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D. JACKSON and J. M. ROBSON

SUMMARY

Methyl cholanthrene applied locally to the vagina of ovariectomized mice antagonizes the vaginal cornification produced by 0·2μg oestradiol. Much larger doses of oestradiol abolish this effect. Previous exposure to the carcinogen does not produce this antagonism. The carcinogen prevents the production of vaginal mucification in pregnant mice and also in mice treated with 750 μg progesterone and 0·05 μg oestradiol. Again, previous exposure to the carcinogen does not produce this antagonism.

The effects of testosterone on the seminal vesicle in the rat and of deoxycorticosterone on the endometrium of the rabbit are antagonized by the local implantation of methyl cholanthrene.

These results suggest that there is competitive antagonism between methyl cholanthrene and the steroid hormones investigated. The possible significance of these findings is discussed.

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D. JACKSON and J. M. ROBSON

SUMMARY

1. Furazolidone (0·75 g/kg) will interrupt pregnancy in mice.

2. Foetal tissue is particularly sensitive to the drug at the time of or before implantation of the ovum.

3. Intra-amniotic injection of furazolidone in rabbits causes foetal death and resorption.

4. Furazolidone applied locally does not antagonize the proliferative effect of progesterone on rabbit endometrium.

5. The mode of action of furazolidone on pregnancy is discussed. It is suggested that it acts directly on the foetus.

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J. D. POWELL-JACKSON and JAMES MACGREGOR

M.R.C. Blood Pressure Unit, Western Infirmary, Glasgow, G11 6NT

(Received 27 August 1975)

The rat has been widely used in the investigation of the physiology and pathology of the renin—angiotensin system. This paper describes an adaptation of the radioimmunoassay of angiotensin II in human plasma (Dusterdieck & McElwee, 1971) for use in the rat.

Antibodies against [Asn1, Val5]-angiotensin II (Hypertensin, Ciba) were raised in rabbits using a minor modification of the method described by Goodfriend, Fasman, Kemp & Levine (1966). The antiserum used cross-reacted 100% with [Asp1, He5]-angiotensin II (Schwartz-Mann), 2–8 heptapeptide (Ile4), and 3–8 hexapeptide (Ile3) fragments but only 0·6% with [Asp1,Ile5]-angiotensin I and 0·008% with rat renin substrate obtained from dialysed nephrectomized rat plasma.

Since the octapeptide native to the rat is thought to be in the Ile5 form (Powell-Jackson, Brown, Lever, Macgregor, Macadam, Titterington, Robertson & Waite, 1972), [Asp1, Ile5]-angiotensin II was iodinated with Na125I as described

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A D Adamson, D Jackson and J R E Davis

The study of gene expression is a major focus in biological research and is recognised to be critical for our understanding of physiological and pathophysiological processes. Methods to study gene expression range from in vitro biochemical assays through cultured cells and tissue biopsies to whole organisms. In the early stages of project development, considerations about which model system to use should be addressed and may influence future experimental procedures. The aim of this review is to briefly describe advantages and disadvantages of the existing techniques available to study eukaryote gene expression in vitro, including the mechanism of transgene integration (transient or stable), the different transgenesis systems available, including plasmids, viruses and targeted integration and knockin approaches, and paying particular attention to expression systems such as bacterial artificial chromosomes and episomal vectors that offer a number of advantages and are increasing in popularity. We also discuss novel approaches that combine some of the above techniques, generating increasingly complex but physiologically accurate expression systems.

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I. M. D. JACKSON, M. T. McKIDDIE and K. D. BUCHANAN

Abnormal glucose tolerance is known to occur in the obese (Butterfield, Hanley & Whichelow, 1965) and Karam, Grodsky & Forsham (1963) have demonstrated increased insulin levels to be a feature of the response to a glucose load in overweight subjects. There has been no previous published work on the effects of prolonged starvation (over 14 days) on the carbohydrate metabolism of obese patients and this paper reports our findings in the first 12 subjects studied.

