长牡蛎闭壳肌肌纤维的组织学特性

分别利用石蜡切片苏木精-伊红染色法、冷冻切片烟酰胺腺嘌呤二核苷酸四唑氧化还原酶(NADH-TR)组化染色法、肌球蛋白ATP酶染色法对长牡蛎闭壳肌平滑肌和横纹肌进行了组织学特性研究,并比较平滑肌和横纹肌肌纤维组成的差异。石蜡切片结果显示,闭壳肌中平滑肌和横纹肌肌纤维形态结构不同,肌纤维直径、肌纤维密度和横截面积存在显著差异,其中平滑肌肌纤维直径为(5.97±0.631)μm,肌纤维密度为(25 485.65±3917.807)根/mm~2,肌纤维横截面积为(26.25±5.365)μm~2;横纹肌肌纤维直径为(7.41±0.847)μm,肌纤维密度为(16 908.25±3917.807)根/mm~2,横截面积为(40.45±10.083)μm~2。NADH-TR染色结果显示,平滑肌中富含NADH,肌纤维染色较深,呈现深蓝紫色,主要是I型肌纤维,为氧化代谢的慢速收缩型肌纤维;横纹肌染色较浅或者基本不着色,主要是II型肌纤维,为糖酵解代谢的快速收缩肌纤维。ATPase酶染色结果显示,横纹肌ATPase活性强,染色较深,呈现黑色,主要是II型肌纤维;平滑肌中ATPase活性弱,着色浅或基本不着色,主要是I型肌纤维。ATPase酶染色结果与NADH-TR染色结果一致。研究阐明了长牡蛎闭壳肌中平滑肌和横纹肌肌纤维的组织学特性及收缩、代谢特性差异,为深入研究长牡蛎肌纤维生物学特性提供了重要的基础资料,为提高我国贝类肉质品质提供理论依据。     

Muscle growth in full-cycle cultured Pacific bluefin tuna Thunnus orientalis from early larval to juvenile stage: histochemical,immunohistochemical and ultrastructural observation

With the development of successful aquaculture techniques, the Pacific bluefin tuna (PBT) has become the most important fish species in Japan. Early muscle growth and cellularity of muscle fibers have a profound effect on ultimate body size and meat quality of fish. Larvae and juveniles of full-cycle cultured PBT were sampled at 3, 15, 29, 41, 70, 128 and 218 days post hatch (dph). Transverse body sections until 41 dph and muscle sections from 41 dph thereafter from dorso-cranial or caudal areas were stained for muscle fiber morphological and morphometric analysis and muscle sections from the dorso-cranial region were used for ultra-structural observation. Red muscle fibers appeared by 15 dph at the horizontal septum both in epaxial and hypaxial regions. Other than a single layer of superficial red fibers and those at the horizontal septum, existence of red muscle fibers was apparent in the PBT myotome. The muscle fiber diameters varied in their size even in adjacent myotomes of PBT. Overall, growth throughout the various stages was a result of both hyperplasia and hypertrophy of muscle fibers. Muscle fiber diameters were greater in the dorso-cranial than in dorso-caudal region at 41, 70 and 128 dph. These results provide additional characterization of PBT growth, which may assist with managing fish production efficiency, harvest age and eating quality.     

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.     

C-protein (MyBP-C) isoforms from carp ordinary and dark muscles and muscle type-specific binding to myosin

ABSTRACT:   C-protein is a myosin-associated protein of vertebrate striated muscle, and its function and properties have been extensively examined. However, there has been no report of C-protein of fish skeletal muscle so far. C-protein was identified in carp skeletal muscle by immunoassay using antibody against chicken C-protein, and the muscle-type specific C-protein was purified from carp ordinary and dark muscles for the first time. Although C-protein could be prepared from crude myosin by the reported procedure, C-protein degraded appreciably during the purification steps. Accordingly, C-protein was selectively extracted from the muscle with 0.15 M K-phosphate buffer (pH 5.8), and purified by ammonium sulfate fractionation, followed by AF-blue chromatography. Myosin free from the accessory proteins was obtained by diethylaminoethyl (DEAE) chromatography and used to assay the binding of C-protein with myosin. Ordinary muscle C-protein bound to ordinary muscle myosin in a saturable manner, but its maximum amount of binding was approximately twice that of dark muscle myosin. Similarly, dark muscle C-protein bound to dark muscle myosin much more than to ordinary muscle myosin. These results suggest that C-protein isoforms specifically bound with myosin isoforms originated from the same type of muscle.     

