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Moore NP, Bogaards JJP, Buscher BAP, Wolterbeek APM, Cnubben NHP. Disposition of glycolic acid into the embryo following oral administration of ethylene glycol during placentation in the rat and rabbit. Toxicol Sci 2024; 198:31-39. [PMID: 38175793 DOI: 10.1093/toxsci/kfad135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2024] Open
Abstract
In order to evaluate the role of the placenta in the etiology of ethylene glycol (EG) developmental toxicity, the distribution of EG and its main metabolites, glycolic acid (GA) and oxalic acid (OX), into the conceptus was determined at the beginning and completion of placentation in the rat and rabbit. Two groups (n = 28) of timed-pregnant Wistar rats were administered EG (1000 mg/kg bw/day, oral gavage) from gestation day (GD) 6 to either GD 11 or GD 16; similarly, two groups (n = 28) of timed-pregnant New Zealand White rabbits were administered EG from GD 6 to either GD 10 or GD 19. Four animals from each group were sacrificed at 1, 3, 6, 9, 12, 18, or 24 h after the final administration, and maternal blood, extraembryonic fluid, and embryonic tissue were removed for analysis of EG, GA, and OX. The three analytes were predominantly cleared from all compartments in both species within 24 h. Neither EG nor OX preferentially accumulated into the conceptus compartments, compared with the maternal blood, in either species. Critically, GA was preferentially accumulated from the maternal blood only into the rat embryo at GD 11, but not at GD 16 and not into the rabbit embryo at either GD 10 or GD 19. The accumulation of GA into the rat embryo, and its decline over the course of placentation, is discussed in relation to the expression of monocarboxylate transporter isoforms across the syncytiotrophoblast.
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Yan X, Chen Q, Zhang Z, Fu Y, Huo Z, Wu Y, Shi H. Chemical features and biological effects of degradation products of biodegradable plastics in simulated small waterbody environment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 904:166829. [PMID: 37673271 DOI: 10.1016/j.scitotenv.2023.166829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 08/30/2023] [Accepted: 09/02/2023] [Indexed: 09/08/2023]
Abstract
A plethora of research has focused on the biosafety of biodegradable plastics (BPs), including their microplastic formation and additives leaching; however, relatively fewer studies have explored biodegradation products. This study aims to investigate the biological effects and chemical features of degradation products from three kinds of BPs, namely polyglycolic acid (PGA), poly (butylene adipate-co-terephthalate) (PBAT), and the blends of PGA/PBAT without the addition of additives, in a simulated small waterbody environment with extracted soil solution for three months. Results showed that exposure to the whole degradation remnants of three BPs had no lethal effects on zebrafish at the current BP environmental concentrations (from 0.24 to 12.72 mg plastic/L) in small waterbodies. However, from the calculated BPs environmental concentrations (from 0.57 to 43.82 mg plastic/L) in 2026, PGA and PGA/PBAT blends may cause adverse effects on the cardiovascular system such as heartbeat rate suppression in zebrafish embryos, and also lead to reduced body length and pericardial edema and spinal curvature in fish larvae. We further qualitatively analyzed the composition of degradation products, and quantitatively measured four dominant degradation monomers (glycolic acid (GA), adipic acid (A), 1,4-butanediol (B), and terephthalic acid (T)) in the degradation remnants. It was found that the observed toxicities were probably due to the presence of GA, A, and T monomers, and their concentrations can reach 0.776, 0.034, and 0.6 mg/L under the calculated future scenario, respectively. It is worth mentioning that either GA or T monomers at the above concentrations were found to cause suppressed heartbeat rate in zebrafish embryos. Collectively, though the degradation products of BPs are temporarily safe at current environmental concentrations, they may lead to non-negligible toxicity with increasing production and continual improper recycling and/or BP waste management.
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Affiliation(s)
- Xiaoyun Yan
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China
| | - Qiqing Chen
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China; Yangtze Delta Estuarine Wetland Ecosystem Observation and Research Station, Ministry of Education & Shanghai Science and Technology Committee, Shanghai 200241, China.
