A protease from the culture supernatant of Bacteroides gingivalis 381, which hydrolyzes the chromogenic substrate Na-benzoyl-DL-arginine-p-nitroanilide (BAPNA), was partially purified by ammonium sulfate precipitation, gel filtration, and anion exchange chromatography. The molecular weight of this protease was determined by SDS-PAGE to be ca. 49,000. The optimum pH was around 7.6. The protease was stable at neutral pH and up to 40 degrees C. The isoelectric point was 4.9. The enzyme activity was enhanced by dithiothreitol, L-cysteine, and 2-mercaptoethanol and inhibited by p-chloromercuribenzoic acid, N-ethylmaleimide, and iodoacetic acid.

Local CBF (LCBF) was compared with the corresponding local tissue concentration of ATP, phosphocreatine (PCr), and lactate in anaesthetized baboons subjected to focal ischaemia produced by middle cerebral artery occlusion (MCAO). LCBF hydrogen electrodes were implanted in cortical regions where MCAO had been previously shown to produce severe and penumbral ischaemia and in posterior regions where blood flow is not altered. Metabolites were assayed in small tissue samples collected either by cryoprobe biopsy in the regions where LCBFs were measured (series 1) or by sampling appropriate regions of the rapidly frozen brain (series 2). Subsequent topographical study of brain tissue pH with umbelliferone was performed in this latter series. The results from these two series are compared and discussed in terms of the more appropriate way to perform simultaneous electrode measurements and analysis of tissue samples for studying focal ischaemia in the primate brain. They confirm that the concentrations of ATP and PCr decrease, and that lactate level increases, with decreasing blood flow. These metabolites tended to change more rapidly below a blood flow threshold, rather than showing a steady decrease as the blood flow was reduced, although the variability of the data precluded us from establishing this with confidence. Topographical study of tissue pH often showed sharp boundaries between zones of very low pH and regions with normal pH.

Susceptibility of Bacteroides gingivalis strains to the complement-mediated bactericidal activity of human serum was examined under anaerobic conditions. Serum containing high concentrations of IgG antibody to B. gingivalis enhanced the bactericidal activity. No enhancement was found in serum which did not contain the specific antibody or in serum absorbed with intact cells. The sensitivity to the killing by pooled serum differed among B. gingivalis strains. Cells of B. gingivalis activated the pooled human serum complement not only through the classic pathway but also through an alternative pathway. It was found that the susceptibility of B. gingivalis to the bactericidal activity was classic-pathway-dependent.

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