Acetylcholinesterase in singly and multiply innervated muscles of normal and dystrophic chickens

Differential effects of methimazole and dexamethasone in avian muscular dystrophy

We showed previously that thyroid antagonists and glucocorticoids partially alleviated the impaired righting ability and abnormally high levels of plasma creatine kinase activity in genetically dystrophic chicks. The goals of the present study were: (1) to ascertain whether the beneficial effects of methimazole (MMI; thyroid antagonist) on muscle function and plasma creatine kinase (CK) activity in dystrophic chickens are correlated with significant reduction in plasma triiodothyronine (T3) and thyroxine (T4); (2) to assess whether the MMI-induced thyroid changes are accompanied by increased plasma corticosterone level and/or changes in muscle glucocorticoid receptors which might account partially for the beneficial effects of MMI; and (3) to determine if plasma T3 and T4 are reduced in dexamethasone (DEX) treated dystrophic chickens which might account at least partially for the beneficial effects of DEX (a potent glucocorticoid) on avian dystrophy. The data show that beneficial effects of MMI are associated with reduced plasma levels of thyroid hormones and increased circulating levels of corticosterone. In addition, DEX actually increases plasma T3 levels. These differential effects indicate that reduced plasma thyroid hormone levels do not represent a common mechanism of beneficial drug effects in avian muscular dystrophy. On the other hand, elevated plasma glucocorticoid levels accompany the beneficial effects of both severe hypothyroidism and DEX treatment. The data also show that MMI induces down-regulation of muscle cytosolic glucocorticoid receptors which are higher than normal in dystrophic muscles.

Thyroidal involvement in the expression of avian muscular dystrophy

We showed previously that propylthiouracil (PTU), a thyroid inhibitor, could alleviate several major signs of hereditary muscular dystrophy in chickens. The goals of the present investigation were to: (1) determine whether a nearly athyroid condition (achieved within two days after hatching by surgical thyroidectomy plus PTU) during an 11-day period beneficially affects the dystrophic condition when followed by triiodothyronine (T3) replacement to 33 days of age; (2) determine the beneficial effects on the expression of avian dystrophy when the thyroidectomized-PTU-treated chickens received a wide range of moderate to low T3 replacement doses beginning by two days after thyroidectomy; and (3) examine the thyroid hormone receptor system in dystrophic muscle for a possible abnormality. Thyroid deprivation increased muscle function (righting ability) and reduced plasma creatine kinase activity in dystrophic chickens. The major thyroid-related abnormality in dystrophic pectoralis muscles was an increased maximum binding capacity of solubilized nuclear T3 receptors.

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.

Responsiveness of normal and dystrophic avian muscle to acetylcholine, carbamylcholine and d-tubocurarine

1. The responsiveness of dystrophic avian muscle to acetylcholine may be altered due to reported elevated acetylcholinesterase activity. 2. To test this hypothesis, the responsiveness of normal and dystrophic muscle in vivo to intra-arterial injection of acetylcholine, carbamylcholine and d-tubocurarine was compared. 3. Results showed that dystrophic muscle was less responsive to acetylcholine, more responsive d-tubocurarine and equally responsive to carbamylcholine when compared to normal suggesting enhanced acetylcholine hydrolysis occurs in vivo in dystrophic avian muscle.

Reciprocal regulation of acetylcholinesterase and butyrylcholinesterase in mammalian skeletal muscle

Developmental regulation, from the fetal period to 11 months of age, and the influence of denervation on the appearance and disappearance of the molecular forms of acetylcholinesterase (AchE) and butyrylcholinesterase (BuchE) in rat skeletal muscle were examined. The enzyme forms were extracted from anterior tibialis in 0.01 M sodium phosphate buffer, pH 7.0, containing 1 N NaCl, 0.01 M EGTA, 1% Triton X-100, and a cocktail of antiproteases, and analyzed by velocity sedimentation on 5-20% linear sucrose gradients. Three principal forms, denoted by sedimentation coefficients of 4, 10.8, and 16 S, were observed in muscle from all age groups. The amounts of each of the molecular forms of AchE and BuchE in skeletal muscle exhibited distinct and reciprocal patterns of appearance and disappearance during pre- and postnatal development. In tissue derived from animals less than 2 weeks of age, BuchE represented the predominant component of activity in the 4 S form, was present equally with AchE in the 10.8 S form, and was subordinate to AchE in the 16 S form. Between 1 and 2 weeks of age a progressive increase in AchE activities coincident with a reduction in BuchE activities resulted in inversion in the amounts of the two enzymes present in adult muscle. Denervation of muscle caused a dramatic reduction in the presence of AchE molecular forms with no discernable influence on the presence of BuchE molecular forms. These results indicate that biosynthesis of BuchE is strictly regulated in a reciprocal manner with that of AchE, and that BuchE metabolism is independent of the state of muscle innervation. Increased synthesis of AchE and either reduced synthesis or increased degradation of BuchE can account for the reciprocal regulation of these enzymes. These characteristics of mammalian muscle contrast sharply with characteristics deduced for avian tissue (Silman et al. (1979) Nature (London) 280, 160-162). The innervation-independent metabolism of BuchE and the diverse modes of its regulation in different tissue from different species signify that BuchE function may be unrelated to cholinergic neurotransmission.

