Biomedical subjects

C Chang

Publications and source records attributed to C Chang.

At least 343 records · Page 19Linked to original sources

PubMed1992

Types of dementia in Taiwan--a prospective study.

We prospectively investigated 100 consecutive inpatients with suspected dementia to evaluate the relative frequency of various types of dementia in a general hospital of Taiwan. Dementia was confirmed in 86 cases (86%) according to the dementia criteria of the third revised edition of the Diagnostic and Statistical Manual of Mental Disorders and Clinical Dementia Rating Scale (greater than or equal to 1). In contrast to the western developed countries, vascular dementia (VD) (35%) was the leading type of dementia, followed by Alzheimer's disease (AD) (27%), mixed VD and AD (MIX) (14%), and other degenerative diseases (10%). Ten cases (11.6%) of potentially treatable dementia were identified and 8 of 10 had good improvement after appropriate treatment. There were significant age differences among patients with MIX, AD and VD (p less than 0.01). Those with MIX were the oldest (72.12 +/- 9.4) followed by AD (69.70 +/- 8.52) and VD (64.81 +/- 9.12). Males were slightly predominant in this series (male:female = 50:36). A comprehensive clinical investigation including laboratory tests, electroencephalography and CT are necessary in the assessment of demented patients in order to make correct etiological diagnoses which lead to appropriate treatment or management of this terrifying syndrome.

Adult↗

PubMed1992

Immunohistochemical and in situ hybridization studies of androgen receptor expression in a transplantable androgen-independent prostatic carcinoma line (AIT) of Noble rats.

BACKGROUND: In a previous study, we had shown that testosterone (T) administration to castrated Noble (NBL) rats, bearing an androgen-independent prostatic carcinoma line (AIT), caused a dramatic increase in high-affinity nuclear-androgen binding sites in the neoplasms. This increase in nuclear androgen receptors (AR) was accompanied by a transient doubling of the mitotic index in the tumors. EXPERIMENTAL DESIGN: In our current study we used immunohistochemistry and in situ hybridization to investigate the effects of androgen withdrawal and replacement on AR expression at the molecular/cellular level in the AIT. Results from immunohistochemical studies of AR expression in the AIT were compared with those from the prostates of intact, castrated, and castrated T-treated rats. RESULTS: Immunopositive staining for AR was found only in the nuclei of prostatic cells from the glands of intact, castrated or castrated T-treated animals. A few immunopositive tumor cells were present in AITs carried in untreated castrated hosts. In all instances, the reaction product was found in the cytoplasm, but it was also present in the nuclei of some tumor cells. Five days of T administration to castrated AIT-bearing rats caused a dramatic increase in immunopositive tumor cells. Nuclear staining was observed in all positive cells, but the reaction product was also present as well in the cytoplasm of some tumor cells. No differences in AR mRNA expression was detected by in situ hybridization studies of the AITs from castrated and castrated T-treated rats. CONCLUSIONS: The differences in localization of AR between normal prostate and carcinoma cells may reflect alterations in DNA binding domains of the AR protein that occurred with neoplastic transformation. Our in situ findings suggest that unlike the normal prostate, where AR mRNA levels are autoregulated by androgen, AIT cells constitutively express these transcripts. Taken together, our findings suggest that the T-mediated increases in nuclear AR in the AIT, detected previously by binding assay and now by immunohistochemistry, are likely the result of post-transcriptional modifications in the receptor protein.

Animals↗

PubMed1992

Absence of genomes of DNA tumor viruses and expression of oncogenes and growth factors in two esophageal carcinoma cell lines of Chinese origin.

To study the oncogenesis of human esophageal carcinoma, the presence of DNA sequences homologous to several DNA tumor viruses and the expression of oncogenes and growth factor genes were examined in two esophageal carcinoma cell lines of Chinese origin, CE48T/VGH and CE81T/VGH. Southern blot analyses failed to detect sequences homologous to hepatitis B virus (HBV), Epstein-Barr virus (EBV), herpes simplex virus type 2 (HSV-2), cytomegalovirus (CMV) or human papilloma virus (HPV) genomes. Northern blot analyses revealed that c-myc, c-src, c-H-ras, c-abl, c-sis, and p53 genes were expressed. In addition, transcripts of transforming growth factor alpha (TGF alpha), TGF beta, and platelet derived growth factor A (PDGF A) genes were detected. These studies suggest that DNA tumor viruses may not be involved in the carcinogenesis of esophageal carcinoma. However, cooperation among different oncogenes and the production of growth factors may play an important role in that carcinogenesis.

