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R A Dean

Publications and source records attributed to R A Dean.

52 records · Page 3Linked to original sources
PubMed1995

Tissue distribution of cocaine methyl esterase and ethyl transferase activities: correlation with carboxylesterase protein.

The tissue distribution of cocaine methyl esterase and ethanol-dependent ethyl transferase activities was determined in the rat and compared to the tissue distribution of three distinct non-specific hydrolases. Rates of formation of benzoylecgonine from cocaine and cocaethylene from ethanol and cocaine were measured in serum and tissue homogenate-supernatants of the brain, heart, kidney, liver, lung and spleen. The tissue distribution of three nonspecific esterases, A, B and C, was defined by nondenaturing gel electrophoresis and measuring the hydrolysis of 4-methylumbelliferyl acetate in the gels. Immunoreactive protein was localized by using Western blot analysis with polyclonal rabbit antihuman liver cocaine methyl esterase antibody after denaturing and nondenaturing gel electrophoresis. The rat liver, lung, kidney and heart exhibited cocaine methyl esterase and ethyl transferase activities and immunoreactive protein. The brain had cocaine methyl esterase activity but no ethyl transferase activity; neither activity was found in serum or spleen. The dominant immunoreactive bands in the liver, lung, kidney and heart comigrated with the 59 kD band of purified human liver cocaine methyl esterase. The rat liver, lung and kidney exhibited a band of nonspecific esterase activity that migrated with purified human liver cocaine methyl esterase and rat hydrolase A. These observations suggest that rat hydrolase A is similar to human cocaine methyl esterase. The lack of straight forward correlation between cocaine methyl esterase activity and immunoreactive protein and nonspecific esterase activity suggests that more than one enzyme catalyzes the hydrolysis of cocaine to benzoylecgonine in the rat.

Animals↗
PubMed1994

Purification and characterization of a human liver cocaine carboxylesterase that catalyzes the production of benzoylecgonine and the formation of cocaethylene from alcohol and cocaine.

The psychomotor stimulant cocaine is inactivated primarily by hydrolysis to benzoylecgonine, the major urinary metabolite of the drug. A non-specific carboxylesterase was purified from human liver that catalyzes the hydrolysis of the methyl ester group of cocaine to form benzoylecgonine. In the presence of ethanol, the enzyme also catalyzes the transesterification of cocaine producing the pharmacologically active metabolite cocaethylene (benzoylecgonine ethyl ester). The carboxylesterase obeys simple Michaelis-Menten kinetics with Km values of 116 microM for cocaine and 43 mM for ethanol. The enzymatic activity suggests that it may play an important role in regulating the detoxication of cocaine and in the formation of the active metabolite cocaethylene. Additionally, the enzyme catalyzes the formation of ethyloleate from oleic acid and ethanol. The carboxylesterase was purified from autopsy liver by gel filtration, chromatofocusing, ion-exchange, and hydrophobic interaction chromatography to purity by SDS-PAGE and agarose gel isoelectric focusing. The subunit molecular weight was determined to be 59,000 and the native molecular weight was estimated to be 170,000 from a calibrated gel filtration column, suggesting that the active enzyme is a trimer. The isoelectric point was approximately 5.8. Digestion of carbohydrate residues on the protein with an acetylglucosaminidase plus binding to several lectins indicates that the enzyme is glycosylated. The esterase was cleaved with two proteases, and the amino acid sequences from fourteen peptides were used to search GenBank. Two identical matches were found corresponding to carboxylesterase cDNAs from human liver and lung.

Amino Acid Sequence↗
PubMed1994

Simultaneous determination of primaquine and carboxyprimaquine in plasma using high-performance liquid chromatography with electrochemical detection.

A selective and sensitive high-performance liquid chromatographic method with electrochemical detection is described for the simultaneous quantitation of primaquine and carboxyprimaquine, its primary metabolite, in plasma. After addition of internal standard, plasma was deproteinized by addition of acetonitrile. Nitrogen-dried supernatants, resuspended in mobile phase were analyzed on a C8 reversed-phase column. Limits of detection for primaquine and carboxyprimaquine were 2 and 5 ng/ml with quantitation limits of 5 and 20 ng/ml, respectively. None of 47 tested antimicrobial agents interfered. In contrast to previously reported methods, the assay sensitivity and specificity are sufficient to permit quantitation of primaquine in plasma for pharmacokinetics following low dose (30 mg, base) oral administration of primaquine, typically used in the treatment of malaria and Pneumocystis carinii pneumonia.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Effects of ethanol on cocaine metabolism: formation of cocaethylene and norcocaethylene.

