Immunolocalization of vgr (BMP-6, DVR-6), a TGF-beta related cytokine, to Schwann cells of the rat peripheral nervous system: expression patterns are not modulated by autoimmune disease

The transforming growth factors type beta (TGF-beta) have been implicated in regulation of peripheral nervous system inflammation and regeneration. Here we demonstrate expression of a TGF-beta-related bone morphogenetic protein, the vgr (BMP-6, DVR-6) in Schwann cells of the rat peripheral nervous system. The expression of vgr in the peripheral nervous system suggests that this factor and probably other TGF-beta-related bone morphogenetic proteins might participate in Schwann cell function during aspects of peripheral nervous system physiology and pathology. However, we did not observe changes in expression patterns in response to autoimmune inflammation (experimental autoimmune neuritis) of the peripheral nervous system.

Structure and function of peripheral nerve myelin proteins

(1) Two glycoproteins, P0 and PASII, are widely distributed in the peripheral myelin, but not in the central myelin of mammals. P0-like protein is expressed in both peripheral and central myelins of some lower vertebrates, such as fish and tadpoles. A close relationship is suggested between P0 expression and neural regenerative activity. (2) PMP22 was reported to show high sequence homology, not only to PASII, but also to the growth arrest specific protein. Human PASII/PMP22 sequence was deduced and the locus of its gene, chromosome 17p12-p11.2, is similar to the region linked to Charcot-Marie-Tooth disease type 1A. (3) P0 expressed on cultured cells mediated strong homophilic cell adhesion and neurite outgrowth. Addition of the P0 glycopeptide inhibited cell adhesion markedly, indicating that the oligosaccharide with peptide is essential for P0 mediated cell adhesion. The active site for neurite outgrowth in P0 appears to be different from the adhesion site. (4) We determined the human chromosomal locus of the P0 gene, 1q22-q23, which corresponded to the locus of hereditary motor and sensory neuropathy, Charcot-Marie-Tooth disease type 1B. Point mutations in the extracellular domain of P0 are found in the patient's chromosome. (5) L1 is a large multifunctional adhesive glycoprotein of 200 kD. Rat and human L1 sequences confirmed a common structure for the mammalian nervous systems. An isoform of L1 (L1cs), lacking four amino acids, appears to localize in non-neuronal cells such as Schwann cells, while the complete L1 is exclusively found in neurons. L1cs in Schwann cells may be functionally different from L1 in neurons.

Lipid composition of neuronal cell bodies and neurites from cultured dorsal root ganglia

The lipid composition of neuronal somata and neuritic processes of cultured root ganglia has been determined. Neuronal soma contained 37% of dry weight as lipid (15.4% cholesterol, 4.8% galactolipid, and 57.1% phospholipid). The major phospholipids were phosphatidylcholine and phosphatidyl ethanolamine. Galactolipids consisted of cerebroside and sulfatide in molar ratio 2:1. The neuronal soma contained tetrasialo-, disialo-, and monosialoganglioside. In contrast, neurites contained 15% of the dry weight as lipid (22.1% cholesterol, 7.7% galactolipid with cerebroside and sulfatide in molar ratio 2:1, and 56.4% total phospholipid). The neuritic galactolipid content was higher, as was the percentage of sphingomyelin, and phosphatidyl serine. The higher cholesterol content in neuritic lipid reflected the higher percentage of plasma membrane in this compartment. The ganglioside pattern of neurites was distinct from that of the neuronal soma and consisted entirely of gangliosides GQ1b, GT1b, GD1b, GD1a, and GD3, with no monosialogangliosides. The results indicate a preferential phospholipid and glycolipid sorting to the neuritic plasma membrane that may be related to the distinctive functions of this neuronal compartment.

