Progressive bone loss during long-term home total parenteral nutrition

Metabolic bone disease occurs in patients receiving prolonged home total parenteral nutrition (HTPN). We studied bone-mass status in 10 patients (seven males, three females, age 19-66 years) who had been receiving HTPN for 0 to 67 months (mean 24 months), mostly for short-bowel syndrome. Four patients had spinal osteoporosis on radiograms. The density of various bone components at the wrist was measured noninvasively using a novel technique based on Compton scattering effect. The density of the cancellous and cortical bone was decreased in nine and six patients, respectively. During a follow-up period of up to 19 months, a further significant decrease in the density of both bone components was found. We conclude that prolonged HTPN is associated with an ongoing bone diminution, affecting mainly the cancellous bone.     

Mass media family planning promotion in three Nigerian cities

Television promotion of family planning and clinic sites in three cities of Nigeria--Ilorin, Ibadan, and Enugu--played a significant role in 1985-88 in increasing the number of new acceptors at family planning clinics in each city. Family planning skits, prepared with advice and support from the local service providers, were included in existing popular entertainment shows. Questions asked in a recall survey among the exposed population in Enugu and Ibadan revealed that about half of those surveyed in both cities had seen the television episodes. Of those who had watched, 79 and 99 percent, respectively, recalled the family planning messages, and 69 and 88 percent, respectively, recalled specific clinic sites mentioned. Following the media promotion, the number of new clinic clients per quarter in Ilorin increased almost fivefold (in the original clinics evaluated); in Enugu, the number of new clients per month more than doubled; and in Ibadan, the number of new clients increased threefold. Use of entertainment through this "enter-educate approach" is a promising technique that can be replicated in different settings to encourage new clients to seek family planning services.     

Effects of propiomazine on the EEG sleep of normal subjects

The effects of 25 mg propiomazine were examined in ten healthy volunteers in a sleep laboratory setting. A significant decrease in sleep latency and a corresponding decrement in subjectively assessed sleep latency was found during drug treatment. The distribution of the different sleep stages was affected to a relatively small extent. Some evidence for a suppression of REM-sleep in the early part of the treatment period was found. Based on subjective assessment, the subjects rated their sleep quality as significantly improved during treatment. Ratings of "drowsiness in the morning" were not different during baseline and drug treatment, but there was a significant decrease at withdrawal.     

An angular motion of a conserved four-helix bundle facilitates alternating access transport in the TtNapA and EcNhaA transporters

There is ongoing debate regarding the mechanism through which cation/proton antiporters (CPAs), like Thermus thermophilus NapA (TtNapA) and Escherichia coli NapA (EcNhaA), alternate between their outward- and inward-facing conformations in the membrane. CPAs comprise two domains, and it is unclear whether the transition is driven by their rocking-bundle or elevator motion with respect to each other. Here we address this question using metadynamics simulations of TtNapA, where we bias conformational sampling along two axes characterizing the two proposed mechanisms: angular and translational motions, respectively. By applying the bias potential for the two axes simultaneously, as well as to the angular, but not the translational, axis alone, we manage to reproduce each of the two known states of TtNapA when starting from the opposite state, in support of the rocking-bundle mechanism as the driver of conformational change. Next, starting from the inward-facing conformation of EcNhaA, we sample what could be its long-sought-after outward-facing conformation and verify it using cross-linking experiments.

