Biomedical subjects

X Fan

Publications and source records attributed to X Fan.

At least 145 records · Page 8Linked to original sources

PubMed1999

[Expression and clinical implication of multidrug resistant-associated protein gene (MRP) in patients with laryngeal squamous cell carcinoma].

OBJECTIVE: To study the relationship between the expression of MRP mRNA and the clinical pathological characteristics of the patients with laryngeal squamous cell carcinoma. METHOD: Reverse transcription polymerase chain reaction (RT-PCR) assay was used to detect the expression of MRP mRAN in 35 patients. RESULT: The positive expression rate of MRP mRAN was 45.7 percent (16/35) in laryngeal carcinoma. It was higher in advanced (T3-4) patients than that in early (T1-2) cases (P < 0.05) and showed a significant correlation with metastases of cervical lymph node (P < 0.01). CONCLUSION: It is suggested that the expression of MRP mRNA may not only play an important role in multidrug resistance of laryngeal carcinoma, but also influence their biological behavior of dissemination and metastases.

Adult↗

PubMed1999

[Relationship between complement activation and reactive oxygen species generation in inflammatory response].

OBJECTIVE: To verify the proposed activation feedback mechanism between complement and polymorphonuclear leukocytes(PMN) derived reactive oxygen species(ROS). METHODS: In vitro tests were designed to identify the activation feedback process by alternative activations of complement by inulin or PMNs by 12-O-tetradecanoylphorbol-13-acetate(TPA) in the test medium in consisting serum complement and isolated PMNs, with chemiluminescence technique to determine the production of ROS and complement fixation trial for complement activations. RESULTS: Evidently that activated complement could activate PMNs to release ROS which further activated complement, so the activating feedback cycle was set. CONCLUSIONS: The complement and PMNs-ROS activation feedback cycle mechanism was recognized. It was expected to serve for delineating the regulation of inflammatory response.

Animals↗

PubMed1999

[Continuous positive airway pressure therapy after uvulopalatopharygoplasty].

OBJECTIVE: To investigate if uvulopalatopharygopalasty (UPPP) compromised continuous positive airway pressure (CPAP) therapy. METHODS: Automated continuous positive airway pressure(Auto CPAP) was applied to treat 15 patients with obstructive sleep apnea syndrome(OSAS) whose apnoea-hypopnoea index (AHI) was still higher than 20 after UPPP, and also it was used in the treatment of 32 randomly selected OSAS patients who had not had any treatment before. The treatment results of these 2 groups were compared. RESULTS: It was found that AHI and apnoea index(AI) between the 2 groups after Auto CPAP treatment were not significantly different (P > 0.05), however, lowest SO2(LSO2) after Auto CPAP treatment of the UPPP group was higher than that of the other group (P < 0.01). The AHI, AI and LSO2 in each group were significantly different before and after Auto CPAP treatment (P < 0.01 in both cases). CONCLUSION: It is suggested that CPAP remains effective after UPPP and UPPP doesn't compromise CPAP therapy.

Adult↗

PubMed1998

Mechanisms of hyaluronan-induced up-regulation of ICAM-1 and VCAM-1 expression by murine kidney tubular epithelial cells: hyaluronan triggers cell adhesion molecule expression through a mechanism involving activation of nuclear factor-kappa B and activating protein-1.

The matrix constituent hyaluronan (HA) markedly accumulates in inflammatory lesions. To gain insight into the biologic significance of this phenomenon we tested the hypothesis that HA could regulate cell adhesion molecule expression in epithelial cells. Using a clonal line of mouse cortical tubular (MCT) cells we found that fragmented intermediate m.w., but not high m.w., HA markedly increased ICAM-1 and VCAM-1 steady state mRNA and cell surface expression. Up-regulation of ICAM-1 and VCAM-1 mRNA by HA was preceded by a marked increase in NF-kappaB and activating protein-1 DNA binding activity in MCT cells. Transcript levels for the NF-kappaB inhibitor IkappaBalpha and for the activating protein-1 constituents c-jun and c-fos also increased in response to HA stimulation of tubular cells. Inhibition of NF-kappaB with the serine protease inhibitor N-tosyl-L-phenylalanine chloromethyl ketone blocked the HA-mediated expression of ICAM-1 and VCAM-1 in MCT cells. In conclusion, HA displays proinflammatory effects by directly stimulating the expression of the cell adhesion molecules ICAM-1 and VCAM-1 in mouse kidney epithelial cells. HA could thereby play an important role in leukocyte adhesion in inflammatory renal diseases.