Characterization of Schwann cells from normal nerves and from neurofibromas in the bicolour damselfish

Schwann cells are an important component of neurofibromas, one of the primary lesions encountered in neurofibromatosis type 1 in man. A central question in studies of neurofibromatosis type 1 has been whether the Schwann cells present in these tumours are intrinsically abnormal or exhibit abnormal phenotypes in response to stimuli from other cell types in these tumours. Damselfish neurofibromatosis is a naturally occurring disease in a species of marine fish, the bicolour damselfish, that is being developed as an animal model of neurofibromatosis type 1. Affected fish exhibit multiple neurofibromas and neurofibrosarcomas (malignant schwannomas). The present study compares the morphology, antigen expression and proliferative capacity in vitro of Schwann cells derived from peripheral nerves of normal, healthy fish with cells isolated from both spontaneously occurring and experimentally induced neurofibromas. Schwann cells from normal nerves expressed S100 antigens but not fibronectin or glial fibrillary acidic protein antigens and were similar in morphology and proliferative capacity to Schwann cells isolated from mammalian peripheral nerves. Tumour-derived cultures contained variable proportions (27-79%) of S100-positive cells that were identified as Schwann cells based on this feature. These tumour-derived Schwann cells exhibited a different morphology than normal Schwann cells, usually exhibited an increased reactivity to anti-S100 antibodies and were able to proliferate in vitro without added mitogens. Repeated subculturing of tumour-derived cultures led to the production of six cell lines all of which were composed exclusively of Schwann cells as indicated by S100 expression. These findings show that Schwann cells are an important component of tumours in Damselfish neurofibromatosis and that these cells are morphologically and physiologically altered in this disease. Observations of cell lines also suggest that tumour-derived Schwann cells are intrinsically abnormal and that this phenotype is not a result of stimuli from other cell types in the tumours.

The neurite growth promoting protease nexin 1 in glial cells of the olfactory bulb of the gerbil: an ultrastructural study

The glia-derived serine protease inhibitor and neurite outgrowth promoter protease nexin-1 (PN-1) is expressed in Schwann cell precursors and astroblasts during embryogenesis. In the adult nervous system, PN-1 persists in the Schwann cells and olfactory glia only. Light-microscopic immunohistochemistry has revealed the presence of PN-1 in the olfactory mucosa and in the nerve fiber layer of the olfactory bulb. The present electron-microscopic study of the gerbil olfactory bulb confirms the occurrence of PN-1 in ensheathing cells of the olfactory nerve fiber layer, a special type of glia which envelopes olfactory axons. In addition, PN-1 is contained in typical astrocytes of the nerve fiber layer and of the glomerular layer. It is inferred that synthesis of PN-1 in the olfactory bulbs is maintained throughout adulthood because its neurite outgrowth promoting action is required for the continuous renewal of olfactory receptor neurons.

The L2/HNK-1 carbohydrate is preferentially expressed by previously motor axon-associated Schwann cells in reinnervated peripheral nerves

The carbohydrate epitope L2/HNK-1 (hereafter designated L2) is expressed in the adult mouse by myelinating Schwann cells of ventral roots and muscle nerves, but rarely by those of dorsal roots or cutaneous nerves. Since substrate-coated L2 glycolipids promote outgrowth of cultured motor but not sensory neurons, L2 may thus influence the preferential reinnervation of muscle nerves by regenerating motor axons in vivo. In the present study, we have analyzed the influence of regenerating axons on L2 expression by reinnervated Schwann cells by directing motor or sensory axons into the muscle and cutaneous branches of femoral nerves of 8-week-old mice. We observed that regenerating axons from cutaneous branches did not lead to immunocytochemically detectable L2 expression in muscle or cutaneous nerve branches. Axons regenerating from muscle branches led to a weak L2 expression by few Schwann cells of the cutaneous branch, but provoked a strong L2 expression by many Schwann cells of the muscle branch. Myelinating Schwann cells previously associated with motor axons thus differed from previously sensory axon-associated myelinating Schwann cells in their ability to express L2 when contacted by motor axons. This upregulation of L2 expression during critical stages of reinnervation may provide motor axons regenerating into the appropriate, muscle pathways with an advantage over those regenerating into the inappropriate, sensory pathways.

