AGE-RELATED CHANGES IN THE HISTOLOGICAL

I – light microscope examination:Examination of haematoxylin and eosin stained sections of young male guinea pigs revealed numerous closely packed nuclei of different pituitary cells in the pars distalis separated by blood sinusoids. Some cells showed pale cytoplasm (chromophobes), others showed acidophilic and basophilic cytoplasm (figs.1&2).Mallory’s trichrome stained sections from the same animal group showed the presence of few collagen fibres in the stroma of the pituitary gland surrounding narrow blood sinusoids (fig.3).Few weak positive immunoreactive cells for anti-glial fibrillary acidic protein (GFAP) were also seen (fig.4).II- Electron microscope examination:Examination of ultrathin sections of young guinea pigs demonstrated various types of cells.Regarding somatotrophs, they were large oval or rounded cells with large euchromatic nuclei, prominent nucleoli and many parallel cisternae of rER. Numerous, large, rounded, electron dense granules were distributed in their cytoplasm. Some somatotrophs appeared with a pair of centrioles. Apoptotic small cells with small irregular nucleui having peripheral condensed heterochromatin were also observed. Also, some chromophobes with large nuclei, pale cytoplasm devoid of granules were observed (figs.5&6).Gonadotrophs with large oval euchromatic nuclei and small granules of different sizes and electron densities were seen distributed allover the cytoplasm. Also, mammotrophs with large oval euchromatic nuclei, parallel arrays of rER forming a nebenkern and many pleomorphic granules of variable shapes and electron densities scattered allover the cytoplasm were also noticed (figs.7&8).Small rounded thyrotrophs with large euchromatic nuclei, prominent nucleoli and very small granules arranged at the cell periphery were noticed. Large blood sinusoids with thin, regular basement membrane can also be seen (fig.9).Folliculo-stellate cells with large nuclei, electron dense cytoplasm and processes interdegitating between secretory cells were also observed (figs.10,11&12).(