Immunolocalization of type IV collagen and laminin during rat gonadal morphogenesis and postnatal development of the testis and epididymis

The distribution of type IV collagen and laminin was studied by immunocytochemistry during rat gonadal morphogenesis and postnatal development of the testis and epididymis. Immunostaining appeared as early as the 12th day of gestation along the basement membranes of the mesonephric-gonadal complex. The connection between some mesonephric tubules and coelomic epithelium was seen between the 12th and 13th day of gestation. Discontinuous immunostained basement membranes delineated the differentiating sexual cords in 13-day-old fetuses; this process probably began in the inner part of the gonadal ridge. The seminiferous cords surrounded by a continuous immunoreactive basement membrane are separated from the coelomic epithelium by the differentiating tunica albuginea in 14-day-old fetuses. During the postnatal maturation of epididymis and testis, the differentiation of peritubular cells is accompanied by a progressive organisation of the extracellular matrix into a continuous basement membrane. This change is associated with a gradual condensation of peritubular cells inducing an increase of immunostaining. In adult animals, the tubular wall of epididymis is thicker than the lamina propria of seminiferous tubules. Both type IV collagen and laminin immunostaining paralleled during ontogenesis at the light-microscope level.     

Earliest renin containing cell differentiation during ontogenesis in the rat

Summary The differentiation of renin containing cells was studied by immunocytochemistry in normal rat fetuses by the use of highly specific renin, angiotensin I and II antisera.Renin synthesizing cells were detectable as early as the 15th day of gestation outside the nephrogen territories within the walls of mesonephrotic-gonadic and renal arteries. Intrarenal differentiation began at the 17th day and progressed along the intrarenal arterial tree. AII immunostaining appeared concomitantly in the renin containing cells and developed considerably during ontogenesis, suggesting intracellular biosynthesis.It can be suggested that in the fetus newly synthesized AH may contribute to the early systemic and renal blood pressure regulation.     

Influence of testicular secretions on differentiation in the rat epididymis: ultrastructural studies after castration, efferent duct ligation and cryptorchidism

The differentiation of the rat epididymis was studied in prepubertal castrated, ligated or cryptorchid rats, in order to assess the influences of blood-borne and luminal androgens. The principal cells showed partial differentiation: decrease in cell height, decreased numbers of cytoplasmic organelles implicated in the elaboration phenomena (Golgi apparatus, smooth endoplasmic reticulum), whereas the organelles implicated in the absorptive function remained relatively intact. The lamina densa of the basement membrane underlying the epithelium was irregular, thicker than normal and followed the irregular outline of the basal parts of the epithelial cells. These changes were evident in castrated rats, to a lesser degree in ligated and cryptorchid rats, and were more prominent in the initial part of the duct. On the other hand, the narrow cells and the clear cells followed a normal differentiation pattern in the experimental rats, suggesting that a differential androgen dependence exists among the various type of epididymal cells.     

The stacking of the thylakoids of two leguminosae. Differential responses to H+ and divalent cations

The stacking of the thylakoids of lupine and horse bean has been studied by the digitonin method in relation to the concentration of H⁺, Ca²⁺ or Mg²⁺. (1) The isolectric point appears to be 4.7 for the two species. At this pH, Ca²⁺ has no effect on the stacking of the lupine thylakoids but it lowers the stacking of those of horse bean. (2) At pH 7.6, for any given Ca²⁺ concentration, the horse bean thylakoids fix a lesser amount of Ca²⁺ than those of lupine but they are more stacked. (3) The surface potential has been estimated by the use of the Gouy-Chapman model, modified to take account of H⁺ and Ca²⁺ binding. Simulation of the experiments indicates that the results may be explained by supposing that (i) the anionic groups are less numerous on the horse bean thylakoids than on those of lupine, (ii) they are arranged such that the affinity for the binding of Ca²⁺ or Mg²⁺ is higher for horse bean and virtually nil for lupine, and (iii) the divalent cation binding per se promotes the stacking when the coulombic repulsion is sufficiently weakened by screening and binding.