Premature Rise Research Articles

Le cycle naturel en fécondation in vitro chez les mauvaises répondeuses

Since the beginning of IVF, natural cycle In Vitro Fertilization (NC-IVF) has been largely replaced by IVF with ovarian stimulation. However, natural cycle IVF has several advantages: low cost, no risk of ovarian hyper stimulation syndrome, very low risk of multiple pregnancy. Nevertheless, natural cycle IVF is less effective with a high risk of cancellation due to premature rise of LH, and an increased risk of failed oocyte retrieval. Using GnRH antagonists in a modified natural cycle decreases the occurrence of a premature LH rise. In the context of a poor responder patient, natural IVF could theoretically yield a better quality oocyte coming from a naturally selected follicle and allow a transfer on an endometrium whose receptivity has not been distorted by controlled ovarian stimulation. However, the real place for it has yet to be defined as we lack published data. Only one randomised controlled study in poor responders showed a similar pregnancy rate to a standard protocol representing a cost-effective alternative. Available retrospective data seem to show the same trend especially in the sub group of younger patients (below 38). Natural cycle IVF is a low-risk, low-cost procedure whose interesting results should be further confirmed by large scale prospective studies.

P-760: Evidence that high serum progesterone (P) levels on day of human chorionic gonadotropin (hCG) injection have no adverse effect on the embryo itself as determined by pregnancy outcome following donor embryo transfer

There is evidence that a premature rise in P on the day of hCG injection has an adverse effect on pregnancy rates following in vitro fertilization-embryo transfer (IVF-ET). The objective of the present study was to determine pregnancy outcome in recipients according to the P level of the donor at the time of hCG injection. Lower pregnancy rates with advancing P levels would suggest that the adverse effect of P is on the embryo itself. No adverse effect at most levels of elevated P would suggest the adverse effect was on the endometrium.

GnRH antagonists in ovarian stimulation for IVF

The present review describes, on the basis of the currently available evidence, the consensus reached by a group of experts on the use of gonadotropin-releasing hormone (GnRH) antagonists in ovarian stimulation for IVF. The single or multiple low-dose administration of GnRH antagonist during the late-follicular phase effectively prevents a premature rise in serum luteinizing hormone (LH) levels in most women. Although controversy remains, most comparative studies suggest a slight, not significant reduction in the probability of pregnancy after IVF using GnRH antagonist versus GnRH agonist co-treatment. Published meta-analyses suggest that this slight difference in pregnancy rates is not attributed to chance. Further studies applying varying treatment regimens and outcome measures are required. Data are not in favour of a need to modify the starting dose of gonadotropins. Data are not in favour of increasing gonadotropin dose at GnRH antagonist initiation. The addition of LH from the initiation of ovarian stimulation or from GnRH antagonist administration does not appear to be necessary. Replacement of human chorionic gonadotropin (HCG) by GnRH agonist for triggering final oocyte maturation is associated with a lower probability of pregnancy. The optimal timing for HCG administration needs to be explored further. GnRH antagonist initiation on day 6 of stimulation appears to be superior to flexible initiation by a follicle of 14-16 mm, although earlier GnRH antagonist administration is worth further evaluation. Luteal phase supplementation in GnRH antagonist protocols remains mandatory in IVF. Effects of GnRH antagonist co-treatment on the incidence of ovarian hyperstimulation syndrome remains uncertain, although a trend is present in favour of the GnRH antagonists. The role of GnRH antagonists in ovarian stimulation for IVF appears to be promising, although many questions regarding preferred dose regimens and effects on clinical outcomes remain.

