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PubMed1976

Rationale for apparent differences in pharmacokinetic aspects of model compounds determined from blood level data and urinary excretion data in rats.

Results of studies carried out in rats for model compounds, D-(-) mandelic acid, benzoylformic acid, and some of their para-alkylated homologs, showed that their biological half-lives determined from the elimination phase of urinary excretion data were longer than those determined from the elimination phase of blood level data. With compounds that followed multicompartment open models, the initial distributive phase (alpha-phase) noted from the blood level data was not detected from the urinary excretion data. Based on the analysis of half-life data obtained in the absence and presence of DL-tropic acid (a competitive renal tubular secretion inhibitor of these compounds), it is proposed that, besides the shortness of the alpha-phase period, the factor accounting for these compounds is their retention and/or detention in the renal tubular membranes during their tubular secretion. Furthermore, it is proposed that the renal tubular membranes do not constitute a part of the central or peripheral compartment. Examples are cited to show that, where studies are reported for the same drugs in the same human subjects in the same laboratory, drugs usually exhibit longer biological half-lives when urinary excretion data rather than blood level data are used.

Animals↗
PubMed2004

Current trends in quantitative structure activity relationships on FXa inhibitors: evaluation and comparative analysis.

This article evaluates the quantitative structure activity relationships of FXa inhibitors, using the C-QSAR program of Biobyte. Diaryloxypyridines, aminophenols, biaryl isoxazoline derivatives, 1,2-dibenzamidobenzenes, 3-amidinophenylalanine derivatives, benzoxazinones, naphthoanilides, tetrazoles, glucolic and mandelic acid derivatives were included in this survey. Clog P plays a significant role in the QSAR, especially as hydrophilicity. In the most of the cases, CMR/MR molar refractivity as well as sterimol parameters (B5 and L) are important. Electronic effects with the exception of the Hammett's constant sigmam, are not found to govern the biological activity. Es was found to be important indicator variables were used after the best model was found to account for the usual structural features.

Algorithms↗
PubMed1999

Stereoinversions using microbial redox-reactions.

This paper aims to provide a summary of the recent literature on the use of redox enzymes to carry out stereoinversion reactions on chiral secondary alcohols. Emphasis has been placed on biotransformations which result in the deracemization of a racemic substrate to give high value synthetic intermediates in a theoretical 100% yield. Most of the biocatalysts which are competent to carry out such transformations are whole cell systems, which contain the necessary cofactor recycling machinery to facilitate this otherwise entropically disfavoured process. The first section deals with deracemization of compounds such as mandelic acid and pantoyl lactone using two microorganisms which display enantiocomplementary stereospecificity. The deracemization of chiral alcohols such as beta-hydroxyesters, aryl ethanols and terminal 1,2-diols with single microorganisms will then be discussed and the influence of growth and reaction conditions on the selectivity observed will be emphasised. Then the ability of several microorganisms to deracemize by double stereoinversion substrates with two stereocentres such as cyclohexan-1,2-diol, cis and trans indan-1,2-diol and pentan-2,4-diol will be presented and some mechanistic rationale proposed. Lastly enzymes known as epimerases which are important in sugar and deoxysugar biosynthesis will be discussed with reference to some recent work on the mechanism of UDP-glucose epimerase.

Bacteria↗
PubMed1987

Stereometabolism of styrene in man. Urinary excretion of chiral styrene metabolites.

Chiral styrene metabolites obtained during initial styrene exposure of test persons were determined in urine samples using capillary gas chromatography. A typical time-dependent urinary concentration profile of one person over a 49-h period is presented and compared with the results of a previous study of occupationally exposed workers and an unexposed control group. Maximum levels of excretion of all styrene metabolites were observed at about the end of a 9-h workshift. Forty hours after exposure, the L/D-ratio of mandelic acid had subsided to the initial value, and the L/D-ratio of phenylethylene glycol to a value equal or slightly above the initial value.

Biotransformation↗
PubMed1996

Otoneurological study in workers exposed to styrene in the fiberglass industry.

