Effects of dorsal aorta cannulation on the stress response of channel catfish (Ictalurus punctatus)

The stress response to dorsal aorta cannulation and serial blood sampling was examined in the channel catfish Ictalurus punctatus. Channel catfish cannulated and repetitively sampled once a day for 7 days did not exhibit a change in response to surgery or to the 24h sample regime as measured by plasma cortisol, glucose, and chloride. In fish that were either serially bled (0, 1, 3, 6, 9, 12, 24, and 48h) immediately after surgery or allowed to recover 6 days before being serially bled, overall plasma cortisol levels were higher than those of fish bled every 24h. Catfish serially bled immediately after surgery had significantly higher plasma glucose levels compared with catfish allowed to recover from surgery 6 days before serial sampling. Although channel catfish recover from cannulation surgery in 24h, a longer recovery period may be needed prior to serial sampling if the samples are taken more frequently than every 24h.     

How does drought tolerance compare between two improved hybrids of balsam poplar and an unimproved native species?

Poplars are one of the woody plants that are very sensitive to water stress, which may reduce the productivity of fast-growing plantations. Poplars can exhibit several drought tolerance strategies that may impact productivity differently. Trees from two improved hybrids, Populus balsamifera?×?Populus trichocarpa Torr. & Gray (clone B?×?T) and P. balsamifera?×?Populus maximowiczii A. Henry (clone B?×?M), having P. balsamifera L. as a parent and trees from native and unimproved P. balsamifera were subjected to a 1-month drying cycle in a growth chamber and then rewatered. The unimproved and native B clone maintained higher stomatal conductance (g(s)) than the hybrids, and high photosynthetic activity and transpiration, even when soil water content was nearly zero. As a result, both instantaneous water use efficiency (WUE(i)) and leaf carbon isotope composition (δ(13)C) indicated that this clone was less affected by drought than both hybrids at maximal drought stress. However, this clone shed its leaves when the drought threshold was exceeded, which implied a greater loss of productivity. The B?×?M hybrid showed a relatively conservative response to water stress, with the greatest decrease in transpiring versus absorbing surface (total leaf area to root biomass ratio). This clone was also the only one to develop new leaves after rewatering, and its total biomass production was not significantly decreased by drought. Among the two hybrids, clone B?×?T was the most vigorous, with the greatest transpiration (E(i)) and net CO(2) assimilation (A) rates, allowing for high biomass production. However, it had a more risky strategy under drought conditions by keeping its stomata open and high E(i) rates under moderate drought, resulting in a lower recovery rate after rewatering. The opposite drought response strategies of the two hybrids were reflected by clone B?×?T having lower WUE(i) values than clone B?×?M at maximal drought, with a very low Ψ(min) value of -3.2 MPa, despite closed stomata and stopped photosynthetic activity. Positive linear relationships between A and g(s) for the three hybrids indicated strong stomatal control of photosynthesis. Moreover, the three poplar clones showed anisohydric behaviour for stomatal control and their use under long-term drought should be of interest, especially the B?×?M clone.     

Experimental bases for a chemical control of Coquillettidia mosquito populations

Coquillettidia mosquitoes are not efficiently controlled by the conventional chemical practices which are known to be satisfactory against the larvae of other mosquito species. A research project was undertaken to conceive a new management strategy using plants as pesticide vectors to reach the Coquillettidia aquatic larvae. Therefore, larval mortality was measured in the presence of plants treated with phloem-translocated pesticides. The herbicide glyphosate at sub-lethal concentrations induced root epidermal cell lyses in maize plantlets cultivated in aqueous media, which clearly decreased larval fixation. Therefore, such herbicide strategy might operate through disturbing the larval physiological activities depending on fixation. The dimethoate insecticide did not affect root viability but at low concentrations seemed to disturb the plant–insect interactions. Larvae showed a lower attraction for roots and a considerable decrease in the root fixation rate. These larval behavior modifications were sufficient to induce mortality, probably due to a lack of fixation on plant roots. The effectiveness of plant foliar treatment with glyphosate or dimethoate under laboratory conditions suggested that it might be the basis for an efficient control strategy for Coquillettidia larvae and mosquitoes having the same living conditions in ponds and for which fixation on macrophyte roots is an absolute requirement (e.g.Mansonia, Mimomyia).     

