Studies on nuclear division in basidia of Poria latemarginata

1974 ◽  
Vol 52 (11) ◽  
pp. 2323-2333 ◽  
Author(s):  
E. C. Setliff ◽  
H. C. Hoch ◽  
R. F. Patton
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Nuclear Division ◽  
Light And Electron Microscopy ◽  
Metaphase Plate ◽  
Longitudinal Axis ◽  
Spindle Pole ◽  
Prophase Nucleus ◽  
Oriented Parallel ◽  
Two Envelopes

Nuclear division in basidia of Poria latemarginata was studied comparatively by light and electron microscopy. Premeiotic mitosis occurred in the lower half of the basidium and was oriented parallel to the longitudinal axis of the basidium. Mitosis was not observed with the light microscope and only late anaphase figures of mitosis were seen with the electron microscope. Mitosis was intranuclear with microtubules oriented between two spindle pole bodies (SPBs). The SPBs were spherical with a central core of material slightly more electron opaque than the surrounding SPB material. The nuclear envelope remained intact except at the SPBs.Divisions I and II of meiosis were chiastobasidial and occurred at the apices of basidia. The major features of meiosis observed by both light and electron microscopy were (1) karyogamy followed by the presence of one or two nucleoli in the prophase nucleus; (2) elongated chromosomes and synapsis at late zygotene – pachytene; (3) occurrence of a spindle at metaphase–anaphase composed of chromosomal and continuous microtubules associated with the SPBs; (4) absence of a metaphase plate with chromosomes arranged randomly around a zone of continuous microtubules; (5) condensation of chromosomes and asynchronous separation at anaphase; (6) kinetochores at anaphase; (7) the nuclear envelope remaining intact throughout meiosis except for discontinuities at the SPBs; (8) membrane-bound vesicles associated with chromosomes during division; and (9) separation of daughter nuclei at telophase. Stages of division II meiosis were observed less frequently and were similar to division I. The four postmeiotic nuclei then migrated back toward the central part of the basidium. Sterigmata developed at this time. Postmeiotic nuclei were surrounded by one or two envelopes of perinuclear endoplasmic reticulum before their migration into basidiospores. Electron-opaque inclusions occurred within the nuclei at this stage.

Mitosis in the Fission Yeast Schizosaccharomyces Pombe: A Comparative Study with Light and Electron Microscopy

1971 ◽  
Vol 9 (2) ◽  
pp. 475-507 ◽  
Author(s):  
E. KATHLEEN McCULLY ◽  
C. F. ROBINOW
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Nuclear Envelope ◽  
Schizosaccharomyces Pombe ◽  
Light And Electron Microscopy ◽  
Metaphase Plate ◽  
Middle Part ◽  
Mitotic Chromosomes ◽  
Nucleolar Material ◽  
Differential Expansion

Mitosis in Schizosaccharomyces pombe has been followed in living cells by phase-contrast microscopy and studied in fixed and suitably stained preparations by light microscopy. Successful preservation of nuclear fine structure in this yeast, not previously achieved, has allowed us to confirm and extend the observations made with light microscopy. Without first arranging themselves on a metaphase plate, mitotic chromosomes become grouped in 2 clusters radiating, finger-like, from 2 points of attachment at opposite poles of an elongating nucleus. At these 2 sites electron microscopy reveals the presence of disk-shaped electron-dense organelles which we have called kinetochore equivalents (KCE). At mitosis the KCEs are connected across the nucleus by a narrow bundle of parallel microtubules which we refer to as the spindle. Integration of our observations has led us to propose that at mitosis the separation of the KCEs and their attached chromosomes is initiated by a differential expansion of the nuclear envelope restricted to the region between recently divided KCEs and that expansion of the nuclear envelope later becomes general, resulting in a marked elongation of the nucleus. Displacement of the nuclear contents to the ends of the elongated nucleus gives it the shape of a dumbbell. The elongation of the microtubule bundle keeps in step with the elongation of the nucleus but does not appear to be the cause of it. It may have the function of keeping the separated KCEs rigidly apart. During mitosis the nucleolus persists and stretches out within the unbroken envelope of the nucleus as it elongates. Towards the end of division equal amounts of nucleolar material are found in the rounded ends of the dumbbell-shaped nucleus. The break up of the dumbbell shape into daughter nuclei seems to involve the breaking of its tenuous middle part and a pivoting of its 2 ends in opposite directions. In the course of our work on mitosis we have become aware of features in the cytoplasm of growing S. pombe cells which are described here for the first time. The cells invariably contain several prominent vacuoles containing an extremely electron-dense material which stains metachromatically with toluidine blue and may be polyphosphate. The mitochondria are of special interest for 2 reasons. First, because they have unique mesosome-like membrane invaginations and secondly, because a mitochondrion is regularly associated with the single KCE by the side of the interphase nucleus, as well as with each one of the 2 KCEs that occupy opposite ends of the intranuclear spindle during mitosis.

