Biomedical subjects

G Vollmer

Publications and source records attributed to G Vollmer.

At least 55 records · Page 3Linked to original sources

PubMed1994

Binding of 2-hydroxyestradiol and 4-hydroxyestradiol to the estrogen receptor of MCF-7 cells in cytosolic extracts and in nuclei of intact cells.

The catechol estrogens (CE), 2-hydroxyestradiol (2-OH-E2) and 4-hydroxyestradiol (4-OH-E2) were analyzed for their binding affinity to the estrogen receptor of MCF-7 cells. Applying a competitive binding assay to cytosols prepared from MCF-7 breast cancer cells, we measured a relative binding affinity of 23% (2-OH-E2) and 26% (4-OH-E2) compared to E2. Nuclear binding assays with the same cell line demonstrated a high specific binding with Kd's of 0.31 nM (2-OH-E2) and 0.21 nM (4-OH-E2). The relative binding affinity measured was 25% and 42% for 2-OH-E2 and 4-OH-E2, respectively. Based on this nuclear binding it can be concluded that the estrogen receptor occupied by CE is bound within the nucleus and might therefore be transcriptionally active.

Binding, Competitive↗

PubMed1994

In vitro interactions of endometrial stromal and epithelial cells in Matrigel: reorganization of the extracellular matrix.

Fragments of human endometrial glands and dispersed endometrial stromal cells were cultured together in a thick layer of reconstituted basement membrane (Matrigel). Epithelial cells kept their glandular morphology whereas stromal cells grew into round clusters of mainly fusiform cells. Transmission electron micrographs showed collagen fibers between stromal cells as well as in surrounding extracellular matrix after 2.5 weeks. A well-defined basement membrane was found when epithelial and stromal cells were in close proximity to each other. Beneath the lamina densa there was a loose network of collagen fibers or a dense fibrillar network arranged parallel to the cell layers. Epithelial cells showed hemidesmosomes at their basal surface where they were close to stromal cells.

Cell Communication↗

PubMed1994

[Detection of tenascin in stomach cancer. An immunohistochemical study].

Tenascin, a glycoprotein of the extracellular matrix, is involved in epithelial proliferation, differentiation and cell migration during embryonic development. Later on, it is important in proliferative processes like tumor growth and wound healing. We examined the distribution of tenascin, especially in the stroma near basement membranes, in paraffin sections from 25 patients with gastric cancer by immunohistological staining with regard to tumor staging, grading and Lauren classification. In two series we used a monoclonal and a polyclonal antibody against human tenascin. In most of the sections there was a more intensive staining of the surrounding stroma in areas close to the tumor, which could indicate the direction of tumor growth. In highly differentiated tumors we found a positive, yet discontinuous staining close to the basement membrane. In contrast to this, we saw a more diffuse reaction of the stroma with network-like staining of the collagen fibres in undifferentiated tumors. In lymph nodes we also detected a small number of tumor cells by staining of the surrounding stroma.

Adenocarcinoma↗

PubMed1994

Tamoxifen and ZK 119010 exert mixed agonistic and antagonistic effects on pS2 expression in MCF-7 cells.

pS2 is a major estradiol-inducible gene in MCF-7 breast cancer cells. In this study we tested the effects of tamoxifen and ZK 119010, a novel nonsteroidal antiestrogen, on pS2 gene expression with or without a pretreatment of cells with estradiol (10(-11), 10(-8) M). Estradiol increased pS2 expression in MCF-7 cells approximately 12-fold. Tamoxifen (10(-6) M) reduced estradiol-induced pS2 expression to 78% of the stimulated level, while ZK 119010 was 50% effective. Given alone, either of the two antiestrogens in the above concentrations evoked a pS2 gene expression in MCF-7 cells significantly above background levels. From these data we conclude that the antiestrogens tamoxifen and ZK 119010 possess both antagonistic and agonistic potencies in MCF-7 cells. However, the antiestrogenic potency of ZK 119010 seems to be higher than that of tamoxifen.

