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T Brenner

Publications and source records attributed to T Brenner.

At least 37 records · Page 2Linked to original sources
PubMed1997

Phorbol esters alter the morphology of cultured guinea-pig myenteric glia via a protein kinase C-independent mechanism.

Cultures of myenteric ganglia from adult guinea-pigs were used to study the influence of neuroactive substances on glial cells by monitoring changes in their morphology. The following substances had no effect on glial morphology: adenosine, ATP, carbachol, glutamate, bradykinin, isoprenaline, prostaglandin E2, sodium nitroprusside and lipopolysaccharide. The only substances found to affect glial morphology were phorbol esters, and in particular phorbol 12-myrisate 13-acetate (PMA), which acted at the nM range. Glial cells, which were normally polygonal, assumed a stellate shape within 30-60 min after the addition of PMA. Protein kinase C (PKC) inhibitors did not block this effect, and PKC activators did not mimic it. The effect of PMA was also not mediated by changes in the intracellular concentrations of either Ca2+, H+ or cyclic AMP. Dye coupling among glial cells was blocked by PMA. The phorbol ester-mediated effect on glial structure may have profound influence on neuronal organization and function.

Animals↗
PubMed1997

Effect of sphingosine on rat glial cells: inhibition of prostaglandin E2 and insensitivity of nitric oxide generation.

The effect of sphingosine on lipopolysaccharide (LPS)-mediated protein kinase C (PKC) activation and prostaglandin E2 (PGE2) and nitric oxide (NO) production was studied in primary cultures of rat glial cells. Incubation of cells with LPS elicited translocation of PKC from the cytosolic to the membranous compartment, as shown by measuring PKC activity and by immunoblotting. Under these conditions, a sustained increase in both PGE2 and NO production was measured. Thus, PGE2 levels were 259 +/- 28 (n = 8) and 230 +/- 48 (n = 4) (control levels 11.4 +/- 5.2 (n = 5) and 13 +/- 7.5 (n = 3)) pg/ml, at 24 and 48 h, respectively. NO levels were 9.3 +/- 0.9 (n = 10) and 11.6 +/- 0.8 (n = 9) (control levels 0.4 +/- 0.18 and 1.0 +/- 0.44) nmol/ml, at 24 and 48 h, respectively. Sphingosine, a naturally occurring compound, which inhibits PKC activity, elicited a concentration-dependent decrease in LPS-mediated PGE2 production. This inhibition was more pronounced after 48 h than after 24 h of incubation (IC50 = 8 and 20 microg sphingosine, respectively). By contrast, sphingosine did not inhibit NO production under the same conditions. We conclude that sphingosine may be involved in modulation of the local inflammatory response in glial cells, at least in part. We also surmise that LPS-mediated PGE2 production and NO production are probably regulated by different mechanisms, i.e., a PKC-dependent and a PKC-independent mechanism.

Animals↗
PubMed1997

Inhibition of nitric oxide synthase for treatment of experimental autoimmune encephalomyelitis.

Aminoguanidine (AG), a selective inhibitor of inducible nitric oxide synthase, prevented the clinical development of experimental autoimmune encephalomyelitis (EAE) with a reduction in inflammation and demyelination. Administration of AG reduced the expression of nitrosotyrosine in inflammatory lesions in the central nervous system. Cytokine expression, determined by semiquantitative PCR, revealed increased expression of IFN-gamma, IL-10, and TGF-beta, which was associated with protection from EAE, and reduced TNF-alpha, associated with the development of EAE. Furthermore, AG blocked the secretion of nitric oxide, TNF-alpha, and PGE2 in astrocyte cultures. AG did not influence the proliferation response of T cells to a pathogenic epitope of myelin basic protein. Down-regulation of nitric oxide by AG has widespread consequences for cytokine production in central nervous system inflammation and prevents EAE.

Animals↗
PubMed1997

Role of ryanodine receptor channels in Ca2+ oscillations of porcine tracheal smooth muscle.

