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Biomedical subjects

B Xiao

Publications and source records attributed to B Xiao.

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

Limitation of nitric oxide production: cells from lymph node and spleen exhibit distinct difference in nitric oxide production.

Many types of cells in the immune system have been found to produce nitric oxide (NO), which performs multiplex functions. However, in myelin basic protein peptide 68-86 (MBP 68-86)-induced experimental autoimmune encephalomyelitis (EAE) in Lewis rats, we found that elevated NO production was generated from spleen cells (SC), not from lymph node cells (LNC). LNC expressed lower NO synthase 2 (NOS2) and produced lower levels of NO than SC upon MBP 68-86 stimulation. Expression of B7-1(CD80) and B7-2(CD86) molecules was much lower on LNC than on SC. Blocking of B7-1 or B7-2 ligation resulted in reduced NO production by SC. Unlike SC, LNC were resistant to interferon-gamma- or lipopolysaccharide-induced NO production. NO derived from SC suppressed cell proliferation and induced apoptosis in vitro. Addition of N(omega)-nitrol-L-arginine methylester (L-NAME) into cell cultures promoted cell expansion and reduced apoptosis. These results indicate that NO production originates from SC, but not from LNC. Low expression of co-stimulatory molecules and NOS2 of LNC limits NO induction. The high levels of NO derived from SC are involved in the self-limiting mechanisms of autoimmune responses by inhibiting cell expansion and promoting cell apoptosis.

Amino Acid Sequence↗
PubMed2000

Structure of the Homer EVH1 domain-peptide complex reveals a new twist in polyproline recognition.

Homer EVH1 (Ena/VASP Homology 1) domains interact with proline-rich motifs in the cytoplasmic regions of group 1 metabotropic glutamate receptors (mGluRs), inositol-1,4,5-trisphosphate receptors (IP3Rs), and Shank proteins. We have determined the crystal structure of the Homer EVH1 domain complexed with a peptide from mGluR (TPPSPF). In contrast to other EVH1 domains, the bound mGluR ligand assumes an unusual conformation in which the side chains of the Ser-Pro tandem are oriented away from the Homer surface, and the Phe forms a unique contact. This unusual binding mode rationalizes conserved features of both Homer and Homer ligands that are not shared by other EVH1 domains. Site-directed mutagenesis confirms the importance of specific Homer residues for ligand binding. These results establish a molecular basis for understanding the biological properties of Homer-ligand complexes.

Animals↗
PubMed2000

Homer: a link between neural activity and glutamate receptor function.

The proteins of the Homer family bind to proline-rich sequences in group I metabotropic glutamate receptors, inositol trisphosphate receptors, ryanodine receptors, and Shank family proteins. Homer proteins also self associate and function as adaptors to couple interacting proteins. Recent observations indicate a role for Homer complexes in signal transduction, synaptogenesis and receptor trafficking.

Animals↗
PubMed2000

The suppression effect of light rare earth elements on proliferation of two cancer cell lines.

To study the suppression effect of light rare earth elements (RE) on proliferation of two cancer cell lines. Two cancer cell lines PAMC82 and K562 were used to examine their colony-forming ability in soft agar, microtubule structure, calmodulin levels and regulation of some gene expressions by Northern blot analysis with and without treatment by RE. The results showed that on soft agar culture the colony-forming ability of human gastric cancer cell line PAMC82 treated by RE chloride decreased and the PAMC82 cell microtubule abnormal structure became normal. The calmodulin (CaM) levels decreased in human leukemia cells (K562) treated with cerium chloride and neodymium chloride. The Northern blot analysis revealed marked up-regulation of p53, p16(MTS1), p21 (WAF1) gene expressions in PAMC82 cells treated with lanthanum chloride and cerium chloride, as compared to control PAMC82 cells. The light rare earth elements studied have certain suppression effects on proliferation of cancer cells. This effect might be related to the decrease of calmodulin and up-regulation of some gene expressions in cancer cells.

Calmodulin↗
PubMed2000

[Simultaneous detection and differentiation of O1 classical E1 Tor, O139 and nonO1 nonO139 strains of Vibrio cholerae by using multiplex PCR].

