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PubMed1992

Changes in cellular dynamics during the development of the ciliary epithelium.

Eye growth and the formation of the ciliary folds during development depend on the maintenance of normal intraocular pressure. In this study we measured labeling index, packing density, height, and volume of the prospective ciliary epithelial cells during the early development of the eye in chicken embryos. Changes in these values were related to the formation of the ciliary folds and to experimental alterations of intraocular pressure. These variables changed independently in the outer, pigmented layer and the inner, non-pigmented epithelial layer of the ciliary epithelium. The labeling index in the pigmented epithelium declined steadily throughout development. Decreases in cell density and increases in cell height resulted in a four-fold increase in calculated average cell volume in the pigmented epithelium during Hamburger-Hamilton stages 29 and 30, the day before the formation of the ciliary folds. In the non-pigmented epithelium, the labeling index increased abruptly at stage 31, the stage at which ciliary folds begin to form. At the same time there was a three-fold increase in average cell volume. When intraocular pressure was reduced by intubating the eye, the formation of ciliary folds was prevented. Intubation also blocked the increase in labeling index and blunted the increase in cell volume that normally occur in the non-pigmented epithelium at the time of fold formation. In the pigmented epithelium, intubation caused a sustained, three- to six-fold increase in cell volume, but had no effect on labeling index. Based on these data, we suggest that increases in cell number and volume just before and during the formation of ciliary folds contribute to the formation of the ciliary folds.

Animals↗
PubMed1992

Coordinated induction of cell proliferation and syndecan expression in dental mesenchyme by epithelium: evidence for diffusible signals.

Epithelial-mesenchymal interactions induce the expression of syndecan, a cell surface proteoglycan, and tenascin, an extracellular matrix glycoprotein in the mesenchymal component of many organ rudiments including the tooth. Experimental recombination cultures of early dental epithelium and mesenchyme were analysed by double immunostaining to compare the distribution of syndecan, tenascin, and proliferating cells (BrdU incorporation) in the induced dental mesenchyme. After 5-9 hr in culture expression of syndecan and tenascin as well as an increase in BrdU incorporation were evident in the mesenchymal cells adjacent to the epithelium and the positive area enlarged with time. Syndecan and tenascin were colocalized only partially in some explants. The expression of syndecan and tenascin in the recombinants correlates with their stage-dependent expression pattern during early tooth development in vivo (Vainio and Thesleff, 1992). The area of increased cell proliferation in the mesenchyme correlated closely with syndecan expression. In none of the explants was increased BrdU incorporation observed in syndecan negative areas. Epithelium induced also condensation of the mesenchymal cells. Induction and spread of the syndecan-positive zone in the dental mesenchyme required close and continuous contact with the epithelium. The mechanism by which the induction of syndecan expression spreads in the mesenchyme was studied in rat-mouse interspecies recombination cultures, using syndecan antibodies that recognize mouse but not rat syndecan. The rat mesenchyme and epithelium were first cultured in contact for 24 hr. Then the epithelium was removed and freshly dissected, "uninduced" mouse mesenchyme was placed in contact with different aspects of the rat mesenchyme. The rat mesenchymal cells that had located next to the epithelial tissue stimulated syndecan expression in adjacent mouse mesenchyme. The induction potential was gradually lost toward the periphery of the rat mesenchyme. Based on these findings we suggest that diffusible signal molecules mediate the spread of syndecan induction in the mesenchyme and that syndecan plays a role in the regulation of cell proliferation.

Animals↗
PubMed1992

Tropic effects of otic epithelium on cochleo-vestibular ganglion fiber growth in vitro.

