Mast cell-associated Renaut bodies in the peroneal nerve of a dog with a history of mastocytosis

Multiple Renaut bodies were identified by light microscopy in the biopsied common peroneal nerve of a dog with generalized neuropathy, hypothyroidism and a history of cutaneous mastocytosis. In addition, numerous granulated cells were associated with most of the Renaut bodies. Electron microscopic examination confirmed these to be mast cells, both central and peripheral to Renaut bodies, a phenomenon never previously reported. Endoneurial fibrosis, myelinated fiber loss, as well as evidence of axonal degeneration, demyelination and remyelination were observed. 'Vacuolation' of endoneurial fibroblasts was also present. The location of these Renaut bodies in the common peroneal nerve, and the absence of any documented or expected nerve compression, implicates other etiological factors. These observations are the first to report an association between mast cells and Renaut bodies. It is possible that mast cells, at least in this case, are involved in the formation of Renaut bodies.     

Renaut body distribution at sites of human peripheral nerve entrapment

In an autopsy study of the pathology of chronic subclinical nerve entrapment Renaut bodies showed a strong predilection for sites of nerve entrapment. They were present at these sites in 43 of 74 peripheral nerves but in none of the control sections of the same nerves. Renaut bodies were most frequently encountered in the median nerve at the wrist and in the lateral femoral cutaneous nerve at the inguinal ligament but were rarely seen in sections of the common peroneal nerve at the neck of the fibula. Renaut bodies were closely associated with thickened subperineurial capillaries and, in successive transverse sections, they terminated in a fibrous mass of these thickened vessels. In several nerves Renaut bodies showed a similar orientation within adjacent fascicles, suggesting that mechanical factors were related to their pathogenesis; despite this finding there was no relationship between their numbers at entrapment sites and the presence of pathological changes in myelinated nerve fibres at the same level. These findings suggest that while mechanical factors are important in the pathogenesis of Renaut bodies there is no evidence to support the theory that these structures protect nerve fibres from mechanical stress.     

Collagen content in human ulnar nerve

Summary A quantitative analysis of ulnar nerve collagen in the arm and forearm was undertaken in nine subjects. While endoneurial collagen was found to be significantly increased within the cubital tunnel, extrafascicular collagen did not increase at the elbow except in two nerves showing fusiform enlargements. Renaut bodies increased in frequency at sites of high endoneurial collagen content. Morphological determinations of cross-sectional area along the ulnar nerve did not correlate with quantitative collagen data.     

Long-term endoneurial changes after nerve transection

Summary Long-term endoneurial changes in the distal stump of transected rat sciatic nerve were examined from 8 to 50 weeks after nerve transection. The morphological alterations were followed both in nerves which were allowed to regenerate and in nerves in which regeneration was prevented by suturing. The nerves prevented from regenerating showed markedly atrophied Schwann cell columns after 20 weeks and a disappearance of some Schwann cell columns after 30 weeks. The surrounding endoneurial fibroblast-like cells gradually lost their delicate cytoplasmic extensions and formed rough fascicles around numerous shrunken Schwann cell columns or around areas from which Schwann cells had apparently disappeared. Inside the fascicles, the Schwann cell loss was replaced by collagen fibrils or occasionally, by a dense accumulation of microfibrils. The loss of endoneurial cytoplasmic processes continued up to 50 weeks, leaving behind patches of thin fibrils around numerous shrunken Schwann cell columns or around collagenous areas where Schwann cells were lost. The endoneurial matrix showed presence of thin 25- to 30-nm collagen fibrils close to shrunken Schwann cell columns up to 50 weeks but in areas with advanced degeneration a shift towards regular 50- to 60-nm collagen fibrils occurred. The degenerated areas resembled those described in Renaut bodies and neurofibromas. Despite suturing of transected nerves to prevent sprouting, occasional regenerating sprouts were noted in the Schwann cell columns. These axons were surrounded in a sheath-like fashion by pre-existing endoneurial cell fascicles covered by a basal lamina. In the reinnervating nerves the endoneurial space gradually lost its compartmentized structures consisting of collagen fibrils and endoneurial fibroblast-like cells. After 20 weeks the endoneurial cells were inconspicuous and the extracelluar matrix consisted mainly of 50- to 60-nm collagen fibrils. During axonal growth and maturation, Schwann cells containing unmyelinated axons surrounded large, myelinated axons in a collar-like fashion. Close to these collars of Schwann cells, thin 25- to 30-nm collagen fibrils were noted in focal areas, even after 50 weeks. Occasionally, numerous clusters of regenerating axonal sprouts were noted in the perineurium. These were surrounded by multiple layers of cells possessing basal lamina. The present results show that after nerve transection the distal stump of the severed nerve shows dynamic changes in the endoneurial space, especially in nerves where reinnervation is prevented. The endoneurial fascicles around occasional axonal sprouts in sutured nerves, representing possibly a delayed type of regeneration, show that axons have a strong ability to grow but on the other hand endoneurial structures are unable to respond normally to axonal growth after advanced degeneration.     

