Elastic properties of grafted microtubules

We use single-particle tracking to study the elastic properties of single microtubules grafted to a substrate. Thermal fluctuations of the free microtubule's end are recorded, in order to measure position distribution functions from which we calculate the persistence length of microtubules with contour lengths between 2.6 and 48 micrometers. We find the persistence length to vary by more than a factor of 20 over the total range of contour lengths. Our results support the hypothesis that shearing between protofilaments contributes significantly to the mechanics of microtubules.Comment: 9 pages, 3 figure

Financial Overconfidence Over Time - Foresight, Hindsight, and Insight of Investors

Overconfidence is among the most popular psychological explanations for investing behavior of private households. It has been linked to portfolio turnover, diversification, and risk taking, with mostly negative consequences for investors. In a panel survey of self-directed investors, who own an online brokerage account at a UK bank, we ask for stock market and portfolio expectations and derive several overconfidence measures from the responses. We find that in general overconfidence is present in our sample. We then match the survey data with investors' actual transactions and portfolio holdings, and find an influence of overplacement on trading activity, of overprecision and overestimation on degree of diversification, and of overprecision and overplacement on risk taking. Overconfidence hereby leads to increased trading activity, higher risk taking, and less diversification. We explore the evolution of overconfidence over time and identify a role of past success and hindsight on subsequent degree of overconfidence

Barriers and facilitators for adherence to antiretroviral therapy in Papua New Guinea

Papua New Guinea (PNG) is in a phase of scaling up access to antiretroviral therapy (ART), and adherence to the newly available drug therapy is becoming an important issue. This paper examines adherence to ART in a sample of 374 HIV-positive people in six provinces in PNG. Participants were recruited to the study using non-probability sampling. Sixty-two % of participants reported complete adherence (no missed or late doses in the past week) and 79% reported not missing any doses in the last week. Revival church members were significantly more likely to report having missing a treatment dose(s) (66%). Those living in the Highlands and those attending Catholic health clinics were significantly more likely to be adherent to their treatment. Age, gender, marital status, education level and employment type did not show significant association with treatment adherence. Adherence rates in PNG are not alarming, indicating that people with HIV can adhere to treatment despite the challenges of living in PNG

Sphingosine 1-Phosphate Induces Myoblast Differentiation through Cx43 Protein Expression: A Role for a Gap Junction-dependent and -independent Function

Although sphingosine 1-phosphate (S1P) has been considered a potent regulator of skeletal muscle biology, acting as a physiological anti-mitogenic and prodifferentiating agent, its downstream effectors are poorly known. In the present study, we provide experimental evidence for a novel mechanism by which S1P regulates skeletal muscle differentiation through the regulation of gap junctional protein connexin (Cx) 43. Indeed, the treatment with S1P greatly enhanced Cx43 expression and gap junctional intercellular communication during the early phases of myoblast differentiation, whereas the down-regulation of Cx43 by transfection with short interfering RNA blocked myogenesis elicited by S1P. Moreover, calcium and p38 MAPK-dependent pathways were required for S1P-induced increase in Cx43 expression. Interestingly, enforced expression of mutated Cx43(Δ130–136) reduced gap junction communication and totally inhibited S1P-induced expression of the myogenic markers, myogenin, myosin heavy chain, caveolin-3, and myotube formation. Notably, in S1P-stimulated myoblasts, endogenous or wild-type Cx43 protein, but not the mutated form, coimmunoprecipitated and colocalized with F-actin and cortactin in a p38 MAPK-dependent manner. These data, together with the known role of actin remodeling in cell differentiation, strongly support the important contribution of gap junctional communication, Cx43 expression and Cx43/cytoskeleton interaction in skeletal myogenesis elicited by S1P