The histochemical demonstration of myoglobin and succinic dehydrogenase activity in the tibialis anterior muscle of the rabbit

Summary The staining reactions for myoglobin and succinic dehydrogenase activity in the tibialis anterior of the rabbit demonstrate four types of muscle fibre. These may be distinguished by their intensity of staining for myoglobin and the distribution of the mitochondria shown by the dehydrogenase reaction.The large fibres (70–80 m diameter) which contain many mitochondria evenly scattered throughout the fibre contain much myoglobin. Smaller fibres (45–60 m diameter) which show an identical staining reaction for the dehydrogenase reaction contain less myoglobin. This suggests that myoglobin may be present to aid the diffusion of oxygen into muscle fibres.     

A comparative microphotometric study of succinate dehydrogenase activity levels in type I,IIA and IIB fibres of mammalian and human muscles

Summary Activity levels of succinate dehydrogenase (SDH) were determined kinetically by means of comparative microphotometric measurements in situ. Activities were correlated with fibre types classified histochemically according to Brooke and Kaiser (1970). Analyses of tibialis anterior muscles in the mouse, rat, guinea pig, rabbit, cat and the human showed pronounced variations in the activity profiles of type I, type IIA and IIB fibres of these muscles. Large scattering of enzyme activity existed in the three fibre populations. Overlaps of varying extent were found for the SDH profiles between the different muscles. Type I fibres reveal species diffeences in aerobic oxidative capacity. Whereas the majority of the IIB fibres in rabbit muscle tended to be low in SDH activity, the main fraction of this fibre population was characterized by high activities in mouse muscle. Similarly, the IIA fibre populations revealed opposite properties in mouse and rabbit muscles. These extremes as well as intermediate activity patterns indicate that no general scheme exists according to which the histochemically assessable myosin ATPase is correlated with the aerobic oxidative capacity of muscle fibres in various mammalian muscles.     

Regeneration of soleus muscles of rat autografted in toto as studied by electron microscopy

Summary Rat soleus muscles were autografted from right to left legs, and regeneration following necrosis of all original myofibres was studied after 7 to 250 days. The best regenerates were from grafts replacing all calf muscles and sutured to the tendon stumps. After 30 days the size of such regenerates was equal to those from minced gastrocnemius muscles: the cross sectional area of muscle tissue was 30% (1.7 mm²) and the number of fibres was 180% (4500) of normal soleus muscles; the fibre diameters were 10 to 40 m. To increase the number of myoblasts before grafting some muscles were injured by Ringer solution of 70° C and transplanted after 2 days. Nevertheless, this did not influence regeneration.After 7 days clusters of myotubes occurred in the periphery of the muscle. These myotubes originated from myoblasts growing like endothelial cells on the inner face of the persisting basal lamina tubes of necrotic fibres. After 30 days the muscles were vascularized. Fibres formed in a common basal lamina detached and so looked split. Satellite cells of new fibres came from undifferentiated cells associated with myotubes, i.e. from myoblasts. After 30 days and more regenerates contained three sorts of fibres. 1. Thin (5 to 20 m) fibres resembling fetal muscle fibres. They were most prominent after 30 days, and probably not yet innervated. 2. Thin (10 m) degenerating fibres as in long-time denervated muscles. 3. Thick (more than 30 m) mature looking fibres which were innervated and revealed end-plates.Half of the grafts studied after 30 and 60 days contained unmyelinated and myelinated axons which had grown along strands of surviving Schwann cells. After 250 days, only two muscles were studied which both lacked innervation. Almost all regenerates contained muscle spindles, which, however, were not innervated. Within the persisting spindle capsules new muscle fibres had been formed from satellite cells of the former intrafusal fibres.This study was supported by grants from the Danish Medical Research Council, and the National Danish Association against Rheumatic Diseases. I wish to thank Miss U. Hellhammer for valuable technical help and Dr. T. Tobias for correcting my English     

An ultrastructural and histochemical study of the axial musculature in the African lungfish

Summary Red, intermediate, and white axial muscle fibres of African lungfish were studied using histochemical techniques and electron microscopy. Gross dissection revealed the presence of a small wedge of red coloured muscle along the lateral line. This wedge was shown by histochemical demonstrations of lactate and succinate dehydrogenases, of adenosine triphosphatases, and of lipid to be composed of a mosaic of red and intermediate fibres measuring 23.63 and 34.30 m in average diameter, respectively. The bulk of the myotome was composed of white fibres having an average diameter of 67.35 m. Mitochondrial density, capillarity and lipid content were very low for all fibres. These data suggest that the axial musculature is geared primarily for anaerobic function. The mosaic arrangement of fibres, and the lack of a subsarcolemmal band of mitochondria suggests that the lungfish have a muscle organisation that is transitional between lower vertebrates and amphibians.     

