共查询到19条相似文献,搜索用时 210 毫秒
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为进一步完善动脉低温保存过程中为解决低温断裂问题而建立的冻结过程的热应力分析物理模型,本文研究家兔主动脉血管从室温到-80℃温度范围内,杨氏模量随温度的变化情况和加抗冻剂CPA的影响。研究发现兔丰动脉低温冻结状态的杨氏模量随温度的降低而增大;加CPA对兔丰动脉血管冻结状态下的杨氏模量有影响,相同温度情况下加CPA试样的杨氏模量比不加CPA试样的要低。 相似文献
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低温生物医学与热物理 总被引:8,自引:0,他引:8
本文阐述了低温生物学、低温医学与热物理的关系;着重讨论生物体低温保存的问题,细胞和组织的低温损伤是溶液冻结相变过程所引起的冰晶损伤和高浓度溶液的损伤;这个过程和传热传质密切相关;而低温保存的机理则是溶液的非晶态化(玻璃化)。本文还讨论了低温生物医学当前的研究热点,以及其中的热物理问题。 相似文献
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Two methods used in artery deep cryopreservation, "Cryopreservation in Medium" and "Cryopreservation in Air", were studied. For the former method, samples were frozen together with a certain amount of cryoprotectants (CPA) in the cryovial or cryobag, while for the other method the arteries were first exposed to CPA and then frozen without the CPA medium surrounding in the cryovial. Study of the cryopreserved arteries using these two methods found that "cryopreservation in air" could substantially reduce the fracture rate of the arteries. To explain the difference theoretically, a two-compartment model is presented to study the thermal stresses generated during the freezing and thawing processes. The properties were measured as inputs to the model. Numerical results showed that the thermal stresses occurring in the "cryopreservation in air" process were much smaller than in the other method. The maximum thermal stress during cryopreservation occurs in the thawing process. The theoretical results could well explain published experimental results. 相似文献
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An experimental study of the mechanical response of frozen arteries to tensile stresses at low temperatures is presented. The Dynamic Mechanical Analyzer was used to perform the mechanical experiments. It was found that the frozen artery shows a kind of elastic-plasticity when the temperature is between -20 C and -40 C. And with the decrease of the temperature, the plasticity deformation decreases. Thus at the temperature of -120 C no plasticity deformation is observed before the artery's fracture and the tissue shows quite perfect elastic brittleness, both peripherally and axially. These kinds of mechanical characteristics help explain the fracture phenomena occurring during cryopreservation of the arteries. The mechanical properties, including elastic modulus and fracture strength, are also given. It is known that Cryoprotectant (CPA) used in cryopreservation is necessary in maintaining the tissue's biological functions. Our investigation of its effect on the artery's mechanical properties found that the existence of CPA can soften the tissue at low temperatures, thus may decrease the possibility of fractures during the cryopreservation. 相似文献
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The rust fungus Puccinia spegazzinii (Basidiomycotina: Uredinales) has been identified as a potential classical biological control agent for the invasive weed Mikania micrantha (Asteraceae). Long-term, live storage of this pathogen is required for reference. As biotrophs, almost all rusts species cannot be preserved by traditional cryopreservation protocols, which rely on in vitro culture techniques. In addition, the embedded teliospores and delicate basidiospores of this microcyclic rust are not amenable to direct plunge freezing. Continuous culture of the rust on living plants is both laborious and expensive, so a variety of approaches for cryopreservation and storage were tested. These methods included traditional approaches to fungal cryopreservation such as variation of cooling rate regime and alginate encapsulation techniques. However, an in situ cryopreservation technique was the only method identified as having any potential for the long-term cryopreservation of the 10 isolates tested. Material from either petiole or stem tissue remained viable after cryopreservation, determined by the ability of the material to produce basidiospores. However, despite great progress being made in developing an optimal cryopreservation method, infection of the host plant by basidiospores produced from previously cryopreserved teliospores, embedded in leaf petioles, was not achieved. 相似文献
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Cryopreservation of reproductive cells and tissues of aquatic species offers many benefits to the field of conservation, aquaculture and biomedicine. Although cryopreservation of fish sperm has been successfully achieved, cryopreservation of embryos and oocytes remains unsuccessful. Several studies have been undertaken on cryopreservation of isolated fish ovarian follicles at different stages, although the protocols used lead to a compromised viability. The present study investigates the effect of cryoprotectants and cryopreservation on the viability of ovarian tissues of zebrafish (Danio rerio). The effect of permeating cryoprotectants (CPAs) methanol, dimethyl sulfoxide (DMSO), and ethylene glycol (EG) on ovarian tissues were investigated in a series of toxicity tests. Controlled slow cooling of ovarian tissues using 1M and 4M methanol was also carried out. Ovarian tissue viability was assessed by trypan blue (TB) and fluorescence diacetate (FDA)-propidium iodide (PI) tests. In addition, the effect of methanol exposure and cryopreservation on ovarian follicle ATP level, mitochondria, actin and tubulin distribution were also investigated. Results showed that cryoprotectant toxicity to ovarian fragments increased in the order of methanol, DMSO and EG. The results from controlled slow cooling showed that 1M methanol was more effective than 4M methanol although subsequent cryopreservation induced decreases in ATP levels. Immunocytochemistry and actin staining results showed impacts of cryopreservation on mitochondria and cytoskeleton proteins distribution. 相似文献
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Shoot-tips of 10 strawberry genotypes were successfully cryopreserved using a modified encapsulation-dehydration method. All genotypes survived cryopreservation with high survival and regeneration rates. Eight Joho single-bud sibling lines were established as a model system for genetic analysis. Although cytological examination found chromosomal variation in both non-cryopreserved and cryopreserved samples, the ploidy constitution remained relatively stable after cryopreservation. DNA samples digested with MseI and PstI were used for amplified fragmentation length polymorphism (AFLP) assay. In 16 primer combinations, only one, namely, PCCA-MCAG, detected one site where band pattern changed after cryopreservation, which might be contributed to the change in DNA methylation status at PstI recognition site. Methylation sensitive amplified polymorphism (MSAP) assay was carried out for further investigation on the influence of cryopreservation on DNA methylation status. It was found that cryopreservation induced a significant change in DNA methylation status. 相似文献
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Cryopreservation of shoot tips and cotyledons of the north american ginseng (Panax quinquefolius l.)