Evolving technology in bipolar perfused radiofrequency ablation: assessment of efficacy, predictability and safety in a pig liver model

Bipolar radiofrequency (RF) ablation, especially with perfusion of saline, has been shown to increase volume over monopolar conventional methods. The aims of this study are to study whether this method is linked to too flattened thermal lesions and premature rise of impedance and to elucidate some safety concerns. Eighteen RF ablations were performed using a 1.8-mm-diameter bipolar applicator in the liver of nine healthy pigs through laparotomy with or without temporary vascular occlusion [the Pringle maneuver (PGM)]: group A (n=9), without PGM; group B (n=9), with PGM. Hypertonic saline solutions (3% and 20 %) were injected through the applicator at a rate of 400 ml/h during the procedure. The pigs were followed up and they were euthanased on the 15th day. Impedance, current, power output, energy output, temperatures, diameters of thermal lesion, volume, sphericity ratio of thermal lesion were correlated among groups. Impedance at the end of the procedure (50.00 Omega+/-28.39 and 52.88 Omega+/-26.77, for groups A and B, respectively) was very similar to the starting impedance (50 Omega). In a median of 1 (range, 0-6) time per RF ablation procedure a reduction of 30 W from the selected power supply was observed during the RF ablation procedure linked to a slight increase of impedance. Volume and short diameter of thermal lesion were 21.28 cm3+/-11.78 and 2.85 cm+/-0.87 for group A, 87.51 cm3+/-25.20 and 4.31 cm+/-0.65 for group B. Continuous thermal between both electrodes were described with a global sphericity ratio of 1.91. One major complication (thermal injury to the stomach) was encountered in a case of cross-sectional necrosis of the targeted liver and attributed to heat diffusion after the procedure. This method has been shown to determine: (1) the relative control of impedance during the procedure; (2) ovoid and relatively large thermal lesions with less dependence upon closest vessels.

Comparison of Pregnancy Rates in IVF Cycles Where Gonadotropin Releasing Hormone (GnRH) Antagonists Were Used to Suppress Luteinizing Hormone (LH) Surge in Place of GnRH Agonists

Comparison of Pregnancy Rates in IVF Cycles Where Gonadotropin Releasing Hormone (GnRH) Antagonists Were Used to Suppress Luteinizing Hormone (LH) Surge in Place of GnRH Agonists

Premature roll-off in radiofrequency ablation using bipolar saline-enhanced electrodes

Sir, We have read with interest the article by Lee et al. [1]. The authors tried to compare two radiofrequency bipolar systems: the Berchtold system with open-perfused electrodes (bipolar saline-enhanced electrodes) and the Radionics system with cooled-wet electrodes in bipolar mode. We would like to congratulate the authors for their experimental design and excellent results. However, the work raises some concerns. First of all, the accumulated energy output was 87,555.1±86,787 Ws (joules) for the open-perfused electrode group when the maximum power output for the generator was 60 W for 20 min (that means a maximum energy output of 72,000 Ws per experience). Furthermore, the huge variability expressed by the standard deviation in output energy deposition means that in some cases, less than 1,000 Ws were deposited, while in other cases more than two times the maximum output energy was employed. Actually, on the basis of the authors’ explanation, the main reason for the reduced ablation dimension in the open-perfused group compared with the cooled-wet group is the premature rise of the impedance over 700 Ω. This premature roll-off of the impedance is related to the more intense desiccation and charring of the tissues in a bipolar mode compared with the monopolar configuration caused by a higher current deposition in the small amount of tissue interposed between the electrodes, when no diversion of the heat occurs. We agree with this latest statement, and in our experiences we adapted the power to the global distance to the electrodes in order to keep the impedance low, as is also discussed in [2]. For example, for a 7-cm distance of the electrodes, we employ advantageously less than 40 W with more perfusion of saline for an in vivo application in a similar configuration [3], whereas Lee et al. employ 60 W for only a 3-cm separation between the electrodes with less perfusion of saline. The power algorithm the authors uses is usually employed for a monopolar configuration when more diversion of heat occurs, but in a bipolar setting one may overheat the tissue prematurely. This can account for the premature roll-off in the authors’ open-perfused group and for their suboptimal employ of an open-perfused electrode. Secondly, in the authors’ bipolar configuration the electrodes must be placed parallel, as we previously considered and abandoned [4, 5], because, as the authors state, the insertion of both electrodes encompassing the tumor could be difficult. In the actual configuration we have integrated both electrodes in one needle, making electrode placement more accurate and safe [3]. Lee et al. state that one of the axes of the coagulation area we created An author’s reply to this letter is available at http://dx.doi.org/10.1007/s00330-005-2650-z.

