Effect of temperature and host species on parasitism,development time and sex ratio of the egg parasitoid Trichogrammatoidea lutea Girault (Hymenoptera: Trichogrammatidae)

The developmental biology of Trichogrammatoidea lutea Girault (Hymenoptera: Trichogrammatidae) was studied at six constant temperatures (18, 21, 24, 27, 30 and 35 °C) on eggs of three lepidopteran host species: Helicoverpa armigera (Hübner) (Noctuidae), Chilo partellus (Swinhoe) (Crambidae) and Cadra cautella (Walker) (Pyralidae). T. lutea did not complete development at 35 °C on any of the three host species. Parasitism levels were highest on H. armigera at 27 °C (58%), C. cautella at 27 and 30 °C (31% and 28%) and C. partellus between 24 and 30 °C (13–17%). Realized progeny of T. lutea per parasitized host egg was influenced by host size. The number of progeny of T. lutea per parasitized host egg was highest on H. armigera, followed by C. partellus and lowest on C. cautella. The sex ratio was female biased on C. partellus, female biased on C. cautella with the exception of 21 °C and close to 1:1 on H. armigera. The rate of development from egg to pupa and egg to adult was fastest on H. armigera and slowest on C. partellus. Lower thresholds for development and degree days (DD) of T. lutea from egg to adult were 12.8 °C and 105.4 DD on H. armigera, 11.3 °C and 141.6 DD on C. partellus and 12.9 °C and 118.2 DD on C. cautella, respectively. Based on these results, H. armigera is the most suitable host for mass rearing of T. lutea for biological control of Lepidoptera pests because of the relatively high parasitism levels, short development time, greater clutch size and balanced sex ratio. C. cautella may also be used although longer exposure times might be required due to lower parasitism levels.     

The serine protease Omi/HtrA2 is involved in XIAP cleavage and in neuronal cell death following focal cerebral ischemia/reperfusion

Omi/HtrA2 is a pro-apoptotic mitochondrial serine protease involved in both forms of apoptosis, caspase-dependent as well as caspase-independent cell death. However, the impact of Omi/HtrA2 in the apoptotic cell machinery that takes place in vivo under pathological conditions such as cerebral ischemia remains unknown. The present study was monitored in order to examine whether Omi/HtrA2 plays a decisive role in apoptosis observed after focal cerebral ischemia in rats. Male adult rats were subjected to 90min of focal cerebral ischemia followed by reperfusion and treated with vehicle or ucf-101, a novel and specific Omi/HtrA2 inhibitor, prior reperfusion. Focal cerebral ischemia/reperfusion induced a mitochondrial up-regulation of Omi/HtrA2 and significantly increased cytosolic accumulation of Omi/HtrA2. Furthermore, ischemia led to activation of caspase-3 and degradation X-linked inhibitor of apoptosis protein (XIAP). Treatment of animals prior ischemia with ucf-101, the specific inhibitor of Omi/HtrA2, was able to (1) reduce the number of TUNEL-positive cells, to (2) attenuate the XIAP-breakdown and to (3) reduce the infarct size. This study shows for the first time that focal cerebral ischemia in rats results in Omi/HtrA2 translocation from the mitochondria to the cytosol, where it participates in neuronal cell death. Blocking the proteolytic activity of Omi/HtrA2 with specific inhibitors, such as the ucf-101, could be a novel way to afford neuroprotection and minimize cellular damage in cerebral ischemia/reperfusion.     

The protective effect of the vagus nerve in a murine model of chronic relapsing colitis

The vagus nerve inhibits the response to systemic administration of endotoxin, and we have recently extended this observation to show that the vagus attenuates acute experimental colitis in mice. The purpose of the present study was to determine whether there is a tonic counterinflammatory influence of the vagus on colitis maintained over several weeks. We assessed disease activity index, macroscopic and histological damage, myeloperoxidase (MPO) activity, and Th1 and Th2 cytokine profiles in chronic colitis induced by administration of dextran sodium sulfate (DSS) in drinking water for three cycles during 5 days with 11 days of rest between each cycle (DSS 3, 2, 2%) in healthy and vagotomized C57BL/6 mice and in mice deficient in macrophage-colony stimulating factor (M-CSF). A pyloroplasty was performed in vagotomized mice. Vagotomy accelerated the onset and the severity of inflammation during the first and second but not the third cycle. Although macroscopic scores were not significantly changed, histological scores as well as MPO activity and colonic tissue levels of IL-1alpha, TNF-alpha, IFN-gamma, and IL-18 but not IL-4 were significantly increased in vagotomized mice compared with sham-operated mice that received DSS. In control mice (without colitis), vagotomy per se did not affect any inflammatory marker. Vagotomy had no effect on the colitis in M-CSF-derived macrophage-deficient mice. These results indicate that the vagus protects against acute relapses on a background of chronic inflammation. Identification of the molecular mechanisms underlying the protective role of parasympathetic nerves opens a new therapeutic avenue for the treatment of acute relapses of chronic inflammatory bowel disease.     