3T3 Cells↗

PubMed1998

The role of C2 domains in Ca2+-activated and Ca2+-independent protein kinase Cs in aplysia.

In the nervous system of the marine mollusk Aplysia there are two protein kinase C (PKC) isoforms, the Ca2+-activated PKC Apl I and the Ca2+-independent PKC Apl II. PKC Apl I, but not PKC Apl II is activated by a short-term application of the neurotransmitter serotonin. This may be explained by the fact that purified PKC Apl II requires a higher mole percentage of phosphatidylserine to stimulate enzyme activity than does PKC Apl I. In order to understand the molecular basis for this difference, we have compared the ability of lipids to interact with the purified kinases and with regulatory domain fusion proteins derived from the kinases using a variety of assays including kinase activity, phorbol dibutyrate binding, and liposome binding. We found that a C2 domain fusion protein derived from PKC Apl I binds to lipids constitutively, while a C2 domain fusion protein derived from PKC Apl II does not. In contrast, fusion proteins containing the C1 domains of PKC Apl I and PKC Apl II showed only small differences in lipid interactions. Thus, while the presence of a C2 domain assists lipid-mediated activation of PKC Apl I, it inhibits activation of PKC Apl II.

Animals↗

PubMed1998

A lightweight universe?

How much matter is there in the universe? Does the universe have the critical density needed to stop its expansion, or is the universe underweight and destined to expand forever? We show that several independent measures, especially those utilizing the largest bound systems known-clusters of galaxies-all indicate that the mass-density of the universe is insufficient to halt the expansion. A promising new method, the evolution of the number density of clusters with time, provides the most powerful indication so far that the universe has a subcritical density. We show that different techniques reveal a consistent picture of a lightweight universe with only approximately 20-30% of the critical density. Thus, the universe may expand forever.

Journal Article↗

PubMed1998

The effect of class II major histocompatibility complex expression on adherence of Helicobacter pylori and induction of apoptosis in gastric epithelial cells: a mechanism for T helper cell type 1-mediated damage.

Helicobacter pylori infection is associated with gastric epithelial damage, including apoptosis, ulceration, and cancer. Although bacterial factors and the host response are believed to contribute to gastric disease, no receptor has been identified that explains how the bacteria attach and signal the host cell to undergo apoptosis. Using H. pylori as "bait" to capture receptor proteins in solubilized membranes of gastric epithelial cells, class II major histocompatibility complex (MHC) molecules were identified as a possible receptor. Signaling through class II MHC molecules leading to the induction of apoptosis was confirmed using cross-linking IgM antibodies to surface class II MHC molecules. Moreover, binding of H. pylori and the induction of apoptosis were inhibited by antibodies recognizing class II MHC. Since type 1 T helper cells are present during infection and produce interferon (IFN)-gamma, which increases class II MHC expression, gastric epithelial cell lines were exposed to H. pylori in the presence or absence of IFN-gamma. IFN-gamma increased the attachment of the bacteria as well as the induction of apoptosis in gastric epithelial cells. In contrast to MHC II-negative cell lines, H. pylori induced apoptosis in cells expressing class II MHC molecules constitutively or after gene transfection. These data describe a novel receptor for H. pylori and provide a mechanism by which bacteria and the host response interact in the pathogenesis of gastric epithelial cell damage.

Animals↗

PubMed1998

Compartmentalization of bacterial antigens: differential effects on priming of CD8 T cells and protective immunity.

Bacterial pathogens synthesize numerous proteins that are either secreted or localized within bacterial cells. To address the impact of antigen compartmentalization on T cell immunity, we constructed recombinant Listeria monocytogenes that express a model CD8T cell epitope as a secreted or nonsecreted fusion protein. Both forms of the antigen, either secreted into the host cell cytoplasm or retained within bacterial cells, efficiently prime CD8 T cell responses. However, epitope-specific CD8 T cells confer protection only against bacteria secreting the antigen but not against the bacteria expressing the nonsecreted form of the same antigen. This dichotomy as a result of antigen compartmentalization suggests that bacterial antigens are presented by multiple MHC class I pathways to prime CD8 T cells, but only the endogenous pathway provides target antigens for CD8 T cell-mediated protective immunity.

Antigens, Bacterial↗

PubMed1998

Identification and characterization of a protein kinase-interacting protein encoded by the Autographa californica nuclear polyhedrosis virus.

