The structure and development of the haustorium in Cuscuta australis

1989 ◽  
Vol 67 (10) ◽  
pp. 2975-2982 ◽  
Author(s):  
Kyu Bae Lee ◽  
Chai Doo Lee
Keyword(s):  
Light And Electron Microscopy ◽  
Cell Types ◽  
Host Tissue ◽  
Cortical Cells ◽  
Meristematic Cells ◽  
Dense Cytoplasm ◽  
Trifolium Repens L ◽  
Tip Cells ◽  
Region Ii ◽  
Host Tissues

The structure and development of the haustorium of a parasitic angiosperm Cuscuta australis R. Brown growing on the host plant Trifolium repens L. was studied with light and electron microscopy. The upper haustorium, which lies external to the host organ, initiates endogenously from cortical cells of the middle layers of the parasite stem. The initial cells develop into a group of meristematic cells. As haustorial maturation progresses, the meristematic cells develop into an endophyte primordium that penetrates the host tissue. The endophyte primordium consists of three cell types: (i) remarkably enlarged elongate cells (digitate cells) with very dense cytoplasm and large nuclei at the central region; (ii) smaller file cells with prominent nuclei proximal to the digitate cells; and (iii) highly compressed cells distal to the digitate cells. Evidence suggests that the digitate cells are metabolically very active. The endophyte, which lies internal to the host tissue, consists of parenchymatous axial cells and elongate tip cells with dense cytoplasm and conspicuous nuclei. The axial and tip cells of endophyte are interpreted as originating from the file and digitate cells of the endophyte primordium, respectively. The tip cells independently penetrate the host tissues and transform into the filamentous hyphae. The hyphae reach the host vascular tissues and eventually differentiate into xylary or phloic conductive hyphae.

Ultrastructural Morphology of the Plastids in Ferocactus Latispinus (Haworth)

1981 ◽  
Vol 39 ◽  
pp. 648-649
Author(s):  
E. R. Rivera
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Apical Meristem ◽  
Plant Cells ◽  
Cortical Cells ◽  
Conventional Transmission Electron Microscopy ◽  
Meristematic Cells ◽  
Dense Cytoplasm ◽  
Transmission Electron ◽  
Peripheral Cytoplasm

Mature plants of Ferocactus latispinus were divided into the apical meristem, cortical and cambial tissue, and young and mature photosynthetic tissue. Pieces 2x2x4 mm were fixed in 0.075 M PIPES buffered 5% glutaraldehyde and further treated for conventional transmission electron microscopy.The shoot meristematic cells contained dense cytoplasm with a few small vacuoles. All organelles expected to be found in unspecialized plant cells were present. The proplastids were 1-2 diameters larger than mitochondria. Some of these plastids were elongated and most contained small amounts of lipid globules in the stroma (Fig. 1). In addition, phytoferritin was sometimes found in the stroma. No starch was found in these organelles. The thylakoids were poorly developed, and when there were no inclusions in the stroma, proplastids were difficult to distinguish from mitochondria (Fig. 1).Cortical cells had very large, well-developed vacuoles. The organelles were restricted to the peripheral cytoplasm of the cell and to a few transvacuolar cytoplasmic strands.

The structure of the gills of the axolotl, Ambystoma mexicanum

1987 ◽  
Vol 45 ◽  
pp. 824-825
Author(s):  
Mohinder S. Jarial
Keyword(s):  
Leydig Cells ◽  
Secretory Granules ◽  
Light And Electron Microscopy ◽  
Cell Types ◽  
Ambystoma Mexicanum ◽  
Basal Cells ◽  
Granular Cells ◽  
Gill Filaments ◽  
Mitotic Figures ◽  
Apical Membranes

The axolotl is a strictly aquatic salamander in which the larval external gills are retained throughout life. The external gills of the adult axolotl have been studied by light and electron microscopy for ultrastructural evidence of ionic transport. The thin epidermis of the gill filaments and gill stems is composed of 3 cell types: granular cells, the basal cells and a sparce population of intervening Leydig cells. The gill epidermis is devoid of muscles, and no mitotic figures were observed in any of its cells.The granular cells cover the gill surface as a continuous layer (Fig. 1, G) and contain secretory granules of different forms, located apically (Figs.1, 2, SG). Some granules are found intimately associated with the apical membrane while others fuse with it and release their contents onto the external surface (Fig. 3). The apical membranes of the granular cells exhibit microvilli which are covered by a PAS+ fuzzy coat, termed “glycocalyx” (Fig. 2, MV).

