Biomedical subjects

M Xu

Publications and source records attributed to M Xu.

At least 91 records · Page 5Linked to original sources

PubMed2001

Selective loss of natural killer T cells by apoptosis following infection with lymphocytic choriomeningitis virus.

Natural killer T (NKT) cells, a unique subpopulation of T cells, coexpress markers also present on NK cells and recognize the major histocompatibility complex class I-like CD1d1 molecule. We studied the effect of an acute virus infection on NKT cells. Mice were infected with the nonhepatotropic Armstrong strain of lymphocytic choriomeningitis virus (LCMV), and at various times postinfection, mononuclear cells from the liver, peritoneum, and spleen were isolated. It was found that within 2 to 3 days, there was a selective loss of NKT cells from the liver with an apparent rapid recovery within 8 to 14 days. There was no increase in peritoneal or splenic NKT cells, indicating that NKT cells did not traffic to these tissues. This loss of NKT cells was independent of gamma interferon (IFN-gamma) and interleukin 12 (IL-12) production, but did occur in mice treated with poly(I-C), a classical inducer of IFN-alpha/beta. The reduction in NKT cells was CD28 and fas/fasL independent and occurred via apoptosis. It was not observed in LCMV-infected DNA fragmentation factor 45-deficient mice, and an increase in active caspase 3-specific staining was found in liver NKT cells from LCMV-infected and poly(I-C)-treated mice compared to uninfected wild-type mice. Interestingly, it was also found that liver NKT cells from LCMV-infected mice were themselves infected. These results suggest that the loss of NKT cells following an acute LCMV infection could be due to the induction of IFN-alpha/beta resulting in NKT-cell apoptosis and is important for the host's immune response to LCMV.

Animals↗

PubMed2001

Development of sequence-characterized amplified regions (SCARs) from amplified fragment length polymorphism (AFLP) markers tightly linked to the Vf gene in apple.

Amplified fragment length polymorphism (AFLP) markers have become widely used in saturating the region of a gene of interest for the ultimate goal of map-based cloning of the gene or for marker-assisted selection. However, conversion of AFLP markers into restriction fragment length polymorphism (RFLP) or polymerase chain reaction (PCR)-based markers will greatly expand their usefulness in genetic applications. Previously, we have identified 15 AFLP markers tightly linked to the Vf gene conferring scab resistance in apple. In this study, we have successfully converted 11 of these AFLPs into sequence-characterized amplified region (SCAR) markers. Of the remaining four nonconverted AFLP markers, one, ET2MC8-1, has been found to be very short (83 base pairs) and is an A/T rich (90%) marker; a second, EA2MG11-1, has shown identical sequences between Malus floribunda 821 (the original source of the Vf gene) and scab-susceptible apple cultivars; while the other two, EA12MG16-1 and ET8MG1-1, have not been cloned. Using the 11 converted SCAR markers along with 5 previously identified SCAR markers, a high-resolution linkage map around the Vf gene has been constructed, and found to be consistent with its corresponding AFLP map. Three converted SCAR markers (ACS-3, -7, and -9) are inseparable from the Vf gene; whereas one (ACS-6) is located left of, and the remaining seven (ACS-1, -2, -4, -5, -8, -10, and -11) are located right of the Vf gene at genetic distances of 0.4 and 0.2 cM, respectively. A reliable and robust procedure for development of SCAR markers from AFLP markers is presented.

Base Sequence↗

PubMed2001

Calcium preconditioning inhibits mitochondrial permeability transition and apoptosis.

We tested the hypothesis whether calcium preconditioning (CPC) reduces reoxygenation injury by inhibiting mitochondrial permeability transition (MPT). Cultured myocytes were preconditioned by a brief exposure to 1.5 mM calcium (CPC) and subjected to 3 h of anoxia followed by 2 h of reoxygenation (A-R). Myocytes were also treated with 0.2 microM/l cyclosporin A (CsA), an inhibitor of MPT, before A-R. A significant increase of viable cells and reduced lactate dehydrogenase release was observed both in CPC- and CsA-treated myocytes compared with the A-R group. Cytochrome c release was predominantly observed in the cytoplasm of myocytes in the A-R group in contrast with CPC- or CsA-treated groups, where it was restricted only to mitochondria. Similarly, the cell death by apoptosis was also markedly attenuated in these groups. Electron-dense Ca(2+) deposits in mitochondria were also less frequent. Atractyloside (20 microM/l), an adenine nucleotide translocase inhibitor, caused changes similar to those in the A-R group, suggesting a role of MPT in A-R injury. Protection by inhibition of MPT by CsA and CPC suggests that MPT plays an important role in reoxygenation/reperfusion injury. The data further suggest that preconditioning inhibits MPT by inhibiting Ca(2+) accumulation by mitochondria.

