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PubMed1985

[Behavior of nucleoli during mitosis in chick and quail embryo myoblasts cultured in vitro].

Mitoses of heart-myoblasts of Chicken and Quail embryos were studied in primary hanging-drop cultures. Some differences of nucleolar behavior were observed: Quail nucleoli, unlike Chicken nucleoli, disappear early in prophase. In telophase nucleoli reappear early and more quickly in Chicken than in Quail. Differences between the cells of Chicken and Quail were noted also with the Ag-NOR staining method, particularly during telophase.

Animals↗
PubMed1989

Validation of the hemizona assay in a monkey model: influence of oocyte maturational stages.

The hemizona assay (HZA) was used in the monkey model to investigate sperm binding to the zona pellucida and to evaluate binding patterns according to various stages of oocyte development. Adult cynomolgus monkeys were superovulated with human menopausal gonadotropin. The oocytes were retrieved by laparoscopy, stored in salt solution, then cut into hemizonae by micromanipulation. Metaphase II oocytes showed significantly tighter binding than prophase I oocytes (P less than 0.001). Metaphase I oocytes showed intermediate binding, significantly different from the other groups (P less than 0.01). It is concluded that: (1) This study demonstrates the feasibility of HZA as a test to evaluate sperm/zona interactions in the monkey, using standards reported for human studies. (2) Oocyte meiotic competence seems to be accompanied by an increase in zona-binding properties.

Animals↗
PubMed1989

In situ analysis of the action of Navelbine on various types of microtubules using immunofluorescence.

Preliminary clinical studies demonstrated that 5' nor-anhydro-vinblastine, Navelbine (NVB) has a broader antitumor activity and fewer neurotoxic effects than vinblastine or vincristine. The tectal plate anlage of mouse embryos at the earliest stages of neuronal differentiation were used to analyze and compare the effect of NVB, vincristine and vinblastine on axonal and mitotic microtubules after culture of post-implantation embryos in a medium containing the agent. All drugs are active on mitotic microtubules at the same concentration (0.1 mumol/L), inducing a depolymerization of microtubules and a blockade of cells at metaphase. At higher concentrations. NVB is the only one of the three drugs that induces a blockade of the cells at prophase. A depolymerization of axonal microtubules occurs at higher concentrations with NVB than with the two other vinca alkaloids. These results demonstrate that NVB is as active on mitotic microtubules and less active on axonal microtubules than vincristine and vinblastine. These findings can be related to the potent antitumor effect of the drug with minor neurotoxicity.

Animals↗
PubMed1988

Immunoelectron microscopic study of nucleolar DNA during mitosis in Ehrlich tumor cells.

In order to investigate the DNA localization within Ehrlich tumor cell nucleoli during mitosis, two recent immunocytochemical methods using either an anti-DNA or an anti-bromodeoxyuridine (BrdU) monoclonal antibody have been applied. In both cases, the immunogold labeling has been performed on ultrathin sections of cells embedded either in Lowicryl K4M or in Epon, respectively. Identical results are observed with both immunocytochemical approaches. In the interphase nucleolus, besides the labeling of the perinucleolar chromatin shell and of its intranucleolar invaginations which penetrate into the nucleolar body and often terminate at the fibrillar centers, a few gold particles are also preferentially found towards the peripheral region of the fibrillar centers. In contrast, the dense fibrillar component and the granular component are never labeled. During mitosis, the fibrillar centers persist at the chromosomal nucleolus organizing regions (NOR's) and can be selectively stained by the silver method. However, these metaphase fibrillar centers are no longer decorated by the DNA- or BrdU antibodies. These results indicate that until the end of prophase, rRNA genes are present inside the fibrillar center material, disappear during metaphase and reappear in reconstituting nucleoli during telophase. Thus, fibrillar centers appear to represent structures sui generis, which are populated by rRNA genes only when the nucleolus is functionally active. In segregated nucleoli after actinomycin D treatment, the DNA labeling is exclusively restricted to the perinucleolar chromatin blocks. These findings also suggest that the DNA content of the fibrillar center material varies according to the rRNA transcription level of the cells. The results are discussed in the light of the present knowledge of the functional organization of the nucleolus.

Animals↗
PubMed1987

Ultrastructure of the mitotic apparatus in Cryptococcus neoformans.