Sensory nerve fibers of the cochleo-vestibular ganglion (CVG) innervate the otic epithelium in the early chick embryo by directed growth. To see if the target tissue could exert a tropic influence, we co-cultured CVGs from chick embryos (Hamburger-Hamilton stages 16-30) in a 3D collagen matrix with their normal target epithelium or with other epithelial tissues taken from the same or different stages of development. The pattern of neurite outgrowth and the viability of the CVG after five days in vitro were assessed histologically with a silver method. On the basis of the patterns of neurite outgrowth directed toward the epithelium, the cultures were classified as having slightly, mostly, exclusively, or no directed outgrowth. Of 49 cultures containing otic epithelium, 33 had mostly or exclusively directed growth patterns. This effect did not depend on any particular stage difference between co-cultures or on their viability in vitro. Cultures of non-sensory otic epithelium (endolymphatic duct) also presented directed growth patterns. Co-cultures with ectoderm from forelimb or visceral arch had little, if any, directed growth. The directed growth could not be explained simply as a result of guidance by non-neuronal cells or of the viability of the explants. The results are consistent with the hypothesis that the otic epithelium provides a tropic factor that attracts growing CVG fibers.

Animals↗
PubMed1993

Transcellular labeling by DiI demonstrates the glossopharyngeal innervation of taste buds in the lingual epithelium of the axolotl.

Innervation of the axolotl lingual epithelium by the glossopharyngeal nerve was examined to reveal its sensory target cells. The carbocyanine dye diI was applied to the nerve stump in the tongue fixed with paraformaldehyde. After a diffusion period of several months, the tongues were examined with a conventional epifluorescence microscope and a confocal laser scanning microscope (LSM) in wholemounts or preparations sectioned with a vibratome. Beneath the epithelium the labeled nerve fibers spread horizontally to form a meshwork of fibers, from which fascicles of fibers extended upward perpendicularly to the epithelium to innervate taste buds. Numerous taste buds were labeled by possible transcellular diffusion of diI. At the base of the taste bud, the nerve fibers branched and formed a basal plexus of fine fibers, on which numerous varicosities were seen. One or at most several taste cells were labeled in a taste bud. In the basal part of taste buds, the cell without an apical process, the basal cell, was also labeled. In the epithelium, between the taste buds, a few solitary cells were labeled. In some cases, a single fascicle of fibers innervating these cells was clearly shown by the LSM. In addition, fine fibers apparently formed free nerve endings in the epithelial cell layer. The results showed that the IX nerve innervated not only taste cells, but also presumed mechanosensory basal cells in the taste bud and the solitary cells of unknown function in the non-taste lingual epithelium. Afferent nerve responses to mechanical stimulation of the tongue may be explained by these non-taste cellular elements in the epithelium.

Ambystoma mexicanum↗
PubMed2001

Atypical squamous epithelium in cytologic specimens from the pancreas: cytological differential diagnosis and clinical implications.

Atypical squamous epithelium is an uncommon finding in cytologic specimens obtained from pancreatic lesions. A variety of pathologic conditions can result in the presence of these cells, including primary or metastatic carcinomas, chronic pancreatitis, and squamous metaplasia related to pancreatic or biliary duct stent placement. Primary adenosquamous and squamous-cell carcinomas of the pancreas are rare, representing 3.4% and 1.4 % of pancreatic carcinomas, respectively. Cytologic separation of these malignancies from less ominous metaplasias has immense clinical importance. We reviewed Indiana University Hospital's and Duke University's experiences with atypical squamous epithelium occurring within pancreatic aspirates. Study cases were identified using a computer to search the cytology records of these two institutions. Nine cases with a diagnosis of squamous-cell carcinoma, adenosquamous carcinoma, or atypical squamous epithelium were retrieved from the two institutions' Department of Pathology files. One case of pure squamous-cell carcinoma occurred in a patient with a known pulmonary primary; a single case of adenosquamous carcinoma was diagnosed in a patient with a coexistent endometrial primary; a single sample of adenocarcinoma with squamous differentiation was diagnosed in a patient without other known disease; and four primary squamous-cell carcinomas of the pancreas were detected. In addition, a single case of atypical squamous metaplasia associated with a stent was identified, and one case of atypical squamous epithelium associated with chronic pancreatitis was diagnosed. Despite the reactive atypia present in the examples of metaplastic squamous epithelium, separation of these cases from true squamous-cell carcinoma and adenosquamous carcinoma was achievable by cytologic evaluation. No cytologic criteria aided in separating primary pancreatic carcinomas with squamous differentiation from metastatic lesions. In this study, we report our findings in a series of nine cases where cytology disclosed atypical squamous epithelium in the aspirates derived from pancreatic lesions.