Muscle fibre types and metabolism in post-larval and adult stages of notothenioid fish

Summary A histochemical study was carried out on muscle fibre types in the myotomes of post-larval and adult stages of seven species of notothenioid fish. There was little interspecific variation in the distribution of muscle fibre types in post-larvae. Slow fibres (diameter range 15–60 m) which stained darkly for succinic dehydrogenase activity (SDHase) formed a superficial layer 1–2 fibres thick around the entire lateral surface of the trunk. In all species a narrow band of very small diameter fibres (diameter range 5–62 m), with only weak staining activity, occurred between the skin and slow fibre layer. These have the characteristics of tonic fibres found in other teleosts. The remainder of the myotome was composed of fast muscle fibres (diameter range 9–75 m), which stain weakly for SDHase, -glycerophosphate dehydrogenase, glycogen and lipid. Slow muscle fibres were only a minor component of the trunk muscles of adult stages of the pelagic species Champsocephalus gunnari and Pseudochaenichthys georgianus, consistent with a reliance on pectoral fin swimming during sustained activity. Of the other species examined only Psilodraco breviceps and Notothenia gibberifrons had more than a few percent of slow muscle in the trunk (20%–30% in posterior myotomes), suggesting a greater involvement of sub-carangiform swimming at cruising speeds. The ultrastructure of slow fibres from the pectoral fin adductor and myotomal muscles of a haemoglobinless (P. georgianus) and red-blooded species (P. breviceps), both active swimmers, were compared. Fibres contained loosely packed, and regularly shaped myofibrils numerous mitochondria, glycogen granules and occasional lipid droplets. Mitochondria occupied >50% of fibre volume in the haemoglobinless species P. georgianus, each myofibril was surrounded by one or more mitochondria with densely packed cristae. No significant differences, however, were found in mean diameter between fibres from red-blooded and haemoglobinless species. The activities of key enzymes of energy metabolism were determined in the slow (pectoral) and fast (myotomal) muscles of N. gibberifrons. In contrast to other demersal Antarctic fish examined, much higher glycolytic activities were found in fast muscle fibres, probably reflecting greater endurance during burst swimming.     

Tumor necrosis factor-α in macrophages of heart,liver, kidney,and in the pituitary gland

The relationship between myonuclear number, cellular size, succinate dehydrogenase activity, and myosin type was examined in single fiber segments (n=54; 9±3 mm long) mechanically dissected from soleus and plantaris muscles of adult rats. One end of each fiber segment was stained for DNA before quantitative photometric analysis of succinate dehydrogenase activity; the other end was double immunolabelled with fast and slow myosin heavy chain monoclonal antibodies. Mean±S.D. cytoplasmic volume/myonucleus ratio was higher in fast and slow plantaris fibers (112±69 vs. 34±21x10³ m³) than fast and slow soleus fibers (40±20 vs. 30±14x10³ m³), respectively. Slow fibers always had small volumes/myonucleus, regardless of fiber diameter, succinate dehydrogenase activity, or muscle of origin. In contrast, smaller diameter (<70 m) fast soleus and plantaris fibers with high succinate dehydrogenase activity appeared to have low volumes/myonucleus while larger diameter (>70 m) fast fibers with low succinate dehydrogenase activity always had large volume/myonucleus. Slow soleus fibers had significantly greater numbers of myonuclei/mm than did either fast soleus or fast plantaris fibers (116±51 vs. 55±22 and 44±23), respectively. These data suggest that the myonuclear domain is more limited in slow than fast fibers and in the fibers with a high, compared to a low, oxidative metabolic capability.     

