Leptin inhibits directly glucocorticoid secretion by normal human and rat adrenal gland.

Different interactions have been described between glucocorticoids and the product of the ob gene leptin. Leptin can inhibit the activation of the hypothalamo-pituitary-adrenal axis by stressful stimuli, whereas adrenal glucocorticoids stimulate leptin production by the adipocyte. The present study was designed to investigate the potential direct effects of leptin to modulate glucocorticoid production by the adrenal. Human adrenal glands from kidney transplant donors were dissociated, and isolated primary cells were studied in vitro. These cells were preincubated with recombinant leptin (10(-10)-10(-7) M) for 6 or 24 h, and basal or ACTH-stimulated cortisol secretion was subsequently measured. Basal cortisol secretion was unaffected by leptin, but a significant and dose-dependent inhibition of ACTH-stimulated cortisol secretion was observed [down by 29 +/- 0.1% of controls with the highest leptin dose, P < 0.01 vs. CT (unrelated positive control)]. This effect of leptin was also observed in rat primary adrenocortical cells, where leptin inhibited stimulated corticosterone secretion in a dose-dependent manner (down by 46 +/- 0.1% of controls with the highest leptin dose, P < 0.001 vs. CT). These effects of leptin in adrenal cells are likely mediated by the long isoform of the leptin receptor (OB-R), because its transcript was found to be expressed in the adrenal tissue and leptin had no inhibitory effect in adrenal glands obtained from db/db mice. Therefore, leptin inhibits directly stimulated cortisol secretion from human and rat adrenal glands, and this may represent an important mechanism to modulate glucocorticoid levels in various metabolic states.

Superconducting p-branes and extremal black holes

In Einstein-Maxwell theory, magnetic flux lines are "expelled" from a black hole as extremality is approached, in the sense that the component of the field strength normal to the horizon goes to zero. Thus, extremal black holes are found to exhibit the sort of ¿Meissner effect¿ which is characteristic of superconducting media. We review some of the evidence for this effect and present new evidence for it using recently found black hole solutions in string theory and Kaluza-Klein theory. We also present some new solutions, which arise naturally in string theory, which are non-superconducting extremal black holes. We present a nice geometrical interpretation of these effects derived by looking carefully at the higher dimensional configurations from which the lower dimensional black hole solutions are obtained. We show that other extremal solitonic objects in string theory (such as p-branes) can also display superconducting properties. In particular, we argue that the relativistic London equation will hold on the world volume of ¿light¿ superconducting p-branes (which are embedded in flat space), and that minimally coupled zero modes will propagate in the adS factor of the near-horizon geometries of "heavy," or gravitating, superconducting p-branes.

Molecular dynamics study of the longitudinal modes in disparate-mass binaryliquid mixtures.

A series of molecular dynamics simulations of simple liquid binary mixtures of soft spheres with disparate-mass particles were carried out to investigate the origin of the marked differences between the dynamic structure factors of some liquid binary mixtures such as the Li0.7Mg0.3 and Li0.8Pb0.2 alloys. It is shown that the facility for observing peaks associated with fast-propagating modes in the partial Li-Li dynamic structure factor of Li0.8Pb0.2 should be mainly attributed to the structure of this alloy, which is characterized by an incipient ABAB ordering as found in molten salts. The longitudinal dispersion relations at intermediate wave vectors obtained from the longitudinal current spectra are very similar for the two alloys and reflect the existence of both fast-and slow-propagating modes of kinetic character associated with light and heavy particles, respectively. The influence of the hardness of the repulsive potential cores as well as the composition of the mixture on the longitudinal collective modes is also discussed.

Insulin modulation of luteinizing hormone secretion in normal female volunteers and lean polycystic ovary syndrome patients.

BACKGROUND/AIMS: Endocrine features of polycystic ovary syndrome (PCOS) include altered ovarian steroidogenesis, hyperinsulinemia and abnormal luteinizing hormone (LH) secretion. This study was undertaken to further evaluate the role of insulin to modulate LH secretion in lean PCOS patients with normal insulin sensitivity and normal volunteers. METHODS: The study was performed in five nonobese patients diagnosed with PCOS on the basis of amenorrhea and a polycystic morphology at ovarian ultrasound, and 5 normal controls in early to mid-follicular phase and matched for weight and age. All subjects were phenotyped, and then admitted for 12 h of frequent (q 10') blood sampling on two separate occasions, once for a baseline study and the other time for a hyperinsulinemic and euglycemic clamp study. LH was measured in samples obtained throughout each admission in order to perform LH pulse analysis. RESULTS: Baseline LH secretion in PCOS subjects was significantly different from controls: they had higher LH levels, higher LH/FSH ratios as well as a faster LH pulse frequency than normal women. Insulin administration did not affect the pattern of LH secretion of PCOS patients, whereas it significantly increased the LH pulse frequency while decreasing the LH interpulse intervals in the controls. CONCLUSIONS: These data confirm that an abnormal pattern of LH secretion characteristic of PCOS can be observed in lean patients, and appears independent of peripheral insulin levels. Furthermore, our results in lean controls provide the first direct evidence that peripheral insulin can modulate the activity of hypothalamic gonadotropin-releasing hormone (GnRH) neurons in the human.

