Multiple forms of acetylcholinesterase and their distribution in endplate and non-endplate regions of rat diaphragm muscle

Neuromuscular adaptations to cross-reinnervation in 12- and 29-mo-old Fischer 344 rats

The aim was to test hypotheses regarding the adaptive response of the extensor digitorum longus (EDL) muscle of 12- and 29-mo rats following denervation and cross-reinnervation by the soleus nerve. The mass of cross-reinnervated EDL muscle was 87 and 86% of self-reinnervated control values in 12-mo (99 +/- 3 mg) and 29-mo (74 +/- 3 mg) rats, respectively. Cross-reinnervated EDL fiber area was 56 and 67% of self-reinnervated values in 12-mo (1,733 +/- 253 microns 2) and 29-mo (1,264 +/- 71 microns 2) rats, respectively. Cross-reinnervation increased the density of neural contact 26% in 12-mo rats and decreased density by 50% in 29-mo animals. In 12-mo rats 17% of motor end plates (MEP) were void of terminal nerves following cross-reinnervation compared with 48% in 29-mo rats. In cross-reinnervated muscles, slow myosin heavy chain (MHC) was 65 +/- 9 and 25 +/- 3% of total MHC in 12- and 29-mo rats, respectively. The percentage of type I fibers derived histochemically was 65 +/- 8% in 12-mo rats and 18 +/- 1% in 29-mo rats. In conclusion, there is an age-associated decrease in the ability of neurons to reinnervate the MEP area after nerve section. The conversion of fiber type in innervated fibers in response to cross-reinnervation may not differ due to age.

Age-dependent changes in acetylcholinesterase activity in the primary somatosensory cortex of the cat

As cortical reorganization in cat somatosensory cortex has been shown to be age-dependent and acetylcholinesterase and acetylcholine have been implicated in the shaping of sensory responses during the developmental process, we decided to investigate the biochemical changes that occur in acetylcholinesterase during postnatal development of the primary somatosensory cortex in normal cat. Somatosensory cortices were removed from cats at various ages between 4 and 144 postnatal days. Three fractions (total, membrane-bound and soluble) were analyzed for activity (esterase assay and sedimentation analysis) and amount of acetylcholinesterase (electrophoresis). Results indicated that both esterase activity levels and amounts were characterized by 4 distinct phases which included a large step increase in all fractions between postnatal days 10 and 12: a gradual rise between days 12 and 28: a 'dip' during the 42- to 82-day interval, and a subsequent recovery. Results may be attributed to concomitant developmental events. Furthermore, we suggest that the observed changes may relate to age-dependent differences in somatosensory cortex reorganization that occur after spinal cord transection.

Differential effects of denervation on acetylcholinesterase activity in parasympathetic and sympathetic ganglia of the frog, Rana pipiens

The transsynaptic regulation of acetylcholinesterase (AChE) was studied by recording the changes in enzymatic activity following denervation in two types of autonomic ganglia in the frog, Rana pipiens. Opposite effects on AChE were found in the parasympathetic cardiac ganglion and in the sympathetic lumbar ganglion; denervation produced a significant increase in AChE activity in cardiac ganglia but a significant decrease in lumbar ganglia. The relative effects of denervation on intracellular and total AChE were examined by selectively inhibiting extracellular AChE with echothiophate, a poorly lipid-soluble cholinesterase inhibitor. Denervation resulted in a significant increase in intracellular AChE in cholinergic cardiac ganglia but had no effect on intracellular AChE activity in adrenergic lumbar ganglia. Histochemical studies revealed little change in extracellular AChE staining upon denervation in the cardiac ganglion, whereas in the lumbar ganglia there was a loss of AChE-specific reaction product. These results raise the possibility that the transsynaptic control of AChE activity by innervation in the frog is influenced by the transmitter synthetic properties of the postsynaptic ganglion cells.

Properties of acetylcholinesterase in axolemma-enriched fractions isolated from bovine splenic nerve

The properties of acetylcholinesterase (AChE) in axolemma-enriched fractions (AEF) from bovine splenic nerve were investigated to see if they differed in any way from those of the AChE in diaphragm muscle. The axolemmal enzyme had a low Km for acetylthiocholine (ca. 90 microM), exhibited substrate inhibition, and had a well-defined optimum of substrate concentration of 1 mM. The rate of hydrolysis of substrate decreased with increasing acyl chain length (acetyl- greater than propionyl- greater than butyryl-). The AChE inhibitors eserine and hexamethonium were competitive inhibitors of the membrane-bound enzyme, whereas lidocaine was a noncompetitive inhibitor; these results were comparable to the effect of these inhibitors on diaphragm muscle AChE. The axolemmal enzyme was more efficiently solubilized and more stable in nonionic detergents such as Triton X-100 and Tween 20 than charged detergents such as lysolecithin and zwitterionic detergents. These results indicate that the AChE present in bovine splenic nerve AEF is identical to the previously characterized AChE from other sources.

Acetylcholinesterase-positive innervation in cochleas from two strains of shaker-1 mice

Shaker-1 is a recessive gene mutation on chromosome 7 in mice, causing both deafness and neurosensory degeneration in the inner ear. A failure of efferent innervation to the outer hair cells is being implicated in the cause of deafness (Green, 1981). To investigate the efferent innervation, we examined the cochleas of two strains of shaker-1 mutants: Sh1/Le (25 and 45 days old) and FS/Ei (28 and 68 days old), using enzymatic staining of acetylcholinesterase (AChE) for the light and electron microscopes, and also by measuring the activities of AChE and of AChE molecular forms. The enzyme levels in the SH1/Le and FS/Ei homozygotes (sh-1/sh-1) were within the range of those in SH1/Le heterozygotes (+/sh-1) and in normal mouse strains (C3H/HeJ, 129/SvJ, ICR). The picture of AChE-positive innervation in both strains differed. In the SH1/Le mutants at 25 days, the innervation appeared normal, but by 45 days it showed a marked atrophy. In the FS/Ei mutants, the degeneration was already evident by the 28th day. In the younger animals of both mutants, large differentiated vesiculated nerve endings were ultrastructurally detected in synaptic contact with outer hair cells. The preservation of AChE activity and of the expression of AChE molecular forms up to 68 days indicate that the shaker-1 cochlea may initially possess a normal input of AChE-positive efferent innervation. The late onset and the slow course of the degeneration of AChE-positive innervation seen in the SH1/Le mutants suggest that the loss of efferent endings may be, contrary to previous suggestions, the consequence rather than the cause of the shaker-1 pathology.

