Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have recently demonstrated that treatment of pregnant baboons with androstenedione (delta 4 A) at midgestation to increase estrogen production induced a pattern of placental cortisol (F) metabolism which was similar to that at term and resulted in de novo F production by the fetus, presumably by activation of the fetal hypothalamic-pituitary-adrenocortical axis. The present study was designed to examine the subcellular events in the fetal adrenal that were apparently stimulated by estrogen-induced alterations in transplacental corticosteroid metabolism. Therefore, we determined the effects of estrogen treatment at midgestation and removal of estrogen action near term on the specific activity of the rate-limiting enzymes delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta HSD) and 17-hydroxylase-17,20-lyase (17 alpha-OHase). Fetal adrenals were obtained on day 100 (n = 11) or day 165 (n = 11) of gestation (term = day 184) from untreated animals, on day 100 from animals receiving delta 4 A daily between days 70-100 (n = 9) to increase placental estrogen production, and on day 165 from baboons treated daily between days 130-164 with antiestrogen ethamoxytriphetol (MER-25; n = 7). The activity of 17 alpha-OHase was determined by incubating adrenal microsomes (105,000 x g) with [3H] progesterone, NAD+, and NADH in phosphate buffer. The radiolabeled products 17-hydroxyprogesterone, delta 4 A, and testosterone were purified, and enzyme activity expressed as picograms of product per min/mg tissue. The activity of 3 beta HSD was determined by incubating adrenal microsomes with [3H]pregnenolone and NAD+ in phosphate buffer. The radiolabeled progesterone product was purified, and enzyme activity was expressed as nanograms per min/mg tissue. Treatment with delta 4 A increased estrogen concentration at midgestation 3-fold to levels comparable to those measured near term. Although fetal adrenal weight was greater at term than at midgestation (p less than 0.05), weight was not increased by delta 4 A treatment. The specific activity (mean +/- SE) of fetal adrenal 17 alpha-OHase at midgestation (181 +/- 29) was increased (P less than 0.05) 3-fold by treatment with delta 4 A to levels (591 +/- 105) comparable to those in adrenal microsomes prepared from untreated animals near term (816 +/- 130). Enzyme activity in adrenals of MER-25-treated baboons was 40%, but not significantly lower than that in term controls.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Activation of the baboon fetal pituitary-adrenocortical axis at midgestation by estrogen: adrenal delta 5-3 beta-hydroxysteroid dehydrogenase and 17 alpha-hydroxylase-17,20-lyase activity. 201 57

Recent studies have suggested a role for Zn2+, distinct from that of Ca2+, in the subcellular distribution and activation of protein kinase C (PKC). Here we show that Zn2+ is required for a cellular response mediated by PKC, the rapid loss of expression of a human B cell receptor MER, detected by rosetting with mouse erythrocytes. Zn2+, in the presence of the Zn2+ ionophore pyrithione, caused rapid inhibition of MER rosetting at concentrations which induce the translocation and activation of PKC. This required cellular uptake of Zn2+ and was blocked by 1,10-phenanthroline and TPEN which chelate Zn2+ but not Ca2+. Gold, a metal with similar properties, also induced translocation of PKC and inhibition of MER. By contrast, Ca2+ ionophores A23187 and ionomycin, which induce a different pathway of translocation of PKC, had no effect on MER. Phenanthroline and TPEN also blocked the inhibition of MER induced by the PKC activators phorbol ester and sodium fluoride, suggesting that endogenous cellular Zn2+ is required. We propose that some cellular actions of PKC require a Zn(2+)-dependent event and that these may be a target for gold during chrysotherapy in rheumatoid arthritis.
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PMID:Role for zinc in a cellular response mediated by protein kinase C in human B lymphocytes. 205 69

