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Biomedical subjects

B Tang

Publications and source records attributed to B Tang.

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

[Study on the characteristic and significance of three dimensional fluorescence spectra of petroleum samples].

Based on studies on the characteristics of three dimensional fluorescence spectrum of a kinds of oils and gases, we found the similarity peak and characteristic peak for the various crude oils and nature gases. This technique can be used not only in judging the types of crude oil and gas, but also in the comparison of oil to oil and oil to source, and studying what oil and gas stemmed from and its organic geochemistry as well. The true of sample is very important due to the volatility and alterability of light aromatic hydrocarbon. Once solving the quantification of fluorescence analysis, the evidence may be provided for predicting oil and gas layers, source rock.

English Abstract↗
PubMed1999

Loss of responsiveness to transforming growth factor beta induces malignant transformation of nontumorigenic rat prostate epithelial cells.

Transforming growth factor (TGF)-betas are multifunctional growth factors, the properties of which include the potent inhibition of epithelial cell growth. Expression patterns of TGF-betas and TGF-beta receptors in the normal prostate indicate that these growth regulators play key roles in prostatic development and proliferative homeostasis. Importantly, TGF-beta receptor levels are frequently diminished in malignant human prostate tissue. To test the hypothesis that loss of TGF-beta responsiveness is causally involved in the tumorigenic process, we have used retroviral transduction to introduce a dominant-negative mutant type II TGF-beta receptor (DNR) into the premalignant rat prostatic epithelial cell line, NRP-152. High-level expression of the DNR abolished the ability of TGF-beta to inhibit cell growth, to promote cell differentiation, and to induce apoptosis, and it partially blocked the induction of extracellular matrix gene expression. When injected into nude mice, NRP-152-DNR cells formed carcinomas at 13 of 34 sites, compared with 0 of 30 sites for parental and control cells (P = 0.0001). We conclude that the type II TGF-beta receptor is an important tumor suppressor in the prostate, and furthermore, that loss of TGF-beta responsiveness can contribute early in the tumorigenic process by causing the malignant transformation of preneoplastic cells.

Animals↗
PubMed1999

Oxidative refolding of recombinant prochymosin.

The disulphide-coupled refolding of recombinant prochymosin from Escherichia coli inclusion bodies was investigated. Prochymosin solubilized from inclusion bodies is endowed with free thiol groups and disulphide bonds. This partially reduced form undergoes renaturation more efficiently than the fully reduced form, suggesting that some native structural elements existing in inclusion bodies and remaining after denaturation function as nuclei to initiate correct refolding. This assumption is supported by the finding that in the solubilized prochymosin molecule the cysteine residues located in the N-terminal domain of the protein are not incorrectly paired with the other cysteines in the C-terminal domain. Addition of GSH/GSSG into the refolding system facilitates disulphide rearrangement and thus enhances renaturation, especially for the fully reduced prochymosin. Based on the results described in this and previous papers [Tang, Zhang and Yang (1994) Biochem. J. 301, 17-20], a model to depict the refolding process of prochymosin is proposed. Briefly, the refolding process of prochymosin consists of two stages: the formation and rearrangement of disulphide bonds occurs at the first stage in a pH11 buffer, whereas the formation and adjustment of tertiary structure leading to the native conformation takes place at the second stage at pH8. The pH11 conditions help polypeptides to refold in such a way as to favour the formation of native disulphide bonds. Disulphide rearrangement, the rate-limiting step during refolding, can be achieved by thiol/disulphide exchange initiated by free thiol groups present in the prochymosin polypeptide, GSH/GSSG or protein disulphide isomerase.

Air↗
PubMed1999

Molecular definition and characterization of recombinant bovine CB8 and CB10: immunogenicity and arthritogenicity.