Blotting, Northern↗

PubMed1993

The EnDA endometrial adenocarcinoma: an oestrogen-sensitive, metastasizing, in vivo tumour model of the rat.

A high percentage of endometrial carcinomas contain oestrogen and progesterone receptors. For endocrine therapy of recurrent endometrial carcinoma, only high-dose progestins are in clinical use. As, therefore, the development of new endocrine treatment strategies is of great interest, suitable animal models for this tumour are essential. Up to now, only human tumour xenografts transplanted in immune-deficient nude mice, but no syngeneic in vivo tumour models, have been available. In the present article we describe the hormone sensitivity of the EnDA endometrial adenocarcinoma of the DA/Han rat growing as s.c. implants in DA/Han rats and athymic nude mice in serial passage. In both species, the tumour expresses oestrogen, but no progesterone receptors. Transplanted in DA/Han rats or nude mice, ovariectomy reduced tumour weight by 64% and 46% respectively. In both species substitution of ovariectomized animals with oestradiol restored tumour weights to intact control levels. Oestradiol substitution of intact animals did not further enhance tumour growth. The growth of the primary tumour was inhibited by medroxyprogesterone acetate (MPA) at a dose of 100 mg/kg by 67% and by tamoxifen at a dose of 20 mg/kg by 38%. Lung metastases were regularly seen in both species, although to a lesser extent in nude mice than in DA/Han rats. Tamoxifen treatment did not alter the number of lung metastases, whereas MPA or ovariectomy produced a significant reduction in the number of lung metastases. The EnDA endometrial carcinoma of the DA/Han rat with respect to its oestrogen sensitivity, oestrogen receptor expression, morphology and metastatic growth, grossly resembles a typical endometrial adenocarcinoma and can therefore be regarded as a useful in vivo experimental model for the evaluation of new endocrine treatment strategies.

Adenocarcinoma↗

PubMed1993

Catecholestrogens are MCF-7 cell estrogen receptor agonists.

Catecholestrogens are important metabolites of estradiol and estrone in the human. Considerable interest has focused on the catecholestrogens 2-hydroxy- and 4-hydroxyestradiol since they bind to the estrogen receptor with an affinity in the range of estradiol. Using the MCF-7 cell line, we analysed the capacity of purified catecholestrogens to transform the estrogen receptor into its high affinity nuclear binding form and to affect receptor-dependent processes such as proliferation and expression of the progesterone receptor (PR). Incubations with 2-hydroxy- and 4-hydroxyestradiol at 10(-8) M for 1 h resulted in tight nuclear binding of the estrogen receptor. During treatment of the cells with catecholestrogens we obtained a marked increase in proliferation rate of 36 and 76% for 2-hydroxy- and 4-hydroxyestradiol, respectively, relative to the inductive effect of estradiol (100%). The PR level, was slightly increased by treatment with 2-hydroxyestradiol (10%), whereas treatment with 4-hydroxyestradiol increased the PR level at 28%, compared to estradiol (100%). From these results we conclude that the 2- and 4-hydroxylated derivatives of estradiol are active hormones and are able to initiate estrogen receptor mediated processes in MCF-7 cells.

Breast Neoplasms↗

PubMed1993

Localization of tenascin in uterine sarcomas and partially transformed endometrial stromal cells.

Normal mesenchymal cells within developing embryonic organs and transformed stromal cells in organs undergoing spontaneous carcinogenesis have the capacity for normal or altered expression of the extracellular matrix glycoprotein tenascin (Tn). Mesenchymal cell constituents of normal adult organs show only a very limited tendency to deposit Tn in their extracellular matrix. In the present study, we investigated whether malignant human mesenchymal cells derived from uterine sarcomas or normal human endometrial stromal cells partially transformed via transfection with selected oncogenes have the capacity to produce and deposit Tn. We reached the following conclusions: (1) compared with normal endometrial tissues, uterine sarcomas show heterogeneous, but increased, immunoreactive staining patterns exclusively within the extracellular compartment, regardless of the histologic subtype of the tumor; (2) in vitro, all normal and transfected stromal cells and cell lines examined secreted Tn into the tissue culture medium; (3) this secretory ability was not translated into morphologic uniformity, since immunoreactivity detected by confocal laser scanning microscopy was observed in only selected cell populations; (4) also, the deposition and the incorporation of Tn depended upon the density of transfected cells, and (5) double-staining experiments revealed that Tn could always be localized in close proximity to fibronectin. In summary, the production of Tn is increased in most cases of human uterine sarcoma. The capacity of stromal cells to deposit Tn in a matrix-like structure in vitro, rather than increase production of Tn, is correlated with the degree of neoplastic progression.

