Density Of Myelinated Nerve Fibers Research Articles

Perineurial cell basement membrane thickening and myelinated nerve fibre loss in diabetic and nondiabetic peripheral nerve

Diabetic neuropathy is associated with changes in the extracellular matrix of the perineurium, including thickening of the basement membrane of the perineurial cells. Peripheral vascular disease (PVD) is a common vascular condition that can occur in the absence or presence of diabetes. Thickening of the vascular basement membrane of the vasa nervorum is associated with both diabetes and nondiabetic peripheral vascular disease. However, perineurial cell basement membrane (PCBM) thickening in the nondiabetic PVD state has not, until now, been investigated. In this study, 36 nerve fascicles were examined from three patient groups: a diabetic group, a nondiabetic PVD group, and a group free of both PVD and diabetes (control group). PCBM thickness, fascicle size, and myelinated nerve fibre (MNF) density were measured in all three groups. Endoneurial blood vessels were also observed for evidence of morphological changes. The results showed that the thickness of the PCBM is significantly greater in the diabetic group in comparison with both the control and the nondiabetic PVD group, and this increase in thickness is linearly related to fascicle size. The thickness of the PCBM was not significantly different between the nondiabetic PVD and control groups. Although both the nondiabetic PVD and diabetic groups showed a loss of myelinated nerve fibres in comparison with the control group, this loss was statistically greater in the diabetic group. The endoneurial blood vessels of both the diabetic and nondiabetic PVD groups showed evidence of endothelial cell hyperplasia, hypertrophy, and basement membrane reduplication.

Diagnostic value of sural nerve demyelination in chronic inflammatory demyelinating polyneuropathy.

The objective of the study was to determine the diagnostic value of features of demyelination and inflammation in sural nerve biopsy specimens of patients with chronic inflammatory demyelinating polyneuropathy (CIDP). The features of (i) demyelination, (ii) axonal de- and regeneration and (iii) inflammation were investigated by measuring the number of onion bulbs, g ratio (axon diameter/total nerve fibre diameter), myelinated nerve fibre density, number of clusters and endoneurial area in 21 patients with CIDP, as well as in 13 patients with chronic idiopathic axonal polyneuropathy (CIAP) and six autopsy controls. In addition, teased fibres were classified and lengths of internodes measured. We found no difference in demyelinating features between patients with CIDP and CIAP, as the percentage of fibres with segmental de- and remyelination and the number of onion bulbs were similar in both polyneuropathy groups. The g ratio, expected to be higher in a demyelinating disease due to thinner myelin sheaths, was significantly lower in CIDP than CIAP. Evidence for axonal degeneration was found in both CIDP and CIAP, as both showed a decrease in myelinated nerve fibre density. There was no evidence of endoneurial oedema in CIDP, as the endoneurial area did not differ between CIDP, CIAP and the autopsy controls. Although significant differences of features of demyelination, axonal degeneration and inflammation were found in sural nerve biopsy specimens, there was a considerable overlap between abnormalities in CIDP and CIAP patients. In the majority of patients, quantitative analysis of light microscopical abnormalities in sural nerves was similar in CIDP and CIAP. Therefore, a sural nerve biopsy is of limited diagnostic value in CIDP.

Myelinated Nerve Fibers In Glabrous Digital Skin

In the last decade, applying multiple immunolabeling with highly specific antibodies and confocal microscopy to skin biopsies, it has been possible to study extensively cutaneous innervation. This technique has proved to be reliable and even more sensitive than sural nerve biopsy to investigate mild dying back neuropathies with only a very distal involvement of nerve fibers. So far it has been used mainly on hairy skin to evaluate small fiber anomalies in congenital, acquired and idiopathic sensory neuropathies. Compared to hairy skin, glabrous skin has a peculiar characteristic: it is rich in mechanoreceptors and myelinated Aβ fibers. To study these structures we selected a group of healthy volunteers and recruited a group of patients affected by hereditary or acquired sensory neuropathies. Skin biopsy was performed using a three mm disposable punch in all subjects on fingertip. We stained the cutaneous samples with a panel of antibodies identifying different neural structures such as the axon, the myelin sheath, the Schwann cell, and the Meissner corpuscle capsula. Three‐D digitized images were acquired using a confocal microscope. We studied Meissner and intrapapillar myelinated nerve fiber density and using a dedicated software we measured in normal and neuropathic subjects area and density of innervation of Meissner corpuscles and thickness, internodal and Ranvier node length of the sensory fibers approaching the mechanoreceptors.

