Immunoassays are now very widely used in the clinical laboratory, either because no other type of assay system is feasible or because they are often the most effective and suitable of the possible analytical methods. The last decade has seen the development and refinement of many new immunoassay reagents and systems. The major trend has been away from liquid-phase assays involving radioisotopic labels, towards fast homogeneous or solid-phase assays capable of operation anywhere; and towards precise and reliable nonisotopic, automated or semi-automated laboratory assays, often with detection limits measured in pico- or attomoles. The use of monoclonal antibodies is now widespread, and the methodologies of labels and of solid-phase components are much more sophisticated. New assay formulations, novel homogeneous systems, immunosensors, free-analyte assays, the importance of thorough validation and of interfering substances, and future trends are discussed.

We have developed a new assay for cortisone (E) in serum, saliva, and urine involving Celite® chromatography followed by RIA with 125I-labeled E and scintillation proximity assay. The chromatography step separates cortisol (F) from E, and in combination with their RIAs, permits assessment of the status of the F–E shuttle. We report the results of basal, postcorticotropin (ACTH), and postdexamethasone E and F concentrations and their circadian fluctuations in the serum, saliva, and urine of healthy volunteers. The serum and urine F/E ratios were increased in patients with ectopic ACTH secretion, whereas in adrenal adenoma and Cushing disease only the urinary ratio was increased. In chronic renal insufficiency this ratio was increased in serum (23.5 ± 3.9) but diminished in saliva (0.38 ± 0.11), and in apparent mineralocorticoid excess the ratios were high in serum (44.3 ± 9.3) and urine (5.35 ± 0.85) compared with those of healthy subjects (serum 9.8 ± 3.5, urine 0.52 ± 0.29, saliva 0.52 ± 0.29).

No abstract

The mean duration of oestrus, ovulation rate, duration of the preovulatory LH discharge, time interval between sponge removal and beginning of the LH discharge, total LH discharged, maximum LH value observed and the concentration of progesterone in the peripheral plasma during the luteal phase of the oestrous cycle was similar in Galway adult ewes and 8-month-old ewe lambs after treatment with intravaginal sponges containing 30 mg cronolone for 12 days and injection of 500 i.u. PMSG. The interval between sponge removal and the onset of oestrus was shorter for adults than for ewe lambs; the interval between the onset of oestrus and the beginning of the LH discharge was longer in adults. During the period 12-36 h after sponge removal the mean plasma total oestrogen concentration was significantly higher in lambs than in adults. In a separate study of the time of ovulation in Galway ewe lambs given the same progestagen-PMSG treatment, ovulation did not occur in any lamb before 17 h after the onset of oestrus and the majority ovulated close to the end of oestrus.

The concentrations of progesterone in the peripheral plasma throughout the oestrous cycle and the preovulatory LH discharge were examined in Finnish Landrace, Galway and Fingalway (Finnish Landrace X Galway) ewes. Progesterone levels were significantly higher in Finnish Landrace ewes during the luteal phase of the cycle (Days 10--13) than in Galways of Fingalways in which the concentrations were similar. Luteal-phase progesterone levels were almost 50% higher during December than during October in all three breeds. The relationship between the number of CL and plasma progesterone was not a simple linear function. All aspects of the preovulatory LH discharge were similar in the three breeds with the exception of the timing of the LH release in relation to the onset of oestrus. This occurred earliest in the Galway and latest in the Finnish Landrace while the Fingalway was intermediate.