Conceptus Polarity and Cell-Zona Adhesion during Early Cleavage (Fertilized Tubal Egg to 8-Cell Stage) in the Marsupial Sminthopsis macroura

This study outlines the ultrastructural changes that occur in Sminthopsis macroura tubal zygotes to the 8-cell stage in relation to observations of development in vitro, oocyte polarity and cell-zona adhesion. The extremely polarized mature oocytes and zygotes have nuclear material at one pole and accumulated vesicular bodies at the other. The first division is associated with extrusion of vesicular bodies and some cytoplasm as a membrane-bound yolk mass into the perivitelline space. Early cleavage is accompanied by the appearance of an extensive, highly structured extracellular matrix (ECM) comprised of amorphous substance, granules and filaments. At the 2- and 4-cell stage the decrease in density of the ECM in the vicinity of the blastomeres may facilitate cell-zona contact. At the 8-cell stage, discharge of vesicular bodies, which mostly appear to be empty, may contribute to the ECM by increasing the area of plasma membrane for synthesis of a hyaluronan-like ECM. As in other marsupials, the precedence of cell-zona adhesion over cell-cell contacts prevents morula formation. The earliest cell-zona contacts appear when microvilli contact the zona in the uterine zygote 12-16 h after uterine entry and continue at later stages. This early contact is possible because of the absence of a dense subzonal ECM in this species. Between late zygote and late 4-cell stage the cytoplasm also contains, beside a large amount of vesicular bodies, demarcated areas where smooth endoplasmic reticulum encloses mitochondria, vesicles, granular material and fibrillar arrays. The latter develop in the late zygote stage and are found outside demarcated areas as well, often closely surrounding large vesicles, probably helping vesicle extrusion. A putative germ plasm was identified at the 4-cell stage.

Presence, but not type or degree of extension, of a cytoplasmic halo has a significant influence on preimplantation development and implantation behaviour

BACKGROUND

Since there is considerable disagreement in grading cytoplasmic haloes, this prospective study was set up to evaluate if certain subtypes of haloes are related to further development.

METHODS

Out of a total of 152 patients, 713 zygotes could be checked for the formation of a halo. Where present, haloes were subdivided into concentric (symmetric) and polar (asymmetric) types. In addition, each halo was measured accurately to see if the extension of the halo might influence further development. In parallel, pronuclear patterns were checked.

RESULTS

Halo-positive zygotes did not differ from halo-negative ones in terms of embryo quality and blastocyst formation rate. However, quality of blastocysts (assessed by their inner cell mass consistency) was significantly increased (P < 0.001) if a halo appeared at zygote stage. This phenomenon was not related to type of halo or degree of halo. In terms of pronuclear pattern, pattern 0 (0A, 0B) led to significantly more blastocysts (P < 0.001) of better quality (P = 0.002) compared with patterns 1-5. A stepwise logistic regression showed no relationship between different halo types and pronuclear pattern 0.

CONCLUSIONS

The present study indicates that any halo has a positive prognostic value on blastocyst quality, irrespective of the fact that it is light or extreme, polar or concentric. In addition, the developmental advantage of pattern 0 is confirmed.

The relationship of pronuclear stage morphology and chromosome status at cleavage stage

PURPOSE

Infertile couples undergoing in vitro fertilization-embryo transfer (IVF-ET) program were included to study the relationship of pronuclear stage morphology and chromosome status at cleavage stage.

METHODS

Eighteen to twenty-one hours after fertilization, zygotes were checked for pronuclear morphology with modified Scott Z-score system. After embryo transfer on day 3, arrested or non-transferred 2 PN embryos were spread for fluorescence in situ hybridization (FISH) staining of probes to chromosomes 18, X and Y.

RESULTS

Ninety-eight embryos were successfully fixed and stained. The chromosome status were recorded in each 2 PN score group: 7 (54%) of 13 embryos in Z2 group, 14 (35%) of 40 in Z3 group and 10 (36%) of 28 in Z4 group being normal diploid. Z1 group has 12 (71%) of 17 embryos being normal diploid, which is significantly more than Z3 (p = 0.020) and Z4 group (p = 0.033).

