The N-terminal portion of the main cytosolic loop mediates K+ sensitivity in the retinal rod Na+/Ca2+-K+-exchanger.

Two types of Na+/Ca2+-exchangers have been characterized in the literature: The first is the cardiac, skeletal muscle and brain type, which exchanges 1 Ca2+ for 3 Na+, the second, found in retinal photosensor cells, transports 1 Ca2+ and 1 K+ in exchange for 4 Na+. The present work describes the properties of chimeric constructs of the two exchanger types. Ca2+ gel overlay experiments have identified a high affinity (Kd in the 1 microM range) Ca2+-binding domain between Glu601 and Asp733 in the main cytosolic loop of the retinal protein, just after transmembrane domain 5. Insertion of the retinal Ca2+-binding domain in the cytosolic loop of the cardiac exchanger conferred K+-dependence to the Ca2+ uptake activity of the chimeric constructs expressed in HeLa cells. The apparent Km of the K+ effect was about 1 mM. Experiments with C-terminally truncated versions of the retinal insert indicated that the sequence between Leu643 and Asp733 was critical in mediating K+ sensitivity of the recombinant chimeras. Thus, the high affinity Ca2+-binding domain in the main cytosolic loop of the retinal exchanger may regulate the activity of the retinal protein by binding Ca2+, and by conferring to it K+ sensitivity.

[Correlation of progesterone and apoprotein B in pregnancy]. / Untersuchungen über den Zusammenhang von Progesteron und Apoprotein B in der Schwangerschaft.

For the synthesis of progesterone the placenta uses cholesterol which is derived from low density lipoproteins (LDL). Apoprotein B (apo B) is the mediator for the uptake of LDL into the cell. This investigation was done to find relations between progesterone and apo B concentrations in the blood serum of pregnant women. 269 patients (8th to 41st week of pregnancy) were studied. Progesterone was estimated by radioimmunoassay, apo B by radial immunodiffusion. The concentration of apo B decreases from 8th/9th to 14th/15th week of pregnancy significantly, and this is followed by a continuous increase of the apo B concentration until parturition. The concentration of progesterone increases during pregnancy. The intermediate decrease after the 14th/15th week is to be seen in connection with the luteoplacental shift.

Dehydroepiandrosterone sulphate loading test and determination of plasma oestetrol concentration in late pregnancy.

Intravenous application of dehydroepiandrosterone sulphate (DHEA-S) was performed in 6 women with normal progress of pregnancy, 3 pregnant women with multiple pregnancy and 4 pregnants with intrauterine death of the foetus (32nd to 38th week). The oestetrol concentrations in blood serum were estimated during 5 h after the injection. In most cases an increase could be observed, but this was inhomogenous. The oestetrol concentration even rises in cases of intrauterine death of the foetus. In 7 cases of uncomplicated pregnancies the DHEA-S loading test was done within 2 to 6 h before delivery. The oestetrol concentration in the cord serum of the newborns was not higher than in controls without DHEA-S application, whereas oestradiol in maternal serum showed the expected rise. We conclude that the determination of oestetrol after DHEA-S loading can not be used for the judgement of the foetal situation.

[Results of treatment in the hyperprolactinemic anovulatory syndrome]. / Behandlungsergebnisse bei dem hyperprolaktinämisch-anovulatorischen Syndrom.

This is a report about the results of Parlodel and neurosurgical treatment of 30 patients with infertility and amenorrhea, in 18 cases combined with galactorrhea. There were 4 cases of non-ovulatory cycles with or without oligomenorrhea. 2 young girls had a primary amenorrhea. All patients wanted to have children. A pituitary tumor was diagnosed in 15 patients, it was microsurgically removed in 7 cases. 18 of 30 patients became pregnant after a drug treatment or combined neurosurgical and drug therapy.

[Relation between steroids and apoprotein B in maternal and fetal blood in late pregnancy]. / Beziehungen zwischen Steroiden und Apoprotein B im mütterlichen und fetalen Blut am Ende der Schwangerschaft.

In 31 pregnant women in the 32nd to 40th week of pregnancy estimations of apoprotein B in the blood serum were done. Besides this, in 15 cases the concentration of apoprotein B in the umbilical cord serum was measured. Furthermore, apoprotein B and dehydroepiandrosterone in cord serum and estriol in the serum of the mothers were measured in 10 cases. Dexamethasone was administered to 6 patients in order to prevent respiratory distress syndrome of the newborns. It has been tried to explain the changes of the parameters.

Pituitary and adrenal hormones in patients after myocardial infarction under ergometer load.

The levels of human growth hormone (HGH), ACTH and cortisol in the plasma of 100 middle-aged men were measured by means of radioimmunoassay (12 patients in the phase of hospitalization after myocardial infarction, 47 patients in convalescence, 31 patients in post-convalescence, 10 healthy men). Twenty patients in the phase of convalescence and all patients in post-convalescence did exercises on bicycle ergometer with submaximal loading. Patients after myocardial infarction showed significantly lower basic levels of HGH than healthy persons, and the increase in the HGH level induced by exercise was significantly lower. The hormones ACTH and cortisol showed only slight differences. The secretion of the pituitary hormones, mainly HGH, seems to be altered in patients after myocardial infarction.