ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

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Kinetic Analysis of Receptor-Mediated Endocytosis and Lysosomal Degradation in Cultured Cells (1984)

TRUSKEY, GEORGE A. ; COLTON, CLARK K. ; DAVIES, PETER F.

Oxford, UK : Blackwell Publishing Ltd

Annals of the New York Academy of Sciences 435 (1984), S. 0

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ISSN: 1749-6632

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Natural Sciences in General

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1749-6632.1984.tb13817.x

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2

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Orientation and length of mammalian skeletal myocytes in response to a unidirectional stretch (2000)

Collinsworth, Amy M. ; Torgan, Carol E. ; Nagda, Suneel N. ; [et al.]

Springer

Cell & tissue research 302 (2000), S. 243-251

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ISSN: 1432-0878

Keywords: Mammalian skeletal myocytes Orientation Mechanical stretch Developmental model Mechanotransduction Skeletal muscle

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract. Effects of mechanical forces exerted on mammalian skeletal muscle cells during development were studied using an in vitro model to unidirectionally stretch cultured C2C12 cells grown on silastic membrane. Previous models to date have not studied these responses of the mammalian system specifically. The silastic membrane upon which these cells were grown exhibited linear strain behavior over the range of 3.6–14.6% strain, with a Poisson's ratio of approximately 0.5. To mimic murine in utero long bone growth, cell substrates were stretched at an average strain rate of 2.36%/day for 4 days or 1.77%/day for 6 days with an overall membrane strain of 9.5% and 10.6%, respectively. Both control and stretched fibers stained positively for the contractile protein, α-actinin, demonstrating muscle fiber development. An effect of stretch on orientation and length of myofibers was observed. At both strain rates, stretched fibers aligned at a smaller angle relative to the direction of stretch and were significantly longer compared to randomly oriented control fibers. There was no effect of duration of stretch on orientation or length, suggesting the cellular responses are independent of strain rate for the range tested. These results demonstrate that, under conditions simulating mammalian long bone growth, cultured myocytes respond to mechanical forces by lengthening and orienting along the direction of stretch.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004410000224

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3

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Kinetic studies and unstructured models of lymphocyte metabolism in fed-batch culturePresented in part at the 80th annual meeting of the American Institute of Chemical Engineers, Washington, DC, November 27-December 2, 1988. (1990)

Truskey, George A. ; Nicolakis, Dimitri P. ; DiMasi, Don ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 36 (1990), S. 797-807

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ISSN: 0006-3592

Keywords: Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: The growth of two lymphocyte cell lines, a hybridoma cell line and a human cutaneous T cell lymphoma (HuT78), was studied in fed-batch culture, and unstructured models of growth developed. A criteria was established to insure that the growth rate varied by less than a specified tolerance throughout the culture period. Glutamine and serum were growth-limiting nutrients for both cell lines with half-maximal growth rates at 0. 53 mM glutamine and 0. 55%(v/v) serum for the hybridoma cells and 0. 21 mM glutamine and 1. 5% serum for the HuT-78 cells. Over the range of glucose concentrations from 5. 5 mM to 28 mM, the specific growth rate of hybridoma cells was independent of glucose concentration, whereas glucose concentrations above 5. 5 mM inhibited HuT-78 growth. For both cell lines, the growth rate was significantly inhibited by the addition of ammonium, although the hybridoma cell line was more affected by ammonia than was the HuT-78 cell line. Growth of HuT-78 cells increased in the presence of interleukin-2. Unstructured models for the hybridoma cells were similar to other models presented in the literature. Applications of these models to adoptive immunotherapy are discussed.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bit.260360807

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4

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A numerical analysis of forces exerted by laminar flow on spreading cells in a parallel plate flow chamber assay (1993)

Olivier, Lauri A. ; Truskey, George A.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 42 (1993), S. 963-973

