Biomedical subjects

J F Chiu

Publications and source records attributed to J F Chiu.

At least 19 recordsLinked to original sources

PubMed1995

Daily rhythm of cell proliferation in the teleost retina.

To determine whether the number of cell divisions in the teleost retina exhibited a regular daily variation, we labeled dividing cells with an antibody to proliferating cell nuclear antigen. The number of dividing rod precursor cells in the outer nuclear layer of the retina were counted in retinas from the telost fish Haplochromis burtoni, sacrificed at 4-h intervals during a standard light-dark cycle and in constant darkness. These rod precursor cells exhibited a striking rhythm of cell division. The highest number of cell divisions (acrophase) was found to occur at night when it was approximately 3 times higher than during the day. The observed rhythm persisted in animals held in constant darkness. We suggest that this endogenous 24-h rhythm of rod precursor cell division may be controlled by a circadian clock. Although there are several examples of continuously proliferating cell populations which exhibit circadian or diurnal rhythms, this appears to be the first documentation of a rhythm of division in cells destined to become neurons.

Animals↗

PubMed1994

cis-acting elements in 5'-flanking region of rat alpha-fetoprotein mediating retinoic acid responsiveness.

A distal RA responsive cis-acting element has been identified in the 5'-flanking region of the alpha-fetoprotein gene by transfection of different deletion mutants of AFP-CAT fusion gene. The retinoic acid receptor specifically binds to this RA responsive cis-acting element in mobility shift assays. Furthermore, this cis-acting element functions in exogenous TK promoter in transient cotransfection assays. This study suggests a role for the RA responsive cis-acting element in the RA induction of alpha-fetoprotein gene expression.

Animals↗

PubMed1994

Transactivation and repression of the alpha-fetoprotein gene promoter by retinoid X receptor and chicken ovalbumin upstream promoter transcription factor.

Retinoic acid (RA) is widely involved in the control of cell proliferation and differentiation, as well as embryo pattern formation. Transcription of the oncodevelopmental protein, alpha-fetoprotein (AFP), is stimulated by retinoic acid (RA) in neoplastic cells. To study RA regulation of AFP gene expression, the 5'-flanking region of AFP gene was cloned and analyzed. In the present study, transfection of deletion mutants and sequence analysis revealed a retinoid X receptor response element (AFP-RXRE) located at position -139 to -127 of the AFP promoter. Synthetic AFP-RXRE was ligated into a reporter construct with the heterologous promoter and chloramphenicol acetyltransferase (CAT). AFP-RXRE conferred a marked RA responsiveness in the cotransfection with retinoid X receptor (RXR), but not with retinoic acid receptors (RARs). Consistent with these data, only RXR bound to AFP-RXRE with high affinity in the mobility shift assays. Chicken ovalbumin upstream promoter transcription factor (COUP-TF), an orphan member of the steroid/thyroid hormone superfamily, also demonstrated specific binding activity to AFP-RXRE in vitro. In cotransfection assays, COUP-TF dramatically repressed the transactivation of RXR on AFP-RXRE. The mechanism of repression by COUP-TF may involve the mutual occupancy of the AFP-RXRE binding site between RXR and COUP-TF.

Animals↗

PubMed1994

Differential regulation of tissue transglutaminase in rat hepatoma cell lines McA-RH7777 and McA-RH8994: relation to growth rate and cell death.

Close correlation between tissue transglutaminase (tTG) induction and growth regulation and/or cell death processes has been suggested in many cell lineages. In this study, the regulation of the tTG levels by various growth and differentiation factors and its relation to growth rate and cell death processes were investigated in two rat hepatoma cell lines, McA-RH7777 and McA-RH8994, using a monoclonal antibody against liver tTG. Transforming growth factor-beta 1 (TGF-beta 1) and retinoic acid (RA) each increased tTG to the level of 8- to 32-fold above that of control cultures in both cell lines after 72-h treatment. Dexamethasone (DEX) induced a 16- to 32-fold of tTG in McA-RH8994 cells while it did not change the enzyme level in McA-RH7777 cells. Simultaneous addition of DEX and RA increased the tTG level to more than 50-fold in McA-RH7777 cells as well as McA-RH8994 cells. Other factors, such as TGF-alpha, hepatocyte growth factor, dimethyl sulfoxide, and protein kinase C activator, did not show significant increases of the tTG levels. Although tTG induction by TGF-beta 1 or DEX appeared to be correlated with their growth suppressive effects, RA increased the tTG level without suppressing the growth rate of hepatoma cells. TGF-beta 1 was also shown to induce cell death in both cell lines. Our results demonstrate that RA and DEX are capable of modulating the TGF-beta 1-induced cell death processes independent of the tTG levels. We present evidence here that tTG induction by itself is not the direct cause of growth suppression and cell death in these hepatoma cells.

