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.     

Subgrouping of fast twitch fibres in skeletal muscles of man

Summary Subgroups of fast twitch (FT) muscle fibres were identified by histochemical techniques on muscle samples of m. quadriceps femoris from six male and six female subjects, who had been assigned to three groups; untrained, active and well trained (endurance runners). Slow twitch (ST) and FT fibres were initially identified using the histochemical stain for myofibrillar ATPase, preincubated at pH 10.3 and 4.3. Three people, working independently, then identified the subgroups FTa and FTb on the basis of the staining intensity for only one of the following reactions: -glycerophosphate dehydrogenase, -GPD; NADH tetrazolium reductase, NADH-TR; and myofibrillar ATPase preincubated at pH 4.6, ATPase (4.6). FTa fibres were clearly distinguished from the darker staining FTb fibres using the ATPase (4.6) reaction. Differences in the staining within the FT fibres using the -GPD and NADH-TR reactions were more subtle, and differences between subject groups were evident. The percentage of FTa fibres was overestimated for the untrained and underestimated for the well trained subjects using NADH-TR. With the -GPD stain the percentage of FTa fibres was generally underestimated. When the data for all three stains were compared, only 27% of the FT fibres were placed in the same subgroups. These results demonstrate that the subgrouping of FT fibres in man is more reliable using the differences in pH sensitivity for the myofibrillar ATPase reaction compared to histochemical reactions for oxidative or glycolytic enzymes.     

Myosin light chain patterns of individual fast and slow-twitch fibres of rabbit muscles

Summary Single muscle fibres were isolated by microdissection from freeze-dried samples of rabbit psoas and soleus muscles. The individual fibres were typed according to qualitative histochemical reactions for succinate dehydrogenase or NADH-tetrazolium reductase and for alkaline Ca²⁺-activated myofibrillar myosin ATPase after acid or alkaline preincubation. Methods are described for electrophoretic analysis by means of polyacrylamide disc electrophoresis in the presence of SDS of total myofibrillar proteins in single fibres after pre-extraction of soluble proteins. Fast-twitch white fibres revealed a myosin light chain pattern characteristic of fast-type myosin with three light chains of apparent molecular weights of 22,300 (LC₁), 18,400 (LC₂) and 16,000 (LC₃). Fast-twitch red fibres were indistinguishable in this respect from fast-twitch white fibres and showed an identical pattern of myosin light chains. Slow-twitch fibres could be characterized by a myosin light chain pattern typical of myosin of slow-twitch muscles with peptides of the apparent molecular weights of 23,500 (LC_1Sa), 23,000 (LC_1Sb) and 18,500 (LS_2S). Slow-twitch fibres isolated from soleus as well as from psoas muscle were indistinguishable with regard to their myosin light chain patterns, thus suggesting that fibres of the same histochemical type correspond in their myosin light chain patterns irrespective of their origin from different muscles.Dedicated to the memory of Ernest Gutmann who has contributed so much to our knowledge on differentiation of muscle and who died on August 6, 1977     

Histochemical heterogeneity of intrafusal muscle fibres in slow and fast skeletal muscles of the rat

Summary Intrafusal muscle fibres of the slow soleus (Sol) and fast vastus lateralis (VL) muscles of the rat were studied histochemically. Serial transverse sections were incubated for the localization of succinate dehydrogenase (SDH), alpha glycerophosphate dehydrogenase (GPD) and adenosine triphosphatase (ATPase). The latter was examined further after preincubation in acidic solution held at either low or room temperature (R_T). The bag₂ intrafusal fibres in both muscles displayed high regular and acid stable ATPase, but low SDH and GPD activities. Bag₁ intrafusal fibres showed low to moderate regular ATPase, a regional heterogeneity after R_T acid preincubation (low activity in juxtaequatorial and high in polar zones), moderate SDH, but low GPD reactions. In both muscles the chain fibres usually exhibited high ATPase for both regular and cold acid preincubated reactions, but usually low activity after R_T acid preincubation; they had high SDH but variable GPD activities. In Sol muscle, however, approximately 25% of spindles contained chain fibres that showed high acid-stable ATPase reaction after both cold and R_T acid preincubation. In contrast, chain fibres in some VL spindles had a characteristically low ATPase reaction even after cold acid preincubation. This study, therefore, has delineated the existence of an inherent heterogeneity among chain fibres (with respect to their histochemical reactions) in muscle spindles located within slow and fast muscles and also between those found within populations of either Sol or VL muscle spindles.     

