Anti-myelin-associated glycoprotein antibodies alter neurofilament spacing

Axon calibre is crucial to efficient impulse transmission in the peripheral nervous system. Neurofilament numbers determine gross axonal diameter, but intra-axonal distribution depends on the phosphorylation status of neurofilament sidearms. Myelin-associated glycoprotein (MAG) has been implicated in the signalling cascade controlling neurofilament phosphorylation and hence in the control of axon calibre. In an electron microscopic morphometric study we measured nearest neighbour neurofilament distances (NNND) in the axons of sural nerves from patients with anti-MAG paraproteinaemic neuropathies and compared these with normal human sural nerves and those from patients with Guillain-Barré syndrome or chronic inflammatory demyelinating polyradiculoneuropathy. Axon calibre was similar in all groups. In normal human sural nerves, axonal NNND was correlated with axonal diameter (r = 0.56). In diseased axons this correlation did not exist. The NNND was significantly reduced in demyelinated axons (30.5+/-2.2 nm) and those with widely spaced myelin (28.9+/-1.3 nm) from patients with anti-MAG antibodies compared with normal axons from normal patients (39.8+/- 3.2 nm) or those with demyelinating neuropathy (35.8+/-4.6 nm). This reinforces the hypothesis that MAG is involved in the control of neurofilament spacing through sidearm phosphorylation and demonstrates a MAG-mediated pathogenic effect of the anti-MAG antibody in peripheral nerves.

The wound healing properties of Channa striatus-cetrimide cream-wound contraction and glycosaminoglycan measurement

Haruan has been proved to influence the different phases of wound healing process. The current research focuses on the effects of haruan on the different constituents of extracellular matrix of healing wounds in normal and diabetic rats. Anaesthetized normal and streptozotocin induced diabetic rats were provided with excision wounds at the back and then animals were divided into four groups as: group 1, wounds treated with cetrimide+haruan cream; group 2, wounds treated with haruan cream; group 3, wounds treated with cetrimide (commercial) cream; and group 4, wounds untreated and served as control. Animals were sacrificed after 3, 6, 9 and 12 days. These wounds were used to determine the hexosamine, protein, uronic acid and glycosaminoglycan contents and the wound contraction. The results suggested a marked increase (P<0.05) in the uronic acid, hexosamine and dermatan sulfate contents on day 3 of group 1 when compared with groups 2-4. Wound contraction of group 1 was also markedly enhanced of group 1 (P<0.01) when compared with groups 2- 4. On the basis of these results, we conclude that haruan enhances the synthesis of different glycosaminoglycans in healing wounds, which are the first component of extracellular matrix to be synthesized during the wound healing process. The enhanced levels of glycosaminoglycans may help in the formation of a resistant scar and enhanced wound contraction represents the positive influence of haruan on the fibroplastic phase of wound healing.

High-affinity anti-ganglioside IgG antibodies raised in complex ganglioside knockout mice: reexamination of GD1a immunolocalization

Gangliosides, sialic acid-bearing glycosphingolipids, are highly enriched in the vertebrate nervous system. Anti-ganglioside antibodies are associated with various human neuropathies, although the pathogenicity of these antibodies remains unproven. Testing the pathogenic role of anti-ganglioside antibodies will be facilitated by developing high-affinity IgG-class complement-fixing monoclonal anti-bodies against major brain gangliosides, a goal that has been difficult to achieve. In this study, mice lacking complex gangliosides were used as immune-naive hosts to raise anti-ganglioside antibodies. Wild-type mice and knockout mice with a disrupted gene for GM2/GD2 synthase (UDP-N-acetyl-D-galactosamine : GM3/GD3 N-acetyl-D-glactosaminyltransferase) were immunized with GD1a conjugated to keyhole limpet hemocyanin. The knockout mice produced a vigorous anti-GD1a IgG response, whereas wildtype littermates failed to do so. Fusion of spleen cells from an immunized knockout mouse with myeloma cells yielded numerous IgG anti-GD1a antibody-producing colonies. Ganglioside binding studies revealed two specificity classes; one colony representing each class was cloned and characterized. High-affinity monoclonal antibody was produced by each hybridoma : an IgG1 that bound nearly exclusively to GD1a and an IgG2b that bound GD1a, GT1b, and GT1aalpha. Both antibodies readily readily detected gangliosides via ELISA, TLC immune overlay, immunohistochemistry, and immunocytochemistry. In contrast to prior reports using anti-GD1a and anti-GT1b IgM class monoclonal antibodies, the new antibodies bound avidly to granule neurons in brain tissue sections and cell cultures. Mice lacking complex gangliosides are improved hosts for raising high-affinity, high-titer anti-ganglioside IgG antibodies for probing for the distribution and physiology of gangliosides and the pathophysiology of anti-ganglioside antibodies.