OBJECTIVE: To explore the rapid and sensitive procedures for detection and differentiation of O1 classical(CVC), El Tor(EVC), O139 and nonO1 nonO139 strains of Vibrio cholerae. METHODS: Four pairs of primers were designed from toxin sub-unit A(ctxA) gene, O139 special gene, Haemolytic subunit A gene and Toxin coregulated pilus subunit A gene. Multiplex PCR was established to simultaneously detect those four genes. CVC, EVC, O139 and nonO1 nonO139 strains can be detected and differentiated by the size and numbers of Multiplex PCR bands via electrophoresis. Two pairs of inside primers were designed from ctx A and O139 special gene, and a nested PCR was established. RESULTS: 60 EVC, 2 CVC, 15 O139 and 30 nonO1 nonO139 strains isolated from patients were detected with multiplex PCR and nested PCR, and the results were correct. 10 EVC and 15 O139 strains isolated from environment samples were detected, and the results meant that EVC were toxic and O139 were non-toxic. The sensitivity of multiplex PCR reached 100 cfu, and that of nested PCR reached 1-10 cfu. CONCLUSION: This method is rapid, specific, and sensitive, and possess great value for practical application.

DNA, Bacterial↗
PubMed2000

Polymorphism of human platelet alloantigen in Chinese patients with acute myocardial infarction and acute ischemic stroke.

OBJECTIVE: To investigate the gene frequencies of 5 major human platelet alloantiqens (HPA 1-5) in Chinese population and to assess if polymorphism of HPA was associated with Chinese acute myocardial infarction (AMI) and acute ischemic stroke (AIS). METHODS: HPA 1-5 genotyping was performed by PCR using allele specific primers and restriction enzyme digestion based on PCR products in 95 AMI cases, 188 AIS cases and 270 normal controls. Gene frequency distribution was tested by Hardy-Weinberg equilibrium and comparison of HPA gene frequencies between the patient and control groups by chi 2 test. RESULTS: The gene frequencies of HPA 1-5 were the followings: HPA1a: 91%; 1b: 9%; HPA 2a: 94%; 2b: 6%; HPA 3a: 83%; 3b: 17%; HPA 4a: 98%; 4b: 2%; HPA5a: 97%; 5b: 3%. We found there were no significant differences in HPA 1-5 gene frequencies between AMI patients and normal controls. In AIS patients group HPA-2a allele frequency was significant higher than in controls, but this allele gene frequency in two groups (0.94 and 0.99) was very close and too many subjects in these two groups were overlapped. Otherwise no differences was found in other 4 HPA systems between cases and controls. CONCLUSION: Polymorphism of HPA were not inherited risky factors and not associated with chinese arterial thrombotic diseases such as AMI and AIS.

Adult↗
PubMed2000

Upregulation of drug sensitivity of multidrug-resistant SGC7901/VCR human gastric cancer cells by bax gene transduction.

OBJECTIVE: To investigate the role of bax in a vincristine (VCR)-induced multidrug-resistant (MDR) human gastric cancer cell line, SGC7901/VCR, in which the Bax protein expression level was significantly lower compared with that in parent cells. METHODS: A bax eukaryotic expression vector was constructed and transfected into SGC7901/VCR cells by lipofectamine, and resistant clones were selected by G418. Western blotting detected Bax expression in transfectants. Tetrazolium blue (MTT) assay evaluated the differences in drug sensitivity and cell cycle changes of transfectants were analyzed using flowcytometry (FCM). RESULTS: The bax eukaryotic expression vector was constructed and transfected into SGC7901/VCR cells. Through G418 selection, resistant clones were obtained. Western blotting demonstrated that the expression of Bax protein was markedly increased in bax transduced cells. These cells were more sensitive to adriamycin (ADR) and VCR than mock vector transducted cells. Moreover, bax transfection enhanced ADR-induced apoptosis and VCR-induced G2/M phase arrest of SGC7901/VCR cells. CONCLUSION: Bax was involved in the MDR of SGC7901/VCR cells.

Antineoplastic Agents, Phytogenic↗
PubMed2000

[Detecting the level of Actinobacillus actinomycetemcomitans leukotoxin].

