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PubMed1999

Induction of labor and the relationship to cesarean delivery: A review of 7001 consecutive inductions.

OBJECTIVE: The goal of this project was to study the increasing risk of induction of labor in a community hospital and to determine whether it had an adverse effect on the rate of cesarean delivery. STUDY DESIGN: From January 1, 1990, through July 31, 1997, 18,055 consecutive singleton pregnancies in women who were candidates for labor were reviewed via a comprehensive perinatal database. The risk of and indication for induction were reviewed. Cesarean delivery rates were calculated for nulliparous and multiparous patients by indication for induction and were compared with rates for patients who had spontaneous labor. Overall trends in cesarean delivery were reviewed for the duration of the study period. RESULTS: The annual induction rate significantly rose from 32% to 43% at the conclusion of the study period. Labor was induced in nearly 40% of nulliparous patients. Postdate pregnancy was the most common indication for induction, although few patients were at or beyond 42 weeks' gestation. The cesarean delivery rate remained at or below 20% for the years of the study. No increase was noted in spite of the increasing risk of induction. However, for nulliparous patients who had elective induction of labor, the risk of cesarean delivery was twice that of nulliparous patients who had spontaneous labor. CONCLUSION: The use of induction methods has significantly increased in this community hospital. More than 40% of patients are now candidates for induction. The cesarean delivery rate remains low in this facility in spite of a marked increase in risk of operative delivery for nulliparous patients who undergo induction.

Causality↗

PubMed2005

Influence of labor induction on obstetric outcomes in patients with prolonged pregnancy: a comparison between elective labor induction and spontaneous onset of labor beyond term.

BACKGROUND: Prolonged pregnancy is the most frequent reason for induction of labor. This study aims to determine the effects of labor induction on delivery outcome and to quantify the risks of cesarean delivery associated with labor induction in post-date pregnancies. PATIENTS AND METHODS: This retrospective case-control study included a total of 205 women who reached 42 weeks' gestation (41 weeks and 3 days) between January 2002 and April 2004 and who were scheduled for induction of labor with vaginal prostaglandins. These cases were matched for age and parity with controls in spontaneous labor beyond 41 weeks' gestation. Women with any additional medical or obstetric risk factors were excluded from the study. Maternal, neonatal and delivery outcomes were the main variables of interest. RESULTS: During the study period the data of 410 women were available for analysis. Our data revealed that the use of amniotomy (p=0.02), oxytocin (p=0.006) and epidural analgesia (p=0.001) was increased significantly in the induction group compared with the control group of women with spontaneous onset of labor beyond term. The frequency of cesarean delivery and vacuum extraction was also significantly higher in the induction group (p=0.0001). The Bishop score before induction was an important factor that affected the delivery outcome, resulting in significantly higher rates of cesarean section and vacuum extraction when the score was unfavorable (p=0.0001). A univariate regression model revealed induction per se (p=0.0001), primiparity (p= 0.0001), increased maternal age (p=0.006) and an unfavorable Bishop score (p=0.0001) as statistically significant risk factors for cesarean section. In a multivariate logistic regression model, primiparity (p=0.03), increased maternal age (p=0.02) and an unfavorable Bishop score (p=0.01) remained independent risk factors for cesarean section. High infant birth weight was also an independent risk factor (p=0.03). CONCLUSIONS: Our data suggest that women undergoing labor induction because of prolonged pregnancy should be sufficiently informed regarding the risks of a cesarean section or a vacuum extraction. Furthermore, the option of elective cesarean section should be considered, particularly in primiparous women with an unfavorable cervix, higher age, and high estimated infant birth weight.

Adolescent↗

PubMed2002

Induction chemoradiation compared with induction radiation for lung cancer involving the superior sulcus.

