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Showing papers on "Metaphase published in 1974"


Journal ArticleDOI
TL;DR: It was concluded that the probability of a chromosome being involved in the formation of a common nucleolus is not a simple function of its rDNA content and other possible factors are considered.
Abstract: 3H-rRNA obtained from Xenopus laevis tissue cultured cells, or a 3H-cRNA made from Xenopus ribosomal DNA, was used for heterologous in situ hybridisation with human lymphocyte metaphase chromosomes. Prior to hybridisation, chromosome spreads were stained with Quinacrine and selected cells showing good Q-banding photographed; the same cells were then rephotographed after autoradiography and pairs of photographs for each cell were used to make dual karyotypes. The chromosomes within each karyotype were divided into equal sized segments (approx. 0.7 μ), with a fixed number of segments for each chromosome type. The distribution of silver grains between segments showed that the 3H-RNAs hybridised specifically to the nucleolar organising regions of the D and G group chromosomes with no other sites of localised labelling in the complement. Control experiments showed no localisation, with insignificant labelling, when metaphase spreads were incubated in a mixture containing Xenopus3H-rRNA and competing cold human (HeLa) rRNA. Filter hybridisation experiments on isolated human DNA showed that the Xenopus derived 3H-RNAs hybridised to a fraction of human DNA which was on the heavy side of the main DNA peak and that these RNAs were competed out in the presence of excess cold human rRNA, confirming the specificity of the heterologous hybridisation. In situ hybridisation experiments were also carried out on cells from individuals with one chromosome pair showing heteromorphism for either a very long stalk (nucleolar constriction) subtending a satellite, or a large satellite. It was shown that the chromosome with the large stalk hybridised four times as much 3H-rRNA as its homologue, whereas differences in the sizes of the subtended satellites did not materially affect hybridisation levels indicating that rDNA is located in the stalks and not the satellites. The amount of 3H-rRNA hybridised differs between chromosomes and individuals; these differences are heritable and rDNA can be detected by in situ hybridisation in all three chromosomes number 21 in cells from Down's patients and in translocated chromosomes conta.ining a nucleolar constriction. Different D and G group chromosomes which hybridised equal amounts of 3H-rRNA participated in rosette associations at metaphase in a random fashion in some individuals and in a non-random fashion in others. In all individuals studied chromosomes with large amounts of rDNA were not found to be preferentially involved in association. It was therefore concluded that the probability of a chromosome being involved in the formation of a common nucleolus is not a simple function of its rDNA content and other possible factors are considered.

273 citations


Book ChapterDOI
TL;DR: This chapter discusses the nature of interactions between oocyte and granulose cells and the triggering effect of luteinizing hormone (LH), and its progress to the metaphase of the second meiotic division refer to as ovum maturation.
Abstract: Publisher Summary This chapter discusses the nature of interactions between oocyte and granulose cells and the triggering effect of luteinizing hormone (LH). The mammalian oocyte embarks on its first reduction division in prenatal life or during the early postnatal period. This division has a protracted and complicated prophase. Just before or shortly after birth, depending on the species, the germ cell reaches the stage of diplotene. By this time, the oocyte has doubled its DNA complement, the chromosomes have condensed, and homologous chromosomes have become paired and are linked by chiasmata permitting the exchange of paternal and maternal genetic information. In murid rodents, the chromosomes decondense and resume their transcriptive activity. In the adult, during each estrous cycle, a number of oocytes characteristic of the species complete their first reduction division, resulting in the abstriction of the first polar body shortly before ovulation. This resumption of meiosis and its progress to the metaphase of the second meiotic division refer to as ovum maturation. Completion of the second meiotic division, with extrusion of a second polar body, occurs only upon penetration of the oocyte by a spermatozoon.