Infection by Phytophthora cinnamomi Rands of Roots of Eucalyptus calophylla R.Br. and Eucalyptus marginata Donn. ex Sm

1977 ◽  
Vol 25 (5) ◽  
pp. 483 ◽  
Author(s):  
N Malajczuk ◽  
AJ Mccomb ◽  
CA Parker
Keyword(s):  
Phytophthora Cinnamomi ◽  
Light And Electron Microscopy ◽  
Inhibitory Effect ◽  
Lateritic Soil ◽  
Root Damage ◽  
Mature Trees ◽  
Cortical Cells ◽  
Eucalyptus Marginata ◽  
Seedling Roots ◽  
Loam Soil

On lateritic podzolic soils in Western Australia Eucalyptus calophylla is resistant to Phytophthora cinnamomi whereas Eucalyptus marginata is susceptible and eventually killed by the pathogen. On loam soils both eucalypts are resistant. Possible mechanisms for resistance of E. calophylla in lateritic soil and the inhibitory action of loam soils were investigated. Aseptically raised eucalypt seedlings succumbed to infection in liquid culture tubes. The mechanism of infection was compared by light and electron microscopy which showed similar fungal invasion and penetration into roots of both eucalypt species. Vegetative hyphae initially penetrated intercellularly and proliferated rapidly within cortical and stelar tissue. Intracellular invasion of these tissues occurred 48hr after initial infection through dissolution of the host cell wall. Chlamydospores were formed within a number of cortical cells. Unsuberized roots of mature trees produced aseptically showed reactions to invasion similar to those of the eucalypt seedling roots. Suberized roots were not invaded. The addition of small quantities of lateritic soil to sterile sand so as to introduce soil micro-organisms without altering the chemical and physical status of the sand, and subsequent inoculation of the sand with P.cinnamomi, resulted in a reduction of root damage on both eucalypts when compared with seedlings raised in sterile sand. Roots of E.calophylla were less severely damaged than those of E.marginata. The addition of small quantities of loam soil significantly reduced root damage in seedlings of both species. These results parallel both pot experiments and field observations, and suggest that microorganisms of the rhizosphere may be an important factor in the resistance of E.calophylla to infection, and in the inhibitory effect of loam soil on P.cinnamomi.

Interpolation of microtubules into cortical arrays during cell elongation and differentiation in roots of Azolla pinnata

1979 ◽  
Vol 37 (1) ◽  
pp. 411-442
Author(s):  
A.R. Hardham ◽  
B.E. Gunning
Keyword(s):  
Cell Differentiation ◽  
Cell Walls ◽  
Unit Length ◽  
Cell Types ◽  
High Rate ◽  
Wall Thickening ◽  
Cortical Microtubules ◽  
Azolla Pinnata ◽  
Outer Cortex ◽  
Cortical Cells

Longitudinal sections of roots of Azolla pinnata R. Br. were prepared for electron microscopy so that cortical microtubules could be counted along the longitudinal walls in cell files in the endodermis, pericycle, and inner and outer cortex, and in sieve and xylem elements. With the exception of the xylem, where there are no transverse cell divisions, each file of cells commences with its initial cell and then possesses a zone of concomitant cell expansion and transverse cell division, followed, after completion of the divisions, by a zone of terminal cell differentiation. The cells augment their population of cortical microtubules as they elongate and divide, showing a net increase of up to 0.6 micron of polymerized microtubule length per min. Two main sub-processes were found: (i) When a longitudinal wall is first formed it is supplied with a higher number of microtubules per unit length of wall than it will have later, when it is being expanded. This initial quota becomes diluted as the second sub-process commences. (ii) The cells interpolate new microtubules at a rate which is characteristic of the cell, and, in the endodermis, of the face of the cell, while the cell elongates. Most cell types thus maintain a set density of cortical microtubules while they elongate and divide. Comparisons of endodermal cells in untreated controls, and roots that had been treated with colchicine, low temperature, or high pressure indicate that the initial quota of microtubules, and the later interpolations, and differentially sensitive to microtuble perturbations. Three types of behaviour, all related to changes in the cell walls, were noted as cortex, xylem and sieve element cells entered their respective phases of cell differentiation. The cortical cells expanded in all dimensions, and the interpolation of microtubules diminished or ceased. The sieve elements continued to elongate, and interpolated at a high rate, reaching unusually high densities of microtubules when the cell walls were being thickened. During this period a net increase of 2.0 micron of polymerized microtubule length per min was calculated. Thereafter interpolation ceased and the density of microtubules declined. The sample applied to developing xylem except that, because wall-thickening is localized rather than widespread, the rise and subsequent fall in the density of microtubules was less marked. The data are discussed in relation to the participation of microtubules in wall deposition and to the hypothesis that cortical microtubules arise in discrete zones along the edges of cells.

