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Showing papers on "Metaphase published in 1976"


Journal ArticleDOI
TL;DR: Human metaphase chromosomes showed a small longitudinal differentiation in CMA fluorescence, which was essentially the reverse of the banding pattern obtained with AMD/DAPI double-staining, but of lower contrast.
Abstract: Two DNA binding guanine-specific antibiotics, chromomycin A3 (CMA) and the closely related mithramycin (MM), were used as chromosome fluorescent dyes. Root-tip metaphase chromosomes of three plant species and human metaphase chromosomes were sequentially stained with CMA or MM and the DNA binding AT-specific fluorochrome 4'-6-diamidino-2-phenylindole (DAPI). In some cases a non-fluorescent counterstain was used as contrasting agent: methyl green in conjunction with CMA, and actinomycin D (AMD) in combination with DAPI.--In all three plant species, Vicia faba, Scilla siberica, and Ornithogalum caudatum, the nucleolus organiser regions and/or associated heterochromatin displayed very bright fluorescence with CMA and MM and, in general, heterochromatic segments (C-bands) which were bright with CMA and MM were pale with DAPI whereas segments which were dim with CMA and MM displayed very bright fluorescence with DAPI.--Human metaphase chromosomes showed a small longitudinal differentiation in CMA fluorescence, which was essentially the reverse of the banding pattern obtained with AMD/DAPI double-staining, but of lower contrast. The cma-banding pattern appears to be similar to the pattern found by R-banding procedures.

908 citations


Journal ArticleDOI
TL;DR: In this paper, differential staining techniques based on the incorporation of bromodeoxyuridine (BUdR) into DNA permits the identification of metaphase cells which have replicated once, twice, and three or more times.

217 citations


Journal ArticleDOI
TL;DR: It is suggested that chromosome elimination in Hordeum hybrids may be caused by a disturbed control of protein metablism in hybrid seeds and perhaps H. bulbosum chromosomes are selectively eliminated because they are less efficient than H. vulgare chromosomes at forming normal attachments to spindle protein.
Abstract: Seed development at 20±1° C in continuous light was studied during the first 5 days after pollination in diploid Hordeum vulgare, diploid H. bulbosum and the cross, H. vulgare x H. bulbosum, where H. bulbosum chromosomes were eliminated. Developing seeds were fixed and stained at known intervals after pollination and the embryo sac contents dissected out for cytological examination. — In all cases, the pattern of development was similar to that previously described for the Triticeae. After intraspecific pollination, the rate of endosperm and embryo development was significantly faster in H. vulgare than in H. bulbosum. In hybrid tissues, the rate was intermediate, but often much nearer to that of H. vulgare at first. Elimination of H. bulbosum chromosomes occurred only during endosperm and embryo mitoses. Usually, 0–3 chromosomes were lost at any one division but up to 7 were lost at some. Elimination, which occurred as early as zygotic anaphase, was nearly or quite complete in all dividing cells in both embryo and endosperm after 5 days. The mean number of chromosomes lost per nucleus per nuclear cycle was low at first but rose rapidly and stayed high for about a day in each tissue before falling quickly. The rate of elimination in each tissue was maximal when that tissue first synthesized significant amounts of new cytoplasm (day 2 after pollination in the endosperm and day 3 in the embryo). At mitosis, chromosomes being eliminated differed from others only in failing to congress at metaphase or to reach a pole at anaphase or both. — It is noted that in several widely different examples where either haploids are produced when only hybrids are expected, or where chromosomes of one species are preferentially eliminated from hybrid cells, nucleolar activity was suppressed in chromosomes of the genome which was selectively or preferentially eliminated. Consequently, it is suggested that chromosome elimination in Hordeum hybrids may be caused by a disturbed control of protein metablism in hybrid seeds and perhaps H. bulbosum chromosomes are selectively eliminated because they are less efficient than H. vulgare chromosomes at forming normal attachments to spindle protein.

