Surface charge of trypanosoma cruzi. Binding of cationized ferritin and measurement of cellular electrophoretic mobility.

The surface charge of epimastigote and trypomastigote forms of Trypanosoma cruzi was evaluated by means of binding of cationized ferritin to the cell surface as visualized by electron microscopy, and by direct measurements of the cellular microelectrophoretic mobility (EPM). Epimastigote forms had a mean EPM of -0.52 micrometer-s-1-V-1-cm and were lightly labeled with cationized ferritin. In contrast, bloodstream trypomastigotes had a much higher EPM (-1.14), and the surface was heavily labeled with cationized ferritin. When trypomastigotes from staionary phase cultures were isolated on DEAE cellulose columns, the mean EPM was found to be significantly lower (-0.63), and labeling with cationized ferritin decreased. With a mixed population containing epimastigote, trypomastigote, and intermediate forms, EPM values ranging between -0.70 to -1.14 were found. From these observations we conclude that there is a definite increase in negative surface charge during development from epi- to trypomastigote forms of T. cruzi.     

Probing vocal fold fibroblast response to hyaluronan in 3D contexts

A number of treatments are being investigated for vocal fold (VF) scar, including designer implants. The aim of the present study was to validate a 3D model system for probing the effects of various bioactive moieties on VF fibroblast (VFF) behavior toward rational implant design. We selected poly(ethylene glycol) diacrylate (PEGDA) hydrogels as our base‐scaffold due to their broadly tunable material properties. However, since cells encapsulated in PEGDA hydrogels are generally forced to take on rounded/stellate morphologies, validation of PEGDA gels as a 3D VFF model system required that the present work directly parallel previous studies involving more permissive scaffolds. We therefore chose to focus on hyaluronan (HA), a polysaccharide that has been a particular focus of the VF community. Toward this end, porcine VFFs were encapsulated in PEGDA hydrogels containing consistent levels of high M _w HA (${\rm HA}_{{\rm H}{M}_{\rm W} } $ ), intermediate M_w HA (${\rm HA}_{{\rm I}{M}_{\rm W} } $ ), or the control polysaccharide, alginate, and cultured for 7 and 21 days. ${\rm HA}_{{\rm H}{M}_{\rm W} } $ promoted sustained increases in active ERK1/2 relative to ${\rm HA}_{{\rm I}{M}_{\rm W} } $ . Furthermore, VFFs in ${\rm HA}_{{\rm I}{M}_{\rm W} } $ gels displayed a more myofibroblast‐like phenotype, higher elastin production, and greater protein kinase C (PkC) levels at day 21 than VFFs in ${\rm HA}_{{\rm H}{M}_{\rm W} } $ and alginate gels. The present results are in agreement with a previous 3D study of VFF responses to ${\rm HA}_{{\rm I}{M}_{\rm W} } $ relative to alginate in collagen‐based scaffolds permissive of cell elongation, indicating that PEGDA hydrogels may serve as an effective 3D model system for probing at least certain aspects of VFF behavior. Biotechnol. Bioeng. 2009; 104: 821–831 © 2009 Wiley Periodicals, Inc.     

Validation of Bateman's principles: a genetic study of sexual selection and mating patterns in the rough-skinned newt

Few studies have influenced thought on the nature of sexual selection to the extent of the classic paper of A. J. Bateman on mating patterns in Drosophila. However, interpretation of his study remains controversial, and a lack of modern empirical evidence prevents a consensus with respect to the perceived utility of Bateman's principles in the study of sexual selection. Here, we use a genetic study of natural mating patterns in the rough-skinned newt, Taricha granulosa, to investigate the concordance between Bateman's principles and the intensity of sexual selection. We found that males experienced strong sexual selection on tail height and body size, while sexual selection was undetectable in females. This direct quantification of sexual selection agreed perfectly with inferences that are based on Bateman's principles. Specifically, males (in comparison with females) exhibited greater standardized variances in reproductive and mating success, as well as a stronger relationship between mating success and reproductive success. Overall, our results illustrate that Bateman's principles provide the only quantitative measures of the mating system with explicit connections to formal selection theory and should be the central focus of studies of mating patterns in natural populations.     

Mitochondrial respirasome works as a single unit and the cross-talk between complexes I,III2 and IV stimulates NADH dehydrogenase activity

Ustilago maydis is an aerobic basidiomycete that depends on oxidative phosphorylation for its ATP supply, pointing to the mitochondrion as a key player in its energy metabolism. Mitochondrial respiratory complexes I, III₂, and IV occur in supramolecular structures named respirasome. In this work, we characterized the subunit composition and the kinetics of NADH:Q oxidoreductase activity of the digitonine-solubilized respirasome (1600 kDa) and the free-complex I (990 kDa). In the presence of 2,6-dimethoxy-1,4-benzoquinone (DBQ) and cytochrome c, both the respirasome NADH:O₂ and the NADH:DBQ oxidoreductase activities were inhibited by rotenone, antimycin A or cyanide. A value of 2.4 for the NADH oxidized/oxygen reduced ratio was determined for the respirasome activity, while ROS production was less than 0.001% of the oxygen consumption rate. Analysis of the NADH:DBQ oxidoreductase activity showed that respirasome was 3-times more active and showed higher affinity than free-complex I. The results suggest that the contacts between complexes I, III₂ and IV in the respirasome increase the catalytic efficiency of complex I and regulate its activity to prevent ROS production.     

