Showing papers on "Apical cytoplasm published in 2005"

Endocytosis and vesicle trafficking during tip growth of root hairs.

Abstract: The directional elongation of root hairs, “tip growth”, depends on the coordinated and highly regulated trafficking of vesicles which fill the tip cytoplasm and are active in secretion of cell wall material. So far, little is known about the dynamics of endocytosis in living root hairs. We analyzed the motile behaviour of vesicles in the apical region of living root hairs of Arabidopsis thaliana and of Triticum aestivum by live cell microscopy. For direct observation of endocytosis and of the fate of endocytic vesicles, we used the fluorescent endocytosis marker dyes FM 1-43 and FM 4-64. Rapid endocytosis was detected mainly in the tip, where it caused a bright fluorescence of the apical cytoplasm. The internalized membranes proceeded through highly dynamic putative early endosomes in the clear zone to larger endosomal compartments in the subapical region that are excluded from the clear zone. The internalized cargo ended up in the dynamic vacuole by fusion of large endosomal compartments with the tonoplast. Before export to these lytic compartments, putative early endosomes remained in the apical zone, where they most probably recycled to the plasma membrane and back into the cytoplasm for more than 30 min. Endoplasmic reticulum was not involved in trafficking pathways of endosomes. Actin cytoskeleton was needed for the endocytosis itself, as well as for further membrane trafficking. The actin-depolymerizing drug latrunculin B modified the dynamic properties of vesicles and endosomes; they became immobilized and aggregated in the tip. Treatment with brefeldin A inhibited membrane trafficking and caused the disappearance of FM-containing vesicles and putative early endosomes from the clear zone; labelled structures accumulated in motile brefeldin A-induced compartments. These large endocytic compartments redispersed upon removal of the drug. Our results hence prove that endocytosis occurs in growing root hairs. We show the localization of endocytosis in the tip and indicate specific endomembrane compartments and their recycling.

Mass flow and pressure-driven hyphal extension in Neurospora crassa

Abstract: Mass flow of cytoplasm in Neurospora crassa trunk hyphae was directly confirmed by injecting oil droplets into the hyphae. The droplets move in a manner similar to cytoplasmic particles and vacuoles within the hyphae. The direction of mass flow is towards the growing hyphal tips at the colony edge. Based on flow velocities (about 5 μm s−1), hyphal radius and estimates of cytoplasm viscosity, the Reynolds number is about 10−4, indicating that mass flow is laminar. Therefore, the Poiseulle equation can be used to calculate the pressure gradient required for mass flow: 0·0005–0·1 bar cm−1 (depending on the values used for septal pore radius and cytoplasmic viscosity). These values are very small compared to the normal hydrostatic pressure of the hyphae (4–5 bar). Mass flow stops after respiratory inhibition with cyanide, or creation of an extracellular osmotic gradient. The flow is probably caused by internal osmotic gradients created by differential ion transport along the hyphae. Apical cytoplasm migrates at the same rate as tip extension, as do oil droplets injected near the tip. Thus, in addition to organelle positioning mediated by molecular motors, pressure-driven mass flow may be an integral part of hyphal extension.

Achlorhydria, parietal cell hyperplasia, and multiple gastric carcinoids : A new disorder

Abstract: We describe a 54-year-old woman who had multiple gastric carcinoid tumors arising in the setting of marked hypergastrinemia associated with a lack of acid production by hypertrophic parietal cells. The serum gastrin level was 1,400 pg/mL, and investigation revealed no evidence for either of the recognized causes for hypergastrinemia-associated carcinoids, autoimmune gastritis, and Zollinger-Ellision syndrome. Partial gastrectomy was performed. Pathologic examination showed multiple intramucosal and invasive carcinoid tumors of the body and fundus in a background of marked ECL cell hyperplasia. There were no gastric or duodenal ulcerations. One perigastric lymph node was metastatically involved. The oxyntic mucosa showed marked hyperplasia and hypertrophy of the parietal cells. Some of these cells were vacuolated, and many displayed protrusions of apical cytoplasm into dilated oxyntic glands filled with inspissated eosinophilic material. Similar findings have occurred in 1 other patient, strongly indicating that the clinicopathologic alterations in the 2 cases are not random but, on the contrary, represent a very rare disorder of gastric carcinoids associated with an intrinsic acid secretion abnormality of the parietal cells.

Immunohistochemical analyses on albumin and immunoglobulin in acute hypertensive mouse kidneys by "in vivo cryotechnique".

