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.

Spindle birefringence of isolated mitotic apparatus analysed by treatments with cold, pressure, and diluted isolation medium

1976 ◽  
Vol 20 (2) ◽  
pp. 329-339
Author(s):  
A. Forer ◽  
A.M. Zimmerman
Keyword(s):  
Electron Microscopy ◽  
Sea Urchin ◽  
Half Life ◽  
Cold Treatment ◽  
Pressure Treatment ◽  
Mitotic Apparatus ◽  
Isolation Medium ◽  
Spindle Structure ◽  
Cold Pressure

Mitotic apparatus (MA) were isolated from sea-urchin zygotes using glycerol-dimethyl-sulphoxide. Cold treatment had no effect on MA birefringence when MA were in isolation medium, but caused a 10–15% reduction of MA birefringence when MA were in quarter-strength isolation medium. Pressure treatment also caused a reduction in MA birefringence, but the cold and pressure treatments were not additive, suggesting that both treatments affected the same MA component. MA were not stable in quarter-strength isolation medium, and birefringence gradually decayed, with a half-life of about 40 h. Electron microscopy after cold treatment, or after decay of 55% of the MA birefringence showed abundant, normal-looking microtubules, suggesting that alterations in non-microtubule components cause the reductions in birefringence. Addition of EGTA eliminates the effect of cold treatment, suggesting that Ca2+ has a role in maintenance of spindle structure. We discuss possible reasons why isolated MA do not respond to cold treatment like MA in vivo.

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.

Generative cell mitosis in pollen tubes of Nicotiana tabacum: Ultrastructure and 3-D reconstruction

1992 ◽  
Vol 50 (1) ◽  
pp. 848-849
Author(s):  
Hong-Shi Yu ◽  
S. D. Russell
Keyword(s):  
Pollen Tube ◽  
Generative Cell ◽  
Three Dimensional ◽  
Metaphase Plate ◽  
Preprophase Band ◽  
Mitotic Division ◽  
Mitotic Apparatus ◽  
Cell Mitosis

In bicellular pollen, the two sperm cells are formed by mitotic division of the generative cell (GC) in the pollen tube. This division is characterized by several unique features, including: lack of a preprophase band (PPB), absence of a metaphase plate, absence of normal spindle formation, and irregular patterns of cytokinesis. Purportedly, this is the result of spatial constraints within the pollen tube, which in vivo may be as narrow as 3 μm (as in Nicotiana) and slightly wider in vitro.Immunofluorescence studies of GC mitosis have been published in the last five years2−7, but only one incomplete ultrastructural report on GC division in vitro is available. This study is the first using three-dimensional (3-D) techniques to reconstruct the mitotic apparatus of the GC in vivo.

Spindle birefringence of isolated mitotic apparatus analysed by pressure treatment

1976 ◽  
Vol 20 (2) ◽  
pp. 309-327
Author(s):  
A. Forer ◽  
A.M. Zimmerman
Keyword(s):  
Electron Microscopy ◽  
Sea Urchin ◽  
Dimethyl Sulphoxide ◽  
Pressure Treatment ◽  
Mitotic Apparatus ◽  
Isolation Medium ◽  
Hexylene Glycol ◽  
X 24 ◽  
Induced Changes

Sea-urchin zygote mitotic apparatus (MA) isolated in a glycerol/dimethylsulphoxide medium were treated with pressure. Pressure treatment had no effect on spindle birefringence when MA were in full-strength isolation medium. After placing MA in quarter-strength isolation medium, pressures of 4-0 X 10(3)-1-8 X 10(4) lbf in.-2 (2 X 76 X 10(4)-I X 24 X 10(5) k N m-2) for 15 min caused reduction of birefringence which occurred in 2 steps: firstly 20–30% of the birefringence was lost, and then, at higher pressures, the rest of the birefringence was lost. Electron microscopy suggested that pressure-induced changes were in non-microtubule material. Pressure treatment had no effect on MA isolated with hexylene glycol when the MA were pressurized in hexylene glycol; but pressure treatment did cause loss of birefringence when MA isolated in hexylene glycol were transferred immediately into glycerol/dimethylsulphoxide medium and were subsequently treated with pressure (after dilution into quarter-strength glycerol/dimethyl-sulphoxide). We discuss the differences in response between isolated MA and in vivo MA, and we discuss the possibility that 2 components contribute to MA birefringence.

