468 research outputs found
Matrici a base di collagene con porosità assiale
No full textOBIETTIVI: Scopo del presente lavoro è la messa a punto di una tecnica per la produzione di scaffold cilindrici a base di collagene, con porosità orientata assialmente. Matrici con questa particolare struttura porosa hanno la potenzialità di migliorare la rigenerazione di nervi periferici o di midollo spinale, guidando fisicamente la crescita longitudinale degli assoni lungo la zona del difetto o lesione. La capacità rigenerativa può essere inoltre ulteriormente aumentata utilizzando gli scaffold come carrier di particolari tipi di cellule e/o determinati fattori di crescita, in grado di stimolare la rigenerazione del sistema nervoso.
METODI: La tecnica per la produzione di scaffold con porosità assiale è basata sul congelamento unidirezionale di una sospensione di collagene e sulla sua successiva liofilizzazione. Matrici con un diametro di 3 mm ed una lunghezza di 5 mm sono state prodotte e caratterizzate, in vista della loro possibile applicazione come scaffold per la rigenerazione del midollo spinale in ratti adulti. Microscopia elettronica (ESEM) e microscopia ottica sono state usate per valutare qualitativamente e quantitativamente la dimensione e l’orientazione medie dei pori.
RISULTATI: Diametri dei pori variabili tra 20 e 60 μm, in grado di supportare la crescita di assoni in vivo e/o permettere la semina e la coltura di cellule in vitro, sono stati ottenuti cambiando la concentrazione di collagene in sospensione e la temperatura di congelamento. Inoltre la definizione di un indice di orientazione (OI) ha permesso di quantificare la direzionalità dei pori, determinandone l’orientazione prevalentemente assiale.
CONCLUSIONI: Scaffold cilindrici a base di collagene, con porosità orientata prevalentemente in direzione assiale, possono essere prodotti attraverso un processo di liofilizzazione. La direzionalità dei pori è determinata controllando la crescita dei cristalli di ghiaccio durante il congelamento di una sospensione di collagene; il diametro medio dei pori è controllato invece variando la concentrazione di collagene in sospensione e la temperatura di congelamento. Gli scaffold descritti sono potenzialmente applicabili nello studio della rigenerazione del sistema nervoso centrale o periferico. La semina di scaffold con cellule staminali neuronali o derivate da midollo osseo è attualmente oggetto di studio
Chondrogenic Differentiation of Adult Mesenchymal Stem Cells and Embryonic Stem Cells
No full textMesenchymal stem cell (MSC) contraction associated with chondrogenesis is attributed to the expression of alpha-smooth muscle actin (alpha-SMA). In this study, pluripotent embryonic carcinoma cells (ECCs) and MSCs were compared for cartilage histogensis. Both cell types expressed alpha-SMA in monolayer. However, when cultured in pellets and in 3-D scaffolds, only MSCs contracted and formed glycosaminoglycan (GAG)- and type II collagen-rich tissue. Under these culture conditions, MSCs appear to be superior over ECCs for cartilage regeneration.United States. Dept. of Veteran Affair
Supplementary_Data - In Situ Cross-linking Hydrogel as a Vehicle for Retinal Progenitor Cell Transplantation
No full textSupplementary_Data for In Situ Cross-linking Hydrogel as a Vehicle for Retinal Progenitor Cell Transplantation by Jeayoung Park, Petr Baranov, Aybike Aydin, Hany Abdelgawad, Deepti Singh, Wanting Niu, Motoichi Kurisawa, Myron Spector, and Michael J. Young in Cell Transplantation</p
The Use of Extracorporeal Shock Wave-Stimulated Periosteal Cells for Orthotopic Bone Generation
No full textThe cambium cells of the periosteum, which are known osteoprogenitor cells, have limited suitability for clinical applications of tissue engineering in their native state due to their low cell number (2–5 cells thick). Extracorporeal shock waves (ESWs) have been shown to cause rapid periosteal cambium cell proliferation and subsequent periosteal osteogenesis. This work investigates a novel strategy for orthotopic bone generation: applying ESW therapy as a noninvasive, inexpensive, and rapid method for stimulating cambium cell proliferation, and combining these cells with a bioactive scaffold for bone growth. ESWs applied to the rabbit medial tibia resulted in a significant 2.7-fold increase in cambium cell number and a 