Extraocular muscles in the lamprey, Lampetra fluviatilis L. I. Muscle fibres

Six extraocular muscles of the river lamprey, Lampetra fluviatilis L., were studied with the light and electron microscope. On the basis of morphology and histochemistry three types of muscle fibres were distinguished: thin, thick mitochondria-rich and thick multifibrillar fibres. In the thin fibres, 2.8-22.4 microns in diameter, myofibrils are distributed peripherally and show strong ATPase activity. The mitochondria are located paraxially. In the thick mitochondria-rich fibres, 19.4-31.0 microns in diameter, myofibrils are also located peripherally, whereas the central part of the fibre is densely packed with very numerous mitochondria possessing tubular cristae. Thick multifibrillar fibres, with a diameter similar to that of the former type, contain thin myofibrils scattered over the entire cross-section of the fibre. The activity of myofibrillar ATPase is lower in both types of thick fibres than in the thin ones. The tubules of the T system were observed frequently only in the thick multifibrillar fibres. The extraocular muscles of the lamprey are composed of large quantities of muscle fibres. Thin and thick fibres do not form separate layers, but are more or less uniformly distributed throughout the muscle. Many muscle fibres show structural features suggesting their degeneration.     

Fatigue and contraction of slow and fast muscles in hypokinetic/hypodynamic rats

This investigation examined the effects of hypokinesia/hypodynamia (H/H) on fatigability and contractile properties of rat soleus (S) and gastrocnemius (G) muscles. Whole-body suspension for 1 wk was used to eliminate hindlimb load-bearing functions and simultaneously permit voluntary isotonic contractions. Train stimulations (45/min, 16 min) resulted in significantly (P less than 0.05) faster rates of fatigue to lower asymptotes in G from H/H rats. Fatigue in the S was minimal at this stimulation frequency and differences between H/H and control animals were not significant. Contractile properties (twitch and tetanic) were measured before and after train stimulations. H/H suspension resulted in an increased twitch tension in G. However, H/H did not change train or tetanic tensions per gram or other G contractile properties. Peak twitch, train, and tetanic tensions, time to peak tension, one-half relaxation time, and twitch and tetanic peak rates of tension development and decline were unchanged by H/H in S muscles. These results indicate that 1 wk of H/H-induced muscle atrophy significantly increases fatigability in G but does not effect contractile properties of fast-twitch (G) or slow-twitch (S) muscles.     

Type IIC fibres in certain muscles of the adult rat (sedentary and exercised)

Samples were taken, at fixed levels, of the vastus lateralis, the caput lateralis of the gastrocnemius muscle and the longissimus lumbaris of 72 Wistar rats which were either sedentary or subjected to various exercise schedules. The samples were analyzed using the histochemical technique of myosin ATPase (m-ATPase) after preincubation at pH 4.2, and the fibre-types I, II (IIA and IIB) and IIC were identified, calculating the percentage of type IIC fibres as well as their minimum diameter. The percentages of these IIC fibres found in the red and mixed parts of the gastrocnemius (caput lateralis) and the longissimus lumbaris were between 0.7% and 2.6%. However, their presence was not detected in the vastus lateralis or in the white part of the gastrocnemius (caput lateralis). The lack of differences in this fibre type between the males and females of the population was shown statistically. Likewise, no significant modification of the IIC fibres between sedentary and exercised animals was seen. With regard to fibrillar size, females showed a smaller minimum diameter than males, the results showing a small increase in the size of these fibres in both sexes after exercise, although in most cases this was not statistically significant.     

