Biomedical subjects

Y Geng

Publications and source records attributed to Y Geng.

At least 73 records · Page 4Linked to original sources

PubMed1995

Cytokine regulation of chondrocyte functions.

Regulation of chondrocyte secretory functions and proliferation by cytokines and growth factors is central to cartilage development and maintenance of homeostasis in the mature organism. Depending on the type of extracellular stimulus, chondrocytes can be induced to enter a catabolic matrix degrading or anabolic matrix forming functional program. Interleukin I and transforming growth factor beta are the prototypic stimuli for the catabolic and anabolic program, respectively. Insight into the regulation of chondrocytes by cytokines and growth factors provides the basis for improved concepts of osteoarthritis pathogenesis and new perspectives for therapeutic interventions.

Cartilage↗

PubMed1995

Effects of caffeine or EDTA post-treatment on EMS mutagenesis in soybean.

Seeds of soybean cultivar LD4 were mutagenically treated with EMS (0.3, 0.5, 0.6, 0.9, 1.5 and 1.8%) for 3 h only or plus caffeine (50 mM) or EDTA (1 mM) post-treatment for 5 h. The experimental results indicated that: (1) of the different concentrations of EMS treatment, the M2 mutation frequency induced with 0.6% EMS was the highest (9.7%). When the EMS concentration was over 0.9%, the mutation frequency decreased rapidly. (2) Of the EMS treatments plus caffeine or EDTA post-treatment, the mutagenic effect of 0.6% EMS was the best for inducing morphological variations. Caffeine post-treatment decreased notably the mutation frequency of EMS treatment; when concentrations of EMS were very high (1.5% and 1.8%), mutation frequencies of EDTA post-treatment were still 5.0% and 4.88%, but no mutants were found in EMS treatment or plus caffeine post-treatment. (3) In the M2 mutation spectrum, 11 kinds of mutant types were observed in EMS treatment or plus caffeine or EDTA post-treatment. Relative frequencies of some mutant types (growth period, plant height, grain size, leaf shape and sterility, etc.) were similar among the three treatments, but EDTA post-treatment could change the relative frequencies of yield characteristics (number of pods and grains, grain weight/plant) induced by EMS treatment only.

Antimutagenic Agents↗

PubMed1995

The retinal nerve fiber layer defects in patients with anterior ischemic optic neuropathy.

PURPOSE: To demonstrate the effects of optic nerve ischemia on retinal nerve fiber layer (RNFL) and the associated visual dysfunction. METHODS: 23 patients (25 eyes) with anterior ischemic optic neuropathy (AION) underwent fundus fluorescein angiography (FFA), and then red-free light pictures were taken via SE-40 exceiter filter. All pictures were printed for RNFL analysis. Humphrey central field analysis was conducted. All data obtained from FFA and visual field defects were analysed statistically. RESULTS: The RNFL defects and the corresponding visual field defects were presented in 23 of 25 eyes (92%). The optic disc filling defects, RNFL defects and visual field defects were found to be highly correspondent to each other. The RNFL defects were mainly the local losses of RNFL which were correspondent to the ischemic regions. CONCLUSION: The poor optic disc filling or ischemia can result in the RNFL defects which cause the associated visual dysfunction. Because RNFL defects are irreversible changes, the potential values in predicting the prognosis of visual field defects caused by RNFL damages were suggested.

Female↗

PubMed1995

Tumor suppressor activity of the human consensus type I interferon gene.

