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Biomedical subjects

D Xu

Publications and source records attributed to D Xu.

At least 91 records · Page 5Linked to original sources
PubMed2001

[The achievement of industrialized healthy aquatic breeding of hippocampus and its application prospects].

The artificial industrialized aquatic breeding of Hippocampus, which is a kind of Chinese medicinal marine material, has been achieved in the artificial aquatic breeding base of Hippocampus of Guangdong Richvast Group Company since 1983. This article reported part of the achievements of the large-scale artificial aquatic breeding experiments. The prospects for the research and application of Hippocampus as health foods and drugs were also analyzed.

Animals↗
PubMed2001

[The associations between concentration of selenium in semen and sperm parameters as well as oxidative DNA damage in human sperm].

OBJECTIVE: To explore the associations between concentrations of selenium (Se) in serum and semen and sperm parameters as well as oxidative DNA damage in human sperm. METHODS: Concentrations of selenium in serum and semen were determined using atomic absorption spectrophotometer (AAS). The sperm parameters were detected according to WHO laboratory manual for the examination of human sperm. The levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and deoxyguanosine (dG) in human sperm DNA were measured using HPLC-ECD and HPLC-UV. RESULTS: Mean semen concentration of selenium was significantly higher in fertile subjects (0.74 mumol/L) than that in infertile subjects (0.56 mumol/L), while there was no significant difference in serum concentrations of selenium between the two groups. Semen volume (3.91 ml vs. 2.79 ml), sperm density (46.4 x 10(9)/L vs. 36.5 x 10(9)/L) and sperm count (168.0 x 10(6) vs. 102.0 x 10(6)) were significantly higher in fertile subjects than those in infertile subjects. There was no significant difference in motility and viability of sperm, and proportion of deformity sperm between the two groups, Significantly positive correlation was observed between semen concentration of Se and sperm density (r = 0.48, P < 0.01 for fertile subjects and r = 0.32, P < 0.05 for infertile subjects) as well as sperm count (r = 0.32, P < 0.05 for fertile subjects and r = 0.26, P < 0.05 for infertile subjects), sperm motility (r = 0.46, P < 0.01 for fertile subjects and r = 0.65, P < 0.01 for infertile subjects) and viability (r = 0.33, P < 0.05 for fertile subjects and r = 0.64, P < 0.01 for infertile subjects). There was no correlation between serum Se concentrations and sperm parameters. Moreover, 8-OHdG levels in sperm DNA inversely correlated with semen Se concentrations in fertile (r = -0.21, P < 0.05) and infertile (r = -0.28, P < 0.05) subjects. However, no significant correlation was found between 8-OHdG levels in sperm DNA and serum Se concentrations in all subjects. CONCLUSIONS: Semen concentrations of Se were associated with sperm quality and 8-OHdG levels in human sperm. Serum concentrations of Se did not affect sperm quality and oxidative DNA damage in human sperm.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

[Therapeutic trial on function bandage for military training injuries].

OBJECTIVE: To evaluate therapeutic effectiveness of "Tianniansu" function bandage used for military training injuries (MTI). METHODS: In a randomized tri-blind controlled trial, recruits of all soft tissue injuries and stress fracture (SF) who took part in basic training in 1998 were separated into two groups--A and B with comparability, except the use of bandage. After close follow up on weekly base, part of the patents were subjected by ECT pre and post therapy. RESULTS: Effective rates of bandage A and B on treating soft tissue injuries were 66.7% and 86.4%, respectively. However, in terms of symptoms, detumescence effect of bandage B showed milder than that of A. The effective rate of bandage A and B in treating SF were 67.2% and 75.0%, respectively, but statistically not significant. The treatment effect in 26 injured tibias evaluated by bone scintigraphy pre and post treatment showed that the degree of osteogen injury after treatment was not significantly improved. CONCLUSION: "Tianniansu" function bandage had significant effect on treating soft tissue injuries, but did not have effect in treating SF.

