Effects of arginine supplementation on growth performance and plasma arginine,ornithine and citrulline dynamics of rainbow trout,Oncorhynchus mykiss

This study aimed to re‐evaluate the effect of excessive arginine supplementation on growth and feed efficiency of rainbow trout, and to assess the effect of dietary arginine supplementation on hepatic amino acid composition, expression of arginase Ⅱ (ARG 2), inducible nitric oxide synthase (iNOS), and heat shock protein 70 (HSP70) genes in the intestine, and plasma arginine, ornithine, citrulline and urea levels at 0, 6, 12 and 18 hr‐postprandial. Rainbow trout (body weight: 60.5–65 g) were fed diets containing 1.47 (control [CTRL]), 3.89 (3.89A) and 5.64% (5.64A) arginine for nine weeks. Higher muscle protein content was observed in 3.89A than CTRL (p < 0.05). In postprandial study, plasma arginine of 5.64A kept increased until 12 hr‐postprandial and reached identical value (around 150 µg/ml) until 18 hr‐postprandial in 5.64A. Significant increase of plasma arginine level was only observed in arginine supplemented group. Meanwhile, plasma citrulline level in CTRL was significantly higher than in 5.64A at 18 hr‐postprandial. A significantly higher hepatic citrulline level was also observed in CTRL than in 5.64A (p < 0.05). Significantly higher plasma and hepatic free ornithine level was observed in 5.64A than CTRL while significantly higher expression of intestinal ARG2 and HSP70 was found in arginine supplemented groups. These results suggest that citrulline availability seems to be stimulated by arginine deficiency in the CTRL and the presence of arginase in the intestine to regulate excess dietary arginine.     

Cytotoxicity of Streptococcus agalactiae secretory protein on tilapia cultured cells

Streptococcus agalactiae secrete virulence factors believed to be able of killing host tissues, especially under elevated water temperature. A direct effect of S. agalactiae secretory products on tilapia cells was tested on the tilapia kidney (TK-1) cell culture. The bacteria were cultured under four different temperature levels: 22, 29, 32 and 37°C; the cell-free portion was processed through SDS-PAGE; and distinct bands were identified by LC-MS/MS. At least, three virulence factors were identified, Bsp, PcsB and CAMP factor, with increasing levels as the cultured temperature rose. Expressions of bsp, pcsB and cfb were also up-regulated with the rising of the temperature in S. agalactiae culture. The supernatant from the bacteria cultured under specified temperatures was added into TK-1 cell-cultured wells. Morphological damage and mortality of the cultured cells, as determined by MTT method, were increased progressively from the supernatant treatment according to the rise of temperature in S. agalactiae culture. This study suggests that the production of the three virulence factors of S. agalactiae reported herein is temperature-dependent, and it is likely that CAMP factor directly kills the TK-1 cells since the other two types of protein are involved in S. agalactiae cell division and the bacterial adherence to host tissues.     

Retention of Rice dwarf virus by Descendants of Pairs of Viruliferous Vector Insects After Rearing for 6 Years

ABSTRACT Rice dwarf virus (RDV) is characterized by its unusual ability to multiply in both plants and leafhopper vector insects and by its transovarial mode of transmission. Colonies of Nephotettix cincticeps, derived originally from pairs of leafhoppers infected with an ordinary strain of RDV, were maintained for 6 years in the laboratory and were found, at the end of this time, still to harbor RDV. Moreover, the isolate of RDV, designated RDV-I, obtained from these colonies retained the ability to infect rice plants. When we raised leafhoppers separately from eggs that had been placed individually on pieces of water-soaked filter paper and reared them in the presence of healthy rice seedlings, we found that all of these leafhoppers harbored RDV. This observation suggested that RDV-I had been maintained in the leafhoppers by transovarial transmission. Two further observations, namely, the low rate of acquisition of RDV by virus-free insect nymphs on symptomless plants on which viruliferous insects had been reared, and the fact that only 2 to 5% of plants had symptoms when rice seedlings were inoculated via RDV-I-viruliferous insects, confirmed that the maintenance of RDV-I by any other mode of transmission through plants and insects was unlikely. This efficient and long-term maintenance of RDV in a population of viruliferous insects might explain the prolonged duration of rice dwarf disease in the field, once there has been a serious outbreak.     

Erythrocyte invasion by Babesia parasites: current advances in the elucidation of the molecular interactions between the protozoan ligands and host receptors in the invasion stage

During an asexual growth cycle of Babesia parasites in a natural host, the extracellular merozoites invade (i.e., attach to, penetrate, and internalize) the host erythrocytes (RBC) via multiple adhesive interactions of several protozoan ligands with the target receptors on the host cell surface. After internalizing the host RBC, they asexually multiply, egress from the RBC by rupturing the host cells, and then invade the new RBC again. In the invasion stage, several surface-coating molecules of merozoites might be involved in the initial attachment to the RBC, while proteins secreted from apical organelles (rhoptry, microneme, and spherical body) are proposed to play roles mainly in erythrocyte penetration or internalization. On the other hand, several components located on the surface of the RBC, such as sialic acid residues, protease-sensitive proteins, or sulphated glycosaminoglycans, are identified or suspected as the host receptors of erythrocyte invasion by Babesia parasites. The detailed molecular interactions between Babesia merozoites and the host RBC are incompletely understood. In this review, these identified or suspected molecules (protozoan ligands/erythrocyte receptors) are described by especially focusing on Babesia bovis.     

