Southern Illinois University Carbondale

About: Southern Illinois University Carbondale is a education organization based out in Carbondale, Illinois, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 13570 authors who have published 24819 publications receiving 667385 citations. The organization is also known as: SIU Carbondale & SIUC.

On the Formation of Interaction Networks in Social Coordination Games

Abstract: There are many situations where two interacting individuals can benefit from coordinating their actions. We examine the endogenous choice of partners in such social coordination games and the implications for resulting play. We model the interaction pattern as a network where individuals periodically have the discretion to add or sever links to other players. A player chooses whether to add or sever a link based on the (prospective) partner's past behavior. With such endogenous interaction patterns we see multiple stochastically stable states of play, including some that involve play of equilibria in the coordination game that are neither efficient nor risk dominant.

The IdhA Gene Encoding the Fermentative Lactate Dehydrogenase of Escherichia Coli

Abstract: Under anaerobic conditions, especially at low pH, Escherichia coli converts pyruvate to D-lactate by means of an NADH-linked lactate dehydrogenase (LDH). This LDH is present in substantial basal levels under all conditions but increases approximately 10-fold at low pH. The IdhA gene, encoding the fermentative lactate dehydrogenase of E. coli, was cloned using λ10E6 of the Kohara collection as the source of DNA. The IdhA gene was subcloned on a 2.8 kb MIuI-MIuI fragment into a multicopy vector and the region encompassing the gene was sequenced. The IdhA gene of E. coli was highly homologous to genes for other D-lactate-specific dehydrogenases but unrelated to those for the L-lactate-specific enzymes. We constructed a disrupted derivative of the IdhA gene by inserting a kanamycin resistance cassette into the unique KpnI site within the coding region. When transferred to the chromosome, the IdhA::Kan construct abolished the synthesis of the D-LDH completely. When present in high copy number, the IdhA gene was greatly overexpressed, suggesting escape from negative regulation. Cells expressing high levels of the D-LDH grew very poorly, especially in minimal medium. This poor growth was largely counteracted by supplementation with high alanine or pyruvate concentrations, suggesting that excess LDH converts the pyruvate pool to lactate, thus creating a shortage of 3-carbon metabolic intermediates. Using an IdhA-cat gene fusion construct we isolated mutants which no longer showed pH-dependent regulation of the IdhA gene. Some of these appeared to be in the pta gene, which encodes phosphotransacetylase, suggesting the possible involvement of acetyl phosphate in IdhA regulation.

Abnormal spermatogenesis and reduced fertility in transition nuclear protein 1-deficient mice

Abstract: Transition nuclear proteins (TPs), the major proteins found in chromatin of condensing spermatids, are believed to be important for histone displacement and chromatin condensation during mammalian spermatogenesis. We generated mice lacking the major TP, TP1, by targeted deletion of the Tnp1 gene in mouse embryonic stem cells. Surprisingly, testis weights and sperm production were normal in the mutant mice, and only subtle abnormalities were observed in sperm morphology. Electron microscopy revealed large rod-like structures in the chromatin of mutant step 13 spermatids, in contrast to the fine chromatin fibrils observed in wild type. Steps 12–13 spermatid nuclei from the testis of Tnp1-null mice contained, in place of TP1, elevated levels of TP2 and some protamine 2 (P2) precursor. Most of the precursor was processed to mature P2, but high levels of incompletely processed forms remained in epididymal spermatozoa. Sperm motility was reduced severely, and ≈60% of Tnp1-null males were infertile. We concluded that TP1 is not essential for histone displacement or chromatin condensation. The absence of TP1 may partially be compensated for by TP2 and P2 precursor, but this dysregulation of nucleoprotein replacement results in an abnormal pattern of chromatin condensation and in reduced fertility.