CONCLUSION

Our results demonstrated a high probability to get normal diploid embryos if good morphology at pronuclear stage was used as selection criteria, especially for Z1 score embryos.

[Zygote formation in Blakeslea trispora: morphological peculiarities and relationship with carotenoid synthesis]

Changes associated with zygospore formation in the mucorous fungus Blakeslea trispora were studied. Zygospores are dormant cells with thickened cell walls and large central lipid vacuoles containing large amounts of lycopene. We established for the first time that B. trispora gametangia of different sexes differ in their carotenoid content and revealed that zygote formation involves a novel structure that consists of densely intertwined hyphae. Using inhibitory analysis (blocking beta-carotene synthesis with diphenylamine and 2-amino-6-methylpyridine), we showed that suppression of carotene production results in the inhibition of zygote formation. Hence, we established a manifest dependence of zygote formation on beta-carotene synthesis.

Fertilization abnormalities following human in vitro fertilization and intracytoplasmic sperm injection

Fertilization abnormalities are commonly encountered following in vitro fertilization. The widespread introduction of assisted fertilization methods has rapidly led to a changes in both the incidence and types of these aberrations. Such abnormalities can be identified by careful morphological evaluation at the early zygote stage, of pronuclei as well as of polar body formation, and may be confirmed by cytogenetic assessment. The recognition and understanding of fertilization abnormalities have led to the development of novel techniques aimed at preventing them, as well as recent bold attempts at correction. Removal of one pronucleus may allow some triploid embryos to revert to a normal diploid stage. These new developments should provide insight into the understanding of parthenogenesis, androgenesis, and gynogenesis in the human. Microsc. Res. Tech. 61:358-361, 2003.

[Prognostic value of the pronuclear morphology pattern of zygotes for implantation rate]

INTRODUCTION

In ICSI and conventional IVF cycles, the embryos are usually selected for transfer based on evaluation of the cleavage speed and the extent of blastomere fragmentation. Pronuclear stage scoring system has been used in IVF recently as an additional parameter.

OBJECTIVES

The aim of this study was to classify embryos from ICSI cycles according to the pronuclear scoring system and its influence on implantation rate.

MATERIAL AND METHODS

62 couples suffering from different types of infertility and treated by ICSI were included in our study. For each embryo, the following data were analyzed: pronuclei (PN) morphology, 16-20 hours after ICSI, and embryo morphology, about 40-42 (day 2) and 65-68 (day 3) hours after ICSI. The embryo transfer was performed on the third day after pick-up.

RESULTS

In 55 (88.7%) cases we transferred at least one embryo from the zygotes of 0 or 1 or 2 pattern. The implantation rate was 30.6% (n = 19). In all of these cases the embryos have been derived from zygotes from pattern 0, 1 or 2.

CONCLUSIONS

Pronuclear scoring system of zygotes appears to be a predictor of the implantation potential. Embryos derived from pattern 0, 1 and 2 of zygotes implant at a higher rate (p = 0.05).

Cytoskeleton and chromatin reorganization in horse oocytes following intracytoplasmic sperm injection: patterns associated with normal and defective fertilization