Influence of interposition of pink muscle fiber into dorsal ordinary muscle on 5'-IMP degrading activity in various fish species

ABSTRACT: To clarify the cause of differences in the temporal change of K -value among fish species living in the same habitat water temperature, the influence of the interposition of pink muscle fibers into dorsal ordinary muscle on 5'-inosine monophosphate (5'-IMP) degrading activity was examined. Fourteen fish species from the Sakishima Islands (habitat water temperature 28°C) and from Nagasaki (habitat water temperature 17°C) were used for the sample fishes. Each of 5'-IMP and ρ-nitrophenol phosphate (ρ-NPP) degrading activities showed a peak at near pH 8.0 and near pH 5.0, respectively. These activities were somewhat higher in fish from Nagasaki than in fish from the Sakishima Islands. The interposition percentage of pink muscle fibers into dorsal ordinary muscle correlated significantly ( P < 0.05) with the 5'-IMP degrading activity at pH 7.0. Furthermore, the activity at pH 7.0 correlated significantly ( P < 0.001) with the increasing rate of K -value at 32°C (ΔK₃₂). These results suggest that the difference in ΔK₃₂ among fish species in the same habitat water temperature might be caused by differences in 5'-IMP degrading activity because of the differences in the interposition rates of pink muscle fibers into dorsal ordinary muscle.     

Influence of interposition of pink muscle fiber into dorsal ordinary muscle on temporal change of K-value in cultured carp

To clarify the influence of the interposition of pink muscle fiber into dorsal ordinary muscle on temporal change of K-value, using cultured carp, the dorsal muscle was divided into five muscle parts towards depth with the naked eye as follows: the dark muscle part (P-1), the intermediate muscle part (P-2) and three ordinary muscle parts (P-3, P-4, P-5). These were organized from the muscle fiber types as follows: P-1 was only red muscle fiber type. P-2 was only pink muscle fiber type in a thin layer and two muscle fiber types of not only pink muscle fiber but also white muscle fiber of the IIa or IIb subtype in a mosaic pattern. All of P-3, P-4 and P-5 were two muscle fiber types, white muscle fiber (IIa or IIb subtype) and pink muscle fiber. The temporal changes of K-values were remarkably faster in the order of P-1, P-2, and three parts of P-3, P-4 and P-5. The changes did not exhibit a remarkable difference among the three ordinary muscle parts. From these results, it was considered that the interposition of pink muscle fiber into the dorsal ordinary muscle might accelerate the temporal change of K-value.     

Effects of Brief Summer or Winter Fasting on the Muscle Quality of Cultured Pacific Bluefin Tuna (Thunnus orientalis)

The effects of fasting on the quality of the dorsal and ventral ordinary muscles from cultured Pacific bluefin tuna (Thunnus orientalis) during chilled storage were investigated. Tuna were subjected to fasting for 2 days in the summer or 6 days in the winter prior to harvesting. The breaking strength of the dorsal ordinary muscle sampled in the summer increased until 24 h and then decreased. There were no significant differences in the lipid and glycogen content of the ordinary muscle after 9 h of storage between the controls and either fasting group. The pH of the ordinary muscle subjected to summer and winter fasting was higher than in the controls after 24–48 h of storage. However, the relationship between the pH and glycogen content was unclear. The metmyoglobin content during chilled storage was lower in the ordinary muscles from either fasting group than in the controls. In conclusion, fasting for 6 days in the winter improved the color stability of the ordinary muscle without a decline in its lipid content.     

