Human endometrial fluid kinetics as observed by scanning electron microscopy

Genetic mechanisms of multiciliated cell development: from fate choice to differentiation in zebrafish and other models

Multiciliated cells (MCCS) form bundles of cilia and their activities are essential for the proper development and physiology of many organ systems. Not surprisingly, defects in MCCs have profound consequences and are associated with numerous disease states. Here, we discuss the current understanding of MCC formation, with a special focus on the genetic and molecular mechanisms of MCC fate choice and differentiation. Furthermore, we cast a spotlight on the use of zebrafish to study MCC ontogeny and several recent advances made in understanding MCCs using this vertebrate model to delineate mechanisms of MCC emergence in the developing kidney.

New insights into human endometrial aminopeptidases in both implantation and menstruation

The endometrium cycle involves proliferation of endometrial epithelial cells in preparation for implantation of fertilized ovum. With ovulation, the endometrium secretes nutrients such as peptides and amino acids into the endometrial cavity. The histological evidence of ovulation in normal menstrual cycle includes subnuclear glycogen vacuoles surrounded by placental leucine aminopeptidase (P-LAP) in endometrial epithelial cells. P-LAP is an essentially involved in intracellular trafficking of glucose transporter (GLUT) 4 which is primarily important for glucose uptake in skeletal muscles and fat tissues. On the other hand, glucose influx from blood into endometrial epithelial cells is not mainly mediated by GLUTs, but by coincident appearing progesterone just after ovulation. Progesterone increases permeability of not only plasma membranes, but also lysosomal membranes, and this may be primarily involved in glucose influx. Progesterone also expands the exocytosis in the endometrium after ovulation, and endometrial secretion after ovulation is possibly apocrine and holocrine, which is augmented and exaggerated exocytosis of the lysosomal contents. The endometrial spiral arteries/arterioles are surrounded by endometrial stromal cells which are differentiated into decidual/pre-decidual cells. Decidual cells are devoid of aminopeptidase A (APA), possibly leading to enhancement of Angiotensin-II action in decidual cell area due to loss of its degradation by APA. Angiotensin-II is thought to exert growth-factor-like effects in post-implantation embryos in decidual cells, thereby contributing to implantation. Without implantation, angiotensin-II constricts the endometrial spiral arteries/arterioles to promote menstruation. Thus, P-LAP and APA may be involved in homeostasis in uterus via regulating glucose transport and vasoconstrictive peptides.

The development and functions of multiciliated epithelia

Multiciliated cells are epithelial cells that are in contact with bodily fluids and are required for the proper function of major organs including the brain, the respiratory system and the reproductive tracts. Their multiple motile cilia beat unidirectionally to remove particles of external origin from their surface and/or drive cells or fluids into the lumen of the organs. Multiciliated cells in the brain are produced once, almost exclusively during embryonic development, whereas in respiratory tracts and oviducts they regenerate throughout life. In this Review, we provide a cell-to-organ overview of multiciliated cells and highlight recent studies that have greatly increased our understanding of the mechanisms driving the development and function of these cells in vertebrates. We discuss cell fate determination and differentiation of multiciliated cells, and provide a comprehensive account of their locations and functions in mammals.

Scanning electron microscopy of human preimplantation endometrium in normal and clomiphene/human chorionic gonadotropin-stimulated cycles

Embryo transfer after in vitro fertilization of oocytes obtained from unstimulated or stimulated women is usually carried out earlier than when an embryo developed in vivo reaches the womb. The possible asynchrony between the developmental stage of the embryo and that of the endometrium at transfer might reduce the prospects for implantation; so also might any secondary effect of stimulation. Preimplantation endometrium dated by plasma hormone analyses of 17 beta-estradiol and progesterone in five unstimulated and eight stimulated women was surveyed. Three features were examined, namely, the frequency, distribution, and appearance of ciliated cells, nonciliated cells, and apical protrusion. Wide regional variations were observed, but no continuous or consistent changes or differences were found from ovulation to the time for implantation in unstimulated and stimulated cycles. Therefore, from the morphologic point of view, the surface might be ready to accept a transferred embryo at any time within a range of days after ovulation.

Evidence for a cholinergic secretory innervation of the guinea-pig endometrium

Uterine mucus secretion was studied by measuring carbohydrate release from everted guinea-pig uteri placed in organ baths. Field stimulation of the organ resulted in a significant increase in carbohydrate out-put, this increase was inhibited by tetrodotoxin, scopolamine and previous destruction of the paracervical ganglia. Previous section of the hypogastric nerve reduced the response to field stimulation, while interruption of the costouterine connexion or the pelvic nerve was without overt effect. Stimulation of the hypogastric nerve increased uterine carbohydrate secretion. Pelvic nerve stimulation produced no significant effect. Carbachol increased the carbohydrate secretion to the same extent as did field stimulation. Isoprenaline and methoxamine were without significant effect. It is suggested that certain endometrial cells have a cholinergic sympathetic secretory innervation with pre- and postganglionic fibers running in the hypogastric nerve.

Histochemical and ultrastructural effects of enovid E on the endometrium of the baboon

Endometrium from a group of baboons treated with the oral contraceptive, Enovid E, was studied histologically, histochemically and ultrastructurally, and compared to endometrium from normally cycling animals. All endometria were obtained by transcervical uterine biopsy between 10 and 14 days of the treatment cycle or the normal menstrual cycle. Histologically, no discernible differences between the control and experimental endometria were apparent. While observable differences were not evident between the endometrial alkaline phosphatase and succinate dehydrogenase activities of control and experimental animals, there was an increased acid phosphatase activity in the Enovid E-treated baboon endometrium. Ultrastructurally, the glandular cells of treated animals appeared to be more physiologically advanced than did those from the control endometria. These advances were evident from the prominent Golgi complex, increased development of the endoplasmic reticulum and increases in the size, number and complexity of mitochondria. The functional correlates of these morphological and histochemical observations are discussed and compared to human endometrial studies.

The re-epithelization of endometrium after menstrual desquamation

MATERIALS

Human uteri were removed by vaginal hysterectomy on the first, second and sixth day of the menstrual cycle.

METHOD

Washing, pinning, fixation in glutaraldehyde 2.5%, dehydration in ascending concentration of ethanol, critical point drying with carbon dioxide, sputter coating with gold.

RESULTS

The re-epithelization of the endometrium starts immediatley after the onset of menstrual bleeding due to desquamation of the premenstrual endometrium. The remaining stumps of endometrial glands after the endometrial break-down, proliferate rapidly, forming marginal collars. Up to the sixth day the proliferative process has produced a continuous layer of fusiform cuboideal epithelial cells, which cover the entire endometrial surface of the uterine cavity. The dynamics of epithelial growth can be "seen" in following three subsequent stages of the process and in analyzing the arrangement of the cells around the openings of the endometrial glands. Accordingly ciliogenesis occurs in some surface endometrial cells. The paper gives an inconographic survey of the early proliferative phase, illustrating changes from glandular epithelium to the lining epithelial layer and ciliogenesis in the latter. The new formation of ciliae in endometrial epithelial cells is an unique phenomenon, being influenced by the cyclic endocrine regulation of the endometrial function in human reproduction.