Modelling the Abundances of Two Major Culicoides (Diptera: Ceratopogonidae) Species in the Niayes Area of Senegal

In Senegal, considerable mortality in the equine population and hence major economic losses were caused by the African horse sickness (AHS) epizootic in 2007. Culicoides oxystoma and Culicoides imicola, known or suspected of being vectors of bluetongue and AHS viruses are two predominant species in the vicinity of horses and are present all year-round in Niayes area, Senegal. The aim of this study was to better understand the environmental and climatic drivers of the dynamics of these two species. Culicoides collections were obtained using OVI (Onderstepoort Veterinary Institute) light traps at each of the 5 sites for three nights of consecutive collection per month over one year. Cross Correlation Map analysis was performed to determine the time-lags for which environmental variables and abundance data were the most correlated. C. oxystoma and C. imicola count data were highly variable and overdispersed. Despite modelling large Culicoides counts (over 220,000 Culicoides captured in 354 night-traps), using on-site climate measures, overdispersion persisted in Poisson, negative binomial, Poisson regression mixed-effect with random effect at the site of capture models. The only model able to take into account overdispersion was the Poisson regression mixed-effect model with nested random effects at the site and date of capture levels. According to this model, meteorological variables that contribute to explaining the dynamics of C. oxystoma and C. imicola abundances were: mean temperature and relative humidity of the capture day, mean humidity between 21 and 19 days prior a capture event, density of ruminants, percentage cover of water bodies within a 2 km radius and interaction between temperature and humidity for C. oxystoma; mean rainfall and NDVI of the capture day and percentage cover of water bodies for C. imicola. Other variables such as soil moisture, wind speed, degree days, land cover or landscape metrics could be tested to improve the models. Further work should also assess whether other trapping methods such as host-baited traps help reduce overdispersion.     

High-fat-diet-induced obesity and heart dysfunction are regulated by the TOR pathway in Drosophila

High-fat-diet (HFD)-induced obesity is a major contributor to diabetes and cardiovascular disease, but the underlying genetic mechanisms are poorly understood. Here, we use Drosophila to test the hypothesis that HFD-induced obesity and associated cardiac complications have early evolutionary origins involving nutrient-sensing signal transduction pathways. We find that HFD-fed flies exhibit increased triglyceride (TG) fat and alterations in insulin/glucose homeostasis, similar to mammalian responses. A HFD also causes cardiac lipid accumulation, reduced cardiac contractility, conduction blocks, and severe structural pathologies, reminiscent of diabetic cardiomyopathies. Remarkably, these metabolic and cardiotoxic phenotypes elicited by HFD are blocked by inhibiting insulin-TOR signaling. Moreover, reducing insulin-TOR activity (by expressing TSC1-2, 4EBP or FOXO), or increasing lipase expression-only within the myocardium-suffices to efficiently alleviate cardiac fat accumulation and dysfunction induced by HFD. We conclude that deregulation of insulin-TOR signaling due to a HFD is responsible for mediating the detrimental effects on metabolism and heart function.     

Influence of glenohumeral mismatch on bone strains and implant displacements in implanted glenoïds. An in vitro experimental study on cadaveric scapulae

In shoulder arthroplasty, there is no consensus about the ideal mismatch between a prosthetic humeral head and a glenoïd component. Thus, investigations into mismatch effects from a biomechanical point of view can be useful. The aim of this in vitro study was to help us understand mismatch influence on bone strains, translational forces in the joint and implant/bone displacements in implanted scapulae.

Five fresh cadaveric scapulae were implanted with a cemented keeled polyethylene implant. The lower part of the scapulae was embedded and the loadings were carried out using five metallic spheres simulating mismatches of 0, 2, 4, 5 and 6 mm. Loadings included a constant compressive preload of 392 N and an anterior, posterior, inferior and superior translation of 2.5 mm. We measured the transversal force necessary to produce the imposed translation, the strains at six locations around the peripheral cortex of the glenoïd using strain gages and the relative implant/bone displacements using CCD cameras.

