Search PubMed⌕ Search

Biomedical subjects

Xia Chen

Publications and source records attributed to Xia Chen.

8 recordsLinked to original sources
PubMed2026

Genetic structure and selection signatures of Beijing-You chicken populations provide insight into breed conservation.

Preserving genetic diversity and maintaining population viability are critical yet challenging goals that demand rigorous evaluation of conservation strategies. Beijing-You chicken, as the sole indigenous chicken breed originating from Beijing, China, is currently maintained as four independent populations under distinct conservation programs. How different conservation regimes have shaped its genomic architecture remains largely unknown, limiting evidence-based evaluation. Here, we generated whole-genome resequencing data from 240 individuals representing four Beijing-You chicken populations to assess population structure, genetic diversity, and signatures of selection over decades of conservation. All four populations formed distinct clusters, reflecting measurable differentiation after decades of separate conservation. The differences in genetic diversity were broadly consistent with the variation in effective population size estimates. Runs of homozygosity and linkage disequilibrium decay patterns further characterized each population, with extended values indicating reduced effective population size and increased inbreeding under long-term conservation. We applied the fixation index (FST) and pairwise diversity ratio (θπ) methods to identify selection signatures. A total of 171 genes were identified as candidates. These genes were enriched in pathways related to reproduction, growth regulation, and environmental adaptation. These findings highlight patterns of reduced diversity and skewed relatedness, which could arise from management-related factors such as breeding preferences or mating strategies. Still, they are also compatible with neutral processes, including drift and founder effects. Regardless of the underlying cause, integrating scientifically informed conservation strategies with routine genomic monitoring across generations is essential for sustaining genetic diversity in Beijing-You chicken and other indigenous breeds.

Beijing-You chicken↗
PubMed2003

[Arterial switch operation in older infants with severe pulmonary hypertension].

OBJECTIVE: To investigate the clinical efficacy of arterial swith operation on transposition of great artery (TGA) and Tausing-Bing anomaly. METHODS: Between June 2000 and December 2002, 30 consecutive patients, aged 3 days to 6 years (mean, 9.4 +/- 15 months) with the mean body weight was 6.1 kg +/- 2.7 kg, underwent arterial switch operation. Among the 30 patients 7 suffered from TGA with intact ventricular septum, 19 from TGA with ventricular septal defect (VSD), 3 from Taussing-Bing anomaly, and 1 from corrected TGA; 12 were complicated by atrial septal defect (ASD) and 18 complicated by patent ductus arteriosus (PDA); 23 had severe pulmonary hypertension; 2 had left ventricular outlet stenosis. Coronary type A distribution was recognized in 26 cases, type D in 4, and one of them having the origin of the left descending artery tunneled in the aortic wall. The operation was performed under general anesthesia and extracorporeal circulation with low temperature and low volume blood flow. Prostaglandin 1 was administered pre-operatively in 3 patients, one of which underwent balloon atrial septostomy and one underwent pulmonary banding and systemic to pulmonary shunt pre-operatively. The aorta and pulmonary artery were transected above the valvular commisures, the coronary ostia with all the adjacent sinus of Valsalva were excised and re-implanted to the proximal neo-aorta, and then aortic anastomosis was completed. The proximal neo-pulmonary trunk was reconstructed with a large autologous native pericardium as a posterior patch. The pulmonary anastomosis was completed after the aortic cross-clamp was released. The VSD was repaired through the atrium or proximal aorta with dacron patches. RESULTS: Two patients died with a hospital mortality rate of 6.7%. No death was directly related to any coronary artery problem. One 5 day-old neonate with TGA and an intact septum having refractory hypotension, hypoxemia, and acidosis pre-operatively underwent a smooth emergency operation. The patient had a refractory low cardiac output syndrome post-operatively and died 20 hours after the operation. Another patient with chylothorax died of allergy from iodophor 22 days postoperatively. The pulmonary pressure decreases significantly in 22 patients who had severe pulmonary hypertension preoperatively with the mean pressure 46.7 mm Hg preoperatively and 31.3 mm Hg postoperatively. 28 patients were discharged from hospital uneventfully. Follow-up of 1 to 31 months showed survival with no late complications and death. CONCLUSION: The arterial switch procedure has a satisfying effect on TGA for patients older than 1 month with severe pulmonary hypertension.

Cardiac Surgical Procedures↗
PubMed2003

Targeted recycling of PECAM from endothelial surface-connected compartments during diapedesis.

