Joachim Seidel - Academia.edu (original) (raw)

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Papers by Joachim Seidel

Metrologia, 2003

An intercomparison of radiation temperature measurements was performed at VNIIOFI during October ... more An intercomparison of radiation temperature measurements was performed at VNIIOFI during October 2000 using a pyrolytic graphite blackbody operating over the temperature range from 1600 K to 3300 K. A pyrometer and two photometers from VNIIOFI, a pyrometer and four broadband glass filter detectors from PTB, and two narrow-band interference filter based radiometers and a broadband glass filter radiometer from NPL were used to perform the temperature measurements in either radiance or irradiance mode. Across almost the entire temperature range the VNIIOFI, NPL and PTB instruments showed results within the combined standard measurement uncertainties.

Human Gene Therapy, 2002

The repair of articular cartilage lesions remains a clinical problem. Two novel approaches to car... more The repair of articular cartilage lesions remains a clinical problem. Two novel approaches to cartilage formation, gene transfer and tissue engineering, have been limited by short-term transgene expression in transplanted chondrocytes and inability to deliver regulatory signals to engineered tissues according to specific temporal and spatial patterns. We tested the hypothesis that the transfer of a cDNA encoding the human insulin-like growth factor I (IGF-I) can provide sustained gene expression in cell-polymer constructs in vitro and in vivo and enhance the structural and functional properties of tissue-engineered cartilage. Bovine articular chondrocytes genetically modified to overexpress human IGF-I were seeded into polymer scaffolds, cultured in bioreactors in serum-free medium, and implanted subcutaneously in nude mice; constructs based on nontransfected or lacZ-transfected chondrocytes served as controls. Transgene expression was maintained throughout the duration of the study, more than 4 weeks in vitro followed by an additional 10 days either in vitro or in vivo. Chondrogenesis progressed toward the formation of cartilaginous tissue that was characterized by the presence of glycosaminoglycans, aggrecan, and type II collagen, and the absence of type I collagen. IGF-I constructs contained increased amounts of glycosaminoglycans and collagen and confined-compression equilibrium moduli as compared with controls; all groups had subnormal cellularity. The amounts of glycosaminoglycans and collagen per unit DNA in IGF-I constructs were markedly higher than in constructs cultured in serum-supplemented medium or native cartilage. This enhancement of chondrogenesis by spatially defined overexpression of human IGF-I suggests that cartilage tissue engineering based on genetically modified chondrocytes may be advantageous as compared with either gene transfer or tissue engineering alone.

Arthritis & Rheumatism, 2002

FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2002

We hypothesized that the mechanically active environment present in rotating bioreactors mediates... more We hypothesized that the mechanically active environment present in rotating bioreactors mediates the effectiveness of three-dimensional (3D) scaffolds for cartilage tissue engineering. Cartilaginous constructs were engineered by using bovine calf chondrocytes in conjunction with two scaffold materials (SM) (benzylated hyaluronan and polyglycolic acid); three scaffold structures (SS) (sponge, non-woven mesh, and composite woven/non-woven mesh); and two culture systems (CS) (a bioreactor system and petri dishes). Construct size, composition [cells, glycosaminoglycans (GAG), total collagen, and type-specific collagen mRNA expression and protein levels], and mechanical function (compressive modulus) were assessed, and individual and interactive effects of model system parameters (SM, SS, CS, SM*CS and SS*CS) were demonstrated. The CS affected cell seeding (higher yields of more spatially uniform cells were obtained in bioreactor-grown than dish-grown 3-day constructs) and subsequently ...