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Biomedical subjects

Z Xiang

Publications and source records attributed to Z Xiang.

At least 37 records · Page 2Linked to original sources

Protein structure prediction.

The prediction of protein structure, based primarily on sequence and structure homology, has become an increasingly important activity. Homology models have become more accurate and their range of applicability has increased. Progress has come, in part, from the flood of sequence and structure information that has appeared over the past few years, and also from improvements in analysis tools. These include profile methods for sequence searches, the use of three-dimensional structure information in sequence alignment and new homology modeling tools, specifically in the prediction of loop and side-chain conformations. There have also been important advances in understanding the physical chemical basis of protein stability and the corresponding use of physical chemical potential functions to identify correctly folded from incorrectly folded protein conformations.

Animals↗

Mast cells express functional CD30 ligand and are the predominant CD30L-positive cells in Hodgkin's disease.

Hodgkin's disease (HD) tumours are characterized by the presence of few tumour cells, the Hodgkin and Reed-Sternberg (HRS) cells, surrounded by a large amount of non-neoplastic cells. The role of this cell infiltrate for the development of HD is not known. CD30, belonging to the tumour necrosis factor receptor superfamily, is highly expressed on HRS cells and believed to be involved in tumourigenesis and tumour progression. Tumour samples from 42 patients were immunohistochemically double-stained for tryptase, a mast cell-specific proteinase and CD30 ligand (CD30L). Tryptase-positive mast cells were present in all tumours. Of these cells, 50% expressed CD30L and 66% of the CD30L-positive cells were mast cells. CD30L mRNA in in vitro developed normal mast cells and malignant human and murine mast cell lines was detected using reverse transcription polymerase chain reaction. CD30L protein expressed on human mast cells was detected using flow cytometry. In a co-culture assay, the human mast cell line HMC-1 stimulated thymidine uptake in HRS cell lines, and the stimulation could be blocked using CD30L-specific monoclonal antibodies. In conclusion, mast cells are present in HD tumours and are the predominant CD30L-expressing cells. CD30L-CD30 interaction is a pathway by which mast cells may stimulate DNA synthesis in HRS cells.

Adult↗

The expression and changes of heat shock protein 70, MDA and haemorheology in rat cortex after diffuse axonal injury with secondary insults.

In the present study the role of heat shock protein 70 (HSP70) expression, changes of malonyldialdehyde (MDA) in rat cortex and haemorheology with time after diffuse axonal injury (DAI) only and DAI with secondary insults (SI) were studied. The rat DAI and DAI with SI model were made according to our previous work and animals were divided into a control and another five injury groups with time after injury. Immunohistochemical assay was used to detect the neuronal expression of HSP70 at 0.5h, 3h, 12h, 24h, 72h after DAI or DAI with SI. In the meantime, the high (etah ) and low whole blood viscosity (etaL ), haematocrit (HCT) and RBC aggregation index (AI = etaL/etah ) were also detected and calculated. MDA in the homogenised brain tissue was assayed by thiobarbituric acid (TBA) reaction. The results showed that HSP70 positive neurons were not detected at 30 minutes, but the number of HSP70 positive neurons begin to increase obviously at 3 hours, reach a peak at 24 hours (P< 0.01), and decrease at 72 hours (P= 0.05) after brain injury. The trend of expression of HSP70 was alike for both DAI only or DAI with SI. Meanwhile, MDA, etah, etaL, HCT and AI changes showed the same tendency. Compared with DAI only group, MDA and blood viscosity indexes in DAI with SI were significantly higher at respective time points (P< 0.01). It is concluded that HSP70 expression, MDA and haemorheology indices increased after brain injury and brain injury with SI. Free radicals and haemorheological changes play an important role in the aggravation of brain damage and HSP70 expression upregulation.

Animals↗

Neuronal free Ca(2+)and BBB permeability and ultrastructure in head injury with secondary insult.

