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PubMed1985

Two methods for monitoring the photodecomposition of sodium nitroprusside in aqueous and glucose solutions.

The photodecomposition of sodium nitroprusside (SNP) in aqueous and 5% glucose solutions results in the accumulation of cyanide and ferricyanide ions. Methods for the determination of these ions in such solutions have been devised. The continuous-flow method for cyanide involved the generation of cyanogen chloride, ClCN, by oxidation with chloramine T and subsequent reaction of the ClCN with barbituric acid and pyridine to produce a chromophore measurable by spectrophotometry at 580 nm. This cyanide method had a detection limit and sensitivity of 10-12 mumol/L and 1.40 X 10(-3) absorbance units (AU)/mumol/L, respectively, with a working concentration range of 0-800 mumol/L. This method employed mild reaction conditions, pH = 4.1, which rendered it suitable for use in time-course studies of cyanide production from SNP solutions exposed to 366 nm UV light. A simple method for the determination of ferricyanide in SNP solutions was developed which involved the addition of a 1% FeSO4 X 7 H2O in 1% H2SO4 reagent to the SNP solutions under test followed by spectrophotometry at 750 nm. The detection limit and sensitivity of the method were 2-3 mumol/L and 4.05 X 10(-3) AU/mumol/L, respectively, with a working concentration range of 0-100 mumol/L. This method was considered suitable for use as a quality control test of SNP solutions close to the site of their clinical use.

Drug Stability↗
PubMed1976

Uptake and incorporation of pyrimidines in Euglena gracilis.

In photoorganotrophically grown cells of Euglena gracilis the uptake and incorporation degree of 12 different pyrimidines were tested. The rate of uptake of pyrimidines has distinct maxima in the late log phase and in the stationary phase of cell multiplication. The kinetics of uptake are linear in the first 2 h, do not show saturation at various concentrations and increase with the concetrations. No accumulation of the pyrimidines at various concentrations could be observed in the first 2 h of incubation. Membrane inhibitors as uranyl acetate inhibit the uptake of the reference substance alpha-AIB, which is wellknown transported by an active transport mechanism, but have no effect on uptake rate of uracil and cytosine. It could not be observed an energy requirement tested in temperature dependence and with electron transport inhibitors. Uptake of uridine, uracil, barbituric acid and alpha-AIB is inhibited by cycloheximide in a different manner after 5 - 10 min.

Biological Transport↗
PubMed1975

Quantitation of phenobarbital and its main metabolites in human urine.

A method for the quantitative determination of phenobarbital and free and conjugated p-hydroxyphenobarbital in urine samples is described. The method includes initial extraction, purification on a small chromatographic column and finally determination by gas chromatography. The barbituric acids are methylated by trimethylanilinium hydroxide which serves as a "flash heater" methylating agent. The conjugate of p-hydroxyphenobarbital, which appears to be a glucuronide, is hydrolysed with hydrochloric acid.

Child↗
PubMed1976

[Assay of carbromal and its main metabolite (2-ethyl-butyryl-urea) in biological fluids (author's transl)].

The materials mentioned above are reextracted from an ether solution by 2 N sodium hydroxide. The UV extinction of the aqueous layer at 232 nm and 30 degrees C is followed by means of a slave recorder. The original extinction is found by back-extrapolating to the time of re-extraction. It has to be corrected for the "biological matrix" by subtracting the extinction value after complete hydrolysis. Most interfering substances in the ether solution (carboxylic acids, barbiturates) may be removed previously by washing with aqueous buffers (pH 7.0 and 10.5).

Humans↗
PubMed1995

A study of symptomatic drug use in migraine without aura.

We assessed the attack drugs taken by 200 migraine without aura patients (International Headache Society criteria, 1988) between 1989 and 1991. A detailed pharmacological history regarding the acute attack therapy adopted up until our initial visit was gathered, including the type of drug used, dosage, administration route, the time of starting therapy, treatment efficacy, and the frequency and types of undesirable effects, all of which were subsequently compared with the guidelines (1993) of the Italian Society for the Study of Headache (SISC). The most commonly used are non steroidal anti-inflammatory drugs (NSAIDs). We observed a similar high frequency in the use of combinations, particularly prophyphenazone and barbituric acid. The pirazolones, such as noramidopyrine and prophyphenazone, are also widely used as single agents, even though they are not considered by the guidelines. Our study underlines the fact that current drug use differs in several respects from the guidelines.

