title: Oxygen free radicals and the cerebral arteriolar response to group B streptococci.
abstract: We used a cranial window preparation to observe the effects of direct application of group B streptococci to the surface of the brain in the adult rat. Continuous exposure to group B streptococci at concentrations of 10(3) and 10(5) organisms/mL caused progressive dilation of surface (pial) cerebral arterioles that became statistically significant (p less than 0.05) after 2.5 h. These results were reproduced with heat-killed organisms at the same concentration, but not with a bacteria-free filtrate of the growth medium. In separate studies, we found that infusion of alkaline cerebrospinal fluid (pH = 7.8) into the window did not reverse vasodilation, suggesting that it was not due to progressive cerebrospinal fluid acidosis. A solution of nitroblue tetrazolium infused into the window at the end of a 3-h exposure to the organism was promptly reduced, suggesting the presence of oxygen free radicals. Treatment with i.v. polyethylene glycol-superoxide dismutase and polyethylene glycol-catalase in doses of 10,000 and 20,000 U/kg, respectively, was itself without effect on pial arterioles, but treatment with these compounds before exposure to group B streptococci eliminated the vasodilation. These data support a role for oxygen free radicals in the pathogenesis of pial arteriolar dysfunction induced by exposure to group B streptococci.
authors.affiliation: Department of Pediatrics (Eudowood Neonatal Pulmonary Division), Johns Hopkins Hospital, Baltimore, Maryland 21205.
authors.forename: A A
authors.initials: AA
authors.lastname: McKnight
authors.forename: W G
authors.initials: WG
authors.lastname: Keyes
authors.forename: M L
authors.initials: ML
authors.lastname: Hudak
authors.forename: M D
authors.initials: MD
authors.lastname: Jones
mesh_terms: D000818:Animals; D001160:Arterioles / Q000503:physiopathology; D002374:Catalase / Q000494:pharmacology; D002536:Cerebral Arteries / Q000503:physiopathology*; D005609:Free Radicals; D008297:Male; D016920:Meningitis, Bacterial / Q000134:cerebrospinal fluid / Q000378:metabolism / Q000503:physiopathology*; D010100:Oxygen / Q000378:metabolism; D010841:Pia Mater / Q000098:blood supply; D051381:Rats; D011919:Rats, Inbred Strains; D013290:Streptococcal Infections / Q000134:cerebrospinal fluid / Q000378:metabolism / Q000503:physiopathology*; D013292:Streptococcus agalactiae; D013482:Superoxide Dismutase / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
chemical_list: D005609:Free Radicals; D002374:Catalase; D013482:Superoxide Dismutase; D010100:Oxygen