Effect of endocytic and metabolic inhibitors on the internalization and intracellular growth of Brucella abortus in Vero cells.

Uptake, transfer to rough endoplasmic reticulum, and intracellular growth of Brucella abortus were studied in Vero cells treated with endocytic and metabolic inhibitors. Infection of Vero cells was suppressed when inhibitors of energy metabolism (iodoacetate, dinitrophenol), receptor-mediated endocytosis (monodansylcadaverine, amantadine, methylamine), or endosomal acidification (chloroquine, ammonium chloride, monensin) were added to the inoculum. Inhibition was not observed when these drugs were added after the inoculation period. Infection of Vero cells by B abortus was inhibited by dibutyryl-cyclic adenosine monophosphate and Vibrio cholerae enterotoxin, but was stimulated by dibutyryl-cyclic guanosine monophosphate and escherichia coli heat-stable enterotoxin a. Uptake of B abortus by Vero cells was not prevented by colchicine, but was abolished by cytochalasin B. Uptake of heat-killed B abortus and noninvasive E coli was similar to that of viable brucellae. Intracellular growth of B abortus was not affected by cycloheximide. Results indicate that: B abortus may be internalized by a receptor-mediated phagocytic process; transfer of B abortus from phagosomes to rough endoplasmic reticulum may require endosomal acidification; and replication of B abortus within the rough endoplasmic reticulum may not depend on protein synthesis by the host cell.     

Spirometric performance in Belgian Blue calves: I. Effects on economic losses due to the bovine respiratory disease complex

The aim of this study was to determine whether high spirometric performances in calves are associated with low economic losses due to the bovine respiratory disease complex (BRDC). Five spirometric variables (SV) were measured in 909 double-muscled Belgian Blue calves from 15 to 60 d of age. Afterward, calves were monitored for 6 mo to determine whether they developed BRDC and to determine the costs due to BRDC (i.e., medicine costs and veterinarians' fees, plus estimated financial losses due to mortality in case of death). To analyze the effects of spirometric performances on BRDC cost, a fixed linear model was used for each SV. In addition to SV, each model included the effects of sex, dam's parity, vaccination status, muscular development score, herd-period, and BW. Only herd-period and the maximal ventilation and the vital capacity had significant effects on costs due to BRDC, indicating that these two SV are major physiological determinants of economic losses associated with BRDC. Accordingly, it is assumed that an amelioration of maximal ventilation and vital capacity could result in increased resistance to BRDC in calves.     

Cross-sectional study of the association between pathological conditions and myxoma-virus seroprevalence in intensive rabbit farms in Europe

Myxomatosis is a major viral disease of the European rabbit (Oryctolagus cuniculus). Two forms of the disease (nodular and amyxomatous) exist. The clinical diagnosis of the nodular form is easily performed on the basis of typical skin lesions whereas that of amyxomatous forms must be based on virus isolation or detection of specific antibodies to myxoma virus (MV). The seroprevalence of MV was studied between March 1998 and February 1999 in 16 farms from three European countries considered free of myxomatosis on the basis of the absence of typical clinical signs. MV antibodies were detected by enzyme-linked immunosorbent assay (ELISA) (sensitivity 100%, specificity 90%) in all 16 farms; the seroprevalences corrected for test inaccuracy (95% confidence interval) were 55+/-7.7% and 37+/-6.1% for does and broilers, respectively. The association between herd sizes, types of rabbitries, and presence of recurrent respiratory or digestive troubles and seroprevalence of MV antibodies was tested in logistic multiple regressions. In all models, the seroprevalence of MV antibodies was significantly higher in herds (does and broilers) with recurrent respiratory or digestive troubles than in herds without these problems. The seroprevalence was also higher in herds (does and broilers) where animals were housed totally or partially in outdoors rabbitries than in totally enclosed rabbitries. The effect of herd sizes on the presence of MV antibodies was the same in does and broilers; intermediate sizes were at lower risk than the smaller and larger ones.     

Morphometric Study of the Equine Navicular Bone: Age-Related Changes and Influence of Exercise

Navicular bones from the four limbs of 95 horses, classified in 9 categories, were studied. The effects of age on navicular bone morphometry and histomorphometry were estimated, after adjustment of the data to even out the effects of front and rear limbs, morphometrical type, sex, weight, and size.All the external measurements of the navicular bone decreased significantly with increasing age. From the histomorphometrical data, cortical bone volume decreased with age in most horses, whereas cancellous bone volume and, in particular, the marrow spaces increased. The increase in the cancellous bone volume could have resulted from tunnelling of the internal part of the cortex, which converted it progressively into a porous trabecular-like structure. Trabecular bone volume also decreased with age and the trabecular lattice changed dramatically to become disconnected in aged horses. These observations corresponded closely to those reported for ageing of the skeletal system in humans.However, in sporting horses, the navicular cortical bone volume increased with age and the cancellous bone volume decreased. Exercise appeared to have decreased bone resorption and increased bone formation at the endocortical junction. The cancellous bone architecture was also improved, in that the trabecular lattice and trabecular bone volume remained unchanged in aged sporting horses. Our findings confirmed that exercise may be good practice to prevent age-related bone loss.     

