Classroom aeroallergen exposure in Arkansas head start centers.

BACKGROUND: The impact of preschool environmental conditions on classroom aeroallergen concentrations is not fully understood. OBJECTIVE: To examine the relationship between school environmental conditions and classroom aeroallergen concentrations in the Pulaski County Head Start (HS) Program. METHODS: Thirty-three HS centers in Pulaski County, Arkansas, underwent a detailed environmental evaluation. Classroom settled dust samples were analyzed for the presence of common indoor allergens. RESULTS: Classroom eating (70%), wall-to-wall carpeting (58%), and water damage (33%) were common. Median classroom allergen levels were as follows: dust mite (Der p 1 and Der f 1), 0.6 microg/g; Fel d 1, 0.4 microg/g; Can f 1, 1.7 microg/g; cockroach, below detection; Mus m 1, 0.18 microg/g; and mold spores, 17,800 CFU/g. Can f 1 and Mus m 1 allergens were detected in 100% of HS centers. Facilities with carpeting, increased humidity, and single-use facilities showed trends toward increased dust mite concentrations. Detectable cockroach allergen was more common in classrooms cleaned by teachers than by professional housekeepers. CONCLUSIONS: Aeroallergens were commonly detected in Pulaski County HS center classrooms, with dog and mouse allergens detected in 100% of centers. Median classroom allergen concentrations were low, and classroom characteristics were not strongly predictive of increased allergen exposure.     

Clearance of Chlamydia trachomatis from the murine genital mucosa does not require perforin-mediated cytolysis or Fas-mediated apoptosis

The molecular mechanisms of resistance to genital infection with the mouse pneumonitis (MoPn) strain of Chlamydia trachomatis are unknown. A role for major histocompatibility complex class II-restricted, interleukin-12-dependent CD4(+) T cells has been established, but the functional activity of these cells does not depend on secretion of gamma interferon. Here we examined the potential contribution of T-cell-mediated cytotoxicity and apoptosis to mucosal clearance of MoPn by using mice deficient in the molecular mediators of target cell lysis. Animals lacking perforin, Fas, Fas ligand, or both perforin and Fas ligand were infected genitally with C. trachomatis MoPn and monitored for expression of immunity to chlamydial antigens and clearance of MoPn from the genital mucosa. In each case, the profile of spleen cytokine production, the magnitude of the host antibody response, and the kinetics of chlamydial clearance were similar to those of genetically intact controls. Compensatory overproduction of tumor necrosis factor alpha, an alternate mediator of apoptosis in certain cell types, did not appear to account for the ability of mutant mice to resolve Chlamydia infections. These results fail to support CD4(+) T-cell-mediated apoptosis or CD8(+) T-cell-mediated cytotoxicity as being critical to the clearance of C. trachomatis MoPn urogenital infections.     

Fine structure of A and M antigens from Brucella biovars.

Brucella A and M epitopes were found on single O-polysaccharide chains of all biotype strains of this species. Lipopolysaccharides from the type and reference strains of five of the six Brucella species, B. abortus, B. melitensis, B. suis, B. canis, and B. neotomae, were extracted and purified. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, in conjunction with silver staining and immunoblotting developed by monoclonal antibodies, showed bands characteristic of A, M, or mixed A and M antigens. The A antigen previously described as an exclusively alpha 1,2-linked homopolymer of 4,6-dideoxy-4-formamido-D-mannopyranose was shown by 1H and 13C nuclear magnetic resonance spectroscopy to possess a fine structure consistent with the low-frequency occurrence of alpha 1, 3-linked 4,6-dideoxy-4-formamido-D-mannopyranose residues. This feature was previously attributed only to the M antigen, which is also a homopolymer of the same sugar. B. melitensis biotype 3 and B. suis biotype 4 lipopolysaccharides showed characteristics of mixed A and M antigens. Immunoabsorption of these O polysaccharides on a column of immobilized A-antigen-specific monoclonal antibody enriched polymer chains with A-antigen characteristics but did not eliminate M epitopes. Composite A- and M-antigen characteristics resulted from O polysaccharides in which the frequency of alpha 1,3 linkages, and hence, M-antigen characteristics, varied. All biotypes assigned as A+ M- expressed one or two alpha 1,3-linked residues per polysaccharide O chain. M antigens (M+ A-) also possessed a unique M epitope as well as a tetrasaccharide determinant common to A-antigen structures. B. canis and B. abortus 45/20, both rough strains, expressed low-molecular-weight A antigen.     

Tetanus toxin-induced seizures cause microglial activation in rat hippocampus

Tetanus toxin (about 20 mouse LD50) injected into the ventral hippocampus of rats leads to brief seizures occurring intermittently over a period of weeks. Toxin injection leads to the appearance of activated microglia (detected with OX42 immunohistochemistry) in the hippocampus. After 7-14 days, many activated microglia are visible in CA1 area of dorsal hippocampus aligned with the pyramidal cell dendrites and having the morphology characteristic of 'rod cells'. Extensive cell loss is found in dorsal CA1, but not at the injection site, in about one third of injected rats.