Adult↗
PubMed2001

[The dynamic study of cytokines pre- and postoperation in patients with carcinoma of larynx].

OBJECTIVE: To observe the dynamic changes of cytokines pre- and postoperation in patients with carcinoma of the larynx and provide reference for recurrence monitor and prognosis evaluation in postoperative patients with head and neck tumor. METHOD: Thirty-four patients with head and neck squamous cell carcinoma were included in this study. Serum levels of IL-2, sIL-2R and TNF-alpha were measured before surgery, 7 days, 30 days and 90 days after surgery with ELISA and RIA. RESULT: The serum levels of sIL-2R and TNF-alpha before surgery in patients with carcinoma of the larynx were significantly elevated compared with controls(P < 0.01), while the level of IL-2 was not different. Serum concentrations of sIL-2R and TNF-alpha in patients without recurrence found at 7 days after operation were slightly higher than those before operation, but there was not significant difference. Moreover, the levels of sIL-2R and TNF-alpha at 30 days and 90 days postoperation decreased gradually, especially the sIL-2R levels decreased more significantly. No statistical difference were found among serum IL-2 levels in non-recurrence patients. The serum levels of sIL-2R and TNF-alpha in patients with recurrence at 30 days after operation were lower than those before operation and increased at 90 days after operation, while the levels of IL-2 decreased gradually. CONCLUSION: Dynamic study of the cytokines pre and postoperation play reference role in recurrence monitor and prognosis evaluation after the larynx carcinoma were removed.

Adult↗
PubMed2001

[Uncommon fluorescent properties of nano-structured terbium (III)-phthalic acid complex in polyvinylpyrrolidone].

Nano-sized terbium(III)-phthalic acid complex was prepared in polyvinylpyrrolidone. It's fluorescent spectrum has been investigated, compared to that of common terbium(III)-phthalic acid complex and terbium(III)-polyvinylpyrrolidone complex. The results show that fluorescent characterizations of Nano-sized terbium(III)-phthalic acid complex is obviously different from that of common terbium(III)-phthalic acid complex and terbium(III)-polyvinylpyrrolidone. The relative intensity and half-height width of main emission peaks are obviously varied, two splitting peaks are displayed.

Chelating Agents↗
PubMed2001

[FTIR study of transition metal 2-acrylamido-2-methyl-1-propanesulfonates].

Compounds of transition metal ion (Cu2+, Co2+, Ni2+) 2-acrylamidomethyl-2-methyl-1-propanesulfonates were studied by FTIR and X-ray powder diffraction techniques. The FTIR spectra of Co and Ni compound are similar but are different from that of Cu compound. The results of X-ray diffraction indicated that the crystal structure of Co and Ni compound are different.

Acrylamides↗
PubMed2001

[Effect of crystallization and branch on fine structure of orthorhombic in polyethylene].

The CH2 rocking bands are used as a probe to monitor the crystalline behavior of polyethylene segments in a series of poly (ethylene-octene) copolymers. High resolution and cryogenic FTIR spectra reveal that different composition and/or crystalline condition of the copolymers result in significant variation on the CH2 rocking bands including the change in peak position, band width and A730/A720. We conclude that side chain in the copolymer can influence the structure of the orthorhombic polyethylene crystallite although they can not enter the crystal lattice.

Crystallization↗
PubMed2000

Subunit structure of a mammalian ER/Golgi SNARE complex.

