Acetylcholinesterase: a histochemical identification of motor and sensory fascicles in human peripheral nerve and its use during operation

To evaluate the precision of acetylcholinesterase histochemical identification of motor and sensory fascicles, this study presents a systematic observation of human peripheral nerves by Karnovsky and Roots' histochemical method. The results indicate that either of the enzymatic activities of myelinated and unmyelinated fibers was different between motor and sensory fascicles. Fifty-seven percent of the myelinated fibers showed enzymatic activity in the motor fascicles, while none of the myelinated fibers in the sensory fascicles showed enzymatic activity. The unmyelinated fibers showing enzymatic activity in the sensory fascicles were far denser than those in the motor fascicles. Our study demonstrated that the unmyelinated fibers were sympathetic postganglionic unmyelinated fibers. From these results it is concluded that the motor and sensory fascicles may be identified not only according to the enzymatic activities of the myelinated fibers, but also according to the enzymatic activities of the sympathetic postganglionic unmyelinated fibers. An improved histochemical method was suggested for its applicability as a method of intraoperative nerve fascicle identification. Simulated experiments were done on the radial nerves and the median nerves in human cadavers. This improved histochemical process can be completed within 50 minutes and can be used in intraoperative nerve fascicle identification.     

A quantitative electron microscope analysis of peripheral nerve in the urodele amphibian in relation to limb regenerative capacity

An approximate 1:1 ratio of myelinated to unmyelinated fibers was established in counts from electron micrograph montages in nerves of the newt, Triturus (Notophthalmus) viridescens. The number of myelinated fibers correspond to the number counted with the light microscope after osmium fixation. Light microscope counts of silver impregnated sections yielded a value slightly higher suggesting that, except for bundles of unmyelinated fibers, the silver technique revealed mainly myelinated fibers. The results were used to reassess previous quantitative studies on the relation between number of nerve fibers and the control which nerves exert on regeneration. For a truer estimate of the number of axons affecting regeneration, fiber values previously reported should now be doubled to include the large number of unmyelinated fibers. However, calculations show that the unmyelinated fibers contribute less than 3% of the total neuroplasm in the peripheral nerve. Finally, counts made of Schwann cells and fibroblasts show that the latter are few in number.     

Morpho-functional characteristics of the optic nerve of the steppe turtle Agrionemys horsfieldi]

The optic nerve of the tortoise Agrionemys horsfieldi contains about 400,000 fibers (90% unmyelinated and 10% myelinated ones). the diameter of unmyelinated fibers varies from 0.3 to 1.1 mu, mean value being equal to 0.5 mu; fibers with a diameter 0.4-0.7 comprise 77%. The diameter of myelinated fibers varies within 0.3-3.0 mu, average value being 0.5-0.8 nu; fibers with a diameter 0.5-0.9 mu amount to 62%. Electrogram of the optic nerve consists of two components which are equal in their amplitudes. These components presumably reflect summary firings of modal groups of unmyelinated and myelinated fibers. The velocity of propagation of excitation along the fibers producing the first component is equal to 1.3 m/sec, wheras that in fibers producing the second component - to 0.5 m/sec. The data obtained are compared with those related for the other tortoise - Emys orbicularis.     

The Fine Anatomy of the Optic Nerve of Anurans—An Electron Microscope Study

In the optic nerve of Anurans numerous myelinated and unmyelinated axons appear under the electron microscope as compact bundles that are closely bounded by one or several glial cells. In these bundles the unmyelinated fibers (0.15 to 0.6 µ in diameter) are many times more numerous than the myelinated fibers, and are separated from each other, from the bounding glial cells, or from adjacent myelin sheaths, by an extracellular gap that is 90 to 250 A wide. This intercellular space is continuous with the extracellular space in the periphery of the nerve through the numerous mesaxons and cell boundaries which reach the surface. Numerous desmosomes reinforce the attachments of adjacent glial membranes. The myelinated axons do not follow any preferential course and, like the unmyelinated ones, have a sinuous path, continuously shifting their relative position and passing from one bundle to another. At the nodes of Ranvier they behave entirely like unmyelinated axons in their relations to the surrounding cells. At the internodes they lie between the unmyelinated axons without showing an obvious myelogenic connection with the surrounding glial cells. In the absence of connective tissue separating individual myelinated fibers and with each glial cell simultaneously related to many axons, this myelogenic connection is highly distorted by other passing fibers and is very difficult to demonstrate. However, the mode of ending of the myelin layers at the nodes of Ranvier and the spiral disposition of the myelin layers indicate that myelination of these fibers occurs by a process similar to that of peripheral nerves. There are no incisures of Schmidt-Lantermann in the optic myelinated fibers.     

