Search PubMed⌕ Search

Biomedical subjects

X M Zhang

Publications and source records attributed to X M Zhang.

At least 55 records · Page 3Linked to original sources
PubMed2000

Ischemia reperfusion-induced dynamic changes of protein tyrosine phosphorylation during human lung transplantation.

BACKGROUND: We have recently demonstrated that more than 20% of lung cells undergo apoptosis within the first 2 hr of graft reperfusion after human lung transplantation. It has been found that changes of protein tyrosine phosphorylation are involved in the regulation of apoptosis in various cell types. METHODS: To determine the protein tyrosine phosphorylation status and related biochemistry changes, lung tissue biopsies were collected from six human lung transplant procedures after cold ischemic preservation (2-5 hr at 4 degrees C), after completing the implantation procedure (approximately 1 hr), and 1 or 2 hr after graft reperfusion. Western blotting was performed to determine protein tyrosine phosphorylation and several signal transduction proteins. Protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP) activities were also measured. RESULTS: Protein tyrosine phosphorylation was significantly increased after lung implantation and before reperfusion, and significantly decreased during the first 2 hr of graft reperfusion. The activity of Src PTKs was reduced by 50% during graft reperfusion, which was associated with a decrease of Src proteins and human actin filament associated protein, a cofactor for Src activation. PTP activity significantly decreased after lung implantation and remained at a low level 1 hr after reperfusion. After 2 hr of reperfusion, however, PTP activity returned to the basal level. CONCLUSION: These dynamic changes of PTK and PTP likely explain the observed alterations of protein tyrosine phosphorylation. The significant decrease in protein tyrosine phosphorylation may be related to the observed apoptotic cell death during human lung transplantation.

Apoptosis↗
PubMed2000

Epitopes of human brain acetylcholinesterase.

The main purpose of the present work was to identify B-cell epitopes on human brain acetylcholinesterase (AChE) by the synthetic peptide approach. Five hundred and seventy-four decapeptides comprising amino acids No. n to n+9 (where n denotes the residue number of the 583 amino acids in the primary structure of human brain AChE and is an integer in the range 1-574) were synthesized, using the multipin combinatorial chemical synthesis technique, and biotinylated. Epitopes of human brain AChE were detected by enzyme-linked immunosorbent assay (ELISA) and compared with the predicted epitopes of human AChE by 'Goldkey' software. Among 574 synthetic decapeptides, 47 decapeptides at 11 antigenic regions showed immunoreactivity with mouse anti-human brain AChE polyclonal antibodies. The minimum sequence of epitope was defined at every antigenic region explored. The locations and sequences of the former ten continuous epitopes at the 11 antigenic regions of the human brain AChE had been identified as follows: TPVLVWIY (112-119), RTVLVSMNY (143-151), LLDQRLALQW (173-182), RRATQLAH (246-253), VFRFSFVPV (294 approximately 302), KDEGSYFLVY (332-341), RVYA (424-427), LMRY (476-479), KAPQWPPY (496-503), GLRAQACAFW (523-532). The rate of hits of the predicted epitopes from the software came out at 33%. In our work, the epitopes of human AChE have been mapped by purified polyclonal antibody at eleven distinct sites in the primary structure.

Acetylcholinesterase↗
PubMed2000

Genetically fused protein A-luciferase for immunological blotting analyses.

The gene expression plasmid pMALU5 for the fusion protein of protein A (SpA) with a complete sequence of firefly luciferase (Luc) was constructed. The fused gene was expressed in Escherichia coli, and the resulting SpA-Luc fusion protein was purified by one-step affinity chromatography on IgG-Sepharose. The protein retained both activities: IgG binding capability of protein A and enzymatic activity of luciferase. Blotting analyses were performed with the fusion protein to determine a tumor marker of alpha-fetoprotein (AFP). AFP was detected at the lowest detection limit of 5 pg by dot blotting and Western blotting. The SpA-Luc fusion protein provides a highly selective, sensitive, and versatile marker for blotting analyses.

Blotting, Western↗
PubMed2000

[Clinical significance of calcitonin expression in lung tissue with bronchiectasis].

OBJECTIVE: To investigate the relation between the pathologic feature of bronchiectasis and the expression of calcitonin(CT) protein within pulmonary neuroendocrine cells(PNEC) in bronchiectasis. METHOD: CT expression of PNEC was detected using immunohistochemistry(SP method) and quantitative analysis was completed by counting CT positive cell number on per 10 cm length of epithelium. RESULT: CT positive PNEC were found both at all levels of airway tree in all 37 cases of bronchiectasis and 10 cases of control, but none were found in alveolar ducts and alveoli. In bronchiectasis, CT positive PNEC was 67.59 +/- 10.57 per 10 cm length of epithelium, and in control group 5.48 +/- 1.06. Statistical analysis revealed a significant difference between bronchiectasis and control(P < 0.001). CONCLUSION: There was a high level CT expression in bronchiectasis. The PNEC hyperplasia may play a role in the chronic inflammation of bronchiectasis.

