scholarly journals The hagfish slime gland thread cell. I. A unique cellular system for the study of intermediate filaments and intermediate filament-microtubule interactions.

1984 ◽  
Vol 98 (2) ◽  
pp. 653-669 ◽  
Author(s):  
S W Downing ◽  
R H Spitzer ◽  
E A Koch ◽  
W L Salo
Keyword(s):  
Cell Differentiation ◽  
Cross Section ◽  
Intermediate Filaments ◽  
Potential Model ◽  
Model System ◽  
Transmission Electron ◽  
Large Numbers ◽  
The Pacific ◽  
History Of ◽  
Phylogenetic Scheme

Thread cell differentiation in the slime gland of the Pacific hagfish Eptatretus stouti has been studied using light microscopy and scanning and transmission electron microscopy. Thread cell differentiation is remarkable in that the life history of the cell is largely dedicated to the production of a single, tapered, cylindrical, highly coiled, and precisely packaged cytoplasmic thread that may attain lengths of 60 cm and diameters approaching 1.5 micron. Each tapered thread, in turn, is comprised almost entirely of large numbers of intermediate filaments (IFs) bundled in parallel. During differentiation of the thread, the IFs become progressively more tightly packed. Various numbers of microtubules (MTs) are found among the bundled IFs during differentiation of the thread but disappear during the latter stages of thread differentiation. Observations of regularly spaced dots in longitudinal bisections of developing threads, diagonal striations in tangential sections of developing threads, and circumferentially oriented, filament-like structures observed at the periphery of developing threads cut in cross section have led us to postulate a helically oriented component(s) wrapped around the periphery of the developing thread. The enormous size of the fully differentiated thread cell, its apparent singular dedication to the production of IFs, the ease of isolating and purifying the threads and IF subunits (see accompanying paper), and the unique position of the hagfish in the phylogenetic scheme of vertebrate evolution all contribute to the attractiveness of the hagfish slime gland thread cell as a potential model system for studying IF subunit synthesis, IF formation from IF subunits, aggregation of IFs into IF bundles and the interaction(s) of IFs and MTs.

Sailing into the Anthropocene

2016 ◽  
Author(s):  
Peter Dauvergne
Keyword(s):  
South Pacific ◽  
The Political ◽  
Pacific Island ◽  
The South ◽  
Large Numbers ◽  
The Pacific ◽  
History Of ◽  
The Pacific Ocean ◽  
Starting Date ◽  
History Of The South

Chapters 2–6 survey the political and socioeconomic forces underlying the global sustainability crisis. Understanding the scale and depth of contemporary forces of capitalism and consumerism requires a close look at the consequences of imperialism and colonialism on patterns of violence and exploitation. This chapter begins this process of understanding by sketching the history of ecological imperialism after 1600, seeing this as a reasonable starting date for the beginning of what many scholars are now calling the Anthropocene Epoch (or the age of humans, replacing the geologic epoch of the Holocene beginning 12,000 years ago). It opens with Captain Pedro Fernandes de Queirós’s voyage across the Pacific Ocean in 1605–06 to “discover” modern-day Vanuatu, before turning to look more globally at the devastation of imperialism – and later colonialism – for the South Pacific, the Americas, Africa, and Asia. Over this time conquerors enslaved and murdered large numbers of indigenous people; cataclysmic change came as well, however, from the introduction of European diseases, plants, and animals. This chapter’s survey of imperialism, colonialism, and globalization sets the stage for Chapter 3, which explores the devastating history of the South Pacific island of Nauru after 1798.

Development of a Seismic Microzoning Map for Lima City and Callao, Peru

2014 ◽  
Vol 9 (6) ◽  
pp. 939-945 ◽  
Author(s):  
Diana Calderon ◽  
◽  
Zenon Aguilar ◽  
Fernando Lazares ◽  
Silvia Alarcon ◽  
...  
Keyword(s):  
Mechanical Characteristics ◽  
Pacific Coast ◽  
Soil Samples ◽  
S Wave ◽  
Seismic Microzoning ◽  
Geophysical Exploration ◽  
Large Numbers ◽  
The Pacific ◽  
History Of ◽  
Microtremor Measurements

The location of Lima city and El Callao in the Pacific coast and the long history of seismic activity were the main reasons to develop a seismic microzoning map. The microzoning study was based on large numbers of geotechnical and geophysical exploration points distributed around the study area. The geotechnical exploration consisted of borehole tests and pits, from which soil samples were taken to the laboratory to determine the soil mechanical characteristics. The geophysical exploration consisted of onepoint microtremor measurements and various methods to estimate the S-wave velocity profile. The results of both, the geotechnical and geophysical exploration were combined to develop a seismic microzoning map for Lima city and El Callao. This map shows five zones, where the zone with the best soil mechanical and dynamic characteristics covers most of the study area.