Axonal and extracellular matrix responses to experimental chronic nerve entrapment

We have analyzed the ultrastructural and histopathological changes that occur during experimental chronic nerve entrapment, as well as the immunohistochemical expression of chondroitin sulfate proteoglycan (CSPG). Adult hamsters (n = 30) were anesthetized and received a cuff around the right sciatic nerve. Animals survived for varying times (5 to 15 weeks) being thereafter perfused transcardially with fixative solutions either for immunohistochemical or electron microscopic procedures. Experimental nerves were dissected based upon the site of compression (proximal, entrapment and distal). CSPG overexpression was detected in the compressed nerve segment and associated with an increase in perineurial and endoneurial cells. Ultrastructural changes and data from semithin sections were analyzed both in control and compressed nerves. We have observed endoneurial edema, perineurial and endoneurial thickening, and whorled cell-sparse pathological structures (Renaut bodies) in the compressed nerves. Morphometrical analyses of myelinated axons at the compression sites revealed: (a) a reduction both in axon sectional area (up to 30%) and in myelin sectional area (up to 80%); (b) an increase in number of small axons (up to 60%) comparatively to the control group. Distal segment of compressed nerves presented: (a) a reduction in axon sectional area (up to 60%) and in myelin sectional area (up to 90%); (b) a decrease in axon number (up to 40%) comparatively to the control data. In conclusion, we have shown that nerve entrapment is associated with a local intraneural increase in CSPG expression, segmental demyelination, perineurial and endoneurial fibrosis, and other histopathological findings.     

Endoneurial blood supply to peripheral nerves is not uniform.

Peripheral nerves are not uniformly susceptible to the effects of ischemia in human and experimental ischemic neuropathies. Since endoneurial blood flow is directly proportional to the number of endoneurial capillaries, we studied endoneurial capillary density at multiple levels of the peripheral nerves of normal rats. Capillary density was lowest in the sciatic and proximal tibial nerves and significantly higher in dorsal and ventral roots and distal tibial and plantar nerves. Endoneurial capillary density corresponds to the hierarchy of susceptibility to ischemic nerve damage in human and experimental ischemic neuropathies. These findings suggest that susceptibility of peripheral nerves to ischemia is determined, at least in part, by the density of endoneurial capillaries.     

Lectin binding to Renaut bodies

Localization of sugar residues of Renaut bodies in human sural nerves was studied using lectin histochemistry. Lens culinaris specific to mannose and Triticum vulgaris specific to glcNAc bound to the capsular and core portions of Renaut bodies strongly. Arachis hypogaea specific to galb(1-3)galNAc and Ulex europaeus I specific to L-fucose bound to Renaut bodies granularly. Lectins specific to galactose or terminal galNAc bound to nowhere. The perineurium showed similar lectin binding to Renaut bodies. Our result suggests that Renaut bodies are rich in mannose and glcNAc. Renaut bodies may be originated from the perineurium.     

