LIMIT CYCLES of DISCONTINUOUS PIECEWISE LINEAR DIFFERENTIAL SYSTEMS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The effect of thermal cycles on the mechanical properties of fiber-metal laminates

The effect of thermal-shock cycles on the mechanical properties of fiber-metal laminates (FMLs) has been evaluated. FML plates were composed by two AA2024 Al sheets (1.6 mm thick) and one composite ply formed by two layers of unidirectional glass fiber epoxy prepreg and two layers of epoxy adhesive tape of glass fiber reinforced epoxy adhesive. The set was manufactured by hand layup and typical vacuum bag technique. The curing cycle was in autoclave at 125 +/- 5 degrees C for 90 min and an autoclave pressure of 400 kPa. FML coupons taken from the manufactured plate were submitted to temperature variations between -50 and +80 degrees C, with a fast transition between these temperatures. Tensile and interlaminar shear strength were evaluated on samples after 1000 and 2000 cycles, and compared to nonexposed samples. 2000 Cycles corresponds to typical C Check interval for commercial aircraft maintenance programs. It was observed that the thermal-shock cycles did not result in significant microstructural changes on the FML, particularly on the composite ply. Similarly, no appreciable effect on the mechanical properties of FML was observed by the thermal-shock cycles. (c) 2012 Elsevier Ltd. All rights reserved.

Bifurcation of limit cycles from an n-dimensional linear center inside a class of piecewise linear differential systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Administration of beta(2)-adrenergic agonists during the peri-implantation period does not improve implantation or pregnancy rates in intracytoplasmic sperm injection (ICSI) cycles

Purpose: the objective of the present investigation was to determine implantation and pregnancy rates in patients undergoing ICSI and treated with beta(2)-adrenergic agonists, considering the uterine-relaxing action of these agents.Methods: A total of 225 women undergoing ICSI at the Center for Human Reproduction, Sinha Junqueira Maternity Foundation, entered the study. Patient participation in each group was random, by drawing lots, using a randomization table previously elaborated for the study (2:2:1). The group I (90 women) received 10 mg of terbutaline daily for 15 days starting on the day of oocyte retrieval; group II (90 women) received 20 mg of ritodrine daily during the same period of time as group I; group III (45 patients) received no treatment and was used as control. The evaluation was interrupted in 3 patients of group I and in 30 patients of group II because of a high incidence of side effects.Results: Pregnancy, implantation, and miscarriage rates were not significantly different (p>0.05) between the three groups: 29.88%, 13.25%, and 26.9% for group I; 33.33%, 17.5%, and 10.0% for group II; 28.88%, 15.07%, and 15.38% for group III, respectively.Conclusions: the results of this study do not support the routine use of beta(2)-adrenergic agonists during the peri-implantation period in assisted reproductive technology cycles.

GnRH agonist versus GnRH antagonist in IVF/ICSI cycles with recombinant LH supplementation: DNA fragmentation and apoptosis in granulosa cells

Objective: To compare the level of apoptosis and DNA fragmentation in the human granulosa cell (GC) layer exposed to an agonist or antagonist of GnRH in intracytoplasmic sperm injection (ICSI) cycles supplemented with recombinant LH (rLH).Study design: Patients without ovulatory dysfunction, aged <= 37 years and in their first ICSI cycle were prospectively randomised to receive either a long GnRH agonist protocol or a multi-dose antagonist protocol. In both groups, recombinant FSH supplemented with rLH was used for ovarian stimulation, and the GCs were collected during oocyte denudation. The GCs were then analysed for DNA fragmentation by TUNEL assay and for apoptosis using the annexin-V assay. The outcomes were given as the percentage of GCs with DNA fragmentation and apoptosis out of the total number of GCs analysed. Comparison of the agonist versus the antagonist group was performed using the Mann-Whitney test.Results: DNA fragmentation: 32 patients were included in either the GnRH agonist group (n = 16) or the antagonist group (n = 16). The percentage of GCs with positive DNA fragmentation did not differ significantly (P = 0.76) between the agonist group (15.5 +/- 9.4%) and the antagonist group (18.8 +/- 13.3%). Apoptosis: 28 patients were included in either the GnRH agonist group (n = 14) or the antagonist group (n = 14). The percentage of GCs positive for apoptosis did not differ significantly (P = 0.78) between the agonist group (34.6 +/- 14.7%) and the antagonist group (36.5 +/- 22%).Conclusions: The results suggest that therapy with either an agonist or antagonist of GnRH is associated with comparable levels of DNA fragmentation and apoptosis in granulosa cells in ICSI cycles supplemented with rLH. (C) 2012 Elsevier B.V. All rights reserved.