Biochemical and cellular properties of three immortalized Schwann cell lines expressing different levels of the myelin-associated glycoprotein

Biochemical and cellular properties of three immortalized Schwann cell lines expressing different levels of the myelin-associated glycoprotein (MAG) were compared. The S16 line generated by repetitive passaging was described previously and expresses a level of MAG comparable to that in adult sciatic nerve. The S42 line was generated independently by the same procedure, divides more slowly than the S16 line, and expresses an even higher level of MAG. The S16Y line arose spontaneously from a passage of the S16 cells, divides much more rapidly, and does not express MAG. The levels of MAG expression in the three lines are inversely related to their rates of proliferation, and MAG mRNA levels parallel the amounts of MAG. The S16 and S42 lines consist mainly of flat cells at low density and develop many processes at high density, whereas most of the S16Y cells are spindle-shaped, resembling primary Schwann cells in appearance. Surface immunostaining with the O4 antibody was positive for the S16 and S42 cells and negative for the S16Y cells, but all three lines were negative for surface staining with the O1 antibody. The overall protein compositions of the three lines are very similar, but the S16 and S42 cells express larger amounts of several glycoproteins than the S16Y cells, including the adhesion proteins, neural cell adhesion molecule, L1, and laminin. S16 and S42 cells (but not S16Y cells) also express P0 glycoprotein, galactocerebroside, and sulfatide, but, unlike MAG, these other myelin-related components were present at much lower levels than in adult nerve. Myelin basic protein and proteolipid protein were not detected in any of the lines, although all three lines contained proteolipid protein mRNA. 2',3'-Cyclic nucleotide 3'-phosphodiesterase and glial fibrillary acidic protein were present in all three lines. Conditions have not yet been found in which any of the lines will myelinate dorsal root ganglion neurons in vitro, but the S16 and S42 cells differ from the S16Y cells by clustering around neurons after 1 week in coculture. In many respects, the S16 and S42 cells biochemically resemble Schwann cells at an early stage in their preparation to myelinate and should be useful for investigating the cell biology of MAG and other myelin-related components.

Mice deficient for the myelin-associated glycoprotein show subtle abnormalities in myelin

Using homologous recombination in embryonic stem cells, we have generated mice with a null mutation in the gene encoding the myelin-associated glycoprotein (MAG), a recognition molecule implicated in myelin formation. MAG-deficient mice appeared normal in motor coordination and spatial learning tasks. Normal myelin structure and nerve conduction in the PNS, with N-CAM overexpression at sites normally expressing MAG, suggested compensatory mechanisms. In the CNS, the onset of myelination was delayed, and subtle morphological abnormalities were detected in that the content of oligodendrocyte cytoplasm at the inner aspect of most myelin sheaths was reduced and that some axons were surrounded by two or more myelin sheaths. These observations suggest that MAG participates in the formation of the periaxonal cytoplasmic collar of oligodendrocytes and in the recognition between oligodendrocyte processes and axons.

Expression of the ret proto-oncogene product in human normal and neoplastic tissues of neural crest origin

The histological localization of the ret proto-oncogene (proto-ret) product was examined in neural crest-derived and neuronal tissues together with their neoplastic counterparts by immunohistochemistry using a polyclonal antibody. Schwann cells, neurons, sympathetic ganglia, and cells of the adrenal medulla were positive for the proto-ret product, whereas melanocytes were negative. Positive results were obtained from neural crest-derived tumours such as schwannoma (69 per cent, 11/16), neurofibroma (59 per cent, 13/22), neuroblastoma (80 per cent, 4/5), phaeochromocytoma (100 per cent, 3/3) and medullary thyroid carcinoma (100 per cent, 3/3). The antibody reacted with all of the 22 astrocytomas examined. With negative proto-ret expression in melanocytic tumours, proto-ret expression was considered to correlate with the differentiation of some lineages of neural crest-derived cells.

