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Biomedical subjects

S Tsai

Publications and source records attributed to S Tsai.

At least 55 records · Page 3Linked to original sources
PubMed1996

Rat kidney glutathione S-transferase 1 subunits have C-terminal truncations.

Cytosolic glutathione S-transferases (GSTs) from rat kidneys were purified by a combination of glutathione and S-hexylglutathione affinity columns. The isolated GSTs were subjected to reverse-phase HPLC and electrospray MS analysis. The major GST isoenzymes expressed in kidney are subunits 1, 2, 7 and 8. GST 1',3 and 4 are expressed in minor amounts. GST 10 is barely detectable in the male kidney cytosol. The molecular masses of these rat kidney GST subunits were determined by MS. The values obtained for subunits 1', 2, 3, 4, 7, 8 and 10 are identical with those obtained for rat liver GSTs. Rat kidney GST 1 consists of three polypeptides, with molecular masses of 25517, 25372 and 24982 Da. Results from peptide mapping, MS and amino-acid-sequencing analyses indicate that the major components were generated by deleting the C-terminal phenylalanine (24982 Da) and the C-terminal IFKF tetrapeptide (25372 Da) from the GST 1 subunit, respectively. The 1-chloro-2,4-dinitrobenzene-conjugating and peroxidase activities of kidney GST 1 are substantially lower than for its counterpart from rat liver. In addition, rat kidney GST 1 has an arginine and a valine residue at positions 151 and 207 respectively. The results are in contradiction with the SWISS-PROT and GenBank rat liver GST 1 cDNA-sequencing data, which give a lysine and a methionine at the corresponding positions. Further analyses indicate that rat liver GST 1 also has a C-terminal phenylalanine deletion, and an arginine and a valine residue at positions 151 and 207 respectively. However, the C-terminal-tetrapeptide-deleted form was not observed for rat liver GST 1.

Amino Acid Sequence↗
PubMed1996

Differential effects of c-fms and c-kit ligands on the lineage development of the lymphohematopoietic cell line EML C1.

The lymphohematopoietic progenitors represent < 0.01% of nucleated marrow cells. We have shown that murine lymphohematopoietic progenitors can be immortalized by a recombinant retroviral vector harboring a dominant-negative retinoic acid (RA) receptor. The immortalized progenitors proliferate as a stem-cell factor-dependent clonal line designated EML C1. The EML C1 cell line spontaneously generates prepro-B-lymphocytes and erythroid and myeloid progenitors. Upon stimulation with interleukin 7 and marrow stromal cells, the prepro-B-lymphocytes express recombination-activating gene 1 (RAG-1) and undergo D-J rearrangements of the immunoglobulin heavy-chain genes. With erythropoietin, the erythroid progenitors proliferate and differentiate into red cells. Generation of the common progenitors for neutrophils and macrophages [colony-forming units-granulocyte-macrophage (CFU-GM)] is suppressed in EML C1 cells but is inducible by high concentrations of RA. An additional block in neutrophil differentiation occurs at the promyelocyte stage, but this can also be overcome by high concentrations of RA. Although c-fms is homologous to c-kit, which encodes the receptor for stem-cell factor (SCF), EML C1 cells neither express c-fms nor respond to macrophage colony-stimulating factor (M-CSF), the ligand for c-fms. Transduction and expression of c-fms cDNA in EML C1 cells confers responsiveness to M-CSF. This finding indicates that c-kit and c-fms share substantially overlapping signal-transduction pathways. However, c-fms-transduced EML C1 cells (EML C1/c-fms cells) exhibit different development patterns when stimulated by SCF alone or by M-CSF alone. When stimulated by SCF alone, EML C1/c-fms cells show mostly erythroid and B-lymphoid development. When stimulated by M-CSF alone, development switches to mostly myeloid (neutrophil and macrophage) development. This observation suggests that c-kit and c-fms must have unique signal-transduction pathways in addition to the common ones.