Acetylcholine (ACh) induces repetitive, propagating intracellular Ca2+ concentration ([Ca2+]i) oscillations in porcine tracheal smooth muscle (TSM) cells. Using real-time confocal microscopy, we examined the role of sarcoplasmic reticulum (SR) Ca2+ release through inositol 1,4,5-trisphosphate (IP3) receptor and ryanodine receptor (RyR) channels in ACh-induced [Ca2+]i oscillations. In beta-escin permeabilized TSM cells, exposure to ACh in the presence of GTP also resulted in [Ca2+]i oscillations. [Ca2+]i oscillations could not be initiated by IP3 alone; however, an elevation of [Ca2+]i was observed. During ongoing [Ca2+]i oscillations, exposure to heparin, an IP3 receptor antagonist, caused a slowing of oscillation frequency but not complete inhibition. In contrast, ruthenium red, a RyR antagonist, completely abolished ACh-induced [Ca2+]i oscillations. Reverse transcriptase-polymerase chain reaction of TSM mRNA demonstrated the expression of RyR-2 and RyR-3 isoforms of the RyR. These results indicate that SR Ca2+ release through RyR channels is critical for ACh-induced [Ca2+]i oscillations in porcine TSM cells.

Acetylcholine↗
PubMed1996

Interleukin 2 pseudomonas exotoxin (IL2-PE66(4)Glu) chimeric protein kills B cells from patients with Myasthenia gravis.

IL2-PE66(4)Glu is a chimeric cytotoxin consisting of interleukin 2 (IL2) fused to a mutant form of Pseudomonas exotoxin (PE66(4)Glu). The chimeric cytotoxin has been previously shown to be extremely toxic to both phytohemagglutinin blasts and mixed leukocyte reaction blasts prepared from monkey and human lymphocytes. To explore the possible clinical utility of IL2-PE66(4)Glu for autoimmune diseases, particularly in which B cells are involved, we tested fresh B cells from patients with myasthenia gravis for sensitivity to this chimeric cytotoxin. Seventy-six percent (16 of 21) of the B cells tested were markedly sensitive to IL2-PE66(4)Glu-mediated cytotoxicity, with inhibition of protein synthesis ranging from 20 to 92%. B cells from control donors were much less sensitive to IL2-PE66(4)Glu cytotoxicity. Moreover, a control protein lacking IL2 as the targeting moiety of the chimera had no effect toward all B cells tested, thus establishing its specific activity. Our results suggest that IL2-PE66(4)Glu could be an effective tool for selective targeted immunotherapy of myasthenia gravis patients.

ADP Ribose Transferases↗
PubMed1995

Interleukin-2 Pseudomonas exotoxin chimeric protein is cytotoxic to B cell cultures derived from myasthenia gravis patients.

IL-2-PE664Glu is a chimeric cytotoxin consisting of interleukin-2 (IL-2) fused to a mutant form of Pseudomonas exotoxin (PE664Glu). The chimeric cytotoxin has been previously shown to be extremely toxic to both phytohaemagglutinin blasts and mixed leukocyte reaction blasts prepared from monkey and human lymphocytes. To explore the possible clinical utility of IL-2-PE664Glu for autoimmune diseases, particularly in which B cells are involved, we tested the sensitivity of B cell lines derived from myasthenia gravis patients to this chimeric cytotoxin. 65% (15 out of 23) of the tested B cell lines were sensitive to IL-2-PE664Glu mediated cytotoxicity. B cell lines from control donors as well as from patients with another autoimmune disease, multiple sclerosis, were much less sensitive to IL-2-PE664Glu cytotoxicity. Moreover, a control protein lacking the IL-2 as the targeting moiety of the chimera, had no effect toward all B cell lines tested, thus establishing its specific activity. A detailed study of the IL-2 receptor of the patients' B cells, using the PCR technique and FACS analysis, showed that the cells express mainly the beta and gamma chains and at a lower level also the alpha-chain of the IL-2 receptor. Our results suggest that IL-2-PE664Glu could be effective for selective targeted immunotherapy of myasthenia gravis patients.

Adult↗
PubMed1994

Direct binding of myelin basic protein and synthetic copolymer 1 to class II major histocompatibility complex molecules on living antigen-presenting cells--specificity and promiscuity.

