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Biomedical subjects

H Steffen

Publications and source records attributed to H Steffen.

11 recordsLinked to original sources
PubMed1979

Steroidogenesis in isolated adrenocortical cells. Correlation with receptor-bound adenosine e 3':5'-cyclic monophosphate.

Because several groups have recently questioned a mediating role for cyclic AMP in adrenocortical steroidogenesis, we analysed the problem in more detail by measuring three different cyclic AMP pools in cells isolated from decapsulated rat adrenals. Extra-cellular, total intracellular and bound intracellular cyclic AMP were determined by radioimmunoassay in comparison with corticosterone production induced by low corticotropin concentrations. The increase in extracellular and total intracellular cyclic AMP with low corticotropin concentrations was dependent on the presence of a phosphodiesterase inhibitor and short incubation times. Bound intracellular cyclic AMP was less dependent on these two parameters. In unstimulated cells cyclic AMP bound to its receptor represents only a small fraction of the total intracellular cyclic AMP. After stimulation by a concentration of corticotropin around the threshold for corticosterone production, an increase in bound cyclic AMP was observed which correlated very well with steroidogenesis both temporally and with respect to corticotropin concentration. This finding was complemented by measuring a concomitant decrease in free receptor sites. Full occupancy of the receptors was not necessary for maximal steroidogenesis. Binding kinetics of cyclic [(3)H]AMP in concentrations equivalent to the intracellular cyclic AMP concentration suggest the presence of at least three different intracellular cyclic AMP pools. These observations are in agreement with a possible role for cyclic AMP as a mediator of acute steroidogenesis induced by low corticotropin concentrations.

Adrenal Cortex↗
PubMed1979

Adrenocorticotropin (ACTH) induces phosphorylation of a cytoplasmic protein in intact isolated adrenocortical cells.

In 32P incorporation experiments with intact adrenocortical cells, adrenocorticotropin (ACTH) or adenosine 3',5'-cyclic monophosphate (cAMP) induced a rapid and transient increase of approximately 300-500% in the phosphorylation of a 32P-containing cytoplasmic protein of about 150,000 daltons (APS150). Half-maximal stimulation of APS150 phosphorylation was observed with about 3 pM ACTH. Receptor-bound cAMP, corticosterone production, and the appearance of phosphorylated APS150 increased in parallel with respect to both time and ACTH concentration. All three responses were dependent on extracellular calcium. Inhibition of protein synthesis with cycloheximide suggested a half-life of APS150 of about 10 min. The time course of 32P incorporation into ACTH-induced APS150 in the absence and presence of nonradioactive phosphate shows that the phosphorylation of APS150 is under simultaneous control of cAMP-dependent protein kinase and of phosphoatase activity. Thus a rapid ACTH-dependent and cAMP-dependent protein phosphorylation in intact adrenocortical cells within steroidogenic ACTH concentrations has now been demonstrated.

Adrenal Cortex↗
PubMed1977

[Psychological consulting of children awaiting leg amputation (author's transl)].

A 2.3 year old boy and a 3.7 year old girl, brother and sister, burnt their feet and calves during a bath tub accident. Both had to undergo amputation of their feet and lower thirds of their calves. For this, both needed psychological help. The body was less anxious and ready for confrontation with reality. The girl had to be guided through her denial and rejection of reality towards acceptance of the situation. Only then was she able to express fear and accept help. This practical playtherapeutical intervention could only take place on the basis of absolute trust. Time, empathy, adaptation to the children's state, age and personality and repetetive, active playing of the situation and the anxiety provoking future were necessary. Thus panic provoking anxiety could be diminished to realistic fear.

Adaptation, Psychological↗
PubMed1976

Lateral diffusion, order parameter and phase transition in phospholipid bilayer membranes containing tocopheryl acetate.

Lateral diffusion coefficient and order parameter measurements were made with pyrene excimer optical probes and fatty acid spin label probes respectively in pure dipalmitoyl phosphatidylcholine membranes and in membranes doped with tocopheryl acetate. The investigation shows, that the lateral diffusion coefficient for pyrene in dipalmitoyl pholphatidylcholine membranes is decreased whereas the order parameter of the fatty acid chains is slightly increased in the inner part of the membranes by the addition of tocopheryl acetate. The fluid-solid equilibrium phase diagram of dipalmitoyl phosphatidylcholine/tocopheryl acetate mixed membranes has been constructed from the measurements of the partition of (2,2,6,6-tetramethylpiperdine-1-oxyl) TEMPO spin labels between lipid and aqueous regions as function of temperature. In the membranes tocopheryl acetate induces a strong broadening of the temperature range of the phase transition. At low tocopheryl acetate concentrations dipalmitoyl phosphatidylcholine and tocopheryl acetate seem to be completely miscible in the solid and in the liquid crystalline state.

Binding Sites↗
PubMedDate not supplied

[Size, structure, and dynamics of bile salt/lecithin mixed micelles (author's transl)].

The structure and size of lecithin/sodium glycocholate mixed micelles was investigated by quasi-elastic laser light scattering and spin label techniques. The investigations are in accordance with a bilayer model for these micelles. The order parameter and the phase transition enthalpy of the micellar bilayer were determined. The lateral and rotational diffusion constants of label molecules are compared with the corresponding diffusion constants in liposomes.

Chemical Phenomena↗