Toad

About: Toad is a research topic. Over the lifetime, 1624 publications have been published within this topic receiving 28732 citations.

Stimulation of active sodium transport by the isolated toad bladder with aldosterone in vitro

Abstract: The tubular reabsorption of sodium in the mammalian kidney is stimulated after administration of aldosterone (1-3). The transport of sodium from the tubular lumen to the interstitial compartments, across the cells lining the renal tubule, represents an active process (4, 5), and one is therefore led to conclude that this process is influenced by aldosterone. However, the failure to observe a sodium retention confined to the treated side after injection of aldosterone into one renal artery of the normal dog (3) could cast doubt that aldosterone is the principle immediately responsible for renal sodium retention. The time lag of 1 to 2 hours regularly observed between intravenous administration of aldosterone and the first changes in sodium excretion by the kidney (6-8) is likewise intriguing. The isolated toad bladder was thought suitable for a more direct examination of the stimulation of sodium reabsorption by aldosterone. This preparation consists of a single layer of mucosal cells supported by thin connective tissue in which blood vessels and isolated bundles of smooth muscle are interspersed; a layer of serosal cells separates the bladder from the peritoneal cavity. This simple biological membrane is capable of moving sodium actively from its mucosal to its serosal border (9), a process that can be conveniently followed by the short-circuit technique of Ussing and Zerahn (10). These investigators have shown that, when an external potential is applied so as to

Induced ovulation and artificial fertilization in the frog

Abstract: The relationship of the anterior pituitary to sexual maturity has been demonstrated by homoplastic implants in every major group of vertebrates. Various effects from precocious sexual maturity to induced ovulation have been reported for fishes (15); for Amphibia as represented by frogs (24, 25), toads (14, 16), Triturus (2, 20), Triton (2, 20); for reptiles as represented by snakes (15, 16); for birds by pigeons (6); and mammals by rats, mice, cats, rabbits, guinea pigs, and monkeys (6). The purpose of this paper is to summarize briefly the work on the Amphibia and to present considerable new evidence as to the quantitative factors involved and a dependable technique for induced ovulation and artificial fertilization in the frog, Rana pipiens. In general, the extract of whole sheep or cattle anterior pituitary (8) has not proven to be effective with frogs and toads, though there are possible exceptions with Rana vulgaris (3) and Discoglossus pictus (17). Both the whole sheep pituitary extract and the Antuitrin-S from pregnant human urine, as dispensed by Parke, Davis and Company, have been useful in inducing ovulation with Triturus and Ambystoma (11, 22), though the Antuitrin-S seems to be more potent. Neither of these extracts has proven useful with toads (18). Heteroplastic implants from the hen, rat, pig, dog, cattle, snake, fish, opossum and frog proved to be ineffective with respect to inducing ovulation in toads (3, 7, 15). This raised the question of "specificity," especially since the toad, Bufo vulgaris, reacts only to homoplastic implants while the toad pituitaries are effective when implanted in the frog, Rana vulgaris (3). Recent evidence (23) does not support this contentention of species specificity of pituitary, since with large doses of pituitary from the garpike, Lepidosteus, both the toad, Bufo americanus, and the frog, Rana pipiens, were induced to ovulate. It was suggested in this paper that previous failures may have been due to insufficient implantations. While heteroplastic implants between fishes and Amphibia may prove effective, no amount of pituitary from the albino rat (23) would induce ovulation in either frog or toad. Further evidence for 22

Astrocytic neuroglial cells, oligodendrocytes and microgliacytes in the spinal cord of the toad. II. Electron microscopy.

Abstract: Three types of glial cells corresponding to astrocytes, oligodendrocytes, and microgliacytes were found in the toad spinal cord stained with a modification of the Golgi-Rio Hortega technique. Each can be correlated with a characteristic type of nucleus stained with toluidine blue.

Vasopressin: induced structural change in toad bladder luminal membrane

Abstract: Freeze-fracture electron microscopy demonstrates that vasopressin stimulation of isolated toad bladder alters the structure of the luminal membrane of granular cells. This alteration consists of an ordered aggression of intramembranous particles, and appears to be of functional significance, since the frequency of aggregation sites per area of membrane is closely correlated with vasopressin-induced osmotic water flow.