Nuclear pore structure in quiescent buds of Tilia europaea

1980 ◽  
Vol 58 (16) ◽  
pp. 1814-1819 ◽  
Author(s):  
J. H. M. Willison ◽  
F. J. Cragg
Keyword(s):  
Electron Microscopy ◽  
Pore Structure ◽  
Pore Diameter ◽  
Nuclear Pore ◽  
Nuclear Pores ◽  
The Relationship

Quiescent shoot apical tissue from buds of the linden tree (Tilia europaea L.), collected during winter months, was frozen without pretreatment and freeze-fractured for electron microscopy. A proportion of the nuclear envelopes bore unusually large nuclear pores, having diameters up to 175 nm. Results from cross-fractured nuclear envelopes were consistent with results from envelopes fractured in the membrane plane, indicating that the larger pores are unlikely to be artefacts of fracturing. In these large pores, it was not possible to determine the relationship between the annulus (the material contained within the membranous pore) and the membranous periphery of the pore. Particularly, it could not be determined whether the annulus expanded concomitantly with the pore. It is proposed that variations in nuclear pore diameter may arise as a result of pulsatory activity occurring in all pores, rather than representing static differences between individual pores.

scholarly journals Relationship between the Shear Strength and Microscopic Pore Parameters of Saline Soil with Different Freeze-Thaw Cycles and Salinities

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1709
Author(s):  
Jiaqi Wang ◽  
Qing Wang ◽  
Sen Lin ◽  
Yan Han ◽  
Shukai Cheng ◽  
...  
Keyword(s):  
Shear Strength ◽  
Pore Structure ◽  
Pore Diameter ◽  
Saline Soil ◽  
Soil Samples ◽  
Average Pore Diameter ◽  
Failure Strength ◽  
Average Pore ◽  
Freeze Thaw ◽  
The Relationship

Saline soil is a widely distributed special soil with poor engineering properties. In seasonally frozen regions, the poor properties of saline soil will cause many types of engineering damage such as road boiling, melt sinking, and subgrade instability. These engineering failures are closely related to the shear strength of saline soil. However, there are relatively few studies on saline soil in cold regions. The strength of the soil is always determined by its microstructure; therefore, the study aims to investigate the relationship between the shear strength and microscopic pore structure of saline soil with different freeze–thaw cycles and salinities. The shear strength characteristics of saline soil with different salinities subjected to different freeze–thaw cycles were obtained by triaxial tests. In addition, the microstructure of the soil samples was investigated by scanning electron microscopy (SEM) tests, and the microscopic pore parameters of the soil samples, including porosity (N), average pore diameter (D¯), average shape coefficient (K), surface fluctuation fractal dimension (F), and orienting probability entropy (Hm), were obtained by image processing software quantitatively. Based on the experimental results, the influence of freeze–thaw cycles and salinity on the shear strength characteristics and microstructure of the soil samples were analyzed. Besides that, in order to effectively eliminate the collinearity between independent variables and obtain a stable and reasonable regression model, principal component regression (PCR) analysis was adopted to establish the relationship between the microscopic pore parameters and the failure strength of the soil samples. The fitting results demonstrated that the failure strength of saline soil is mainly related to the size and direction of the pores in the soil, and it has little correlation with pore shape. The failure strength of the soil was negatively correlated with the average pore diameter (D¯) and porosity (N), and it was positively correlated with the orienting probability entropy of the pores (Hm). This study may provide a quantitative basis for explaining the variation mechanism of the mechanical properties of saline soil from a microscopic perspective and provide references for the symmetry between the changes of the macroscopic properties and microscopic pore structure of the saline soil in cold regions.

scholarly journals Plugging A Small Hole

1997 ◽  
Vol 5 (1) ◽  
pp. 3-4
Author(s):  
Stephen W. Carmichael
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Nuclear Pore ◽  
Nuclear Pores ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
A Cell ◽  
Scanning Electron