The functional characteristics of Schwann cells cultured from human peripheral nerve after transplantation into a gap within the rat sciatic nerve

The use of human Schwann cells (SCs) in transplantation to promote regeneration in central and peripheral neural tissues must be preceded by efforts to define the factors that regulate their functional expression. Adult-derived human SCs can be isolated and purified in culture, but the culture conditions that allow their full differentiation have not yet been defined. We tested the functional capacity of these cells to enhance axonal regeneration and myelinate regenerating axons in vivo by transplanting them into the damaged PNS of an immune-deficient rat. SCs were purified from human peripheral nerve obtained from organ donors. Semi-permeable guidance channels were filled with a 30% Matrigel containing solution with or without human SCs suspended at a density of 80 x 10(6) cells/ml. Channels were implanted within an 8 mm gap of the transfected sciatic nerve of nude female rats for a period of 4 weeks. Survival of the transplanted human SCs was established by dissociating nerve explants taken from the regenerated cable (after first placing them in culture for 5 d) and staining individual cells for a primate-specific NGF receptor (PNGFr) and S 100. Only one-half of the S 100-positive cells stained for the PNGFr, which indicated that the regenerated cable contained an approximately equal number of human and rat (host) SCs. The presence of some human myelin segments was confirmed by immune staining with an HNK-1 antibody that specifically labels human but not rat myelin. The majority of the myelin segments in the regenerated cable, however, were produced by the rat SCs. The number of myelinated axons and the cross-sectional area of the cable were significantly greater in channels seeded with human SCs when compared to channels containing the diluted Matrigel solution alone. We conclude that purified cultured human SCs can survive and substantially enhance axonal regeneration when transplanted into the injured PNS of an immune-deficient rat. Some of the transplanted human SCs are capable of myelinating regenerating rat axons but are less successful than the host SCs.

Specific expression of the neurofibromatosis type 1 gene (NF1) in the hamster Schwann cell

The gene responsible for neurofibromatosis type 1 (NF1) has sequence homology to the GTPase-activating protein (GAP) and demonstrates GAP activity against ras p21. To study tissue-specific and/or tumor-specific expression of the NF1 gene product, now called neurofibromin, immunostaining and immunoblotting were applied to the N-nitroso-N-ethylurea (ENU)-induced Syrian hamster neurofibromatosis model using polyclonal antibodies against the NF1 fusion protein and a synthetic peptide. Strong expression was observed specific to the Schwann cells of the normal peripheral nerves by immunostaining. Neoplastic Schwann cells showed specific binding of anti-NF1; however, the frequency of positive cells was diminished. Immunoblotting also revealed positive expression of the 250-kd NF1 gene product in the brain, the normal peripheral nerves, and 7 of 14 ENU-induced neurofibromas. Although ENU-induced melanoma and Wilms' tumor were negative for neurofibromin, foci of Schwannian differentiation in both primary and transplanted melanomas were positive. These results suggest that neurofibromin plays some role in differentiation and growth regulation of the Schwann cell.

Post-embedding tem signal-to-noise ratio of S-100

We assessed the reactivity of purified S-100 antiserum in immuno-electron microscopy by counting the number of gold particles per microns 2 over inner ear tissues embedded in different media. Sections containing predominantly Schwann's cell cytoplasm and nucleus, afferent fiber axoplasm and myelin sheath of chick cochleae were reacted with anti-S-100 IgG, an antibody to a calcium binding protein of neuronal tissues, then labeled with anti-IgG-gold conjugate. This investigation was conducted because previously published procedures, unmodified, did not yield acceptable results. Preparation of all specimens was identical. Only the medium (PolyBed 812, Araldite or Spurr epoxies; and LR White, LR Gold or Lowicryl plastics) was changed. The medium was made the changing variable because antigens available in post-embedding immuno-electron microscopy are decreased by heat, either used and/or released during polymerization of the embedding medium. The results indicate that: (a) none of the embedding media above provided optimal signal-to-noise ratio for all parts of the nerve stained in the same section; (b) aggregation of gold particles over cells was highest in embedding media with high background labeling over areas devoid of tissue (noise); (c) aggregation occurred randomly throughout both cellular and acellular regions; and (d) particles aggregated less and were distributed more evenly in tissues from media yielding good ultrastructural integrity.

