Katsuyasu Tachibana

Effects of feeding of β-carotene-supplemented rotifers on survival and lymphocyte proliferation reaction of fish larvae (Japanese parrotfish ( Oplegnathus fasciatus) and Spotted parrotfish(Oplegnathus punctatus)): preliminary trials

Japanese parrotfish (Oplegnathus fasciatus) and Spotted parrotfish(Oplegnathus punctatus) larvae were fed with β-carotene supplemented rotifers or unsupplemented control rotifers for 24 days after hatchout. Results show that survival rates of β-carotene supplemented groups of both Japanese parrotfish and Spotted parrotfish larvae were higher than that of control groups. β-carotene supplemented and unsupplemented control groups exhibited similar growth in both species during this experiment. Proliferation of spleen lymphocytes with 100µg m1−1 of ConA, 10 or 50µg ml−1 of Poke weed mitogen from β-carotene supplemented group was higher than that of a control group of Japanese parrotfish. In Spotted parrotfish treated with 100µg ml−1 of ConA from the β-carotene supplemented groups lymphocytes proliferated to a higher degree than in the control. Results suggest that the supplementation of β-carotene to rotifers, might be of benefit in production of healthy, resistive larvae against infectious disease.

Influence of storage temperatures and killing procedures on post‐mortem changes in the muscle of horse mackerel caught near Nagasaki Prefecture, Japan

The effect of storage temperature (0, 5, 10, and 15°C) and killing procedure (instant, struggled, temperature shocked, and spinal cord destruction killing) on post-mortem changes in the muscle of the horse mackerel caught near Nagasaki, Japan, was investigated. Temporal changes in adenosine triphosphate (ATP), inosine monophosphate (IMP), and lactic acid concentrations were slowest at 10°C storage temperature. The increase in K-values was slower at 10°C and below than at 15°C storage temperature. In addition, 10°C storage temperature was most suitable for maintaining a constant breaking strength value of the muscle. Regarding the effect of killing procedure, temporal changes in ATP, IMP, and lactic acid concentrations were slowest then killed by spinal cord destruction. The increase in K-value and the decrease in breaking strength were also slowest in the spinal cord destruction group. From these results, it was considered that storage at 10°C temperature and spinal cord destruction killing procedure were most effective in delaying post-mortem change in the horse mackerel.

Characteristics of burnt meat in cultured yellowtail Seriola quinqueradiata

In order to understand the characteristics of burnt meat in cultured yellowtail Seriola quinqueradiata, fish were kept at two different temperatures (13 and 30°C) and slaughtered by either spinal cord destruction (SCD) or suffocation in air (SA). Early postmortem changes during storage at 32°C were analyzed by rheological, biochemical, and histological methods. The burnt meat (with lightness parameter, L*≥55) was observed at 1-h storage in the SA 30°C group, at 2 h in SCD 30°C, and at 4 h in SA 13°C; meat was normal for the SCD 13°C group until 6h of storage. Breaking strength scores were higher for the normal meat (200 g/cm2) than burnt meat (70 g/cm2) at 4 h of storage. Expressible water content was higher for the burnt meat than for the normal meat. Adenosine triphosphate concentrations for the SCD groups were higher than for the SA counterparts. Moreover, pH decrease was much faster in the 30°C groups, showing pH 5.6 at 2 h of storage. A negative correlation between the pH and lactic acid contents in muscle (P<0.001) was found. Histological analysis evidenced a larger pericellular area (40%) in the burnt samples than in the normal samples (16%). It was confirmed that a higher fish-keeping water temperature and a stressful slaughter method (faster glycolytic process) were determinative factors that influence the occurrence of burnt muscle in yellowtail, and that the effect of the former is larger than the latter.

