scholarly journals Ultrastructure of the proximal region of somatic cilia in Paramecium tetraurelia.

1978 ◽  
Vol 78 (2) ◽  
pp. 451-464 ◽  
Author(s):  
R Dute ◽  
C Kung
Keyword(s):  
Transition Zone ◽  
Membrane Surface ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Proximal Region ◽  
Paramecium Tetraurelia ◽  
Three Dimensional Model ◽  
Anionic Sites ◽  
Ciliary Beating ◽  
20 Nm

The morphology of the transition zone between the terminal plate of the basal body and the 9 + 2 region of the somatic (non-oral) cilium has been examined in Paramecium tetraurelia. Freeze-fracture and thin-section techniques disclosed both membrane specializations and various internal structural linkages. Freeze-fracture material revealed sets of particles interrupting the unit membrane. The more distal of these form plaquelike arrays while the proximal set of particles forms the ciliary "necklace." The plaque regions correspond to anionic sites on the outer membrane surface as revealed by binding of polycationic ferritin. Both the plaque particles and the necklace particles appear to be in contact with outer doublet microtubules via a complex of connecting structures. In the interior of the transition zone an axosomal plate supports an axosome surrounded by a ring of lightly packed material. Only one of the two central tubules of the axoneme reaches and penetrates the axosome. Below the axosomal plate four rings, each approx. 20 nm wide, connect adjacent outer doublets. An intermediate plate lies proximal to these rings, and a terminal plate marks the proximal boundary of this zone. Nine transitional fibers extend from the region of the terminal plate to the plasmalemma. The observations described above have been used to construct a three-dimensional model of the transition region of "wild-type" Paramecium somatic cilia. It is anticipated that this model will be useful in future studies concerning possible function of transition-zone specializations, since Paramecium may be examined in both normal and reversed ciliary beating modes, and since mutants incapable of reverse beating are available.

scholarly journals Tracking ultrafast hot-electron diffusion in space and time by ultrafast thermomodulation microscopy

2019 ◽  
Vol 5 (5) ◽  
pp. eaav8965 ◽  
Author(s):  
A. Block ◽  
M. Liebel ◽  
R. Yu ◽  
M. Spector ◽  
Y. Sivan ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Nonequilibrium Dynamics ◽  
Hot Electron ◽  
Temperature Model ◽  
Three Dimensional Model ◽  
Electron Diffusion ◽  
Diffusion Dynamics ◽  
Electron Phonon Coupling ◽  
20 Nm ◽  
Two Temperature

The ultrafast response of metals to light is governed by intriguing nonequilibrium dynamics involving the interplay of excited electrons and phonons. The coupling between them leads to nonlinear diffusion behavior on ultrashort time scales. Here, we use scanning ultrafast thermomodulation microscopy to image the spatiotemporal hot-electron diffusion in thin gold films. By tracking local transient reflectivity with 20-nm spatial precision and 0.25-ps temporal resolution, we reveal two distinct diffusion regimes: an initial rapid diffusion during the first few picoseconds, followed by about 100-fold slower diffusion at longer times. We find a slower initial diffusion than previously predicted for purely electronic diffusion. We develop a comprehensive three-dimensional model based on a two-temperature model and evaluation of the thermo-optical response, taking into account the delaying effect of electron-phonon coupling. Our simulations describe well the observed diffusion dynamics and let us identify the two diffusion regimes as hot-electron and phonon-limited thermal diffusion, respectively.

HRSEM of the nuclear envelope (NE): Nuclear pore substructure; baskets and fibrous components

1992 ◽  
Vol 50 (1) ◽  
pp. 492-493 ◽  
Author(s):  
Martin W. Goldberg ◽  
Terence D. Allen
Keyword(s):  
Nuclear Envelope ◽  
Low Voltage ◽  
Ion Beam ◽  
Membrane Surface ◽  
Three Dimensional ◽  
Nuclear Lamina ◽  
Ring Structure ◽  
Objective Lens ◽  
Nuclear Pore ◽  
Three Dimensional Model

