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W B Butler

Publications and source records attributed to W B Butler.

At least 19 recordsLinked to original sources
PubMed1995

Induction of tissue plasminogen activator mRNA and activity by structurally altered estrogens.

The effect of structure of the estrogen ligand on the accumulation of tPA mRNA and the activity of extracellular fibrinolytic enzyme has been examined in cultures of MCF-7 cells. Estradiol(E2)-stimulated fibrinolytic activity was preceded by an increase in actinomycin D sensitive tPA mRNA synthesis which peaked at 18 h. Ten A- and D-ring structural analogs of E2 affected tPA mRNA accumulation and extracellular fibrinolytic activity. Only in the case of two A-ring isomers (2- and 4-hydroxyestratrien-17 beta-ol) was the decreased effect of the ligand's structural change on tPA mRNA accumulation and fibrinolysis not explained by a comparable decline in affinity of the ligand for estrogen receptor. Both of these analogs functioned as antiestrogens. The stimulatory capacity of androstanediols on the tPA gene required that the 3-hydroxyl group be positioned in the beta-configuration. Absence of the 17 beta-hydroxy group was beneficial to the maximum accumulation of tPA mRNA. As has been reported for other estrogen responsive genes (progesterone receptor, cathepsin D and pS2), regulation by estrogens is not related directly to the affinity of the ligand for ER, but this activity may be determined by the location of the electronegative isopotential above the A-ring of estrogenic ligands.

Dactinomycin↗
PubMed1992

Responses to retinoic acid of tamoxifen-sensitive and -resistant sublines of human breast cancer cell line MCF-7.

Growth of the human breast cancer cell line MCF-7 is known to be inhibited both by antiestrogens such as 4-hydroxytamoxifen (OHTAM) and by retinoic acid (RA). Uncloned MCF-7 cells (UNC) and two cloned sublines, one sensitive to antiestrogens (E-3) and the other resistant to them (RR), were used in this study. Growth of UNC and E-3 was inhibited by either OHTAM (10(-7) M) or RA (10(-6) M), and this inhibition could not be overcome by the simultaneous addition of estradiol. Subline RR, which was originally selected for resistance to tamoxifen, was resistant to both OHTAM and RA as measured by either growth in culture or colony forming ability. RR was resistant to RA at all concentrations tested between 10(-9) M and 10(-6) M. The inhibition of uncloned MCF-7 cells by RA was dose dependent between 10(-9) M and 10(-6) M. Subline E-3, however, exhibited a mixed response to RA. At 10(-9) M and 10(-8) M, growth was stimulated, but at 10(-7) M and 10(-6) M it was inhibited. The level of estrogen receptor was measured in the same experiment by using a whole cell assay. In the uncloned MCF-7 cultures and in both the RR and E-3 sublines the level of estrogen receptor was increased between 50 and 200% by RA. The production of plasminogen activator by MCF-7 cells is stimulated by estrogen. RA had a dual effect on plasminogen activator production. In the absence of estrogen, RA inhibited production below the unstimulated level, but in cells stimulated by estrogen, RA increased plasminogen activator production. The results reported here support possible interactions between the mechanisms by which cells respond to estrogen, antiestrogens, and retinoids.

Breast Neoplasms↗
PubMed1988

Effects of tamoxifen and 4-hydroxytamoxifen on synchronized cultures of the human breast cancer cell line MCF-7.

The effect of antiestrogens on cultures of synchronized MCF-7 human breast cancer cells was studied. Cultures were synchronized by an eighteen hour block with 1.5 mM hydroxyurea. Tamoxifen or 4-hydroxytamoxifen was added at various times following removal of the hydroxyurea block and the cell number and rate of incorporation of 3H-thymidine by the cultures were followed for 48 hours through two waves of DNA synthesis. Antiestrogens added when hydroxyurea was removed inhibited only the second wave of DNA synthesis. Inhibition of the second wave only occurred if the antiestrogen was added before or at about the time of mitosis. To determine whether antiestrogen had to be present before mitosis in order to block the next round of DNA synthesis, cells in mitosis were selected by shaking them loose. The subsequent division of these cells was followed to determine the effect of treating them with antiestrogens before, after, or both before and after mitosis. The addition of antiestrogens at the time of mitosis proved sufficient to block the next round of cell division. Thus antiestrogens are cell cycle specific agents and appear to act at a point early in G1 to block the next round of DNA synthesis and cell division.

Breast Neoplasms↗
PubMed1988

Heterogeneity of prostaglandin E2 binding in murine mammary tumor cells differing in metastatic potential.

