CYTOLOGICAL STUDIES OF THE DEVELOPMENT OF METAPHASE I IN HYBRIDS BETWEEN TRITICUM TIMOPHEEVI ZHUK. AND T. DURUM DESF.

1961 ◽  
Vol 39 (1) ◽  
pp. 81-108 ◽  
Author(s):  
E. B. Wagenaar
Keyword(s):  
Late Stage ◽  
Developmental Stages ◽  
Progressive Increase ◽  
Cell Populations ◽  
Equatorial Plate ◽  
Triticum Timopheevi ◽  
Late Stages ◽  
I Cells ◽  
Metaphase I

In two hybrids between Triticum timopheevi Zhuk. and T. durum Desf., which have irregular meioses, metaphase I was subdivided into four developmental stages, early, medium, late, and very late. This subdivision was based on the presence in the anthers of other stages that occurred together with metaphase I. It was then discovered that in metaphase I cell populations there was a progressive increase of univalents from the early and medium stages to the very late stage. This phenomenon can be explained on the assumption that metaphase I is of shorter duration in the less irregular cells which pass into anaphase I earlier than the more irregular cells. As a consequence of this developmental phenomenon at metaphase I, the anaphase I and telophase I cells in the late anthers contained fewer lagging chromosomes than the anaphase I and telophase I cells in the very late anthers. Despite these numerical differences, the degrees of lagging were remarkably similar in both stages; approximately 70% of these univalents lagged at late and very late stages in both hybrids.During metaphase I many univalents of the irregular cells moved towards the equatorial plate, became oriented, and lagged at anaphase I and telophase I. It was found that the univalents of the least irregular cells accumulated somewhat faster at the plates than those of the more irregular cells.Considering the relationships between all of the available data, the hypothesis is advanced that when a certain number of univalents have accumulated at the equatorial plate a state of equilibrium is established and anaphase I is initiated. On the basis of this hypothesis an explanation of the trends observed at metaphase I is given.

THE ULTRASTRUCTURE OF KINETOCHORES OF UNPAIRED CHROMOSOMES IN A WHEAT HYBRID

1973 ◽  
Vol 15 (4) ◽  
pp. 801-806 ◽  
Author(s):  
E. B. Wagenaar ◽  
D. F. Bray
Keyword(s):  
Sister Chromatid ◽  
Metaphase Plate ◽  
Polar Regions ◽  
Equatorial Plate ◽  
Univalent Chromosome ◽  
Wheat Hybrid ◽  
Opposite Pole ◽  
Kinetochore Region ◽  
Metaphase I

The kinetochore region of unpaired chromosomes (univalents) consists of two kinetochores, each belonging to a sister chromatid, that are located adjacent to one another on the surface of the univalent chromosome. This condition results in a movement by the univalent towards one of the polar regions at the onset of metaphase I. Once arrived in this region, one of the sister kinetochores obtains attachments of microtubules from the opposite pole. This results in a gradual return of the univalent to the equatorial plate, where it reaches an equilibrium. The sister kinetochores remain adjacent during the movement, but once arrived at the metaphase plate they develop a typical mitotic appearance, in which the sister kinetochores have opposite positions on the chromosomes.

Researches on the intestinal protozoa of monkeys and man

Parasitology ◽  
1943 ◽  
Vol 35 (3) ◽  
pp. 134-158 ◽  
Author(s):  
Clifford Dobell
Keyword(s):  
Life History ◽  
Special Reference ◽  
Entamoeba Histolytica ◽  
Cyst Wall ◽  
Equatorial Plate ◽  
Intestinal Protozoa ◽  
E Coli ◽  
Additional Information ◽  
First Time

1. This memoir amplifies my accounts ofEndolimax nanapublished in 1919 and 1933. The complete life-history, as observable in cultures, is now described—special attention being devoted to the nuclear structure at all stages.2. Additional information is also given about methods of cultivation, viability of the cystsin vitro, the ‘nucleal reaction’, natural parasites (Sphaerita, etc.), and other details.3. The life-history has been found to comprise trophic, precystic, cystic, and metacystic stages, comparable with those described inEntamoeba histolytica(1928) andE. coli(1938).4. The trophic amoeba is redescribed, with special reference to the polymorphism of its karyosome.5. Division of the trophic amoeba (by binary fission) has been studied, and the mitosis of its nucleus is now first described in detail. It is characterized by the formation of an intranuclear spindle, with well-developed centrioles and centrodesmus. The granular chromosomes are 10 in number, and arranged in a ring on the equatorial plate.6. Precystic amoebae are smaller than trophic forms —the reduction in size being effected during the last two divisions before encystation.7. The cyst is formed by a precystic amoeba in the usual way. Inside the cyst, the nucleus undergoes two successive mitotic divisions similar to those seen in trophic forms. The ripe cyst is therefore 4-micleate, though supernucleate specimens—which are viable— occur occasionally. Glycogen is normally present in young (1- and 2-nucleate) cysts, but not in those which are mature.8. The process of excystation is described for the first time, and closely resembles that seen inE. histolytica. The entire protoplasmic contents emerge as a single 4-nucleate amoeba through a minute pore in the cyst wall.9. Metacystic development—not previously studied —consists in simple division, by successive cytoplasmic bipartitions without division of the nuclei, into 4 uninucleate amoebulae. These grow into trophic amoebae once more.10. The whole life-history is thus asexual, with no gametes, conjugation, or autogamy, at any stage.

