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... and mice [25, 29, 30]. Microvillous surface on the matured oocytes may be a prerequisite for sperm penetration, because the actual contribution of the MV to gamete membrane fusion has been presented =-=[33]-=-. Several studies showed that cell-to-cell communications via gap junctions, as well as other junctional complexes, form the major anchorage between the oocyte and cumulus cells during all stages of f...

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...al and ultrastructural observations in this study indicate that when the COC matured in vitro, the disconnection of transzonal cumulus cell projections may occur as a result of cumulus mass expansion =-=[1]-=- and contractions in the ooplasm [11]. After maturation, however, intercumulus projections still remained, and thus, the cumulus-cumulus cell communications were preserved. The oocyte may be firmly he...

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..., which utilized techniques including light and electron microscopy and binding of lectins, antibodies, and a cationic dye, have revealed the apparent heterogeneity of the ZP (see review by Wassarman =-=[31]-=-). It has been suggested that a higher density of lectin, antibody, and ruthenium red binding sites exist in the exterior compared to the interior region of the ZP [27, 31]. Our SEM analysis demonstra...

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... very similar to those observed in those matured in vivo [14]. The surface changes in the porcine cumulus masses are similar to those reported previously in cattle [10–12, 22], mice [23–25], hamsters =-=[13, 25]-=-, and humans [26–28]. Cumulus oophorus mucification seemed to be much greater in the pig COCs than in the bovine and hamster COCs that were examined using a similar protocol [11–13]. The reason for th...

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...[4–6] and to mediate the effects of hormones on the cumulus-oocyte complex (COC) [7]. The proportion of oocytes capable of in vitro maturation (IVM) is lower when cumulus cells are previously removed =-=[8, 9]-=-. The maturation status of the oocyte may be directly influenced via modifications in the mode of interaction be1 Supported by a grant-in-aid for Scientific Research C (10660263) from the Japanese Min...

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...e oocyte and cumulus cells during all stages of follicle development [3, 15, 34– 39]. In the pig, the junctions between the cumulus cell projections and the oocyte are present up to 20–30 h after hCG =-=[40]-=-. The present observations clearly demonstrated threedimensionally that the cumulus cell projections were directed toward and terminated at the oocyte. These transzonal projections appeared as extreme...

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...[4–6] and to mediate the effects of hormones on the cumulus-oocyte complex (COC) [7]. The proportion of oocytes capable of in vitro maturation (IVM) is lower when cumulus cells are previously removed =-=[8, 9]-=-. The maturation status of the oocyte may be directly influenced via modifications in the mode of interaction be1 Supported by a grant-in-aid for Scientific Research C (10660263) from the Japanese Min...

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...ugh the outer surface of the porcine ZP did not change during IVM, the inner surface morphologies were profoundly different before versus after IVM. Similar observations had been made in the human ZP =-=[27]-=-. Several studies, which utilized techniques including light and electron microscopy and binding of lectins, antibodies, and a cationic dye, have revealed the apparent heterogeneity of the ZP (see rev...

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...d less porous than the bovine ZP, which was characterized by a fibrous meshwork structure with many wide mesh holes [11, 12], but the porcine ZP resembled the ZP surface in hamsters [13, 25] and mice =-=[25, 29, 30]-=-. Although the outer surface of the porcine ZP did not change during IVM, the inner surface morphologies were profoundly different before versus after IVM. Similar observations had been made in the hu...

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...g electron microscopy (SEM) analysis was used throughout the study. Furthermore, fluorescence staining was employed to examine the cytoskeleton distribution, and freeze-fractured surface SEM analysis =-=[17]-=- was used to examine ultrastructural changes in the cumulus cell projections and the ZP inner surface during maturation. MATERIALS AND METHODS Preparation and Culture of Oocytes Ovaries were collected...

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...ns of dimethyl sulfoxide (DMSO) for 30 min each in order to prevent ice-crystal damage during freezing [17]. Groups of 20 COCs were embedded in either 7% gelatin [19] or 1% chitosan plus 2.5% gelatin =-=[20]-=- before freezing. Specimens were frozen on a metal plate chilled with LN2 (Eiko Engineering, Tokyo, Japan), cracked into two parts with a razor blade and hammer, and immediately placed in a 50% DMSO s...

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...d less porous than the bovine ZP, which was characterized by a fibrous meshwork structure with many wide mesh holes [11, 12], but the porcine ZP resembled the ZP surface in hamsters [13, 25] and mice =-=[25, 29, 30]-=-. Although the outer surface of the porcine ZP did not change during IVM, the inner surface morphologies were profoundly different before versus after IVM. Similar observations had been made in the hu...

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...d less porous than the bovine ZP, which was characterized by a fibrous meshwork structure with many wide mesh holes [11, 12], but the porcine ZP resembled the ZP surface in hamsters [13, 25] and mice =-=[25, 29, 30]-=-. Although the outer surface of the porcine ZP did not change during IVM, the inner surface morphologies were profoundly different before versus after IVM. Similar observations had been made in the hu...

