Morphology of the Nephron in the Mesonephros of Bufo bufo (Amphibia, Anura, Bufonidae)

Abstract

U~b j e r g . N., Lorsen, E. H. & Jespersen, A. 1998. Morphology of the nephron in the mesonephros of Bufo bufo (Amphibia, Anura, Bufonidae).-Acta Zoologica (Stockholm) 79: 3 1-50.The present study deals with the morphology and ultrastructure of the nephron in the mesonephros of the toad, Bufo bufo (Linnaeus, 1758). Based on serial sections in paraffin, Araldite and Epon, the position of the different segments of the nephron within the kidney tissue was determined, and a nephron subsequently reconstructed. The nephron consists of the following parts: Malpighian corpuscle, neck segment, proximal tubule, intermediate segment, early distal tubule, late distal tubule and collecting tubule. The late distal tubule was subdivided into three morphologically different sections. The total number of nephrons in the toad mesonephros was estimated at 6OOO units. The length of the segments in the reconstructed nephron was calculated. The cytology of the epithelial cells constituting the segments was described using transmission and scanning electron microscopy. Heterocellularity was found in the late distal tubule section I and 111 and in the collecting tubule. The proportional distribution and number of intercalated (mitochondria-rich) cells in the late distal tubule and collecting tubule was calculated. Only one morphological type of intercalated cell could be distinguished. Late distal tubules were removed from fresh Bufo kidneys for preliminary studies of the intercalated cells with Nomarski optics. 0 1997 The Royal Swedish Academy of Sciences.Published by

The prepattern transcription factor Irx3 directs nephron segment identity

“…Importantly, pronephric development is regulated by many of the same genes necessary for nephrogenesis in mammals, including Wnt4 and FGF8 (Saulnier et al 2002b; Urban et al 2006). First evidence for segmental organization of the pronephric nephron was provided by histological analysis (Mobjerg et al 2000), and has recently been supported by studies demonstrating regionalized expression of transporter and ion channel genes along the proximodistal axis (Eid et al 2002;Zhou and Vize 2004).…”

The atrial natriuretic peptide (ANP) system in the pronephros and mesonephros of Bufo bufo larvae

“…In the X larval stage, the mesonephros is already present and is located in the posterior region of the abdominal cavity, beside the spine, and reveals dorsal nephrons development in progress, while few ventral nephrons are differentiated [15]. A complete nephron is made up of a Malpighian corpuscle and tubule.…”

“…At this stage, the mesonephric tubule consists of a neck segment that connects the Bowman's capsule to the proximal tubule, from the proximal and distal tracts that are separated by an intermediate, ciliated segment [15]. The morphology of the proximal and distal tubule resembles the same parts of the pronephric tubule.…”

“…In the distal tubule, the ANP receptors only were present in the basal compartment of the epithelial cells. This tubular pronephric tract resembles the distal tubule of the adult amphibian mesonephros [9,14,15,69] that is considered to be a diluent segment since it is waterproof and actively reabsorbs NaCl [70]. The ANP receptors may indicate hormonal involvement in the flow of sodium toward the inside compartment.…”

“…The development, morphology and ultrastructure of the amphibian pronephros and mesonephros have been extensively studied [3][4][5][6][7][8][9][10][11][12][13][14][15]. Previous studies [1,[16][17][18][19] on larval and adult amphibians show that the organs involved in the osmoregolatory functions are targets of atrial natriuretic peptide (ANP).…”