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Biomedical subjects

E B Thompson

Publications and source records attributed to E B Thompson.

At least 127 records · Page 7Linked to original sources
PubMed1985

Pharmacological actions of diaspirins, potential antisickling agents: analgesic and anti-inflammatory effects.

Three aspirin analogs, dibromoaspirin, bis(3,5-dibromosalicyl) succinate and bis(3,5-dibromosalicyl) fumarate, potential antisickling agents, were compared with acetylsalicylic acid (aspirin) for their analgesic, body temperature and anti-inflammatory effects in the laboratory mouse and rat. In the analgesic assay, using the "writhing method", only a 200 mg/kg dose of the diaspirin succinate significantly reduced the writhing response induced by phenylacetic acid. Only a dose of 800 mg/kg of acetylsalicylic acid significantly decreased writhing. These analog compounds had only slight hypothermic effects, the reduction in body temperature not being appreciable. On the other hand, they were effective anti-inflammatory agents, comparable to aspirin; a dose of 200 mg/kg very significantly reduced the paw edema due to injected carrageenan.

Analgesics↗
PubMed1984

Methylation of either cytosine in the recognition sequence CGCG inhibits ThaI cleavage of DNA.

ThaI (CGCG) sites which overlap HhaI (GCGC) sites in phi X174 and pBR322 DNA were methylated in vitro with HhaI methylase and S-adenosylmethionine to yield CGmCG, mCGCG or mCGmCG (5-methylcytosine, mC). Methylation of either cytosine in the ThaI recognition sequence rendered the DNA resistant to ThaI cleavage. Rat pituitary cell genomic DNA was digested with ThaI or 2 other known methylation-sensitive enzymes, AvaI or XhoI. After electrophoresis and ethidium bromide straining of the DNA, all 3 enzymes showed the infrequent DNA cleavage characteristic of methylation-sensitive enzymes. Comparison of pituitary growth hormone (GH) genes bearing strain-specific degrees of methylation showed the less methylated gene to be more frequently cut by either AvaI or ThaI. ThaI resistant sites in GH genes were cleaved by ThaI after exposing cells to 5-azacytidine, an inhibitor of DNA methylation. We conclude that ThaI is a useful restriction enzyme for the analysis of mC at CGCG sequences in eukaryotic DNA.

5-Methylcytosine↗
PubMed1984

Molybdate-sensitive and molybdate-resistant activation-labile glucocorticoid-receptor mutants of the human lymphoid cell line CEM-C7.

The basis for the glucocorticoid resistance of three (3R7, 3R43 and 4R4) genetically independent mutants derived from the glucocorticoid-sensitive human lymphoid cell line CEM-C7 was examined. Each mutant contained significant, albeit reduced, amounts of steroid binding activity measured in both whole and broken cell assays. These activities were of similar high affinity and specificity to that seen in the sensitive parent, suggesting that the steroid binding portion of the receptors in these mutants was normal. However, nuclear translocation of steroid-receptor (SR) complexes was defective in all three clones. Analysis of SR complex activation by DEAE-cellulose chromatography established that receptors from the mutant clones were extremely labile under conditions which would activate normal SR complexes. Such lability was not exhibited by the unoccupied or occupied but unactivated forms of these receptors, indicating that all three were "activation labile" (act1). SR complexes of clones 3R7 and 4R4 were completely protected by the inclusion of molybdate during attempted activation and were classified as act1:molybdate-sensitive. However, SR complexes of clone 3R43 were unstable during attempted activation, even in the presence of 50 mM molybdate, and were thus classified as act1:molybdate-resistant. Our results suggest that while the act1 phenotype may predominate among spontaneously derived glucocorticoid-resistant mutants derived from CEM-C7, this phenotype may be the consequence of at least two different mutations.

Cell Line↗
PubMed1984

Rat growth hormone expression in cell hybrids.

