The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Gordana Vunjaknovakovic - One of the best experts on this subject based on the ideXlab platform.
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cardiac tissue engineering cell seeding cultivation parameters and tissue construct characterization
Biotechnology and Bioengineering, 1999Co-Authors: Maria Papadaki, Nenad Bursac, Robert Langer, Maria Rupnick, Frederick J Schoen, Lisa E Freed, Gordana VunjaknovakovicAbstract:Cardiac tissue engineering has been motivated by the need to create functional tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell-polymer constructs can be cultivated using isolated cells, 3-dimensional scaffolds, and bioreactors. In the present work, we examined the effects of (1) cell source (neonatal rat or embryonic chick), (2) initial cell seeding density, (3) cell seeding Vessel, and (4) tissue Culture Vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed conditions with rat heart cells at a high initial density ((6-8) x 10(6) cells/polymer scaffold) maintained structural integrity and contained macroscopic contractile areas (approximately 20 mm(2)). Seeding in rotating Vessels (laminar flow) rather than mixed flasks (turbulent flow) resulted in 23% higher seeding efficiency and 20% less cell damage as assessed by medium lactate dehydrogenase levels (p < 0.05). Advantages of culturing constructs under mixed rather than static conditions included the maintenance of metabolic parameters in physiological ranges, 2-4 times higher construct cellularity (p &le 0.0001), more aerobic cell metabolism, and a more physiological, elongated cell shape. Cultivations in rotating bioreactors, in which flow patterns are laminar and dynamic, yielded constructs with a more active, aerobic metabolism as compared to constructs Cultured in mixed or static flasks. After 1-2 weeks of cultivation, tissue constructs expressed cardiac specific proteins and ultrastructural features and had approximately 2-6 times lower cellularity (p < 0.05) but similar metabolic activity per unit cell when compared to native cardiac tissue.
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cardiac tissue engineering cell seeding cultivation parameters and tissue construct characterization
Biotechnology and Bioengineering, 1999Co-Authors: Maria Papadaki, Nenad Bursac, Robert Langer, Maria Rupnick, Frederick J Schoen, Lisa E Freed, Gordana VunjaknovakovicAbstract:Cardiac tissue engineering has been motivated by the need to create functional tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell–polymer constructs can be cultivated using isolated cells, 3-dimensional scaffolds, and bioreactors. In the present work, we examined the effects of (1) cell source (neonatal rat or embryonic chick), (2) initial cell seeding density, (3) cell seeding Vessel, and (4) tissue Culture Vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed conditions with rat heart cells at a high initial density ((6–8) × 106 cells/polymer scaffold) maintained structural integrity and contained macroscopic contractile areas (approximately 20 mm2). Seeding in rotating Vessels (laminar flow) rather than mixed flasks (turbulent flow) resulted in 23% higher seeding efficiency and 20% less cell damage as assessed by medium lactate dehydrogenase levels (p < 0.05). Advantages of culturing constructs under mixed rather than static conditions included the maintenance of metabolic parameters in physiological ranges, 2–4 times higher construct cellularity (p ≤ 0.0001), more aerobic cell metabolism, and a more physiological, elongated cell shape. Cultivations in rotating bioreactors, in which flow patterns are laminar and dynamic, yielded constructs with a more active, aerobic metabolism as compared to constructs Cultured in mixed or static flasks. After 1–2 weeks of cultivation, tissue constructs expressed cardiac specific proteins and ultrastructural features and had approximately 2–6 times lower cellularity (p < 0.05) but similar metabolic activity per unit cell when compared to native cardiac tissue. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 580–589, 1999.
Maria Papadaki - One of the best experts on this subject based on the ideXlab platform.
