Quantitative trait loci mapping reveals candidate pathways regulating cell cycle duration in \u3cem\u3ePlasmodium falciparum\u3c/em\u3e

Background: Elevated parasite biomass in the human red blood cells can lead to increased malaria morbidity. The genes and mechanisms regulating growth and development of Plasmodium falciparum through its erythrocytic cycle are not well understood. We previously showed that strains HB3 and Dd2 diverge in their proliferation rates, and here use quantitative trait loci mapping in 34 progeny from a cross between these parent clones along with integrative bioinformatics to identify genetic loci and candidate genes that control divergences in cell cycle duration. Results: Genetic mapping of cell cycle duration revealed a four-locus genetic model, including a major genetic effect on chromosome 12, which accounts for 75% of the inherited phenotype variation. These QTL span 165 genes, the majority of which have no predicted function based on homology. We present a method to systematically prioritize candidate genes using the extensive sequence and transcriptional information available for the parent lines. Putative functions were assigned to the prioritized genes based on protein interaction networks and expression eQTL from our earlier study. DNA metabolism or antigenic variation functional categories were enriched among our prioritized candidate genes. Genes were then analyzed to determine if they interact with cyclins or other proteins known to be involved in the regulation of cell cycle. Conclusions: We show that the divergent proliferation rate between a drug resistant and drug sensitive parent clone is under genetic regulation and is segregating as a complex trait in 34 progeny. We map a major locus along with additional secondary effects, and use the wealth of genome data to identify key candidate genes. Of particular interest are a nucleosome assembly protein (PFL0185c), a Zinc finger transcription factor (PFL0465c) both on chromosome 12 and a ribosomal protein L7Ae-related on chromosome 4 (PFD0960c)

Characterization of thromboxane A2 receptor and TRPV1 mRNA expression in cultured sensory neurons

Thromboxane A2 (TxA2) is an arachidonic acid metabolite that stimulates platelet aggregation and vasoconstriction when released from platelets and other cell types during tissue trauma. More recent research has demonstrated that TxA2 can also stimulate vagal and spinal sensory nerves. The purpose of this study was twofold. One, we compared the expression of the TxA2 receptor (TxA2R) in neurons from two sensory ganglia: the nodose ganglion (NG) containing cell bodies of vagal afferent nerves and the thoracic dorsal root ganglion (DRG) containing cell bodies of spinal afferent nerves. Two, we determined if TxA2R co-localizes with mRNA for the nociceptive marker, TRPV1, which is the receptor for the noxious substance capsaicin. We found a greater percentage of neurons in the NG that are positive for TxA2R expression than in the DRG. We also found that there was no correlation of expression of TxA2R with TRPV1. These data suggest that while TxA2R is expressed in both vagal and spinal neurons, TxA2 may elicit stronger vagal or parasympathetic reflexes in the rabbit when released during tissue trauma depending on the location of release. Our data also indicate that TxA2 is likely to stimulate both nociceptive and non-nociceptive neurons thereby broadening the types of neurons and reflexes that it may excite

Effects of impurity scattering on electron-phonon resonances in semiconductor superlattice high-field transport

A non-equilibrium Green's function method is applied to model high-field quantum transport and electron-phonon resonances in semiconductor superlattices. The field-dependent density of states for elastic (impurity) scattering is found non-perturbatively in an approach which can be applied to both high and low electric fields. I-V curves, and specifically electron-phonon resonances, are calculated by treating the inelastic (LO phonon) scattering perturbatively. Calculations show how strong impurity scattering suppresses the electron-phonon resonance peaks in I-V curves, and their detailed sensitivity to the size, strength and concentration of impurities.Comment: 7 figures, 1 tabl

Biogenic Macroporosity and lts Lattice Boltzmann Method Permeability in the Karst Biscayne Aquifer

We focus on two major problems in the study of paleokarst of the Biscayne aquifer in southeastem Florida: ( 1 ), current conceptual models of karst aquifers do not adequately characterize much of the eogenetic rnacropore system within the carbonate rocks of the Biscayne aquifer, and (2) standard laboratory core-analysis rnethods cannol be used lo accurately measure the permeability of highly macroporous carbonate core samples

Cardiac thromboxane A2 receptor activation does not directly induce cardiomyocyte hypertrophy but does cause cell death that is prevented with gentamicin and 2-APB

