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Biomedical subjects

C T Bever

Publications and source records attributed to C T Bever.

At least 37 records · Page 2Linked to original sources
PubMed1996

Treatment with oral 3,4 diaminopyridine improves leg strength in multiple sclerosis patients: results of a randomized, double-blind, placebo-controlled, crossover trial.

To examine the efficacy and toxicity of oral 3,4 diaminopyridine (DAP) in dosages up to 100 mg/day, 36 patients with multiple sclerosis (MS) enrolled in a randomized, double-blind, placebo-controlled, crossover trial. The primary outcome measure was improvement of a prospectively defined neurologic deficit, which was leg weakness in 34 patients. Secondary outcome measures included the patient's subjective response, scored manual motor testing (MMT) of leg strength, scored leg strength from videotaped motor testing (VMT), quadriceps and hamstrings strength (QMT) measured by isometric dynamometry, neuropsychological testing (NPT), ambulation index (AI), and Expanded Disability Status Scale (EDSS) score. Paresthesias and abdominal pain were common and were dose limiting in eight patients. Three patients had episodes of confusion, and one patient had a seizure while on DAP. Eight patients withdrew from the study, leaving 28 evaluable patients for the efficacy analysis. The prospectively defined neurologic deficit improved in 24 patients-22 on DAP and 2 on placebo (p = 0.0005). All improvements were in leg weakness. Subjective response and measures of leg strength and function (MMT, VMT, QMT, and AI) improved on DAP compared with placebo. Neither NPT nor EDSS scores improved. DAP treatment can induce improvements in leg strength in MS patients, but toxicity is limiting in many patients.

4-Aminopyridine↗
PubMed1996

Gamma interferon induced increases in intracellular cathepsin B activity in PMA primed THP-1 cells are blocked by inhibitors of protein kinase C.

Macrophage proteinases including cathepsin B (CB) are implicated in the tissue injury of inflammatory lesions. We have previously shown that interferon-gamma (IFN-gamma) increases intracellular levels of the lysosomal proteinase, CB, in THP-1 cell primed with phorbol 12-myristate 13-acetate (PMA). We have now examined the role of protein kinase C (PKC) in this effect. Following activation with PMA, the intracellular CB activity was significantly increased in the presence of 500 U/ml IFN-gamma. With the addition of protein kinase C (PKC) inhibitors bisindolylmaleimide, staurosporine, H-7, or phloretin a reversal of the effect of IFN-gamma was noted whereas the addition of the cyclic nucleotide-dependent protein kinase inhibitors HA 1004, H-8, H-89, or cAMP-Dependent Protein Kinase (PKA) Inhibitor did not block the effect. Although diacylglycerol (DAG) did not replace PMA in the study. Diacylglycerol Kinase Inhibitor induced a more pronounced augmentation and PKC depletion inhibited the effect. This suggests that a PKC-dependent pathway is involved in the response of CB in PMA primed THP-1 cells to IFN-gamma.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1995

Increased cathepsin B activity in multiple sclerosis brain.

Cathepsin B (CB) activity was measured in aqueous extracts of frozen autopsy specimens of centrum semiovale from three MS patients, five control patients with other neurological diseases, and five normal individuals. Mean activity was significantly increased in the MS tissue compared with controls. The mean activity in MS tissue containing demyelinating lesions was higher than that in normal appearing white matter which was higher than that in normal control specimens but the differences were not statistically significant. The mean CB activity in patients with other neurological diseases was higher than normal control activity and, although the difference was not statistically significant, this observation suggests that increases in CB may not be specific for MS. Immunohistochemical studies of the MS brain tissue analyzed biochemically suggested that monocytes, macrophages and reactive astrocytes are potential sources of increased CB in MS brain.

Amino Acid Sequence↗
PubMed1995

The Brief Repeatable Battery of Neuropsychological Tests for Multiple Sclerosis: a preliminary serial study.

The Brief Repeatable Battery of Neuropsychological Tests (BRB-N) for MS consisting of the selective reminding, 10/36 spatial recall, symbol digit modalities, paced auditory serial addition (PASAT) and word list generation tests is a sensitive measure of early cognitive impairment in MS patients. We administered it to 19 chronic stable MS patients every 60 days for 120 days to examine variability. The mean coefficient of variation for the tests ranged from 18% to 22%. A significant practice effect was seen in the PASAT results (P < 0.05) using the Wilcoxon signed rank test. These results suggest that cognitive fluctuations analogous to motor fluctuations may occur in MS patients and that the BRB-N may be useful in clinical trials of agents expected to alter cognitive function in MS patients if test-retest variability and practice effects are taken into account. Further study is warranted.