A secondary active transporter harnesses the electrochemical gradient created by the movement of an ion across a biological membrane to facilitate the transport of another ion or molecule against its electrochemical gradient. Structural data obtained throughout the past decade have revealed that these transporters share some common structural features and can be classified under three main structural folds: the MFS fold (major facilitator superfamily), the LeuT fold (leucine transporters), and the NhaA fold (Na⁺/H⁺ antiporters) (1, 2).When folded, these transporters are organized in two functional domains: 1) a mobile core domain that harbors an ion-binding site and 2) a dimerization/oligomerization domain (1). To carry out their function, they alternate between at least two main states—inward-facing and outward-facing (IF and OF) —such that their binding sites are accessible from different sides of the membrane in each state in what is known as an alternating access model (3). Extensive research has been devoted to elucidating the mechanisms underlying the alternating access model in secondary active transporters. In particular, studies of the LeuT fold have suggested that a four-helix bundle in the core domain undergoes significant conformational changes during transport (4). Notably, this four-helix bundle is structurally conserved across many transporters, suggesting that it may be implicated in the conformational changes underlying their function as well.Herein, using simulations, we contribute new insights with regard to the alternating access mechanism of the cation/proton antiporter (CPA) superfamily of secondary active transporters. CPAs exchange monovalent cations with protons, and their malfunction is associated with a growing number of human pathologies (5) affecting millions worldwide. However, there is still an ongoing debate regarding the structural mechanism underlying the alternating access model in CPAs (6, 7). One possibility is a rocking-bundle mechanism, which involves a tilting movement of the core domain relative to a stationary dimerization domain on the plane of the membrane; this mechanism was originally proposed on the basis of the structure of the bacterial LeuT transporter (4) (Fig. 1). An alternative possibility is the elevator mechanism, first described in a bacterial homolog of the glutamate transporter Glt_Ph. Glt_Ph is a member of the proton/sodium glutamate symport protein fold (1) that shares some similar structural features with the MFS, LeuT, and NhaA folds. This mechanism involves a prominent vertical movement of the transporter’s core domain along the membrane’s normal, which is accompanied by a tilting movement (8) (Fig. 1).Open in a separate windowFig. 1.Rocking bundle vs. elevator mechanism. Schematic representation of TtNapA oriented in the membrane such that the periplasm is at the top and the cytoplasm is at the bottom. Transmembrane helices are shown as cylinders, where the core domain is designated in orange and the dimerization domain in green. The core domain’s direction of movement relative to the dimerization domain that correlates with each of the two mechanisms underlying the alternating access model for cation/proton transport is marked with black arrows.Thus far, three-dimensional structures of four CPAs have been determined experimentally (6, 9–11). Most notably, the structure of the CPA member NapA from Thermus thermophilus (TtNapA) was solved in both IF and OF states (6). Consistent with observations obtained for LeuT (4), these structures revealed that the main rearrangements between the alternating states of TtNapA occur in the conserved four-helix bundle in the core domain (6). This bundle includes the two discontinuous transmembrane helices (TMs) 4 and 11 (2), as well as TM-5, which includes the ion-binding site, and TM-12; the numbering of the helices follows the prevalent helix nomenclature of Escherichia coli NhaA (EcNhaA), which will be used throughout the text (12). A comparison of the two oppositely facing structures of TtNapA reveals an angular motion of one domain relative to the other that is also accompanied by a 6-Å vertical displacement of the antiporter’s core domain relative to the membrane and 7 Å relative to the dimer domain (6). This is consistent with the elevator mechanism proposed for Glt_Ph that involves the two types of motions. It was thus suggested that the structural data favor the elevator mechanism in CPAs.While this interpretation is straightforward, the extreme conformations represented by the crystal structures do not provide any direct information about the actual conformational changes that take place during the transport processes. Accordingly, on its own, the structural information obtained for TtNapA is insufficient for determining whether the angular motion, vertical translation, or both underlie the alternating access model of cation/proton antiport in CPAs. Okazaki et al. (13) used molecular-dynamics (MD) simulations to predict the transition path between the IF and OF conformations of an archaeal member of the CPA superfamily. Their work demonstrated how insightful simulations can be in CPAs, but it did not address the question of which mode of motion is essential for the IF–OF transition.Here, we used metadynamics, an enhanced sampling MD protocol, to study the conformational dynamics of two CPA members, TtNapA and EcNhaA, embedded in a lipid bilayer. We focused on the structurally conserved four-helix bundle in an attempt to predict which mode of motion is most likely to drive the IF–OF transition in CPAs. Specifically, we applied external potential to bias the conformational sampling along the two axes of motion in TtNapA that underlie the rocking-bundle and elevator mechanisms. The first axis corresponds to an angular motion of the conserved four-helix bundle in the antiporter’s core domain relative to a separate four-helix bundle in the dimerization domain, and the second axis corresponds to a vertical translation of the four-helix bundle along the membrane normal. By applying the bias potential for both axes simultaneously, as well as for the angular motion axis alone, we successfully reproduced each of the two known states of TtNapA when starting from the opposite state, with accuracy of between 0.80 and 1.51 Å. Importantly, although both types of motions are observed, our results suggest that conformational changes depend mainly on the angular motion rather than on the translation. This dominance of the angular motions in determining the IF-to-OF transition is more in line with the rocking-bundle mechanism of ion/proton antiport. Furthermore, by biasing the conformational sampling of the IF conformation of EcNhaA along the angular motion axis, we sampled a conformation that seems to fit the long-sought-after OF conformation of this protein, and we verified it experimentally. Accordingly, in addition to providing a better understanding of the transport mechanism of CPAs, our findings point to the potential of computational methods to predict, for example, additional conformations for CPA members with only one known experimental structure, as well as to obtain more metastable states.     

Optease Vena Cava Filter Optimal Indwelling Time and Retrievability

The purpose of this study was to assess the indwelling time and retrievability of the Optease IVC filter. Between 2002 and 2009, a total of 811 Optease filters were inserted: 382 for prophylaxis in multitrauma patients and 429 for patients with venous thromboembolic (VTE) disease. In 139 patients [97 men and 42 women; mean age, 36 (range, 17–82) years], filter retrieval was attempted. They were divided into two groups to compare change in retrieval policy during the years: group A, 60 patients with filter retrievals performed before December 31 2006; and group B, 79 patients with filter retrievals from January 2007 to October 2009. A total of 128 filters were successfully removed (57 in group A, and 71 in group B). The mean filter indwelling time in the study group was 25 (range, 3–122) days. In group A the mean indwelling time was 18 (range, 7–55) days and in group B 31 days (range, 8–122). There were 11 retrieval failures: 4 for inability to engage the filter hook and 7 for inability to sheathe the filter due to intimal overgrowth. The mean indwelling time of group A retrieval failures was 16 (range, 15–18) days and in group B 54 (range, 17–122) days. Mean fluoroscopy time for successful retrieval was 3.5 (range, 1–16.6) min and for retrieval failures 25.2 (range, 7.2–62) min. Attempts to retrieve the Optease filter can be performed up to 60 days, but more failures will be encountered with this approach.     

