Showing papers on "Apical cytoplasm published in 1989"

Actin accumulation at sites of bacterial adhesion to tissue culture cells: basis of a new diagnostic test for enteropathogenic and enterohemorrhagic Escherichia coli.

Abstract: Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) adhere to the intestinal mucosa and produce an attaching and effacing (AE) lesion in the brush border microvillous membrane; the AE lesion is characterized by localized destruction of microvilli and intimate attachment of bacteria to the apical enterocyte membrane. A similar lesion is seen when bacteria adhere in vitro to a variety of human tissue culture cell lines. In both cases, dense concentrations of microfilaments are present in the apical cytoplasm beneath attached bacteria. Using a fluorescein-labeled phallotoxin, we have shown that these microfilaments are composed of actin. Cells infected with EPEC and EHEC strains known from electron microscopic studies to produce the AE lesion all exhibited intense spots of fluorescence which corresponded in size and position with each adherent bacterium; cells infected with adherent E. coli strains known not to produce the AE lesion did not produce this striking pattern of fluorescence and were indistinguishable from uninfected control cells. These results indicate that such site-specific concentrations of cytoskeletal actin are characteristic of the AE membrane lesion and can form the basis of a simple, highly sensitive diagnostic test for EPEC and EHEC. Images

Differential localization of villin and fimbrin during development of the mouse visceral endoderm and intestinal epithelium.

Abstract: The apical surface of transporting epithelia is specially modified to absorb nutrients efficiently by amplifying its surface area as microvilli. Each microvillus is supported by an underlying core of bundled actin filaments. Villin and fimbrin are two actin-binding proteins that bundle actin filaments in the intestine and kidney brush border epithelium. To better understand their function in the assembly of the cytoskeleton during epithelial differentiation, we examined the pattern of villin and fimbrin expression in the developing mouse using immunofluorescence and immunoelectron microscopy. Villin is first detected at day 5 in the primitive endoderm of the postimplantation embryo and is later restricted to the visceral endoderm. By day 8.5, villin becomes redistributed to the apical surface in the visceral endoderm, appearing in the gut at day 10 and concentrating in the apical cytoplasm of the differentiating intestinal epithelium 2–3 days later. In contrast, fimbrin is found in the oocyte and in all tissues of the early embryo. In both the visceral endoderm and gut epithelium, fimbrin concentrates at the apical surface 2–3 days after villin; this redistribution occurs when the visceral endoderm microvilli first contain organized microfilament bundles and when microvilli first begin to appear in the gut. These results suggest a common mechanism of assembly of the absorptive surface of two different tissues in the embryo and identify villin as a useful marker for the visceral endoderm.

In vivo ciliogenesis in human fetal tracheal epithelium.

Abstract: Development of ciliated cells (CC) in the fetal human trachea was studied by light and electron microscopy in specimens obtained from 45 embryos or fetuses aged from 9 to 27 weeks of gestation (menstrual age). Four stages could be recognized during tracheal development. Up to 11 weeks (stage I), the trachea was covered with a columnar undifferentiated epithelium with abundant glycogen, apical microvilli, and primary cilia. From 12 to 18-19 weeks (stage II), centriologenesis and secondary ciliogenesis were very active, and the percentage of CC and secretory cells (SC) progressively increased. From 20 to 22-23 weeks, the density of CC was higher but, in parallel, the percentage of SC decreased (stage III). Throughout this period, the different steps of ciliogenesis could be identified in the same field, and the ciliated borders consisted of ciliary shafts with a disorderly arrangement. Megacilia were identified. Some of the preciliated cells had both cilia and secretory granules in their apical cytoplasm. After 24 weeks (stage IV), the ciliated border was apparently mature, the rootlets lengthened, and the cilia were correctly orientated. Whatever the fetal age, the density of CC was significantly higher (P less than .01) in the dorsal trachea compared to the ventral trachea. There are many similarities between animal and human ciliogenesis, but in human fetuses, most of the ciliary differentiation occurs early, during the first half of gestation. As demonstrated in experimental models, SC likely play a major role in genesis of CC during the fetal development of the human trachea.