Biological activity of natural phytoecdysteroids from Ajuga iva against the sweetpotato whitefly Bemisia tabaci and the persea mite Oligonychus perseae

BACKGROUND: Ecdysteroids are steroid hormones that control moulting and govern several changes during metamorphoses in arthropods. The discovery of the same molecules (phytoecdysteroids) in several plant species displayed a wide array of rather beneficial agricultural impact. Many representatives of the genus Ajuga plants contain phytoecdysteroids with a 5β‐7‐ene‐6‐one system exhibiting physiological activities in insects. RESULTS: By means of chromatographic (silica gel column, TLC) and LC‐MS, two major ecdysteroids (20‐hydroxyecdysone and cyasterone) have been isolated and identified from Israeli carpet bugle Ajuga iva (L.) Schreber (Lamiales: Lamiaceae) plants. Ajuga iva extract fractionated on the silica gel column yielded two fractions that showed high activity against the sweetpotato whitefly Bemisis tabaci and the persea mite Oligonychus perseae. A dose of 5 mg AI L^?1 of the purely identified A. iva ecdysterone significantly reduced fecundity, fertility and survival of these pests, while commercial 20‐hydroxyecdysone at the same dose had lesser effects. CONCLUSION: The results demonstrate considerable efficacy of natural phytoecdysteroids against major agricultural pests, and suggests that these materials should be considered for potential development of friendly control agents. Copyright © 2011 Society of Chemical Industry     

Fertilization of declining conifer stands in the vosges and in the French Ardennes

Twenty fertilization experiments were set up in 1985 and 1986 in the Vosges mountains, using mostly calcareous or Mg fertilizers, in order to verify whether fertilization can attenuate defoliation and yellowing recently recorded in Silver fir and Norway spruce. In the Ardennes, a fertilization experiment set up in Norway spruce stands prior to the appearance of yellowing was assessed. In these areas, the total acid deposition is about 2 kg eq H⁺ ha^–1 yr^–1. Nitrogen deposition is much more important in the Ardennes (52 kg N ha^–1 yr^–1 in form of wet and dry deposition) than in the Vosges (16 kg N ha^–1 yr^–1). The results in the eight adult stands showed no uniform reaction to the treatments. Spontaneous improvement, further deterioration independently of the treatment, as well as a positive reaction to fertilization were observed. Additional N or P fertilization sometimes had a beneficial effect on Ca or Mg treatments. The selection of the stands with the best response turns out to be difficult, as the nutrient contents of needles alone seem not to be a satisfactory criterion for selection. Young plantations reacted positivley to the treatments. Soluble Mg fertilizer leads to an immediate response. Low solubility Ca-Mg fertilizers (Ca-Mg lime) did not produce reactions until three years after the application. In the Ardennes, in a 40 yr old spruce stand suffering from severe Mg deficiency, a Ca and Ca-phosphate fertilization applied 5 yr before yellowing appeared had positive effects on crown density, discoloration and wood production. Conversely, a single N fertilization in this experiment, as well as in a young plantation in the Vosges, had a marked negative effect on Mg nutrition, even at low levels.     

Genetic studies of selection criteria for productive and stable peas

In this study we investigated the genetic determinism of criteria suitable for breeding for seed yield and yield stability in dry pea (Pisum sativumL.) using a diallel cross involving eight genotypes. Seven criteria related to plant and seed development were evaluated including: onset of flowering, node of first flower, leaf appearance rate, rate of progression of flowering, number of podded nodes on the main stem, mean dry seed weight per podded node and number of basal branches per plant. Most of these traits measured are related to timing of seed set and are thought to be critical in determining yield stability. We combined different diallel analyses (Hayman,1954; Griffing, 1956) with a Principal Component Analysis, to divide the parental lines into groups sharing similar genetic control for the traits studied. We found that the two main groups, defined according to their genetic control of node of first flower, also differed for all the others characters and, in particular, did not reach the same levels of productivity. These results indicated that crosses within the group with the highest productivity, but between lines with differing development and architectural features, could be a good starting point for breeding high-yield pure lines. This revised version was published online in August 2006 with corrections to the Cover Date.     

