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Preserving fertility
Published in David J Cahill, Practical Patient Management in Reproductive Medicine, 2019
There is ongoing debate as to which method should be used to freeze ovarian tissue, slow freezing or vitrification. When 14 studies were analysed in a meta-analysis, there was no significant difference between slow freezing versus vitrification in terms of the proportion of intact primordial follicles, but vitrification was associated with less primordial follicular DNA strand breaks and better preservation of stromal cells (27). A further study was undertaken in seven healthy volunteers undergoing caesarean section who had ovarian cortex samples collected at the time of their section (28). Each sample was divided in three and was then treated by vitrification, slow freezing and controls which were not frozen (28). Findings from this study related to gene expression: the BAX: BCL-2 ratio was significantly increased in the vitrified group compared to slow frozen and control groups, and slow freezing did not change the susceptibility of the ovarian tissue to apoptotic signals (the BAX: BCL-2 ratio alters the ability of a cell to respond to an apoptotic signal, BCL-2 results in cell protection and BAX promotes apoptosis – and vitrification promotes apoptosis and cell loss) (28). On this and other findings, they concluded slow freezing is optimal for ovary cryopreservation (28). Their views were supported by others after experiments demonstrated that vitrification reduces cell viability (29).
Radiation protection in the nuclear industry
Published in Alan Martin, Sam Harbison, Karen Beach, Peter Cole, An Introduction to Radiation Protection, 2018
Alan Martin, Sam Harbison, Karen Beach, Peter Cole
Of the product streams, the uranium stream does not present any significant radiological problem but the plutonium stream demands extremely high standards of containment to prevent any leakage that could lead to a potentially severe contamination hazard. The high-level waste stream is routed initially into special storage tanks, where it remains for a few years until it is ready for vitrification. This is a process in which the waste is mixed with glass, turning it into a solid form and reducing its volume to about one-third of its original amount. Vitrification allows the material to be stored safely in a form that should be suitable for long-term storage or eventual permanent disposal. In addition to the highly active waste streams, there are a number of subsidiary streams, the treatments of which depend on local conditions. The management of radioactive waste is covered in Chapter 14.
The human embryo: Vitrification Vitrification
Published in David K. Gardner, Ariel Weissman, Colin M. Howles, Zeev Shoham, Textbook of Assisted Reproductive Techniques, 2017
Zsolt Peter Nagy, Ching-Chien Chang, Gábor Vajta
The overwhelming majority of the studies/publications support the application of vitrification by emphasizing its advantages: the simple, inexpensive, and rapid procedure leading to higher survival and developmental rates than those achievable with alternative methods. Concerns regard- ing disease transmission are theoretically justified, but safer methods are now available to mitigate this risk. Outstanding results like the breakthrough in human oocyte vitrification and the excellent (and improved) results on embryo cryo- preservation have changed the way we practice routine IVF, providing more efficient and safer options for patients.
Human oocyte cryopreservation: revised evidence for practice
Published in Human Fertility, 2023
Virginia N. Bolton, Catherine Hayden, Michele Robinson, Dima Abdo, Angela Pericleous-Smith
Successful cryopreservation of living cells relies on preventing the formation of ice crystals that may cause cryodamage (Mazur, 1963) and minimising the toxic effects of exposure to cryoprotectant agents (Kleinhans & Mazur, 2007). With slow freezing, this is achieved through the gradual dehydration and permeation of cells with cryoprotectants through a combination of exposure to progressively increasing concentrations of cryoprotectants and controlled slow cooling. The relative lack of success of early attempts at slow freezing oocytes compared with embryos has been attributed to several characteristics that distinguish mammalian oocytes from embryos (Friedler et al., 1988), including relatively low permeability to cryoprotectants (Edashige & Kasai, 2016), low surface area:volume ratio and high water content (K. Goldman et al., 2016), and thus their greater susceptibility to cryo damage. With vitrification, cryodamage is reduced by rapid cooling combined with brief exposure to relatively high concentrations of cryoprotectants, so that ice crystal formation is prevented, and cells achieve a glass-like state (Nakagata, 1989). Based on the large body of evidence now available for the superior efficacy of vitrification for oocyte cryopreservation, slow freezing is no longer considered appropriate for routine use in clinical practice and will not be considered further in this guideline.
Spray freeze-drying for inhalation application: process and formulation variables
Published in Pharmaceutical Development and Technology, 2022
Mostafa Rostamnezhad, Hossein Jafari, Farzad Moradikhah, Sara Bahrainian, Homa Faghihi, Reza Khalvati, Reza Bafkary, Alireza Vatanara
Vitrification is a process that material enters a glassy state and prevents crystallization. The formation of ice crystals was allowed by regular freezing rate due to the slow freezing process. In contrast, during the fast freezing process, the temperature quickly dropped below the Tg and avoided the formation of the ice crystals. Consequently, fewer ice crystals formed, but the crystals were very fine. As a result, SEM images showed significant differences between particles formed by SFV/L and SFL methods. The particles produced by SFL were more spherical and smaller (50 nm) but, the SFV/L particles exhibited an open-cell structure. The structures formed in liquid nitrogen and isopentane were identical. Also, using suitable excipients such as sugars makes it possible to form an amorphous matrix and increase the Tg (Engstrom et al. 2007).
Should artificial shrinkage be performed prior to blastocyst vitrification? A systematic review of the literature and meta-analysis
Published in Human Fertility, 2022
Juliette Boyard, Arnaud Reignier, Sana Chtourou, Tiphaine Lefebvre, Paul Barrière, Thomas Fréour
Embryo cryopreservation techniques have largely improved over the last 15 years and play a key role in assisted reproductive techniques (ART) as they enhance the overall effectiveness of in vitro fertilisation (IVF) (Rodriguez-Wallberg, 2015). The onset of vitrification, allowing almost absolute embryo survival when expertly performed, has constituted a major breakthrough (Argyle, Harper, & Davies, 2016). In parallel, prolonged embryo culture up to the blastocyst stage has gained interest over the past decade. Although not universally accepted, it is generally considered to optimise some aspects of IVF such as increased implantation potential and lower number of cryopreserved embryos (Glujovsky, Farquhar, Quinteiro Retamar, Alvarez Sedo, & Blake, 2016). Altogether, blastocyst culture associated with vitrification is an effective strategy, provided blastocyst survival rate and clinical outcome after vitrified–warmed blastocyst transfer (commonly named frozen-thawed blastocyst transfer - FBT) cycle are maximal.