Theoretically, the ability to produce recombinant type II collagen (CII) peptide fragments in a prokaryotic expression system would be extremely useful for preparing adequate amounts of CII peptides suitable for therapeutic uses. Bacteria do not contain the enzymes involved in the extensive posttranslational modifications that occur during the biosynthesis of CII, such as the hydroxylation of prolyl and lysyl residues and glycosylation of hydroxylysyl residues. As these posttranslational modifications may play a role in the immune and arthritogenic response to CII, it was unclear whether collagen expressed in Escherichia coli would be immunologically comparable to tissue-derived CII. Therefore, we prepared recombinant proteins for CB8 and CB10 by cloning CB8 (CII 403-551) and CB10 (CII 552-897) genes from bovine chondrocytes by RT-PCR technique and expressing them in an E. coli expression system. Characterization of these recombinant proteins revealed that both rCB8 and rCB10 stimulated T cell proliferation in a T cell determinant-specific manner. The T cells from mice immunized with rCB8 respond specifically to a synthetic peptide, CII 445-453, the CB8 T cell determinant. Conversely, rCB10-primed T cells respond strongly to CII 610-618, the CB10 T cell determinant. Recombinant CB8-induced autoantibodies that bound to mouse CB8 as effectively and in the same topographic distribution as tissue-derived CB8. Finally, when rCB8 and rCB10 proteins were used to immunize B10.RIII (H-2(r)) mice, rCB8 induced arthritis in 33% of the mice, very similar to the incidence induced by tissue-derived CB8 peptide. As was found to be the case with tissue-derived CB10, rCB10 was completely ineffective in inducing arthritis. Pathological changes of arthritic joints in the mice immunized with rCB8 were similar to those observed in mice immunized with tissue-derived CB8. Thus, these recombinant CII peptides expressed in E. coli can induce an effective immunologic response and suggest that functionally useful CII peptides can be generated by the prokaryotic expression system.

Amino Acid Sequence↗
PubMed1999

Observer reliability in grading nephrocalcinosis on ultrasound examinations in children.

BACKGROUND: Nephrocalcinosis is often associated with a variety of hypercalcemic conditions. Diagnostic ultrasound is often used for assessing nephrocalcinosis in children, but its reliability has not been proven. OBJECTIVE: To determine the reliability of expert interpretation of sonographic films with a grading scale of severity for nephrocalcinosis. MATERIALS AND METHODS: Fifty-eight ultrasonographic films of 30 children with Williams syndrome and other conditions know to be associated with nephrocalcinosis were assessed. We used a blinded randomized design to assess intra- and interobserver reliability. RESULTS: Grades I, II, and III nephrocalcinosis were noted in 13 %, 19 %, and 27 % of the examinations, respectively. The weighted kappa coefficient was 0.80 (standard error 0.12; 95 % confidence interval 0.68-0.92) for intraobserver agreement and 0.76 (standard error 0.13; 95 % confidence interval 0.63 to 0.89) for interobserver agreement. Reliability in assessing change from one examination to the next, with independently graded films, was fair with an unweighted kappa coefficient of 0.68 (95 % confidence interval 0.38-0.96) and 0.51 (95 % confidence interval 0.21-0.80) for intra- and interobserver reliability, respectively. CONCLUSION: The severity of nephrocalcinosis can be reliably interpreted with an ultrasonography grading scale.

Child↗
PubMed1999

[CAG trinucleotide mutation detection in patients with hereditary spinocerebellar ataxia].

OBJECTIVE: To assess the frequency of the SCA1, SCA2,SCA3/MJD, SCA6, SCA7 and DRPLA CAG trinucleotide repeat expansions(CAG)n among individuals diagnosed with hereditary spinocerebellar ataxia(SCA) from Chinese families. METHODS: The SCA1, SCA2, SCA3/MJD, SCA6, SCA7 and DRPLA(CAG)n mutations were detected by polymerase chain reaction (PCR), denaturing polyacrylamide gel electrophoresis and silver staining technique in 167 patients with autosomal dominant SCA from 85 Chinese families and 37 sporadic SCA patients. RESULTS: Among 85 families, four families(4.70%) had seven SCA1 patients with the CAG repeat expanded to 53 to 62 repeats, five (5.88%) had twelve SCA2 patients with the CAG repeat expanded to 43 to 47 repeats, and 41 (48.23%) had 83 SCA3/MJD patients with the CAG repeat expanded to 68 to 83 repeats. Analysis of the mutation in these families showed a strong negative correlation between the size of the expanded CAG repeat and the age of disease onset. None of the SCA patients were positive for SCA6, SCA7, or DRPLA. Nor was any of the sporadic SCA patients positive for the CAG repeat expansion in the SCA1, SCA2, SCA3/MJD, SCA6, SCA7, or DRPLA gene. CONCLUSION: The frequency of SCA3/MJD is substantially higher than that of SCA1 and SCA2 in the autosomal dominant SCA from Chinese families. Chinese SCA3/MJD patients are non-Portuguese. Clinical expressions of the various SCAs overlap one another and hence can make the phenotype-based diagnostic classification inaccurate in many instances. It is important for SCA clinical studies to make an SCA gene diagnosis and genotype analysis.

