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  • Author: M Maier x
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A.R.C. Institute of Animal Physiology, Babraham, Cambridge, CB2 4AT

(Received 17 January 1978)

For over 30 years, the method by which the brain regulates the secretion of gonadotrophic hormones has been studied by electrical stimulation of those parts of the central nervous system thought to be implicated in the control process. Much of the work has been performed on the female rat. In this species, anaesthetic doses of sodium pentobarbitone, administered immediately before the pro-oestrous 'critical period', block the preovulatory surge of luteinizing hormone (LH) for 24 h. The same treatment also reduces the early phase of the pro-oestrous secretion of follicle-stimulating hormone (FSH; Daane & Parlow, 1971). Electrical stimulation of the preoptic part of the hypothalamus can overcome this blocking effect and analysis of the optimum parameters required to restore normal secretion of gonadotrophins may give some insight into the endogenous process (e.g. Everett, 1965; Fink & Aiyer, 1974;

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M Kurtz, E Capobianco, V Careaga, N Martinez, M B Mazzucco, M Maier, and A Jawerbaum

Maternal diabetes impairs fetal lung development. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors relevant in lipid homeostasis and lung development. This study aims to evaluate the effect of in vivo activation of PPARs on lipid homeostasis in fetal lungs of diabetic rats. To this end, we studied lipid concentrations, expression of lipid metabolizing enzymes and fatty acid composition in fetal lungs of control and diabetic rats i) after injections of the fetuses with Leukotriene B4 (LTB4, PPARα ligand) or 15deoxyΔ12,14prostaglandin J2 (15dPGJ2, PPARγ ligand) and ii) fed during pregnancy with 6% olive oil- or 6% safflower oil-supplemented diets, enriched with PPAR ligands were studied. Maternal diabetes increased triglyceride concentrations and decreased expression of lipid-oxidizing enzymes in fetal lungs of diabetic rats, an expression further decreased by LTB4 and partially restored by 15dPGJ2 in lungs of male fetuses in the diabetic group. In lungs of female fetuses in the diabetic group, maternal diets enriched with olive oil increased triglyceride concentrations and fatty acid synthase expression, while those enriched with safflower oil increased triglyceride concentrations and fatty acid transporter expression. Both olive oil- and safflower oil-supplemented diets decreased cholesterol and cholesteryl ester concentrations and increased the expression of the reverse cholesterol transporter ATP-binding cassette A1 in fetal lungs of female fetuses of diabetic rats. In fetal lungs of control and diabetic rats, the proportion of polyunsaturated fatty acids increased with the maternal diets enriched with olive and safflower oils. Our results revealed important changes in lipid metabolism in fetal lungs of diabetic rats, and in the ability of PPAR ligands to modulate the composition of lipid species relevant in the lung during the perinatal period.

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The effects of tamoxifen on cortisol binding globulin (CBG) and sex hormone binding globulin (SHBG) were studied in 25 women and one man with breast cancer. These patients were in various endocrine states according to age (15 post-menopausal women) or previous endocrine surgery (ovariectomy, two patients; ovariectomy plus adrenal surgery, five patients; hypophysectomy, three patients; ovariectomy plus hypophysectomy, two patients). The administration of tamoxifen (20–40 mg/day) resulted in increases in the level of CBG in all patients (mean rise in binding capacity 10·8 μg cortisol/100 ml plasma) and in the level of SHBG in 21 patients (mean rise in binding capacity 0·79 μg dihydrotestosterone/ 100 ml plasma for all patients). These increases were positively correlated. They were not associated with any alteration in the association constants of the steroid binding globulins. The effect of tamoxifen on CBG diminished with increasing age. The changes in the levels of CBG and SHBG were independent of the endocrinological state of the patient. It is inferred that tamoxifen has a direct oestrogen-like action on the liver which results in increased production of CBG and SHBG. Tamoxifen therapy for carcinoma of the breast appeared to be least effective in those patients in whom the drug caused the highest increase in the concentration of CBG.

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W Karges, K Jostarndt, S Maier, A Flemming, M Weitz, A Wissmann, B Feldmann, H Dralle, P Wagner, and BO Boehm

Germ line mutations of the multiple endocrine neoplasia type 1 (MEN1) tumour suppressor gene cause MEN1, a rare familial tumour syndrome associated with parathyroid hyperplasia, adenoma and hyperparathyroidism (HP). Here we investigated the role of the MEN1 gene in isolated sporadic and familial HP. Using RT-PCR single-strand conformational polymorphism screening, somatic (but not germ line) mutations of the MEN1 coding sequence were identified in 6 of 31 (19.3%) adenomas from patients with sporadic primary HP, but none in patients (n=16) with secondary HP due to chronic renal failure. MEN1 mutations were accompanied by a loss of heterozygosity (LOH) for the MEN1 locus on chromosome 11q13 in the adenomas as detected by microsatellite analysis. No DNA sequence divergence within the 5' region of the MEN1 gene, containing the putative MEN1 promoter, was detectable in HP adenomas. Clinical characteristics were not different in HP patients with or without MEN1 mutation. Heterozygous MEN1 gene polymorphisms were identified in 9.6% and 25% of patients with primary and secondary HP respectively. In a large kindred with familial isolated familial HP, MEN1 germ line mutation 249 del4 and LOH was associated with the HP phenotype and a predisposition to non-endocrine malignancies. We suggest that the bi-allelic somatic loss of MEN1 wild-type gene expression is involved in the pathogenesis of a clinically yet undefined subset of sporadic primary HP adenomas. MEN1 genotyping may further help define the familial hyperparathyroidism-MEN1 disease complex, but it seems dispensable in sporadic primary HP.