OBJECTIVE: To detect the level of Actinobacillus actinomycetemcomitans (Aa) leukotoxin and distinguish the highly and the minimally toxic strains. METHODS: The polymerase chain reaction (PCR) assay was used to detect the difference of the nucleotide sequence of Aa leukotoxic promoter. 68 Aa isolates were examined, including 17 serotype b, 42 serotype c and 9 serotype a strains. The positive control strains were the highly toxic strain JP2 and 7 minimally toxic strains such as ATCC43717; the negative control strains were 12 other species of reference strains. RESULTS: The PCR fragments of JP2 was about 492 bp and that of the other Aa reference strains and 68 clinical isolates were 1,022 bp. PCR products not found in 12 other species. CONCLUSION: All of the 68 clinical isolates were minimally toxic strains.

Adolescent↗
PubMed2000

[A study of polysaccharide-protein complex and glycosyls in the tissue surrounding titanium implant of rabbit].

OBJECTIVE: The absorption of the polysaccharide-protein complex to the implant surface may be the first reaction between the implant and the surrounding tissue. So we observed the distribution and the relative amount of the polysaccharide-protein complex and glycosyls in order to find out the possible functions and changing rules of these substances. METHODS: 12 rabbits were selected according to the age, sex, weight, and health conditions. Bilateral mandibular premolar teeth of rabbits were extracted under abdomen anesthesia (2% glutababituratic acid), then 12 titanium implants were placed into the teeth extraction holes of one side and left the other side to be the control one. All of the implants were required to be placed 2 mm below the alveolar crest, and tissue closure was achieved with mattress and interrupted single sutures. Antibiotic injections were given to the rabbits in the following 3 days. The animals were sacrificed at the end of 1 week, 4 weeks and 24 weeks. Tissue blocks (4 mm x 4 mm x 4 mm) containing the titanium implants and the control ones were removed, then fixed with 10% formaldehyde for 2 weeks, and decalcified with 10% EDTA (pH7.0) for 8 weeks. Carefully removed the titanium implants, the tissue blocks were embedded into the paraffin wax, then the sections were obtained and stained using following methods. 1. Alcian Blue Method: Alcian blue (pH 2.5) staining displayed the acidic proteoglycans; Alcian blue (pH 1.0) displayed the proteoglycans containing sulfonyl; Alcian blue/periodix acid-shiff staining demonstrated the acidic and neutral proteoglycans respectively. Alcian blue-MgCl2 with different ionic concentration identified the different kinds of proteoglycans. 2. Lectin Method: 5 kinds of lectins were used to locate 5 kinds of glycosyls. 2.5 micrograms/ml ConA located the glucose; 10 micrograms/ml PNA located the galactose; 10 micrograms/ml WGA located the N-acetylglucosamine; 25 micrograms/ml PHA-E located N-acetylgalactosamine, 10 micrograms/ml WPL loacted the fucose. RESULTS: High level of proteoglycans and glycosyls were observed in the peri-implant connective tissue during all phases of the experiment. It was also observed that polysaccharide-protein complex and glycosyls reached a high level in new bone matrix as well as osteoblasts. CONCLUSION: Polysaccharide-protein complex and glycosyls do play an important role in the implant-bone attachment, and titanium compatibility and may be closely related to the bone metabolic activity.

Animals↗
PubMed2000

[The role of heat shock protein 70 and its autoantibody in experimental autoimmune inner ear disease].

OBJECTIVE: To examine the effect of antigen stimulation on induction of the heat shock protein 70(HSP70) in the guinea pig cochlea and to explore the role of HSP70 and its autoantibody in the pathogenesis and diagnosis of autoimmunize inner ear disease (AIED). METHODS: To establish the animal model of AIED, homologous crude inner ear antigen was used to immunize the guinea pig. The expression of HSP70 was detected by immunocytochemistry and the relative staining densities were quantified with a light microscope image analysis system. The autoantibodies against HSP71 in the plasma of animals were tested by Western blot using purified recombinant human HSP71 as antigen. RESULTS: HSP70 presented in the normal guinea pig cochlea at a lower level. After immunological challenge, the levels of HSP70 immunoreactivity in the immunized animals were significantly increased as compared with control animals. Optical densities of cochleae of immunized animals were significantly greater than those of animals in the control group (P < 0.01). Most of the immunized animals had developed autoantibodies against HSP71. The incidence of autoantibody in the experimental group was significantly different (P < 0.01) from the control group. CONCLUSION: Antigen stimulation could lead to an increase in the synthesis of HSP70 in the guinea pig cochlea. The detection of autoantibody against HSP71 might have significance in the diagnosis of AIED.

