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At least 253 records · Page 14Linked to original sources
PubMed2001

Preferential induction of apoptosis by interferon (IFN)-beta compared with IFN-alpha2: correlation with TRAIL/Apo2L induction in melanoma cell lines.

On the basis of in vitro inhibition of tumor cell growth, IFNs have been generally considered to be antiproliferative proteins. To probe further the potential mechanisms of the antitumor effects of IFNs, we have assessed apoptosis in response to IFN-alpha2 and IFN-beta in cell lines of varied histologies, with a focus on melanomas. Many of the cell lines tested underwent apoptosis in response to IFN-beta, as assessed both by Annexin V and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. In general, IFN-beta had greater growth inhibitory and proapoptotic effects than IFN-alpha2 on all cell lines. The melanoma cell line WM9, sensitive to growth inhibition by IFNs, had a greater degree of apoptosis than A375 melanoma cells, which were largely resistant to antigrowth effects of IFNs. IFN-beta-induced apoptosis was dependent on activation of the caspase cascade with cleavage of caspases 3, 8, and 9 and of the caspase 3 substrate, poly(ADP-ribose) polymerase. Caspase inhibitors benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl keton or benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethyl keton, inhibited IFN-beta-induced apoptosis. Other changes associated with apoptosis, including the movement of cytochrome c from mitochondria to cytoplasm and DNA fragmentation, were also identified in response to IFN-beta. Apo2L ligand [tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)] was one of the early genes induced by IFN-beta in apoptosis-sensitive WM9 cells. Other sensitive melanoma cell lines had a similar IFN-beta-specific induction of TRAIL. Neutralizing antibody to TRAIL inhibited IFN-beta-induced apoptosis in WM9 cells. In resistant A375 cells, IFN-beta did not induce TRAIL/Apo2L expression. Thus, induction of TRAIL by IFNs in some tumor types may initiate the apoptotic cascade. This study offers another mechanism for the antitumor effects of IFNs.

Annexin A5↗
PubMed2002

Induction of long-term peripheral microchimerism in non-human primates in a model of xenogeneic peripheral tolerance induction.

Xenotransplantation represents a promising solution to the ever increasing shortage of donor organs in allotransplantation. However, due to different and stronger modes of rejection, successful xenotransplantation will require different organ-protective regimes from those used in allogeneic transplantation today. Since one can not simply increase the dosage of the drugs used, immunomodulation or tolerance induction of the recipient would be the most desirable approach. Transfusion of donor leukocytes has been shown to downregulate recipient responses or even induce peripheral tolerance in small animal models. Since the infusion of donor cells represents a relatively simple approach, as one can purify and compose the inoculum exactly before infusion, we studied whether this approach can be successfully employed in a preclinical swine to non-human primate model of peripheral tolerance induction/immunomodulation. In our model, baboons underwent sequential column adsorption and complement blockade. The animals received only initial immunosuppression with cyclophosphamide. No further immunosuppression was given. Subsequently all animals received 1-3 x 10(10) porcine splenocytes i.v. Development and maintenance of chimerism was analyzed by sequential flow cytometric and PCR analyses. Other parameters studied included effects of the preparatory induction protocol. We could show that a low level of chimerism is maintained in these animals for up to 1.5 years, despite the fact that they received no additional immunosuppression after the initial one. At no time of the experiment did any animal display symptoms of poor health. Thus we demonstrate that the concept of donor leukocyte transfusion is transferable into preclinical xenotransplantation. We are currently conducting organ transplantation experiments into animals thus treated to directly analyze the immunomodulatory effect of the donor cells.

Animals↗
PubMed1992

[Investigation of maternal peripheral plasma concentration of PG in induction of labor by nutrition food inductive drug].

The used nutrition food inductive drug to induce labor in 33 pregnant women, 22 of 33 succeeded and 11 failed. The PGs level in maternal peripheral blood was measured twice. One before taking and the second sample was drawn blood during second stage of labor. Another 13 pregnant women of spontaneous labor were measured as control group. The 6-keto-PGF1 alpha level was significantly increased in the succeeding group than in the tailed induced group, the PGE concentration seems no significant change in these three groups. The data suggested that the nutritional food inductive drug may accelerate the synthesis of prostaglandin in the succeeding group.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Induction of class I major histocompatibility complex antigens in human teratocarcinoma cells by interferon without induction of differentiation, growth inhibition, or resistance to viral infection.