4-fold increase in cambium cell thickness at 4 days post-ESW. ESW-stimulated, or nontreated control, periosteal cells were elevated in situ and overlaid on an anorganic bovine bone scaffold to interrogate their ability to form bone. At 2 weeks post-surgery, there was a significant increase in all key outcome variables for the ESW-stimulated group when compared with controls: a 4-fold increase in osseous tissue in the upper half of the scaffold underlying the periosteum; a 12-fold increase in osseous tissue overlying the scaffold; and a 2-fold increase in callus size. These results successfully demonstrated the efficacy of ESW-stimulated periosteum for orthotopic bone generation
Engineering Endostatin-Producing Cartilaginous Constructs for Cartilage Repair Using Nonviral Transfection of Chondrocyte-Seeded and Mesenchymal-Stem-Cell-Seeded Collagen Scaffolds
No full textAlthough there is widespread recognition of the importance of angiogenesis in tissue repair, there is little work on the inhibition of angiogenesis in the context of tissue engineering of naturally avascular tissues, like articular cartilage. The objective was to engineer a collagen-scaffold-based cartilaginous construct overexpressing a potent antiangiogenic factor, endostatin, using nonviral transfection. Endostatin-plasmid-supplemented collagen scaffolds were seeded with mesenchymal stem cells and chondrocytes and cultured for 20–22 days. The effects of the following variables on endostatin expression and chondrogenesis were examined: collagen scaffold material, method of nonviral vector incorporation, plasmid load, culture medium, and oxygen tension. An increase and peak of endostatin protein was observed during the first week of culture, followed by a decrease to low levels, suggesting that overexpression of endostatin could be sustained for several days using the nonviral vector. The amount of endostatin produced was tunable with the external factors. Chondrogenesis was observed in the engineered constructs cultured in chondrogenic medium at the 3-week time point, demonstrating that endostatin did not inhibit the chondrogenic potential of mesenchymal stem cells or the general viability of the cells. The ability to engineer endostatin-expressing cartilaginous constructs will be of value for future work exercising regulatory control of angiogenesis in cartilage repair.United States. Dept. of Veterans Affairs. Rehabilitation Research and Development ServiceUnited States. Dept. of DefenseNational Science Foundation (U.S.). Graduate Research Fellowship Progra
A study of a hydro-electric development at Kezar Falls, Maine
No full textThesis (B.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1930 [first author], and Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of General Engineering, 1930 [second author].MICROFICHE COPY AVAILABLE IN ENGINEERING.by Myron George Ridlon and Irvin Rea Mitchell.B.S
1913 Flood Damage
No full textLocal author, Myron Barnes, who once served for the the Seneca County Museum, collected various photographs from the March 1913 flood, copied them for this booklet and described the contents of each photo. He states that the originals had been given to the museum by Mrs. Robert Benner, whose husband had been the photographer
Theoretical Aspects of Source Studies in Scientific Heritage of Myron Korduba
No full textThe author examines the contribution of Myron Korduba, a Ukrainian scientist and historian (1876-1947), to the development of theoretical source studies. The publication includes analysis of his “Methodology of History” which deals with sources classification
Theoretical Aspects of Source Studies in Scientific Heritage of Myron Korduba
No full textThe author examines the contribution of Myron Korduba, a Ukrainian scientist and historian (1876-1947), to the development of theoretical source studies. The publication includes analysis of his “Methodology of History” which deals with sources classification
Theoretical Aspects of Source Studies in Scientific Heritage of Myron Korduba
No full textThe author examines the contribution of Myron Korduba, a Ukrainian scientist and historian (1876-1947), to the development of theoretical source studies. The publication includes analysis of his “Methodology of History” which deals with sources classification
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