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cardiac tissue engineering cell seeding cultivation parameters and tissue construct characterization
Biotechnology and Bioengineering, 1999Co-Authors: Maria Papadaki, Nenad Bursac, Robert Langer, Maria Rupnick, Frederick J Schoen, Lisa E Freed, Gordana VunjaknovakovicAbstract:Cardiac tissue engineering has been motivated by the need to create functional tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell-polymer constructs can be cultivated using isolated cells, 3-dimensional scaffolds, and bioreactors. In the present work, we examined the effects of (1) cell source (neonatal rat or embryonic chick), (2) initial cell seeding density, (3) cell seeding Vessel, and (4) tissue Culture Vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed conditions with rat heart cells at a high initial density ((6-8) x 10(6) cells/polymer scaffold) maintained structural integrity and contained macroscopic contractile areas (approximately 20 mm(2)). Seeding in rotating Vessels (laminar flow) rather than mixed flasks (turbulent flow) resulted in 23% higher seeding efficiency and 20% less cell damage as assessed by medium lactate dehydrogenase levels (p < 0.05). Advantages of culturing constructs under mixed rather than static conditions included the maintenance of metabolic parameters in physiological ranges, 2-4 times higher construct cellularity (p &le 0.0001), more aerobic cell metabolism, and a more physiological, elongated cell shape. Cultivations in rotating bioreactors, in which flow patterns are laminar and dynamic, yielded constructs with a more active, aerobic metabolism as compared to constructs Cultured in mixed or static flasks. After 1-2 weeks of cultivation, tissue constructs expressed cardiac specific proteins and ultrastructural features and had approximately 2-6 times lower cellularity (p < 0.05) but similar metabolic activity per unit cell when compared to native cardiac tissue.
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cardiac tissue engineering cell seeding cultivation parameters and tissue construct characterization
Biotechnology and Bioengineering, 1999Co-Authors: Maria Papadaki, Nenad Bursac, Robert Langer, Maria Rupnick, Frederick J Schoen, Lisa E Freed, Gordana VunjaknovakovicAbstract:Cardiac tissue engineering has been motivated by the need to create functional tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell–polymer constructs can be cultivated using isolated cells, 3-dimensional scaffolds, and bioreactors. In the present work, we examined the effects of (1) cell source (neonatal rat or embryonic chick), (2) initial cell seeding density, (3) cell seeding Vessel, and (4) tissue Culture Vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed conditions with rat heart cells at a high initial density ((6–8) × 106 cells/polymer scaffold) maintained structural integrity and contained macroscopic contractile areas (approximately 20 mm2). Seeding in rotating Vessels (laminar flow) rather than mixed flasks (turbulent flow) resulted in 23% higher seeding efficiency and 20% less cell damage as assessed by medium lactate dehydrogenase levels (p < 0.05). Advantages of culturing constructs under mixed rather than static conditions included the maintenance of metabolic parameters in physiological ranges, 2–4 times higher construct cellularity (p ≤ 0.0001), more aerobic cell metabolism, and a more physiological, elongated cell shape. Cultivations in rotating bioreactors, in which flow patterns are laminar and dynamic, yielded constructs with a more active, aerobic metabolism as compared to constructs Cultured in mixed or static flasks. After 1–2 weeks of cultivation, tissue constructs expressed cardiac specific proteins and ultrastructural features and had approximately 2–6 times lower cellularity (p < 0.05) but similar metabolic activity per unit cell when compared to native cardiac tissue. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 580–589, 1999.
Toyoki Kozai - One of the best experts on this subject based on the ideXlab platform.
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development and application of photoautotrophic micropropagation plant system
Plant Cell Tissue and Organ Culture, 2011Co-Authors: Yulan Xiao, Genhua Niu, Toyoki KozaiAbstract:Research has revealed that most chlorophyllous explants/plants in vitro have the ability to grow photoautotrophically (without sugar in the Culture medium), and that the low or negative net photosynthetic rate of plants in vitro is not due to poor photosynthetic ability, but to the low CO2 concentration in the air-tight Culture Vessel during the photoperiod. Moreover, numerous studies have been conducted on improving the in vitro environment and investigating its effects on growth and development of Cultures/plantlets on nearly 50 species since the concept of photoautotrophic micropropagation was developed more than two decades ago. These studies indicate that the photoautotrophic growth in vitro of many plant species can be significantly promoted by increasing the CO2 concentration and light intensity in the Vessel, by decreasing the relative humidity in the Vessel, and by using a fibrous or porous supporting material with high air porosity instead of gelling agents such as agar. This paper reviews the development and characteristics of photoautotrophic micropropagation systems and the effects of environmental conditions on the growth and development of the plantlets. The commercial applications and the perspective of photoautotrophic micropropagation systems are discussed.
