Early steps of insulin receptor signaling in chicken and rat: apparent refractoriness in chicken muscle

The early steps of insulin receptor (IR) signaling (tyrosine phosphorylation of IR beta-subunit, IRS-1 and Shc and PI 3'-kinase activity) have been characterized in two target tissues in the chicken: liver and muscle. The signaling cascade appeared to depend on nutritional status in the liver, but not in muscle (with a possible exception for a minor tyrosine phosphorylation of the 52 kDa Shc isoform). In this study, we compared the responses of the liver and muscle to exogenous insulin (10 or 1000 mU/kg) in chickens and rats. In the liver, IRS-1 and Shc proteins were present in smaller amounts and the regulatory subunit p85 of PI 3'-kinase was present in larger amounts in chickens than in rats. In the basal state (saline injection), the level of tyrosine phosphorylation of IR was lower, and that of Shc higher, in chickens than in rats. PI 3'-kinase activity in chickens was half that in rats. Insulin activated all components of the cascade in a dose-dependent manner in both species. A different pattern was observed in the muscle. In the basal state, the levels of tyrosine phosphorylation of IR and of PI 3'-kinase activity were much higher in chickens than in rats (by factors of 2 and 30, respectively). Insulin strongly activated all components of the cascade in rats (but with no significant increase in the phosphorylation of Shc). No activation was observed in chickens (with only a slight but significant increase in the tyrosine phosphorylation of Shc). The insulin cascade therefore appears to respond normally in chicken liver but to be refractory in chicken muscle. The large amount of p85 and high levels of PI 3'-kinase activity in muscle may contribute to this situation, making chicken muscle an interesting model of insulin resistance.     

Respective roles of recent hedges and forest patch remnants in the maintenance of ground-beetle (Coleoptera: Carabidae) diversity in an agricultural landscape

We compared three kinds of habitats: small remnants of native forests, recent hedges and barley crops, in order to investigate their respective roles in the maintenance of carabid-beetle diversity in a 950-ha area of an intensive agricultural landscape. Carabid faunas in remnants differed weakly from these found in hedges and crops. In particular, small remnants had few typical forest carabid species and a large number of open-area or ubiquitous species. Different approaches in the measurement of and -diversity (classical indices, and additive partitioning of Simpson's index) showed similar results: hedges supported a high -diversity but habitat types were quite similar overall, with weak differences between open and closed or disturbed and undisturbed habitats.A comparison of species dispersal powers in the various habitat types showed that species with a low dispersal power were rare in all habitats. However, wing development measured on two dimorphic species revealed, surprisingly, that brachypterous individuals were mainly present in hedges, which were expected a priori to be more disturbed, than remnants hence less suitable for the establishment of populations with a low dispersal power.These results suggest that small remnants do not behave as 'climax' habitats in this intensive agricultural landscape, probably because of their small size and strong isolation. We discuss the interest of new undisturbed habitats, such as recent hedges, for the maintenance of carabid diversity at both the local and landscape scale.     

New Cases of Negative Cross-resistance between Fungicides,Including Sterol Biosynthesis Inhibitors

A survey of fungicide resistance in Mycosphaerella graminicola and Tapesia acuformis, two major pathogens of winter wheat in France, respectively responsible for speckled leaf blotch and eyespot, led to the characterization of two types of resistant strains to sterol 14α-demethylation inhibitors (DMIs). Most of the strains of M. graminicola collected in France in 1997–1998 were resistant to all DMIs, and only in a few strains was the resistance to several triazoles associated with increased susceptibility to pyrimidine derivatives (i.e., fenarimol, nuarimol) and triflumizole. On the other hand, in T. acuformis the most prevalent strains were those which exhibited negative-cross resistance between DMIs. In both fungi such a phenomenon could be related to changes in cytochrome P450 sterol 14α-demethylase, the target site of these fungicides. For Botryotinia fuckeliana, the causal agent of grey mould, the extensive monitoring conducted in French vineyards before the marketing of fenhexamid revealed the presence of highly resistant strains to this promising botryticide (only in tests involving mycelial growth measurements). Negative cross-resistance to edifenphos and several sterol biosynthesis inhibitors, such as prochloraz and fenpropimorph, was observed in fenhexamid resistant strains. Synergism of the antifungal action of fenhexamid by cytochrome P450 inhibitors, such as the DMI fungicides, was only recorded in fenhexamid resistant strains. These data and those previously obtained with edifenphos resistant strains of Magnaporthe grisea (rice blast pathogen) suggest that in fenhexamid resistant strains of B. fuckeliana the same cytochrome P450 monooxygenase could be involved in detoxification of fenhexamid and activation of edifenphos. Received 6 September 1999/ Accepted in revised form 13 September 1999     

Insecticide resistance in vector mosquitoes in China

Because of their special behaviour, physiology and close relationship with humans, mosquitoes act as one of the most important vectors of human diseases, such as filariasis, Japanese encephalitis, dengue and malaria. The major vector mosquitoes are members of the Culex, Aedes and Anopheles genera. Insecticides play important roles in agricultural production and public health, especially in a country with a huge human population, like China. Large quantities of four classes of insecticides, organochlorines, organophosphates, carbamates and pyrethroids, are applied annually to fields or indoors in China, directly or indirectly bringing heavy selection pressure on vector populations. The seven major species of vector mosquito in China are the Culex pipiens L. complex, C. tritaeniorhynchus Giles, Anopheles sinensis Wied., A. minimus Theobald, A. anthropophagus Xu & Feng, Aedes albopictus (Skuse) and Ae. aegypti L., and all have evolved resistance to all the above types of insecticide except the carbamates. The degree of resistance varies among mosquito species, insecticide classes and regions. This review summarizes the resistance status of these important vector mosquitoes, according to data reported since the 1990s, in order to improve resistance management and epidemic disease control, and to communicate this information from China to the wider community.     

