Brucella abortus is an intracellular pathogen that causes disease in cattle and in humans. The response against B. abortus involves the whole gamut of the immune system, from innate to adaptive immunity resulting from stimulation of antigen-presenting cells, NK cells, CD4(+) and CD8(+) T cells, and B cells.
View Article and Find Full Text PDFThe nuclear enzyme poly(ADP-ribose) polymerase (PARP) facilitates the repair of DNA strand breaks and is implicated in the resistance of cancer cells to certain DNA-damaging agents. Inhibitors of PARP have clinical potential as resistance-modifying agents capable of potentiating radiotherapy and the cytotoxicity of some forms of cancer chemotherapy. The preclinical development of 2-aryl-1H-benzimidazole-4-carboxamides as resistance-modifying agents in cancer chemotherapy is described.
View Article and Find Full Text PDFA series of O(6)-allyl- and O(6)-(2-oxoalkyl)guanines were synthesized and evaluated, in comparison with the corresponding O(6)-alkylguanines, as potential inhibitors of the DNA-repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT). Simple O(6)-alkyl- and O(6)-cycloalkylguanines were weak AGT inactivators compared with O(6)-allylguanine (IC(50) = 8.5 +/- 0.
View Article and Find Full Text PDFWe have developed a procedure to directly clone large fragments from the genome of the soil bacterium Sinorhizobium meliloti. Specific regions to be cloned are first flanked by parallel copies of an origin of transfer (oriT) together with a plasmid replication origin capable of replicating large clones in Escherichia coli but not in the target organism. Supplying transfer genes in trans specifically transfers the oriT-flanked region, and in this process, site-specific recombination at the oriT sites results in a plasmid carrying the flanked region of interest that can replicate in E.
View Article and Find Full Text PDFSubstituted guanines and pyrimidines were tested as inhibitors of cyclin B1/CDK1 and cyclin A3/CDK2 and soaked into crystals of monomeric CDK2. O6-Cyclohexylmethylguanine (NU2058) was a competitive inhibitor of CDK1 and CDK2 with respect to ATP (Ki values: CDK1, 5 +/- 1 microM; CDK2, 12 +/- 3 microM) and formed a triplet of hydrogen bonds (i.e.
View Article and Find Full Text PDFThe supernucleophilic cobalt compound, cob(I)alamin, has been kinetically characterized with respect to its ability to bring about transalkylation of adducts to DNA phosphates (phosphotriesters). The reactivity of cob(I)alamin toward different phosphotriesters (model compounds and methylated DNA), as well as its specificity toward DNA-phosphate adducts, has been investigated. Through nucleophilic displacement on the alkyl by cob(I)alamin, the alkyl groups (methyl and ethyl) were transferred from phosphotriesters within minutes at room temperature.
View Article and Find Full Text PDFThe synthesis and biological evaluation of potent 4,8-dibenzylaminopyrimidopyrimidine nucleoside transport inhibitors, with reduced binding to alpha1-acid glycoprotein, is reported.
View Article and Find Full Text PDFWe review the history of the toxicology of benzene and consider current exposure levels, the metabolism of benzene, reactions of the metabolites with biomolecules and possible mechanisms of carcinogenesis due to benzene. Epidemiological evidence indicates a relationship between exposure to benzene and the occurrence of acute non-lymphocytic leukaemia in humans. Working groups convened by IARC and other organizations have therefore judged that there is sufficient evidence for classifying benzene as a human carcinogen.
View Article and Find Full Text PDFDipyridamole has been shown to enhance the in vitro activity of antimetabolite anticancer drugs through the inhibition of nucleoside transport. However, the clinical potential of dipyridamole has not been realized because of the avid binding of the drug to the plasma protein alpha1-acid glycoprotein (AGP). Dipyridamole analogues that retain potent nucleoside transport inhibitory activity in the presence of AGP are described and their ability to enhance the growth inhibitory and cytotoxic effects of thymidylate synthase (TS) inhibitors has been evaluated.