Carcinoma, Adenosquamous↗
PubMed1993

Morphological study of the effects of intranasal zinc sulfate irrigation on the mouse olfactory epithelium and olfactory bulb.

The effects of intranasal zinc sulfate (ZnSO4) irrigation on the morphology of the olfactory epithelium and olfactory bulb were studied in mice with short survival times (as early as 1 day) and with long survival times (up to 593 days) after the irrigation procedure. As in several previous studies, the olfactory epithelium was completely destroyed within a few days after the ZnSO4 treatment. Within 2-4 days, the septum and turbinates were covered by a new, cuboidal epithelium, the cells of which differed significantly from any cells normally seen in the olfactory epithelium. Slowly, over several months, small areas of the olfactory epithelium regenerated in many of the animals. The ultrastructural changes occurring in the olfactory bulb from 1 to 25 days (the reactive stage) were characterized by degenerating olfactory axons and axon terminals, hypertrophy of astroglial cell processes, and proliferation of or extravasation by phagocytic cells. By 25 days after intranasal ZnSO4 irrigation, the number of reactive glial processes and phagocytic cells returned to normal. In some mice with survival times of 150 days or longer, there was reinnervation of small areas of the olfactory bulb by regenerated olfactory axons. These new olfactory axons innervated only superficial glomeruli or the outer portions of deeper glomeruli, but they formed synaptic contacts with mitral/tufted cells and periglomerular cells that did not differ from control animals. These findings were supported by tract-tracing experiments with 3H-amino acids and by behavioral analysis. In summary, the ultrastructural changes observed in the olfactory bulb in this study were not significantly different from those observed after surgical lesions of the olfactory epithelium or nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Intranasal↗
PubMed1995

Morphological studies of the developing human esophageal epithelium.

This article focusses on the structural development of human esophageal ciliated epithelium. A combination of transmission electron microscopic (TEM), scanning electron microscopic (SEM), radioautographic, and light microscopic (LM) analyses were carried out using intact fetal tissues between 8 and 20 weeks of gestation as well as cultured esophageal explants. Up to the age of 10 weeks, the stratified esophageal epithelium consisted of two longitudinal primary folds. The surface cells were undifferentiated and contained large glycogen aggregates. Between 11 and 16 weeks, the primary folds (now up to four) had developed secondary folds. The thickness of the epithelium drastically increased (123%) in concomittance with a differentiation of surface columnar ciliated cells. These highly specialized surface cells exhibited junctional complexes and well-developed organelles with numerous microvilli interspersed among the cilia. Transverse sections revealed the internal structure of the cilia with a consistent pattern of nine doublet microtubules surrounding a central pair of single microtubules. Freeze-fracture studies illustrated the presence of a ciliary necklace composed of 6 ring-like rows of intramembranous particles. They also revealed the structure of ciliary cell tight junctions consisting of up to nine anastomosing strands (P-face) or complementary grooves (E-face). Ultrastructural studies (LM, TEM, SEM) of the esophageal squamous epithelium obtained after 15 days of culture showed that the newly formed epithelium was similar to adult human epithelium. Finally LM and SEM observations established that the esophagogastric junction was not yet well delineated, consisting of a transitional area composed of a mixture of esophageal ciliated cells and gastric columnar mucous cells.

Autoradiography↗
PubMed2006

Structural changes and cell properties of human ovarian surface epithelium in ovarian pathophysiology.

