Fluctuations of a membrane nanotube revealed by high-resolution force measurements.

Pulling membrane nanotubes from liposomes presents a powerful method to gain access to membrane mechanics. Here we extend classical optical tweezers studies to infer membrane nanotube dynamics with high spatial and temporal resolution. We first validate our force measurement setup by accurately measuring the bending modulus of EPC membrane in tube pulling experiments. Then we record the position signal of a trapped bead when it is connected, or not, to a tube. We derive the fluctuation spectrum of these signals and find that the presence of a membrane nanotube induces higher fluctuations, especially at low frequencies (10-1000 Hz). We analyse these spectra by taking into account the peristaltic modes of nanotube fluctuations. This analysis provides a new experimental framework for a quantitative study of the fluctuations of nanotubular membrane structures that are present in living cells, and now classically used for in vitro biomimetic approaches.

Cell-sized liposome doublets reveal active tension build-up driven by acto-myosin dynamics.

Cells modulate their shape to fulfill specific functions, mediated by the cell cortex, a thin actin shell bound to the plasma membrane. Myosin motor activity, together with actin dynamics, contributes to cortical tension. Here, we examine the individual contributions of actin polymerization and myosin activity to tension increase with a non-invasive method. Cell-sized liposome doublets are covered with either a stabilized actin cortex of preformed actin filaments, or a dynamic branched actin network polymerizing at the membrane. The addition of myosin II minifilaments in both cases triggers a change in doublet shape that is unambiguously related to a tension increase. Preformed actin filaments allow us to evaluate the effect of myosin alone while, with dynamic actin cortices, we examine the synergy of actin polymerization and myosin motors in driving shape changes. Our assay paves the way for a quantification of tension changes triggered by various actin-associated proteins in a cell-sized system.

Respiratory tract infections after cardiac surgery: impact on hospital morbidity and mortality.

AIM: Nosocomial pneumonia (NP) and tracheobronchitis after cardiac surgery are associated with worse outcomes. The aim of this study was to identify risk factors associated with NP and tracheobronchitis after cardiac surgery and to determine the impact of these infections on hospital morbidity and mortality. METHODS: We evaluated 1600 adult patients undergoing cardiac surgery under standard cardiopulmonary bypass. Data were collected prospectively. All NP and tracheobronchitis episodes were confirmed by a semiquantitative culture of endotracheal aspirate. Logistic regression analysis was done to identify risk factors for respiratory tract infection and mortality. RESULTS: The rate of NP was 1.2% (15.6 episodes per 1000 days of mechanical ventilation) and that of tracheobronchitis was 1.6% (21 episodes per 1000 days of mechanical ventilation). Significant independent risk factors for respiratory tract infection (pneumonia or tracheobronchitis) were: left ventricular ejection fraction < 30% (P = 0.001), chronic renal failure (P < 0.0001) and urgent surgery (P < 0.0001). Patients with NP had significantly higher mortality (42% versus 0.9%, P < 0.0001) than patients without respiratory tract infection. The median hospital length of stay was significantly longer in patients with pneumonia (42 days) and tracheobronchitis (28 days) than in patients without any respiratory tract infection (11 days, P < 0.0001). CONCLUSION: NP after cardiac surgery is associated with severe outcomes. Independent risk markers for respiratory tract infection were left ventricular ejection fraction < 30%, chronic renal failure and urgent surgery.

Fluctuations of a membrane nanotube covered with an actin sleeve.

Many biological functions rely on the reshaping of cell membranes, in particular into nanotubes, which are covered in vivo by dynamic actin networks. Nanotubes are subject to thermal fluctuations, but the effect of these on cell functions is unknown. Here, we form nanotubes from liposomes using an optically trapped bead adhering to the liposome membrane. From the power spectral density of this bead, we study the nanotube fluctuations in the range of membrane tensions measured in vivo. We show that an actin sleeve covering the nanotube damps its high-frequency fluctuations because of the network viscoelasticity. Our work paves the way for further studies of the effect of nanotube fluctuations on cellular functions.

