Cell deformation

Hydroxyurea is a ribonucleotide reductase inhibitor that prevents DNA synthesis and traditionally has been used in chemotherapy regimens. Studies in the 1990s also found that hydroxyurea increases HbF levels as well as increasing the number of HbF-containing reticulocytes and intracellular HbF. Other beneficial effects of hydroxyurea include antioxidant properties, reduction of neutrophils and monocytes, increased intracellular water content leading to increased red cell deformability, decreased red cell adhesion to endothelium, and increased levels of nitric oxide, which is a regulator involved in physiologic disturbances.22... 

Gorodeski GI [1998] Estrogen increases the permeability of the cultured human cervical epithelium by modulating cell deformability. Am J Physiol 275 ... 

Li X, Zhou L, and Gorodeski GI [2006] Estrogen regulates epithelial cell deformability by modulation of cortical acto-myosin through phosphorylation of non-muscle myosin-heavy-chain II-B filaments. Endocrinology 147 5236-5248... 

A study was made of the impact and recovery behaviour of three HDPE closed-cell foams with varying densities. Impact stress-strain curves were measured using a falling striker impact rig and the recovery monitored from 10s after the impact. Cell deformation was observed during compression and recovery using SEM. Recovery was found to occur by the viscoelastic straightening of the buckled faces and to be incomplete due to plastic deformation in the structure. 6 refs. 

It was found that increasing Ca caused the yield stress and yield strain to increase, along with cell deformation at the yield point. At sufficiently high values of Ca, cell distortion is so severe that film thinning and rupture can occur, resulting in mechanical failure of the foam (Fig. 6). This implies the presence of a shear strength for foams and HIPEs. The initial orientation of the cells was also found to affect the stress/strain behaviour of the system in the presence of viscous forces [63]. For some particular orientations, periodic flow was not observed for any value of Ca. 

Miyata, Hidetake, see Akashi, Kenichirou, 6, 45 see also Cell deformation Mechanisms Studied with Actin-containing Giant Vesicles, a Cell-mimicking System.,... 

Bruels, R.G.M., Sengers, B.G., Oomens, C.W.J., Bouten, C.V.C. and Baaijens, F.P.T. (2002) Predicting local cell deformations in engineered tissue constructs a multilevel finite element approach. Journal of Biomechanical Engineering 124, 198-206... 

Mechanism of action that provides symptom relief with pentoxifylline is poorly understood but is thought to involve red blood cell deformability as well as a reduction in fibrinogen concentration, platelet adhesiveness and whole blood viscosity (75). The recommended dose of pentoxifylline is 400 mg three times daily with meals. Pentoxifylline causes a marginal but statistically significant improvement in pain-free and maximal walking distance (a net benefit of 44 m in the maximal distance walked on a treadmill (95% Cl, 0 14 to 0 74) based on meta-analyses of randomized, placebo-controlled, double-blind clinical trials (76). At the same time pentoxifylline does not increase the ABI at rest or after exercise (56). Pentoxifylline may be used to treat patients with intermittent claudication however, it is likely to be of marginal clinical importance (56,77). Medical therapies... 

Tracey, M.C., Greenaway, F.S., Das, A., Kaye, PH., Barnes, A.J., A silicon micro-machined device for use in blood cell deformability studies. IEEE Trans. Biomed. Eng. 1995, 42(8), 751-761. 

Fig. 14.9 Snapshots of a system of twenty 100 carbon atom long polyethylene chains deformed at 300 K. The initial slab at the top rapidly deforms with the applied stress in the x dimension of the slab, roughly doubling in the first 500 ps to / — 2.64 (second image from the top) then the rate of deformation is slower and doubles again in 1500ps to X — 5.15 (third image from the top). Beyond this point the cell deforms even more slowly to reach a final deformation of X = 6.28 (bottom image). In absolute values, the initial cell of dimensions 1.88 x 5.32 x 5.32 nm deforms to 11.8 x 2.23 x 1.96nm. [Reprinted by permission from M. C. Levine, N. Waheed, and G. C. Rutledge, Molecular Dynamics Simulation of Orientation and Crystallization of Polyethylene during Uniaxial Extension, Polymer, 44, 1771-1779, (2003).]...

Labow RS, Card RT, Rock G. 1987. The effect of the plasticizer di(2-ethylhexyl)phthalate on red cell deformability. Blood70 19-323. 

Actin is one of the most abundant cellular proteins and is present in all mammalian cells. F-actin is physically crosslinked to form the cellular cytoskeleton and its contraction allows cell deformation and movement... 

The importance of the spleen in the pathophysiology of the hemolysis of HS has been substantiated. Two factors determine the selective destruction of the HS cells in the spleen (1) poor HS red cell deformability, which is a reflection of a decreased surface-to-volume ratio resulting from the loss of membrane and (2) the unique anatomy of the splenic vasculature, which acts as a microcirculation filter. As shown in Table 6-2, the underlying molecular basis of HS is heterogeneous, and the primary molecular lesion in HS is likely to involve several membrane proteins, including spectrin, ankyrin,... 

Primary and secondary cells (accumulators) are in the scope of the m-standards. Only cells, which in normal use (under the specified conditions given by their manufacturer) are not expected to release gas, do not release electrolyte or produce excessive temperature rise, may be encapsulated. The m-apparatus shall be so constructed as to allow a venting to the outside atmosphere of any gas which may be generated, or precautions shall be taken to avoid gas release or cell deformation adversely affecting the type of protection m. These precautions should be based upon an agreement between the testing house or the notified body and the manufacturer. 

The structure of a foam, which deforms in a specific manner also influences physical properties. Upon initial compression there is a deformation of the structure that requires an increase in the amount of force applied. Once the foam has been deformed significantly the sides of the cell walls buckle leading to cell collapse and the production of elliptically deformed structures. A picture of such cells deformed under extreme compression is shown in Figure 14. During this phase of the compression the rate of increase in the force applied is significantly decreased. 

Ochalek, T., Nordt, F. J., Tullberg, K. and Burger, M. M. (1988). Correlation between cell deformability and metastatic potential in B16-F1 melanoma cell variants. Cancer Res. 48, 5124—5128. 

Weiss, L. (1976). Cell deformability some general considerations. In Fundamental Aspects of Metastasis (Weiss, L., ed.). North-Holland, Amsterdam/American Elsevier, New York, pp. 305-310. 

Simchon, S. Jan, K.M. Chien, S. Influence of reduced red cell deformability on regional flow. Am. J. Physiol. 1987, 253, H895-H903. 

If vacuum is applied, the phase boundary between liquid and vapour is reached at a certain pressure and water starts to vaporize. To prevent a loss of temperature, heat -the so-called heat of evaporation - has to be introduced from the outside. If all water has been evaporated, a rise in temperature will ensue that can be taken as an indicator for the end of the drying process. Although this method is gentle, the material to be dried is puffed up and structural and cell deformations follow. 

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