Animals↗
PubMed1996

Tumor necrosis factor-alpha suppresses the regrowth of fractionated irradiated endothelial cells in vitro.

Cytokines from two sources may affect endothelial cells (ECs) in tumor therapy: endogenously from cells in tumors and exogenously from therapeutic applications. These cytokines could modulate the influence of other therapy on tumor ECs. We use the colorimetric MTT method to assess the growth of irradiated ECs isolated from bovine pulmonary artery (CPAEC) and human umbilical cord vein (HUVEC) treated by cytokines. CPAECs given a single radiation dose of 2.5 to 15 Gy showed a small reduction in viable cells 2 to 3 days post-treatment. Neither tumor necrosis factor-alpha (TNF), interleukin-1 alpha (IL-1), nor interferon-gamma (INF) altered the growth of CPAECs treated by single radiation doses. HUVECs irradiated by a single dose of 12 Gy showed continuous reduction in viable cell numbers while those treated by 3 fractions of 4 Gy in 3 days or 6 fractions of 2 Gy in 3 days began to regrow 7 to 8 days after irradiation. Addition of TNF during the fractionated irradiation period limits the regrowth of HUVECs. Addition of IL-1 does not have the same effect. We have also tested the combined effect of another EC active agent flavone acetic acid (FAA), which has also been shown to stimulate the expression of TNF, with radiation, FAA (200 micrograms/ml) has a greater inhibitory effect on the growth and regrowth of fractionatedly irradiated HUVECs than TNF. These data suggest that TNF or FAA should be explored along with radiotherapy for their anti-tumor effect.

Animals↗
PubMed1996

Noninvasive quantification of dopamine D2 receptors with iodine-123-IBF SPECT.

UNLABELLED: Iodine-123-iodobenzofuran (IBF) is a potent dopamine D2 receptor ligand suited for quantitative receptor studies. The purpose of this study was to evaluate three noninvasive methods of estimating the receptor parameter k3/k4 in humans with IBF-SPECT. METHODS: Scans were acquired every 5 min for 180 min using a triple-headed SPECT system following a bolus injection of IBF (296 +/- 37 MBq) in 14 normal volunteers. k3/k4 was estimated by the peak equilibrium ratio (RPE) method and two proposed methods: a variation of the graphic method that derives the ratio of ligand distribution volumes (RV) and area ratio (RA) method, in which the ratio is calculated from the areas under the specific binding and nondisplaceable activity curves. RESULTS: The mean RPE, RV and RA were 2.74 +/- 0.40, 3.06 +/- 0.42 and 2.26 +/- 0.28, respectively. Both RPE and RA underestimated RV. The relationship between RPE or RA and RV was linear (p < or = 10(-5), RA showed higher correlation (r = 0.94) with RV than did RPE (r = 0.90). Simulations based on a tracer kinetic model showed that RV, unlike RPE or RA, is affected by neither regional cerebral blood flow (rCBF) nor peripheral clearance rate (CR) of IBF. All three measures showed a significant decline with increasing age (r = 0.54-0.58, p < 0.05). CONCLUSION: RV is preferred because it provides a theoretically valid estimate of k3/k4, independently of rCBF or CR. Alternatively, RA might be preferred to RPE because the former is simpler than the latter to implement yet the former provides a measure that equally well correlates with k3/k4.

Adult↗
PubMed1996

Neuropsychologic deficits and clinical features of posttraumatic temporomandibular disorders.

