Four cases of late onset metachromatic leucodystrophy in a family: clinical, biochemical and neuropathological studies

Four cases of familial metachromatic leucodystrophy are described: the age of onset ranged from 15 to 21 years. Mental deterioration was the earliest clinical sign to be noted and all progressed to severe dementia. The arylsulphatase activity in peripheral leucocytes of the patients was very low, 5 to 15 nmol/h/mg protein, moderately reduced in the heterozygote, 40 nmol/h/mg protein, compared with control values of 60-160 nmol/h/mg protein. Sural nerve biopsies in two cases showed perivascular macrophages filled with metachromatic material and electron microscopy showed typical inclusions in Schwann cell cytoplasm. Necropsy in one of the cases revealed severe demyelination mainly in the cerebral hemispheres with metachromatic material in macrophages and neurons.

Quantitative diameter analysis of lingual nerve axons in man

Previous studies on axon counts and fiber-diameter spectra in lingual nerves have been carried out only on animal models. This study reports an histological investigation on a series of 20 lingual nerves removed post mortem from human subjects. The results show wide variation in the myelinated fiber counts--a variation which does not appear to be related to the ages of the subjects. When the results are compared with those of a previous study (Heasman and Beynon, 1983), it is seen that the lingual nerve:inferior dental nerve ratio of axon counts is not a consistent index. The fiber-diameter spectrum for the human lingual nerve is characterized by a bimodal curve with the more pronounced peak in the small-diameter fiber range.

Myelination of the corpus callosum in the cat: time course, topography, and functional implications

The parameters of myelin development were ascertained in two specific regions of the corpus callosum in a series of cats aged 12 postnatal days through adult. The posteriormost portion of the splenium and the anterior-most portion of the genu were examined in cross section by using the electron microscope. Measurements were made to determine the age at which myelin first appeared, the number and distribution of myelinated fibers, the number and distribution of myelin lamellae, and cross-sectional area of ensheathed axons during development. The results indicate that myelination begins and ends earlier in the anterior region of the callosum. Measurements of myelin lamellae indicate similarities between anterior and posterior regions of the callosum, although development occurs earlier in the genu than in the splenium. No evidence was found for a sequence in the size of axons acquiring myelin sheaths, except that extremely small fibers are the last to begin myelinating. Myelination of the splenium of the corpus callosum begins at the very end of the behavioral and physiological critical period for the corpus callosum's role in visual functional development (Elberger: Behav. Brain Res. 11:223-231, '84; Elberger and Smith: Exp. Brain Res. 57:213-223, '85). Since myelination of a pathway is used as an index of functional reliability, this indicates that the basis for the callosal role in developing visual functions is probably not based on its physiological input to visual cortex.

Motor, sympathetic and sensory innervation of rat skeletal muscles

This study reports on the location, number and size of motor, sympathetic and sensory neurons innervating the following muscles of rat: quadriceps femoris (QF), tibialis anterior (TA), extensor digitorum longus (EDL), peroneus longus (PL), gastrocnemius medius (GM) and soleus (SOL). Cells were labelled by application of horseradish peroxidase (HRP) to transected muscle nerves. Counts of neurons were compared with counts of myelinated (MF) and unmyelinated (UMF) fibers in normal, deafferented and chemically sympathectomized nerves. The topographical arrangement of spinal motor nuclei resembled that reported previously in other mammals and birds. Sensory somata were aggregated without precise somatotopic organization, preferentially in one of the lumbar dorsal root ganglia at a segmental level corresponding to that of the motor innervation. Because lumbar sympathetic ganglia were often poorly circumscribed, the segmental position of sympathetic ganglion cells could not be localized with certainty. Sensory and sympathetic somata demonstrated a unimodal size-frequency distribution, while QF, TA and PL motoneurons could be subdivided according to size in alpha and gamma cells. For all muscles except unsuccessfully deafferented QF, counts of motor fibers after deafferentation correlated closely with counts of labelled motoneurons. Similarly, estimates of sympathetic axons, averaging 30,7% of the UMF, in most instances exceeded only marginally the ganglion cell population. In contrast, the number of peripheral afferent fibers outnumbered markedly that of sensory cell bodies, with an average of 2.8 axons per ganglion cell.

Numbers of rat dorsal root axons and ganglion cells during postnatal development

The present study demonstrates that T4 and S2 rat dorsal root axons decrease significantly from birth to adulthood with almost all of the decrease occurring in the first two weeks of life. Dorsal root ganglion cell numbers do not change during this time period. This is thus an example of postnatal axon elimination not associated with death of the cells that give rise to the axons. Presumably this regressive process is important in the formation of the normal adult nervous system. In addition, these findings raise the possibility that certain types of neonatal denervation may increase adult axon numbers by stopping a regressive process, the loss of axons, rather than initiating a progressive process, the formation of new axons.

[Age and features of the content of myelinated fibers in nerves of the splenic plexus of man]

The amount of the myelin fibers (MF) has been calculated in transversal serial sections of the nervous-vascular complexes of the splenic artery in newborns, in persons of mature (the 1st and 2d periods), elderly and old ages. In each age group 20 complexes have been studied. The total amount of the MF in persons of mature age (the 1st period) in 4.2-6 times greater (initial--terminal parts of the plexus) than in newborns, in the persons of old age it is 4-2.1 times less than in persons of mature age (in both cases P less than 0.001). Thin MF predominate, their relative contents in the aggregate of all classes of the MF in newborns are 92%, in mature persons--87%, in old persons--65%. Decreasing part of the thin MF together with increase of their absolute amount in the mature persons, comparing to the newborns, depends on higher rates in differentiation of middle and thick MF. Phenotyping peculiarities and stages of productive development, stabilization (the 1st-2d periods of the mature age), involutions of the nerve connections are defined in the splenic artery. The amount of the MF predominates in the nerves of the initial part of the plexus comparing to its terminal part. There is a direct correlative dependence between the amount of the MF in the plexus nerves and the size of the lumen in the splenic artery. Changes in the amount of the MF of different classes reflects qualitative differences of the splenic innervation relations at certain stages of the human postnatal development.