236 citations


Journal ArticleDOI
TL;DR: It is concluded that f1 phosphorylation is one of the earliest biochemical events associated with conversion of nonproliferating cells to proliferating cells occurring on old f1 before synthesis of new f1 during the S phase.
Abstract: Preparative polyacrylamide gel electrophoresis was used to examine histone phosphorylation in synchronized Chinese hamster cells (line CHO). Results showed that histone f1 phosphorylation, absent in G1-arrested and early G1-traversing cells, commences 2 h before entry of traversing cells into the S phase. It is concluded that f1 phosphorylation is one of the earliest biochemical events associated with conversion of nonproliferating cells to proliferating cells occurring on old f1 before synthesis of new f1 during the S phase. Results also showed that f3 and a subfraction of f1 were rapidly phosphorylated only during the time when cells were crossing the G2/M boundary and traversing prophase. Since these phosphorylation events do not occur in G1, S, or G2 and are reduced greatly in metaphase, it is concluded that these two specific phosphorylation events are involved with condensation of interphase chromatin into mitotic chromosomes. This conclusion is supported by loss of prelabeled 32PO4 from those specific histone fractions during transition of metaphase cells into interphase G1 cells. A model of the relationship of histone phosphorylation to the cell cycle is presented which suggests involvement of f1 phosphorylation in chromatin structural changes associated with a continuous interphase "chromosome cycle" which culminates at mitosis with an f3 and f1 phosphorylation-mediated chromosome condensation.

213 citations


Journal ArticleDOI
05 Jul 1974-Science
TL;DR: The bromodeoxyuridine; sensitivity of 33258 Hoechst fluorescence allows microfluorometric analysis of sister chromatid exchanges in human metaphase chromosomes, which appears to occur predominantly in interband regions, as defined by quinacrine fluorescence, or very near band-interband junctions.
Abstract: The bromodeoxyuridine; sensitivity of 33258 Hoechst fluorescence allows microfluorometric analysis of sister chromatid exchanges in human metaphase chromosomes. The frequency of sister chromatid exchanges among chromosomes correlates with chromosome length. Exchanges appear to occur predominantly in interband regions, as defined by quinacrine fluorescence, or very near band-interband junctions. A few regions are involved unusually frequently.

190 citations


Journal ArticleDOI
TL;DR: The results indicate that the PCC method has a greater senstivity in the detection of induced chromosome damage than the standard method of scoring metaphase chromosomes.
Abstract: A new method is described to visualize chromosome damage in interphase cells immediately after exposure to mutagenic agents This method involves the fusion of treated interphase cells with untreated mitotic cells which results in the induction of premature chromosome condensation (PCC) Chinese hamster ovary (CHO) cells were treated with X-rays and chromosome aberrations were scored in G2-PCC and the mitotic chromosomes The incidence of aberrations was significantly higher in PCC than that observed in the mitotic chromosomes of the treated cells Post-irradiation incubation for I h before fusion allowed the repair of some of the chromosome damage Data are also presented which indicate that the extent of radiation damage visualized in PCC is inversely proportional to the degree of chromosome condensation These results indicate that the PCC method has a greater senstivity in the detection of induced chromosome damage than the standard method of scoring metaphase chromosomes

153 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that the final plane of division is not determined by the orientation of the spindle at metaphase, but instead is established during late anaphase-telophase as a result of directed reorientation movements of spindle-phragmoplast and associated daughter nuclei.
Abstract: Division of the guard mother cell (GMC) in Allium cotyledons has been examined in epidermal slices viewed with Nomarski optics and electron microscopy Special attention has been directed towards elucidating the process by which the dividing cell determines its plane of division In normal development, the cell plate formed during GMC division ultimately lies along the longitudinal axis of the cotyledon, in contrast to the transverse planes formed in other epidermal divisions Our observations reveal that the final plane of division is not determined by the orientation of the spindle at metaphase but instead is established during late anaphase-telophase as a result of directed reorientation movements of the spindle-phragmoplast and associated daughter nuclei The metaphase plate may lie at an oblique angle, even as great as 90°, from the final plane of the plate Thus, daughter chromosomes separate into opposite corners of the cell During late anaphase-telophase, movement of the spindle is activated; the daughter nuclei move along the sides of the cell while the interzone rotates Movement continues until daughter nuclei reach positions opposite each other along the sides of the cell and the midzone or cell plate is positioned in the longitudinal orientation Movement requires 15–20 minutes for completion, is highly directional, and does not overshoot the correct alignment Following movement cytokinesis proceeds to completion forming two young guard cells Possible mechanisms for reorientation are discussed, including one that suggests that interzone microtubules may interact with a cortical site on the plasmalemma adjacent to the end and paradermal walls Such a site may be related to and governed by the same properties which controlled the prior formation of the preprophase band of microtubules in these cells