The endometrial cycle: the expression of a secretory component correlated with the luteinizing hormone peak

Abstract: This paper reports the pattern of production and secretion of a secretory phase epitope in the endometrium of 44 normal fertile women. Peroxidase immunochemistry was used to detect the monoclonal antibody D9B1, which binds to a peptide-associated sialylated oligosaccharide, in endometrial biopsies all chronologically dated from the luteinizing hormone (LH) peak. During the proliferative phase, the epitope was shown to be absent from tissue sections. It first made its appearance within gland cells 2 days after the LH peak. By LH+3 a rapid accumulation of the D9B1 epitope was noted in the base of the cell, below the nucleus. On subsequent days, increasing amounts of the antigen were detected in the apical cytoplasm, apparently in a more concentrated form than in the basal cell zone. On day LH+6, around the time of implantation, secretory vesicles in the cell apex were discharged into the gland lumen where the glycoconjugate finally accumulated. This immunohistochemical approach introduces a new parameter for evaluation of endometrial function and could be used to improve the accuracy of histological assessment of the endometrial cycle.

Early biochemical responses of the small intestine of coeliac patients to wheat gluten.

Abstract: The pathogenesis of coeliac disease has been investigated by studying the response of small intestinal hydrolases in patients with coeliac disease subject to gluten challenge. Small intestinal biopsies taken before and two and a half hours after a gluten challenge in five patients with coeliac disease who had been maintained on a gluten free diet were examined by a combination of electron and light microscopy, organ culture, pulse chase biosynthetic labelling, SDS-PAGE and autoradiography. Before the challenge, the small intestinal biopsies showed nearly normal morphology. Two and a half hours after the challenge there was deterioration in villus architecture, distortion of microvillus structure, disorganisation of the intermicrovillus pit region, an increase in lysosome like bodies in the apical cytoplasm of the luminal enterocytes and pronounced hypertrophy of the rough endoplasmic reticulum of these cells. SDS-PAGE of small intestinal biopsies from four treated coeliac patients before gluten challenge revealed normal microvillus membrane and hydrolase composition. There was a generalised reduction but no specific alteration in the pattern of polypeptide synthesis in the mucosa of the small intestine in these subjects two and a half hours after the gluten challenge. These results suggest that the generalised reduction in small intestinal brush border enzymes in coeliac patients is not the primary pathogenetic mechanism and represents a secondary effect.

C-myc oncogene product P62c-myc in ovarian mucinous neoplasms: immunohistochemical study correlated with malignancy.

Abstract: The monoclonal antibody Myc 1-6E10 was used to determine the cellular distribution of the c-myc oncogene product p62c-myc in 60 mucinous ovarian tumours. Three patterns of immunostaining were apparent: (i) nuclear staining alone; (ii) staining of the nucleus and basal cytoplasm; and (iii) staining of the entire cell. Of the 21 cases of mucinous cystadenoma, 11 showed nuclear staining alone, and a further case showed additional weak staining of the basal cytoplasm. Nuclear staining alone was not present in any of the 17 borderline mucinous tumours examined. Strong staining of the nucleus and basal cytoplasm was seen in 16 of these borderline cases, six of which also showed focal staining of the apical cytoplasm. All 22 cases of mucinous cystadenocarcinoma showed staining of the cell nucleus and entire cell cytoplasm. Focal staining of the apical cytoplasm in six of 17 borderline mucinous tumours produced a pattern of c-myc immunostaining similar to that of cystadenocarcinoma. Retrospective analysis of the clinical data showed that no significant differences between patients with borderline tumours of these two categories could be defined. Although immunostaining with Myc 1-6E10 can be used in the categorisation of mucinous ovarian tumours, it is concluded that standard histological criteria are more accurate indicators of tumour behaviour than is an assessment of c-myc expression.

