Epithelial kinetics affect Langerhans' cells of mouse vaginal epithelium

Langerhans' cells were found to vary in their morphology and density in the vaginal epithelium of ovariectomized mice stimulated by single daily injections of oestrogen. In ATPase-stained epithelial sheet preparations, Langerhans' cells were small and stellate in dense distribution after ovariectomy produced epithelial atrophy. They became highly dendritic in sparse distribution as epithelial thickness increased with high mitotic activity. Keratinization when prolonged by daily oestrogen injections did not affect their morphology or distribution.     

Diffusion barriers in the vaginal epithelium during the estrous cycle in guinea pigs

Summary In the present study the permeability barriers of the multilayered vaginal epithelium were examined using tracer perfusion techniques, freeze-fracture and thin sectioning. During diestrus and proestrus the upper layers of mucified epithelial cells exhibit tight-junctional belts, which restrict tracer molecules such as lanthanum and horseradish peroxidase. When the highly mucified cells begin to degenerate toward the end of proestrus the underlying epithelium is already keratinized as typical for estrus. The keratinized epithelial cells have a tight-junctional network that joins the basal plasma membranes with the apical membranes of subjacent cells and blocks paracellular diffusion of the tracer molecules. During conversion of the cornified epithelium to a mucified epithelium in metestrus the intercellular space of the epithelium is stained by tracer molecules even though tight-junctional belts can be observed.These results indicate that during cyclic changes of the vaginal epithelium tight junctions can, in general, be considered for the restriction of paracellular diffusion. In metestrus, however, junctions become functionally leaky although they remain morphologically intact.Intercellular lipids, which are normally common in cornified epithelia, are extremely rare and cannot constitute an effective barrier to diffusion in the vagina of the guinea pig. The significance of a strategy that bases the regulation of the permeability on tight junctions rather than on intercellular lipids is discussed.     

Estradiol induces E-cadherin degradation in mouse uterine epithelium during the estrous cycle and early pregnancy

Mouse uterine epithelium is a tissue that undergoes cyclic endocrine-regulated cell dissociation and regeneration. It shows a dramatic cell loss following normal estrus. If pregnancy ensues, cell loss is averted during the first 2.5–3.5 days. However, this is followed by a precipitous loss of basal-lateral cell adhesion and apoptosis in preparation for blastocyst invasion. By comparing epithelia isolated by protease treatment, we show that a reduction of lateral cell adhesion is a primary event in these instances of normal tissue loss. It was readily induced in ovariectomized adult and immature mice by injections of estradiol (E₂), and to some extent also by progesterone (P₄). The reduction of lateral adhesion induced by including ethylene glycol-bis (β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA) in the isolation medium mimicked and was additive to the effect of E₂ injection. However, the E₂ effect was different in not being prevented by adding Ca²⁺. The E₂ effect also was mimicked by the action on isolated epithelium of monoclonal antibody against the calcium-dependent cell adhesion molecule, E-cadherin, suggesting that inactivation of E-cadherin was induced by E₂. In detergent extracts of estrous and metestrous epithelium there was an increase in 80-kDa extracellular domain of E-cadherin relative to the intact 120-kDa molecule. The loss of adhesion between 3.5 and 4.5 days of pregnancy was associated with a loss of both intact membrane-associated 120-kDa E-cadherin and cleavage products. Cleavage of 80-kDa E-cadherin was uniquely induced by E₂ in ovariectomized adult and immature mice; P₄ was without effect. The cleavage of E-cadherin correlated with increased basal accumulation of E-cadherin antigen in estrous and E₂-injected mice and a loss of both basal and lateral antigen at 4.5 days of pregnancy. Only the E-cadherin antigen within junctional complexes appeared unaffected. The data are consistent with the hypothesis that the cyclic and pregnancy-dependent disruption of uterine epithelial integrity are promoted by E₂-dependent modification of E-cadherin, including its extracellular cleavage. © 1996 Wiley-Liss, Inc.     

Langerhans cells phagocytose vaginal epithelial cells undergoing apoptosis during the murine estrous cycle.

Langerhans' cells (LCs) have been studied extensively in the epidermis, where they function as antigen-presenting cells. LCs are also present in the stratified epithelia of the murine vagina and cervix, but their function at these sites is not known. Recent reports noted the association of LCs with vaginal epithelial cells undergoing apoptosis and suggested that LCs might be involved in phagocytosis of dead cells. The present study describes the ultrastructural details of this process. The results demonstrate that LCs in murine vaginal epithelium during late metestrus and early diestrus phagocytose apoptotic epithelial cells and may thereby contribute to the normal turnover of the vaginal epithelium during the estrous cycle.     

