scholarly journals The meiotic phase in certain mammals

1926 ◽  
Vol 99 (698) ◽  
pp. 366-374 ◽  
Keyword(s):  
Cell Division ◽  
Meiotic Division ◽  
Longitudinal Division ◽  
Previous Occasion ◽  
Definite Reference

Cytological literature is very voluminous and is scattered in many journals of varying importance published in different languages. It may be, therefore, that the resemblance between certain stages of the early telophase of cell division in some cells and the stages in the 1st Meiotic Division, very commonly known as “synaptic,” has been recorded on several occasions. I have, however, only found one definite reference to this similarity (Blackman, 1903). If the observations recorded here and my interpretation of them are correct, this similarity should be of usual occurrence. That the daughter chromosomes of a somatic division frequently show longitudinal fission has, as I have pointed out on a previous occasion, been observed frequently. (Walker, 1925.) Flemming called it “precocious longitudinal division” as long ago as 1891.

scholarly journals Longitudinal cell division is associated with single mutations in the FtsZ-recruiting SsgB in Streptomyces

2019 ◽  
Author(s):  
Xiansha Xiao ◽  
Joost Willemse ◽  
Patrick Voskamp ◽  
Xinmeng Li ◽  
Meindert Lamers ◽  
...  
Keyword(s):  
Cell Division ◽  
Biochemical Analysis ◽  
Amino Acid Substitutions ◽  
Free Living ◽  
Division Plane ◽  
Z Ring ◽  
Living Bacterium ◽  
Longitudinal Division ◽  
Longitudinal Cell ◽  
Free Living Bacterium

ABSTRACTIn most bacteria, cell division begins with the polymerization of the GTPase FtsZ at the mid-cell, which recruits the division machinery to initiate cell constriction. In the filamentous bacterium Streptomyces, cell division is positively controlled by SsgB, which recruits FtsZ to the future septum sites and promotes Z-ring formation. Here we show via site-saturated mutagenesis that various amino acid substitutions in the highly conserved SsgB protein result in the production of ectopically placed septa, that sever spores diagonally or along the long axis, perpendicular to the division plane. Ectopic septa were especially prominent when cells expressed SsgB variants with substitutions in residue E120. Biochemical analysis of SsgB variant E120G revealed that its interaction with - and polymerization of - FtsZ had been maintained. The crystal structure of S. coelicolor SsgB was resolved and the position of residue E120 suggests its requirement for maintaining the proper angle of helix α3, thus providing a likely explanation for the aberrant septa formed in SsgB E120 substitution mutants. Taken together, our work presents the first example of longitudinal division in a free living bacterium, which is explained entirely by changes in the FtsZ-recruiting protein SsgB.

Memoirs: Cleavage of Blastomeres in the Absence of Nuclei

1936 ◽  
Vol s2-79 (313) ◽  
pp. 57-72
Author(s):  
F. GROSS
Keyword(s):  
Cell Division ◽  
Low Temperature ◽  
Meiotic Division ◽  
Artemia Salina ◽  
Metaphase Stage

After exposure to low temperature, at the metaphase stage of the first meiotic division, parthenogenetic eggs of Artemia salina may show abnormal cleavage resulting in blastulae with a very big nucleus in only one blastomere. The rest of the blastomeres contain cytasters alone which are apparently sufficient to determine cell division. In shape and arrangement around the cleavage cavity they look very like those of normal blastulae. If the oocytes are fixed immediately after the exposure to low temperature they show, in some cases, a number of cytasters scattered near the surface, although the meiotic division has not yet taken place. It is suggested that the cytasters originated from the ectoplasmic layer, and that their formation and division is independent of nuclear divisions.

scholarly journals Efficient Detection of Longitudinal Bacteria Fission Using Transfer Learning in Deep Neural Networks

2021 ◽  
Vol 12 ◽  
Author(s):  
Carlos Garcia-Perez ◽  
Keiichi Ito ◽  
Javier Geijo ◽  
Roman Feldbauer ◽  
Nico Schreiber ◽  
...  
Keyword(s):  
Cell Division ◽  
Transfer Learning ◽  
Binary Classification ◽  
Classification Model ◽  
Cell Counting ◽  
Cellular Division ◽  
Microscopic Images ◽  
Efficient Detection ◽  
Longitudinal Division

A very common way to classify bacteria is through microscopic images. Microscopic cell counting is a widely used technique to measure microbial growth. To date, fully automated methodologies are available for accurate and fast measurements; yet for bacteria dividing longitudinally, as in the case of Candidatus Thiosymbion oneisti, its cell count mainly remains manual. The identification of this type of cell division is important because it helps to detect undergoing cellular division from those which are not dividing once the sample is fixed. Our solution automates the classification of longitudinal division by using a machine learning method called residual network. Using transfer learning, we train a binary classification model in fewer epochs compared to the model trained without it. This potentially eliminates most of the manual labor of classifying the type of bacteria cell division. The approach is useful in automatically labeling a certain bacteria division after detecting and segmenting (extracting) individual bacteria images from microscopic images of colonies.

