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Biomedical subjects

A Veiga

Publications and source records attributed to A Veiga.

At least 19 recordsLinked to original sources

Prevention of multiple pregnancy following IVF in Spain.

Since the development of assisted reproduction techniques most countries have witnessed increased rates of multiple pregnancy. Despite the guidelines proposed by various scientific societies these rates continue to be abnormally high. In Spain, as in other Mediterranean countries, a greater number of embryos are transferred than in northern and central European countries and the incidence of multiple pregnancies is greater in comparison. Effective strategies must be established to prevent multiple pregnancy without reducing overall pregnancy rates. In the authors' institute, taking into account the authors' experience, the relevant literature, and despite the limitation of retrospective studies, it is recommended that a maximum of two embryos are transferred in young women with good quality embryos at the time of transfer. The transfer of three embryos is only recommended in women >or=38 years who have one or no good quality embryos available at the time of transfer. The responsibility for preventing multiple pregnancy lies with health professionals, who must be aware of the risks involved in twin and triplet pregnancy. Couples must be provided with objective information before starting an IVF cycle. Professional societies should highlight the problem and make suitable recommendations.

Adult↗

A European multicentre prospective randomized study to assess the use of assisted hatching with a diode laser and the benefit of an immunosuppressive/antibiotic treatment in different patient populations.

BACKGROUND: Assisted hatching (AH) techniques, designed for facilitating the embryo escape out of the zona pellucida (ZP) have been used in IVF centres since 1992. The initial indications for AH were patient's age, ZP thickness, high basal FSH and repeated IVF failures. Several retrospective and prospective studies assessing AH in these indications have given disparate results. Our aims were to evaluate the benefits of AH and immunosuppressive/antibiotic treatment (IA) in patients with either a poor prognosis of success, previous implantation failures or transfers of cryopreserved embryos. METHODS: Four IVF centres allocated 426 patients, randomized for AH and IA, into four groups of AH indications between 1997 and 1999. AH was performed with a diode laser. ZP thickness, opening size and embryo score were recorded. Outcome measures were implantation and delivery rates. RESULTS: Patients coming for a first or third transfer of cryopreserved embryos and poor prognosis patients admitted for a first trial did not benefit from AH. Even patients with repeated implantation failures of fresh embryos did not gain significantly from AH. CONCLUSIONS: Among AH indications, absence of implantation after several transfers of good quality embryos remains the strongest patient selection criterion. Prescription of an immunosuppressive/antibiotic treatment is essential.

Adult↗

Preimplantation genetic diagnosis in patients with male meiotic abnormalities.

Indications and candidates for preimplantation genetic diagnosis (PGD) have increased in recent years. This study evaluates whether IVF-intracytoplasmic sperm injection (ICSI) results could be improved by selecting embryos through PGD-AS (aneuploidy screening) in couples in whom the male partner presents meiotic abnormalities. Two hundred and fifty-six embryos were biopsied and 183 were suitable for analysis (73.2%). Ninety-two embryos showed normal chromosomal analysis (50.3% of the analysed embryos and 57.5% of the diagnosed embryos). Pregnancy, abortion and implantation rates were compared with 66 IVF-ICSI cycles performed in 44 patients with meiotic abnormalities without PGD (control group). No statistically significant differences in the pregnancy rate (52 versus 43.9%), implantation rate (32.1 versus 23.5%) and miscarriage rate (15.4 versus 10.3%) were observed between the groups. Although the embryos obtained from men with meiotic abnormalities showed a high frequency of chromosome abnormalities, no improvements in pregnancy and implantation rates were obtained after PGD-AS in the series analysed.

Abortion, Spontaneous↗

Stress situations induce cyanide-resistant respiration in spoilage yeasts.

AIMS: To investigate the conditions that promote the expression of cyanide-resistant respiration (CRR) in the spoilage yeasts Pichia membranifaciens and Debaryomyces hansenii. METHODS AND RESULTS: CRR was detected by sensitivity of oxygen consumption to salicylhydroxamic acid. It was absent in both yeasts in the early exponential phase, but was triggered by several stress situations. Starvation under aerobic conditions, decreasing pH or incubation of the culture in a narrow temperature range below the maximum temperature for growth promoted the emergence of CRR in both yeasts. In D. hansenii, CRR was also induced by 1.5-2 mol l(-1) NaCl. Although the presence of H2O2 and menadione induced CRR, radical scavengers had no effect on the emergence of CRR. Also, the level of reactive oxygen species did not vary with the CRR activity. CONCLUSIONS: Under aerobic conditions, a respiratory pathway alternative to the cytochrome chain is triggered by stress conditions in P. membranifaciens and D. hansenii. SIGNIFICANCE AND IMPACT OF THE STUDY: The relationship between stress situations and CRR must be taken into account in studies on the performance of spoilage yeasts in the food processing environments where several forms of stress are common.