Thermal denaturation profiles of catfish and tilapia myofibrils as affected by pH for heating

Thermal denaturation profiles of catfish myosin when heated as myofibrils (Mf) were compared with those of tilapia. The Ca²⁺-ATPase inactivation rate of catfish myofibrils was the same as that of tilapia myofibrils. The conclusion was the same with isolated myosin. Catfish Mf was clearly distinguished from tilapia Mf in terms of subfragment-1 (S-1) and rod denaturation. Quick denaturation of rod relative to S-1 was characteristic of catfish Mf, while slower denaturation of rod relative to S-1 was the pattern for tilapia Mf. These patterns were greatly affected by the pH for heating. Rod denaturation was accelerated with increasing pH for heating and oppositely suppressed by lowering the pH, for both Mf. Tilapia Mf showed a S-1 and rod denaturation pattern similar to that for catfish Mf, but at 1 pH unit higher; for example, the pattern of catfish Mf at pH 7.5 was similar to that for tilapia Mf at pH 8.5. Less rigid filament structure of catfish Mf than tilapia Mf was demonstrated by studying chymotryptic digestion at various pH values. Accordingly, the difference in the S-1/rod denaturation patterns between the two fish species can be explained by the different rigidity of their myosin filaments.     

Effect of variation in the dietary ratio of linseed oil to fish oil on growth,body composition,tissues fatty acid composition,flesh nutritional value and immune indices in Manchurian trout,Brachymystax lenok

In order to study the effects of linseed oil substitution on the growth, body composition, tissue fatty acid composition, flesh nutritional value and immune indices of juvenile Manchurian trout, five feed types containing different levels of linseed oil (LO) mixed with fish oil (FO) were prepared: 0 (0 LO); 250 g/kg (25 LO); 500 g/kg (50 LO); 750 g/kg (75 LO); and 1000 g/kg (100 LO); and fed to juvenile Manchurian trout (initial weight 6.43 ± 0.02 g) for 9 weeks. The results showed that substitution of FO with 750 g/kg LO did not affect the growth of juvenile trout, with protein content in the dorsal muscle, and lipid content in the liver not showing any significant difference (p > 0.05). The highest lipid content found in muscle samples occurred for the 25 LO diet. The fatty acid composition found in the dorsal muscle and the liver of the Manchurian trout reflects the fatty acid composition in the diet, where the relative amount of linolenic acid (ALA), linoleic acid (LA) and docosahexaenoic acid (DHA) found in these organs has a positive linear correlation with their relative composition in the diet (p < 0.05). As the amount of LO in the diet was increased, the composition of ALA found in the sampled organs increased, while the composition of DHA and eicosapentaenoic acid (EPA) decreased. At the same time, the index of atherogenicity (IA) and thrombogenicity (IT) of the muscle samples from the 75 LO and 100 LO diets was significantly lower than for the 0 LO and 25 LO diets (p < 0.05), while the flesh lipid quality (FLQ) in the 100 LO diet was significantly lower than for the other diets (p < 0.05). The aspartate transaminase (AST) activity decreased initially, and then increased, as the level of LO replacement for FO was increased, with the 25 LO diet being significantly lower than for other groups (p < 0.05). The alanine aminotransferase (ALT) activity in serum samples from the 100 LO diet was higher than that from other diets. The lysozyme (LZM) activity in both serum and liver tissue first increased to a peak for the 25 LO and 50 LO diets, respectively, and then decreased as the level of LO was further increased. There was no significant change in the alkaline phosphatase (AKP) activity in the liver samples; however, the acid phosphatase (ACP) activity decreased significantly from the highest value for 0 LO feed group. In conclusion, the composition of fatty acids in the dorsal muscle and the liver was found to be modified by the diets, and with the diet containing less than 750 g/kg LO, being both beneficial for growth, and improved immunity, while maintaining the nutritional value of the lipid content in the dorsal muscle during the 9‐week period.     

