Positive and negative modulation of virus infectivity and envelope glycoprotein incorporation into virions by amino acid substitutions at the N terminus of the simian immunodeficiency virus matrix protein

The matrix (MA) protein of the simian immunodeficiency viruses (SIVs) is encoded by the amino-terminal region of the Gag precursor and is the component of the viral capsid that lines the inner surface of the virus envelope. Previously, we identified domains in the SIV MA that are involved in the transport of Gag to the plasma membrane and in particle assembly. In this study, we characterized the role in the SIV life cycle of highly conserved residues within the SIV MA region spanning the two N-terminal alpha-helices H1 and H2. Our analyses identified two classes of MA mutants: (i) viruses encoding amino acid substitutions within alpha-helices H1 or H2 that were defective in envelope (Env) glycoprotein incorporation and exhibited impaired infectivity and (ii) viruses harboring mutations in the beta-turn connecting helices H1 and H2 that were more infectious than the wild-type virus and displayed an enhanced ability to incorporate the Env glycoprotein. Remarkably, among the latter group of MA mutants, the R22L/G24L double amino acid substitution increased virus infectivity eightfold relative to the wild-type virus in single-cycle infectivity assays, an effect that correlated with a similar increase in Env incorporation. Furthermore, the R22L/G24L MA mutation partially or fully complemented single-point MA mutations that severely impair or block Env incorporation and virus infectivity. Our finding that the incorporation of the Env glycoprotein into virions can be upregulated by specific mutations within the SIV MA amino terminus strongly supports the notion that the SIV MA domain mediates Gag-Env association during particle formation.     

Nutritional plasticity of the predatory ladybeetle Harmonia axyridis (Coleoptera: Coccinellidae): comparison between natural and substitution prey

The predatory coccinellid Harmonia axyridis is a polyphagous species, efficient at controlling certain aphid species and already commercialized in Europe for that purpose. The complete development of this predator can be accomplished using the aphid Acyrthosiphon pisum or Ephestia kuehniella eggs as substitution prey. Biochemical analyses were conducted on the proteins, lipids, and carbohydrates of these two different prey species. E. kuehniella eggs were 2 times richer in amino acids than A. pisum adults (12% of the fresh weight vs. 6%). E. kuehniella eggs were 3 times richer in lipids than the aphids but, on the contrary, the aphids were 1.5 times richer in glycogen. The impact of these two kinds of food on the body composition of the coccinellid was evaluated to appreciate the degree of nutritional plasticity of the coccinellid. The composition of the coccinellids feeding either on E. kuehniella eggs or on aphids was compared for amino acid, fatty acid and glycogen contents, revealing a good capability of H. axyridis to develop on foods that are very different in their biochemical composition. Nevertheless, when fed on aphids, the crude protein content of the predator was reduced and the lipid content decreased by a factor of two, with a change in amino and fatty acid patterns. Some biological parameters, such as larval mortality, adult weight, and fecundity, were modified according to the food eaten.     

Protection afforded by ischemic preconditioning is not mediated by effects on cell-to-cell electrical coupling during myocardial ischemia-reperfusion

The end-effectors of ischemic preconditioning (IPC) are not well known. It has been recently shown that transgenic mice underexpressing the gap junction protein connexin43 (Cx43) cannot be preconditioned. Because gap junctions allow spreading of cell death during ischemia-reperfusion in different tissues, including myocardium, we hypothesized that the protection afforded by IPC is mediated by effects on gap junction-mediated intercellular communication. To test this hypothesis, we analyzed the effect of IPC (5 min ischemia-5 min reperfusion x 2) on the changes in electrical impedance (four electrode probe) and impulse propagation velocity (transmembrane action potential) induced by ischemia (60 min) and reperfusion (60 min) in isolated rat hearts. IPC (n = 8) reduced reperfusion-induced lactate dehydrogenase release by 65.8% with respect to control hearts (n = 9) (P = 0.04) but had no effect on the time of onset of rigor contracture (increase in diastolic tension), electrical uncoupling (sharp changes in tissue resistivity and phase angle in impedance recordings), or block of impulse propagation during ischemia. Normalization of electrical impedance during reperfusion was also unaffected by IPC. The lack of effect of IPC on ischemic rigor contracture and on changes in tissue impedance during ischemia-reperfusion were validated under in vivo conditions in pigs submitted to 48 min of coronary occlusion and 120 min of reperfusion. IPC (n = 12) reduced infarct size (triphenyltetrazolium) by 64.9% (P = 0.01) with respect to controls (n = 17). We conclude that the protection afforded by IPC is not mediated by effects on electrical coupling. This result is consistent with recent findings suggesting that Cx43 could have effects on cell survival independent on changes in cell-to-cell communication.     

Molecular characterization and chromosomal distribution of Galileo, Kepler and Newton, three foldback transposable elements of the Drosophila buzzatii species complex

Galileo is a foldback transposable element that has been implicated in the generation of two polymorphic chromosomal inversions in Drosophila buzzatii. Analysis of the inversion breakpoints led to the discovery of two additional elements, called Kepler and Newton, sharing sequence and structural similarities with Galileo. Here, we describe in detail the molecular structure of these three elements, on the basis of the 13 copies found at the inversion breakpoints plus 10 additional copies isolated during this work. Similarly to the foldback elements described in other organisms, these elements have long inverted terminal repeats, which in the case of Galileo possess a complex structure and display a high degree of internal variability between copies. A phylogenetic tree built with their shared sequences shows that the three elements are closely related and diverged approximately 10 million years ago. We have also analyzed the abundance and chromosomal distribution of these elements in D. buzzatii and other species of the repleta group by Southern analysis and in situ hybridization. Overall, the results suggest that these foldback elements are present in all the buzzatti complex species and may have played an important role in shaping their genomes. In addition, we show that recombination rate is the main factor determining the chromosomal distribution of these elements.     