The wound healing properties of Channa striatus-cetrimide cream-- tensile strength measurement

Channa striatus, a fresh water snakehead fish, is reported to enhance dermal wound healing. Biochemical components such as amino acids and fatty acids are important for the synthesis of collagen fibers during wound healing. Arachidonic acid, a precursor of prostaglandin plays a vital role in healing the wounds. Haruan (C. striatus) contains all the essential amino acids for wound healing particularly glycine as well as high contents of arachidonic acid and polyunsaturated fatty acids that can promote prostaglandin synthesis. In the present work we have studied the wound healing effect of C. striatus in Sprague-Dawley rats. Cream formulations having different haruan fish extract concentrations as the active ingredient were prepared and stabilized, and they were applied to the wounds. The healing of wounds was characterized by an increase in the tensile strength of the skin, determined on the 7th post-operative day in each case. Haruan treatment of wounds promotes remodeling of collagen, by the synthesis of inter- and intra-molecular protein crosslinking and thus produces a marked increase (P<0.05) in tensile strength as compared to the cetrimide treated group. On the basis of our experiment we conclude that C. striatus helps in wound healing as indicated by the increase in tensile strength. We hypothesise that this effect may be due to its high content of arachidonic acid, glycine and polyunsaturated fatty acids. The mechanism of wound healing will be investigated in future studies.

Physiologic-pathologic correlation in Guillain-Barré syndrome in children

OBJECTIVE

To correlate electrophysiologic patterns with sural nerve pathology in children with Guillain-Barré syndrome (GBS).

BACKGROUND

Based on electrophysiologic and pathologic observations, GBS has been divided into demyelinating and axonal subtypes. The acute motor axonal neuropathy (AMAN) involves predominantly motor nerve fibers with a physiologic pattern suggesting axonal damage, whereas the acute inflammatory demyelinating polyneuropathy (AIDP) involves both motor and sensory nerve fibers with a physiologic pattern suggesting demyelination. In this study, we sought to confirm these observations by correlating sural nerve pathology with electrophysiologic findings in GBS patients.

METHODS

Biopsies of sural nerve from 29 of 50 prospectively studied GBS patients were obtained. Nerves were examined by light and electron microscopy, and with immunocytochemistry for macrophages, lymphocytes, and complement activation products.

RESULTS

Sural nerves from AMAN patients were normal or had only a few (0.1% to 0.7%) degenerating fibers without lymphocytic infiltration or complement activation. One patient with reduced sural sensory nerve action potential classified as acute motor sensory axonal neuropathy (AMSAN) had many degenerating fibers (2.3%) in the sural nerve. All three AIDP patients displayed active demyelination, and in two patients, lymphocytic infiltration and complement activation products were observed on the abaxonal Schwann cell surface.

CONCLUSION

Classification of Guillain-Barré syndrome subtypes based on motor conduction studies correlates closely with pathologic changes seen in sural nerve. In acute motor axonal neuropathy cases, the sural nerve is almost completely spared pathologically. In acute inflammatory demyelinating polyneuropathy cases, macrophage-mediated demyelination and lymphocytic infiltration are common in the biopsies of sural nerves.

Mice lacking complex gangliosides develop Wallerian degeneration and myelination defects

Gangliosides are a family of sialic acid-containing glycosphingolipids highly enriched in the mammalian nervous system. Although they are the major sialoglycoconjugates in the brain, their neurobiological functions remain poorly defined. By disrupting the gene for a key enzyme in complex ganglioside biosynthesis (GM2/GD2 synthase; EC 2.4.1.92) we generated mice that express only simple gangliosides (GM3/GD3) and examined their central and peripheral nervous systems. The complex ganglioside knockout mice display decreased central myelination, axonal degeneration in both the central and peripheral nervous systems, and demyelination in peripheral nerves. The pathological features of their nervous system closely resemble those reported in mice with a disrupted gene for myelin-associated glycoprotein (MAG), a myelin receptor that binds to complex brain gangliosides in vitro. Furthermore, GM2/GD2 synthase knockout mice have reduced MAG expression in the central nervous system. These results indicate that complex gangliosides function in central myelination and maintaining the integrity of axons and myelin. They also support the theory that complex gangliosides are endogenous ligands for MAG. The data extend and clarify prior observations on a similar mouse model, which reported only subtle conduction defects in their nervous system [Takamiya, K., Yamamoto, A., Furukawa, K., Yamashiro, S., Shin, M., Okada, M., Fukumoto, S., Haraguchi, M., Takeda, N., Fujimura, K., et al. (1996) Proc. Natl. Acad. Sci. USA 93, 10662-10667].

