Mizuho Ogawa

Comparative Studies of the Juxtaglomerular Apparatus

Publisher Summary Specific components of the mammalian juxtaglomerular apparatus (JGA) are juxtaglomerular (JG) cells containing renin-forming granules, the macula densa (MD), and the extraglomerular niesangiuni (EGM) JG granules are present in tetrapods, glomerular and aglomerular teleosts, and holocephalians. Some sarcoptrrygians and primitive bony fishes have also JG granules. JG cells appear to have approached closer to the glomeruli during tetrapod evolution. The MD and the EGM are present only in mammals. Avian kidneys have a transitional MD, but no EGM. The MD and the EGM are absent in reptiles, amphibians, and fishes. Renin has been found in the kidneys of tetrapods and bony fishes, although some bony fishes lack JG granules. The renin–angiotensin system (RAS) appeared first in primitive forms during the early evolution of bony fishes. A variety of possible physiological roles of the RAS have been proposed. These include blood pressure regulation, control of aldosterone secretion, control of glomerular filtration rate by constricting afferent or efferent glomerular arterioles, stimulation of intestinal transfer of sodium and water, and stimulation of a dipsogenic mechanism in the central nervous system. The physiological roles of the RAS in nonmanimalian vertebrates are unknown.

The effect of prolactin on water influx in isolated gills of the goldfish, Carassius auratus L.

Abstract 1. 1. The effect of prolactin on water influx into the isolated gills of the goldfish, Carassius auratus, was studied by an in vitro technique. The weight increase of isolated gills of intact, hypophysectomized, prolactin-injected and growth-hormone injected goldfish in deionized water after preincubation in saline solution was measured. 2. 2. Bovine prolactin injection and prolactin given into the preincubation saline medium significantly reduced the weight increase of the isolated gills. On the other hand, growth hormone showed no effect. 3. 3. Hypophysectomized fish showed almost the same range of weight increase of the isolated gills as intact fish, but prolactin injection of hypophysectomized goldfish significantly reduced the weight increase. 4. 4. Prolactin administered either by a peritoneal injection or by addition into a preincubation medium may inhibit the water influx into the gills of goldfish.

Prolactin-like immunoreactivity in the granules of neural complex cells in the ascidian Halocynthia roretzi

Abstract.Electron-microscopic studies of the neural complex (neural gland, dorsal strand, and cerebral ganglion) of an ascidian, Halocynthia roretzi, were performed, paying particular attention to the secretory systems. We found that cells scattered along the dorsal strand and neural cells in the cerebral ganglion contained electron-dense secretory granules of variable size. Immunoelectron-microscopic studies with an antiserum to bullfrog prolactin revealed that the secretory granules (100–250 nm in diameter) of some granulated cells contained a prolactin-like substance. Cells belonging to the neural gland and dorsal strand neither contained electron-dense granules nor showed immunoreactivity. The possibility that cells in the cerebral ganglion and those along the dorsal strand are phylogenetic progenitors of vertebrate adenohypophyseal cells is discussed.

The effects of prolactin, cortisol and calcium-free environment on water influx in isolated gills of Japanese eel, Anguilla japonica.

Abstract 1. The effects of prolactin, cortisol and a calcium-free environment on water influx into the isolated gills of the Japanese eel, Anguilla japonica were studied by an in vitro technique. 2. It was confirmed that the prolactin injection significantly reduced the water influx into the isolated gills and/or water permeability. Cortisol injection, on the other hand, increased the water influx and/or water permeability. 3. Calcium-free environments, deionized water and calcium-free sea water, served to increase the water influx and/or water permeability compared with its values in normal environments. 4. The possible roles of prolactin, cortisol and environmental calcium in the osmoregulation of the eel in fresh water and sea water are discussed.

