Germinal cell

Damage induced in whole animals can be detected in in vivo chromosome assays in either somatic or germinal cells by examination of metaphases or the formation of micronuclei. The micronucleus test can also detect whole chromosome loss or aneuploidy in the absence of clastogenic activity and is considered comparable in sensitivity to chromosome analysis (Tsuchimoto and Matter, 1979). 

Male rat germinal cells Rat hepatocytes Rat hepatocytes Ch7ordecone... 

The methylation of DNA at CpG islands has also turned out to be an important regulator for cell development, the differentiated proteome and the regulation of cell survival [237,238]. Indeed the implications of this chemical modification have been linked to DNA accessibility, chromatin fluidity and cell transformation [239,240]. DNA methylation is required for genomic stability and believed to act as an inert epigenetic marker in germinal cells and preimplantation embryos [238]. Presumably, DNA methylation is required for the heritable transmission of chromatin structure, which prevents the expression of terminally silenced genes in differentiated tissues, and provides a host-defense mechanism against parasitic transposable elements [241]. 

Basal cells are the germinative cells of the comeal epithelium. They are 18-pm long cylindrical cells with a 10-urn diameter. They are arranged in one layer set on the basement membrane. Their nucleus is oval and oriented along the big axis of fire cell (Fig. 4.6). 

Leopardi, P, Zijno, A.. Bassani. B. Pacchierotti, F. (1993) In vivo studies on chemically induced aneuploidy in mouse somatic and germinal cells. Mutat. Res., 287, 119-130... 

Plewa, M.J., and E.D. Wagner. Germinal cell mutagenesis in specially designed maize genotypes. Environ. 

Figure 2-9. Section of the testis in rat unexposed to toxic chemicals. Note the tubular structure with different types of germinal cells.

The process of hatching in the Cyclophyllidea, which results in the release of the oncosphere, has been discussed in Chapter 7. The basic structure of a mature oncosphere (Fig. 8.16), which will not be discussed in detail here, does not vary substantially between species. It is composed essentially of (a) a thin covering epithelium with cytoplasmic extensions, (b) an additional complex system of muscles operating the three pairs of hooks, (c) a pair of large penetration glands, (d) a small core of germinative cells from which the next larval stage develops and (e) a primitive nervous system. 

Ultrastructural study of the tetrathyridium of Mesocestoides corti Hoeppli, 1925 (Cestoda) pool of germinative cells and suckers. Revue Suisse de Zoologie, 88 661-74. 

Weismann gave the name of somatic cells to those that divide only by mitosis (and are thus destined to die with the body), and called germinal cells those that can divide both by mitosis and meiosis. These are potentially immortal, because they can have descendants for an indefinite number of generations. 

The discoveries of fertilisation, meiosis and germinal cells, in conclusion, made it possible to give a precise answer to the generation problem in cellular terms the generation of a new individual starts with two meioses, when gametes are formed, and is realised at fertilisation, when a zygote is formed. 

DNA damage (unwinding rate) in hepatocytes Chromosomal aberrations in bone marrow cells Chromosomal aberrations in male germinal cells Chromosomal aberrations in male germinal cells Dominant lethality... 

Relative germinal cell number Relative interstitial cell number (low power field) Number of seminiferous tubule cut ends Number of spermatozoa in epididymal tubules... 

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