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Biomedical subjects

G Reck

Publications and source records attributed to G Reck.

At least 37 records · Page 2Linked to original sources
PubMed1988

Diurnal variations in unconjugated oestriol levels during early pregnancy and their relation to maternal cortisol levels.

We studied maternal plasma levels of oestriol (measured by radioimmunoassay) and total cortisol (measured by a protein binding method) in 11 women from 8 to 22 weeks gestation. Blood specimens (5 ml) were drawn over a 24-h period at 60 and 30 min intervals. The diurnal rhythm of cortisol with higher values in the morning than in the afternoon and evening was present at all gestational ages studied. Unconjugated plasma oestriol showed a similar circadian rhythm to maternal cortisol (r = 0.576, P less than 0.01) in the 8th week. From the 9th to the 11th week oestriol values rose and there was no evidence of a circadian rhythm. In the 12th week plasma oestriol again showed a circadian rhythm, with higher values at night (117.3 +/- 9.5 pg/ml) than during day-time (104 +/- 7.5 pg/ml, P less than 0.001). This pattern remained until the 22nd week, when plasma oestriol levels at night (3.78 +/- 0.49 ng/ml) were markedly higher than in the day-time (3.16 +/- 0.3 ng/ml, P less than 0.001). An inverse relation between oestriol and cortisol levels as shown in late human pregnancy could not be demonstrated for the early stages we studied. The interval between rising cortisol and falling oestriol levels decreased from 6 h in the 12th week to 3.5 h in the 22nd week of gestation. This suggests an increasing sensitivity of the fetal hypothalamus to the feedback effect of maternal cortisol.

Circadian Rhythm↗
PubMed1988

[Regulation of the fetoplacental unit. 3. Suppression of the fetoplacental unit by cortisol in relation to the maturity of the fetus].

The present study investigates the suppression of free plasma oestriol by cortisol in mature and immature foetuses. 6 patients in the 32nd week of gestation and 6 patients in the 38th week received an infusion of 100 mg cortisol (Hydrocortison Hoechst) from 10 a.m. to 12 a.m. Blood specimens (5 ml) were drawn from 8 a.m. to 5 p.m. in 60 or 30 minutes intervals, respectively. Free plasma oestriol was measured by radioimmunoassay, total plasma cortisol by the protein binding method. In the 32nd week of gestation plasma oestriol rose from 501 +/- 240 ng/ml to 1035 +/- 301 ng/ml, whereas oestriol decreased from 5.2 +/- 1.0 ng/ml to 3.9 +/- 1.5 ng/ml (p less than 0.001). After an analogous rise of cortisol, oestriol levels in the 38th week were suppressed from 12.5 +/- 3.3 ng/ml to 4.0 +/- 1.6 ng/ml (p less than 0.001). The degree of oestriol suppression of 68 percent in the 38th week markedly exceeded that of the 32nd week (25%). According to these results, the hypothalamic-hypophyseal system of mature foetuses exhibits a higher sensitivity to the feed back action of cortisol than immature foetuses.

Estriol↗
PubMed1988

[Regulation of the fetoplacental unit. 1. Comparison of the suppressive effect of cortisol and cortisone on estradiol synthesis].

The present study compares the negative feed back action of cortisol and cortison on oestriol production in late human pregnancy. 10 women from the 38th to 40th week of gestation volunteered in this study. All had uncomplicated courses of pregnancy and delivered healthy babies at term. 5 patients received a continuous infusion of 100 mg Cortisol from 10 a.m. to 12 a.m. To the other 5 patients 100 mg Cortison were infused during the same period. Blood specimens (5 ml) were drawn in 60 and 30 minutes intervals from 8 a.m. to 5 p.m. Plasma levels of unconjugated oestriol were measured by radioimmunoassay. The suppression of oestriol levels was nearly identical in both groups: After Cortisol oestriol concentrations decreased from 17.1 +/- 9.1 ng/ml to 6.0 +/- 1.2 ng/ml (p less than 0.001) and after Cortison from 15.5 +/- 5.8 ng/ml to 5.9 +/- 1.8 ng/ml (p less than 0.001), respectively. According to these results the placental metabolism of maternal cortisol to cortison does not impair the negative feed back action of this hormone on the foetal hypothalamus-hypophysis-system.