Alternative approaches to ovarian stimulation for IVF

Ovarian stimulation protocols applied world-wide today may take several weeks per stimulated cycle, are complex, expensive and associated with a certain degree of risk. Gonadotrophin preparations are administered to stimulate multiple follicle development usually at daily doses of 150–300 IU (and sometimes higher) for one to three weeks. A premature rise in serum luteinizing hormone (LH) levels, generally believed to be detrimental for in vitro fertilization (IVF) outcome, is prevented by the co-administration of a gonadotrophin-releasing hormone (GnRH) agonist. This is usually initiated in the preceding cycle to allow for pituitary downregulation to occur before the initiation of exogenous follicle-stimulating hormone (FSH). Finally, the resumption of oocyte meiotic maturation is induced by a single bolus injection of human chorionic gonadotrophin (hCG) during the late follicular phase. In addition, the corpus luteum is supported during the luteal phase by repeated administration of hCG or supplemented by exogenous progesterone.

New concepts in superovulation strategies for assisted conception treatments.

Controlled ovarian stimulation for in-vitro fertilization treatment using preparations that contain follicle-stimulating hormone has been routinely performed since the 1980s. The early preparations were urinary human menopausal gonadotrophins, containing follicle-stimulating hormone and luteinizing hormone. In the early 1990s, highly purified follicle-stimulating hormone preparations were introduced because of a desire to provide drugs for subcutaneous administration with a lower risk of allergic reactions. Intensive research resulted in the discovery of recombinant follicle-stimulating hormone, which is more potent that the highly purified follicle-stimulating hormone, resulting in significantly higher clinical pregnancy rates. The two recombinant follicle-stimulating hormone preparations available appear to be equally effective and provide comparable results. Gonadotrophin-releasing hormone antagonists, which have recently been introduced, appear to be effective in preventing a premature rise in luteinizing hormone during ovarian stimulation for in-vitro fertilization, as well as improved response to lower doses of gonadotrophins. It is envisaged that the availability of recombinant gonadotrophins and gonadotrophin-releasing hormone antagonists will ultimately lead to shorter, cheaper and safer treatments, using reduced dosages.

Terpenoid ω-hydroxylase (CYP4C7) messenger RNA levels in the corpora allata: a marker for ovarian control of juvenile hormone synthesis in Diploptera punctata

Ribonuclease protection assays were used to measure changes in allatal transcript levels of the CYP4C7 gene which encodes a cytochrome P450 terpenoid ω-hydroxylase thought to play a role in the metabolism of JH and its precursors. Denervation of the corpora allata does not affect the pattern of expression of the CYP4C7 gene. Transplantation experiments show that CYP4C7 mRNA levels are dependent on a humoral factor characteristic of the reproductive state of the insect. Messenger RNA levels rise substantially in mated or denervated females, or in mated or virgin females treated with hydroprene, when the follicle length is over 1.5 mm. Vitellogenic ovaries however exert a negative influence on CYP4C7 expression, as ovariectomy in mated females causes a premature rise in CYP4C7 mRNA levels. The half-life of the CYP4C7 transcript is approx. 2 h when the corpora allata are incubated in vitro. Under these conditions, coincubation with a post-vitellogenic ovary maintains high CYP4C7 transcript levels in the glands. Excess juvenile hormone or analog applied at the end of vitellogenesis blocks ovulation or causes abortion of embryos deposited in the brood sac. We conclude that expression of the CYP4C7 gene is tightly controlled by the ovary, and it coincides with the ovarian signal to turn off juvenile hormone synthesis. The role of the CYP4C7 enzyme may be to ensure the clearance of allatal juvenile hormone and its precursors at the end of the gonotrophic cycle.

Regulation of follicle development and novel approaches to ovarian stimulation for IVF.

