Ulli Nollert

• University of Oklahoma

The human amniotic membrane (hAM) is a collagen-based extracellular matrix whose applications are restricted by its moderate mechanical properties and rapid biodegradation. In this work, we investigate the use of riboflavin, a water-soluble vitamin, to crosslink and strengthen the human amniotic membrane under UVA light. The effect of riboflavin-UV...

Cardiovascular mechanical stresses trigger physiological and pathological cellular reactions including secretion of Transforming Growth Factor β1 ubiquitously in a latent form (LTGF-β1). While complex shear stresses can activate LTGF-β1, the mechanisms underlying LTGF-β1 activation remain unclear. We hypothesized that different types of shear stres...

Adipose-derived stem cells represent a reliable adult stem cell source thanks to their abundance, straightforward isolation, and broad differentiation abilities. Consequently, human adipose-derived stem cells (hASCs) have been used in vitro for several innovative cellular therapy and regenerative medicine applications. However, the translation of a...

The mechanical properties of soft materials are critically important for a wide range of applications ranging from packaging to biomedical purposes. We have constructed a simple mechanical testing apparatus using off-the-shelf materials and open-source software for a total cost of less than $100. The device consists of a wooden frame supporting a c...

Many secondary math and science teachers don’t understand the nature and application of engineering adequately to transfer that understanding to their students. Research is needed that investigates and illuminates the process and characteristics of development that addresses this gap. This mixed-method study examines the developmental experiences o...

This study examines the design and evaluation strategies for a year-long teacher learning and development experience, including their effectiveness, efficiency and recommendations for strategic redesign. Design characteristics include programmatic features and outcomes: cognitive, affective and motivational processes; interpersonal and social devel...

The objective of this study is to fabricate a small-diameter tissue engineered blood vessel (TEBV) by using human adipose-derived stem cells (ADSC) in combination with the human amniotic membrane as a mechanically-sound biological substrate. Our technology begins by differentiating adipose-derived stem cells into smooth muscle cells (SMC) and seedi...

Although there have been significant advances in the development of fully functional vascular grafts suitable for coronary artery bypass graft surgery, so far no technology has been developed that meets all of the requirements suitable for clinical use. Here we present an approach using a decellularized biological membrane, seeded with smooth muscl...

This study examines the inputs (processes and strategies) and outputs (perceptions, skill development, classroom transfer, disciplinary integration, social networking, and community development) of a yearlong, interdisciplinary teacher learning and development experience. Eleven secondary math and science teachers partnered with an interdisciplinar...

Because of their unique physical, chemical, and electrical properties, carbon nanotubes are an attractive material for many potential applications. Their interactions with biological entities are however not yet completely understood. To fill this knowledge gap, we present experimental results for aqueous systems containing single walled carbon nan...

There exists a clear need for alternative sources of small-diameter vascular grafts for treating the millions of patients who suffer from cardiovascular disease each year. Bypass surgery or replacement of defective vessels is often required to treat coronary heart disease, but there is a limited supply of suitable autologous grafts, and synthetic g...

Accurate assessment of blood platelet function is essential in understanding thrombus formation which plays a central role in cardiovascular disease. Parallel plate flow chambers have been widely used as they allow for platelet adhesion on a collagen surface at physiologically relevant fluid mechanical forces. Standard parallel plate flow chambers...

Single walled carbon nanotubes (SWNTs) continue to demonstrate the potential of nanoscaled materials in a wide range of applications. The ability to modulate the mechanical or electrical properties of a material by varying the SWNT component may result in diverse "application tunable" materials. Similarly, biomaterials used in tissue engineering ap...

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Integrins are a class of cell adhesion molecules that bind to ligands containing the RGD peptide sequence. There is increasing evidence that peptide sites other than the RGD site are required for optimal binding of integrins with their ligands. We have examined the sites on the protein fibronectin that are needed for optimal binding to the platelet...

The University of Oklahama (OU) incorporated a research proposal in four biochemical or biological engineering courses for graduate students and upper-level undergraduates to provide them excellent learning experience in these courses. The proposals ranged from a series of graded writing assignments which include objectives, rough or first draft, a...

Single-walled carbon nanotubes (SWNT) have been the focus of considerable attention as a material with extraordinary mechanical and electrical properties. SWNT have been proposed in a number of biomedical applications, including neural, bone, and dental tissue engineering. In these applications, it is clear that surrounding tissues will come into s...

Nitric oxide (NO) is a free radical that plays an important role in modulating platelet adhesion and aggregation. Platelets are a source of vascular NO, but since erythrocytes avidly scavenge NO, the functional significance of platelet-derived NO is not clear. Our purpose was to determine if NO from platelets affects platelet thrombus formation in...

Leukocytes roll on selectins at nearly constant velocities over a wide range of wall shear stresses. Ligand-coupled microspheres roll faster on selectins and detach quickly as wall shear stress is increased. To examine whether the superior performance of leukocytes reflects molecular features of native ligands or cellular properties that favor sele...