Estradiol↗
PubMed1988

[Regulation of the fetoplacental unit. 2. Circadian changes in the sensitivity of the fetal hypothalamo-hypophyseal system for the feedback effect of cortisol].

The present study investigates the significance of a circadian changing sensitivity on the feed back action of cortisol for the foetal hypothalamic hypophyseal system. 9 patients with uncomplicated courses of pregnancy in the 37th to 40th week volunteered in this study. All of them delivered healthy babies at term. 5 patients received a continuous infusion of 0.25 mg ACTH1-24 (Synacthen) in the morning from 10 a.m. to 4 p.m. (group I). To 4 patients an analogous ACTH infusion was applied in the evening from 8 p.m. to 2 a.m. (group II). Blood specimens (5 ml) were drawn from 8 a.m. to 5 p.m. in group I and from 5 p.m. to 3 a.m. in group II in 60 and 30 minutes intervals, respectively. Free plasma oestriol was measured by radioimmunoassay, total plasma cortisol by the protein binding method. In group I cortisol increased from 294.3 +/- 52.9 ng/ml to 774.5 +/- 170 ng/ml, whereas oestriol decreased from 13.1 +/- 6.1 ng/ml to 6.8 +/- 2.1 ng/ml (p less than 0.001). In group II cortisol rose from 267.5 +/- 76.2 ng/ml to 1010 +/- 284 ng/ml, whereas oestriol levels were suppressed from 21.7 +/- 10.5 ng/ml to 10.8 +/- 3.2 ng/ml (p less than 0.001). Two hours after starting ACTH infusion rising cortisol and falling oestriol concentrations were negatively correlated (r = -0.9657, p less than 0.001 in the morning; r = -0.9119, p less than 0.001 in the evening). Plasma oestriol levels were in the evening suppressed on an average of 10.9 ng/ml and exceeded the oestriol decrease in the morning (6.3 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1988

X-ray studies on piroxicam modifications.

The anti-inflammatory drug piroxicam, 4-hydroxy-2-methyl-N-(2-pyridyl)2H-1,2- benzothiazine-3-carboxamide-1,1-dioxide, crystallizes in three different forms, two anhydrates and one monohydrate. Crystal structure analyses of the monohydrate and one of the anhydrate were carried out by Bordner et al. and Kojić-Prodić et al., respectively. In this paper the results of the analysis of the third piroxicam modification and of an independently performed structure determination of the monohydrate are reported. Molecular structures and hydrogen bonding of all modifications are discussed.

Chemical Phenomena↗
PubMed1988

[X-ray crystallographic studies of diclofenac-sodium--structural analysis of diclofenac-sodium tetrahydrate].

The crystal structure of the hydrate of the antiphlogistic drug diclofenac sodium was determined to explain the unusual dissolution behaviour in ethyl acetate. The compound crystallizes in the monoclinic space group P2(1)/m with a = 9.464(2), b = 39.405(7), c = 9.972(3) A und beta = 90.74(2) degrees. The unit cell contains two symmetry independent formula units (C14H10Cl2NO2)-Na+.3,94 H2O. There are molecule layers and sodium-water layers which show order-disorder phenomena.

Crystallization↗
PubMed1988

[Crystal modifications of 3-cyan-6-methyl-5-(pyrid-4-yl)-1,2-dihydropyrid-2-one (milrinone)].

The preparation and characterisation of crystalline alpha-, beta- and gamma modifications of 3-cyan-6-methyl-5-(4-pyrid-4-yl)-1,2-dihydropyrid-2-on e are described. The thermic transformation of alpha- and beta-modification into gamma-modification was proved by thermogravimetric analysis (t.g.a.), differential scanning calorimetry (d.s.c.), IR and powder diffraction pattern. In dissolution behaviour no significant differences were found between the modifications.