The behavior of human teratocarcinoma cells, and especially their stem cells (embryonal carcinoma cells), may provide insights into the properties of human early embryonic cells. We report here that human recombinant gamma-interferon (IFN-gamma) induced the expression of major histocompatibility complex Class I (HLA-A, B, C) antigens and beta 2-microglobulin in the two human embryonal carcinoma cell lines, 2102Ep cl.4D3 and NTERA-2 cl.D1, and in the yolk sac carcinoma cell line, 1411H; human recombinant IFN-alpha and IFN-beta were less effective inducers of these cell surface molecules. No induction was observed in the gestational choriocarcinoma cell line, JAR. Neither IFN-alpha, IFN-beta, nor IFN-gamma caused growth inhibition, expression of major histocompatibility complex Class II (HLA-DR) antigens, resistance to viral (vesicular stomatitis virus) infection, or expression of 2',5'-oligo(A)synthetase in any of the cells. Also, IFN-gamma neither induced differentiation of NTERA-2 cl.D1 cells, which are pluripotent human stem cells, nor influenced their differentiation induced by retinoic acid. However, developmental regulation of responsiveness to IFN was evident, since IFN-gamma induced higher levels of surface expression of HLA-A, B, C and beta 2-microglobulin in the retinoic acid-induced differentiated NTERA-2 cl.D1 cells than in the undifferentiated parental cells. Also, 2',5'-oligo(A)synthetase was inducible in the NTERA-2 cl.D1 differentiated cells by IFN-alpha and -beta, although not by IFN-gamma, and slight resistance to vesicular stomatitis virus infection was evident in aged cultures of differentiated cells exposed to IFN-alpha. The effect of recombinant mouse IFN-gamma on major histocompatibility complex expression by several murine teratocarcinoma cells was also examined: H-2 Class I (H-2Db), but not class II (I-Ab), antigens were induced in the parietal yolk sac carcinoma lines, PYS and F9Ac cl.9; in cultures of PCC3/A/1 containing both embryonal carcinoma (EC) and differentiated cells; and in cultures of the EC cells, PCC4azaR and PCC4AO, without evidence of differentiation. No induction was observed in the murine EC cell lines, F9 or FA (H-2Kk). Our results indicate that human EC cells, like murine EC cells, exhibit only a partial response to the interferons, and that the extent of this response is developmentally regulated.

Antigens, Surface↗
PubMed1994

Double-blind comparison between inverse sequence induction with atracurium and rapid sequence induction with succinylcholine.

In this double-blind randomized study of 60 patients, a new rapid sequence induction technique (RSI), the so-called inverse sequence induction technique (ISI), is compared to the standard RSI using succinylcholine (SUX). All patients were premedicated with midazolam 0.07 mg.kg-1 and morphine 5 mg im. The patients in the ISI group received atracurium 0.6 mg.kg-1 followed after 1 min by thiopental 5 mg.kg-1. The patients in the SUX group were precurarized with atracurium 0.06 mg.kg-1 followed after 3 min by thiopental 5 mg.kg-1 and succinylcholine 1.5 mg.kg-1. In both groups patients were intubated 1 min after thiopental injection by a trained blinded anesthetist who graded intubation conditions from 1 (excellent) to 4 (impossible). Intubation scores (ISI: 1 and SUX: 1 (range 1-3)) and intubation times (from laryngoscopy to cuff inflation: ISI 18 +/- 10 s, SUX 19 +/- 8 s) as well as mean arterial pressure, heart rate, SpO2 and EtCO2 values were not significantly different between groups. Three patients in the ISI group failed to maintain a handgrip. In both groups all patients were able to cough forcefully at the time of thiopental injection. These data emphasize the reliability and safety of ISI as an alternative for RSI when succinylcholine is contraindicated. However, the unpleasantness of awake partial curarization may limit its acceptance.

Adult↗
PubMed1997

[Stress free anesthesia induction ZESTRANI (ZEro STRess ANesthesia Induction) in Göttingen minipigs. An experimental method].

The Göttingen Mini-pig is a popular laboratory animal, that is used i.a. in experimental surgery and anaesthesia. For ethical and scientific reasons it is mandatory to minimize the stress the laboratory animals are exposed to. The presented stress-free experimental anaesthesia induction (ZESTRANI) is based on innovative means to achieve adequate analgesia using different substances appropriate for the animal's state of consciousness. Markedly lower heart rates and mean arterial pressures are seen when the ZESTRANI-method is used as compared retrospectively to the previously used "conventional" anaesthesia induction. With the ZESTRANI method no "fight or flight"-reactions are seen.