Fibre-optic spectrophotometry of immature bovine skeletal muscles and the cellular distribution of myoglobin and succinate dehydrogenase

Summary Samples of diaphragm and pectoralis profundus were taken from nine calves with a range of blood haemoglobin levels of 4 to 8.5 g/100 ml. In both muscles, fibres with strong succinate dehydrogenase activity contained myoglobin, but in the pectoralis there were many fibres with strong alkaline ATPase activity and weak succinate dehydrogenase activity that had low or undetected levels of myoglobin. The whole cross-sectional area of individual fibres was scanned to map the distribution of succinate dehydrogenase activity. Among fibres with similar levels of ATPase activity, those from the diaphragm had greater succinate dehydrogenase activity than those from the pectoralis. Subsarcolemmal succinate dehydrogenase activity was greater than the axial succinate dehydrogenase activity, and radial gradients of succinate dehydrogenase activity were steepest in the diaphragm. For pectoralis fibres with weak ATPase, the mean and the axial succinate dehydrogenase activities were correlated with blood haemoglobin levels (r=0.62 and r=0.61, respectively;P<0.05 with a Student'st-test). Muscle colour was measured directly by fibre-optic spectrophotometry and correlations of absorbance with succinate dehydrogenase activity were obtained. Absorbance at 620 nm 24 h post-mortem was correlated with succinate dehydrogenase activity in pectoralis fibres with weak ATPase (r=0.81;P<0.005).     

Do enzyme activities vary along muscle fibres?

Summary Distribution of succinate dehydrogenase activity along muscle fibres has been studied qualitatively by histochemistry on single microdissected rat muscle fibres and quantitatively by comparative kinetic microphotometry on longitudinal muscle sections. Qualitative staining reactions showed no appreciable variations in enzyme activity along the fibres regardless of fibre type. By quantitative assessment, minor variations were found along fibres but were within the range of the experimental error. These variations are of the same magnitudes as those observed in enzyme activities of pieces of the same fibre by means of quantitative microchemical methods performed in our laboratory (Spamer and Pette 1979; Nemeth et al. 1980a, b). Our results provide evidence that the enzyme levels are the same along the course of a muscle fibre.     

Microphotometric analysis of NADH-tetrazolium reductase and alpha-glycerophosphate dehydrogenase in human quadriceps muscle.

Synopsis In serial cross-sections of human skeletal muscles stained for either NADH-tetrazolium reductase (NADH-TR) or -glycerophosphate dehydrogenase (-GPD), a linear relation was found between the total content of enzyme in a cell (expressed as the thickness of the section) and the absorbance of the formazan reaction product formed. Little variation (<4.8%) was found in the concentration of formazan (absorbance per unit thickness) when the same cell was measured in serial cross-sections of various thicknesses (2–10 m) along a longitudinal distance of at least 200 m along the cell. The reduction in enzyme activity was found to be negligible after aqueous preincubation. A maximum of 10–12% of the formazan produced in the NADH-TR reaction might be the result of nothing dehydrogenase activity, whereas this unspecific reaction might account for up to 20% of the formazan deposited in the -GPD reactions after 30 min incubation. The diffusion of Nitro BT into the tissue during the incubation period was found to be unhindered. The rates of formazan production decreased with increasing incubation time, especially in the -GPD reaction in both fibre types. The ratio of the mean absorbance of the formazan in type I fibres to that in type II fibres (in the same section) was 1.41 (coefficient of variation, 2.5%) in the NADH-TR reaction and 0.68 (coefficient of variation, 3.8%) in the -GPD reaction. These values were not affected either by variations in the incubation time (5–40 min) or by the thickness of the section (2–8 m). The concentrations of NADH-TR and -GPD seem to be constant along the length of the muscle fibre. The histochemical reactions reported, together with measurements of the thickness of the sections, seem suitable for the microphotometric quantification of the two enzymes in single fibres of human skeletal muscles.     

Intrafibre distribution of succinate dehydrogenase in cat tibialis anterior motor units.