Adult↗
PubMed1999

[Cloning of rat beta-defensin rBD-1 cDNA].

This is a study aimed at the molecular mechanisms of beta-defensins gene expression and it's gene transfer experiments for preventing mucosal infection. A rat rBD-1 cDNA was cloned. The total RNA was isolated from rat kidney. The cDNA fragment was amplified by RT-PCR with specific primers. The purified RT-PCR product was cloned in pGEM-T Easy vector. The results of restriction endonuclease pattern analysis of the recombinant plasmid, DNA sequencing, and aligning of the putative amino acid sequence with hBD-1 and mBD-1 demonstrated that rat beta-defensin rBD-1 gene was cloned successfully.

Amino Acid Sequence↗
PubMed1999

[Role of red nucleus in inhibiting nociceptive responses of rat spindle afferent].

Using extracellular recording techniques, the effect of excitation of red nucleus (RN) on C-responses of wide dynamic range (WDR) neurons and the roles of RN in the inhibitory effect of spindle afferent activated by succinycholine (SCH) on C-responses of WDR neurons were studied. Stimulation of RN caused a significant reduction of nociceptive responses of WDR neurons, which was significantly attenuated by intravenous cyproheptadine and contralateral lesion of RN. These results suggest that the inhibitory effect on nociceptive responses of WDR neurons caused by RN stimulation was partly mediated by 5-HT and RN plays an important role in analgesia induced by the muscle spindle afferent activity.

Afferent Pathways↗
PubMed1999

[Detection of HNP1 gene expression by RT-PCR in transfected tracheal epithelial cells].

By using lipofection reagent DOSPER, the plasmid vector carrying the human neutrophil defensin HNP1 gene(pBabe-Neo-HNP1) was transferred into human, rabbit tracheal epithelial cells cultured in serum-free complement medium. Determination of HNP1 mRNA expression in tracheal epithelial cells was performed by reverse transcription-polymerase chain reaction (RT-PCR). The result showed that HNP1-gene expression was detected both in human and rabbit transfected epithelial cells; while in untransfected epithelial cells, no specific signals were detected by RT-PCR. This result and the result of our previous determination by immunocytochemical staining both demonstrated that the epithelial cells could express the antibiotic peptide when transfected with its gene, suggesting that the mucosal antibiotic peptide gene transfer might develop a new antimicrobial approach to prevention and treatment of respiratory infections.

Animals↗
PubMed1999

[Isolation, purification and antibacterial activities of salivary histidine-rich polypeptides].

OBJECTIVE: To isolate and purify salivary histidine-rich-polypeptides (HRPs) and observe their antibacterial activities. METHODS: By using of preparative acid urea polyacrylamide gel electrophoresis (AU-PAGE), three major HRPs(HRP-1, HRP-3 and HRP-5) were purified from parotid saliva collected from healthy adults. Their antibacterial activities were tested in the ultrasensitive antibacterial assay, named radial diffusion assay. RESULTS: Each fraction of the three purified HRPs appeared as a single protein zone both in AU-PAGE and Tricine-SDS-PAGE. Their molecular weights are 3-5 kD as determined by Tricine-SDS-PAGE. All the three major HRPs showed potent bactericidal effects on Streptococcus mutans MT6R and Staphylococcus aureas ATCC25923. As to Escherichia coli ML-35P and Pseudomonas aeruginosa ATCC27853, HRP-3 and HRP-5 also demonstrated significant antibacterial activities, whereas HRP-1 did not show any inhibitory effects on the viability of them. CONCLUSION: The above results suggested that the method of preparative AU-PAGE we used in this study has the benefits of high resolution, simple manipulation and perfect results of purification. HRPs are important components to prevent oral tissue from bacterial infections, therefore play a potent role in the maintenance of the oral health.

Adult↗
PubMed1999

[Study on the surface diffuse reflectance ultraviolet-visible spectra of the multicomponent metal catalysts].

