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Biomedical subjects

D Xu

Publications and source records attributed to D Xu.

At least 253 records · Page 14Linked to original sources
PubMed1998

[Studies on the synthesis and experimental therapeutic effects of metal chlorin on 60Co-irridiated mice].

Pheophorbide a and pyropheophorbide a were prepared by acid degradation of crude chlorophylls isolated from silkworm excrement. Pheophorbide a was further degraded to chlorin e6 monomethyl ester in alkaline methanol in absence of oxygen. Pure purpurin 18 was directly prepared from alkali degradation of silkworm excrement crude chlorophylls in presence of oxygen. Nine chlorin complexes of Co, Cu and Zn were synthesized for the first time. Preliminary pharmacological tests showed that chlorin e6 monomethyl ester copper complex(7) could increase survival and prolong the surviving time of 60Co-irridiated mice significantly.

Animals↗
PubMed1998

[Investigation and manufacture of intellectualized tonometer bassed on the principle of linearly measuring the applanation area diameter of ocular cornea].

The design principle of intellectualized tonometer based theory of linearly measuring the applanation area diameter of ocular cornea has been mainly introduced, which inclueds optics and construction design principle, principle of hardware and software design of intellectualized instrument and the calculation method of ocular pressure etc. The method and result of calibration of the tonometer are also included.

Cornea↗
PubMed1998

[Comparative observation on the efficacy of several test/probe systems for detecting schistosome circulating antigen].

AIM: To compare the efficacy of 5 test/probe systems for the detecting of schistosomal circulation antigen (SCA) in sera from infected rabbits. METHODS: Nine rabbits were infected with monosexual cercariae (either male or female), 7 rabbits were infected with bisexual cercariae as controls. Blood samples were collected periodically post infection (p.i). 15 rabbits were infected each with 250 bisexual cercaria and divided into 3 groups, 2 groups were treated with allyl thiourea (295-590 mg/kg) from 19 d or 46 d respectively, to inhibit their egg formation. One untreated group was used as control. Blood samples were collected weekly until 8 wk post infection. SCA detecting methods include (1) dot-ELISA/McAb anti-surface membrane antigen of adult worms (8SE4), (2) dot-ELISA/McAb anti-CCA (3D10), (3) Sandwich dot-ELISA/McAb anti-egg antigen (MG2), (4) Sandwich-ELISA/McAb anti-egg antigen (2H10), (5) Sandwich-ELISA/McAb anti-CAA (1B10). RESULTS: Using method (1) all of the 18 rabbits infected with monosexual cercariae were negative. Using method (2) only 1 rabbit harboured 133 male worms showed positive. Using method (5) no SCA were detected in sera from female cercariae-infected rabbits but 3 out of 9 male cercariae-infected rabbits showed positive reaction. SCA detecting results from rabbits treated with allyl thiourea: both method (1) and (3) showed negative in rabbits treated from 19 d (p.i.) but all gave positive reaction in 6-7 wk in rabbits treated from 46 d (p.i.). There were all negative detected by using method (4) and all positive at 6 wk (p.i.) detected by method (5) in rabbits of 3 groups whether treated or non-treated. CONCLUSION: Various test/probe systems have different efficacy in detecting SCA but (5) of the methods (1)(2) tests/probe systems could not detect SCA in rabbits with single female cercariae infection. From the egg formation inhibition study, the SCA detected by McAb 8SE4 dot-ELISA might be related to egg maturation. Whether the surface membrane antigen of adult worm has common antigenic component with egg antigen remains to be studied.

Animals↗
PubMed1998

[Observation on the factors influencing infection rate of Meriones unguiculatus with Brugia malayi].

