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Biomedical subjects

X J Yu

Publications and source records attributed to X J Yu.

At least 19 recordsLinked to original sources
PubMed2007

Compensatory recovery of vagal control of hemodynamics after unilateral vagotomy.

This study investigated whether each part of the heart is evenly innervated by the left or right vagus and observed the mechanism of compensatory recovery after unilateral cervical vagotomy. HR, BP, LVSP and +/-dp/dt max all decreased one week after left vagotomy, whereas only BP and -dp/dt max decreased one week after right vagotomy. Western blot analyses revealed that the expression of M(2) receptors in the left atrium and left ventricle was upregulated after subacute (1 week) left/right vagotomy. However, significantly more cholinesterase-positive nerves in LV and RV were seen one week after unilateral vagotomy compared to the sham-operated group. In addition, baroreflex sensitivity was increased after subacute right vagotomy. The decreasing effects of ACh (0.5 microg/kg) on LVSP and +/-dp/dt max (but not on HR and BP) were facilitated by subacute unilateral vagotomy. Our present experiments indicate that 1) the working myocardium is innervated bilaterally by the vagus, 2) ventricular contractility is influenced more by denervation of the left than the right vagus and 3) up-regulation of M(2) muscarinic receptors in the left heart, increase of cholinergic nerves, and high baroreflex sensitivity could be involved in the mechanism of compensatory hemodynamic recovery via contralateral vagus overactivity, thereby amplifying contralateral vagal activity and decreasing cardiac contractility.

Acetylcholine↗
PubMed2006

Synthesis, characterization, and photocatalytic activity of TiO(2-x)N(x) nanocatalyst.

Nitrogen-doped titanium dioxide powders were prepared by wet method, that is, the hydrolysis of acidic tetra-butyl titanate using aqueous ammonia solution, followed by calcination at temperatures about 350 degrees C. The catalysts exhibited photocatalytic activity in the visible light region owing to N-doping. The light absorption onset of TiO(2-x)N(x) was shifted to the visible region at 459 nm compared to 330 nm of pure TiO(2). An obvious decrease in the band gap was observed by the optical absorption spectroscopy, which resulted from N2p localized states above the valence band of TiO(2-x)N(x) (compared to TiO(2)). The TiO(2-x)N(x) catalyst was characterized to be anatase with oxygen-deficient stoichiometry by X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS) and X-ray photoelectron spectroscopy (XPS). The binding energy of N1s measured by XPS characterization was 396.6 eV (TiN bonds, beta-N) and 400.9 eV (NN bonds, gamma-N(2)), respectively. The photocatalytic activity of TiO(2-x)N(x) under visible light was induced by the formation of beta-N in the structure. Photocatalytic decomposition of benzoic acid solutions was carried out in the ultraviolet and visible (UV-vis) light region, and the TiO(2-x)N(x) catalyst showed higher activity than pure TiO(2).

Benzoic Acid↗
PubMed2006

Assessment of hemodynamics properties of a new-type artificial heart valve prosthesis using catheterization and echocardiography.

OBJECTIVE: The objectives of this study were to assess the hemodynamic properties of the newly developed artificial heart valve prosthesis experimentally in laboratory simulation, in an animal model, and clinically in a human model and to compare the results measured by catheterization and echocardiography. METHODS: (1) Laboratory simulation. The prosthesis was tested using a pulsatile flow simulator in the aortic position. Hydrodynamics parameters were automatically analyzed through a custom-designed data processing program. (2) Animal experiment. Six sheep subjected to mitral replacement with 21-mm-valve prosthesis were measured by open cardiac catheterization intraoperatively. Doppler echocardiography and open cardiac catheterization under dobutamine stress were performed in two sheep subjected to implantation 2.5 years ago. (3) Clinical patient observation. Observations were carried out on 14 patients with aortas replacement and 10 patients with bicuspid replacement using both doppler echocardiography and open cardiac catheterization. RESULTS: (1) Laboratory simulation. The results showed that the value of the transvalvular gradient (DeltaP) decreased with the increase of heart rate, and the values were not greater that 10 mm Hg at any given tissue annulus diameter. (2) Animal experiment. The mean DeltaP value of the six sheep was 5.2 +/- 1.7 mm Hg intraoperatively, while the corresponding DeltaP value of the two sheep 2.5 years after implantation was 6.1 +/- 0.3 mm Hg measured by open cardiac catheterization. (3) Clinical patient observation. The mean DeltaP values in the aortic position measured by catheterization and echocardiography were 6.26 approximately 4.10 and 9.42 approximately 7.48 mm Hg, respectively. The gradients in the mitral position were 2.10 approximately 1.9 and 5.28 approximately 4.10 mm Hg, respectively. CONCLUSIONS: The results demonstrate that the new-type bileaflet heart valve prosthesis only generates a relatively low transvalvar gradient and thus has good hemodynamic properties.

