Distribution and intensity of <Emphasis Type="BoldItalic">Echinococcus granulosus</Emphasis> infections in dogs in Moroto District,Uganda

This study was carried out during August 2007–March 2008 in pastoral areas of Moroto District, Uganda. It investigated the distribution and infection intensity of Echinococcus granulosus in the dog population and involved the postmortem examination of 327 dogs (106 domesticated; 80 semi-domesticated, and 141 strays; comprised of 163 females and 164 males). The overall prevalence of E. granulosus was 66.3% (95% CI = 60.8–71.4) with parasite burdens of 6–5,213 among the infected dogs. The prevalence of E. granulosus was primarily associated with the season. While the dogs were more likely to have high parasite burdens during the rainy as opposed to the dry season, the parasite burden of E. granulosus infection was also highly associated with age and husbandry. Young dogs were at greater risk of carrying a heavy burden of E. granulosus infection than adults. Likewise, stray dogs were more likely to have a heavy parasite burden. As the study documented a high prevalence and intensity of E. granulosus infection in the dog population in Moroto District of Uganda, further studies need to be carried out in human and intermediate hosts to elucidate the cycle of transmission that could help to design appropriate controlling measures.     

Drought susceptibility and recovery of transplanted Quercus rubra seedlings in relation to root system morphology

? Transplant shock, implicated by depressed seedling physiological status associated with moisture stress immediately following planting, limits early plantation establishment. Large root volume (Rv) has potential to alleviate transplant shock because of higher root growth potential and greater access to soil water.

? We investigated impacts of drought and transplant Rv on photosynthetic assimilation (A), transpiration (E), stomatal conductance (g _s ), predawn leaf xylem water potential (Ψ_L), and growth of northern red oak (Quercus rubra L.) seedlings to explain mechanisms associated with susceptibility to transplant shock. One year-old barerooot seedlings were graded into four Rv categories and either well watered or subjected to drought consisting of low, medium, or high moisture stress by discontinuing irrigation at 22-day intervals for 3 months. Thereafter, all treatments were re-watered to examine recovery.

? Transplant shock was signified by reduced A, E, g _s, and Ψ_L, which generally increased with increasing moisture stress and Rv. Physiological status improved during recovery, though stress was still evident in seedlings exposed to medium or high moisture stress and in larger Rv seedlings. Growth declined with increasing moisture stress but was generally similar among Rv treatments, likely reflecting greater A at the whole plant level and/or reliance upon stored reserves in large Rv seedlings.

? The most effective drought avoidance mechanisms were root growth, stomatal regulation, reduced leaf area, and higher growth allocation to roots relative to shoots. Our results suggest that large initial Rv does not enhance drought avoidance during the first season after transplant in northern red oak seedlings.

     

Combining X-ray computed tomography with relevant techniques for analyzing soil–root dynamics – an overview

The study of below-ground features of roots and soil and their interactions is essential for understanding the configuration and diversities in such a dynamic environment. X-ray computed tomography is recognized as a tool for visualizing the physical interactions in the soil. In many studies, it has been used as a stand-alone tool to describe soil and root parameters. However, in recent times, attempts to couple it with other complementary tools are gaining rapid interest among researchers. The paper therefore provides an overview of the major application of combining X-ray computed tomography with other relevant methods in analyzing the structural characteristics of roots and soil media. The relevance of using this multidisciplinary approach for unraveling the mysteries surrounding root–soil dynamic interactions is stressed. The current and future trends of such studies are also pointed out.     

Coevolution in natural pathosystems: effects of dominance on host-pathogen interactions

ABSTRACT We have developed a new complementary model of gene interaction between diploid host and haploid pathogen by allowing for arbitrary levels of dominance in the host. This model enables us to assess the effects of overdominance, incomplete dominance, and underdominance on the equilibrium frequencies of resistance and virulence genes and on the stability of equilibria. Our model reduces to a gene-for-gene model when complete dominance of resistance is assumed. Computer simulations show that our model has two new features. First, when there is overdominance or underdominance of resistance, the internal equilibrium points exist even when there is no cost of unnecessary virulence or when there is a cost of necessary virulence at the balance between cost of unnecessary virulence and effectiveness of resistance. Second, the occurrence of stable resistance and virulence polymorphism is strongly dependent on the level of dominance. These two features suggest the need for caution when using the gene-for-gene model, especially in the presence of overdominance or underdominance. Our model is particularly suitable for studying the coevolutionary dynamics between hybrid populations and their pathogens in natural pathosystems.     