Previous studies have shown that characteristics of posttraumatic temporomandibular disorders (pTMD) differ considerably from those of nontraumatic or idiopathic temporomandibular disorders (iTMD). Both the rate of recovery and the amount of treatment required appear to be different for both groups. In this blinded study, 14 patients with iTMD and 13 patients with pTMD were examined. Patients submitted to a variety of reaction-time tests and neuropsychologic assessments to test their ability to cope with simple and more complex tasks with and without a variety of cognitive interferences. Clinical examination was used to assess signs of TMD. Eleven of the subjects (six iTMD, five pTMD) consented to a second phase of the investigation, whereby the patients were studied with single-photon emission computerized tomography (SPECT) using 99mTc-hexamethylpropyleneamineoxime (HMPAO). For simple and complex reaction-time tests, the pTMD group was significantly slower than the iTMD group (P < .05 to P < .001). Other neuropsychologic assessment tools such as the Consonant Trigram Test and the California Verbal Learning Test indicated that pTMD patients were more affected by both proactive and retroactive interferences and were more likely to perseverate on a single thought. In clinical examination, pTMD patients demonstrated greater reaction to muscle palpation than did iTMD patients (P < .05). The SPECT results suggested that there were mild differences between the two populations, and further ther studies are required to confirm this finding. The results lend support to the concept that there are differences between pTMD and iTMD populations. It is suggested that although patients with pTMD may have some similarities to those with iTMD, the former population may benefit from being handled somewhat differently and should be assessed and treated using a more broad, multidisciplinary treatment paradigm. These results must be confirmed in studies of larger populations.

Accidents, Traffic↗
PubMed1995

Mycoplasmas and oncogenesis: persistent infection and multistage malignant transformation.

Oncogenic potential of human mycoplasmas was studied using cultured mouse embryo cells, C3H/10T1/2 (C3H). Mycoplasma fermentans and Mycoplasma penetrans, mycoplasmas found in unusually high frequencies among patients with AIDS, were examined. Instead of acute transformation, a multistage process in promotion and progression of malignant cell transformation with long latency was noted; after 6 passages (1 wk per passage) of persistent infection with M. fermentans, C3H cells exhibited phenotypic changes with malignant characteristics that became progressively more prominent with further prolonged infection. Up to at least the 11th passage, all malignant changes were reversible if mycoplasmas were eradicated by antibiotic treatment. Further persistent infection with the mycoplasmas until 18 passages resulted in an irreversible form of transformation that included the ability to form tumors in animals and high soft agar cloning efficiency. Whereas chromosomal loss and translocational changes in C3H cells infected by either mycoplasma during the reversible stage were not prominent, the onset of the irreversible phase of transformation coincided with such karyotypic alteration. Genetic instability--i.e., prominent chromosomal alteration of permanently transformed cells--was most likely caused by mutation of a gene(s) responsible for fidelity of DNA replication or repair. Once induced, chromosomal alterations continued to accumulate both in cultured cells and in animals without the continued presence of the transforming microbes. Mycoplasma-mediated multistage oncogenesis exhibited here shares many characteristics found in the development of human cancer.

AIDS-Related Opportunistic Infections↗
PubMed1995

Support versus inhibition of hematopoiesis by two characterized stromal cell types.

Stromal cells are believed to regulate hematopoiesis through direct cell-cell contact interactions and the release of growth factors. Many questions remain, however, about their lineage derivation and functional heterogeneity. We have previously shown that the adherent nontransformed, nonimmortalized murine bone marrow stromal cell population consists of three cell types which could be grown separately in vitro. Based on the phenotype characterization and expression of surface antigens, we proposed a classification listing for murine bone marrow stromal cells as macrophages, endothelial-like cells and myofibroblasts that display smooth muscle-like characteristics in culture. The present study describes the ability of each of these freshly isolated separated murine stromal cell populations to support the growth of primitive hematopoietic stem cells previously characterized as highly enriched in long-term repopulating cells (LTRC). Of the three stromal cell types tested only the myofibroblasts were capable of support for multilineage hematopoiesis derived in vitro from LTRC in a cloning ring culture system. Endothelial-like cells had an inhibitory effect on the proliferation of LTRC and their descendant cells that was induced by exogenous growth factors. This inhibitory activity was present in a low molecular weight filtrate of endothelial-like cells culture medium. This suggests an essential role for marrow stroma myofibroblasts in the support of proliferation of hematopoietic cells at the stage of early divisions of primitive hematopoietic stem cells and endothelial-like cells as negative regulators of this proliferation.