Numbers of axons in the optic nerve and of retinal ganglion cells during development in the marsupial Setonix brachyurus

Numbers of axons during postnatal development in the optic nerve of the marsupial Setonix brachyurus were estimated from electron micrographs. Between 14 and 45 days axon totals rose 10-fold from 95,000 to 961,000. Thereafter, counts decreased gradually by almost 5-fold stabilising at the adult level of 180,000-224,000 between 130-150 days. Myelinated axons were first seen at 85 days and constituted 76% of all axons by 150 days, compared to almost 100% in the adult. At comparable stages of development, estimates of cell number in the ganglion cell layer were made from sectioned and whole-mounted retinae. Ganglion cells, labelled with horseradish peroxidase (HRP) injected into the optic tract and visual brain centres, reached a maximum of 304,000 by 50 days. This value was only one-third higher than the adult ganglion cell estimate of 202,000, to which counts fell by 70 days. Such a fall of ca. 100,000 ganglion cells was matched by a reduction from 443,000 to 361,000 in the total number of cells in the retinal ganglion cell layer, that is, cells labelled by HRP plus those which remained unlabelled. Thus, during development axon counts exceeded adult values 4-fold whereas ganglion cell totals were only one-third higher than the mature value. The shortfall of ganglion cells to optic axons indicates that during development the transiently high axon number cannot be explained by a correspondingly raised count of ganglion cells. It is therefore necessary to hypothesise a substantial fibre population which temporarily projects into the nerve from either the brain or the opposite eye. Alternatively, optic axons may branch extensively during development with subsequent loss of collaterals.

[Variability in the myeloarchitectonics of the nerves of the thyroid arteries during postnatal human development]

Serial transversal sections on the nerve-vascular complexes of four thyroid arteries in newborns, in persons of the 1st and 2d periods of mature age, in elderly and old persons (40 complexes in each age group) are stained after Weigert--Pahl. Amount of myelin fibers (MF) of three dimensional classes are defined micromorphometrically. Total amount of the MF in the nerves of all thyroid plexuses is the greatest in the persons belonging to the second mature period of age: it is 2.7 times as great as in the newborns. In the elderly persons it is 1.5 times, and in the old persons--1.8 times as little as in the persons of the second period of maturity. Thin MF make the absolute majority. The amount of the MF with middle caliber in the thyroid nerves of the mature persons is 6.6 times as great as in the newborns. Their amount in the old persons is 1.7 times as little as in the mature persons. Thick MF are absent in the newborns; in the mature and elderly persons they are observed now and then. The thick MF are characterized by a high variation coefficient (up to 84%). According to the criteria of absolute and relative contents of both total and group composition of the MF in postnatal period, three stages in development of the thyroid innervational connections performed by the MF are revealed: productive, stabilization and involution. The correlative analysis reveales a direct dependence in the system diameter of each thyroid artery--number of the MF in nerves of its plexus in the newborns and mature persons. This dependence becoms negative in the elderly and old persons.(ABSTRACT TRUNCATED AT 250 WORDS)

A detailed morphometrical analysis of the pyramidal tract of the rat

The present study is aimed at a quantitative analysis and comparison of the fibers of the pyramidal tract of the rat at two levels: the pyramis medullae and the second cervical segment. For this purpose both levels of the pyramidal tracts of 5 rats have been studied morphometrically at the ultrastructural level. Fiber numbers as well as fiber diameter distributions are presented for both myelinated and unmyelinated axons. At the level of the pyramis medullae the number of unmyelinated fibers (140,000 +/- 7000) exceeds the number of myelinated axons (103,000 +/- 6000). In contrast at the level of the second cervical segment the numbers of fibers of the axon populations studied are not significantly different, viz. 43,000 +/- 2000 myelinated and 35,000 +/- 8000 unmyelinated fibers. However, these numbers mean a significant decrease of myelinated axons (48%) compared with the pyramis medullae level and an even much larger decrease (75%) in the numbers of unmyelinated fibers. Diameter distributions, obtained from the minimal fiber diameter, show a similar, monomodal shape for all axon and myelin profiles. For unmyelinated axons the minimal diameter ranges from 0.05 to 1.21 micron with a mean of 0.18 +/- 0.03 micron. For myelinated axons a mean minimal diameter of 0.72 +/- 0.12 micron has been found (range 0.13-4.92 micron), whereas their diameter measured with myelin sheath measure 1.08 +/- 0.13 micron (range 0.25-6.03 micron). The average thickness of the myelin sheath is 0.2 micron and is strongly correlated to axon diameter. Furthermore, g-ratio has been computed at a mean of 0.65 and is fairly constant throughout the diameter spectrum. Several possibilities concerning the functional and anatomical qualities of the numerically important unmyelinated axon population in the pyramidal tract of the rat are discussed.