Adult↗
PubMed1994

The current status of studies of aminopyridines in patients with multiple sclerosis.

Because the symptomatic treatments for multiple sclerosis (MS) are limited, new approaches have been sought. Anatomical studies of MS lesions show a relative preservation of axons, and clinical studies suggest that some of the neurological impairment in patients with MS is physiological. Electrophysiological studies suggest that demyelination exposes axonal potassium channels that decrease action-potential duration and amplitude, hindering action-potential propagation. Potassium channel blockers, including aminopyridines, have been shown to improve nerve conduction in experimentally demyelinated nerves. Two potassium channel blockers, 4-aminopyridine (AP) and 3,4 diaminopyridine (DAP) have been tested in patients with MS. Preliminary studies of AP demonstrated benefit in many temperature-sensitive patients with MS, and improvement of function was found in a large randomized double-blind, placebo-controlled crossover trial of 3 months of oral treatment in 68 patients with MS. An open-label trial of DAP showed improvement in some deficits, and a double-blind placebo-controlled trial showed significant improvements in prospectively defined neurological deficits. A crossover comparison of the two agents suggested that AP produces more central nervous system side effects (dizziness and confusion), whereas DAP produces more peripheral side effects (paresthesias and abdominal pain). Both agents have rarely caused seizures. These studies suggest that aminopyridines may provide a new approach to the symptomatic treatment of MS.

4-Aminopyridine↗
PubMed1994

Increased cathepsin B activity in peripheral blood mononuclear cells of multiple sclerosis patients.

Proteinase levels are increased in multiple sclerosis (MS) lesions and are implicated in demyelination. The cellular origins of the activity are not known, but inflammatory cells of hematogenous origin are one possibility. We studied the levels of two lysosomal proteinases implicated in the proteolysis of myelin basic protein, cathepsin B (CB) and cathepsin D (CD), in peripheral blood mononuclear cells (PBMCs) of 20 stable relapsing-remitting MS patients. We prepared and assayed cell lysates of PBMCs from the MS patients, 10 patients with other neurologic diseases (OND), and 12 normal controls (NC). Mean CB activity expressed as milliunits of activity per million cells was significantly increased in MS patients (7.86 +/- 0.54) compared with OND (6.80 +/- 0.74) and NC (5.94 +/- 0.28) cells (p < 0.05). CD levels were not significantly increased. To determine whether the increase was generalized or limited to a subset of cells, PBMCs were fractionated by plate adherence. CB levels in the adherent fraction (AD) of the 20 MS patients were higher than in the nonadherent fraction (NA), and the AD:NA ratio of CB in MS was higher than that in controls. This would be consistent with an increase in CB levels in monocytes and macrophages, cells known to be activated in the peripheral blood of MS patients and implicated as effectors of demyelination.

Adult↗
PubMed1994

The effects of 4-aminopyridine in multiple sclerosis patients: results of a randomized, placebo-controlled, double-blind, concentration-controlled, crossover trial.

Because 4-aminopyridine (AP) improves residual deficits in some multiple sclerosis (MS) patients but has a narrow toxic-to-therapeutic margin, we compared the safety and efficacy of two target peak serum concentration ranges (low: 30 to 59 ng/ml and high: 60 to 100 ng/ml). We enrolled eight MS patients with temperature-sensitive visual and motor deficits in a randomized, placebo-controlled, double-blind, crossover trial of short-term oral AP treatment. We randomized patients to a sequence of three treatments on three separate days: placebo, low serum concentration, and high serum concentration. We determined dosing to achieve the desired steady-state peak serum concentration ranges from a test dose and population pharmacokinetic parameters using bayesian estimation. Contrast sensitivity, standard neurologic examination, ratings of videotaped neurologic examinations, and quantitative strength assessment all improved with treatment, but flicker fusion frequency, visual evoked response latencies, and Expanded Disability Status Scale scores did not. All patients experienced side effects during the high-serum-concentration arm. A grand mal seizure occurred at a serum AP level of 104 ng/ml, and an acute confusional episode occurred at 114 ng/ml. AP treatment produced improvements in residual deficits in MS patients, but the occurrence of significant toxicity suggests that AP serum levels should be monitored and peak levels above 100 ng/ml should be avoided. Concentration-control methodology may be useful in testing putative treatments for other neurologic diseases.

4-Aminopyridine↗
PubMed1993

Clinical trials of interferons in multiple sclerosis. What have we learned?