BACKGROUND: The usual approach of induction radiation therapy (RT) followed by resection of superior sulcus tumors results in many incomplete resections, a high local recurrence rate, and suboptimal survival. Induction chemoradiotherapy (CT/RT) has been shown to reduce local and distant recurrences and improve survival in stage III lung cancer. We investigated the role of induction CT/RT in superior sulcus patients. METHODS: This was a single-institution, retrospective study. RESULTS: From 1985 to 2000, 35 consecutive patients underwent induction treatment followed by resection of a superior sulcus tumor. All patients had mediastinoscopy first to exclude N2 disease, and all were N0 at final pathologic examination. Twenty patients had induction RT (mean, 39 Gy), and 15 had induction CT/RT (mean, 51 Gy) with concurrent cisplatin-based chemotherapy. There was no treatment mortality. Complete resection was performed in 16 of 20 (80%) of the RT patients and in 14 of 15 (93%) of the CT/RT patients (p = 0.15). The pathologic response from the induction treatment was complete or near complete in 7 of 20 (35%) of the RT patients and in 13 of 15 (87%) of the CT/RT patients (p = 0.001). The median follow-up was 167 months in the RT patients and 51 months in the CT/RT patients. Two-year and 4-year survival was 49% and 49% (95% confidence interval, 26% to 71%) in the RT patients and 93% and 84% (95% confidence interval, 63% to 100%) in the CT/RT patients, respectively (p = 0.01). The local recurrence rate was 6 of 20 (30%) in the RT patients and 0 in the CT/RT patients (p = 0.02). CONCLUSIONS: Induction CT/RT for superior sulcus tumors appears to offer improved survival compared with induction RT alone.

Adult↗

PubMed2002

Factors affecting the likelihood of successful induction after intravaginal misoprostol application for cervical ripening and labor induction.

OBJECTIVE: Our purpose was to determine whether maternal age, height and weight, parity, duration of pregnancy, cervical dilatation or Bishop score, and birth weight could be used to predict the likelihood of successful induction in women given intravaginal misoprostol. STUDY DESIGN: A computerized database was compiled of 1373 pregnancies in which intravaginal misoprostol was given for cervical ripening and labor induction. Most of these women were placed on investigational protocols in which the dose of misoprostol administered was 25 to 50 microg and the dosing intervals ranged from 3 to 6 hours. No more than 24 hours of administration was permitted. Induction was undertaken in women with unfavorable cervical examinations (Bishop scores of 4 or less) and without spontaneous labor or ruptured membranes. Univariate and stepwise multiple regression analyses were performed to identify those factors associated with successful induction, defined as vaginal delivery within 24 hours of induction. RESULTS: Six hundred fifty-seven (48%) had successful induction. Parity (odds ratio [OR] 2.5, 95% CI 2.0-2.9, P <.0001), initial cervical dilatation (OR 1.9, 95% CI 1.6-2.3, P <.0001), Bishop score (OR 1.6, 95% CI 1.3, 1.8, P <.0001), and gestational age at entry (OR 1.3, 95% CI 1.1-1.5, P =.002) were significant at the.05 level for predicting successful induction. A multivariate stepwise logistic regression was then performed to evaluate each of these as independent predictors. Parity (OR 2.4, 95% CI 2.0-3.0, P <.0001), initial cervical dilatation (OR 1.7, 95% CI 1.4-2.1, P <.0001), and estimated gestational age (OR 1.3, 95% CI 1.1-1.6, P =.003) are significant independent predictors for successful induction, but initial Bishop score is not significant (P =.19) after adjustment for other significant predicting factors. CONCLUSIONS: The clinical characteristics of parity, initial cervical dilatation, and gestational age at entry are predictors of the likelihood of success of cervical ripening and labor induction with intravaginal misoprostol administration.

Administration, Intravaginal↗

PubMed1996

Induction of c-fos, c-jun, junB and junD mRNA and AP-1 by alkylating mutagens in cells deficient and proficient for the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) and its relationship to cell death, mutation induction and chromosomal instability.

