Electrostatically driven lipid-lysozyme mixed fibers display a multilamellar structure without amyloid features

Understanding the interactions between anionic lipid membranes and amyloidogenic proteins/peptides is key to elucidate the molecular mechanisms underlying the membrane-driven amyloid fiber formation. Here, hen egg-white lysozyme was used as a model protein to test whether this same process also occurs with non-amyloidogenic lipid-binding proteins/peptides. A complementary set of biophysical techniques was employed to study the structure and dynamics of the lipid-lysozyme mixed fibers produced at a low lipid/protein molar ratio that have been proposed earlier to present "amyloid-like" characteristics. The multilamellar architecture of these elongated mesoscopic structures was established by performing time-resolved Förster resonance energy transfer measurements, at both bulk (ensemble) and single-fiber level. The predominantly oligomeric lysozyme and phospholipids were both found to display significantly decreased lateral mobility when embedded in these mixed fibers. Notably, two-photon microscopy of Laurdan revealed that a pronounced membrane surface dehydration/increased molecular interfacial packing was produced exclusively in these elongated mixed supramolecular fibers present in the highly polymorphic samples. Infrared spectroscopic studies of lysozyme in these samples further showed that this protein did not exhibit a rich β-sheet structure characteristic of amyloid fibrils. These results support the conclusion that negatively charged lipid membranes do not have the general ability to trigger amyloid fibril formation of non-amyloidogenic proteins.

Ca(2+) induces PI(4,5)P2 clusters on lipid bilayers at physiological PI(4,5)P2 and Ca(2+) concentrations

Calcium has been shown to induce clustering of PI(4,5)P2 at high and non-physiological concentrations of both the divalent ion and the phosphatidylinositol, or on supported lipid monolayers. In lipid bilayers at physiological conditions, clusters are not detected through microscopic techniques. Here, we aimed to determine through spectroscopic methodologies if calcium plays a role in PI(4,5)P2 lateral distribution on lipid bilayers under physiological conditions. Using several different approaches which included information on fluorescence quantum yield, polarization, spectra and diffusion properties of a fluorescent derivative of PI(4,5)P2 (TopFluor(TF)-PI(4,5)P2), we show that Ca(2+) promotes PI(4,5)P2 clustering in lipid bilayers at physiological concentrations of both Ca(2+) and PI(4,5)P2. Fluorescence depolarization data of TF-PI(4,5)P2 in the presence of calcium suggests that under physiological concentrations of PI(4,5)P2 and calcium, the average cluster size comprises ~15 PI(4,5)P2 molecules. The presence of Ca(2+)-induced PI(4,5)P2 clusters is supported by FCS data. Additionally, calcium mediated PI(4,5)P2 clustering was more pronounced in liquid ordered (lo) membranes, and the PI(4,5)P2-Ca(2+) clusters presented an increased affinity for lo domains. In this way, PI(4,5)P2 could function as a lipid calcium sensor and the increased efficiency of calcium-mediated PI(4,5)P2 clustering on lo domains might provide targeted nucleation sites for PI(4,5)P2 clusters upon calcium stimulus.

Analysis of health stories in daily newspapers in the UK

Objectives

To assess what makes a good piece of medical reporting in newspapers, to quantify what is being reported on in the major British newspapers, to identify the sources of the news threads, and to assess how these are reported.

Study design

Development and validation of a tool to assess the quality of reporting of health-related articles, and assessment of the quality of these articles in British newspapers.

Methods

Eight national daily newspapers from the UK were reviewed for 20 days over a 2-month period. All articles reporting newly emerging research pertaining to health in humans were included and reviewed independently by two raters. A descriptive analysis was performed. Subsequently, a quality assessment tool for use by a non-expert was developed and validated to objectively assess the quality of a newspaper article on a health-related topic.

Results

The quality assessment tool was found to have good internal consistency and inter-rater reliability. The Daily Mail published almost twice as many articles as its nearest rival, The Daily Express, and over eight times as many articles as The Guardian. Articles in The Times were, on average, more than twice as long as those in The Sun and The Daily Telegraph. The highest quality articles were in The Times and The Independent, with the lowest quality articles in The Sun. The quality scores of anonymous articles were significantly lower than those attributed to named journalists.

Conclusions

There are significant differences in the quality of reporting within and between major daily UK newspapers, with anonymous articles being the poorest quality, and widespread reliance on press releases from the major UK scientific journals.

