scholarly journals THE FINE STRUCTURE OF CORTICAL COMPONENTS OF PARAMECIUM MULTIMICRONUCLEATUM

1955 ◽  
Vol 1 (6) ◽  
pp. 583-604 ◽  
Author(s):  
Albert W. Sedar ◽  
Keith R. Porter
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Basal Body ◽  
Three Dimensional ◽  
Cell Types ◽  
The Body ◽  
Fiber System ◽  
Thin Sections ◽  
Ciliary Membrane ◽  
The Matrix

The electron microscope was used to study the structure and three dimensional relationships of the components of the body cortex in thin sections of Paramecium multimicronucleatum. Micrographs of sections show that the cortex is covered externally by two closely apposed membranes (together ∼250 A thick) constituting the pellicle. Beneath the pellicle the surface of the animal is molded into ridges that form a polygonal ridgework with depressed centers. It is these ridges that give the surface of the organism its characteristic configuration and correspond to the outer fibrillar system of the light microscope image. The outer ends of the trichocysts with their hood-shaped caps are located in the centers of the anterior and posterior ridges of each polygon. The cilia extend singly from the depressed centers of the surface polygons. Each cilium shows two axial filaments with 9 peripheral and parallel filaments embedded in a matrix and the whole surrouned by a thin ciliary membrane. The 9 peripheral filaments are double and these are evenly spaced in a circle around the central pair. The ciliary membrane is continuous with the outer member of the pellicular membrane, whereas the plasma membrane is continuous with the inner member of the pellicular membrane. At the level of the plasma membrane the proximal end of the cilium is continuous with its tube-shaped basal body or kinetosome. The peripheral filaments of the cilium, together with the material of cortical matrix which tends to condense around them, form the sheath of the basal body. The kinetodesma connecting the ciliary kinetosomes (inner fibrillar system of the light microscopist) is composed of a number of discrete fibrils which overlap in a shingle-like fashion. Each striated kinetosomal fibril originates from a ciliary kinetosome and runs parallel to other kinetosomal fibrils arising from posterior kinetosomes of a particular meridional array. Sections at the level of the ciliary kinetosomes reveal an additional fiber system, the infraciliary lattice system, which is separate and distinct from the kinetodesmal system. This system consists of a fibrous network of irregular polygons and runs roughly parallel to the surface of the animal. Mitochondria have a fine structure similar in general features to that described for a number of mammalian cell types, but different in certain details. The structures corresponding to cristae mitochondriales appear as finger-like projections or microvilli extending into the matrix of the organelle from the inner membrane of the paired mitochondrial membrane. The cortical cytoplasm contains also a particulate component and a system of vesicles respectively comparable to the nucleoprotein particles and to the endoplasmic reticulum described in various metazoan cell types. An accessory kinetosome has been observed in oblique sections of a number of non-dividing specimens slightly removed from the ciliary kinetosome and on the same meridional line as the cilia and trichocysts. Its position corresponds to the location of the kinetosome of the newly formed cilium in animals selected as being in the approaching fission stage of the life cycle.

Cell Fine Structure as Revealed in Dessicator-Dried Resinless Sections

1981 ◽  
Vol 39 ◽  
pp. 622-623
Author(s):  
R. P. Becker ◽  
J. J. Wolosewick ◽  
J. Ross-Stanton
Keyword(s):  
Fine Structure ◽  
Tannic Acid ◽  
Three Dimensional ◽  
Albino Rats ◽  
Cell Organelles ◽  
Vascular Perfusion ◽  
Thin Sections ◽  
Carbon Coated ◽  
Embedding Medium ◽  
Polyethylene Glycol 6000