Impaired muscle-nerve interaction (motility) characterizes the brachial region of dystrophic embryos

During development ex ovo, the avian mutant with an hereditary form of muscular dystrophy demonstrates biochemical, histochemical, and physiological (functional) abnormalities which may result from impaired muscle-nerve interaction. To investigate if impaired functional activity also characterizes the dystrophic process during development in ovo, limb motility, an index of embryonic functional muscle-nerve interaction, was compared between normal and dystrophic embryos from day 6E through day 16E. A highly significant reduction in this parameter was exhibited by dystrophic wings from day 11E to day 14E inclusive. In contrast, genotypically dystrophic hind limbs demonstrated values equivalent to normal legs. Thus, in the dystrophic embryo, impaired muscle-nerve interaction characterized the brachial region exclusively during a specific period of embryogenesis.

Quantitative freeze-fracture studies of membrane changes in chicken muscular dystrophy

Muscular dystrophy induces extensive changes in the patterning of sarcolemmal caveolae of fast-twitch fibers from the chicken posterior latissimus dorsi (PLD) muscle, which in healthy fibers are arranged in striking bands over the myofibrillar I-bands. In dystrophic fibers the caveolae lack this patterned arrangement, and instead are dispersed over the entire sarcolemma, are irregular in shape, and are more numerous in older birds. Quantitative analysis of these differences provides three independent numerical indices of the dystrophic state and suggests that constraints responsible for normal patterning are lost in diseased fibers. These observations support theories that defects of the muscle plasma membrane are important for dystrophic pathogenesis. In contrast, the sarcolemma of slow tonic fibers from anterior latissimus dorsi (ALD) and metapatagialis latissimus dorsi (MLD) muscles have randomly dispersed caveolae whose appearance and distribution are unaffected by the disease.

Effects of percutaneous electrical stimulation on functional ability, plasma creatine kinase, and pectoralis musculature of normal and genetically dystrophic chickens

The breast musculature of genetically dystrophic Line 413 and genetically related normal Line 412 chickens were treated in three separate trials with high-frequency electrical stimulation (ES). Beginning on days 7 or 14 ex ovo, each bird received three ES treatments per week. Each stimulation cycle repeated five times per day consisted of 15 s "on" followed by 50 s "off". In the third trial only, the birds were additionally treated beginning day 3 ex ovo with either leucine (100 mg/kg) or the proteinase inhibitor Ep475 (10 mg/kg). ES significantly delayed the onset of righting disability in the dystrophic chickens. However, this improvement was temporary and could be masked by single treatments of either leucine or Ep475. Plasma creatine kinase activities were increased generally in both the stimulated normal and dystrophic birds. In two trials ES increased the relative muscle mass, and in one trial increased protein. ES had little effect on normal muscle mass or protein. However, ES treatment together with either leucine or Ep475 appeared to improve both normal and dystrophic muscle mass and protein. Furthermore ES decreased dystrophic muscle calcium but not acetylcholinesterase activity. On the other hand, ES had no effect on the total normal muscle calcium but increased normal acetylcholinesterase values. In both normal and dystrophic muscle samples, ES treatment in combination with leucine appeared to increase the mean muscle fiber diameters and number of myonuclei, and in the case of the dystrophic muscle, appeared to decrease the relative proportion of vacuolated, degenerating, and intensely oxidative histochemical fibers. In general, stimulation (especially in combination with leucine) appears to alter in varying degrees the phenotypic expression of the muscle disease exhibited in the dystrophic chicken.