The density of myelinated fibres is related to the fascicle diameter in human superficial peroneal nerve. Statistical study of 41 normal samples

The density of myelinated fibres in the superficial peroneal nerve was studied in 41 samples from 24 control human subjects. Photographic montages of the whole nerve fascicle were made from semithin and ultrathin transverse sections and used for a statistical analysis of sampling procedures, range of variations and relations between density and other variables. The results indicate that the spatial distribution of myelinated fibres within a nerve is often non-uniform. Therefore, it was not possible to define a statistically valid sampling system. The study of relations between variables shows the lack of any correlation between density and age and a considerable variation in the density. In contrast, there is a strong positive linear correlation between the surface area of the nerve fascicle and its content of myelinated fibres. That is, the fibre density of a given normal nerve is related to its diameter and can be predicted within a narrow range of error. We propose the term "derived density" for this value, and its application as a tool in the diagnosis of peripheral neuropathies is now being studied.

Morphology of terminations of small and large myelinated trigeminal primary afferent fibers in the cat

Horseradish peroxidase was injected intra-axonally into functionally identified cutaneous primary afferent fibers in the cat's spinal trigeminal nucleus in order to study the morphology of their central terminations. They were determined physiologically to be large, myelinated primary afferents including vibrissa, G1-hair, and slowly adapting type I afferents, as well as small, myelinated primary afferents including D-hair and A-delta high-threshold mechanoreceptive (HTM) afferents. The axons were stained for distances of 4-12 mm at the levels of the subnuclei interpolaris (Vi) and caudalis (Vc) of the spinal trigeminal nucleus. The collaterals of large, myelinated primary afferents formed terminal arbors in the outer part of the spinal trigeminal nucleus when they were rostral to or near the obex (rostral-type collaterals), in lamina V when in the rostral part of Vc (caudalis-type collaterals), and in lamina III/IV when in the caudal part of Vc (spinal dorsal horn-type collaterals). There were no transitional forms between the rostral and caudalis types, but there was a transitional type which terminated in laminae III/IV and V between the caudalis and spinal dorsal horn types. Major morphological differences were not observed among the three functional types of large, myelinated primary afferents. The collaterals of D-hair afferents showed the same types of collaterals as were seen in the large, myelinated primary afferents, except that terminal arbors of the spinal dorsal horn-type collaterals were distributed in lamina IIb in addition to lamina III/IV. Collaterals of A-delta HTM afferents formed extensive terminal arbors in the superficial part of Vi. In Vc they were distributed mainly in lamina I and few terminals existed in lamina IIa. The frequency of collaterals of A-delta HTM afferents was less than that of the other types of afferents. The collaterals of A-delta HTM afferents in Vi were distributed less frequently than those in Vc. The terminal arbors of A-delta HTM afferents were less extensive than those of the other types of afferents. The average size of varicosities of A-delta HTM afferents was smaller and that of vibrissa afferents was larger than that of the other types of afferents. This study demonstrated that there are large differences in the terminations of nociceptive and non-nociceptive primary afferents and that Vi receives direct nociceptive input from facial skin. However, the sparse distribution of collaterals of HTM afferents in Vi suggests that the rostral trigeminal nucleus contributes partially to sensory processing of facial pain.

[Nerve elements of the heart of the rat after right-sided vagotomy]

A quantitative electron microscopical investigation of the sinus node of the atrioventricular His' bundle and of the perinodal working myocardium in intact rats and 7, 15 and 30 days after right-sided vagotomy has revealed variable character of changes in the neural elements of the zones mentioned. Certain ultrastructural rearrangements in the neural apparatus are described; they reflect a combination of destructive and regenerative processes in the heart under vagotomy. Thirty days after the operation, regeneration of the neural elements in the sinoauricular area is of restorative and in the atrioventricular area--of excess character. The data are presented on dynamics of changes in the diameter of the amyelinated neural fibers in the cardiac areas investigated. Participation of both nervi vagi in innervation of the main and additional pacemakers of the organ is discussed.

Developmental morphometry of the vagus nerve in the opossum

Developmental morphology of the vagus nerve has been described for placental but not marsupial mammals such as the opossum which undergo even greater postnatal maturation. In the present study, the cervical vagus nerve of opossums from the seventh postnatal day to the adult were compared after 3% glutaraldehyde immersion, postfixation in osmium tetroxide and staining with uranyl acetate and lead citrate. At 7 days of age, axons were unmyelinated. Only 4 myelinated axons were present at the 25th postnatal day and by 50 days of age only 11% of adult values were reached. The number of Schwann cells increased from 105 at age 7 days up to 640 in the adult. The number of myelin lamellae surrounding the largest axons increased from 9 at 25 days up to 102 +/- 9 at adulthood. In the newborn kitten and rabbit, the number of myelinated vagal fibers comprised 10% (n = 326) and 18% (n = 653), respectively, of that reached in the adult animal. Comparable values are not obtained in the opossum until the 50th postnatal day.

Numbers of myelinated and unmyelinated axons in the dorsal, lateral, and ventral funiculi of the white matter of the S2 segment of cat spinal cord

The present work determines the numbers of myelinated and unmyelinated axons in the dorsal, lateral, and ventral funiculi of the S2 segment of the cat spinal cord. The major finding is that unmyelinated axons are almost as numerous as myelinated axons in these pathways. The myelinated axons tend to be distributed uniformly, although there is a slight concentration of these fibers in the dorsal part of the lateral funiculus. By contrast, the unmyelinated fibers, although found in significant numbers in all parts of these funiculi, concentrate in the dorsal part of the lateral funiculus and in the dorsal funiculus. Of particular note are the unmyelinated fibers in the dorsal funiculus, because it is highly likely that some of these are sensory. The findings in this study will serve as a basis for experimental studies to determine the numbers, locations, and types of unmyelinated fibers in the white matter of the mammalian cord.

