Ultrastructural and cytological observations of apothecial tissues of Geopyxis carbonaria (Pezizales, Ascomycetes)

1990 ◽  
Vol 68 (2) ◽  
pp. 243-257 ◽  
Author(s):  
James W. Kimbrough ◽  
Jack L. Gibson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Key Words ◽  
Mother Cell ◽  
Secondary Wall ◽  
Cell Stage ◽  
Wall Structures ◽  
Transmission Electron ◽  
Secondary Wall Formation ◽  
Characteristic Features

Cytological observations are made on apothecial tissues of Geopyxis carbonaria, using transmission electron microscopy. Characteristic features of both the medullary and ectal excipula are examined. Changes in ascus apex and wall structures are examined during ascus ontogeny, especially in relation to operculum position and structure. Ultrastructure of septum configuration is observed and compared in the excipulum, ascogenous hyphae, paraphyses, and at the base of young asci. Ascosporogenesis is observed from the ascus mother cell stage and initial spore delimitation until secondary wall formation. The cytological and ultrastructural observations on this species are discussed in relation to their possible taxonomic or phylogenetic value. Key words: ascosporogenesis, Discomycetes, ascospore ultrastructure, septal ultrastructure, cytochemistry.

Sporophytes, megaspores, and massulae of Azolla stanleyi from the Paleocene Joffre Bridge locality, Alberta

1994 ◽  
Vol 72 (3) ◽  
pp. 301-308 ◽  
Author(s):  
Georgia L. Hoffman ◽  
Ruth A. Stockey
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Key Words ◽  
Red Deer ◽  
The Other ◽  
Evolutionary Trends ◽  
Reproductive Structures ◽  
Transmission Electron ◽  
New Material

Several hundred vegetative and fertile specimens of Azolla Lam. have been recovered from the Paleocene Paskapoo Formation at the Joffre Bridge locality (Middle Tiffanian (Ti3) age) near Red Deer, Alberta. The spore complexes closely resemble those of the Paleocene A. stanleyi Jain & Hall, and the vegetative material is referred to that species. The specimens are unusually complete in that the remains of the fragile sporophyte are preserved, commonly with reproductive structures in place. Plants reaching up to 2.25 cm in length consist of alternately branched rhizomes bearing alternate, imbricate, sessile leaves. Leaves are ovate with entire margins, papillate surfaces, and a single midvein. Reproductive structures have been examined using light, scanning, and transmission electron microscopy. This new material is compared with the other Paleocene species for which sporophytes are known and discussed in terms of evolutionary trends for the genus. The specimens suggest that most of the vegetative characteristics of modern Azolla species were established by the middle Paleocene. Key words: Azolla, Salviniaceae, megaspore, massula, ultrastructure, Paleocene.

Morphology of Precipitates in Ni-Al-Cr Intermetallic Alloy

2007 ◽  
Vol 130 ◽  
pp. 159-162
Author(s):  
Mirosław Pilawa ◽  
Elżbieta Jezierska
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Intermetallic Alloy ◽  
Nickel Base Superalloy ◽  
Transmission Electron ◽  
Characteristic Features ◽  
Secondary Precipitates ◽  
Nickel Base ◽  
Base Superalloy

Transmission electron microscopy was used to study various morphologies of ordered precipitates in Ni3Al-Cr intermetallic alloy. It was found that γ’ precipitates in the interdendritic regions have the microstructure of a nickel base superalloy with its characteristic features. In addition to the primary γ’ precipitates some fine secondary precipitates were found.

Characteristic Features of the Modulated Structure Appearing in the Multiferroic Material Bi1-xSmxFeO3 around x = 0.15

2016 ◽  
Vol 879 ◽  
pp. 1393-1398 ◽  
Author(s):  
Masashi Nomoto ◽  
Takumi Inoshita ◽  
Yasuhide Inoue ◽  
Yoichi Horibe ◽  
Yasumasa Koyama
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Transverse Waves ◽  
Modulated Structure ◽  
Transmission Electron ◽  
Multiferroic Bifeo ◽  
State Boundary ◽  
Characteristic Features ◽  
Coexistence State ◽  
Transverse Modulation