The changes in proximate compositions and glycogen contents in the dorsal ordinary muscles of the full-cycle cultured Pacific bluefin tuna Thunnus orientalis occurring with growth

ABSTRACT:   Using full-cycle cultured (FC) Pacific bluefin tuna (body length [BL], 42.6–66.4 cm; body weight [BW], 1.66–7.40 kg, n  = 15), the changes in chemical compositions and histological structure of the cephalal parts of the dorsal ordinary muscles (DOM) occurring with growth were investigated. A positive correlation ( r  = 0.9644, P  < 0.05) was observed between BL and BW with growth. The protein, lipid and ash contents of DOM and condition factor did not change with growth. However, the glycogen content of DOM increased ( P  < 0.05) from approximately 55 cm (BL) in this study. Using optical microscopic photographs, the various shapes of muscle fibers were observed and it was noted that the muscle fiber diameter increased ( P  < 0.05) with growth. Using transmission electron microscopic observation, many glycogen granules were observed in muscle fibers (especially, side of connective tissue) of DOM throughout the growth stage in this study. These results indicate that the glycogen content of DOM of FC Pacific bluefin tuna increases before the lipid with growth.     

Myosin denaturation in “Burnt” Bluefin tuna meat

A quantitative conversion of tuna meat into muscle homogenate made it possible to study myosin denaturation in Bluefin tuna meat. Myosin denaturation was accessed by measuring Ca²⁺-ATPase activity, salt-solubility with and without Mg-ATP, monomeric myosin content, and amount of subfragment-1 (S-1) and rod produced by chymotryptic digestion. Commercially available tuna used in this study showed a pH around 5.4–5.7. Myosin in the meat lost the salt-solubility measured in the absence of Mg-ATP; however, such myosin showed full salt-solubility when released from actin in the presence of Mg-ATP. Incubation of tuna meat at 30 °C for up to 90 min caused obvious myosin denaturation. However, the tuna meat dialyzed against neutral pH buffer showed practically no myosin denaturation by the same heating. It was suggested that exposure to lowered pH to around 5.5 and increased temperature of 30 °C led myosin denaturation. Myosin denaturation in the “Burnt” Bluefin tuna sample was analyzed. A significant myosin denaturation was observed with the part showing the “Burning” symptom, the inner part of the tuna meat near the spine. Myosin in that part showed almost no Ca²⁺-ATPase activity, no salt-solubility even with Mg-ATP, no recovery of monomeric myosin, and almost no production of S-1 by chymotryptic digestion. However, myosin denaturation was not detectable for the meat taken from outer parts of the same tuna near the skin with normal appearance. It was demonstrated that “Burning” of tuna meat occurring in the deep part of the body is accompanied by myosin denaturation. The above results suggested that insufficient cooling of the deep part of body would be the reason for “Burning” of tuna meat.     

Comparison of the proximate compositions,breaking strength and histological structure by the muscle positions of the full-cycle cultured Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis>

ABSTRACT:   Using the skeletal muscle of full-cycle cultured Pacific bluefin tuna (body weight: 13.1 ± 2.6 kg, cultured for about 21 months), the proximate compositions, breaking strength and histological structure of the front and rear parts of the dorsal ordinary muscles (FD-OM and RD-OM) and the ventral ordinary muscles (FV-OM and RV-OM) were compared. The FV-OM showed low moisture, protein, ash and high fat contents ( P  < 0.05, respectively) for the other three positions. The breaking strength of FD-OM, RD-OM and RV-OM increased up to 15–18 h and decreased later. However, the breaking strength of FV-OM was maintained during chilled storage. The pH of all muscles decreased up to 15 h, and then stayed at pH 5.7–5.8. However, the pH of FV-OM stayed at a higher level (pH 5.9). The histological structure observed by optical microscopy showed a space extension among muscle cells after 24 h in all positions, and these results were also supported by image analysis.     