Safety of anticoagulation therapy in well-informed older patients

BACKGROUND: In older populations, oral anticoagulation therapy (OAT) is underused by physicians, mainly because of fear of bleeding complications. The aim of this study was to determine the incidence of bleeding complications and associated risk factors in a large heterogeneous group of older patients. METHODS: Combined retrospective and prospective cohort study conducted in geriatric and internal medicine departments. All patients 80 years or older discharged with the recommendation of OAT were followed up for a mean +/- SD of 28.8 +/- 36.3 months. The rate of bleeding events and the quality of anticoagulation were compared across a wide range of demographic and clinical variables and cognitive and functional status. In addition, we assessed the quality of education given to the patient or caregiver on the use of OAT. RESULTS: Among 15 387 patients 80 years or older, 323 (2.1%) were discharged with the recommendation of OAT. The rate of major bleedings was 2.4 events per 1000 patient-months. Socioeconomic and cognitive variables and functional impairments were not associated with an increased rate of bleeding. In multivariate analysis, insufficient education on OAT as perceived by the patient or caregiver (odds ratio [OR], 8.83), polypharmacy (OR, 6.14), and international normalized ratio values above the therapeutic range (OR, 1.08) were the only significant predictive factors for bleeding complications. CONCLUSIONS: The rate of bleeding complications, especially major bleedings, was low in this large group of older patients, many with comorbidities and cognitive and functional impairments. Insufficient OAT education was the major factor that predicted bleeding. Therefore, improving and fostering better methods of OAT education may further reduce bleeding complications.     

Thrombosed giant left atrium mimicking a mediastinal tumor.

A patient with rheumatic heart disease, mitral stenosis, and mitral insufficiency is described. The thrombosed giant left atrium paralyzed the left vocal cord and completely obstructed the bronchi to the middle and lower lobes of the right lung. The giant left atrium mimicked a mediastinal tumor on the chest x-ray film.     

The Plasmin Inhibitors of Human Plasma

La stabilité des inhibiteurs plasmatiques de la plasmine à différentes concentrations d'éthanol à différentes températures et pH a été étudiée. Les conditions optimales pour une stabilité maximale ont été déterminées. Un processus de fractionnement à l'éthanol a été, par la suite, développé pour la préparation de fraction plasmatique riche en inhibiteur de la plasmine. Avec l'inhibiteur >>lent«, on obtient une récupération à 70% et une substance six fois plus pure. Avec l'inhibiteur >>immédiat«, on obtient une récupération à 45% et une substance quatre fois plus pure.

Zusammenfassung

Es wurde die Stabilität der Plasmininhibitoren des Plasmas in Abhängigkeit von verschiedenen Alkoholkonzentrationen, Temperaturen und pH-Werten untersucht. Es wurden die optimalen Bedingungen für eine maximale Stabilität ermittelt. An-schließend wurde ein Alkoholfraktionierverfahren zur Gewinnung einer Plasma-fraktion mit einem möglichst großen Gehalt an Plasmininhibitoren entwickelt. Es gelang den >>langsamen« Inhibitor 6fach anzureichern; die Ausbeute betrug 70%. Die Anreicherung des >>sofortigen« Inhibitors betrug das 4fache; die Ausbeute lag bei 45%.     

Topology of the lac carrier protein in the membrane of Escherichia coli.

Proteolysis of topologically sealed right-side-out and inside-out membrane vesicles from Escherichia coli with chymotrypsin, trypsin, or papain inactivates lac carrier function in a symmetrical manner. Concomitantly, the electrophoretic mobility of lac carrier protein photoaffinity labeled in situ with p-nitro[2-3H]phenyl-alpha-D-galactopyranoside is altered from a relative Mr of 33,000 to 20,000, and the time course of proteolysis is almost identical in vesicles of opposite polarities. In contrast, solubilization of the vesicles in NaDodSO4 followed by proteolysis causes fragmentation of the Mr 33,000 band into material that electrophoreses at the solvent front. Notably, proteolysis has no effect whatsoever on the ability of the lac carrier protein to bind substrate, as judged by photoaffinity-labeling experiments. Furthermore, the electrophoretic patterns of samples proteolyzed prior to photoaffinity labeling are the same as those observed when the procedures are reversed. These results show that the lac carrier protein spans the membrane and indicate that the binding site resides within a segment that is embedded in the bilayer.