Fine Structure of the Ventral Disk Apparatus and the Mechanism of Attachment in the Flagellate Giardia Muris

1973 ◽  
Vol 13 (1) ◽  
pp. 11-41 ◽  
Author(s):  
D. V. HOLBERTON
Keyword(s):  
Fine Structure ◽  
Surface Membrane ◽  
Ventral Surface ◽  
Surface Coat ◽  
Suction Force ◽  
Sinusoidal Waveform ◽  
The Face ◽  
Ventral Disk ◽  
Host Epithelium ◽  
Duodenal Epithelium

The topography of the Giardia trophozoite is dominated by the large domed sucking disk of the ventral surface. Attached to the host duodenal epithelium, the rim of this disk penetrates the enteric surface coat and interdigitates with microvilli of the epithelial cells, approaching to within 20 nm of the host surface membrane. Distortion of the host brush border within the disk suggests an applied suction force. A mechanical explanation of disk action is sought in a detailed description of the fine structure of components of the ventral surface - but is found to be untenable. The disk is supported by a platform of modified 25-nm microtubules, linked to the ventral membrane by side arms and bearing heavily cross-linked vertical dense ribbons. It is argued that such is the architecture of rigidity rather than relative movement. Around the disk a mobile cytoplasmic flange is supported by 2 lateral plates of periodic substructure. The flange has no clear mechanical role in attachment; a likely evolutionary origin from a component of the anterior axonemal axis is suggested. The cavity of the ventral disk leads posteriorly through a portal into the ventrocaudal groove: a shallow depression that houses the ventral flagella. Observation of isolated living trophozoites suggests that attachment depends on the continuing activity of the ventral flagella, which normally beat synchronously in a sinusoidal waveform. Electron micrographs confirm that this waveform is maintained in situ on the host epithelium. Of the 4 pairs of flagella, the ultrastructure of the ventral flagella is notable for additional components in the flagellar shaft, including an intraflagellar dense rod linked to 3 axonemal doublets by fine connectives. From a consideration of analogous macroscopic systems, a preliminary hydrodynamic analysis is advanced in which the suction force of attachment follows from the pattern of fluid flow induced by the beating ventral flagella. The significance of the conclusion that cytoplasmic microtubules (or structures derived from them) apparently maintain cell shape in the face of an applied external force is discussed.

Cell surface saccharides of Trypanosoma lewisi. I. Polycation-induced cell agglutination and fine-structure cytochemistry

1975 ◽  
Vol 19 (3) ◽  
pp. 621-644
Author(s):  
D.M. Dwyer
Keyword(s):  
Fine Structure ◽  
Cell Surface ◽  
Alcian Blue ◽  
Chondroitin Sulphate ◽  
Surface Membrane ◽  
Ruthenium Red ◽  
Surface Coat ◽  
Cell Agglutination ◽  
Trypanosoma Lewisi ◽  
Cationic Compounds

Trypanosoma lewisi bloodstream and culture forms were agglutinated differentially with low concentrations of the cationic compounds: ruthenium red, ruthenium violet, Alcian blue chloride, 1-hexadecylpyridinium chloride, lanthanum chloride, and cationized ferritin. The bloodstream form trypanosomes gave the highest agglutination levels with each of the compounds tested. Ruthenium red was the most effective inducer of cell agglutination among the several cations used. Trypsin-treated bloodstream forms were agglutinated less in the presence of ruthenium red than untreated controls. Ruthenium red-induced cell agglutination also was lowered with chondroitin sulphate and dextran sulphate, but not with alpha-D-glucose, alpha-D-mannose or with several methyl glycosides. Treatment of the bloodstream trypanosomes with alpha-amylase, dextranase, or neuraminidase had little effect on agglutination levels obtained with ruthenium red. Fine-structure cytochemical staining with ruthenium red, ruthenium violet, and Alcian blue-lanthanum nitrate was used to ascertain the presence and distribution of presumptive carbohydrates in the trypanosome cell surface. The extracellular surface coat of the bloodstream forms stained densely with each of the polycationic dyes. Trypsin treatment removed the surface coat from bloodstream trypanosomes; however, the surface membranes of the organisms were stained densely with the several dyes. Similar surface-membrane staining was obtained with the cationic compounds and the culture forms, which lack a cell surface coat. Cationized ferrin was used at the fine-structure level to visualize the negative surface charge present in the cell surface coat and external membrane of the several trypanosome stages. Results obrained from the agglutination and cytochemistry experiments indicate that complex polysaccharides are present in the surface membranes and cell surface coat of T. lewisi bloodstream forms. Similar conclusions also pertain to the surface membranes of the T. lewisi culture from trypanosomes. The carbohydrates probably represent glycopeptide and glycoprotein structural components of the surface membrane of this organism.

