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Biomedical subjects

D J Berry

Publications and source records attributed to D J Berry.

At least 91 records · Page 5Linked to original sources
PubMed1988

A rapid, enzymatic method for the determination of chloramphenicol in serum.

A simple, rapid assay of serum chloramphenicol has been developed which combines the specificity of the enzyme chloramphenicol acetyltransferase with the convenience of a colorimetric detection system. The assay is linear over the drug concentration range 5-200 microM (1.5-65 mg/l) and therefore is suitable for detection below and above the therapeutic range (31-62 microM, 10-20 mg/l with potential toxicity above 75 microM, 24 mg/l). This method does not detect the microbiologically inactive succinate or palmitate pro-drugs of chloramphenicol and evidence suggests that the major metabolite, chloramphenicol glucuronide also is not detected. Good correlation with an HPLC method has been achieved (r = 0.9860). The assay is based on a two reagent system with very simple methodology, the only instrumentation required being a spectrophotometer. However, the assay could be adapted to run on a range of discrete analysers.

Bilirubin↗
PubMed1988

The clinical use and measurement of theophylline.

This report reviews the clinical use, metabolism and toxicity of theophylline (Section 1). Current chromatographic and immunoassay methods for theophylline measurement are discussed and practical methods using high-performance liquid chromatography are described (Section 2). Results from the UK National scheme for theophylline quality control and from an experiment to investigate the degree of interference by 1,7-dimethylxanthine in routine assays for theophylline are discussed in Section 3.

Humans↗
PubMed1988

A laboratory and clinical evaluation of an immunochemiluminometric assay of thyrotropin in serum.

We evaluated an immunochemiluminometric assay for human thyrotropin. A chemiluminescent acridinium ester is used as a label, with magnetic-particle separation. The lower limit of detection of the assay (mean + 3 SD of the zero standard) was 0.07 milli-int. unit/L, with a working range of 0.5 to greater than 60.0 milli-int. units/L. Assay accuracy was good as judged from analytical recovery, analysis of external quality-assessment samples, and comparison with an enzyme-amplified immunoassay. There were no significant interferences or cross-reactivities. Twenty-four samples assayed showed aggregation of the magnetic particles. On re-assay, four of these samples showed a significant increase in the measured TSH by the luminescence assay. Assay time for 60 tubes was approximately 3.5 h with the use of a semi-automated luminometer. The reference interval, determined from data on 144 healthy euthyroid subjects, was 0.3-4.0 milli-int. units/L. Sixteen of 19 thyrotoxic patients showed clearly suppressed concentrations of thyrotropin in serum.

Cross Reactions↗
PubMed1987

Gas chromatographic analysis of phenylethylmalonamide in human plasma.

A method is described for the analysis of phenylethylmalonamide in human plasma. Analysis of plasma requires only 200 microliter of sample which is extracted with dichloroethane. After filtration and evaporation of the solvent the residue is reconstituted in 50 microliter of chloroform and 5 microliter are injected onto the gas chromatograph. The column used is a mixture of CDMS/WG11 coated on Chromosorb W HP 100-120 mesh. The method is suitable for use in single-dose pharmacokinetic studies.

Anticonvulsants↗
PubMed1987

Pharmacokinetics of phenylethylmalonamide (PEMA) in elderly men.

The pharmacokinetics of phenylethylmalonamide (PEMA) were studied in 6 elderly men after oral administration of a single 400 mg dose. Peak PEMA serum levels were obtained within 4 h of intake, half-life values ranged from 30.7-57.9 h in these elderly men. The elimination half-life was twice as long when compared to a study previously performed in young volunteers.

Aged↗
PubMed1986

Are there connections between the thalamic reticular nucleus and the brainstem reticular formation?

Increasing awareness that the thalamic reticular nucleus (TRN) plays an important role in controlling the output of cortically projecting cells in nuclei of the dorsal thalamus has focused attention on the question of whether there exist ascending projections to the TRN from the mesencephalic or other parts of the brainstem reticular formation (BRF). We have examined this and the related question of whether the neurons of TRN project to the BRF, by anterograde and retrograde tracing experiments with horseradish peroxidase (HRP) and HRP conjugated to wheat germ agglutinin. Injections of tracer were placed stereotaxically in the BRF at various depths and rostrocaudal and mediolateral coordinates, and the TRN and adjacent nuclei were examined in serial coronal sections, using tetramethylbenzidine as the principal chromogen. Retrogradely labelled cell bodies were consistently seen in hypothalamus and zona incerta but never in TRN, suggesting that, in the rat, TRN neurons do not project caudal to the thalamus. After 54 out of 60 injections, no terminal label was detected in any part of the TRN although such label was present in other parts of the thalamus, including the intralaminar nuclei, in the same sections. We therefore conclude that direct projections from the BRF to the TRN must be extremely sparse, and that those effects of BRF stimulation upon thalamocortical transmission that are mediated by the TRN (rather than by direct projections to dorsal thalamic nuclei) probably depend chiefly on indirect polysynaptic pathways.

