Biomedical subjects
Publications and source records attributed to S Huang.
In this paper, through atomic absorption detector, we determined the content of micro-elements, such as Sr, Ba, Fe, Al, Cu, Cr, Zn, Mo, Ni, Co, Mn, Cd, Mg, in six condiments. From the result, we found there is a differing content of micro-element in different condiments. At the same time, we also made a reclaiming experiment for these micro-elements in ginger, the rate of reclamation is about 90%-108%.
In this work, we have a designation and preparation of MFT glasses for upconversion, the glasses consisted of TeO2 and fluoride: PbF2, AlF3, BaF2, NaF and the impurity Tm2O3. In this glass system the oxide improve forming ability, the fluorides improve the microscopic environment around RE ions in glasses. In this glass host the content of Tm2O3 achieves to 4% mol and crystallization no occurred. A detail study on the concentration quenching of upconversion luminescence for 1G4-->3H6 and 1D2-->3H4 transitions was completed. The experimental results directed that the quenching concentration was 0.6 mol.% and higher 3 times than in other glasses materials. The cross relaxation and mechanism of concentration quenching were discussed.
OBJECTIVE: To investigate the epidemiological conditions of Stenotrophomonas maltophilia (S. maltophilia) and their origins in intensive care units (ICU). METHODS: (1) Antibiotic susceptibility data of S. maltophilia of respiratory wards and surgical ICU(SICU) from 1998 to 1999 were collected. (2) Clinic isolates of S. maltophilia of respiratory ICU(RICU) and SICU from June 1999 to February 2000 were collected, then their homology was analyzed by the method of ERIC-PCR. RESULTS: (1) Antibiotic susceptibility data showed its antibiotic resistance phenomena were severe. (2) The results of ERIC-PCR showed that there was no significant relationship between the genotype and antibiotic type with S. maltophilia. (3) Multiple subsets were found in RICU. However, only two subsets (A,B) in SICU. CONCLUSIONS: The antibiotic resistance of S. maltophilia was so severe that it was difficult to deal with; in the study on its molecular epidemiology, ERIC-PCR is helpful to homogenous analysis, and it is a simple, quick, efficient and dependent method.
The basic helix-loop-helix transcription factor TAL1 (or SCL) is a critical regulator of hematopoietic and vascular development and is misexpressed in the majority of patients with T-cell acute lymphoblastic leukemia. We found previously that TAL1 could interact with transcriptional co-activator and co-repressor complexes possessing histone acetyltransferase and deacetylase activities, respectively. Here, we report that TAL1 is subject to acetylation in vivo and can be acetylated by p300 and the p300/CBP-associated factor P/CAF in vitro. P/CAF-mediated acetylation, which mapped to a lysine-rich motif in the loop region, increased TAL1 binding to DNA while selectively inhibiting its interaction with the transcriptional co-repressor mSin3A. Furthermore, P/CAF protein, TAL1-P/CAF interaction and TAL1 acetylation increased significantly in murine erythroleukemia cells induced to differentiate in culture, while enforced expression of an acetylation-defective P/CAF mutant inhibited endogenous TAL1 acetylation, TAL1 DNA-binding activity, TAL1-directed transcription and terminal differentiation of these cells. These results reveal a novel mechanism by which TAL1 activity is regulated and implicate acetylation of this transcription factor in promotion of erythroid differentiation.
GPI 6150 (1,11b-dihydro-[2H]benzopyrano[4,3,2-de]isoquinolin-3-one) is a novel inhibitor of poly(ADP-ribose) polymerase (PARP). It has demonstrated efficacy in rodent models of focal cerebral ischemia, traumatic brain injury, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine damage to dopaminergic neurons, regional myocardial ischemia, streptozotocin-induced diabetes, septic shock, and arthritis. Here we report the structure of GPI 6150, its enzymatic characteristics, and biochemical property in cytoprotection. As a competitive PARP inhibitor (K(i) = 60 nM), GPI 6150 protected the P388D1 cells against hydrogen peroxide cytotoxicity, by preventing PARP activation and the depletion of NAD(+), the substrate for PARP. To address the concerns of potential side effects of PARP inhibition, we tested GPI 6150 and found it had no effect on the repair and expression of a plasmid DNA damaged by N-methyl-N'-nitro-N-nitrosoguanidine. Neither did it affect dehydrogenases with NAD co-enzyme. GPI 6150 was much less potent to inhibit mono-ADP-ribosyltransferase. There was no selectivity for GPI 6150 between PARP isozymes. These attributes render GPI 6150 a useful tool to probe the functions of PARP.
