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Results for “Serum Response Factor”

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At least 19 recordsLinked to original sources
PubMed2004

Ternary complex factor-serum response factor complex-regulated gene activity is required for cellular proliferation and inhibition of apoptotic cell death.

Members of the ternary complex factor (TCF) subfamily of the ETS-domain transcription factors are activated through phosphorylation by mitogen-activated protein kinases (MAPKs) in response to a variety of mitogenic and stress stimuli. The TCFs bind and activate serum response elements (SREs) in the promoters of target genes in a ternary complex with a second transcription factor, serum response factor (SRF). The association of TCFs with SREs within immediate-early gene promoters is suggestive of a role for the ternary TCF-SRF complex in promoting cell cycle entry and proliferation in response to mitogenic signaling. Here we have investigated the downstream gene regulatory and phenotypic effects of inhibiting the activity of genes regulated by TCFs by expressing a dominantly acting repressive form of the TCF, Elk-1. Inhibition of ternary complex activity leads to the downregulation of several immediate-early genes. Furthermore, blocking TCF-mediated gene expression leads to growth arrest and triggers apoptosis. By using mutant Elk-1 alleles, we demonstrated that these effects are via an SRF-dependent mechanism. The antiapoptotic gene Mcl-1 is identified as a key target for the TCF-SRF complex in this system. Thus, our data confirm a role for TCF-SRF-regulated gene activity in regulating proliferation and provide further evidence to indicate a role in protecting cells from apoptotic cell death.

Alleles↗
PubMed1978

Detection and separation of two serum factors responsible for depression of lymphocyte activity in pregnancy.

Studies using the rosette inhibition test have demonstrated a depression of lymphocyte activity in pregnant mice which occurs as early as 6 hr after fertilization and persists until just before delivery. This depression of lymphocyte activity is induced by two serum factors, the relative contributions of which vary with the time of gestation. The first, a high molecular weight early pregnancy factor, appears within hours of fertilization and then slowly declines in activity as gestation proceeds. The second, a lower molecular weight substance which cross-reacts with antiserum to human chorionic gonadotrophin, appears after the formation of the trophoblast at 4--5 days and persists until parturition.

Animals↗
PubMed1976

Production of tumor-specific inducer of cellular cytotoxicity by lethally irradiated mice.

Antisera taken 1 or 2 days after inoculation of BALB/c mice with transplantable sarcoma cells or Moloney sarcoma virus (MSV) induce tumor-specific cell-dependent cytotoxicity in vitro. In the present experiments, lethally irradiated ("immunosuppressed") mice were tested for the early appearance of the serum factor responsible for this anti-serum-dependent cell-mediated cytotoxicity (E-ADC). BALB/c mice were infected with MSV, syngeneic sarcoma cells or sheep red blood cells 24 h following irradiation with 900 R. Sera were obtained from MSV and tumor cell recipients 48 or 72 h later and tested for E-ADC activity. Spleen cells from SRBC recipients were tested at day 4 or 5 for ability to form direct plaques in a modified Jerne plague assay. Although the anti-SRBC response was obliterated in the irradiated mice, the E-ADC response appeared to be unimpaired. These studies indicate that newly synthesized immunoglobulin is not required for the formation of the E-ADC factor.

Animals↗
PubMed2003

A role for VASP in RhoA-Diaphanous signalling to actin dynamics and SRF activity.

Vasodilator-stimulated phosphoprotein (VASP) is involved in multiple actin-mediated processes, including regulation of serum response factor (SRF) activity. We used the SRF transcriptional assay to define functional domains in VASP and to show that they coincide with those required for F-actin accumulation, as determined by a quantitative FACS assay. We identified inactive VASP mutants that can interfere both with F-actin assembly and with SRF activation by wild-type VASP. These VASP mutants also inhibit actin-based motility of Vaccinia virus and Shigella flexneri. VASP-induced F-actin accumulation and SRF activation require both functional Rho and its effector mDia, and conversely, mDia-mediated SRF activation is critically dependent on functional VASP. VASP and mDia also associate physically in vivo. These findings show that VASP and mDia function cooperatively downstream of Rho to control F-actin assembly and SRF activity.

