The University of Arizona

Department of Physiology - The University of Arizona

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Faculty

Timothy Secomb

Professor

Contact Information

Address: P.O. Box 245051
Tucson, AZ 85724
Phone: (520) 626-4513
Email: secomb@u.arizona.edu


Website: http://www.physiology.arizona.edu/people/secomb/

Research Interests


The microcirculation is a network of extremely small blood vessels that supplies oxygen and nutrients to all parts of our tissues. The focus of work in our research group is the use of mathematical and computational approaches to study blood flow and mass transport in the microcirculation. Working in collaboration with experimentalists, we aim to understand quantitatively the processes involved. The main areas of our work are:



Mechanics of blood flow in microvessels. We are examining the relationship between red blood cell mechanics and flow resistance in microvessels. Theoretical predictions agree well with observations in glass tubes, but resistance is higher living tissue. We have found that the major cause is the presence of a relatively thick macromolecular lining (endothelial surface layer) on the walls of microvessels.



Mass transport to tissue. We are simulating oxygen exchange between networks of microvessels and surrounding tissues in skeletal muscle and tumors. In skeletal muscle, we have shown how oxygen can be exchanged diffusively between arterioles and capillaries, and we are studying the determinants of maximal oxygen consumption. In tumors, we are studying the relationship between network structure and occurrence of local hypoxic (radiation-resistant) regions. Also, we are analyzing the delivery of chemotherapeutic drugs in tumor tissues.



Structural adaptation of microvascular networks. We are developing models for the stuctural responses of microvessels to functional demands. We have found that maintenance of a stable, functionally adequate distribution of vessel diameters can be achieved if each vessel responds to changes in wall shear stress, intravascular pressure and local metabolic conditions, and if mechanisms exist for information transfer upstream and downstream along flow pathways.



Regulation of blood flow: We are developing models for the active regulation of blood flow by changes in vascular tone, taking into account vascular responses to wall shear stress, pressure and local metabolic state, and including effects of conducted responses along vessel walls.

Graduate Program Affiliations

Applied Mathematics

Biology, Math, and Physics IGERT Program

Biomedical Engineering

Physiological Sciences

Publications

Hicks KO, Pruijn FB, Secomb TW, Hay MP, Hsu R, Brown JM, Denny WA, Dewhirst MW, Wilson WR.. Aug 2006. Use of three-dimensional tissue cultures to model extravascular transport and predict in vivo activity of hypoxia-targeted anticancer drugs. J Natl Cancer Inst, 98:1118-28

Lanzen J, Braun RD, Klitzman B, Brizel D, Secomb TW, Dewhirst MW. Feb 2006. Direct demonstration of instabilities in oxygen concentrations within the extravascular compartment of an experimental tumor. Cancer Res, 66:2219-23

Secomb TW. Dec 2005. Comments on Point:Counterpoint "Positive effects of intermittent hypoxia (live high:train low) on exercise performance are/are not mediated primarily by augmented red cell volume". J Appl Physiol, 99:2454-5

Pries AR, Reglin B, Secomb TW. Oct 2005. Remodeling of blood vessels: responses of diameter and wall thickness to hemodynamic and metabolic stimuli. Hypertension, 46:725-31

Pries AR, Secomb TW. Jul 2005. Microvascular blood viscosity in vivo and the endothelial surface layer. Am J Physiol Heart Circ Physiol,2005 Jul 22;

El-Kareh AW, Secomb TW. Jul 2005. Two-mechanism peak concentration model for cellular pharmacodynamics of Doxorubicin. Neoplasia, 7:705-13

Carlson BE, Secomb TW. Jun 2005. A theoretical model for the myogenic response based on the length-tension characteristics of vascular smooth muscle. Microcirculation, 12:327-38

Pries AR, Secomb TW. Mar 2005. Control of blood vessel structure: insights from theoretical models. Am J Physiol Heart Circ Physiol, 288:H1010-5

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