Copolymer 1 (Cop 1) is a synthetic basic random copolymer of amino acids that has been shown to be effective in suppression of experimental allergic encephalomyelitis and is being tested as a candidate drug for multiple sclerosis. It has been previously demonstrated that Cop 1 is immunologically cross-reactive with the autoantigen myelin basic protein (BP) and competitively inhibits the response to BP of T-cell lines and clones of different major histocompatibility complex (MHC) restrictions, of both mouse and human origin. In the present study we demonstrated the direct binding of Cop 1, using its biotinylated derivative, to MHC molecules on living antigen-presenting cells. Binding of biotinylated BP and peptide p84-102 (an immunodominant epitope of BP) was also demonstrated. Cop 1 and BP bound in a promiscuous manner to different types of antigen-presenting cells of various H-2 and HLA haplotypes. The specificity of the binding was confirmed by its inhibition with either the relevant anti-MHC class II antibodies or unlabeled analogs. Cop 1 exhibited the most extensive and fast binding to antigen-presenting cells. In addition, Cop 1 inhibited the binding of biotinylated derivatives of BP and of p84-102 to the MHC class II molecules and even displaced these antigens when already bound. Thus, these results suggest that Cop 1 indeed competes with BP for MHC binding and, thereby, inhibits T-cell responses to BP. The binding of Cop 1 to different DR alleles, probably because of its multiple MHC binding motifs, may indicate its potential as a broad-spectrum drug for multiple sclerosis.

Amino Acid Sequence↗
PubMed1994

Mycoplasma triggering of nitric oxide production by central nervous system glial cells and its inhibition by glucocorticoids.

The same cytokines that have been implicated in the pathology of central nervous system (CNS) inflammatory diseases and demyelinating diseases are also associated with the induction of nitric oxide (NO) production by macrophages and other somatic cells. Recently we have showed that mycoplasma can trigger the production of tumor necrosis factor (TNF)alpha and eicosanoids in rat astrocytes. In the present study, the effect of mycoplasma on NO production in rat glial cells was assessed. The addition of 10 micrograms/ml of membranes derived from M. capricolum (sheep isolate), M. fermentans (human isolate), or lipopolysaccharide (LPS) led to a 15- to 20-fold increase in NO production. The glucocorticoids dexamethasone and corticosterone, but not progesterone, markedly inhibited NO production. The addition of glucocorticoid prior or conjointly with the activator prevented large amounts of NO from being formed. Even when glucocorticoids were added 5 or 24 h after activation, effective inhibition of NO production was obtained. Thus, it is likely that glucocorticoids exert some of their ameliorating effects in neurological diseases by reducing the production of NO, cytokines and prostaglandins in the CNS.

Animals↗
PubMed1994

Variable effect of calcium channel blockers on the decremental response in experimental autoimmune myasthenia gravis.

We tested the effect of intravenous administration of verapamil and nimodipine on the decremental response in rabbits with experimental autoimmune myasthenia. Nimodipine produced an immediate augmentation of the decremental response to 3-Hz nerve stimulation, which lasted about 30 min. In contrast, verapamil caused marked amelioration of the decrement beginning 30 min after injection. Our findings are consistent with previous reports suggesting that verapamil has a presynaptic effect of enhanced acetylcholine release at the neuromuscular junction. Since evaluation of a drug effect in vivo in animals with experimental autoimmune myasthenia gravis may be more pertinent to its effect on patients with myasthenia gravis (MG), verapamil might prove to be safer in MG than nimodipine. However, due to the additional effects of calcium channel blockers, the safety of their use in myasthenia gravis cannot be inferred from the experimental results.

Action Potentials↗
PubMed1994

Mast cells in experimental allergic encephalomyelitis: characterization, distribution in the CNS and in vitro activation by myelin basic protein and neuropeptides.

Mast cells (MC) have been implicated in the pathogenesis of experimental allergic encephalomyelitis (EAE). In order to further evaluate their role, several morphological and functional studies were performed. Semiquantitative counts of histological sections showed a significant reduction in MC numbers in EAE brains. In addition, a higher proportion of EAE MC (about 50-70%) appeared degranulated compared with about 20% degranulation in controls. Central nervous system (CNS) MC exhibited staining properties of connective tissue MC and about 98% of them, both in diseased and control rats, were located in the thalamus. They were not present in the spinal cord and did not relate to EAE lesions. In vitro incubation of peritoneal MC (of connective tissue phenotype) with either MBP, or with neuropeptides such as substance P or bradykinin resulted in release of beta-hexosaminidase and histamine. The latter responses were similar in both EAE and control rats. It is suggested that the decrease in number and in granular content of CNS MC in EAE may reflect prior in vivo activation. The fact that MC were activated by MBP and by neuropeptides in vitro suggests a possible mechanism of MC activation in EAE.

