Browsing by Subject "Capillary"

Now showing 1 - 3 of 3
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    Characterization of blood flow in the retinal vascular network
    (2015-01) Kornfield, Tess Ellen
    The primary goal of the work presented here is to understand how blood flow is regulated in the retinal vascular network in response to neuronal activity. In order to accurately quantify blood flow, we developed a multitude of streamlined techniques capable of measuring many properties of blood flow. These techniques were used to investigate retinal functional hyperemia, defined as the increase in local blood flow that occurs in response to nearby neuronal activity. We did a comprehensive survey of all retinal vessels to investigate the magnitude and timing of the functional hyperemia response as it presents in the different compartments of the retinal vascular network. We found that arterioles are primarily responsible for generating functional hyperemia in the retina and that, with prolonged stimulation, blood flow through the three vascular layers in the retina is differentially regulated. This result implies the presence of active capillary dilation. The work in this dissertation informs our understanding of blood flow regulation within the retinal vascular network.
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    Development of Improved Ion-Selective and Reference Electrodes for In Situ Monitoring of Ion Concentrations
    (2019-07) Anderson, Evan
    This dissertation is focused on the application of electrochemistry for the fundamental understanding, development, and application of electrochemical sensors. In particular, my research focused on the development and understanding of reference electrodes and ion-selective electrodes for potentiometric sensing applications. Recently, following the needs of point-of-care and wearable sensors, electrode designs have transitioned from bulky devices with an aqueous inner filling solution (e.g. pH electrodes) to planarizable solid-contact electrodes. However, unless their polymeric sensing and reference membranes are held in place mechanically, delamination of the physically adhering membranes limits sensor lifetime, as even minimal external mechanical stress or thermal expansion can result in membrane delamination and, thereby, device failure. To address this problem, we designed a sensing platform based on inexpensive polymers to which membranes are attached covalently through photopolymerization. Even extreme mechanical stress does not result in the delamination of the sensing and reference membranes from the underlying polymer, which results in electrodes that exhibit much improved long-term performance and greatly reduced size. This method of sensor preparation is broadly applicable to a wide range of electrode types and allows for long-term measurements of numerous ions that are of environmental and medical significance. Moreover, the applicability of these ion-selective electrodes for long-term measurements requires reference electrodes that also provide stable responses. Reported here are two types of improved reference electrodes based on capillaries and ionic liquids.
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    Mechanisms of Blood Flow Regulation in the Retina: Glial Calcium Signaling Regulates Capillary, but Not Arteriole Diameter
    (2016-12) Biesecker, Kyle
    Blood flow is tightly regulated in the central nervous system to ensure neurons receive sufficient oxygen and glucose. When neuronal activity increases, nearby blood vessels dilate to increase local blood flow, a phenomenon termed functional hyperemia. Two key controversies have arisen concerning the mechanisms that underlie functional hyperemia. Firstly, the role of glial Ca2+ signaling in triggering vessel dilations is unclear. Some evidence suggests that glial Ca2+ signals precede vessel dilations, but blocking glial Ca2+ signaling does not alter functional hyperemia. Secondly, data has been presented arguing both for and against the ability of capillaries to actively dilate during functional hyperemia. Herein, I demonstrate that glial Ca2+ signaling does play a key role in regulating capillary diameter, but is not necessary for regulating arteriole diameter. Additionally, capillaries can actively dilate during functional hyperemia responses. These findings suggest that glial Ca2+ signaling contributes to blood flow regulation in the central nervous system by triggering capillary dilations during functional hyperemia.