Factors affecting plant species distribution in hedgerows of southern Quebec

Woody linear features of farmlands have received much attention as pools of diversity in European countries, but they have, in comparison, been little considered in eastern North American ecological studies. Here, we evaluate the relative contribution of environmental conditions, history of management practices within hedgerows, and adjacent land-use on herb and shrub species distribution in woody hedgerows of agricultural landscapes of southern Quebec, Canada. We pay particular attention to the distribution of forest herbs and weed species and identify the main factors that explain their presence. We also evaluate the amount of spatial structuring in the species data and explanatory variables.Our results show significant differences in species composition related to the unique influence of all sets of factors considered. Adjacent land-use (from intensive crop to fallow land) remains the best predictor of overall species distribution, followed by environmental conditions and history of management practices. The probability of finding forest herbs in hedgerows increases as intensity of adjacent agricultural practices (from intensive crop to fallow land) decreases. Potential weed species, on the other hand, are more likely to be found within narrow hedgerows adjacent to the more intensively managed fields. We discuss the results in terms of the interactions between the different determinants of plant diversity in hedgerows and demonstrate the necessity to distinguish between multiple structuring factors to devise proper conservation strategies. Such strategies will have to take into account the ecological as well as the agricultural exploitation context in which linear features are found to be effective.     

Marihuana: standardized smoke administration and dose effect curves on heart rate in humans

A spirometer was used to deliver marihuana and placebo smoke to human subjects. This procedure produced linear dose-effect curves on heart rate and replicable dose effects in individual subjects. No differences were observed between experienced and inexperienced smokers in responsiveness to heart rate increases produced by marihuana.     

Effect of recombinant human thyroid stimulating hormone on serum thyroxin and thyroid scintigraphy in euthyroid cats

This study investigated the thyroidal response to administration of recombinant human thyroid stimulating hormone (rhTSH) by means of serum total thyroxine (TT(4)) concentration and pertechnetate uptake by the thyroid gland in six healthy euthyroid spayed female cats. A pertechnetate scan was performed on day 1 to calculate thyroid/salivary gland (T/S) uptake ratio. On day 3, 25 microg rhTSH was injected intravenously. Six hours later the thyroid scan was repeated as on day 1. Blood was drawn for serum TT(4) measurement prior to injection of rhTSH and performance of the pertechnetate scan. Statistically significant differences in mean serum TT(4) concentration, T/S uptake ratio before and 6h after rhTSH administration and T/S uptake ratio between left and right lobes were noted. We can conclude that 25 microg rhTSH increases pertechnetate uptake in the thyroid glands of cats, this should be taken into account when thyroid scintigraphy after rhTSH administration is interpreted.     

A herpes-like virus infecting Crassostrea gigas and Ruditapes philippinarum larvae in France

Concomitant sporadic high mortalities were reported in June 1997 among batches of larval Pacific oyster, Crassostrea gigas, and Manila clam, Ruditapes philippinarum , in a French commercial hatchery. Histological observation showed the presence of cellular abnormalities in affected animals. Electron transmission microscopy revealed the presence of herpes-like virus particles in infected larvae of both bivalve species. Viruses observed in C. gigas and R. philippinarum are closely related with respect to ultrastructure and morphogenesis. They were detected simultaneously in both bivalve species larvae indicating possible interspecific transmission. Moreover, PCR analysis using oyster herpes-like virus specific primers allowed amplification of fragments of expected sizes for both bivalve species and demonstrated the presence of viral DNA. The PCR products obtained for both bivalve species and digested by restriction enzymes displayed the same patterns. These data suggest that the same herpes-like virus may infect larval oysters and clams.     

Herpes-like virus infections in hatchery-reared bivalve larvae in Europe: specific viral DNA detection by PCR

Periodic losses in oyster hatcheries are regularly reported in Europe. Herpes-like virus infections seem to play a key role. Polymerase chain reaction (PCR) was used to investigate the presence of herpes-like virus DNA in larval samples belonging to different bivalve species from different geographical origins. Seventeen samples of the 81 analysed appeared positive for the herpes-like virus DNA by PCR. These results confirm previous data indicating that herpes-like virus infections occur in commercial French hatcheries. Polymerase chain reaction positive results were also obtained for bivalve larval samples originating from Spain and the UK. The number of virus DNA positive samples depended on the primer pair used. The primer pair C2/C6 appears well adapted for herpes-like virus DNA detection because of processing ease and great sensitivity. Positive samples were observed in four bivalve species: Crassostrea gigas , Ostrea edulis , Ruditapes decussatus and Ruditapes philippinarum . Herpes-like virus DNA detection is reported in larval R. decussatus for the first time. Many samples in which viral DNA was detected by PCR correspond to larval batches presenting mortalities. Herpes-like viruses may be one of the causative agents of mortalities observed in bivalve hatcheries.     