It has long been appreciated that communication between the nucleus and the cytoplasm of a cell occurs through the nuclear pores. Regulation of this communication has remained a mystery. A breakthrough in our understanding of this regulation was recently presented by Carmen Perez- Terzic, Jason Pyle, Marisa Jaconi, Lisa Stehnc-Bittel, and David Clapham of Mayo Clinic. Using field emission scanning electron microscopy (FESEM), transmission electron microscopy, and atomic force microscopy (AFM), they demonstrated the presence of a small plug within the nuclear pore that was present under certain physiologic circumstances. This “plug“ may regulate the movement of molecules through the pore.

scholarly journals Exploring the Nuclear Envelope of Herpes Simplex Virus 1-Infected Cells by High-Resolution Microscopy

2008 ◽  
Vol 83 (1) ◽  
pp. 408-419 ◽  
Author(s):  
Peter Wild ◽  
Claudia Senn ◽  
Céline L. Manera ◽  
Esther Sutter ◽  
Elisabeth M. Schraner ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Herpes Simplex ◽  
Nuclear Envelope ◽  
Nuclear Pore ◽  
Nuclear Pores ◽  
Herpes Simplex Virus 1 ◽  
Infected Cells ◽  
The Mean ◽  
Simplex Virus ◽  
Hsv 1

ABSTRACT Herpesviruses are composed of capsid, tegument, and envelope. Capsids assemble in the nucleus and exit the nucleus by budding at the inner nuclear membrane, acquiring tegument and the envelope. This study focuses on the changes of the nuclear envelope during herpes simplex virus 1 (HSV-1) infection in HeLa and Vero cells by employing preparation techniques at ambient and low temperatures for high-resolution scanning and transmission electron microscopy and confocal laser scanning microscopy. Cryo-field emission scanning electron microscopy of freeze-fractured cells showed for the first time budding of capsids at the nuclear envelope at the third dimension with high activity at 10 h and low activity at 15 h of incubation. The mean number of pores was significantly lower, and the mean interpore distance and the mean interpore area were significantly larger than those for mock-infected cells 15 h after inoculation. Forty-five percent of nuclear pores in HSV-1-infected cells were dilated to more than 140 nm. Nuclear material containing capsids protrude through them into the cytoplasm. Examination of in situ preparations after dry fracturing revealed significant enlargements of the nuclear pore diameter and of the nuclear pore central channel in HSV-1-infected cells compared to mock-infected cells. The demonstration of nucleoporins by confocal microscopy also revealed fewer pores but focal enhancement of fluorescence signals in HSV-1-infected cells, whereas Western blots showed no loss of nucleoporins from cells. The data suggest that infection with HSV-1 alters the number, size, and architecture of nuclear pores without a loss of nucleoporins from altered nuclear pore complexes.

scholarly journals The Relationship between Compressive Strength and Pore Structure of the High Water Grouting Material

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 865
Author(s):  
Youmin Han ◽  
Junwu Xia ◽  
Linli Yu ◽  
Qiong Su ◽  
Xiaomiao Chen
Keyword(s):  
Compressive Strength ◽  
Pore Structure ◽  
Pore Diameter ◽  
High Water ◽  
Hydration Products ◽  
Characteristic Parameters ◽  
Grey Correlation ◽  
Grouting Material ◽  
Binder Ratio ◽  
The Relationship

To elucidate the relationship between compressive strength and pore structure of the high water grouting material with different water-binder ratios and CaO contents, the compressive strength was tested while pore structure including pore characteristic parameters and pore diameter distribution were investigated by BET, MIP, and 3D-XRM. Moreover, the evolution of hydration products was observed by TGA and SEM, illustrating the reactive mechanism of the material. Furthermore, the grey correlation coefficients between compressive strength and pore structure parameters were illustrated according to the grey correlation theory. The results show that CaO content in lime is proportional to the compressive strength with the water-binder ratio of 1.0 or 1.5, while the inverse trend appears with the water-binder ratio of 2.0. The high water grouting material belongs to the macropore material with the pores mainly within 100 nm to 2 μm. Its hydration products contain ettringite crystals, aluminum gels, and C-S-H gels. The productions of the hydration products are positively correlated with its compressive strength. In addition, the compressive strength of the high water grouting material is closely related to the pore characteristic parameters and the pore size distribution, especially the porosity, the most probable pore diameter, and the pore volumes within 100~500 nm and 10~100 nm.

scholarly journals A complex of nuclear pore proteins required for pore function.