Carcinoma↗

PubMed1992

Analysis of embryonic mouse development: construction of a high-resolution, two-dimensional gel protein database.

Numerous studies have revealed stage specific alterations in protein synthesis that occur in mouse embryos. A thorough analysis of these changes has been hampered by limitations in the ability to resolve individual proteins, the ability to accurately quantify and manage data from two-dimensional gel images, and by variation in the staging of the embryos used. To learn more of the changes in protein synthesis that occur during early development, we constructed a protein database for the mouse embryo using the QUEST system of high-resolution, two-dimensional gel electrophoresis and computerized gel image analysis (Garrels, 1989, J. Biol. Chem., 264:526). Synchronous cohorts of embryos were labeled at 3 h intervals throughout the entire preimplantation period from fertilization to blastocyst stage in order to characterize in detail the changes in protein synthesis pattern that occur during normal preimplantation development. Additional samples were prepared from early post-implantation embryos, isolated inner cell mass and trophoblast cells, and cultured embryonic stem cells. These provide the means for identifying cell and tissue specific proteins and for characterizing changes in protein synthesis that accompany early cellular differentiation in the embryo. We present here a description of the mouse embryo database and discuss its potential usefulness to the study of mammalian embryogenesis.

Animals↗

PubMed1992

A new mutation responsible for severe G6PD deficiency in two ethnic Chinese with different clinical presentations: determination by a direct PCR sequencing technique.

To test the hypothesis that clinical manifestation in G6PD deficiency correlates with a molecular lesion, we investigated the G6PD gene of two Chinese Americans both of whom had G6PD deficiency, but who manifested different clinical presentations. In this study, we have developed a direct PCR sequencing protocol to examine the human G6PD gene. By using optimized PCR conditions with internal primers, we were able to amplify a 4.2 kb DNA fragment (covering exon 3 through 13 of the G6PD gene) of consistently high quality. From this we were then able to generate high quality single-stranded DNA templates by asymmetric PCR for subsequent sequencing. We also overcame the crossband problem by using internal primers, high temperature reaction with Taq I DNA polymerase, and/or sequencing with gene 32 protein. We could consistently amplify exons 1 and 2 despite their high G/C content by substituting 75% of dGTP with deoxy-7-deaza-guanosine triphosphate. By using this novel approach, we have identified a new mutation at cDNA position 1376 from G to T, which causes substitution of Leu for Arg at amino acid position 459. This mutation has not been reported in other ethnic groups. It is the only genetic defect in the coding regions of the G6PD gene of these two G6PD deficient individuals. We speculate that in addition to a defect in the G6PD gene, other factors also play a role in the clinical manifestation of G6PD deficiency.

Base Sequence↗

PubMed1992

Human smooth muscle myosin light chain-2 gene expression is repressed in ras transformed fibroblast cells.

We have previously characterized human smooth muscle myosin light chain (MLC)-2 isoform by complementary DNA cloning and have shown that this isoform is expressed in a number of nonmuscle cells such as fibroblast cells. In this report, we show that when human osteosarcoma derived clonal cells (TE 85 clone F-5) (HOS), which are immortalized and nontumorigenic, undergo transformation following infection by Kirsten murine sarcoma virus (K-HOS) or by a chemical carcinogen [N-methyl-N-nitro-N-nitrosoguanidine (MNNG-HOS)], the smooth muscle MLC-2 mRNA is repressed. Revertants of transformed K-HOS cells (K-HOS312H) show normal levels of smooth muscle MLC-2 mRNA. Transformation of HOS cells by Ha-ras oncogene sequences, either by retroviral infection or by transfection followed by selection for tumorigenic cells in nude mice, results in complete repression of smooth muscle MLC-2 mRNA level. Treatment of HOS cells with tumor promoting phorbol ester, 12-O-tetradecanoylphorbol-13-acetate, results in repression of smooth muscle MLC-2 mRNA. Smooth muscle MLC-2 mRNA level is repressed in many, but not all, transformed cell lines, suggesting that it is not an indirect consequence of transformation but is specific to the agent that brings about transformation. HOS cells synthesize three MLC-2 protein species resolved by the two-dimensional gel electrophoretic system. The identity of the smooth muscle MLC-2 isoform was established by coelectrophoresis of the in vitro synthesized MLC-2 protein corresponding to the cloned complementary DNA in the two-dimensional gel system along with total [35S]methionine labeled HOS cell proteins. Quantitative analysis of MLC-2 isoforms in different HOS cells indicates that the synthesis of smooth muscle MLC-2 isoform is specifically repressed to an undetectable level in ras transformed and MNNG transformed cells and also following treatment with 12-O-tetradecanoylphorbol-13-acetate.