Twelve obese subjects (11F, 1M; aged 16–55 yr., 125–245% standard weight) were admitted to hospital and treated by complete starvation for 2½–18 weeks (mean 7). None were known to be diabetic. Before fasting an oral glucose tolerance test (50 g.) was performed and venous blood was removed for the determination of blood sugar, plasma insulin and free fatty acid (FFA) levels at 0, 30, 60, 90 and 120 min. The fast was terminated by administering

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D. JACKSON, J. M. ROBSON and A. C. E. WANDER

SUMMARY

Intraperitoneal and intra-amniotic administration of 6-diazo-5-oxo-l-norleucine (DON) will interrupt pregnancy in mice at all stages of gestation with doses which are only a small fraction of the LD50 for this compound. The intra-amniotic injection of DON into pregnant rabbits kills the foetus but leaves the placenta intact. Rabbits are relatively resistant to the toxic action of this compound. The available evidence indicates that DON acts directly on the developing embryo.

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I. M. D. JACKSON, K. D. BUCHANAN, M. T. McKIDDIE and C. R. M. PRENTICE

SUMMARY

An oral glucose tolerance test was performed in eight patients with gonadal dysgenesis and in two a diabetic response was found. The plasma insulin levels were estimated in response to the glucose load and were abnormal in five out of the six patients examined.

The blood sugar response to the standard insulin tolerance test was normal in six patients and showed increased insulin sensitivity in two. Plasma cortisol concentration was measured in response to the hypoglycaemia induced by insulin and in seven out of the eight patients rose considerably indicating a normally functioning pituitary-adrenal system.

The sera of all eight patients were examined for auto-antibodies and were essentially negative.

Possible reasons for the abnormalities in carbohydrate metabolism are discussed and it is suggested that gonadal dysgenesis may predispose to diabetes.

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D. B. COOK, G. V. GILL, I. M. D. JACKSON and G. A. SMART

SUMMARY

The effect of intravenous infusions of ATP and dibutyryl cyclic AMP (DB cyclic AMP) on adrenocorticotrophin (ACTH) and corticosteroid release was investigated in piglets.

A consistent increase of both plasma ACTH and plasma cortisol was observed in response to infusions of 600 mg ATP/h. These responses were abolished by pretreating the animals with dexamethasone. A similar pattern of response was observed with DB cyclic AMP infused intravenously. No response occurred when 100 mg DB cyclic AMP were infused in 1 h, but there was a marked plasma corticosteroid response to an infusion of 600 mg DB cyclic AMP in 1 h. Surprisingly, this response was also abolished by pretreatment with dexamethasone.

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T V Novoselova, D Jackson, D C Campbell, A J L Clark and L F Chan

The melanocortin receptor (MCR) family consists of five G-protein-coupled receptors (MC1R–MC5R) with diverse physiological roles. MC1R controls pigmentation, MC2R is a critical component of the hypothalamic–pituitary–adrenal axis, MC3R and MC4R have a vital role in energy homeostasis and MC5R is involved in exocrine function. The melanocortin receptor accessory protein (MRAP) and its paralogue MRAP2 are small single-pass transmembrane proteins that have been shown to regulate MCR expression and function. In the adrenal gland, MRAP is an essential accessory factor for the functional expression of the MC2R/ACTH receptor. The importance of MRAP in adrenal gland physiology is demonstrated by the clinical condition familial glucocorticoid deficiency, where inactivating MRAP mutations account for ∼20% of cases. MRAP is highly expressed in both the zona fasciculata and the undifferentiated zone. Expression in the undifferentiated zone suggests that MRAP could also be important in adrenal cell differentiation and/or maintenance. In contrast, the role of adrenal MRAP2, which is highly expressed in the foetal gland, is unclear. The expression of MRAPs outside the adrenal gland is suggestive of a wider physiological purpose, beyond MC2R-mediated adrenal steroidogenesis. In vitro, MRAPs have been shown to reduce surface expression and signalling of all the other MCRs (MC1,3,4,5R). MRAP2 is predominantly expressed in the hypothalamus, a site that also expresses a high level of MC3R and MC4R. This raises the intriguing possibility of a CNS role for the MRAPs.

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I. M. D. JACKSON, K. D. BUCHANAN, M. T. McKIDDIE and C. R. M. PRENTICE

SUMMARY

Carbohydrate metabolism has been investigated in eight patients with Klinefelter's syndrome. Seven of the eight had a normal oral glucose tolerance curve; one patient had slightly impaired tolerance. Plasma insulin levels were measured in response to the glucose load and were normal in six and slightly abnormal in two patients; one of the latter had an early increased and the other a delayed insulin response. No definite conclusions are reached regarding the possibility of a significant association between Klinefelter's syndrome and diabetes mellitus.