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Biomedical subjects

X Yuan

Publications and source records attributed to X Yuan.

At least 55 records · Page 3Linked to original sources
PubMed2001

[Studies of the resistance of the recombinant alphavirus RNAs containing dengue-2 PrM gene to virus infection].

The amplified PrM gene of dengue-2 virus was cloned into the downstream SP6 promoter-pSFV vector and the recombinant plasmid (pSF.rM2) DNA which contained sense- or antisense-PrM gene, was selected. pSF.rM2 DNA and helper DNA linearized by the enzyme SpeI digestion were both transcribed in vitro into recombinant RNAs which contained the capping analog on the 5'-end and contaansfected into BHK cells by electroportation. The the transfected host cells were challenged with dengue-2 virus and the resistant efficiency of recombinant virus RNAs containing sense- or antisense-PrM gene to virus infection were observed, respectively. The recombinant plasmids (pSFV-PrM) containing sense- or antisense-PrM gene were selected with determination of the nucleotide sequence. The recombinant virus particles were obtained with recombinant RNA and helper RNA co-transfected into BHK cells. Host cells transfected with antisense-PrM RNA derived complete resistance to dengue-2 virus replication and the efficiency was higher than that of the recombinant virus RNA containing sense-PrM gene.

Alphavirus↗
PubMed2001

[The comparisons of fluorescence quenching between perylene and pyrene].

The fluorescence quenching of perylene and pyrene by dimethyl terephthalate (DMTP) and N,N-dimethylaniline (DMA) have been investigated. The results show that pyrene can form exciplex with DMTP or DMA at room temperature and perylene can only form exciplex with DMA. The fluorescence quenching date is in conformity with the Stern-Volmer equation: F0/F = 1 + KSV[Q] = 1 + Kq.tau 0[Q], the F0/F-[Q] straight lines are drawn. The Stren-Volmer constants and fluorescence quenching rate constants (KSV and Kq) are obtained. The Stern-Volmer quenching constants of pyrene is larger than that of perylene. The differences is due to the molecular structure of perylene which is not a typical large conjugated system and less coplanar configuration than pyrene.

Aniline Compounds↗
PubMed2000

Eumetazoan fossils in terminal proterozoic phosphorites?

Phosphatic sedimentary rocks preserve a record of early animal life different from and complementary to that provided by Ediacaran fossils in terminal Proterozoic sandstones and shales. Phosphorites of the Doushantuo Formation, South China, contain eggs, egg cases, and stereoblastulae that document animals of unspecified phylogenetic position; small fossils containing putative spicules may specifically record the presence of sponges. Microfossils recently interpreted as the preserved gastrulae of cnidarian and bilaterian metazoans can alternatively be interpreted as conventional algal cysts and/or egg cases modified by diagenetic processes known to have had a pervasive influence on Doushantuo phosphorites. Regardless of this interpretation, evidence for Doushantuo eumetazoans is provided by millimeter-scale tubes that display tabulation and apical budding characteristic of some Cnidaria, especially the extinct tabulates. Like some Ediacaran remains, these small, benthic, colonial fossils may represent stem-group eumetazoans or stem-group cnidarians that lived in the late Proterozoic ocean.

Animals↗
PubMed2000

Mapping the Hawaiian plume conduit with converted seismic waves

The volcanic edifice of the Hawaiian islands and seamounts, as well as the surrounding area of shallow sea floor known as the Hawaiian swell, are believed to result from the passage of the oceanic lithosphere over a mantle hotspot. Although geochemical and gravity observations indicate the existence of a mantle thermal plume beneath Hawaii, no direct seismic evidence for such a plume in the upper mantle has yet been found. Here we present an analysis of compressional-to-shear (P-to-S) converted seismic phases, recorded on seismograph stations on the Hawaiian islands, that indicate a zone of very low shear-wave velocity (< 4 km s(-1)) starting at 130-140 km depth beneath the central part of the island of Hawaii and extending deeper into the upper mantle. We also find that the upper-mantle transition zone (410-660 km depth) appears to be thinned by up to 40-50 km to the south-southwest of the island of Hawaii. We interpret these observations as localized effects of the Hawaiian plume conduit in the asthenosphere and mantle transition zone with excess temperature of approximately 300 degrees C. Large variations in the transition-zone thickness suggest a lower-mantle origin of the Hawaiian plume similar to the Iceland plume, but our results indicate a 100 degrees C higher temperature for the Hawaiian plume.