155 citations


Journal ArticleDOI
TL;DR: Both in vivo and in vitro experiments show that griseofulvin, like other c-mitotic drugs, acts at the level of tubulin polymerization and that its effects are concentration dependent.

146 citations


Journal ArticleDOI
TL;DR: The combination of centromere staining asymmetry and sister chromatid differentiation at metaphase permits unambiguous determination of the number of replications in BrdU and dT (deoxythymidine) undergone by individual cells.
Abstract: BrdU (5-bromodeoxyuridine)-33258 Hoechst methods have been adapted for in vivo analyses of replication kinetics, sister chromatid differentiation and sister chromatid exchange (SCE) formation in mice. Sufficient in vivo BrdU substitution for cytological detection was effected with multiple intraperitoneal injections of the analogue. The combination of centromere staining asymmetry and sister chromatid differentiation at metaphase permits unambiguous determination of the number of replications in BrdU and dT (deoxythymidine) undergone by individual cells. Late-replicating regions in marrow and spermatogonial chromosomes are highlighted by bright fluorescence after sequential incorporation of BrdU followed by dT during a single DNA synthesis period. SCEs are analyzed in marrow and spermatogonial metaphases after successive complete cycles of BrdU and dT incorporation. Significant induction of SCE was observed with both mitomycin C and cyclophosphamide; the latter drug requires host-mediated activation to be effective. In meiotic metaphase cells harvested two weeks after BrdU incorporation, satellite DNA asymmetry, sister chromatid differentiation and SCE could be detected in a few chromosomes, most frequently the X and the Y.

114 citations


Journal ArticleDOI
TL;DR: Nucleolus organizer regions were detected by the Ag-AS silver method in fixed metaphase chromosomes from human and primates in each case the sites which have been shown by in situ hybridization to contain the ribosomal RNA genes.
Abstract: Nucleolus organizer regions were detected by the Ag-AS silver method in fixed metaphase chromosomes from human and primates. In the human, silver was deposited in the secondary constriction of a maximum of five pairs of acrocentric chromosomes: 13, 14, 15, 21 and 22. The chimpanzee also had five pairs of acrocentric chromosomes stained, corresponding to human numbers 13, 14, 18, 21 and 22. A gibbon had a single pair of chromosomes with a secondary constriction, which corresponded to the nucleolus organizer region. In each case the Ag-AS method detected the sites which have been shown by in situ hybridization to contain the ribosomal RNA genes. An orangutan had eight pairs of acrocentric chromosomes stained with Ag-AS, probably corresponding to human numbers 13, 14, 15, 18, 21 and 22, plus two others. Two gorillas had silver stain over two pairs of small acrocentric chromosomes and at the telomere of one chromosome 1. The larger gorilla acrocentric chromosomes had no silver stain although they all had secondary constrictions and entered into satellite associations.

104 citations


Journal ArticleDOI
TL;DR: Various aspects of the spindle and NAOs appear to be evolutionary intermediates between Ascomycetes and higher Basidiomycete, thus supporting the theory of Basidiologycete evolution from the former group and demonstrating an encouraging correlation between mitotic characteristics and other phylogenetic markers.
Abstract: Aspects of the ultrastructure of mitotic nuclei of the fungus Uromyces phaseoli var. vignae are described from both intercellular hyphae in the cowpea host and infection structures induced to differentiate in vitro. The interphase nucleus-associated organelle (NAO) consists of two trilamellar acircular disks connceted by an osmiophilic bar. The intranuclear spindle develops between these disks when they separate. The spindle contains pole to pole, interdigitating, chromosomal, and fragmentary microtubules arranged to form a central bundle along the surface of which lie the metaphase chromosomes. No metaphase plate is found. There are up to three microtubules per kinetochore and approximately 14 chromosomes on the haploid spindle. Telophase elongation appears to involve extension of pole to pole microtubules with no evidence for the remaining presence of interdigitating microtubules. Concomitantly, numerous cytoplasmic microtubules develop from each NAO disk where few or none are present in other phases. Reformation of the interphase NAO involves the formation of a sausage-shaped intermediate at late telophase. The nuclear envelope remains intact and the nucleolus persists throughtout division. Various aspects of the spindle and NAOs appear to be evolutionary intermediates between Ascomycetes and higher Basidiomycetes, thus supporting the theory of Basidiomycete evolution from the former group and demonstrating an encouraging correlation between mitotic characteristics and other phylogenetic markers.