In Bi1-xSmxFeO3 (BSFO) having the multiferroic BiFeO3 as an end material, when the Sm content increases from x = 0, it has been reported that the ferroelectric-R3c state is changed into the paraelectric-Pnma state around x = 0.14. The R3c/Pnma state boundary around x = 0.14 can be regarded as a temperature-independent morphotropic-phase boundary (MPB). The notable feature in BSFO is that, in addition to these two states, the antiferroelectric PbZrO3-type state was also found in the vicinity of the MPB. Although the PbZrO3-type state appears as a modulated structure, its detailed features have not been understood yet. We have thus examined the crystallographic features of prepared BSFO samples around x = 0.14, mainly by transmission electron microscopy. The PbZrO3-type state was confirmed to be present in samples with x = 0.15 on the basis of x-ray powder diffraction profiles measured from prepared samples at 300 K. On the other hand, the observation made by transmission electron microscopy indicated that the state for x = 0.15 is characterized by a coexistence state consisting of the ferroelectric-R3c and antiferroelectric PbZrO3-type states. In particular, the crystal structure of the PbZrO3-type state could be identified as a modulated structure with two transverse modulation waves, whose wave vectors are given by q1 = [1/2 0 0]o and q2 = [0 1/2 0]o in the orthorhombic-Pnma notation. In addition, eigenvectors of these two transverse waves were also determined to be parallel to the same [001]o direction.

Electron microscopy study of the bacteria adherent to the rumen wall in young conventional lambs

1990 ◽  
Vol 36 (2) ◽  
pp. 140-144 ◽  
Author(s):  
Franoise Rieu ◽  
G. Fonty ◽  
Brigitte Gaillard ◽  
P. Gouet
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Epithelial Cell ◽  
Key Words ◽  
Bacterial Population ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Transmission Electron ◽  
Scanning Electron

The lamb rumen walls were rapidly colonized by an abundant bacterial population after birth. This colonization was examined by electron microscopy in neonatal conventional lambs. The sequence of establishment of the epimural species during the 3 weeks following birth, and the distribution of bacteria on the different sacs of the rumen, were examined by scanning electron microscopy. The population was very dense and consisted of a limited number of morphological types by 2 days after birth. Three types of rods were dominant at that time. The microflora was more complex 2 weeks later. Observations by transmission electron microscopy of desquamated epithelial cells revealed the presence of adherent bacteria that are surrounded by fibrous carbohydrate coats and sometimes partially enclosed by invaginations of the epithelial cell. Key words: rumen, lamb, microflora, scanning electron microscopy, adherence.

LOCALIZATION OF RUMEN WALL-ADHERENT UREOLYTIC BACTERIA

1984 ◽  
Vol 64 (5) ◽  
pp. 60-61 ◽  
Author(s):  
R. J. C. McLEAN ◽  
J. W. COSTERTON ◽  
K.-J. CHENG
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Key Words ◽  
Histochemical Technique ◽  
Tissue Samples ◽  
Associated Bacteria ◽  
Transmission Electron ◽  
Ureolytic Bacteria

Treatment of rumen tissue samples with a newly developed histochemical technique for urease localization resulted in an electron dense reaction product deposition in several wall-associated bacteria. This represents the first instance in which ureolytic rumen wall-associated bacteria can be identified with transmission electron microscopy. Key words: Histochemical, rumen, urease, localization

Zygosporangium and zygospore formation in Phycomyces nitens

1978 ◽  
Vol 56 (1) ◽  
pp. 91-100 ◽  
Author(s):  
K. L. O'Donnell ◽  
S. L. Flegler ◽  
G. R. Hooper
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Light Microscopy ◽  
Secondary Wall ◽  
Wall Layer ◽  
Central Vacuole ◽  
Transmission Electron ◽  
Large Central Vacuole ◽  
Outer Primary

Zygosporangium and zygospore formation in Phycomyces nitens was followed by correlative light microscopy and scanning and transmission electron microscopy. Compatible multibranched zygophores became interlocked by the interdigitation of their lobes. Progametangia grew up from the substratum in pairs and then differentiated into gametangia and tongs-shaped suspensors. Plasmogamy was deferred until the gametangia were delimited. Development of rings of hyaline appendages on the suspensors was concomitant with plasmogamy. The appendages originated from the tertiary suspensor wall layer and ruptured the outer primary and secondary wall layers prior to development of their terminal thornlike processes.Developing zygosporangia contained a large central vacuole and some organelle zonation; however, these features were not discernible in more mature zygosporangia. A reticulum of electron-opaque fluted warts developed within the secondary zygosporangial wall layer. Cryofractured zygosporangia revealed a smooth hyaline zygospore with truncate ends. Wall layer relations of mature zygosporangia and zygospores were presented. Information obtained was correlated with existing ultrastructural observations on zygosporangiogenesis in the Mucorales.

