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Biomedical subjects

X M Tang

Publications and source records attributed to X M Tang.

At least 19 recordsLinked to original sources
PubMed2002

Effects of GnRH analogues, 'add-back' steroid therapy, antiestrogen and antiprogestins on leiomyoma and myometrial smooth muscle cell growth and transforming growth factor-beta expression.

The objective of this study was to elucidate the biological significance of GnRH and antiprogestins and antiestrogen in leiomyoma and their interactions with ovarian steroid 'add-back' therapy. Leiomyoma and myometrial smooth muscle cells (LSMC and MSMC) were isolated and exposed to GnRH agonist (leuprolide acetate, LA), 17beta-estradiol (E2), medroxyprogesterone acetate (MPA), GnRH antagonist (Antide), estrogen antagonist, ICI182780 (Fulvestrant) and progesterone antagonists RU486 (Mifepristone) and ZK98299 (Onapristone) and combinations thereof. The rate of DNA synthesis, cell proliferation and transforming growth factor-beta (TGF-beta) expression were then determined. In both cell types, we found that in a dose-dependent manner, LA inhibited, whereas E2, MPA and the combination of E2 + MPA stimulated, the rate of DNA synthesis in these cells. Antide reversed the inhibitory effect of LA, while LA partly inhibited the stimulatory effect of the steroids. In addition, RU486, ICI182780 and ZK98299 at 0.1 micro mol/l or higher doses inhibited the rate of DNA synthesis and partly reversed the effects of E2 and/or MPA. We also found that LSMC expressed elevated levels of TGF-beta1 compared with MSMC. In both cell types, the effects of LA, E2, MPA, RU, ZK and ICI and combinations thereof on TGF-beta1 production were reflective of their effects on DNA synthesis. In line with this, TGF-beta1 was found to stimulate DNA synthesis and the E2-, TGF-beta1- or E2 + TGF-beta1-induced DNA synthesis was found to be inhibited by TGF-beta1 neutralizing antibodies and/or LA. In conclusion, the results provide further evidence that GnRH agonist- and RU486-induced leiomyoma regression is mediated in part through an interactive mechanism that results in altered cell growth and suppression of TGF-beta production.

Estradiol↗
PubMed2001

Differentiation of glial cells and motor neurons during the formation of neuromuscular junctions in cocultures of rat spinal cord explant and human muscle.

Motor axons extending from embryonic rat spinal cord explants form fully mature neuromuscular junctions with cocultured human muscle. This degree of maturation is not observed in muscle innervated by dissociated motor neurons. Glial cells present in the spinal cord explants seem to be, besides remaining interneurons, the major difference between the two culture systems. In light of this observation and the well documented role of glia in neuronal development, it can be hypothesized that differentiated and long-lived neuromuscular junctions form in vitro only if their formation is accompanied by codifferentiation of neuronal and glial cells and if this codifferentiation follows the spatial and temporal pattern observed in vivo. Investigation of this hypothesis necessitates the characterization of neuronal and glial cell development in spinal cord explant-muscle cocultures. No such study has been reported, although these cocultures have been used in numerous studies of neuromuscular junction formation. The aim of this work was therefore to investigate the temporal relationship between neuromuscular junction formation and the differentiation of neuronal and glial cells during the first 3 weeks of coculture, when formation and development of the neuromuscular junction occurs in vitro. The expression of stage-specific markers of neuronal and glial differentiation in these cocultures was characterized by immunocytochemical and biochemical analyses. Differentiation of astrocytes, Schwann cells, and oligodendrocytes proceeded in concert with the differentiation of motor neurons and neuromuscular junction formation. The temporal coincidence between maturation of the neuromuscular junction and lineage progression of neurons and glial cells was similar to that observed in vivo. These findings support the hypothesis that glial cells are a major contributor to maturity of the neuromuscular junction formed in vitro in spinal cord explant-muscle cocultures.

ATP-Binding Cassette Transporters↗
PubMed2001

The expression and action of granulocyte macrophage-colony stimulating factor and its interaction with TGF-beta in endometrial carcinoma.