Using isolated ventral root filament stimulation and glycogen depletion techniques, 14 motor units from the cat tibialis anterior were studied. Based on their mechanical properties, the units were classified as either slow-fatigue resistant, fast-fatigue resistant, fast-fatigue intermediate, or fast-fatigable. Quantitative histochemical and computer assisted image analysis techniques were used to determine the activity of succinate dehydrogenase in a population of fibres in each unit. In addition, the intrafibre distribution of succinate dehydrogenase activity was measured in those same fibres by calculating the enzymatic activity of circumferential layers every 0.5 microns starting from the fibre edge to its centre. It was established that enzymatic activity and radial distance were linearly related in the fibres. A range in succinate dehydrogenase activity (mean coefficient of variation, 29%) was observed among the fibres of a unit. In contrast, the intrafibre distribution of that activity was rather consistent (mean variation, 4%) across the fibres of a unit. Further, the intrafibre distribution was similar among the fibres of units classified as the same type. However, the intrafibre distribution was disparate among the different unit types. These data suggest that the intrafibre distribution of mitochondrial enzymes may contribute to the mechanical properties of a motor unit. In this regard, a hypothesis is proposed that describes how the absolute activity of a mitochondrial enzyme, and the intrafibre distribution of that activity, may interactively contribute to the fatigue resistance of a unit.     

Histoenzymatic characterization of sub-types of type I fibres in fast muscles of rats.

The histochemical activities of succinic dehydrogenase (SDH), myofibrillar Adenosine triphosphatase (ATPase) and alpha glycerophosphate dehydrogenase were studied in serial sections of rat vastus lateralis (red) (RVL), gastrocnemius and diaphragm muscles. Three main fibre-types were distinguished. The "Type I" fibres of RVL and gastrocnemius muscles fell into two distinct groups: one category--"Type IA" showed very low ATPase activity. The second category of "Type IB" fibres displayed moderate ATPase reaction. The "Type IA" fibres were divisible into two sub-groups when tested for SDH reaction. "Type IA1" fibres possessed a homogenous distribution of diformazan granules throughout the fibre: "Type IA2" fibres displayed characteristic "moth-eaten" pattern of diformazan localization. The diaphragm muscle did not show either "Type IB" or "Type IA2" varieties. The great majority of TypeI fibres were sub-type IA1 in the three fast muscles studied. It is also demonstrated here that an inherent heterogeneity exists between Type I filores of diaphragm and leg muscles in regard to alpha-GPD localization. This histochemical data emphasizes the fact that subdivision of TypeI striated muscle fibres of mammalian animals into two sub-types is only approximate and that a further subcategorization is possible.     

The fine structure of red and white myotomal muscle fibres of the coalfish (Gadus virens)

Summary The fine structure of the red and white myotomal muscles of a marine teleost, the coalfish Gadus virens, has been examined and ultrastructural measurements and analyses carried out. The sarcomere lengths of the red and white fibres were found to be 1.60 minimum, 1.82 maximum and 1.70 minimum, 1.85 maximum, respectively. No significant difference was found between the red and white fibres in their percentage of sarcoplasmic reticulum and T system. Both were found to have regularly occurring triads at the Z disk level, to have distinctive M lines and to be multiply innervated. Ultrastructurally the two fibres can be distinguished by the thicker Z line and more abundant mitochondria of the red fibre, and by the ribbon-shaped peripheral myofibrils of the white fibres. The structure of the fibres in these two types of muscle is discussed in relation to their possible role in swimming.This work was supported by a research grant from the National Environmental Research Council.     

The effect of strength training on estimates of mitochondrial density and distribution throughout muscle fibres

The purpose of this study was to investigate the effect of strength training (12 weeks, 3 days/week, four lower-body exercises) of young individuals (mean age 23.6 years) on estimates of mitochondrial distribution throughout muscle fibres. A control group (mean age 21. 7 years) was followed simultaneously. Skeletal muscle biopsy samples were obtained from the vastus lateralis, pre- and post-training. The regional distribution of subsarcolemmal and intermyofibrillar mitochondrial populations was determined using quantitative histochemical staining of succinate dehydrogenase (SDH) in type I and II muscle fibres. Strength training resulted in significant increases of 26% and 28% in the cross-sectional area of type I and II fibres, respectively (P < 0.05). Overall SDH activity decreased by 13% with strength training (P < 0.05). The decrease in SDH activity with strength training between fibre types and between subsarcolemmal and intermyofibrillar regions of muscle fibres was not different. Fibre area and SDH activity was unchanged in the control group. We conclude that the muscle hypertrophy associated with strength training results in reduced density of regionally distributed mitochondria, as indicated by the reduction in the activity of SDH.     

