Search PubMed⌕ Search

Biomedical subjects

D E Brown

Publications and source records attributed to D E Brown.

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

Metabolic abnormalities in feline Niemann-Pick type C heterozygotes.

Niemann-Pick disease type C (NPC) is an autosomal recessive neurovisceral lysosomal storage disorder in which cholesterol lipidosis results from defective intracellular transport of unesterified cholesterol. The primary molecular defect of NPC is unknown; regulatory mechanisms of cholesterol metabolism are impaired, resulting in retarded esterification of exogenous cholesterol with accumulation of unesterified cholesterol in lysosomes and secondary storage of glycolipids and sphingomyelin. In obligate heterozygotes from a feline NPC model, cultured skin fibroblasts challenged with exogenously derived cholesterol exhibited intermediate rates of cholesterol esterification and accumulation of unesterified cholesterol. Liver lipid analyses of obligate heterozygote cats demonstrated intermediate cholesterol and sphingomyelin concentrations. Vacuolated skin fibroblasts were found in 2 of 3 heterozygote cats, and occasional cortical neurons exhibited intracellular inclusions immunoreactive for GM2-ganglioside. Ultrastructural studies provided evidence of storage in liver and brain. We believe these morphological and biochemical findings are the first example of manifestations of CNS abnormalities in a genetic carrier for a neuronal storage disease.

Animals↗
PubMed1996

The effect of ondansetron on pyridostigmine-induced blood acetylcholinesterase inhibition in the guinea pig.

The purpose of this study was to assess the compatibility, in terms of red blood cell acetylcholinesterase (AChE) inhibition, of ondansetron (OND; a 5-hydroxytryptamine subtype-3 receptor antagonist) with the organophosphorus pretreatment compound pyridostigmine (PYR) after simultaneous oral (p.o.) administration to guinea pigs. The time-course of PYR-induced (0.94 mg/kg, p.o.) AChE inhibition was determined in the absence and presence of OND. Ondansetron (10, 20 and 30 mg/kg; p.o.) did not modify AChE inhibition, whereas concurrent administration of PYR with OND (10 or 20 mg/kg; p.o.) produced significantly greater decreases in AChE activity than PYR alone. The decreases in AChE activity for PYR plus OND, 10 and 20 mg/kg, (between 30 -240 min) were 12.3 +/- 2.8% and 16.1 +/- 2.3% (mean +/- SD) respectively relative to PYR alone. The slope for recovery of AChE activity (120 - 240 min) was 0.0914 for PYR alone; recovery rates (slopes) for PYR plus OND, 10 and 20 mg/kg, were 0.0796 and 0.0433 respectively. Additionally, altered PYR-induced AChE activity profiles were ameliorated when PYR and OND (20 mg/kg) were administered 150 min apart. Since the results of this study provided evidence that the oral administration of OND alone did not inhibit AChE, the changes in PYR-induced AChE activity by the simultaneous administration of OND suggest mechanisms other than a direct action on the enzyme. The significance of these findings is that the increased AChE inhibition resulting from simultaneous oral administration of both component could result in undesirable cholinergic toxicities and subsequent perform decrements.

Acetylcholinesterase↗
PubMed1995

Clenbuterol: a substitute for anabolic steroids?

Clenbuterol is a recently popular drug used by athletes in many sports for its purported anabolic effects and reduction of subcutaneous fat. It is a beta-2 (beta 2) agonist prescribed overseas as a bronchodilator, but not approved for use in this country. It is on the banned substance list of the United States Olympic Committee. To avoid any erosion of confidence, physicians caring for athletes need accurate information regarding clenbuterol. Such information is unavailable within the routine medical environs. A review of the literature of animal husbandry reveals that this drug, when administered in doses far greater than those required for bronchodilation, does indeed increase the deposition rate of lean mass and retard adipose gain. There are no human studies available. Animal studies were conducted on laboratory and slaughter stock. No investigation into long-term cardiovascular side effects has been undertaken. The rate of extrapolation from animal studies to unsupervised human usage is alarming. If this category of drugs does preserve lean mass in humans, there are legitimate medical applications. Trials of efficacy and safety are needed.

Adipose Tissue↗
PubMed1994

Purification and active-site characterization of equine plasma amine oxidase.

