Ultrastructure of Mitosis in the Aquatic Phycomycete Chytriomyces Hyalinus

1980 ◽  
Vol 38 ◽  
pp. 498-499
Author(s):  
David G. Pechak
Keyword(s):  
Life Cycle ◽  
Nuclear Envelope ◽  
Nuclear Division ◽  
Condensed Chromatin ◽  
Nuclear Pores ◽  
Interphase Nuclei ◽  
Aquatic Phycomycete ◽  
Simple Life

The aquatic Phycomycetes, particularly the Chytridiales, are a group of fungi with a rather simple life cycle and morphology. With the advent of ultrastructural investigations on these organisms, two stable characteristics (zoospore ultrastructure and nuclear division) have proven helpful in elucidating relationships in this perplexing taxon. The latter is described in this communication. Conventional techniques were employed in the preparation of the material. Interphase nuclei of C. hyalinus are essentially spherical in shape, measure approximately 2.8 μm in diameter, and have a single, centrally located, nucleus. Prophase nuclei, while not exhibiting condensed chromatin, are characterized by the presence of migrating centrioles and a fusiform or spindle-shape to the nuclear profile (Fig. 1). Nuclear pores predominate near the polar ends of the nuclear envelope. No evidence has been found to indicate that centrioles replicate during prophase.

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.

Sequential degradation of proteins from the nuclear envelope during apoptosis

2001 ◽  
Vol 114 (20) ◽  
pp. 3643-3653 ◽  
Author(s):  
Madeleine Kihlmark ◽  
Gabriela Imreh ◽  
Einar Hallberg
Keyword(s):  
Nuclear Envelope ◽  
Apoptotic Cell ◽  
Nuclear Periphery ◽  
Condensed Chromatin ◽  
Nuclear Pore ◽  
Dependent Manner ◽  
Nuclear Pores ◽  
Double Labeling ◽  
Lamin B ◽  
Nuclear Apoptosis

We have produced new antibodies specific for the integral pore membrane protein POM121. Using these antibodies we show that during apoptosis POM121 becomes proteolytically degraded in a caspase-dependent manner. The POM121 antibodies and antibodies specific for other proteins of the nuclear envelope were used in a comparative study of nuclear apoptosis in staurosporine-treated buffalo rat liver cells. Nuclei from these cells were classified in three different stages of apoptotic progression: stage I, moderately condensed chromatin surrounded by a smooth nuclear periphery; stage II, compact patches of condensed chromatin collapsing against a smooth nuclear periphery; stage III, round compact chromatin bodies surrounded by grape-shaped nuclear periphery. We have performed double labeling immunofluorescence microscopy of individual apoptotic cells and quantitative immunoblotting analysis of total proteins from apoptotic cell cultures. The results showed that degradation of nuclear envelope marker proteins occurred in a specific order. POM121 degradation occurred surprisingly early and was initiated before nucleosomal DNA degradation could be detected using TUNEL assay and completed before clustering of the nuclear pores. POM121 was eliminated significantly more rapid compared with NUP153 (a peripheral protein located in the nucleoplasmic basket of the nuclear pore complex) and lamin B (a component of the nuclear lamina). Disappearance of NUP153 and lamin B was coincident with onset of DNA fragmentation and clustering of nuclear pores. By contrast, the peripheral NPC protein p62 was degraded much later. The results suggest that degradation of POM121 may be an important early step in propagation of nuclear apoptosis.

Ultrastructure of the Fungal Nucleus

1971 ◽  
Vol 9 (2) ◽  
pp. 453-473
Author(s):  
M. GIRBARDT
Keyword(s):  
Nuclear Envelope ◽  
Direct Contact ◽  
Nuclear Division ◽  
Higher Plants ◽  
Compound Structure ◽  
Interphase Nuclei ◽  
Electron Dense Material ◽  
Nuclear Age ◽  
Division Process ◽  
Polar Organelle