Animals↗

PubMed1994

Identification of a retinoic acid response element upstream of the rat alpha-fetoprotein gene.

Retinoic acid (RA) is known to have potent effects on development and differentiation. alpha-Fetoprotein (AFP), an oncodevelopmental protein, is transcriptionally activated by RA in several cell lines, but little is known about the mechanism of RA regulation of AFP gene expression. In the present study, we have identified a RA response element (RARE) in the 5'-flanking region of the AFP gene. Using deletion mapping, the RARE was located between -6337 to -6266 of the rat AFP 5'-flanking region, which confers RA responsiveness in a heterologous promoter. Further sequence analysis of this cis-acting element demonstrated a RARE direct repeat sequence of AGGTCA and RARE-like motifs at -6327 and -6319, respectively. This far upstream RARE (AFP-RARE1) can specifically bind to both RAR and RXR proteins in gel mobility shift assays. In co-transfections with RAR alpha, beta, gamma and RXR alpha expression vectors, a reporter gene construct consisting of the AFP-RARE1 sequence ligated upstream of the chloramphenicol acetyltransferase (CAT) gene showed strong RA responsiveness to RAR alpha and RXR alpha with 15- and 25-fold increases in CAT activity, respectively. Furthermore, responsiveness of AFP-RARE1 to RA was independent of orientation. These studies present a novel target for RA action by identifying a RARE in the AFP gene.

Animals↗

PubMed1993

Induction of apoptosis by transforming growth factor-beta 1 in the rat hepatoma cell line McA-RH7777: a possible association with tissue transglutaminase expression.

We report here that transforming growth factor-beta 1 induces cell death in the Morris hepatoma cell line McA-RH7777. We assessed the type of cell death induced by transforming growth factor-beta 1 in this hepatoma cell line on the basis of morphological and biochemical characteristics. Dying cells, which detached from the cell monolayer, showed morphological characteristics of apoptosis (programmed cell death) such as chromatin condensation, nuclear disintegration and cellular fragmentation into clusters of eosinophilic globules. DNA isolated from these cells showed a ladder pattern consisting of multimers of 180 to 190 bp, indicating extensive DNA cleavage into oligonucleosomal units by an endogenous endonuclease. Treatment of the dead cells with detergents and chaotropic agents resulted in formation of insoluble shells, so-called apoptotic bodies, suggesting extensive cross-linking of cell proteins by tissue transglutaminase. Furthermore, increased amounts of cytosolic tissue transglutaminase, which has been recognized as a possible marker of apoptosis, and extensive cross-linking of cytokeratin polypeptides was demonstrated in TGF-beta 1-treated hepatoma cells on immunoblot analysis. These results provide strong evidence that the cell death induced by TGF-beta 1 in McA-RH7777 hepatoma cells is mainly apoptotic. It also suggests that a specific induction of the cytosolic tissue transglutaminase may be involved in the TGF-beta 1-induced pathways of apoptotic cell death in McA-RH7777 hepatoma cells.

Animals↗

PubMed1993

Cross-linked cytokeratin polypeptides in liver and hepatoma cells: possible association with the process of cell degeneration and death.