Cocaine modulation in vitro of tumor necrosis factor production by macrophages from retrovirally infected mice

The effect of cocaine and LP-BM5 murine leukemia retrovirus infection on tumor necrosis factor (TNF) production were investigated. Three types of macrophages were used 1) peritoneal macrophage (PM), 2) thioglycollate induced peritoneal macrophage (TPM), and 3) alveolar macrophage (AM). Cells were cultured with and without cocaine during in vitro stimulation by lipopolysaccharide (LPS) and gamma-interferon (IFN). Retroviral infection enhanced the TNF production by PM and AM, but not by TPM. Intraperitoneal cocaine injection reduced TNF production by PM, but increased TNF production by AM and TPM. TNF production by AM from cocaine injected mice was stimulated by cocaine applied in vitro. In contrast, 100 micrograms/ml of cocaine in vitro significantly inhibited the TNF production by TPM from uninfected and retrovirally infected mice. Thus, TNF production by macrophages is modulated by murine retroviral infection and cocaine treatment. This could play an important role in host defense.

Mung bean trypsin inhibitor is effective in suppressing the degradation of myofibrillar proteins in the skeletal muscle of blue scad (Decapterus maruadsi).

Mung bean trypsin inhibitor (MBTI) of the Bowman-Birk family was purified to homogeneity with a molecular mass of approximately 9 kDa on tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and 8887.25 Da as determined by matrix-assisted laser desorption/ionization-quadrupole ion trap-time-of-flight mass spectrometry (MALDI-QIT-TOF MS). Using blue scad myofibrillar proteins as targets, it was found that, in the absence of MBTI, proteolysis of myofibrillar proteins, especially myosin heavy chain (MHC), could be identified after incubation at 55 °C for 2 h, while in the presence of MBTI, with a final concentration of 25 ng/mL, proteolysis of these proteins was greatly suppressed even after incubation for 3 h. Although cysteine proteinase inhibitor E-64 was also effective in preventing protein degradation, inhibitors for metallo- and asparatic proteinases did not reveal obvious inhibitory effects. Our present results strongly suggested that the naturally occurring legume bean seed protein MBTI can be used as an effective additive in preventing marine fish blue scad surimi gel softening, which is quite possibly caused by myofibril-bound serine proteinase (MBSP).

Some properties of β-1,3-glucan hydrolyzing enzymes from the rotifer Brachionus plicatilis

We examined some characteristics of hydrolyticenzymes, especially β-1,3-glucanase, to obtain theinformation of cell wall lytic enzymes forrotifers.Crude enzyme (ammonium sulfate fraction) of rotifershydrolyzed starch, β-1,3-glucan, glycol chitinand CM-cellulose. Optimum pH for hydrolysis ofstarch and CM-cellulose was 6.5, and that for β-1,3glucan and glycol chitin was pH 6.0. Pectic acid,xylan and agarose were not hydrolyzed at pH 3–10.β-1,3 glucanase was purified about 73-fold from crudeenzyme by ion-exchange chromatography and gelfiltration. Optimum pH and temperature of the enzymewere 6 and 60 °C, respectively. The molecular weight ofthe enzyme was estimated about 260 kDa by gelfiltration. The enzyme was inhibited byHgCl2 and MnCl_2.

Dietary Supplementation with Isoflavones Prevents Muscle Wasting in Tumor-Bearing Mice

Proinflammatory cytokines contribute to the progression of muscle wasting caused by ubiquitin-proteasome-dependent proteolysis. We have previously demonstrated that isoflavones, such as genistein and daidzein, prevent TNF-α-induced muscle atrophy in C2C12 myotubes. In this study, we examined the effect of dietary flavonoids on the wasting of muscle. Mice were divided into the following four groups: vehicle-injected (control) mice fed the normal diet (CN); tumor-bearing mice fed the normal diet (TN); control mice fed the isoflavone diet (CI); and tumor-bearing mice fed the isoflavone diet (TI). There were no significant differences in the intake of food or body weight gain among these four groups. The wet weight and myofiber size of gastrocnemius muscle in TN significantly decreased, compared with those in CN. Interestingly, the wet weight and myofiber size of gastrocnemius muscle in TI were nearly the same as those in CN and CI, although isoflavone supplementation did not affect the increased tumor mass or concentrations of proinflammatory cytokines, such as TNF-α and IL-6, in the blood. Moreover, increased expression of muscle-specific ubiquitin ligase genes encoding MAFbx/Atrogin-1 and MuRF1 in the skeletal muscle of TN was significantly inhibited by the supplementation of isoflavones. In parallel with the expression of muscle-specific ubiquitin ligases, dietary isoflavones significantly suppressed phosphorylation of ERK in tumor-bearing mice. These results suggest that dietary isoflavones improve muscle wasting in tumor-bearing mice via the ERK signaling pathway mediated-suppression of ubiquitin ligases in muscle cells.