Mitosis in Cryptococcus neoformans was examined by electron microscopy. Observation of serial sections showed that the separation of chromosomes occurred in the karyokinetic nucleus in the bud, that the microtubule organizing center (MTOC) was composed of two globular elements and a bridged middle piece, and that the nuclear envelope of the karyokinetic nucleus was partially destroyed during mitosis. These findings are similar to those reported in the heterobasidiomycetous yeasts. In addition, some of the prophase cells showed extension of the karyokinetic nucleus into the bud unaccompanied by the MTOC and swelling of the middle piece of the MTOC.

Anaphase↗
PubMedDate not supplied

[Prolongation of occult damage to the liver after cessation of chronic gamma irradiation].

A study was made of the effect of continuous gamma-irradiation on changes in the mitotic index (MI), the ratio of the number of metaphases to that of prophases (M/P), and the frequency of chromosome aberrations at the post-metaphase in the regeneration rat liver. The data obtained indicate that the injury to the intact liver of exposed rats persists throughout the entire period of observation which is displayed by a relative stability of M/P ratio and the frequency of chromosome aberrations. On the other hand, the MI changes indicate the trend toward the repair of the injury.

Animals↗
PubMedDate not supplied

[Effect of methotrexate and actinomycin D on the frequency and ratio of early mitotic cells].

Different methods for obtaining early mitotic chromosomes have been comparatively analyzed. Lymphocyte cultures have been treated with methotrexate, actinomycin-D and with a combination of both agents. It is shown that a high rate of chromosomes in prophase, prometaphase and mid-metaphase can be achieved by the combined methotrexate and actinomycin-D treatment of the lymphocyte culture. Methotrexate treatment of cultures is preferable to obtain the great number of early metaphase chromosomes.

Cells, Cultured↗
PubMed1986

Protein requirements for germinal vesicle breakdown in ovine oocytes.

The regulation of the cell cycle during the transition from prophase to metaphase I was studied by analysing protein changes and introducing protein blocks during the transition phase. The results show that the progression to metaphase in ovine oocytes is totally dependent on new protein synthesis. By delaying the addition of the inhibitor, cycloheximide, for progressively longer periods after the resumption of meiosis it was established that the required synthesis occurs in the 1-2 h immediately preceding germinal vesicle breakdown (GVBD). The action of cycloheximide was fully reversible: removal of the drug resulted in GVBD between 3 and 4 h later. The synthesis and modification of proteins during these first few hours of maturation were studied by short-term radiolabelling of oocytes with [35S]methionine and [32P]phosphate followed by rapid assessment of their precise nuclear configuration. Changes in phosphorylation of two polypeptides were detected 4-5 h after the beginning of culture, but these changes were not dependent upon protein synthesis. The earliest change in synthesis was the appearance of a new polypeptide 6-8 h after explantation, immediately before GVBD. This polypeptide (Mr 47 X 10(3), pI 5.8) was not significantly phosphorylated and was relatively stable. Oocytes released from cycloheximide treatment began to synthesize this molecule 3-4 h later, again coinciding with GVBD. Synthesis of the polypeptide was suppressed by inhibition of transcription with alpha-amanitin.

Amanitins↗
PubMed1979

Relationships between hormone-induced calcium release and 86rubidium uptake stimulation in starfish oocytes.

86Rubidium+ uptake, but not 86Rubidium efflux, is strongly stimulated after addition of the meiosis inducing hormone 1-methyladenine (1-MeAde) to prophase blocked oocytes of the starfish Marthasterias glacialis. This stimulation is a transient process which does not require the continuous presence of 1-MeAde and is elicited within 1 minute of contact. 1-MeAde and its biologically active structural analogs fully stimulate Rb+ uptake at concentrations which are about two orders of magnitude lower than those required to trigger meiosis reinitiation but which already release underthreshold levels of Ca2+ from the inner part of the plasma membrane. External Ca2+ concentrations effective in triggering meiosis reinitiation also stimulate Rb+ influx, while drugs like D600, theophyllin and caffein which suppress the hormone induced Ca2+ release, simultaneously preclude the stimulation of Rb+ uptake. Dithiothreitol (DTT) which mimicks 1-MeAde action in releasing Ca2+ and inducing meiosis acts both on the efflux and on active and passive Rb+ influxes. Ouabain, the classical inhibitor of the Na+, K+ pump does not preclude meiosis reinitiation under the influence of 1-MeAde, its agonists of mimetics. It suppresses the active component of Rb+ uptake both in control or stimulate oocytes. When applied only in preincubation before starting the hormone treatment, it cannot however inhibit the stimulation of Rb+ uptake, while basal pump inhibition is preserved. These results demonstrate that stimulation of the active Rb+ or K+ transport is not indispensable to meiosis reinitiation. They suggest moreover that the hormone induced Ca2+ release from the plasma membrane may be responsible for unmasking new ouabain sensitive transport sites.

