Chondroitin sulfate E downregulates N-cadherin and suppresses myotube formation

Myogenesis, the formation of muscle fibers, is affected by certain glycoproteins, including chondroitin sulfate (CS), which are involved in various cellular processes. We aimed to investigate the mechanism underlying CS-E-induced suppression of myotube formation using the myoblast cell line C2C12. Differentiated cells treated with 0.1 mg/ml CS-E for nine days showed multinucleated and rounded myotubes with myosin heavy chain positivity. No difference was found between the CS-E-treated group with rounded myotubes and CS (−) controls with elongated myotubes in the levels of phospho-cofilin, a protein involved in the dynamics of actin cytoskeleton. Interestingly, N-cadherin, which is involved in the gene expression of myoblast fusion factors (myomaker and myomixer), was significantly downregulated at both the mRNA and protein levels following CS-E treatment. These results suggest that N-cadherin downregulation is one of the mechanisms underlying the CS-E-induced suppression of myotube formation.     

Genetic assessment of milkfish (Chanos chanos Forsskal) stocks based on novel short tandem repeats for marker‐aided broodstock management

Milkfish hatchery broodstock are either from on‐grown wild‐caught or hatchery‐produced fry/juveniles. To determine if a marker‐assisted management scheme can be formulated for improved milkfish hatchery production, milkfish stocks were genetically characterized using nine novel short tandem repeats or microsatellites. Eight wild‐bred Philippine stocks (CLA, CUR, CAM, SIH, SBH‐I1, HH, PAL and ZH‐P₀), four hatchery‐bred stocks (SBH‐I2, SBH‐D, BoH and ZH‐F₁), two farm stocks of known mixed lineages (SPH and BDH) and one Indonesian hatchery‐bred stock (WJH) were assessed. WJH was included since milkfish fingerlings from Indonesia reared in Philippine farms could be developed into future broodstock. Mean allelic richness (Ar) was highest in wild‐bred stocks (9.5) and lowest in hatchery‐bred spawners (9.1). Mean expected heterozygosities (He) were relatively similar in all stocks with wild‐bred stocks slightly higher (0.67) than the others. An analysis of molecular variance indicated significant yet low genetic differentiation among stocks (F_ST = 0.013; p = .000) where variation (98.6%) was explained by intra‐stock differences. In some of the domesticated stocks, reductions in mean allelic richness were observed in first generation hatchery broodstock (e.g. ZH‐F₁; Ar = 8.3), compared with their founder stock (e.g. ZH‐P₀; Ar = 9.4). The Indonesian stock was similar to local wild‐bred stocks based on genetic variability indices; thus, it might be likely that the local stocks’ fitness traits could be comparable with the imported milkfish stock which has been perceived to be better. The quality of locally available farmed milkfish and prospects of formulating a broodstock management scheme for the production of good quality milkfish seedstock are herewith discussed.     

Hyposmoregulatory ability and ion- and water-regulatory mechanisms during the leptocephalus stages of Japanese eel Anguilla japonica

We explored osmoregulatory ability and mechanisms of ion and water regulation in Japanese eel leptocephali. Tissue osmolality of leptocephali ranged from 360 to 540 mOsm/kg·H₂O. Immunocytochemical observations revealed that Na⁺/K⁺-ATPase-immunoreactive mitochondrion-rich (MR) cells were distributed over the entire body surface of leptocephali. Using a fluorescent sodium indicator and the chloride test, we localized Na⁺ and Cl^? secreting sites at the apical region of cutaneous MR cells. To further examine drinking behavior and water absorption in the intestine, leptocephali were exposed to seawater containing dextran labeled with Alexa Fluor. To calculate relative water absorption, fluorescent intensity was measured along the digestive tract. Whereas water was hardly absorbed in the stomach and intestine, water absorption predominantly took place in the rectum. Our findings indicate that Japanese eel exert hyposmoregulatory ability as early as during leptocephalus stages, secreting Na⁺ and Cl^? through cutaneous MR cells and primarily absorbing water from ingested seawater in the rectum.     