Adult↗
PubMed1984

Structure-activity relationship of pyrimidine base analogs as ligands of orotate phosphoribosyltransferase.

Eighty pyrimidine base analogs were evaluated as inhibitors of mouse liver orotate phosphoribosyltransferase (OPRTase, EC 2.4.2.10). Based on these findings and an extensive literature review, a structure-activity relationship has been formulated for the binding of pyrimidine base analogs to OPRTase. This study provides a basis for the rational design of new inhibitors of this enzyme, and several such compounds are proposed. Additionally, 4,6-dihydroxypyrimidine has been found to be a potent OPRTase inhibitor. Eleven OPRTase inhibitors were also evaluated as inhibitors of orotidine 5'-monophosphate decarboxylase (ODCase, EC 4.1.2.23). 5-Azauracil, 5-azaorotate, and barbituric acid inhibited ODCase significantly only after preincubation with PRPP and MgCl2 in the presence of cytosol.

Animals↗
PubMed1975

Sensory and motor representation in the cerebral cortex of the three-toed sloth (Bradypus tridactylus).

Cortical sensory receiving areas were studied in 32 specimens of the three-toed sloth, Bradypus tridactylus, using the evoked response technique and barbiturate anaesthesia. Somatotopic organization in the somesthetic first area (S-I) was shown to be similar to that reported in higher mammals. The area devoted to the representation of the forelimb was considerably larger than that for the remaining body parts. The second somatosensory area (S-II), showing bilateral representation without a precise topographical organization, was identified in the rostral portion of the ectosylvian gyrus. Visual and auditory projections, occupying restricted areas, were found along the caudal banks of the ectosylvian fissure. Electrically excitable cortical motor area was explored in 8 animals anesthetized with diallyl barbituric acid in urethane. The motor representation of the various body parts was shown to coincide with the sensory projections, demonstrating the existence in a Eutherian mammal of a sensorimotor amalgam, identical to that described in marsupials. These findings suggest that sloths display a primitive pattern of neural organization, and that the sensory motor amalgam is a generalized form of cortical organization of primitive Therian mammals.

Acoustic Stimulation↗
PubMed1984

Alteration of hepatic lipidperoxide levels during cataract formation caused by glucocorticoids in developing chick embryos.

The level of hepatic lipidperoxides in chick embryos was determined during cataract formation resulting from glucocorticoid treatment. When 15 day old chick embryos were administered 0.25 mumol of hydrocortisone acetate their hepatic lipidperoxide level, determined by thio-barbituric acid, increased after a lag time of 20 hr and reached approximately 8-fold of control at 48 hr after the treatment. These studies indicate that the peroxidation of lipid in tissues should be considered in elucidating mechanisms of action or adverse effects of glucocorticoids.

Animals↗
PubMed1996

Soluble thrombomodulin antigen in plasma is increased in patients with acute myocardial infarction treated with thrombolytic therapy.

Thrombomodulin (TM) is an integral endothelial cell membrane protein that functions as a cofactor for thrombin mediated activation of protein C. The anticoagulant functions of the protein C system are important in contributing to a hemostatic balance and prevention of thromboembolic disease. It has been suggested that impaired TM cofactor function could also constitute a prothrombotic abnormality leading to thromboembolic diseases. TM exists not only on the surface of endothelial cells but also as soluble fragment(s) circulating in plasma. The concept of a thrombotic occlusion as the critical event in acute myocardial infarction (AMI) forms the rationale for thrombolytic therapy. After successful reperfusion, patients remain at substantial risk for recurrent infarctions due to rethrombosis. The balance between procoagulant and anticoagulant mechanisms in the postthrombolytic phase have not been studied in detail. We have studied whether the plasma levels of soluble TM are influenced by thrombolytic therapy with streptokinase in patients suffering from AMI. Soluble TM concentrations increased significantly by 24 to 48 h after thrombolytic treatment, simultaneously with an increase in C-reactive protein (CRP, a marker of the inflammatory component of the cell damage) and in thio-barbituric acid reactive substances (TBARS, an indirect marker of lipid peroxidation).

