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Urechis caupo is a marine worm that lives and reproduces in sediments containing a variety of potentially toxic environmental chemicals (xenobiotics). Its embryos have a multixenobiotic transporter, which is similar to the multidrug transporter in mammals, as indicated by their ability to transport a variety of moderately hydrophobic compounds such as dyes, drugs, and pesticides out of the cells. The cell membranes of the embryos contain a protein of approximately 145 kD that is immunologically related to the mammalian multidrug transport protein and that can be cross-linked by a photoactivatable substrate of the mammalian multidrug transport protein. The sediments in which the worm lives contain potential substrates for the transporter, indicating that this multixenobiotic transport activity may protect Urechis embryos from naturally occurring toxic compounds. Embryos of a sea urchin from a pristine environment do not have this transport activity and are sensitive to hydrophobic toxins. These data strongly support a role for multixenobiotic transport as a mechanism of protection from environmental toxins and indicate an unsuspected mode of protection in invertebrate embryos.

Hydrogen sulfide (H2S) at concentrations of about 0.05 to 1 mmol.l(-1) appears to function as a gasotransmitter in vertebrates, analogous to nitric oxide (NO) and carbon monoxide, but the actions of H2S in invertebrate tissue have not been well studied. In this study, we investigated the role of H2S in modulating body wall muscle tone in the marine echiuran worm Urechis caupo (Echiuridae). We first determined that U. caupo body wall homogenates produce H2S upon addition of L-cysteine and pyridoxal-5'-phosphate (PLP), and that the rate is increased by addition of 2-mercaptoethanol, suggesting the presence of an activated L-serine sulfhydrase pathway. We then measured the contractile response of U. caupo body wall circular muscle strips to sodium hydrosulfide (NaHS)--which produces H2S in solution--and the NO donor sodium nitroprusside (SNP), both with and without subsequent application of acetylcholine (ACh). We found that NaHS alone stimulated contraction in muscle strips equivalent to about one-third the force of ACh alone, whereas SNP alone had no effect on muscle tone. However, simultaneous addition of NaHS with SNP elicited a much stronger contraction, reaching more than twice that of ACh alone, which could be increased further by subsequent application of ACh.

Axenic (bacteria-free) larval cultures of the marine echiuran worm, Urechis caupo, were reliably obtained by aseptically removing gametes directly from the gamete storage organs. Trochophore larvae only removed neutral amino acids from seawater as measured by high-performance liquid chromatography (HPLC). There was no detectable uptake, as measured by HPLC, of acidic or basic amino acids. Kinetic analysis showed that the transport system for alanine in 4-day-old larvae had a Kt of 4-6 µM and a Jmax of 9-10 pmol larva-1 h-1. Following a 50-min exposure, the majority of the radioactivity (95%) from 14C-alanine was found in the trichloroacetic acid-soluble fraction. Very little label appeared as acid-insoluble material, and there was no detectable lipid biosynthesis from 14C-alanine. Approximately 12% of the total alanine transported was released in the form of 14CO2. Thin-layer chromatography of intracellular free amino acid pools demonstrated that aspartic acid and glutamic acid were radiolabeled from the alanine precursor. A comparison of the energy acquired from the transport of alanine, with the metabolic rate of 4-day-old larvae, revealed that 51% of the metabolic demand could be provided by the transport and complete catabolism of this single amino acid at a concentration of 595 nM in seawater.

1. Alcohol has no effect on the rate of cell division of Urechis eggs except to retard and inhibit. In 2 per cent alcohol the first cell division is inhibited, although the nucleus usually divides.2. In 1½ per cent alcohol the time lapse to first cleavage is increased approximately 15 per cent. In 1 per cent alcohol it is increased approximately 3.5 per cent. (See Table I.)3. A series of sub-narcotizing concentrations of alcohol covering the range ½ per cent to 1/64 per cent does not stimulate the rate of cell division nor affect it within limits of 1 per cent (see Fig. 1).4. This covers the ranges in which stimulation to the extent of 30 per cent or more has in some cases been observed in Protozoa. In other cases, with the same and with other protozoan forms, no stimulation has been found.5. It is suggested that the stimulation in the Protozoa, when it occurs, may be largely a nutritive phenomenon, where food supply is acting as a limiting factor to division rate. This involves the assumption that alcoho...