Biomedical subjects

Jian Tan

Publications and source records attributed to Jian Tan.

22 records · Page 2Linked to original sources

PubMed2002

Topographical control of human neutrophil motility on micropatterned materials with various surface chemistry.

Controlling cell responses to an implantable material is essential to tissue engineering. Because the surface is in direct contact with cells, both chemical and topographical properties of a material surface can play a crucial role. In this study, parallel ridges/grooves were micropatterned on glass surfaces using photosensitive polyimide to create transparent substrates. The migratory behavior of live human neutrophils on the patterned surfaces was observed using a light microscope with transmitted light source. The width (2 microm) and length (400 microm) of the ridges were kept constant. The height (5 or 3 microm) and the repeat spacing (6-14 microm) of the ridges were systematically changed to investigate the effect of microgeometry on neutrophil migration. In addition, the effect of surface chemistry on neutrophil migration was studied by deposition of a thin layer of "inert", biocompatible metal such as Au-Pd alloy and titanium on patterned substrates. More than 95% of neutrophils moved in the direction of the long axis of ridges/grooves regardless of the topographical geometry and chemistry, consistent with a phenomenon termed "contact guidance". Therefore, cell migration was characterized using a one-dimensional persistent random walk. The rate of cell movement was strongly dependent on the topographical microgeometry of the ridges. The random motility coefficient mu, 9.8 x 10(-9) cm2/s, was the greatest at a ridge height of 5 microm and spacing of 10 microm, about 10 times faster than on smooth glass surface. The Au-Pd coating did not change neutrophil migratory behavior on patterned surfaces, whereas titanium decreased cell motility substantially. The results of this study suggest that optimization of both surface chemistry and topography may be important when designing biomaterials for tissue engineering. In addition, parallel ridges/grooves can be used to control the direction and rate of cell migration on the surface.

Biocompatible Materials↗

PubMed2002

Evidence for coordinated interaction of cyclin D3 with p21 and cdk6 in directing the development of uterine stromal cell decidualization and polyploidy during implantation.

Uterine decidualization, characterized by stromal cell proliferation, and differentiation into specialized type of cells (decidual cells) with polyploidy, during implantation is critical to the pregnancy establishment in mice. The mechanisms by which the cell cycle events govern these processes are poorly understood. The cell cycle is tightly regulated at two particular checkpoints, G1-S and G2-M phases. Normal operation of these phases involves a complex interplay of cyclins, cyclin-dependent kinases (cdks) and cdk inhibitors (CKIs). We previously observed that upregulation of uterine cyclin D3 at the implantation site is tightly associated with decidualization in mice. To better understand the role of cyclin D3 in this process, we examined cell-specific expression and associated interactions of several cell cycle regulators (cyclins, cdks and CKIs) specific to different phases of the cell cycle during decidualization in mice. Among the various cell cycle molecules examined, coordinate expression and functional association of cyclin D3 with cdk4 suggest a role for proliferation and, that of cyclin D3 with p21 and cdk6 is consistent with the development of polyploidy during stromal cell decidualization.

Animals↗

PubMed2002

IGF-2 is a mediator of prolactin-induced morphogenesis in the breast.

The mechanisms by which prolactin controls proliferation of mammary epithelial cells (MECs) and morphogenesis of the breast epithelium are poorly understood. We show that cyclin D1(-/-) MECs fail to proliferate in response to prolactin and identify IGF-2 as a downstream target of prolactin signaling that lies upstream of cyclin D1 transcription. Ectopic IGF-2 expression restores alveologenesis in prolactin receptor(-/-) epithelium. Alveologenesis is retarded in IGF-2-deficient MECs. IGF-2 and prolactin receptor mRNAs colocalize in the mammary epithelium. Prolactin induces IGF-2 mRNA and IGF-2 induces cyclin D1 protein in primary MECs. Thus, IGF-2 is a mediator of prolactin-induced alveologenesis; prolactin, IGF-2, and cyclin D1, all of which are overexpressed in breast cancers, are components of a developmental pathway in the mammary gland.

Animals↗

PubMed1999

Survey of coverage, strategy and cost of hepatitis B vaccination in rural and urban areas of China.

AIM:In order to understand the coverage, immunization strategy and cost of hepatitis B (HB) vaccination of China in recent years.METHODS:A two-stage household random sampling method was used in the survey.RESULTS:The survey carried out at 112 Disease Surveillance Points (DSPs) of 25 provinces, autonomous regions and municipalities of China in 1996, showed that the coverage rates of HB vaccination among neonates were 96.9% in the urban DSPs and 50.8% in the rural DSPs in 1993-1994,while in students aged 7-9 years, they were 85.8% and 31.5% in 1994, respective-ly. Up to 1994, 97.5% of the urban DSPs and 73.9% of the rural DSPs on a neonate vaccination against HB program were included in EPI. About 93% of the urban DSPs and 44% of the rural DSPs did HBsAg and HBeAg screening for all or part of pregnant women. The neonates received the regimen of high-dose HB vaccine in combination with hepatitis B immune globin (HBIG) if their mothers were HBsAg and/or HBeAg positive in pregnancy,otherwise they received the low-dose vaccine (10&mgr;gX3). Part of DSPs had a lower neonate coverage due to unreasonable allocation of the vaccines (used for adults not at risk) or higher cost or insufficient supply of the vaccines. It is necessary to evaluate the quality of serological lab test to HBVMs in the maternal prescreening.CONCLUSION:Remarkable achievements have been made according to the national planning and policy of HB immunization in China.

Journal Article↗