Subsarcolemmal mitochondria and capillarization of soleus muscle fibers in young rats subjected to an endurance training

Summary Rats, 6 weeks old, were subjected to a program of endurance running for 3, 6 and 12 weeks. 0.5 to 0.8 m thick sections of Epon embedded soleus muscles were studied with morphometric methods.In cross-sections the area occupied by subsarcolemmal mitochondria was independent of the age, but was 53% higher after 12 weeks of training. The mean depth of the zones with subsarcolemmal mitochondria increased only 15% to about 0.9 m. Thus, the subsarcolemmal mitochondria showed a pronounced spreading at the muscle fiber surface in trained muscles. — The number of capillaries per fiber decreased slightly in controls and increased not significantly in trained muscles.It is concluded that the subsarcolemmal mitochondria supply the energy for the active transport of metabolites through the sarcolemma in oxidative muscle fibers, and that they are the limiting factor for endurance performance of the soleus muscle fibers because the changes in the capillarization were only small. It is suggested that the subsarcolemmal and the interfibrillar mitochondria have different functions and may therefore represent different types of mitochondria which can be distinguished by their morphology as well as by their biochemical properties.     

The ultrastructure and innervation of muscles controlling chromatophore expansion in the squid,Loligo vulgaris

Squid chromatophores are organs of colour change, consisting of a pigment sac opened by contraction of 10–24 radial muscle fibres. The ultrastructure and innervation of these muscle fibres were examined by electron microscopy and diagramatic reconstructions made on the basis of serial ultra-thin sections. At the proximal end of the fibre, nearest the pigment sac a cortical myofilament zone surrounds 2 cores containing mitochrondria; further along the fibre these merge to form one central core. The myofilament zone forms a groove containing a nerve bundle consisting of 2 to 4 axons per muscle fibre. The axons are surrounded by glial cell processes, and either originate from a neighbouring fibre, or join the fibre at some point along its length. Axons twist around each other, forming a series of synapses with the muscle fibre. As many as 6–37 synapses exist along the length of each muscle fibre; the mean synapse interval is 9.05 m, but the largest may be 123 m. At the distal end of the muscles, the nerve is located towards the middle of the fibre, which it penetrates as the muscle splits up. Electron-lucent vesicles are present in all synaptic regions, but electron-dense vesicles are only found towards the distal end of the fibre. There is thus a possibility that more than one neurotransmitter is present in the nerves innervating chromatophores. Electron-lucent and dense-cored vesicles are not colocalised.This work was carried out during the tenure of a BBSRC CASE studentship     

Clycerolphosphate oxidase and succinate dehydrogenase activities in IIA and IIB fibres of mouse and rabbit tibialis anterior muscles

Summary Quantitative microphotometric measurements of two mitochondrial flavoproteins, glycerolphosphate oxidase (GP-OX) and succinate dehydrogenase (SDH), were performed on serial sections of mouse and rabbit tibialis anterior (TA) muscles in order to study the distribution of these two enzymes and their activity ratios in IIA and IIB fibres. The measurements showed a large scatter of the two enzyme activities in these two myosin-based fibre types. In rabbit TA, IIA and IIB fibres have similar GP-OX activities, whereas generally IIA fibres have higher SDH activities than IIB fibres. An inverse distribution of the two enzymes exists in mouse muscle. Generally, IIA fibres of mouse TA display low SDH and IIB fibres high SDH activities. The mean activity of GP-OX is slightly higher in IIA than in IIB fibres of mouse TA. Since measurements of both enzymes were taken in the same fibres, the ratio of their activities in each fibre could be evaluated. The SDH/ GP-OX activity ratios vary significantly between the two fibre populations both in rabbit and in mouse. The ratio is high in IIA and low in IIB fibres of rabbit TA, whereas it is low in IIA and high in IIB fibres of mouse TA.     

