Search PubMed⌕ Search

Biomedical subjects

M Ernst

Publications and source records attributed to M Ernst.

At least 217 records · Page 12Linked to original sources
PubMed1989

Phenol red mimics biological actions of estradiol: enhancement of osteoblast proliferation in vitro and of type I collagen gene expression in bone and uterus of rats in vivo.

Since osteoblasts are direct targets for estradiol in vitro, and Phenol Red has been reported to bear estrogen-like bioactivity, we investigated whether the pH indicator also mimicked the biological effects of estradiol on bone cells in vitro. We then asked whether estrogenic effects of Phenol Red could be observed in vivo, firstly on the uterus, and if so, whether Phenol Red could also effect bone in vivo. The proliferation of calvarial osteoblasts was stimulated by commercially available preparations of Phenol Red in a dose-dependent manner at 1.5-50 microM. This effect was not abolished in the presence of an antibody against insulin-like growth factor I. In addition, Phenol Red increased alpha 1 (I) collagen mRNA levels of osteoblasts in vitro. 17 beta-estradiol (1.5 micrograms) or Phenol Red (10 mg) administration to immature female rats (45-50 g) resulted in a weight gain of the uterus, and alpha 1(I) procollagen transcripts were more abundant in RNA prepared from uterus of drug-treated rats than observed in the control rats. Similarly, higher procollagen mRNA steady-state levels were observed in RNA prepared from parietal bones of Phenol Red or estradiol-treated rats compared to RNA from control rats. The data extend previous findings in vitro by demonstrating that Phenol Red also exerts estrogen-like effects in vivo. Moreover, we show that Phenol Red stimulates bone cells and, therefore, is likely to interfere at least in experiments designed to investigate estrogen effects on osteoblasts.

Animals↗
PubMed1989

Interleukin 2 as an inducer of proliferation in Klebsiella-stimulated human B cells.

Klebsiella membranes (KLEBS M), a membrane preparation from Klebsiella pneumoniae, acts as a T-cell independent polyclonal B-cell activator (PBA), stimulating B cells to mature into Ig-secreting cells without prior proliferation. The KLEBS M-activated B cells express Tac antigen. Recombinant interleukin 2, used in costimulation with KLEBS M, induces proliferation and increases the Ig secretion of B cells. On the other hand, KLEBS M-activated B cells do not respond to human BCGF. The lack of proliferation in KLEBS M-stimulated mononuclear cells is shown to be due to the inability of this PBA to induce the production of interleukin 2 in T cells.

B-Lymphocytes↗
PubMed1989

Effect of dexamethasone on mechanisms responsible for regulation of polyclonal B-cell response.

The effect of dexamethasone (Dex) on the differentiation of pokeweed mitogen (PWM), or Staphylococcus aureus Cowan I (SAC)-stimulated human peripheral blood mononuclear cells (PBMC), into immunoglobulin secreting cells (ISC) was studied with special emphasis on the regulatory role of IL-2 in these systems. Dex, known to reduce endogenous IL-2 production and expression of IL-2 receptors, reduced the proliferation of pokeweed mitogen-activated T-cells, and the proliferation was restored by exogenous recombinant interleukin 2 (rIL-2). Furthermore, Dex enhanced in PWM and in SAC-stimulated cultures, the number of ISC. Addition of rIL-2 resulted in a further increase of ISC in SAC-stimulated cultures, whereas in PWM-stimulated cultures the enhancing effect of Dex was reversed. When IL-2 receptors were blocked by a monoclonal anti-IL-2 receptor antibody rIL-2 was no longer suppressive. Addition of monocytes to PWM-stimulated cultures resulted in suppression or the number of ISC, which was even more pronounced when monocytes were pretreated with rIL-2. In contrast to ISC, neither a suppressive effect of rIL-2 nor an enhancing effect of Dex was observed when PWM-stimulated cultures were evaluated for cells with intracytoplasmic immunoglobulin (plasma cells). From these results we conclude that Dex, by blocking IL-2 production and receptor expression, interferes with IL-2 mediated induction and/or activation of suppressor mechanisms.

B-Lymphocytes↗
PubMed1989

The effect of interleukin 2 on Fc-gamma receptor function of human monocytes requires specific intercellular interaction.

