Human alpha tumor necrosis factor does not damage cultures containing rat Schwann cells and sensory neurons.

The effects of recombinant human alpha tumor necrosis factor (alpha-TNF) were compared with those of cytotoxic serum from patients with the acute Guillain-Barré syndrome (GBS) in myelinated cultures containing only rat Schwann cells and dorsal root ganglion neurons. Alpha-TNF did not damage rat peripheral nervous system tissue in culture. These observations suggest that alpha-TNF is not responsible for the cytotoxic activity of acute GBS serum in culture.

Effects of A23187 in cultures containing only rat Schwann cells and sensory neurons.

Serum from approximately 40% of patients with the acute Guillain-Barré syndrome (GBS) selectively destroys myelin and myelin-related Schwann cells in cultures containing only rat dorsal root ganglion neurons and Schwann cells. To determine if the effects of GBS serum on myelin and myelin-related Schwann cells could be mediated through elevations in the intracellular concentration of calcium ions, we compared the effects of cytotoxic serum to A23187, a divalent cation ionophore. Both myelin- and nonmyelin-related Schwann cells were killed along with neurons in the presence of A23187 and extracellular calcium ions. Myelin sheaths also underwent vesicular disruption. The ultrastructural appearance of myelin and myelin-related Schwann cell lysis caused by A23187 were essentially identical to damage produced by GBS serum. These observations suggest that GBS serum factors might damage myelin and myelin-related Schwann cells in culture by an increase in myelin-related Schwann cell permeability to extracellular calcium ions. In contrast, A23187 causes necrosis of Schwann cells and neurons as well as myelin lysis by a nonselective increase in membrane permeability to extracellular calcium ions.

Ultrastructural effects of Guillain-Barré serum in cultures containing only rat Schwann cells and dorsal root ganglion neurons.

Serum from patients with the acute form of the Guillain-Barré syndrome was applied to cultures containing only rat dorsal root ganglion neurons and Schwann cells. Serum taken from 4 of 10 patients during the first 1-3 weeks of clinical onset had previously been shown to have significant demyelinating activity in this culture system when observed at the light microscopic level. More detailed assessment made at the ultrastructural level showed that: (1) wide-spread myelin-related Schwann cell lysis occurred in concert with vesicular myelin breakdown; (2) non-myelin-related Schwann cells avidly phagocytized necrotic cell debris and fragments of compact myelin; and (3) neurites and non-myelin-related Schwann cells remained structurally undamaged. Cultures treated with convalescent phase serum from patients whose acute phase serum had cytolytic activity displayed no significant ultrastructural damage to either neurites or Schwann cells. This is the first electron microscopic study to provide direct evidence that acute Guillain-Barré serum can be cytolytic for myelin-related Schwann cells and peripheral myelin in an experimental setting free of leukocytes, lymphocytes and mononuclear phagocytes.

Effects of Guillain-Barré sera containing antibodies against glycolipids in cultures of rat Schwann cells and sensory neurons.

Serum samples from 52 patients with the acute Guillain-Barré syndrome (GBS), 19 patients with other neurological disorders, and 18 healthy volunteers were tested for cytotoxicity in cultures of rat Schwann cells and dorsal root ganglion neurons. The samples were also examined by enzyme-linked immunosorbent assay for IgG and IgM antibodies against various acidic and neutral glycolipids. Samples from 16 of the 52 (31%) acute GBS patients and from 1 of the 6 patients with chronic inflammatory demyelinating polyneuropathy produced myelin breakdown in culture. Although 10 of the 16 cytotoxic acute GBS serum samples contained anti-glycolipid immunoglobulins, there was no correlation in individual samples between cytotoxic activity and the presence of antibodies against specific glycolipids. While our results do not exclude a role for anti-glycolipid antibodies in the pathogenesis of the acute GBS, the cytotoxic effects of acute GBS serum in cultures of Schwann cells and sensory neurons are probably not due to these antibodies alone.

Identification of oleoresin in epoxy-embedded slash pine tissue.

Sudan black B stains oleoresin blue-black in epoxy-embedded material as well as in living tissue. The Sudan black B staining properties of oleoresin are similar to those of lipid, but it can be distinguished from tannin, which stains brown. Pratically all oleoresin present in resin ducts and intercellular spaces, and much of that contained in epithelial and ray cells, is extracted in preparatory procedure for electron microscopy. A fixation procedure is proposed which preserves significantly more oleoresin in situ. The use of Sudan black B enables one to localize oleoresin by light microscopy, and permits direct comparison of adjacent sections of epoxy-embedded material at the ultrastructure level. Ultrastructurally oleoresin and lipid possess similar electron densities and can be distinguished from the highly electron-opaque tannin deposits.

Effects of ethanol on rat Schwann cell proliferation and myelination in culture.

It is possible to treat dissociated embryonic rat dorsal root ganglia in culture to inhibit proliferation of all nonneuronal cells except Schwann cells. Neurons have been shown to produce a mitogenic stimulus for Schwann cells under these conditions. Additionally, myelin-competent neurons induce Schwann cells to elaborate myelin sheaths. Groups of sibling cultures were exposed to various nonlethal concentrations of ethanol (0, 43, 86, or 172 mM) for 4 wk. Cultures were assessed weekly by light microscopy in a blind fashion for evidence of Schwann cell proliferation and myelin formation. Ethanol adversely affected both Schwann cell proliferation and myelin formation in culture. No obvious differences in neuronal morphology were observed among the various groups of cultures by light or electron microscopy. These observations suggest that ethanol might interfere with Schwann cell proliferation and myelin formation in culture by one or both of the following means: a) inhibit neuronal production of signals for Schwann cell proliferation and myelination or b) impede Schwann cell responses to neuronal signals. Investigation of these possibilities in culture may provide insight into neuropathologic mechanisms operative in the fetal alcohol syndrome or alcohol-associated peripheral neuropathy in humans.

The extracellular matrix of Volvox: a comparative study and proposed system of nomenclature.

The structure of the extracellular matrix (ECM) of representatives of all four sections of the genus Volvox was examined by a combination of light- and electron-microscopic methods. On the basis of these observations, plus published descriptions of aspects of ECM organization in other members of the order Volvocales, a system of nomenclature is proposed, to facilitate discussion of comparative morphology and phylogeny of the ECM in the order. In this system the ECM is divided into four main zones: the flagellar zone (FZ), which consists of attachments to and specializations of the ECM around the flagella; the boundary zone (BZ), which consists of portions of the ECM that (except in periflagellar regions) are continuous over the surface of the organism and are not structurally continuous with deeper layers; the cellular zone (CZ), which consists of specializations, other than those of the FZ, around individual cells; and the deep zone (DZ), which consists of components that fill the central region of the organism, internal to CZ. An empirically based set of hierarchical subdivisions of these zones is then proposed that permits specific identification of most morphologically distinct ECM components. The fact that not all zones and subzones are present in all members of the order means that this system permits identification of those ECM structures that have been gained or lost during Volvocalean evolution. Species-specific differences in the structure of virtually all aspects of the ECM were seen among the Volvox species examined in this study. However, the fact that such differences cannot always be used as diagnostic characters for the four divisions of the genus was demonstrated by the observation that in certain ECM features two members of the same division (V. carteri f. nagariensis and V. carteri f. weismannia) differ markedly in structure from one another, with one member of the pair resembling a member of another division. Thus many details of ECM organization appear to be under separate control, and capable of independent evolution.