An Ultrastructural and Radio-Autographic Study of the Evolution of the Interphase Nucleus in Plant Meristematic Cells (Allium Porrum)

1974 ◽  
Vol 14 (2) ◽  
pp. 263-287
Author(s):  
J. G. LAFONTAINE ◽  
A. LORD
Keyword(s):  
Interphase Nucleus ◽  
Structural Changes ◽  
Tritiated Thymidine ◽  
Light And Electron Microscopy ◽  
Allium Porrum ◽  
Meristematic Cells ◽  
Fibrillar Material ◽  
Nuclear Structures ◽  
S Period ◽  
Dense Chromatin

Radioautography under both light and electron microscopy was exploited to investigate the structural changes of the chromatin reticulum which characterizes the interphase nucleus of a number of plants. Allium porrum meristematic plant cells were used for this purpose. In this species, the telophase chromosomes uncoil into dense strands which, during the G1 period, gradually give rise to a coarse reticulum. There then follows an extensive unravelling of portions of these strands, and high-resolution radioautography reveals that labelling with tritiated thymidine predominantly occurs over zones of the nucleus consisting of diffuse fine fibrillar material. As the S-period progresses, a chromatin reticulum reappears throughout the nuclear cavity, the tortuous strands being approximately 0.25 µm in diameter. Most of the radioautographic grains still remain over the light nucleoplasmic areas but a number of these are now located on the outermost portion of the dense chromatin profiles. By the end of the S-period, the chromatin strands are slightly thicker (ca. 0.3 µm) and form a looser reticulum. Labelling has decreased noticeably in nuclei of that period, the radioautographic grains being grouped into clusters resting over more or less spherical regions of the chromatin reticulum. Judging from their localization at the surface of the nucleolus or close to the nuclear envelope, these structures correspond to chromocentres. The additional interesting finding that such nuclear structures appear much less compactly organized strongly suggests that chromocentres undergo important conformational modifications during duplication of their DNA.

scholarly journals Muscle contracture and passive mechanics in cerebral palsy

2019 ◽  
Vol 126 (5) ◽  
pp. 1492-1501 ◽  
Author(s):  
Richard L. Lieber ◽  
Jan Fridén
Keyword(s):  
Extracellular Matrix ◽  
Cerebral Palsy ◽  
Satellite Cells ◽  
Neuromuscular Disorders ◽  
Light And Electron Microscopy ◽  
Cell Types ◽  
Underlying Mechanism ◽  
Muscle Stiffness ◽  
Muscle Satellite Cells ◽  
Cord Injury

Skeletal muscle contractures represent the permanent shortening of a muscle-tendon unit, resulting in loss of elasticity and, in extreme cases, joint deformation. They may result from cerebral palsy, spinal cord injury, stroke, muscular dystrophy, and other neuromuscular disorders. Contractures are the prototypic and most severe clinical presentation of increased passive mechanical muscle force in humans, often requiring surgical correction. Intraoperative experiments demonstrate that high muscle passive force is associated with sarcomeres that are abnormally stretched, although otherwise normal, with fewer sarcomeres in series. Furthermore, changes in the amount and arrangement of collagen in the extracellular matrix also increase muscle stiffness. Structural light and electron microscopy studies demonstrate that large bundles of collagen, referred to as perimysial cables, may be responsible for this increased stiffness and are regulated by interaction of a number of cell types within the extracellular matrix. Loss of muscle satellite cells may be related to changes in both sarcomeres and extracellular matrix. Future studies are required to determine the underlying mechanism for changes in muscle satellite cells and their relationship (if any) to contracture. A more complete understanding of this mechanism may lead to effective nonsurgical treatments to relieve and even prevent muscle contractures.

Oxidative stress in isolated rat renal proximal and distal tubular cells

1990 ◽  
Vol 259 (2) ◽  
pp. F338-F347 ◽  
Author(s):  
L. H. Lash ◽  
J. J. Tokarz
Keyword(s):  
Rat Kidney ◽  
Gradient Centrifugation ◽  
Buthionine Sulfoximine ◽  
Oxidative Injury ◽  
Cell Types ◽  
Protective Role ◽  
Cortical Cells ◽  
Percoll Density Gradient Centrifugation ◽  
Tert Butyl Hydroperoxide ◽  
Percoll Density Gradient

Suspensions of purified proximal tubular (PT) and distal tubular (DT) cells were isolated from rat kidney cortical cells by Percoll density-gradient centrifugation and were used to investigate susceptibility of these regions of the nephron to oxidative injury. Exposure to tert-butyl hydroperoxide (tBH), menadione (MD), or H2O2 produced significantly greater cytotoxicity, as assessed by leakage of lactate dehydrogenase, in DT cells than in PT cells. The order of cytotoxic potency in both cell types was MD greater than tBH greater than H2O2. Preincubation of PT and DT cells with 5 mM glutathione (GSH) or 5 mM dithiothreitol delayed tBH-induced cytotoxicity, indicating a protective role of GSH. Addition of buthionine sulfoximine and acivicin with GSH, to inhibit GSH synthesis and degradation, eliminated the protective effect of GSH, indicating that protection by GSH in DT cells is not dependent on uptake of the intact tripeptide. Incubation of both PT and DT cells with tBH resulted in oxidation of GSH to glutathione disulfide. Activities of five detoxication enzymes were significantly higher in PT cells, indicating that a diminished ability to detoxify reactive metabolites may contribute to the higher intrinsic susceptibility of DT cells to oxidative injury.