Ultrastructure of M cells in the conjunctival epithelium of the guinea pig.

Abstract: The part of the guinea pig conjunctival epithelium overlying a lymphoid follicle contains specialized M (membranous) cells The M cells are located in the superficial epithelial layer and are interposed between the epithelial surface and invading intraepithelial lymphocytes The morphology of the M cells is characterized by irregular microvilli on the epithelial surface and numerous vesicles and vacuoles concentrated in the apical cytoplasm opposite the lymphocytes These morphological features indicate pronounced functions of uptake and transport of material from the epithelial surface to closely apposed lymphocytes The present morphological findings are in accordance with previous reports stressing the function of M cells as rapid carriers of antigenic information from the epithelial surface to intraepithelial lymphocytes

Structural features of the epididymis in a dasyurid marsupial (Antechinus stuartii).

Abstract: The ductus epididymidis of the marsupial mouse Antechinus stuartii was divided into caput, corpus, and caudal regions using several constant morphological landmarks. Tubule diameter and epithelial height increased gradually from caput to cauda. In contrast, the surface area of the lumen of the ductus epididymidis increased to a maximum in the distal caput region, but decreased markedly in the distal cauda in association with characteristic changes in lumen shape (from circular to slit-shaped) and epithelial height. Epithelial cells of the ductus epididymidis were generally similar in structure to those described in other mammalian species. Principal and basal cells were common throughout the epithelium. Clear and mitochondria-rich cells were also identified, but occurred less frequently. Regional variations in cell ultrastructure were observed only in principal cells. Numerous vesicular inclusions occurred in the apical cytoplasm of cells in caput segments, membrane-bounded, electron-dense bodies were common in distal corpus regions, and a brush border of microvilli characterized the luminal surface of principal cells in caudal segments. Sperm index increased in the proximal caput, declined to basal levels in the distal caput and proximal corpus, and then increased to a maximum in segment 9 of the distal corpus and remained at about this level throughout the cauda epididymidis. Nuclear rotation, loss of cytoplasmic droplets, and other sperm maturational changes were observed along the epididymis. Discarded cytoplasmic droplets collected in large masses interspersed between aggregates of spermatozoa throughout the distal regions of the duct. There was no evidence of phagocytosis by principal cells of cytoplasmic droplets. The epididymis of A. stuartii differs from that of other mammals. The unusual caudal region, which has little storage capacity for sperm, is an unusual adaptation in a species in which the male is known to be polygamous.

Variations in immunocytochemical localization of cathepsin B and thyroxine in follicular cells of the rat thyroid gland and plasma TSH concentrations over 24 hours

Abstract: Immunocytochemical localization of cathepsin B and thyroxine (T4) in follicular cells of the rat thyroid gland and plasma concentrations of thyroid stimulating hormone (TSH) were examined at six evenly spaced times over 24 h. By light- and electron microscopy, immunodeposits for cathepsin B were localized in cytoplasmic granules of various sizes, whereas those for T4 were detected mainly in larger granules of the cells and in the colloid lumen. The size and location of cytoplasmic granules showing immunoreactivity for cathepsin B and T4 in the cells varied over 24 h, corresponding to a change in plasma TSH concentrations. These immunopositive large granules appeared in the apical cytoplasm at 12.00 h, when the level of TSH was highest. At 20.00 h when the level of TSH was lowest, T4-positive granules almost disappeared, and cathepsin B-positive small granules were abundantly seen in the basal region. From 00.00 h to 08.00 h, these positive granules changed in the same manner as those seen from 12.00 h to 20.00 h, associated with an increase in plasma TSH levels. These results suggest that newly formed colloid droplets migrate from the apical to the basal regions. Cathepsin B may play a role not only in the degradation of thyroglobulin but in the maturation of thyroid hormones during the migration of the granules.

