Nonlinear elasticity of stiff biopolymers connected by flexible linkers

Networks of the biopolymer actin, cross-linked by the compliant protein filamin, form soft gels. They can, however, withstand large shear stresses due to their pronounced nonlinear elastic behavior. The nonlinear elasticity can be controlled by varying the number of cross-links per actin filament. We propose and test a model of rigid filaments decorated by multiple flexible linkers that is in quantitative agreement with experiment. This allows us to estimate loads on individual cross-links, which we find to be less than 10 pN. © 2009 The American Physical Society

Self-organized Vortex State in Two-dimensional Dictyostelium Dynamics

We present results of experiments on the dynamics of Dictyostelium discoideum in a novel set-up which constraints cell motion to a plane. After aggregation, the amoebae collect into round ''pancake" structures in which the cells rotate around the center of the pancake. This vortex state persists for many hours and we have explicitly verified that the motion is not due to rotating waves of cAMP. To provide an alternative mechanism for the self-organization of the Dictyostelium cells, we have developed a new model of the dynamics of self-propelled deformable objects. In this model, we show that cohesive energy between the cells, together with a coupling between the self-generated propulsive force and the cell's configuration produces a self-organized vortex state. The angular velocity profiles of the experiment and of the model are qualitatively similar. The mechanism for self-organization reported here can possibly explain similar vortex states in other biological systems.Comment: submitted to PRL; revised version dated 3/8/9

A bibliometric analysis of research productivity in Parasitology by different world regions during a 9-year period (1995–2003)

BACKGROUND: The objective of this study was to estimate the research productivity of different world regions in the field of Parasitology. METHODS: Using the PubMed database we retrieved articles from journals included in the "Parasitology" category of the "Journal Citation Reports" database of the Institute for Scientific Information for the period 1995–2003. Research productivity was evaluated based on a methodology we developed and used in other bibliometric studies by analysing: (1) the total number of publications, (2) the mean impact factor of all papers, and (3) the product of the above two parameters, (4) the research productivity in relation to gross domestic product of each region, and (5) the research productivity in relation to gross national income per capita and population of each region. RESULTS: Data on the country of origin of the research was available for 18,110 out of 18,377 articles (98.6% of all articles from the included journals). Western Europe exceeds all world regions in research production for the period studied (34.8% of total articles), with USA ranking second (19.9%), and Latin America & the Caribbean ranking third (17.2%). The mean impact factor in articles published in Parasitology journals was highest for the USA (1.88). Oceania ranked first in research productivity when adjustments for both the gross national income per capita (GNIPC) and population were made. Eastern Europe almost tripled the production of articles from only 1.9% of total production in 1995 to 4.3% in 2003. Similarly, Latin America and the Caribbean and Asia doubled their production. However, the absolute and relative production by some developing areas, including Africa, is still very low, despite the fact that parasitic diseases are major public health problems in these areas. CONCLUSION: Our data suggest that more help should be provided by the developed nations to developing areas for improvement of the infrastructure of research

Ligand-Receptor Interactions

The formation and dissociation of specific noncovalent interactions between a variety of macromolecules play a crucial role in the function of biological systems. During the last few years, three main lines of research led to a dramatic improvement of our understanding of these important phenomena. First, combination of genetic engineering and X ray cristallography made available a simultaneous knowledg of the precise structure and affinity of series or related ligand-receptor systems differing by a few well-defined atoms. Second, improvement of computer power and simulation techniques allowed extended exploration of the interaction of realistic macromolecules. Third, simultaneous development of a variety of techniques based on atomic force microscopy, hydrodynamic flow, biomembrane probes, optical tweezers, magnetic fields or flexible transducers yielded direct experimental information of the behavior of single ligand receptor bonds. At the same time, investigation of well defined cellular models raised the interest of biologists to the kinetic and mechanical properties of cell membrane receptors. The aim of this review is to give a description of these advances that benefitted from a largely multidisciplinar approach

Hypothesis: are neoplastic macrophages/microglia present in glioblastoma multiforme?