The pelota locus encodes a protein required for meiotic cell division: an analysis of G2/M arrest in Drosophila spermatogenesis

Development ◽  
1995 ◽  
Vol 121 (10) ◽  
pp. 3477-3486 ◽  
Author(s):  
C.G. Eberhart ◽  
S.A. Wasserman
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Nuclear Envelope ◽  
Germ Cells ◽  
Meiotic Division ◽  
Meiotic Cell ◽  
Spindle Formation ◽  
Nuclear Envelope Breakdown ◽  
G2 Phase

During Drosophila spermatogenesis, germ cells undergo four rounds of mitosis, an extended premeiotic G2 phase and two meiotic divisions. In males homozygous for mutations in pelota, the germline mitotic divisions are normal, but the cell cycle arrests prior to the first meiotic division; pelota males are therefore sterile. Chromosomes begin to condense in these mutants, but other meiotic processes, including nuclear envelope breakdown and spindle formation, do not occur. The arrest phenotype closely resembles that of mutations in the Drosophila cdc25 homolog twine. Although meiosis is blocked in pelota and twine homozygotes, spermatid differentiation continues. pelota is also required for patterning in the eye and mitotic divisions in the ovary. We have cloned the pelota locus and show it encodes a 44 × 10(3) M(r) protein with yeast, plant, worm and human homologs.

THE EMBRYOLOGY OF LYTTA VIRIDANA LE CONTE (COLEOPTERA: MELOIDAE): I. MATURATION, FERTILIZATION, AND CLEAVAGE

1965 ◽  
Vol 43 (6) ◽  
pp. 915-925 ◽  
Author(s):  
J. G. Rempel ◽  
N. S. Church
Keyword(s):  
Cell Division ◽  
Embryonic Development ◽  
Equatorial Plane ◽  
Meiotic Division ◽  
Bilateral Symmetry ◽  
First Record ◽  
Central Axis ◽  
Vitelline Membrane ◽  
Insect Egg ◽  
Chromatin Elimination

This paper describes the embryonic development of Lytta viridana from oviposition to the formation of the blastema. The egg has the features commonly found in an insect egg. Bilateral symmetry is shown by the shape of the egg, variation in thickness of the vitelline membrane, and distribution of the yolk components. In the newly laid egg the vitelline membrane is porous. This is believed to be the first record of this phenomenon in insects. During cell division chromatin elimination occurs along the spindle to the equatorial plane. It is especially marked in the first meiotic division, but continues into late cleavage. During the first 4 hours the periplasm flows first forward to the cephalic region and then caudad along the central axis. The belief is expressed that this movement is associated with the prefusion movements of the sperm and fertilization. Fertilization occurs at about 3 hours. During the first 14 hours of development, marked morphogenetic movements of the deutoplasm occur.

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

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

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

Stimulated Virus Production in Vinblastine and Cytochalasin-Induced Multinucleate Cells

1970 ◽  
Vol 28 ◽  
pp. 186-187
Author(s):  
Krishan Awtar
Keyword(s):  
Cell Division ◽  
Normal Cell ◽  
Virus Production ◽  
Multinucleate Cells ◽  
Daughter Cells ◽  
Cell Divisions ◽  
Nuclear Membranes ◽  
Division 2 ◽  
Vinblastine Sulfate

Exposure of cells to low sublethal but mitosis-arresting doses of vinblastine sulfate (Velban) results in the initial arrest of cells in mitosis followed by their subsequent return to an “interphase“-like stage. A large number of these cells reform their nuclear membranes and form large multimicronucleated cells, some containing as many as 25 or more micronuclei (1). Formation of large multinucleate cells is also caused by cytochalasin, by causing the fusion of daughter cells at the end of an otherwise .normal cell division (2). By the repetition of this process through subsequent cell divisions, large cells with 6 or more nuclei are formed.