Leukocytes enter sites of inflammation by squeezing through the borders between endothelial cells that line postcapillary venules at that site. This rapid process, called transendothelial migration (TEM) or diapedesis, is completed within 90 s after a leukocyte arrests on the endothelial surface. In this time, the leukocyte moves in ameboid fashion across the endothelial borders, which remain tightly apposed to it during transit. It is not known how the endothelial cell changes its borders rapidly and reversibly to accommodate the migrating leukocyte. Here we show that there is a membrane network just below the plasmalemma at the cell borders that is connected at intervals to the junctional surface. PECAM-1, an integral membrane protein with an essential role in TEM, is found in this compartment and constitutively recycles evenly along endothelial cell borders. During TEM, however, recycling PECAM is targeted to segments of the junction across which monocytes are in the act of migration. In addition, blockade of TEM with antibodies against PECAM specifically blocks the recruitment of this membrane to the zones of leukocyte migration, without affecting the constitutive membrane trafficking.

Cell Adhesion↗
PubMed2003

[Cloning, genomic organization and promoter activity of the mouse zinc finger protein gene ZF-12].

The human zinc finger protein ZNF191 is a krüppel-like transcription factor, which may be relevant to many diseases such as neuropsychiatric, cardiovascular and liver caner diseases. To elucidate the function of ZNF191 by gene targeting, it is necessary to clone and characterize of the homologous gene in model organisms (mice). The mouse homologous gene (ZF-12) was cloned and sequenced for the first time, the GenBank accession number is AY052495. It contains four exons and three introns; all intronic splice sites exhibited consensus GT/AG sequences. The single nucleotide polymorphisms (SNPs) in exon 2 and the alternative length of 3'-untranslated region (3'-UTR) have been found. The linkage of the ZF-12 gene and the zinc finger protein gene Zfp-35 has been found, so the ZF-12 gene can be localized to B3 to C or beside of chromosome 18. We assessed approximately 1.2 kb of 5'-flanking region of the ZF-12 gene for basal promoter activity. A series of deletion mutants of 5'-flanking region linked to the luciferase gene was constructed. Basal level expression of these constructs was tested in COS-7 cells, NIH3T3 cells and HeLa cells. By measuring luciferase activity, which was transiently expressed in the transfected cells, we found that regulatory elements sufficient for basal expression lie between -762 and +70 bp relative to the transcription start site and that a negative regulatory region lie between -824 and -762 bp. This research provides a basis for further study on ZF-12 by gene targeting.

3T3 Cells↗
PubMed2002

CD99 plays a major role in the migration of monocytes through endothelial junctions.

CD99 is a heavily O-glycosylated 32-kD type I transmembrane protein that is expressed on most hematopoietic cells. We show here that CD99 is expressed on endothelial cells and is concentrated at the borders between confluent cells. We found that a monoclonal antibody to CD99, hec2, selectively inhibited diapedesis of monocytes across endothelial cells by >90%. Diapedesis involved the homophilic interaction of CD99 on monocytes with CD99 on endothelial junctions. CD99 functioned distally to the point at which platelet-endothelial cell adhesion molecule 1 (PECAM-1, also known as CD31), another adhesion molecule involved in transmigration, played its critical role. Confocal microscopy showed that anti-PECAM-1 arrested leukocytes on the apical surface of endothelium, whereas blocking CD99 arrested monocytes at a point where they were partially through the junction. Therefore, diapedesis, the forward migration of leukocytes through endothelial junctions, is regulated sequentially by two distinct molecules, PECAM-1 and CD99.

12E7 Antigen↗
PubMed2002

The three typical aspartic proteinase genes of Arabidopsis thaliana are differentially expressed.

Genomic sequencing has identified three different typical plant aspartic proteinases in the genome of Arabidopsis thaliana, named Pasp-A1, A2 and A3. A1 is identical to a cDNA we had previously isolated and the two others produce proteins 81 and 63% identical to that predicted protein. Sequencing of the aspartic proteinase protein purified from Arabidopsis seeds showed that the peptides are derived from two of these genes, A1 and A2. Using gene specific probes, we have analyzed RNA from different tissues and found these three genes are differentially expressed. A1 mRNA is detected in all tissues analyzed and more abundant in leaves during the light phase of growth. The other two genes are expressed either primarily in flowers (A3) or in seeds (A2). Insitu hybridization demonstrated that all three genes are expressed in many cells of the seeds and developing seed pods. The A1 and A3 genes are expressed in the sepals and petals of flowers as well as the outer layer of the style, but are not expressed in the transmitting tract or on the stigmatal surface. The A2 gene is weakly expressed only in the transmitting tissue of the style. All three genes are also expressed in the guard cells of sepals. These data suggest multiple roles for aspartic proteinases besides those proposed in seeds.

Amino Acid Sequence↗