Glycerolphosphate oxidase and succinate dehydrogenase activities in IIA and IIB fibres of mouse and rabbit tibialis anterior muscles

Quantitative microphotometric measurements of two mitochondrial flavoproteins, glycerolphosphate oxidase (GP-OX) and succinate dehydrogenase (SDH), were performed on serial sections of mouse and rabbit tibialis anterior (TA) muscles in order to study the distribution of these two enzymes and their activity ratios in IIA and IIB fibres. The measurements showed a large scatter of the two enzyme activities in these two myosin-based fibre types. In rabbit TA, IIA and IIB fibres have similar GP-OX activities, whereas generally IIA fibres have higher SDH activities than IIB fibres. An inverse distribution of the two enzymes exists in mouse muscle. Generally, IIA fibres of mouse TA display low SDH and IIB fibres high SDH activities. The mean activity of GP-OX is slightly higher in IIA than in IIB fibres of mouse TA. Since measurements of both enzymes were taken in the same fibres, the ratio of their activities in each fibre could be evaluated. The SDH/GP-OX activity ratios vary significantly between the two fibre populations both in rabbit and in mouse. The ratio is high in IIA and low in IIB fibres of rabbit TA, whereas it is low in IIA and high in IIB fibres of mouse TA.     

Inter- and intraspecies comparisons of fibre type distribution and of succinate dehydrogenase activity in type I, IIA and IIB fibres of mammalian diaphragms

Fibre types in the costal region of the diaphragm muscle of several mammalian species with widely different respiratory rates were examined microphotometrically for succinate dehydrogenase (SDH) activity. Mean activities indicated no significant (p greater than 0.05) difference between the type I and IIA fibres for any of the species examined. SDH activities in type IIB fibres were significantly lower (p less than 0.05) than either the type I or type IIA fibres in the cat, guinea pig, rat and rabbit whereas in the mouse no difference was found. The dog had no classical type 1B fibres. Analysis of the distribution of SDH activities by fibre type indicated a wide scattering of scores with no distinct separation between fibre types. Large differences in SDH activity were noted between species. Mean SDH activities were highest in the mouse and rat, intermediate in the rabbit and guinea pig and lowest in the cat and dog. These data suggest an association between respiratory rate and aerobic oxidative potential of the various fibre types in diaphragms of the species examined.     

„Rote“ Muskelfasern

Zusammenfassung Die Fasern des roten und langsamen M. soleus von Ratte, Kaninchen und Katze und des roten, jedoch schnellen, M. vocalis des Kaninchens wurden licht- und elektronenmikroskopisch untersucht und mit den verschiedenen Fasertypen aus dem M. tibialis anterior der Ratte und dem M. gastrocnemius des Kaninchens und der Katze verglichen. M. soleus und M. vocalis (einschließlich M. thyreoarytenoideus) enthalten nur einen mitochondrienreichen Fasertyp. Im schnellen M. vocalis ist der Z-Streifen schmal (50–60 nm), das sarcoplasmatische Reticulum ist gut entwickelt. Die Anordnung von Reticulum und Mitochondrion ist ähnlich wie in Herzmuskelzellen. Wie auch in anderen langsamen Muskeln verschiedener Tiere ist im M. soleus der Z-Streifen breit (100–120 nm), Triaden und Reticulum sind selten, und die Filamente bilden unregelmäßige Areale anstelle von Fibrillen. Hierin gleichen die Fasern des M. soleus den (mitochondrienreichen) C-Fasern eines entsprechenden gemischten Muskels; dagegen zeigen die Zwischentyp-(B-)Fasern schmale Z-Linien (50–70 nm), isodiametrische Fibrillen und mehr Triaden als die C-Fasern. Entgegen der bisherigen Vermutung, die auf der histochemischen Zuordnung der SoleusFasern zum Typ B und der Vocalis-Fasern zum Typ C beruht, ist daher anzunehmen, daß die langsamen motorischen Einheiten eines gemischten Muskels aus C- und nicht aus B-Fasern bestehen.In einigen Muskeln sind die Sarcomere der C-Fasern länger als die der B-(und A-) Fasern. Im M. tibialis anterior der Ratte verschwindet der Unterschied von 8,5% bei 2,6 m Sarcomerlänge bei der Dehnung auf 2,8 m mittlere Sarcomerlänge; vermutlich weil die Ruhedehnungskurve zunehmend steiler wird. Die isometrische Extraspannung im Tetanus ist bei 120% der Ruhelänge, d.h. bei 2,7 m Sarcomerlänge. am größten. Daher muß bei 2,6 m mittlerer Sarcomerlänge die Kraft der C-Fasern die der B-Fasern übertreffen.Rote Muskeln sind besser vaskularisiert als weiße Muskeln. Für die Mm. soleus und gastrocnemius der Katze verhalten sich die Kapillardichten (Kapillaren/mm² Muskelfaserquerschnitt) wie 2,7:1. Dieser Wert entspricht dem Verhältnis zwischen den Größen für die Durchblutung (ml/min × 100 g) in Ruhe und bei maximaler Gefäßerweiterung.

