3-D reconstruction and analysis of mammalian mitotic spindle structure

1992 ◽  
Vol 50 (1) ◽  
pp. 578-579
Author(s):  
Kent McDonald ◽  
David Mastronarde ◽  
Rubai Ding ◽  
Eileen O'Toole ◽  
J. Richard McIntosh
Keyword(s):  
Cross Sections ◽  
Mitotic Spindle ◽  
Experimental Studies ◽  
Video Camera ◽  
Three Dimensions ◽  
Mitotic Spindles ◽  
Black And White ◽  
Reconstruction Methods ◽  
Spindle Structure ◽  
Tissue Culture Line

Mammalian spindles are generally large and may contain over a thousand microtubules (MTs). For this reason they are difficult to reconstruct in three dimensions and many researchers have chosen to study the smaller and simpler spindles of lower eukaryotes. Nevertheless, the mammalian spindle is used for many experimental studies and it would be useful to know its detailed structure.We have been using serial cross sections and computer reconstruction methods to analyze MT distributions in mitotic spindles of PtK cells, a mammalian tissue culture line. Images from EM negatives are digtized on a light box by a Dage MTI video camera containing a black and white Saticon tube. The signal is digitized by a Parallax 1280 graphics device in a MicroVax III computer. Microtubules are digitized at a magnification such that each is 10-12 pixels in diameter.

Architecture of the microtubule component of mitotic spindles from Dictyostelium discoideum

1985 ◽  
Vol 75 (1) ◽  
pp. 93-129
Author(s):  
J.R. McIntosh ◽  
U.P. Roos ◽  
B. Neighbors ◽  
K.L. McDonald
Keyword(s):  
Dictyostelium Discoideum ◽  
Cross Sections ◽  
Direct Evidence ◽  
Structural Data ◽  
Three Dimensions ◽  
Serial Sections ◽  
Mitotic Spindles ◽  
Central Spindle ◽  
Nearest Neighbours ◽  
Early Anaphase

Ten mitotic spindles from Dictyostelium discoideum have been studied by electron microscopy of serial sections. We have used computer graphics to track individual microtubules (MTs) in three dimensions and to compare seven spindles at different stages of anaphase and telophase. The central spindle of early anaphase is formed by the interdigitation of two sets of pole-associated MTs. The distribution of MT lengths at this stage is hetero-disperse. During anaphase total MT length decreases by a factor of about 2 as a result of two opposing changes in MT length: the longer MTs that interdigitate become even longer, while the short MTs, including those attached to kinetochores, become shorter still and decrease in number. The extent of MT interdigitation is less in longer spindles than in short ones. In metaphase and early anaphase, the MTs are not in an ordered arrangement as seen in spindle cross-sections, but as anaphase proceeds the MTs cluster into a square-packed, paracrystalline bundle in which most of the nearest neighbours come from opposite poles. This arrangement and the condensation-like increase in order suggest the existence of specific interactions between antiparallel MTs. A quantitative analysis of MT positions supports this interpretation, but direct evidence for convincing bridges between MTs is lacking. The pole-distal ends of the MTs that interdigitate show an irregular termination (C-shaped ends in transverse view), as is characteristic of MTs that are either adding or losing subunits. Since it is these interdigitating MTs that elongate, and since the shortening MTs show the customary blunt endings, we conclude that subunits add to the interdigitating MTs at their pole-distal ends. This inference, combined with other structural data, suggests that the interdigitating MTs of Dictyostelium are sliding over one another as they polymerize in anaphase. It also suggests a simple model for why the spindle becomes thinner as it elongates. We propose that MT interdigitation defines a region where MTs bind a factor that will associate only with antiparallel MTs. This factor biases the MT assembly equilibrium toward polymer. As the shorter MTs slide out of this region, they lose their polymerization advantage and depolymerize, releasing subunits to contribute to the further elongation of the already longer MTs. The properties of the Dictyostelium spindle are compared with those of both higher and lower eukaryotes.

