Metabolism of energy substrates following fertilization or parthenogenetic activation of mouse oocytes

Journal of Reproduction and Development

Futatsumata

2000

Abstract. The hatching ability was evaluated in diploid parthenogenetic mouse blastocysts based on the hatching rate, the embryonic contraction, the ultrastructure of the zona pellucida, and the activity of trypsin-like proteinase. The hatching rate of parthenogenetic blastocysts was 24.7% (87/350), which was significantly lower than 48.6% (184/383) in control blastocysts developed from fertilized 1-cell embryos (fertilized blastocysts). During observation for 32 h after blastocoel formation, strong contractions (20% or more volume reduction) occurred more frequently in parthenogenetic blastocysts (2.4 times) than in fertilized blastocysts (1.4 times, P<0.01). The lengths of time needed for re-expansion following both weak (less than 20% volume reduction) and strong contractions were significantly longer in parthenogenetic blastocysts (147.7 and 345.0 min) than in fertilized blastocysts (107.7 and 242.6 min). The zona pellucida showed a dense and homogeneous microgranular appearance in both parthenogenetic and fertilized blastocysts, while the zona pellucida of parthenogenetic blastocysts showed a few cracks in the outer surface. A similar morphological change was also observed in fertilized blastocysts developed following ethanol treatment, suggesting that the zona crack may be induced by ethanol treatment. The thickness of the zona pellucida and the activity of trypsin-like proteinase did not differ between parthenogenetic and fertilized blastocysts. These results suggest that the lower rate of hatching in parthenogenetic blastocysts might be due to the large number of strong contractions that require longer duration for re-expansion rather than changes in the structure of the zona pellucida or the activity of trypsin-like proteinase of the embryos. Key words: Parthenogenetic mouse blastocyst, Hatching ability, Contraction, Time-lapse videomicrography.(J. Reprod. Dev. 46: [367][368][369][370][371][372][373][374] 2000) h e h a t c h i n g o f m o u s e b l a s t o c y s t s i s accompanied by regional dissolution of the zona pellucida by a trypsin-like proteinase synthesized in trophectoderm cells [1,2] and trophectoderm cells protrude from the dissolved hole of the zona pellucida [3][4][5]. Then the zona pellucida is slit as hatching proceeds due to blastocyst expansion [3][4][5]. During hatching, the blastocyst repeats contractions, leading to the enlargement of the zona slit, and finally escapes from the zona pellucida [3][4][5].In our previous study [6], however, diploid parthenogenetic mouse blastocysts formed a larger slit in the zona pellucida at the beginning of hatching than did control blastocysts developed f ro m f e rt i l i z e d 1 -c el l e m b ry o s ( f e r ti l i z ed blastocysts), and the duration of hatching in the former was significantly longer than that in the latter. Thus, it was inferred that the hatching ability of parthenogenetic blastocysts is different from that of fertilized blastocysts.In the present study, therefore, the hatching rate,

Section: Discussionsupporting

confidence: 67%

Roles of Embryonic Contractions in Hatching of Parthenogenetic Mouse Blastocysts.

Journal of Reproduction and Development

Futatsumata

2000

“…Therefore, it is inferred that the process of early development differs between parthenogenetic embryos and fertilized embryos. Recently, ethanol treatment has been widely used to prepare parthenogenetic embryos [6][7][8][9][10][11], but there have been no reports with regard to the process of early development in those embryos.…”

mentioning

confidence: 99%

Time-Lapse Videomicrographic Observations of Parthenogenetic Mouse Embryos during Early Development.

Futatsumata

1999

J.Mamm.Ova.Res.

Abstract:The process of early development in diploid parthenogenetic mouse embryos from the 2-cell to the blastocyst stages was observed by time-lapse videomicrography, and was compared with that in fertilized embryos. Parthenogenetic 2-cell embryos cleaved and developed to 8-cell embryos after 23.0 hrs of culture. Transformation of blastomeres occurred at the 8-cell stage: namely, outer blastomeres were flattened. The embryos compacted at the morula stage, and then developed to blastocysts after 54.0 hrs of culture. A slit in the zona pellucida was formed 42.7 hrs after blastocyst formation, and trophectoderm cells protruded out of the zona pellucida through the slit. Protrusion of trophectoderm cells from the zona pellucida could arise from either side, polar trophectoderm or mural trophectoderm. After 7.0 hrs, the blastocysts completely escaped from the zona pellucida in either state, expansion or contraction. Fertilized 2-cell embryos showed morphological changes similar to those of parthenogenetic embryos and developed to blastocysts after 51.9 hrs of culture. Fertilized blastocysts took a significantly shorter time, 31.1 hrs, to start hatching, but required a significantly longer time, 23.8 hrs, to complete hatching, compared with parthenogenetic blastocysts. Hatching patterns of fertilized blastocysts were consistent with those of parthenogenetic blastocysts, except that hatching began with protrusion of trophectoderm cells from small holes in zonae pellucidae of fertilized blastocysts. From these results, it was confirmed that the developmental ability of early diploid parthenogenetic embryos prepared by the treatment with ethanol and cytochalasin B is comparable to that in fertilized embryos.