132 citations


Journal ArticleDOI
TL;DR: To discover the role of the elongation of the micronucleus, called crescent formation, autoradiographic analysis of RNA and DNA synthesis were undertaken using [3H]uridine and [3 H]thymidine.
Abstract: SYNOPSIS Micronuclear changes of variety 1 of Tetrahymena pyriformis during meiotic prophase have been observed by the light microscope. Morphologic changes in the micronucleus are divided into 6 stages. In stage I, chromatin begins to polarize; in stage II, the micronucleus becomes spindle shaped; and in stage III, one end of the micronucleus protrudes to form a “neck.” In stage IV, where the micronucleus elongates to maximal length, the whole micronucleus consists of 2 chromatin threads pairing longitudinally. One thread probably contains one genome. In stage V, the elongated thread becomes shorter and thicker. Finally, in stage VI, separate chromosomes appear and enter into metaphase. To discover the role of the elongation of the micronucleus, called crescent formation, autoradiographic analysis of RNA and DNA synthesis were undertaken using [3H]uridine and [3H]thymidine. Pulse label and chase experiments show that the crescent in stages II and III is actively synthesizing RNA. Though no remarkable DNA synthesis was observed during meiosis, a small amount of DNA synthesis occurred during the 1st and 2nd prezygotic divisions.

130 citations


Book ChapterDOI
TL;DR: The exchange theory explained in the chapter starts from the interpretation of radiation-induced chromatid aberrations as these are seen at mitosis, and is found on two direct observations.
Abstract: Publisher Summary This chapter discusses the breakage-and-reunion theory and the exchange theory for chromosomal aberrations induced by ionizing radiations. If a population of proliferating cells is exposed to ionizing radiation, three types of structural chromosome change appear as these cells reach their next mitosis; the change type depends on which part of the cell cycle received the radiation dose. These types are called subchromatid, chromatid, and chromosome changes. Aberrations in mitoses of cells, which were in prophase when irradiated, are of apparently subchromatid type, and these are clearly demonstrable in cells fixed at anaphase. Aberrations in mitoses of cells, which are in S or G2 stage of interphase when irradiated, are of the chromatid type. Aberrations in mitoses of cells, which are in Gl stage of interphase when irradiated, are of the chromosome type. Chromatid aberrations have two typical appearances at metaphase; some appear to be simple breaks while others are reciprocal chromatid exchanges. The exchange theory explained in the chapter starts from the interpretation of radiation-induced chromatid aberrations as these are seen at mitosis, and is found on two direct observations.

109 citations



Journal ArticleDOI
TL;DR: Pregnant guinea-pigs exposed to an environmental temperature of 42·0–42·5 °C for 1 h on day 21 of gestation and their embryos were removed at periods from 45 min of heating to 48 h following exposure, indicating blocks to the cell generation cycle before prophase and in metaphase.
Abstract: Pregnant guinea-pigs were exposed to an environmental temperature of 42·0–42·5 °C for 1 h on day 21 of gestation. Their embryos were removed at periods from 45 min of heating to 48 h following exposure. Histological preparations of embryos showed clumping of nuclear chromatin and subsequent death of cells which were at about the stage of mitosis. Affected cells were particularly numerous in the central nervous system. Further mitotic activity was inhibited for 6–8 h. Squash preparations of the telencephalon at 1 h after heating showed an increase from 3 to 86 % in the number of mitotic cells showing damage in the form of nuclear clumping; this number fell progressively to 30% by 24 h after heating. The proportion of cells in various stages of mitosis changed considerably at 1–8 h after heating, but had returned to pre-heating values by 24 h. The proportion of cells in prophase fell markedly, while the proportion of metaphase cells was doubled at 4 h after heating, indicating blocks to the cell generation cycle before prophase and in metaphase.

80 citations


Journal ArticleDOI
TL;DR: Embryonic oogonia as well as the preovulatory phase of oogenesis proved to be most sensitive for the induction of chromosomal aberrations, related to an additional induction of aneuploidies.
Abstract: The stage sensitivity in oogenesis of C 3 H mice was investigated by transplacental treatment of embryonic oogonia and oocytes at meiotic prophase I. After birth the stages of early and late dictyotene as well as the preovulatory and ovulatory phases were treated. Chromosome analysis was performed in unfertilized metaphase II-oocytes after induced ovulation [pregnant mare's serum (PMS) and human chorionic gonadotrophin (HCG)]. As test compounds both the folic acid antagonist amethopterin (M) and the alkylating agent cyclophosphamide (C) were used. Embryonic oogonia as well as the preovulatory phase of oogenesis proved to be most sensitive for the induction of chromosomal aberrations. The investigation with graded doses during the preovulatory stage demonstrated the dose-dependent frequency of the induced types of chromosomal abnormalities. The high sensitivity of these stages where chromosome segregation takes place, e.g. oogonia, preovulatory stage, seems to be related to an additional induction of aneuploidies.