Actin modulates shape and mechanics of tubular membranes.

The actin cytoskeleton shapes cells and also organizes internal membranous compartments. In particular, it interacts with membranes for intracellular transport of material in mammalian cells, yeast, or plant cells. Tubular membrane intermediates, pulled along microtubule tracks, are formed during this process and destabilize into vesicles. While the role of actin in tubule destabilization through scission is suggested, literature also provides examples of actin-mediated stabilization of membranous structures. To directly address this apparent contradiction, we mimic the geometry of tubular intermediates with preformed membrane tubes. The growth of an actin sleeve at the tube surface is monitored spatiotemporally. Depending on network cohesiveness, actin is able to entirely stabilize or locally maintain membrane tubes under pulling. On a single tube, thicker portions correlate with the presence of actin. These structures relax over several minutes and may provide enough time and curvature geometries for other proteins to act on tube stability.

Agreement in the interpretation of magnetic resonance images of the lumbar spine.

BACKGROUND: Correlation between clinical features and magnetic resonance imaging (MRI) findings is essential in low-back-pain patients. Most previous studies have analyzed concordance in the interpretation of lumbar MRI among a few radiologists who worked together. This may have overestimated concordance. PURPOSE: To evaluate intra- and interobserver agreement in the interpretation of lumbar MRI performed in an open 0.2 T system. MATERIAL AND METHODS: Seven radiologists from two different geographic settings in Spain interpreted the lumbar MRIs of 50 subjects representative of the general Danish population aged 40 years. The radiologists interpreted the images in routine clinical practice, having no knowledge of the clinical and demographic characteristics of the subjects and blinded to their colleagues' assessments. Six of the radiologists evaluated the same MRIs 14 days later, having no knowledge of the previous results. Data on the existence of disc degeneration, high-intensity zones, disc contour, Schmorl nodes, Modic changes, osteophytes, spondylolisthesis, and spinal stenosis were collected in the Nordic Modic Consensus Group Classification form. Intra- and interobserver agreement was analyzed for variables with a prevalence >or=10% and

Breakfast, plasma glucose and beta-hydroxybutyrate, body mass index and academic performance in children from Extremadura, Spain.

OBJECTIVES: Nutritional aspects of breakfast, plasma levels of glucose and beta-hydroxybutyrate, body mass index and academic performance have been studied in urban and rural children (Extremadura, Spain). METHODS: Representative samples of schoolchildren (3 to 12 years old, random cluster-sampling in schools). RESULTS: Children's mean caloric intake with breakfast was 331 kcal. Rural population ingested more carbohydrates (46,9 +/- 12,3% versus 43,3 +/- 13,2% of the total caloric intake) and fewer lipids (40,5 +/- 11,8% versus 43,9 +/- 12,8% of the total caloric intake) than the urban population. Academic performance was significantly better in the children inhabiting the rural zone than in those of the urban zone. The glycaemia was higher in the urban than in the rural children, and that the contrary was the case for the beta-hydroxybutyrate values. Neither glucose nor beta-hydroxybutyrate levels were correlated with academic performance values. BMI was significantly increased in the urban versus rural children. CONCLUSION: The present results emphasize the importance of breakfast and life style in the weight and the academic performance of children.

How cellular membrane properties are affected by the actin cytoskeleton.

Lipid membranes define the boundaries of living cells and intracellular compartments. The dynamic remodelling of these membranes by the cytoskeleton, a very dynamic structure made of active biopolymers, is crucial in many biological processes such as motility or division. In this review, we present some aspects of cellular membranes and how they are affected by the presence of the actin cytoskeleton. We show that, in parallel with the direct study of membranes and cytoskeleton in vivo, biomimetic in vitro systems allow reconstitution of biological processes in a controlled environment. In particular, we show that liposomes, or giant unilamellar vesicles, encapsulating a reconstituted actin network polymerizing at their membrane are suitable models of living cells and can be used to decipher the relative contributions of membrane and actin on the mechanical properties of the cellular interface.