An Immunohistochemical Study of Cytokeratin and Vimentin in Benign and Malignant Thyroid Lesions

Abstract: Intermediate filaments in benign and malignant thyroid lesions were immunohistochemically studied using polyclonal and monoclonal anti-cytokeratin (CK), and monoclonal anti-vimentin antibodies. Antigenicity of CK and vimentin was almost completely destroyed during formalin fixation in normal thyroid and all thyroid lesions except for some cases of papillary and squamous cell carcinoma, although the latter showed negative immunostaining with anti-vimentin antibody. In sections fixed with Carnoy's fixative, most cases of papillary carcinoma showed an intense reaction product for polyclonal anti-CK, monoclonal anti-CK-7, CK-19 and anti-vimentin antibodies. The reaction product for anti-CK antibodies was located mainly in the apical cytoplasm and that for anti-vimentin antibody in the basal cytoplasm. However antigenicity was still destroyed by the fixative in many specimens of normal thyroid, benign thyroid lesions and follicular carcinoma. In frozen sections, all specimens showed preserved antigenicity for both antigens with an intense reaction product in papillary carcinoma, but this was weaker in normal thyroid, benign thyroid lesions and follicular carcinoma. Therefore, follicular cells under normal and pathological conditions contain intermediate filaments of CK and vimentin in their cytoplasm and co-expression of the antigens is significantly increased in papillary carcinoma.

Immunoelectron microscopy of fodrin in the rat uriniferous and collecting tubular epithelium.

Abstract: We examined the localization of fodrin in epithelial cells of rat uriniferous and collecting tubules by immunofluorescence and immunoelectron microscopy of frozen sections. In the uriniferous tubule, fodrin was found along the cell membrane and in the well-developed terminal web, as previously reported in other epithelial cells: in the terminal web and along the basolateral cell membrane in the proximal tubule; all around the cell surface in the thin limb of Henle; along the basolateral surface in the thick limb of Henle's thick segment and the distal tubule. In the intercalated cells of the collecting tubule, fodrin was found not only along the basolateral cell membrane but also in the apical cytoplasm. The most peculiar labeling was obtained in the principal cells of the collecting tubule. In addition to labeling in the basolateral cell membrane, fodrin was found diffusely in the cytoplasmic matrix. Association of fodrin with any particular structure could not be identified, but the Golgi area was apparently free of labeling. Cytoplasmic labeling was more conspicuous in the principal cells of the medulla than in those of the cortex. The present results show that fodrin need not always exist in association with the cell membrane or the cytoskeleton but can occur in the cytoplasmic matrix, at least in epithelial cells. We discuss the possible physiological significance of the latter distribution.

Endocytosis of native and glycosylated bovine serum albumin by duct cells of the rat parotid gland.

Abstract: The ability of duct cells of the rat parotid gland to internalize bovine serum albumin (BSA) and several glycosylated albumins (glucosamide, galactosamide, fucosamide, lactosyl, p-aminophenyl-N-acetyl-D-glucosamide, p-aminophenyl-N-acetyl-D-mannopyranoside, p-aminophenyl-N-acetyl-D-galactosamide) was investigated. The various BSA preparations were infused into the gland via the main excretory duct, after which the tissues were fixed and prepared for light and electron microscopy. Immunolocalization of native BSA, as well as the glycosylated BSAs, was performed on thin sections, using an unlabeled antibody to BSA followed by protein A-colloidal gold. Gold particles were present over the lumina of both intercalated ducts and striated ducts, and over small endocytic structures and large vacuoles in the apical cytoplasm of both duct cell types. Endocytosis of the glycosylated BSAs by duct cells was greater than native BSA. Fucosylamide-BSA and mannopyranoside-BSA were taken up to a greater extent than the other glycosylated BSAs. Uptake by intercalated duct cells was greater than by striated duct cells, was independent of the concentration of the glycosylated BSA, and was reduced by an excess of the corresponding sugar. Striated duct cells showed some damage by the glycosylated BSAs that was concentration-dependent, and which was reduced in the presence of an excess of the corresponding sugar. These results suggest that endocytosis by salivary gland duct cells may involve specific recognition of carbohydrate residues and that the endocytosis of acinar secretory proteins observed in certain conditions may be due to increased and/or altered protein glycosylation.

