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C C Chang

Publications and source records attributed to C C Chang.

At least 487 records · Page 27Linked to original sources
PubMed1987

Flow cytometry and scrape-loading/dye transfer as a rapid quantitative measure of intercellular communication in vitro.

We describe two flow cytometric assays performed on populations of cells which have been stained with various fluorescent tracer molecules by the scrape-loading technique. One assay uses a simple one-color analysis on a flow cytometer by quantitating the fluorescence intensity of scrape-loaded lucifer yellow CH (LY) in individual cells. The other assay utilizes a two-color analysis on a cell sorter whereby cells which are initially loaded (donors) are identified by their uptake of both rhodamine isothiocyanate-dextran and LY, whereas the recipients of dye transfer are identified as having LY only. Agents which have been shown to inhibit intercellular communication in other assays exhibit similar blocking activity in LY transfer and this is readily quantitated by flow cytometry. The two-color analysis has the added advantage of being able to identify both donors and recipients in a highly quantitative manner.

Cell Communication↗
PubMed1987

Contact insensitivity of a subpopulation of normal human fetal kidney epithelial cells and of human carcinoma cell lines.

Early passage normal human fetal kidney epithelial cells were inoculated on top of a confluent monolayer of X-ray lethally irradiated human fibroblasts to determine the colony-forming ability of these epithelial cells. The results indicate that the great majority of the epithelial cells did not have the clonogenic ability on the fibroblast cell mat, although they were capable of colony formation on plastic surface without the cell mat. A small subpopulation of these epithelial cells, however, was able to proliferate on the cell mat. These contact-insensitive fetal epithelial cells were found to be deficient in gap junction-mediated intercellular communication, to contain keratin and gamma-glutamyl transpeptidase but not fibronectin. These contact-insensitive cells appear to have greater proliferative potential than the parental cell population and to exist transiently in early passage but not in late passage culture. The ability of proliferation on cell mat was found to be shared by 22 different human carcinoma cell lines that were tested. This unique clonogenic ability of normal contact-insensitive and human carcinoma cells on the cell mat could provide a selection method for presumptive normal stem and tumor cells and for an assay for screening potential antitumor drugs and assessing the efficacy of chemotherapeutic drugs against a given tumor.

Carcinoma↗
PubMed1987

Effect of biological toxins on gap-junctional intercellular communication in Chinese hamster V79 cells.

Since chemical modulation of gap-junctional intercellular communication has been implicated in several toxicological endpoints, a study to examine the ability of several biological toxins to inhibit this process was undertaken. Eight biological toxins were tested for their ability to inhibit metabolic cooperation, a measure of gap-junctional intercellular communication, in the Chinese V79 cell system. Aplysiatoxin, anhydrodebromoaplysiatoxin and debromoaplysiatoxin showed the strongest ability to inhibit metabolic cooperation while T2-toxin and vomitoxin inhibited metabolic cooperation to a lesser degree. Aflatoxin B1, aflatoxin B2 and palytoxin were inactive in the Chinese V79 system. Palytoxin, which was extremely cytotoxic, might act as a tumor promoter if it induces compensatory hyperplasia in vivo.

Animals↗
PubMed1987

Characterization of a rat liver epithelial cell line to detect inhibitors of metabolic cooperation.

A normal rat liver epithelial cell line, with phenotype characteristics of "oval" cells (WB-F344), was examined for its ability to perform gap-junctional intercellular communication as measured by metabolic cooperation. To test for gap-junctional intercellular communication, 6-thioguanine-sensitive cells were cocultivated with 6-thioguanine-resistant cells. It was found that the recovery of 6-thioguanine-resistant cells depended on the densities of the 6-thioguanine-sensitive cells. Higher densities of 6-thioguanine-sensitive cells reduced the recovery of 6-thioguanine-resistant cells. These observations demonstrate that rat liver epithelial cells could metabolically cooperate, implying they could perform gap-junctional intercellular communication. Two tumor-promoting organochlorine pesticides, aldrin and dieldrin, were potent inhibitors of metabolic cooperation for these cells, but 12-0-tetradecanoyl-phorbol-13-acetate and teleocidin, known mouse skin tumor promoters, were not significantly effective in inhibiting metabolic cooperation. The results suggest that these cells might provide the basis for an in vitro assay specifically to study liver tumor promoters.

Animals↗
PubMed1987

Characteristics of long-term human epithelial cell cultures derived from normal human fetal kidney.

