Publications

Export 2 results:
Sort by: Author Title Type [ Year  (Desc)]
2004
Hamdoun, AM, Cherr GN, Roepke TA, Epel D.  2004.  Activation of multidrug efflux transporter activity at fertilization in sea urchin embryos (Strongylocentrotus purpuratus). Developmental Biology. 276:452-462.   10.1016/j.ydbio.2004.09.013   AbstractWebsite

This study presents functional and molecular evidence for acquisition of multidrug transporter-mediated efflux activity as a consequence of fertilization in the sea urchin. Sea urchin eggs and embryos express low levels of efflux transporter genes with homology to the multidrug resistance associated protein (mrp) and permeability glycoprotein (p-gp) families of ABC transporters. The corresponding efflux activity is low in unfertilized eggs but is dramatically upregulated within 25 min of fertilization; the expression of this activity does not involve de novo gene expression and is insensitive to inhibitors of transcription and translation indicating activation of pre-existing transporter protein. Our study, using specific inhibitors of efflux transporters, indicates that the major activity is from one or more mrp-like transporters. The expression of activity at fertilization requires microfilaments, suggesting that the transporters are in vesicles and moved to the surface after fertilization. Pharmacological inhibition of mrp-mediated efflux activity with MK571 sensitizes embryos to the toxic compound vinblastine, confirming that one role for the efflux transport activity is embryo protection from xenobiotics. In addition, inhibition of mrp activity with MK571 alone retards mitosis indicating that mrp-like activity may also be required for early cell divisions. (C) 2004 Elsevier Inc. All rights reserved.

2002
Hamdoun, AM, Griffin FJ, Cherr GN.  2002.  Tolerance to biodegraded crude oil in marine invertebrate embryos and larvae is associated with expression of a multixenobiotic resistance transporter. Aquatic Toxicology. 61:127-140.   10.1016/s0166-445x(02)00050-4   AbstractWebsite

The toxicity of water-soluble fractions of biodegraded crude oil (BWSF) to embryos and larvae of two marine invertebrates, the white sea urchin (Lytechinus anamesus) and the fat innkeeper (Urechis caupo), was studied. Santa Barbara Channel crude oil was artificially weathered and subjected to biodegradation using a mixed microbe culture obtained from natural oil seep sites. The degradation culture inoculated with seep sediment microbes accumulated 43.7 mug/l water-soluble hydrocarbons. In contrast water-soluble fractions from the non-degraded cultures (NWSF) only accumulated 3.05 mug/l. BWSF proved deleterious to Lytechinus embryo development at low concentrations (EC50 = 0.33 mg/l) but was essentially non-toxic to Urechis embryos/larvae up to 3.0 mg/l. An established mechanism for handling of a wide array of xenobiotics in Urechis embryos is the multixenobiotoic resistance transporter multixenobiotic response (MXR, also known as multidrug resistance, MDR). This mechanism is primarily mediated by ATP-dependent, efflux pumps that extrude a wide array of xenobiotic compounds. In this study, we show that Lytechinus larvae do not appear to express MXR efflux. protein nor MXR mediated dye efflux capacity. In contrast, BWSF acts as a competitive inhibitor of MXR transport-mediated dye efflux in Urechis larvae. These results suggest that MXR may be an important mechanism for extrusion of the by-products of crude oil degradation by microbes, and that the level of its expression may determine the susceptibility of organisms to degraded oil hydrocarbons. (C) 2002 Elsevier Science B.V. All rights reserved.