Genetic factors affecting susceptibility of dairy cows to udder pathogens

Bovine mastitis remains the most costly disease in dairy cattle. Breeding for resistance to udder pathogens has been proposed as a complementary tool to therapeutic and prophylactic measures not totally effective against the disease. This paper reviews factors affecting cows' susceptibility to pathogens at the animal, cellular/hormonal and DNA levels. Such factors will be useful in achieving genetic improvement for resistance only if they have desirable properties at the genetic and immunological levels. Because such properties are not always of significant magnitude, further research is necessary to identify characteristics of resistance in cows, considering the constant and complex interactions that occur between hosts and pathogens.     

Estimation of genetic and crossbreeding parameters for daily milk yield of Ayrshire × Sahiwal × Ankole crossbred cows in Burundi

The pedigree of 317 cows of which 184 were controlled for milk production has been used to estimate crossbreeding parameters for daily milk yield of Ayrshire, Sahiwal and Ankole crosses in the Mahwa station. Lactating cows belonged to one of 6 different genetic groups defined on the basis of the mating system used to produce them. REML estimates of the genetic parameters were obtained with a repeated animal model using daily milk records. Estimated heritability (h²) and repeatability (r²) were 0.27 and 0.36, respectively. The genetic group effects were used to estimate crossbreeding parameters following Dickerson's genetic model. Estimates for the additive effects for daily milk yield of Ankole, Sahiwal and Ayrshire breeds were − 1.66l, − 0.48l and 5.22l, respectively. Estimates of direct heterosis for daily milk yield for Sahiwal × Ankole, Ayrshire × Ankole, and Ayrshire × Sahiwal crosses were 1.97l, 2.30l and − 2.33l, respectively.     

Adapting ecotoxicological tests based on earthworm behavior to assess the potential effectiveness of forest soil liming

Two laboratory experiments were carried out to determine the potential effects of lime application on the behavior of earthworms inoculated in an acidified forest soil from Vosges Mountains. Several field soils were studied: (i) a non-limed soil that had received decades of atmospheric acid depositions $({\text{pH}}_{{\text{H}}_2\text{O}}=3.9)$, (ii) an in situ limed soil that had been limed 6 years before at 2.5 t ha^?1 $({\text{pH}}_{{\text{H}}_2\text{O}}=4.2)$ and (iii) in vitro limed soils composed of non-limed soil mixed with several lime amounts in the laboratory corresponding to field rates of 1, 2.5, 5, 10 and 20 t ha^?1. Firstly, we adapted the earthworm avoidance test (ISO, 2006) by using Eisenia fetida as the model organism and Lumbricus castaneus, a local species, to determine earthworm preference between non-limed and limed soils. Secondly, a cast production (CP) study was performed according to Capowiez et al. (2009) with Lumbricus terrestris, in seven different treatments (non-limed soil, in situ limed and five in vitro limed soils with pH from 5 to 6.3). Both species avoided the non-limed soil in favour of in situ and in vitro limed soils for both species. Results of the CP bioassay showed that the bioturbation behavior of L. terrestris significantly increased with the increase of soil pH, following a dose–response curve. However, in the long term (>6 years), the application of lime was insufficient to significantly improve soil conditions for enhancing earthworm activity. In conclusion, we may recommend this kind of earthworm laboratory tests with field soils to assess any changes in soil quality over time due to liming application.     

Comparison of natural transmission of bovine leukemia virus in Holstein cows of two genetic lines selected for high and average milk production.

One hundred and fifty lactating Holstein cows from 2 genetic lines selected for high and average milk production were used in the study. Sera from 6 annual herd tests were analyzed by agar-gel immunodiffusion test for antibodies to bovine leukemia virus. Odds of being seropositive were analyzed by use of stepwise and backward logistic regression procedures. Analysis within birth year revealed that estimated in odds increased by 0.19/year of age among cows of the high genetic line and by 0.43 among cows of the average genetic line. This was accompanied by a more important cohort effect among high producers than among average producers.