The surface epithelial cells of the ovary, which are modified peritoneal cells, form a single, focally pseudostratified layer. The Müllerian ducts differentiate after invagination of the coelomic mesothelium over the gonadal ridges during the 6th week of embryonic life. On the basis of the embryologically putative Müllerian potential of this epithelium, endometriosis can be explained by coelomic metaplasia from the peritoneum, including ovarian surface epithelium. Some pelvic endometriosis specimens have shown that epithelial cells on the ovary or pelvis are serially changed to endometriotic gland cells. Immunohistochemistry as well as scanning electron microscopy also reinforce the light-microscopical findings. A three-dimensional culture system demonstrated that human ovarian surface epithelial cells exhibited a glandular-stromal structure when they were cocultured with endometrial stromal cells in an estrogen-rich environment. Ovarian carcinomas in the epithelial-stromal category are thought to arise from the surface epithelium and its inclusions. The ovarian surface epithelium is physiologically involved in follicular rupture, oocyte release, and the subsequent repair of follicle wall during reproductive age. Simultaneously, ovulation may cause a loss of integrity of the surface epithelium, followed by accumulation of multiple mutations. The cortical invagination, surface stromal proliferation, and Müllerian differentiation of these cells are likely not to be an early step in the cancer development. However, the inclusion cysts are closely related with carcinogenesis because they are significantly more common in ovaries contralateral to those containing epithelial cancers than in control ovaries. As an in vitro study, ovarian carcinoma cell lines were established from simian virus 40 large T antigen-transformed human surface epithelial cells of the ovary. Further investigations of these cell lines may lead to insights into the preneoplastic and early stages of carcinomas. To clarify the pathogenesis of endometriosis and epithelial ovarian cancer, specifically designed studies of ovarian surface epithelium are required.

Endometriosis↗
PubMed1993

The wound epithelium of regenerating limbs of Pleurodeles waltl and Notophthalmus viridescens: studies with mAbs WE3 and WE4, phalloidin, and DNase 1.

The wound epithelium of regenerating limbs of the American newt, Notophthalmus viridescens (Nv), up-regulates a number of antigens, including those recognized by mAbs WE3 and WE4. In the present study, we show that the WE3 antigen is up-regulated in a similar fashion in the wound epithelium of the European newt, Pleurodeles waltl (Pw). mAb WE3 and WE4 reactivities to secretory/transport body cell types, including integumentary glands, perineurium, endothelium, and conjunctiva, are also similar in these two species of newt. However, mAb WE4 reacts to both the epidermis and wound epithelium in Pw, whereas in Nv, mAb WE4 reacts only to the wound epithelium. Because the WE3 antigen is cytoskeleton-associated and Western blots reveal a 43 kDa species, we compared mAb WE3 reactivity with that of rhodamine-labeled phalloidin, a known actin-binding compound. Phalloidin did not react preferentially to the wound epithelium, conjunctiva, or other cell types strongly reactive to mAb WE3. Pretreatment of sections and tissue extracts with DNAse 1, a protein known to bind to actin, nearly abolished mAb WE3 reactivity in tissue sections and both WE3 and WE4 reactivity in ELISA assays, respectively. The results lead to the hypothesis that the WE3 and WE4 antigens are actin-binding proteins unique to the wound epithelium and other secretory/transport cell types.

Actins↗
PubMed1997

Na+/K+ ATPase in lower airway epithelium from cystic fibrosis and non-cystic-fibrosis lung.

The basolateral Na+/K+ ATPase plays a critical role in sodium reabsorption across airway epithelium. Nasal epithelium shows increased Na+/K+ ATPase activity in cystic fibrosis (CF) but Na+/K+ ATPase has not been characterized in human lung epithelium or compared in CF and normal lung. We measured 3[H] ouabain binding and Na+/K+ ATPase activity in human tracheal epithelium and compared Na/K ATPase activity in bronchial epithelium in CF and control subjects. In tracheal epithelium Na+/K+ ATPase pumps were abundant and of high 3[H] ouabain affinity (Kd 4.7 nM, Bmax 38 pmol/mg) and Na+/K+ ATPase activity was 55 +/- 8 nmol/mg protein/min. Bronchial epithelial Na+/K+ ATPase activity was twofold higher in CF patients than in controls. The increased Na+/K+ ATPase activity may contribute to the increased sodium reabsorption seen in cystic fibrosis.

Adolescent↗
PubMed1997

Light-induced apoptosis: differential timing in the retina and pigment epithelium.

