Comparison of Axonal Transport of Cytoplasmic- and Particulate-Associated Tubulin in Rat Optic System

Abstract: Adult rats were injected intraocularly with [³⁵S]methionine and killed from 1 to 10 weeks later. Optic nerves, optic tracts, and superior colliculi were dissected and then homogenized and separated into soluble and particulate fractions by centrifugation. Radioactivity coelectrophoresing with tubulin in buffers containing sodium dodecyl sulfate was determined (in cytoplasmic fractions, preliminary enrichment was achieved by vinblastine precipitation). Accumulation of radioactive tubulin along the optic pathway occurred in parallel (and in approximately equal amounts) in cytoplasmic and particulate fractions. Transported tubulin peaked at approximately 2 and 4 weeks in the optic nerve and tract, respectively, corresponding to a transport rate of ～ 0.4 mm/ day. There was little diminution in the amount of transported tubulin between optic nerve and tract, suggesting tubulin was not degraded in the axon. Accumulation in the superior colliculus reached a plateau by 4 weeks at less than 20% of the peak in the optic nerve, indicating turnover of tubulin at the nerve endings. The α/β subunit labeling ratio (radioactivity distribution between the tubulin subunits) was 0.57 for both cytoplasmic- and particulate-transported tubulin. In contrast, this ratio was 0.69 for whole brain tubulin prepared by vinblastine precipitation of soluble material. Isoelectric focusing and two-dimensional gel electrophoresis showed that the subunit compositions (microheterogeneity of the α and β bands) of transported tubulins in the cytoplasmic and particulate fractions were very similar. However, some differences relative to whole brain tubulin were noted; a tubulin subunit not identifiable in whole brain tubulin preparations but present in both soluble- and particulate-transported tubulin was observed. Because of the compositional and metabolic similarities of transported tubulin in the soluble and particulate fractions, we conclude that they form a common metabolic pool. This suggests either that, at least for some membranes, the well-characterized tight association between particulate tubulin and membranes may be artifactual or else that an equilibrium exists between soluble and particulate tubulin.     

TRANSPORT, TURNOVER AND DISTRIBUTION OF CHOLINE ACETYLTRANSFERASE AND ACETYLCHOLIN-ESTERASE IN THE VAGUS AND HYPOGLOSSAL NERVES OF THE RABBIT

Abstract— The transport, distribution and turnover of choline O -acetyltransferase (ChAc, EC 2.3.1.6) and acetylcholinesterase (AChE, EC 3.1.1.7) in the vagus and hypoglossal nerves were studied in adult rabbits. The enzymes accumulated proximally and distally to single and double ligatures on both nerves and thus indicated both a proximo-distal and retrograde flow of the enzymes. Double ligature experiments indicated that only 5–20 per cent of the enzymes were mobile in the axon. The rate of accumulation of both enzymes above a single ligature corresponded to the slow rate of axonal flow provided that all the enzymes were mobile, but to an intermediate or fast flow if only a small part of the enzymes was transported. The distribution of ChAc along the hypoglossal neurons was studied and only 2 per cent of ChAc was confined to cell bodies, 42 per cent was localized to the main hypoglossal nerve trunks and 56 per cent to the preterminal axons and axon terminals in the tongue. The ratio of AChE to ChAc was about 3 in the hypoglossal nerve and 32 in the vagus nerve.
Transection of the hypoglossal nerve was followed by a decrease in the activity of ChAc in the hypoglossal nucleus and nerve and in the axons and their terminals in the tongue. The activity of AChE decreased in the hypoglossal nucleus and nerve but not in the tongue. The half-life of ChAc in preterminal axons and terminals of the hypoglossal nerve was estimated to be 16-21 days from the results obtained on transport, axotomy and distribution of the enzyme. Intracisternal injection of colchicine inhibited the cellulifugal transport of both enzymes and led to an increase in enzyme activity in the hypoglossal nucleus.     

A reversible abnormal form of myelin: an X-ray scattering study of human sural and rat sciatic nerves

A sural nerve dissected from a recently dead patient displayed an unusual X-ray diffraction pattern, suggesting that in situ and at the time of the patient's death the myelin sheaths were in a swollen state. Diffraction patterns of the swollen type were also recorded from: (1) a sural nerve from the corpse of a neurologically healthy person after soaking the nerve with Ringer solution at pH 5.5; (2) sciatic nerves dissected from rat cadavers at increasing time after death. In all the cases the swollen patterns reversed to the native type upon superfusion with Ringer solution at pH 7.3. The postmortem effect is to decrease the pH of the fluids surrounding the nerves in the cadavers. Our experiments show that the early postmortem processes have the effect of acidifying PNS nerves and that as a consequence of acidification the myelin sheaths swell.     

