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Carmen Mendoza

Publications and source records attributed to Carmen Mendoza.

At least 19 recordsLinked to original sources
PubMed2007

Treatment of severe male infertility by micromanipulation-assisted fertilization: an update.

In the past 5-10 years the evolution of micromanipulation-assisted fertilization for the treatment of severe male infertility was marked by the introduction of new technical support, refinement of diagnostic methods for the evaluation of sperm developmental potential, and development of new treatment regimens for the newly discovered abnormalities. The new technical support involves the use of non-contact laser technology to assist micromanipulation for fertilization, the evolution of polarized microscopy-based optical systems to non-invasively detect the position of the meiotic spindle in living human oocytes, and the development of high-magnification optical systems for a better morphological selection of spermatozoa to be used for fertilization. Diagnostic approaches were enriched by commercial availability of kits for the analysis of sperm DNA integrity, leading to the definition of sperm nuclear DNA damage as a distinct cause of male infertility, and by the development of tests, based on heterologous ICSI, for detection of sperm failure to activate oocytes. Several treatment options for these conditions have been proposed and are currently being tested in larger-scale trials. Some technical improvement was also achieved in the field of in vitro maturation of germ cells from men with in vivo maturation arrest, but only a modest clinical improvement resulted from their application. As to the risk for the offspring, recent data are rather reassuring. Except for the risk of transmission of genetically based infertility, no straightforward evidence for a health risk derived from these techniques has been provided. Nevertheless, caution is necessary, particularly concerning the eventual increase in genomic-imprinting abnormalities.

DNA Damage↗
PubMed2006

Beneficial effect of luteal-phase GnRH agonist administration on embryo implantation after ICSI in both GnRH agonist- and antagonist-treated ovarian stimulation cycles.

BACKGROUND: GnRH agonist was recently suggested as a novel luteal-phase support that may act at different levels, including the pituitary gonadotrophs, the endometrium and the embryo itself. This prospective randomized study evaluates the effect of GnRH agonist administered in the luteal phase on ICSI outcomes in both GnRH agonist- and GnRH antagonist-treated ovarian stimulation protocols. METHODS: Six hundred women about to undergo ovarian stimulation for ICSI (300 using a long GnRH agonist protocol and 300 using a GnRH antagonist protocol) were enrolled in this study. Patients treated with each of these two protocols were randomly assigned to receive a single injection of GnRH agonist or placebo 6 days after ICSI. Implantation and live birth rates were the primary outcomes. RESULTS: Administration of 0.1 mg of GnRH agonist triptorelin on day 6 after ICSI led to a significant improvement of implantation and live birth rates after ICSI as compared with placebo. In GnRH antagonist-treated ovarian stimulation cycles, luteal-phase GnRH agonist also increased ongoing pregnancy rate. Moreover, luteal-phase GnRH agonist administration increased luteal-phase serum HCG, estradiol and progesterone concentrations in both ovarian stimulation regimens. CONCLUSIONS: Luteal-phase GnRH agonist administration enhances ICSI clinical outcomes after GnRH agonist- and GnRH antagonist-treated ovarian stimulation cycles, possibly by a combination of effects on the embryo and the corpus luteum.

Adult↗
PubMed2006

Sperm nuclear DNA damage: update on the mechanism, diagnosis and treatment.

Previous studies have shown that repeated intracytoplasmic sperm injection failures can be associated with sperm DNA damage. This paper reviews the current understanding of the mechanism of sperm DNA damage, discusses different diagnostic methods and their threshold values to discriminate between good- and poor-prognosis patients, and outlines the currently available treatment options. A rational approach to the interpretation of sperm DNA fragmentation data and to the choice of the optimal treatment method is suggested.

Antioxidants↗
PubMed2005

Improvement of delivery and live birth rates after ICSI in women aged >40 years by ovarian co-stimulation with growth hormone.

BACKGROUND: Growth hormone (GH) is required for ovarian follicular development, and its administration during ovarian stimulation improves pregnancy rate in cow and sheep. Data on the use of exogenous GH in human assisted reproduction treatment are inconsistent. This prospective randomized study evaluates the usefulness of GH administration in women of >40 years undergoing ovarian stimulation for assisted reproduction treatment. METHODS: One hundred women of >40 years undergoing assisted reproduction treatment were randomized between a GH treatment group and a placebo group. Assisted reproduction treatment outcomes were evaluated. RESULTS: In patients of the GH treatment group, a similar number of oocytes, embryos and pregnancies was achieved as compared with the placebo group. However, the patients treated with GH suffered fewer pregnancy losses, resulting in higher delivery and live birth rates. These patients also showed higher peak serum estradiol concentration and higher concentrations of GH and estradiol in pre-ovulatory follicular fluid as compared with the placebo group. CONCLUSIONS: Administration of GH during ovarian stimulation alleviates age-related decrease in assisted reproduction treatment efficiency. This effect appears to be mainly due to an improvement of oocyte developmental potential, but GH action on the uterus cannot be excluded.