| | - Zhuolan Zhang
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China
| | - Ye Fu
- College of Chemistry and Materials Engineering, Beijing Technology and Business University, Beijing 100037, China
| | - Zhanbin Huo
- College of Chemistry and Materials Engineering, Beijing Technology and Business University, Beijing 100037, China
| | - Yan Wu
- Key Laboratory of Geographic Information Science (Ministry of Education), School of Geographic Sciences, East China Normal University, Shanghai 200241, China
| | - Huahong Shi
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China
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Priyadarshini M, Ahmad A, Das I, Ghangrekar MM, Dutta BK. Efficacious degradation of ethylene glycol by ultraviolet activated persulphate: reaction kinetics, transformation mechanisms, energy demand, and toxicity assessment. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:85071-85086. [PMID: 37227630 DOI: 10.1007/s11356-023-27596-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 05/09/2023] [Indexed: 05/26/2023]
Abstract
Ethylene glycol or 1,2-ethanediol (EG) is a persistent and toxic substance in the environment and extensively applied in petrochemical, surfactants, antifreeze, asphalt emulsion paints, cosmetics, plastics, and polyester fiber industries. Degradation of EG by using ultraviolet (UV) activated hydrogen peroxide (H2O2) and persulfate (PS) or persulfate anion (S2O82-) based advanced oxidation processes (AOPs) were explored. The result obtained demonstrate that UV/PS (85.7 ± 2.5%) has exhibited improved degradation efficiency of EG as compared to UV/H2O2 (40.4 ± 3.2%) at optimal operating conditions of 24 mM of EG concentration, 5 mM of H2O2, 5 mM of PS, 1.02 mW cm-2 of UV fluence, and pH of 7.0. Impacts of operating factors, including initial EG concentration, oxidant dosage, reaction duration, and the impact of different water quality parameters, were also explored in this present investigation. The degradation of EG in Milli-Q® water followed pseudo - first order reaction kinetics in both methods having a rate constant of about 0.070 min-1 and 0.243 min-1 for UV/H2O2 and UV/PS, respectively, at optimum operating conditions. Additionally, an economic assessment was also conducted under optimal experimental conditions, and the electrical energy per order and total operational cost for treating per m3 of EG-laden wastewater was observed to be about 0.042 kWh m-3 order-1 and 0.221 $ m-3 order-1, respectively, for UV/PS, which was slightly lower than UV/H2O2 (0.146 kWh m-3 order-1; 0.233 $ m-3 order-1). The potential degradation mechanisms were proposed based on intermediate by-products detected by Fourier transform infrared (FTIR) spectroscopy and gas chromatography-mass spectroscopy (GC-MS). Moreover, real petrochemical effluent containing EG was also treated by UV/PS, demonstrating 74.7 ± 3.8% of EG and 40.7 ± 2.6% of total organic carbon removal at 5 mM of PS and 1.02 mW cm-2 of UV fluence. A toxicity tests on Escherichia coli (E. coli) and Vigna radiata (green gram) confirmed non-toxic nature of UV/PS treated water.
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Affiliation(s)
- Monali Priyadarshini
- School of Environmental Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Azhan Ahmad
- Department of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Indrasis Das
- Environmental Engineering Department, CSIR-Central Leather Research Institute, Adyar, Chennai, Tamil Nadu, 600020, India
| | - Makarand Madhao Ghangrekar
- School of Environmental Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
- Department of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
| | - Binay K Dutta
- School of Environmental Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
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Menezo Y, Dale B, Elder K. The negative impact of the environment on methylation/epigenetic marking in gametes and embryos: A plea for action to protect the fertility of future generations. Mol Reprod Dev 2019; 86:1273-1282. [PMID: 30653787 DOI: 10.1002/mrd.23116] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 01/15/2019] [Indexed: 12/31/2022]
Abstract
Life expectancy has increased since World War II, and this may be attributed to several aspects of modern lifestyles. However, now we are faced with a downturn, which seems to be the result of environmental issues. This paradigm is paralleled with reduced human fertility, decreased sperm quality, increased premature ovarian failure, and diminished ovarian reserve syndromes. Endocrine disruptor chemicals and other toxic chemicals, herbicides, pesticides, plasticizers, to mention a few, are a rising concern in today's environment. Some of these are commonly used in the domestic setting: cleaning material and cosmetics and they have a known impact on epigenesis and imprinting via perturbation of methylation processes. Pollution from polyaromatic hydrocarbons, particulate matter <10 and <2.5 μm, and ozone released into the air, all affect fertility. Poor food processing management is a source of DNA adduct formation, which impairs the quality of gametes. An important concern is the nanoparticles that are present in food and are thought to induce oxidative stress. Now is the time to take a step backward. Global management of the environment and food production is required urgently to protect the fertility of future generations.
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Affiliation(s)
- Yves Menezo
- Scientific Consultant Assited Reproductive Technology, Laboratoire Clement, Paris, France.,Scientific Consultant Assited Reproductive Technology, London Fertility Associates, London, UK
| | - Brian Dale
- Head of the ART and Genetic Program, Clinica Villa del Sole, Napoli, Italy
| | - Kay Elder
- Scientific Consultant, Bourn Hall Clinic, Cambridge, UK
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5
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de Almeida Monteiro Melo Ferraz M, Henning HHW, Ferreira da Costa P, Malda J, Le Gac S, Bray F, van Duursen MBM, Brouwers JF, van de Lest CHA, Bertijn I, Kraneburg L, Vos PLAM, Stout TAE, Gadella BM. Potential Health and Environmental Risks of Three-Dimensional Engineered Polymers. ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS 2018; 5:80-85. [PMID: 29911125 PMCID: PMC5997463 DOI: 10.1021/acs.estlett.7b00495] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 12/30/2017] [Accepted: 01/05/2018] [Indexed: 05/21/2023]
Abstract
Polymer engineering, such as in three-dimensional (3D) printing, is rapidly gaining popularity, not only in the scientific and medical fields but also in the community in general. However, little is known about the toxicity of engineered materials. Therefore, we assessed the toxicity of 3D-printed and molded parts from five different polymers commonly used for prototyping, fabrication of organ-on-a-chip platforms, and medical devices. Toxic effects of PIC100, E-Shell200, E-Shell300, polydimethylsiloxane, and polystyrene (PS) on early bovine embryo development, on the transactivation of estrogen receptors were assessed, and possible polymer-leached components were identified by mass spectrometry. Embryo development beyond the two-cell stage was inhibited by PIC100, E-Shell200, and E-Shell300 and correlated to the released amount of diethyl phthalate and polyethylene glycol. Furthermore, all polymers (except PS) induced estrogen receptor transactivation. The released materials from PIC100 inhibited embryo cleavage across a confluent monolayer culture of oviduct epithelial cells and also inhibited oocyte maturation. These findings highlight the need for cautious use of engineered polymers for household 3D printing and bioengineering of culture and medical devices and the need for the safe disposal of used devices and associated waste.
