The Experts below are selected from a list of 23520 Experts worldwide ranked by ideXlab platform
J. Philippe Kretzer - One of the best experts on this subject based on the ideXlab platform.
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How do gait frequency and Serum-Replacement interval affect polyethylene wear in knee-wear simulator tests?
Journal of Materials Science: Materials in Medicine, 2014Co-Authors: Jörn Reinders, Robert Sonntag, J. Philippe KretzerAbstract:Polyethylene wear (PE) is known to be a limiting factor in total joint Replacements. However, a standardized wear test (e.g. ISO standard) can only replicate the complex in vivo loading condition in a simplified form. In this study, two different parameters were analyzed : (a) Bovine Serum, as a substitute for synovial fluid, is typically replaced every 500,000 cycles. However, a continuous regeneration takes place in vivo. How does Serum-Replacement interval affect the wear rate of total knee Replacements? (b) Patients with an artificial joint show reduced gait frequencies compared to standardized testing. What is the influence of a reduced frequency? Three knee wear tests were run: (a) reference test (ISO), (b) testing with a shortened lubricant Replacement interval, (c) testing with reduced frequency. The wear behavior was determined based on gravimetric measurements and wear particle analysis. The results showed that the reduced test frequency only had a small effect on wear behavior. Testing with 1 Hz frequency is therefore a valid method for wear testing. However, testing with a shortened Replacement interval nearly doubled the wear rate. Wear particle analysis revealed only small differences in wear particle size between the different tests. Wear particles were not linearly released within one Replacement interval. The ISO standard should be revised to address the marked effects of lubricant Replacement interval on wear rate.
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How do gait frequency and Serum-Replacement interval affect polyethylene wear in knee-wear simulator tests?
Journal of Materials Science: Materials in Medicine, 2014Co-Authors: Jörn Reinders, Robert Sonntag, J. Philippe KretzerAbstract:Polyethylene wear (PE) is known to be a limiting factor in total joint Replacements. However, a standardized wear test (e.g. ISO standard) can only replicate the complex in vivo loading condition in a simplified form. In this study, two different parameters were analyzed : (a) Bovine Serum, as a substitute for synovial fluid, is typically replaced every 500,000 cycles. However, a continuous regeneration takes place in vivo. How does Serum-Replacement interval affect the wear rate of total knee Replacements? (b) Patients with an artificial joint show reduced gait frequencies compared to standardized testing. What is the influence of a reduced frequency? Three knee wear tests were run: (a) reference test (ISO), (b) testing with a shortened lubricant Replacement interval, (c) testing with reduced frequency. The wear behavior was determined based on gravimetric measurements and wear particle analysis. The results showed that the reduced test frequency only had a small effect on wear behavior. Testing with 1 Hz frequency is therefore a valid method for wear testing. However, testing with a shortened Replacement interval nearly doubled the wear rate. Wear particle analysis revealed only small differences in wear particle size between the different tests. Wear particles were not linearly released within one Replacement interval. The ISO standard should be revised to address the marked effects of lubricant Replacement interval on wear rate.
Buom-yong Ryu - One of the best experts on this subject based on the ideXlab platform.
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Effect of Serum Replacement on murine spermatogonial stem cell cryopreservation.
