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Biomedical subjects

R H Brown

Publications and source records attributed to R H Brown.

At least 145 records · Page 8Linked to original sources
PubMed1995

Inhibition of cartilage and bone destruction in adjuvant arthritis in the rat by a matrix metalloproteinase inhibitor.

Considerable evidence has associated the expression of matrix metalloproteinases (MMPs) with the degradation of cartilage and bone in chronic conditions such as arthritis. Direct evaluation of MMPs' role in vivo has awaited the development of MMP inhibitors with appropriate pharmacological properties. We have identified butanediamide, N4-hydroxy-2-(2-methylpropyl)-N1-[2-[[2-(morpholinyl)ethyl]-,[S- (R*,S*)] (GI168) as a potent MMP inhibitor with sufficient solubility and stability to permit evaluation in an experimental model of chronic destructive arthritis (adjuvant-induced arthritis) in rats. In this model, pronounced acute and chronic synovial inflammation, distal tibia and metatarsal marrow hyperplasia associated with osteoclasia, severe bone and cartilage destruction, and ectopic new bone growth are well developed by 3 wk after adjuvant injection. Rats were injected with Freund's adjuvant on day 0. GI168 was was administered systemically from days 8 to 21 by osmotic minipumps implanted subcutaneously. GI168 at 6, 12, and 25 mg/kg per d reduced ankle swelling in a dose-related fashion. Radiological and histological ankle joint evaluation on day 22 revealed a profound dose related inhibition of bone and cartilage destruction in treated rats relative to rats receiving vehicle alone. A significant reduction in edema, pannus formation, periosteal new bone growth and the numbers of adherent marrow osteoclasts was also noted. However, no significant decrease in polymorphonuclear and mononuclear leukocyte infiltration of synovium and marrow hematopoietic cellularity was seen. This unique profile of antiarthritic activity indicates that GI168 is osteo- and chondro-protective, and it supports a direct role for MMP in cartilage and bone damage and pannus formation in adjuvant-induced arthritis.

Animals↗
PubMed1995

CuZn superoxide dismutase (SOD-1):tetanus toxin fragment C hybrid protein for targeted delivery of SOD-1 to neuronal cells.

Increased levels of CuZn superoxide dismutase (SOD-1) are cytoprotective in experimental models of neurological disorders associated with free radical toxicity (e.g. stroke, trauma). Targeted delivery of SOD-1 to central nervous system neurons may therefore be therapeutic in such diseases. The nontoxic C-fragment of tetanus toxin (TTC) possesses the nerve cell binding/transport properties of tetanus holotoxin and has been used as a vector to enhance the neuronal uptake of proteins including enzymes. We have now produced a recombinant, hybrid protein in Escherichia coli tandemly joining human SOD-1 to TTC. The expressed hybrid protein (SOD:Tet450) has a subunit molecular mass of 68 kDa and is recognized by both anti-SOD-1 and anti-TTC antibodies. Calculated per mol, SOD:Tet450 has approximately 60% of the expected SOD-1 enzymatic activity. Analysis of the hybrid protein's interaction with the neuron-like cell line, N18-RE-105, and cultured hippocampal neurons by enzyme immunoassay for human SOD-1 revealed that SOD:Tet451 association with cells was neuron-specific and dose-dependent. The hybrid protein was also internalized, but there was substantial loss of internalized hybrid protein over the first 24 h. Hybrid protein associated with cells remained enzymatically active. These results suggest that human SOD-1 and TTC retain their respective functional properties when expressed together as a single peptide. SOD:Tet451 may prove to be a useful agent for the targeted delivery of SOD-1 to neurons.

Animals↗
PubMed1995

Apolipoprotein E epsilon 4 allele is not associated with earlier age at onset in amyotrophic lateral sclerosis.

