Discrimination of isolates of Mycobacterium bovis in Northern Ireland on the basis of variable numbers of tandem repeats (VNTRs).

The ability to reproducibly discriminate Mycobacterium bovis isolates and trace their transmission has the potential to clarify sources of infection and major routes of transmission for bovine tuberculosis (TB). A PCR-based genotyping assay has been developed to discriminate between strains of M bovis by examining multiple sites in its genome that consist of variable numbers of tandem repeats (VNTRS). The discriminatory power and reproducibility of this VNTR typing has been compared with that of the established PCR-based spoligotyping technique by using a panel of 461 isolates of M bovis prevalent in Northern Ireland. The VNTR assay discriminated 40 different profiles, the most prevalent of which constituted 21 per cent of the total, compared with 14 profiles discriminated by spoligotyping, the most prevalent of which constituted 65 per cent. No significant differences were observed between the prevalences of the VNTR profiles in the years from 1999 to 2003. A preliminary evaluation indicated that most genotypes predominated in particular areas of the country. This VTNR typing assay was found to be highly discriminating, with the performance characteristics to support its systematic application to the molecular epidemiology of bovine TB.

Modulation by presynaptic adenosine A1 receptors of nicotinic receptor antagonist-induced neuromuscular block in the mouse.

We have investigated how altering the activation of adenosine A1 receptors modifies nicotinic receptor antagonist-induced fade of tetanic contractions in the mouse isolated hemi-diaphragm. Vecuronium-induced tetanic fade was attenuated by an adenosine A1 receptor antagonist (8-cyclopentyl-1,3-dipropylxanthine, DPCPX, 10(-7) M) and by an inhibitor of the synthesis of extracellular adenosine from ATP (alpha,beta-methylene ADP, MeADP, 5 x 10(-5) M). Conversely, vecuronium-induced tetanic fade was potentiated by an adenosine A1 receptor agonist (N6-cyclohexyladenosine, CHA, 10(-7) M) and an inhibitor of the extracellular destruction of adenosine (erythro-9-[2-hydroxy-3-nonyl]adenine, EHNA, 10(-4) M). The ability of an adenosine A1 receptor antagonist to attenuate vecuronium-induced tetanic fade indicates that a component of this fade is due to endogenous adenosine. Further, the ability of the inhibitor of adenosine synthesis to attenuate vecuronium-induced tetanic fade indicates that this endogenous adenosine is derived from ATP. Hexamethonium-induced tetanic fade was also potentiated by increasing adenosine A1 receptor activation, albeit with a higher concentration of CHA (10(-4) M). However, unlike for vecuronium, hexamethonium-induced tetanic fade was not attenuated by reducing adenosine A receptor activation. This latter observation suggests that the tetanic fade produced by hexamethonium and vecuronium does not share a common mechanism of action.