Antimycin A↗

Preimplantation genetic diagnosis: patients' experiences and attitudes.

BACKGROUND: This study aims to report the experiences and attitudes of patients who have undergone preimplantation genetic diagnosis (PGD). The extent to which this technique is acceptable to the individuals for whom it is intended is relatively unexplored, and remains a crucial issue that may ultimately determine the value of PGD as an alternative to prenatal diagnosis in high-risk couples. METHODS: An information sheet and questionnaire was distributed to 67 couples who had been treated at the Hammersmith Hospital, London and the Dexeus Institute, Barcelona. RESULTS: One-third of patients had an affected child, over half had previous experience of conventional prenatal diagnosis and over one-third had had terminations of pregnancy because of a genetic risk. Patients perceive the main advantage of PGD to be that only unaffected embryos are transferred to the uterus and thus therapeutic termination of pregnancy can be avoided; the main disadvantage is the low success rate. A total of 41% of patients found the treatment cycle extremely stressful, and, of the 20 patients who had experienced both prenatal diagnosis and PGD, 40% of patients found PGD less stressful, although 35% experienced more stress. Of those couples who contemplated a further pregnancy 76% would choose PGD, 16% would opt for prenatal diagnosis, and 8% no tests at all. CONCLUSIONS: The experience of prenatal diagnosis and termination of pregnancy can be an unwelcome memory and this leads to a demand for an alternative approach. Our data suggest that PGD is acceptable to patients and is a valuable alternative to prenatal diagnosis.

Abortion, Induced↗

Preimplantation genetic diagnosis (PGD), a collaborative activity of clinical genetic departments and IVF centres.

Preimplantation genetic diagnosis (PGD) requires the combined efforts of geneticists and workers in the field of reproductive medicine. This was studied on the basis of a questionnaire, sent to 35 members of the PGD Consortium of the European Society of Human Reproduction and Embryology (ESHRE). A reply was obtained from 20 centres. They represent the majority of activities in the field of PGD in the world. It is obvious that many of the activities (in vitro fertilisation, embryo culture and biopsy) take place in IVF units while others (counselling and diagnosis) are the responsibility of genetic diagnostic centres. The distances between both units vary considerably. In all but one centre sex determination is offered. Aneuploidy screening is offered in 13 out of 20 centres. PGD of translocations and other structural chromosome abnormalities is offered in all but one centre. The number of monogenic diseases offered varies considerably. In comparison to prenatal diagnosis PGD is more expensive. The majority of these costs are due to the IVF or ICSI procedure. The charges for PGD vary between about 600 euro and 4000 euro. In 16 out of 20 centres the parents to be must sign an informed consent form.

Aneuploidy↗

In vitro fertilization and blastocyst transfer for carriers of chromosomal translocation.

Blastocyst transfers (BT), may benefit chromosomal translocation-carrier couples who suffer multiple miscarriages or are unable to achieve pregnancy following classical ART techniques. In vitro culture applies an additional selection pressure, so that those embryos which achieve blastocyst formation have higher survival probability as healthy balanced translocation carriers or unaffected embryos. Sixteen IVF cycles were performed in 11 patients. When blastocyst are obtained, implantation rate per blastocyst and delivery rates (7/11 cycles, eight healthy babies born) are high. However, the overall blastocyst formation rate is low (20%), and as a consequence in nearly half of the cycles, no blastocyst can be obtained. We propose that this strategy may be used initially as an alternative or a complement to preimplantation genetic diagnosis, and to apply the forces of natural selection in vitro.

Adult↗

A physiological replacement for polyvinylpyrrolidone (PVP) in assisted reproductive technology.

