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Biomedical subjects

S Xu

Publications and source records attributed to S Xu.

At least 127 records · Page 7Linked to original sources
PubMed2001

Cyclohexylamino-demethoxy-hypocrellin B and photodynamic therapy decreases human cancer in vitro.

2-Cyclohexylamino-2-demethoxy-hypocrellin B (CHAHB) is a new photosensitizer synthesized by the mild reaction between hypocrellin B (HB) and cyclohexylamine, in which the peri-hydroxylated perylenequinone structure of the parent HB is preserved and the photoresponse is enhanced markedly. Electron paramagnetic resonance (EPR) spin trapping measurements and 9,10-diphenylanthracene (DPA) bleaching studies were employed to investigate the photodynamic action of CHAHB in the presence of oxygen. Singlet oxygen ((1)O2) and superoxide anion radical (O2*-) generated by illuminating CHAHB in aerobic solution have been observed. Compared with HB, CHAHB distinctly enhanced the O2(*-)-generating abilities, although (1)O2-generating abilities were lowered. The photodynamic action of CHAHB in the therapy of cancer was investigated in vitro. The results in vitro revealed a much more significant decrease in cancer cell growth than with HB. Laser or dye alone had no effect, indicating that intratumor CHAHB and laser therapy may prove useful in unresectable cancer.

Cell Line↗
PubMed2001

[Investigation of group A rotavirus infection in several cities in China and prevalence of VP7 serotype].

OBJECTIVE: To study the prevalence of Group A rotavirus infection in China. METHODS: 374 samples from infants with diarrhea were collected from six cities (Beijing, Shenyang, Xinxiang, Shanghai, Shenzhen and Guangzhou) in autumn and winters of 1997 and/or 1998. The incidence of rotavirus infection and the prevalence of the four dominant serotypes G1, G2, G3, G4(VP7 serotype) were detected by PAGE and RT-PCR. RESULTS: Of the 374 samples detected, 181 were rotavirus positive. The positive rate was 48.4%, ranging from 32%-63% in different cities. The positive rates between 1997 and 1998 in Beijing and Shanghai were similar. Serotyped by RT-PCR method based on VP7 sequence, the positive rates of type G1, G2, G3 and G4 was 89.5%, 6.1%, 2.8% and 0, respectively. Two cases were found being coinfected with G1 and G2, and one case was confirmed to be infected with G9 by cDNA sequence analysis. There was a little difference in prevalence of G type rotavirus infection among samples from different cities and different years. CONCLUSION: The results indicated that rotavirus was the most important etiologic agent in this country, and the predominant serotypes were G1, G2 and G3.

Antigens, Viral↗
PubMed2001

[The influence of somatostatin 14 on the proliferation of human retroocular fibroblasts].

OBJECTIVE: To elucidate the possible mechanism of Somatostatin 14 in the treatment of Graves' ophthalmopathy, thus providing laboratory data with the intent to underpin therapeutic developments. METHODS: The human retro-ocular fibroblasts (HROFb) was cultured and MTT colorimetry assay was used to determine the proliferation of HROFb. RESULTS: MTT colorimetry assay could precisely reflect the proliferation of HROFb. The absorbance was directly proportional to the numbers of the cells (r = 0.996, P < 0.001). Somatostatin 14 could enhance the cell proliferation percentage at lower levels (< 25 nmol/L) and inhibit that at higher levels (> 25 nmol/L). The cell proliferation correlated positively to Somatostatin 14 levels significantly (r = -0.9054, P < 0.001). CONCLUSION: Somatostatin 14 has a dual effect on HROFb.

Cell Division↗
PubMed2001

[Cloning and expression of two garlic virus coat protein genes].

The coat protein(CP) genes of garlic mosaic virus(GMVc) and garlic latent virus(GLVc) isolated from garlic(Allium) plants in Tianjin, China, were amplified from an established cDNA library by PCR method and subsequently expressed in E. coli. using the pET-30a expression system. The determined sequences of GMVc and GLVc CP genes show that the complete GMVc CP gene has 867 nucleotides encoding 289 amino acids. It has 88.5% and 97.2% homology, at the levels of nucleotide and amino acid, respectively, to a reported GMV, indicating that it belongs to Potyvirus. The complete GLVc CP gene has 885 nucleotides coding for 294 amino acids. It has 73.6% and 90.9% homologous percents, in nucleotide and amino acid, respectively, compared to a previously reported GLV, suggesting that it is a member of Carlavirus. The expressed products presented in inclusion body and were analyzed by SDS-PAGE. The molecular weights of GMVc and GLVc CPs appear in 32 kD and 34 kD size, respectively, which are consistent with the deduced sizes of these two CPs. These data will be virtually significant to the further investigation of viruses infecting parlic plant, the control of garlic virus diseases and the production of virus-freed garlic plants.