OBJECTIVE: Previous studies have demonstrated that normal human endometrium expresses granulocyte macrophage-colony stimulating factor (GM-CSF) and GM-CSF receptors. Because GM-CSF is administer to cancer patients following chemotherapy, GM-CSF may directly or through interaction with ovarian steroids and other cytokines alter the behavior of endometrial cancer. The aim of this study was to determine the expression of GM-CSF and receptors in endometrial carcinoma and its direct effect and interaction with transforming growth factor beta (TGF-beta) on Ishikawa cells, a human endometrial carcinoma cell line. METHODS: GM-CSF, GM-CSF receptors, TGF-beta1, and TGF-beta type II receptor expression were evaluated using quantitative reverse transcription polymerase chain reaction (Q-RT-PCR). The effect of GM-CSF on DNA synthesis, cell proliferation, expression of GM-CSF, TGF-beta1, and TGF-beta receptor, and their regulation by ovarian steroids was determined by the rate of [(3)H]thymidine incorporation, MTT assay, Q-RT-PCR, and ELISA, respectively. RESULTS: Endometrial carcinomas express significantly higher GM-CSF and GM-CSF alpha and beta receptor mRNA compared with normal postmenopausal endometrium. GM-CSF at various doses had no significant effect on the rate of [(3)H]thymidine incorporation or proliferation of Ishikawa cells, whereas TGF-beta1 inhibited [(3)H]thymidine incorporation. GM-CSF and TGF-beta1 regulate their own expression and the expression of TGF-beta type II receptor, which were both upregulated by 17beta-estradiol and medroxyprogesterone acetate treatment and reversed following cotreatment with their respective receptor antagonists. CONCLUSION: Endometrial carcinoma expresses an elevated level of GM-CSF and GM-CSF receptors. GM-CSF is not a mitogen for the endometrial cancer cell line; however, either alone or through interaction with TGF-beta1, it regulates its own expression and the expression of TGF-beta1 and TGF-beta type II receptor which inhabits endometrial cancer cells. This interaction may represent a regulatory feedback mechanism that could serve to suppress endometrial carcinoma growth.

Antineoplastic Agents, Hormonal↗
PubMed2001

p16 gene methylation in colorectal cancers associated with Duke's staging.

AIM: To explore the association of methylation of the CpG island in the promotor of the p16 tumor suppressor gene with the clinicopathological characteristics of the colorectal cancers. METHODS: Methylation-specific PCR (MSP) was used to detect p16 methylation of 62 sporadic colorectal cancer specimens. RESULTS: p16 methylation was detected in 42% of the tumors.Dukes'staging was associated with p16 methylation status.p16 methylation occurred more frequently in Dukes'C and D patients (75.9%) than in Dukes'A and B patients (12.1%). CONCLUSION: p16 methylation plays a role in the carcinogenesis of a subset of colorectal cancer, and it might be linked to poor prognosis.

Colorectal Neoplasms↗
PubMed2000

[Extension of life-span of normal human fibroblasts by reconstitution of telomerase activity].

Most of normal human somatic cells can divide only a finite number of times and inevitably become senescent. Telomerase is an enzyme that imparts replicative immortality by maintaining the length of the telomeres when expressed in reproductive and cancer cells. Cells that are mortal do not express the telomerase. Recently it was reported that the life-span of the normal human cells could be successfully extended by introduction of telomerase into these cells. We have found, in the previous work, that fibroblasts exhibited an osteogentic potential, and therefore, can be considered as a type of "seed cells" in tissue engineering for bone repairing and reconstruction. But this potential was impaired by the limitation in life-span and proliferative capacity of the normal fibroblasts. In the present work, plasmid pGRN145 bearing a cDNA insert of human telomerase reverse transcriptase (hTERT) was introduced into the fibroblasts with osteogenic potential by electroporation. The stable hTERT+ fibroblast clones was established and cultured for long-term in a medium containing hygromycin-B. The exogenous hTERT mRNA expression and telomerase activity were detected. The hTERT+ fibroblasts showed shorter population doubling time and no beta-galactosidase stain, which indicated a stronger proliferative capacity and fewer signs of cell senescence, compared to their hTERT- counterpart. These evidenced that the life-span of hTERT+ fibroblasts was extended. The assays for DNA euploidy by flow cytometry and chromosome karyotype by cytogenetic technique showed no signs of heteroploidy, providing the data for cell carcinogenesis and utilization safety. The results of the present study suggested that the introduction of hTERT could make the life-span of normal fibroblast extended without causing their malignant transformation, and such type of "longevous" fibroblasts might be clinically useful in tissue engineering for bone repairing and reconstruction.

