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Biomedical subjects

A Castro

Publications and source records attributed to A Castro.

At least 505 records · Page 28Linked to original sources
PubMed1978

An automated turbidimetric rate method for immunoglobulin assays.

A turbidimetric rate method for the determination of immunoglobulins IgG, IgA, and IgM has been adapted to an automatic kinetic rate analyzer. The procedure can be run on mildly lipemic sera without correction for sample light scatter. We report correlations with results by an immunodiffusion method and a manual laser nephelometric technique. The automated rate procedure described provides a rapid, accurate, precise and sensitive way to measure immunoglobulins.

Humans↗
PubMed1978

HI rubella antibody determination. (A comparison of methods proposed for the removal of non-specific inhibitors).

The Authors consider the different methods so far proposed for the selective removal of non-specific inhibitors for HI rubella antibodies. They show that the best results are obtained by dextran sulphate and acetone treatments, while the kaolin and heparin-MnCl2 procedures should be avoided especially in the serological diagnosis of acute rubella infection. The presence of specific IgM was demonstrated by 2-mercaptoaethanol.

Acetone↗
PubMed1978

A practical routine gas chromatographic determination of phenobarbital, primidone and diphenylhydantoin.

A gas chromatographic method for the routine determination of phenobarbital, primidone and diphenylhydantoin using alkaline extraction and on-column methylation has been developed. The procedure has been optimized for recovery of all three anticonvulsant drugs with particular attention to primidone. Correlation with photometric methods for phenobarbital and diphenylhydantoin show the technique offers significant advantages in both accuracy and precision over other methods.

Chromatography, Gas↗
PubMed1978

Kinetic studies on the formation of nitrosamines I. Formation of dimethylnitrosamine in aqeous solution of perchloric acid.

The kinetics of nitrosation of dimethylamine (DMA) in aqueous perchloric acid solution have been studied using a differential spectrophotometric technique. The rate law is Initial rate = e[DMA]0 [nitrite]2 0 [H+]/(f + [H+])2 where [DMA]0 and [nitrite]0 represent initial stoichiometric concentrations. At 310.0 K and mu = 2.0 M, e = (2.2 +/- 0.2) X 10(-5) M-1 s-1 and f = (1.28 +/- 0.02) X 10(-3) M. The associated activation energy is 56 +/- 3 kJ mol-1. A clear inhibition of the nitrosation rate by ionic strength has been observed in which only the kinetic parameter (f) has an effective change. It is concluded that under the experimental conditions of this work only the dinitrogen trioxid is the effective carrier for the nitrosation.

Dimethylnitrosamine↗
PubMed1978

Determination of drugs of abuse in body fluids by radioimmunoassay.

Only recently has radioimmunoassay been used for the detection of drugs of abuse in body fluids. The radioimmunoassay method is rapid, sensitive, specific, and can be performed with a minimum of sample, while conventional assay methods are time-consuming, relatively insensitive, and require a larger sample volume. Performance of individual radioimmunoassays is identical, and requires about one hour to complete. The radioimmunoassays which have been developed for measurement of drugs of abuse in humans are reviewed in this paper. These new techniques are of importance in individual and/or emergency testing, in screening, and in further research into the effect of these drugs on the functions of the human body.

Amphetamines↗
PubMed1978

Evaluation of EMIT methods for the determination of the five major antiepileptic drugs on an automated kinetic analyser.

We have evaluated the performance of enzyme-multipled immunoassay methods for the five major antiepileptic drugs on an automated system, the Perkin-Elmer Model KA-150 Kinetic Analyzer. The precision in the normal duplicate mode was found to be in the range of 6% to 10% for all five tests over a typical working day. All EMIT methods were compared to gas-liquid chromatographic procedures and, in addition, the phenytoin and phenobarbital assays were compared to a liquid-chromatographic method. The phenytoin assay was also compared to RIA and to a manual spectroscopic method. In general, most of the comparison studies resulted in acceptable correlation, although one gas chromatographic method did not correlate very well with the phenytoin and phenobarbital immunoassays.

Anticonvulsants↗
PubMed1978

Inhibition of testosterone 5 alpha-reductase by and antiandrogenicity of allenic 3-keto-5,10-secosteroids.

(4R)-5,10-seco-19-norpregna-4,5-diene-3,10,20-trione(II), A 3-keto-5,10-secosteroid which is an irreversible inhibitor of delta 5-3-ketosteroid isomerase was tested for its possible antiandrogenicity in the hamster flank organ test. The organs of female animals topically treated with 4 microgram of testosterone propionate (TP) for 4 weeks enlarged in size and showed pigmentation resembling adult males. When compound II was applied concomitantly with TP, androgenic stimulation was completely blocked and the flank organs remained small like those of female animals. These results suggest that compound II may be a useful anti-androgen when applied topically. It may well act mainly by inhibition of the formation of 5alphs-reduced metabolites was markedly inhibited.

5-alpha Reductase Inhibitors↗
PubMed1978

Pyrimidine nucleotide synthesis in rat embryo cells infected with X14 or H-1 parvovirus.

The activity of some enzymes involved in pyrimidine nucleotide synthesis was studied in rat embryo cell (REC) cultures infected with X14 or H-1 parvovirus. dCMP aminohydrolase activity of the infected cells was 64--121% greater than that of the mock-infected cells. dTMP synthetase activity was 18% greater in X14 virus-infected cells and 34% lower in H-1 virus-infected cells. These results suggest some differences in the infected cells, as regards the biosynthesis of dTMP. Orotate phosphoribosyltransferase and orotidylate decarboxylase activities appeared nearly unmodified compared to the mock-infected cells. The addition of phosphoribosylpyrophosphate (PRPP) to the cell suspension incubated with [6-14C] orotate increased the specific radioactivity of acid-soluble uracil, 5-fold in the mock-infected cells and 15- --24-fold in the X14 or H-1 virus-infected cells (72 hr p.i.). This result suggests that the lowered pyrimidine nucleotide synthesis in infected cells depends to a large extent on the diminished PRPP pool.

Carboxy-Lyases↗