Adult↗
PubMed2006

The genome of the obligately intracellular bacterium Ehrlichia canis reveals themes of complex membrane structure and immune evasion strategies.

Ehrlichia canis, a small obligately intracellular, tick-transmitted, gram-negative, alpha-proteobacterium, is the primary etiologic agent of globally distributed canine monocytic ehrlichiosis. Complete genome sequencing revealed that the E. canis genome consists of a single circular chromosome of 1,315,030 bp predicted to encode 925 proteins, 40 stable RNA species, 17 putative pseudogenes, and a substantial proportion of noncoding sequence (27%). Interesting genome features include a large set of proteins with transmembrane helices and/or signal sequences and a unique serine-threonine bias associated with the potential for O glycosylation that was prominent in proteins associated with pathogen-host interactions. Furthermore, two paralogous protein families associated with immune evasion were identified, one of which contains poly(G-C) tracts, suggesting that they may play a role in phase variation and facilitation of persistent infections. Genes associated with pathogen-host interactions were identified, including a small group encoding proteins (n = 12) with tandem repeats and another group encoding proteins with eukaryote-like ankyrin domains (n = 7).

Animals↗
PubMed2005

Analysis of STR polymorphisms in the Chao Shan population in South China.

Chao Shao area is a littoral under the jurisdiction of Guangdong province, abutting on Fujian. Historically, the area was relatively isolated from other parts of China until 1990s, when it started to take a small number of immigrants from other regions. People residing in this area speak in unique dialect and have distinct lifestyle. Allele frequencies for the 15 short tandem repeats (STR) loci included in the AmpFLSTR Identifiler kit were obtained from a sample of 144 unrelated Chinese born and living in the Chao Shan area, South China.

China↗
PubMed2004

Comparison of effects of acetylcholine on electromechanical characteristics in guinea-pig atrium and ventricle.

The direct negative effects of acetylcholine (ACh) on guinea-pig atria and ventricles were investigated using standard microelectrodes, a force transducer and a video edge-detection system. It was found that: (1) ACh (at 0.001-100 microm) decreased the force of contraction and shortened the action potential duration (APD) in both atria and ventricles in a concentration-dependent manner, and that the atria were more sensitive to ACh than the ventricles; and (2) the direct negative inotropic effect of ACh (1 microm) on an isolated cardiac cell was similar to that on the isolated myocardium. But this effect was not present in all isolated ventricular cells, while all the atrial cells responded to ACh. In conclusion, ACh had direct inhibitory effects on both atrial and ventricular tissue and myocytes, although the effects were greater in atria than in ventricles; and the negative inotropic effect of ACh was closely related to the shortening of the APD.

Acetylcholine↗
PubMed2001

Enhanced anthocyanin production by repeated-batch culture of strawberry cells with medium shift.