Fluid-phase transcytosis in the primate epididymis in vitro and in vivo.

Abstract: Summary Ligated tubules from the corpus epididymidis of men and monkeys were incubated in medium containing horseradish peroxidase (HRP) as a marker for fluid-phase endocytosis. HRP was localized by light and electron microscopy after 0, 15, 30 and 60 min of incubation. Movement between the cells was prevented by tight junctions, but bypass of this barrier was apparently achieved by an intracellular vesicular mechanism leading to a time-dependent appearance of HRP in the lumen. Uptake of HRP into basal cells and capture by the lysosomal apparatus of principal cells were also observed. HRP-filled vesicles also appeared in the basal, mid and apical cytoplasm of epithelial cells in the caput 1 h after injection of the tracer into the epididymal circulation of the monkey, suggesting that this pathway also operates in vivo.

Analysis of lectin binding in benign and malignant thyroid nodules.

Abstract: The lectin binding properties of ten cases each of adenomatoid nodule, follicular adenoma, and papillary carcinoma and five cases of microinvasive follicular carcinoma were examined histochemically and compared with adjacent normal thyroid tissue. Wheat germ agglutinin, concanavalin A, Ulex europaeus agglutinin I, peanut agglutinin, soybean agglutinin, Dolichos biflorus agglutinin, Ricinus communis agglutinin, and Helix pomatia agglutinin were employed. All the lectins but Ulex europaeus agglutinin I, peanut agglutinin, and Helix pomatia agglutinin were bound to thyroid parenchymal cells, colloid and stromal cells, but none uniquely to thyroid parenchymal cells. Helix pomatia agglutinin binding was present in stromal cells but not in parenchymal cells. Ulex europaeus agglutinin I binding to parenchymal cells was weakly positive only in five cases of papillary carcinoma. The binding in adenomatoid and neoplastic cells and their colloid was stronger than in adjacent normal thyroid tissue in all cases examined. Wheat germ agglutinin and concanavalin A binding was most intense among the lectins examined. In papillary carcinoma, lectin binding was observed mostly in the apical cytoplasm of carcinoma cells, whereas a diffuse surface binding pattern was predominant in follicular adenoma and carcinoma, adenomatoid nodules and normal thyroid gland. No consistent differences in lectin binding were found between follicular adenoma and carcinoma, or between adenomatoid nodules and follicular neoplasia.

Fine structure observations on rat jejunal epithelial cells during fat processing and resorption following L-81 exposure and reversal.

Abstract: In order to more easily follow membrane interaction following L-81 administration and subsequent lipid processing tannic acid was used to highlight cell membrane contrast in intestinal epithelial cells of Sprague-Dawley male rats. Jejunal epithelial cells were examined with the electron microscope following 4 h of L-81 administration and 45 min, 1, 1.5 and 2 h after the cessation of L-81 administration. After 4 h of L-81 administration the apical cytoplasm was seen to be filled with large, lipid droplets limited by a single, 4-5 nm thick, electron-dense rim. During the reversal process changes noted in the cytoplasm included the following. As early as 45 min clear and electron-dense-filled vesicles appeared scattered in the apical cytoplasm and juxtaposed to the lipid droplets. The large, non-membrane bound lipid droplets decreased in size and number over the two hour period while the number and size of electron-dense containing vesicles increased. The vesicles were subsequently found concentrated in the Golgi region where assimilation and production of chylomicron and VLDL size particles occurred. Eventually multiple groups of such particles were found intercellularly and basally. Thus the re-cycling of lipid and chylomicron production and secretion following L-81 reversal is similar to that following experimental studies on normal fat over-loading and following recovery after puromycin treatment. This data is discussed in light of previous data on fat processing and secretion in rat intestinal epithelial cells with particular reference to membrane events visible following tannic acid membrane highlighting.