SNAP receptor (SNARE) complexes bridge opposing membranes to promote membrane fusion within the secretory and endosomal pathways. Because only the exocytic SNARE complexes have been characterized in detail, the structural features shared by SNARE complexes from different fusion steps are not known. We now describe the subunit structure, assembly, and regulation of a quaternary SNARE complex, which appears to mediate an early step in endoplasmic reticulum (ER) to Golgi transport. Purified recombinant syntaxin 5, membrin, and rbet1, three Q-SNAREs, assemble cooperatively to create a high affinity binding site for sec22b, an R-SNARE. The syntaxin 5 amino-terminal domain potently inhibits SNARE complex assembly. The ER/Golgi quaternary complex is remarkably similar to the synaptic complex, suggesting that a common pattern is followed at all transport steps, where three Q-helices assemble to form a high affinity binding site for a fourth R-helix on an opposing membrane. Interestingly, although sec22b binds to the combination of syntaxin 5, membrin, and rbet1, it can only bind if it is present while the others assemble; sec22b cannot bind to a pre-assembled ternary complex of syntaxin 5, membrin, and rbet1. Finally, we demonstrate that the quaternary complex containing sec22b is not an in vitro entity only, but is a bona fide species in living cells.

Animals↗
PubMed2000

Interferon alpha down-regulates telomerase reverse transcriptase and telomerase activity in human malignant and nonmalignant hematopoietic cells.

Recently, the derepressed expression of the catalytic subunit of telomerase, human telomerase reverse transcriptase (hTERT), the enzyme that elongates telomeres, has been implicated as an important step in the immortalization process. The exact regulation of hTERT expression, which is the rate-limiting factor for telomerase activity, is at present unclear. As transformed cells seem to be dependent on a constitutive telomerase activity, the availability of inhibitors would potentially be of great value in antineoplastic therapy. Interferons (IFNs) have been successfully used in the treatment of several forms of malignancies, but the underlying molecular mechanisms responsible for the antitumor activity are poorly defined. In this study we have investigated the effects of IFNs on hTERT expression and telomerase activity. We found that IFN-alpha rapidly (commonly within 4 hours) and significantly down-regulates the expression of hTERT and telomerase activity in a number of human malignant hematopoietic cell lines, primary leukemic cells from patients with acute leukemia as well as T-lymphocytes from healthy donors. This effect of IFN-alpha did not seem to depend on IFN-alpha-mediated cell growth arrest or alterations in c-myc expression. The finding that IFN induces a repression of hTERT and a decrease in telomerase activity suggests a novel mechanism that may play a significant role in the antitumor action of IFN. (Blood. 2000;96:4313-4318)

Acute Disease↗
PubMed2000

Frequent amplification of the telomerase reverse transcriptase gene in human tumors.

Activation of telomerase is a crucial step during cellular immortalization and malignant transformation of human cells and requires the induction of the catalytic component, human telomerase reverse transcriptase (hTERT), encoded by the hTERT gene. It is poorly understood how the hTERT gene is activated in human cancer cells. In the present study, we examined the hTERT gene copy number in human cancer cell lines and in primary tumor tissues. Amplification of the hTERT gene was observed in 8 of 26 (31%) tumor cell lines and 17 of 58 (30%) primary tumors examined (8 of 21 lung tumors, 3 of 10 cervical tumors, 5 of 19 breast carcinomas, and 1 of 8 neuroblastomas). In addition, 13 of 26 (50%) cell lines and 13 of 58 (22%) primary tumors displayed gain of hTERT gene copies with 3-4 copies/cell. The present findings imply that the hTERT locus may be a frequent target for amplification during tumorigenesis and that this genetic event probably contributes to the dysregulation of telomerase activity occurring in human tumors.

Catalytic Domain↗
PubMed2000

Interorganellar communication. Altered nuclear gene expression profiles in a yeast mitochondrial dna mutant.

