The role of microtubule movement in bidirectional organelle transport

We study the role of microtubule movement in bidirectional organelle transport in Drosophila S2 cells and show that EGFP-tagged peroxisomes in cells serve as sensitive probes of motor induced, noisy cytoskeletal motions. Multiple peroxisomes move in unison over large time windows and show correlations with microtubule tip positions, indicating rapid microtubule fluctuations in the longitudinal direction. We report the first high-resolution measurement of longitudinal microtubule fluctuations performed by tracing such pairs of co-moving peroxisomes. The resulting picture shows that motor-dependent longitudinal microtubule oscillations contribute significantly to cargo movement along microtubules. Thus, contrary to the conventional view, organelle transport cannot be described solely in terms of cargo movement along stationary microtubule tracks, but instead includes a strong contribution from the movement of the tracks.Comment: 24 pages, 5 figure

What is the role of the kink instability in solar coronal eruptions

ABSTRACT We report the results of two simple studies which seek observational evidence that solar coronal loops are unstable to the MHD kink instability above a certain critical value of the total twist. First, we have used Yohkoh SXT image sequences to measure the shapes of 191 X-ray sigmoids and to determine the histories of eruption (evidenced by cusp and arcade signatures) of their associated active regions. We find that the distribution of sigmoid shapes is quite narrow and the frequency of eruption does not depend significantly on shape. Second, we have used Mees Solar Observatory vector magnetograms to estimate the largescale total twist of active regions in which flare-related signatures of eruption are observed. We find no evidence of eruption for values of large-scale total twist remotely approaching the threshold for the kink instability

Anti-cancer drug validation: the contribution of tissue engineered models

Abstract Drug toxicity frequently goes concealed until clinical trials stage, which is the most challenging, dangerous and expensive stage of drug development. Both the cultures of cancer cells in traditional 2D assays and animal studies have limitations that cannot ever be unraveled by improvements in drug-testing protocols. A new generation of bioengineered tumors is now emerging in response to these limitations, with potential to transform drug screening by providing predictive models of tumors within their tissue context, for studies of drug safety and efficacy. Considering the NCI60, a panel of 60 cancer cell lines representative of 9 different cancer types: leukemia, lung, colorectal, central nervous system (CNS), melanoma, ovarian, renal, prostate and breast, we propose to review current Bstate of art^ on the 9 cancer types specifically addressing the 3D tissue models that have been developed and used in drug discovery processes as an alternative to complement their studyThis article is a result of the project FROnTHERA (NORTE-01-0145-FEDER-000023), supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This article was also supported by the EU Framework Programme for Research and Innovation HORIZON 2020 (H2020) under grant agreement n° 668983 — FoReCaST. FCT distinction attributed to Joaquim M. Oliveira (IF/00423/2012) and Vitor M. Correlo (IF/01214/2014) under the Investigator FCT program is also greatly acknowledged.info:eu-repo/semantics/publishedVersio

Pseudophakic astigmatism reduction with femtosecond laser-assisted corneal arcuate incisions: a pilot study

Clayton Blehm,1 Richard Potvin2 1Gainesville Eye Associates, Gainesville, GA, 2Science in Vision, Akron, NY, USA Purpose: The aim of this study was to assess the effectiveness of the Verion-LenSx guided arcuate incision technique to reduce refractive astigmatism in a pseudophakic population. Patients and methods: A prospective single-arm study was conducted in which one or both eyes of subjects required reduction of 1.0–2.0 D of refractive astigmatism after previous cataract surgery or refractive lens exchange. The surgeon used the refractive cylinder in the eye and the Woodcock astigmatism nomogram for preoperative planning, while the LenSx femtosecond laser with the Verion Image Guided System was used to create all arcuate incisions. The primary outcome measure was the uncorrected monocular distance visual acuity (UCVA). Secondary outcome measures included the change in corneal astigmatism, the change in refractive astigmatism, the best-corrected visual acuity and spectacle independence at distance from preoperative stage to 1 month and 2 months postoperatively. Results: Twenty-eight eyes of 18 subjects were treated. The best-corrected visual acuity at the 2-month postoperative (PO) stage was not statistically significantly different from the preoperative visual acuity (0.02 logarithm of the minimum angle of resolution [logMAR] in both cases, P>0.05). Uncorrected visual acuity was statistically significantly better at the 2-month PO stage relative to the preoperative value (0.14 versus 0.34 logMAR, P<0.01). The mean change in refractive cylinder from the preoperative stage to the 2-month PO stage was 1.0 D. At the 2-month PO stage, two-thirds of the subjects (12/18) reported that they did not use glasses for distance vision and that their spectacle use for distance vision at 2 months was “lower” or “much lower” than the preoperative stage; in 71% of eyes (20/28), the residual refractive cylinder was ≤0.50 D. Vector changes in keratometric astigmatism were weakly associated with changes in refractive cylinder. Conclusion: Arcuate incisions made with a femtosecond laser to treat moderate levels of residual refractive astigmatism after previous cataract surgery may reduce dependence on spectacles for distance vision. Keywords: Verion, LenSx, cylinder, cataract surgery, visual acuity, spectacl

Formation of ring-shaped microtubule assemblies through active self-organization on dynein

Microtubule (MT)-kinesin, a biomolecular motor system, is a promising candidate for construction of artificial biomachines for a variety of nanotechnology applications. An active self-organization (AcSO) method involving a specific streptavidin (St)-biotin (Bt) interaction has been developed to assemble MTs into a highly ordered structure by exploiting their motility on a kinesincoated surface. Dynein is another biomolecular motor that moves along the MTs in the opposite direction from kinesin. Dynein has not yet been used to demonstrate the AcSO of MTs. In this study, we report the first successful demonstration of the AcSO of MTs on a dynein-coated surface to produce ring-shaped MT assemblies similar to those of kinesin. We found that ring-shaped MT assemblies obtained on dynein showed equal clockwise and counterclockwise rotational motion. This work will enrich the building blocks for designing future oriented motor protein-based artificial devices