Morphology and Ultrastructure of the Dufours and Venom Gland in the Ant Myrmecia-Gulosa (Fabr) (Hymenoptera, Formicidae)

1990 ◽  
Vol 38 (3) ◽  
pp. 305 ◽  
Author(s):  
J Billen
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Epithelial Cells ◽  
Cell Membrane ◽  
Control Mechanism ◽  
Smooth Endoplasmic Reticulum ◽  
Apical Cell ◽  
Venom Gland ◽  
Apical Cell Membrane ◽  
Cuticular Layer

The morphology and fine structure of the two major sting glands in the primitive Australian bull ant, Myrmecra gulosa, are described. The cells of the glandular epithelium of the tubiform Dufour's gland are characterised by a well developed vesicular smooth endoplasmic reticulum, numerous lamellar inclusions, and microvillar differentiations of the apical cell membrane. The cells of the secretory filaments of the venom gland contain a very extensive granular endoplasmic reticulum and numerous Golgi vesicles. The highly proteinaceous secretion reaches the filament lumen through the intracellular end apparatus. Passage through the convoluted gland probably accompanies the modification or production of additional secretory components, as is suggested by the ultrastructural organisation of the convoluted gland cells. The large venom gland reservoir is lined with squamous epithelial cells and a thick cuticular layer, that protects the ant from self-toxication by the powerful venom. Each sting gland opens separately through the sting, and possesses its own muscular control mechanism that allows independent discharge of secretion.

Fine structure of the rectal papillae of the oriental fruuit fly, Dacus dorsalis Hendel (Tephritidae, Diptera Insecta)

1990 ◽  
Vol 48 (3) ◽  
pp. 498-499
Author(s):  
Len Wen-Yung ◽  
Mei-Jung Lin
Keyword(s):  
Fine Structure ◽  
Cell Membrane ◽  
Intercellular Space ◽  
Anterior Part ◽  
Apical Cell ◽  
Posterior Part ◽  
Apical Cell Membrane ◽  
Dacus Dorsalis ◽  
Radial Cell ◽  
Circular Base

Four cone-shaped rectal papillae locate at the anterior part of the rectum in Dacus dorsalis fly. The circular base of the papilla protrudes into the haemolymph (Fig. 1,2) and the rest cone-shaped tip (Fig. 2) inserts in the rectal lumen. The base is surrounded with the cuticle (Fig. 5). The internal structure of the rectal papilla (Fig. 3) comprises of the cortex with the columnar epithelial cells and a rod-shaped medulla. Between them, there is the infundibular space and many trabeculae connect each other. Several tracheae insert into the papilla through the top of the medulla, then run into the cortical epithelium and locate in the intercellular space. The intercellular sinuses distribute in the posterior part of the rectal papilla.The cortex of the base divides into about thirty segments. Between segments there is a radial cell (Fig. 4). Under the cuticle, the apical cell membrane of the cortical epithelium is folded into a regular border of leaflets (Fig. 5).

Bovine pancreatic duct cells express cAMP- and Ca(2+)-activated apical membrane Cl- conductances

1997 ◽  
Vol 273 (1) ◽  
pp. G204-G216 ◽  
Author(s):  
L. al-Nakkash ◽  
C. U. Cotton
Keyword(s):  
Epithelial Cells ◽  
Cell Membrane ◽  
Pancreatic Duct ◽  
Apical Membrane ◽  
Apical Cell ◽  
Primary Cultures ◽  
Apical Cell Membrane ◽  
Anion Secretion ◽  
Duct Epithelium ◽  
Cl Permeability

Secretion of salt and water by the epithelial cells that line pancreatic ducts depends on activation of apical membrane Cl- conductance. In the present study, we characterized two types of Cl- conductances present in the apical cell membrane of bovine pancreatic duct epithelial cells. Primary cultures of bovine main pancreatic duct epithelium and an immortalized cell line (BPD1) derived from primary cultures were used. Elevation of intracellular adenosine 3',5'-cyclic monophosphate (cAMP) or Ca2+ in intact monolayers of duct epithelium induced sustained anion secretion. Agonist-induced changes in plasma membrane Cl- permeability were accessed by 36 Cl- efflux, whole cell current recording, and measurements of transepithelial Cl- current across permeabilized epithelial monolayers. Elevation of intracellular cAMP elicited a sustained increase in Cl- permeability, whereas elevation of intracellular Ca2+ induced only a transient increase in Cl- permeability. Ca(2+)- but not cAMP-induced increases in Cl- permeability were abolished by preincubation of cells with the Ca2+ buffer 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, tetra(acetoxymethyl) ester (BAPTA-AM). N-phenylanthranilic acid (DPC; 1 mM) and glibenclamide (100 microM), but not 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS; 500 microM), inhibited the cAMP-induced increase in Cl- permeability. In contrast, DPC and DIDS, but not glibenclamide, inhibited the Ca(2+)-induced increase in Cl- permeability. We conclude from these experiments that bovine pancreatic duct epithelial cells express at least two types of Cl- channels, cAMP and Ca2+ activated, in the apical cell membrane. Because the Ca(2+)-activated increase in Cl- permeability is transient, the extent to which this pathway contributes to sustained anion secretion by the ductal epithelium remains to be determined.