Keratinization of rat vaginal epithelium. III. Effect of estradiol on keratinization

Effect of estradiol-17 beta on rat vaginal epithelial cells (VEC) was studied by transmission electron microscopy. During the normal estrous cycle in adult rats keratinization and exfoliation of VEC was observed only in the estrus phase, though tonofilament bundles were seen distributed in the cytoplasm of the VEC during the proestrus and, to a lesser extent, in the diestrus phase. Electron microscope data on adult ovariectomised, immature and neonatally estradiol-primed rats demonstrated keratinization of the VEC within 24 h of injection. Proliferative activity was observed in the basal cells in primed animals. The basal cells remained cuboidal whereas cells of intermediate and luminal layers became flattened. These cells showed irregular profiles and, therefore, enhanced numbers of cellular junctions (desmosomes) were observed compared to control groups. Many tonofilament bundles were seen in the cytoplasm of cells belonging to intermediate and luminal layers in primed animals.     

Apoptosis in endometrium of mouse during estrous cycle

The present study was carried out to evaluate apoptosis in endometrium and to correlate these changes with the circulating levels of estradiol and progesterone in the mouse. Apoptosis was observed in various compartments of mouse uterus i.e. stroma, glandular epithelium and luminal epithelium depending on the stage of cycle. Stromal cell apoptosis was observed during various stages of cyclicity except on estrus day. Luminal epithelial cells showed apoptotic changes during all stages of cyclicity except on diestrus day. During metestrus, apoptosis was observed in glandular and luminal epithelia as well as stromal cells. Steroid antagonists such as tamoxifen and onapristone altered the apoptotic changes in the uterus. The results suggest that epithelial cell apoptosis is regulated by estrogen while stromal cell apoptosis is under the control of progesterone.     

The ultrastructure of the uterine epithelium of the pig during the estrous cycle and early pregnancy

Summary In the compound eye of the moth Antheraea polyphemus, three types of visual pigments were found in extracts from the retina and by microspectrophotometry in situ. The absorption maxima of the receptor pigment P and the metarhodopsin M are at (1) P 520–530 nm, M 480–490 nm; (2) P 460–480 nm, M 530–540 nm; (3) P 330–340 nm, M 460–470 nm. Their localization was investigated by electron microscopy on eyes illuminated with different monochromatic lights. Within the tiered rhabdom, constituted of the rhabdomeres of nine visual cells, the basal cell contains a blue-and the six medial cells have a greenabsorbing pigment. The two distal cells of most ommatidia also have the blue pigment; only in the dorsal region of the eye, these cells contain a UV-absorbing pigment, which constitutes a portion of only 5% of the visual pigment content within the entire retina. The functional significance of this distribution is discussed.     

The rodent estrous cycle: characterization of vaginal cytology and its utility in toxicological studies

While an evaluation of the estrous cycle in laboratory rodents can be a useful measure of the integrity of the hypothalamic-pituitary-ovarian reproductive axis, it can also serve as a way of insuring that animals exhibiting abnormal cycling patterns are disincluded from a study prior to exposure to a test compound. Assessment of vaginal cytology in regularly cycling animals also provides a means to establish a comparable endocrine milieu for animals at necropsy. The procedure for obtaining a vaginal smear is relatively non-invasive and is one to which animals can become readily accustomed. It requires few supplies, and with some experience the assessments can be easily performed in fresh, unstained smears, or in fixed, stained ones. When incorporated as an adjunct to other endpoint measures, a determination of a female's cycling status can contribute important information about the nature of a toxicant insult to the reproductive system. In doing so, it can help to integrate the data into a more comprehensive mechanistic portrait of the effect, and in terms of risk assessment, may provide some indication of a toxicant's impact on human reproductive physiology.     

