Coping with mild inflammatory catamenial acne

BACKGROUND: Acne is a multifactorial disease exhibiting distinct clinical presentations. Among them, the catamenial type is a matter of concern for young women. Some oral contraceptives may help without, however, clearing the skin condition. AIM: The present open study aimed at evaluating the effect of overnight applications of a paste made of petrolatum,15% zinc oxide and 0.25% miconazole nitrate. METHOD: The split-face trial was conducted in 35 women. A non-medicated cream was used as control. Clinical evaluations and biometrological assessments on cyanoacrylate follicular biopsies were performed monthly for 3 months. Comedometry and the density in autofluorescent follicular casts were used as analytical parameters. In addition, the five most severe cases at inclusion were tested at the completion of the study for follicular bacterial viability using dual flow cytometry. RESULTS: Compared with baseline and to the control hemi-face, the medicated paste brought significant improvement of acne. The number of papules and their redness were reduced beginning with the first treatment phase. A reduction in the follicular fluorescence was yielded beginning with the second treatment phase. The ratios between injured and dead bacteria, on the one hand, and live bacteria, on the other hand were significantly increased at completion of the study. CONCLUSION: A miconazole paste applied for 1 week at the end of the ovarian cycle has a beneficial effect on catamenial acne.     

Strategy for Rapid Detection of Carbapenemase-Producing Enterobacteriaceae

A prospective survey was conducted on 862 Enterobacteriaceae isolates with reduced susceptibility to carbapenems. The Carba NP test, UV spectrophotometry, and a DNA microarray were used to detect carbapenemase producers, and the results were compared to those from PCR and sequencing. The 172 carbapenemase producers were detected using the Carba NP test and UV spectrophotometry, whereas the DNA microarray failed to detect IMI producers. The use of the Carba NP test as a first screening, followed by the use of molecular techniques, has been determined to be an efficient strategy for identifying carbapenemase-producing Enterobacteriaceae.     

Iron metabolism imbalance at the time of listing increases overall and infectious mortality after liver transplantation

BACKGROUND Liver transplantation(LT) is the best treatment for patients with liver cancer or end stage cirrhosis, but it is still associated with a significant mortality. Therefore identifying factors associated with mortality could help improve patient management. The impact of iron metabolism, which could be a relevant therapeutic target, yield discrepant results in this setting. Previous studies suggest that increased serum ferritin is associated with higher mortality.Surprisingly iron deficiency which is a well described risk factor in critically ill patients has not been considered.AIM To assess the impact of pre-transplant iron metabolism parameters on posttransplant survival.METHODS From 2001 to 2011, 553 patients who underwent LT with iron metabolism parameters available at LT evaluation were included. Data were prospectively recorded at the time of evaluation and at the time of LT regarding donor and recipient. Serum ferritin(SF) and transferrin saturation(TS) were studied as continuous and categorical variable. Cox regression analysis was used to determine mortality risks factors. Follow-up data were obtained from the local and national database regarding causes of death.RESULTS At the end of a 95-mo median follow-up, 196 patients were dead, 38 of them because of infections. In multivariate analysis, overall mortality was significantly associated with TS 75% [HR: 1.73(1.14; 2.63)], SF 100 μg/L [HR: 1.62(1.12;2.35)], hepatocellular carcinoma [HR: 1.58(1.15; 2.26)], estimated glomerular filtration rate(CKD EPI Cystatin C) [HR: 0.99(0.98; 0.99)], and packed red blood cell transfusion [HR: 1.05(1.03; 1.08)]. Kaplan Meier curves show that patients with low SF( 100 μg/L) or high SF( 400 μg/L) have lower survival rates at 36 mo than patients with normal SF(P = 0.008 and P = 0.016 respectively). Patients with TS higher than 75% had higher mortality at 12 mo(91.4% ± 1.4% vs 84.6% ±3.1%, P = 0.039). TS 75% was significantly associated with infection related death [HR: 3.06(1.13; 8.23)].CONCLUSION Our results show that iron metabolism imbalance(either deficiency or overload)is associated with post-transplant overall and infectious mortality. Impact of iron supplementation or depletion should be assessed in prospective study.     