Anesthesia, General↗
PubMed1994

Inhibition by recombinant human interleukin-6 of the glucagon-dependent induction of phosphoenolpyruvate carboxykinase and of the insulin-dependent induction of glucokinase gene expression in cultured rat hepatocytes: regulation of gene transcription and messenger RNA degradation.

The influence of recombinant human interleukin-6, the major mediator of the inflammatory response in liver, on the glucagon- and insulin-dependent induction of the phosphoenolpyruvate carboxykinase and glucokinase gene, respectively, was monitored on the level of gene transcription, mRNA abundance and enzyme activity in cultured rat hepatocytes. As control markers of the interleukin-6-induced acute-phase response the mRNA levels of the acute phase proteins alpha 2-macroglobulin and beta-fibrinogen were determined. In cultured rat hepatocytes, recombinant human interleukin-6, added simultaneously with glucagon and insulin, lowered the maximal increase in glucagon-induced phosphoenolpyruvate carboxykinase mRNA levels after 2 hr and the maximal increase in glucokinase mRNA levels after 3 hr to about 30%, respectively. It inhibited the glucagon-induced increase in phosphoenolpyruvate carboxykinase gene transcription and phosphoenolpyruvate carboxykinase enzyme activity, as well as the insulin-induced increases in glucokinase gene transcription and glucokinase enzyme activity. Recombinant human interleukin-6 increased the mRNA levels of the acute-phase proteins alpha 2-macroglobulin and beta-fibrinogen gradually over 4 to 6 hr. Recombinant human interleukin-6, added 2 hr after glucagon or 3 hr after insulin at the maximum of the hormone-induced enzyme mRNA levels, almost doubled the decay rate of phosphoenolpyruvate carboxykinase mRNA and glucokinase mRNA. The results show that interleukin-6 induced the expression of inflammatory proteins and simultaneously inhibited the hormone-induced expression of enzymes of intermediary metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Dose requirements, assay procedures and tissue specificity for PCB inductation of P-450 dependent mono-oxygenase activity in the rat: implications for design of studies measuring in vivo induction of human placental mono-oxygenases.

Pregnant Sprague-Dawley and Fisher 344 rats were treated on day 15 of gestation with Aroclor 1254 in a single dose ranging from 0 to 500 mg kg-1 body weight and killed on day 18 of gestation. In the small groups of animals used for this study, no effect was observed on mean maternal liver or placental weight, or the number of fetal resorptions at any of the doses tested. Measurement of aryl hydrocarbon hydroxylase (AHH) and 7-ethoxycoumarin O-deethylase (7ECD) activity in tissue homogenates, however, showed that administration of Aroclor 1254 (15 mg kg-1 body weight or greater) induced mono-oxygenase activity in fetal liver. Both the AHH and 7ECD assay detected effects of PCBs with similar sensitivity, and the findings were comparable when homogenates were assayed instead of microsomes. These data were used to suggest technical approaches to the detection of mono-oxygenase induction in placental tissue human populations exposed to PCBs.

Animals↗
PubMed1995

E-selectin gene induction by ionizing radiation is independent of cytokine induction.

The mechanism of the x-ray-mediated inflammatory response in normal tissues is unknown. To determine whether leukocyte infiltration into irradiated tissue is regulated by adhesion molecule expression, we quantified the synthesis of glycoproteins that participate in inflammation. We found that E-selectin is synthesized in a time-dependent manner following exposure to doses as low as 0.5 Gy. Northern blot analysis demonstrated that E-selectin mRNA expression increased at 2 h after x-irradiation and increased expression required no de novo protein synthesis. Transcription of the promoter region of E-selectin (-578 to +35) was transiently induced following x-irradiation, whereas deletion of the NFkB binding site eliminated x-ray induction. Electrophoretic mobility gel shift analysis confirmed increased binding of nuclear proteins from irradiated endothelial cells to the NFkB binding sequence from the E-selectin promoter. Nuclear protein binding to the NFkB binding sequence was altered by antibodies to the p50 and p65 components of NFkB. These data demonstrate that E-selectin expression does not require cytokine synthesis, but involves NFkB activation.