Repeated-batch cultures of strawberry cells (Fragaria ananassa cv. Shikinari) subjected to four medium-shift procedures (constant LS medium, constant B5 medium, alternation between LS and B5 starting from LS and alternation between LS and B5 starting from B5) were investigated for the enhanced anthocyanin productivity. To determine the optimum period for repeated batch cultures, two medium-shift periods of 9 and 14 days were studied, which represent the end of the exponential growth phase and the stationary phase. By comparison with the corresponding batch cultures, higher anthocyanin productivity was achieved for all the repeated-batch cultures at a 9-day medium-shift period. The average anthocyanin productivity was enhanced 1.7- and 1.76-fold by repeated-batch cultures in constant LS and constant B5 medium at a 9-day shift period for 45 days, respectively. No further improvement was observed when the medium was alternated between LS (the growth medium) and B5 (the production medium). Anthocyanin production was unstable at a 14-day shift period regardless of the medium-shift procedures. The results show that it is feasible to improve anthocyanin production by a repeated-batch culture of strawberry cells.

Anthocyanins↗
PubMed2001

Genome-wide analyses on loss of heterozygosity in hepatocellular carcinoma in Southern China.

BACKGROUND/AIMS: To conduct a genome-wide analysis of loss of heterozygosity (LOH) and its clinical significance in hepatocellular carcinoma (HCC) in Southern China where high incidence of HCC was documented. METHODS: LOH of 382 microsatellite loci on all autosomes were detected with polymerase chain reaction-based microsatellite polymorphism analyses in 104 HCC tumor tissues. RESULTS: High frequency of LOH (>55.7%) was observed on chromosome 1p, 1q, 2q, 3p, 4q, 6q, 8p, 9p, 13q, 16q, and 17p. LOH rates on loci D4S2964 (4q21.21), D8S277 (8p23.1-pter) and D17S938 (17p13.1-p13.3) were significantly higher in cases with positive HBsAg than in those with negative HBsAg. Similarly, LOH on loci D1S214 (lp36.3), D1S2797 (1p34) and D3S3681 (3p11.2-p14.2) were more frequently detected in tumors with intrahepatic metastasis than in those without. CONCLUSIONS: Status of LOH in HCC in Southern China is similar to that reported previously in other countries and areas. However, we firstly identified high-frequency LOH on chromosome 3p in HCC. Furthermore, HBV infection, as well as tumor intrahepatic metastasis, may be correlated with allelic losses on certain chromosome regions.

Adolescent↗
PubMed2001

Phylogenetic relationships of Anaplasma marginale and 'Ehrlichia platys' to other Ehrlichia species determined by GroEL amino acid sequences.

The heat-shock protein (GroEL) genes of Anaplasma marginale, Ehrlichia muris and 'Ehrlichia platys' were sequenced and compared with the GroEL of other species of Ehrlichia. The GroEL amino acid sequences of A. marginale and 'E. platys' were most similar to the GroEL sequence of Ehrlichia phagocytophila, with which they formed one group with 6-10% divergence. The E. muris GroEL was most closely related to the GroEL of two unclassified strains (HF-565 and Anan), then to Ehrlichia chaffeensis, Ehrlichia canis, Ehrlichia ewingii and Cowdria ruminantium, forming a second distinct group (0.3-8.6% divergence). The GroELs of Ehrlichia risticii and Ehrlichia sennetsu were very similar to one another (only 2% divergence), forming the third group. The first two groups were relatively closely related (17-20% divergence), while the third group was only distantly related to the first two groups (62-73% divergence).

Amino Acid Sequence↗
PubMed2001

[A study on pathological changes of closed diffuse brain injury in rats with H.E., esterification-silver stain and albumin immunohistochemical stain].

OBJECTIVE: To observed the pathological changes of closed diffuse brain injury in the rats died immediately and 15 min to 5 days after the injury. METHODS: H.E. staind and esterification-silver stain were applied to investigate the closed diffuse brain injury. RESULTS: In rats died immediately after the concussive injury, a number of shrunken neurons(type I change), distended neurons(type II change) and wave-like nerve fibers were identified in the brain tissue, especially in brain-stem. At 2 h and 8 h after injury, brain edema and axonal swelling appeared clearly in the cortex and white matter, especially in brain-stem. At post-traumatic 8 h and 24 h, the axonal retraction balls began to appear. The amount of neurons undergoing type I and II changes and constraction balls increased along with the survivor time. After 4 days and 5 days, brain edema alleviated, but the retraction balls and axonal swelling still existed. With Esterifica-tion silver stain, the above changes of neurons and nerve fibers were more obvious. With ABC stain, the distribution of albumin(Al) was extended from the perio-vascular area to diffuse distribution. Al positive staining were more obvious in injuried neurons and nerve fibers. CONCLUSION: The distribution of the concussive damage in the brain are coup, contra-coup and centripental.

