Body Composition QTLs Identified in Intercross Populations Are Reproducible in Consomic Mouse Strains

Genetic variation contributes to individual differences in obesity, but defining the exact relationships between naturally occurring genotypes and their effects on fatness remains elusive. As a step toward positional cloning of previously identified body composition quantitative trait loci (QTLs) from F₂ crosses of mice from the C57BL/6ByJ and 129P3/J inbred strains, we sought to recapture them on a homogenous genetic background of consomic (chromosome substitution) strains. Male and female mice from reciprocal consomic strains originating from the C57BL/6ByJ and 129P3/J strains were bred and measured for body weight, length, and adiposity. Chromosomes 2, 7, and 9 were selected for substitution because previous F₂ intercross studies revealed body composition QTLs on these chromosomes. We considered a QTL confirmed if one or both sexes of one or both reciprocal consomic strains differed significantly from the host strain in the expected direction after correction for multiple testing. Using these criteria, we confirmed two of two QTLs for body weight (Bwq5-6), three of three QTLs for body length (Bdln3-5), and three of three QTLs for adiposity (Adip20, Adip26 and Adip27). Overall, this study shows that despite the biological complexity of body size and composition, most QTLs for these traits are preserved when transferred to consomic strains; in addition, studying reciprocal consomic strains of both sexes is useful in assessing the robustness of a particular QTL.     

Acid adaptation in Streptococcus mutans UA159 alleviates sensitization to environmental stress due to RecA deficiency

Abstract A RecA-deficient stain of Streptococcus mutans , isolated previously, was found to be more susceptible than the prototroph organism to acid killing and also showed reduced colony-forming ability on sucrose-containing medium. The deficient strain was able to grow in chemostat culture at a low pH value of 5 and did not show reduced capacity to produce acid in standard pH-drop experiments with excess glucose. Moreover, it was able to undergo an adaptive response when grown at a low pH to become more resistant to acid killing and also to killing by ultraviolet radiation or hydrogen peroxide. In fact, after adaptation, it was nearly as resistant as the prototroph strain. These findings were interpreted, in part, in terms of an acid-inducible DNA repair system which functions independently of RecA.     

Amino acid metabolism during batch culture of a murine hybridoma,AFP-27

This paper presents batch culture data of the murine hybridoma, AFP-27, cultured in conventional basal media and in a nutrient-rich modified version. Expression of antibody was fivefold higher in the enriched formulation, with significant product secretion in the decline phase. Cultures were initiated at conventional inculation densities (1 2 × 10⁵ viable cells ml^–1) and high inoculation densities (1.5 1.7 × 10⁶ viable cells ml^–1). Amino acid levels have been reported for all cultures, with apparent differences described. Relative levels of intracellular amino acids are also reported, with significant accumulation of proline, glycine and alanine. The results have significance in the design of enriched media which are clearly beneficial for commercial production of antibodies from hybridomas.     

Intra-crown variation in leaf herbivory and seed production in striped maple,Acer pensylvanicum L. (Aceraceae)

Summary Patterns of spatial variation in leaf herbivory and the effects of this variation on seed production and twig growth were studied in striped maple, Acer pensylvanicum (Aceraceae). Experimental removal of 25% of the leaf area from each of four leaves directly subtending a developing infructescence significantly reduced seed number in that infructescence. When leaf area was removed from leaves neighboring to, but not directly subtending developing infructescences, no reduction in seed production occurred. Together, these results suggest that only photosynthate from leaves directly subtending infructescences contributes to seed production in nearby infructescences. Effects of the experimental removal of leaf area did not persist the second year, suggesting that mobilization of storage products the following spring occurred independent of prior treatment. There was probably little negative impact of leaf herbivores on this plant species during the study year due to (1) low occurrence of localized damage within the crowns of censused trees and (2) delay of leaf area loss until completion of fruit development.     

Kinetics of chondrocyte growth in cell-polymer implants

In vitro cultivation of cartilage cells (chondrocytes) on biodegradable polyglycolic acid (PGA) scaffolds resulted in implants which could potentially be used to repair damaged joint cartilage or for reconstructive surgery. Cell growth kinetics were studied to define conditions under which the cellularity of implants made from isolated calf chondrocytes reached that of the parent calf cartilage. In static cultures, condrocyte growth rates decreased as either implant thickness or implant cell density increased. Over 4 weeks of cultivation, implant permeability to glucose decreased to 3% that of the plain polymer scaffold; this effect was attributed to the decrease in effective implant porosity associated with cartilage tissue regeneration.In a well-mixed culture, implants 1 cm in diameter by 0.3 cm thick maintained high cell growth rates over 7 weeks and hard normal cell densities. Regenerated cartilage with these dimensions is large enough to resurface small joints such as the trapezium bone at the base of the human thumb. Such implants could not be grown statically, since cell growth stopped at 3-4 weeks and cell densities remained below normal. Optimization of the tissue culture environment is thus essential in order to cultivate clinically useful cartilage implants in vitro. (c) 1994 John Wiley & Sons, Inc.     

Form and environment of Gryphaea arcuata

Gryphaea arcuata is one of the most studied fossils, but its detailed palaeoecology has been largely neglected. Specimens were collected within a short stratigraphic range (three ammonite zones) in the 'Calcaire à gryphées' of Xeuilley (Lorraine, France) dated Hettangian to Lower Sinemurian. As far as possible, they were sampled from each marly bed of the section. A biometric study and an isotopic analysis are compared in regard to organic matter measurements and palynological data, the results demonstrating a clear relationship between the shape of G. arcuata and environmental parameters. Factors responsible for the various shapes are temperature, oxygen levels on the sea floor and nutrient levels. Two main morphotypes can be related to two kinds of environment. In the first, controlled by a relatively hot and humid climate and tending towards eutrophication, the growth rate of Gryphaea was low, and the shells small, wide and thin. In the second environment, cooler than the first one and closer to the optimal living conditions of G. arcuata, the shell was large, thick and narrow, and exhibited a high growth rate.