Apoptosis is a genetically regulated form of cell death. Individual cells show condensed nuclear chromatin and cytoplasm, and biochemical analysis reveals fragmentation of the DNA. Ensuing cellular components, apoptotic bodies, are removed by macrophages or neighboring cells. Genes involved in the regulation of apoptosis as well as stimuli and signal transduction systems, are only beginning to be understood in the retina. Therefore, we developed a new in vivo model system for the investigation of events leading to apoptosis in the retina and the pigment epithelium. We induced apoptosis in retinal photoreceptors and the pigment epithelium of albino rats by exposure to 3000 lux of diffuse, cool white fluorescent light for short time periods of up to 120 minutes. Animals were killed at different time intervals during and after light exposure. The eyes were enucleated and the lower central retina was processed for light- and electron microscopy. DNA fragmentation was analysed in situ by TdT-mediated dUTP nick-end labeling (TUNEL) or by gel electrophoresis of total retinal DNA. We observed that the timing of apoptosis in the photoreceptors and pigment epithelium was remarkably different, the pigment epithelium showing a distinct delay of several hours before the onset of apoptosis. In photoreceptors, apoptosis was induced within 90 minutes of light exposure, with the morphological appearance of apoptosis preceding the fragmentation of DNA. In the pigment epithelium, the morphological appearance of apoptosis and DNA fragmentation were coincident. Different regulative mechanisms may lead to apoptotic cell death in the retinal photoreceptors and pigment epithelium. This in vivo model system will allow measurement of dose-responses, a potential spectral dependence and the molecular background of apoptotic mechanisms in the retina.

Animals↗
PubMed1998

The establishment of spermatogenesis in the seminiferous epithelium of the pubertal golden hamster (Mesocricetus auratus).

The present study deals with initial spermatogenesis in the pubertal golden hamster (Mesocricetus auratus), in the course of which both the complex process of germ cell proliferation and differentiation and the cyclic pattern of organization of spermatogenesis are established. Germ cells pass through the complete sequence of spermatogenic differentiation from the A-spermatogonium up to the mature spermatid between days 12 and 38. During this period, germ cell development is already based on the pattern of organization and synchronization characteristic of adult spermatogenesis: 1. Judged by the germ cell types present, each of the successively appearing germ cell associations conforms to one of the adult stages of the seminiferous epithelium (stage conformity of the developmental steps of the pubertal seminiferous epithelium). 2. The overall intratesticular variance of the developmental levels reached in different tubular segments each covers almost exactly one cycle length of spermatogenesis. 3. There is a regular, continuous succession of developmental steps along the longitudinal course of the tubules which, in every single tubule, comprises the interval of one spermatogenic cycle ("wave" of the pubertal seminiferous epithelium). 4. Taken together, the latter two results indicate that the tubules of one given testis are equal to one another with respect to their developmental level, i.e., they develop synchronously. Germ cell propagation follows the clonal mode of proliferation. In quantitative terms, stage-related S-phase indices largely parallel the values of adult spermatogenesis. Both the frequently found germ cell apoptosis and degenerating intrameiotic spermatocytes correspond to degenerative phenomena in the adult seminiferous epithelium with respect to degenerative mode and stage-related occurrence. Germ cell development is closely related to the maturation of both Sertoli cells and Leydig cells. At two developmental phases, localized disturbances of germ cell differentiation occur which are specific to the pubertal period and which correlate with a maturational delay of Sertoli cells and Leydig cells, respectively: 1. Completion of Sertoli cell barrier formation may temporarily follow the initial onset of meiosis in the neighboring germ cells. As a result, mitotically dividing germ cells fall under the influence of a (hitherto hypothetic) "meiotic milieu" and characteristically degenerate (arrested germ cell mitoses). This relationship emphasizes the functional significance of the separation of the two seminiferous compartments and, in addition, heightens the understanding of the necessity of normal termination of Sertoli cell proliferation before germ cells initially enter meiosis. 2. The Leydig cell enzyme 11 beta-HSD, which is known to promote testosterone output, is established several days after the leading spermatids initially reach step 6 of spermiogenesis (which is immediately prior to the particularly testosterone-dependent start of elongation). The resulting selective developmental arrest of round spermatids of steps 6-6/7 between days 26 and 30 leads to a localized, partial desynchronization of the seminiferous epithelium, which can be traced for several days after the above-mentioned maturational delay of Leydig cells has been overcome and which is accompanied by an extensive degenerative disposition of the spermatids involved. The present investigation documents an organizational and synchronizational level of initial spermatogenesis that is similar to the situation in the adult animal. The analysis of temporarily occurring perturbations in the process of establishing the pubertal seminiferous epithelium emphasizes and specifies the close structural and functional relationships between the maturational state of somatic cells and germ cell differentiation.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1990

Epithelium-derived inhibition of [3H]acetylcholine release from the isolated guinea-pig trachea.