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Affiliation(s)
| | - Heiko H. W. Henning
- Department
of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
| | - Pedro Ferreira da Costa
- Department
of Orthopedics, Utrecht Medical Center, Utrecht 3584CX, The Netherlands
- Utrecht
Biofabrication Facility, Utrecht Medical
Center, Utrecht 3584CX, The Netherlands
| | - Jos Malda
- Department
of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
- Department
of Orthopedics, Utrecht Medical Center, Utrecht 3584CX, The Netherlands
- Utrecht
Biofabrication Facility, Utrecht Medical
Center, Utrecht 3584CX, The Netherlands
| | - Séverine Le Gac
- Applied
Microfluidics for Bioengineering Research, MESA+ Institute for Nanotechnology
and MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede 7522 NB, The
Netherlands
| | - Fabrice Bray
- Miniaturization
for Synthesis, Analysis and Proteomics, USR CNRS 3290, University of Lille, Lille 59650, France
| | - Majorie B. M. van Duursen
- Institute
for Risk Assessment Sciences, Division of Toxicology and Pharmacology,
Faculty of Veterinary Medicine, Utrecht
University, Utrecht 3584CM, The Netherlands
| | - Jos F. Brouwers
- Department
of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
| | - Chris H. A. van de Lest
- Department
of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
- Department
of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
| | - Ingeborg Bertijn
- Department
of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
- Department
of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
| | - Lisa Kraneburg
- Department
of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
- Department
of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
| | - Peter L. A. M. Vos
- Department
of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
| | - Tom A. E. Stout
- Department
of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
- Department
of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
| | - Barend M. Gadella
- Department
of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
- Department
of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht 3584CM, The Netherlands
- E-mail: . Phone: +31302535386
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6
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Schaefer HR, Myers JL. Guidelines for performing systematic reviews in the development of toxicity factors. Regul Toxicol Pharmacol 2017; 91:124-141. [DOI: 10.1016/j.yrtph.2017.10.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 10/04/2017] [Accepted: 10/06/2017] [Indexed: 12/27/2022]
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Affiliation(s)
- Monice M Fiume
- 1 Senior Director, Cosmetic Ingredient Review, Washington, DC, USA
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8
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Fowles J, Banton M, Klapacz J, Shen H. A toxicological review of the ethylene glycol series: Commonalities and differences in toxicity and modes of action. Toxicol Lett 2017; 278:66-83. [PMID: 28689762 DOI: 10.1016/j.toxlet.2017.06.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2017] [Revised: 05/23/2017] [Accepted: 06/21/2017] [Indexed: 11/27/2022]
Abstract
This review summarizes the hazards, exposure and risk that are associated with ethylene glycols (EGs) in their intended applications. Ethylene glycol (EG; CAS RN 107-21-1) and its related oligomers include mono-, di-, tri-, tetra-, and penta-EG. All of the EGs are quickly and extensively absorbed following ingestion and inhalation, but not by the dermal route. Metabolism involves oxidation to the mono- and dicarboxylic acids. Elimination is primarily through the urine as the parent compound or the monoacid, and, in the case of EG, also as exhaled carbon dioxide. All EGs exert acute toxicity in a similar manner, characterized by CNS depression and metabolic acidosis in humans and rodents; the larger molecules being proportionally less acutely toxic on a strict mg/kg basis. Species differences exist in the metabolism and distribution of toxic metabolites, particularly with the formation of glycolic acids and oxalates (OX) from EG and diethylene glycol (DEG); OX are not formed to a significant degree in higher ethylene glycols. Among rodents, rats are more sensitive than mice, and males more sensitive than females to the acute and repeated-dose toxicity of EG. The metabolic formation of glycolic acid (GA), diglycolic acid (DGA), and OX are associated with nephrotoxicity in humans and rodents following single and repeated exposures. However, physiological and metabolic differences in the rate of formation of GA, DGA and OX and their distribution result in EG and DEG causing embryotoxicity in rats, but not rabbits. This rodent-specific sensitivity indicates that EG and its higher oligomers are not anticipated to be embryotoxic in humans at environmentally relevant doses. None of the compounds present developmental toxicity concerns at doses that do not also cause significant maternal toxicity, nor do any of the EGs cause adverse effects on fertility. The EGs are neither genotoxic nor carcinogenic. A read-across matrix is presented, which considers the common and distinct toxicological properties of each compound. It is concluded that EGs pose no risk to human health as a result of their intended use patterns.
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Affiliation(s)
| | | | | | - Hua Shen
- Shell Oil Company, Houston, TX, USA
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9
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Human embryo cryopreservation: one-step slow freezing does it all? J Assist Reprod Genet 2014; 31:921-5. [PMID: 24752713 DOI: 10.1007/s10815-014-0238-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 04/14/2014] [Indexed: 10/25/2022] Open
Abstract
PURPOSE Previous studies have shown that a modified one-step slow freezing method with higher sucrose concentration (0.2 M) can achieve higher embryo and blastomere survival rates that are comparable to vitrification. However, no study has evaluated the efficacy of a one-step method using commercial slow freezing kit without altering its composition. This retrospective study examines the effects of using 1.5 M PROH with 0.1 M sucrose (F2 medium) alone in a one-step slow freezing method compared to the conventional two-step method. METHODS Cleavage stage embryos from 526 thaw cycles previously cryopreserved by either the conventional two-step slow freezing method or the modified one-step method were studied. The embryo and blastomere survival rates, cleavage rate, clinical pregnancy rate and live birth rate were compared between the two groups. RESULTS The results showed that the embryo survival rate was significantly higher in the modified one-step method compared to the conventional two-step method (86.9 % and 83.1 %, respectively; p = 0.04). Total blastomere survival rate was also significantly increased as a result of the modification (81.0 % versus 76.5 %; p < 0.001). However, there was no statistical difference in the cleavage rates, clinical pregnancy rates (CPR/ET) and live birth rates between the two methods. CONCLUSIONS Slow freezing using the one-step method is superior to the conventional two-step method in terms of embryo and blastomere survival rates without affecting cleavage rate and clinical outcomes. It can be routinely applied to cleavage stage embryo cryopreservation in IVF centres for greater workflow efficiency.