Chemical Phenomena↗
PubMed1988

[X-ray structural analysis of 3 crystalline modifications of 3-cyan-5-methyl-5-(pyridinyl)-1,2-dihydro-pyrid-2-one (milrinone)].

The crystal and molecular structures of the alpha-, beta-, and gamma-modification of the cardiotonic compound milrinone have been determined by X-ray structure analyses. In all modifications the molecules exist in the lactam form. Because of steric hindrances the pyridine rings deviate considerably from coplanarity. The dihedral angle amounts to 45 degrees in milrinone-alpha, 43.7 degrees in milrinone-beta, and 57.5 degrees in milrinone-gamma. In the three crystal structures molecules are connected via hydrogen bonds forming dimers. These are centrosymmetric in milrinone-alpha and -beta. In milrinone-gamma the molecules within a dimer are symmetry related by a twofold axis. The dimers are linked by charge transfer interactions. This leads to infinite chains in the alpha- and beta-modification and to infinite layers in milrinone-gamma.

Crystallization↗
PubMed1987

Quantitative structure-activity relationships of estrogenic steroids substituted at C14, C15.

The uterotropic activity of thirty 3-methoxyestradiol derivatives is measured and discussed on the basis of X-ray crystallographic results and quantitative structure-activity relationship analyses involving hydrophobic substituent constants pi and f as well as steric parameters Pr and L. In addition, estrogenicity is compared to data of interceptive activity and receptor binding affinity. All the biological data exhibit a high degree of intercorrelation. 17 beta-Hydroxysteroids having 14 alpha configuration reveal a generally better capability of high-affinity binding than those being 14 beta configurated. Between the uterotropic activity and the hydrophobicity of C14, C15 substituents, statistically significant correlations are found which suggest a close contact between the steroidal D-ring subsite and the receptor protein (e.g. for 14 alpha steroids: log UDD = -0.996 pi -0.392; n = 9, r = -0.943, s = 0.235, t = -7.5, alpha less than 0.001). The hydrophobic nature of both 14 alpha and 14 beta medium-sized substituents employed is shown by QSAR regressions to exert a stronger influence than steric effects. Furthermore, there are indications to additional hydrogen bonding and steric repulsion phenomena. As to the receptor-binding models discussed in the literature, it is concluded that the receptor protein has a high conformational flexibility to accommodate very different drug structures all having the common phenolic ring A. But, if an appropriate spacing of steroidal key atoms is recognized by the receptor and, consequently, the steroid-receptor complex is formed, the binding is complemented by hydrophobic interactions also in the D-ring region.

Animals↗
PubMed1987

[Significance of the estriol profile as an endogenous function test of the fetoplacental unit].

Oestriol profile represents a functional parameter of the foetal placental unit. Basing on the fact that maternal cortisol regulates oestriol production via a negative feedback action on foetal hypothalamus, relative low serum oestriol concentrations in the morning are compared with increasing oestriol concentrations in the evening, spaced out at short-time intervals, pointing to a dynamic oestriol production of the foetal placental unit. The mean oestriol concentration in the morning and maximum peak values in the evening were determined as criteria of the oestriol profile. In normal pregnancies (n = 74) the oestriol concentration in the morning increases from an average value of 8.0 ng/ml in the 32nd/33rd week to 11.6 ng/ml in the 40th/41st week of gestation. During the same period the peak values in the evening rise from 8.8 to 15.9 ng/ml. The mean cortisol concentrations in normal pregnancies (n = 49) from 32nd to 41st week are in the range of 333 +/- 88 ng/ml in the morning and 205 +/- 66 ng/ml in the evening. There is no significant difference between individual weeks. The predictive value of the oestriol profile was assessed regarding the foetal outcome of 55 high-risk pregnancies. 32 newborn infants exhibited intrauterine growth retardation with birth weights below the 10th and 5th percentile, respectively. In this group 6 patients exhibited low oestriol values in the morning, whereas 12 demonstrated a pathological profile in the evening. In 11 of 12 high-risk pregnancies exhibiting pathological oestriol profile growth, retardation of the newborn was found to be below the 5th percentile. Cortisol concentrations do not significantly differ between normal and high-risk pregnancies.(ABSTRACT TRUNCATED AT 250 WORDS)

Circadian Rhythm↗
PubMed1985

A-ring conformational stability and progesterone-receptor binding affinity of 4-en-3-one steroids.

