Comparison of Ashdown's medium, Burkholderia cepacia medium, and Burkholderia pseudomallei selective agar for clinical isolation of Burkholderia pseudomallei

Ashdown's medium, Burkholderia pseudomallei selective agar (BPSA), and a commercial Burkholderia cepacia medium were compared for their abilities to grow B. pseudomallei from 155 clinical specimens that proved positive for this organism. The sensitivity of each was equivalent; the selectivity of BPSA was lower than that of Ashdown's or B. cepacia medium.     

Risk and protective factors for suicidal behavior in abused African American women

This study examined risk and protective factors that differentiate low-income, abused African American women (N = 200) who attempted suicide from those who had never made a suicide attempt. Results from multivariate analyses revealed that numerous and/or severe negative life events, a history of child maltreatment, high levels of psychological distress and depression, hopelessness about the future, and alcohol and drug problems were factors associated with attempter status. Protective factors associated with nonattempter status included hopefulness, self-efficacy, coping skills, social support, and effectiveness in obtaining material resources. Culturally competent intervention approaches for abused women should target increasing their protective factors and reducing their risk factors to decrease the likelihood that these women engage in suicidal behavior.     

Homologues of insecticidal toxin complex genes in Yersinia enterocolitica biotype 1A and their contribution to virulence

Yersinia enterocolitica is an enteric pathogen that consists of six biotypes: 1A, 1B, 2, 3, 4, and 5. Strains of the latter five biotypes can carry a virulence plasmid, known as pYV, and several well-characterized chromosomally encoded virulence determinants. Y. enterocolitica strains of biotype 1A lack the virulence-associated markers of pYV-bearing strains and were once considered to be avirulent. There is growing epidemiological, clinical, and experimental evidence, however, to suggest that some biotype 1A strains are virulent and can cause gastrointestinal disease. To identify potential virulence genes of pathogenic strains of Y. enterocolitica biotype 1A, we used genomic subtractive hybridization to determine genetic differences between two biotype 1A strains: an environmental isolate, Y. enterocolitica IP2222, and a clinical isolate, Y. enterocolitica T83. Among the Y. enterocolitica T83-specific genes we identified were three, tcbA, tcaC, and tccC, that showed homology to the insecticidal toxin complex (TC) genes first discovered in Photorhabdus luminescens. The Y. enterocolitica T83 TC gene homologues were expressed by Y. enterocolitica T83 and were significantly more prevalent among clinical biotype 1A strains than other Yersinia isolates. Inactivation of the TC genes in Y. enterocolitica T83 resulted in mutants which were attenuated in the ability to colonize the gastrointestinal tracts of perorally infected mice. These results indicate that products of the TC gene complex contribute to the virulence of some strains of Y. enterocolitica biotype 1A, possibly by facilitating their persistence in vivo.     

Urban adolescents' perceptions of their neighborhoods: An examination of spatial dependence

Spatial dependence exists when the variation between observations is dependent on spatial location. In the present study, geostatistical methods were used to examine spatial dependence in adolescents' perceptions of their neighborhoods: whether adolescents living in close proximity perceived their neighborhoods more similarly than adolescents living further apart. Participants included 343 adolescents (53% male; 91% African American) enrolled in sixth grade, residing in Baltimore City, with geocoded home addresses. These addresses were used in combination with a measure of perceived neighborhood disorder and disadvantage to compute variogram plots, a geostatistical technique used to evaluate spatial dependence. Results indicated that perceptions of youth residing in close geographic proximity were more similar than perceptions of youth residing further apart. Adjusting for census‐level characteristics, but not individual and family characteristics, resulted in decreased variation among participants but did not eliminate the spatial dependence. Findings highlight the utility of geostatistical methods for social science research. © 2004 Wiley Periodicals, Inc. J Comm Psychol 32: 277–293, 2004.     

