Polar bodies

Pol-klemme, /. Elec.) pole terminal, pole clamp, -kdrper, m., -kdrperchen, n. Biol.) polar body, polar cell. 

Figure 2. Role of c-mos in meiosis of mouse oocytes. Mouse oocytes microinjected with antisense c-mos oligonucleotides fail to progress from meiosis I to meiosis II, instead reforming nuclei following polar body extrusion (O Keefe et al., 1989).

Fig. 7 TEM micrographs of seed coat and aleurone cells of radish treated seed 18 h after sowing in presence of rue extract, e, epidermis pi, pigment layer al, aleurone layer (A). Bar = 30 pm. Particulars of aleurone cell showing different profile respect to those of control. Id, lipid droplets pb, polar bodies n, nucleus. (B). Bar = 5 mm.

The first cell division of meiosis occurs in the primary oocyte but the process is arrested during prophase and remains so until puberty. Just before ovulation, meiosis, which has been arrested since before birth, resumes. The first division halves the number of chromosomes to produce the haploid secondary oocyte. The process is the same as that in spermatozoa (Chapter 20 see Figure 20.29 ) except that the two resulting haploid daughter cells are unequal in size. One is the large functional secondary oocyte whereas the other is much smaller and is known as the first polar body. The second meiotic division is arrested at metaphase. It is completed only at fertilisation. Once again, the division is unequal. One cell is large, the secondary oocyte. The other is small, a second polar body, which is discarded. 

When an ovum is formed three cells disintegrate and become polar bodies in sperm formation all four cells develop into spermatozoa... 

The fact that the potential distribution, in and around a polarized body, can be described in terms of a surface and a volume distribution of charge does not in any way contradict the fact that electrical neutrality, on a macroscopic scale, can be maintained at every point of the body. 

Follicle bioassay (mouse) FBA Ovarian function Oogenesis polar body oocytes on day 13 upon ovulatory stimulus Folliculogenesis and oogenesis... 

It is not necessary that bodies which combine together shall have opposite poles. . . one gifted with the greater polarity can, by contact only, induce the opposite polarity in a less polar body. 

Female Total No. oocytes injected Time examined after injection (hours) Extracted progesterone (pmoles/oocyte) Percent maturation first dot or polar body No. of injected oocytes exposed to exogenous progesterone Time exposed after injection (hours) Percent maturation, 2nd dot and activation... 

Fig. 11.5 Fertilisation and development of mnssel embryos (a) unfertilised egg and sperm (b) polar bodies developing, 24 min post-fertilisation (c) two cells with polar lobe ( trefoil stage ), 50 min post-fertilisation (d) 4-8 cell embryos, 1 h 40 min post-fertilisation (e) trochophore stage, 23 h post-fertilisation (f) D-veliger, 48 h...

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