Animals↗

PubMed2001

Mitochondrial K(ATP) channel activation reduces anoxic injury by restoring mitochondrial membrane potential.

Mitochondrial membrane potential (DeltaPsi(m)) is severely compromised in the myocardium after ischemia-reperfusion and triggers apoptotic events leading to cell demise. This study tests the hypothesis that mitochondrial ATP-sensitive K(+) (mitoK(ATP)) channel activation prevents the collapse of DeltaPsi(m) in myocytes during anoxia-reoxygenation (A-R) and is responsible for cell protection via inhibition of apoptosis. After 3-h anoxia and 2-h reoxygenation, the cultured myocytes underwent extensive damage, as evidenced by decreased cell viability, compromised membrane permeability, increased apoptosis, and decreased ATP concentration. Mitochondria in A-R myocytes were swollen and fuzzy as shown after staining with Mito Tracker Orange CMTMRos and in an electron microscope and exhibited a collapsed DeltaPsi(m), as monitored by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1). Cytochrome c was released from mitochondria into the cytosol as demonstrated by cytochrome c immunostaining. Activation of mitoK(ATP) channel with diazoxide (100 micromol/l) resulted in a significant protection against mitochondrial damage, ATP depletion, cytochrome c loss, and stabilized DeltaPsi(m). This protection was blocked by 5-hydroxydecanoate (500 micromol/l), a mitoK(ATP) channel-selective inhibitor, but not by HMR-1098 (30 micromol/l), a putative sarcolemmal K(ATP) channel-selective inhibitor. Dissipation of DeltaPsi(m) also leads to opening of mitochondrial permeability transition pore, which was prevented by cyclosporin A. The data support the hypothesis that A-R disrupts DeltaPsi(m) and induces apoptosis, which are prevented by the activation of the mitoK(ATP) channel. This further emphasizes the therapeutic significance of mitoK(ATP) channel agonists in the prevention of ischemia-reperfusion cell injury.

Animals↗

PubMed2001

Molecular cloning, structure and expression of a novel nuclear RNA-binding cyclophilin-like gene (PPIL4) from human fetal brain.

The cyclophilins are members of a highly conserved, ubiquitous family, and play an important role in protein folding, immunosuppression by cyclosporin A (CsA), and infection of HIV-1 virions. Here we report that a novel member of the cyclophilin family, PPIL4, was cloned and identified during the large-scale sequencing analysis from a human fetal brain cDNA library. The PPIL4 gene encodes a protein which shares 96% amino acid identity with a protein encoded by a putative gene recently cloned from several different early stages of mouse embryo, and its homologues are found in several other organisms. According to bioinformatics analysis, the PPIL4 gene was found to be located in chromosome 6q24-->q25. Besides the PPIase motif, PPIL4 also has an RNA recognition motif (RRM), a pair of bipartite nuclear targeting sequences, and a lysine rich domain. RT-PCR analysis indicated that PPIL4 gene expression is abundant in kidney but has a ubiquitously low expression pattern in other human adult tissues.

Amino Acid Motifs↗

PubMed2001

Toward a molecular understanding of psychostimulant actions using genetically engineered dopamine receptor knockout mice as model systems.

A major focus in studying the progression and prevention of addictive diseases has been to understand the molecular and cellular mechanisms underlying drug addiction. The brain dopaminergic system plays a central role in reward and motivation and is thought to be the main neural substrate for the actions of abusive drugs. We have used the gene targeting technology to generate dopamine D1 and D3 receptor knockout mice and used these mice as model systems to gain a molecular understanding of acute effects of psychostimulants cocaine and amphetamine. The use of a combined approach involving behavioral, electrophysiological as well as molecular studies has allowed us to define initially the roles of dopamine D1 and D3 receptors in the acute effects of psychostimulants and will enable us to understand mechanisms underlying their chronic actions in the future.

Amphetamine↗

PubMed2001

Time-resolved Fourier optical diffuse tomography.

Time-resolved Fourier optical diffuse tomography is a novel approach for imaging of objects in a highly scattering turbid medium with use of an incident (near) plane wave. The theory of the propagation of spatial Fourier components of the scattered wave field is presented, along with a fast algorithm for three-dimensional reconstruction in a parallel planar geometry. Examples of successful reconstructions of simulated hidden absorptive or scattering objects embedded inside a human-tissue-like semi-infinite turbid medium are provided.

Algorithms↗

PubMed2001

Modification by exercise training of activity and enzyme expression of hepatic branched-chain alpha-ketoacid dehydrogenase complex in streptozotocin-induced diabetic rats.