Adult↗

PubMed1992

Functions of estrogens and anti-estrogens in the rat endometrial adenocarcinoma cell lines RUCA-I and RUCA-II.

Inbred rats of the DA/Han and BDII/Han strains have been proposed as suitable model systems for studying hormonal carcinogenesis, because they die mainly from hormone-dependent endometrial adenocarcinoma. Here we characterize the RUCA-I cell line derived from an endometrial adenocarcinoma of an inbred DA/Han rat and the RUCA-II cell line derived from an endometrial adenocarcinoma of an inbred BDII/Han rat. The RUCA-I cell line, if transplanted to the neck of female DA/Han rats, gives rise to endometrial adenocarcinomas at the ectopic site. The morphology of these ectopically grown tumors is predominantly of the moderately differentiated sub-class. In contrast, ectopic tumor growth of the RUCA-II cell line can be observed only if cells are transplanted to athymic nude mice. Biochemically, both cell lines are characterized by the stable expression of estrogen receptors. However, no statistically significant mitotic response of RUCA-I and RUCA-II cells to estradiol was measurable, and no induction of expression of the progesterone receptor by estradiol was detectable, although estradiol transformed the estrogen receptor into its stable DNA-binding state. In contrast, the rate of proliferation of RUCA-I but not of RUCA-II cells was reduced in the presence of 10(-6) M tamoxifen. From these results we conclude that (i) both cell lines, RUCA-I and RUCA-II, represent a new and promising endometrial tumor model; (ii) the mechanism of the hormone-dependent growth regulation of RUCA-I and RUCA-II cells is obviously impaired; (iii) the RUCA-I cell line appears to be a suitable model system for the study of molecular aspects of estrogen- and tamoxifen-dependent gene expression.

Adenocarcinoma↗

PubMed1992

Down-regulation of tenascin expression by antiprogestins during terminal differentiation of rat mammary tumors.

Studies on tenascin expression in hormonally dependent growing tissues of breast and endometrium suggested that its expression parallels the progression of normal or malignant proliferative alteration of the tissue. With the study presented here we addressed the question of whether antiprogestin-induced terminal differentiation down-regulates tenascin expression. By comparative immunolocalization of tenascin in sections of untreated 7,12-dimethylbenz[alpha]anthracene-induced tumors, tumors grown in ovariectomized animals, tamoxifen-treated tumors, and antiprogestin-treated tumors, we obtained the following results. (a) The entire extracellular space of the stromal mesenchyme was filled by tenascin immunoreactivity in cases of untreated control tumors. (b) Both ovariectomy and antiestrogen treatment with tamoxifen did not affect the overall staining pattern and resulted in a slight increase of the arbitrarily judged staining intensity. (c) Within antiprogestin-treated tumors tenascin-like immunoreactivity predominantly was restricted to fiber-like, collagenous connective tissue structures, which appeared in the stromal compartment as a result of the antiprogestin treatment. In large areas of the tumor composed of apparently secretory active tumor cells we failed to immunolocalize tenascin. Our results provide further evidence that expression of tenascin reflects both benign and malignant proliferative alterations of the tissue, whereas its down-regulation is correlated to differentiation of the tissue. Additionally, evidence is provided that the mechanism of tumor growth inhibition by antiprogestins indeed is induction of terminal differentiation of tumor cells.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1992

Effects of the SV40 large T antigen and EJ ras oncogene on fibronectin localization in human endometrial cells as viewed by confocal laser scanning microscopy.