OBJECTIVE: To study changes in free calcium (Ca(2+)), neuronal and blood-brain barrier (BBB) permeability and ultrastructure in brain after diffuse axonal injury (DAI) with secondary brain insults (SBIs). METHOD: One hundred and twenty Sprague-Dawley (SD) rats were randomised into control, DAI alone and DAI with SBI groups which were sub-divided into 5 groups that were 0.5 h, 2 h, 12 h, 24 h, 48 h post trauma. The animal models of DAI and DAI with SBI have been described before (2). Fluorescence probe Fluo-3/Am was used to measure free Ca(2+)in neurons. Laser scan microscopy was used to detect fluorescence intensity. After the animals were anesthetized, Lanthanum nitrate liquid was used for intracardiac perfusion to assess BBB permeability. Under the transmission electron microscope, changes in cerebral ultrastructure and BBB permeability were observed. RESULTS: The fluorescence intensity was weak in the control. The concentration of free Ca(2+)in neurons was obviously increased at 30 min after brain injury, reached a peak at 12 h-24 h (P< 0.01), and appeared to decrease at 48 h after injury. In the DAI alone group, BBB tight junction opening with particles of Lanthanum nitrate outside the vessels was found at 30 min after injury, and peaked at 24 h. In DAI with SBI, the changes in ultrastructure and BBB permeability were more severe than that in the DAI alone group at the same time interval. The shape of the fluorescence concentration curve was basically the same for both kinds of brain injury. The intensity of fluorescence in DAI with SBI was higher than that in the DAI alone group at the same time interval (P< 0.05). CONCLUSION: In DAI alone and DAI with SBI, Ca(2+)overload and BBB permeability changes interact and both play important roles in the aggravation of brain damage.

Animals↗

IgE-mediated mast cell degranulation and recovery monitored by time-lapse photography.

BACKGROUND: Mast cells are long-lived resident cells that are of great importance in an allergic reaction. It has previously been suggested that after IgE-mediated degranulation mast cells can undergo regranulation. Such a process is probably of great importance with respect to the severity and perpetuation of the allergic response. OBJECTIVE: Our purpose was to investigate whether mast cells recover from degranulation and whether they still have the potential to release a granule-associated mediator and upregulate certain cytokine genes. METHODS: Mouse mast cells were repeatedly activated by IgE and specific antigen with a 24-hour or 48-hour interval. During each of the 2 activation stages, release of beta-hexosaminidase was measured by means of enzymatic colorimetric analysis, and IL-13 and IL-6 mRNA was detected by ribonuclease protection assay. Both scanning electron microscopy and time-lapse photography were used to reveal the process of mast cell recovery. RESULTS: We found that re-activation of degranulated mast cells in response to high-affinity IgE-receptor cross-linkage triggers beta-hexosaminidase release and upregulation of IL-13 and IL-6 gene expression levels similar to what is seen in the initial activation. Scanning electron microscopy documented cells at various stages during the recovery process 30 minutes after the activation. With time-lapse photography, a single cell that had undergone degranulation could be visualized consecutively during its recovery process. CONCLUSION: Mast cells can recover after an IgE-mediated activation and can repeatedly release beta-hexosaminidase and express IL-6 and IL-13 mRNA after re-activation.

Animals↗

An amplified fragment length polymorphism map of the silkworm.

The silkworm (Bombyx mori L.) is a lepidopteran insect with a long history of significant agricultural value. We have constructed the first amplified fragment length polymorphism (AFLP) genetic linkage map of the silkworm B. mori at a LOD score of 2.5. The mapping AFLP markers were genotyped in 47 progeny from a backcross population of the cross no. 782 x od100. A total of 1248 (60.7%) polymorphic AFLP markers were detected with 35 PstI/TaqI primer combinations. Each of the primer combinations generated an average of 35.7 polymorphic AFLP markers. A total of 545 (44%) polymorphic markers are consistent with the expected segregation ratio of 1:1 at the significance level of P = 0.05. Of the 545 polymorphic markers, 356 were assigned to 30 linkage groups. The number of markers on linkage groups ranged from 4 to 36. There were 21 major linkage groups with 7-36 markers and 9 relatively small linkage groups with 4-6 markers. The 30 linkage groups varied in length from 37.4 to 691.0 cM. The total length of this AFLP linkage map was 6512 cM. Genetic distances between two neighboring markers on the same linkage group ranged from 0.2 to 47 cM with an average of 18.2 cM. The sex-linked gene od was located between the markers P1T3B40 and P3T3B27 at the end of group 3, indicating that AFLP linkage group 3 was the Z (sex) chromosome. This work provides an essential basic map for constructing a denser linkage map and for mapping genes underlying agronomically important traits in the silkworm B. mori L.

