Biomedical subjects

J D Stripeikis

Publications and source records attributed to J D Stripeikis.

3 recordsLinked to original sources

PubMed2005

A link between lead and cadmium kinetic speciation in seawater and accumulation by the green alga Ulva lactuca.

In this work, studies on the bioaccumulation of Cd and Pb by Ulva lactuca at different sites of Gulf San Jorge (Patagonia, Argentina) are presented. Higher values of bioaccumulated Cd were found in Punta Maqueda - a site believed to serve as a control - in comparison to those in Punta Borja, a place highly exposed to urban and industrial activities. Consequently; the labile fractions of Cd and Pb in seawater were determined with a flow injection-preconcentration manifold interfaced to a graphite furnace-atomic absorption spectrometer (FI-GFAAS). The results obtained by kinetic speciation showed that the variable that correctly explains heavy metals accumulation in the alga, is the labile metal fraction in seawater. We propose to use an enhancement ratio - on the basis of the kinetically labile metal fraction - for calculation of the metal accumulated by the alga relative to its environment.

Argentina↗

PubMed1997

Fully automatic on-line separation preconcentration system for electrothermal atomic absorption spectrometry: determination of cadmium and lead in sea-water.

An automatic separation preconcentration system coupled to an electrothermal (graphite furnace) atomic absorption spectrometer is described. The preconcentration step is performed on a chelating resin microcolumn (Chelex-100) placed in the injection tip of the autosampler. A time based manifold with two- and three-way solenoid valves commanded by an eight channel microcomputer programmable controller is used for column conditioning, preconcentration and washing steps; no manual operations are involved. Elution is performed by the programmable graphite furnace autosampler and achieved in only one step. Operations involving complete and partial injection of the eluate into the graphite furnace are also discussed. The system was applied to the determination of Cd and Pb in near shore sea-water from Patagonia, Argentina. Detection limits of 1 and 8 ng l-1 were obtained for Cd and Pb respectively. Analysis of a certified reference material (CASS-3) showed good agreement with the certified values.

Cadmium↗

PubMed1995

Changes induced by zinc on thyroxine deiodination by rat liver in vivo and in vitro.

The effects of in vivo administration or in vitro addition of zinc on 5'-deiodination of thyroxine (T4) and the concentration of nonprotein sulfhydryl groups (NPSH) in rat liver were studied in 200-240 g body weight male Wistar rats. Twelve rats were injected i.p. with zinc sulphate 2 mg/kg body weight 24 h before the experiments were started. Animals were killed by cervical dislocation and the liver was immediately removed and homogenized. Dithiothreitol (DTT) (0, 2.5, 5 or 10 mM, final concentration) and 1 microCi 125I-T4 were added to homogenates. For the in vitro studies, animals were killed by cervical dislocation and the liver removed and added zinc or cadmium (2.5 or 5 mM) plus DTT and labelled T4. Homogenates were incubated for 90 min at 37 degrees C and thereafter chromatographed in Whatman 1 paper. Zinc-injected rats had a significant (P < 0.01) decrease in T4 deiodination and in the generation of iodine (P < 0.02) and T3 (P < 0.05). In the in vitro studies, both zinc and cadmium reduced (P < 0.02) the deiodination of T4, and the generation of iodine (P < 0.02) for zinc and P < 0.05 for cadmium) as well as the generation of T3 (p < 0.05). The NPSH in zinc-injected rats were within normal levels. Serum T4 and T3 in zinc-treated rats were normal, whereas in cadmium-treated rats were both significantly decreased (P < 0.01 for T4 and P < 0.02 for T3). The data indicate that zinc blocks the activity of liver 5'-deiodinase through a mechanism probably related to its binding to the sulfhydryl groups of the enzyme.

Analysis of Variance↗