The structure of the chorion and associated surface filaments in Oryzias—evidence for the presence of extracellular tubules

Abstract

The structure of the chorion with its associated surface filaments has been examined in Oryzias latipes using several techniques, including scanning and transmission electron microscopy, enzymatic digestion, and sodium dodecylsulfate-polyacrylamide gel electrophoresis. The chorion of the recently fertilized egg was found to be organized into three zones: an outer, fuzzy electron-lucent zone that was continuous over the surface of filaments, a middle, homogeneous electron-dense zone, and an inner zone of ten to 12 horizontal, fibrous lamellae. Two topographically distinct types of filaments were found on the chorionic surface: nonattaching and attaching. Nonattaching filaments showed a regular spatial distribution over the chorion with an interfilament distance of about 60-70 microns. Attaching filaments originated from a localized portion of the chorion and united with those of neighboring eggs to anchor the egg cluster to the gonoduct of the female. Both nonattaching and attaching filaments were morphologically regionalized into basal and distal segments. Internally, nonattaching and attaching filaments were constructed of unbranched, packed tubules with an average outside diameter of approximately 19.5 and 18.8 nm, respectively. Using the attaching filament for further study, it was determined by rotational analysis (Markham et al., '63) that the wall of each tubule was a cylinder composed of 14 globular subunits. Two structural types of attaching filaments were identified. The type I attaching filament was similar in internal organization to the nonattaching filament and consisted of only tubules. The type II attaching filament, however, showed a highly osmiophilic, electron-dense bar surrounded by packed tubules. Tubules of attaching filaments of the adult were resistant to the action of Triton X-100 and colchicine, but sensitive to a 0.1% protease solution. However, colchicine-treated ovary tissue showed an absence and pattern of disorganization of tubules at the periphery of developing filaments. Solubilized attaching filament samples electrophoresed on 7.5% polyacrylamide-SDS gels were resolved into a pair of Coomassie-blue-positive bands that comigrated with purified porcine brain tubulin. The apparent molecular weight of the attaching filament polypeptide was determined to be approximately 55,000 daltons. These data suggest that the extracellular, tubular components of attaching filaments (as well as nonattaching filaments) are proteinaceous and show properties similar to those of cytoplasmic microtubules. Tubular precursor material was electron-dense and appeared to originate in the cisternae of the rough endoplasmic reticulum of ovarian foll

Ultrastructure of ovarian follicular epithelium of the Amazonian fish Pseudotylosurus microps (Teleostei: Belonidae): morphological and histochemical characterization of the intercellular deposits

“…However there is a possibility that the remaining material form some sort of appendages, that associated with the egg surface, may serve for eggs flutuation or fixation to a substrate, as verified in certain species (Anderson, 1966;Hart et al, 1984).…”

“…The ultrastructure of oogenesis in fishes have been studied by several authors concerning the developmental stages of oocytes growth (Anderson, 1974;Iwasaki, 1973;Bruslé, 1980;Cruz-Landim & Cruz-Höfling, 1979;Droller & Roth, 1966;Norrevang, 1968;Wourms, 1976;Shackley & King, 1977), the cellular envelopes of the developing oocyte (Chaudry, 1956;Cruz-Landim et al, 1987;Nicholls & Maple, 1972;Lambert, 1970;Shelton, 1978;Cruz-Höfling & Cruz-Landim, 1992;Hirose, 1972;Cruz-Landim, 1990;Khoo, 1975) and the oocyte acellular covers, during its growth and after egg maturation (Anderson, 1966(Anderson, , 1967Busson-Mabillot, 1977;Cruz-Höfling & Cruz-Landim, 1990;Dumont & Brummett, 1980;Hart et al, 1984;Lopes et al, 1982;Wourms & Sheldon, 1976;Tesoriero, 1978;Fleger, 1977). However although seems to have accordance among the authors about the phases of the oocyte growth and the description of the characteristic structures present in it the same do not happens concerning the egg cellular and acellular covers.…”

Zebrafish and medaka: model organisms for a comparative developmental approach of brain asymmetry

“…it is delayed in medaka compared with zebrafish. As the onset of expression of hatching enzyme genes is comparable in zebrafish and medaka (figure 3b; Inohaya et al 1995Inohaya et al , 1997, it is likely that the differences in hatching time are a result of dissimilar chorion composition and thickness between the two species (Hart et al 1984;Hart & Donovan 2005). Regardless of the underlying developmental mechanism, a main consequence of the heterochronic shift in hatching is the definition of zebrafish as altricial (immature) and medaka as precocial (more developed) species (MacArthur & Wilson 1967).…”

Medaka Oocytes Rotate Within the Ovarian Follicles During Oogenesis

“…3-2 in [26]). The movement of living oocytes during incubation was traced by observing the positions of attaching and nonattaching filaments (defined by [7]) on the chorion when viewed under an ordinary light microscope with a 20x objective and a projection lens ( 3 . 3~) connected to a camera and a video cassette recorder (Victor Co., Tokyo).…”