Biomedical subjects

Kenneth A Barbee

Publications and source records attributed to Kenneth A Barbee.

6 recordsLinked to original sources

PubMed2006

Real-time analysis of cell-surface adhesive interactions using thickness shear mode resonator.

The cell adhesion process and the molecular interactions that determine its kinetics were investigated using a thickness shear mode (TSM) sensor. The goal of this study was to correlate sensor readings with the progression of cell adhesion. In particular, the specific effects of receptor-mediated adhesion, the glycocalyx, and surface charge on initial cell-surface attachment and steady-state adhesion of endothelial cells were investigated. We found a strong correlation between resistance changes (DeltaR) and the development of cell adhesion strength by comparing the sensor readings with independently assessed cell adhesion. The result showed that integrin binding determines the kinetics of initial cell attachment while heparan sulfate proteoglycan (HSPG) modulates steady-state adhesion strength. Coating the sensor surface with the positively charged poly-d-lysine (PDL) enhanced the initial interaction with substratum. These data confirm our current understanding of the contribution of these three phenomena to the adhesion process. The real-time monitoring capability of this technique with high temporal resolution provides more detailed information on the kinetics of the different stages of the adhesion process. This technique has the potential to facilitate the evaluation of biomaterials and surface treatments used for implants and tissue-engineering scaffolds for their bioactive effects on the cell adhesion process.

Animals↗

PubMed2005

Quantifying the L-arginine paradox in vivo.

NO and PO(2) microelectrodes were used to quantify the effects of increased availability of L-arginine in an exteriorized rat mesentery and small intestine microcirculatory preparation in n = 16 rats. During short periods of elevated L-arginine added to the superfusion bath, transient changes in perivascular NO or PO(2) were measured at 171 perivascular sites near intestinal arterioles and venules, simultaneously with tissue perfusion using laser Doppler flowmetry (LDF). Excess L-arginine increased perivascular NO over twofold, by 411 +/- 42 nM above the baseline of 329 +/- 30 nM (P < 0.0001), and increased tissue perfusion by 35.5 +/- 7.5% (P < 0.0001). No difference between arterioles and venules was observed in the magnitude or time course of the NO responses. Both increases and decreases in perivascular PO(2) were observed after excess L-arginine, with a similar increase in tissue perfusion by 42.0 +/- 12.3% (P < 0.0001). Our NO measurements confirm that increased bioavailability of L-arginine causes a significant increase in NO production throughout the microcirculation of this preparation, with increased tissue perfusion, and provides direct in vivo evidence for the L-arginine paradox.

Animals↗

PubMed2005

The influence of radial RBC distribution, blood velocity profiles, and glycocalyx on coupled NO/O2 transport.

The purpose of this investigation was to study the effect of the presence of red blood cells (RBCs) in the plasma layer near the arteriole wall on nitric oxide (NO) and oxygen (O2) transport. To this end, we extended a coupled NO and O2 diffusion-reaction model in the arteriole, developed by our group, to include the effect of the presence of RBCs in the plasma layer and the effect of convection. Two blood flow velocity profiles (plug and parabolic) were tested. The average hematocrit in the bloodstream was assumed to be constant in the central core and decreasing to zero in the boundary layer next to the endothelial surface layer. The effect of the presence or absence of RBCs near the endothelium was studied while varying the endothelial surface layer and boundary layer thickness. With RBCs present in the boundary layer, the model predicts that 1) NO decreases significantly in the endothelium and vascular wall; 2) there is a very small increase in endothelial and vascular wall Po2; 3) scavenging of NO by hemoglobin decreases with increasing thickness of the boundary layer; 4) the shape of the velocity profile influences both NO and Po2 gradients in the bloodstream; and 5) the presence of RBCs in the boundary layer near the endothelium has a much larger effect on NO than on O2 transport.

Arterioles↗

PubMed2005

Mechanical cell injury.

The tissues of the body are continually subjected to mechanical stimulation by external forces, such as gravity, and internally generated forces, such as the pumping of blood or muscle contraction. Within a physiological range, the forces elicit adaptive responses acutely (to rapidly alter function) and chronically (to remodel tissue structure to optimize load-bearing capabilities). When the forces exceed certain thresholds, injury results. To understand the mechanisms of mechanical injury at the cellular level, we must analyze the structural response of the cell to various modes of deformation and examine the biological consequences of the structural alterations caused by the trauma. This chapter reviews the mechanics of cell membrane deformation and failure. Evidence for the strain-rate-dependent, transient disruption of cell membranes, or mechanoporation, is presented for a variety of cell types. The complex interactions between the structural damage and the biological sequelae are illustrated using clinically relevant forms of cell injury. Finally, novel therapeutic approaches targeting membrane integrity are described.

Angioplasty↗

PubMed2004

Ceramic-based multisite electrode arrays for chronic single-neuron recording.

A method is described for the manufacture of a microelectrode array for chronic, multichannel, single neuron recording. The ceramic-based, multisite electrode array has four recording sites patterned onto a ceramic shaft the size of a single typical microwire electrode. The sites and connecting wires are applied to the ceramic substrate using a reverse photolithographic procedure. Recording sites (22 x 80 microm) are separated by 200 microm along the shaft. A layer of alumina insulation is applied over the whole array (exclusive of recording sites) by ion-beam assisted deposition. These arrays were capable of recording single neuron activity from each of their recording sites for at least three weeks during chronic implantation in the somatosensory cortex of rats, and several sites had recordings that lasted for more than 8 weeks. The vertical arrangement of the recording sites on these electrodes is ideal for simultaneously recording across the different layers of brain areas such as the cerebral cortex and hippocampus in chronic preparations.

Action Potentials↗

PubMed2002

Role of subcellular shear-stress distributions in endothelial cell mechanotransduction.

The endothelium of blood vessels presents a wavy surface to the flowing blood. The subcellular distribution of shear stress depends on the shape and orientation of the cells and on their spatial arrangement within the monolayer. By studying details of the distribution of stress at this scale and the morphological responses that serve to modify the distribution, we can gain insight into the physical mechanisms by which the cell senses its fluid mechanical environment. The rapidly growing body of evidence indicates that endothelial cells discriminate between subtle variations in the exact loading conditions including differences in temporal and spatial gradients of shear stress, steady and pulsatile laminar flow, and laminar and turbulent flows. While in a few studies the effects of these individual flow characteristics have been carefully isolated, it is difficult to assess the relative importance of any one parameter. To interpret the relationships between isolated flow characteristics or the integrated effects of combined loading conditions and the biochemical signaling events that mediate the cell response, a full stress analysis of the cell is needed. The microscopic distribution of shear stress acting upon the cell surface provides the boundary condition for such an analysis. Experimental and analytical tools are being developed to assess the stress distribution throughout the cellular structures that might be involved in mechanotransduction.

Arteries↗