Intracytoplasmic sperm injection (ICSI) is the method of choice for fertilizing horse oocytes in vitro. Nevertheless, for reasons that are not yet clear, embryo development rates are low. The aims of this study were to examine cytoskeletal and chromatin reorganization in horse oocytes fertilized by ICSI or activated parthenogenetically. Additional oocytes were injected with a sperm labeled with a mitochondrion-specific vital dye to help identify the contribution of the sperm to zygotic structures, in particular the centrosome. Oocytes were fixed at set intervals after sperm injection and examined by confocal laser scanning microscopy. In unfertilized oocytes, microtubules were present only in the metaphase-arrested second meiotic spindle and the first polar body. After sperm injection, an aster of microtubules formed adjacent to the sperm head and subsequently enlarged such that at the time of pronucleus migration and apposition it filled the entire cytoplasm. During syngamy, the microtubule matrix reorganized to form a mitotic spindle on which the chromatin of both parents aligned. Finally, after nuclear and cellular cleavage were complete, the microtubule asters dispersed into the interphase daughter cells. Sham injection induced parthenogenetic activation of 76% of oocytes, marked by the formation of multiple cytoplasmic microtubular foci that later developed into a dense microtubule network surrounding the female pronucleus. The finding that a parthenote alone can produce a microtubule aster, whereas the aster invariably forms at the base of the sperm head during normal fertilization, indicates that both gametes contribute to the formation of the zygotic centrosome in the horse. Finally, 25% of sperm-injected oocytes failed to complete fertilization, mostly due to absence of oocyte activation (65%), which was often accompanied by failure of sperm decondensation. In conclusion, this study demonstrated that union of the parental genomes in horse zygotes is accompanied by a series of integrated cytoskeleton-mediated events, failure of which results in developmental arrest.

Birth of normal kids after microinjection of pronuclear embryos in a transgenic goat (Capra hircus) production program in Brazil

This pilot project was designed to determine if normal kids could be produced after microinjection in pronuclear embryos and subsequent transfer to recipients in a transgenic goat program in Brazil. Twelve donors of the Saanen breed and 17 recipients of an undefined breed were used. The estrus of both donors and recipients was synchronized by a standard progestagen treatment and superovulation obtained by six pFSH injections. Donors in estrus were mated with fertile Saanen bucks. Zygotes were recovered surgically by flushing oviducts. The recovered zygotes with visible pronuclei were microinjected with 500 to 1000 copies of the human G-CSF gene. Two or four embryos were surgically transferred into the oviducts of recipients. One recipient became pregnant and two kids were born. No transgenic goat was identified after PCR analysis. Even though transgenic goats were not obtained, this experiment establishes the basis of a synchronization and superovulation regimen for use in goats raised in Brazil, for the purpose of collecting and manipulating the pronuclear embryos. This project also showed that microinjected one-cell goat embryos can survive to produce live young following surgical transfer.

Normal birth after microsurgical enucleation of tripronuclear human zygotes: case report

Microsurgical enucleation of a single pronucleus from each of three tripronuclear zygotes was performed and the embryos were transferred to a 38-year-old woman on day 3 after fertilization. A normal healthy baby boy was born at 38 weeks and 4 days gestation, demonstrating that with polyspermic fertilization, removal of the extra male pronucleus allows the zygote to develop normally.

[Clinical application of a modified pronuclear stage scoring system following conventional in-vitro fertilization]

OBJECTIVE

To assess the clinical value of pronuclear stage scoring system in human conventional in vitro fertilization-embryo transfer (IVF-ET) program.

METHODS

A modified pronuclear scoring system was used to score zygotes 16 - 18 hours after insemination during conventional IVF.

RESULTS

A total of 178 IVF cycles were recruited in this study. Cycles with mean pronuclear score (sum of pronuclear scores of all transferred embryos divided by total number of transferred embryos) > or = 13 had significant high pregnancy and implantation rate, as compared to those with less than 13 (49.1% and 26.5% Vs 29.4% and 15.0% respectively). Although the pregnancy, implantation rate and multiple pregnancy rate tend to increase with the increasing number of zygotes with full pronuclear score (= 15) among transferred embryos, no significant difference could be found (P > 0.05). When all embryos were analyzed, 77.2% zygotes with pronuclear score > or = 11 could be transferred or cryopreserved, while those with pronuclear score less than 11 decreased to 46.1%.

CONCLUSIONS

Pronuclear stage scoring system provides additional parameter for embryo selection. However, pronuclear morphology could only partly represent embryonic viability. Combination with the scoring of both pronuclear stage and cleavage stage embryos for selecting transferred embryos is indispensable.

Developmental competence of oocytes showing increased cytoplasmic viscosity

BACKGROUND

The objective of the study was to investigate the developmental fate of oocytes with increased cytoplasmic viscosity as assessed by the persistence of the injection funnel after withdrawal of the ICSI pipette.