We have reported that ACTH stimulation of dehydroepiandrosterone (DHA) formation by the baboon fetal adrenal at midgestation was suppressed by estrogen. Because fetal adrenal regulation changes with advancing gestation, the action of estrogen on fetal adrenal steroidogenesis may also be dependent on the degree of fetal adrenal maturation. We examined this possibility in the present study by determining the effects of ACTH and estrogen on DHA formation by adrenal cells of fetuses obtained from baboons at mid- and late gestation and from animals administered the antiestrogen MER-25 throughout late gestation. Because low density lipoprotein (LDL) provides substrate for the fetal adrenal, we also determined whether the effect of estrogen was mediated by LDL uptake. Adrenals were removed from baboon fetuses on day 100 (midgestation; n = 7) and day 170 (late gestation; n = 6; term, day 184) of gestation from untreated animals and on day 170 from fetuses whose mothers were treated with MER-25 on days 140-170 (25 mg/kg BW.day; n = 7). Cells were dispersed with 0.2% collagenase and incubated at 37 C for 3 h in 4 ml medium 199 with 10 nM ACTH, 10(-6) M estradiol and/or 500 micrograms LDL. The secretion of DHA into medium was determined by RIA. At midgestation, mean (+/- SE) basal DHA formation (nanograms per 10(5) cells/3 h) was 5.8 +/- 2.1, and DHA was increased (P less than 0.01) by ACTH to 20.0 +/- 5.9. Although estradiol alone had no effect, estradiol prevented the increase in DHA obtained with ACTH. Basal DHA production by adrenals of late gestation (0.7 +/- 0.3 ng/10(5) cells) was lower (P less than 0.01) than at midgestation. ACTH increased (P less than 0.01) DHA in a comparable manner near term in the presence (2.0 +/- 0.4) or absence (1.7 +/- 0.4) of estradiol. Thus, in contrast to day 100, estrogen did not attenuate the action of ACTH on adrenal cells on day 170. In fetal adrenal cells obtained on day 170 from MER-25-treated baboons, DHA formation (1.4 +/- 0.6 ng/10(5) cells) was comparably increased (P less than 0.05) to 2.4 +/- 0.2 and 3.0 +/- 0.5 ng/10(5) cells by ACTH in the absence or presence of estradiol. Thus, ACTH remained effective in enhancing DHA by adrenal cells of fetuses exposed in utero to antiestrogen. DHA formation by adrenals of midgestation was increased (P less than 0.05) to 15.4 +/- 4.8 and 27.4 +/- 7.5 ng/10(5) cells, respectively, by LDL and ACTH plus LDL.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Modulation of adrenocorticotropin-stimulated baboon fetal adrenal dehydroepiandrosterone formation in vitro by estrogen at mid- and late gestation. 216 46

This paper describes the laboratory discovery and clinical testing of the first nonsteroidal antiestrogen, MER-25 (ethamoxytriphetol). The compound blocks estrogen action in all species tested and has only slight but transient estrogenic effects. No other antisteroidal actions are noted. MER-25 is antiestrogenic in primates and was investigated in the clinics in a wide range of gynecological conditions, including breast and endometrial cancer. Unfortunately toxic side effects (hallucinations, etc.) precluded further investigation. A derivative of triphenylethylene, clomiphene, has some partial agonist (estrogen-like) actions in laboratory animals and following clinical evaluation is now an established agent for the induction of ovulation in subfertile women. Although clomiphene is active in advanced breast cancer, it was not developed further. In the late 1960s a related compound, tamoxifen, was evaluated to treat a number of estrogen-responsive disorders but was successfully introduced in the 1970s for the treatment of advanced breast cancer. Although there was only modest initial interest in the palliative use of tamoxifen, an enormous increase in basic and applied studies with antiestrogens resulted in a definition of the target site-specific and tumoristatic actions of tamoxifen. Close cooperation between laboratory and clinical evaluation has guided the subsequent development of tamoxifen which is now available to treat all stages of breast cancer. Long-term adjuvant tamoxifen therapy, a concept developed in the laboratory, is currently the treatment strategy of choice. The considerable success of tamoxifen has focused attention on new antiestrogens with different pharmacological properties for other potential clinical applications.
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PMID:Development of antiestrogens and their use in breast cancer: eighth Cain memorial award lecture. 219 50