Type I interferons have potent antiproliferative activity both in vitro and in vivo, and their tumor suppressor activity has been suggested. A series of eukaryotic vectors containing a synthetic human consensus type I interferon gene (IFN-con1) under the control of different promoters (cytomegalovirus early promoter, murine metallothionein promoter and the Rous sarcoma virus LTR) were constructed and stably transfected into type I IFN-deficient myelogenous leukemic K562 cells. Constitutive expression of IFNcon1 reverted the malignant phenotype, as indicated by loss of tumorgenicity in nude mice. When stably transformed cells were mixed with parental tumor cells, there was retardation of tumor growth. Constitutive expression of IFNcon1 reverted the malignant phenotype in vitro, as indicated by growth inhibition in culture, and reduction in colony formation on soft agar. Furthermore, IFNcon1 gene expression resulted in elevated erythroid differentiation, growth arrest in S phase and induced apoptosis. Thus the presence of an active IFNcon1 gene overcomes the oncogenic potential of K562 by coordinated modulation of cell proliferation, differentiation and programmed cell death, and it acts as a tumor suppressor in vivo.

Animals↗

PubMed1994

In vitro transcription of the TATAA-less mouse thymidylate synthase promoter: multiple transcription start points and evidence for bidirectionality.

The mouse thymidylate synthase (TS) promoter (pTS) lacks a TATAA box and an initiator element, and has multiple transcription start points (tsp) located across a 90-bp region. We have developed an in vitro transcription system for pTS using circular templates and nuclear extracts from HeLa cells or mouse 3T6 fibroblasts. The amount of RNA synthesized and the locations of the tsp were determined by S1 nuclease protection assays. The transcription system reproduced the complex pattern of in vivo tsp, except that the downstream tsp were used preferentially. The reaction temperature, concentrations of DNA template and MgCl2, and incubation time were optimized. The pTS core region contains binding sites for the Sp1 and Ets transcription factors. Inactivation of the Sp1-binding element led to a twofold reduction in transcription and a preferential use of upstream tsp. Inactivation of the Ets-binding element, which reduced promoter activity tenfold in vivo, had only a minor effect in vitro. Addition of a strong initiator element introduced a new tsp, but did not eliminate the complex tsp pattern. To determine if pTS had bidirectional promoter activity, the promoter was inverted and analyzed for transcriptional activity. The inverted promoter was found to initiate transcription at multiple tsp and had approximately the same strength as the normal pTS.

Animals↗

PubMed1994

Monocyte deactivation by interleukin 10 via inhibition of tyrosine kinase activity and the Ras signaling pathway.

Activation of monocytes by bacterial lipopolysaccharides (LPSs) is a central component in the pathogenesis of septic shock syndrome. Interleukin 10 (IL-10) is a potent monocyte-deactivating factor and transcriptionally inhibits LPS-induced expression of proinflammatory mediators. The intracellular signaling pathways of LPS have been only partially characterized and mechanisms of IL-10 signaling remain unknown. We show that LPS activates the protein tyrosine kinase (PTK) p56lyn and that this is associated with tyrosine phosphorylation of the protooncogene product Vav. These events are completely blocked by the tyrosine kinase inhibitor herbimycin A. LPS also increases Ras activation in monocytes. LPS-triggered phosphorylation of mitogen-activated protein kinase is a downstream activation event that is also reduced by herbimycin A. Analysis of the IL-10 effects shows that it completely inhibits the p56lyn tyrosine kinase activation and all other subsequent events in this pathway including Ras activation. The IL-10 effects are selective since it reduced PTK-dependent cytokine mRNA expression but not the PTK independent induction of c-jun and c-fos mRNA in LPS-activated monocytes. These results identify the Ras signaling pathway as a component of intracellular signaling in LPS-stimulated monocytes and define early events in this response as targets of monocyte deactivation by IL-10.

Base Sequence↗

PubMed1994

Transcriptional protein binding domains governing basal expression of the rat luteinizing hormone receptor gene.