Theriogenology, 2020Co-Authors: Sang-eun Jung, Ju-hee Jin, Jin Seop Ahn, Yong-hee Kim, Min-hyung Yun, Seo-hee Kim, Bang-jin Kim, Buom-yong RyuAbstract:Abstract Cryopreservation of spermatogonial stem cells (SSCs) is a necessity to preserve the genetic information of valuable livestock herds and to produce transgenic animals. However, Serum, a key component that allows efficient cryopreservation, has many limitations attributed to its undefined composition, inter-batch variations, and contamination potential. Therefore, we aimed to establish a method for Serum-free cryopreservation of SSCs. To evaluate the cryopreservation efficiency of Serum Replacements, we assessed the recovery rate, relative proliferation potential, proliferation capacity, and apoptosis capacity. SSCs were characterized, and their functional activity was determined through immunofluorescence, RT-qPCR, and spermatogonial transplantation. The efficiency of each Serum Replacement was compared to that of the negative control (10% DMSO in DPBS) and positive control (10% DMSO and 40% FBS in DPBS). Our results indicated that cryopreservation with 5% human Serum albumin (rHSA) exhibited a higher relative proliferation potential (274.0 ± 13.4%) than with DMSO control (100 ± 8.6%), with no significant difference from the 40% FBS (190.0 ± 20.1%). Moreover, early apoptosis also significantly decreased to a greater extent with 5% rHSA (5.1 ± 0.7%) than with DMSO control (12.9 ± 0.8%) and was at a level comparable to the 40% FBS (4.9 ± 0.8%). In addition, the SSCs cryopreserved with 5% rHSA exhibited normal self-renewal and differentiation abilities. In conclusion, 5% rHSA is a potential Serum Replacement for SSC cryopreservation, with properties comparable to that of Serum. These results would contribute to the application of SSCs in improving livestock and in future clinical trials for human infertility treatment.
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Effect of Antioxidants and Apoptosis Inhibitors on Cryopreservation of Murine Germ Cells Enriched for Spermatogonial Stem Cells.
PloS one, 2016Co-Authors: Byung-gak Kim, Sang-eun Jung, Yong-hee Kim, Bang-jin Kim, Yong-an Lee, Myeong-geol Pang, Buom-yong RyuAbstract:Spermatogonial stem cells (SSCs) are germline stem cells that serve as the foundation of spermatogenesis to maintain fertility throughout a male’s lifetime. To treat male infertility using stem cell banking systems and transplantation, it is important to be able to preserve SSCs for long periods of time. Therefore, this study was conducted to develop an optimal cryopreservation protocol for SSCs using antioxidants and apoptosis inhibitors in freezing medium. No differences were observed compared to controls when SSCs were cryopreserved in the presence of apoptosis inhibitors by themselves. However, mouse germ cells cryopreserved in basal medium containing the antioxidant hypotaurine (14 mM) resulted in significantly greater proliferation potential and mitochondrial activity. Furthermore, treatment groups with combinations containing 200 mM trehalose and 14 mM hypotaurine showed higher proliferation rates compared to controls. In addition, several Serum free conditions were evaluated for SSC cryopreservation. Treatment media containing 10% or 20% knockout Serum Replacement resulted in similar cryopreservation results compared to media containing FBS. SSC transplantation was also performed to confirm the functionality of SSCs frozen in 14 mM hypotaurine. Donor SSCs formed normal spermatogenic colonies and sperm in the recipient testis. These data indicate that inclusion of 14 mM hypotaurine in cryopreservation media is an effective way to efficiently cryopreserve germ cells enriched for SSCs and that knockout Serum Replacement can replace FBS in germ cell cryopreservation media.
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Effect of sugar molecules on the cryopreservation of mouse spermatogonial stem cells
Fertility and sterility, 2014Co-Authors: Yong-an Lee, Yong-hee Kim, Bang-jin Kim, Ki-jung Kim, Mi-seon Jung, Byung-gak Kim, Buom-yong RyuAbstract:Objective To study the influence of sugars and establish a Serum-free freezing method for the cryopreservation of spermatogonial stem cells (SSCs). Design Animal study. Setting University laboratory. Animal(s) C57BL/6-TgEGFP, C57BL/6 mice. Intervention(s) Germ cells enriched from testis cells were frozen using standard freezing medium containing sugars, including monosaccharides, disaccharides, and trisaccharides at 50, 100, and 200 mM, respectively. To study the feasibility of establishing a Serum-free freezing method, fetal bovine Serum was substituted with knockout Serum Replacement. Main Outcome Measure(s) Freeze-thawed germ cells were evaluated for recovery rate, proliferation capacity, and stem cell activity after transplantation to recipient testes. Result(s) Supplementation of freezing medium with 200 mM disaccharide is an effective method for cryopreservation of SSCs. Trehalose is the most effective cryoprotectant among all the sugars tested and only lactose was comparable to trehalose. Our proliferation and transplantation data show that Serum-free freezing can be achieved in freezing medium supplemented with 200 mM trehalose, 10% knockout Serum Replacement, and 10% dimethyl sulfoxide (DMSO) for cryopreservation of SSCs. Conclusion(s) These findings raise the possibility of effectively banking frozen SSCs from various species, including humans, in a traditional Serum-free medium for germ cell research and male infertility treatments.
