scholarly journals Polarity of midbody and phragmoplast microtubules.

1980 ◽  
Vol 87 (2) ◽  
pp. 509-515 ◽  
Author(s):  
U Euteneuer ◽  
J R McIntosh
Keyword(s):  
Cross Section ◽  
Mammalian Cells ◽  
Opposite Polarity ◽  
The Other ◽  
Fast Growing ◽  
Hook Curvature ◽  
Molecular Polarity

A newly discovered method (Heidemann and McIntosh, 1980, Nature [Lond.] 286:517) for displaying the molecular polarity of microtubules (MTs) has been slightly modified and applied to the midbodies of cultured mammalian cells and the phragmoplasts of Haemanthus endosperm. The method involves the decoration of preexisting MTs in lysed cells with curved ribbons of tubulin protofilaments; the direction of curvature of these C-shaped appendages as seen in cross section reflects the intrinsic polarity of the MTs. In travsverse sections of midbodies from HeLa and PtK cells, we find that essentially all the MTs in a given region of the structures have the same direction of hook curvature, and hence the same polarity. The midbody MTs that lie on one side of the spindle equator show the opposite polarity from those on the other side, indicating that the midbody is constructed from two families of antiparallel MTs. Midbody MTs are arranged with their fast-growing ends overlapping at the spindle equator, consistent with the hypothesis that the midbody is formed by the interdigitation of aster MTs. The polarities of the MTs from the phragmoplast of endosperm cells are the same as those found in the mammalian midbody. Our results eliminate one model for mitosis, but are consistent with others. The systematic and reproducible polarities observed favor the concept that MT polarity is an important factor in the formation and/or the function of these two mitotic structures.

A New Approach to the Demonstration of Oxidase-Localization Using Tannic Acid Or Catechin

1973 ◽  
Vol 31 ◽  
pp. 698-699
Author(s):  
V. Mizuhira ◽  
Y. Futaesaku
Keyword(s):  
Cross Section ◽  
Tannic Acid ◽  
Elastic Fiber ◽  
The Other ◽  
New Approach ◽  
Tissue Block ◽  
Active Reaction ◽  
The Cross

Previously we reported that tannic acid is a very effective fixative for proteins including polypeptides. Especially, in the cross section of microtubules, thirteen submits in A-tubule and eleven in B-tubule could be observed very clearly. An elastic fiber could be demonstrated very clearly, as an electron opaque, homogeneous fiber. However, tannic acid did not penetrate into the deep portion of the tissue-block. So we tried Catechin. This shows almost the same chemical natures as that of proteins, as tannic acid. Moreover, we thought that catechin should have two active-reaction sites, one is phenol,and the other is catechole. Catechole site should react with osmium, to make Os- black. Phenol-site should react with peroxidase existing perhydroxide.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

scholarly journals The fractionation of nuclei from mammalian cells by zonal centrifugation

1968 ◽  
Vol 109 (1) ◽  
pp. 127-135 ◽  
Author(s):  
I R Johnston ◽  
A P Mathias ◽  
F. Pennington ◽  
D. Ridge
Keyword(s):  
Rat Liver ◽  
Mammalian Cells ◽  
Mouse Liver ◽  
The Other ◽  
Slow Speed ◽  
Adult Rats ◽  
Sucrose Solutions ◽  
Liver Nuclei ◽  
Effect Of Age ◽  
Zonal Rotor

1. Purified liver nuclei from adult rats separate into two main zones when centrifuged in the slow-speed zonal rotor. One zone contains diploid nuclei, the other tetraploid. 2. The effect of age on the pattern of rat liver ploidy was examined. Tetraploid nuclei are virtually absent from young animals. They increase in proportion steadily with age. Partial hepatectomy disturbs the pattern of ploidy. 3. The zonal centrifuge permits the separation of diploid, tetraploid, octaploid and hexadecaploid nuclei from mouse liver. 4. Rat liver nuclei are isopycnic with sucrose solutions of density 1·35 at 5°.

scholarly journals Calmodulin-microtubule association in cultured mammalian cells.

1984 ◽  
Vol 98 (3) ◽  
pp. 904-910 ◽  
Author(s):  
W J Deery ◽  
A R Means ◽  
B R Brinkley
Keyword(s):  
Plasma Membrane ◽  
Mammalian Cells ◽  
Cell System ◽  
The Other ◽  
Microtubule Assembly ◽  
Cytoplasmic Microtubule ◽  
Hypotonic Treatment ◽  
Cytoplasmic Microtubules ◽  
Triton X ◽  
Ca Sensitivity

A Triton X-100-lysed cell system has been used to identify calmodulin on the cytoskeleton of 3T3 and transformed SV3T3 cells. By indirect immunofluorescence, calmodulin was found to be associated with both the cytoplasmic microtubule complex and the centrosomes. A number of cytoplasmic microtubules more resistant to disassembly upon either cold (0-4 degrees C) or hypotonic treatment, as well as following dilution have been identified. Most of the stable microtubules appeared to be associated with the centrosome at one end and with the plasma membrane at the other end. These microtubules could be induced to depolymerize, however, by micromolar Ca++ concentrations. These data suggest that, by interacting directly with the microtubule, calmodulin may influence microtubule assembly and ensure the Ca++-sensitivity of both mitotic and cytoplasmic microtubules.