Acetylcholinesterase histochemistry in the non-endplate region of skeletal muscles and effect of denervation

We measured acetylcholinesterase (AChE) in the non-endplate region of rat muscle, documenting its intrinsic activity within muscle fibers, as well as the extrinsic level in the capillaries and endomysium. When each muscle was considered as a whole, intrinsic AChE activity detected within the fibers was stronger in the fast-twitch extensor digitorum longus than in the slow-twitch soleus. Analysis of individual muscle fibers also showed the same tendency with a higher value in the fast-twitch type II fibers than in the slow-twitch type I fibers. On the average, 73% of the fibers showed intermediate or strong enzymatic activity in the fast-twitch muscle, whereas 56% of the slow-twitch muscle had only low activity. Sectioning or ligation of the sciatic nerve resulted in nearly complete abolition of the enzyme in the non-endplate region of the denervated muscles within 7 days, suggesting that nerve transmission regulates AChE activity not only in the endplate, as is well known, but also outside this region. Human skeletal muscles showed the same pattern of AChE activity in the non-endplate region as seen in rat muscles.

Interaction of asymmetric and globular acetylcholinesterase species with glycosaminoglycans

Chicken muscle and retina, and rat muscle asymmetric acetylcholinesterase (AChE) species were bound to immobilized heparin at 0.4 M NaCl. Binding efficiency was between 50 and 80% for crude fraction I A-forms (AI; muscle), and nearly 100% for fraction II A-forms (AII; muscle and retina). Antibody-affinity-purified AI-forms (chicken) were, however, quantitatively bound to heparin-agarose gels, whereas diisopropylfluorophosphate-inactivated high-salt extracts partially prevented the binding of both AI and AII AChE forms, thus suggesting the presence in crude AI extracts of heparin-like molecules interfering with the tail-heparin interaction. All bound A-forms were progressively displaced from the heparin-agarose columns by increasing salt concentrations, with maximal release at about 0.6 M. They were also efficiently eluted by heparin solutions (1 mg/ml), other glycosaminoglycans being much less effective. Chicken globular AChE forms (G-forms, both low-salt-soluble and detergent-soluble) also bound to immobilized heparin in the absence of salt. Stepwise elution with increasing NaCl concentrations showed maximal release of G-forms at 0.15 M, all globular forms being totally displaced from the column at 0.4 M NaCl. Heparin (1 mg/ml) had the same eluting capacity as 0.4 M NaCl, whereas other glycosaminoglycans were only marginally effective. We conclude that the molecular forms of AChE in these vertebrate species interact with heparin, at salt concentrations that are characteristic for asymmetric and globular forms. Within the A and G molecular form groups, no differences were found in the behavior of the different fractions or subtypes, provided that the enzyme samples were free of interfering molecules.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification and isolation of an axonal plasma membrane enriched fraction from cerebellar granule cell neurites

A procedure is described to isolate a fraction enriched in cerebellar granule cell neuritic membranes. Morphological markers that are specific for either the granule cell perikarya or neuritic membranes have been identified. Concanavalin A (Con A) has been shown to bind predominantly to the granule cell neurites whereas, the enzymes acetylcholinesterase (AChE) and 2',3',cyclic nucleotide-3'-phosphohydrolase (CNPase) are localized predominantly in the neuronal cell bodies. The membrane fraction enriched in Con A binding has been used to generate a monoclonal antibody which morphologically recognized the cerebellar granule cell neuritic membrane. Following fractionation of the granule cells, each marker was used to identify the cellular origin of the fractions. The neuritic markers Con A and the neuritic membrane antibody MR2 bound predominantly to membranes found in the 29.1% and 31.5% region of the sucrose gradient. The perikaryal markers, CNPase and AChE activity were most enriched in membrane fractions found at a sucrose concentration of 23% and 21%, respectively. Morphological examination of the neuritic enriched fraction shows that it contains predominantly membranous material with few subcellular organelles. The protein profiles of the cerebellar granule cell fractions are unique when compared with the protein profiles of other neuronal and non-neuronal fractions. The membrane fraction isolated from the cerebellar granule cells should prove useful in furthering our understanding of the axonal influence on glial development.

On the specificity of the acetylcholinesterase defect in dystrophic mice

The tetrameric form of acetylcholinesterase (AChE) in ReJ/129 dystrophic mice was demonstrated to be absent from endplate-poor regions of skeletal muscle but present in endplate-rich regions. Skeletal muscle secreted normal amounts of this form of AChE. Visceral organs had normal amounts and distribution of the AChE molecular forms. These results suggest that the AChE defect in dystrophic mice is limited to skeletal muscle, and the defect does not reflect an abnormality of AChE synthesis but probably reflects an inability to incorporate the enzyme into skeletal muscle membranes.

Selective complexing of acetylcholinesterase in brain by intravenously administered monoclonal antibody

Rats injected intravenously with monoclonal antibodies reactive with brain acetylcholinesterase (AChE) developed a prolonged depression of plasma AChE without changes in butyrylcholinesterase, lactic acid dehydrogenase, or hematocrit. One antibody, ZR1, accumulated in the brain and spinal cord. Within 3 days of injection, ZR1 bound to most of the AChE in cerebral cortex and certain other regions of the CNS. Examination of the molecular forms of cortical 10S AChE, whereas 4S AChE remained free. In vitro, however, ZR1 bound equally to solubilized 4S and 10S forms. These data provide direct evidence for the compartmentalization of different AChE forms in the CNS, 10S being mainly extracellular and 4S apparently intracellular. Development of a striking and persistent bilateral ptosis within hours of injection suggests that AChE in the autonomic nervous system is also accessible to antibodies and, furthermore, is the site of an immunopathological lesion. This novel model of cholinergic autoimmunity may have relevance for human neurological disorders of unknown etiology.

