A freeze-fracture and lanthanum tracer study of the complex junction between Sertoli cells of the canine testis.

Abstract

What appear to be true septate junctions by all techniques currently available for the cytological identification of intercellular junctions are part of a complex junction that interconnects the Sertoli cells of the canine testis. In the seminiferous epithelium, septate junctions are located basal to belts of tight junctions. In thin sections, septate junctions appear as double, parallel, transverse connections or septa spanning an -90-A intercellular space between adjacent Sertoli cells. In en .face sections of lanthanum-aldehyde-peffused specimens, the septa themselves exclude lanthanum and appear as electron-lucent lines arranged in a series of double, parallel rows on a background of electron-dense lanthanum. In freezefracture replicas this vertebrate septate junction appears as double, parallel rows of individual or fused particles which conform to the distribution of the intercellular septa. Septate junctions can be clearly distinguished from tight junctions as tight junctions prevent the movement of lanthanum tracer toward the lumen, appear as single rows of individual or fused particles in interlacing patterns within freeze-fracture replicas, and are seen as areas of close membrane apposition in thin sections. Both the septate junction and the tight junction are associated with specializations of the Sertoli cell cytoplasm. This is the first demonstration in a vertebrate tissue of a true septate junction.

Sertoli cell ultrostructure. I. A comparative study in immature, pubescent, adult and cryptorchid pigs

“…Present observations agree with this hypothesis because the crystalloids are found near the plasma membrane, oriented in a way foreshadowing the formation of specialized Sertoli cell junctions. ' The description of these junctions in pig (Toyama, 1975), rat (Gilula et al, 1976) and dog (Connell, 1978) is comparable to those of the present study. Toyama (1976) proved that microfilaments found in the junctions were composed of a substance similar to actin, thus indicating that they could play on active role in sex cell displacement (Toyama, 1976 ;Gilula et al, 1976 ;Nagano and Suzuki, 1976).…”

“…Recent works show that this cell has enzymatic activity permitting the transformation of testosterone into dihydrotestosterone, androstenedione and androstanediols (Dorrington and Fritz, 1975 ;Tence and Drosdowsky, 1976 ;Welsh and Wiebe, 1976) and the conversion of testosterone into 17p-estradiol (Dorrington and Armstrong, 1975). Moreover, this cell may also transform progesterone into testosterone (Christensen and Mason, 1965 ;Lacy et al, 1969 ;Hall et al, 1969 ;Tence and Drosdowsky, 1976 Br6-kelmann (1963), Nicander (1967), Flickinger and Fawcett (1967), Dym and Fawcett (1970), Dierichs and Wrobel (1975), Bigliardi and Vegni Talluri (1976), Gilula et al (1976), Russell (1977a) and Connell (1978) ; those joining Sertoli cells to germ cells were reported by Ross (1976Ross ( , 1977, Ross and Dobler (1975), Wrobel and Dierichs (1975) and Russell (1977a, b, c). Charcot-B6ttcher's crystalloids have been studied by Bawa (1963), Nagano (1966Nagano ( , 1968, Sohval et at.…”

Modifications ultrastructurales des cellules germinales femelles au cours de la prophase méiotique chez le rat : étude particulière des membranes après cryofracture

“…Les quelques études des mitochondries réalisées chez la femelle (lapin : Anderson, 1968 ;Anderson et al, 1970) Connell, 1975Connell, , 1976Connell, , 1978rat : Nagano, 1980) …”

Blood-Tissue Barriers in the Male Reproductive Tract of the Dog: A Morphological Study Using Lanthanum Nitrate as an Electron-Opaque Tracer

“…The blood-testis barrier has been investigated extensively in a number of species [Setchell et al, 1969;Dym and Fawcett, 1970;Howards et al, 1976;Connell, 1978Connell, , 1980Turner et al, 1981;De Kretser and Kerr, 1994;Cavicchia et al, 1996;Setchell, 1998]. In all animals studied, Sertoli cell junctions ultimately prevent paracellular exchange of substances between basal and adluminal compartments.…”

“…It has been studied in a number of species such as man [Cavicchia et al, 1996], horse [Lopez et al, 1997], rat [Cavicchia et al, 1998], mink [Pelletier, 1994], and dog [Connell, 1978[Connell, , 1980. The blood-testis barrier plays a crucial role in normal spermatogenesis by shielding developing germ cells from blood-borne mutagenic substances and by preventing autoimmune reactions against sperm cells from occurring.…”