RESUMEN
Skeletogenesis in the sea urchin embryo is a simple model of biomineralization, pattern formation, and cell-cell communication during embryonic development. The calcium carbonate skeletal spicules are secreted by primary mesenchyme cells (PMCs), but the skeletal pattern is dictated by the embryonic ectoderm. Although the process of skeletogenesis is well characterized, there is little molecular understanding of the basis of patterning within this system. In this study, we examined the contribution of phosphatidylinositide 3-kinase (PI3K)-mediated signaling to the skeletogenic process in sea urchin embryos by using the well-established PI3K inhibitors LY294002 and wortmannin. Our results show that PI3K inhibitors specifically and reversibly block skeletogenesis, and that this blockade occurs within the PMCs rather than in the ectoderm, because the inhibitors block spiculogenesis in cultured micromeres. Our results are consistent with a model in which PI3K signaling is required, not for pattern sensing or interpretation but rather for the biomineralization process itself in the sea urchin embryo.
Asunto(s)
Tipificación del Cuerpo/efectos de los fármacos , Calcificación Fisiológica/efectos de los fármacos , Inhibidores de las Quinasa Fosfoinosítidos-3 , Erizos de Mar/embriología , Androstadienos/metabolismo , Androstadienos/farmacología , Animales , Cromonas/metabolismo , Cromonas/farmacología , Embrión no Mamífero/anatomía & histología , Embrión no Mamífero/efectos de los fármacos , Embrión no Mamífero/enzimología , Inhibidores Enzimáticos/farmacología , Microscopía Fluorescente , Morfolinas/metabolismo , Morfolinas/farmacología , Erizos de Mar/citología , Erizos de Mar/enzimología , WortmaninaRESUMEN
Metronidazole pharmacokinetics were studied in patients with different degrees of liver cirrhosis, classified according to the Child-Pugh algorithm (A, B or C, as liver disease severity increases) and in schistosomic patients. Metronidazole (500 mg) was administered i.v. as a slow infusion over 20 min, and blood samples were collected at set intervals after the end of the infusion. The plasma concentrations of metronidazole and its main metabolite hydroxy-metronidazole were quantified by reversed-phase h.p.l.c. with u.v. detection. The metronidazole and hydroxy-metronidazole areas under the curve from 0 to 24 h (AUC0,24h), the metronidazole terminal elimination half-life (t1/2), the total clearance (CL), the metronidazole volume of distribution (V) values and the hydroxy-metronidazole/metronidazole concentration ratios as a function of time were calculated for each group. Comparison of the metronidazole AUC0,24h, t1/2 and CL values revealed that metronidazole metabolism is progressively impaired as the severity of liver disease increases. There were no variations in these parameters between the schistosomic and Child-Pugh A groups. In addition, there were no differences in the V and hydroxy-metronidazole AUC0,24h among the various groups studied. However, metronidazole metabolism was delayed in patients with hepatic disease, as illustrated by the hydroxy-metronidazole/metronidazole ratio 10 min after the end of metronidazole infusion. These results indicate that the clinical assessment of liver disease is paralleled by an impairment of metronidazole metabolism. Of the studied variables, we propose the hydroxy-metronidazole/metronidazole ratio 10 min after metronidazole infusion as a suitable and practical index for liver function evaluation.