Alkaline Phosphatase↗
PubMed1995

A method of two-dimensional mapping of cortical perfusion by cylindrical transformation of HMPAO SPET data.

In order to synthesize three-dimensional information on relative regional blood flow (rCBF) from the cortical grey matter in 99Tcm-hexamethylpropyleneamine oxime (HMPAO) single photon emission tomographic (SPET) images into a single two-dimensional 'cortical peel' (CP) image, we developed a program that performs cylindrical transformation of SPET data. A sub-routine of this program performs measurements of cortex-to-cerebellum rCBF ratios for 54 cortical regions in the CP image. This program was used to establish a normative database derived from 30 young normal control subjects aged 28.7 +/- 6.9 years. The database was then used to express cortex-to-cerebellum rCBF ratios in four colour-coded ranges of normal standard deviation of the mean rCBF ratio across the cortical regions in the CP image. This CP method was implemented for 30 clinical HMPAO SPET studies in patients (n = 30, aged 71.8 +/- 4.2 years) with suspected dementia as well as several studies in aged healthy subjects (n = 8, aged 67 +/- 9.8 years). In 25/30 (83%) patients, all abnormalities seen on the tomographic display were evident on the corresponding CP image. No aged healthy subjects showed abnormalities on either the tomographic display or the corresponding CP image. An advantage of this technique is that the extent and severity of rCBF abnormalities are readily appreciated in one single image. This technique, in conjunction with the conventional multi-slice tomographic display, was a useful tool in identifying various patterns of rCBF abnormalities in the patients with clinically suspected dementia.

Adult↗
PubMed1995

Biological characteristics of human hepatocellular carcinoma cell lines with or without prior nude mouse passages.

A cell line, J5, derived directly from the human hepatocellular carcinoma (HCC) by in vitro culture, and three other lines, J2-23, J3-27 and J3-28, which were established in culture only after passages in nude mice were examined. Since nude mice as well as various strains of normal mice often produce infectious murine retroviruses, the HCC cells passaged as a heterotransplant in nude mice may be infected with these viruses. The supernatant of the J2-23, J3-27 and J3-28 cell co-cultured with a wild mouse cell line, SC-1, which supports the murine ecotropic retroviruses, showed the presence of a murine N-tropic virus. No murine xenotropic retrovirus was detected in these cells using S+L- mink cell assay method. A clone (J3-28 Clone 1) was derived from the above mentioned J3-28 cells, since the latter contained a mixture of human and murine cells. The J3-28 Clone 1 was found to be entirely of human karyotype. This clone as well as the J5 and the PLC/PRF/5 cel lines which have never been passaged in nude mice, showed none of these murine retroviruses. By Southern-blot hybridization, no change was detectable for c-abl, c-ras, c-mos, and c-myc protooncogenes in the chromosomal DNA of J2-23, J3-27, J3-28 Clone 1, and J5 cell lines. The karyotypes of all the HCC cell lines were aneuploid, and those of the J2-23 and J3-27 cell lines were of mouse, while the J3-28 Clone 1 and J5 cell lines were of human. The chromosomes of the J2-23 and J3-27 cells showed, except for the presence of a few marker chromosomes in the former, no apparent changes in the length were observed. In contrast, those of the J3-28 Clone 1 and J5 cells exhibited various changes, including 6-8 marker chromosomes, and an increase or decrease in the length of p and/or q arms of various chromosomes.

Animals↗
PubMed1994

Lymphohematopoietic progenitors immortalized by a retroviral vector harboring a dominant-negative retinoic acid receptor can recapitulate lymphoid, myeloid, and erythroid development.

