High-Precision Spectroscopy of

The excited states of unstable ^{20}O were investigated via γ-ray spectroscopy following the ^{19}O(d,p)^{20}O reaction at 8 AMeV. By exploiting the Doppler shift attenuation method, the lifetimes of the 2_{2}^{+} and 3_{1}^{+} states were firmly established. From the γ-ray branching and E2/M1 mixing ratios for transitions deexciting the 2_{2}^{+} and 3_{1}^{+} states, the B(E2) and B(M1) were determined. Various chiral effective field theory Hamiltonians, describing the nuclear properties beyond ground states, along with a standard USDB interaction, were compared with the experimentally obtained data. Such a comparison for a large set of γ-ray transition probabilities with the valence space in medium similarity renormalization group ab initio calculations was performed for the first time in a nucleus far from stability. It was shown that the ab initio approaches using chiral effective field theory forces are challenged by detailed high-precision spectroscopic properties of nuclei. The reduced transition probabilities were found to be a very constraining test of the performance of the ab initio models.

A robust assay for dexamethasone in plasma using a heterologous 125I radioligand and a magnetizable solid-phase antiserum.

An assay using an antiserum raised against a dexamethasone 21-hemisuccinate conjugate and the heterologous radioligand dexamethasone 21-(carboxymethyl) ether was developed, validated, and used to study the pharmacokinetics of this steroid for 12 h following administration to patients with congenital adrenal hyperplasia. Coupling the antiserum to magnetizable cellulose allowed rapid separation of bound/free steroid. A C-21 rather than a C-3 antiserum was used to minimize interference with a main metabolite, 6 beta-hydroxydexamethasone. Close correspondence of assay (0.35 nmol/L) and curve (0.25 nmol/L) sensitivities suggests that interference by matrix effects is minimal. This was confirmed by good agreement in data from the in-house assay and that of a reference procedure. Good precision was demonstrated by the precision profile and Shewhart chart quality control data. The latter also demonstrated the assay was robust and reliable in routine practice.

Specific determination of plasma dexamethasone by HPLC and RIA--application to standard dexamethasone suppression test in psychiatric patients.

Three radioimmunoassays (RIA), with or without preparative HPLC, were applied to the monitoring of plasma dexamethasone (DXM) levels during standard dexamethasone suppression test (DST) in psychiatric patients. Due to the robotic ease of the fully automated HPLC process, precision of the chromatographic assay was equivalent to that of the direct assays, but prepurification improved both sensitivity and specificity. These improvements allowed the elucidation of the following features: (1) half (36) of the patients (68) displayed infranormal DXM levels (less than or equal to 0.40 ng/ml) whatever the cortisol response; (2) 22% (15) patients (68) with DXM levels in the low control range showed a strong inhibition of cortisol suppression. These observations raise some doubts on the validity of the DST test and introduce the following questions. (1) What is the dependence of cortisol suppression upon DXM absorption and catabolism? (2) Does plasma DXM measurement several hours after its physiological action still reflect its effect on the hypothalamo-hypophyseal axis? (3) What is the reliability of DXM direct assays when measuring low DXM levels in the presence of high cortisol?

Control of circadian and episodic variations of adrenal androgens secretion in man.