Animals↗
PubMed1999

[New method for the isolation of astroglial cells and oligodendrocytes].

Based on the different properties of cellular adhesions, developmental time-courses and growth pattern of astroglial cells and oligodendrocytes, a method of isolating glial cells in vitro was developed. The observations under inverted light microscope and scan electronic microscope identified that the morphology of isolated cells were consistent with the previous description. Immunocytochemical examination showed the expressions of markers, the glial fibrillary acidic protein (GFAP) of astroglia cells and the myelin basic protein (MBP) of oligodendrocytes were consistent with the isolated cells. All parameters showed that the isolated glial cells were pure, and the new methods were easy and reliable.

Animals↗
PubMed1999

Crystal structure of a murine glutathione S-transferase in complex with a glutathione conjugate of 4-hydroxynon-2-enal in one subunit and glutathione in the other: evidence of signaling across the dimer interface.

mGSTA4-4, a murine glutathione S-transferase (GST) exhibiting high activity in conjugating the lipid peroxidation product 4-hydroxynon-2-enal (4-HNE) with glutathione (GSH), was crystallized in complex with the GSH conjugate of 4-HNE (GS-Hna). The structure has been solved at 2.6 A resolution, which reveals that the active site of one subunit of the dimeric enzyme binds GS-Hna, whereas the other binds GSH. A marked asymmetry between the two subunits is evident. Most noticeable are the differences in the conformation of arginine residues 69 and 15. In all GST structures published previously, the guanidino groups of R69 residues from both subunits stack at the dimer interface and are related by a (pseudo-) 2-fold axis. In the present structure of mGSTA4-4, however, the two R69 side chains point in opposite directions, although their guanidino groups remain in contact. In the subunit with bound GSH, R69 also interacts with R15, and the guanidino group of R15 points away from the active site, whereas in the subunit that binds GS-Hna, R15 pivots into the active site, which breaks its interaction with R69. According to our previous results [Nanduri et al. (1997) Arch. Biochem. Biophys. 335, 305-310], the availability of R15 in the active site assists the conjugation of 4-HNE with GSH. We propose a model for the catalytic mechanism of mGSTA4-4 in conjugating 4-HNE with GSH-i.e., the guanidino group of R15 is available in the active site of only one subunit at any given time and the stacked pair of R69 residues act as a switch that couples the concerted movement of the two R15 side chains. The alternate occupancy of 4-HNE in the two subunits has been confirmed by our kinetic analysis that shows the negative cooperativity of mGSTA4-4 for 4-HNE. Disruption of the signaling between the subunits by mutating the R69 residues released the negative cooperativity with 4-HNE.

Aldehydes↗
PubMed1999

Homer 1b regulates the trafficking of group I metabotropic glutamate receptors.

The molecular basis for glutamate receptor trafficking to the plasma membrane is not understood. In the present study, we demonstrate that Homer 1b (H1b), a constitutively expressed splice form of the immediate early gene product Homer (now termed Homer 1a) regulates the trafficking and surface expression of group I metabotropic glutamate receptors. H1b inhibits surface expression of the metabotropic glutamate receptor mGluR5 in heterologous cells, causing mGluR5 to be retained in the endoplasmic reticulum (ER). In contrast, mGluR5 alone or mGluR5 coexpressed with Homer 1a successfully travels through the secretory pathway to the plasma membrane. In addition, point mutations that disrupt mGluR5 binding to H1b eliminate ER retention of mGluR5, demonstrating that H1b affects metabotropic receptor localization via a direct protein-protein interaction. Electron microscopic analysis reveals that the group I metabotropic receptor mGluR1alpha is significantly enriched in the ER of Purkinje cells, suggesting that a similar mechanism may exist in vivo. Because H1b is found in dendritic spines of neurons, local retention of metabotropic receptors within dendritic ER provides a potential mechanism for regulating synapse-specific expression of group I metabotropic glutamate receptors.

