Biomedical subjects
J Moser
Publications and source records attributed to J Moser.
Methanopyrus kandleri glutamyl-tRNA reductase.
The initial reaction of tetrapyrrole formation in archaea is catalyzed by a NADPH-dependent glutamyl-tRNA reductase (GluTR). The hemA gene encoding GluTR was cloned from the extremely thermophilic archaeon Methanopyrus kandleri and overexpressed in Escherichia coli. Purified recombinant GluTR is a tetrameric enzyme with a native M(r) = 190,000 +/- 10,000. Using a newly established enzyme assay, a specific activity of 0.75 nmol h(-1) mg(-1) at 56 degrees C with E. coli glutamyl-tRNA as substrate was measured. A temperature optimum of 90 degrees C and a pH optimum of 8.1 were determined. Neither heme cofactor, nor flavin, nor metal ions were required for GluTR catalysis. Heavy metal compounds, Zn(2+), and heme inhibited the enzyme. GluTR inhibition by the newly synthesized inhibitor glutamycin, whose structure is similar to the 3' end of the glutamyl-tRNA substrate, revealed the importance of an intact chemical bond between glutamate and tRNA(Glu) for substrate recognition. The absolute requirement for NADPH in the reaction of GluTR was demonstrated using four NADPH analogues. Chemical modification and site-directed mutagenesis studies indicated that a single cysteinyl residue and a single histidinyl residue were important for catalysis. It was concluded that during GluTR catalysis the highly reactive sulfhydryl group of Cys-48 acts as a nucleophile attacking the alpha-carbonyl group of tRNA-bound glutamate with the formation of an enzyme-localized thioester intermediate and the concomitant release of tRNA(Glu). In the presence of NADPH, direct hydride transfer to enzyme-bound glutamate, possibly facilitated by His-84, leads to glutamate-1-semialdehyde formation. In the absence of NADPH, a newly discovered esterase activity of GluTR hydrolyzes the highly reactive thioester of tRNA(Glu) to release glutamate.
Surface Modification of a Hydrogen-Bonded Pigment: A Fluorescence Spectroscopy Study.
The effect of hydrogen-bonding additives on the surface modification of a hydrogen-bonded organic pigment is studied using absorption and fluorescence spectroscopy. Evidence for surface dissolution that occurs during the mixing of solids is presented. The spectral signatures of monomers and hydrogen-bonded aggregates of the pigment that are present on the surface of crystallites of the pigment are quite distinct, as revealed by fluorescence excitation and emission spectra. Copyright 1999 Academic Press.
[Migration and pain. Need for epidemiologic research].
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Plasma von Willebrand factor changes during various reproductive cycle stages in mixed-breed dogs with normal von Willebrand factor and in Doberman pinschers with type-I von Willebrand's disease.
OBJECTIVE: To determine whether plasma von Willebrand factor (vWf) concentration changes during the estrous cycle and pregnancy in Doberman Pinschers with type-I von Willebrand's disease (vWd) and in mixed-breed dogs with normal vWf, and if so, whether alterations in vWf concentration are associated with changes in serum concentrations of reproductive hormones. ANIMALS: 5 sexually intact female Doberman Pinschers with type-I vWf and 8 sexually intact female mixed-breed dogs with normal vWf. PROCEDURE: Concentrations of plasma vWf and serum progesterone and estradiol-17 beta were measured during the estrous cycle of nonpregnant dogs and during pregnancy, parturition, and lactation. Serum concentrations of total triiodothyronine, total thyroxin, and free thyroxin were measured during pregnancy, parturition, and lactation. RESULTS: Von Willebrand factor concentration did not change during the estrous cycle, but during pregnancy, vWf concentration gradually increased. Peak concentrations were obtained at parturition and were 103 and 92% higher in mixed-breed dogs and dogs with type-I vWd, respectively, than were mean prepregnancy (anestrus) values. At parturition, total triiodothyronine concentration decreased from the prepregnancy value. The increase in vWf concentration during pregnancy was positively associated with changes in concentration of estradiol-17 beta and was negatively associated with changes in concentration of progesterone. CONCLUSIONS: The increase in vWf concentration in pregnant bitches may be associated with changes in concentrations of reproductive hormones. However, the increase in vWf concentration during pregnancy may involve other factors because vWf concentration did not change during the estrous cycle of nonpregnant dogs despite increases in concentrations of estradiol-17 beta and progesterone.
[Beyond silence--the nurse and the tortured patient].
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Crystal structure of the phosphatidylinositol-specific phospholipase C from the human pathogen Listeria monocytogenes.