The technique of intracytoplasmic sperm injection (ICSI) requires mechanical immobilization of the sperm that are to be injected; damage thus caused to the sperm membrane is considered to be necessary to activate the sperm for fertilization. Mechanical immobilization and the injection procedure are facilitated by introducing the sperm into a viscous medium that will hinder motility: a solution of polyvinylpyrrolidone (PVP) has been used successfully for this purpose. PVP is an artificial polymer, which has been regarded as chemically inert, although adverse effects have been reported as a result of its use both in vivo and in vitro. Therefore, the use of hyaluronate, the natural component of the extracellular matrix of the cumulus-oocyte complex, was investigated as a replacement for PVP during ICSI. A solution of hyaluronate was found to be as effective as PVP in facilitating the injection procedure, its effect on sperm motility was readily reversible, and its use did not affect the outcome of the treatment cycles in terms of fertilization, pregnancy and live birth rates. Every attempt should be made to eliminate artificial factors in assisted reproductive procedures. Hyaluronate, a natural and readily degradable glycosaminoglycan can be used as a substitute for the artificial PVP polymer without jeopardising the outcome of the treatment cycle.

Adult↗

Cyanide-resistant respiration is frequent, but confined to yeasts incapable of aerobic fermentation.

In Pichia membranifaciens, cyanide-resistant respiration (CRR) sensitive to salicylhydroxamic acid emerged after forced aeration of starved cells for 4 h. Surveying a large number of species by this simple methodology, we found that CRR is very frequent among yeasts. Remarkably, considering our results together with previous data in the literature, CRR was present in 24 out of 28 non-fermentative or Crabtree-negative yeasts and absent in 10 out of 12 Crabtree-positive yeasts. We submit that, as alternatives to cytochromic respiration, yeasts developed two strategies: either aerobic fermentation in Crabtree-positive yeasts or CRR in non-fermentative or Crabtree-negative yeasts.

Aerobiosis↗

Stimulation protocols for poor responders and aged women.

There is a general consensus on the clinical fact that the more embryos replaced the higher pregnancy rates are achieved. For this reason those IVF cycles with a low response and a reduced number of oocytes and embryos will have very few chances of producing a pregnancy. It is very important to diagnose, by means of the anamnesis and hormonal tests which patients are most likely to present a poor response to conventional ovarian stimulation protocols. It is mandatory to know the patient's plasmatic levels of FSH and estradiol together with personal data such as the age and the previous history of the patient. Only young poor responders with a normal basal hormonal profile will have some chances that by applying new protocols and combining new drugs, improve their response and have higher pregnancy rates. For the old poor responders who have already failed to alternative protocols including natural cycles, oocyte donation is the last and best hope.

Adult↗

Effects of weak acid preservatives on the growth and thermal death of the yeast Pichia membranifaciens in a commercial apple juice.

Pichia membranifaciens exhibited a dissociative temperature profile (the temperature range of thermal death was distinct from the temperature range of growth) when incubation took place either in a commercial apple juice (AJ) or in a synthetic mineral medium with glucose and vitamins (MGV). In AJ the maximum temperature for growth (Tmax) was 38.6 degrees C, which decreased to 36 degrees C in the presence of either 1 mM sorbic or 1 mM benzoic acid. The minimum temperatures of thermal death (Tmind) were, respectively, 40 and 38 degrees C with either of the acids. The yeast could grow with up to 2 mM sorbic or 3 mM benzoic acid, at 25 degrees C, which is close to the optimum temperature for growth (Top). At temperatures slightly above Tmind, sorbic acid was an actual enhancer of death rather than benzoic, the latter conferring some protection. However, these effects were reversed at higher temperatures (above 43 degrees C), at which benzoic acid was the most operative, in contrast to sorbic which was highly protective of the yeast against thermal death. The addition of acetaldehyde to sulphur-dioxide-containing juice reduced the lag phase and increased the overall specific growth rates. Sporulated or stationary vegetative cultures were more heat-resistant than exponential cultures, particularly at temperatures above 45 degrees C.

Benzoic Acid↗

Assisted reproductive technology (ART) in humans: facts and uncertainties.

Since the first in vitro fertilization (IVF) in human, the number of patients using Assisted Reproductive Technologies (ART) has increased tremendously. ART technologies have increased in number and their spectrum has also widened. The first IVF babies are now more than 20 years old. All the retrospective analyses have demonstrated that the obstetrical and pediatrical impact has not really affected single births. The main problems observed occur with multiple pregnancies, including high costs for the couples and for society. The decrease in the number of embryos transferred has improved the situation and moreover does not impair the final results. IntraCytoplasmic Sperm Injection (ICSI) is a more debatable and questionable technique with a real negative genetic impact. The main problem is chromosome abnormalities more specifically related to the sex chromosomes. The question of a systematic genetic work-up on the patients entering ICSI programs is discussed. No negative impact of cryopreservation has been demonstrated even though some controversy arises from time to time. Pre-implantation Genetic Diagnosis (PGD) is now a interesting tool for patients carrying genetic defects. Blastocyst biopsy now has a future role in reproductive medicine. Gender selection through sperm sorting is also now a reality. As with the other developing bio-technologies related to reproduction, there are ethical questions. The decisions concerning these technologies do not belong solely to scientists but are rather a matter for society to decide.

