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Biomedical subjects

J E Stafford

Publications and source records attributed to J E Stafford.

18 recordsLinked to original sources
PubMed1989

Evaluation of antisera to 5-(2-bromo-E-ethenyl)-2'-deoxyuridine for the radioimmunoassay of a potent antiviral agent.

The production and evaluation of antibodies specific for 5-(2-bromo-E-ethenyl)-2'-deoxyuridine (BVDU) is described. Antibodies were raised against 5-(2-carboxy-E-ethenyl)-2'-deoxyuridine bovine albumin conjugates (CVDU20-BA and CVDU54-BA) and 5'-carboxy-propionyl-BVDU7-BA. The molar substitution ratio of the conjugates was determined by differential ultraviolet absorption or isotope dilution and compared to a newer method based upon the determination of unsubstituted protein residues. Usable antibody titers were obtained from all the New Zealand White rabbits immunized, but only one-third of the half-lop rabbits responded. The antisera were highly specific for BVDU and did not significantly cross-react with naturally occurring nucleosides, pyrimidines, or sugars. However, the lowest cross-reaction observed (0.21%) for the major metabolite bromovinyl uracil using antisera raised to CVDU-BA could not ensure adequate assay specificity under all conditions of use. An alternative approach using 5'-carboxy-propionyl-BVDU7-BA proved unsuccessful because the antisera could not discriminate between BVDU and bromovinyl uracil.

Animals↗
PubMed1987

The evaluation and application of a radioimmunoassay for the measurement of diphenoxylic acid, the major metabolite of diphenoxylate hydrochloride (Lomotil), in human plasma.

Antibodies to diphenoxylic acid, the pharmacologically active metabolite of Lomotil, were successfully used to develop a precise and specific radioimmunoassay for the measurement of diphenoxylic acid in human plasma. The observed cross-reaction of the antiserum with Lomotil (23.5%) and p-hydroxy diphenoxylic acid (2.9%) was not considered to affect significantly the accuracy of the direct determination of diphenoxylic acid in plasma from human volunteers after ingestion of Lomotil tablets. Within-day and between-day coefficients of variation were better than 3 and 6%, respectively, over the concentration range of 3.4 to 255 ng ml-1. Comparable precision could be achieved at 2 ng ml-1 by doubling the volume of sample analyzed. The assay was used to measure plasma concentrations of diphenoxylic acid in 12 human volunteers for up to 24 hr after ingestion of Lomotil (10mg) tablets. Plasma diphenoxyllic acid levels rose to a mean (SE) maximum level of 87.8 (2.7) ng ml-1 3.3 (0.3) hr after dosing. By 24 hr after dosing plasma levls had decreased to 14.26 (1.67) ng ml-1. The appearance and elimination of plasma diphenoxylic acid could be described by a biexponential function. The appearance half-life was calculated to be 0.82 (0.09) hr, and the elimination half-life was 7.24 (0.73) hr.

Diphenoxylate↗
PubMed1987

Single- and multiple-dose pharmacokinetics of nufenoxole in healthy human subjects.

1. In 12 healthy subjects, after single doses of 20, 40 and 80 mg of nufenoxole, mean peak plasma drug concentrations of 400, 815 and 1463 ng/ml were reached at 2.2, 2.5 and 2.5 h respectively. 2. Nufenoxole was absorbed with an apparent half-life of less than one hour at all three doses. Nufenoxole concentrations declined biphasically after the peak, with an initial and terminal half-life of four to five hours and about 27 h respectively. These half-lives were independent of the administered dose. 3. AUC and Cmax increased with increasing dose, but AUC did not increase proportionately to dose, due to a lower value for 80 mg than expected, possibly reflecting reduced absorption. 4. Observed nufenoxole concentrations, in another 12 healthy subjects receiving single, daily 80 mg oral doses of nufenoxole for eight days, were in excellent agreement with those predicted from single-dose pharmacokinetics.

Adolescent↗
PubMed1982

Application of 125I-labelled second antibody to the solid-phase immunoassay of norethisterone in plasma.

The concept of employing 125I-labelled second antibodies for making quantitative measurements of small molecules in biological fluids was evaluated. In a model system 125I-labelled second antibodies were used to monitor the binding of purified norethisterone antibodies to albumin-norethisterone complexes immobilised upon plastic tube surfaces. Conditions were established to provide an assay response similar to other immunoassays for norethisterone using the same primary antiserum. The specificity and accuracy of the assay were comparable to the conventional solid and liquid-phase assays, but precision tended to be less at low levels of norethisterone (less than 200 pg/tube). A reduction in assay variance may be achieved through more efficient tube-washing procedures.

Contraceptives, Oral, Combined↗
PubMed1981

Haloperidol pharmacokinetics: a preliminary study in rhesus monkeys using a new radioimmunoassay procedure.