We examined the effect of interleukin 2 (IL 2) on the capacity of human monocytes to secrete reactive oxygen species triggered via Fc-gamma receptor (Fc gamma R) function as measured by chemiluminescence (CL). IL 2 did not activate highly purified (hp) monocytes to respond to Fc gamma R-mediated phagocytic stimulation with an enhanced respiratory burst activity, unless low numbers of T lymphocytes had been cocultured with hp monocytes. The degree of monocyte activation in peripheral blood mononuclear cells (PBMC) by IL2 was dependent on T lymphocytes to monocytes ratios as well as on IL 2 concentrations. Optimal Fc gamma R function was detected with IL 2 concentrations of 60 to 600 U/ml and one to two T lymphocytes per monocyte, whereas higher cellular ratios were suppressive. Supernatants from IL 2-treated PBMC contained interferon-gamma (IFN-gamma) and monocyte activating factor (MAF) activity (= enhanced monocytic Fc gamma R mediated CL). The secretion of both cytokine activities was strongly enhanced by a cooperative function of monocytes. The correlation of IL 2-induced secretion of IFN-gamma and MAF activity was striking; however, monoclonal anti-IFN-gamma antibodies failed to abrogate IL 2-stimulated and lymphocyte-dependent monocyte activation. Although IL 2 had no direct monocyte activating effect, pretreatment of hp monocytes with IL 2 led to a monocyte priming: subsequent coculture with autologous control T lymphocytes enhanced the monocyte Fc gamma R-mediated CL response. The priming of monocytes by IL 2 was dependent on the interaction of IL 2 with the monocytic IL 2 receptor, as shown by inhibition experiments with anti-IL 2 receptor monoclonal antibodies. Thus, we observed an IL 2-driven monocyte/T lymphocyte interaction leading to an increased Fc gamma R-mediated monocytic respiratory burst activity and to the secretion of a soluble MAF activity, but there were no detectable amounts of IFN-gamma.

Antigens, Differentiation↗
PubMed1989

Mechanism of activation of the human trk oncogene.

The human trk oncogene was generated by a genetic rearrangement that replaced the extracellular domain of the normal trk tyrosine kinase receptor by sequences coding for the 221 amino-terminal residues of a nonmuscle tropomyosin. Molecular dissection of a cDNA clone of the trk oncogene indicated that both the tropomyosin and tyrosine kinase domains were required for proper transforming activity. Replacement of nonmuscle tropomyosin sequences with those of other tropomyosin isoforms had no deleterious effect. However, when tropomyosin sequences were replaced with those of another cytoskeletal gene, such as beta-actin or beta-globin, transforming activity was completely abolished. These results illustrate the important role of tropomyosin sequences in endowing the trk kinase with transforming properties. Functionally unrelated subdomains of the tropomyosin molecule were equally efficient in activating the trk gene. Moreover, the transforming activity of the trk oncogene was not affected when its subcellular localization was drastically altered. Therefore, tropomyosin sequences are likely to contribute to the malignant activation of the trk oncogene not by facilitating its interaction with defined cytoskeletal structures as initially suspected, but by allowing its kinase domain to fold into a constitutively active configuration.

Amino Acid Sequence↗
PubMed1989

Estradiol effects on proliferation, messenger ribonucleic acid for collagen and insulin-like growth factor-I, and parathyroid hormone-stimulated adenylate cyclase activity in osteoblastic cells from calvariae and long bones.

