Infection of beech leaves (Fagus sylvatica) by the endophyte Discula umbrinella (teleomorph: Apiognomonia errabunda): low-temperature scanning electron microscopy studies

1993 ◽  
Vol 71 (11) ◽  
pp. 1520-1527 ◽  
Author(s):  
Olivier Viret ◽  
Christoph Scheidegger ◽  
Orlando Petrini
Keyword(s):  
Electron Microscopy ◽  
Germ Tube ◽  
Ultrastructural Level ◽  
Malt Extract ◽  
Leaf Extracts ◽  
Sequence Of Events ◽  
Transmission Electron ◽  
Specific Induction ◽  
Temperature Scanning ◽  
Germ Tubes

The sequence of events leading to infection by Discula umbrinella of leaves taken from axenically grown beech seedlings was studied at the ultrastructural level. On the host surface, even under optimal conditions and when contact with the host is established, only approximately 70% germination can be observed. In hanging drops containing malt extract, germination is only approximately 10%, suggesting that abundant nutrient supply alone is not enough to promote germination. Incubation of conidia in leaf extracts, on the other hand, results in the induction of germination even if no contact with an appropriate support is established. Between 16 and 24 h after infection four stages of germination can be observed on beech leaves: (i) ungerminated conidia; (ii) germinating conidia producing long superficial hyphae; (iii) conidia with distinct, appressorium-like swelling at the end of the germ tube; and (iv) germinated conidia with a halo around the tip of the germ tube. Transmission electron microscopy shows that subcuticular penetration into the host occurs at places where halos are seen. Apparently only germination with formation of appressorium-like structures and halos leads to successful penetration. Application of conidia to the abaxial side of the host leaf results in the formation of structures similar to those observed on the adaxial surface. Conidial germ tubes penetrate the cuticular layers of the outer edges of the guard cells, but direct penetration through the stomata was rarely observed. Appressorium or halo formation, observed only on the host surface and never on other substrates, suggests host-specific induction of penetrating structures. The mode of penetration observed for D. umbrinella bears some similarities with that described for some biotrophs and pathogens, suggesting affinities between endophytes and pathogens. Key words: beech anthracnose, electron microscopy, endophytes, latent pathogens, ultrastructure.

Ultrastructure of conidia and conidium germination in the plant pathogenic fungus Alternaria cassiae

1997 ◽  
Vol 75 (2) ◽  
pp. 252-260 ◽  
Author(s):  
C. W. Mims ◽  
M. A. Rogers ◽  
C. G. Van Dyke
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Germ Tube ◽  
Pathogenic Fungus ◽  
Freeze Substitution ◽  
Dialysis Membrane ◽  
Common Mode ◽  
Plant Pathogenic Fungus ◽  
Transmission Electron ◽  
Germ Tubes

Transmission electron microscopy of plunge-frozen and freeze-substituted samples was used to examine germinating conidia of Alternaria cassiae, a plant pathogenic fungus used as a biological control agent for sicklepod (Cassia obtusifolia). Hydrated conidia on small pieces of dialysis membrane were incubated for 1, 2, or 3 h on the surface of corn meal agar prior to fixation. Conidia were large, darkly pigmented, and surrounded by a thick, two-layered wall. Each conidium was divided by transverse and longitudinal septa into multiple cells, a few of which sometimes appeared necrotic. Each septum tapered to a small central pore region with which Woronin bodies were associated. Each healthy cell of a conidium contained a typical complement of cellular organelles including multiple nuclei. With the exception of lipid bodies, all the various organelles were well preserved by plunge freezing and freeze substitution. Evidence of germ tube development was visible by 2 h post-incubation and well-developed germ tubes were present by 3 h. Two modes of germ tube development were observed. In the less common mode germ tubes developed inside conidia and grew internally through one or more adjacent cells before emerging from the conidium surface. Cells penetrated by internal germ tubes appeared necrotic. In the more common mode of germination, germ tubes developed directly from the conidium surface. Multiple germ tubes usually arose from each conidium and grew out in all directions. Germ tubes that contacted the underlying dialysis membrane continued to grow along its surface. Extracellular material was produced in association with developing germ tubes and coated the sides of germinated conidia and covered germ tubes growing along membranes. Key words: transmission electron microscopy, cryofixation, freeze substitution, germ tube development.

