scholarly journals Localization of Ca++-containing antimonate precipitates during mitosis.

1980 ◽  
Vol 86 (2) ◽  
pp. 500-513 ◽  
Author(s):  
S M Wick ◽  
P K Hepler
Keyword(s):  
Mitotic Spindle ◽  
Divalent Cations ◽  
Structural Components ◽  
Mitotic Apparatus ◽  
Stomatal Complex ◽  
Complex Cells ◽  
Major Cation ◽  
Marsilea Vestita ◽  
Spermatogenous Cells

Intracellular bound Ca++ has been localized throughout mitosis and cytokinesis in two plant species by means of in situ precipitation with potassium antimonate and electron microscope visualization. Identification of Ca++ as the major cation precipitated was made by comparing solubility properties in water, EDTA, and EGTA of the intracellular deposits with respect to those of K+-, Mg++-, and Ca++-antimonate standards. In spermatogenous cells of the water fern, Marsilea vestita, and stomatal complex cells of barley, Hordeum vulgare, antimonate deposits have been found associated with the endoplasmic reticulum (ER), vacuoles, euchromatin/nucleoplasm, and mitochondria. The last contain a much higher density of precipitates in Marsilea than in Hordeum. Dictyosomes and the nuclear envelope of Marsilea also contain antimonate deposits, as do the plasmalemma, cell wall, and phragmoplast vesicles of Hordeum. Microtubule-organizing centers such as kinetochores and the blepharoplast of Marsilea do not stain. In spite of differences in associated antimonate between certain organelles of the two species, the presence of antimonate aong the ER throughout the cell cycle is common to both. Of particular interest are those precipitates seen along the tubules and cisternae of the extensive smooth ER that surrounds and invades the mitotic spindle in both species. The ability to bind divalent cations makes the mitotic apparatus (MA)-associated ER a likely candidate for regulation of free Ca++ levels in the immediate vicinity of structural components and processes that are Ca++-sensitive and proposed to be Ca++-regulated.

Structural Studies on Mitotic Spindle Fibres

1978 ◽  
Vol 36 (3) ◽  
pp. 615-626
Author(s):  
J.R. Mcintosh
Keyword(s):  
Chemical Composition ◽  
Mitotic Spindle ◽  
Structural Studies ◽  
Mitotic Apparatus ◽  
Chemical Studies ◽  
Medical Interest ◽  
Spindle Fibres

The mitotic apparatus is a structure of obvious biological and medical interest, but it has proved to be a difficult cellular machine to understand. The chemical composition of the spindle is only slightly elucidated, largely because of the difficulties in preparing useful isolates of the structure. Chemical studies of the mitotic spindle have been reviewed elsewhere (Mcintosh, 1977), and will not be discussed further here. One would think that structural studies on the mitotic apparatus (MA) in situ would be straightforward, but even with this approach there is some disagreement in the results obtained with various methods and by different investigators. In this paper I will review briefly the approaches which have been used in structural studies of the MA, pointing out the strengths and problems of each approach. I will summarize the principal findings of the different methods, and identify what seem to be fruitful avenues for further work.

Filaments and membranes in the mitotic apparatus

1983 ◽  
Vol 41 ◽  
pp. 544-547
Author(s):  
Kent McDonald
Keyword(s):  
Intermediate Filaments ◽  
Mitotic Spindle ◽  
Mitotic Apparatus ◽  
Light Microscope Level ◽  
Microtubule Associated Proteins ◽  
Recent Developments ◽  
Associated Proteins ◽  
Force Generator ◽  
Spindle Function ◽  
Antibody Technology

At the light microscope level the recent developments and interest in antibody technology have permitted the localization of certain non-microtubule proteins within the mitotic spindle, e.g., calmodulin, actin, intermediate filaments, protein kinases and various microtubule associated proteins. Also, the use of fluorescent probes like chlorotetracycline suggest the presence of membranes in the spindle. Localization of non-microtubule structures in the spindle at the EM level has been less rewarding. Some mitosis researchers, e.g., Rarer, have maintained that actin is involved in mitosis movements though the bulk of evidence argues against this interpretation. Others suggest that a microtrabecular network such as found in chromatophore granule movement might be a possible force generator but there is little evidence for or against this view. At the level of regulation of spindle function, Harris and more recently Hepler have argued for the importance of studying spindle membranes. Hepler also believes that membranes might play a structural or mechanical role in moving chromosomes.

