Observations on the Fine Structure and Development of the Spindle at Mitosis and Meiosis in a Marine Centric Diatom (Lithodesmium Undulatum)

1969 ◽  
Vol 5 (1) ◽  
pp. 271-298
Author(s):  
IRENE MANTON ◽  
K. KOWALLIK ◽  
H. A. VON STOSCH
Keyword(s):  
Fine Structure ◽  
Chromosome Structure ◽  
Centric Diatom ◽  
Serial Sections ◽  
Ground Plan ◽  
Living Culture ◽  
Full Discussion ◽  
Two Stages ◽  
Mitosis And Meiosis ◽  
Spindle Structure

Various cytoplasmic phenomena, including spindle structure and development during prophase of the first meiotic division, are described and illustrated. The living culture is represented by a timed sequence of photographs continuing those previously published with respect to mitotic stages in the same filament. The meiotic preliminaries include the so-called swelling phase, by which the parental frustule is forced open, liberating the contained spermatocytes. This occurs during pachytene on evidence of chromosome structure which is illustrated. A spindle precursor is shown to be present before opening of the frustule; this resembles structurally the mitotic equivalent though the ground plan is oblong instead of square. Growth of the precursor continues until after opening of the frustule, when the spindle itself begins to be laid down. Two stages of developing spindles during the later prophases are illustrated by sections cut in three planes and by serial sections. Preliminary comparisons are made with metaphase I and with mitosis, both qualitatively and quantitatively, but a full discussion is deferred pending completion of the record for the later meiotic stages.

Observations on the Fine Structure and Development of the Spindle at Mitosis and Meiosis in a Marine Centric Diatom (Lithodesmium Undulatum)

1970 ◽  
Vol 7 (2) ◽  
pp. 407-443
Author(s):  
IRENE MANTON ◽  
K. KOWALLIK ◽  
H. A. VON STOSCH
Keyword(s):  
Centric Diatom ◽  
Serial Sections ◽  
Late Prophase ◽  
Haploid Chromosome Number ◽  
Male Gametogenesis ◽  
Common Time ◽  
Precursor Material ◽  
Mitosis And Meiosis ◽  
Meiosis I ◽  
Unusual Shape

The second meiotic division is shown to be of critical importance for interpretation of structures and events already seen at other divisions. The development of flagellar bases at interkinesis is demonstrated in relation to precursor material seen to accumulate near each pole at meiosis I. The name ‘paracentrosome’ is suggested for this material, which is used up in forming the flagellar bases and spindle precursor. The spindle at late prophase, metaphase and telophase II is shown to resemble those of other divisions except that it is consistently smaller; this fact is numerically demonstrated from serial sections of metaphase II cells. The greatly reduced size and unusual shape of the polar plates present in addition to flagellar bases at metaphase II suggest that these are in a sense equivalent structures with a mutually competitive relation to the paracentrosome. Preliminary observations with the light microscope on the relatively large nuclei of oogonia during meiosis I have shown that the haploid chromosome number is not less than 19 nor more than 23 and that chromatid separation in relation to the kinetochores at anaphase I is normal; the bearing of these findings on interpretation of the spindle is discussed. Comparisons with other organisms are carried out in a preliminary way and the investigation ends with a résumé of the more important externally visible events in male gametogenesis adjusted to a common time scale in the course of one day.

Observations on the fine structure and development of the spindle at mitosis and meiosis in a marine centric diatom (Lithodesmium Undulatum)

1970 ◽  
Vol 6 (1) ◽  
pp. 131-156
Author(s):  
IRENE MANTON ◽  
K. KOWALLIK ◽  
H. A. VON STOSCH
Keyword(s):  
Living Cells ◽  
Slight Variation ◽  
Centric Diatom ◽  
Serial Sections ◽  
Spindle Microtubules ◽  
Physical Forces ◽  
First Time ◽  
Mitosis And Meiosis ◽  
Chromosome Movements ◽  
Different Parts

Numerical information with respect to spindle microtubules in serial sections of 3 cells at metaphase of the first meiotic division has been compiled and illustrated sufficiently to supplement the previous accounts with respect to both longitudinal and transverse views. At the equator the microtubules of the spindle are united laterally into bundles, the number of bundles being of the same order as that encountered at a premeiotic mitosis, though there is slight variation from cell to cell. The number of microtubules is greater than that at mitosis in a normal spermatogonium, though the distribution in different parts of the spindle is qualitatively similar. Stages of anaphase have been illustrated for the first time and shown to involve at least types of physical forces mediating chromosome movements of various kinds. The later stages of cytokinesis have been timed and are illustrated from living cells and from sections. The relation of the spindle to the cord which unites the separating protoplasts towards the end of cytokinesis has been traced in outline. The cord itself is shown to contain micro- tubules in limited number and it is therefore not the whole spindle. The interpretation of these findings is discussed in a preliminary way.

scholarly journals A STUDY OF PHAGOCYTOSIS IN THE AMEBA CHAOS CHAOS

1965 ◽  
Vol 25 (3) ◽  
pp. 443-457 ◽  
Author(s):  
Richard G. Christiansen ◽  
John M. Marshall
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Living Cell ◽  
Serial Sections

The process of phagocytosis was investigated by observing the interactions between the ameba Chaos chaos and its prey (Paramecium aurelia), by studying food cup formation in the living cell, and by studying the fine structure of the newly formed cup using electron microscopy of serial sections. The cytoplasm surrounding the food cup was found to contain structures not seen elsewhere in the ameba. The results are discussed in relation to the mechanisms which operate during food cup formation.