Sorbitol and myo-inositol levels and morphology of sural nerve in relation to peripheral nerve function and clinical neuropathy in men with diabetic, impaired, and normal glucose tolerance.

Sorbitol and myo-inositol levels and morphology of sural nerve were compared with nerve function and clinical neuropathy in men with diabetic, impaired (IGT), and normal glucose tolerance. After neurography of sural nerve and determinations of sensory thresholds for vibration, warm and cold on the foot, whole nerve sural nerve biopsy was performed in 10 men with Type 1 diabetes mellitus, 10 with IGT, and 10 with normal glucose tolerance. Polyol levels were assessed by gas-liquid chromatography/mass spectrometry. Sural nerve amplitudes were significantly lower and sorbitol levels significantly higher in diabetic patients (median (interquartile range)) (3.7 (3.5) microV and 643 (412) pmol/mg protein, respectively) both compared with IGT (11.3 (10.6)microV; P = 0.04 and 286 (83) pmol/mg protein; P = 0.0032, respectively) and normally glucose tolerant (10.0 (11.6); P = 0.0142 and 296 (250) pmol/mg protein; P = 0.0191, respectively) subjects. There were no differences in nerve morphology between the three groups. Nerve myo-inositol levels correlated, however, positively with cluster density (rs = 0.56; P = 0.0054). In diabetic and IGT subjects, sural nerve amplitudes (2.6 (3.8) vs. 12.1 (10.6) microV; P = 0.0246) and myelinated nerve fibre density (MNFD; 4,076 (1091) vs. 5,219 (668) nerve fibres/mm2; P = 0.0021) were significantly lower in nine subjects with clinical neuropathy than in 10 without. Nerve degeneration (i.e. MNFD) correlated with clinical neuropathy but not with glucose tolerance status whereas nerve myo-inositol levels positively correlated with signs of nerve regeneration (i.e. increased cluster density).

Verification of the two-dimensional disector, a method for the unbiased estimation of density and number of myelinated nerve fibers in peripheral nerves

Quantification of the number of myelinated fibers in peripheral nerves is a common requirement in quantitative morphology. This parameter provides important information on the consequences of various physiological, pathological and experimental conditions on the nerve structure and is one of the main indicators of success of peripheral nerve repair. In this paper, the theoretical rationale for the application of stereological principles to obtain unbiased estimates of the density and total number of myelinated fibers in peripheral nerves is discussed and a simple stereological method is described. The method is applied together with a systematic random sampling scheme, that was optimized for the purposes of the present study, and with sampling scheme analysis by calculating the coefficient of error (CE). The stereological method, which consists of a two-dimensional variation of the classical disector procedure (two-dimensional disector), and the sampling scheme are verified by comparing estimates with the true density and total number of myelinated fibers in peripheral nerve trunks where true values have been accurately determined by extensive counting. The verification of the 2-D disector method, both of normal and regenerated nerves, showed that estimates of density and total number of myelinated nerve fibers are unbiased. The method also proved to be efficient (time-saving): Estimation of density and total number of myelinated fibers in a single nerve takes about 2-3 hours.

Nerve repair by means of vein filled with muscle grafts. II. Morphological analysis of regeneration.

The morphological features of regeneration in long-distance (3 cm) muscle-vein-combined grafts were experimentally investigated in the rat sciatic nerve by means of light and electron microscopy. In the early phases of regeneration (14 days after surgery), many regenerating nerve fibers were detected along the muscle-vein-combined graft. Six months after surgery, quantitative morphometrical analysis of myelinated nerve fibers showed that both the total number and density of myelinated nerve fibers were significantly greater in regenerated nerves than in control nerves. The contrary appeared true for the mean fiber size, with fiber size significantly smaller in regenerated nerves. Ultrastructural observations allowed the description of some peculiar aspects of the relationship between muscle fibers, nerve fibers, and Schwann cells in both early and late phases of regeneration.