The role of Ca2+ channels of the L-type in neurotransmitter plasticity of cultured sympathetic neurons

We have studied the effects of Ca2+ antagonists and agonists on the development of choline acetyltransferase (ChAT), tyrosine hydroxylase (TOH) and acetylcholinesterase (AChE) in cultures of rat sympathetic neurons maintained for 6-9 days in low K+ (5 mM) or high K+ (35 mM) medium. Previous experiments have shown that high K+ medium increases TOH activity and TOH-mRNA level up to 3.5-fold and depresses the development of AChE, in particular of its asymmetric A12 form. Moreover, high K+ medium inhibits ChAT induction by 90% in muscle-conditioned medium (Raynaud et al., Dev. Biol., 119 (1987) 305-312; 121 (1987) 548-558). None of the Ca2+ antagonists tested affected the development of ChAT, TOH or AChE in low K+ medium. In high K+ medium, nitrendipine (3 microM) or fluspirilene (1 microM) fully restored ChAT induction by conditioned medium to the level observed in low K+ medium. Other drugs (1 microM) gave partial reversion: flunarizine greater than (+)-PN 200-110 greater than (-)-D-888 greater than cinnarizine = lidoflazine. On the other hand, ChAT induction was not restored by a calmodulin inhibitor, calmidazolium (1 microM). Fluspirilene, PN 200-110, and nitrendipine also totally abolished TOH induction by high K+ medium; fluspirilene (1 microM) suppressed the inhibitory effect of high K+ medium on AChE development and restored the development of A12 AChE. Conditioned medium also depresses AChE and blocks the development of A12 AChE (Swerts et al., Dev. Biol., 103 (1984) 230-234), but these effects were insensitive to fluspirilene. The Ca2+ agonist Bay K 8644 (1 microM) potentiated the effects of elevated K+ on both ChAT and TOH. The data suggest that the effects of long-term depolarization on ChAT, TOH and AChE are mediated by Ca2+ entry specifically through voltage-sensitive channels of the L-type. Our results on cultured sympathetic neurons raise the possibility that Ca2+ antagonists, which are widely used clinically, may affect the expression of neurotransmitter phenotypic traits in vivo and interfere with trans-synaptic induction of enzymes.

Phosphatidylinositol-specific phospholipase C solubilized G2 acetylcholinesterase from plasma membranes of chromaffin cells

Using whole homogenates and defined subcellular fractions of bovine adrenal medulla, we investigated the properties of the dimeric G2 molecular form of acetylcholinesterase (AChE), its distribution, and the mode of attachment to chromaffin cells. Our studies indicate that a substantial fraction of the G2 form is specifically susceptible to solubilization by phosphatidylinositol-specific phospholipase C (PIPLC) from subcellular fractions enriched with plasma membrane fragments. The results suggest that the G2 form of AChE is anchored in the plasma membrane to a glycolipid domain that contains phosphatidylinositol. Since a Ca+2-dependent PIPLC has been previously described in chromaffin granules, it is possible that the adrenal AChE could be released by a system reminiscent of that involved in the case of the surface glycoprotein of Trypanosoma brucei.

Axonal transport in mdx mouse sciatic nerve

Anterograde and retrograde flows of acetylcholinesterase (AChE) in sciatic nerves of adult mdx mice were compared with those of normal mice. Specific molecular forms of AChE were resolved by high-performance liquid chromatography such that slow anterograde (G1 + G2), fast anterograde and fast retrograde (G4 and A12) flows could be simultaneously studied. Although we found no difference in the total AChE activity and the molecular forms in non-ligated nerves between mdx and the normal mice, ligated nerves showed significant differences. The total AChE activity accumulated at the proximal segment of ligated nerve was higher in mdx mice than in normal mice after 24 h ligation. The G1 + G2 molecular forms were accumulated more in the proximal segment of mdx than the normal. A12, on the other hand, was more abundant in both segments of mdx mice than the normal. No statistically significant difference in the accumulated amount of G4 molecular form was present between mdx and the normal mice at either proximal or distal segment. These results indicated that axonal flow in sciatic nerve likely plays a role in muscle regeneration, and that the transport machinery in dystrophin-deficient mdx neuron is probably normal.

Tissue-specific processing and polarized compartmentalization of clone-produced cholinesterase in microinjected Xenopus oocytes

1. To approach the involvement of tissue-specific elements in the compartmentalization of ubiquitous polymorphic proteins, immunohistochemical methods were used to analyze the localization of butyrylcholinesterase (BuChE) in Xenopus oocytes microinjected with synthetic BuChEmRNA alone and in combination with tissue-extracted mRNAs. 2. When injected alone BuChEmRNA efficiently directed the synthesis of small membrane-associated accumulations localized principally on the external surface of the oocyte's animal pole. Tunicamycin blocked the appearance of such accumulations, suggesting that glycosylation is involved in the transport of nascent BuChE molecules to the oocyte's surface. Coinjection with brain or muscle mRNA, but not liver mRNA, facilitated the formation of pronounced, tissue-characteristic BuChE aggregates. 3. These findings implicate tissue-specific mRNAs in the assembly of the clone-produced protein and in its nonuniform distribution in the oocyte membrane or extracellular material.

A simple assay to estimate the acetylcholinesterase molecular forms in crude extracts of rat skeletal muscle

All the current methods available for analyzing the acetylcholinesterase (AChE) molecular forms are time consuming and require the use of expensive equipment. We have found that by using the differential inactivation of globular (G4 + G1) and asymmetric AChE forms by high Mg2+ concentration, we can set up a very easy and quick assay that allows us to determine the relative proportions of AChE molecular forms present in rat skeletal muscles. This assay will be of great help in estimating changes in the muscle AChE forms under experimental conditions that require several simultaneous determinations.