Characterization of activities and forms of cholinesterases in human primary brain tumors

The activities and molecular forms of cholinesterases were studied in a collection of primary brain tumors consisting of primarily gliomas and meningiomas, together with samples of forebrain taken postmortem from patients suffering from diseases unrelated to the nervous system. Both types of tumors, as well as normal forebrain, contained substantial amounts of cholinesterase activity and some gliomas contained exceptionally high levels. In both normal forebrain and meningiomas, acetylcholinesterase (acetylcholine hydrolase; EC 3.1.1.7) accounted for almost all the cholinesterase activity, but in almost all gliomas elevated pseudocholinesterase (acylcholine acylhydrolase; EC 3.1.1.8) could be detected. The cholinesterase activity of both normal forebrain and gliomas migrated on sucrose gradients as a major component of 10-11 S together with a minor component of 4-5 S. In meningiomas a light (4.5 S) form was the principal component.

Involvement of fast and slow twitch muscle fibres in avian muscular dystrophy

The extent of differential fibre type involvement in chicken muscular dystrophy can be assessed quantitatively by the statistical parameters of fibre area, nuclei content and nuclei distribution in the individual fibre types. Two muscles, the posterior latissimus dorsi (PLD) and the serratus metapatagialis (SMP), were found to have similar overall fibre type composition, although the latter contains two subtypes of type I fibres, one of which has not previously been recognised in avian muscle. In both muscles, type IIB fibres are most affected by the progressive pathology. Nuclear proliferation is one of the histopathological features which can be measured, and in the PLD, the mean number of total nuclei in type IIB fibre cross-sections (Nt) is increased from 2.23 in normal chickens to 3.70 in dystrophic chickens, by 60 days. The corresponding values for Nt in type IIB muscle fibres of the SMP at 50 days are 1.74 and 5.10. Likewise, statistical analyses of the distribution of the fibre areas and their variability demonstrate that the incidence of abnormality in chicken dystrophy is greatest in type IIB fibres in both these muscles. Although type I fibres in the PLD are resistant to dystrophic change, it is noteworthy that in the SMP the type I fibres, also, are severely affected from an early stage, by these quantitative criteria. On the other hand, all fibres in a tonic muscle, the metapatagialis latissimus dorsi, are unaffected, as is true of all other tonic muscles previously studied. It is concluded that any twitch fibre type can, in principle, be affected by the actions of the gene concerned, and that this expression can be greatly modified in individual muscles by various physiological features, for example their natural pattern of use or relative disuse.

Fibre types in chicken skeletal muscles and their changes in muscular dystrophy

1. Five major fibre types in chicken skeletal muscles are recognized, based upon their histochemical and morphological characteristics. A classification of these which is readily related to a commonly used classification of mammalian muscle fibre types is given.2. Seven muscles of the chicken were analysed in recognizing this range of fibre types. The proportions of the different types in each of these were determined. In some cases a gradient of fibre type composition exists across a single muscle.3. Measurements of muscle contraction were used in defining tonic muscles, which contain two fibre types. It was shown that in addition to the anterior latissimus dorsi (a.l.d.), previously well known to be a tonic muscle, two other muscles, the plantaris and the adductor profundus, are of the same class, but differ subtly from the a.l.d. in certain features. Gross red colouration is not a useful diagnostic feature of slow muscles, since the tonic adductor profundus, for example, is white.4. Fibres similar histochemically to mammalian type I (slow-twitch) occur in some of the avian twitch muscles investigated. These are oxidative in character, and despite the fact that they are multiply innervated we suggest that these are avian slow-twitch fibres.5. The patterns of cholinesterases found in a skeletal muscle correspond to its fibre type composition, with regard to both the concentrations and the proportions of the multiple forms of enzyme present. The distinctive patterns of those forms of acetylcholinesterase in the different fibre types are described.6. The fibre type composition is changed by inherited muscular dystrophy in a characteristic manner. This change has so far been found (at the earlier stages of the disease) only in the muscles with a predominance of type II B fibres in the normal chicken. Pathological changes within the fibres occur selectively in the type II B fibres, but there are exceptions to this and the effect can be greatly modified by the type of neighbouring fibres.

Comparison of the molecular forms of the cholinesterases in tissues of normal and dystrophic chickens

