Epidemiology and risk factors associated with Anaplasma marginale infection of cattle in Peninsular Malaysia

Bovine anaplasmosis is a major concern to cattle farming in most parts of the world. Anaplasmosis negatively impacts the profitability of cattle farming by reducing the production, reproduction, and draft ability of cattle. Here, we report results from a one-year cross sectional study to determine the epidemiology and the risk factors for Anaplasma marginale infection of cattle in Peninsular Malaysia. Examination of one thousand and forty five blood samples of apparently healthy cattle from forty-three farms in all the states of Peninsular Malaysia by polymerase chain reaction (PCR) assay revealed an overall prevalence of A. marginale infection of cattle of 72.6%, showing high endemicity of this heamoprotozoan among cattle in the country. Cattle breeds, production type, herd owner, herd size, management system, farm size, farm age, prophylactic treatment against blood parasites, presence of ticks, frequency of deticking, zones, closeness to forest, closeness to waste area, closeness to human settlement and closeness to body of water were the risk factors significantly associated (P?<?0.05) with the detection of A. marginale in cattle. Results of this first molecular study on the epidemiology and risk factors for A. marginale infection of cattle from all the states of Peninsular Malaysia suggest policies and strategies for the prevention and control of the parasite to improve profitability of cattle farming in the country.     

A comparison of the cuticular properties of the female ticks <Emphasis Type="Italic">Ixodes pacificus</Emphasis> and <Emphasis Type="Italic">Amblyomma hebraeum</Emphasis> (Acari: Ixodidae) throughout the feeding period

The mechanical properties of the cuticle of Ixodes pacificus (Ip) are compared to those of Amblyomma hebraeum (Ah) from our earlier work. The 10-fold size difference between the species is expected to lead to significant differences in mechanical properties, because cuticular stretch depends on high internal hydrostatic pressure during the rapid phase of engorgement. We demonstrate here: (1) The cuticle of partially fed Ip is less stiff and viscous than that of Ah. (2) A stretch-recoil cycle in both ticks consists of recoverable deformation (ESv) and permanent deformation (ESp); ESp is higher in Ip, and increases sharply during the slow phase of engorgement, but not in Ah. (3) Injected dopamine (DA) increases ESp and reduces all measures of stiffness and viscosity, suggesting that a catecholaminergic neurotransmitter plays a fundamental role in modulating mechanical properties of the cuticle. However, unlike Ah, DA’s effect was not different from that of the control (1.2% NaCl). Mere insertion of the needle may have punctured the gut, causing the release of perhaps a catecholamine that increases ESp, an hypothesis supported by the fact that inserting a needle without any injection also caused an increase in ESp. (4) Stretch reduces ESp, but subjecting loops to pH 6.5 in vitro restores it. (5) Despite the smaller size of Ip, later onset of the rapid phase of engorgement, a thinner cuticle and different mechanical properties all reduce the internal pressure needed for stretch.     

Effects of caffeine on crayfish muscle fibers. II. Refractoriness and factors influencing recovery (repriming) of contractile responses

When caffeine evokes a contraction, and only then, crayfish muscle fibers become refractory to a second challenge with caffeine for up to 20 min in the standard saline (5 mM K_o). However, the fibers still respond with contraction to an increase in K_o, though with diminished tension. Addition of Mn slows recovery, but the latter is greatly accelerated during exposure of the fiber to high K_o, or after a brief challenge with high K_o. Neither the depolarization induced by the K, nor the repolarization after its removal accounts for the acceleration, which occurs only if the challenge with K had itself activated the contractile system; acceleration is blocked when contractile responses to K are blocked by reducing the Ca in the bath or by adding Mn. Recovery is accelerated by redistribution of intracellular Cl and by trains of intracellularly applied depolarizing pulses, but not by hyperpolarization. The findings indicate that two sources of Ca can be mobilized to activate the contractile system. Caffeine mobilizes principally the Ca store of the SR. Depolarizations that are induced by high K_o, by transient efflux of Cl, or by intracellularly applied currents mobilize another source of Ca which is strongly dependent upon the entry of Ca from the bathing medium. The sequestering mechanism of the SR apparently can utilize this second source of Ca to replenish its own store so as to accelerate recovery of responsiveness to a new challenge with caffeine.     