Cell Line, Transformed↗

PubMed1991

Molecular and functional analysis of human natural killer cell-associated neural cell adhesion molecule (N-CAM/CD56).

The neural cell adhesion molecule (N-CAM/CD56) is a member of the Ig supergene family that has been shown to mediate homophilic binding. Several isoforms of N-CAM have been identified that are expressed preferentially in different tissues and stages of embryonic development. To examine the primary structure of N-CAM expressed in leukocytes, N-CAM cDNA were generated by polymerase chain reaction from RNA isolated from normal human NK cells and the KG1a hematopoietic leukemia cell line. The sequence of leukocyte-derived N-CAM cDNA was essentially identical with N-CAM cDNA from human neuroblastoma cells that encode the 140-kDa isoform of N-CAM. Inasmuch as N-CAM is preferentially expressed on human NK cells and a subset of T lymphocytes that mediate MHC-unrestricted cell-mediated cytotoxicity, we examined the potential role of N-CAM in cell-mediated cytotoxicity and heterotypic lymphocyte-tumor cell adhesion. N-CAM loss mutants were established from the human N-CAM+ KG1a leukemia cell line, and N-CAM cDNA was transfected into a human colon carcinoma cell line and murine L cells. Using this panel of mutants and transfectants, it was determined that expression of N-CAM on these target cells does not affect susceptibility to resting or IL-2-activated NK cell-mediated cytotoxicity. Moreover, expression of N-CAM in these transfectants failed to induce homotypic or heterotypic cellular adhesion. Collectively, these studies indicate that homophilic N-CAM interactions probably do not mediate a major role in the cytolytic interaction between NK cells and N-CAM+ tumor cell targets.

Antigens, CD↗

PubMed1991

Autoregulation of androgen receptor expression in rodent prostate: immunohistochemical and in situ hybridization analysis.

Autoregulation of androgen receptor mRNA and protein was investigated by immunohistochemical and in situ hybridization techniques. In both mouse and rat prostate, the epithelial cell nuclei were stained with the monoclonal or polyclonal antibodies raised against human androgen receptor. It was observed that 3 days after castration, nuclear staining of the epithelium was greatly reduced, while androgen treatment restored the staining intensity to a normal level. In situ hybridization using an androgen receptor cDNA fragment as probe demonstrated that the change in androgen receptor mRNA level correlated with the change in antibody staining intensity. These data suggested an up-regulation of androgen receptor expression by androgen.

Animals↗

PubMed1991

GdDTPA-enhanced magnetic resonance imaging of the aqueous flow in the rabbit eye.

Magnetic resonance imaging with gadolinium-diethylenetriaminepentaacetic acid complex (GdDTPA) as the contrast agent was used to image the aqueous chamber of the eye. This method, in addition to providing spatial information, permits quantitative study of the aqueous flow. GdDTPA solution was applied either topically or intravenously, entering the anterior chamber via different pathways. The wash-in and wash-out of GdDTPA follow a two-compartment model which enables determination of the aqueous flow rate by multiplying the aqueous chamber volume by the wash-out rate constant. Rabbit eyes showed a flow rate of 1.5-2 microliters/min which was retarded by the systemic administration of acetazolamide (Diamox).

Acetazolamide↗

PubMed1991

Purification and characterization of an epoxide hydrolase from the peroxisomal fraction of mouse liver.

Epoxide hydrolase (EH) activity has been reported to occur in most subcellular fractions of mouse liver. The EHs in the microsomal and cytosolic fractions have been purified and characterized; however, the nature of the EH(s) in the peroxisomal fraction is not known. Therefore an EH, pEH, was purified from the solubilized 12,000g fraction, which contain peroxisomes. Previous studies have demonstrated that the EH activity in this crude solubilized 12,000g fraction resides mostly in the peroxisomes. Thus the crude 12,000g pellet from mouse liver, free from cytosolic contamination, was sonicated to obtain a 105,000g soluble fraction containing 80% of the original EH activity in this fraction. The pEH was purified, using trans-stilbene oxide (TSO) as substrate, by a combination of affinity and hydroxyapatite chromatography. The purified pEH had a native molecular weight of 57 kDa, a molecular weight of 59 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a pI of 5.7. The purified pEH was observed to be immunologically similar to the cytosolic EH (cEH). The kinetics of hydrolysis of TSO, however, were slightly different. Lineweaver-Burk plots for the inhibition of pEH suggest a probable noncompetitive, mixed-type inhibition. The purified pEH thus appears to be very similar to the cEH. There are minor differences between the purified cEH and pEH, particularly in the kinetic parameters. However, these minor differences are insignificant. These results demonstrate that the cEH and pEH are substantially similar, if not identical.

