Z. Nagy

Bio: Z. Nagy is an academic researcher from Vrije Universiteit Brussel. The author has contributed to research in topics: Intracytoplasmic sperm injection & Sperm. The author has an hindex of 29, co-authored 34 publications receiving 3987 citations.

Pregnancies after testicular sperm extraction and intracytoplasmic sperm injection in non-obstructive azoospermia

Abstract: In this study (May 1 until August 31, 1994) a total of 15 azoospermic patients suffering from testicular failure were treated with a combination of testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI). Spermatozoa were available for ICSI in 13 of the patients. Out of 182 metaphase II injected oocytes, two-pronuclear fertilization was observed in 87 (47.80%); 57 embryos (65.51%) were obtained for either transfer or cryopreservation. Three ongoing pregnancies out of 12 replacements (25%) were established, including one singleton, one twin and one triplet gestation. The ongoing implantation rate was 18% (six fetal hearts out of 32 embryos replaced).

The result of intracytoplasmic sperm injection is not related to any of the three basic sperm parameters.

Abstract: High success rates have been reported for the use of intracytoplasmic sperm injection (ICSI) in alleviating essentially andrological infertility. However, neither the relationship between any of the sperm parameters and the result of ICSI nor the minimal sperm requirements for ICSI have been investigated so far. In this paper, our objective was therefore to study the relationship between three basic sperm parameters (total sperm count, sperm motility and morphology) and the outcome of ICSI by retrospective analyses of fertilization, embryo development and pregnancy rates in 966 micro-injection cycles, performed with ejaculated semen. The results showed that there was no important influence from either the type or the extent of sperm impairment on the outcome of ICSI. Even in the most extreme cases of male-factor infertility, where cryptozoospermia or total astheno- or total teratozoospermia was diagnosed in the initial semen sample, high fertilization and pregnancy rates were obtained by ICSI. Only one condition had a strongly negative influence on the result of ICSI: where an immotile (presumably dead) spermatozoon was injected into the oocyte. Thus the only ultimate criterion for successful ICSI is the presence of at least one living spermatozoon per oocyte in the pellet of the treated semen sample used for micro-injection.

High fertilization and pregnancy rate after intracytoplasmic sperm injection with spermatozoa obtained from testicle biopsy

Abstract: In cases requiring microsurgical epididymal sperm aspiration (MESA) for congenital absence of the vas deferens (CAVD) or irreparable obstructive azoospermia, often no spermatozoa can be retrieved from the epididymis, or there may even be no epididymis present. We wished to see whether testicular biopsy with testicular sperm extraction (TESE) in such cases could yield spermatozoa that would result in successful fertilization and pregnancy (despite the absence of epididymal spermatozoa) using intracytoplasmic sperm injection (ICSI). In the same setting during the same 2-week period, 28 patients with CAVD or irreparable obstruction were treated; 16 consecutive fresh MESA-ICSI cycles and 12 cycles which required testicular biopsy with testicular sperm extraction (TESE-ICSI) were performed. Normal two-pronuclear fertilization rates were similar in both groups: 45% for epididymal spermatozoa and 46% for testicular biopsy-extracted spermatozoa. Cleavage rates were also similar (68% for epididymal and 65% for testicular spermatozoa). The ongoing pregnancy rates in this series were 50 and 43% respectively. We conclude that epididymal spermatozoa and testicular spermatozoa yield similar fertilization, cleavage and ongoing pregnancy rates using ICSI. When epididymal spermatozoa cannot be retrieved, a testicular biopsy can be performed and the few barely motile spermatozoa thus obtained can be used for ICSI. It appears that all cases of obstructive azoospermia can now be successfully treated.

Intracytoplasmic sperm injection in the mouse

Abstract: Intracytoplasmic sperm injection (ICSI) into mouse oocytes involves a very low survival rate. This study was designed to determine why ICSI frequently fails in mice. Metaphase II oocytes were obtained from superovulated 4-6 week old F1 hybrid mice. Spermatozoa were retrieved from the epididymis of 12-14 week old F1 hybrid mice. The spiked microinjection pipette used to inject a spermatozoon into the ooplasm had outer and inner diameters of 10 and 8 microns respectively. The oocytes used in the first part of the study were not activated (group 1). Some oocytes were incubated with calcium ionophore for 5 min (group 2). The injected oocytes were evaluated 6, 20, 48 and 72 h after injection. A total of 143 eggs in each group underwent ICSI. In group 1, sperm heads escaped into the perivitelline space. In all, 63 (47%) of the remaining oocytes were damaged during the injection or had degenerated by the first evaluation. The survival rate was 53%, but fertilization did not occur. In group 2, 31 oocytes (22%) were damaged during microinjection or soon degenerated. Two oocytes underwent accidental subzonal insemination. Six oocytes were fertilized (4.2%) among the 78% of survivors. After injection, the sperm tail was found in the cytoplasm (27 and 31% in groups 1 and 2 respectively), the perivitelline space (45% in both groups) or protruding through the zona pellucida (28 and 23% respectively). More oocytes degenerated when the tail remained in the cytoplasm, i.e. 78% in group 1 and 36% in group 2.

Time-course of oocyte activation, pronucleus formation and cleavage in human oocytes fertilized by intracytoplasmic sperm injection.