Confocal microscopy of the cytoskeleton in living plant cells following microinjection of fluorescent probes

1993 ◽  
Vol 51 ◽  
pp. 130-131
Author(s):  
Ann Cleary
Keyword(s):  
Cell Division ◽  
Fluorescent Probes ◽  
Actin Filaments ◽  
Intracellular Transport ◽  
Cell Structure ◽  
Plant Cells ◽  
Cell Plate ◽  
Cell Cortex ◽  
Living Plant ◽  
Rhodamine Phalloidin

Microinjection of fluorescent probes into living plant cells reveals new aspects of cell structure and function. Microtubules and actin filaments are dynamic components of the cytoskeleton and are involved in cell growth, division and intracellular transport. To date, cytoskeletal probes used in microinjection studies have included rhodamine-phalloidin for labelling actin filaments and fluorescently labelled animal tubulin for incorporation into microtubules. From a recent study of Tradescantia stamen hair cells it appears that actin may have a role in defining the plane of cell division. Unlike microtubules, actin is present in the cell cortex and delimits the division site throughout mitosis. Herein, I shall describe actin, its arrangement and putative role in cell plate placement, in another material, living cells of Tradescantia leaf epidermis.The epidermis is peeled from the abaxial surface of young leaves usually without disruption to cytoplasmic streaming or cell division. The peel is stuck to the base of a well slide using 0.1% polyethylenimine and bathed in a solution of 1% mannitol +/− 1 mM probenecid.

Electronmicroscopic localization of ribonucleic acids in ciliate Bursaria truncatella during cell division

1990 ◽  
Vol 48 (3) ◽  
pp. 132-133
Author(s):  
Vladimir Popenko ◽  
Natalya Cherny ◽  
Maria Yakovleva
Keyword(s):  
Cell Division ◽  
High Specificity ◽  
Longitudinal Axis ◽  
Gold Complexes ◽  
Somatic Nucleus ◽  
Ribonucleic Acids ◽  
Biological Meaning ◽  
Bivalent Cations ◽  
Lowicryl K4m ◽  
Short Time

Highly polyploid somatic nucleus (macronucleus) of ciliate Bursaria truncatella under goes severe changes in morphology during cell division. At first, macronucleus (Ma) condences, diminishes in size and turns perpendicular to longitudinal axis of the cell. After short time, Ma turns again, elongates and only afterwards the process of division itself occurs. The biological meaning of these phenomena is not clear.Localization of RNA in the cells was performed on sections of ciliates B. truncatella, embedded in “Lowicryl K4M” at various stages: (1) before cell division (Figs. 2,3); (11) at the stage of macronucleus condensation; (111) during elongation of Ma (Fig.4); (1111) in young cells (0-5min. after division). For cytochemical labelling we used RNaseAcolloidal gold complexes (RNase-Au), which are known to bind to RNA containing cell ularstructures with high specificity. The influence of different parameters on the reliability and reproducibility of labelling was studied. In addition to the factors, discussed elsewhere, we found that the balance of mono- and bivalent cations is of great significance.

Centromere assembly and non-random sister chromatid segregation in stem cells

2020 ◽  
Vol 64 (2) ◽  
pp. 223-232 ◽  
Author(s):  
Ben L. Carty ◽  
Elaine M. Dunleavy
Keyword(s):  
Stem Cells ◽  
Cell Division ◽  
Cell Fate ◽  
Sister Chromatid ◽  
Asymmetric Cell Division ◽  
Protein A ◽  
Germline Stem Cells ◽  
Sister Chromatids ◽  
Centromere Protein A ◽  
Oocyte Meiosis

Abstract Asymmetric cell division (ACD) produces daughter cells with separate distinct cell fates and is critical for the development and regulation of multicellular organisms. Epigenetic mechanisms are key players in cell fate determination. Centromeres, epigenetically specified loci defined by the presence of the histone H3-variant, centromere protein A (CENP-A), are essential for chromosome segregation at cell division. ACDs in stem cells and in oocyte meiosis have been proposed to be reliant on centromere integrity for the regulation of the non-random segregation of chromosomes. It has recently been shown that CENP-A is asymmetrically distributed between the centromeres of sister chromatids in male and female Drosophila germline stem cells (GSCs), with more CENP-A on sister chromatids to be segregated to the GSC. This imbalance in centromere strength correlates with the temporal and asymmetric assembly of the mitotic spindle and potentially orientates the cell to allow for biased sister chromatid retention in stem cells. In this essay, we discuss the recent evidence for asymmetric sister centromeres in stem cells. Thereafter, we discuss mechanistic avenues to establish this sister centromere asymmetry and how it ultimately might influence cell fate.

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