Smad1 belongs to a family of receptor-activated proteins which mediate signals from TGF-beta superfamily ligands, including TGF-beta and BMPs. Although much is known about the biochemistry of Smad1 signal transduction, the role of Smad1 in vivo is still unclear. Here we present the first description of the genomic structure of the mouse Smad1 gene and the characterization of its expression pattern in adult mouse tissues by immunohistochemistry. The Smad1 gene contains 7 exons and spans >42 kb of genomic DNA. Its coding region is contained within 6 exons and all introns, except intron 1, follow the GT/AG rule. Immunohistochemical analysis shows that Smad1 is widely expressed in adult mouse tissues, with a varying degree of nuclear localization in different cell types, suggesting a regulated function for this protein. This study assigns all of the exon-intron boundaries of the mouse Smad1 gene and provides the basis for assessing the functional significance of this gene using targeted gene manipulation in the mouse.
Development of characteristic tissue patterns requires that individual cells be switched locally between different phenotypes or "fates;" while one cell may proliferate, its neighbors may differentiate or die. Recent studies have revealed that local switching between these different gene programs is controlled through interplay between soluble growth factors, insoluble extracellular matrix molecules, and mechanical forces which produce cell shape distortion. Although the precise molecular basis remains unknown, shape-dependent control of cell growth and function appears to be mediated by tension-dependent changes in the actin cytoskeleton. However, the question remains: how can a generalized physical stimulus, such as cell distortion, activate the same set of genes and signaling proteins that are triggered by molecules which bind to specific cell surface receptors. In this article, we use computer simulations based on dynamic Boolean networks to show that the different cell fates that a particular cell can exhibit may represent a preprogrammed set of common end programs or "attractors" which self-organize within the cell's regulatory networks. In this type of dynamic network model of information processing, generalized stimuli (e.g., mechanical forces) and specific molecular cues elicit signals which follow different trajectories, but eventually converge onto one of a small set of common end programs (growth, quiescence, differentiation, apoptosis, etc.). In other words, if cells use this type of information processing system, then control of cell function would involve selection of preexisting (latent) behavioral modes of the cell, rather than instruction by specific binding molecules. Importantly, the results of the computer simulation closely mimic experimental data obtained with living endothelial cells. The major implication of this finding is that current methods used for analysis of cell function that rely on characterization of linear signaling pathways or clusters of genes with common activity profiles may overlook the most critical features of cellular information processing which normally determine how signal specificity is established and maintained in living cells.
Many biological processes require proteins to undergo conformational changes at the surface of membranes. For example, some precursor proteins unfold at the surface of mitochondria and chloroplasts before translocation into the organelles, and toxins such as colicin A unfold to the molten globule state at bacterial surfaces before inserting into the cell membrane. It is commonly thought that the membrane surfaces and the associated protein machinery destabilize the substrate proteins and that this effect is required for membrane insertion or translocation. One of the best characterized translocation processes is protein import into mitochondria. By measuring the contributions of individual interactions within a model protein to its stability at the mitochondrial surface and in free solution, we show here that the mitochondrial surface neither induces the molten globule state in this protein nor preferentially destabilizes any type of interaction (e.g., hydrogen bonds, nonpolar, etc.) within the protein. Because it is not possible to measure absolute protein stability at the surface of mitochondria, we determined the stability of a tightly associated protein-protein complex at the mitochondrial import site as a model of the stability of a protein. We found the binding constants of the protein-protein complex at the mitochondrial surface and in free solution to be identical. Our results demonstrate that the mitochondrial surface does not destabilize importing precursor proteins in its vicinity.
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We determined whether blockade of nuclear factor (NF)-kappaB/relA activity in human ovarian cancer cells can suppress angiogenesis and growth in an orthotopic nude mouse model. The human ovarian cancer cells SKOV3ip.1 and HEY-A8 were transfected with a mutated IkappaBalpha (IkappaBalphaM), ie., resistant to phosphorylation and degradation, and hence blocks NF-kappaB activity. NF-kappaB signaling blockade significantly inhibited in vitro and in vivo expression of two major proangiogenic molecules, vascular endothelial growth factor and interleukin 8, in cultured cells and in cells implanted into the peritoneal cavity of nude mice. The decreased expression of vascular endothelial growth factor and interleukin 8 directly correlated with decreased tumorigenicity, decreased vascularization of lesions, decreased formation of malignant ascites, and prolonged survival of mice. These findings suggest that inhibition of NF-kappaB/relA activity in ovarian cancer cells can suppress angiogenesis and progressive growth.