The molecular structure and strain energy of 4-en-3-one steroids in two different A-ring conformations are calculated by means of a molecular mechanics technique. The computations for the isolated molecules provide the following order of increasing stability of the inverted A-ring conformers: 10-methyl, 19-nor, 9-ene compound. This tendency is in agreement with X-ray structure data for single crystals. The normal 1 alpha, 2 beta-half chair conformation of 10-methyl steroids is found to be stabilized by bond angles, mainly at C10, and non-bonded interactions from the 10-methyl group. Pitzer strains favour the inverted 1 beta, 2 alpha-half chair conformation in the case of 4,9-diene-3-one compounds. Binding affinities to the progesterone receptor decrease in the series: 19-nor, 9-ene, 10-methyl compound. In view of this ordering, the calculated relative stabilities of A-ring conformers are in conflict with a conformation-controlled receptor binding. Variations of receptor bond strengths are supposed to be more strongly influenced by a steric hindrance of the 10-methyl group and/or steroid-backbone flexibility.

Animals↗
PubMed1984

Quantitative structure-activity relationships of cardiotonic steroids using empirical molecular electrostatic potentials and semiempirical molecular orbital calculations.

Empirical molecular electrostatic potentials and a rigid receptor H atom model are used to calculate differences in the interaction energy of cardiotonic steroids with the digitalis receptor. An attempt is made to map the receptor H binding sites for two different steroid conformations with respect to 17 beta side-chain orientation. The calculated interaction energies using single-crystal X-ray structure data indicate linear relationships with the Na+, K+-ATPase inhibitory activity. On the basis of these correlations, the activity of 8 so far pharmacologically not investigated steroids containing C = O in 17 beta substituents are estimated with the help of structural data determined by means of the semiempirical CNDO molecular orbital theory.

Cardiac Glycosides↗
PubMed1980

A new case of Y to X translocation in a female.

An unbalanced Y to X translocation due to a de novo mutation is described in a female with some clinical features of the Turner syndrome. Her karyotype is defined as 46,X,t(X;Y)(Xp11.2;Yq11). Hae III restriction analysis revealed an amount of male-specific DNA sequences in the normal male range. DNA replication analysis showed that in all cells studied the translocation X chromosome was late replicating and that the X segment of the translocation chromosome was later replicating while replication of the Y segment varied. A serologic test indicated a reduced titer of H-Y antigen, and biochemical studies for the enzyme steroid sulfatase revealed activity in the male range.

Adult↗
PubMed1980

Plasma levels of FSH and LH in patients with gonadal dysgenesis during sequential estrogen and progestogen therapy.

We describe the plasma levels of FSH and LH in ten patients with gonadal dysgenesis during treatment with a low dosage sequential estrogen-progestogen preparation. The daily dose of mestranol ranged from 12.5--50 microgram. Norethisterone was administered from day 16 onwards, the dose ranging between 0.75 and 1.5 mg. It was shown that 25 microgram mestranol was effective in lowering the elevated FSH levels significantly (alpha < 0.001). LH levels remained unaffected. The combination of 25 microgram mestranol and 1 mg norethisterone produced an increase of FSH and LH within 12 h, maximum levels being reached within 36 h after which there was a progressive decline. Low doses of estrogen and progestogen appeared capable of evoking physiological hypothalamic and pituitary responses in patients with gonadal dysgenesis. The doses employed were sufficient to induce breast development, growth of sexual hair, and withdrawal bleeding and were probably not high enough to induce rapid bone maturation and consequent stunting of growth.

Adolescent↗