Apolipoprotein E allele 4 (apo E epsilon 4) is known to be in genetic disequilibrium with Alzheimer's disease and is associated with an earlier age at onset of dementia. Whether apo E epsilon 4 is a specific risk factor for Alzheimer's disease or is a more general susceptibility factor that shifts the age at onset of neurodegenerative diseases to earlier ages is unknown. To test these possibilities, we determined the apolipoprotein E genotypes of subjects with familial or sporadic amyotrophic lateral sclerosis (ALS). ApoE allele frequencies of the apoE gene of the ALS subjects (n = 170, epsilon 2 = 0.071, epsilon 3 = 0.771, epsilon 4 = 0.159) were found to be comparable to the allele frequencies of the general population. Furthermore, no significant association was observed between the age at onset or the duration of ALS and the inheritance of apoE epsilon 4: subjects with at least one copy of epsilon 4 (sporadic ALS: n = 15, onset at 57.7 +/- 13.9 years; familial ALS: n = 23, onset at 53.6 +/- 9.5 years, duration [n = 14] of 2.6 +/- 1.6 years) had comparable ages at onset and durations to subjects without epsilon 4 (sporadic ALS: n = 28, onset at 53.1 +/- 17.0 years; familial ALS: n = 56, onset at 50.8 +/- 12.1 years, duration [n = 30] of 1.9 +/- 0.8 years). The lack of association of apoE epsilon 4 with the age at onset and the duration of ALS suggests that apoE epsilon 4 does not have a global effect on the pathogenesis of other neurodegenerative diseases.

Age of Onset↗
PubMed1995

Analysis of aldehyde oxidase and xanthine dehydrogenase/oxidase as possible candidate genes for autosomal recessive familial amyotrophic lateral sclerosis.

Recently, point mutations in superoxide dismutase 1 (SOD1) have been shown to lead to a subset of autosomal dominantly inherited familial amyotrophic lateral sclerosis (ALS). These findings have led to the hypothesis that defects in oxygen radical metabolism may be involved in the pathogenesis of ALS. Therefore, we decided to analyze other enzymes involved in oxygen radical metabolism for possible involvement in other forms of ALS. We report here analysis of two genes encoding the molybdenum hydroxylases aldehyde oxidase (AO) and xanthine dehydrogenase/oxidase (XDH) for involvement in ALS. Of particular interest, one gene identified as encoding aldehyde oxidase is shown to map to 2q33, a region recently shown to contain a gene responsible for a familial form of ALS with autosomal recessive inheritance (FALS-AR). The AO gene appears to be located within 280,000 bp of simple sequence repeat marker D2S116, which shows no recombination with the FALS-AR locus. The AO gene is highly expressed in glial cells of human spinal cord. In addition, we mapped a gene for XDH to 2p22, a region previously shown to contain a highly homologous but different form of XDH. Neither of these XDH genes appears to be highly expressed in human spinal cord. This evidence suggests that AO may be a candidate gene for FALS-AR.

Aldehyde Oxidase↗
PubMed1995

Absence of mutations in the Mn superoxide dismutase or catalase genes in familial amyotrophic lateral sclerosis.

Familial amyotrophic lateral sclerosis (FALS) is an autosomal dominant, adult onset, neurological disorder caused by the degeneration of motor neurons of the cortex, brainstem and spinal cord. Recently, the defective gene in some FALS families was identified as the Cu/Zn superoxide dismutase (SOD1) gene. However, SOD1 mutations are present in approximately 20% of patients with FALS. We have tested the genes of two more free radical detoxifying enzymes, Mn superoxide dismutase (SOD2) and catalase by single strand conformation analysis (SSCA) for mutations in the remaining FALS cases. No mutations were found in the catalase enzyme in 73 unrelated FALS cases; mutations were not detected in the 66% of the SOD2 gene analyzed. FALS does not appear to be caused by mutations in the SOD2 nor the catalase genes.

Amyotrophic Lateral Sclerosis↗
PubMed1995

Identification of three novel mutations in the gene for Cu/Zn superoxide dismutase in patients with familial amyotrophic lateral sclerosis.

About 10% of cases of amyotrophic lateral sclerosis (ALS), a paralytic disorder characterized by death of motor neurons in the brain and spinal cord, exhibit autosomal dominant inheritance. A subgroup of these familial cases are caused by mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1). We report here three additional mutations occurring in the SOD1 gene in three families with ALS. Two of these changes are missense mutations in exon 5 of the SOD1 gene, resulting in leucine 144 to serine and alanine 145 to threonine substitutions. The third, a single base pair change in intron 4 immediately upstream of exon 5, results in an alternatively spliced mRNA. The alternate transcript conserves the open reading frame of exon 5, producing an SOD1 protein with three amino acids inserted between exons 4 and 5 (following residue 118). These three mutations bring to 29 the total number of distinct SOD1 mutations associated with familial ALS.

Adult↗
PubMed1995

Neodymium: YAG membranectomy for pupillary membranes on posterior chamber intraocular lenses.