Lactate dehydrogenase isozymes in type I,IIA and IIB fibres of rabbit skeletal muscles

Summary Lactate dehydrogenase (LDH) isozyme patterns were analysed by polyacrylamide (PAA) slab gel electrophoresis in extracts prepared from various rabbit skeletal muscles of defined fibre composition and by PAA microelectrophoresis of microdissected, histochemically typed single muscle fibres. The results obtained by electrophoresis of whole muscle extracts generally agreed with the data obtained from single fibre electrophoresis, i.e. the LDH isozyme pattern corresponded to that of the predominant fibre type. Type I Fibres from soleus and semitendinosus muscles were characterized by a unique pattern of all 5 LDH isozymes with a predominance of LDH-1, 2 and 3. The major fraction (80%) of the type II fibres from extensor digitorum longus and tibialis anterior muscles contained only LDH-5 (M₄). About 20% of the type II fibres contained in addition to LDH-5 small amounts of LDH-4 and LDH-3. The fraction of fibres containing LDH-5, LDH-4, and LDH-3 was similar (ca. 20%) in the histochemically defined IIA and IIB subpopulations In view of the fact that the major fractions of rabbit IIB fibres display low and of IIA fibres high aerobic oxidative capacities (Reichmann and Pette 1982), these data indicate that the expression of the H-subunit of LDH is not correlated with the aerobic-oxidative capacity of the fibre. It also appears not to be correlated with the presence of different myosin isoforms in IIA and IIB fibres.     

Alteration of regulatory enzyme activities in fast-twitch and slow-twitch muscles and muscle fibres in low-intensity endurance-trained rats

The effect of progressive, low-intensity endurance training on regulatory enzyme activities in slow-twitch (ST) and fast-twitch (FT) muscle fibres was studied in 32 rats. Of those rats 16 were trained on a treadmill at a running speed of 10m · min^–1 5 days a week over an 8-week period. Running time was progressively increased from 15 min to 2 h · day^–1. Of the rats 4 trained and 4 sedentary rats were also subjected to acute exhausting exercise. Enzyme activities of phosphofructokinase 1 (PFKI) from glycolysis, -ketoglutarate dehydrogenase (-KGDH) from the Krebs cycle and carnitine palmitoyltransferase (CPT I and II) from fatty acid metabolism in soleus, tibialis anterior and gastrocnemius muscles were measured in trained and sedentary rats. Enzyme activities of individual ST and FT fibres were measured from the freeze-dried gastrocnemius muscle of 8 trained and 8 sedentary rats. In the sedentary rats the activity of PFK1 in tibialis anterior and soleus muscles was 141% and 41% of the activity in gastrocnemius muscle, respectively. The activity of -KGDH in tibialis anterior and soleus muscles was 164% and 278% of the activity in gastrocnemius muscle, respectively. The activity of CPT I in tibialis anterior and gastrocnemius muscles were at the same level, but in soleus muscle the activity was 127% of that in mixed muscle. Endurance training increased enzyme activities of -KGDH and CPT I significantly (P < 0.05) in gastrocnemius muscle but not in soleus or tibialis anterior muscle. After training both -KGDH and CPT II activities were elevated significantly (P < 0.05) in the ST fibres of gastrocnemius muscle, whereas in FT fibres only -KGDH was increased. For PFK1 activity no significant change was observed in ST or FT fibres. After acute exercise, activities of mitochondrial enzymes -KGDH and CPT I tended to be elevated in all muscles. Thus, low-intensity endurance training induced significant peripheral changes in regulatory enzyme activities in oxidative and fatty acid metabolism in individual ST or FT muscle fibres.     

Denervation and reinnervation of fast and slow muscles. A histochemical study in rats.

