The flagellar apparatus in zoospores of Phytophthora, Pythium, and Halophytophthora

1992 ◽  
Vol 70 (11) ◽  
pp. 2163-2169 ◽  
Author(s):  
D. J. S. Barr ◽  
N. L. Désaulniers
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Flagellar Apparatus ◽  
Posterior Root ◽  
Transmission Electron ◽  
Structure Morphology ◽  
Cytoplasmic Microtubules ◽  
Relationship Of ◽  
The Relationship

The flagellar apparatuses of 14 species of Phytophthora, 2 of Halophytophthora, and 4 of Pythium are compared in the transmission electron microscope. Except for Phytophthora infestans and Phytophthora mirabilis there were no significant differences in fine structure morphology. There are six flagellar roots: a ribbed triplet consisting of three main microtubules and secondary microtubules; an anterior doublet; a multistranded, band-shaped root of five to nine microtubules; a posterior root of two to four microtubules; and roots consisting of arrays of cytoplasmic microtubules and nuclear-associated microtubules. In P. infestans and P. mirabilis the multistranded root is missing, the posterior root contains five or six microtubules, and the anterior ribbed root contains four main microtubules. The transitional zones in all species are similar. The relationship of the Pythiaceae with other Oomycetes is discussed. Key words: taxonomy, phytogeny, cytology, Oomycetes, Pythiaceae.

Zygospores of the Harpellales: an ultrastructural study

1977 ◽  
Vol 55 (24) ◽  
pp. 3099-3110 ◽  
Author(s):  
S. T. Moss ◽  
R. W. Lichtwardt
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Ultrastructural Study ◽  
Storage Materials ◽  
Transmission Electron ◽  
Relationship Of ◽  
The Relationship ◽  
Thickened Wall

Structure of zygospores, their zygosporophores, and conjugants in Harpella melusinae, Trichozygospora chironomidarum, Genistellospora homothallica, and Zygopolaris ephemeridarum is described from light and transmission electron microscope studies. Possession of a thickened wall, presence of storage materials, and formation after hyphal conjugation supports the interpretation of these as zygospores. The relationship of the harpellaceous zygospores to those of other members of the Zygomycotina is discussed.

scholarly journals DNA AND THE FINE STRUCTURE OF SYNAPTIC CHROMOSOMES IN THE DOMESTIC ROOSTER (GALLUS DOMESTICUS)

1964 ◽  
Vol 23 (1) ◽  
pp. 63-78 ◽  
Author(s):  
James R. Coleman ◽  
Montrose J. Moses
Keyword(s):  
Electron Microscopy ◽  
Heavy Metal ◽  
Fine Structure ◽  
Electron Microscope ◽  
Meiotic Prophase ◽  
Gallus Domesticus ◽  
Feulgen Staining ◽  
Synaptinemal Complex ◽  
Relationship Of ◽  
The Relationship

The indium trichloride method of Watson and Aldridge (38) for staining nucleic acids for electron microscopy was employed to study the relationship of DNA to the structure of the synaptinemal complex in meiotic prophase chromosomes of the domestic rooster. The selectivity of the method was demonstrated in untreated and DNase-digested testis material by comparing the distribution of indium staining in the electron microscope to Feulgen staining and ultraviolet absorption in thicker sections seen with the light microscope. Following staining by indium, DNA was found mainly in the microfibril component of the synaptinemal complex. When DNA was known to have been removed from aldehyde-fixed material by digestion with DNase, indium stainability was also lost. However, staining of the digested material with non-selective heavy metal techniques demonstrated the presence of material other than DNA in the microfibrils and showed that little alteration in appearance of the chromosome resulted from DNA removal. The two dense lateral axial elements of the synaptinemal complex, but not the central one to any extent, also contained DNA, together with non-DNA material.

