Increased estradiol-estrone quotient in rat liver by hydroxysteroids: an effect of the specific hydrogen transfer between steroids]

After addition of estrone to rat liver slices, a quotient of estradiol/estrone of ca. 0.1 is reached within 1 - 2 min. By additional application of 17 beta-hydroxysteroids this quotient is changed in the direction of estradiol, although the applied concentrations of both steroids are far below the concentration of the cytoplasmic redox couple NADH/NAD. Of all the steroids tested, testosterone had the strongest influence on the quotient, especially in the liver of female rats. This influence is smaller in the livers of male rats and infantile animals. The changing of the E2/E1 quotient by testosterone can be inhibited by the antiandrogen cyproteron acetate. Steroids with hydroxy groups at C-3 or C-20 or high concentrations of non-steroids, which can be oxidized by NAD, change the E2/E1 quotient only minimally. The experiments demonstrate that in liver, the redox couple estradiol/estrone is not in equilibrium with the main redox couple of the cytoplasmic NADH/NAD. Only on account of this fact it is possible that relatively low concentrations of testosterone change the E2/E1 quotient via the C-17 leads to C-17 hydrogen transfer between steroids. Biological consequences are discussed.     

Increased concentrations of a circulating sodium pump inhibitor in essential hypertension and uraemia and its partial purification from haemofiltrate

Patients with essential hypertension have 3.2 fold and patients with chronic uraemia 11.7 fold higher serum concentrations of endogenous digitalis-like activity than normotensives (76.3 +/- 9.3 nM). Upon haemodialysis this serum activity drops to almost normal values. A low molecular factor could be partially purified from 4000 l haemofiltrate.     

Somatic Hybridization of Dihaploid Potato Protoplasts as a Tool for Potato Breeding*

Using electrofusion of protoplasts from different dihaploid potato breeding clones, 308 somatic hybrids, i.e. 16.7% of the totally regenerated plants, were obtained. The results indicate that factors such as ‘combining ability’ strongly influence hybrid formation in these intraspecific fusion experiments. Hybrid identification was predominantly carried out by isoenzyme analysis of the peroxidases and/or esterases in polyacrylamide-gradient gel electrophoresis. Further confirmation of the hybrid character was obtained by scoring phenotypic markers (petal colour, stem anthocyanin production, tuber characteristics, etc.) and, in some combinations, by evaluating tolerance against the herbicide metribuzin and nematode resistance against Globodera rostochiensis (Ro 1). The successful inheritance of metribuzin tolerance and nematode resistance confirm that monogenic dominant inherited traits are combined in the hybrids.