Animals↗
PubMed1986

Phenylethylmalonamide serum levels in patients treated with primidone and the effects of other antiepileptic drugs.

Data are presented for the serum levels of 2-ethyl-2-phenylmalonamide (PEMA) in patients receiving anticonvulsant medication. Statistical analysis of these data indicates that the serum level of PEMA, which is a metabolite of primidone, is affected not only by the dose of primidone but also by the serum levels of other prescribed anticonvulsant drugs. In particular, phenobarbitone is shown to be a major perturbation upon the PEMA serum level.

Anticonvulsants↗
PubMed1982

Further characterization of a Chinese hamster ovary cell mutant defective in lanosterol demethylation.

Sensitive in vitro lanosterol 14 alpha- and 4 alpha-methylsterol oxidase assays, particularly suitable for cell extracts of tissue culture cells, were developed and validated. Using these assays, we showed that the biochemical lesion of mutant 215, a cholesterol-requiring Chinese hamster ovary cell auxotroph isolated and partially characterized previously [Chang, T. Y., Telakowski, C., Vanden Heuvel, W., Alberts, A. W., & Vagelos, P. R. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 832-836], was localized at the 4 alpha-methylsterol oxidase enzyme system. The defect in 4 alpha-methylsterol oxidase activity in mutant 215 cells could be demonstrated by using either 4,4-dimethylcholestanol or 4 alpha-methylcholestanol as the substrate, suggesting that the enzyme systems responsible for 4 alpha-methyl- and 4,4-dimethylsterols may share a common component. However, demethylation of the C-14 alpha methyl group was found to occur at identical rates in wild-type and mutant 215, suggesting that C-14 alpha demethylation and C-4 alpha demethylation may occur by separate enzyme systems. A [3H]dihydrolanosterol incorporation experiment in intact cells of wild-type and mutant 215 supported these conclusions. Despite these results, a [14C]acetate pulse experiment indicated that [14C]lanosterol, instead of its 14C-labeled 14-demethylated sterol derivative(s), accumulated in intact cells of mutant 215. Possible implications of these findings for the mechanisms of lanosterol demethylation reactions are discussed.

Animals↗
PubMed1982

Pharmacokinetics of phenylethylmalonamide (PEMA) in normal subjects and in patients treated with antiepileptic drugs.

The pharmacokinetics of phenylethylmalonamide (PEMA), a major metabolite of primidone, were investigated following administration of single oral doses (400 mg) to six normal subjects and six patients receiving chronic treatment with antiepileptic drugs. Peak serum PEMA levels were usually attained with 2-4 h after intake. The oral bioavailability estimated on the basis of the recovery of unchanged drug in the urine of normal subjects was at least 80%. Half-life values ranged from 17 to 25 h in normal subjects and from 10 to 23 h in the patients. No statistically significant difference in any of the calculated kinetic parameters could be found between the two groups. The data indicate that PEMA is readily absorbed from the gastrointestinal tract and that it is eliminated predominantly unchanged in the urine of man.

Adult↗
PubMed1979

Determination of sulthiame, tetrahydro-2-p-sulphamoyl-phenyl-2h-1,2-thiazine-1,1-dioxide, in plasma at therapeutic concentrations, using high-performance liquid chromatography.

A specific and sensitive liquid chromatographic method for the determination of sulthiame in small (0.5 ml) plasma samples is described. After adding an internal standard, a direct extract of the sample is examined by reversed-phase liquid chromatography with ultraviolet spectrophotometric detection. The method is rapid, simple and capable of determining plasma levels after therapeutic ingestion of sulthiame.

Anticonvulsants↗
PubMed1978

Determination of valproic acid (dipropylacetic acid) in plasma by gas-liquid chromatography.

A specific and sensitive procedure for the determination of valproic acid at therapeutic concentrations in human plasma has been developed. The method involves a microscale extraction of the drug from acidified plasma into chloroform. Caproic acid is added as internal standard. The extract is subsequently analysed on a gas chromatography fitted with a flame ionisation detector, and quantitation achieved by the relative-peak-height technique.

Chromatography, Gas↗
PubMed1977

Routine analysis of barbiturates and some other hypnotic drugs in the blood plasma as an aid to the diagnosis of acute poisoning.

A gas-liquid chromatographic method has been devised whereby both the qualitative and the quantitative analysis of a number of hypnotic drugs in the blood may be accomplished simultaneously. Small (50-mul) plasma aliquots are required. The technique is rapid and will detect 2 mg/l concentrations of these compounds. The barbiturates glutethimide, methaqualone, and meprobamate are the principal drugs covered by the scheme. After overdose the concentrations that occur in man are at, or above, this minimum level of detection.

Barbiturates↗
PubMed1976

Some studies of feprazone.

Feprazone, 200 mg t.d.s., was compared with indomethacin, 25 mg t.d.s. rising to 50 mg t.d.s., in an eight-week double-blind cross-over study in twenty-three patients with active rheumatoid arthritis. Both therapies proved equally efficacious and acceptable. Measurement of the plasma levels of the two drugs showed no consistent correlation between efficacy and plasma concentrations.

Adult↗