Abstract: Knowledge of the timing of the stages of fertilization in humans is still limited because the time of gamete fusion is not known when pre-ovulatory or in-vitro matured cumulus-enclosed oocytes are inseminated. We therefore studied the morphological nuclear changes in 14 patients' oocytes by means of light microscopic observation at 2, 4, 6, 8, 16, 18 and at 20 h after intracytoplasmic single sperm injection (ICSI). A total of 144 metaphase II oocytes were injected with the spermatozoa of the patients' partners. Out of the 134 oocytes that survived the injection, 93 displayed two pronuclei in the course of the observation period (69%). Out of the 93 normally fertilized oocytes, 21 extruded the second polar body at 2 h after micro-injection (23%) and 63 oocytes at 4 h (68%). Pronuclei appeared as early as 6 h after ICSI in 16 normally fertilized oocytes (17%). At 8 h, 75 (80%) oocytes had two visible pronuclei, at 16 h 92 (99%), at 18 h 76 (82%) and at 20 h 63 (68%). In 24 oocytes (26%) the appearance of pronuclei was asynchronous, while the disappearance of the pronuclei was always synchronous, except in one oocyte. Nine of the 134 successfully injected oocytes showed three equal-sized pronuclei (6.7%). Four of the nine multi-pronucleated oocytes did not extrude the second polar body at all, while the time sequence of appearance of pronuclei was similar to that of the normally fertilized oocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

The Istanbul consensus workshop on embryo assessment: proceedings of an expert meeting

Abstract: Background: Many variations in oocyte and embryo grading make inter-laboratory comparisons extremely difficult. This paper reports the proceedings of an international consensus meeting on oocyte and embryo morphology assessment. Methods: Background presentations about current practice were given. Results: The expert panel developed a set of consensus points to define the minimumcriteria for oocyte and embryomorphology assessment. Conclusions: It is expected that the definition of common terminology and standardization of laboratory practice related to embryo morphology assessment will result in more effective comparisons of treatment outcomes. This document is intended to be referenced as a global consensus to allow standardized reporting of the minimum data set required for the accurate description of embryo development.

The role of Tet3 DNA dioxygenase in epigenetic reprogramming by oocytes

Abstract: Sperm and eggs carry distinctive epigenetic modifications that are adjusted by reprogramming after fertilization. The paternal genome in a zygote undergoes active DNA demethylation before the first mitosis. The biological significance and mechanisms of this paternal epigenome remodelling have remained unclear. Here we report that, within mouse zygotes, oxidation of 5-methylcytosine (5mC) occurs on the paternal genome, changing 5mC into 5-hydroxymethylcytosine (5hmC). Furthermore, we demonstrate that the dioxygenase Tet3 (ref. 5) is enriched specifically in the male pronucleus. In Tet3-deficient zygotes from conditional knockout mice, paternal-genome conversion of 5mC into 5hmC fails to occur and the level of 5mC remains constant. Deficiency of Tet3 also impedes the demethylation process of the paternal Oct4 and Nanog genes and delays the subsequent activation of a paternally derived Oct4 transgene in early embryos. Female mice depleted of Tet3 in the germ line show severely reduced fecundity and their heterozygous mutant offspring lacking maternal Tet3 suffer an increased incidence of developmental failure. Oocytes lacking Tet3 also seem to have a reduced ability to reprogram the injected nuclei from somatic cells. Therefore, Tet3-mediated DNA hydroxylation is involved in epigenetic reprogramming of the zygotic paternal DNA following natural fertilization and may also contribute to somatic cell nuclear reprogramming during animal cloning.

Long-Term Proliferation in Culture and Germline Transmission of Mouse Male Germline Stem Cells

Abstract: Spermatogenesis is a complex process that originates in a small population of spermatogonial stem cells. Here we report the in vitro culture of spermatogonial stem cells that proliferate for long periods of time. In the presence of glial cell line-derived neurotrophic factor, epidermal growth factor, basic fibroblast growth factor, and leukemia inhibitory factor, gonocytes isolated from neonatal mouse testis proliferated over a 5-month period (>10(14)-fold) and restored fertility to congenitally infertile recipient mice following transplantation into seminiferous tubules. Long-term spermatogonial stem cell culture will be useful for studying spermatogenesis mechanism and has important implications for developing new technology in transgenesis or medicine.

The biology of infertility: research advances and clinical challenges

Abstract: Reproduction is required for the survival of all mammalian species, and thousands of essential 'sex' genes are conserved through evolution. Basic research helps to define these genes and the mechanisms responsible for the development, function and regulation of the male and female reproductive systems. However, many infertile couples continue to be labeled with the diagnosis of idiopathic infertility or given descriptive diagnoses that do not provide a cause for their defect. For other individuals with a known etiology, effective cures are lacking, although their infertility is often bypassed with assisted reproductive technologies (ART), some accompanied by safety or ethical concerns. Certainly, progress in the field of reproduction has been realized in the twenty-first century with advances in the understanding of the regulation of fertility, with the production of over 400 mutant mouse models with a reproductive phenotype and with the promise of regenerative gonadal stem cells. Indeed, the past six years have witnessed a virtual explosion in the identification of gene mutations or polymorphisms that cause or are linked to human infertility. Translation of these findings to the clinic remains slow, however, as do new methods to diagnose and treat infertile couples. Additionally, new approaches to contraception remain elusive. Nevertheless, the basic and clinical advances in the understanding of the molecular controls of reproduction are impressive and will ultimately improve patient care.