Selenium-induced autometallographic demonstration of endogenous zinc in organs of the rainbow trout, Salmo gairdneri.

Abstract: Autometallographic (AMG) silver enhancement of endogenous zinc was studied in seven organs of the rainbow trout Salmo gairdneri. Groups of trout were injected intraperitoneally with sodium selenite in doses ranging from 0.08 to 25 ppm, administered 1 h before being killed. The concentration of selenium obtained by each organ was determined by gamma-spectrometry, and compared with the autometallographic deposition of silver grains. The relative accumulation of selenium in the organs was: liver > spleen > kidney > intestine > gills > brain > muscle. In the fish labelled with 10 and 25 ppm Se, AMG-deposits were found (1) within lysosomes of liver cells, (2) within the granules and on the nuclear membrane of melanophores in the spleen, (3) on the microvilli and in the apical cytoplasm of renal proximal tubular cells, (4) within the granules and along the plasma membrane of intestinal eosinophilic granule cells, and in the apical portion of the intestinal epithelium, and (5) in the gills, within granule cells and on the surface of the ionocytes. In the trouts injected with 5 ppm Se, silver grains were still observed in the liver, the intestine, and the gills, whereas, no such grains were found in preparations from fish having received 1 ppm Se. The use of selenium for the histochemical demonstration of endogenous zinc versus exogenous metals is discussed. Also, consideration is given to the question of which part of the total tissue zinc that is histochemically reactive.

The ultrastructure of bovine ileal follicle-associated epithelial (FAE) cells during the perinatal period.

Abstract: The ileal follicle-associated epithelial (FAE) cells in bovine fetuses and neonates were examined by light and electron microscopy. In 7-9 months old fetuses (68, 82 and 86 cm CRL) the dome epithelium was usually a little thinner than elsewhere and contained more intra-epithelial leucocytes. FAE cells were already distinguishable by their being more cuboidal and eosinophilic than the other epithelial cells. The cytoplasm of the FAE cells bulged noticeably into the lumen and contained numerous mitochondria and vacuoles. At 18 hours and 21 hours after birth, the dome epithelium was more columnar and eosinophilic than previously and contained more intra-epithelial leucocytes. The FAE cells showed characteristic bulging of large cytoplasmic processes into the lumen, as seen in the previous stage. In the cytoplasm, moderate numbers of mitochondria, numerous vesicles and microtubules could be seen. Frequently degenerated FAE cells could also be found among normal FAE cells in the epithelium. After this stage the cytoplasmic processes almost disappeared but distribution of the other organelles was similar to that seen at the previous stage except that multivesicular bodies were frequently seen in the apical cytoplasm. These histological results suggest that bovine ileal FAE cells are histologically and functionally mature by birth and that at birth they seem to be able to react against the penetration of pathogenic substances from the extrauterine environment.

Dynamics of apical membrane responses to ADH in amphibian bladder

Abstract: The dynamic insertion and retrieval of membrane at the apical surface plays an important role in the action of antidiuretic hormone (ADH). The addition of membrane with water channels is a crucial event in initiating the water permeability response. ADH-stimulated bladders display distinctive differentiations in the apical membrane that represent sites where intracellular vesicles carrying intramembrane particle aggregates have fused with the apical surface. In the absence of an osmotic gradient these fusion sites appear to be relatively stable structures, but in the presence of an osmotic gradient there seems to be continuous addition and retrieval of membrane during sustained exposure to ADH. It is now clear that a dynamic feedback process is present, such that the water permeability of the apical membrane is adjusted by retrieval or addition of membrane depending on the magnitude of the transepithelial osmotic gradient. Removal of ADH leads to a striking retrieval of apical membrane, and intact aggregates have been demonstrated in the membrane of the vesicles that form in the apical cytoplasm after reversal of the response. Structure-function analysis has provided unique information, demonstrating that membrane dynamics is central to the mechanism whereby ADH regulates osmotic permeability in the toad urinary bladder.

