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Biomedical subjects

N A Gregson

Publications and source records attributed to N A Gregson.

At least 55 records · Page 3Linked to original sources
PubMed1994

Coordinated pattern of expression and localization of insulin-like growth factor-II (IGF-II) and IGF-binding protein-2 in the adult rat brain.

Insulin-like growth factors (IGFs) have numerous actions on neuronal and glial cell function in vitro, although their in vivo roles within the central nervous system (CNS) remain undefined. Levels of IGF-II are high in most rat tissues before the third postnatal week, but rapidly decrease thereafter, except in the brain and spinal cord, where elevated titers are present in the adult. This suggests a function of IGF-II within the CNS. IGF-binding proteins (IGFBPs) modify the type 1 IGF receptor-mediated activity of IGFs, thereby regulating the activities of IGF-II in the CNS. In this study, we use a ribonuclease protection assay, in situ hybridization, and immunohistochemistry to demonstrate that IGF-II and one of the major CNS binding proteins, IGFBP-2, show a striking congruency in their anatomical pattern of expression and localization throughout the adult rat brain. Both proteins are synthesized predominantly in the leptomeninges, choroid plexus, and parenchymal microvasculature, but become localized, remote from the site of synthesis, in the myelin sheaths of individual myelinated axons and in all of the myelinated nerve tracts in the brain, which presumably represents the site of IGF-II bioactivity. The spatial disparity between sites of synthesis and sites of bioactivity suggests a key role for IGFBP-2 in the regulation of IGF-II bioavailability within the brain.

Animals↗
PubMed1993

Campylobacter jejuni and Guillain-Barré syndrome.

Campylobacter jejuni is the most frequently identified bacterial cause of gastroenteritis in the UK, and commonly precedes Guillain-Barré syndrome (GBS). There is some evidence that the resultant neurological disease may be a more severe variant of GBS with predominant axonal degeneration. Crossreactivity between neural antigens and C. jejuni may be one of the mechanisms by which GBS is triggered. Unravelling the immunopathogenesis of GBS following C. jejuni enteritis may shed light on the way in which bacterial infections induce autoimmune disease.

Adolescent↗
PubMed1993

Antibodies to gangliosides in Guillain-Barré syndrome: specificity and relationship to clinical features.

Antibodies to ganglioside GM1 have been associated with Guillain-Barré syndrome. To clarify their role we have studied their frequency, fine specificity and relationship to clinical features in a series of patients with this disease. Antibodies to ganglioside GM1 were identified, by both enzyme-linked immunosorbent assay and binding to thin-layer chromatograms of human brain, in 12 (28.6%) of 42 patients with Guillain-Barré syndrome and in only 1 (2.4%) of 41 normal control subjects (p = 0.002). Eight sera contained IgM antibodies and six sera contained IgG antibodies, including 2 sera which contained both. The fine specificity of the sera varied. Only four of the 12 sera also showed reactivity with ganglioside GD1b and gangliotetraosyl-ceramide (asialo-GM1), consistent with reactivity with the terminal Gal beta 1-3GalNAc disaccharide. Two sera had low titre anti-asialo-GM1 antibodies of a different class to the anti-ganglioside GM1 antibodies. The antibodies in these sera therefore react with a variety of epitopes. There was a strong relationship between the presence of anti-ganglioside GM1 antibodies in the acute stage and prolonged disability, especially if IgG antibodies were present. Seven of 12 patients with anti-ganglioside GM1 antibodies had serological evidence of recent Campylobacter jejuni infection, but antigens from a strain of this bacterium not associated with Guillain-Barré syndrome did not absorb the anti-ganglioside GM1 antibodies.

Adult↗
PubMed1992

An immunohistochemical study of phospholipase A2 in peripheral nerve during Wallerian degeneration.