Most malignant brain tumours contain various numbers of cells with characteristics of activated or dysmorphic macrophages/microglia. These cells are generally considered part of the tumour stroma and are often described as TAM (tumour-associated macrophages). These types of cells are thought to either enhance or inhibit brain tumour progression. Recent evidence indicates that neoplastic cells with macrophage characteristics are found in numerous metastatic cancers of non-CNS (central nervous system) origin. Evidence is presented here suggesting that subpopulations of cells within human gliomas, specifically GBM (glioblastoma multiforme), are neoplastic macrophages/microglia. These cells are thought to arise following mitochondrial damage in fusion hybrids between neoplastic stem cells and macrophages/microglia

Recent trends in publication of basic science and clinical research by United States investigators in anesthesia journals

<p>Abstract</p> <p>Background</p> <p>United States anesthesia research production declined sharply from 1980-2005. Whether this trend has continued despite recent calls to improve output is unknown. We conducted an observational internet analysis to quantify American basic science and clinical anesthesia research output in 14 anesthesia journals with impact factors greater than one at three-year intervals during the past decade.</p> <p>Results</p> <p>American investigators published 1,486 (21.7%) of the total of 6,845 research articles identified in anesthesia journals in 2001, 2004, 2007, and 2010. Approximately two-thirds of all US articles were published in <it>Anesthesiology </it>and <it>Anesthesia and Analgesia</it>. There was a significant correlation (r²= 0.316; P = 0.036) between the number of articles published by American authors in each anesthesia journal and the corresponding journal's impact factor in 2010. Significantly (P < 0.05; Pearson's Chi-square) fewer basic science articles were published in 2007 and 2010 compared with 2001. US clinical research output also declined in 2007 (201; 15.7%) compared with 2001 (266; 19.1%) and 2004, but an increase occurred in 2010 (279; 21.8%, P < 0.05 versus 2007).</p> <p>Conclusions</p> <p>The results indicate that US anesthesia research output continued to decrease from 2001 to 2007. An increase in clinical but not basic science research was observed in 2010 compared with 2007, suggesting that a modest recovery in clinical research production may have begun.</p

Worldwide trends in quantity and quality of published articles in the field of infectious diseases

BACKGROUND: Trying to confront with the widespread burden of infectious diseases, the society worldwide invests considerably on research. We evaluated the contribution of different world regions in research production in Infectious Diseases. METHODS: Using the online Pubmed database we retrieved articles from 38 journals included in the "Infectious Diseases" category of the "Journal Citation Reports" database of the Institute for Scientific Information for the period 1995–2002. The world was divided into 9 regions based on geographic, economic and scientific criteria. Using an elaborate retrieval system we obtained data on published articles from different world regions. In our evaluation we introduced an estimate of both quantity and quality of research produced from each world region per year using: (1) the total number of publications, (2) the mean impact factor of publications, and (3) the product of the above two parameters. RESULTS: Data on the country of origin of the research was available for 45,232 out of 45,922 retrieved articles (98.5 %). USA and Western Europe are by far the most productive regions concerning publications of research articles. However, the rate of increase in the production of articles was higher in Eastern Europe, Africa, Latin America and the Caribbean, and Asia during the study period. The mean impact factor is highest for articles originating in the USA (3.42), while it was 2.82 for Western Europe and 2.73 for the rest of the world (7 regions combined). CONCLUSION: USA and Western Europe make up a striking 80% of the world's research production in Infectious Diseases in terms of both quantity and quality. However, all world regions achieved a gradual increase in the production of Infectious Diseases articles, with the regions ranking lower at present displaying the highest rate of increase

Molecular basis of filamin a-filGAP interaction and its impairment in congenital disorders associated with filamin a mutations

Peer reviewe