1991 ◽  
Vol 114 (1) ◽  
pp. 169-183 ◽  
Author(s):  
D R Finlay ◽  
E Meier ◽  
P Bradley ◽  
J Horecka ◽  
D J Forbes
Keyword(s):  
Pore Structure ◽  
Protein Interactions ◽  
Linear Correlation ◽  
Nuclear Transport ◽  
Gel Filtration ◽  
Nuclear Pore ◽  
Protein Protein Interactions ◽  
Nuclear Pores ◽  
The Family ◽  
Nuclear Reconstitution

A family of proteins bearing novel N-acetylglucosamine residues has previously been found to be required to form functional nuclear pores. To begin to determine which of the proteins in this family are essential for pore function, antisera were raised to each of three members of the family, p62, p58, and p54. With these antisera, it was possible to deplete nuclear reconstitution extracts of the proteins and to test the depleted nuclei for nuclear transport. In the course of the experiments, it was found that the three proteins exist as a complex; antisera to any one, while specific on a protein blot, coimmunoprecipitated all three proteins. This complex of pore proteins is stable to 2 M salt, 2 M urea, and the detergent Mega 10, indicating the presence of specific and tight protein-protein interactions. By gel filtration, the complex has a molecular mass of 550-600 kD. Nuclei containing pores depleted of the complex are found to be defective for nuclear transport; moreover, we observe a strict linear correlation between the amount of complex present in nuclei and the amount of nuclear transport of which those nuclei are capable. Thus, the p62-p58-p54 complex defines a group of proteins with strong protein-protein interactions that form a unit of pore structure essential for pore function.

scholarly journals Two structurally distinct domains of the nucleoporin Nup170 cooperate to tether a subset of nucleoporins to nuclear pores

2009 ◽  
Vol 185 (3) ◽  
pp. 387-395 ◽  
Author(s):  
Dirk Flemming ◽  
Phillip Sarges ◽  
Philipp Stelter ◽  
Andrea Hellwig ◽  
Bettina Böttcher ◽  
...  
Keyword(s):  
Pore Structure ◽  
Structure And Function ◽  
Nuclear Pore ◽  
Nuclear Pores ◽  
Terminal Domain ◽  
C Terminus ◽  
N Terminus ◽  
The Individual ◽  
And Function

How individual nucleoporins (Nups) perform their role in nuclear pore structure and function is largely unknown. In this study, we examined the structure of purified Nup170 to obtain clues about its function. We show that Nup170 adopts a crescent moon shape with two structurally distinct and separable domains, a β-propeller N terminus and an α-solenoid C terminus. To address the individual roles of each domain, we expressed these domains separately in yeast. Notably, overexpression of the Nup170 C domain was toxic in nup170Δ cells and caused accumulation of several Nups in cytoplasmic foci. Further experiments indicated that the C-terminal domain anchors Nup170 to nuclear pores, whereas the N-terminal domain functions to recruit or retain a subset of Nups, including Nup159, Nup188, and Pom34, at nuclear pores. We conclude that Nup170 performs its role as a structural adapter between cytoplasmically oriented Nups and the nuclear pore membrane.