The branched-chain alpha-ketoacid dehydrogenase (BCKDH) complex is the rate-limiting enzyme in the catabolism of branched-chain amino acids. In the present study, we examined the effects of exercise training on the activity and enzyme expression of the hepatic BCKDH complex in diabetic rats. The rats were prepared by intravenous injections of streptozotocin (50 mg/kg BW), and exercise training was accomplished by treadmill running for 45 min/d for 4 wk. The total and actual activities of hepatic BCKDH complex were significantly increased to approximately 160% by 4 wk of diabetes. On the other hand, diabetic rats in the trained group had the same level of activities as those in the normal rats, indicating that exercise training inhibited the diabetes-induced increase in the enzyme activities. The activity state (% active form) of the enzyme complex was about 100% in all groups and was not affected by diabetes or training. The protein amounts of the enzyme subunits (E1alpha and E2) and the abundance of mRNA for the E2 subunit, but not for the other subunits, in the liver had the same trend as the activities. These results suggest that the capacity for branched-chain amino acid catabolism in streptozotocin-induced diabetic rats is reduced by exercise training and that this modification is associated with the suppression of diabetes-induced BCKDH complex expression in the liver.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed2001

[Study on the noninvasive measurement of cerebral oxygen saturation and cerebral phronetal function].

With the use of Near-infrared spectroscopy(NIRS), the noninvasive measurement of cerebral oxygen concentration can be achieved in vivo based on the Lambert-Beer Law. In this paper, we discuss the possibility of studying higher brain functions through a combination of cerebral oxygen saturation and cerebral function measurement. Event-related experiments are introduced to measure the cerebral phronetal function. Time domain curves show sight differences among these experiment results. However, with the aid of DFT, experiment data of all five human volunteers show that the frequency near 20 Hz or 40 Hz is evoked depending on the difficulty of the mental tasks. The results demonstrate the feasibility of cerebral function studies by means of cerebral oxygen saturation measurement analysis in the frequency domain.

Adult↗

PubMed2001

Presence of DNA fragmentation and lack of neuroprotective effect in DFF45 knockout mice subjected to traumatic brain injury.

BACKGROUND: Apoptosis plays an important pathophysiologic role in neuronal cell loss and associated neurologic deficits following traumatic brain injury (TBI). DNA fragmentation represents one of the characteristic biochemical features of neuronal apoptosis and is observed after experimental TBI. DFF45 and DFF40 are essential for DNA fragmentation in various models of apoptosis. MATERIALS AND METHODS: We used mice deficient in DFF45 and wild-type controls. Oligonucleosomal DNA fragmentation induced by TBI was analyzed using in vivo and in vitro assays. Expression and integrity of DFF45 and DFF40 proteins was assessed by Western analysis. Other outcome measurements included neurologic scoring, learning/memory tests, lesion volume measurements (MRI), and assessment of cell viability in vitro among others. RESULTS: We compared the effects of controlled cortical impact (CCI) trauma in DFF45 knockout mice and wild-type controls. Analysis of TBI-induced DNA fragmentation in brain cortex from wild-type and DFF45 knockout mice indicates that, although somewhat delayed, oligonucleosomal cleavage of DNA occurs after TBI in DFF45 knockout mice. DFF45 knockouts showed no significant differences in behavioral outcomes or lesion volumes after TBI as compared to wild-type controls. Using an in vitro reconstitution system, we also demonstrated that cleavage of DFF45 by caspase-3 is not sufficient for DNA fragmentation induced by protein extracts from rat brain cortex. We found that endonuclease activity induced in rat brain cortex following TBI depends on the presence of Mg2+ and Ca2+, but is not inhibited by Zn2+. Primary neuronal cultures from DFF45 knockouts failed to show DNA laddering in response to staurosporine, but did show prominent, albeit delayed, DNA fragmentation following treatment with etoposide. In contrast, primary neurons from wild-type animals demonstrated marked DNA fragmentation following treatment with staurosporine or etoposide. CONCLUSIONS: The results of this study suggest that, in addition to DFF45/40, other endonucleases may be essential for chromatin degradation during neuronal apoptosis in adult brain after TBI.

Animals↗

PubMed2001

[The effect of "qingxiangsan" on inhibiting oxidation and hepatic cells apoptosis in the wet-heat syndrome rat model].

