Toad

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

Cyclic 3',5'-AMP-dependent protein kinase activity in toad bladder epithelium.

Abstract: SummaryA cyclic AMP-dependent protein kinase was partially purified from toad urinary bladder epithelium. Cyclic AMP-stimulated protein kinase activity as well as the unstimulated (control) activity of the enzyme was maximal at pH 6.5 using Tris-maleate, sodium cacodylate or sodium acetate buffers. The apparent Km value of cyclic AMP for the stimulation of the enzyme (in sodium acetate buffer and in the presence of 10 mM Mg2+) was 1.5 × 10-9M. The acyclic nucleotide 5'-AMP (in the concentration range 5 × 10-10 to 5 × 10-5M) failed to activate bladder protein kinase. Ca2+ was found to be inhibitory at concentrations higher than 5 × 10-4M. A role for cyclic AMP-dependent protein kinase in neurohypophyseal hormone-induced permeability changes is discussed.

Effect of chloride on Ca2+ release from the sarcoplasmic reticulum of mechanically skinned skeletal muscle fibres.

Abstract: The effect of intracellular Cl– on Ca2+ release in mechanically skinned fibres of rat extensor digitorum longus (EDL) and toad iliofibularis muscles was examined under physiological conditions of myoplasmic [Mg2+] and [ATP] and sarcoplasmic reticulum (SR) Ca2+ loading. Both in rat and toad fibres, the presence of 20 mM Cl–in the myoplasm increased Ca2+ leakage from the SR at pCa (i.e. –log10 [Ca2+]) 6.7, but not at pCa 8. Ca2+ uptake was not significantly affected by the presence of Cl–. This Ca2+-dependent effect of Cl– on Ca2+ leakage was most likely due to a direct action on the ryanodine receptor/Ca2+ release channel, and could influence channel sensitivity and the resting [Ca2+] in muscle fibres in vivo. In contrast to this effect, acute addition of 20 mM Cl– to the myoplasm caused a 40–50% reduction in Ca2+ release in response to a low caffeine concentration both in toad and rat fibres. One possible explanation for this latter effect is that the addition of Cl– induces a potential across the SR (lumen negative) which might reduce Ca2+ release via several different mechanisms.

The Response of the Water-Regulating Mechanism of Developmental Stages of the Common Toad, Bufo Bufo Bufo (L.), to Treatment with Extracts of the Posterior Lobe of the Pituitary Body

Abstract: 1. The effects of extracts of the posterior lobe of the pituitary on the body water of the developmental stages of the toad, Bufo bufo bufo (L.) have been investigated by injecting extracts and weighing the animals at short intervals afterwards. 2. No response was shown until marked absorption of the tail had occurred. From this stage onwards it became progressively established and gradually increased in magnitude. The adult Salientian type of response was only elicited at the very end of metamorphosis. 3. By staining tadpoles with phenol red and measuring the rate of elimination of this dye, it has been shown that the action of the extracts is not antidiuretic except in completely metamorphosed animals. 4. It is provisionally concluded that the extracts have a double effect, first to increase the rate of water uptake and second, to diminish water loss. During the life-history of the toad, the first response is established when tail absorption is progressing rapidly, i.e. at a comparatively early stage, whereas the latter only comes into play at the very end of metamorphosis. 5. Data at present available suggest that an influence of the posterior pituitary on body water is characteristic of terrestrial but not of primarily aquatic vertebrates.