Cells, Cultured↗
PubMed1999

Cell cycle arrest induced by ectopic expression of p27 is not sufficient to promote oligodendrocyte differentiation.

Oligodendrocyte differentiation is accompanied by dramatic changes in gene expression as well as cell cycle arrest. To determine whether cell cycle arrest is sufficient to induce the changes in cell phenotype associated with differentiation, we inhibited oligodendrocyte precursor proliferation in vitro by overexpressing p27, a cyclin kinase inhibitor, using a recombinant adenovirus. Ectopic expression of p27 efficiently inhibited oligodendrocyte precursor cell division, even in the presence of exogenous mitogens, by blocking the activity of the cyclin-dependent kinase, cdk2. Although the cells had stopped dividing, they did not express galactocerebroside (GalC) or myelin basic protein (MBP), changes associated with oligodendrocyte differentiation, suggesting that they had not differentiated. After removal of exogenous mitogens, however, adenovirus-expressing oligodendrocyte precursors differentiated with a temporal profile similar to that of control, uninfected oligodendrocytes, as indicated by expression of GalC and MBP. We conclude that cell cycle arrest is not sufficient to induce differentiation of dividing oligodendrocyte precursors, and that modulation of additional, as yet unknown, signaling pathways is required for this to occur.

Adenoviridae↗
PubMed1999

The convergent point of the endocytic and autophagic pathways in leydig cells.

Endocytic tracers and marker enzyme of lysosomes were used in the present study to analyze the processes of autophagocytosis and endocytosis, and the convergent point of these two pathways in Leydig cells. The endocytic and autophagic compartments can be easily identified in Leydig cells, which makes easier to define the stages of two pathways than was possible before. The evidences indicated that the late endosomes (dense MVBs) deliver their endocytosed gold tracers together with lysosomal enzymes to the early autophagosomes and they are the convergent point of the two pathways. During this convergent process, the early autophagosomes transform into late autophagosomes and the late endosomes transform into mature lysosomes.

Animals↗
PubMed1999

The expression, activity and regulation of granulocyte macrophage-colony stimulating factor in human endometrial epithelial and stromal cells.

The expression of granulocyte macrophage-stimulating factor (GM-CSF) and GM-CSF receptors in the human endometrium suggests an autocrine/paracrine role for GM-CSF in this tissue. Using primary cultures of isolated endometrial glandular epithelial and stromal cells, the present study examined: (i) the cell specific expression of GM-CSF and GM-CSF receptor mRNA and protein; (ii) direct action of GM-CSF on the rate of DNA synthesis and cell proliferation; and (iii) regulation of GM-CSF expression through its interaction with transforming growth factor (TGF)-beta1 in these cells. Quantitative reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay and immunocytochemistry indicates that glandular epithelial and stromal cells express GM-CSF, GM-CSF alpha and GM-CSF beta receptor mRNA and protein. The epithelial cells express a significantly higher level of GM-CSF mRNA than stromal cells while both types produce low concentrations of protein. At 0.01-100 ng/ml GM-CSF did not have a significant effect on the rate of [3H]-thymidine incorporation or proliferation of epithelial and stromal cells. However, GM-CSF (1 ng/ ml) up-regulates its own protein expression, but does not effect TGF-beta1 mRNA protein expression in epithelial and stromal cells, and actually inhibits the cell-associated TGF-beta1 protein in stromal cells (P<0.05). At 1 ng/ ml TGF-beta1 up-regulates its own mRNA and protein expression in epithelial and stromal cells (P<0.05), with no significant effect on GM-CSF expression. Co-treatment of the cells with GM-CSF + TGF-beta1 resulted in an increased production of GM-CSF protein as well as TGF-beta1 mRNA and protein expression by epithelial and stromal cells, compared with untreated controls (P<0,001). In conclusion, the results suggest that GM-CSF is not a mitogenic factor for endometrial glandular epithelial and stromal cells, however, in an interactive manner with TGF-beta1 it regulates its own and the expression of TGF-beta1.

Adult↗
PubMed1999

Regulation of transforming growth factor-beta1 expression by granulocyte macrophage-colony-stimulating factor in leiomyoma and myometrial smooth muscle cells.

