A micro-anatomical model of the distribution of myocardial endomysial collagen

Myocardial connective tissue probably provides passive support for regulating heart tensile strength and stiffness and ultimately for controlling heart mechanics through its endomysial part. However, endomysial collagen micro-arrangement is still a matter of debate. In order to define the fine distribution of left ventricle endomysial collagen, we applied the NaOH-scanning electron microscopy (SEM) maceration method (one of the techniques of choice for studying collagen micro-arrangement) to rabbit heart. Gomori-reticulum staining was used for correlated light microscopy (LM) observations. The SEM-NaOH method allowed isolation of collagen by removing other extracellular matrix components and cells and preserved collagen structure and position. Endomysial collagen appeared arranged in laminae that delimited the lacunae that were left empty by macerated myocytes and small vessels (mostly capillaries). These laminae were formed by reticular fibers, as confirmed by LM observations of Gomorireticulum-stained samples, and were organized in irregularly meshed networks made of thin (single) and thick (composed) filaments. In longitudinal views, collagen laminae extended the entire length of lacunae. In transversal views, the cut surface of the laminae appeared to be made of collagen bundles. These observations provide an updated microanatomical view of endomysial collagen distribution, which integrates previous studies. This model is based on the evidence that collagen laminae enveloped the surface of small vessels and myocytes. Thus, a type of myocyte-myocyte or capillary-myocyte "laminar connection" anchored to the entire cell length here is emphasized, rather than a type of "strut connection" anchored to defined loci, as usually described. This structure explains better how endomysium may provide the necessary support for heart compliance and protection against overstretch.

The human zona pellucida and scanning electron microscopy. Reality or artifacts?

The surface micro-morphology of the zona pellucida (ZP) was investigated in 158 inseminated but unfertilized mature human oocytes derived from assisted reproduction trials (ART) by means of traditional scanning electron microscopy (SEM) techniques (gold coating and conductive staining methods) and saponin-ruthenium red-osmium tetroxide-thiocarbohydrazide method (Sap-RR-Os-TC). The main aspect of the ZP by traditional SEM (122 oocytes) consisted in a porous, net-like structure (97 oocytes), whereas a nearly smooth or compact structure of ZP was detected in 25 oocytes (79.5% vs 20.5%). Using Sap RR-Os-TC method on 36 oocytes, 31 oocytes showed ZP with alternating tight and large meshed networks, whereas 5 oocytes displayed only tight meshed network (86.1% vs 13.9%). Due to our well standardized procedures, to the stabilizing action of the conductive staining on the zona material and similar results obtained with the use of Sap RR-Os-TC method, we confidentially regard the ZP changes, occurring in oocytes of various groups, as genuine features, likely related to their actual maturation status, rather than as artifacts. In addition, we emphasize the concept that a modern view of the ZP surface implies the best evidence of crossing filaments' network. We think that the ZP "spongy" or "compact" appearance is only the result of microfilaments network collapse, not the true three-dimensional (3-D) representation of ZP structure.

Ultrastructural dynamic features of in vitro fertilization in humans

The present study on in vitro fertilization in humans demonstrates that three-dimensional (3-D) fine morphology by high resolution scanning electron microscopy (SEM) combined with parallel light and transmission electron microscopy (TEM) can reveal a number of new cellular detailed findings which cannot be detected with other methods. In this study the following aspects have been investigated in early human embryos. 1. Micro-topographical features of the zona pellucida (ZP), surface blastomeres and polar body. 2. Intracytoplasmic features of mature and healthy oocyte, in vitro fertilized (IVF) oocyte and early embryo development. 3. Comparison of general views of intracytoplasmic sperm injection (ICSI) and conventional IVF (C-IVF) of early embryos. 4. Presence of unusual large tubular smooth endoplasmic reticulum (SER) aggregates in 4, 5, and 6-cell embryos after ICSI. 5. Inside views of 3-D blastocysts such as inner cell mass and trophoblast. To our knowledge, this is the first time that such images are reported by using these techniques.

In vitro fertilized human eggs. An electron microscopic study

This paper describes by scanning and transmission electron microscopy the ultrastructure of the human fertilized egg and its vestments (cumulus oophorus and zona pellucida). Data are reported on the ultrastructure of a. conventional in vitro fertilized eggs (pronuclear eggs and cleaving eggs at two-to-four cell stage); b. eggs at the same developmental stage deriving fro intracytoplasmic sperm injection. The present results showed that: 1. The cumulus-enclosed fertilized egg is a highly dynamic structure in which egg vestments play a crucial role, positively affecting fertilization and healthy embryo development; 2. Intracytoplasmic sperm injection technique does not seem to significantly alter fertilized egg morphology.

Is there a mesonephric cell contribution to the gonadal primordium before sexual differentiation in humans?: An ultrastructural study

Differentiation of the intermediate mesoderm involves a complex series of events that result in the formation of the rudiment of the entire adult renal system, gonads and gonoducts. This work, using light, transmission, and scanning electron microscopy describes in human embryos of different ages, the development and spatiotemporal organization of the mesonephric nephron, and the development of the gonadal primordium, with the purpose of knowing if and how these two blastemas contribute to the origin of the non germinal cell content of the gonad primordium. Our results show that between Carnegie stage 13 and 20, the mesonephric nephrons facing the gonadal area, are separated by a band of mesenchymal tissue from the gonad primordium and they retain their structural integrities at the level of epithelial wall and their basement membrane. The morphological stability of basement membranes of different nephric structures, as well as the mesonephric duct during the period studied, confirm the previous opinion that the mesonephros is functional. During the same period of time, the structural events underlying gonad development show that primordial germ cells (PGCs) first invade the gonadal area, and thereafter interact both with epithelial coelomic cells and mesenchymal cells. Both types of cells surround PGCs, initiating the growth and differentiation of the gonadal primordium. Therefore, a mesonephric cell contribution to the genesis of the somatic cell components of the gonadal primordium should be discarded in humans. The present work emphasizes the need for more research in this field.

Ultrastructural morphodynamics of human Sertoli cells during testicular differentiation

Our study reviews and ultrastructurally characterises human pre-Sertoli cells between the 6th and the 20th week of gestation by means of integrated light microscopy, transmission electron microscopy and high resolution scanning electron microscopy (standard or following ODO maceration). The morphofunctional differentiation of Sertoli cells defines testicular differentiation. These somatic cells are mostly of mesonephric origin and can be first morphologically recognised in 7 week-old embryos altogether with the formation of testicular cords. The latter organise as primordial germ cells surrounded by pre-Sertoli cells. Due to the great synthetic activity of pre-Sertoli cells the rough endoplasmic reticulum develops. The basal lamina of the cords becomes distinguishable at 7 to 8 weeks of gestation. Both prespermatogonia and pre-Sertoli cells actively proliferate but the latter greatly outnumber prespermatogonia. Many interdigitations and cytoplasmic processes are observed between neighbouring pre-Sertoli cells. Due to cell proliferation a sort of compartmentalisation is established inside the cords in which pre-Sertoli cells tend to localise closer to the basal membrane embracing prespermatogonia with long and thin cytoplasmic processes. One of the main typical features of differentiating pre-Sertoli cells is the irregular nucleus and the prominent nucleolus. When the embryo is 14 to 20 weeks-old pre-Sertoli cells maintain their general morphology whereas the most significant change is the maximum development of Leydig cells. Testicular cords do not show any lumen at all so they cannot be termed "tubules".

Changes of ovarian microvasculature in hCG stimulated rabbits. A scanning electron microscopic study of corrosion casts

The microvasculature of the ovarian cortex was studied by means of scanning electron microscopy of vascular corrosion casts in estrous and hCG stimulated rabbits in order to establish a better understanding of the structural as well as functional vascular changes which accompany the evolution of the luteofollicular complex. According to the various shape and size seven different morphological types of vascular plexuses corresponding respectively to antral follicles (Types 1-2), atretic follicles (Types 3-4), periovulatory follicles (Type 5), growing pseudopregnant corpora lutea (Type 6) and regressing pseudopregnant corpora lutea (Type 7) were identified. Growing to mature cycling type follicles (Types 1-2) showed a gradual enlargement and proliferation of the theca capillaries. These changes, associated with capillary hyper-permeabilization were observed in ovulatory and post-ovulatory follicles (Types 5), after hCG stimulation. The corpus luteum formation (Types 6) was accompanied by additional capillary dilatation, diffuse angiogenetic sprouts and organization of a more conspicuous venous drainage. The regression of the corpus luteum (Type 7) was characterized by the appearance of avascular areas within the glandular tissue and by regression of vascular dilatation. The atretic follicle (Types 3-4) wall showed large interruptions (avascular areas) and focal invasion of the central cavity by newly formed capillaries randomly arranged. The hCG stimulation did not affect consistently the atretic follicle microvasculature. The present observation shows that both thecal capillary vasodilatation and angiogenetic processes support the gradual increase of ovarian blood flow during follicle growth and corpora lutea formation and that microvascular changes of atretic follicles are possibly related to a type of inflammatory reaction since they seem to be a consequence rather than a primary cause of atresia.