Reinnervation of the canine tooth pulp after section of the inferior alveolar nerve in the cat

The apices of lower canine teeth have been examined 9 weeks after unilateral section of the inferior alveolar nerve. The teeth were extensively reinnervated although there was considerable variation in the number of axons present. The myelinated axons were smaller than normal with thinner myelin sheaths. There were fewer axons per non-myelinated fibre (Remak bundle). The proportions of myelinated and non-myelinated fibres were normal.

Numbers of regenerating axons in parent and tributary peripheral nerves in the rat

This study is concerned with numerical parameters of axonal regeneration in peripheral nerves. Our first finding is that the number of axons that regenerate into the distal stump of a somatic nerve at a particular time after transection is partially dependent on the type of lesion used to interrupt the axons. The second question concerns the proportion of axons that regenerate into the distal stump of a parent nerve compared to the proportions that regenerate into tributary nerves that arise from the parent. The proportions of regenerated myelinated axons in the nerve to the medial gastrocnemius muscle and myelinated and unmyelinated axons in the sural nerve are the same as the proportions of myelinated and unmyelinated axons that regenerate into the distal stump of the sciatic nerve for the crush, 0 and 4 mm gap transections. Proportionally fewer axons regenerate into the tributary nerves following the 8 mm gap transection, however. This implies that the length of the gap has an influence on whether or not axons in tributary nerves regenerate in concert with axons in the distal stump of the parent nerve. The unmyelinated fibers in the nerve to the medial gastrocnemius muscle are different because they do not regenerate in proportion to those in the distal stump of the sciatic nerve. We also provide evidence to indicate that myelinated axons branch whereas unmyelinated fibers end blindly when they enter the distal stump after crossing a sciatic nerve transection. Finally the normal arrangement of perineurial cells seems to be disrupted after the sciatic nerve regenerates across a gap.

[Morphometric analysis of diameter and density of myelinated and unmyelinated fibers of normal human sural nerves]

Diameter and density of both myelinated and unmyelinated fibers were morphometrically analyzed in 8 sural nerves obtained from 8 normal volunteers by utilizing a TGA-10 particle analyzer (Carl Zeiss Co., West Germany). The density of total myelinated fibers was (7.4 +/- 1.3) X 10(3) (mean +/- standard deviation) per square millimeter. The border diameter between small and large myelinated fibers was 5.4 +/- 0.5 micron. The densities of small and large myelinated fibers in cross sectional areas were (4.5 +/- 0.9) X 10(3) and (2.9 +/- 0.7) X 10(3) per square millimeter, respectively. The density of unmyelinated fibers was (27.9 +/- 5.8) X 10(3) per square millimeter. The peak and the median diameters in the size distribution of unmyelinated fiber diameters were 0.88 +/- 0.15 and 0.86 +/- 0.12 micron, respectively. The mean distribution histograms of the sizes of both myelinated and unmyelinated fibers of 8 sural nerves were also established. The morphometric findings obtained in this study serve as control in histopathologic analysis of the sural nerves from the patients with various peripheral neuropathies.

A quantitative electron microscopic analysis of the infraorbital nerve in the newborn rat

The infraorbital nerve (n = 3) was examined in newborn rats using electron microscopic techniques. Counts of the entire nerve revealed an average of 42,051 (S.D. = 2083) unmyelinated and 168 (S.D. = 47) myelinated fibers. The unmyelinated axons averaged 0.46 micron (S.D. = 0.16) in diameter while the myelinated fibers averaged 1.71 micron (S.D. = 0.17).

Regeneration of axons in tributary nerves

The present study tests 2 hypotheses: (1) that the numbers of axons that regenerate into a tributary nerve are in part dependent on the type of lesion used to transect the axons in the parent nerve; and (2) that the numbers of axons that regenerate will be different in different tributary nerves. Axons were counted in the sural nerve and the nerve to the medial gastrocnemius muscle 8 weeks following crush, simple transection, transection with removal of 4 mm and transection with removal of 8 mm of the sciatic nerve in the rat. The counts of myelinated and unmyelinated axons are presented in the text. If axon numbers in the 2 nerves are normalized, the proportion of regenerated to normal myelinated axon numbers are approximately the same in the 2 nerves, with more regenerated axons than normal following crush, simple transection, or 4 mm gap transection and fewer following 8 mm gap transection. The unmyelinated axons behave differently. In the nerve to the medial gastrocnemius muscle, the numbers of unmyelinated axons are greater than or equal to the normal numbers following our various surgical paradigms whereas in the sural nerve there are always fewer unmyelinated axons than normal. These findings indicate that the above hypotheses are correct for the nerves tested in the rat.

Laminar-related projection of primary trigeminal fibers in the caudal medulla demonstrated by transganglionic transport of horseradish peroxidase

The mode of termination of primary afferent fibers within the cat trigeminal nucleus caudalis was investigated by means of the transganglionic transport of horseradish peroxidase (HRP). Several types of laminar-related labeling were observed, depending upon the survival time after HRP application. At the earliest survival time (28-34 h) the highest density of labeling was found in laminae I and II. At 2 and 3 days survival laminae III and IV were heavily labeled, in addition to laminae I and II where the amount of labeling was greatly increased in lamina I, but not in lamina II. At 5 days survival time an abrupt drop of labeling occurred in laminae I and II, while this pattern was not predominant in laminae III and IV. In lamina V the pattern of labeling was less intense and not changeable through all survival times observed. These findings indicating a differentiation of the primary afferent terminals have good correspondence with a functional specialization of neuronal locations since the functional properties of neurons vary according to their locations.