Human myometrium and leiomyomas express granulocyte macrophage-colony-stimulating factor (GM-CSF), transforming growth factor-beta (TGFbeta), and their receptors. Overexpression of TGFbeta and, to a limited extent, GM-CSF has been associated with tissue fibrosis throughout the body, including leiomyomas. The objective of the present study was to determine the action of GM-CSF on leiomyoma and myometrial smooth muscle cells (LSMC and MSMC) and examine whether the action of GM-CSF is mediated through the induction of TGFbeta1 expression. Using competitive quantitative RT-PCR and enzyme-linked immunosorbent assay, we found that LSMC express significantly higher GM-CSF messenger ribonucleic acid (mRNA; 0.6 +/- 0.1 x 10(3) copies of mRNA/microg total RNA) and protein (0.75 +/- 0.2 ng/mL) than MSMC (0.5 +/- 0.1 x 10(2) copies of mRNA and 0.45 +/- 0.07 ng/mL protein; P < 0.05). In addition, LSMC expressed significantly higher TGFbeta1 mRNA (1.6 +/- 0.3 x 10(4) copies of mRNA/microg total RNA) than MSMC (2.4 +/- 0.4 x 10(3) copies) and synthesized and secreted more TGFbeta1 protein (1.7 +/- 0.2 vs. 0.5 +/- 0.02 ng/mL); whereas MSMC contained more cell-associated TGFbeta1 (56.2 +/- 1.2 ng/mL) than LSMC (35.2 +/- 1.2 ng/mL; P < 0.05). We found that GM-CSF (0.01-100 ng/mL) has limited mitogenic activity for LSMC but not for MSMC determined by the rate of [3H]thymidine incorporation and cell proliferation assay. However, GM-CSF at 1 ng/mL increased its own production, the expression of TGFbeta1 mRNA, the cell-associated TGFbeta1 protein content in both cell types, and TGFbeta1 released into the culture-conditioned medium of LSMC (P < 0.05). TGFbeta1 also increased its own mRNA and protein expression, but had no effect on cell-associated TGFbeta1 in both cell types (P < 0.05). Cotreatment of LSMC and MSMC with GM-CSF and TGFbeta1 induced changes similar to those produced by GM-CSF in both cells. In conclusion, our data suggest that GM-CSF is not a mitogen for MSMC and LSMC, but it regulates its own expression and the expression of TGFbeta1 by these cells, a regulatory interaction that may account for the GM-CSF-induced tissue fibrosis that occurs in leiomyomas.

Culture Media, Conditioned↗
PubMed1999

Arsenic trioxide induces apoptosis of oesophageal carcinoma in vitro.

The arsenic compounds in traditional Chinese medicine have been recorded to have therapeutic effects on the treatment of psoriasis, syphilis, rheumatosis and a number of malignant tumours. Recent studies showed that arsenic trioxide can induce clinical remission in patients with acute promyelocytic leukemia, including those who have relapsed after retinoic acid treatment. however, the mechanism of how arsenic trioxide targets tumour cells is not clearly understood. We have examined the effects of arsenic trioxide on oesophageal carcinoma cell line EC8712. Our results demonstrated that the growth and survival of tumour cells were markedly inhibited by arsenic trioxide. The half dose effect (ED50) was at the concentration of 1 microM. Electron microscopic study demonstrated that EC8712 tumour cells treated with arsenic trioxide display a typical morphological appearance of apoptosis, including chromatin condensation and fragmentation of the nuclei. In contrast, no apoptotic features were observed in tumour cells without arsenic trioxide treatment. TUNEL assay also showed the biological features of apoptosis in cells treated with arsenic trioxide. Flow cytometry analyses showed that apoptotic peak was identified in arsenic trioxide treated cells but not in the control. Apoptotic cells in arsenic trioxide treated group account for 35% of total cell populations after three days treatment at a dose of 3 microM. In short, our results suggested that the anticancer effect of arsenic trioxide is due, at least in part, to the induction of apoptosis in cancer cells.

Antineoplastic Agents↗
PubMed1998

Changes in the activity of cdk2 and cdk5 accompany differentiation of rat primary oligodendrocytes.