Cholangiocarcinoma in a 4-month-old double yellow-cheeked Amazon parrot (Amazona autumnalis).

Abstract: A cholangiocarcinoma was diagnosed in a 4-month-old double yellow-cheeked Amazon parrot (Amazona autumnalis). Histologically, neoplastic cells effaced hepatocellular architecture. Ultrastructurally, variably dilated bile ductules were lined by simple cuboidal to low columnar ciliated epithelial cells with sparse cellular organelles and prominent junctional complexes. Elongated single cilia arising from basal bodies in the apical cytoplasm were occasionally evident. The presence of such a neoplasm in a 4-month-old parrot is extremely unusual.

Endocytotic pathways across the human gall-bladder mucosa: permeability studies using horseradish peroxidase.

Abstract: Human gall-bladder epithelium obtained straight from the operating theatre was incubated in an Ussing chamber with the fluid phase marker, horseradish peroxidase (HRP), for up to 60 min. When the marker was presented on the apical surface, within 30 min it had moved readily across the apical cytoplasm in transport vesicles to receptosomes and into the lateral intercellular space, extending across the basement membrane into the lamina propria. When HRP was presented at the basal aspect, within 30 min it had moved through the lamina propria, across the basement membrane and into the lateral intercellular space. By 60 min, only small amounts had been taken up by the epithelial cells and transported to receptosomes. These data indicate a rapid transmucosal endocytotic pathway for blood-or bile-borne macromolecules.

Morphological observations of the apical surface of chick retinal pigment epithelium.

Abstract: Chick embryonic retina was examined in order to investigate morphological changes of the apical portion of retinal pigment epithelial (RPE) cells. Whole retina and RPE sheets were observed by fluorescence microscopy (rhodamine-phalloidin preparation) and transmission electron microscopy. Photoreceptor cells had no inner and outer segments on the 8th day in ovo. The inner segments have been formed on the 15th day and the outer segments on the 19th day. RPE sheets had short and blunt apical processes on the 8th day, elongated and slender ones on the 15th day, and well-developed and melanin-containing processes on the 19th day. RPE of the 19th day had numerous bundles of actin filaments associated with melanin pigments in the basal portion of the apical processes and in the apical cytoplasm. In rhodamine-phalloidin preparations, intense fluorescence was localized in the RPE apical processes and cytoplasm on the 19th day. We concluded that RPE apical processes develop in accordance with the photoreceptor development.

Retrospective Study of Campylobacter Species Isolated from Porcine Diagnostic Case Material

Abstract: Porcine proliferative enteritis (PPE) is an enteric disease of weaned pigs characterized by proliferation of intestinal cryptal epithelial cells and the presence of bacteria in the apical cytoplasm of these cells 5,9 (Fig. 1). What role, if any, these bacteria play in the disease is unclear. The exact identity of the bacteria is not known, but their morphology is consistent with Campylobacter species. Several Campylobacter species have been isolated from intestines of diseased and healthy pigs. 1-4,6,8 In some laboratories diagnosis of enteric disease has included culture of ileal mucosa for Campylobacter species, despite uncertainty of the role these organisms play in the disease. A retrospective study of porcine diagnostic cases submitted to the University of Minnesota Diagnostic Laboratory in 1986 was conducted to determine what Campylobacter species were isolated from animals with histologically confirmed PPE or other disease conditions and to evaluate the diagnostic significance of their isolation and identification.

Cytoskeleton in the apical region of mouse taste bud cells.