Fine structure of Classopollis exines

1986 ◽  
Vol 64 (12) ◽  
pp. 3059-3074 ◽  
Author(s):  
John R. Rowley ◽  
Satish K. Srivastava
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Upper Jurassic ◽  
Thin Sheets ◽  
Serial Sections ◽  
Thin Sections ◽  
Band Area ◽  
Transmission Electron ◽  
Oxidative Etching

Serial sections for light microscopy or transmission electron microscopy of two Classopollis pollen tetrads show that the exine structure, except for the nexine, has radially arranged rodlike units interwoven with transverse subunits. The nexine consists of strands or thin sheets except in the equatorial infratectal striate band area, where it is up to ca. 1 μm thick. Nexine is absent in the areas of the distal cryptopore and the subequatorial circumpolar infratectal canal. It is very thin or absent in the tetrad scar. Native contrast and reactivity to stain disappeared on immersion of thin sections in 1 M NaOH or HCl or in water. Reactivity to stains was regained after oxidizing the sections in KMnO4. Reactivity to stains appears to be dependent upon non-sporopollenin molecules embedded within exines. The above immersions remove stain reactive sites. Oxidative etching of sporopollenin exposes new sites. The specimens of Classopollis classoides Pflug studied and illustrated were picked from an Upper Jurassic sample (CRC 31519-2) collected at Osmington Mills locality, Dorset, England.

The fine structure of ascospore delimitation in the yeast Wickerhamia fluorescens

1973 ◽  
Vol 19 (11) ◽  
pp. 1389-1392 ◽  
Author(s):  
Lynn Rooney ◽  
Peter B. Moens
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fine Structure ◽  
Outer Membrane ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Spore Wall ◽  
Serial Sections ◽  
Spore Body ◽  
Pole Body ◽  
Spindle Pole Bodies

Photographic records of complete serial sections of asci in different stages of sporulation show that one of the four nuclear lobes produced during meiosis in the ascus of the yeast Wickerhamia fluorescens has a complex spindle-pole body, which is the site from where the presumptive ascospore wall, or prospore wall, develops and eventually surrounds the ascospore nucleus and associated cytoplasm. The three remaining nuclei develop spindle-pole bodies and prospore walls to lesser and varying degrees. With few exceptions, all three degenerate. The outer membrane of the prospore wall forms a fold, or rim, on the outside of the spore. Thickening of the spore wall takes place first in the asymmetric ring, then around the spore body, and finally at the site where the nucleus is associated with the wall. It is shown that ascospore delimitation in W. fluorescens and Saccharomyces cerevisiae are similar to each other, and that it differs from the type observed in a number of Euascomycetes.

scholarly journals Random chromosome distribution in the first meiosis of F1 disomic substitution line 2R(2D) x rye hybrids (ABDR, 4× = 28) occurs without bipolar spindle assembly

2020 ◽  
Vol 14 (4) ◽  
pp. 453-482
Author(s):  
Dina B. Loginova ◽  
Anastasia A. Zhuravleva ◽  
Olga G. Silkova
Keyword(s):  
Genome Structure ◽  
Spindle Assembly ◽  
Wheat Chromosome ◽  
Cell Plate ◽  
Spindle Formation ◽  
Bipolar Spindle ◽  
Chromosome Distribution ◽  
Bipolar Spindles ◽  
Mitosis And Meiosis ◽  
Spindle Structure

The assembly of the microtubule-based spindle structure in plant meiosis remains poorly understood compared with our knowledge of mitotic spindle formation. One of the approaches in our understanding of microtubule dynamics is to study spindle assembly in meiosis of amphyhaploids. Using immunostaining with phH3Ser10, CENH3 and α-tubulin-specific antibodies, we studied the chromosome distribution and spindle organisation in meiosis of F1 2R(2D)xR wheat-rye hybrids (genome structure ABDR, 4× = 28), as well as in wheat and rye mitosis and meiosis. At the prometaphase of mitosis, spindle assembly was asymmetric; one half of the spindle assembled before the other, with simultaneous chromosome alignment in the spindle mid-zone. At diakinesis in wheat and rye, microtubules formed a pro-spindle which was subsequently disassembled followed by a bipolar spindle assembly. In the first meiosis of hybrids 2R(2D)xR, a bipolar spindle was not found and the kinetochore microtubules distributed the chromosomes. Univalent chromosomes are characterised by a monopolar orientation and maintenance of sister chromatid and centromere cohesion. Presence of bivalents did not affect the formation of a bipolar spindle. Since the central spindle was absent, phragmoplast originates from “interpolar” microtubules generated by kinetochores. Cell plate development occurred with a delay. However, meiocytes in meiosis II contained apparently normal bipolar spindles. Thus, we can conclude that: (1) cohesion maintenance in centromeres and between arms of sister chromatids may negatively affect bipolar spindle formation in the first meiosis; (2) 2R/2D rye/wheat chromosome substitution affects the regulation of the random chromosome distribution in the absence of a bipolar spindle.

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