Albumins↗
PubMed2001

[Influence of Salvia miltiorrhizae and Astragalus membranaceus on hemodynamics and liver fibrosis indexes in liver cirrhotic patients with portal hypertension].

OBJECTIVE: To observe the influence of Salvia miltiorrhiza (SM) and Astragalus membranaceus (AM) on hemodynamics and liver fibrosis indexes in patients of liver cirrhosis with portal hypertension. METHODS: Eighty-four cases of liver cirrhosis were enrolled and divided randomly into two groups, 42 in each. The control group was treated with conventional therapy and the tested group treated with SM and AM. The parameters, including diameter of portal vein and splenic vein (Dpv and Dsv), speed of blood flow in portal vein and splenic vein (Spv and Ssv), quantity of blood flow in portal vein and splenic vein (Qpv and Qsv) as well as liver fibrosis indexes, such as HA, PC III and LN, were determined before, 1, 2 and 3 months after treatment. RESULTS: After treatment, in the tested group, Dpv and Dsv decreased, Spv and Ssv increased, and Qpv and Qsv reduced, showing a significant difference in comparison with those in the control group (P < 0.05 or P < 0.01). The liver fibrosis indexes were improved significantly in the tested group, also showed significant difference from those in the control group (P < 0.01). CONCLUSION: SM and AM could improve portal hypertension effectively in liver cirrhosis patients, one of the mechanism may be related with the improvement of liver fibrosis.

Adult↗
PubMed2000

A conserved, transcriptionally active p28 multigene locus of Ehrlichia canis.

Antigenic diversity of Ehrlichia chaffeensis and Ehrlichia canis may involve independent or differential expression of the P28 outer membrane proteins genes, enabling persistent infections of the natural hosts. In this study, we analyzed the transcriptional activity of a five gene locus in E. canis encoding homologous, but non-identical, p28 genes. The p28 multigene locus contained three previously identified complete gene sequences and one partial gene sequence. A new p28 gene was identified and sequenced, and the complete sequence of a second partial p28 gene was determined. The new p28 gene joined two previously separate loci, forming the single p28 multigene locus. The amino acid homology of the E. canis P28 proteins ranged from 51 to 74%. The nucleic acid sequence of regions compared within the locus spanning four p28 genes from two geographically distinct E. canis isolates was completely conserved. Analysis of the five p28 genes demonstrated that all were transcriptionally active in in-vitro cultures of E. canis incubated at the vertebrate host (37 degrees C) and ambient tick temperatures (27 degrees C). Polycistronic copies of multiple p28 genes were not detected by RT-PCR, but monocistronic p28 mRNA transcripts were detected by Northern blotting from E. canis infected DH82 cells, indicating that the genes are transcribed as monocistronic messages.

Amino Acid Sequence↗
PubMed2000

Lentiviral vectors for efficient delivery of CD80 and granulocyte-macrophage- colony-stimulating factor in human acute lymphoblastic leukemia and acute myeloid leukemia cells to induce antileukemic immune responses.

