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H Duan

Publications and source records attributed to H Duan.

At least 19 recordsLinked to original sources
PubMed2006

The immunoglobulin heavy-chain gene 3' enhancers deregulate bcl-2 promoter usage in t(14;18) lymphoma cells.

In t(14;18) lymphomas, bcl-2 is juxtaposed to the immunoglobulin heavy-chain gene (IgH), resulting in increased bcl-2 transcription and resistance to apoptosis. Regulatory elements of both the bcl-2 promoter and the IgH enhancers are believed to play a role in the increased expression of bcl-2 in t(14;18) lymphoma cells. In addition, transcription of the translocated bcl-2 allele is deregulated with activation of the normally minor bcl-2 P2 promoter. The mechanisms involved in the promoter shift from P1 to P2 are not known. We found that the murine IgH 3' enhancers increased bcl-2 P2 promoter activity in an episomal model of the translocation, and IgH enhancer region HS12 had the greatest effect. Quantitative chromatin immunoprecipitation (ChIP) assays revealed that localized histone H3 hyperacetylation of the P2 promoter was observed on the translocated allele in t(14;18) DHL-4 cells and also on the stably transfected bcl-2 promoter-IgH enhancer episomal construct. Analysis of the HS12 enhancer region revealed that a previously identified nuclear factor-kappaB (NF-kappaB) site and a previously uncharacterized downstream Cdx site, both of which are conserved in the human and murine IgH enhancers, were important for its enhancer activity and promoter activation. ChIP assays showed that C/EBPbeta bound to the HS12 Cdx site in vivo, and mutation of this site abrogated the binding of C/EBPbeta. Reduced expression of C/EBPbeta by transfection of small interfering RNA or interference with NF-kappaB activity decreased transcription from the bcl-2 promoters. These results demonstrate that the IgH 3' enhancers, particularly HS12, are important for the deregulation of bcl-2 promoter usage in t(14;18) lymphomas.

Acetylation↗
PubMed2006

Oct transcription factors mediate t(14;18) lymphoma cell survival by directly regulating bcl-2 expression.

Oct-1 and Oct-2 are members of the POU homeodomain family of transcriptional regulators and are critical for normal embryonic development. Gene-targeting studies showed that Oct-1 and Oct-2 are largely dispensable for B-cell development and immunoglobulin production, although both Oct-2 and Bob-1 are required for a proper immune response and germinal center formation. In these studies, we investigated the role of Oct factors in B-cell lymphomas. Recent investigations have shown increased expression of Oct-2 and Bob-1 in lymphomas, and we observed greatly increased levels of Oct-2 in lymphoma cells with the t(14;18) translocation. Decreased expression of Oct-1, Oct-2, or Bob-1 by RNA interference resulted in apoptosis and down-regulation of bcl-2 expression. Furthermore, Oct-2 induced bcl-2 promoter activity and mediated this effect through three regions in the bcl-2 P2 promoter. Although these regions did not contain canonical octamer motifs, we observed the direct interaction of Oct-2 with all three sites both in vitro by EMSA and in vivo by chromatin immunoprecipitation assay. Moreover, by mutation analysis we found that the ability of Oct-2 to activate bcl-2 required C/EBP, Cdx, and TATA-binding sites. Oct-2, therefore, acts as a cell survival factor in t(14;18) lymphoma cells by directly activating the antiapoptotic gene bcl-2.

Apoptosis↗
PubMed2003

Basal cell carcinomas in association with basaloid follicular hamartoma.

We describe a unique case of various types of basal cell carcinoma (BCC) associated with basaloid follicular hamartoma (BFH) in a 56-year-old female patient. The lesion consisted of a dark brown and elastic soft nodule and papules within the area of a birthmark on the neck. The lesion was surgically excised. Histological examination of the nodular region revealed aggregations of neoplastic basaloid cells. We diagnosed the nodule as BCC with a racemiform or reticular pattern. In addition, a specimen taken from brownish black papules within the birthmark was found to be composed of anastomosing cords of basaloid cells accompanied by infundibular cystic structures. These features were consistent with an infundibulocystic BCC. In contrast, specimens from a hamartomatous plaque showed distinctive branching strands of basaloid cells that are suggestive of BFH. Therefore, our findings indicate that several types of BCC may develop within a BFH.

Adult↗
PubMed2002

Self-organization of supramolecular helical dendrimers into complex electronic materials.