The electron-dense material which regularly occurs at the poles of the nuclei of certain fungi during division has been studied in hyphal interphase nuclei of 4 basidio- and 3 ascomycetes. The shape of this material varies with the species and the nuclear age and may be that of a sphere or a dumbbell. In some instances paired diskoidal structures are found in the place of the globular elements of the dumbbell configuration. The organelle in question lies in an invagination of the nuclear envelope preferentially at the forward pointing pole of the nucleus. Its size (0.1-0.5 µm) is correlated with the size of the nucleus. In Polystictus versicolor the diameter of both globular elements of the polar organelle increases during initiation of the division process. The structure is identical with the fungal ‘centriole’ of light-microscopical studies but lacks the characteristic organization of a true centriole. It is suggested that the polar organelle is the equivalent of a kinetochore because it maintains continuous and direct contact with the nuclear envelope (on its cytoplasmic aspect), seems to be connected with the karyoplasm, exhibits oscillating movements, is continuous with microtubules during division and resembles in its fine structure the kinetochores of the chromosomes of higher plants and animals. In addition to its function as an organelle of nuclear motility it also seems to play a part in the initiation of DNA synthesis and nuclear division. If this is correct one would expect to find the genome of the fungal nucleus having the form of a unitary, coherent compound structure (chain) extending from or incorporating a single, solitary kinetochore.

Spindle Microtubules in the Dividing Nuclei of Trypanosomes

1970 ◽  
Vol 6 (2) ◽  
pp. 365-383 ◽  
Author(s):  
K. VICKERMAN ◽  
T. M. PRESTON
Keyword(s):  
Electron Microscope ◽  
Nuclear Envelope ◽  
Nuclear Division ◽  
Sleeping Sickness ◽  
Condensed Chromatin ◽  
Division Process ◽  
Spindle Microtubules

Stages in nuclear division have been identified in sections of bloodstream and cultured trypanosomes examined with the electron microscope. In the sleeping sickness trypanosome Trypanosoina rhodesiense at division the nuclear envelope and nucleolus-like endosome persist and become stretched along an axis. An acentric spindle of microtubules encases the elongating endosome As division proceeds the endosomal material fragments In bloodstream forms condensed chromatin (chromosomal material) appears to be associated with the nuclear envelope during the phase of nuclear elongation but to fall away from the envelope late in the phase of nuclear constriction. In culture forms the chromatin is not so abundant The discrete chromosomes envisaged by some light microscopists in stained preparations have not been identified using the electron microscope. The spindle may contain only continuous microtubules. It is suggested that the spindle serves to push the two halves of the nucleus apart, and that the nuclear envelope of each half may act as a vehicle in separation of the daughter genomes. In culture forms of the elasmobranch parasite T. raiae, the endosome appears to disintegrate as the spindle is formed, and from then onwards it becomes difficult to distinguish endosomal material from what might be chromatin. There is no noticeable association between chromatin-like material and the nuclear envelope. Some of the spindle tubules converge on kinetochore-like plaques and the presence of chromosomal microtubules cannot be ruled out. These preliminary studies indicate that the nuclear division process of trypanosomes is not closely akin to eukaryote mitosis, though it may bear some resemblance to nuclear division in Euglena. Within the genus Trypanosoma, moreover, the nuclear division process may vary from species to species and, possibly, even from one strain to another within a species.

The Ultrastructure of the Nuclear Events of Binary Fission in Paramecium bursaria and the Effects of Colchicine on Cell Division

1974 ◽  
Vol 32 ◽  
pp. 276-277
Author(s):  
L. M. Lewis
Keyword(s):  
Cell Division ◽  
Nuclear Envelope ◽  
Condensed Chromatin ◽  
Binary Fission ◽  
Paramecium Bursaria ◽  
Nuclear Events ◽  
Division Axis

The effects of colchicine on extranuclear microtubules associated with the macronucleus of Paramecium bursaria were studied to determine the possible role that these microtubules play in controlling the shape of the macronucleus. In the course of this study, the ultrastructure of the nuclear events of binary fission in control cells was also studied.During interphase in control cells, the micronucleus contains randomly distributed clumps of condensed chromatin and microtubular fragments. Throughout mitosis the nuclear envelope remains intact. During micronuclear prophase, cup-shaped microfilamentous structures appear that are filled with condensing chromatin. Microtubules are also present and are parallel to the division axis.

