Fast-twitch Posterior Latissimus Dorsi Research Articles

Denervation of Chicken Skeletal Muscle Causes an Increase in Acetylcholinesterase mRNA Synthesis

We have examined the changes in enzymatic activity and the levels of transcripts for AChE following denervation of chicken skeletal muscle. Quantitation of RNA blots indicates that AChE transcripts are increased following denervation. AChE transcripts increased ∼17-fold in the fast-twitch posterior latissimus dorsi muscle and ∼4-fold in the tonic anterior latissimus dorsi muscle 10 days after denervation of adult chickens. Both AChE transcript levels and enzyme activity increased in parallel for the two muscles. AChE transcripts also increased ∼4-fold in the shank muscles of 2-day-old chicks following denervation. Transcript synthesis, measured by run-on transcription, increased ∼3-fold in these denervated muscles. These results suggest that the increase in AChE transcripts following denervation in the chicken is due, at least in part, to an increase in the rate of its synthesis.

Effects of Electrical Stimulation on Molecular Forms of Butyrylcholinesterase in Denervated Fast and Slow Latissimus Dorsi Muscles of Newly Hatched Chicken

The effects of denervation and direct electrical stimulation upon the activity and the molecular form distribution of butyrylcholinesterase (BuChE) were studied in fast-twitch posterior latissimus dorsi (PLD) and in slow-tonic anterior latissimus dorsi (ALD) muscles of newly hatched chicken. In PLD muscle, denervation performed at day 2 substantially reduced the rate of rapid decrease of BuChE specific activity which takes place during normal development, whereas in the case of ALD muscle little change was observed. Moreover, the asymmetric forms which were dramatically reduced in denervated PLD muscle were virtually absent in denervated ALD muscle at day 14. Denervated PLD and ALD muscles were stimulated from day 4 to day 14 of age. Two patterns of stimulation were applied, either 5-Hz frequency (slow rhythm) or 40-Hz frequency (fast rhythm). Both patterns of stimulation provided the same number of impulses per day (about 61,000). In PLD muscle, electrical stimulation almost totally prevented the postdenervation loss in asymmetric forms and led to a decrease in BuChE specific activity. In ALD muscle, electrical stimulation partially prevented the asymmetric form loss which occurs after denervation. This study emphasizes the role of evoked muscle activity in the regulation of BuChE asymmetric forms in the fast PLD muscle and the differential response of denervated slow and fast muscles to electrical stimulation.

Ventricular myosin expression in developing and regenerating muscle, cultured myotubes, and nascent myofibers of overloaded muscle in the chicken

In embryonic chicken skeletal muscle, the presence of a ventricular myosin heavy chain (MHC) is demonstrated by reactivity with an anti-ventricular MHC antibody. Developmental repression of the ventricular MHC expression occurs earlier in embryonic fast twitch posterior latissimus dorsi (PLD) than in embryonic slow-tonic anterior latissimus dorsi (ALD) muscles. Ventricular MHC expression also occurs in developing myotube cultures and in regenerating ALD muscles. Following the application of a weight overload, a population of nascent myofibers emerges in ALD but not PLD muscles which express a ventricular MHC. Localization of cells reactive with anti-ventricular and anti-fast MHC antibodies suggests that satellite cells participate in nascent myofiber formation. In addition, some mature ALD muscle fibers demonstrate reactivity with these antibodies, suggesting that satellite cell fusion with mature myofibers also occurs in overloaded ALD muscles and results in the reinitiation of the embryonic phenotype in hypertrophying fibers. The presence of cells reacting exclusively with the anti-fast antibody after removal of the overload for 9 wk indicates that nascent myofiber formation results in the establishment of a new myofiber population with an abnormal phenotype in overloaded ALD muscles. These cells form a lattice-like network around normal fascicles.

Acetylcholinesterase in chick embryo latissimus dorsii muscles: effects of curarization and electrical stimulation

Abstract The accumulation of acetylcholinesterase (AChE), the changes in AChE-specific activity and in AChE molecular form distribution were studied in slowtonic anterior latissimus dorsi (ALD) and in fast-twitch posterior latissimus dorsi (PLD) muscles of the chick embryo. From stage 36 (day 11) to stage 42 (day 17) of Hamburger and Hamilton, the AChE-specific activity decreased, while the relative proportion of asymmetric A 12 and A 8 forms increased. Repetitive injection of curare resulted at stage 42 (day 17) in a decrease in AChE-specific activity, in the accumulation of the synaptic AChE and in the expression of AChE asymmetric forms. Electrical stimulation at a relatively high frequency (40 Hz) of curarized ALD and PLD muscles resulted in a normal increase in AChE asymmetric forms, whereas a lower frequency (5 Hz) resulted in a dominance of globular forms. Both patterns of stimulation partly prevented the loss in synaptic AChE accumulations. These results suggest that in chick embryo muscles, muscle activity and its rhythms are involved in the normal evolution of AChE.