Phrenic nerves and diaphragms in sudden infant death syndrome

Disturbances of the respiratory system may be an important factor in the cascade of events leading to sudden infant death syndrome (SIDS). Even though the diaphragm is the major respiratory muscle in infants, little is known about alterations of this muscle and of the phrenic nerve in SIDS. In the present study, diaphragms and phrenic nerves of 24 SIDS infants and seven controls were analyzed. Morphometric analysis revealed only slightly larger cross sectional areas of phrenic nerve axons but no increase in myelin sheath thickness in SIDS cases. However, in one SIDS case, myelinated nerve fibre density was severely reduced. Using electron microscopy, several nerve fibres of SIDS infants showed focal accumulations of neurofilaments. Muscle fibre diameters in SIDS diaphragms were significantly larger compared to controls ( P<0.0001). However, in almost all SIDS and control cases, axons and myelin sheaths were artificially swollen, and acute segmental muscle fibre ruptures and contracture bands were found. These prominent nonspecific ultrastructural alterations should advise caution in the interpretation of morphometric data. Thus, in some cases exemplified by one case of the present series, decreased density of phrenic nerve myelinated axons might contribute to SIDS. Still, the present results indicate that development of phrenic nerves and diaphragms is not delayed in most SIDS infants.

Tolrestat improves nerve regeneration after crush injury in streptozocin-induced diabetic rats

To delineate the ability of diabetic nerves to regenerate and to determine the effect of aldose reductase (AR) inhibitors (ARIs) on nerve regeneration in diabetic neuropathy, we evaluated nerve regeneration electrophysiologically and morphologically after sciatic nerve crush injury in three groups of male Sprague-Dawley rats: untreated diabetic (streptozocin [STZ]-induced, n = 16), tolrestat-treated diabetic (n = 16), and age-matched controls (n = 16). Compound muscle action potentials (CMAPs) appeared 4 weeks after crush injury in the control group and 5 weeks after injury in both diabetic groups. Motor nerve conduction velocity (MNCV) in the crushed nerves was decreased in both diabetic groups compared with the control group throughout the experiment. However, this decrease was significantly prevented at 24 weeks with tolrestat treatment. Morphologically, the density of myelinated nerve fibers (MNFs) and the number of MNFs per fascicle were significantly decreased in untreated diabetic rats, but tolrestat significantly prevented the former decrease at 5 weeks and the latter at 24 weeks. The mean diameter of large MNFs (>4 μm) was smaller in the untreated diabetic group than in the control group, but this decrease also was significantly prevented with tolrestat treatment. These results suggest that nerve regeneration is impaired in diabetic neuropathy and that tolrestat can prevent this impairment.

Changes of unmyelinated nerve fibers in sural nerve in amyotrophic lateral sclerosis, Parkinson’s disease and multiple system atrophy

Quantitative changes in unmyelinated nerve fibers (UMNFs) of sural nerves in patients of amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD) and multiple system atrophy (MSA) were evaluated using autopsy materials whose pathological diagnosis had been confirmed by careful postmortem examinations. Ordinary ALS cases demonstrated no involvement in cutaneous UMNFs; however, the patients with long survival due to the application of ventilatory support showed bimodality in UMNF diameter histograms, and a patient with involvement of systems other than motor pathways showed an abnormal value in two indices: a low percentage of subunits containing axon(s) and a high mean number of Schwann cell profiles per axon. A significant reduction of the mean value of UMNF density (21%) was found in PD patients. Because the density of myelinated nerve fibers did not show any significant decrease as compared with age-matched controls, the change of nerve fibers in peripheral nervous system was considered to be confined to UMNFs in PD. Elderly PD cases showed enhanced changes in the ageing process, as expressed by the two indices described above. In MSA, the mean value of UMNF density was significantly decreased (23%), and this decrease almost paralleled that of myelinated nerve fiber density. Abnormal values for the two indices described above were found and two out of four cases demonstrated bimodality in the diameter histogram of UMNFs. Unlike MSA, ALS and PD have not been included in the disorders with cutaneous UMNF involvement. Our results supply the first evidence of morphological changes in cutaneous UMNFs in PD cases. In ordinary ALS cases, the emergence of such morphological changes is suggested in cases with long survival.