Quantitative studies on the intermediate nerve of the mouse with the electron microscope.

Quantitative counts of the intermediate nerve fibers of the mouse with electron microscope have shown that, on an average, 1,267 (79.3%) and 301 (18.9%) of the total nerve fibers (1,597) were myelinated and unmyelinated fibers, respectively. The number of unmyelinated fibers in the intermediate nerve was less than one-half the number of unmyelinated fibers in the greater petrosal nerve found in previous studies. Therefore, it is postulated that some of the unmyelinated fibers in the greater petrosal nerve may come from the intermediate nerve, while the rest may be derived from another source.     

The chorda tympani and glossopharyngeal nerves in the adult hamster

The numbers and diameters of axons in the intact chorda tympani(CT) and lingual branch of the glossopharyngeal nerve (GN) arequantified with the use of electron microscopic photomontages.The cross-sectional diameters of the CT and GN average 68 and86 microns, respectively. The intact CT contains {small tilde}1050 fibers, 63% are unmyelinated and 37% are myelinated. TheGN contains {small tilde} 1600 fibers, 79% are unmyelinatedand 21% are myelinated. Both nerves are made up of relativelysmall unmyelinated and myelinated fibers, although the GN showsa broader distribution of diameters for its myelinated fibersdue to the presence of general somatosensory fibers. Followingde-efferentation, there is a 48% reduction in the number ofunmyelinated fibers in the CT. Fifty-two per cent of the unmyelinatedfibers are sensory. The number of myelinated fibers is not significantlyreduced and nearly all of the myelinated fibers are sensory.Sixty-seven per cent of the fibers within the CT are sensory.The de-efferented CT contains an equal number of unmyelinatedand myelinated axons and a total of {small tilde} 700 fibers.Comparable data in the rat indicate that its intact and de-efferentedCT are organized differently in regards to the numbers of sensoryand motor, and myelinated versus unmyelinated fibers. The findingsof the present study, together with the available data fromother species, suggest that anatomical differences in the make-upof the major gustatory nerves do not contribute in any obviousway to the known differences in the response properties betweenthe rat and hamster CT, and that the number of myelinated fibersin the visceral motor component of the CT varies considerablyacross species.     

Quantitative studies on the motor root of the mouse facial nerve. An electron-microscopic study.

Fiber count analysis was performed with the electron microscope on the motor root of the facial nerve in six mice. On an average, 3,433 (84.9%) of the total nerve fibers (4,046) were myelinated and 592 (14.6%) unmyelinated. The motor root consisted mostly of large myelinated fibers (large fiber group), but a part of the root consisted of small myelinated and unmyelinated fibers (small fiber group). The nerve fibers of the small fiber group appear to correspond with those of the intermediate nerve, and to pass through the motor root and enter the intermediate nerve near the geniculate ganglion.     

Morphometry and ultrastructure of the squirrel monkey (Saimiri sciureus) vestibular nerve

Vestibular nerves of squirrel monkeys (Saimiri sciureus) embedded in plastics and epoxies were examined with light microscopy (LM) and transmission electron microscopy (TEM), and computerized measures were obtained and analyzed statistically. An average of 12,412 perikarya and 12,005 myelinated nerve fibers was obtained. Approximately 0.7% of the perikarya appeared unmyelinated under LM. About 500 unmyelinated fibers were counted. The cross-sectional area of 1,864 perikarya was 200-650 micron 2. The cross-sectional area of 1,346 nerve fibers was 3-11 micron 2 for the axoplasm and 11-12 micron 2 for the myelin sheath of the same fiber. Myelin thickness was directly proportional to the axoplasm cross-sectional area of the nerve fibers. The cross-sectional area of central axons and peripheral dendrites differed significantly (p less than 0.001). The initial segments of peripheral dendrites were usually smaller, but longer than the initial segments of the central axons. Both initial segments increased in diameter after the first node of Ranvier. Schmidt-Lantermann incisures were more abundant in thick and heavily myelinated fibers than in thin and lightly myelinated fibers. Larger perikarya usually had larger fibers and vice versa, within the first 100-200 micron from the first node of Ranvier. No major ultrastructural differences were found between myelinated and unmyelinated perikarya, except at the hillock region. The Nissl substance was preferentially located in the peripheral cytoplasm.     

