Epithelial ultrastructure and the distribution of an estradiol sensitive antigen in the vagina of adult mice

Summary The distribution of an antigenic material specific for the cervicovaginal epithelium (CVA) was studied in the vaginal epithelium of the adult mouse with immunofluorescence and immunoferritin techniques. The antigen localization has been correlated to the fine structure of the vaginal epithelium in various states of functional activity. The antigen distribution in adult ovariectomized mice and in ovariectomized mice treated with estradiol was compared with that in normal cycling mice. CVA was found to be associated with the exterior of the cell membrane of vaginal epithelium cells, being part of the glycocalyx.Two cell types, mucous or keratinized, are derived from the germinative cell layer of the vaginal epithelium, depending on the hormonal environment. Mucous cells with morphological features that characterize cells about to cornify have been demonstrated. Fluorescence as well as ferritin particles, indicating the presence of antigen-antibody complexes, were seen within the mucous droplets of the mucous cells. The CVA production is apparently connected with vaginal mucus formation. The CVA distribution in the adult vaginal epithelium is discussed in relation to the distribution demonstrated earlier in the cervicovaginal epithelium of neonatal mice.This investigation was supported by grants from the Norwegian Cancer Society (Landsforeningen mot Kreft) and the Norwegian Research Council.     

Effects of d-propranolol and estradiol on the cervicovaginal epithelium

Summary The cervicovaginal epithelium of neonatal mice produces a material with specific antigenic properties (CVA) and this material is produced in increased amounts after estradiol treatment. Using a cytochemical method, estradiol treatment was shown to result in an increase of adenylate cyclase activity in the same epithelium.When d-propranolol is injected together with estradiol, the increase in CVA is inhibited, while the hormone-induced proliferation of epithelial cells is not influenced. When adenylate cyclase activity is studied under identical conditions, the estradiol-promoted increase in enzyme activity is largely counteracted by d-propranolol. These findings would suggest that Adenosine 35-cyclic monophosphate (cAMP) has a role in some, but not all, estradiol-mediated effects in the neonatal cervicovaginal epithelium.This work was supported by grants from the Norwegian Research Council for Science and the Humanities and from the Norwegian Cancer Society (Landsforeningen mot Kreft)     

Studies on the differentiation pattern and hormonal sensitivity of an antigenic material specific for the cervicovaginal epithelium in fetal and neonatal mice.

By use of an indirect mixed haemagglutination method for tissue sections, the Müllerian cervicovaginal epithelium of fetal and neonatal mice has been shown to contain a material (CVA) with antigenic properties specific for this epithelium. The method is highly sensitive and permits a semiquantitative estimation of CVA in the epithelium. The studies showed that the cervicovaginal epithelium undergoes a multiphasic differentiation pattern. An estradiol injection 1 day prior to killing the animals strongly increased the amount of demonstrable CVA. The quantitative response to estradiol varied with the age of the animals. Notably, estradiol given as early as the day of birth stimulated CVA accumulation in the vaginal epithelium. Differences between the cervical epithelium and the vaginal epithelium regarding the response to estradiol are described.     

Electron microscopic study of the anterior midgut in Cenocorixa bifida Hung. (Hemiptera: Corixidae) with reference to its secretory function

The epithelium of anterior midgut of adult Cenocorixa bifida was examined with light and electron microscopy. The folded epithelium is composed of tall columnar cells extending to the lumen, differentiating dark and light cells with interdigitating apices and regenerative basal cells in the nidi surrounded by villiform ridges that penetrate deeply into the epithelium. The columnar cells display microvilli at their luminal surface. Microvilli lined intercellular spaces and basal plasma membrane infoldings are associated with mitochondria. These ultrastructural features suggest their role in absorption of electrolytes and nutrients from the midgut lumen. The columnar cells contain large oval nuclei with prominent nucleoli. Their cytoplasm is rich in rough endoplasmic reticulum, Golgi complexes and electron-dense secretory granules indicating that they are also engaged in synthesis of digestive enzymes. The presence of secretory granules in close proximity of the apical plasma membrane suggests the release of secretion is by exocytosis. The presence of degenerating cells containing secretory granules at the luminal surface and the occurance of empty vesicles and cell fragments in the lumen are consistent with the holocrine secretion of digestive enzymes. Apical extrusions of columnar cells filled with fine granular material are most likely formed in response to the lack of food in the midgut. The presence of laminated concretions in the cytoplasm is indicative of storageexcretion of surplus minerals. The peritrophic membrane is absent from the midgut of C. bifida.     