Characterization of a Schwann cell neurite-promoting activity that directs motoneuron axon outgrowth

Schwann cells support and facilitate axonal growth during development and successful regeneration in the peripheral nerve. In the regenerating rat sciatic nerve, Schwann cells provide a trophic milieu for primary sensory, sympathetic, and motoneurons. We have characterized a neurotrophic activity produced by adult rat sciatic nerve Schwann cells and a spontaneously immortal Schwann cell clone (iSC). This activity elicits neurite outgrowth from chick embryo explants of both CNS and PNS. The iSC activity has been concentrated by cation-exchange chromatography and compared to known neurotrophins in bioassay. Pooled bound fractions elicit neurite outgrowth from sympathetic, ciliary and motoneurons. In collagen matrix cocultures of iSC and E4 ventral horn (before motor axon extension to muscle targets), the iSC activity can direct the initial axonal extension from motoneurons. The data presented suggest that Schwann cell-produced activity may mediate motoneuron axonal extension before contact with their peripheral source of neurotrophin.

Plexiform schwannoma. Immunohistochemistry of Schwann cell markers, intermediate filaments and extracellular matrix components

An immunohistochemical study using a comprehensive panel of antibodies to Schwann cell markers, intermediate filaments and extracellular matrix components has been performed on three cases of plexiform schwannoma. All tumour cells expressed S 100 protein, Leu 7-HNK 1 antigen and vimentin; glial fibrillary acidic protein was detected in many tumour cells. In addition, expression of cytokeratin was also demonstrated in one case. The associated extracellular matrix was found to be reactive with antibodies to laminin, heparan sulfate proteoglycan, fibronectin, type I, III, IV and VI collagen. It is concluded that Schwann cells producing their own extracellular matrix are the main components of these tumours. The significance of the cytokeratin expression and the possible role of the extracellular matrix in regulating Schwann cells' proliferation in peripheral nerve tumours are discussed.

Acrylamide disrupts elemental composition and water content of rat tibial nerve. III. Recovery

We have previously demonstrated that subacute and subchronic acrylamide (ACR) intoxication are associated with a loss of subcellular elemental regulation in myelinated axons and Schwann cells of rat tibial nerve (LoPachin et al., Toxicol. Appl. Pharmacol. 115, 21-34, 1992; LoPachin et al., Toxicol. Appl. Pharmacol. 115, 35-43, 1992). In the present study, rats were allowed to recover partially from subchronic oral ACR intoxication (2.8 mM in drinking water for approximately 30 days). Elemental composition and water content of tibial nerve myelinated axons and Schwann cells were measured by electron probe X-ray microanalysis. Results show that K and Cl concentrations in larger tibial nerve axons were shifted toward normal values or above. For the most part, small axons also exhibited elemental changes that reflected recovery from ACR intoxication. Mitochondria displayed elemental changes that were similar to corresponding axoplasm. Schwann cells in tibial nerve of recovering animals had altered Na, P, Cl, K, and Mg concentrations that were similar in magnitude and extent to those occurring during ACR intoxication. In contrast, myelin displayed few changes. These results suggest that the recovery process following ACR intoxication is associated with characteristic changes in subaxonal elemental composition that might be related to repair mechanisms. That recovery-related elemental changes differ from those associated with intoxication provides additional support for the hypothesis (LoPachin et al., Toxicol. Appl. Pharmacol. 115, 21-34, 1992) that perturbation of elemental regulation is a specific component of ACR neurotoxicity. The observation of persistent Schwann cell disruption during recovery might reflect either long-term secondary consequences or delayed recovery from direct injury. Further studies are necessary to resolve this issue.

Immunohistochemical localization of S-100 protein in the saccule of the rainbow trout (Salmo gairdnerii R.)