Demonstration of functional acetylcholinesterase on the soma of individual neurones of Aplysia by in vivo microspectrophotometry

The presence of functional acetylcholinesterase is demonstrated in vivo on somatic membranes of single ganglionic neurones of Aplysia using concurrently microspectrophotometry and electrophysiology. The similarity of the effects of an irreversible blocker of acetylcholinesterase and of phospholipase C from Bacillus cereus suggests that acetylcholinesterase is anchored in the membrane via phosphatidylinositol.

Different membrane-bound forms of acetylcholinesterase are present at the cell surface of hepatocytes

In the present study we have determinated the acetylcholinesterase molecular forms present in rat liver hepatocytes; we have also studied the association of acetylcholinesterase with the cell surface of the hepatocytes. Subcellular fractionation indicated that rough endoplasmic reticulum and plasma-membrane-enriched fractions contains G4 and G2 acetylcholinesterase forms bound to membranes. Hepatocytes incubated with phosphatidylinositol-specific phospholipase C released about 70% of the surface acetylcholinesterase. Sedimentation analysis showed that all the solubilized acetylcholinesterase activity comes exclusively from a G2 dimer. The G4 hydrophobic form of acetylcholinesterase accounts for the additional cell-surface activity. The existence of these two forms of acetylcholinesterase on the surface of hepatocytes was further established by analyzing the phosphatidylinositol-specific phospholipase C sensitivity of the acetylcholinesterase molecular forms present in isolated rat liver plasma membranes.

Distribution and solubilization of the molecular forms of acetylcholinesterase in rat urinary bladder and sphincter

The distribution and solubility of the molecular forms of acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) were examined in adult, male rat bladder body and sphincter. Four distinct forms of the enzyme solubilized from bladder body were separated on sucrose density gradients. Two of the forms (A8 and A12) corresponded to asymmetric proteins and were solubilized with high ionic strength buffer. The other two forms represented globular forms. The smallest form (G1) was soluble in low ionic strength buffer without detergent. About 33% of the larger globular form (G4) required detergent for solubilization. There were only minor differences in the distribution of these forms in juvenile rat bladder and adult, female rat bladders. Sphincter tissue lacked one of the asymmetric forms but otherwise resembled the bladder bodies. These results demonstrate that some smooth muscle organs have significant amounts of asymmetric, as well as globular, forms of acetylcholinesterase and suggest that additional studies should be performed to characterize the enzyme in this and other smooth muscle systems.

Nerve regulation of class I and class II-asymmetric forms of acetylcholinesterase in rat skeletal muscles

Two classes of collagen-tailed, asymmetric forms (A-forms) of acetylcholinesterase (AChE) have been described in skeletal muscles of vertebrates. They are distinguished by their different solubilization requirements: class I A-forms are solubilized in the presence of high salt, whereas class II A-forms require in addition a chelating agent for solubilization. We report here that class II A-forms are less sensitive to nerve section than are class I A-forms. The latter form decreases faster and to a lower level of activity after denervation. The decay of both AChE classes is more rapidly in short-stump nerves than in long ones. The effect of nerve section on class II A-forms appears to be dependent on the particular muscle group being studied. Both classes of A-forms reappear after muscle reinnervation, but the class I A-forms recovered earlier. More interestingly, both classes of A-forms increase in normally innervated skeletal muscles after contralateral nerve injury. In this case, however, the class II A-forms change first. Muscular disuse induced by contralateral tenotomy is also followed by a rise in class II A-forms. Our results, showing differences in response and flexibility in the changes of the two classes of A-forms in several experimental conditions, represent a relevant contribution to the understanding of the regulation and functional role of the asymmetric forms of AChE in vertebrate skeletal muscles.

Development of acetylcholinesterase-positive neuronal pathways in the cochlea of the mouse

Development of the cholinergic enzymes, choline acetyltransferase (ChAT) and AChE, and of the AChE-positive innervation in the cochlea was studied biochemically and morphologically in the postnatal mouse up to 26 days. Both ChAT and AChE are already present at birth in levels comparable to 50 and 20% of near-adult values, respectively. Increases in the enzymatic activities occur mainly during the second postnatal week. ChAT increases primarily in the basal turn; the specific activities in the basal and mid turns become about equal and at least twice of the values found in the apex. AChE increase continues throughout the entire cochlea; at all times its activity is highest in the base and lowest in the apex. In the light microscope, AChE-positive fibres are seen to enter the organ in the intraganglionic bundle during late foetal development and travel upwards via radial bundles. The fibres destined for outer hair cells usually differentiate first and take a separate route. They either cross the prospective tunnel of Corti directly or take a spiral course in front of inner pillar cells to form the inner pillar bundle. The tunnel fibres are radially oriented and provide the innervation to outer hair cells in narrow vertical sectors. In most cases, the outer hair cells are being innervated by the 4th day. Between the 4th and the 6th day, the tunnel fibres reach the outer hair cells in the third row; the first and second outer spiral bundles are formed. The AChE-positive innervation of the inner spiral bundle and plexus forms in short segments, and the bundle may be still discontinuous even by the 6th day. By the 12th day the innervation is complete. In the electron microscope, the stain for AChE may allow identification of growing efferent fibres before their ultrastructural differentiation. Both ChAT and AChE activities are early markers of the differentiating efferent system. An ingrowth of the cholinergic fibres to the entire cochlea occurs before birth. The greatest increase of AChE occurs between the 4th and 10th day, relating in time to efferent synaptogenesis.