Five Drosophila genomes reveal nonneutral evolution and the signature of host specialization in the chemoreceptor superfamily

The insect chemoreceptor superfamily comprises the olfactory receptor (Or) and gustatory receptor (Gr) multigene families. These families give insects the ability to smell and taste chemicals in the environment and are thus rich resources for linking molecular evolutionary and ecological processes. Although dramatic differences in family size among distant species and high divergence among paralogs have led to the belief that the two families evolve rapidly, a lack of evolutionary data over short time scales has frustrated efforts to identify the major forces shaping this evolution. Here, we investigate patterns of gene loss/gain, divergence, and polymorphism in the entire repertoire of approximately 130 chemoreceptor genes from five closely related species of Drosophila that share a common ancestor within the past 12 million years. We demonstrate that the overall evolution of the Or and Gr families is nonneutral. We also show that selection regimes differ both between the two families as wholes and within each family among groups of genes with varying functions, patterns of expression, and phylogenetic histories. Finally, we find that the independent evolution of host specialization in Drosophila sechellia and D. erecta is associated with a fivefold acceleration of gene loss and increased rates of amino acid evolution at receptors that remain intact. Gene loss appears to primarily affect Grs that respond to bitter compounds while elevated Ka/Ks is most pronounced in the subset of Ors that are expressed in larvae. Our results provide strong evidence that the observed phenomena result from the invasion of a novel ecological niche and present a unique synthesis of molecular evolutionary analyses with ecological data.     

Effects of Prenatal Multiple Micronutrient Supplementation on Fetal Growth Factors: A Cluster-Randomized,Controlled Trial in Rural Bangladesh

Prenatal multiple micronutrient (MM) supplementation improves birth weight through increased fetal growth and gestational age, but whether maternal or fetal growth factors are involved is unclear. Our objective was to examine the effect of prenatal MM supplementation on intrauterine growth factors and the associations between growth factors and birth outcomes in a rural setting in Bangladesh. In a double-blind, cluster-randomized, controlled trial of MM vs. iron and folic acid (IFA) supplementation, we measured placental growth hormone (PGH) at 10 weeks and PGH and human placental lactogen (hPL) at 32 weeks gestation in maternal plasma (n = 396) and insulin, insulin-like growth factor-1 (IGF-1), and IGF binding protein-1 (IGFBP-1) in cord plasma (n = 325). Birth size and gestational age were also assessed. Early pregnancy mean (SD) BMI was 19.5 (2.4) kg/m² and birth weight was 2.68 (0.41) kg. There was no effect of MM on concentrations of maternal hPL or PGH, or cord insulin, IGF-1, or IGFBP-1. However, among pregnancies of female offspring, hPL concentration was higher by 1.1 mg/L in the third trimester (95% CI: 0.2, 2.0 mg/L; p = 0.09 for interaction); and among women with height <145 cm, insulin was higher by 59% (95% CI: 3, 115%; p = 0.05 for interaction) in the MM vs. IFA group. Maternal hPL and cord blood insulin and IGF-1 were positively, and IGFBP-1 was negatively, associated with birth weight z score and other measures of birth size (all p<0.05). IGF-1 was inversely associated with gestational age (p<0.05), but other growth factors were not associated with gestational age or preterm birth. Prenatal MM supplementation had no overall impact on intrauterine growth factors. MM supplementation altered some growth factors differentially by maternal early pregnancy nutritional status and sex of the offspring, but this should be examined in other studies.

Trial Registration

ClinicalTrials.gov NCT00860470     

Liposomes with polyribonucleotides as model of precellular systems

A study of the encapsulation of poly(U) and poly(C) within liposomes made from dipalmitoylphosphatidyl choline (DPPC), from egg yold phosphatidyl choline (PC), and from PC with cholesterol (CHOL) was made. The liposomes were prepared under anoxic conditions following the reverse-phase evaporation method. Determinations showed that 36 to 70% of the available lipids form liposomes and 2 to 5% of the polyribonucleotides can be entrapped by liposomes. The encapsulation of polyribonucleotides has also been measured in the presence of urea, cyanamide and Zn⁺⁺, condensing agents in prebiotic polymerization reactions. DPPC and PC:CHOL liposomes were formed in the presence of 1.0 M urea, although no PC liposomes were formed. The three types of liposomes were readily formed at 0.01 M urea, but in no case an enhancement of encapsulation efficiency of poly(U) was observed due to the presence of urea. Similar results were obtained with cyanamide. An enhanced encapsulation of poly(U) by the three types of liposomes was observed when Zn⁺⁺ was in the range of 0.001 to 0.01 M. Poly(U) encapsulation was 15 to 25 times higher when liposomes were prepared from DPPC at 0.01 M Zn⁺⁺. Similar results were obtained with poly(C). The advantages of DPPC-polyribonucleotide liposomes as precellular systems are discussed.