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Biomedical subjects

Y Jiang

Publications and source records attributed to Y Jiang.

At least 415 records · Page 23Linked to original sources
PubMed1998

[Structural elucidation of the anticoagulation and anticancer constituents from Allium chinense].

Six compounds were isolated from the anticoagulation and anticancer fractions of the bulbs of Allium chinense G. Don. On the basis of chemical evidence and spectral analysis (IR, EI-MS, 1HNMR, 13CNMR, 1H-1H COSY, HMBC, HMQC and NOESY), their structures were established as (25R, S)-5 alpha-spirostane-3 beta-ol 3-O-(beta-D-glucopyranosyl-(1-->2)-[beta-D-glucopyranosyl-(1-->3)]-beta-D- glucopyranosyl-(1-->4)-beta-D-galactopyranoside) (1), (25R, S)-5 alpha-spirostane-3 beta-ol 3-O-(beta-D-glucopyranosyl (1-->2)-[beta-D-glucopyranosyl-(1-->3)](6-acetyl-beta-D-glucopyranosyl)- (1-->4)-beta-D-galactopyranoside) (2), (25R, S)-5 alpha-spirostane-2 alpha, 3 beta-diol 3-O-(beta-D-glucopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->4)-beta-D- galactopyranoside) (3), (25S)-24-O-beta-D-glucopyranosyl-3 beta, 24 beta-dihydroxy-5 alpha-spirost-3-O-alpha-arabinopyranosyl-(1-->6)-beta-D-glucopyranoside (4), chinenoside II (5) and 2,3,4,9-tetrahydro-1-methyl-1H-pyrido [3,4-b] indole-3-carboxylic acid (6). 4 is a new steroidal saponin, named chinenoside VI. Compounds 1 to 3 are three pairs of steroidal saponin epimers. Among them, the 25S epimer of 2 is first reported, the 25R epimer of 2 and compound 6 were isolated from this title plant for the first time. The relative configuration of compound 6 was firstly determined by NOESY spectrum, and signals of C, H were assigned definitely.

Allium↗
PubMed1998

[Chimpanzee model of hepatitis E virus infection].

For the study of the hepatitis E virus infection animal model, two chimpanzee were inoculated with hepatitis E virus. After one month of the inoculation, the animal got typical hepatitis profile. ALT, anti virus-IgM, antivirus-IgG, were detected in detail. The results showed solid HEV infection evidence of typical hepatitis within one month after the inoculation.

Alanine Transaminase↗
PubMed1998

[A 5-year follow-up study of antiviral effect of interferon in patients with chronic hepatitis C].

In order to discuss the anti-viral effects of IFN alpha-2a and IFN alpha-2b on chronic hepatitis C in a short and long period of time after treatment, 70 cases of chronic hepatitis C treated with IFN alpha-2a, 46 cases with IFN alpha-2b and 28 cases as controls had been investigated in this study. The follow-up time began from half to 5 years. The serum negative conversion rate of HCV RNA and the normalization of serum alanine transaminase(ALT) were detected at the end of treatment and up to 5 years after therapy. The negative seroconversion rate of HCV RNA and the serum ALT normalization were 67.14% and 70.00% respectively in IFN alpha-2a group and 69.56%, 71.71% respectively in IFN alpha-2b group at the end of the treatment. After 5-year follow-up, the above two Indexes were 35.71%, 47.14% respectively in IFN alpha-2a group, and 39.13%, 52.17% respectively in IFN alpha-2b group. The effectiveness in treated patients was higher than that of controls (P < 0.01 and P < 0.05). Recombinant IFN alpha-2a and IFN alpha-2b are effective medicines for HCV infection. And interferon therapy had a high short-term complete response but a low long-term complete response in the treatment of chronic hepatitis C. HCV genotype seems to be an important factor in determining the response rate of IFN treatment in patients with chronic hepatitis C.

Adolescent↗
PubMed1998

[Construction and identification of recombinant fowlpox virus for expressing haemagglutinin-neuraminidase glycoprotein of Newcastle disease virus strain F48E8].