Compartmentalization of acetylcholinesterase in the chick retina

Using selective inhibitor treatments, we have studied the distribution of asymmetric (A) and globular (G) forms of acetylcholinesterase (AChE) in the extra- and intracellular compartments of chick retina, a specialized region of chick central nervous system (CNS). Our results show that the chick retinal collagen-tailed AChE (an example of class II asymmetric molecular forms) is essentially an extracellular form of the enzyme; this is the first demonstration of the extracellular localization of asymmetric AChE in the vertebrate CNS. The active site of most of the hydrophobic, membrane-bound G4-form is also exposed to the external environment. In turn, the smaller molecular weight G-forms (G2 and G1) are localized within the cells, where they may represent intermediate components in the assembly or degradation of the more complex enzymatic molecular species. Histoenzymatic ultrastructural techniques show internal AChE in amacrine as well as in ganglion cell bodies, and external enzyme, specifically associated with synapses and axons, in the inner plexiform layer. The probable cooperation of the extracellular A12-forms and the membrane-bound G species (mainly G4) of the enzyme to the hydrolysis of acetylcholine (ACh) released into the external compartment is suggested and discussed.

Electron microscopical study of non-specific cholinesterase activity in simple lamellar corpuscles of glabrous skin from cat rhinarium: a histochemical evidence for the presence of collagenase-sensitive molecular forms and their secretion

The distribution of nCHE activity was studied histochemically in simple lamellar corpuscles (SLCs) of glabrous skin from cat rhinarium. The Schwann cells forming myelin sheaths in preterminal part of SCLs exhibited no positive reaction for nCHE activity. Prevalent reaction product was localized extracellularly in the inne core enveloping terminal portion of unmyelinated sensory axon. A dot-like shaped reaction product was deposited in the basal lamina of the inner core cells and their cytoplasmic lamellae or was scattered in enlarged interlamellar spaces. Only small amount of fine end product was found to be associated with the plasma membrane of inner core lamellae. Fine reaction product for nCHE activity was consistently localized in perinuclear and rER cisternae and saccules of the Golgi apparatus of inner core cells. Some vesicles around rER and the Golgi apparatus, ones beneath the plasma membrane, and tubular-like cisternal profiles oriented towards the surface contained nCHE end product, as well. The intracellular and extracellular localization of nCHE reaction product suggests that this enzyme behaves in cat SLCs as a secreted rather than as an integral membrane protein. A large amount of dot-like reaction product in the interlamellar spaces disappeared if the skin sections were treated with collagenase before incubation in the medium for histochemical detection of nCHE activity. The decrease of nCHE end product in SLCs of the skin sections after collagenase digestion was corroborated by means of light microdensitometer and electrometrical measurement. The histochemical detection and electrometrical measurement revealed that the majority of the reaction product in the interlamellar spaces of inner core corresponds with the nCHE molecules sensitive to collagenase treatment and they are probably counted among asymmetrical molecular forms.

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

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 A8 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.

Changes in contralateral synaptic acetylcholinesterase following motor nerve section in rats

We report here that denervation of rat extensor digitorum longus, soleus and diaphragm muscle results in an increase of a subset of asymmetric acetylcholinesterase (class II A-forms) in the contralateral muscle, within a few days. This observation is interesting because it suggests a specific regulation of one asymmetric enzyme fraction, which is solubilized only in the presence of chelating agents and is thought to reside in the basal lamina.

Isolation and characterization of axolemma-enriched fractions from discrete areas of bovine CNS

Myelinated axons were isolated by flotation from bovine pons, middle cerebellar peduncle, cervical spinal cord and three regions of the subcortical white matter. The myelinated axons were osmotically and mechanically shocked, followed by fractionation on a linear 15% sucrose to 45% sucrose density gradient. Axolemma-enriched fractions (AEF) found in the 28% to 32% sucrose region of the gradient from brainstem and cord white matter had high acetylcholinesterase (AChE) while little or nil AChE activity was found in corresponding AEF derived from the subcortical white matter. Morphologically, the subcortical white matter from all regions contained a heterogeneous population of well-myelinated to thinly myelinated axons, while brainstem and cord regions contained a more homogeneous population of well-myelinated axons. Histochemical analysis of AChE localized this enzyme to axonal elements. The AEF derived from any white matter source had similar polypeptide compositions. AEF derived from subcortical white matter contained two-fold more myelin basic protein and a three-fold greater content of 2' 3' cyclic nucleotide 3' phosphodiesterase (CNP) compared with AEF derived from well myelinated white matter. We conclude that the purity of the AEF is related to the degree of myelination of the white matter from which the AEF is derived. Homogeneously well myelinated white matter (pons, cerebellar peduncle, cervical spinal cord) yields the highest purity AEF, as judged by the low CNP and myelin basic protein content and highest enrichment in AChE specific activity.

Embryonic and neonatal myosin heavy chain in denervated and paralyzed rat skeletal muscle

Using immunofluorescence procedures with specific polyclonal and monoclonal antimyosin antibodies we have found that embryonic and neonatal myosin heavy chains (MHCs), which in rat skeletal muscle disappear during the first weeks after birth, are reexpressed in adult muscle after denervation. Reactivity for embryonic and neonatal MHCs was detected in some fibers as early as 3 days after denervation, became more evident by 7 days, and occurred exclusively in the type 2A fiber population. Paralysis of innervated muscles by tetrodotoxin block of the sciatic nerve also resulted in the reappearance of embryonic and neonatal MHCs in type 2A fibers. Significant variation in the degree of immunoreactivity was observed in different segments of the same muscle fiber, suggesting that coordination of muscle fiber nuclei in the control of myosin heavy chain gene expression is partially lost following denervation.

Two types of focal accumulations of acetylcholinesterase appear in noninnervated regenerating skeletal muscles of the rat

Muscle fibers in the soleus muscle of the rat, injured by bupivacaine and free autografting, were allowed to regenerate within their old basal laminae. Histochemical and cytochemical analysis of newly synthesized acetylcholinesterase (AChE) revealed that two kinds of focal accumulations of AChE appeared in regenerating myotubes. First, AChE gets concentrated at the sites of the former motor endplates. Accumulation of AChE starts in places where a tight contact between the remnants of the old junctional basal lamina and the budding surface of the myotube engulf the extracellular material. Appearance of these AChE accumulations can be prevented by papain treatment of the soleus muscle before autografting but not by predenervating it for 1 month. Focalization of AChE is probably induced by a component of the junctional basal lamina, possibly a protein, the existence of which is not dependent upon continuous presence of the motor nerve and may be produced by the muscle. This view is corroborated by the fact that an additional kind of AChE accumulation appeared in regenerating muscles in regions remote from the sites where motor endplates were located in the muscles of origin. Although differing in localization, size, and appearance, both kinds of AChE accumulations ultrastructurally resemble the postsynaptic specialization of the motor endplate: they consist of tubelike sarcolemmal invaginations containing AChE. The extrajunctional AChE accumulations seem to arise spontaneously and are usually located more than 750 micron away from the junctional ones as if some local inhibitory mechanism prevents their formation in the immediate vicinity.