Spindle-shaped,cross-banded structures in human peripheral nerves

Summary Fusiform, cross-banded structures (fibrous long-spacing collagen, or Luse bodies) were found in a nerve contained in the perivascular connective tissue of the short saphenous vein and in the sural nerve in man. The periodicity of cross-bandings was 140–170 nm and there was no intraperiod striation. The banded structures were found either isolated in the endoneurial spaces or contiguous with the surface of Schwann cells or fibroblasts. The nature, origin, and pathological significance of structures of this type in peripheral nerve are briefly discussed.     

CHRONIC HUMAN NERVE COMPRESSION – A HISTOLOGICAL ASSESSMENT

While compression neuropathy is a common clinical problem, the opportunity to study human nerve material is rare. A histological assessment of the superficial radial nerve of four human cases with entrapment syndrome is reported. Changes in the perineurium and the endoneurial microvessels as well as the presence of Renaut bodies were the earliest histological abnormalities noted. Connective tissue changes included epineurial and perineurial fibrosis. Nerve fibre pathology varied from fascicle to fascicle. The myelinated and unmyelinated fibre populations responded differently to this compression. In the myelinated fibre population, marked thinning of the myelin was noted. In the unmyelinated fibre population, a shift in the fibre histogram due to a new population of very small fibres was observed suggesting degeneration with subsequent regeneration of this fibre population.     

Reversible endoneurial changes after nerve injury

Summary Endoneurial changes in the rat sciatic nerve were studied during Wallerian degeneration and subsequent regeneration. After total axotomy two different experimental models were used. In the first the cut ends of the sciatic nerves were left free to allow reinnervation. In the second model the distal end of the transected nerve was sutured to the adjoining muscle to prevent regeneration. Within 2 weeks after the axomoty, a Wallerian type of degeneration was seen with axonal destruction and phagocytosis of myelin sheaths. After 4 weeks endoneurial fibroblastic cells formed circular structures around the Schwann cell columns, i.e., the bands of Buengner in both groups. These fascicle-like structures became more pronounced in the non-regenerating nerves up to 8 weeks, while during reinnervation the cellular reaction in the endoneurium nearly disappeared within this time. Ultrastructurally, the endoneurial fibroblast-like cells showed marked phagocytotic activity and also fragments of basement membrane on their surface. The appearance of thin (25–30 nm in diameter) collagen fibrils closely related to the basement membrane was noted around the bands of Buengner, as well as the appearance of an amorphous extracellular gap between the newly synthetized thin collagen fibrils and normal endoneurial collagen (50–60 nm). The reversible endoneurial compartmentation seems to be important for maintaining the nerve structure, serving as a support for axonal regeneration in addition to the bands of Buengner.Supported in part by grants from the Emil Aaltonen Foundation and from the Research and Science Foundation of Farmos (to V. S.) and institutional grants (to Dept. Med. Chem.) from the Sigrid Jusélius Foundation and the Turku University Foundation     

Adult polyglucosan body myopathy with subclinical peripheral neuropathy: case report and review of diseases associated with polyglucosan body accumulation

A 65-year-old female had polyglucosan body myopathy, usually called "polysaccharide storage myopathy" that presented with increasing distal paresis and only slight weakness of the proximal limb girdle musculature. Muscle biopsy revealed dystrophic changes that could have been mistaken for muscular dystrophy, and the characteristic light as well as electron microscopic features of polyglucosan bodies varying in number at the three sites of muscle biopsies studied (deltoid, quadriceps femoris, and anterior tibial muscle). In addition, there were occasional nonspecific paracristalline mitochondrial inclusions. No abnormal polyglucosan deposits were found in the sural nerve biopsy. Morphometric evaluation of nerve fiber cross sectional areas revealed some degree of demyelination and remyelination, and of nerve fiber degeneration and regeneration. Unlike a series of 10 unselected control sural nerves with Renaut bodies, hypomyelinated nerve fibers were more numerous adjacent to Renaut bodies. This is the first case of polyglucosan body myopathy in which the axon/myelin ratio and the axonal circularity factor in the sural nerve is evaluated and in which a definite lack of polyglucosan bodies or other abnormal glycogen storage products in a peripheral nerve is documented.     