Binding Sites↗
PubMed1999

Structure and function of residue 104 and water molecules in the xenobiotic substrate-binding site in human glutathione S-transferase P1-1.

Two variants of human class pi glutathione (GSH) S-transferase 1-1 with either isoleucine or valine in position 104 (hGSTP1-1[I104] and hGSTP1-1[V104]) have distinct activity toward (+)-anti-7, 8-dihydroxy-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+)-anti-BPDE]. To elucidate their structure-function relationship, we determined the crystal structures of the two variants in complex with GSBpd, the GSH conjugate of (+)-anti-BPDE, at 2.1 and 2.0 A resolution, respectively. The crystal structures reveal that residue 104 in the xenobiotic substrate-binding site (H-site) dictates the binding modes of the product molecule GSBpd with the following three consequences. First, the distance between the hydroxyl group of Y7 and the sulfur atom of GSBpd is 5.9 A in the hGSTP1-1[I104].GSBpd complex versus 3.2 A in the V104 variant. Second, one of the hydroxyl groups of GSBpd forms a direct hydrogen bond with R13 in hGSTP1-1[V104].GSBpd; in contrast, this hydrogen bond is not observed in the I104 complex. Third, in the hydrophilic portion of the H-site of the I104 complex, five H-site water molecules [Ji, X., et al. (1997) Biochemistry 36, 9690-9702] are observed, whereas in the V104 complex, two of the five have been displaced by the Bpd moiety of GSBpd. Although there is no direct hydrogen bond between Y108 (OH) and the hydroxyl groups of GSBpd, indirect hydrogen bonds mediated by water molecules are observed in both complexes, supporting the previously suggested role of the hydroxyl group of Y108 as an electrophilic participant in the addition of GSH to epoxides.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1999

[Effects of alcohol on membrane lipid fluidity of astrocytes and oligodendrocytes].

To explore the mechanism of neuron development retardation and myelination abnormality caused by alcohol, the membrane lipid fluidity of astrocytes and oligodendrocytes which is related to neuron and myelin development were measured by using DPH fluorescence probe. The results showed that 5 mmol/L alcohol could lead to decrease the polarization of fluorescence (Pr) and increase the lipid fluidity unit of membrane in both cells. The alteration was in obvious dose-response relationship. The effect of alcohol on astrocytes was stronger than that of oligodendrocytes. It indicated that alcohol could change lipid fluidity of cell membrane. Alcohol probably plays major role in the dysfunction of astrocytes and oligodendrocytes.

Animals↗
PubMed1999

[Effect of lead on the expression of immediate early genes in different regions of rat brain].

In order to study the role of immediate early genes (IEG) in the neurotoxic mechanism of lead, expression of c-fos and c-jun genes in different regions of rat brain treated with lead (13 and 130 mg/kg) were observed by using immuno-histochemical method. The observation and image analysis showed that after rats treated by lead for 2 hours, the c-fos and c-jun expression in cortex, CA3 area of hippocampus and cerebellum of rats were higher than those of control rats significantly (P < 0.05). The results indicated that IEG, as a transcription regular factor, may participate in the neurological toxicity damaging the learning and memory ability induced by lead. The study provided experimental basis for revealing the molecular neurotoxic mechanism of lead.

Animals↗
PubMed1999

Shank, a novel family of postsynaptic density proteins that binds to the NMDA receptor/PSD-95/GKAP complex and cortactin.

NMDA receptors are linked to intracellular cytoskeletal and signaling molecules via the PSD-95 protein complex. We report a novel family of postsynaptic density (PSD) proteins, termed Shank, that binds via its PDZ domain to the C terminus of PSD-95-associated protein GKAP. A ternary complex of Shank/GKAP/PSD-95 assembles in heterologous cells and can be coimmunoprecipitated from rat brain. Synaptic localization of Shank in neurons is inhibited by a GKAP splice variant that lacks the Shank-binding C terminus. In addition to its PDZ domain, Shank contains a proline-rich region that binds to cortactin and a SAM domain that mediates multimerization. Shank may function as a scaffold protein in the PSD, potentially cross-linking NMDA receptor/PSD-95 complexes and coupling them to regulators of the actin cytoskeleton.

Actins↗