In one experiment in which electric shock was applied to Paramecium
cells to trigger trichocyst discharge the macronucleus in one cell was
observed to undergo morphological changes of two types. First, a large
area of the nucleus, normally found to contain electron-opaque foci,
had changed into whorls of more electron-transparent filamentous
material. Secondly, a section of the nuclear envelope had folded into
a stack like the annulate lamellae seen in oocytes of many vertebrate
and invertebrate cells (see Kessel, Int. Rev. Cytol. 82:181-303,
1983). The nuclear pores were present in part of this stack of the
nuclear envelope while in other parts the pores were reduced or absent
and a layer of dots or lines occupied the nucleoplasmic space between
the two envelope segments. Presumably these annulate lamellae
represent a temporary storage mechanism for excess nuclear envelope.
EM taken on 2/28/84 by R. Allen with Zeiss 10A TEM. Neg. 12,000X. Bar
= 0.5µm.
|