Adult↗
PubMed2004

Efficient treatment of infertility due to sperm DNA damage by ICSI with testicular spermatozoa.

BACKGROUND: Sperm DNA damage (fragmentation) is a recently discovered cause of male infertility for which no efficient treatment has yet been found. Previous findings have suggested that clinically relevant sperm DNA damage may occur at the post-testicular level. This study was undertaken to assess the clinical usefulness of ICSI with testicular spermatozoa in this indication. METHODS: The percentage of spermatozoa with fragmented DNA, assessed by terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labelling assay, and ICSI outcomes were compared in two sequential attempts performed, respectively, with ejaculated and testicular spermatozoa in 18 men with increased sperm DNA fragmentation. RESULTS: The incidence of DNA fragmentation was markedly lower in testicular spermatozoa as compared with ejaculated spermatozoa. No differences in fertilization and cleavage rates and in embryo morphological grade were found between the ICSI attempts performed with ejaculated and with testicular spermatozoa. However, eight ongoing clinical pregnancies (four singleton and four twin) were achieved by ICSI with testicular spermatozoa (44.4% pregnancy rate; 20.7% implantation rate), whereas ICSI with ejaculated spermatozoa led to only one pregnancy which was spontaneously aborted. CONCLUSIONS: These data show that ICSI with testicular spermatozoa provides the first efficient assisted reproduction treatment option for men with high levels of sperm DNA damage.

Adult↗
PubMed2004

Enhancement of embryo developmental potential by a single administration of GnRH agonist at the time of implantation.

BACKGROUND: Several reports have shown that inadvertent administration of a GnRH agonist in the luteal phase does not compromise pregnancy. Moreover, some studies suggested that, unexpectedly, the embryo developmental potential is improved in these conditions. This prospective controlled study was designed to test this hypothesis. METHODS: In an oocyte donation programme, oocytes from each donor (n = 138) were shared by two recipients, one of whom was given a single dose of a GnRH agonist (0.1 mg triptorelin) 6 days after ICSI, and the other received placebo at the same time. RESULTS: Oocyte recipients treated with GnRH agonist 6 days after ICSI had higher implantation (36.9 versus 25.1%), twin pregnancy (16.7 versus 3.6%), twin delivery (13.8 versus 2.2%) and birth (31.1 versus 21.5%) rates and similar miscarriage and abortion rates as compared with the placebo group. CONCLUSIONS: GnRH agonist administration at the time of implantation enhances embryo developmental potential, probably by a direct effect on the embryo.

Adult↗
PubMed2004

Late, but not early, paternal effect on human embryo development is related to sperm DNA fragmentation.

BACKGROUND: It is known that repeated failure of assisted reproduction treatment (ART) can be due to a paternal effect. This study was undertaken to analyse the possible relationship between ART failure and sperm DNA fragmentation. METHODS: Zygote morphology and the percentage of spermatozoa with fragmented DNA (assessed by TUNEL) were compared in two groups using donor oocytes for ICSI attempts. The experimental group consisted of 18 infertile couples who had each undergone three previous failed ART attempts. The control group included 18 randomly selected infertile couples undergoing their first ICSI attempt. Both groups used sibling oocytes from the same donors. RESULTS: In 10 couples of the experimental group, the adverse paternal effect was evident as early as the zygote stage. This early paternal effect was not associated with sperm DNA fragmentation. In eight couples of the experimental group, the adverse paternal effect did not produce any perceptible deterioration of zygote morphology. However, this late paternal effect was associated with an increased percentage of spermatozoa with fragmented DNA. CONCLUSIONS: Early paternal effect can compromise ART outcomes in the absence of increased sperm DNA fragmentation. Evaluation of sperm DNA integrity is useful to detect late paternal effect, which is not associated with morphological abnormalities at the zygote and early cleavage stages.

DNA Fragmentation↗
PubMed2004

Apoptosis and necrosis in human ejaculated spermatozoa.