For the construction of transfer vector pFGHN1175-1, the gene encoding haemagglutinin-neuraminidase(HN) glycoprotein of newcastle disease virus(NDV) strain F48E8 was removed from plasmid pGEMHN, and inserted into the HindIII site of insertion vector pFG1175-1, downstream of P7.5 promotor. Chicken embryo fibroblast (CEF) cell cultures which had been infected with fowlpox virus (FPV) Chinese vaccine strain 282E4 for 3-4 hours were transfected with pFGHN1175-1 plasmid DNA by liposomal transfection. Recombinant FPV with blue plaques were selected and purified 3 times in CEF cell cultures overlaid agarose containing X-gal. PCR analysis and DNA dot-blotting hybridization assay indicated that the HN gene had inserted into the FPV genomic DNA. The expression of the NDV HN gene in recombinant FPV was confirmed by indirect immunofluorescence assay with specific monoclonal antibody.

Animals↗
PubMed1998

[Effect of AHMED valve implantation surgery for the treatment of neovascular glaucoma].

PURPOSE: To evaluate the efficacy of the valve implantation for the treatment of neovascular glaucoma. METHODS: 15 cases (15 eyes) neovascular glaucoma were treated with AHMED valve implantation surgery, and followed up for 6 to 42 months. RESULTS: The IOP of the cases is lowered from 6.01 +/- 1.28 kPa (1 kPa = 7.5 mmHg) preoperatively to 1.96 +/- 0.68 kPa postoperatively. The success rate was 80.0% (The criteria of success is 0.80 kPa < or = IOP < or = 2.80 kPa and without severe complication that influence the visual acuity). The common postoperative complications included hyphema, shallow anterior chamber. CONCLUSION: The AHMED valve implantation surgery can lower the IOP, increase the operative success rate and preserve the visual function effectively. It is regarded to be an effective, safe method to treat neovascular glaucoma.

Adult↗
PubMed1998

[Infrared spectroscopy application in soil organic matter].

As an important method to study the constitution and properties of macromolecular organic compounds, the infrared spectroscopy has been more and more widely taken in the researches of soil organic matters (SOM). Especially,the application of FTIR and the combined uses of FTIR with chromatogram etc. have made the researches of SOM get a great progress in many aspects. In this paper, the infrared spectroscopy applications were reviewed in SOM. It includes the following contents: the methods to study SOM by IR, studies on the constitution of soil humic substances (SHS), extraction of SOM and classification of SHS, decomposition, transformation and humification of organic matters, the differences of SOM in different situations, the interactions of SHS with metais, clay minerals and other organics in soil.

Humic Substances↗
PubMed1997

Characterization of the structure and function of the fourth member of p38 group mitogen-activated protein kinases, p38delta.

We have cloned and characterized a new member of the p38 group of mitogen-activated protein kinases here termed p38delta. Sequence comparisons revealed that p38delta is approximately 60% identical to the other three p38 isoforms but only 40-45% to the other mitogen-activated protein kinase family members. It contains the TGY dual phosphorylation site present in all p38 group members and is activated by a group of extracellular stimuli including cytokines and environmental stresses that also activate the other three known p38 isoforms. However, unlike the other p38 isoforms, the kinase activity of p38delta is not blocked by the pyridinyl imidazole, 4-(4-fluorophenyl)-2-2(4-hydroxyphenyl)-5-(4-pyridyl)-imidazole (identicalto SB202190). p38delta can be activated by MKK3 and MKK6, known activators of the other isoforms. Nonetheless, in-gel kinase assays provide evidence for additional activators. The data presented herein show that p38delta has many properties that are similar to those of other p38 group members. Nonetheless important differences exist among the four members of the p38 group of enzymes, and thus each may have highly specific, individual contributions to biologic events involving activation of the p38 pathways.

Amino Acid Sequence↗
PubMed1997

Novel modifications to the farnesyl moiety of the a-factor lipopeptide pheromone from Saccharomyces cerevisiae: a role for isoprene modifications in ligand presentation.