Capsid Proteins↗
PubMed2001

[Synthesis of substituted 4-styrylcoumarin and their antitumor activities].

AIM: A series of 4-styrylcoumarin derivatives had been designed and synthesized in order to find compounds of antitumor activities by screening. METHODS: Title compounds (1-20) were synthesized by Phase-Transfer Wittig-Horner reaction, and screened by several antitumor models in vitro. Their structures were determined by 1HNMR, MS and elemental analysis. RESULTS: Twenty compounds (1-20) are new compounds. Compound 18 had effects on KB cell lines in vitro. CONCLUSION: It was seen that compound 18 had certain antitumor activities, and it was worth further studying.

Antineoplastic Agents↗
PubMed2001

[Pharmacological comparison between virosecurinine and securinine].

Pharmacological activities of virosecurinine (Vse) and securinine (Sec) were studied. The results showed that acute toxicity of Vse was 1/13.6 that of Sec, and Vse had no convulsive effects on rats or frogs, while Sec had. The results also showed that Vse and Sec could elevate blood pressure and excite respiration in cats.

Alkaloids↗
PubMed2001

[Retrospective analysis of supracricoid partial laryngectomy with epiglottis preserved and reconstruction of laryngeal function].

OBJECTIVE: To retrospectively evaluate the curative and functional consequences of supracricoid partial laryngectomy with epiglottis preserved. METHODS: From 1980 to 1996, 78 patients underwent supracricoid partial laryngectomy with the epiglottis preserved. The survival rate and the functional results were analyzed. RESULTS: Overall three-year survival rate was 87.2%(68/78), overall five-year survival rate was 75.6% (59/78), and ten-year survival rate was 21.1% (8/38). All patients resumed normal oral feeding. 97.4% (76/78) achieved tracheal extubation. Respiratory and speaking functions were good. CONCLUSION: Supracricoid partial laryngectomy with epiglottis preserved and reconstruction of laryngeal function not only improved local cancer control, but also preserves laryngeal physiologic function.

Adult↗
PubMed2001

Role of calcineurin in angiotensin II-induced cardiac myocyte hypertrophy of rats.

OBJECTIVE: The present study investigated the role of calcineurin in angiotensin II(AngII) -induced cardiac myocyte hypertrophy of rats. METHOD: The primary cardiac myocytes were cultured under the standard conditions. The calcineurin activity in AngII-treated cardiomyocytes was tested by using PNPP; protein synethsis rate was assessed by 3H-leucine incorporation; atrial natriuretic factor(ANF) mRNA level was determined by Northern blot analysis. Cell viability was estimated by lactate dehydrogenase (LDH) levels in cultured medium and by dyed cell numbers. RESULT: After stimulation of 10, 100 and 1 000 nmol/L of AngIi, calcineurin activities in the cardiomyocytes were increased by 13%, 57% (P < 0.05) and 228% (P < 0.01) respectively, compared with control group. Cyclosporin A(CsA), a specific inhibitor of calcineurin, markedly inhibited the calcineurin activity and decreased the 3H-leucine incorporation in AngII-treated cardiomyocytes in a dose-dependent manner. It was also found that CsA slightly reduced the mRNA level of ANF gene in AngII-stimulated cardiomyocytes. CONCLUSION: During AngII-induced cardiac myocyte hypertrophy, calcineurin signal pathway is activated, and inhibition of the pathway can attenuate AngII-induced cardiac myocyte hypertrophy, which suggests that the calcineurin signal pathway may play an important role in AngII-induced myocardial hypertrophy of rats.

Angiotensin II↗
PubMed2000

MEKK1 binds raf-1 and the ERK2 cascade components.

Mitogen-activated protein (MAP) kinase cascades are involved in transmitting signals that are generated at the cell surface into the cytosol and nucleus and consist of three sequentially acting enzymes: a MAP kinase, an upstream MAP/extracellular signal-regulated protein kinase (ERK) kinase (MEK), and a MEK kinase (MEKK). Protein-protein interactions within these cascades provide a mechanism to control the localization and function of the proteins. MEKK1 is implicated in activation of the c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) and ERK1/2 MAP kinase pathways. We showed previously that MEKK1 binds directly to JNK/SAPK. In this study we demonstrate that endogenous MEKK1 binds to endogenous ERK2, MEK1, and another MEKK level kinase, Raf-1, suggesting that it can assemble all three proteins of the ERK2 MAP kinase module.

