Biomedical subjects

J F Chiu

Publications and source records attributed to J F Chiu.

At least 55 records · Page 3Linked to original sources

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↗

PubMed1991

[The study of Apgar score and infant birth weight in the central Taiwan].

The objective of this study was to assess the relationship between birth weight and the Apgar Score. We collected data on the birth weights and the 1 min and 5 min Apgar Score of new born infants between 1982 and 1987 at a teaching hospital in Central Taiwan. Compared to babies with normal Apgar Score, infants with low Apgar Scores were found to born with low and very low birth weights. In the 1 min of life test, the relative risks of low birth weights among infants with Apgar Scores of 0 to 3 and 4 to 6 were 115.0 and 5.9 times higher than those of normal infants, respectively. In the very low birth weight category, the relative risks of the above score were 252.5 and 51.1, in this order. In the 5 min of life test, the relative risks of the above scores were 16.2 and 12.1 in the low birth weight category, respectively. However, among babies of very low birth weight, the relative risks of the same scores were 121.2 and 84.9, in this order. In conclusion, the 5 min Apgar Score might be a useful prognostic index for the relationship between health and birth weight of new born infants.

Apgar Score↗

PubMed1991

[A study of weight and weight/birth at birth by gestational week].

A study of 35,919 live neonates was conducted from 1976 to 1987 (excluding 1980) at a teaching hospital in Central Taiwan. Our goal was to determine the proportions of low birth weight (LBW) and very low birth weight (VLBW) and birth weight/birth length ratios by gestational week. The results showed that LBW and VLBW neonates were 6.3% and 1.1%, respectively. In LBW neonates groups, there was a rapid decline after the 33rd gestational week, then as low as 6.9% by the 38th gestational week. After the 28th gestational week, there was a rapid decline in VLBW proportion, then a further decline to 9.3% at the 32nd gestational week. Birth weight/birth length ratios were 2.94 and 6.25 at the 28th and 39th gestational weeks, respectively. There were no differences in birth weight/birth length ratios between male and female babies. Based on the above findings, we tried to set a norm from birth weight/birth length ratios by gestational week.

Birth Weight↗

PubMed1990

Induction of F9 cell differentiation by transient exposure to retinoic acid.

The F9 cell is a mouse embryonal teratocarcinoma which can be induced to differentiate into visceral endoderm by treatment with retinoic acid (RA). Treatment with RA in conventional studies was carried out in the constant presence of RA. Here we demonstrate that treatment with RA can be as short as 3 hrs to induce differentiation of F9 cells. Morphology, alpha-fetoprotein gene activity, and temporal patterns of F9 cell differentiation are the same with both short- and long-term treatment with RA.

Animals↗

PubMed1990

The appearance of hepatoma-associated chromosomal non-histone proteins in rat liver after a single dose of 3'-MDAB followed by treatment of phenobarbital.

Previously we have described polyclonal antibodies that recognized a group of nuclear nonhistone proteins whose molecular weights ranged in size from 170 to 220 kDa. These antigenic nonhistone chromosomal proteins are abundant in rat hepatoma chromatin. In this report we discuss the synthesis and cellular localization of these particular proteins during the multistage process of hepatocarcinogenesis. The appearance of these antigenic proteins in rat liver nuclei approximately parallels the appearance of alpha-fetoprotein in the cytosol of hepatocytes. However, the immunoreactivity of antigenic proteins increased steadily even during the prominent dip in the AFP concentration between 50 and 100 days of carcinogenesis. The effect of the tumor promoting agent, phenobarbital, on the synthesis of antigenic nuclear proteins was also studied. The appearance of hepatoma-associated non-histone chromosomal proteins at early stages of tumor promotion during hepatocarcinogenesis was observed. The results of these studies demonstrate that the hepatoma-associated non-histone proteins are expressed not only in hepatoma cells, but also in hepatocyte cells committed to carcinogenesis.

Animals↗

PubMed1990

Association of fibronectin-like antigens in chromatin preparations from rat hepatoma cells.

High molecular weight hepatoma-associated nonhistone chromosomal proteins (NHPs) in transplantable rat hepatoma cells were reported previously from this laboratory. A cDNA library prepared from Morris hepatoma 7777 cells was screened with the polyclonal antibodies against hepatoma NHPs and a positive cDNA clone (lambda P2A1) was isolated. DNA sequence analysis revealed that the cDNA clone was identical to that of rat fibronectin (FN). The polyclonal antibodies against hepatoma NHPs were shown to bind specifically to both rat plasma FN and the fusion proteins encoded by lambda P2A1. A monoclonal antibody specific to rat plasma FN also recognized high molecular weight antigens of hepatoma NHPs in a pattern similar to that demonstrated with the polyclonal antibodies. These results suggest the existence of FN or FN-like antigens in the chromatin preparations from rat hepatoma cells. The antigenic proteins are localized in the nuclei of neoplastic foci of liver undergoing hepatocarcinogenesis.

Animals↗

PubMed1990

Hepatoma-associated non-histone proteins are phosphoproteins preferentially localized in nuclear matrix.

1. High molecular weight non-histone proteins (NHP) were isolated from Morris hepatoma 7777 by Sephadex G-100, S-200 chromatography. 2. Specific polyclonal antibodies were raised against these NHP in rabbits. These antibodies recognized specific NHP components present in Morris hepatoma 7777 and 8994, but not in normal rat liver. Hepatoma-associated antigens are phosphoproteins. 3. Immunologically specific NHP of Morris hepatoma are intensively concentrated in nuclear matrix fraction.