We have used a yeast two-hybrid system to identify a baculoviral gene encoding a protein kinase-interacting protein (PKIP). The pkip gene is located at 15.8-16.2 m.u (map units) and represents ORF 24 in the sequence of Ayres et al. (1994) of the Autographa californica nuclear polyhedrosis virus. PKIP is a 19.2-kDa protein and appears to stimulate the activity of the viral protein kinase-1 in vitro. Northern blotting analysis revealed that pkip is a late gene. Attempts to plaque purify a pkip- virus were unsuccessful.

Amino Acid Sequence↗

PubMed1998

Lymphocytes in the human gastric mucosa during Helicobacter pylori have a T helper cell 1 phenotype.

BACKGROUND & AIMS: Studies have shown that gastric T cells are increased during Helicobacter pylori infection. The purpose of this study was to characterize the human gastric T-cell responses in the presence or absence of H. pylori. METHODS: T-cell surface antigens were examined by immunohistochemistry or after isolation for evaluation of surface antigens and cytoplasmic cytokines using flow cytometry. RESULTS: CD4+ and CD8+ T cells were increased in situ during infection with H. pylori. Freshly isolated gastric T cells expressed cytoplasmic interferon gamma (IFN-gamma) and interleukin (IL)-2 after a brief stimulation. Simultaneous four-color flow cytometry demonstrated that both CD8+ and CD4+ T cells expressed IFN-gamma. Because stimulation through CD30 favors the induction of IL-5 and Th2 cells, gastric and colonic T cells were examined for CD30 expression. Consistent with the notion that Th2 cells are found in the intestine, CD30 was evident throughout the lamina propria of the colon but was virtually absent in the stomach. Furthermore, freshly isolated gastric T cells produced little IL-4 and virtually no IL-5 or tumor necrosis factor beta. CONCLUSIONS: These observations show that gastric T cells resemble the Th1 type, which may explain their failure to induce immunity to H. pylori and their ability to contribute to the pathogenesis of gastric disease.

Adult↗

PubMed1998

Listeria monocytogenes as a probe to study cell-mediated immunity.

The intracellular bacterium Listeria monocytogenes continues to serve as a model to define general paradigms of cell-mediated immunity. Genetic manipulations of the bacterium and its murine host have allowed us to begin dissecting the intricate interactions between this bacterium and the immune system. As a result, we have gained new insights into the mechanisms of immune surveillance, achieved better understanding of bacterial tactics for immune evasion and developed novel strategies in vaccine development.

Animals↗

PubMed1998

Antioxidative activities in some common seaweeds.

Dietary antioxidants from plants are believed to help prevent aging and other diseases through radical scavenging activity. Free radical scavenging activities by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and deoxyribose assay were ascertained among 27 species of common seaweeds using a sequential extraction method. The results indicated that, DPPH scavenging activity existed in 15 species; Gelidium amansii, Gloiosiphonia capillaris, Polysiphonia urceolata, Sargassum kjellmanianum, Desmarestia viridis, and Rhodomela teres showed the strongest activities. On the other hand, the deoxyribose results showed that almost all the seaweed species had good ability to scavenge hydroxyl radicals. The most active species were Rhodomela teres and Chorda filum.

Antioxidants↗

PubMed1998

Characterization of CD44-mediated hyaluronan binding by renal tubular epithelial cells.

BACKGROUND: CD44 is the main receptor for the extracellular polysaccharide hyaluronan (HA). We have recently shown that CD44 is strongly induced on renal tubular epithelial cells (TEC) in autoimmune renal injury and that HA accumulates in the renal interstitium (Kidney Int 1996; 50: 156-163 and Nephrol Dial Transplant 1997; 12: 1344-1353). The functional significance of enhanced tubular CD44 expression and its interaction with HA are not known. The purpose of the present study was to characterize renal tubular CD44 expression and CD44-mediated HA binding in vitro and to investigate the growth modulating effects in response to HA binding by TEC. METHODS: RT-PCR analysis, flow cytometry, confocal microscopy and Western blotting were used to examine cell surface and soluble CD44 expression by cultured TEC, using SV40-transformed mouse cortical tubular (MCT) cells. HA binding characteristics were examined by flow cytometry and effects of HA on TEC cell growth by [3H]thymidine incorporation. RESULTS: By RT-PCR analysis MCT cells expressed predominantly the standard form of CD44 mRNA, whereas the expression of variant forms was very weak. Confocal microscopy showed that CD44 was expressed basolaterally and apically on MCT cells with strong staining on microvilli. Shedding of CD44 from MCT cells could be induced with crosslinking of anti-CD44 mAbs or with PMA stimulation. MCT cells constitutively bound HA and this binding could be modulated with anti-CD44 mAbs. Soluble and plate-bound HA markedly inhibited MCT cell growth. CONCLUSIONS: CD44 is a regulated HA receptor on MCT cells which can be shed into the cellular environment. Upon binding of HA, CD44 functions as a growth inhibitory cell surface protein in MCT cells. We speculate that the interaction of CD44 with HA may have important regulatory effects on cell proliferation in tubulointerstitial renal diseases.