An improved purification scheme for an amine oxidase from equine plasma (EPAO), a nonruminant source, is described and the protein's active-site is characterized. EPAO is dimeric and contains one Type-2 Cu(II) ion per monomer. The EPAO Cu(II) site is spectroscopically very similar to the Cu(II) sites in other amine oxidases. Unlike the extensively investigated nonruminant amine oxidase from porcine plasma, EPAO does not display half-of-the-sites reactivity; titrations with p-nitrophenylhydrazine and phenylhydrazine indicate two active cofactors per dimer. This cofactor is determined to be the same as that of other copper-containing amine oxidases, 6-hydroxydopa quinone (topa quinone). Upon anaerobic reduction with substrate at ambient temperature, the EPR spectrum of EPAO exhibits a sharp signal at g congruent to 2, attributable to the topa semiquinone. Equine plasma amine oxidase possesses novel in vitro substrate specificity; while other mammalian amine oxidases oxidize norepinephrine only slowly or not at all, EPAO displays significant activity toward this biogenic amine.

Amine Oxidase (Copper-Containing)↗
PubMed1994

Echinocytosis associated with rattlesnake envenomation in dogs.

A retrospective study of 28 cases of rattlesnake bites in dogs indicated an association of envenomation with echinocytosis; 25/28 dogs (89%) had echinocytosis within 24 hours of a rattlesnake bite being reported. Eighteen of the 28 dogs had marked type III echinocytosis (95-100% of mature erythrocytes affected), and seven dogs had moderate echinocytosis (15-30% of mature erythrocytes affected). The echinocytosis was transient, resolving within 48 hours of envenomation in those for which subsequent blood films were available (13/25). Hypokalemia was noted in 14 of 18 dogs for which biochemical data were available. The hypokalemia was not consistently associated with echinocytosis. The observation of echinocytosis in dogs supports a clinical diagnosis of rattlesnake envenomation.

Animals↗
PubMed1993

Biodegradation of a synthetic lubricant by Micrococcus roseus.

A bacterium that was able to utilize Emkarate 1550 (E1550), a synthetic lubricant ester, as the sole source of carbon was isolated. The isolate was tentatively identified as Micrococcus roseus. The components of the E1550 ester, octanoate, decanoate, and 1,1,1-tris(hydroxymethyl)propane (TMP), were detected in the culture medium of cells growing on the ester. The TMP tertiary alcohol accumulated during growth and was not utilized by this isolate. The detection of the components of the ester in the supernatant of cultures indicated that one of the first steps in its degradation was cleavage of the ester bonds. Esterase activity was significantly enhanced in cells grown on E1550 compared with esterase activity measured in cells grown on acetate.

Biodegradation, Environmental↗
PubMed1993

Metabolism of xenobiotics by Beauveria bassiana.

1. Diazepam, warfarin and testosterone were metabolized by whole resting cells of the fungus Beauveria bassiana IMI 12939 via oxidative reactions such as hydroxylation and N-demethylation. 2. Metabolism of each substrate was inhibited by the cytochrome P450 inhibitors SKF-525A and metyrapone, consistent with the involvement of this enzyme system in the metabolism of these drugs by B. bassiana. 3. Substrate concentration-dependent inhibition was observed during diazepam metabolism by this organism, as has been observed in some mammalian systems. 4. Unlike most mammalian P450 systems, the warfarin-metabolizing activity of B. bassiana could not be induced by growing the organism in the presence of phenobarbitone, beta-naphthoflavone, 3-methylcholanthrene, 1-benzylimidazole or warfarin. 5. Overall findings indicate that B. bassiana possesses an oxidative metabolizing system capable of producing metabolites found in mammalian systems.

Chromatography, High Pressure Liquid↗
PubMed1992

Identification of topaquinone and its consensus sequence in copper amine oxidases.

The nature of the active site cofactor and the amino acid sequence flanking this structure have been determined in a range of copper amine oxidases. For enzymes from porcine plasma, porcine kidney, and pea seedlings, proteolytic digestion was performed on phenylhydrazone or p-nitrophenylhydrazone derivatives. Thermolysin treatment leads to relatively small active site peptides, which have been characterized by Edman degradation and by resonance Raman spectroscopy. Resonance Raman spectra of peptides show identical peak positions and intensities relative to each other and to a model p-nitrophenylhydrazone derivative of topaquinone hydantoin, establishing topaquinone as the cofactor in each instance. Edman degradation of peptides provides active site sequences for comparison to previous determinations with bovine serum and yeast amine oxidases. The available data establish a consensus sequence of Asn, Topa, Asp/Glu. Trypsin leads to significantly longer peptides, which reveal a high degree of sequence identity between plasma proteins from bovine and porcine sources (89%), with significantly decreased identity between the porcine serum and intracellular amine oxidases (56%). A lower degree of identity (45%) is observed between the pea seedling and mammalian enzymes. As an alternative to the isolation of active site peptides for topaquinone identification, visible spectra of intact proteins have been investigated. It is shown that p-nitrophenylhydrazone derivatives of native enzymes, active site-derived peptides, and a topaquinone model exhibit identical behavior, absorbing at 457-463 nm at neutral pH (pH 7.2) and at 575-587 nm in basic solution (1-2 M KOH). These spectral properties, which appear unique to topaquinone, provide a rapid and simple test for the presence of this cofactor in intact enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Amine Oxidase (Copper-Containing)↗
PubMed1992

