Helicobacter pylori possesses two CheY response regulators and a histidine kinase sensor, CheA, which are essential for chemotaxis and colonization of the gastric mucosa

Infection of the mucous layer of the human stomach by Helicobacter pylori requires the bacterium to be motile and presumably chemotactic. Previous studies have shown that fully functional flagella are essential for motility and colonization, but the role of chemotaxis remains unclear. The two-component regulatory system CheA/CheY has been shown to play a major role in chemotaxis in other enteric bacteria. Scrutiny of the 26695 genome sequence suggests that H. pylori has two CheY response regulators: one a separate protein (CheY1) and the other (CheY2) fused to the histidine kinase sensor CheA. Defined deletion mutations were introduced into cheY1, cheY2, and cheA in H. pylori strains N6 and SS1. Video tracking revealed that the wild-type H. pylori strain moves in short runs with frequent direction changes, in contrast to movement of cheY2, cheAY2, and cheAY2 cheY1 mutants, whose motion was more linear. The cheY1 mutant demonstrated a different motility phenotype of rapid tumbling. All mutants had impaired swarming and greatly reduced chemotactic responses to hog gastric mucin. Neither cheY1 nor cheAY2 mutants were able to colonize mice, but they generated a significant antibody response, suggesting that despite impaired chemotaxis, these mutants were able to survive in the stomach long enough to induce an immune response before being removed by gastric flow. Additionally, we demonstrated that cheY1 failed to colonize gnotobiotic piglets. This study demonstrates the importance of the roles of cheY1, cheY2, and cheA in motility and virulence of H. pylori.     

The acute physiological and mood effects of tea and coffee: the role of caffeine level

The objective of this study was to determine the effect of caffeine level in tea and coffee on acute physiological responses and mood. Randomised full crossover design in subjects after overnight caffeine abstention was studied. In study 1 (n = 17) the caffeine level was manipulated naturalistically by preparing tea and coffee at different strengths (1 or 2 cups equivalent). Caffeine levels were 37.5 and 75 mg in tea, 75 and 150 mg in coffee, with water and no-drink controls. In study 2 (n = 15) caffeine level alone was manipulated (water, decaffeinated tea, plus 0, 25, 50, 100, and 200 mg caffeine). Beverage volume and temperature (55 degrees C) were constant. SBP, DBP, heart rate, skin temperature, skin conductance, and mood were monitored over each 3-h study session. In study 1, tea and coffee produced mild autonomic stimulation and an elevation in mood. There were no effects of tea vs. coffee or caffeine dose, despite a fourfold variation in the latter. Increasing beverage strength was associated with greater increases in DBP and energetic arousal. In study 2, caffeinated beverages increased SBP, DBP, and skin conductance and lowered heart rate and skin temperature compared to water. Significant dose-response relationships to caffeine were seen only for SBP, heart rate, and skin temperature. There were significant effects of caffeine on energetic arousal but no consistent dose-response effects. Caffeinated beverages acutely stimulate the autonomic nervous system and increase alertness. Although caffeine can exert dose-dependent effects on a number of acute autonomic responses, caffeine level is not an important factor. Factors besides caffeine may contribute to these acute effects.     

Dermatitis from phenyl salicylate in safety spectacle frames

We report 3 cases of allergic contact dermatitis behind the ears from wearing the same brand of industrial safety spectacles. In each case, a positive patch test was obtained with scrapings of the plastic frame. In 2 cases further patch tests with constituents of the plastic were carried out; positive patch tests were obtained with phenyl salicylate. Phenyl salicylate is used as an ultraviolet inhibitor in some cellulose acetate butyrate and cellulose acetate propionate formulae. It has previously been reported as a contact sensitizer from its use as a sun screen in a lip salve. Positive patch test reactions were also obtained variously in these patients with balsam of Peru, resorcinol monobenzoate, and epoxy resin.     

Allergic contact sensitization to the glycidyl ester of hexahydrophthalic acid in a cutting oil

Allergic contact dermatitis is reported in 5 machine operatives working with a cutting oil containing an epoxy compound used as a stabilizer. Positive patch test reactions to this compound were obtained in all 5 men and were negative in 25 controls.     

Dermatitis from slimicides in a paper mill

Dermatitis is reported from slimicides added to wood pulp slurry in a paper mill. The active constituents of the slimicides involved were bis-1,4-bromoacetoxy-2-butene and 2,3-dichloro-4-bromotetrahydrothiophene-1,1-dioxide. Wood pulp slimicides include many chemicals which are highly irritant and potentially sensitizing to the skin.