Development of primary germ tubes by conidia of Blumeria graminis f.sp. hordei on leaf epidermal cells of Hordeum vulgare

2002 ◽  
Vol 80 (10) ◽  
pp. 1121-1125 ◽  
Author(s):  
H H Edwards
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Hordeum Vulgare ◽  
Host Cell ◽  
Germ Tube ◽  
Tube Wall ◽  
Blumeria Graminis ◽  
Transmission Electron ◽  
Host Cell Wall ◽  
Germ Tubes

Development of primary germ tubes from conidia of Blumeria graminis f.sp. hordei on primary leaf segments of Hordeum vulgare was investigated from 3 to 13 h postinoculation (hpi) using transmission electron microscopy. By 3 hpi, the primary germ tube wall that makes contact with the host cuticle develops a small protrusion that breaches the host cuticle and touches the host cell wall but does not penetrate any further. This protrusion is the cuticular peg. From 3 to 13 hpi, the cuticular peg swells, becomes quite electron dense, and finally develops a loose fibrillar texture. The structure of the primary germ tube with the terminal cuticular peg is consistent with the hypothesis that it allows the conidium to absorb water and solutes present in the host cell wall.Key words: powdery mildew, barley, ultrastructure.

Dipetalonema viteae: ultrastructural study on the in vitro interaction between rat macrophages and microfilariae in the presence of IgE antibody

Parasitology ◽  
1981 ◽  
Vol 82 (1) ◽  
pp. 55-62 ◽  
Author(s):  
M. A. Ouaissi ◽  
A. Haque ◽  
A. Capron
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ultrastructural Study ◽  
Peritoneal Macrophages ◽  
Immune Serum ◽  
Sequence Of Events ◽  
Transmission Electron ◽  
Dipetalonema Viteae ◽  
In Vitro Interaction

SUMMARYThe in vitro interaction between rat peritoneal macrophages and Dipetalonema viteae microfilariae in the presence of amicrofilaraemic rat immune serum was studied by transmission electron microscopy. The probable sequence of events leading to the killing of D. viteae microfilaria by macrophages is as follows. (a) Rat peritoneal macrophages in the presence of amicrofilaraemic rat immune serum adhere to the parasite surface, (b) the macrophages extend their pseudopodia around the parasite, (c) the ‘lysosome-like’ granules discharge their contents on to the parasite surface, (d) the lytic activity of these products begins at the parasite surface and (e) subsequent breaking of the microfilarial cuticle occurs, exposing the parasite intracellular material.

scholarly journals Bioactivities of Geranium wallichianum Leaf Extracts Conjugated with Zinc Oxide Nanoparticles

Biomolecules ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 38 ◽  
Author(s):  
Banzeer Ahsan Abbasi ◽  
Javed Iqbal ◽  
Riaz Ahmad ◽  
Layiq Zia ◽  
Sobia Kanwal ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Zinc Oxide ◽  
Zinc Oxide Nanoparticles ◽  
Energy Dispersive ◽  
Oxide Nanoparticles ◽  
X Ray Diffraction ◽  
Leaf Extracts ◽  
Tem Analysis ◽  
X Ray ◽  
Transmission Electron

This study attempts to obtain and test the bioactivities of leaf extracts from a medicinal plant, Geranium wallichianum (GW), when conjugated with zinc oxide nanoparticles (ZnONPs). The integrity of leaf extract-conjugated ZnONPs (GW-ZnONPs) was confirmed using various techniques, including Ultraviolet–visible spectroscopy, X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, energy-dispersive spectra (EDS), scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The size of ZnONPs was approximately 18 nm, which was determined by TEM analysis. Additionally, the energy-dispersive spectra (EDS) revealed that NPs have zinc in its pure form. Bioactivities of GW-ZnONPs including antimicrobial potentials, cytotoxicity, antioxidative capacities, inhibition potentials against α-amylase, and protein kinases, as well as biocompatibility were intensively tested and confirmed. Altogether, the results revealed that GW-ZnONPs are non-toxic, biocompatible, and have considerable potential in biological applications.

Synthesis of α–SiO2 nanowires using Au nanoparticle catalysts on a silicon substrate

2001 ◽  
Vol 16 (3) ◽  
pp. 683-686 ◽  
Author(s):  
Z. Q. Liu ◽  
S. S. Xie ◽  
L. F. Sun ◽  
D. S. Tang ◽  
W. Y. Zhou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Large Scale ◽  
Device Fabrication ◽  
Au Nanoparticle ◽  
Large Panels ◽  
Transmission Electron ◽  
Temperature Scanning ◽  
Uniform Diameter ◽  
20 Nm

Large-scale SiO2 nanowires were synthesized by using a simple but an effective approach at low temperature. Scanning electron microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy were employed to characterize the samples. The results indicated that SiO2 nanowires with a uniform diameter of about 20 nm and a length up to 10 μm have been synthesized. Photoluminescence measurement showed that the SiO2 nanowires emitted blue light at 2.8 and 3.0 eV. The possible growth process of the SiO2 nanowires is discussed. Using this method, large panels of SiO2 nanowires can be made under conditions that are suitable for device fabrication.