Myelinated axons of ganglion cells in the retinae of teleosts

Summary In the retina of the goldfish and the rainbow trout, the axons of ganglion cells belong to the unmyelinated or the myelinated types. The unmyelinated fibers are either arranged in bundles in direct contact with neighboring fibers or they are separated by intervening lamellae of oligodendroglial cytoplasm. The myelin sheaths of the myelinated fibers differ greatly in thickness. Most fibers show 3 to 5 myelin layers; single fiber elements, however, show 10 or even more layers.     

Composition of the medial and posterior articular nerves of the mouse knee joint

The number and the distribution of fiber size in the medial (MAN) and posterior (PAN) articular nerves of the mouse knee joint were studied by electron microscopy. The MAN contained 75 +/- 28 nerve fibers consisting of 63 +/- 24 unmyelinated and 12 +/- 6 myelinated fibers. The PAN was composed of 195 +/- 50 nerve fibers, namely 129 +/- 28 unmyelinated and 66 +/- 24 myelinated fibers. A skewed unimodal distribution of the unmyelinated nerve fiber diameters was seen in both nerves ranging from 0.1 to 1.2 microm with a maximum between 0.3 and 0.6 microm. The myelinated nerve fibers in the MAN ranged from 1 to 8 microm with a peak between 2 and 5 microm. In the PAN, their diameters ranged from 1 to 12 microm with a clearly visible peak at 4-5 microm and a plateau at 8-9 microm that may represent a second maximum. These data show that the knee joint innervation of the mouse is comparable to those of the cat and rat concerning the types of nerve fibers and the composition of the two nerves. However, in relation to the much smaller area of tissue to be innervated the total number of primary afferents is considerable smaller in the mouse.     

扬子鳄视神经的研究

本文研究了扬子鳄的视神经。结果明明,视神经中可见有髓纤维和无髓纤维。有髓纤维分布均匀,无髓纤维常聚集成团;胶质细胞核,在视神经中可看到两种类型,有髓纤维总数为２００,０００－３００,０００根,纤维直径范围为０．４１－６．６６μｍ,只有一个峰值,峰直径为１．３１μｍ;纤维轴突径与纤维直径之比（ｄ／Ｄ）约为０．７３－０．７５。经统计分析,同个体左右侧神经纤维数目有差异,同一神经中周围区与中央区数目分布     

Fiber size and sensory endings of the middle cardiac nerve of the domestic fowl (Gallus domesticus)

The middle cardiac nerve, a branch of the vagus, innervates the ventricles of the avian heart. Of 533 myelinated sensory fibers, the size range was 2 micron. The ratio of myelinated to unmyelinated sensory fibers ranged from 2.17 to 3.48. Sensory endings resembled a network pattern with no distinct receptor-like endings. Frequency of nerve population increased from apex to base of the heart.     

Ultrastructure and functional characteristics of the optic nerve of Rana temporaria L. in the norm and during degeneration

Results of electron microscopy and electrophysiological studies of the frog optic nerve are presented. The nerve contains 96% unmyelinated (about 210,000) and 4% myelinated (8700–14,800) fibers. The peripheral zone of the nerve (20–30 µm) has relatively few myelinated fibers, whereas in other zones these fibers are distributed uniformly (counting area 300–400 µm²). The curve of the distribution of the diameters of myelinated fibers has a number of peaks: a main peak at 1 µm and additional peaks at 0.6 and 1.6 µm (the latter is more prominent). Individual fibers have a diameter of 0.4–3.9 µm. The diameter of the unmyelinated fibers are 0.1–0.4 µm; 64% of these fibers have a diameter of 0.2 µm. Most fibers at a temperature of 18–20° conduct at 0.3–0.4 m/sec and a few (myelinated with a diameter of 1.0–1.6 µm) at 3 and 6 m/sec. After enucleation the myelinated fibers degenerate at first and are phagocytized by neuroglia; the ultrastructure and function of the unmyelinated fibers at 18–20° remain unchanged up to 100 days postoperation.A. N. Severtsov Institute of Evolutionary Animal Morphology and Ecology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 6, pp. 627–635, November–December, 1970.     