Cellular expression patterns of acetylcholinesterase activity during grasshopper development

We examined the expression of acetylcholinesterase (AChE) in the nervous system and epidermal body structures during embryonic and larval development of two grasshopper species: Locusta migratoria and Schistocerca americana. Histochemical labelling was blocked by the enzyme inhibitors eserine and BW284c51, but not by iso-OMPA, showing that the staining reflected true AChE activity. The majority of staining was localized on the cell surface but granular intracellular staining was also visible in many cell bodies. In both species, the cellular expression of AChE followed a similar but complex spatiotemporal staining pattern. Initially, mainly epidermal tissue structures were stained in the various body appendages (stages 25%–30%). Labelling subsequently appeared in outgrowing neurons of the central nervous system (CNS) and in the nerves innervating the limbs and dorsal body wall (stages 30%–40%). The latter staining originated in motoneurons of the ventral nerve cord. In a third phase (after 45%), the somata of certain identified mechanosensory neurons started to express AChE activity, presumably reflecting cholinergic differentiation. Staining was also found in repo-positive glial cells of the CNS, longitudinal glia of connectives, glia of the stomatogastric nervous system and glial cells ensheathing peripheral nerves. Glial cells remained AChE-positive during larval to adult development, whereas motoneurons lost their AChE expression. The expression pattern in non-neuronal cells and glutamatergic motoneurons and the developmental appearance of AChE prior to synaptogenesis in the CNS suggest non-cholinergic functions of AChE during grasshopper embryogenesis. Financial support was provided by the Deutsche Forschungsgemeinschaft (Bi 262/7-1 and 262/11-1)     

COMPARISON OF THE BEHAVIOUR OF A SOLUBLE AND A MEMBRANE-BOUND ENZYME IN TRANSECTED PERIPHERAL NERVES

Phosphoglucoisomerase (PGI), a soluble enzyme, and AChE, a membrane-bound enzyme were studied in transected peroneal nerves of dog and in isolated segments of these nerves. Although activities of both enzymes increased at the ends of transected nerves, marked differences in their behaviour were observed. The increment in AChE activity was much sharper than that of PGI and continued to grow with time whereas the increase in PGI developed fully within the initial hours after transection and did not change thereafter. In an isolated nerve segment AChE accumulated at both ends with a concomitant decrease in the middle part, whereas changes in PGI activity appeared only in the terminal parts, the rest of the nerve remaining at the normal level. The terminal increase of PGI did not, contrary to that of AChE, depend on the length of the isolated segment. The changes in PGI activity may be features of a local peritraumatic reaction whereas those of AChE indicate involvement of the whole segment along which the enzyme containing organelles are transported.     

THE SUBCELLULAR LOCALIZATION OF ACETYLCHOLINESTERASE AND ITS MOLECULAR FORMS IN PIG CEREBRAL CORTEX

Abstract— The distribution of acetylcholinesterase among the subcellular fractions of pig cerebral cortex was determined. The crude mitochondrial and microsomal fractions obtained by differential centrifugation accounted for 75% of the enzyme, with the remainder divided between the crude nuclear and soluble fractions.
The occurrence and distribution of the multiple molecular forms of AChE was the same in all four fractions with the dominant species of molecular weights 350,000, 270,000 and 60,000. Further purification of the mitochondrial fraction by density gradient centrifugation gave a series of membrane fractions with very similar multiple forms. The one possible exception was the fraction containing the purified synaptosomal membranes where one band of mol wt 270,000 predominated, although the other molecular weight entities were present. The electrophoretic pattern of AChE present in the fractionated microsomes was the same as in the crude preparation. The content and pattern of the multiple molecular forms of AChE was therefore the same in all fractions of pig brain, apart from that containing the purified synaptosomal membranes.     