scholarly journals Imaging Analysis and Digital Restoration of the Holy Face of Manoppello—Part I

Heritage ◽  
2018 ◽  
Vol 1 (2) ◽  
pp. 289-305 ◽  
Author(s):  
Liberato De Caro ◽  
Emilio Matricciani ◽  
Giulio Fanti
Keyword(s):  
Fine Structure ◽  
Physical Mechanism ◽  
Empty Space ◽  
Imaging Analysis ◽  
Digital Restoration ◽  
The Face ◽  
Spatial Terms ◽  
The Veil ◽  
Optical Behavior ◽  
Fiber Fabric

The Veil of Manoppello is an icon of the face of Christ (Holy Face). Its particular characteristic is being semitransparent. The face is visible on both sides (front–back) and, depending on the lighting and observation conditions, shows some differences in the anatomical details. An analysis of this icon has allowed us to clarify some aspects of the possible physical mechanism underlying its unusual optical behavior. It is a linen fiber fabric consisting of very thin threads with a thickness of about 0.1 mm, separated by distances even double the thickness of the threads, so that about 42% of the Veil is empty space. The fibers constituting the linen threads may have been cemented by an organic substance of chemical composition similar to cellulose, presumably starch, eliminating the air between them. Such a structure causes the optical behavior of the medium to be intermediate between those of a translucent medium (thin cemented linen threads) and a transparent one (empty space between the threads). The problem of digital image restoration in spatial terms has also been tackled, since the Holy Face is deformed due to distortions of the meshes of the Veil, caused by the yielding of the very fine structure of the fabric.

Fine structure and development of schizonts, merozoites and macrogamonts of Eimeria acervulina in the goblet cells of the duodenal epithelium of experimentally infected birds

Parasitology ◽  
1975 ◽  
Vol 70 (2) ◽  
pp. 223-229 ◽  
Author(s):  
E. Michael
Keyword(s):  
Fine Structure ◽  
Epithelial Cells ◽  
Golgi Apparatus ◽  
Host Cell ◽  
Goblet Cells ◽  
Cellular Level ◽  
Site Specificity ◽  
Eimeria Acervulina ◽  
Duodenal Epithelium

The fine structure of trophozoites, schizonts, merozoites and macrogamonts of Eimeria acervulina found in goblet cells of the duodenal epithelium of chicks is described and compared with the corresponding stages formed in other epithelial cells. Complete schizogony, with the formation of mature merozoites, occurred freely in goblet cells. Developing macrogamonts (but no microgamonts) were rarely found in goblet cells. The stages observed were confined to the cytoplasm of the host cell above the Golgi apparatus and were usually seen between the mucous granules. The stages seen appeared normal, and contained similar structures to corresponding stages developing in other cells. The finding of developing stages of E. acervulina in goblet cells provides further evidence that site specificity of Eimeria at the cellular level is not as strict as previously thought.

scholarly journals Identification of a surface membrane proton-translocating ATPase in promastigotes of the parasitic protozoan Leishmania donovani

1988 ◽  
Vol 256 (1) ◽  
pp. 13-21 ◽  
Author(s):  
D Zilberstein ◽  
D M Dwyer
Keyword(s):  
Fine Structure ◽  
Leishmania Donovani ◽  
Surface Membrane ◽  
Proton Pumping ◽  
Maximal Inhibition ◽  
Parasitic Protozoan ◽  
Immunochemical Methods ◽  
Ic50 Concentration ◽  
Proton Translocating Atpase