92 citations


Journal ArticleDOI
TL;DR: A technique is described for labeling mammalian chromosomes in vivo with BUdR, which shows that metaphase cells that have gone through two or three cycles of DNA synthesis reveal characteristic differential chromatid fluorescence after staining with Hoechst dye.

74 citations


Journal ArticleDOI
TL;DR: Indirect antibody techniques have been used to monitor deoxyribonucleic acid synthesis in nuclei; anti-BrdU treatment was followed by goat anti-rabbit immunoglobulin G labeled with either fluorescein or horseradish peroxidase.
Abstract: Antibodies to 5-bromodeoxyuridine (BrdU) or iododeoxyuridine may be used to identify cells or regions of chromosomes in which de novo deoxyribonucleic acid synthesis has occurred. The antibodies to BrdU were produced in rabbits by injection of the antigen, a conjugate between bovine serum albumin and bromouridine (BrU), or iodouridine. Specific antibodies were produced by affinity chromatography on AH-Sepharose 4B to which had been coupled BrU. Anti-BrU cross-reacts with iodeodeoxyuridine. Indirect antibody techniques have been used to monitor deoxyribonucleic acid synthesis in nuclei; anti-BrdU treatment was followed by goat anti-rabbit immunoglobulin G labeled with either fluorescein or horseradish peroxidase. By use of these techniques, labeling indices were determined in cell cultures which had been pulsed with 3H-BrdU. The immunologic technique compared favorably with the autoradiographic methods performed concurrently on the same cultures. Metaphase chromosomes from synchronous CHO cell which had been pulse labled with BrdU at different time intervals during S phase were subjected to these immunologic procedures. Chromosome banding was observed with both the fluoresence and peroxidase methods. Chromosomes from cells not containing BrdU did not exhibit banding.

62 citations


Journal ArticleDOI
TL;DR: Methodology is described which yields three-way Giemsa differentiation (light-medium-dark) in human metaphase chromosomes exposed to 5-bromode-oxyuridine for 3 DNA synthetic periods by means of which all of the sister chromatid exchanges (SCEs) occurring during S1, S2 and S3 can be accurately counted and distinguished from one another.
Abstract: In this paper methodology is described which yields three-way Giemsa differentiation (light-medium-dark) in human metaphase chromosomes exposed to 5-bromode-oxyuridine (BrdU) for 3 DNA synthetic periods (or exposed for 2 DNA synthetic periods and removed from exposure for the third) by means of which all of the sister chromatid exchanges (SCEs) occurring during (or shortly after) S1, S2 and S3 can be accurately counted and distinguished from one another. Using these methods it has been demonstrated that approximately twice as many SCEs occur during the first S-period in the presence of the drug (labeling= B1T0×T0B1)1 as occur during the second S-period (labeling=B2B1× T0B2)1. The three-way differentiation pattern is thought to result from a stepwise decrease in the amount of BrdU incorporated during the first, second and third DNA synthetic periods. These methods can also be used to differentiate between unlabeled (T2T0) and unifilarly labeled (B1T2) sister chromatids and are potentially useful in the detection of sub-chromatid exchanges (none were detected).

58 citations


Journal ArticleDOI
01 Dec 1976-Cell
TL;DR: The concept that clusters of similar purine or pyrimidine residues exist along the arms of condensed metaphase chromosomes, with the possibility that concentrations of 5-methylcytosine residues might have been enhanced at the surface of the chromosomes during the condensation process, is supported.