The lymphohematopoietic progenitors represent < 0.01% of nucleated marrow cells. Here, we describe the immortalization of the murine lymphohematopoietic progenitors by a retroviral vector harboring a dominant-negative retinoic acid receptor. The immortalized progenitors proliferate as a stem-cell-factor-dependent clonal line EML that spontaneously generates pre-pro-B lymphocytes and erythroid and myeloid progenitors. Upon stimulation with interleukin-7 and stromal cells, the pre-pro-B lymphocytes express RAG-1 and undergo D-J rearrangements of the immunoglobulin heavy-chain genes. With erythropoietin the erythroid progenitors proliferate and differentiate into red cells. Generation of the common progenitors for neutrophils and macrophages is suppressed in EML but is inducible by high concentrations of retinoic acid. An additional block in neutrophil differentiation occurs at the promyelocyte stage but can also be overcome by high concentrations of retinoic acid. These studies demonstrate a reproducible way to immortalize lymphohematopoietic progenitors and implicate specific roles for retinoic acid receptors at two distinct stages of hematopoiesis.

Animals↗
PubMed1994

Dysregulated bcl-2 expression inhibits apoptosis but not differentiation of retinoic acid-induced HL-60 granulocytes.

The bcl-2-proto-oncogene appears to contribute to the development of certain malignancies by inhibiting programmed cell death (apoptosis). Mature granulocytes show a markedly limited life span and rapidly undergo apoptosis. To further define the relationship between apoptosis and granulocyte differentiation, we used retroviral vector-mediated gene transduction to introduce the normal bcl-2 gene into the HL-60 myeloid leukemia cell line and determined the response of these bcl-2-transduced HL-60 cells to the induction of granulocyte differentiation by retinoic acid (RA). Although the bcl-2-transduced HL-60 cells showed the same differentiative response to RA as did the parental HL-60 cells, the life span of the RA-induced, bcl-2-transduced HL-60 granulocytes was markedly prolonged compared with that of the RA-induced parental HL-60 granulocytes. DNA fragmentation studies indicate that this prolonged life span resulted from diminished apoptosis in the bcl-2-transduced cells. These studies indicate that bcl-2 is involved in regulating apoptosis in maturing granulocytes. Because bcl-2 over-expression did not interfere with RA-induced granulocyte differentiation, it appears that granulocyte differentiation and apoptosis are under distinct and separate regulatory controls.

Apoptosis↗
PubMed1993

Interaction of human thyroid hormone receptor beta with transcription factor TFIIB may mediate target gene derepression and activation by thyroid hormone.

The human thyroid hormone receptor beta (hTR beta) is capable of both transcriptional silencing and hormone-dependent activation. However, the detailed mechanism of this transcriptional regulation remains to be elucidated. One possibility is that hTR beta interacts directly with factors of the basal transcriptional machinery, thereby modulating basal promoter activity in a direct manner, as has been shown for other transcription factors. Here, we show that hTR beta interacts specifically with the human basal transcription factor TFIIB. Deletion analysis revealed two contact sites in the receptor: one is located in the N terminus, while the other is part of the ligand-binding domain (LBD) and is located at the C terminus. Interestingly, each receptor contact site interacts with different sites in TFIIB. Cotransfection experiments revealed that, when fused to the DNA-binding domain of yeast transcription factor GAL4, the C-terminal interaction site of hTR beta was transcriptionally inactive; however, when it was cotransfected with the remaining part of the LBD on a separate molecule, silencing function was restored. In agreement with that, we show that thyroid hormone is able to significantly decrease the interaction of its receptor LBD with TFIIB. Our data suggest that hTR beta acts as a transcriptional silencer by interacting with TFIIB and that thyroid hormone may act in part by preventing transcriptional repression at this level.

Actins↗
PubMed1993

A dominant negative retinoic acid receptor blocks neutrophil differentiation at the promyelocyte stage.