Mechanically cut mitotic spindles: clean cuts and stable microtubules

1989 ◽  
Vol 94 (3) ◽  
pp. 415-423
Author(s):  
R.B. Nicklas ◽  
G.M. Lee ◽  
C.L. Rieder ◽  
G. Rupp
Keyword(s):  
Electron Microscopy ◽  
Mitotic Spindle ◽  
Dynamic Instability ◽  
Microtubule Dynamics ◽  
Mitotic Spindles ◽  
Mechanical Method ◽  
Spindle Structure ◽  
Main Spindle ◽  
Spindle Body

We have discovered an easy way to cut through the mitotic spindle at any desired place. Spindles of demembranated cricket or grasshopper spermatocytes were severed with a microneedle between the chromosomes and one pole, and the cut-off polar piece was swept away. Spindle structure and microtubule dynamics in cut spindles were studied by anti-tubulin immunostaining and electron microscopy. The cut is clean: all microtubules are severed and only a few extend beyond the others. This provides the basis for a clear test of whether traction fibers pull chromosomes to the pole in anaphase, because the putative traction fiber is cleanly severed. Cutting creates new plus ends on microtubules in the cut-off polar piece and new minus ends on microtubules in the main spindle body. The microtubules with new plus ends are unstable, as expected from the dynamic instability of microtubules. However, the microtubules with new minus ends are as stable as uncut microtubules in the same spindle. Our mechanical method of cutting microtubules very likely creates native, reactive ends, and therefore the surprising stability of new minus ends is genuinely interesting, not an artifact of cutting.

High-resolution scanning electron microscopy (HRSEM) of mitochondria from various rat tissues

1988 ◽  
Vol 46 ◽  
pp. 14-15
Author(s):  
P.J. Lea ◽  
M.J. Hollenberg
Keyword(s):  
Electron Microscopy ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Rat Hepatocytes ◽  
Three Dimensions ◽  
Objective Lens ◽  
Rat Tissues ◽  
Thin Sections ◽  
Reconstruction Methods ◽  
Scanning Electron

Our current understanding of mitochondrial ultrastructure has been derived primarily from thin sections using transmission electron microscopy (TEM). This information has been extrapolated into three dimensions by artist's impressions (1) or serial sectioning techniques in combination with computer processing (2). The resolution of serial reconstruction methods is limited by section thickness whereas artist's impressions have obvious disadvantages.In contrast, the new techniques of HRSEM used in this study (3) offer the opportunity to view simultaneously both the internal and external structure of mitochondria directly in three dimensions and in detail.The tridimensional ultrastructure of mitochondria from rat hepatocytes, retinal (retinal pigment epithelium), renal (proximal convoluted tubule) and adrenal cortex cells were studied by HRSEM. The specimens were prepared by aldehyde-osmium fixation in combination with freeze cleavage followed by partial extraction of cytosol with a weak solution of osmium tetroxide (4). The specimens were examined with a Hitachi S-570 scanning electron microscope, resolution better than 30 nm, where the secondary electron detector is located in the column directly above the specimen inserted within the objective lens.

Laser Scanning Confocal Microscopy and Three-Dimesnsional Reconstruction of the Mitotic Spindles of Unequally Dividing Embryonic Cells

1990 ◽  
Vol 48 (3) ◽  
pp. 166-167
Author(s):  
J. Holy ◽  
G. Schatten
Keyword(s):  
Confocal Microscopy ◽  
Mitotic Spindle ◽  
Laser Scanning ◽  
Three Dimensional ◽  
Laser Scanning Confocal Microscopy ◽  
Two Dimensions ◽  
Embryonic Cells ◽  
Mitotic Spindles ◽  
Cleavage Division ◽  
Scanning Confocal Microscopy