scholarly journals Cyclic Deformation of Microcantilevers Using In-Situ Micromanipulation

2021 ◽  
Author(s):  
A. H. S. Iyer ◽  
M. H. Colliander
Keyword(s):  
Degrees Of Freedom ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Structural Components ◽  
Cyclic Testing ◽  
Phase Boundaries ◽  
Bulk Specimen ◽  
Arbitrary Position ◽  
Three Degrees Of Freedom

Abstract Background The trend in miniaturisation of structural components and continuous development of more advanced crystal plasticity models point towards the need for understanding cyclic properties of engineering materials at the microscale. Though the technology of focused ion beam milling enables the preparation of micron-sized samples for mechanical testing using nanoindenters, much of the focus has been on monotonic testing since the limited 1D motion of nanoindenters imposes restrictions on both sample preparation and cyclic testing. Objective/Methods In this work, we present an approach for cyclic microcantilever bending using a micromanipulator setup having three degrees of freedom, thereby offering more flexibility. Results The method has been demonstrated and validated by cyclic bending of Alloy 718plus microcantilevers prepared on a bulk specimen. The experiments reveal that this method is reliable and produces results that are comparable to a nanoindenter setup. Conclusions Due to the flexibility of the method, it offers straightforward testing of cantilevers manufactured at arbitrary position on bulk samples with fully reversed plastic deformation. Specific microstructural features, e.g., selected orientations, grain boundaries, phase boundaries etc., can therefore be easily targeted.

Claudin-2 is selectively expressed in proximal nephron in mouse kidney

2001 ◽  
Vol 281 (5) ◽  
pp. F966-F974 ◽  
Author(s):  
Alissa H. Enck ◽  
Urs V. Berger ◽  
Alan S. L. Yu
Keyword(s):  
Tight Junction ◽  
Large Family ◽  
Mouse Kidney ◽  
High Rate ◽  
Structural Components ◽  
Water Reabsorption ◽  
Junction Protein ◽  
Confocal Images ◽  
Leaky Epithelium

First published August 15, 2001; 10.1152/ajprenal.00021.2001.—The proximal nephron possesses a leaky epithelium with unique paracellular permeability properties that underlie its high rate of passive NaCl and water reabsorption, but the molecular basis is unknown. The claudins are a large family of transmembrane proteins that are part of the tight junction complex and likely form structural components of a paracellular pore. To localize claudin-2 in the mouse kidney, we performed in situ hybridization using an isoform-specific riboprobe and immunohistochemistry using a polyclonal antibody directed against a COOH-terminal peptide. Claudin-2 mRNA and protein were found throughout the proximal tubule and in the contiguous early segment of the thin descending limb of long-looped nephrons. The level of expression demonstrated an axial increase from proximal to distal segments. In confocal images, the subcellular localization of claudin-2 protein coincided with that of the tight junction protein ZO-1. Our findings suggest that claudin-2 is a component of the paracellular pathway of the most proximal segments of the nephron and that it may be responsible for their uniquely leaky permeability properties.

Distributed Modal Voltages of Nonlinear Paraboloidal Shells With Distributed Neurons

2004 ◽  
Vol 126 (1) ◽  
pp. 47-53 ◽  
Author(s):  
H. S. Tzou ◽  
J. H. Ding
Keyword(s):  
Dynamic Responses ◽  
Dynamic State ◽  
Structural Components ◽  
Shells Of Revolution ◽  
Membrane Component ◽  
Fully Integrated ◽  
In Situ Sensors ◽  
Membrane Components ◽  
Paraboloidal Shell

Effective health monitoring and distributed control of advanced structures depends on accurate measurements of dynamic responses of elastic structures. Conventional sensors used for structural measurement are usually add-on “discrete” devices. Lightweight distributed thin-film piezoelectric neurons fully integrated (laminated or embedded) with structural components can serve as in-situ sensors monitoring structure’s dynamic state and health status. This study is to investigate modal voltages and detailed signal contributions of linear or nonlinear paraboloidal shells of revolution laminated with piezoelectric neurons. Signal generation of distributed neuron sensors laminated on paraboloidal shells is defined first, based on the open-voltage assumption and Maxwell’s principle. The neuron signal of a linear paraboloidal shell is composed of a linear membrane component and a linear bending component; the signal of a nonlinear paraboloidal shell is composed of nonlinear and linear membrane components and a linear bending component due to the von Karman geometric nonlinearity. Signal components and distributed modal voltages of linear and nonlinear paraboloidal shells with various curvatures and thickness are investigated.

scholarly journals Immunodetection of RNA on ultra-thin sections incubated with polyadenylate nucleotidyl transferase.