Artificial oocyte activation using calcium ionophore in ICSI cycles with spermatozoa from different sources

The present study evaluated the effect of artificial oocyte activation (AOA) with calcium ionophore A23187 oil intracytoplasmic sperm injection (ICSI) cycles using spermatozoa from different sources. The 314 cycles evaluated were divided into three groups according to sperm origin, the ejaculated group (n = 92), the epididymal group (n = 82). and the testicular roup (n = 140). Each group was further split into experimental subgroups, depending oil whether or no AOA was performed. In additions the cycles of women younger than 36 years were evaluated separately. For each experimental group, ICSI outcomes were compared between subgroups. No significant difference was observed between subgroups for all sperm origin groups. When evaluating only the cycles of women younger than 36 years of age, AOA increased the percentage of high-quality embryos (74.5 versus 53.0%. P = 0.011) and the implantation rate (19.3 versus 10.5%, P = 0.0025) when it was used with ejaculated spermatozoa, and the percentage of high-quality embryos (64.4 versus 50.3%, P = 0.006) when epididymal spermatozoa were used. These results may suggest that both sperm maturity and oocyte quality play a role in oocyte activation. However. this study is to be continued to confirm these findings.

Artificial oocyte activation with calcium ionophore A23187 in intracytoplasmic sperm injection cycles using surgically retrieved spermatozoa

Objective: To evaluate the effect of artificial oocyte activation (AOA) on intracytoplasmic sperm injection (ICSI) cycles using surgically retrieved sperm.Design: Laboratory study.Setting: Fertility/assisted fertilization center.Patient(s): Couples undergoing surgical sperm retrieval for ICSI (n = 204).Intervention(s): Application of calcium ionophore A23187 for AOA.Main Outcome Measure(s): Cycles were divided into experimental groups according to the origin of the sperm used for injection and the type of azoospermia: [1] testicular sperm aspiration in nonobstructive-azoospermic patients (TESA-NOA group, n = 58), [2] TESA in obstructive-azoospermic patients (TESA-OA group, n = 48), [3] and percutaneous epididymal sperm aspiration in obstructive-azoospermic patients (PESA-OA, n = 98). For each experimental group, cycles where AOA was applied (subgroup: activation) were compared with cycles in which AOA was not applied (Subgroup: control). The fertilization, high-quality embryo, implantation, and pregnancy rates were compared among the subgroups.Result(s): For patients undergoing TESA, AOA did not improve ICSI outcomes for either type of azoospermia. However, for cases in which the injected sperm were retrieved from the epididymis, a statistically significantly increased rate of high-quality embryos was observed with AOA.Conclusion(s): Artificial oocyte activation may improve ICSI outcomes in azoospermic patients when epididymal, but not testicular spermatozoa, are injected. (Fertil Steril (R) 2009;92:131-6. (C)2009 by American Society for Reproductive Medicine.)

Sperm Organelle Morphologic Abnormalities: Contributing Factors and Effects on Intracytoplasmic Sperm Injection Cycles Outcomes

OBJECTIVE To (1) analyze possible relationships between motile sperm organelle morphology examination (MSOME) and sperm chromatin status, aneuploidy incidence, and patient's age; (2) determine the effects of sperm morphologic abnormalities on intracytoplasmic sperm injection (ICSI) outcomes; and (3) identify the benefits of intracytoplasmic morphologically selected sperm injection (IMSI) in patients with high DNA fragmentation rate.METHODS The study was performed in 50 patients undergoing ICSI cycles. The MSOME, sperm DNA fragmentation, and sperm aneuploidy incidence were performed in 200 sperm cells of each patient. Regression models were used to assess the relationships among sperm morphology and sperm aneuploidy, sperm DNA fragmentation, patient's age, and ICSI outcomes. In cycles with patients showing a high incidence of DNA fragmentation, oocytes were split into 2 groups according to the sperm selection method: Standard-ICSI (n = 82) and IMSI (n = 79). Fertilization and high-quality embryo rates were compared between the groups.RESULTS A close relationship between sperm DNA fragmentation and the presence of vacuoles in the MSOME was noted. The patient's age was correlated to the presence of vacuoles. No correlation between sperm aneuploidy and IMSI was observed. Vacuolated cells were negatively correlated with fertilization, pregnancy, and implantation. In patients with a high incidence of sperm DNA fragmentation, fertilization and high-quality embryo rates were similar when comparing IMSI and Standard-ICSI.CONCLUSIONS Our data demonstrate a correlation between paternal age and the incidence of nuclear vacuoles, as well as an effect of large and small vacuoles on late embryo development. UROLOGY 78: 786-791, 2011. (C) 2011 Elsevier B.V.