Ultrastructure of human Leydig cells at early gonadal embryogenesis

The ultrastructure of human Leydig cells at different stages of the testicular prenatal development is described by means of transmission and scanning electron microscopy. Between 5 and 7 weeks of gestation (w.g.) the interstitial tissue of the gonad is filled with small undifferentiated mesenchymal cells, migrating primordial germ cells and blood vessels. When the embryo is 7 to 8 weeks-old Leydig cells (LC) appear in basically two morphological patterns, light and dark cells. Their most significative feature is the development of the smooth endoplasmic reticulum (SER) as a dense tubulo-vesicular network and the presence of numerous pleomorphic mitochondria with mainly lamellar cristae. At 14 and 16 w.g. the testicular interstitium reaches the maximum development; the cytoplasm of the LC shows a widespread network of anastomosing tubules of the SER and mitochondria with tubular cristae. Fetal LC show a partial cell coat, lack the crystals of Reinke, have few lipid droplets and show no signs of massive cell degeneration, at least until 16 w.g. These ultrastructural modifications in fetal LC are in accordance with the changes in both steroidogenic activity and hCG levels reported by the literature to occur at this stage of development. Junctional complexes were often observed among LC from 7 to 8 w.g. onwards.

Scanning electron microscopy study of the palatine salivary glands of rabbits

The structure of the palatine salivary glands of rabbits was studied employing scanning electron microscopic methods. The fractured surface of the palatine salivary glands revealed that they were formed of small lobuli separated by interlobular spaces containing numerous bundles of collagen fibers. The NaOH treated specimens showed the organization of the collagen fibrils in their original location. In the interstitial stroma compartment, the collagen fibrils revealed a complex three-dimensional arrangement forming channel-like structures for supporting nerve fibers, small vessels and capillaries. Single groups of acinar cells were clearly demonstrated, and each acinus was enveloped by a characteristic basal lamina showing a sponge-like structure made up of several interconnected meshes of collagen fibrils. Furthermore, taking advantage of the ODO method and field emission scanning electron microscopy, within the cytoplasm of secretory acinar cells numerous organelles were clearly observed in a three-dimensional way such as Golgi complex lamellae, rough endoplasmic reticulum, mitochondria and secretory granules. All these cytoplasmic components revealed their real and microtopographical arrangement in some areas of the acinar cytoplasm clearly suggesting their direct involvement in energetic as well as secretory activities.

Egg-sperm interactions in humans: ultrastructural aspects

A large cumulus mass usually covers the human ovulated oocyte, and voluminous clusters of cumulus cells are still seen after fertilization around the egg. Cumulus cells surround oocytes and fertilized eggs also during in vitro fertilization (IVF) procedures. This study describes, by transmission and scanning electron microscopy, the morphology and the microtopography of the cells forming the human cumulus mass surrounding IVF samples (insemined but not fertilized oocytes and fertilized eggs). Particularly emphasized is their morphodynamic role in sperm-egg interactions. A comparison with the behavior in vivo of cumulus-enclosed oocyte/fertilized eggs has been also performed. All patients have given their informed consent to participate in this protocol. An inner layer (corona radiata cells) and an outer layer (proper cumulus cells) can be microtopographically recognized in the cumulus mass. Numerous cumulus-corona cells, particularly after fertilization, showed ultrastructural characteristics typical for steroid synthetic cells, thus undergoing a sort of "luteinization" parallel to that occurring in the sister granulosa cells of the postovulatory follicle. This steroid synthetic activity, particularly enhanced in vitro but present also in vivo, may be finalized to the release of small amount of steroids (estrogens and progesterone) in the oocyte/fertilized egg milieu. Various proteins, secreted by other cell subpopulations--as revealed in other studies by our research group--, may even enrich this milieu. Lymphocytes and macrophages were often found in the cumulus mass. They may modulate the steroid secretion of the neighboring cumulus cells by production of cytokines, mimicking what occurs in the ovarian follicle and, later, in the corpus luteum. Spermatozoa, both normal (acrosome-intact or--reacted) and abnormal, were frequently seen in the cumulus mass, free in the intercellular spaces or close to the cumulus cells, that can induce sperm capacitation and acrosome reaction. Leukocytes and cumuluscorona cells appeared both capable of actively phagocytizing supernumerary and/or abnormal sperms. Such spermiophagic response is present in a lesser extent around oocytes and eggs fertilized in vivo. In vitro, instead, cumulus spermiophagy leads to the elimination of a large part of the excess spermatozoa that have reached the oocyte, thus restoring in an extracorporeal medium the spermiophagic activity physiologically exerted by leukocytes and epithelial cells in the female and male genital tracts. In conclusion, the cumulus mass surrounding oocytes and fertilized eggs appears as a highly dynamic system, in which various subpopulations of cells cooperate in order to provide a suitable and healthy microenvironment for fertilization and early embryo development.

The microvasculature of the corpus luteum in pregnant rabbit. A scanning electron microscopy study of corrosion casts

The vascular network of pregnant rabbit ovaries was studied by means of scanning electron microscopy (SEM) of corrosion casts, in order to evaluate the morphofunctional changes of the microcirculation of corpus luteum (CL). Pregnant rabbit ovary showed an overwhelming vascularization. Ovarian hilus displayed an increase in the arterial spirallisation. The arterial spiral pattern was present along the entire vessel course, up to CL tissues. The CL of pregnancy was supplied by wide vascular plexuses (2-5 plexuses were found in each pregnant ovary) whose major axis was about 2 mm. Luteal capillaries showed a tortuous course and were arranged in a three-dimensional, wide and rounded-meshed network. Postcapillary venoconstrictions were present. The venous drainage appeared more developed then the arterial supply. Tight artero-venous contacts in hilar, juxtamedullar and medullar regions of the ovary were observed. These results clearly show that the morphofunctional expression of CL of pregnancy is greatly dependent on its hemodynamic control. In particular, the increase of spirallisation exhibited by the arteries during pregnancy is likely to be considered a significant functional change. The spirallisation likely is a device for reducing the blood pressure through the CL. The artero-venous contacts, also previously described in hCG stimulated (pseudopregnant) ovaries, may support a counter-current like system that may allow a veno-arterial exchange of small molecules through the wall of the facing vessels. In addition, in 10-day pregnant rabbit CL the consolidation of a well-developed capillary network was revealed, which is a sign that the CL of pregnancy reached the full morphofunctional maturation. Furthermore, the CL of 10-day pregnant rabbit did not present significant capillary permeabilization and dilation or angiogenic processes, aspects that were previously found in stimulated periovulatory ovaries. Indeed, changes of the arterial supply and venous drainage of the CL of pregnancy were demonstrated. This suggests that the control of the blood flow through the CL of pregnancy may be transferred from the local capillary microcirculation to the regional artero/venous circulation. This may be probably related to the significant increase of the ovarian blood flow necessary for the maintenance of CL endocrine functions during pregnancy.