An early and immediate response of cells upon irradiation with UV light and various other forms of genotoxic stress is the induction of the proto-oncogenes c-fos and c-jun. To address the questions of whether (a) methylating agents that are powerful carcinogens are effective in induction of fos and jun mRNAs, (b) induction is affected by the repair capacity of the cells, and (c) induction is accompanied by genotoxic effects, the levels of c-fos, c-jun, junB and junD mRNA were analysed in isogenic Chinese hamster cell lines deficient (phenotypically Mex-) and proficient (Mex+) for the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) after treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and methyl methanesulfonate (MMS). Both methylating agents were very effective in inducing fos and jun mRNAs, although they differ markedly in their potency to induce O6-methylguanine in DNA. Most responsive were c-fos and c-jun (up to 80-fold increases in mRNA level) whereas junB (up to ninefold) and junD (up to twofold) displayed an intermediate and weak response, respectively. No difference in the dose-dependence of induction of these mRNAs was observed between Mex- and Mex+ cells indicating that the critical genotoxic and mutagenic lesion induced by MNNG, i.e. O6-methylguanine, which is rapidly repaired by MGMT, does not act as a trigger for this response. Induction of fos and jun mRNAs by MNNG and MMS was accompanied by a dose-dependent increase in the activity of the transcription factor AP-1. To induce fos and jun mRNAs as well as AP-1, doses of MNNG were required which were more than 50-fold higher than those inducing gene mutations, recombination events (SCEs) and reproductive cell death, and fivefold higher than those inducing chromosomal aberrations in Mex cells. Therefore, the immediate induction of fos and jun mRNAs and AP-1 in Mex- cells upon their exposure to MNNG appears not to be essential for the generation of MNNG-induced mutagenic and genotoxic effects, which is possibly due to the high genotoxic potential of non-repaired O6-methylguanine. However, for MMS and UV light, which was included in this study for comparison, c-fos, c-jun, junB and junD mRNA as well as AP-1 induction paralleled the dose-response for induction of cell killing effects, recombination and chromosomal breakage indicating that increased expression of Fos and Jun is related to the generation of MMS and UV-induced genetic changes. These data are in line with a model according to which the induced c-Fos and Jun proteins are involved in defense against UV radiation and other DNA damaging agents.

Alkylating Agents↗

PubMed1997

[The effects of premedication on induction doses of propofol and hemodynamic responses during induction].

We chose five sedatives for premedication and investigated the effect of these drugs on the induction doses of propofol. One hundred patients were allocated into one of five groups of 20. These groups consisted of control group (C) given only atropine 0.5 mg i.m.; CL group (plus clonidine 0.15 mg orally); H group (plus hydroxyzine 25 mg i.m.); M group (plus midazolam 3 mg i.m.) and D group (plus diazepam 10 mg orally). The induction dose was measured using loss of count technique. Arterial pressure and heart rate were measured, before and after propofol induction as well as after intubation. We also calculated rate pressure products (RPP) at each point. The induction doses were significantly lower in M-group than those in C-group. On the other hand, in hemodynamic responses, RPP was unchanged in any groups after propofol induction and after the intubation. Both propofol and midazolam have been known to have a depressive effect on the central nervous system via GABA-A receptor-mediated inhibition, although the exact receptor for propofol is unknown. We thought, therefore, that when the interaction occurred, both midazolam and propofol had the same effect on the GABA-A receptor and increased chloride ion flux through the channels. Hydroxyzine and clonidine, however, do not share a common receptor or exert effect on the GABA-A receptor. We consider that this was one of the reasons why induction doses of both H and CL group could not decrease significantly. We concluded that midazolam 3 mg decreased propofol induction dose significantly. Both midazolam 3 mg and clonidine 0.15 mg decreased RPP before induction and hemodynamic responses to induction and intubation were stable.

Adult↗

PubMed1993

Genetic susceptibility to the induction of murine experimental autoimmune orchitis (EAO) without adjuvant. II. Analysis on susceptibility to EAO induction using F1 hybrid mice and adoptive transfer system.