大鼠食管胸段，腹段乙酰胆碱酯酶阳性神经的配布

大鼠食管胸段和腹段壁内乙酰胆碱酯酶（ＡＣｈＥ）阳性神经存在于神经束和分支的粗细神经纤维内,也见于外膜丛,肌间丛,粘膜下丛和粘膜肌内。食管肌层内ＡＣｈＥ阳性神经纤维多而密集,而食管腹段肌内尤为丰富,肌间神经纤维末梢分布于肌束表面,可能与控制肌纤维活动有关;分布于肌内,粘膜下层和上皮基部的ＡＣｈＥ阳性神经中,尚含有内脏感觉神经纤维。食管壁的肌间丛和粘膜下丛内散在有多极形和卵园形的ＡＣｈＥ阳性神经元,在食管腹段内数多,而以中小型神经元为主。     

Biochemical aspects of the visual process. XXV. Light-induced calcium movements in isolated frog rod outer segments

Suspensions of isolated rod outer segments are shown to have a high calcium content of up to 11 moles calcium per mole rhodopsin. Osmotic lysis of the outer segments demonstrates the presence of two calcium fractions, a soluble one and a particulate one. The particulate fraction apparently coincides with the rod disks or with disk fragments. Illumination of intact rod outer segments in calcium-free ATP-containing Ringer solution has no measurable effect upon their total caclium content, but causes a significant shift of calcium from the particulate to the soluble fraction. This light effect is retained in lysed outer segments resuspended in calcium-free ATP-containing Ringer. These results support a function of calcium as a transmitter in light transduction in rod outer segments.     

Retinal Hexokinase: Kinetic Properties and the Effect of Cyclic 3',5'-Adenosine Monophosphate

Abstract: We measured hexokinase (EC 2.7.1.1) activity in particulate and soluble fractions isolated from bullfrog ( Rana catesbeiana ) retinas. Seventy-three percent of the hexokinase (HK) activity was associated with the particulate fraction, 27% with the soluble fraction. Both HK fractions could phosphorylate fructose, glucose, 2-deoxy-d-glucose, and mannose, but not galactose. The K _m for glucose was 0.14 m M , for 2-deoxy-d-glucose. 3.6 m M . With glucose as substrate, the V _max for particulate HK was 125–148 μ M retina⁻¹ min⁻¹, for soluble HK, 37 μ M retina⁻¹ min⁻¹. Product inhibition of particulate HK activity by glucose 6-phosphate was marked, whereas 2-deoxy-d-glucose 6-phosphate did not inhibit the activity. Cyclic AMP stimulated the HK activity of both retinal fractions nearly twofold at concentrations of 0.2–0.8 m M; AMP was much less effective in this regard.     

Nitric oxide synthase-containing, peptide-containing, and acetylcholinesterase-positive nerves in the cat lower oesophagus

Summary The innervation of the cat lower oesophagus, including the lower oesophageal sphincter, was studied by enzyme histochemistry, immunohistochemistry, and confocal microscopy. In the lower oesophageal sphincter, and at a level 2 cm above it, no apparent differences were seen in the nerve distribution pattern. Among the nerve populations studied, acetylcholinesterase (AChE)-positive nerves were the most abundant in both these regions. The density of AChE-positive nerves was particularly marked in the circular muscle layer. A rich supply of nitric oxide synthase (NOS)-containing nerves was identified by using an antiserum against neuronal NOS, or by enzyme histochemical staining for NADPH diaphorase activity. Vasoactive intestinal peptide (VIP)-immunoreactive nerves had a similar distribution pattern as NOS-immunoreactive nerves, and nerves displaying immunoreactivity for NOS and VIP often showed profiles coinciding with AChE-positive nerves. As judged by confocal microscopy, immunoreactivities for helospectin, pituitary adenylate cyclase-activating peptide (PACAP) and VIP, to a large extent were found in the same nerves. At a level 7 cm above the lower oesophageal sphincter, the total nerve supply was less than in the sphincter itself and 2 cm above it. Immunoreactivity towards VIP, PACAP and helospectin was also found to co-exist with NOS and neuropeptide Y within the same nerve structures. It is concluded that there is an intricate innervation pattern in the feline lower oesophagus reflecting the complexity in the regulation of its motility.     

Isolation and characterization of axolemma-enriched fractions from rabbit and bovine peripheral nerve

Axolemma-enriched fractions were isolated from bovine spinal accessory nerves, bovine intradural dorsal roots, and rabbit sciatic nerve by differential centrifugation and separation on a linear 10–40% sucrose (w/w) gradient. The fractions were enriched 4 to 10 fold in acetylcholinesterase, a biochemical marker for axolemma. Axolemma-enriched fractions isolated from uniformly well-myelinated fibers (bovine spinal accessory nerve) contained lower CNPase activity and higher acetylcholinesterase activity than comparable fractions isolated from variably myelinated fibers (rabbit sciatic nerve and bovine intradural roots). Separation by polyacrylamide electrophoresis showed that the molecular weight distribution of all peripheral nerve axolemma-enriched fractions was similar and ranged from 20 to over 150 kilodaltons. All axolemma-enriched fractions appeared to contain a small but variable amount of myelin-specific proteins. Based on biochemical properties, peripheral nerves containing uniformly well-myelinated fibers yield an axolemma-enriched fraction which is least contaminated with myelin-related membranes.     

