Deformities of chironomid larvae and heavy metal pollution: from laboratory to field studies.

Mouthpart deformities of Chironomus riparius larvae (Diptera) have been investigated to evaluate the toxic effects of contamination by heavy metals in the Genna Stream (Central Italy), situated in an area subjected to intensive swine farms (40000 heads). The livestock farming (fertirrigation) contributes to metal pollution of the Genna Stream with an increase of copper, zinc, cadmium, chromium and nickel in the sediments of the downstream stations. The incidence of mentum deformities was very high at all sampling stations, about 56%. The highest values of deformities were found in the intermediate river reach (St. 3: 65%) and in March (66%), mainly due to an increase in severe deformities. The high incidence of severe deformities (30%) is attributed to the high pollution level by heavy metals in the sediments, in particular to copper and zinc, which showed the highest average value at St. 3 and in March. This field study reflected the relationships between sediment metal concentrations and chironomid mouthpart deformities, previously observed in laboratory tests, and highlighted these deformities as toxicity endpoints. This feature paves the way for their use as an effective tool in freshwater bioassessment monitoring programs to evaluate the toxic effects of metal contamination in freshwater ecosystems.

Chemical analysis and biological activity of airborne particulate matter.

We examined the chemical composition of the suspended particulate matter in a typical, middle-sized, nonindustrial Italian town in terms of total carcinogenic PAH, heavy metal, and polynuclear azo-aromatic compounds. The chemical data relate to the biological activity of the organic extract of the particulate matter (mutagenicity and mice alveolar macrophage phagocytosis inhibition). The concentration values of benz(a)pyrene, the concentration ratios of selected PAH's, and the GC-MS profile of some typical samples indicate that motor vehicle traffic is the main pollution source. PAH concentration is significantly correlated with mutagenicity and a phagocytosis inhibition of up to 75% was observed at the highest PAH concentration. As far as the effect of meteorological variables on PAH concentration and mutagen-icity is concerned, a statistically significant inverse correlation with temperature was found.

Effects of repeated boluses of sucrose on proliferation and on AOM-induced aberrant crypt foci in rat colon.

Colonic mucosal proliferation, aberrant crypt foci (ACF) induction, and fecal bile acids, parameters connected to the risk of colon cancer development, were studied in female F344 rats treated with starch or sucrose boluses or with a sucrose diet. Cell proliferation was higher in animals treated with a single sucrose bolus than in those given a starch bolus (15 g/kg body wt), with 4.3 +/- 0.64 and 2.17 +/- 0.57 (SE) mitotic figures (MF) per crypt in the sucrose and starch bolus groups, respectively (p < 0.01). When azoxymethane (AOM, 20 mg/kg) was administered 24 hours after a single sucrose or starch bolus, the number of ACF per colon after 30 days was higher in the sucrose bolus group [107.5 +/- 9.5 (SE)] than in the starch bolus group (67.8 +/- 0.9, p < 0.01). In additional experiments, colon cell proliferation (MF/crypt) was higher in rats given boluses of sucrose three times per week for 40 days after AOM (20 mg/kg) [5.9 +/- 0.7 (SE)] than in rats given starch boluses (2.96 +/- 0.4) or fed sucrose continuously (3.6 +/- 0.5). On the contrary, after 40 days of dietary treatment, the number, dimension, and percentage of ACF secreting sulfomucins and sialomucins were not varied among these three groups. However, the percentage of "large ACF" (ACF with > or = 4 crypts) secreting sialomucins or predominantly sialomucins was higher (p < 0.05) in the sucrose bolus group than in the starch group. The concentration of fecal bile acids and long-chain fatty acids was the same in the sucrose and starch groups, but the concentrations of deoxycholic and oleic acid were significantly higher in the sucrose bolus group. In conclusion, the administration of sucrose as a bolus had a stronger effect than continuous sucrose feeding on some parameters related to colon carcinogenesis and might be considered a risk factor in colon carcinogenesis.

The presence of high-molecular weight proteins with a strong affinity for cadmium in environmental Escherichia coli strains.

High molecular weight proteins, with a strong affinity for cadmium, were found in two environmental strains of Escherichia coli isolated from a wastewater treatment plant and were resistant up to 128 ppm of Cd+2. The fraction containing intracellular cadmium binding proteins was obtained by affinity chromatography and the single components of the same fraction were separated by SDS-gel electrophoresis in order to calculate molecular weights ranging from 48 to 89 kD. Plasmid analysis, carried out by agarose gel electrophoresis, and transformation experiments demonstrated that the plasmids, isolated from one of the strains which was resistant to tetracycline and streptomycin, are not related to the synthesis of cadmium-binding proteins.

Cadmium uptake by growing cells of gram-positive and gram-negative bacteria.

The present study evaluates the effect of the cadmium (Cd2+) on the growth and protein synthesis of some Gram-positive (Staphylococcus aureus, Bacillus subtilis and Streptococcus faecium) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and the cadmium uptake by the same micro-organisms. The Gram-negative bacteria tested were less sensitive to metal ions than the Gram-positive, and P. aeruginosa was the most resistant. The Gram-negative bacteria were also able to accumulate higher amounts of cadmium during growth than the Gram-positive bacteria. The maximum values of specific metal uptake (microgram of Cd2+ incorporated per mg of protein) were: 0.52 for S. aureus, 0.65 for S. faecium, 0.79 for B. subtilis, 2.79 for E. coli and 24.15 for P. aeruginosa, respectively. The differences in the ability to accumulate metal found between Gram-negative and Gram-positive bacteria seems to account for different mechanisms of metal resistance.