The levels and molecular forms of acetylcholinesterase (AChE, EC 3.1.1.7) and pseudocholinesterase (psiChE, EC 3.1.1.8) were examined in various skeletal muscles, cardiac muscles, and neural tissues from normal and dystrophic chickens. The relative amount of the heavy (Hc) form of AChE in mixed-fibre-type twitch muscles varies in proportion to the percentage of glycolytic fast-twitch fibres. Conversely, muscles with higher levels of oxidative fibres (i.e., slow-tonic oxidative-glycolytic fast-twitch, or oxidative slow-twitch) have higher proportions of the light (L) form of AChE. The effects of dystrophy on AChE and psiChE are more severe in muscles richer in glycolytic fast-twitch fibres (e.g., pectoral or posterior latissimus dorsi, PLD); there is no alteration of AChE or psiChE in a slow-tonic muscle. In the pectoral of PLD muscles from older dystrophic chickens, however, the AChE forms revert to a normal distribution while the pesChE pattern remains abnormal. Muscle psiChE is sensitive to collagenase in a similar way as is AChE, thus apparently having a similar tailed structure. Unlike skeletal muscle, cardiac muscle has very high levels of psiChE, present mainly as the L form; AChE is present mainly as the medium (M) form, with smaller amounts of L and Hc. The latter pattern of AChE forms resembles that seen in several neural tissues examined. No alterations in AChE or psiChE were found in cardiac or neural tissues from dystrophic chickens.

Cholinesterase in muscle of dystrophic hamsters (Bio-40.54)

Isozyme patterns of cholinesterase (ChE) from heart, tongue, and skeletal muscle of normal and dystrophic hamsters are presented. Two principal bands, bands 1 and 2, were evaluated. Band 1 migrates faster towards the anode than does band 2. While bands 1 and 2 stain for AChE and were found in control muscles, only band 2 was stained by a pseudocholinesterase (BuChE) and was decreased in samples from dystrophic hamsters. The decrease in BuChE was most pronounced in dystrophic heart muscle. The low level of BuChE measured for dystrophic animal tissue was similar to isozyme patterns found in embryonic tissue and in denervated muscle. BuChE obtained by acrylamide gel electrophoresis along with 16S AchE appears to be a useful biochemical marker of nerve-muscle interactions.

Properties of muscles from chickens with inherited muscular dystrophy

Inherited muscular dystrophy of the chicken is an abnormality affecting the normal development and function of fast-twitch skeletal muscles. Several different strains of dystrophic chickens have been developed by selection for high lipid content in the pectoralis muscle and early onset of the disorder or by outcrossing the original New Hampshire stock into an inbred White Leghorn breed. The purpose of this study was to determine whether fast-twitch dystrophic muscles differ in expressed properties within the same bird and to examine the differences in gene expression between dystrophic New Hampshire and White Leghorn breeds. The biochemical and physiological properties examined were lactate dehydrogenase and acetylcholinesterase activities, total lipid content, muscle fiber diameter and electromyographic insertion activity. Results showed that fiber diameter and lipid levels were different in muscles within individual birds of two dystrophic lines and that the dystrophic gene causes rapid fiber atrophy and high lipid content in the White Leghorn breed. In addition, differences in lactate dehydrogenase activity and electromyographic patterns were found between two dystrophic lines. The results suggest that the expressed properties differ within each muscle of the dystrophic bird and that the expression of the dystrophic genes is dependent upon the nature of the genetic background of the breed.

Altered protein synthesis and creatine kinase in breast muscle cell cultures from dystrophic chick embryos

The total protein synthesis (TPS), myosin synthesis (MS) and creatine kinase (CK) levels in muscle cell cultures obtained from 400 normal (strain 454) and 400 dystrophic chick embryos (strain 455) were investigated. The cultures were obtained from breast muscles of 12 day chick embryos by dissociation in 0.25% trypsin, preplating and plating of 5 x 10(5) floating cells on gelatin coated dishes in Minimal Essential Medium, 10% horse serum and 2% chick embryo extract. After 6 days, when electron-microscopic studies demonstrated good muscle differentiation, cell cultures were labeled with [3H]leucine. TPS and MS, respectively, showed 85% and 65% increases in breast muscle cell cultures from dystrophic chick embryos. The half-life times for total protein and myosin from dystrophics were 19 and 32 hr, respectively as compared with 36 and 48 hr from controls. Noncollagen protein content (NCP) showed 27% decrease in postfusion stage (12 days) of cell cultures from dystrophics. The CK level showed 30% lower values in the cells from dystrophics but 50% higher values in their culture medium. The addition of leupeptin plus pepstatin (50 microgram/ml) to these cultures resotred NCP content, total protein and myosin turnover to normal values and significantly increased TPS and MS. The addition of diphenylhydantoin (DPH) (20 microgram/ml) to cell cultures from dystrophics did not change the NCP content nor the turnover for total protein and myosin but significantly increased TPS, MS and CK while medium CK significantly decreased. The addition of leupeptin plus pepstatin or DPH to muscle cell cultures from normal chick embryos also significantly stimulated TPS and MS.