Current ovarian stimulation regimens for IVF are complex and not without risk. Increasing our knowledge of the physiology of follicle development and dominant follicle selection may enable the design of less complex, safer and cheaper ovarian stimulation regimens for IVF. Decremental serum FSH concentrations during the follicular phase of the menstrual cycle are required for single dominant follicle selection. Only the most mature follicle will continue its development due to increased sensitivity for stimulation by FSH. FSH stimulation becomes insufficient for less mature follicles and remaining cohort follicles will therefore go into atresia. The number of days during which FSH is above the threshold for stimulation of follicle development is limited, resulting in a narrow FSH window. More medium sized and large pre-ovulatory follicles and increased oestradiol output can be induced by the administration of small doses of exogenous FSH during the mid- to late follicular phase, preventing the physiological decrease in FSH stimulation. Intervention with decremental serum FSH concentrations in combination with gonadotrophin-releasing hormone (GnRH) antagonists to prevent a premature rise in serum LH may induce ongoing growth of multiple follicles sufficient for IVF. The benefits and risks of these minimal hyperstimulation protocols require further evaluation.

Fetal and Maternal Adaptations to Chronic Hypoxia: Prevention of Premature Labor in Response to Chronic Stress

Both mother and fetus have the remarkable ability to adapt to conditions of chronic hypoxia during the course of gestation. One of these adaptations appears to be mechanisms that prevent premature delivery despite the chronic stress of hypoxia. Our studies in the chronically hypoxic sheep revealed that the fetal adrenal is less responsive to ACTH stimulation. This in turn may prevent a premature rise in cortisol that would normally trigger labor and delivery. In the rat, the myometrium is affected with a decrease in contractile sensitivity to oxytocin following chronic hypoxia. This response is mediated by a significant reduction in myometrial oxytocin receptors. Our preliminary studies have also suggested that this blunting of myometrial responsiveness also occurs in the chronically hypoxic sheep. Taken together, these data indicate an adaptive response by both mother and fetus to prevent preterm delivery in the face of a chronic stress.

Inhibition of the LH surge in cyclic rats by stress is not mediated by opioids.

The effects of intravenous (iv) administration of the opioid antagonists naloxone and naltrexone on the restraint-induced suppression of the pro-estrous LH surge were studied in cyclic female rats. To minimize stress during repeated blood sampling, the rats were provided with a jugular vein cannula. Restraint stress for 6 hrs starting at t = -1 h (the onset of the LH surge being at t = 0 h) caused a suppression of LH levels (including peak height) during the period of the LH surge. Repeated naloxone injections, given 3 h (1 mg), 4 h (0.5 mg) and 5 h (0.5 mg) after the onset of the LH surge, did not affect the restraint-induced inhibition neither did pretreatment with 1 mg naloxone at t = -75 min (i.e. 15 min before application of restraint). Naltrexone (2 mg) administered at t = -15 min induced higher plasma LH levels at t = -6 min. When rats were subsequently subjected to restraint for 5 hrs starting at t = -5 min, the restraint-induced inhibition of surge levels of LH was not affected. The results indicate that withdrawal of opioid activity in cyclic female rats before the presumed onset of the LH surge results in a premature rise of LH levels. This is in accordance with the notion that LH levels prior to the surge are under tonic inhibition of endogenous opioid peptides (EOP). In addition, the data show that opioid receptor antagonism during or before application of restraint does not alter the restraint-induced suppression of the LH surge. It is therefore concluded that EOP do not mediate the inhibitory effect of restraint stress on the LH surge in cyclic rats.

Wing flutter boundary prediction using unsteady Euler aerodynamic method

Modifications to an existing three-dimensional, implicit, upwind Euler/Navier-Stokes code (CFL3D Version 2.1) for the aeroelastic analysis of wings are described. These modifications, which were previously added to CFL3D Version 1.0, include the incorporation of a deforming mesh algorithm and the addition of the structural equations of motion for their simultaneous time-integration with the government flow equations. The paper gives a brief description of these modifications and presents unsteady calculations which check the modifications to the code. Euler flutter results for an isolated 45 degree swept-back wing are compared with experimental data for seven freestream Mach numbers which define the flutter boundary over a range of Mach number from 0.499 to 1.14. These comparisons show good agreement in flutter characteristics for freestream Mach numbers below unity. For freestream Mach numbers above unity, the computed aeroelastic results predict a premature rise in the flutter boundary as compared with the experimental boundary. Steady and unsteady contours of surface Mach number and pressure are included to illustrate the basic flow characteristics of the time-marching flutter calculations and to aid in identifying possible causes for the premature rise in the computational flutter boundary.