A possible transepithelial pathway via endoplasmic reticulum in foetal sheep choroid plexus

1977 ◽  
Vol 199 (1135) ◽  
pp. 321-326 ◽  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cerebrospinal Fluid ◽  
Epithelial Cells ◽  
Cell Membrane ◽  
Choroid Plexus ◽  
Tight Junctions ◽  
Apical Cell ◽  
Cell Surfaces ◽  
Ion Gradients ◽  
Choroid Plexuses

Choroid plexuses from early (30–60 days gestation) and late (125 days) sheep foetuses were examined by various ultrastructural techniques in order to investigate possible explanations for the greater penetration of protein and non-electrolytes from blood into cerebrospinal fluid (c. s. f.), which occurs in the early foetus in contrast to later stages. The greater penetration occurs despite the presence of well-formed tight junctions between the epithelial cells and the development of some of the characteristic ion gradients between c. s. f. and plasma. A tubulocisternal system of endoplasmic reticulum appears to connect the basolateral and the apical cell surfaces in the early but not in the late foetuses. Several types of connection between the endoplasmic reticulum and the cell membrane were present in the early foetuses; these may account for some of the different permeability properties of the immature choroid plexus.

scholarly journals Neutrophil interaction with influenza-infected epithelial cells

Blood ◽  
1988 ◽  
Vol 72 (1) ◽  
pp. 142-149 ◽  
Author(s):  
DR Ratcliffe ◽  
SL Nolin ◽  
EB Cramer
Keyword(s):  
Influenza Virus ◽  
Epithelial Cells ◽  
Cell Membrane ◽  
Mdck Cells ◽  
Apical Cell ◽  
Apical Cell Membrane ◽  
Protein Insertion ◽  
Neutrophil Adherence ◽  
Vitro Model

Abstract An in vitro model system was used to study the early neutrophil response to influenza-infected epithelia. In the absence of serum, neutrophil adherence to influenza-infected confluent monolayers of Madin-Darby canine kidney epithelial cells (MDCK) was approximately 590 times greater than neutrophil binding to control cultures. The leukocytes bound specifically to virus-infected cells. Neutrophil adherence to influenza-infected MDCK cells was monitored during the course of one replication cycle, and binding began at a time (4.5 hours) that coincided with viral protein insertion in the apical cell membrane. Ultrastructural examination at 4.5 hours showed that greater than 90% of the neutrophils adhered to the epithelial cell membrane in the absence of budding virus and, at 6.5 hours, 100% of the neutrophils adhered to the epithelium with emerging virions. The number of neutrophils bound to influenza-infected MDCK cells was not affected by the presence or absence of calcium or magnesium but did depend on the amount of viral inoculum and on the temperature of the culture. In direct contrast to hemadsorption of RBCs, neutrophil binding to influenza-infected MDCK cells was 100% greater at 37 degrees C than at 4 degrees C. The neutrophil surface molecules that bound influenza virus appeared to become functionally polarized because the adherence of neutrophils to budding influenza virus or to a virus-coated surface inhibited the neutrophils from binding additional influenza virus to their nonadherent surface.

A preliminary study of the fine structure of the oökinete, oöcyst, and sporozoite formation of Leucocytozoon simondi Mathis and Leger

1968 ◽  
Vol 46 (3) ◽  
pp. 303-307 ◽  
Author(s):  
Sherwin S. Desser ◽  
K. A. Wright
Keyword(s):  
Energy Source ◽  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Epithelial Cells ◽  
Cell Membrane ◽  
Light Microscope ◽  
Dense Material ◽  
Blue Staining ◽  
Preliminary Study

The major features of the cytology of oökinetes, oöcysts, and sporozoites of Leucocytozoon simondi Mathis and Leger as seen in KMnO4-fîxed midguts of Simulium rugglesi and examined in the electron microscope, are related to their appearance in Giemsa-stained light microscope preparations. Thus, blue-staining regions of oökinete and oöcyst and the posterior, darkly stained region of sporozoites correspond to regions of endoplasmic reticulum; light "vacuole-like" regions correspond to accumulations of dense material which were not membrane enclosed; and minute red-stained spots at the anterior tip of sporozoites correspond to paired organelles. The dense material of oökinetes which, in oöcysts, is segregated into developing sporozoites may function as an energy source for sporozoites. The structure and development of these stages is similar to that of Plasmodium spp. The oöcyst of L. simondi develops extracellularly, enclosed by the basal lamina of the midgut with most of its surface surrounded by the basal cell membrane of midgut epithelial cells. This location of the oöcyst may be important in determining the subsequent pattern of development of this species.