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ISSN: 0006-3592

Keywords: hydrodynamics ; cell shape ; numerical models ; cell adhesion ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Exposure of spreading anchorage-dependent cells to laminar flow is a common technique to measure the strength of cell adhesion. Since cells protrude into the flow stream, the force exerted by the fluid on the cells is a function of cell shape. To assess the relationship between cell shape and the hydrodynamic force on adherent cells, we obtained numerical solutions of the velocity and stress fields around bovine aortic endothelial cells during various stages of spreading and calculated the force required to detach the cells. Morphometric parameters were obtained from light and scanning electron microscopy measurements. Cells were assumed to have a constant volume, but the surface area increased during spreading until the membrane was stretched taut. Two-dimensional models of steady flow were generated using the software packages ANSYS (mesh generation) and FIDAP (problem solution). The validity of the numerical results was tested by comparison with published results for a semicircle in contact with the surface. The drag force and torque were greatest for round cells making initial contact with the surface. During spreading, the drag force and torque declined by factors of 2 and 20, respectively. The calculated forces and moments were used in adhesion models to predict the wall shear stress at which the cells detached. Based upon published values for the bond force and receptor number, round cells should detach at shear stresses between 2.5 and 6 dyn/cm2, whereas substantially higher stresses are needed to detach spreading and fully spread cells. Results from the simulations indicate that (1) the drag force varies little with cell shape whereas the torque is very sensitive to cell shape, and (2) the increase in the strength of adhesion during spreading is due to increased contact area and receptor densities within the contact area. © 1993 John Wiley & Sons, Inc.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bit.260420807

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Engineering the tissue which encapsulates subcutaneous implants. III. Effective tissue response times (1998)

Sharkawy, A. Adam ; Klitzman, Bruce ; Truskey, George A. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 40 (1998), S. 598-605

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ISSN: 0021-9304

Keywords: tissue response ; implants ; sensors ; vascularity ; foreign-body response ; subcutaneous implants ; PVA ; PTFE ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: The results of two previous studies have shown that implant porosity can be used to increase both the measured diffusion coefficients and the vascularity within the tissue encapsulating long-term subcutaneous implants. This study investigates the hypothesis that the analyte concentrations within the tissue surrounding porous implants will respond more quickly to changes in plasma levels than does the densely packed, avascular fibrous capsule surrounding nonporous implants. The average concentration of lissamine-rhodamine was measured in tissue within 100 μm of the following implants at four different times following injection of the tracer: PVA-skin, PVA-5, PVA-60, PVA-700 (polyvinyl alcohol nonporous, 5 μm, 60 μm, and 700 μm mean pore sizes, respectively) and PTFE-0.5 and PTFE-5 (polytetrafluoroethylene 0.5 μm and 5 μm mean pore sizes, respectively). The results were compared to those of unimplanted subcutaneous tissue (SQ). In addition, the data were analyzed with a simple two-compartment model in which a tissue response time constant (τp) was extracted. As in the case of vascular density, the cellular dimension of the PVA-60 pore sizes produced surrounding tissue with the optimum response times to changes in plasma concentrations. The concentrations of rhodamine within the tissue surrounding the PVA-60 implant were the highest at all time points and responded to the change in plasma rhodamine concentration approximately three times more quickly (τp = 764 s) than the fibrous tissue encapsulating the nonporous PVA-skin (τp = 2058 s) and more than twice as quickly as SQ (τp = 1627 s). The overall mass transfer rate between plasma and the tissue surrounding the different implants calculated from the permeability and density of vessels from the previous study correlated very well (r2 = 0.7, p 〈 .02, slope of 0.98) with the reciprocal of the tissue response time constant (τp). © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 598-605, 1998.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

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6

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The effect of fluid shear stress upon cell adhesion to fibronectin-treated surfaces (1990)

Truskey, George A. ; Pirone, John S.

