Ultrastructure of the attachment and feeding sites of Gracilacus latescens Raski, 1976 in timber bamboo roots and selected anatomical details of the female stylet

Nematology ◽  
2003 ◽  
Vol 5 (2) ◽  
pp. 307-312
Author(s):  
Dianne Achor ◽  
Larry Duncan ◽  
Renato Inserra ◽  
Alberto Troccoli
Keyword(s):  
Cell Wall ◽  
Cross Sections ◽  
Cortical Cell ◽  
Root Surface ◽  
Mature Female ◽  
Dense Material ◽  
Anterior Portion ◽  
Electron Dense Material ◽  
Transmission Electron ◽  
Phyllostachys Bambusoides

AbstractMature female Gracilacus latescens are sedentary and remain attached by the stylet to the surface of timber bamboo roots (Phyllostachys bambusoides) for their entire life. Observations by transmission electron microscopy (TEM) of the anatomy of the anterior portion of the female body showed the stylet shaft surrounded by a thick stomatal wall sensu Endo (1983) and by large protractor muscles. Cross sections of the root at the site of nematode attachment showed accumulation of electron-opaque material between the nematode body and the epidermal wall penetrated by the stylet. Electron-dense material enwrapped the stylet from the point of its insertion in an epidermal cell wall until its end in the lumen of a sclerenchymal or cortical cell. Two to three cells are penetrated by the stylet. The electron-dense material appeared to originate from the walls of epidermal, cortical parenchymal and sclerenchymal cells perforated by the stylet. The thickness of this material increased with the number of sclerenchyma cell walls penetrated by the stylet. Cross sections of the enwrapped stylet showed it tightly encased in the electron-dense material, which appeared to anchor the stylet and consequently the nematode body to the root surface. A syncytium originates from the innermost cell reached by the enwrapped stylet and expands into the inner cortex and stele. Cell wall dissolution and pit fields are characteristics of the syncytium.

Spermiogenesis and spermatozoon of the tapeworm Parabothriocephalus gracilis (Bothriocephalidea): Ultrastructural and cytochemical studies

2010 ◽  
Vol 55 (1) ◽  
Author(s):  
Lenka Šípková ◽  
Céline Levron ◽  
Mark Freeman ◽  
Tomáš Scholz
Keyword(s):  
Electron Microscopy ◽  
Anterior Extremity ◽  
Mature Spermatozoon ◽  
Dense Material ◽  
Apical Region ◽  
Cortical Microtubules ◽  
Electron Dense Material ◽  
Dense Granules ◽  
Cytoplasmic Extension ◽  
Transmission Electron

AbstractSpermiogenesis and spermatozoon ultrastructure of the tapeworm Parabothriocephalus gracilis were described using transmission electron microscopy (TEM). Spermiogenesis is characterized by the formation of a zone of differentiation with two centrioles associated with striated rootlets, and an intercentriolar body between them. The two flagella undergo a rotation of 90° until they become parallel to the median cytoplasmic extension with which they fuse. Electron-dense material is present in the apical region of the zone of differentiation in the early stages of spermiogenesis. This electron-dense material is characteristic for the orders Bothriocephalidea and Diphyllobothriidea. The mature spermatozoon contains two axonemes of the 9 + ‘1’ trepaxonematan pattern, nucleus, parallel cortical microtubules and electron-dense granules of glycogen. The anterior extremity of the spermatozoon exhibits a single helical electron-dense crested body 130 nm thick. One of the most interesting features is the presence of a ring of cortical microtubules surrounding the axoneme. This character has been reported only for species of the order Bothriocephalidea and may be unique in this cestode group.

Direct Insights on Flax Fiber Structure by Focused Ion Beam Microscopy

2010 ◽  
Vol 16 (2) ◽  
pp. 175-182 ◽  
Author(s):  
Bernadette Domenges ◽  
Karine Charlet
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Cross Sections ◽  
Secondary Cell Wall ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Flax Fibers ◽  
Transmission Electron ◽  
Transition Modes ◽  
Beam Currents

AbstractIn this article, it is shown that focused ion beam (FIB) systems can be used to study the inner structure of flax fibers, the use of which as a reinforcing material in polymer composites still draws much interest from multiple disciplines. This technique requires none of the specific preparations necessary for scanning electron microscopy or transmission electron microscopy studies. Irradiation experiments performed on FIB prepared cross sections with very low Ga+ion beam currents revealed the softer material components of fibers. Thus, it confirmed the presence of pectin-rich layers at the interfaces between the fibers of a bundle, but also allowed the precise localization of such layers within the secondary cell wall. Furthermore, it suggested new insights on the transition modes between the sublayers of the secondary cell wall.

