Interactions of gonadotropins with corpus luteum membranes. XI. Internalization of 125I-hCG in the rat.
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Animals↗
Biomedical subjects
S Murray
Publications and source records attributed to S Murray.
An assay for paracetamol, produced by the O-deethylation of phenacetin in vitro, using gas chromatography/electron capture negative ion chemical ionization mass spectrometry.
A sensitive gas chromatographic/mass spectrometric assay for paracetamol, produced by the O-deethylation of phenacetin by microsomal fractions of human liver, has been developed. The method uses the 3,5-bistrifluoromethyl-benzoyl derivative of paracetamol and electron capture negative ion chemical ionization. This derivative has a negative ion mass spectrum which contains only a molecular ion at m/z 391 and, when this ion is specifically monitored, an amount of derivative equivalent to 1 pg of paracetamol can be detected. (2H3)Paracetamol was available for use as an internal standard and this allowed the development of an assay with a precision of 8% (SD) at 0.5 ng paracetamol per microsomal incubation and a lower limit of quantitative determination of 0.2 ng paracetamol per microsomal incubation.
Acetaminophen↗
Bis-trifluoromethylbenzoyl derivatives for steroid analysis by gas chromatography electron capture negative ion chemical ionisation mass spectrometry.
3,5-Bis-trifluoromethylbenzoyl derivatives of eight monohydroxy steroids and eight dihydroxy steroids were synthesised. Under the reaction conditions described, the monohydroxy steroids each gave a single derivative while the dihydroxy steroids, with the exception of corticosterone, showed multiple product formation. The reactivity of hydroxyl groups relative to their stereochemistry is discussed. The electron capture negative ion chemical ionisation mass spectra of these derivatives were recorded. When the derivatised hydroxyl group was alicyclic or aromatic, a molecular ion was normally the base peak in the mass spectrum. Selected ion monitoring of molecular ions indicated that, in certain cases, as little as 1 pg of the parent steroid could be detected. The potential use of this derivative in the quantitative analysis of steroids by gas chromatography-mass spectrometry is discussed.
Gas Chromatography-Mass Spectrometry↗
Quinidine and the identification of drugs whose elimination is impaired in subjects classified as poor metabolizers of debrisoquine.
Quinidine and its diastereoisomer quinine were tested in vitro for their effect on the 4-hydroxylation of debrisoquine, the O-deethylation of phenacetin and the 1'-hydroxylation of bufuralol, by human liver microsomal samples; quinidine was studied for its effect on debrisoquine 4-hydroxylation in vivo. Quinidine was a potent inhibitor of the 4-hydroxylation of debrisoquine and the 1'-hydroxylation of bufuralol, with IC50 values of 0.7 and 0.2 microM, being around 100 times more potent in this respect than quinine. Very much higher (1000-fold) levels of quinidine were required to inhibit the O-deethylation of phenacetin, being rather less potent in this than quinine. Eight subjects were phenotyped for their debrisoquine oxidation status and found to be extensive metabolisers (EM). They were tested again after the co-administration of 50 mg of quinidine with the debrisoquine. The concomitant administration of quinidine increased the metabolic ratios (MRs) by a mean of 26-fold. The effects of quinidine at a dose of only 50 mg, on the metabolism of a new drug in EM subjects may prove a useful method of assessing the contribution of the debrisoquine 4-hydroxylase isozyme to the elimination of the drug tested.
Cytochrome P-450 CYP1A2↗
Circulating immune complexes in cystic fibrosis and their correlation to clinical parameters.
Circulating immune complexes (CIC) have been found to be elevated in individuals with cystic fibrosis (CF). Previous investigators, using a variety of assays, have reported high levels of CIC in as many as 86% of these patients. Our study followed the progress of 25 patients with CF over a period of 10 months to determine which, if any, clinical parameters correlated with the occurrence and/or concentration of CIC. Immune complex determinations were performed using a coprecipitation method with equine rheumatoid-complement complex. One hundred percent of the CF patients had CIC elevated above normal levels, however, levels of CIC did not correlate with the severity of an individual's acute exacerbation. Clinical parameters including pulmonary function tests, vital signs, total serum IgG levels, and other laboratory studies, were obtained on each individual and analyzed with respect to their relationship to CIC. Only four of 38 parameters examined had p less than 0.05. Factors that showed significant correlation to elevated CIC's in the highly elevated portion of our CIC population were poor NIH score, increased patient age, low peak expiratory flow rate, and elevated total serum IgG. These clinical values are associated more with the measurement of chronic disease. These data suggest that CICs cannot be used as an indication of short-term prognosis or as a monitor to follow the course of acute severe lung infections in the CF patient. Of interest was the observation that all patients who died during the course of the investigation had CIC levels greater than 80 micrograms/ml.
