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N Cashman

Publications and source records attributed to N Cashman.

16 recordsLinked to original sources
PubMed2005

Lymphoid signal transduction mechanisms linked to cellular prion protein.

The normal cellular isoform of the prion protein (PrPC) is a glycosylphosphatidylinositol-anchored cell surface protein that is expressed widely, including in lymphoid cells. We compared lectin-induced mitogenesis and selected cell signaling pathways in splenocytes from wild-type BALB/c mice and Zrch Prnp0/0 (PrP0/0) mice bred on a BALB/c background for more than 10 generations. 3H-thymidine incorporation induced by concanavalin A (Con A) or phytohemagglutinin (PHA) was significantly reduced in PrP0/0 splenocytes, most prominently early in activation (24 and 48 h). Con A activation in PrP0/0 splenocytes was associated with differences in the phosphorylation (P) patterns of protein kinase C (PKC alpha/beta, but not delta) and the PKC downstream effectors p44/42MAPK (mitogen-activated protein kinase). P-PKC and P-MAPK profiles were similar in wild-type and PrP0/0 splenocytes following PMA treatment, indicating that the ability of these 2 enzymes to be phosphorylated is not impaired in the absence of PrPC. Con A-induced calcium fluxes, monitored by indo-1 fluorescence, were equivalent in PrP0/0 and PrP+/+ splenocytes, suggesting that calcium-dependent mechanisms are not directly implicated in the differential phosphorylation patterns or mitotic responses. Our data indicate that PrP0/0 splenocytes display defects in upstream or downstream mechanism(s) that modulate PKCalpha/beta phosphorylation, which in turn affects its capacity to regulate splenocyte mitosis, consistent with a role for PrPC in immune function.

Animals↗
PubMed2001

Deletion of the hypoxia-response element in the vascular endothelial growth factor promoter causes motor neuron degeneration.

Hypoxia stimulates angiogenesis through the binding of hypoxia-inducible factors to the hypoxia-response element in the vascular endothelial growth factor (Vegf) promotor. Here, we report that deletion of the hypoxia-response element in the Vegf promotor reduced hypoxic Vegf expression in the spinal cord and caused adult-onset progressive motor neuron degeneration, reminiscent of amyotrophic lateral sclerosis. The neurodegeneration seemed to be due to reduced neural vascular perfusion. In addition, Vegf165 promoted survival of motor neurons during hypoxia through binding to Vegf receptor 2 and neuropilin 1. Acute ischemia is known to cause nonselective neuronal death. Our results indicate that chronic vascular insufficiency and, possibly, insufficient Vegf-dependent neuroprotection lead to the select degeneration of motor neurons.

Amyotrophic Lateral Sclerosis↗
PubMed2000

Monitoring signals for vaccine safety: the assessment of individual adverse event reports by an expert advisory committee. Advisory Committee on Causality Assessment.

Monitoring vaccine safety is a complex and shared responsibility. It can be carried out in many ways, one of which is the reporting of individual cases of adverse reactions thought to be due to vaccination. The task is difficult because ascribing causality to an individual case report is fraught with challenges. A standardized evaluation instrument--known as the causality assessment form--was therefore developed for use by an expert advisory committee to facilitate the process. By following the several sections in this form, the members of the committee are taken through a series of points to establish causality. These points include the basic criteria for causation such as biological plausibility, the time elapsed between the vaccine administration and the onset of the adverse event, and whether other factors (drugs, chemicals or underlying disease) could account for the adverse symptoms. The form concludes with a consensus assessment of causality, a commentary about the assessment, and advice for further study or follow-up. This method of assessing the more serious cases of adverse reaction reported to vaccination has proven useful in evaluating ongoing safety of vaccines in Canada. Through analyses such as this, new signals can be identified and investigated further.

Adverse Drug Reaction Reporting Systems↗
PubMed1995

Binding and internalization of neurotensin in hybrid cells derived from septal cholinergic neurons.

Autoradiographic studies from our laboratory have previously demonstrated a selective association of high affinity neurotensin (NT) binding sites with basal forebrain cholinergic neurons. In search of an in vitro model for further characterization of the role and regulation of these sites, we have examined the binding and internalization of 125I-Tyr3-NT (125I-NT) and fluorescein isothiocyanate (FITC)-conjugated NT (fluo-NT) on SN17 hybrid cells, produced by fusion of embryonic murine septal cells with neuroblastoma. 125I-NT binding to SN17 membrane preparations was specific and saturable. Scatchard analysis of the data was suggestive of an interaction with a single population of sites, the affinity (Kd = 1.7 nM) and pharmacological profile of which were comparable to those of neural NT receptors. No specific binding was observed on the parent neuroblastoma cell line, confirming that the expression of those sites is a neuronal trait. Incubation of whole SN17 cells with 125I-NT resulted in a time- and temperature-dependent internalization of the specifically bound peptide. The t1/2 of this internalization was estimated at 13 min, a value nearly identical to that reported for neurons in culture. Confocal microscopic analyses using fluo-NT indicated that the internalization process was endocytic in nature in that: 1) it was entirely blocked by the endocytosis inhibitor phenylarsine oxide; and 2) it was mediated through small intracytoplasmic particles the size and maturation of which corresponded to that of endosomes. It is proposed that the expression and internalization of NT receptors by SN17 hybrid cells represent a new facet of these cells' cholinergic phenotype that makes them amenable to the study of NT interactions with cholinergic cells.