Arsenic has been used effectively as a chemotherapeutic drug for the treatment of acute promyelocytic leukemia patients. Numerous studies have demonstrated that arsenic induces apoptosis in various cell types. In the present study, we showed that approximately 35% of arsenite-treated HeLa S3 cells arrested in mitosis. After release from arsenite treatment, more than 80% of arsenite-arrested mitotic cells subsequently underwent apoptosis, as indicated by anachronistic nuclear envelope reformation, DNA ladder occurrence, chromatin condensation, and activation of caspases 3 and 9. In exploring how these cells entered apoptosis mechanistically, we found an inverse correlation between mitotic indexes and apoptotic frequencies. As shown by using Percoll density gradient fractionation and flow cytometric analysis, the mitosis-mediated apoptosis induced by arsenite was accompanied by delayed cyclin B degradation and altered mitotic exit. Furthermore, treatment of arsenite-arrested mitotic cells with staurosporine or 2-aminopurine resulted in a rapid degradation of cyclin B, moved these cells forward to interphase without cell division, and abrogated apoptosis. These results suggest that apoptosis occurs in arsenite-arrested mitotic cells that exit mitosis abnormally.
Many lines of evidence suggest that the retinoblastoma protein interacting zinc finger gene RIZ is a strong candidate for the tumor suppressor locus on 1p36, a region commonly deleted in many human cancers with chromosomal instability. In addition, a role for RIZ in tumors of the microsatellite instability pathway is suggested by frequent frameshift mutations in hereditary non-polyposis colorectal carcinomas. Here we studied RIZ mutations in sporadic cancers with microsatellite instability. Frameshift mutations in the two coding polyadenosine tracks of RIZ were found in 19 (48%) of 40 gastric carcinomas, 6 (33%) of 18 endometrial carcinomas, 14 (26%) of 51 of colorectal carcinomas, and 7 (54%) of 13 cell lines. Eleven tumor tissues showed biallelic inactivation of RIZ. In contrast, no frameshift mutations were found in 70 microsatellite stable tumors. These results suggest an important role for RIZ in sporadic cancers with microsatellite instability.
Werner's syndrome (WS) is an autosomal recessive disorder in humans characterized by the premature development of a partial array of age-associated pathologies. WRN, the gene defective in WS, encodes a 1432 amino acid protein (hWRN) with intrinsic 3'-->5' DNA helicase activity. We recently showed that hWRN is also a 3'-->5' exonuclease. Here, we further characterize the hWRN exonuclease. hWRN efficiently degraded the 3' recessed strands of double-stranded DNA or a DNA-RNA heteroduplex. It had little or no activity on blunt-ended DNA, DNA with a 3' protruding strand, or single-stranded DNA. The hWRN exonuclease efficiently removed a mismatched nucleotide at a 3' recessed terminus, and was capable of initiating DNA degradation from a 12-nt gap, or a nick. We further show that the mouse WRN (mWRN) is also a 3'-->5' exonuclease, with substrate specificity similar to that of hWRN. Finally, we show that hWRN forms a trimer and interacts with the proliferating cell nuclear antigen in vitro. These findings provide new data on the biochemical activities of WRN that may help elucidate its role(s) in DNA metabolism.
Activating transcription factor-1 (ATF-1) and cAMP-responsive element (CRE)-binding protein (CREB) have been implicated in cAMP and Ca2+-induced transcriptional activation. The expression of the transcription factors CREB and ATF-1 is upregulated in metastatic melanoma cells. However, how overexpression of ATF-1/CREB contributes to the acquisition of the metastatic phenotype remains unclear. Here, the effect of disrupting ATF-1 activity was investigated using intracellular expression of an inhibitory anti-ATF-1 single chain antibody fragment (ScFv). Intracellular expression of ScFv anti-ATF-1 in MeWo melanoma cells caused significant reduction in CRE-dependent promoter activation. In addition, expression of ScFv anti-ATF-1 in melanoma cells suppressed their tumorigenicity and metastatic potential in nude mice. ScFv anti-ATF-1 rendered the melanoma cells susceptible to thapsigargin-induced apoptosis in vitro and caused massive apoptosis in tumors transplanted subcutaneously into nude mice, suggesting that ATF-1 and its associated proteins act as survival factor for human melanoma cells. This is the first report to demonstrate the potential of ScFv anti-ATF-1 as an inhibitor of tumor growth and metastasis of solid tumor in vivo. Oncogene (2000).
