Structure and Function of the Ductuli Efferentes - University of Illinois ...

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DUCTULI EFFERENTES445TABLE 2. References to the ultrastructure of ductuli efferentesSpeciesReferencesHuman Schmidt (1964)Morita (1966)Nagano and Suzuki (1980)Jonte and Holstein (1987)Yeung et al. (1991)Hamster Young and Ladman (1957)Sedar (1966)Montorzi and Burgos (1967)Yokoyama and Chang (1971)Flickinger et al. (1978)Nagy (1990)Vicentini et al. (1990)Opossum Ladman (1967)Martan et al. (1967)Bull Wrobel (1972)Goyal and Hrudka (1980, 1981)Mouse Hoffer (1972)Nagano and Suzuki (1980)Rat Hoffer (1972)Hoffer et al. (1975)Hamilton (1975)Hamilton et al, (1977)Morales and Hermo (1983)Hermo and Morales (1984)Hermo et al. (1985)Francavilla et al. (1986)Jones and Jurd (1987)Koyama (1987)Rambourg et al. (1987)Hermo et al. (1988)Robaire and Hermo (1988)Ilio and Hess (1992)Guttroff et al. (1992)Hermo et al. (1992a)Hermo et al. (1992b)Monkey Ramos and Dym (1977)Marsh and Alexander (1982)Lohiya et al. (1988)Guinea pig Burgos t1957; 1960)Vitale-Calpe and Aoki (1969)Hoffer and Greenberg (1978)Nagano and Suzuki (1980)Rabbit Jones et al. (1979)Echidna Djakiew and Jones (1981)Elephant Jones and Brosnan (1981)Jones and Holt (1981)Goat Gray et al. (1983)Goyal and Williams (1988)Goyal et al. (1992)Squirrel Pudney and Fawcett 1 1977)Pudney and Fawcett (1984)Dog Holstein (1964)Chandler et al. (1981)Hess and Bassily (1988)Boar Wystub et al. (1989)Stallion Arrighi et al. (1993)Shrew Suzuki and Racey (1984)Donkey Aureli et al. (1984)Bat Azzali et al. (1983)Bird Aire (1980)Aire et al. (1979)Bellamy and Kendall (1985)Budras et al. (1979)Hess et al. (1976)Hess and Thurston (1977)Nakai et al. (1988)Nakai et al. (1989)Nakai and Nasu (1991)Tingari (1972)FrogKobayashi and Iwasawa (.1989a,b)membrane-bound bodies that stain with different intensities.In the initial zone of the ductules, these membrane-boundlent material, while in the terminal zone such bodies have ahomogenous dark staining pattern. These membrane-boundbodies stain positive with acid phosphatase and thus areconsidered to be lysosomes.Appropriate markers for electron microscopy havedemonstrated that the coated pits, apical tubules, endosomes,multivesicular bodies, and lysosomes are components of anelaborate endocytotic apparatus which is capable of fluidphaseand adsorptive (Hermo and Morales, 1984; Hermo et al.,1985; Morales and Hermo, 1983) and possibly receptormediatedendocytosis (Byers et al., 1985; Veeramachaneni andAmann, 1991; Veeramachaneni et al., 1990). Testicular fluid istaken up sequentially by the endocytotic apparatus from coatedpits to multivesicular bodies and then to lysosomes andbroken down by means of hydrolytic enzymes (Hermo andMorales, 1984; Wrobel, 1972; Yokoyama and Chang, 1971).The following route of endocytosis has been proposed byHermo et al. (1988). Tubular coated pits invaginate from theapical plasma membrane, pinch off, and undergo constrictionaccompanied by the gradual loss of their bristle cytoplasmiccoat to form apical tubules. The average time required for thisprocess is 5 min. Apical tubules fuse to form endosomes; 30%of the apical tubules recycle back to the apical plasmamembrane; the rest partake in the transformation of endosomesto multivesicular bodies to secondary lysosomes. The averagetime required for an apical tubule to fuse with an endosome is 2min. Recycling of apical tubules back to the apical plasmamembrane requires an average turnover time of 39 min,Functionally, the endocytotic activity of the epithelium hasbeen implicated in the regulation of the composition andquantity of the intraluminal fluid (Morales and Hermo, 1983).The differential staining characteristic between lysosomesof the initial zone, where these granules are pale staining, andthe terminal zone, where they are deeply osmiophilic, issuggestive of regional differences in the endocytotic activityalong the duct. Thus, it is believed that nonciliated cells in theinitial zone take up more fluid, while these cells in theterminal zone take up more particulate matter (Robaire andHermo, 1988). In contrast, an opposite situation occurs in thebull and goat in which more fluid is taken up in the terminalzone, where