Abstract: The cytoskeletal structures in the apical region of mouse taste bud cells were examined by immunocytochemistry and electron microscopy. Immunostaining for actin showed positive reactions in the apical portions of the taste buds. These regions contained bundles of longitudinally oriented filaments (5-7 nm in diameter) extending from the tip of microvilli to the apical cytoplasm of type-I, -II, and-III cells. After incubation with heavy meromyosin, arrowhead formation was observed along these filaments, thus indicating these filaments to be composed of actin. The plasmalemmal undercoat, which was composed of vertical and horizontal layers, was observed on the zonula occludens. It is supposed that this undercoat gives the structural support for the lateral membrane of the apical region in the taste bud cells.

DISTRIBUTION OF FODRIN AND α-ACTININ IN THE RAT RETINAL PIGMENT EPITHELIUM IN VIVO

Abstract: Localization of fodrin and α-actinin in the rat retinal pigment epithelium (RPE) in vivo was examined by immunolabeling of frozen sections as well as en face preparations. Fodrin was found densely in the apical cytoplasm and in the basal infolding; it was sparse in the lateral cell membrane and hardly present in the microvillus. On the other hand, α-actinin was concentrated in the dense material underlying the zonula adherens. Notably the protein was also seen along the microfilament bundle arising from the junction; it was present continuously in the vicinity of the junction, but localized only in electron-dense bodies deep in the cytoplasm. Fodrin was seen on both sides of the bundle but not in the bundle itself.The present results showed that the distribution of fodrin and α-actinin in RPE is distinctive among simple epithe1ia; fodrin is more concentrated in the basal cell membrane than in the lateral cell membrane; α-actinin is present in the actin filament bundle running through the apical cytoplasm and not in the terminal web. These differences are likely to be related to the specialized function and location of RPE.

Ultrastructural effects of phosphorothionates and other inhibitors of lung monooxygenases: protection against trialkylphosphorothiolate-induced lung injury.

Abstract: An oral dose (25 mg/kg) of O,O,S-triethylphosphorothiolate (OOSEtO) to rats results in selective injury of type I pneumocytes, degranulation of Clara cells, and pronounced increase in lung weight. A dose (12.5 mg/kg) of the related compound O,O,S-trimethylphosphorothionate (OOSMeS) causes neither injury nor degranulation but, when administered 2 h before OOSEtO (25 mg/kg), protects against all the signs of lung injury that would otherwise result from this dose of the compound. The administration of OOSMeS also results in the formation of large, electron-lucent granules within the apical cytoplasm of the Clara cells. The granules are not birefringent, and histochemical procedures indicate that they do not contain carbohydrate but may consist of lipid accumulated around a proteinaceous core. Similar granules are also observed after administration of p-xylene, pseudocumene, and the pesticide bromophos. These compounds, like OOSMeS, inhibit 7-ethoxycoumarin O-deethylase activity in the lung and are capable of protecting against trialkylphosphorothiolate toxicity. This inhibition of 7-ethoxycoumarin O-deethylase activity suggests loss of pulmonary cytochrome P-450. This loss may account for both the protective action of these compounds and the formation of abnormal granules within Clara cells.

A Comparative Study of Actin Filaments in Cochlear Hair Cells: Outer Hair Cells in the Apex of the Guinea Pig Cochlea Contain a Unique Ultrastructural Feature

Abstract: Rhodamine-labelled phalloidin, a specific marker for filamentous actin, was used to describe the distribution of F-actin in the hair cells of the organs of Corti of guinea pigs, hooded rats, chinchillas and squirrel monkeys using surface preparations, cryosections, and isolated outer hair cells. The stereocilia and cuticular plates of all inner and outer hair cells were labelled, as were the lateral margins of outer hair cells of all species. In the outer hair cells of the apical turns of the guinea pig organ of Corti, an additional labelled structure was present in the apical cytoplasm of the cell. This infracuticular network of F-actin was never observed in outer hair cells of the basal turn of the guinea pig, nor in outer hair cells at any location in the organs of Corti of the other species examined.