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number of air exchanges sucrose concentration photosynthetic photon flux and differences in photoperiod and dark period temperatures affect growth of rehmannia glutinosa plantlets in vitro
Plant Cell Tissue and Organ Culture, 2000Co-Authors: Eunjoo Hahn, Toyoki Kozai, Kee-yoeup PaekAbstract:Rehmannia glutinosa plantlets were Cultured for 4 weeks under different Culture conditions to determine the optimum environment for in vitro growth and ex vitro survival. Plantlet growth increased with an increasing number of air exchanges of the Culture Vessel, exhibiting greatest shoot weight, total fresh weight, leaf area, and chlorophyll content at 4.4 h−1 of air exchanges. High sucrose concentration (30 g l−1) increased root weight but reduced shoot growth. Net photosynthetic rates of the plantlets were greatest when sucrose was not added to the medium. On the other hand, ex vitro survival of the plantlets was not influenced by sucrose concentration. In the experiment on difference in photoperiod and dark period temperatures (DIF) and photosynthetic photon flux (PPF), plantlet growth increased as DIF and PPF levels increased. Particularly, increasing PPF level had a more distinctive effect on plantlet growth than increasing DIF level. The interaction of DIF × PPF was also significant, showing the greatest plantlet growth in positive DIF (+8 DIF) and a high PPF (210 μmol m−2 s−1). In conclusion, the results of this experiment suggest that increased number of air exchanges of the Culture Vessel, decreased sucrose concentration, and positive DIF in combination with high PPF level enhanced growth and acclimatization of Rehmannia glutinosa plantlets.
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mass propagation of eucalyptus camaldulensis in a scaled up Vessel under in vitro photoautotrophic condition
Annals of Botany, 2000Co-Authors: S M A Zobayed, F Afreenzobayed, Chieri Kubota, Toyoki KozaiAbstract:Abstract A scaled-up Culture Vessel was designed for the large-scale photoautotrophic micropropagation of chlorophyllous plants. The Culture Vessel (volume 20 l) contained a plug cell tray with 448 plantlets, and had a forced ventilation system to supply CO 2 -enriched air. A nutrient-reservoir was connected to the Culture Vessel from which nutrient solution was circulated to the Culture Vessel every 24 h. Nodal leafy cuttings of Eucalyptus camaldulensis L. were Cultured photoautotrophically in this system without sugar in the nutrient medium, but with an enriched CO 2 concentration and a high photosynthetic photon flux. The growth and the net photosynthetic rate of the in vitro grown plantlets and the survival percentage of the plantlets after transplanting to ex vitro conditions were compared with those of plantlets grown photoautotrophically under natural ventilation in conventional small Culture Vessels (Magenta-type Vessels; volume 0.4 l). Fresh and dry masses and net photosynthetic rate were significantly higher in plantlets grown in the scaled-up Vessel compared to plantlets grown in the conventional small Vessels (control). The environmental conditions created in this scaled-up Vessel (with forced ventilation) also facilitated acclimatization in vitro . Importantly, after transplanting to the ex vitro condition, plantlets grew well without any specialized ex vitro acclimatization treatment.
Rafael Villasenor - One of the best experts on this subject based on the ideXlab platform.
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effect of Culture volume and adult density on the neonate production of daphnia magna as a test organism for aquatic toxicity tests
Environmental Toxicology, 2000Co-Authors: Fernando Martinezjeronimo, Felix Espinosachavez, Rafael VillasenorAbstract:Neonates of Daphnia magna are widely used for bioassays in aquatic toxicology. Although this species is considered as a world-wide reference, its low repeatability of the results in the ecotoxicological studies, are due to the differences in maintenance conditions of the brood stock. We studied the combined effects of adult parthenogenetic female density and Culture volume on the total fecundity. Extrapolated densities from 5 to 40 adults L - 1 , in volumes from 100 to 400 mL were tested. The green microalga Scenedesmus incrassatulus was used as food (1.30E+06 cells mL -1 ) Once the reproduction began, the neonates produced were counted daily and discarded to avoid crowding effects. The experiments were carried out for 40 days. The maximal total offspring per female, i.e., 832 and 755 neonates, were obtained in the extrapolated densities of 5 and 10 ind. L -1 , respectively, using one adult female per Culture Vessel (in 200 and 100 mL of medium). When the quantity of the Culture medium increased, despite a lower female density, the fecundity decreased and also the total offspring per female. For optimal neonate production, the parthenogenetic females should be individually Cultured in small volumes (100 or 200 mL).