The effect of ice crystals formations on the flesh quality of frozen horse mackerel (Trachurus japonicus)

It is known that the formation of ice crystals has a negative impact on the flesh quality of frozen meat. This study focuses on how the formation of ice crystals in the dorsal ordinary muscle affects the flesh quality of frozen horse mackerel (Trachurus japonicus). Freeze-thawed muscle specimens (F-TMS) of horse mackerel were first stored at -24C and then thawed. The K-value, expressible water, breaking strength of unfrozen muscle specimens (UMS) and F-TMS, and histological structure (light microscope [LM], scanning electron microscope [SEM] of UMS, frozen muscle specimens [FMS], and F-TMS) were investigated. K-values were higher in the F-TMS than in the UMS, and the increasing rate of K-value in F-TMS was approximately 1.4-fold higher than UMS. Similarly, the percentage of expressible water was higher in the F-TMS than in the UMS. The breaking strength of the UMS decreased with storage period, but it remained at a higher level than that of F-TMS. Numerous ice crystal formations in muscle cells of FMS and small interstices between cells of F-TMS were observed under LM. Moreover, we observed a relatively collapsed honeycomb structure of the extracellular matrix (ECM) under SEM, and found that collagen fibril networks of endomysiums became looser after thawing. Therefore, ice crystals contribute to vulnerabilities in the ECM. These results suggest that a decrease of freshness and the degradation of physical properties caused by ECM destruction may be due to the formation of ice crystals in muscle structures during freezing, leading to the deterioration of flesh quality during storage. PRACTICAL APPLICATIONS The flesh quality deteriorated after thawing on the basis of degradation of physical properties. Moreover, it could be presumed that the K-value increase was exacerbated by ice crystals, and the decreasing speed of chemical freshness was sped up accompanied by ice storage after thawing. Thus, the formation of ice crystals, which destroyed the muscle cells and structures, may be one of the dominant factors causing the deterioration in the flesh quality.

Dietary supplementation with alkylresorcinols prevents muscle atrophy through a shift of energy supply

It has been reported that phytoextracts that contain alkylresorcinols (ARs) protect against severe myofibrillar degeneration found in isoproterenol-induced myocardial infarction. In this study, we examined the effect of dietary ARs derived from wheat bran extracts on muscle atrophy in denervated mice. The mice were divided into the following four groups: (1) sham-operated (control) mice fed with normal diet (S-ND), (2) denervated mice fed with normal diet (D-ND), (3) control mice fed with ARs-supplemented diet (S-AR) and (4) denervated mice fed with ARs-supplemented diet (D-AR). The intake of ARs prevented the denervation-induced reduction of the weight of the hind limb muscles and the myofiber size. However, the expression of ubiquitin ligases and autophagy-related genes, which is associated with muscle proteolysis, was slightly higher in D-AR than in D-ND. Moreover, the abundance of the autophagy marker p62 was significantly higher in D-AR than in D-ND. Muscle atrophy has been known to be associated with a disturbed energy metabolism. The expression of pyruvate dehydrogenase kinase 4 (PDK4), which is related to fatty acid metabolism, was decreased in D-ND as compared with that in S-ND. In contrast, dietary supplementation with ARs inhibited the decrease of PDK4 expression caused by denervation. Furthermore, the abnormal expression pattern of genes related to the abundance of lipid droplets-coated proteins that was induced by denervation was improved by ARs. These results raise the possibility that dietary supplementation with ARs modifies the disruption of fatty acid metabolism induced by lipid autophagy, resulting in the prevention of muscle atrophy.

Year‐round gelation characteristic of bassy chub Kyphosus lembus meat

Year-round change in gelation of bassy chub (Kyphosus lembus) meat, collected from October 2001 to September 2002 off the coast of Nagasaki, was investigated. The fish meat exhibited a similar high gel-forming ability for all seasons, including pre- and post-spawning seasons. Freshwater washing of the meat did not improve its gel-forming ability. It was concluded that bassy chub meat could be used for thermal gel production in all seasons.