Quantitative histologic study of the sural nerve in Lesch-Nyhan syndrome

The sural nerve of a 31-year-old man with Lesch-Nyhan syndrome obtained at autopsy was studied histologically. Large, myelinated nerve fibers were reduced in number and no myelinated nerve fibers larger than 5 μm were seen. Diameter distribution of myelinated nerve fibers did not demonstrate a bimodal pattern. The density of myelinated nerve fibers was 5,530/mm 2 and was decreased as compared to the controls. On electron microscopic examination, lipid-like inclusions were observed in the cytoplasm of some Schwann cells. The role of these inclusions could not be elucidated, but reduction of larger myelinated nerve fibers suggests a peripheral nervous disorder in patients with this syndrome; therefore, patients with Lesch-Nyhan syndrome must be reappraised for disorders of the peripheral nervous system.

Effect of ACTH 4–10 on nerve fiber regeneration after sciatic nerve crush in rabbits: An electrophysiological and morphological study

Crush of sciatic nerve in rabbits supported by morphologic and electrophysiologic data was used to evaluate the effects of ACTH 4–10 on nerve fiber regeneration. Treated animals showed a statistically significant higher regeneration rate than did control rabbits. Fiber density and mean diameters of myelinated nerve fibers were measured in semithin nerve sections at 1 and 3 cm distal from the crushed point at three different time points. Nerve fiber density results were higher in ACTH 4–10 − than in vehicletreated rabbits. This difference showed an unequivocal trend and attained a statistically significant level in the sections 3 cm distal from the crush. ACTH 4–10 seemed therefore to have a beneficial effect on nerve fiber regeneration.

Morphometric analysis of sural nerve in elderly diabetes mellitus.

Biopsy specimens of the sural nerve obtained from 28 middle-aged and elderly diabetics suffering from neuropathy were studied morphometrically. Myelinated nerve fiber density, especially large fibers, was decreased, and the bimodal distribution of myelinated fiber diameter shifted to unimodal distribution containing only a small fiber peak and the mean diameter of myelinated fiber was decreased. An insulin-treated group and a group with severe retinopathy showed a prominent decrease of myelinated fiber density; the severity and duration of diabetes may be a factor in this decrease. Large unmyelinated nerve fibers were also decreased and the mean diameter of unmyelinated fibers was reduced. Three patients with prominent autonomic nervous system symptoms showed a significant reduction of total unmyelinated fibers. The linear correlation between the square root of the transverse axis cylinder area and the number of myelin lamellae was obscured, and the plots were towards two directions, axonal atrophy and remyelination in diabetes. The latter process tended to be dominant in the middle-aged patients, but the importance of these two processes was reversed with age. To discuss the morphological changes of the sural nerve in diabetic neuropathy, the influence of aging as well as the duration, severity and clinical symptoms should be considered.

Density of myelinated nerve fibers in the chinchilla cochlea.

Baseline values for the density of myelinated nerve fibers at 11 locations in the chinchilla cochlea were obtained as a prerequisite for studying the relationship between sensory cell degeneration and spiral ganglion cell loss. Myelinated nerve fibers were counted within the osseous spiral lamina near the habenulae perforata. The data were expressed as myelinated nerve fibers per inner hair cell (MNF/IHC). Since the vast majority of the afferent fibers innervate the inner hair cells and since the percentage of myelinated efferent fibers at the level of the osseous spiral lamina is estimated to be quite small, MNF/IHC is a useful value which will permit the comparison of data from normal and damaged specimens. An average density of 9.4 MNF/IHC was found at the apex. This rose to a peak of 18.8 MNF/IHC in the first turn and then decreased to 14.2 MNF/IHC in the round window region. The standard deviations at the different locations ranged from 0.8 to 1.5 MNF/IHC.

In vivo effect of methylcobalamin on the peripheral nerve structure in streptozotocin diabetic rats.