High linear energy transfer (LET) fast neutrons for the local control of advanced head and neck tumours are currently being evaluated at several centres. Fast neutrons are believed to produce more direct, and less OH mediated damage than photons, and consequently be less affected by intracellular thiol levels. Chemoresistant tumours with elevated thiol levels may therefore be more effectively controlled by fast neutron therapy than by photons. The "in vitro" radiation response of melphalan sensitive and resistant human ovarian tumour cell lines has demonstrated that melphalan resistance confers a 1.5-fold level of cross-resistance to photons, primarily attributable to a 2-fold decrease in the alpha component in the resistant OAW42/MER cell line. Pretreatment of the melphalan-resistant line with the thiol depleting agent buthionine sulphoximine (BSO) restored the magnitude of alpha to a value similar to that in the chemosensitive cell line. The survival curves of these cell lines following neutron irradiation were near exponential, with similar values of alpha. This study has demonstrated that melphalan resistant tumour cells are cross-resistant to photon irradiation, but not to fast neutrons. The mechanism of cross-resistance has yet to be determined, but glutathione (GSH) appears to be involved.
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PMID:Melphalan resistant human ovarian tumour cells are cross-resistant to photons, but not to high LET neutrons. 224 22

Results obtained from gated equilibrium blood pool (GBP) studies are not only dependent on intrinsic variations, but also on the way in which images are acquired and analysed. The aim of this study was to investigate factors which could affect left ventricular time-activity curves. Temporal resolution was studied by comparing studies of 20 and 40 frames beat-1. Forty frames per beat resulted in a mean left ventricular ejection fraction of 0.48 compared to 0.46 for 20 frames beat-1. The mean difference of 0.02 was significant (P less than 0.01) as was the mean difference in maximum emptying rate (MER = 0.28, P less than 0.01) and in maximum filling rate (MFR = 0.38, P less than 0.01). No significant differences in ejection fraction (EF) values were found between acquisitions made in list and frame mode, but the mean differences for MER = 0.03 (P less than 0.05) and MFR = 0.01 (P less than 0.02) were significant. For patient repositioning and intra-observer variations no significant differences were found. In patients with normal EF values (greater than 0.5) no significant differences were found in the inter-observer study. In patients with anterior myocardial infarction (AMI), significant differences were found in EF, MER and MFR (EF = 0.02, P less than 0.001; MER = 0.2, P less than 0.01; MFR = 0.24, P less than 0.01). Significant differences were found in all values when comparing a semi-automatic method of evaluation with two automatic methods. In conclusion the results from this study suggest that acceptable reproducibility can be achieved in GBP studies, provided the method of analysis is not changed between studies.
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PMID:Effect of acquisition and analysis routines on gated blood pool measurements. 224 94

Quantitative Southern blotting analysis has demonstrated that mouse cells contain about 70 copies per haploid genome of a DNA sequence related to the gene for elongation factor 2. The restriction maps of seven cosmids that each carry one copy of the EF2-related sequence (MER) and nucleotide sequences of MERs were highly conserved among the cosmids. Data obtained by such analyses suggest that MERs were produced by the integration of one copy of MER derived from poly(A)+ mRNA for EF2 into a specific site in the mouse genome, with subsequent amplification of MER together with its large flanking sequences during the evolution of the mouse. Furthermore, it appears that the size of each repeating unit is more than 60 kb. Analysis by pulse-field gel electrophoresis suggested that multiple copies of a repeating unit of more than 400 kb (or two units) are clustered at a specific site (or each specific site) in the mouse genome.
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PMID:Amplification of a long sequence that includes a processed pseudogene for elongation factor 2 in the mouse. 230 63

An attempt was made to characterize the genetic regulation of the human DNA repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT) in the absence of the cloned gene. Four human cell lines, differing in AGT activity from very proficient to essentially absent, were assayed for gene amplification as a possible mediator of the methylation repair phenotype (Mer+, AGT activity and MER-, no AGT activity) using in-gel DNA renaturation and G-banded karyotype analysis. The former technique allows subsequent analysis of amplification units and cloning of observed amplified DNA fragments, a hopeful approach to the isolation of the human AGT gene. Within the sensitivities of the techniques, no correlation between AGT activity and gene amplification was observed in the four cell lines tested.
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PMID:Gene amplification affecting O(6)-alkylguanine-DNA alkyltransferase activity is not detected in nitrosourea resistant or sensitive human cell lines. 231 Nov 91