OBJECTIVE: To observe the changes of oxidation and hepatic cells apoptosis in the wet-heat syndrome rat model, and the effect of "qingxiangsan" on inhibiting oxidation and hepatic cells apoptosis. METHODS: Wistar rats were divided into wet-heat syndrome group, qingxiangsan group and normal control group. Flow cytometry and electron microscopy were employed to detect hepatic cells apoptosis. SOD and MDA in the serum, LPO in the hepatic tissue were also estimated. RESULTS: Apoptotic morphogenetic changes, apoptotic rate increasing, activity of SOD decreasing, content of MDA and LPO increasing were obvious in the wet-heat syndrome group. In the "qingxiangsan" group, apoptotic rate decreasing, activity of SOD increasing, content of MDA and LPO decreasing were examined. CONCLUSION: "qingxiangsan" possesses the function of inhibiting oxidation and apoptosis in the wet-heat syndrome rat model.

Animals↗

PubMed2001

Salvianolate inhibits proliferation and endothelin release in cultured rat mesangial cells.

AIM: To study the effects of salvianolate, an aqueous extract of Radix Salviae Miltiorrhizae, on the proliferation and endothelin release of cultured rat mesangial cells. METHODS: The proliferation of mesangial cells was determined in terms of [3H]thymidine uptake. The concentration of endothelin was measured by radioimmunoassay. The cytotoxicity of salvianolate was tested by tetrazolium (MTT) and lactic dehydrogenase (LDH) assay. RESULTS: Lipopolysaccharide (LPS) 10 mg/L increased the proliferation and endothelin release in cultured mesangial cells. When mesangial cells pretreated with 3, 10, and 30 mg/L of salvianolate were incubated for 4 h with LPS, salvianolate exhibited a concentration dependent inhibitory effect on proliferation and endothelin levels in the mesangial cells induced by LPS. Furthermore, the increased basal levels of mesangial cells proliferation and the endothelin release were also effectively inhibited by salvianolate 30 mg/L at 4, 8, and 12 h. Besides, no cytotoxicity of salvianolate was observed. CONCLUSION: These results indicate that salvianolate can inhibit mesangial cells proliferation, which may be related to the decrease of endothelin release.

Animals↗

PubMed2001

A bacterial artificial chromosome (BAC) library of Malus floribunda 821 and contig construction for positional cloning of the apple scab resistance gene Vf.

The apple scab resistance gene Vf, originating from the wild species Malus floribunda 821, has been incorporated into a wide variety of apple cultivars through a classical breeding program. With the aim of isolating the Vf gene, a bacterial artificial chromosome (BAC) library consisting of 31 584 clones has been constructed from M. floribunda 821. From the analysis of 88 randomly selected BAC clones, the average insert size is estimated at 125 kb. If it is assumed that the genome size of M. floribunda 821 is 769 Mb/haploid, the library represents about 5x haploid genome equivalents. This provides a 99% probability of finding any specific sequence from this library. PCR-based screening of the library has been carried out using eight random genomic sequence-characterized amplified regions (SCARs), chloroplast- and mitochondria-specific SCARs, and 13 high-density Vf-linked SCAR markers. An average of five positive BAC clones per random SCAR has been obtained, whereas less than 1% of BAC clones are derived from the chloroplast or mitochondrial genomes. Most BAC clones identified with Vf-linked SCAR markers are physically linked. Three BAC contigs along the Vf region have been obtained by assembling physically linked BAC clones based on their fingerprints. The overlapping relatedness of BAC clones has been further confirmed by cytogenetic mapping using fiber fluorescence in situ hybridization (fiber-FISH). The M. floribunda 821 BAC library provides a valuable genetic resource not only for map-based cloning of the Vf gene, but also for finding many other important genes for improving the cultivated apple.

Chromosomes, Artificial, Bacterial↗

PubMed2001

Stable clonal expansion of the T-cell receptor V beta 6, V beta 17 and V beta 19 T cells in a cGVHD case using genescan analysis.

OBJECTIVE: To investigate the distribution and clonality of the T-cell receptor (TCR) V beta repertoire in chronic graft versus host disease (cGVHD). METHODS: The complementarity determining region 3 (CDR3) of the TCR beta gene with 24 variable regions was amplified in peripheral blood mononuclear cells drawn from one cGVHD patient after allogenic bone marrow transplantation (allo-BMT) 35, 39, 43 or 45 months respectively, using RT-PCR, to observe the expression of TCR V beta repertoire T cells. The PCR products were further analyzed by genescan to evaluate clonality of T cells. RESULTS: Fourteen or 16 TCR V beta subfamily T cells were detected in each sample of cGVHD case. Oligoclonal T cells were identified in TCR V beta 6, 16, 17, 19 and 21 subfamilies. The stable clonal T cells in all samples were identified in V beta 6, V beta 17 and V beta 21 subfamilies. CONCLUSION: Skewing distribution and stable clonal expansion of T cells can be found in cGVHD cases and it may be related to the initiation of cGVHD.