Ringing induces the accumulation of vegetative storage proteins in poplar bark

Poplar branches were ringed in late spring to determine whether the interruption of the phloem flow could induce the accumulation of vegetative storage proteins (VSPs) in the bark of adult trees. Eight days after ringing, an increased deposition of starch as well as a premature rise in the soluble-protein level occurred in the bark tissues located 1 cm above the ring. Changes in the SDS-PAGE pattern of bark proteins were characterized by the accumulation of three polypeptides (32, 36 and 38 kDa), which exhibited the same molecular weight as VSPs described in poplar bark during winter, cross-reacted to antibodies raised against a poplar VSP, and bound to several lectins in the same way as poplar bark VSPs. These results indicate that during the vegetative period, ringing induces the accumulation of VSPs in the bark of poplar.

Stimulatory effects of insulin on DNA synthesis in suckling mouse colon.

The influence of insulin on the postnatal development of DNA synthesis and epithelial and muscular cell proliferation has been studied in suckling mice. Daily administration of insulin (12.5 mU/g body weight) during 3 days to 8-day-old mice induced a significant increase of the incorporation of [3H]-thymidine into DNA in the small intestine and the proximal and distal halves of the colon. The esophagus and the glandular portion of the stomach did not respond. A detailed analysis of the proximal and distal colon between 4 and 30 days revealed a decrease of [3H]-thymidine incorporation into total DNA during this period. However, the establishment of the labeling indices in specific compartments such as the epithelium and the muscularis externa revealed that the epithelial cellular proliferation increased around weaning period in both segments while a drastic reduction of cellular proliferation occurred in the muscle layer. A premature rise of the circulating insulin level induced a significant increase of the epithelial labeling indices in both colonic segments but remained without effects on the muscular layer. These results suggest an important role of insulin in the modulation of the ontogenic changes in epithelial cell proliferation of the mouse colon.

The effect of chlamydial infection on the initiation of premature labour: Serial measurements of intrauterine Prostaglandin E 2 in amniotic fluid, allantoic fluid and utero-ovarian vein, using catheterised sheep experimentally infected with an ovine abortion strain of Chlamydia psittaci

The initiation of premature labour by an ovine abortion strain of Chlamydia psittaci was studied in relation to Prostaglandin E 2 (PGE 2), which plays a major role in parturition. The local intrauterine concentration of PGE 2 was monitored after experimental infection with C. psittaci, during late gestation, using a catheterised sheep model. Indwelling catheters were implanted into the amniotic and allantoic cavities of six control sheep, and into six sheep infected with an ovine abortion strain of C. psittaci. The release of PGE 2 into the utero-ovarian vein of these sheep was also monitored. Infection with C. psittaci was associated with a premature rise in PGE 2 in the amniotic fluid between days 122 and 135 of gestation (P<0.01). A premature increase in PGE 2 was defected between days 127 and 136 of gestation (P<0.05) in the allantoic fluid of sheep infected with C. psittaci, but not in the control uninfected sheep. Chlamydial infection significantly decreased the secretion of PGE 2 into the utero-ovarian vein: The mean concentration of PGE 2 in the utero-ovarian vein of infected sheep was 68.8 ± 5.2% of the PGE 2 concentration of control sheep between days 122 to 141 of gestation (P<0.01). The release of PGE 2 into the utero-ovarian vein increased between days 126 to 136 of gestation in infected and control sheep (P<0.01). The results from the catheterised sheep model indicate that C. psittaci infection is associated with a local intrauterine release of PGE 2. The magnitude of this release was similar to the PGE 2 release in control sheep prior to parturition. The PGE 2 released during chlamydial infection may be active in initiating premature labour.