Differential signaling and regulation of apical vs. basolateral EGFR in polarized epithelial cells

1998 ◽  
Vol 275 (6) ◽  
pp. C1419-C1428 ◽  
Author(s):  
Scott K. Kuwada ◽  
Kirk A. Lund ◽  
Xiu Fen Li ◽  
Peter Cliften ◽  
Kurt Amsler ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Epithelial Cells ◽  
Cell Membrane ◽  
Apical Cell ◽  
Biologically Active ◽  
Apical Surface ◽  
Apical Cell Membrane ◽  
Collagen Protein ◽  
Epidermal Growth ◽  
Mediate Cell

Overexpression of the epidermal growth factor receptors (EGFR) in polarized kidney epithelial cells caused them to appear in high numbers at both the basolateral and apical cell surfaces. We utilized these cells to look for differences in the regulation and signaling of apical vs. basolateral EGFR. Apical and basolateral EGFR were biologically active and mediated EGF-induced cell proliferation to similar degrees. Receptor downregulation and endocytosis were less efficient at the apical surface, resulting in prolonged EGF-induced tyrosine kinase activity at the apical cell membrane. Tyrosine phosphorylation of EGFR substrates known to mediate cell proliferation, Src-homologous and collagen protein (SHC), extracellularly regulated kinase 1 (ERK1), and ERK2 could be induced similarly by activation of apical or basolateral EGFR. Focal adhesion kinase was tyrosine phosphorylated more by basolateral than by apical EGFR; however, β-catenin was tyrosine phosphorylated to a much greater degree following the activation of mislocalized apical EGFR. Thus EGFR regulation and EGFR-mediated phosphorylation of certain substrates differ at the apical and basolateral cell membrane domains. This suggests that EGFR mislocalization could result in abnormal signal transduction and aberrant cell behavior.

scholarly journals The Fine Structure of the Epithelial Cells of the Mouse Prostate

1960 ◽  
Vol 7 (3) ◽  
pp. 511-513 ◽  
Author(s):  
David Brandes ◽  
Adolfo Portela
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Muscle ◽  
Fine Structure ◽  
Epithelial Cells ◽  
Connective Tissue ◽  
Cell Membrane ◽  
Secretory Cells ◽  
Ventral Lobe ◽  
Cytoplasmic Matrix ◽  
Mouse Prostate

The fine structure of the epithelial cells of one component of the prostatic complex of the mouse—the ventral lobe—has been investigated by electron microscopy. This organ is composed of small tubules, lined by tall simple cuboidal epithelium, surrounded by smooth muscle and connective tissue. Electron micrographs of the epithelial cells of the ventral lobe show these to be limited by a cell membrane, which appears as a continuous dense line. The nucleus occupies the basal portion of the cell and the nuclear envelope consists of two membranes. The cytoplasmic matrix is of moderately low density. The endoplasmic reticulum consists of elongated, circular, and oval profiles representing the cavities of this system bounded by rough surfaced membranes. The Golgi apparatus appears localized in a region between the apical border and the nucleus, and is composed of the usual elements found in secretory cells (3, 9). At the base of the cells, a basement membrane is visible in close contact with the outer aspect of the cell membrane. A space of varying width, which seems to be occupied by connective tissue, separates the epithelial cells from the surrounding smooth muscle fibers and the blood vessels. Bodies with the appearance of portions of the cytoplasm, mitochondria, or profiles of the endoplasmic reticulum can be seen in the lumina of the acini and on the bases of these pictures and others of the apical region the mechanism of secretion by these cells is discussed. The fine structural organization of these cells is compared with that of another component of the mouse prostate—the coagulating gland.