The metastatic murine mammary tumor cell line 410.4 and its nonmetastatic counterpart tumor line 410 were examined for the presence of prostaglandin E2 (PGE2) binding using a 3H-PGE2 ligand binding assay. Inhibition of endogenous prostaglandin synthesis with indomethacin was shown to increase markedly binding of 3H-PGE2. Equilibrium binding data for tumor 410.4 show that specific binding is saturable, reversible by unlabeled PGE2, temperature-dependent and specific. PGE1, PGE2 or 16-16-dimethyl PGE2 compete well with 3H-PGE2 for binding. PGD2 partially inhibits 3H-PGE2 binding, whereas PGA2 does not compete. Scatchard analysis of equilibrium binding data reveals a high affinity (Kd = 3.9 X 10(-9) M) and an average of 33,785 binding sites/cell. In contrast, binding of 3H-PGE2 to nonmetastatic line 410 has a slightly lower affinity (Kd = 8.8 X 10(-9) M) and an average of 368,857 binding sites/cell. 3H-PGE binding to line 410 cells is comparatively nonspecific as PGD2 is nearly as effective as PGE1, PGE2 and an analogue of PGE2 in competing with 3H-PGE2 and PGA2 also inhibits 3H-PGE2 binding.

Animals↗
PubMed1986

Acceptor sites on chromatin for receptor bound by estrogen versus antiestrogen in antiestrogen-sensitive and -resistant MCF-7 cells.

We examined the chromatin binding characteristics of estrogen receptor from MCF-7 cells when bound by [3H] estradiol vs. the high affinity antiestrogen [3H]H1285 [4-(N,N-diethylaminoethoxy) 4'-methoxy-alpha-(p-hydroxyphenyl)alpha-ethylstilbene]. Two sublines of MCF-7 cells were used: E-3, which is sensitive to antiestrogens, and RR, which is antiestrogen resistant and was selected for its ability to grow in the presence of tamoxifen. Chromatin was prepared from both E-3 and RR cells, linked covalently to cellulose and deproteinized sequentially by 0-8 M guanidine hydrochloride (Gdn X HCl). The chromatin acceptor activity unmasked by Gdn X HCl was determined using partially purified (30-fold) activated [3H]estradiol- or [3H] H1285-receptor complexes obtained by KCl step elution from DEAE-cellulose columns. With chromatin from E-3 cells, maximal binding (acceptor activity) for [3H]estradiol-receptor complexes prepared from either type of MCF-7 cells (E-3 or RR) was unmasked by 1 and 6 M Gdn X HCl, whereas [3H]H1285-receptor complexes exhibited maximal binding to 1 and 4 M Gdn X HCl-extracted chromatin subfractions. Chromatin prepared from RR cells was similar to that from E-3 cells in its binding activity for [3H]estradiol-receptor complexes. It differed, however, in that [3H]H1285-receptor complexes showed less chromatin acceptor site binding in general to 1-8 M Gdn X HCl-deproteinized RR chromatin, and the binding peak unmasked by 4 M Gdn X HCl was absent in chromatin from these cells. Receptor binding to chromatin was stable and was competitively inhibited by radioinert estradiol- or H1285-receptor complexes (but not by denatured receptors), demonstrating the saturability and specificity of these acceptor sites. Thus, estrogen receptor binds differently to chromatin depending on whether estradiol or an antiestrogen is bound to it. In addition, the acquisition of antiestrogen resistance by the RR subline of MCF-7 cells appears to result from alterations in the state of its chromatin rather than changes in the receptor itself. Finally, the observation that the chromatin from the resistant cells differs from that of the sensitive cells suggests that antiestrogens may be able to inhibit the growth of MCF-7 and other antiestrogen-sensitive cells not only by antagonizing the stimulatory effect of estrogens, but also by exerting some separate effect of their own.

Breast Neoplasms↗
PubMed1986

Relation of in vitro properties to tumorigenicity for a series of sublines of the human breast cancer cell line MCF-7.

The relation of in vitro properties to tumorigenicity was studied using eight sublines of the human breast cancer cell line MCF-7. Four of the eight were tumorigenic in estrogen-treated nude mice. The sublines differed for each of the in vitro properties measured, and no property correlated perfectly with tumorigenicity. Cytochalasin B-induced multinucleation was a property of all four tumorigenic sublines but of only one of the four nontumorigenic ones. Anchorage-independent growth and concanavalin A-mediated hemadsorption levels were higher in all sublines than reported levels for nontransformed fibroblasts and normal human or mouse mammary epithelial cells. The production of both plasminogen activator and a plasminogen-independent fibrinolytic activity showed no relationship to tumorigenicity but was higher in those sublines producing more invasive tumors. It appears that no one of these in vitro properties is sufficient to make a subline tumorigenic. Rather, the first three properties studied here and, perhaps, also production of plasminogen activator may each be necessary, but not sufficient, to make a subline tumorigenic. In addition, properties such as production of plasminogen activator and other proteases, while perhaps not essential to tumorigenicity, may confer characteristics, such as invasiveness, on the tumors produced by a given subline.

Animals↗
PubMed1984

Preparing nuclei from cells in monolayer cultures suitable for counting and for following synchronized cells through the cell cycle.