Morphological and cytochemical study of extracellular matrix during the migratory phase of human and mouse primordial germ cells

Primordial germ cells (PGCs), the ancestors of functional gametes in mammals, originate in an extragonadal location, and then migrate to and colonize the genital ridges during early organogenesis period. PGCs move actively from their original site, the wall of the hindgut, through the extracellular matrix (ECM) of the dorsal mesentery. This movement is controlled in part by components of the ECM. Cells are known to bind to individual ECM glycoproteins in a complex and poorly understood way. During migration in embryos, PGCs must alter their overall adhesiveness to the endodermal epithelium to allow locomotion. This study examined the ECM material of the migratory route during mouse and human PGCs migration. Mouse embryos obtained from Swiss Rockefeller mouse and normal human embryos between 4 and 7 weeks of development, collected during salpingectomy performed on patients with tubal ectopic pregnancies, were analyzed. The study was based on a morphological analysis using scanning electron microscopy (SEM), and on the histochemical and ultracytochemical identification of glycosaminoglycans (GAGs) and proteoglycans. In each age group, the mesenchyme was widely separated by intercellular spaces and materials. Fine filamentous strands extended between the surface of mesenchymal cells and the surface of PGCs. Hyaluronan and chondroitin and/or dermatan sulfate were localized in the ECM of the PGC migratory pathway both in mouse and human embryos. Hyaluronan was clearly reduced in the later stage of the migratory processes; on the contrary, the chondroitin sulfate reaction product increased. These results are consistent with previous observations showing that hyaluronan is a major component of the ECM, and are also suggestive of the significant role played by hyaluronan, chondroitin sulfate and dermatan sulfate during migration, thus providing a permissive substrate for cell migration during development. The observed temporal and regional patterns suggest that these GAGs are important morphogenetic factors both in the mouse and human although the precise biological function of the proteoglycans are not currently clear.

Ultrastructural dynamics of human testicular cords from 6 to 16 weeks of embryonic development. Study by transmission and high resolution scanning electron microscopy

When the embryo is 6-week-old the gonad is composed mostly of migrating primordial germ cells, surface coelomic mesothelium and mesenchymal cells. At 7 weeks of gestation (wg) testicular cords consist of prespermatogonia, larger, with a more regular outline and higher mitotic activity than primordial germ cells, embraced by somatic pre-Sertoli cells. The morphofunctional development of Sertoli cells defines testicular differentiation. Towards 7.5 wg the gonad is finally in its differentiated stage; the basal lamina of the cords becomes distinguishable, testicular cords radially branch and elongate, and Leydig cells are clearly recognized. Primordial germ cells are large and spherical, with rounded and eosinophilic nuclei and large nucleoli. Pre-Sertoli cells, in turn, show round or columnar nuclei and rough endopasmic reticulum. Prespermatogonia and mostly pre-Sertoli cells actively proliferate. Many interdigitations and cytoplasmic processes are observed between neighboring pre-Sertoli cells and between pre-Sertoli cells and prespermatogonia. A sort of com partmentalization is established inside the cords in which pre-Sertoli cells tend to localize closer to the basal membrane embracing the prespermatogonia with long and thin cytoplasmic processes. Between 14 and 16 wg the most significant changes besides maximum development of Leydig cells are differentiation of mesenchymal cells around the cords into future peritubular cells and maturational changes of pre-Sertoli cells. These likely reveal a peak coinciding in time with reported increases in either testosterone production and Müllerian Inhibiting Substance secretion. During the period herein considered testicular cords show no lumen neither any sign of canalization so they cannot be termed "tubules".

The extracellular matrix of normal human placental villi at term: a scanning electron microscopy study

The three-dimensional organisation of the extracellular fibrillar matrix in normal human placental villi at term is investigated by scanning electron microscopic after 2N-NaOH-maceration technique. The latter method consists of a chemical digestion of cellular components of the villi that allows the visualisation of the extracellular fibrillar network in a real three-dimensional fashion by scanning electron microscope. By this approach, the extracellular fibrillar matrix, mainly composed by collagen fibrils, forms a continuous skeleton within the whole villous system of the placenta. This sort of collagenous fibrillar skeleton forms the axis of chorionic villi and connects them with the basal plates. Significant differences in quantity and arrangement of the extracellular matrix are observed at the various levels of the villous ramification. In fact, in the stem villi, the fibrillar extracellular matrix is considerable and the fibres are arranged longitudinally at the villous surface (outer fibrils) and circularly in the inner core of the villous around the wall of the fetal vessels (inner fibrils). On the contrary, in mature intermediate and terminal vili, the extracellular fibrillar matrix is significantly reduced and the fibrils are mainly arranged in a thin circular layer around the capillaries and sinusoids. The present study confirms morphologically the existence of a diverse organization of the extracellular matrix specific for the various levels of the villous ramification as suggested by previous immunohistochemical studies. Moreover, the presence of a highly organized collagenous fibrillar skeleton as observed in our study, stress the important mechanical role of the extracellular matrix in sustaining the chorionic fetal vessels and the trophoblastic layer. Furthermore, the fine reticular-meshed network of this skeleton observed in the terminal villi suggests an additional role of the extracellular matrix to ensure a favorable milieu for active feto-maternal exchanges at this level of the villous tree.

Bifurcation of the left superior pulmonary vein, associated with an anomalous connection with the left atrium

An unusual case of bifurcation of the left superior pulmonary vein (LSPV) just before it enters the pericardium is described. The LSPV, which at the hilus of the lung originated from normal confluence of a superior and inferior root, bifurcated near the left atrium (LAt) of the heart into anterior (AB) and posterior (PB) branches that, separately invaginating the parietal pericardium, formed two individual serous sheaths. The PB coursed almost horizontally and opened, as usual, into the supero-dorsal wall of the LAt. The AB turned downward, reached the superior margin of the left auricle (LAu) and emptied into it. Thus, the AB was interposed between the pulmonary trunk and the LAt obstructing on the left side the communication between the transverse sinus of the pericardium and the pericardial cavity. The auricular opening of the AB was avalvular, but, unlike those of the normal pulmonary veins (PVs) which are surrounded by a large smooth inner surface, was, except for a narrow smooth-walled zone, close to the pectinate muscles. Moreover, an inferior muscular ridge at the inferior margin of its orifice of entrance into the LAu, separated it from the cavity of the LAt. It is well known that in development the PVs arise from convergence of capillaries belonging to the mediastinal part of the primitive splanchnic plexus and drain this into the systemic (cardinal and vitello-umbilical) veins of the embryo. As a consequence, it might be hypothesized that the AB of the LSPV probably represents a partial remnant either of a pulmonary-cardinal anastomotic mediastinal vein, or of a diverging vessel of the mediastinal plexus from which the PVs originate. In either case the AB became absorbed by the LAu, which, while it was developing on the left side of the primitive truncus arteriosus, drew the AB forward and downward, in the direction of its movement. The influence of such an anomaly of the PVs for altered intracardiac hemodynamics of the oxygenated blood flow has to be emphasized. Furthermore, the particular location of the AB, obstructing the communication between transverse sinus and pericardial cavity, can be a hindrance during cardio-pulmonary surgery.

Extracellular fibrillar matrix architecture of human placental villi at term

The spatial organisation of the extracellular fibrillar matrix of normal human placental villi at term can be directly visualised by scanning electron microscopy after 2N-NaOH maceration technique. By these methods, the extracellular fibrillar matrix of placental villi appears as a continuous network of isolated collagen fibrils and/or small fibrillar bundles interwoven each other. This sort of "collagenous fibrillar skeleton" forms the axis of chorionic villi and connects them with the basal plates running through the whole villous system of the placenta. Significant variations in the spatial arrangement as well as in the quantity of the extracellular matrix is observed at different levels of the villous ramification. Within the stem villi, the fibrillar extracellular matrix are abundant and, whereas the fibrils near the villous surface run parallel to the longitudinal axis of the villous (outer fibrils), those located in the inner core of the villous are arranged circularly around the wall of the fetal vessels (inner fibrils). In mature intermediate and terminal villi, viceversa, the extracellular fibrillar matrix is significandy reduced and the fibrils are mainly organised in a thin circular layer around the capillaries and sinusoids. The present study demonstrated the existence of a diverse spatial architecture of the extracellular matrix that results to be peculiar to the various levels of the ramification of the villous tree. Therefore, these morphological data strongly suggest a "compartmentalisation" of the villous tree as suggested by previous immunohistochemical study. Such a highly organised "collagenous fibrillar skeleton" stresses the important mechanical role of the extracellular matrix in sustaining the chorionic fetal vessels and the trophoblastic layer. Furthermore, the fine reticular-meshed network observed within the terminal villi suggests that at this level an additional role ensuring a favourable milieu for active feto-maternal exchanges may exist.