A light and electron microscopic study of microsporogenesis in Azolla microphylla

1985 ◽  
Vol 86 ◽  
pp. 53-58 ◽  
Author(s):  
Y. R. Herd ◽  
E. G. Cutter ◽  
I. Watanabe
Keyword(s):  
Dense Material ◽  
Electron Microscopic ◽  
Electron Dense Material ◽  
Azolla Microphylla ◽  
Dense Cytoplasm ◽  
Transmission Electron ◽  
Tapetal Cells ◽  
Electron Microscopes ◽  
Mother Cells ◽  
Membranous Material

SynopsisMicrosporogenesis in cultured material of Azolla microphylla was studied with the light and transmission electron microscopes. The first formed sporangium, a megasporangium, aborts and several microsporangia develop below. Initially, a single sporogenous cell is present, surrounded by a single layered tapetum and the microsporangial wall. Subsequently, several sporogenous cells are connected by plasmodesmata. The microspore mother cells are less densely cytoplasmic than the tapetal cells. Callose-like material is deposited around the microspore mother cells, but disappears before meiosis. The tetrads of microspores contain well defined organelles but less dense cytoplasm than the surrounding periplasmodium. Electron dense material deposited on the plasma membrane of the microspores eventually forms the endospore. The unornamented exospore develops by continued deposition of electron dense material. Degeneration of the periplasmodium gives rise to membranous material which appears to form a template for the massulae.

Spore wall ultrastructure in the liverwort Fossombronia longiseta

1984 ◽  
Vol 62 (9) ◽  
pp. 1871-1879 ◽  
Author(s):  
M. P. Steinkamp ◽  
W. T. Doyle
Keyword(s):  
Spore Wall ◽  
Dense Material ◽  
White Line ◽  
Electron Dense Material ◽  
Transmission Electron ◽  
Wall Ultrastructure ◽  
Electron Microscopes ◽  
Electron Lucent

Mature spores of Fossombronia longiseta (Metzgeriales, Codoniaceae) were examined with both scanning and transmission electron microscopes. Sporoderms are highly sculptured. The distal face markings consist of parallel ridges (cristae) or spines. The flattened proximal face has a series of short spinelike cristae, and a triradiate ridge mark sometimes is apparent. In section, the sporoderm consists of an intine and a two-layered exine. The inner exine layer consists of two lamellae, each of which contains a series of long, thin (3–4 nm), closely spaced, electron-lucent subunits; the subunits are separated by electron-dense material. The more or less solid outer exine consists of highly irregularly shaped lamellae, which also have a "white line" component. Amorphous, electron-dense material permeates these lamellae and fills the channels between the lamellae. The intine and much of the electron-dense material of the exine is removed by acetolysis. Spore wall ultrastructure in this species is complex compared with other species of the Metzgeriales and Jungermanniales that have been studied so far.

scholarly journals THE PARASPORAL BODY OF BACILLUS LATEROSPORUS LAUBACH

1957 ◽  
Vol 3 (6) ◽  
pp. 1001-1010 ◽  
Author(s):  
Christopher L. Hannay
Keyword(s):  
Cross Sections ◽  
Vegetative Cell ◽  
Culture Medium ◽  
Lateral Position ◽  
The Body ◽  
Dense Material ◽  
Spore Coat ◽  
Thin Sections ◽  
Electron Dense Material ◽  
Ultrathin Sections