AIM: To explore the factors influencing the infection rate of M. unguiculatus with B. malayi. METHODS: The survival rate, infection rate and infection intensity were observed in M. unguiculatus infected with the infective larvae of B. malayi contained in normal saline, antibiotic, glucose or culture medium RPMI1640, respectively. RESULTS: The survival rate, infection rate and rate of infection intensity in normal saline group, antibiotic group, glucose group and RPMI1640 group were 80.9%, 60.5%, and 43.4%; 98.8%, 52.9% and 30.6%; 98.0%, 68.8% and 50.0%; 91.2%, 67.7% and 51.6%, respectively. The rate and the infection intensity were higher in the jirds infected with the 6th generation of Zhejiang strain than that with the 31st generation of Guizhou strain. CONCLUSION: The antibiotic was found to raise the living rate of the infected jirds, but reduce the infection rate and infection degree intensity; whereas glucose and culture medium RPMI1640 could raise the positive rate and the infectino. The jird was more susceptible to the 6th generation of Zhejiang strain than the 31st generation of Guizhou strain of B. malayi.

Animals↗
PubMed1998

[Observation on the susceptibility of Anopheles sinensis to periodic Brugia malayi microfilariae].

AIM: To explore the susceptibility of Anopheles sinensis to Brugia malayi microfilariae of different densities. METHODS: The survival rate of mosquitoes, the rate of microfilariae penetrating through midgut, the mature rate of larvae into infective larvae (L3) and the mean number of L3 in the survived mosquitoes were observed. RESULTS: With the microfilariae densities of 32.5 mf/microliter and 141.5 mf/microliter, the rate of larvae matured into L3 was 36.2% and 8.7%, respectively, the mean number of L3 recovered from infected mosquitoes was 8.24 and 0.30, respectively. CONCLUSION: An apparently higher susceptibility of An. sinensis to B. malayi was found by using B. malayi microfilariae density of 32.5-66.4 mf/microliter.

Animals↗
PubMed1998

[Synthesis and preliminary study on cleavage activity of ribozyme to hepatitis B virus preS2 gene in vitro].

In this paper, a multi-target hammerhead ribozyme gene was synthesized directed against 110, 122 and 132 sites of nucleotide of HBV preS2 gene. The target gene fragment was cut from HBV genome containing plasmid pCP10. Both of the ribozyme and the target gene fragments were cloned into pGEM3Zf(-) plasmid and sequenced by dideoxy chain termination method. The transcription of both gene fragments was performed in vitro utilizing T7 RNA promoter in pGEM3Zf (-) plasmid. The cleavage activity of ribozyme to substrate was confirmed in vitro. For further evaluating intracellular function of ribozyme, two ribozyme-retroviral recombinant plasmids with different promoter type pDOR-ripe and tRNA-ripe were constructed. Pseudo-virus was collected through routine packaging procedure and transduted into 2.2.15 cells. RIA data showed a stable inhibition of pHSA-R antigen expression to the lowest extent of 41.01% +/- 4.16 and the highest extent of 51.45% +/- 4.57 within 4 weeks after transduction. No influence, however, on HBsAg and HBeAg expression was demonstrated after ribozyme gene transfer.

Cloning, Molecular↗
PubMed1998

[The study on detection of human parvovirus B19 DNA in spontaneous abortion tissues].

116 spontaneous abortion tissues were detected for human parvovirus B19 (HPV B19) DNA by nested polymerase chain reaction. Of the abortion tissues detected, 66 were paraffin embedded and 50 were fresh abortion tissues, At the same time, 25 abortion tissues from healthy artificial abortion women were collected as control. The results showed that 27.3% (34/116) of 116 spontaneous abortion tissues were positive for HPV B19 DNA, and only 4% (1/25) were positive in the control group, the discrepancy was significant chi 2 = 5.769(P < 0.05). It suggests that there is a relationship between spontaneous abortion and HPV B19 infection. HPV B19 infection may be an important factor in spontaneous abortion.

Abortion, Spontaneous↗
PubMed1998

[Effect of eel oil capsule on mice memory].

Step-down test, step-through test and water maze in mice were used to observe the effect of eel oil capsule on mice memory. The results indicated that during the administration period (30 days), the eel oil capsule treating groups with dosages of 0.129, 0.387, and 1.161 g/kg obviously improved the learning and memory abilities. Compared with the control test, the eel oil capsule promoted the memory and smart.

Animals↗
PubMed1998

[FTIR study on structure of pearl and nacre of mollusk shell].