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effect of Culture volume and adult density on the neonate production of daphnia magna as a test organism for aquatic toxicity tests
Environmental Toxicology, 2000Co-Authors: Fernando Martinezjeronimo, Felix Espinosachavez, Rafael VillasenorAbstract:Neonates of Daphnia magna are widely used for bioassays in aquatic toxicology. Although this species is considered as a world-wide reference, its low repeatability of the results in the ecotoxicological studies, are due to the differences in maintenance conditions of the brood stock. We studied the combined effects of adult parthenogenetic female density and Culture volume on the total fecundity. Extrapolated densities from 5 to 40 adults L - 1 , in volumes from 100 to 400 mL were tested. The green microalga Scenedesmus incrassatulus was used as food (1.30E+06 cells mL -1 ) Once the reproduction began, the neonates produced were counted daily and discarded to avoid crowding effects. The experiments were carried out for 40 days. The maximal total offspring per female, i.e., 832 and 755 neonates, were obtained in the extrapolated densities of 5 and 10 ind. L -1 , respectively, using one adult female per Culture Vessel (in 200 and 100 mL of medium). When the quantity of the Culture medium increased, despite a lower female density, the fecundity decreased and also the total offspring per female. For optimal neonate production, the parthenogenetic females should be individually Cultured in small volumes (100 or 200 mL).
Maria Rupnick - One of the best experts on this subject based on the ideXlab platform.
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cardiac tissue engineering cell seeding cultivation parameters and tissue construct characterization
Biotechnology and Bioengineering, 1999Co-Authors: Maria Papadaki, Nenad Bursac, Robert Langer, Maria Rupnick, Frederick J Schoen, Lisa E Freed, Gordana VunjaknovakovicAbstract:Cardiac tissue engineering has been motivated by the need to create functional tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell-polymer constructs can be cultivated using isolated cells, 3-dimensional scaffolds, and bioreactors. In the present work, we examined the effects of (1) cell source (neonatal rat or embryonic chick), (2) initial cell seeding density, (3) cell seeding Vessel, and (4) tissue Culture Vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed conditions with rat heart cells at a high initial density ((6-8) x 10(6) cells/polymer scaffold) maintained structural integrity and contained macroscopic contractile areas (approximately 20 mm(2)). Seeding in rotating Vessels (laminar flow) rather than mixed flasks (turbulent flow) resulted in 23% higher seeding efficiency and 20% less cell damage as assessed by medium lactate dehydrogenase levels (p < 0.05). Advantages of culturing constructs under mixed rather than static conditions included the maintenance of metabolic parameters in physiological ranges, 2-4 times higher construct cellularity (p &le 0.0001), more aerobic cell metabolism, and a more physiological, elongated cell shape. Cultivations in rotating bioreactors, in which flow patterns are laminar and dynamic, yielded constructs with a more active, aerobic metabolism as compared to constructs Cultured in mixed or static flasks. After 1-2 weeks of cultivation, tissue constructs expressed cardiac specific proteins and ultrastructural features and had approximately 2-6 times lower cellularity (p < 0.05) but similar metabolic activity per unit cell when compared to native cardiac tissue.
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cardiac tissue engineering cell seeding cultivation parameters and tissue construct characterization
Biotechnology and Bioengineering, 1999Co-Authors: Maria Papadaki, Nenad Bursac, Robert Langer, Maria Rupnick, Frederick J Schoen, Lisa E Freed, Gordana VunjaknovakovicAbstract:Cardiac tissue engineering has been motivated by the need to create functional tissue equivalents for scientific studies and cardiac tissue repair. We previously demonstrated that contractile cardiac cell–polymer constructs can be cultivated using isolated cells, 3-dimensional scaffolds, and bioreactors. In the present work, we examined the effects of (1) cell source (neonatal rat or embryonic chick), (2) initial cell seeding density, (3) cell seeding Vessel, and (4) tissue Culture Vessel on the structure and composition of engineered cardiac muscle. Constructs seeded under well-mixed conditions with rat heart cells at a high initial density ((6–8) × 106 cells/polymer scaffold) maintained structural integrity and contained macroscopic contractile areas (approximately 20 mm2). Seeding in rotating Vessels (laminar flow) rather than mixed flasks (turbulent flow) resulted in 23% higher seeding efficiency and 20% less cell damage as assessed by medium lactate dehydrogenase levels (p < 0.05). Advantages of culturing constructs under mixed rather than static conditions included the maintenance of metabolic parameters in physiological ranges, 2–4 times higher construct cellularity (p ≤ 0.0001), more aerobic cell metabolism, and a more physiological, elongated cell shape. Cultivations in rotating bioreactors, in which flow patterns are laminar and dynamic, yielded constructs with a more active, aerobic metabolism as compared to constructs Cultured in mixed or static flasks. After 1–2 weeks of cultivation, tissue constructs expressed cardiac specific proteins and ultrastructural features and had approximately 2–6 times lower cellularity (p < 0.05) but similar metabolic activity per unit cell when compared to native cardiac tissue. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 580–589, 1999.
