Growth dynamics of myotomal muscle fibres in a carangid, Caranx malabaricus (Cuv. et Val.)

The growth pattern of myotomal red, pink and white muscle and its relation to somatic growth in Caranx malabaricus are described. The growth pattern of red muscle was by an increase in fibre number in early size classes (< 22 cm f.l.) and thereafter mainly by increase in fibre diameter and partly by increase in fibre number. The growth of pink muscle was mainly by an increase in fibre diameter, but in smaller fish an increase in fibre number was also evident. White muscle growth was mainly by an increase in fibre diameter and partly by increase in fibre numbers in fish < 22 cm f.l., but only by an increase in fibre diameter from 22 cm f.l. onwards. Caranx malabaricus is a slow-to-moderate growing species and its fibre growth pattern matches with such somatic growth.     

Numbers of muscle nuclei and myosatellite cell nuclei in red and white axial muscle during growth of the carp (Cyprinus carpio)

We determined the percentages of muscle fibie nuclei and satellite nuclei over a growth range of carp ( Cyprinus carpio ), as the increase in the number of muscle fibre nuclei is an important aspect of the increase in muscle mass, and myosatellite cells are believed to be the source of new muscle fibre nuclei. In white as well as in red axial muscle the percentage of the nuclei present in muscle that are muscle nuclei (muscle fibre nuclei+myosatellite nuclei) remained constant during growth (54 and 32% respectively). The difference in the percentage of non-muscle nuclei between white and red axial muscle is mainly caused by the higher content of endothelial nuclei in red axial muscle.
In white axial muscle the DNA/protein ratio (nucleus/sarcoplasm ratio) decreased between 3 and 15 cm S.l. In red axial muscle we found a continuous decrease in DNA/protein ratio over the entire investigated size range (3–50 cm s.l.). This may be related to a longer occurrence of hyperplasia in red than in white axial muscle.
In both fibre types the percentage of muscle nuclei being myosatellite nuclei decreased with increasing length, In white axial muscle it decreased from about 5% in carp of 5 cm s.l. to less than 1% in carp of 20 cm S.L.; for red muscle these values were 11 and 3% respectively.
For white axial muscle we calculated that, especially in larger fish, the myosatellite ceils alone cannot account for the increase in the number of muscle fibre nuclei during growth. The percentage of proliferating nuclei in muscle tissue, measured by the uptake of 5-bromo-2'-deoxy-uridine, is high enough to account for the total increase in nuclei. So indirect evidence is available that another cell type present in the muscle tissue may also be involved in the formation of additional muscle fibre nuclei.     

Effect of sex on muscular development of Muscovy ducks

Muscovy ducks display marked sexual dimorphism. The aim of our study was to analyse the consequences of dimorphism on muscular growth and, particularly, on the myofibrillar typology of the Pectoralis major and Sartorius muscles. In the Pectoralis muscle, we only found two fibre types: red fast-twitch oxido-glycolytic fibres (about 90%) and white fast-twitch glycolytic fibres. In the Sartorius, the innermost part contained both white (30%) and red (55%) fast fibres and red slow-twitch oxidative fibres (15%). For both muscles, neither sex nor age had a significant effect on the percentage of each fibre type. The cross-sectional areas of fibres increased with age. The difference in muscle weight observed between sexes could be explained by a higher size and/or total fibre number in the male muscles.     

Hyperplasia and hypertrophy in the growth of skeletal muscle in juvenile Atlantic salmon, Salmo salar L.

Both red and white muscle fibre numbers in juvenile Atlantic salmon increased gradually with fish length throughout the freshwater growth period. Mean fibre area increased as fish grew to 6.5 cm f.l. , but thereafter was unrelated to fish length. Hyperplasia was most obvious when fish were growing fastest, and was the dominant growth process in fish over 6.5 cm f.l. Hypertrophy was most important when growth was slow, as in autumn and winter.
Mean white fibre area was significantly smaller in deep muscle than at medial and superficial sites. Total cross-sectional area of red, white and total trunk muscle increased with fish length. The ratio of red: white cross-sectional area increased with fish length to a plateau at about 10% after 6.5 cm f.l.     

Growth dynamics of white and red muscle fibres in fast- and slow-growing strains of rainbow trout

Compared with fish of a slow-growing strain, fast-growing rainbow trout exhibited significantly smaller white fibre diameters, throughout development from hatching to 24 cm body length, although possessing similar total number of fibres. In contrast, in red muscle, no differences were observed in fibre diameter between the two strains, but the fast growing fish showed a significantly higher number of red fibres. The differences in growth rate between the two strains were related to the mean white fibre diameter and were found to be matched by proportional adjustments in recruitment of new fibres to the growing muscle. Thus, the largest and fastestgrowing strain showed evidence of sustained higher recruitment of muscle fibres that endowed this strain with the potential to maintain rapid somatic growth for longer and accomplish greater muscle growth.     