Adolescent↗
Quantitative analysis of (3-methoxy-4-sulphooxyphenyl)ethylene glycol (MHPG sulphate) in human urine.
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Chromatography, Gas↗
Genetic polymorphism in drug oxidation: in vitro studies of human debrisoquine 4-hydroxylase and bufuralol 1'-hydroxylase activities.
A sensitive, specific assay utilizing fluorescence-HPLC has been developed for determining the 1'-hydroxylation of bufuralol by human liver. The 1'-hydroxylation of the isomers of bufuralol varied threefold, both the Vmax and the Km for the (+) isomer being greater than the corresponding values for the (-) isomer. Debrisoquine was a competitive inhibitor of the 1'-hydroxylation of both isomers and of the racemate of bufuralol. Both isomers and the racemate of bufuralol were competitive inhibitors of debrisoquine 4-hydroxylase activity. The competitive inhibition of debrisoquine and bufuralol of each other's metabolism, together with the similarity in the values for Km and Ki, support the conclusion that the same form of cytochrome P-450 catalyses these two reactions.
Cytochrome P-450 CYP2D6↗
Bistrifluoromethylaryl derivatives for drug analysis by gas chromatography electron capture negative ion chemical ionization mass spectrometry. Application to the measurement of (N-dicyclopropylmethyl)amino-2-oxazoline in plasma.
A gas chromatographic mass spectrometric assay for (N-dicyclopropylmethyl) amino-2-oxazoline in plasma with a detection limit of 0.1 ng ml-1 was required. Various fluoroaryl derivatives of this compound (code name S3341) were synthesized and their positive ion chemical ionization and electron capture negative ion chemical ionization mass spectra recorded. While fluorobenzyl derivatives of S3341 could be made by heating with the requisite benzyl bromide and diisopropylethylamine in acetonitrile, initial efforts to synthesize corresponding fluorobenzoyl derivatives using a benzoyl chloride in dry ethyl acetate at 60 degrees C were unsuccessful. Mass spectral data indicated that only a fragment of the oxazoline ring was retained in the reaction product and that an N-(2-chloroethyl)benzamide was formed. However, when diisopropylethylamine was included in the reaction mixture, a benzoyl derivative of the complete molecule was obtained. The mechanisms of these reactions are discussed. The negative ion mass spectrum of the 3,5-bistrifluoromethylbenzoyl derivative of S3341 has a base peak at m/z 420 (the molecular ion) and, when this ion is specifically monitored, an amount of derivative equivalent to 1 pg of S3341 can be detected. This allowed the development of an assay for S3341 in plasma with a precision of 9% (SD) at 0.2 ng ml-1 and a lower limit for quantitative determination of 0.1 ng ml-1.
Adrenergic alpha-Agonists↗
A comparison of standard and sustained release clonidine with respect to plasma concentration and blood pressure changes.
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Adult↗
Attempts to phenotype human liver samples in vitro for debrisoquine 4-hydroxylase activity.
Twenty-eight samples of human liver have been characterised for cytochrome P-450 content, aldrin epoxidase, debrisoquine 4-hydroxylase and bufuralol 1'-hydroxylase activities. Evidence is presented here and elsewhere that bufuralol 1'-hydroxylase and debrisoquine 4-hydroxylase are activities catalysed by the same form of cytochrome P-450 in man, and that this form is different from that catalysing the epoxidation of aldrin. Attempts to phenotype liver samples in vitro, in the absence of any metabolic data in vivo for debrisoquine 4-hydroxylation status, met with limited success. A combination of enzyme assays will most probably be required in any such phenotyping of human liver samples.
Cytochrome P-450 CYP2D6↗
Phenacetin O-deethylase: an activity of a cytochrome P-450 showing genetic linkage with that catalysing the 4-hydroxylation of debrisoquine?
