Mycoplasma bovis suppression of bovine lymphocyte response to phytohemagglutinin.

The effect of viable Mycoplasma bovis on the in vitro bovine peripheral blood lymphocyte response to phytohemagglutinin (PHA) was studied. Results showed that M. bovis did not act as a mitogen for bovine lymphocytes. Viable M. bovis produced a dose and time dependent suppression of the PHA stimulated lymphocyte response. Suppression was not a result of differences in the viability of infected or control lymphocyte cultures. The suppressive effect of M. bovis was found to be independent of the concentration of PHA used in the test and the lymphocyte response could not be restored by supplementation of the culture medium with arginine. Delay for 48 h after PHA stimulation before adding M. bovis to the lymphocyte cultures diminished, but did not prevent, the suppression of the lymphocyte response. These results show that suppression of the lymphocyte response does not require the presence of M. bovis during the period of PHA stimulation, and that M. bovis was capable of interrupting [3H]-thymidine incorporation in lymphocytes which were actively synthesizing DNA.

Coffee consumption and the incidence of coronary heart disease.

We conducted a prospective investigation of the effect of coffee consumption on coronary heart disease in 1130 male medical students who were followed for 19 to 35 years. Changes in coffee consumption and cigarette smoking during follow-up were examined in relation to the incidence of clinically evident coronary disease in comparisons of three measures of coffee intake--base-line intake, average intake, and most recent intake reported before the manifestation of coronary disease. Clinical evidence of coronary disease included myocardial infarction, angina, and sudden cardiac death. In separate analyses for each measure of coffee intake, the relative risks for men drinking five or more cups of coffee per day, as compared with nondrinkers, were approximately 2.80 for all three measures in the univariate analyses (maximum width of 95 percent confidence intervals, 1.27 to 6.51). After adjustment for age, current smoking, hypertension status, and base-line level of serum cholesterol, the estimated relative risk for men drinking five or more cups of coffee per day (using the most recent coffee intake measure), as compared with those drinking none, was 2.49 (maximum width of 95 percent confidence interval, 1.08 to 5.77). The association between coffee and coronary disease was strongest when the time between the reports of coffee intake and the coronary event was shortest. These findings support an independent, dose-responsive association of coffee consumption with clinically evident coronary heart disease, which is consistent with a twofold to threefold elevation in risk among heavy coffee drinkers.

The oxidation of some polysaccharides by the hydroxyl radical: an e.s.r. investigation.

E.s.r. Experiments employing a flow system in conjunction with the TiIII-H2O2 couple show that dextrans react with the hydroxyl radical (HO.) via indiscriminate attack (except that abstraction of hydrogen atoms from carbons which are both linked by glycosidic bonds and included in the pyranose ring may be inhibited, possibly for steric reasons). Acid- and base-catalysed transformations of first-formed radicals have been demonstrated; the suggestion that such reactions can lead to glycosidic cleavage is supported by viscosity studies which confirm the pH-dependence of radical-initiated degradation. For galacturonan and related compounds, e.s.r. results indicate that reaction with HO. proceeds preferentially via abstraction of the hydrogen on the carbon adjacent to the carboxyl group. The crucial step in the subsequent degradation pathway probably involves a pH-independent rearrangement.