Carotenoid oxidation products are stress signals that mediate gene responses to singlet oxygen in plants

(1)O(2) (singlet oxygen) is a reactive O(2) species produced from triplet excited chlorophylls in the chloroplasts, especially when plants are exposed to excess light energy. Similarly to other active O(2) species, (1)O(2) has a dual effect: It is toxic, causing oxidation of biomolecules, and it can act as a signal molecule that leads to cell death or to acclimation. Carotenoids are considered to be the main (1)O(2) quenchers in chloroplasts, and we show here that light stress induces the oxidation of the carotenoid β-carotene in Arabidopsis plants, leading to the accumulation of different volatile derivatives. One such compound, β-cyclocitral, was found to induce changes in the expression of a large set of genes that have been identified as (1)O(2) responsive genes. In contrast, β-cyclocitral had little effect on the expression of H(2)O(2) gene markers. β-Cyclocitral-induced reprogramming of gene expression was associated with an increased tolerance to photooxidative stress. The results indicate that β-cyclocitral is a stress signal produced in high light that is able to induce defense mechanisms and represents a likely messenger involved in the (1)O(2) signaling pathway in plants.     

A repulsion mechanism explains magnesium permeation and selectivity in CorA

Magnesium (Mg²⁺) plays a central role in biology, regulating the activity of many enzymes and stabilizing the structure of key macromolecules. In bacteria, CorA is the primary source of Mg²⁺ uptake and is self-regulated by intracellular Mg²⁺. Using a gating mutant at the divalent ion binding site, we were able to characterize CorA selectivity and permeation properties to both monovalent and divalent cations under perfused two-electrode voltage clamp. The present data demonstrate that under physiological conditions, CorA is a multioccupancy Mg²⁺-selective channel, fully excluding monovalent cations, and Ca²⁺, whereas in absence of Mg²⁺, CorA is essentially nonselective, displaying only mild preference against other divalents (Ca²⁺ > Mn²⁺ > Co²⁺ > Mg²⁺ > Ni²⁺). Selectivity against monovalent cations takes place via Mg²⁺ binding at a high-affinity site, formed by the Gly-Met-Asn signature sequence (Gly312 and Asn314) at the extracellular side of the pore. This mechanism is reminiscent of repulsion models proposed for Ca²⁺ channel selectivity despite differences in sequence and overall structure.Among biological divalent cations, Mg²⁺ is not only the most abundant, but also plays an essential role in a wealth of cellular processes, including enzymatic reactions, and the stability of nucleic acids and biological membranes (1). Although the biological importance of Mg²⁺ is well established, the molecular entities and mechanisms that govern its cellular homeostasis are not well understood. In bacteria, Mg²⁺ influx is primarily catalyzed by members of the CorA family of divalent ion transport systems (2, 3). The X-ray structure of CorA has provided an excellent template toward a molecular understanding of the mechanisms underlying Mg²⁺ influx (4–7). However, although CorA has been crystallized in a wide range of conditions, so far all available CorA structures seem to correspond to nonconductive conformations, which obviously limits the basic mechanistic insights regarding Mg²⁺ selectivity and translocation that can be derived from these high-resolution structures. Computational analyses, together with NMR, X-ray absorption, and Raman spectroscopy studies, have established that Mg²⁺ holds to its first hydration shell much more tightly than any other physiological cation (8–11); this implies that any Mg²⁺-selective transport system must either compensate for the high hydration energy (and accommodate the invariable octahedral geometry of this hexacoordinated ion) or establish a selectivity mechanism able to discriminate a hydrated or partially hydrated Mg²⁺ ion from monovalent and other divalent cations.Several hypotheses have been postulated to explain CorA’s function, including its role as a Mg²⁺ -selective channel (12), a Co²⁺ transporter (13), and even as an exporter of divalent cations (14). However, detailed mechanistic evaluation of CorA’s functional properties has been limited by the resolution of existing functional assays (15). Mg²⁺ transport through CorA depends on the combination of three