Ascus and ascospore development in Eleutherascus peruvianus. 2. Nuclear cytology and early ascus ontogeny

1983 ◽  
Vol 61 (6) ◽  
pp. 1599-1617 ◽  
Author(s):  
W. L. Steffens ◽  
J. P. Jones
Keyword(s):  
Electron Microscopy ◽  
Nuclear Division ◽  
Spore Wall ◽  
Giemsa Staining ◽  
Double Membrane ◽  
Vesicle Membranes ◽  
Ascospore Development ◽  
High Degree ◽  
Nuclear Cytology ◽  
Internal Order

A study was undertaken of the cytological events leading to ascus initiation through delimitation of the ascospores prior to spore wall deposition in Eleutherascus peruvianus Huang. As revealed by Giemsa staining, nuclei in asci which are derived from croziers in the classical manner undergo the three divisions, with each division occurring in a different plane. The result is a globose ascus with eight nuclei displaying a high degree of internal order with respect to the arrangement of the ascospores. Electron microscopy reveals that subsequent to the final nuclear division, the ascus becomes filled with several elongate segments of double membrane underlying the ascus plasmalemma. These membrane segments appear to result from marked focal invaginations of the ascus plasmalemma and ultimately fuse together to form the ascus vesicle. Occasional observations of nuclei outside of the ascus vesicle membranes are believed to account for the often observed phenomenon of asci with odd numbers of ascospores. The significance of these findings relative to those for some close allies is discussed.

ASCOSPORE DEVELOPMENT IN HANSENULA ANOMALA

1967 ◽  
Vol 45 (3) ◽  
pp. 361-366 ◽  
Author(s):  
R. J. Bandoni ◽  
A. A. Bisalputra ◽  
T. Bisalputra
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Wall Layer ◽  
Double Membrane ◽  
Initial Layer ◽  
Hansenula Anomala ◽  
Ascospore Development

The development of ascospores of Hansenula anomala (Hansen) H. & P. Syd. was studied by electron microscopy. Within the young ascus, a double membrane develops around each of the haploid nuclei enclosing mitochondria, oil vacuoles, and endoplasmic reticulum as well. Two ascospore wall layers are deposited within the intercisternal space. The initial wall layer develops centripetally from the extremities of the base, then around the crown of the hat-shaped spore. In many spores, this initial wall is thin or incomplete around the upper portion of the crown. The second wall layer is less electron dense and is formed adjacent to and immediately within the initial layer. At maturity of the spores, no organelles remain in the epiplasm.

Electron microscopy of urediospore formation in Puccinia coronata avenae and P. graminis avenae

1976 ◽  
Vol 54 (9) ◽  
pp. 1010-1019 ◽  
Author(s):  
D. E. Harder
Keyword(s):  
Electron Microscopy ◽  
Lipid Droplets ◽  
Nuclear Division ◽  
Spore Wall ◽  
Puccinia Coronata ◽  
Sporogenous Cell ◽  
Cytoplasmic Inclusions ◽  
Puccinia Coronata Avenae ◽  
Variable Morphology ◽  
Spore Cell

Electron microscopy revealed that the sporogenous cells in urediosori of Puccinia coronata avenae and P. graminis avenae were enlarged at one end, and the cytoplasm was dense, vacuolated, and showed an early accumulation of lipid droplets. Urediospore formation was initiated by the outgrowth of a spore bud from the enlarged end of a sporogenous cell. A nuclear division occurred in the spore bud, the spore bud then grew to form the urediospore initial, and a septum formed to delineate the urediospore initial from the sporogenous cell. A further nuclear division occurred in the urediospore initial followed by septation to form the pedicel and spore cell. The urediospores rapidly grew to full size and further differentiation was marked by increased density of the cytoplasm, disappearance of vacuoles, increased lipid droplet accumulation, thickening of the spore wall, and spine formation. Nucleoli were not found in nuclei of mature urediospores. Possible paraphysis cells were intermixed with urediospores near the margins of urediosori of P. coronata. These cells were characterized by small nuclei which contained densely staining patches, a fine membranous network throughout the cytoplasm, and numerous cytoplasmic inclusions of variable morphology.

Tissue section lifting for electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 86-87
Author(s):  
Adrian F. van Dellen
Keyword(s):  
Infectious Disease ◽  
Electron Microscopy ◽  
Tissue Culture ◽  
Organ System ◽  
Surrounding Tissue ◽  
Paraffin Sections ◽  
Surface Areas ◽  
Specific Determination ◽  
High Degree ◽  
Accuracy And Repeatability

The morphologic pathologist may require information on the ultrastructure of a non-specific lesion seen under the light microscope before he can make a specific determination. Such lesions, when caused by infectious disease agents, may be sparsely distributed in any organ system. Tissue culture systems, too, may only have widely dispersed foci suitable for ultrastructural study. In these situations, when only a few, small foci in large tissue areas are useful for electron microscopy, it is advantageous to employ a methodology which rapidly selects a single tissue focus that is expected to yield beneficial ultrastructural data from amongst the surrounding tissue. This is in essence what "LIFTING" accomplishes. We have developed LIFTING to a high degree of accuracy and repeatability utilizing the Microlift (Fig 1), and have successfully applied it to tissue culture monolayers, histologic paraffin sections, and tissue blocks with large surface areas that had been initially fixed for either light or electron microscopy.

