Staphylococcus aureus serotype 5 capsular polysaccharide is antiphagocytic and enhances bacterial virulence in a murine bacteremia model.

Controversy persists over the role that the capsular polysaccharide plays in the pathogenesis of Staphylococcus aureus infections. To address this issue, we compared the mouse virulence of S. aureus Reynolds and capsule-defective mutant strains cultivated under conditions of high or low capsule expression. Strain Reynolds cells cultivated on Columbia salt agar plates expressed approximately 100-fold more type 5 capsular polysaccharide than did cells cultivated in Columbia salt broth. The relative virulence of strain Reynolds and its capsule-defective mutants after growth on either solid or liquid medium was examined in mice challenged intraperitoneally or intravenously. The results indicated that agar-grown Reynolds cells were cleared from the bloodstream of mice less readily than broth-grown Reynolds cells. When the parental and mutant strains were cultivated on solid medium, strain Reynolds sustained a higher level of bacteremia than did the capsular mutants. We performed in vitro opsonophagocytic killing assays to determine whether staphylococcal virulence for mice correlated with resistance to phagocytosis. S. aureus Reynolds cultivated on solid medium was susceptible to phagocytic killing only in the presence of specific capsular antibodies and complement. Strain Reynolds grown in broth showed opsonic requirements for phagocytic killing that were similar to those of the capsular mutants (grown in broth or on agar); i.e., the bacteria were opsonized for phagocytosis by nonimmune serum with complement activity. These studies indicate that optimal expression of capsule enhances bacterial virulence in the mouse model of bacteremia, probably by rendering the organisms resistant to opsonophagocytic killing by leukocytes.

Preserved number of entorhinal cortex layer II neurons in aged macaque monkeys.

The perforant path, which consists of the projection from the layer II neurons of the entorhinal cortex to the outer molecular layer of the dentate gyrus, is a critical circuit involved in learning and memory formation. Accordingly, disturbances in this circuit may contribute to age-related cognitive deficits. In a previous study, we demonstrated a decrease in N-methyl-D-aspartate receptor subunit 1 immunofluorescence intensity in the outer molecular layer of aged macaque monkeys. In this study, we used the optical fractionator, a stereological method, to determine if a loss of layer II neurons occurred in the same animals in which the N-methyl-D-aspartate receptor subunit 1 alteration was observed. Our results revealed no significant differences in the number of layer II neurons between juvenile, young adult, and aged macaque monkeys. These results suggest that the circuit-specific decrease in N-methyl-D-aspartate receptor subunit 1 reported previously occurs in the absence of structural compromise of the perforant path, and thus may be linked to an age-related change in the physiological properties of this circuit.

A prospective study of abdominal computerized tomography and colonoscopy in the diagnosis of colonic disease in an elderly population.

OBJECTIVE: The aim of this prospective study was to compare the accuracy of abdominal computed tomography (CT) and colonoscopy in diagnosing colonic pathology in an elderly population. METHODS: Patients over the age of 70 for whom an outpatient diagnostic colonoscopy had been requested, were invited to attend for a CT scan of the abdomen following oral colonic preparation. CT was carried out within 1 month of the colonoscopy and all images were evaluated by a single consultant radiologist with no prior knowledge of the colonoscopy result. RESULTS: Of 72 patients who fulfilled entry criteria and attended for colonoscopy, 55 (29 female) had abdominal CT of the abdomen (mean age 76.6 years, range 70-92). Colonoscopy was successful in 67% of cases and the following colonoscopic diagnoses were made: diverticular disease (26), normal (14), colonic carcinoma (6), polyps (9) colitis (2) and angiodysplasia (1). There was agreement between colonoscopic and CT diagnoses in 38 patients (69%) including all those with carcinoma of the colon. There was disagreement in 12 patients with diverticular disease, CT missed three polyps in three patients and angiodysplasia in one patient. CT provided additional important information in 9 patients: gastric leiomyosarcoma (1), aortic aneurysm (1), absence of metastases (3), liver metastases (2), cirrhosis and portal hypertension (1) and a large pleural effusion (1). One patient thought to have a carcinoma of the colon by both techniques was subsequently found to have a diverticular mass at laparotomy. Two patients undergoing colonoscopy had colonic perforations and one of these died. CONCLUSION: CT may provide an alternative to colonoscopy in diagnosis of colonic disease in the elderly population.

Occupational health problems among workers handling Virginia tobacco.

The prevalence of "green symptoms" among 289 tobacco workers handling Virginia tobacco leaves was investigated. The frequency of these symptoms was high (53.29%). Urinary excretion rate of nicotine and cotinine increased significantly only among the subjects suffering from "green symptoms".

Thin-layer chromatographic method for estimation of gamma-aminobutyric acid from brain.

The present method describes the estimation of gamma-aminobutyric acid (GABA) from adult rat brain by thin layer chromatography (TLC). The major advantage of this TLC method is the sensitivity and repidity of estimation. About 93 to 98 percent recovery is possible by this procedure and this shows linearity up to 9 micrograms. Replicate analysis of GABA by this method shows a co-efficient variation of 1.31%