Generally, the increase of mismatch reduced the translational forces, the strains around the glenoïd and, except for the anterior loading, the relative implant/bone displacements. Few and even no significant differences were observed when the mismatch varied from 0 to 2 mm; the number of significant differences increased when the mismatch varied from 0 to 4 mm and from 0 to 5 mm; the results obtained for a 0–6 mm variation in mismatch were comparable to those obtained for a 0–5 mm variation.

This study underlines that the mismatch has a significant effect on bone strains, relative implant/bone displacements and induced translational forces when a compressive preload and imposed translations were applied on implanted scapulae.     

Plasmacytoid dendritic cell dynamics and alpha interferon production during Simian immunodeficiency virus infection with a nonpathogenic outcome

We addressed the role of plasmacytoid dendritic cells (PDC) in protection against AIDS in nonpathogenic simian immunodeficiency virus (SIVagm) infection in African green monkeys (AGMs). PDC were monitored in blood and lymph nodes (LNs) starting from day 1 postinfection. We observed significant declines in blood during acute infection. However, PDC then returned to normal levels, and chronically infected AGMs showed no decrease of PDC in blood. There was a significant increase of PDC in LNs during acute infection. Blood PDC displayed only weak alpha interferon (IFN-alpha) responses to TLR9 agonist stimulation before infection. However, during acute infection, both blood and LN PDC showed a transiently increased propensity for IFN-alpha production. Bioactive IFN-alpha was detected in plasma concomitant with the peak of viremia, though levels were only low to moderate in some animals. Plasma interleukin 6 (IL-6) and IL-12 were not increased. In conclusion, PDC were recruited to the LNs and displayed increased IFN-alpha production during acute infection. However, increases in IFN-alpha were transient. Together with the lack of inflammatory cytokine responses, these events might play an important role in the low level of T-cell activation which is associated with protection against AIDS in nonpathogenic SIVagm infection.     

Early divergence in lymphoid tissue apoptosis between pathogenic and nonpathogenic simian immunodeficiency virus infections of nonhuman primates

The events that contribute to the progression to AIDS during the acute phase of a primate lentiviral infection are still poorly understood. In this study, we used pathogenic and nonpathogenic simian models of simian immunodeficiency virus (SIV) infection of rhesus macaques (RMs) and African green monkeys (AGMs), respectively, to investigate the relationship between apoptosis in lymph nodes and the extent of viral replication, immune activation, and disease outcome. Here, we show that, in SIVmac251-infected RMs, a marked increased in lymphocyte apoptosis is evident during primary infection at the level of lymph nodes. Interestingly, the levels of apoptosis correlated with the extent of viral replication and the rate of disease progression to AIDS, with higher apoptosis in RMs of Indian genetic background than in those of Chinese origin. In stark contrast, no changes in the levels of lymphocyte apoptosis were observed during primary infection in the nonpathogenic model of SIVagm-sab infection of AGMs, despite similarly high rates of viral replication. A further and early divergence between SIV-infected RMs and AGMs was observed in terms of the dynamics of T- and B-cell proliferation in lymph nodes, with RMs showing significantly higher levels of cycling cells (Ki67⁺) in the T-cell zones in association with relatively low levels of Ki67⁺ in the B-cell zones, whereas AGMs displayed a low frequency of Ki67⁺ in the T-cell area but a high proportion of Ki67⁺ cells in the B-cell area. As such, this study suggests that species-specific host factors determine an early immune response to SIV that predominantly involves either cellular or humoral immunity in RMs and AGMs, respectively. Taken together, these data are consistent with the hypotheses that (i) high levels of T-cell activation and lymphocyte apoptosis are key pathogenic factors during pathogenic SIV infection of RMs and (ii) low T-cell activation and apoptosis are determinants of the AIDS resistance of SIVagm-infected AGMs, despite high levels of SIVagm replication.     

