Effects of photoperiod on growth, lipid metabolism and oxidative stress of juvenile gibel carp (Carassius auratus).

A 58-day cultivation experiment was carried out to investigate the effects of photoperiods on growth, lipid metabolism and oxidative stress of juvenile gibel carp. Juveniles (5.41 ±â€¯0.01 g) were cultured under seven light photoperiods (0 h of light (L):24 h of darkness (D), 4L:20D (12:00-16:00 light), 8L:16D (10:00-18:00 light), 12L:12D (8:00-20:00 light), 16L:8D (6:00-22:00 light), 20L:4D (4:00-24:00 light) and 24L:0D) in an indoor recirculating aquaculture system. The light intensity was 1.02 µmol·m-2·s-1 (at the tank bottom in a 0.5-m water depth). The fish were fed to satiety three times daily (8:30, 14:30 and 18:30). At the end of the experiment, final body weight, specific growth rate, feed efficiency and feed intake were significantly higher in 16L:8D, 20L:4D and 24L:0D groups than those in other groups (P < 0.05). Long-day photoperiods (16L:8D, 20L:4D and 24L:0D) simultaneously promoted lipogenesis, lipolysis and fatty acid oxidation. The increases in lipid retention efficiency, whole body lipid concentration and liver lipid content (P < 0.05) indicated that lipogenesis exceeded fatty acid oxidation. Liver oxidative stress was induced in juvenile gibel carp by short day lengths. The hepatic total antioxidant capacity, superoxide dismutase, glutathione peroxidase and the contents of metabolite glutathione were the highest in the short-day-length groups (0L:24D, 4L:20D and 8L:16D) (P < 0.05). Based on the growth performance and health status in the long-term cultivation experiment, the optimal photoperiods were 16L:8D, 20L:4D and 24L:0D in juvenile gibel carp.

Antimicrobial activity-specific to Gram-negative bacteria and immune modulation-mediated NF-kappaB and Sp1 of a medaka beta-defensin.

Defensins are a group of cationic antimicrobial peptides which play an important role in the innate immune system by exerting their antimicrobial activity against pathogens. In this study, we cloned a novel beta-defensin cDNA from medaka (Oryzias latipes) by rapid amplification of cDNA ends (RACE) technique. The full-length cDNA consists of 480 bp, and the open reading frame (ORF) of 189 bp encodes a polypeptide of 63 amino acids (aa) with a predicted molecular weight of 7.44 kDa. Its genomic organization was analyzed, and Southern blot detection confirmed that only one copy of beta-defensin exists in the medaka HNI strain. RT-PCR, Western blot and immunohistochemistry detections showed that the beta-defensin transcript and protein could be detected in eyes, liver, kidney, blood, spleen and gill, and obviously prevalent expression was found in eyes. Antimicrobial activity of the medaka beta-defensin was evaluated, and the antibacterial activity-specific to Gram-negative bacteria was revealed. Furthermore, the lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, was demonstrated to be able to induce about 13-fold up-regulation of the beta-defensin within first 12h. In addition, promoter and promoter mutagenesis analysis were performed in the medaka beta-defensin. A proximal 100 base pair (bp) sequence (+26 to -73) and the next 1700 bp sequence (-73 to -1755) were demonstrated to be responsible for the basal promoter activity and for the transcription regulation. Three nuclear factor kappa B (NF-kappaB) cis-elements and a Sp1 cis-element were revealed by mutagenesis analysis to exist in the 5' flanking sequence, and they were confirmed to be responsible for the up-regulation of medaka beta-defensin stimulated by LPS. And, the Sp1 cis-element was further revealed to be related to the basal promoter activity, and transcriptional factor II D (TFIID) was found to be in charge of the gene transcription initiation. All the obtained data suggested that the novel medaka beta-defensin should have antimicrobial activity-specific to Gram-negative bacteria, and the antibacterial immune function should be modulated by NF-kappaB and Sp1.