Emerging and re-emerging viruses of the honey bee (Apis mellifera L.)

Until the late 1980s, specific viral infections of the honey bee were generally considered harmless in all countries. Then, with the worldwide introduction of the ectoparasite mite Varroa destructor, beekeepers encountered increasing difficulties in maintaining their colonies. Epidemiological surveys and laboratory experiments have demonstrated that the newly acquired virulence of several viruses belonging to the family Dicistroviridae (acute bee paralysis virus, Kashmir bee virus and Israeli acute paralysis virus) in Europe and the USA had been observed in relation with V. destructor acting as a disseminator of these viruses between and within bee colonies and as an activator of virus multiplication in the infected individuals: bee larvae and adults. Equal emphasis is given to deformed wing virus (DWV) belonging to the Iflaviridae. Overt outbreaks of DWV infections have been shown to be linked to the ability of V. destructor to act not only as a mechanical vector of DWV but also as a biological vector. Its replication in mites prior to its vectoring into pupae seemed to be necessary and sufficient for the induction of a overt infection in pupae developing in non-viable bees with deformed wings. DWV in V. destructor infested colonies is now considered as one of the key players of the final collapse. Various approaches for combating bee viral diseases are described: they include selection of tolerant bees, RNA interference and prevention of new pathogen introduction. None of these approaches are expected to lead to enhanced bee-health in the short term.     

Quantitative transmission characteristics of different H5 low pathogenic avian influenza viruses in Muscovy ducks

EU annual serosurveillance programs show that domestic duck flocks have the highest seroprevalence of H5 antibodies, demonstrating the circulation of notifiable avian influenza virus (AIV) according to OIE, likely low pathogenic (LP). Therefore, transmission characteristics of LPAIV within these flocks can help to understand virus circulation and possible risk of propagation. This study aimed at estimating transmission parameters of four H5 LPAIV (three field strains from French poultry and decoy ducks, and one clonal reverse-genetics strain derived from one of the former), using a SIR model to analyze data from experimental infections in SPF Muscovy ducks. The design was set up to accommodate rearing on wood shavings with a low density of 1.6 ducks/m²: 10 inoculated ducks were housed together with 15 contact-exposed ducks. Infection was monitored by RNA detection on oropharyngeal and cloacal swabs using real-time RT-PCR with a cutoff corresponding to 2–7 EID50. Depending on the strain, the basic reproduction number (R₀) varied from 5.5 to 42.7, confirming LPAIV could easily be transmitted to susceptible Muscovy ducks. The lowest R₀ estimate was obtained for a H5N3 field strain, due to lower values of transmission rate and duration of infectious period, whereas reverse-genetics derived H5N1 strain had the highest R₀. Frequency and intensity of clinical signs were also variable between strains, but apparently not associated with longer infectious periods. Further comparisons of quantitative transmission parameters may help to identify relevant viral genetic markers for early detection of potentially more virulent strains during surveillance of LPAIV.     

A Genome-Wide Association Study for Morphometric Traits in Quarter Horse

A genome-wide association study for morphometric traits was conducted in 184 Quarter Horses, 120 from a racing population, and 64 from a cutting population, which were genotyped using the Illumina EquineSNP50 chip. Association analysis was performed with 42,058 single-nucleotide polymorphisms (SNPs) (after quality control) using Qxpak5 software. The following traits were measured: weight (W), rump length (RL), and body length (BL). These morphometric traits are important for the best performance in race and cutting events. For weight, three SNPs associated (P < .0001) were found on chromosomes (Equus caballus autosomes [ECA]) 2 and 3. For rump length, eight SNPs associated (P < .0001) were found on ECA 2, 3, 6, 7, 9, 21, and 26. On ECA 3 and ECA 8, two SNPs were associated (P < .0001) with body length. So, a total of 13 important chromosomal regions were identified with Q values of 0.53 (SNPs for W), 0.40 (SNPs for RL), and 0.99 (SNPs for BL). Positional and functional candidate genes emerging from this study were WWOX and AAVPR1A. Further studies are required to confirm these associations in other populations.     

Feeding Magnesium Supplement to Foals Reduces Osteochondrosis Prevalence

The influence of supplements containing magnesium on the etiology of osteochondrosis (OC) is unknown. We did two studies to measure the effect of additional minerals (especially magnesium) on OC. In study 1 (five studs, in total 64 mares and foals aged 0 to 5 months, equally divided into two groups), supplementation with minerals and placebo was used. Blood samples were taken from foals at age of 2, 8, and 16 weeks. At the same time, milk samples were taken from the mare. Bone biomarkers (osteocalcin and C-terminal telopeptide [CTx] of type I [CTx-1] collagen) and minerals (calcium, phosphorus, and magnesium) were measured in blood and the same minerals in milk of the mare. At the end of the study, the femoropatellar (knee), tarsocrural (hock), and metacarpophalangeal and/or metatarsophalangeal (fetlock) were radiographed and scored for the presence and grade of osteochondrotic lesions. In study 2 (six studs, 54 foals aged 5 to 12 months, equally divided into two groups), the same was repeated. At the start and end of the study, again blood samples were taken and analyzed on the same parameters as in study 1. Also, the same radiography was done. In study 1 in the mineral supplemented group, 21.9% were diagnosed with osteochondrosis compared with 41.9% in the placebo group. In study 2, there was no change in OC between 5 and 12 months in the placebo group whereas there was a drop of 14.3% in incidence in the supplement group. We concluded that magnesium supplementation reduced OC prevalence.