The nuclear envelope (NE) of eukaryotic cells has been studied for many years by a variety of em techniques yielding a three dimensional model of the nuclear pore complex (NPC) consisting of two rings (∼120nm diameter), one at the outer NE and one at the inner NE. Between the rings are eight spoke structures and a central plug. The cytoplasmic ring may be decorated with up to eight particles. The NPCs are embedded in a proteinaceous network: the nuclear lamina. Recently, low voltage HRSEM was used to show the existence of a basket-like structure attached to the nucleoplasmic ring. SEM is an ideal technique for the study of membrane surfaces. High resolution can be achieved in SEMs by the use of a field emission source which produces a high brightness probe of less than lnm diameter and a specimen stage within the objective lens, reducing chromatic abberations and production of SEIII electrons. Resolution of biological specimens can be further enhanced by coating with thin, continuous films of refractory metals such as chromium or tantalum which allows the use of higher accelerating voltages and magnifications. The NEs of Xenopus oocyte germinal vesicles have been prepared as previously described for HRSEM without detergent except they have been coated nominally with 3nm of tantalum by magnetron sputtering instead of ion beam sputtered platinum. NEs have then been examined at 30kV. The ring, plug/spoke complex and particles can all be seen at the cytoplasmic surface as well as details of the outer membrane structure and particles associated with it (Fig. 1). On the nucleoplasmic surface (Fig. 2) the inner ring is observed. It has a subunit appearance with eight filaments extending from between the subunits to a third ring structure: these make up the basket-like structure. When ‘baskets’ are close together they are joined by fibres at the ‘basket ring’ (Fig. 2). When several baskets are in close proximity these fibres form a network like a canopy over the baskets (Fig. 3). Other fibres are present on the inner membrane surface which may be membrane associated fibres or canopy fibres that have collapsed. It is uncertain which, if any, of these fibres are lamins as a further level of fibres is observed at the level of the nucleoplasmic ring when the membrane is removed with detergent (Fig. 4). These fibres are consistent with previously described lamina.

Effect of Humeral Stem Shape on Displacement in Elbow Implant

2013 ◽  
Vol 393 ◽  
pp. 467-471 ◽  
Author(s):  
Milad Heidari ◽  
Muhamad Noor Harun ◽  
Mohammed Rafiq Abdul Kadir ◽  
Jamal Kashani ◽  
Ardiyansyah Syahrom
Keyword(s):  
Three Dimensional ◽  
Distal Region ◽  
Proximal Region ◽  
Implant Loosening ◽  
Torsional Loading ◽  
Three Dimensional Model ◽  
Cross Sectional ◽  
Humeral Component ◽  
Implant Displacement ◽  
Tomography Scan

The daily activities are restricted by elbow architecture changes which causes instability and pain. Total elbow arthroplasty is considered last way to relief pain and instability. Various stem cross sectional shapes are designed to reduce loosening of the cemented stemmed implants. The purpose of this study is to analyse the effect of three different humeral stem shapes on implant displacement. Computed tomography scan image was used to reconstruct humerus bone. A three dimensional model of elbow humeral component with three different stem shapes (rectangular, triangular with round edges and circular) with the same length were modelled to be inserted in the constructed bone. All materials were assumed linear, homogenous, elastic and isotropic. A 4 N.m torque was applied and displacement for each implant was analysed. The results of this study showed displacement is more for distal region compared with proximal region. It was also found that rectangular stem had more resistance to torsional loading in comparison with circular and triangular. The present study demonstrates that changing the stem shapes affects the implant displacement and consequently the implant loosening.

