The fine structure of Monoblepharella sp. zoospores

1968 ◽  
Vol 46 (3) ◽  
pp. 279-283 ◽  
Author(s):  
Melvin S. Fuller ◽  
Rudolf E. Reichle
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Cross Section ◽  
Cross Sections ◽  
Aquatic Fungi ◽  
Tubular Structure ◽  
Phylogenetic Distribution ◽  
Photosensitive Structure

Zoospores of Monoblepharella sp. a representative of the order Monoblepharidales, no members of which had ever been studied with the electron microscope, were fixed with glutaraldehyde, followed by OsO4, and their ultrastructure is described. The kinetosome, to which the flagellum is attached, has the appearance of a centriole in cross section. Radiating laterally from the kinetosome is a striated disc which is anchored in a pair of annular lamellae. Microtubules run forward in the cell from a ring in the striated disc. The nucleus is surrounded by a concentration of ribosomes, the latter being partially surrounded and traversed by membranous elements. The zoospores of this Monoblepharella sp. do not have a nuclear cap of the type found in the Blastocladiales. The nature and phylogenetic distribution of nuclear caps in the aquatic fungi is discussed. A highly organized tubular structure at the posterior end of the zoospores is described and its possible function as a photosensitive structure discussed. At encystment the flagellum is withdrawn and cross sections of the flagellum are shown within cysts.

scholarly journals Electron Microscope Study of the Normal Rat Aorta

1960 ◽  
Vol 7 (3) ◽  
pp. 533-537 ◽  
Author(s):  
M. K. Keech
Keyword(s):  
Smooth Muscle ◽  
Fine Structure ◽  
Electron Microscope ◽  
Cross Section ◽  
Electron Microscope Study ◽  
Rat Aorta ◽  
Endothelial Layer ◽  
Signet Ring ◽  
Normal Rat ◽  
Elastic Laminae

The fine structure of the normal rat aorta is described. The presence of a sub-endothelial layer, the oblique orientation of the smooth muscle cells with respect to the aortic axis, and the occurrence of desmosomes between these cells and adjacent elastic laminae, are emphasized. Lead-stained collagen presented a characteristic signet-ring appearance on cross-section. The rats examined were the pair-fed controls for the lathyritic series described in a separate communication.

scholarly journals Proteins transported in slow components a and b of axonal transport are distributed differently in the transverse plane of the axon.

1985 ◽  
Vol 100 (4) ◽  
pp. 1167-1172 ◽  
Author(s):  
K Heriot ◽  
P Gambetti ◽  
R J Lasek
Keyword(s):  
Electron Microscope ◽  
Axonal Transport ◽  
Cross Section ◽  
Cross Sections ◽  
Polyacrylamide Gel Electrophoresis ◽  
Transverse Plane ◽  
Hypoglossal Nucleus ◽  
Electron Microscope Autoradiography ◽  
Microscope Autoradiography ◽  
Slow Transport

The distribution of the proteins migrating with the slow components a (SCa) and b (SCb) of axonal transport were studied in cross-sections of axons with electron microscope autoradiography. Radiolabeled amino acids were injected into the hypoglossal nucleus of rabbits and after 15 d, the animals were killed. Hypoglossal nerves were processed either for SDS-polyacrylamide gel electrophoresis fluorography to identify and locate the two components of slow transport, or for quantitative electron microscope autoradiography. Proteins transported in SCa were found to be uniformly distributed within the cross-section of the axon. Labeled SCb proteins were also found throughout the axonal cross-section, but the subaxolemmal region of the axon contained 2.5 times more SCb radioactivity than any comparable area in the remainder of the axon.

Energy Loss Imaging in Biology

1982 ◽  
Vol 40 ◽  
pp. 416-419
Author(s):  
H. Shuman ◽  
A.V. Somlyo ◽  
A.P. Somlyo ◽  
T. Frey ◽  
D. Safer
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Cross Section ◽  
Cross Sections ◽  
Count Rate ◽  
Electron Flux ◽  
Characteristic Energy ◽  
Spectrometer Slit ◽  
Electron Energy Loss ◽  
Sensitive Method

It has been recognized for sometime that electron energy loss spectroscopy (EELS) is potentially the most sensitive method of measuring elemental composition in the electron microscope. Magnetic sector spectrometers currently in use collect most of the inelastically scattered electrons, while the cross sections for ionization of the L2 3 levels of the biologically important elements are large. The energies of the theoretically predicted L2 3 absorption edge maxima and their corresponding differential cross section for lOmrad collection and 80keV incident electrons are shown in Table I. The characteristic energy loss electron count rate expected from one atom with lOeV spectrometer slit width and lOOA/cm2 (the maximum available from a tungsten hairpin) electron flux at the specimen, indicates that the minimum detectable mass sensitivity of EELS will be high. An experimentally determined count rate and cross section for the Fe M2, 3 edge was determined from the ferritin images shown in Fig. 1.