Further observations on nucleolar tails in amphibian oocytes

1991 ◽  
Vol 99 (3) ◽  
pp. 515-521
Author(s):  
PEDRO LEÓN ◽  
JAMES KEZER ◽  
ERIC SCHABTACH
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Outer Surface ◽  
Light And Electron Microscopy ◽  
Nuclear Pores ◽  
Core Component ◽  
Amphibian Species ◽  
Attachment Structures ◽  
Convoluted Tubules

Large oocytes from some amphibian species possess beaded or unbeaded intranuclear tails that penetrate the extrachromosomal nucleoli through a distinct pit in their surface and attach to the central core component Here we show, using light and electron microscopy, that tails anchor nucleoli to the nuclear envelope through intricate attachment structures. These structures are composed of interconnected spherical masses containing highly convoluted tubules and associated extratubular proteins, directly directly in contact with the inner nuclear membrane. Fibers emerging from the nuclear pores seemingly hold the attachment complex in place. Beads on the nucleolar tails are formed by the accumulation of proteins on the outer surface of smooth tubules. The function of these intranuclear tubules is unknown

Nuclear division in the marine dinoflagellate Oxyrrhis marina

1986 ◽  
Vol 85 (1) ◽  
pp. 161-175
Author(s):  
X.P. Gao ◽  
J.Y. Li
Keyword(s):  
Nuclear Envelope ◽  
Phylogenetic Relationships ◽  
Nuclear Division ◽  
Metaphase Plate ◽  
Active Role ◽  
Ultrastructural Changes ◽  
Interphase Nuclei ◽  
Oxyrrhis Marina ◽  
Two Stages ◽  
Anaphase B

The nuclear division of Oxyrrhis marina is a very distinct one among the mitoses of dinoflagellates that have been studies. Using synchronized populations, we have investigated the ultrastructural changes in this nuclear division. In interphase, nuclei can be classified into two groups on the basis of the shapes of the chromosomes. Y- and U-shaped chromosomes have been observed in both types of interphase nuclei. By prophase the nucleus becomes oval, many nuclear plaques appear on the nuclear envelope, and many microtubules radiate from these nuclear plaques within the nucleus. Metaphase can be identified by the characteristic arrangement of the chromosomes; an equatorial metaphase plate is absent. As in many higher organisms, anaphase includes two stages: anaphase A and anaphase B. During anaphase A the nucleus does not apparently elongate and the chromosomes migrate towards the poles by a combination of the shortening of the chromosome-associated microtubules and the elongation of those located between daughter chromosomes. During anaphase B the nucleus elongates to about twice its former length. This elongation may result from growth of the interzonal nuclear envelope. Dividing nucleoli are associated with microtubules, which suggests that microtubules may play an active role in the division of the nucleolus. The evolution of mitosis and the phylogenetic relationships between Oxyrrhis, typical dinoflagellates and Syndinium are discussed.

Conidiogenesis in Termitaria snyderi (Fungi Imperfecti)

1973 ◽  
Vol 51 (12) ◽  
pp. 2307-2314 ◽  
Author(s):  
Saeed R. Khan ◽  
Henry C. Aldrich
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Lipid Droplets ◽  
Light And Electron Microscopy ◽  
Cross Wall ◽  
Transverse Septum ◽  
Conidiogenous Locus ◽  
Oriented Parallel ◽  
Fungi Imperfecti

Termitaria snyderi Thaxter forms small discoid lesions on the exoskeleton of different species of termites. Its conidiogenesis has been studied by light and electron microscopy. The phialides are oriented parallel in a closely packed sporodochium. The conidia are produced endogenously in basipetal succession from a fixed conidiogenous locus and are liberated when the tip is broken off the phialide as a result of the force applied by the formation of new conidia. The area of the phialide beyond the locus forms a tubular collarette. The conidium initial buds out at the locus and after it has received its organelles and reached a certain size it is delimited by a centripetally growing transverse septum. The region of the growing septum has many vesicles which may be involved in cross wall synthesis. Conidia are cylindrical, uninucleate, and double-walled. They have mitochondria, endoplasmic reticulum (ER), conspicuous lipid droplets, and vacuoles. Each conidiophore has long mitochondria, elongate nuclei, and much endoplasmic reticulum. The plasmalemma of the conidiophore is highly convoluted.

