Post-weaning Nutritional Programming of Ovarian Developmentin Beef Heifers

The nutritional management of replacement females from weaning to breeding is critical to lifetime productivity. Traditionally, cereal grains have been used to develop replacement heifers to attain puberty and enter the breeding system at a younger age. However, overfeeding heifers decreases number of calves weaned, while peri-pubertal caloric restriction increased primordial follicle numbers in the developing ovary. The number of primordial follicles a female has can determine her overall fertility; females with a greater amount of follicles have greater reproductive lifespans. In this study, two groups of heifers were developed to prebreeding status. One group received a control diet (228 kcal ME/BW kg0.75) while the other received a restricted diet (157 kcal ME/BW kg0.75) for 84 days, and were then stepped up to receive a diet containing 277 kcal ME/BW kg0.75. Both groups were evaluated at three different time points for number of primordial follicles. Heifers on the restricted diet had more primordial follicles than control heifers at 13 mo of age. In summary, heifer input costs could be decreased without negatively effecting overall fertility and perhaps improve fertility

For science, love and money: the social worlds of poultry and rabbit breeding in Britain, 1900-1940

This paper traces the joint histories of poultry and rabbit breeding by fanciers, and for commercial and scientific purposes, in early 20th-century Britain. I show that the histories of the social worlds that bred for these different purposes are intertwined, as are the histories of poultry and rabbit breeding in general. To properly understand the history of scientific breeding we must therefore understand the general context of breeding in which this occurred. In the paper I show that as fancy poultry and rabbits were taken up for scientific research at the start of the 20th century they became scientific specimens and boundary objects between the social worlds. Their existence as boundary objects motivated the social worlds to coordinate their work through translators and trading zones. By the 1930s all three coordination methods were being used simultaneously

The Structure of a Rigorously Conserved RNA Element within the SARS Virus Genome

We have solved the three-dimensional crystal structure of the stem-loop II motif (s2m) RNA element of the SARS virus genome to 2.7-Å resolution. SARS and related coronaviruses and astroviruses all possess a motif at the 3′ end of their RNA genomes, called the s2m, whose pathogenic importance is inferred from its rigorous sequence conservation in an otherwise rapidly mutable RNA genome. We find that this extreme conservation is clearly explained by the requirement to form a highly structured RNA whose unique tertiary structure includes a sharp 90° kink of the helix axis and several novel longer-range tertiary interactions. The tertiary base interactions create a tunnel that runs perpendicular to the main helical axis whose interior is negatively charged and binds two magnesium ions. These unusual features likely form interaction surfaces with conserved host cell components or other reactive sites required for virus function. Based on its conservation in viral pathogen genomes and its absence in the human genome, we suggest that these unusual structural features in the s2m RNA element are attractive targets for the design of anti-viral therapeutic agents. Structural genomics has sought to deduce protein function based on three-dimensional homology. Here we have extended this approach to RNA by proposing potential functions for a rigorously conserved set of RNA tertiary structural interactions that occur within the SARS RNA genome itself. Based on tertiary structural comparisons, we propose the s2m RNA binds one or more proteins possessing an oligomer-binding-like fold, and we suggest a possible mechanism for SARS viral RNA hijacking of host protein synthesis, both based upon observed s2m RNA macromolecular mimicry of a relevant ribosomal RNA fold

A functional model, eigenvalues, and finite singular critical points for indefinite Sturm-Liouville operators

Eigenvalues in the essential spectrum of a weighted Sturm-Liouville operator are studied under the assumption that the weight function has one turning point. An abstract approach to the problem is given via a functional model for indefinite Sturm-Liouville operators. Algebraic multiplicities of eigenvalues are obtained. Also, operators with finite singular critical points are considered.Comment: 38 pages, Proposition 2.2 and its proof corrected, Remarks 2.5, 3.4, and 3.12 extended, details added in subsections 2.3 and 4.2, section 6 rearranged, typos corrected, references adde