Animals↗

PubMed1998

Dexamethasone promotes expression of membrane-bound macrophage colony-stimulating factor in murine osteoblast-like cells.

The mechanisms by which glucocorticosteroids promote osteoclastogenesis in vitro are uncertain. As macrophage colony-stimulating factor (MCSF) is critical for osteoclastogenesis, we hypothesized that glucocorticosteroids might regulate membrane-bound MCSF (mMCSF) and soluble MCSF (sMCSF) production by stromal cells or osteoblasts. ST2 cells or murine calvarial osteoblasts (MOBs) were treated with dexamethasone (Dex; 100 nM) and/or 1,25-dihydroxyvitamin D [1,25(OH)2D; 10 nM] for 3 days. Control values for mMCSF and sMCSF as units per 100,000 cells were 9 +/- 1.4 and 511 +/- 56 in ST2 cells and 5.9 +/- 0.8 and 379 +/- 47 in MOB cells, respectively. Dex increased mMCSF to 156 +/- 16% and 143 +/- 26% compared with the control value in ST2 and MOB cells, respectively, whereas 1,25-(OH)2D caused increases of 195 +/- 16% and 164 +/- 21%. In the presence of both Dex and 1,25-(OH)2D, mMCSF increased to 209 +/- 24% and 216 +/- 26% in the two cell types, respectively. 1,25-(OH)2D caused modest increases in sMCSF, as expected, in both cell types (153 +/- 6% and 122 +/- 4%). Dex inhibited 1,25-(OH)2D-stimulated sMCSF (115 +/- 7% of control) in ST2 cells. Analysis of mMCSF transcript levels by semiquantitative RT-PCR revealed Dex-stimulated increases of 170 +/- 11% in ST2 cells and 126 +/- 16% in MOB cells compared with the control level. The increased expression of the transcript for sMCSF in the presence of Dex and 1,25-(OH)2D, measured by both RT-PCR and Northern analysis (219 +/- 53% and 242%, respectively), despite inhibition of sMCSF protein, indicated that the inhibitory effect of Dex in ST2 cells was posttranscriptional. Half-life studies showed that Dex prolonged MCSF messenger RNA from 2.8 to 7.5 h. These results suggest that Dex influences osteoclastogenesis by increasing the expression of mMCSF by accessory cells in culture.

Animals↗

PubMed1998

Orchidectomy induces a wave of apoptotic cell death in the epididymis.

The epididymis is the site where spermatozoa are matured and stored. After orchidectomy, this tissue loses up to 80% of its weight. In the prostate, androgen withdrawal by orchidectomy is associated with apoptotic cell death. The objective of the present study was to investigate whether apoptotic cell death is involved in the androgen-dependent weight loss found in the rat epididymis after orchidectomy. Adult male Sprague-Dawley rats were orchidectomized, and apoptotic cells were identified by in situ TUNEL (TdT-mediated dUTP-digoxigenin nick end-labeling) apoptosis detection. Apoptosis first appeared in the epithelium of the initial segment of the epididymis 18 h after orchidectomy, reached a maximum on day 2, and disappeared by day 5 postorchidectomy. In the caput epididymidis, apoptosis was first found after 24 h, reached a maximum by day 3, and was detectable until day 5. In the corpus epididymidis, apoptosis was first seen on day 4, peaked on day 5, and was undetectable by day 6 postorchidectomy. In the cauda epididymidis, apoptosis was first seen on day 5, peaked on day 6, and was occasionally detected on day 7. Throughout the rat epididymis, apoptotic cell death was localized specifically to principal cells. The presence of apoptosis was confirmed with the observation of a ladder of nucleosomal sized DNA fragmentation by using agarose gel electrophoresis. Androgen replacement therapy after orchidectomy demonstrated that apoptosis in the caput, corpus, and cauda epididymidis was androgen dependent. However, androgens alone could not completely prevent apoptosis in the initial segment of the epididymis. Efferent duct ligation induced a similar pattern of apoptosis in the initial segment of the epididymis as that seen after orchidectomy, but there were fewer apoptotic cells in the caput epididymidis, and no apoptotic cell death in the corpus and cauda epididymidis. We conclude that withdrawal of androgen by orchidectomy induces a wave of apoptotic cell death in the epididymis; we hypothesize that apoptosis in the initial segment is caused primarily by withdrawal of androgen as well as by luminal components coming from the testis.