Ultrastractural features of the principal cell in the epididymis of the rhesus monkey

The ultrastructural features of the principal cell in the epididymal epithelium of the monkey epididymis are suggestive of the cell carrying out a dual function of absorption and secretion. Both these functions occur on the luminal surface of the cell as well as on the lateral and basal aspects of the cell which face the intercellular spaces. Transmision Electron Microscopic studies of epididymal tissues following their impregnation with lanthanum nitrate indicated that the intercellular spaces are effectively sealed-off from the luminal space by the apically situated tight junctions between adjoining principal cells. The intercellular spaces are contiguous with the perivascular spaces of the subepithelial blood capillaries. It is suggested that the absorptive and secretory functions occuring on the apical surface of cells may be related to the creation of an appropriate intraluminal milieu for the maturation of spermatozoa while the occurrence of these functions in the intercellular spaces may represent an exchange of substances between the principal cells and the subepithelial capillaries.     

A correlated scanning and transmission electron microscopic study of maturation ameloblasts in developing molar teeth of rats

Summary Maturation ameloblasts of developing molar teeth of the rat were studied by both scanning and transmission electron microscopy. After fixation, teeth were frozen and split. One face of the fractured tooth was used for SEM, the other for TEM.It was found that in some regions proximal junctional complexes separate the interameloblast space from the intercellular space of the papillary layer. Thereby an intercellular ameloblastic compartment is delineated which in some specimens contains a substance interpreted to be colloidal. Elsewhere the proximal junctions of ameloblasts are not present and free communication between the extracellular spaces is evident. The apical pole of ameloblasts varies in structure. Over some areas there is a distinct distal border zone with membranous infoldings which in some regions resembles a striated or ruffled border, but in other regions the membranes show whorl configurations. The distal border zone also contains granules with flocculent material. Elsewhere the ameloblasts display no distal border zone and the cells show a smooth membrane (except for pinocytotic vesicles and hemidesmosomes) facing the enamel surface. The lateral surface of ameloblasts exhibits a variety of surface configurations similar to but not as pronounced as those reported previously in rat incisor maturation ameloblasts.The authors wish to thank Pauletta Sanders and Helen Ruane for technical assistance. This project was supported in part by USPHS NIH Grant DE04059-03 and by the Medical Research Council of Great Britain     

Uptake of horseradish peroxidase from CSF into the choroid plexus of the rat,with special reference to transepithelial transport

Summary Protein uptake from cerebral ventricles into the epithelium of the choroid plexus, and transport across the epithelium were studied ultrastructurally in rats. Horseradish peroxidase (HRP, MW 40,000) was used as protein tracer. Steady-state ventriculo-cisternal perfusion with subatmospheric pressure (-10cm of water) in the ventricular system was applied. HRP dissolved in artificial CSF was perfused from the lateral ventricles to cisterna magna for various times, and ventriculo-cisternal perfusion, vascular perfusion or immersion fixation with a formaldehyde-glutaraldehyde solution was performed.Coated micropinocytic vesicles containing HRP were seen both connected with the apical, lateral and basal epithelial surface and within the cells. Heavily HRP-labeled vesicles were often fused with the lining membrane of slightly labeled or unlabeled intercellular spaces. Since the apical tight junctions of the epithelium never appeared open or never contained HRP in the spaces between the fusion points, and since the intercellular spaces between adjacent epithelial cells below the junctions only infrequently contained tracer after 5 min, by increasing amounts after 15–60 min of HRP perfusion, a vesicular transport of HRP from the apical epithelial surface to the intercellular spaces, bypassing the tight junctions, is suggested.In addition to the transepithelial transport, micropinocytic vesicles also transported HRP to the lysosomal apparatus of the epithelial cells. With increasing length of exposure to HRP, a sequence of HRP-labeled structures could be evaluated, from slightly labeled apical vacuoles and multivesicular bodies to very heavily labeled dense bodies.     