Acute Disease↗
PubMed1985

High-pressure liquid chromatography separation of phenobarbitone, thiourea, and thioacetamide of toxicological interest.

It was possible, by reverse-phase high-pressure liquid chromatography (HPLC) to separate thiourea, thioacetamide, and phenobarbitone with retention times of 1.4, 1.7, and 4.7 min, respectively. Thiourea and thioacetamide are known carcinogens. Substances such as phenobarbitone, thiourea, and thioacetamide, which may be encountered in our environment, can now be identified by this technique. It is also recommended that this HPLC technique should be used routinely in the screening of the purity of substances which are being subjected to toxicity, carcinogenicity, mutagenicity, and teratogenicity evaluation. A mixture of impurities in the sodium phenobarbitone was removed in the synthesis of the 5-ethyl-5-phenyl-barbituric acid (phenobarbitone). These substances which were not thiourea or thioacetamide could have been responsible for the positive result in the in vitro degranulation test for carcinogens with sodium phenobarbitone.

Abnormalities, Drug-Induced↗
PubMed1986

Fast estimation of ATP/ADP ratio as a special step in pharmacological and toxicological studies using the cell-free translation systems.

We have developed a simple and effective reversed-phase HPLC procedure for rapid estimation of the ATP/ADP ratio in a cell-free translation system containing creatine kinase. Analysis of the acetone-extractable pool derived from a reticulocyte lysate cell-free system was carried out by automatic chromatography on S5CN-ODS stationary phase using a linear 10-65% pyridine elution gradient formed on the basis of methanol/water (9:1, v/v) mobile phase. This method was used to detect and characterize the inhibition of translation induced by considerable suppression of ATP resynthesis in vitro. It was shown that methyl mercury, unlike cycloheximide, pactamycin, CCl4 and barbituric acid, exerts inhibitory effect on the ATP regeneration in a cell-free translation system.

Adenosine Diphosphate↗
PubMed1987

Simultaneous quantitation of phenobarbitone and p-hydroxyphenobarbitone and their perdeuteroethyl analogues in biological fluids by combined gas chromatography-mass spectrometry.

In order to develop 5-pentadeuteroethyl-5-phenyl barbituric acid as an alternative tracer in pharmacokinetic and metabolic studies of phenobarbitone, and to search for possible isotope effects associated with such labelling, we propose a gas chromatographic-mass spectrometric assay for simultaneous measurement of phenobarbitone, p-hydroxyphenobarbitone and their perdeuteroethyl analogues, using [1,3-15N2,2-13C] phenobarbitone as internal standard. These compounds were extracted from plasma (50 microliter) or urine (500 microliter) and pentylated according to Greeley's method. Linear calibration curves were obtained in the concentration range from 0.5 to 3 micrograms/ml. The interday precision, mean accuracy and detection limit were 0.77-5.28%, 99.99-100.80% and 0.03-0.05 microgram/ml, respectively. Results for plasma and urine concentrations, and pharmacokinetic parameters in humans, are presented to illustrate this method.

Deuterium↗
PubMed2005

[Influence of hemodialysis on total and free malondialdehyde measured by a new HPLC method].

Accurate evaluation of oxidative stress is needed for patients on chronic hemodialysis (HD), as cardiovascular risk level seems related to it. Oxidative stress is often evaluated by measuring an end product of lipoperoxidation named malondialdehyde (MDA). However, the most common technique for measuring MDA, the Thio Barbituric Acid Reactive Substances method (TBARS), is known to be sensitive but poorly specific. We measured true total and free plasma MDA in fifty-four unselected patients on long-term HD, before and after HD sessions, by a new, highly specific HPLC method. Total and free MDA were higher before than after dialysis. Essentially, free MDA was decreased by HD but its fractional decrease was lower than that of urea or creatinine. This confirms that, in fact, free MDA is more or less bound to low molecular weight compounds and/or suggests that MDA may be produced mainly during HD sessions. We propose this new tool to further explore the relationship between oxidative stress, HD and true MDA.