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Redmuscle fibres

Summary Muscle fibres of the red and slow contracting soleus of rat, rabbit and cat and of the red however fast contracting thyreoarytenoid of rabbit are compared with different fibre types in the anterior tibial muscle of rat and in the gastrocnemius of rabbit and cat. With respect to fibre types soleus and thyreoarytenoid (including m. vocalis) are homogeneous and both being rich in mitochondria. The fast thyreoarytenoid shows a narrow Z-line (50–60 nm) and a well developed sarcoplasmic reticulum. The pattern of reticulum and mitochondria resembles more that of heart muscle cells than of skeletal muscle fibres. Like many slow contracting muscles of different animals the soleus fibres display a wide Z-line (100–120 nm), few triads, little reticulum and irregularly shaped areas of myofilaments instead of fibrils. In that soleus fibres equal fibres of type C (rich in mitochondria) in a corresponding heterogeneous muscle, whereas intermediate (type B) fibres reveal narrow Z-lines (50–70 nm), isodiametrically shaped myofibrils and more triads than C-fibres. Therefore it is far more likely that the slow motor units of a mixed muscle consist of C-fibres than of B-fibres. This is at variance with the histochemical designation of soleus fibres as type B and thyreoarytenoid fibres as type C.In some muscles in C-fibres the sarcomeres are longer than in B-(and A-)fibres. In the anterior tibial muscle of rat this difference is 8.5% at a mean sarcomere length of 2.6 m, and disappears at a mean length of 2.8 m, probably due to the steeper slope of the length tension diagram at rest. Since the isometric extratension in a tetanus is highest at 120% resting length (corresponding to about 2.7 m sarcomere length), the force of C-fibres exceeds that of B-fibres at 2.6 m but not at 2.8 m sarcomere length.Red and white muscle differ with respect to vascularisation. The relation between the densities of capillaries in soleus and gastrocnemius of cat is 2.7:1 and equals the relation between the blood flows through these muscles during rest and maximum vasodilatation.

Herrn Prof. Dr. Bargmann nachträglich zum 65. Geburtstag.     

Quantitative analysis of muscle breakdown during starvation in the marine flatfish Pleuronectes platessa

Summary The present study describes the effects of starvation for a duration of four months on the ultrastructure of skeletal muscles from the marine flatfish (Pleuronectes platessa L.). Starvation is associated with a decrease in resting metabolic rate from 20.1±2.2 to 11.6±1.5mg-O₂/kg/h (P<0.05) and muscle wasting. Median fibre size fell from 700 m² to 500 m² in intermediate (fast oxidative) and from 1,800 m² to 600 m² in starved, white (fast-glycolytic) muscle fibres. In contrast, median fibre size in red (slow oxidative) muscle remained within the range 300–400 m². The fraction of red fibre volume occupied by myofibrils (58.6%) and mitochondria (24.5%) did not change significantly with starvation. There was, however, a decrease in stored lipid (10.7% to 3.2%) and an alteration in the structure of the cristae in mitochondria from red muscle.Atrophy of white muscle fibres is associated with a decrease in both the diameter and fractional volume occupied by myofibrils (85.7% to 61.9% P < 0.01). In a high proportion of white fibres peripheral degeneration of Z-discs is evident causing an unravelling of the thin filament lattice. It is suggested that this allows a partial decrease in myofibril diameter and hence the maintenance of contractile function in muscle from starved fish. In severely degenerating white fibres, disorganised thick and thin filaments and numerous multimembrane lysosome-like vesicles are observed.Starvation results in an increase in the average content of mitochondria in white fibres from 2.2 to 6.7% (P<0.01). In fed plaice mitochondria constitute less than 1% of the volume of the white fibre in 43.5% of the fibres. The proportion of white fibres containing more than 6% mitochondria increases from 6.5% to 58% with starvation.