Sampling schemes for estimating nerve fibre size. I. Methods for nerve trunks of mixed fascicularity

Using the tibial nerves of diabetic rats, alternative sampling schemes have been compared for estimating the sizes of fibres in nerve trunks of mixed fascicularity. The merits of each scheme were evaluated by comparing their reliability, precision, cost in time, and efficiency with 'absolute' values obtained by first measuring every fibre. The external diameter of all myelinated fibres was measured in each of six nerves (c. 2900 fibres/nerve). Total measurement time was about 29 hours. All sampling schemes produced group means within +/-4% of the absolute value of 5.52 micron. The most efficient schemes were those in which only 6% of all fibres were selected for measurement. For these the measurement time was 2 hours or less. Results are discussed in the general context of measurement of the sizes of nerve fibres. It is concluded that future studies should place more emphasis on sampling fewer fibres from more animals rather than on measuring all fibres very precisely. These considerations are likely to be of special concern to those wanting to analyse specimens with large fibre complements and those screening large numbers of specimens.

On the organization of the thoracic spinal ganglion and nerve in the rat

The location of spinal ganglion cells projecting into various thoracic spinal nerve branches in the rat has been investigated using retrograde transport of horseradish peroxidase (HRP). In addition, total numbers of myelinated and unmyelinated axons in three consecutive pairs of thoracic spinal nerves have been analyzed. The animals were perfused one to 2 days after application of HRP to thoracic spinal nerve branches and several ipsilateral spinal ganglia sectioned and processed for HRP histochemistry. Labeled cells were found in ganglia corresponding to the level of operation, as well as several adjacent rostrally and caudally located ganglia. No somatotopic organization was found within the ganglia, but occasionally a clustering of labeled cells belonging to the same peripheral nerve was observed. Pieces from three consecutive pairs of ventral and dorsal spinal nerve rami were removed from two normal rats and embedded in Vestopal. Semithin sections including the entire cross-sectional area of the rami were used to count the total number of myelinated axons. The number of unmyelinated axons was estimated by sample counting in the electron microscope. The ventral ramus of the spinal nerve contained about twice as many axons and a lower proportion of unmyelinated fibers in comparison with the dorsal ramus. Large differences in the number of axons between the two sides in pairs of spinal nerve rami and entire spinal nerves were found. These differences diminished when comparing the total number of axons from three consecutive rami or nerves on each side.(ABSTRACT TRUNCATED AT 250 WORDS)

Short internodal lengths of canine tooth pulp axons in the young adult cat

Light-microscopical measurements have been made on teased pulpal nerve fibers from young adult cat canine teeth. In the root canal portion (apical to first branching point) the mean internodal length was approximately 250 micron. In the pulpal chamber portion (coronal to the first branching point) the pulpal nerve fibers had a mean internodal length of approximately 125 micron. A local decrease in internodal length was evident at bifurcations and in preterminal regions. These internodal lengths are shorter than in similarly sized stem axons. The possible functional significance of this difference is discussed.

Silver impregnation of intrinsic sensory innervation of rat iris in toto

A silver impregnation technique (Linder, 1978) has been applied to whole mounts of the rat iris. The results suggest that only sensory fibres, both myelinated and non-myelinated, are stained. They disappear only after a trigeminal lesion and their distribution is different from that of catecholaminergic intrinsic fibres. Staining of the iris reveals a conspicuous pattern of innervation, characterised by a circular bundle and a thin plexus in the ciliary body, and by prominent bundles of fibres with a loose network of thin smooth fibres in the external part of the dilator plate and with a denser network in the central area. Nerve endings are seen on the dilator plate, in the sphincter as well as in the ciliary body. It is possible by a slight modification of the technique to stain myelinated and non-myelinated fibres separately. It results in a deep staining of the myelin while thin fibres are relatively clear. This method provides clear and reproducible staining of the nerves of the iris. It can be combined with various histochemical and immunocytochemical techniques. This will permit further studies to be made on the development of sensory and central nervous tissues, when grafted to the normal or the selectively denervated iris.

Neovascularization associated with myelinated nerve fibers: a case report

Myelinated retinal nerve fibers are fairly common developmental abnormalities and are benign in most cases. Occasionally, associated complications including myopia, anisometropic amblyopia, strabismus, macular aplasia, and colobomas have been reported. We present a case report of a patient in whom neovascularization in a region of myelinated nerve fibers developed. These vessels caused repeated vitreous hemorrhage. Although local laser therapy was unsuccessful, panretinal ablation caused involution of the neovascularity.

The treatment of experimental allergic neuritis by plasma exchange

Experimental allergic neuritis (EAN) is a demyelinating disease of the peripheral nervous system that can be induced in laboratory animals. This disorder has been considered to show many similarities to acute inflammatory polyneuropathy (Guillain-Barré syndrome, GBS). Reports that plasma exchange may benefit patients with GBS prompted the investigation of the effect of plasma exchange in EAN. A controlled study was performed on New Zealand White rabbits. Sixteen animals were allocated to control or treatment groups at the onset of the disease. Clinical assessment on days 7 and 14 showed that treated animals were less severely affected neurologically (P = 0.05, day 7; P less than 0.001 day 14), with a commensurate reduction in the severity of the histological lesions in peripheral nerves.

Unmyelinated axon ratios in cat motor, cutaneous and articular nerves

The goal of this electron microscopic study is to determine ratios of unmyelinated to myelinated axons and afferent unmyelinated to postganglionic autonomic (sympathetic) efferent axons in representative cat motor, cutaneous and articular nerves. Of the total axons in the tibial, medial gastrocnemius, sural and medial and posterior articular nerves, 70% or more are unmyelinated. The afferent unmyelinated axon components range from 49% and 45% in the medial and posterior articular nerves, respectively, to 58% in the medial gastrocnemius nerve and 61% in the sural nerve.

