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Prefreezing Temperature (prefreezing + temperature)
Selected AbstractsLongevity and resistance to cold stress in cold-stress selected lines and their controls in Drosophila melanogasterJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2002F. M. Norry Abstract Thermal environments can influence many fitness-related traits including life span. Here, we assess whether longevity in Drosophila melanogaster can experimentally evolve as a correlated response to cold-stress selection, and whether genotype-by-temperature and sex-by-temperature interactions are significant components of variation in life span. Three replicated S lines were cold-stress selected and compared with their respective unselected controls (Clines) in the 16th generation of thermal selection. Cold-stress resistance exhibited a substantial direct response to selection, and also showed a significant interaction between sex and type of line. Mean longevity exhibited a significant interaction between adult test temperature (14 and 25 °C) and line (with suggestive evidence for increased longevity of S lines when tested at 14 °C), but there was no evidence for increased longevity in S lines at normal temperatures (i.e. 25 °C). Another temperature-dependent effect was sex-specific, with males being the longer lived sex at 25 °C but the less long-lived sex at 14 °C. Additionally, we tested in an exploratory way the relationship between longevity and cold-stress resistance by also measuring resistance to a prefreezing temperature before and after one generation of longevity selection at 14 °C (selection intensity, i = 1.47 for S lines, and 1.42 for C lines). In this longevity selection, we found that cold-stress resistance increased by about 6% in S lines and 18% in C lines. However, taken together, the results indicate no simple relationship between longevity and cold-stress resistance, with genotype-by-sex interactions in both traits. Temperature dependent interaction in longevity is apparent between S and C lines, and sex-specific variation in mean longevity also depends on temperature. [source] Effect of genipin-crosslinked chitin-chitosan scaffolds with hydroxyapatite modifications on the cultivation of bovine knee chondrocytesBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2006Yung-Chih Kuo Abstract Chitin and chitosan were hybridized in various weight percentages by genipin crosslinkage under various prefreezing temperatures to form tissue-engineering scaffolds via lyophilization. In addition, deposition of hydroxyapatite (HA) on the surface of the porous scaffolds was performed by precipitation method to achieve modified chemical compositions for chondrocyte attachments and growths. The experimental results revealed that a lower prefreezing temperature or a higher weight percentage of chitin in the chitin-chitosan scaffolds would yield a smaller pore diameter, a greater porosity, a larger specific surface area, a higher Young's modulus, and a lower extensibility. Moreover, a higher chitin percentage could also result in a higher content of amine groups after crosslink and a lower onset temperature for the phase transition after thermal treatment. A decrease in the prefreezing temperature from ,4°C to ,80°C, an increase in the chitin percentage from 20% to 50%, and an increase in the cycle number of alternate immersion for HA deposition from 1 to 5 generated positive effects on the cell number, the content of glycosaminoglycans, and the collagen level over 28-day cultivation of bovine knee chondrocytes. © 2006 Wiley Periodicals, Inc. [source] | ||||||||||