Twenty workers exposed to styrene and acetone in small fiberglass factories were monitored for 8 h using passive dosimeters. Urine samples were collected at the end of the workshift and before the start of work on the next morning. The 8-h time-weighted average exposure values for styrene and acetone ranged from 14 to 416 mg/m3 and from 70 to 277 mg/m3, respectively. The sum of styrene metabolites, mandelic acid and phenylglyoxylic acid (MA + PGA), in the next-morning urine samples ranged from 81 to 943 mg/g creatinine. Different test sensitivity was identified in the otoneurological battery: it was low for audiometric tests and ABR, and relatively high for vestibular tests. The vestibular system seems partially sensitive to the toxic effects of styrene in the absence of clinical signs and symptoms. The actual exposure levels for styrene cannot be considered devoid of functional subclinical consequences.

Acetone↗
PubMed1985

Investigations on neurotoxicity of chemical substances at the workplace. VII. Longitudinal study with determination of nerve conduction velocities in persons occupationally exposed to styrene.

The aim of this longitudinal study was to investigate whether long-term exposure to styrene is associated with functional disorders of the peripheral nervous system. Eleven workers (age: 24 to 54 years) of a polyester resin boat industry were studied neurophysiologically and biochemically in 1980 and 1983. The duration of styrene-exposure varied from 3 to 7 years, with a median of 4 years. The control group was comprised of 11 non-styrene-exposed workers of similar age. Air Monitoring with passive samplers was performed on different days for each person. The mean styrene concentrations were 114, 97 and 92 ppm respectively and therefore in the magnitude of the current MAK-value of 100 ppm in the Federal Republic of Germany (FRG). For Biological Monitoring styrene in blood (S-B) and mandelic acid (MA) as well as phenylglyoxylic-acid (PGA) in urine were determined in post-shift samples. The median values for MA at four different sampling times were 816, 1660, 1101 and 1224 mg/g creatinine and for PGA 200, 273, 342 and 336 mg/g creatinine respectively. These levels were below the current "Biologischer Arbeitsstoff Toleranzwert (BAT-Wert)" for MA (2000 mg/l) and MA + PGA (2500 mg/l). The S-B concentrations ranged from 0.05 mg/l to 3.26 mg/l, with mean values of 0.92 and 0.70 mg/l. The nerve conduction velocities (NCV) of motor and sensory nerve fibers (N. ulnaris and/or N. medianus) showed no significant differences between styrene-exposed workers and age-matched control persons. There were no hints of "dose-effect-relationships" by correlation analyses. Furthermore the follow-up determination revealed no significant changes regarding NCV.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1982

Prazosin depression of baroreflex function in hypertensive man.

Prazosin is a post synaptic alpha adrenergic blocker effective in hypertension, whose hypotensive effect is unaccompanied by reflex tachycardia or hyperreninemia, nor by other evidence of increased sympathetic activity. We studied the baroreceptor reflex arc as a potential mediator of these effects. Twenty-two essential hypertensive men were treated with prazosin alone versus placebo, and experienced a blood pressure fall (from 114.8 +/- 3.6 down to 101.1 +/- 2.5 mmHg, p less than 0.005) unaccompanied by any change in heart rate, plasma renin activity, or several other indices of sympathetic nervous system activity (plasma dopamine-beta-hydroxylase activity; urinary excretion of free catecholamines and vanillyl mandelic acid; all p less than 0.1). Concomitant with the blood pressure fall, there was a significant depression of baroreflex arc sensitivity, from 11.4 +/- 2.0 ms/mmHg down to 6.6 +/- 1.9 ms/mmHg (p less than 0.05), without an associated change in cardiac vagal inhibition (291.2 +/- 46.2 versus 300.3 +/- 19.2 ms, p greater than 0.1). Baroreflex arc sensitivity depression may in part explain the lack of reflex sympathetic outflow noted during prazosin treatment of hypertension.

Adult↗
PubMed1988

Imaging evaluation of infants with neuroblastoma detected by VMA screening spot test.

In the Saitama prefecture in Japan, VMA (vanillyl mandelic acid) screening spot test for detection of neuroblastoma has been performed in 173,046 infants in the years 1981-1986 and 15 infants were found to have neuroblastoma. Two infants had mediastinal tumors and the remainder 13 had intraabdominal tumors. Only 7 infants had palpable masses. Although CT was documented to be the best imaging procedure to provide sufficient information for treatment, conventional radiographic examinations of the chest and abdomen, and abdominal ultrasonography were able, as initial imaging procedures, to detect reasonably small neuroblastomas in infants with a positive VMA screening test.