Journal Article↗
PubMed2000

Induction of cell death by the lysosomotropic detergent MSDH.

Controlled lysosomal rupture was initiated in lysosome-rich, macrophage-like cells by the synthetic lysosomotropic detergent, O-methyl-serine dodecylamide hydrochloride (MSDH). When MSDH was applied at low concentrations, resulting in partial lysosomal rupture, activation of pro-caspase-3-like proteases and apoptosis followed after some hours. Early during apoptosis, but clearly secondary to lysosomal destabilization, the mitochondrial transmembrane potential declined. At high concentrations, MSDH caused extensive lysosomal rupture and necrosis. It is suggested that lysosomal proteases, if released to the cytosol, may cause apoptosis directly by pro-caspase activation and/or indirectly by mitochondrial attack with ensuing discharge of pro-apoptotic factors.

Amides↗
PubMed2000

Identification of polymorphic loci in the promoter region of the serotonin 5-HT2C receptor gene and their association with obesity and type II diabetes.

AIMS/HYPOTHESIS: Polymorphisms in the upstream region of the 5-HT2C receptor gene could play a part in the development of obesity. METHODS: We screened the upstream region from 27 men by the single strand conformational polymorphism analysis and PCR-direct sequencing and then genotyped 466 non-obese (body mass index < 28 kg/m2) and 123 obese (> or = 28 kg/m2) men including 138 patients with Type II (non-insulin-dependent) diabetes mellitus. RESULTS: Three loci of single nucleotide substitution (G-->A at -995, C-->T at -759, G-->C at -697) and a (GT)n dinucleotide repeat polymorphism at -1,027 were identified. The frequency of -995/-759 and -697 variants was higher in non-obese subjects and that of -995/-759 variants in non-diabetic subjects. In the dinucleotide repeat locus, five alleles were detected including Z containing 17 repeats. The Z - 6 allele was more common in non-obese subjects and the Z + 2 allele in obese subjects. Haplotype 3 (Z - 6, -995A, -759T, -697C) was associated with leanness (p = 0.02) and the absence of diabetes (p = 0.033) and haplotype 9 (Z + 2, -995G, -759C, -697G) with obesity (p = 0.007). Haplotype 2 (Z - 6, -995G, -759C, -697C) tended to be more common in non-obese subjects. A luciferase reporter assay showed that haplotype 2 and haplotype 3 had 1.44- or 2.58-fold higher promoter activities than the most common haplotype 6 (Z, -995G, -759C, -697G). CONCLUSION/INTERPRETATION: The haplotypes containing the nucleotide substitutions could be associated with higher transcription levels of the gene and thereby with resistance to obesity and Type II diabetes. Promoter polymorphisms of the 5-HT2C receptor gene may play an important part in genetic predisposition to the disorders.

Adult↗
PubMed2000

Wear particle diffusion and tissue differentiation in TKA implant fibrous interfaces.

In the context of mechanical loosening, we studied the hypothesis that wear-particle migration in the fibrous membrane under tibial plateaus after total knee arthroplasty can be explained by the pumping effects of the interstitial fluid in the tissue. Further, as a secondary objective we investigated the possibility that interface-tissue differentiation is influenced by interstitial fluid flow and strain, as mechanical effects of interface motions. For comparative reasons, we analyzed a previously published simplified two-dimensional finite-element model, this time assuming biphasic tissue properties. We wanted to determine hydrostatic pressure and flow velocities in the fluid phase, in addition to stresses and strains, for time-dependent loading of the plateau. We found that fluid flow in the interface was extremely slow, except in the periphery. Hence, loosening due to particle-induced bone resorption appears improbable. The results, however, do support the idea that particles migrate with fluid flow, when such flow occurs. Where fibrous tissue tends to be prominent in reality, the fluid is repeatedly extruded and reabsorbed in the model. Where these values are low, fibrocartilage is commonly found. When material properties were varied to subsequently represent fibrocartilage and two stages of mineralization, the strains and fluid velocities is reduced. Fluid pressure, however, did not change. Our results refute the hypothesis that wear particles are pumped through the interface tissue below a TKA but support the hypothesis that interface tissue type and loosening processes are influenced by mechanical tissue variables such as tissue strain and interstitial fluid velocity.

