Biomedical subjects

Dan W Urry

Publications and source records attributed to Dan W Urry.

8 recordsLinked to original sources

PubMed2006

Human amniotic cell sheet harvest using a novel temperature-responsive culture surface coated with protein-based polymer.

Human amniotic epithelial (hAE) and mesenchymal (hAM) cells are believed to have the potential to differentiate into various functional cells, such as neurons, hepatocytes, cardiomyocytes, and pancreatic beta cells. However, cell transplantation has been performed by injection of cell suspensions, and thus it is difficult to control shape, size, location, and functions of differentiated cells. To overcome these problems, we developed a novel temperature-responsive culture surface coated with elastic protein-based polymer. By reducing the temperature using a polyvinylidene difluoride (PVDF) membrane, the primary hAE and hAM cell sheet can detach from the coated surface. The recovered cell sheet can be transferred and can re-adhere and re-proliferate on another surface. This represents the first report of harvesting of primary hAE and hAM cell sheets using the novel temperature- responsive polymer. These findings suggest that this new technique of cell sheet detachment from noncytotoxic, highly biocompatible protein-based polymer-coated surfaces may be useful in tissue engineering, as well as in the investigation of hAE and hAM cell sheets for transplantation.

Amnion↗

PubMed2005

Function of the F1-motor (F1-ATPase) of ATP synthase by apolar-polar repulsion through internal interfacial water.

THESIS: Within the structurally-confined internal aqueous cavity of the F1-motor of ATP synthase, function results from free energy changes that shift the balance between interfacial charge hydration and interfacial hydrophobic hydration. TRANSITION STATE DESCRIPTION: At the beta-P end of ADP x Mg occurs an inorganic phosphate, P(i). This P(i) resides at the base of a water-filled cleft that functions like an aperture to focus, into an aqueous chamber, a competition for hydration (an apolar-polar repulsion) between charged phosphate and hydrophobic surface of the gamma-rotor. Two means available for the phosphate and the hydrophobic surface to improve their hydration free energies are physically to separate by rotation of the gamma-rotor or chemically to combine P(i) with ADP to form less charged ATP. This proposal derives from calculated changes in Gibbs free energy for hydrophobic association of amino acid side chains and chemical modifications thereof and from experimentally demonstrated water-mediated repulsion between hydrophobic and charged sites that resulted from extensive studies on designed elastic-contractile model proteins.

Catalytic Domain↗

PubMed2005

Crystal structure of cyclic (APGVGV)2, an analog of elastin, and a suggested mechanism for elongation/contraction of the molecule.

Tropoelastin is a complex polymeric protein composed primarily of repeating segments of Val-Pro-Gly-Gly, Val-Pro-Gly-Val-Gly, and Ala-Pro-Gly-Val-Gly-Val that occurs in connective tissue and arteries. It has rubber-like extensible properties. A synthetic cyclic dodecapeptide, with a double repeat of the hexapeptide sequence, has been shown to undergo a reversible inverse temperature transition; that is, crystals grow at 60 degrees C and dissolve in the mother liquor upon cooling. An x-ray crystal structure analysis established that the cyclic backbone formed an elongated loop with a Pro-Gly, type II beta turn at both ends. Six internal cross strand NH...OC hydrogen bonds form between six NH donors and four O=C acceptors where two of the carbonyl O atoms are bifurcated acceptors. As a result, the molecule is pulled up into a corrugated profile. The corrugated loops form extended beta-sheets by additional intermolecular hydrogen bonds. An analysis of the dome region in a corrugated sheet suggests a reversible mechanism for extending and contracting the length of the whole molecule, akin to the motion of opening and closing an umbrella, caused by the motion of a water molecule with its associated hydrogen bonds acting as spokes. Crystal parameters: C44H72N12O12.3H2O, sp. gr. P2(1)2(1)2(1), a = 9.212 angstroms, b = 19.055 angstroms, c = 32.247 angstroms, d = 1.157 g/cm3.

Crystallography, X-Ray↗

PubMed2004

In vitro skin penetration of dazmegrel delivered with a bioelastic matrix.

The penetration of dazmegrel, a selective thromboxane synthetase inhibitor, through excised human and greyhound skin was measured. A bioelastic matrix was used for topical delivery. Results demonstrated that dazmegrel readily penetrated the skin. Penetration through greyhound skin was significantly greater than penetration through human skin. Penetration through greyhound skin was not significantly different between 4, 24, and 48 h of exposure for the low and intermediate doses studied.

Animals↗

PubMed2003

Prevention of postlaminectomy epidural fibrosis using bioelastic materials.

