Ph.D. Bioengineering,
University of California, San Diego, 1975
Professor and Chairman of Bioengineering
205 Hallowell Bldg.
Tel: 814-865-1407
Fax: 814-863-0490
Email: hhlbio@engr.psu.edu
Microcirculation Lab
The central theme of the research studies conducted by Dr.
Lipowsky is to apply engineering techniques and methods to
the solution of problems in the physiology of microvascular function
in health and disease. Studies are conducted to elucidate the
rheological behavior of blood in the microcirculation in normal
and abnormal
(disease) flow states. This work entails a delineation of factors
which contribute to the apparent viscosity of blood, and hence
govern the resistance to blood flow in the arterioles, capillaries
and venules of the microcirculation proper.
Attention is given to such disorders as polycythemia, inflammation,
shock and blood cell pathologies, to name a few. Particular attention
is paid to the role of the intrinsic mechanical properties of the
blood which affect the aggregability and deformability of red and
white blood cells, and their interaction with the microvascular
endothelium.
State of the art techniques of intravital microscopy are applied
to quantitate microvascular blood flow in the living animal. For
example, small laboratory animals are anesthetized and a region
of tissue is exteriorized for observation under the microscope,
such as the intestinal mesentery and cremaster muscle of the rat.
Sophisticated optical, electrical and mechanical techniques are
employed to measure vascular topography, intravascular pressure
gradients and flow rates, microvessel hematocrit and hemoglobin
oxygen saturation under normal flow conditions and during a variety
of abnormal flow states. With these methods, experimental data
are acquired to describe fundamental transport phenomena in the
microcirculation and are then analyzed by mathematical models and
computer simulations to obtain an integrated and comprehensive
view of microvascular function.
Current research efforts focus upon delineating the rheological
properties of the endothelial surface layer and how it affects
the resistance to flow in the microvascular network. These studies
entail quantitative analysis of changes in the molecular coating
on the walls of small blood vessels in response to alterations
in shear stress and flow. This coating, referred to as the glycocalyx,
results from the continual biosynthesis of sugars attached to membrane
bound proteins, and their removal due to disruption of the layer
by shear stresses and enzymatic degradation. We have shown that
molecular components of the glycocalyx are shed during inflammation,
and upon resumption of flow following recovery from a no-flow state.
It is hypothesized that continued growth of the endothelial surface
layer may obstruct the lumen of capillary sized microvessels and
hence increase the resistance to flow, thus impeding recovery from
a low flow state. Techniques of intravital microscopy are used
to quantify changes in the composition of the endothelial surface
layer in response to flow and shear stress.
These studies are conducted in the Microcirculation Laboratory
located in the Hallowell Building of the University Park campus.
Major facilities include three intravitial microscopes with associated
instrumentation for video microscopy and the measurement of intravascular
pressures and flows in the living animal. Support for data analysis
and digital video image processing is provided by several PCs with
the capability of on and off-line data and image acquisition.
Representative Publications
Lipowsky, H. H. Microvascular rheology and hemodynamics, Mircrocirculation
12: 5-15, 2005. (pdf)
Mulivor, A. W. and Lipowsky, H. H. Inflammation- and ischemia-induced
shedding of venular glycocalyx. Am J Physiol Heart Circ Physiol
286: H1672-H1680, 2004. (pdf)
Pearson, M. J. and Lipowsky, H. H. Effect of Fibrinogen on Leukocyte
Margination and Adhesion in Post-capillary Venules, Microcirculation
11: 295-306, 2004. (pdf)
Mulivor, A.M. and Lipowsky, H. H. Role of glycocalyx in leukocyte-endothelial
cell adhesion. Am J Physiol Heart Circ Physiol. 2002 Oct;283(4):H1282-91.
(pdf)
Zhao, Yihua, Chien, S., Skalak, R. and Lipowsky, H.H. Leukocyte
Rolling in Rat Mesenteric Venules: Distribution of Adhesion Bonds
and the Effects of Cyto-active Agents. Annals of Biomedical Engineering
29: 360-372, 2001.
Pearson, M.J. and Lipowsky, H.H. Influence of erythrocyte aggregation
on leukocyte margination in post-capillary venules of rat mesentery.
Amer J. Physiol. Heart and Circ Physiology 279: H1460-H1471, 2000.
Parthasarathi, K. and Lipowsky, H.H. Capillary recruitment in
response to tissue hypoxia and its dependence on red cell deformability.
Amer J. Physiol. Heart and Circ Physiology 46: H2145-H2157, 1999.
Dong, C., Jian, C., Struble, E. and Lipowsky, H.H. Mechanics of
leukocyte deformation and adhesion to endothelium in shear flow.
Annals of Biomedical Engineering 27: 298-312, 1999.
Lipowsky, H. H. and Williams, M. Shear dependency of red cell
sequestration in human skin capillaries in sickle cell disease.
Microcirculation 4(2): 289301, 1997.
Shen, Z. and Lipowsky, H. H. Image Enhancement of the In Vivo
LeukocyteEndothelium Contact Zone Using Optical Sectioning Microscopy.
Annals of Biomedical Engineering, 25: 521535, 1997.
Eppihimer, M. J. and Lipowsky, H. H. Effects of leukocytecapillary
plugging on the resistance to flow in the microvasculature of cremaster
for normal and activated leukocytes, Microvasc. Res. 51: 187201,
1996.
Eppihimer, M. J. and Lipowsky, H. H. Effects of leukocytecapillary
plugging on the resistance to flow in the microvasculature of cremaster
for normal and activated leukocytes, Microvasc. Res. 51: 187201,
1996.
Lipowsky, H. H., Scott, D. A. and Cartmell, J. S. Leukocyte rolling
velocity and its relation to leukocyteendothelium adhesion and
cell deformability. Am. J. Physiol. 270: H1371H1380, 1996.
Dong, C., Cao, J., Lei, X. X. and Lipowsky, H. H. Mechanics of
white blood cell and endothelium adhesion. In Proceedings of the
1995 Joint ASME, AICHE, ASCE, BMES Summer Bioengineering Conference,
Bioengineering Division of ASME: 29, 459460, 1995.
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