Impact of HIV-1 subtype and antiretroviral therapy on protease and reverse transcriptase genotype: results of a global collaboration

BackgroundThe genetic differences among HIV-1 subtypes may be critical to clinical management and drug resistance surveillance as antiretroviral treatment is expanded to regions of the world where diverse non-subtype-B viruses predominate.ConclusionGlobal surveillance and genotypic assessment of drug resistance should focus primarily on the known subtype B drug-resistance mutations.     

Structure of 2',5'-linked tetraribonucleotide loops: a novel RNA motif

We report on the three dimensional structure of an RNA hairpin containing a 2',5'-linked tetraribonucleotide loop, namely, 5'-rGGAC(UUCG)GUCC-3' (where UUCG = U(2'p5')U(2'p5')C(2'p5')G(2'p5')). We show that the 2',5'-linked RNA loop adopts a conformation that is quite different from that previously observed for the native 3',5'-linked RNA loop. The 2',5'-RNA loop is stabilized by (a) U:G wobble base pairing, with both bases in the anti conformation, (b) extensive base stacking, and (c) sugar-base contacts, all of which contribute to the extra stability of this hairpin structure.     

The COP9 signalosome is vital for timely repair of DNA double-strand breaks

The DNA damage response is vigorously activated by DNA double-strand breaks (DSBs). The chief mobilizer of the DSB response is the ATM protein kinase. We discovered that the COP9 signalosome (CSN) is a crucial player in the DSB response and an ATM target. CSN is a protein complex that regulates the activity of cullin ring ubiquitin ligase (CRL) complexes by removing the ubiquitin-like protein, NEDD8, from their cullin scaffold. We find that the CSN is physically recruited to DSB sites in a neddylation-dependent manner, and is required for timely repair of DSBs, affecting the balance between the two major DSB repair pathways—nonhomologous end-joining and homologous recombination repair (HRR). The CSN is essential for the processivity of deep end-resection—the initial step in HRR. Cullin 4a (CUL4A) is recruited to DSB sites in a CSN- and neddylation-dependent manner, suggesting that CSN partners with CRL4 in this pathway. Furthermore, we found that ATM-mediated phosphorylation of CSN subunit 3 on S410 is critical for proper DSB repair, and that loss of this phosphorylation site alone is sufficient to cause a DDR deficiency phenotype in the mouse. This novel branch of the DSB response thus significantly affects genome stability.     

Arginine metabolism in insects. Role of arginase in proline formation during silkmoth development

1. Ornithine delta-transaminase (l-ornithine-2-oxo acid aminotransferase, EC 2.6.1.13) and Delta(1)-pyrroline-5-carboxylate reductase [l-proline-NAD(P) 5-oxidoreductase, EC 1.5.1.2] were demonstrated in fat-body and flight-muscle tissues of the silkmoth Hyalophora gloveri. Arginase (l-arginine ureohydrolase, EC 3.5.3.1) is also present in these tissues. 2. Arginase, ornithine transaminase and pyrroline-carboxylate reductase are generally considered to make up the catabolic pathway for the conversion of arginine into proline. The conversion of l-[U-(14)C]arginine into [(14)C]proline by intact fat-body tissue was used to show that the enzymes in insect fat body also function in this capacity. 3. Of the three enzymes of the catabolic pathway, only arginase increased during adult development and the increase coincided with the emergence of the winged adult moth. Since proline appears to be a major substrate utilized in insect flight metabolism, the increase in arginase activity at this stage suggests a major role for arginase in proline formation.     

Characterization of articular cartilage by combining microscopic analysis with a fibril-reinforced finite-element model

Load-bearing characteristics of articular cartilage are impaired during tissue degeneration. Quantitative microscopy enables in vitro investigation of cartilage structure but determination of tissue functional properties necessitates experimental mechanical testing. The fibril-reinforced poroviscoelastic (FRPVE) model has been used successfully for estimation of cartilage mechanical properties. The model includes realistic collagen network architecture, as shown by microscopic imaging techniques. The aim of the present study was to investigate the relationships between the cartilage proteoglycan (PG) and collagen content as assessed by quantitative microscopic findings, and model-based mechanical parameters of the tissue. Site-specific variation of the collagen network moduli, PG matrix modulus and permeability was analyzed. Cylindrical cartilage samples (n=22) were harvested from various sites of the bovine knee and shoulder joints. Collagen orientation, as quantitated by polarized light microscopy, was incorporated into the finite-element model. Stepwise stress-relaxation experiments in unconfined compression were conducted for the samples, and sample-specific models were fitted to the experimental data in order to determine values of the model parameters. For comparison, Fourier transform infrared imaging and digital densitometry were used for the determination of collagen and PG content in the same samples, respectively. The initial and strain-dependent fibril network moduli as well as the initial permeability correlated significantly with the tissue collagen content. The equilibrium Young's modulus of the nonfibrillar matrix and the strain dependency of permeability were significantly associated with the tissue PG content. The present study demonstrates that modern quantitative microscopic methods in combination with the FRPVE model are feasible methods to characterize the structure-function relationships of articular cartilage.