The development of the kidney of the pink salmon was traced from the earliest stages to the year-old finger-ling. The development of the pronephros has been treated separately. The mesonephros develops from the intermediate cell mass of the twelfth to the thirty-ninth segments. Differentiation of the unsegmented intermediate cell mass closely follows segmentation of the somites. The vascular strand is established beneath the hypochord by migration of cells from the intermediate mesoderm of either side. A solid cylindrical duct rudiment forms as a fold of the dorsolateral aspect of the mass on either side. Mesonephrogenic material separates as a narrow bridge of cells passing from one duct to the other between the cardinal vein and the aorta. Primary mesonephrogenic rudiments appear as condensations of the bridge cells closest to the ducts. Tubule rudiments are formed by elongation of the condensations. The free end of each tubule rudiment dilates to form a thin walled Bowman capsule whose lumen later extends into the tubule rudiment and finally opens to the duct. A glomerulus develops in the Bowman capsule as a solid invagination of cells from the vascular strand. This mass of cells subsequently becomes vascularised. Differentiation of the tubule into regions follows the appearance of the glomerulus. Secondary and subsequent tubule generations are similarly formed but open into previously formed primary tubules. The intertubular spaces become filled with myeloid tissue richly supplied with blood sinuses. The myeloid tissue is derived from the vascular strand. Three pairs of corpuscles of Stannius appear early in development as outgrowths of the segmental duct epithelium. Smaller unpaired corpuscles appear later to make the total number twelve. The fully differentiated nephron has five regions:- 1. a Bowman capsule and glomerulus 2. a short neck segment which opens directly from the Bowman capsule 3. a segment characterised by its low columnar epithelium and high brush border 4. a segment with tall columnar cells and a low brush border 5. a segment of low simple columnar cells. Several nephrons enter a collecting tubule. At least three generations of tubules open to the segmental duct by way of a common collecting duct formed by modification of the primary collecting tubule. Involution of the pronephros commences at about the time the fry normally enter the water at the river mouth. Retention in fresh water does not appear to affect the time of onset of involution. The pronephric region becomes very richly permeated with blood sinuses and may serve as a blood storage organ in older fish. In the oldest specimens studied arterial blood is supplied by paired arterioles in the intersegmental septa. Venous blood from the tail passes directly into a large median vein which passes anteriad in the kidney tissue. This vein originates as the right postcardinal vein in the young embryo. The left postcardinal does not develop posterior to the pronephros. Portal blood from the dorsal and ventral musculature reaches the kidney by way of venules in the myosepta. In the posterior region two large median arteries (arteria primitiva mesenterica) pass through the kidney to the hind gut. In the pronephric region the large median coeliaco-mesenteric artery passes through the kidney to supply the viscera. Glomerular counts made on samples taken from fresh and salt water over a period of two months suggest that the increased osmotic concentration of the marine environment has the effect of retarding the rate of development of new glomeruli in a logarithmic relation to length. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.-Biology)--Catholic University of America. / "Reprinted from Biological bulletin, v. 117, no. 2, pp. 208-221, October, 1959." Bibliography: p. 219-21.

Abstract The embryonic urogenital system (UGS) generates the metanephric kidney, gonad and the adrenal gland. It is well known that the development of the UGS is regulated by sequential and reciprocal epithelial and mesenchymal tissue interactions but the secreted mediators involved are still poorly known. The action of such inductive signals is typically regulated by specific antagonists. The Sprouty (Spry) proteins compose one family of cytoplasmic regulators that typically repress the function of the receptor tyrosine kinase (RTK) signal transduction pathways. The DAN/Cerberus (Cer) family that encodes secreted proteins bind and antagonize the Bmp, Wnt and Nodal signals. In this study the roles of Spry and Cer1 was addressed during mouse UGS development by targeted expression of SPROUTY2 (SPRY2) and Cer1 in the ureteric bud and Wolffian duct under the Pax2 promoter. Changes induced in the UGS assembly process were analyzed in detail to reveal the normal developmental roles of these proteins. SPRY2 expression led to either complete lack of the kidney, reduction in the kidney size or formation of unilateral kidney with reduced size. The SPRY2 mediated reduction in kidney size was accompanied by inhibition of expression of genes that are known to regulate kidney development. The results indicated that the Spry may take part in kidney development by coordinating the reciprocal cell signaling between the ureteric bud, the mesenchymal cells and stromal cells. In addition to the kidney, the gain of SPRY2 function revealed an important role in the control of male gonadogenesis. SPRY2 over expression in the Wolffian duct malformed the Wolffian duct derivatives, diminished the number of seminiferous tubules and the amount of the interstitial tissue associated with reduced mesonephric cell migration to the testis. Exogenous FGF9 rescued mesonephric cell migration inhibited by SPRY2. It was concluded that Spry protein contribute to male sexual organogenesis by antagonizing Fgf9 signaling. When the Cer1 gene was over expressed in the ureteric bud this lead unexpectedly to increased kidney size. The Cer1 mediated promotion of kidney size was demonstrated to involve enhanced ureteric bud morphogenesis. At the molecular level Cer1 protein function lead to inhibition of Bmp4 gene expression and concurrent upregulation of Gdnf and Wnt11 expression. Notably, excess BMP4 reduced the Cer1 stimulated ureteric bud branching and downregulated normally expression of Gdnf and Wnt11 in the embryonic kidney. Based on the presented data it is proposed that the establishment of mammalian organ size is under the control of both systemic and the intrinsic factors. Together the work demonstrates significant roles for the proteins that typically inhibit growth factor signaling or signal transduction. Hence organogenesis is controlled by coordination between positive and negative growth factor regulator signals.