Mechanochemical properties of ordinary and dark muscle myosins from seawater fish

Myosin was isolated from two types of muscle, ordinary and dark muscles, of three species of fish living in sea water. The compositions of light chains were visualized by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the mechanochemical activity was examined by in vitro motility and ATPase assays. Ordinary muscle myosin of either species had three species of light chain, whereas dark muscle myosin had another two species of light chain judged by SDS-PAGE. Sliding velocity of ordinary muscle myosin was in the range of 4.92–6.89 μm/S, whereas that of dark muscle myosin was in the range of 3.07–4.25 μm/s. Therefore, ordinary muscle myosin showed 1.26–1.95 times higher sliding velocity than dark muscle myosin in either species. The ratios of V_max of actin-activated Mg²⁺-ATPase activity of ordinary to dark muscle myosins were correlated quite well to the ratios of sliding velocity. Activity of ordinary muscle myosin was comparable to that of mammalian fast muscle myosin, but that of dark muscle myosin was twice of that of mammalian slow muscle myosin. These results may reflect the essential role of fish dark muscle myosin always used in slow cruising.     

Site of acid-base relevant ion transfer in the gills of rainbow trout (Oncorhynchus mykiss) exposed to environmental hypercapnia

In order to delineate the contribution of primary vs. secondary circulatory circuits in the gill for acid-base and ionic regulation, the flow and composition of the fluids in the central venous sinus (CVS) and the systemic circuit of rainbow trout were studied by application of a previously developed microcannulation technique during normocapnic and hypercapnic conditions. The average haematocrit (Hct) of blood from dorsal aorta (DA) and sinus venosus (SV) ranged from 20.1 to 26.7%, whereas average Hct in the fluid from the branchial vein (BV), representing drainage from the central venous sinus (CVS), was in the range of 4.2 to 7.0%. Under normocapnic conditions, the largest fraction of cardiac output, 92.9%, was directed through the systemic vascular circuit, whereas the CVS circuit was perfused with 7.1 % of cardiac output. Hypercapnia did not significantly affect the blood flow distribution between the two circuits. The pattern of acid-base regulation in dorsal aortic blood reflected the characteristic response of fish exposed to environmental hypercapnia. Upon initiation of environmental hypercapnia (2% CO₂), plasma P_{CO 2} was elevated in all three flow compartments (CVS, DA, SV), inducing an extracellular respiratory acidosis of about 0.4 pH units. pH and [HCO₃ ^-] values in the DA were consistently lower, than those for both CVS and SV sites throughout the hypercapnic period. During the 8h of exposure plasma bicarbonate concentration was elevated by about 12 mM, complemented by a fall in extracellular [Cl^-] of about 10 mM in all three compartments. The amount of HCO₃ ^- gained at the CVS site during 8h of hypercapnia (3.3 mmol · kg^-1) exceeds the amount accumulated in the extracellular space (2.1 mmol·kg^-1), suggesting the CVS as the main site of ionic acid-base regulation in trout.     

Estimation of flow in a rearing tank of marine fish larvae by simplified numerical computation—a case of two-dimensional flow

Marine fish larvae are fragile against physical stress. However, few studies have been conducted to evaluate the flow field in a rearing tank, which is assumed to provide a high degree of physical stress to marine fish larvae. The flow field in a rearing tank (volume of 1 m³) is generated by aerators, which are commonly used to provide oxygen.

This paper is a report on the estimation of stationary flow in the rearing tank of marine fish larvae. The larvae are seven band grouper larvae of Epinephelus septemfasciatus, which have a very low survival rate immediately after the hatching of eggs. The experiments of rearing of seven band grouper larvae were carried out using rearing tanks with four aeration rates (1000, 200, 50 ml/min, and no aeration). The effects of aeration on the survival and floating death of seven band grouper larvae were examined. The experiments confirmed that the mass mortality of seven band grouper larvae depends on the flow rate in the rearing tank. Aeration at 200 ml/min resulted in the highest survival and growth rates of grouper larvae.

Larvae-rearing experiments provided evidence that the flow rates of the rearing tanks are very important design aspects of rearing tanks. The estimation of flow in a rearing tank for an aerating rate of 200 ml/min was carried out by numerical calculation. The computation was simplified by a two-dimensional flow based on experimental results. The calculated flow in the rearing tank was compared with the experimental one. The calculation of the stationary flow in the rearing tank showed good qualitative and quantitative agreement with the experimental results. The numerical estimation of the flow in a rearing tank of marine fish larvae was confirmed to be effective and satisfactory for the design of a tank that would provide optimum performance.     

Effect of taurine supplemented practical diet on growth performance and taurine contents in whole body and tissues of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

ABSTRACT:   The effect of dietary taurine on juvenile Japanese flounder was determined by feeding three taurine-supplemented experimental diets (TAU) and a commercial diet (CD) to evaluate a practical diet for juvenile Japanese flounder. Juvenile Japanese flounder were reared on the three experimental diets supplemented with taurine at 0, 0.5, 1.0% and CD. These diets were fed to juvenile Japanese flounder of an initial mean body weight of 0.2 g for 6 weeks at 20°C and the taurine contents of the whole body and tissues were analyzed. The final average body weight of juvenile Japanese flounder fed the 1.0% TAU was significantly higher than that of the other groups. Taurine contents in the whole body and tissues increased with the increase in dietary taurine level. These results indicate that juvenile Japanese flounder require at least 15 mg/g taurine in the diet, even though a combined mix of fish, krill and squid meal was the main protein source in the experimental diets.     