Methodology has been introduced recently which allows transmission and scanning electron microscopy of cell fine structure in semi-thin sections unencumbered by an embedding medium. Images obtained from these “resinless” sections show a three-dimensional lattice of microtrabeculfee contiguous with cytoskeletal structures and membrane-bounded cell organelles. Visualization of these structures, especially of the matiiDra-nous components, can be facilitated by employing tannic acid in the fixation step and dessicator drying, as reported here.Albino rats were fixed by vascular perfusion with 2% glutaraldehyde or 1.5% depolymerized paraformaldehyde plus 2.5% glutaraldehyde in 0.1M sodium cacodylate (pH 7.4). Tissues were removed and minced in the fixative and stored overnight in fixative containing 4% tannic acid. The tissues were rinsed in buffer (0.2M cacodylate), exposed to 1% buffered osmium tetroxide, dehydrated in ethyl alcohol, and embedded in pure polyethylene glycol-6000 (PEG). Sections were cut on glass knives with a Sorvall MT-1 microtome and mounted onto poly-L-lysine, formvar-carbon coated grids while submerged in a solution of 95% ethanol containing 5% PEG.

scholarly journals Petiole-Lamina Transition Zone: A Functionally Crucial but Often Overlooked Leaf Trait

Plants ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 774
Author(s):  
Max Langer ◽  
Thomas Speck ◽  
Olga Speck
Keyword(s):  
Transition Zone ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Body Plan ◽  
The Body ◽  
Vascular Bundles ◽  
Cross Sectional ◽  
Thin Sections ◽  
Transition Zones ◽  
The Cross

Although both the petiole and lamina of foliage leaves have been thoroughly studied, the transition zone between them has often been overlooked. We aimed to identify objectively measurable morphological and anatomical criteria for a generally valid definition of the petiole–lamina transition zone by comparing foliage leaves with various body plans (monocotyledons vs. dicotyledons) and spatial arrangements of petiole and lamina (two-dimensional vs. three-dimensional configurations). Cross-sectional geometry and tissue arrangement of petioles and transition zones were investigated via serial thin-sections and µCT. The changes in the cross-sectional geometries from the petiole to the transition zone and the course of the vascular bundles in the transition zone apparently depend on the spatial arrangement, while the arrangement of the vascular bundles in the petioles depends on the body plan. We found an exponential acropetal increase in the cross-sectional area and axial and polar second moments of area to be the defining characteristic of all transition zones studied, regardless of body plan or spatial arrangement. In conclusion, a variety of terms is used in the literature for describing the region between petiole and lamina. We prefer the term “petiole–lamina transition zone” to underline its three-dimensional nature and the integration of multiple gradients of geometry, shape, and size.

The fine structure of Sphaerotilus nutans

1973 ◽  
Vol 19 (3) ◽  
pp. 309-313 ◽  
Author(s):  
Judith F. M. Hoeniger ◽  
H.-D. Tauschel ◽  
J. L. Stokes
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Lateral Position ◽  
Thin Sections ◽  
Liquid Cultures ◽  
Sphaerotilus Natans ◽  
Stationary Liquid ◽  
Basal Disk ◽  
Polar Organelle

Sphaerotilus natans developed sheathed filaments in stationary liquid cultures and motile swarm cells in shaken ones. Electron microscopy of negatively stained preparations and thin sections showed that the sheath consists of fibrils. When the filaments were grown in broth with glucose added, the sheath was much thicker and the cells were packed with granules of poly-β-hydroxybutyrate.Swarm cells possess a subpolar tuft of 10 to 30 flagella and a polar organelle which is usually inserted in a lateral position and believed to be ribbon-shaped. The polar organelle consists of an inner layer joined by spokes to an accentuated plasma membrane. The flagellar hook terminates in a basal disk, consisting of two rings, which is connected by a central rod to a second basal disk.

The formation and function of the extraacrosomal layer and modification of the plasma membrane in spermiogenesis of Acrida lata motschulsky (Orthoptera)

1978 ◽  
Vol 36 (2) ◽  
pp. 570-571
Author(s):  
Gonpachiro Yasuzumi ◽  
Toshikatsu Asai
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Cell Surface ◽  
Membrane Structure ◽  
Early Stage ◽  
Cell Types ◽  
Unit Membrane ◽  
Sharp Point ◽  
Specific Proteins ◽  
And Function

Receptor-specific proteins are now being widely and usefully applied to the study of cell-surface topography. We have been actively interested in this field from the standpoint of spermiogenesis of the grasshopper. The surface of developing spermatids is in contact with other cells or with their environment, and in addition to carrying on metabolic processes necessary for maturation they must also exhibit the specificity that distinguishes cells from the same cell types from different individuales. The cell bodies of the grasshopper, Acrida lata Motschulsky, spermatids are spherical in the early stage of metamorphosis, but later they become conical and more and more elongate until they are long slender rods, rounded at the base and tapering at the tip to a sharp point. Concurrently with these changes in the spermatid cell bodies, the remarkable trans formation occurs in the fine structure of the cell-surface. In the early stage of maturation of spermatids, the cell-surface is smooth and consists of the unit membrane structure.