The discovery of electrically conducting organic crystals and polymers has widened the range of potential optoelectronic materials, provided these exhibit sufficiently high charge carrier mobilities and are easy to make and process. Organic single crystals have high charge carrier mobilities but are usually impractical, whereas polymers have good processability but low mobilities. Liquid crystals exhibit mobilities approaching those of single crystals and are suitable for applications, but demanding fabrication and processing methods limit their use. Here we show that the self-assembly of fluorinated tapered dendrons can drive the formation of supramolecular liquid crystals with promising optoelectronic properties from a wide range of organic materials. We find that attaching conducting organic donor or acceptor groups to the apex of the dendrons leads to supramolecular nanometre-scale columns that contain in their cores pi-stacks of donors, acceptors or donor-acceptor complexes exhibiting high charge carrier mobilities. When we use functionalized dendrons and amorphous polymers carrying compatible side groups, these co-assemble so that the polymer is incorporated in the centre of the columns through donor-acceptor interactions and exhibits enhanced charge carrier mobilities. We anticipate that this simple and versatile strategy for producing conductive pi-stacks of aromatic groups, surrounded by helical dendrons, will lead to a new class of supramolecular materials suitable for electronic and optoelectronic applications.

Journal Article↗
PubMed2002

Quantitative analysis of the dendritic morphology of corticocortical projection neurons in the macaque monkey association cortex.

The polymodal association areas of the primate cerebral cortex are heavily interconnected and play a crucial role in cognition. Area 46 of the prefrontal cortex in non-human primates receives direct inputs from several association areas, among them the cortical regions lining the superior temporal sulcus. We examined whether projection neurons providing such a corticocortical projection differ in their dendritic morphology from pyramidal neurons projecting locally within area 46. Specific sets of corticocortical projection neurons were identified by in vivo retrograde transport in young macaque monkeys. Full dendritic arbors of retrogradely labeled neurons were visualized in brain slices by targeted intracellular injection of Lucifer Yellow, and reconstructed three-dimensionally using computer-assisted morphometry. Total dendritic length, numbers of segments, numbers of spines, and spine density were analyzed in layer III pyramidal neurons forming long projections (from the superior temporal cortex to prefrontal area 46), as well as local projections (within area 46). Sholl analysis was also used to compare the complexity of these two groups of neurons. Our results demonstrate that long corticocortical projection neurons connecting the temporal and prefrontal cortex have longer, more complex dendritic arbors and more spines than pyramidal neurons projecting locally within area 46. The more complex dendritic arborization of such neurons is likely linked to their participation in cortical networks that require extensive convergence of multiple afferents at the cellular level.

Animals↗
PubMed2002

Immunohistochemical detection of interferon-gamma-producing cells in granuloma formation of sporotrichosis.

Granuloma formation is a common response in the skin infection of sporotrichosis. The involvement of interferon-gamma (IFN-gamma) and inducible nitric oxide synthase (iNOS) in the granuloma formation of sporotrichosis is less known. The aim of this study was to describe by immunohistochemistry the exact tissue distribution of IFN-gamma-positive cells and iNOS-positive cells in the granuloma of skin lesions from patients with sporotrichosis. Formalin-fixed paraffin-embedded skin biopsy sections from five patients were stained by immunohistochemical methods. Mixture of CD4-positive T cells and CD8-positive T cells were present in and around the granulomatous lesions. IFN-gamma-positive cells, like mononuclear lymphoid cells, were detected in the periphery of the granulomas in all samples. The pattern of IFN-gamma staining appeared to be a combination of intracellular staining in mononuclear lymphoid cells and extracellular deposition in the surrounding tissue. The majority of the epitheloid cells and multinucleated giant cells within the granuloma were identified by immunostaining for CD68. In contrast, no expression of immunoreactive iNOS was observed in those cells in all samples. These findings indicate that granulomas of sporotrichosis are coupled with Th1 response.

Antibodies, Monoclonal↗
PubMed2001

Definitive support by transmission electron microscopy, electron diffraction, and electron density maps for the formation of a BCC lattice from poly[N-[3,4,5-tris(n-dodecan-1-yloxy)benzoyl]ethyleneimine].

Transmission electron microscopy (TEM), electron diffraction (ED), and electron density maps (EDM) experiments were carried out on a poly[N-[3,4,5-tris(n-dodecan-1-yloxy)benzoyl]ethyleneimine] [poly[(3,4,5)12G1-Oxz]] with a degree of polymerization (DP) of 20. All experiments confirmed the thermotropic body-centered cubic (BCC) Im3m lattice suggested previously by X-ray diffraction (XRD) experiments. The unit cell parameter determined by ED at 23 degrees C is a = 42.4 A, in good agreement with XRD results which show a = 42.6 A after quenching from 70 degrees C. EDM of the XRD results confirm that the supramolecular minidendrimer obtained from poly[(3,4,5)12G1-Oxz] adopts a spherical "inverse micellar-like" structure, with the polyethyleneimine backbone and the aromatic groups microsegregated and concentrated in the corners and in the center of the cubic unit cell. A space-filling continuum is realized by the n-alkyl groups that radiate out of the aromatic core of the spherical dendrimer. This manuscript is only the second example of complete structural analysis of a lattice generated from supramolecular objects and complements the previous example reported from our laboratory on the Pm3n lattice.