Electron-microscopic analysis of the mouse facial nerve near the geniculate ganglion

An electron-microscopic analysis of the mouse facial nerve near the geniculate ganglion shows that there are, on the everage, 603 more nerve fibers in the portion of the nerve distal to the geniculate ganglion than there are in the part proximal to the ganglion. The average distal increase in the number of unmyelinated fibers is 444 and that in the myelinated fibers is 165. The somatic motor nerve fibers and the parasympathetic fibers in the mouse facial nerve may not contribute to the distal excess. It is possible that the increase in the number of unmyelinated fibers distal to the geniculate ganglion is mainly due to the presence of postganglionic sympathetic fibers in the facial trunk distal to the geniculate ganglion and the greater petrosal nerve. The distal increase in the number of myelinated fibers may be mainly contributed by the sensory fibers.     

Neurogenic inflammation of gingivomucosal tissue in streptozotocin-diabetic rat

Previously it was assumed that nerve fibres are involved in the neurogenic inflammation induced by mechanical or chemical irriations. It has been also suggested that in diabetes mellitus the unmyelinated small diameter fibers are impaired as a result of diabetic neuropathy. Therefore, our aim was to study the alterations of the nerve processes in the gingivomucosal tissue in streptozotocin (STZ)-diabetic rats. Light- and electronmicroscopical examinations were made to analyze the changes in nerve fibres. After one week of steptozotocin treatment, the gingivomucosal tissue had inflammatory cell infiltration and some degenerated nerve fibres were also observed. Dense mitochondria, disorganization of cell organelles, and appearance of myelin-like dense bodies were found in the axons of degenerared nerve fibres. Semiquantitative analysis showed that 14 +/- 4% of the unmyelinated nerve fibres degenerated after one week of STZ treatment. However, degeneration of the myelinated nerve fibers was not observed. Two weeks after STZ treatment, most of the unmyelinated and myelinated nerve fibers showed degeneration (86 +/- 5%) and the placement of the ligature revealed a non-inflammatory connective tissue adjacent to a normal epithelium. The myelin sheath was disrupted and dark axoplasm with cytolysosomes became manifest. These findings demonstrated that both unmyelinated and myelinated nerve fibers are altered and inflammatory reaction exists in the gingivomucosal tissue only in the early stage of diabetes mellitus.     

Composition of the medial and posterior articular nerves of the mouse knee joint

The number and the distribution of fiber size in the medial (MAN) and posterior (PAN) articular nerves of the mouse knee joint were studied by electron microscopy. The MAN contained 75 &#45 28 nerve fibers consisting of 63 &#45 24 unmyelinated and 12 &#45 6 myelinated fibers. The PAN was composed of 195 &#45 50 nerve fibers, namely 129 &#45 28 unmyelinated and 66 &#45 24 myelinated fibers. A skewed unimodal distribution of the unmyelinated nerve fiber diameters was seen in both nerves ranging from 0.1 to 1.2 &#119 m with a maximum between 0.3 and 0.6 &#119 m. The myelinated nerve fibers in the MAN ranged from 1 to 8 &#119 m with a peak between 2 and 5 &#119 m. In the PAN, their diameters ranged from 1 to 12 &#119 m with a clearly visible peak at 4-5 &#119 m and a plateau at 8-9 &#119 m that may represent a second maximum. These data show that the knee joint innervation of the mouse is comparable to those of the cat and rat concerning the types of nerve fibers and the composition of the two nerves. However, in relation to the much smaller area of tissue to be innervated the total number of primary afferents is considerable smaller in the mouse.     

Pathological changes of human unmyelinated nerve fibers: a review

In the cutaneous nerves, unmyelinated nerve fibers outnumber the myelinated ones but are scarcely analyzed, especially at autopsy. This indifference toward the pathology of unmyelinated nerve fibers may be due to the necessity of electron microscopic analyses and, more importantly, the obscurity of pathological alteration of unmyelinated nerve fibers in aging as well as in peripheral nerve disorders. The aim of this article is to review (1) the normal appearance including postmortem changes, (2) the age-related changes, and (3) the pathological alteration in various neuropathic and non-neuropathic conditions, of unmyelinated nerve fibers in the sural nerve. For the complete analyses of sural nerve, qualitative and quantitative estimation of unmyelinated nerve fibers in all specimens should be recommended and it sometimes has an important diagnostic value.     

