ag. Con A capping was also inhibited. Actin polymerization in FMLP-stimulated PMN, as measured by flow cytometry and phalloidin binding to F-actin, was inhibited by K 562 products. The inhibitory factor present in K 562 products (cell and culture supernatant) was purified in three steps including gel filtration, ion-exchange chromatography, and IEF. The eluted active fraction corresponded to single band of about 8 kDa on SDS-PAGE. From these experiments, it is concluded that K 562 malignant cells in culture contain and release a low molecular mass factor (congruent to 8 kDa) that inhibits all adherence-related functions of neutrophils, whereas it does not alter FMLP- or PMA-induced oxidative burst. Further studies are needed to assess whether products of other tumor cells also act on the neutrophil by inhibiting adherence-related functions, Mo1 function and capping, and actin polymerization.