Bronchiectasis↗
PubMed2000

Sonic hedgehog-mediated ventralization disrupts formation of the midbrain-hindbrain junction in the chick embryo.

The secreted signaling molecule Sonic hedgehog (Shh) plays critical roles in pattern formation of the vertebrate central nervous system. During neurulation, Shh is produced by the ventral midline mesoderm as well as by the ventral neural tube, and its activity is required for the determination of ventral characteristics along the anterior-posterior neuraxis. The morphological boundary between midbrain and hindbrain, the isthmus, is an important tissue organizer that regulates the development of both the midbrain and the anterior hindbrain. In this study, we report that retrovirus-mediated misexpression of Shh in the early chick neural tube disrupts formation of the boundary between the midbrain and the hindbrain, and causes a fusion of the bilateral cerebellum primordia. Dorsally expressed Shh signals induce ectopic transcription of its receptor Ptc1 in the midbrain and the hindbrain. The expression of several genes (Noggin, Lmx1, BMP7) along the dorsal midline of the midbrain is abolished, and ventral or lateral markers (HNF3 beta, Ptc1, ELF1) are induced in the dorsal brain. Furthermore, the normally restricted expression of two genes (En1 and Pax2) in the mid/hindbrain junction region are expanded, reflecting the morphological defects. These results suggest that maintaining proper dorsal-ventral patterns of the neural tube is essential for normal development of the mid/hindbrain region.

Animals↗
PubMed2000

[Properties and nucleotide sequence of mitochondrial plasmid-like DNA pC1 of cucumber].

Four kinds of plasmid-like DNA, designated pC1, pC2, pC3 and pC4 were found in the mitochondrion of cucumber Jinyan No. 4. The circle plasmid-like DNA pC1 was cloned into the EcoR I site of pUC19 using E. coli JM109 as host. The cloned pC1 DNA was isolated and used as probes in Southern analyses of total mitochondrial DNA, nuclear DNA and chloroplast DNA. Evidences were obtained that the pC1 did not show any homology with nuclear, chloroplast, main mitochondrial genomes and the other plasmid-like DNAs. Sequence analysis revealed that pC1 was 2,889 bp long. It contained many forward and reverse repeat sequences. Three main open reading frames in pC1 were longer than 800 bp. Computer-assisted searching the nucleotide sequence in GenBank database revealed pC1 had no significant homology with known sequences of mitochondrial and plasmid-like DNA, but had homology with the E. coli, Mycobaterium tuberculosis and Anacystis nidulans genomes. The predicted proteins of pC1 main ORFs show homology with the sulfate transport system in bacteria, alga and liverwort. It suggested that pC1 may encode functional proteins.

Base Sequence↗
PubMed2000

Blocking effects of heteroclitin D and gomisin J on L-type calcium channels in ventricular cells of guinea pig.

AIM: To study the effects of heteroclitin D (HD) and gomisin J (GJ), two lignans from Kadsura medicinal plants, on L-type calcium channels in ventricular cells of guinea pig. METHODS: The calcium currents were measured by whole-cell patch-clamp recording technique. RESULTS: HD 1 and 10 mumol/L decreased the L-type calcium current from (770 +/- 155) to (482 +/- 104) and (384 +/- 85) pA, respectively. GJ 10 mumol/L inhibited calcium current from (822 +/- 169) to (436 +/- 143) pA. Neither HD nor GJ affected the steady-state activation curve. But they had impact on steady-state inactivation curve. HD 10 mumol/L changed the half inactivation voltage (V0.5) from -22.7 to -40.9 mV, and slope factor (kappa) from 10.2 to 20.6 (n = 4 cells from 3 guinea pigs, P < 0.05). GJ 10 mumol/L changed the V0.5 from -17.7 to -33.3 mV, and kappa from 15.9 to 27.8 (n = 5 cells from 3 guinea pigs, P < 0.05). CONCLUSION: HD and GJ inhibited L-type calcium channels.

Animals↗
PubMed2000

Effect of melittin on potassium currents and action potential in ventricular myocytes of guinea pig.