scholarly journals Evidence from rat liver nuclear preparations that latency of microsomal UDP-glucuronosyltransferase is associated with vesiculation

1980 ◽  
Vol 186 (3) ◽  
pp. 687-691 ◽  
Author(s):  
G J Wishart ◽  
D J Fry
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Rat Liver ◽  
Glucuronic Acid ◽  
Udp Glucuronosyltransferase

1. Nuclear, nuclear-envelope and microsomal preparations were prepared from rat liver, and their purity and morphology monitored by electron microscopy. 2. UDP-glucuronosyltransferase activity in microsomal preparations, but not in standard nuclear or nuclear-envelope preparations, displays latency from the criterion of being enhanced (‘activated’) by a range of detergents or the endogenous activator UDP-N-acetyl-glucosamine. 3. Nuclear preparations resemble activated rather than native microsomal preparations in failing to transfer glucuronic acid from 4-nitrophenyl glucuronide to 2-aminophenol. 4. Electron microscopy indicates that membranes of nuclear preparations and of our standard nuclear-envelope preparations remain, as in vivo, in a cisternal arrangement, whereas those of microsomal preparations are vesiculated. 5. In nuclear-envelope preparations in which vesiculation has been encouraged, the transferase can be activated by detergents. 6. We suggest that latency of UDP-glucuronosyltransferase results from vesiculation of membranes during preparation and that the latency of the microsomal transferase is largely a preparative artefact.

The Structure and Some Properties of the Isolated Mitotic Apparatus

1969 ◽  
Vol 4 (1) ◽  
pp. 179-209
Author(s):  
R. D. GOLDMAN ◽  
L. I. REBHUN
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Structural Changes ◽  
Close Association ◽  
Light And Electron Microscopy ◽  
Mitotic Apparatus ◽  
Isolation Medium ◽  
Oriented Parallel ◽  
Differential Interference Microscope

The morphology of the isolated sea-urchin mitotic apparatus (MA) was examined by light and electron microscopy. With the polarization microscope and the Nomarski differential interference microscope, the isolated MAs appeared to be similar to in vivo MAs. Electron microscopy of the isolated MAs revealed the presence of microtubules, ribosome-like particles and vesicles. A close association between the ribosome-like particles and the MA microtubules resulted in the appearance of chains of particles running along the length of the microtubules. Isolated MAs washed two to three times in isolation medium showed fine-structural changes in the electron microscope, which were reflected by lower retardation values obtained with the polarization microscope. The addition of magnesium and calcium or sucrose to the washing medium prevented these structural changes. Varying the pH of the isolation medium also resulted in changes in birefringence and ultrastructure of unwashed MAs. Isolated MAs stored in the original isolation medium gradually became less birefringent and lost their microtubules. At pH 6.1 and pH 6.2 a residual birefringence was retained, even after several weeks of storage. Electron microscopy of these MAs revealed the presence of linear aggregates of ribosome-like particles oriented parallel to the long axis of the spindle. On the other hand, at pH 6.3and pH 6.4, MAs lost their birefringence completely, and the ribosome-like particles became more randomly dispersed. 2M sucrose or 0.003 M Mg2+ greatly retarded the loss of birefringence in stored MAs. Glutaraldehyde-fixed MAs stained intensely with azure B bromide, demonstrating the presence of RNA. Treatment with RNase resulted in a loss of this staining. RNase-treated MAs examined with the electron microscope, revealed changes in the ribosome-like particles. The results are discussed in the light of recent biochemical analyses of the isolated MA, structural similarities to in situ MAs and the interpretation of the birefringence of the MA.

scholarly journals The organizational fate of intermediate filament networks in two epithelial cell types during mitosis.