Posthatching changes in levels and molecular forms of acetylcholinesterase in slow and fast muscles of the chicken: Effects of denervation and direct electrical stimulation

Abstract The evolution of acetylcholinesterase (AChE) activity and AChE molecular form distribution were studied in slow-tonic anterior latissimus dorsi (ALD) and in fast-twitch posterior latissimus dorsi (PLD) muscles of chickens 2–18 days of age. In ALD as well as in PLD muscles, the AChE-specific activity increased transiently from day 2 to day 4; the activity then decreased more rapidly in PLD muscle. During this period asymmetric AChE forms decreased dramatically in ALD muscle and the globular forms increased. In PLD muscle, the most striking change was the decline in A 8 form between days 2 and 18 of development. Denervation performed at day 2 delayed the normal decrease in AChE-specific activity in PLD muscle, whereas little change was observed in ALD muscle. Moreover, A forms in these two muscles were virtually absent 8 days after denervation. Direct electrical stimulation depressed the rise in AChE-specific activity in denervated PLD muscle and prevented the loss of the A forms. Furthermore, the different molecular forms varied according to the stimulus pattern. In ALD muscle, electrical stimulation failed to prevent the effect of denervation. This study emphasizes the differential response of denervated slow and fast muscles to electrical stimulation and stresses the importance of the frequency of stimulation in the regulation of AChE molecular forms in PLD muscle during development.

Effects of denervation on spectrin concentration in avian skeletal muscle

The effect of denervation on avian muscle alpha-spectrin was examined in fast and slow muscles. Using immunofluorescence, the surgically denervated fast-twitch posterior latissimus dorsi (PLD) exhibited a significant increase in spectrin antigen associated with the sarcolemma and within the sarcoplasm compared with the contralateral innervated control muscle. Using gel electrophoresis followed by immunoblotting, we found a two- to three-fold increase in the levels of spectrin in the denervated PLD over that found in the innervated PLD. These levels were comparable to those found previously in slow and dystrophic muscle. The intrafiber distribution of spectrin is similar between the denervated PLD and the slow-tonic anterior latissimus dorsi (ALD). When spectrin was examined in dystrophic PLD muscle, denervation was found to have no effect. These results support our hypothesis that the concentration of spectrin within muscle fibers reflects the physiological state of those fibers. Changes in spectrin concentration may be a useful probe to study the various alterations in physical parameters found among fast, slow, dystrophic, and denervated fibers.

Numbers of myonuclei and satellite cell nuclei in latissimus dorsi muscles of the chicken

In the 3-, 33- and 66-day-old chicken, two muscles, the oxidative slow tonic anterior latissimus dorsi and the glycolytic fast twitch posterior latissimus dorsi were compared by the measurement of muscle fibre diameter and the fraction of total muscle tissue nuclei which were either myonuclei or satellite cell nuclei. Between 3 and 33 days there was a period of rapid growth (more marked in the posterior latissimus dorsi) which coincided with a sharp fall in numerical density of myonuclei and satellite cell nuclei (number per cubic millimetre muscle tissue). The fraction of all nuclei which were satellite cell nuclei declined steadily. The higher levels of myonuclei and satellite cell nuclei in the anterior latissimus dorsi were thought to be a reflection of its oxidative metabolism and the presence of multiple endplates. The volume of sarcoplasm occupied by single myonuclei in anterior and posterior latissimus dorsi muscles was shown to be considerably greater than that occupied by nuclei in other cell systems.

Effects of denervation on spectrin concentration in avian skeletal muscle

The effect of denervation on avian muscle alpha-spectrin was examined in fast and slow muscles. Using immunofluorescence, the surgically denervated fast-twitch posterior latissimus dorsi (PLD) exhibited a significant increase in spectrin antigen associated with the sarcolemma and within the sarcoplasm compared with the contralateral innervated control muscle. Using gel electrophoresis followed by immunoblotting, we found a two- to three-fold increase in the levels of spectrin in the denervated PLD over that found in the innervated PLD. These levels were comparable to those found previously in slow and dystrophic muscle. The intrafiber distribution of spectrin is similar between the denervated PLD and the slow-tonic anterior latissimus dorsi (ALD). When spectrin was examined in dystrophic PLD muscle, denervation was found to have no effect. These results support our hypothesis that the concentration of spectrin within muscle fibers reflects the physiological state of those fibers. Changes in spectrin concentration may be a useful probe to study the various alterations in physical parameters found among fast, slow, dystrophic, and denervated fibers.