STUDY DESIGN: The use of elastic protein-based polymers for the prevention of epidural fibrosis following lumbar spine laminectomy was investigated in a rabbit model. OBJECTIVES: To determine the safety and efficacy of two bioelastic polymers in matrix and gel forms as interpositional materials in preventing postlaminectomy epidural fibrosis. SUMMARY OF BACKGROUND DATA: Postlaminectomy epidural fibrosis complicates revision spine surgery and is implicated in cases of "failed back syndrome." Materials employed as mechanical barriers to limit tethering of neural elements by the fibrosis tissue have met with little success. A recent family of protein-based polymers, previously reported to prevent postoperative scarring and adhesions, may hold promise in treating this condition. METHODS: Sixteen female New Zealand White rabbits underwent laminectomy at L4 and L6. Two polymer compositions, each in membrane and gel forms, were implanted at a randomly assigned level in four rabbits each, with the remaining level serving as an internal control. The animals were killed at 8 weeks, and qualitative and quantitative histology and gross pathologic examination were performed for both the control and the experimental sites to assess the polymers' efficacy in preventing dorsal epidural fibrosis. RESULTS: The use of the polymers caused no adverse effects. Compared to the control sites, both polymers in either gel or membrane form significantly reduced the formation of epidural fibrosis and its area of contact with the dura postlaminectomy. However, no significant difference in efficacy was detected between either the polymers or their respective forms in preventing epidural fibrosis. CONCLUSIONS: The selected compositions of biosynthetic, bioelastic polymers were safe and effective in the limiting the direct contact and consequent tethering of the underlying neural elements by the postlaminectomy epidural fibrosis in rabbits.

Animals↗

PubMed2002

Flow cytometry as a useful tool for process development: rapid evaluation of expression systems.

Flow cytometry is an established tool in fundamental studies of single-cell microbial physiology. Here we show that it can also provide valuable information for process development. Using recombinant Escherichia coli strains, which express the protein-based polymer (GVGIP)(260)GVGVP, the utility of flow cytometry in monitoring and optimization of fermentations is demonstrated. Single cell right angle light scatter was found to be significantly affected by intracellular product formation possibly due to the formation of inclusion bodies. Translational fusions with green fluorescent protein (GFP) enabled monitoring of product accumulation, as well as plasmid free cell fraction (PFCF). Such fusions also allowed rapid evaluation of induction strategies and three different expression systems based on the T7 promoter, T7-lac promoter and the P(BAD) promoter. The expression system based on the P(BAD) promoter was found to be superior to the T7-based system.

Arabinose↗

PubMedDate not supplied

Controlled release of phosphorothioates by protein-based polymers.

Protein-based polymers are water soluble at lower temperatures but undergo a phase transition with increasing temperature. The polymers' hydrophobicity controls the transition temperature and the free energy of its charged groups through an apolar-polar repulsive free energy of hydration, which drives the binding of charged drugs. Binding and release of phosphorothioates were obtained with polymers containing 1 lysine alone or coupled with 2 to 5 phenylalanines per 30 residues. Release rates from 4 to 64 nmol/ cm2/day were maintained constant for 8 to 2 weeks/mm, respectively. We demonstrated the ability of protein-based polymers to deliver nucleic acid based therapeutics with high programmability.

Delayed-Action Preparations↗

PubMedDate not supplied

Bioelastic membranes for topical application of a thromboxane synthetase inhibitor for protection of skin from pressure injury: a preliminary study.

A previous study showed that topical exposure to bioelastic-thromboxane synthetase inhibitor-matrix resulted in local tissue concentrations of thromboxane synthetase inhibitor sufficient for thromboxane synthetase inhibition. The objective of this research was to use an animal model to determine if a dressing having controlled release of thromboxane synthetase inhibitor (dazmegrel) could be used to prevent tissue breakdown over pressure points, i.e., lesion at the assistive device-skin interface. The animal model studies utilized the greyhound, a dog that has thin skin, angular conformation, limited body fat and is predisposed to pressure ulcers similar to those occurring in humans. The model uses a short-limb walking cast on one pelvic limb with the severity of the dermal pressure lesions induced over the medial malleolus controlled by the amount of padding in the cast and length of time the cast is in place. The bioelastic matrix loaded with dazmegrel provided protection from shearing and pressure skin injury over the medial malleolus, as evidenced by a decrease in epidermal abrasion/ulceration as measured with planimetry. Histopathologic evaluation of the skin over the medial malleolus indicated a protective function of the bioelastic matrix as measured as lower numbers of neutrophils, lymphocytes, and decreased collagen density compared to such numbers when no bioelastic matrix was present. These studies provided evidence that bioelastic-thromboxane sythetase inhibitor- matrix helps in preventing or reducing the severity of pressure lesions, e.g., assistive device-skin interface wounds.

Administration, Topical↗