Changes in Volatile Compounds of Dark and Ordinary Muscles of Yellowtail (Seriola quinqueradiata) During Short-Term Cold Storage

ABSTRACT

Changes in volatile compounds in dark and ordinary muscle of yellowtail during 2 days of refrigerated storage at 5°C were investigated. Twenty-seven compounds were identified in ordinary muscle and 39 in dark muscle during 2 days of storage at 5°C. Thirteen compounds at Day 0 of storage and 29 compounds at Day 2—such as 2,3-pentadione, 1-penten-3-ol, (Z)-2-penten-1-ol, and (E,Z)-2,4-heptadienal—identified in the dark muscle showed significantly higher values compared to ordinary muscle. Levels of thiobarbituric acid-reactive substances (TBARS) in dark muscle were significantly higher than those in ordinary muscle throughout 2 days of storage period, and a significant increase in TBARS occurred in just dark muscle at Day 2 of storage. In ordinary muscle, viable cells remained at the same order of magnitude as their initial values for 2 days. Eight aldehydes in ordinary muscle and 25 volatile compounds in dark muscle increased significantly without microbial action prior to increase in TBARS during short-term cold storage. Principal component analysis of the volatile compounds in dark and ordinary muscle was able to differentiate between different storage time samples of same muscle type as well as different muscle samples of same storage time.     

Control of lipid oxidation and meat color deterioration in skipjack tuna muscle during ice storage

The present study investigated the effects of lipid oxidation on quality deterioration in the ordinary and dark muscles of skipjack tuna Katuwonus pelamis during the early stages of ice storage for 72 h. The lipid hydroperoxide content of the dark muscle was significantly higher (P < 0.01) than that of the ordinary muscle throughout 72 h of ice storage. The metmyoglobin content of the ordinary muscle gradually increased, and was accompanied with darkening in the fish meat color. On the other hand, the addition of sodium ascorbate or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox^®) to the ordinary muscle of skipjack tuna significantly inhibited the formation of lipid hydroperoxide as well as metmyoglobin formation. Thus, a decrease in α-tocopherol content in the ordinary muscle with antioxidant addition was not observed during ice storage period. In conclusion, the rate of lipid oxidation of skipjack tuna ordinary muscle is closely related to metmyoglobin formation, and the addition of antioxidants to fish meat is effective at inhibiting lipid oxidation as well as myoglobin oxidation in post-mortem meat.     

Changes in the pericellular connective tissue and breaking strength of the three types of muscles of the cultured carp Cyprinus carpio during storage in ice

To elucidate the structural changes in pink (P), white (W), and red (R) muscles during storage in ice, we measured the breaking strength and changes in pericellular connective tissues of cultured carp. The breaking strength just after killing was highest in R muscle (1.00 ± 0.20 N), lowest in W muscle (0.37 ± 0.07 N), and intermediate (0.84 ± 0.12 N) in P muscle. During the storage period, the breaking strength decreased first in R muscle, then in P muscle, followed by W muscle. The diameter of muscle fibers was greater in W muscle (113 ± 15 μm) than in P muscle (72 ± 3 μm) and R muscle (48 ± 2 μm). Destruction of the honeycomb structure of the pericellular connective tissue occurred most rapidly in W muscle and most slowly in R muscle. These results suggest that the interposing of P muscle fibers in the dorsal ordinary muscle contributes to the acceleration of post-mortem tenderization in fish.     

Early temperature effects on muscle growth dynamics and histochemical profile of muscle fibres of sea bass Dicentrarchus labrax L., during larval and juvenile stages