To investigate presynaptic, regulatory mechanisms on parasympathetic nerve fibres innervating the airways, the release of newly-synthesized [3H]acetylcholine from the isolated trachea was studied. Reverse phase HPLC followed by liquid scintillation spectrometry was used to separate and quantify the radioactive compounds choline, phosphorylcholine and acetylcholine in the incubation medium and the tissue. During the incubation of the tracheae with [3H]choline a significant synthesis of [3H]acetylcholine (35,000 dpm/preparation) and [3H]phosphorylcholine (500,000 dpm/preparation) occurred. In epithelium-deficient tracheae the formation of [3H]phosphorylcholine was enhanced, whereas the content of [3H]acetylcholine remained unchanged. The spontaneous outflow of tritium consisted mainly of [3H]phosphorylcholine (900 dpm/3 min) and [3H]choline (800 dpm/3 min); [3H]acetylcholine was only a minor fraction (50 dpm/3 min). Electrical stimulation of tracheae with intact epithelium caused only a small release of [3H]acetylcholine (460 dpm in the sample obtained during stimulation), but a considerable outflow of [3H]phosphorylcholine (1,900 dpm) without affecting the outflow of [3H]choline. Electrical stimulation of epithelium-deficient tracheae, however, induced a substantial release of [3H]acetylcholine (2,400 dpm), but only a small outflow of [3H]phosphorylcholine. Chemical stimulation (30 mumol/l veratridine) also caused a large release of [3H]acetylcholine (1,700 dpm) without affecting the outflow of [3H]phosphorylcholine or [3H]choline. Indomethacin (3 mumol/l) enhanced the electrically-evoked release of [3H]acetylcholine from tracheae with intact epithelium by 89%. The present experiments demonstrate a strong inhibition by the epithelium of the electrically-evoked release of [3H]acetylcholine from the isolated guinea-pig trachea. Cyclooxygenase products of arachidonic acid do not appear as the main mediators of the epithelium-derived inhibition of acetylcholine release.

Acetylcholine↗
PubMedDate not supplied

The effect of thiorphan and epithelium removal on contractions and tachykinin release produced by activation of capsaicin-sensitive afferents in the guinea-pig isolated bronchus.

(1) We have studied the effect of epithelium removal (rubbing) and the endopeptidase 24.11 inhibitor, thiorphan, on the contractile response of the guinea-pig isolated bronchi (atropine and indomethacin in the bath) produced by electrical field stimulation, capsaicin or exogenously administered tachykinins (substance P and neurokinin A). (2) The response to field stimulation, thought to involve release of endogenous tachykinins, was potentiated by thiorphan in both epithelium-free and intact bronchi. However, at low frequencies (1-5 Hz), the effect of thiorphan was more evident in intact preparations. (3) The response to capsaicin was enhanced by both epithelium removal and thiorphan administration. (4) The response to exogenous substance P or neurokinin A was potentiated by thiorphan both in epithelium-free and intact bronchi. (5) Capsaicin (1 microM) evoked a consistent release of substance P-like immunoreactivity (determined by radioimmunoassay) and tachykinin-like immunoreactivity (determined by a novel immunoenzyme assay), which was enhanced by thiorphan in both epithelium-free and intact bronchi. (6) These findings suggest that a thiorphan-sensitive mechanism, presumably 'enkephalinase' (endopeptidase 24.11), plays a major role in inactivating endogenous tachykinins released from sensory nerves and that this enzymatic activity is still present after removal of the bronchial epithelium.

Animals↗
PubMed1985

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

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.

Animals↗
PubMed1978

Morphological changes in the esophageal epithelium of the eel, Anguilla japonica, during adaptation to seawater.