Cell Line↗
PubMed2000

Mixed model analysis of quantitative trait loci.

We develop a mixed model approach of quantitative trait locus (QTL) mapping for a hybrid population derived from the crosses of two or more distinguished outbred populations. Under the mixed model, we treat the mean allelic value of each source population as the fixed effect and the allelic deviations from the mean as random effects so that we can partition the total genetic variance into between- and within-population variances. Statistical inference of the QTL parameters is obtained by using the Bayesian method implemented by Markov chain Monte Carlo (MCMC). This unified QTL mapping algorithm treats the fixed and random model approaches as special cases of the general mixed model methodology. Utility and flexibility of the method are demonstrated by using a set of simulated data.

Algorithms↗
PubMed2000

Transcriptional activity of the distal CD40 ligand promoter.

CD40 ligand (CD40L, CD154) is a T cell cytokine with highly regulated expression that requires the transcription factor nuclear factor of activated T cells (NF-AT) to bind at two sites in the proximal CD40L promoter. We have determined that the distal CD40L promoter (-500 to -1300 bp from start of transcription) conveys superior promoter activity in reporter gene assays. Within the distal promoter, we have identified a third NF-AT binding site, at -761 to -756. Oligonucleotides incorporating each of the three NF-AT sites cross-compete for binding of nuclear extracts from activated T cells and bind NF-ATc2 by antibody supershift. Mutation of the distal NF-AT site reduces activity of the 1300 bp CD40L promoter construct to that of the proximal 500 bp construct, which includes only two NF-AT sites. This suggests that the newly identified NF-AT site is the major mediator of transcriptional activation in the distal CD40L promoter.

Base Sequence↗
PubMed2000

CD2-mediated IL-12-dependent signals render human gamma delta-T cells resistant to mitogen-induced apoptosis, permitting the large-scale ex vivo expansion of functionally distinct lymphocytes: implications for the development of adoptive immunotherapy strategies.

The ability of human gamma delta-T cells to mediate a number of in vitro functions, including innate antitumor and antiviral activity, suggests these cells can be exploited in selected examples of adoptive immunotherapy. To date, however, studies to examine such issues on a clinical scale have not been possible, owing in large measure to the difficulty of obtaining sufficient numbers of viable human gamma delta-T cells given their relative infrequency in readily available tissues. Standard methods used to expand human T cells often use a combination of mitogens, such as anti-T-cell receptor antibody OKT3 and interleukin (IL)-2. These stimuli, though promoting the expansion of alpha beta-T cells, usually do not promote the efficient expansion of gamma delta-T cells. CD2-mediated, IL-12-dependent signals that result in the selective expansion of human gamma delta-T cells from cultures of mitogen-stimulated human peripheral blood mononuclear cells are identified. It is first established that human gamma delta-T cells are exquisitely sensitive to apoptosis induced by T-cell mitogens OKT3 and IL-2. Next it is shown that the CD2-mediated IL-12-dependent signals, which lead to the expansion of gamma delta-T cells, do so by selectively protecting subsets of human gamma delta-T cells from mitogen-induced apoptosis. Finally, it is demonstrated that apoptosis-resistant gamma delta-T cells are capable of mediating significant antitumor cytotoxicity against a panel of human-derived tumor cell lines in vitro. Both the biologic and the practical implications of induced resistance to apoptosis in gamma delta-T cells are considered and discussed because these findings may play a role in the development of new forms of adoptive cellular immunotherapy. (Blood. 2000;96:3827-3837)

Adult↗
PubMed2000

Effects of galanin on wide-dynamic range neuron activity in the spinal dorsal horn of rats with sciatic nerve ligation.

Galanin is a 29-amino acid peptide with a suggested role in nociception. The effect of galanin on wide-dynamic range neuron discharge frequency in rats with nerve ligation, used as a model of neurogenic pain, was investigated by extracellular recording methods. Seven to 14 days after sciatic nerve ligation, 0.1, 0.5 or 1 nmol of galanin was administered directly on the dorsal surface of the L3-L5 spinal cord of rats with sciatic nerve ligation. It was found that galanin inhibited the activity of wide-dynamic range neurons dose-dependently, an effect was more pronounced in sciatic nerve ligated rats than intact rats. Furthermore, when 1 nmol of galantide, the galanin antagonist, was administered on the dorsal surface of the L3-L5 spinal cord, the wide-dynamic range neuron discharge frequency increased significantly. The results suggest that galanin plays an important role in the modulation of presumed nociception in mononeuropathy.