Animals↗

PubMed1990

Alpha-fetoprotein mRNA: variation of half-life in rat hepatoma cell lines and destabilization by sodium butyrate.

The half-life of alpha-fetoprotein (AFP) mRNA was determined in two rat hepatoma cell lines. In the 7777 cell line, AFP mRNA half-life is 30-35 h, consistent with earlier observations (Innis and Miller, 1979). However, the half-life in McA-RH8994 cells is only 14-16 h. Dexamethasone does not affect AFP mRNA half-life in either cell line, indicating that glucocorticoid-mediated alterations in AFP mRNA levels in these cells is at the transcriptional level. The naturally-occurring fatty acid sodium butyrate did, however, cause significantly more rapid degradation of AFP mRNA in McA-RH8994 cells, decreasing the half-life from 14-16 h to only 5-6 h. The ability of sodium butyrate to block glucocorticoid action on AFP gene expression in this cell line is therefore due to both transcriptional and post-transcriptional effects.

Animals↗

PubMed1990

The expression of c-myc and c-N-ras in human cirrhotic livers, hepatocellular carcinomas and liver tissue surrounding the tumors.

To study the possible role of proto-oncogenes in the multistep process of human liver hepatocarcinogenesis, we have examined the expression of c-N-ras and c-myc in human hepatocellular carcinomas and liver tissue surrounding the tumors as well as cirrhotic livers which are generally considered to precede the formation of human hepatocellular carcinoma. One to four-fold higher expression of the c-N-ras proto-oncogene was observed in twelve hepatoma patients as compared to normal liver. Increased expression of c-N-ras was also observed in liver tissue surrounding these tumors. Eight patients exhibited an apparent higher expression of the c-N-ras oncogene in adjacent liver tissue than in their corresponding tumor tissues. Six human liver cirrhosis patients also exhibited a slight increase in c-N-ras expression. Southern blot analysis demonstrated an amplified c-N-ras sequence in these tissues surrounding the tumors. In the study of the c-myc gene, variable degrees of highly enhanced expression were found in all twelve hepatoma patients as compared to normal liver. The c-myc gene was also expressed in the adjacent liver tissue and in some of the human cirrhotic livers. Our studies give further evidence that the expression of c-N-ras and c-myc proto-oncogenes are involved in the process of human hepatocarcinogenesis.

Carcinoma, Hepatocellular↗

PubMed1989

Specific interactions of histone H1 and a 45 kilodalton nuclear protein with a putative matrix attachment site in the distal promoter region of a cell cycle-regulated human histone gene.

Protein-DNA interactions within the promoter of a cell cycle-regulated human H4 histone gene were examined by binding of 5'-end-labeled DNA segments to Western blots of nuclear protein fractions. Specific protein interactions were observed with DNA segments located between -500 bp and -1,070 bp upstream of the ATG initiation codon and included a histone H1 binding segment flanked on both sides by binding sites for a 45 kD nuclear protein. This region of the gene contains a DNase I-sensitive site in the center (-720 to -820 bp), and sequence analysis revealed the presence of scaffold attachment sequences in the two flanking segments. Topoisomerase II consensus sequences and in vitro topoisomerase II cleavage sites were also detected in the two flanking segments. Our results suggest that the 45 kd nuclear protein may preferentially interact with these two segments of the H4 histone gene to mediate association with the nuclear matrix. The presence of negative regulatory elements in this putative matrix attachment region provides a basis for the speculation that such nuclear proteins are associated with alterations in gene-matrix interaction that are functionally related to gene expression.

Binding Sites↗

PubMed1989

The role of methylation in regulating the expression of the alpha-fetoprotein gene in developing rat liver and hepatoma cell lines.

We have examined four possible sites of methylation in the 5' flanking region of the alpha-fetoprotein (AFP) gene during liver development in the rat, paying particular attention to the neonatal period, in which AFP gene transcription changes rapidly. These sites are found in MspI/HpaII sites located at -4197, -3038, -2431, and +3 bp relative to the transcription start site. Three of these sites are associated with sequence regions important for the regulation of AFP gene transcription. We found that, in general, the 5' flanking region of the gene was methylated more in the adult liver than in the livers of fetal and neonatal rats. In addition, the degree of methylation of all four sites examined was increased in the adult liver. One of these sites showed increased methylation as AFP gene activity decreased, whereas the other became more methylated only after transcriptional activity of the gene had ceased. In particular, the site (+3 bp) just adjacent to the transcriptional initiation site of the gene was fully methylated in the adult liver. In various rat hepatoma and liver cell lines methylation of this same site showed a particularly close correlation with the amount of transcriptional activity of the AFP promoter in these cell lines. Treatment of the hepatoma and liver cell lines with dexamethasone, which influences AFP gene expression, did not result in any changes in methylation of these sites in the 5' flanking region.

Animals↗

PubMed1989

Zhi-mu saponin inhibits alpha-fetoprotein gene expression in developing rat liver.

1. A saponin isolated from the Chinese herb zhi-mu (Anemarrhena asphodeloides Bunge) modifies alpha-fetoprotein production when injected into newborn rats. 2. The serum level of AFP was determined quantitatively by immunorocket electrophoresis. 3. AFP serum levels were reduced to 60% of the control by zhi-mu saponin (ZMS). 4. The lower AFP level in drug treated rat serum is not due to a change in the pattern of serum AFP variants. 5. AFP mRNA levels in ZMS-treated rat livers, measured by RNA dot hybridization, decreased to about 50% of control levels after 4 days treatment. 6. Results from tritium labeled dexamethasone competition assays suggest that ZMS may act on AFP gene expression through glucocorticoid receptor mediated action.

Animals↗