Low frequency chronic electrical stimulation of normal and dystrophic chicken muscle.

The fast-twitch posterior latissimus dorsi muscle of normal and genetically dystrophic chickens was subjected to continuous indirect electrical stimulation at 10 Hz for periods of 4-8 weeks. To sustain this in vivo nerve stimulation an internally implantable miniature stimulator device was designed. This regime of stimulation caused complete fatigue of the normal muscle within 5 min of its initiation. The dystrophic muscles maintained a very small degree of contractile activity during this initial phase. Tangible twitching of the muscle returned in 5 week birds between 3 and 5 days and in 10 week birds between 11 and 16 days after implantation. After 4 weeks of stimulation, no significant change was measured in the time-to-peak of the isometric twitch response, nor in the half-relaxation time. The resistance to fatigue was significantly increased in the stimulated muscles when tested with a series of tetani at 40 Hz. The mean fibre area was decreased, in all muscles stimulated for longer than 3 weeks, in comparison to their contralateral controls, except where fibre splitting in dystrophic birds abnormally reduced the control value. The majority fibre type of the muscle was changed from type IIB to IIA. The histochemical reactions for both NADH-linked oxidation and phosphorylase were distinctly increased in the stimulated muscles. In normal muscle, stimulation increased somewhat the number of nuclei per unit area and changed their intracellular distribution, so that a greater proportion was found adjacent to the sarcolemma. The normal posterior latissimus dorsi muscle responded to chronic stimulation with increases of 3-6-fold in its acetylcholinesterase (AChE) activity. The maximum change in AChE occurred after 2 weeks stimulation; a steady level, 3 times that of the control unstimulated muscle, persisted at later times. Chronic stimulation suppressed the over-production of AChE that is characteristic of dystrophic chicken fast-twitch muscle, to attain a level comparable to the AChE activity in a stimulated normal muscle. Stimulation exerted a strong normalizing influence on dystrophic muscle, as assessed morphologically. The characteristic fibre rounding, fibre hypertrophy and myonuclear proliferation were reduced. This influence was most marked where the stimulation was initiated before the major pathological changes had occurred, but was also significant when commenced in strongly affected birds of 10-11 weeks.

Freeze-fractured sarcoplasmic reticulum in adult and embryonic fast and slow muscles.

There is evidence to suggest that 8 nm calcium transport particles in the sarcoplasmic reticulum are involved in the regulation of twitch properties in adult muscles. We have studied ultrastructural characteristics of the sarcoplasmic reticulum in relation to previously defined physiological changes that take place in the normal course of development. The fast twitch posterior latissimus dorsi (PLD) and the slow tonic anterior latissimus dorsi (ALD) of the chicken were compared using the procedure of freeze-fracture. In the adult PLD, the sarcoplasmic reticulum was composed of longitudinal tubules which gave rise to fenestrated cisternae at the centre of the H band and to terminal cisternae that form triads regularly at each A-I junction. In most of the fibres (85%), 8 nm intramembrane particles were closely packed in the concave fracture face (P-face). In the ALD, a tubular network with an open circular pattern extended the entire length of the A band and usually throughout the I band as well. Dyads or triads, which were infrequent, were often oriented obliquely. The density of intramembrane particles was low in the majority of the fibres, but there was a significant minority population (30%) in which particle density was relatively high. At 10 days in ovo, when speed of contraction in both the ALD and PLD is slow, there was a circular configuration of sarcoplasmic reticulum components in both muscles, and particle density was low. Surprisingly, at 18 days in ovo, when the rate of tension development and relaxation have reached nearly adult values in the fast PLD, this muscle, like the ALD, continued to exhibit a circular arrangement of sarcoplasmic reticulum tubules. The density of P-face particles, although greater than at 10 days, was still low relative to the adult PLD. Estimated values for the 18-day PLD were similar to those calculated for the adult slow muscle. Our observations, along with those of other investigators, suggest that abundant intramembrane particles may be related to the fast twitch properties of the adult PLD. However, they indicate that neither the pattern of membranes typical of the adult fast muscle nor the high content of calcium transport particles is required for the differentiation of fast twitch characteristics.

Conversion of muscle fiber types in regenerating chicken muscles following cross-reinnervation.