Phenacetin O-deethylase activity was impaired, both in vivo and in vitro, in poor metabolisers of debrisoquine, consistent with the work of others. No impairment was observed in the oxidation of acetanilide, amylobarbitone or antipyrine in the PM phenotype. There was a good correlation (r = 0.804) between the high affinity component of phenacetin O-deethylase and debrisoquine 4-hydroxylase activities. No such correlation was observed with the low affinity component of phenacetin O-deethylase activity. Although debrisoquine was a competitive inhibitor of phenacetin O-deethylase activity, phenacetin was without effect on debrisoquine 4-hydroxylation. There was also marked differences in the effects of sparteine, guanoxan and alpha-naphthoflavone on the two activities. Cigarette smoking was associated with a significant, two-fold, increase in phenacetin O-deethylase activity whilst debrisoquine 4-hydroxylase activity was not affected. It is concluded that the high affinity component of phenacetin O-deethylase and debrisoquine 4-hydroxylase activities are catalysed by different isozymes of cytochrome P-450 but that these are most probably regulated by closely linked genes.
Adult↗
Bis(trifluoromethyl)aryl derivatives for drug analysis by gas chromatography electron capture negative ion chemical ionization mass spectrometry. Application to the measurement of low levels of clonidine in plasma.
A gas chromatographic mass spectrometric assay for clonidine in plasma with a detection limit of a few picograms per ml was required. The p-trifluoromethylbenzyl, pentafluorobenzyl and pentafluorobenzoyl derivatives of clonidine were synthesized and the electron capture negative ion chemical ionization mass spectra of these compounds show extensive fragmentation with prominent ions at m/z 35 and 37 due to the two chlorine atoms in the clonidine molecule. Selected ion monitoring of specific high mass ions in these mass spectra indicated that the required sensitivity could not be obtained with these derivatives. Several bis(trifluoromethyl)pyrimidines were synthesized and these compounds were found to give an intense negative ion current under conditions of resonance electron capture. Consequently, a derivative of clonidine containing a bis(trifluoromethyl)aryl group was synthesized by reacting the drug with 3,5-bis(trifluoromethyl)benzoyl chloride. The negative ion mass spectrum of the reaction product has a base peak at m/z 673 and, when this ion is specifically monitored, an amount of derivative equivalent to 1 picogram of clonidine can be detected. This allowed the development of an assay for clonidine in plasma with a precision of 8% (SD) at 50 pg ml-1, 22% (SD) at 20 pg ml-1 and a lower limit for quantitative determination of 10 pg ml-1. Plasma concentrations of clonidine in 10 subjects given a single 50 micrograms oral dose are reported.
Clonidine↗
Is anterior ST depression with acute transmural inferior infarction due to posterior infarction? A vectorcardiographic and scintigraphic study.
The hypothesis that anterior ST segment depression represents concomitant posterior infarction was tested in 49 patients admitted with a first transmural inferior myocardial infarction. Anterior ST depression was defined as 0.1 mV or more ST depression in leads V1, V2 or V3 on an electrocardiogram recorded within 18 hours of infarction. Serial vectorcardiograms and technetium pyrophosphate scans were obtained. Eighty percent of the patients (39 of 49) had anterior ST depression. Of these 39 patients, 34% fulfilled vectorcardiographic criteria for posterior infarction, and 60% had pyrophosphate scanning evidence of posterior infarction. Early anterior ST depression was neither highly sensitive (84%) nor specific (20%) for the detection of posterior infarction as defined by pyrophosphate imaging. Of patients with persistent anterior ST depression (greater than 72 hours), 87% had posterior infarction detected by pyrophosphate scan. In patients with inferior myocardial infarction, vectorcardiographic evidence of posterior infarction correlated poorly with pyrophosphate imaging data. Right ventricular infarction was present on pyrophosphate imaging in 40% of patients with pyrophosphate changes of posterior infarction but without vectorcardiographic evidence of posterior infarction. It is concluded that: 1) the majority of patients with acute inferior myocardial infarction have anterior ST segment depression; 2) early anterior ST segment depression in such patients is not a specific marker for posterior infarction; and 3) standard vectorcardiographic criteria for transmural posterior infarction may be inaccurate in patients with concomitant transmural inferior myocardial infarction or right ventricular infarction, or both.
Diphosphates↗
Mixed venous oxygen saturation changes during tension pneumothorax and its treatment.
A case is reported of tension pneumothorax following left subclavian venous cannulation for placement of a fibreoptic pulmonary artery flotation catheter. Mixed venous oxygen saturation was continuously monitored and a fall in this was the first indication of the problem. Observations on the cardiovascular consequences of tension pneumothorax were made and followed during its treatment. The value of continuous monitoring of mixed venous oxygen saturation in the early detection of haemodynamic disturbances is emphasized.