A histochemical study, using myosin-adenosine triphosphatase activity at pH 9.4, was conducted in soleus and plantaris muscles of adult rats, after bilateral crushing of the sciatic nerve at the sciatic notch. The changes in fiber diameter and per cent composition of type I and type II fibers plus muscle weights were evaluated along the course of denervation-reinnervation curve at 1, 2, 3, 4 and 6 weeks postnerve crush. The study revealed that in the early denervation phase (up to 2 weeks postcrush) both the slow and fast muscles, soleus and plantaris, resepctively, atrophied similarly in muscle mass. Soleus increased in the number of type II fibers, which may be attributed to "disuse" effect. During the same period, the type I fibers of soleus atrophied as much or slightly more than the type II fibers; whereas the type II fibers of plantaris atrophied significantly more than the type I fibers, reflecting that the process of denervation, in its early stages, may affect the two fiber types differentially in the slow and fast muscles. It was deduced that the type I fibers of plantaris may be essentially different in the slow (soleus) and fast (plantaris) muscles under study. The onset of reinnervation, as determined by the increase in muscle weight and fiber diameter of the major fiber type, occurred in soleus and plantaris at 2 and 3 weeks postcrush, respectively, which confirms the earlier hypotheses that the slow muscles are reinnervated sooner than the fast muscles. It is suggested that the reinnervation of muscle after crush injury may be specific to the muscle type or its predominant fiber type.     

Peripheral pathway of proprioceptive fibres from feline extra-ocular muscles. I. A histological study.

The findings of the previous study (1976) involving orbital operations in 12 cats have been confirmed in this study involving intracranial operations in 20 more cats. The perikarya of origin of afferent fibres from feline extra-ocular msucles have been clearly localised to the trigeminal mesencephalic nucleus. The functional subdivision in the nucleus that was noted earlier has been reaffirmed. Thus the caudal or pontine part was the location of cell bodies from the lateral rectus muscle, the intermediate part contained those from the superior oblique, while the other muscles were represented by cell bodies in the rostral part, there being some degree of overlap in the last two zones. In every instance the representation was shown to be bilateral and the total ratio of cellular representation was in the region of 4:1 (ipsilateral-contralateral). The peripheral pathway of the proprioceptive fibres has been shown to be exclusively along the oculomotor, trochlear and abducent nerves which are therefore sensorimotor.     

Differentiation of slow and fast muscles in chickens

1. The development of the characteristic histochemical appearance of the slow anterior latissimus dorsi (ALD) and fast posterior latissimus dorsi (PLD) was studied in chickens during embryonic development as well as during regeneration of minced muscle. 2. During embryonic development the activity of the oxidative enzyme succinic dehydrogenase (SDH) is higher in the slow ALD muscle already at 16 days of incubation. At this time the fast PLD has a higher activity of the glycolytic enzyme, phosphorylase. Although the histochemical appearance of the two types of muscle is already different at 16 days, their contractile speeds are still similar. No difference in myosin ATP-ase was found in the two muscles in young embryos but in 20-day old embryos the two muscles became distinctly different when stained for this enzyme. 3. When PLD muscles in hatched chickens redeveloped during regeneration in place of ALD the histochemical characteristics of the regenerated muscle resembled ALD, and when ALD regenerated in place of PLD it resembled PLD. 4. It is concluded that the histochemical characteristics of slow and fast muscles become determined during early development, even before any difference in contractile properties can be detected and that they are determined by the nerve.     