Adenine↗
PubMed1982

Interactive image enhancement and analysis of prometaphase chromosomes and their band patterns.

An interactive computer system for measuring banding patterns on prometaphase and prophase chromosomes is described. Cells are digitized, and the images are enhanced by digital filtering. A chromosome's medial axis is determined either automatically by a skeletonization procedure or interactively by an operator. A straightened image of a bent chromosome is made by straightening the axis without distorting its length. Landmark bands on the straightened image can be labeled interactively by the operator. Sets of labeled homologous chromosomes can be normalized to have the same apparent interlandmark spacing and can be displayed side by side for visual comparison.

Animals↗
PubMed1983

[DNA metabolism in the process of the maturation of male sex cells. I. Amplification of ribosomal genes in the spermatogenesis of rats].

It has been shown that amplification of ribosomal genes takes place in prophase I of rat spermatogenesis. At the pachytene I step, a 2-fold excess of rDNA was found. Amplification of ribosomal genes starts in the premeiotic interphase on the chromosomal DNA. At the initial stage of rDNA amplification, a rDNA-RNA hybrid was detected. Our results allow the suggestion to be made that RNA plays the role of a primer in synthesis of the excess rDNA. It is possible that AT-rich prenucleolar DNA is involved in amplification of rDNA.

Animals↗
PubMed1984

Composition and role of the synaptonemal complex.

The role of the synaptonemal complex (SC) in synapsis during meiotic prophase is examined in spermatocytes and oocytes of mice heterozygous for rearrangements, using light and electron microscopy of whole mount spreads. The duration of cytologically-characterized substages provides a morphological time axis for synaptic events. At zygotene, synapsis is restricted to homologous regions. A second phase of synapsis, indifferent to homology, follows in early pachytene. By a progressive process of synaptic adjustment, SC configurations, such as duplication buckles and inversion loops, are regularly eliminated and form straight, non-homologously synapsed SCs by late pachytene. In the mouse, crossing over probably occurs during the period of homologous synapsis in the first half of pachytene, suggesting an association between recombination events and synaptic adjustment. During this period, a low level of DNA synthesis, distinct from S-phase replication, is found by 3H-thymidine autoradiography to be localized to the SC, as would be expected if repair synthesis involved with crossing over occurred in SC-associated DNA. This DNA synthesis reaches a peak in pachytene concurrently with synaptic adjustment, suggesting that the two events may be related, possibly through the mediation of DNA-binding SC proteins. Using immunocytological techniques to identify SC proteins, a monoclonal antibody has been isolated that binds to formed SCs but not unpaired axes. Apparently specific for a central region component, the antibody also binds to intermediate filaments in the cytoplasm of cultured somatic cells, indicating possible functional attributes common to the meiotic and mitotic proteins.

Animals↗
PubMed1981

Surface topography and other characteristics of non-transformed and carcinogen transformed C3H/10T 1/2 cells in mitosis, as revealed by quantitative scanning electron microscopy.

Scanning electron microscopy (SEM) has been used for the characterization of the different phases of mitosis in normal and transformed C3H/10T 1/2 cells after the stages had been confirmed by light microscopy. Our findings suggest that it is only possible to separate the different phases of mitosis by SEM after having evaluated a great number of cells and after having established the SEM features for the light microscopically identified mitotic phases (Feulgen staining). The main finding in the study is that both the normal and all three types of transformed cells, type I, II and III, have the same shape in the different stages of mitosis but that transformed cells seem to exhibit a larger number of pleomorphic microvilli than do non-transformed cells. We also found that in contrast to the other mitotic phases, prophase cells have a very low concentration of microvilli in the nuclear area.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

Effect of low temperature on the nucleolus of larkspur (Delphinium Ajacis L.) meiocytes.