parameters: (i) number of open gates, (ii) the electrical potential across the membrane, and (iii) the Mg²⁺ driving force, none of which can be properly controlled with sufficient time-resolution in in vivo experiments. Although a prokaryotic membrane protein, we have been able to heterologously express CorA in Xenopus oocytes, which, in combination with standard electrophysiological approaches, allowed us to measure CorA-catalyzed divalent macroscopic currents under a variety of ionic conditions. Crystallographic studies have suggested that intracellular Mg²⁺ act as the main regulator of CorA gating under physiological conditions (6). That Mg²⁺ acts as both a gating ligand and charge carrier ultimately complicates functional studies of CorA permeation and selectivity properties. To circumvent this issue we used a mutation at the divalent cation sensor that abolishes CorA Mg²⁺-dependent gating (Fig. 1A). This construct is ideally suited to evaluate ion permeation because it stabilizes steady-state currents by inhibiting the divalent ion-driven negative-feedback loop that defines CorA gating. Our results demonstrate that CorA is a bona fide multioccupancy ion channel, and that its divalent cation permeation and tight selectivity against monovalent cations can be explained on the basis of a block and repulsion mechanism, where the canonical “signature sequence” Gly-Met-Asn (GMN) plays a central role.Open in a separate windowFig. 1.CorA-driven Mg²⁺ currents recorded from TEVC. (A) The divalent cation sensor is highlighted on a cartoon representation of CorA crystal structure. Residues Asp89 and Asp253 are shown as purple sticks (B). The membrane potential (Vm) is clamped and held at −60 mV. The external solution is exchanged between two isosmotic buffers: one containing no monovalent or divalent cation (colored in gray on the horizontal bar), and one containing 20 mM Mg²⁺ (noted Mg²⁺). A representative trace recorded on a CorA–WT-expressing oocyte is shown in teal, and control oocyte trace is shown in gray and D253K in purple. The horizontal dotted line indicates the 0 A current level. (C) Representative traces of CorA D253K mutant in TEVC. The voltage pulse protocol is shown on top of the current traces. The dotted line represents the 0 current levels. (D) The corresponding I/V relationships recorded at different external Mg²⁺ concentrations are shown. The GHK-flux equation fits are displayed as solid lines, and experimental values are dots. (E) Mg²⁺ current recorded at −60 mV under external solution perfusion. The external solution is changed stepwise and the corresponding solution exchange protocol is superimposed to the trace. (F) Mean values (±SD) of several traces (n ≥ 5) were recorded and normalized to the maximum current. The values were plotted against the external [Mg²⁺] and fitted with a single-site binding curve.     

A microdevice for parallelized pulmonary permeability studies

We describe a compartmentalized microdevice specifically designed to perform permeability studies across a model of lung barrier. Epithelial cell barriers were reproduced by culturing Calu-3 cells at the air-liquid interface (AIC) in 1 mm² microwells made from a perforated glass slide with an embedded porous membrane. We created a single basolateral reservoir for all microwells which eliminated the need to renew the growth medium during the culture growth phase. To perform drug permeability studies on confluent cell layers, the cell culture slide was aligned and joined to a collection platform consisting in 35 μL collection reservoirs connected at the top and bottom with microchannels. The integrity and functionality of the cell barriers were demonstrated by measurement of trans-epithelial electrical resistance (TEER), confocal imaging and permeability assays of ¹⁴C-sucrose. Micro-cell barriers were able to form confluent layers in 1 week, demonstrating a similar bioelectrical evolution as the Transwell systems used as controls. Tight junctions were observed throughout the cell-cell interfaces, and the low permeability coefficients of ¹⁴C-sucrose confirmed their functional presence, creating a primary barrier to the diffusion of solutes. This microdevice could facilitate the monitoring of biomolecule transport and the screening of formulations promoting their passage across the pulmonary barrier, in order to select candidates for pulmonary administration to patients.