METHODS

For this purpose, 1008 oocytes showing a characteristic injection funnel during ICSI were subdivided into two groups according to the oocyte's ability to restore its spherical shape within 2-3 min after ICSI. Fertilization and further development was evaluated in both groups. In addition, implantation and pregnancy rates were analysed.

RESULTS

In the funnel positive cohort (group 1) significantly fewer oocytes degenerated after injection (P < 0.01) compared with oocytes without persistent funnel (group 2). However, at zygote stage, presence of a halo (P < 0.05) and a optimal pronuclear pattern 0 (P < 0.01) was increased in group 2. In addition, significantly fewer poor quality embryos were found in this group (P < 0.01). The number of good quality blastocysts but not blastocyst formation was increased in group 2 (P < 0.05). This resulted in an increased clinical pregnancy rate if embryos which derived exclusively from funnel negative oocytes were transferred (P < 0.05).

CONCLUSIONS

Our data suggest that cytoplasm of higher viscosity delays development up to cleavage stage and impairs optimal development. Injection funnel persistence was found to be a negative prognostic marker of preimplantation development.

Early degradation of paternal mitochondria in domestic pig (Sus scrofa) is prevented by selective proteasomal inhibitors lactacystin and MG132

Ubiquitin-dependent proteolysis has been implicated in the recognition and selective elimination of paternal mitochondria and mitochondrial DNA (mtDNA) after fertilization in mammals. Initial evidence suggests that this process is contributed to by lysosomal degradation of the ubiquitinated sperm mitochondrial membrane proteins. The present study examined the role of the proteasome-dependent protein degradation pathway of the ubiquitin system, as opposed to lysosomal proteolysis of the ubiquitinated proteins, in the regulation of sperm mitochondrion elimination after fertilization. Boar spermatozoa prelabeled with vital fluorescent mitochondrial probes MitoTracker were used to trace the degradation of paternal mitochondria after in vitro fertilization (IVF) of porcine oocytes. The degradation of sperm mitochondria in the cytoplasm of fertilized oocytes started very rapidly, i.e., within 12-20 h after insemination. Four stages of paternal mitochondrial degradation were distinguished, ranging from an intact mitochondrial sheath (type 1) to complete degradation (type 4). At 27-30 h postinsemination, 96% of zygotes contained the partially (type 3) or completely (type 4) degraded sperm mitochondria. Highly specific peptide inhibitors of the ubiquitin-proteasome pathway, lactacystin (10 and 100 microM) and MG132 (10 microM), efficiently blocked the degradation of the sperm mitochondria inside the fertilized egg when applied 6 h after insemination. Using 10 microM MG132, only 13.6% of fertilized oocytes screened 27-30 h after IVF displayed type 3 sperm mitochondria, and there was no incidence of type 4, completely degraded mitochondria. Although lactacystin is not a reversible agent, the effect of MG132 was fully reversible: zygotes transferred to regular culture medium after 24 h of culture with 10 microM MG132 resumed development and degraded sperm mitochondria within the next cell cycle. Surprisingly, penetration of the zona pellucida (ZP) was also inhibited by MG-132 and lactacystin when the inhibitors were added at insemination. Altogether, these data provide the first evidence of the participation of proteasomes in the control of mammalian mitochondrial inheritance and suggest a new role of the ubiquitin-proteasome pathway in mammalian fertilization.