Estradiol-17 β and cAMP: in vitro studies on the cervicovaginal epithelium of neonatal mice

Summary In organ culture of the cervicovaginal epithelium from neonatal mice, the epithelium synthesizes a material with specific antigenic properties (CVA). CVA was studied with immunofluorescence and the amount estimated semiquantitatively. In line with earlier studies, adenosine 3,5-cyclic monophosphate (dibutyryl derivative) (dcAMP), increased the amount of CVA, but adenosine 2,3-cyclic monophosphate did not. Addition of histamine to the culture medium moderately increased the amount of CVA, whereas the antihistamine diphenhydramine (H₁-antagonist) slightly reduced the strong increase induced by dcAMP and estradiol in combination. No effect was seen under similar conditions using the H₂-antagonist metiamide. Taken together with earlier results it is considered possible that the action of histamine and diphenhydramine is related to effects on the cell membranes. Phentolamine had no effect. The dcAMP effect was inhibited by actinomycin D and cycloheximide.This investigation was supported by grants from the Norwegian Research Council for Science and the Humanities     

The mucigenous glandular mucosa in the comples stomach of two new-world camelids, the llama and guanaco

In contrast to the so-called true ruminants, the compartmentalized stomach of these camelids contained an extensive mucigenous glandular mucosa. This mucosal epithelium was studied with the light and electron microscope. Surface, foveolar, isthmic, and end-piece regions were identified. Undifferentiated cells with many free ribosomes and few mucigen granules were found in the gland isthmus. More fully differentiated mucigenous cells with fewer free ribosomes, an extensive Golgi complex and a large heterogeneous population of secretory granules were observed in the subjacent end-piece. These cells were compared with cardiac and other gastric glandular epithelia. The cells in the foveola contained a more extensive granular reticulum, a prominent Golgi complex, and large numbers of mucigen granules and mitochondria. In the upper foveolar cells, large supranuclear and narrow apical accumulations of mucigen granules were separated by an intervening mitochondrial mass. In the tall surface cells there was a diminution in the number of mucigen granules and a concomitant supranuclear massing of mitochondria. Basally, these cells were often separated by prominent intercellular spaces. Effete surface cells were also noted. These lacked desmosomal attachments and sometimes appeared partially extruded. These findings suggested that cells derived from the undifferentiated isthmic cells moved up the foveola and onto the luminal surface. During this migration, these cells appeared to undergo sequential cytologic differentiation. The possible functional significance of these differentiations was considered.     

The interphotoreceptor space. I. Postnatal ontogeny in mice and rats

The postnatal ontogeny of the retinal interphotoreceptor space of mice and rats was studied by electron microscopy to elucidate the cytological developments in the surrounding cells relevant to the accumulation of extracellular glycosaminoglycans and glycoproteins constituting the interphotoreceptor matrix. This extracellular material at birth is principally the cell coat on all the immature cells that border the space at that time, but later additional weblike strands are seen in the space. The cells delimiting the space in the adult are the pigment epithelium (PE), the photoreceptors, and the glial cells of Müller. The Golgi complex of the PE is large at birth but involutes by day 15. Melanogenesis is the principal activity in this cell at birth but as the melanin granules mature, lysosomes gradually accumulate. Growth of the apical microvilli of the PE is most pronounced between day 5 and 15, which is also the time of rapid expansion of the interphotoreceptor space. The Golgi complex of the photoreceptor enlarges during this interval also, and remains voluminous thereafter. Müller's cells insert only slender apical processes lacking in secretory vesicles, into the interphotoreceptor space. All the adult cells have a cell coat on the surfaces facing the interphotoreceptor space. Secretory vesicles were not identified in any of the cells impinging on the space.     

Ultrastructural and Fluorescence Microscopical Characterization of the Intestinal Endocrine Cells in a Cyclostome,Myxine glutinosa

Endocrine cells of so-called basal-granulated-open type in the intestinal epithelium of a cyclostome, the Atlantic hagfish (Myxine glutinosa), are characterized ultrastructurally and fluorescence microscopically. These cells regularly extend from the basal lamina to the gut lumen, ending in an apical process with microvilli and a filamentous surface coat. Fasting results in an accumulation of secretion granules in all cytoplasmic portions, except for the terminal web area. A similarity is recorded between the distribution of secretion granules and the finely granular fluorescamine-induced fluorescence, suggesting that the fluorescence is associated to some component(s) of the secretory granules. Granule release may take place at the base after an adequate stimulus (presence of food?) at the luminal portion of the cells. The formaldehyde condensation technique shows that insulin-containing hagfish islet parenchymal cells, but not intestinal endocrine cells, store dopamine after intestinal supply of the amine precursor. Acidification of formaldehyde vapour-fixed intestinal epithelium induces fluorescence in the granules of zymogen cells but not of endocrine cells, indicating a low concentration of tryptophyl-peptide(s) in the secretory granules of hagfish intestinal endocrine cells.     