A tilting high temperature gas reaction chamber for the JEM 7A T.E.M.

1978 ◽  
Vol 36 (1) ◽  
pp. 70-71
Author(s):  
Brian L. Rhoades
Keyword(s):  
Cross Section ◽  
Reaction Chamber ◽  
Objective Lens ◽  
Reduced Cross Section ◽  
Cross Sectional ◽  
Structural Investigations ◽  
Transmission Electron ◽  
Dynamic Experiments ◽  
Successful Design ◽  
Thermocouple Junction

A gas reaction chamber has been designed and constructed for the JEM 7A transmission electron microscope which is based on a notably successful design by Hashimoto et. al. but which provides specimen tilting facilities of ± 15° aboutany axis in the plane of the specimen.It has been difficult to provide tilting facilities on environmental chambers for 100 kV microscopes owing to the fundamental lack of available space within the objective lens and the scope of structural investigations possible during dynamic experiments has been limited with previous specimen chambers not possessing this facility.A cross sectional diagram of the specimen chamber is shown in figure 1. The specimen is placed on a platinum ribbon which is mounted on a mica ring of the type shown in figure 2. The ribbon is heated by direct current, and a thermocouple junction spot welded to the section of the ribbon of reduced cross section enables temperature measurement at the point where localised heating occurs.

Microstructure of laser-irradiated, conducting Kapton polyimide

1995 ◽  
Vol 53 ◽  
pp. 502-503
Author(s):  
D. L. Callahan ◽  
Z. Ball ◽  
H. M. Phillips ◽  
R. Sauerbrey
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
Cross Section ◽  
Film Surface ◽  
Cross Sectional ◽  
General Utility ◽  
Transmission Electron ◽  
Considerable Debate ◽  
Potential Applications

Ultraviolet laser-irradiation can be used to induce an insulator-to-conductor phase transition on the surface of Kapton polyimide. Such structures have potential applications as resistors or conductors for VLSI applications as well as general utility electrodes. Although the percolative nature of the phase transformation has been well-established, there has been little definitive work on the mechanism or extent of transformation. In particular, there has been considerable debate about whether or not the transition is primarily photothermal in nature, as we propose, or photochemical. In this study, cross-sectional optical microscopy and transmission electron microscopy are utilized to characterize the nature of microstructural changes associated with the laser-induced pyrolysis of polyimide.Laser-modified polyimide samples initially 12 μm thick were prepared in cross-section by standard ultramicrotomy. Resulting contraction in parallel to the film surface has led to distortions in apparent magnification. The scale bars shown are calibrated for the direction normal to the film surface only.

Some early history of replica techniques for electron microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1076-1077
Author(s):  
Robert M. Fisher
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Optical Microscope ◽  
Early History ◽  
Bulk Materials ◽  
Thin Sections ◽  
Transmission Electron ◽  
Reflected Light ◽  
History Of ◽  
Electron Microscopes

By 1940, a half dozen or so commercial or home-built transmission electron microscopes were in use for studies of the ultrastructure of matter. These operated at 30-60 kV and most pioneering microscopists were preoccupied with their search for electron transparent substrates to support dispersions of particulates or bacteria for TEM examination and did not contemplate studies of bulk materials. Metallurgist H. Mahl and other physical scientists, accustomed to examining etched, deformed or machined specimens by reflected light in the optical microscope, were also highly motivated to capitalize on the superior resolution of the electron microscope. Mahl originated several methods of preparing thin oxide or lacquer impressions of surfaces that were transparent in his 50 kV TEM. The utility of replication was recognized immediately and many variations on the theme, including two-step negative-positive replicas, soon appeared. Intense development of replica techniques slowed after 1955 but important advances still occur. The availability of 100 kV instruments, advent of thin film methods for metals and ceramics and microtoming of thin sections for biological specimens largely eliminated any need to resort to replicas.

The use of an energy-filtering electron microscope to reduce chromatic aberration in images of thick biological specimens

1986 ◽  
Vol 44 ◽  
pp. 88-91
Author(s):  
L. D. Peachey ◽  
J. P. Heath ◽  
G. Lamprecht
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Beam ◽  
Cross Section ◽  
Electron Scattering ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Incident Electron Energy ◽  
Energy Filtering ◽  
Transmission Electron

Biological specimens of cells and tissues generally are considerably thicker than ideal for high resolution transmission electron microscopy. Actual image resolution achieved is limited by chromatic aberration in the image forming electron lenses combined with significant energy loss in the electron beam due to inelastic scattering in the specimen. Increased accelerating voltages (HVEM, IVEM) have been used to reduce the adverse effects of chromatic aberration by decreasing the electron scattering cross-section of the elements in the specimen and by increasing the incident electron energy.