Pearl and nacre of mollusk shell (Hyriopsis cumingii) were studied with high resolution Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results of X-ray diffraction indicate that the samples are still aragonite after thermal treatment at 160 degrees C for 5hr, however, the significant variations of peak position and band width of FTIR spectra reveal the interaction between organic matrix and inorganic crystal in biomineralized materials. The variations of spectra were studied by a curve-fitting algorithm and the band related to the interaction is revealed.

Animals↗
PubMed1998

[Investigation on the luminescence properties of Er ions in Er-doped sol-gel silica glasses].

Er-doped sol-gel silica glasses which have room temperature photoluminescence at 1.54 microm and doped concentration of 10(20)/cm(3) have been prepared. The examination results Indicated: (1) PL spectrum has largest intensity at the 0.5W% doped concentration; (2) the intensity of PL decreased 74%, when the temperature raised form 4K to 300K; (3) The Er ion and O ions formed complexes with coordinated numbers of 8 or 9.

English Abstract↗
PubMed1998

[Application of computer simulation in the study of vibrational distributions for the products from energy transfer reaction].

The method of computer simulation in the study of vibrational distributions for the products from the energy transfer reaction is discussed. Taking the Ar (3P(0.2)) + PCl --> PCl (A3II) reaction as an example, we analysed the process of the simulation and the problems that should be paid attention to. The Franck-Condon factors of PCl (A3II --> X3sigma(-1)) are reported for the first time.

English Abstract↗
PubMed1997

Tacrolimus (FK506) and sirolimus (rapamycin) in combination are not antagonistic but produce extended graft survival in cardiac transplantation in the rat.

Combined use of tacrolimus (FK506) with sirolimus (rapamycin [RAPA]) was examined in a model of vascularized heart allograft in the rat. For prevention of acute rejection, three different combinations of low doses of FK506 and RAPA from day 1 up to day 14 after transplantation produced significantly longer cardiac allograft survival than each agent alone (P<0.05). Identical results were observed in a model of reversal of ongoing acute rejection, where two combinations of low doses of FK506 and RAPA from day 4 up to day 18 after surgery also demonstrated significantly longer graft survival than each immunosuppressant alone (P<0.05). All the low-dose-treated groups in these two models presented significantly longer heart graft survival than naive controls (P<0.05), confirming that both agents are potent immunosuppressants in the models chosen. These results also indicate that, in contrast with in vitro studies, the combined use of FK506 and RAPA in vivo did not produce antagonism, but rather had synergistic effect in prolonging the allograft survival as compared with each agent alone. It appears likely that the abundance of FKBP-12 available for binding in vivo prevents inhibitive competition of the two agents for their receptor.

Acute Disease↗
PubMed1997

PLAB, a novel placental bone morphogenetic protein.

Bone morphogenetic proteins (BMP) constitute a sub-group of the large transforming growth factor-beta (TGF-beta) family. They play important roles in the embryonic development of multiple structures and in adult bone modeling. We have recently isolated a novel member of the BMP family from placenta, termed PLAB. PLAB is expressed highly in placenta, but can be found upon stringent analysis in low levels in most other tissues. At the amino acid level, PLAB is most closely related to BMP-8/OP-2, another member of the BMP family. Like TGF-beta, PLAB inhibits the proliferation of primitive hematopoietic progenitors. The high expression of PLAB by placenta raises the possibility that it may be a mediator of placental control of embryonic development.

3T3 Cells↗
PubMed1997

Genetic evidence for selective degradation of RNA polymerase subunits by the 20S proteasome in Saccharomyces cerevisiae.