We utilized confocal laser scanning microscopy to examine the localization of fibronectin deposition in cultures of human endometrial stromal cells. We found that fibronectin in normal human endometrial stromal cell cultures was both intracellular, occurring in rough endoplasmic reticulum and in perinuclear regions, and extracellular, occurring diffusely over the entire cell surface. Endometrial stromal cells were transfected with a plasmid containing an origin-defective Simian Virus 40 (SV40) which codes for a temperature-sensitive large T antigen. When these cells were placed under temperature-restrictive conditions for large T-antigen function, they exhibited staining patterns similar to normal endometrial cells. Fibronectin deposition in cultures of partially or fully transformed endometrial cells was not intracellular as in normal cells, but was localized primarily between cells. Cells expressing the SV40 large T antigen deposited fibronectin mainly in parallel clumps between cells. Cells expressing both the SV40 large T antigen and the EJ ras oncogene, at high cell density, displayed networks of fibronectin arranged in matrix-like patterns between cells. The malignant cell line examined, sarcoma cells, also exhibited fibronectin networks between cells. Cell density affected fibronectin deposition in endometrial stromal cells expressing the EJ ras oncogene. At low density, cells expressing the SV40 large T antigen and the EJ ras oncogene displayed diffuse fibronectin patterns and, at high density, these cells formed colonies with networks of fibronectin between cells.

Antigens, Polyomavirus Transforming↗

PubMed1991

Specific low affinity binding sites for gonadotropin-releasing hormone in human endometrial carcinomata.

Specific low-affinity high-capacity binding sites for gonadotropin-releasing hormone (GnRH) have recently been discovered in human breast and ovarian carcinomata. We checked whether similar binding sites are present in human endometrial cancer. Plasma membrane preparations were incubated with [125I,D-Ala6-desGly10]-GnRH-ethylamide in the presence or absence of unlabelled GnRH agonists or other peptides. GnRH-binding could be demonstrated in all 12 tumor samples tested. The mathematical analysis of the binding data was consistent with a single class of low affinity (Ka = (0.8-1.4) x 10(5) M-1) and high-capacity (Bmax = (134-142) x 10(-12) M/mg membrane protein) binding sites. Native GnRH had a similar affinity to the binding sites as the GnRH agonist used. Other peptides such as oxytocin, somatostatin and thyrotropin-releasing hormone did not crossreact with the binding sites. A photolabelled derivative of [D-Lys6]-GnRH was prepared with the bifunctional photolabile reagent (4-azidobenzyl)-N-hydroxysuccinimide. Photoaffinity labelling of endometrial carcinoma membranes and subsequent sodium dodecyl sulfate electrophoresis in 10% polyacrylamide gel revealed the presence of a single molecular mass component of 62 +/- 1.9 kDa. The appearance of this photolabelled binding site could be largely suppressed by the addition of unlabelled GnRH-agonist (10(-4) M) and thus represents the specific binding site for GnRH in endometrial cancer.

Affinity Labels↗

PubMed1991

[Algorithms, brains, computers. What they know and what they do not. I].

Our concern for machines and for their abilities, though quite ancient, has increased with the outstanding achievements of modern computers. What, then, is typical of a machine? Is its output really limited by our input? For questions like these, an appropriate tool is the concept of algorithm. Algorithms are best characterized as mental tools ("Denkzeuge").

Algorithms↗

PubMed1991

[Algorithms, brains, computer. What they know and what not. II].

In order to say something substantial about the fundamental limits of machines (especially of computers) and of human calculations, we must explicate the concept of algorithm. Such an explication is provided by the Turing machine. Thus, problems have been discovered which cannot be solved algorithmically. For other problems there are problem-solving procedures, but no elegant algorithms. That men are fundamentally superior to machines has not been shown as yet.

Algorithms↗

PubMed1991

Altered tenascin expression during spontaneous endometrial carcinogenesis in the BDII/Han rat.