Extinction of rat growth hormone (rGH) gene expression occurs in somatic cell hybrids of GH3 cells (rat pituitary adenoma) and L cells (mouse transformed fibroblast). We have suggested that this is due to transacting factors contributed directly or indirectly by the L cells. To study this in more detail, the cloned rGH gene was introduced into clones of these hybrid cells by microinjection or calcium phosphate transfection. GH peptides were detected 24 hr later in the microinjected cells by immunofluorescence. Production of rGH gene transcripts in the stably transformed hybrid cells was also detected by Northern hybridization. Although the overall patterns of transcripts differed from those present in GH3 cells, normal-sized rGH mRNA species were detected, whereas these had not been observed in previous studies in which the GH gene was transfected into L cells and other mouse fibroblasts. No more than one or two extra GH gene copies per cell were required to restore GH gene expression in the hybrids. Whereas GH gene expression in the hybrid cells transfected with the GH gene might reflect activation of the endogenous GH gene, this was not the case in at least one transfected hybrid cell line which had lost the endogenous gene. These results suggest: (i) the putative transactive repressors of GH gene expression in the hybrid cells do not recognize the transfected genes; and (ii) elements in the hybrid cells, unlike the case with L cells, allow for the production of normal-sized GH mRNA that can also produce GH peptides.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Glucocorticoid versus antiglucocorticoid activity: can a single functional group modification of glucocorticoid steroids always convey antiglucocorticoid activity?

Single functional group modifications of glucocorticoid steroids have been performed in an effort to obtain antiglucocorticoids with high affinity and specificity for glucocorticoid receptors. This approach tests the hypothesis that the structural determinants of biological activity and receptor binding are independent so that modification of more potent glucocorticoids could yield more potent antiglucocorticoids . In this study, a new functional group capable of conferring antiglucocorticoid activity has been identified, i.e. the spiro C-17 oxetan -3'-one group. Using three glucocorticoids of greatly different potency ( deacylcortivazol greater than dexamethasone greater than cortisol), we examined the effects of incorporation of the oxetanone group and the previously described, alkylating C-21 mesylate group on steroid affinity for receptors and biological activity. In both series of modified steroids, the receptor affinity of the derivatives paralleled that of the parent steroids. The biological activities of the dexamethasone and cortisol derivatives were predominantly or totally antagonistic, while both deacylcortivazol derivatives were full agonists. We conclude that antiglucocorticoid activity can arise from the incorporation of a single functional group into glucocorticoid steroid structures, but that the expression of agonist vs. antagonist activity is determined by a balance of structural group determinants which are not restricted to a common region of the steroid. Within a given class of derivatives, receptor affinity correlated with the amount of agonist activity. The structure-activity relationships for dexamethasone oxetanone and deacylcortivazol mesylate were studied in detail. Dexamethasone oxetanone is a potent antiglucocorticoid in HTC cells. [3H]Dexamethasone oxetanone binds to cell-free glucocorticoid receptors with a Kd of 3.2 X 10(-8) M. No specific antiglucocorticoid binder was detected. Direct binding experiments with [3H]dexamethasone oxetanone as well as indirect studies of the kinetics of cell-free competition of [3H]dexamethasone binding demonstrated that dexamethasone oxetanone binds to receptors faster (by about a factor of 2) and dissociates from receptors much faster than does dexamethasone. Deacylcortivazol mesylate was a more potent agonist and binder to receptors than dexamethasone, but displayed no irreversible interactions with HTC cell receptors under those conditions that afforded a covalent receptor-steroid complex with the closely related dexamethasone mesylate.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Identification of human leukemic glucocorticoid receptors using affinity labeling and anti-human glucocorticoid receptor antibodies.

