PubMed · 9454338
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S K Sessions. 1998-01-23. Frog deformities.. https://doi.org/10.1126/science.279.5350.459d
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The generation of bradykinin (BK) in blood by the action of the kallikrein-kinin system has been studied intensively in mammals but the system has received relatively little attention in non-mammalian vertebrates. The plasma of crocodilians and Testudines (turtles and tortoises) contains all the components of the kallikrein-kinin system found in mammals (prekallikrein activator, prekallikrein, kininogen, and kininases) and activation results in generation of [Thr6]-BK. Plasma of birds and snakes probably lacks a prekallikrein activator analogous to mammalian Factor XII but treatment with exogenous proteases (pig pancreatic kallikrein and/or trypsin) generates [Thr6, Leu8]-BK (chicken), [Ala1, Thr6]-BK (python) and [Val1, Thr6]-BK (colubrid snakes). The skins of certain frogs, particularly of the genus Rana, contain very high concentrations of BK-related peptides but their pathway of biosynthesis involves the action of cellular endoproteinase(s) cleaving at the site of single arginyl residues rather than by the action of the kallikrein-kinin system. Evidence for a prekallikrein activator in fish plasma is lacking but treatment with exogenous proteases generates [Arg0, Trp5, Leu8]-BK (trout and cod), [Trp5]-BK (bowfin and gar), [Met1, Met5]-BK (sturgeon). The cardiovascular actions and effects upon gastrointestinal smooth muscle of these peptides in their species of origin differ markedly. For example, intra-arterial injections of the native BK peptides into unanesthetized fish produce transient hypertension in the cod, complex depressor and pressor responses in the trout and bowfin and hypotension in the sturgeon. Pharmacological studies in snakes and fish and with the recombinantally expressed chicken BK receptor have demonstrated that the BK receptors in the tissues of non-mammalian vertebrates have appreciably different ligand binding properties from the well-characterized mammalian B1 and B2 receptors.
We sought to characterize podocytes in the kidneys of numerous species from amphibians to mammals because of the pivotal function of these cells in renal diseases. For this purpose, intermediate filament (IF) proteins of podocytes were examined by immunofluorescence microscopy using antibodies against vimentin, cytokeratins, and desmin. These staining patterns were then compared to those of parietal cells of Bowman's capsule and tubular cells of the first portion of the proximal tubule from the same sources. As a result, podocytes from mammals (rat, rabbit, dog, cow, and human) and birds (chicken) showed intense vimentin staining without exception, but rarely staining for cytokeratins or desmin. Parietal cells from all these animals were highly heterogeneous with respect to cytokeratin or vimentin staining. Of the tubular cells, only those from humans and chickens were reactive and then only with anti-cytokeratin antibodies. In the reptiles (Chrysemys scripta elegans, Chinemys reeveri, Elaphe quadrivirgata, and Anolis carolinensis), podocytes and other epithelial cells were positive for cytokeratins. Vimentin staining differed among the species, but was not characteristic for podocytes. Anti-desmin antibody reacted strongly only with podocytes from Anolis. In amphibians (Rana catesbeiana and Xenopus laevis), anti-desmin antibody stained podocytes more intensely than any other cell. Cytokeratin and vimentin staining did not differentiate podocytes from the other cell types. These findings indicate that podocytes are characterized by intense vimentin staining in the higher vertebrates and by desmin staining in the lower vertebrates denoting potentially distinctive physiological functions of IF proteins in podocytes from each of these groups.
Ichthyophis kohtaoensis is a tropical, limbless amphibian species with extremely small eyes (540 microm in adults). Adapted to a subterranean, burrowing mode of life, orientation and prey capture are predominantly guided by olfaction. The only visually guided behavior seems to be negative phototaxis. As electrophysiological single cell recordings have so far failed, immunohistochemical transmitter studies are a starting-point for a functional investigation of the visual system of this group of amphibians. In the present study, the organization and development of the serotonergic system have been examined in the retinae of embryonic, larval and adult I. kohtaoensis, using an antiserum against serotonin. Labeled somata are situated in the inner nuclear layer, presumably representing amacrine cells, and in the ganglion cell layer. However, some immunoreactive cells are located in the middle of the inner nuclear layer that send processes to both plexiform layers, probably representing bipolar cells. An additional type of immunoreactive soma, situated in the inner plexiform layer, have been found only in retinae of embryonic stages. Varicose serotonergic fibers form a diffuse plexus that covers the whole inner plexiform layer. Immunolabeled fibers can occasionally be demonstrated in the optic nerve head. During retinal development, the distribution and number of transmitter-expressing cells changes but no general reduction of the visual system is detectable. Adult stages still have a serotonergic system comparable to amphibians with a well-developed visually guided behavior indicating that the eyes of I. kohtaoensis although being of minor importance in a subterranean habitat, retain all the elements of functioning sense organs.