Animals↗

PubMed1991

Analysis of concurrent glucose consumption by the hexose monophosphate shunt, glycolysis, and the polyol pathway in the crystalline lens.

A method based on 13C-NMR spectroscopy is described, in which the metabolism of [13C2]glucose was assessed in intact rat lenses. By analysing the ratio of 13C3/(13C2 + 13C3) lactate, a quantitative measurement of the hexose monophosphate shunt (HMPS) activity could be derived. Similarly, measurements of the time-dependent increase of lactate and sorbitol permitted the determination of the activity of the Embden-Meyerhof pathway and the polyol pathway, respectively. This method offers significant advantages over other biochemical and spectroscopic methods and allows for the first time a direct correlation between the activities of the polyol pathway and the HMPS.

Animals↗

PubMed1991

Plant genome studies: restriction fragment length polymorphism and chromosome mapping information.

The detection of sequence variation with restriction fragment length polymorphisms is advancing our knowledge of plant genetics on several fronts. In the past year, there has been progress in genetic map construction, phylogeny studies, and the dissection of multigenic traits. In addition, new methods that are independent of restriction sites are being developed for polymorphism detection.

Chromosome Mapping↗

PubMed1991

Regulation of androgen receptor mRNA in rat Sertoli and peritubular cells.

Regulation of 9.5-kb androgen receptor mRNA concentrations in Sertoli and peritubular cells from 20-day-old rats was studied by Northern blot analysis. Treatment of cells in vitro for 1-7 days with 300 ng/ml FSH increased androgen receptor mRNA up to 4-fold in Sertoli cells but not in peritubular cells. Testosterone (100 ng/ml) had no effect or slightly decreased androgen receptor mRNA in Sertoli and peritubular cells. Androgen receptor mRNA concentrations in Sertoli and peritubular cells from rats killed 15 days after hypophysectomy were elevated 4-5-fold over those in cells from intact rats. The androgen receptor mRNA concentration was decreased in both Sertoli and peritubular cells isolated from hypophysectomized animals treated with 500 micrograms/day testosterone propionate in vivo and subsequently with 100 ng/ml testosterone in vitro. FSH treatment (100 micrograms/day in vivo, followed by 300 ng/ml in vitro) did not increase androgen receptor mRNA over that in cells from hypophysectomized controls but rather decreased its concentration to varying degrees in Sertoli and peritubular cells. The rise in androgen receptor mRNA in both Sertoli and peritubular cells isolated from hypophysectomized animals is attributable, at least in part, to the absence of the inhibitory influence of testosterone. Other data in the literature suggest positive regulation of Sertoli cell androgen receptor protein by FSH and androgens. Consequently, complex mechanisms involving transcriptional, translational, and post-translational regulation probably control androgen receptor concentrations in the cells of the rat seminiferous tubule.

Animals↗

PubMed1991

Target frequency and integration pattern for insertion and replacement vectors in embryonic stem cells.

Gene targeting has been used to direct mutations into specific chromosomal loci in murine embryonic stem (ES) cells. The altered locus can be studied in vivo with chimeras and, if the mutated cells contribute to the germ line, in their offspring. Although homologous recombination is the basis for the widely used gene targeting techniques, to date, the mechanism of homologous recombination between a vector and the chromosomal target in mammalian cells is essentially unknown. Here we look at the nature of gene targeting in ES cells by comparing an insertion vector with replacement vectors that target hprt. We found that the insertion vector targeted up to ninefold more frequently than a replacement vector with the same length of homologous sequence. We also observed that the majority of clones targeted with replacement vectors did not recombine as predicted. Analysis of the recombinant structures showed that the external heterologous sequences were often incorporated into the target locus. This observation can be explained by either single reciprocal recombination (vector insertion) of a recircularized vector or double reciprocal recombination/gene conversion (gene replacement) of a vector concatemer. Thus, single reciprocal recombination of an insertion vector occurs 92-fold more frequently than double reciprocal recombination of a replacement vector with crossover junctions on both the long and short arms.

Animals↗

PubMed1991

Quantitative analysis of protein synthesis in mouse embryos. I. Extensive reprogramming at the one- and two-cell stages.