Faceted antiphase boundaries in GaAs grown on Ge

1987 ◽  
Vol 45 ◽  
pp. 314-315
Author(s):  
N.-H. Cho ◽  
S. McKernan ◽  
C.B. Carter ◽  
K. Wagner
Keyword(s):  
Cross Section ◽  
Atomic Resolution ◽  
Face Centered Cubic ◽  
Electrical Behavior ◽  
Sphalerite Structure ◽  
Antiphase Boundaries ◽  
Transmission Electron ◽  
Face Centered ◽  
Quality Material ◽  
Simulated Images

Interest has recently increased in the possibility of growing III-V compounds epitactically on non-polar substrates to produce device quality material. Antiphase boundaries (APBs) may then develop in the GaAs epilayer because it has sphalerite structure (face-centered cubic with a two-atom basis). This planar defect may then influence the electrical behavior of the GaAs epilayer. The orientation of APBs and their propagation into GaAs epilayers have been investigated experimentally using both flat-on and cross-section transmission electron microscope techniques. APBs parallel to (110) plane have been viewed at the atomic resolution and compared to simulated images.Antiphase boundaries were observed in GaAs epilayers grown on (001) Ge substrates. In the image shown in Fig.1, which was obtained from a flat-on sample, the (110) APB planes can be seen end-on; the faceted APB is visible because of the stacking fault-like fringes arising from a lattice translation at this interface.

An Ultrastructural Comparison of Hepatocytes from ADH+ and ADH−Peromyscus Maniculatus

1996 ◽  
Vol 54 ◽  
pp. 30-31
Author(s):  
J. T. Ellzey ◽  
D. Borunda ◽  
B. P. Stewart
Keyword(s):  
South Carolina ◽  
Adult Male ◽  
Uranyl Acetate ◽  
Model System ◽  
Deer Mice ◽  
En Bloc ◽  
Genetic Stock ◽  
Hepes Buffer ◽  
Transmission Electron ◽  
Color Scanner

Genetically alcohol deficient deer mice (ADHN/ADHN) (obtained from the Peromyscus Genetic Stock Center, Univ. of South Carolina) lack hepatic cytosolic alcohol dehydrogenase. In order to determine if these deer mice would provide a model system for an ultrastructural study of the effects of ethanol on hepatocyte organelles, 75 micrographs of ADH+ adult male deer mice (n=5) were compared with 75 micrographs of ADH− adult male deer mice (n=5). A morphometric analysis of mitochondrial and peroxisomal parameters was undertaken.The livers were perfused with 0.1M HEPES buffer followed by 0.25% glutaraldehyde and 2% sucrose in 0.1M HEPES buffer (4C), removed, weighed and fixed by immersion in 2.5% glutaraldehyde in 0.1M HEPES buffer, pH 7.4, followed by a 3,3’ diaminobenzidine (DAB) incubation, postfixation with 2% OsO4, en bloc staining with 1% uranyl acetate in 0.025M maleate-NaOH buffer, dehydrated, embedded in Poly/Bed 812-BDMA epon resin, sectioned and poststained with uranyl acetate and lead citrate. Photographs were taken on a Zeiss EM-10 transmission electron microscope, scanned with a Howtek personal color scanner, analyzed with OPTIMAS 4.02 software on a Gateway2000 4DX2-66V personal computer and stored in Excel 4.0.

Electron microscope study of the secretory activity of epithelial cells in embryonic thymus

1990 ◽  
Vol 48 (3) ◽  
pp. 382-383
Author(s):  
H. Alasam
Keyword(s):  
Cell Differentiation ◽  
T Cell ◽  
Epithelial Cells ◽  
Electron Density ◽  
Secretory Activity ◽  
T Cell Differentiation ◽  
High Electron ◽  
Transmission Electron ◽  
Medullary Epithelial Cells ◽  
Thymic Factor

The possibility that intrathymic T-cell differentiation involves stem cell-lymphoid interactions in embryos led us to study the ultrastructure of epithelial cell in normal embryonic thymus. Studies in adult thymus showed that it produces several peptides that induce T-cell differentiation. Several of them have been chemically characterized, such as thymosin α 1, thymopoietin, thymic humoral factor or the serum thymic factor. It was suggested that most of these factors are secreted by populations of A and B-epithelial cells.Embryonic materials were obtained from inbred matings of Swiss Albino mice. Thymuses were disected from embryos 17 days old and prepared for transmission electron microscopy. Our studies showed that embryonic thymus at this stage contains undifferentiated and differentiated epithelial cells, large lymphoblasts, medium and few small lymphocytes (Fig. 5). No differences were found between cortical and medullary epithelial cells, in contrast to the findings of Van Vliet et al,. Epithelial cells were mostly of the A-type with low electron density in both cytoplasm and nucleus. However few B-type with high electron density were also found (Fig. 7).

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