Biomechanical Phenomena↗
PubMed2000

Accuracy analysis for RSA: a computer simulation study on 3D marker reconstruction.

In this paper, error analysis of three-dimensional marker coordinates reconstructed from noisy two-dimensional measurement in RSA was performed. Mathematical models to predict error propagation of focus position and object points were derived and computer simulations were performed to validate these models. Two clinical calibration cages were compared by testing the error propagation at each RSA step. The results revealed that errors of reconstructed object points were related to the focus position error, two-dimensional measurement error, position of focus and positions of object points, while errors of reconstructed focus position were determined by the two-dimensional measurement error, number of control points and location of the focus. The maximum difference between the mathematical model and the simulation for the assessment of errors of focus position was 14 microm and the maximum difference of object point positions was 1.1 microm. These differences were small and judged irrelevant, hence the simulations indicated that our models were accurate.

Computer Simulation↗
PubMed2000

Photophysical processes of a copolymer containing naphthalene and carbazole rings.

The photophysical processes of copolymer formed by copolymerization of beta-naphthyl-methacrylate (NMA) with vinylcarbazole (VCZ) were studied. The results show that when the solution of copolymer (NMA-VCZ) in THF is located in a low concentration range (about 10(-8) mol/l), the fluorescence emission is in good agreement with that of NMA monomer and the excimer is formed with gradual increase in concentration of copolymer (NMA-VCZ). The fluorescence of copolymer (NMA-VCZ) can be efficiently quenched both by electron donors and acceptors where the quenching effects follow the Stern-Volmer equation. The dimolecular exciplex between copolymer (NMA-VCZ) and N,N-dimethylaniline (DMA) is formed and the triple exciplex is also observed in the same system.

Carbazoles↗
PubMed2000

Methods for determining the accuracy of radiostereometric analysis (RSA).

The problem of determining the noise level in any measuring system remains urgent. Radiostereometric analysis (RSA) is a radiographic system of unique accuracy which has applications in areas where minute motions or no motion at all occurs. Examples are micromotion between endoprostheses and bone and in fracture healing. We have determined the accuracy of the RSA system as applied to a clinical series of spinal fusions, where the conditions for RSA were not optimal. Using the usual test-retest methodology on a phantom, we showed that its accuracy can be grossly overestimated in the individual case. We found considerable variations in the accuracy in the individual case, depending on the rigid-body configuration. The overall accuracy, expressed as 3-D "vectors" for rotation and translation, respectively, correlated with the condition number, a method for characterizing the marker configuration. Indeed, the condition number explained as much as 92% of the variation in overall rotation. This condition number, however, cannot be used to analyze the accuracy of one degree of freedom of rotation alone. Mathematical simulation of the accuracy in the individual case of the individual dimension, using in-house software, showed that the accuracy (95% confidence) varied between 0.4 and 4.6 degrees of rotation about the transverse axis, corresponding to a clinical stress series of extension and flexion.

Artifacts↗
PubMed2000

Different Wnt-5A gene expressions in the renal cell carcinoma GRC-1 cell line during the cell cycle.

OBJECTIVE: To investigate the gene expression at transcription level of growth factor Wnt-5A in different phase during the cell cycle. METHODS: We synchronized the renal cell carcinoma GRC-1 cell line by double thymidine blocks and high-pressure N2O gae methods and amplified Wnt-5A cDNAs from different phase using Semi-quantitative RT-PCR (reverse transcriptase polymerase chain reaction). The PCR products were electrophoresized on the agrose gel and detected by Gel Doc 1000 computer controlled system integrating the volumes of each band, representing the intensities of all pixels in a defined band. RESULTS: The different mRNA expressions of growth factor Wnt-5A was detected in RCC GRC-1 cell line. In S phase, the highest level of Wnt-5A transcript was observed, and in G1 and M phase, medial and lowest, respectively. The differences between S and M stages were statistically significant (P < 0.05). CONCLUSION: Growth factor Wnt-5A has the potential effect on tumorigenesis. It contributes to all phases during cell cycle but in S phase especially.

Carcinoma, Renal Cell↗
PubMed2000

[The attractive effects of nerve regeneration chamber fluid and degenerated nerve segments on the growth and the migration of the cocultured dorsal root ganglion neuron].