Antisera raised against human lymphoid glucocorticoid receptors were used in combination with the glucocorticoid receptor affinity label [3H]dexamethasone 21-mesylate [( 3H]DM) to identify the glucocorticoid receptors of the human B-lymphoblastoid cell line IM-9 and the human T-cell leukemic cell line CEM-C7. Antisera were obtained following immunization of New Zealand White rabbits with [3H]triamcinolone acetonide [( 3H]TA)-glucocorticoid receptor complexes partially purified by two-stage DNA-cellulose chromatography. The presence of anti-human glucocorticoid receptor antibodies was verified by: (a) adsorption of [3H]TA-receptor-antibody complexes to Protein A; (b) a shift to higher apparent molecular weight in the elution position from Sephacryl S300 of [3H]TA-receptor complexes incubated with immune serum; and (c) the ability of immune serum to displace [3H]TA-receptor complexes on sucrose gradients. These antibodies also recognized rat liver and murine S49 cell glucocorticoid receptors. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [3H]DM-labeled IM-9 cytosol identified a major competable band with a molecular weight of approximately 90,000, three minor competable components with molecular weights of approximately 78,000, approximately 51,000, and approximately 38,500, and at least 21 other noncompetable components. Following immunoprecipitation of [3H]DM-labeled cytosol with immune serum, only the Mr 90,000 and 78,000 components were seen. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of [3H]DM-labeled CEM-C7 cytosol revealed a larger number of [3H]DM-labeled components. However, after immunoprecipitation of [3H]DM-labeled CEM-C7 cytosol, a predominant competable component with a molecular weight of 90,000 was easily identified. This component was markedly diminished when cytosols from the glucocorticoid receptor-deficient cell line ICR-27 were used. Thus, the combination of affinity labeling and anti-human glucocorticoid receptor antibodies is capable of providing direct physical identification of human lymphoid glucocorticoid receptors.

Affinity Labels↗
PubMed1984

Pharmacological properties of two amino esters of diphenylpropanoic acid.

N, N-Diethylaminoethyl ester and 3-quinuclidinyl ester of 2, 2-diphenylpropanoic acid (compound 1 and 2, respectively) were prepared and pharmacologically evaluated in vitro and in the intact animal. Both compounds attenuated the effects of increasing doses of ACh in the isolated rat ileum (pA2 = 8.40 and 8.55, respectively). These effects were comparable to that of atropine (pA2 = 8.73). The duration of methacholine-induced salivation in male Swiss-Webster mice was significantly decreased by compound 2 but not by compound 1. Cardiorespiratory studies in adult male Sprague-Dawley rats revealed that both compounds shifted the dose-response curves to methacholine in terms of arterial blood pressure, heart rate and respiration upwards; indicative of cholinergic blockade. The observed pharmacological differences between the two compounds may be attributed to apparent in vivo hydrolysis of compound 1 by esterases.

Acetylcholine↗
PubMed1983

Sequential comparative hybridizations analyzed by computerized image processing can identify and quantitate regulated RNAs.

A method to analyze shifts in the relative abundance of many specific RNAs following any stimulus is presented. Hybridizations of two complex "total" cDNA probes (from the pre- and poststimulus states) to each member of a cDNA library are quantitatively analyzed and mathematically compared by using computer-assisted image processing and statistical analysis of sequential filter hybridizations. Experiments indicate that shifts in abundance between two states can be identified and reproducibly quantitated without purified probes. Direct isolation of recombinant cDNA colonies containing inserts corresponding to regulated RNAs is thus possible. The use of this system is demonstrated for partial analysis of the response in vivo of rat liver to glucocorticoids. Application to other biological systems in which a shift between two states occurs is discussed.

Animals↗
PubMed1983

Dissociation of steroid binding to receptors and steroid induction of biological activity in a glucocorticoid-responsive cell.

Glucocorticoid responses in two independently derived lines of rat hepatoma tissue culture cells (HTC and FU5-5) were examined. FU5-5 cells exhibited induction of the enzyme tyrosine aminotransferase (TAT) at concentrations of dexamethasone that were approximately 7-fold lower than that required for HTC cells. FU5-5 cells also displayed substantial TAT induction with steroids that were partial agonists, or antagonists, in HTC cells. The increased sensitivity of FU5-5 cells was not, however, due to an increased affinity of FU5-5 cell receptors for dexamethasone, as determined from cell-free and whole cell binding experiments. The differential steroid sensitivity for TAT induction was observed with three other, structurally different glucocorticoids, thus apparently ruling out steroid metabolism in one of the cell lines as a cause. Also, induction of TAT in FU5-5 cells occurred at approximately 9-fold lower steroid concentrations than were required for the induction of glutamine synthetase (GS) in the same cells. Thus, the dose-response curves for TAT induction in HTC cells and for GS induction in FU5-5 cells are closely correlated with the saturation curve for whole cell steroid binding to receptor sites, while the dose-response curve for TAT induction in FU5-5 cells is shifted to lower steroid concentrations. This represents the first report of dissociation of two supposedly primary, glucocorticoid-induced functions and indicates that identical receptor-mediated processes cannot be utilized by FU5-5 cells for the induction of TAT and GS. The involvement of second messengers or different nuclear processes are possible explanations for the unusual behavior of FU5-5 cells during glucocorticoid induction of TAT.