The development, validation, and application of a new radioimmunoassay for haloperidol in biological fluids is described. The antiserum, raised against N-amino-butyl chlorophenyl piperidine bovine albumin conjugate, could not distinguish between haloperidol and its reduced metabolite, but it could discriminate against chlorophenyl piperidine (cross-reaction 2.6%). The fluorophenyl metabolites of haloperidol were not recognized by the antiserum. Haloperidol determinations were made on less than 100 microliter aliquots of human and rhesus monkey plasma or diluted urine without prior extraction of the sample. The radioimmunoassay was applied to the study of the pharmacokinetics of intravenous haloperidol administration to two male rhesus monkeys. Salient features of the results are as follows. As with man, the plasma concentration versus time curve could be resolved into three compartments, but there were differences in the distribution of haloperidol between the compartments. The apparent volume of distribution for the two monkeys examined was 5.87 L kg-1 and 7.37 L kg-1, considerably smaller than in man, a difference almost entirely due to a much smaller tissue compartment. The biological half-life of 15.97 hr and 7.56 hr was similar to man. The mean hepatic extraction ratio was calculated to be 0.032 and 0.056, and the data suggested that hepatic metabolism of haloperidol may be of lesser importance in rhesus monkey than in man. An insignificant proportion (0.01%) of the administered dose was excreted as haloperidol in the urine.

Animals↗
PubMed1980

Universal reagent immunosorbent assay (URI) for haptens.

Preliminary data on the use of a universal reagent, 125I-labelled second antibody, for the measurement of small molecules using immunosorbent techniques are described. The results showed that for two chemically unrelated haptens, norethisterone and diphenoxylic acid, the procedure could be optimised to measure these molecules at concentrations similar to those measurable using conventional liquid-phase or solid-phase techniques. No significant loss of norethisterone-antibody specificity could be demonstrated.

Animals↗
PubMed1979

Solid-phase radioimmunoassay for norethisterone.

Exposure of polystyrene tubes to solutions of glutaraldehyde was shown to provide a stable and consistent surface for immobilising an unpurified norethisterone-specific antiserum. Properties of the solid-phase antiserum were evaluated with respect to its application in developing a solid-phase radioimmunoassay for norethisterone. The assay proved to be sufficiently accurate, precise and sensitive for routine use. The technology is considered to be suited to automation.

Antibody Specificity↗
PubMed1979

Bioavailability and pharmacokinetics of norethisterone in women after oral doses of ethynodiol diacetate.

Measurement by radioimmunoassay of plasma norethisterone (NE) has been used to compare the bioavailability of tablets containing ethynodiol diacetate (EDA) with that of a standard oral solution of this progestogen in 12 normal women. The tablets investigated were from three batches which showed different in vitro dissolution rates. There were no significant differences in the bioavailability of the tablet formulations, which were essentially bioequivalent to the solution. Peak blood levels of NE were reached within 4h of EDA administration in solution or tablets. After the peak, NE plasma levels declined in two phases, with a mean terminal elimination half lives of 4 to 6.9h. The pharmacokinetics of NE after EDA administration showed some similarity to those observed by other workers after oral doses of NE itself.

Adult↗
PubMed1976

Ultraviolet enhanced reactivation of a human virus: effect of delayed infection.

The ability of UV-irradiated herpes simplex virus to form plaques was examined in monolayers of CV-1 monkey kidney cells preexposed to UV radiation at different intervals before virus assay. From analysis of UV reactivation (Weigle reactivation) curves it was found that as the interval between cell UV irradiation (0-20 J/m2) and initiation of the virus assay was increased over a period of five days, (1) the capacity of the cells to support unirradiated virus plaque formation, which was decreased immediately following UV exposure to the monolayers, increased and returned to approximately normal levels within five days, and (2) at five days an exponential increase was observed in the relative plaque formation of irradiated virus as a function of UV fluence to the monolayers. For high UV fluence (20 J/m2) to the cells, the relative plaque formation by the UV-irradiated virus at five days was about 10-fold higher than that obtained from assay on unirradiated cells. This enhancement in plaque formation is interpreted as a delayed expression of Weigle reactivation. The amount of enhancement resulting from this delayed reactivation was several fold greater than that produced by the Weigle reactivation which occurred when irradiated herpes virus was assayed immediately following cell irradiation.

Animals↗
PubMed1976

Serum triiodothyronine determination in clinical use.

Two radioimmunassays for the determination of serum triiodothyronine (T3) were developed. The assay of T3 in unextracted serum had several advantages over the assay on extracted serum and was chosen for the routine determination of T3 in serum from 117 patients requiring assessment of their thyroid status. In 53 subjects considered retrospectively not to have thyroid dysfunction nor to have been on steroid contraceptives or therapy, the pooled mean serum T3 concentration was 1-92 (actual range 0-88-2-62) nmol/l. A significant inverse relationship was observed between the serum T3 level and the age of the subject. Serum total T3 levels discriminate clearly between hypo-,eu- and hyperthyroid patients and provide a rather more sensitive index of hyperthyroid function than total serum T4. In the face of normal serum T4 the T3 level was depressed in five patients with marked hypoproteinaemia and elevated in two patients taking heroin.

Age Factors↗
PubMed1973

A comparative study of five laboratory tests for foeto-placental dysfunction in late pregnancy.

Five foeto-placental function tests were studied in parallel in normal and abnormal late pregnancies with a view to establishing which test or tests is most satisfactorily able to identify the mother whose foetus is in danger.A critical examination of the levels in blood serum of two enzymes, placental phosphatase isoenzyme and cystine aminopeptidase, the polypeptide hormone placental lactogen (chorionic somatomammotrophin), and the oestrogen oestriol-17beta is described.A correlation was attempted beween clinical data and the results of the above laboratory analyses and also with the daily urine oestrogen output. The plasma and urine oestriol levels proved generally to be the more useful warning tests in late pregnancy, whilst the plasma cystine aminopeptidase was the least sensitive indicator of foeto-placental dysfunction.

Aminopeptidases↗