Biomedical subjects
Publications and source records attributed to V Marks.
1. Serum concentrations of phenytoin were studied by radioimmunoassay in five normal volunteers following a single oral dose of phenytoin sodium (100 mg). 2. Two distinct peaks were found at 2.5-3.5 and 10-12 h after ingestion. Maximum serum concentrations ranged from 1.56 mug/ml. The mean plasma half-life of the drug under these conditions was 9.81 +/- 0.66 (s.e. mean) hours.
A report on the progress of the M.Sc. courses in clinical biochemistry run at the University of Surrey over the past 7 years is given. The previous experience and qualifications of the students and their careers subsequent to taking the course are analysed. A description of the course structure and syllabus is given. It is concluded that the course has been useful in attracting both science graduates and medical graduates of high calibre, in providing them with a sound laboratory-based training in clinical biochemistry, and in stimulating their interest in following a career in clinical biochemistry and chemical pathology.
Antibodies, for use in radioimmunoassay, have been raised in sheep by immunization with a conjugate of delta9-tetrahydrocannabinol hemisuccinate and bovine serum albumin. Antiserum titre and avidity were increased by successive booster doses of conjugate. The high degree of non-specific binding encountered in the radioimmunoassay of cannabinoids was reduced by the use of the solubilizing detergent Triton X-405 and by restricting protein concentration in the assay medium. Plasma samples were deproteinized with ethanol before assay, but urine was directly assayed. High avidity antibodies and high specific activity [3H]-delta9-tetrahydrocannabinol permitted the detection of 50 pg of cross-reacting cannabinoids--a sensitivity of 7-5 ng ml-1 of plasma and 1-0 ng ml-1 of urine. Whilst apparently specific for the three-ringed cannabinoid nucleus, the assay antiserum cross-reacted with several cannabinoids, both natural compounds and metabolites. Partial identification of cross-reacting cannabinoids was achieved by the use of pure compounds and by the assay of plasma and urine samples collected from rabbits given pure cannabinoids intravenously.
This paper describes the use of screened transfusion plasma as a source of human thyroid stimulating hormone (h-TSH) free protein for standardization of a conventional "double antibody" h-TSH radioimmunoassay. Serum and plasma immunoreactive h-TSH levels have been shown to be stable for up to four days at 4 degrees C and 25 degrees C. A 37 degrees C incubation procedure has been developed which gives an acceptable standard curve, but with some loss of "between batch" precision.
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An antiserum raised in sheep against a conjugate of tetrahydrocannabinol with bovine serum albumin has been used as the basis of a radioimmunoassay for cannabinoids in the blood of rabbits given tetrahydrocannabinol, 11-hydroxy-tetrahydrocannabinol, cannabinol or cannabidiol by rapid intravenous injection. In the case of both 11-hydroxy-tetrahydrocannabinol and cannabinol plasma cannabinoid concentrations fell exponentially from an initial peak plasma level attained immediately after the completion of intravascular distribution of the injected bolus. In the case of tetrahydrocannabinol itself, however, there was a progressive rise in plasma cannabinoid concentration between five and fifteen minutes after the rapid intravenous injection. The reasons for this rise in plasma cannabinoid concentration are discussed.
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A radioimmunoassay for etorphine has been developed using antibodies raised in a rabbit against an etorphine-3-hemisuccinate-bovine serum albumin conjugate. Using tritiated etorphine as the label, the antiserum could be used at a final dilution of 1:4 and had an avidity of 1.8 times 10-9 L.M.-1. The sensitivity of the assay was 0.88 plus or minus 0.04 ng etorphine per ml of serum and there was no cross-reactivity with any of the six opiate alkaloids examined over the range 0-100 ng/ml.
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The effectiveness of (Fab')2 G-Anti-D regarding elimination of D-incompatible fetal erythrocytes, and suppression of the formation of specific antibody, was investigated in 16 probands. Using 51Cr labelled D-incompatible fetal erythrocytes and simultaneous HbF-cell counting, fast elimination of incompatible red cells, and selective accumulation in the spleen, were observed after injection of small doses of (Fab')2 G-Anti-D. None of the probands showed active formation of anti-D after 3-12 months. The doses of the (Fab')2 G-Anti-D preparation used were similar to those employed in routine use of IgG-Anti-D. The results emphasize the importance of fast immunelimination of potentially antigenic red cells and thus point to a peripheral mechanism of anti-D prophylaxis by specific anti-D.
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A radioimmunoassay (R.I.A.), using a sheep antiserum and 3-H-T.H.C., has been developed for the measurement of tetrahydrocannabinol (T.H.C.) in plasma and urine. The antiserum cross-reacts with T.H.C. metabolites, but nevertheless possesses sufficient group specificity and sensitivity to permit measurement of cannabinoids in plasma and urine of animals and volunteers following the administration of pure T.H.C. Subjective effects experienced by the volunteers seemed to correlate with plasma-T.H.C. levels. The examination of random plasma urine samples collected from patients attending a drug-addiction clinic revealed the presence of measurable amounts of cannabinoids in several of them.
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