Journal ArticleDOI
TL;DR: Two linked human genes which code for the expression of cytosol thymidine kinase and galactokinase have been cotransferred via purified metaphase chromosomes from the human lymphoblastoid cell line WI-L2a, into mouse L-cells and no human chromosome or chromosomal fragment could be detected by karyotype analyses.
Abstract: Two linked human genes which code for the expression of cytosol thymidine kinase (ATP:thymidine 5'-phosphotransferase, EC 2.7.1.75) and galactokinase (ATP:D-galactose 1-phosphotransferase, EC 2.7.1.6) have been cotransferred via purified metaphase chromosomes from the human lymphoblastoid cell line WI-L2a, into mouse L-cells [B82 and LM(TK-)]. Both genes have previously been shown to be closely linked on the human chromosome E17, band q21-22. Coexpression of both human enzyme markers was detected in two out of eight gene transfer clones, whilst the remaining six clones contained only human cytosol thymidine kinase, as shown by electrophoretic techniques. A further 23 human enzyme markers corresponding to 15 different human chromosomes were found to be absent in these gene transfer clones. No human chromosome or chromosomal fragment could be detected by karyotype analyses. Some of the gene transfer clones rapidly lost the transferred donor material when grown in nonselective medium, whereas others expressed a stable phenotype under these conditions. Prolonged maintenance in selective medium favors the survival of gene transfer cells expressing a stable phenotype. Possibly these cells harbor the donor genes integrated into a recipient chromosome.

Journal ArticleDOI
TL;DR: An active role played by a tubulin‐dynein system in mitosis is suggested, together with the finding that the chromosome motion in the isolated MAs was completely inhibited by anti‐dynesin serum, but not with the anti‐myosin serum.
Abstract: Detection and localization of dynein in cleaving sea urchin eggs were attempted using antidynein serum (prepared against a tryptic fragment of dynein, Fragment A, of sea urchin sperm flagella) and fluorescein conjugated goat antiserum to rabbit γ-globulin. In both unfertilized and newly fertilized eggs, fluorescence was distributed rather uniformly within the cells but was absent from the nuclei. At prophase, intense fluorescence was observed on both sides of nucleus, suggesting accumulation of dynein in developing asters. From metaphase to anaphase, the whole mitotic apparatus (MA) was stained with the exceptions of the chromosomes and pole areas. Fluorescence then again became dispersed within the eggs. Throughout the mitotic process and cytokinesis, the egg cortex including the cleavage furrow was stained intensely, presumably reflecting the presence of dynein in this region. Similar distributions of fluorescence were obtained with the isolated MAs. Neither non-immune serum nor the antiserum to which Fragment A was absorbed stained the eggs. Little staining was obtained with the antiserum against starfish egg myosin. The results, together with the finding that the chromosome motion in the isolated MAs was completely inhibited by anti-dynein serum, but not with the anti-myosin serum, suggest an active role played by a tubulin-dynein system in mitosis.

Journal ArticleDOI
TL;DR: The results prove that the injection of detergent‐treated sperm employed here provides an excellent means of studying the cytoplasmic state that regulates nuclear behavior.
Abstract: Spermatozoa of Bufo bufo japonicus were briefly treated with Triton X-100 to remove their plasma membrane, and were injected into oocytes at various stages of maturation division. All the sperm injected into mature coelomic eggs transformed into pronuclei and synthesized DNA, as a normally fertilizing sperm does. The sperm injected into oocytes at the germinal vesicle (GV) stage did not show any change as long as the GV remained intact. In the oocytes which were induced to mature by progesterone, the injected sperm displayed characteristic features in synchrony with those of the resident female nucleus. These included the formation of several sperm-derived chromosomes in association with multipolar spindles in the oocytes from the stage of the germinal vesicle breakdown to the first polar spindle; the appearance of swollen, vesicular nuclei without concomitant DNA synthesis in those at the stage of the first polar body emission; and the reappearance of the condensed chromosomes with giant spindles in those at the stage of the second meiotic metaphase. Pricking of these last oocytes induced the formation of several male pronuclei and DNA synthesis. These results prove that the injection of detergent-treated sperm employed here provides an excellent means of studying the cytoplasmic state that regulates nuclear behavior.