Immunofluorescence studies on the effect of cyclic adenosine 3′,5′-monophosphate in tissue culture preparations of the cervicovaginal anlage from neonatal mice

Summary The authors have studied the production of antigenic material, specific for the cervicovaginal epithelium, in organ cultures of the cervicovaginal region from neonatal mice. In control cultures the antigenic material appeared at a time corresponding to the normal appearance under in vivo conditions. When cyclic adenosine 3, 5-monophosphate (dibutyryl derivate) was added to the medium, a strong increase of the fluorescent material was seen.This investigations was supported by grants from the Norwegian Research Council and the Norwegian Cancer Society (Landsforeningen mot Kreft).     

Morphological changes in the middle intestine of the rainbow trout,Salmo gairdneri,induced by a hyperosmotic environment

Summary The structural modifications in the middle intestine of the trout, Salmo gairdneri, induced by transfer to seawater have been studied. During the first two days in seawater, significant distensions of the intercellular spaces are observed between the apical tight junctions and the basement membrane. These dilations are more frequent in the apical part of the intestinal folds. At the basal part of the cell, numerous lamellar processes open in the intercellular spaces. They are closely associated with elongated mitochondria, and are often mixed with small clear vesicles. After seven days in seawater, intercellular spaces are less expanded. Numerous mitochondria are observed in the apical part of the cell, and numerous myelinic bodies with dense granules lie near the nucleus. After one month in seawater, the epithelium resembles that of the freshwater controls; mitochondria are more numerous and other organelles are well developed. The most important modifications of the ultrastructure of the intestine mucosa occur during the first two days in seawater, in correlation with important physiological changes following the abrupt increase of environmental salinity.     

Morphological and histochemical observations on the intestinal epithelium of Ascardia galli (Nematoda: Ascaridida).

The intestinal epithelium of Ascardia galli has been studied with various cytological and cytochemical techniques. It consists of large epithelial cells resting on a thick collagenous basal lamina. Their luminal surface is provided with microvilli. The intestinal cells store considerable amounts of glycogen and neutral lipids. Some intracellular granular inclusions, which stain for proteins, phospholipids and lipoproteins, are distributed throughout the cytoplasm. The brush border is composed of microvilli whereas the outer surface coat consists of saliva resistant PAS-positive material. The detailed histochemical analysis of surface material has revealed that it is composed of nonacetylated acid mucopolysaccharides rich in hyaluronic acid with carboxylate polyanions. The brush border shows intense activities of acid phosphatase and glucose-6-phosphatase, moderate of ATPase, and lipase, weak of 5'-nucleotidase. Acid phosphatase-positive intracellular structures are seen in the intestinal epithelium which form distinct aggregations.     

Immunohistochemical localization of epididymal secretory glycoprotein EP1 in the adult male chimpanzee.

Proteins, synthesized by the epididymal epithelium, are secreted sequentially into the lumen of the ducts epididymis where they effect sperm maturation and enable functional motility and fertilizing capacity. EP1 is a major secretory glycoprotein of chimpanzee (Pan troglodytes) epididymis. The epididymal duct exhibits diverse histology (Smithwick & Young, 1997). Epithelia I-V of the efferent ducts show no characteristic anti-EP1 binding. The densest granules of anti-EP1 reaction product appear in epithelium VI adjacent to the basal lamina in the infranuclear region of the principal cells (PCs), in the cytoplasm of the apical half of the PCs, and in the perinuclear and perivacuolar cytoplasm of the basal cells. In epithelia VII-XIV of the ductus epididymis proper, anti-EP1 binding decreases distally and is localized in the cytoplasm of the PCs and basal cells, among the stereocilia of the luminal border, within various microvillar borders, and in the luminal fluid. Therefore, EP1 appears to be synthesized and secreted primarily in the caput region of the ductus epididymis and may be reabsorbed nonselectively across epithelia with apical microvilli, including the non-ciliated cells of efferent ducts, the distal corpus and cauda of the ductus epididymis, and the proximal ductus deferens.     