Estradiol (E2) replacement therapy effectively prevents or delays postmenopausal bone loss, but the mode of E2 action on bone is still unknown. Recently, the presence of E2 receptors was described for bone-derived cells. In this study we examined the estrogen responsiveness of osteoblastic cells using the experimentally immortalized calvarial cell lines RCT-1 and RCT-3 as well as primary cultures of calvarial and trabecular bone cells. E2 treatment reduced PTH-stimulated adenylate cyclase activity by 20-30% in RCT cells; the maximum effect was observed after treatment with 1 nM E2 for 4 h or longer. In trabecular cells E2 decreased PTH-stimulated adenylate cyclase activity by 60-80%. After a lag period of at least 48 h, E2 treatment (0.01-10 nM) increased cell number and [3H]thymidine incorporation in both RCT-3 cells and primary cultures of trabecular cells to 20-60% above control values. Half-maximal effects were observed at about 1 nM E2. Antibodies against insulin-like growth factor-I (IGF-I) inhibited the E2-induced proliferation in a dose-dependent manner without affecting basal growth. Furthermore, E2 treatment increased the steady state levels of IGF-I mRNA 2- to 2.5-fold in calvarial and RCT-3 cells compared to control levels. In addition, E2 (10 nM) increased the level of collagen mRNA more than 2-fold and opposed the suppression of collagen mRNA produced by PTH treatment. The E2 effects were specific to 17 beta-E2, since they were not observed with the biologically less active stereoisomer 17 alpha-E2 and were blocked by the E2 antagonist tamoxifen (1 microM). Thus, for osteoblastic cells in culture, E2 can directly stimulate proliferation as well as collagen and IGF-I mRNA while decreasing PTH responsiveness; these effects could explain the anabolic and anticatabolic effects of E2 on bone.

Adenylyl Cyclases↗
PubMed1989

Characterization of a platelet derived factor modulating phagocyte functions and cooperating with interleukin 1.

During experiments aiming at the generation of monoclonal antibodies against native human interleukin 2 an antibody of different specificity was obtained, recognizing a polypeptide contaminant within the antigen preparation used for immunization. This antigen was shown to represent a release protein from human blood platelets. Amino acid sequence analysis of the immunopurified antigen revealed its identity as beta-thromboglobulin antigen. Depending on the source of antigen (freshly lysed platelets, platelet containing cell culture supernatants) various forms of the polypeptide, differing in the degree of N-terminal truncation, were found. Beta-thromboglobulin antigen preparations differing in peptide composition also had different capacities for modulating spontaneous as well as Fc-receptor dependent chemiluminescence of human monocytes and granulocytes. In contrast to former reports, no mitogenic activity for human dermal fibroblasts was found with beta-TG antigen (CTAP III) alone, but only in combination with human interleukin 1 and heparin, the three molecules acting synergistically. These findings indicate that beta-TG antigen could play a functional role in linking the blood clotting system to the immune system.

Antibodies, Monoclonal↗
PubMed1989

Tumor cell growth fractions in human malignant melanomas and the correlation to histopathologic tumor grading.

The growth fraction (GF) of 72 human malignant melanomas was determined by immunostaining with monoclonal antibody Ki-67. A positive correlation of GF and histopathologically-assessed prognostic variables, such as tumor thickness, mitotic rate, and prognostic index, was found. Individual Ki-67 values were considerably scattered in all histologically defined groups of malignancy. Thus, GF as determined by Ki-67 was used to calculate a modified prognostic index. In contrast to the histologically defined prognostic index, the Ki-67 based prognostic index allows further subdivision of thin malignant melanomas with no or few mitotic figures. This may be of help in identifying tumors with a high recurrence potential.

Antibodies, Monoclonal↗
PubMed1989

[Determination of immunologic parameters in patients with lung tuberculoses of various stages with special reference to serum IgE concentration].

In patients with lung tuberculosis--depending on the severity of the disease--delayed-type hypersensitivity reaction is weakened, also in cases of non-miliary tuberculosis. On analysing the mononuclear cells of peripheral blood, abnormalities are found, in particular an increase in the monocyte count. In addition to increasing levels of serum immunoglobulin A and G, circulating immune complexes were detected in 50% of the patients. In 50% of the patients we found elevated IgE-serum levels, which decreased in response to treatment but did not return to normal.

Adolescent↗
PubMed1988

Growth hormone dependent stimulation of osteoblast-like cells in serum-free cultures via local synthesis of insulin-like growth factor I.

Gene-recombinant human growth hormone (rhGH) elicited a dose-dependent stimulation of the proliferation of osteoblast-like cells (OB), when grown in strictly serum-free longterm cultures. A half-maximal effect was observed at concentrations of 15-20 ng/ml and the maximal stimulation was 160% of hormone-free controls. The rhGH-induced effect on proliferation could be inhibited dose-dependently by the addition of an insulin-like growth factor (IGF) I-antiserum to the medium. Moreover, IGF I and rhGH had additive effects only when the exogenous IGF I concentration exceeded that of endogenously produced IGF I by a large margin. Thus, direct stimulation of OB proliferation by rhGH is, at least in part, mediated by IGF I-like immunoreactivity.

