Genetic background influences adaptation to cardiac hypertrophy and Ca(2+) handling gene expression.

Genetic variability has a profound effect on the development of cardiac hypertrophy in response to stress. Consequently, using a variety of inbred mouse strains with known genetic profiles may be powerful models for studying the response to cardiovascular stress. To explore this approach we looked at male C57BL/6J and 129/SvJ mice. Hemodynamic analyses of left ventricular pressures (LVPs) indicated significant differences in 129/SvJ and C57BL/6J mice that implied altered Ca(2+) handling. Specifically, 129/SvJ mice demonstrated reduced rates of relaxation and insensitivity to dobutamine (Db). We hypothesized that altered expression of genes controlling the influx and efflux of Ca(2+) from the sarcoplasmic reticulum (SR) was responsible and investigated the expression of several genes involved in maintaining the intracellular and sarcoluminal Ca(2+) concentration using quantitative real-time PCR analyses (qRT-PCR). We observed significant differences in baseline gene expression as well as different responses in expression to isoproterenol (ISO) challenge. In untreated control animals, 129/SvJ mice expressed 1.68× more ryanodine receptor 2(Ryr2) mRNA than C57BL/6J mice but only 0.37× as much calsequestrin 2 (Casq2). After treatment with ISO, sarco(endo)plasmic reticulum Ca(2+)-ATPase(Serca2) expression was reduced nearly two-fold in 129/SvJ while expression in C57BL/6J was stable. Interestingly, ß (1) adrenergic receptor(Adrb1) expression was lower in 129/SvJ compared to C57BL/6J at baseline and lower in both strains after treatment. Metabolically, the brain isoform of creatine kinase (Ckb) was up-regulated in response to ISO in C57BL/6J but not in 129/SvJ. These data suggest that the two strains of mice regulate Ca(2+) homeostasis via different mechanisms and may be useful in developing personalized therapies in human patients.

Saprotrophy of Conidiobolus and Basidiobolus in leaf litter.

This study of the putative saprotrophs of Conidiobolus and Basidiobolus aids the understanding of their ecological roles in litter, and their relationship with the entomogenous fungi of the Entomophthorales. A total of 47 isolates (ten spp.) were screened for their ability to utilise pure compounds, arthropod cadavers, and plant leaf fragments as substrates. Isolates co-occurred in a larch plantation (Larix sp.) or were from adjacent habitats. Of the 21 isolates (nine spp.) tested on potential prime carbon sources, none could utilise common plant structural polymers. Conidiobolus adiaeretus, C. iuxtagenitus, and B. ranarum from litter and some soil isolates of C. heterosporus, C. pumilus, and C. firmipilleus could use starches and glycogen. In marked contrast, all could utilise animal chitin, gelatine, casein, N-acetyl glucosamine, and trehalose. The lipids tributyrin and sunflower oil also supported growth. Conidia on cadavers usually led to high levels of colonisation as was the case for 30 isolates (ten species). Collembola were more frequently and rapidly colonised than mites. Cadavers of many other arthropods were also internally colonised. The ability to utilise cadavers of diverse arthropods indicates that trophic competition between co-occurring test species may be minimal. Niche differentiation may depend more on non-trophic features of their life history. Negative correlation of performance with the presence of naturally occurring, non-test fungi suggests competition with (or antibiosis from) at least some of the other fungi. In washed or unwashed plant fragments of larch litter (F-layer) only occasional local growth and resting spore formation occurred. Extra nutrients did not facilitate colonisation. Alternative forms of repetitional conidia showed a strong association with plant fragments but not with cadavers.

Cellular effects of small molecule PTP1B inhibitors on insulin signaling.

Protein tyrosine phosphatase 1B (PTP1B) is implicated as a negative regulator of insulin receptor (IR) signaling and a potential drug target for the treatment of type 2 diabetes and other associated metabolic syndromes. To further define the role of PTP1B in insulin signaling and to test the hypothesis that blocking the activity of PTP1B would augment the action of insulin, we prepared several cell permeable, potent and selective, small molecule PTP1B inhibitors, and evaluated their biological effects in several insulin sensitive cell lines. Our data indicate that PTP1B inhibitors bind to and colocalize with PTP1B on the surface of the endoplasmic reticulum and PTP1B exerts its negative effect on insulin signaling upstream of phosphatidylinositol 3-kinase and MEK1. Treatment of cells with PTP1B inhibitors, both in the presence and in the absence of insulin, markedly enhances IRbeta and IRS-1 phosphorylation, Akt and ERK1/2 activation, Glut4 translocation, glucose uptake, and Elk1 transcriptional activation and cell proliferation. These results indicate that small molecule inhibitors targeted to PTP1B can act as both insulin mimetics and insulin sensitizers. Taken together, our findings combined with results from PTP1B knockout, antisense, and biochemical studies provide strong evidence that PTP1B negatively regulates insulin signaling and that small molecule PTP1B inhibitors have the ability to potentiate and augment the action of insulin.