Genetic basis for unresponsiveness to lipopolysaccharide in C57BL/10Cr mice

The unresponsiveness to LPS detected in C57BL/10Cr mice is inherited as a recessive trait and is determined by an autosomal gene linked to theMup-1 locus on chromosome 4. Since no complementation for LPS responsiveness was observed in F(1) hybrid mice between C3H/HeJ and C57BL/10Cr, we conclude that C57BL/10Cr mice carry a defective allele at the sameLps locus, previously identified by the mutation detected in the C3H/HeJ strain.

Complement and antibody primary immunodeficiency in juvenile systemic lupus erythematosus patients

OBJECTIVE

To evaluate the frequency of primary immunodeficiencies (PID) in juvenile systemic lupus erythematosus (JSLE) patients.

METHODS

Some 72 JSLE patients were analyzed for levels of immunoglobulin classes and IgG subclasses and early components of the classical complement pathway. Determination of C4 gene copy number (GCN) and detection of type I C2 deficiency (D) were also performed.

RESULTS

PID was identified in 16 patients (22%): C2D in three, C4D in three, C1qD in two, IgG2D (<20 mg/dl) in four, IgAD (<7 mg/dl) in three, and IgMD (<35 mg/dl) in three; one of these patients presented IgA, C2 and C4D. Two patients had low C4 GCN and two had type I C2D. Demographic data, family history of autoimmune disease and PID, JSLE clinical findings, occurrence of infections, disease activity and therapies were similar in patients with and without PID (p > 0.05). Remarkably, the median of Systemic Lupus International Collaborating Clinics/ACR-damage index (SLICC/ACR-DI) was significantly higher in JSLE patients with PID compared with patients without these abnormalities (p = 0.0033), likewise the high frequency of SLICC/ACR-DI > 1 (p = 0.023).

CONCLUSIONS

A high frequency of PID was observed in JSLE patients, suggesting that these defects may contribute to lupus development. Our findings indicate that these two groups of PID should be investigated in severe pediatric lupus.

FRET studies of lipid-protein aggregates related to amyloid-like fibers

Acidic lipids are known to both catalyze amyloid fiber formation by amyloidogenic peptides/proteins and induce formation of 'amyloid-like' fibrils by non-amyloidogenic proteins. In this work, we describe the application of state-of-the-art time-resolved Förster resonance energy transfer methodologies to the characterization of the supramolecular structure of the aggregates formed by both a cationic peptide (hexalysyltryptophan) and a basic non-amyloidogenic protein (lysozyme) upon their interaction with negatively-charged fluid membranes (mixtures of zwitterionic phosphatidylcholine and anionic phosphatidylserine). It was concluded that both the peptide and protein induce the formation of multistacked lipid bilayers. Furthermore, upon using conditions that are described in the literature to cause the formation of amyloid-like fibers, lysozyme was found to induce the formation of a 'pinched lamellar' structure, with reduced interbilayer distance in the regions where there is bound protein, and increased interbilayer distance (stabilized by hydration repulsion) outside these areas. No significant lateral domains (lipid demixing) were induced in the membrane by either the cationic peptide or lysozyme.

Quantitative analysis of bone density in direct digital radiographs evaluated by means of computerized analysis of digital images

OBJECTIVES

minimal density variations of mineralized tissues can be reliably detected with quantitative image subtraction analysis. The aim of this study was to evaluate quantitative variations of in vitro mineral density by varying the exposure time of direct digital radiographs using a computer assisted densitometric image analysis (CADIA) program.

METHODS

in a human mandibular segment a three-wall periodontal defect was created mesial to a molar. Bone chips were created from the marrowbone of the same mandible with masses of 1 to 5 mg. A triplicate radiograph of the defect was taken as a baseline for seven different exposure times. The bone chips were inserted into the defect and another triplicate series of radiographs for the seven exposure times were taken as follow-up images. The images were analysed using CADIA software to detect variations in bone density.

RESULTS

the results of CADIA revealed increased density when the size of the inserted bone chip increased. The 2 mg chip was underestimated owing to mass reduction during insertion. The regression line of the CADIA values was consistent with the weight of the bone chips of 1, 3, 4 and 5 mg. The exposure time f6 (0.178 s) showed the best correlation with the bone chip weight. Loss of information in the images occurred when the exposure time exceeded the sensor's latitude.

CONCLUSIONS

CADIA analysis is a reliable and sensitive tool for detecting subtle bone density variations. More reliable results are obtained with increased exposure time; however, excessive exposure should be avoided.

