Primordial germs

Ginsburg, M., Snow, M. H. L., and McLaren, A. (1990). Primordial germ cells in the mouse embryo during gastrulation. Development 110 521-528. 

Godin, I., Deed, R., Cooke, J., Zsebo, K., Dexter, M., and Wylie, C. C. (1991). Effects of steel gene product on mouse primordial germ cells in culture. Nature 352 807-809. 

Matsui, Y Toksoz, D., Nishikawa, S., Nishikawa, S-I., Williams, D Zsebo, K., and Hogan, B. L. M. (1991). Effect of Steel factor and leukaemia inhibitory factor on murine primordial germ cells in culture. Nature 353 750-752. 

Mintz, B., and Russell, E. S. (1957). Gene-induced embryological modifications of primordial germ cells in the mouse. J. Exp. Zool. 134 207-230. 

Resnik, J. L., Bixler, L. S., Cheng, L., and Donovan, P. J. (1992). Long-term proliferation of mouse primordial germ cells in culture. Nature 359 550-551. 

Pridantseva T., Savchenkova I., Abdrakhmanov I. Isolation of primordial germ cells from pig fetuses // Proceedings of the VHth International Congress of Andrology Andrology in the 21st Century . -Montreal, Quebec, Canada. - 2001. - P. 143-148. 

Fig. 1. Dynamics of DNA methylation levels during mouse development. The methylation patterns of the oocyte and the rapidly demethylated after fertilization sperm create the combined methylation patterns in the early mouse zygote. During the first two to three cleavage divisions, the 5mC levels decrease further and stay low through the blastula stage. Post-implantation, the mouse embryo genome is methylated de novo the CpG islands remain mostly unmethylated. The primordial germ cells remain unmethylated. During gametogenesis specific parental (maternal or paternal) patterns of DNA methylation are established at imprinted loci (for further details see Refs. [13, 14]) (re-drawn from Ref [4]).

Oogenesis is the process of ovum formation and maturation. During oogenesis, primordial germ cells are formed, which become oogonia and subsequently oocytes in the fetus. In the adult, oocytes mature into ova, which contain the nutrients that support the early embryo s energy requirements (Wasserman, 1996 Wasserman Albertini, 1996). 

In the humans, the primordial germ cells are differentiated from about the sixth week of gestation and are consequently susceptible from then onward. In the female, production of the primary oocytes, which involves the first meiotic division, occurs in fetal life. These primary oocytes do not mature into ova until puberty, with the second meiotic division yielding one ovum from each primary oocyte (Fig. 6.48). 

Lee J, Inoue K, Ono R, Ogonuki N, Kohda T, Kaneko-Ishino T, Ogura A, Ishino F. Erasing genomic imprinting memory in mouse clone embryos produced from day 11.5 primordial germ cells. Development 2002 129 1807— 1817. 

Shamblott MJ, Axelman J, Wang S, Bugg EM, Littlefield JW, Donovan PJ, Blumenthal PK, Huggins GR, Gearhart JD. Derivation of pluripotent stem cells form cultured human primordial germ cells. Proc Nat Acad Sci USA 1998 95 13726-31. 

Richardson, B.E., and Lehmann, R. (2010). Mechanisms guiding primordial germ cell migration strategies from different organisms. Nat Rev Mol Cell Biol 11 37 9. 

Human embryonic stem cells were first collected in 1998 by two different research teams. The cells obtained from the inner cell mass of the blastocyst (4- to 5-day embryo) are embryonic stem cells (ESC) in contrast, cells cultured from the primordial germ cells of 5- to 9-week fetuses are embryonic germ cells (EGC). In the laboratory, ES or EG cells can proliferate indefinitely in an undifferentiated state but can also be manipulated to become specialized or partially specialized cell types, a process known as directed differentiation. Both ES and EG cells are pluripotent, meaning they have the potential to develop into more than 200 different known cell types. This class of human stem cells holds the promise of being able to repair or replace cells or tissues that are damaged or destroyed by many of our most devastating diseases and disabilities. 

Embryonic Germ Cells (EGC) Primordial germ cells of 5-to 9-week fetuses Infinite Totipotent (Can differentiate into every cell of the organism)... 

In other words, atoms are the basic stuff of nature, the primary and most foundational, and all of matter was built up of these primordial germs. The suggestion that the structure of atoms was hard (since they were indivisible) implied that atoms could not fill all space and there had to be regions that did not contain atoms. This would be like filling a jar with marbles. Where Aristotle and Plato objected to the very idea of a void, the Epicureans were comfortable with the idea, and it provided an easier way to describe motion. Since the void could not oppose motion, atoms were free to move about, while a universe filled with matter suggested that motion was unnecessarily complicated or might even be impossible. Lucretius went on to say ... 

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