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Biomedical subjects

T Zhang

Publications and source records attributed to T Zhang.

At least 163 records · Page 9Linked to original sources
PubMed2000

[Taxol-induced apoptosis in Jurkat T cell lymphoma cell line and its molecular mechanisms].

OBJECTIVE: To observe whether antimicrotubular drug taxol can induce apoptosis in Jurkat T cell lymphoma cell line and the role of bcl-2 gene family in this process. METHODS: Different concentrations of taxol were used to treat Jurkat cells. Cell morphology was observed under light and electron microscope. Flow cytometry and electrophoresis were used to analyze DNA contents and DNA fragments. bcl-2 gene family proteins and mRNAs were studied by immunohistochemistry and semi-quantitative RT-PCR technique. RESULTS: Taxol could inhibit Jurkat cell growth. Within a certain range of treating time and dose, cells were induced apoptosis with a time and dose related manner. The expressions of bax protein and mRNA were increased and bcl-x(s) mRNA became detectable after taxol treatment. CONCLUSION: Taxol can specifically induce Jurkat cell apoptosis. It might provide a theoretical basis for clinical treatment and a good model for studying apoptotic gene modulation. Bax and bcl-x(s) participate in the taxol induced apoptosis of Jurkat cells.

Antineoplastic Agents, Phytogenic↗
PubMed2000

[A comparative study on the expressions of IL-4, IFN-gamma and TNF-alpha in BMMNC of acute and chronic aplastic anemia patients].

OBJECTIVE: To detect the induced levels of IL-4, IFN-gamma and TNF-alpha in the supernatant of bone marrow mononuclear cells (BMMNC) and compare the difference of immune status between acute (SAA) and chronic (CAA) aplastic anemia patients. METHODS: Concentrations of IL-4, IFN-gamma and TNF-alpha in PHA-P-induced BMMNC supernatants were determined by ELISA assay in 11 SAA and 13 CAA patients as well as 16 controls. Concentration differences between the two groups were compared. RESULTS: (1) The IFN-gamma and TNF-alpha levels in AA patients studied were much higher than that in controls, and IL-4 levels were normal in SAA group but elevated in CAA group. (2) TNF-alpha levels were comparable between the two AA groups, but both IL-4 and IFN-gamma levels were significantly different between them. CONCLUSION: Enhanced cellular immunity seems to play an important role in the pathogenesis of SAA, and enhancement of both cellular and humoral immunity might contribute to the pathogenesis of CAA.

Acute Disease↗
PubMed2000

[Studies on chemical constituents of aerial parts of Verbena officinalis L].

OBJECTIVE: To search for new effective ant-early-pregnancy components from the aerial part of Verbena officinalis. METHOD: Compounds were isolated from the methanol extract of the herb by chromatography on silica gel column, and the structures were determined by physical and chemical evidences and spectroscopic analysis. RESULT: Two compounds were obtained and identified as 3,4-dihydroverbenalin and daucosterol. CONCLUSION: The two compounds were obtained from this the herb for the first time and 3,4-didydroverbenalin is a new product.

Heterocyclic Compounds, 2-Ring↗
PubMed2000

[Studies on human cytokine responses before and after praziquantel chemotherapy in an endemic area of schistosomiasis japonica].

OBJECTIVE: To observe the cellular immune responses in a population of an endemic area of schistosomiasis japonica and the influence of praziquantel treatment. METHODS: Blood was taken from 129 residents (64 cases were egg-positive, 65 cases were egg-negitive) of an endemic area of Poyang Lake before and 45 days after praziquantel treatment. Cytokines induced by the schistosome soluble egg antigen (SEA) and soluble worm antigen preparations (SWAP) in the peripheral blood cells including IL-5, IL-10 and IFN-gamma were measured. RESULTS: Among 129 cases, the cytokine levels were found much higher in egg negative individuals than in egg-positive individuals. The cytokine levels induced by both antigens were increased significantly after praziqantel treatment especially IL-5 and IFN-gamma. CONCLUSION: The cellular immune responses in the population in schistosomiasis japonica endemic area exhibited a general trend of down-regulation and were elevated significantly after praziquantel treatment.

Adolescent↗
PubMed2000

[Cloning and sequence analysis of SSU rRNA gene of cutaneous leishmaniasis pathogen from Xinjiang of China].