Aged↗
PubMed2004

Spectroscopic studies on some azo compounds and their cobalt, copper and nickel complexes.

Synthesis and characterization of [o-carboxy phenylazo] moiety of barbituric acid, thiobarbituric acid, thiouracil, citrazinic acid, and disodium chromotropate and their complexes derived from cobalt (II), nickel (II), and copper (II) salts were done. The stereochemistry and the mode of bonding of the complexes were achieved based on elemental analysis, NMR, UV-Vis, IR and ESR. The dissociation constants of the free azo ligands are evaluated by spectrophotometric methods.

Azo Compounds↗
PubMed2001

Fast, simple and cost-effective determination of thiopental in human plasma by a new HPLC technique.

BACKGROUND: Thiopental is an anaesthetic drug that is largely used in both short-term and long-term infusion. After long-term infusion of thiopental, non-linear and inter-individual-dependent pharmacokinetics occur because of the saturation and/or induction of the metabolism. Clinical monitoring is important so that therapeutic adjustments can be made in many of the different pharmacological treatments, especially when long-term infusion is required. We describe a new, rapid HPLC method for the determination of plasma thiopental. METHODS: Sample preparation involved precipitation of plasma proteins using a mixture of methanol, zinc sulfate and ethylene glycol, and containing the internal standard 5-ethyl-5-p-tolyl-barbituric acid. After adding trichloroacetic acid, the sample was centrifuged and the supernatant was injected into a C(18) reversed-phase column. The mobile phase used was water-methanol-acetonitrile (50:40:10, v/v). The eluent was monitored at 290 nm. RESULTS: The calibration curve was linear from 0.2 to 100 microg/mL. Precision, calculated as the coefficient of variation (%), was in the range of 3.62-0.70% for the within-day assay and 5.77-1.51% for the between-day assay. The absolute recoveries obtained from supplemented samples were never less than 100%. CONCLUSIONS: This technique shows good reliability and seems to be suitable for a very fast and simple therapeutic monitoring of plasma thiopental.

Anesthetics, Intravenous↗
PubMed2000

New calixarene-bonded stationary phases in high-performance liquid chromatography: comparative studies on the retention behavior and on influences of the eluent.

The chromatographic behavior of six calixarene-bonded stationary phases is reported. Varying analyte selectivities (i.e., for phenols, substituted aromatics, polycyclic aromatic hydrocarbons, barbituric acid derivatives, xanthines) exist as a function of the ring-size of the calix[n]arenes (n=4, 6, 8) and the substitution at the "upper rim" with para-tert.-butyl groups. Although eluents with unusually high proportions of water were used, a comparison with conventional reversed-phase (RP) columns shows a predominantly reversed-phase character with remarkable selectivities of these phases. The influences of several organic solvents on retention variations of solutes are compared for RP-C18, phenyl and calixarene phases.

Calixarenes↗
PubMed2002

Substrate binding induces domain movements in orotidine 5'-monophosphate decarboxylase.

Orotidine 5'-monophosphate decarboxylase (ODCase) catalyses the decarboxylation of orotidine 5'-monophosphate to uridine 5'-monophosphate (UMP). We have earlier determined the structure of ODCase from Escherichia coli complexed with the inhibitor 1-(5'-phospho-beta-d-ribofuranosyl)barbituric acid (BMP); here we present the 2.5 A structure of the uncomplexed apo enzyme, determined from twinned crystals. A structural analysis and comparison of the two structures of the E. coli enzyme show that binding of the inhibitor is accompanied by significant domain movements of approximately 12 degrees around a hinge that crosses the active site. Hence, the ODCase dimer, which contains two active sites, may be divided in three domains: a central domain that is fixed, and two lids which independently move 12 degrees upon binding. Corresponding analyses, presented herein, of the two Saccharomyces cerevisiae ODCase structures (with and without BMP) and the Methanobacterium thermoautotrophicum ODCase structures (with and without 6-aza UMP) show very similar, but somewhat smaller domain movements. The domain movements seem to be initiated by the phosphoryl binding to the enzyme and can explain why the binding of the phosphoryl group is essential for the catalytic function.

Binding Sites↗