PURPOSE: To evaluate the effectiveness of neodymium: YAG laser for the removal of membranes from the anterior surface of intraocular lenses. METHODS: Seven patients had reduced vision due to a membrane on the anterior surface of a posterior chamber intraocular lens (PC IOL). Six of the membranes developed after extracapsular cataract surgery and PC IOL combined with trabeculectomy and one after pars plana vitrectomy. Six of the membranes developed in the early postoperative period in association with a fibrinous reaction of the anterior chamber. One formed 7 months after surgery in an eye with iris capture behind the IOL. The membranes persisted despite intensive topical steroid therapy. A neodymium: YAG (Nd:YAG) laser was used to remove the membranes from the anterior of the IOL in all the seven cases. RESULTS: The Nd:YAG laser effectively severed the peripheral connections of the membranes to the iris and lens, creating a clear central zone within the visual axis. The settings were fundamental mode, 1.2-to 3.1-mJ energy per shot and 48.3 +/- 20.1 single pulses. Vision improved significantly in six patients, whereas elevated intraocular pressure was observed in one patient. CONCLUSION: Postoperative pupillary membranes may be successfully lysed with use of the Nd:YAG laser.

Aged↗
PubMed1995

Superoxide dismutase concentration and activity in familial amyotrophic lateral sclerosis.

Some cases of autosomal-dominant familial amyotrophic lateral sclerosis (FALS) have been associated with mutations in SOD1, the gene that encodes Cu/Zn superoxide dismutase (Cu/Zn SOD). We determined the concentrations (microgram of Cu/Zn SOD/mg of total protein), specific activities (U/microgram of total protein), and apparent turnover numbers (U/mumol of Cu/Zn SOD) of Cu/Zn SOD in erythrocyte lysates from patients with known SOD1 mutations. We also measured the concentrations and activities of Cu/Zn SOD in FALS patients with no identifiable SOD1 mutations, sporadic ALS (SALS) patients, and patients with other neurologic disorders. The concentration and specific activity of Cu/Zn SOD were decreased in all patients with SOD1 mutations, with mean reductions of 51 and 46%, respectively, relative to controls. In contrast, the apparent turnover number of the enzyme was not altered in these patients. For the six mutations studied, there was no correlation between enzyme concentration or specific activity and disease severity, expressed as either duration of disease or age of onset. No significant alterations in the concentration, specific activity, or apparent turnover number of Cu/Zn SOD were detected in the FALS patients with no identifiable SOD1 mutations, SALS patients, or patients with other neurologic disorders. That Cu/Zn SOD concentration and specific activity are equivalently reduced in erythrocytes from patients with SOD1 mutations suggests that mutant Cu/Zn SOD is unstable in these cells. That concentration and specific activity do not correlate with disease severity suggests that an altered, novel function of the enzyme, rather than reduction of its dismutase activity, may be responsible for the pathogenesis of FALS.

Adult↗
PubMed1995

Wheezing during induction of general anesthesia in patients with and without asthma. A randomized, blinded trial.

BACKGROUND: Patients with asthma who require general anesthesia and tracheal intubation are at increased risk for the development of bronchospasm during induction. The incidence of wheezing during induction with different intravenously administered agents is unknown. A randomized, double-blinded prospective study was undertaken to evaluate the incidence of wheezing in asymptomatic asthmatic and nonasthmatic patients receiving three commonly used intravenous anesthetic agents for induction of anesthesia. METHODS: Fifty-nine asymptomatic asthmatic and 96 nonasthmatic patients of ASA physical status 1 and 2 were studied. All patients received 1.5 micrograms/kg fentanyl, oxygen, followed by either 5 mg/kg thiopental or thiamylal, 1.75 mg/kg methohexital or 2.5 mg/kg propofol, 1.5 mg/kg succinylcholine, tracheal intubation, and inhalational anesthesia. Wheezing was assessed by an independent blinded observer, auscultating the lungs at 2 and 5 min postintubation. Data were analyzed by Pearson's chi-squared, Fisher's exact test, and multiple logistic regression with significance set at P < 0.05. RESULTS: Both asthmatic and nonasthmatic patients who received a thiobarbiturate for induction had a greater incidence of wheezing than did patients receiving propofol. In asthmatic patients, 45% (23, 67) (mean and 95% confidence interval) who received a thiobarbiturate, 26% (8, 44) who received an oxybarbiturate, and none (0, 17) who received propofol wheezed after intubation. In nonasthmatic patients, 16% (3, 28) who received thiobarbiturate and 3% (0, 9) who received propofol wheezed. CONCLUSIONS: This study suggests that propofol should be considered for induction of anesthesia in patients, particularly those with asthma, who require timely intubation.