Entamoeba aulastomi Nöller

Parasitology ◽  
1932 ◽  
Vol 24 (2) ◽  
pp. 225-232 ◽  
Author(s):  
Ann Bishop
Keyword(s):  
Liquid Medium ◽  
Direct Method ◽  
Horse Serum ◽  
Rice Starch ◽  
Equatorial Plate ◽  
Nacl Solution ◽  
Mature Cyst

1. Entamoeba aulastomi and Hexamita sp. from Haemopis sanguisuga have been cultivated in inactivated horse-serum diluted 1 : 10 in 0·5 NaCl solution + solid sterile rice-starch, and upon an inspissated horse-serum slope covered with the liquid medium + sterile rice-starch. Cysts of E. aulastomi appeared on or after the 9th day from subcultivation, but cysts of Hexamita have not appeared in the cultures.2. The amoeboid phase of E. aulastomi divides by a simple direct method, without the formation of a spindle. There is no equatorial plate. It was not possible to count the number of chromatin granules.3. The mature cyst is quadrinucleate, though occasional octonucleate cysts are found. Chromatoids are present but are absorbed before hatching. A. large glycogen vacuole is present in the uninucleate cyst. The nucleus divides by the formation of a delicate spindle but no chromosomes were found.4. E. aulastomi are not harmed by being kept at 2° C. but they die out in the 2nd subculture if kept at 30° C. and within 24 hours if kept at 37° C. The cysts also are killed at 37° C.5. If treated with N/20 HCl all amoebae are killed in less than 10 min. but the cysts are unharmed.

Notes on certain points in the Cytology Of Trypanosoma raiae and Bodo caudatus

Parasitology ◽  
1927 ◽  
Vol 19 (4) ◽  
pp. 375-393 ◽  
Author(s):  
Muriel Robertson
Keyword(s):  
Nuclear Membrane ◽  
Hollow Sphere ◽  
Fibre Type ◽  
Mitotic Figure ◽  
Nuclear Space ◽  
Spindle Fibre ◽  
Equatorial Plate ◽  
Inner Surface ◽  
Division Process ◽  
Metazoan Cell

1. T. raiae and Bodo caudatus are investigated using Feulgen's nucleal reaction in addition to the usual nuclear stains. The nature and value of this method is discussed.2. In T. raiae the parabasal body or kinetonucleus is found to consist of chromatin as shown by the nucleal reaction. An achromatic element in its composition is suggested in the division by the desmose between the two halves being achromatic.The blepharoplast is an achromatic structure. It seems probable that it persists in the aflagellar phase of the trypanosome. In T. raiae the division of the blepharoplast precedes but does not apparently orientate the division of the parabasal body. The division of the parabasal body does not present a mitotic figure.3. The nucleus in T. raiae consists of an achromatic karyosome body with some chromatin surrounding it, there is also chromatin arranged upon the inner surface of the nuclear membrane.4. At division the karyosome apparently draws out into an achromatic spindle figure, the chromatin collects in the prophase into a loose granular mass and then becomes arranged at the equator. The mass divides into two portions; it is not possible to distinguish chromosomes with sufficient certainty. The nuclei are finally reconstructed from the achromatic ends of the spindle and the chromatin which has travelled to either pole.5. In Bodo caudatus the parabasal body (kinetonucleus) is composed of chromatin and of an achromatic substance, the blepharoplasts or basal granules are achromatic bodies which play an orientating part in the division of the parabasal body: this division does not show an equatorial plate stage. The nucleus is made up of an achromatic nucleolus-karyosome surrounded by a hollow sphere of chromatin; there is a very definite division process which takes place apparently within the nuclear space. There is no equatorial plate formed and the achromatic figure which is derived directly from the karyosome is a division column which inserts itself into the already dividing chromatin and is not of the spindle fibre type found in the mitosis of the metazoan cell and of many protozoa.

scholarly journals Aggregations of organelles in meiotic cells of higher plants

2014 ◽  
Vol 57 (4) ◽  
pp. 637-654 ◽  
Author(s):  
Bohdan Rodkiewicz ◽  
Ewa Duda
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Higher Plants ◽  
Early Prophase ◽  
Equatorial Plate ◽  
Prophase I

During early prophase I in microsporocytes and sporocytes of various plants all mitochondria and plastids aggregate in a group, where some plastids seem to undergo division. This group desintegrates by middle prophase I. Further aggregations of plastids and mitochondria occur in microsporogenesis and sporogenesis is of a simultaneous type. Organelles aggregate the second time at the end of prophase 1 and during or after telophase I they form a dense equatorial plate which lasts until telophase IL Since the phragmoplast is dismantled after telophase I and there is no cytokinesis, organelles aggregated in the plate apparently prevent merging of the nuclei and spindles of meiosis II, thus taking over a role of a phragmoplast and cell wall. In some plants after telophase II organelle aggregation changes shape and occupies the planes where cell walls will be built in simultaneous cytokinesis. Positioning of plastids and mitochondria along these planes may facilitate their equal apportionment among the postmeiotic cells.