Communication between mitochondria and the nucleus is important for a variety of cellular processes such as carbohydrate and nitrogen metabolism, mating and sporulation, and cell growth and morphogenesis. It has long been known that the functional state of mitochondria can influence nuclear gene expression. For example, in yeast cells lacking the mitochondrial genome, the expression of several nuclear genes, such as CIT2 (citrate synthase), MRP13 (mitochondrial ribosomal protein), and DLD3 (d-lactate dehydrogenase) has been reported to be altered. Here we show by microarray analysis of the genome-wide transcription profile of Saccharomyces cerevisiae that yeast petite mutants lacking mitochondrial DNA induce genes coding for mitochondrial proteins, enzymes of the glycolytic pathway and of the citric acid cycle, cell wall components, membrane transporters, and genes normally induced by nutrient deprivation and a variety of stresses. Consistent with the observed induction of genes related to cell stress and those encoding membrane transporters, yeast petite cells showed increased resistance to severe heat shock and exhibited a pleiotropic drug resistance phenotype. The observed changes in nuclear gene expression in cells lacking mitochondrial DNA may have implications for the role of mitochondria in processes such as carcinogenesis and aging.

Cell Nucleus↗
PubMed2000

Downregulation of telomerase reverse transcriptase mRNA expression by wild type p53 in human tumor cells.

The p53 tumor suppressor protein inhibits the formation of tumors through induction of cell cycle arrest and/or apoptosis. In the present study we demonstrated that p53 is also a powerful inhibitor of human telomerase reverse transcriptase (hTERT), a key component for telomerase. Activation of either exogenous temperature-sensitive (ts) p53 in BL41 Burkitt lymphoma cells or endogenous wild type (wt) p53 at a physiological level in MCF-7 breast carcinoma cells triggered a rapid downregulation of hTERT mRNA expression, independently of the induction of the p53 target gene p21. Co-transfection of an hTERT promoter construct with wt p53 but not mutant p53 in HeLa cells inhibited the hTERT promoter activity. Furthermore, the activation of the hTERT promoter in Drosophila Schneider SL2 cells was completely dependent on the ectopic expression of Sp1 and was abrogated by wt p53. Finally, wt p53 inhibited Sp1 binding to the hTERT proximal promoter by forming a p53-Sp1 complex. Since activation of telomerase, widely observed in human tumor cell lines and primary tumors, is a critical step in tumorigenesis, wt p53-triggered inhibition of hTERT/telomerase expression may reflect yet another mechanism of p53-mediated tumor suppression. Our findings provide new insights into both the biological function of p53 and the regulation of hTERT/telomerase expression.

Breast Neoplasms↗
PubMed2000

Th1 and Th2 CD4+ T cells provide help for B cell clonal expansion and antibody synthesis in a similar manner in vivo.

The relative ability of Th1 and Th2 T cells to help B cells remains controversial as do the mechanisms by which both T cell subsets provide help in vivo. Whether this help affects the clonal expansion and/or differentiation of B cells has been difficult to assess due to the low frequency of Ag-specific T and B lymphocytes. We have employed a novel technique to directly monitor the clonal expansion of Ag-specific T and B lymphocytes in vivo. OVA-specific TCR transgenic T lymphocytes were polarized toward a Th1 or Th2 phenotype in vitro. These cells were then transferred into syngeneic recipients, along with B cell receptor transgenic hen egg lysozyme-specific B lymphocytes. Our results indicate that Th1 and Th2 cells support B cell responses to a similar extent in vivo and that they achieve this in the same manner by migrating into B cell follicles to promote CD154-dependent B cell clonal expansion and Ab production.

Adoptive Transfer↗
PubMed2000

Protein threading using PROSPECT: design and evaluation.

The computer system PROSPECT for the protein fold recognition using the threading method is described and evaluated in this article. For a given target protein sequence and a template structure, PROSPECT guarantees to find a globally optimal threading alignment between the two. The scoring function for a threading alignment employed in PROSPECT consists of four additive terms: i) a mutation term, ii) a singleton fitness term, iii) a pairwise-contact potential term, and iv) alignment gap penalties. The current version of PROSPECT considers pair contacts only between core (alpha-helix or beta-strand) residues and alignment gaps only in loop regions. PROSPECT finds a globally optimal threading efficiently when pairwise contacts are considered only between residues that are spatially close (7 A or less between the C(beta) atoms in the current implementation). On a test set consisting of 137 pairs of target-template proteins, each pair being from the same superfamily and having sequence identity </= 30%, PROSPECT recognizes 69% of the templates correctly and aligns 66% of the structurally alignable residues correctly. These numbers may be compared with the 55% fold recognition and 64% alignment accuracy for the same test set using only scoring terms i), ii), and (iv), indicating the significant contribution from the contact term. The fold recognition and alignment accuracy are further improved to 72% and 74%, respectively, when the secondary structure information predicted by the PHD program is used in scoring. PROSPECT also allows a user to incorporate constraints about a target protein, e.g., disulfide bonds, active sites, and NOE distance restraints, into the threading process. The system rigorously finds a globally optimal threading under the specified constraints. Test results have shown that the constraints can further improve the performance of PROSPECT. Proteins 2000;40:343-354.