Abstract: Summary The purpose of this study is to visualize topographical changes of serum proteins, albumin and immunoglobulin, passing through mouse glomerular capillary loops and their reabsorption in renal proximal tubules by immunohistochemistry in combination with our ?in vivo cryotechnique? The ?in vivo cryotechnique? was performed on left mouse kidneys under normotensive, experimentally acute hypertensive and heart-arrest conditions The cryofixed tissues by the technique were routinely processed for freeze-substitution Serial deparaffinized sections were stained with hematoxylin-eosine and immunostained with anti-mouse albumin, immunoglobulin G (IgG), kappa or lambda light chain and IgG1 heavy chain antibodies Under the normotensive and heart-arrest conditions, albumin and IgG were clearly immunolocalized in blood vessels and slightly in apical cytoplasmic parts of some proximal tubules Under the acute hypertensive condition, the albumin and kappa or lambda light chains, but not IgG1 heavy chain, were strongly immunolocalized in the apical cytoplasm of almost all proximal tubules This study is the first in vivo visualization for glomerular passage of serum proteins and their transtubular absorption Thus, the ?in vivo cryotechnique? with freeze-substitution can be used for clarifying not only the functional morphology of living animal cells, but also in situ immunohistochemical localization of their components Histol Histopathol 20, 807-816 (2005)

Ultrastructure of the mushroom body: digestion during metamorphosis of Utterbackia imbecillis (Bivalvia: Unionidae)

Abstract: Larvae of the freshwater mussel Utterbackia imbecillis metamorphose to juveniles either during their attachment to a host fish, or in vitro in a culture medium. This transformation includes degeneration of larval structures and development of the juvenile morphology. Early in metamorphosis the cells comprising the larval mantle enlarge and project into the mantle cavity, forming a structure referred to as the mushroom body. Its cells, which are ultrastruc- turally very similar to digestive cells of adult bivalves, are involved in pinocytosis or phago- cytosis of the larval adductor muscle and of tissue from the host fish that is enclosed between the larval shells. Ingested material is passed from pinosomes to heterophagosomes which in turn fuse with heterolysosomes, where final degradation of ingested material occurs. Acid phos- phatase activity was detected in heterophagosomes and heterolysosomes of all animals exam- ined. In larvae that metamorphosed in vitro, the apical cytoplasm of the cells of the mushroom body, and the extracellular spaces among them, also exhibited acid phosphatase activity. Larvae reared on a host fish accumulated substantial deposits of lipids and glycogen within larval mantle cells during metamorphosis, whereas larvae reared in vitro did not. The larval mantle cells which constitute the mushroom body appear to be the primary sites of intracellular di- gestion of the larval adductor muscle and host tissue during metamorphosis.

Adaptation to hypoosmotic challenge in brachyuran crabs: a microanatomical and electrophysiological characterization of the intestinal epithelia.

Abstract: Besides its role in digestion and nutrient absorption, the crustacean gut participates in osmo/ionic regulation. We investigate microanatomy, ionic permeability and transepithelial electrophysiological parameters in the mid- and hindguts of three hyperosmoregulat- ing crabs that inhabit estuarine waters (Chasmagnathus granulata), brackish mangrove swamp (Sesarma rectum) or freshwater (Dilocarcinus pagei). The abdominal hindguts are cuticle lined, the single-layered epithelia consisting of narrow, columnar cells exhibiting apically dense, unvesiculated cytoplasm. In the saltwater species, the thoracic midgut epithelium consists of tall, narrow, columnar cells displaying numerous, apical microvilli above dense apical cytoplasm. However, the corresponding gut segment in the hololimnetic species, D. pagei, consists of squat cells lacking apical microvilli, overlain by a heavy cuticle, constituting a thoracic or anterior hindgut. The midgut/ thoracic hindgut epithelia in all three crabs, and abdominal (posterior) hindgut of D. pagei, exhibit similar, small, lumen-negative voltages when perfused symmetrically with hemolymph-like salines. The hindguts of the saltwater species show similar, small, lumen-positive voltages. Small short- circuit currents are detectable after voltage clamping. Washout and/or addition of luminal glucose or amino acids do not alter current or conductance, suggesting the absence of active, electrogenic nutrient absorption. Ion substitution did not disclose active, electrogenic absorption or secretion of Na 1 and/or Cl � . The midguts of the saltwater species exhibit similar conductances, greater than in D. pagei, but no ion selectivity; hindgut conductance is low, the epithelia showing moderate anion selectivity. The thoracic (anterior) and abdominal (posterior) hindgut epithelia of D. pagei, the freshwater species, exhibit similar, low conductances, and are ion selective. These findings reveal that active, electrogenic, salt and nutrient transport is undetectably low or absent. The reduced transepithelial conductances and notable ion selectivities in the abdominal and thoracic hindguts of D. pagei may reduce passive salt losses in fresh water, contributing to osmotic and ionic regulation. J. Exp. Zool. 303A:880-893, 2005. r 2005 Wiley-Liss, Inc.

