study on the postnatal development and aging changes of the neurosecretory nuclei of the hypothalamus [supraoptic and paraventricular nuclei] in the albino rat

The hypothalamus is a distinct neurological entity concerned with a variety of regulatory processes. Recently, the prescence of variations in the level of neurosecretions wth the progress of age was reported. To study the changes in the structure of magnocellular neurons in the paraventricular and supraoptic nuclei during the period of postnatal development. Furthermore, to study the changes which occurred in the structure of these neurons in the old age had been studied. A total of 52 albino rats were used. The age groups of the animals include: one day, 10 days, 20 days, 2 months and 2 years old animals. Brains were processed to be studied with Einarson's gallocyanin-chrome alum stain, Golgi- Cox method and transmission electron microscope. In addition, the number of cells in the magnocellular part of the paraventricular and supraoptic nuclei were measured in all studied age groups and statistically analyzed. In the newly born rats, the paraventricular and supraoptic nuclei were composed of small rounded condensed cells. At the age of 10 days old rats, the paraventricular nucleus appeared to be well differentiated into ventromedial [parvocellular] and dorsolateral [magnocellular] parts. With the progress of age from 10 days up to the adult stage, the cells of the supraoptic nucleus and the magnocellular part of the paraventricular nucleus appeared to be densely stained which indicated increase in the Nissl granules. Ultrastructural study showed that the cells had abundant amount of free ribosomes, rough endoplasmic reticulum and mitochondria. The nucleus had fine dispersed chromatin. Golgi-Cox study showed marked increase in extension and branching of dendrites with the progress of age during the developmental period. Morphometric study showed significant increase in the number of cells from the new born up to the adult stage. In old aged rats, the cells of the paraventricular nucleus and the supraoptic nucleus appeared to be faintly stained. Some cells had vacuolated cytoplasm. Ultrastructural study showed marked decrease in the free ribosomes and the presence of many lipofuscin pigment in the cytoplasm of cells. The nucleus showed chromatin condensation and irregularity of the nuclear membrane. In addition, there was apparent decrease in the amount of the synaptic vesicles in the presynaptic terminals making contacts with the magnocellular neurons. Golgi-Cox study revealed marked decrease in the extension and branching of dentrites. Morphometric analysis showed significant decrease in the number of cells. This study demonstrated in the presence of structural changes in the magnocellular part of the paraventricular nucleus and supraoptic nucleus during the period of development. In old age, the presence of many degenerative changes was observed. This cytoarchitectonic analysis and morphological study could help in the explanation of the functional differences in the various ages

study on postnatal development and ageing changes of red nucleus in the albino rat

The red nucleus is one of the most important structures in the midbrain tegmentum. It plays an important role in the control of motor activities. The aim of the present work is to demonstrate the structure of the red nucleus and the characteristics of its constituent neurons during the various stages of postnatal development, it also includes the study of the ageing effect on the features of its cells. In this work, a total number of 40 albino rats was used. The following postnatal age groups of animals were studied; newly born, seven days, fifteen days and three months old [adult rats] in addition to the aged group of animals [two years old rats]. Animals were sacrificed and the midbrain region was dissected. In each age group, three midbrain specimens were processed to be studied by Einarson's Gallocyanin stain and another three specimens were processed to be studied by Golgicox method. The ultrastructural study for the cells of the red nucleus was done by transmission electron microscope. By using Gallocyanin stain, the red nucleus appeared as a circumscribed mass of cells. The caudal magnocellular part was composed mainly of large neurons and few medium and small sized neurons. The rostral parvocellular part consisted mainly of medium and small sized neurons. The cellular content of Nissl granules increased gradually from the newly born age up to the adult stage. In the aged group of animals, the cells of the red nucleus appeared to be lightly stained as compared to the adult animals indicating loss of Nissl granules. Golgi stain revealed that the caudal magnocellular part of the red nucleus was formed of different types of cells [multipolar, pyramidal and fusiform cells]. Their nerve processes showed gradual increase in the length and branching with the progress of age up to the adult stage. In the aged group of animals, these neurons showed a decrease in the extension of the nerve processes as compared to the adult group. The ultrastructural study of the caudal magnocellular part of the red nucleus in the adult animals revealed that the large neurons were characterized by the presence of rounded nucleus while the medium sized neurons had an invaginated nucleus. The cytoplasm of these cells was rich with ribosomes, rough endoplasmic reticulum and mitochondria. Several types of axosomatic synaptic terminals appeared to be present. In the aged animals, the ultrastructural study of these cells showed marked decrease in the amount of ribosomes and rough endoplasmic reticulum as compared to the adult animals. There was also accumulation of lipofuscin granules in their cytoplasm. It was concluded from this study that during the development of the red nucleus, its constituent neurons showed a progressive increase in their content of Nissil granules from the newly born age up to the adult stage. Their nerve processes also showed increase in the extension and branching. The wide variety of synaptic terminals with rubral neurons indicated the presence of several sources involved in the integration of descending motor information. In the aged animals, the rubral neurons showed several degenerative changes that could lead to impairment of motor activities