Molecular dynamics calculations suggest a conduction mechanism for the M2 proton channel from influenza A virus

The M2 protein of the influenza A virus is activated by low endosomal pH and performs the essential function of proton transfer into the viral interior. The resulting decrease in pH within the virion is essential for the uncoating and further replication of the viral genetic material. The x-ray crystal [Stouffer AL, et al. (2008) Nature 451:596–599] and solution NMR [Schnell JR, Chou JJ (2008) Nature 451:591–595] structures of the transmembrane region of the M2 homo-tetrameric bundle both revealed pores with narrow constrictions at one end, leaving a question as to how protons enter the channel. His-37, which is essential for proton-gating and selective conduction of protons, lies in the pore of the crystallographic and NMR structures. Here, we explore the different protonation states of the His-37 residues of the M2 bundle in a bilayer using molecular dynamics (MD) simulations. When the His-37 residues are neutral, the protein prefers an Open_out-Closed_in conformation in which the channel is open to the environment on the outside of the virus but closed to the interior environment of the virus. Diffusion of protons into the channel from the outside of the virus and protonation of His-37 residues in the tetramer stabilizes an oppositely gated Closed_out-Open_in conformation. Thus, protons might be conducted through a transporter-like mechanism, in which the protein alternates between Open_out-Closed_in and Closed_out-Open_in conformations, and His-37 is protonated/deprotonated during each turnover. The transporter-like mechanism is consistent with the known properties of the M2 bundle, including its relatively low rate of proton flux and its strong rectifying behavior.     

From the Cover: High-pressure photodissociation of water as a tool for hydrogen synthesis and fundamental chemistry

High-pressure methods have been demonstrated to be efficient in providing new routes for the synthesis of materials of technological interest. In several molecular compounds, the drastic pressure conditions required for spontaneous transformations have been lowered to the kilobar range by photoactivation of the reactions. At these pressures, the syntheses are accessible to large-volume applications and are of interest to bioscience, space, and environmental chemistry. Here, we show that the short-lived hydroxyl radicals, produced in the photodissociation of water molecules by near-UV radiation at room temperature and pressures of a few tenths of a gigapascal (GPa), can be successfully used to trigger chemical reactions in mixtures of water with carbon monoxide or nitrogen. The detection of molecular hydrogen among the reaction products is of particular relevance. Besides the implications in fundamental chemistry, the mild pressure and irradiation conditions, the efficiency of the process, and the nature of the reactant and product molecules suggest applications in synthesis.     

Drug-induced liver injury due to ＂natural products＂ used for weight loss： A case report

Taking herbal-extracts to lose weight is an underestimated health hazard. Often, these products contain active agents that can cause acute liver damage. In this case report, a 22-year-old female patient, who presented with a feature of cholestatic syndrome, was so sure that the ＂natural products＂were not dangerous that she did not inform her physicians that she had taken them, making their task that much more challenging. Clinical presentation mimicked acute cholecystitis and the patient underwent a cholecystectomy. Surgery was without any consequences and complications, although it did not completely cure the illness. She later admitted to having taken herbal remedies and this led to the correct diagnosis of phytotherapy-related hepatotoxicity and a successful therapeutic approach. The true incidence of phytotherapy-related hepatotoxicity and its pathogenic mechanisms are largely unknown. It is important to increase the awareness of both clinicians and patients about the potential dangers of herbal remedies.     

Metallic elements in exhaled breath condensate of patients with interstitial lung diseases

Epidemiological data support the hypothesis that environmental and occupational agents play an important role in the development of interstitial lung diseases such as idiopathic interstitial pneumonia (IIPs) and sarcoidosis. The aim of this study was to assess the elemental composition of exhaled breath condensate (EBC) in patients with interstitial lung diseases (ILDs) of unknown etiology and healthy subjects as an indirect evaluation of tissue burden, which could improve our understanding of the role of metals in the pathogenesis of ILDs. EBC was obtained from 33 healthy subjects, 22 patients with sarcoidosis, 15 patients with non-specific interstitial pneumonia (NSIP) and 19 with IIPs. Trace elements and toxic metals in the samples were measured by means of inductively coupled plasma-mass spectrometry. There are only small overall differences in the EBC levels of a number of metallic elements among patients with idiopathic pulmonary fibrosis (IPF), NSIP or sarcoidosis, and no pattern is capable of distinguishing them with a high degree of sensitivity and specificity. However, a pattern of pneumotoxic (Si, Ni) and essential elements (Zn, Se and Cu) with the addition of Co distinguished the patients with ILDs from healthy non-smokers with relatively high degrees of sensitivity (96.4%) and specificity (90.9%). Assessing the elemental composition of EBC in patients with different ILDs seems to provide useful information. The non-invasiveness of the EBC method makes it suitable for patients with pulmonary diseases, although further studies are required to confirm the usefulness of this approach and to better understand the underlying pathophysiological processes.     

