Anaphase Movements in the Living Cell

1948 ◽  
Vol 25 (1) ◽  
pp. 45-72 ◽  
Author(s):  
A. F. HUGHES ◽  
M. M. SWANN
Keyword(s):  
Fibre Length ◽  
Polarized Light ◽  
Embryonic Cells ◽  
Contractile Mechanism ◽  
Spindle Poles ◽  
Chromosome Separation ◽  
Relationship Of ◽  
The Relationship ◽  
Chromosome Movements ◽  
Spindle Fibres

1. The anaphase movements of living embryonic cells of the chick in tissue culture have been studied in phase contrast illumination, and in polarized light. Ciné-photographic records of chromosome movements and spindle changes have thereby been obtained simultaneously. 2. Chromosome separation in the chick is made up of two components--a movement of chromosomes towards the spindle poles, and an elongation of the spindle as a whole. 3. The assumption is made that the force acting on a chromosome is directly proportional to the velocity with which the chromosome moves. If this assumption is accepted as an approximation, it is possible to interpret the relationship of chromosome velocity to chromosome separation and spindle-fibre length. This leads to the conclusion that anaphase movement is due, not to repulsion between chromosomes, but to a contractile mechanism operating from the spindle poles. 4. Polarized light studies indicate that the orientation of the spindle material is high at the poles, and weaker at the equator. There is a small aster at either end of the spindle. 5. The centrosomes are interpreted as centres of an orienting force, which build up the contractile mechanism of the spindle from isotropic protoplasm. It is suggested that asters may also be contractile, and cause elongation of the spindle. 6. The inadequacy of the old conception of spindle fibres is discussed in the light of more modern views on molecular behaviour.

scholarly journals Association of TCTP with Centrosome and Microtubules

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Mariusz K. Jaglarz ◽  
Franck Bazile ◽  
Katarzyna Laskowska ◽  
Zbigniew Polanski ◽  
Franck Chesnel ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Mammalian Cells ◽  
Double Labelling ◽  
Spindle Poles ◽  
Pericentriolar Material ◽  
Indirect Association ◽  
Species Specific ◽  
Relationship Of ◽  
First Time ◽  
The Relationship

Translationally Controlled Tumour Protein (TCTP) associates with microtubules (MT), however, the details of this association are unknown. Here we analyze the relationship of TCTP with MTs and centrosomes inXenopus laevisand mammalian cells using immunofluorescence, tagged TCTP expression and immunoelectron microscopy. We show that TCTP associates both with MTs and centrosomes at spindle poles when detected by species-specific antibodies and by Myc-XlTCTP expression inXenopusand mammalian cells. However, when the antibodies against XlTCTP were used in mammalian cells, TCTP was detected exclusively in the centrosomes. These results suggest that a distinct pool of TCTP may be specific for, and associate with, the centrosomes. Double labelling for TCTP and γ-tubulin with immuno-gold electron microscopy inXenopus laevisoogonia shows localization of TCTP at the periphery of the γ-tubulin-containing pericentriolar material (PCM) enveloping the centriole. TCTP localizes in the close vicinity of, but not directly on the MTs inXenopusovary suggesting that this association requires unidentified linker proteins. Thus, we show for the first time: (1) the association of TCTP with centrosomes, (2) peripheral localization of TCTP in relation to the centriole and the γ-tubulin-containing PCM within the centrosome, and (3) the indirect association of TCTP with MTs.

Mitotic motors and chromosome segregation: the mechanism of anaphase B

2011 ◽  
Vol 39 (5) ◽  
pp. 1149-1153 ◽  
Author(s):  
Ingrid Brust-Mascher ◽  
Jonathan M. Scholey
Keyword(s):  
Chromosome Segregation ◽  
Cyclin B ◽  
Spindle Poles ◽  
Mitotic Motors ◽  
Balance Of Forces ◽  
Spindle Elongation ◽  
Anaphase B ◽  
Relationship Of ◽  
The Relationship ◽  
Acting In Concert

Anaphase B spindle elongation plays an important role in chromosome segregation. In the present paper, we discuss our model for anaphase B in Drosophila syncytial embryos, in which spindle elongation depends on an ip (interpolar) MT (microtubule) sliding filament mechanism generated by homotetrameric kinesin-5 motors acting in concert with poleward ipMT flux, which acts as an ‘on/off’ switch. Specifically, the pre-anaphase B spindle is maintained at a steady-state length by the balance between ipMT sliding and ipMT depolymerization at spindle poles, producing poleward flux. Cyclin B degradation at anaphase B onset triggers: (i) an MT catastrophe gradient causing ipMT plus ends to invade the overlap zone where ipMT sliding forces are generated; and (ii) the inhibition of ipMT minus-end depolymerization so flux is turned ‘off’, tipping the balance of forces to allow outward ipMT sliding to push apart the spindle poles. We briefly comment on the relationship of this model to anaphase B in other systems.