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... February 2000. Accepted: 11 April 2000. � 2000 by the Society for the Study of Reproduction, Inc. ISSN: 0006-3363. http://www.biolreprod.org 723 tween the oocyte and the surrounding follicular cells =-=[10]-=-. Our previous studies in cattle [11, 12] and hamsters [13] showed that oocyte maturation was accompanied by expansion of the cumulus masses and alterations in the ultrastructure of the oocyte surface...

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...00. � 2000 by the Society for the Study of Reproduction, Inc. ISSN: 0006-3363. http://www.biolreprod.org 723 tween the oocyte and the surrounding follicular cells [10]. Our previous studies in cattle =-=[11, 12]-=- and hamsters [13] showed that oocyte maturation was accompanied by expansion of the cumulus masses and alterations in the ultrastructure of the oocyte surface. These observations suggest that an inti...

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...auge needle fixed to a 10-ml disposable syringe. Groups of 10–15 COCs were washed and transferred to NCSU23 medium supplemented with 10% (v/v) porcine follicular fluid, 10 IU/ml eCG, and 10 IU/ml hCG =-=[18]-=-. The COCs were cultured for 24 h, then incubated in NCSU23 without hormonal supplements until the 44-h time point in an atmosphere of 5% CO2 at 39�C. At 0, 24, 36, and 44 h IVM, oocytes were processe...

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...ion culture. In cattle, it has been recently reported that the oviduct alters the ZP’s digestibility by pronase, thus suggesting the role of oviductal factor(s) with regard to the block to polyspermy =-=[32]-=-. Further studies are needed to clarify the localization and function of the cortical granules during IVM of porcine oocytes as well as the effect(s) of oviductal factors. The observations here sugges...

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...ety for the Study of Reproduction, Inc. ISSN: 0006-3363. http://www.biolreprod.org 723 tween the oocyte and the surrounding follicular cells [10]. Our previous studies in cattle [11, 12] and hamsters =-=[13]-=- showed that oocyte maturation was accompanied by expansion of the cumulus masses and alterations in the ultrastructure of the oocyte surface. These observations suggest that an intimate relationship ...

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...rated, critical-point dried, sputter-coated, and observed by SEM, as described above. Fluorescent Observations Methods for preparing samples for fluorescent observations have been reported previously =-=[21]-=-. Oocytes with or without cumulus cells were fixed in a microtubule stabilization buffer [15] at 37�C for 1 h, washed extensively, and blocked overnight at 4�C in the wash medium (calciumfree DPBS con...

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... and maturation. They are known to supply nutrients [1–3] and/or messenger molecules for the development of the oocyte [4–6] and to mediate the effects of hormones on the cumulus-oocyte complex (COC) =-=[7]-=-. The proportion of oocytes capable of in vitro maturation (IVM) is lower when cumulus cells are previously removed [8, 9]. The maturation status of the oocyte may be directly influenced via modificat...

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...mate relationship exists between the surface characteristics and the maturation status of oocytes in these species. The ultrastructural morphology of porcine oocytes and the surrounding cumulus cells =-=[14]-=- has not been fully investigated during oocyte maturation in vitro or in vivo. Recent studies in cattle have demonstrated that redistribution of cytoskeletal proteins coincided with cumulus expansion ...

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...uring oocyte maturation in vitro or in vivo. Recent studies in cattle have demonstrated that redistribution of cytoskeletal proteins coincided with cumulus expansion during oocyte maturation in vitro =-=[15, 16]-=-. However, the morphological changes in the cellular associations between the oocyte and its investments during oocyte maturation in the pig are poorly understood. Information relating to this would i...

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...uring oocyte maturation in vitro or in vivo. Recent studies in cattle have demonstrated that redistribution of cytoskeletal proteins coincided with cumulus expansion during oocyte maturation in vitro =-=[15, 16]-=-. However, the morphological changes in the cellular associations between the oocyte and its investments during oocyte maturation in the pig are poorly understood. Information relating to this would i...

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...d in 15%, 30%, and 50% aqueous solutions of dimethyl sulfoxide (DMSO) for 30 min each in order to prevent ice-crystal damage during freezing [17]. Groups of 20 COCs were embedded in either 7% gelatin =-=[19]-=- or 1% chitosan plus 2.5% gelatin [20] before freezing. Specimens were frozen on a metal plate chilled with LN2 (Eiko Engineering, Tokyo, Japan), cracked into two parts with a razor blade and hammer, ...

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...secreted by cumulus-corona cells, which may function in cell-cell adhesion, thereby transferring soluble factors from cumulus-corona cells to the oocytes and vice versa (see review by Salustri et al. =-=[44]-=-). Recent studies have pointed out the importance of glycosaminoglycans in ovarian follicles [44]. Their biological functions in ovarian biology remain to be determined. Further studies are needed to ...

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...uring oocyte maturation in vitro or in vivo. Recent studies in cattle have demonstrated that redistribution of cytoskeletal proteins coincided with cumulus expansion during oocyte maturation in vitro =-=[15, 16]-=-. However, the morphological changes in the cellular associations between the oocyte and its investments during oocyte maturation in the pig are poorly understood. Information relating to this would i...