Page 18 - Headlines Histology2024_Neat

• The histones are involved in the folding of DNA strands and regulation of
DNA activity.

• The non-histones are involved in the regulation of gene activity. The
nuclear RNA represents newly synthesized transfer and ribosomal RNA
that has not yet passed into the cytoplasm.

• With LM, the nuclei appear as basophilic structure located either centrally,
eccentric or in a peripheral position. Most commonly nuclei are spherical or
ovoid but they may be spindle-shaped (smooth muscle), bean or kidney-
shaped (monocytes), or multilobulated (neutrophils).

• Most often, cells are mononucleated. Some however, may be binucleated or
even multinucleated.

• The interphase (not engaged in cell division) nucleus consists of nuclear
envelope, chromatin, nucleolus and nuclear sap (karyolymph).

Nuclear envelope

• With LM, it appears as a single basophilic line due to the presence of
condensed chromatin adherent to its inner surface (peripheral chromatin) as
well as ribosomes on the outer surface of the nuclear envelope.

• With EM, he nuclear envelope consists of two membranes separated by a
perinuclear space 25nm wide.

• The outer membrane is continuous with the membranes of both the rER and
sER and it may be studded with ribosomes.

• At the inner surface of the inner membrane, a layer of condensed chromatin
known as granular lamina is usually encountered.

• Numerous pores through which the nucleus communicates with the
cytoplasm interrupt the nuclear envelope.

• The nuclear pore is guarded by two annuli, an outer and an inner annulus,
each with eight globular subunits 15-20 nm diameter, projecting inwards
from them are eight radially arranged spokes. In the center of the pore there
is a central granule or plug. Such structure is called nuclear pore complex.

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