One of the classic limitations of light microscopy has been the fact that three dimensional biological events could only be visualized in two dimensions. Recently, this shortcoming has been overcome by combining the technologies of laser scanning confocal microscopy (LSCM) and computer processing of microscopical data by volume rendering methods. We have employed these techniques to examine morphogenetic events characterizing early development of sea urchin embryos. Specifically, the fourth cleavage division was examined because it is at this point that the first morphological signs of cell differentiation appear, manifested in the production of macromeres and micromeres by unequally dividing vegetal blastomeres.The mitotic spindle within vegetal blastomeres undergoing unequal cleavage are highly polarized and develop specialized, flattened asters toward the micromere pole. In order to reconstruct the three-dimensional features of these spindles, both isolated spindles and intact, extracted embryos were fluorescently labeled with antibodies directed against either centrosomes or tubulin.

Video Graphics and High-Voltage Electron Microscopy For Analysis of Microtubule Distributions In Fixed Cells

1990 ◽  
Vol 48 (1) ◽  
pp. 524-525
Author(s):  
Richard Mcintosh ◽  
David Mastronarde ◽  
Kent McDonald ◽  
Rubai Ding
Keyword(s):  
Electron Microscopy ◽  
Cross Sections ◽  
Cell Shape ◽  
Video Camera ◽  
Computer Memory ◽  
High Voltage Electron Microscopy ◽  
Thin Sections ◽  
Voltage Electron ◽  
Morphogenetic Event ◽  
Set Of Points

Microtubules (MTs) are cytoplasmic polymers whose dynamics have an influence on cell shape and motility. MTs influence cell behavior both through their growth and disassembly and through the binding of enzymes to their surfaces. In either case, the positions of the MTs change over time as cells grow and develop. We are working on methods to determine where MTs are at different times during either the cell cycle or a morphogenetic event, using thin and thick sections for electron microscopy and computer graphics to model MT distributions.One approach is to track MTs through serial thin sections cut transverse to the MT axis. This work uses a video camera to digitize electron micrographs of cross sections through a MT system and create image files in computer memory. These are aligned and corrected for relative distortions by using the positions of 8 - 10 MTs on adjacent sections to define a general linear transformation that will align and warp adjacent images to an optimum fit. Two hundred MT images are then used to calculate an “average MT”, and this is cross-correlated with each micrograph in the serial set to locate points likely to correspond to MT centers. This set of points is refined through a discriminate analysis that explores each cross correlogram in the neighborhood of every point with a high correlation score.

Experimental Studies Of Multilayer Glass Structures On Compression, Compression With Bending And Simple Bending

2019 ◽  
pp. 22-30
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Applied Load ◽  
Experimental Studies ◽  
Strength Properties ◽  
Research Topic ◽  
Normative Values ◽  
Laminated Glass ◽  
The Cross ◽  
Experimental Values

The work of multilayer glass structures for central and eccentric compression and bending are considered. The substantiation of the chosen research topic is made. The description and features of laminated glass for the structures investigated, their characteristics are presented. The analysis of the results obtained when testing for compression, compression with bending, simple bending of models of columns, beams, samples of laminated glass was made. Overview of the types and nature of destruction of the models are presented, diagrams of material operation are constructed, average values of the resistance of the cross-sections of samples are obtained, the table of destructive loads is generated. The need for development of a set of rules and guidelines for the design of glass structures, including laminated glass, for bearing elements, as well as standards for testing, rules for assessing the strength, stiffness, crack resistance and methods for determining the strength of control samples is emphasized. It is established that the strength properties of glass depend on the type of applied load and vary widely, and significantly lower than the corresponding normative values of the strength of heat-strengthened glass. The effect of the connecting polymeric material and manufacturing technology of laminated glass on the strength of the structure is also shown. The experimental values of the elastic modulus are different in different directions of the cross section and in the direction perpendicular to the glass layers are two times less than along the glass layers.