The BDII/Han rat develops spontaneous endometrial adenocarcinoma, which appears virtually identical histologically to human endometrial adenocarcinoma. The incidence rate of cancer formation in the rat is 90% and the mean lifetime of the animals is 22 months. This animal model therefore, is useful in the study of molecular aspects of spontaneous transformation as well as mammalian neoplastic progression. In this study we address the in-situ expression of tenascin, an extracellular matrix glycoprotein, during normal cyclic growth, during development of proliferative states, and during malignant transformation of the endometrium. Trace amounts of immunocytochemically detectable tenascin were found in 10% of young BDII/Han rats with a normal estrus cycle. In these inbred animals no tenascin was detectable in uteri without neoplastic progressive alterations of the endometrium. Tenascin immunoreactivity first appeared during proliferation in one of three uteri with cystic glandular hyperplasia. Prominent tenascin expression was detectable in all adenomatous hyperplasia, but restricted to the stromal mesenchyme, that surrounded the glands. In all endometrial adenocarcinomas tested, essentially the entire extracellular space of the stromal mesenchyme was immunoreactive with anti-tenascin antibodies while the epithelial glands themselves were negative. This staining pattern was observed independent of the degree of tumor differentiation or extent of myometrial invasion. The tenascin staining pattern was not significantly altered in tumors transplanted into the soft tissues of the neck of female BDII/Han rats. From our studies we conclude that tenascin may be a marker for the early detection of proliferative endometrial states.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗

PubMed1991

Changes in the cellular phenotype and extracellular matrix during progression of estrogen-induced mesenchymal kidney tumors in Syrian hamsters.

The cellular origin of estrogen-induced kidney tumors in male Syrian hamsters has been repeatedly the subject of controversy. Several authors have proposed that the tumors arise from proximal tubules, from a combination of tubular and interstitial stromal cells, or solely from interstitial cells. Because of the model character of this tumor for hormone-associated cancer, it was further investigated in this study with respect to morphology, enzyme and intermediate filament pattern, the expression of alpha-smooth muscle actin and the extracellular matrix proteins fibronectin and tenascin. These analyses were carried out with early and late tumors as well as metastases to determine possible changes in expression of biochemical parameters during the development and progression of this neoplasm. The enzyme histochemical and intermediate filament patterns were usually the same as those described previously for proliferative foci and early tumors, i.e. highly elevated activities of glucose-6-phosphate dehydrogenase, adenylate cyclase and alkaline phosphatase, a lack of glucose-6-phosphatase and gamma-glutamyltransferase and coexpression of vimentin and desmin, alpha-smooth muscle actin could not be detected in early lesions. In five of 24 advanced tumors inclusions of kidney tubules were found which showed various degrees of alteration in their morphology and enzyme histochemical pattern, but were often directly connected with tubular segments of normal appearance outside the tumor. Like the normal tubules, the enclosed tubular segments were strongly positive for cytokeratin but never expressed vimentin or desmin. Among the 24 tumors studied, two contained cysts which expressed cytokeratin and sometimes also vimentin but not desmin. The enzyme histochemistry of the cells lining the cysts was similar to that of the surrounding tumor mass, except adenylate cyclase was lacking and alkaline phosphatase was not uniformly distributed. In tumors containing cytokeratin-positive cysts, there often were cytokeratin-positive, vimentin-negative and desmin-negative tumor formations in close contact to these cysts. With the exception of cyst formation, the pattern of metastases were identical to that of the primary tumors. All large tumors and the main component of the metastases expressed vimentin, desmin and fibronectin. Mesothelia surrounding metastatic tumor complexes were positive for vimentin, desmin, alpha-smooth muscle actin, fibronectin, cytokeratin and tenascin. It was concluded from these and previous observations on early stages of tumor development that the estrogen-induced hamster kidney tumor originates from mesenchymal interstitial cells (probably pericytes) which may rarely acquire an epithelial phenotype by metaplastic transformation during tumor progression.

Adenylyl Cyclases↗

PubMed1991

Methyl and bromo derivatives of estradiol are agonistic ligands for the estrogen receptor of MCF-7 breast cancer cells.