In our novel murine model of experimental autoimmune orchitis (EAO) induced by two or three injections of viable syngeneic testicular germ cells (TC) alone, significant differences in susceptibility to the induction of EAO were found, and the disease susceptibility did not seem to be associated with a particular H-2 haplotype. The H-2 identical background disparate (highly susceptible x low susceptible)F1 hybrids, (C3H/He x C3H/HeJ)F1 and (C3H/HeJ x C3H/He)F1 mice, were highly susceptible to the induction of EAO. The H-2 identical background disparate (highly susceptible x resistant)F1 hybrids, (C3H/He x C3H/BiKi)F1 and (C3H/BiKi x C3H/He)F1 mice, were low susceptible to the induction of EAO. Both the H-2 and background disparate (highly susceptible x resistant)F1 hybrids, (C3H/He x DBA/2N)F1 and (DBA/2N x C3H/He)F1 mice, were equally resistant to EAO induction. In the susceptible hybrids, both delayed footpad reaction (DFR) and antibody responses to TC increased. On the other hand, in the resistant hybrids, the levels of anti-TC antibodies were elevated but the DFR to TC remains depressed. This suggests that the antibody production and induction of DFR may be under different genetic controls and that cellular immunity plays an important role in this EAO induction. In order to search for the mechanistic basis for low susceptible C3H/HeJ and resistant C3H/BiKi mice, these mice received orchitis-inducible spleen cells (SPCs) from C3H/He mice. C3H/HeJ mice were highly susceptible to passive EAO. In contrast, disease-resistant C3H/BiKi mice failed to develop passive EAO. In addition, we examined whether or not regulatory cells capable of preventing the disease induction were generated in low susceptible C3H/HeJ and resistant C3H/BiKi mice immunized with TC. Transfer of SPCs from TC-immunized C3H/HeJ and C3H/BiKi mice into C3H/He mice before the EAO challenge had no suppressive effect on subsequent disease induction.

Animals↗

PubMed1999

Histamine release during the induction of anesthesia with propofol in allergic patients: a comparison with the induction of anesthesia using midazolam-ketamine.

OBJECTIVE: A prospective randomized controlled study was performed for patients with a history of allergy to evaluate the effect of the induction of anesthesia with propofol against histamine release, skin reactions, hemodynamic changes and other clinical symptoms, while also comparing these parameters during the induction of anesthesia with midazolam-ketamine for patients with a history of allergy. SUBJECTS: We examined 40 patients undergoing oral surgery, who had a history of allergy and/or the percentage of eosinophils in the leukocytes was more than 3%. METHODS: Forty patients were randomly allocated into two groups and thus received either midazolam-ketamine (M-K group, n = 20) or fentanyl-propofol (propofol group, n = 20) for the induction of anesthesia. Venous blood samples (4 ml each) were obtained before induction as a control and at 0.5, 1, 3, 5 minutes after the administration of each induction agent, and then furthermore at 0.5, 1, 3, 5 minutes after tracheal intubation in order to measure the plasma histamine level by using the HPLC post-label system. In addition, the blood pressure and heart rate were also simultaneously recorded. Skin reactions were also evaluated by two anesthesiologists. RESULTS: The incidence of 50% histamine release during the induction of anesthesia with propofol occurred in 15% of the patients with a history of allergy. Sixteen patients out of 20 (80%) showed a decrease in the systolic blood pressure after the administration of propofol without any evidence of histamine release. The incidence of 50% histamine release, skin reactions and an increase in the heart rate between the two groups were not statistically significant after the administration of each anesthetic agent. Moreover, some patients also demonstrated histamine release after tracheal intubation. Hemodynamic changes after tracheal intubation showed a similar tendency in both groups. No significant difference was observed regarding the incidence of histamine release, skin reactions and hemodynamic changes between both groups after tracheal intubation. CONCLUSIONS: Propofol was found to show a similar incidence of histamine release during the induction of anesthesia using midazolam-ketamine, and thus was also found to be a useful induction agent against histamine release for patients with a history of allergy when hydroxizine was used as a premedication.

Adult↗

PubMedDate not supplied

Inductive electronegativity scale. Iterative calculation of inductive partial charges.