The relationship of orthopyroxene to pigeonite

1947 ◽  
Vol 28 (198) ◽  
pp. 164-172 ◽  
Author(s):  
Arie Poldervaart
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Polarized Light ◽  
Number Of Publications ◽  
Relationship Of ◽  
The Relationship

Interest in the orthopyroxene series is evidenced by the great number of publications on that subject which appeared in the literature. Correlations of the chemical composition and optical properties were attempted by Winchell (1923, 1933), Walls (1935), Henry (1935), and Hess and Phillips (1940). The nomenclature of the series was discussed by Winchell (1923), Alling (1936), and Hess and Phillips (1940). The obscure phenomena exhibited by certain orthopyroxenes in polarized light, attributed by some to twinning, by others to exsolution, was noted by a great many petrologists, of whom are mentioned here Lewis (1908), Holmes and Harwood (1928), Guimarães (1933), Scholtz (1936), Hess and Phillips (1938, 1940), Kuschke (1939), Wager and Deer (1939), Nel (1940), Walker (1940, 1943), Walker and Poldervaart (1940, 1941), Edwards (1942), Henry (1942), and Poldervaart (1944, 1946).

Progression of Artificial Caries in Fluorotic and Nonfluorotic Enamel. An in vitro Study

2008 ◽  
Vol 33 (2) ◽  
pp. 127-130 ◽  
Author(s):  
Suma R ◽  
KK Shashibhushan ◽  
ND Shashikiran ◽  
VV Subba Reddy
Keyword(s):  
Dental Caries ◽  
Dental Fluorosis ◽  
Polarized Light ◽  
Public Health Problem ◽  
In Vitro Study ◽  
P Value ◽  
Fluoride Level ◽  
Relationship Of ◽  
The Relationship

Background and objectives: Fluorosis is an important clinical and public health problem in several parts of the world. Although the relationship of fluoride level in drinking water to dental caries and dental fluorosis is known, relationship of fluorosis with the caries is not clear. This study was conducted to evaluate and compare the thickness of enamel and depth of lesion after inducing artificial caries in fluorotic and nonfluorotic teeth. Methods: Study group included 15 fluorosis affected and 15 normal teeth. Artificial caries was induced and teeth were sectioned to 150 microns and observed under polarized light microscope to measure the enamel thickness and depth of lesion in microns. Results: Statistical analyses of the measurements were made using student's unpaired t-test. Thickness of the enamel of nonfluorotic teeth was found to be significantly more when compared with the fluorotic teeth(p-value 0.0404) and depth of lesion was significantly more in fluorotic teeth when compared with the nonfluorotic teeth(p-value 0.0218). Conclusion:Although fluoride is acknowledged as an essential factor in the prevention of dental caries there has to be careful balance in the amount consumed to ensure that fluorosis does not occur.

scholarly journals Comparative Cytology of Female Meiosis I Among Drosophila Species

2020 ◽  
Vol 10 (5) ◽  
pp. 1765-1774
Author(s):  
Ahmed Majekodunmi ◽  
Amelia O. Bowen ◽  
William D. Gilliland
Keyword(s):  
Natural Populations ◽  
Meiotic Spindle ◽  
Female Meiosis ◽  
Closely Related Species ◽  
Spindle Poles ◽  
Chromosome Separation ◽  
The Mean ◽  
Chromosome Movements ◽  
Meiosis I

The physical connections established by recombination are normally sufficient to ensure proper chromosome segregation during female Meiosis I. However, nonexchange chromosomes (such as the Muller F element or “dot” chromosome in D. melanogaster) can still segregate accurately because they remain connected by heterochromatic tethers. A recent study examined female meiosis in the closely related species D. melanogaster and D. simulans, and found a nearly twofold difference in the mean distance the obligately nonexchange dot chromosomes were separated during Prometaphase. That study proposed two speculative hypotheses for this difference, the first being the amount of heterochromatin in each species, and the second being the species’ differing tolerance for common inversions in natural populations. We tested these hypotheses by examining female meiosis in 12 additional Drosophila species. While neither hypothesis had significant support, we did see 10-fold variation in dot chromosome sizes, and fivefold variation in the frequency of chromosomes out on the spindle, which were both significantly correlated with chromosome separation distances. In addition to demonstrating that heterochromatin abundance changes chromosome behavior, this implies that the duration of Prometaphase chromosome movements must be proportional to the size of the F element in these species. Additionally, we examined D. willistoni, a species that lacks a free dot chromosome. We observed that chromosomes still moved out on the meiotic spindle, and the F element was always positioned closest to the spindle poles. This result is consistent with models where one role of the dot chromosomes is to help organize the meiotic spindle.