Animals↗
PubMed1988

Enhanced osteoblast proliferation and collagen gene expression by estradiol.

Estrogens play a crucial role in the development of postmenopausal osteoporosis. However, the mechanism by which estrogens exert their effects on bone is unknown. To examine possible direct effects of 17 beta-estradiol on bone-forming cells, we used pure rat osteoblast-like cells in vitro as a model. Osteoblast-like cells prepared from calvaria of newborn rats were cultured serum-free in methylcellulose-containing medium for 21 days. Osteoblast-like cells proliferate selectively into clonally derived cell clusters of spherical morphology. 17 beta-Estradiol at concentrations of 0.1 nM and 1 nM enhanced osteoblast-like cell proliferation by 41% and 68% above vehicle-treated controls. The biologically inactive stereoisomer 17 alpha-estradiol (same concentrations) had no effect. Moreover, the antiestrogen tamoxifen abolished the stimulation of osteoblast-like cell proliferation by 17 beta-estradiol. After 21 days of culture, RNA was prepared and analyzed in a dot-hybridization assay for the abundance of pro alpha 1(I) collagen mRNA. Steady-state mRNA levels were increased in cultures treated with 17 beta-estradiol in a dose-dependent manner with maximal stimulation at 1 nM and 10 nM. At the same concentrations, the percentage of synthesized protein (labeled by [3H]proline pulse) that was digestible by collagenase was increased, indicating that 17 beta-estradiol acts at pretranslational levels to enhance synthesis of bone collagen. These data show that the osteoblast is a direct target for 17 beta-estradiol.

Animals↗
PubMed1988

Frequent generation of oncogenes by in vitro recombination of TRK protooncogene sequences.

Transfection of NIH 3T3 cells with cDNA clones containing either the entire coding sequences or the tyrosine protein kinase domain of the human TRK protooncogene results in the frequent generation of transforming genes. Activation of most of these TRK oncogenes involves acquisition of DNA sequences. These sequences, unlike those present in the original human TRK oncogene, are not derived from tropomyosin genes. The products of these in vitro-generated TRK oncogenes retain the parental tyrosine protein kinase activity and contain an intact carboxyl terminus. However, they exhibit distinct biochemical properties. Whereas some of them are nonglycosylated cytoplasmic molecules, others were found to be transmembrane glycoproteins. These results suggest that TRK oncogenes may induce malignant transformation by allowing their tyrosine kinase to interact with various substrates depending on the nature of their activating sequences. If so, the TRK kinase may serve as a pleiotropic marker to identify various cellular proteins whose unscheduled phosphorylation on tyrosine residues contributes to neoplastic transformation.

Animals↗
PubMed1988

[Animal experiment studies of cryosurgical treatment of DS sarcomas and Morris hepatomas implanted in the liver].

Cryosurgical treatment was applied to solid liver tumours of rats with a view to studying the effects of freezing temperatures upon liver carcinoma. Such treatment was applied to twelve rats to which carcinomas, 0.5 cm to 3.0 cm in size, had been implanted. Cryosurgical treatment was successful in one case. Many of the animals died of complications which resulted from freezing of surrounding organs, such as stomach or greater liver vessels.

Animals↗
PubMed1987

Triiodothyronine stimulates proliferation of osteoblast-like cells in serum-free culture.

Primary rat osteoblast-like cells (Ob) were grown under strictly serum-free conditions for up to 20 days. In the presence of triiodothyronine (T3) at concentrations of 0.01 and 0.1 nM, Ob proliferation was enhanced. Moreover, a decrease of alkaline phosphatase (AP) activity, a differentiation marker for Ob, was prevented, whereas protein synthesis (collagen and noncollagen protein) was decreased. T3 at much higher concentration (10 nM) had no significant effect on cell proliferation and matrix formation but decreased AP activity disproportionately. Thus, T3 at close to physiological concentrations stimulates growth and maintains differentiation of Ob.

Alkaline Phosphatase↗