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This mouse ES cell line has been shown to be germline competent. 129 and the more common, 129Sv are widely used mouse strains in gene targeting experiments.  The embryonic stem cells derived from 129Sv are part of the genetic background of most mutants generated using homologous recombination. RefThreadgill DW, et al. Genealogy of the 129 inbred strains: 129/SvJ is a contaminated inbred strain. Mamm. Genome. 8(6):390-393 1997. PubMed: 9166580  The 129/SvEv cell lines tested at early passages were found to contribute extensively to chimeras and produce germ-transmitting male chimeras.  Furthermore, this cell line was able to maintain these characteristics after many passages in vitro. RefAuerbach W, et al. Establishment and chimera analysis of 129/SvEv- and C57BL/6-derived mouse embryonic stem cell lines. BioTechniques 29: 1024-1028, 1030, 1032, 2000. PubMed: 11084865

Note: To insure the highest level of viability, pre-warm media and Trypsin/EDTA to 37ºC before adding to cells. Volumes used in this protocol are for T75 flasks. Proportionally adjust the volumes for culture vessels of other sizes. A split ratio of 1:4 to 1:7 is recommended.

Feeder Cell Preparation for Subcultures

1. Daily maintain a sufficient number of flasks that have been pre-plated with MEFs in complete medium for feeder cells.
2. One hour before subculturing the ES cells, perform a 100% medium change for the MEFs using complete growth medium for ES cells.

Dissociation and Transfer of ES Cells

1. Aspirate the medium from the flask(s) containing ES cells.
2. Wash with PBS Ca+2/Mg+2-free (ATCC® SCRR-2201).
3. Add 3.0 mL of 0.25% (w/v) Trypsin / 0.53 mM EDTA solution (ATCC® 30-2101) and place in incubator. After about one minute the ES colonies will dissociate and all cells will detach from the flask.
4. Dislodge the cells by gently tapping the side of the flask then wash the cells off with 7-10 mL of fresh culture medium. Triturate cells several times with a 10 mL pipette in order to dissociate the cells into a single-cell suspension.
5. Spin the cells at 270 x g for 5 min. Aspirate the supernatant.
6. Resuspend in enough complete growth medium for ES cells to reseed new vessels at the desired split ratio (i.e. a split ratio of 1:4 to 1:7 is recommended). Perform a cell count to determine the total number of cells. ES cells should be plated at a density of 30,000 – 50,000 cells/ cm².
7. Add separate aliquots of the cell suspension to the appropriate size flask containing feeder cells and add an appropriate volume of fresh complete growth medium for ES cells to each vessel.
8. Incubate the culture at 37°C in a humidified 5% CO₂/95% air incubator. Perform a 100% medium change every day, passage cells every 1-2 days.

Festing MF, et al. Revised nomenclature for strain 129 mice. Mamm. Genome. 10(8):836, 1999.[PubMed: 10430671]

Simpson EM, et al. Genetic variation among 129 substrains and its importance for targeted mutagenesis in mice. Nat. Genet. 16(1):19-27, 1997. PubMed: 9140391

Threadgill DW, et al. Genealogy of the 129 inbred strains: 129/SvJ is a contaminated inbred strain. Mamm. Genome. 8(6):390-393 1997. PubMed: 9166580

Auerbach W, et al. Establishment and chimera analysis of 129/SvEv- and C57BL/6-derived mouse embryonic stem cell lines. BioTechniques 29: 1024-1028, 1030, 1032, 2000. PubMed: 11084865

Hay RJ, Caputo JL, Macy, ML, Eds. (1992) ATCC Quality Control Methods for Cell Lines. 2nd edition, Published by ATCC.

Caputo JL. Biosafety procedures in cell culture. J. Tissue Culture Methods 11:223-227, 1988