Numbers of axons in lateral and ventral funiculi of rat sacral spinal cord

The present study determines the numbers of myelinated and unmyelinated axons in the ventral and lateral funiculi of rat sacral spinal cord. On average, there are 55,000 myelinated and 110,000 unmyelinated axons in the lateral funiculus and 26,000 myelinated and 9,000 unmyelinated axons in the ventral funiculus at these levels. These figures combined with data from earlier studies of the posterior funiculus and the tract of Lissauer give approximate figures of 88,500 myelinated and 131,500 unmyelinated axons for the entire white matter of one side of the rat sacral spinal cord. Thus unmyelinated axons predominate in the white matter of the rat sacral spinal cord. The majority of axons, particularly the unmyelinated axons, are located in the lateral funiculus. The axons are concentrated in the dorsolateral part of the lateral funiculus, and so the dorsal part of the lateral funiculus, often referred to as the dorsolateral funiculus, contains more than half the fibers in the white matter of the spinal cord. A small nick in the dorsal and lateral part of the lateral funiculus, which is often done for various experimental reasons, could thus remove 40% of the axons in the white matter of rat sacral spinal cord. The data reported in the present paper will serve as a basis for future studies on the white matter of the isolated spinal cord.

Quantification of gray/white matter in neonates and adults

Quantitation of gray/white matter is important in evaluation of cerebral blood flow, atrophy, and development of the brain. First-order statistical analysis of neonatal computed tomographic (CT) images revealed that there was only a 6 Hounsfield unit (H) difference between gray and white matter compared with the observed 3 H for the standard deviation over the field of a skull water phantom. Scene segmentation methods based on first-order statistics proved unsuccessful in separating gray and white matter. A new regional clustering algorithm based on local textural properties was developed for separation of these structures.

Loss of intracortical myelinated fibers: a distinctive age-related alteration in the human striate area

The amount of myelin in Gennari's stripe in the human striate cortex has been measured in normal individuals ranging in age from 18 to 96 years. From the third decade onward, the amount of myelin in this intracortical plexus is gradually reduced with advancing age.

A quantitative neurohistological study of the long term effects in the rat brain of stimulation in infancy

Infant rats were either handled daily during the first 10 days of life or left undisturbed. Brains were examined, using quantitative histological methods, at 22 days postnatum and at 6 months postnatum. At 22 days the handled animals showed a deficit in glial cells in both the anterior limb of the anterior commissure and in the indusium griseum. The deficit in the former was in the oligodendrocyte fraction, whereas in the latter the deficit was in astrocytes. Myelination was unaffected, the percentage of myelinated axons, the diameter of myelinated and unmyelinated axons and the mean number of myelin lamellae being identical in handled and control groups. The numbers of mitotic figures in the subependymal layer were also similar in both groups. At 6 months of age the handled group contained more glial cells in both the rostral part of the anterior limb of the anterior commissure and the indusium griseum. In the former, the increase in glial cells was due to an increase in the number of oligodendrocytes in the handled group compared with controls; in the latter, the main increase was in astrocytes. The percentage of myelinated axons and the number of subependymal mitotic figures were both significantly higher in handled animals. It was concluded that infantile handling leads to an initial growth retardation associated with a long term increase in glial cell number. It was suggested that the initial retardation might be the result of glial cells remaining for a longer than normal time in the proliferative subependymal pool before migrating to the periphery. It was noted that the timing of the handling coincided with the period of normal rapid proliferation of oligodendrocytes in the anterior commissure and of astrocytes in the indusium griseum.

The effects of 2,5-hexanedione on axonal regeneration after nerve crush in the rat

The pattern of recovery of myelinated axons in the posterior tibial nerve after crushing was studied in rats chronically intoxicated with 2,5-hexanedione. It was given for 2 weeks before crushing (200 mg/kg i.p. 5 times a week) or additionally for two further weeks after the nerve crush. Two animals were examined from each group at approximately 1,2,3,4 and 8 weeks later. Return of function in poisoned animals was slower than in the controls. The numbers of regenerating myelinated fibres was severely reduced in poisoned animals up to 4 weeks later, but by 8 weeks the numbers equalled those in the control nerves. Marked impairment of initiation of neurite outgrowth was found, but once begun, axonal growth was comparable to controls and myelination occurred normally. Above the crush for 10 mm, filament-filled axonal swellings were found in poisoned animals accompanied by varying amounts of retrograde axonal degeneration. These findings are discussed in relation to the role of normal neurofilaments in axonal growth and the effects of probably cross-linking of these by 2,5-hexanedione on regenerating neurites.

A correlative quantitative study comparing the nerve fibers in the cervical sympathetic trunk and the locus of the somata from which they originate in the rat

Correlative quantitative analyses were performed on the rat comparing the number of fibers in the cervical sympathetic trunk (CST) and the horseradish peroxidase (HRP)-labeled neurons in the superior cervical sympathetic ganglion (SCG), stellate ganglion, as well as in the spinal cord. The total number of nerve fibers in the left CST was 4180 +/- 169 (mean +/- S.E.M.) among which 92 +/- 3 (mean +/- S.E.M.) were myelinated. The diameter of unmyelinated fibers was 0.68 +/- 0.22 (mean +/- S.D.) microns and showed single-peaked distribution. After the application of HRP to the proximal cut end of the CST, labeled neurons were found in the stellate ganglion as well as in the ipsilateral spinal cord from C7 to T4 segments. The total number of HRP-labeled neurons in the spinal cord was 1334 +/- 45 (mean +/- S.E.M.) with the range between 844 and 1808. Ninety-nine percent of labeled neurons were located in the intermediolateral column and in the lateral funiculus while 1% were in the intercalated region and central autonomic area. Labeled neurons were encountered only sporadically in the dorsal root ganglia (DRG) from C8 to T3 level. After the application of HRP to the distal cut end of the CST, about 200 labeled neurons were observed in the caudal part of the SCG. The present results were discussed with special reference to the organization of the CST of the rat.