BACKGROUND: Features of both apoptosis and necrosis have been reported in ejaculated human spermatozoa. This study examines the relative contribution of these two modes of cell death to the demise of these terminally differentiated cells. METHODS: Sperm fractions were prepared from aliquots of semen samples from young normozoospermic donors by simple washing from seminal plasma, by discontinuous density gradient centrifugation or by swim-up technique. They were subsequently incubated in vitro at 37 degrees C for 24 h. Sperm motility, viability, and the presence of two apoptotic markers, phosphatidylserine externalization (annexin-V binding) and DNA fragmentation (TUNEL), were examined before incubation and again after 4 and 24 h of incubation. RESULTS: The swim-up technique was the most efficient in terms of the recovery of viable, motile and non-apoptotic spermatozoa, followed by density gradient centrifugation and finally simple washing. No changes in the parameters tested were observed after 4 h of incubation, but a significant decrease in sperm motility and viability was detected after 24 h irrespective of the sperm preparation technique employed. However, these changes were not accompanied by any increase in the incidence of spermatozoa showing markers of an active apoptotic process. CONCLUSIONS: Healthy human ejaculated spermatozoa appear incapable of initiating apoptosis, at least under in vitro conditions.

Adult↗
PubMed2004

Caspase-dependent and -independent DNA fragmentation in Sertoli and germ cells from men with primary testicular failure: relationship with histological diagnosis.

BACKGROUND: Germ cell elimination and sperm DNA fragmentation in men with primary testiculopathies involve apoptosis-related processes whose mechanisms are poorly understood. This study examines the participation of typical (caspase-dependent) and atypical (caspase-independent) pathways in these processes. METHODS: Caspase activity and DNA fragmentation were evaluated in Sertoli and germ cells from 63 men with non-obstructive azoospermia and with different histological diagnoses who were undergoing testicular biopsy for an assisted reproduction attempt. In eight of these men, phosphatidylserine externalization was also examined. RESULTS: The percentage of Sertoli cells showing caspase activity and DNA fragmentation was low and uniform in all diagnoses. In germ cells that remained tightly associated with Sertoli cells despite vigorous mechanical treatment, the incidence of both caspase activity and DNA fragmentation was high, particularly in men with maturation arrest. In Sertoli cell-free germ cells, high incidence of DNA fragmentation contrasted with low incidence of caspase activity and phosphatidylserine externalization. CONCLUSIONS: In men with primary testicular failure, apoptosis of Sertoli cells is insignificant. Some germ cells undergo caspase-dependent apoptosis, show phosphatidylserine externalization and are tightly associated with Sertoli cells. Other germ cells show caspase-independent DNA fragmentation, do not externalize phosphatidylserine and lack a tight association with Sertoli cells.

Apoptosis↗
PubMed2003

Microfilament disruption is required for enucleation and nuclear transfer in germinal vesicle but not metaphase II human oocytes.

OBJECTIVE: To evaluate the usefulness of microfilament disruption before enucleation and nuclear transfer in human oocytes at different stages of maturation. DESIGN: Prospective experimental study. SETTING: Private clinics. PATIENT(S): Infertile couples undergoing assisted reproduction attempts. INTERVENTION(S): Oocyte enucleation and nuclear transfer, activation of reconstructed oocytes. MAIN OUTCOME MEASURE(S): Oocyte survival, nuclear transfer efficacy, activation outcomes. RESULT(S): Survival rate and nuclear transfer efficacy of germinal vesicle oocytes exposed to the microfilament disrupting agent cytochalasin B before enucleation were 88% and 80%, respectively. These figures dropped, respectively, to 8% and 2% when cytochalasin treatment was omitted. By contrast, cytochalasin-treated and -untreated metaphase II oocytes showed similar survival rate (87% vs. 90%) and nuclear transfer efficacy (78% vs. 87%). This also applied to metaphase II oocytes matured in vitro from the germinal vesicle stage. Cytochalasin treatment did not affect activation rate of reconstructed oocytes, but it increased the occurrence of oocytes with multiple female pronuclei. CONCLUSION(S): Microfilament disruption before enucleation is required for germinal vesicle oocytes but not for metaphase II oocytes.

Actin Cytoskeleton↗
PubMed2002

Pharmacological concentrations of follicle-stimulating hormone and testosterone improve the efficacy of in vitro germ cell differentiation in men with maturation arrest.