An asymmetric form of muscle acetylcholinesterase contains three subunit types and two enzymic activities in one molecule

We have purified completely the principal asymmetric ("heavy") form of acetylcholinesterase (Ac-ChoEase; EC 3.1.1.7) from chick muscle (i.e., the synaptic form in the twitch muscle fibers) by using a monoclonal antibody that recognizes AcChoEase but not pseudocholinesterase (ChoEase; cholinesterase, EC 3.1.1.8). The purified protein exhibits catalytic and inhibition properties characteristic of AcChoEase and ChoEase and contains three distinct subunits of apparent sizes 110 kDa, 72 kDa, and 58 kDa in the ratio 2:2:1. The discovery of an AcChoEase/ChoEase hybrid asymmetric form has been further supported by (i) the identification of active site properties of AcChoEase in the 110-kDa subunit and of ChoEase in the 72-kDa subunit, (ii) the purification or precipitation of both activities together by, also, a ChoEase-specific monoclonal antibody, and (iii) evidence that all subunits are bound in the asymmetric forms by disulfide bonds. The 58-kDa subunit is the only one that is sensitive to digestion with purified collagenase; it carries the collagenous "tail" of the asymmetric form. A model is proposed for this form of AcChoEase.

Differentiation and distribution of acetylcholinesterase molecular forms in the mouse cochlea

The activities of the globular and asymmetric forms of acetylcholinesterase (AChE) were measured in the whole cochlea and cochlear turns of the developing postnatal mouse. The globular AChE forms (G4, G2 and G1) were present in each cochlear turn at birth. An asymmetric AChE form (A12) was detected in the midturn on the 4th postnatal day, and in the base and apex on the 7th postnatal day. The activities of all AChE molecular forms increased rapidly during the second postnatal week and reached a plateau by the 19th postnatal day. In the 26-day old mouse, G4 constitutes the largest proportion of total cochlear AChE (57%), G2/G1 being 37% and A12 being 6%. The distribution of the AChE forms among the different turns is as follows: the combined value of the activities of G2 and G1 AChE was the same in each turn; G4 was the major form in the base and midturn; and A12, the least abundant AChE form of all, was localized mainly in the base. Our results indicate that in the cochlea (1) the content of molecular forms is similar to that of other neuronal systems, (2) the expression of AChE molecular forms is developmentally regulated, and (3) the AChE isoenzymes develop and are distributed differentially along the cochlear length; resulting near maturity in the greater proportional expression of G4 and A12 in the base and midturn and G2/G1 in the apex.

Axonal transport of 16S acetylcholinesterase is increased in regenerating peripheral nerve in guinea-pig, but not in rat

The axonal transport of the molecular forms of acetylcholinesterase was investigated in regenerating facial nerves of guinea-pig and rat. Four forms were separated by velocity sedimentation corresponding to 16S (A12), 10S (G4), 6S (G2) and 4S (G1) acetylcholinesterase. They displayed species-specific changes, which are in good accordance with those previously found in the neuronal perikarya. In the rat, axonal transport decreased for all forms. In the guinea-pig, however, the molecular forms showed differential changes. Whereas after transection, the nerve content of 10S acetylcholinesterase decreased, 16S activity was considerably increased. Anterograde transport of 16S acetylcholinesterase was found to be enhanced, whilst transport of the 10S from decreased. The two lighter forms showed only minor changes. Similar results were obtained for the guinea-pig sciatic nerve. Changes in the localization of acetylcholinesterase activity were investigated by electron microscopical cytochemistry. In the normal facial nerve of both species, activity was located intra-axonally in tubular membraneous structures and on the outer surface of the axonal membrane. In the regenerating facial nerve of the rat, intra-axonal as well as axolemmal activity decreased. Axonal sprouts at the end of the proximal nerve stump showed no activity. In the guinea-pig, however, activity of the axonal membrane increased. This was especially prominent on the surface of axonal sprouts. Strong activity was found also in the extracellular space between the sprouting axons and in the endoneurial space filled by collagen fibres. Biochemical analysis of this region revealed that the histochemical activity was mainly due to the A12 form. Thus it was concluded that, in the guinea-pig, axonal sprouts represent a target for axonally transported A12 acetylcholinesterase, which may also be secreted to extracellular sites.

Acetylcholinesterase and butyrylcholinesterase in the gut mucosal cells of various mammal species: distribution along the intestine and molecular forms

1. A cholinesterase activity was shown to be present in the homogenates of the gut mucosal cells from seven mammal species examined. 2. The distribution of the cholinesterase activity in the mucosal cells along the intestine differs from one species to another. This distribution is not correlated with that of the aminopeptidase which is a specific marker of the enterocyte plasma membranes. 3. Except rabbit, all the other species contain a (G4) globular tetrameric form and either a (G1) monomeric form (pig, ox) or a (G2) dimeric form (mouse, rat, sheep). Both (G1) and (G2) forms are found with the (G4) form in the mucosal cells of kitten and cat. The solubility characteristics of these various forms were studied by sucrose gradient centrifugations in the presence and the absence of 1% Triton X-100. 4. The mucosal cells from the studied species essentially possess either acetylcholinesterase (rabbit, kitten, cat) or butyrylcholinesterase (ox, pig, sheep, rat, mouse). These findings indicate that both enzymes probably present identical physiological functions in this cell type.