ATPase activities were measured in surface membranes and mitochondria isolated from promastigotes of the parasitic protozoan Leishmania donovani. The two enzymes were differentiated on the basis of pH optima, inhibitor sensitivity and by immunochemical methods. The surface-membrane (SM-) ATPase had an activity of 100 nmol/min per mg of protein, which was optimal at pH 6.5. The enzyme was Mg2+-dependent, partially inhibited by Ca2+, and unaffected by Na+ or K+. The SM-ATPase was inhibited by orthovanadate, NN'-dicyclohexylcarbodi-imide, and N-ethylmaleimide [IC50 (concentration causing half-maximal inhibition) 7.5, 25 and 520 microM respectively]; however, it was unaffected by ouabain, azide or oligomycin. The SM-ATPase demonstrated a Km of 1.05 mM and a Vmax. of 225 nmol/min per mg of protein. Moreover, fine-structure cytochemical results demonstrated that the SM-ATPase was localized to the cytoplasmic lamina of the parasite SM. A method was devised for the isolation of SM-derived vesicles. These were used to demonstrate the proton-pumping capacity of the SM-ATPase. Cumulatively, these results constitute the first demonstration of a surface-membrane proton-translocating ATPase in a parasitic protozoan.

Structure of the variant glycoproteins and surface coat of Trypanosoma brucei

1984 ◽  
Vol 307 (1131) ◽  
pp. 3-12 ◽  
Keyword(s):  
Antigenic Variation ◽  
Surface Membrane ◽  
Dodecanoic Acid ◽  
Surface Coat ◽  
African Trypanosomes ◽  
Individual Gene ◽  
Amino Terminal ◽  
Amino Acid Sequence Variation ◽  
Carboxy Terminal ◽  
Variant Surface Glycoproteins

The pathogenic African trypanosomes have a unique mechanism for antigenic variation. Each cell is covered by a surface coat consisting of about seven million essentially identical glycoprotein molecules drawn from a large repertoire of variants, each encoded by an individual gene. Amino acid sequence variation extends throughout the molecule but reduces from the amino terminus to the carboxy terminus, where certain features, especially the grouping of cysteine residues, are quite conserved. The range of diversity within the thousand or so variant glycoprotein genes that exist in each cell is large. New variants may arise instantaneously by segmental gene conversion. Variant surface glycoproteins are synthesized with amino terminal signal sequences and hydrophobic carboxy terminal tails. The tails are extraordinarily conserved. After synthesis, they are replaced by a complex glycolipid structure in which myristic (dodecanoic) acid serves to anchor the polypeptide to the surface membrane. Enzymic cleavage of myristic acid releases variant glycoproteins from the surface coat.

scholarly journals A COMPARATIVE STUDY OF THE ULTRASTRUCTURE OF MICROVILLI IN THE EPITHELIUM OF SMALL AND LARGE INTESTINE OF MICE

1967 ◽  
Vol 34 (2) ◽  
pp. 447-461 ◽  
Author(s):  
T. M. Mukherjee ◽  
A. Wynn Williams
Keyword(s):  
Small Intestine ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Epithelial Cells ◽  
Surface Coat ◽  
Free Zone ◽  
Colonic Crypts ◽  
Mouse Intestine ◽  
Different Levels ◽  
Small And Large Intestine

A comparative analysis of the fine structure of the microvilli on jejunal and colonic epithelial cells of the mouse intestine has been made. The microvilli in these two locations demonstrate a remarkably similar fine structure with respect to the thickness of the plasma membrane, the extent of the filament-free zone, and the characteristics of the microfilaments situated within the microvillous core. Some of the core microfilaments appear to continue across the plasma membrane limiting the tip of the microvillus. The main difference between the microvilli of small intestine and colon is in the extent and organization of the surface coat. In the small intestine, in addition to the commonly observed thin surface "fuzz," occasional areas of the jejunal villus show a more conspicuous surface coat covering the tips of the microvilli. Evidence has been put forward which indicates that the surface coat is an integral part of the epithelial cells. In contrast to the jejunal epithelium, the colonic epithelium is endowed with a thicker surface coat. Variations in the organization of the surface coat at different levels of the colonic crypts have also been noted. The functional significance of these variations in the surface coat is discussed.

scholarly journals THE FINE STRUCTURE OF GIARDIA MURIS

1966 ◽  
Vol 29 (2) ◽  
pp. 317-332 ◽  
Author(s):  
Daniel S. Friend
Keyword(s):  
Fine Structure ◽  
Osmium Tetroxide ◽  
Smooth Endoplasmic Reticulum ◽  
Dorsal Surface ◽  
Ventral Surface ◽  
Cell Periphery ◽  
Adhesive Disc ◽  
Medial Surfaces ◽  
Dorsal Portion ◽  
Giardia Muris

