List of abbreviations
of micros-
specialist terms
explained in
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Dr. med.
H. Jastrow

of use
Overview heterochromatine (Heterochromatin):
Pages with explanations are linked to the text below the images if available! (Labelling is in German)
An entire English version of this page is in preparation!
nucleus of a lympho-
cyte (rat)
nucleus with pores,
jejunum (rat)
nucleus of a Schwann
cell (monkey)
cochlear ganglion cell
(guinea pig)
human segmentonuclear
nucleus of a parietal cell
stomach (rat)
nucleus of a
lymphocyte (monkey)
nucleus of a glial
cell (rat)
segmented nucleus of
a human eosinophil
typical orientation of euchromatin as
"spoke of a wheel" in a plasma cell (rat)
"spoke of a wheel" oriented
euchromatin in a human plasma cell
nucleus of a smooth muscle
cell (rat)
hepatocyte nucleus
nucleus of a Sertoli
cell, testis (rat)
massive concentration of heterochromatine
in a sperm cell (monkey)
Sertoli cells 
spiny cell nucleus
nucleus of a basophil
spleen (rat)
nuclei of retinal rods
lots of euchromatin in a nucleus of a prolactin cell, hypophysis (rat) changes in heterochromatin before a mitosis, adrenal gland (rat)

The heterochromatin (Terminologia histologica: Heterochromatinum) comprises the dense areas of chromatin (Terminologia histologica: Chromatinum) in the karyoplasm of a cell. Due to its high absorption of electrons it apperas dark, i.e. electron-dense in transmission electron microscopic images. Heterochromatin is basophilic in light microscopy. In heterochromatin desoxyribonucleic acid (DNA) is present in spiral form, i.e. it is bound to histon- and non-histon piation will always remain unused and are termed constitutive heterochromatin (missing in Terminologia histologica; proposal: Heterochromatinum constitutivum). In contrast, the facultative heterochromatin (missing in Terminologiroteins (see chromosomes). Thus the DNA is present here only as double-helix and cannot be read, i.e. it is inactive genetic informationThose sections of chromosomes which in a cell will never be transcribed due to its differenta histologica; proposal: Heterochromatinum facultativum) comprises chromosomal regions which are only transcribed during short, limited time intervals. Cells with high content of heterochromatin and only few euchromatin  have a low synthetic activity (e,g., fibrocytes) or only a mall portion of the genetic information is necessary to be transcribed for proper cell function as, e.g., in case of plasma cells which secrete only one type of immune globulineCondensations of chromatin, i.e., heterochromatin often is associated to the nucleolus (nucleolus-associated heterochromatin; missing in Terminologia histologica; proposal: Heterochromatinum adjunctum nucleoli) or it is attached to the nuclear lamina (nuclear lamina associated heterochromatin; missing in Terminologia histologica; proposal: Heterochromatinum adjunctum laminae nuclearis). There is a very characteristic distribution of eu- and heterochromatin in plasma cells that reliably allows cell identification: the spokes-of-a-wheel chromatin structure, wherby the spokes are formed by the lighter euchromatin which then in ideal case runs from a central dark nucleolus towards the nuclear poresSmall areas of very electron-dense heterochromatin which mainly are surrounded by euchromatin are termed chromatin granules (Terminologia histologica: Granumum chromatini).
Only in females about 25 - 30% of all nuclei show a very considerable lump of heterochromatin associated to the nuclear lamina in light microscopy, the sexchromatin (Barr's body; Terminologia histologica: Chromatinum sexuale). The latter comprises an inactive and thus condensed X-chromosome which is connected to the nuclear lamina with both of its terminals (telomer regions). From the beginning of somite formation on day 20 of embryonic development one and the same X-chromosome of each cell and daughter cells gets inactivated. In about 3% of all neutrophilic granulocytes of females this condened X-chromosome appears as drop- or drum-like appendix, i.e. drumstick on one of the nuclear segments (it is also called Chromatinum sexuale in the Terminologia histologica). Only with help of Quinacrin fluorescence staining it is possible to visualise a small spot called Y-chromatin (missing in Terminologia histologica; proposal Chromatinum Y) on the nuclear membrane in males which corresponds to a large heterochromatine part of the Y-chromosome.

--> nucleus, nuclear membrane, nuclear pore, nucleoplasm, euchromatin, nucleolus, chromosomes
--> Electron microscopic atlas Overview
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Three images were kindly provided by Prof. H. Wartenberg; other images, page & copyright H. Jastrow.