Dose-dependent effect of atrial natriuretic peptide on blood pressure, heart rate, and skin blood flow of normal volunteers.

Synthetic atrial natriuretic peptide, containing 26 amino acids in the rat sequence, L-364, 343 (Ileu-ANP), was infused intravenously at increasing rates (1-40 micrograms/min) into four normal volunteers. Mean intraarterial blood pressure decreased and heart rate increased in cumulative-dose-dependent fashion. Skin blood flow as measured with a laser Doppler device rose already with a cumulative dose of 55 micrograms Ileu-ANP and further rises were directly related to dose. The only side effects observed were those accompanying symptomatic hypotension at higher doses. These findings provide strong evidence that Ileu-ANP acts as a vasodilator in normal volunteers.

Quasi-two-dimensional electrodeposition under forced fluid flow

Experimental quasi-two-dimensional Zn electrodeposits are grown under forced convection conditions. Large-scale effects, with preferential growth towards the impinging flow, together with small-scale roughness suppression effects are evidenced and separately analyzed by using two different radial cell configurations. Interpretations are given in terms of primary concepts concerning current and concentration distributions.

Dispersion of passive particles by a quasi-two-dimensional turbulent flow

Using the experimental data of Paret and Tabeling [Phys. Rev. Lett. 79, 4162 (1997)] we consider in detail the dispersion of particle pairs by a two-dimensional turbulent flow and its relation to the kinematic properties of the velocity field. We show that the mean square separation of a pair of particles is governed by rather rare, extreme events and that the majority of initially close pairs are not dispersed by the flow. Another manifestation of the same effect is the fact that the dispersion of an initially dense cluster is not the result of homogeneously spreading the particles within the whole system. Instead it proceeds through a splitting into smaller but also dense clusters. The statistical nature of this effect is discussed.

Further insights on dynamic morphological transitions in quasi-two-dimensional electrodeposition

Dynamic morphological transitions in thin-layer electrodeposits obtained from copper sulphate solutions have been studied. The chemical composition of the electrodeposits indicates that they appear as a consequence of the competition between copper and cuprous oxide formation. In addition, the Ohmic control of the process is verified at initial stages of the deposit growth. At higher deposit developments, gravity-induced convection currents play a role in the control of the whole process and affect the position of these transitions.

Influence of an inert electrolyte on the morphology of quasi-two-dimensional electrodeposits

The influence of an inert electrolyte (sodium sulfate) on quasi-two-dimensional copper electrodeposition from a nondeaerated aqueous copper sulfate solution has been analyzed. The different morphologies for a fixed concentration of CuSO4 have been classified in a diagram in terms of the applied potential and the inert electrolyte concentration. The main conclusion is the extension of the well-known Ohmic model for the homogeneous growth regime for copper sulfate solutions with small amounts of sodium sulfate. Moreover, we have observed the formation of fingerlike deposits at large applied potential and inert electrolyte concentration values, before hydrogen evolution becomes the main electrode reaction.

Les modes à travers trois siècles : exposition rétrospective organisée par la Société Nationale des Beaux-Arts, dans les Palais du domaine de Bagatelle, du 15 mai au 15 juillet 1911 : catalogue

[Exposition. Paris, Palais du domaine de Bagatelle. 1911]

Comparison of thermogenic activity induced by the new sympathomimetic Ro 16-8714 between normal and obese subjects.

In a previous study, we demonstrated that the new beta-adrenoceptor agonist Ro 16-8714 possesses thermogenic property in normal male volunteers. The aim of the present study was to compare the metabolic response of lean vs obese individuals to a similar dose of this compound. Following an overnight fast, Ro 16-8714 (0.17 mg/kg fat free mass) or a placebo was given per os to six normal-weight subjects and to six moderately obese subjects. The rate of energy expenditure (EE) and the substrate utilization were determined by indirect calorimetry (hood system) before and for 6 h following the drug administration. Heart rate and blood pressure as well as plasma glucose, insulin and free fatty acid (FFA) concentrations were also measured at regular intervals throughout the study. The increment relative to base-line (mean +/- s.e.m.) in EE was similar in the two groups and averaged 4.0 +/- 1.4 per cent and 12.2 +/- 1.4 per cent with placebo and with Ro 16-8714 respectively in lean subjects, whereas the values reached 3.5 +/- 1.2 per cent and 14.4 +/- 2.0 per cent in obese subjects. Heart rate, systolic blood pressure, insulin and FFA were increased without any significant difference between the two groups. This study shows that Ro 16-8714 is a potent thermogenic agent both in normal and obese subjects.