Xanthomatous neuropathy of liver

A 36-year-old man with juvenile-onset diabetes mellitus developed cholestatic hepatitis of unknown cause, possibly drug-induced. He remained jaundiced for four months, until he died unexpectedly. At autopsy, severe and macroscopically identifiable xanthomatous neuropathy was found in the liver; it involved the unmyelinated nerves in the hilus and in all portal tracts examined. Microscopic evidence of minimal extrahepatic involvement of unmyelinated nerves was also found. Somatic nerves were affected by diabetic neuropathy but not by xanthomatous neuropathy. The condition seems to be a rare complication of diseases that are characterized by accumulations of lipids.

[Biometric characteristics of correlative intratruncal neurovascular relations of the peripheral nerves of dogs]

By methods of a combined revealing of blood vessels and neural fibres (the latter were stained after Kulchitsky, Masson and Ranson), by impregnation of microvessels after V. V. Kuprianov using histometric and mathematical analysis, correlative peculiarities of myelinated and unmyelinated neural fibres with intratruncal blood vessels were studied in the median, ulnar, musculocutaneous, radial and ischiatic nerves of 20 mature dogs. Every intratruncal capillary provides nutrition to a group of neural fibres and their endoneural environment in a certain zone. The size of the radius and area of these zones is directly proportional to the diameters of the capillaries. Nutritional zones of adjacent capillaries overlap each other, thus reliably securing the neural fibre feeding. There is a close positive correlative interrelation between the number of the neural fibres and that of the intratruncal capillaries, as well as between indices of their metric distribution; that demonstrates a morpho-functional dependence of the myelo- and angioarchitectonics of the nerves studied.

[Myeloarchitectonics of visceral nerves during human ontogeny]

In transversal electively stained histological sections of the vascular-neural complexes of the nephric ovarian, proper hepatic, common carotid, femoral arteries neural trunklets were counted, their diameters were measured, myelin fibres were divided into thin, middle and thick groups. In mature persons, the number of the neural trunklets (including those of microscopic diameter) in every paravasal plexus is greater than in newborns and in old persons. Total number of the myelin fibres, in mature persons, is greater than in newborns: in nerves of the ovarian plexus 13, in nerves of the nephric plexus 4.5, in nerves of the hepatic plexus 2.5, in nerves of common carotid artery 6, in the femoral artery 1.5 times as great in the former than in the latter. In old persons total number of myelin fibres grows smaller comparing to those in mature persons. The thick and middle fibres (their part is maximal in mature persons) undergo resorption to a greater extent than the thin ones in the nerves of old persons. In the individuals of the same age group, as well as in separate groups, the total number of myelin fibres varies within a wide range. As quantitative factors demonstrate, the definitive ensemble of the myelin conductors mature asynchronously in nerves of different organs. Difference in quantitative and qualitative contents of the myelin component reflect certain specificity of the conductive link of innervation, peculiar for each organ at every stage of the individual development.

Funduscopic observations in a colony of african green monkeys (Cercopithecus aethiops)

Funduscopic examinations were performed on 139 African green monkeys (Cercopithecus aethiops). Notable observations were made in 5% including varying degrees of retinal hypopigmentation and nerve fiber myelination. Bilateral optic nerve head colobomas were found in one monkey. This species was easily tranquilized and examined using the described methods.

Ultrastructural alterations in the initial segments and in the recurrent collateral terminals of Purkinje cells following axotomy

Transection of Purkinje cell axons in adult male rats made 1.5 mm or further from the cell body does not lead to the death of the neuron and results in compensatory structural alterations of the surviving axonal portions of the nerve cell. Near to, and at the emergence of recurrent collaterals of Purkinje cell axons, huge varicosities filled with filaments, granular material, lysosomes and mitochondria develop. Terminals of recurrent axon collaterals also exhibit different degrees of structural changes. Most striking of the morphological alterations is the regular presence of nematosomes in the hypertrophic axonal branches, especially in synaptic terminals. Since nematosomes were shown to contain RNA in other types of neurons, their presence in recurrent collaterals may indicate an enhanced synthetic activity in Purkinje axonal processes and endings after axotomy.

Histochemical changes of brain dopamine in an acute stage of cerebral ischemia in gerbils

The fluorescence histochemical method of Falck et al. was applied to 40 gerbil brains after ligation of a unilateral common carotid artery to investigate alterations of brain dopamine in the acute stage of cerebral ischemia. The distribution of dopaminergic terminals and cell bodies in gerbils is the same as in other mammals. On the ligated side after one hour of ischemia, diffuse green fluorescence of dopaminergic terminals showed only a slight decrease in intensity when compared to the nonligated side. But white matter and bundles of myelinated fibers adjacent to and in the dopamine-rich regions had an intense green fluorescence in contrast to the non-ligated side where they are normally non-fluorescent. This is considered to indicate the extraneuronal leakage and diffusion of dopamine. The intensity of extraneuronal green fluorescence was especially high in glial cells. Occasionally, there was also an unusual green fluorescence in the lumen of small vessels in dopamine-rich regions on the ligated side. Dopaminergic cell bodies in the substantia nigra on the ligated side revealed a conspicuous reduction in the fluorescence intensity in severely affected cases. After 2 or 3 hours of ischemia, there was a marked reduction or disappearance of the diffuse green fluorescence on the ligated side. This may be attributed in part to further diffusion of leaked dopamine.