Lectin histochemistry of mouse vagina during the estrous cycle

Estrous cycle-related histochemical changes in the vaginal epithelium of sexually mature female mice were studied with 30 fluorescein isothiocyanate (FITC)-labeled lectins. On the basis of the staining pattern the lectins were divided into five groups: I, seventeen lectins that reacted with mucinous surface layer of proestrus. This group comprised two subgroups: Ia, seven lectins that reacted exclusively with the mucinous layer, and Ib, ten lectins that reacted with mucinous cells and the underlying squamous epithelium of proestrus; II, two lectins that reacted with squamous epithelium of proestrus only but were unreactive with mucinous cells; III, three lectins that reacted in a phase-specific manner with squamous epithelium; IV, six lectins that showed increased luminal surface reactivity in diestrus and/or metestrus; and V, eleven lectins that were unreactive with vaginal epithelium. These data indicate that the cyclic changes in the morphology of the vaginal epithelium are accompanied by distinct lectin reactivity patterns.     

Ultrastructural changes in the oviductal epithelium of Merino ewes during the estrous cycle

Isthmic and ampullary oviductal epithelia sampled from Merino ewes at days -1, 1, 3, and 10 of the estrous cycle (estrus = day 0) were studied by scanning and transmission electron microscopy after fixation by vascular perfusion. Secretory cells, ciliated cells, and lymphocytelike basal cells were observed in both isthmic and ampullary epithelium at all stages of the estrous cycle studied and their ultrastructural features were analyzed. Synthesis of lamellated secretory granules occurred in the ampullary secretory cells during the follicular and early luteal phases, and their contents were released by exocytosis into the oviductal lumen during the luteal phase. Granule release was associated with nucleated apical protrusion of these cells into the oviductal lumen. No such secretory activity was displayed by isthmic secretory cells even though a few cells contained nonlamellated granules. Apocrine release of apical vesicles and accompanying cytoplasmic material from apical protrusions of ciliated cells occurred in the isthmus around estrus but not in the ampulla. This unexpected feature has not previously been reported in any other mammal. Dendritic basal cells were distinguished in the lower part of the epithelium by their heterochromatic nuclei, electron-lucent cytoplasm, and lack of attachment zones. No migration of basal cells was observed, and their ultrastructural features were similar in the ampulla and isthmus and at all stages of the estrous cycle examined. The function of these lymphocytelike cells in the epithelium is uncertain, but the presence of phagocytic bodies and lysosomes in 20% of them may indicate a phagocytic role.     

The effect of 5-fluorouracil on the mitotic cycle and DNA synthesis in the epithelium of mouse small intestine.

The examinations were performed on 42 mice of the Porton strain. The experimental animals were injected intraperitoneally with the dose of 75 mg of 5-fluorouracil per kg body weight. The first experimental group received injections of [3H]thymidine within 48 hours and the second group within 96 hours of the injection of 5-fluorouracil. Two mice from each group were killed at within 1, 2, 4, 8, 12, 24, and 48 hours of the [3H]thymidine injection. Calculations of the mitotic index and time of duration of individual phases of the mitotic cycle in epithelial cells of the small intestine were based on application of the autoradiographic method. These studies lead to the conclusion that 5-fluorouracil disturbs the course of metabolic processes in the cell, which are also related with the distribution of the genetic material. Histological examinations show that 5-fluorouracil produces profound morphological changes in the intestine, which affect both the intestinal epithelium and the connective tissue stroma. The autoradiographic tests revealed a considerable suppression of the mitotic activity of the epithelium of intestinal crypts. Moreover, it was shown that 5-fluorouracil inhibits the mitotic activity of the intestinal epithelium by diminishing the number of cells capable of entering into mitosis. Nevertheless, by 96 hours following introduction of a single dose of 5-fluorouracil normal morphological structure and mitotic activity of the intestinal wall cells are restored.     

Effect of probe location on changes in vaginal electrical impedance during the porcine estrous cycle

The impedance technique is one of many methods that can be used for noninvasive monitoring of reproductive events occurring in cyclic animals. The influence of the depth of probe insertion on changes in vaginal impedance in sows during the estrous cycle was examined. Sows were checked twice a day for estrus via exposure to a sexually mature boar. The criterion for confirmation of ovulation was an increase in plasma progesterone levels above 4.0 ng/ml 8 and 12 days after the beginning of estrus. The impedance measurements were carried out using a four-terminal method at a distance of 8, 10, 12, 14, 16 and 18 cm from the vulva. In all six locations of the vagina the mean impedance values decreased gradually after weaning (P<0.01), achieved a nadir 1-2 days before estrus and increased during estrus (P<0.01). It was found that the probe location within the vagina and the parity of sows significantly affected the impedance measured by means of a four-terminal method. The study suggests that the causes of impedance fluctuation are not only technical but also include a number of poorly understood biological causes.