type III cells with light staining vacuoles abound(Goyal and Williams, 1988; Goyal and Hrudka,1980,1981).Aside from lysosomes, other organelles such asmitochondria, rough endoplasmic reticulum, and Golgiapparatus are also found in the supranuclear region. The Golgiappears to show no evidence of secretory granule formation(Robaire and Hermo, 1988). Thus, in the rat the nonciliatedcells are not thought to be secretory (Hoffer, 1972; Robaireand Hermo, 1988), in contrast to the situation reported for thebull and the goat in which the granules and vacuoles,presumably of Golgi origin, are thought to be secretory (Goyaland Hrudka, 1980, 1981; Gray et al., 1983). Instead, from anelectron microscope stereoscopic study, the Golgi has beendetermined to actively produce lysosomal enzymes destined forthe numerous secondary lysosomes in the supranuclearcytoplasm of the cell (Rambourg et
446 K.Y. ILIO AND R.A. HESStains nonciliated cells with numerous lipid droplets in the basal cy-toplasm (arrows), while the opposite side contains relatively few lipiddroplets. x 330.Figs. 19-21. Lipid droplets in the epithelium of rat proximalductuli efferentes.Fig. 19. Cryostat sections stained with Oil Red 0 show a heavylocalization of lipids in the basal cytoplasm. x 650.Fig. 21. A cryostat section stained with Oil Red 0 showing a regionthat is devoid of lipid, with only a few droplets along one sideFig. 20. Hematoxylin and eosin stained section of ductuli effer- (arrows). x 650.entes embedded in glycol methacrylate. One side of the tubule con-al., 1987). Peroxisomes of unknown function also arefound in the supranuclear area of the cell.A pale indented nucleus is present in the basal region ofthe nonciliated cell. Also in the basal region roughendoplasmic reticulum, mitochondria, and lipid droplets arecommon. Since lipids and lysosomes are often found to beclosely associated and both are sometimes found enclosedby a common unit membrane, it is thought that lipids arethe eventual fate of digested material taken up by thenonciliated cells (Robaire and Hermo, 1988). In fact, thelipids disappear entirely from the epithelium after the lossof testicular fluids and sperm from the ductal lumen (Niemiand Kormano, 1965). Principal cells of the ductulus efferensterminus region contain no vacuoles (Jones and Jurd, 1987)or rare apical vacuoles (Fig. 10). Without histochemicalevaluation it is difficult to determine which vacuolesrepresent lipid structures. We have observed numerous lipidlikevacuoles in the basal cytoplasm of some efferent ductalepithelia in the proximal zone, but in adjacent areas theepithelium may be entirely devoid of these vacuoles (Fig.20). However, using Oil Red 0 staining of frozen sections,large areas of lipid content are clearly denoted in the basalcytoplasm of nonciliated cells (Fig. 19), and in adjacenttubules the lipids are greatly reduced (Fig. 21).Nonciliated cells in the avian species are remarkablycal cytoplasm), but in the distal region the dense granulesare sparse (Aire, 1980). A well-developed apparatus forfluid and particulate reabsorption is present in the apicalcytoplasm. Perinuclear and basal lipid droplets arecommonly associated with mitochondria and lysosomalgranules (Hess and Thurston, 1977), similar to thatreported for the rat (Robaire and Hermo, 1988). Under adiseased condition called "Yellow Semen Syndrome," thelipid droplets and lysosomal granules are greatly increasedin both nonciliated and ciliated cells in the domestic turkey(Hess et al., 1982).Ciliated CellThe electron microscopic appearance of the ciliated cellsis less studied. These cells have been characterized asunremarkable, possessing the organelles and organizationtypical of ciliated cells elsewhere (Hoffer, 1972). Thesewere also found to possess, in reduced amounts, vesicularstructures that are involved in the uptake of material fromthe lumen through adsorptive as well as fluid-phaseendocytosis (Hermo et al., 1985). Thus, aside from thefunction of moving fluid and spermatozoa through the duct,ciliated cells appear to be capable of modifying thecomposition of the luminal fluid by the process ofendocytosis. In the dog, most ciliated cells are typical in
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