We have investigated the roles of retinoic acid receptors in the development of neutrophils by using an interleukin 3-dependent multipotent hematopoietic cell line (FDCP mix A4) as well as normal mouse bone marrow cells. Treatment of the FDCP mix A4 cells with murine granulocyte/macrophage-colony-stimulating factor (GM-CSF) induced these cells to differentiate into neutrophils and macrophages. When the endogenous retinoic acid receptor activity in FDCP mix A4 cells was suppressed by a dominant negative retinoic acid receptor construct, this GM-CSF-induced neutrophil differentiation was blocked at the promyelocyte stage. The blocked promyelocytes proliferated continuously as a GM-CSF-dependent cell line but could be induced to terminally differentiate into neutrophils with supraphysiological concentrations of all-trans-retinoic acid (1-10 microM). The ability of the dominant negative retinoic acid receptor to block neutrophil differentiation at the promyelocyte stage was also demonstrated in normal, primary mouse bone marrow cells. Our results indicate that retinoic acid receptors in conjunction with hematopoietic growth factors play a crucial role in the terminal differentiation of normal neutrophil precursors. The system described here may also serve as a model for studying the pathogenesis of human acute promyelocytic leukemia.

Animals↗
PubMed1993

HLA class II DNA typing in two Brazilian populations.

Brazil constitutes a melting pot of populations arising from three major groups, including Amerindians, Africans, and Europeans predominantly from Portugal who were later supplemented by migrations from other European countries. Although every possible combination of racial mixture exists in Brazil, we have selected for this study two groups of subjects residing in Rio de Janeiro. A predominant White population, among whom some Amerindian admixture may exist, and a predominantly African population having little admixture from the other races. We have used the polymerase chain reaction (PCR) and hybridization with oligonucleotide probes to perform a complete typing of the HLA class II alleles. We report the allele frequencies for HLA-DRB1, DQA1, DQB1 and DPB1. We also report on the postulated DR-DQ haplotypes based on family studies and observations in homozygous B-cell lines. These results may serve as background for various types of clinical studies in Brazilian populations.

Alleles↗
PubMed1993

Taiwanese patient with recurrent polyserositis: report of a case.

A 26-year-old man had suffered from recurrent abdominal pain, ascites and arthralgia since childhood. The symptoms occurred usually during the winter, and each attack lasted for two to three days. Initially, the frequency was about once a year, but it had increased to once every one to four months after an exploratory laparotomy carried out four years ago. Leukocytosis accompanied each episode. Many laboratory examinations and imaging studies failed to show pathologic lesions. Laparoscopic examination revealed only yellowish ascites with a hyperemic mesentery and omentum. There were never any sequelae after the attacks. After prophylaxis with colchicine 0.6 mg three times a day, no more attacks occurred. Familial Mediterranean fever (familial paroxysmal polyserositis) was the most likely diagnosis. Recognizing this disease entity in Taiwanese patients may help to avoid unnecessary operations.

Adult↗
PubMed1993

Cytotoxicity and manganese superoxide dismutase induction by tumor necrosis factor-alpha and ionizing radiation in MCF-7 human breast carcinoma cells.

Both tumor necrosis factor-alpha (TNF) and ionizing radiation cause active-oxygen radical-mediated cell injuries and cell death. Thus cells treated by both TNF and radiation may suffer greater injuries than cells treated by either agent alone. On the other hand, TNF or radiation treatment can stimulate the expression of a mitochondrial superoxide scavenging enzyme, manganese superoxide dismutase (MnSOD), which can lower the cytotoxic effects of both agents. Thus, the induction of MnSOD by radiation may interfere with the cytotoxic action of TNF and vice versa. We used a human breast tumor cell line, MCF-7, to determine the interaction of TNF and radiation on cytotoxicity and MnSOD expression. TNF was found to be more effective as a cytotoxic agent when used before than after radiation treatment. These observations suggest that radiation induced-MnSOD was more effective in reducing the cytotoxic effect of TNF whereas TNF induction of MnSOD was less effective in counteracting the radiation action. Our results not only underscore the different effects of the treatment order of TNF and radiation, but also point to potential implication in the radiotherapy of breast tumors.

Breast Neoplasms↗