Journal Article↗
PubMed2001

v-Ha-RaS oncogene upregulates the 92-kDa type IV collagenase (MMP-9) gene by increasing cellular superoxide production and activating NF-kappaB.

Matrix metalloproteinase 9 (MMP-9) degrades basement membrane type IV collagen and is expressed during cellular migration and invasion. Here we show that v-Ha-Ras overexpression in rat kidney epithelial cells (REC) caused upregulation of MMP-9 gene expression in part by increasing cellular oxidant levels. v-Ha-Ras mediated the production of superoxide in Ras-transfected cells, which was associated with upregulated MMP-9 gene expression. Conversely, v-Ha-Ras expression decreased steady-state levels of mRNAs from tissue inhibitor of metalloproteinase 1 (TIMP-1), an inhibitor of MMP-9; plasminogen activator inhibitor 1 (PAI-1), which indirectly activates MMP-9 by increasing plasmin levels; and collagen IV, a substrate of MMP-9 and a major component of basement membrane. Gel mobility shift assays demonstrated that Ras overexpression enhanced NF-kappaB, but not AP-1 DNA binding to motifs in the MMP-9 gene promoter. The Ras-induced increase in NF-kappaB DNA binding could be inhibited by treatment with the antioxidants N-acetyl-L-cysteine and glutathione monoester, suggesting that intracellular oxidant levels can mediate MMP-9 transcription. Our findings identify an important role for Ras in the regulation of MMP-9 expression, and suggest that increased superoxide production can upregulate MMP-9 expression and thus contribute to malignant conversion.

Animals↗
PubMed2001

Promotion of S-phase entry and cell growth under serum starvation by SAG/ROC2/Rbx2/Hrt2, an E3 ubiquitin ligase component: association with inhibition of p27 accumulation.

The sensitive-to-apoptosis gene (SAG) was initially identified as a redox-inducible, apoptosis-protective protein and subsequently found to be the second family member of regulator of cullins (ROC)/RING box protein (Rbx)/Hrt, which acts as a component of E3 ubiquitin ligase. We report here that SAG promoted cell growth under serum starvation. Microinjection of SAG mRNA into quiescent NIH/3T3 cells induced S-phase entry as determined by [(3)H]-thymidine incorporation. Likewise, overexpression of SAG by either adenovirus infection of immortalized human epidermal keratinocytes (Rhek-1) or DNA transfection of SY5Y human neuroblastoma cells induced cell proliferation under serum starvation. Because cyclin-dependent kinase inhibitors (CKIs), including p21, p27, and p57, are degraded through the ubiquitin pathway, we tested whether SAG-induced cell growth is associated with CKI degradation. Although there was no significant difference in the levels of p21 and p57 between the vector controls and SAG-overexpressing cells, serum starvation induced 10- to 18-fold accumulation of p27 in control Rhek-1 cells. Accumulation of p27 was remarkably inhibited (only 2 to 5-fold) in SAG-infected cells. Inhibition of p27 accumulation was also observed in stably SAG-overexpressing SY5Y cells. Significantly, SAG-associated inhibition of p27 accumulation was largely abolished by the treatment with a proteasome inhibitor. In vivo binding of SAG and Skp2, an F-box protein that promotes p27 ubiquitination, was detected, and the binding was enhanced in SAG-overexpressing cells grown under serum starvation. Thus, SAG-induced growth with serum withdrawal appears to be associated with SAG-mediated p27 degradation. Mol. Carcinog. 30:37-46, 2001.

Animals↗
PubMed2001

Determination of synthesized alpha-vitamin E by micellar electrokinetic chromatography.

We developed a micellar electrokinetic chromatography method (MEKC) for the direct determination of the content of synthesized alpha-vitamin E. It was found that under the optimum separation conditions 7 mM borate + 14 mM phosphate + 15 mM sodium dodecyl sulfate (SDS) + 10 mM sodium cholate (NaCh) + 8% acetonitrile (pH 9.2) with UV detection wavelength at 214 nm, 16 kV constant voltage, and 26 degrees C constant temperature, alpha-vitamin E and its isomers can be baseline separated and alpha-vitamin E was quantitatively analyzed. In addition, the sample recovery, the limit of detection and the repeatability of the method were investigated. The influence of various parameters on the separation such as SDS concentration, NaCh concentration, buffer pH and acetonitrile percentage were also discussed.