Succinic Dehydrogenase Distribution in the Pectoralis Muscle of Several East African Birds

The distribution of succinic dehydrogenase activity was investigated in the pectoralis muscle of thirteen East African birds, representing five Orders. It was found that the pectoralis muscle of the most primitive birds studied (Galliformes) contained all “white” muscle fibres whereas the more advanced birds (Passeriformes) had all “red” muscle fibres. Intermediate Orders had mostly a mixture of red and white muscle fibres. There also appeared to be a direct relationship between body size and average muscle fibre size. However, it was concluded that the most important factor in relation to the muscle structure is the bird's mode of flight. The relationship with the degree of evolution and body size only held true in so far as the birds which had developed the facility for sustained flight, by increasing their red muscle fibre content, were also smaller in size and constituted the more “evolved” Orders of birds. In support of this it was noted that migratory birds (i.e. engaging in sustained flight) from more primitive Orders also had a high red muscle fibre content in their pectoralis muscles.     

Effects of sustained swimming on rainbow trout muscle structure, blood oxygen transport, and lactate dehydrogenase isozymes: evidence for increased aerobic capacity of white muscle

Groups of rainbow trout (Salmo gairdneri, Richardson) were continuously swum at 20 cm s-1 (1.0 body lengths s-1) for 0, 3, 30, and 200 days. No significant changes in fish condition factor, combined red and white muscle mass, muscle fibre size or fibre size distribution were observed. After 200 days of swimming there was a significant 2.2 fold increase in red muscle mass. Number of capillaries per red muscle fibre increased significantly in each group by a maximum of 27% after 200 days exercise. Number of capillaries per white muscle fibre increased significantly by 95% after 200 days exercise. Blood lactate, haemoglobin (Hb) concentration haematocrit, erythrocyte adenosine triphosphate, and whole blood oxygen affinity P50 were unchanged by swimming. After 30 and 200 days swimming there was a shift in expression of white muscle lactate dehydrogenase (LDH) isozymes from LDH-A to LDH-B. Within the duplicated LDH-B isozyme complex, there was a shift in expression from LDH-B to LDH-B' subunits. These results suggest that sustained swimming at 1(-1) bl s-1 increased the aerobic capacity of red and particularly white (fast) muscle of rainbow trout but did not alter the gas transport characteristics of the blood.     

Differences in protein mobilization between ventral and dorsal parts of white epaxial muscle from fed, fasted and refed white sturgeon (Acipenser transmontanus)

The effect of starvation-refeeding on protein mobilization in the lateral line, lateral (midway between lateral line and dorsum) and dorsal parts of white sturgeon ( Acipenser transmonlanus ) white epaxial muscle (type IIB) were compared by measuring muscle cross-sectional fibre areas. Effects on red (type I) and pink (type IIA) muscle were also studied. Fish starved throughout the experiment (5 weeks) showed a uniform response, i.e. the cross-sectional fibre area decreased at all sampled locations in the white muscle as well as in red and pink muscle. Fibre size in fish refed for 3 weeks after 2 weeks of fasting (S/F) was reduced mainly in the dorsal region of the white muscle. Starvation for 3 weeks after 2 weeks of initial feeding (F/S) also reduced fibre size mainly in the dorsal regions of the white muscle and in the pink muscle. The results indicate that in sturgeon exposed to short periods of low food availability, protein is utilized preferentially from trie more dorsal regions of the white epaxial muscle and from pink muscle. Protein in white muscle located closer to the lateral line and in red muscle seems to be spared. With the onset of refeeding, protein deposition occurred rapidly in pink muscle, but was delayed significantly in the dorsal part of the white muscle.     

Growth dynamics of caudal and pectoral fin muscle fibres in a carangid, Caranx malabaricus (Cuv. & Val.), and their possible relation with somatic growth

The growth dynamics of red, pink and white fibres of the caudal and pectoral fin muscles are described in Carans malabaricus (Cuv. & Val.) in relation to their somatic growth. In all three fibre types growth occurred by an increase in fibre number and diameter in small size classes of fish and by an increase in diameter only in larger fish. The growth dynamics of the three fibre types were similar to those of the myotomal muscle fibres and paralleled the somatic growth pattern of this fish.     

