On the fine structure of the aglomerular renal tubule in Lophius piscatorius

Gross, histological and ultrastructural morphology of the aglomerular kidney in the lined seahorse Hippocampus erectus

Histologic evaluation of the renal system in the lined seahorse Hippocampus erectus reveals a cranial kidney with low to moderate cellularity, composed of a central dorsal aorta, endothelial lined capillary sinusoids, haematopoietic tissue, fine fibrovascular stroma, ganglia and no nephrons. In comparison, the caudal kidney is moderately to highly cellular with numerous highly convoluted epithelial lined tubules separated by interlacing haematopoietic tissue, no glomeruli, fine fibrovascular stroma, numerous capillary sinusoids, corpuscles of Stannius and clusters of endocrine cells adjacent to large calibre vessels. Ultrastructural evaluation of the renal tubules reveals minimal variability of the tubule epithelium throughout the length of the nephron and the majority of tubules are characterized by epithelial cells with few apical microvilli, elaborate basal membrane infolding, rare electron dense granules and abundant supporting collagenous matrix.

Video-enhanced microscopy of organelle movement in an intact epithelium

Digitally enhanced video microscopy has provided improved optical resolution in the study of intracellular organelle/particle movement, particularly in extruded axoplasm and certain thin single cell systems. We report here, for the first time, particle movement in an intact, isolated epithelium, the killifish proximal convoluted tubule. Cytoplasmic particles exhibited predominantly unidirectional linear movement approaching several microns in length, sometimes with multiple turns. The velocities of 34 particles measured in 11 cells averaged 0.29 microns/sec (range, 0.007-3.1 microns/sec). Microtubules--the well-established basis for organelle movement in cells--were present but were sparsely represented in electron micrographs of these cells. Video-enhanced microscopic techniques can now be applied to the study of organelle/particle movement in an intact epithelium.

The structure of the kidney from the freshwater teleost Carassius auratus

The structure of the kidney of the crucian carp (Carassius auratus; a freshwater teleost, Cypriniformes) was studied by means of reconstruction from serial paraffin and semithin sections. In C. auratus, the Wolffian duct traverses the entire kidney. At various levels collecting ducts of different length and thickness join the Wolffian duct at right angles. Each collecting duct accepts a large number of connecting tubules, which are established by the joining of many nephrons. A regular pattern concerning the distribution of nephrons and the fusion of renal tubules is not apparent. Four segments have been distinguished in renal tubules; 1) proximal tubule, 2) distal tubule, 3) connecting tubule and 4) collecting duct. A neck and an intermediate segment are absent. The proximal tubule is established by proximal tubule cells which bear a brush border and have a conspicuous apical cytoplasmic rim containing few cell organelles, ciliated cells, mucous cells and dark cells. In the first part of the proximal tubule the brush border and the apical cytoplasmic rim of proximal tubule cells are well developed. Ciliated cells are interposed between proximal tubule cells, decreasing in number toward the end of this part. In the second part ciliated cells are absent and dark cells are numerous. In the third part the brush border and the apical cytoplasmic rim of proximal tubule cells are scarcely developed. Ciliated cells reappear and increase in number toward the distal tubule. The distal and connecting tubule are similar in epithelial structure. Connecting tubules are joined distal tubules and thus they belong to two or more nephrons.(ABSTRACT TRUNCATED AT 250 WORDS)

The aglomerular nephron of antarctic teleosts: a light and electron microscopic study

Complete serial sections demonstrated that ten species of Antarctic teleost fishes representing two families had aglomerular kidneys. The aglomerular nephron of such kidneys consists of two distinct regions: (1) a highly contorted principal segment and (2) a system of collecting tubules and ducts. Throughout the principal segment the cells are characterized by densely packed microbilli and a single cilium projecting into the lumen. Within the cytoplasm, lysosomes are rarely encountered, as would be expected if there is little or no reabsorption of protein from the urine. At the base of these cells, the plasma membrane is prominently infolded in close association with abundant mitochondria. The overall fine structure of the principal segment cells is consistent with their probable function in the secretion of ions into the formative urine. Between the principal segment and the collecting tubule is a very short transitional zone characterized by transitional mucus cells and multiciliated cells. The collecting tubule and duct system is lined entirely by mucus cells. In comparison with principal segment cells, the mucus cells have a well-developed Golgi complex and abundant secretory granules in the apical cytoplasm; these granules presumably contain the non-sulfated acid mucopolysaccharide demonstrable by light microscopic histochemistry.