View Article and Find Full Text PDFDown-regulation of the Th2-like response induced by ovalbumin-alum (OVA/alum) immunization by heat-killed Brucella abortus was not reversed by anti-IL-12 antibody treatment or in gamma interferon (IFN-gamma) knockout mice, suggesting that induction of Th1 cytokines was not the only mechanism involved in the B. abortus-mediated inhibition of the Th2 response to OVA/alum. The focus of this study was to determine whether an alternative pathway involves alteration in expression of costimulatory molecules.
View Article and Find Full Text PDFChem Res Toxicol
December 1998
Differences in the metabolism of 1,3-butadiene (Bd) in rats and mice may account for the observed species difference in carcinogenicity. Previous studies of the metabolic fate of Bd have identified epoxide formation as a key metabolic transformation which gives 1, 2-epoxy-3-butene (BMO), although some evidence of aldehyde metabolites is reported. In this study, male Sprague-Dawley rats and male B6C3F1 mice received single doses of [4-14C]BMO at 1, 5, 20, and 50 mg/kg of body weight (0.
View Article and Find Full Text PDFClinical studies concerning the role of poly(ADP-ribose) polymerase (PARP) in the repair of drug- and radiation-induced DNA damage have been impeded by the poor solubility, lack of potency, and limited specificity of currently available inhibitors. A series of 2-alkyl- and 2-aryl-substituted 8-hydroxy-, 8-methoxy-, and 8-methylquinazolin-4(3H)-ones has been synthesized and evaluated for PARP inhibitory activity in permeabilized L1210 murine leukemia cells. 8-Methoxy- and 8-methylquinazolinones (14-34) were readily prepared by acylation of 3-substituted anthranilamides with the appropriate acid chloride, followed by base-catalyzed cyclization.
View Article and Find Full Text PDFThe ability of the potent poly(ADP-ribose) polymerase (PARP) inhibitor, NU1025 (8-hydroxy-2-methyl-quinazolin-4-[3H]one) to potentiate the cytotoxicity of a panel of mechanistically diverse anti-cancer agents was evaluated in L1210 cells. NU1025 enhanced the cytotoxicity of the DNA-methylating agent MTIC, gamma-irradiation and bleomycin 3.5-, 1.
View Article and Find Full Text PDFA colinearly synthesized peptide consisting of a H-2d restricted T-helper cell epitope of Semliki Forest virus (SFV) and triple repeats of sequence GPGRAF, derived from the V3 domain of HIV-1 strains, was used to immunize BALB/c (H-2d) mice. Pepscan analysis of sera from peptide-immunized mice revealed that the chimaeric peptide GREKFTIRPHYGKEIGPGRAFGPGRAFGPGRAF contains three distinct antibody-reactive sequences GREKFTIR, PHYGKEI and GPGRAF. The chimaeric peptide evoked HIV-1 IIIb neutralizing antibodies in serum as measured in vitro by reduction of syncytia formation and reduction of p24 production as well.
View Article and Find Full Text PDFBifunctional alkylating agents, such as those based on nitrogen mustard, form important parts of many anti-cancer chemotherapy protocols and are responsible for increased incidences of secondary tumors in successfully treated patients. These drugs generally form a majority of monofunctional DNA adducts, although the bifunctional adducts appear to be necessary for their powerful cytotoxic and antitumor effects. The relative importance of bifunctional as opposed to monofunctional adducts in the varied biological consequences of drug exposure has not been studied in detail, particularly in relation to the role and specificity of biochemical responses to therapy-related DNA damage.
View Article and Find Full Text PDFEnhancement of immunity in the setting of HIV infection is difficult owing to loss of functional CD4+ T cells. The MHC class II-deficient mouse (II-/-) environment simulates that of the immunocompromised HIV-infected individual, since these mice have low CD4+ T cell numbers, defective CD4-dependent responses, and are susceptible to opportunistic infection. This strain was used to test whether heat-killed Brucella abortus (BA), covalently conjugated to the V3 peptide of HIV-1 (MN), could elicit anti-HIV responses.
View Article and Find Full Text PDF1. Isoprene is metabolised in vitro by oxygenation of either double bond to 2-ethenyl-2-methyloxirane (epoxide A) and 2-(1'-methylethenyl)oxirane (epoxide B). The reactivity in vitro and formation in vivo of the monoepoxides of isoprene were studied by the formation of adducts to N-terminal valines in haemoglobin (Hb).