Effect of different colchicine concentrations on microtubules and membranes in tomato root tip cells

1988 ◽  
Vol 46 ◽  
pp. 306-307
Author(s):  
T.E. Jensen
Keyword(s):  
Plasma Membrane ◽  
Phosphate Buffer ◽  
Cell Types ◽  
Root Tip ◽  
Distilled Water ◽  
Root Tips ◽  
Cell Organelles ◽  
Tomato Root ◽  
Thin Sections ◽  
Numerous Cell

The effect of colchicine on microtubules has been investigated in numerous cell types. In this present study we have used different concentrations of colchicine to determine if the two major groups of microtubules in plant cells, plasma membrane associated and mitotic, are differentially sensitive to this drug.Tomato seeds “Michigan forcing” were germinated on filter paper saturated with distilled water. Radicles 1.5 to 2.0cm were selected and placed into either distilled water or colchicine, 0.001, 0.01, 0.03, 0.04, 0.05, 0.1%, for 20 hrs. During this time they were kept at 20°C in dim light. Root tips were fixed in 3% glutaraldehyde in phosphate buffer at pH7.2 for lh at 4°C. After 5 rinses in buffer they were placed in 1% OsO4 in phosphate buffer at pH7.2 for 1h at 4°C. Root tips were then dehydrated in ethanol, treated with propylene and embedded in Epon.No growth occurred in any of the colchicine treated radicles. Observation of thin sections of control cells revealed many plasma membrane associated microtubules, many cells in division stages and the usual arrangement of cell organelles.

Immunoelectron microscopy of the intracellular compartments of prespore cells of dictyostelium discoideum

1990 ◽  
Vol 48 (3) ◽  
pp. 606-607
Author(s):  
Gregory W. Erdos ◽  
Bonnie J. O'Brien ◽  
Christopher M. West
Keyword(s):  
Three Dimensional ◽  
Cell Types ◽  
Dense Layer ◽  
Slime Molds ◽  
Thin Sections ◽  
Dimensional Reconstruction ◽  
Intracellular Compartments ◽  
Cellular Slime ◽  
Secretory System ◽  
Acidic Compartments

In the amoeboid cellular slime molds two cell types are formed during differentiation, prestalk cells and prespore cells which ultimately become the stalk and spore cells of the mature sorocarp. The prespore cells can be identified ultrastructurally by the prespore vesicles (PSV), which have a dense layer lining the inside of the compartment (Fig. 1). The PSV's are known to contain several glycoproteins and a galactose polysaccharide that are released to the cell surface to become major components of the spore coat. Further investigations in this laboratory, by three dimensional reconstruction from serial thin sections and by confocal fluorescence microscopy have shown that the PSV's are not a collection of separate vesicles, but rather a tubular reticulum asymmetrically disposed in the cell. Similar geometry has been shown for some lysosomal systems. A recent report has shown that the lysosomal enzyme, α-mannosidase, can be localized to the PSV. These pieces of evidence suggest a possible lysosomal function or lysosomal origin for the prespore secretory system. In an effort to better characterize the PSV compartment we have chosen two monoclonal antibodies, 5G7 which recognizes a common lysosomal epitope and 81.2 which recognizes a carbohydrate epitope on the plasma membrane and on compartments of phagocytotic and autophagic origin. We further chose to characterize the distribution of acidic compartments using the DAMP method of Anderson, which would give us an indication of functional lysosomal activity.

scholarly journals Functional properties of multiple isoforms of human divalent metal-ion transporter 1 (DMT1)

