Toad

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

Somatostatin: occurrence in urinary bladder epithelium and renal tubules of the toad, Bufo marinus

Abstract: Immunohistochemical techniques were used to detect immunoreactive somatostatin-like material in toad urinary bladder epithelium and in kidney distal tubules and collecting ducts. This material has immunological and chromatographic properties identical to those of synthetic cyclic somatostatin. The occurrence of somatostatin-like material in antidiuretic hormone-sensitive portions of the renal urinary system suggests a local regulatory or paracrine role for somatostatin.

Beta-adrenergic relaxation of smooth muscle: differences between cells and tissues.

Abstract: The present studies were carried out in an attempt to resolve the controversy about the Na+ dependence of beta-adrenergic relaxation in smooth muscle. Previous studies on isolated smooth muscle cells from the toad stomach had suggested that at least some of the actions of beta-adrenergic agents, including a stimulatory effect on 45Ca efflux, were dependent on the presence of a normal transmembrane Na+ gradient. Studies by other investigators using tissues derived from mammalian sources had suggested that the relaxing effect of beta-adrenergic agents was Na+ independent. Uncertainty remained as to whether these discrepancies reflected differences between cells and tissues or differences between species. Thus, in the present studies, we utilized both tissues and cells from the same source, the stomach muscle of the toad Bufo marinus, and assessed the Na+ dependence of beta-adrenergic relaxation. We found that elimination of a normal Na+ gradient abolished beta-adrenergic relaxation of isolated cells. In tissues, however, similar manipulations had no effect on relaxation. The reasons for this discrepancy are unclear but do not appear to be attributable to changes in smooth muscle function following enzymatic dispersion. Rather they may be attributable to unique properties of tissues, such as the presence of pacemaker cells, nerves, and so on. Thus the controversy concerning the mechanism of beta-adrenergic relaxation may reflect inherent differences between tissues and cells.

Insulin stimulates active sodium transport in toad bladder by two mechanisms.

Abstract: INSULIN has been shown to increase sodium and potassium fluxes in a series of tissues including muscle1, and colon2 and the isolated perfused kidney3. Attempts to define the exact mechanisms by which insulin stimulates ion transport in these tissues have been hindered by their anatomical complexity and heterogeneous cell populations. Tracer flux studies, using 22Na, in frog muscle1 and toad bladder4 have suggested a direct stimulatory action of insulin on the sodium pump. Preincubation of intact frog muscle with insulin for 1 h has been shown to increase the amount of ouabain binding by this tissue suggesting that insulin unmasks latent sodium pumps in this structure5. The urinary bladder of the toad (Bufo marinus) has been shown to transport sodium actively from the urinary (mucosal) side to the blood (serosal) side and has been used extensively to study cation transport and the effects and mode of action of numerous hormones and drugs6–8. We have now examined the mechanisms by which insulin increases short circuit current (a measure of active sodium transport) in the toad bladder.

The Delayed Development of the Stomach in the Frog (Rana temporaria) and the Toad (Bufo bufo).

Abstract: Summary An account is given of the structure of the anterior end of the alimentary canal of the frog and toad tadpole It is shown that there lies between the pharynx and the main intestine (mid-gut) a clearly defined fore-gut, characterized by the possession of an epithelium composed of ciliated and mucous cells which are distributed according to a definite pattern At metamorphosis the oesophagus and stomach differentiate out of the fore-gut, and the presence in the latter of the ciliated and mucous cells clearly foreshadows this fate, since cilia are found in the oesophagus of the adult, and mucous cells characterize both this region and the stomach It is further possible that two types of mucous cell visible in the fore-gut may foreshadow the goblet cells of the future oesophagus and the gastric epithelial cells of the future stomach, but this is less certain The so-called “stomach” of the frog tadpole lies in the fore-gut region and possesses gland-like structures which, however, differ histologically from those of the adult stomach Tests for pepsin and amylase have given negative results, and it is doubtful whether the organ is zymogenous It is altogether absent from the toad Pepsin first becomes identifiable in the fore-gut region of the frog and toad after the emergence of the anterior limbs, at the time when the definitive glands are forming Thus gastric digestion does not occur in the larva, and the structure of the epithelium indicates that this may be ascribed to a retardation in the rate of differentiation of the oesophagus and stomach Possible reasons for this are discussed in the light of the reported occurrence of true gastric digestion in urodele larvae, and of the differences in feeding habits of the larvae of the two groups