Biomedical subjects
Publications and source records attributed to M R Redshaw.
Progesterone levels in the milk of cows were determined by two radioimmunoassay methods. Excellent correlation (r = 0.95) was found between the method using an iodinated radioligand and that using a conventional tritiated tracer.
We have used a simple and precise radioimmunoassay to measure trypsin in human plasma. Fasting plasma trypsin concentrations were extremely low in patients with chronic pancreatitis with steatorrhoea (5 +/- 2 ng/ml) when compared to healthy controls (86 +/- 7 ng/ml, p less than 0.001). In patients with chronic pancreatitis but no steatorrhoea basal plasma trypsin levels were similar to those of the normal controls (99 +/- 25 ng/ml). A small but significant postprandial rise in plasma trypsin concentrations was observed in normal subjects (mean increment 15 +/- 4%, p less than 0.005, paired t test) but was absent in patients with chronic pancreatitis with steatorrhoea. In contrast to exocrine deficient chronic pancreatitis, other malabsorptive conditions associated with steatorrhoea (active coeliac disease and acute tropical sprue) demonstrated mean fasting trypsin concentrations similar to controls. Patients with adenocarcinoma of the pancreas had basal trypsin concentrations similar to healthy subjects as did patients with adenocarcinoma of the stomach, colon, rectum, brochus, and breast. In some cases measurement of plasma trypsin may be of help in the differential diagnosis of steatorrhoea.
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Eight homologous and heterologous 125I-radioligand systems for the radioimmunoassay of progesterone were examined. Using an antiserum raised to 11alpha-hydroxyprogesterone 11-succinyl-bovine serum albumin, standard curves were set up with the homologous radioligands, 11alpha-hydroxyprogesterone 11-succinyl-[125I]-iodotyramine, -[125I]-iodohistamine and -[125I]-iodotyrosine methyl ester. Heterologous bridge systems were represented by progesterone-11alpha-oxycarbonyl-[125I]-iodotyrosine methyl ester and 11alpha-hydroxyprogesterone 11-phthalyl-[125I]-iodotyrosine methyl ester, and heterologous site systems by progesterone-3-(O-carboxymethyl)oxime-[125I]-iodotyramine, progesterone-12-(O-carboxymethyl)oxime-[125I]-iodotyramine, and progesterone-20-(O-carboxymethyl)oxime-[125I]-iodohistamine. The preparation of the steroid derivatives and iodination by a two-phase method are described. The curves obtained from the homologous radioligands were relatively insensitive compared with a tritiated system, with the tyrosine methyl ester derivative providing a more sensitive assay than the corresponding tyramine or histamine analogues. The heterologous bridge systems gave more sensitive curves than the homologous tracers whilst the 3- and 12-(O-carboxymethyl)oxime derivatives of progesterone furnished curves as sensitive as the tritiated reference. Progesterone-20-(O-carboxymethyl)oxime-[125I]-iodohistamine was not bound by the antibody.
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A single lipophosphoprotein complex, vitellogenin, was isolated and purified from the plasma of oestrogen-stimulated female toads by preparative ultracentrifugation and chromatography on TEAE-cellulose (triethylaminoethylcellulose). The protein contains 12% lipid, 1.5% phosphorus, 1.6% calcium and smaller amounts of carbohydrates and biliverdin. In amino acid composition it is identical with total yolk-platelet protein. The platelet protein, however, is fractionated on TEAE-cellulose into two components, a high-molecular-weight lipovitellin and a smaller phosvitin. Analyses of the soluble plasma vitellogenin suggest that it is a complex of two phosvitin molecules covalently bound to one lipovitellin dimer, and that it is the immediate precursor of the yolk proteins, into which it is converted by a molecular rearrangement. Uptake of vitellogenin from the plasma into the growing oocyte, and its subsequent crystallization as a yolk platelet, appear to be enhanced by gonadotrophic hormones.
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A new conventional simple and direct 125I-radioimmunoassay (RIA) for serum progesterone is described. In comparison with the classical tritiated assays which are preceded by extraction, the assay is more simple, less time-consuming, less subject to error and hence less expensive. In normal cycling females the serum progesterone range during the follicular phase was 0.9 to 5.5 ng/ml (mean 2.5 ng/ml). Levels above 12 ng/ml occurring during the luteal phase are indicative of adequate luteal function. The actual progesterone levels assayed with this method are significantly greater than those found using the classical tritiated technique, and the reasons for this discrepancy are discussed. The assay is also capable of being used to assess the response to treatment for infertility, thus indicating that, in spite of the higher values obtained, there is no impairment in diagnostic sensitivity.