Memoirs: The Germ-Cell Cycle in Phytophaga destructor Say

1935 ◽  
Vol s2-77 (308) ◽  
pp. 585-604
Author(s):  
MARGOT E. METEALFE
Keyword(s):  
Germ Cells ◽  
Growth Stage ◽  
Germ Line ◽  
Polar Body ◽  
Metaphase Plate ◽  
Body Formation ◽  
Polar Bodies ◽  
Complicated Process ◽  
Female Pronucleus ◽  
Polar Body Formation

1. The somatic cells in both sexes of Phytophaga destructor Say contain four pairs of V-shaped chromosomes, the sex-group being indistinguishable in size or form. 2. The germ-cells in both sexes contain eight pairs of chromosomes. 3. The maturation of the egg follows the normal course of development, eight bivalents being formed. After polar body formation the female pronucleus has eight chromosomes. The polar bodies are never extruded from the egg. 4. Spermatogenesis is a complicated process, the details of which have not been satisfactorily determined. The growth stage appears to take place before the last spermatogonial division. No pairing of chromosome has been observed, and apparently no metaphase plate is formed at meiosis. Eeduction is effected by the expulsion of two buds each containing four chromosomes. Thus only one sperm is produced from each spermatocyte. 5. One or more sperms may enter the egg at fertilization. 6. The germ-line is differentiated from the soma at the eightcell stage. 7. At the fifth cleavage the somatic nuclei eliminate half their number of chromosomes, and are left with eight chromosomes. 8. Migration of the germ nuclei takes place at the sixteencell stage. 9. The relation of the chromosome numbers in the somatic and germ lines is discussed.

scholarly journals Meiotic Spindle Formation Following Inhibition of First Polar Body Formation in the Zhikong Scallop (Chlamys farreri Jones et Preston)

2021 ◽  
Vol 8 ◽  
Author(s):  
Yongren Li ◽  
Baolu Zhang ◽  
Shuang Liang ◽  
Yongjun Guo
Keyword(s):  
Chromosome Segregation ◽  
Polar Body ◽  
Metaphase Plate ◽  
Fluorescein Isothiocyanate ◽  
Chlamys Farreri ◽  
Meiotic Spindle ◽  
Zhikong Scallop ◽  
Body Formation ◽  
First Polar Body ◽  
Polar Body Formation

Fertilized Zhikong scallop (Chlamys farreri) eggs were treated with cytochalasin B (CB 0.5 mg/L) at 14–15 min postfertilization to inhibit first polar body formation. The eggs were then stained with fluorescein isothiocyanate (FITC) -anti-α-tubulin and propidium iodide (PI) to examine their microtubule patterns and chromosome, respectively. Fluorescent microscope observations of treated eggs sampled every 2–3 min during meiotic maturation revealed meiotic apparatus assembly and correlated chromosome segregation. In CB-treated groups, meiosis I proceeded normally and produced two groups of dyads, with 19 in each group. Both dyad groups were retained in the eggs as they entered meiosis II. Two, three, or four asters (centrosome with microtubules around it) in meiosis II rearranged the spindle in several patterns: bipolar [24.0 ± 4.1 μm (long axis) × 18.3 ± 4.1 μm (diameter: metaphase plate)], tripolar (18.6 ± 3.9 μm × 9.9 ± 1.3 μm), separated bipolar (18.3 ± 2.8 μm × 11.2 ± 1.8 μm), and other unclassified spindle patterns. Corresponding chromosome segregation, including bipolar (18.9%), tripolar (38.9%), double bipolar (16.5%), and unclassified (25.6%), was observed during meiosis II in CB-treated eggs. The data indicated that chromosome segregation patterns determined by spindle patterns were critically influenced by the number of centrosomes in meiosis II eggs following inhibition of polar body 1 (PB1) formation with CB.

The establishment of the oral-aboral axis in the ctenophore embryo

Development ◽  
1977 ◽  
Vol 42 (1) ◽  
pp. 237-260
Author(s):  
Gary Freeman
Keyword(s):  
Polar Body ◽  
Causal Role ◽  
Cleavage Furrow ◽  
Cell Stage ◽  
Body Formation ◽  
Cleavage Initiation ◽  
Polar Bodies ◽  
Polar Body Formation ◽  
A Site

In a small percentage of normal embryos and in a higher percentage of embryos centrifuged prior to the first cleavage the positions of the polar bodies and the site of the first cleavage furrow do not coincide. These cases have been used to establish whether polar body formation sites or first cleavage initiation sites correlate best with the oral-aboral axis of the embryo. In all cases when the first cleavage is initiated at a site different from the site where the polar bodies were given off, the pattern of the first four cleavages is normal, the segregation of comb plate potential at these stages is normal, and the larvae that form are normal. The extent to which comb plate potential is localized along the oral-aboral axis of the embryo prior to the first cleavage, during the first cleavage and at the 2-cell stage was also examined. These experiments demonstrate that the oral-aboral axis is established at the time of the first cleavage, that cleavage plays a causal role in setting up the axis, and that comb plate-forming potential begins to be localized in the aboral region of the embryo at this time.

Polar Body Formation in Tubifex Eggs

1990 ◽  
Vol 582 (1 Cytokinesis) ◽  
pp. 260-272 ◽  
Author(s):  
TAKASHI SHIMIZU
Keyword(s):  
Polar Body ◽  
Body Formation ◽  
Polar Body Formation

Preimplantation development of gynogenetic diploid mouse embryos

Development ◽  
1982 ◽  
Vol 69 (1) ◽  
pp. 215-222
Author(s):  
Ewa Borsuk
Keyword(s):  
Cytochalasin B ◽  
Polar Body ◽  
Mouse Embryos ◽  
Fertilization In Vitro ◽  
Body Formation ◽  
Male Pronucleus ◽  
Step Procedure ◽  
Gynogenetic Diploid ◽  
Polar Body Formation

Diploid gynogenetic mouse embryos were produced in a three-step procedure: fertilization in vitro, suppression of the 2nd polar body formation by Cytochalasin B, and microsurgical removal of the male pronucleus. The operated eggs were transplanted to the oviduct of recipient females for 72 or 96 h. The overall recovery rate was 73%, but compacted morulae and blastocysts constituted only 28·6% of transplanted eggs. After 72 h blastocysts were rare (3·5%) but 24 h later their incidence increased to 21·2%. In eggs homozygous for T6 chromosome it was possible to prove karyologically that the male pronucleus was effectively removed and that the diploid genome was of purely maternal origin.

Induction of Tetraploidy in Mussels by Suppression of Polar Body Formation.

1993 ◽  
Vol 59 (12) ◽  
pp. 2017-2023 ◽  
Author(s):  
John Scarpa ◽  
Katsuhiko T.Wada ◽  
Akira Komaru
Keyword(s):  
Polar Body ◽  
Body Formation ◽  
Polar Body Formation
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