AIM: To examine the effects of melittin (Mel), the major component of bee venom, on delayed rectifier K+ current (Ik), inward rectifier K+ current (Ikl) and action potential (AP) in guinea pig ventricular myocytes. METHODS: Ik, Ikl, and AP were recorded using the whole-cell patch-clamp technique. RESULTS: The action potential duration (APD) was shortened by Mel in a concentration-dependent manner. Mel 0.05, 0.1, 0.2 mumol.L-1 shortened APD50 from (520 +/- 55) to (459 +/- 91) (n = 5, P > 0.05), (385 +/- 102) (n = 5, P < 0.01), and (281 +/- 81) ms (n = 5, P < 0.01), respectively; and APD90 from (613 +/- 96) to (536 +/- 93) (n = 5, P > 0.05), (467 +/- 96) ms (n = 5, P < 0.01), and (354 +/- 95) ms (n = 5, P < 0.01), respectively. Mel increased the amplitude of Ik also in a concentration-dependent manner. Mel 0.05, 0.1, 0.2 mumol.L-1 increased Ik from (295 +/- 109) to (371 +/- 142) (n = 5, P < 0.05), (467 +/- 180) (n = 5, P < 0.05), (552 +/- 248) pA (n = 5, P < 0.05), respectively at testing potential of + 40 mV. But no significant effect of Mel on Ikl was observed at these concentrations. CONCLUSION: Mel significantly increased Ik in a concentration-dependent manner which contributed to shortening of APD.

Action Potentials↗
PubMed2000

[Determination of volatile halohydrocarbons in drinking water by gas chromatography with direct aqueous injection].

The volatile CHCl3, CCl4, CHBrCl2, CHBr2Cl, CHBr3 in drinking water have been determined by wide bore capillary gas chromatography/electron capture detector(GC/ECD) with direct aqueous injection method. The method is simple, fast and highly sensitive. It has better accuracy and precision. When the average mass concentration of five halohydrocarbons ranged from 9.03 to 20.19 micrograms/L, the relative deviations ranged from 5.7% to 9.1%, RSD ranged from 2.9% to 7.5%. The standard deviations ranged from 0.3 to 0.9. Correlation coefficients were 0.998 and 0.999. The detection limits ranged from 0.1 to 0.7 microgram/L and were lower than those in other work when the temperature of ECD was 350 degrees C.

Carbon Tetrachloride↗
PubMed2000

[Pediatric intranasal and skull base needle endoscopic surgery and examination].

OBJECTIVE: To explore the values of the application of needle endoscope in pediatric nasal cavity and skull base surgery. METHOD: Using a kind of needle endoscope with the diameter of 1.9 mm and digital video image system, 8 cases of pediatric nasal cavity and skull base examination and surgery were performed. RESULT: Of 3 cases of congenital choanal atresia, one improved, the others recovered. One case (2.5 years old) of traumatic cerebrospinal fluid (CSF) fistulae was successfuly repaired under the 1.9 mm needle endoscope. There were 2 cases of congenital meningoencephalocele. One was 1 month newborn. When the diagnosis was confirmed by needle endoscopy and CT scan, the operation was postponed. The other got endoscopic operation and had recovered. Of 2 cases of skull base malignant tumour, the diagnosis was confirmed by intranasal biopsy under needle endoscope. CONCLUSION: With the application of needle endoscope, the pediatric skull base surgery and examination can be performed in the narrow nasal cavities and sinuses with less invasion and good result.

Cerebrospinal Fluid Rhinorrhea↗
PubMed2000

[Sequence analyzing and genotyping of the gene encoding glutamate rich protein of geographically different Plasmodium falciparum isolates obtained from different malaria endemic areas].

OBJECTIVE: To sequence a gene encoding GLURP and identify the genotypes of geographically different Plasmodium falciparum isolates from Yunnan and Hainan Provinces, China. METHODS: The gene of R2 repeat region of GLURP was amplified by the nested polymerase chain reaction and cloned into T-vector. The nucleotide sequence of the GLURP gene was determined using automatic sequencer (dideoxy chain termination method), and analyzed by DNA Star software. RESULTS: At least 7 different GLURP genotypes ranging from 600 bp to 1,500 bp were found in different P. falciparum isolates from Yunnan and Hainan Provinces. R2 region of GLURP gene consisted of several repeat units, each was composed of 19-20 residues which were shown to be highly conserved. The GLURP gene was also size polymorphic due to differences in the number of repeat units, whereas the repeat sequence was conserved. Sequence analysis showed that DNA sequences and deduced amino acid sequences were highly homologous among the geographically dispersed isolates or various isolates from the same geographical region. No obvious differences were found in the GLURP gene sequences among geographically different isolates. CONCLUSION: The GLURP gene of geographically different P. falciparum isolates is highly conserved and size polymorphic, being useful in searching for malaria vaccine candidate antigen and developing a genotyping method for malaria research.

