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R J W Currie and A S McNeilly

Abstract

Changes in LH secretory granules in pituitary gonadotrophs throughout the sheep oestrous cycle were determined by immunogold localisation of LH at ultrastructural level by electron microscopy. Oestrous cycles in Welsh Mountain ewes were initially synchronised with progestagen sponges and studies carried out in the subsequent cycle. Animals were allocated at random to six groups each of five animals, one killed on day 12 of the luteal phase and the other groups after prostaglandin (PG)-induced luteal regression at PG plus 18 h (early follicular phase), oestrus (PG plus 33·6±1·0 h), oestrus plus 9 h just before the preovulatory LH surge, 1 h after GnRH agonist-induced LH surge at PG plus 48 h (mid-LH surge) and oestrus plus 24 h, after the preovulatory LH surge. Blood samples collected throughout confirmed the pulsatile secretion of LH before and the timing in relation to the preovulatory LH surge. Pituitaries were dissected and processed for transmission electron microscopy and frozen for later extraction of mRNA. Only a single type of LH cell was present in the sheep pituitary. In the luteal phase, LHimmunopositive secretory granules were distributed throughout the cytoplasm in 80% of cells while in 20% of cells granules were polarised to the region of the cell next to a vascular sinusoid. The percentage of polarised cells increased during the follicular phase to 45% at oestrus, 75% at oestrus plus 9 h just before the LH surge and 90% in mid-LH surge. Cell size increased in parallel with polarisation. Gonadotrophs after the LH surge were almost totally devoid of LH granules but prominent LHβ immunoreactivity was observed in the rough endoplasmic reticulum. Analysis of granule diameters revealed a single class of granules with a maximum diameter of 300 nm. Polarised cells had significantly fewer 130–150 nm granules than non-polarised cells, suggesting preferential exocytosis of LH-containing granules of this size from polarised cells. Northern analysis showed that LHβ mRNA levels decreased from luteal through the follicular phase. These results suggest that the preovulatory LH surge in sheep is not related to a change in synthesis of LH but to a progressive recruitment of gonadotrophs into a releasing state, priming, as indicated by polarisation of secretory granules to the region of the cell next to the vascular system.

Journal of Endocrinology (1995) 147, 259–270

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G. D. THORBURN, R. I. COX, W. B. CURRIE, B. J. RESTALL, and W. SCHNEIDER

Prostaglandin F. (PGF) is luteolytic in the ewe when infused into the ovarian artery (Barrett, Blockey, Brown, Cumming, Goding, Mole & Obst, 1971; McCracken, Baird & Goding, 1971) or the ipsilateral uterine vein (Thorburn & Nicol, 1971). These observations, together with the identification of PGF in the uterine venous plasma of anaesthetized ewes towards the end of the oestrous cycle (Bland, Horton & Poyser, 1971; McCracken et al. 1971), strongly suggest that PGF is the uterine luteolytic factor in sheep. This paper describes in detail the changes in PGF concentration in utero—ovarian venous plasma of conscious ewes during the oestrous cycle.

Polyvinyl catheters (1·5 mm o.d.) were inserted into the right and left utero—ovarian veins via uterine vein branches in two Merino ewes 10 and 11 days after oestrus.

Utero—ovarian venous samples were collected every 2–3 h from the day after surgery.

Concentrations of PGF

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A. M. Wallace, G. H. Beastall, B. Cook, A. J. Currie, A. M. Ross, R. Kennedy, and R. W. A. Girdwood

ABSTRACT

We have assessed the feasibility of screening newborn babies for congenital adrenal hyperplasia (CAH) by the direct measurement of 17-hydroxyprogesterone (17-OHP) in blood spots collected on filter paper (Guthrie cards) for the phenylketonuria, hypothyroidism and galactosaemia screening programmes run in Scotland. The procedure described for CAH uses an iodinated 17-OHP tracer and a specific 17-OHP antiserum sheathed within semipermeable nylon microcapsules. The method does not require a solvent extraction step, is inexpensive, precise, efficient and, therefore, practical for large-scale use. With this system the value of a neonatal screening programme was assessed in a retrospective analysis and a prospective trial.

The retrospective study of 15 paediatric cases of CAH illustrated that at least half were not diagnosed within 3 weeks of birth. Analysis of the original Guthrie card samples revealed increased levels of 17-OHP in all cases. The prevalence of CAH as calculated in the retrospective study was 1 in 20 907 with a range (within 95% confidence limits) of from 1 in 12 675 to 1 in 32 604 (n = 301 450). In the prospective trial a total of 92 051 consecutive samples was screened. Five cases of CAH were correctly identified with a current false positive rate of 0·042%. Analysis of urinary steroids confirmed defective adrenal 21-hydroxylase activity in all positive cases. In the prospective trial the prevalence was 1 in 18 401 with a range of from 1 in 7 422 to 1 in 50006.

We conclude that mass screening for CAH is both feasible and desirable.

J. Endocr. (1986) 108, 299–308