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Ellis-Hutchings RG, Moore NP, Marshall VA, Rasoulpour RJ, Carney EW. Disposition of glycolic acid into rat and rabbit embryos in vitro. Reprod Toxicol 2014; 46:46-55. [PMID: 24598581 DOI: 10.1016/j.reprotox.2014.02.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 12/23/2013] [Accepted: 02/22/2014] [Indexed: 11/25/2022]
Abstract
High dose gavage administration of ethylene glycol (EG) induces teratogenicity in rodents, but not in rabbits, resulting from saturation of intermediate EG metabolism and glycolic acid (GA) accumulation. In vivo, rat embryos sequester GA 2-4-fold higher than maternal blood, a phenomenon absent in rabbits and proposed not to occur in humans. This research explored the mechanisms of GA disposition into rat and rabbit conceptuses using whole embryo culture (WEC). Rat and rabbit embryos concentrated GA from the culture medium. In vitro to in vivo discordance in the rabbit plausibly stemmed from anatomical differences between these models. GA sequestration was attenuated at 4°C in both species. Rat embryos further demonstrated pH-dependence of GA sequestration and inhibition by D-lactic acid. These data suggest GA disposition into rat and rabbit embryos is energy- and pH-dependent, and carrier-mediated. Anatomical and maternal-to-conceptal pH gradient differences likely underlie the lack of enhanced GA disposition in non-rodent species.
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Affiliation(s)
- Robert G Ellis-Hutchings
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland 48674, USA.
| | - Nigel P Moore
- Toxicology and Environmental Research and Consulting, Dow Europe GmbH, Horgen, Switzerland
| | - Valerie A Marshall
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland 48674, USA
| | - Reza J Rasoulpour
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland 48674, USA
| | - Edward W Carney
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland 48674, USA
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Amstislavsky SY, Igonina TN, Rozhkova IN, Brusentsev EY, Rogovaya AA, Ragaeva DS, Naprimerov VA, Litvinova EA, Plyusnina IF, Markel AL. Rederivation by embryo transfer in strains of laboratory mice and rats. RUSSIAN JOURNAL OF GENETICS: APPLIED RESEARCH 2013; 3:305-315. [DOI: 10.1134/s2079059713040023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/04/2023]
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12
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Edgar DH, Gook DA. A critical appraisal of cryopreservation (slow cooling versus vitrification) of human oocytes and embryos. Hum Reprod Update 2012; 18:536-54. [PMID: 22537859 DOI: 10.1093/humupd/dms016] [Citation(s) in RCA: 215] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Vitrification is now a commonly applied technique for cryopreservation in assisted reproductive technology (ART) replacing, in many cases, conventional slow cooling methodology. This review examines evidence relevant to comparison of the two approaches applied to human oocytes and embryos at different developmental stages. METHODS Critical review of the published literature using PubMed with particular emphasis on studies which include data on survival and implantation rates, data from fresh control groups and evaluation of the two approaches in a single setting. RESULTS Slow cooling is associated with lower survival rates and compromised development relative to vitrification when applied to metaphase II (MII) oocytes, although the vitrification results have predominantly been obtained using direct contact with liquid nitrogen and there is some evidence that optimal protocols for slow cooling of MII oocytes are yet to be established. There are no prospective randomized controlled trials (RCTs) which support the use of either technique with pronuclear oocytes although vitrification has become the method of choice. Optimal slow cooling, using modifications of traditional methodology, and vitrification can result in high survival rates of early embryos, which implant at the same rate as equivalent fresh counterparts. Many studies report high survival and implantation rates following vitrification of blastocysts. Although slow cooling of blastocysts has been reported to be inferior in some studies, others comparing the two approaches in the same clinical setting have demonstrated comparable results. The variation in the extent of embryo selection applied in studies can lead to apparent differences in clinical efficiency, which may not be significant if expressed on a 'per oocyte used' basis. CONCLUSIONS Available evidence suggests that vitrification is the current method of choice when cryopreserving MII oocytes. Early cleavage stage embryos can be cryopreserved with equal success using slow cooling and vitrification. Successful blastocyst cryopreservation may be more consistently achieved with vitrification but optimal slow cooling can produce similar results. There are key limitations associated with the available evidence base, including a paucity of RCTs, limited reporting of live birth outcomes and limited reporting of detail which would allow assessment of the impact of differences in female age. While vitrification has a clear role in ART, we support continued research to establish optimal slow cooling methods which may assist in alleviating concerns over safety issues, such as storage, transport and the use of very high cryoprotectant concentrations.
