Biomedical subjects

Yifan Dai

Publications and source records attributed to Yifan Dai.

9 recordsLinked to original sources

PubMed2006

Cloned transgenic swine via in vitro production and cryopreservation.

It has been notoriously difficult to successfully cryopreserve swine embryos, a task that has been even more difficult for in vitro-produced embryos. The first reproducible method of cryopreserving in vivo-produced swine embryos was after centrifugation and removal of the lipids. Here we report the adaptation of a similar process that permits the cryopreservation of in vitro-produced somatic cell nuclear transfer (SCNT) swine embryos. These embryos develop to the blastocyst stage and survive cryopreservation. Transfer of 163 cryopreserved SCNT embryos to two surrogates produced 10 piglets. Application of this technique may permit national and international movement of cloned transgenic swine embryos, storage until a suitable surrogate is available, or the long-term frozen storage of valuable genetics.

Animals↗

PubMed2006

Lattice design for subaperture stitching test of a concave paraboloid surface.

Lattice design is subtle and complicated for the subaperture stitching test of aspheric surfaces. Methods are described in this paper for the collection and arrangement of subapertures, and calculation of the best-fit sphere for each subaperture. The best-fit sphere is determined by minimizing the mean-square aspheric deviations in the form of a surface integral. Finally, a numerical example is given to illustrate the procedure, and also to verify the validity of our proposed methods.

Journal Article↗

PubMed2006

Generation of cloned transgenic pigs rich in omega-3 fatty acids.

Meat products are generally low in omega-3 (n-3) fatty acids, which are beneficial to human health. We describe the generation of cloned pigs that express a humanized Caenorhabditis elegans gene, fat-1, encoding an n-3 fatty acid desaturase. The hfat-1 transgenic pigs produce high levels of n-3 fatty acids from n-6 analogs, and their tissues have a significantly reduced ratio of n-6/n-3 fatty acids (P < 0.001).

Animals↗

PubMed2006

Iterative algorithm for subaperture stitching test with spherical interferometers.

Recently we have proposed an iterative algorithm for subaperture stitching interferometry. It was referred to as the subaperture stitching and localization (SASL) algorithm. The limitation of the algorithm is that three-dimensional Cartesian coordinates are required, whereas the standard spherical interferometer can read out only the phase differences on the pixels. On the basis of the SASL algorithm, we propose an iterative algorithm for a spherical subaperture stitching test. It deals with data directly from the spherical interferometer. Unknown radii of best-fit spheres for a null test of subapertures are included in the optimization variables. The developed algorithm inherits the advantages of the SASL algorithm.

Journal Article↗

PubMed2005

Acute rejection is associated with antibodies to non-Gal antigens in baboons using Gal-knockout pig kidneys.

We transplanted kidneys from alpha1,3-galactosyltransferase knockout (GalT-KO) pigs into six baboons using two different immunosuppressive regimens, but most of the baboons died from severe acute humoral xenograft rejection. Circulating induced antibodies to non-Gal antigens were markedly elevated at rejection, which mediated strong complement-dependent cytotoxicity against GalT-KO porcine target cells. These data suggest that antibodies to non-Gal antigens will present an additional barrier to transplantation of organs from GalT-KO pigs to humans.

Animals↗

PubMed2005

Iterative algorithm for subaperture stitching interferometry for general surfaces.

A novel iterative algorithm for subaperture stitching interferometry for general surfaces is presented. It is based on the alternating optimization technique and the successive linearization method. The computer-aided-design model of the tested surface is used to determine the overlapping region precisely. Subapertures are simultaneously stitched by minimizing deviations among them as well as deviations from the nominal surface. Precise prior knowledge of the six degrees-of-freedom nulling and alignment motion is no longer required.

Journal Article↗

PubMed2002

Production of alpha 1,3-galactosyltransferase-deficient pigs.

The enzyme alpha1,3-galactosyltransferase (alpha1,3GT or GGTA1) synthesizes alpha1,3-galactose (alpha1,3Gal) epitopes (Galalpha1,3Galbeta1,4GlcNAc-R), which are the major xenoantigens causing hyperacute rejection in pig-to-human xenotransplantation. Complete removal of alpha1,3Gal from pig organs is the critical step toward the success of xenotransplantation. We reported earlier the targeted disruption of one allele of the alpha1,3GT gene in cloned pigs. A selection procedure based on a bacterial toxin was used to select for cells in which the second allele of the gene was knocked out. Sequencing analysis demonstrated that knockout of the second allele of the alpha1,3GT gene was caused by a T-to-G single point mutation at the second base of exon 9, which resulted in inactivation of the alpha1,3GT protein. Four healthy alpha1,3GT double-knockout female piglets were produced by three consecutive rounds of cloning. The piglets carrying a point mutation in the alpha1,3GT gene hold significant value, as they would allow production of alpha1,3Gal-deficient pigs free of antibiotic-resistance genes and thus have the potential to make a safer product for human use.

Alleles↗

PubMed2002

Targeted disruption of the alpha1,3-galactosyltransferase gene in cloned pigs.

Galactose-alpha1,3-galactose (alpha1,3Gal) is the major xenoantigen causing hyperacute rejection in pig-to-human xenotransplantation. Disruption of the gene encoding pig alpha1,3-galactosyltransferase (alpha1,3GT) by homologous recombination is a means to completely remove the alpha1,3Gal epitopes from xenografts. Here we report the disruption of one allele of the pig alpha1,3GT gene in both male and female porcine primary fetal fibroblasts. Targeting was confirmed in 17 colonies by Southern blot analysis, and 7 of them were used for nuclear transfer. Using cells from one colony, we produced six cloned female piglets, of which five were of normal weight and apparently healthy. Southern blot analysis confirmed that these five piglets contain one disrupted pig alpha1,3GT allele.

Animals↗

PubMed2002

Efficient production of transgenic cloned calves using preimplantation screening.

The genetic manipulation of donor cells before nuclear transfer (NT) enables prior selection for transgene integration. However, selection for genetically modified cells using antibiotic drugs often results in mixed populations, resulting in a mixture of transgenic and nontransgenic donor cells for NT. In this study, we attempted to develop efficient strategies for the generation of human bile salt-stimulated lipase (BSSL) transgenic cows. Preimplantation screening by either biopsy or green fluorescent protein (GFP) expression was used to detect NT-derived BSSL transgenic embryos to ensure that the calf born would be transgenic. We compared the development rates of NT-derived embryos from G418- and GFP-selected donor cells. There were no significant differences (P < 0.001) in cleavage rate (67.2% vs. 60.0%) and blastocyst formation rate (44.9% vs. 41.2%). We also compared the pregnancy rates of the G418/biopsy and GFP preimplantation screened NT-derived blastocysts. The Day 40 pregnancy rate of the G418/biopsy group (40%) was lower than that of the GFP group (57%), but the calf birth rate of the G418/biopsy group (40%) was higher than that of the GFP group (21%). Healthy BSSL transgenic calves were born after both screening processes. This is the first report of biopsy-screened cloned transgenic animals. The results suggest that both selection methods are useful for detecting transgenic NT embryos without negatively affecting their development into viable transgenic offspring.

Animals↗