Animals↗

Vascular endothelial growth factor in human lung transplantation.

STUDY OBJECTIVES: To determine levels of the vascular endothelial growth factor (VEGF) isoform consisting of 165 amino acids (VEGF(165)) in BAL fluid (BALF) from lung transplant recipients (LTXs). DESIGN: Bronchoscopy with BAL was performed on LTXs and normal volunteers (NVs). SETTING: University hospital. PARTICIPANTS: LTXs (n = 57) and NVs (n = 15). MEASUREMENTS AND RESULT: VEGF(165) concentrations in BALF were higher (mean +/- SEM, 240 +/- 32 pg/mL) for NVs (n = 15) vs 133 +/- 14 pg/mL for LTXs (n = 37) who were stable without evidence of significant rejection or infection at 6 months after transplantation (p < 0.0001). BALF VEGF concentrations sampled at 24 to 48 h, 2 weeks, 4 weeks, and 6 months after transplantation for 11 LTXs who lacked rejection or infection at any time point were 71 +/- 8 pg/mL, 80 +/- 20 pg/mL, 82 +/- 13 pg/mL, and 167 +/- 31 pg/mL, respectively. VEGF concentrations in BALF for LTXs with cytomegalovirus (CMV) pneumonia were 55 +/- 12 pg/mL (n = 10), 117 +/- 33 pg/mL for grade A3 acute rejection (n = 9), and 82 +/- 17 pg/mL (n = 14) for active bronchiolitis obliterans syndrome (BOS). Concentrations of VEGF in BALF at 6 months for the 32 stable recipients with bilateral lung transplantation were significantly higher for those with higher values for FEV(1), and BALF VEGF concentrations were significantly lower in BALF at 6 months for those recipients who subsequently went on to develop BOS (86 +/- 19 pg/mL) vs those who did not (158 +/- 18 pg/mL; p = 0.03). Serum concentrations of VEGF did not correlate with VEGF concentrations in BALF, but serum VEGF was 291 +/- 62 pg/mL at 10 to 14 days after transplantation vs 130 +/- 20 pg/mL at 4 weeks for nine LTXs with paired samples (p < 0.02). Serum VEGF concentrations for NVs (n = 15) were 102 +/- 15 pg/mL vs 94 +/- 17 for stable LTXs (n = 12) at 24 weeks after transplantation and 123 +/- 33 pg/mL for LTXs with active BOS (n = 10). CONCLUSIONS: BALF VEGF concentrations are particularly depressed at early time points following lung transplantation, gradually improve in the absence of significant rejection or infection, and are lower with active rejection or CMV pneumonia.

Bronchoalveolar Lavage Fluid↗

[Allogeneic humeral shaft transplantation with vascular anastomosis: twenty years follow-up].

OBJECTIVE: To sum up the clinical results of allogeneic humeral transplantation with vascular anastomosis, and evaluate the clinical significance. METHODS: From September to November 1979, 1 case with humeral shaft defect of 10 cm in length and 2 cases with tibia shaft defect of 12 cm in length were repaired by allogeneic humeral transplantation with vascular anastomosis. Azathiopurine and prednisone were applied for 3 months postoperatively. All cases were followed up for 20 years. RESULTS: Case 1 recovered well with good bone union and reconstruction after operation, and could work normally. In case 2, five chronic rejections were occurred during 3 years after operation, and recovered after treatment, the allograft bone was fractured after 2 years of operation, and unioned by autogeneous iliac bone transplantation. In case 3, the distal part of allograft bone was fractured after 46 months, and unioned by autogeneous iliac bone transplantation. The middle part of allograft bone was non-unioned after 20 years follow-up in case 3, but the patient could still work normally. CONCLUSION: The clinical results of allogeneic long bone transplantation can be improved by rational tissue matching test, application of effective immunosuppressive drugs in a certain period according to the principles of modern transplantation immunology.

