Topic
Toad
About: Toad is a research topic. Over the lifetime, 1624 publications have been published within this topic receiving 28732 citations.
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TL;DR: It is suggested that the granules in the media cells of the afferent arteriole are formed from the Golgi apparatus, which comprises nerve fibres innervating the juxtaglomerular cells.
Abstract: The fine structure of the juxtaglomerular apparatus in the toad, Bufo bufo was investigated.—It is suggested that the granules in the media cells of the afferent arteriole are formed from the Golgi apparatus. Many granules have a content of lamellar material. The media cells do not show the ultrastructural features of active secretory cells. In the media cells, the myofilaments are situated near the vascular lumen. The other cell organelles, including the granules, are preferentially located at the opposite pole of the cell in the neighbourhood of the macula densa cells and the adventitial nerve fibres. In these regions the media cells show many pinocytotic vesicles. The nerve fibres innervating the juxtaglomerular cells are non-myelinated and their varicosities contain dense core vesicles. The basement membranes of media cells and adjacent macula densa cells occasionally fuse, which may indicate a functional relationship between these cells.
15 citations
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TL;DR: The similarity of Cpl1 to prostaglandin D(2) synthase and its functional homology to transthyretin will be discussed.
15 citations
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TL;DR: Using the short circuit current techniques developed by Ussing and Zerahn for measuring active Na+ transport across isolated tissues, it was shown that physiological concentrations of aldosterone administered in vitro, augmented Na' transport across the toad urinary bladder.
Abstract: The toad urinary bladder has been used extensively as a simple in vitro model for the mammalian distal nephron.' The tissue is composed of a single layer of epithelial cells (luminal mucosa) supported by a submucosa of connective tissue and smooth muscle.' Fine structural studies have shown that mucosa, the hormone-sensitive cell layer, is made up of four distinct cell types: (1) basal cells; (2) goblet cells; (3) granular cells; and (4) mitochondria-rich (MR) cells.'-4 Granular cells, characterized by the presence of numerous electron dense apical granules, are the most numerous and constitute 80-85'70 of the total cell number; MR-cells represent 10-15% of the total. Scanning electron microscopic observations have shown that these two cells form the major cellular lining of the bladder lumen where they are dispersed in a characteristic pattern! Using the short circuit current techniques developed by Ussing and Zerahn for measuring active Na+ transport across isolated tissues,B it was shownthat physiological concentrations of aldosterone administered in vitro, augmented Na' transport across the toad urinary bladder.'-' This response is characterized by a latent period (45-120 minutes) and is thought to involve de novo RNA and protein synthesis, since preincubation of the tissue with protein synthesis inhibitors, i.e., the antibiotics actinomycin D or puromycin, inhibits the aldosteroneinduced increase in short circuit current.\" Such data can generally be explained by invoking the usually accepted hypothesis that steroid hormones (such as aldosterone) act on their specific target tissues through gene activation and the subsequent synthesis of tissue specific proteins.\" The mode of action of aldosterone has been previously thought to involve one or more of the following processes:\" (1) the steroid enhances the passive entry of Na across the luminal membrane of the mucosal epithelial cells; (2) aldosterone enhances the supply of energy (ATP) available to the sodium pump located along
15 citations
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TL;DR: The available data strongly support the theory that both in urodeles and anurans the hormones merely exert a permissive action, so that rhythmic processes that are inherent in the skin will result in the formation and shedding of sloughs at intervals when the concentration of the hormones in the blood exceeds critical levels.
15 citations
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TL;DR: Rapid, extensive inactivation of angiotensin II, as judged from measurements of vasopressor activity, was a constant feature and had to be taken into account for proper experimental setting.
15 citations