A quantitative, high-resolution, two-dimensional gel protein database has been constructed for the mouse embryo. This database has been used to obtain a detailed accounting of the amount and relative timing of changes in protein synthesis that occur during the 1-, 2-, and 4-cell stages along with a description of the most prevalent developmentally regulated patterns of synthesis. We find that during these early stages of development the pattern of proteins synthesized changes to a much greater extent than previously appreciated. During the 1- and 2-cell stages, the majority (60% and 85%, respectively) of the analyzed proteins exhibit twofold or greater changes in their rates of synthesis. The periods of greatest change are the late 1-cell and mid 2-cell stages, during which an extensive remodelling of protein synthetic pattern occurs that is largely complete by 15 h following the first cleavage. Once this reprogramming is complete, very little change is observed during the late 2-cell and 4-cell stages. Cluster analysis of individual protein synthesis patterns reveals a limited number of coordinately regulated protein sets that are responsible for most of the changes observed during the 1- and 2-cell stages. During the 2-cell stage, one third of the proteins increase by an average of fivefold, another third decrease by an average of sevenfold, and 10% undergo transient changes in rates of synthesis. These patterns reflect the switch from zygotic to maternal mRNA utilization following transcriptional activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Immunohistochemical and in-situ hybridization analysis of androgen receptor expression during the development of the mouse prostate gland.

Ontogeny of the androgen receptor in the mouse prostate during fetal and post-natal periods was re-evaluated by histochemistry using a monoclonal antibody and by in-situ hybridization using a cDNA probe. Unlike steroid autoradiographic techniques which show ligand-binding sites in autoradiographs, these two techniques make it possible to investigate the expression of receptor protein and the transcription of its mRNA directly at the cellular level. Our previous autoradiographic data have demonstrated that only the mesenchyme takes up androgen during the fetal period; no incorporation of androgen by the epithelium has been observed in the fetus, although this does occur in later development. This observation indicated that the morphogenesis of prostatic epithelium is induced by the androgen-activated surrounding mesenchyme. In the post-natal prostate, the present data are nearly the same as those obtained by autoradiographic techniques; ligand-binding activity and expression of the receptor and its mRNA are much higher in the epithelium than in the stroma. On the other hand, the present study indicated that the fetal epithelium, which had shown no ligand-binding activity by autoradiographic analysis, expressed the same amount of receptor protein and its mRNA as the fetal mesenchyme. The results suggest that androgen receptor protein is expressed in the fetal epithelium but may not be able to bind to androgens until post-natal development.

Animals↗

PubMed1991

[Expression of androgen receptor gene in normal subjects and patients with complete androgen insensitivity].

The Androgen Receptor (AR) mRNA was studied in cultured cells from normal subjects and 10 patients with Complete (CAI, 9 patients, 5: R-, 4: R+) or Partial (PAI, 1 patient) Androgen Insensitivity. The probe was a 3,4 cDNA coding for the entire AR. AR mRNA appears as a 10 kb band. It is strongly expressed in genital skin fibroblasts, 50 to 100 times less in non genital skin. In genital skin fibroblasts, a 3 to 5 fold increase is observed after 1 h of treatment of the cultures with dihydrotestosterone (DHT, 5 nM) whereas a 22 fold decrease is observed after 24 h. A 3 fold increase is also observed after 1 h of treatment with progesterone (50 nM) or cyproterone acetate (500 nM) which does not seem to act as an antiandrogen in this model. The 10 kb band was present in all 10 A1 patients studied, though expressed at a much lower level. It is therefore possible that an abnormal regulation of the AR gene expression is involved in the mechanism of Androgen Insensitivity.

Androgens↗

PubMed1991

Transcriptional activation by TR3 receptor, a member of the steroid receptor superfamily.

TR3 receptor is a human homolog of mouse Nurr77 and N10 protein and the rat NGFI-B protein. A cDNA encoding a chimeric nuclear receptor composed of the N-terminal domain and C-terminal putative ligand-binding domain of the orphan receptor TR3 receptor and the DNA-binding domain of the androgen receptor was constructed. The chimeric receptor, called TR3/AR/TR3 receptor, when expressed in COS-1 monkey kidney cells or PC-3 human prostate tumor cells, cotransfected with an ARE-containing mouse mammary tumor virus long terminal repeat-linked reporter gene encoding chloramphenicol acetyltransferase (CAT), activated CAT expression in the absence of any added factor. The activation was dependent on the amount of expression vector transfected and appeared to be independent of the concentration of serum supplement. Intact TR3 receptor was not active in this system. A TR3/AR/TR3 receptor protein truncated in the putative ligand-binding domain also induced CAT activity. TR3 receptor appears to be a transcriptional factor that activates transcription independently of ligand or binds an endogenous ligand present constitutively in cultured cells.

Base Sequence↗