3 research outputs found
Cellular proliferation in the rat pineal gland during postnatal development
To establish a possible correlation between
the rate of cellular proliferation and already documented
functional and morphological characteristics of the rat
pineal gland during postnatal development, the
bromodeoxyuridine labelling method was used to
evaluate the fraction of cells at the S phase of the cell
cycle in paraffin sections from I-, 7-, 14- and 28-day-old
rats. Numerical density, taken as an indirect measure of
cell hypertrophy, was also evaluated. During the first
week after birth the percentage of S phase-cells in the rat
pineal gland sharply decreased from around 9% to 1.3%.
A smaller but also significant decrease was found from
the 7th to the 14th postnatal day where S phase cells
were less than 0.5% of all pineal cells. A very low
percentage was also seen in samples from 28-day-old
rats. Numerical density, namely, the total number of cells
per surface unit of pineal section, decreased from birth to
the end of the first month. This decrease was also steeper
from birth to the 7th postnatal day than at any other
period of the study. These results support the idea that a
strong expansion of the cellular population of the rat
pineal gland precedes morphological and functional
maturation and opens the way to further exploration of
the relationship between functional and proliferative
responses of the pineal gland
Myelinated Herring bodies in the median eminence of the cat
An electron-microscopic study was carried
out on the median eminence of cats during post-natal
development. From the moment of birth (observations
performed 12 hours later) Herring bodies were seen in
the fibrillary layer of the median eminence. At 45 days
after birth, myelinated nerve fibres could be observed,
some of them containing neurosecretory granules. The
number of myelinated fibres in the median eminence
increased with age and at 90 days some Herring bodies
appeared surrounded by myelin sheaths; these mainly
contained neurosecretory granules and a few mitochondria
The ependymal surface of the fourth ventricle of the rat: a combined scanning and transmission electron microscopic study
The morphological features of the
ependymal surface and supraependymal elements of
the fourth ventricle of the rat were examined by
scanning electron microscopy (SEM) and by the
transmission electron rnicroscopy (TEM). The results
confirm the following aspects: 1) The presence of
supraependymal elements and microvilli in the
ependymal territories, including the sites where the
cilia completely cover the ependymal surface; 2) The
existence of cilia with oval or sphencal thickenings
together with supraependymal bulbs similar in size to
those of the larger ciliary swellings; 3) Identification
of the long supraependymal fibres with intermittent
fusiform dilations observed under the SEM with the
neme fibres seen under the TEM; 4) The existence of
intraventricular axodendritic synapses