Biomedical subjects

Z H Fan

Publications and source records attributed to Z H Fan.

15 recordsLinked to original sources

PubMed2002

Complexities in ETS-domain transcription factor function and regulation: lessons from the TCF (ternary complex factor) subfamily. The Colworth Medal Lecture.

The ETS-domain transcription factor family can be divided into a series of subfamilies. Elk-1 represents the founding member of the ternary complex factor (TCF) subfamily. By focusing on the TCF subfamily, we can demonstrate the complexities that exist in the function and regulation of ETS-domain transcription factors. This article focuses on Elk-1 in detail and summarizes the functions of other TCFs. The key themes covered include the domain structure of the TCFs, the mechanisms of complex formation with serum response factor, regulation of TCFs by mitogen-activated protein kinase cascades, and transcriptional regulatory properties of the TCFs. Finally, the emerging role of the TCFs in vivo is discussed. A picture is developing indicating that, while these proteins exhibit significant sequence and functional conservation, key differences in their structure and regulation are being identified which may relate to unique functions of these proteins in vivo.

Amino Acid Sequence↗

PubMed1999

Dynamic DNA hybridization on a chip using paramagnetic beads.

Dynamic DNA hybridization is presented as an approach to perform gene expression analysis. The method is advantageous because of its dynamic supplies of both DNA samples and probes. The approach was demonstrated on a microfluidic platform by incorporating paramagnetic beads as a transportable solid support. A glass chip was fabricated to allow simultaneous interrogation of eight DNA target samples by DNA probes. DNA targets were immobilized on beads via streptavidin-biotin conjugation or base pairing between oligonucleotide residues. The DNA/bead complex was introduced into the device in which hybridization took place with a complementary probe. The hybridized probe was then removed by heat denaturation to allow the DNA sample to be interrogated again by another probe with a different sequence of interest. A pneumatic pumping apparatus was constructed to transport DNA probes and other reagents into the microfluidic device while hydrostatic pumping was used for the introduction of paramagnetic beads with samples. After investigating three types of paramagnetic beads, we found Dynabeads Oligo(dT)25 best suited this application. Targets on the beads could be sequentially interrogated by probes for 12 times, and the hybridization signal was maintained within experimental variation. Demonstration of specific hybridization reactions in an array format was achieved using four synthesized DNA targets in duplicate and five probes in sequence, indicating the potential application of this approach to gene expression analysis.

Actins↗

PubMed1999

Effects of injector geometry and sample matrix on injection and sample loading in integrated capillary electrophoresis devices.

The double-T injector design employed in many microchip capillary electrophoresis devices allows for the formation of very small (50-500 pL) sample plugs for subsequent analysis on-chip. In this study, we show that sample plugs formed at the channel junction can be geometrically defined. The channel width and injector symmetry prove to be of great importance to good performance. A unique pushback of solvent into the side channels can be induced when the side channels have a very low resistance to flow, and this helps to better define the injected sample plug. Samples and running buffers of differing ionic strength (e.g., 10 mM KCl buffer and 20 mM KCl sample) can yield widely variable results in terms of plug shape and amount injected (variations of 1.5 to 10x). Applying bias voltages to all the intersecting channels aids in controlling the plug shape. However, when the ionic strengths of buffer and sample are not matched, the actual amount injected (up to 10x variations) can be inconsistent with the appearance of the plug formed in the injector (up to only 30 % variations). Operating at constant pH and ionic strength produced the most consistent results. This report examines the effects of altering the injector geometry and solution ionic strengths, and presents the results of using bias voltages to control plug formation. The observed results should provide a benchmark for modeling of the fluid dynamics in channel intersections.

Electrophoresis, Capillary↗

PubMed1999

[Review on transforming growth factor beta and repair of tissue injury].

OBJECTIVE: To review the progress of the relation between transforming growth factor beta (TGF-beta) and repair of tissue injury. METHODS: The recent articles about TGF-beta and tissue reconstruction were extensively reviewed. The gene identification, production, activation of TGF-beta and its role in the repair course of tissue injury were investigated. RESULTS: TGF-beta belongs to a family of multifunctional polypeptides, its gene structure is highly conservative. Many animal models about TGF-beta and tissue injury have been established. The research mainly focuses on the classification, distribution of TGF-beta receptors and their signal pathway. CONCLUSION: TGF-beta plays an important roles in the regulation of repair of tissue injury.

Animals↗

PubMed1998

Microglial NO induces delayed neuronal death following acute injury in the striatum.