Selectins mediate rolling of leukocytes by rapid formation and dissociation of selectin-ligand bonds, which are assumed to require high mechanical strength to prevent premature dissociation by the forces applied in shear flow. This assumption is based largely on the observation that increasing wall shear stress increases only modestly the dissociat...

Endothelial cells line the vasculature and are exposed to mechanical shear stress because of blood motion. Previous studies have shown that endothelial cells respond to shear stress by altering their metabolism and genetic expression, but the mechanism for shear stress signal transduction remains unclear. In the current study, we investigated the r...

Platelet microparticles (PMPs) are released from activated platelets and express functional adhesion receptors, including P-selectin, on their surface. PMP concentrations are elevated in many disorders, and their role in accelerating coagulation has been studied. However, their role in leukocyte aggregation has not been defined. We hypothesized tha...

Selectins are adhesion molecules that initiate tethering and rolling of leukocytes on the vessel wall. Rolling requires rapid formation and breakage of selectin–ligand bonds that must have mechanical strength to resist premature dissociation by the forces applied in shear flow. P- and L-selectin bind to the N-terminal region of P-selectin glycoprot...

The recruitment of white blood cells to areas of infection or injury is an important aspect of the immune response system. White blood cells initially attach and roll along the blood vessel wall before becoming firmly attached and emigrating into the subendothelial matrix. The initial rolling event is mediated by the selectin family of adhesion mol...

One of the most important functions of the immune response system is the recruitment of leukocytes to areas of infection or tissue damage. The initial rolling interaction of leukocytes on the blood vessel wall is largely mediated by the selectin family of adhesion molecules. However, recent data has suggested another possibly important mechanism in...

Under physiological shear stress, neutrophils roll on P-selectin on activated endothelial cells or platelets through interactions with P-selectin glycoprotein ligand-1 (PSGL-1). Both P-selectin and PSGL-1 are extended molecules. Human P-selectin contains an NH2-terminal lectin domain, an EGF domain, nine consensus repeats (CRs), a transmembrane dom...

Both P-selectin glycoprotein ligand-1 (PSGL-1) and L-selectin are localized on the microvilli of neutrophils and have been implicated in the attachment of neutrophils to P-selectin or E-selectin. We directly compared the attachment and rolling of neutrophils on P-selectin and E-selectin under flow, with emphasis on the functions of PSGL-1 and L-sel...

There is increasing evidence that endothelial cells respond to the initiation of mechanical stress by the generation of certain second messengers and the activation of specific metabolic pathways. These rapid alterations in cellular function are accompanied by alterations in protein synthesis that are detectable several hours after initiation of th...

Endothelial cells, which line the vasculature, respond to specific agonists such as adenosine triphosphate (ATP) by elevating cytosolic calcium levels and increasing production of the vasoactive compounds, prostacyclin and endothelial derived relaxing factor (EDRF). Endothelial cells express ecto-enzymes which metabolize ATP. If the activity of the...

Mammalian cells responds to physical forces by altering their growth rate, morphology, metabolism, and genetic expression. We have studied the mechanism by which these cells detect the presence of mechanical stress and convert this force into intracellular signals. As our model systems, we have studied cultured human endothelial cells, which line t...

Human umbilical vein endothelial cells (HUVECS) were challenged with thrombin in the presence of [3H]acetate to stimulate the production of radiolabeled platelet activating factor (PAF, 1-O-alkyl-2-[3H]acetyl-sn-glycero-3-phosphocholine, 1-O-alkyl-2-[3H]acetyl-GPC). The 3H-product was isolated by thin-layer chromatography, and 1-radyl-2[3H],3- diac...

In arterial vessels, endothelial cells are subjected to both significant periodic mechanical strain and fluid flow induced shear stress. We have examined the effect of strain (0-10%) uniaxial) and fluid shear stress (0-40 dynes/cm2) on the secretion of the arachidonic acid metabolite prostacyclin, the peptide endothelin and the protein tissue plasm...

To elucidate some of the early mechanisms underlying the response of primary human endothelial cells to the initiation of flow, we investigated the changes in inositol lipid metabolism in cells exposed to arterial and venous levels of shear stress. We used a radioimmunoassay specific for inositol-1,4,5-trisphosphate (Ins1,4,5P3) to demonstrate that...

The uptake and metabolism of arachidonic acid (AA) by human umbilical vein endothelial cells was studied for cells in stationary culture and for cells exposed to physiological levels of shear stress. For cells grown in stationary culture, the initial incorporation of arachidonic acid was primarily into diacylglycerol and phospholipids. Cells expose...

The response of a dumbbell model for dilute polymer solutions is examined for periodic sequences of homogeneous flows chosen to approximate the unsteady kinematics appropriate for flow through porous media. The evolution of particle shape depends on the kinematic history of the flow and on microrheological properties of the dumbbell such as a varia...

Students in four bioengineering courses for upper-level juniors, seniors, and graduate students were required to write a research proposal. For these courses, the proposals ranged from a series of writing assignments to one writing assignment for the entire proposal. We observed that writing a research proposal was a challenge for the students. Bre...