A new morpho-functional classification of the Fallopian tube based on its three-dimensional myoarchitecture

The recent direct observations, under scanning electron microscopy (SEM), of the three-dimensional architecture of myosalpinx in different mammals allows us classify salpinxes according to the myoarchitecture of their tubo-uterine junction (TUJ) and isthmus segments. Based upon the myoarchitecture of the outer wall of the TUJ we could find barrier-like species (rat and sow), sphincter-like species type a (rabbit and ewe) and sphincter-like species type b (cow and woman). The different architecture of TUJ can be explained by the different nature of the mating process. Based upon the myoarchitecture of the isthmus we could distinguish type 1 (rat) and type 2 (rabbit, ewe, sow, cow and woman) salpinxes. In the latter the close fusion of musculature deriving from the meso (extrinsic musculature) with the musculature of salpinx (intrinsic musculature) suggests the existence of a unique mesosalpinx contractile system. The myosalpinx is mostly made up of a single network of muscular fibers. Such a plexiform structure, owing to the uneven distribution of fibers, rather than producing a series of regular contraction waves, is more likely to generate random contraction waves. The random propagation of muscular network contraction may deform the plexiform wall of the myosalpinx causing the stirring of tubal contents. By such a stirring movement the contact between hormones and nutrients and the eggs or embryos is intensified, thus favoring a correct fertilization and early embryo development. Taken all together, these systematic results probably suggest an additional and rather new function for the musculature of the tube, namely to increase fertility in a large number of species.

Ultrastructure and distribution of interstitial glandular cells and associated elements in human fetal ovaries

In order to understand the fine structure and distribution of the interstitial glandular cells (IGCs) and associated elements in the human fetal ovary, we studied human fetal ovaries at 16 weeks post fertilization (p. f.) by transmission electron microscopy. Semithin sections revealed voluminous typical IGCs usually grouped in clusters, located in the interstitium among the ovigerous cords. Isolated primordial follicles were seen in the cords located close to the interstitium in which IGCs were present. Besides the main ultrastructural characteristics of steroid secreting cells, the IGCs showed lipofuscin granules and stacks of annulate lamellae in their cytoplasm. Fibrocytes, macrophages and mast cells were detected close to the IGCs. In particular, the fibrocytes were located around the IGCs, with which they occasionally formed focal cell contacts. Fibrocytes issued numerous long projections, which, together with collagen fibers, surrounded the clusters of IGCs and small vessels (mainly capillaries), often extending into the intercellular spaces among IGCs. These data indicated that, already at the initiation of folliculogenesis, the IGCs are present numerously in a close association with the ovigerous cords. The morphological aspects of IGCs were comparable to that of fetal testis interstitial (Leydig) cells and hilar cells in adult ovary, and suggest that fetal IGCs may be source of adult ovary hilar cells. In addition, we have here demonstrated for the first time that IGCs are associated with stromal cells whose distribution seems to support IGCs microtopography. Fetal ovarian fibrocytes revealed a structural arrangement similar to that of the "compartmentalizing cells" previously described in the adult testis. Macrophages and mast cells presumably have a role as local modulators of steroid synthesis. Mast cells may also affect fibrocyte organization and vascular permeability. We thus suggest that IGCs and associated cells may form a glandular unit in the human fetal ovary similar to that in the adult testis, and this structure is likely involved in early steroid secretion during gonadal differentiation.

Mitochondrial morphology in human fetal and adult female germ cells

The aim of this study has been to observe, by electron microscopy, the morphological changes affecting mitochondria and associated organelles in the human female germ cell during oogenesis, maturation and fertilization. In the primordial germ cell (PGC), rounded mitochondria with a pale matrix and small vesicular cristae are disposed near the nucleus and significantly increase in number during PGC migration and settlement in the gonadal ridge, where they differentiate into oogonia. In these early stages of mammalian oogenesis, aggregates of mitochondria are typically clustered around or in close relationship with the nuage. In oocytes at early prophase stage, mitochondria proliferate while aligned along the outer surface of the nuclear membrane, contain a more dense matrix than before, and have lamellar cristae. Oocytes of primordial and primary follicles mostly contain round or irregular mitochondria whose matrix has become very light. These mitochondria show typical parallel, arched cristae, and are clustered near the nucleus with other organelles forming the Balbiani's vitelline body. When follicles grow, the mitochondria of the oocytes become even more numerous and are dispersed in the ooplasm. Both paranuclear accumulation and subsequent dispersion of mitochondria in the cytoplasm are likely to be regulated by microtubules. By ovulation, mitochondria are the most prominent organelles in the ooplasm. They form voluminous aggregates with smooth endoplasmic reticulum (SER) tubules and vesicles. These mitochondrial-SER aggregates (M-SER) and the mitochondrial-vesicle complexes (MV) could be involved in the production of a reservoir of substances or membranes anticipating subsequent fertilization and early embryogenesis. Just after fertilization, the mitochondria of the oocyte undergo a further substantial change in size, shape, and microtopography. In the pronuclear zygote, mitochondria concentrate around the pronuclei. During the first embryonic cleavage divisions, round or oval mitochondria with a dense matrix and few arched cristae are gradually replaced by elongated ones with a less dense matrix and numerous transverse cristae. A progressive reduction in size and number of M-SER aggregates and MV complexes also occurs. In summary, oocyte mitochondria show dynamic morphological changes as they increase in number and populate different cell domains within the oocyte. They form complex relationships with other cell organelles, according to the different energetic -metabolic needs of the cell during differentiation, maturation, and fertilization, and are ultimately inherited by the developing embryo, where they eventually assume a more typical somatic cell form.

Human embryo development and pregnancies in an homologous granulosa cell coculture system

PURPOSE

Our purpose was to determine the effects of the coculture of embryos on human granulosa cells (GCs) in patients in the first cycle of IVF-ET treatment and in patients with repeated implantation failures and to investigate the presence of specific proteins in a 48-hr GC conditioned medium and the GC ultrastructural characteristics.

METHODS

Eighteen patients with tubal or idiopathic infertility were enrolled in this study: 7 patients (Trial 1) were in the first cycle of IVF-ET treatment and 11 patients (Trial 2) had repeated implantation failures (one to five). Embryos from each patient were cocultured randomly either on homologous granulosa cells or on a conventional culture medium.

RESULTS

At the end of the coculture period (day 5 or 6), 50% of the embryos (Trial 1) reached the blastocyst stage, with respect to 35% in Trial 2. The pregnancy rate per retrieval was 14.2 and 9%, respectively, in Trial 1 and in Trial 2. Many conditioned media showed proteins of 24-29 kDa. and some of them showed additional proteins of 90 kDa. The ultrastructural analysis of GCs showed healthy, metabolically active, protein-synthesizing, and mostly steroidogenic cells.

CONCLUSIONS

GC cultures improve embryo development but not pregnancy rates both in Trial 1 and in Trial 2.

The fetal development of the human uterine cervix from the 12th to the 31st postmenstrual week as revealed by scanning electron microscopy. Anatomical and clinical correlations

To clarify the differentiation of the human uterine cervix, fetuses of the 12th, 15th, 18th, 20th, 21st, 22nd, and 31st postmenstrual week were studied by Scanning Electron Microscopy. At the 12th week the endocervical epithelium consisted of microvillous cells, often showing single cilia and anlages of tubular glands. At the 15th week the cervical canal was entirely formed and its surface cells appeared columnar. At the 18th week these cells were replaced by flat or slightly raised cells, provided with thin microplicae. At the 20th week the endocervical epithelium appeared pseudostratified with higher, apically-convex and shorter basal cells; glands developed in form of tubular invaginations of the luminal epithelium. At the 21st week in the lower part of the endocervix polymorphic, globose cells with short and stubby microvilli and others elongated, having short microplicae, were observed. These latter likely corresponded to the so-called columnar cells undergoing squamous metaplasia. Among microvillous and/or metaplastic cells, a number of apoptotic cells, as globose elements with a ruffled and invaginated surface, were also noted. At the 22nd week evident plicae palmatae were found, covered by microvillous secreting cells. These showed smooth bulged apices releasing droplets by a "micro-apocrine" mechanism. These features increased at the 31st week, when many droplets were noted also around the mouth of the cervical glands. Only at this phase of development fully ciliated cells were found often contacting secretory material. Mature squamous exfoliating cells with complex microplicae covered an hypertrophied portio vaginalis. The squamous cells extended toward a squamo-columnar junction in form of flat, tongue-like projections. Their tips consisted of immature squamous metaplastic cells, which were endocervical columnar progressively becoming elongated elements, exhibiting short microvilli. The above features are rather similar to those occurring during the adult reproductive age. Therefore, it might be hypothesized that, during pregnancy, a common gestational hormonal background may induce somewhat similar morpho-dynamic processes in the cells and tissues of the fetal reproductive tract mimicking what occurs in the adult female.