The X-ray crystal structure of the phosphatidylinositol-specific phospholipase C (PI-PLC) from the human pathogen Listeria monocytogenes has been determined both in free form at 2.0 A resolution, and in complex with the competitive inhibitor myo-inositol at 2.6 A resolution. The structure was solved by a combination of molecular replacement using the structure of Bacillus cereus PI-PLC and single isomorphous replacement. The enzyme consists of a single (beta alpha)8-barrel domain with the active site located at the C-terminal side of the beta-barrel. Unlike other (beta alpha)8-barrels, the barrel in PI-PLC is open because it lacks hydrogen bonding interactions between beta-strands V and VI. myo-Inositol binds to the active site pocket by making specific hydrogen bonding interactions with a number of charged amino acid side-chains as well as a coplanar stacking interaction with a tyrosine residue. Despite a relatively low sequence identity of approximately 24%, the structure is highly homologous to that of B.cereus PI-PLC with an r.m.s. deviation for 228 common C alpha positions of 1.46 A. Larger differences are found for loop regions that accommodate most of the numerous amino acid insertions and deletions. The active site pocket is also well conserved with only two amino acid replacements directly implicated in inositol binding.
Inheritance of von Willebrand factor deficiency in Doberman pinschers.
OBJECTIVE: To determine the inheritance of von Willebrand factor (vWF) deficiency in Doberman Pinschers. DESIGN: Prospective, observational study. ANIMALS: 26 adult Doberman Pinschers or mixed-breed dogs and 101 pups produced from 18 matings between adult dogs. PROCEDURE: Measurement of plasma vWF concentrations in parents and progeny. On the basis of plasma vWF concentrations, dogs were grouped as normal (75 to 160 U of vWF/dl), midrange (> or = 30 and < 75 U of vWF/dl), or low (< 30 U of vWF/dl). RESULTS: The percentile distribution of vWF concentrations was trimodal. Distribution between dogs with low and midrange plasma vWF concentrations changed sharply, whereas the change between dogs with midrange and normal plasma vWF concentrations was gradual. Three matings between dogs with low vWF concentrations produced 13 offspring, all with low vWF concentrations. Two matings between dogs with normal plasma vWF concentrations produced 14 offspring, all with normal vWF concentrations. Eight matings between dogs with normal and low plasma vWF concentrations produced 54 offspring 40 with midrange, 13 with normal, and 1 with low vWF concentrations. There were 5 matings of dogs with midrange plasma vWF concentrations to dogs with low, midrange, or high vWF concentrations. The results of all matings were consistent with a single gene defect where each normal allele produced half the total amount of vWF when both alleles are normal and each defective allele produced < 15 U of vWF/dl. CLINICAL IMPLICATIONS: Dogs with low plasma vWF concentrations may be homozygous for the defective allele, whereas dogs with midrange plasma vWF concentrations may be heterozygous. It can be difficult to distinguish normal homozygotes from heterozygotes if evaluation is based only on plasma vWF concentration.
Temporal variation and factors affecting measurement of canine von Willebrand factor.
OBJECTIVE: To determine whether canine plasma von Willebrand factor (vWf) varies between and within individuals over time and with different blood sample collection and processing procedures. ANIMALS: 26 adult dogs and 6 pups. PROCEDURE: Blood was obtained from the jugular or cephalic vein daily for 8 to 19 days and weekly for 9 to 23 weeks in adult dogs and periodically up to 180 days of age in pups. Temporal variation in vWf concentration and the effect of vascular occlusion, venipuncture site, lipemia, hemolysis, anticoagulant, storage time, freeze-thawing, and centrifugation speed on plasma vWf concentration, measured by ELISA, were determined. RESULTS: Plasma vWf concentration varied over time. In dogs with mean vWf concentration > or = 79 U/dl, the largest intraindividual range in vWf spanned 64 U/dl with daily and 53 U/dl with weekly sample collection. In dogs with mean vWf concentration < or = 24 U/dl, the largest individual variation was 12 U/dl with daily and weekly sample collection. In dogs with mean vWf concentration > or = 53 and < or = 74 U/dl, the largest intraindividual range spanned 35 U/ dl. Mean vWf concentration of pups from 3 to 180 days of age did not change. Sample hemolysis decreased mean vWf by 37%. Mean vWf concentration was 9% higher in cephalic than jugular vein samples (P = 0.056). Other sample collection/preparation procedures did not affect vWf concentration. CONCLUSION: There was substantial temporal variation in vWf concentration within individual dogs. CLINICAL RELEVANCE: Multiple tests may be necessary to obtain a reliable estimate of vWf concentration in dogs.
Quantitative determination of urinary lipid metabolites by high pressure liquid chromatography as indicators of menadione-induced in vivo lipid peroxidation.
