The publication data currently available has been vetted by Vanderbilt faculty, staff, administrators and trainees. The data itself is retrieved directly from NCBI's PubMed and is automatically updated on a weekly basis to ensure accuracy and completeness.
If you have any questions or comments, please contact us.
The ideal bone graft substitute requires osteoconductive, osteoinductive, and osteogenic components. This study introduces an "in vivo bioreactor," a model in which pluripotent cells are recruited from circulating blood to a vascularized coralline scaffold supplemented with bone morphogenetic protein-2 (BMP-2). The bioreactor generates new, ectopic host bone with the capability of vascularized tissue transfer. More importantly, bone is reproducibly formed in a closed and malleable environment. In a rat model, the superficial inferior epigastric vessels were isolated, ligated, and then threaded through a prefabricated coral cylinder (hydroxyapatite, ProOsteon 500). Experimental groups were characterized by the following variables: (1) with/without incorporation of vascular pedicle; (2) with/without addition of BMP-2 (0.02 mg/cm3). Scaffolds were harvested 6 weeks after implantation, embedded and sectioned. Tissue samples were decalcified, fixed, and stained with H&E, trichrome green, and CD31/PECAM-1 (a marker of endothelial cells). Vascularized coral scaffolds supplemented with BMP-2 presumably recruited circulating mesenchymal stem cells to generate bone. Bone formation was quantified through histological analysis, and reported as a percentage, area bone/area cross section scaffold x 100. Mean bone formation was 11.30%+/-1.19. All scaffolds supplied by the vascular pedicle, regardless of BMP-2 supplementation, demonstrated neo-vascular ingrowth. Scaffolds lacking a pedicle showed no evidence of vascular ingrowth or bone formation. This paper introduces a model of a novel "in vivo bioreactor" that has future clinical and research applications. The tissue engineering applications of the "bioreactor" include treatment of skeletal defects (nonunion, tumor post-resection reconstruction). The bioreactor also may serve as a unique model in which to study primary and metastatic cancers of bone.
There is a need for microminiaturized cell-culture environments, i.e. NanoLiter BioReactors (NBRs), for growing and maintaining populations of up to several hundred cultured mammalian cells in volumes three orders of magnitude smaller than those contained in standard multi-well screening plates. These devices would enable the development of a new class of miniature, automated cell-based bioanalysis arrays for monitoring the immediate environment of multiple cell lines and assessing the effects of drug or toxin exposure. We fabricated NBR prototypes, each of which incorporates a culture chamber, inlet and outlet ports, and connecting microfluidic conduits. The fluidic components were molded in polydimethylsiloxane (PDMS) using soft-lithography techniques, and sealed via plasma activation against a glass slide, which served as the primary culture substrate in the NBR. The input and outlet ports were punched into the PDMS block, and enabled the supply and withdrawal of culture medium into/from the culture chamber (10-100 nL volume), as well as cell seeding. Because of the intrinsically high oxygen permeability of the PDMS material, no additional CO(2)/air supply was necessary. The developmental process for the NBR typically employed several iterations of the following steps: Conceptual design, mask generation, photolithography, soft lithography, and proof-of-concept culture assay. We have arrived at several intermediate designs. One is termed "circular NBR with a central post (CP-NBR)," another, "perfusion (grid) NBR (PG-NBR)," and a third version, "multitrap (cage) NBR (MT-NBR)," the last two providing total cell retention. Three cells lines were tested in detail: a fibroblast cell line, CHO cells, and hepatocytes. Prior to the culturing trials, extensive biocompatibility tests were performed on all materials to be employed in the NBR design. To delineate the effect of cell seeding density on cell viability and survival, we conducted separate plating experiments using standard culture protocols in well-plate dishes. In both experiments, PicoGreen assays were used to evaluate the extent of cell growth achieved in 1-5 days following the seeding. Low seeding densities resulted in the absence of cell proliferation for some cell lines because of the deficiency of cell-cell and extracellular matrix (ECM)-cell contacts. High viabilities were achieved in all designs. We conclude that an instrumented microfluidics-based NanoBioReactor (NBR) will represent a dramatic departure from the standard culture environment. The employment of NBRs for mammalian cell culture opens a new paradigm of cell biology, so far largely neglected in the literature.
Semiconductor nanocrystals with narrow and tunable fluorescence are covalently linked to oligonucleotides. These biocompounds retain the properties of both nanocrystals and DNA. Therefore, different sequences of DNA can be coded with nanocrystals and still preserve their ability to hybridize to their complements. We report the case where four different sequences of DNA are linked to four nanocrystal samples having different colors of emission in the range of 530-640 nm. When the DNA-nanocrystal conjugates are mixed together, it is possible to sort each type of nanoparticle by using hybridization on a defined micrometer-size surface containing the complementary oligonucleotide. Detection of sorting requires only a single excitation source and an epifluorescence microscope. The possibility of directing fluorescent nanocrystals toward specific biological targets and detecting them, combined with their superior photostability compared to organic dyes, opens the way to improved biolabeling experiments, such as gene mapping on a nanometer scale or multicolor microarray analysis.