FAST AXOPLASMIC TRANSPORT OF ACETYLCHOLINESTERASE IN MAMMALIAN NERVE FIBRES

Abstract— Acetylcholinesterase (acetylcholine acetyl-hydrolase, EC 3.1.1.7) is carried down mammalian nerve fibres by the fast axoplasmic transport system. This conclusion was derived from experiments involving the ligation of cat sciatic nerves at two sites placed 83.5 mm apart. The enzyme accumulated in segments of nerve proximal to the upper ligation in a linear fashion over a period of at least 20 h. At approximately 5 h the accumulation of enzyme ceased in the nerve segment proximal to the distal ligation within the isolated length of nerve, an observation indicating that the portion of AChE free to move within the isolated nerve had been depleted during this period of time. The freely moving fraction of AChE was estimated to be 15% of the total enzyme activity present in the nerve (10% in the proximo-distal direction and 5% in the retrograde direction). The rate of AChE downflow (as estimated from the intercept of the curve plotting accumulation with the line denoting when depletion started) was 431 mm/day within a 95% confidence interval of 357–543 mm/day. In view of the variability, our results demonstrated that AChE was being carried by the fast axoplasmic transport system, which in earlier studies was estimated to have a characteristic rate close to 410 mm/day.
An accumulation of AChE was also found on the distal side of the ligations that represented a movement of AChE in the distal-proximal direction in the fibres. This retrograde transport was smaller in amount (about one-half) than the proximo-distal rate of transport, or close to 220 mm/day. The rate of AChE transport was discussed in relation to the 'transport filament' hypothesis of fast axoplasmic transport.     

Soluble and Particulate Organophosphorus Neuropathy Target Esterase in Brain and Sciatic Nerve of the Hen, Cat, Rat, and Chick

Considerable evidence exists suggesting that the so-called neuropathy target esterase (NTE) is involved in the mechanisms responsible for organophosphorus-induced delayed polyneuropathy (OPIDP). Earlier studies in the adult hen, the habitually employed experimental model in OPIDP, have shown that most NTE activity in the brain is centered in paniculate fractions, whereas approximately 50% of this activity in the sciatic nerve is encountered in soluble form, with the rest being paniculate NTE. In the present work, we have studied the paniculate and soluble fractional distribution of paraoxon-resistant phenylvalerate esterase activity (B activity), parabxon- and mipafox-resistant phenylvalerate esterase activity (C activity), and NTE activity (B - C) according to ultracentrifugation criteria (100,000 g for 1 h). To this effect, two sensitive (adult hen and cat) and two scarcely sensitive (rat and chick) models were used. In all four experimental models, the distribution pattern was qualitatively similar: B activity and total NTE were much greater in brain (900–2, 300 nmol/min/g of tissue) than in sciatic nerve (50–100 nmol/min/g of tissue). The proportion of soluble NTE in brain was very low (<2%), whereas its presence in sciatic nerve was substantial (30–50%). The NTE/B ratio in brain was high for the particulate fraction (>60%) and low in the soluble fraction (7–30%); in sciatic nerve the ratio was about 50% in both fractions. Slight quantitative differences were observed in terms of OPIDP sensitivity: the proportion of soluble NTE in sciatic nerve was slightly higher in the sensitive animals (hen and cat: 49 and 44%, respectively) than in the rat and chick (41 and 37%, respectively), although no differences were noted in terms of concentration (in nanomoles per minute per gram of tissue). It is concluded that the distribution pattern of the activities studied is similar in all four experimental models, with no important quantitative differences directly related to species sensitivity or age.     