Acetylcholinesterase↗
PubMed1991

Gamma-interferon promotes proliferation of adult human astrocytes in vitro and reactive gliosis in the adult mouse brain in vivo.

Reactive gliosis is a characteristic response of astrocytes to inflammation and trauma of the central nervous system. To investigate whether soluble factors (cytokines) from inflammatory mononuclear cells that accumulate at lesion sites can provide the cellular signals to initiate gliosis and to identify such cytokines, we have tested and found that supernatants derived from subsets of activated human T lymphocytes (CD8+ or CD4+) are potent mitogens for cultured human adult astrocytes. This effect is blocked by a neutralizing antibody to gamma-interferon (IFN). Recombinant IFN alone can induce proliferation of human adult astrocytes in vitro and increase the extent of trauma-initiated gliosis in the adult mouse brain. The astrocyte proliferation-inducing activity of supernatants of glial cultures treated with IFN can be completely blocked with IFN-neutralizing antibody, suggesting that the proliferative effect does not require intermediary cytokines or cells. These results implicate IFN as an important mediator of the gliosis observed in pathologic conditions of the adult central nervous system associated with infiltrating lymphocytes.

Animals↗
PubMed1991

An LRE (leucine-arginine-glutamate)-dependent mechanism for adhesion of neurons to S-laminin.

S-laminin is a homolog of laminin that is concentrated in the synaptic cleft of the neuromuscular junction. We previously showed that the tripeptide LRE is a crucial determinant for binding of ciliary motoneurons to recombinant s-laminin. Here, we describe a neuroblastoma-spinal neuron hybrid cell line, NSC-34, that binds to an LRE-containing s-laminin fragment and to a synthetic LRE-protein conjugate. NSC-34 cells exhibit several properties of motoneurons; other cell lines tested were not motoneuron-like and did not display LRE-dependent adhesion. We therefore used NSC-34 cells to characterize the LRE-dependent adhesion mechanism. Inhibition studies with a series of 20 tripeptide LRE analogs showed that the cells exhibit a high degree of selectivity for LRE, and suggested that ligand binding requires a combination of electrostatic and hydrophobic interactions. The effects of cations on LRE-dependent adhesion are unlike those of previously described adhesion molecules including the integrins, a family of receptors for extracellular matrix proteins, including laminin. Specifically, adhesion to LRE does not require divalent cations and is inhibited by Ca2+ (but not by Mg2+) in the physiological range. In contrast, adhesion of NSC-34 cells to laminin is LRE- and Ca2+ independent but Mg2+ dependent, and appears to be mediated by integrins. Additionally, experiments using mixed substrates demonstrated that LRE-protein conjugates inhibit neurite outgrowth promoted by laminin. Finally, we show that, under ionic conditions that minimize integrin-dependent adhesion, NSC-34 cells bind to s-laminin-rich basal laminae in tissue sections in an LRE-dependent manner. Together, these results suggest that LRE comprises a motoneuron-selective adhesion site that is accessible in native basal laminae and that acts to inhibit neurite outgrowth.

Amino Acid Sequence↗
PubMed1989

Increased N-myc mRNA expression associated with dibutyryl cyclic AMP induced neuroblastoma differentiation.

The N-myc cellular oncogene is frequently amplified and expressed at a high level in neuroectodermal tumor cells such as neuroblastoma and retinoblastoma. We examined N-myc expression in NCB-20 hybrid (N18TG2 neuroblastoma x embryonic Chinese Hamster brain) cells. After five days of culture, cells treated with 1 mM db cAMP show extensive neurite outgrowth and secrete acetylcholinesterase into the media at a level three times higher than untreated control. In situ hybridizations, dot blots, and Northern analyses reveal four- to eight-fold higher levels of N-myc mRNA in the treated, differentiated cells than in the untreated, undifferentiated controls. Our results show that the highly differentiated state is not incompatible with a high level of N-myc mRNA.

Acetylcholinesterase↗
PubMed1986

Activated suppressor cell dysfunction in progressive multiple sclerosis.