Single-embryo transfer reduces clinical pregnancy rates and live births in fresh IVF and Intracytoplasmic Sperm Injection (ICSI) cycles: a meta-analysis

Background: It has become an accepted procedure to transfer more than one embryo to the patient to achieve acceptable ongoing pregnancy rates. However, transfers of more than a single embryo increase the probability of establishing a multiple gestation. Single-embryo transfer can minimize twin pregnancies but may also lower live birth rates. This meta-analysis aimed to compare current data on single-embryo versus double-embryo transfer in fresh IVF/ICSI cycles with respect to implantation, ongoing pregnancy and live birth rates.Methods: Search strategies included on-line surveys of databases from 1995 to 2008. Data management and analysis were conducted using the Stats Direct statistical software. The fixed-effect model was used for odds ratio (OR). Fixed-effect effectiveness was evaluated by the Mantel Haenszel method. Seven trials fulfilled the inclusion criteria.Results: When pooling results under the fixed-effect model, the implantation rate was not significantly different between double-embryo transfer (34.5%) and single-embryo transfer group (34.7%) (P = 0.96; OR = 0.99, 95% CI 0.78, 1.25). on the other hand, double-embryo transfer produced a statistically significantly higher ongoing clinical pregnancy rate (44.5%) than single-embryo transfer (28.3%) (P < 0.0001; OR: 2.06, 95% CI = 1.64,2.60). At the same time, pooling results presented a significantly higher live birth rate when double-embryo transfer (42.5%) (P < 0.001; OR: 1.87, 95% CI = 1.44,2.42) was compared with single-embryo transfer (28.4%).Conclusion: Meta-analysis with 95% confidence showed that, despite similar implantation rates, fresh double-embryo transfer had a 1.64 to 2.60 times greater ongoing pregnancy rate and 1.44 to 2.42 times greater live birth rate than single-embryo transfer in a population suitable for ART treatment.

Administration of single-dose GnRH agonist in the luteal phase in ICSI cycles: a meta-analysis

Background: The effects of gonadotrophin-releasing hormone agonist (GnRH-a) administered in the luteal phase remains controversial. This meta-analysis aimed to evaluate the effect of the administration of a single-dose of GnRH-a in the luteal phase on ICSI clinical outcomes.Methods: The research strategy included the online search of databases. Only randomized studies were included. The outcomes analyzed were implantation rate, clinical pregnancy rate (CPR) per transfer and ongoing pregnancy rate. The fixed effects model was used for odds ratio. In all trials, a single dose of GnRH-a was administered at day 5/6 after ICSI procedures.Results: All cycles presented statistically significantly higher rates of implantation (P < 0.0001), CPR per transfer (P = 0.006) and ongoing pregnancy (P = 0.02) in the group that received luteal-phase GnRH-a administration than in the control group (without luteal-phase-GnRH-a administration). When meta-analysis was carried out only in trials that had used long GnRH-a ovarian stimulation protocol, CPR per transfer (P = 0.06) and ongoing pregnancy (P = 0.23) rates were not significantly different between the groups, but implantation rate was significant higher (P = 0.02) in the group that received luteal-phase-GnRH-a administration. on the other hand, the results from trials that had used GnRH antagonist multi-dose ovarian stimulation protocol showed statistically significantly higher implantation (P = 0.0002), CPR per transfer (P = 0.04) and ongoing pregnancy rate (P = 0.04) in the luteal-phaseGnRH- a administration group. The majority of the results presented heterogeneity.Conclusions: These findings demonstrate that the luteal-phase single-dose GnRH-a administration can increase implantation rate in all cycles and CPR per transfer and ongoing pregnancy rate in cycles with GnRH antagonist ovarian stimulation protocol. Nevertheless, by considering the heterogeneity between the trials, it seems premature to recommend the use of GnRH-a in the luteal phase. Additional randomized controlled trials are necessary before evidence-based recommendations can be provided.

Evaluation of zona pellucida birefringence intensity during in vitro maturation of oocytes from stimulated cycles

Background: This study evaluated whether there is a relationship between the zona pellucida birefringence (ZP-BF) intensity and the nuclear (NM) and cytoplasmic (CM) in vitro maturation of human oocytes from stimulated cycles.Results: The ZP-BF was evaluated under an inverted microscope with a polarizing optical system and was scored as high/positive (when the ZP image presented a uniform and intense birefringence) or low/negative (when the image presented moderate and heterogeneous birefringence). CM was analyzed by evaluating the distribution of cortical granules (CGs) throughout the ooplasm by immunofluorescence staining. CM was classified as: complete, when CG was localized in the periphery; incomplete, when oocytes presented a cluster of CGs in the center; or in transition, when oocytes had both in clusters throughout cytoplasm and distributed in a layer in the cytoplasm periphery Nuclear maturation: From a total of 83 germinal vesicle (GV) stage oocytes, 58 of oocytes (69.9%) reached NM at the metaphase II stage. From these 58 oocytes matured in vitro, the high/positively scoring ZP-BF was presented in 82.7% of oocytes at the GV stage, in 75.8% of oocytes when at the metaphase I, and in 82.7% when oocytes reached MII. No relationship was observed between NM and ZP-BF positive/negative scores (P = 0.55). These variables had a low Pearson's correlation coefficient (r = 0.081). Cytoplasmic maturation: A total of 85 in vitro-matured MII oocytes were fixed for CM evaluation. Forty-nine oocytes of them (57.6%) showed the complete CM, 30 (61.2%) presented a high/positively scoring ZP-BF and 19 (38.8%) had a low/negatively scoring ZP-BF. From 36 oocytes (42.3%) with incomplete CM, 18 (50%) presented a high/positively scoring ZPBF and 18 (50%) had a low/negatively scoring ZP-BF. No relationship was observed between CM and ZP-BF positive/negative scores (P = 0.42). These variables had a low Pearson's correlation coefficient (r = 0.11).Conclusions: The current study demonstrated an absence of relationship between ZP-BF high/positive or low/negative score and nuclear and cytoplasmic in vitro maturation of oocytes from stimulation cycles.

