Calcium ions are involved in egress of Babesia bovis merozoites from bovine erythrocytes

Bovine babesiosis is a livestock disease known to cause economic losses in endemic areas. The apicomplexan parasite Babesia bovis is able to invade and destroy the host’s erythrocytes leading to the serious pathologies of the disease, such as anemia and hemoglobinuria. Understanding the egress mechanisms of this parasite is therefore a key step to develop new therapeutic strategies. In this study, the possible involvement of Ca²⁺ in the egress of B. bovis merozoites from infected erythrocytes was investigated. Egress was artificially induced in vitro using calcium ionophore A23187 and thapsigargin to increase Ca²⁺ concentration in the cytosol of the parasite cells. The increased intracellular Ca²⁺ concentration following these treatments was confirmed using live cell Ca²⁺ imaging with confocal laser scanning microscopy. Based on our findings, we suggest a Ca²⁺ signalling pathway in the egress of B. bovis merozoites.     

Synovial fluid total protein concentration as a possible marker for canine idiopathic polyarthritis

Idiopathic polyarthritis (IPA) is a very common inflammatory arthropathy in the dog. Canine IPA is diagnosed mainly by detecting increased number of leukocytes in the synovial fluid (SF), which is easily influenced by glucocorticoid therapy. We obtained 31 SF samples from 24 IPA dogs prior to (n=19) and/or after (n=12) 1 to 10 weeks of glucocorticoid therapy. The SF total protein concentrations of IPA dogs were significantly higher than those of dogs with non-arthritis diseases (n=34) and healthy controls (n=10). Our data revealed that the SF total protein concentrations are not influenced by several weeks of glucocorticoid therapy. Hence, the SF total protein concentration is applicable as a diagnostic marker of canine IPA even when the patients are receiving glucocorticoid therapy.     

Dietary calcium/phosphorus ratio influences the efficacy of microbial phytase on growth,mineral digestibility and vertebral mineralization in juvenile tiger puffer,Takifugu rubripes

A 2 × 3 factorial feeding trial was conducted to determine effects of dietary Ca/P ratio and dietary microbial phytase on growth, mineral digestibility and vertebral mineralization in tiger puffer. The treatments consisted of three levels of Ca/P ratios (0.5, 1.0 and 1.5) combined either with phytase (2000 FTU kg^?1 diet) or without supplementation, respectively. The Ca/P ratios were achieved by supplementing calcium at 0, 6 and 12 g kg^?1 combined with the same level of inorganic P at 5 g kg^?1. After a 50‐day feeding trial, puffer fish fed the diet at low Ca/P ratio (0.5) together with phytase had significantly higher growth rate and feed intake (FI) than other groups. Both dietary Ca/P ratio and phytase supplement were independent effects on plasma minerals and alkaline phosphatase. Interactive effect between both dietary treatments was observed on P and Zn contents in vertebrae and whole body. P and Zn digestibilities tended to increase with increased Ca/P ratio from 0.5 to 1.0, especially when phytase was supplemented. In conclusion, fish fed a diet with highest Ca/P ratio (1.5) showed the poorest growth performance and nutrients utilization. Dietary Ca/P ratio of 0.5 (without Ca supplement) with 2000 FTU phytase per kg would be the optimum combination in the diet of tiger puffer.     

Isolation and pathogenic characterization of an OB1 variant of Babesia rodhaini which has a glycophorin A-independent pathway to murine red blood cells

Recent studies using several Babesia spp. have demonstrated that these species commonly recognize host sialic acids of red blood cells (RBCs) for their invasion. Glycophorin A (GPA), which is a major carrier of the sialic acids on RBCs, is a possible invasive receptor for Babesia parasites. In the present study, a variant of Babesia rodhaini was successfully isolated from a GPA homozygous knockout (GPA^−/−) mouse infected with an Australian strain of B. rodhaini which had originally been unable to replicate in GPA^−/− mice. The isolated parasite (designated as an OB1 variant) caused lethal infection to wild-type mice, as in the case of the parent Australian strain. However, although the growth of the OB1 variant in GPA^−/− mice was comparable with that in wild-type mice at 1–4 days after infection, the growth was significantly inhibited from day 5 onward, leading to the eventual survival of the GPA^−/− mice. Resistance of GPA^−/− mice against OB1 infection was lost by splenectomy, although the cytokine responses to the infection in the sera of GPA^−/− mice were similar to those of wild-type mice. The autoantibody levels to GPA-defective RBCs in the sera of GPA^−/− mice were depressed at a lower level at 0–2 days after infection than those of wild-type mice, while the levels of GPA^−/− mice progressively increased and reached comparable levels to those of wild-type mice at day 3 or later. These results indicate that the isolated OB1 variant has a GPA-independent invasion pathway into murine RBCs and suggest that the resistance of GPA^−/− mice against infection with the OB1 variant may be attributed to the effective clearance of the parasitized RBCs lacking GPA in the spleen, possibly mediated by preferential autoantibody binding to the RBC membrane.     

Optimal dietary taurine level for growth of juvenile Japanese flounder Paralichthys olivaceus

The requirement for taurine in juvenile Japanese flounder Paralichthys olivaceus was determined by feeding diets containing various levels of taurine and cystine. Test diets supplemented with 0.5, 1.0 and 1.5% of taurine or with 0.5, 1.0 and 1.5% of L -cystine were prepared. The basal diet contained 55% protein from white fish meal. These diets were fed to juvenile Japanese flounder with an initial mean bodyweight of 0.9 g (total length (TL) 48 mm) for 5 weeks. Approximately 1.4% taurine content in the diet was required for optimum growth of juvenile flounder. A positive linear relationship was noted between the content of taurine accumulated in the muscle, liver and brain and the level of taurine in the diet. However, there was no increased taurine content in tissues of fish fed the cystine-supplemented diet. In contrast, the fish fed control and cystine-supplemented diets showed higher contents of cystathionine in the tissues. The concentration of cystathionine in tissues rapidly decreased with an increase of taurine in the diet. It was also observed that for each of the dietary groups, a trace amount of taurine was excreted. These results suggest that the taurine content in the diet affects the sulfur amino acid metabolism of juvenile Japanese flounder, and indicate that juvenile flounder are unable to biosynthesize taurine from cystine.     

Evaluation of shrimp polyculture system in Thailand based on stable carbon and nitrogen isotope ratios

ABSTRACT: To quantify the contribution by cocultured animals to waste assimilation in an intensive shrimp farm in Thailand, the food web structures of the macrobenthos in a reservoir pond, a shrimp culture pond and water treatment ponds were examined using the stable C and N isotope ratio technique. Seawater for aquaculture was drawn from a creek, and stored in a reservoir pond, used for farming the banana prawn Fenneropenaeus merguiensis in culture ponds, and then recycled through treatment ponds where the green mussel Perna viridis was cultured to remove organic wastes discharged from the farming. The clam worm Nereididae sp. and the mud creeper Cerithideopsilla cingulata in the culture pond had δ ¹³C values of −21.0‰ and −18.4‰, respectively, suggesting that shrimp feed (mean δ ¹³C = −20.7‰) was the main food source for these species. The δ ¹³C analysis also suggested that sediments (−23.7‰) in the reservoir pond and particulate organic matter (POM) (−24.0‰) and/or sediments (−25.0‰) in the treatment pond supplied carbon for most macrobenthic animals. However, green mussels in the treatment pond had a mean δ ¹³C value of −20.5‰, suggesting that shrimp feed was the main food source for this species.