Adult↗
Relationship between oxidative metabolism of 2-acetylaminofluorene, debrisoquine, bufuralol, and aldrin in human liver microsomes.
The capacity of human liver microsomes from 28 individuals to metabolize debrisoquine and bufuralol, two drugs oxidized polymorphically in humans, as well as the carcinogen 2-acetylaminofluorene (AAF), was determined. In addition, the cytochrome P-450 content and the capacity of these microsomes to carry out the epoxidation of aldrin were measured. Interindividual differences in debrisoquine 4-hydroxylation, bufuralol 1-hydroxylation, and aldrin epoxidation were 12-, 20-, and 2.4-fold, respectively. The metabolism of debrisoquine was not correlated with cytochrome P-450 content (r = 0.26), whereas both the metabolism of bufuralol (r = 0.45; r2 = 0.20) and the epoxidation of aldrin (r = 0.72; r2 = 0.52) were correlated. Rates of debrisoquine and bufuralol metabolism were significantly correlated (r = 0.73), whereas only weak correlations existed between debrisoquine:aldrin (r = 0.49) and bufuralol:aldrin (r = 0.51). Because biphasic kinetics have been observed in human liver microsomes for the 7- and 5-hydroxylation of AAF, two concentrations of this substrate were used. The disappearance of AAF at either 0.37 or 50 microM was not correlated with debrisoquine, bufuralol, or aldrin metabolism. Similarly, at 0.37 microM AAF, no correlation existed between the formation of N-, 1-, 3-, 5-, 7-, and 9-hydroxylation products of AAF and debrisoquine, bufuralol, or aldrin metabolism. At 50 microM AAF, only the 7-hydroxylation of this substrate correlated with bufuralol metabolism (r = 0.47). This lack of, or weak correlation between pathways leading to metabolic activation (N-hydroxylation) or detoxication (C-hydroxylation) of the carcinogen AAF and debrisoquine, bufuralol, and aldrin metabolism strongly suggests that different forms of cytochrome P-450 are involved in these pathways. In contrast, exceptionally high correlations (r greater than 0.94) existed between N-OH-AAF:1-OH-AAF. N-OH-AAF:7-OH-AAF, and 7-OH-AAF:1-OH-AAF at the low concentration of AAF, and imply that similar forms of cytochrome P-450 produce these metabolites. However, at 50 microM AAF, these correlations are considerably weaker and explain less than 35% of the variance in the data. It is concluded, based on these multiple cross-correlations, that common cytochrome P-450 isoenzymes are involved in the formation of AAF metabolites, while the metabolism of debrisoquine, bufuralol, and aldrin is unrelated to the metabolism of this carcinogen in human liver microsomes.
2-Acetylaminofluorene↗
A comparison of results-oriented and trait-based performance appraisals.
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Employee Performance Appraisal↗
Substrate specificity of the form of cytochrome P-450 catalyzing the 4-hydroxylation of debrisoquine in man.
In the present study we have investigated the substrate specificity of the form of cytochrome P-450 catalyzing the 4-hydroxylation of debrisoquine in man by analyzing the kinetics of inhibition of this activity by potential alternative substrates for the enzyme. All three compounds for which there is good in vivo evidence for an association between their metabolism and the debrisoquine oxidation polymorphism (viz., sparteine, guanoxan and phenformin) were potent competitive inhibitors of the reaction. The Ki for sparteine was 85 microM, for guanoxan it was 30 microM, and for phenformin it was 205 microM. Two compounds, acetanilide and antipyrine, for which the in vivo evidence was against an association between their metabolism and that of debrisoquine, were weak, noncompetitive inhibitors of debrisoquine 4-hydroxylase activity. The Ki values were 1.23 mM and 19.3 mM, respectively. Two additional compounds, tolbutamide and amylobarbitone, for which the in vivo evidence was also against an association between their metabolism and the debrisoquine oxidation polymorphism, did not appreciably inhibit the reaction. In fact, amylobarbitone caused a slight stimulation of activity. It is concluded that debrisoquine 4-hydroxylase is a specific form of cytochrome P-450 with a well-defined substrate specificity. Furthermore, it should be possible to identify compounds that might be subject to an oxidation polymorphism prior to the exposure of any subjects to the compound.
Antipyrine↗