Hen egg yolk and skinned krill as possible foods for rearing leptocephalus larvae of Anguilla japonica Temminck & Schlegel

Usual diets for rearing leptocephalus larvae of Japanese eel Anguilla japonica include eggs of the endangered spiny dogfish Squalus acanthias (SE). We investigated the effects of alternative food materials, hen egg yolk (HEY) and exoskeleton‐free (skinned) Antarctic krill (SAK), on the growth and survival of eel larvae. We found that feed comprising whole krill including exoskeleton (WAK) containing higher levels of fluoride (37.89 mg kg^?1) was acutely toxic to eel larvae exposed to this alone. In contrast, extract from SAK containing lower concentrations of fluoride (4.25 mg kg^?1) showed no apparent adverse effects. Growth of larvae fed a mixture of SE and SAK in a feed trial of 58 days [mean body weight (BW), 6.0 mg] was about twofold higher than that of larvae fed a mixture of SE and WAK (3.2 mg) (P < 0.01). A mixture of HEY and SAK also had some dietary benefits for eel larvae, enabling them to survive for up to 58 days and to grow significantly (mean BW, 2.4 mg), compared with their initial weight (mean BW, 0.2 mg) (P < 0.001). Although additional nutritional improvements are needed, the present results suggest that combination diet HEY and SAK may be a good alternative to SE as an effective diet for eel larvae.     

Long-afterglow phosphorescent pigment is a potent tool for manipulation of reproductive performance in the tropical damselfish <Emphasis Type="Italic">Chrysiptera cyanea</Emphasis>

Photoperiod plays a role in the regulation of reproduction in many fish. We examined the effectiveness of the long-afterglow phosphorescent pigment LumiNova on the reproductive performance of the sapphire devil Chrysiptera cyanea, a tropical damselfish that reproduces under long-day conditions. During the breeding season, the experimental fish, but not the control fish, were reared in aquaria covered with LumiNova sheets for 75 days under natural photoperiod and temperature. At days 60 and 75 after onset of the experiment, the gonadosomatic index of experimental fish was higher than that of control fish. Histological observations at 60 and 75 days revealed that the ovaries of experimental fish contained large oocytes laden with yolk, whereas the control fish had few yolky oocytes at 60 days and mostly immature oocytes at 75 days. Spawning occurred repeatedly in experimental fish, but not in control fish, throughout the study period. Because LumiNova sheets continue to emit green light for some time after sunset, the extended light conditions probably contributed to active reproduction in experimental fish. In conclusion, long-afterglow phosphorescent pigment can be used for energy-efficient aquaculture to regulate the reproduction of fish, although its effect needs to be evaluated in different species.     

The immunohistochemical detection of peroxiredoxin 1 and 2 in canine spontaneous vascular endothelial tumors

Peroxiredoxin (PRDX) is an antioxidant enzyme family with six isoforms (PRDX1–6). The main function of PRDXs is to decrease cellular oxidative stress by reducing reactive oxygen species, such as hydrogen peroxide, to H₂O. Recently, it has been reported that PRDXs are overexpressed in various malignant tumors in humans, and are involved in the development, proliferation, and metastasis of tumors. However, studies on the expression of PRDXs in tumors of animals are limited. Therefore, in the present study, we immunohistochemically investigated the expression of PRDX1 and 2 in spontaneous canine hemangiosarcoma (HSA) and hemangioma (HA), as well as in selected normal tissue and granulation tissue, including newly formed blood vessels. Although there were some exceptions, immunolocalization of PRDX1 and 2 in normal canine tissues was similar to those in humans, rats, or mice. In granulation tissue, angiogenic endothelial cells were strongly positive for PRDX1 and 2, whereas quiescent endothelial cells in mature vessels were negative. Both PRDX1 and 2 were significantly highly expressed in HSA compared to HA. There were no significant differences in the expression of PRDX1 and 2 among the subtypes and primary sites of HSA. These results suggest that PRDX1 and 2 may be involved in the angiogenic phenotypes of endothelial cells in granulation tissue as well as in the behavior in the malignant endothelial tumors.     

Long-term rearing of Japanese eel larvae using a liquid-type diet: food intake,survival and growth

Fisheries Science - The efficiency of a new liquid-type diet for long-term rearing of Japanese eel larvae until metamorphosis was examined, as was the effect of diet viscosity on diet intake and on...