Asunto(s)
Bufo arenarum/metabolismo , Concanavalina A/metabolismo , Fitohemaglutininas/metabolismo , Aglutininas del Germen de Trigo/metabolismo , Animales , Sitios de Unión , Bufo arenarum/embriología , Matriz Extracelular/metabolismo , Fluoresceína-5-Isotiocianato , Fluoresceínas , Coloración y Etiquetado/métodos , Tiocianatos , Membrana Vitelina/metabolismo , Saco Vitelino/metabolismoRESUMEN
Soluble extracts of Bufo ovaries agglutinate sialidase-treated rabbit erythrocytes. Unlike other amphibian lectins this agglutination activity does not require the presence of calcium ions. It is specifically inhibited by D-galactose and its derivatives. Thiodi-D-galactoside is the most potent saccharide inhibitor followed by lactose and methyl-beta-D-galactoside, respectively. D-Fucose, D-glucose and D-mannose do not inhibit the activity at concentrations at or above 100 mM. The lectin has been purified 500-fold to apparent homogeneity from the ovaries by salt extraction and affinity chromatography on lactose-aminophenyl-agarose, with a yield of about 0.2%. The molecular mass determined by gel filtration under native conditions was 30 kDa; polyacrylamide gel electrophoresis in SDS gave a molecular mass of 15 kDa, suggesting that the lectin is a dimer. The lectin has an isoelectric point of 40 and contains a high proportion of acidic amino acids.
Asunto(s)
Galactósidos/metabolismo , Glicósidos/metabolismo , Lectinas/aislamiento & purificación , Ovario/análisis , Aminoácidos/análisis , Animales , Bufonidae , Femenino , Hemaglutininas/aislamiento & purificación , Punto Isoeléctrico , Peso MolecularRESUMEN
We report the levels of an endogenous beta-galactoside lectin activity from Bufo arenarum whole embryos extracts and specific inhibition by saccharides at different developmental stages. Specific activity measured against trypsinized rabbit red blood cells showed relatively high and fluctuating levels during early stages (up to about 76 h post-fertilization) which fell to significantly lower and more constant values at late stages (77-264 h post-fertilization). Lactose is the most potent inhibitor of this lectin activity, and saccharides having alpha-galactoside configurations are weaker inhibitors. At the last embryonic stage, the agglutinating activity showed a different sugar specificity which suggests either the modification of the preexistent lectin or the synthesis of another type of lectin. The possible physiological roles of these lectins in the blockage of polyspermy or in embryonic cell-cell interactions are discussed.
Asunto(s)
Bufo arenarum/embriología , Embrión no Mamífero/metabolismo , Hemaglutininas/metabolismo , Animales , Sitios de Unión , Desarrollo Embrionario y Fetal , Galectinas , Hemaglutininas/antagonistas & inhibidores , Lactosa/farmacologíaRESUMEN
The contents of ATP, ADP and AMP were determined by HPLC and adenylic energy charge (AEC) was estimated during different stages of the embryonic development of Bufo arenarum up to the tailbud stage. All the developmental stages studied showed a high ATP content (about 1.04-1.48 nmol/emb.). The concentration of ADP was low (0.025-0.041 nmol/emb.) but rose slightly at the neural tube stage. AMP was undetectable before the tailbud stage. AEC values were almost constant (about 0.987-0.992) throughout the period studied. Only a fall at the tailbud stage could be detected which can be related to this more advanced cellular differentiation stage.