The influence of probiotic drug Biolax-U on morphological and biochemical parameters of blood in cows

2020 ◽  
pp. 70-76
Author(s):  
A. Farkhutdinova
Keyword(s):  
Biochemical Parameters ◽  
Hematological Parameters ◽  
Experimental Studies ◽  
Positive Influence ◽  
Biologically Active ◽  
Feed Consumption ◽  
Control Group ◽  
Animal Blood ◽  
Black And White ◽  
White Breed

The expediency of using the probiotic drug Biolax-U in the rations of lactating and dry cows of Black-and-White breed has been studied and scientifically proved. The influence of this drug on the morphological and biochemical parameters of animal blood has been determined. The composition of the probiotic drug Biolax-U consists of eight strains of a balanced complex of living lactic acid bacteria, yeast and actinomycetes, as well as biologically active substances. For experimental studies conducted on 2 groups of cows have been selected by the method of pairs-analogs, the influence of feeding of feed have been prepared with the use of the microbiological drug with probiotic action Biolax-U on feed consumption, morphological and biochemical changes in blood has been studied. Analysis of the rations of cows indicates that the content of calcium, phosphorus, magnesium, sulfur and trace elements such as manganese, copper, zinc and cobalt in the feed has been reduced. It has been found by studies that the use of probiotic drug Biolax-U had the positive influence on the feed intake, digestibility and better assimilation of feed nutrients and contributed to the improvement of blood morphological and biochemical parameters. For example, in animals of the experimental group hemoglobin has increased by 3,6 % (Р < 0,05), red blood cells by 10,1 (P ≤ 0,05), the content of leukocytes by 4,43, carotene by 9,6, glucose by 3,4; reserve alkalinity by 15,6, calcium by 19,4 (P ≤ 0,01), and phosphorus by 18,4 % compared with the control group of animals. During the lactation significantly improved hematological parameters including alkalinity reserve by 5,11 %, calcium level by 11,1, phosphorus by 8,6, hemoglobin by 14,2 %, the content of erythrocytes by 12,3, leukocyte by 3,86, and carotene 11,1 % against the parameters of animals of control group. The improvement of morphological and biochemical parameters of blood of cows indicates about stimulating effect on hematopoiesis and the general clinical condition of animals that contributes to the improvement of metabolic processes when using feed prepared with the use of microbiological drug with probiotic action Biolax-U.

scholarly journals Photoionization Cross-Sections of Carbon-Like N+ Near the K-Edge (390–440 eV)

Atoms ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 27
Author(s):  
Jean-Paul Mosnier ◽  
Eugene T. Kennedy ◽  
Jean-Marc Bizau ◽  
Denis Cubaynes ◽  
Ségolène Guilbaud ◽  
...  
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
Cross Sections ◽  
Experimental Studies ◽  
Photoionization Cross Section ◽  
Theoretical Work ◽  
Rydberg Series ◽  
R Matrix ◽  
Resonance Strengths ◽  
Nitrogen Ion

High-resolution K-shell photoionization cross-sections for the C-like atomic nitrogen ion (N+) are reported in the 398 eV (31.15 Å) to 450 eV (27.55 Å) energy (wavelength) range. The results were obtained from absolute ion-yield measurements using the SOLEIL synchrotron radiation facility for spectral bandpasses of 65 meV or 250 meV. In the photon energy region 398–403 eV, 1s⟶2p autoionizing resonance states dominated the cross section spectrum. Analyses of the experimental profiles yielded resonance strengths and Auger widths. In the 415–440 eV photon region 1s⟶(1s2s22p2 4P)np and 1s⟶(1s2s22p2 2P)np resonances forming well-developed Rydberg series up n=7 and n=8 , respectively, were identified in both the single and double ionization spectra. Theoretical photoionization cross-section calculations, performed using the R-matrix plus pseudo-states (RMPS) method and the multiconfiguration Dirac-Fock (MCDF) approach were bench marked against these high-resolution experimental results. Comparison of the state-of-the-art theoretical work with the experimental studies allowed the identification of new resonance features. Resonance strengths, energies and Auger widths (where available) are compared quantitatively with the theoretical values. Contributions from excited metastable states of the N+ ions were carefully considered throughout.

