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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: The results indicate that Ca2+ release in enzymatically dissociated mammalian Muscle fibres inactivates to a smaller extent than in intact amphibian muscle fibres.
Abstract: MagFluo-4 fluorescence (Ca2+) transients associated with action potentials were measured in intact muscle fibres, manually dissected from toads (Leptodactylus insularis) or enzymatically dissociated from mice. In toads, the decay phase of the Ca2+ transients is described by a single exponential with a time constant (τ) of about 7 ms. In mice, a double exponential function with τ's of 1.5 and 15.5 ms, respectively gives a better fit. In both species the amplitude of Ca2+ transients diminished during repetitive stimulation: in amphibian muscle fibres, the decrease was about 20% with 1 Hz stimulation and 55% at 10 Hz. In mammalian fibres, repetitive stimulation causes a less conspicuous decrease of the transient amplitude: 10% at 1 Hz and 15 % at 10 Hz. During tetanic stimulation at 100 Hz the transient amplitude decays to 20 % in toad fibres and 40 % in mouse fibres. This decrease could be associated with the phenomenon of inactivation of Ca2+ release, described by other authors. Recovery from inactivation, studied by a double stimuli protocol also indicates that in toad fibres the ability to release Ca2+ is abolished to a greater extent than in mouse fibres. In fact the ratio between the amplitudes of the second and first transient, when they are separated by a 10 ms interval, is 0.29 for toad and 0.58 for mouse fibres. In toad fibres, recovery from inactivation, to about 80 % of the initial value, occurs with a τ of 32 ms at 22 °C; while in mouse fibres recovery from inactivation is almost complete and occurs with a τ of 36 ms under the same conditions. The results indicate that Ca2+ release in enzymatically dissociated mammalian muscle fibres inactivates to a smaller extent than in intact amphibian muscle fibres.
19 citations
TL;DR: It is concluded that a highly ouabain-sensitive Na+,K(+)-ATPase activity is present and functional in toad brain but that its function may be partially inhibited in vivo.
19 citations
Journal Article•
19 citations
TL;DR: Calcium and barium are found in melanin granules of toad retinal pigment epithelial cells and choroidal melanocytes and this suggests that barium may not serve a major role in the normal processes of dark adaptation in vertebrate photoreceptors.
19 citations
TL;DR: The morphological changes observed in the integument of tadpoles are associated with the gradual adaptation to terrestrial environments by preparing the individual for future chemical defence against predators and micro-organisms.
Abstract: In this study, the development of integument and cutaneous glands in the toad Rhinella granulosa (Bufonidae) at different larval stages and in postmetamorphic and adult forms was examined. The analyses were conducted using histological, ultrastructural and morphometric methods. The results showed that cellular aggregations of precursor epidermal glands start to appear in stage 31 of (Herpetologica, 16, 1960 and 183) and then proliferate and invade the dermis. After stage 41, granular and mucous glands are very similar to those found in adults. The granular glands are syncytial and are surrounded by a distinct layer of myoepithelial cells. In the region of parotoid macroglands, the granular glands accumulate and their alveoli progressively increase until they reach adult size. An analysis by scanning electron microscopy showed the inner distribution of the syncytial nuclei and the myoepithelial cells. The morphological changes observed in the integument of tadpoles are associated with the gradual adaptation to terrestrial environments by preparing the individual for future chemical defence against predators and micro-organisms.
19 citations