The binding affinity and relative estrogenic potency of 2-bromo-, 4-bromo-, 2-methyl- and 4-methylestradiol was evaluated in MCF-7 breast cancer cells. The relative binding affinities compared to estradiol were 47% for 2-methyl-, 25% for 4-methyl-, 37% for 4-bromo- and 17% for 2-bromoestradiol. However, both 2- and 4-methyl- as well as 2- and 4-bromoestradiol were able (a) to translocate the cytosolic estrogen receptor into the nucleus and (b) to induce the progesterone receptor in a concentration dependent manner. Finally, all ring-A substituted estrogens used in this study induced the pS2 mRNA as demonstrated by Northern-blotting. From these findings we conclude that 2-bromo-, 4-bromo-, 2-methyl- and 4-methylestradiol are agonistic ligands for the estrogen receptor in MCF-7 breast cancer cells.

Blotting, Northern↗

PubMed1990

Regeneration of a chimeric retina from single cells in vitro: cell-lineage-dependent formation of radial cell columns by segregated chick and quail cells.

We report here that similar to E6-chicken retinal cells, dissociated cells from 5.5-day-old (E5.5) quail retinae reaggregate in rotary culture, multiply about tenfold and reestablish histotypical areas. These cellular aggregates include all nuclear layers either with inversed or correct laminar polarity, depending on the local origin of the cells (called "rosetted" and "laminar" in-vitro-retinae (IVR), respectively; Layer and Willbold 1989). In combined cultures, chick and quail cells are evenly mixed only during the first two days of culture. Along with the assembly of single cells into rosettes and then into discrete laminae, sectors of chick and quail cells begin to segregate. They are delineated by borders running radially through all three nuclear layers. Thus, interspecies migration of cells at this advanced stage of differentiation is strongly inhibited. Concomitant with this segregation, coherent radial columns spanning all three layers but containing cells from either species only, can be traced histologically. We conclude that a weak segregation of chick and quail retinal cells takes place already at the single cell level, but that the permanent segregation of entire tissue parts must be due to clonal cellular proliferation within the IVR in conjunction with some developmental-structure mechanism retaining clonal progenies within a columnar order.

Animals↗

PubMed1990

Spatial and molecular aspects of estrogen and progesterone receptor expression in human uteri and uterine carcinomas.

The expression of steroid hormone receptors as molecules reflecting processes of development and differentiation in the human uterine tissue was analysed in a spatial distinct fashion: tissue samples were excised at the fundus and at different, spatially distinct positions of the uterus. They were analysed for concentrations of cytosolic estrogen and progesterone receptors in supernatants from frozen sections using an isoelectric focusing technique. The spatial and molecular distinct, qualitative and quantitative pattern of their expression in the human uterus and uterine adenocarcinomas were studied by sectioning tissue sample from the functionalis through the basalis of the endometrium until reaching deep myometrial parts of the tissue: (1) Specific spatial patterns of estrogen and progesterone receptor levels were detectable throughout the menstrual cycle. (2) For proliferative endometrium from the functionalis to the basalis of the endometrium, the content of both cytosolic receptor species increased up to 6-fold. (3) Differences detectable were less pronounced in the myometrial part of the tissue. (4) Differences of steroid receptor concentrations measured in the endometrium at different uterine positions were highest between fundus and corpus of the endometrium. (5) Maximal differences were detectable around ovulation. (6) After secretory transformation of the organ, specific patterns were still detectable, however quantitative differences were less pronounced. (7) Additionally, quantitative differences measurable were accompanied by variations of molecular properties of the progesterone receptor as demonstrated in an isoelectric focusing gel. (8) In endometrial adenocarcinomas, not only significant quantitative alterations in steroid receptor content were measured, but also a significantly changed spatial pattern of receptor concentrations, also a change of the molecular properties of the progesterone receptor was resolved if these tumor parameters were compared to those detected in the normal tissue of the same organ surrounding the tumor.

Adenocarcinoma↗