scholarly journals Further Observations on the Nuclear Envelope of the Animal Cell

1959 ◽  
Vol 6 (2) ◽  
pp. 147-156 ◽  
Author(s):  
Michael L. Watson
Keyword(s):  
Electron Microscope ◽  
Nuclear Envelope ◽  
Cross Section ◽  
Cross Sections ◽  
Nuclear Membrane ◽  
Animal Cell ◽  
Nuclear Surface ◽  
Apparent Discrepancy ◽  
Outer Nuclear Membrane ◽  
Direct Association

The term pore complex is proposed for approximately cylindrical formations which are observed with the electron microscope to penetrate the nuclear envelope of cells. Cross-sections of the pore complex are somewhat annular in shape, but differ in appearance depending upon the level of the cross-section with respect to the nuclear surface. An explanation is offered for the apparent discrepancy between the width of pores in sections perpendicular to the nuclear envelope and the width of cross-sections of the pore complex in tangential sections. Channels associated with the pore complex extend deep into the nucleus. Although crescents and spirals of ribonucleoprotein particles were often seen in the immediate vicinity of the outer nuclear membrane, direct association with the pore complex was not observed. Many examples were found of pores that were not covered by a continuous membrane although the possibility of such a covering in some cases is not precluded.

Photoneutron cross sections in 7Li

1977 ◽  
Vol 55 (5) ◽  
pp. 428-433 ◽  
Author(s):  
H. Ferdinande ◽  
N. K. Sherman ◽  
K. H. Lokan ◽  
C. K. Ross
Keyword(s):  
Fine Structure ◽  
Excited State ◽  
Cross Section ◽  
Cross Sections ◽  
Ground State ◽  
Reasonable Agreement ◽  
Branching Ratio ◽  
Energy Spectra ◽  
Average Value ◽  
First Excited State

Photoneutron energy spectra from 7Li have been measured by time-of-flight methods, for bremsstrahlung end-point energies increasing in 2 MeV steps from 13 to 25 MeV. The ground-state and approximate first-excited-state differential cross sections at 90° have been obtained from 8.5 to 23 MeV. No pronounced fine structure has been observed. The measured branching ratio to the first excited state falls from an average value of 0.70 between 10.3 and 14.5 MeV to an average of 0.29 between 14.5 and 18 MeV, and rises again to an average of 0.38 between 18 and 23 MeV. This behaviour can be explained by a crude theoretical model in which 1p → 2s and 1p → 1d single particle transitions dominate below 18 MeV. The calculation predicts a branching ratio of 0.50 near threshold, falling to 0.23 at higher energies, in reasonable agreement with the experiment. The integrated value of the ground-state cross section up to 23 MeV is about (38.7 ± 3.9) MeV mb, while that for the first excited state is about (17.2 ± 3.4) MeV mb. Together they account for 39% of the exchange-augmented dipole sum of 7Li.

scholarly journals STUDIES ON CILIA

1963 ◽  
Vol 18 (2) ◽  
pp. 345-365 ◽  
Author(s):  
Peter Satir
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Cross Section ◽  
Osmium Tetroxide ◽  
Freshwater Mussel ◽  
Structure And Function ◽  
Spring Water ◽  
Fine Structure And Function ◽  
And Function ◽  
Active Preparation

Upon excision into spring water, the lateral cilia of the gill of the freshwater mussel Elliptio complanatus (Solander) stop beating, but 0.04 M potassium ion can activate the gill so that these cilia again beat with metachronal rhythm. One per cent osmium tetroxide quickly pipetted onto a fully activated gill fixes the lateral cilia in a pattern that preserves the form and arrangement of the metachronal wave, and permits the cilia to be studied with the electron microscope in all stages of their beat cycle. Changes are seen in the fixed active preparation that are not present in the inactive control, i.e., in the packing of the cilia, the position of the axis of the ciliary cross-section, and the diameter of the ring of peripheral filaments. Analysis of these parameters may lead to new correlations between ciliary fine structure and function.

scholarly journals Measurement of the differential cross sections of natLi(d,d0) for EBS purposes