Adolescent↗

Establishment of an animal model of chronic atrophic gastritis and a study on the factors inducing atrophy.

OBJECTIVE: To establish a rat model of chronic atrophic gastritis and explore the factors inducing atrophy. METHODS: In accordance with repeated orthogonal design of L8(2(7)), 60% alcohol and 20 mmol/L sodium deoxycholate (served as factor A), 0.05%-0.1% ammonia water (factor B), 0.05% indomethacin (factor C) were given, alone or in combination, to rats in three experiments for 3 months, 6 months or 9 months respectively. Then the rats were dissected, and their pathologic changes of the gastric mucosa were assessed. RESULTS: Typical signs of chronic atrophic gastritis (CAG) were found in all rats which were treated with factor A, B, C alone or in combination for 6 or 9 months. No significant difference of pathologic changes of gastric mucosa was found between the rats treated for 6 months and those for 9 months. No obvious CAG signs were found in the rats treated with factor A, B, C for 3 months. CONCLUSION: Sixty percent of alcohol, 20 mmol/L sodium deoxycholate, 0.05%-0.1% ammonia water and 0.05% indomethacin given to Sprague-Dawley rats for 6 months can successfully establish the animal model of CAG. Prolongation of the model-establishment time is not able to further facilitate the atrophy of gastric mucosa.

Ammonia↗

Synaptic depression and neuronal loss in transiently acidic hippocampal slice cultures.

Acidosis is a rapid and inevitable event accompanying cerebral ischemia or trauma. We used hippocampal slice cultures to examine an immediate effect of acidosis, synaptic depression; and a delayed effect, neuronal loss. Exposure to low bicarbonate artificial cerebral spinal fluid (aCSF), pH 6.70 for 30 min at 32 degrees C, acidified intracellular pH from 7.31+/-0.12 to 6.53+/-0.08. Accompanying intracellular acidosis was a depression of synaptic responses. Both effects rapidly reversed after treatment with normal aCSF pH 7.35. Death analysis after acidosis treatment revealed no delayed neuronal loss. Increasing the duration of the acidosis to 60 min, however, induced irreversible synaptic depression and delayed neuronal loss. Increasing acidosis temperature to 37 degrees C acidified intracellular pH and depressed synaptic responses. Delayed neuronal loss was also observed. Acidosis using lactate aCSF, pH 6. 70 for 30 min at 32 degrees C acidified intracellular pH from 7. 19+/-0.13 to 6.43+/-0.07 and depressed synaptic responses. After reperfusion with lactate containing aCSF pH 7.35, intracellular pH recovered yet synaptic responses remained depressed and delayed neuronal loss was observed. This suggested that, for a 30-min treatment at 32 degrees C, lactate acidosis was neurotoxic while low bicarbonate acidosis was not. Increasing the duration or temperature of low bicarbonate acidosis induced neuronal loss. These data provide additional evidence that acidosis contributes to the neurotoxicity during stroke and trauma.

Acidosis↗

Adult dogs receiving a rabies booster dose with a recombinant adenovirus expressing rabies virus glycoprotein develop high titers of neutralizing antibodies.

Retired greyhound dogs, with low or absent antibody titers to rabies virus following previous vaccinations with commercially available vaccines, were immunized either subcutaneously or intramuscularly with a replication-defective recombinant adenovirus expressing the rabies virus glycoprotein termed Adrab.gp. Immunized animals developed high titers (geometric mean titers of 2630 and 5329) of viral neutralizing antibodies (VNA) against rabies virus by 10 days after vaccination. The antibody titers were even higher (geometric mean titers of 19349 and 122086) by 21 days after vaccination. The results indicate that the recombinant adenovirus expressing rabies virus glycoprotein is capable of inducing antibody immune responses in dogs and therefore may be developed as a rabies virus vaccine for dogs.

Adenoviruses, Human↗

Long-term maintenance of mature hippocampal slices in vitro.