The Retinal Pigment Epithelium

Abstract: The retinal pigment epithelium (RPE) is a monolayer of cuboidal epithelial cells intercalated between the photoreceptors and the choriocapillaries The human RPE incorporates some 35 million epithelial cells arranged in a regular hexagonal pattern The density of RPE cells is relatively uniform throughout the retina, approximately 4000 cells/mm 2 With age, the cell density decreases particularly in the periphery, where it is reduced to approximately 2000 cells/mm 2 in individuals over 40 years The peripheral RPE cells are larger and more pleomorphic than central cells (Harman et al, 1997; del Priore et al, 2002) In the primate retina, each RPE cell faces 30–40 photoreceptors, a number that is rather constant throughout the retina, although perhaps somewhat lower in the fovea (Robinson and Hendrickson, 1995) In fully developed primate retinas, no mitoses are seen in the RPE, and the epithelium is currently believed to consist of a stable, nondividing, pool of cells (Tso and Friedman, 1967) The retinal membrane of the RPE faces the subretinal space, which is the extracellular space surrounding the photoreceptor outer segments (Figure 1) Between the optic disc and the ora serrata, there are no anatomical contacts between the photoreceptors and the RPE The RPE forms numerous long microvilli that interdigitate with the rod outer segments In mammals, the cone outer segments are ensheathed by multilamellar specializations of the RPE, the so‐called cone sheaths The epithelial cells are bound together by junctional complexes with tight junctions that separate the cells into an apical half that faces the retina and a basal half that faces the choroid The nucleus and mitochondriae are located in the basal half of the cell Numerous pigment granules, located predominantly in the apical cytoplasm, give the epithelium its macroscopic black appearance, from which it derives its name The choroidal side of the RPE directly apposes Bruch's membrane, a pentalaminar, approximately 2 μm thick, elastic membrane The innermost part of Bruch's membrane is the basement membrane of the RPE The outer part of Bruch's membrane is the basement membrane of the choriocapillaries In between are two collagenous layers and a central elastic layer

Morphological alterations of submandibular glands caused by cisplatin in the rat.

Abstract: Cisplatin is a platinum-containing antineoplastic agent, widely used in the treatment of various malignant neoplasms including head and neck cancer. In this study we examined ultrastructural changes of rat submandibular glands (SMGs) after cisplatin treatment. Male Wistar rats aged 8 weeks were used in the experiments. Cisplatin was injected intraperitoneally into the rats (5 mg/kg/day) for three consecutive days. After 1, 3, 5, and 7 days, the SMGs were removed and observed under an electron microscope. The terminal portion of the SMG is seromucosal. Acinar cells contained a parallel array of rough-surfaced endoplasmic reticulum in the basal cytoplasm, and the apical cytoplasm was filled with homogeneous secretory granules. Vacuolation of cells was observed on the first day after cisplatin treatment. On the third and fifth days, the rough-surfaced endoplasmic reticulum showed an irregular arrangement. Mitochondrial swelling, and the presence of autophagolysosomes was also confirmed. On the seventh day, the damage to organelles began to decrease and the SMG exhibited a tendency towards improvement.

Colonic adenocarcinoma in a leopard gecko (Eublepharis macularius).

Abstract: Histologically, the wall of the thickened colonic segment was markedly expanded by moderate amounts of collagenous tissue containing numerous irregularly shaped, small tubules lined by single layers of tumour cells. The tumour tissue largely replaced the normal architecture of the mucosa, submucosa and muscularis externa, and extended into the serosa (Fig 1). The tumour cells were cuboidal, with a small amount of palestaining, eosinophilic cytoplasm and a basal, ovoid nucleus containing sparse, finely granular chromatin and a small, central, deeply eosinophilic nucleolus. There was mild anisocytosis and anisokaryosis, and small numbers of mitotic figures were observed. Most tubules contained small amounts of PASpositive amphophilic material (mucin), which was also noted within the apical cytoplasm of many tumour cells (Fig 2). There were extensive areas of necrosis of the tubules, with infiltration by small numbers of granulocytes. Additionally, the tubular structures were infiltrating and markedly expanding some areas of the oviduct wall. Radiating clusters of acicular spaces were deposited on the pleural surfaces of the lungs, this being the typical histological appearance of urate tophi following loss of the crystalline material during normal aqueous fixation. The tophi were associated with granulomatous inflammation in the pulmonary parenchyma, peritracheal adipose tissue, kidneys, myocardium, pancreas and liver. These histological findings were consistent with the diagnosis of tophaceous visceral gout. Additionally, the hepatocytes contained numerous small, clear, intracytoplasmic vacuoles suggestive of lipid deposition. No other histological abnormalities were detected. There was no evidence of Cryptosporidium species infection in the intestinal tract (Terrell and others 2003). The faecal parasitological examination was negative. The colonic neoplasm in this case was diagnosed histologically as an adenocarcinoma due to the formation of tubules by the epithelial tumour cells, with evidence of mucus production. Colonic adenocarcinoma in domestic species occurs most often in aged dogs and is predominantly of this type, with similar amounts of fibrous stroma (Head and others 2002). In the lizard, there was obstruction of the distal colonic lumen due to marked thickening of the wall by neoplastic cells and the associated scirrhous reaction, which is typical of this tumour type in the colon. Constipation due to luminal structure would only be detected by close monitoring, as the faeces of reptiles vary widely in consistency and frequency, and there are no specific guidelines for detecting constipation in any one species (Frye 1991a, Latimer and Rich 1998). Constipation or abdominal swelling was not noted clinically in this case. Colonic adenocarcinomas in domestic animals commonly metastasise via lymphatic vessels to mesenteric lymph nodes, and sometimes to other internal organs; metastasis to the lung is rare before the emergence of clinical signs that result in euthanasia (Head and others 2002). Intestinal adenocarcinomas may spread transperitoneally (Head and others 2002), Colonic adenocarcinoma in a leopard gecko (Eublepharis macularius)