A stochastic predictive model for the natural spread of bluetongue

In recent years the vector-borne diseases (VBD) are (re)-emerging and spreading across the world having a profound impact on human and veterinary health, ecology, socio-economics and disease management. Arguably the best-documented example of veterinary importance is the recent twofold invasion of bluetongue (BT) in Europe. Much attention has been devoted to derive presence-absence habitat distribution models and to model transmission through direct contact. Limited research has focused on the dynamic modelling of wind mediated BT spread. This paper shows the results of a stochastic predictive model used to assess the spread of bluetongue by vectors considering both wind-independent and wind-mediated movement of the vectors. The model was parameterised using epidemiological knowledge from the BTV8 epidemic in 2006/2007 and the BTV1 epidemic in 2008 in South-France. The model correctly reflects the total surface of the infected zone (overall accuracy=0.77; sensitivity=0.94; specificity=0.65) whilst slightly overestimating spatial case density. The model was used operationally in spring 2009 to predict further spread of BTV1. This allowed veterinary officers in Belgium to decide whether there was a risk of introduction of BTV1 from France into Belgium and thus, whether there was a need for vaccination. Given the far distance from the predicted infected zone to the Belgian border, it was decided not to vaccinate against BTV1 in 2009 in Belgium.     

Epidemiology and impact of Neospora caninum infection in three Queensland tropical dairy herds

This study investigated the epidemiology of Neospora caninum in three tropical dairy herds in North Queensland, Australia. All animals in the herds were bled, and the sera were tested by ELISA for N. caninum antibodies. Herd records were examined, and the number of calves carried to term and the number of abortions which occurred over the lifetime of each animal were recorded to determine the abortion rate for each animal. Pedigrees were constructed for two of the herds to investigate whether vertical transmission was occurring. The seroprevalence of N. caninum ranged from 23% to 34%. The abortion rate in seropositive animals was significantly (p < 0.001) higher than in seronegative animals in all three herds (12-20.1% cf. 3.6-7%). Overall, the probability of a calf being seropositive was 3.5 times higher when the dam was also seropositive than when the dam was seronegative. Subsequent selective breeding employed by one herd reduced the N. caninum seroprevalence from 23% to 5% over a 9-year period. This study shows that N. caninum infection is prevalent in North Queensland dairy cattle, and both post-natal infection and vertical transmission are common.     

Diffuse idiopathic skeletal hyperostosis (DISH) and spondylosis deformans in purebred dogs: a retrospective radiographic study

A retrospective radiographic study was performed to investigate the prevalence of diffuse idiopathic skeletal hyperostosis (DISH) and spondylosis deformans (spondylosis) in 2041 purebred dogs and to determine association with age, gender and breed. Four cases of DISH provided information on the appearance of canine DISH. The prevalence of DISH and spondylosis was 3.8% (78/2041) and 18.0% (367/2041), respectively. Of dogs with DISH, 67.9% (53/78) also had spondylosis, whereas 14.0% (53/367) of dogs with spondylosis also had DISH. Dogs with DISH and/or spondylosis were significantly older than those without spinal exostosis. The prevalence of DISH and spondylosis was 40.6% (28/69) and 55.1% (38/69), respectively, in Boxer dogs. Nineteen smaller breeds were not affected by DISH, but showed signs of spondylosis; only standard Poodles appeared not to be affected by either disorder. Radiography, computed tomography (CT), magnetic resonance imaging (MRI), and/or histopathology were used to investigate four DISH cases. It was concluded that spondylosis and DISH can co-occur in dogs. DISH has probably been previously under-diagnosed and mistaken for severe spondylosis. The diagnosis can be made using radiography, CT or MRI. On histology, DISH can be distinguished from spondylosis by the location (ventral longitudinal ligament) and extent of new bone formation.     

Kinetics of antibody formation after the reactivation of bovine herpesvirus-1 infection in cattle

Holstein heifers previously infected with bovine herpesvirus-1 were treated with corticosteroids to reactivate latent infection. The kinetics of serum immunoglobulin (Ig) M, IgG1, and IgG2 antibody formation were determined. The secondary immune response which developed as a consequence of virus reactivation was characterized by an anamnestic IgG antibody response. Secondary IgG1 and IgG2 antibody formation constituted the IgG antibody response. In addition, secondary IgM antibody formation was elicited by this form of bovine herpesvirus-1 antigenic exposure.