On sporulation the slender vegetative rods swell and form larger spindle-shaped cells in which the spores are formed. When the spores mature they lie in a lateral position cradled in canoe-shaped parasporal bodies which are highly basophilic and can be differentiated from the surrounding vegetative cell cytoplasm with dilute basic dyes. On completion of sporulation the vegetative cell protoplasm and the cell wall lyse, leaving the spore cradled in its parasporal body. This attachment continues indefinitely on the usual culture medium and even persists after the spores have germinated. In thin sections of sporing cells the bodies are differentiated from the cell protoplasm by differences in structure. Whereas the protoplasm has a granular appearance, in both longitudinal and cross-sections the parasporal body comprises electron-dense lamellae running parallel with the membranes of the spore coat and less electron-dense material in the interstices of the lamellae. The inner surface of the body is contiguous with that of the spore coat as if it were part of the spore, rather than a separate body attached to the spore. The staining reactions of the parasporal body are not consistent with those of any substance described in bacteria. With Giemsa the bodies stain like chromatin, but the Feulgen reaction indicates that they do not contain the requisite nucleic acid. With an aqueous solution of toluidine blue they stain metachromatically, but with an acidified solution the results are variable. Neisser's stain for polyphosphate is negative. The basophilic substance is removed from the body with some organic solvents. This basophilic substance has not been specifically identified with any material seen in ultrathin sections, but it is suggested that it might be the less electron-dense material in the interstices of the lamellar structure. In contrast to the spore coat of B. laterosporus, those of its two relatives B. brevis and B. circulans take up basic stain like the parasporal body. Thin spore sections of these species have shown that the walls are thicker than those surrounding the spores of B. laterosporus, and it is suggested that the outer stainable layer of brevis and circulans spores is an accessory coat which in laterosporus may have been deformed to give a parasporal body.

Techniques to preserve soluble surface components in birch pollen wall: a scanning and transmission electron microscopic study.

1989 ◽  
Vol 37 (7) ◽  
pp. 981-987 ◽  
Author(s):  
M Grote
Keyword(s):  
Cetylpyridinium Chloride ◽  
Birch Pollen ◽  
Pollen Grain ◽  
Dense Material ◽  
Surface Coat ◽  
Electron Microscopic ◽  
Electron Dense Material ◽  
Transmission Electron ◽  
Cuprolinic Blue ◽  
Thin Electron

The exine of birch pollen was examined by scanning and transmission electron microscopy in the native state and after fixation in different aqueous fixatives: glutaraldehyde + OsO4; glutaraldehyde + cetylpyridinium chloride (CPC) + OsO4; glutaraldehyde + cuprolinic blue (CB); and periodate + lysine + paraformaldehyde (PLP). The native pollen exine showed a thin (3-5-nm) border of electron-dense material lining the tectum and electron-dense material within microchannels and bacula cavities. Fixation with the addition of CPC resulted in a voluminous surface coat surrounding the pollen grain, but empty microchannels and bacula cavities. After fixation with the addition of CB, there was a thin surface coat, whereas microchannels and bacula cavities were partially filled with electron-dense material. The other fixatives led to empty microchannels and bacula cavities. There was no surface coat on the pollen grain. However, after all fixation procedures, a thin electron-dense border of the tectum remained visible. Concerning the electron-dense material filling microchannels and bacula cavities in the native pollen grain, the results obtained in the present study suggest that it is either completely lost (after conventional and PLP fixation) or, after fixation with a precipitating additive, partially (CB) or completely (CPC) solubilized and precipitated on the surface of the pollen grain as a surface coat.

scholarly journals Novel multiscale insights into the composite nature of water transport in roots

2017 ◽  
Author(s):  
Valentin Couvreur ◽  
Marc Faget ◽  
Guillaume Lobet ◽  
Mathieu Javaux ◽  
François Chaumont ◽  
...  
Keyword(s):  
Cell Wall ◽  
Hydraulic Conductivity ◽  
Cross Sections ◽  
Cortical Cell ◽  
Cell Permeability ◽  
List Type ◽  
Cell Plasma ◽  
Apoplastic Barriers ◽  
Composite Nature ◽  
The Impact

Summary-MECHA is a novel mathematical model that computes the flow of water through the walls, membranes and plasmodesmata of each individual cell throughout complete root cross-sections, from a minimal set of cell level hydraulic properties and detailed root anatomical descriptions.-Using the hydraulic anatomical framework of the Zea mays root reveals that hydraulic principles at the cell and root segment scales, derived independently by Katchalsky and Curran [1967] and Fiscus and Kramer [1975], are fully compatible, irrespective of apoplastic barriers leakiness.-The hydraulic anatomy model accurately predicts empirical root radial permeability (kr) from relatively high cell wall hydraulic conductivity and low plasmodesmatal conductance reported in the literature.-MECHA brings novel insights into contradictory interpretations of experiments from the literature by quantifying the impact of intercellular spaces, cortical cell permeability and plasmodesmata among others on root kr, and suggests new experiments efficiently addressing questions of root water relations.SymbolsKPDsingle plasmodesma hydraulic conductancekrroot radial hydraulic conductivitykwcell wall hydraulic conductivityLpcell plasma membrane hydraulic conductivity