Jörn Reinders - One of the best experts on this subject based on the ideXlab platform.
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How do gait frequency and Serum-Replacement interval affect polyethylene wear in knee-wear simulator tests?
Journal of Materials Science: Materials in Medicine, 2014Co-Authors: Jörn Reinders, Robert Sonntag, J. Philippe KretzerAbstract:Polyethylene wear (PE) is known to be a limiting factor in total joint Replacements. However, a standardized wear test (e.g. ISO standard) can only replicate the complex in vivo loading condition in a simplified form. In this study, two different parameters were analyzed : (a) Bovine Serum, as a substitute for synovial fluid, is typically replaced every 500,000 cycles. However, a continuous regeneration takes place in vivo. How does Serum-Replacement interval affect the wear rate of total knee Replacements? (b) Patients with an artificial joint show reduced gait frequencies compared to standardized testing. What is the influence of a reduced frequency? Three knee wear tests were run: (a) reference test (ISO), (b) testing with a shortened lubricant Replacement interval, (c) testing with reduced frequency. The wear behavior was determined based on gravimetric measurements and wear particle analysis. The results showed that the reduced test frequency only had a small effect on wear behavior. Testing with 1 Hz frequency is therefore a valid method for wear testing. However, testing with a shortened Replacement interval nearly doubled the wear rate. Wear particle analysis revealed only small differences in wear particle size between the different tests. Wear particles were not linearly released within one Replacement interval. The ISO standard should be revised to address the marked effects of lubricant Replacement interval on wear rate.
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How do gait frequency and Serum-Replacement interval affect polyethylene wear in knee-wear simulator tests?
Journal of Materials Science: Materials in Medicine, 2014Co-Authors: Jörn Reinders, Robert Sonntag, J. Philippe KretzerAbstract:Polyethylene wear (PE) is known to be a limiting factor in total joint Replacements. However, a standardized wear test (e.g. ISO standard) can only replicate the complex in vivo loading condition in a simplified form. In this study, two different parameters were analyzed : (a) Bovine Serum, as a substitute for synovial fluid, is typically replaced every 500,000 cycles. However, a continuous regeneration takes place in vivo. How does Serum-Replacement interval affect the wear rate of total knee Replacements? (b) Patients with an artificial joint show reduced gait frequencies compared to standardized testing. What is the influence of a reduced frequency? Three knee wear tests were run: (a) reference test (ISO), (b) testing with a shortened lubricant Replacement interval, (c) testing with reduced frequency. The wear behavior was determined based on gravimetric measurements and wear particle analysis. The results showed that the reduced test frequency only had a small effect on wear behavior. Testing with 1 Hz frequency is therefore a valid method for wear testing. However, testing with a shortened Replacement interval nearly doubled the wear rate. Wear particle analysis revealed only small differences in wear particle size between the different tests. Wear particles were not linearly released within one Replacement interval. The ISO standard should be revised to address the marked effects of lubricant Replacement interval on wear rate.
Derrick E. Rancourt - One of the best experts on this subject based on the ideXlab platform.
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An Effective and Reliable Xeno-free Cryopreservation Protocol for Single Human Pluripotent Stem Cells.
Methods in molecular biology (Clifton N.J.), 2016Co-Authors: Guoliang Meng, Anna Poon, Shiying Liu, Derrick E. RancourtAbstract:Efficient cryopreservation of human pluripotent stem cells (hPSCs) in chemically defined, xeno-free conditions is highly desirable for medical research and clinical applications such as cell-based therapies. Here we present a simple and effective slow freezing-rapid thawing protocol for the cryopreservation of feeder-free, single hPSCs. This cryopreservation protocol involves the supplementation of 10 % dimethyl sulfoxide (DMSO) and 10 μM Rho-associated kinase inhibitor Y-27632 into two types of xeno-free, defined media supplements (Knockout Serum Replacement and TeSR2). High post-thaw cell recovery (~90 %) and cell expansion (~70 %) can be achieved using this protocol. The cryopreserved single cells retain the morphological characteristics of hPSCs and differentiation capabilities of pluripotent stem cells.