Myosin and the PAR proteins polarize microfilament-dependent forces that shape and position mitotic spindles in Caenorhabditis elegans

In Caenorhabditis elegans, the partitioning proteins (PARs), microfilaments (MFs), dynein, dynactin, and a nonmuscle myosin II all localize to the cortex of early embryonic cells. Both the PARs and the actomyosin cytoskeleton are required to polarize the anterior-posterior (a-p) body axis in one-cell zygotes, but it remains unknown how MFs influence embryonic polarity. Here we show that MFs are required for the cortical localization of PAR-2 and PAR-3. Furthermore, we show that PAR polarity regulates MF-dependent cortical forces applied to astral microtubules (MTs). These forces, which appear to be mediated by dynein and dynactin, produce changes in the shape and orientation of mitotic spindles. Unlike MFs, dynein, and dynactin, myosin II is not required for the production of these forces. Instead, myosin influences embryonic polarity by limiting PAR-3 to the anterior cortex. This in turn produces asymmetry in the forces applied to MTs at each pole and allows PAR-2 to accumulate in the posterior cortex of a one-cell zygote and maintain asymmetry.

Crossing over as assessed by late recombination nodules is related to the pattern of synapsis and the distribution of early recombination nodules in maize

Recombination nodules (RNs) are multicomponent proteinaceous ellipsoids found in association with the synaptonemal complex (SC) during prophase I of meiosis. Numerous early RNs (ENs) are observed during zygotene, and they may be involved in homologous synapsis and early events in recombination. Fewer late RNs (LNs) are observed during pachytene, and they occur at crossover sites. Here we describe the pattern of synapsis and the distribution of ENs and LNs in maize. Synapsis starts almost exclusively at chromosome ends, although later in zygotene there are many interstitial sites of synaptic initiation. ENs do not show interference, except possibly at distances < or = 0.2 micron. The frequency of ENs is higher on distal compared to medial SC segments, and the highest concentration of ENs occurs at synaptic forks. The number of ENs on an SC segment does not change during zygotene. These observations are interpreted to indicate that ENs are assembled at synaptic forks. Like ENs, LNs are more concentrated distally on bivalents but, unlike ENs, LNs show interference. A model is presented that relates the pattern of synapsis and ENs to the pattern of late nodules and crossing over.

Gene expression and chromatin structure in the pre-implantation embryo

The pre-implantation period of mammalian development includes the formation of the zygote, the activation of the embryonic genome (EGA), and the beginning of cellular differentiation. During this period, protamines are replaced by histones, the methylated haploid parental genomes undergo demethylation following formation of the diploid zygote, and maternal control of development is succeeded by zygotic control. Superimposed on this activation of the embryonic genome is the formation of a chromatin-mediated transcriptionally repressive state requiring enhancers for efficient gene expression. The development of this transcriptionally repressive state most likely occurs at the level of chromatin structure, because inducing histone hyperacetylation relieves the requirements for enhancers. Characterization of zygotic mRNA expression patterns during the pre-implantation period and their relationship to successful development in vitro and in vivo will be essential for defining optimized culture conditions and nuclear transfer protocols. The focus of this review is to summarize recent advances in this field and to discuss their implications for developmental biology.

Pronuclear and morphological features as a cumulative score to select embryos in ICSI (intracytoplasmic sperm injection) cycles according to sperm origin

PURPOSE

To analyze best parameter to select embryos according to sperm origin in ICSI cycles.

METHODS

One hundred seventy-two ICSI cycles were divided among three different groups: A (ejaculated spermatozoa from nonmale factor infertility), B (ejaculated spermatozoa from oligospermia), and C (spermatozoa from azoospermia). Embryos were divided on Day 1 into two patterns: S0 (pronuclei (PN) aligned and close with normal arrangement of nucleoli) and S1 (when these characteristics were absent) and also on transfer day according to morphological features.

RESULTS

Relationships of PN patterns related to sperm origin were noted. More S0 embryos were detected with better sperm quality. Higher number of good quality embryos was obtained when male factor was absent. Ejaculated and epididymal spermatozoa provide better quality embryos than do testicular spermatozoa.

CONCLUSIONS

PN classification associated with transfer day morphology is valuable additional noninvasive criterion for elective embryo transfer, mainly in the cases with severe male factor.

Pronuclear morphology scoring and chromosomal status of embryos in severe male infertility

BACKGROUND

The study aim was to evaluate the relationship between pronuclei morphology scoring (PNMS) and the chromosomal complement of embryos in couples with severe male infertility undergoing ICSI. A total of 3116 pre-embryos was scored according to PNMS in 452 cycles.