2007 ◽  
Vol 403 (1) ◽  
pp. 59-69 ◽  
Author(s):  
Bryan Mackenzie ◽  
Hitomi Takanaga ◽  
Nadia Hubert ◽  
Andreas Rolfs ◽  
Matthias A. Hediger
Keyword(s):  
Plasma Membrane ◽  
Functional Properties ◽  
Metal Ion ◽  
Cell Types ◽  
Divalent Metal ◽  
The Body ◽  
Ion Transporter ◽  
Voltage Dependent ◽  
Divalent Metal Ion ◽  
Responsive Element

DMT1 (divalent metal-ion transporter 1) is a widely expressed metal-ion transporter that is vital for intestinal iron absorption and iron utilization by most cell types throughout the body, including erythroid precursors. Mutations in DMT1 cause severe microcytic anaemia in animal models. Four DMT1 isoforms that differ in their N- and C-termini arise from mRNA transcripts that vary both at their 5′-ends (starting in exon 1A or exon 1B) and at their 3′-ends giving rise to mRNAs containing (+) or lacking (−) the 3′-IRE (iron-responsive element) and resulting in altered C-terminal coding sequences. To determine whether these variations result in functional differences between isoforms, we explored the functional properties of each isoform using the voltage clamp and radiotracer assays in cRNA-injected Xenopus oocytes. 1A/IRE(+)-DMT1 mediated Fe2+-evoked currents that were saturable (K0.5Fe≈1–2 μM), temperature-dependent (Q10≈2), H+-dependent (K0.5H≈1 μM) and voltage-dependent. 1A/IRE(+)-DMT1 exhibited the provisional substrate profile (ranked on currents) Cd2+, Co2+, Fe2+, Mn2+>Ni2+, V3+≫Pb2+. Zn2+ also evoked large currents; however, the zinc-evoked current was accounted for by H+ and Cl− conductances and was not associated with significant Zn2+ transport. 1B/IRE(+)-DMT1 exhibited the same substrate profile, Fe2+ affinity and dependence on the H+ electrochemical gradient. Each isoform mediated 55Fe2+ uptake and Fe2+-evoked currents at low extracellular pH. Whereas iron transport activity varied markedly between the four isoforms, the activity for each correlated with the density of anti-DMT1 immunostaining in the plasma membrane, and the turnover rate of the Fe2+ transport cycle did not differ between isoforms. Therefore all four isoforms of human DMT1 function as metal-ion transporters of equivalent efficiency. Our results reveal that the N- and C-terminal sequence variations among the DMT1 isoforms do not alter DMT1 functional properties. We therefore propose that these variations serve as tissue-specific signals or cues to direct DMT1 to the appropriate subcellular compartments (e.g. in erythroid cells) or the plasma membrane (e.g. in intestine).

scholarly journals THE FINE STRUCTURE OF THE TRANSITIONAL EPITHELIUM OF RAT URETER

1965 ◽  
Vol 26 (1) ◽  
pp. 25-48 ◽  
Author(s):  
R. M. Hicks
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Basement Membrane ◽  
Transitional Epithelium ◽  
Permeability Barrier ◽  
Basal Cells ◽  
Thin Sections ◽  
Squamous Cells ◽  
Intermediate Cells ◽  
Nucleoside Triphosphatase

The fine structure of the transitional epithelium of rat ureter has been studied in thin sections with the electron microscope, including some stained cytochemically to show nucleoside triphosphatase activity. The epithelium is three to four cells deep with cuboidal or columnar basal cells, intermediate cells, and superficial squamous cells. The basal cells are attached by half desmosomes, or attachment plates, on their basal membranes to a basement membrane which separates the epithelium from the lamina propria. Fine extracellular fibres, ca. 100 A in diameter, are to be found in the connective tissue layer immediately below the basement membrane of this epithelium. The plasma membranes of the basal and intermediate cells and the lateral and basal membranes of the squamous cells are deeply interdigitated, and nucleoside triphosphatase activity is associated with them. All the cells have a dense feltwork of tonofilaments which ramify throughout the cytoplasm. The existence of junctional complexes, comprising a zonula occludens, zonula adhaerens, and macula adhaerens or desmosome, between the lateral borders of the squamous cells is reported. It is suggested that this complex is the major obstacle to the free flow of water from the extracellular spaces into the hypertonic urine. The free luminal surface of the squamous cells and many cytoplasmic vesicles in these cells are bounded by an unusually thick plasma membrane. The three leaflets of this unit membrane are asymmetric, with the outer one about twice as thick as the innermost one. The vesicles and the plasma membrane maintain angular conformations which suggest the membrane to be unusually rigid. No nucleoside triphosphatase activity is associated with this membrane. Arguments are presented to support a suggestion that this thick plasma membrane is the morphological site of a passive permeability barrier to water flow across the cells, and that keratin may be included in the membrane structure. The possible origin of the thick plasma membrane in the Golgi complex is discussed. Bodies with heterogeneous contents, including characteristic hexagonally packed stacks of thick membranes, are described. It is suggested that these are "disposal units" for old or surplus thick membrane. A cell type is described, which forms only 0.1 to 0.5 per cent of the total cell population and contains bundles of tubular fibres or crystallites. Their origin and function are not known.