OBJECTIVE: By sequencing of SSU rRNA gene cloning from Xinjiang cutaneous leishmaniasis pathogen (XJCLP) to provide evidence for identification of the pathogen. METHODS: By PCR assay with primers R222 and R333, the specific fragment had been produced from SSU rRNA gene of XJCLP, L. infantum, L. tropica and cloned into pGEM-T Easy vector. The clones were sequenced by the Sanger dideoxy-mediated chain termination method, analysis of SSU rRNA gene sequences from XJCLP, L. tropica, L. infantum with DNASIS. RESULTS: Sequence analysis showed that the specific fragment of SSU rRNA gene from XJCLP, L. infantum, L. tropica, were all 394 bp in length. There were 391 bases identical and three point mutations between the sequences of XJCLP and L. tropica, the similarity being 99.2%; 390 bases identical and three point mutations and one insertion/deletion between the sequences of XJCLP and L. infantum, the similarity being 99.0%. One insertion/deletion between the sequences of L. tropica and L. infantum, the similarity being 99.7%. The primary and secondary structures of SSU rRNA gene from XJCLP differed from those of L. infantum and L. tropica. A retrieval from GenBank confirmed that these 394 bp sequence are new gene sequences. CONCLUSION: The primary and secondary structures of SSU rRNA gene from XJCLP, L. infantum, L. tropica were different. 394 bp sequence from SSU rRNA gene of XJCLP is a new gene sequence.

Animals↗
PubMed2000

[Changes of trace elements in cells of lung cancer and cervix cancer before apoptosis and after apoptosis].

The sensitivity of total reflection X-ray fluorescence analysis (TXRF) is higher than normal X-ray fluorescence analysis (XRF). The cells of lung cancer and cervix cancer were researched before apoptosis and after apoptosis employed the method of TXRF on new transformed synchrotron radiation XRF experimental station of new 3W1A beam line which built on Beijing Synchrotron Radiation Facility (BSRF) of BEPC (new detector and spectrometer systems). We acquired their fluorescence spectrum of various elements before apoptosis and after apoptosis. We discovered there were interesting results that changes even remarkable changes of some elemental contents had occurred in these cells before apoptosis and after apoptosis. These alterations of elemental contents have served an inspiration for us: if their regularities of change are found, we will hope that some contributions would be done at the treatments of cancer.

Apoptosis↗
PubMed1999

DNA vaccination with the serine rich Entamoeba histolytica protein (SREHP) prevents amebic liver abscess in rodent models of disease.

Amebiasis remains one of the leading parasitic causes of death worldwide. A vaccine that prevented amebic liver abscess would significantly reduce mortality from this disease. To test the feasibility of a DNA vaccine to prevent amebic liver abscess, we immunized both mice and gerbils with plasmid DNA encoding the serine rich Entamoeba histolytica protein (SREHP). Animals receiving the SREHP DNA vaccine developed both antibody and cell mediated immune responses that recognized amebic trophozoites. A single dose of the SREHP DNA vaccine protected 80% of vaccinated mice and 60% of vaccinated gerbils from developing amebic liver abscess after direct hepatic inoculation of amebic trophozoites. Our study indicates that DNA vaccination with SREHP can provide high levels of protection against amebic liver abscess in animal models of disease.

Animals↗
PubMed1999

Calcium influx through L-type channels is required for selective activation of extracellular signal-regulated kinase by gonadotropin-releasing hormone.

The hypothalamic decapeptide gonadotropin-releasing hormone stimulates mobilization of two discrete pools of calcium in clonal (alphaT3-1) and primary pituitary gonadotropes. A multidisciplinary approach was implemented to investigate the effects of discrete calcium fluctuations on the signaling pathways linking the gonadotropin-releasing hormone receptor to activation of mitogen-activated protein kinases and immediate early genes. Blockade of calcium influx through nifedipine-sensitive voltage-gated calcium channels reduced buserelin-induced activation of extracellular signal-regulated kinase (ERK) and c-Fos while activation of c-Jun N-terminal kinase and c-Jun was unaffected. Inhibition of buserelin-stimulated ERK activity by nifedipine was also observed in rat pituitary cells in primary culture. Direct activation of alphaT3-1 cell L-type calcium channels with the agonist Bay-K 8644 resulted in phosphorylation of ERK and induction of c-Fos. However, simple voltage-induced channel activation did not produce a sufficient calcium signal, since depolarization with 35 mM KCl failed to induce activation of ERK. Depletion of intracellular calcium stores with thapsigargin did not affect buserelin-induced ERK activation. An inhibitor of protein kinase C decreased calcium influx through nifedipine-sensitive calcium channels and phosphorylation of ERK induced by buserelin. Pharmacological inhibition of protein kinase C did not block Bay-K 8644-induced ERK activation. These observations suggest that calcium influx through L-type channels is required for GnRH-induced activation of ERK and c-Fos and that the influence of calcium lies downstream of protein kinase C.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1999

Interleukin-4 weakens host resistance to pulmonary and disseminated cryptococcal infection caused by combined treatment with interferon-gamma-inducing cytokines.