Although multiple sclerosis (MS) is generally believed to be an immune-mediated disease, conventional therapy with ACTH, corticosteroids, or immunosuppressive drugs is unsatisfactory. Aside from their unpredictable therapeutic effects, these agents are potentially hazardous and can only be given for short periods of time. There is an urgent need for less toxic yet effective immunotherapy, that that can be administered early in the disease and continued indefinitely. Clinical trials of the interferons (IFNs) have not only led to a promising new approach to treatment, but have also stimulated basic research in the immunological mechanisms of underlying disease activity. Administration of IFN-gamma promotes exacerbations of MS, whereas recombinant IFN-beta has been shown, in controlled clinical trials, to suppress them. Other ongoing studies are likely to provide further information about its long-term therapeutic value. More importantly, laboratory studies performed in conjunction with these clinical trials have provided fresh insights into the pathogenesis of MS by revealing immunoregulatory mechanisms in which endogenous IFN-gamma, TNF-alpha, and other cytokines appear to play central roles. The 'Decade of the Brain' may therefore see answers both to the therapeutic dilemma of MS, and to more basic questions about the function of IFNs and other cytokines in activation and regulation of the disease process.

Clinical Trials as Topic↗
PubMed1992

A comparison of interferon responses to poly ICLC in males and females.

Interferon (IFN) responses to polyriboinosinic acid polyribocytidylic acid in poly-L-lysine and carboxymethylcellulose (poly ICLC) have been studied in detail in 6 men and 3 women as part of a preliminary trial in patients with multiple sclerosis (MS). Patients received intravenous (i.v.) doses of 100 micrograms/kg poly ICLC, and serum IFN levels were determined serially every 4 h for 16 h. Men and women produced substantial levels of IFN at 8, 12, and 16 h after infusion, but levels in men were consistently and significantly higher (p less than 0.05). Interferon responses were examined also in 3 male and 3 female Rhesus monkeys. Serum samples were obtained 8 and 24 h after i.v. injections of 1 mg/kg of poly ICLC. Again, there were significantly higher levels of IFN in males. The observed differences may reflect sex-linked differences in either drug metabolism or specific sensitivity to IFN induction by poly ICLC. The most interesting possibility is that the difference is due to a more general difference in IFN response between males and females. Studies are currently in progress to evaluate these possibilities.

Adult↗
PubMed1991

Augmented IgG anti-acetylcholine receptor response following chronic penicillamine administration.

A model of D-penicillamine (DP) induced myasthenia gravis (MG) was developed in which the anti-acetylcholine receptor (anti-AChR) antibody response to AChR challenge was increased in mice chronically treated with DP. To investigate the mechanism of the DP induced increase, IgM and IgG anti-AChR responses to AChR challenge were studied. IgG responses were significantly greater in the DP treated mice than in the control group while IgM responses were not significantly different. This change appeared to be relatively specific for the AChR response because neither serum immunoglobulin levels nor the IgG response to a second antigen (purified protein derivative) were increased by DP treatment. These results suggest that a specific sensitization to AChR occurs during chronic DP treatment.

Animals↗
PubMed1991

Changes in leukocyte recirculation, NK cell activity, and HLA-DR expression in peripheral blood mononuclear cells of MS patients treated with Poly ICLC.

To investigate the cellular immune effects of the interferon inducer, Poly ICLC, in humans, peripheral blood mononuclear cells from patients with multiple sclerosis receiving Poly ICLC as part of a preliminary clinical trial were studied. Peripheral blood mononuclear cell phenotype analysis using fluoresceinated monoclonal antibodies and flow microfluorometry showed decreases in the percentages and absolute numbers of all lymphocyte subsets 24 h after infusion. These changes returned toward baseline at 48 h except the percentage of CD-4 positive cell which increased above baseline levels. The percentage of HLA-DR antigen positive cells and CD-16 (Leu 11a) positive cells were increased 24 h after infusion but returned to baseline at 48 h. NK activity as determined by chromium release from K562 target cells was decreased at 24 h but increased 48 h after drug infusion. The increases in percentages of HLA-DR antigen and CD-16 positive cells at 24 h and NK activity at 48 h are consistent with the in vitro effects of IFN while the decreases in peripheral blood mononuclear cells are suggestive of changes in cell recirculation.

Antigens, CD↗
PubMed1991

Gamma-interferon induction in patients with chronic progressive MS.