Duplicative and conservative transpositions of larval serum protein 1 genes in the genus Drosophila

Interspecific comparative molecular analyses of transposed genes and their flanking regions can help to elucidate the time, direction, and mechanism of gene transposition. In the Drosophila melanogaster genome, three Larval serum protein 1 (Lsp1) genes (alpha, beta and gamma) are present and each of them is located on a different chromosome, suggesting multiple transposition events. We have characterized the molecular organization of Lsp1 genes in D. buzzatii, a species of the Drosophila subgenus and in D. pseudoobscura, a species of the Sophophora subgenus. Our results show that only two Lsp1 genes (beta and gamma) exist in these two species. The same chromosomal localization and genomic organization, different from that of D. melanogaster, is found in both species for the Lsp1beta and Lsp1gamma genes. Overall, at least two duplicative and two conservative transpositions are necessary to explain the present chromosomal distribution of Lsp1 genes in the three Drosophila species. Clear evidence for implication of snRNA genes in the transposition of Lsp1beta in Drosophila has been found. We suggest that an ectopic exchange between highly similar snRNA sequences was responsible for the transposition of this gene. We have also identified the putative cis-acting regulatory regions of these genes, which seemingly transposed along with the coding sequences.     

Usefulness of non-invasive tests for diagnosing Helicobacter pylori infection in patients undergoing dialysis for chronic renal failure

BACKGROUND: Helicobacter pylori infection in chronic renal failure patients has been linked to peptic ulcer and gastric neoplasia after kidney transplantation. It may also contribute to the accelerated arteriosclerosis that is usual in this population. Few data are available on the usefulness of noninvasive diagnostic tests for H. pylori infection in dialyzed patients, especially regarding the new fecal antigen detection tests. The objective of this study was to determine the efficacy of a noninvasive test for H. pylori infection in patients with chronic renal failure. METHODS: Eighty-six patients were included in a cross-sectional study. Urea breath test, serology and three fecal tests--FemtoLab H. pylori (Connex, Germany), Premier Platinum HpSA (Meridian, USA) and Simple H. pylori (Operon SA, Spain) were performed. Helicobacter pylori status was determined by concordance of the tests. Sensitivity, specificity and positive and negative predictive values were calculated for each test. RESULTS: Sensitivity, specificity, positive and negative predictive values were 94%, 96%, 94% and 96% for the urea breath test; 97%, 64%, 66% and 97% for serology; 86%, 100%, 100% and 91%, for FemtoLab H. pylori; 58%, 96%, 91% and 76% for Premier Platinum HpSA and 61%, 78%, 74% and 67% for Simple H. pylori. CONCLUSIONS: The urea breath test seems to be the most reliable diagnostic method for H. pylori infection in patients with chronic renal failure. Serology has a low specificity, and the results of the fecal tests vary widely.     

Antibody-mediated phagocytosis of the amyloid beta-peptide in microglia is differentially modulated by C1q

Microglial ingestion of the amyloid beta-peptide (Abeta) has been viewed as a therapeutic target in Alzheimer's disease, in that approaches that enhance clearance of Abeta relative to its production are predicted to result in decreased senile plaque formation, a proposed contributor to neuropathology. In vitro, scavenger receptors mediate ingestion of fibrillar Abeta (fAbeta) by microglia. However, the finding that cerebral amyloid deposition in a transgenic mouse model of Alzheimer's disease was diminished by inoculation with synthetic Abeta has suggested a possible therapeutic role for anti-Abeta Ab-mediated phagocytosis. Microglia also express C1qR(P), a receptor for complement protein C1q, ligation of which in vitro enhances phagocytosis of immune complexes formed with IgG levels below that required for optimal FcR-mediated phagocytosis. The data presented here demonstrate FcR-dependent ingestion of Abeta-anti-Abeta complexes (IgG-fAbeta) by microglia that is a function of the amount of Ab used to form immune complexes. In addition, C1q incorporated into IgG-fAbeta enhanced microglial uptake of these complexes when they contained suboptimal levels of anti-Abeta Ab. Mannose binding lectin and lung surfactant protein A, other ligands of C1qR(P), also enhanced ingestion of suboptimally opsonized IgG-fAbeta, whereas control proteins did not. Our data suggest that C1qR(P)-mediated events may promote efficient ingestion of Abeta at low Ab titers, and this may be beneficial in paradigms that seek to clear amyloid via FcR-mediated mechanisms by minimizing the potential for destructive Ab-induced complement-mediated processes.     

Crustacean metamorphosis: an omics perspective

We quantified the independent impacts of flooding salinity, flooding depth, and flooding frequency on the native species, Phragmites australis and Scirpus mariqueter, and on the invasive species Spartina alterniflora in the Yangtze River Estuary, China. Total biomass of all three species decreased significantly with increasing salinity, but S. alterniflora was less severely affected than P. australis and S. mariqueter. Elevated flooding depth significantly decreased their live aboveground biomass of P. australis and S. mariqueter, while S. alterniflora still had high live aboveground biomass and total biomass even at the highest flooding depth. These findings indicated that S. alterniflora was more tolerant to experimental conditions than the two native species, and an unavoidable suggestion is the expansion of this non-native species in relation to the native counterparts in future scenarios of increased sea-level and saltwater intrusion. Even so, environmental stresses might lead to significant decreases in total biomass and live aboveground biomass of all three species, which would potentially weaken their ability to trap sediments and accumulate organic matter. However, the relatively high belowground-to-aboveground biomass ratio indicated phenotypic plasticity in response to stressful environmental conditions, which suggest that marsh species can adapt to sea-level rise and maintain marsh elevation.