High-voltage cytochemistry for three-dimensional observation of nuclei and calculation of total numbers of nuclear pores in retinal Mueller glia

1990 ◽  
Vol 48 (3) ◽  
pp. 956-957
Author(s):  
H. Ishigooka ◽  
S. Ueno ◽  
L.M. Hjelmeland ◽  
M.B. Landers ◽  
K. Ogawa
Keyword(s):  
Nuclear Envelope ◽  
High Voltage ◽  
Three Dimensional ◽  
Reaction Medium ◽  
Nuclear Pores ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
G6pase Activity ◽  
Mueller Glia

Introduction: We have demonstrated that Glucose-6-phosphatase (G6Pase) activity is localized to the endoplasmic reticulum and nuclear envelope of Mueller glia in the normal and pathological guinea pig retina. Using a combination of this cytochemical technique and high voltage electron microscopy, the distribution of nuclear pores could be clearly observed on the nuclear envelope of Mueller glia because of their anatomical lack of reaction products. This technique was developed to study the three-dimensional structure of nuclei and to calculate total numbers of nuclear pores utilizing a computer graphic analysis system in the normal and pathological retina.Materials and methods: Normal and photocoagulated retina of pigmented adult guinea pigs were perfused with a cold mixture of 0.25% glutaraldehyde and 2% paraformaldehyde in 0.1M cacodylate buffer, and the enucleated globes were hemisected and immersed in the same fixative for 30 min. After sectioning and incubation in the reaction medium for the detection of G6Pase activity by the method of Wachstein-Meisel, the sections were postfixed, dehydrated and embedded in Spurr’s epoxy resin. Serial thick sections (1.0um) were prepared for the observation by a Hitachi high voltage electron microscope (H 1250-M) with an accelerating voltage of 1000 Kv. and pictures were analyzed and three-dimensionally reconstructed by TRI (RATOC Co., Ltd.).

Fine structure of the haplosporidan Kernstab, a persistent, intranuclear mitotic apparatus

1975 ◽  
Vol 18 (2) ◽  
pp. 327-346
Author(s):  
F.O. Perkins
Keyword(s):  
Fine Structure ◽  
Nuclear Envelope ◽  
Light Microscope ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Interphase Nuclei ◽  
Mitotic Apparatus ◽  
Pole Body

The fine structure of the haplosporidan mitotic apparatus is described from observations of plasmodial nuclei of Minchinia nelsoni, M. costalis, Minchinia sp., and Urosporidium crescens. The apparatus, which is the Kernstab of light-microscope studies, consists of a bundle of microtubules terminating in a spindle pole body (SPB) at each end of the bundle. A few microtubules extend from SPB to SPB, but most either extend from an SPB and terminate in the nucleoplasm or lie in the nucleoplasm, free of either SPB. The bundle lengthens during mitosis, increasing the SPB-to-SPB distance by a factor of 2 to 3 as compared to interphase nuclei. SPBs are not in contact with the nuclear envelope, being found always in the nucleoplasm which is delimited by the nuclear envelope throughout mitosis. The mitotic apparatus is persistent through interphase, at least in a form which is not significantly different from that found in mitotic nuclei.

scholarly journals Nuclear selection is effectively policed by mating restrictions of the dikaryotic life cycle of mushroom-forming fungi

2020 ◽  
Author(s):  
Ben Auxier ◽  
Tamas Czaran ◽  
Duur Aanen
Keyword(s):  
Life Cycle ◽  
Nuclear Envelope ◽  
Social Interactions ◽  
Haploid Nucleus ◽  
Fitness Consequences ◽  
Nuclear Selection ◽  
Related Individuals ◽  
Nuclear Exchange ◽  
Basidiomycete Fungi

AbstractAltruistic social interactions generally evolve between genetically related individuals or other replicators, whereas sexual interactions usually occur among unrelated individuals. This tension between social and sexual interactions is resolved by policing mechanisms enforcing cooperation among genetically unrelated entities. For example, most organisms with two haploid genomes are diploid, both genomes encapsulated inside a single nuclear envelope. A fascinating exception to this are Basidiomycete fungi, where the two haploid genomes remain separate. Uniquely, the haploid nuclei of the dikaryon can fertilize subsequent gametes encountered, the presumed benefit of this lifecycle. The implications for the balance of selection within and among individuals are largely unexplored. We modelled the implications of a fitness tradeoff at the level of the haploid nucleus versus the level of the fungal individual. We show that the most important policing mechanism is prohibition of fusion between dikaryons, which can otherwise select for detrimental levels of nuclear mating fitness. An additional policing mechanism revealed by our model is linkage between loci with fitness consequences. Our results show that benefits of di-mon matings must be paired with policing mechanisms to avoid uncontrolled selection at the level of the nuclei. Furthermore, we discuss evolutionary implications of recent claims of nuclear exchange in related fungal groups.

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