Disease Progress Curve Parameters Help to Characterise the Types of Resistance to Late Blight Segregating in Cultivated Potato

To decrease the environmental impact of treatments against late blight caused by Phytophthora infestans on potato, plant genetic resistance is a keystone in developing new culture strategies. Nonspecific resistance to late blight is a complex trait which is difficult to evaluate, while selection is both difficult and time consuming. However, we consider it is important to select for this type of resistance as it is a promising way to achieve durable resistance. In this study, parameters derived from disease progress curves (DPCs) were used to characterise the types of resistance among individuals of three tetraploid full-sib families named G1, B2, and K2. These families were composed of 280 (G1), 280 (B2), and 150 (K2) genotypes. Our aim was to avoid visual inspection of 5,710 DPCs and to identify genotypes exhibiting stable resistance. We used three parameters: the slope of the DPC, the date of appearance of the first symptoms in the tested genotypes compared with a susceptible standard, and the relative area under the disease progress curve (rAUDPC). Using an appropriate threshold for each parameter, we demonstrated that it is possible to classify the response of each genotype in one of the following categories: susceptible, non-specific resistance, specific resistance, non-specific resistance plus specific resistance (or specific resistance not overcome). Data were obtained each year from 2005 to 2007 under conditions of natural infection. According to the parameters analysed, non-specific resistance and specific resistance segregated in the families. The year effect was more than double the family effect for rAUDPC. Empirical adjustment of threshold values in a subsample of the tested genotypes led to an increase in the effectiveness of our classification method. Calculated classification enabled detection of stable genotypes in each family. The impact of the year effect differed with the family. In the G1 family, the distribution of genotypes in each category was relatively stable over the 3 years, whereas in K2, the proportion of genotypes demonstrating specific resistance alone increased, particularly in 2007. In the B2 family, the proportion of genotypes in the non-specific resistance category decreased from 40% to 15% from 2005 to 2006, and then remained stable in 2007. The heritabilities of the parameters ranged from 61% to 96% depending on the family and on the parameter concerned.     

An electronic micropenetrometer (EMP) for field measurements of biological soil crust stability

Despite the importance of biological soil crusts (BSC) for ecosystem functions in arid and semiarid areas, little information on their mechanical stability is available. Goal of this study was to develop a micropenetrometer (EMP) that allows to determine BSC stability at high spatial resolutions. First results show that differences in BSC stability at 39 μm resolution can be detected and that cyanobacterial BSC has an average penetration resistance of 0.75 MPa.     

Twenty year experience of the oral rabies vaccine SAG2 in wildlife: a global review

The SAG2 vaccine (RABIGEN® SAG2) is a modified live attenuated rabies virus vaccine, selected from the SAD Bern strain in a two-step process of amino acid mutation using neutralizing monoclonal antibodies. The strain is genetically stable and does not spread in vivo or induce a persistent infection. Its absence of residual pathogenicity was extensively demonstrated in multiple target and non target species (such as wild carnivores and rodent species), including non-human primates. The efficacy of SAG2 baits was demonstrated according to the EU requirements for the red fox and raccoon dog. The use of safe and potent rabies vaccines such as SAG2 largely contributed to the elimination of rabies in Estonia, France, Italy and Switzerland. Importantly, these countries were declared free of rabies after few years of oral vaccination campaigns with SAG2 baits distributed with an appropriate strategy. The excellent tolerance of the SAG2 vaccine has been confirmed in the field since its first use in 1993. No safety issues have been reported, and in particular no vaccine-induced rabies cases were diagnosed, after the distribution of more than 20 million SAG2 baits in Europe.     

Genotyping of a microsatellite locus to differentiate clinical Ostreid herpesvirus 1 specimens

Ostreid herpesvirus 1 (OsHV-1) is a DNA virus belonging to the Malacoherpesviridae family from the Herpesvirales order. OsHV-1 has been associated with mortality outbreaks in different bivalve species including the Pacific cupped oyster, Crassostrea gigas. Since 2008, massive mortality events have been reported among C. gigas in Europe in relation to the detection of a variant of OsHV-1, called μVar. Since 2009, this variant has been mainly detected in France. These results raise questions about the emergence and the virulence of this variant. The search for association between specific virus genetic markers and clinical symptoms is of great interest and the characterization of the genetic variability of OsHV-1 specimens is an area of growing interest. Determination of nucleotide sequences of PCR-amplified virus DNA fragments has already been used to characterize OsHV-1 specimens and virus variants have thus been described. However, the virus DNA sequencing approach is time-consuming in the high-scale format. Identification and genotyping of highly polymorphic microsatellite loci appear as a suitable approach. The main objective of the present study was the development of a genotyping method in order to characterise clinical OsHV-1 specimens by targeting a particular microsatellite locus located in the ORF4 area. Genotyping results were compared to sequences already available. An excellent correlation was found between the detected genotypes and the corresponding sequences showing that the genotyping approach allowed an accuraté discrimination between virus specimens.