We investigated transglutaminase-induced cross-linking of cytokeratin polypeptides in liver and hepatoma cells. To overcome the difficulties in the biochemical analysis of highly cross-linked polymers and aggregates of cytokeratins, cross-linked cytokeratin dimers were analyzed by immunoblotting to evaluate the degree of cross-linking of cytokeratins. Covalently cross-linked cytokeratin dimers were not detectable in normal rat liver cells. However, cytokeratin dimers and high-molecular-weight cytokeratin polymers were detected in liver tissue with histological evidence of coagulative necrosis induced by ischemia or carbon tetrachloride. Treatment of cultured hepatoma cells with the Ca2+ ionophore A23187 showed a dose-dependent, time-dependent decrease of cell viability. The appearance of cytokeratin dimers was shown to be correlated with cell death. These results suggest that the transglutaminase-induced cross-linking of cytokeratin polypeptides in liver and hepatoma cells is closely associated with the process of cell degeneration and death.

Animals↗

PubMed1993

[An investigation on public awareness, attitude and behavior toward drinking water quality in Taiwan].

The objective of this study was to investigate the public awareness, attitude and behavior toward drinking water quality. The results showed that (1) Overall, 80.6% of those responding to the survey rated their local drinking water quality as above average or better. (2) Even though most people were happy with the present quality of their drinking water, 79.2% of the public characterized themselves as concerned about encountering substances in drinking water in their lifetime that could lead to bad health effect or death. (3) 73.8% of the survey respondents never examined the water facilities for their own use.

Adult↗

PubMed1993

[Workplace risk factors associated with eye syndrome in office workers].

Four large sealed office buildings were investigated to determine the relationship between the prevalence of sick building syndrome and the indoor air quality. Questionnaires were distributed to all building occupants. Respondents suffered from upper airway, eye, lower airway and many less specific complaints. Multivariate logistic regression analyses were conducted to assess workplace risk factors associated with eye syndrome. Working with visual display terminals, glare, use of desk lamp, fabric-covered partitions, new carpet, too dim, too bright and lack of openable windows correlated significantly with the prevalence of eye syndrome.

Adult↗

PubMed1993

Demonstration of extensive chromatin cleavage in transplanted Morris hepatoma 7777 tissue: apoptosis or necrosis?

Cell death may occur by either of two mechanisms: necrosis or apoptosis (programmed cell death). In this paper, we demonstrate extensive chromatin cleavage into oligonucleosome-length fragments (DNA ladder) in transplanted Morris hepatoma 7777 tissue, which is suggestive of the stimulation of an endogenous endonuclease activity previously found to be involved in the process of apoptosis. The existence of many apoptotic cells, which are morphologically characterized by condensed cytoplasm and basophilic nuclear fragments, were also seen in this tissue. In vivo and in vitro experiments were designed to further differentiate the morphological and biochemical features of necrosis and apoptosis in liver and hepatoma cells. Liver tissue undergoing ischemic necrosis showed a distinct DNA ladder pattern without demonstrating the morphology of apoptosis, indicating that chromatin cleavage into oligonucleosomal-length fragments is not confined to apoptotic cell death, at least in liver cells. In in vitro-cultured McA-RH7777 cells, however, DNA ladder pattern was detected only in cells showing characteristic morphology of apoptosis. From these two criteria (i.e., characteristic morphology and DNA ladder), it was strongly suggested that the apoptotic process is highly activated in the transplanted 7777 tissue. Based on the results obtained from in vitro experiments, it was suggested that tumor apoptosis may represent a residual attempt at autoregulation within the expanding tumor population and/or may result from mild cellular injuries such as hypoxia, nutrient deficiency, or other unknown noxious factor(s). We also showed evidence that apoptosis is inducible in hepatoma cells in vitro by a wide range of mild injuries or stimuli.

Animals↗

PubMed1992

Hepatitis B virus DNA integration and expression of an erb B-like gene in human hepatocellular carcinoma.

Southern blot studies on Hepatitis B Virus (HBV) DNA integration in 13 human hepatocellular carcinomas (HCCs) patients revealed the presence of several distinct HBV integration sites in different human liver disease patients. In one HCC patient the DNA fragment containing the HBV integration also hybridized to an erb B probe. The erb B/HBV co-migrating DNA fragment was cloned and sequenced, and showed that HBV DNA is integrated next to a cellular DNA fragment which is homologous to the tyrosine protein kinase domain of the human epidermal growth factor receptor gene and other cell surface receptor genes. The virus-integrated cellular DNA sequence is expressed in this HCC patient, suggesting a possible role for this gene in hepatocarcinogenesis.