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Affiliation(s)
- David H Edgar
- Reproductive Services/Melbourne IVF, Royal Women's Hospital, Parkville, Victoria 3052, Australia
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13
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Carney EW, Tornesi B, Liberacki AB, Markham DA, Weitz KK, Luders TM, Studniski KG, Blessing JC, Gies RA, Corley RA. The impact of dose rate on ethylene glycol developmental toxicity and pharmacokinetics in pregnant CD rats. Toxicol Sci 2010; 119:178-88. [PMID: 20952502 DOI: 10.1093/toxsci/kfq310] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
High-dose bolus exposure of rats to ethylene glycol (EG) causes developmental toxicity mediated by a metabolite, glycolic acid (GA), whose levels increase disproportionately when its metabolism is saturated. However, low-level exposures that do not saturate GA metabolism have a low potential for developmental effects. Toward the goal of developing EG risk assessments based on internal dose metrics, this study examined the differences between fast (bolus) and slow (continuous infusion) dose-rate exposures to EG on developmental outcome and pharmacokinetics. Time-mated female CD rats received sc bolus injections of 0, 1000, or 2000 mg/kg/day of EG on gestation day (GD) 6-15 once daily, whereas three corresponding groups were given the same daily doses as an infusion administered continuously from GD 6-15 via an sc implantable pump. In the sc bolus groups, increases in 11 fetal malformations (major defects) and 12 variations (minor alterations) were seen at the 2000 mg/kg/day dose level, whereas increases in 2 malformations and 2 variations occurred at 1000 mg/kg/day. In contrast, equivalent daily doses of EG given slowly via infusion did not cause any developmental effects. A pharmacokinetics time course was then conducted to compare GD 11-12 kinetics from oral bolus (gavage) exposure versus sc infusion of EG. Although dose rate had a modest impact (8- to 11-fold difference) on peak EG levels, peak levels of GA in maternal blood, kidney, embryo, and exocoelomic fluid were 59, 100, 49, and 56 times higher, respectively, following gavage versus the same dose given by infusion. These data illustrate how high-dose bolus exposure to EG causes a dramatic shift to nonlinear GA kinetics, an event which is highly unlikely to occur following exposures to humans associated with consumer and worker uses.
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Affiliation(s)
- Edward W Carney
- Toxicology & Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan 48674, USA.
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14
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One decade of experience with vitrification of human embryos in straws, hemi-straws, and high security vitrification straws. ACTA ACUST UNITED AC 2010. [DOI: 10.3109/9780203090022.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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15
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Ellis-Hutchings RG, Carney EW. Whole embryo culture: a “New” technique that enabled decades of mechanistic discoveries. ACTA ACUST UNITED AC 2010; 89:304-12. [DOI: 10.1002/bdrb.20263] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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16
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Kader A, Agarwal A, Abdelrazik H, Sharma RK, Ahmady A, Falcone T. Evaluation of post-thaw DNA integrity of mouse blastocysts after ultrarapid and slow freezing. Fertil Steril 2009; 91:2087-94. [DOI: 10.1016/j.fertnstert.2008.04.049] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 04/22/2008] [Accepted: 04/22/2008] [Indexed: 11/30/2022]
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Carney EW, Tornesi B, Markham DA, Rasoulpour RJ, Moore N. Species-specificity of ethylene glycol-induced developmental toxicity: toxicokinetic and whole embryo culture studies in the rabbit. ACTA ACUST UNITED AC 2009; 83:573-81. [PMID: 19025792 DOI: 10.1002/bdrb.20178] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
High-dose gavage exposure to ethylene glycol (EG) is teratogenic in rats, but not rabbits. To investigate the reason for this species difference, toxicokinetic and whole embryo culture (WEC) studies were conducted in gestation day 9 New Zealand White rabbits, and the data compared to very similar data previously generated in pregnant rats. In the toxicokinetic study, maximal levels of unchanged EG in rabbits were comparable to those reported for rats. However, maximal levels of EG's teratogenic metabolite, glycolic acid (GA), in rabbit maternal blood and embryo were only 46% and 10% of the respective levels in rats. The toxicokinetic profile suggested that the lower GA levels in rabbits were due to a slower rate of maternal metabolism of EG to GA, slow uptake of GA into the yolk sac cavity fluid which surrounds the embryo, and negligible transfer via the visceral yolk sac (VYS) placenta. In the WEC study, exposure of rabbit conceptuses to high concentrations (< or = 12.5 mM) of GA was without effect, which contrasts with reported effects in rat WEC at > or = 3 mM. Overall, these data implicate toxicokinetics as an important factor underlying the species difference, although intrinsic insensitivity of the rabbit embryo might also be involved. Integration of these findings with published human data suggest that the rabbit is the more relevant model for human EG exposure, based on the negligible role of the rabbit VYS in placental transfer (humans lack a VYS) and similar rates of EG metabolism and extraembryonic fluid turnover.
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Affiliation(s)
- Edward W Carney
- Toxicology & Environmental Research and Consulting, The Dow Chemical Company, Midland, MI 48674, USA.