Evidence for copper and 3,4,6-trihydroxyphenylalanine quinone cofactors in an amine oxidase from the gram-negative bacterium Escherichia coli K-12.

The cofactors present in a amine oxidase induced in Escherichia coli K-12 by growth on 2-phenylethylamine have been studied by spectroscopic methods. E.s.r. spectroscopy establishes the presence of cupric copper while resonance Raman spectroscopy on the phenylhydrazine derivative of the enzyme provides strong evidence for the oxidized form of 3,4,6-trihydroxyphenylalanine (TOPA) quinone. The amine oxidase should accordingly be classified as EC 1.4.3.6. This is the first report of such an amine oxidase in a Gram-negative bacterium.

Amine Oxidase (Copper-Containing)↗
PubMed1992

The declining risk of post-transfusion hepatitis C virus infection.

BACKGROUND: The most common serious complication of blood transfusion is post-transfusion hepatitis from the hepatitis C virus (HCV). Blood banks now screen blood donors for surrogate markers of non-A, non-B hepatitis and antibodies to HCV, but the current risk of post-transfusion hepatitis C is unknown. METHODS: From 1985 through 1991, blood samples and medical information were obtained prospectively from patients before and at least six months after cardiac surgery. The stored serum samples were tested for antibodies to HCV by enzyme immunoassay, and by recombinant immunoblotting if positive. RESULTS: Of the 912 patients who received transfusions before donors were screened for surrogate markers, 35 seroconverted to HCV, for a risk of 3.84 percent per patient (0.45 percent per unit transfused). For the 976 patients who received transfusions after October 1986 with blood screened for surrogate markers, the risk of seroconversion was 1.54 percent per patient (0.19 percent per unit). For the 522 patients receiving transfusions since the addition in May 1990 of screening for antibodies to HCV, the risk was 0.57 percent per patient (0.03 percent per unit). The trend toward decreasing risk with increasingly stringent screening of donors was statistically significant (P less than 0.001). After we controlled for the method of donor screening, the risk of seroconversion was strongly associated (P less than 0.001) with the volume of blood transfused, but not with the use of particular blood components. CONCLUSIONS: The incidence of post-transfusion hepatitis C has decreased markedly since the implementation of donor screening for surrogate markers and antibodies to HCV. The current risk of post-transfusion hepatitis is about 3 per 10,000 units transfused.

Alanine Transaminase↗
PubMed1992

Tyrosine codon corresponds to topa quinone at the active site of copper amine oxidases.

The recently discovered organic cofactor of bovine serum amine oxidase, topa quinone, is an uncommon amino acid residue in the polypeptide backbone (Janes, S. M., Mu, D., Wemmer, D., Smith, A. J., Kaur, S., Maltby, D., Burlingame, A. L., and Klinman, J. P. (1990) Science 248, 981-987). The amine oxidase gene from the yeast Hansenula polymorpha has been cloned and sequenced (Bruinenberg, P. G., Evers, M., Waterham, H. R., Kuipers, J., Arnberg, A. C., and Geert, A. B. (1989) Biochim. Biophys. Acta 1008, 157-167). In order to understand the incorporation of topa quinone in eukaryotes, we have isolated yeast amine oxidase from H. polymorpha. Following protocols established with bovine serum amine oxidase, yeast amine oxidase was derivatized with [14C]phenylhydrazine, followed by thermolytic digestion and isolation of a dominant radiolabeled peptide by high pressure liquid chromatography. Comparison of resonance Raman spectra for this peptide to spectra of a model compound demonstrates that topa quinone is the cofactor. By alignment of a DNA-derived yeast amine oxidase sequence with the topa quinone-containing peptide sequence, it is found that the tyrosine codon, UAC, corresponds to topa quinone in the mature protein. In a similar manner, alignment of a tryptic peptide from bovine serum amine oxidase implicates tyrosine as the precursor to topa quinone in mammals.