A number of novel QSAR descriptors have been introduced on the basis of the previously elaborated models for steric and inductive effects. The developed "inductive" parameters include absolute and effective electronegativity, atomic partial charges, and local and global chemical hardness and softness. Being based on traditional inductive and steric substituent constants these 3D descriptors provide a valuable insight into intramolecular steric and electronic interactions and can find broad application in structure-activity studies. Possible interpretation of physical meaning of the inductive descriptors has been suggested by considering a neutral molecule as an electrical capacitor formed by charged atomic spheres. This approximation relates inductive chemical softness and hardness of bound atom(s) with the total area of the facings of electrical capacitor formed by the atom(s) and the rest of the molecule. The derived full electronegativity equalization scheme allows iterative calculation of inductive partial charges on the basis of atomic electronegativities, covalent radii, and intramolecular distances. A range of inductive descriptors has been computed for a variety of organic compounds. The calculated inductive charges in the studied molecules have been validated by experimental C-1s Electron Core Binding Energies and molecular dipole moments. Several semiempirical chemical rules, such as equalized electronegativity's arithmetic mean, principle of maximum hardness, and principle of hardness borrowing could be explicitly illustrated in the framework of the developed approach.

Journal Article↗

PubMed2002

A comparison between midazolam co-induction and propofol predosing for the induction of anaesthesia in the elderly.

In a prospective, double-blind, randomised, placebo-controlled trial, we have compared the effects of midazolam co-induction with propofol predosing on the induction dose requirements of propofol in elderly patients. We enrolled 60 patients aged > 70 years, attending for urological surgery. The patients were allocated randomly to one of three groups, to receive either midazolam 0.02 mg.kg(-1), propofol 0.25 mg.kg(-1), or normal saline 2 ml (placebo) 2 min prior to induction of anaesthesia using propofol 1% infusion at 300 ml.h(-1). The propofol dose requirements for induction were recorded for two end-points (loss of verbal contact and insertion of an oropharyngeal airway). Cardiovascular parameters were recorded at 1-min intervals for each patient until induction was complete. The midazolam group showed a significant reduction in propofol dose requirements for induction (p = 0.05) compared to the placebo group. The propofol group did not show a significant dose reduction compared to placebo. There were no demonstrable differences in terms of improved cardiovascular stability between groups. We conclude that propofol predosing does not significantly reduce the induction dose of propofol required in the elderly, and there were no cardiovascular benefits to either midazolam co-induction or propofol predosing in the elderly.

Aged↗

PubMedDate not supplied

When induction meets memory: evidence for gradual transition from similarity-based to category-based induction.

The ability to perform induction appears early; however, underlying mechanisms remain unclear. Some argue that early induction is category based, whereas others suggest that early induction is similarity based. Category- and similarity-based induction should result in different memory traces and thus in different memory accuracy. Performing induction resulted in low memory accuracy in adults and 11-year-olds, whereas 5-, and 7-year-olds were highly accurate (Experiment 1). After training to perform category-based induction, 5- and 7-year-olds exhibited patterns of accuracy similar to those of adults (Experiment 2). Furthermore, 7-year-olds, but not 5-year-olds, retained this training over time (Experiment 3). With novel categories, even adults performed similarity-based induction, exhibiting high memory accuracy (Experiment 4). These results suggest a gradual transition from similarity- to category-based induction with familiar categories.

Adolescent↗

PubMed2000

Laparoscopic "drilling" by diathermy or laser for ovulation induction in anovulatory polycystic ovary syndrome.