Sodium bicarbonate secretion indicated by ultrastructural cytochemical localization of HCO3−, Cl−, and Na+ ions on rat bile duct brush cells

Abstract: Brush cells are widely distributed in the digestive and respiratory apparatus, but their function is still unknown. Because brush cells (BC) are found in organs secreting NaHCO3, it was hypothesized that these cells may secrete NaHCO3. To test this possibility, rat common bile duct epithelia were examined by ultrastructural cytochemical methods for localizing HCO3(-), Cl-, and Na+ ions. All three ion precipitates were few in or on BCs of rats without stimulation. Lead carbonate precipitates, which localized HCO3(-) ions by the lead nitrate-osmium method, increased markedly on the surface of the microvilli (MV) of BCs after secretin or meal stimulation, but similar precipitates were few on the luminal surface of principal cells (PCs). Silver chloride precipitates, which indicate the presence of Cl- ions by the silver-osmium method, increased in the apical cytoplasm and in MV of BCs after secretin or meal stimulation, but they were few in PCs. Sodium pyroantimonate precipitates, which localize Na+ ions by the potassium pyroantimonate-osmium method, increased on the surface of the MV, along the basolateral membrane, and in the apical cytoplasm of BCs after secretin or meal stimulation, but they were few in PCs. These results strongly suggest that BCs may be a significant source of NaHCO3 secretion.

Ultrastructure of the Submandibular Gland in the Big White-Toothed Shrew, Crocidura lasiura

Abstract: The ultrastructure and histochemical characteristics of the submandibular gland was examined in the big white-toothed shrew, Crocidura lasiura. A submandibular gland of Crocidura lasiura was a mixed gland composed of serous and mucous acinar cells. Secretory granules from the acini were discharged through the intercalated duct, the granular duct and the striated duct into the oral cavity. Serous and mucous acinar cells and granular duct cells had large amount of rough endoplasmic reticulum, free ribosome and prominent Golgi apparatus at the basal cytoplasm of the cell, and many granules at the apical cytoplasm. Oval type serous granules had a homogeneously pale round shape of bead at the center. Mucous granules were distinct from those of the other mammalian species having variety patterns with several dense bands into homogeneous pale matrix. A serous-like secretory granules and myelin-like body were observed in the cytoplasm and the lumen of granular duct cells. The myelin-like body is a characteristic structure only reported in the salivary glands of two shrews, Suncus murinus and C. dsinezumi. Striated duct cell had numerous well-developed mitochondria but secretory granule was not shown at all.

Papillary Adenocarcinoma of the Extrahepatic Bile Duct in a Holstein Cow

Abstract: A 15-year-old female Holstein cow was presented with a history of anorexia and weight loss. Abnormal physical examination findings included poor body condition, dehydration, icterus, and photodermatitis on nonpigmented areas of the skin of the dorsum. At necropsy, the common bile duct was greatly enlarged, with thickened walls, and tightly adhered to the hepatic capsular surface and serosa of adjacent loops of the small intestine. Two sessile, yellowish, friable, well-circumscribed, cauliflower-like, bulging masses (14 and 8 cm in diameter) were attached to the inner surface of the common bile duct blocking its lumen. Microscopically, the tumor was composed of well-differentiated, columnar epithelial cells with oval or round, vesicular, basal nuclei arranged in papillary projections. Periodic acid-Schiff-positive material accumulated in the apical cytoplasm of the neoplastic cells. Immunostaining of the tumor cells was positive for cytokeratin (CK) of wide-spectrum screening and for CK 7. The diagnosis of papillary adenocarcinoma of the extrahepatic bile duct was based on the morphologic features of the neoplasm and evidence of local invasion. To the best of our knowledge, extrahepatic bile duct carcinomas have not been described in cattle.