The functional importance of specific protein binding domains on transcription within the GC-rich 173-base pair promoter of the luteinizing hormone receptor gene was studied by mutagenesis and gel retardation analysis. Transcription was dependent on the presence of two Sp1 elements in the promoter domain of transfected expressing mouse Leydig tumor cells (mLTC) and nonexpressing Chinese hamster ovary cells. Mutation of two protein binding domains located downstream of the Sp1 elements (M1 and C-box) revealed tissue-specific regulation of promoter activity by each domain. Also, gel retardation studies indicated the presence of multiple trans factors that bind to the C-box and M1 domains. Removal of the AP-2 element from the C-box resulted in mLTC-specific transcriptional activation that may involve an M1/C-box interaction. In addition, competition by overlapping NF-1 and AP-2 elements was demonstrable in both the C-box and upstream R domain for separate trans factors that exhibit neutral or inhibitory functions, respectively. Competition between the inhibitory and neutral DNA binding factors within both upstream and promoter domains may be responsible for a mechanism that controls the on/off state of luteinizing hormone receptor gene expression in gonadal cells. These studies reveal a complex pattern of transcriptional regulation that may reflect targeted mechanisms for the control of luteinizing hormone receptor gene expression.

Animals↗

PubMed1994

Differential expression of scavenger receptor isoforms during monocyte-macrophage differentiation and foam cell formation.

Scavenger receptors mediate binding and uptake of chemically modified lipoproteins. cDNA cloning of the human macrophage scavenger receptor (MSR) reveals the presence of two mRNA species, the type I and II isoforms, which are generated by 3' alternative splicing of a single MSR gene and translated into two proteins with different C-terminal domains. We studied MSR isoform expression during the differentiation from circulating monocytes to adherent macrophages and subsequently to lipid-laden foam cells. Differentiation from monocyte to macrophage was associated with a prominent increase in MSR expression on the mRNA, protein, and cell surface levels, leading to an increased uptake of acetylated low-density lipoprotein (LDL). Further analyses of mRNA and proteins revealed that both MSR isoforms were present in low and approximately equal amounts on the surface of CD14+ peripheral blood monocytes; these cells had approximately similar levels of type I and type II MSR mRNA species. During differentiation to macrophages, there was a rapid, selective increase in type I MSR mRNA, with type II mRNA being expressed at approximately the same level as in the monocyte. This, in turn, resulted in an increase in type I MSR protein on the cell surface during differentiation from monocyte to macrophage. Type I MSR mRNA also dominated during the transformation of macrophages to foam cells in the presence of acetylated LDL. These findings suggest that the increased uptake of modified LDL during differentiation from monocyte to macrophage is accomplished by a selective upregulation of type I MSRs on the mRNA level. The increased expression of type I MSRs may be important for foam cell formation.

Base Sequence↗

PubMed1994

[Effect of the changes of amino acids on both signal peptide C-terminal and mature protein N-terminal region to the secretion of alpha-amylase in B. subtilis].

By site-directed mutagenesis, G and C have taken the place of T and G at nucleotide sequence 287 and 291 of B. licheniformis alpha-amylase gene to generate pAm-y413B and the N-terminal sequence of mature protein have been changed from 7Leu 8Met to 7Arg8Ile. By the insertion of polylinker into the C-terminal of the signal sequence of alpha-amylase gene of pAmy413, the signal peptide of alpha-amylase produced by pAmy413L is 13 amino acids more than the pAmy413 (which is 29 amino acids long) and also, a new recognition cleavage sequence for signal peptidase I (Ala-Gln-Ala decreases Ser) is created; The secondary structure of the signal peptide has been analyzed by computer programs. The alpha-amylase relative activity of the two mutant strains is 3% and 36% of pAmy413, respectively. The molecular weight of extracellular alpha-amylase is the same as pAmy413. Terminal analysis shows that the N-terminal amino acid of mature protein is Ala, not Ser, and suggests that SPase I prefers to cleavage at the wild type recognition site (Ala-Ala-Ala decreases Ala). Therefore, all of the above results show that the secretion of alpha-amylase in B. subtilis is in accordance with the co-translational transportation model.

Amino Acid Sequence↗

PubMed1993

Protein tyrosine kinase activation is required for lipopolysaccharide induction of cytokines in human blood monocytes.