Animals↗
PubMed1983

Glucocorticoid-resistant human acute lymphoblastic leukemic cell line with functional receptor.

A receptor-containing, steroid-resistant clone of CEM cells, CEM-C1, was isolated without selective pressure from the wild-type population. The biological and physicochemical properties of glucocorticoid receptors in CEM-C1 cells were compared to those from a clone (CEM-C7) sensitive to glucocorticoid-mediated lysis. In a whole-cell binding assay, CEM-C1 cells exhibited high affinity for [3H]dexamethasone (Kd, 22 nM), nuclear translocation of steroid:receptor complex (nt, 43%) and were found to contain, on the average, 12,000 receptor sites/cell (R0). These steroid-binding parameters were similar to those displayed by wild-type CEM-C7 cells: Kd, 19 nM; nt, 47%; and R0, approximately 14,000 sites/cell. The ion-exchange and gel permeation profiles were indistinguishable from those of identically treated CEM-C7 cytosols. Thus, diethylaminoethyl cellulose chromatography of CEM-C1 cytosol showed that [3H]triamcinolone acetonide:receptor complex was eluted at 50 mM phosphate and 220 mM phosphate under "activating" and "nonactivating" conditions, respectively. Receptor complex of activated CEM-C1 cytosol bound to DNA-cellulose and was eluted at 100 mM salt. Filtration of unactivated CEM-C1 cytosol over Sephacryl S-300 generated a single peak of radioactivity for receptor complex with a calculated Stokes' radius of 55 to 59 A. Dexamethasone induced glutamine synthetase in CEM-C1. The dose dependence (50% effective dose, approximately 20 nM) and maximal fold increase (1.9, 1 microM dexamethasone) were comparable to those observed in CEM-C7. Since CEM-C1 cells contain apparently normal, functional cytosolic receptor, the results suggest that resistance to glucocorticoid in these cells involves a defect(s) at another locus.

Cell Membrane↗
PubMed1983

Cardiovascular effects of "Fansidar" (an antimalarial drug) in anaesthetized cats.

The effects of Fansidar on systemic arterial blood pressure, mean arterial pressure, heart rate, and carotid artery occlusion of anaesthetized cats have been investigated. Fansidar decreased the systolic, diastolic and mean arterial blood pressures in a dose-related manner. The drug also reduced the left ventricular systolic pressure and heart rate in a similar fashion. Relatively moderate to high doses (greater than or equal to 0.4 ml/kg ml/kg i.e. 80 mg/kg sulfadoxine and 4 mg/kg pyrimethamine) of Fansidar decreased, but did not completely abolish the response due to carotid artery occlusion.

Anesthesia↗
PubMed1982

Somatic cell hybridization of growth hormone-producing rat pituitary cells and mouse fibroblasts results in extinction of growth hormone expression via a defect in growth hormone RNA production.

In the GH3 line of pituitary cells, growth hormone (GH) production is stimulated by thyroid and glucocorticoid hormones, yet non-pituitary cells, for example mouse fibroblast cells, which also contain receptors for these hormones do not produce GH. We have chosen to study both types of control over GH production in GH3 rat pituitary x GH nonexpressing LB82 mouse fibroblast hybrid cells. Most hybrid cells fail to produce GH in either the absence or presence of the inducers triiodothyronine and dexamethasone although these hormone receptors are present. Rat and mouse GH genes were detected in the hybrid cells' DNA by Southern hybridization following restriction enzyme digestion and gel electrophoresis. The probe was a cloned, full length rat GH cDNA which cross-hybridizes with the mouse GH gene. Analyses with multiple restriction enzymes that cut inside and outside the rat and mouse GH coding sequences were performed. We conclude that 1) both rat and mouse GH genes are present in the hybrid cells in copy number equivalent to those in the parental cell lines, and 2) the rat GH structural gene and flanking sequences are identical in the GH3 and hybrid cell DNA at the level of sensitivity afforded by restriction enzyme analyses. GH mRNA was not detected in total cell or poly(A+) RNA isolated from control or hormone-treated hybrid cells assayed by translation in 2 in vitro systems or by Northern hybridization analyzes. The latter experiments showed that no hybridizable GH mRNA sequences were present in the hybrids as either incomplete transcripts, mature mRNA, or unprocessed high molecular weight precursors. We conclude that extinction of GH in these hybrid cells results from a transcriptional block and/or rapid transcript degradation.