Degree of Immunity Induced by Killed Vaccines to Experimental Salmonellosis in Mice

Killed vaccines, deoxycholate-extracted or heated, were shown to induce an effective degree of immunity which protected against death (100%), prevented extensive multiplication, and left the mice with low residual salmonella populations in spleen and liver after intravenous (iv) or intraperitoneal (ip) challenge with virulent Salmonella typhimurium. Protection was most effective against the ip challenge route and less effective against the iv route. A study of the kinetics of the population of bacteria in the spleens and livers of immunized animals showed that after ip challenge there was an initial reduction of 99% at 6 hr after challenge, maintenance of levels of less than 10(3) bacteria per organ, and a final population of 10(2) to 10(3) per organ at 21 days. With iv challenge, after an initial reduction of 90% at 6 hr, growth ensued to levels above 10(6) bacteria per organ until 8 days, followed by a steady decline yielding residual populations of 10(3) to 10(4) in some cases. Organ hypertrophy correlated with bacterial population. Morbidity was prevented (as measured by gain in body weight) by immunization against ip challenge but not against iv challenge. Killed vaccines protected by their ability to induce an immune state which reduced the initial challenge population, prevented extensive multiplication, yet allowed "cellular immunity" to develop due to response to the living challenge infection itself. The consequence was a low-level carrier state similar to that induced by recovery from sublethal virulent infection.     

Volume and surface area estimates of astrocytes in the sensorimotor cortex of the cat

Electron micrographs of random sections through 133 astrocytes taken from the anterior and posterior sigmoid gyri of adult cats were used to estimate average astrocyte cell volume. Average soma volume was derived by two methods: (1) assuming that each approximated the shape of a prolate spheroid, a value of 2.2 ± 0.1 × 10^?13l. was calculated by substituting measurements of major (mean 10.4 ± 0.2 μm) and minor (mean 6.2 ± 0.1 μm) cell axes into the formula for volume; (2) applying Weibel's point-counting method of morphometry, a value of 1.9 ± 0.09 × 10^?13l. was obtained based on ratios of volume density and nuclear volume, calculated from measurements of nuclear axes. Because of the use of random sections through the cells sampled, the axial measurements on which both methods depend represent possible underestimations by as much as 21%; the resulting average value for soma volume might be as much as 3.2 × 10^?13l. Astrocyte somata from the deepest layer of the cortex had a significantly larger average volume than those from more superficial layers (P < 0.05). Average total cell volume (soma plus processes), estimated by calculating the volume of the tissue sample that was occupied by astrocytes and dividing that value by the number of astrocytes in the sample, amounted to 5.7 × 10^?13l. Point-counting morphometry revealed that 15.5% of the cortex consists of astrocytic cytoplasm. Average total cell surface area, estimated from intercepts of grid lines with cell membrane profiles of astrocytes within the sample, was 1.9 × 10^?5 cm²; average surface area of astrocyte somata, based on axial measurements, amounted to 2.5 × 10^?6 cm² or 13% of the surface area of the whole cell.Only 18 gap junctions were identified in the random sections through 133 astrocytes; these and other considerations bearing on the possible relationship of the data presented to electrical measurements in living astrocytes are discussed.     

Epidemic pathogenic selection: an explanation for hereditary hemochromatosis?

Hereditary hemochromatosis (HH) is a disorder associated with progressive iron overload and deposition in multiple organs. It is the most common inherited single gene disorder in people of Northern and Western European descent. About 80% of individuals of European descent with HH are homozygous for a cysteine-to-tyrosine substitution (C282Y) in the gene now called HFE. The function of HFE protein, a major histocompatibility class I-like transmembrane protein, has not been fully elucidated. Three consequences of the C282Y mutation are lack of expression of HFE on the cellular surface, a lowered iron level in macrophages, and an increased rate of clearance of iron from the intestinal lumen. These changes could confer protection against certain pathogens early in life before iron overload occurs. Furthermore, the C282Y mutation might have been selected for during the European plagues caused by Yersinia spp. and other pathogens because of the conferred resistance to infection, i.e., by epidemic pathogenic selection.