Toad

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

Winter Hibernation and UCHL1-p34cdc2 Association in Toad Oocyte Maturation Competence

Abstract: Currently, it is believed that toad oocyte maturation is dependent on the physiological conditions of winter hibernation. Previous antibody-blocking experiments have demonstrated that toad ubiquitin carboxyl-terminal hydrolase L1 (tUCHL1) is necessary for germinal vesicle breakdown during toad oocyte maturation. In this paper, we first supply evidence that tUCHL1 is highly evolutionarily conserved. Then, we exclude protein availability and ubiquitin carboxyl-terminal hydrolase enzyme activity as factors in the response of oocytes to winter hibernation. In the context of MPF (maturation promoting factor) controlling oocyte maturation and to further understand the role of UCHL1 in oocyte maturation, we performed adsorption and co-immunoprecipitation experiments using toad oocyte protein extracts and determined that tUCHL1 is associated with MPF in toad oocytes. Recombinant tUCHL1 absorbed p34(cdc2), a component of MPF, in obviously larger quantities from mature oocytes than from immature oocytes, and p13(suc1) was isolated from tUCHL1 with a dependence on the ATP regeneration system, suggesting that still other functions may be involved in their association that require phosphorylation. In oocytes from hibernation-interrupted toads, the p34(cdc2) protein level was significantly lower than in oocytes from toads in artificial hibernation, providing an explanation for the different quantities isolated by recombinant tUCHL1 pull-down and, more importantly, identifying a mechanism involved in the toad oocyte's dependence on a low environmental temperature during winter hibernation. Therefore, in toads, tUCHL1 binds p34(cdc2) and plays a role in oocyte maturation. However, neither tUCHL1 nor cyclin B1 respond to low temperatures to facilitate oocyte maturation competence during winter hibernation.

Effect of rapid cooling on toad and guinea pig cardiac muscles.

Abstract: When bathing solution temperature was lowered rapidly to below 5 degrees C, contracture was observed in toad and guinea pig cardiac muscles (Rapid Cooling Contracture, RCC). RCC in toad cardiac muscle was observed even in the presence of TTX and Mn, and enhanced by reducing [Na]o and caffeine. RCC in guinea pig cardiac muscle showed two components; phasic component was dependent on stimulation frequency before cooling, stimulation period, [Ca]o, and [Na]o; tonic component was not dependent on these factors, but was enhanced by reducing [Na]o and in high [K]o solution. From these results, the possible role of Ca ion accumulated at intracellular sequestered sites in cardiac muscle was discussed in relation to excitation-contraction (E-C) coupling.