Design of a Retrovirus-Derived Vector for Expression and Transduction of Exogenous Genes in Mammalian Cells

1983 ◽  
Vol 3 (6) ◽  
pp. 1123-1132
Author(s):  
Archibald S. Perkins ◽  
Paul T. Kirschmeier ◽  
Sebastiano Gattoni-Celli ◽  
I. Bernard Weinstein
Keyword(s):  
Mammalian Cells ◽  
High Efficiency ◽  
Leukemia Virus ◽  
Restriction Enzymes ◽  
Virus Genome ◽  
Opposite Polarity ◽  
High Yield ◽  
Animal Cells ◽  
Murine Sarcoma Virus ◽  
Sarcoma Virus

We have developed a transfection vector for animal cells that contains long terminal repeat (LTR) sequences to promote expression. Plasmid p101/101, a derivative of plasmid pBR322 containing the complete Moloney murine sarcoma virus genome, was cut with restriction enzymes and religated so that both the 5′ and 3′ LTRs were retained and all but about 700 base pairs of the intervening viral sequences were removed. To test this vector, the Escherichia coli gene gpt was cloned into a unique Pst I site, between the two LTRs, with guanine and cytosine tailing, a method that can be generalized for insertion of any DNA segment into this vector. When DNA from recombinant plasmids in which the gpt gene was inserted in the same transcriptional polarity as the LTR sequences was transfected onto murine or rat fibroblast cultures, we obtained a high yield of Gpt + colonies. However, plasmid constructs with the gpt gene in the opposite polarity were virtually devoid of activity. With gpt in the proper orientation, restriction enzyme cuts within the LTRs or between the 5′ LTR and the gpt gene reduced transfection by more than 98%, whereas a cut between the gpt gene and the 3′ LTR gave an 80% reduction in activity. Thus, both 5′ and 3′ LTR sequences are essential for optimal gpt expression, although the 5′ LTR appears to play a more important role. When the LTR- gpt plasmid was transfected onto murine leukemia virus-infected mouse fibroblasts, we obtained evidence that RNA copies became pseudotyped into viral particles which could transfer the Gpt + phenotype into rodent cells with extremely high efficiency. This vector should prove useful for high-efficiency transduction of a variety of genes in mammalian cells.

Effective, Shortened Drying of Agar-Gelcasting Al2O3 Tube Through Immersing in Acetone

2021 ◽  
Author(s):  
Ramnaree Kaemkit ◽  
Supawan Vichaphund ◽  
Anukorn Phureungrat ◽  
Methee Promsawat ◽  
Suksawat Sirijarukul ◽  
...  
Keyword(s):  
Cross Section ◽  
Concentration Gradient ◽  
Water Concentration ◽  
Drying Shrinkage ◽  
The Other ◽  
Air Drying ◽  
Al2o3 Tube ◽  
Acetone Water ◽  
Porous Microstructure ◽  
Glass Tubes

Abstract A liquid drying agent, i.e. acetone, was employed for allowing the faster drying of Al2O3 tubes fabricated by agar gelcasting than the conventional air drying. The mixture of Al2O3 slurry and agar solution was separately prepared and then mixed prior to molding out of a set of warmed glass tubes. After the mixture transformed into gelled tube, the gelled tube was demolded and then immersed in acetone at different periods of time from 0 to 50 h. The immersed periods of 50 h led to the acetone replacement for water being inside of the gelling tube by 74 wt.% and then shortened the drying period to be 25 min. On the other hand, the conventional air drying spent 420 min drying completely. After drying, the immersed tubes possessed spherical cross section; whereas, no immersed tubes showed the deformation of cross section. The shortened drying was in line with the smaller drying shrinkage (4.7%), broader pore-size distribution and higher porous microstructure, comparing to the conventional air drying. The mechanism of acetone replacement for water was attributed to the acetone-water concentration gradient creating their inter-diffusion.