A narrow window of cortical tension guides asymmetric spindle positioning in the mouse oocyte.

Cell mechanics control the outcome of cell division. In mitosis, external forces applied on a stiff cortex direct spindle orientation and morphogenesis. During oocyte meiosis on the contrary, spindle positioning depends on cortex softening. How changes in cortical organization induce cortex softening has not yet been addressed. Furthermore, the range of tension that allows spindle migration remains unknown. Here, using artificial manipulation of mouse oocyte cortex as well as theoretical modelling, we show that cortical tension has to be tightly regulated to allow off-center spindle positioning: a too low or too high cortical tension both lead to unsuccessful spindle migration. We demonstrate that the decrease in cortical tension required for spindle positioning is fine-tuned by a branched F-actin network that triggers the delocalization of myosin-II from the cortex, which sheds new light on the interplay between actin network architecture and cortex tension.

Alcoholic beverage consumption in India, Mexico, and Nigeria: a cross-cultural comparison.

Drinking practices vary substantially among different countries. An understanding of such differences can help researchers, clinicians, and policymakers develop prevention, diagnostic, and treatment measures as well as overall alcohol policies that are appropriate for a given country. Accordingly, researchers have conducted cross-cultural analyses of drinking patterns and practices. Three countries included in such analyses are India, Mexico, and Nigeria. These countries differ substantially in their ethnic and cultural characteristics, including the role that alcohol plays in daily life. To gain a better insight into the attitudes toward alcohol in these countries, researchers have analyzed the alcoholic beverage preferences, gender and age differences in alcohol consumption patterns, drinking contexts and drinking patterns, alcohol-related problems, approaches to prevention and treatment, and drinking indicators in each nation. These analyses demonstrate that no single definition of "normal" drinking, problem drinking, or alcohol dependence can apply equally to all countries or cultures.

Lack of association of apolipoprotein E polymorphism in obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) could be considered a neurodevelopmental disorder, from several lines of evidence. One of the most widely studied genes in these disorders is the apolipoprotein E gene, particularly allele 4. We analyzed for association among patients with OCD versus normal controls and cognitively impaired patients. There were no significant differences between OCD probands compared with population controls. However, the cognitively impaired group showed a higher frequency of allele apolipoprotein E gene compared with normal controls and patients with OCD.

Problems associated with hazardous and harmful alcohol consumption in Mexico.

This chapter presents research findings from a collaborative project between Mexican investigators from the Mexican Institute of Psychiatry and the World Health Organization on the identification and treatment of harmful and hazardous drinking. A sample of 189 individuals who met criteria for hazardous drinking was selected for the study after screening 2319 outpatients attending clinics in two general hospitals in Mexico City. We present here the characteristics of this sample along dimensions that include alcohol related problems, history of trauma, alcohol dependence scores and family history of alcoholism. We rated, utilizing structures interviews, situations that place these individuals at risk of drinking. The possibility of constructing a typology of harmful and hazardous drinking was also explored. The significance of the findings of this investigation for health care clinicians is discussed.

Influence of nomenclature in the interpretation of lumbar disk contour on MR imaging: a comparison of the agreement using the combined task force and the nordic nomenclatures.