Amino Acid Sequence↗
PubMed1999

A small region in HMG I(Y) is critical for cooperation with NF-kappaB on DNA.

The high mobility group HMG I(Y) protein has been reported to promote the expression of several NF-kappaB-dependent genes by enhancing the binding of NF-kappaB to DNA. The molecular origins of cooperativity in the binding of NF-kappaB and HMG I(Y) to DNA are not well understood. Here we have examined the determinants of specificity in the binding of HMG I(Y), both alone and in cooperation with NF-kappaB, to two different DNA elements, PRDII from the interferon-beta enhancer and IgkappaB from the immunoglobulin kappa light chain enhancer. Of particular interest was the influence of a flanking AT-rich sequence on binding by HMG I(Y). Utilizing yeast one-hybrid screening assays together with alanine-scanning mutagenesis, we have identified mutations of residues in HMG I(Y) that decrease cooperative binding of NF-kappaB to PRDII and IgkappaB sites. These same mutations similarly decreased the binding of HMG I(Y) alone to DNA, and paradoxically, decreased the strength of protein-protein interactions between HMG I(Y) and NF-kappaB. Of the three tandemly repeated basic regions that represent putative DNA-binding motifs in HMG I(Y), the residues within the second repeat are most important for recognition of core NF-kappaB sites, whereas the second and third repeats both appear to be involved in binding to sites that are flanked by AT-rich sequences. Overall, the second repeat of HMG I(Y) is primarily responsible for the stimulatory effect of this protein on the binding of NF-kappaB to PRDII and IgkappaB elements.

Amino Acid Sequence↗
PubMed1999

Inhibition of ubiquitin-proteasome pathway activates a caspase-3-like protease and induces Bcl-2 cleavage in human M-07e leukaemic cells.

The ubiquitin-proteasome pathway is the principal mechanism for the degradation of short-lived proteins in eukaryotic cells. Here we examine the possibility that ubiquitin-proteasome is involved in regulating the levels of Bcl-2, which is abundantly expressed in M-07e cells, a granulocyte/macrophage colony-stimulating factor (GM-CSF)-dependent human leukaemic cell line. Apoptosis in M-07e cells, induced by GM-CSF withdrawal, was associated with a gradual cleavage of Bcl-2 into a 22 kDa fragment. Treatment of M-07e cells with benzyloxycarbonyl-Leu-Leu-l-leucinal (Z-LLL-CHO; MG-132), a reversible ubiquitin-proteasome inhibitor, markedly accelerated the cleavage of Bcl-2 and promoted cell death through the apoptotic pathway. The cleavage of Bcl-2 was inhibited by a caspase-3 (CPP32)-specific inhibitor [acetyl-Asp-Glu-Val-Asp-CHO (DEVD-CHO)] but not caspase 1 inhibitor (acetyl-Tyr-Val-Ala-Asp-CHO), suggesting that Bcl-2 is a proteolytic substrate of a caspase-3-like protease activated during apoptosis. The simultaneous addition of recombinant human GM-CSF (rhGM-CSF) to M-07e cultures delayed the activation of caspase 3 and Bcl-2 cleavage triggered by Z-LLL-CHO, suggesting that the activation of the GM-CSF signalling pathway can partly overcome the apoptotic effect induced by Z-LLL-CHO. Apoptosis induced by inhibition of the proteasome pathway was verified in studies with lactacystin, a highly specific and irreversible proteasome inhibitor. Lactacystin-induced apoptosis in M-07e cells was remarkably similar to that induced by Z-LLL-CHO, which included caspase 3 activation, cleavage of Bcl-2 into a 22 kDa fragment and, ultimately, cell death. These results showed that inhibition of the ubiquitin-proteasome pathways can lead to the activation of a DEVD-CHO-sensitive caspase and induces Bcl-2 cleavage, which might have a role in mediating apoptosis in M-07e cells.

Acetylcysteine↗
PubMed1999

Golli-induced paralysis: a study in anergy and disease.