Bacterial LPS induce production of cytokines such as IL-1, IL-6, and TNF in mononuclear phagocytes, and this represents a central component in the pathogenesis of septic shock syndrome. However, the mechanisms by which LPS activates these cells to express cytokines are not completely characterized. The present study addressed the role of different protein kinases in the LPS induction of cytokines. It is shown that LPS induced a 12- to 16-fold increase in IL-1 beta, IL-6, and TNF-alpha mRNA levels, and this was completely or more than 80% blocked by the protein tyrosine kinase specific inhibitors herbimycin A and genistein at the concentrations of 1.7 and 37 microM, respectively. Protein kinase C inhibition by staurosporine reduced LPS induction of TNF-alpha, whereas it had no effects on IL-6 and IL-1 beta. Inhibition of protein kinase A by H89 reduced IL-6 mRNA levels but did not detectably change IL-1 beta or TNF-alpha mRNA levels. In contrast, LPS did not increase leukemia inhibitory factor mRNA, which was constitutively expressed and not significantly reduced by these inhibitors. In addition to cytokine mRNA levels, LPS-induced IL-6 protein synthesis and IL-6 bioactivity were also reduced to baseline levels by the PTK inhibitors herbimycin A and genistein. Both PTK inhibitors also reduced the LPS activation of nuclear factor-kappa B (NF-kappa B), which is a transcription factor involved in the expression of cytokine genes such as IL-6 and TNF-alpha. The activation of NF-kappa B was also reduced by H89, whereas staurosporine had no effect on this response. In summary, these findings suggest that protein kinase C and protein kinase A appear to have selective effects in the LPS induction of cytokines, whereas PTK is required for LPS induction of a broad spectrum of cytokines and NF-kappa B activation in monocytes.

Base Sequence↗

PubMed1993

Transforming growth factor beta effects on expression of G1 cyclins and cyclin-dependent protein kinases.

Transforming growth factor beta 1 (TGF-beta 1) is a potent growth-inhibitory polypeptide. The mechanism of TGF-beta 1 inhibition has been related to its ability to prevent the hyperphosphorylation of retinoblastoma protein (pRb). Several lines of evidence have suggested that cell cycle-regulated protein kinases are responsible for the hyperphosphorylation of pRb. We demonstrate here that TGF-beta 1 has profound effects on the expression of genes encoding certain G1 cyclins and their associated kinases, which provides one explanation of TGF-beta 1 effects on pRb hyperphosphorylation. These results also suggest that the growth-inhibitory effects of TGF-beta 1 in many cells are attributable to its effects on the cell cycle apparatus involved in programming G1 transit.

Blotting, Northern↗

PubMed1993

Mapping of a liver phosphorylase kinase alpha-subunit gene on the mouse X chromosome.

Phosphorylase kinase (PHK) is a regulatory enzyme of the glycogenolytic pathway composed of a complex of four subunits. We recently mapped the muscle alpha-subunit gene (Phka) to the mouse X chromosome in a region syntenic with the proximal long arm of the human X chromosome and containing the human homologue of this gene, PHKA. We now report the mapping of the liver alpha-subunit gene to the telomeric end of the mouse X chromosome. This mapping position would suggest a location for the human liver alpha-subunit gene on the proximal short arm of the X chromosome, a region recently implicated in X-linked liver glycogenosis (XLG).

Animals↗

PubMed1993

Regulation of interleukin-6 (IL-6) expression: evidence for a tissue-specific role of protein kinase C.