Abstract Background We have previously shown that the thromboxane (TXA2) receptor agonist, U46619, can directly induce ventricular arrhythmias that were associated with increases in intracellular calcium in cardiomyocytes. Since TXA2 is an inflammatory mediator and induces direct calcium changes in cardiomyocytes, we hypothesized that TXA2 released during ischemia or inflammation could also cause cardiac remodeling. Methods U46619 (0.1-10 μM) was applied to isolated adult mouse ventricular primary cardiomyocytes, mouse ventricular cardiac muscle strips, and cultured HL-1 cardiomyocytes and markers of hypertrophy and cell death were measured. Results We found that TXA2 receptors were expressed in ventricular cardiomyocytes and were functional via calcium imaging. U46619 treatment for 24 h did not increase expression of pathological hypertrophy genes (atrial natriuretic peptide, β-myosin heavy chain, skeletal muscle α-actin) and it did not increase protein synthesis. There was also no increase in cardiomyocyte size after 48 h treatment with U46619 as measured by flow cytometry. However, U46619 (0.1-10 μM) caused a concentration-dependent increase in cardiomyocyte death (trypan blue, MTT assays, visual cell counts and TUNEL stain) after 24 h. Treatment of cells with the TXA2 receptor antagonist SQ29548 and inhibitors of the IP3 pathway, gentamicin and 2-APB, eliminated the increase in cell death induced by U46619. Conclusions Our data suggests that TXA2 does not induce cardiac hypertrophy, but does induce cell death that is mediated in part by IP3 signaling pathways. These findings may provide important therapeutic targets for inflammatory-induced cardiac apoptosis that can lead to heart failure.Peer Reviewe

Fibroblast Growth Factor 23 Does Not Directly Influence Skeletal Muscle Cell Proliferation and Differentiation or Ex Vivo Muscle Contractility

Skeletal muscle dysfunction accompanies the clinical disorders of chronic kidney disease (CKD) and hereditary hypophosphatemic rickets. In both disorders, fibroblast growth factor 23 (FGF23), a bone-derived hormone regulating phosphate and vitamin D metabolism, becomes chronically elevated. FGF23 has been shown to play a direct role in cardiac muscle dysfunction; however, it is unknown whether FGF23 signaling can also directly induce skeletal muscle dysfunction. We found expression of potential FGF23 receptors ( Fgfr1-4) and α-Klotho in muscles of two animal models (CD-1 and Cy/+ rat, a naturally occurring rat model of chronic kidney disease-mineral bone disorder) as well as C2C12 myoblasts and myotubes. C2C12 proliferation, myogenic gene expression, oxidative stress marker 8-OHdG, intracellular Ca2+ ([Ca2+]i), and ex vivo contractility of extensor digitorum longus (EDL) or soleus muscles were assessed after treatment with various amounts of FGF23. FGF23 (2-100 ng/ml) did not alter C2C12 proliferation, expression of myogenic genes, or oxidative stress after 24- to 72-h treatment. Acute or prolonged FGF23 treatment up to 6 days did not alter C2C12 [Ca2+]i handling, nor did acute treatment with FGF23 (9-100 ng/ml) affect EDL and soleus muscle contractility. In conclusion, although skeletal muscles express the receptors involved in FGF23-mediated signaling, in vitro FGF23 treatments failed to directly alter skeletal muscle development or function under the conditions tested. We hypothesize that other endogenous substances may be required to act in concert with FGF23 or apart from FGF23 to promote muscle dysfunction in hereditary hypophosphatemic rickets and CKD

Differential effects of dietary whey, casein and soya on colonic DNA damage and large bowel SCFA in rats fed diets low and high in resistant starch

Feeding higher levels of dietary animal protein (as casein or red meat) increases colonic DNA damage and thins the colonic mucus barrier in rats. Feeding resistant starch (RS) reverses these changes and increases large bowel SCFA. The present study examined whether high dietary dairy (casein or whey) or plant (soya) proteins had similar adverse effects and whether dietary RS was protective. Adult male rats were fed diets containing 15 or 25 % casein, whey or soya protein with or without 48 % high amylose starch (as a source of RS) for 4 weeks. DNA damage was measured in isolated colonocytes using the comet assay. Higher dietary casein and soya (but not whey) increased colonocyte DNA damage. DNA damage was highest with soya when fed at 15 or 25 % protein without RS. Dietary RS attenuated protein-induced colonocyte DNA damage in all groups but it remained significantly higher in rats fed 25 % soya compared with those fed 15 % protein. Dietary protein level did not affect colonic mucus thickness overall but the barrier was thinner in rats fed high dietary casein. This effect was reversed by feeding RS. Caecal total SCFA and butyrate pools were higher in rats fed RS compared with digestible starch. Caecal and faecal SCFA were unrelated to genetic damage but correlated with mucus thickness. The present data confirm that higher dietary protein affected colonocyte DNA and colonic mucus thickness adversely but that proteins differ in their effects on these indices of colon health. The data show also that these changes were reversed by RS.Shusuke Toden, Anthony R. Bird, David L. Topping and Michael A. Conlo