Epithelial cell cultures were prepared from normal human fetal kidney and established in long-term culture. The growth characteristics and production of keratin, and alkaline phosphatase (AP) and gamma-glutamyl transpeptidase (GGT) activities were compared in a modified minimal essential medium (mMEM), D-valine-containing modified alpha-MEM (mALPHA) and L-valine mALPHA. The mean number of cumulative population doublings (CPDL) was significantly (P less than 0.001) enhanced with the L-valine mALPHA (40.8 CPDL) over that achievable in mMEM (14.2 CPDL) or D-valine mALPHA (18.3 CPDL) media. In all three media, greater than 95% of the cells in culture produced keratin throughout the life span of these cultures. Surface-associated fibronectin was absent in these cell cultures. AP and GGT activities increased as a function of subpassage and time in culture, with the greatest activity in the L-valine mALPHA. The expression of these renal cell-associated functions suggests that these cells in culture are proximal tubule epithelial cells. The conditions and procedures described in this paper can provide a human kidney epithelial cell culture system for studying human renal function, metabolism, cytotoxicity, genotoxicity, and transformation.

Alkaline Phosphatase↗
PubMed1987

Scrape-loading and dye transfer. A rapid and simple technique to study gap junctional intercellular communication.

Gap junction-mediated intercellular communication has been recognized in cells from different tissues of various organisms and has been implicated in a variety of cellular functions and dysfunctions. Here we describe a new, direct and rapid technique with which to study this cellular phenomenon. It employs scrape-loading to introduce a low molecular weight (MW) fluorescent dye, Lucifer yellow CH (MW 457.2) into cells in culture and allows the monitoring of its transfer into contiguous cells. In communication-competent cells the dye transmission occurred within minutes after loading. The involvement of membrane junctions in Lucifer yellow transfer was verified by the concurrent loading of a high MW marker dye conjugate, rhodamine dextran (MW 10,000). Once introduced intracellularly the rhodamine dextran is unable to cross the relatively narrow membrane junctions. Chemicals of variable potency known to block junctional communication were tested in Chinese hamster V79 cells and other mammalian cells. The results showed effective blockage of the dye transfer at non-cytotoxic doses. This new technique can be applied to a wide variety of mammalian (including human) cells. In addition, it has the potential to be utilized as a rapid screening assay to detect chemicals that can modulate intercellular communication and to study their mechanism of action.

Animals↗
PubMed1987

Dissociation of the end-plate potential run-down and the tetanic fade from the postsynaptic inhibition of acetylcholine receptor by alpha-neurotoxins.

The effects of so-called postsynaptic snake alpha-neurotoxins (alpha-bungarotoxin, cobratoxin, erabutoxin b) on the wanings of tetanic contraction (tetanic fade) and the run-down of end-plate potentials during stimulation at 100 Hz were studied, respectively, in intact and cut mouse phrenic nerve-diaphragm preparations. No tetanic fade was evident with high concentrations of toxins until the complete failure of contractile response whereas the tetanic fade was evident after prolonged incubation with lower concentrations of toxins. The proportion of junctions exhibiting end-plate potential run-down increased progressively during toxin incubation. However, depression of end-plate potential amplitude by the toxins was not necessarily accompanied by run-down. The tetanic fade and the run-down became more pronounced for a time shortly after washout of toxins despite the restoration of single twitches and end-plate potential amplitudes, indicating the presynaptic origin of these effects induced by alpha-neurotoxins. We demonstrated that the functions of the pre- and postsynaptic acetylcholine receptors can be dissociated by using the different kinetics of toxin-receptor interactions. The results also implicate that a positive feedback enhancement of transmitter release operates via the presynaptic acetylcholine receptor in the neuromuscular junction in normal physiological conditions during repetitive pulses.

Action Potentials↗
PubMed1987

Effect of various polybrominated biphenyls on cell-cell communication in cultured human teratocarcinoma cells.

Firemaster BP-6 (FM), a mixture of polybrominated biphenyls (PBB), and the congeners 2,2',4,4',5,5'-hexabromobiphenyl (245-HBB), 3,3',4,4',5,5'-hexabromobiphenyl (345-HBB), and 3,3',4,4'-tetrabromobiphenyl (34-TBB) were tested for their ability to inhibit cell-cell communication between human teratocarcinoma cells in culture. Both FM and 245-HBB were capable of inhibiting cell-cell communication in these cells, with only slight effects on cell survival. 345-HBB was highly cytotoxic, but did not show the ability to interrupt cell-cell communication. 34-TBB was moderately cytotoxic and was also ineffective at blocking cell-cell communication. The results agree with previously published findings in Chinese hamster V79 cells, and are in accordance with proposed structure-activity relationships for these compounds. Inhibition of cell-cell communication, either directly (FM and 245-HBB) or indirectly through necrosis-induced compensatory hyperplasia (345-HBB), may be involved in the promotion of hepatocellular neoplasms by these compounds.