Ultrastructure of the thread cells in the slime gland of japanese hagfishes paramyxine atami and eptatretus burgeri

SummaryThe thread cells in the slime gland of Japanese hagfishes, Paramyxine atami and Eptatretus burgeri were studied by light and electron microscopy.The mature thread cells are large elements (180×80 μ) filled with an intricately coiled thread, approximately 2 μ in diameter. The protein nature of the thread has been confirmed by histochemical examination. In the initial stage of growth, the thread consists of a bundle of distinctly parallel filaments approximately 90–120 Å in diameter and a centrally located tubular component approximately 230–260 Å in diameter which occurs singly or occasionally as a double and triple structure. The developing thread displays thin filaments, approximately 30–60 Å in diameter. The thin filaments are composed of fine fibrous structures, subfilaments, approximately 10–30 Å in diameter. On the outer surface of the thread a coating is apparent, giving it a fluffy appearance. Polysomal clusters consisting of five or six ribosomes are predominant. Fine fibrous structures are also found among the threads. They seem to have a spatial relationship with the polysomes and resemble the subfilament constituents of the thin filaments.From these results, it may be suggested that the fine fibrous structures synthesized by polysomes, twist together and coalesce into a thread. The problem of the polysome size and the molecular weight of the fibrous protein synthesized is discussed.

Hypocalcemic effect of homologous angiotensin-like substances produced by the renin-like enzyme in the corpuscles of stannius in the Japanese eel Anguilla japonica

Abstract In the intact Japanese eel kept in fresh water, a homogenate of the corpuscles of Stannius (CS) from the carp produces hypocalcemia when 50 mg/kg body weight of the tissue is injected intraperitoneally each day for 3 days. Angiotensin-like substances formed by incubating the eel CS extract with homologous plasma are also hypocalcemic when 250 ng equivalent to [Asp 1 , Ile 5 ]angiotensin II per kilogram body weight is injected according to the above schedule. Angiotensin-like substances formed by incubating the eel kidney extract with homologous plasma are less hypocalcemic. CS, plasma, and unicubated controls for CS angiotensin preparation are not hypocalcemic. They are made by eliminating plasma, CS extract, or incubation from the incubation mixture, respectively. This indicates that only the incubation product of the CS extract with plasma is hypocalcemic. When the CS secretes renin-like enzyme into blood, the enzyme may produce angiotensin-like substances in vivo . Formed angiotensin-like substances may cause hypocalcemia. Therefore, the present results suggest that the renin-like enzyme in the CS may be identical to hypocalcin in the Japanese eel.

Juxtaglomerular apparatus in the vertebrates

Abstract Renin and juxtaglomerular (JG) cells are present in tetrapod vertebrates and teleosts the macula densa (MD) and extraglomerular mesangium (EGM) are seen only in mammals. Detailed studies of the evolution of juxtaglomerular apparatus (JGA) are presented in this paper. No granules were stained with Bowies method in the kidneys of Chondrostei: Polypterus senegalus, Calamoichthys calabaricus, Acipenser brevirostris, and Holostein: Amia calva, Lepisosteus osseus. In the kidney of the lungfish, Protopterus aethiopicus, JG cells were found in the arterial wall distant from the glomeruli. Three types of distribution of JG cells were observed in aglomerular teleosts. In the kidney of Opsanus tau, JG cells were distributed in the walls of small arteries. In Lophius litulon, JG cells were distributed in several regions of the kidney. In Phrynelox nox, P. tridens and Histrio histrio, JG cells were concentrated in a limited area of the kidney. The MD site was examined with the light microscope in Gallus gallus v. domesticus and Coturnix coturnix japonica, and with the electron microscope in G. gallus. The avian cells possess some of the characteristics of mammalian MD cells, and can be considered as structurally transitional between typical MD cells in mammals and the ordinary cells of the distal tubule.

The macula densa site of avian kidney

SummaryThe macula densa (MD) site of the kidney, at which the distal tubule is attached to the vascular pole of the glomerulus, was examined with the light microscope in domestic fowl and Japanese quail; and in the fowl also with the electron microscope. The characteristics of mammalian MD cells, as reported in the literature, are compared with those of the cells in the avian MD site. The avian cells possess some of the characteristics of mammalian MD cells and they are distinguishable from the cells in adjacent portions of the distal tubule. The Golgi system in the avian cells is apical to the nucleus, unlike in mammals where its location is basal. The cells in the avian MD sites can be considered as structurally transitional between the typical MD cells in mammals and the ordinary cells of the distal tubule. These findings are discussed in relation to the function of the avian kidney and to its control by the renin mechanism.