Journal ArticleDOI
TL;DR: A method is described which, through the combined use of warm phosphate saline and a Giemsa-trypsin mixture, consistently produces G-bands in metaphase chromosomes of human leukocytes.
Abstract: SUMMARYA method is described which, through the combined use of warm phosphate saline and a Giemsa-trypsin mixture, consistently produces G-bands in metaphase chromosomes of human leukocytes.

Journal ArticleDOI
TL;DR: The effect of 5-bromodeoxyuridine on DNA synthesis has been studied in this article, where the authors show that the effect of the dye 33258 Hoechst when bound to chromosomes can be partially quenched by the incorporation of 5bromodesoxyURidine into chromosomal deoxyribonucleic acid.
Abstract: Fluorescence of the dye 33258 Hoechst, when bound to chromosomes, is partially quenched by the incorporation of 5-bromodeoxyuridine into chromosomal deoxyribonucleic acid (DNA). This effect allows microfluorometric analysis of DNA synthesis. Metaphase chromosomes from cultured human leukocytes which have incorporated 5-bromodeoxyuridine for a portion of the DNA synthesis period exhibit reduced 33258 Hoechst fluorescence in 5-bromodeoxyuridine-containing regions. Regions synthesizing DNA during a particular interval can thus be highlighted by the appropriate protocol of 5-bromodeoxyuridine administration. Chromosomes from cells which have replicated twice in medium containing 5-bromodeoxyuridine exhibit one brightly and one dully fluorescing chromatid, reflecting incorporation of 5-bromodeoxyuridine into one or two chains of chromatid DNA, respectively. Sister chromatid exchanges, evident as sharply demarcated reciprocal alterations in fluorescence along chromosomes, can be located relative to quinacrine b...

Journal ArticleDOI
TL;DR: Electrophoretic studies indicate that this is adequate to completely remove the histones from fixed and dried chromatin thus indicating that histones are not involved in C- or G-banding.

Journal ArticleDOI
TL;DR: Rye chromosomes were selectively stained in the meiosis of triticale by means of heterochromatin banding techniques and showed reduced pairing at first meiotic metaphase, which could arise from an overlap between the processes of chromosome replication and chromosome pairing.
Abstract: Rye chromosomes were selectively stained in the meiosis of triticale by means of heterochromatin banding techniques. Compared to wheat chromosomes, rye chromosomes showed reduced pairing at first meiotic metaphase. Within the rye genome this pairing failure was associated with the presence of large, terminal heterochromatic bands. Since these terminal bands of rye chromosomes are late replicating, the effect of heterochromatin could arise from an overlap between the processes of chromosome replication and chromosome pairing.

Journal ArticleDOI
TL;DR: Ultraviolet irradiation of methanol: acetic acid-fixed human and mouse metaphase chromosomes rendered them capable of binding antibodies specific for purine or pyrimidine bases indicated that UV irradiation generated single-stranded regions in chromosomal DNA.

Journal ArticleDOI
01 Mar 1974-Nature
TL;DR: A hamster cell mutant is isolated in which mitosis is blocked in metaphase and the processing of ribosomal RNA10 is inhibited.
Abstract: SEVERAL temperature-sensitive mammalian cell mutants in culture have been isolated1–10, including three defective in protein syntheses6, cytokinesis5 and the processing of ribosomal RNA10, respectively. I have now isolated a hamster cell mutant in which mitosis is blocked in metaphase.

Journal ArticleDOI
TL;DR: The functional and phylogenetic significance of the observations is discussed, and the events of cell division are compared with these events in other green algae and in Ochromonas.
Abstract: SUMMARY Scaly green monads are often placed in a separate class, Prasinophyceae, and have been considered to be among the most, primitive of green algae. Platymonas possesses rhizoplasts which resemble sarcomeric structures. At prophase, extranuclear spindle micro-tubules emanate from a granular region which appears to arise through dissolution or dispersion of the rhizoplasts. It is probable that the rhizoplasts are largely consumed during the formation of the spindle and only small fragments are left at metaphase. The rhizoplasts can be seen again at telophase but are short at this stage. The basal bodies are not at the spindle poles but remain at their interphase position. The interzonal spindle collapses early at telophase, and shortly thereafter cleavage microtubules appear. These microtubules extend from the region of the basal bodies to the posterior of the cell. The events of cell division are compared with these events in other green algae and in Ochromonas. The functional and phylogenetic significance of the observations is discussed.