SILICON CARBIDE NANOWIRES FROM POLYVINYL ALCOHOL/SILICA ELECTROSPUN NANOFIBERS

NANO ◽  
2011 ◽  
Vol 06 (01) ◽  
pp. 41-45 ◽  
Author(s):  
H. DELAVARI H. ◽  
M. KOKABI
Keyword(s):  
Electron Microscopy ◽  
Silicon Carbide ◽  
Polyvinyl Alcohol ◽  
Gas Flow ◽  
Electrospun Nanofibers ◽  
Average Diameter ◽  
Sic Nanowires ◽  
Transmission Electron ◽  
Temperature Scanning ◽  
Vs Mechanism

The catalyst-free synthesis of silicon carbide (SiC) nanowires was carried out from polyvinyl alcohol (PVA)/silica electrospun nanofibers at high temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and thermogravimetery analysis (TGA) were employed to study morphology and formation of SiC nanowires. Based on the TGA analysis, the carbon yield was increased when inert gas flow rate and heating rate decreased and polymeric nanofibers has been stabilized. The XRD and TEM results showed that the produced nanowires were crystalline β- SiC and rather homogeneous in thickness with an average diameter around 50 to 70 nm and a length of more than 10 μm. Finally, a possible growth mechanism of β- SiC nanowire based on a vapor–solid (VS) mechanism was proposed.

Visualization, adhesiveness, and cytochemistry of the extracellular matrix produced by urediniospore germ tubes of Puccinia sorghi

1991 ◽  
Vol 69 (9) ◽  
pp. 2044-2054 ◽  
Author(s):  
Rajendra Chaubal ◽  
V. A. Wilmot ◽  
Willard K. Wynn
Keyword(s):  
Electron Microscopy ◽  
Extracellular Matrix ◽  
Rust Fungus ◽  
Cetylpyridinium Chloride ◽  
Freeze Substitution ◽  
Ruthenium Red ◽  
Puccinia Sorghi ◽  
Temperature Scanning ◽  
Germ Tubes ◽  
Scanning Electron

Adherence of germinating urediniospores of the common maize rust fungus (Puccinia sorghi Schw.) to substrata was studied by ultrastructural and cytochemical examination of extracellular matrix produced by germ tubes in conjunction with measurements of adhesion to plastic and glass surfaces. Copious amounts of extracellular matrix on germ tubes could consistently be visualized by scanning and transmission electron microscopy only when (i) a cationic detergent (cetylpyridinium chloride, polydiallyldimethylammonium chloride) or a cationic stain (ruthenium red, alcian blue, cuprolinic blue) was added to the fixation solutions, (ii) germ tubes were fixed by rapid-freezing and freeze-substitution and observed with a scanning electron microscope, or when (iii) germ tubes were observed in a frozen-hydrated state by low-temperature scanning electron microscopy. Incubation of germinated spores with dilute alkalies (NaOH, KOH), pronase E (nonspecific protease), and laminarinase (β-1,3 (1,3; 1,4-glucanase) removed the extracellular matrix and detached germ tubes from surfaces. Treatments with water, dilute acids, ionic and neutral detergents, organic solvents, hydrocarbons, and several polysaccharide-degrading enzymes did not remove the extracellular matrix and also did not detach germ tubes. These results, together with staining patterns obtained with lectins and other polysaccharide-specific reagents, indicate that the extracellular matrix is composed mainly of glycoproteins rich in acidic amino acids and β-1,3-glucan polymers, and that it is probably responsible for the adhesion of the rust germ tubes to the host leaf surfaces. Key words: Puccinia sorghi, germ tube adhesion, extracellular matrix, cytochemistry.

Papilla response of barley epidermal cells caused by Erysiphe graminis: rate and method of deposition determined by microcinematography and transmission electron microscopy

1979 ◽  
Vol 57 (8) ◽  
pp. 898-913 ◽  
Author(s):  
Richard J. Zeyen ◽  
W. R. Bushnel
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Amorphous Material ◽  
Time Lapse ◽  
Epidermal Cells ◽  
Erysiphe Graminis ◽  
Sequence Of Events ◽  
Transmission Electron ◽  
Wall Appositions ◽  
Entire Sequence