A procedure is described for preparing nuclei from cells in monolayer culture so that they may be counted using an electronic particle counter. It takes only 10 to 15 min, and consists of swelling the cells in hypotonic buffer and then lysing them with the quaternary ammonium salt, ethylhexadecyldimethylammonium bromide. The cells are completely lysed, yielding a suspension of clean single nuclei which is stable, free of debris, and easily counted. The method was developed for a cell line of epithelial origin (MCF-7), which is often difficult to trypsinize to single cells. It works equally well at all cell densities up to and beyond confluence, and has been used with a variety of cells in culture, including 3T3 cells, bovine macrophages, rat mammary epithelial cells, mouse mammary tumor cell lines, and human fibroblasts. The size of the nuclei produced by this procedure is related to their DNA content, and the method is thus suitable for following cultures of synchronized cells through the cell cycle, and for performing differential counts of cells with substantial differences in DNA content.

Breast Neoplasms↗
PubMed1983

Steroid stimulation of plasminogen activator production in a human breast cancer cell line (MCF-7).

The production of plasminogen activator by the human breast cancer cell line MCF-7 was stimulated by physiological concentrations of estradiol under conditions where the growth of the cells was neither dependent on nor stimulated by estradiol. Stimulation was measurable within 8 hr after the addition of estradiol and was evident in both the level of plasminogen activator released into the culture medium and the level within the cells. The level of production varied with cell density, but production was stimulated by estradiol at all densities tested. The antiestrogen tamoxifen inhibited estrogen stimulation, and this inhibition could be overcome by increased concentrations of estradiol. Production was also stimulated by progesterone and could be stimulated by lower levels of progesterone in cells pretreated with estradiol or tamoxifen, both of which have been reported to increase the level of progesterone receptor in these cells. It has been reported that estrogen is essential and that progesterone is stimulatory for the formation of tumors by MCF-7 cells in athymic mice. The ability of these same two hormones to stimulate the production of plasminogen activator by these cells, under conditions where they have no effect on cell growth, raises the possibility that estrogen may not play a mitogenic role in the growth of these tumors. Rather, it may support tumor growth by inducing the cells to produce products, such as plasminogen activator, and possibly take on other characteristics essential to the malignant state.

Breast Neoplasms↗
PubMed1981

Effects of serum and insulin on the sensitivity of the human breast cancer cell line MCF-7 to estrogen and antiestrogens.

The effect of the antiestrogens tamoxifen and nafoxidine on the growth of the human breast cancer cell line MCF-7 is modified by both serum and insulin. Tamoxifen inhibition of the growth of MCF-7 cells in culture is reduced as the concentration of serum in the medium is increased from 0.1% to 5 to 10%. Estradiol does not stimulate cell growth over the same range of serum levels. Insulin changes the sensitivity of MCF-7 cells to both estrogen and antiestrogens. Cells growing in media containing insulin are less sensitive to inhibition by either tamoxifen or nafoxidine than are cells growing in its absence. In addition, higher concentrations of estradiol are required to stimulate the production of plasminogen activator when cells are grown in media containing insulin. This effect of insulin can be accounted for by the finding that insulin lowers the level of estrogen receptor in MCF-7 cells without altering the binding constant for the hormone. Cells grown with insulin have an average of 21,000 +/- 4,700 (S.D.) estrogen binding sites/cell compared to 62,000 +/- 9,700 sites/cell in cells grown in the absence of insulin. This difference in receptor level is sufficient to account for the difference in the concentration of estradiol needed for equivalent induction of plasminogen activator in cultures with or without insulin. These results indicate that the level of estrogen receptor in breast cancer cells can be changed and that the sensitivity of such cells, both to estrogen and to antiestrogens, is altered by changes in the level of estrogen receptor. They also have implications concerning the mechanism by which antiestrogens act to inhibit the growth of mammary tumor cells.

Breast Neoplasms↗
PubMed1976

Puromycin inhibition of eucaryotic ribosomes. Differences in sensitivity between polypeptide synthesis directed by endogenous mRNA and synthetic templates including poly(U).

In a protein synthesis sytem derived from porcine uteri we have made the following observations: 1. Synthesis directed by the endogenous mRNA of the system is more sensitive to inhibition by puromycin than poly(U) directed synthesis. 2. Synthesis directed by the synthetic templates poly(G,U) and poly(C,U) is more sensitive to inhibition by puromycin than poly(U) directed synthesis and frequently shows a sensitivity to puromycin similar to that directed by endogenous mRNA. 3. Protein synthesis was inhibited by three aminoacyloligonucleotides (C-A-Phe, C-A-Asp, and C-A-Pro) which are analogs of the 3' terminus of aminoacyl tRNAs. Of the three, C-A-Phe was the most active and C-A-Asp the least active but, unlike puromycin, inhibition by these compounds was the same for endogenous and poly(U) directed synthesis. These results are interpreted as supporting the proposal that the acceptor site of ribosomes contains an hydrophobic binding region which interacts with the side chain of aliphatic amino acids, and particularly with the aromatic side chain of phenylalanine.

Amino Acids↗
PubMed1975

Use of a flutter valve in treatment of pneumothorax in dogs and cats.

The use of a catheter and flutter valve to accomplish continuous thoracic drainage was evaluated in 12 dogs and 2 cats over a 2-year period. The system was found to be safe, reliable, and well tolerated. Compared with other drainage systems, this system requires less care from the veterinary staff.

Animals↗