Biochemical and physical responses of red blood cells with shear exposure

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Simmonds, Michael

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Sabapathy, Surendran

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Red blood cells (RBC), the essential oxygen-transporters of the human body, are near constantly exposed to deforming forces (i.e., shear stress) as they traverse the circulatory system. Given that the diameter of microcirculatory blood vessels may be as narrow as ~2 μm, RBC with a resting diameter of ~8 μm require an exceptional capacity to deform and change shape, while sustaining cell function. RBC are equipped with unique physical properties to accommodate cellular deformation under mechanical stress; the characteristic bi-concave disc-shape yielding favourable surface area to volume ratio, paired with a flexible, cytoskeletal mesh-network in the cell membrane, support flexibility of RBC. Recent studies, however, support the notion that RBC deformability is actively regulated by pathways involving second messenger molecules, primarily calcium-ions (Ca2+) and nitric oxide (NO). Exposure of RBC to shear stress is thought to increase endogenous production of NO enzymatically via nitric oxide synthase (RBC-NOS), while mechanically-gated ion channels permit entry of Ca2+ under shear. The physiological magnitude of shear stress exerted upon blood is thought to be limited to ~15 Pa; however, when patients require extracorporeal circulatory devices such as rotary blood pumps or dialysis machines, the resulting mechanical forces approximate values of >100 Pa, that are known to impair the physical properties of RBC. Thus, the aim of the current thesis was to explore the physical and biochemical properties of RBC when exposed to either physiological (i.e., <15 Pa) or supraphysiological (i.e., ~64 Pa) shear stress. To assess the primary aims, three distinct studies comprised of multiple respective experiments were conducted. [...]

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Thesis (Masters)

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Master of Medical Research (MMedRes)


School of Medical Science

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The author owns the copyright in this thesis, unless stated otherwise.

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Cellular deformation under mechanical stress

Extracorporeal circulatory devices

Recoverability of shear-induced changes in cell deformability

Complex intracellular messaging

Supraphysiological shear exposure

Intracellular free radical generation

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