BACKGROUND: Problems in inducing ovulation in women with polycystic ovary syndrome (PCOS) and anovulation (failure to ovulate) are well recognised. Surgical ovarian wedge resection was the first established treatment for anovulatory PCOS patients but was largely abandoned of the risk of post-surgical adhesion formation. It was replaced by medical ovulation induction with clomiphene and gonadotrophins. However patients with PCOS treated with gonadotrophins often have a polyfollicular response and are exposed to the risks of ovarian hyperstimulation syndrome (OHSS) and multiple pregnancy. Although effective, it is an expensive, stressful and time consuming form of treatment requiring intensive monitoring. A new surgical therapy, laparoscopic ovarian "drilling", may avoid or reduce the need, or facilitate the use, of gonadotrophins for inducing ovulation. The procedure can be done on an outpatient basis with less trauma and fewer postoperative adhesions. It has been claimed in many uncontrolled observational studies that it is followed, at least temporarily, by a high rate of spontaneous postoperative ovulation and conception, or that subsequent medical ovulation induction becomes easier. OBJECTIVES: To determine the effectiveness of laparoscopic ovarian drilling for ovulation induction in subfertile women with anovulation (failure to ovulate) and polycystic ovarian syndrome (PCOS). SEARCH STRATEGY: The search strategy of the Menstrual Disorders and Subfertility Group was used for the identification of randomised controlled trials (RCTS). A computerised MEDLINE search was used to identify non randomised controlled trials. SELECTION CRITERIA: Trials were eligible for inclusion if treatment consisted of laparoscopic ovarian drilling in order to induce ovulation in subfertile women with PCOS and compared with a concurrent control group. DATA COLLECTION AND ANALYSIS: Fourteen trials were identified; eight were included in the review of which seven were randomised. All trials were assessed for quality criteria. The main studied outcomes were ovulation and pregnancy rates. Miscarriage rate, multiple pregnancy rate, and incidence of overstimulation and ovarian hyperstimulation syndrome rate were secondary outcomes. MAIN RESULTS: With the exception of multiple pregnancy rates no differences were demonstrated for any of the interventions studied but the numbers of patients who have been randomised to controlled studies at this time is insufficient to conclude that laparoscopic ovarian drilling is more effective than gonadotrophin therapy for other outcomes. REVIEWER'S CONCLUSIONS: The value of laparoscopic ovarian drilling as a primary treatment for subfertile patients with anovulation (failure to ovulate) and polycystic ovarian syndrome (PCOS) is undetermined. There is insufficient evidence to determine a difference in ovulation or pregnancy rates when compared to gonadotrophin therapy as a secondary treatment for clomiphene resistant women. Multiple pregnancy rates are reduced in those women who conceive following laparoscopic drilling. None of the studied modalities of drilling technique had any obvious advantages.

Anovulation↗

PubMed1991

Synergistic induction of delta-aminolevulinate synthase by glutethimide and iron: relationship to the synergistic induction of heme oxygenase.

Relationships between activities of delta-aminolevulinate synthase and heme oxygenase, respectively the rate-limiting enzymes of heme biosynthesis and degradation, have been studied in chick embryo liver cell cultures following exposure of the cultures to glutethimide and iron, a combination known to produce a synergistic induction of both enzymes. In time-course experiments, synergistic induction of heme oxygenase activity by glutethimide and iron preceded that of delta-aminolevulinate synthase by 4 h. Effects of selective inhibitors of both heme synthesis and degradation have also been studied with respect to effects on delta-aminolevulinate synthase and heme oxygenase activities. The synergistic induction of heme oxygenase by glutethimide and iron appears to be dependent upon cellular heme synthesis because addition of inhibitors of heme biosynthesis, 4,6-dioxoheptanoic acid or N-methyl-mesoporphyrin abolishes this synergistic induction. Exposure of cultures to tin-mesoporphyrin, a potent inhibitor of heme oxygenase, prevented the synergistic induction of delta-aminolevulinate synthase produced by glutethimide and iron, or, when added after induction was already established, promptly halted any further induction. These results suggest that the level of activity of heme oxygenase can reciprocally modulate intracellular heme levels and thus activity of delta-aminolevulinate synthase.

5-Aminolevulinate Synthetase↗

PubMed1994

Involvement of testosterone in the induction of hepatic microsomal cytochrome P-450 2B1/2 (P-450 2B1/2) by 1-benzylimidazole in male and female rats: sex-differentiated induction of P-450 2B1/2 species.

We examined the effect of 1-benzylimidazole on the induction of cytochrome P-450 1A1/2 (P-450 1A1/2) and cytochrome P-450 2B1/2 (P-450 2B1/2) in normal, castrated, ovariectomized and hypophysectomized male rats, and in castrated rats treated with testosterone. 1-Benzylimidazole markedly increased P-450 content in male and female rats. Parallel to the dose-dependent increase in P-450 content, 1-benzylimidazole produced a significant increase in P-450 2B1/2 in male rats, but not in female rats. 1-Benzylimidazole failed to induce P-450 2B1/2 in castrated male and ovariectomized female rats. Treatment of castrated male rats with testosterone restored the induction of P-450 2B1/2 by 1-benzylimidazole. Treatment of ovariectomized female rats with 1-benzylimidazole or phenobarbital led to the increase in P-450 content, accompanying by the induction of P-450 2B1/2 by the latter treatment, but not the former. In hypophysectomized male rats, 1-benzylimidazole was able to induce P-450 2B1/2 in contrast to castrated male rats. Neonatal male and female rats responded well to the induction of P-450 2B1/2 by 1-benzylimidazole. The present findings suggest that P-450 2B1/2 induction by 1-benzylimidazole would be coupled with circulating testosterone regulated by hypophysis-testis axis. 1-Benzylimidazole produced sex-differentiated induction of P-450 2B1/2 in pubertal rats, but not in neonatal animals. The present findings would be provide information on a unique effect of 1-benzylimidazole on P-450 2B1/2 induction in rats.