The 24-h profiles of plasma cortisol (F), 11-beta-hydroxyandrostenedione (11OHAD), androstenedione (AD), dehydroisoandrosterone (DHEA) and testosterone (T) were obtained simultaneously in 11 normal males sampled at 15-min intervals. The data were submitted to a detailed quantitative analysis including the estimation of the circadian rhythm and of the episodic variations as well as the evaluation of the concomitance of episodic pulses of different hormones. A bimodal circadian rhythm was detected in the various individual profiles. The major acrophase occurred in the morning earlier for T (around 04:00 h) than for the hormones of totally or partially adrenal origin (around 07:00 h); the secondary acrophase (around 17:00 h) and the main midnight nadir were common to all hormones. The amplitude of the rhythm was highest for purely adrenal hormones (F and 11OHAD), averaging 79 and 75%, respectively, lower for hormones of mixed origin (DHEA and AD), averaging 44 and 42%, respectively, and minimal for T (22%). The possible relationship between the circadian and pulsatile variations of the various steroids was estimated in each individual by calculating Pearson's standard coefficient of variation on all pairs of hormonal profiles. A very tight relationship (r greater than 0.75; p less than 0.001) was found between the 4 adrenal hormones in each individual; a looser but significant correlation (r greater than 0.30; p less than 0.001) was also detected between T and its partial precursors (AD and DHEA) and between T and the purely adrenal hormones: F and 11OHAD (r greater than 0.30; p less than 0.01). The pulsatility of the corticotrophic axis was readily transmitted to the secretory pattern of 11OHAD, DHEA and AD. Ninety-six percent of the F pulses were reflected in at least one other hormonal profile. Finally, we showed that concomitant pulses common to the five adrenal and gonadal patterns were more frequent than would be expected on the basis of chance. These results: demonstrate a total parallelism between the long-lasting secretory events and the episodic bursts of the 4 adrenal hormones showing that the reticular and fascicular zones of the adrenal respond to pituitary control as an homogeneous structure; demonstrate the existence of a partial synchronization of adrenal and testicular pulsatile variations; suggest that, throughout the afternoon, a common mechanism may influence the slow variations of adrenal hormones and of testicular testosterone.

The dynamics of 11-beta-hydroxy-androstenedione (11 OHAD) metabolism in man.

The aim of the study was to determine the main metabolic parameters of 11-beta-hydroxy-androstenedione (11 OHAD) in man. Seven normal subjects were investigated at 1-3 months interval by 2 types of isotope dilution techniques using a tritiated tracer: constant infusion and bolus iv injection. 3H-11 OHAD and 3H-11-beta-hydroxy-androsterone (3H-11 OA) were isolated by gel column chromatography, unlabeled 11 OHAD was determined by RIA, unlabelled 11 OA by GLC. The results included computation of free and conjugated catabolite fractions. 3H-11 OHAD MCR determined from the infusion or the injection data averaged ca 1250 ml/min or 1800 L/d (CV: +/- 10%) providing a mean estimation of unlabelled 11 OHAD BPR of 1.5 +/- 0.15 mg/d. UPR estimations gave similar values. 3H-11 OHAD fractional catabolic rate drawn from the postinfusion or the injection curve averaged ca 1.4% per min (CV: +/- 7%). Mean total distribution volume ranged between 90 and 120 L according to the type of experiment. Extrapolation to time zero of the injection curve (2 exponentials) provided an estimation of 32 +/- 5 L for rapid exchange compartment. Urinary recovery of labelled compounds was complete within 24 h whereas the excretion of undegraded 3H-11 OHAD was undetectable; urinary clearance rate of 3H-conjugates approached that of creatinine. The present data show that: the secretion rate of 11 OHAD is equivalent to that of its direct precursor, adrenal androstenedione; its large MCR value results from the size of its exchange volume-equivalents.(ABSTRACT TRUNCATED AT 250 WORDS)

Evolution of the delta 4-adrenal androgens responsiveness in childhood during insulin test.

Serum 11-beta-hydroxy-androstenedione (11OHAD), androstenedione (AD) and cortisol (F) were estimated during an i.v. insulin test in 2 large groups of normal prepubertal children and in normal adults. The results revealed that the basal level and responsiveness of AD were much lower in both groups of children than in adults whereas the corresponding 11OHAD data were similar or superior to those of adults. This suggests that during childhood the limited amount of adrenal AD is preferentially switched to the 11-hydroxylation step. Comparison of hormonal data observed in adults after i.v. insulin (mild ACTH stimulation) and a maximal stimulating dose of synacthen showed that the sensitivity of delta 4-3 keto-androgens pathway is inferior to that of F.