Journal ArticleDOI
18 Aug 1974-Heredity
TL;DR: The Giemsa-stained C-bands account for all the heterochromatin in rye nuclei, including metaphase chromosomes within the complement, as revealed by Feulgen staining.
Abstract: C-banding, by Giemsa staining, is largely restricted to distal regions of rye chromosomes. This applies, also, to B chromosomes. The distribution of C-bands coincides with that of distally localised heterochromatin. The area of metaphase chromosomes staining with Giemsa corresponds to the area occupied by heterochromatin in interphase nuclei as revealed by Feulgen staining. The Giemsa-stained C-bands account, therefore, for all the heterochromatin in rye nuclei. Individual chromosomes within the complement are readily identified following Giemsa staining.

Journal ArticleDOI
S. Matsui1
TL;DR: Findings strongly suggest the existence of ribosomal gene-specific non-histone proteins which probably represent the structural chromatin element rather than the primary gene product in mammalian and marsupial chromosomes.

Journal ArticleDOI
Harald Fuge1
TL;DR: Analysis of serial sections oriented parallel to the interpolar spindle axis revealed the following results: — At the level of anaphase plates the concentration of nkMTs is higher than in the interzone, possibly indicating an overall MT shortening in anaphases.
Abstract: Analysis of serial sections oriented parallel to the interpolar spindle axis revealed the following results. Autosomes in anaphase of the 1. meiotic division of Pales ferruginea spermatocytes are attached to the spindle in two ways: 1. The short kinetochoric microtubules (kMTs) diverge and interdigitate with the axial mass of non-kinetochoric microtubules (nkMTs). 2. The chromosome surface shows projections which protrude between the mass of nkMTs. — At the level of anaphase plates the concentration of nkMTs is higher than in the interzone. — The lagging sex chromosomes at the equator become stretched by anaphase forces during autosomal movement. — The mean length of nkMTs in metaphase is 3.0±0.1 μm, in anaphase 2.6±0.1 μm, possibly indicating an overall MT shortening in anaphase. Spindle architecture and aspects of anaphase forces are discussed.

Journal ArticleDOI
TL;DR: Scanning electron microscopy of DNase-treated whole-mount chromosomes might allow for more detailed analyses of deletions and translocations by chromomere number and position than is possible by light microscopy banding techniques.

Journal ArticleDOI
TL;DR: The XY pair of the Armenian hamster has been studied in spreads and in three-dimensional reconstructions during the main stages of first meiotic prophase and metaphase I and the location of the axes at the interchromatid space in the differential region has been established.
Abstract: The XY pair of the Armenian hamster has been studied in spreads and in three-dimensional reconstructions during the main stages of first meiotic prophase and metaphase I. The general pattern of the axes is similar to that of other mammals. There is a differential and a common region. In the latter a synaptonemal complex (SC) is formed by the pairing of the axes. This SC is longer than in other mammals. Heteropycnosis in the differential region is mirrored by differential chromatin packing at the ultrastructural level. The differential regions of the X and Y chromosomes can be identified both at the light and at the electron microscope level. The location of the axes at the interchromatid space in the differential region has been established. The visualization of the axes with the light microscope is facilitated by their bulgings at the beginning of mid-pachytene. These intermittent deformities change into a coiled and thinner axis during mid-pachytene. A chiasma originates in the common region of the XY body and it is seen near the ends of the sex chromosomes at diakinesis and metaphase I. The ultrastructure of this chiasmatic region is similar to that of autosomal chiasmata in the mouse. The axes separate from each other and leave a remaining piece of SC in which the central space is replaced by dense fibrillar material. During metaphase I the ultrastructure of this chiasmatic region cannot be identified because of the partial loss of the marker axes.

Journal ArticleDOI
TL;DR: In this article, the base analogue 5-bromodeoxyuridine (BUdR) was incorporated into PHA activated human lymphocyte cultures and subsequent staining with the benzimidazol compound “33258 Hoechst” and with Giemsa stain.
Abstract: After incorporation of the base analogue 5-bromodeoxyuridine (BUdR) into PHA activated human lymphocyte cultures and subsequent staining with the benzimidazol compound “33258 Hoechst” and with Giemsa stain, the sister chromatids of metaphase chromosomes are stained differently in the 2nd and 3rd cycle of cell division.

