Search results for "preservation"
showing 10 items of 484 documents
Cell inactivation and membrane damage after long-term treatments at sub-zero temperature in the supercooled and frozen states.
2008
The survival of cells subjected to cooling at sub-zero temperature is of paramount concern in cryobiology. The susceptibility of cells to cryopreservation processes, especially freeze-thawing, stimulated considerable interest in better understanding the mechanisms leading to cell injury and inactivation. In this study, we assessed the viability of cells subjected to cold stress, through long-term supercooling experiments, versus freeze-thawing stress. The viability of Escherichia coli, Saccharomyces cerevisiae, and leukemia cells were assessed over time. Supercooled conditions were maintained for 71 days at -10 degrees C, and for 4 h at -15 degrees C, and -20 degrees C, without additives or…
Cui prodest servāre? Due ipotesi di destinazione per gli embrioni crioconservati
2022
The essay analyses the general ban for the donation of embryos placed into cryopreservation, stated by the Italian legislation n. 40/2004. Such a prevision causes a sine die conservation not only for embryos suitable for implantation, but also for those affected by genetic defects or diseases. The essay points out that donating both types of embryos, respectively, to adoption or to scientific fertility research preserves the dignity of the cells in storage, as a will supported by the consent of both gametes’ providers to the ultimate scope of solidarity.
Zygotic and nucellar embryo survival following dehydration and cryopreservation of citrus intact seeds.
2004
A cryopreservation procedure by dehydration and direct immersion in liquid nitrogen was developed for seeds of four polyembryonic Citrus species, and the sexual or nucellar origin of the recovered seedlings was investigated. Seeds of three species could be desiccated in a sterile air flow to 16 percent (C. sinensis) or 10 percent (C. aurantium and C. limon) moisture content with a negligible reduction in germination levels. Differently, the germinability of C. deliciosa seeds dropped to 50 percent after drying to 15 percent moisture content. Following dehydration treatments, a reduction in the average number of seedlings per germinated seed was always observed. However, all four species ben…
Ovarian tissue cryopreservation and transplantation in menopause: new perspective of therapy in postmenopausal women and the importance of ethical an…
2023
Menopausal transition entails a progressive decrease in hormone production by the ovaries that lead to important physical and psychological changes that could significantly affect quality of life. Hormone replacement therapy (HRT) administered from the onset of menopausal symptoms usually improves quality of life and life expectancy. Nevertheless, it is not risk-free. Ovarian tissue cryopreservation (OTC) has been investigated as a potential new strategy for delaying menopause and/or to avoid HRT. This review analyzes the critical points of HRT to assess whether OTC and subsequent reimplantation can affect postmenopausal management. We assessed available randomized clinical trials in PubMed…
Investigating the cryopreservation of nodal explants of Lithodora rosmarinifolia (Ten.) Johnst., a rare, endemic Mediterranean species
2012
In this study, we investigated the possibility of using the droplet-vitrification technique for cryopreserving nodal segments of in vitro plantlets of the endangered plant species Lithodora rosmarinifolia. Among the three vitrification solutions tested, only solutions B1, containing (w/v) 50 % glycerol and 50 % sucrose, and B3, containing 40 % glycerol and 40 % sucrose, were able to induce cryotolerance in nodal explants, resulting in intermediate survival and recovery after cryopreservation. A three-step vitrification protocol, including an additional dehydration treatment with half-strength vitrification solution for 30 min before the treatment with full-strength vitrification solution, d…
Vitrification of Immature Porcine Oocytes: Effects of Lipid Droplets, Temperature, Cytoskeleton, and Addition and Removal of Cryoprotectant
1998
Three experiments were conducted to investigate the effects of single-step and stepwise exposure to and removal of cryoprotectant, of temperature, and of a cytoskeletal relaxant on the development of germinal vesicle porcine oocytes to the M-II stage. In experiment I, noncooled cumulus-oocyte complexes (COCs) were treated using single-step/stepwise exposure to ethylene glycol (EG) and removal at 23 or 42 degrees C. Stepwise exposure to EG and dilution at 42 degrees C were found to have a positive effect on the COC developmental rate. In experiment II, also without cooling, COCs were treated with Cytochalasin B at 42 degrees C using single-step and stepwise protocols of exposure to and remov…
Three-dimensional structure of hepatitis B virus core particles determined by electron cryomicroscopy
1994
Human hepatitis B virus core protein expressed in E. coli assembles into two sizes of particle. We have determined their three-dimensional structures by electron cryomicroscopy and image processing. The large and small particles correspond to triangulation number T = 4 and T = 3 dimer clustered packings, containing 240 and 180 protein subunits, respectively. The local packing of subunits is very similar in the two sizes of particle and shows holes or channels through the shell. The native viral core particle packages RNA and is active in reverse transcription to DNA. The holes we observe may provide access for the necessary small molecules. Shells assembled from the intact core protein cont…
Vitrification in assisted reproduction: myths, mistakes, disbeliefs and confusion
2009
The purpose of this work is to update embryologists and clinicians on different approaches in human oocyte and embryo cryopreservation, by clarifying some misunderstandings and explaining the underlying reasons for controversial opinions. The work is based on literature review and critical analysis of published papers or conference abstracts during the last 24 years, with special focus on the last 3 years. Due to the latest advancements in techniques, cryopreservation now offers new perspectives along with solutions to many demanding problems, and has developed from a backup procedure to a successful alternative that is an indispensable constituent of assisted reproductive techniques. Howev…
New perspectives in medically assisted procreation.
2008
Vitrification of human mature oocytes in clinical practice.
2009
Oocyte cryopreservation has long been the focus of unsuccessful efforts to perfect its clinical application. Lately, vitrification has been shown to provide high degrees of success by different research groups. This review attempts to address the efficiency of oocyte vitrification in clinical practice through an analysis of reports of IVF cycles in which embryo transfers have been conducted with vitrified metaphase-II human oocytes.