scholarly journals Cytoplasmic lattices are not linked to mouse 2-cell embryos developmental arrest

2018 ◽  
Vol 62 (4) ◽  
Author(s):  
Marianna Longo ◽  
Michele Boiani ◽  
CarloAlberto Redi ◽  
Manuela Monti
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Oocyte Maturation ◽  
Mouse Embryos ◽  
Cell Stage ◽  
Developmental Arrest ◽  
Stage Of Development ◽  
Transmission Electron ◽  
Protein Synthesis Machinery ◽  
Intra Cytoplasmic Sperm Injection

Cytoplasmic lattices are important regulators of oocyte maturation. They store components of the protein synthesis machinery including ribosomes and, among others, they are involved in the regulation of microtubule dynamics in both mouse and human. Cytoplasmic lattices undergo dramatic reorganizations at crucial stages of oocyte maturation, where they are abundantly present in the cytoplasm of developmentally competent oocytes named SN (Surrounded Nucleolus) while they are rare in the cytoplasm of 2-cell stage-arresting NSN (Not Surrounded Nucleolus) oocytes, suggestive of a requirement of cytoplasmic lattices for development past the 2-cell stage. Here, to elucidate this requirement, 2-cell mouse embryos derived from SN and NSN oocytes were analyzed by transmission electron microscopy. Contrary to what had been proposed hitherto, cytoplasmic lattices are present in 2-cell embryos derived not only from SN, but also from NSN oocytes, irrespective of the embryo production system (intra cytoplasmic sperm injection, parthenogenesis). Hence our conclusion that cytoplasmic lattices do not count among the factor(s) responsible for the embryo arrest at this crucial stage of development.

scholarly journals Ultrastructure of sporophyte of Cladosiphon okamuranus Tokida (Ectocarpales, Phaeophyceae)

1970 ◽  
Vol 38 (2) ◽  
pp. 177-180 ◽  
Author(s):  
Qinghua Zhu ◽  
Xuecheng Zhang ◽  
KKIU Arunakumara
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cell Wall ◽  
Plasma Membrane ◽  
Key Words ◽  
Hair Cells ◽  
Brown Algae ◽  
Lipid Bodies ◽  
Transmission Electron ◽  
Cladosiphon Okamuranus

Transmission Electron Microscopy of 35 day old culture of Cladosiphon okamuranus Tokida, revealed several chloroplasts and other organelles in each cell of assimilatory filaments. Each chloroplast possesses single pyrenoid and Lipid bodies while in hair cells, there were few chloroplasts clinging to plasma-membrane and many pathholes were seen in the cell wall. Key words: Cladosiphon okamuranus; Brown algae; Ultrastructure; Pathhole DOI: 10.3329/bjb.v38i2.5143 Bangladesh J. Bot. 38(2): 177-180, 2009 (December)  

The Development of Fibre-Tracueid Pit Membranes in Pyrus Communis L.

IAWA Journal ◽  
1987 ◽  
Vol 8 (2) ◽  
pp. 134-142 ◽  
Author(s):  
J.R. Barnett
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Secondary Wall ◽  
Transverse Section ◽  
Pyrus Communis ◽  
Cell Enlargement ◽  
Transmission Electron ◽  
Pit Membrane ◽  
Pyrus Communis L ◽  
Cambial Cells

The development of fibre-tracheid pit membranes in Pyrus communis L. has been studied using transmission electron microscopy. Pit fields in the radial walls of cambial cells in transverse section contain isolated plasmodesmata. As cell enlargement proceeds, groups of plasmodesmata develop within thickenings of the future pit membrane. These thickenings are covered by amorphous, secondary-wall-like material (the torus-like structures found in mature pits by Parameswaran ' Liese, 1981) just prior to the end of differentiation and cytoplasmic autolysis. It is suggested that this cap of material acts as aseal, preventing passage of autolytic enzymes from a dying cell to its living neighbour via the perforations occupied by plasmodesmata.

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