The coabuse of cocaine and ethanol occurs with high frequency and increases the risk of cocaine-related morbidity and mortality. The mechanisms mediating the toxic interactions of cocaine and ethanol are not clearly defined. This study examined the effects of acute ethanol administration on the metabolism of cocaine in the male Wistar rat. Intraperitoneal administration of 2 g/kg ethanol 30 min prior to administration of 25 mg/kg cocaine resulted in the formation of two ethylated derivatives of cocaine, benzoylecgonine ethyl ester (cocaethylene) and benzoylnorecgonine ethyl ester (norcocaethylene) in liver, brain, and serum. Fifteen minutes after cocaine administration, the tissue levels of cocaethylene were 22, 10, and 9% of the cocaine recovered from liver, serum, and brain, respectively. Ethanol pretreatment increased cocaine concentrations in liver and benzoylnorecgonine concentrations in liver and serum. The increased morbidity and hepatotoxicity seen with acute combined administration of cocaine and ethanol may be due to the formation of the toxic ethylated and N-demethylated metabolites of cocaine. Ethanol pretreatment decreased benzoylecgonine concentrations in serum and liver. The most important consequence of ethanol-induced inhibition of the normally rapid hydrolysis of cocaine to benzoylecgonine may be a decrease in benzoylecgonine-mediated vasoconstriction.

Animals↗
PubMed1992

Efficacy of intermittent dosage of 8-aminoquinolines for therapy or prophylaxis of Pneumocystis pneumonia in rats.

Experimental 8-aminoquinolines from Walter Reed Army Institute for Research are effective for prophylaxis or therapy of Pneumocystis carinii pneumonia in rat models. In the present study, primaquine, WR6026, and WR238605 were tested in prophylaxis and treatment models of P. carinii pneumonia to compare the effectiveness of continuous versus intermittent dosing. For treatment of P. carinii pneumonia, the drugs showed detectable effects when given once every 4 days (primaquine and WR6026 at doses greater than 8 mg/kg; WR238605 at doses greater than 2 mg/kg). For prophylaxis, WR6026 and WR238605 were effective given alone daily (WR6026 at doses greater than 0.25 mg/kg; WR238605 at doses greater than 0.57 mg/kg). WR6026 and WR238605 at 4 mg/kg given once every 4 days for prophylaxis were as effective as daily trimethoprim-sulfamethoxazole. These studies suggest that higher doses of 8-aminoquinolines administered at appropriate intervals may be as effective as continuous dosing for prophylaxis of P. carinii pneumonia.

Aminoquinolines↗
PubMed1991

Human liver cocaine esterases: ethanol-mediated formation of ethylcocaine.

A new, pharmacologically active metabolite of cocaine, ethylcocaine, has been reported in individuals after concurrent use of cocaine and ethanol. Formation of ethylcocaine may contribute to the common coabuse of these two drugs and the apparent danger of this practice. We have identified a nonspecific carboxyl-esterase that catalyzes the ethyl transesterification of cocaine to ethylcocaine in the presence of ethanol. In the absence of ethanol, this human liver esterase catalyzes the hydrolysis of cocaine to benzoylecgonine, a metabolite that is inactive as a psychomotor stimulant. A second human liver esterase is also described. This enzyme catalyzes hydrolysis of cocaine to ecgonine methyl ester, also inactive as a stimulant. These two liver esterases may play important roles in regulating the metabolic inactivation of cocaine.

Carboxylic Ester Hydrolases↗
PubMed1991

Rodletless, a new Aspergillus developmental mutant induced by directed gene inactivation.

The Aspergillus nidulans CAN41 transcription unit is activated by the brlA regulatory gene early during development of the asexual reproductive apparatus, the conidiophore. Disruption of CAN41 results in a novel mutant phenotype in which conidiophore cells and spores lack an external wall layer, the rodlet layer, making them less hydrophobic than in the wild type and leading to inefficient spore dispersal. The rodletless mutation defines a new locus on chromosome III, rodA. rodA encodes a small, moderately hydrophobic polypeptide containing 8 cysteines arranged in a pattern similar to that observed in three hydrophobic cell wall proteins from the Holobasidiomycete Schizophyllum commune. We propose that the Aspergillus and Schizophyllum 8-cysteine polypeptides define a class of secreted, hydrophobic, fungal cell wall proteins that are important in the formation and function of aerial structures such as conidiophores and mushrooms.

Amino Acid Sequence↗
PubMed1991

Transient porphyrinemia in a liver transplant recipient.

We report a case of acquired porphyrinemia in a liver transplant recipient. Thrombosis of the portal vein and hepatic artery led to massive necrosis of the patient's first donor liver, necessitating its removal. After an 18-hour anhepatic period, a second donor liver was transplanted. During this interval, the patient was warmed with an infrared heat lamp that emitted bright visible light. Following the anhepatic period, a photodistributed cutaneous erythema was noted. The level of total serum porphyrins during the anhepatic period was significantly elevated at 1.548 mumol/L (normal, less than 0.018 mumol/L). Fractionation showed that the levels of the hydrophobic porphyrins, coproporphyrin and protoporphyrin, were elevated, while the levels of the hydrophilic porphyrins remained normal. Following the successful second liver transplantation, the patient's porphyrin levels declined. This is the first reported case of acquired porphyrinemia in a liver transplant recipient.

Child↗
PubMed1989

Production of cell wall-degrading enzymes by Aspergillus nidulans: a model system for fungal pathogenesis of plants.