Oligodendrocytes, the myelinating cells of the central nervous system, are terminally differentiated cells that originate through asynchronous waves of proliferation and differentiation of precursors present at birth. Withdrawal from cell cycle and onset of differentiation are tightly linked and depend on an intrinsic program modulated by the action of growth factors. p27 plays a central and obligatory role in the initiation of oligodendrocyte differentiation and cessation of proliferation. In this paper, we have characterized the role of modulation of cdk2 and cdk5 kinase activity during the process of oligodendrocyte precursor differentiation. As rat primary oligodendrocytes differentiate in culture there is a fall in cdk2 activity and a rise in cdk5 activity as well as an increase in the cdk inhibitor, p27 protein. The decline in cdk2 activity is not accompanied by a drop in cdk2 protein level, suggesting that it results from inhibition of cdk2 activation rather than decreased protein expression. Taken together, these data suggest that oligodendrocytes may withdraw from the cell cycle at G1-S transition through inactivation of cdk2 activity, possibly initiated by increasing amount of p27, and that cdk5 may have a role until now unrecognized in the differentiation of oligodendrocytes.

Animals↗
PubMed1998

[Experimental study on the induced-differentiation of human esophageal cancer cells treated with dimethylsulfoxide].

The fact that treatment of leukemia (Acute Promyelocytic Leukemia) with ATRA (All-Trans Retinoic Acid) was so succeeded that it was considered as a good example for tumor therapy. In the treatment of solid tumors by means of induced differentiation, however, has not been yet so broken-through. DMSO (Dimethylsulfoxide) was a common and simple organic compound, which comprised a variety of biological activities. For example, DMSO induced differentiation of leukemia in many reports. However, the effect of DMSO on solid tumors was to be explored further. In the present study, DMSO was used to human esophageal cancer cell lines in vitro in comparison with the classical inducer ATRA. From the view of morphology, cell cycle, growth inhibition, cytokeratin 4 expression, dye transfer and tumorigenecity, the results demonstrated that DMSO as well as ATRA could induce differentiation of human esophageal cancer cells. Interestingly, DMSO was confirmed to be more effective in inducing differentiation of esophageal cancer cells than ATRA. It suggests that DMSO showed some good prospects for the treatment of solid tumors.

Carcinoma, Squamous Cell↗
PubMed1997

Proteolipid protein is necessary in peripheral as well as central myelin.

Alternative products of the proteolipid protein gene (PLP), proteolipid protein (PLP) and DM20, are major components of compact myelin in the central nervous system, but quantitatively minor constituents of Schwann cells. A family with a null allele of PLP has a less severe CNS phenotype than those with other types of PLP mutations. Moreover, individuals with PLP null mutations have a demyelinating peripheral neuropathy, not seen with other PLP mutations of humans or animals. Direct analysis of normal peripheral nerve demonstrates that PLP is localized to compact myelin. This and the clinical and pathologic observations of the PLP null phenotype indicate that PLP/DM20 is necessary for proper myelin function both in the central and peripheral nervous systems.

Adolescent↗
PubMed1997

The expression of transforming growth factor-beta s and TGF-beta receptor mRNA and protein and the effect of TGF-beta s on human myometrial smooth muscle cells in vitro.

In this study we investigated the expression of transforming growth factor-beta (TGF-beta) isoform and TGF-beta receptor mRNA and protein, and the effect of TGF-beta 1-3 on the rate of DNA synthesis and proliferation of human myometrial smooth muscle cells in vitro. To determine these, we utilized primary cultures of myometrial smooth muscle cells, standard and competitive quantitative reverse transcription-polymerase chain reaction (RT-PCR), immunocytochemistry, enzyme-linked immunoassay, radioreceptor assay, [3H] thymidine incorporation and cell proliferation assay. Standard RT-PCR and immunocytochemistry revealed that myometrial smooth muscle cells express TGF beta 1-3 and TGF-beta type I-III receptor (TGF-beta R) mRNA and protein. Quantitative RT-PCR, using an external synthetic RNA standard, indicated that the cells express 10 copies/cell of TGF-beta 1 and TGF-beta 2, less than one copy/cell of TGF-beta 3 and TGF-beta type IR, three copies/cell of type IIIR, and > 200 copies/cell, of TGF-beta type IIR mRNA. The cells also synthesized and released TGF-beta 1 at the rate of 7.8 +/- 0.7 ng/10(6) cells, of which 1.4 +/- 0.2 ng/10(6) cells was in an active form. The rate of [3H] thymidine incorporation or proliferation of subconfluent quiescent smooth muscle cells was not altered by TGF-beta s (0.1-10 ng/ml) under serum-free conditions, nor in the presence of 10% fetal bovine serum (FBS). TGF-beta 1-3 at 0.25-0.5 ng/ml in the presence of 2% FBS, which induces half maximal stimulation of these cells, stimulated the rate (P < 0.05), whereas at higher doses it reduced the rate of [3H]-thymidine incorporation compared to the controls. The effect of TGF-beta was partially reversible using neutralizing antibodies specific to TGF-beta 1, TGF-beta 2 (10 micrograms/ml) or TGF-beta 3 (3-6 micrograms/ml). TGF-beta s had no significant effect on cell proliferation determined by cell counting. The data indicate that human myometrial smooth muscle cells express the necessary components of the TGF-beta system, suggesting an autocrine/paracrine role for TGF-beta s in myometrium.