Base Sequence↗
PubMed1984

Increased glutathione in cultured hepatocytes associated with induction of cytochrome P-450. Lack of effect of glutathione depletion on induction of cytochrome P-450 and delta-aminolevulinate synthase.

Cellular glutathione concentrations in primary cultures of chick embryo hepatocytes were 15.3 +/- 5.3 nmoles/mg protein (mean +/- S.D.) and remained stable for up to 3 days in culture. The presence of insulin was not essential for the maintenance of glutathione concentrations. Induction of cytochrome P-450 by phenobarbital-like inducers (2-propyl-2-isopropylacetamide, 2-allyl-2-isopropylacetamide, and 2,4,5,2',4',5'-hexabromobiphenyl) was accompanied by 2- to 3-fold increases in glutathione concentrations and by increased glucuronidation of phenol red. The 3-methylcholanthrene-like inducers of cytochrome P-450 (beta-naphthoflavone and 3,4,3',4'-tetrachlorobiphenyl) did not have these effects. Glutathione was rapidly depleted to 15-30% of control levels in hepatocytes treated with buthionine sulfoximine, an inhibitor of gamma-glutamylcysteine synthase. No toxicity was observed with glutathione depletion. Glutathione depletion did not affect the ability of 2-propyl-2-isopropylacetamide to induce cytochrome P-450, glucuronidation of phenol red, or delta-aminolevulinate synthase.

5-Aminolevulinate Synthetase↗
PubMed1988

Cytochrome P450 induction by phenobarbital (PB) is inhibited by 12-O-tetradecanoylphorbol-13-acetate (TPA): evidence that protein kinase C regulates induction.

The hepatic microsomal monooxygenase system was studied in hypophysectomized male rats exposed for 24 or 48 h to PB and/or TPA, an activator of kinase C. TPA attenuated basal and PB-induced levels of P450, aniline hydroxylase (ANH), ethylmorphine demethylase (EDM) and cytochrome c reductase. Hence, PB may effect induction via the inhibition of kinase C. Supporting this is spectral evidence that PB and TPA do not bind and the fact that TPA did not decrease P450 when co-incubated with O2 and NADPH. Hemin failed to increase P450 levels previously depressed by TPA indicating that TPA acts by lowering apocytochrome levels. This is consistent with its attenuation of PB-effected increases in hepatic RNA. TPA effects were associated with increased hepatic RNA and were blocked by puromycin.

Aniline Hydroxylase↗
PubMed1995

Induction of pre-ovulatory gonadotrophin surge with gonadotrophin-releasing hormone agonist compared to pre-ovulatory injection of human chorionic gonadotrophins for ovulation induction in intrauterine insemination treatment cycles.

The clinical outcome of intrauterine insemination (IUI) treatment cycles employing a gonadotrophin-releasing hormone agonist [GnRHa, triptorelin (Decapeptyl)] or human chorionic gonadotrophin (HCG) for ovulation induction was compared. A group of 48 patients presenting with amenorrhoea, oligomenorrhoea or unexplained infertility were all treated with human menopausal gonadotrophins (HMG) from day 5 of the cycle, on an individualized schedule. They were then randomly divided into two groups to receive either a single s.c. injection of 0.1 mg triptorelin or a single i.m. injection of 10,000 IU HCG after follicular maturation. IUI was performed approximately 24 and 48 h following the injection. A transitory increase in serum luteinizing hormone and follicle stimulating hormone concentrations was achieved following injection of GnRHa. A total of 24 patients received 72 treatment cycles with GnRHa, producing 11 conceptions (15.3%) and two abortions (18.2%), resulting in a term pregnancy rate of 13.6%. There were four cases of grade 3-4 ovarian hyperstimulation syndrome (OHSS), two of which were conception cycles. In all, 24 patients underwent 68 cycles treated with HCG, producing 18 conceptions (26.5%) and six abortions (33.3%), resulting in a term pregnancy rate of 19.0%. There were eight cycles of grade 3-4 OHSS, two of which were conception cycles. These results show that an s.c. injection of a relatively low dose of GnRHa can be as effective as HCG in producing pregnancy in IUI treatment cycles.

Abortion, Spontaneous↗
PubMed2003

Induction of hepatic phase II drug-metabolizing enzymes by 1,7-phenanthroline in rats is accompanied by induction of MRP3.