Cultures of primary neurons or thin brain slices are typically prepared from immature animals. We introduce a method to prepare hippocampal slice cultures from mature rats aged 20-30 days. Mature slice cultures retain hippocampal cytoarchitecture and synaptic connections up to 3 months in vitro. Spontaneous epileptiform activity is rarely observed suggesting long-term retention of normal neuronal excitability and of excitatory and inhibitory synaptic networks. Picrotoxin, a GABAergic Cl(-) channel antagonist, induced characteristic interictal-like bursts that originated in the CA3 region, but not in the CA1 region. These data suggest that mature slice cultures displayed long-term retention of GABAergic inhibitory synapses that effectively suppressed synchronized burst activity via recurrent excitatory synapses of CA3 pyramidal cells. Mature slice cultures lack the reactive synaptogenesis, spontaneous epileptiform activity, and short life span that limit the use of slice cultures isolated from immature rats. Mature slice cultures are anticipated to be a useful addition for the in vitro study of normal and pathological hippocampal function.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

Analysis of 114 kb of DNA sequence from fission yeast chromosome 2 immediately centromere-distal to his5.

One hundred and fourteen kilobase pairs (kb) of contiguous genomic sequence have been determined immediately distal to the his5 genetic marker located about 0.9 Mb from the centromere on the long arm of Schizosaccharomyces pombe chromosome 2. The sequence is contained in overlapping cosmid clones c16H5, c12D12, c24C6 and c19G7, of which 20 kb are identical to previously reported sequence from clone c21H7. The remaining 93 781 bp of sequence contains 10 known genes (cdc14, cdm1, cps1, gpa1, msh2, pck2, rip1, rps30-2, sad1 and ubl1), 32 open reading frames (ORFs) capable of coding for proteins of at least 100 amino acid residues in length, one 5S rRNA gene, one tRNA(Pro) gene, one lone Tf1-type long terminal repeat (LTR) and one lone Tf2-type LTR. There is a density of one protein-coding gene per 2.2 kb and 22 of the 42 ORFs (52%) incorporate one or more introns. Twenty-one of the novel ORFs show sequence similarities which suggest functions of their products, including a cyclin C, a MADS box transcription factor, mad2-like protein, telomere binding protein, topoisomerase II-associated protein, ATP-dependent DEAH box RNA helicase, G10 protein, ubiquitin-activating e1-like enzyme, nucleoporin, prolyl-tRNA synthetase, peptidylprolyl isomerase, delta-1-pyrroline-5-carboxylate dehydrogenase, protein transport protein, coatomer epsilon, TCP-1 chaperonin, beta-subunit of 6-phosphofructokinase, aminodeoxychorismate lyase, a phosphate transport protein and a thioredoxin.

Base Sequence↗

Murine mast cell lines as indicators of early events in mast cell and basophil development.

To study early events in mast cell / basophil development, the phenotype of a panel of murine cell lines at various stages of differentiation was determined. Based on the expression on various mast cell-specific proteases and several additional hematopoietic differentiation markers, the cell lines CFTL-15 and MCP5 / L were clearly identified as mast cells, although with a relatively immature phenotype. These two cell lines express the high-affinity IgE receptor alpha-chain, the mouse mast cell protease (MMCP)-5 and the carboxypeptidase A (CPA). Bone marrow-derived mast cells and the transplantable mast cell tumor MTC were shown to express the IgE receptor alpha-chain, MMCP-5 and CPA, as well as the mast cell tryptase MMCP-6 and the chymase MMCP-4, a protease expressed only during late stages of mast cell differentiation. These two cell types thus display a more mature mast cell phenotype. In contrast, the cell lines P815 and 32D cl3 did not express any mast cell differentiation markers. Interestingly, the IC-2 cell line was shown to express several markers for immature mast cells and in addition MMCP-8, a serine protease which may represent a marker for mouse basophils. By antibody staining, almost all IC-2 cells were shown to express MMCP-8. This indicates that individual cells may simultaneously express both mast cell and basophil markers. Moreover, these findings suggest that an early branch point in hematopoietic development where mast cells and basophils have a common precursor cell may exist.

Animals↗

Establishment of a multiplex PCR system to diagnose tuberculosis and other bacterial infections.

