Ultrastructural studies on the testis of the domestic fowl, gallus domesticus

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 1975
Thesis identifier
  • T75(1975)
Qualification Level
Qualification Name
Department, School or Faculty
  • The ultrastructure of the fowl testis from hatch to maturity is compared following immersion fixation using different fixatives with a variety of buffers. Glutaraldehyde buffered with sodium cacodylate is found to give the best fixation over the whole age range. The effect on fine structure of varying the osmolality of the glutaraldehyde/ buffer solution is investigated. The best fixation image is obtained with an osmolality higher than that of the blood plasma or semen. Changes in the concentration of the buffer had a greater effect on the fine structure than changes in the concentration of the fixative. A method for obtaining uniform fixation of the testis of the domestic fowl by vascular perfusion is presented. The differentiation of the germ cells during spermatogenesis and spermiogenesis is described and found similar to that of other vertebrates.' Two types of spermatogonia are noted and the number and type of cytoplasmic bridges between spermatogonia and spermatocytes are described. The paucity of cytoplasmic bridges in the fowl compared to mammals is related to the lack of germ cell synchronisation in avian testes. The relationship between the spermatid acrosome and the A Sertoli cell cytoplasm^examined and related to the mechanism of sperm release. This thesis presents the first ultrastructural demonstration of spermiation in the domestic fowl. Pour main stages are i-ecognised: (l) the swelling of the smooth endoplasmic reticulum of the spermatid to form vesicles, (2) invagination of these vesicles increasing their surface area, (3) coalesence of the vesicles around the spermatid, so it lies free within a large vesicle, (4) release of the acrosome by the Sertoli cell cytoplasm. This mechanism is compared to those described for amphibian and mammal. Aspects of the morphological pathway taken by substances passing from the blood stream to the seminiferous tubules that have not been previously examined in the fowl testis are described. The organisation and differentiation of the intertubular tissue is studied and compared to the organisation in mammals. The relationship between the blood vessels, lymphatic vessels, Leydig cells and seminiferous tubules is noted. Five types of Sertoli-Sertoli cell junctions are described: zonula occludens, zonula adhaerena desmosomes, interdigitating membranes, subsurface cisternal junctions and tight junctions. The differentiation of the Sertoli-Sertoli tight junction is correlated with the onset of spermatogenesis. There are no gap junctions like those of mammalian testis. The tracers, lanthanum rsitrate and horseradish peroxidase are used to delineate the pathway from the bloodstream to the tubules. Lanthanum perfused intravascularly with the fixative and peroxidase injected intravascularly are seen lying in the endothelial inter¬ cellular clefts, in the interstitial spaces, in the intercellular clefts of the peritubular boundary cells and the' surrounding intercellular spaces of the spermatogonia. Further penetration towards the lumen is prevented by tight junctions between adjoining Sertoli cells above the spermatogonia! layer. Thus the morphological basis of the blood-testis barrier in the fowl appears to be the Sertoli-Sertoli tight junctions. No barrier is present until the differentiation of the pachytene spermatocytes and the appearance of the Sertoli-Sertoli junctions after the onset of spermatogenesis. The possible functional significance of the barrier is discussed.
Resource Type