Although gamma interferon (gamma-IFN) may be involved in the pathogenesis of exacerbations of multiple sclerosis (MS), whether it plays a role in chronic progressive MS is not known. To investigate this, we retrospectively analyzed serum samples from nine chronic progressive MS patients who were treated with monthly intravenous infusions of the interferon inducer polyinosinic acid polycytidylic acid polylysine in carboxymethylcellulose (poly ICLC). Using a bioassay we found that the mean peak total interferon level was 177 U/ml 12 hours after infusion, and using a radioimmunoassay we found that the mean peak gamma-IFN level was 15.9 U/ml 12 hours after infusion, so that gamma-IFN made up approximately 10% of the total. Greater gamma-IFN induction did not correlate with clinical worsening; induced gamma-IFN levels were not higher in two patients who worsened on treatment, and the highest levels were found in a patient who remained stable. Either chronic progressive MS is not sensitive to gamma-IFN or the effects of gamma-IFN are masked by other mediators induced by poly ICLC.

Antigens, CD↗
PubMed1990

Preliminary trial of 3,4-diaminopyridine in patients with multiple sclerosis.

Ten patients with multiple sclerosis (MS) were enrolled in a preliminary trial of the potassium channel blocker, 3,4-diaminopyridine, to evaluate drug toxicity and pharmacokinetics. The patients were treated with oral 3,4-diaminopyridine, first with increasing single doses up to 100 mg and then with divided dosage for up to 3 weeks. Paresthesias were reported by all patients and abdominal pain was dose limiting in 6 patients. 3,4-Diaminopyridine levels and half-life varied widely from patient to patient. Cerebrospinal fluid levels of 3,4-diaminopyridine were about 10% of those in serum. Neither seizures nor epileptiform changes on electroencephalographic examination occurred. Small reversible improvements in specific neurological deficits were seen on examination in all patients and reversible improvement in visual evoked response latencies were found in 2 patients. These results suggest that further study of 3,4-diaminopyridine in patients with MS is warranted.

4-Aminopyridine↗
PubMed1990

Astrocytosis and cathepsin D activity in experimental measles encephalomyelitis.

The temporal relationship between the activity of cathepsin D (CD), the major brain acid proteinase, inflammatory cell infiltration and reactive astrocytosis was examined in a hamster model of measles virus infection of the central nervous system. Twenty-five day old hamsters were inoculated intracerebrally with the HBS strain of measles virus and sacrificed 6, 10, and 16 days later. Mean CD levels in aqueous extracts of infected brain were significantly elevated on days 10 and 16 compared to control animals. Histologic examination showed that while the degree of inflammatory cell infiltration did not correlate with the elevations in CD activity (r = .38), there was a correlation with the degree of astrocytosis (r = .995). This suggests that the increase in CD was due to astrocytic changes and not directly related to mononuclear inflammatory cell infiltration.

Animals↗
PubMed1989

Cathepsin D activity in human peripheral blood mononuclear leukocytes.

To investigate the cellular origins of cathepsin D (CD) in inflammatory lesions, the CD content of lymphocyte subsets, monocytes, and macrophages were compared. Human monocytes, B lymphocytes, CD4+ T lymphocytes, and CD8+ T lymphocytes were separated from peripheral blood of normal donors. CD content was 0.13 +/- .01 micrograms equivalents of CD per million cells and significant differences between different cell types were not found. To determine the CD content of macrophages, differentiation of peripheral blood monocytes was induced by either in vitro culture or treatment with 4 beta-phorbol-12-myristate-13-acetate (PMA). Macrophages induced by five-day culture contained four times more CD than unstimulated monocytes, and macrophages induced by 18-h treatment with 20 mg/ml 4 beta-PMA contained nine times more CD than monocytes treated with 4 alpha-PMA, an inactive stereoisomer of 4 beta-PMA. These results suggest that macrophages are one of the enriched sources of CD in inflammatory lesions.

B-Lymphocytes↗
PubMed1989

Activation of astrocytic lysosomal proteinases by factors released by mononuclear leukocytes.

Lysosomal proteinases are increased in the tissue lesions of experimental allergic encephalomyelitis and have been implicated in the degradation of myelin proteins. The cellular origins of the increased proteinases are not known but reactive astrocytes found in areas of increased activity are candidate cells. To evaluate the potential of astrocytes as the source of these proteinases, cathepsin B (CB) and cathepsin D (CD) levels were measured in lysates of cultured astrocytes from neonatal rats. Because astrocytes are activated by inflammatory mediators in demyelinating lesions the effect of activation on proteinase levels was examined. Culture supernatants from mononuclear leukocytes stimulated with either concanavalin A or phytohemagglutinin (PHA) induced significant increases in the astrocytic proteinases. Neither PHA alone, interleukin-1, interleukin-2, nor gamma-interferon induced significant increases. Fractions of the supernatant from PHA stimulated mononuclear leukocytes were tested and activity was found in fractions corresponding to a molecular weight of 45-50,000. These studies demonstrate that astrocytes contain significant amounts of CB and CD activity which can be increased by a factor or factors released by activated mononuclear leukocytes.

Animals↗