Modes of attachment of acetylcholinesterase to the surface membrane

Acetylcholinesterase (AChE) occurs in multiple molecular forms differing in their quaternary structure and mode of anchoring to the surface membrane. Attachment is achieved by post-translational modification of the catalytic subunits. Two such mechanisms are described. One involves attachment to catalytic subunit tetramers, via disulfide bridges, of a collagen-like fibrous tail. This, in turn, interacts, primarily via ionic forces, with a heparin-like proteoglycan in the extracellular matrix. A second such modification involve the covalent attachment of a single phosphatidylinositol molecule at the carboxyl-terminus of each catalytic subunit polypeptide; the diacylglycerol moiety of the phospholipid serves to anchor the modified enzyme hydrophobically to the lipid bilayer of the plasma membrane. The detailed molecular structure of these two classes of acetylcholinesterase are discussed, as well as their biosynthesis and mode of anchoring.

Distributions of molecular forms of acetylcholinesterase and butyrylcholinesterase in nervous tissue of the cat

We analyzed the activities of acetylcholinesterase and butyrylcholinesterase, and of the metabolic enzymes enolase and lactate dehydrogenase, in the superior cervical ganglion, ciliary ganglion, dorsal root ganglion, stellate ganglion, and caudate nucleus of the cat; we found that these tissues possess very different levels of enzymic activities. The proportions of the alpha alpha, alpha gamma, and gamma gamma enolase isozymes are also quite variable. We particularly studied the molecular forms of acetylcholinesterase and butyrylcholinesterase, in normal tissues and in preganglionically denervated SCG, in comparison with earlier histochemical findings. The results are consistent with the premise that the G1 (globular monomer) forms of both enzymes are located in the cytoplasm, the G4 (globular tetramer) forms are at the plasma membranes, and the A12 (collagen-tailed, asymmetric dodecamer) form of acetylcholinesterase is at synaptic sites.

Biochemistry of an olfactory purinergic system: dephosphorylation of excitatory nucleotides and uptake of adenosine

The olfactory organ of the spiny lobster, Panulirus argus, is composed of chemosensory sensilla containing the dendrites of primary chemosensory neurons. Receptors on these dendrites are activated by the nucleotides AMP, ADP, and ATP but not by the nucleoside adenosine. It is shown here that the lobster chemosensory sensilla contain enzymes that dephosphorylate excitatory nucleotides and an uptake system that internalizes the nonexcitatory dephosphorylated product adenosine. The uptake of [3H]-adenosine is saturable with increasing concentration, linear with time for up to 3 h, sodium dependent, insensitive to moderate pH changes and has a Km of 7.1 microM and a Vmax of 5.2 fmol/sensillum/min (573 fmol/micrograms of protein/min). Double-label experiments show that sensilla dephosphorylate nucleotides extracellularly; 3H from adenine-labeled AMP or ATP is internalized, whereas 32P from phosphate-labeled nucleotides is not. The dephosphorylation of AMP is very rapid; 3H from AMP is internalized at the same rate as 3H from adenosine. Sensillar 5'-ectonucleotidase activity is inhibited by ADP and the ADP analog alpha, beta-methylene ADP. Collectively, these results indicate that the enzymes and the uptake system whereby chemosensory sensilla of the lobster inactivate excitatory nucleotides and clear adenosine from extracellular spaces are very similar to those present in the internal tissues of vertebrates, where nucleotides have many neuroactive effects.

The ultrastructural localization of acetylcholinesterase-like immunoreactivity in the chicken retina

The localization of acetylcholinesterase (AChE) in the chicken retina was studied using histochemical and immunohistochemical techniques. Using histochemistry, reaction end product was found in amacrine cells, ganglion cells, horizontal cells and in 4 bands in the inner plexiform layer. Ultrastructurally, the reaction end product was located between membranes of the endoplasmic reticulum, between the membranes of the nuclear envelope, surrounding neurites in the inner plexiform layer and filling synaptic clefts. Immunohistochemical techniques using a monoclonal antibody against AChE showed a similar staining pattern to that obtained with histochemistry. Ultrastructurally, AChE-like immunoreactivity was located on, not between, the membranes of the endoplasmic reticulum and nuclear envelope of amacrine cells, ganglion cells and horizontal cells. In the inner plexiform layer, immunoreactivity was on both pre- and postsynaptic membranes, and there was no immunoreactivity in non-terminal regions of the dendritic membranes and none within the synaptic clefts.

Choline acetyltransferase and acetylcholinesterase activities in muscles of aged mice

The activities of choline acetyltransferase (CAT) and acetylcholinesterase (AChE) were assayed in intact diaphragm, extensor digitorum longus (EDL), and soleus muscles or their homogenates of young (2-6 months) and aged (24-34 months) mice. CAT activity (per mg of protein) was significantly higher in diaphragm and soleus of old mice in comparison with the young but the age change in EDL was negligible. On the other hand, AChE activity (per mg of protein) was significantly higher in EDL of old mice but in diaphragm and soleus muscles the enzyme activity did not show any significant change statistically. The diaphragm muscle was divided into two fractions, one being neuromuscular (NM) fraction and the other the remainder of the muscle (M fraction). No appreciable change in the ratio of the enzyme activities of NM fraction to the one of M fraction was obtained between the young and aged preparations. Thus, it seems likely that there is an age-related change in CAT and AChE activities which might be affected by the degree to which muscle activity is maintained.

