YOLK OF THE H E N ' S EGG
237
5. Lining Bodies
These structures can be seen as dense patches lining the follicle cell
membranes (Figs. 11 and 12). They are found not only where one follicle
cell lies adjacent to another, but also where follicle cells lie against the
oocyte. In some ways these regions resemble desmosomes in that their
most conspicuous feature is a thickening beneath the cell membrane,
but they differ from desmosomes in that they are not arranged in pairs
that are mirror images of each other. They are also much bigger than
desmosomes, being frequently about 0-5 μ in length.
The total thickening is about 150 Â and consists of two dense membranes with some slightly less dense material between them. Large
granules, of about 150-250 Â diameter, are arranged at fairly regular
intervals along the side furthest from the cell membrane (see Figs. 12
and 13).
Some lining bodies appear flat or slightly convex in section, whereas
others project as finger-like processes indenting the cell membrane of
the oocyte (Fig. 12). Even in the ovary of the infant chicken of about
7 days these processes are found (Greenfield, unpublished). Structures
similar to the lining bodies are seen in the oocyte in vesicles and have
probably been pinched off from the follicle cells.
Relatively low power electron micrographs of the lining bodies have
been published by Schjeide et al. (1963a, b) who have put forward the
hypothesis that these structures are concerned in the formation of
mitochondria, and for this reason they have called them 'pre-mitochondria'. This interesting suggestion seems somewhat unlikely to be
correct, however, for the following reasons.
Firstly, these processes are highly specialized and I have found no
account of comparable structures in any other tissue. In particular,
they are apparently not present in the oocytes and follicle cells of
mammals (e.g. Sotelo and Porter, 1959; Wartenberg and Stegner, 1962)
or of amphibians (Wartenberg, 1962; Witschnitzer, 1963), where a
similar increase in the numbers of mitochondria takes place. It seems
improbable, therefore, that the domestic fowl possesses a unique mode
of mitochondrial formation.
Secondly, there is some lack of correspondence between the structure
of the membranes of a lining patch and of a mitochondrion (see Fig. 16).
The mitochondrion consists of two membranes (i and ii), each of these
having a 'unit membrane
5
structure. The lining patch has four membranes. Membrane a is a unit membrane formed from the invaginated
cell membrane of the receiving cell ; b is formed from the evaginated cell
membrane of the donor cell and in this region it has lost its unit mem -
brane structure so that it now consists of a single line of about 30 Â
237
5. Lining Bodies
These structures can be seen as dense patches lining the follicle cell
membranes (Figs. 11 and 12). They are found not only where one follicle
cell lies adjacent to another, but also where follicle cells lie against the
oocyte. In some ways these regions resemble desmosomes in that their
most conspicuous feature is a thickening beneath the cell membrane,
but they differ from desmosomes in that they are not arranged in pairs
that are mirror images of each other. They are also much bigger than
desmosomes, being frequently about 0-5 μ in length.
The total thickening is about 150 Â and consists of two dense membranes with some slightly less dense material between them. Large
granules, of about 150-250 Â diameter, are arranged at fairly regular
intervals along the side furthest from the cell membrane (see Figs. 12
and 13).
Some lining bodies appear flat or slightly convex in section, whereas
others project as finger-like processes indenting the cell membrane of
the oocyte (Fig. 12). Even in the ovary of the infant chicken of about
7 days these processes are found (Greenfield, unpublished). Structures
similar to the lining bodies are seen in the oocyte in vesicles and have
probably been pinched off from the follicle cells.
Relatively low power electron micrographs of the lining bodies have
been published by Schjeide et al. (1963a, b) who have put forward the
hypothesis that these structures are concerned in the formation of
mitochondria, and for this reason they have called them 'pre-mitochondria'. This interesting suggestion seems somewhat unlikely to be
correct, however, for the following reasons.
Firstly, these processes are highly specialized and I have found no
account of comparable structures in any other tissue. In particular,
they are apparently not present in the oocytes and follicle cells of
mammals (e.g. Sotelo and Porter, 1959; Wartenberg and Stegner, 1962)
or of amphibians (Wartenberg, 1962; Witschnitzer, 1963), where a
similar increase in the numbers of mitochondria takes place. It seems
improbable, therefore, that the domestic fowl possesses a unique mode
of mitochondrial formation.
Secondly, there is some lack of correspondence between the structure
of the membranes of a lining patch and of a mitochondrion (see Fig. 16).
The mitochondrion consists of two membranes (i and ii), each of these
having a 'unit membrane
5
structure. The lining patch has four membranes. Membrane a is a unit membrane formed from the invaginated
cell membrane of the receiving cell ; b is formed from the evaginated cell
membrane of the donor cell and in this region it has lost its unit mem -
brane structure so that it now consists of a single line of about 30 Â