MicroRNA Transcriptome Profile Analysis in Porcine Muscle and the Effect of miR-143 on the MYH7 Gene and Protein

Porcine skeletal muscle fibres are classified based on their different physiological and biochemical properties. Muscle fibre phenotype is regulated by several independent signalling pathways, including the mitogen-activated protein kinase (MAPK), nuclear factor of activated T cells (NFAT), myocyte enhancer factor 2 (MEF2) and peroxisome proliferator-activated receptor (PPAR) signalling pathways. MicroRNAs are non-coding small RNAs that regulate many biological processes. However, their function in muscle fibre type regulation remains unclear. The aim of our study was to identify miRNAs that regulate muscle fibre type during porcine growth to help understand the miRNA regulation mechanism of fibre differentiation. We performed Solexa/Illumina deep sequencing for the microRNAome during 3 muscle growth stages (63, 98 and 161 d). In this study, 271 mature miRNAs and 243 pre-miRNAs were identified. We detected 472 novel miRNAs in the muscle samples. Among the mature miRNAs, there are 23 highest expression miRNAs (over 10000 RPM), account for 85.3% of the total counts of mature miRNAs., including 10 (43.5%) muscle-related miRNAs (ssc-miR-133a-3p, ssc-miR-486, ssc-miR-1, ssc-miR-143-3p, ssc-miR-30a-5p, ssc-miR-181a, ssc-miR-148a-3p, ssc-miR-92a, ssc-miR-21, ssc-miR-126-5p). Particularly, both ssc-miR-1 and ssc-miR-133 belong to the MyomiRs, which control muscle myosin content, myofibre identity and muscle performance. The involvement of these miRNAs in muscle fibre phenotype provides new insight into the mechanism of muscle fibre regulation underlying muscle development. Furthermore, we performed cell transfection experiment. Overexpression/inhibition of ssc-miR-143-3p in porcine skeletal muscle satellite cell induced an/a increase/reduction of the slow muscle fibre gene and protein (MYH7), indicating that miR-143 activity regulated muscle fibre differentiate in skeletal muscle. And it regulate MYH7 through the HDAC4-MEF2 pathway.     

Hyperplastic and hypertrophic growth of lateral muscle in blackspot seabream Pagellus bogaraveo from hatching to juvenile

To understand better the growth mechanisms in the economically important fish Pagellus bogaraveo, in terms of muscle fibre hyperplasia v. hypertrophy, the lateral muscle of this fish was studied morphometrically from hatching to juvenile comparing rostral and caudal locations. Fish were sampled at 0, 5, 23, 40, 70, 100, 140 and 180 days. Fibre types were first identified by succinate dehydrogenase (SDH) and immunostaining with a polyclonal antibody against fish slow myosin (4–96). Morphometric variables were then measured in transverse body sections, at both post‐opercular and post‐anal locations, to estimate the following variables: total muscle area [A (muscle)], total fibre number [N (fibres)], fibre number per unit area of muscle [N_A(fibres, muscle)] and cross‐sectional fibre area [ (fibres)] of the two main muscle fibre types (white and red). Overall, growth throughout the various stages resulted from increases both in the number and in the size of muscle fibres, paralleled by an expansion of the [A (muscle)]. Nonetheless, that increase was not significant between 0–5 days on one hand and 100–140 days, on the other hand. On the contrary, the [N_A(fibres, muscle)] declined as the body length increased. Analysis of the muscle growth kinetics suggested that, within the important time frame studied, hyperplasia gave the main relative contribution to the increase of white muscle [A (white muscle)], whereas red muscle [A (red muscle)] mainly grew by hypertrophy, with both phenomena occurring at a faster pace posteriorly in the body. Finally, when comparing rostral and caudal locations, a greater [N (fibres)] and [A (muscle)] of the posterior white and red fibres were the consistent features. It was also observed that the proportion of the cross‐sectional area of the myotomal muscle comprised of white muscle was greater in the anterior part of the fish.     

Comparative aspects of muscle fibre size and succinic dehydrogenase distribution in the longissimus dorsi muscle of several species of East African mammals

The distribution of succinic dehydrogenase enzyme activity was investigated in frozen sections of longissimus dorsi muscle taken from several species of East African game animal (giraffe, hartebeest, wildebeest, oryx, gerenuk and dik-dik) as well as local zebu cattle. Muscle fibres were classified as red (high succinic dehydrogenase activity), white (low activity) or intermediate. The mean diameter and percentage distribution of each fibre type were noted as well as the overall mean muscle fibre diameter (MFD) for each species. The diameters of red muscle fibres were found to be between 54 and 62% of the diameters of the white muscle fibres for all species with MFD differences between species being up to over 100%. The variation in MFD was found to be significantly and positively correlated with live weight, when zebu values were omitted. It was found that the variation in MFD was significantly related to the diameter of muscle fibre types and not to the percent distribution of these fibre types.     

