Labor induction was successful inmost patients.
In the cases in which the final outcome was a cesarean section, the most strongly associated factors were: previous history of cesarean delivery, presence of fetuses with IUGR, and either excessively short or excessively long periods of induction. The onset of labor depends on a series of coordinated and synchronized processes, such as persistent uterine contractions, cervical maturation, and descent of the fetal presentation. Labor induction can also be recommended due to logistical issues, such as risk of rapid labor, fetal malformation incompatible with extrauterine life, distance to the location of the hospital, or psychosocial issues.
On the other hand, the indication for induction of elective labor for the sake of convenience is becoming ever more frequent. In a meta-analysis including 7 studies, it was noted that the elective induction rate ranges from 0. Several methods have been described to promote both cervical maturation and labor itself.
Among the most commonly used methods are the administration of prostaglandins misoprostol and dinoprostone , oxytocin, and Foley probe, which either alone or in a combination thereof help in the process of uterine cervix maturation and stimulate labor. The traditional method to assess the ripeness of the cervix prior to labor induction is the cervical scoring system described by Bishop, known as the Bishop score.
Historically, there is no well-accepted definition to characterize labor induction failure. On the other hand, Spong et al 16 point out as the criterion for induction failure the inability to generate regular contractions and cervical alteration after 24 hours of oxytocin administration with artificial rupture of the membranes, when possible. In the last decades, the national rate of cesarean operations has progressively increased, and cesarean section surgery has become the most common mode of birth in the country. Therefore, the present study aimed to evaluate the results of labor induction and to determine the main factors associated with intrapartum cesarean section in women who were submitted to this procedure and eventually progressed to the active phase of labor in a public university hospital in the southern region of Brazil.
Data were collected from birth records, medical charts, and from the eletronic information system of the hospital. Women who failed the induction method were excluded from the present study for a better evaluation of the outcomes. Fetal death was also excluded so that postinduction results could be compared with those of other studies. As for the patients whose induction resulted in labor whether vaginal delivery or cesarean section , the associations between the induction outcome and the following variables were tested: induction indication, induction method s , maternal age, parity, gestational age, integrity of the amniotic membranes, total time of labor induction, and status of the cervix at the beginning of the induction procedure Bishop score.
Neonatal aspects, such as birthweight, 5-minute Apgar score, and any record of meconium amniotic fluid, were also related to the delivery route. The Bishop score is an assessement of the position, of the consistency, of the effacement shortening of the cervix , and of the dilatation of the maternal cervix, as well as of the station of the fetal presenting part.
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When there was no response to the complete misoprostol regimen, intravenous oxytocin, initiated after 4 hours of the last dose of misoprostol, was indicated in the regimen described above. In cases of previous cesarean section and unfavorable cervix, the method used was the Foley catheter, with intravenous oxytocin initiation either as soon as it was spontaneously ejected or 24 hours after its introduction.
Induction failure was considered either when the patient did not trigger effective contractions 3 contractions every 10 minutes after the maximal oxytocin dose, or when there was no cervical maturation after maximal misoprostol or Foley catheter timeout, even after the administration of an intravenous oxytocin combination.
Intrauterine growth restriction had a lower percentage 3. It was defined according to the relation between birthweight and gestational age at the time of labor. Next, a multivariate analysis was performed with logistic regression, including all of the factors that were associated with cesarean section in the univariate analysis.
In cases of induction Within this group, the induction protocol was not completed in 36 cases Out of these cases, In the induction failure group, there were 21 cases of pregnant women withdrawal due to incomplete protocol, 7 cases of fetal changes in cardiotocography tests, and 8 cases in which the cause of the suspension of induction was not addressed in the records of the patients. This corresponds to only 2. The average age of the analyzed patients was Table 1. Pregnant women with a history of previous vaginal delivery presented a higher rate of current vaginal delivery On the other hand, pregnant women with a history of previous cesarean section had more intrapartum cesarean sections When the time between the onset of induction and birth was between 12 and 24 hours, there were lower rates of cesarean sections There was no relationship between the delivery route and maternal age, amniotic membrane status, Apgar score, initial Bishop score, or the presence of meconium Table 4.
The presence of meconium was evaluated during labor after the rupture of the amniotic membranes or during the expulsive period. Labor induction is indicated when continuation of the pregnancy is thought to be associated with greater maternal or fetal risk than intervention to deliver the pregnancy, when there is no contraindication to vaginal birth. Previous studies attempting to identify risk factors for cesarean delivery in patients undergoing labor induction have a more specific objective. Most of the times they analyzed only one variable, which makes it difficult to evaluate the implementation of a protocol.
The main purpose of labor induction is vaginal delivery, but it is well known that when labor is induced, the chances of vaginal delivery are lower than in spontaneous labor, especially in nulliparous women.
Given these data, several institutions seek to implement protocols to prevent the first unnecessary cesarean section, since this way of delivery has effects on the future reproductive life by increasing the risk of uterine rupture, as well as placental accretion, among others. According to Lappen et al, 35 women with previous cesarean section had a higher risk of induction failure. Moreover, in induced labor, a history of previous cesarean section is a risk factor for a repeat cesarean section, which corroborates the data obtained in the present study.
