13,123 research outputs found
The size, shape, and dynamics of cellular blebs
A cellular bleb grows when a portion of the cell membrane detaches from the
underlying cortex under the influence of a cytoplasmic pressure. We develop a
quantitative model for the growth and dynamics of these objects in a simple
two-dimensional setting. In particular, we first find the minimum cytoplasmic
pressure and minimum unsupported membrane length for a stationary bleb to
nucleate and grow as a function of the membrane-cortex adhesion. We next show
how a bleb may travel around the periphery of the cell when the cytoplasmic
pressure varies in space and time in a prescribed way and find that the
traveling speed is governed by the speed of the pressure change induced by
local cortical contraction while the shape of the traveling bleb is governed by
the speed of cortical healing. Finally, we relax the assumption that the
pressure change is prescribed and couple it hydrodynamically to the cortical
contraction and membrane deformation. By quantifying the phase space of bleb
formation and dynamics, our framework serves to delineate the range and scope
of bleb-associated cell motility and synthesizes a variety of experimental
observations
A PDE model for bleb formation and interaction with linker proteins
The aim of this paper is to further develop mathematical models for bleb
formation in cells, including cell-membrane interactions with linker proteins.
This leads to nonlinear reaction-diffusion equations on a surface coupled to
fluid dynamics in the bulk. We provide a detailed mathematical analysis and
investigate some singular limits of the model, connecting it to previous
literature. Moreover, we provide numerical simulations in different scenarios,
confirming that the model can reproduce experimental results on bleb initation
Novel approaches to model effects of subconjunctival blebs on flow pressure to improve clinical grading systems after glaucoma drainage surgery
Clinical grading systems following glaucoma filtration surgery do not include any effects of the bleb on the intra-ocular pressure and are relatively subjective, therefore carrying the risk of inter and/or intra-observer variability. The main objective of the study is to quantify and model the effect of subconjunctival bleb on flow pressure for assessment of clinical grading following glaucoma surgery. Subconjunctival bleb was created by inserting a tube into ex vivo rabbit eyes via an ab externo approach through the anterior chamber and exiting into the subconjunctival space. Sterile dyed water was injected through the tube into the developing bleb. For the in vitro approach a silicone bleb was created by clamping a circular silicone sheet, injecting dyed water through a fixed resistance outlet tube. Photographic measurements of the bleb height, planform area and pressure were taken as a function of time. Clinical blebs were also collected over a few months. Mathematical algorithm software was used to build the bleb model. Bleb height and volume increase as pressure in the bleb increases. The bleb planform area tended to a constant determined by the section of conjunctiva prior to shunt insertion. These increases were in accordance with the bleb model developed in the Appendix. They show that the pressure in the bleb is related to the resistance of the outflow. The linearity of clinical grading systems is reviewed and a new grading approach is proposed. The pressure in the bleb has a strong dependence on bleb extent, height and a weak dependence on conjunctival thickness. The pressure in a bleb can be estimated from bleb height, radius, and flow rate inlet in agreement with the bleb flow model. These results provide support for an improved bleb categorization system
Stem cell differentiation increases membrane-actin adhesion regulating cell blebability, migration and mechanics
This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder in order to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/K. S. is funded by an EPSRC PhD studentship. S.T. is funded by an EU Marie Curie Intra European Fellowship (GENOMICDIFF)
Volume changes during active shape fluctuations in cells
Cells modify their volume in response to changes in osmotic pressure but it
is usually assumed that other active shape variations do not involve
significant volume fluctuations. Here we report experiments demonstrating that
water transport in and out of the cell is needed for the formation of blebs,
commonly observed protrusions in the plasma membrane driven by cortex
contraction. We develop and simulate a model of fluid mediated membrane-cortex
deformations and show that a permeable membrane is necessary for bleb formation
which is otherwise impaired. Taken together our experimental and theoretical
results emphasize the subtle balance between hydrodynamics and elasticity in
actively driven cell morphological changes.Comment: Phys. Rev. Lett. in press. 13 pages 4 figures, 9 supplementary
figure
Adult skeletal muscle stem cell migration is mediated by a blebbing/amoeboid mechanism
Adult skeletal muscle possesses a resident stem cell population called satellite cells which are responsible
for tissue repair following damage. Satellite cell migration is crucial in promoting rapid tissue
regeneration but is a poorly understood process. Furthermore, the mechanisms facilitating satellite cell
movement have yet to be elucidated. Here the process of satellite cell migration has been investigated
revealing that they undergo two distinct phases of movement; firstly under the basal lamina and then
rapidly increasing their velocity when on the myofibre surface. Most significantly we show that satellite
cells move using a highly dynamic blebbing based mechanism and not via lamellopodia mediated
propulsion. We show that nitric oxide and non-canonical Wnt signalling pathways are necessary for
regulating the formation of blebs and the migration of satellite cells. In summary, we propose that the
formation of blebs and their necessity for satellite cell migration has significant implications in the future
development of therapeutic regimes aimed at promoting skeletal muscle regeneration
Intraoperative Optical Coherence Tomography-Guided Bleb-sparing Epithelial Exchange: A Modified Approach
With the advent of newer technologies, real-time anterior segment optical coherence tomography (OCT) integrated with the operating microscope has become possible. We are proposing the technique of bleb revision with greater precision under direct visualization of bleb anatomy and extent of tissue depth allowing better localization and easy maneuvering with lesser complications. In this surgical technique, bleb revision was performed using intraoperative real-time OCT incorporated in OPMI LUMERA 700 microscope. Live surgical and OCT view were seen on a common screen together. A moderately elevated, diffuse functional bleb was noted after three months of bleb revision in both cases with controlled intraocular pressure. Intraoperative OCT-guided bleb-sparing epithelial exchange is an adjunctive technique for bleb repair surgery with an increased precision of surgery which can reduce complications, minimize surgical time and maximize surgical outcome
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