scholarly journals THE CYTOCHEMICAL LOCALIZATION OF ASCORBIC ACID IN ROOT TIP CELLS

1956 ◽  
Vol 2 (1) ◽  
pp. 87-92 ◽  
Author(s):  
William A. Jensen ◽  
Leroy G. Kavaljian
Keyword(s):  
Ascorbic Acid ◽  
Cell Surface ◽  
Silver Nitrate ◽  
Ribonucleic Acid ◽  
Root Tip ◽  
Root Tips ◽  
Cytochemical Localization ◽  
Meristematic Cells ◽  
Tip Cells ◽  
Root Tip Cells

The intracellular distribution of ascorbic acid was studied in frozen-dried root tips of Allium cepa and Vicia faba by the silver nitrate procedure. The sites of the ascorbic acid as indicated by the deposited silver appear as spherical (0.2 to 0.6 µ in diameter) cytoplasmic particles. The site appears to have small amounts of lipides and to be rich in ribonucleic acid. These particles are concluded to be submicroscopic in size and associated, in the elongating cell, with the cell surface. In the meristematic cells they appear fewer in number and are distributed throughout the cytoplasm.

scholarly journals Symplekin, a novel type of tight junction plaque protein.

1996 ◽  
Vol 134 (4) ◽  
pp. 1003-1018 ◽  
Author(s):  
B H Keon ◽  
S Schäfer ◽  
C Kuhn ◽  
C Grund ◽  
W W Franke
Keyword(s):  
Tight Junction ◽  
Tight Junctions ◽  
Sertoli Cells ◽  
Light And Electron Microscopy ◽  
Cell Types ◽  
Calculated Molecular Weight ◽  
Zonula Occludens ◽  
Cytoplasmic Face ◽  
Wide Range ◽  
Vascular Endothelia

Using a monoclonal antibody we have identified and cDNA-cloned a novel type of protein localized, by light and electron microscopy, to the plaque associated with the cytoplasmic face of the tight junction-containing zone (zonula occludens) of polar epithelial cells and of Sertoli cells of testis, but absent from the junctions of vascular endothelia. The approximately 3.7-kb mRNA encodes a polypeptide of 1142 amino acids (calculated molecular weight 126.5 kD, pI 6.25), for which the name "symplekin" (from Greek sigma upsilon mu pi lambda epsilon kappa epsilon iota, nu, to tie together, to weave, to be intertwined) is proposed. However, both the mRNA and the protein can also be detected in a wide range of cell types that do not form tight junctions or are even completely devoid of any stable cell contacts. Careful analyses have revealed that the protein occurs in all these diverse cells in the nucleoplasm, and only in those cells forming tight junctions is it recruited, partly but specifically, to the plaque structure of the zonula occludens. We discuss symplekin as a representative of a group of dual residence proteins which occur and probably function in the nucleus as well as in the plaques exclusive for either tight junctions, adherens junctions, or desmosomes.

The subcellular concentration of ions and elements in thin cryosections of onion root meristem cells. An electron-probe EDS study

1984 ◽  
Vol 72 (1) ◽  
pp. 295-306
Author(s):  
I.L. Cameron ◽  
K.E. Hunter ◽  
N.K. Smith
Keyword(s):  
Electron Probe ◽  
Dry Weight ◽  
Cell Types ◽  
Meristematic Cells ◽  
Freeze Dried ◽  
Concentration Of Ions ◽  
Intracellular Compartments ◽  
Root Meristematic Cells ◽  
Storage Granules ◽  
First Time

Quantitative electron-probe energy dispersive X-ray microanalysis has, for the first time, been accomplished at a subcellular level in plant tissue using cryofixed and thin freeze-dried cryosections. The subcellular concentrations of Na+, Cl-, K+, P, S, Mg2+ and Ca2+ were measured in mol/kg dry weight in two types of root meristematic cells of the onion, Allium cepa. The cell wall of the meristematic cells had much higher concentrations of K+ and Ca2+ than was found in the intracellular compartments. Storage granules in the protoderm cells were about 6–12 times lower in P and were about four times higher in S as compared to other intracellular compartments. Comparison between the concentrations of ions and other elements in meristematic plant cells and in mouse cardiac myocytes confirms that major differences in cytoplasmic Na+ and Cl- concentrations do indeed exist between these cell types.

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