The one- and two-electron-reduction reactions of menadione result in the generation of reactive oxygen species which are believed to mediate the cytotoxicity of this xenobiotic. The induction of lipid peroxidation in liver and isolated hepatocytes occurs in response to the menadione-mediated formation of reactive oxygen species. However, studies on the effects of menadione on the urinary excretion of lipid metabolites have not been conducted. The effect of a single oral dose of 60 mg menadione/kg to rats on the urinary excretion of the lipid metabolites malondialdehyde (MDA), formaldehyde (FA), acetaldehyde (ACT), and acetone (ACON) has been examined over 48 h post-treatment. The urinary metabolites were identified by gas chromatography-mass spectrometry and quantitated by high pressure liquid chromatography. Time-dependent increases in the urinary excretion of the four metabolites were observed after menadione administration. Over the 48 h of the study, the menadione-induced urinary excretion of MDA, FA, ACT, and ACON increased by approximately 1.5-, 2.0-, 1.7-, and 3.2-fold, respectively, relative to control animals. The data were expressed in nmoles/kg body weight/4.5 h. The results clearly demonstrate that menadione increases the urinary excretion of four lipid metabolites. These metabolites may have widespread applicability as biomarkers of altered lipid metabolism in disease states and exposure to environmental pollutants/xenobiotics which induce enhanced lipid peroxidation. The non-invasive methods offer advantages over most other methods for assessing oxidative stress in vivo.
Shielding effects and hypoxia in photodynamic therapy.
Photodynamic therapy (PDT) is a new modality to treat cancer. In clinical use, the procedure is limited by the poor penetration depth of the curative light, which ranges between 3 and 6 mm. The cause of this situation is not clear. Two hypotheses are discussed: shielding effect or hypoxia. To test both hypotheses, we designed an in vitro model. Suspensions and sediments of OAT-75 cells were incubated at 37 degrees C with pheophorbide a or 13(2)-hydroxy-bacteriopheophorbide a methyl ester, both second-generation sensitizers. Irradiation was done with laser light of suitable wavelength. In all experiments, cell death was seen on the surface of the sediment, i.e., near the border of the oxygen-containing atmosphere and opposite the site of the irradiation beam. Therefore, we should accept the hypoxia thesis.
[Which educational policies for tomorrow?].
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Management after arthroscopy.
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EuAl2 at pressures up to 41 GPa: A localized magnet exhibiting highly nonlinear electronic effects.
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Effects of carbon tetrachloride, menadione, and paraquat on the urinary excretion of malondialdehyde, formaldehyde, acetaldehyde, and acetone in rats.
Excretions of the lipid peroxidation products, formaldehyde (FA), acetaldehyde (ACT), malondialdehyde (MDA), and acetone (ACON), were simultaneously identified and quantitated in the urine of female Sprague-Dawley rats by gas chromatography-mass spectroscopy (GC-MS) and high pressure liquid chromatography (HPLC) following the acute administration of carbon tetrachloride, a model alkylating agent that does not induce glutathione depletion, and the redox cycling compounds paraquat and menadione. All three xenobiotics are well-known inducers of oxidative stress. Oxidative stress was induced by oral administration of single doses of 2.5 mL of carbon tetrachloride/kg, 60 mg menadione/kg, and 75 mg paraquat/kg. These doses are approximately 50% of the LD50's for the three xenobiotics. Urinary excretion of FA, ACT, MDA, and ACON increased relative to control animals following treatment with all xenobiotics. Over the 48 hours of the study, the greatest increases in the excretion of MDA, FA, ACT, and ACON occurred after paraquat administration, with increases of approximately 2.7-, 2.6-, 4.3-, and 11.0-fold, respectively. This technique may have wide-spread applicability as an effective biomarker for investigating altered lipid metabolism in disease states and exposure to environmental pollutants/xenobiotics.
Excretion of malondialdehyde, formaldehyde, acetaldehyde and acetone in the urine of rats following acute and chronic administration of ethanol.
Recent studies have shown that xenobiotics which induce oxidative stress result in an increased production and excretion of acetaldehyde (ACT), formaldehyde (FA), acetone (ACON) and malondialdehyde (MDA) in the urine of rats. We have therefore examined the effect of acute and chronic ethanol administration on the excretion of these four lipid metabolites in female Sprague-Dawley rats. Urine samples were collected over dry ice for 6 hr time periods. Aliquots of urine were derivatized with 2,4-dinitrophenylhydrazine HCl, and extracted with n-pentane. High pressure lipid chromatogrpahy (HPLC) was used to quantitate and the hydrazones of the four lipid metabolite products. Following a single, oral, acute dose of 5 g ethanol/kg, urinary excretion of ACT increased approximately 5.8-fold from 6 to 12 hr posttreatment, and decreased thereafter. FA excretion decreased by approximately 50% from 0 to 12 hr, returned to control values in the 18-24 hr urine samples, and was 1.3-fold greater than control values at 42-48 hr. ACON increased 3.1-fold over control values from 0 to 30 hr and remained elevated throughout the remaining 18 hr of the study. The excretion of MDA increased approximately 1.5-fold from 18 to 36 hr, then remained constant through the 48 hr time point. In a separate series of experiments, a chronic oral dose of 0.5 g ethanol/kg was administered to rats for 10 consecutive days and the urinary excretion of the lipid metabolites MDA, FA, ACT and ACON was examined for 11 days, beginning with the first day of ethanol administration.(ABSTRACT TRUNCATED AT 250 WORDS)
[Professional education in Switzerland and relations with the European Economic Community. The recognition is--on principle--assured].
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Infections in adult liver transplant patients under FK 506 immunosuppression.
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