3T3 Cells↗
PubMed1978

Anticomplementarity in complement-fixation test with soluble antigens of the spotted fever group rickettsiae.

Anticomplementarity occurring in the complement-fixation (CF) test with soluble antigens of rickettsiae of the spotted fever (SF) group is caused by interaction of soluble antigens with guinea pig sera serving as the source of complement. The serum factor responsible for anticomplementarity is thermostable and cannot be removed by treatment of guinea pig serum with CO2 or nitrogen. An adverse effect of such serum was also observed upon its mixing with other guinea pig sera lacking anticomplementarity properties. An anticomplementarity factor present in the soluble rickettsial antigens was sensitive to treatment with potassium periodate.

Animals↗
PubMed1978

Passive sensitization of mice and rats with IgE antibodies.

The strain-dependent variation in susceptibility to passive sensitization of the skin and peritoneal mast cells with homologous IgE antibodies was observed in inbred strains of mice. Strain 129 showed low susceptibility to passive sensitization and high efficiency of normal serum in blocking mouse reagin-induced PCA in rats. Balb/c and C3H/A strains showed higher susceptibility to passive sensitization and the efficiency of normal serum in blocking rat PCA lower than strain 129. The serum factor responsible for rat PCA inhibiting effect was heat-labile. The anaphylactic response of peritoneal mast cells of inbred strains to the challenge with anti-mouse IgE and anti-rat IgE in vitro was low in Balb/c mice, as compared with the response of C57BL/6J and 129 mice. The results suggest, that non-specific IgE present in the serum or bound to the mast cells may be one of the factors determining the susceptibility of mouse strains to reagin-induced passive sensitization. However, the results obtained with C57BL/6J strain suggest the existence of other factors effecting this susceptibility.

Animals↗
PubMed1975

Suppression of in vitro antibody response by a serum factor (SAA) in experimentally induced amyloidosis.

Serum from CBA/J mice made amyloidotic by chronic casein injections has been shown to suppress in vitro antibody response to SRBC. Similar suppression was also found with normal mouse serum but to a much lesser degree. This suppressive activity of both amyloidotic serum and normal serum was removed by absorption of the sera with antiserum to protein AA, the major constituent of casein-induced (secondary) amyloid fibrils. This antiserum to the amyloid fibril protein AA (mol wt 8,400 daltons) detects an immunologically cross-reacting serum alpha globulin (SAA) (mol wt approx. 100,000). It is postulated that the serum factor (SAA) is a regulator of antibody response and may be present in elevated amounts as the result of chronic antigenic stimulation.

Alpha-Globulins↗
PubMed1979

Pseudothrombocytopenia due to agglutinins.

Pseudothrombocytopenia may have any of a number of causes, one of which is agglutination in vitro. This phenomenon was found in samples of blood from six patients. A serum factor responsible for the agglutination was demonstrated. The factor was dependent upon the presence of EDTA and was more active at room temperature than at 37 C. It could be identified as an IgM immunoglobulin in four cases. In the other two cases definite characterization was not possible, but there was some evidence in favor of an IgM factor. All six patients had elevated serum IgM levels, but they had different and unrelated clinical disorders.

Adolescent↗
PubMed1979

A simple method to detect complement receptors using baker's yeast: Y C rosettes.

A technique is described to identify complement-receptor-bearing cells, using serum-treated baker's yeast as a ligand. The method consists of incubation of heat-killed baker's yeasts with fresh AB normal serum, freezing, thawing, and washing of the particles, followed by mixing with the cells. Serum is required to coat the yeasts for the rosette formation. Experiments designed to establish the serum factors responsible for the attachment of the particles to cells show that heat inactivation, chelating agents, or anti-C3 treatment prevent rosette formation. This is taken as evidence that yeasts (Y) are coated with complement (C) to compose the reagent for the YC rosette technique. The application of this technique to twenty-five normal individuals demonstrated that a mean of 11.6 per 100 lymphocytes (+/- 4.3) form rosettes; absolute number: 275 (+/- 160) rosette-forming lymphocytes per mm3. Either AB or autologous fresh serum can be used to coat the yeasts. A combined technique for YC plus E rosettes can be performed allowing the identification and enumeration of four populations of lymphocytes: (a) those having receptors for sheep erythrocytes, (b) complement-receptor-bearing lymphocytes, (c) those having both receptors (D lymphocytes), and (d) non-rosette-forming non-phagocytic cells.