Tamoxifen (TAM), a nonsteroidal antiestrogen, is used in the adjuvant treatment of breast cancer. Previous studies, however, have indicated that some human breast and endometrial tumors are stimulated to grow with TAM in the athymic mouse. One such TAM-stimulated tumor is the EnCa101 human endometrial adenocarcinoma. Our aim was to evaluate the ability of different doses of TAM or other nonsteroidal antiestrogens to stimulate the growth of EnCa101 tumors in athymic mice. Additionally we have evaluated less estrogenic antiestrogens (two steroidal antiestrogens, RU 39,411 and ICI 164,384, and two nonsteroidal antiestrogens, keoxifene and MER-25) for their ability to inhibit TAM-stimulated growth. All experiments were done in ovariectomized athymic mice transplanted in the axillary mammary fat with 1-mm3 pieces of EnCa101 tumor. Sustained release preparations (0.5-2.0-cm Silastic capsule or 5-mg TAM cholesterol pellet) of TAM caused similar tumor growth. The growth rate was not altered by an additional daily i.p. injection of 1 mg TAM in 0.1 ml peanut oil. A 3-mg TAM daily dose was toxic. Four weeks of treatment (100-micrograms s.c. injections, every other day) with nonsteroidal antiestrogens, trioxifene mesylate, enclomiphene, or nafoxidine stimulated tumor growth. However, keoxifene stimulated this tumor to a lesser degree than TAM and partially inhibited TAM-stimulated growth. ICI 164,384 showed no stimulatory activity (1-mg s.c. injections every other day) alone compared to controls but inhibited TAM-stimulated (0.25-cm Silastic capsule) growth. In a parallel experiment, RU 39,411 (1-mg s.c. injections every other day) stimulated EnCa101 to grow. In contrast when RU 39,411 was administered in a sustained release preparation (2.0-cm Silastic capsule) there was no stimulatory growth compared to controls. Additionally RU 39,411 inhibited TAM-stimulated growth, but the low-potency antiestrogen, MER-25, was less effective in this regard. These data suggest that less "estrogenic" antiestrogens can inhibit TAM-stimulated tumor growth in vivo. Thus these compounds or derivatives may prove useful as a second-line endocrine therapy should TAM-stimulated tumor growth occur in the clinic.
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PMID:Effect of steroidal and nonsteroidal antiestrogens on the growth of a tamoxifen-stimulated human endometrial carcinoma (EnCa101) in athymic mice. 233 15

We report the molecular cloning of a human gene MER-2 located on chromosome 11 that encodes a cell surface antigen which is polymorphic on red blood cells. An essential element of the cloning strategy was cotransfection-induced linkage of pSV2-neo, which encodes resistance to the antibiotic G418, to the human MER-2 gene. An important feature of the pSV2-neo construct is that the same gene (the transposon, Tn5) that encodes G418 resistance in eukaryotic cells confers neomycin resistance in bacteria. Chinese hamster ovary (CHO) cells were cotransfected with pSV2-neo and genomic DNA from a CHO X human cell hybrid containing a single human chromosome (chromosome 11). Transfectants expressing both the human MER-2 gene and G418 resistance were isolated by selection in the antibiotic G418, followed by indirect immunofluorescence using the monoclonal antibody 1D12, which recognizes the MER-2 antigen, manual enrichment, and single-cell cloning. Genomic DNA from a primary transfectant positive for MER-2 expression and G418 resistance was used to construct a cosmid library and cosmid clones able to grow in neomycin were isolated. Of 150,000 cosmid clones screened, 90 were resistant to neomycin and of these, 11 contained human repetitive sequences. Five neomycin-resistant cosmid clones containing human repetitive DNA were able to transfect CHO cells for G418 resistance and MER-2 expression.
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PMID:Molecular cloning of MER-2, a human chromosome-11-encoded red blood cell antigen, using linkage of cotransfected markers. 282 33


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