Blastomere lineages are differentially biased to produce different neurotransmitter subtypes of amacrine cells (Huang and Moody, 1995, 1997,). To elucidate when this bias is acquired, we examined amacrine lineages at different early developmental times. Our experiments demonstrate that the bias to express dopamine and neuropeptide Y amacrine fates involves several steps before the formation of the definitive optic cup. At cleavage stages, a retinal progenitor that contributes large numbers of cells is already biased to produce its normal repertoire of dopamine amacrine cells, as revealed by transplantation to a new location, whereas the amacrine fate of a progenitor that contributes fewer cells is modified by its new position. At neural plate stages, not all retinal progenitors are multipotent. Nearly one-half populate only the inner nuclear layer and are enriched in amacrine cells. During early optic vesicle stages, an appropriate mitotic tree is required for dopamine and neuropeptide Y, but not serotonin, amacrine cell clusters to form. Thus, the acquisition of amacrine fate bias involves intrinsic maternal factors at cleavage, fate restriction in the neural plate, and specified mitotic patterns in the optic vesicle. At each of these steps only a subset of the embryonic retinal progenitors contributing to amacrine subtypes is biased; the remaining progenitors maintain multipotency. Thus, from the earliest embryonic stages, progenitors of the retina are a dynamic mosaic. This is the first experimental demonstration of amacrine fate decisions that occur during early embryonic periods in advance of the events described in the later, committed retina.
Overexpression of urokinase plasminogen activator (uPA) and its receptor (uPAR) has been well documented in a wide variety of tumor cells. In breast cancer, expression of uPA/uPAR is essential for tumor cell invasion and metastasis. However, the mechanism responsible for uPA/uPAR expression in cancer cells remains unclear. In the studies reported here, we show that endogenous p38 MAPK activity correlates well with breast carcinoma cell invasiveness. Treatment of highly invasive BT549 cells with a specific p38 MAPK inhibitor SB203580 diminished both uPA/uPAR mRNA and protein expression and abrogated the ability of these cells to invade matrigel, suggesting that p38 MAPK signaling pathway is involved in the regulation of uPA/uPAR expression and breast cancer cell invasion. We also demonstrated that SB203580-induced reduction in uPA/uPAR mRNA expression resulted from the de- stabilization of uPA and uPAR mRNA. Finally, by selectively inhibiting p38alpha or p38beta MAPK isoforms, we demonstrate that p38alpha, rather than p38beta, MAPK activity is essential for uPA/uPAR expression. These studies suggest that p38alpha MAPK signaling pathway is important for the maintenance of breast cancer invasive phenotype by promoting the stabilities of uPA and uPAR mRNA.
alpha(v) integrins have been shown to play an important role in epithelial-derived cell migration, cell growth and tumor invasion/metastasis, however their role on cells of hematopoietic origin is less clear. Epstein-Barr virus (EBV), a human herpesvirus associated with several lymphoproliferative disorders in man, induces expression of alpha(v) integrins on transformed B lymphocytes. In the studies reported here, we show that EBV infection increases alpha(v), beta3 and beta5 integrin subunit mRNAs as well as upregulates the expression of the alphavbeta3 integrin protein on human B cells. Among the nine different EBV proteins expressed in latently infected B cells (nuclear and plasma membrane-associated), only LMP1, LMP2A and EBNA2 were shown to selectively transactivate the alpha(v) integrin promoter. Treatment of EBV-transformed B cells with alpha(v) antisense oligonucleotides specifically reduced cell surface expression of alpha(v) integrins, inhibited cell growth in low serum, reduced cell invasion in matrigels and decreased expression of metalloprotease, MMP9. These studies indicate that alpha(v) integrins play a significant role in EBV-induced B-lymphocyte proliferation and invasion. Strategies to interfere with alphav integrin expression and/or function may therefore be of potential value in the treatment of EBV-associated lymphoproliferative disorders.
Three-dimensional microfluidic systems were fabricated and used to pattern proteins and mammalian cells on a planar substrate. The three-dimensional topology of the microfluidic network in the stamp makes this technique a versatile one with which to pattern multiple types of proteins and cells in complex, discontinuous structures on a surface. The channel structure, formed by the stamp when it is in contact with the surface of the substrate, limits migration and growth of cells in the channels. With the channel structure in contact with the surface, the cells stop dividing once they form a confluent layer. Removal of the stamp permits the cells to spread and divide.