Feeding and growth responses of the snail Theba pisana to dietary metal exposure.

The effects of dietary exposure to copper (Cu), lead (Pb), and zinc (Zn) on feeding activities, growth response, and mortality of Theba pisana snails were studied in 5-week feeding tests. Snails were fed on an artificial diet containing the following Cu, Pb, or Zn concentrations: 0, 50, 100, 500, 1000, 5000, 10,000, and 15,000 µg/g dry food. At the end of 5 weeks, the food consumption rate was decreased with increasinges in both metal concentrations and time of exposure. The estimated concentrations of metals that reduces food consumption to 50% (EC50) after 5 weeks were 56, 118, and 18 µg/g dry food for Cu, Pb, and Zn, respectively. All tested metals in the diet were found to inhibit growth of the snails in a dose-dependent manner. The toxic effect on growth of the tested metals could be arranged in the order Cu > Zn > Pb. The cumulative percentage mortality among snails fed a Cu- or Zn-contaminated diet was 73.3% and the respective value for a Pb-contaminated diet was 13.3%. There was a positive correlation between growth coefficient and food consumption for all tested metals.

Respiratory exposure to lead: epidemiological and experimental dose-response relationships.

Epidemiologic studies of blood lead levels in general and occupational groups show a logarithmic regression on estimated atmospheric exposure. Experimental results at the same and higher levels show a dose-response relationship which fits the same regression. The data imply that long-term increases in atmospheric lead will result in predictably higher blood lead levels in the exposed populations.

Ultrastructural changes in the kidney cortex of rats treated with lead acetate / Cambios ultraestructurales en la corteza renal de ratas tratadas con acetato de plomo

The purpose of this study was to investigate the ultrastructural effects of lead on the kidney cortex of rats. Wistar Albino rats (180-200g body weight) were divided into a controlled and lead acetate-exposed group. Rats received lead acetate at 500 ppm in their drinking water for 60 days. Both groups were fed with the same standard food, but lead acetate was added to the drinking water. During the experimental period, blood samples were taken from the abdominal aorta of the anesthetised animals. At the end of exposure, body weight and blood lead levels were measured. The kidney tissue samples were prepared and analyzed by light and transmission electron microscopy. Cortical renal tubules show various degenerative changes with focal tubular necrosis invaded by inflammatory cells. The ultrastructural alterations found in lead acetate-treated rats were a diminution in the amount of filtration slits, increased fusion of foot processes in epithelial cells of the glomeruli, increase of lysosomal structures and pinocytic vesicles as well as large mitochondria in proximal tubule cells.

El propósito de este estudio fue investigar los efectos ultraestructurales del plomo en la corteza renal. Ratas Wistar albinas (180-200g de peso corporal) fueron divididas en grupo control y grupo experimental. Las ratas recibieron 500 ppm de acetato de plomo en el agua potable durante 60 días. Ambos grupos fueron alimentados con el mismo alimento estándar, pero acetato de plomo se le añadió al agua potable al grupo experimental. Durante el período experimental, se tomaron bajo anestesia muestras sanguíneas desde la parte abdominal de la aorta. Al final de la exposición, fueron medidos el peso corporal y los niveles de plomo en la sangre. Fueron preparadas las muestras de tejido renal y se analizaron mediante microscopía de luz y electrónica de transmisión. Los túbulos renales corticales mostraron varios cambios degenerativos con necrosis tubular focal invadida por células inflamatorias. Las alteraciones ultraestructurales encontradas en las ratas tratadas con acetato de plomo correspondieron a una disminución en la cantidad de ranuras de filtración, aumento de la fusión de los procesos podales en las células epiteliales de los glomérulos, aumento de la estructura lisosomal y las vesículas pinocíticas, así como grandes mitocondrias en las células del túbulo proximal.

Multisite interactions between Pb2+ and protein kinase C and its role in norepinephrine release from bovine adrenal chromaffin cells.

We investigated the interaction between Pb2+ and protein kinase C (PKC) in the Pb(2+)-induced release of norepinephrine (NE) from permeabilized adrenal chromaffin cells. Our analysis of endogenous PKC activity in permeabilized cells suggests that Pb2+ interacts with the adrenal enzyme at multiple sites. Pb2+ activates the enzyme through high-affinity (KA(Pb) = 2.4 x 10(-12) M) interactions and inhibits the enzyme by competitive and noncompetitive interactions with nanomolar-(Ki = 7.1 x 10(-9) M) and micromolar-(Ki = 2.8 x 10(-7) M) affinity sites, respectively. Activation of PKC by 12-O-tetradecanoyl-phorbol 13-acetate (TPA) in Ca(2+)-deficient, Pb(2+)-containing medium, enhances the Pb(2+)-induced NE release from permeabilized chromaffin cells by lowering the concentration of Pb2+ required for half-maximal activation of the secretory response from 7.5 x 10(-10) to 5.7 x 10(-11) M. The PKC inhibitors staurosporine and pseudosubstrate PKC (19-36) abolish the effect of TPA without affecting the Pb(2+)-induced secretion in the absence of TPA. These results indicate that (a) Pb2+ is a partial agonist of PKC, capable of both activating and inhibiting the enzyme and (b) synergistic activation of PKC by TPA and Pb2+ results in increased sensitivity of exocytosis to Pb2+ but is not obligatory for Pb(2+)-triggered secretion.

The environment of two metal ions surrounding the splice site of a group I intron.

Several divalent metal ions (Ca2+, Sr2+ and Pb2+) do not promote splicing, but instead induce cleavage at a single site in the conserved group I intron core in the absence of the guanosine cofactor at elevated pH, generating products with 5'-OH and 3'-phosphate ends. The reaction is competed by Mg2+, which does not cleave at this position, but hydrolyses the splice sites producing 3'-OH and 5'-phosphate ends. Mn2+ promotes both core cleavage and splice site hydrolysis under identical conditions, suggesting that two different metal atoms are involved, each responsible for one type of cleavage, and with different chemical and geometric requirements. Based on the core cleavage position and on the previously proposed coordination sites for Mg2+, we propose a structural location for two metal ions surrounding the splice site in the Michel-Westhof three-dimensional model of the group I intron core. The proposed location was strengthened by a first mutational analysis which supported the suggested interaction between one of the metal ions and the bulged residue in P7.

Valores de plomo y arsénico en hígado, riñon, bazo y cerebro de sujetos aparentemente sanos / Lead and arsenic value in liver, kidney, spleen and brain in human beings

La investigación se realizó de 25 cadáveres (16 hombres y 9 mujeres) procedentes de la Morgue Central de Lima, con edades comprendidas entre 18-25 años. la destrucción de la muestra se realizó por el método sulfonetrico. Las concentraciones de Pb, arsénico se obtuvieron empleando lé espectrofotométrico por absorción atómica y de vasos y sedivec respectivamente. Las concentraciones medias de plomo, arsénico en higado fueron: 86.96 ug por ciento, 11.83 ug por ciento y C.E 54.61-113/19, 4.79-18.88 respectivamente; en riñon fueron 75.17 ug por ciento y C.E 50.97-109-15, 361-16-37 respectivamente; en bazo fueron; 63.18 ug por ciento, 4 ug por ciento y L.E. 30.37-92.99, 086-846 respectivamente, en cerebro fueron: 22 ug por ciento, 0.05 por ciento y C.E. 4.11-40.47 0.01 respectivamente. Las cifras promedios encontrados coinciden con algunos "valores normales" reportados por estos investigadores de estos países.