METHODS

Pre-embryos were classified into eight categories based on the alignment, size, linear or irregular distribution of pronuclear bodies (PNB), position and clarity of cytoplasmic halo and abutting of the pronucleus. These categories were subdivided into groups I and II according to the similarity and distribution of PNB.

RESULTS

In total, 2574 pre-embryos formed by using ejaculated sperm, while 542 pre-embryos developed by injection of testicular sperm or round spermatids. More group II pre-embryos with markedly different morphology from group I were formed after ICSI with testicular sperm than with fresh ejaculated sperm (32.1 versus 22.7%, P < 0.01). Of 490 pre-embryos in which pronuclear morphology was evaluated, 263 were biopsied for preimplantation genetic diagnosis. The rate of chromosomal abnormality was higher in embryos developed from group II pre-embryos (52.2%) than in embryos developed from group I prezygotes (37.6%, P < 0.05).

CONCLUSIONS

Group II pre-embryos had markedly different morphology from group I, and had a low rate of blastocyst formation and high risk of chromosomally abnormal embryos. When testicular sperm and round spermatids were used for ICSI, more group II pre-embryos and chromosomally abnormal embryos were produced than with ejaculated sperm. Pronuclear morphology was correlated with chromosomal complement, and impacted upon by the sperm source.

Reorganization and translocation of the ectoplasmic cytoskeleton in the leech zygote by condensation of cytasters and interactions of dynamic microtubules and actin filaments

The formation and bipolar translocation of an ectoplasmic cytoskeleton of rings and meridional bands was studied in interphase zygotes of the glossiphoniid leech Theromyzon trizonare. Zygotes consisted of a peripheral organelle-rich ectoplasm and an internal yolk-rich endoplasm. After microinjection of labeled tubulin and/or actin, zygotes were examined by time-lapse video imaging, immunofluorescence and confocal microscopy. The rings and meridional bands were formed by condensation of a network of moving cytasters that represented ectoplasmic secondary centers of microtubule and actin filament nucleation. In some cases the network of cytasters persisted between the rings. The cytoskeleton had an outer actin layer and an inner microtubule layer that merged at the irregularly-shaped boundary zone. Bipolar translocation of the rings, meridional bands, or the network of cytasters led to accumulation of the cytoskeleton at both zygote poles. Translocation of the cytoskeleton was slowed or arrested by microinjected taxol or phalloidin, in a dose-dependent fashion. Results of drug treatment probably indicate differences in the degree and speed at which the cytoskeleton becomes stabilized. Moreover, drugs that selectively stabilized either microtubules or actin filaments stabilized and impaired movement of the entire cytoskeleton. Microtubule poisons and latrunculin-B failed to disrupt the cytoskeleton. It is concluded that the microtubule and actin cytoskeletons are dynamic, presumably cross-linked and resistant to depolymerizing drugs. They probably move along each other by a sliding mechanism that depends on the instability of microtubules and actin filaments.

Embryological strategies for overcoming recurrent assisted reproductive technology treatment failure

In every assisted reproductive technology (ART) programme there are patients who experience repeated failure. If all laboratory and stimulation parameters are controlled, it is assumed that the underlying cause of failure is physiological, and is attributable to either of the gametes or the embryo. Within the laboratory, few tools are available, other than careful observation and embryo selection, to aid in selecting the right embryo to overcome this failure. The morphology of the zygote, the state of the cleaving embryos on day 2 and day 3 of development, and the blastocyst can influence implantation rates. However, without functional gametes it is unlikely that success can be achieved. An early indicator of this functionality is the morphology of the zygote, which can be influenced by either the oocyte or the spermatozoon, and can be altered by either improving oocyte quality during stimulation or by using donor sperm if the failure to conceive is attributable to the male gamete. Subsequently, selecting embryos for transfer on the basis of the morphology of zygotes and embryos at day 3 or day 5 of development with the addition of fragmentation scoring and assisted hatching has been found to overcome many cases of repetitive failure to conceive after ART.