The ultrastructure of nuclear division in Armillaria mellea: meiosis

1979 ◽  
Vol 57 (18) ◽  
pp. 1860-1872 ◽  
Author(s):  
Diane Cope Peabody ◽  
Jerome J. Motta
Keyword(s):  
Nuclear Envelope ◽  
Membrane Structure ◽  
Nuclear Division ◽  
Spindle Pole ◽  
Armillaria Mellea ◽  
Spindle Pole Bodies ◽  
Late Telophase ◽  
Meiosis I ◽  
Metaphase I

Meiosis I in isolates of Armillaria mellea in which subhymenial hyphae are uninucleate and lack clamp connections was examined ultrastructurally. Although the overall pattern of development and basidiosporogenesis appears similar to other Homobasidiomycetes it was observed that spindle pole bodies are predominantly monoglobular and are associated with a unique membrane structure of the subtending nuclear envelope. The nuclear envelope also disappears at metaphase I and reforms by the coalescence of membrane fragments around the compacted chromatin at late telophase I. The significance of these features in relation to other Basidiomycetes is briefly discussed.

scholarly journals CENTROSOMES AND MICROTUBULES DURING MEIOSIS IN THE MUSHROOM BOLETUS RUBINELLUS

1971 ◽  
Vol 50 (3) ◽  
pp. 737-745 ◽  
Author(s):  
David J. McLaughlin
Keyword(s):  
Electron Microscope ◽  
Longitudinal Axis ◽  
Spindle Pole ◽  
Middle Part ◽  
Prophase I ◽  
Cytoplasmic Microtubules ◽  
Oriented Parallel ◽  
Relationship Of ◽  
The Relationship

The double centrosome in the basidium of Boletus rubinellus has been observed in three planes with the electron microscope at interphase preceding nuclear fusion, at prophase I, and at interphase I. It is composed of two components connected by a band-shaped middle part. At anaphase I a single, enlarged centrosome is found at the spindle pole, which is attached to the cell membrane. Microtubules mainly oriented parallel to the longitudinal axis of the basidium are present at prefusion, prophase I and interphase I. Cytoplasmic microtubules are absent when the spindle is present. The relationship of the centrosome in B. rubinellus to that in other organisms and the role of the cytoplasmic microtubules are discussed.

scholarly journals ELECTRON MICROSCOPY OF MITOSIS IN AMEBAE

1967 ◽  
Vol 34 (1) ◽  
pp. 47-59 ◽  
Author(s):  
L. E. Roth
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Metaphase Plate ◽  
Test Sequence ◽  
Partial Loss ◽  
Mitotic Apparatus ◽  
In Vivo Test ◽  
Characteristic Sequences ◽  
Inhibitor Compounds

The mitotic apparatus (MA) of the giant ameba, Chaos carolinensis, has characteristic sequences of microtubule arrays and deployment of nuclear envelope fragments. If mitotic organisms are subjected to 2°C for 5 min, the MA microtubules are completely degraded, and the envelope fragments are released from the chromosomes which remain condensed but lose their metaphase-plate orientation. On warming, microtubules reform but show partial loss of their parallel alignment; displacement of the envelope fragments persists or is increased by microtubule reformation. This study demonstrates that cooling causes destruction of microtubules and intermicrotubular cross-bonds and further shows that such controlled dissolution and reformation can provide an in vivo test sequence for studies on the effects of inhibitor-compounds on microtubule subunit aggregation. Urea, at the comparatively low concentration of 0.8 M, inhibited reformation following cooling and rewarming but was ineffective in altering microtubules that had formed before treatment.

scholarly journals FINE STRUCTURE AND ORGANELLE ASSOCIATIONS IN BROWN ALGAE

1965 ◽  
Vol 26 (2) ◽  
pp. 523-537 ◽  
Author(s):  
G. Benjamin Bouck
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Golgi Apparatus ◽  
Nuclear Envelope ◽  
Brown Algae ◽  
Algal Cell ◽  
Plant Cells ◽  
Membrane Systems ◽  
Two Envelopes

The structural interrelationships among several membrane systems in the cells of brown algae have been examined by electron microscopy. In the brown algae the chloroplasts are surrounded by two envelopes, the outer of which in some cases is continuous with the nuclear envelope. The pyrenoid, when present, protrudes from the chloroplast, is also surrounded by the two chloroplast envelopes, and, in addition, is capped by a third dilated envelope or "pyrenoid sac." The regular apposition of the membranes around the pyrenoid contrasts with their looser appearance over the remainder of the chloroplast. The Golgi apparatus is closely associated with the nuclear envelope in all brown algae examined, but in the Fucales this association may extend to portions of the cytoplasmic endoplasmic reticulum as well. Evidence is presented for the derivation of vesicles, characteristic of those found in the formative region of the Golgi apparatus, from portions of the underlying nuclear envelope. The possibility that a structural channeling system for carbohydrate reserves and secretory precursors may be present in brown algae is considered. Other features of the brown algal cell, such as crystal-containing bodies, the variety of darkly staining vacuoles, centrioles, and mitochondria, are examined briefly, and compared with similar structures in other plant cells.

