A sharp estimate for the first Robin-Laplacian eigenvalue with negative boundary parameter

In this paper we prove that the ball maximizes the first eigenvalue of the Robin Laplacian operator with negative boundary parameter, among all convex sets of \mathbb{R}^n with prescribed perimeter. The key of the proof is a dearrangement procedure of the first eigenfunction of the ball on the level sets of the distance function to the boundary of the convex set, which controls the boundary and the volume energies of the Rayleigh quotient

The Influence of Electro-Mechanical Effects on Resonant Electron Tunneling Through Small Carbon Nano-Peapods

The influence of a fullerene molecule trapped inside a single-wall carbon nanotube on resonant electron transport at low temperatures and strong polaronic coupling is theoretically discussed. Strong peak to peak fluctuations and anomalous temperature behavior of conductance amplitudes are predicted and investigated. The influence of the chiral properties of carbon nanotubes on transport is also studied.Comment: 17 pages, 3 figures. Replaced with published version. Important changes. Open access: http://stacks.iop.org/1367-2630/10/04304

Physiological and pathophysiological role of somatostatin receptors in the human thymus

This is a review summarizing the physiological and pathophysiological role of somatostatin receptors in the human thymus

The Metabolic Profile in Active Acromegaly is Gender-Specific.

CONTEXT: The sexual dimorphism of the somatotroph axis has been documented, but whether the acromegaly-related metabolic alterations are gender-dependent has never been investigated. OBJECTIVE: The aim of the study was to evaluate the impact of gender on the metabolic parameters in acromegaly. DESIGN: We conducted a retrospective, comparative, multicenter study. PATIENTS: The 307 newly diagnosed acromegalic patients included in the study were grouped by gender: 157 men (aged 48.01 ± 14.28 yr), and 150 women (aged 48.67 ± 14.95 yr; of which 77 were premenopausal and 73 postmenopausal). OUTCOME MEASUREMENTS: We measured each component of the metabolic syndrome (MS), hemoglobin A1c, the areas under the curve (AUCs) of glucose and insulin during 2-h oral glucose tolerance test, basal insulin resistance using the homeostasis model assessment of the insulin resistance index, stimulated insulin sensitivity using the insulin sensitivity index, early insulin-secretion rate using the insulinogenic index, β-cell function relative to insulin sensitivity using the oral disposition index and the visceral adiposity index (VAI) as the surrogate of visceral fat function. RESULTS: Women showed a higher prevalence of MS (P < 0.001), higher fasting insulin levels (P < 0.001), AUC for insulin (P = 0.002), homeostasis model assessment of the insulin resistance index (P < 0.001), and VAI (P < 0.001) and a lower insulin sensitivity index (P = 0.002) than men, whereas no difference was found in fasting glucose, AUC for glucose, hemoglobin A1c, insulinogenic index, and oral disposition index. In women, fasting glucose and fasting insulin showed a significant trend toward increase (P < 0.001) and decrease (P = 0.004), respectively, from the first to the fourth quartiles of age, whereas VAI showed a trend toward increase in both groups (P < 0.001). A significantly higher prevalence of MS (P < 0.001), increased waist circumference (P < 0.001), low high-density lipoprotein cholesterol (P < 0.001), and overt diabetes mellitus (P < 0.001) was found in postmenopausal women compared with premenopausal women, as well as with men. CONCLUSIONS: The majority of metabolic features in acromegaly are gender-specific. Active acromegaly in women is strongly associated with higher visceral adiposity dysfunction, insulin resistance, and the features of MS. We suggest more accurate metabolic management in acromegalic women, especially in the postmenopausal years

Somatostatin receptor subtypes in human thymoma and inhibition of cell proliferation by octreotide in vitro

Somatostatin (SS) and SS receptor (SSR) subtypes, code-named sst1-5, are heterogeneously expressed in the normal human thymus. This suggests their involvement in controlling the immune and/or neuroendocrine functions in this organ. Moreover, recently a high in vivo uptake of [111In-DTPA-D-Phe1]octreotide has been reporte

Local and global behaviour of nonlinear equations with natural growth terms

This paper concerns a study of the pointwise behaviour of positive solutions to certain quasi-linear elliptic equations with natural growth terms, under minimal regularity assumptions on the underlying coefficients. Our primary results consist of optimal pointwise estimates for positive solutions of such equations in terms of two local Wolff's potentials.Comment: In memory of Professor Nigel Kalto

In vitro characterization of somatostatin receptors in the human thymus and effects of somatostatin and octreotide on cultured thymic epithelial cells