大白鼠交感节前神经再生的研究Ⅰ.生化、组化与功能观察

用液氮骤冻造成大白鼠交感节前神经变性后,通过神经末梢乙酰胆碱含量、胆碱酯酶活性测定以及电刺激交感干时外周反应等研究其再生规律。结果表明冻伤后3周内再生过程进展迅速,神经结构与功能均有相当程度的恢复;3周后再生过程转慢,直至一年时各指标仍远未达到正常。这证明交感节前神经的再生过程不同于中枢及其它外周神经而独具特征。     

LOCAL CHANGES IN SUBCELLULAR DISTRIBUTION OF DOPAMINE-β-HYDROXYLASE (EC 1.14.2.1) AFTER BLOCKADE OF AXONAL TRANSPORT

Abstract— The distribution of DBH activity between soluble and sedimentable fractions of hypotonic homogenates was examined in rat sympathetic ganglia and nerves after interruption of axonal transport. Local application of colchicine to superior cervical ganglia caused an increase mainly in particulate DBH activity, which was presumably bound to membranes. Likewise, in sciatic nerves, particulate DBH activity accumulated on both sides of a ligature and disappeared from a region well below a ligature much faster than did soluble activity. On the other hand, 18 h after simultaneous application of two ligatures to the nerve, neither total DBH activity nor subcellular distribution of this activity changed in the isolated nerve region. More detailed analysis showed that ligation affected the distribution of DBH activity within a fraction that sedimented at 140,000 g after homogenization of nerves in isotonic sucrose. Just above a ligature, osmotically releasable DBH activity was a smaller proportion of the sedimentable activity than in control nerves. However, as compared to controls, osmotically releasable DBH activity was a larger proportion of the activity in the sedimentable fraction from a region well below a ligature. A model was developed which accounts for some of these results by postulating that DBH is associated with different compartments in sciatic nerve which have different rates of transport and different proportions of soluble and bound enzyme.     

CELLULAR DISTRIBUTION OF 16S ACETYLCHOLINESTERASE

Multiple molecular forms of acetylcholinesterase (AChE; EC 3.1.1.7), in crude extracts of various tissues from the rat, were distinguished by velocity sedimentation analysis on linear sucrose gradients. Skeletal muscle samples containing end-plate regions showed three different forms of AChE with apparent sedimentation coefficients of 16, 10 and 4s. The 16s form was not detected in non-innervated regions of skeletal muscle, large intestine smooth muscle, whole brain tissue, red blood cells or plasma. Spinal cord, a predominantly motor cranial nerve and mixed (sensory and motor) peripheral nerves contained 16, 10, 6.5 and 4S AChE. Ventral motor roots, supplying the sciatic nerve, contained these four forms of the enzyme, while corresponding dorsal sensory roots were devoid of the 16S form. The 16s-AChE confined to ventral roots can be attributed totally to motor neurons and not to Schwann cells composing these roots. Whether the 16s-AChE presently found in motor nerves has chemical identity with that found at motor end-plates is the basis of future experiments.     

DISTRIBUTION OF AMINO ACIDS AND OF EXO- AND ENDOPEPTIDASES ALONG VERTEBRATE AND INVERTEBRATE NERVES

Abstract— The proximo-distal gradients for representative peptidases, peptidylpeptide hydrolases, and amino acids were measured in segments of peripheral nerve from invertebrates and vertebrates and in the lobster brain and ventral cord.
Crustacean nerve was characterized by a large pool of free amino acids totaling 100–200 μmoles/g wet wt. In lobster nerve, the principal free amino acid was aspartic acid which comprised 55 per cent of the free pool, whereas in the rat sciatic nerve it comprised only 5 per cent. The principal free amino acid in rat sciatic nerve was taurine (32 per cent of the pool) and in lobster brain glycine comprised 30 per cent of the pool. No consistent patterns emerged for the gradients along the nerves for amino acids and hydrolytic enzymes. In the leg nerve of the lobster, concentrations of aspartic acid and arginine were higher in the proximal region, and concentrations of proline and alanine were higher in the distal region. Concentrations of most amino acids were higher in the proximal regions of crab nerve, of lobster brain and ventral cord, and of rat sciatic nerve.
Rat sciatic nerve exhibited a pronounced proximo-distal increase in activity of aminopeptidase (Leu-Gly-Gly). In lobster leg nerve, activity of neutral proteinase was higher in the proximal segment, whereas activity of acid proteinase was higher in the distal segment. The best examples of proximo-distal gradients were found in lobster brain and ventral cord; activities of endopeptidases, arylamidases (Leu- and Arg-βNA), and aminopeptidase were higher in the supra-esophageal ganglia or cephalothorax segments than in the distal regions.     