Concanavalin A (Con A)-induced suppressor activity has previously been shown to be reduced in multiple sclerosis (MS) patients with active clinical disease. In this study, we demonstrate that OKT3, as well as Con A induced suppressor activity mediated by unfractionated peripheral blood mononuclear cells is reduced in patients with the progressive form of MS. By performing reconstitution experiments involving E+, T4+, or T8+ cells derived from either MS patients or controls, and normal allogeneic macrophages or E- cells, we sought to define the cellular basis for this suppressor defect. In both MS and control groups, E+ cells were required to obtain measurable levels of suppression. Suppressor levels induced by Con A-activated cultures containing E+ cells from MS patients were lower than those induced by those containing control donor E+ cells. Suppression mediated by T8+ cells from MS patients was also lower than for controls. In the control group, suppression mediated by T8+ cells exceeded that mediated by T4+ cells; such differences were not apparent in the MS group. These results suggest that although Con A-induced suppression can be mediated by a number of T and non-T cell subsets, the functional suppressor defect measured in the MS population does involve the T8+ cell subset.

Adult↗
PubMed1984

Inhibition of terminal axonal sprouting by serum from patients with amyotrophic lateral sclerosis.

To investigate the pathogenesis of amyotrophic lateral sclerosis, we compared the effect of serum from patients with this disease on the regenerative sprouting of terminal axons in botulinum-treated mouse gluteus muscle with the effects of serum from controls and from patients with diabetic peripheral neuropathy. Serum from 9 of 19 patients with the sporadic form of amyotrophic lateral sclerosis and from 2 of 6 patients with the familial form caused a reduction in the proportion of sprouting terminal axons, as compared with that found in muscles treated with serum from controls or diabetic patients. Immunoglobulin from patients with amyotrophic lateral sclerosis, when tested on immunoblots, recognized a 56-kilodalton protein secreted by denervated rat diaphragm muscle; rabbit antiserum raised against this protein also suppressed terminal axonal sprouting. Thus, we have detected an antibody in the serum of patients with amyotrophic lateral sclerosis that inhibits sprouting of neurons and subsequent reinnervation of skeletal muscle. Whether this antibody is of primary pathogenic importance or represents a secondary response to neuromuscular destruction is not known. In either case, serum from patients with amyotrophic lateral sclerosis may provide reagents for studies of the trophic communications between muscle and motor neurons.

Adult↗
PubMed1984

Intraluminal clot of the carotid artery detected radiographically.

Nine patients had intraluminal filling defects identifiable as clot within the internal carotid artery at angiography. Thrombus was unilateral in eight, bilateral in one. Eight of the 10 clots were attached to atheromatous plaques. Three patients had serious concurrent illness: pancreatic cancer, rheumatoid arthritis with arteritis, and chronic pulmonary disease with polycythemia. In three patients, the clot was related to severe atherosclerosis. In three other patients, all young, the carotid thrombi remained unexplained though two of these patients had coagulation abnormalities. No patient had a new stroke after surgical or anticoagulant treatment.

Adult↗
PubMed1982

Monoclonal antibody-defined immunoregulatory cells in multiple sclerosis cerebrospinal fluid.

To determine if previously reported peripheral blood suppressor cell defects are also found in the central nervous system (CNS) of patients with multiple sclerosis (MS), we studied cerebrospinal fluid (CSF) and peripheral blood lymphocytes from 40 MS patients and 15 patients with other neurological diseases. With an indirect immunofluorescence technique using the OKT series of monoclonal antibodies (OKT4, marking helper/inducer cells, OKT5 and OKT8 marking suppressor/cytotoxic cells, and OKT3 marking all peripheral T cells) we found that MS patients tested in the first 2 wk of exacerbation had invariably diminished CSF suppressor/cytotoxic cells, which was followed by an elevation of these cells in the 3rd wk of exacerbation. Repeat studies of three patients showed that perturbations of CSF suppressor/cytotoxic cells were dependent on clinical status. These observations add to the accumulating data that suggest altered immunity in the pathogenesis of MS.

Antibodies, Monoclonal↗
PubMedDate not supplied

Experimental allergic encephalitis; treatment with drugs which alter CNS serotonin levels.

Lennon and Carnegie have proposed that the clinical symptomatology of experimental allergic encephalitis (EAE), an acute autoimmune demyelinating disease, may be due, at least in part, to an immune response directed against CNS serotonin receptors. To test this hypothesis we treated strain 13 guinea pigs, which had been immunized with guinea pig basic protein (GPBP) in complete Freund's adjuvant (CFA), with drugs known to affect central nervous system (CNS) serotonin levels. These drugs included imipramine hydrochloride, tryptophan and carbidopa which increase CNS serotonin and reserpine which decreases it. Five experiments were conducted in which all immunized animals treated with saline only died, as expected, as did all animals treated with reserpine which died even more quickly. A significant proportion of animals treated with the other three drugs, alone or in combination, survived or lived longer than controls. We conclude that survival of animals with EAE is enhanced by treatment with these drugs. We suggest that further evaluation of a possible blockade in serotonin transmission in EAE and multiple sclerosis (MS) is warrented, since, if such a blockade were demonstrated, it is possible that these drugs may have potential for therapeutic efficacy in patients with MS.

Animals↗