The Formation, Structure, Distribution and Frequency of Nuclear Pores

1971 ◽  
Vol 29 ◽  
pp. 518-519
Author(s):  
G. G. Maul
Keyword(s):  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Dynamic Structure ◽  
Nuclear Pore ◽  
Nuclear Pores ◽  
Filter Function ◽  
Etching Technique ◽  
Selective Filter ◽  
Membranous Part

The chromatin of eukaryotic cells is separated from the cytoplasm by a double membrane. One obvious structural specialization of the nuclear membrane is the presence of pores which have been implicated to facilitate the selective nucleocytoplasmic exchange of a variety of large molecules. Thus, the function of nuclear pores has mainly been regarded to be a passive one. Non-membranous diaphragms, radiating fibers, central rings, and other pore-associated structures were thought to play a role in the selective filter function of the nuclear pore complex. Evidence will be presented that suggests that the nuclear pore is a dynamic structure which is non-randomly distributed and can be formed during interphase, and that a close relationship exists between chromatin and the membranous part of the nuclear pore complex.Octagonality of the nuclear pore complex has been confirmed by a variety of techniques. Using the freeze-etching technique, it was possible to show that the membranous part of the pore complex has an eight-sided outline in human melanoma cells in vitro. Fibers which traverse the pore proper at its corners are continuous and indistinguishable from chromatin at the nucleoplasmic side, as seen in conventionally fixed and sectioned material. Chromatin can be seen in octagonal outline if serial sections are analyzed which are parallel but do not include nuclear membranes (Fig. 1). It is concluded that the shape of the pore rim is due to fibrous material traversing the pore, and may not have any functional significance. In many pores one can recognize a central ring with eight fibers radiating to the corners of the pore rim. Such a structural arrangement is also found to connect eight ribosomes at the nuclear membrane.

Studies on Leukemogenic and Sarcomagenic Viruses

1970 ◽  
Vol 28 ◽  
pp. 156-157
Author(s):  
Leon Dmochowski
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Morphological Properties ◽  
Mode Of Development ◽  
Relationship Of ◽  
The Relationship

Electron microscopy has proved to be an invaluable discipline in studies on the relationship of viruses to the origin of leukemia, sarcoma, and other types of tumors in animals and man. The successful cell-free transmission of leukemia and sarcoma in mice, rats, hamsters, and cats, interpreted as due to a virus or viruses, was proved to be due to a virus on the basis of electron microscope studies. These studies demonstrated that all the types of neoplasia in animals of the species examined are produced by a virus of certain characteristic morphological properties similar, if not identical, in the mode of development in all types of neoplasia in animals, as shown in Fig. 1.

A SEM/TEM examination of a ceramic membrane

1986 ◽  
Vol 44 ◽  
pp. 682-683
Author(s):  
C.E. Voegele-Kliewer ◽  
A.D. McMaster ◽  
G.W. Dirks
Keyword(s):  
Electron Microscopy ◽  
Gas Separation ◽  
Ceramic Membrane ◽  
Hydrogen Iodide ◽  
Separation Processes ◽  
Corning Glass ◽  
Gas Transport Properties ◽  
Porous Microstructure ◽  
Microscopy Techniques ◽  
The Relationship

Materials other than polymers, e.g. ceramic silicates, are currently being investigated for gas separation processes. The permeation characteristics of one such material, Vycor (Corning Glass #1370), have been reported for the separation of hydrogen from hydrogen iodide. This paper will describe the electron microscopy techniques applied to reveal the porous microstructure of a Vycor membrane. The application of these techniques has led to an increased understanding in the relationship between the substructure and the gas transport properties of this material.

Profile Imaging of Silicon Surface Reconstructions

1985 ◽  
Vol 43 ◽  
pp. 262-263
Author(s):  
O.L. Krivanek ◽  
G.J. Wood
Keyword(s):  
Electron Microscopy ◽  
Surface Structure ◽  
Structure Determination ◽  
Silicon Surface ◽  
Good Resolution ◽  
Surface Reconstructions ◽  
Bulk Structure ◽  
Point To Point ◽  
The Relationship

Electron microscopy at 0.2nm point-to-point resolution, 10-10 torr specimei region vacuum and facilities for in-situ specimen cleaning presents intere; ing possibilities for surface structure determination. Three methods for examining the surfaces are available: reflection (REM), transmission (TEM) and profile imaging. Profile imaging is particularly useful because it giv good resolution perpendicular as well as parallel to the surface, and can therefore be used to determine the relationship between the surface and the bulk structure.

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