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18
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Saki G, Rahim F, Moradi L. The study of developmental capacity of vitrified mouse blastocysts in different straws after transfer to mouse pseudo pregnant. Pak J Biol Sci 2008; 11:1809-14. [PMID: 18817221 DOI: 10.3923/pjbs.2008.1809.1814] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Vitrification is the commonly used method for long-term storage of pre-implantation mammalian embryos. It is an essential part of assisted reproductive technologies. The re-expansion rate, pregnancy and birth rate of vitrified blastocysts using CPS were compared with OPS and Conventional Straw. Female NMRI mice were injected with Gonadotrophins in order induce them for super ovulation. At that time the mice were sacrified by cervical dislocation and dissected of mouse abdomen. The uterine horns were existed blastocysts were collected in PBS and randomly allocated to four groups: vitrification in CPS, conventional straw, OPS and untreated controls. The vitrification solution was EFS40%. After storage for 1 month in liquid nitrogen, the blastocysts were thawed in 0.5 M sucrose for in vitro culture in M16 medium. After 6 h of culture, the numbers of expanded blastocysts was recorded and ready for transfer to uterus of pseudo pregnant mouse. The re-expansion rate of the CPS group (72.1%) was significantly higher (p < 0.05) than OPS (52.55) and C.S. (38.6%) groups. The pregnancy (70%) and birth rate (45%) of blastocysts in CPS were similar to those of fresh blastocysts (80% and 45.5%) and the pregnancy (10%) and birth rate (5.1%) in Conventional Straws lower than OPS (20 and 7.5%), but were not significantly different. Mouse blastocysts vitrified using CPS had a better result compared with OPS and Conventional Straw. The value of CPS for vitrification of blastocysts may also merit investigation.
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Affiliation(s)
- Ghasem Saki
- Laboratory of Cell Culture, Faculty of Medicine, Ahwaz Jondishapour University of Medical Sciences (AJUMS), Ahwaz, Iran
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19
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Corley RA, Meek ME, Carney EW. Mode of Action: Oxalate Crystal-Induced Renal Tubule Degeneration and Glycolic Acid-Induced Dysmorphogenesis—Renal and Developmental Effects of Ethylene Glycol. Crit Rev Toxicol 2008; 35:691-702. [PMID: 16417036 DOI: 10.1080/10408440591007322] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Ethylene glycol can cause both renal and developmental toxicity, with metabolism playing a key role in the mode of action (MOA) for each form of toxicity. Renal toxicity is ascribed to the terminal metabolite oxalic acid, which precipitates in the kidney in the form of calcium oxalate crystals and is believed to cause physical damage to the renal tubules. The human relevance of the renal toxicity of ethylene glycol is indicated by the similarity between animals and humans of metabolic pathways, the observation of renal oxalate crystals in toxicity studies in experimental animals and human poisonings, and cases of human kidney and bladder stones related to dietary oxalates and oxalate precursors. High-dose gavage exposures to ethylene glycol also cause axial skeletal defects in rodents (but not rabbits), with the intermediary metabolite, glycolic acid, identified as the causative agent. However, the mechanism by which glycolic acid perturbs development has not been investigated sufficiently to develop a plausible hypothesis of mode of action, nor have any cases of ethylene glycol-induced developmental effects been reported in humans. Given this, and the variations in sensitivity between animal species in response, the relevance to humans of ethylene glycol-induced developmental toxicity in animals is unknown at this time.
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Affiliation(s)
- Richard A Corley
- Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
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20
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Upadhyay S, Carstens J, Klein D, Faller TH, Halbach S, Kirchinger W, Kessler W, Csanády GA, Filser JG. Inhalation and epidermal exposure of volunteers to ethylene glycol: kinetics of absorption, urinary excretion, and metabolism to glycolate and oxalate. Toxicol Lett 2008; 178:131-41. [PMID: 18430528 DOI: 10.1016/j.toxlet.2008.02.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Revised: 02/22/2008] [Accepted: 02/22/2008] [Indexed: 11/17/2022]
Abstract
Ethylene glycol (EG) is a widely used liquid. Limited data are published regarding inhaled EG and no data regarding transdermal EG uptake in humans. In order to gain information on the quantitative fate of EG, four male volunteers inhaled between 1340 and 1610 micromol vaporous 13C-labeled EG (13C2-EG) for 4h. Separately, three of these subjects were epidermally exposed for up to 6h to liquid 13C2-EG (skin area 66 cm2). Plasma concentrations and urinary amounts of 13C2-EG were determined by gas chromatography with mass selective detection. Additionally, plasma was assayed for 13C-labeled glycolic acid 13C2-GA) and urine for 13C2-GA and 13C-labeled oxalic acid (13C2-OA). Both EG metabolites were nephrotoxic in animals and humans and embryotoxic in rodents. 13C-labels enabled to differentiate from also determined endogenous EG, glycolic acid (GA), and oxalic acid (OA). Of 13C2-EG inhaled, 5.5+/-3.0%, 0.77+/-0.15%, and 0.10+/-0.12% were detected in urine as 13C2-EG, 13C2-GA, and 13C2-OA, respectively. The skin permeability constant of liquid EG was 2.7 x 10(-5)+/-0.5 x 10(-5)cm/h. Of the dose taken up transdermally, 8.1+/-3.2% and up to 0.4% were excreted in urine as 13C2-EG and 13C2-GA, respectively. It is calculated that equally long-lasting exposure to 10 ppm vaporous EG or wetting of both hands by liquid EG leads to about the same body burden by EG and metabolites. The amounts of GA and OA excreted daily in urine as a result of exposure (8h/day) to 10 ppm EG are about 15% and 2%, respectively, of those excreted from naturally occurring endogenous GA and OA.