The a-factor of Saccharomyces cerevisiae is a dodecapeptide pheromone [YIIKGVFWDPAC(farnesyl)-OCH3] in which posttranslational modification with a farnesyl isoprenoid and carboxymethyl group is required for full biological activity. Utilizing novel synthetic techniques and a well-characterized array of biological assays, we prepared original modifications to the farnesyl moiety of the pheromone in order to assess the importance of this part of the lipopeptide for biological activity. Specifically, the 3-methyl group was replaced to create analogs containing the ethyl, vinyl, tert-butyl, and phenyl moieties at the 3-position of the farnesyl chain. Subsequent biological analyses demonstrated that all of these modifications render an active pheromone, with the vinyl and ethyl analogs exhibiting higher activity than the native a-factor. However, the level of activity varied with the modification; the bulkier and more hydrophobic groups (tert-butyl and phenyl) exhibited lower biological activity than the smaller moieties (ethyl and vinyl). Furthermore, two analogs with phenyl substitutions that differ only in the presumed isomerization of the allylic double bond show up to an 8-fold difference in bioactivity. It has previously been surmised that the role of isoprenoid additions is solely to target the attached polypeptides to membranes by increasing their hydrophobicity. However, these studies demonstrate that even modest structural changes to the isoprenoid can significantly affect biological activity. These results are clearly inconsistent with a simple hydrophobic role for the isoprenoid and instead illustrate that it plays an active role in mediating optimal a-factor/receptor interaction.

Butadienes↗
PubMed1997

Identification of a flexible loop region (297-313) of urokinase-type plasminogen activator, which helps determine its catalytic activity.

Pro-urokinase has a much higher intrinsic catalytic activity than other zymogens of the serine protease family. Lys300(c143) in an apparent "flexible loop" region (297-313) was previously shown to be an important determinant of this intrinsic catalytic activity. This was related to the loop allowing the positive charge of Lys300(c143) to transiently interact with Asp355(c194), thereby inducing an active conformation of the protease domain (Liu, J. N., Tang, W., Sun, Z., Kung, W., Pannell, R., Sarmientos, P., and Gurewich, V. (1996) Biochemistry 35, 14070-14076). To further test this hypothesis, the charge at position 300(c143) and the flexibility of the loop were altered using site-directed mutagenesis designed according to a computer model to affect the interaction between Lys300(c143) and Asp355(c194). When the charge at Lys300(c143) but not Lys313(c156) was reduced, a significant reduction in the intrinsic catalytic activity occurred. Similarly, when the flexibility (wobbliness) of the loop was enhanced reducing the size of side chain, the intrinsic catalytic activity was also reduced. By contrast, when the loop was made less flexible, the intrinsic catalytic activity was increased. These findings were consistent with the hypothesis. The effects of these mutations on two-chain activity were less and often discordant with the intrinsic catalytic activity, indicating that they can be modulated independently. This structure-function disparity can be exploited to create a more zymogenic pro-urokinase (lower intrinsic catalytic activity) with a high catalytic activity, as exemplified by two of the mutants. The changes in intrinsic catalytic activity and two-chain activity induced by the mutations were due to changes in kcat rather than Km. Some significant structure-function differences between pro-urokinase and its highly homologous counterpart, tissue plasminogen activator, were also found.

Catalysis↗
PubMed1997

Precursor B cells for autoantibody production in genomically Fas-intact autoimmune disease are not subject to Fas-mediated immune elimination.

The Fas/Fas ligand (FasL) system participates in regulation of the immune system through the apoptotic process. However, the extent to which abnormalities in this system are involved in the loss of self-tolerance and development of autoimmune disease not associated with Fas/FasL mutations remains unknown. The present study addresses this issue in Fas/FasL-intact, systemic lupus erythematosus (SLE)-prone (NZB x NZW) (NZB/W) F1 mice. While splenic B cells from 2-month-old mice before overt SLE expressed Fas poorly, in vitro stimulation with an agonistic anti-CD40 mAb up-regulated their Fas expression, thus revealing the existence of two populations: one was Fashigh and highly susceptible to anti-Fas mAb-induced apoptosis, and the other was Faslow and apoptosis-resistant. The Faslow cells were included in the CD5(+) B cell subpopulation and contained most of the cells that produced IgM anti-DNA antibodies. The isotype of anti-DNA antibodies switches from IgM to IgG in NZB/W F1 mice at ages beginning at about 6 months. These IgG anti-DNA antibodies were produced almost exclusively by a subpopulation of splenic B cells that spontaneously expressed low levels of Fas in vivo and were apoptosis-resistant. The findings indicate that precursor B cells for autoantibody production and presumably autoantibody-secreting cells in these mice are relatively resistant to Fas-mediated apoptosis, a finding supporting the concept that abnormalities of Fas-mediated apoptotic process are involved in the development of autoreactive B cells in Fas/FasL-intact autoimmune disease.

Animals↗
PubMed1997

Activators of the nuclear hormone receptors PPARalpha and FXR accelerate the development of the fetal epidermal permeability barrier.