Studies to improve fixation of human nerves. 1. Effect of duration of glutaraldehyde fixation on peripheral nerve morphometry

No change in the transverse fascicular area of rat peroneal nerve occurred when the duration of fixation in 2% glutaraldehyde was increased from 1 to 12 hr. Shrinkage in endoneurial area was inferred from the development of clefts. The number of myelin lamellae remained constant when the nerve was fixed in glutaraldehyde for 1 or for 12 hr. Unequivocal shrinkage of axis cylinders occurred with prolongation of glutaraldehyde fixation beyond 1 hr. In nerves fixed for 12 hr, this shrinkage was approximately 20%, compared to the area at 1 hr.     

The persistence and possible externalization of axonal debris during Wallerian degeneration.

The sequence of changes in transected rat sciatic nerves were subjected to parallel ultrastructural and biochemical studies. Widespread granular disintegration of axoplasmic microtubules and neurofilaments occurred in the 24--72 hour interval following nerve transection. These changes were associated with a loss of neurofilament proteins and a marked enhancement of 53,000, 70--73,000 and 85,000 MW proteins in transected nerve. The emergence of prominent nerve proteins during the aftermath of axonal degeneration supports their derivation from axonal sources. These three proteins remained prominent components in transected nerves and comprised the major proteins found in 34-day transected nerves. Amorphous granular breakdown products from myelinated and unmyelinated nerve fibers were encountered with progressively decreasing frequency after 48 hours. This diminution of intracellular axonal debris was accompanied by the appearance and increasing prominence of amorphous granular deposits within the endoneurium of transected nerves. These endoneurial deposits became closely associated with collagen fibers and persisted as a prominent component in 34-, 80- and 120-day transected nerves. It is suggested that the amorphous endoneurial granular deposits arise in part from the externalization of granular axoplasmic breakdown products. Externalized axonal components could have important implications for tissue reaction to injury.     

Lateral plantar neuropathy.

We report 8 cases of lateral plantar neuropathy (LPN). All had sensory impairment over the territory of the lateral plantar nerve. Near-nerve needle sensory nerve conduction study (NCS) of the plantar nerves showed abnormality confined to the lateral plantar nerve, confirming LPN. The most common cause for LPN was trauma and the most common site of injury was at the passage of the lateral plantar nerve through the abductor tunnel at the instep of the foot.     

Plantar motoneuron columns in the rat

In the rat, the numbers and locations of motoneurons innervating the short plantar muscles of the hindlimb (supplied by the medial and lateral plantar nerves, as well as a branch of the sural nerve) were determined by using both horseradish peroxidase (HRP) and fluorochromes as retrograde labels. Topographical organization within the plantar motor nucleus was examined by exposing individually the cut ends (encapsulated in low melting-point paraffin) of medial plantar, lateral plantar, and sural nerves to HRP. In addition, double-labeling experiments were conducted in which the medial plantar nerve was labeled with one fluorochrome (either true blue or diamidino yellow) and the lateral plantar nerve with another. The plantar motor pool is located in the extreme dorsolateral portion of the ventral horn, usually concentrated in the fifth lumbar (L5) spinal segment. Labeled motoneurons extended caudally into the sixth lumbar (L6) segment and rostrally into portions of the fourth lumber (L4) segment. Motoneurons of the medial plantar, lateral plantar, and sural nerve have overlapping territories. Sural motoneurons (about 70 cells per side) are generally confined to L5, medial plantar motoneurons (about 180 cells per side) tend to be concentrated in caudal L5 and rostral L6, whereas the lateral plantar motoneurons (about 310 cells per side) extend throughout the entire length of the plantar motor pool. The distribution of motoneuronal cell size is unimodal (mean cross-sectional area = 610 +/- 150 microns2). Cell bodies of plantar motoneurons tend to have similar geometries in all three major planes of sectioning. In all, the combined plantar plus sural nerve population amounts to about 560 motoneurons on each side of the spinal cord. On the basis of these data, and those published by others, the innervation of the small muscles of the foot accounts for about 25% of the motor axons carried by the entire sciatic nerve.     