Slow-tonic anterior latissimus dorsi (ALD) and fast-twitch posterior latissimus dorsi (PLD) muscles of 7 to 10-day-old White Leghorn chickens were crushed and allowed to be reinnervated by their own nerve, or crushed and transplanted to the other side and allowed to be reinnervated by the nerve of the side to which they were transplanted. Following transplantation, changes in the weight of the muscle, fiber-type composition and innervation pattern during regeneration were investigated. Normal growth rate of PLD was about twice that of ALD. Regenerating PLD, however, atrophied rapidly after crushing and denervation whether innervated by its own nerve or the other nerve type, whereas ALD reinnervated by its own nerve showed marked hypertrophy. PLD fibers transformed rapidly to fast-twitch alpha or slow-tonic (ST) fibers when they were reinnervated by PLD or ALD nerve, respectively. When ALD fibers were reinnervated by their own nerve, they differentiated into ST fibers that were surrounded by smaller immature fibers. ALD fibers were, however, resistant to complete control by fast-twitch PLD nerve and contained a large number of slow fibers (ST and beta) long after transplantation. Slow fibers in regenerates were initially multiply innervated, but later transformed into fast-twitch alpha fibers that were focally innervated. The mode of differentiation and innervation pattern of different muscle fiber types in regenerating muscles are discussed.

Light chain distribution of chicken skeletal muscle myosin isoenzymes

Fast-twitch and slow-twitch muscle myosins contain 2 heavy chains and 2 pairs of light chains [l] . There are 3 types of light chains in fast-twitch muscle myosln: LCf (alkali 1 light chain), LC$ (DTNB light chain) and LCf, (alkali 2 light chain). LC; forms 2 mol/mol myosin while LCf and LCf together form 2 mol/mol myosin. Two types of light chains distinct from those in fast-twitch myosin are found in slowtwitch muscle myosln, LC: and q, and these occur ln equal molar ratio. Analysis of Intact myosin in pyrophosphate gels has revealed that myosin from both types of muscles are electrophoretically heterogeneous [2] , there being 3 components ln the fasttwitch posterior latissimus dorsi muscle myosln and 2 components in the slow-twitch anterior latisslmus dorsi muscle myosin. It has been suggested that these multiple forms ln each type of muscle are isoenzymes of myosin. In this work, the light chain distribution of these individual myosin forms are analysed by SDS-gel electrophoresls after separation ln pyrophosphate gel. It will be shown that multiple forms in fasttwitch muscle myosins do differ in light chain distribution, thereby demonstrating their isoenxymic nature. Slow-twitch muscle myosins however, do not appear to differ in light chain distribution.

Electrophoretic analysis of multiple forms of myosin in fast-twitch and slow-twitch muscles of the chick

1. A method is described for the electrophoretic analysis of intact myosin in polyacrylamide gel in a buffer system containing 0.02 M-pyrophosphate and 10% (v/v) glycerol, pH 8.8. 2. In this system chicken skeletal-muscle myosins reveal five distinct electrophoretic components, three components from the fast-twitch posterior latissimus dorsi muscle and two slower-migrating components from the slow-twitch anterior latissimus dorsi muscle. 3. The Ca2+-activated ATPase (adenosine triphosphatase) activity of myosin components was measured by densitometric scanning of the gel for the Ca3(PO4)2 precipitate formed during the ATPase reaction and subsequently for stained protein. Each component from the same muscle appears to have identical ATPase activity, but components from the fast-twitch muscle had an activity 2.2 times higher than those from the slow-twitch muscle. 4. On re-electrophoresis in the same buffer system, individual fractions of fast-twitch myosin did not reproduce the three-band pattern of the original myosin, but migrated at rates consistent with their original mobility. 5. Analysis of the mobility of the three fast-twitch myosin components in gels of different concentrations suggests that they are not stable oligomers of each other. 6. It is suggested that these components of fast-twitch myosin and slow-twitch myosin are isoenzymes of myosin.

Acetylcholinesterase in singly and multiply innervated muscles of normal and dystrophic chickens. II. Effects of denervation.

Neural regulation of mature normal fast twitch muscle of the chicken suppresses high activity, extrajunctional localization, and isozyme forms of acetylcholinesterase (AChE) characteristic of embryonic, denervated and dystrophic muscle. Normal adult slow tonic muscle ofthe chicken retains intermediate levels of activity and embryonic isozyme forms but not extrajunctional activity; it is not affected by muscular dystrophy. The hypothesis that neural regulation of the AChE system is lacking in slow tonic muscle and thus not affected by dystrophy was tested by denervating the fast twitch posterior latissimus dorsi and slow tonic anterior latissimus dorsi muscles of normal and dystrophic chickens. Extrajunctional AChE activity and embryonic isozyme forms increased, then declined, in both muscles. The results suggest that ocntrol of AChE is qualitatively similar in slow tonic and fast twitch muscle of the chicken.