What Can Experimental Studies of Bias Tell Us About Real-World Group Disparities?

2021 ◽  
pp. 1-82
Author(s):  
Joseph Cesario
Keyword(s):  
Real World ◽  
Experimental Studies ◽  
White Men ◽  
Human Mind ◽  
Behavioral Differences ◽  
Social Categories ◽  
Systematic Testing ◽  
Black And White ◽  
Research Tradition ◽  
The Social

Abstract This article questions the widespread use of experimental social psychology to understand real-world group disparities. Standard experimental practice is to design studies in which participants make judgments of targets who vary only on the social categories to which they belong. This is typically done under simplified decision landscapes and with untrained decision makers. For example, to understand racial disparities in police shootings, researchers show pictures of armed and unarmed Black and White men to undergraduates and have them press "shoot" and "don't shoot" buttons. Having demonstrated categorical bias under these conditions, researchers then use such findings to claim that real-world disparities are also due to decision-maker bias. I describe three flaws inherent in this approach, flaws which undermine any direct contribution of experimental studies to explaining group disparities. First, the decision landscapes used in experimental studies lack crucial components present in actual decisions (Missing Information Flaw). Second, categorical effects in experimental studies are not interpreted in light of other effects on outcomes, including behavioral differences across groups (Missing Forces Flaw). Third, there is no systematic testing of whether the contingencies required to produce experimental effects are present in real-world decisions (Missing Contingencies Flaw). I apply this analysis to three research topics to illustrate the scope of the problem. I discuss how this research tradition has skewed our understanding of the human mind within and beyond the discipline and how results from experimental studies of bias are generally misunderstood. I conclude by arguing that the current research tradition should be abandoned.

Influence of different factors on the growth rate of young animals and the quality of beef

2021 ◽  
pp. 28-39
Author(s):  
V. N. Pristupa ◽  
D. S. Torosyan
Keyword(s):  
Experimental Studies ◽  
Live Weight ◽  
Federal District ◽  
Steppe Zone ◽  
Industrial Complex ◽  
Black And White ◽  
Dry Steppe ◽  
Intensive Rearing ◽  
Meat Productivity

The purpose of the work was to study and identify the main factors aff ecting the quantity and quality of beef produced and sold in the Southern Federal district. A comparative assessment of the growth, development, formation of meat productivity and quality of beef of young animals of beef, dual and dairy breeds with stall-pasture technology and intensive rearing in the industrial complex. Experimental studies have been carried out in farms in the Rostov region. The object of research was cows with calves of Kalmyk, Hereford, Aberdeen-Angus, Russian komolaya, Kazakh White-headed breeds, as well as young animals of the same breeds, in addition, Black-and-White and Swiss breeds. Removable live weight in Hereford steers at 18 months of age was 658,0 kg, and Aberdeen-Angus – 655,2 kg. Domestic steers of Kalmyk were 41–44 kg lower in live weight than their herdmates of two imported breeds. However, with intensive rearing at 18 months of age, steers of Kalmyk breed had a removable live weight of more than 613,7 kg and a carcass weight of 326 kg. The yield of hot carcass was 55,4 %, and the slaughter yield was 58,89 %, which was only 1–2 % lower than the world’s leading beef breeds. It has been found when analyzing the results of boning the half-carcasses of experimental steers that the biggest weight of half-carcasses and the content of muscle and fat tissue in them in absolute terms were in Hereford steers. Steers of Kalmyk breed took the third place in terms of weight of large-sized semi–fi nished products and signifi cantly lost to Aberdeen-Angus herdmates by 7,3 kg or 6,5 %, and Hereford steers by 9,2 kg or 8,3 %. The results obtained prove the expediency of using stallpasture technology in the dry-steppe zone of the Southern Federal district when rearing young animals for beef up to 350–400 kg live weight at 15 months of age and its subsequent intensive rearing under industrial technology, in order to obtain the live weight of more than 570 kg and produce cost-eff ective beef.

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