Journal ArticleDOI
TL;DR: Laser UV microirradiation of Chinese hamster interphase cells combined with caffeine post-treatment produced different patterns of chromosome damage in mitosis following irradiation of a small area of the nucleus that may be classified in three categories: I) intact metaphase figures, II) chromosome damage confined to a small Area of the metaphase spread, III) mitotic figures with damage on all chromosomes.
Abstract: Laser UV microirradiation of Chinese hamster interphase cells combined with caffeine post-treatment produced different patterns of chromosome damage in mitosis following irradiation of a small area of the nucleus that may be classified in three categories: I) intact metaphase figures, II) chromosome damage confined to a small area of the metaphase spread, III) mitotic figures with damage on all chromosomes. Category III might be the consequence of a non-localized distortion of nuclear metabolism. By contrast, category II may reflect localized DNA damage induced by microirradiation, which could not be efficiently repaired due to the effect of caffeine. If this interpretation is right, in metaphase figures of category II chromosome damage should occur only at the irradiation site. The effect might then be used to investigate neighbourhood relationships of individual chromosomes in the interphase nucleus.

Journal ArticleDOI
TL;DR: Monitoring of the cell cycle using autoradiographic techniques suggested that turmeric interfered with cell-cycle progression, and the spice turmeric arrested mitosis, altered chromosome morphology and interfered with nucleic acid synthesis.

Journal ArticleDOI
TL;DR: The results suggest that metaphase I oocyte cytoplasm stimulates synthesis of brain nuclear RNAs that are translated into proteins necessary for chromosome condensation, whereas metaphase II oocytes possess all the factors for chromosomes condensation.
Abstract: We studied the effects of actinomycin D, alpha-amanitin, puromycin, and cycloheximide on the cytoplasmic activity of maturing Rana pipiens oocytes that induces chromosome condensation in transplanted brain nuclei. Treatment of oocytes with each inhibitor suppressed the chromosome condensation induced by metaphase oocytes to varying degrees depending upon the dose of inhibitor, despite the fact that untreated metaphase I oocytes already possessed chromosome condensation activity (CCA). Treatment of brain nuclei before injection completely suppressed condensation at all doses used. Chromosome condensation induced by metaphase II oocyte cytoplasm, however, was insensitive to all the inhibitors, even when the brain nuclei were pretreated. Oocytes treated with alpha-amanitin throughout maturation induced chromosome condensation when tested at metaphase II. Removal of the oocyte chromosomes after the germinal vesicle (GV) broke down did not prevent the development of CCA, whereas removal of the entire GV before initiation of maturation deprived oocytes of CCA. The results suggest that metaphase I oocyte cytoplasm stimulates synthesis of brain nuclear RNAs that are translated into proteins necessary for chromosome condensation, whereas metaphase II oocytes possess all the factors for chromosome condensation. In both cases, GV nucleoplasm appears indispensable for the development of CCA, whereas immediate activity of the oocyte genome is not required.

Journal ArticleDOI
TL;DR: Cell cultures of a Chinese hamster cell line treated with CdSO4 in concentrations of between 10(-4) and 10(-8) mol/l for different time periods yielded a stathmokinetic effect and the mitotic index increased, mitoses were blocked in metaphase stage and "initial C-mitoses'' and "C-Mitoses'' were present.
Abstract: Cell cultures of a Chinese hamster cell line were treated with CdSO4 in concentrations of between 10(-4) and 10(-8) mol/l for different time periods. After a treatment of 16 h the mitotic index was reduced. Strong stickiness and pycnosis of chromosomes occurred at the highest concentrations. A treatment period of 3 h with concentrations of 10(-5) and 10(-4) mol/l without additional application of Colcemid and hypotonic solution yielded a stathmokinetic effect. The mitotic index increased, mitoses were blocked in metaphase stage and "initial C-mitoses'' and "C-mitoses'' were present. Structural chromosome aberrations were present in the recovery period of more than 12 h following a treatment of 1 h with 10(-4) mol/l CdSO4. The observed aberrations were mainly of the chromatid type.

