BACKGROUND: Dietary nucleotide has been shown to improve growth indices, nutritional function and higher vertebrates in fish. OBJECTIVES: We investigated the effect of different levels of dietary nucleotide on growth parameters, whole-body composition and fluctuations of cortisol and glucose due to acute stress in Snow trout (Schizothorax zarudnyi). METHODS: One-hundred-twenty Snow trout fingerlings with average weight 7.58±0.05g, were fed with four levels of dietary nucleotides including 0 (control), 0.15, 0.25, and 0.5 percent for 8 weeks. Ten fingerlings were stocked into each 300l tank with triplicate in four treatments and fed three times daily at 3-5% body weight rate. At the end of feeding trial, weight gain, Weight gain rate, feed efficiency, Food efficiency ratio and survival were computed. Also, the numbers of fish that were exposed to acute stress (temperature and pH). RESULTS: The results showed that none of the nucleotide-supplemented diets had any significant effect on growth indices (p>0.05). None of the dietary treatments resulted in any significant changes to dry matter, ash and protein. The only significant difference was observed in the fat (p>0.05). The fish fed 0.25% nucleotide showed higher whole lipid compared to other dietary treatments. Stress test results showed no significant difference at the beginning of the experiment, whereas after, acute stress cortisol levels were significantly higher in trials. The lowest response was observed in trial with 0.50% nucleotide and the highest was in control groups. Glucose levels were not significantly different, neither before nor after acute stress. CONCLUSIONS: The nucleotide composition used in the present study failed to provide significant effects on growth of Snow trout juveniles but could improve response to acute stress.

Two nonoverlapping clones, pOH405 and pOH632, containing cDNA inserts in the VP2 coding region of genome segment A were selected from a cDNA library prepared from the double-stranded RNA genome of the OH strain of infectious bursal disease virus (IBDV) of serotype 2. Clone pOH405, which is located in the hypervariable segment of VP2, is 328 base pairs long, has nucleotide sequence homology of 72 to 73%, and amino acid sequence homology of 64 to 67% with IBDV strains of serotype 1. Clone pOH632, which is located in the highly conserved C-terminal part of VP2, is 230 base pairs long, has nucleotide sequence homology of 87 to 88%, and amino acid sequence homology of 100% with IBDV serotype 1. The lower detection limit of 32P-labeled probes prepared from both clones was 10 ng of OH-IBDV double-stranded RNA, using high-stringency conditions of hybridization (54 C, 50% formamide) and washing (55 C, 0.015M NaCl, 0.0015M trisodium citrate, pH 7.0, with 0.1% sodium dodecyl sulfate), and autoradiography for 24 hours. Under these conditions, the dot-blot hybridization assay for detection of serotype 2 IBDV double-stranded RNA was 1,000 times more sensitive, using probe pOH632, but only 10 times more sensitive, using probe pOH405, compared with the assay for IBDV serotype 1, using the same probes. Thus, probe pOH632 could differentiate between the 2 IBDV serotypes by nucleic acid hybridization.

To provide information for the molecular pathogenesis and antigenic structures of Korean isolates of porcine epidemic diarrhea virus (PEDV), the small membrane (sM) protein gene of Chinju99 strain, which was previously isolated from piglets suffering from severe diarrhea was characterized and further analyzed with other PEDV strains. The sM gene of Chinju99 generated by reverse transcription and polymerase chain reaction had a single open reading frame with 231 bases consisting of 24.2% adenine, 18.6% cytosine, 18.1% guanine and 39.0% thymine nucleotides.

Porcine epidemic diarrhea virus (PEDV) strain Chinju99, which was previously isolated from piglets suffering from severe diarrhea was used to characterize the membrane (M) protein gene to establish the molecular information, and the results will be useful in elucidating concepts related to molecular pathogenesis and antigenic structures of PEDV isolates. The Chinju99 M gene generated by reverse transcription and polymerase chain reaction (RT-PCR) consisted of 681 bases containing 22.3% adenine, 22.3% cytosine, 23.1% guanine and 32.3% thymine nucleotides, and the GC content was 45.4%.