Ultrastructural features of bovine cumulus-corona cells surrounding oocytes, zygotes and early embryos

Integrated transmission and scanning electron microscopic (TEM and SEM) techniques have provided the first detailed description of the ultrastructural features of the bovine cumulus-corona (CC) cells surrounding oocytes at the time of final maturation, zygotes and early cleaving embryos (2/4 to 6/8 blastomeres). TEM revealed the presence of rough endoplasmic reticulum and Golgi complexes in the cytoplasm of CC cells surrounding immature, mature and fertilized eggs, and also revealed an increasing amount of smooth endoplasmic reticulation membranes, lipid droplets and mitochondria with villiform and/or tubular cristae in the cytoplasm of CC cells during maturation and fertilization of the oocyte. In addition, a loss of cell-to-cell junctions between CC cells was evident. TEM also demonstrated that a few residual CC cells were still associated with early embryos and that these cells showed rather degenerative or apoptotic patterns, the latter pattern also observed on cells associated with fertilized eggs. SEM revealed that the complex of CC cells of immature oocytes was compact with narrow intercellular spaces, which progressively enlarged in size around mature oocytes. This phenomenon is mostly due to the production of abundant extracellular matrix. Immature CC cell complexes possessed characteristic long and filiform microvilli whereas the surface of CC cells surrounding mature oocytes showed numerous blebs and occasional large cytoplasmic protrusions as well as microvilli. Zygotes and early embryos were covered with a few polyhedral CC cells possessing scarce and short microvilli and a large amount of pleomorphic blebs. This study demonstrated a precocious luteinization occurring in bovine CC cells at ovulation until zygote segmentation, and this process was associated with a progressive apoptotic mechanism that ended in the complete denudation of the zona pellucida covering the early embryo. The presence of CC cells around the maturing oocyte and fertilized egg could have important functions related to the microenvironmental requirements of ovum maturation as well as facilitating activities related to fertilization.

A three-dimensional study of human fetal endocervix with special reference to its epithelium

The development of human fetal cervix has been systematically studied by SEM, obtaining a detailed map of its fine structure, particularly concerning the differentiation and maturation of the endocervical epithelium, including its "eversion" and "squamous metaplasia", normally occurring in postnatal life, but not yet observed in detail by electron microscopy in the fetus. Cervices from spontaneous abortion at 12, 15, 18, 20, 21 and 22 weeks and from intrauterine fetal death (hydrocephalus) at 31 weeks of development have been examined. At 12-15 weeks, as the canalization of the cervix proceeded, the endocervical epithelium consisted of high polyhedral cells, with regularly flattened or concave apices exhibiting scarce microvilli and often single primary cilia. Some narrow intercellular infoldings probably corresponded to primordial tubular glands. At the 18th week the epithelium was made up of a mosaic of flat or slightly raised polygonal cells, whose apical surface showed thin microplicae. At the 20th week a pseudostratified epithelium with many apically convex cells lined the cervical canal and the tubular glands. At 21 and 22 weeks "plicae palmatae" developed, covered by cells, often showing a smooth central area surrounded by microvilli, provided with a primary cilium and swollen by secretory material. This also formed rounded masses on the epithelium. In the lower part of the endocervix some very elongated cells showed short microplicae resulting from fusion of microvilli. At the 31st week secretion increased and its products spreading from the bottom of the glands contacted isolated ciliated cells at their openings and diffusely covered the surface epithelium. Most of the ectocervix exhibited squamous elements, with well-developed labyrinthine microplicae. These cells could overlap each other and also desquamate. The zone of the portio vaginalis around the os of the cervical canal appeared infolded and hypertrophic. Here, an indented squamo-columnar junction between the ectocervical and endocervical epithelium, caused by tongue-like prolongations of squamous epithelium directed toward the endocervix, was found. Their tips consisted of elongated cells, rich only in short microvilli. Our data indicate that the features of the microvillous cells are an expression of a hormone-dependent differentiative process. Thus, their secretion might be stimulated by progesterone. Similarly microplicae on the ectocervical epithelium (a sign of squamous maturation) might be promoted by estrogens. Furthermore, two aspects were significative: 1) the finding--in an early phase only (18th week)--of endocervically-located squamous cells, although devoid of microplicae; and 2) the occurrence--in the latest phase (31st week)--of an indented squamo-columnar junction on the surface of the portio. These features are in agreement with the caudal shift of the squamo-columnar junction near the uterine cavity to the ectocervix after cervico-vaginal demarcation; the squamous metaplasia of this everted endocervical epithelium has been reported by some authors. It is likely that these processes, occurring in fetal life as well as in pregnant women, are related to a common hormonal background, arising from the mother to her fetus.

Functional and ultrastructural evidence of myocardial stunning after acute carbon monoxide poisoning

OBJECTIVE

To study human myocardial ultrastructural changes after carbon monoxide (CO) poisoning inducing reversible cardiac failure.

DESIGN

CASE REPORT

clinical, functional and morphologic findings.

SETTINGS

Public university-affiliated hospital and electron microscopy laboratory.

PATIENT

A 25-yr-old woman with functional evidence of cardiac failure after acute CO poisoning.

INTERVENTIONS

Hyperbaric and intensive care treatment over 10 days. Scintigraphic and cardiac angiography with endomyocardial biopsy.

MEASUREMENTS AND MAIN RESULTS

Scintigraphy with 99mTc hexakis 2-methoxy-2-isobutyl isonitrile (sestaMIBI) showed an uptake defect in the left anterior descending artery territory. The cardiac angiography demonstrated a slight hypokinesis of the superior two thirds of the anterior wall and of the septal region with completely normal coronary angiograms. Electron microscopy of left ventricular biopsies showed slight ultrastructural changes in the myocytes. In addition, large glycogen deposits were mostly associated with swollen mitochondria. The patient was discharged in good clinical condition on day 10.

CONCLUSIONS

Presence of glycogen deposits associated with abnormal mitochondria may be signs of the incapability of myocardial cells in utilizing energy substrata. In the presence of normal myocardial perfusion, our findings are consistent with the presence of a stunned myocardium-like syndrome. Early recognition and treatment of this clinical syndrome allow the prevention of myocardial infarction.

Microanatomy of the female reproductive organs in postmenopause by scanning electron microscopy

The detailed three-dimensional ultrastructural features of the reproductive organs of menopausal and postmenopausal women were studied by means of integrated transmission and scanning electron microscopy (SEM) and reported in a new colored microtopographical fashion. These methods revealed significant alterations in the microanatomy of the various reproductive organs specifically related to the decline of plasma estrogen levels. In particular, the ovary progressively showed characteristic wide areas of loss of epithelium with consequent exposure of the underlying connective tissue. Both endometrial and tubal mucosa demonstrated a gradual but often dramatic decrease in the number of ciliated cells which was more evident in the tube. In addition, the non-ciliated (microvillous secretory) cells of the uterus, including both endocervix and tubal mucosa, became flattened and, in some instances, their apical poles developed unusual wrinkles (microridges or microplicae). The ectocervix and vaginal squamous cells presented a reduction in the number of their microridges and changes in the typical structural organization. These microtopographical results showed that the decline of estrogen during the menopause and postmenopause induces important and complex structural changes of the woman's reproductive system, much more detailed than those revealed to date by the use of only conventional optical and transmission electron microscopy (TEM). The three-dimensional findings offer the opportunity to re-evaluate the classic histopathology of the above aging organs using more refined microtopographical and morphophysiopathological parameters.

Natural history of the female germ cell from its origin to full maturation through prenatal ovarian development

This paper contains a number of sketches concerning the main morphological ultrastructural features of the human female germ cell during the prenatal period. The morphodynamic outline of primordial germ cells has been traced, both in their extraembryonic site of origin and during their migration towards the developing ovary. After gonadal settlement, the intraovarian differentiation of the germ cells into primary oocytes through the stage of oogonia, as well as the dramatic fall in the number of germ cells before birth, is described. The presence of morphofunctionally relevant interactions between the differentiating female gamete and the surrounding somatic microenvironment has also been evaluated and discussed.