The purpose of the present study was to evaluate the effect of 1,7-phenanthroline (PH), which has been proposed to be a selective phase II enzyme inducer, on the gene expression of xenobiotic transporters, as well as hepatic and renal drug-metabolizing enzymes. After oral administration of PH for 3 days to male Sprague-Dawley rats, mRNA levels in liver (75 and 150 mg/kg doses) and kidney (75 mg/kg dose only) were determined using real-time quantitative polymerase chain reaction. At 150 mg/kg/day, PH treatment resulted in significant increases in hepatic mRNA levels of Mrp3 (36-fold), UGT1A6 (20-fold), UGT2B1 (4-fold), and quinone reductase (QR, 5-fold), compared with the vehicle-treated group. Similar increases in Mrp3 (99-fold), UGT1A6 (17-fold), UGT2B1 (3-fold), and QR (11-fold) mRNA levels were observed in the liver after PH treatment of rats at 75 mg/kg/day. In contrast, the expression levels of CYP2C11 and Oatp2 were decreased by approximately 80 and 50%, respectively. In addition, PH (75 mg/kg/day) elicited statistically significant changes in renal gene expression of CYP3A1, UGT1A6, QR, and Mrp3, but the magnitude of renal Mrp3 induction was less than 2-fold over control. Although PH is known to modulate hepatic glucuronidation in vivo, these data indicated that PH induced mRNA levels of the efflux transporter, Mrp3, which may also affect the disposition of xenobiotics.

Animals↗
PubMed1998

Induction of rat hepatic cytochromes P450 by toxic ingredients in plants: lack of correlation between toxicity and inductive activity.

"Animal-Plant Warfare" is one of the hypotheses for the evolution of drug-metabolizing P450s. To address the validity of this hypothesis, we examined the induction of xenobiotic-metabolizing P450s by 12 plant toxins in rats, using hepatic activity for testosterone metabolism as the index. The compounds tested were aconitine, morphine, tubocurarine, physostigmine, pilocarpine, muscarine, cocaine, atropine, amygdalin, digitonin, nicotine and solanine. Drinking water containing a test compound was given to rats for 4 days, and the hepatic activity of testosterone metabolism was determined together with monitoring body weight gain and liver weight as the indices of toxicity. The results showed that while cocaine and nicotine have a minor ability to increase testosterone 16 beta-hydroxylase activity, a marker activity for the CYP2B1 and 2, all other compounds did not have any such effect. No correlation was observed between a change in 16 beta-hydroxylase and toxicity caused by toxins. Therefore, these results did not support the idea that the inducibility of the CYP2B subfamily in animals is acquired through "Animal-Plant Warfare". Several compounds examined here increased or decreased hepatic activities of testosterone 2 alpha-, 6 beta-, 7 alpha- and 16 alpha-hydroxylation and 17-oxidation, indicating a possible effect on the CYP2A, 2C and 3A subfamily. Of these effects, a moderate correlation (r < 0.49) was observed in the changes in the activities of 2 alpha-/16 alpha-hydroxylation and 17-oxidation vs. that in toxicity. It is therefore suggested that inhibition or suppression of the expression of CYP2C11 is one of the mechanisms in the toxicity of plant toxins for rats, although it comes from an examination using limited numbers of compounds.

Aconitine↗
PubMed2000

The induction of cell death in human osteoarthritis chondrocytes by nitric oxide is related to the production of prostaglandin E2 via the induction of cyclooxygenase-2.