Interaction of Colicins with Bacterial Cells IV. Immunity Breakdown Studied with Colicins Ia and Ib

Colicinogenic cells are immune to the lethal effect of the colicin which they produce. In the presence of very high concentrations of colicin, however, colicinogenic cells are no longer immune to the homologous colicin. This phenomenon, immunity breakdown, was studied with colicins Ia and Ib. The biochemical effects of colicin Ib on Escherichia coli were studied with a standard noncolicinogenic strain. At multiplicities of about 10 or higher, colicin Ib inhibited incorporation of leucine into protein and incorporation of (32)P-inorganic phosphate into deoxyribonucleic acid and ribonucleic acid by more than 95%. Under the same conditions, (32)P incorporation into phospholipid and nucleotide fractions was inhibited only partially (about 80 and 60%, respectively). Inhibition of (32)P incorporation into the terminal phosphorus of adenosine triphosphate was also considerably less than that of macromolecular synthesis (50 to 60%). (32)P incorporation into the nonnucleotide organic phosphate fraction was not inhibited. Respiration was not affected. Colicin Ia showed the same biochemical effects as colicin Ib. A mutant of an Ib-colicinogenic E. coli strain selected for resistance to low concentrations of colicin Ia was shown to be resistant to high concentrations of homologous colicin Ib, whereas the parent Ib-colicinogenic strain is sensitive to high concentrations of colicin Ib. This mutant lost its specific receptors for colicin Ib. Moreover, the biochemical effects of high concentrations of colicin Ib on Ib-colicinogenic cells during immunity breakdown were similar to the effects found in sensitive cells exposed to low concentrations of the same colicin. It is concluded that the killing of colicinogenic cells in the presence of high concentrations of homologous colicin is indeed caused by the homologous colicin molecules.     

Environmental correlates for tropical tree diversity and distribution patterns in Borneo

Aim Identify environmental correlates for tropical tree diversity and composition. Location Borneo, Southeast Asia. Methods A GIS‐environmental database with 5 arc minute (c. 10 × 10 km) resolution was combined with tree inventory data. Tree diversity, phylogenetic diversity (PD) and the two main compositional gradients were determined for 46 tree inventories. Akaike's information criterion and a data jackknifing procedure were used to select 50 explanatory models for diversity and composition gradients. The average of these models was used as our final diversity and compositional model. We applied Moran's I to detect spatial autocorrelation of residuals. Results Tree diversity, PD and the two main compositional gradients in Borneo were all significantly correlated with the environment. Tree diversity correlated negatively with elevation, soil depth, soil coarseness (texture) and organic carbon content, whereas it correlated positively with soil C:N ratio, soil pH, moisture storage capacity and annual rainfall. Tree PD was correlated positively with elevation and temperature seasonality and was largely determined by gymnosperms. However, angiosperm PD also correlated positive with elevation. Compositional patterns were strongly correlated with elevation but soil texture, cation‐exchange‐capacity, C:N ratio, C and N content and drainage were also important next to rainfall seasonality and El Niño Southern Oscillation drought impact. Main conclusions Although elevation is the most important correlate for diversity and compositional gradients in Borneo, significant additional variability is explained by soil characteristics (texture, carbon content, pH, depth, drainage and nutrient status) and climate (annual rainfall, rainfall seasonality and droughts). The identified environmental correlates for diversity and composition gradients correspond to those found in other tropical regions of the world. Differences between the regions are mainly formed by differences in the relative importance of the environmental variables in explaining diversity and compositional gradients.     

Choosing the right path: enhancement of biologically relevant sets of genes or proteins using pathway structure

A method is proposed that finds enriched pathways relevant to a studied condition using the measured molecular data and also the structural information of the pathway viewed as a network of nodes and edges. Tests are performed using simulated data and genomic data sets and the method is compared to two existing approaches. The analysis provided demonstrates the method proposed is very competitive with the current approaches and also provides biologically relevant results.