Animals↗
PubMed1982

Glutamine synthetase induction by glucocorticoids in the glucocorticoid-sensitive human leukemic cell line CEM-C7.

Treatment of CEM-C7 cells with glucocorticoids produces a 2.5-fold increase in the activity of the enzyme glutamine synthetase (GS). This increase is specific for steroids with glucocorticoid activity adn occurs over a range of steroid concentrations consistent with a receptor-mediated mechanism. Half-maximal and maximal inductions by dexamethasone (dex) occur at 2 X 10(-8) M and 2 X 10(-7) M dex, respectively, concentrations approximately equal to those necessary to produce half and full occupancy of glucocorticoid receptors. GS activity began to increase 1 hour after dex treatment and was complete by 12 hours. This is well before any of the growth inhibitory or cytolytic effects of dex on this cell line occur. This increase was dependent on the presence of glucocorticoid receptors and required both RNA and protein synthesis. Removal of dex following stimulation to maximal levels resulted in a decrease of GS activity to preinduced levels with a half-time of 5 hours. Glutamine deprivation of cells resulted in increased GS activity. However, even in the total absence of glutamine, dex treatment elicited a 2.0-2.5-fold increase in GS activity, ruling out inhibition of glutamine uptake as a mechanism for the dex-induced increase. Experiments with 5'-bromodeoxyuridine (BrdU) demonstrated that GS elevation was sensitive to BrdU substitution of DNA, while dex-induced growth inhibition was not. Therefore GS elevation and growth inhibition in this cell line appear to be independently expressed steroid responses.

Bromodeoxyuridine↗
PubMed1982

Non-glucocorticoid receptor-mediated effects of the potent glucocorticoid deacylcortivazol.

Deacylcortivazol (DAC), a potent glucocorticoid, contains a phenyl-pyrazole moiety fused to the 2--3 position of the traditional steroid nucleus. When incubated with glucocorticoid-resistant mutants derived from the glucocorticoid-sensitive human leukemic cell line CEM-C7, DAC caused significant growth inhibition. However, this effect required 1 microM DAC, a concentration 50 times higher than that necessary for glucocorticoid receptor saturation. Cytotoxicity was observed in both mutants containing high-affinity glucocorticoid receptors defective in nuclear translocation and a mutant completely devoid of receptors. Further, in dexamethasone-resistant clones, DAC elicited only marginal increases in the activity of the glucocorticoid-inducible enzyme glutamine synthetase. Clones resistant to high concentrations of DAC could not be directly isolated from CEM-C7. However, stable DAC-resistant clones could be isolated from dexamethasone-resistant subclones of CEM-C7 with a frequency of 1 to 8 x 10(-4). These data are consistent with resistance to DAC being acquired in a two-step process. Our results suggest that the cytotoxicity of DAC at concentrations higher than necessary for glucocorticoid receptor saturation is not mediated by glucocorticoid receptors. Thus, DAC may be a bifunctional compound having both steroid receptor-mediated and receptor-independent cytotoxicity.

Cell Division↗
PubMed1982

Pharmacological actions of diaspirins, potential antisickling agents I: A preliminary study.

The acute toxicity (LD50) and effects on locomotor activity of three alternative aspirin analogs were determined in mice of both sexes. Dibromoaspirin, bis(dibromosalicyl) succinate and bis(dibromosalicyl) fumarate were administered in oral suspension. The 24-hour LD50 values in both male and female mice were within the same range as that of commercial aspirin (i.e., 1100 mg/kg). The effects of 1/40, 1/20, 1/10 and 1/5 LD50 doses of each compound were tested on locomotor activity of male mice. These compounds decreased locomotor activity in a dose-dependent fashion.

Animals↗