Electron microscope examinations indicated that mature centrioles
consist of nine doublet and triplet microtubules connected with proteins
(mainly actin and myosin). The newly formed centrioles possess only one
microtubule. It is supposed, that every microtubule serves as a matrix for
forming doublets and triplets, typical of the mature centrioles. In their base
there is a basal small body, also called blepharoplast.
image
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Figure 2–62. Flagellum apparatus (A) and basal small bodies (B) in Chlamydomonas (After Sager, 1975).
Many investigators share the opinion, that the
centrioles and basal small bodies are similar or
identical structures and they are interchangeable. As an
illustration the unicellular green alga Chamydomonas
reinhardii is cited. It possesses two flagella with
basal small bodies in their bases (Fig. 2–62). Before
the start of mitosis the flagella disappear, and the
basal small bodies move inside the cell near to the
nucleus where they take part in forming and determining
the plane of division spindle. After the completion of
mitosis, served their purpose, they turn again into
basal small bodies from which the new flagella grow.
That suggests the idea on “organelle-phantom”, but it
needs more precise studies. It remains unclear how the migration in cells
by basal small bodies is realized when their number is more than two (there
are such cases in nature), and also which and how many of them will
participate in the formation of division spindle.
Endoplasmic Reticulum
It is discovered by Porter et al. (1945) in the cytoplasm of fibroplast in
chicken tissue cultures examined under electron microscope. Later it has
been confirmed by many other investigators. It is observed in all eukaryotic
cells, exept for mature erythrocytes which lack nuclei.
Endoplasmic reticulum (ER) or the endoplasmic net is a system of
channels, bubbles and cisterns encircled by a membrane, 5—6 nm in