Morphological features of lipid droplet transition during porcine oocyte fertilisation and early embryonic development to blastocyst in vivo and in vitro

Lipid content in mammalian oocytes or embryos differs among species, with bovine and porcine oocytes and embryos showing large cytoplasmic droplets. These droplets are considered to play important roles in energy metabolism during oocyte maturation, fertilisation and early embryonic development, and also in the freezing ability of oocytes or embryos; however, their detailed distribution or function is not well understood. In the present study, changes in the distribution and morphology of porcine lipid droplets during in vivo and in vitro fertilisation, in contrast to parthenogenetic oocyte activation, as well as during their development to blastocyst stage, were evaluated by transmission electron microscopy (TEM). The analysis of semi-thin and ultra-thin sections by TEM showed conspicuous, large, electron-dense lipid droplets, sometimes associated with mitochondrial aggregates in the oocytes, irrespective of whether the oocytes had been matured in vivo or in vitro. Immediately after sperm penetration, the electron density of the lipid droplets was lost in both the in vivo and in vitro oocytes, the reduction being most evident in the oocytes developed in vitro. Density was restored in the pronculear oocytes, fully in the in vivo specimens but only partially in the in vitro ones. The number and size of the droplets seemed, however, to have decreased. At 2- to 4-cell and blastocyst stages, the features of the lipid droplets were almost the same as those of pronuclear oocytes, showing a homogeneous or saturated density in the in vivo embryos but a marbled or partially saturated appearance in the in vitro embryos. In vitro matured oocytes undergoing parthenogenesis had lipid droplets that resembled those of fertilised oocytes until the pronuclear stage. Overall, results indicate variations in both the morphology and amount of cytoplasmic lipid droplets during porcine oocyte maturation, fertilisation and early embryo development as well as differences between in vivo and in vitro development, suggesting both different energy status during preimplantation development in pigs and substantial differences between in vitro and in vivo development.

Thalamic neuron theory: meridians=DNA. The genetic and embryological basis of traditional Chinese medicine including acupuncture

This hypothesis proposes a mechanism by which the genetic information contained in the one-dimensional genome may be converted into a three-dimensional body plan for development. Prior to mitosis of the fertilized egg, the chromatids, after being unpackaged from the chromosomes, link up to form a giant circular loop which is then folded upon itself into a wired-frame structure that embodies the architectural embryological developmental scheme. This intranuclear spatial body design is then translated into a three-dimensional cellar plan surrounding the fertilized egg with the positional value of each surrounding daughter cell preferentially activated by specific spatially oriented gene products diffused through the neatly arranged nuclear pores of the cell nucleus of the fertilized egg. This group of cells of the primitive embryo then leads to the formation of the Spemann Organizer, which directs embryological development of the brain as well as the rest of the body. The Spemann Organizer thus retains control over the CNS which in turn controls the development and functions of the peripheral tissues. The chains of cells that compose the Spemann Organizer, forming a homunculus in the image of the wired frame formed by the chromatids are believed to be the equivalents of acupuncture meridians. To support the hypothesis, evidence is also presented to substantiate the intimate relationships between the acupuncture meridians and embryological development, evolution, the central nervous system as well as the genome. This theoretical model is capable of dispelling the mystery of acupuncture, traditional Chinese medicine and myriads of modern clinical observations, and may have the potential to usher in a multitude of innovative therapeutic methods for many difficult to treat medical conditions.

Electron microscopic observations of karyogamy in the fish egg

In the initial step of pronuclear association in fertilized fish eggs, the female and male pronuclei (containing large nucleolus-like bodies) were juxtaposed in the center of the blastodisc and formed nucleoplasmic projections along adjacent surfaces. After contact of the pronuclei, small internuclear bridges joining them were formed by fusion at several regions of the nuclear envelope projections. No specific site of fusion or breakdown of nuclear envelopes was recognized in the pronuclei during karyogamy. In the advanced stage, clumps of condensing chromatin appeared in the nucleoplasm of the newly fused pronuclei. The number and diameter of the internuclear bridges increased gradually by progressive fusion in many regions, finally yielding a spherical zygote nucleus. Following complete formation of the zygote nucleus, the pronuclear envelope began to break down concomitantly with shrinkage of the nucleoplasm, which was highly convoluted around the entire nuclear surface. The nucleoplasm containing chromosomes then mingled with the perinuclear cytoplasm.