Changes in the metaphase transit times and the pattern of sister chromatid separation in stamen hair cells of Tradescantia after treatment with protein phosphatase inhibitors

1992 ◽  
Vol 102 (4) ◽  
pp. 691-715 ◽  
Author(s):  
S.M. Wolniak ◽  
P.M. Larsen
Keyword(s):  
Nuclear Envelope ◽  
Transit Time ◽  
Okadaic Acid ◽  
Hair Cells ◽  
Protein Phosphatase ◽  
Metaphase Plate ◽  
Spindle Pole ◽  
Phosphatase Inhibitors ◽  
Nuclear Envelope Breakdown ◽  
Transit Times

Stamen hair cells from the spiderwort plant, Tradescantia virginiana, exhibit remarkably predictable metaphase transit times, making them uniquely suitable for temporal studies on mitotic regulation. In this study, we describe two kinds of experiments that test whether protein phosphatase activity is a necessary prerequisite for entry into anaphase in living, mitotic cells. We treated cells at specific points during prophase, prometaphase and metaphase with the broad-spectrum protein phosphatase inhibitor, alpha-naphthyl phosphate (administered by microinjection), or with the naturally occurring, potent phosphatase inhibitors okadaic acid, microcystin-LR or microcystin-RR (administered by perfusion), and we have observed changes in the metaphase transit time that are primarily dependent on the time of initial exposure to the inhibitor. Maximal extensions of the metaphase transit time result from alpha-naphthyl phosphate microinjections initiated in mid-metaphase, 10–20 min after nuclear envelope breakdown. Perfusions with okadaic acid started during a specific interval in mid-metaphase, 15–20 min after nuclear envelope breakdown, resulted in a statistically significant extension of the metaphase transit time. Perfusions with either microcystin-LR or microcystin-RR initiated 15–26 min after nuclear envelope breakdown extended the metaphase transit times significantly. Treatments of cells with okadaic acid or with either of the microcystins initiated outside this mid-metaphase interval either were without effect or, alternatively, resulted in a significant shortening of the metaphase transit time. In addition to their effects on the timing of anaphase onset, treatments with these protein phosphatase inhibitors also resulted in a remarkable change in the way in which these cells enter anaphase. Sister chromatid separation in stamen hair cells typically requires only 5 seconds, but after treatment with any of these inhibitors some, but not all, of the chromatids split apart at anaphase onset. Those that split begin to migrate toward the spindle pole regions, while those that fail to split remain at the metaphase plate. Later, more of the paired chromatids split apart and begin moving toward the spindle pole regions. Those that fail to separate remain at the metaphase plate. This process can be repeated several times before all of the chromatids have separated. Thus, entry into anaphase becomes extremely asynchronous, and as much as 30 min can transpire between the centromeric separation of the first and last chromosomes. Some of the chromosomes complete their anaphase movements before others have even split apart at the metaphase plate. Asynchronous separation did not result in a permanent segregation anomaly.(ABSTRACT TRUNCATED AT 400 WORDS)

Somatic mitosis in Erysiphe graminis hordei

1972 ◽  
Vol 18 (12) ◽  
pp. 1915-1922 ◽  
Author(s):  
W. E. McKeen
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Nuclear Membrane ◽  
Osmium Tetroxide ◽  
Central Body ◽  
Nuclear Division ◽  
Light And Electron Microscopy ◽  
Erysiphe Graminis ◽  
The Other ◽  
Erysiphe Graminis Hordei

Somatic nuclear division in Erysiphe graminis hordei was studied by light and electron microscopy after various fixation and staining procedures. Electron microscopy studies of alcohol – acetic acid fixed material aided in providing an understanding of nuclear division and showing the gross alterations which occurred. Light microscopy indicated that a central body was always present at a specific site on the nuclear membrane in the interphase nucleus and was connected to chromatic spherical bodies. Microtubules were preserved when a short glutaraldehyde – osmium tetroxide fixation was used. Some microtubules extend from plaque to plaque while others terminate in kinetochores. A microtubular spindle, oblique to the nuclear and mildew-cells axes formed within the nuclear membrane. Typical prophases, metaphases, anaphases, and telophases were observed. Then one set of daughter chromatids bypassed the nucleolus which persisted intranuclearly until the daughter nuclei reached their destination, and the other set of daughter chromatids moved to midpoint in the other daughter cell. A narrow corridor, which connected daughter nuclei for some time, was filled mainly with microtubules and probably was the filament which was observed in the nucleus by light microscopy during nuclear division. At least six chromosomes were present in each nucleus.

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