Algorithms↗
PubMed2000

Promotion of activated human B cell apoptosis and inhibition of Ig production by soluble CD95 ligand: CD95-based downregulation of Ig production need not culminate in activated B cell death.

CD95/CD95L interactions are vital to normal lymphoid homeostasis and in the protection against autoimmunity. To directly assess the effects of CD95L on activated B cell survival and Ig responses, purified human peripheral blood B cells, activated in vitro with SAC + rIL2, were incubated with a soluble CD95L fusion protein (fp) and assayed for apoptosis and IgG/IgM production. CD95L fp reproducibly increased apoptosis of these activated B cells and inhibited their Ig production. However, CD95L fp-mediated effects on activated B cell survival could be uncoupled from those on Ig production in that a soluble CD40L fp was incapable of reversing CD95L fp-mediated downregulation of Ig responses despite inhibiting CD95L fp-mediated apoptosis. Moreover, despite the specific caspase-8 inhibitor z-IETD-fmk substantially protecting transformed CL-01 B cells from CD95L fp-mediated apoptosis and permitting their ongoing proliferation, caspase-8 inhibition had no protective effects on CD95L fp-mediated inhibition of constitutive IgM production by CL-01 B cells. Collectively, these results point to a CD95-based downregulatory pathway in activated B cells that need not necessarily culminate in their death.

ADP-ribosyl Cyclase↗
PubMed2000

Newly isolated archaerhodopsin from a strain of Chinese halobacteria and its proton pumping behavior.

A strain of extremely salt-loving halobacteria Halobacterium species xz515 from a salt lake in Tibet was isolated. SDS-polyacrylamide gel electrophoresis shows that there is only one protein on claret membrane, which is the same membrane fraction as purple membrane from Halobacterium salinarum, with a molecular weight close to bacteriorhodopsin (br). The purified retinal containing protein from xz515 has an absorption peak at around 550 nm. These facts indicate that it is a br-like protein. The partial sequence determination [H. Wang et al., Chin. Sci. Bull., 45 (2000)] shows that this br-like protein belongs to the archaerhodopsin family. The measurements of light-induced medium pH change in intact cells and cell envelope vesicles of xz515 suggest that this type of archaerhodopsin has a proton pumping function. However, the study about the dynamics of pumped protons across the membrane reveal that the proton release and proton uptake is in reverse order compared to br. The probable reason, attributing to regulating the rate of proton release is discussed.

Archaeal Proteins↗
PubMed2000

Leu-enkephalin induced by IL-2 administration mediates analgesic effect of IL-2.

Interleukin-2 (IL-2) was found to have an analgesic effect in both central and peripheral nervous systems. This effect is related to opioid receptors and mediated mainly by IL-2 directly binding to opioid receptors. Using radioimmunoassay, the content of Leu-enkephalin (LEK) in some nuclei were measured at intervals after the injection of IL-2 into the lateral ventricle of rats. Levels of LEK increased in both paraventricular hypothalamic nucleus (PVN) and locus ceruleus (LOC) after IL-2 administration, suggesting that the analgesic effect of IL-2 is also related to the change of LEK in PVN and LOC induced by IL-2 administration.

Analgesics↗