We examined the role of interleukin (IL)-4 in host resistance against infection with Cryptococcus neoformans. First, we examined the effects of a neutralizing anti-IL-4 monoclonal antibody (mAb) on survival of mice infected intratracheally with this fungal pathogen. We also compared the number of live C. neoformans in lungs and brains of treated and untreated mice. Treatment with anti-IL-4 mAb significantly prolonged survival of infected mice and reduced the lung and brain burdens of C. neoformans, which was associated with increased production of IFN-gamma in lungs. In the next experiments, infected mice were treated with two IFN-gamma-inducing cytokines, IL-12 and IL-18, known to enhance protection against infection. We then evaluated the effect of such treatment on the number of live microorganisms and concentration of IL-4 in lungs. These two parameters showed a statistically significant relationship, suggesting a negative regulation of host protection by IL-4. Finally, we examined the effects of IL-4 treatment and administration of neutralizing anti-IL-4 mAbs on host protection against C. neoformans and local production of IFN-gamma in lungs induced by treatment with IL-12/IL-18. The former treatment suppressed host protection and reduced IFN-gamma production, while the latter produced the opposite effects. Our results indicated that IL-4 suppressed the host defense mechanisms against infection with C. neoformans potentiated by IFN-gamma-inducing cytokines probably through the suppression of local production of IFN-gamma.

Animals↗
PubMed1999

Preparative isolation and purification of hydroxyanthraquinones from Rheum officinale Baill by high-speed counter-current chromatography using pH-modulated stepwise elution.

Analytical and preparative high-speed counter-current chromatography was successfully used for the isolation and purification of hydroxyanthraquinones from Rheum officinale Baill (Dahuang) using pH-modulated stepwise elution. Four major components including chrysophanol, emodin, physcion and aloe-emodin were isolated each at over 98% purity.

Anthraquinones↗
PubMed1999

CCR5 HIV-1 coreceptor activity. Role of cooperativity between residues in N-terminal extracellular and intracellular domains.

Human (H-) CCR5 is the primary coreceptor for ENV-mediated fusion by R5 strains of human immunodeficiency virus type 1, whereas mouse (M-) CCR5 lacks this function. An array of 23 H/M-CCR5 hybrids containing increasing amounts of H-CCR5 extending from the N terminus generated by random chimeragenesis had a biphasic pattern of coreceptor activity with JRFL and 89.6, revealing active regions in the N-terminal extracellular domain (N-ED) and at the junction of cytoplasmic loop 3. The M-CCR5 mutant in which divergent residues were replaced with the corresponding H-CCR5 N-ED sequence (NyYTsE) gained coreceptor function in fusion but not infection experiments. A M-CCR5 double mutant with substitution of human sequences for divergent residues from the N-ED and cytoplasmic loop 3 had augmented coreceptor activity in fusion assays and gain of function in infection experiments. The SIV-251 ENV utilized H- and M-CCR5 and variants. Flow cytometric analysis of M-CCR5 mutants and bifunctional receptors composed of CD4 domains fused to M-CCR5 mutants excluded the possibility that differences in coreceptor activity resulted from variations in cell surface expression. These results demonstrate that the coreceptor activity of the H-CCR5 N-ED is modulated by intracellular residues, illustrating the complexity of CCR5 requirements for interaction with ENV.

Amino Acid Sequence↗
PubMed1999

Genomic sequence, structural organization, molecular evolution, and aberrant rearrangement of promyelocytic leukemia zinc finger gene.

The promyelocytic leukemia zinc finger gene (PLZF) is involved in chromosomal translocation t(11;17) associated with acute promyelocytic leukemia. In this work, a 201-kilobase genomic DNA region containing the entire PLZF gene was sequenced. Repeated elements account for 19.83%, and no obvious coding information other than PLZF is present over this region. PLZF contains six exons and five introns, and the exon organization corresponds well with protein domains. There are at least four alternative splicings (AS-I, -II, -III, and -IV) within exon 1. AS-I could be detected in most tissues tested whereas AS-II, -III, and -IV were present in the stomach, testis, and heart, respectively. Although splicing donor and acceptor signals at exon-intron boundaries for AS-I and exons 1-6 were classical (gt-ag), AS-II, -III, and -IV had atypical splicing sites. These alternative splicings, nevertheless, maintained the ORF and may encode isoforms with absence of important functional domains. In mRNA species without AS-I, there is a relatively long 5' UTR of 6.0 kilobases. A TATA box and several transcription factor binding sites were found in the putative promoter region upstream of the transcription start site. PLZF is a well conserved gene from Caenorhabditis elegans to human. PLZF paralogous sequences are found in human genome. The presence of two MLL/PLZF-like alignments on human chromosome 11q23 and 19 suggests a syntenic replication during evolution. The chromosomal breakpoints and joining sites in the index acute promyelocytic leukemia case with t(11;17) also were characterized, which suggests the involvement of DNA damage-repair mechanism.