A histochemical and ultrastructural study of the development of the propulsive musculature of the brown trout, Salmo trutta L., in relation to its swimming behaviour

The differentiation of the myotomal muscle types in the propulsive musculature of Salmo trutta has been investigated histochemically and ultrastructurally from late embryonic to free-swimming fish at 5° months post fertilisation and related to observed changes in swimming behaviour. A histochemical and ultrastructural characterisation was also made of the major myotomal muscle fibre types in fingerling and yearling S. trutta . Two distinct populations of muscle cell types can be recognised prior to hatching. The early development of the white fibre population is related to the short, burst-type swimming activity at early stages. The later increase in the development of the red fibre population is directly related to the appearance of sustained swimming activity. The swimming performance of freeswimming alevins has been investigated and the results are discussed in comparison to adult fish.     

The distribution of capillaries in the somatic musculature of two vertebrate types with particular reference to teleost fish

The distribution of capillaries in teleost and rat striated muscles was investigated using a number of different methods. A new method for directly viewing capillaries was developed. Teleost white muscle has a capillary: fibre (C:F) ratio of between 0.2 and 0.3; and 0.6 to 1.0 peripheral capillaries per muscle fibre. 26-49% of fibres had no peripheral capillaries. Values for the rat gastrocnemius were 1.2, 2.6 and 4.8% respectively which compares well with literature values. Flathead red muscle had a C:F ratio of between 1.9 and 2.5; and between 5.3 and 6.6 peripheral capillaries per muscle fibre depending on the method used. Values for rat soleus were 1.8 and 4.1 respectively. Teleost pink fibres had an intermediate number of capillaries. Rat striated muscle, particularly the gastrocnemius, was found to be heterogeneous with respect to the distribution of capillaries. Flathead red muscle was homogeneous whilst teleost white muscle was only slightly variable. Flathead red muscle fibres are well suppled with subsarcolemmal mitochondria. These show a clumped distribution corresponding to the position of capillaries. In contrast teleost white fibres are almost totally devoid of these and all other mitochondria. No differences were observed in the vascularisation of either muscle type along the length of the fish. The results are discussed in relation to the division of labour between fibre types during swimming.     

Capillary distribution and metabolic histochemistry of the lateral propulsive musculature of pelagic teleost fish

Metabolic and vascular adaptation of teleost lateral propulsive musculature to an active mode of life was investigated in four pelagic teleosts (mackerel, yellowtail scad, pilchard and Australian salmon). Histochemical profiles and capillarisation data of the red and white muscle were compared to those of less active demersal species. Pelagic white muscle stained positively for the aerobic enzymes succinate dehydrogenase and NADH diaphorase, and had both subsarcolemmal and intermyofibrillar mitochondria which corresponded to the loci of the histochemical stain. Subsarcolemmal mitochondria tended to be localised close to capillaries. In contrast, white muscle from demersal species was unstained for the same enzymes and was devoid of mitochondria. Red muscle of all species had abundant mitochondria and stained intensely for aerobic enzymes. Capillarisation was quantified by determining the percentage of fibres surrounded by a given number of peripheral capillaries, mean fibre diameter, mean number of peripheral capillaries, capillary: fibre ratio and sharing factor where appropriate. Red muscle of mackerel, Australian salmon, pilchard and scad are better vascularised than red muscle of the flathead having 153, 200, 242, 291 and 309 microns 2 of cross-sectional fibre area per peripheral capillary, respectively. White muscle of mackerel, pilchard and scad are better vascularised than white muscle of the Australian salmon and flathead having 2040, 3367, 4992, 9893 and 10,469 microns 2 of cross-sectional fibre area per peripheral capillary, respectively. Red muscle of Australian salmon had distinct regional variation. Deep red muscle was found to be more highly vascularised (4.2 peripheral capillaries per muscle fibre) than lateral red muscle (1.9 peripheral capillaries per muscle fibre). Red muscle of the other species was less heterogeneous. White muscle capillarisation was slightly variable in all species. It is concluded that the white muscle of the pelagic species studied is functionally and structurally adapted for sustained aerobic activity with relatively abundant mitochondria being preferentially situated close to the source of gas and metabolite exchange.     