The regulation of IL-6 mRNA expression was studied in human blood monocytes and in the human epidermoid carcinoma cell line HEp-2. In human monocytes phorbol-12-myristate 13-acetate (PMA) did not induce IL-6 but it increased IL-1 beta and IL-8 mRNA levels. Furthermore, in monocytes, protein kinase C (PKC) activation by PMA even reduced IL-1-induced IL-6 mRNA, and IL-1-induced IL-6 synthesis was increased by the PKC inhibitor staurosporine. IL-6 synthesis in HEp-2 cells was induced by IL-1, PMA, and calcium ionophore A 23187 but not by dibutyryl-cAMP. PMA-, but not IL-1-induced IL-6 synthesis in HEp-2 cells was inhibited by staurosporine. PMA pretreatment of HEp-2 cells abolished PMA-induced IL-6 but the IL-1 effect was not reduced. These data indicate that IL-6 can be induced by a PKC-independent pathway in monocytes and HEp-2 cells. In monocytes PKC activation does not induce IL-6 and PMA interferes with the IL-1 effect. Transcription factors known to be involved with the regulation of IL-6 expression were studied by gel retardation assays. NF-IL-6 and AP-1 activity were constitutively expressed in monocytes and HEp-2 cells under conditions where IL-6 mRNA was not detectable and levels did not change in response to stimulation by IL-1 or PMA. In contrast, NF-kB was increased by both IL-1 and PMA, but only the effect of PMA, and not that of IL-1, was inhibited by staurosporine. In summary, these results show tissue-specific differences in the regulation of IL-6 expression. Induction of IL-6 in monocytes is PKC independent. In the epithelial cell line HEp-2 IL-6 is inducible by PKC as well as by a PKC-independent pathway.

Alkaloids↗

PubMed1993

Lack of an initiator element is responsible for multiple transcriptional initiation sites of the TATA-less mouse thymidylate synthase promoter.

The mouse thymidylate synthase promoter lacks a TATA box and initiates transcription at many sites across a 90-nucleotide initiation window. We showed previously that wild-type promoter activity is maintained with a promoter that extends only 13 nucleotides upstream of the first start site. G/A-rich and G/C-rich promoter elements were identified in the vicinity of the first transcriptional start site. The goals of the present study were to determine whether there are additional promoter elements in the initiation window and to determine why transcription initiates across such a broad region. Minigenes containing a variety of substitution, deletion, and insertion mutations in the promoter region were transfected into cultured cells, and the effects on expression and the pattern of start sites were determined. The results indicate that there are no additional promoter elements downstream of the G/C box. The boundaries of the transcription window are established by elements near the 5' end of the window, whereas the pattern of start sites is determined by sequences within the window. The promoter lacks an initiator element. When an initiator element was inserted, transcription initiated predominantly at the position directed by the initiator when it was inserted within the initiation window but not when it was inserted immediately upstream of the window.

Animals↗

PubMed1993

Induction of cytokine expression by leukemia inhibitory factor.

Biological effects of cytokines are in part determined by their interactions in the regulation of cytokine production. This study analyzes the effects of leukemia inhibitory factor (LIF) on cytokine expression in different cell lineages. Recombinant human LIF increases levels of IL-1 beta, IL-6, and IL-8 mRNA in human articular chondrocytes as demonstrated by Northern blotting. These cytokine mRNAs are detectable as early as 1.3 h after stimulation and reach their maximum after 5 h. The LIF effects are dose dependent and of similar magnitude to those of IL-1. By metabolic labeling and immunoprecipitation it is shown that LIF induces synthesis and secretion of IL-6. IL-6 bioactivity in conditioned media, as measured by the B9 hybridoma proliferation assay, is increased by LIF. Effects of LIF on cytokine expression are not confined to connective tissue cells. By PCR it is shown that human blood monocytes express IL-6 mRNA after stimulation with LIF. An increase in IL-6 mRNA levels is detectable 2 h after stimulation, and this starts to decline by 5 h. The response is of shorter duration as compared with IL-1 beta. In addition to increased mRNA expression, LIF also stimulates release of biologically active IL-6 from blood monocytes. In synoviocytes and neuronal as well as epithelial cell lines, LIF increases IL-1 beta and IL-6 gene expression. In summary, LIF induces cytokine expression in a wide variety of tissues. These results suggest that through the induction of cytokines, LIF can modulate inflammation, immune responses, and connective tissue metabolism, and act as a pathogenetic mediator in different disease states.