Two Loci from Lycopersicon hirsutum LA407 Confer Resistance to Strains of Clavibacter michiganensis subsp. michiganensis

ABSTRACT We used molecular markers to identify quantitative trait loci (QTL) that contribute to resistance to bacterial canker of tomato caused by Clavibacter michiganensis subsp. michiganensis. Resistance was first identified as a marker-trait association in an inbred backcross (IBC) population derived from crossing Lycopersicon hirsutum accession (LA407) with L. esculentum. Single-marker QTL analysis suggested that at least two loci originating from L. hirsutum LA407, Rcm 2.0 on chromosome 2 and Rcm 5.1 on chromosome 5, contribute to resistance in replicated trials. Two segregating F(2) populations were developed by crossing resistant inbred backcross lines (IBLs) to elite L. esculentum lines and used to confirm QTL associations detected in the IBC population. In these populations, realized heritability estimates were higher for selection based on maximal disease than for selection based on disease progression. Realized heritability in the population carrying Rcm 2.0 was 0.63 and 0.14, respectively, for each selection criteria. Realized heritability estimates were 0.85 for selection based on maximal disease and 0.37 for selection based on disease progression in a population carrying Rcm 5.1. The disease response of F(3) families selected for resistance suggested that both Rcm 2.0 and Rcm 5.1 confer resistance to bacterial strains in the repetitive sequence-based polymerase chain reaction DNA fingerprint classes A and C. Markers linked to Rcm 2.0 explained up to 56% of the total phenotypic variation for resistance in one population, and markers linked to Rcm 5.1 explained up to 73% of the total phenotypic variation for resistance in a separate population.     

Comparison of Multistage Versus One-Stage Destabilization of a Type II External Fixator Used to Stabilize an Oblique Tibial Osteotomy in Dogs

OBJECTIVE: To compare the biomechanical effects of multistage versus one-stage destabilization of a type II external skeletal fixator (ESF) used to stabilize an oblique unstable tibial osteotomy in dogs. STUDY DESIGN: In vitro, in vivo, and ex vivo experimental study. ANIMAL POPULATION: Twelve healthy adult dogs. METHODS: The biomechanical characteristics of the type II ESF used in this study were determined. This fixator was applied to both tibiae of two groups of 6 dogs to stabilize a 2-mm-wide oblique osteotomy. One fixator on each dog remained unchanged throughout the 11-week study (control group). The fixator on the opposite limb was destabilized late and acutely in one group of dogs (single-stage) and early and progressively in the other (multistage). Clinical examination, radiographic examination, and force-plate analysis were used to evaluate the results. All dogs were euthanatized at 11 weeks. All tibiae were scanned to determine the cross-sectional area of the callus in the center of the osteotomy and subjected to biomechanical tests to determine mean pull-out strength of pins and callus strength and stiffness. RESULTS: Stiffness of the type II ESF used in this study was 578 N/mm in axial compression, 0.767 Nm/deg in torsion, 261 N/mm in medio-lateral bending, and 25 N/mm in cranio-caudal bending. Peak vertical forces of the hindlimbs were significantly lower at 2.5 and 5 weeks than before surgery. Peak vertical forces of the hindlimbs did not change before and after destabilization. No significant differences could be detected between the two destabilization sequences or between all control tibiae and pooled destabilized tibiae with regards to radiographic evaluation of the healing osteotomy, cross-sectional periosteal callus area, mean pull-out strength of transfixation pins, callus strength, and callus stiffness. CONCLUSIONS AND CLINICAL RELEVANCE: Bone healing of unstable osteotomies stabilized with a type II ESF is not significantly enhanced by staged destabilization of the fixation as performed in this study.