High outcome predictability after IVF using a combined score for zygote and embryo morphology and growth rate

BACKGROUND

A scoring system has been developed to determine preimplantation embryo quality, and used to select embryos for transfer into the uterus of patients.

METHODS AND RESULTS

The system was used to study early embryo development and to test whether these scores alone can accurately predict IVF outcome. Following zygote and embryo scores through early development, the data showed that a top quality zygote does not necessarily indicate that the resulting embryo will be top quality after in-vitro culture. The embryo quality score can change dramatically when embryos are cultured to day 2 or 3 post-fertilization. Pregnancy rates and implantation rates were compared with the cumulative and separated zygote and embryo scores. Analysis of the predictability of scoring systems suggested that morphological scores alone are relatively unpredictive of IVF outcome. When weighted for in-vitro growth rate, scores were highly predictive, more so than the rate of development alone.

CONCLUSIONS

These data suggested that a combination of in-vitro growth rate and morphological analysis both of zygotes and embryos was highly indicative of outcome after IVF. The results can be adopted to the single embryo transfer approach to IVF.

Morphological and cytogenetic analysis of human giant oocytes and giant embryos

BACKGROUND

Giant binuclear oocytes occur with considerable frequency in human ovaries, but their ultimate fate remains unknown. We report the morphology, cytogenetics and developmental potential of human giant oocytes from patients undergoing assisted reproductive technologies.

METHODS AND RESULTS

A total of 44 giant oocytes was collected from patients aged 22-44 years old, with an overall frequency of 0.3% (44/14 272 oocytes). Giant oocytes were approximately 30% larger in diameter than normal oocytes (mean 200.4 versus 154.7 micro m, P = 0.0001). Two different morphological patterns were observed among giant unfertilized and fertilized oocytes. All unfertilized oocytes appeared to be diploid and contained either one or two metaphase plates (46 or 2 x 23 chromosomes), and one or two polar bodies respectively. Consequently, fertilized giant oocytes exhibited either two or three pronuclei, or two or four polar bodies. Both types of giant zygotes were capable of normal cleavage and development to blastocyst stage. Four giant embryos were analysed by interphase fluorescence in-situ hybridization using probes for chromosomes 9, 22, X and Y, and all appeared chromosomally abnormal with numerical alterations indicative of ploidy change.

CONCLUSIONS

Giant oocytes might be a possible source of human digynic triploidy. To avoid undesired miscarriages, giant embryos originated from either two- or three-pronuclear giant zygotes should be excluded from uterine transfers.

Microtubules and parental genome organisation during abnormal fertilisation in humans

We analysed the distribution of beta-tubulins, acetylated alpha-tubulins and chromatin configuration in 113 human zygotes showing abnormal fertilisation, 16-18 h after conventional in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI). After a first characterisation using phase contrast microscopy, immunofluorescence staining was performed in 67 IVF and 46 ICSI zygotes that developed one, three or more pronuclei and/or subnuclei, with or without extrusion of the second polar body. Independently of the number of pronuclei found, beta-tubulins were uniformly distributed throughout the cytoplasm of the abnormal zygotes. We did not observe any kind of microtubule alteration with respect of the ploidy level and/or its origin. The most frequent abnormal fertilisation pattern found after IVF was the presence of three or four pronuclei (74.6%). On the other hand, the presence of one pronucleus (63.0%) was the main pattern found after ICSI. No differences between the two groups were seen in terms of development of subnuclei. Anamolies detected after IVF and ICSI showed different aetiologies such as parthenogenetic activation, gynogenetic or androgenetic development, as well as digynic or diandric fertilisation.