Routine versus clinically driven laboratory monitoring of HIV antiretroviral therapy in Africa (DART): a randomised non-inferiority trial

BACKGROUND

HIV antiretroviral therapy (ART) is often managed without routine laboratory monitoring in Africa; however, the effect of this approach is unknown. This trial investigated whether routine toxicity and efficacy monitoring of HIV-infected patients receiving ART had an important long-term effect on clinical outcomes in Africa.

METHODS

In this open, non-inferiority trial in three centres in Uganda and one in Zimbabwe, 3321 symptomatic, ART-naive, HIV-infected adults with CD4 counts less than 200 cells per microL starting ART were randomly assigned to laboratory and clinical monitoring (LCM; n=1659) or clinically driven monitoring (CDM; n=1662) by a computer-generated list. Haematology, biochemistry, and CD4-cell counts were done every 12 weeks. In the LCM group, results were available to clinicians; in the CDM group, results (apart from CD4-cell count) could be requested if clinically indicated and grade 4 toxicities were available. Participants switched to second-line ART after new or recurrent WHO stage 4 events in both groups, or CD4 count less than 100 cells per microL (LCM only). Co-primary endpoints were new WHO stage 4 HIV events or death, and serious adverse events. Non-inferiority was defined as the upper 95% confidence limit for the hazard ratio (HR) for new WHO stage 4 events or death being no greater than 1.18. Analyses were by intention to treat. This study is registered, number ISRCTN13968779.

FINDINGS

Two participants assigned to CDM and three to LCM were excluded from analyses. 5-year survival was 87% (95% CI 85-88) in the CDM group and 90% (88-91) in the LCM group, and 122 (7%) and 112 (7%) participants, respectively, were lost to follow-up over median 4.9 years' follow-up. 459 (28%) participants receiving CDM versus 356 (21%) LCM had a new WHO stage 4 event or died (6.94 [95% CI 6.33-7.60] vs 5.24 [4.72-5.81] per 100 person-years; absolute difference 1.70 per 100 person-years [0.87-2.54]; HR 1.31 [1.14-1.51]; p=0.0001). Differences in disease progression occurred from the third year on ART, whereas higher rates of switch to second-line treatment occurred in LCM from the second year. 283 (17%) participants receiving CDM versus 260 (16%) LCM had a new serious adverse event (HR 1.12 [0.94-1.32]; p=0.19), with anaemia the most common (76 vs 61 cases).

INTERPRETATION

ART can be delivered safely without routine laboratory monitoring for toxic effects, but differences in disease progression suggest a role for monitoring of CD4-cell count from the second year of ART to guide the switch to second-line treatment.

FUNDING

UK Medical Research Council, the UK Department for International Development, the Rockefeller Foundation, GlaxoSmithKline, Gilead Sciences, Boehringer-Ingelheim, and Abbott Laboratories.

Pharmacogenetics and anticoagulant therapy: two cases of genetically determined response to warfarin

Inter- and intra-individual variability of response to warfarin means that its anticoagulant effect must be monitored, given the risk of thromboembolic complications and bleeding. This variability is influenced by gender, age, body mass index, smoking, diet, comorbid conditions, drug interactions and genetic factors. Pharmacogenetics refers to the study of genetic background to predict drug response, effectiveness and risk of adverse effects in a given patient. The authors illustrate its relevance in two case reports. A 40-year-old woman admitted for massive pulmonary thromboembolism underwent anticoagulant and fibrinolytic therapy, following which warfarin was needed in unusually high doses to achieve effective anticoagulation. The genetic variants c.430CC and c.1075AA of the CYP2C9 gene were identified, predisposing to rapid warfarin metabolism, as well as the c.-1639GG variant of the VKORC1 gene, associated with low sensitivity to the drug. Together, these variants give high resistance to warfarin. In the second case, a 76-year-old man with permanent atrial fibrillation developed excessive prolongation of prothrombin time after being treated with 5 mg/day warfarin for 5 days. The genetic variants c.430CC and c.1075AC of the CYP2C9 gene and 1639AA of the VKORC1 gene were identified. Together, these polymorphisms confer high sensitivity to warfarin, necessitating smaller doses to maintain therapeutic anticoagulation levels. The authors review the relevance of the study of genetic polymorphisms related to anticoagulant therapy and discuss its potential usefulness in clinical practice.

