Primary cultures of pituitary cells from adult female rats were exposed to increasing concentrations (10(-13) to 10(-6)M) of selected prostaglandins (PGE2, PGF2 alpha, PGI2, 6-keto-PGF1 alpha, and ...sulproston). The release of luteinizing hormone (LH) by the pituicytes was monitored. In a second series of experiments, pituitary cells were treated with prostaglandins as described above and additionally challenged with a submaximal stimulus of gonadotrophin-releasing hormone (GnRH; 10(-9) M). The spontaneous LH-release in all prostaglandin treated cultures did not differ from the controls. When stimulated with 10(-9) M GnRH, the LH-release increased approx. six-fold in all cultures, with no difference between prostaglandin treated cells and the respective controls. Thus, the prostaglandins tested - at least at concentrations less than or equal to 10(-6) M - have neither a direct positive or negative effect on pituitary LH-release, nor do they enhance or decrease the LH-releasing effect of GnRH. These prostaglandins are probably not involved in the cellular regulation of LH-release by the pituicyte.
Phenol Red (Phr) which is widely used as a pH indicator in cell culture media has recently been described to possess estrogenic activity in different cell types. In the present study we investigated ...if the dye shows such activity on LH secretion of cultivated rat pituitary cells and controlled the established effects of estradiol (E2) and keoxifene (K) in this model in the absence of Phenol Red. 24 h treatment of pituitary cell cultures with Phr led to enhancement of GnRH-stimulated LH secretion whereas 4 h treatment reduced LH secretion. When the cells received E2 instead of Phr for the indicated incubation periods we observed nearly identical results i.e. a short-term inhibitory and a long-term stimulatory effect on LH secretion. 24 h treatment of pituitary cell cultures with increasing concentrations of Phr led to a stimulatory effect on GnRH-stimulated LH secretion an effect that occurred at 10 microM got maximal at 100 microM and was lost at higher concentrations resulting in a bell-shaped dose-response curve. The inhibitory action of Phr was present at concentrations greater than or equal to 10 microM. Both effects could be blocked by the antiestrogen K indicating their specificity. K has recently been described to induce an antigonadotrophic effect in this model. Although high concentrations of the antiestrogen were still able to inhibit LH secretion this effect was not present at lower concentrations when Phr-free culture medium was used in the experiments. Thus Phr showed weak estrogenic activity in the gonadotroph. The established actions of E2 and K on LH secretion were qualitatively reproducible when Phr was excluded from the culture medium.
The effects of RU 486 on the modulation of LH release by progesterone were investigated in cultured anterior pituitary cells from ovariectomized adult female rats. The inhibitory effect of ...progesterone on LH secretion was demonstrable in estrogen-treated pituitary cells, in which addition of 10(-6) M progesterone to cells cultured in the presence of 10(-9) M estradiol for 52 h reduced the LH response to GnRH (10(-11) to 10(-7) M). When RU 486 was superimposed upon such combined treatment with estradiol and progesterone, the suppressive effect of progesterone on GnRH-induced LH release was completely abolished. The converse (facilitatory) effect of progesterone on LH secretion was observed in pituitary cells pretreated with 10(-9) M estradiol for 48 h and then with 10(-6) M progesterone for 4 h. When RU 486 was added together with progesterone during the 4 h treatment period, the facilitatory effect of progesterone was blocked and LH release fell to below the corresponding control value. The direct effect of RU 486 on LH secretion in the absence of exogenous progesterone was evaluated in cells cultured in the absence or presence of 10(-9) M estradiol and then treated for 4 to 24 h with increasing concentrations of RU 486 (10(-12) to 10(-5) M) and stimulated with GnRH (10(-9) M) during the last 3 h of incubation. In estrogen-deficient cultures, 4 h exposure to RU 486 concentrations of 10(-6) M and above decreased the LH response to GnRH by up to 50%. In cultures pretreated with 10(-9) M estradiol, GnRH-stimulated LH responses was inhibited by much lower RU 486 concentrations, of 10(-9) M and above. After 24 h of incubation the effects of RU 486 were similar in control and estradiol-pretreated pituitary cell cultures. Thus, RU 486 alone has a significant inhibitory effect on LH secretion that is enhanced in the presence of estrogen. The antiprogestin is also a potent antagonist of both the inhibitory and the facilitatory actions of progesterone upon pituitary gonadotropin release in vitro.
As a first step to investigate whether gonadotropin releasing hormone (GnRH) analogs might be able to modulate directly the proliferation of human epithelial ovarian carcinomata, we checked if ...binding sites for GnRH are present in these malignancies. Specific binding of 125ID-Ala6-des Gly10-GnRH-ethylamide (GnRH agonist = GnRH-A) could be demonstrated in plasma membranes from 32 out of 40 ovarian carcinomata tested. This binding was dependent on temperature, time and plasma membrane concentration. Mathematical analysis of the binding data showed that the interaction of GnRH-A with the binding sites was consistent with a single class of low affinity, high capacity binding sites (Ka = 1.42 +/- 0.14 X 10(5) M-1; range: 0.3-3.8 X 10(5) M-1; R = 209 +/- 69 X 10(-12) M/mg membrane protein; range 16-400 X 10(-12) M/mg MP; means +/- S.E., n = 32). Native GnRH and the GnRH antagonist D-p-Glu1, D-Phe2, D-Trp3,6-GnRH had Ka values comparable to those of the GnRH-A used. 125IGnRH-A binding could not be displaced by oxytocin, thyrotropin releasing hormone and corticotropin releasing factor in concentrations up to 10(-4) M. Somatostatin cross-reacted with binding sites from some carcinomata, while it did not displace GnRH-A binding in membranes from others. Though the functional role of this specific binding site for GnRH in human epithelial ovarian carcinomata is still obscure, it might be part of an autocrine regulatory system and provide a possible point of attack for therapeutic approaches using GnRH analogs in this malignancy.