BACKGROUND AND PURPOSE: The CTF nomenclature had not been tested in clinical practice. The purpose of this study was to compare the reliability and diagnostic confidence in the interpretation of disk contours on lumbar 1.5T MR imaging when using the CTF and the Nordic nomenclatures. MATERIALS AND METHODS: Five general radiologists from 3 hospitals blindly and independently assessed intravertebral herniations (Schmorl node) and disk contours on the lumbar MR imaging of 53 patients with low back pain, on 4 occasions. Measures were taken to minimize the risk of recall bias. The Nordic nomenclature was used for the first 2 assessments, and the CTF nomenclature, in the remaining 2. Radiologists had not previously used either of the 2 nomenclatures. κ statistics were calculated separately for reports deriving from each nomenclature and were categorized as almost perfect (0.81-1.00), substantial (0.61-0.80), moderate (0.41-0.60), fair (0.21-0.40), slight (0.00-0.20), and poor (<0.00). RESULTS: Categorization of intra- and interobserver agreement was the same across nomenclatures. Intraobserver reliability was substantial for intravertebral herniations and disk contour abnormalities. Interobserver reliability was moderate for intravertebral herniations and fair to moderate for disk contour. CONCLUSIONS: In conditions close to clinical practice, regardless of the specific nomenclature used, a standardized nomenclature supports only moderate interobserver agreement. The Nordic nomenclature increases self-confidence in an individual observer's report but is less clear regarding the classification of disks as normal versus bulged.

[Preoperative anemia in coronary surgery: a risk factor?]. / Anemia preoperatoria en la cirugía coronaria: ¿un factor de riesgo?

INTRODUCTION AND OBJECTIVES: Preoperative anemia as a risk factor of adverse outcomes after coronary surgery has not been well-established. This study has aimed to analyze the association between preoperative anemia and postoperative adverse events and in-hospital mortality in the patients undergoing isolated coronary artery bypass graft surgery in the Son Dureta hospital. METHODS: All the patients undergoing isolated coronary artery bypass graft surgery with extracorporeal circulation from November 2002 to June 2007 were included. Preoperative anemia was defined as hemoglobin (Hb)<13g/dL in men and Hb<12g/dL in women. The association between postoperative cardiac and noncardiac adverse events and the presence or absence of preoperative anemia and concomitant surgical risk, assessed by logistic EuroScore, were analyzed. RESULTS: A total of 623 patients were included. The rate of preoperative anemia was 34.5%. Patients with Euroscore > or =4 had higher incidence of preoperative anemia than patients with Euroscore<4 (41% vs. 27%; p=0.0001). There were no statistically significant differences in the rate of postoperative adverse events related to the presence or absence of preoperative anemia. Median ICU and hospital length of stay were longer in patients with preoperative anemia than in patients without preoperative anemia (ICU: 3.2+/-2.5 days vs. 3.7+/-2.8, p=0.004; in-hospital: 17.5+/-11.3 days vs. 14.7+/-10.2, p=0.001). Hospital mortality rate was 0.8% (95% CI 0.3-1.9). There were no differences in the mortality rate of the patients with and without preoperative anemia (0.9% vs 0.7%, p=0.8). CONCLUSIONS: In this study, preoperative anemia in patients undergoing coronary artery bypass graft surgery was not associated with increased hospital morbidity-mortality. However, ICU and hospital length of stay were longer in patients with preoperative anemia. The limitation of the sample size prevents us from confirming whether preoperative anemia is a risk factor after coronary surgery or not.

Primidone is associated with interictal depression in patients with epilepsy.

Depressive symptoms are common in epilepsy. To determine associations between depression and demographic, clinical, and pharmacological factors among epileptic patients, we conducted a cross-sectional survey. We evaluated 241 epileptic outpatients at a neurological center in a 6-month period. Depressive syndrome was diagnosed when both the Montgomery-Asberg Scale and the Beck Depression Inventory were rated above the standard cutoff points. Bivariate and multivariate analyses were performed to assess the differences between depressed and nondepressed patients with respect to demographic, clinical, and pharmacological features. Depressive syndrome was diagnosed in 42.7% of patients (n=103). Factors associated in the bivariate analysis were: cryptogenic etiology, posttraumatic epilepsy, use of primidone, and inadequate seizure control. After logistic regression, inadequate seizure control (OR 3.08, 95% CI 1.40-6.77, P=0.005) and use of primidone (OR 4.08, 95% CI 2.09-7.98; P<0.001) remained significantly associated. Depression was common and associated with inadequate seizure control and use of primidone.