Antiserum raised against purified Crotalus adamanteus venom phospholipase A2 (PLA2) was used to localise the enzyme in normal and crushed sciatic nerve to determine the effect of nerve trauma on PLA2 distribution in the PNS. The tissue was Bouin's fixed, and stained immunohistochemically using the Vectastain ABC technique. Anti-PLA2 antiserum showed weak reactivity with normal rat myelin, while only 'resident' macrophages stained in normal mouse sciatic nerve. Post-crush, in the mouse, myelin staining was localised close to the crush site, with strong lysosomal staining within both 'resident' and invading haematogenously derived macrophages. In the rat, myelin sheaths stained strongly throughout the nerve very soon after crush, but no macrophages were detected using these antisera. Paranodal myelin and some Schmidt-Lanterman incisures were the first regions of the sheath to show an increase in PLA2 staining post-crush, areas where the first ultrastructural changes occur in myelin after trauma, with staining of compact myelin closely following. Our findings support the idea that PLA2 may be involved in the early process of myelin breakdown seen in Wallerian degeneration.

Animals↗
PubMed1991

Acute motor neuropathy with antibodies to GM1 ganglioside.

We describe a 52-year-old man who had an acute-onset purely motor neuropathy fulfilling the diagnostic criteria for the Guillain-Barré syndrome, in whom virtually complete spontaneous recovery occurred by 1 year, and in whom high titres of polyclonal serum antibody to GM1, GD1b, asialo-GM1 and lacto-N-tetraose were detected. The titre of IgM antibody to GM1 fell during the course of the disease with a concomitant rise in the IgG titre. This case adds to the widening spectrum of disease associated with anti-GM1 antibodies and provides further evidence for a relationship between anti-GM1 antibodies and motor system disease.

Acute Disease↗
PubMed1991

The clinical spectrum of peripheral neuropathies associated with benign monoclonal IgM, IgG and IgA paraproteinaemia. Comparative clinical, immunological and nerve biopsy findings.

Observations have been made on a consecutive series of 62 patients with peripheral neuropathy associated with benign monoclonal paraproteinaemia. The paraprotein class was IgM in 46 cases, IgG in 11 and IgA in 5. Although showing variations between patients, the clinical picture was similar for those with either IgM or IgG paraproteins, usually consisting of a late-onset, slowly progressive, distal sensorimotor demyelinating polyneuropathy, often with tremor and ataxia as prominent features. Tremor was slightly more common in patients with IgM paraproteins, in whom there was a male preponderance. The patients with both paraprotein classes were indistinguishable clinically and electrophysiologically from chronic idiopathic demyelinating polyneuropathy. In the 5 patients with an IgA paraprotein, there was a distal sensorimotor neuropathy in 4 which was demyelinating in 1. In 1 there was proximal demyelinating motor neuropathy. Immunoglobulin deposition on myelin was observed only in the patients with IgM paraproteinaemia, more commonly with a kappa light chain. No deposition of immunoglobulin in the endoneurium was seen. IgM deposits on the perineurium are a feature of normal nerve and were present in all cases. Widely spaced myelin was confined to cases with IgM paraproteins in which immunoglobulin deposition was detected on myelin. The response to treatment could not be assessed systematically but, in general, the patients with IgG and IgA paraproteins responded more satisfactorily (to corticosteroids, cytotoxic drugs, or plasma exchange) than did those with an IgM paraprotein.

Adult↗
PubMed1989

A novel metalloproteinase associated with brain myelin membranes. Isolation and characterization.

Brain myelin membrane preparations contain a metalloproteinase activity which degrades myelin basic protein (MBP). The activity was associated with lentil lectin-binding glycoproteins solubilized from myelin and could be detected in the presence of the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonate (CHAPS). The metalloproteinase represented about 5% of this glycoprotein fraction and was isolated from it by chromatography on DEAE-Sephacel, CM-Sepharose, and Superose 6. The proteinase had an apparent relative molecular weight (Mr) of approximately 58,000 both by gel filtration and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The Mr value was unaffected by the presence of reducing agents but was diminished to about 52,000 by treating the proteinase with endoglycosidase F. The purified proteinase cleaved many bonds in MBP but did not generate trichloroacetic acid-soluble products. Two major polypeptides, putatively MBP1-73 and MBP74-170, were prominent in digests of MBP by either the purified enzyme or myelin membranes. The proteinase was active between pH 7 and 9 and was inhibited by phenanthroline and dithiothreitol but not phosphoramidon or inhibitors of serine or cysteine proteinases. Histones, but not azocasein, also served as substrates for the proteinase. From its enzymic and molecular characteristics the myelin-derived metalloproteinase appears distinct from previously described enzymes.