Adult↗
PubMed1979

Factors causing the clumping reaction of streptococcal strains with human plasma.

Fresh isolates of 204 strains of Streptococcus haemolyticus, 75 strains of viridans group Streptococcus, and 45 strains of Streptococcus pneumoniae were studied for their clumping reactions with human plasma. The plasma and serum factors that clumped the streptococcal strains were compared with those that clumped a Staphylococcus aureus strain. One hundred eleven strains of S. haemolyticus, 10 strains of viridans group Streptococcus, and none of the strains of S. pneumoniae tested were clumped by human plasma. However, clumping activity was remarkably unstable after subculturing on plates containing Todd-Hewitt blood agar. The strain with the highest level of activity was clumped by fibrinogen and normal human serum. Results of tests of the clumping reactions of staphylococci and streptococci with human serum indicated that the serum factors responsible for those reactions may be identical.

Bacteriological Techniques↗
PubMed1978

Intraerythrocytic parasitosis in humans with Entopolypoides species (family Babesiidae). Association with hepatic dysfunction and serum factors inhibiting lymphocyte response to phytohemagglutinin.

We have observed two cases of human infection with intraerythrocytic protozoa. The organisms appeared to be in the Entopolypoides group, which had not previously been associated with human infection. One patient was asplenic. Both patients had hepatic dysfunction, and their serum samples contained blocking factors that interfered in vitro with the stimulation of normal lymphocytes by phytohemagglutinin. It appears that in humans, as well as in experimental animals, host factors are important in resistance to infection by intraerythrocytic parasites. These factors include the presence of a spleen and cell-mediated and humoral immunities. Possibly similar infections will be observed in patients with other impairments of T-cell function, such as those induced by malignancy, thymic dysfunction, or immunosuppressive drugs.

Adult↗
PubMed1977

Acute energy deprivation in man: effect on serum immunoglobulins antibody response, complement factors 3 and 4, acute phase reactants and interferon-producing capacity of blood lymphocytes.

The effects of 10 days of total energy deprivation on serum levels of immunoglobulins, antibodies acute phase reactants and on interferon production were evaluated in fourteen healthy, normal-weight males. A significant depression was noted of the serum levels of complement factor 3, haptoglobin and orosomucoid. The titres of mercaptoethanol-sensitive specific antibodies to flagellin were higher in the subjects inoculated at the end of the starvation period than in controls and those inoculated at the start of the period. The serum levels of IgG, IgM, IgA, IgE, alpha-1-antitrypsin and complement factor 4, and the interferon-producing capacity of blood lymphocytes, were not changed. Thus, 10 days of total energy deprivation depresses the serum levels of several acute phase reactants and re-feeding may enhance antibody production.

Antibodies↗
PubMed1976

Modification of immunologic response. IV. A factor in the serum of mice treated with streptomycin, its character and mode of action in vitro.

A factor contained in the serum of mice treated with streptomycin (SM) when added to spleen cell cultures stimulated the primary immunologic humoral response to sheep red blood cells (SRBC) in vitro. The magnitude of the immunologic response was measured as the number of specific antibody-producing cells. By the use of an immunoadsorbent, it was shown that the factor is not SM or a protein-SM complex remaining in trace amounts in the serum of mice treated with this antibiotic. Studies on the mechanism of stimulation by this factor showed that it reacts in a late stage of the immunologic response to already differentiated precursors of antibody-producing cells, and that higher concentrations of this substance added to cultures, instead of stimulating, inhibit producing of antibodies to SRBC. The mechanism of the stimulating action of this factor on antibody-producing cells is discussed.

Animals↗
PubMed1977

Stimulation of the in vitro immune response by factors present in the human serum.

Two distinct factors which stimulate the recovery of plaque-forming cells in the vitro immune response have been found in human serum. One acts in the presence of fetuin and the other augments the recovery of plaque-forming cells in its absence. The molecular weight of the former is higher than 1 X 10(5). The two factors could be separated from each other by ammonium sulphate fractionation. Large differences were found in the amount of these factors in sera obtained from different human donors.

Ammonium Sulfate↗