A possible mechanism of phenotypic expression of normal and dystrophic genomes on succinic dehydrogenase activity and fiber size within a single myofiber of muscle transplants

Muscle transplantation was used to evaluate the ability of normal and dystrophic chickens to support regeneration of both normal and dystrophic muscle fragments. Pectoralis muscles were grafted into the site of the biceps muscle of host chickens. Identification of dystrophic characteristics of intact and regenerating muscle fibers was made by cytochemical analysis of mitochondrial succinic dehydrogenase (SDH) and by fiber size. In the biceps muscle of dystrophic chicks at 40 days ex ovo, the mean size of muscle fibers with low activity of SDH and fibers with high SDH activity was 29.0 +/- 5.9 micrometers and 42.0 +/- 10.4 micrometers, respectively. The mean size of normal muscle fibers was notably smaller than in dystrophic muscle and was 17.8 + 3.1 micrometers. The hypertrophy of fibers coupled with elevation of SDH activity tended to increase with age. Transplants were examined at 56 days postoperatively. The results of cross-transplantation between normal and dystrophic genotypes were similar to unoperated muscles in the correlation between SDH activity and fiber size. Donor muscles determined the type of myofibers regenerated in transplants regardless of whether the host was normal or dystrophic. In addition, combined transplantation was attempted to produce a single hybrid myofiber in which normal and dystrophic pectoralis muscle were mixed in equal volume. The mixtures were then allowed to regenerate in host chicks. A number of mosaic myofibers appeared in transplants and had regional differences in SDH activity along their length. It was concluded that: (1) The characteristics of high SDH activity and fiber hypertrophy are an expression of dystrophic nuclei, (2) combined transplantation of both normal and dystrophic muscle fragments can produce mosaic myofibers in SDH reaction; and (3) the local control of SDH activity and fiber size within nuclear territories in mosaic myofibers seems likely to be due to phenotypic expression of either normal or dystrophic genomes.

Incidence of acetylcholinesterase in the sarcoplasm of human and chicken muscles

Fifty-nine biopsies of human muscle, 53 of them abnormal, 6 normal, were studied for the histochemical localization of acetylcholinesterase (AChE) using frozen sections and light microscopy. In addition to AChE which was found at the myoneural and myotendon junction, specific staining was found around the periphery of many fibers from normal and abnormal muscles. Moreover, AChE activity was found to be high in the sarcoplasm of more than 10% of the fibers from 28 biopsies of abnormal muscle including cases of hemiplegia, spinal cord injury, denervation and neuropathy, infantile spinal muscle atrophy, Duchenne, limb-girdle and facioscapulohumeral dystrophies, Schwartz-Jampel syndrome and a myasthenic syndrome. Of the muscles from experimental animals examined, only the Rhesus monkey exhibited AChE around the periphery of the fibers, and only the dystrophic chicken and not the dystrophic mouse or hamster, showed extensive sarcoplasmic AChE. Histograms of muscle fiber diameters indicated that AChE in the sarcoplasm was associated with fibers of all sizes, depending on the nature of the disorder examined. Fibers containing AChE were smaller than unstained fibers in dystrophic chicken muscle. The results suggest that in the human, sarcoplasmic AChE is reversibly repressed during muscle maturation and that its mode of regulation by motor neurons is similar to that found in the chicken.

Appearance of acetylcholinesterase and creatine kinase in plasma of normal chickens after denervation

Evidence that acetylcholinesterase (AChE) activity is released from normal chick embryonic muscle fibers and from muscles of chickens with inherited muscular dystrophy suggested that denervated chick muscles, which have AChE properties similar to dystrophic muscles, would also release AChE. Bilateral denervation of the breast and wing muscles of normal chickens was followed by the appearance of AChE activity, distinguished from plasma cholinesterase by differential substrate hydrolysis, inhibitor sensitivity, and electrophoretic migration. Plasma creatine kinase (CK) activity was also elevated after denervation.

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.

Myogenic defect in acetylcholinesterase regulation in muscular dystrophy of the chicken

To determine whether inherited muscular dystrophy of the chicken is neurogenic or myogenic in origin, limb buds from homozygous normal and dystrophic chick embryos were exchanged prior to muscle differentiation and innervation. Biceps muscles of hatched chicks, in which muscle of the donor was innervated by nerves of the host, were analyzed for embryonic properties of muscle acetylcholinesterase and for fiber diameter, two distinctive markers for expression of the dystrophic gene. The results indicate that muscular dystrophy of the chicken is caused by an initial biochemical lesion in the limb and its muscle rather than in its innervating nerve.