Cartilage, Articular↗

PubMed1993

[Construct of the stable-produced strain for the thermostable alpha-amylase].

The plasmid pE194 as a vector is used to subclone the thermostable alpha-amylase gene of B. licheniformis and construct recombinant plasmid pNW102. The plasmid pNW102 was transduced into B. subilis BF 7658 by bacteriophage PBS1. The B. subtilis BF7658 (pNW102) strain was treated at non-permissive temperature for a long time, and obtained many recombinant strains. This is the homologous recombination results between alpha-amylase genes of pNW102 and BF7658. The homologous recombination occurs at any site in alpha-amylase gene but there are some heat-spots. We have already screened 2 strains from the recombination strains which can stably produce the thermostable alpha-amylase in B. subtilis BF7658. The analysis of enzymology shows that the characters of the thermpstable alpha-amylase produced from the recombinants strains are the same with that of B. licheniformis.

Bacillus subtilis↗

PubMed1992

Activation of bovine immunodeficiency-like virus expression by bovine herpesvirus type 1.

Bovine immunodeficiency-like virus (BIV) is a recently identified lentivirus that infects cattle. The virus has structural and genetic similarities to human HIV. The present study demonstrates that BIV can be activated by bovine herpesvirus type 1 (BHV-1), a pathogen frequently associated with cattle diseases. Activation of BIV expression can be detected as increased BIV reverse transcriptase activity, increased in the number of syncytia induced by BIV, and increased in the steady state level of BIV-specific RNA upon BHV-1 super-infection. Additional transactivation studies using the BIV-LTR (long terminal repeat) were conducted. The BIV-LTR was linked to the chloramphenicol acetyl transferase gene (CAT) and transfected into bovine cell cultures in order to quantitate the levels of BIV-LTR expression. When the transfected cells were infected by BHV-1, there was an increase in CAT expression, indicating transactivation of the BIV-LTR by BHV-1. Most of the transactivation activities were abolished with an LTR construct that has deleted the NF-kappa B-like sequence located in the U3 region of the LTR. In order to further demonstrate that activation of the BIV-LTR involves factors that may bind to the LTR sequences, gel retardation assays were carried out using the BIV-LTR U3 region as probe. Our results showed that BHV-1 infection resulted in an induction of factor(s) that binds to the NF-kappa B-like sequence on the BIV-LTR. This suggests that transactivation of BIV by BHV-1 may be mediated by a bovine NF-kappa B-like protein that binds to the target sequence in the BIV promoter region.

Animals↗

PubMed1992

Interferon-gamma and tumor necrosis factor synergize to induce nitric oxide production and inhibit mitochondrial respiration in vascular smooth muscle cells.

Nitric oxide (NO) is an important signal substance in cell-cell communication and can induce relaxation of blood vessels by activating guanylate cyclase in smooth muscle cells (SMCs). NO is synthesized from L-arginine by the enzyme NO synthase, which is present in endothelial cells. It was recently shown that SMCs may themselves produce NO or an NO-related compound. We have studied NO production and its effects on energy metabolism in cultured rat aortic smooth muscle cells. It was observed that the cytokines, interferon-gamma and tumor necrosis factor-alpha, synergistically induced an arginine-dependent production of NO in these cells. This was associated with an inhibition of complex I (NADH: ubiquinone oxidoreductase) and complex II (succinate: ubiquinone oxidoreductase) activities of the mitochondrial respiratory chain, suggesting that NO blocks mitochondrial respiration in these cells. Lactate accumulated in the media of the cells, implying an increased anaerobic glycolysis, but there was no reduction of viability. An NO-dependent inhibition of mitochondrial respiration and a switch to anaerobic glycolysis would reduce energy production of the SMCs. This would in turn reduce the contractile capacity of the cell and might represent another NO-dependent vasodilatory mechanism. It could be of particular importance in inflammation, since cytokines released by inflammatory cells may induce autocrine NO production in SMCs.

Animals↗