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 24 (1990), S. 1333-1353

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: Cell attachment to and spreading upon a surface is mediated by adhesion molecules, such as fibronectin. The role of fibronectin in maintaining cell adhesion was examined by measuring cell attachment following exposure of cells to laminar flow in a parallel-plate flow channel. 3T3 fibroblasts were allowed to adhere to glass slides with or without preadsorbed fibronectin for 2 h before exposure to shear stresses ranging from 5 to 140 dyne/cm2. For cells which adhered to glasss surfaces, cell loss was biphasic with a significant loss of cells during the first 2 min of flow, followed by a much slower decline in the number of attached cells with time. Following exposure to shear stresses greater than 5 dyne/cm2, the number of attached cells decreased exponentially as the shear stress increased. The distribution of adhesive stresses among the population of cells was log-normal with a median of 50 dyne/cm2, a mean of 82 dyne/cm2 and a standard deviation of 108 dyne/cm2. After exposure to flow for 2 h, the adhesive stress of the remaining cells decreased to a mean value of 50 dyne/cm2. Cell adhesion after exposure to flow was increased by preadsorbing fibronectin to the glass surface. The initial loss of cells from fibronectin-treated glass following exposure to flow correlated with the degree of cell spreading. Preadsorbed fibronectin resulted in a greater number of bonds between the surface and the cell, which in turn promoted cell spreading and increased the adhesive strength of the cell.

Additional Material: 9 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jbm.820241006

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Effect of the conformation and orientation of adsorbed fibronectin on endothelial cell spreading and the strength of adhesion (1993)

Iuliano, Denise J. ; Saavedra, Steven S. ; Truskey, George A.

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 27 (1993), S. 1103-1113

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: The effect of surface hydrophobicity upon the conformation of the cell binding domain of fibronectin (Fn) and the influence of Fn conformation on bovine aortic endothelial cell (BAEC) adhesion were examined. The free sulfhydryl group of Fn located near the cell binding domain was selectively labeled with acrylodan, a polarity sensitive fluor. Fluorescence emission was monitored in solution and upon adsorption to hydrophilic glass and hydrophobic silanized glass. The acrylodan-labeled Fn emission maximum shifted to longer wavelengths upon adsorption and the shift was greater for acrylodan-labeled Fn adsorbed to hydrophilic glass than hydrophobic silane, suggesting that the acrylodan was in a more solvent accessible environment on glass than silane. BAEC, suspended in serum-free medium, attached for 15 or 120 min onto glass or silane surfaces containing preadsorbed Fn, after which cell spreading and the strength of adhesion in a parallel plate flow chamber were measured. Cell spreading was similar on both surfaces after 15 min attachment, but BAECs were more spread on glass than silane after 120 min. At low surface concentrations of Fn, BAECs were more adherent on glass than silane. At higher surfaces concentrations, adhesion was similar. After a 2-h incubation in serum-free medium, cells on glass showed more extensive development of focal contacts as determined by immunofluorescent staining for vinculin. Cell adhesion under flow was reduced on silane by inhibition of protein synthesis with cycloheximide, suggesting that cell attachment to silane was promoted by cellular synthesis of Fn. The results indicate that changes in the conformation of the Fn cell binding domain affect Fn affinity for its cell surface receptor. © 1993 John Wiley & Sons, Inc.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jbm.820270816

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Engineering the tissue which encapsulates subcutaneous implants. I. Diffusion properties (1997)

Sharkawy, A. Adam ; Klitzman, Bruce ; Truskey, George A. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 37 (1997), S. 401-412

