Lissothuria caboblanquensis n. sp., a new species of sea cucumber (Holothuroidea: Dendrochirotida: Psolidae) from Costa Rica.

A new species of sea cucumber of the genus Lissothuria Verrill, 1867 is described. Lissothuria caboblanquensis n. sp. was found in the Costa Rican Pacific, at 17 m depth. The presence of towers with spiny apex and the elaborated shape of the hourglasses in the dorsal body wall, make this species unique among the species of this genus. This species is distinctive within the genus. The shape of the ossicles shows some similarities with L. nutriens H. L. Clark, 1901 and L. hancocki (Deichmann, 1941).

Portable device for magnetic stimulation: assessment survival and proliferation in human lymphocytes.

A device's instrumentation for magnetic stimulation on human lymphocytes is presented. This is a new procedure to stimulate growing cells with ferrofluid in vortices of magnetic field. The stimulation of magnetic vortices was provided at five different frequencies, from 100 to 2500 Hz and intensities from 1.13 to 4.13 mT. To improve the stimulation effects, a paramagnetic ferrofluid was added on the cell culture medium. The results suggest that the frequency changes and the magnetic field variation produce an important increase in the number of proliferating cells as well as in the cellular viability. This new magnetic stimulation modality could trigger an intracellular mechanism to induce cell proliferation and cellular survival only on mitogen stimulated cells.

Equinodermos del Parque Nacional Marino Ballena, Pacífico, Costa Rica / Echinoderms from Marino Ballena National Park, Pacific, Costa Rica

A total of 25 species of echinoderms (four asteroids, six ophiuroids, five echinoids and ten holothurians) were recorded at Marino Ballena National Park, using 25 m2 quadrants, parallel to the coast, at seven sites. The ophiuroids were the most abundant group with 581 individuals and the asteroids the less abundant (48 individuals). Echinoderms densities were low, with the exception of the ophiuroids. Diversity, density and the number of groups were higher where sedimentation was lower. We suggest that sedimentation is having a negative effect on the diversity of echinoderms and on the development of the coral reefs in this park

Diversidad y abundancia de equinodermos en la laguna arrecifal del Parque Nacional Cahuita, Caribe de Costa Rica / Diversity and abundance of echinoderms from the reef lagoon at Cahuita National Park, Caribbean from Costa Rica

A total of 15 species of echinoderms (one asteroid, seven ophiuroids, five echinoids and two holothurians) were recorded at the Cahuita National Park reef lagoon, between September and October 2003, using a 1 m2 quadrant. The sites with coral substrate and algae were the most diverse, while those with seagrass and sand were the least. Ophiuroids were the most abundant group with 170 individuals, asteroids were the least abundant. Adding other studies and reports of echinoderms to this study, a total of 23 species have been found at Cahuita National Park, which is the most diverse area on the Caribbean of Costa Rica. We report nine new echinoderm records for Costa Rica's Caribbean.

Gastric activity studies using a magnetic tracer.

A magnetic pulse generator has been set up in order to study gastric activity. Two coils 1.05 m in diameter, arranged in a Helmholtz configuration, were used. The system generated magnetic field pulses higher than 15 mT, of duration 17.3+/-1.2 ms. Measurements were performed in 11 male volunteers, with average age 29.3+/-6.4 years and body mass index 26.0+/-4.8 kg m(-2). Magnetite (Fe3O4) particles with diameters from 75 to 125 microm were used as magnetic tracers, which were mixed in 250 ml of yogurt in concentrations from 2 to 5 g. Signals were registered by using a high speed 3 axis fluxgate digital magnetometer and processed to determine the relaxation of the magnetic tracers by fitting a first-order exponential function to the data, a mean relaxation constant K = 116+/-40 s(-1) was obtained. Also, an average gastric peristaltic frequency was measured; a value of 3.2+/-0.3 cpm was determined.

Recuperacion de agar-agar a partir de medios de cultivo usados. / The agar-agar recovery from used culture media

En el presente trabajo se describen metodos para la recuperacion de agar a partir de medios de cultivo usados. Los metodos fueron valores a traves de los siguientes parametros: fuerza de gelificacion, temperatura de fusion, temperatura de gelificacion y porcentaje de recuperacion. Se encontro muy poca variacion en cuanto a la temperatura de fusion y de gelificacion del agar antes de ser utilizado y posterior a los tratamientos de recuperacion.Los rendimientos de los metodos fueron de un 92.8 por ciento para Mac Conckey 65 por ciento para agar sangre y un 78 por ciento de recuperacion para el agar eosina-azul de metileno (Levine). Los metodos son sencillos y economicos y su alto rendimiento justifica el proceso de recuperacion