Independent segregation of two functional markers expressed on the same B-cell subset in the mouse: the Mls determinants and LPS receptors

Mice of the C3H/Tif strain display a mixed leukocyte reaction (MLR) with all H-2k strains carrying any of the known alleles of the Mls locus. In particular, C3H/Tif is incompatible with the related substrain C3H/HeJ, from which it also differs at the locus responsible for the recognition of lipopolysaccharides (LPS) as B-cell mitogens, and at the Mod-1 locus. Our genetic analysis indicates that the MLR incompatibility between these strains is not H-2-linked and segregates as controlled by a single locus, most probably identical to Mls, for which the C3H/Tif strain expresses a previously unidentified allele, Mlse. Moreover, segregation data show that this locus assorts independently of LPS responsiveness and that neither marker is closely linked to the Mod-1 locus in linkage group II.

'What if they ask how I got it?' Dilemmas of disclosing parental HIV status and testing children for HIV in Uganda

BACKGROUND

Limited research has been conducted outside Western settings on how HIV-positive parents decide to test and disclose their own HIV status to children. We conducted a qualitative study in 2001 and 2005 to assess parent attitudes and current counselling policy and practice regarding child testing and parental disclosure in Uganda prior to the roll-out of antiretroviral therapy.

METHODS

Parent perspectives were obtained through extended in-depth interviews with 10 HIV-positive parents recruited from The AIDS Support Organization (TASO), Entebbe branch. Counselling policy and practice were explored through key informant interviews with directors and two counsellors from each of five Ugandan counselling institutions with national or regional coverage.

RESULTS

Respondents had 51 children ranging from 4 to 36 years with a median age of 13. Five of 10 parents had disclosed their status to their children, usually to all, and four of these had tested one child for HIV. All those who tested any child had also disclosed their status to some or all of their children. Parents regularly worried that their children may be infected, but all preferred to wait for emergence of symptoms before considering HIV tests, citing fear of children's emotional reaction and lack of perceived benefits from knowing status. Counselling policy directors confirmed the absence of policy and training guidelines on the subject of parent-child disclosure. Counsellors reported improvising and giving inconsistent advice on this common concern of clients.

CONCLUSIONS

Concerns over disclosure to children of parent's HIV status and testing children for HIV represent a major psychological burden for HIV-positive parents. Further research is needed, but current counselling practice could be improved now by adapting lessons learned from existing research.

Conformational changes in human integrin alphaIIbbeta3 after platelet activation, monitored by FRET

Integrin alpha(IIb)beta(3), an abundant heterodimeric receptor at the surface of blood platelets, binds adhesive proteins after platelet activation and plays a primary role in haemostasis. In solution, it has been observed mainly in two conformations: the bent and the extended forms. Based on X-ray crystallography, electron microscopy and immunochemical observations of full-length integrin ectodomains and intact integrins, it has been agreed that unactivated integrins are in the bent conformation, both isolated in solution and in living cells. However, consensus is yet to emerge on the bent or extended conformation of activated integrins and on their mechanism of activation (the switchblade, the deadbolt and the S-S reduction models), which require further experimental tests at the cell level to become established facts. Here, we tested the proposed structural rearrangements undergone by integrin alpha(IIb)beta(3) after cell activation, by using Förster-type fluorescence resonance energy transfer (FRET) and attached fluorescent labels to Fab fragments of monoclonal antibodies directed to the betaA domain of the beta(3) subunit (donor, Alexa488-P97 Fab) and to the Calf-2 domain of the alpha(IIb) subunit (acceptor, Cy3-M3 Fab or Cy3-M10 Fab). The FRET efficiencies observed after ADP or TRAP platelet activation changed less than 20% from the resting values, showing that the distance between the labeled Fab fragments changes only modestly after platelet activation by physiological agonists. This observation is consistent with a conformational model of the activated integrin in the cell less extended than in the switchblade model.

E-learning at Porto Faculty of Medicine. A case study for the subject 'Introduction to Medicine'

The main objective of the Introduction to Medicine (IM) subject of the first year of the Medical Course at the Faculty of Medicine of the University of Porto is to provide students with a first contact with the areas of Biostatistics, Medical Informatics, Bioethics and the History of Medicine in the belief that they will be better prepared to learn, research, evaluate, share and decide within their practice. This paper presents a case study that describes how the subject IM is organized and how the b-learning tool (Moodle) is used to correct and grade the students' work. From the 239 students registered to attend the Introduction to Medicine subject 12% failed. The average grade among the successful students was 16 (out of 20). In the previous academic year only 2% of the students failed. However, among the successful students, the average grade was inferior (15 out of 20). The e-learning model that was described in this paper was successful because the results show that the students that made use of the Moodle got better grades.