The distribution of ganglioside-like moieties in peripheral nerves

GM1 ganglioside has been implicated as a target of immune attack in some diseases of the peripheral nervous system. Anti-GM1 ganglioside antibodies are associated with certain acquired immune-mediated neuropathies. It is not clear how anti-GM1 antibodies cause nerve dysfunction and injury; however, sodium and/or potassium ion channel dysfunction at the node of Ranvier has been implicated. To gain insight into the pathogenesis of these neuropathies, we examined the distribution of GM1 ganglioside and Gal(beta1-3)GalNAc moieties in nerve fibres and their relationship to voltage-gated sodium and potassium (Kv1.1, 1.5) channels at the nodes of Ranvier in peripheral nerves from human, rat and dystrophic mice. Gal(beta1-3)GalNAc moieties were localized via the binding of cholera toxin and peanut agglutinin. As a control for the specificity of these findings, we compared the distribution of GM1 moieties to that of the ganglioside GT1b. Our study provides definitive evidence for the presence of Gal(beta1-3)GalNAc bearing moieties on the axolemmal surface of mature myelinated fibres and on Schwann cells. Gal(beta1-3)GalNAc binding sites did not have an obligatory co-localization with voltage-gated sodium channels or the potassium ion channels Kv1.1 and Kv1.5 and are thus not likely carried by these ion channels. In contrast with Gal(beta1-3)GalNAc, GT1b-like moieties are restricted to the axolemma.

Campylobacter jejuni lipopolysaccharides in Guillain-Barré syndrome: molecular mimicry and host susceptibility

OBJECTIVE

This study was designed to determine if the presence of specific ganglioside-like moieties in Campylobacter lipopolysaccharides (LPSs) is related to the development of Guillain-Barré syndrome (GBS), and to discover how frequently such moieties, including GM1, are present in these LPSs.

METHODS

We studied Campylobacter isolates and sera from seven patients with GBS (five acute motor axonal neuropathy, one acute inflammatory demyelinating polyneuropathy, and one Fisher's syndrome), and compared them with similar specimens from patients with Campylobacter enteritis alone.

RESULTS

All GBS patients had antiganglioside antibodies. Anti-GM1 and anti-GD1a titers were significantly elevated in post-Campylobacter GBS, both axonal and demyelinating, compared with normal control subjects or those with uncomplicated Campylobacter diarrhea. Campylobacter isolated from patients with GBS and with enteritis alone had similar ganglioside-like moieties.

CONCLUSIONS

These results indicate that patients who develop GBS respond differently to the ganglioside-like epitopes on Campylobacter than do non-GBS diarrhea patients. Our findings support a role for host susceptibility as a determinant for the outcome following Campylobacter infection. These findings have important implications for the development of vaccines against Campylobacter jejuni.

Molecular mimicry in Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is the commonest cause of acute flaccid paralysis worldwide. Recent pathological and electrodiagnostic studies indicated that there are different patterns within this syndrome. The demyelinating pattern predominates in North America and Europe, whereas axonal variants of GBS occur more frequently in Northern China. Infection with Campylobacter jejuni is one of the most frequently recognized antecedent events in all variants of GBS. The lipopolysaccharides of these organisms share ganglioside-like epitopes with peripheral nerves, and patients with GBS have antiganglioside antibodies. These observations have given rise to the hypothesis that "molecular mimicry" is the immunopathogenic mechanism of injury to peripheral nerve fibers. With this hypothesis in view, we summarize our experience of GBS as it occurs in Northern China. To explore the role of molecular mimicry in this cohort we sought evidence of preceding Campylobacter infection and correlated this with clinical characteristics and antiganglioside serology. Based on our results we propose a sequence of pathogenic events leading to peripheral nerve injury in GBS.

Immune attack on the Schwann cell surface in acute inflammatory demyelinating polyneuropathy

The localization, mode of action, and roles of complement in the Guillain-Barre syndrome have been controversial. We used high-resolution immunocytochemistry to localize complement activation products in early stages of the acute inflammatory demyelinating polyneuropathy (AIDP) pattern of Guillain-Barre syndrome. Three AIDP subjects who were autopsied had had symptoms for 3 to 9 days at the time of death. Immunocytochemistry was performed on etched, epoxy resin-embedded sections, and the next thin section was compared by electron microscopy (thick/thin sections). Many fibers had a rim of the complement activation marker C3d and the terminal complement complex neoantigen C5b-9 along the outer surface of the Schwann cells. Ultrastructural analysis of these C3d-positive fibers showed mild vesicular changes of the outermost myelin lamellae. Vesicular degeneration was seen before the invasion of macrophages into the myelin, and was the predominant change in the subject with symptoms for 3 days. C3d staining was not found on myelin membranes. The results suggest that at least some forms of AIDP are complement mediated. We speculate that complement is activated by antibody bound to epitopes on the outer surface of the Schwann cell and that the resulting complement activation initiates the vesiculation of myelin.