Microarchitecture of the cat testis with special reference to Leydig cells: a three-dimensional study by alkali maceration method and scanning electron microscopy

Testes from adult cats were studied by means of parallel transmission and scanning electron microscopy (SEM) after NaOH digestion technique, which selectively removed connective tissues or cells. The testis is covered by a dense fibroconnective tunica albuginea that partially divides the organ in lobules by sending septa into the parenchyma. The lamina propria of the seminiferous tubules consisted of one or two rows of cells. The interstitium was made up of randomly arranged collagen bundles. The most significant feature was the numerous Leydig cells rich in lipid droplets and displaying epithelioid features. Following alkali digestion and SEM these cells showed a cord-like arrangement. The cords were formed by one or two closely apposed cells, in between which some labyrinthine or canalicular-like spaces were left that in some areas opened in wide perivascular spaces. This particular arrangement of Leydig cells and the labyrinthine intercellular spaces is very likely designed to improve cell secretion of hormones, facilitating their transport into the blood, as well as the traffic of fluids and metabolites. The present techniques allowed the visualization of a real three-dimensional testicular microarchitecture and microtopography, not detectable with other methods. Such a study may help to better highlight the testicular morphophysiology.

The architecture of the myosalpinx in the sow as revealed by scanning electron microscopy

OBJECTIVE

To provide a definitive settlement of data on the architecture of myosalpinx in the sow in consideration of controversial data existing in literature.

STUDY-DESIGN

To allow direct visualization of muscular architecture, segments of tube from fifteen sows were investigated by means of scanning electron microscopy after the removal of interstitial connective tissue with NAOH digestion.

RESULTS

In the extramural portion of the tubo-uterine junction, in the isthmus and ampulla, the myosalpinx is mainly constituted by oblique bundles of variable length, which run around the tube and merge into the surrounding musculature, giving origin to a plexiform arrangement. In the ampulla the fibers join in short bundles variously oriented.

CONCLUSION

The three-dimensional architecture of the sow myosalpinx consists of muscular bundles independent of one another which follow multiple spatial arrangements and form a complex network. Such a muscular structure is likely more suitable for stirring rather than pushing the embryo and gametes.

Histology of the exocrine pancreas

The morphology of the exocrine secretory unit of the pancreas, i.e. the pancreatic acinus, is reviewed. The histological features of the acini and their relation with the duct system are described. The acinar three-dimensional architecture was studied by means of different ultrastructural techniques, some of which are complementary. The fine structure and morphodynamics of the acinar cells are also described. In addition, the location of the organelles in specific cytoplasmic domains and their close morphofunctional relationship with the sequential stages of secretion of the digestive enzymes are specially emphasized. Finally, morphological approaches are suggested to achieve a better comprehension of the physiological and pathological pancreatic activities whose morphodynamics need to be further elucidated or are almost totally unknown.

The angioarchitecture of estrous, pseudopregnant and pregnant rabbit ovary as seen by scanning electron microscopy of vascular corrosion casts

Ovarian angioarchitecture was studied by scanning electron microscopy of vascular corrosion casts in estrous, pseudopregnant (stimulated with human chorionic gonadotropin) and pregnant rabbits. In all samples, the proper ovarian branch of the ovarian artery (ramus ovaricus) entered the ovarian hilus near the caudal pole of the organ and ran parallel to the major axis of the hilus. The extraovarian venous drainage was formed by several vessels emptying into a distal large vein. The ramus ovaricus exhibited various degrees of coiling and branched in the medulla. The coiling of the ramus ovaricus and its ramifications were maintained in all samples. A venous meshwork and/or flat vein branches closely enveloped the arterial coils found in the hilus and outer medulla. At this level numerous arteriovenous contacts were demonstrated in all samples. The coiled arteries, prior to entering the ovarian cortex, supplied several small peripheral follicles which were drained by the hilar veins. In the cortex the coiled arteries branched in numerous thin, straight or slightly undulated arterioles which supplied developing estrous follicles and pseudopregnant corpora lutea. The arterioles supplying the pregnant corpora lutea were long, large and tightly spiraled. The venous drainage followed the modifications of the arterial supply. These data demonstrate that ovarian cycle and pregnancy induced significant changes in the cortical vessels, which adapted their structure to the temporary functional needs of the recruited follicles or corpora lutea. Hilar and medullary vessels have permanent structures that may represent morphological devices for (a) a continuous control of the blood flow (spiral arteries) and (b) a local recirculation of endocrine products (arteriovenous contacts) comparable to the "countercurrent mechanism" previously shown to operate in ovaries of other species, but not yet found in rabbits.

The ultrastructure of human reproduction. I. The natural history of the female germ cell: origin, migration and differentiation inside the developing ovary

This presentation, on both printed copy and CD-ROM, summarizes a series of original data on the ultrastructure of human reproduction produced by our research group. In particular, female germ cell behaviour at the time of migration and colonization of the gonad and germ-somatic cell interactions inside the developing ovary are reviewed from a morphodynamic point of view. The results mostly consist of black-and-white transmission and scanning electron microscopy (TEM and SEM) images. Artificially coloured SEM pictures, light microscopy images and drawings have also been selected for iconography to render complex microanatomical details and their morphofunctional relationships more comprehensible. In all, 35 images are presented in this article, each related to a concise text section and accompanied by a self-explaining caption. A list of pertinent references is also provided.

The three-dimensional architecture of the myosalpinx in the cow as revealed by scanning electron microscopy

The three-dimensional architecture of the myosalpinx in the cow has been investigated by means of scanning electron microscopy after removal of interstitial connective tissue with NaOH digestion. In the extramural portion of the tubo-uterine junction, in the isthmus and ampulla, the myosalpinx is made up of oblique bundles of variable orientation and length, which are loosely distributed in the tubo-uterine junction and densely packed in both isthmus and ampulla. These bundles intersect and merge into the surrounding musculature. Our observations demonstrate how myosalpinx consists mainly of bundles of muscular fibers independent one of another, which show a multiple spatial arrangement and form a complex network. Such a muscular architecture is likely more suitable for stirring rather than pushing the embryos and gametes through the tube.

Development of mouse submandibular gland studied by field emission scanning electron microscopy

The ultrastructural organization of mouse submandibular gland from 15 days gestation to 180 days of age was studied by field emission scanning electron microscopy. At 15 days of gestation several groups of acini, intercalated and striated ducts were present. They consisted of numerous pyramidal and/or polyhedral cells with spherical or elongated nuclei and short microvilli. At 3 days after birth different shapes of acinar structures covered by a network of fine collagen bundles were observed. The acinar portions corresponded to the terminal tubules and showed the acinar cells containing immature secretory granules. Fractured specimens of ducts revealed a flat surface with large central nuclei. At 14 days after birth acinar terminal portions possessed a round shape; branches of either intercalated and striated ducts were also observed. Gap junctions and interdigitations were numerous at the base of acinar cells. At 30 days after birth the acinar terminal portions and striated ducts revealed a large number of secretory granules. Acinar cells showed a pyramidal shape and basal nuclei. Freeze-cracked surfaces of the striated ductal cells evidenced also a pyramidal shape. Secretory granules ranged from 0.3 to 1.2 microns in size and were clearly observed by infoldings of the basement membranes. At 90 days after birth the ultrastructural features were more differentiated when compared with the previous ages. The freeze-cracked specimens showed very numerous secretory granules in all acinar and striated ductal cells. The granules occupied almost all the apical region of the cells. The outer surface of the basement membrane of acinar and myoepithelial cells was constituted by a spongy-like material covered by fine collagen fibrils. At 180 days after birth numerous secretory granules were seen either in acinar and ductal cells. A morphofunctional polarization of the cell was finally clearly observed in that the cytoplasmic organelles were concentrated in the basal portion whereas the secretory granules were located in the apical region of the cells.

The three-dimensional architecture of the myosalpinx in the rat (Rattus norvegicus) as revealed by scanning electron microscopy

The three-dimensional (3-D) architecture of myosalpinx in the rat has been investigated by means of scanning electron microscopy after microdissection and removing interstitial connective tissue with 6N NaOH digestion. In the extramural portion of tube-uterine junction the myosalpinx shows circularly arranged fibers originating from the uterus, together with oblique fibers typical for the salpinx, which occur more frequently in the deeper layers. As fibers approach the mucous folds they assume a plexiform arrangement, which is maintained through all tubal segments. In the isthmus surface fibers form wide muscle rings around the elbow of loops, peculiar to the rat tubal morphology. Surface fibers in the ampulla and pre-ampulla have an even circular course. Our 3-D results reveal that the muscular architecture of rat tube is mainly organized in concentric, monolayered shells with a plexiform arrangement tightly fastened together. Functionally, this muscular arrangement seems to be capable of stirring rather than pushing the embryo and gametes. Finally, such a plexiform network might work as a mechanism of "tube locking" in proximity of isthmic loops as well as at the level of the ampullary-isthmic junction.