“…It has been also confirmed that parthenogenetic mouse embryos develop only until 13.5 days of pregnancy when transplanted [20]. Although the reason for such a low potential of development in parthenogenones remains unclear, ultrastructural disorder [1][2][3], low metabolic activity [5][6][7][8], delay of cell division [18,19] and lack of paternal genome imprinting [20][21][22][23][24] are supposed.…”

Section: Discussionmentioning

confidence: 99%

“…In parthenogenetic embryos, the metabolism of glucose [5], pyruvate [5] and nucleic acid [6], and protein synthesis [7] have been studied in the mouse, and the metabolism or synthesis of these substances has been found to be low, compared with that of fertilized embryos. It has also been reported histochemically that the ability of digestion and of interconversion between carbohydrate and lipid are lower in parthenogenetic mouse blastocysts than in blastocysts developed from fertilized ova [8].…”

Section: -Research Note-mentioning

confidence: 99%

“…It has also been reported histochemically that the ability of digestion and of interconversion between carbohydrate and lipid are lower in parthenogenetic mouse blastocysts than in blastocysts developed from fertilized ova [8]. Thus, such low metabolic activities in parthenogenetic embryos are thought to be a reason for lower potentials of development in these embryos [5][6][7][8]. However, there have been no reports in which the metabolism of substances, other than is stated that the proportion of nucleolonema in the nucleolus in these embryos is higher than that in fertilized embryos, and parthenogenetic embryos have many mitochondria with vacuolated cristae, but very few cytoplasmic organelles, such as Golgi apparatus, lysosomes and ribosomes.…”

mentioning

confidence: 99%

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A Histochemical Study of the Steroid Metabolism in Parthenogenetic Mouse Blastocysts.

Journal of Reproduction and Development

Asami

1997

Abstract. The activities of hydroxysteroid dehydrogenases (HSDs) and adenylate cyclase in parthenogenetic mouse blastocysts derived from the ova activated and diploidized by the treatment of ethanol and cytochalasin B were histochemically examined, and were compared with those in control blastocysts developed from fertilized ova. Although the activities of ∆ 5 -3β-HSD with DHA and 17α-hydroxypregnenolone as the substrates, 17β-HSD with testosterone, 20α-HSD and 20β-HSD did not differ between parthenogenetic and control blastocysts, the activities of ∆ 5 -3β-HSD with pregnenolone as the substrate, 17β-HSD with estradiol-17β and adenylate cyclase were significantly lower in parthenogenetic blastocysts. These results suggest that the metabolism of 17α-hydroxyprogesterone, 20α-hydroxyprogesterone, 20β-hydroxyprogesterone and androgen in parthenogenetic blastocysts is comparable to that in control blastocysts, whereas the metabolism of progesterone, estrogen and cyclic AMP in parthenogenetic blastocysts is low compared with that in control blastocysts. When parthenogenetic blastocysts were treated with hCG, the activities of ∆ 5 -3β-HSD with pregnenolone as the substrate and 17β-HSD with estradiol-17β were stimulated, but were still lower than those of control blastocysts. The low potential of development in parthenogenetic embryos was discussed in relation to their steroid metabolism. [7] have been studied in the mouse, and the metabolism or synthesis of these substances has been found to be low, compared with that of fertilized embryos. It has also been reported histochemically that the ability of digestion and of interconversion between carbohydrate and lipid are lower in parthenogenetic mouse blastocysts than in blastocysts developed from fertilized ova [8]. Thus, such low metabolic activities in parthenogenetic embryos are thought to be a reason for lower potentials of development in these embryos [5][6][7][8]. However, there have been no reports in which the metabolism of substances, other than is stated that the proportion of nucleolonema in the nucleolus in these embryos is higher than that in fertilized embryos, and parthenogenetic embryos have many mitochondria with vacuolated cristae, but very few cytoplasmic organelles, such as Golgi apparatus, lysosomes and ribosomes. It has also been determined in morphological studies of the mouse that the contents of lipid droplets and crystalloids are fewer in parthenogenetic blastocysts than in blastocysts developed from fertilized ova [1,4]. From these results, it has been assumed that the metabolic activity is lower in parthenoge-