Animals↗
PubMed1994

Immunomodulation of experimental autoimmune myasthenia gravis with linomide.

Linomide, a synthetic immunomodulator, increases natural killer (NK) activity and markedly activates several lymphocyte populations in both experimental animals and humans. It has been shown to ameliorate the autoimmune manifestations of lupus-like disease in MRL/lpr mice and the clinical and pathological signs of acute and chronic-relapsing experimental autoimmune encephalomyelitis (EAE) in SJL/J mice. We examined the effect of linomide (100 mg/kg/day; administered in drinking water) on rabbits and rats with experimental autoimmune myasthenia gravis (EAMG). Following immunization with Torpedo acetylcholine receptor (AChR), all control rabbits developed clinical signs of severe weakness and exhibited a decrement of muscle action potential upon repetitive stimulation. In contrast, mild signs of weakness appeared in only two of five linomide-treated rabbits, with EMG borderline positive in one of them. Booster immunization with Torpedo AChR induced severe relapse and death in two EAMG control rabbits, whereas the two linomide-treated animals remained free of myasthenic symptoms. The serum level of antibodies against both Torpedo and rat AChR were markedly suppressed in the linomide-treated animals. Similar inhibition of clinical signs of EAMG was observed in the EAMG rat model. Furthermore, the in vitro proliferative response of lymph node cells to Torpedo AChR and the purified protein derivative of Mycobacterium tuberculosis was significantly lower in the linomide-treated EAMG rats than in the controls. Linomide may constitute a new immunomodulating agent for the treatment of myasthenia gravis.

Adjuvants, Immunologic↗
PubMed1993

Stimulation of tumor necrosis factor-alpha production by mycoplasmas and inhibition by dexamethasone in cultured astrocytes.

Elevated levels of tumor necrosis factor-alpha (TNF alpha) and other cytokines and eicosanoids in the central nervous system (CNS) have been noted in several human neurologic diseases, including multiple sclerosis and AIDS dementia. Recently it was shown that glial cells, especially astrocytes, are a major source of cytokines and eicosanoids. In the present study we have shown that astrocytes derived from fetal rat brain triggered by mycoplasmas produce TNF alpha and prostaglandin E2 (PGE2). Addition of mycoplasma (Mycoplasma capricolum isolated from sheep and M. fermentans KL-4 from human) at a concentration of 1-50 micrograms protein/ml (2 x 10(7)-10(9) colony forming units/ml), as well as lipopolysaccharide (5 micrograms/ml), led to a 200-500-fold increase in TNF alpha and a 2.5-4.5-fold increase in PGE2 production. Preincubation of the cells with the synthetic glucocorticoid, dexamethasone (2 x 10(-5)-2 x 10(-8) M), as well as with the natural hormone, corticosterone, markedly inhibited the secretion of both TNF alpha and PGE2. Thus, mycoplasmas can be added to the wide variety of agents that stimulate glial cells to produce cytokines and eicosanoids, and may contribute to various CNS pathological manifestations. In addition, the ability of glucocorticoids to inhibit particularly the stimulated productions of TNF alpha and PGE2 may explain at least in part the therapeutic benefit of these agents in CNS inflammation and demyelination.

Animals↗
PubMed1993

Differential effects of phorbol myristate acetate and dexamethasone on protein kinase C activity and eicosanoids production in cultured rat astrocytes.

The effects of phorbol myristate acetate (PMA) and dexamethasone on protein kinase C (PK-C) activity and eicosanoid production were characterized in primary cultures of rat glial cells. PMA (1,000 ng/ml) treatment for 2 hr resulted in a maximal effect (a 4-fold increase in PGE2 production). Longer exposure to PMA (up to 96 hr) resulted in attenuation of PGE2 production. Down-regulation of PK-C activity was assessed in glial cell homogenates under these conditions. Although a 70% inhibition of PK-C activity was measured upon staurosporine treatment, PGE2 production was not affected both under basal conditions and following PMA activation. The production of thromboxane B2 did not change following exposure to PMA. Pretreatment of the cultures with dexamethasone markedly inhibited the PMA-stimulated production of PGE2 but had only a moderate (approximately 26%) inhibitory effect on PGE2 production under basal conditions. Dexamethasone had no effect on basal or PMA-stimulated PK-C activity. Forskolin, which activates adenylate cyclase, did not affect PGE2 production. These data may suggest that activation of PGE2 production by PMA in glial cells is not unequivocally mediated by PK-C activation. The inhibitory effect of dexamethasone on the PMA-stimulated synthesis of PGE2 supports previous findings that glucocorticoids are more effective in inhibiting stimulated rather than basal PGE2 production.