Pineal melatonin rhythms in the lizard Anolis carolinensis: I. Response to light and temperature cycles.

Both light and temperature can influence the pineal's synthesis of the indoleamine melatonin. An investigation of the effects of light and temperature cycles on the pineal melatonin rhythm (PMR) showed the following: (1) Both daily light cycles and daily temperature cycles could entrain the PMR; melatonin levels peaked during the dark phase of a light-dark cycle or the cool phase of a temperature cycle. (2) The PMR could be entrained by a temperature cycle as low as 2 degrees C in amplitude in lizards held in constant light or constant darkness. (3) The length of the photoperiod or thermoperiod affected the phase, amplitude, or duration of the PMR. (4) When presented together, the effects of light and temperature cycles on the PMR depended on the phase relationship between the light and temperature cycles, as well as on the strength of the entraining stimuli, such as the amplitude of the temperature cycle. (5) Exposure to a constant cold temperature (10 degrees C) eliminated the PMR, yet a rhythm could still be expressed under a 24-hr temperature cycle (32 degrees C/10 degrees C), and the rhythm peaked during the 10 degrees C phase of the cycle. (6) A 6-hr dark pulse presented during the day did not elicit a premature rise in melatonin levels. These studies show how environmental stimuli can control the pineal rhythm of melatonin synthesis and secretion. Previous studies have supported a model in which the lizard's pineal acts as a circadian pacemaker within a multioscillator circadian system, and have implicated melatonin as a hormone by which the pineal may communicate with the rest of the system. The lizard pineal, therefore, may act as a photo- and thermoendocrine transducer translating light and temperature information into an internal cue in the form of the PMR. The PMR, in turn, may control the phase and period of circadian clocks located elsewhere, insuring that the right internal events occur at the right time of day.

Environmental control of larval behaviour and its consequences for ecdysteroid content and pupation in Ephestia kuehniella

ABSTRACT. The behaviour of postfeeding larvae of Ephestia kuehniella Zell. (Lepidoptera, Pyralidae) depends on environmental conditions. Long day and high larval density (LG) stimulate larvae to spin the outer envelope of the pupal cocoon which, in turn, accelerates pupal ecdysis. Constant darkness and isolation in a limited space (DS) inhibit spinning of the outer envelope, and cause extension of the wandering stage and a delay in pupation. This behaviour was also observed in larvae confined in the diet.In postfeeding LG larvae, an increase in ecdysteroid content coincides with spinning of the outer envelope. In DS larvae, which fail to spin the outer envelope, the ecdysteroid content remains low during the wandering stage, and rises to a prepupal peak after a considerable delay. Wandering larvae inserted into empty outer envelopes showed a premature rise of ecdysteroids, and it is thus concluded that sensory stimulation from the outer envelope is a cue promoting further development.

The dedifferentiated pattern of enzymes in livers of tumor-bearing rats.

Summary Seven days after the s.c. implantation of a neoplasm, there are significant decreases of ornithine aminotransferase and glucokinase, as well as an increase of hexokinase in livers of adult rats. The concentration of 10 additional enzymes changes in the course of the following week, while the levels of nine other enzymes and the liver size remain normal. Growth of tumors in suckling rats inhibits the appearance of liver enzymes that normally emerge at this stage of differentiation. An implanted tumor inhibits the developmental formation in liver of ornithine aminotransferase, glucokinase, glutamine synthetase, and malate-NADP dehydrogenase, but it does not prevent glucocorticoids from inducing a premature rise of ornithine aminotransferase. The enzymes that increase in host liver upon tumor transplantation are among those that are relatively high in fast-growing hepatomas and in fetal liver. Those that decrease are those that are low or absent in hepatomas and fetal liver. Thus, by gain or partial loss of these enzyme activities, the quantitative pattern of enzymes in host liver diverges from normal adult liver toward that of immature liver and the well-differentiated hepatomas.