Advancing Edge Speeds of Epithelial Monolayers Depend on Their Initial Confining Geometry

Collective cell migrations are essential in several physiological processes and are driven by both chemical and mechanical cues. The roles of substrate stiffness and confinement on collective migrations have been investigated in recent years, however few studies have addressed how geometric shapes influence collective cell migrations. Here, we address the hypothesis that the relative position of a cell within the confinement influences its motility. Monolayers of two types of epithelial cells--MCF7, a breast epithelial cancer cell line, and MDCK, a control epithelial cell line--were confined within circular, square, and cross-shaped stencils and their migration velocities were quantified upon release of the constraint using particle image velocimetry. The choice of stencil geometry allowed us to investigate individual cell motility within convex, straight and concave boundaries. Cells located in sharp, convex boundaries migrated at slower rates than those in concave or straight edges in both cell types. The overall cluster migration occurred in three phases: an initial linear increase with time, followed by a plateau region and a subsequent decrease in cluster speeds. An acto-myosin contractile ring, present in the MDCK but absent in MCF7 monolayer, was a prominent feature in the emergence of leader cells from the MDCK clusters which occurred every ~125 μm from the vertex of the cross. Further, coordinated cell movements displayed vorticity patterns in MDCK which were absent in MCF7 clusters. We also used cytoskeletal inhibitors to show the importance of acto-myosin bounding cables in collective migrations through translation of local movements to create long range coordinated movements and the creation of leader cells within ensembles. To our knowledge, this is the first demonstration of how bounding shapes influence long-term migratory behaviours of epithelial cell monolayers. These results are important for tissue engineering and may also enhance our understanding of cell movements during developmental patterning and cancer metastasis.

Traction cytometry: regularization in the Fourier approach and comparisons with finite element method

Traction forces exerted by adherent cells are quantified using displacements of embedded markers on polyacrylamide substrates due to cell contractility. Fourier Transform Traction Cytometry (FTTC) is widely used to calculate tractions but has inherent limitations due to errors in the displacement fields; these are mitigated through a regularization parameter (γ) in the Reg-FTTC method. An alternate finite element (FE) approach computes tractions on a domain using known boundary conditions. Robust verification and recovery studies are lacking but essential in assessing the accuracy and noise sensitivity of the traction solutions from the different methods. We implemented the L2 regularization method and defined a maximum curvature point in the traction with γ plot as the optimal regularization parameter (γ*) in the Reg-FTTC approach. Traction reconstructions using γ* yield accurate values of low and maximum tractions (Tmax) in the presence of up to 5% noise. Reg-FTTC is hence a clear improvement over the FTTC method but is inadequate to reconstruct low stresses such as those at nascent focal adhesions. FE, implemented using a node-by-node comparison, showed an intermediate reconstruction compared to Reg-FTTC. We performed experiments using mouse embryonic fibroblast (MEF) and compared results between these approaches. Tractions from FTTC and FE showed differences of ∼92% and 22% as compared to Reg-FTTC. Selection of an optimum value of γ for each cell reduced variability in the computed tractions as compared to using a single value of γ for all the MEF cells in this study.

Critical illness myopathy

Critical illness myopathy is one of the causes for failure to wean from ventilator. Although associate factors of dyselectrolytemia is to be ruled out and other causes for failure to wean is to be ruled out before diagnosing critical illness myopathy. Several factors play role in development of this condition. Here we present a case report of a post partum patient where we had encountered failure to wean despite several attempts and at last was successfully weaned and discharged from intensive care unit.

Anesthetic management of a child with Down's syndrome having atlanto axial instability

Down's syndrome is the most commonly encountered congenital anomaly in medical practice. These patients are of special concern to medical practice because of their associated problems with regard to respiratory, cardiovascular and other systemic problems. As these patients present for repeated surgeries like dental extraction, facial reconstruction and fixation of cervical spine, these patients pose challenges to the anesthesiologist because of their unique set of problems, namely atlantoaxial instability, small trachea, congenital heart disease and repeated chest infections due to lowered immunity. Their reactivity to inhalational anesthetics and atropine is variable. Here we present an interesting case report of a child with Down's syndrome who presented with atlantoaxial instability for MRI of cervical spine under general anesthesia.

Anesthetic management of a child with Down’s Syndrome having atlanto axial instability

Down's syndrome is the most commonly encountered congenital anomaly in medical practice. These patients are of special concern to medical practice because of their associated problems with regard to respiratory, cardiovascular and other systemic problems. As these patients present for repeated surgeries like dental extraction, facial reconstruction and fixation of cervical spine, these patients pose challenges to the anesthesiologist because of their unique set of problems, namely atlantoaxial instability, small trachea, congenital heart disease and repeated chest infections due to lowered immunity. Their reactivity to inhalational anesthetics and atropine is variable. Here we present an interesting case report of a child with Down's syndrome who presented with atlantoaxial instability for MRI of cervical spine under general anesthesia.KeyWords:atlanto axial instability, down’s syndrome, trisomy 21

Anesthetic consideration in downs syndrome--a review

Downs syndrome constitutes to be the most common chromosomal disorder. Patients with Downs's syndrome are posted for several surgeries including dental procedures and even for facial reconstruction. They are associated with several congenital anomalies in different organ system. There is also increased incidence of atlanto axial instability and risk of spinal cord injury. These children are susceptible to infection and they are also considered to be hypersensitive to the effect or atropine. These all factors modify the anesthetic implication and also anesthetic management in these cases. We have highlighted all these factors and reviewed the anesthetic implication of these child posted for several procedures under anesthesia.