In this paper, the surface diffuse reflectance ultraviolet-visible spectra (DRUVS) of two and three components supported metal catalysts for methanation of CO2 by hydrogenation were studied, and the relationship between the activity of catalytic-hydrogenation and the interaction among the components of the catalysts was revealed. Based on the analysis of the DRUVS of the catalysts with defferent amount of promoters in two component catalysts system, the dependence relationship between the characteristic strength of the DRUVS and the catalytic activity was worked out.

English Abstract↗
PubMed1998

Characterization of a peptide analog of a determinant of type II collagen that suppresses collagen-induced arthritis.

Immunization of susceptible strains of mice with type II collagen (CII) elicits an autoimmune arthritis known as collagen-induced arthritis (CIA). One analogue peptide of the immunodominant T cell determinant, A9 (CII245-270 (I260-->A, A261-->B, F263-->N)), was previously shown to induce a profound suppression of CIA when coadministered at the time of immunization with CII. In the present study, A9 peptide was administered i.p., orally, intranasally, or i.v. 2 to 4 wk following CII immunization. We found that arthritis was significantly suppressed even when A9 was administered after disease was induced. To determine the mechanism of action of A9, cytokine responses to A9 and wild-type peptide A2 by CII-sensitized spleen cells were compared. An increase in IL-4 and IL-10, but not in IFN-gamma, was found in A9 culture supernatants. Additionally, cells obtained from A9-immunized mice produced higher amounts of IL-4 and IL-10 when cultured with CII compared with cells obtained from mice immunized with A2, which produced predominantly IFN-gamma. Suppression of arthritis could be transferred to naive mice using A9-immune splenocytes. Lastly, phosphorylation of TCRzeta was not altered in the immunoprecipitates from the lysates of cells exposed to analogue peptides (A9 and A10) together with wild-type A2 in a T cell line and two I-Aq-restricted, CII-specific T hybridomas. We conclude that analogue peptide A9 is effective in suppressing established CIA by inducing T cells to produce a Th2 cytokine pattern in response to CII.

Administration, Intranasal↗
PubMed1998

Characterization of signal transduction through the TCR-zeta chain following T cell stimulation with analogue peptides of type II collagen 260-267.

The immunodominant T cell determinant of type II collagen (CII) recognized by DBA/1 mice (I-Aq) is CII 260-267. The aims of this study were to determine the role of the amino acid residues within CII 245-270 in T cell signal transduction. To that end, we utilized I-Aq-restricted, CII-specific T cell hybridomas and examined tyrosine phosphorylation of TCR-zeta following stimulation with either wild-type CII 245-270 or a panel of analogue peptides. A variety of patterns occurred, ranging from increased phosphorylation of TCR-zeta to either partial or a complete abrogation of phosphorylation. Critical substitutions also completely abrogated the phosphorylation of ZAP70, a downstream molecule in TCR-zeta signaling. Evaluation of the supernatants of the T cell hybridomas for cytokine production in response to the peptides revealed a close correlation between the induction of phosphorylation of TCR-zeta and the amount of cytokine induced. Selected analogue peptides were tested as tolerogens in neonatal mice. Analogues that did not induce the phosphorylation of zeta chain, such as B3 (CII 251-270s263F-->N), were completely unable to induce tolerance, while analogues that caused a partial phosphorylation, such as B6 (CII 251-270s267Q-->T) and A3 (CII 245-270s269P-->A), induced partial tolerance judged by intermediate degrees of suppression of arthritis. We conclude that discrete alterations in specific amino acid residues of antigenic peptides had profound effects on T cell signaling and that the signaling correlated with T cell cytokine secretion and T cell function in the induction of tolerance and suppression of arthritis.

Amino Acid Sequence↗
PubMed1998

Disabled-2 (Dab2) is an SH3 domain-binding partner of Grb2.