1993 ◽  
Vol 41 (5) ◽  
pp. 657-665 ◽  
Author(s):  
M Thiry
Keyword(s):  
Divalent Cations ◽  
Ultrastructural Level ◽  
Ehrlich Tumor ◽  
Precise Location ◽  
Great Precision ◽  
Thin Sections ◽  
Nucleotidyl Transferase ◽  
Ehrlich Tumor Cells ◽  
Labeling Pattern

A new method is described for locating RNA on ultra-thin sections. Sections of aldehyde-fixed, plastic-embedded cells were incubated in a medium containing polyadenylate nucleotidyl transferase (PnT) and biotinylated ATP. The labeled nucleotides bound to RNA at the surface of the ultra-thin sections were than visualized by an indirect immunogold labeling technique. The resulting labeling pattern was dependent on the presence of divalent cations in the PnT medium. The method revealed with great precision the specific RNA-containing structures within Ehrlich tumor cells. The method is applicable to Epon sections. However, the labeling intensity varies according to the fixation used. Best results were obtained on acetylated cell sections. The method can be combined with EDTA regressive staining. The in situ PnT method provides a very useful tool for pinpointing the precise location of RNA within biological material at the ultrastructural level.

scholarly journals Kinesin-14 motors drive a right-handed helical motion of antiparallel microtubules around each other

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Aniruddha Mitra ◽  
Laura Meißner ◽  
Rojapriyadharshini Gandhimathi ◽  
Roman Renger ◽  
Felix Ruhnow ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Three Dimensional ◽  
Helical Motion ◽  
In Vitro Motility Assay ◽  
In Vitro Motility ◽  
Torque Generation ◽  
Free Microtubules ◽  
20 Nm

Abstract Within the mitotic spindle, kinesin motors cross-link and slide overlapping microtubules. Some of these motors exhibit off-axis power strokes, but their impact on motility and force generation in microtubule overlaps has not been investigated. Here, we develop and utilize a three-dimensional in vitro motility assay to explore kinesin-14, Ncd, driven sliding of cross-linked microtubules. We observe that free microtubules, sliding on suspended microtubules, not only rotate around their own axis but also move around the suspended microtubules with right-handed helical trajectories. Importantly, the associated torque is large enough to cause microtubule twisting and coiling. Further, our technique allows us to measure the in situ spatial extension of the motors between cross-linked microtubules to be about 20 nm. We argue that the capability of microtubule-crosslinking kinesins to cause helical motion of overlapping microtubules around each other allows for flexible filament organization, roadblock circumvention and torque generation in the mitotic spindle.

scholarly journals Divalent Cations Affect the Stability and Structure of Dad2p, a Subunit of the Candida Albicans Kinetochore Dam1 Complex

2016 ◽  
Vol 6 (1) ◽  
pp. 26
Author(s):  
Jennifer Turner Waldo ◽  
Tsering Dolma ◽  
Emily Rouse
Keyword(s):  
Candida Albicans ◽  
Mitotic Spindle ◽  
Divalent Cations ◽  
Dynamic Structure ◽  
Biochemical Properties ◽  
Differential Scanning Fluorimetry ◽  
A Subunit ◽  
Dam1 Complex ◽  
The Stability ◽  
Shed Light

<p class="1Body">The heterodecameric Dam1 complex is involved in establishing and maintaining the connection between the kinetochore and the mitotic spindle during mitosis. Biochemical studies of the reconstituted complex have shed light upon how it interacts with microtubules. However, little information about the biochemical properties of the isolated subunits has been available. This report examines the stability and structure of Dad2p, one of the Dam1 complex subunits isolated from <em>Candida albicans</em>. By employing differential scanning fluorimetry, protease protection and hydrodynamic analyses, we show that Dad2p is specifically responsive to the presence of divalent cations. This observation may be important for understanding the dynamic structure and regulation of the Dam1 complex in fungal cells.</p>

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