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vol-34HISTOCHEMICAL AND FINE STRUCTUR STUDIES OF CELL
TYPE IDENTIFICATION, LOCALIZATION AND SEASONAL
VARIATION IN PITUITARY GLAND IN RELATION TO
GONADAL MATURATION OF FEMALE OBLADA MELANURA
MOHAMED, ABD. EL. G. AL-ABSAWY
National Institute of Oceanography and Fisheries, Kayet Bay, Alex. Egypt.
Keywords: Pituitary gland – Histochemistry – Ultrastructure – Oblada melanura.
ABSTRACT
Oblada melanura adenohypophysis is subdivided into three distinct zones innervated
by the process of neurohypophysis. Six cell types were identified and localized in the
adenohypophysis using histochemical and electron microscopy methods. The acidophilic
prolactin (PRL) and adrenocorticotropic hormone secreting cell (ACTH) were found in the
rostral pars distails region (RPD). The PRL cells showed strong affinity to Azan stain and
gave red colour. The ACTH cells showed strong tinctorial response to lead Hematoxylin
and gave dark gray colour. The ACTH cell gave brown colour when stained with Azan
technique. These cells were generally interlocated between neurohypophysis and PRL cells,
forming a defined cell population clearly distinct from PRL cells which were restricted to
RPD region. The third and the fourth acidophilic melanocyte stimulating hormone secreting
cells (MSH) and somatotrops cells (STH) were observed in the proximal pars distails
region (PPD). They were mostly rounded with indented nucleus in case of MSH, while the
nucleus of STH was irregular in shape. The MSH cells stained light red with Azan. All
acidophilic cell types did not change their activity throughout the year. The basophilic
gonadotrophic cells (GTH) and thyrotrophic cells (TSH) react positively with PAS. One
type of GTH cells were detected, Herlant technique gave blue colour for GTH cells. The
GTH cells exhibited both quantitative and qualitative variations during the ovarian cycle.
During resting period (immature and mature) and pre-spawning period, the GTH cells were
characterized by gradual accumulation of granules and reached to maximum diameters at
the pre-spawning period as reflected by electron microscope. The activity of GTH cells was
reflected by staining affinity and vacuolization of the cells. During ripening and spawning
period (from May to August), slight decrease in the GTH diameters and staining affinity
were recorded. During the spent stage (from September to November), the GTH cells was
stained weakly with presence of vacuolated and atretic cells. The neurohypophysis in
Oblada melanura consisted of nerve fibers which extended below the pituitary stalk.