The distribution of S-100-like immunoreactivity in the trout saccule (a presumed organ of hearing in fish) has been determined by means of immunohistochemistry. Within the sensory epithelium of the saccular macula, hair cells and myelinated saccular nerve fibers were found to be immunoreactive. Hair-cell immunoreactivity was relatively uniform throughout the macula except at the extreme periphery (rostral, caudal, ventral and dorsal), where staining was either decreased or absent. The immunoreactivity associated with myelinated nerve fibers was greatest at the peripheral edges of the nerve processes, a position corresponding to the location of Schwann cells. However, the nerve processes themselves (within and subjacent to the sensory epithelium), as well as cell bodies within the saccular nerve, were also immunoreactive. Thus, the immunoreactivity of the saccular nerve observed above the basal lamina can be attributed to the saccular nerve processes as well as to nerve-associated Schwann cells. Overall, the immunoreactivity displayed by hair cells was less intense than that associated with myelinated saccular nerve, as evidenced by a disappearance of signal in hair cells first, upon serial dilution of antibody. No S-100-like immunoreactivity was observed in supporting cells within the sensory epithelium or in epithelial cells in non-sensory regions. A concentration of S-100-like immunoreactivity in hair cells and saccular nerve is suggestive of the presence of S-100 calcium-binding protein-mediated activities in these cell types.

Distribution of fibroblast growth factor in cultured dorsal root ganglion neurons and Schwann cells. I. Localization during maturation in vitro

The distribution of acidic and basic fibroblast growth factor in co-cultures of dorsal root ganglion neurons and Schwann cells was examined as a function of time in culture. After two days in vitro, the cytoplasm of the neuronal cell bodies demonstrated both acidic and basic FGF immunoreactivity, whereas the cytoplasm of the neurites was not immunoreactive. Schwann cells, in contrast, exhibited both acidic and basic fibroblast growth factor cytoplasmic immunoreactivity. After two days in culture, immunoreactivity was not detected on the plasma membrane surface of either the neurons or the Schwann cells. By 10 days in vitro, fibroblast growth factor immunoreactivity was observed in the cytoplasm of the most proximal portion of some, but not all, neurites but was unchanged in Schwann cells. At 20 days in vitro, immunoreactivity was still restricted to the intracellular compartment of both Schwann cells and neurons. Acidic fibroblast growth factor was primarily localized to the cytoplasm of Schwann cells, neuron cell bodies and along the entire length of the neurites. In contrast, basic fibroblast growth factor was predominantly localized to the nuclei of Schwann cells and small to medium size neurons. In many cases, the nucleolar region demonstrated the most intense basic fibroblast growth factor. The cytoplasm of the neurites was also immunoreactive for basic fibroblast growth factor. At 30 days in vitro the intracellular distribution of fibroblast growth factor immunoreactivity was similar to that observed at 20 days. However, both acidic and basic fibroblast growth factor were detected on the surface of the neurites. In contrast, no fibroblast growth factor immunoreactivity was detected at the Schwann cell surface at any time point examined. The distribution of fibroblast growth factor in Schwann cells cultured by themselves was similar to that of Schwann cells co-cultured with neurons after 20 days in vitro. Both Schwann cells and dorsal root ganglia exhibited increased fibroblast growth factor immunoreactivity with increased time in culture and an increased expression of basic fibroblast growth factor in the nucleus. Of particular interest was the appearance of fibroblast growth factor on the surface of neurites after 30 days in vitro where it could function to modulate neuron-glial cell interactions.

Distribution of fibroblast growth factor in cultured dorsal root ganglion neurons and Schwann cells. II. Redistribution after neural injury

The localization of fibroblast growth factor was examined in both immature (< 20 days in vitro) and mature (> 30 days in vitro) dorsal root ganglion neuron-glial cell co-cultures as a function of time after in vitro crush injury of the neurites. In the 20 day cultures, neuritic membrane vesicles were seen adhering to Schwann cells following neurite injury. Fibroblast growth factor was not detected on the surface of these membrane vesicles when they were associated with either the degenerating neurites or the surface of Schwann cells. However, the cytoplasm of the Schwann cells demonstrated fibroblast growth factor immunoreactivity at all times. In contrast, injury to neurites after 30 days in vitro resulted in demonstrable fibroblast growth factor immunoreactivity on the surfaces of the neuritic membrane vesicles both before and after their association with the Schwann cells. Furthermore, there was a change in the pattern of fibroblast growth factor immunoreactivity on the surface of Schwann cells after injury: initially the staining was patchy but with increasing time it became more uniform and more intense. A similar pattern of staining was noted on the surface of oligodendrocytes co-cultured with dorsal root ganglion neurons. However, astrocytes which were co-cultured with dorsal root ganglion neurons did not show any fibroblast growth factor immunoreactivity. Also, after injury at 30 days in vitro, the neuronal cell bodies began to express fibroblast growth factor immunoreactivity on their extracellular surfaces and the regenerating neurites exhibited fibroblast growth factor immunoreactive material on the surface of their plasma membranes. This redistribution of fibroblast growth factor via degenerating neuritic membrane vesicles to the plasma membrane of Schwann cells may be involved in neuronal signalling to glial cells after neuronal injury.