Development of fast singing muscles in a katydid

In males of the katydid Neoconocephalus robustus, mesothoracic wings are used in flight (wing stroke frequence = 20 Hz) and stridulation (200 Hz), while the metathoracic wings are used in flight alone. Most mesothoracic wing muscles produce much briefer isometric twitches than metathoracic counterparts. The mesothoracic first tergocoxal muscle (TCX1) has a twitch duration (onset to 50% relaxation, 35 degrees C) of 6-8 ms and the metathoracic TXC1 a twitch duration of 12-15 ms. The TCX1 muscles from animals one and two instars from adulthood produce twitches similar in duration to those of the adult metathoracic TCX1. The twitch duration of the mesothoracic TCX1 acquires its adult brevity gradually over the first 5 days of adult life. Both TCX1 muscles increase greatly in size and mitochondrial content around the time of the terminal molt. During this period the mesothoracic TCX1 develops narrower myofibrils and a smaller ratio of fibril volume to sarcoplasmic reticulum volume than is characteristic of the metathoracic TCX1. Changes in the ultrastructure of the mesothoracic TCX1 precede changes in contraction kinetics around the time of the terminal molt so that there is not a strict correlation between muscle structure and performance during the period of rapid growth.     

Growth hormone, IGF-I, and exercise effects on non-weightbearing fast muscles of hypophysectomized rats

Grossman, Elena J., Richard E. Grindeland, Roland R. Roy,Robert J. Talmadge, Juliann Evans, and V. Reggie Edgerton. Growth hormone, IGF-I, and exercise effects on non-weight-bearing fast musclesof hypophysectomized rats. J. Appl.Physiol. 83(5): 1522-1530, 1997.The effects ofgrowth hormone (GH) or insulin-like growth factor I (IGF-I) with orwithout exercise (ladder climbing) in countering the effects ofunweighting on fast muscles of hypophysectomized rats during 10 days ofhindlimb suspension were determined. Compared with untreated suspendedrats, muscle weights were 16-29% larger in GH-treated and5-15% larger in IGF-I-treated suspended rats. Exercise alone hadno effect on muscle weights. Compared with ambulatory control, themedial gastrocnemius weight in suspended, exercised rats was largerafter GH treatment and maintained with IGF-I treatment. The combinationof GH or IGF-I plus exercise in suspended rats resulted in an increasein the size of each predominant fiber type, i.e., types I, I+IIa andIIa+IIx, in the medial gastrocnemius compared with untreated suspendedrats. Normal ambulation or exercise during suspension increased theproportion of fibers expressing embryonic myosin heavy chain inhypophysectomized rats. The phenotype of the medial gastrocnemius wasminimally affected by GH, IGF-I, and/or exercise. These resultsshow that there is an IGF-I, as well as a GH, and exercise interactiveeffect in maintaining medial gastrocnemius fiber size in suspendedhypophysectomized rats.

     

大鼠骨骼肌快肌肌钙蛋白T的同工型

骨骼肌快肌的收缩主要是由钙离子通过肌钙蛋白所调节控制。这些肌钙蛋白位于肌纤维之中。肌蛋白包括肌钙蛋白T、肌钙蛋白C、肌钙蛋白I。采用双向聚丙烯酰胺凝胶电泳和免疫学技术,对大鼠胚胎、新生大鼠和成年大鼠的骨能肌快肌肌钙蛋白T的同工型进行了研究。在成年大鼠的骨能肌快肌中,发现了10种肌钙蛋白T同工型。在大鼠胚胎和新生大鼠的骨能肌中,发现了7种肌钙蛋白T同工型。作为不同动物、不同发育阶段和不同组织发育的特殊标记,这些肌钙蛋白T同工型具有重要意义[动物学报49(3)：362—369,2003]。     

Antennal muscles and fast antennal movements in ants

The antennal movements of eight ant species (subfamilies Ponerinae, Myrmicinae, and Formicinae) are examined by high-frequency videography. They show a wide range of antennal velocities which is generated by antennal muscles composed of particularly diverse muscle fibers. Fiber diameter, sarcomere length and histochemically assessed myosin ATPase activity suggest that some thin fibers are fairly slow, while the bulk of antennal muscle fibers show intermediate or fast properties. These morphological properties correlate with the antennal movement velocities measured for the respective species. Based on their morphology, the fibers that generate the fast antennal retraction in some trap-jaw ants appear particularly fast and comprise the shortest sarcomeres yet described (1.1 μm). Accepted: 2 January 1997