Animals↗
PubMed1989

The conditioning effect of optic nerve injury upon axonal regrowth from adult rat retinal ganglion cells explanted in vitro.

An in vitro assay was used to determine the effects of conditioning nerve lesions on the regeneration of adult rat retinal ganglion cell (RGC) axons from retinal explants. Following the conditioning lesion (CL) of unilateral optic nerve transection, maximal regrowth was seen from RGC explanted from ipsilateral retinae 10 days post-CL. Explants from this group initiated axonal regrowth earlier and a greater percentage regrew axons when compared with explants from normal rats. Axonal regrowth from explants of retinae contralateral to CL was also seen earlier than normal. In further experiments, the effects of both exposure of the optic nerve sheath in the orbit and the incision of the dura without injury to optic nerve axons were studied. The conditioning effect of a dural incision was found to be the same as that of optic nerve transection, whilst exposure of the optic nerve sheath had no conditioning effect on RGC axonal regrowth in vitro.

Animals↗
PubMed1989

Peripheral neuropathy associated with Castleman's disease.

Four patients with polyneuropathy complicating the plasma cell variant of Castleman's disease (angiofollicular lymph node hyperplasia) are described. The neuropathy was predominantly motor and severely disabling. Vasculopathy, papilloedema, organomegaly, endocrinopathy, oedema and paraproteinaemia were variably present in these patients. Sural nerve biopsy showed changes of both demyelination and axonal loss. Capillary proliferation and endothelial hypertrophy in the epineurium and endoneurium, similar to that seen in affected lymph nodes, suggested that a diffuse vasculopathy may contribute to the neuropathy. Serum antibody activity against a variety of neural antigen preparations was not detected in any of the patients. Two untreated patients died. Substantial improvement in the neuropathy occurred in the two patients treated with cyclophosphamide and prednisolone.

Adult↗
PubMed1988

Development of macroglial cells in rat cerebellum. I. Use of antibodies to follow early in vivo development and migration of oligodendrocytes.

The origin of oligodendrocytes and astrocytes in the CNS is still a focus of much experimentation and controversy. We have used antibodies against ganglioside GD3 and galactocerebroside (GC) to follow the origin and development of rat cerebellar oligodendrocytes both in vitro and in vivo. The immunofluorescent identification of GC+ cells in the rat neonatal cerebellum in vivo, revealed that cells initially GD3+/GC- appeared to make the transition via GD3+/GC+ cells to GD3-/GC+ oligodendrocytes. This sequence of events closely paralleled the maturation of cerebellar oligodendrocyte precursors found in serum-free dissociated culture. In contrast, whereas both GD3+ and glial fibrillary acidic protein-positive cells were seen in serum-containing dissociated culture and also in freshly dissociated suspensions of cerebellum at postnatal days 0 to 6, such cells could not be identified in situ. Putative GD3+/GC- oligodendrocyte precursor cells arose from the deeper regions of the cerebellum at birth, perhaps initially from the superior medullary velum adjacent to the fourth ventricle, and appeared to migrate into the developing folia just prior to myelination and the acquisition of GC.

Animals↗
PubMed1988

Neither laminin nor prior optic nerve section are essential for the regeneration of adult mammalian retinal ganglion cell axons in vitro.

Retinal explants obtained from normal adult rats and from operated animals in which the optic nerve had been sectioned 10 days previously were cultured in either serum-containing or serum-free medium on poly-L-lysine and laminin substrata. Regenerating ganglion cell axons growing from these explants have been identified using monoclonal antibodies against Thy-1.1 cell surface glycoprotein and the 200-kDa subunit neurofilament protein. Irrespective of substratum or medium composition, axons regenerated from 28-49% of normal rat retinal explants. This percentage increased to 60-84% of explants from operated rats. There were no significant differences in percentages of explants from normal or operated rats showing neurite outgrowth when substrata of either poly-L-lysine or laminin were compared in serum-free medium. In serum-containing medium the results were less easily interpreted due to the presence of an outgrowth of non-neuronal (glia and mesenchymal) 'flat cells', which served as a preferred axonal substratum in many cases. Thus we show that adult rat retinal ganglion cell axons will regrow in vitro, and that a 'priming' optic nerve section will increase this response. In neither case is the response laminin-dependent.

Animals↗