There is increasing evidence suggesting that chondrocyte death may contribute to the progression of osteoarthritis (OA). This study focused on the characterization of signaling cascade during NO-induced cell death in human OA chondrocytes. The NO generator, sodium nitroprusside (SNP), promoted chondrocyte death in association with DNA fragmentation, caspase-3 activation, and down-regulation of Bcl-2. Both caspase-3 inhibitor Z-Asp(OCH3)-Glu(OCH3)-Val-Asp(OCH3)-CH2F and caspase-9 inhibitor Z-Leu-Glu(OCH3)-His-Asp(OCH3)-CH2F prevented the chondrocyte death. Blocking the mitogen-activated protein kinase pathway by the mitogen-activated protein kinase kinase 1/2 inhibitor PD98059 or p38 kinase inhibitor SB202190 also inhibited the SNP-mediated cell death, suggesting possible requirements of both extracellular signal-related protein kinase 1/2 and p38 kinase for the NO-induced cell death. Furthermore, the selective inhibition of cyclooxygenase (COX)-2 by NS-398 or the inhibition of COX-1/COX-2 by indomethacin blocked the SNP-induced cell death. The chondrocyte death induced by SNP was associated with an overexpression of COX-2 protein (as determined by Western blotting) and an increase in PGE2 release. PD98059 and SB202190, but neither Z-DEVD FMK nor Z-LEHD FMK completely inhibited the SNP-mediated PGE2 production. Analysis of interactions between PGE2 and the cell death showed that PGE2 enhanced the SNP-mediated cell death, whereas PGE2 alone did not induce the chondrocyte death. These data indicate that NO-induced chondrocyte death signaling includes PGE2 production via COX-2 induction and suggest that both extracellular signal-related protein kinase 1/2 and p38 kinase pathways are upstream signaling of the PGE2 production. The results also demonstrate that exogenous PGE2 may sensitize human OA chondrocytes to the cell death induced by NO.

Aged↗
PubMed2000

Induction of final follicular maturation and early luteinization in women undergoing ovulation induction for assisted reproduction treatment--recombinant HCG versus urinary HCG. The European Recombinant Human Chorionic Gonadotrophin Study Group.

This multicentre, double-blind, double-dummy, randomized, parallel-group study compared the efficacy and safety of recombinant human chorionic gonadotrophin (rHCG) (Ovidrel((R))) and urinary HCG (uHCG) (Profasi((R))) for inducing final follicular maturation and early luteinization in women undergoing ovulation induction for assisted reproduction treatment. Following long down-regulation and stimulation with recombinant human FSH (rFSH) (Gonal-F((R))), a total of 190 women received a single, s.c. injection of either 250 microg rHCG or 5000 IU uHCG. For evaluable patients (n = 172), the mean number of oocytes retrieved per patient (primary efficacy endpoint) was 11.6 for rHCG and 10.6 for uHCG (not significant). The mean number of mature oocytes was statistically higher (P = 0.027) for the rHCG group than the uHCG (9.4 versus 7.1). Serum progesterone concentrations on day 1 and days 6-7 post-HCG, and serum HCG concentrations at all post-HCG time points were statistically significantly in favour of rHCG. The clinical pregnancy rate was somewhat higher (not significant) in the rHCG group (33 versus 25%) as was the live birth rate (27 versus 23%, not significant). Both treatments were well tolerated, though the incidence of adverse events was significantly higher in the uHCG group (45.1 versus 22.7%, P = 0.0004). The incidence of injection-site reactions was significantly lower in the rHCG group (P = 0.0001). In conclusion, for triggering ovulation, rHCG seems to have significant advantages compared with uHCG in terms of number of mature oocytes retrieved, luteal progesterone and local tolerance.

Adult↗
PubMed1975

[Enzyme induction in Streptomyces hydrogenans. IV. (1) Qualitative and quantitative changes in RNA content and RNA synthesis during induction].

For isolation of RNA, freeze-dried cells of Streptomyces hydrogenans were disrupted by grinding with kieselguhr. Application of diethylpyrocarbonate (diethyl oxydiformate) in an extraction procedure yielded undegraded nucleic acids of high purity. Best separation of extracted nucleic acids was achieved by electrophoresis on 2% mixed agarose-acrylamide gels. After application of 11beta, 21-dihydroxy-4,14 (20)-pregnadien-3-one to the culture medium, the amount of acid-precipitable RNA in the cells decreased to 50% within 20 min. Concimitantly, the rate of incorporation of precursors into RNA is much slower immediately after addition of the inducer but increases during the next 2 h. 3-4 h after induction there is no difference in the RNA content of induced and control cells. Degradation of stable as well as unstable RNA was observed. Simultaneous addition of inducer and rifamycin inhibits the production of 20beta-hydroxysteroid dehydrogenase, suggesting the synthesis of special mRNA for this enzyme. Based on experiments with antibiotics, the half-life of total mRNA was calculated to be 3 min in control cells, and about 4 min in induced cells. Using a double isotope labelling technique, we established the existence of specific mRNA in the induced cells. Together with the longer half-life of mRNA in the induced cells, the increased transcription may allow the 40-fold stimulation of the synthesis of 20beta-hydroxysteroid dehydrogenase.

Cortisone Reductase↗