The three-dimensional architecture of the myosalpinx in the sheep as revealed by scanning electron microscopy

The three-dimensional (3-D) architecture of the myosalpinx in the sheep was studied by scanning electron microscopy after the removal of interstitial connective tissue with NaOH digestion. In the extramural portion of the tubo-uterine junction, the myosalpinx is made up of densely packed, circularly arranged superficial fibers and of innermost loose fiber bundles following an almost longitudinal course. In the isthmus and ampulla, the myosalpinx is constituted by oblique bundles of variable length, which run around the tube and merge into the surrounding musculature, giving rise to a plexiform arrangement. The present 3-D observations demonstrate that the sheep myosalpinx consists mainly of single muscular fibers and more complex bundles which show a multiple spatial arrangement and a plexiform distribution. Such a muscular architecture is more likely suited for stirring rather than pushing the embryos and gametes through the tube.

The collagen skeleton of the cat testis. A scanning electron microscopy study after 2N-NaOH maceration

Testes from adult cats were studied by means of scanning electron microscopy (SEM) after 2N-NaOH maceration method which selectively digests cells and tissue compounds. As seen by this technique, the testis appears covered by a dense fibroconnective tunica albuginea that divides partially the organ by sending septa into the parenchyma. The interstitium is made up by a rich connective tissue composed by randomly-arranged fine collagen bundles that clearly outline the spaces occupied by the seminiferous tubules. The basement membrane of the seminiferous tubules consists in two rough layers of collagen fibers that in some places leave small fenestrations. The three-dimensional arrangement of collagen fibers in the interstitium outlines a system of cavities likely to be lacunar spaces for Leydig cells and vascular imprints. Especially, the above chemical technique followed by deep observations under the SEM allowed a clear and complete view of the real three-dimensional microarchitecture of the connective tissue of the testis. Therefore, the collagen component was revealed to actually form a unique and complex skeleton for the whole organ. This three-dimensional figure closely follows indeed the classical histological compartmentalization of the testis with a better insight of its spatial microtopographical features. Moreover, this structural pattern is also likely to give rise to very fine morphofunctional subcompartmentalization, especially regarding the basement membrane of the seminiferous tubules and the lacunar spaces for Leydig cells including satellite vessels.

Collagen fibrillar skeleton in pregnant rabbit endometrium at term: a SEM study after NaOH maceration

This paper describes the spatial organization of the collagen fibrillar skeleton in pregnant rabbit endometrium at term, employing an alkali/low temperature/maceration technique followed by scanning electron microscopic (SEM) observations. Parallel light microscopic (LM) and transmission electron microscopic (TEM) investigations were made to identify the location and possible changes in the endometrial collagen network. Two different types of NaOH maceration were applied, demonstrating separately: 1) the collagen structures (2N-NaOH maceration removes the cells and basal laminae); and 2) the cellular elements (6N-NaOH maceration removes the collagen fibrils). After 2N-NaOH maceration, the collagen network of the endometrium is seen in a superficial compartment around the glands and a deep compartment situated near the endometrial-myometrial junction. Significant changes are observed only in the superficial compartment. The luminal mucosal surface is characterized by numerous thin projections reducing the uterine cavity which, as a consequence, further appears very irregular and highly convoluted. The subepithelial collagen network is composed of densely packed fibrils with a woven course. It contains many tubular or channel-like invaginations (100-150 microns in width and 200-300 microns in length) where endometrial glands are located. These invaginations, corresponding to the glandular impressions, are extremely dilated, enlarged and variable in shape. The collagen fibrils are arranged concentrically around the glandular orifices without forming bundles. At the bottom of the spaces between the mucosal projections, small fenestrations (4-8 microns in diameter each) are present. They form small groups of about 10-20 in number and are due to the endometrial blood capillaries. The deep compartment of the endometrial collagen network is little altered, preserving its general lamellar arrangement. The changes in the endometrial collagen skeleton are due to a variety of complex mechanical and hormonal stimuli affecting the uterus during pregnancy. These may be significant for correct implantation, placentation and delivery.

Heterogeneous distribution of fibronectin, tenascin-C, and laminin immunoreactive material in the cumulus-corona cells surrounding mature human oocytes from IVF-ET protocols--evidence that they are composed of different subpopulations: an immunohistochemical study using scanning confocal laser and fluorescence microscopy

Monoclonal antibodies and immunofluorescence microscopy, including laser confocal microscopy, were used in this study to point out the production of fibronectin, tenascin-c, and laminin in the cumulus-corona (CC) cells surrounding mature human oocytes from IVF-ET protocols in view of their presumptive importance in the coordination of the processes leading to fertilization and early embryo cleavage, including the final maturation of the ovum, the sperm-egg interaction, and the "complex biochemical dialogue" between the gamete and the oviduct through the tubal luminal environment. One hundred fifty mature oocyte-CC complexes were obtained from IVF-ET protocols and fixed in 4.0% buffered paraformaldehyde. Specimens were incubated with a panel of primary monoclonal antibodies (mabs) recognizing different epitopes of fibronectin, tenascin-c, and laminin and then with fluorescein isothiocyanate-conjugated goat anti-mouse IgG. Observations were made by a scanning confocal microscope (Sarastro 2000) and a photomicroscope (Polyvar, Reichert-Jung) equipped with epifluorescence optics. The immunohistochemical data demonstrated that human CC cells are capable of producing fibronectin and tenascin-c but that their production is not homogeneous in the CC population. In fact, fibronectin immunoreactivity was shown mostly by inner CC cells (mainly corona cells), whereas tenascin was produced by some cells scattered in the entire cumulus mass. Moreover, fibronectin and tenascin-c immunoreactive material was observed in the intracytoplasmic areas, at the plasma membrane level as well as in the extracellular matrix. On the contrary, laminin immunofluorescent material was found around plasma membranes of almost all CC cells, but a clear intracytoplasmic reaction was never observed. This leads us to assume that laminin in the extracellular matrix remains entrapped once produced by granulosa follicular cells and that in the postovulatory period no active secretion occurs in CC cells. Even though the functional role of these extracellular matrix proteins remains still unclear, it is reasonable to suggest that they are necessary in various steps of the reproductive process, i.e., from the pick-up of the oocyte, its transport through the oviduct, and fertilization, up until the early cleavage of the embryo. Finally, functional differences between "corona radiata" and "cumulus" cells during the oocyte denudation may be accounted for particular distribution of these adhesive proteins.

The collagen skeleton of the human umbilical cord at term. A scanning electron microscopy study after 2N-NaOH maceration

The organization of the collagen fibrils in the human umbilical cord at term is directly visualized by means of a scanning electron microscopy cell maceration method. This technique clearly reveals that there is a much more extensive collagen fibrillar architecture within the umbilical cord than that reported in the classical histological descriptions. The Wharton's jelly, in fact, appears as a spongy network of interlacing collagen fibres and small woven bundles apparently arranged at random and forming a continuous soft skeleton that encases the umbilical vessels. The collagen fibrillar network shows the presence of a wide system of interconnected cavities consisting of canalicular-like structures as well as cavernous and perivascular spaces. This system of cavities might play a mechanical role allowing the storing of the ground substance of the jelly and its diffusion during twisting or compression. Furthermore, it may have an important role facilitating the diffusion throughout the jelly of diffused materials (i.e. water and trophic metabolites) either from or to the umbilical vessels and the amniotic cavity, thus overcoming the lace of a proper vasculature with the jelly.