2019 ◽  
Vol 24 ◽  
pp. 272
Author(s):  
E. Ntemou ◽  
K. Preketes-Sigalas ◽  
X. Aslanoglou ◽  
V. Foteinou ◽  
M. Kokkoris ◽  
...  
Keyword(s):  
Fine Structure ◽  
Elastic Scattering ◽  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Differential Cross ◽  
Beam Energy ◽  
Deuteron Beam ◽  
Differential Cross Sections

In the present work, the 6,7Li(d,d0)6,7Li elastic scattering differential cross sections were measured in the energy range Elab = 900 – 2000 keV for EBS purposes, using thin lithium targets, made by evaporating natLiF and isotopically enriched 6LiF powder on self-supporting carbon stripping foils, with an ultra-thin Au layer on top for charge normalization purposes. The experiment was carried out in deuteron beam energy steps of 5 to 30 keV, depending on the fine structure of each studied cross section, and for the laboratory scattering angles of 125˚, 140˚, 150˚, 160˚, and 170˚.

Investigation of Fine Structure in the Photoneutron Cross Sections of 16O and 208Pb

1975 ◽  
Vol 53 (15) ◽  
pp. 1434-1442 ◽  
Author(s):  
R. G. Johnson ◽  
J. D. Irish ◽  
K. G. McNeill
Keyword(s):  
Fine Structure ◽  
High Resolution ◽  
Differential Cross Section ◽  
Cross Section ◽  
Cross Sections ◽  
Ground State ◽  
Center Of Mass ◽  
Energy Spectra ◽  
Neutron Time ◽  
Good Agreement

The structure in the photoneutron cross sections of 16O and 208Pb has been studied by the measurement of high resolution photoneutron energy spectra using the neutron time-of-flight technique and bremsstrahlung irradiations. For 16O, the ground state differential cross section at 98° has been deduced between 17.3 and 28.5 MeV and is in good agreement with most previous studies. Fine structure is seen throughout the cross section. Eight neutron energy spectra for 208Pb from bremsstrahlung endpoint energies in the range 11.0 to 15.5 MeV were obtained. Strong peaks are seen at center of mass neutron energies of 1.67, 1.85, 2.06, 2.19, 2.68, 3.15, 3.27, 3.50, 3.77, and 4.03 MeV with weaker peaks elsewhere. The energies of these peaks are in good agreement with previous measurements in this laboratory. The energies of peaks in the spectra are compared with recent cross section measurements.

scholarly journals FINE STRUCTURE OF THE RETINULAE IN THE COMPOUND EYE OF THE HONEY-BEE

1962 ◽  
Vol 14 (3) ◽  
pp. 489-494 ◽  
Author(s):  
Timothy H. Goldsmith
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Honey Bee ◽  
Cross Sections ◽  
Compound Eye ◽  
Parallel Array ◽  
Retinular Cells

The retinula of the compound eye of the worker honey-bee has been examined with the electron microscope. The rhabdom lies on the ommatidial axis; it is usually cylindrical in shape, about 3 to 4 µ in diameter, and lacks an axial cavity. Cross-sections show it to be four parted, although it is formed from eight retinular cells (Figs. 2, 3). Each quadrant of the rhabdom consists of a closely packed parallel array of tubules with long axes perpendicular to the axis of the rhabdom. The tubules in adjacent quadrants of the rhabdom are mutually perpendicular. At the distal end of the ommatidium these tubules are seen to be microvilli of the retinular cells. Immediately surrounding the rhabdom, the cytoplasm of the retinular cells contains a membranous endoplasmic reticulum which is oriented approximately radially with respect to the axis of the ommatidium. Farther away from the rhabdom the cytoplasm contains numerous mitochondria.

scholarly journals Spin Effects in the (e, 2e) Cross Section of Xenon

1996 ◽  
Vol 49 (2) ◽  
pp. 383 ◽  
Author(s):  
B Granitza ◽  
X Guo ◽  
JM Hum ◽  
J Lower ◽  
S Mazevet ◽  
...  
Keyword(s):  
Electron Beam ◽  
Fine Structure ◽  
Electron Impact ◽  
Cross Section ◽  
Cross Sections ◽  
Ground State ◽  
Closed Shell ◽  
Spin Effects ◽  
Incident Electron Beam ◽  
Series Of Experiments

In a series of experiments investigating the spin-dependent aspects of electron impact induced ionisation of atoms with a spin-resolved incident electron beam we have measured spin-resolved (e, 2e) cross sections for xenon. By experimentally resolving the fine structure levels of the ground state residual ion the existence of an effect analogous to the fine structure effect in excitation has been established, whereby strong and opposite polarisation effects are observed in the ionisation of a spinless closed shell target leading to a fine structure doublet.

Sign in / Sign up

Export Citation Format

Share Document