Animals↗

PubMed1998

Enhanced osteopontin expression and macrophage infiltration in MRL-Fas(lpr) mice with lupus nephritis.

MRL-Fas(lpr) mice spontaneously develop a chronic lupus-like renal disease, characterized by immune complex-mediated glomerulonephritis and abundant mononuclear cell infiltration in the interstitium. In the present study we have examined whether the macrophage chemoattractant osteopontin (Opn) could be important in the recruitment of macrophages in this murine model of autoimmune renal injury. We have examined the expression of Opn in the kidney of MRL-Fas(lpr) mice and have correlated Opn synthesis with the degree of macrophage infiltration. Immunofluorescence staining revealed prominent expression of Opn by proximal tubules in MRL-Fas(lpr) mice but not in MRL-++ control mice. Northern blot analysis demonstrated that steady-state transcript levels for Opn mRNA were also significantly increased in MRL-Fas(lpr) kidneys compared with control kidneys. Furthermore, in situ hybridization showed massive Opn mRNA transcripts in proximal tubules in MRL-Fas(lpr) mice but not in controls. The diffuse macrophage infiltration in the kidney of MRL-Fas(lpr) correlated with the enhanced Opn expression. Opn secretion in vitro by cultured renal tubular epithelial cells was upregulated by TNF-alpha and 1,25(OH)2-vitamin D3, whereas no regulation was observed in a control macrophage cell line. We conclude that the enhanced expression of the chemotactic molecule Opn by tubular cells is a prominent feature of murine lupus nephritis and might be promoted by the proinflammatory cytokine environment in MRL-Fas(lpr). The chronic upregulation of Opn could participate in the recruitment of monocytes in the kidney of MRL-Fas(lpr) mice, thereby contributing to the pathogenesis of autoimmune renal disease.

Animals↗

PubMed1998

Differential polymerase chain reaction: a technical comparison of three methods for the detection of CDK4 gene amplification in glioblastomas.

Among the different techniques used to detect oncogene amplification in tumor DNA, Southern blot and differential PCR have been the most frequently used. We report on a technical comparison of three different methods to detect gene amplification by differential PCR: ethidium bromide staining, silver staining (both after standard differential PCR), and fluorescent differential PCR. We explored the relative densitometric measure of a 119 bp fragment of the CDK4 gene versus an 82 bp fragment of the IFNG gene. In total agreement with previous studies carried out by Southern blot and differential PCR by other authors, we were able to detect CDK4 amplification in 3 of the 21 glioblastomas (14%), but only by the fluorescent differential PCR method. In conclusion, fluorescent differential PCR is more sensitive than standard differential PCR for detection oncogene amplification in tumor DNAs.

Brain Neoplasms↗

PubMed1998

[Applied anatomy of insular skin flap of nasolabial groove with retrograde superior labial artery].

In order to study the feasibiliy of the insular skin flap of the nasolabial groove with the retrograde superior labial artery, 8 adult cadavers were dissected and the relation between the superior labial artery and the skin of nasolabial groove was observed. The result revealed that superior labial artery was one of the branches of the facial artery and could be found in every cadaver. The diameter of the artery was 0.8 +/- 0.1 mm and the length was about 90 mm. The left and right facial arteries were connected with each other in the mid-line in the formation of the arcuate artery. The arcuate artery lay within the submucous tissue beyond the vermilion border about 6 mm. The concomitant veins were constant. If the facial artery being sectioned was beyond its initial site of superior labial artery, the skin of nasolabial groove on the same side could receive blood supply from contralateral supperior labial artery. The conclusion was that the insular skin flap of the nasolabial groove with the retrograde superior labial artery could be used in patients, because it had support from anatomical research.

Adult↗