In comparison with stage specific modifications of nucleolus in the early stages of meiotic prophase in Delphinium Ajacis meiocytes, the effect of low temperature is described. On the contrary to control leptotene nucleolus, exhibiting intermingled fibrillar and granular components, cold induced a disappearance of fibrillar material from these organelles. Disappearance of fibrillar material was accompanied by marked diminishment of 3H-uridine incorporation. NOR in control as well as in cold treated material was present. Zygotene nucleolus being in eccentric position displayed segregation of granular and fibrillar components, especially well visible in cold treated cells. In the area occupied in control material by NOR, cold treated cells were found to contain the numerous dark granules. The application of Bernhard's EDTA technique and enzymatic digestion with RNase, DNase and pepsine have proved that the dark granules are composed of RNA. Although pachytene nucleolus still pressed to nuclear envelope exhibited compact structure, composed probably of fibrillar and granular elements, in cold treated meiocytes it showed only the presence of granular component. Moreover, in cold treated cells some dark granules of RNA character were visible at the surface of nucleolus. No was absent. In addition to these changes, in the cytoplasm of cold treated cells in pachytene stage a material of nucleolar origin has appeared. The meiotic irregularities described in the present paper are discussed in relation to the partial male sterility that occurs in Delphinium meiocytes growing in a low temperature.

Cell Nucleolus↗
PubMed1980

Mitotic division of oligodendrocytes which have begun myelination.

Examination of spinal cords of 5 days old mice showed a number of examples of oligodendrocytes, in various phases of mitosis, which remained in contact with the axons which they were myelinating. Cells in prophases had thick processes between the perikaryon and the myelinating axons but as mitosis proceeded the oligodendrocyte processes became thin and spider-like, probably due to the extrusion of cytoplasm from the processes into the perikaryon. Mitotic astrocytes were also present.

Animals↗
PubMed1981

[Mitotic activity and chromosome aberrations in regenerating rat liver following x-ray irradiation].

Changes in the mitotic index (MI), the ratio of the metaphase to prophase number (M/P) and the chromosome aberration frequency in the regenerating rat liver were followed after single irradiation with exposures 77.4; 154.8 and 258 mC/kg (300, 600, 1000 R). The animals were partially hepatectomized immediately after irradiation and from the 18th hour to the 21st day after the treatment they were tested simultaneously with non-irradiated control animals. Irradiation resulted in approximately 6-hour delay in initiation of the mitotic activity in the regenerating liver. The inhibition extent depended on the magnitude of the exposure. A single exposure 77.4 mC/kg caused a 15% decrease in the mitotic activity, exposures 154.8 mC/kg and 258 mC/kg a 39% and 76% decrease, respectively, compared with control animals. M/P ratio in the regenerating liver in control and irradiated animals (77.4 and 154.8 mC/kg) manifested cyclic changes during the first 3 days. M/P values were about the highest level in irradiated animals depending on the exposure. postmetaphase figures in animals exposed to 77.4 mC/kg were aberrant in 50%. In animals exposed to 154.8 and 258 mC/kg, the percentage of chromosome aberrations ranged within 80-100%.

Animals↗
PubMed1993

[Antibodies against Escherichia coli RecA protein reveal two nuclear proteins in bovine spermatocytes which interact with synaptonemal complex structures of meiotic chromosomes of various eukaryotic organisms].

Three RecA-like proteins were detected in bovine meiotic cells using antibodies against Escherichia coli RecA protein. After isolation and purification of these RecA-like proteins their molecular weights appeared to be equal to 37, 70 and 130 kD. The 37 kD protein accompanies all the stages of spermatogenesis up to the stage of mature spermatozoa. The 70 kD protein is detectable only in nuclei of cells at the stage of prophase I of meiotic division. These RecA-like proteins are involved in the formation of structural elements of the synaptonemal complex (SC) and are detected in the SC composition in meiotic cells not only of mammals but also of plants and insects, which suggests the evolutionary conservative character of these proteins.

Animals↗
PubMed1977

Comparative ultrastructural morphometric studies of micromyeloblastoid and lymphoblastoid paramyeloblasts.

One hundred lymphoblastoid and one hundred micromyeloblastoid paramyeloblasts, isolated from peripheral blood of untreated leukaemia patients, were studied by electron microscopic morphometry. Considerable differences are to be found between the micromyeloblastoid and lymphoblastoid paramyeloblasts as regards the size of the nucleolar "apparatus", both in the absolute average values and in the index showing the ratio of the nucleolous of the remaining nuclear surface (4.76% for myeloblastoid and 9.96% for lymphoblastoid paramyeloblasts). The central heterochromatin (scattered), which is discussed to be essential for the detection of an early prophase, was found in 3% of the myeloblastoid cells and in 14% of lymphoblastoid ones. The effect of cytostatic therapy is discussed by taking these data into consideration.

Cell Nucleolus↗