Thermal stability of carp G-actin monitored by loss of polymerization activity using an extrinsic fluorescent probe

ABSTRACT:   The thermal stability of carp G-actin was investigated by monitoring loss of actin polymerization ability. To determine the amount of native actin remaining after heat treatment, actin was labeled with a fluorescence reagent, N-(1-pyrene)iodoacetamide. The loss of polymerization ability of carp actin during heat treatment, at between 45 and 55°C, occurred faster than that of chicken actin. The inactivation rate was influenced by concentrations of ATP and Ca²⁺ in solution. With the increase of Ca²⁺ concentration, the inactivation of carp actin was markedly suppressed. Furthermore, the activation energy of the inactivation of carp actin obtained from an Arrhenius plot was similar to that of chicken actin. These results indicated that the thermal instability of carp G-actin was due to the low affinites of ATP and Ca²⁺ for carp actin described in a previous report.     

Lectin binding patterns in the olfactory bulb of mallard ducks (Anas platyrhynchos)

We histologically examined lectin binding patterns in the olfactory bulb of mallard ducks (Anas platyrhynchos) using 21 biotinylated lectins. Positive staining for the N‐acetylglucosamine‐specific lectins (Bandeiraea simplicifolia II, Datura stramonium, Lycopersicon esculentum, Solanum tuberosum, Triticum vulgare), galactose or N‐acetylgalactosamine‐specific lectins (Artocarpus intergrifolia, Phaseolus vulgaris erythroagglutinin, Phaseolus vulgaris leucoagglutinin, Ricus communis) and the mannose‐specific lectins (Lens culinaris and Pisum sativum) was observed in the olfactory nerve and glomerular layers. Canavalia ensiformis staining showed a similar pattern to that obtained with the lectins and there was also faint staining in the mitral cells. Olfactory nerve axons terminate in the glomeruli, where they make excitatory synapses with the dendrites of mitral cells. This finding indicates that glycoconjugates that bind Canavalia ensiformis play an important role in formation of glomeruli. No positive staining for the other lectins was seen in the olfactory bulb. Based on these results, we conclude that cell surface sugar moieties of the olfactory bulb in mallard ducks express N‐acetylglucosamine and mannose residues rather than N‐acetylgalactosamine residues. The carbohydrate composition of mallard duck olfactory bulb differed from that of other vertebrates found in previous studies.     

Yield estimation of 1-year-old asparagus grown using rootstock-planting forcing culture

Rootstock-planting forcing culture was developed in asparagus to harvest spears even during the seasons when the plants become dormant, but the demand for them high. In this study, cumulative hours during which the air temperature remained lower than 5°C, i.e. chilling hours (CHs), were calculated to determine dormancy breakage for asparagus cultures. We also measured CIELab colour values for cut stems immediately before rootstock digging, and determined whether they could be substituted and/or compensated for CHs while evaluating asparagus plant productivity in different low-temperature backgrounds, and obtained regression equations for yield estimation. Asparagus seedlings were cultivated in seven different regions across Japan and brought to the study site for harvesting. Our regression equation based on CHs and rootstock weight for yield estimation had relatively high fitness (adjusted R² = 0.5795). The colour values of cut stalks at rootstock digging can also be used to evaluate their productivity. These values can be useful in regions where CHs cannot be determined, although their effectiveness was slightly lower than that of CHs of areas adjacent to the study sites.     

Establishment of an attenuated strain of bovine respiratory syncytial virus for live virus vaccine

To develop a live virus vaccine for the prevention of bovine respiratory syncytial (BRS) virus infection in calves, an attempt was made to produce an attenuated virus. The RS-52 strain of BRS virus, isolated from the nasal secretions of a naturally infected calf, was subjected to serial passages in adult hamster lung established (HAL) cells at 30 degrees C and the attenuated rs-52 strain as a live virus vaccine was established. The rs-52 strain multiplied better at 30 degrees C than at 34 or 37 degrees C in HAL cells. The differences in the highest virus titers of this strain between the culture temperature of 30 degrees C and that of 34 or 37 degrees C were more than 2.25 log TCID50. Colostrum-deprived newborn calves and 2 approximately 4 months old calves inoculated with the rs-52 strain manifested no abnormal clinical sings at all. However, all inoculated calves produced serum neutralization antibody. When the colostrum-deprived newborn calves immunized with the rs-52 strain were challenged with the virulent NMK7 strain of BRS virus, they exhibited no pyrexia or other abnormal clinical signs at all. An attempt was made to recover the virus from nasal secretions of these calves, but in vain. On the other hand, a nonimmunized control colostrum-deprived newborn calf developed slight fever, mild cough, and slight serous nasal discharge after challenge exposure. The virus was recovered from nasal secretions of this calf. From these results, it was considered that the rs-52 strain could be used as an attenuated live virus vaccine for prevention of BRS virus infection.