Effect of growth on the estrogen receptor levels in MCF-7 cells

MCF-7 cells have been shown to contain estrogen receptor in several cell fractions following homogenization: nuclei, microsomes, and cytosol. The amount of 17 beta-estradiol-binding capacity found in each cellular compartment depended on the inclusion of detergent in homogenization buffers and on the use of 0.25 M sucrose in the nuclear washes. 17 beta-Estradiol receptor (E2R) associated with nuclei (whole nuclei exchange assay, 0.6 M KCl soluble, and that found on membranes sheared from crude nuclear pellets by centrifugation in 0.25 M sucrose buffer) displayed a dissociation constant (Kd) of 0.77 +/- 0.01 (S.D.) nM (n = 7). KdS of the cytoplasmic (microsomes and soluble) receptors were determined to be 0.33 +/- 0.10 nM (n = 9). Exchangeable ligand on partially purified nuclei assumed its highest level in MCF-7 cells during logarithmic growth in serum-containing media (0.8 pmol/micrograms DNA) but declined after the culture reached confluence (0.2 pmol/micrograms DNA). Seventy-five % of the nuclear E2R declined linearly after feeding MCF-7 cells in logarithmic growth phase an estrogen- and serum-free medium (t1/2 3.5 days). Another class of salt-extractable nuclear receptor (0.2 pmol/micrograms DNA) persisted in postconfluent cultures whether fed estrogen (serum-containing media) or not (serum-free media). This residual binding capacity remained in nuclei of MCF-7 cells for an extended period of time. MCF-7 cells demonstrated functionality of E2R throughout their growth phases as evidenced by the replenishment of cytosolic E2R and the induction of progesterone receptor when given 17 beta-estradiol.

Estrone receptor formation during the processing of estradiol-receptor complex in MCF-7 cells

Human breast cancer cells (MCF-7, maintained in long-term culture) contain separate estrogen receptors specific for either 17 beta-estradiol or estrone. Utilizing optimum conditions for the protamine sulfate assay, it has been possible to demonstrate both receptors in the 0.6 M KCl extract of nuclei and in the cytosol. Similarly, in the exchange assay, high-affinity low-capacity binding sites for 17 beta-estradiol and estrone have been found in the salt-extracted nuclear residue. Dissociation constants and binding capacities were determined for either receptor in the absence of the other [e.g., estrone receptor (E1R) in the cytosol or nuclear residue from 17 beta-estradiol-stimulated cells] or, when both receptors were present, a saturating amount of the other estrogen (unlabeled) was added to the assay mixture (e.g., the salt-extractable nuclear receptors). Specificity was demonstrated by the inability of estrone to compete with 17 beta-[2,4,6,7-3H]estradiol for the 17 beta-estradiol receptor (E2R) at molar excesses less than 10-fold. Likewise, there was no inhibition of [6,7-3H]estrone binding to its receptor by molar excesses of 17 beta-estradiol below 100-fold. Other steroid hormones were very weak competitors of [6,7-3H]estrone, even at 1000-fold molar excesses. The quantitative relationships of these two estrogen receptors were shown to fluctuate in the various cellular compartments following incubation (37 degrees) of MCF-7 cells with 10(-8) M 17 beta-estradiol. This level of 17 beta-estradiol elicited the translocation of all detectable cytosolic E2R to the nucleus, where, after an incubation of 1 hr, the salt-resistant 17 beta-estradiol disappeared and 40% of the extractable 17 beta-estradiol-binding capacity was lost (processed). Simultaneously, the E1R which remained in the nuclear residue appeared in the nuclear extract, and ultimately this receptor accumulated in the cytosol. The estrone-binding capacity (0.78 pmol/mg DNA) which appeared following the processing of E2R nearly equalled the loss of 17 beta-estradiol binding sites per cell (0.85 pmol/mg DNA). Concentrations of 17 beta-estradiol which elicited the greatest processing of E2R in these incubations brought about the appearance of maximum levels of E1R in MCF-7 cells. Considering these results in the light of data previously reported from this laboratory concerning the metabolic and ligand fate of 17 beta-[3H]estradiol in MCF-7 cells, processing would appear to involve the formation of E1R in the salt-resistant nuclear compartment followed by the accumulation of E1R in the cytosol.

Caries experience of Danish children evaluated by the child dental health recording system

The purpose of this report is to describe certain features of the child dental health care in Denmark. The caries picture and the caries distribution pattern in Danish children aged 2--15 years are demonstrated and some regional variations are analyzed. The study is based on epidemiologic data collected in the school year 1977--78 from about 500 000 children being treated in accordance with the Child Dental Care Act. The data collection is being effectuated annually under a child dental health recording system, and the aim and function of this system is discussed. The mean defs- and DMFS-indices are illustrated for individual age groups reflecting the natural history of dental caries. Certain trends in relation to different geographical distributions of caries and in relation to different cohorts of children from 1972 to 1977 are discussed. The analysis of the caries picture is extended by means of the distribution pattern according to caries severity zones. Finally, the use of caries epidemiologic data for planning and resource allocation purposes is illustrated and some policy implications for the development of the child dental health services in Denmark are discussed.

Utilization of dental services in the adult Danish population 1975

Lack of information on the dental behavior of adults in Denmark has become a major problem in the national planning of dental services. The purpose of this study was to establish the pattern of utilization of dental services among adult Danes (aged 15 and above). A three-stage cluster sampling design covering the total adult population of Denmark was used to draw a representative sample comprising 1,600 persons. Household interviews by trained interviewers were carried out. Of the adults interviewed, 58% reported yearly dental visits the last 5 years, 32% had not seen a dentist or only when in pain, and 10% went irregularly. Differences according to place of living, age, sex, occupation and school dental care were found. 63% of those who had seen a dentist reported bad teeth or were edentulous with or without dentures. 10% reported fear, 9% had good teeth and 5% reported economic difficulties. The most frequent treatments at the latest dental visit were cleaning and filling for the regular patients and extractions and dentures for the nonregular patients. A multiple classification analysis revealed that the number of teeth was the strongest predictor for dental services, with the following predictors in descending order: age, occupation, place of living, economy, sex and school dental care. These variables could explain 58% of the variation in utilization.

Public attitudes concerning water fluoridation in Denmark

Attitudes towards water fluoridation were assessed in a national probability sample of 1,600 adult Danes. 23% favored and 48% opposed water fluoridation while 29% didn't know. Differences in opinion were found in relation to sex and age, occupation, residence, and dental behavior. Compared with an earlier Danish study, a shift towards more expressed opposition to water fluoridation seems to have taken place.