OBJECTIVE: To examine whether in vitro differentiation of germ cells from men with maturation arrest is improved by augmenting FSH and T concentrations above the values effective in samples from men with normal spermatogenesis. DESIGN: Prospective, controlled in vitro study. SETTING: Private assisted reproduction centers and a university department. PATIENT(S): Men with meiotic or postmeiotic maturation arrest. INTERVENTION(S): Testicular spermatid extraction, in vitro culture of testicular biopsy samples, intraoocyte injection of elongated spermatids, embryo culture and transfer. MAIN OUTCOME MEASURE(S): Progression of in vitro germ cell differentiation, fertilization, and pregnancy outcomes with in vitro cultured germ cells. RESULT(S): In some cases of meiotic and postmeiotic maturation arrest, more advanced germ cell stages were achieved by in vitro culture in the presence of 500 IU/L FSH as compared with 50 IU/L FSH. The beneficial effect of 500 IU/L FSH was further potentiated by a simultaneous increase of T concentration from 1 to 10 microM. Fertilizations with germ cells recovered after incubation with these pharmacological hormone concentrations gave rise to viable embryos and the births of five healthy babies. CONCLUSION(S): Pharmacological concentrations of FSH and T are beneficial for in vitro maturation of germ cells from some men with in vivo maturation arrest.

Biopsy↗
PubMed2002

Use of a modified intracytoplasmic sperm injection technique to overcome sperm-borne and oocyte-borne oocyte activation failures.

OBJECTIVE: To examine whether sperm-borne and oocyte-borne oocyte activation failures can be overcome by mechanical means that entail modifying the ICSI technique. DESIGN: Case report series. SETTING: Private clinics. PATIENT(S): Six infertile couples undergoing ICSI. INTERVENTION(S): Standard ICSI and modified ICSI based on mechanical manipulation that facilitated entry of calcium into the oocyte. MAIN OUTCOME MEASURE(S): Fertilization rate and pregnancy outcome. RESULT(S): In three cases of sperm-borne and three cases of oocyte-borne oocyte activation deficiencies, the modified ICSI technique enabled normal fertilization and development of embryos with good morphology. In terms of fertilization, the efficacy of modified ICSI was similar to use of a calcium ionophore, without producing extensive embryo fragmentation during postfertilization development. Term pregnancies resulting in the birth of normal children were achieved with the modified ICSI technique in five cases. CONCLUSION(S): Sperm-borne and oocyte-borne oocyte activation failures can be overcome by modifying the ICSI technique. The modification obviates the need to use insufficiently tested and potentially harmful drugs.

Adult↗
PubMed2002

Paternal effects acting during the first cell cycle of human preimplantation development after ICSI.

BACKGROUND: The ability of human embryos to undergo normal development has been shown previously to be subject to strong paternal (sperm-derived) effects. This study was undertaken to determine whether paternal influences on human embryo quality are detectable as early as the first cell cycle after fertilization. METHODS: The quality of zygotes and cleaving embryos resulting from sibling donor oocytes fertilized by sperm from different patients were compared in a donor oocyte-sharing programme. RESULTS: Fertilizations with sperm from certain individuals repeatedly resulted in the formation of high proportions of zygotes with abnormal pronuclear morphology that subsequently tended to cleave slowly and to show extensive fragmentation and blastomere irregularities. This phenomenon was observed with oocytes from two different donors for each of these individuals and contrasted with normal developmental performance of embryos resulting from sibling oocytes fertilized by sperm from other men with similar basic sperm characteristics. Fertilization rates were not related to these differences. CONCLUSIONS: These data point to a very early onset of paternal effects that condition human embryo development. These effects may be both of genetic (related to the minor gene activity of the male pronucleus) or epigenetic (related to the sperm-derived oocyte-activating factor or sperm centrosome) origin.

Adult↗
PubMed2002

Effects of exogenous LH administration during ovarian stimulation of pituitary down-regulated young oocyte donors on oocyte yield and developmental competence.

BACKGROUND: The role of exogenous LH supplementation in ovarian stimulation is a matter of debate. Here we evaluate the impact of exogenous LH on oocyte yield and developmental competence in an oocyte donation programme. METHODS: Oocyte donors were randomized (computer-generated randomization list) to groups stimulated with FSH alone or with a combination of FSH and LH after pituitary down-regulation with a GnRH agonist administered in the mid-luteal phase. RESULTS: In donors with deep suppression of pituitary LH (<1 IU/l) before the beginning of ovarian stimulation, the inclusion of exogenous LH resulted in an increase in the number of mature oocytes and good-quality zygotes and embryos as well as higher implantation rates when compared with stimulation with FSH alone. In contrast, the inclusion of exogenous LH in the stimulation of donors with pre-stimulation serum LH of >or=1 IU/l impaired embryo morphology and lowered the implantation rate, although it increased the number of metaphase II oocytes. CONCLUSIONS: The inclusion of exogenous LH to the ovarian stimulation protocol can have beneficial or detrimental effects on oocyte yield and quality, depending on the level of endogenous LH. These data support the concept of a 'window' for LH requirement in ovarian stimulation.