Cell vaccines engineered to express immunomodulators have shown feasibility in eliminating leukemia in murine models. Vectors for efficient gene delivery to primary human leukemia cells are required to translate this approach to clinical trials. In this study, second-generation lentiviral vectors derived from human immunodeficiency virus 1 were evaluated, with the cytomegalovirus (CMV) promoter driving expression of granulocyte-macrophage-colony-stimulating factor (GM-CSF) and CD80 in separate vectors or in a bicistronic vector. The vectors were pseudotyped with vesicular stomatitis virus G glycoprotein and concentrated to high titers (10(8)-10(9) infective particles/mL). Human acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), and chronic myeloid leukemia cell lines transduced with the monocistronic pHR-CD80 vector or the bicistronic pHR-GM/CD vector became 75% to 95% CD80 positive (CD80(+)). More important, transduction of primary human ALL and AML blasts with high-titer lentiviral vectors was consistently successful (40%-95% CD80(+)). The average amount of GM-CSF secretion by the leukemia cell lines transduced with the pHR-GM-CSF monocistronic vector was 2182.9 pg/10(6) cells per 24 hours. Secretion was markedly lower with the bicistronic pHR-GM/CD vector (average, 225.7 pg/10(6) cells per 24 hours). Lower amounts of CMV-driven messenger RNA were detected with the bicistronic vector, which may account for its poor expression of GM-CSF. Primary ALL cells transduced to express CD80 stimulated T-cell proliferation in an autologous mixed lymphocyte reaction. This stimulation was specifically blocked with monoclonal antibodies reactive against CD80 or by recombinant cytotoxic T-lymphocyte antigen 4-immunoglobulin fusion protein. These results show the feasibility of efficiently transducing primary leukemia cells with lentiviral vectors to express immunomodulators to elicit antileukemic immune responses. (Blood. 2000;96:1317-1326)

Acute Disease↗
PubMed2000

Intrakines--evidence for a trans-cellular mechanism of action.

Human CXCR4 is the receptor for the CXC chemokine SDF-1alpha and also acts as a coreceptor for T lymphotropic HIV-1 strains. Blocking the surface expression of this receptor via an intrakine approach has recently been shown to efficiently prevent HIV-1 infection of T cells. The CXC-chemokine gene is fused to an endoplasmic reticulum retention signal (KDEL) that retains the newly synthesized chemokine and its receptor within the cell, where both are subsequently degraded. We constructed MoMuLV-based vectors containing the SDF-KDEL construct driven by the "MND" long terminal repeat, using eGFP as a marker gene (MND-SDF-KDEL-IRES-eGFP) and a control vector (MND-X-IRES-eGFP). CEM human T lymphoblastic leukemia cells were transduced with the intrakine vector or the control vector. We detected a marked downregulation of CXCR4 expression in the cells transduced with the intrakine vectors as opposed to the cells transduced with the control vector. However, the eGFP-negative fraction of the cells transduced with the intrakine vector displayed the same CXCR4 downregulation as the eGFP-positive fraction, suggesting an effect in trans. The possibility of this being due to eGFP being silenced while SDF-KDEL was still expressed was excluded by Southern and Northern blot analyses. Upon cultivating the control cells with supernatant of the cells transduced with the intrakine vector, we observed a downregulation of CXCR4 expression on the control cells. Experiments using rhSDF-1alpha showed downregulation by the supernatant to be comparable to that achieved by the exogenous addition of 30 ng/ml SDF-1alpha. To assess the bioactivity of the secreted substance in the supernatant, a chemotaxis assay was performed. The transmigration observed was, once again, within the range of that achieved by the addition of 30 ng/ml SDF-1alpha. We conclude that the intrakine SDF-KDEL, apart from acting within the cell, is also in part secreted and causes the downregulation of the receptor by acting like a secreted chemokine.

Blotting, Northern↗
PubMed2000

Expression of human Wiskott-Aldrich syndrome protein in patients' cells leads to partial correction of a phenotypic abnormality of cell surface glycoproteins.