Animals↗
PubMed2000

Lipocalins as biochemical markers of disease.

Lipocalins as biochemical markers of disease have been used extensively. The clinical indications relate to almost any field of medicine, such as inflammatory disease, cancer, lipid disorders, liver and kidney function. Some of the more well-known lipocalins that have been used as markers of disease are orosomucoid, Protein HC (alpha(1)-microglobulin), apolipoprotein D, retinol-binding protein, complement C8 gamma, prostaglandin D synthase and human tear prealbumin, and these markers will be briefly reviewed in this article. Emphasis, however, will be put on the description of another newly described lipocalin, i.e. human neutrophil lipocalin/neutrophil gelatinase-associated lipocalin (HNL/NGAL), since the body fluid measurement of HNL/NGAL was shown to be a superior means to distinguish between acute viral and bacterial infections and also to accurately reflect the activity and involvement of neutrophils in a variety of other diseases.

Acute-Phase Proteins↗
PubMed2000

Cutting edge: B cell linker protein is dispensable for the allelic exclusion of immunoglobulin heavy chain locus but required for the persistence of CD5+ B cells.

The pre-B cell receptor (pre-BCR) and the BCR are required for B lymphopoiesis and for the allelic exclusion of Ig genes. Mice lacking B cell linker (BLNK) protein that is a component of the BCR signaling pathway have impaired B cell development. In this report, we show that allelic exclusion is intact in BLNK(-/-) mice harboring a V(H)12 transgene. This differs from mice lacking the tyrosine kinase Syk that is upstream of BLNK in BCR signaling and contrasts with mice lacking SLP-76 that is the equivalent adaptor molecule in TCR-signal transduction. We also show that, whereas most wild-type V(H)12-expressing B cells are CD5(+), the majority of the splenic V(H)12-expressing BLNK(-/-) B cells are CD5(-). A small population of V(H)12-expressing, BLNK(-/-) CD5(+) B cells is detectable in the peritoneal cavity of younger but not older mice. This suggests that BLNK deficiency affects not only the generation but also the persistence of B-1 cells.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Optical gain and stimulated emission in nanocrystal quantum dots.

The development of optical gain in chemically synthesized semiconductor nanoparticles (nanocrystal quantum dots) has been intensely studied as the first step toward nanocrystal quantum dot lasers. We examined the competing dynamical processes involved in optical amplification and lasing in nanocrystal quantum dots and found that, despite a highly efficient intrinsic nonradiative Auger recombination, large optical gain can be developed at the wavelength of the emitting transition for close-packed solids of these dots. Narrowband stimulated emission with a pronounced gain threshold at wavelengths tunable with the size of the nanocrystal was observed, as expected from quantum confinement effects. These results unambiguously demonstrate the feasibility of nanocrystal quantum dot lasers.

Journal Article↗
PubMed2000

The leucine zipper of NRL interacts with the CRX homeodomain. A possible mechanism of transcriptional synergy in rhodopsin regulation.

Photoreceptor-specific expression of rhodopsin is mediated by multiple cis-acting elements in the proximal promoter region. NRL (neural retina leucine zipper) and CRX (cone rod homeobox) proteins bind to the adjacent NRE and Ret-4 sites, respectively, within this region. Although NRL and CRX are each individually able to induce rhodopsin promoter activity, when expressed together they exhibit transcriptional synergy in rhodopsin promoter activation. Using the yeast two-hybrid method and glutathione S-transferase pull-down assays, we demonstrate that the leucine zipper of NRL can physically interact with CRX. Deletion analysis revealed that the CRX homeodomain (CRX-HD) plays an important role in the interaction with the NRL leucine zipper. Although binding with the CRX-HD alone was weak, a strong interaction was detected when flanking regions including the glutamine-rich and the basic regions that follow the HD were included. A reciprocal deletion analysis showed that the leucine zipper of NRL is required for interaction with CRX-HD. Two disease-causing mutations in CRX-HD (R41W and R90W) that exhibit reduced DNA binding and transcriptional synergy also decrease its interaction with NRL. These studies suggest novel possibilities for protein-protein interaction between two conserved DNA-binding motifs and imply that cross-talk among distinct regulatory pathways contributes to the establishment and maintenance of photoreceptor function.

Amino Acid Sequence↗