Ultrastructural Investigations of the Contractile Filaments of Amoebae

1974 ◽  
Vol 32 ◽  
pp. 188-189
Author(s):  
P.L. Moore
Keyword(s):  
Cytoplasmic Streaming ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Amoeboid Movement ◽  
Different Types ◽  
Chemical Conditions ◽  
Complete Interpretation

Previous freeze fracture results on the intact giant, amoeba Chaos carolinensis indicated the presence of a fibrillar arrangement of filaments within the cytoplasm. A complete interpretation of the three dimensional ultrastructure of these structures, and their possible role in amoeboid movement was not possible, since comparable results could not be obtained with conventional fixation of intact amoebae. Progress in interpreting the freeze fracture images of amoebae required a more thorough understanding of the different types of filaments present in amoebae, and of the ways in which they could be organized while remaining functional.The recent development of a calcium sensitive, demembranated, amoeboid model of Chaos carolinensis has made it possible to achieve a better understanding of such functional arrangements of amoeboid filaments. In these models the motility of demembranated cytoplasm can be controlled in vitro, and the chemical conditions necessary for contractility, and cytoplasmic streaming can be investigated. It is clear from these studies that “fibrils” exist in amoeboid models, and that they are capable of contracting along their length under conditions similar to those which cause contraction in vertebrate muscles.

Freeze-Fracture Replication in the Ultrastructure of Blue-Green Algae

1967 ◽  
Vol 25 ◽  
pp. 74-75
Author(s):  
L. V. Leak
Keyword(s):  
Cell Wall ◽  
Electron Microscope ◽  
Green Algae ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Electron Microscopic ◽  
Photosynthetic Membranes ◽  
Blue Green Algae ◽  
Cell Biol ◽  
Cellular Components

Electron microscopic observations of freeze-fracture replicas of Anabaena cells obtained by the procedures described by Bullivant and Ames (J. Cell Biol., 1966) indicate that the frozen cells are fractured in many different planes. This fracturing or cleaving along various planes allows one to gain a three dimensional relation of the cellular components as a result of such a manipulation. When replicas that are obtained by the freeze-fracture method are observed in the electron microscope, cross fractures of the cell wall and membranes that comprise the photosynthetic lamellae are apparent as demonstrated in Figures 1 & 2.A large portion of the Anabaena cell is composed of undulating layers of cytoplasm that are bounded by unit membranes that comprise the photosynthetic membranes. The adjoining layers of cytoplasm are closely apposed to each other to form the photosynthetic lamellae. Occassionally the adjacent layers of cytoplasm are separated by an interspace that may vary in widths of up to several 100 mu to form intralamellar vesicles.

Three-Dimensional Immunoelectron Microscopy of Yeast Cells by a New High-Resolution Replica Method

1985 ◽  
Vol 43 ◽  
pp. 562-563
Author(s):  
Hirano T. ◽  
M. Yamaguchi ◽  
M. Hayashi ◽  
Y. Sekiguchi ◽  
A. Tanaka
Keyword(s):  
High Resolution ◽  
Plasma Polymerization ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Replica Method ◽  
Yeast Cells ◽  
Dynamic Aspect ◽  
Replica Technique ◽  
Gaseous Hydrocarbon ◽  
Transmission Electron

A plasma polymerization film replica method is a new high resolution replica technique devised by Tanaka et al. in 1978. It has been developed for investigation of the three dimensional ultrastructure in biological or nonbiological specimens with the transmission electron microscope. This method is based on direct observation of the single-stage replica film, which was obtained by directly coating on the specimen surface. A plasma polymerization film was deposited by gaseous hydrocarbon monomer in a glow discharge.The present study further developed the freeze fracture method by means of a plasma polymerization film produces a three dimensional replica of chemically untreated cells and provides a clear evidence of fine structure of the yeast plasma membrane, especially the dynamic aspect of the structure of invagination (Figure 1).

Three-Dimensional Model for Virtual Surgical Simulation, during Complex Skull Base Surgery and Aneurysm Surgery

Skull Base ◽  
2008 ◽  
Vol 18 (S 01) ◽  
Author(s):  
Akio Morita ◽  
Toshikazu Kimura ◽  
Shigeo Sora ◽  
Kengo Nishimura ◽  
Hisayuki Sugiyama ◽  
...  
Keyword(s):  
Skull Base ◽  
Surgical Simulation ◽  
Skull Base Surgery ◽  
Three Dimensional ◽  
Aneurysm Surgery ◽  
Dimensional Model ◽  
Three Dimensional Model
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