Somatostatin (SS) and its analogs exert inhibitory effects on secretive and proliferative processes of various cells via high affinity SS receptors (SS-R). SS analogs bind with different affinity to the five cloned SS-R subtypes. Octreotide, an octapeptide SS analog, binds with high affinity to the SS-R subtype 2 (sst2). SS-R have been demonstrated in vivo and in vitro on cells from endocrine and immune systems. Among the lymphatic tissues, the thymus has been shown to contain the highest amount of SS, suggesting a local functional role of the peptide. We investigated the SS distribution and SS-R expression pattern in the normal human thymus using autoradiography, membrane homogenate binding studies, and RT-PCR. In addition, the effect of SS and octreotide on growth of cultured thymic epithelial cells (TEC) was studied. By autoradiography, binding of [125I-Tyr0]-SS-28 and [125I-Tyr3]-octreotide was detected in all seven thymuses studied. Specific [125I-Tyr3]-octreotide binding was shown on membrane preparations from thymuses, while not from cultured thymocytes. RT-PCR showed the expression of sst1, sst2A and sst3 messenger RNA (mRNA) in the thymic tissue, whereas sst1 and sst2A mRNAs were found in isolated TEC. SS mRNA was present in thymic tissue and in isolated TEC. SS and octreotide significantly inhibited 3H-thymidine incorporation in 3 of 3 and 6 of 6 TEC cultures, respectively. The percent inhibition ranged from 38.8 to 66.8% for SS and from 19.1 to 59.5% for octreotide. In conclusion, SS mRNA and sst1, sst2A, and sst3 mRNAs are expressed in the normal human thymus. Cultured TEC selectively express sst1 and sst2A mRNA and respond in vitro to SS and octreotide administration with an inhibition of cell proliferation. These data suggest a paracrine/autocrine role of SS and its receptors in the regulation of cell growth in thymic microenviron

Physiological and pathophysiological role of somatostatin receptors in the human thymus

During the first half of the previous century, the evidence that the endocrine and nervous systems integrate and regnlate different functions in the human body coincided with the new findings supporting the concept that immune mechanisms may be influenced by these systems as well. In the past decades, many studies were carried out to understand the molecular and cellular basis of interactions between the immune system and neuroendocrine activities. TIle interactions between the inunune, endocrine and nervous systems are very complex. Although the accumulated information is enormous, many reciprocal interactions are poorly understood, several mechanisms are still difficult to interpret, and in some cases the results are even contradictory. Nevertheless, increasing numbers of researchers and many laboratories are nowadays focused on understanding how hormones, neuropeptides, neurotransmitters and specific products of inunWle cells exert their regulatory functions and act in integrating such different systems

Fibre-reinforced geopolymer concretes for sensible heat thermal energy storage: Simulations and environmental impact

Power plants based on solar energy are spreading to accomplish the incoming green energy transition. Besides, affordable high-temperature sensible heat thermal energy storage (SHTES) is required. In this work, the temperature distribution and thermal performance of novel solid media for SHTES are investigated by finite element method (FEM) modelling. A geopolymer, with/without fibre reinforcement, is simulated during a transient charging/discharging cycle. A life cycle assessment (LCA) analysis is also carried out to investigate the environmental impact and sustainability of the proposed materials, analysing the embodied energy, the transport, and the production process. A Multi-Criteria Decision Making (MCDM) with the Analytical Hierarchy Process (AHP) approach, taking into account thermal/environmental performance, is used to select the most suitable material. The results show that the localized reinforcement with fibres increases thermal storage performance, depending on the type of fibre, creating curvatures in the temperature profile and accelerating the charge/discharge. High-strength, high-conductivity carbon fibres performed well, and the simulation approach can be applied to any fibre arrangement/material. On the con-trary, the benefit of the fibres is not straightforward according to the three different scenarios developed for the LCA and MCDM analyses, due to the high impact of the fibre production processes. More investigations are needed to balance and optimize the coupling of the fibre material and the solid medium to obtain high thermal performance and low impacts

Dopamine receptor expression and function in corticotroph pituitary tumors

The role of dopamine agonist treatment in corticotroph pituitary tumors is controversial. The aim of this study was to evaluate D(2) receptor expression in 20 corticotroph pituitary tumors and to correlate it to the in vitro effect of dopamine agonists on ACTH secretion and the in vivo effect of short-term cabergoline treatment on cortisol secretion. D(2) expression was evaluated by receptor-ligand binding, immunohistochemistry, and RT-PCR. A 50% or more decrease in daily urinary cortisol levels was considered a significant clinical response. At receptor-ligand binding, specific binding of [(125)I]epidepride was found in 80% of cases. At immunohistochemistry, specific D(2) immunostaining was found in 75% of cases. D(2) expression was found in 83.3% of cases (D(2long) in 40%, D(2short) in 20%, and both in 40%) by RT-PCR. Significant in vitro inhibition of ACTH secretion was found in 100% of D(2)-positive cases, but not in 100% of D(2)-negative cases by either bromocriptine or cabergoline. A significant in vivo inhibition of cortisol secretion after 3-month cabergoline treatment was found in 60%, although a normalization of cortisol secretion was found in 40% of cases. All cabergoline-responsive cases were associated with D(2) expression, whereas all noncabergoline-responsive cases but one were not associated with D(2) expression. In conclusion, functional D(2) receptors were expressed in approximately 80% of corticotroph pituitary tumors. The effectiveness of cabergoline in normalizing cortisol secretion in 40% of cases supports its therapeutic use in the management of Cushing's disease