Adult↗

PubMed1992

Strategies for blood screening for the hepatitis C virus and for the human immunodeficiency virus in high risk groups.

For many infectious agents, seroprevalence rate is low but has serious consequences and must therefore be kept out of donated blood supplies. However, screening to ensure the safety of blood supplies has an associated very high cost. For example, in blood banks, detection of all the harmful items in a large number of samples is an expensive and tedious process. The laboratory and statistical approaches to obtain significant savings by the pooling method were discussed from 1943, recently, there have been further discussions of pooling sera as a means to determining the HIV seroprevalence rate in the general population or the weed out all HIV-positive individuals in blood screening. Here we describe a simple mathematical method to weed out all HIV, and HCV seropositive units. The method is designed to maximize possible savings. Two examples illustrate the application of this method in determining the number to be pooled in each stage, and the resulting savings. When the prevalence rate is lower than 2 percent. our method offers savings of over 80 percent.

Blood Donors↗

PubMed1992

Expression of c-fos in human and murine multidrug-resistant cells.

In both mouse sarcoma 180 and human KB cells selected for the multiple drug resistance (MDR) phenotype, there is an elevation in the steady state mRNA level of c-fos. There is no detectable gene amplification for c-fos, nor is there any significant change in the rate of mRNA transcription or degradation, suggesting that other factors are responsible for the increased expression level in resistance. Cells selected for resistance to methotrexate, a drug not in the MDR group, do not have an increase in c-fos mRNA expression. When drug-sensitive cells are exposed for 30 min to an ED50 concentration of vinblastine, Adriamycin, colchicine, or VP-16, but not to methotrexate or cisplatin, there is a 3-6-fold induction in the level of c-fos message. Because the former drugs are members of the MDR class and the latter are not, the results are consistent with the hypothesis that induction of c-fos by low levels of cytotoxic drugs may be an early event in the acquisition of the MDR phenotype. If this were the case, then c-fos would be expected to act in concert with c-jun to control transcription by binding to a specific DNA regulatory site. Consistent with this explanation is the existence of an AP-1 sequence in the promotor region for the P-glycoprotein gene (mdr1), as well as the fact that c-jun is also overexpressed in MDR cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1991

Regulation of alpha-fetoprotein gene expression by antagonism between AP-1 and the glucocorticoid receptor at their overlapping binding site.

We show here that the alpha-fetoprotein gene (AFP) promoter can be regulated by AP-1 activity using transient transfection assays. AFP promoter activity induced by c-jun/c-fos can be repressed by cotransfected glucocorticoid receptor. The DNA sequence conferring AP-1 activity was located in the proximal promoter region. Gel retardation assays using the AFP proximal promoter identified an AP-1-like sequence which can bind to bacterially expressed c-jun protein. This AP-1-like element, when cloned into the tk promoter, responds to the AP-1 activity of c-jun/c-fos products in both CV-1 and F-9 cells. The element overlaps with a consensus glucocorticoid-responsive element which was shown to confer negative modulation of AFP promoter activity. A 23-base pair DNA element containing the overlapping glucocorticoid-responsive element and AP-1 sites can be positively regulated by glucocorticoid receptor in the absence of c-jun/c-fos products. When plasmids expressing glucocorticoid receptor, c-jun and c-fos are cotransfected together, they repress each other. Thus, these data demonstrate that negative regulation of the AFP gene by glucocorticoid may be due to the interference of AP-1 activity by glucocorticoid receptor either by direct competition for DNA binding or via protein-protein interaction. They provide another example of transcriptional regulation of developing-associated genes between two major signal transduction pathways in response to extracellular stimuli. This supports the model that expression of alpha-fetoprotein is regulated during development by the effect on transcription of antagonism between glucocorticoid receptor and fos/jun.