Cell Communication↗
PubMed1987

The transport of reactive intermediates in a co-cultivation system: the role of intercellular communication.

The transport of reactive intermediates through gap junctions was studied in a co-cultivation system consisting of primary chick-embryo liver cells and V79 Chinese hamster cells. The formation of gap junctions was studied by measurement of the incorporation of [3H]hypoxanthine in HGPRT deficient V79 mutant cells after co-cultivation with the hepatocytes. Under control conditions the heterologous gap junctions allowed for the transfer of [3H]hypoxanthine resulting in an average value of 13 grains/cell. Addition of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), inhibited this transfer in a dose related way to background values. The transfer of reactive intermediates was measured as the number of sister chromatid exchanges (SCEs) induced in the V79 cells. For both compounds tested, benzo[a]pyrene and dimethylnitrosamine, transport of reactive intermediates through gap junctions was observed. When the inhibitory effects of TPA were investigated at different time points after start of the co-cultivation, inhibition was measurable after 6 h and increased to a maximal inhibition of 50%, observed after 24 h. No effect of TPA was observed on the number of SCEs. When the metabolic cooperation deficient V79 mutant cell line MC--27, was used the effects were completely comparable to those of TPA for both compounds. The lower mutagenic effects in the MC--27 cells cannot be attributed to a lower intrinsic sensitivity for mutagens of these cells.

Animals↗
PubMed1987

Intravaginal administration of RU 486 in humans and rats: inadequate absorption in humans.

Vaginal absorption of the antiprogesterone steroid RU 486 was studied in humans and rats. In rats, RU 486 was sufficiently absorbed to terminate early pregnancy following vaginal, oral or intramuscular administration. The quantitation of RU 486 in serum showed that the ratios of the areas under the concentration curves per mg administered were 1:2.8:3.4 for the vaginal, intramuscular and oral routes, respectively. Female volunteers received RU 486 vaginally in polyethylene glycol (PEG) suppositories, in tampons and in oil solution. Following vaginal (PEG-suppository) and oral administration of 100 mg of RU 486, the ratio of the areas under the serum concentration curves was 1:56, respectively. From tampons and oil, RU 486 was absorbed in a similar manner to that of the PEG-suppositories, resulting in nanomolar serum concentrations. In humans no biological effects were noted following vaginal administration of RU 486. These data suggest that vaginal release of RU 486 is not a successful route of administration in humans.

Administration, Intravaginal↗
PubMed1987

Purification and characterization of phospholipase A2 from Trimeresurus gramineus venom.

Phospholipase A2 was purified to homogeneity from the venom of Trimeresurus gramineus (the Green Habu snake) via three steps consisting of Sephadex G-75, DEAE-cellulose, and DEAE-Toyopearl 650M column chromatographies. Molecular weight determinations showed that the enzyme consists of a single polypeptide chain with a molecular weight of approximately 14,000. The isoelectric point was 4.5. The enzyme is characterized by high contents of acidic amino acids, glycine, and half-cystine. Calcium ion was essential for eliciting activity. The enzyme was inactivated by alkylation of a single histidine residue with p-bromophenacyl bromide following pseudo first-order kinetics, and the rate of the inactivation was depressed in the presence of Ca2+. The N-terminal sequence of this enzyme determined to the 40th residue was found to be highly homologous to that of Trimeresurus okinavensis phospholipase A2 but not to that of Trimeresurus flavoviridis phospholipase A2. The phenylalanine residue at the 27th position of T. gramineus phospholipase A2 is noteworthy because all other phospholipases A2, with only two exceptions, contain a tyrosine residue at this position.

Acetophenones↗
PubMed1987

Further application of VM-plasty.

The use of VM-plasty in the repair of web contracture and its application for other regions are presented. We refined VM-plasty so that both ends remain in the "dog ear" form, eschewing the conventional excision and instead making flaps that are set in a zigzag shape. This procedure results in an increase in the effect of extension to the lateral direction, in addition to preventing recontracture. This method is used not only to repair finger web contracture but also for other contracted scars. No recontracture has been observed, and good results have been obtained.

Adult↗
PubMed1987

A potential anti-pregnancy vaccine built by conjugation of the beta-subunit of human chorionic gonadotropin to adjuvant-active muramyl peptide.