Ultrastructure of human cumulus oophorus: a transmission electron microscopic study on oviductal oocytes and fertilized eggs

The aim of the present study was to assess the heterogeneity of cumulus cells that occurs in human cumuli associated with oviductal oocytes and fertilized eggs. Transmission electron microscopy was used to study the cumulus masses surrounding both unfertilized oocytes and fertilized eggs (a pronuclear and a 4-cell stage) recovered at different intervals after ovulation. The specimens were obtained by flushing the oviducts of normal cycling women who underwent surgical sterilization. The cumuli were expanded due to large and irregular intercellular spaces; small linear gap junctions were seen at cell contacts, whereas annular gap junctions were found only in the cytoplasm of some cells. Both types of junction were less abundant in fertilized specimens. Cells surrounding fertilized eggs projected numerous long, thin microvilli into the intercellular spaces. As a rule, the inner layer of the cumulus mass (corona cells) was composed of cells whose surface was relatively smooth. Cumulus cells showed oval nuclei with one or more nucleoli. The cytoplasm of most cells possessed abundant organelles typical of steroidosynthesis: (i) mitochondria with tubular or villiform cristae; (ii) a well-developed smooth endoplasmic reticulum; and (iii) electron dense lipid droplets often surrounded by a few concentric membranes of smooth endoplasmic reticulum and/or in close contact with microtubules and microfilaments. Microperoxisome-like structures were also present. After fertilization, an enhancement of the steroidosynthetic characteristics occurred in the outer layers of the cumulus mass, but not in the corona cells, which still appeared capable of protidosynthesis. Together, these morphological features support the hypothesis that the cumulus of oviductal oocytes and particularly of fertilized eggs, luteinizes like parietal granulosa cells, generating a steroid hormonal micro-environment in the oviduct which may affect fertilization and zygote segmentation. Cumulus cells showing spermiophagic activity, as well as activated macrophages, leukocytes and red blood cells, were also found in the cumulus mass. The macrophages may play a local role both by phagocytic activity and by modulating the steroid secretion of the neighbouring cumulus cells which occurs in the ovarian follicle and corpus luteum. In conclusion, the cumulus mass surrounding tubal oocytes and fertilized eggs appears to be a heterogeneous and dynamic system, in which the micro-environment for fertilization and early embryo development is provided by diverse cell populations in addition to the oviductal cells.

The three-dimensional organization of the smooth musculature in the ampulla of the human fallopian tube: a new morpho-functional model

The three-dimensional organization of the smooth musculature around the human ampulla is revealed by means of scanning electron microscopy after NaOH maceration and ultrasonic microdissection of the interstitial connective tissue. The muscular wall of the ampulla appears as a continuous network of randomly anastomosed smooth muscle cell bundles that showed a multidirectional arrangement. The smooth muscle cell bundles modify their orientation along their course, intertwine repeatedly with each other and dichotomize, generating new bundles with a different orientation from that at the origin. These results demonstrate that the myosalpinx of the human ampulla is not organized into clear cut longitudinally, circularly or spirally arranged layers, as suggested in previous light microscopy studies. In contrast, the presence of a network of multidirectional smooth muscle cell bundles revealed in this study suggests that there is no morphological evidence for unidirectional peristalsis, and that the musculature is probably structurally designed to stir rather than push the tubal contents. These morphological findings better explain the random pattern of propagation of the contraction waves and the electrical impulses through the smooth musculature of the human ampulla, as postulated in early experimental physiological studies. Further, they suggest a specific function for the ampullar musculature which may not be only strictly related to tubal content transport.

In-vitro effects of cardioplegic solutions on human saphenous vein endothelium--a scanning electron microscopy study

In order to evaluate the effects of potassium cristalloid cardioplegic solutions (CPS) on the endothelial morphology, human saphenous veins were studied by scanning electron microscopy after exposure to three CPS named MKP (magnesium-potassium-procaine cardioplegia), LK (low-potassium cardioplegia), and HKA (high-potassium-albumin cardioplegia) and to their main components. Vein rings, selected from the saphenous veins sampled for graft harvesting in 63 patients undergoing aorto-coronary bypass surgery, were exposed for 30, 60, and 120 minutes to the following buffered solutions: Krebs bicarbonate (as control); MKP cardioplegia; KCl (16.0 mmol/L); MgCl2(2).6H2O (16.0 mmol/L); Procaine (0.05 mmol/L); NaCl (92.5 mmol/L); LK cardioplegia; KCl (10.0 mmol/L); Mannitol (74.3 mmol/L); Glucose (27.7 mmol/L); HKA cardioplegia; KCl (30 mmol/L). Severe endothelial lesions, consisting of diffuse disendothelialization and diffuse signs of endothelial suffering, were induced by KCl (30 and 16 mmol/L) after 60-120 min, and by MKP cardioplegia and KCl (10 mmol/L) after 120 min. Moderate endothelial lesions, characterised by diffuse endothelial surface changes and focal cellular loss, were induced by KCl (30 and 16 mmol/L) after 30 min, MKP cardioplegia and KCl (10 mmol) 30-60 min, LK cardioplegia, HKA cardioplegia, and MgCl2.6H2O after 120 min. Slight endothelial lesions, consisting of diffuse endothelial bulging, or absence of significant endothelial changes, were found in samples otherwise treated. Our findings showed a significant damaging effect of CPS on the human saphenous vein endothelium in-vitro. The endothelial lesions seemed related to the presence of potassium and magnesium, and to prolongation of the time of exposure to the cardioplegic solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

Oocyte follicle cells association during development of human ovarian follicle. A study by high resolution scanning and transmission electron microscopy

Morphodynamics of oocyte follicle cells association during the development of human ovarian follicles were studied by transmission electron microscopy and high resolution scanning electron microscopy including the ODO method. For this study primordial, primary, growing preantral and antral follicles were systematically analysed in a total of 20 adult and fetal (3-8 months and at term) ovaries. In early stages of follicle development (primordial and primary stages) the flattened and/or polyhedral cells, closely associated with the growing oocyte, project an increasing number of microvillous processes. These are in apposition with the oolemma, and form bulbous terminals presenting attachment zones such as zonula adherens, desmosomes and communicating junctions (gap junctions). "Focal contacts" between oolemma, and lateral microvillous extensions of follicle cells were also present. Unusual forms of contact between follicle cell microvilli and oocytes in the early stages of growing primordial and primary follicles were also observed. These consist of long, thin extensions penetrating into the oocyte through deep invaginations of the oolemma. The aid of high resolution SEM of specimens subjected to the ODO method clearly reveals their 3-D arrangement within the ooplasm. They appear as long tortuous microvilli coming very close to the nucleus, and in their course are closely associated with a variety of organelles such as Golgi vesicles, endoplasmic reticulum membranes and nascent forms of smooth endoplasmic reticulum. Using integrated observations by TEM and SEM, there may be as many as 3-5 "intraooplasmic processes" even in only one plane of fracture of an oocyte. Therefore, if the total volume of the oocyte and associated cells is considered, their amounts appear to be higher than previously reported. Thus, they have to be considered as normal devices of deep contact between the ooplasm and associated follicle cell extensions. The presence of such structures within the ooplasm in early developing follicles well coincides with the great increase in volume of the oocyte. Although it is commonly believed that the activation of the growing oocyte may depend on the numerous contacts between the oolemma and follicle cells (mostly via gap junctions), the finding of these additional intraoocytic extensions suggests that they may in someway contribute to the initiation of growth in the human. In fact, these microvilli penetrate deep into the ooplasm, much like a sword in its sheath.(ABSTRACT TRUNCATED AT 400 WORDS)

The structure of the human yolk sac: a scanning and transmission electron microscopic analysis

Human yolk sacs were studied by light, transmission and scanning electron microscopy. Twelve human embryos at Carnegie stages ranging from 13 to 20 (28-49 days of gestation) were used for this research. The series of events which occur in the yolk sac wall during its period of maximum functional activity were recorded. The endodermal epithelium consisted of a single layer of columnar cells which, through cellular proliferation, formed endodermal cords which became cavitated, thereby forming endodermal vesicles. At the peak of yolk sac activity, intercellular spaces became very large and isolated individual endodermal cells. The epithelial cells were characterized by numerous microvilli on their free surface, high pinocytotic activity and by the formation of dense cisternae. Abundant intracellular vesicles fused together to empty their contents into the endodermal vesicles. The luminal surfaces of both intracellular and endodermal vesicles presented microvilli. The endodermal cells were characterized by an abundant granular endoplasmic reticulum, a well-developed Golgi apparatus, numerous mitochondria and glycogen particles. Endodermal vesicles were normally seen opening into the vitelline cavity through an endodermal orifice. The surface of the outer mesothelium was covered by numerous lengthy microvilli which were denser here than in the endodermal layer. A mucus-like material, present on the surface of the mesothelium, showed relatively few alterations during the study period. The mesothelial cells were less rich in organelles and far less active than the endodermal cells. The microanatomy of the endoderm supports the contention that its cells serve as absorptive structures as well as sites of protein synthesis during early embryonic development. Therefore, the endodermal vesicles could function as a pump regulating the fluid volume into the vitelline cavity, thereby avoiding the collapse of the organ due to the absorptive activity of the endodermal cells. Furthermore, mesothelial microvilli together with their mucous material harbor a layer of serous exudate and thus create a lubricated cushion designed to protect the thin mesothelium from frictional damage.