Origin of Schwann cells in peripheral nerve allografts in the rat after withdrawal of cyclosporine

The origin of Schwann cells in peripheral nerve allografts following rejection was determined by immunohistochemistry. Sciatic nerve allografts from ACI-RT1a rats were transplanted into Lewis-RT1l sciatic nerves using epineurial sutures. Isografts were taken from Lewis-RT1l rats. Cyclosporine (CsA) was administered subcutaneously daily, 5 mg/kg for 12 weeks, to the rats in each group. Allografts with CsA were sacrificed in groups at 12, 14, 16, 20, 24, and 36 weeks postoperatively during the rejection and recovery phase. Allografts and isografts without CsA were evaluated at 3, 6, 12, and 24 weeks. Nerves were frozen and cross sections immunohistochemically stained against Lewis rat HLA (RT1) and against Schwann cells (S-100 antigen). Allografts without CsA demonstrated minimal reaction to anti-Lewis compared to control isografts, which stained positively at all times. Schwann cells were not as well-stained in the allografts. Allografts with CsA showed reactivity to S-100 at 12 weeks, but minimal activity to Lewis antibody. Minimal reactivity to both S-100 and Lewis existed at 16 weeks, but increased gradually by 24 and 36 weeks. Therefore, Schwann cells from the recipient migrate into the graft and replace the Schwann cells from the donor following rejection.

Carbohydrate recognition in the peripheral nervous system: a calcium-dependent membrane binding site for HNK-1 reactive glycolipids potentially involved in Schwann cell adhesion

The carbohydrate determinants recognized by the HNK-1 antibody are potential cell-cell recognition ligands in the peripheral nervous system (PNS). The HNK-1 reactive sulfoglucuronylneolacto (SGNL) glycolipids specifically support Schwann cell adhesion, suggesting the presence of a cell surface receptor specific for SGNL-oligosaccharides. We directly probed PNS membranes for receptors complementary to SGNL determinants using a synthetic radioligand consisting of radioiodinated serum albumin derivatized with multiple SGNL-oligosaccharides. A high-affinity, saturable, calcium-dependent binding site for this ligand was found in PNS myelin membranes. Binding activity was carbohydrate-specific (most potently inhibited by SGNL-lipids compared to other glycolipids) and PNS-specific (absent from comparable central nervous system membranes). The SGNL-specific binding activity on PNS membranes reported here may be involved in peripheral myelination or myelin stabilization.

Symmetrical neurofibroma with Schwann cell predominance and focal formation of microneurinomas

A case of symmetrical neurofibroma with onion bulbs in various stages of development and progression to microneurinomas is presented. Immunohistochemistry with differentiation and growth factor markers as well as electron microscopy showed a Schwann cell origin of the concentrically arranged cells. The onion bulbs differed from those of hypertrophic neuropathy by their more compact structure. A partial expression of cellular proliferation markers in the onion bulbs was consistent with a multifocal proliferative activity, confirming the neoplastic nature of the lesion.