Journal ArticleDOI
TL;DR: Gene transfer between two closely related mouse cell lines has been carried out, using as the vector a cell-free preparation of metaphase chromosomes and nuclei a mutationally altered hypoxanthine-guanine phosphoribosyltransferase.
Abstract: Gene transfer between two closely related mouse cell lines has been carried out, using as the vector a cell-free preparation of metaphase chromosomes and nuclei. Distinction between gene transferents and revertants of the recipient mutant phenotype was achieved by the use of a donor strain carrying a mutationally altered (8-azaguanine-resistant) hypoxanthine-guanine phosphoribosyltransferase (HPRTase; IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8). The transferred HPRTase gene is initially unstable; in nonselective medium, it is lost at a rate of about 0.1 per cell per generation. Stabilization occurs as a rare event, with a frequency on the order of 1 X 10(-5) per cell per generation. The unstable state can be maintained for at least 200 generations through serial passages of the transferent in selective medium. Under the conditions of cultivation used in these experiments, the unstable HPRTase-positive cells are eventually replaced by the stable HPRTase-positive cells in the population.

Journal ArticleDOI
TL;DR: Results suggest that the rate of the normal prometaphase increase in retardation and spindle size may be determined by factors other than the maximum rate of tubulin polymerization in the cell.
Abstract: Spindle assembly is studied in the eggs of the sea urchin Lytechinus variegatus by experimentally varying the amount of polymerizable tubulin within the egg. Aliquots of fertilized eggs from the same female are individually pulsed for 1-6 min with 1 X 10(-6) M Colcemid at least 20 min before first nuclear envelope breakdown. This treatment inactivates a portion of the cellular tubulin before the spindle is formed. Upon entering mitosis, treated eggs form functional spindles that are reduced in length and birefringent retardation but not width. With increased exposure to Colcemid, the length and retardation of the metaphase spindles are progressively reduced. Similar results are obtained by pulsing the eggs with Colcemid before fertilization, which demonstrates that the tubulin found in unfertilized sea urchin eggs is later used in spindle formation. Spindles, once assembled, are responsive to increases in the amount of polymerizable tubulin within the cell. Rapid increases in the amount of polymerizable tubulin within a Colcemid-treated cell can be experimentally effected by irradiating the cells with 366-nm light. This treatment photochemically inactivates the Colcemid, thereby freeing the tubulin to polymerize. Upon irradiation, the small prometaphase spindles of Colcemid-treated cells immediately increase in length and retardation. In these irradiated cells, spindle length and retardation increase as much as four times faster than they do during prometaphase for normal spindles. This suggests that the rate of the normal prometaphase increase in retardation and spindle size may be determined by factors other than the maximum rate of tubulin polymerization in the cell.

Journal ArticleDOI
Roger L. Blackman1
TL;DR: Somatic cell divisions, spermatogenesis, and the prophase stages of primary oocytes, are described for two species of birch aphid, Euceraphis betulae and E. punctipennis, and results are discussed in relation to previous work on aphid cytogenetics.
Abstract: Somatic cell divisions, spermatogenesis, and the prophase stages of primary oocytes, are described for two species of birch aphid, Euceraphis betulae (Koch) and E. punctipennis (Zetterstedt). Females of E. betulae have two autosome pairs, two pairs of X-chromosomes of different lengths, and two B-chromosomes. Females of E. punctipennis have the same number of X-chromosomes and B-chromosomes as E. betulae, but only a single pair of autosomes. The sex determination system is X1X20. E. punctipennis males sometimes have only one B-chromosome. In the spermatogenesis of E. betulae, pairing of homologous autosomes occurs in early prophase I, but no evidence was found of chiasmata or end-to-end alignment of homologues. Instead, homologues remain closely aligned in parallel as they condense into metaphase, and anaphase I separates the products of pairing in a strictly reductional manner. The two unpaired X-chromosomes and both B-chromosomes are stretched on the anaphase I spindle and all four pass into the larger secondary spermatocyte. The second division is equational. The B-chromosomes thus show accumulation in spermatogenesis, which must be compensated in some way by an elimination mechanism in oogenesis. Meiosis of E. punctipennis is highly anomalous. The two autosomes pair but separate again in early prophase I, then one homologue becomes heterochromatic and is apparently rejected from the late prophase nucleus. A single, equational maturation division follows. In female meiosis I, both species show highly characteristic diplotene figures with multiple chiasmata, the B-chromosomes remaining unpaired. These results are discussed in relation to previous work on aphid cytogenetics.