Taurine synthesis via the cysteic acid pathway: effect of dietary cysteic acid on growth,body taurine content,and gene expression of taurine-synthesizing enzymes,growth hormone,and insulin-like growth factor 1 in Japanese flounder Paralichthys olivaceus

Here, we investigated the effect of dietary cysteic acid on the growth performance, sulfur amino acid content, and gene expression levels of taurine-synthesizing enzymes, growth hormone (GH), and insulin-like growth factor 1 (IGF-1) in Japanese flounder Paralichthys olivaceus. Juvenile flounder (0.9 g) were fed one of four diets for 30 days: with 0.25, 0.5, or 1.0% cysteic acid (C0.25, C0.5, C1.0) supplementation and without supplementation (control). Fish in the C0.25 and C0.5 groups showed significantly better growth than those in the control group (P < 0.05). Body taurine content was significantly higher in C0.25, C0.5, and C1.0 fish than in control fish (P < 0.05). Although there was no significant difference in gene expression levels of taurine-synthesizing enzymes and GH among groups (P > 0.05), the expression level of IGF-1 in C1.0 fish was significantly higher than that in controls (P < 0.05). Our results suggest that Japanese flounder can synthesize taurine from cysteic acid, that dietary supplementation with up to 0.5% cysteic acid promotes fish growth, and that dietary cysteic acid can affect the GH-IGF axis in Japanese flounder. These findings thus highlight the importance of the cysteic acid pathway for taurine synthesis and growth in this species.

     

Molecular and serological prevalence of Babesia bovis and Babesia bigemina in cattle from central region of Syria

A total of 207 bovine blood samples were collected from clinically healthy cattle bred in central region of Syria and examined by Giemsa-stained blood smears, nested PCR, ELISA, and IFAT to determine the molecular and serological prevalence of Babesia bovis and B. bigemina. All samples were negative to Babesia spp. by microscopic examination of blood smears. On the other hand, the overall prevalence of B. bovis and B. bigemina was 9.18% and 15.46% by nPCR, 15.46% and 18.84% by ELISA, and 18.36% and 21.74% by IFAT, respectively. Mixed infections were detected in a total of 5 samples (2.4%) by nPCR, 16 (7.73%) by ELISA and 27 (13.04%) by IFAT. Statistically significant differences in the prevalence of the two infections were observed on the basis of age and location. These data provide valuable information regarding the occurrence and epidemiology of B. bovis and B. bigemina infections in Syrian cattle, which can be employed in developing rational strategies for disease control and management.     

Molecular typing of Salmonella enterica serovar 4,[5],12:i:- isolates from humans,animals and river water in Japan by multilocus variable-number tandem repeat analysis and pulsed-field gel electrophoresis

Fifty-one Salmonella enterica serovar 4,[5],12:i:- (S. 4, [5],12:i:-) isolates (14 human strains, 34 animal strains and 3 river water strains) which are assumed to be monophasic variants of S. Typhimurium were analyzed using pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem repeat analysis (MLVA) in order to investigate their genetic diversities and relationships. PFGE, MLVA and combination of them identified 28, 27 and 34 profiles (Simpson’s diversity indices [DI]=0.94, 0.96 and 0.97), respectively. No correlations were detected between MLVA clustering and PFGE clustering or phage typing. These results suggested that S. 4,[5],12:i:- originated from multiple S. Typhimurium ancestors. Two cattle and one pig isolates showing identical phage types as well as PFGE and MLVA profiles to human isolates S. 4,[5],12:i:- suggested the existence of the links between human infections and animal reservoirs.     

Runoff nitrogen from a large sized paddy field during a crop period

Nutrient load management is an important environmental issue because nutrient loads from farmlands degrade surface waters as a result of anthropogenic eutrophication. Nitrogen load from a large sized paddy field during the crop period was examined from the results of field measurements carried out in 2004. The 1.5 ha paddy field was located east of Biwa Lake. Irrigation water volume and ponded water depth were continuously observed. Field measurements were carried out at least once a week to analyze total nitrogen (TN) concentration in the irrigation water and ponded water. Daily inflow and outflow of nitrogen was obtained by multiplication of the nitrogen concentration and transported water volume, consisting of irrigation, precipitation, evapotranspiration, percolation and surface discharge. Water outflow volume was calculated by a tank model that consisted of three small tanks connected to represent ponded water depth differences in the large paddy field. The calculated nitrogen load was 18.8 kg ha⁻¹, with 7.2 kg ha⁻¹ from surface drainage and 11.6 kg ha⁻¹ from percolation loss. The runoff nitrogen value of 18.8 kg ha⁻¹ was within the range of the reported values investigated in a medium-sized paddy field. The observed value was close to the value for a low percolation flux paddy field where less irrigation water has been applied. These results suggest that less irrigation water keep runoff nitrogen low. This also indicates that irrigation water management can reduce nitrogen load from large sized paddy fields.