The cell wall-degrading enzymes polygalacturonase and pectate lyase have been suggested to be crucial for penetration and colonization of plant tissues by some fungal pathogens. We have found that Aspergillus nidulans (= Emericella nidulans), a saprophytic Ascomycete, produces levels of these enzymes equal to those produced by soft-rotting Erwinia species. Induction of polygacturonase and pectate lyase in A. nidulans requires substrate and is completely repressed by glucose. Surprisingly, inoculation of excised plant tissues with A. nidulans conidia leads to formation of necrotic, water-soaked lesions within which the organism sporulates. Thus, A. nidulans has phytopathogenic potential. The release of glucose and other sugars from wounded tissues may repress pectolytic enzyme production and limit disease development. Therefore, we tested creA204, a mutation that relieves glucose repression of some A. nidulans carbon utilization enzymes, for its effect on production of pectolytic enzymes. creA204 failed to relieve catabolite repression of polygalacturonase or pectate lyase and had no effect on disease severity.

Aspergillus nidulans↗
PubMed1989

Regulation of the Aspergillus nidulans pectate lyase gene (pelA).

Aspergillus nidulans pectate lyase was purified from culture filtrates. The enzyme catalyzed a random eliminative cleavage reaction, had an apparent molecular weight of 40,000, and a pl of 4.2. Pectate lyase antisera were produced and used to identify pectate lyase clones in a cDNA expression library. Thirteen of 14 clones identified immunologically cross-hybridized. The identity of the single-copy pectate lyase gene, which we designated pelA, was confirmed in two ways. First, several cDNA clones expressed pectate lyase activity in Escherichia coli. Second, targeted mutation of the gene in A. nidulans resulted in complete loss of enzyme activity. pelA encodes a 1,300-nucleotide mRNA that was present in cells grown with polygalacturonic acid as carbon source but absent from cells grown with glucose or acetate as carbon source. Thus, pectate lyase expression is regulated at the level of mRNA accumulation.

Antibodies, Fungal↗
PubMedDate not supplied

Occupational stress in hospice care: causes and coping strategies.

Thirty-three nurses from three hospice services in a large Midwestern city participated in this study, which investigated responses to difficult or demanding work-related situations. Three tools (the Self Inventory of Situational Responses-TC questionnaire, the Spielberger State Anxiety Inventory questionnaire and rank-ordered listing of likely causes of difficult or demanding situations) were used to collect data. Findings indicated that anxiety is an issue for hospice workers but that difficult or demanding situations were viewed as challenges rather than threats. Management of intractable symptoms and communication issues were of primary concern. Administrative concerns were identified as the third-ranking source of difficult situations. Issues related to death and dying were of notably less concern. Strategies for staff support also are identified.

Adaptation, Psychological↗
PubMedDate not supplied

Cytologic diagnosis of liver fluke infestation in a patient with subsequently documented cholangiocarcinoma.

In a 32-year-old Laotian immigrant who presented with a two-day history of vomiting, abdominal pain and jaundice, ultrasound examination revealed a posthepatic obstruction. Characteristic parasitic ova were present in bile fluid submitted for cytologic evaluation. Subsequent biopsy of the patient's bile duct lesion revealed a coexistent cholangiocarcinoma. The life cycles of Clonorchis sinensis and Ospisthorchis viverrini are reviewed along with the clinical and pathologic complications of infestation by these parasites in humans. The cytologic features of liver fluke infestation are characteristic and should be appreciated, as should the importance of its early diagnosis in the prevention of bile duct neoplasms.

Adenoma, Bile Duct↗
PubMedDate not supplied

Umbilical cord thiocyanate and thyroid function in intrauterine growth-restricted infants of the smoking gravida.

OBJECTIVE: We evaluated maternal and umbilical cord thiocyanate and thyroid function in intrauterine growth-restricted infants of smoking mothers. STUDY DESIGN: One hundred six mother-infant pairs were studied and divided into four groups: smokers with appropriate for gestational age infants (n = 37), smokers with intrauterine growth-restricted infants (n = 19), nonsmokers with appropriate for gestational age infants (n = 33), and nonsmokers with intrauterine growth-restricted infants (n = 17). Sera from mothers were analyzed for thiocyanate levels. Serum from umbilical cord blood was analyzed for thiocyanate, thyroxine, resin triiodothyronine uptake, and thyroid-stimulating hormone. The free thyroxine index was then calculated. RESULTS: A significant correlation was found between maternal and umbilical cord thiocyanate levels (r = 0.90, p < 0.0001). Maternal and umbilical cord thiocyanate concentrations correlated with increased maternal cigarette use. For appropriate for gestational age and intrauterine growth-restricted infants, mean maternal and umbilical cord thiocyanate levels were not significantly different. The umbilical cord thiocyanate level did not correlate with thyroid function or birth weight. The umbilical cord thyroxine level was lower in nonsmokers than in smokers. CONCLUSION: Thiocyanate was not more concentrated in the intrauterine growth-restricted infant and did not correlate with thyroid function or birth weight. The thyroxine level was decreased significantly in intrauterine growth-restricted infants born to nonsmoking mothers. Further studies are necessary to evaluate the effects of smoking on thyroid function and on fetal growth and development.

Case-Control Studies↗