Structure and development of Pinus banksiana – Wilcoxina ectendomycorrhizae

1991 ◽  
Vol 69 (10) ◽  
pp. 2135-2148 ◽  
Author(s):  
Pamela F. Scales ◽  
R. L. Peterson
Keyword(s):  
Electron Microscopy ◽  
Pinus Banksiana ◽  
Cortical Cell ◽  
Root Surface ◽  
Cell Plasma Membrane ◽  
Cortical Cells ◽  
Hartig Net ◽  
Transmission Electron ◽  
Cell Plasma ◽  
Wilcoxina Mikolae

Seedlings of Pinus banksiana were grown in growth pouches and inoculated with Wilcoxina mikolae var. mikolae, Wilcoxina mikolae var. tetraspora, and Wilcoxina rehmii. Ectendomycorrhizae formed between P. banksiana and W. mikolae var. mikolae developed rapidly following inoculation. The mantle was of variable width, and a large amount of mucigel was evident on the root surface. Intracellular penetration of the cortical cells by hyphae occurred one to two cells distal to Hartig net formation. Both light and transmission electron microscopy revealed labyrinthic growth of Hartig net hyphae that were densely cytoplasmic during early penetration stages but became vacuolate as the association aged. Intracellular colonization of the cortex was extensive, with the hyphae highly branched and surrounded by an interfacial matrix and cortical cell plasma membrane. The external morphology and anatomy of ectendomycorrhizae formed between W. mikolae var. tetraspora and W. rehmii and P. banksiana were similar to those described for W. mikolae var. mikolae. Key words: ectendomycorrhizae, Wilcoxina, Pinus banksiana, intracellular, Hartig net, E-strain.

Influence of Cell Wall Composition on the Fossilisation of Bacteria and the Implications for the Search for Early Life Forms

1997 ◽  
Vol 161 ◽  
pp. 491-504 ◽  
Author(s):  
Frances Westall
Keyword(s):  
Cell Wall ◽  
Life Forms ◽  
Cation Binding ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Transmission Electron ◽  
Hydrothermal Sediments ◽  
Identification Of Bacteria ◽  
The Difference

AbstractThe oldest cell-like structures on Earth are preserved in silicified lagoonal, shallow sea or hydrothermal sediments, such as some Archean formations in Western Australia and South Africa. Previous studies concentrated on the search for organic fossils in Archean rocks. Observations of silicified bacteria (as silica minerals) are scarce for both the Precambrian and the Phanerozoic, but reports of mineral bacteria finds, in general, are increasing. The problems associated with the identification of authentic fossil bacteria and, if possible, closer identification of bacteria type can, in part, be overcome by experimental fossilisation studies. These have shown that not all bacteria fossilise in the same way and, indeed, some seem to be very resistent to fossilisation. This paper deals with a transmission electron microscope investigation of the silicification of four species of bacteria commonly found in the environment. The Gram positiveBacillus laterosporusand its spore produced a robust, durable crust upon silicification, whereas the Gram negativePseudomonas fluorescens, Ps. vesicularis, andPs. acidovoranspresented delicately preserved walls. The greater amount of peptidoglycan, containing abundant metal cation binding sites, in the cell wall of the Gram positive bacterium, probably accounts for the difference in the mode of fossilisation. The Gram positive bacteria are, therefore, probably most likely to be preserved in the terrestrial and extraterrestrial rock record.

Direct Observation of Heat Exchanger Deposits by Cross Sectioning

1967 ◽  
Vol 25 ◽  
pp. 364-365
Author(s):  
R. W. Anderson ◽  
D. L. Senecal
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Heat Exchanger ◽  
Direct Observation ◽  
Cross Sections ◽  
Preparation Method ◽  
Specimen Preparation ◽  
Flowing Water ◽  
Transmission Electron ◽  
Deposit Layer

A problem was presented to observe the packing densities of deposits of sub-micron corrosion product particles. The deposits were 5-100 mils thick and had formed on the inside surfaces of 3/8 inch diameter Zircaloy-2 heat exchanger tubes. The particles were iron oxides deposited from flowing water and consequently were only weakly bonded. Particular care was required during handling to preserve the original formations of the deposits. The specimen preparation method described below allowed direct observation of cross sections of the deposit layers by transmission electron microscopy.The specimens were short sections of the tubes (about 3 inches long) that were carefully cut from the systems. The insides of the tube sections were first coated with a thin layer of a fluid epoxy resin by dipping. This coating served to impregnate the deposit layer as well as to protect the layer if subsequent handling were required.

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