Electron Microscopy in Molecular Biology

1967 ◽  
Vol 25 ◽  
pp. 2-3
Author(s):  
Cecil E. Hall
Keyword(s):  
Electron Microscopy ◽  
Molecular Biology ◽  
Noise Level ◽  
Molecular Structures ◽  
Material Structure ◽  
The Arts ◽  
Shadow Casting ◽  
Electron Image ◽  
High Degree ◽  
Very High

The visualization of organic macromolecules such as proteins, nucleic acids, viruses and virus components has reached its high degree of effectiveness owing to refinements and reliability of instruments and to the invention of methods for enhancing the structure of these materials within the electron image. The latter techniques have been most important because what can be seen depends upon the molecular and atomic character of the object as modified which is rarely evident in the pristine material. Structure may thus be displayed by the arts of positive and negative staining, shadow casting, replication and other techniques. Enhancement of contrast, which delineates bounds of isolated macromolecules has been effected progressively over the years as illustrated in Figs. 1, 2, 3 and 4 by these methods. We now look to the future wondering what other visions are waiting to be seen. The instrument designers will need to exact from the arts of fabrication the performance that theory has prescribed as well as methods for phase and interference contrast with explorations of the potentialities of very high and very low voltages. Chemistry must play an increasingly important part in future progress by providing specific stain molecules of high visibility, substrates of vanishing “noise” level and means for preservation of molecular structures that usually exist in a solvated condition.

CHARACTERIZATION AND ELECTRICAL PROPERTIES OF ALIGNED CARBON NANOTUBES WITH HIGH ASPECT RATIO

2011 ◽  
Vol 10 (01n02) ◽  
pp. 23-28
Author(s):  
RAVI BHATIA ◽  
V. PRASAD ◽  
M. REGHU
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Aspect Ratio ◽  
Multiwall Carbon Nanotubes ◽  
High Quality ◽  
Transmission Electron Microscopy Analysis ◽  
Transmission Electron ◽  
Electron Microscopy Analysis ◽  
High Degree

High-quality multiwall carbon nanotubes (MWNTs) were produced by a simple one-step technique. The production of MWNTs was based on thermal decomposition of the mixture of a liquid phase organic compound and ferrocene. High degree of alignment was noticed by scanning electron microscopy. The aspect ratio of as-synthesized MWNTs was quite high (more than 4500). Transmission electron microscopy analysis showed the presence of the catalytic iron nanorods at various lengths of MWNTs. Raman spectroscopy was used to know the quality of MWNTs. The ratio of intensity of the G-peak to the D-peak was very high which revealed high quality of MWNTs. Magnetotransport studies were carried out at low temperature and a negative MR was noticed.

Fabrication and characterization of highly textured (Bi,Pb)2Sr2Ca2Cu3Ox superconducting ceramics using high magnetic field and cold isostatic pressing

1995 ◽  
Vol 10 (10) ◽  
pp. 2433-2443 ◽  
Author(s):  
Wai Lo ◽  
R. Stevens ◽  
R. Doyle ◽  
A.M. Campbell ◽  
W.Y. Liang
Keyword(s):  
Magnetic Field ◽  
Electron Microscopy ◽  
Cold Isostatic Pressing ◽  
Sintered Ceramic ◽  
Grain Alignment ◽  
Isostatic Pressing ◽  
Transmission Electron ◽  
Superconducting Ceramics ◽  
High Degree

High textured (Bi,Pb)2Sr2Ca2Cu3Ox ceramics have been fabricated by aligning deflocculated flakes of (Bi,Pb)2Sr2Ca2Cu3Ox suspended in an organic medium by means of a high de magnetic field (6 T) at room temperature followed by cold isostatic pressing. The proportion of the (Bi,Pb)2Sr2Ca2Cu3Ox phase in the precursor powder was carefully controlled, and the characteristics of the powder, such as size distribution and morphology, were determined. A high degree of grain alignment was found in the specimens after the magnetic alignment, although the bulk density of the materials was low. Cold isostatic pressing substantially increased the density of the magnetically prealigned specimens which also resulted in a slight decrease in the degree of grain alignment. This minor realignment was found to be due to the various kinds of processing defects that appeared in the specimens during compaction due to the grinding and cracking of the grains and their interlocking. The microstructural and superconducting properties of the sintered ceramic have been studied using texture goniometry, high resolution scanning electron microscopy, transmission electron microscopy, ac magnetic susceptometry, and critical current measurements.