North American ginseng (NAG) (Panax quinqueolius L.) is a medicinal plant in high demand due to its health benefits. Cryopreservation is a good alternative for long-term conservation of NAG germplasm. Pretreatments of shoot tips (0.8-1 mm) and cotyledons (1-2 mm) on sucrose and abscisic acid (ABA) enriched medium were tested to determine the effects on regrowth following cryopreservation in liquid nitrogen. The maximum regrowth (60 percent) following PVS2 vitrification occurred with shoot tips after three weeks of cold acclimation and pretreatment on sucrose (0.3 M) or a combination of ABA (0.1 M) and sucrose in the third week. Cotyledon recovery was best with the combination pretreatment. Shoot tips showed normal development and cotyledons produced embryogenic callus after the cryopreservation process. This is the first report on cryopreservation of shoot tips and cotyledons of Panax species. This cryopreservation protocol provides a safe long-term storage method for important NAG selections and makes it possible to use cryopreservation for improving the security of NAG germplasm. 相似文献
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Polyamines and fatty acids were studied in proliferating meristem cultures of 3 banana cultivars with high (Cachaco), medium (Williams Bronze free) and low (Mbwazirume) survival rates after cryopreservation. A 2-week preculture on medium containing 0.4 M sucrose which is essential to obtain survival after cryopreservation resulted in increased polyamine levels, especially putrescine. This increase in putrescine content was positively correlated with the survival rate after simple freezing or after vitrification. The total fatty acid content also increased after a 0.4 M sucrose pretreatment. However, only the ratio of unsaturated/saturated fatty acids correlated positively with the survival rate after cryopreservation. This is the first report showing a correlation of both putrescine increase and level of unsaturation of membrane lipids after sucrose treatment with survival rate after cryopreservation. 相似文献
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A simple cryopreservation method is described for proliferating meristem cultures of banana (Musa spp.). It relies on a 2-week preculture on media containing 0.4 M sucrose followed by rapid cooling in liquid nitrogen. Different preculture media were screened for efficient protection of banana meristems against cryopreservation. Sucrose can be replaced by both fructose and glucose without significantly affecting post-thaw survival rates. A high BA concentration (0.1 mM) in the preculture medium results in less material available for cryopreservation, but does not affect cryoprotection. Culture in liquid media significantly improved post-thaw regeneration. The optimized cryopreservation protocol was applied on 36 banana accessions belonging to 8 different genomic groups. It is shown that post-thaw regeneration frequencies (ranging between 0 and 66 percent) are highly dependent on the genomic constitution of the banana cultivar. 相似文献
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Cryopreservation of umbilical cord blood-derived mesenchymal stem cells (UCB-derived MSCs) is crucial step for its clinical applications in cell transplantation therapy. In the cryopreservation of MSCs, dimethyl sulfoxide has been widely used as a cryoprotectant (CPA). However, it has been proved that DMSO has toxic side effects to human body. In this study, DMSO-free CPA solutions which contained ethylene glycol (EG), 1, 2-propylene glycol (PG) and sucrose as basic CPAs, supplemented with polyvinyl alcohol (PVA) as an additive, were developed for the cryopreservation of UCB-derived MSCs. The cryopreservation of UCB-derived MSCs was achieved by vitrification via plunging into liquid nitrogen and by programmed freezing via an optical-DSC system respectively. The viability of thawed UCB-derived MSCs was tested by trypan blue exclusion assay. Results showed that the viability of thawed UCB-derived MSCs was enhanced from 71.2% to 95.4% in the presence of PVA for vitrification, but only < 10% to 45% of viability was found for programmed freezing. These results indicate that PVA exerts a beneficial effect on the cryopreservation of UCB-derived MSCs and suggest the vitrification in combination with the dimethyl sulfoxide free CPA solutions supplemented with PVA would be an efficient protocol for the cryopreservation of UCB-derived MSCs. 相似文献