View Article and Find Full Text PDFLittle is known about the formation and disposition of benzene oxide (BO), the initial metabolite arising from oxidation of benzene by cytochrome P450. In this study, reactions of BO with hemoglobin (Hb) and albumin (Alb) were investigated in blood from B6C3F1 mice, F344 rats, and humans in vitro. The estimated half-lives of BO in blood were 6.
View Article and Find Full Text PDFA series of 2H- and 13C-labeled glutamates were used as substrates for coenzyme B12-dependent glutamate mutase, which equilibrates (S)-glutamate with (2S,3S)-3-methylaspartate. These compounds contained the isotopes at C-2, C-3, or C-4 of the carbon chain: [2-2H], [3,3-2H2], [4,4-2H2], [2,3,3,4,4-2H5], [2-13C], [3-13C], and [4-13C]glutamate. Each reaction was monitored by electron paramagnetic resonance (EPR) spectroscopy and revealed a similar signal characterized by g'xy = 2.
View Article and Find Full Text PDFOxidation of 7-oxabicyclo[4.1.0]hepta-2,4-diene (benzene oxide)/oxepin with dimethyldioxirane (DMDO) gave mainly (Z,Z)-muconaldehyde, with complete diastereoselectivity.
View Article and Find Full Text PDFXenobiotica
November 1997
1. Comparative studies on the stereochemistry of the metabolism of isoprene in vitro have been carried out using liver microsomes from rats, mice, monkeys, dogs, rabbits and humans. Differences between strains and gender were also investigated.
View Article and Find Full Text PDFAlthough it is generally assumed that metabolism of benzene proceeds through an initial step involving oxidation to benzene oxide (BO) by CYP450 in the liver, the production of BO has never been unambiguously confirmed in animals dosed with benzene. Furthermore, prevailing hypotheses of the mechanism by which benzene causes cancer have ignored the possibility that BO might play a direct role, despite the fact that BO is electrophilic, binds covalently to cell macromolecules and is presumably genotoxic. A likely reason for this lack of attention to the role of BO in the carcinogenesis of benzene is the presumption that this epoxide is too reactive to escape the hepatocyte after it is formed.
View Article and Find Full Text PDFA phylogenetic portrait of the genus Calicivirus in the family Caliciviridae was developed based upon published sequences and newly characterized calicivirus (CV) strains, including additional Sapporo-like HuCV strains in pediatric diarrhea stool specimens from South Africa, the United Kingdom, and the United States. Distance and parsimony methods were applied to nucleotide and amino acid sequences of human and animal calicivirus 3D RNA-dependent RNA polymerase (approximately 470nt) and capsid hypervariable regions (approximately 1,200nt) to generate phylogenetic trees. Pairwise amino acid identity in the 3D region among the Sapporo-like strains ranged from 61% to 100%.
View Article and Find Full Text PDFAllergic responses are characterized by the production of Ag-specific IgE Abs that are dependent upon Th2-mediated T cell help. We determined whether heat-killed Brucella abortus (BA), an inducer of Th1 responses, could influence the allergic Th2-mediated IgE response to OVA adsorbed to alum (O/A). BA plus O/A, but not O/A alone, induced high levels of mRNA for IFN-gamma and IL-12 promptly after injection.
View Article and Find Full Text PDFEnviron Health Perspect
December 1996
(Z,Z)-Muconaldehyde reacted with primary amines to give N-substituted-2(2'-oxoethyl)-pyrroles, which were reduced to N-substituted-2-(2'-hydroxyethyl)-pyrroles by sodium borohydride. The pyrrole-forming reaction is exhibited by valine and its methyl ester, and is being developed with terminal valine in hemoglobin as a means of dose monitoring (Z,Z)-muconaldehyde, a putative metabolite of benzene. Reactions in aqueous solution between (Z,Z)-muconaldehyde and adenosine, deoxyadenosine, guanosine, or deoxyguanosine leading to pyrrole-containing adducts are described.
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