OBJECTIVES: We intended in this study to investigate the neurotropic effects of regeneration chamber fluid (RCF) and the degenerated nerve segments from distal of the regeneration chamber on the dorsal root ganglion (DRG). METHODS: The capillary model was first tested for its reliability to form concentration gradient with a dye being contained in the capillaries. The tissue culture in RCF test was divided into two groups each with 8 DRGs implanted in 8 dishes. RCF was contained in capillaries inserted down to the bottom of the dishes with their lower ends at a distance of about 1 mm to the DRGs in the experimental group, and DMEM media was contained in the control group. Segments of degenerated sciatic nerve from distal of the regeneration chamber were implanted with DRGs at a distance of about 0.5 - 1 mm in the coculturing experiment. DRGs were observed for the direction of the growth of the cells and the fibres. RESULTS: While the capillary containing the dye was put down to the bottom of the culture dish coated with a piece of nylon pad, the red color slowly disseminated with heavier staining in the center and lighter staining in the peripheral portion. We believe this pattern of shade could simulate the concentration gradient of tropic factors in this model. There were significantly more nerve fibres growing from the DRGs towards the capillaries in 6 of the 8 dishes in the experimental group after 72 hours of culture. The tissue and nerve fibers grew evenly in the control group. 76.5% of all the nerve fibres were growing in the direction facing the degenerated nerve segments after 12 hours of coculturing, and only 33.3% of the nerve fibres growing in that direction in the control group. Cells from the DRGs migrated towards the degenerated nerve segments, yet they tended to avoid the normal nerve segments. The migration index of the cells was 0.98 in average in the coculturing experiment with the degenerated nerve segments, but only 0.43 in average with the normal nerve coculturing. CONCLUSION: The capillary model was effective in studying the chemotactic growth of nerve tissue. RCF and the degenerated nerve segments had definite neurotropic effects on DRGs tissue.

Animals↗
PubMed2000

[Tissue engineered neo-cartilage using polymer substrates and chondrocytes: experimental study].

OBJECTIVE: To investigate the possibility of using poly beta-hydroxybutyrate (PHB) as a scaffold for chondrocytes and the feasibility of generating tissue engineered cartilage in rabbit animal model. METHODS: The articular cartilage from 4-week-old rabbits was enzymatically dissolved by type II collagenase, and chondrocytes were harvested and seeded into foams of PHB. After incubation for 1 week in vitro, chondrocyte-polymer constructs were implanted subcutaneously into rabbits. Two respective control groups were established by subcutaneous implantation of PHB foams and chondrocytes alone. The rabbits were killed at 4, 8, 12 weeks postoperatively, and the specimens were dissected and examined macroscopically, histologically and immunohistochemically. RESULTS: Specimens harvested from chondrocyte-polymer constructs and subjected to gross morphologic and histologic analysis demonstrated new cartilage formation, and those from control groups showed no cartilage formation. CONCLUSION: These findings demonstrate that the foam of PHB is not only a good "matrix" for cartilage tissue engineering, but also optimal scalffold for the seeding of chondrocytes to generate new cartilage that would be useful in plastic and reconstructive surgery.

Animals↗
PubMed2000

[Postoperative recurrence of T2 stage gastric cancer].

OBJECTIVE: To study the clinicopathological characteristics of T(2) gastric cancer and its postoperative recurrence. METHOD: 124 T(2) gastric cancer patients were divided into two groups: 42 patients with postoperative recurrence (Group 1) and 82 patients without recurrence (Group 2). RESULTS: The recurrence rate of local tumor was significantly lower in Group 1 (26.2%) than in Group 2 (45.1%). Deep invasion was highly different between the two groups. Circular muscle tumors were seen in Group 1 (4.8%) and in Group 2 (30.5%), whereas sub-serosa tumors were seen in Group 1 (61.8%) and in Group 2 (25.6%). The rate of lymph node metastasis was significantly higher in Group 1 (88.1%) than in Group 2 (57.3%). The mean number of positive nodes was (7.02 +/- 6.50) in Group 1 and (2.16 +/- 2.04) in Group 2(P < 0.01). Local recurrence rate and distant metastasis rate in Group 1 were 54.8% and 46.2% respectively. The median survival was 26.5 months in Group 1 and 57.0 months in Group 2 (P < 0.01). The 1-, 3-, 5-year survival rate in Group 1 and Group 2 were 61.4% vs 97.6%, 18.7% vs 95.9%, and 8.3% vs 95.9%, respectively. CONCLUSION: Poor prognosis is seen in T(2) gastric cancer patients with postoperative recurrence. Extended gastrectomy and multi-therapy are necessary for the patients with the risk factors so as to decrease local recurrence.