Disabled-2 (Dab2), a mammalian structural homolog of Drosophila Disabled (Dab), is a mitogen-responsive phosphoprotein. It has been speculated to be a negative regulator of growth since its expression is lost in ovarian carcinomas. Dab2 contains a C-terminal proline-rich domain with sequences similar to those found in Sos, a guanine nucleotide exchange factor for Ras. The proline-rich sequences of Sos mediate the interaction of Sos with Grb2, an adaptor protein which coupled tyrosine kinase receptors to Sos. Herein, we have investigated the possibility that Dab2 interacts with Grb2. In experiments of co-immunoprecipitation from BAC1.2F5 macrophage cell lysates, significant quantities of Grb2 were associated with both Sos and Dab2, although Dab2 and Sos were not present in the same complex. Transfection of Dab2 into a Dab2-negative cell line (293 cells) decreased the amount of Grb2 associated with Sos, suggesting that Dab2 competes with Sos for binding to Grb2. Proline-rich peptides corresponding to Dab2 (#661-669) and to Sos (#1146-1161) inhibited the binding of Dab2 to Grb2, but were less effective in disrupting the Grb2-Sos complex. The expressed proline-rich domain of Dab2 (#600-730) bound Grb2, but other regions of Dab2 failed to bind Grb2. Both of the individual SH3 domains of Grb2 bound to Sos (N-terminal SH3 domain >> C-terminal SH3 domain), but binding to Dab2 required the intact Grb2, suggesting cooperative binding using both SH3 domains of Grb2. These data indicate that Dab2 binds to the SH3 domains of Grb2 via its C-terminal proline-rich sequences. Dab2 may modulate growth factor/Ras pathways by competing with Sos for binding to Grb2.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Transforming growth factor-beta1 is a new form of tumor suppressor with true haploid insufficiency.

Components of the transforming growth factor-beta (TGF-beta) signal pathway function as classic tumor suppressors, but the role of the TGF-betas themselves is less clear. Here we show that mice heterozygous for deletion of the TGF-beta1 gene express only 10-30% of wild-type TGF-beta1 protein levels. Although grossly normal, these mice have a subtly altered proliferative phenotype, with increased cell turnover in the liver and lung. Treatment of these mice with chemical carcinogens resulted in enhanced tumorigenesis when compared with wild-type littermates. However, tumors in the heterozygous mice did not lose the remaining wild-type TGF-beta1 allele, indicating that the TGF-beta1 ligand is a new form of tumor suppressor that shows true haploid insufficiency in its ability to protect against tumorigenesis.

Animals↗
PubMed1998

Studies of the role for NSP4 in the pathogenesis of homologous murine rotavirus diarrhea.

A rotavirus (RV) nonstructural protein, NSP4, has recently been proposed to function as an enterotoxin in the pathogenesis of RV diarrhea. The role of NSP4 in the pathogenesis of RV diarrhea was examined by infecting cystic fibrosis transmembrane conductance regulator (CFTR) knockout mice with virulent murine RV and by comparing deduced amino acid sequences of RV gene 10 encoding NSP4 from three distinct sets of virulent and tissue culture-adapted avirulent variant RVs. Homozygous CFTR (CFTR-/-) mice, which do not respond to any known intestinal secretagogues, experienced diarrhea comparable to that in normal CFTR+/+ littermates after RV challenge. Comparison of amino acid sequences of NSP4 from virulent and attenuated pairs of RVs failed to show consistent or significant changes. Together, these data suggest that enterotoxigenic properties of RV NSP4 are not critical in the pathogenesis of murine RV diarrhea and that attenuation of murine RVs is not usually mediated by mutations in the gene encoding NSP4.

Animals↗
PubMed1998

Identification of mutations in the rotavirus protein VP4 that alter sialic-acid-dependent infection.

To explore further the role of VP4 as the rotavirus cell attachment protein, VP7 monoreassortants derived from the sialic-acid-dependent simian strain RRV and from the sialic-acid-independent human strains D, DS-1 and ST-3 were tested for susceptibility of infectivity of neuraminidase-treated MA-104 cells. Infectivity of RRV x D VP7 and RRV x ST-3 VP7 monoreassortants decreased when sialic acid was removed from the cell surface. However, of three separate RRV x DS-1 VP7 monoreassortants tested, only one was sialic-acid-dependent. Sequence analysis showed that both sialic-acid-independent strains contained a single amino acid change, Lys to Arg, at position 187. In addition, sialic-acid-independent infectivity was seen in one of 14 RRV VP4 neutralization escape mutants tested, and this strain was found to have a Gly to Glu change at amino acid position 150. These results indicate that positions 150 and 187 of VP4 play an important role in early rotavirus-cell interactions.

Animals↗