scs32 was isolated as an extragenic suppressor of a temperature-sensitive (ts) mutation (rpo26-31) in the gene encoding Rpo26p, a subunit common to yeast nuclear RNA polymerases (RNAPs). rpo26-31 also confers inositol auxotrophy, inhibits the assembly of RNAPI and RNAPII and reduces the steady-state level of Rpo26p and the largest subunit of RNAPI (Rpo11p or A190p) and RNAPII (Rpo21p). rpo26-31p accumulated to wild-type levels in the scs32 strain; nevertheless, the amount of assembled RNAPII remained at a reduced level at high temperature. Hence, scs32 only partially suppressed the ts phenotype and was unable to suppress the Ino-phenotype of rpo26-31. SCS32 is identical to PUP3, which encodes a subunit of the yeast proteasome. scs32 was able to suppress the phenotype of other ts alleles of RPO26, all of which reduce the steady-state level of this subunit. However, scs32 was unable to suppress the ts phenotype of mutant alleles of RPO21, or result in accumulation of the unstable rpo21-4p. These observations suggest that the stability of non-functional or unassembled forms of Rpo26p and Rpo21p are regulated independently.

Amino Acid Sequence↗
PubMed1997

Investigation of the enzymatic mechanism of the yeast chorismate mutase by docking a transition state analog.

The structure of the complex of the chorismate mutase from the yeast Saccharomyces cerevisiae with a transition state analog is constructed using a suite of docking tools. The construction finds the best location for the active site in the enzyme, and the best orientation of the analog compound in the active site. The resulting complex shows extensive salt links and hydrogen bonds between the enzyme and the compound, including those mediated by water molecules. A network of polar interactions between amino acid residues is found to solidify the active site of the enzyme. The enzymatic mechanism suggested for a bacterial chorismate mutase, that the active site is by design capable of selecting an active conformer of the substrate, and of stabilizing the transition state, is apparently intact in the yeast enzyme. No direct evidence is found to support an alternative mechanism which involves specific catalytic groups, although the possibility is not eliminated. This finding reinforces the notion of a function being evolutionarily conserved via a common mechanism, rather than via sequential or structural homology.

Binding Sites↗
PubMed1997

Transduction of cytosine deaminase gene makes rat glioma cells highly sensitive to 5-fluorocytosine.

To investigate the potential use of E. coli cytosine deaminase (CD) gene instead of the commonly used HSV-TK gene in the gene therapy of brain tumors, we constructed a retrovirus vector carrying the CD gene. We then transduced a rat glioma cell line C6 with CD gene by the retrovirus vector. Transduction of the CD gene made C6 cells become highly sensitive to the anti-fungi drug 5-fluorocytosine (5FC). IC50 for 5FC was 6,000 microM in CD-negative cells, while it was 3 microM in CD-positive cells. Mixed cellular assay showed that CD-positive cells had a strong "bystander effect" on CD-negative cells when exposed to 5FC. Significant anti-tumor effects were observed in nude mice bearing s.c. tumors derived from CD-positive cells when these animals were given 250 mg/kg 5FC twice a day for 20 consecutive days. A marked decrease in tumor weight occurred when a mixture containing 50% CD-positive and 50% CD-negative C6 cells was injected s.c., followed by 5FC treatment, suggesting the bystander effect in vivo. Concerning the pharmacokinetics of 5FC, especially its high oral bio-availability and good penetration into cerebrospinal fluid, we suppose that the combination of CD-gene transfer and 5FC oral administration may have potential use in the gene therapy of brain tumors.

Animals↗
PubMed1997

Short tandem repeat typing by capillary array electrophoresis: comparison of sizing accuracy and precision using different buffer systems.

Polymorphic microsatellite markers are widely used in gene discovery and mapping, human identification, agricultural genetics, and diagnosis of triplet-repeat expansion disorders. Reliable genotyping of these markers requires polymerase chain reaction (PCR) amplification and very-high-resolution electrophoresis. Capillary array electrophoresis offers extremely fast, high-resolution separation of DNA and more automated sample processing because labor-intensive slab-gel pouring and sample loading are eliminated. We report a simple, reliable procedure for preparing PCR samples for electrokinetic injection into capillaries using a 96-well tray and float dialysis. We developed an improved sizing standard for genotyping and used it to evaluate systematically the sizing accuracy and precision of low-viscosity, replaceable matrix formulations. Our study sizing over 28,000 alleles yielded an average precision of +/- 0.12 bp for fragments up to 350 bp. Low-viscosity formulations permit low-pressure matrix injection (40 psi) and a turnaround time of 70 min for 48-96 samples.

Alleles↗