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Paul Bernhardt

Publications and source records attributed to Paul Bernhardt.

4 recordsLinked to original sources
PubMed2006

Estimating the relative contributions of virulence factors for pathogenic microbes.

Many pathogenic microbes have multiple virulence factors that can cause damage to the host and thus contribute to an overall virulence phenotype for that organism. Although current techniques are suitable for demonstrating that a particular microbial characteristic contributes to virulence, no formal approach for defining the relative contributions of multiple virulence factors to overall virulence has been proposed. This paper describes the use of multivariate linear regression to estimate the relative contributions of virulence factors to the overall phenomenon of virulence. The approach is illustrated here with sample calculations of the relative contributions of individual Cryptococcus neoformans and Bacillus anthracis virulence factors to the overall virulence phenotype. These calculations were derived from a small underpowered experimental data set for the fungus and two larger sets of randomly generated data for both microbes. The major limitation of this method is a requirement for large data sets of microbial strains that differ in virulence and virulence factor expression. Multivariate linear regression can be used to identify the relative levels of importance of virulence factors in virulence studies, and this information can be used to prioritize antigen identification for vaccine development and the design of antimicrobial strategies that target virulence mechanisms.

Analysis of Variance↗
PubMed2004

Infection-dependent phenotypes in MHC-congenic mice are not due to MHC: can we trust congenic animals?

BACKGROUND: Congenic strains of mice are assumed to differ only at a single gene or region of the genome. These mice have great importance in evaluating the function of genes. However, their utility depends on the maintenance of this true congenic nature. Although, accumulating evidence suggests that congenic strains suffer genetic divergence that could compromise interpretation of experimental results, this problem is usually ignored. During coinfection studies with Salmonella typhimurium and Theiler's murine encephalomyelitis virus (TMEV) in major histocompatibility complex (MHC)-congenic mice, we conducted the proper F2 controls and discovered significant differences between these F2 animals and MHC-genotype-matched P0 and F1 animals in weight gain and pathogen load. To systematically evaluate the apparent non-MHC differences in these mice, we infected all three generations (P0, F1 and F2) for 5 MHC genotypes (b/b, b/q and q/q as well as d/d, d/q, and q/q) with Salmonella and TMEV. RESULTS: Infected P0 MHC q/q congenic homozygotes lost significantly more weight (p = 0.02) and had significantly higher Salmonella (p < 0.01) and TMEV (p = 0.02) titers than the infected F2 q/q homozygotes. Neither weight nor pathogen load differences were present in sham-infected controls. CONCLUSIONS: These data suggest that these strains differ for genes other than those in the MHC congenic region. The most likely explanation is that deleterious recessive mutations affecting response to infection have accumulated in the more than 40 years that this B10.Q-H-2q MHC-congenic strain has been separated from its B10-H-2b parental strain. During typical experiments with congenic strains, the phenotypes of these accumulated mutations will be falsely ascribed to the congenic gene(s). This problem likely affects any strains separated for appreciable time and while usually ignored, can be avoided with the use of F2 segregants.

Animals↗
PubMed2004

Relationship between achievement goal constructs and physical self-perceptions in a physical activity setting.

The relations of achievement goal theory constructs and physical self-perceptions were explored with 225 students (91 men, 109 women, and 25 nonindicators; M age=23.5 yr., SD=9.2), enrolled in basic physical activity classes (aerobics, weight training, modern dance, badminton, yoga, tai chi, basketball, racquetball, gymnastics, bowling, aquatone, and step aerobics) in a university setting. Goal orientations (Task and Ego Orientation in Sport Questionnaire), perceptions of the motivational climate (Perceived Motivational Climate in Sport Questionnaire-2), and physical self-perceptions (Physical Self-perception Profile) were assessed. Data were analyzed separately by sex. Ego orientation was the only predictor of Physical Self-perceptions in men, accounting for between 12 and 15% of the variance in Physical Self-worth, Sport Competence, Physical Conditioning, and Body Attractiveness. Constructs of achievement goal theory were not predictive of Physical Self-perceptions in the women. The results are discussed in light of achievement goal theory and the nature of the sample.

Achievement↗