Adult↗
PubMed2000

[Expression of telomerase genes in human tumors].

OBJECTIVE: To investigate the correlation between the expression of telomerase genes and malignant phenotypes of human tumors and to compare the expression of telomerase genes and its activity reported in order to evaluate the role of detection of telomerase genes in tumor diagnosis. METHODS: With in situ hybridization, the expression and distribution of telomerase hTR and hTRT genes were observed in 78 cases of human cancer tissues, 20 cases of precancerous lesions and 28 of benign lesions. The results were statistically analyzed. RESULTS: hTR and hTRT were detected in 85% (66/78) and 82% (64/78) of the primary cancers. While in the adjacent tissues, the positive rates were only 3% (2/78) and 5% (4/78). In 20 precancerous cases, the positive rate for hTR and hTRT were 20% (4/20) and 15% (3/20) and the positive cases in 28 benign lesions were 0 and 1/28 (4%), respectively. The positive detection of hTR and hTRT expression in cancer group were significantly different from those in the adjacent tissues, precancerous cases and benign lesion group (P < 0.01). In analysing main types of the human cancers, the positive frequency of hTR and hTRT were 94% (15/16) and 88% (14/16) for the breast cancer, 85% (17/20) and 90% (18/20) for the colon cancer, 80% (8/10) and 80% (8/10) for the gallbladder cancer, 75% (6/8) and 75% (6/8) for the lung cancer, 75% (6/8) and 75% (6/8) for the stomach cancer, and 83% (5/6) and 83% (5/6) for the esophagus cancer, respectively. The expression level of telomerase hTR and hTRT correlated well with the malignancy and metastatic potentials in breast cancer, colon cancer and bladder cancer. Besides, the expressions of hTR and hTRT were noticed to be also highly correlated (P < 0.01). CONCLUSIONS: The expression of telomerase genes correlates with tumor malignant phenotypes, and may reflect the progression of tumors, and the detection of telomerase gene expression may be useful in a retrospective cancer research. It is worthwhile for further study to clarify whether screening of telomerase gene expression is able to become a new index for tumor diagnosis and prognosis.

Breast Neoplasms↗
PubMed2000

[T-lymphocyte subsets and inflammatory cytokines of interleukin-5 and interleukin-10 expression in human nasal polyp tissue].

OBJECTIVE: To investigate the distribution of T-lymphocyte subsets (CD4+ and CD8+ cells) and the expression of IL-5 and IL-10 protein-positive cells in nasal polyps. METHODS: The specimens of thirty-two nasal polyps and six control subjects were studied by Immunohistochemical method to detect CD4+, CD8+, IL-5+ and IL-10+ cells. A mean numbers of positive cells per high power field (10 x 40) were counted. All data were analyzed with t-test and correl-test. RESULTS: There were significantly large number of CD4+ and CD8+ cells in nasal polyps (P < 0.001). A significant predominance of CD4+ cells over CD8+ cells was found in the two subgroups (subepithelia, arounding glands and blood vessels) of nasal polyp (P < 0.001). There were an abundant number of IL-5+ IL-10+ cells, whereas significantly difference higher concentrations than that in the controls (P < 0.001). IL-5+ cells were more than IL-10+ cells in nasal polyps (P < 0.05), and most of IL-5+ cells were plasmacytes and lymphocytes. There was a significant correlation between the counts of CD4+/CD8+ and IL-5+/IL-10+ in the subgroup of nasal polyps arounding glands and blood vessels (r = 0.78, P < 0.01). CONCLUSIONS: This study indicated that CD4+ T-lymphocytes and IL-5 high expression may play an important role in the nasal polyps. Migration of plasmacytes and lymphocytes in polyps may participate in the inflammatory reaction. The disturbance of cellular and humoral immunity and imbalance of cytokines distribution may play a crucial role in the pathogenesis of nasal polyps.

Adult↗