Fine structure of the retinal pigment epithelium in the mud minnow (Umbra limi)

1980 ◽  
Vol 58 (2) ◽  
pp. 258-265 ◽  
Author(s):  
C. R. Braekevelt
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Epithelial Cells ◽  
Smooth Endoplasmic Reticulum ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Apical Surface ◽  
Phagocytic Cells ◽  
Bruch's Membrane ◽  
Bruch’S Membrane

The fine structure of the retinal pigment epithelial layer and associated regions has been studied by electron microscopy in the adult mud minnow Umbra limi. The pigment epithelium is composed of a single layer of large columnar cells. Each epithelial cell has abundant small mitochondria, much smooth endoplasmic reticulum (often in highly organized arrays), myeloid bodies, phagosomes and pigment granules. Rough endoplasmic reticulum and ribosomes are scarce. The scleral or basal border of the epithelial cells is but minimally infolded whereas the vitreal or apical surface displays numerous elongated processes which surround the inner and outer segments of the photoreceptors. Unattached, presumably phagocytic cells are a constant feature both between the retinal epithelial cells and within Bruch's membrane. Bruch's membrane lacks a central elastic layer and is composed only of three layers. The endothelial wall of the choriocapillaris bordering Bruch's membrane is typically very thin with a few fenestrations. This region of the mud minnow eye is morphologically similar to that described in other teleost species but differs from that described in most mammals.

scholarly journals Neutrophil interaction with influenza-infected epithelial cells

Blood ◽  
1988 ◽  
Vol 72 (1) ◽  
pp. 142-149
Author(s):  
DR Ratcliffe ◽  
SL Nolin ◽  
EB Cramer
Keyword(s):  
Influenza Virus ◽  
Epithelial Cells ◽  
Cell Membrane ◽  
Mdck Cells ◽  
Apical Cell ◽  
Apical Cell Membrane ◽  
Protein Insertion ◽  
Neutrophil Adherence ◽  
Vitro Model

An in vitro model system was used to study the early neutrophil response to influenza-infected epithelia. In the absence of serum, neutrophil adherence to influenza-infected confluent monolayers of Madin-Darby canine kidney epithelial cells (MDCK) was approximately 590 times greater than neutrophil binding to control cultures. The leukocytes bound specifically to virus-infected cells. Neutrophil adherence to influenza-infected MDCK cells was monitored during the course of one replication cycle, and binding began at a time (4.5 hours) that coincided with viral protein insertion in the apical cell membrane. Ultrastructural examination at 4.5 hours showed that greater than 90% of the neutrophils adhered to the epithelial cell membrane in the absence of budding virus and, at 6.5 hours, 100% of the neutrophils adhered to the epithelium with emerging virions. The number of neutrophils bound to influenza-infected MDCK cells was not affected by the presence or absence of calcium or magnesium but did depend on the amount of viral inoculum and on the temperature of the culture. In direct contrast to hemadsorption of RBCs, neutrophil binding to influenza-infected MDCK cells was 100% greater at 37 degrees C than at 4 degrees C. The neutrophil surface molecules that bound influenza virus appeared to become functionally polarized because the adherence of neutrophils to budding influenza virus or to a virus-coated surface inhibited the neutrophils from binding additional influenza virus to their nonadherent surface.

Mineralocorticoid regulation of apical cell membrane Na+ and K+ transport of the cortical collecting duct

1985 ◽  
Vol 248 (6) ◽  
pp. F858-F868 ◽  
Author(s):  
S. C. Sansom ◽  
R. G. O'Neil
Keyword(s):  
Cell Membrane ◽  
Tight Junction ◽  
Apical Membrane ◽  
Collecting Duct ◽  
Apical Cell ◽  
Cortical Collecting Duct ◽  
Apical Cell Membrane ◽  
K Secretion ◽  
Junction Conductance ◽  
K Transport

The effects of mineralocorticoid (DOCA) treatment of rabbits on the Na+ and K+ transport properties of the cortical collecting duct apical cell membrane were assessed using microelectrode techniques. Applying standard cable techniques and equivalent circuit analysis to the isolated perfused tubule, the apical cell membrane K+ and Na+ currents and conductances could be estimated from the selective effects of the K+ channel blocker Ba2+ and the Na+ channel blocker amiloride on the apical membrane; amiloride treatment was observed also to decrease the tight junction conductance by an average of 10%. After 1 day of DOCA treatment, the Na+ conductance and current (Na+ influx) of the apical cell membrane doubled and remained elevated with prolonged treatment for up to 2 wk. The apical cell membrane K+ conductance was not influenced after 1 day, although the K+ current (K+ secretion) increased significantly due to an increased driving force for K+ exit. After 4 days or more of DOCA treatment the K+ conductance doubled, resulting in a further modest stimulation in K+ secretion. After 2 wk of DOCA treatment the tight junction conductance decreased by near 30%, resulting in an additional hyperpolarization of the transepithelial voltage, thereby favoring K+ secretion. It is concluded that the acute effect (within 1 day) of mineralocorticoids on Na+ and K+ transport is an increase in the apical membrane Na+ conductance followed by delayed chronic alterations in the apical membrane K+ conductance and tight junction conductance, thereby resulting in a sustained increased capacity of the tubule to reabsorb Na+ and secrete K+.

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