Energy-dependent transport of nickel by Clostridium pasteurianum.

The mechanism of nickel transport by Clostridium pasteurianum was investigated by using 63NiCl2 and a microfiltration transport assay. Nickel transport was energy dependent, requiring either glucose or sucrose; xylose and o-methyl glucose did not support growth, butyrogenesis, or transport. Transport was optimum at pH 7 and 37 degrees C, and early-stationary-phase cells had the highest propensity for nickel transport. The apparent Km and Vmax for nickel transport approximated 85 microM Ni and 1,400 pmol of Ni transported per min per mg (dry weight) of cells, respectively. On the basis of metal specificity, nickel appears to be transported primarily by a magnesium transporter, although an alternative nickel transporter may also be involved. ATPase inhibitors (N,N'-dicyclohexylcarbodiimide, tributyltin chloride, 7-chloro-4-nitrobenz-2-oxa-1,3-diazole, and quercetin), protonophores (carbonyl cyanide m-chlorophenylhydrazone, 2,4-dinitrophenol, and gramicidin D), metal ionophores (valinomycin, monensin, and nigericin), benzyl viologen, carbon monoxide, and oxygen inhibited nickel transport. Nickel transport was coupled indirectly to butyrogenesis and was dependent on the energy state of the cell.     

Impaired production of gamma-interferon by newborn cells in vitro is due to a functionally immature macrophage

The decreased production of gamma-(PHA-induced) interferon (IFN) by leukocytes of normal newborns could be due to functionally immature T cells, macrophages, or both. We studied gamma-IFN production by macrophages and T cells, alone and in combination, obtained from 50 cord blood samples and 14 adult blood samples in a series of experiments. Adherent macrophages were cultivated for 7 days before the addition of T cells. After 48 hr, PHA-stimulated macrophage-T cell supernatants were harvested and assayed for IFN by a microassay. Macrophage-T cell cultures of autologous and nonautologous cells in 14 adults showed enhanced IFN production (GMT 121 +/- 5 IU) as compared with Ficoll-Hypaque mononuclear cells (GMT 42 +/- 5 IU). No IFN was detected in supernatants from PHA-stimulated Ficoll-Hypaque cord cells alone or macrophage-T cord combined cultures. Combined cord macrophages and adult T cells produced minimal IFN (GMT 13 +/- 3 IU); however, cord T cells combined with adult macrophages showed enhanced IFN production (GMT 195 +/- 47 IU). This cord macrophage dysfunction was not due to an inhibitor and improved with the time of in vitro cultivation. These results indicate that the neonatal macrophage is primarily responsible for the impaired gamma-IFN response by the newborn cells.     

Mutator Gene of Escherichia coli B

An azaserine-resistant derivative of Escherichia coli B/UV, AZA/R(1), was found to carry a mutator gene. This gene, designated mutS1, was mapped by means of conjugation and P1kc-mediated transduction. The mutS1 gene was cotransduced with argB at a frequency of 2.4%; the gene order in this region of the chromosome is thy argB mutS1. To determine whether a relationship commonly exists between azaserine resistance and the mutator property, 12 additional azaserine-resistant derivatives of B/UV were developed and tested for the mutator phenotype. None of the twelve was a mutator strain. The level of azaserine resistance was not increased over that of the recipient parent when mutS1 was transduced to an azaserine-susceptible strain. Reversion studies indicated that mutS1 induced adenosine-ribosylthymine to guanosine-cytidine and guanosine-cytidine to adenosine-ribosylthymine transitions. Because such mutational changes are suppressible with deoxynucleosides when induced by base analogues, an attempt was made to suppress the mutator activity of mutS1 by the addition of deoxyribonucleosides to the medium. No suppression was found. Recombinants were prepared containing mutS1 and the Treffers mutator gene of E. coli K-12. The effect of the mutator genes appears to be additive.     

Evaluation of the Escherichia coli K12 inductest for detection of potential chemical carcinogens

46 chemicals of diverse classes and structures, including 30 known animal carcinogens, were evaluated for prophage-inducing ability using the Escherichia coli inductest with lysogenic strain GY5027 envA - uvrB- and indicator strain GY4015 ampR . The inductest detected 9 of 30 known carcinogens as genotoxic agents, including 3 polycyclic hydrocarbons, 2 aflatoxins, and 2 antitumor antimicrobials. Among the 21 carcinogens ineffective as prophage inducers were 3 aromatic amines (other than 2-aminoanthracene), 3 azo-aminoazo compounds, 2 methanesulfonates, and 2 nitro aromatics. In contrast, 18 and 17 of the 30 animal carcinogens were detected as genotoxic agents in the Salmonella/Ames test and E. coli WP2/ WP100 rec assay, respectively. The threshold sensitivity of the inductest was less than that of the Salmonella/Ames test for chemicals genotoxic in both tests. The ineffectiveness of the inductest as a routine test for detecting potential chemical carcinogens may be related to the nature of the DNA damage lesions formed by various genotoxic agents.     