Journal ArticleDOI
TL;DR: The present work supports earlier views that only one chromosome is evident during the nuclear division of these organisms and indicates that the mitosis is completely different from that of the Dinophyceae with which theCryptophycesae were formerly linked.
Abstract: A detailed account of the ultrastructure of mitosis in a member of theCryptophyceae is given for the first time. The initial indication of mitosis is the duplication of the flagellar bases. The nucleus migrates towards the anterior of the cell and its envelope and nucleolus break down. The chromatin which at interphase is in the form of scattered clumps, condenses into a solid mass through which run narrow tunnels. Each tunnel allows the passage of one to four microtubules. At metaphase the dense plate of chromatin is situated on the equator and the spindle has a rectangular shape. Individual chromosomes cannot be recognized and no morphologically differentiated kinetochores have been observed. The flagella remain functional, their bases stay at the anterior side of the nucleus and do not move to the poles. At anaphase two plates of chromatin separate and these move apart until they come to lie against the ER sheath surrounding the chloroplasts. The new nuclear envelope starts to form on the opposite side of the daughter nucleus. Cytokinesis may commence early in mitosis and consists of a constriction of the parent cell, starting from the posterior end, followed by separation of the two daughters. The present work supports earlier views that only one chromosome is evident during the nuclear division of these organisms. The mitosis is completely different from that of theDinophyceae with which theCryptophyceae were formerly linked.

Journal ArticleDOI
26 Aug 1976-Nature
TL;DR: It is observed that mouse C1300 neuroblastoma cells reversibly arrested in G0 by serum limitation7 are unable to re-enter the cell cycle in the presence of colchicine.
Abstract: CELLS in G1 or G0 usually progress through the cell cycle and stop in metaphase when colchicine is added to the growth medium1–6. I have observed, however, using two different experimental techniques, that mouse C1300 neuroblastoma cells reversibly arrested in G0 by serum limitation7 are unable to re-enter the cell cycle in the presence of colchicine.

Journal ArticleDOI
TL;DR: Whether the chromosome can still extend during the M-G1 transition even if the F1 histone is maintained in the hyperphosphorylated form is asked and an apparently normal extension of the chromosomal material is observed.
Abstract: Treatment of metaphase HTC cells with ZnCl2 inhibits histone phosphatase activity and leads to an increase in the hyperphosphorylated forms of the lysine-rich (F1) histone. Under normal conditions a massive phosphatase activity is triggered as the cells shift from M into G1 phase. In the presence of ZnCl2 this activity is abolished and thehyperphosphorylated form of F1 persists intact into G1. We have asked the simple question of whether the chromosome can still extend during the M-G1 transition even if the F1 histone is maintained in the hyperphosphorylated form. We observe an apparently normal extension os the chromosomal material under these conditions, though it is evident that high levels of ZnCl2 have rather substantial effects on other cell functions.