Immunological and ultrastructural studies of neurofilaments isolated from rat peripheral nerve

Neurofilaments were isolated from desheathed and minced segments of rat peripheral nerve by osmotic shock into 0.01 M Tris-HCI buffer, pH 7.2. Freshly isolated neurofilaments were observed to undergo disassembly by progressive fragmentation upon exposure of dilute tissue extracts to this buffer. Low- and high-speed centrifugations of these tissue extracts separated membranous and particulate constituents and produced a progressive enrichment of 68,000-dalton polypeptide band in successive supernates, as determined by analyses of soluble proteins by SDS-polyacrylamide electrophoresis. The final high-speed supernatant fractions (S3) of nerve extracts, which were predominantly composed of 68,000-dalton polypeptide, were used to raise a specific experimental antisera in rabbits. Utilizing techniques of immune electron microscopy, experimental rabbit antisear was shown to contain antibodies against neurofilaments. Intact neurofilaments isolated from rat nerves and attached to carbon-coated grids became decorated when exposed to experimental rabbit antisera or purified gamma globulin (IgG) derivatives. The decoration of neurofilaments closely resembled the IgG coating seen in immune electron microscopy. Antibody absorption techniques were used to identify the biochemical constituency of neurofilamentous antigenic determinants. The decoration of neurofilament by experimental IgG was not altered by additions of tubulin or bovine serum albumin, but was prevented by additions of S3 fractions as well as the 68,000-dalton polypeptide of this fraction which was eluted and recovered from polyacrylamide gels. These findings are indicative that a 68,000-dalton polypeptide is a constituent subunit of rat peripheral nerve neurofilaments.     

Bidirectional axonal transport of 16S acetylcholinesterase in rat sciatic nerve

Axonal transport of the 16S Molecular form of acetylcholinesterase (16S-AChE) in doubly ligated rat sciatic nerves was studied by means of velocity sedimentation analysis on sucrose gradients. This form of AChE was selectively confined to motor, and not to sensory, fibers in the sciatic nerve, where it represented 3--4% of total AChE. Its activity increased linearly with time (4--20 hr) in nerve segments (7 mm) proximal to the central ligature (4.5 mU/24hr) and distal to the peripheral ligature (2.0 mU/24 hr). From the linear rates of accumulation of 16S-AChE, we conclude that the enzyme is conveyed by anterograde and retrograde axonal transport at velocities close to those previously defined for the movement of total AChE (410 mm/day, anterograde; 220 mm/day, retrograde). The transport of AChE molecular forms, other than the 16S form, could not be resolved presumably due to their presence in blood as well as at extraaxonal sites. The present findings are consistent with the view that in rat sciatic nerve most, if not all, of the small portion of total AChE (approximately 3%) which is transported may be accounted for by 16S-AChE.     

Decreased G4 (10S) Acetylcholinesterase Content in Motor Nerves to Fast Muscles of Dystrophic 129/ReJ Mice: Lack of a Specific Compartment of Nerve Acetylcholinesterase?

Acetylcholinesterase (AChE; EC 3.1.1.7) activity and the distribution of its molecular forms were studied in the nervous system of normal and dystrophic 129/ReJ mice, including the sciatic-tibial nerve trunk and motor nerves to slow- and fast-twitch muscles. In normal mice, motor nerves to the slow-twitch soleus exhibited a low AChE activity together with a low level of G4 (10S form) as compared with nerves of the predominantly fast-twitch plantaris and extensor digitorum longus. In contrast, in dystrophic mice, the AChE activity as well as the G4 content of nerves to the fast-twitch muscles were low, displaying an AChE content similar to that of the nerve of the soleus muscle. In the sciatic-tibial nerve trunk, the AChE activity decreased along the nerve in an exponential mode, at rates that were similar in both conditions. However, in dystrophic mice, the AChE activity was reduced throughout the nerve length by a constant value of approximately 180 nmol/h/mg protein. Further analyses indicated that AChE in this nerve trunk was distributed among two compartments, a decaying and a constant one. The decay involved exclusively the globular forms. The activity of A12 (16S form) remained constant along the nerve and was similar in both normal and dystrophic mice. In addition, according to the equation describing the decay of AChE, the reduction in enzymatic activity observed in the dystrophic mice affected mainly G4 in the constant compartment. Brain, spinal cord, sympathetic ganglia, and serum, which were also examined, showed no remarkable differences between the two conditions in their G4 content. The AChE abnormalities that we found in nervous tissues of 129/ReJ dystrophic mice were confined to the motor system.