Papillae were deposited in barley epidermal cells directly beneath appressoria of Erysiphe graminis f. sp. hordei and appeared as hemispherical, internal wall appositions. The papilla response began shortly after the formation of a rapidly moving cytoplasmic aggregate beneath the appressorium. As documented in coleoptile tissue by time-lapse light microcinematography, the papillae grew rapidly for 20–30 min after becoming visible, their radii increasing by 0.1 μm/min. For small papillae, deposition continued for about 30 min; for larger papillae, deposition continued for 120–180 min. Results with transmission electron microscopy on leaf epidermal cells suggested that papilla deposition by host cytoplasmic aggregates can be divided into four sequential stages: (i) the deposition of osmiophilic (lipidic) materials, (ii) the deposition and partial compaction of nonosmiophilic, amorphous material (probably insoluble polysaccharides), (iii) compaction of nonosmiophilic, amorphous material, and (iv) the incorporation of osmiophilic material into the host wall and into the compacted nonosmiophilic, amorphous material. At maturity, the papillae are hardened, electron-opaque wall appositions that may be effective in preventing fungal penetration and development. Failure of papillae to prevent fungal penetration and development may be related to the inability of the epidermal cells to complete the entire sequence of events in papilla deposition before attempted fungal penetration.

scholarly journals The non-brain anterior nerve center and tentacle crown structure of Owenia borealis (Annelida, Oweniidae): the evolution of the nervous system and tentacles in Bilateria

2021 ◽  
Author(s):  
Nadezhda Rimskaya-Korsakova ◽  
Vyacheslav Dyachuk ◽  
Elena Temereva
Keyword(s):  
Electron Microscopy ◽  
System Development ◽  
Sister Group ◽  
Ultrastructural Level ◽  
Myoepithelial Cells ◽  
Coelomic Cavity ◽  
Head Region ◽  
Blood Capillaries ◽  
Crown Structure ◽  
Transmission Electron

Abstract The Oweniidae are marine annelids with many unusual features of organ system, development, morphology, and ultrastructure. Together with magelionds, oweniids have been placed within the Palaeoannelida, a sister group to all remaining annelids. The study of this group may increase our understanding of the early evolution of annelids (including their radiation and diversification) and of the morphology of the last common bilaterian ancestor. In the current research, scanning electron microscopy revealed that the tentacle apparatus consists of 10 branched arms. The tentacles are covered by monociliary cells that form a ciliar groove that extends along the oral side of the arm base. Light, confocal, and transmission electron microscopy revealed that head region contains two circular intraepidermal nerves (outer and inner) that give rise to the neurites of each tentacle, i.e., intertentacular neurites are absent. Each tentacle contains a coelomic cavity with a network of blood capillaries. Monociliar myoepithelial cells of the tentacle coelomic cavity form both the longitudinal and the circular muscles. The structure of this myoepithelium is intermediate between simple and pseudo-stratified myepithelium. Overall, tentacles lack prominent zonality, i.e., co-localization of ciliary zones, neurite bundles, and muscles. This organization, which indicates a non-specialized tentacle crown in O. borealis and other oweniids with tentacles, is probably ancestral for annelids and for all Bilateria. The outer circular nerve of O. borealis is a dorsal medullary commissure that apparently functions as an anterior nerve center and is organized at the ultrastructural level as a stratified neuroepithelium. Given the hypothesis that the anterior nerve center of the last bilateral ancestor might be a diffuse neural plexus network, these results suggest that the ultra anatomy of that plexus brain might be a stratified neuroepithelium. Alternatively, the results could reflect the simplification of structure of the anterior nerve center in some bilaterian lineages.

Ultrastructure of Leiomyosarcoma Invasive Phenotype

1997 ◽  
Vol 3 (S2) ◽  
pp. 19-20
Author(s):  
A. Márquez ◽  
H.J. Fino ◽  
M. Correa ◽  
P. Tonino ◽  
L. Sosa
Keyword(s):  
Electron Microscopy ◽  
Malignant Tumors ◽  
Ultrastructural Level ◽  
Electron Microscopic ◽  
Invasive Phenotype ◽  
Primary Tumors ◽  
Heterogeneous Cell Population ◽  
Metastatic Cells ◽  
Transmission Electron ◽  
Nuclear Changes

Malignant tumors are known to have an heterogeneous cell population. Metastases are supposed to be formed by subpopulations with high metastatic capability. These metastatic cells constitute the so called invasive phenotype. In that order of ideas, metastases could be pathologically different from their parent tumors if the invasive phenotype had distinct morphological features. The similarities or differences between primary tumors and their metastases have not been adequately studied at the ultrastructural level. In this work we report an electron microscopic study of liver leiomyosarcoma metastases which shows alterations not described in primary tumors of that kind.Biopsies of liver metastases from a colon leiomyosarcoma were surgically obtained. Samples were processed with routine techniques for transmission electron microscopy and observed in a Hitachi H-500 electron microscope.Some alterations usually observed in primary leiomyosarcomas were seen. They were presence of myofilaments with focal densities, nuclear changes, swollen mitochondria, and abundance of rough endoplasmic reticulum (Fig. 1).

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