Many authors point out that the longer the induction time, especially when the latent phase is prolonged, the greater the risk of induction failure. One approach to diagnosing a failed induction is based on the duration of the latent phase. C , gel mobility shift assay. Surprisingly, a protein with a higher mobility was also detected in this assay. A similar result was observed with the SVL substrate data not shown This result is interesting in light of the observation that the Drosophila ELAV protein is co-immunoprecipitated with dCstF64 when added to the non-neuronal nuclear extract to examine binding of dCstF64 to the non-neuronal poly A site of the ewg pre-mRNA.
Hu proteins interact with poly A factors. A , Hu proteins block CstF64 binding to the exon 4 poly A site.
C , co-immunoprecipitation of CstF64 with Hu proteins. The mouse brain nuclear extract was subjected to immunoprecipitation with the Hu patient sera. The CstF64 binding result indicates that Hu proteins block polyadenylation of SVL and the calcitonin exon 4 by interfering with the interaction of poly A factors to the poly A sites and also suggests that CstF64 interacts with Hu proteins. RNase was included to ensure that any interaction detected was not mediated by RNA.
Thus, Hu proteins block polyadenylation by interacting, mostly likely directly, with CstF and CPSF, which are required for both cleavage and poly A addition steps. To test whether the interaction between Hu proteins and poly A factors occurs in vivo in cells where Hu proteins are naturally expressed, we carried out a co-immunoprecipitation assay using nuclear extract isolated from the mouse brains.fr.bexaxuduzese.tk
The Van Deemter equation
HuR Blocks Polyadenylation of the SVL Poly A Site in Cultured Cells —To demonstrate the biological relevance of our findings in vitro , we tested whether the results could be duplicated in a cell transfection experiment. The two reporters were individually transfected with either a vector control or the HuR expression plasmid in HeLa cells.
A third plasmid, LacZ expression vector, was included as an internal control. One set of primers was used to detect the precursor transcript and the other set, including an oligo dT primer, to detect the polyadenylated mRNA.
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Interestingly, we observed reduced splicing when the transcript containing the SVL poly A site was blocked at polyadenylation. This result is consistent with the previously demonstrated coupling of polyadenylation and splicing during RNA processing Refs. It has been documented that mutations of polyadenylation signal AAUAAA or downstream sequences decreases not only polyadenylation but also splicing efficiency. HuR blocks SVL polyadenylation in transfected cells. A , diagram showing the transfected reporters. Sizes of exons and introns are indicated. Oligonucleotides used to analyze polyadenylation are shown.
The signals in the HuR and vector lanes were first normalized to the LacZ level in the corresponding transfections. The normalized signal in the HuR lane was then divided by the normalized signal in the vector lane. The numbers are an average of two transfections.
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C , Western blot analysis. Total protein lysate isolated from the transfected cells were probed with anti-Xpress antibody Invitrogen and anti-U1 kDa subunit antibody. In this report, we have demonstrated that the mammalian Hu proteins regulate polyadenylation by blocking poly A sites containing U-rich sequences. Our studies expand the very short list of polyadenylation regulators in mammals.
The polyadenylation-regulating activity of Hu proteins correlates with their binding to the U-rich sequences upstream of the cleavage site. These U-rich sequences are similar to the previously characterized USEs present in some of the cellular and viral poly A sites and necessary for efficient polyadenylation at those sites harboring them In the case of the calcitonin exon 4 poly A site, mutation of the U-rich sequence did not reduce the polyadenylation efficiency Fig.
Thus, whether the U-rich sequence functions as a classical USE in this poly A site remains to be further determined. Recently, Kaufmann et al. Interestingly, in this study, Fip1 was also found to bind to the SVL poly A site, the same site that can be blocked by Hu proteins In a more recent study by Zhao et al. In light of another recent discovery 7 that CFIm68 binds to a number of USE sequences containing UGUAN repeats and promotes polyadenylation and that the SVL poly A site contains such repeats, it remains a formal possibility that Hu proteins and CFIm may modulate the polyadenylation activity of sites that contain binding sites for both proteins through their competing activities.
Given that USEs have been identified in an increasing number of cellular poly A sites 23 , 35 — 40 , it will be of particular interest to further investigate the role of Hu proteins in USE-mediated polyadenylation regulation. How do Hu proteins regulate polyadenylation? We demonstrate that all three of the RRMs of Hu proteins are required for the polyadenylation-blocking activity of these proteins, suggesting that RNA-binding activity alone is not sufficient.
Presumably, RRM3 and the hinge region are involved in interacting with the poly A factors. Such interactions may modulate the structure of the poly A complex formed on the U-rich sequence-containing sites in a way that renders the complex non-functional. Presumably, neither RNA binding nor interaction with poly A factors alone can induce such a rearrangement. Given that three of the Hu proteins are neuron-specific and interact with CstF64 in brain nuclear extract Fig. It was previously demonstrated that inclusion of exon 4 is promoted by a number of factors bound at an intronic element in non-neuronal cells 20 , 24 , 41 , Of these factors, U1 small nuclear ribonucleoprotein and SRp20 were shown to promote polyadenylation of this exon 20 , It is highly likely that, in neurons, Hu proteins block polyadenylation of exon 4, thereby promoting the neuron-specific pathway.
A similar example is the Drosophila ewg pre-mRNA.
Although both Hu proteins and ELAV block polyadenylation, major differences exist between the functions of these proteins. However, it is possible that Hu proteins function through binding at the downstream U-rich sequences of those sites, such as SVL, that contain such sequences Fig. These results suggest potential distinct or different variations of mechanisms for these two putative orthologous proteins in regulating polyadenylation.