The Defect Structure of BaTiO3 Thin Films

1993 ◽  
Vol 310 ◽  
Author(s):  
L.A. Wills ◽  
B.W. Wessels
Keyword(s):  
Thin Films ◽  
Cross Section ◽  
Defect Structure ◽  
Oxygen Vacancies ◽  
Vacuum Annealing ◽  
Deep Level ◽  
Energy Levels ◽  
The Other ◽  
Optical Cross Section ◽  
Impurity Defects

AbstractThe defect structure of BaTiO3 thin films grown on (100) Si was examined using transient photocapacitance spectroscopy. The concentration, optical cross section and associated energy levels of both native and impurity defects in as-grown and annealed BaTiO3 films were evaluated. Deep level defects withpeak energies of Ev+1.8, Ev+2.4, Ev+2.7, Ev+3.0-3.1 and Ev+3.2-3.3 eV were observed in the as-grown films. Upon vacuum annealing, the concentration of the traps at Ev+3.0 and Ev+3.2 eV increased while the concentration of the traps at Ev+ 1.8 and Ev+2.4 eV decreased. The levels at Ev+3.0-3.1 and Ev+3.2-3.3 eV are attributed to oxygen vacancies. The other levels are tentatively ascribed to Fe and Fe related defects.

scholarly journals I Like Vegetables: A Touch-and-Feel Board Book by L. Siminovich

2011 ◽  
Vol 1 (1) ◽  
Author(s):  
Kim Frail
Keyword(s):  
Cross Section ◽  
Public Services ◽  
Picture Book ◽  
The Other ◽  
Learning Method ◽  
University Of Alberta ◽  
Young Readers ◽  
Dinner Table ◽  
Wood Grain ◽  
The University

Siminovich, Lorena. I Like Vegetables: A Touch-and-Feel Board Book. Somerville: Candlewick Press, 2011. Print.“I Like Vegetables” is a dream come true for any nutritionally conscience parent, children’s librarian or teacher. The brightly hued collage illustrations are intriguingly textured with patterns and “touch & feel” inlays. Silky peas and rough-skinned carrots invite young readers to learn about vegetables. The layout is quite clever as it leverages contrast and comparison as a learning method. On one side of the page vegetables are depicted as they would appear growing in the garden while on the other side they are in the home being prepared for the dinner table. In addition, the nature side of the page illustrates the concept of opposites. For example, there are “tall” and “short” cornstalks. Orange carrot roots are “below” the ground, while the feathery green tops are “above”. The indoor side of the page features close-ups of vegetables against a wood-grain background that evokes a cutting board. Here children get a different perspective on the harvested veggies. We see shelled peas, open cornhusks and a cross-section of a pumpkin. The concluding series of images features an “empty” gardener’s basket next to a basket “full” of colourful vegetables on a blue and white gingham picnic tablecloth inlay.  This is primarily a picture book with only the names of the vegetables and the two opposing concepts appearing on each page. The typeset is Helvetica and is large and easy to read.  It is a sturdy board book and the inlays could not be easily ripped out or damaged. It is therefore a welcome addition to any toddler’s library. Other titles in the “I Like” series by Siminovich include: “I Like Toys “, “I Like Bugs” and “I Like Fruit”. “I Like Vegetables” is sure to engage children from ages 1-3. Highly recommended: 4 out of 4 stars Reviewer: Kim FrailKim is a Public Services Librarian at the H.T. Coutts Education Library at the University of Alberta. Children’s literature is a big part of her world at work and at home. She also enjoys gardening, renovating and keeping up with her two-year old. 

scholarly journals OBSERVATIONS ON THE FINE STRUCTURE OF THE DEVELOPING SPERMATID IN THE DOMESTIC CHICKEN

1962 ◽  
Vol 14 (2) ◽  
pp. 193-205 ◽  
Author(s):  
Toshio Nagano
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Cross Section ◽  
Neck Region ◽  
Structural Features ◽  
Dense Granule ◽  
Domestic Chicken ◽  
The Other ◽  
Dense Structure ◽  
Distal Centriole

The kinetic apparatus, the acrosome and associated structures, and the manchette of the spermatid of the domestic chicken have been studied with the electron microscope. The basic structural features of the two centrioles do not change during spermiogenesis, but there is a change in orientation and length. The proximal centriole is situated in a groove at the edge of the nucleus and oriented normal to the long axis of the nucleus and at right angles to the elongate distal centriole. The tail filaments appear to originate from the distal centriole. The plasma membrane is invaginated along the tail filaments. A dense structure which appears at the deep reflection of the plasma membrane is identified as the ring. The fine structure of the ring has no resemblance to that of a centriole and there is no evidence that it is derived from or related to the centrioles. The tail of the spermatid contains nine peripheral pairs and one central pair of tubular filaments. The two members of each pair of peripheral filaments differ in density and in shape: one is dense and circular, and the other is light and semilunar in cross-section. The dense filaments have processes. A manchette consisting of fine tubules appears in the cytoplasm of the older spermatid along the nucleus, neck region, and proximal segment of the tail. The acrosome is spherical in young spermatids and becomes crescentic and, finally, U-shaped as spermiogenesis proceeds. A dense granule is observed in the cytoplasm between acrosome and nucleus. This granule later becomes a dense rod which is interpreted as the perforatorium.

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