The leakage of serum proteins across the blood-nerve barrier in hereditary and inflammatory neuropathies

Summary The suprascapular nerve from 14 horses, which had no clinical evidence of spinatus muscle atrophy, were obtained to determine whether the nerve was sub-clinically compressed at the scapular edge. The nerves were divided into three portions, proximal and distal to the scapular edge and as it reflected around it. In nine horses there was evidence of a chronic neuropathy which varied in severity and which was most severe at the site of reflection, where the nerve appeared constricted by a tendinous band. At this site the predominant change was that of chronic demyelination and remyelination, with many scattered thinly myelinated fibres and occasionally profuse onion bulb formation. There were also occasional regenerating clusters, which were the only abnormalities seen in the distal nerve. Renaut bodies appeared to be more common and larger in nerves with chronic focal neuropathy. Teased fibres confirmed the chronic myelin sheath changes, and the presence of many paranodal swellings suggested a possible chronic compressive aetiology. This is the first reported spontaneous entrapment neuropathy in the domestic animals.Supported by a grant from the Grayson Foundation     

Tarsal tunnel syndrome: electrophysiological study.

Tarsal tunnel syndrome (TTS) is a rare compression neuropathy of the posterior tibial nerve. Typical symptoms are burning pain and paresthesia in the toes and along the sole of the foot. The presence of Tinel's sign and objective sensory loss in the territory of any of the terminal branches of the posterior tibial nerve are diagnostically helpful. The terminal latency and sensory nerve conduction velocity in medial and lateral plantar nerves were studied in 20 normal controls and 21 cases of TTS in 17 patients. Prolonged terminal latency was observed in 11 cases, with TTS, while sensory nerve conduction abnormality (either absent nerve potential or slow sensory nerve conduction velocity) was found in 19. The sensory nerve conduction velocity in the lateral and medial plantar nerves is a superior objective diagnostic index of TTS.     

Peripheral nerve in type III glycogenosis: selective involvement of unmyelinated fiber Schwann cells

Electron microscopy of intramuscular nerves in biopsy material from a child with glycogenosis type III showed massive glycogen accumulation in the Schwann cells of unmyelinated nerve fibers. Other cells, including Schwann cells of myelinated fibers, perineurial cells, endoneurial fibroblasts, endothelial cells, and pericytes, were not similarly affected.     

Expression of Thy–1 Antigen in Reactive Endoneurial Capillaries of the Rat Following Peripheral Nerve Damage

Immunohistochemical staining of Thy-1 antigen was studied in rat peripheral nerves shortly after a complete crush lesion and after an epineural depot injection of lysophosphatidylcholine-palmitate (lysoPC). The Thy-1 antigen was expressed in endoneurial capillaries after 20-30 h and was visible previous to alterations in the axolemma or other signs of neural damage with the exception of endoneurial oedema formation. Thy-1 positive capillaries were restricted to the vicinity of degenerating nerve fibres in partially damaged nerves following epineural depot injection of lysoPC. It is therefore concluded that expression of the Thy-1 antigen in response to peripheral nerve damage in reactive endoneurial capillaries is an active process and not due to diffusion from degenerating axolemmata. Thy-1 staining could be used as a marker of reactive endoneurial capillaries in pathological conditions of peripheral nerves.