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The three-dimensional architecture of the human isthmic myosalpinx is directly visualized by means of scanning electron microscopy after removal of interstitial connective tissue through NaOH maceration and ultrasound microdissection. These investigations show that the myosalpinx is composed of irregularly running bundles of smooth muscle cells, changing their orientation within the myosalpinx and displaying longitudinal, oblique and circular directions. The muscular bundles anastomose and intermingle with other bundles running at different levels in the oviduct wall, and actually give rise to a wide and complex muscular network in which no distinct layers are readily discernible. These morphological data are consistent with the physiological findings that the transport of gametes and embryo in very early stages in the isthmic portion of the oviduct tube is the result of a discontinuous pattern of forward and backward movements. [ABSTRACT FROM AUTHOR]

This study describes and compares the possible effects of vitrification on the ultrastructural morphology of 20 human mature oocytes vitrified using two different supports, cryoleaf (n = 10) and cryoloop (n = 10). Fresh human mature oocytes (n = 15) were used as controls. Fresh and vitrified--warmed oocytes appeared rounded, with a homogeneous cytoplasm, an intact oolemma and a continuous zona pellucida. Sparse microvacuolization was only occasionally detected in fresh and vitrified--warmed oocytes, to the same extent. About 50% of the vitrified oocytes contained atypical, small and slender mitochondria--smooth endoplasmic reticulum aggregates, whereas a non-homogeneous microvillar pattern was observable in only 30% of the oocytes subjected to vitrification, regardless of the support utilized. Cortical granule content appeared generally reduced after vitrification, but cryoleaf-supported oocytes contained more cortical granules than cryoloop-supported oocytes (P < 0.05). Thus good overall preservation and virtual absence of cytoplasmic vacuolization seem to be the most relevant markers of quality in vitrified--warmed oocytes, using either support. In addition, cryoleaf-supported oocytes retained a higher number of cortical granules than cryoloop-supported oocytes. The variety of ultrastructural alterations recorded emphasizes the need for further studies aimed at assessing the actual tolerance of human oocytes to vitrification. [ABSTRACT FROM AUTHOR]

The morphological characteristics of frozen thawed human mature oocytes (n = 12) were studied by light and transmission electron microscopy following cryopreservation using a slow cooling protocol including increasing concentrations of ethylene glycol (0.5-1.5 mol/l) and sucrose 0.2 mol/l in the freezing solution. Fresh human mature oocytes (n = 12) were used as controls. Fresh and frozen--thawed oocytes appeared rounded in section, with a homogeneous cytoplasm, an intact oolemma and a continuous zona pellucida. Disorganization of mitochondria-smooth endoplasmic reticulum aggregates and a decreased complement of microvilli and cortical granules were frequently observable in frozen-thawed oocytes. Increased density of the inner zona pellucida, possibly related to the occurrence of zona 'hardening', was sometimes found associated with a reduced amount of cortical granules. In addition, delamination of the zona pellucida was evident in some frozen--thawed samples. Finally, numerous vacuoles and secondary lysosomes were detected in the ooplasm of most frozen--thawed oocytes. In conclusion, frozen--thawed oocytes treated with ethylene glycol may show a variety of ultrastructural alterations, possibly related, at least in part, to the use of this cryoprotectant. Thus, the ethylene glycol-based protocol of slow cooling herein described does not seem to offer significant advantages in terms of oocyte structural preservation. [ABSTRACT FROM AUTHOR]

Vitrification currently offers interesting perspectives in the field of oocyte cryopreservation, being judged more tolerable than slow cooling by the oocyte. The present study was therefore aimed to investigate the possible effects of vitrification on the fine morphology of human oocytes at different stages of maturation. Immature (at the germinal vesicle -- GV -- stage and after GV breakdown) and mature oocytes were obtained from consenting IVF patients and vitrified according to the Cryotop method, using ethylene glycol and dimethylsulfoxide as cryoprotectants. After warming, the oocytes were fixed with glutaraldehyde and processed for light and transmission electron microscopy (LM and TEM) observations. By LM all vitrified-warmed oocytes appeared rounded in sections, measuring about 90-100 microns in diameter. All the observed oocytes displayed a homogeneous cytoplasm, an intact oolemma and a continuous zona pellucida. By TEM immature oocytes showed characteristic organelles such as dense, rounded mitochondria, isolated smooth endoplasmic reticulum (SER) membranes, dictyosomes belonging to the Golgi system, small mitochondria-vesicle complexes and scattered cortical granules (CGs), the latter found in subplasmalemmal areas or located deeply in the cytoplasm. In some cases, minute vacuoles were also present in the inner cytoplasm, particularly around the nucleus of the GV-stage oocytes. Mature oocytes showed rounded mitochondria with peripheral, arch-like cristae, typical mitochondria-SER aggregates in the cytoplasm and a rim -- often discontinuous -- of CGs just beneath the oolemma. A reduced complement of microvilli was also sporadically found in these oocytes. Isolated vacuoles of different sizes were sometimes detected, mostly in the cortical cytoplasm, irrespective of the maturational stage of the oocyte. In conclusion, the oocytes subjected to the described vitrification method show good overall preservation. However, the presence of alterations in CG and microvillar patterns in mature oocytes, as well as the finding of oocyte vacuolization emphasize the need of further ultrastructural studies on human vitrified oocytes, to confirm the actual safety and efficiency of this method. [ABSTRACT FROM AUTHOR]