Journal ArticleDOI
TL;DR: It is suggested that microtubules are the basis for birefringence in fixed spindles at metaphase of the first meiotic division of Nephrotoma suturalis, and the possibility that other factors may influence bireFringence of the spindle in vivo is discussed.

Journal ArticleDOI
TL;DR: Results indicate a close phyletic relationship between Stichococcus and Klebsormidium, two organisms which are now considered to be more closely related to the progenitors of the higher land plants than most of the other members of the Ulotrichales.
Abstract: Except for the lack of a centriole, interphase cell morphology and cell division in Stichococcus is similar to that in Klebsormidium. The cell in Stichococcus is largely filled by a chloroplast and pyrenoid, at the side of which are two mitochondria and one small peroxisome. The chloroplast/pyrenoid cleaves early in prophase, probably completely, and the nucleus is inserted between the two halves. A band of 3–5 microtubules always encircles the prophase nucleus; these disappear by metaphase. The spindle is open, the daughter nuclei remain far apart at telophase and during cytokinesis, and vacuoles collect between them; no phycoplast is associated with the cleavage furrow. These results indicate a close phyletic relationship between Stichococcus and Klebsormidium, two organisms which are now considered to be more closely related to the progenitors of the higher land plants than most of the other members of the Ulotrichales.

Journal ArticleDOI
TL;DR: The statistics of prophasing and nuclear envelope formation in the homo- and heterokaryon populations were consistent with the notion that disruption or formation of the nuclear envelope depends on the balance attained between disruptive and formative processes.
Abstract: Fusing human HeLa metaphase cells with HeLa interphase cells resulted within 30 min in either of two phenomena in the resultant binucleate cell: either prophasing of the interphase nucleus or formation of a normal-appearing nuclear envelope around the metaphase chromosomes. The frequency of either occurrence was strongly dependent on environmental pH. At pH's of 6.6–8.0, prophasing predominated; at pH 8.5 nuclear envelope formation predominated. Additionally, the frequencies of the two events in multinucleate cells depended on the metaphase/interphase ratio. When the ratio was 0.33 nuclear envelope formation predominated; when it was 2.0 prophasing predominated. In their general features, the results with fused HeLa cells resembled those reported earlier with fused Chinese hamster Don cells. However, the results provided an indication that between pH 6.6 and 8.0 the HeLa metaphase cells possessed a much greater capacity than the Don metaphase cells to induce prophasing. Fusion of Don metaphase cells with HeLa interphase cells or of Don interphase cells with HeLa metaphase cells at pH 8.0 resulted in nuclear envelope formation or prophasing in each kind of heterokaryon. As in the homokaryons, the frequencies of the two events in the heterokaryons depended on the metaphase/interphase ratio. The statistics of prophasing and nuclear envelope formation in the homo- and heterokaryon populations were consistent with the notion that disruption or formation of the nuclear envelope depends on the balance attained between disruptive and formative processes.

Journal ArticleDOI
TL;DR: Cells exposed to NaCl-supplemented medium exhibit a concentration dependent inhibition of macromolecular synthesis, protein synthesis being most affected, DNA synthesis less so and RNA synthesis least, except at slightly elevated tonicities which often produced a slight stimulation of the rate of synthetic activity.

Journal ArticleDOI
TL;DR: It is suggested that essential proteins are synthesized, which determine the continuation of the cells in mitosis, which determines the duration of the transition from metaphase to anaphase.

Journal ArticleDOI
TL;DR: Cultured soybean cells recovered from a marked decrease in cell division 20 hours after removal of their cell walls with enzymes and exhibited sustained mitotic activity, which may contribute to the new nuclear envelope at telophase.
Abstract: Cultured soybean cells recovered from a marked decrease in cell division 20 hours after removal of their cell walls with enzymes and exhibited sustained mitotic activity. Mitosis was essentially similar in both cultured cells and protoplasts. At prophase microtubules aggregated in a clear zone surrounding the nucleus prior to forming the spindle. During metaphase and anaphase chromosomal microtubules were attached to diffuse kinetochores and extended to broad spindle poles; few interzonal microtubules were evident. Considerable endoplasmic reticulum was present at the spindle poles throughout division and may contribute to the new nuclear envelope at telophase. A typical phragmoplast consisting of vesicles, overlapping microtubules and associated electron-dense material appeared earlier in the protoplasts and developed into a thicker cell plate than found in the cultured cells.