Members of the superfamily of nuclear hormone receptors which are obligate heterodimeric partners of the retinoid X receptor may be important in epidermal development. Here, we examined the effects of activators of the receptors for vitamin D3 and retinoids, and of the peroxisome proliferator activated receptors (PPARs) and the farnesoid X-activated receptor (FXR), on the development of the fetal epidermal barrier in vitro. Skin explants from gestational day 17 rats (term is 22 d) are unstratified and lack a stratum corneum (SC). After incubation in hormone-free media for 3-4 d, a multilayered SC replete with mature lamellar membranes in the interstices and a functionally competent barrier appear. 9-cis or all-trans retinoic acid, 1,25 dihydroxyvitamin D3, or the PPARgamma ligands prostaglandin J2 or troglitazone did not affect the development of barrier function or epidermal morphology. In contrast, activators of the PPARalpha, oleic acid, linoleic acid, and clofibrate, accelerated epidermal development, resulting in mature lamellar membranes, a multilayered SC, and a competent barrier after 2 d of incubation. The FXR activators, all-trans farnesol and juvenile hormone III, also accelerated epidermal barrier development. Activities of beta-glucocerebrosidase and steroid sulfatase, enzymes previously linked to barrier maturation, also increased after treatment with PPARalpha and FXR activators. In contrast, isoprenoids, such as nerolidol, cis-farnesol, or geranylgeraniol, or metabolites in the cholesterol pathway, such as mevalonate, squalene, or 25-hydroxycholesterol, did not alter barrier development. Finally, additive effects were observed in explants incubated with clofibrate and farnesol together in suboptimal concentrations which alone did not affect barrier development. These data indicate a putative physiologic role for PPARalpha and FXR in epidermal barrier development.

Animals↗
PubMed1997

A 2.8-Mb clone contig of the multiple endocrine neoplasia type 1 (MEN1) region at 11q13.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder that results in parathyroid, anterior pituitary, and pancreatic and duodenal endocrine tumors in affected individuals. The MEN1 locus is tightly linked to the marker PYGM on chromosome 11q13, and linkage analysis has placed the MEN1 gene within a 2-Mb interval flanked by D11S1883 and D11S449. As a step toward cloning the MEN1 gene, we have constructed a 2.8-Mb clone contig consisting of YAC and bacterial clones (PAC, BAC, and P1) for the D11S480 to D11S913 region. The bacterial clones alone represent nearly all of the 2.8-Mb contig. The contig was assembled based on a high-density STS-content analysis of 79 genomic clones (YAC, PAC, BAC, and P1) with 118 STSs. The STSs included 22 polymorphic markers and 20 transcripts, with the remainder primarily derived from the end sequences of the genomic clones. An independent cosmid contig for the 1-Mb PYGM-SEA region was also generated. Support for correctness of the 2.8-Mb contig map comes from an independent ordering of the clones by fiber-FISH. This sequence-ready contig will be a useful resource for positional cloning of MEN1 and other disease genes whose loci fall within this region.

Chromosomes, Artificial, Yeast↗
PubMed1997

Expression and characterization of the small subunit of human DNA polymerase delta.

DNA polymerase delta is a heterodimer consisting of a catalytic subunit of 125 kDa and a small subunit of 50 kDa (p50). We have overexpressed p50 in Escherichia coli and have characterized the recombinant protein. p50 was readily overexpressed using the pET vector as an insoluble protein. A procedure was developed for its purification and renaturation. Examination of the physicochemical properties of renatured p50 showed that it is a monomeric protein with an apparent molecular weight of 60,000, a Stokes radius of 34 A, and a sedimentation coefficient of 4.1 S. Its physical properties were indistinguishable from p50 expressed as a soluble protein using the pTACTAC vector. Examination of the effects of recombinant p50 on the activity of DNA polymerase delta showed that p50 is able to slightly stimulate (about 2-fold) the activity of the recombinant 125-kDa catalytic subunit using poly(dA).oligo(dT) as a template in the absence of proliferating cell nuclear antigen. In the presence of proliferating cell nulear antigen, activity is stimulated about 5-fold. Seven stable hybridoma cell lines were established that produced monoclonal antibodies against p50. One of these antibodies (13D5) inhibited the activity of calf thymus DNA polymerase delta. This antibody, when coupled to a solid support, also was found to provide a method for the immunoafffinity purification of recombinant p50 and of DNA polymerase delta from calf thymus or HeLa extracts. Immunoprecipitation and enzyme-linked immunosorbent assays also confirmed that p50 interacts with the catalytic subunit of DNA polymerase delta.