The esophageal epithelium of the Japanese eel, Anguilla japonica, was studied by light and electron microscopy. In freshwater-adapted eels, longitudinal folds of the mucosal surface are simple in form and lined by a stratified epithelium composed of mucous cells, filament- and ribosome-rich cells. Mucous cells are numerous. The filament-rich cells form the outermost and the basal layers of the stratified epithelium and are scattered in the middle zone among the mucous cells. They are firmly bound to one another by many desmosomes and prominent interdigitations of plasma membrane. The distal free surface of the filament-rich cell has a fingerprint-like pattern of microridges. A small number of columnar cells occur at the apices of the folds. They are rich in mitochondria and their distal surfaces bear short microvilli. In seawater-adapted eels, irregularly meandering folds increase the surface area of the mucosa. The stratified epithelium is extensively replaced by a simple columnar epithelium free of mucous cells. The columnar cells resemble in many respects those found in freshwater-adapted eels. They are rich in mitochondria and their distal free surface were provided with short microvilli. However, prominent lateral intercellular spaces and elaborate interdigitations of cytoplasmic processes in the distal zone distinguish the former from the latter. Results are considered in connection with the changes in ion and water permeability of the epithelium after seawater adaptation.

Adaptation, Physiological↗
PubMed1994

Basement membrane components of bronchial epithelium in humans suffering from chronic nonspecific lung diseases.

Collagen IV and laminin are important constituents of the basement membrane (BM). By use of immunocytochemistry we examined the occurrence and distribution of these two components in the BM beneath normal, mucoid and metaplastic epithelium of large bronchi in 22 adults suffering from chronic nonspecific lung diseases. Both collagen IV and laminin were expressed as a thin and continuous layer beneath the epithelium in most tissue specimens with normal epithelium. In a few specimens the layer showed interruptions with a patchy distribution of the immunoreactivity. Three patterns of distribution of BM components were found under the metaplastic epithelium. Total absence of immunoreactive collagen IV and laminin was the most common variant. Weak and scarce staining for both proteins in the BM characterized the second pattern. The third variant showed strong collagen IV immunoreactivity but lack of laminin. The BM beneath the mucoid epithelium was characterized by irregular distribution of collagen IV and laminin. We suggest that the occurrence and distributional pattern of the BM components are related to the type of overlying epithelium and connected with an altered synthesis of these components.

Adult↗
PubMed1990

Transfer of carbonic anhydrase-positive particles from the follicle-associated epithelium to lymphocytes of Peyer's patches in foetal sheep and lambs.

Carbonic anhydrase cytochemistry of the ileal Peyer's patch in foetal and neonatal lambs has indicated secretion from the follicle-associated epithelium to the follicles. Reaction for carbonic anhydrase in the follicle-associated epithelium was found in the luminal plasma membrane, in cytoplasmic vesicles, and in vacuoles containing 50-nm membrane-bounded particles that seemed to be shed to the intercellular space. The lateral plasma membrane was negative for carbonic anhydrase, indicating that formation of carbonic anhydrase-positive particles was restricted to vacuoles. Administration of ferritin to ileal loops of sheep foetuses showed ferritin localized in vesicles and vacuoles of the follicle-associated epithelium followed by exocytosis, together with carbonic anhydrase-positive particles, into the indentations of the lateral cell border. The carbonic anhydrase-positive particles seemed to be transported to the centres of lymphoid follicles where many were attached to the plasma membrane of lymphocytes. Carbonic anhydrase-positive particles were also seen in vesicles and sometimes free in the cytoplasm of the lymphocytes or attached to their nuclear envelope. Light microscopically, carbonic anhydrase reactivity of the follicle-associated epithelium was associated with the early formation of the ileal Peyer's patch at about 100 days gestation. At this time the follicle-associated epithelium showed a strong luminal but at most a weak lateral staining. With further foetal development there was a progressive increase in the amount of carbonic anhydrase-positive reaction product in extracellular particles, both along the lateral cell borders of the follicle-associated epithelium and among the lymphocytes of the follicle centres.

Animals↗