Journal ArticleDOI
TL;DR: Comparison of the early and limit digestion products of metaphase chromosomes with those obtained from interphase nuclei indicates that although significant morphologic changes occur within the chromatin fiber during mitosis, the basic subunit structure of the Chromatin fiber is retained by the mitotic chromosome.
Abstract: Previous studies of the structure of metaphase chromosomes have relied heavily on electron micrography and have revealed the existence of a 10-nm unit fiber that is thought to generate the native 23-30-nm fiber by higher order folding. The structural relationship of these metaphase fibers to the interphase fiber remains obscure. Recent studies on the digestion of interphase chromatin have revealed the existence of a regularly repeating subunit of DNA and histone, the nucleosome that generates the appearance of 10-nm beads connected by a short fiber of DNA seen on electron micrographs. It was therefore of interest to probe the structure of the metaphase chromosome for the presence of nucleosomal subunits. To this end metaphase chromosomes were prepared from colchicine-arrested cultures of mouse L-cells and were subjected to digestion with stayphylococcal nuclease. Comparison of the early and limit digestion products of metaphase chromosomes with those obtained from interphase nuclei indicates that although significant morphologic changes occur within the chromatin fiber during mitosis, the basic subunit structure of the chromatin fiber is retained by the mitotic chromosome.

Journal ArticleDOI
TL;DR: A CHO-cell mutant was isolated which has a defect in cytokinesis as the basis of its temperature-sensitive phenotype and behaved as recessive in tetraploid cell hybrids constructed by fusing the mutant with a CHO strain which was wild-type with respect to temperature sensitivity.
Abstract: In a selection procedure designed to enrich for temperature-sensitive mutant cells blocked in mitosis a CHO-cell mutant was isolated which has a defect in cytokinesis as the basis of its temperature-sensitive phenotype. Cultures of the mutant had an abnormally high percentage (ie, 34%) of polyploid cells at the permissive temperature of 34°C and showed further increased frequencies of polyploidy as well as many multinucleated cells at 38.5° and 39.5°. When the mutant cells were synchronized in metaphase by Colcemid arrest and then placed into fresh medium at nonpermissive temperature, they did not divide although the completion of mitosis appeared cytologically normal. Ultrastructural examination by electron microscopy of such synchronized cells at telophase revealed no specific defects in cellular components other than failure of development of a normal midbody. The sensitivity of the mutant to cytochalasin B and to Colcemid was the same as for wild-type cells. This mutation behaved as recessive in tetraploid cell hybrids constructed by fusing the mutant with a CHO strain which was wild-type with respect to temperature sensitivity.

Journal ArticleDOI
TL;DR: Mitotic metaphase chromosomes of cold-treated Triturus cristatus and spermatogonia show spiral structure throughout the metaphase chromatids; the packing of chromatin fibrils is much tighter in theconstricted regions than elsewhere, and the gyres in the constricted regions are narrower and of shorter pitch.
Abstract: Mitotic metaphase chromosomes of cold-treated Triturus cristatus show a characteristic pattern of constrictions, most of which lie close, though not immediately adjacent, to the centromeres. The chromatin in these cold-induced constrictions stains intensely with Giemsa. Cold-treated spermatogonia show spiral structure throughout the metaphase chromatids; the packing of chromatin fibrils is much tighter in the constricted regions than elsewhere, and the gyres in the constricted regions are narrower and of shorter pitch.

Journal ArticleDOI
TL;DR: A late replicating X or Y chromosome can be detected by Hoechst staining and fluorescence microscopy in a large proportion of female or male mouse embryo cells, respectively, which have been cultured in medium containing 5-bromodeoxyuridine for part of one DNA synthesis period.

Journal ArticleDOI
TL;DR: The experiments presented addressed the question, are the nucleosomes characteristic of interphase also present at mitosis, and answered the question whether or not the histones are arranged in the same supramolecular structure.

Journal ArticleDOI
TL;DR: Cells of the Chinese hamster strain C-125 were treated for different time intervals with H 33258, a bibenzimidazole derivative and the same compound was used to stain fixed cells of the same strain.
Abstract: Cells of the Chinese hamster strain C-125 were treated for different time intervals with H 33258, a bibenzimidazole derivative. The same compound was used to stain fixed cells of the same strain. — H 33258 induced in cells in culture specific areas of reduced spiralization on the metaphase chromosomes of some cells. These probably correspond to DNA segments rich in A-T bases interspersed along the chromosomes. Probably H 33258 acts during S period of cell cycle. — The banding obtained by staining with H 33258 is similar to that induced by quinacrine dihydrochloride but shows a better resolution.