To study in vivo effect of methylcobalamin (CH3-B12) on the peripheral nerve structures, rats with experimental diabetes induced by streptozotocin were administered with daily intramuscular injection of CH3-B12 (500 microgram/kg) for 16 weeks. By isolated nerve fiber studies, CH3-B12-treated diabetic rats showed less incidence of paranodal demyelination as an early sign of segmental demyelination than non-treated diabetic rats. From morphometrical analysis on sural nerves, the reduction in the density of myelinated nerve fibers, nerve fiber size and axon size of myelinated fibers was definitely protected in treated diabetic rats. The results suggested that continuous treatment with CH3-B12 had an ameliorative effect on the peripheral nerve lesions in experimental diabetic neuropathy.

The cochlear nerve in Meniere's disease.

Cochlear nerves of 11 patients with advanced Meniere's disease were studied by light and electron microscopy. All the nerves appeared normal on light microscopy. In cross sections, the density of myelinated nerve fibers was approximately 20,000 fibers per square millimeter in most cases. In two cases, the density was reduced, about 14,000/sq mm. No correlation was found between the age of patients or the duration of the disease and the density of myelinated nerve fibers. On electron microscopy, there were several features that suggested primary axonal degeneration or segmental demyelination in the cochlear nerve.

Quantitative Analysis of the Effect of Methylcobalamin on the Peripheral Nerve Structures in Experimental Diabetic Neuropathy

To study in vivo effect of methylcobalamin (CH3-B12) on the peripheral nerve structures, rats with experimental diabetes induced by streptozotocin were administered with daily intramuscular injection of CH3-B12 (500μg/kg). Improved general conditions such as an increase in body weight or ameliorated glucose intolerance were observed in the diabetic rats treated continuously with CH3-B12 for 16 weeks.There were no definite morphometrical differences between the diabetic rats treated with CH3-B12 only for 8 weeks during the latter half of this experiment, and non-treated iabetic rats. However, the diabetic rats continuously treated with CH3-B12 for 16 weeks showed low incidence of degenerated nerve fibers and less reduction of myelinated nerve fiber density than those of npn-treated diabetic rats (p<0.01 and p<0.05).The reduction of myelinated nerve fibers predominantly of large diameter (5-8μ) were prevente in the treated diabetic rats in contrast with those of nontreated diabetic rats on the histograms of the diameter of myelinated nerve fibers.The results suggested that an early continuous treatment with CH3-B12 inhibited the evolution of peripheral nerve lesions in rats with experimental diabetes.

QUANTITATIVE HISTOLOGY OF NERVE IN PROTEIN‐CALORIE MALNUTRITION AND WELL‐NOURISHED CHILDREN*

Dastur D.K., Dewan A., Manghani D.K. &amp; Udani P.M. (1977) Neuropathology Applied Neurobiology 3, 405–422Quantitative histology of nerve in protein‐calorie malnutrition and well‐nourished childrenQuantitative histological data is presented on the sural nerve from four well‐nourished control children between the ages of 5 months and 10 years. The average myelinated nerve fibre density was 14 460/mm2 with a range of 13 020/mm2 to 15 700/mm2, and bore no relation to chronological age, both the oldest and the youngest, children showing high counts. An age‐related increase in size of myelinated fibres was seen in the histograms to become bimodal at age 1 year and then remained essentially unchanged until 10 years. One well‐nourished 9‐month‐old infant born 2 months preterm showed features suggesting retardation in myelination and nerve fibre growth, medium‐sized nerve fibres (&gt; 5μm) having not yet developed, while the fibre density was greater (17 420/mm2). Quantitative histological data on the sural nerve is also presented in 8 of 14 children with protein‐calorie malnutrition (PCM), varying in age from 1.5 to 9 years, either with protein deficiency (kwashiorkor) predominating or with calorie malnutrition predominating. The majority had acquired some secondary infection as well. Twelve of the fourteen children suffered from severe malnutrition or marasmus (grade III or IV according to Harvard standards). The myelinated nerve fibre densities varied from 7940 to 22 820/mmz with a mean of 16 199/mm2, not significantly different from the mean densities in the four comparable control children. The histograms, however, showed a persistence of small diameter fibres (&lt;5 μm) in children with PCM especially those above 2 years of age, suggesting an arrest of, or delay in, myelination. This arrest, and the frequent paucity of thick axons in silver stained preparations, suggested a lack of development of medium and large myelinated nerve fibres. There was also an inverse relationship betweeen the size of myelinated fibres and the grade of malnutrition as also the age of the patients.