Acetonitriles↗
PubMed2001

Interleukin-8-positive neutrophils in psoriasis.

We performed an immunohistochemical study to try to determine the cellular source of interleukin-8 (IL-8) in psoriatic skin lesions. IL-8 was positively stained in the vast majority of neutrophils but not in the mononuclear cells, macrophages, or keratinocytes. IL-8-positive neutrophils were seen both in Munro's microabcesses in cases of psoriasis vulgaris and in a small spongiform pustule and much larger macropustules of Kogoj in cases of pustular psoriasis. Some IL-8-positive neutrophils were observed in the upper dermis of pustular psoriasis. The staining was considered to be specific because it could be completely blocked by preabsorption with recombinant IL-8. In addition, stimulation of human neutrophils with lipopolysaccharide (LPS) or tumor necrosis factor-alpha (TNF-alpha) for 18 h induced IL-8 production in vitro. In our study, IL-8 was expressed in the neutrophils of psoriasis, suggesting that neutrophils are one of the sources of IL-8 in psoriasis. The expression of IL-8 and the influx of neutrophils led us to speculate that the IL-8 autocrine and/or paracrine system functions in the formation of the microabcesses and pustules in proriasis.

Humans↗
PubMed2001

Transgenics in crops.

With rapid world population growth and declining availability of fresh water and arable land, a new technology is urgently needed to enhance agricultural productivity. Recent discoveries in the field of crop transgenics clearly demonstrate the great potential of this technology for increasing food production and improving food quality while preserving the environment for future generations. In this review, we briefly discuss some of the recent achievements in crop improvement that have been made using gene transfer technology.

Agriculture↗
PubMed2001

Poly(oxazolines)s with tapered minidendritic side groups. The simplest cylindrical models to investigate the formation of two-dimensional and three-dimensional order by direct visualization.

The synthesis of 2-[3,4-bis(n-alkan-1-yloxy)phenyl]-2-oxazolines with alkan = octan, decan, dodecan, and tridecan is presented. Their living cationic ring opening polymerization produces cylindrical macromolecules that self-organize in a hexagonal columnar two-dimensional phase. The structural analysis of these polymers was carried out by a combination of techniques including differential scanning calorimetry, thermal optical polarized microscopy, X-ray diffraction, transmission electron microscopy, electron diffraction, scanning force microscopy, and atomic force microscopy (AFM). The diameter of these cylindrical macromolecules ranges from 33 to 44 A, and therefore they represent the simplest cylindrical macromolecules that can be directly visualized by AFM on a surface. Preliminary experiments have demonstrated the use of these cylindrical macromolecules as models to investigate the creation of two-dimensional and three-dimensional order via direct visualization and thus they represent the simplest nonbiological systems that mimic the role played by the complexes of nucleic acids with proteins in structural analysis by direct visualization.

Calorimetry, Differential Scanning↗
PubMed2001

Immunosuppressive sesquiterpene alkaloids from Tripterygium wilfordii.

Nine new sesquiterpene pyridine alkaloids [wilfornines A (1), B (2), C (3), D (4), E (5), F (8), and G (9); wilfordinines I (6) and J (7)] and six known compounds (10-15) were isolated from a clinically used extract (T(II)) of Tripterygium wilfordii. The structures of 1-9 were elucidated by spectroscopic and chemical methods. The inhibitory effects on cytokine production of 1-3 and several related compounds were evaluated. Compounds 10 and 14 showed significant inhibitory effects on cytokine production.

Alkaloids↗
PubMed2001

Spontaneous regression of multiple seborrheic keratoses associated with nasal carcinoma.

Seborrheic keratoses are very common epidermal neoplasms. We describe a patient with seborrheic keratoses presenting multifocal spontaneous regression. The patient had a concurrent nasal adenoid cystic carcinoma. The simultaneous regression of seborrheic keratoses ceased after total resection of the nasal carcinoma. Histological examination revealed marked infiltration of mononuclear cells, including CD4+, CD8+, CD68+ and cutaneous lymphocyte-associated antigen-positive cells, with profound accumulation of CD1a+ dendritic cells. Although apoptotic keratinocytes were not found in the lesional epidermis by histology, the majority of keratinocytes in the regressing seborrheic keratosis were positively stained by the TUNEL method. We postulate that the internal malignancy may induce spontaneous regression of seborrheic keratoses.

Aged↗