The effects of the antiprogestins (APs) ZK 98.299, ZK 98.734 and RU 486 on GnRH-stimulated LH secretion and their antagonistic activity on progesterone (P) actions were investigated in cultured ...pituitary cells from adult female Wistar rats. P (100 nM) was able to exert a facilitatory effect on GnRH (1 nM)-induced LH secretion after short-term (4 h) treatment of estradiol-primed (1 nM, 48 h) rat pituitary cells. When the APs (10 pM-10 microM) were introduced during the 4 h incubation period with P the facilitatory effect of P was totally abolished at concentrations greater than 10 nM (ZK 98.299, ZK 98.734) and greater than 1 nM (RU 486). Also the APs were shown to block the inhibitory action of P which occurs after long-term incubation of pituitary cells with this steroid. However at concentrations greater than 10 nM (ZK 98.734, RU 486) and greater than 100 nM (ZK 98.299) this antagonistic action of the APs was lost. To evaluate whether the APs have direct effects on GnRH-induced LH secretion in the absence of exogenous P pituitary cells cultivated for 48 h with or without 1 nM estradiol were incubated for 4 or 24 h with increasing concentrations of the APs (10 pM-10 microM). Four hour treatment of non-estradiol-primed cells with ZK 98.299 or ZK 98.734 was without any effect on the LH response to a 1 nM GnRH-stimulus. Only the highest concentration of RU 486 (10 microM) reduced the LH response. Twenty-four hour treatment of the cultures with the APs led to enhancement of GnRH-stimulated LH secretion by up to 113, 37 and 33% for ZK 98.734, ZK 98.299 and RU 486, respectively. When estradiol-primed cells were used for the same experiments we observed exclusively inhibitory effects on GnRH-induced LH secretion after 4 and 24 h treatment periods. It is concluded that these new APs are potent inhibitors of P-actions, but also per se they induce diverse effects on GnRH-stimulated LH secretion in cultured rat pituitary cells which have to be taken into account.
GnRH-like substances have been isolated from interstitial fluid from the rat testis and have been found to exert direct, mainly inhibitory effects on steroidogenesis. In rat testis, specific GnRH ...receptors have been shown, but so far no GnRH-receptors have been isolated from the human testis. In this study testicular tissue from nine elderly men was incubated with either 3H-pregnenolone or 3H-progesterone and the steroid metabolic patterns were analyzed. In parallel incubations a GnRH-agonist was added to the incubate in concentrations of 10(-6) M or 10(-7) M. Furthermore, receptor studies were performed in tissue specimens from four of these untreated patients as well as in tissue specimens from five GnRH-agonist treated patients. No consistent effects were elicited by the addition of GnRH-agonist on the steroid metabolic patterns in vitro after three hours incubation. In the receptor studies the GnRH-agonist was bound to the testicular tissue, although the binding sites were of low affinity and high capacity, indicating a less specific kind of binding than classical receptor binding.
The standard treatment of locally advanced esophageal cancer comprises multimodal treatment concepts including preoperative chemoradiotherapy (CRT) followed by radical surgical resection. However, ...despite intensified treatment approaches, 5-year survival rates are still low. Therefore, new strategies are required to overcome treatment resistance, and to improve patients’ outcome. In this study, we investigated the impact of Wnt/β-catenin signaling on CRT resistance in esophageal cancer cells. Experiments were conducted in adenocarcinoma and squamous cell carcinoma cell lines with varying expression levels of Wnt proteins and Wnt/β-catenin signaling activities. To investigate the effect of Wnt/β-catenin signaling on CRT responsiveness, we genetically or pharmacologically inhibited Wnt/β-catenin signaling. Our experiments revealed that inhibition of Wnt/β-catenin signaling sensitizes cell lines with robust pathway activity to CRT. In conclusion, Wnt/β-catenin activity may guide precision therapies in esophageal carcinoma patients.
Purpose - To describe the development of a novel polyether(meth)acrylate-based resin material class for stereolithography with alterable material characteristics.Design methodology approach - A ...complete overview of details to composition parameters, the optimization and bandwidth of mechanical and processing parameters is given. Initial biological characterization experiments and future application fields are depicted. Process parameters are studied in a commercial 3D systems Viper stereolithography system, and a new method to determine these parameters is described herein.Findings - Initial biological characterizations show the non-toxic behavior in a biological environment, caused mainly by the (meth)acrylate-based core components. These photolithographic resins combine an adjustable low Young's modulus with the advantages of a non-toxic (meth)acrylate-based process material. In contrast to the mostly rigid process materials used today in the rapid prototyping industry, these polymeric formulations are able to fulfill the extended need for a soft engineering material. A short overview of sample applications is given.Practical implications - These polymeric formulations are able to meet the growing demand for a resin class for rapid manufacturing that covers a bandwidth from softer to stiffer materials.Originality value - This paper gives an overview about the novel developed material class for stereolithography and should be therefore of high interest to people with interest in novel rapid manufacturing materials and technology.
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