Cytological evidence for assortment mitosis leading to loss of heterozygosity in rice

Genome ◽  
2006 ◽  
Vol 49 (5) ◽  
pp. 556-557 ◽  
Author(s):  
Richard R.-C Wang ◽  
Xiaomei Li ◽  
N Jerry Chatterton
Keyword(s):  
Loss Of Heterozygosity ◽  
Homologous Chromosome ◽  
Root Meristem ◽  
Mitotic Metaphase ◽  
Equatorial Plate ◽  
Cytological Evidence ◽  
Rice Line ◽  
Daughter Cells ◽  
Normal Mitosis

In the root meristem cells of the rice line AMR, which causes loss of heterozygosity in its hybrids, both normal and assortment mitoses were observed. During normal mitosis, chromosomes did not form homologous pairs at metaphase; all chromosomes lined up at the equatorial plate and 2 chromatids of each chromosome disjoined at the centromere and moved toward opposite poles. During assortment mitosis, varying numbers of paired homologues were observed at mitotic metaphase. Two groups of 12 chromosomes separated and moved towards the opposite poles of daughter cells with few chromosomes having their chromatids separated at anaphase. These observations support the proposed mechanism that is responsible for early genotype fixation in rice hybrids involving AMR.Key words: mitosis, homologous chromosome, genotype fixation, loss of heterozygosity, rice.

Arrangement of Human Cell Metaphase Chromosomes on the Equatorial Plate

2019 ◽  
Vol 10 (3) ◽  
Author(s):  
Tao Jiang ◽  
Chunxiao Wu ◽  
Ali Wajid ◽  
Donyun Jiang ◽  
Han Huan ◽  
...  
Keyword(s):  
Human Cell ◽  
Equatorial Plate ◽  
Metaphase Chromosomes

Ultrastructure of Persisting Mitotic Nucleoli of Mung Beans

1975 ◽  
Vol 33 ◽  
pp. 308-309
Author(s):  
J. P. Braselton
Keyword(s):  
Methylene Blue ◽  
Light Microscopy ◽  
Mung Bean ◽  
Higher Plants ◽  
The Other ◽  
Equatorial Plate ◽  
Cell Divisions ◽  
Primary Roots

Although nucleoli are generally believed to disperse during mitotic prophase, various groups of algae, fungi, and protozoans regularly possess persisting, in some cases “autonomous,” nucleoli during mitosis. Persisting nucleoli also occur in some higher plants and animals, but there have been only a few ultrastructural observations of such nucleoli. This study was initiated to better characterize cell divisions of a plant in which nucleoli regularly persist during mitosis.Aceto-carmine squash preparations for staining nucleoli for light microscopy reveal that mung bean primary roots possess mitotic divisions in which over 90% of the metaphases exhibit nucleoli. One micrometer sections of plastic embedded tissue stained with aqueous methylene blue for light microscopy also show nucleoli at metaphase (Fig. 1). Light microscopic observations show that some metaphase nucleoli are roughly spherical and occur on or near the equatorial plate; some are elongated perpendicularly to the plane of the equatorial plate and extend toward one or the other, or both, pole(s); while others appear spherical and occur at either pole.

Memoirs: The Meiotic Phase of Calandra oryzae

1945 ◽  
Vol s2-85 (338) ◽  
pp. 107-116
Author(s):  
MARY M. GUNSON
Keyword(s):  
Chromosome Number ◽  
Meiotic Division ◽  
Somatic Chromosome ◽  
Diploid Number ◽  
Haploid Number ◽  
Equatorial Plate ◽  
Somatic Chromosome Number ◽  
Complete Dissociation

1. The somatic chromosome number for the female of Calandra oryzae is twelve; for the male, eleven. The latter is presumably of XO composition. 2. In both sexes the haploid number of loosely paired threads is present at early diplotene. Upon condensation, the exconjugant chromosomes undergo a temporary complete dissociation into their univalent constituents, so that the diploid number of separate elements is reconstituted. 3. At the equatorial plate stage the twelve univalent chromosomes associate once again into six bivalents. 4. In the female this is followed by a precocious separation of the anaphase chromatids, so that by the conclusion of the first meiotic division the diploid number of chromosome elements is evident at both ends of the spindle. There is no comparable process during the course of spermatogenesis; at anaphase I the haploid set of chromosomes passes to each pole, the nuclei so produced entering a resting condition.

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