Toad

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

Structures and inhibitory activity against breast cancer cells of new bufadienolides from the eggs of toad Bufo bufo gargarizans

Abstract: Two new 19-norbufadienolides (1 and 2), one new 14,15-epoxy bufadienolide (3), and eight rare bufadienolide–fatty acid conjugates (4–11), together with four known ones (12–15) were isolated from the eggs of toad Bufo bufo gargarizans. Their chemical structures were elucidated by extensive spectroscopic methods in combination with X-ray diffraction analyses. Furthermore, we tested the inhibitory effect of these compounds against breast cancer cell lines MCF-7 and MDA-MB-231. Most of them showed strong cytotoxicity with IC50 values less than 0.1 μM. The further mechanistic study showed that they could induce apoptosis and cycle arrest in the G2/M phase in MCF-7 cells.

Effects of sympathetic nerve stimulation on membrane potential, [Ca2+]i and force in the arrested sinus venosus of the toad, Bufo marinus

Abstract: 1. The effects of sympathetic nerve stimulation on membrane potential and on the intracellular concentration of calcium ions, [Ca2+]i, were recorded concurrently from the sinus venosus of the toad, Bufo marinus, in preparations where beating had been abolished by adding an organic calcium antagonist to the physiological saline. In a separate set of experiments the effects of sympathetic nerve stimulation on force production were examined. 2. Stimulation of the sympathetic nerves caused a membrane depolarization and a simultaneous increase in [Ca2+]i. Both responses were reduced by dihydroergotamine (20 microM). 3. The membrane depolarization and increase in [Ca2+]i evoked by sympathetic nerve stimulation were abolished by ryanodine (10 microM), or caffeine (3 mM). The effects of caffeine, but not those of ryanodine, were fully reversible. 4. Although the Ca(2+)-ATPase inhibitor thapsigargin (30 microM) itself had little effect on the responses to sympathetic nerve stimulation, in its presence caffeine (3 mM) irreversibly abolished the responses. 5. In the presence of nifedipine (10 microM), sympathetic nerve stimulation caused contractions of the sinus venosus. These responses were abolished by either ryanodine (10 microM) or caffeine (3 mM). 6. The results suggest that neuronally released transmitter activates a complex biochemical pathway which triggers the release of Ca2+ from internal stores.