Giardia is a noninvasive intestinal zooflagellate. This electron microscope study demonstrates the fine structure of the trophozoite of Giardia muris in the lumen of the duodenum of the mouse as it appears after combined glutaraldehyde and acrolein fixation and osmium tetroxide postfixation. Giardia muris is of teardrop shape, rounded anteriorly, with a convex dorsal surface and a concave ventral one. The anterior two-thirds of the ventral surface is modified to form an adhesive disc. The adhesive disc is divided into 2 lobes whose medial surfaces form the median groove. The marginal grooves are the spaces between the lateral crests of the adhesive disc and a protruding portion of the peripheral cytoplasm. The organism has 2 nuclei, 1 dorsal to each lobe of the adhesive disc. Between the anterior poles of the nuclei, basal bodies give rise to 8 paired flagella. The median body, unique to Giardia, is situated between the posterior poles of the nuclei. The cytoplasm contains 300-A granules that resemble particulate glycogen, 150- to 200-A granules that resemble ribosomes, and fusiform clefts. The dorsal portion of the cell periphery is occupied by a linear array of flattened vacuoles, some of which contain clusters of dense particles. The ventrolateral cytoplasm is composed of regularly packed coarse and fine filaments which extend as a striated flange around the adhesive disc. The adhesive disc is composed of a layer of microtubules which are joined to the cytoplasm by regularly spaced fibrous ribbons. The plasma membrane covers the ventral and lateral surfaces of the disc. The median body consists of an oval aggregate of curved microtubules. Microtubules extend ventrally from the median body to lie alongside the caudal flagella. The intracytoplasmic portions of the caudal, lateral, and anterior flagella course considerable distances, accompanied by hollow filaments adjacent to their outer doublets. The intracytoplasmic portions of the anterior flagella are accompanied also by finely granular rodlike bodies. No structures identifiable as mitochondria, smooth endoplasmic reticulum, the Golgi complex, lysosomes, or axostyles are recognized.

scholarly journals THE FINE STRUCTURE OF THE ELECTRIC ORGAN OF TORPEDO MARMORATA

1965 ◽  
Vol 24 (1) ◽  
pp. 129-141 ◽  
Author(s):  
Michael N. Sheridan
Keyword(s):  
Fine Structure ◽  
Connective Tissue ◽  
Basement Membrane ◽  
Intercellular Space ◽  
Electric Organ ◽  
Dorsal Surface ◽  
Ventral Surface ◽  
Nerve Fibers ◽  
Nerve Endings ◽  
Torpedo Marmorata

The fine structure of the electric organ of the fish Torpedo marmorata has been examined after osmium tetroxide or potassium permanganate fixation, acetone dehydration, and Araldite embedment. This organ consists of stacks of electroplaques which possess a dorsal noninnervated and a ventral richly innervated surface. Both surfaces are covered with a thin basement membrane. A tubular membranous network whose lumen is continuous with the extracellular space occupies the dorsal third of the electroplaque. Nerve endings, separated from the ventral surface of the electroplaque by a thin basement membrane, contain synaptic vesicles (diameter 300 to 1200 A), mitochondria, and electron-opaque granules (diameter 300 A). Projections from the nerve endings occupy the lumina of the finger-like invaginations of the ventral surface. The cytoplasm of the electroplaques contains the usual organelles. A "cellular cuff" surrounds most of the nerve fibers in the intercellular space, and is separated from the nerve fibre and its Schwann cell by a space containing connective tissue fibrils. The connective tissue fibrils and fibroblasts in the intercellular space are primarily associated with the dorsal surface of the electroplaque.

Fine Structure of the Cell Surface Coat of Trypanosoma musculi Bloodstream and Metacyclic Forms Using the Thiosemicarbazide-Silver Proteinate Method

1987 ◽  
Vol 73 (2) ◽  
pp. 415
Author(s):  
Michel Roger ◽  
Simon Garzon ◽  
Henri Strykowski ◽  
Pierre Viens
Keyword(s):  
Fine Structure ◽  
Cell Surface ◽  
Surface Coat
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