1985 ◽  
Vol 100 (1) ◽  
pp. 93-102 ◽  
Author(s):  
J C Jones ◽  
A E Goldman ◽  
H Y Yang ◽  
R D Goldman
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cell ◽  
Nuclear Envelope ◽  
Hela Cells ◽  
Close Association ◽  
Cell Types ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Mitotic Apparatus ◽  
Mouse Keratinocytes

Intermediate filaments (IF) appear to be attached to the nuclear envelope in various mammalian cell types. The nucleus of mouse keratinocytes is enveloped by a cagelike network of keratin-containing bundles of IF (IFB). This network appears to be continuous with the cytoplasmic IFB system that extends to the cell surface. Electron microscopy reveals that the IFB appear to terminate at the level of the nuclear envelope, frequently in association with nuclear pore complexes (Jones, J. C .R., A. E. Goldman, P. Steinert, S. Yuspa, and R. D. Goldman, 1982, Cell Motility, 2:197-213). Based on these observations of nuclear-IF associations, it is of interest to determine the fate and organizational states of IF during mitosis, a period in the cell cycle when the nuclear envelope disassembles. Immunofluorescence microscopy using a monoclonal keratin antibody and electron microscopy of thin and thick sections of mitotic mouse keratinocytes revealed that the IFB system remained intact as the cells entered mitosis and surrounded the developing mitotic spindle. IFB were close to chromosomes and often associated with chromosome arms. In contrast, in HeLa, a human epithelial cell, keratin-containing IFB appear to dissemble as cells enter mitosis (Franke, W. W., E. Schmid, C. Grund, and B. Geiger, 1982, Cell, 30:103-113). The keratin IFB in mitotic HeLa cells appeared to form amorphous nonfilamentous bodies as determined by electron microscopy. However, in HeLa, another IF system composed primarily of a 55,000-mol-wt protein (frequently termed vimentin) appears to remain morphologically intact throughout mitosis in close association with the mitotic apparatus (Celis, J.E., P.M. Larsen, S.J. Fey, and A. Celis, 1983, J. Cell Biol., 97:1429-34). We propose that the mitotic apparatus in both mouse epidermal cells and in HeLa cells is supported and centered within the cell by IFB networks.

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.

The Infection of Cells by Bullet-Shaped Viruses

1969 ◽  
Vol 27 ◽  
pp. 372-373
Author(s):  
Frederick A. Murphy ◽  
Alyne K. Harrison ◽  
Sylvia G. Whitfield
Keyword(s):  
Electron Microscopy ◽  
Physical Properties ◽  
Host Cell ◽  
Thin Section ◽  
Cultured Cells ◽  
Cell Infection ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Section Electron Microscopy

The bullet-shaped viruses are currently classified together on the basis of similarities in virion morphology and physical properties. Biologically and ecologically the member viruses are extremely diverse. In searching for further bases for making comparisons of these agents, the nature of host cell infection, both in vivo and in cultured cells, has been explored by thin-section electron microscopy.

Probing the ultrastructure of the mitotic and meiotic spindle in eggs: An expeditious approach based on semi-thin (0.25 μm) serial sections

1983 ◽  
Vol 41 ◽  
pp. 552-555
Author(s):  
Conly L. Rieder ◽  
S. Bowser ◽  
R. Nowogrodzki ◽  
K. Ross ◽  
G. Sluder
Keyword(s):  
Small Sample Size ◽  
Small Sample ◽  
Meiotic Spindle ◽  
Serial Sections ◽  
Mitotic Apparatus ◽  
Thin Sections ◽  
Cell Cycles ◽  
Ultrastructural Studies

Eggs have long been a favorite material for studying the mechanism of karyokinesis in-vivo and in-vitro. They can be obtained in great numbers and, when fertilized, divide synchronously over many cell cycles. However, they are not considered to be a practical system for ultrastructural studies on the mitotic apparatus (MA) for several reasons, the most obvious of which is that sectioning them is a formidable task: over 1000 ultra-thin sections need to be cut from a single 80-100 μm diameter egg and of these sections only a small percentage will contain the area or structure of interest. Thus it is difficult and time consuming to obtain reliable ultrastructural data concerning the MA of eggs; and when it is obtained it is necessarily based on a small sample size.We have recently developed a procedure which will facilitate many studies concerned with the ultrastructure of the MA in eggs. It is based on the availability of biological HVEM's and on the observation that 0.25 μm thick serial sections can be screened at high resolution for content (after mounting on slot grids and staining with uranyl and lead) by phase contrast light microscopy (LM; Figs 1-2).

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