Microstructural Evolution and Stress Relaxation in Sputtered Tungsten Films

1993 ◽  
Vol 318 ◽  
Author(s):  
F. M. Ross ◽  
R. R. Kola ◽  
R. Hull ◽  
J. C. Bean
Keyword(s):  
Electron Microscope ◽  
Stress Relaxation ◽  
Microstructural Evolution ◽  
Transmission Electron Microscope ◽  
Specimen Geometry ◽  
Β Phase ◽  
Transmission Electron ◽  
The Relationship

ABSTRACTWe have investigated the relationship between microstructure and stress in very thin sputtered W films. We discuss features of the microstructure, in particular the presence of voids in compressively stressed films, in terms of the evolution of the structure from a metastable β-phase. By developing a novel specimen geometry for the transmission electron microscope (TEM), we present dynamic observations of the β-W→α-W transformation.

scholarly journals CENTROSOMES AND MICROTUBULES DURING MEIOSIS IN THE MUSHROOM BOLETUS RUBINELLUS

1971 ◽  
Vol 50 (3) ◽  
pp. 737-745 ◽  
Author(s):  
David J. McLaughlin
Keyword(s):  
Electron Microscope ◽  
Longitudinal Axis ◽  
Spindle Pole ◽  
Middle Part ◽  
Prophase I ◽  
Cytoplasmic Microtubules ◽  
Oriented Parallel ◽  
Relationship Of ◽  
The Relationship

The double centrosome in the basidium of Boletus rubinellus has been observed in three planes with the electron microscope at interphase preceding nuclear fusion, at prophase I, and at interphase I. It is composed of two components connected by a band-shaped middle part. At anaphase I a single, enlarged centrosome is found at the spindle pole, which is attached to the cell membrane. Microtubules mainly oriented parallel to the longitudinal axis of the basidium are present at prefusion, prophase I and interphase I. Cytoplasmic microtubules are absent when the spindle is present. The relationship of the centrosome in B. rubinellus to that in other organisms and the role of the cytoplasmic microtubules are discussed.

scholarly journals Fine Structure in Multi-Phase Zr8Ni21-Zr7Ni10-Zr2Ni7 Alloy Revealed by Transmission Electron Microscope

Materials ◽  
2015 ◽  
Vol 8 (7) ◽  
pp. 4618-4630 ◽  
Author(s):  
Haoting Shen ◽  
Leonid Bendersky ◽  
Kwo Young ◽  
Jean Nei
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Transmission Electron ◽  
Multi Phase

Flagellar apparatus of male gametes and other aspects of gamete and zygote ultrastructure in Prasiola and Rosenvingiella (Chlorophyta, Prasiolales) from British Columbia

1989 ◽  
Vol 67 (2) ◽  
pp. 505-514 ◽  
Author(s):  
Charles J. O'Kelly ◽  
David J. Garbary ◽  
Gary L. Floyd
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Rotational Symmetry ◽  
Flagellar Apparatus ◽  
Zygote Formation ◽  
Structural Elements ◽  
Male Gametes ◽  
Transmission Electron ◽  
Close Relatives ◽  
Flagellar Axoneme

We examined gametes, syngamy, and zygote formation in Prasiola meridionalis Setchell & Gardner and Rosenvingiella constricta (S. & G.) Silva with the transmission electron microscope. We compare the structures we observed with those of the Atlantic species P. stipitata Suhr and describe some previously unreported features. The sperm possessed a number of unusual structural elements in the flagellar apparatus and elsewhere, in particular a 9 + 1 microtubule configuration in the flagellar axoneme. The flagellar apparatus exhibited 180° rotational symmetry and counterclockwise absolute orientation of major components. At syngamy, the flagellar apparatus changed little in composition and arrangement, suggesting that it has a minimal, if any, function in syngamy or the planozygote. Karyogamy occurred within a few hours of plasmogamy, after settlement of the planozygote and concurrently with wall formation. The three species, P. meridionalis, P. stipitata, and R. constricta, are very similar in gamete structure, which indicates that the genera Prasiola and Rosenvingiella are close relatives. The flagellar apparatus features provide evidence supporting recognition of the order Prasiolales, which may be assigned to either the class Ulvophyceae or the class Pleurastrophyceae.