Displacement of Boophilus decoloratus by Boophilus microplus in the Soutpansberg region, Limpopo Province, South Africa

Boophilus ticks (n = 25,987) were collected from cattle at 30 communal dip tanks and five commercial farms in the Soutpansberg region, Limpopo Province, South Africa, between May 1999 and December 2001. Only 6.6% were Boophilus decoloratus, while 93.4% were Boophilus microplus, a tick that had not been reported from this area previously. B. microplus was the most common Boophilus tick on communal dip tank cattle, while B. decoloratus was more commonly found on commercial farms. Where the two species occurred together, B. microplus tended to displace B. decoloratus. The displacement was almost complete at the communal dip tanks, while on the commercial farms the population change was still in progress at the end of the survey. The present study demonstrated that a postulated reproductive interference was insufficient in preventing B. microplus from spreading when the climatic conditions were favourable to this species, as the displacement in most of the areas appeared to be rapid and complete.     

Discovery of a potent, selective and orally active canine COX-2 inhibitor, 2-(3-difluoromethyl-5-phenyl-pyrazol-1-yl)-5-methanesulfonyl-pyridine

Structure-activity relationship (SAR) studies of 2-[3-di(and tri)fluoromethyl-5-arylpyrazol-1-yl]-5-methanesulfonylpyridine derivatives for canine COX enzymes are described. This led to the identification of 12a as a lead candidate for further progression. The in vitro and in vivo activity of 12a for the canine COX-2 enzyme as well as its in vivo efficacy and pharmacokinetic properties in dog are highlighted.     

Highly conserved cysteines of mouse core 2 beta1,6-N-acetylglucosaminyltransferase I form a network of disulfide bonds and include a thiol that affects enzyme activity

Core 2 beta1,6-N-acetylglucosaminyltransferase I (C2GnT-I) plays a pivotal role in the biosynthesis of mucin-type O-glycans that serve as ligands in cell adhesion. To elucidate the three-dimensional structure of the enzyme for use in computer-aided design of therapeutically relevant enzyme inhibitors, we investigated the participation of cysteine residues in disulfide linkages in a purified murine recombinant enzyme. The pattern of free and disulfide-bonded Cys residues was determined by liquid chromatography/electrospray ionization tandem mass spectrometry in the absence and presence of dithiothreitol. Of nine highly conserved Cys residues, under both conditions, one (Cys217) is a free thiol, and eight are engaged in disulfide bonds, with pairs formed between Cys59-Cys413, Cys100-Cys172, Cys151-Cys199, and Cys372-Cys381. The only non-conserved residue within the beta1,6-N-acetylglucosaminyltransferase family, Cys235, is also a free thiol in the presence of dithiothreitol; however, in the absence of reductant, Cys235 forms an intermolecular disulfide linkage. Biochemical studies performed with thiolreactive agents demonstrated that at least one free cysteine affects enzyme activity and is proximal to the UDP-GlcNAc binding site. A Cys217 --> Ser mutant enzyme was insensitive to thiol reactants and displayed kinetic properties virtually identical to those of the wild-type enzyme, thereby showing that Cys217, although not required for activity per se, represents the only thiol that causes enzyme inactivation when modified. Based on the pattern of free and disulfide-linked Cys residues, and a method of fold recognition/threading and homology modeling, we have computed a three-dimensional model for this enzyme that was refined using the T4 bacteriophage beta-glucosyltransferase fold.     

The effects of a mutant connexin 26 on epidermal differentiation

To elucidate the mode of action of dominant mutant connexins in causing inherited skin diseases, transgenic mice were produced that express the true Vohwinkel syndrome-associated mutant Cx26 (D66H), from a keratin 10 promoter, specifically in the suprabasal epidermal keratinocytes. Following birth, the transgenic mice developed keratoderma similar to that of human carriers of Cx26 (D66H). Expression of the transgene resulted in a loss of Cx26 and Cx30 at intercellular junctions of epidermal keratinocytes and accumulation of these connexins in the cytoplasm. Injection of primary mouse keratinocytes with Lucifer Yellow showed no difference in terms of dye spreading between transgenic and non transgenic keratinocytes in vitro. Expression of the mutant Cx26 (D66H) did not interfere with the formation of the epidermal water barrier during late embryonic development. Attempts to produce transgenic mice expressing the wild type form of Cx26 from the K10 promoter failed to produce viable animals although transgenic embryos were recovered at days 9 and 12 of gestation, suggesting that the transgene might be embryonic lethal.