Abdominal Neoplasms↗
PubMed1986

Electron microscopic cytochemical localization of alpha-hydroxyacid oxidase in rat kidney cortex. Heterogeneous staining of peroxisomes.

The substrate specificity of alpha-hydroxyacid oxidase in the rat kidney has been investigated cytochemically by the cerium technique and biochemically with a luminometric assay applied to isolated renal peroxisomes. Rat kidneys were fixed by perfusion via the abdominal aorta with a low concentration (0.25%) of glutaraldehyde. Vibratome sections were incubated for 60 min at 37 degrees C in a medium containing 3 mM CeCl3, 100 mM NaN3 and 5 mM of an alpha-hydroxyacid in 0.1 M Pipes or 0.1 M Tris-maleate buffer both adjusted to pH 7.8. Ten aliphatic alpha-hydroxyacids with chain lengths between 2 and 8 carbon atoms and two aromatic substrates were tested. The alpha-hydroxyacid oxidase in the kidney exhibited a markedly different substrate specificity than the corresponding enzyme in the liver. Thus glycolate gave a negative reaction while two aromatic substrates, mandelic acid and phenyllactic acid, stained prominently. With aliphatic substrates a stronger reaction was obtained in Pipes than in the Tris-maleate buffered incubation media. The best reaction in the kidney was obtained with hydroxybutyric acid. These cytochemical findings were confirmed by the luminometric determination of the oxidase activity in isolated purified peroxisome fractions. By electron microscopy the electron dense reaction product of cerium perhydroxide was found in the matrix of peroxisomes in the proximal tubules. The intensity of reaction varied markedly in neighbouring epithelial cells but also in different peroxisomes within the same cell. Thus heavily stained particles were seen next to lightly reacted ones. These observations establish the substrate specificity of alpha-hydroxyacid oxidase in the rat kidney and demonstrate the marked heterogeneity in the staining of renal peroxisomes for this enzyme.

Alcohol Oxidoreductases↗
PubMed1976

Alteration of O,O-dimethyl S-[alpha-(carboethoxy)benzyl] phosphorodithioate (phenthoate) in citrus, water, and upon exposure to air and sunlight.

The fate of 32P- and 14C-labeled O,O-dimethyl S-[alpha-(carboethoxy)benzyl] phosphorodithioate (phenthoate) was determined in citrus, water, and upon exposure to air and sunlight. The products recovered from citrus and glass plates exposed to sunlight were unchanged phenthoate, phenthoate oxon, demethyl phenthoate, mandelic acid, bis-[alpha-(carboethoxy)benzyl] disulfide, O,O-dimethyl phosphorothioic and phosphorodithioic acid. Similar products generally were found in citrus leaf and fruit extracts. Phenthoate was fairly stable in phosphate buffered water with a half-life of approximately 12 days at pH 8.0. The major hydrolysis products were phenthoate acid, demethyl phenthoate and demethyl phenthoate oxon.

Air↗
PubMedDate not supplied

Lack of uniformity in the clinical approach to the interpretation of urinary catecholamines and their metabolites.

A study of the case notes from 101 of the 113 instances where at least one of the results was abnormal from the analysis of 24 hr urinary collections for noradrenaline, adrenaline, and dopamine and their metabolites 4-hydroxy-3-methoxy-mandelic acid (HMMA) and homovanillic acid (HVA) in screening for phaeochromocytomas in hospitals affiliated to the Royal College of Surgeons in Ireland Medical School from a total of 199 false positives from all sources shows that 51% had a second sample, 33% had ultra sound, 12% had a CT scan, 6% had an 131I metaiodobenzylguanadine (MIBG) scan, 40% had no imaging performed and in 5% the reports were not received by the referring medical team. The 12 sets of data where case notes could not be retrieved were disregarded. Of the 22 patients with one or more biochemical value greater than twice the upper reference range, 8 had not, by our criteria had a phaeochromocytoma positively excluded. The sensitivity and specificity for phaeochromocytoma diagnosis for the free catecholamines together was 82% and 88.4%; for HMMA 60% and 95.8%; and for catecholamines and HMMA together 82% and 93.2% respectively. A protocol which includes repeat samples where results are abnormal and the appropriate use of diagnostic imaging should be systematically pursued to minimise false negative diagnoses.