An improved method for the detection of heterozygosity of congenital virilizing adrenal hyperplasia.

A modified short ACTH test for the detection of heterozygote carriers of 21-hydroxylase deficiency (21-OHD) was applied to twenty-one controls and fourteen parents of children with 21-OHD. The following modifications were introduced: (1) Endogenous ACTH was suppressed by dexamethasone administration prior to the test, (2) Plasma 17-hydroxyprogesterone (17-OHP), cortisol (F), progesterone (P), corticosterone (B) and delta 4- androstenedione (A) were measured, (3) Variables studied were the ratio of plasma increments (delta) between precursors and end products, (4) Data were analysed by a step-wise discriminant analysis. Significant alterations in the metabolic pathway of F, B and A were demonstrated. The discriminant analysis showed that the addition of B pathway data did not improve the discrimination potency of the test performed on F pathway data. The combination of variates which provided the best discrimination was the logarithmic sum of delta 170HP/delta F at 15 and 30 min. It led to a 94% correct classification for normals and carriers.

Determination of reference standards for adrenal steroids excretion in normal prepuberal children.

An improved method of gas-liquid chromatography (GLC) for routine estimation of adrenal steroids in urine is presented. It was applied to the exploration of steroid output in 120 normal prepuberal children to both sexes aged 3 months-12 years. Urinary data were compared to plasmatic values of adrenal hormones estimated by radio-immuno-assays (RIA). Analysis of the relationships between steroids outputs and bone age revealed that the excretion of cortisol catabolites was expressed by a saturation curve whereas that of delta 4-3 keto androgens catabolites were expressed by geometrical pregression curves; urine dehydroepiandrosterone (DHEA) and plasma DHEA-sulfate showed outbreaks of high values beyond 6 years of age which ruled out all curve fitting attempts. The computation of these relationships allowed to determine the confidence belts of the various regressions which appear as a useful tool to estimate the delayed or accelerated character of adrenal activity in prepuberal childhood. Comparison of the various urinary (GLC) and plasmatic (RIA) parameters enabled us to comment on adrenal puberty.

A direct radio-immunoassay for plasma delta 4-androstenedione. Application to children.

A RIA for the estimation of delta 4-androstenedione in human plasma without chromatographic purification is analyzed. Sensitivity, accuracy, precision and specificity are shown to be, at least, equivalent to those of methods involving chromatography.

Kinetics of plasma corticosteroids during metyrapone infusion in man.

The effect of metyrapone on plasma kinetics of cortisol (F), 11-deoxycortisol (S), corticosterone (B), 11-deoxycorticosterone (DOC), aldosterone (Aldo) and 17 hydroxyprogesterone (17 OHP) was studied in ten normal prepubertal children intravenously infused with the drug (1 gm/1.73 m2 body surface area in 4 h). Similar falls in F, B and Aldo were observed during the first hour expressing similar sensitivity of the 11 hydroxylases to the drug. The effect of the compensatory increase of endogenous ACTH could be detected after 1 hour by the rise in 17 OHP. However the concentrations of the 11-hydroxy compounds, F, B and Aldo, remained low throughout the infusion period. From the second hour onwards, facilitation of the synthesis of DOC was noticed. After the end of infusion, the levels of the precursors decreased and F and B were restored to initial values. Aldo remained low probably due to the inhibitory effect of the elevated DOC on the renin-angiotensin system.

Serial measurements of vitamin B-12 and vitamin B-12-binding capacity in marasmic kwashiorkor.

Vitamin B-12 and total vitamin B-12-binding capacity (TBBC) have been determined by a radio-saturation assay in the blood of a large group of patients suffering from marasmic kwashiorkor on admission, and during their whole re-feeding. The results have been compared with values obtained in control children of the same ethnic group and with normal children living in Belgium. Vitamin B-12 levels are high on admission and only normalize during the second month of re-feeding. TBBC is normal on admission but significantly increases during re-feeding.