Effects of glutamine, glucose, and oxygen concentration on the metabolism and proliferation of rabbit adipose-derived stem cells.

The use of adipose-derived stem cells (ASCs) for tissue engineering involves exposing them to metabolically adverse conditions. This study examined the metabolism, proliferation, and viability of ASCs under various oxygen, glucose, and glutamine concentrations to determine how these cells respond to such environments. ASCs were cultured in each of 8 media preparations containing 4.8 or 21.5 mM glucose, and 0, 2, 4, or 6 mM glutamine. The ASCs were cultured under normoxic (20% O(2)) and hypoxic (0.1% O(2)) conditions. Conditioned media were collected and assayed for glucose, glutamine, lactate, pyruvate, and glutamate. Cell proliferation and cell death were measured after 5 days of culture. ASCs remained metabolically active under all culture conditions; however, their proliferation rate was significantly reduced in the absence of glutamine. Hypoxia resulted in increased cell death. ASCs are a viable source of stem cells for tissue engineering purposes, although substantial challenges remain. These cells are able to survive in environments with limited oxygen and glutamine and thus may be able to survive brief periods of limited nutrient transport after implantation.

[Current perspectives of orthogonal polarization spectral imaging in plastic surgery]. / Orthogonal Polarization Spectral Imaging und derzeitige Perspektiven in der Plastischen Chirurgie.

The technology of Orthogonal Polarization Spectral Imaging (OPSI), patented in the United States in 1999, has been heralded as an alternative to conventional intravital microscopy for several reasons, including ease of application and ability to perform continued observations. In the following examples, OPSI was applied to reconstructive plastic surgery. Two experimental and one clinical model are presented. Currently, the image quality does not allow a qualitative analysis of the microvasculature. The data analysis of images remains inconclusive. However, a technically modified version with improved image resolution and software could become a valuable experimental as well as clinical tool in the field of reconstructive plastic surgery in the future.

Long- and short-term effects of biological hydrogels on capsule microvascular density around implants in rats.

Fibrous capsule formation around implants can inhibit solute exchange between implantable devices and the circulation. Parylene-n coated polycarbonate disks surrounded with growth factor reduced Matrigel (MG) or several gelatin-based matrices were implanted intramuscularly into rats for 21 or 50 days. MG supplemented with vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF) increased capsule microvascular density at 21 days (p < 0.05) when compared to bare parylene-coated polycarbonate disks (control). The increased microvascular density around VEGF- and bFGF-treated implants regressed by 50 days and was no longer significantly different from controls. The microvascular density induced by the gelatin-based matrices was not significantly different from controls at 21 days, but was increased at 50 days (p < 0.05), suggesting a slower, long-term effect. Disks treated with MG and gelatin-based matrices had thinner capsules at 21 days (p < 0.05). By 50 days, the capsule thicknesses around these implants were no longer statistically thinner than controls. The capsule thickness around implants treated with VEGF, bFGF, and essential gelatin-based matrix was thinner than controls at 50 days (p < 0.05). These results indicate that it is possible to increase functional microvascular density within fibrous capsules using angiogenic growth factors and gelatin-based matrices. However, this effect may be short-lived, requiring chronic administration of growth factors.

Effect of chain length and unsaturation on elasticity of lipid bilayers.

Micropipette pressurization of giant bilayer vesicles was used to measure both elastic bending k(c) and area stretch K(A) moduli of fluid-phase phosphatidylcholine (PC) membranes. Twelve diacyl PCs were chosen: eight with two 18 carbon chains and degrees of unsaturation from one double bond (C18:1/0, C18:0/1) to six double bonds per lipid (diC18:3), two with short saturated carbon chains (diC13:0, diC14:0), and two with long unsaturated carbon chains (diC20:4, diC22:1). Bending moduli were derived from measurements of apparent expansion in vesicle surface area under very low tensions (0.001-0.5 mN/m), which is dominated by smoothing of thermal bending undulations. Area stretch moduli were obtained from measurements of vesicle surface expansion under high tensions (>0.5 mN/m), which involve an increase in area per molecule and a small-but important-contribution from smoothing of residual thermal undulations. The direct stretch moduli varied little (< +/-10%) with either chain unsaturation or length about a mean of 243 mN/m. On the other hand, the bending moduli of saturated/monounsaturated chain PCs increased progressively with chain length from 0.56 x 10(-19) J for diC13:0 to 1.2 x 10(-19) J for diC22:1. However, quite unexpectedly for longer chains, the bending moduli dropped precipitously to approximately 0.4 x 10(-19) J when two or more cis double bonds were present in a chain (C18:0/2, diC18:2, diC18:3, diC20:4). Given nearly constant area stretch moduli, the variations in bending rigidity with chain length and polyunsaturation implied significant variations in thickness. To test this hypothesis, peak-to-peak headgroup thicknesses h(pp) of bilayers were obtained from x-ray diffraction of multibilayer arrays at controlled relative humidities. For saturated/monounsaturated chain bilayers, the distances h(pp) increased smoothly from diC13:0 to diC22:1 as expected. Moreover, the distances and elastic properties correlated well with a polymer brush model of the bilayer that specifies that the elastic ratio (k(c)/K(A))(1/2) = (h(pp) - h(o))/24, where h(o) approximately 1 nm accounts for separation of the headgroup peaks from the deformable hydrocarbon region. However, the elastic ratios and thicknesses for diC18:2, diC18:3, and diC20:4 fell into a distinct group below the correlation, which showed that poly-cis unsaturated chain bilayers are thinner and more flexible than saturated/monounsaturated chain bilayers.

Surfaces modified with covalently-immobilized adhesive peptides affect fibroblast population motility.

Cell population motility and adhesion of rat skin fibroblasts were evaluated on aminophase glass modified with covalently-immobilized biologically active peptides, specifically, either arginine glycine-aspartic acid-serine (RGDS) or tyrosine-isoleucine-glycine-serine-arginine-glycine (YIGSRG). Fibroblast population motility was decreased and adhesion was increased on substrates modified with covalently immobilized RGDS peptide compared to substrates with the covalently immobilized non-adhesive peptides arginine-glycine-glutamic acid-serine and arginine-aspartic acid-glycine-serine. Fibroblast motility was not significantly changed on substrates modified with covalently-immobilized YIGSRG peptide; however, fibroblast adhesion was decreased on that substrate.

Computerized long-term trending of respiratory parameters.

This paper presents a program that analyzes data recorded from a Puritan-Bennett 7200a mechanical ventilator. The program generates graphs of major ventilatory parameters, as well as the derivatives of the parameters, such as respiratory rate and minute volume with respect to time. The program also creates a series of reports that summarizes setting changes, alarm violations and resets, and lung mechanics maneuvers during the process of respiratory therapy. These graphs and reports provide clinicians with information, which was not captured for review before, in an organized format allowing them to easily identify trends and, in some cases, events that may affect the patient. The results of a clinical study are also presented. The study was designed to determine the effect of routine patient care on the primary and derived respiratory data so that a correct interpretation of the recorded data could be made. The study showed that the data acquisition program was not sensitive to routine bedside activities, and some significant events, such as patient disconnects, are identifiable in a timely manner and with good accuracy.