Animals↗
PubMed1997

Biotin and digoxigenin as labels for light and electron microscopy in situ hybridization probes: where do we stand?

Biotin was recently applied to detect cellular DNA or RNA. In combination with avidin, streptavidin or antibody, it can be conjugated with fluorescent dye, enzyme, ferritin, or gold. However, emphasis has recently been placed on the false-positive results that are obtained when this probe is used, because endogenous biotin may sometimes interfere with specific signals. Digoxigenin appears to be an interesting alternative because it is present exclusively in Digitalis plants as a secondary metabolite. We discuss in this review the efficiency and the respective advantages and disavantages of these two probes for in situ hybridization, mainly at the electron microscopic level.

Biotin↗
PubMed1997

[The immunohistochemical study to comparing PCNA and p53 expression in oral squamous cells carcinoma]

We have studied expression of the PCNA and p53 protein in oral squamous cells carcinoma by ABC immunhistochemical technique,and analyzed the characteristic about clinical pathological parameters and metastasis between them.This result showed PCNA expression were corrected with tumor grading,but not with tumor invasion.There was strong correlation between p53 over expression and tumor invasion and lymph node metastasis.p53 positive tumours have highly lymph node metastasis(60%),but p53 negative tumours have lower(29%).Overexpression of p53 was found to be relatively higher,although not statistically significant in buccal mucosa than in other sites.p53 and PCNA may be an useful indication to the clinician to predict tumour behavior and prognosis.

Journal Article↗
PubMed1996

Refined genetic mapping and proteolipid protein mutation analysis in X-linked pure hereditary spastic paraplegia.

X-linked hereditary spastic paraplegias (HSP) present with two distinct phenotypes, pure and complicated. The pure form is characterized by spasticity and gait difficulties but lacks the additional features (nystagmus, dysarthria, mental retardation) present in the complicated form. The complicated form is heterogeneous, caused by mutations of the L1CAM gene at Xq28 (SPG1) or the PLP gene at Xq22 (SPG2) that is allelic to Pelizaeus-Merzbacher disease (PMD). Since in one kindred (K313) the pure form of HSP was also mapped to Xq22, this raises the issue as to whether a pure form of HSP exists that is allelic to X-linked complicated HSP (SPG2) and PMD. To answer this question, we carried out linkage analysis in a new pedigree with pure HSP (K101) and refined linkage in pedigree K313. The PLP gene was also screened for mutation by direct sequencing and reverse-transcriptase polymerase chain reaction (RT-PCR). In both families, the disease locus mapped to Xq22 with Lod scores at zero recombination of 5.3 for COL4A5 2B6 in K313 and 2.4 for DXS101 in K101. A T to C transition in exon 5 of the PLP gene was identified from affected individuals of K313. This transition causes a Ser to Pro mutation in the major extracellular loop of PLP/DM20. This finding demonstrates that a form of X-linked pure spastic paraplegia, X-linked complicated HSP (SPG2) and PMD are allelic disorders. There was no evidence of mutations in either coding sequences or the intron/exon junctions of PLP in pedigree K101, suggesting that the disease-producing mutation may be in the noncoding portions of PLP or in a nearby gene.

Adult↗