Acetylcholinesterase from the skeletal muscle of the lamprey Petromyzon marinus exists in globular and asymmetric forms

To obtain information about the evolution of acetylcholinesterase (AChE), we undertook a study of the enzyme from the skeletal muscle of the lamprey Petromyzon marinus, a primitive vertebrate. We found that the cholinesterase activity of lamprey muscle is due to AChE, not pseudocholinesterase; the enzyme was inhibited by 1,5-bis(4-allyldimethylammonium phenyl) pentane-3-one (BW284C51), but not by tetramonoisopropyl pyrophosphortetramide (iso-OMPA) or ethopropazine. Also, the enzyme had a high affinity for acetylthiocholine and was inhibited by high concentrations of substrate. A large fraction of the AChE was found to be glycoprotein, since it was precipitated by concanavalin A-agarose. Optimal extraction of AChE was obtained in a high-salt detergent-containing buffer; fractional amounts of enzyme were extracted in buffers lacking salt and/or detergent. These data suggest that globular and asymmetric forms of AChE are present. On sucrose gradients, enzyme that was extracted in high-salt detergent-containing buffer sedimented as a broad peak of activity corresponding to G4; additionally, there was usually a peak corresponding to A12. Sequential extraction of AChE in conjunction with velocity sedimentation resolved minor forms of AChE and revealed that the G1, G2, G4, A4, A8, and A12 forms of AChE could be obtained from the muscle. The identity of the forms was confirmed through high-salt precipitation and collagenase digestion. The asymmetric forms of AChE were precipitated in low ionic strength buffer, and their sedimentation coefficients were shifted to higher values by collagenase digestion.(ABSTRACT TRUNCATED AT 250 WORDS)

A postsynaptic Mr 58,000 (58K) protein concentrated at acetylcholine receptor-rich sites in Torpedo electroplaques and skeletal muscle

In the study of proteins that may participate in the events responsible for organization of macromolecules in the postsynaptic membrane, we have used a mAb to an Mr 58,000 protein (58K protein) found in purified acetylcholine receptor (AChR)-enriched membranes from Torpedo electrocytes. Immunogold labeling with the mAb shows that the 58K protein is located on the cytoplasmic side of Torpedo postsynaptic membranes and is most concentrated near the crests of the postjunctional folds, i.e., at sites of high AChR concentration. The mAb also recognizes a skeletal muscle protein with biochemical characteristics very similar to the electrocyte 58K protein. In immunofluorescence experiments on adult mammalian skeletal muscle, the 58K protein mAb labels endplates very intensely, but staining of extrasynaptic membrane is also seen. Endplate staining is not due entirely to membrane infoldings since a similar pattern is seen in neonatal rat diaphragm in which postjunctional folds are shallow and rudimentary, and in chicken muscle, which lacks folds entirely. Furthermore, clusters of AChR that occur spontaneously on cultured Xenopus myotomal cells and mouse muscle cells of the C2 line are also stained more intensely than the surrounding membrane with the 58K mAb. Denervation of adult rat diaphragm muscle for relatively long times causes a dramatic decrease in the endplate staining intensity. Thus, the concentration of this evolutionarily conserved protein at postsynaptic sites may be regulated by innervation or by muscle activity.

Nerve-related 3S acetylcholinesterase in murine thymus

One form of acetylcholinesterase (AChE), 3S, has been identified in the thymus of normal mice as the predominant species. Histochemical studies show that the AChE is localized to nerves or to nerve-related tissues. The form isolated is composed of a salt and a detergent-sensitive fraction. Since the sedimentation values and the kinetics of the two fractions are identical, it is proposed that only one gene encodes for this globular 3S species of AChE.

Biochemical and histochemical alterations following acute soman intoxication in the rat

Rats injected with a nonlethal acute dose (100 micrograms/kg, sc) of soman (pinacolyl methylphosphonofluoridate) exhibited signs of anticholinesterase toxicity beginning at 5-15 min with increasing severity and lasting for 4-6 hr. Generalized tremors and seizure activity indicated comparatively greater involvement of the central cholinergic system than peripheral neuromuscular effects. During peak toxicity, all the brain regions tested showed more than 95% inhibition of acetylcholinesterase (AChE) activity. The cortex area was maximally affected (99% inhibition). Among skeletal muscles, soleus AChE was most severely affected (94%) and extensor digitorum longus (EDL) the least (72%). Inhibition of EDL AChE occurred at a much slower rate than in brain and other muscles. Significant recovery of AChE activity was seen by 48-72 hr after soman treatment in both brain and skeletal muscles. By Day 7, recovery was virtually complete in skeletal muscles but not in brain, although significant recovery had occurred by this time. Muscle fiber necrosis developed within 6 hr in the soleus and diaphragm, while no necrotic fibers were found in the EDL. The 16 S AChE molecular form showed the fastest recovery of the AChE isozymes in all three muscles. Full recovery was seen after 7 days in soleus and was increased to greater than control activity in diaphragm and EDL. The inhibition pattern of butyrylcholinesterase (BuChE) activity was similar to that described for AChE activity, but the recovery was comparatively faster. Carboxylesterase activity in plasma was decreased to less than 10% of control within 1 hr and recovered to 53% of control within 24 hr. No significant inhibition was seen in hepatic carboxylesterase activity. It can be concluded that soman-induced acute toxicity is directly related to the rate and degree of AChE inhibition. A significant amount of soman binds to non-AChE enzymes with serine sites such as BuChE and carboxylesterases.

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.

Molecular forms and localization of acetylcholinesterase and nonspecific cholinesterase in regenerating skeletal muscles

Molecular forms and histochemical localization of acetylcholinesterase and nonspecific cholinesterase were analysed in muscle regenerates obtained from rat EDL and soleus muscles after ischaemic-toxic degeneration and irreversible inhibition of preexistent enzymes. Regenerating myotubes and myofibres produce the 16S AChE form in the absence of innervation. The 10S AChE form prevails over 4S form with maturation into striated fibres. Although the patterns of AChE molecular forms in normal EDL and soleus muscles differ significantly no such differences were observed in noninnervated regenerates from both muscles. Two types of focal accumulation of AChE appear on the sarcolemma of regenerating muscles: first, in places of former motor endplates and, second, in extra-junctional regions. The 4S form of nonspecific cholinesterase is prevailing in regenerating myotubes whereas its asymmetric forms or focal accumulations could not be identified reliably. The satellite cells which survive after muscle degeneration probably originate from some type of late myoblasts and transmit the information concerning the ability to synthesize the asymmetric AChE forms and to focally accumulate AChE to regenerating muscle cells. Synaptic basal lamina from former motor endplates may locally induce AChE accumulations in regenerating muscles.