DNA Polymerase III↗
PubMed1997

Structure-function studies of p38 mitogen-activated protein kinase. Loop 12 influences substrate specificity and autophosphorylation, but not upstream kinase selection.

Several mitogen-activated protein kinase (MAPK) cascades have been identified in eukaryotic cells. The activation of MAPKs is carried out by distinct MAPK kinases (MEKs or MKKs), and individual MAPKs have different substrate preferences. Here we have examined how amino acid sequences encompassing the dual phosphorylation motif located in the loop 12 linker (L12) between kinase subdomains VII and VIII and the length and amino acid sequence of L12 influence autophosphorylation, substrate specificity, and upstream kinase selectivity for the MAPK p38. Conversion of L12 of p38 to an "ERK-like" structure was accomplished in several ways: (i) by replacing glycine with glutamate in the dual phosphorylation site, (ii) by placing a six-amino acid sequence present in L12 of ERK (but absent in p38) into p38, and (iii) by mutations of amino acid residues in loop 12. Two predominant effects were noted: (i) the Xaa residue in the dual phosphorylation motif Thr-Xaa-Tyr as well as the length of L12 influence p38 substrate specificity, and (ii) the length of L12 plays a major role in controlling autophosphorylation. In contrast, these modifications do not result in any change in the selection of p38 by individual MAPK kinases.

Amino Acid Sequence↗
PubMed1997

Activation of the transcription factor MEF2C by the MAP kinase p38 in inflammation.

For cells of the innate immune system to mount a host defence response to infection, they must recognize products of microbial pathogens such as lipopolysaccharide (LPS), the endotoxin secreted by Gram-negative bacteria. These cellular responses require intracellular signalling pathways, such as the four MAP kinase (MAPK) pathways. In mammalian cells the MAPK p38 is thought to play an important role in the regulation of cellular responses during infection through its effects on the expression of proinflammatory molecules. One means of understanding the role of p38 in these responses is to identify proteins with functions regulated by p38-catalysed phosphorylation. Here we demonstrate a link between the p38 pathway and a member of the myocyte-enhancer factor 2 (MEF2) group of transcription factors. We found that in monocytic cells, LPS increases the transactivation activity of MEF2C through p38-catalysed phosphorylation. One consequence of MEF2C activation is increased c-jun gene transcription. Our results show that p38 may influence host defence and inflammation by maintaining the balance of c-Jun protein consumed during infection.

Binding Sites↗
PubMed1997

Analysis of selenium in bovine liver by gas chromatography with mass-selective, electron-capture and nitrogen-phosphorus detection.

The concentration of selenium (Se) in liver was determined by gas chromatography (GC) with mass-selective (GC-MS), electron capture (GC-ECD) and nitrogen-phosphorus (GC-NPD) detection. Liver samples were digested in a mixture containing HNO3 and Mg(NO3). SeVI was converted to SeIV. SeIV was derivatized with 4-nitrophenylenediamine and then extracted in toluene. A 1-microliter volume of the toluene extract was analyzed by the GC-MS, GC-ECD or GC-NPD methods. The detection limits of the GC-ECD, the GC-NPD and the GC-MS methods were 25, 50 and 800 pg, respectively. The GC-NPD method was more selective for the derivatized Se than the GC-ECD method. The GC-MS method had the advantage of using the 76Se isotope as the internal standard. Se concentrations in liver samples determined by the three methods were comparable.

Animals↗
PubMed1997

Identification and characterization of a predominant isoform of human MKK3.

We have obtained a novel cDNA species of MKK3, termed MKK3b. MKK3b cDNA differs from its original form, MKK3, at the 5'-end, encoding 29 extra amino acids in the N-terminus. Analysis of MKK3 genomic DNA structure revealed that the MKK3b-unique 5'-end sequence is derived from an exon different from that of MKK3, and that they share identical sequences thereafter. This suggests that the two cDNA forms of MKK3 are either generated by differential splicing of the same gene or derived from differential promoter utilization. Northern blotting analysis showed that MKK3b mRNA is much more abundant than MKK3. Functional characterization based on the activation of p38 revealed that MKK3b is more efficient than MKK3 in mediating downstream signalling events.

Amino Acid Sequence↗