We have established a novel injury model in the central nervous system by a stereotaxic injection of ethanol into rat striatum to induce necrosis. With this model, we clarify a function of inducible nitric oxide synthase (iNOS) in a healing mechanism around a necrotic lesion. A semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that the iNOS mRNA arose at 6 h, peaked at 24 h, and declined to a lower level 48 h after an intrastriatal 5-microL ethanol injection. From in situ hybridization, this iNOS mRNA was expressed in the area surrounding the injury. By immunohistochemistry, mononuclear cells at this boundary area of necrosis were stained with anti-iNOS antibody on the first day after the injury. These cells turned out to be reactive microglia from the positive staining of GSA-I-B4, ED-1 and OX-42. Haematoxylin-eosin (HE) staining showed that neurons in this boundary area gradually disappear up to 5 days after the injury with an increment of microglial cells, and this area became cavernous. Nuclei of neurons in this area were stained positive by the terminal deoxynucleotidyl-transferase-mediated dUTP-biotin nick end-labelling (TUNEL) assay on the first day after the injury. These TUNEL-positive neurons gradually disappeared toward the third day, while microglial cells increased. L-Ng-nitro-arginine methylester (L-NAME), a competitive NOS inhibitor, administration diminished the elimination of neurons by microglia in this boundary area surrounding necrosis. Microglial NO may act as a neurotoxic agent to eliminate damaged neurons near the necrosis in the form of delayed neuronal death, and may reintegrate the neuronal circuits with functionally intact neurons.

Animals↗

PubMed1997

In vitro and in vivo expression of inducible nitric oxide synthase during experimental endotoxemia: involvement of other cytokines.

In this study, we investigated the expression of genes for inducible nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNF-alpha), interleukin 1 beta (IL-1 beta), interleukin 6 (IL-6) of Kupffer cells in the presence of lipopolysaccharide (LPS), and the tissue expression of iNOS in a rat liver after LPS injection at various time intervals. The effects of L-NG-nitroarginine-methyl-esther HCI (L-NAME), a NO inhibitor, also were examined. The mRNA transcripts of TNF-alpha, IL-1 beta, and IL-6 were rapidly detected no more than at 1 h after LPS stimulation, whereas the iNOS transcript was detectable from 3 h after LPS stimulation and maximally increased at 12 h. This fact suggested that these early induced cytokines were related to expression of iNOS. Using an anti-iNOS antiserum raised against recombinant iNOS protein, immunohistochemical analysis was made to reveal kinetics of NO producing cells. The cells immunoreactive for iNOS appeared at 6 h post-LPS injection in the sinusoids of the liver. By structural and immunohistochemical studies, almost all iNOS positive cells were identified as Kupffer cells and endothelial cells. The number of cells immunoreactive for iNOS increased until 12 h post-LPS injection. At 24 h after LPS injection, iNOS positive cells were restricted to the foci of spotty necrosis. Hepatic injury measured by released enzymes was increased by pretreatment of L-NAME before LPS injection.

Animals↗

PubMed1997

Nitric oxide as an inflammatory mediator of radiation pneumonitis in rats.

Radiation pneumonitis is a major complication of radiation therapy. To elucidate the mechanisms of radiation-induced pneumonitis, we studied nitric oxide (NO) produced from lung tissues using a model of unilaterally irradiated rats. Our results demonstrated that alveolar macrophages (AM) produced NO after irradiation, and the expression of inducible NO synthase (NOS) in both AM and alveolar epithelial cells was increased. Furthermore, the progression of radiation pneumonitis was reduced with the in vivo treatment of the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). The effect of L-NAME was further confirmed by the inhibition of mRNA expression for procollagen-alpha1 type III of the lung. With these results, NO produced from AM and alveolar epithelial cells after irradiation may be an important mediator in the progression of radiation pneumonitis.

Animals↗

PubMed1995

Enhancement of nitric oxide production from activated macrophages by a purified form of ginsenoside (Rg1).

We studied the actions of purified ginsenosides Rg1 and Rb1 on nitric oxide production from macrophages and a macrophage cell line RAW264-7. Although neither Rg1 nor Rb1 induced nitric oxide from resting macrophages, Rg1 enhanced the production of nitric oxide from IFN-gamma activated-macrophages or RAW cells. Rg1 also enhanced the production of nitric oxide from macrophages cocultured with nonadherent spleen cells stimulated by conA, LPS or anti-CD3. Rb1, however, did not significantly enhance nitric oxide production from stimulated macrophages or RAW cells. Rg1 enhanced the tumor cell killing by nitric oxide produced from IFN-gamma-activated macrophages.

Animals↗

PubMed1994

Gene transfer of TNF receptor for treatment of cancer by TNF.

Tumor necrosis factor-alpha receptors (TNFR-55 and TNFR-75) were inserted into retrovirus derived vector. They were transfected into a packaging cell line. The high titer of transfectants, which produced virus containing TNFR-55 or TNFR-75, was obtained. TNFR-55 and TNFR-75 negative human colon cancer cells were infected with this virus as a model experiment of gene therapy. Although the original colon cancer cell line did not express TNFR-55 or TNFR-75, the colon cancer cells, which were infected by recombinant virus, expressed a high level of TNFR-55 or TNFR-75. TNFR-55 or TNFR-75 transformed colon cancer cells were killed by recombinant TNF.

Cell Line↗

PubMed1993