Comparative study of the lamina cribrosa and the pial septa in the vertebrate optic nerve and their relationship to the myelinated axons

The optic nerve contains the connective tissues, i.e. the lamina cribrosa and pial septa. This report presents a histological comparison of the lamina cribrosa and pial septa in the five classes (mammals, birds, reptiles, amphibians and teleosts) of vertebrates. Furthermore, the distribution of myelinated fibers was observed from the optic nerve through the retina in the same animals. The lamina cribrosa is found in mammals except for mice, and in birds. Structural complexity of the lamina was different in animals but generally dependent of the optic nerve thickness. The pial septa were present in the optic nerve proper of the mammals except for the mice, in birds and in a part of teleosts. Fasciculation of the optic nerve by the pial septa tended to be more prominent as the optic nerve become thicker. The optic nerve consisted of largely myelinated fibers in vertebrates. The retina contained some myelinated fibers in submammals but was thoroughly devoid of myelinated fibers in mammals. The borderline between myelinated and unmyelinated portions in the optic nerve of different species did not related to the lamina cribrosa. Amphibians had exceptionally only a few myelinated fibers in the optic nerve and no myelinated fibers in the retina.     

Morpho-functional changes in the turtle midbrain tectum after enucleation

Morpho-functional changes in the tectum mesencephali during degeneration after enucleation were studied inEmys orbicularis L. Comparison of amplitude-time characteristics of evoked potentials of the visual center with degenerative changes in axon terminals and fibers of the optic nerve in the same animals revealed a "light" type of degeneration of the terminals of unmyelinated axons and a "dark" type in terminals of myelinated axons. During "dark" degeneration (4–5 months after enucleation) the low-amplitude presynaptic component of the evoked potential, reflecting excitation of large myelinated fibers, disappeared and changes occurred in the characteristics of the first high-amplitude component, the appearance of which is connected with excitation of myelinated fibers of medium diameter. The last component disappeared 7 months after the operation, along with disappearance of the "dark" degeneration. During "light" degeneration (2.5–3.5 months) changes took place in the characteristics of the second high-amplitude component of the evoked potential, which reflects excitation of thin fibers, both myelinated and unmyelinated, whose ranges of diameters overlap. This component disappeared after 6–7 months, almost simultaneously with disappearance of the first high-amplitude component, as the result of simultaneous completion of degeneration of myelinated fibers of medium and small diameter.     

Acetylcholinesterase activity of motor and sensory nerve fibers in the spinal nerve roots of the rat

Summary The histochemical and cytochemical distribution of acetylcholinesterase activity in the anterior and posterior spinal nerve roots and ganglia of the rat was demonstrated by the Karnovsky method using acetyl and butyrylthiocholine as substrates and eserine and DFP as inhibitors. Light and electron microscopic examination of transverse frozen sections enabled the simultaneous visualization of end product in relationship to the various fiber components of each nerve root. While the enzymatic activity of the anterior roots was consistantly observed in the large extrafusal and small intrafusal motor fibers a relatively greater amount of precipitate occurred in aggregates of myelinated and unmyelinated fibers believed to represent preganglionic sympathetic nerves. In contrast, no significant enzymatic activity could be demonstrated in the myelinated nerve fibers of the posterior root. In the sensory sytem, the limited enzymatic precipitate was largely restricted to the unmyelinated afferent fibers and to their small cell bodies in the dorsal root ganglia. The ultrastructural distribution of enzymatic activity was located in the granular endoplasmic reticulum and perinuclear spaces of the ganglion cells. Within peripheral nerves this end product occurred between the apposing axonal and Schwann cell membranes and along the membranous aspect of occasional axoplasmic vesicles of both myelinated and unmyelinated nerve fibers.This study was supported by grants NB 04161-04 and NB 04161-05 of the National Institute of Neurological Diseases and Blindness. — The author would like to thank MissMaria C. la Valle for her skillful technical assistance.