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ISSN: 0021-9304

Keywords: subcutaneous implants ; sensors ; capsules ; diffusion ; transport barrier ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: This report uses normal rat subcutis as a reference point to provide a quantitative analysis of small analyte transport through the tissue which encapsulates implants. Polyvinyl alcohol (PVA) with 60- and 350-μm mean pore size (PVA-60, PVA-350), nonporous PVA (PVA-skin), and stainless-steel cage (SS) specimens were implanted in the subcutis of Sprague-Dawley rats for 4 weeks to elicit a range of capsular wound-healing tissues. Histologic examination showed that the capsular tissue which formed around PVA-skin and SS specimens was densely fibrous and avascular. That forming around PVA-60 and PVA-350 was less densely fibrous and more vascular. The fibrous content of capsular tissue and subcutis was determined from eosin-stained histologic sections. Dual-chamber diffusion measurements of sodium fluorescein (Mw 376 g/mol) through capsular tissue and normal rat subcutis were used to quantitatively compare the effective diffusion coefficients of small analytes on the order of glucose. The two most fibrous capsular tissues exhibited diffusion coefficients that were statistically (p 〈 0.05) less than that determined for rat subcutis by 50 and 25% for PVA-skin and SS, respectively. The diffusion coefficients of the less dense capsular tissue which formed around the porous implants were not statistically different from subcutis. The experimentally measured diffusion coefficients of the two most fibrous capsular tissues were closely predicted by a simple two-component diffusion model consisting of an aqueous interstitium with an array of impenetrable bodies equal in volume fraction to the fibrous content of the tissue. This model overestimates the diffusion coefficients measured for the least fibrous tissues. Using the diffusion coefficient measured for the PVA-skin capsular tissue, a finite difference model predicts that a 200-μm-thick capsular layer would increase from 5 to 20 min the time required for subcutaneously implanted sensor to detect 95% of the blood analyte concentration. This study suggests that the fibrous capsule forming around a subcutaneously implanted smooth-surface sensor imposes a significant diffusion barrier to small analytes such as glucose, thus increasing the lag time of the sensor by as much as threefold. A corollary observation is that a sensor with a porous surface which allows tissue ingrowth may be more responsive to blood analyte fluctuations as a result of its a more vascular and less fibrous encapsulation tissue. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 37, 401-412, 1997.

Additional Material: 10 Ill.

Type of Medium: Electronic Resource

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Engineering the tissue which encapsulates subcutaneous implants. II. Plasma-tissue exchange properties (1998)

Sharkawy, A. Adam ; Klitzman, Bruce ; Truskey, George A. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 40 (1998), S. 586-597

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ISSN: 0021-9304

Keywords: subcutaneous implants ; porosity ; vasculature ; permeability ; PVA ; PTFE ; encapsulation ; foreign body response ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: This study assesses the plasma-tissue exchange characteristics of the capsular tissue that forms around implants and how they are affected by implant porosity. The number of vessels and their permeability to rhodamine were measured by intravascular injection of the fluorophore tracer into Sprague-Dawley rats that hosted for 3-4 months polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE) subcutaneous implants. Rats were implanted with four pore sizes of PVA - a nonporous PVA (PVA-skin), and 5, 60, and 700 micron mean pore sizes (PVA-5, PVA-60, and PVA-700, respectively) - and two pore sizes of PTFE: 0.50 (PTFE-0.5) and 5.0 (PTFE-5) mean micron pore sizes. Photodensitometric image analysis was used to quantify the local tracer extravasation and, hence the permeability coefficients of isolated vessels around the implants. The number of functional vessels within 100 μm of the implants highlighted by the lissamine-rhodamine tracer were counted with fluorescence microscopy and with H&E stained sections using brightfield microscopy. The permeability of vessels did not vary substantially with implant pore size but generally were lower than those measured for surrounding subcutis. Pore size, however, had a dramatic effect on the vascular density of tissue-encapsulating implants: the number of microvessels (under 10 μm in radius) within the tissue surrounding the porous implants was higher than the number around nonporous implants. Pore sizes on the order of cellular dimensions incited optimal neovascularization; the vascular density around PVA-60 implants was six times higher (p 〈 .001) and three times higher (p 〈 .001) than those around PVA-0 implants in the fluorescent images and in brightfield, respectively. Moreover, brightfield microscopy showed the number of vessels around PVA-60 implants was almost double those in normal subcutis. The results suggest that optimal vascular density around long-term implants, such as sensors, biofluid cell constructs, and immunoisolated cell systems, may be engineered with pore size. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 586-597, 1998.

Additional Material: 11 Ill.

Type of Medium: Electronic Resource

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