Chromosome Aberrations↗

Increased incidence of meiotic anomalies in oligoasthenozoospermic males preselected for intracytoplasmic sperm injection.

PURPOSE: Based on data from the literature, to detect the possible presence of an increased frequency of meiotic anomalies in oligoasthenozoospermic (OA) patients preselected for intracytoplasmic sperm injection. METHODS: Meiotic studies in as many successive patients with a clinical indication for a diagnostic testicular biopsy as needed to complete at least 100 cases with a severe OA (motile sperm concentration < or = 1.5 x 10(6)/ml). RESULTS: An increased incidence of meiotic anomalies was found in 102 patients with a severe OA (17.6%) compared to the mean for 105 patients with other etiologies in the series (5.7%) or the mean for patients reviewed in the literature (6.5%). CONCLUSIONS: Patients with a severe OA have a higher incidence of synaptic anomalies. This may result in the malsegregation of chromosomes at meiosis I, producing abnormal sperm, and could explain the high incidence of sterility and some cases of abortion (in two thirds of the couples with abortions the husband had meiotic anomalies) in this group.

Biopsy↗

Embryo transfer under ultrasound guidance improves pregnancy rates after in-vitro fertilization.

Between October 1998 and January 1999, we examined the influence of ultrasound guidance in embryo transfer on pregnancy rate in 362 patients from our in-vitro fertilization (IVF)-embryo transfer programme. These patients were prospectively randomized into two groups: 182 had ultrasound-guided embryo replacement, and 180 had clinical touch embryo transfer. There were no statistically significant differences between the two groups with respect to age, cause of infertility and in the characteristics of the IVF cycle. The pregnancy rate was significantly higher among the ultrasound-guided embryo transfer group (50%) compared with the clinical touch group (33.7%) (P < 0.002). Furthermore, there was also a significant increase in the implantation rate: 25.3% in the ultrasound group compared with 18.1% in the clinical touch group (P < 0.05). In conclusion, ultrasound assistance in embryo transfer significantly improved pregnancy and implantation rates in IVF.

Adult↗

Birth weight and sex ratio after transfer at the blastocyst stage in humans.

OBJECTIVE: To analyze the birth weights and sex ratio of infants born after blastocyst transfer. DESIGN: Retrospective analysis. SETTING: Three infertility clinics. PATIENT(S): Patients admitted for IVF with blastocyst transfer. INTERVENTION: None. MAIN OUTCOME MEASURE(S): Birth weights and sex ratio of infants born after blastocyst transfer. RESULT(S): Statistically significantly more male infants were born after transfer of fresh blastocysts, either cocultured or cultured in sequential media. No specific differences in birth weight were observed between infants born after blastocyst transfer and those born after spontaneous conception. CONCLUSION(S): More male infants than female infants were born after blastocyst transfer when transfers were performed as soon as the blastocyst stage was reached and male embryos had a faster cleavage rate.

Birth Weight↗

Screening for abnormalities of chromosomes X, Y, and 18 and for diploidy in spermatozoa from infertile men participating in an in vitro fertilization-intracytoplasmic sperm injection program.

OBJECTIVE: To evaluate the frequency of disomy (for chromosomes X, Y, and 18) and of diploidy in the spermatozoa of infertile men undergoing intracytoplasmic sperm injection (ICSI). DESIGN: Prospective analysis of sperm nuclei by fluorescence in situ hybridization (FISH). SETTING: University-affiliated IVF-ICSI program. PATIENT(S): Semen samples from 19 patients participating in an IVF-ICSI program. INTERVENTION(S): Semen samples were analyzed and prepared for FISH. MAIN OUTCOME MEASURE(S): Semen parameters were evaluated. The frequency of disomy for chromosomes X, Y, and 18 and the frequency of diploidy were analyzed by FISH. RESULT(S): A total of 9,373 spermatozoa from 19 infertile patients were analyzed and compared with spermatozoa from a control group of 5 healthy men. No differences in the frequency of disomy 18 were found, but statistically significant differences in the incidence of sex chromosome disomy and of diploidy were observed. CONCLUSION(S): The study of sperm nuclei by FISH is useful to improve genetic counseling in infertile patients selected for ICSI.

Adult↗