[Quantitative characteristics of myeloarchitectonics of the fibrillar radial system of the infraparietal area of the human brain]

A complex and in each layer investigation of cyto- and myeloarchitectonics of the fibrillar radial system in fields 40, 39 of the inferioparietal area has been performed in histological preparations of the left and right hemispheres of one mature human brain. In "cellular" preparations the width of cytoarchitectonic layers has been measured, in "fibrillar" preparations in layers 4, 5, 6 the external diameter of the fibrillar fasciculi, that of fibres in the fasciculi have been measured, the number of fasciculi, as well as the number of fibres in the fasciculi have been counted. Each left and right cytoarchtectonic layer has its own degree in changeability of the width. Fibrillar radial system is characterized by a rather high degree of changeability. As to the distribution of the fibrillar radial fasciculi in each layer and that of fibres according to their caliber in the left and right hemispheres, it does not obey any normal law, has rather considerable coefficients of the right-sided asymmetry and, on the whole, great positive meanings of excess. Reliability of interhemispheric differences has been stated according to the caliber of the fasciculi and fibres, as well as the difference between the layers of every hemisphere. The data obtained seem to demonstrate certain differences existing in the rate of impulse transmission for each layer and between the hemispheres.

Myelination in rabbit optic nerves is accelerated by artificial eye opening

Artificial opening of the eyes of young rabbits on the 5th postnatal day led to accelerated myelination: the myelin-specific basic and proteolipid proteins nearly doubled between the 7th and the 10th postnatal days when compared to controls; 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) activity also increased by about 60%. Conversely, lowered AChE activities presumably reflected elevated myelin/axolemma ratios. Myelination in treated animals normalized during later ontogenetic stages (greater than 20th postnatal day).

[Structural and ultrastructural quantitative study of skin and nerve biopsies in the diagnosis of congenital indifference to pain]

The muscolo-cutaneous nerve, and skin biopsies from 3rd and 5th finger-tips and the back were studied in a 8-year-old girl with congenital indifference to pain, and in a control child of the same age. The tips of the fingers, and the toes were the most damaged areas. The diameters of myelinated and unmyelinated fibers of the nerve in the sick child and the control child were compared. A loss of 54% of myelinated fibers and 33% of unmyelinated fibers was observed. In the skin, the loss of myelinated fibers was 82% in the 3rd finger-tip, 78% in the 5th, and 35% in the back, and of unmyelinated fibers, 97%, 87%, and 8%, respectively. Eighty four per cent of free endings were absent in the 3rd finger-tip and they were completely absent in the 5th. As for Meissner's corpuscles, 97% were absent in the 3rd finger, and 75% in the 5th. The absence of degenerating fibers and the unimodal distribution of unmyelinated fibers raise the problem of the nosological position of this case of congenital indifference to pain, as compared to the sensory neuropathies.

Nerve supply to the inner sensory cells in a human cochlea

A choclear apical turn taken from a 66-year-old woman showed an area with marked decrease in number of the inner sensory cells. After observation by scanning electron microscope, the same specimen was thin-sectioned tangentially to the osseous spiral lamina. Numbers of myelinated nerve fibers were counted and the thickness of the fiber was measured by computed measuring equipment. Compared to the area with inner sensory cells intact, the area without inner sensory cells showed a 70% decrease in number of myelinated fibers. These degenerated fibers might have had intimate relationship with the inner sensory cells, probably being the afferent nerve supply to the inner sensory cells.

The role of Schmidt-Lanterman incisures in Wallerian degeneration. I. A quantitative teased fibre study

It is conventionally accepted that during the early stages of Wallerian degeneration of myelinated peripheral nerve fibres Schmidt-Lanterman incisures represent the sites at which the myelin sheath, together with enclosed axoplasm, is segmented into myelin ovoids. This mechanism is considered by some authors to be facilitated by the progressive intercalation of additional incisures in order to allow the later division of primary ovoids. We have demonstrated that this reported increase in the number of incisures is a misinterpretation of the changes occurring. By 36 h after crush of the rat sural nerve most myelinated fibres showed segmentation at incisures to form myelin ovoids. At 12 h and 24 h after crush, however, no ovoids were apparent and the number of incisures present was determined from teased fibres by light microscopy using oil immersion. There was no increase in the number of incisures either internodally or paranodally at 12 h and 24 h compared with a normal control population of fibres. However at 12 h, and to a greater extent at 24 h, incisures were more readily apparent than in normal fibres. It is likely, therefore, that previous reports have confused an increase in the number of incisures with an increase in their perceptibility resulting from their progressive dilatation.

Optic nerve decompression. Presumed postoperative development of medullated nerve fibers

A child had an inoperable arterial venous malformation with chronic papilledema first noticed at age 7 months. Bilateral optic nerve decompressions were performed with satisfactory results. What appeared to be medullated nerve fibers developed in the retina of one eye 5 1/2 months after surgery.

Afferent and efferent myelinated fibres in branches of the avian vagus

The numbers of afferent and efferent myelinated fibres in the branches of the vagus nerve in the domestic fowl were studied. The vago-glossopharyngeal anastomosis contained large fibres (up to 14 micrometer), the majority of which were efferent. The right recurrent nerve contained more fibres than the left one; in the right recurrent nerve about one third of the myelinated fibres were afferent. Almost all the myelinated fibres in the right cranial cardiac nerve were afferent. About half of those in the pulmono-oesophageal nerve and in the thoracic vagus were afferent.