In order to rapidly diagnose and differentiate tuberculosis from other bacterial infections, a 16S rRNA gene (16s rDNA)-directed multiplex PCR system was developed. In this system, a pair of universal primers and a tubercle bacillus (Tb)-specific primer were designed based on highly conserved regions and Tb species-specific variable region of bacterial 16s rDNA. A 360 bp fragment was detected in all bacteria tested, and a 210 bp fragment was found only in Tb. 19 species of known bacteria including Tb were used for evaluating specificity, universality and sensitivity of the PCR. Candida albicans and human diploid cell served as controls. It was found that both 210 bp and 360 bp fragments were amplified only in Tb, and only 360 bp fragment was detected in other 18 species of general bacteria. Candida albicans and human cells were negative for both 360 bp and 210 bp fragments. The lowest detectable level of the PCR was 10 fg of DNA for Escherichia coli and 100 fg of DNA for Tb. The results indicated that this multiplex PCR system for the simultaneous detection of Tb and other common bacteria had higher specificity and sensitivity, as well as good universality and might be useful to rapidly diagnose bacterial infections and effectively distinguish tuberculosis from other bacterial involvement.

Amidohydrolases↗

IgE receptor-mediated release of nerve growth factor by mast cells.

BACKGROUND: It has previously been demonstrated that the level of nerve growth factor (NGF) is increased in serum from humans with allergic diseases and asthma. AIM: A question raised by these observations is whether NGF could be released from degranulating mast cells during an allergic reaction. The aim of this study was to investigate if NGF is released from mast cells after activation through cross-linkage of the high-affinity IgE receptor. METHODS: Mouse and human in vitro cultured mast cells were activated by IgE and specific antigen, stem cell factor or lipopolysaccharide. Release of NGF was measured by ELISA and mRNA expression was detected by RT PCR. RESULTS: We found that mast cells not only express NGF transcripts, but also release NGF polypeptide in response to IgE and specific antigen. Activation of mouse mast cells for 30 min induced significant release of NGF (32.9 +/- 1.3 pg/2 x 106 cells) compared to spontaneous release (13.9 +/- 2.7 pg/2 x 106 cells) (P < 0.01). Similarly, activation of human cultured mast cells also resulted in a significant increase of NGF release (733 +/- 310 pg/3 x 105 cells) compared to spontaneous release (9.2 +/- 4. 0 pg/3 x 105 cells). Two other mast cell secretogogues studied, stem cell factor and lipopolysaccharide, were not able to induce release of NGF. CONCLUSION: This study provides evidence that NGF could be specifically released by stimuli causing an allergic reaction, and mast cells can thereby be the source of NGF in IgE-mediated allergic diseases. Our findings add further support for a close correlation between NGF and mast cells that could be of importance for the allergic inflammation.

Animals↗

Diffuse axonal injury due to lateral head rotation in a rat model.

OBJECT: The authors investigated the ramifications of producing diffuse axonal injury (DAI) by lateral head rotation in a rat model. METHODS: Using a special injury-producing device, the rat's head was rapidly rotated 90 degrees in the coronal plane at an angular velocity of at least 753.13 rad/second and an angular acceleration of at least 1.806 x 10(5) rad/second2; the rotation was complete within 2.09 msec. There were no statistically significant changes in PO2, PCO2, pH, or blood pressure values at 5, 15, or 60 minutes after head rotation compared with their respective preinjury baseline values. The rats exhibited posttraumatic behavior suppression for an average of 12.6 minutes. The mortality rate was 17%. The rats that survived had diffuse subarachnoid hemorrhage around the brainstem and upper cervical cord, but no obvious brain contusion. In sections stained with silver or hematoxylin and eosin, axonal swelling and bulblike protrusions at the axonal axis were observed in the medulla oblongata, midbrain, upper cervical cord, and corpus callosum between 6 hours and 144 hours postinjury. The axonal injuries were most severe in the brainstem and were accompanied by parenchymal bleeding. The density of bulblike axonal protrusions peaked 6 hours postinjury in the medulla oblongata and 24 hours postinjury in the midbrain. CONCLUSIONS: Rapid lateral head rotation can produce DAI characterized by severe damage to the rat brainstem.

Animals↗