Animals↗

PubMed1991

Demonstration of cross-linked cytokeratin polypeptides in transplantable rat hepatoma cells.

Covalently cross-linked multimers of cytokeratins were shown to be present in transplantable Morris hepatoma 7777 cells. These high molecular weight antigens were not detectable in normal rat liver cells. However, identical high molecular weight antigens were also demonstrated in rat liver cells when the cells were homogenized in solutions containing Ca2+. The cross-linking reaction was suggested to be mediated by the action of tissue transglutaminases.

Animals↗

PubMed1991

Hepatoma-associated nuclear matrix nonhistone antigens.

Polyclonal antibodies generated against a group of high molecular weight nonhistone proteins from Morris hepatoma 7777 were used in immunological studies of hepatoma-associated nonhistone proteins in rat and hamster. We revealed the presence of cross-reactive antigens in rat Morris hepatomas 7777 and 8994, and in hamster Kirkman-Robbins hepatoma, but not in normal rat or hamster livers. These specific nonhistone proteins were found to be preferentially localized in the nuclear matrix of rat Morris hepatoma 7777 as well as hamster Kirkman-Robbins hepatoma.

Animals↗

PubMed1991

Bidirectional morphological changes induced by dexamethasone in Morris hepatoma cell lines McA-RH7777 and McA-RH8994: independence of fibronectin and its receptor.

Two Morris hepatoma-derived cell lines, McA-RH7777 (7777) and McA-RH8994 (8994), exhibit different alterations in morphology upon exposure to glucocorticoid. After treatment with synthetic glucocorticoid dexamethasone (DEX), 7777 cells show increased adhesiveness and more flattened shape, while DEX-treated 8994 cells show decreased adhesiveness to substratum and exhibit a marked increase of round and detached cells. Since fibronectin has been thought to play an important role in cell adhesiveness to substratum in hepatoma cell culture, we have also compared the effects of DEX on the biosynthesis of fibronectin (FN) and the functional level of FN receptor in 7777 and 8994 cells. Northern blot analysis and immunofluorescent studies showed that 7777 cells have a high basal expression level of FN synthesis and that DEX treatment induces FN expression two- to threefold with establishment of an extensive fibrillar FN network around the cells. On the other hand, 8994 cells were shown to express little FN and no apparent FN was localized on nonstimulated 8994 cells. However, DEX-treatment drastically increased FN expression in 8994 cells to the level of more than that of DEX-treated 7777 cells and induced a detectable level of cell-associated FN around DEX-treated 8994 cells, which appears to be contradictory to the decreased adhesiveness to the substratum in DEX-treated 8994 cells. Cell attachment assays using FN-coated plates demonstrated that DEX does not exhibit significant effects on the attachment of either 7777 or 8994 cells to FN-coated dishes. Our results suggest that decrease of adhesiveness to the substratum and increase of round detached cells in DEX-treated 8994 cells are independent of changes in the FN expression and the function of FN receptor.

Animals↗

PubMed1991

Alteration of cellular oncogene expression in L1210 cells by a nitrosourea analog of thymidine.

3'[3-(2-Chloroethyl)-3'nitrosoureido]-3'-deoxythymidine (3'-CTNU), a chloroethylnitrosourea analog of thymidine, is a potent antineoplastic agent against murine leukemia L1210. In this study, we have examined the effects of 3'-CTNU on cellular oncogene (proto-oncogene) expression. We found that the expression of the c-myb proto-oncogene was dramatically enhanced in a concentration- and time-dependent manner by 3'-CTNU in murine leukemia L1210 cells, whereas the expression of the c-myc proto-oncogene was suppressed. The enhancement of c-myb gene expression was found to be cell type-specific and to involve an increase of the c-myb transcription rate rather than an alteration of c-myb gene structure or increased stability of c-myb mRNA. Further analysis demonstrated that the altered c-myb gene expression was largely due to the presence of 3'-amino-3'-deoxythymidine, a decomposition product of 3'-CNTU. The expression of five other proto-oncogenes was unaffected by 3'-CTNU treatment. Our study showed that an antineoplastic agent can increase or decrease the expression of proto-oncogenes.

Actins↗