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Affiliation(s)
- Swapna Upadhyay
- Institute of Toxicology, Helmholtz Zentrum München, German Research Center for Environmental Health, D-85764 Neuherberg, Germany
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21
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Siu TL, Morley JW, Coroneo MT. Toxicology of the retina: advances in understanding the defence mechanisms and pathogenesis of drug- and light-induced retinopathy. Clin Exp Ophthalmol 2008; 36:176-85. [DOI: 10.1111/j.1442-9071.2008.01699.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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22
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Huang JYJ, Chung JT, Tan SL, Chian RC. High survival and hatching rates following vitrification of embryos at blastocyst stage: a bovine model study. Reprod Biomed Online 2007; 14:464-70. [PMID: 17425829 DOI: 10.1016/s1472-6483(10)60894-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Cryopreservation of embryos at the blastocyst stage may provide an effective method to increase the cumulative pregnancy rate for each treatment cycle of ovarian-stimulated IVF. The objective of this study was to evaluate the survival rate and hatching rate of bovine blastocysts following vitrification using a method designed for oocytes, with a view to introducing this methodology into human assisted reproduction technology and reproductive medicine. Bovine blastocysts were produced from abattoir materials subjected to in-vitro maturation and in-vitro fertilization. Survival rate of the bovine blastocysts was 100% (94/94) following vitrification using a method designed for oocyte cryopreservation. There was no difference in the hatching rate of the bovine blastocysts between control (62.5%: 60/96) and vitrified (61.7%: 58/94) groups. The number of dead cells in the blastocysts was not significantly different between control (5.0 +/- 2.9) and vitrified (9.5 +/- 4.0) groups. In conclusion, the results of this study indicate that bovine blastocysts can be vitrified successfully using a procedure designed for oocyte cryopreservation. It is possible that this method may also be successful for the cryopreservation of human embryos. A further study into this is currently being organized.
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Affiliation(s)
- Jack Y J Huang
- Department of Obstetrics and Gynecology, McGill University, Montreal, Canada H3A 1A1
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23
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Vanderzwalmen P, Zech N, Greindl AJ, Ectors F, Lejeune B. Cryopréservation des embryons humains par vitrification. ACTA ACUST UNITED AC 2006; 34:760-9. [PMID: 16959523 DOI: 10.1016/j.gyobfe.2006.07.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2006] [Accepted: 07/21/2006] [Indexed: 11/19/2022]
Abstract
Vitrification is a cryopreservation strategy where cells are converted into a glass-like amorphous solid which is free of any crystalline structure. Such process is achieved by a combination of high concentration of cryoprotectant and an extremely high cooling rate. In the last years, survival rates of up to 80% after thawing and pregnancy rates of almost 30% could be achieved after transfer of vitrified embryos at the zygote, cleavage, morula and blastocyst stages. Also deliveries of healthy babies have been reported numerous times. To this day, a limited interest in this technique can be noted. The explanation may lye in the apprehension of many ART units regarding exposure of embryos to high concentrations of cryoprotectants and storage in non sterile conditions. The aim of the first part of this article, is to analyse if such fears are justified on the basis that vitrification mimics conditions already in use for many years in slow-cooling procedures where cells are plunged into liquid nitrogen at around -30 degrees C and secondly since storage of embryos are now possible in high aseptic conditions. In the second part, results on survival after thawing, pregnancy rates and baby take home rates of vitrified embryos will be presented and the problems associated with vitrification of blastocysts will be discussed.
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Affiliation(s)
- P Vanderzwalmen
- Institute for reproductive medicine and endocrinology, Ramerstr. 2, Bregenz, Austria.
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24
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Vajta G, Nagy ZP. Are programmable freezers still needed in the embryo laboratory? Review on vitrification. Reprod Biomed Online 2006; 12:779-96. [PMID: 16792858 DOI: 10.1016/s1472-6483(10)61091-7] [Citation(s) in RCA: 249] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The predictable answer to the provocative question of whether programmable freezers are still needed in the embryo laboratory is an even more provocative 'no'. However, such a radical statement needs strong support. Based on the extensive literature of the past 5 years, the authors collected arguments either supporting or contradicting their opinion. After an overview of the causes of cryoinjuries and strategies to eliminate them, the evolution of vitrification methods is discussed. Special attention is paid to the biosafety issues. The authors did not find any circumstance in oocyte or embryo cryopreservation where slow freezing offers considerable advantages compared with vitrification. In contrast, the overwhelming majority of published data prove that the latest vitrification methods are more efficient and reliable than any version of slow freezing. Application of the proper vitrification methods increases the efficiency of long-term storage of stem cells and opens new perspectives in cryopreservation of oocytes, both for IVF and somatic cell nuclear transfer. However, lack of support from regulatory authorities, and conservative approachs regarding novel techniques can slow down the implementation of vitrification. The opinion of the authors is that vitrification is the future of cryopreservation. The public have the final say in whether they want and allow this future to arrive.
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Affiliation(s)
- Gábor Vajta
- Population Genetics and Embryology, Department of Genetics and Biotechnology, Danish Institute of Agricultural Sciences, Research Centre Foulum, DK-8830 Tjele, Denmark.
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25
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Harish Prashanth KV, Tharanathan RN. Crosslinked chitosan—preparation and characterization. Carbohydr Res 2006; 341:169-73. [PMID: 16297896 DOI: 10.1016/j.carres.2005.10.016] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Revised: 10/21/2005] [Accepted: 10/30/2005] [Indexed: 11/18/2022]
Abstract
Chitosan undergoes radical-induced depolymerization in the presence of potassium persulfate at 60 degrees C, leading to extensive crosslinking of the fragmented chains on subsequent cooling at 4 degrees C. As a result, a possible conformational change leading to higher crystallinity, as evidenced by IR, X-ray and 13C NMR was observed.