Animals↗

PubMed1988

The induction, desensitization and de-induction of tyrosine aminotransferase by 8-bromo-cyclic AMP in rat hepatoma cells.

Addition of 1-3 mM-8-bromo-cyclic AMP to monolayer cultures of H-4 rat hepatoma cells resulted in a rapid but short-lived increase in tyrosine aminotransferase (EC 2.6.1.5) activity. The transient nature of this induction is due to desensitization to 8-bromo-cyclic AMP. Throughout this time course of induction and desensitization, removal of 8-bromo-cyclic AMP resulted in a rapid and significant decrease in tyrosine aminotransferase activity, a process referred to as 'de-induction' in this study. We showed that the changes in tyrosine aminotransferase activity in its induction, desensitization and de-induction by 8-bromo-cyclic AMP were directly attributable to changes in the synthesis rate of the protein, and the amount of translatable and hybridizable mRNA encoding for tyrosine aminotransferase (mRNATAT). We further showed that this desensitization was specific to cyclic AMP. First, only active analogues of cyclic AMP and agents which increased cellular concentrations of cyclic AMP elicited this desensitization. Second, the desensitized cells were refractory only to the effects of 8-bromo-cyclic AMP; dexamethasone and insulin induced the tyrosine aminotransferase activity in the 8-bromo-cyclic AMP-desensitized cells in a manner similar to that of the controls. Studies on the metabolism of 8-bromo-cyclic AMP suggest that neither its degradation nor the accumulation of its primary metabolite, 8-bromoadenosine, played a significant role in modulating the expression of tyrosine aminotransferase during the time course of action of 8-bromo-cyclic AMP. These results provide evidence for a specific pretranslational mode of action of cyclic AMP in the control of tyrosine aminotransferase expression in its desensitization and de-induction, in addition to the early phase of induction.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2003

Induction of CYP3As in HepG2 cells by several drugs. Association between induction of CYP3A4 and expression of glucocorticoid receptor.

The cytochrome P-450 3A (CYP3A) enzyme family is responsible for most of the drug metabolism in the human liver. In this study, we demonstrated the inductive effects of phenobarbital, rifampicin, carbamazepine, phenytoin, prednisolone, ciclosporin and clotrimazole on CYP3A4, CYP3A5 and CYP3A7 mRNA expression, and established the relationship between the expression of human glucocorticoid receptor alpha (hGR) mRNA and the induction of CYP3A4 mRNA in cultured HepG2 cells by reverse transcription polymerase chain reaction (RT-PCR). Treatment with prednisolone, rifampicin and carbamazepine rapidly induced the level of CYP3A4 mRNA expression by 3- to 6-fold. However, phenytoin and phenobarbital gradually induced CYP3A4 mRNA level by 3 to 4-fold. The induction of CYP3A4 mRNA expression by clotrimazole and ciclosporin was negligible. Treatment with phenytoin, rifampicin, carbamazepine and ciclosporin induced approximately 2-fold increases in the expression of CYP3A5 mRNA, although prednisolone, phenytoin and clotrimazole had no effect. Treatment with rifampicin, phenytoin, clotrimazole and ciclosporin resulted in approximately a 2-fold induction of the CYP3A7 mRNA level. Treatment with rifampicin and ciclosporin induced the expression of hGRalpha mRNA significantly in comparison with controls, although the induction of hGRalpha mRNA following treatment with other drugs was negligible. In cluster analysis, the induced level of CYP3A4, CYP3A5, CYP3A7 and hGRalpha mRNA by these drugs could be classified into four major clusters. This suggested that each cluster might be associated with different mechanism(s) of induction by these drugs. Furthermore, we studied the associations between the expression of hGRalpha mRNA and the induced level of CYP3A4 mRNA by prednisolone and ciclosporin. Treatment with both prednisolone and ciclosporin showed synergistic effects on induction of CYP3A4 mRNA and, following treatment with both drugs, the expression level of CYP3A4 mRNA was 2-fold greater compared with prednisolone alone after the fifth day. Positive correlations were observed between the levels of hGRalpha mRNA expression and those of CYP3A4 mRNA. This observation shows that the regulation of CYP3A4 gene expression was hGRalpha-dependent and that ciclosporin may function as a regulator of expression via hGRalpha.