Recently, it has been found that the thermal experience during the earliest phases of development could determine the larval and postlarval growth characteristics of teleosts. In order to investigate the effects of the early temperature regime on the advanced stages of growth of sea bass, Dicentrarchus labrax L., this species was reared during the vitelline phase at two temperatures: natural temperature (15 °C) and 17.7±0.1 °C, and then larvae transferred to common temperature (natural temperature). Muscle growth was studied by morphometric and histochemical techniques (mATPase and NADH-TR). Body length and body mass were also measured. During the vitelline phase, muscle growth was similar in both experimental groups, but at 25 days, both hypertrophy and hyperplasia of white muscle fibres were greater in the prewarmed group (p<0.05). At the end of metamorphosis (80 days) and at 120 days, the average diameter of white muscle fibres, as well as the body length, were greater in the prewarmed group (p<0.05), but the number of white fibres did not differ significantly between groups. The morphological mosaic of white muscle fibres was observed at the end of metamorphosis, and the histochemical mosaic appeared gradually since the early postlarval stages. Thus, at 120 days, some specimens in both experimental groups showed three or four different mATPase staining white fibres: low (L), moderate (M), high (H) and/or very high (vH), whereas in other specimens, only L or M mATPase activity fibres were observed. Early T influenced the histochemical maturity of the white muscle. By 120 days, the proportion of H and vH fibres was greater in the prewarmed group (p=0.027; p=0.051, respectively). By 154 days, the four mATPase staining profiles (L, M, H, vH) were observed in all specimens of both groups, but the proportion of vH fibres was still higher in the prewarmed group. By 188 days, 3774 °C-day for the prewarmed group and 3759 °C-day for the natural temperature group, only slight differences between groups were observed in the histochemical properties and no differences were found in the number and size of white muscle fibres, neither in the body length and body mass of specimens.

In conclusion, a slight increase of temperature during the vitelline phase of sea bass increased the muscle growth and body length of fish in subsequent larval and postlarval stages, and advanced the histochemical maturity of the white muscle.     

Comparison of 5′-inosine monophosphate and p-nitrophenyl phosphate degrading activities among red,pink, and white muscle fibers of cultured carp

ABSTRACT:   As part of a study to clarify the differences in the temporal change in K -value among fish species, the temporal change in K -value and the 5'-inosine monophosphate (5'-IMP) and p-nitrophenol phosphate (p-NPP) degrading activities in the red, pink, and white muscle fibers in the dorsal muscle of the carp were compared. The temporal change in K -value was fastest in red, followed by pink, and white muscle fibers, at both 0°C and 32°C. Moreover, the 5'-IMP and p-NPP degrading activities were highest in red, followed by pink, and white muscle fibers at near optimum pH concentrations. The 5'-IMP degrading activity at pH 7.0 had a positive correlation with the increasing rate of K -value at 32°C for all types of muscle fibers. These results suggest that differences in increasing rates of K -values between red, pink, and white muscle fibers corresponded to the 5'-IMP degrading activities.     

Fish muscle: the exceptional case of notothenioids

Fish skeletal muscle is an excellent model for studying muscle structure and function, since it has a very well-structured arrangement with different fiber types segregated in the axial and pectoral fin muscles. The morphological and physiological characteristics of the different muscle fiber types have been studied in several teleost species. In fish muscle, fiber number and size varies with the species considered, limiting fish maximum final length due to constraints in metabolites and oxygen diffusion. In this work, we analyze some special characteristics of the skeletal muscle of the suborder Notothenioidei. They experienced an impressive radiation inside Antarctic waters, a stable and cold environment that could account for some of their special characteristics. The number of muscle fibers is very low, 12,700–164,000, in comparison to 550,000–1,200,000 in Salmo salar of similar sizes. The size of the fibers is very large, reaching 600 μm in diameter, while for example Salmo salar of similar sizes have fibers of 220 μm maximum diameter. Evolutionary adjustment in cell cycle length for working at low temperature has been shown in Harpagifer antarcticus (111 h at 0°C), when compared to the closely related sub-Antarctic species Harpagifer bispinis (150 h at 5°C). Maximum muscle fiber number decreases towards the more derived notothenioids, a trend that is more related to phylogeny than to geographical distribution (and hence water temperature), with values as low as 3,600 in Harpagifer bispinis. Mitochondria volume density in slow muscles of notothenioids is very high (reaching 0.56) and since maximal rates of substrate oxidation by mitochondria is not enhanced, at least in demersal notothenioids, volume density is the only means of overcoming thermal constraints on oxidative capacity. In brief, some characteristics of the muscles of notothenioids have an apparent phylogenetic component while others seem to be adaptations to low temperature.