Mouse genetic locus Lps influences susceptibility to Neisseria meningitidis infection.

We surveyed a number of inbred mouse strains for susceptibility to meningococcemia. Mice of all strains became bacteremic after intraperitoneal injection of a serogroup C, serotype 2a human disease isolate, but the strains differed in levels of bacteremia, indicating influences of the host genome on susceptibility. There was no significant correlation between level of bacteremia and differences at major histocompatibility or immunoglobulin loci; the Salmonella susceptibility locus, Ity; the complement C5 locus, Hc; the antibody response locus, xid; or the transferrin locus, Trf. However, the Lps locus, which influences a range of host cellular responses to endotoxin and affects susceptibility to Salmonella typhimurium, did influence susceptibility to meningococcemia. There were significant differences in levels of bacteremia between C3H/HeJ (Lpsd) mice and each of the other strains (all Lpsn). We confirmed the association of the Lpsd genotype with susceptibility by using coisogenic strains from two widely separated mouse lineages: C3H and B10. Lpsd mice experienced a 1,000-fold proliferation of bacteria and were bacteremic for days before clearing the infection. In contrast, Lpsn mice cleared the bacteremia in less than 1 day. There was no difference in meningococcal growth in vitro in serum from C3H/HeJ and coisogenic C3H/HeN (Lpsn) mice, suggesting that the Lps-related difference in susceptibility may involve a cellular response

Metabolic Scaling in Birds and Mammals: How Taxon Divergence Time, Phylogeny, and Metabolic Rate Affect the Relationship between Scaling Exponents and Intercepts

Analysis of metabolic scaling in currently living endothermic animal species allowed us to show how the relationship between body mass and the basal metabolic rate (BMR) has evolved in the history of endothermic vertebrates. We compared six taxonomic groups according to their energetic characteristics and the time of evolutionary divergence. We transformed the slope of the regression lines to the common value and analyzed three criteria for comparing BMR of different taxa regardless of body size. Correlation between average field metabolic rate (FMR) of the group and its average BMR was shown. We evaluated the efficiency of self-maintenance in ordinary life (defined BMR/FMR) in six main groups of endotherms. Our study has shown that metabolic scaling in the main groups of endothermic animals correlates with their evolutionary age: the younger the group, the higher the metabolic rate, but the rate increases more slowly with increasing body weight. We found negative linear relationship for scaling exponents and the allometric coefficient in five groups of endotherms: in units of mL O2/h per g, in relative units of allometric coefficients, and also in level or scaling elevation. Mammals that diverged from the main vertebrate stem earlier have a higher “b” exponent than later divergent birds. A new approach using three criteria for comparing BMR of different taxa regardless of body mass will be useful for many biological size-scaling relationships that follow the power function