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a novel method for generating xeno free human feeder cells for human embryonic stem cell culture
Stem Cells and Development, 2008Co-Authors: Guoliang Meng, Roman Krawetz, Michael Chan, Judy Chernos, Derrick E. RancourtAbstract:Long-term cultures of human embryonic stem (hES) cells require a feeder layer for maintaining cells in an undifferentiated state and increasing karyotype stability. In routine hES cell culture, mouse embryonic fibroblast (MEF) feeders and animal component-containing media (FBS or Serum Replacement) are commonly used. However, the use of animal materials increases the risk of transmitting pathogens to hES cells and therefore is not optimal for use in cultures intended for human transplantation. There are other limitations with conventional feeder cells, such as MEFs, which have a short lifespan and can only be propagated five to six passages before senescing. Several groups have investigated maintaining existing hES cell lines and deriving new hES cell lines on human feeder layers. However, almost all of these human source feeder cells employed in previous studies were derived and cultured in animal component conditions. Even though one group previously reported the derivation and culture of human foreskin...
Robert Sonntag - One of the best experts on this subject based on the ideXlab platform.
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How do gait frequency and Serum-Replacement interval affect polyethylene wear in knee-wear simulator tests?
Journal of Materials Science: Materials in Medicine, 2014Co-Authors: Jörn Reinders, Robert Sonntag, J. Philippe KretzerAbstract:Polyethylene wear (PE) is known to be a limiting factor in total joint Replacements. However, a standardized wear test (e.g. ISO standard) can only replicate the complex in vivo loading condition in a simplified form. In this study, two different parameters were analyzed : (a) Bovine Serum, as a substitute for synovial fluid, is typically replaced every 500,000 cycles. However, a continuous regeneration takes place in vivo. How does Serum-Replacement interval affect the wear rate of total knee Replacements? (b) Patients with an artificial joint show reduced gait frequencies compared to standardized testing. What is the influence of a reduced frequency? Three knee wear tests were run: (a) reference test (ISO), (b) testing with a shortened lubricant Replacement interval, (c) testing with reduced frequency. The wear behavior was determined based on gravimetric measurements and wear particle analysis. The results showed that the reduced test frequency only had a small effect on wear behavior. Testing with 1 Hz frequency is therefore a valid method for wear testing. However, testing with a shortened Replacement interval nearly doubled the wear rate. Wear particle analysis revealed only small differences in wear particle size between the different tests. Wear particles were not linearly released within one Replacement interval. The ISO standard should be revised to address the marked effects of lubricant Replacement interval on wear rate.
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How do gait frequency and Serum-Replacement interval affect polyethylene wear in knee-wear simulator tests?
Journal of Materials Science: Materials in Medicine, 2014Co-Authors: Jörn Reinders, Robert Sonntag, J. Philippe KretzerAbstract:Polyethylene wear (PE) is known to be a limiting factor in total joint Replacements. However, a standardized wear test (e.g. ISO standard) can only replicate the complex in vivo loading condition in a simplified form. In this study, two different parameters were analyzed : (a) Bovine Serum, as a substitute for synovial fluid, is typically replaced every 500,000 cycles. However, a continuous regeneration takes place in vivo. How does Serum-Replacement interval affect the wear rate of total knee Replacements? (b) Patients with an artificial joint show reduced gait frequencies compared to standardized testing. What is the influence of a reduced frequency? Three knee wear tests were run: (a) reference test (ISO), (b) testing with a shortened lubricant Replacement interval, (c) testing with reduced frequency. The wear behavior was determined based on gravimetric measurements and wear particle analysis. The results showed that the reduced test frequency only had a small effect on wear behavior. Testing with 1 Hz frequency is therefore a valid method for wear testing. However, testing with a shortened Replacement interval nearly doubled the wear rate. Wear particle analysis revealed only small differences in wear particle size between the different tests. Wear particles were not linearly released within one Replacement interval. The ISO standard should be revised to address the marked effects of lubricant Replacement interval on wear rate.