Adult↗

PubMed2001

Immunotoxin depletion of T cells and its effect on hematopoietic progenitor cells in human cord blood.

OBJECTIVE: To study the selective toxicity of immunotoxin (IT) on T cells in cord blood and simultaneously determine its effect on hematopoietic progenitor cells. METHODS: The percentage of CD5 and CD8 T cell subsets in cord blood (CB) and bone marrow (BM) as well as peripheral blood (PB) was measured by immunoenzymatic labeling of monoclonal antibodies using immune complexes of alkaline phosphatase and monoclonal anti-alkaline phosphatase (APAAP complexes). One-way mixed lymphocyte cultures (MLC) were performed to compare the proliferative response of CB with that of PB. The proliferative capability of cord blood T cells and T lymphocyte transformation capacity were evaluated in the presence of anti-CD8 or anti-CD5 immunotoxin by one-way MLC and colorimetric MTT (tetrazolium) assay, respectively. The effect of IT on the growth of hematopoietic progenitor cell of colony forming unit-granulocyte and macrophage (CFU-GM), burst forming unit-erythroid(BFU-E), multipotential hemotapoietic progenitors (CFU-Mix) from CB were estimated by colony-forming assays. RESULTS: A certain proportion of CD5 and CD8 T cells existed in CB. The alloproliferative capacity of CB was similar to that of PB. CD5: Ricin at a dosage of 1 x 10(-10)-1 x 10(-8) mmol/L and CD8: Ricin concentration in the range of 1 x 10(-9)-1 x 10(-8) mmol/L effectively decreased both the proliferative capability of T cells in MLC during CB and T cell transformation. Over the dosage of 1 x 10(-10)-1 x 10(-9) mmol/L, both kinds of IT didn't obviously affect the growth of hematopoietic progenitor cells. CONCLUSION: CD5: Ricin and CD8: Ricin may effectively deplete T cells and may not significantly inhibit the function of hemaptopoietic cells at a specific dosage.

CD5 Antigens↗

PubMed2001

Effects of nimodipine on changes of endothelin after head injury in rabbits.

OBJECTIVE: To investigate the effects of nimodipine on changes of endothelin after head injury. METHODS: Sixty-five adult rabbits were randomized into an injury group (IG, n=30), a nimodipine-treatment group (NTG, n=30) and a control group (CG, n=5). With their heads unfixed, the animals in IG and NTG were injured in the frontal-parietal zone with BIM-II bioimpact. Blood samples and brain tissue were collected before and after injury. The endothelin level was measured with RIA. RESULTS: The endothelin level in plasma and brain tissue was significantly increased 24 hours after injury. At the 8th or/and 24th hours postinjury, the endothelin level was significantly lower in NTG than that in IG. CONCLUSIONS: Nimodipine can prevent endothelin from elevation and act as a practical endothelin antagonist after head injury clinically.

Animals↗

PubMed2001

[The experiences in correction of cicatricial foot drop in 28 patients].

OBJECTIVE: To summarize the experiences in correction of cicatricial foot drop. METHODS: 37 cicatricial drop feet in 28 postburn patients were treated in recent 4 years. The cicatricial flap survival rate was documented to compare the effects of two surgical designs, the different intervals from burn to the operation and three surgical methods used in early burn stage. RESULTS: All of the 37 wounded feet got satisfactory correction. There was no significant statistic difference in flap survival between the two surgical designs. More necrosis of the flap was observed in patients who received early escharectomy (including full thickness skin and fat) or had been burned for less than 1.5 years. CONCLUSIONS: The reverse design of the Achilles tendon flap for correction of drop foot was as safe and effective as a routine design. The operation method used in early burn stage and the interval from burn to the corrective operation should be considered in cicatricial flap design.

Achilles Tendon↗

PubMed2001

[Effects of air staging with absorbents on trace metal during coal combustion].

Staged combustion was carried out on laboratory-scale pulverized coal combustion with different absorbents. The experiment indicated staged combustion increased emission of submicron particles, which went against the control of trace elements, especially for those of high volatile elements, such as Cu, Ni. The thermodynamics calculation also indicate the transformation of trace metal was different with different atmosphere, suboxidized and reduced species were more easily formed under reduced condition. In both conditions, absorbents show a certain absorptive ability to trace metal, and different absorbent had different ability. For unstaged combustion, kaolinite was the best for Co, Cr and Ni; dolomite for Be, and CaO for Cu. But for under staged condition, HZ- dolomite was the best for Be, Cr and Ni; Kaolinite for Co and Cu.

Absorption↗