Identification of G protein subtypes in peripheral nerve and cultured Schwann cells

In this study, we investigated the expression of various G proteins in whole sciatic nerves, in myelin and nonmyelin fractions from these nerves, and in membranes of immortalized Schwann cells. In myelin, nonmyelin, and Schwann cell membranes we detected two 39-40-kDa pertussis toxin substrates that were resolved on separation on urea-gradient gels. Two cholera toxin substrates with apparent molecular masses of 42 and 47 kDa were present in nerve and brain myelin and in Schwann cell membranes. In these membranes, a third 45-kDa cholera toxin substrate, which displayed the highest labeling, was also present. Immunoblotting with specific antisera allowed the identification of G(o) alpha, Gi1 alpha, Gi2 alpha, Gi3 alpha, Gq/G11 alpha, and the two isoforms of Gs alpha in nerve homogenates, nerve, and brain myelin fractions. In Schwann cell membranes we identified G(o) alpha, Gi2 alpha, Gi3 alpha, and proteins from the Gq family, but no immunoreactivity toward anti-Gi1 alpha antiserum was detected. In these membranes, anti-Gs alpha antibody recognized the three cholera toxin substrates mentioned above, with the 45-kDa band displaying the highest immunoreactivity. Relative to sciatic nerve myelin, the Schwann cell membranes revealed a significantly higher expression of Gi3 alpha and the absence of Gi1 alpha. The different distribution of G proteins among the different nerve compartments might reflect the very specialized function of Schwann cells and myelin within the nerve.

Electron microscopic immunocytochemistry of GAP-43 within proximal and chronically denervated distal stumps of transected peripheral nerve

Growth-associated protein, GAP-43 was initially described as a neuron-specific molecule thought to play a critical role in axonal growth and regeneration. However, it is also expressed in vitro in certain CNS glia, Schwann cell precursors and non-myelinating Schwann cells. In this paper, we report the subcellular localization of GAP-43 in vivo in chronically-denervated Schwann cells in the distal stumps of previously transected rat sciatic nerve. We have used a progressive lowering of temperature method combined with the non-polar acrylic resin Lowicryl HM20 and a post-embedding labelling regime to visualize the distribution of GAP-43, S-100 (marker for Schwann cells), RT97 and NF68 (markers for different subunits of the neurofilament molecule). We report that (1) the smallest calibre regrowing axons were GAP-43-positive, sometimes NF68-positive but always RT97-negative; (2) regenerating myelinated axons and larger unmyelinated axons (> 0.7 microns diameter) were NF68-positive, RT97-positive but GAP-43-negative; (3) cytoplasmic processes within Schwann cell basal lamina tubes in the distal stumps were S-100-positive, GAP-43-positive but RT97- and NF68-negative. The similar localization of GAP-43 within regrowing axons and denervated Schwann cells suggests that GAP-43 may function similarly in both situations, and may thus be involved in motility and/or elongation of axons and Schwann cells during regeneration.

Immunocytochemical localization of annexin V (CaBP33), a Ca(2+)-dependent phospholipid- and membrane-binding protein, in the rat nervous system and skeletal muscles and in the porcine heart

We investigated the ultrastructural localization of annexin V a Ca(2+)-dependent phospholipid- and membrane-binding protein in the nervous system, heart, and skeletal muscles. The results indicate that in the cerebellum the protein is restricted to glial cells, where it is found diffusely in the cytoplasm as well as associated with plasma membranes. Bergmann glial cell bodies and processes and astrocytes in the cerebellar cortex and oligodendrocytes in the cerebellar white matter displayed an intense immune reaction product. In sciatic nerves, the protein was exclusively found in Schwann cells with a subcellular localization similar to that seen in glial cells in the cerebellum. Pituicytes in the neurohypophysis were intensely immunostained, whereas axons were not. In the heart, annexin V was restricted to the sarcolemma, transverse tubules, and intercalated discs. In skeletal muscles the protein was localized to the sarcolemma and transverse tubules. No evidence for the presence of the protein in the sarcoplasm or in association with mitochondria, the sarcoplasmic reticulum, or contractile elements was obtained. The observation that plasma membranes in cells expressing annexin V have the protein associated with them is in agreement with previous data on Ca(2+)-dependent binding of the protein to brain and heart membranes, and on existence of both EGTA- and Triton X-100-extractable and resistant fractions of annexin V in these membranes. The present data support the hypothesis that annexin V might be involved in membrane trafficking and suggest a role for this protein in the regulation of cytoplasmic activities in glial cells.