scholarly journals THE FINE STRUCTURE OF THE MID-BODY OF THE RAT ERYTHROBLAST

1962 ◽  
Vol 13 (1) ◽  
pp. 109-115 ◽  
Author(s):  
Robert C. Buck ◽  
James M. Tisdale
Keyword(s):  
Bone Marrow ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Electron Microscope ◽  
Cleavage Furrow ◽  
Intercellular Bridge ◽  
Spindle Fiber ◽  
Thin Sections ◽  
Rat Bone ◽  
Spindle Fibers

The development of the mid-body has been studied in mitotic erythroblasts of the rat bone marrow by means of thin sections examined with the electron microscope. A differentiated region on the continuous spindle fibers, consisting of a localized increase in density, is observed at the equatorial plane. The mid-body seems to develop by the aggregation of such denser lengths of spindle fiber. Its appearance precedes that of the cleavage furrow. A plate-like arrangement of fibrillary material lies transversely across the telophase intercellular bridge. Later, this material becomes amorphous and assumes the form of a dense ring closely applied to a ridge in the plasma membrane encircling the middle of the bridge. Although the mid-body forms in association with the spindle fibers, it is a structurally distinct part, and the changes which it undergoes are not shared by the rest of the bundle of continuous fibers.

scholarly journals THE CILIARY NECKLACE

1972 ◽  
Vol 53 (2) ◽  
pp. 494-509 ◽  
Author(s):  
Norton B. Gilula ◽  
Peter Satir
Keyword(s):  
Sea Urchin ◽  
Energy Transduction ◽  
Thin Sections ◽  
Ciliary Membrane ◽  
Membrane Particles ◽  
The Matrix ◽  
Longitudinal Fractures ◽  
Rat Trachea ◽  
Sea Urchin Sperm ◽  
Ciliary Shaft

Cilia, primarily of the lamellibranch gill (Elliptio and Mytilus), have been examined in freeze-etch replicas. Without etching, cross fractures rarely reveal the 9 + 2 pattern, although suggestions of ninefold symmetry are present. In etched preparations, longitudinal fractures through the matrix show a triplet spoke alignment corresponding to the spoke periodicity seen in thin sections. Dynein rows can be visualized along the peripheral microtubules in some preparations. Fracture faces of the ciliary membrane are smooth with few membrane particles, except in the regions adjacent to the basal plate. In the transition region below the plate, a unique particle arrangement, the ciliary necklace, is found. In the Elliptio gill, on fracture face A the necklace is comprised of three well-defined rows or strands of membrane particles that encircle the ciliary shaft. The rows are scalloped and each scallop corresponds to a peripheral doublet microtubule. In thin sections at the level of these particles, a series of champagne-glass structures link the microtubular doublets to the ciliary membrane. The ciliary necklace and this "membrane-microtubule" complex may be involved in energy transduction or the timing of ciliary beat. Comparative studies show that these features are present in all somatic cilia examined including those of the ameboflagellate Tetramitus, sea urchin embryos, rat trachea, and nonmotile cilia of cultured chick embryo fibroblasts. The number of necklace strands differs with each species. The necklace has not been found in rat or sea urchin sperm.

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