Cell Line, Tumor↗

PubMedDate not supplied

Induction of avidin in the chick oviduct by tissue damage. Effect of promethazine chloride, CaCl2 and hydrocortisone on local induction.

The local effect of the mechanical induction of avidin by ligature was studied in diethylstilbestrol-primed chicks. The highest induction of avidin was always found in the immediate vicinity of the silk ligature of the oviduct. The locality of the induction was highly dependent on the position of the ligature. The nonligated parts of the ligated oviduct also showed a slight avidin induction. These results indicate a strictly local effect of avidin induction by ligature. An antihistamine, promethazine chloride, has a potentiating effect on the avidin induction by ligature when administered after the ligature. On the other hand, membrane stabilization by hydrocortisone or CaCl2 did not influence the ligature-induced avidin synthesis. On the basis of these results it is concluded that the avidin induction is not mediated by histamine activation or membrane damage.

Animals↗

PubMed1990

Induction of fatty acid binding protein by peroxisome proliferators in primary hepatocyte cultures and its relationship to the induction of peroxisomal beta-oxidation.

The induction of liver fatty acid binding protein (L-FABP) by the peroxisome proliferators bezafibrate and clofibrate was compared with the induction of peroxisomal (cyanide-insensitive) palmitoyl-CoA oxidation in cultured rat hepatocytes maintained on a substratum of laminin-rich (EHS) gel. This substratum was chosen because marked induction of both L-FABP and peroxisomal palmitoyl-CoA oxidation was effected by bezafibrate in hepatocytes supported on EHS gel, whereas only peroxisomal palmitoyl-CoA oxidation was induced in hepatocytes maintained on collagen-coated plates. In control cells on EHS, activity of peroxisomal palmitoyl-CoA oxidation remained stable, while L-FABP abundance declined with time, and L-FABP mRNA was undetectable after 5 days. In cultures exposed to bezafibrate or clofibrate, peroxisomal palmitoyl-CoA oxidation activity was induced earlier and more rapidly than L-FABP. When fibrates were withdrawn, peroxisomal palmitoyl-CoA oxidation declined rapidly, whereas L-FABP continued to increase. L-FABP induction was accompanied by a striking increase in mRNA specifying this protein. Tetradecylglycidic acid, an inhibitor of carnitine palmitoyltransferase I, effectively doubled peroxisomal palmitoyl-CoA oxidation activity. However, tetradecylglycidic acid markedly inhibited fibrate induction of L-FABP and peroxisomal palmitoyl-CoA oxidation but, unexpectedly, did not prevent the fibrate-induced proliferation of peroxisomes. Maximal induction of both L-FABP and peroxisomal palmitoyl-CoA oxidation was produced at a bezafibrate concentration in the culture medium (0.05 mM) much lower than that of clofibrate (0.3 mM). Also, bezafibrate, but not clofibrate, inhibited [1-14C]oleic acid binding to L-FABP with a Ki = 9.5 microM. We conclude that hepatocytes maintained on EHS gel provide an important tool for investigating the regulation of L-FABP. These studies show that the induction of peroxisomal beta-oxidation and L-FABP by peroxisome proliferators are temporally consecutive but closely related processes which may be dependent on a mechanism distinct from that which leads to peroxisome proliferation. Furthermore, the mechanism of action of the more potent peroxisome proliferator, bezafibrate, may be mediated, in part, by interaction of this agent with L-FABP.

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