Behavioral evidence for intraspecific signaling with achromatic and polarized light by cuttlefish (Mollusca: Cephalopoda)

Behaviour ◽  
2004 ◽  
Vol 141 (7) ◽  
pp. 837-861 ◽  
Author(s):  
Nadav Shashar ◽  
Katrina Vaughan ◽  
Ellis Loew ◽  
Jean Boal ◽  
Roger Hanlon ◽  
...  
Keyword(s):  
Polarized Light ◽  
Linearly Polarized ◽  
Males And Females ◽  
Body Patterns ◽  
Behavioral Evidence ◽  
Dermal Cells ◽  
Relationship Of ◽  
The Relationship ◽  
Source Of Information ◽  
Visible Body

AbstractIntraspecific visual communication was studied quantitatively by testing the behavior of Sepia officinalis, the common cuttlefish, as senders and receivers of body pattern signals. These signals can be achromatic and/or linearly polarized and are produced by specialized dermal cells. Experiment 1 addressed whether the presence of conspecifics affected the visible, achromatic body patterns of males. These patterns tended to vary among conditions, suggesting limited sensitivity to audience. One set of body patterns varied with the number of conspecifics viewed while an uncorrelated set of body patterns varied with the sex of conspecifics viewed. Males showed high-contrast zebra banding when viewing another male, supporting previous studies of body patterns in male-male agonistic behavior. Experiment 2 addressed the relationship of polarized light patterns with visible body patterns of males and females, and tested whether senders modified their polarization patterns in response to conspecifics. Polarization patterning was only weakly associated with visible body patterns. Females showed more polarized body patterns than did males, but polarized patterns did not differ among conditions; thus, no sensitivity to audience by senders was found. Experiment 3 addressed whether conspecific receivers used information from polarized body patterns. Limited evidence was found for changes in the behavior of female but not male observers, suggesting that female receivers may use polarized patterns as a source of information about conspecifics. The information contained in polarization patterning may complement that contained in zebra patterning such that both males and females advertise their species, sex, location, and size to conspecific receivers.

scholarly journals Dentin reactions to caries are misinterpreted by histological “gold standards”

F1000Research ◽  
2014 ◽  
Vol 3 ◽  
pp. 13 ◽  
Author(s):  
Priscila Florentino Silva ◽  
Danilo Augusto de Holanda Ferreira ◽  
Kássia Regina Simões Meira ◽  
Franklin Delano Soares Forte ◽  
Ana Maria Barros Chaves ◽  
...  
Keyword(s):  
Polarized Light ◽  
Occlusal Caries ◽  
Dentin Mineralization ◽  
The One ◽  
Relationship Of ◽  
The Relationship ◽  
Caries Lesions ◽  
Gold Standards

Dentin reactions to caries, crucial for pathogenesis and for the determination of the severity of caries lesions, are believed to be reasonably detected by stereomicroscopy (SM) and polarized light microscopy in quinoline (PLMQ), but accuracies are not available. Here, stereomicroscopy of wet (SW) and dry (SD) ground sections of natural occlusal caries lesions resulted in moderate (0.7, for normal dentin) and low accuracies (< 0.6, for carious and sclerotic dentin) as validated by contrast-corrected microradiography. Accuracies of PLMQ were moderate for both normal (0.71) and carious dentin (0.71). The hypothesis that detection of dentin reactions by SM and PLMQ would be influenced by the contrast quality of micrographic images was rejected. Dentin reactions were scored by SW, SD, PLMQ, and three types of microradiographic images with varying contrast qualities and each technique was compared against the one that resulted in the highest number of scores for each dentin reaction. Large differences resulted, mainly related to the detection of sclerotic dentin by both SW and SD, and normal and carious dentin by PLMQ. It is concluded that contrast-corrected microradiography should be preferred as the gold standard and SM and PLMQ should be avoided, but the relationship of PLMQ with dentin mineralization deserves further investigation.

The relationship of the scleractinian corals to the rugose corals

Paleobiology ◽  
1980 ◽  
Vol 6 (02) ◽  
pp. 146-160 ◽  
Author(s):  
William A. Oliver
Keyword(s):  
Critical Points ◽  
Scleractinian Corals ◽  
Convincing Evidence ◽  
Early Triassic ◽  
Rugose Corals ◽  
History Of ◽  
The Subject ◽  
Relationship Of ◽  
The Relationship ◽  
Biologic Factors

The Mesozoic-Cenozoic coral Order Scleractinia has been suggested to have originated or evolved (1) by direct descent from the Paleozoic Order Rugosa or (2) by the development of a skeleton in members of one of the anemone groups that probably have existed throughout Phanerozoic time. In spite of much work on the subject, advocates of the direct descent hypothesis have failed to find convincing evidence of this relationship. Critical points are:(1) Rugosan septal insertion is serial; Scleractinian insertion is cyclic; no intermediate stages have been demonstrated. Apparent intermediates are Scleractinia having bilateral cyclic insertion or teratological Rugosa.(2) There is convincing evidence that the skeletons of many Rugosa were calcitic and none are known to be or to have been aragonitic. In contrast, the skeletons of all living Scleractinia are aragonitic and there is evidence that fossil Scleractinia were aragonitic also. The mineralogic difference is almost certainly due to intrinsic biologic factors.(3) No early Triassic corals of either group are known. This fact is not compelling (by itself) but is important in connection with points 1 and 2, because, given direct descent, both changes took place during this only stage in the history of the two groups in which there are no known corals.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

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.

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