Observations on the Fine Structure of the Nuclear Apparatus of Blepharisma intermedium Bhandary (Ciliata: Spirotricha)

Abstract

SYNOPSIS. An electron‐microscope study of the macronucleus and the micronucleus of Blepharisma intermedium Bhandary has been made. Sections show that the macronucleus is bounded by a double membrane. Inside, there are two types of bodies: (a) small irregular bodies, from 0.05 to 0.2 μ in diameter, and (b) larger bodies, from 0.4 to 0.6 μ in diameter. The former are intrepreted as cut ends of long, branching filaments traversing the nuclear cavity in all directions. They correspond to the DNA filaments obtained by centrifugation and KCN action on the macronucleus. Each filament is made of fibrils aboue 150 Å thick. The large bodies correspond to the nucleoli; they also show a fibrillar structure. They offer the added interest of displaying dense particles, from 100 to 800 Å in size, whose nature and significance are obscure. The micro‐nucleus has a double membrane, and the contents are divisible into an electron‐dense network and a material of low density which fills the interstices of the network.

Fine Structure of Division in Ciliate Protozoa

“…1, CR). The structure of the interphase nucleus is essentially identical with that described by Seshachar (42) and similar to that described for other ciliates (7,8,17,43). Occasionally, micronuclei similar to those described by Kennedy (18) are observed which seemingly lack the less dense cortex but are thought not to represent the interphase condition.…”

“…The import of large amounts of material into the micronucleus is possibly made more difficult by the apparent absence of pores in the nuclear envelope. Recently, pores have been reported for the micronuclear envelopes of Blepharisma (18) and Urostyla (15), and reported as absent from the micronuclear envelopes of Paramecium caudatum (17) and Blepharisma intermedium (42). Many dozens of micronuclei were examined in this investigation and at no time were obvious pores seen in the micronuclear envelope.…”

Osmium tetroxide vapor fixation of dividing and regenerating Blepharisma

“…46, GR). The structure of the micronucleus is essentially identical to that described for B. intermedium (Seshachar, 1964). Micronuclei may be located throughout the cytoplasm but most are localized near the macronucleus (Fig.…”

“…The most recently reported electron microscope study is that of Seshachar (1964) Comprehensive studies of the infraciliature are not presently avail able .…”

The Mitosis of Entamoeba histolytica Trophozoites

“…Both nuclei contain DNA and RNA [32]. The chromatin of the macronucleus of the ciliated protozoa is commonly organized into numerous discrete masses called "small bodies" [33] although it has also been observed in the form of spongy masses [34], reticular formations, long chains of chromatin thin plexuses [7], discretely elongated bodies [35], compact spheres, spherical masses, and clear halo granules [28]. The macronucleus of these protozoa contains a structure made visible by light microscope called the replication band, which is a specific site of DNA replication that migrates from the macronucleus and advances along the edge of this band generating the rearrangement of the chromatin in two zones: the proximal and the distal.…”