GnRH agonist versus GnRH antagonist in assisted reproduction cycles: oocyte morphology

Background: The selection of developmentally competent human gametes may increase the efficiency of assisted reproduction. Spermatozoa and oocytes are usually assessed according to morphological criteria. Oocyte morphology can be affected by the age, genetic characteristics, and factors related to controlled ovarian stimulation. However, there is a lack of evidence in the literature concerning the effect of gonadotropin-releasing hormone (GnRH) analogues, either agonists or antagonists, on oocyte morphology. The aim of this randomized study was to investigate whether the prevalence of oocyte dysmorphism is influenced by the type of pituitary suppression used in ovarian stimulation.Methods: A total of 64 patients in the first intracytoplasmic sperm injection (ICSI) cycle were prospectively randomized to receive treatment with either a GnRH agonist with a long-term protocol (n: 32) or a GnRH antagonist with a multi-dose protocol (n: 32). Before being subjected to ICSI, the oocytes at metaphase II from both groups were morphologically analyzed under an inverted light microscope at 400x magnification. The oocytes were classified as follows: normal or with cytoplasmic dysmorphism, extracytoplasmic dysmorphism, or both. The number of dysmorphic oocytes per total number of oocytes was analyzed.Results: Out of a total of 681 oocytes, 189 (27.8 %) were morphologically normal, 220 (32.3 %) showed cytoplasmic dysmorphism, 124 (18.2%) showed extracytoplasmic alterations, and 148 (21.7%) exhibited both types of dysmorphism. No significant difference in oocyte dysmorphism was observed between the agonist- and antagonist- treated groups (P > 0.05). Analysis for each dysmorphism revealed that the most common conditions were alterations in polar body shape (31.3%) and the presence of diffuse cytoplasmic granulations (22.8%), refractile bodies (18.5%) and central cytoplasmic granulations (13.6%). There was no significant difference among individual oocyte dysmorphisms in the agonist- and antagonist-treated groups (P > 0.05).Conclusions: Our randomized data indicate that in terms of the quality of oocyte morphology, there is no difference between the antagonist multi-dose protocol and the long-term agonist protocol. If a GnRH analogue used for pituitary suppression in IVF cycles influences the prevalence of oocyte dysmorphisms, there does not appear to be a difference between the use of an agonist as opposed to an antagonist.

Flexural strength of acrylic resins polymerized by different cycles

Despite the large number of studies addressing the effect of microwave polymerization on the properties of acrylic resin, this method has received limited clinical acceptance. This study evaluated the influence of microwave polymerization on the flexural strength of a denture base resin. A conventional heat-polymerized (Classico), a microwave-polymerized (Onda-Cryl) and a autopolymerizing acrylic (Jet) resins were used. Five groups were established, according to polymerization cycles: A, B and C (Onda-Cryl, short cycle - 500W/3 min, long - 90W/13 min + 500W/90 see, and manufacturing microwave cycle - 320W/3 min + OW/3 min + 720W/3 min); T(Classico, water bath cycle - 74 degrees C/9h) and Q (Jet, press chamber cycle - 50 degrees C/15 min at 2 bar). Ten specimens (65 x 10 x 3.3 mm) were prepared for each cycle. The flexural strength of the five groups was measured using a three-point bending test at a cross-head speed of 5 mm/min. Flexural strength values were analyzed by one-way ANOVA and the Tukey's test was performed to identify the groups that were significantly different at 5% level. The microwave-polymerized groups showed the highest means (p<0.05) for flexural strength (MPa) (A = 106.97 +/- 5.31; B = 107.57 +/- 3.99; C = 109.63 +/- 5.19), and there were no significant differences among them. The heat-polymerized group (T) showed the lowest flexural strength means (84.40 +/- 1.68), and differ significantly from all groups. The specimens of a microwavable denture base resin could be polymerized by different microwave cycles without risk of decreasing the flexural strength.