Red muscle fibre and capillary dimensions in different sizes of a tilapia, Oreochromis niloticus (Trewavas)

Measurements of muscle dimensions that affect respiration in relation to body weight were carried out in a tilapia, Oreochromis niloticus . The fish used in all measurements weighed 0.65–812.3 g. The data were analysed with respect to body weight using logarithmic transformations (log Y=log a + b log W ).
The slopes (b) of the log/log regression lines for weight of body trunk red muscle, average cross-sectional area of muscle fibre, average number of capillaries in direct contact with a muscle fibre, average capillary contact length with a fibre as a fraction of average fibre circumference and number of capillaries mm² of fibre cross-sectional area [N_A(cƒ)] were 1.16, 0.221, 0.084, 0.015, and −0.137 respectively.
These results show that there is an increase in muscle cross-sectional fibre area and number of capillaries in contact with muscle fibres whereas number of capillaries supplying a unit area of muscle fibre decreases during development. There is development of new capillaries with increase in cross-sectional area of red muscle fibres.     

Characterization of swimming muscle in the Atlantic mackerel, Scomber scombrus L.

Both red and white muscle were removed from juvenile and adult Atlantic mackerel, Scomber scombrus L., for histochemical characterization of the muscle fibre types. Staining of white muscle for myosin ATPase, SDH, NADH diaphorase, GPDH and LDH revealed that these fibres are homogeneous. Red muscle was shown to be heterogeneous, of at least two fibre types recognizable on the basis of myosin ATPase staining with preincubation at a pH of 9·8. These two red types are dispersed throughout the red muscle and are present in both juveniles and adults. Red muscle is located both deep within the myotomes and as a superficial layer of muscle fibres. A third group of muscle fibres, intermediate in nature, was distinguished at the apex of the red muscle 'triangle,' between the epaxial and hypaxial muscle, using NADH diaphorase and myosin ATPase stains. This paper discusses the possibility that functionally different muscle fibres occur in the red swimming muscle of the Atlantic mackerel.     

Growth characteristics of skeletal muscle tissue in Oreochromis niloticus larvae fed on a lysine supplemented diet

The effect of lysine amino acid supplementation on the growth characteristics and morphological pattern of skeletal muscle tissue in Nile tilapia Oreochromis niloticus larvae was evaluated. There were four treatments (T) with increasing levels of lysine supplement (T1 = 0·0%; T2 = 1·1%; T3 = 1·7%; T4 = 4·0%) and one treatment with a commercial diet (T5). In all treatments, morphological and histochemical muscle tissue analyses were similar. Two distinct layers were identified: a superficial red layer, more developed in the lateral line region, formed by fibres with intense to moderate NADH‐TR reaction and strong acid‐stable mATPase activity, and a deep white one, most of the muscle mass, formed by fibres with weak NADH‐TR reaction and strong alkali‐stable mATPase activity. There was an intermediate layer between these two layers with fibres exhibiting either weak acid‐stable or acid‐labile mATPase activity. Body mass increase was significantly higher in T5 than in the lysine treatments (T1–T4). There was no difference in number and diameters of muscle fibres between lysine treatments. In T5, muscle fibre diameter and number were higher. The frequency of red fibres with diameters ≤8 μm was higher in the lysine treatments, and with diameters between 16 and 24 μm, was higher in T5. Most white fibre diameters in T5 were significantly larger than 24 μm and in T1–T4 were between 8 and 16 μm. Cell proliferation was higher in the lysine treatments and muscle growth in T5 was mainly by fibre hypertrophy.     

Posthatch development of the axial musculature of the common dentex Dentex dentex, L (Teleostei)

The common dentex is a promising candidate for Mediterranean aquaculture. The present work is aimed at describing the development of the axial musculature from hatching to postlarval life. Transmission electron microscopy, histochemical (NADH-TR and mATPase) and immunohistochemical techniques (S-58 and TUNEL) have been used. At hatching superficial red and deep white muscles can be distinguished. Presumptive dermomyotome (external) cells are initially located over the superficial red muscle but shortly (2 days) tend to concentrate towards the epaxial and hipaxial limits of the myotome. Then, these cells enter the myotome and spread around and within the white muscle thus being apparently responsible for the stratified hyperplasia of the myotome. Mosaic hyperplasia is activated during the second half of the larval period and initially relies on differentiation of a population of atypical premyoblastic cells (APC). APC are mononuclear cells with euchromatic nuclei, cytoplasms full of thin longitudinally projected tubules, occasional mitochondria and scattered ribosomes. By the end of the larval period these cells tend to disappear, partly due to apoptosis, but postlarval mosaic hyperplasia continues by differentiation of presumptive myosatellite cells. APC are an unexpected and singular finding of this study which deserves more research, so as to further characterize their ancestry, developmental programme and fate. In addition to the white and superficial red muscle fibres, intermediate (pink) and tonic fibres appear during larval metamorphosis. Later, during the early postlarval life, a new type of slow twitch red muscle fibre is differentiated (red adult type).