Amine Oxidase (Copper-Containing)↗
PubMed1992

Occult fracture patterns of the knee associated with anterior cruciate ligament tears: assessment with MR imaging.

One hundred consecutive magnetic resonance (MR) images of the knee in patients with acute complete anterior cruciate ligament (ACL) tears were reviewed to evaluate the prevalence and patterns of associated occult fractures. Eighty-nine occult fractures were identified in 56 knees. All occult fractures were in the posterior aspect of the lateral tibial plateau. Of these, occult fractures were isolated in 24 cases (43%) and were in combination with fractures in the middle aspect of the lateral femoral condyle in 26 (46%), with fractures in the posterior aspect of the medial tibial plateau in four (7%), and with fractures involving all three areas in one (2%). Disruption of the ACL under valgus stress leads to anterior translation of the tibia and relative external rotation of the femur. This allows impaction of the posterior portion of the lateral tibial plateau against the middle of the lateral femoral condyle and accounts for the unique pattern of occult fractures associated with ACL tears. An occult fracture of the posterior lateral tibial plateau with or without an associated fracture in the lateral femoral condyle ("kissing contusion") is a relatively frequent finding in acute ACL tears and, when present, is highly suggestive of such an associated tear.

Adolescent↗
PubMed1992

Shoulder injuries.

Shoulder injuries result from acute or repetitive over-use mechanisms. An outline for a careful history and physical examination is presented along with recommendations for radiographic imaging of shoulder injuries dependent on the suspected diagnosis and injury mechanism. Descriptions of the more common shoulder problems are presented with recommendations for non-surgical treatment. Indications for surgical treatment that will allow the primary practitioner to best manage these injuries are presented.

Diagnosis, Differential↗
PubMed1991

The organic functional group in copper-containing amine oxidases. Resonance Raman spectra are consistent with the presence of topa quinone (6-hydroxydopa quinone) in the active site.

Resonance Raman spectroscopy has been used to probe the structure of the organic cofactor in copper-containing amine oxidases from bovine plasma, porcine kidney, pea seedlings, and the bacterium Arthrobacter P1. The enzymes were first derivatized with phenylhydrazine or p-nitrophenylhydrazine; resonance Raman spectra were obtained on the intact derivatized enzymes and on a derivatized active-site peptide isolated from bovine plasma amine oxidase. Spectra of the intact amine oxidase phenylhydrazones are practically identical, consistent with the enzymes examined containing a similar cofactor. Only minor frequency shifts and some intensity variations are detected between the resonance Raman spectra of intact bovine plasma amine oxidase and the isolated peptide. These spectral perturbations are attributable to differences in the micro-environment between the intact, folded protein and the isolated small peptide in aqueous solution. This rules out the possibility that a new structure is formed during the isolation of the derivatized active-site peptide. Importantly, the resonance Raman spectra of the phenylhydrazine and p-nitrophenylhydrazine derivatives of the bovine plasma amine oxidase peptide are identical to the spectra of the corresponding derivatives of topa quinone (6-hydroxydopa quinone). Hence these data provide strong, independent support for the recent identification of topa as the organic functional group in bovine plasma amine oxidase (Janes, S. M., Mu, D., Wemmer, D., Smith, A. J., Kaur, S., Maltby, D., Burlingame, A. L., and Klinman, J.P. (1990) Science 248, 981-987).

Amine Oxidase (Copper-Containing)↗
PubMed1991

A Cu(I)-semiquinone state in substrate-reduced amine oxidases.

The role of copper in copper-containing amine oxidases has long been a source of debate and uncertainty. Numerous electron paramagnetic resonance (EPR) experiments, including rapid freeze-quench studies, have failed to detect changes in the copper oxidation state in the presence of substrate amines. One suggestion that copper reduction might occur, has never been confirmed. Copper amine oxidases contain another cofactor, recently identified as 6-hydroxydopa quinone (topa quinone), which is reduced by substrates. Copper has been implicated in the reoxidation of the substrate-reduced enzyme, but the failure to detect any copper redox change has led to proposals that Cu(II) acts as a Lewis acid, that it has an indirect role in catalysis, or that it serves a structural role. We present evidence for the generation of a Cu(I)-semiquinone state by substrate reduction of several amine oxidases under anaerobic conditions, and suggest that the Cu(I)-semiquinone may be the catalytic intermediate that reacts directly with oxygen.

Amine Oxidase (Copper-Containing)↗