Specific Binding of [3H]Rauwolscine to α2-Adrenoceptors in Rat Cerebral Cortex: Comparison Between Crude and Synaptosomal Plasma Membranes

[3H]Rauwolscine, a specific, potent, radiolabelled alpha 2-antagonist, binds to distinct high- and low-affinity alpha 2-adrenoceptors in crude membrane preparations of the rat cerebral cortex. The concentration of high-affinity alpha 2-adrenoceptors was increased by addition of sodium ions or guanylnucleotides. In synaptosomal plasma membrane preparations, only the low-affinity component was found. Neither sodium or guanylnucleotides caused any increase in the concentration of these low-affinity receptors for [3H]rauwolscine.     

Adult behavior of an ambrosia gall midge Illiciomyia yukawai (Diptera: Cecidomyiidae) and synchronization between its emergence and host plant phenology

The adult behavior of an ambrosia gall midge Illiciomyia yukawai (Diptera: Cecidomyiidae) that induces leaf galls on Illicium anisatum (Illiciaceae) was studied at the population level from 1977 to 1995 in Kagoshima, Japan. Most males emerged between 0:00 and 08:00 h and females between 05:00 and 11:00 h. Males swarmed around the host trees between 05:00 and 11:00 h. Mating occurred on the host leaves mainly between 06:00 and 08:00 h. Females then left the host trees for somewhere else, possibly to collect symbiont fungal conidia. From 08:00 to 16:00 h, females were observed ovipositing into the host shoots. The low development threshold temperature for overwintered larvae was 14°C, while the thermal constant for emergence differed with individuals. Thermal totals above 14°C up to the 50% emergence date varied yearly from 33.1 to 68.7 degree‐days. The 50% emergence date varied from 9 to 18 May. The thermal totals significantly correlated with the 50% emergence date but did not correlate with the date when 50% of shoots became suitable for oviposition. Thus, the host‐plant responded to thermal effects differently from the gall midge. Illiciomyia yukawai has been synchronizing well with the host‐plant phenology but will suffer from asynchrony when global warming becomes more conspicuous.     

Restriction of transpiration rate under high vapour pressure deficit and non‐limiting water conditions is important for terminal drought tolerance in cowpea

Drought stress is a major constraint on cowpea productivity, since the crop is grown under warm conditions on sandy soils having low water‐holding capacity. For enhanced performance of crops facing terminal drought stress, like cowpea, water‐saving strategies are crucial. In this work, the growth and transpiration rate (TR) of 40 cowpea genotypes with contrasting response to terminal drought were measured under well‐watered conditions across different vapour pressure deficits (VPD) to investigate whether tolerant and sensitive genotypes differ in their control of leaf water loss. A method is presented to indirectly assess TR through canopy temperature (CT) and the index of canopy conductance (Ig). Overall, plants developed larger leaf area under low than under high VPD, and there was a consistent trend of lower plant biomass in tolerant genotypes. Substantial differences were recorded among genotypes in TR response to VPD, with tolerant genotypes having significantly lower TR than sensitive ones, especially at times with the highest VPD. Genotypes differed in TR response to increasing VPD, with some tolerant genotypes exhibiting a clear VPD breakpoint at about 2.25 kPa, above which there was very little increase in TR. In contrast, sensitive genotypes presented a linear increase in TR as VPD increased, and the same pattern was found in some tolerant lines, but with a smaller slope. CT, estimated with thermal imagery, correlated well with TR and Ig and could therefore be used as proxy for TR. These results indicate that control of water loss discriminated between tolerant and sensitive genotypes and may, therefore, be a reliable indicator of terminal drought stress tolerance. The water‐saving characteristics of some genotypes are hypothesised to leave more soil water for pod filling, which is crucial for terminal drought adaptation.     

Girolline interferes with cell-cycle progression, but not with translation

Girolline is a 2-aminoimidazole derivative with cytotoxic activity. It affects the survival of exponentially growing leukaemic cultured cells and has a significant antitumour activity on grafted murine tumours in vivo. In vitro studies showed that girolline affected protein synthesis by interfering with the translation termination process. Here, we investigate the effect of girolline on translation termination in human cultured cells. We show that girolline neither induces an increase in translational readthrough of stop codons nor affects the polysome profile in treated cells. This suggests that girolline does not act on translation in vivo. Then, we examine the effect of girolline on cell-cycle progression and we show that girolline induces an arrest of the cell cycle at the G2 stage.