Adult↗
PubMed2002

Follicular fluid markers of oocyte developmental potential.

BACKGROUND: Concentrations of certain substances in follicular fluid (FF) are related to fertilization outcome and early post-fertilization development. The study aim was to identify FF markers with which to predict embryo implantation potential. METHODS: Concentrations of selected hormones, cytokines and growth factors in individual FF samples obtained during assisted reproduction treatment were related with treatment outcomes. RESULTS: Mean concentrations of LH, growth hormone (GH), prolactin (PRL), 17beta-estradiol (E2) and insulin-like growth factor (IGF)-I were higher, and that of interleukin-1 (IL-1) was lower, in treatment attempts leading to a clinical pregnancy as compared with those in which no pregnancy was established. Concentrations of FSH, progesterone, tumour necrosis factor-alpha and IGF-II were similar in successful and unsuccessful attempts. In successful attempts, LH and GH levels were higher in those follicles from which oocytes giving rise to transferred embryos (i.e. embryos with best morphology and fastest cleavage rate) originated, as compared with other follicles from which a mature oocyte was recovered but was cryopreserved for later use. CONCLUSIONS: FF levels of LH, GH, PRL, E2, IGF-I and IL-1 may serve to analyse cases of repeated assisted reproduction failures and to assess effects of modifications of the ovarian stimulation protocol.

Adult↗
PubMed2002

Caspase activity in preimplantation human embryos is not associated with apoptosis.

BACKGROUND: Previous studies on mammalian preimplantation embryos have suggested an association between caspase activation, blastomere fragmentation and apoptosis. However, some reports on human embryos questioned the causal relationship between blastomere fragmentation and apoptosis, and information about the presence and activity of caspases in human embryos is lacking. METHODS: A fluorochrome-labelled universal caspase inhibitor was used to visualize active caspases in blastomeres and fragments of preimplantation human embryos. RESULTS: Caspase activity was detected only after fertilization, and was rare in blastomeres but frequent in fragments. The incidence of caspase activity in blastomeres and fragments was stable between the 2-cell and 12-cell stages. Caspase-positive blastomeres were only seen in poor-morphology embryos. The percentage of caspase-positive fragments was increased in embryos with multinucleated blastomeres but was unrelated to embryo morphology. Moreover, caspase-positive fragments detached from healthy blastomeres that were isolated by embryo biopsy and subsequently underwent mitotic division in culture. CONCLUSIONS: These data suggest that caspases in preimplantation human embryos are involved in developmental processes unrelated to cell death.

Apoptosis↗
PubMed2002

In-vitro effects of FSH and testosterone withdrawal on caspase activation and DNA fragmentation in different cell types of human seminiferous epithelium.

BACKGROUND: Caspases are downstream elements of apoptosis-mediating pathways initiated by the Fas ligand/Fas receptor system which is supposed to play a central role in the regulation of apoptosis in the human seminiferous epithelium. However, caspase activity in different cell types of this epithelium has never been addressed. METHODS AND RESULTS: We evaluated caspase activity and DNA integrity in Sertoli and germ cells within in-vitro cultured segments of human seminiferous tubules after induction of apoptosis by FSH or testosterone withdrawal. FSH withdrawal increased the incidence of DNA fragmentation in meiotic (primary spermatocytes) and post-meiotic (spermatids) germ cells without producing any detectable effect on caspase activity in these cells and without affecting DNA integrity or caspase activity in Sertoli cells. Testosterone withdrawal stimulated caspase activity and produced DNA fragmentation in Sertoli cells, but showed only a weak effect on DNA fragmentation in germ cells and did not alter germ cell caspase activity. CONCLUSIONS: These findings confirm the central role of caspases in apoptosis of Sertoli cells. However, they also suggest that acute apoptosis of germ cells in the adult human testis occurs in a caspase-independent way and is controlled by Sertoli cells via an as yet undetermined mechanism.

Apoptosis↗