The purpose of this study was to measure the response to dynamic loading of sand surfaces typically encountered in beach running. An instrumented drop test rig was constructed and used to guide a drop mass through impact with two surfaces (i) dry, uncompacted sand; and (ii) wet, compacted sand. Four drop masses (3.86, 7.24, 10.62 and 14.0 kg) were chosen and dropped from four different drop heights (100, 200, 300 and 400 mm) to represent the kinetic energies typically experienced during heelstrike in running. Accelerations were measured using a piezoelectric accelerometer and the trajectory of the drop head was measured using a displacement transducer. The following response variable were calculated for each trial: (i) peak impact force, (ii) mean impact force, (iii) impulse, (iv) total impact time, (v) rise time, (vi) fall time, (vii) maximum penetration, (viii) energy absorbed by the surface, and (ix) surface stiffness. Mean and peak impact forces were approximately 4 times greater for the wet surface while penetration, impact time and rise time were approximately 3-4 times greater for the uncompacted surface condition. The wet surface was also found to be 6 times stiffer than the uncompacted surface indicating the presence of water substantially altered surface compliance. Results are discussed in terms of their implications for performance and the potential for injury to athletes who run on these surfaces.
A population-based case-control study of cancer of the salivary glands, involving interviews of 41 incident cases and 414 controls, was conducted in Shanghai. After adjustment for other risk factors, occupational exposure to silica dust was linked to a 2.5-fold increased risk of salivary-gland cancer. The risk was also significantly elevated among individuals who reported ever using kerosene as cooking fuel or having a prior history of head X-ray examinations. Dietary analyses revealed a significant protective effect of consumption of dark-yellow vegetables or liver, with about 70% reduced risk of salivary-gland cancer among individuals in the highest intake group of these foods. Our findings are consistent with previous observations on a possible role of environmental exposure and radiation in the etiology of salivary-gland cancer, and suggest that dietary factors may contribute to the development of this malignancy.
Rod outer segments (ROS) from frog retina have been purified by Percoll density gradient centrifugation, a procedure that preserves their form and intactness. One- and two-dimensional electrophoretic analysis reveals a smaller number of proteins than is observed in many cell organelles and permits quantitation of the 20 most abundant polypeptides. Rhodopsin accounts for 70% of the total protein (3 X 10(9) copies/outer segment), and approximately 70 other polypeptides are present at more than 6 X 10(4) copies/outer segment. Another 17% of the total protein is accounted for by the G-protein (3 X 10(8) copies/outer segment) that links rhodopsin bleaching and the activation of cyclic GMP phosphodiesterase (PDE). The phosphodiesterase accounts for 1.5% of the protein (1.5 X 10(7) copies/outer segment), and a 48,000-dalton component that binds to the membrane in the light accounts for a further 2.6%. The function of approximately 90% of the total protein in the outer segment is known, and two-thirds of the non-rhodopsin protein is accounted for by enzyme activities associated with cyclic GMP metabolism. The relative molar abundance of rhodopsin, G-protein, and PDE is 100:10:1. Apart from these major membrane-associated proteins, most of the other proteins are cytosolic. Thirteen other polypeptides are found at an abundance of one or more copies per 1000 rhodopsins, nine soluble and four membrane-bound, and their abundance relative to rhodopsin has been quantitated. ROS have been separated into subcellular fractions which resolve three classes of soluble, extrinsic membrane, and integral membrane proteins. A listing of the proteins that are phosphorylated and their subcellular localization is given. Approximately 25 phosphopeptides are detected, and most are in the soluble fraction. Fewer phosphorylated proteins are associated with the purified outer segments than with crude ROS. Distinct patterns of phosphorylation are associated with intact rods incubated with [32P]Pi and broken rods incubated with [gamma-32P]ATP.
Although the histologic changes occurring during healing on the lumen surface of large vessel synthetic vascular grafts have been well characterized, the cells populating the interstices of microvascular grafts have not been examined in detail. Since microvascular grafts are required to provide vascular continuity under quite different physiological and hemodynamic conditions as compared with large vessel grafts, these interstitial cells within the synthetic graft material may also vary as a function of graft size. Monoclonal antibodies, light microscopy, and scanning and transmission electron microscopy were used in this study to identify the cells present within the 30-microns pores of 1-mm diameter polytetrafluoroethylene and replamineform silicone rubber grafts. Identified cells included few capillary endothelial cells enclosing erythrocytes, rare proliferating endothelial cells, few macrophages, rare foreign body giant cells, and a majority of fibroblasts. There was no evidence of smooth muscle cells or myofibroblasts within the interstices of these microvascular prostheses 12 weeks after implantation in the rabbit central ear artery. The graft types differed by the presence of foreign body giant cells and more densely packed collagen between cells in the replamineform silicone rubber graft interstices.
t-Butyldimethylsilyl and trimethylsilyl ether derivatives of a series of methylated prostaglandin F2alpha metabolites have been compared with respect to their gas chromatographic and mass spectrometric properties. The t-butyldimethylsilyl derivatives had considerably higher retention indices (approximately 2.2 C units per silyl group) than their trimethylsilyl ether counterparts when analysed on the (non-polar) OV-1 stationary phase. Electron impact induced fragmentation patterns were strongly dependent upon the type of silyl ether employed and on the nature of the prostaglandin omega sidechain; the mass spectra of pairs of t-butyldimethylsilyl and trimethylsilyl ether derivatives were found to differ appreciably in several respects and to afford complementatary structural information.