Alternative Splicing↗
PubMed1999

Separation and purification of isoflavones from Pueraria lobata by high-speed counter-current chromatography.

High-speed counter-current chromatography (HSCCC) was applied to the semipreparative separation and purification of puerarin and related isoflavones from a crude extract of Pueraria lobata. Analytical HSCCC was used for the preliminary selection of a suitable solvent system composed of ethyl acetate-n-butanol-water (2:1:3, v/v/v). Using the above solvent system the preparative HSCCC was successfully performed yielding six relatively pure isoflavones including puerarin from 80 mg of the crude extract in one-step separation.

Chromatography↗
PubMed1999

Protein kinase C delta associates with and phosphorylates Stat3 in an interleukin-6-dependent manner.

Stat3 is activated by phosphorylation on Tyr-705, which leads to dimer formation, nuclear translocation, and regulation of gene expression. Serine phosphorylation of Stat3 by mitogen-activated protein kinase has also been observed in cells responding to epidermal growth factor and shown to affect its tyrosine phosphorylation and transcriptional activity. Serine phosphorylation of Stat3 is also induced by interleukin-6 (IL-6) stimulation, which is shown to be independent of mitogen-activated protein kinase and sensitive to the Ser/Thr kinase inhibitor H7. In this study, we investigated whether protein kinase C (PKC) is the kinase that is induced and responsible for Stat3 serine phosphorylation by IL-6 stimulation and which isoform of PKCs is likely to be involved. Here, we report that Stat3 was specifically associated with PKC delta in vivo in an IL-6-dependent manner in several cell types. Furthermore, Stat3 was phosphorylated by PKC delta in vivo on Ser-727, which could be inhibited either by a specific PKC delta inhibitor or by a dominant-negative mutant of PKC delta. Finally, we showed that the phosphorylation of Stat3 by PKC delta led to a negative regulation of Stat3 DNA binding and transcriptional activity. These results indicate that PKC delta is likely to be the kinase that phosphorylates Stat3 in response to IL-6 stimulation and suggest a possible regulatory role of PKC delta on Stat3 function.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1999

Evidence for both the nucleus and cytoplasm as subcellular sites of pathogenesis in Huntington's disease in cell culture and in transgenic mice expressing mutant huntingtin.

A unifying feature of the CAG expansion diseases is the formation of intracellular aggregates composed of the mutant polyglutamine-expanded protein. Despite the presence of aggregates in affected patients, the precise relationship between aggregates and disease pathogenesis is unresolved. Results from in vivo and in vitro studies of mutant huntingtin have led to the hypothesis that nuclear localization of aggregates is critical for the pathology of Huntington's disease (HD). We tested this hypothesis using a 293T cell culture model system by comparing the frequency and toxicity of cytoplasmic and nuclear huntingtin aggregates. Insertion of nuclear import or export sequences into huntingtin fragments containing 548 or 151 amino acids was used to reverse the normal localization of these proteins. Changing the subcellular localization of the fragments did not influence their total aggregate frequency. There were also no significant differences in toxicity associated with the presence of nuclear compared with cytoplasmic aggregates. These studies, together with findings in transgenic mice, suggest two phases for the pathogenesis of HD, with the initial toxicity in the cytoplasm followed by proteolytic processing of huntingtin, nuclear translocation with increased nuclear concentration of N-terminal fragments, seeding of aggregates and resultant apoptotic death. These findings support the nucleus and cytosol as subcellular sites for pathogenesis in HD.

Animals↗
PubMed1999

Technical and clinical comparison of two fully automated methods for the immunoassay of CA 125 in serum.

The sensitivity and precision of two fully automated enzyme immunoassays, a chemiluminescent enzyme immunoassay (CLEIA) and an enzyme-linked immunosorbent assay (ELISA), for the determination of the ovarian carcinoma antigen CA 125 were evaluated by comparison with an immunoradiometric assay (IRMA). Sera were obtained from patients with ovarian carcinoma (N = 28 before treatment and N = 24 after treatment), digestive system cancer (N = 21 before treatment) and from healthy women (N = 90). The CLEIA showed a good agreement with the IRMA in terms of the positivity rate, accuracy and assay linearity, whereas the ELISA gave some false positive results. The mean value of CA 125 in the sera of healthy women was 14, 16 and 20 U/ml determined using the CLEIA, IRMA and ELISA procedures with standard deviations (SD) of 6.9, 7.3 and 8.8 U/ml, respectively. Both the reproducibility and precision of the CLEIA with coefficients of variation (CV) of 4.6% intra-assay and 7.6% inter-assay were better than those of the ELISA with CV of 6.2% intra-assay and 15.2% inter-assay (N = 16). We conclude that the CLEIA is the preferable method for CA 125 determinations and the diagnosis of ovarian carcinoma.

CA-125 Antigen↗