Social Status and Resistance to Disease in House Mice (Mus musculus): Status-related Modulation of Hormonal Responses in Relation to Immunity Costs in Different Social and Physical Environments

Unrelated and previously unfamiliar male mice were maintained in groups of six tor different periods and at different ambient temperatures. High- and low-ranking males differed in hormone-related resistance to a subsequent experimental infection with the blood protozoan Babesia microti and there were rank differences in the apparent modulation of immunodepressive hormones relative to an individual's internal, social and physical environment. Resistance to B. microti was influenced by serum concentrations of corticosterone and testosterone. Associations between aggressiveness and measures of immunocompetence and resistance were related to corticosterone concentration, but only among low rankers. Effects of testosterone on resistance were confined to high rankers but were not associated with aggressiveness, although high rankers maintained greater aggressiveness than low rankers in all experimental treatments. The effects of group duration and temperature on resistance can be interpreted in terms of changing hormone and antibody levels in relation to metabolic stress. The results emphasize the importance of interactions between underlying physiological changes in relationships between behaviour, immune function and disease.     

The larval morphology and ecology of a new species of Ecnomus from lake Naivasha,Kenya (Trichoptera: Ecnomidae)

Ecnomus mennelli sp.n. from Lake Naivasha, Kenya, belongs to the natalensis‐group. E. thomasseti was also found at the lake, and these are the first records of Trichoptera from Naivasha. Adults and larvae of both species were collected, and an analysis of the gut contents of the larvae showed them to be mainly predator y on small invertebrates. The ecological requirements and distribution of the African species of Ecnomus are discussed.     

Conserved Organization of γ-Aminobutyric AcidAReceptor Genes: Cloning and Analysis of the Chicken β4-Subunit Gene

A series of genomic clones containing DNA that encodes the chicken gamma-aminobutyric acidA (GABAA) receptor beta 4 subunit have been isolated. These have been restriction mapped and partially sequenced to determine the structural organization and the size of the beta 4-subunit gene. This gene, which comprises nine exons, spans more than 65 kb. The organization of the chicken GABAA receptor beta 4-subunit gene has been compared to that of the murine GABAA receptor delta-subunit gene and to those of the genes that encode other members of the ligand-gated ion-channel superfamily, namely muscle and neuronal nicotinic acetylcholine receptors (AChRs). Although the positions of the intron/exon boundaries of GABAA receptor subunit genes are seen to be highly conserved, there are significant differences between the genes that encode GABAA receptor and AChR subunits. These results are discussed in relation to the proposal that this superfamily of ligand-gated ion-channel receptor genes arose by duplication of an ancestral receptor gene.     

Comparison of competitively primed and conventional allele-specific nucleic acid amplification

A simulation of competitively primed allele-specific DNA amplification has been constructed and its behavior examined. This has shown that when the ratio of the amount of homoduplex misprime product to the total amount of amplimer is low, it increases by approximately one-fourth of the mispriming frequency with each doubling of the total amount of amplimer. When the ratio is high and reverse mispriming becomes significant, it asymptotes toward a value <0.5. An analogous simulation was carried out on conventional allele-specific DNA amplification. As expected, the ratio of the amount of amplimer in the positive and negative reactions closely approximates the mispriming frequency provided that amplification is exponential in both cases. This suggests that conventional allele-specific amplification has somewhat higher inherent specificity than competitively primed amplification. However, conventional allele-specific reactions are subject to a "catch-up" phase in which the positive reaction slows or stops, thus reducing the specificity. It was hypothesized that competitively primed reactions may be easier to optimize than conventional allele-specific reactions. This conjecture was supported experimentally. In addition, it was shown that the specificity of competitively primed reactions is a function of the degree of amplification.     

A novel high-cell-density protein expression system based on Ralstonia eutropha

We describe the development of a novel protein expression system based on the industrial fermentation organism Ralstonia eutropha (formerly known as Alcaligenes eutrophus) NCIMB 40124. This new system overcomes some of the shortcomings of traditional Escherichia coli-based protein expression systems, particularly the propensity of such systems to form inclusion bodies during high-level expression. Using a proteomics approach, we identified promoters that can be induced by simple process parameters or medium compositions in high-density cell culture or shake flasks, respectively. By combining newly developed molecular biological tools with a high-cell-density fermentation process, we were able to produce high levels (>1 g/liter) of soluble, active organophosphohydrolase, a model enzyme prone to inclusion body formation in E. coli.     

Analysis and Application of an Equilibrium Model forin vitroBioassay Systems with Three Components: Receptor, Hormone and Hormone-Binding-Protein

A simple theoretical framework is presented for bioassay studies using three componentin vitrosystems. An equilibrium model is used to derive equations useful for predicting changes in biological response after addition of hormone-binding-protein or as a consequence of increased hormone affinity. Sets of possible solutions for receptor occupancy and binding protein occupancy are found for typical values of receptor and binding protein affinity constants. Unique equilibrium solutions are dictated by the initial condition of total hormone concentration. According to the occupancy theory of drug action, increasing the affinity of a hormone for its receptor will result in a proportional increase in biological potency. However, the three component model predicts that the magnitude of increase in biological potency will be a small fraction of the proportional increase in affinity. With typical initial conditions a two-fold increase in hormone affinity for its receptor is predicted to result in only a 33% increase in biological response. Under the same conditions an 11-fold increase in hormone affinity for receptor would be needed to produce a two-fold increase in biological potency. Some currently used bioassay systems may be unrecognized three component systems and gross errors in biopotency estimates will result if the effect of binding protein is not calculated. An algorithm derived from the three component model is used to predict changes in biological response after addition of binding protein toin vitrosystems. The algorithm is tested by application to a published data set from an experimental study in anin vitrosystem (Limet al., 1990,Endocrinology127,1287–1291). Predicted changes show good agreement (within 8%) with experimental observations.