Adolescent↗
PubMed2003

Clinical usefulness of iodine-123-MIBG scintigraphy for patients with neuroblastoma detected by a mass screening survey.

UNLABELLED: The purpose of this study was to evaluate the usefulness in a clinical setting of iodine-123-metaiodobenzylguanidine (123I-MIBG) scintigraphy, planar and single photon emission computed tomography (SPECT) images, in patients with neuroblastoma as detected by a mass screening survey. METHODS: 123I-MIBG planar whole body images, and regional SPECT images of patients with neuroblastoma in 51 studies were reviewed. They were all detected by a mass screening survey performed in the 6th month after birth using vanil mandelic acid (VMA), and homovanillic acid (HVA) and the neuroblastoma had been confirmed by surgery. Scintigraphy was performed 24 hours after injection of 111 MBq of 123I-MIBG. We assessed the accuracy of the planar whole body images in order to demonstrate the extent of the lesion and the correlation between the degree and extent of the lesions of 123I-MIBG accumulation and clinical staging with tumor markers, such as urinary VMA, urinary HVA, serum neuron specific enolase (NSE) and serum lactate dehydrogenase (LDH). Additionally, we evaluated SPECT how useful supplemental SPECT might be in a clinical setting as compared with planar whole body images. RESULTS: 123I-MIBG planar whole body images revealed all 33 (100%) primary lesions, 4 of the 5 cases (80%) with liver metastasis, 3 of the 13 (23%) with lymph nodes metastasis and 1 of 3 (33%) with bone marrow infiltration. The extent and degree of accumulation correlated with the values of urinary VMA, urinary HVA and serum NSE. SPECT images helped to understand the positional relation in all cases and provided useful additional information for clinical staging in 7 cases. CONCLUSION: 123I-MIBG scintigraphy with planar and SPECT images is useful for evaluating patients with neuroblastoma, following detection by a mass screening survey.

3-Iodobenzylguanidine↗
PubMed1994

Cyclic Cushing's syndrome due to ectopic ACTH secretion by an adrenal pheochromocytoma.

Pheochromocytoma is a rare cause of ectopic Cushing's syndrome. We report on such a patient in whom ectopic ACTH secretion displayed a cyclic pattern. A 35-year-old woman was referred to us with a diagnosis of ACTH-dependent Cushing's syndrome. A 3.3 cm left-sided adrenal mass was noted at abdominal computerized tomography. At admission, clinical and hormonal data were unrewarding, so it was decided to continue to observe the patient. Four months later, she became symptomatic with hypertensive and psychotic crises and glycemic decompensation. By that time, a full-blown Cushing picture was evident. Severe hypercortisolism was documented with urinary free cortisol ranging 1500-2200 micrograms/24 h, serum cortisol 143-160 micrograms/dl and plasma ACTH 167-218 pg/ml. Neither ACTH nor cortisol values were significantly modified after high-dose dexamethasone, oCRH or metyrapone. Urinary catecholamine and vanilyl mandelic acid excretion were moderately elevated. Chest CT and total body MIBG scan were negative and magnetic resonance of the sella region was inconclusive. No center to periphery ACTH gradient was observed by inferior petrosal sinus catheterization, whereas a significant left to right gradient was found on selective adrenal vein catheterization. A left adrenalectomy was performed and a 4 cm medullary neoplasia was removed. The cells were immunostained for ACTH, neuron-specific enolase and A chromogranin. Signs and symptoms of Cushing's syndrome resolved with normalization of basal and dynamic endocrine evaluations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗
PubMed2005

Purification and characterization of an enantioselective arylacetonitrilase from Pseudomonas putida.

The highly enantioselective arylacetonitrilase of Pseudomonas putida was purified to homogeneity using a combination of (NH4)2SO4 fractionation and different chromatographic techniques. The enzyme has a molecular weight of 412 kDa and consisted of approximately nine to ten identical subunits (43 kDa). The purified enzyme exhibited a pH optimum of 7.0 and temperature optimum of 40 degrees C. The nitrilase was highly susceptible to thiol-specific reagents and metal ions and also required a reducing environment for its activity. These reflected the presence of a catalytically essential thiol group for enzyme activity which is in accordance with the proposed mechanism for nitrilase-catalyzed reaction. The enzyme was highly specific for arylacetonitriles with phenylacetonitrile and its derivatives being the most preferred substrates. Higher specificity constant (kcat/K(m)) values for phenylacetonitrile compared to mandelonitrile also revealed the same. Faster reaction rate achieved with this nitrilase for mandelonitrile hydrolysis was possibly due to the low activation energy required by the protein. Incorporation of low concentration (<5%) of organic solvent increased the enzyme activity by increasing the availability of the substrate. Higher stability of the enzyme at slightly alkaline pH and ambient temperature provides an excellent opportunity to establish a dynamic kinetic resolution process for the production of (R)-(-)-mandelic acid from readily available mandelonitrile.