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Victor P Bilan, Eman M Salah, Sheldon Bastacky, Huw B Jones, Rachel M Mayers, Bradley Zinker, Simon M Poucher, and Stevan P Tofovic

Diabetic nephropathy (DN) is a major cause of end-stage renal disease. Yet the pathogenic mechanisms underlying the development of DN are not fully defined, partially due to lack of suitable models that mimic the complex pathogenesis of renal disease in diabetic patients. In this study, we describe early and late renal manifestations of DN and renal responses to long-term treatments with rosiglitazone or high-dose enalapril in ZSF1 rats, a model of metabolic syndrome, diabetes, and chronic renal disease. At 8 weeks of age, obese ZSF1 rats developed metabolic syndrome and diabetes (hyperglycemia, glucosuria, hyperlipidemia, and hypertension) and early signs of renal disease (proteinuria, glomerular collagen IV deposition, tubulointerstitial inflammation, and renal hypertrophy). By 32 weeks of age, animals developed renal histopathology consistent with DN, including mesangial expansion, glomerulosclerosis, tubulointerstitial inflammation and fibrosis, tubular dilation and atrophy, and arteriolar thickening. Rosiglitazone markedly increased body weight but reduced food intake, improved glucose control, and attenuated hyperlipidemia and liver and kidney injury. In contrast, rosiglitazone markedly increased cardiac hypertrophy via a blood pressure-independent mechanism. High-dose enalapril did not improve glucose homeostasis, but normalized blood pressure, and nearly prevented diabetic renal injury. The ZSF1 model thus detects the clinical observations seen with rosiglitazone and enalapril in terms of primary and secondary endpoints of cardiac and renal effects. This and previous reports indicate that the obese ZSF1 rat meets currently accepted criteria for progressive experimental diabetic renal disease in rodents, suggesting that this may be the best available rat model for simulation of human DN.

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D S Gardner, B W M Van Bon, J Dandrea, P J Goddard, S F May, V Wilson, T Stephenson, and M E Symonds

Glucocorticoids are proposed to act as intermediary factors that transcribe the developmental programming sequelae of maternal nutrient restriction (NR). Periconceptional under-nutrition of sheep markedly activates fetal hypothalamic–pituitary–adrenal (HPA) axis activity leading to preterm birth, while transient undernutrition during late gestation in sheep programs adult HPA axis function. To date, no study has examined resting or stimulated HPA axis function in young adult offspring following a periconceptional nutritional challenge. In the present study, 20 ewes were either periconceptionally undernourished (50% metabolisable energy requirements from days 1 to 30 gestation; NR, n = 8) or fed to control levels (100% requirement; controls, n = 12) to term (147 days gestation). Ewes were blood sampled remotely at 2 and 30 days using automated blood sampling equipment. Thereafter, offspring (controls, n = 6/6 males/females; NR, n = 4/4 males/females) were reared to 1 year of age and on separate days received either an i.v. corticotrophin-releasing hormone (CRH; 0.5 μg/kg) and vasopressin (AVP; 0.1 μg/kg) challenge or a synthetic ACTH i.v. bolus (Synacthen; 1.25 μg/kg), and blood samples were taken (manually and remotely) at appropriate intervals for measurement of plasma ACTH and cortisol accordingly. Resting plasma cortisol, assessed remotely, was similar in ewes during undernutrition (control 18.3 ± 1.4 vs NR 23.4 ± 1.9 nmol/l) and in offspring at 4 months of age (control male 17.6 ± 2.9; control female 17.2 ± 0.4, NR male 16.5 ± 3.1, NR female 21.7 ± 4.0 nmol/l). At 12 months of age, however, resting plasma cortisol was significantly increased in NR females (control male 28.0 ± 1.5, control female 32.9 ± 9, NR male 32 ± 7, NR female 53 ± 10 nmol/l, F 5.7, P = 0.02) despite no difference in plasma ACTH concentration. There was an interaction between nutritional group and gender for both the pituitary and adrenal responses to CRH and AVP, i.e. for controls, females exhibited increased plasma ACTH or cortisol relative to males but for NR this trend was either not present or reversed. The adrenocortical response to synthetic ACTH was gender-dependent only, being greater in female offspring. Combined CRH and AVP provoked a transient hypertension and marked bradycardia in all animals, irrespective of dietary group or gender and could be effectively reproduced by an AVP bolus alone. In conclusion, the present study has shown that periconceptional undernutrition of sheep has only a minor influence on HPA axis function in their young adult offspring when considered alongside the effect of gender per se.