Analysis of Cellular Organelles and Macromolecular Assemblies by Electron Energy Loss Spectroscopy

1996 ◽  
Vol 54 ◽  
pp. 290-291
Author(s):  
R.D. Leapman ◽  
S.B. Andrews
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Energy Loss ◽  
Field Emission ◽  
Transmission Electron Microscope ◽  
Electron Energy Loss Spectroscopy ◽  
Low Loss ◽  
Macromolecular Assemblies ◽  
Transmission Electron ◽  
Electron Energy Loss

Recent advances in electron energy loss spectroscopy (EELS) have significantly extended the range of applications for biological microanalysis. For example, EELS can now detect physiological concentrations of the important element calcium in rapidly frozen cells with a sensitivity greater than that achievable by energy-dispersive x-ray spectroscopy (EDXS). It can also detect small numbers of phosphorus atoms bound to macromolecular assemblies, and measure water distributions in frozen hydrated tissue. Here we discuss some of these developments in the context of detection limits and mapping techniques in the scanning transmission electron microscope (STEM) and energy-filtering transmission electron microscope (EFTEM).The useful information about elemental composition in EELS of biological specimens generally resides in weak core-edge signals corresponding to atomic concentrations in the 10−5−10−3 (1–100 mmol/kg dry weight) range. For example, the Ca L2,3 signal/background ratio is typically only 10−3 and it is necessary to measure differences in signal that are only 104 of the background. Changes in low-loss fine structure corresponding to varying chemical composition are also very subtle; for example, detection of a 3% change in water content requires reliable measurement of a 0.1 eV shift in the low-loss intensity maximum. To extract such information requires efficient parallel detection of the energy loss spectrum and a high-brightness source to provide a sufficient number of incident electrons. The dedicated STEM is particularly well-suited for analyzing low concentrations of biological elements. If desired, the probe current can be reduced into the picoampere range for low-dose, high-resolution imaging prior to elemental analysis. The STEM’S field-emission source can then be used to deliver a current approaching 10 nA into a ~10 nm diameter probe. High electron flux conditions are ideal for spectrum-imaging applications where adequate counting statistics must be achieved within a limited pixel dwell time. The cold field-emission source of the STEM has the additional advantage of providing electrons with a narrow energy spread of <0.5 eV which is important in fine structure studies.

Lamellae and their organization in melt-crystallized polymers

1994 ◽  
Vol 348 (1686) ◽  
pp. 29-43 ◽  
Keyword(s):  
Fine Structure ◽  
Thermal Properties ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Molecular Mechanisms ◽  
Mechanical And Thermal Properties ◽  
Screw Dislocations ◽  
Transmission Electron ◽  
Gain Material

Significant advances in knowledge of lamellae and their organization in meltcrystallized polymers have stemmed from the ability to examine internal morphologies systematically with the transmission electron microscope. Spherulites form because the first-forming (dominant) lamellae branch repetitively, often at giant screw dislocations, then diverge substantially creating a skeleton to which later-forming lamellae must accommodate. This sequence promotes chain-folding, invites fractional crystallization and modulates chemical, mechanical and thermal properties of spherulites at the inter-dominant spacing. The key feature of lamellar divergence at screw dislocations is present in individual crystals, probably deriving from pressure of uncrystallized molecular cilia; growing lamellae will also distort very substantially to gain material. If necessary, spacefilling is achieved without lamellar and crystallographic continuity by nucleating new growth at large misorientations. Individual melt-grown crystals have been studied both after extraction from a quenched matrix and in situ in thinned specimens. For polyethylene different lamellar profiles have been placed in context while their fine structure provides insights into molecular mechanisms of growth.

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