Alkaloids↗
PubMed1993

Age-dependent sensitivity of cultured rat glial cells to bilirubin toxicity.

The results of studies conducted in neural tissues and neuronal cell lines suggest that bilirubin is toxic to various cellular functions. Using stable bilirubin solutions and primary cultures of fetal rat glial cells we report on the toxic effects of bilirubin on cell morphology, cell viability, and mitochondrial function. Glial cells in culture exhibit age-in-culture-dependent sensitivity to bilirubin toxic effects. Between the ages of 2 and 12 days in vitro, a gradual tolerance to bilirubin developed. Bilirubin exposure resulted in 55, 22, and 5% decreases in mitochondrial function in 4-, 8-, and 12-day-old cells in culture, respectively. In addition, bilirubin toxicity was dependent on bilirubin-albumin molar ratio and bilirubin concentration and only partially dependent on length of exposure. The age-dependent phenomenon raises concern regarding the potential toxicity associated with exposure of premature neural cells to bilirubin.

Animals↗
PubMed1993

Separation of rare cell subpopulations with the aid of biotin-labelled ligands.

A universal method for selection of surface marker-positive cells is described. The cells, admixed with an excess of surface marker-negative cells, are first labelled with a specific biotinylated ligand and then isolated with the aid of monoclonal, anti-biotin coated beads. The method enables selection and isolation of cells with a frequency as low as 10(-4). The ligand can be an antigen (for selection of infrequent antibody-producing cells), an antibody (for selection of surface antigen-positive cells) or other molecules (for selection of specific receptor-positive cells).

Animals↗
PubMed1993

Natural and experimental transfer of anti-Pertussis antibodies confers resistance to experimental autoimmune encephalomyelitis.

Pregnant rats challenged with Bordetela Pertussis vaccine, with or without encephalitogenic antigen during pregnancy, transferred a resistance to induction of experimental autoimmune encephalomyelitis (EAE) to their offspring. Cross-fostering experiments showed that the protection against EAE is conferred during the lactation period through the transfer of anti pertussis antibodies in the milk. The degree of protection correlated with antibody levels. Passive transfer of these antibodies through intraperitoneal injection to naive adult rats also conferred the same degree of protection against EAE induction. It is suggested that such transfer of resistance and antibodies may serve as a model for the study of milk transmitted immunocompetent factors, as well as a model for the mechanisms involved in the resistance to EAE.

Aging↗
PubMed1993

Electroencephalographic changes in experimental autoimmune myasthenia gravis.

A number of reports have suggested that central disturbances of cholinergic function may occur in patients with myasthenia gravis. The present study was designed in order to examine cortical electroencephalographic (EEG) activity in Lewis rats with experimental autoimmune myasthenia gravis (EAMG). Experiments were performed on conscious rats with clinical EAMG and demonstrable antibodies against the acetylcholine receptor. The animals showed no gross changes in cortical EEG discharge in terms of cycles and durations of wake, desynchronized sleep, and synchronized sleep, as compared with control rats. However, abnormalities characterized by single spikes or waves, and by spike and wave complexes, were observed, most commonly during synchronization of the EEG. Use of computerized frequency analysis of the EEG records revealed the presence of three basic differences in EEG discharge in myasthenic animals: (1) additional high-amplitude, low frequency (< 4 Hz) activity was recorded, especially during synchronized sleep; (2) decreases in mid-range (4-7 Hz) activity were recorded, particularly during periods of wakefulness; and, (3) increases in high frequency (> 8 Hz) spike discharge were observed at all times, although this was most evident during periods of synchronized sleep. The data provide further evidence for alterations in central cholinergic function in myasthenia gravis.

Action Potentials↗