scholarly journals The Core and Holoenzyme Forms of RNA Polymerase from Mycobacterium smegmatis

2018 ◽  
Vol 201 (4) ◽  
Author(s):  
Tomáš Kouba ◽  
Jiří Pospíšil ◽  
Jarmila Hnilicová ◽  
Hana Šanderová ◽  
Ivan Barvík ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Rna Polymerase ◽  
Conformational Changes ◽  
Mycobacterium Smegmatis ◽  
Drug Target ◽  
Conformational Dynamics ◽  
Three Dimensional ◽  
Cryo Electron Microscopy ◽  
Bacterial Rna ◽  
High Degree

ABSTRACT Bacterial RNA polymerase (RNAP) is essential for gene expression and as such is a valid drug target. Hence, it is imperative to know its structure and dynamics. Here, we present two as-yet-unreported forms of Mycobacterium smegmatis RNAP: core and holoenzyme containing σA but no other factors. Each form was detected by cryo-electron microscopy in two major conformations. Comparisons of these structures with known structures of other RNAPs reveal a high degree of conformational flexibility of the mycobacterial enzyme and confirm that region 1.1 of σA is directed into the primary channel of RNAP. Taken together, we describe the conformational changes of unrestrained mycobacterial RNAP. IMPORTANCE We describe here three-dimensional structures of core and holoenzyme forms of mycobacterial RNA polymerase (RNAP) solved by cryo-electron microscopy. These structures fill the thus-far-empty spots in the gallery of the pivotal forms of mycobacterial RNAP and illuminate the extent of conformational dynamics of this enzyme. The presented findings may facilitate future designs of antimycobacterial drugs targeting RNAP.

scholarly journals Parasitism of spores of the vesicular-arbuscular mycorrhizal fungus, Glomus dimorphicum

2005 ◽  
Vol 72 (1) ◽  
pp. 27-32 ◽  
Author(s):  
S.M. Boyetchko ◽  
J.P. Tewari
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Host Response ◽  
Arbuscular Mycorrhizal Fungus ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
Spore Wall ◽  
Vesicular Arbuscular ◽  
Scanning Electron

Spores of Glomus dimorphicum were examined for parasitism. Light and scanning electron microscopy revealed perforations, approximately 0.25 to 1.0 µm in diameter, in the spore wall. The presence of papillae, a dynamic host response, suggested that the parasitism occurred while the vesicular-arbuscular mycorrhizal fungus was still alive. No filamentous structures were detected in the spores; however, cysts of amoeba-like organisms were found in the spores and were also observed on agar plates on which surface-sterilized spores of G. dimorphicum containing such organisms were placed. It is postulated that an amoeba-like organism was the parasite, since the perforations on the spore wall were minute and no bacteria or fungi were seen inside the spores.

scholarly journals Defects of copper patina / Vady mìdìných patin

2015 ◽  
Vol 59 (3) ◽  
pp. 87-90 ◽  
Author(s):  
J. Stoulil ◽  
P. Šedá ◽  
M. Anisová ◽  
Z. Fencl ◽  
P. Novák ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Image Analysis ◽  
Compact Surface ◽  
Historical Buildings ◽  
X Ray Diffraction ◽  
X Ray ◽  
Destructive Analysis ◽  
High Degree ◽  
Scanning Electron

Abstract The paper is focused on analyses of dark copper patina defects that were formed on one sheet under the same conditions. Roofs of ten historical buildings were studied by image analysis and samples of two roofs were subjected to more detailed destructive analysis. These samples were studied by means of scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction and infrared spectroscopy. Both types of patina are composed of brochantite. Green patinas consisted of a pure brochantite and they had a fl at and compact surface. Conversely, black patina contained a high degree of impurities (ammonia cations, nitrates, silicates) and the surface was rough. The proportion of dark patina was higher in south and east facing surfaces, where washing by rainfall is more difficult.

scholarly journals Structural characterization of Yba2Cu3O7–δ/Y2O3 composite films

1998 ◽  
Vol 13 (4) ◽  
pp. 954-958 ◽  
Author(s):  
P. R. Broussard ◽  
M. A. Wall ◽  
J. Talvacchio
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Coincidence Site Lattice ◽  
Composite Films ◽  
X Ray Diffraction ◽  
Plane Orientation ◽  
Transmission Electron ◽  
Two Phases ◽  
High Degree

Using 4-circle x-ray diffraction and transmission electron microscopy, we have studied the microstructure and in-plane orientation of the phases present in thin film composite mixtures of Yba2Cu3O7–δ and Y2O3. We see a high degree of in-plane orientation and have verified a previous prediction for the in-plane order of Y2BaCuO5 on (110) MgO. Transmission electron microscopy shows the composite films to be a mixture of two phases, with YBCO grain sizes of ≈1 μm. We have also compared our observations of the in-plane order to the predictions of a modified near coincidence site lattice model.

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