851 research outputs found
Shape mode analysis exposes movement patterns in biology: flagella and flatworms as case studies
We illustrate shape mode analysis as a simple, yet powerful technique to
concisely describe complex biological shapes and their dynamics. We
characterize undulatory bending waves of beating flagella and reconstruct a
limit cycle of flagellar oscillations, paying particular attention to the
periodicity of angular data. As a second example, we analyze non-convex
boundary outlines of gliding flatworms, which allows us to expose stereotypic
body postures that can be related to two different locomotion mechanisms.
Further, shape mode analysis based on principal component analysis allows to
discriminate different flatworm species, despite large motion-associated shape
variability. Thus, complex shape dynamics is characterized by a small number of
shape scores that change in time. We present this method using descriptive
examples, explaining abstract mathematics in a graphic way.Comment: 20 pages, 6 figures, accepted for publication in PLoS On
Active phase and amplitude fluctuations of flagellar beating
The eukaryotic flagellum beats periodically, driven by the oscillatory
dynamics of molecular motors, to propel cells and pump fluids. Small, but
perceivable fluctuations in the beat of individual flagella have physiological
implications for synchronization in collections of flagella as well as for
hydrodynamic interactions between flagellated swimmers. Here, we characterize
phase and amplitude fluctuations of flagellar bending waves using shape mode
analysis and limit cycle reconstruction. We report a quality factor of
flagellar oscillations, (means.e.). Our analysis shows
that flagellar fluctuations are dominantly of active origin. Using a minimal
model of collective motor oscillations, we demonstrate how the stochastic
dynamics of individual motors can give rise to active small-number fluctuations
in motor-cytoskeleton systems.Comment: accepted for publication in Physical Review Letter
Die Palfersche Waage : ueber die in Liv-, Cur- und Ehstland unter den Necrolivonicis gefundenen Waagen und Gewichte
Digiteeritud Euroopa Regionaalarengu Fondi rahastusel, projekti "Eesti teadus- ja õppekirjandus" (2014-2020.12.03.21-0848) raames.https://www.ester.ee/record=b2229100*es
Mehrere für die ältere Geschichte Dänemarks und der Ostseeprovinzen wichtige, bisher bestrittene Urkunden d. X.-XIV. Jahrhunderts
http://www.ester.ee/record=b1981376*es
Wound healing in rabbit corneas after flapless refractive lenticule extraction with a 345 nm ultraviolet femtosecond laser
Purpose
To characterize corneal wound healing in a rabbit model after flapless refractive lenticule extraction with a 345 nm ultraviolet femtosecond laser.
Setting
Departments of Ophthalmology and Anatomy II, University of Erlangen-Nürnberg and Wavelight GmbH, Erlangen, Germany.
Design
Methods
Flapless refractive lenticule extraction was performed in 1 eye each of 20 New Zealand white rabbits (−5.0 diopters). Groups of 4 animals were euthanized after 48 hours, 1 week, 2 weeks, 4 weeks, and 3 months, respectively. Corneal samples were prepared for histology and fluorescence microscopy. To assess corneal cell death, proliferation, and myofibroblastic transdifferentiation, terminal uridine deoxynucleotidyl nick end-labeling (TUNEL) assay as well as immunostaining for Ki67 and α-smooth muscle actin (αSMA) were performed on sagittal cryosections.
Results
Histology revealed a zone of keratocyte depletion with a thickness of approximately 50 μm around the extraction site. At 48 hours, pronounced TUNEL staining of keratocytes was detected around the interface (159.9 cells/mm ± 18.4 [SD]), which steadily decreased to 74.9 ± 19.8 cells/mm at 1 week and 5.7 ± 4.8 cells/mm at 2 weeks. Ki67 staining of keratocytes was evident at 48 hours (10.0 ± 3.8 cells/mm), which then decreased at 1 week (5.2 ± 1.7 cells/mm) and 2 weeks (0.4 ± 0.5 cells/mm). From 4 weeks onward, no TUNEL or Ki67 staining was detected. The corneal stroma was αSMA-negative at all timepoints.
Conclusion
Application of the 345 nm laser showed no signs of problematic repair processes in the cornea, which supports the initiation of the clinical phase
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