The beta-subunit of human chorionic gonadotropin (hCG) conjugated to tetanus toxoid is being investigated as a vaccine for human fertility control. Initial clinical trials indicated that the level of antibody response induced by such an immunogen was not always sufficient to prevent pregnancy. Therefore, efforts are being made to evaluate new carriers for the beta-subunit and to select adjuvants to yield a more efficient vaccine. In the present report, we demonstrate that conjugates of the beta-subunit of hCG with muramyl dipeptide (MDP), or its nonpyrogenic derivative murabutide, may have potential as an effective antipregnancy vaccine. The copolymer of beta hCG and MDP administered with Al(OH)3 to mice induced a high anti-beta hCG response, better than that induced by the conjugate of beta hCG to tetanus toxoid given with Al(OH)3. Moreover, the antibodies induced by such an immunogen were competent for neutralizing the biological activity of hCG in vivo. Even more interesting, a copolymer of beta hCG and of murabutide induced high levels of biologically active antibodies. This immunogen may represent a promising candidate for the development of an efficient vaccine for human fertility control.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1987

Apurinic endonucleases from Saccharomyces cerevisiae also recognize urea residues in oxidized DNA.

Saccharomyces cerevisiae apurinic endonucleases E cochromatographed with activity against a DNA substrate containing urea residues. The urea-recognizing activity of endonuclease E was competitively inhibited by apurinic DNA, and the heat labilities of both activities were the same. The apparent VmaxS of endonuclease E for both substrates were about the same, while the apparent Km for urea-containing DNA was about threefold greater than that for apurinic DNA. These results were similar to those obtained previously with Escherichia coli exonuclease III (Y. Kow and S. Wallace, Proc. Natl. Acad. Sci. USA 82:8354-8358, 1985) and suggest that the ability to recognize urea residues may be a general property of apurinic endonucleases.

DNA↗
PubMed1987

Does endogenous adenosine modulate the release of acetylcholine from motor nerve during single and repetitive stimulations in the mouse diaphragm?

In order to elucidate the physiological role of endogenous adenosine in regulating the release of acetylcholine, the effects of 8-phenyltheophylline, an antagonist of adenosine receptors and dipyridamole, an uptake inhibitor of adenosine, on the contractile response and quantal release of acetylcholine during single and repetitive stimulations of isolated mouse phrenic nerve-diaphragm preparations were studied. The curves relating the concentration vs. inhibition of contractile response to added adenosine and ATP were shifted parallel to the left by dipyridamole, but were shifted to the right by 8-phenyltheophylline at concentrations with little Ca2+-mobilization or phosphodiesterase inhibition. In the absence of exogenously added adenosine, 8-phenyltheophylline increased the quantal content of end-plate potentials (1 Hz), whereas dipyridamole decreased the quantal content. Successive decrease of the amplitude of end-plate potentials (e.p.p. run-down) evoked at 50 Hz was not changed either by 8-phenyltheophylline or by dipyridamole, suggesting that adenosine or ATP released from the motor nerve does not accumulate to an effective concentration even after repetitive stimulation for a feed-back regulation of the transmitter release. It is concluded that endogenous adenosine does inhibit the release of acetylcholine from motor nerve. However, the source of adenosine may be mostly from the muscle and is probably not involved in the feedback autoregulation.

Acetylcholine↗
PubMed1987

Developmental outcome in children exposed to chloride-deficient formula.

The developmental outcome of 2- and 4-year-old children who had been exposed as infants to chloride-deficient formula was studied. A negative dose-response relationship was demonstrated between use of the formula without additional nutritional supplementation and cognitive outcome as measured by the Bayley Scales of Infant Development (Pearson r = -.55, P = .01) at 2 years of age. A similar negative relationship was demonstrated between this exclusive use of the defective formula and perceptual (Pearson r = -.51, P less than .05), motor (Pearson r = -.52, P less than .05), and fine motor (Pearson r = -.75, P less than .002) ability as measured by the McCarthy Scales of Children's Abilities at 4 years of age. When other know predictors of developmental outcome were taken into account by means of multiple linear regression analyses, exclusive formula use emerged as an important predictor of the children's cognitive functioning at 2 years (model R2 = .59, P less than .005) and of quantitative (model R2 = .58, P less than .006), perceptual (model R2 = .63, P less than .009), and fine motor ability (model R2 = .74, P less than .003) at 4 years of age. These data raise concern about the developmental outcome of the children exposed to chloride-deficient formula.

Child, Preschool↗