Localization and transport of lipids in the avian ovarian follicular layers and the structural relationship of theca and granulosa to the basement membrane

Abstract

We describe the localization of lipids in the wall and superficial ooplasm of the largest avian ovarian follicles by the use of different fixatives and light and electron microscopy. We demonstrate that each yolk globule is always accompanied by one or more highly osmiophilic and sudanophilic alcohol insoluble yolk masses, which we have called satellite yolk. Together with the protein containing yolk globule it forms an integral morphological part of a compartmentalized, bipartite yolk system. Cytochemical, histoautoradiographic, biochemical, and light and electron microscopical aspects of satellite yolk were studied. At the start of satellite yolk formation in the 3-4 mm diameter follicle (when the oocyte begins to yellow) the distribution of the microcirculation of the follicle wall becomes printed on the underlying superficial ooplasm of the oocyte. The oocyte then presents so-called yolk mountains (containing satellite yolk), only localized below the thecal capillary sinus and not below the efferent and radially perforating thecal veins (black hole regions). We also describe the structural continuity between the thecal intercellular spaces and the microvilli-associated extracellular spaces of the granulosa cells via the basement membrane. The thecal cells present centripetal extensions into the basement membrane and the basement membrane material extends centripetally into the granulosa microvillar channels. Therefore, at least two cellular barriers are crossed when fat or fat precursors are transported from the thecal capillary sinus to the ooplasm.

Ovarian follicular development in the hawksbill turtle (Cheloniidae: Eretmochelys imbricata L.)

“…Notwithstanding this, the fatty yolk was chemically neutral and it was positively dyed with the Nile red component of the sulfate of Nile blue. This is in agreement with the reported increase of blood triglycerides during vitellogenesis in C. mydas (Kwan,1994; Hamman et al,2002), and the presence of “satellite yolk insoluble in alcohol” reported in T. s. elegans (Callebaut et al,1997) and in birds (Callebaut et al,1991).…”

Oogenesis and ovarian histology of the American alligatorAlligator mississippiensis

“…a,b: Oocyte in Stage IX (IX). This type of yolk unit has been described in birds (Perry and Gilbert, 1985;Callebaut et al, 1991Callebaut et al, , 1997. The polyhedral shape is observed in several of these platelets that are situated at the extreme periphery of the ooplasm.…”

Basal lamina of ovarian follicle regulates an inward Cl− current in differentiated granulosa cells

“…Furthermore, basal lamina of avian ovarian follicle regulated progesterone synthesis in avian granulosa cells in a homologous system (7). Moreover, different types of extracellular matrix proteins such as collagen matrix have been shown to alter steroid hormone synthesis in rat and human granulosa cells in vitro (1,12,13).…”

“…This homologous system was made possible by the anatomical structure of the avian ovarian follicle. In the mature avian ovarian follicle, the granulosa cell layer (membrana granulosa) consists of a single layer of cells located between the basal lamina and perivitelline layer (11,13,41,42,52); this arrangement made possible the isolation of intact basal lamina in hypotonic solution (4,7).…”