The Golli-MBP transcription unit contains three Golli-specific exons as well as the seven exons of the classical myelin basic protein (MBP) gene and encodes alternatively spliced proteins that share amino acid sequence with MBP. Unlike MBP, which is a late Ag expressed only in the nervous system, Golli exon-containing gene products are expressed both pre- and postnatally at many sites, including lymphoid tissue, as well as in the central nervous system. To investigate whether Golli-MBP peptides unique to Golli would result in neurological disease, we immunized rats and observed a novel neurological disease characterized by mild paralysis and the presence of groups of lymphocytes in the subarachnoid space but not in the parenchyma of the brain. Disease was induced by Th1-type T cells that displayed an unusual activation phenotype. Primary stimulation in vitro induced T cell proliferation with increased surface CD45RC that did not become down-regulated as it did in other Ag-stimulated cultures. Secondary stimulation of this CD45RChigh population with Ag, however, did not induce proliferation or IL-2 production, although an IFN-gamma-producing population resulted. Proliferation could be induced by secondary stimulation with IL-2 or PMA-ionomycin, suggesting an anergic T cell population. Cells could adoptively transfer disease after secondary stimulation with IL-2, but not with Ag alone. These responses are suggestive of a chronically stimulated, anergic population that can be transiently activated to cause disease, fall back into an anergic state, and reactivated to cause disease again. Such a scenario may be important in chronic human disease.

Adoptive Transfer↗
PubMed1999

Tolerance induction by acylated peptides: effect on encephalitogenic T cell lines.

We reported previously that acylation of an encephalitogenic peptide of myelin basic protein (MBP68-86) by attachment of palmitoyl chloride (PAL68-86) converted this peptide into a powerful tolerogen for EAE in the Lewis rat. In this study we show that T cell lines derived from a PAL68-86-protected rat proliferated poorly to MBP68-86 in vitro, even after repeated passages in this peptide and IL-2. Conversely, T cell lines derived from untreated rats that were challenged with MBP68-86 or PAL68-86 in CFA responded vigorously to MBP68-86 when propagated for many passages in this peptide but became gradually unresponsive after being propagated in the presence of PAL68-86. The modulation of the T cell lines by PAL68-86 in vitro was reflected by a significant reduction in their ability to transfer EAE to recipients. A high percentage of cells stained with an anti-Vbeta8.2 antibody, regardless of whether they were propagated in the presence of unmodified or acylated peptide. The results are consistent with the notion that tolerance induced by PAL68-86 operates by functional inactivation and provide the basis for the use of acylated peptides in the antigen-specific treatment of autoimmune diseases.

Acylation↗
PubMed1999

Expression of CD41 and c-mpl does not indicate commitment to the megakaryocyte lineage during haemopoietic development.

Haemopoietic progenitors with the phenotype expected of early megakaryocyte precursors (CD34+ CD41+) were isolated from normal human bone marrow or induced in culture from CD34+ CD41- bone marrow cells by treatment with thrombopoietin (TPO) or IL-3. We found that although this population included the majority of cells that can form CFU-MK in culture, it also contained both erythroid and myeloid progenitors. The clonogenic potential of the CD34+ CD41+-induced cells was greater than that of isolated CD34+ CD41+ cells in that the isolated cells only formed CFU-MK and BFU-e, whereas the induced cells formed myeloid colonies as well. Glycophorin was found on isolated CD34+ CD41+ cells, not on induced cells. Its presence distinguished between MK and erythroid progenitors. Separation of a CD34+ CD41+ glycophorin A+ population resulted in the isolation of a highly purified population of BFU-e. A major portion of the cells that expressed CD34+ CD41+, in either cohort, were of the erythroid lineage. True MK progenitors were present in the CD34+ population in greater proportion than in whole marrow and were further enriched amongst CD34+ populations that expressed CD41. The presence of the thrombopoietin (TPO) receptor, c-mpl, did not correlate with inducibility of the gpIIbIIIa complex since essentially all CD34+ progenitors, including the earliest identifiable human haemopoietic progenitors (CD34+ CD38- cells), expressed c-mpl mRNA detectable by PCR regardless of their ultimate fate. Thus neither the expression of CD41 nor the expression of c-mpl was predictive of commitment to the MK lineage.

Cell Differentiation↗
PubMed1999

The unique properties of dipeptidyl-peptidase IV (DPP IV / CD26) and the therapeutic potential of DPP IV inhibitors.

This review deals with the properties and functions of dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5). This membrane anchored ecto-protease has been identified as the leukocyte antigen CD26. The following aspects of DPP IV/CD26 will be discussed : the structure of DPP IV and the new family of serine proteases to which it belongs, the substrate specificity, the distribution in the human body, specific DPP IV inhibitors and the role of CD26 in the intestinal and renal handling of proline containing peptides, in cell adhesion, in peptide metabolism, in the immune system and in HIV infection. Especially the latest developments in the search for new inhibitors will be reported as well as the discovery of new natural substrates for DPP IV such as the glucagon-like peptides and the chemokines. Finally the therapeutical perspectives for DPP IV inhibitors will be discussed.

Animals↗