Morphology and distribution of cystic cavities in the normal murine thymus

Summary The normal murine thymus was examined by lightand electron microscopy to determine the distribution and morphology of extracellular cystic cavities. Most cavities were confined to the cranial half of each gland, situated at the junction between cortex and medulla. They varied in size and shape, and gave rise to narrow channels that coursed to the capsular surface of the gland. Large cavities could be divided into three zones. A short cranial zone exhibited gland-like features, consisting of cells lining a clear lumen. A central zone was lined by a diverse population of cells. Some possessed secretory granules, while others exhibited an apical ciliated border. Lining cells interdigitated with each other and were joined laterally by intercellular junctions. The lumen of the central zone contained lymphocytes and macrophages in an amorphous extracellular matrix. The caudal zone of each cavity had an attenuated and incomplete cellular lining, communicating directly with the surrounding thymic parenchyma. Thymic cavities may represent the initial part of the efferent lymphatic system of the gland, beginning in the tissue spaces at the corticomedullary junction. Selected cells could then enter and interact with the luminal contents in the central zone of the cavity. Ciliated cells may then propel lymphocytes and secretions into the narrow channels radiating from the uppermost part of the chamber, leaving a cell-free lumen in this region. These cavities may function in sequestering lymphocytes, macrophages and thymic secretions before their exit from the gland.     

An ultrastructural study of the submandibular glands of the squirrel monkey, Saimiri sciureus

In squirrel monkey (Saimiri sciureus) the position of submandibular glands in the neck, on either side of the trachea, more closely resembles that of rodents than that of other primates. The glands exhibit seromucous acini and mucous tubules with seromucous demilunes. Electron microscopy shows basal cytoplasmic folds and well-developed intercellular tissue spaces and canaliculi only in relation to seromucous cells. Greatly dilated cisternae of the granular endoplasmic reticulum and prominent Golgi membranes are characteristic of the mucous cells. The secretory granules of seromucous and mucous cells are morphologically distinct and indicate chemically different products for the two cell types. Histochemically, the seromucous cell shows the presence of acid mucosubstance as indicated by the PAS and Alcian blue techniques. Preliminary studies showed no appreciable quantity of amylase in submandibular glands. The intercalated duct cell is juxtaposed with the acinar cell or mucous tubule cell. Short luminal microvilli, prominent Golgi complexes and scant apical granules are notable features of intercalated duct cells. Four cell types compose the striated ducts, viz., granular light cells, agranular dark cells, vesiculated dark cells, and basal cells. Peripheral nerves are found in five different locations: in the connective tissue (interstitial), between adjacent myoepithelial and mucous-secreting cells, in the intercellular space between adjacent secretory cells, and between basal plications of striated ducts and between adjacent myoepithelial and intercalated duct cells.     

Occurrence of unusual heterogeneous lipid-containing granule-storing cells in the main excretory duct epithelium of the male mouse submandibular gland

Summary The fine structure of the main excretory duct epithelium of the male mouse submandibular glands was investigated by scanning and transmission electron microscopy. Three principal cell-types were observed: type I and II, and basal cells. This epithelium was characterized by the presence of intercellular canaliculi. Type-I cells were the most numerous. They had an abundance of mitochondria, well-developed Golgi apparatus, a few electron-lucent lipid-containing granules and poorly developed basal infoldings. These cells were also characterized by many glycogen granules throughout the cytoplasm and abundant smooth endoplasmic reticulum in the apical cytoplasm. Type-II cells were the second most numerous. Their most characteristic feature was the presence of abundant heterogeneous lipid-containing granules having acid phosphatase activity at the periphery. They were concentrated in the infra- and supranuclear cytoplasm. The granules may be derived from mitochondrial transformation and seem to be a special kind of secondary autolysosome. Type-II cells also contained abundant mitochondria throughout the cytoplasm, much smooth endoplasmic reticulum in the apical cytoplasm, a well developed Golgi apparatus adjacent to the heterogeneous lipid-containing granules and no basal infoldings. Basal cells were situated adjacent to the basal lamina. They had a large nucleus and the cytoplasm was filled with glycogen granules.     

EPITHELIAL CELL MIGRATION IN THE INTESTINE

Despite significant advances in our understanding of the roles of the cytoskeleton and matrix receptors in cell locomotion, derived largely fromin vitrostudies on the movement of epithelial cell sheets and isolated cells, the mechanism of epithelial cell migration in the adult intestine remains an enigma. The primary function of the epithelial cell cytoskeleton seems to be in the maintenance of the apical region of the epithelium facing the gut lumen. There we find the brush border, with its associated enzymes, and the intercellular adhesion complexes that give the epithelium its cohesiveness and its barrier function. Curiously, there is little in the way of an organized cytoskeleton in the basal region of the epithelium adjacent to the basement membrane on which the epithelium is presumed to migrate. In this short review, I focus on what is known about epithelial migration from our understanding of the structure of the epithelium and from studies on wound healing, and indicate some avenues for future study.