Acetonitriles↗
PubMed2002

Simultaneous determination of styrene, toluene, and xylene metabolites in urine by gas chromatography/mass spectrometry.

Exposure to styrene, toluene, and xylene (STX) frequently occurs in various industrial settings leading to several adverse health effects. Therefore, the biological monitoring by determination of urinary mandelic acid (MA) and phenylglyoxylic acid (PGA), hippuric acid (HA), and 2-, 3-, and 4-methylhippuric acids (2-, 3-, and 4-MHAs), the metabolites of STX, is required or at least recommended in case of workers exposed by these agents. Considering the fact that co-exposure to STX frequently occurs, methods that have been described for the separate analysis of these compounds in urine samples cannot be used effectively for monitoring. Therefore, a reliable gas chromatographic/mass spectrometric (GC/MS) method was developed for the simultaneous identification and quantification of these metabolites. Following solid phase extraction of the urine samples, the extracts were silylated and analyzed by GC/MS using a HP-5MS capillary column. The method was evaluated for linearity, limits of detection and quantification, and specificity, as well as for precision, extraction efficiency, and stability at three different concentrations prepared in urine. The assay was linear up to 0.16 mg/ml for MA, and 0.32 mg/ml for PGA, HA, and 2-, 3- and 4-MHAs. The limits of detection and quantification of STX metabolites varied between 0.001 and 0.02 mg/ml, and from 0.01 to 0.04 mg/ml, respectively. The within-day and between-day precision, determined at low, medium, and high concentrations, ranged from 2 to 12% and 2 to 19%, respectively. The extraction efficiency was 70-80%. No degradation of the metabolites occurred in the urine samples under the possible working conditions. The method was applied for the analysis of the urine samples from exposed workers. The cost- and time-effectiveness, the technical advantages and validity parameters of this GC/MS analysis make it suitable for biological monitoring of mixed exposure to styrene, toluene and xylene.

Environmental Monitoring↗
PubMed2000

Analytical control of silica glass production. Voltammetric determination of titanium and iron in raw materials and silica glass samples.

Adsorptive stripping voltammetric (AdSV) methods are presented for the determination of titanium and iron in quartz and silica glass samples obtained after pressure decomposition. Mandelic acid and catechol were used as complexing agents for titanium and iron, respectively. The method for titanium determination is based on the catalytic effect of chlorate ions. An insoluble residue remaining after decomposition of quartz and silica glass samples in HF+H2SO4 mixture was checked by energy-dispersive X-ray analyses. ET-AAS was applied as a reference method to AdSV measurements.

Journal Article↗
PubMed1997

Ethnic differences in biological monitoring of several organic solvents. I. Human exposure experiment.

OBJECTIVES: In order to improve the reliability of biological monitoring and the development of biological limit values, ethnic differences for several organic solvents were studied in Orientals and Caucasians. METHODS: Six Caucasian and six Oriental volunteers were exposed to each organic solvent in an exposure chamber for 6 h. Exposure concentration to each organic solvent studied was 50 ppm for perchloroethylene, 50 ppm for styrene and 100 ppm for m-xylene, respectively. Biological monitoring was carried out for the parent organic solvents in exhaled air and in blood, and for the metabolites in urine during and after exposure. RESULTS: Caucasians showed higher concentrations of perchloroethylene in exhaled air than Orientals after exposure. But Caucasians showed lower concentrations of styrene in the exhaled air than Orientals during the second half of exposure and after it. Orientals showed lower concentrations of urinary metabolites than Caucasians except for mandelic acid. There were no statistically significant differences in the concentrations of solvent in blood for all three solvents. CONCLUSIONS: Implications of these differences in biological levels, under identical exposure conditions, are discussed in the context of biological monitoring.

Adult↗