Adolescent↗
PubMed1995

Visualization of airway obstruction in vivo during pulmonary vascular engorgement and edema.

Although pulmonary vascular engorgement has often been hypothesized to decrease airway caliber, leading to airway obstruction in asthma, direct evidence for this hypothesis is lacking. In the present study, we used high-resolution computed tomography to directly measure the changes in the caliber and wall thickness of conducting airways after volume loading with normal saline (NS) and homologous blood. Five anesthetized dogs received 0.2 mg/kg of atropine followed by either three sequential fluid challenges of 50 ml/kg of NS or two sequential challenges of 25 ml/kg of blood. Several weeks later, the same dogs received the other fluid challenge. Volume loading with 150 ml/kg of NS decreased the average airway luminal area to 68 +/- 3% (+/- SE) of baseline. Concomitantly, airway wall thickness increased to 150 +/- 6% of baseline. Volume loading with 50 ml/kg of blood decreased the average airway luminal area to 81 +/- 2% of baseline. Concomitantly, airway wall thickness increased to 108 +/- 2% of baseline. Therefore, for comparable changes in pulmonary vascular pressure, an infusion of NS caused a significantly greater decrease in airway luminal area and a larger increase in airway wall thickness than an infusion of blood. This suggests that the presence of edema fluid in or immediately surrounding the airway wall acts to decrease the airway lumen. However, since the degree of airway narrowing was only moderate, even with a most extreme fluid load, it seems unlikely that airway wall thickening or edema could be a primary cause of conducting airway obstruction in patients with asthma or impaired left ventricular function.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Obstruction↗
PubMed1995

Airway edema potentiates airway reactivity.

Thickening of the airway wall has been hypothesized to be one of the mechanisms contributing to airway hyperresponsiveness in asthma. If such thickening of the wall is internal to the airway smooth muscle or otherwise causes a decrease in baseline airway caliber, it should also cause exaggerated airway responsiveness. In the present study, we used high-resolution computed tomography to directly measure the changes in the caliber and wall thickness of conducting airways after aerosol histamine challenge before and after normal saline volume loading. On separate days, five anesthetized dogs received either a baseline aerosol challenge of 3 mg/ml of histamine for five breaths or the same aerosol challenge immediately after a 100 ml/kg bolus of normal saline infused over a 10-min period. Baseline aerosol histamine challenge decreased airway area to 71 +/- 2% (SE) of the control value (P < 0.05). Intravenous administration of 100 ml/kg of normal saline increased wall area by decreasing airway luminal area to 78 +/- 3% of the control value (P < 0.01), with no change in outer airway area. Aerosol histamine challenge superimposed on this engorgement with normal saline challenge further decreased airway luminal area to 54 +/- 3% of the control value (P < 0.01). Quantitative modeling indicated that the edema in the airway wall was mostly outside the smooth muscle and that the smooth muscle shortening with histamine was similar with and without edema. We conclude that a moderate degree of acute airway wall thickening can lead to a potentiated constrictor response to histamine.

Aerosols↗
PubMed1995

Sodium channel inactivation is impaired in equine hyperkalemic periodic paralysis.

1. Equine hyperkalemic periodic paralysis (E-HPP) is a dominantly inherited disorder of muscle that causes recurrent episodes of stiffness (myotonia) and weakness in association with elevated serum K+. Affected horses carry a mutant allele of the skeletal muscle isoform of the Na channel alpha-subunit. To understand how this mutation may cause the disease phenotype, the functional defect in Na channel behavior was defined physiologically by recording unitary currents from cell-attached patches on normal and affected equine myotubes. 2. The presence of the mutation was confirmed in our cell line by restriction digest of polymerase chain reaction (PCR)-amplified genomic DNA. Myotubes from the affected horse were heterozygous for the point mutation that codes for a Phe to Leu substitution in S3 of domain IV. This assay provides a rapid technique to screen for the mutation in horses at risk. 3. The primary physiological defect in mutant Na channels was an impairment of inactivation. This defect was manifest as bursts of persistent activity during which the channel closed and reopened throughout a maintained depolarization. Disrupted inactivation slowed the decay of the ensemble-averaged current and produced an eightfold increase in the steady-state open probability measured at the end of a 40-ms pulse. This point mutation identifies a new region of the alpha subunit that is important for rapid inactivation of the channel. 4. The persistent Na current was produced by a distinct mode of gating. Failure of a mutant channel to inactivate was infrequent and occurred in groups of consecutive trials.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