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Affiliation(s)
- Keelara V Harish Prashanth
- Department of Biochemistry and Nutrition, Central Food Technological Research Institute, Mysore 570020, India
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26
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Corley RA, Bartels MJ, Carney EW, Weitz KK, Soelberg JJ, Gies RA, Thrall KD. Development of a Physiologically Based Pharmacokinetic Model for Ethylene Glycol and Its Metabolite, Glycolic Acid, in Rats and Humans. Toxicol Sci 2005; 85:476-90. [PMID: 15716482 DOI: 10.1093/toxsci/kfi119] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
An extensive database on the toxicity and modes of action of ethylene glycol (EG) has been developed over the past several decades. Although renal toxicity has long been recognized as a potential outcome, in recent years developmental toxicity, an effect observed only in rats and mice, has become the subject of extensive research and regulatory reviews to establish guidelines for human exposures. The developmental toxicity of EG has been attributed to the intermediate metabolite, glycolic acid (GA), which can become a major metabolite when EG is administered to rats and mice at high doses and dose rates. Therefore, a physiologically based pharmacokinetic (PBPK) model was developed to integrate the extensive mode of action and pharmacokinetic data on EG and GA for use in developmental risk assessments. The resulting PBPK model includes inhalation, oral, dermal, intravenous, and subcutaneous routes of administration. Metabolism of EG and GA were described in the liver with elimination via the kidneys. Metabolic rate constants and partition coefficients for EG and GA were estimated from in vitro studies. Other biochemical constants were optimized from appropriate in vivo pharmacokinetic studies. Several controlled rat and human metabolism studies were used to validate the resulting PBPK model. When internal dose surrogates were compared in rats and humans over a broad range of exposures, it was concluded that humans are unlikely to achieve blood levels of GA that have been associated with developmental toxicity in rats following occupational or environmental exposures.
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Affiliation(s)
- R A Corley
- Battelle Pacific Northwest Division, Richland, Washington 99352, USA.
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27
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NTP-CERHR Expert Panel report on the reproductive and developmental toxicity of ethylene glycol. Reprod Toxicol 2004; 18:457-532. [PMID: 15135850 DOI: 10.1016/j.reprotox.2004.01.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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28
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Abstract
Blastocyst are preimplantation embryos that have successfully passed the critical step of genomic activation and have so a high developmental potential, thus allowing to reduce the number of embryos transferred. Blastocyst culture and freezing have really started in IVF programs in the early nineties, when it was possible to obtain good blastocysts (essentially using coculture) on a large scale. Blastocysts freezing has been performed since the beginning using glycerol as cryoprotectant in slow protocols. The transition from coculture to sequential media has been a little bit delicate with a drop in the results. Few modifications including a change in the freezing curves and thawing at 37 degrees C have allowed to reach the same results with the two culture techniques. Vitrification with ethylene glycol (EG) has been proposed recently. However, the toxicity of the metabolites of EG for rat embryos has to be considered before moving to this technology on a large scale.
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Affiliation(s)
- Yves J R Ménézo
- Laboratoire Marcel Mérieux, 1 Rue Laborde, 69500 Bron, France.
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29
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Abstract
Embryo freezing is a mandatory tool in IVF technology as controlled ovarian hyperstimulation usually leads to extra embryos which are not transferred. One dilemma is the embryonic stage at which the embryos are to be frozen. Early stage freezing (PNs or cleavage stage) leads to a two step selection: at the time of thawing and a few hours or a day after. Then the recovering embryos are submitted to the classical in vitro developmental arrests in relation with maternal, paternal and cytogenetic factors. The "take home baby rate" per frozen embryo is low, rarely over 5%. Blastocyst have overcome the blocks in vitro: a first selection has already been made. The quality of freezing at this stage depends greatly on the culture conditions. It allows freezing of fewer embryos, but with higher yields: a >10% take home baby rate can be expected. It is clear to us that vitrification, beside the technical problems, has to be handled with care, especially if ethylene glycol (EG) is used. Metabolic products of EG might have negative effects on organogenesis.
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Affiliation(s)
- Y Menezo
- Laboratoire Marcel Mérieux, Institute Rhonalpin, 1 Rue Laborde, 69500 Bron, France.
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30
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Berger J, Reist M, Mayer JM, Felt O, Peppas NA, Gurny R. Structure and interactions in covalently and ionically crosslinked chitosan hydrogels for biomedical applications. Eur J Pharm Biopharm 2004; 57:19-34. [PMID: 14729078 DOI: 10.1016/s0939-6411(03)00161-9] [Citation(s) in RCA: 1261] [Impact Index Per Article: 63.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
This review presents a critical analysis of covalently and ionically crosslinked chitosan hydrogels and related networks for medical or pharmaceutical applications. The structural basis of these hydrogels is discussed with reference to the specific chemical interactions, which dictate gel formation. The synthesis and chemistry of these hydrogels is discussed using specific pharmaceutical examples. Covalent crosslinking leads to formation of hydrogels with a permanent network structure, since irreversible chemical links are formed. This type of linkage allows absorption of water and/or bioactive compounds without dissolution and permits drug release by diffusion. pH-controlled drug delivery is made possible by the addition of another polymer. Ionically crosslinked hydrogels are generally considered as biocompatible and well-tolerated. Their non-permanent network is formed by reversible links. Ionically crosslinked chitosan hydrogels exhibit a higher swelling sensitivity to pH changes compared to covalently crosslinked chitosan hydrogels. This extends their potential application, since dissolution can occur in extreme acidic or basic pH conditions.
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Affiliation(s)
- J Berger
- School of Pharmacy, University of Lausanne, Lausanne, Switzerland
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