The Wiskott-Aldrich syndrome (WAS) is an uncommon X-linked recessive disease characterized by thrombocytopenia, eczema and immunodeficiency. The biochemical defect of this disorder primarily affects cells derived from bone marrow. To understand better the molecular mechanisms underlying this disease and to evaluate the possibility of correcting the genetic defects in hematopoietic cells, a Moloney murine leukemia virus (MoMLV)- based retroviral vector carrying a functional Wiskott-Aldrich syndrome protein (WASp) cDNA driven by an SV40 promoter (LNS-WASp) was constructed. A packaging cell line containing this vector produced a stable level of WAS protein and maintained a high titer of viral output. Epstein-Barr virus (EBV)-transformed B lymphoblastoid cell lines (B-LCL) from WAS patients, which lack expression of the WAS protein, were transduced by the LNS-WASp retroviral vector and showed expression of WASp by Western blot. Analysis of the O-glycan pattern on cell surface glycoproteins from WAS patients' B-LCL showed an altered glycosylation pattern, due to increased activity of beta-1, 6-N-acetylglucosaminyltransferase (C2GnT). Transduction by the retroviral vector carrying the functional WASp cDNA partially restored the abnormal glycosylation pattern, and was accompanied by a decreasing C2GnT activity. These findings imply a functional linkage between the WAS protein and the expression of the glycosyltransferase involved in the O-glycosylation, and also suggest a potential gene therapy via transferring a functional WASp cDNA into hematopoietic cells for Wiskott-Aldrich syndrome. Gene Therapy (2000) 7, 314-320.

Cells, Cultured↗
PubMed2000

Glycosylation of homologous immunodominant proteins of Ehrlichia chaffeensis and Ehrlichia canis.

The glycoprotein genes of Ehrlichia chaffeensis (1,644 bp) and Ehrlichia canis (2,064 bp) encode proteins of 548 to 688 amino acids with predicted molecular masses of only 61 and 73 kDa but with electrophoretic mobilities of 120 kDa (P120) and 140 kDa (P140), respectively. The 120-kDa protein gene of E. chaffeensis contains four identical 240-bp tandem repeat units, and the 140-kDa protein gene of E. canis has 14 nearly identical, tandemly arranged 108-bp repeat units. Conserved serine-rich motifs identified in the repeat units of P120 and P140 were also found in the repeat units of the human granulocytotropic ehrlichiosis agent 130-kDa protein and of the fimbria-associated adhesin protein Fap1 of Streptococcus parasanguis. Nearly the entire (99%) E. chaffeensis P120 gene (1,616 bp), the 14-repeat region (78%) of the E. canis P140 gene (1,620 bp), and a 2-repeat region from the E. chaffeensis P120 gene (520 bp) were expressed in Escherichia coli. The recombinant proteins exhibited molecular masses ranging from 1.6 to 2 times larger than those predicted by the amino acid sequences. Antibodies against the recombinant proteins reacted with E. chaffeensis P120 and E. canis P140, respectively. Carbohydrate was detected on the E. chaffeensis and E. canis recombinant proteins, including the two-repeat polypeptide region of E. chaffeensis P120. A carbohydrate compositional analysis identified glucose, galactose, and xylose on the recombinant proteins. The presence of only one site for N-linked (Asn-Xaa-Ser/Thr) glycosylation, a lack of effect of N-glycosidase F, the presence of 70 and 126 Ser/Thr glycosylation sites in the repeat regions of P120 and P140, respectively, and a high molar ratio of carbohydrate to protein suggest that the glycans may be O linked.

Amino Acid Sequence↗
PubMed2000

Molecular cloning and characterization of the 120-kilodalton protein gene of Ehrlichia canis and application of the recombinant 120-kilodalton protein for serodiagnosis of canine ehrlichiosis.

The 120-kDa outer membrane protein (p120) is a potential adhesin of Ehrlichia chaffeensis, and recombinant p120 is very useful for serodiagnosis of human monocytotropic ehrlichiosis. The analogous gene of p120 in Ehrlichia canis was cloned, sequenced, and expressed. Like the E. chaffeensis p120, the E. canis p120 contains tandem repeat units. However, neither the repeat number nor the amino acid sequences in the repeats are identical in the two Ehrlichia species. The repeat units are hydrophilic and by probability analysis are predicted to be surface exposed in both species. The repeat regions of the p120s of the two species have common amino acid sequences that are predicted to be surface exposed. The overall amino acid sequence of the E. canis p120 is 30% homologous to that of E. chaffeensis p120. Protein immunoblotting demonstrated that the recombinant E. canis p120 reacted with convalescent sera from dogs with canine ehrlichiosis. These results indicate that the recombinant p120 is a potential antigen for the serodiagnosis of canine ehrlichiosis.

Amino Acid Sequence↗