Diagnostic utility of flow cytometry in low-grade myelodysplastic syndromes: a prospective validation study

Background

The diagnosis of myelodysplastic syndromes is not always straightforward when patients lack specific diagnostic markers, such as blast excess, karyotype abnormality, and ringed sideroblasts.

Design and Methods

We designed a flow cytometry protocol applicable in many laboratories and verified its diagnostic utility in patients without those diagnostic markers. The cardinal parameters, analyzable from one cell aliquot, were myeloblasts (%), B-cell progenitors (%), myeloblast CD45 expression, and channel number of side scatter where the maximum number of granulocytes occurs. The adjunctive parameters were CD11b, CD15, and CD56 expression (%) on myeloblasts. Marrow samples from 106 control patients with cytopenia and 134 low-grade myelodysplastic syndromes patients, including 81 lacking both ringed sideroblasts and cytogenetic aberrations, were prospectively analyzed in Japan and Italy.

Results

Data outside the predetermined reference range in 2 or more parameters (multiple abnormalities) were common in myelodysplastic syndromes patients. In those lacking ringed sideroblasts and cytogenetic aberrations, multiple abnormalities were observed in 8/26 Japanese (30.8%) and 37/55 Italians (67.3%) when the cardinal parameters alone were considered, and in 17/26 Japanese (65.4%) and 42/47 Italians (89.4%) when all parameters were taken into account. Multiple abnormalities were rare in controls. When data from all parameters were used, the diagnostic sensitivities were 65% and 89%, specificities were 98% and 90%, and likelihood ratios were 28.1 and 8.5 for the Japanese and Italian cohorts, respectively.

Conclusions

This protocol can be used in the diagnostic work-up of low-grade myelodysplastic syndromes patients who lack specific diagnostic markers, although further improvement in diagnostic power is desirable.     

Clinical implications of left superior vena cava persistence in candidates for pacemaker or cardioverter-defibrillator implantation

Persistence of a left superior vena cava (LSVC) has been reported in 0.3%–0.4% of candidates for pacemaker (PM) or cardioverter-defibrillator (ICD) implantation. The aim of the study was to evaluate the clinical implications of LSVC persistence for proper device performance. We observed the prevalence of LSVC during a 15-year period. A total of 2077 consecutive patients underwent PM implantation over a 15-year period: 7 had persistent LSVCs (0.34%). Among 599 patients undergoing ICD implantation, 4 LSVCs (0.66%) were observed. Overall LSVC persistence was found in 11/2676 (0.41%) patients. The right superior vena cava was absent in 4/11 (36%) patients. The leads were placed from the left subclavian approach in 5/7 PM patients: 2 received an elective right sided approach due to physician preference. All ICD patients had the device placed left pectoral with a single-coil lead: defibrillation therapy was effective in the long term in all but one patient, who required the addition of a subcutaneous array. Left superior vena cava persistence in PM/ICD patients is similar to the general population (0.41% in our study). The left-sided implant may be skill-demanding during lead placement; however, this task can be accomplished in the majority of cases, with a reliable outcome in the short term and appropriate device performance at follow-up.     

Telecardiology applied to a region-wide public emergency health-care service

Aim To assess feasibility and reliability of telecardiology technologies applied to a region-wide public emergency health-care service. Methods About 27,841 patients from all over Apulia (19.362 km², 4 million inhabitants) were referred from October 2004 until April 2006 to public emergency health-care number “118” and underwent ECG evaluation according to a previously fixed inclusion protocol. Data recorded were transmitted with mobile telephone support to a telecardiology “hub” active 24-h a day. Hospitalization or further examinations were arranged by emergency physicians on the basis of ECG diagnosis and consultation. Results Thirty-nine percent of patients complained of chest pain (CP) or epigastric pain, 26% loss of consciousness, 10% breathlessness, and 7% palpitations. Atrial fibrillation (AF) was diagnosed in 11.68% of patients and ST-elevation acute myocardial infarction (STEMI) in 1.91%. Among patients with CP, ECG showed STEMI in only 3.84% of cases, theoretically eligible for fibrinolysis or primary PCI; patients with STEMI complained of CP in 78.94% of cases. Of the patients, 65.28% with STEMI were from small towns without coronary care units, thus benefiting from an immediate pre-hospital diagnosis. Among patients with palpitations, only 10.27% of subjects showed ECG signs of supra-ventricular tachycardia and 25.18% of AF; other subjects avoided further improper hospitalization or emergency department monitoring. Conclusions This first region-wide leading experience shows the feasibility and reliability of telecardiology applied to a public emergency health-care service. Telemedicine protocols would probably be useful in lowering the number of improper hospitalizations and shortening delay in the diagnosis process of some heart diseases.