In situ compositional analysis of acidocalcisomes in Trypanosoma cruzi

We measured the elemental content of different compartments in Trypanosoma cruzi epimastigotes using quick freezing, ultracryomicrotomy, and electron probe microanalysis. Vacuoles identified by high electron density contained (in units of mmol/kg dry weight +/- S.E.) large amounts of phosphorus (1390 +/- 13), magnesium (646 +/- 19), calcium (171 +/- 5), sodium (161 +/- 18), and zinc (148 +/- 6). No other compartment had appreciable calcium or zinc content. Iron (128 +/- 16 mmol/kg) was detected only in vacuoles distinct from the electron-dense vacuoles and other organelles. Incubation of cells for 70 min in culture medium in the presence of ionomycin plus nigericin led to a very significant 3- or 2-fold increase in potassium in the electron-dense vacuoles and the iron-rich vacuoles, respectively, with no significant change in the other elements investigated. This indicated the acidic nature of the vacuoles and demonstrated that the electron-dense vacuoles correspond to what were described previously as acidocalcisomes, i.e. acidic compartments rich in Ca2+. The acidocalcisomes were investigated by separation of epimastigote fractions on Percoll gradients in combination with Triton WR-1339 treatment. This detergent caused a rapid vacuolation; these vacuoles were shown by electron microscopy to be largely transparent, with a diffuse matrix. Percoll gradient fractionation demonstrated decreases in the density of various organelle markers in detergent-treated cells compared with controls. Large decreases in the density of the acidocalcisome and the mitochondrion were seen, as well as smaller decreases in the density of the other markers. Conventional electron microscopy of epimastigotes loaded with gold-labeled transferrin indicated that the endosomal system was separate from vacuoles that probably corresponded to the calcium-containing organelles detected by electron probe microanalysis. The combined results provide evidence that acidocalcisomes are organelles different from lysosomes or other organelles previously described in these parasites.     

Comparative effects of the chelators sodium 4,5-dihydroxybenzene-1,3-disulfonate (Tiron) and diethylenetriaminepentaacetic acid (DTPA) on acute uranium nephrotoxicity in rats

The effect of transient, global cerebral ischemia on the distribution of endothelin (ET) in blood-brain barrier (BBB) in CA1 area of hippocampus long-time after ischemia was estimated using post-embedding immunogold technique. ET-like immunoreactivity as a gold particles was localized in all compartments of the blood-brain barrier e.g. in endothelial cells, in pericytes, in periendothelial space including basement membrane, and in astroglial processes. In control animal the density of labelling in all elements of BBB in CA1 area of hippocampus was moderate. ET-like immunoreactivity (ET-like IR) was estimated 1 week-12 months after ischemia. Intense ET-like IR in all elements of BBB was noted 2 and 6 months after ischemia. A potential pathophysiological role of endothelin in cerebral vasospasm in long-time after ischemia is well documented.     

Lead in children's hair, as related to exposure in Tarragona Province, Spain

Concentrations of lead were determined in the hair of 478 school children living in an industrial and an agricultural area of Tarragona Province, Spain. The influence of age, sex, hair colour and family occupation on the children's hair lead concentration was also evaluated. Girls had more lead in their hair than boys (10.54 vs 6.55 micrograms g-1), and the lead levels decreased with age. Lead concentrations in hair with respect to hair colour decreased in the order red, blond, brown, black. Family occupation was one of the most significant factors influencing the lead content of children's hair. Although the average lead content was higher in the industrial area (9.38 micrograms g-1) than in the agricultural area (7.80 micrograms g-1), this difference was not statistically significant.     

Surface-enhanced micro-Raman detection and characterization of calix[4]arene-polycyclic aromatic hydrocarbon host-guest complexes

Surface-enhanced micro-Raman spectroscopy (micro-SERS) was used to detect traces of the hazardous pollutant polycyclic aromatic hydrocarbons (PAHs) pyrene and benzo[c]phenanthrene deposited onto a calix[4]arene-functionalized Ag colloidal surface. High spectral reproducibility and very low molecular detection limits (10(-8) M) were obtained by using 25,27-carboethoxy-26,28-hidroxy-p-tert-butylcalix[4]arene as host molecule. Films of immobilized aggregated Ag nanoparticles, obtained by chemical reduction with hydroxylamine, were prepared by direct adhesion on a glass surface. The influence of the aggregation degree of the initial Ag nanoparticles on the micro-SERS detection effectiveness was checked. Different relative concentrations of the host (calixarene receptor) and the guest (PAHs) were attempted in order to optimize detection of the pollutant. The obtained results indicated that the detection limit is much lower in the case of benzo[c]phenanthrene than in pyrene when exciting with the 785 nm line of a diode laser. A detailed interpretation of the Raman spectra was accomplished in order to obtain more information about the interaction mechanism of the host-guest complex, which could be useful in the future for the design of powerful detection systems.     

Protective effect of biliary lipids on rat pancreatic lipase and colipase

The effect of biliary components on the inactivation of rat pancreatic lipase and colipase was studied. In vitro incubations of these proteins were performed at 37 C in the presence or absence of trypsin, under various conditions. The influences of bile lipoprotein complex, bile salts below or above the critical micellar concentration (CMC), or albumin were investigated. The results showed that albumin and bile salts below the CMC had no protective effect on the inactivation rate of lipase or colipase. Under both denaturating conditions, bile salts above the CMC had a very slight effect, whereas the presence of the bile lipoprotein complex maintained lipase and colipase activity. The magnitude of this effect was related to the biliary phospholipid concentration. By means of gel filtration, the protective effect of bile was found to be due to associations of bile lipoprotein complex with these proteins in presence of bile salts. A correlation between the amount of colipase and the protection of lipase in the presence of biliary phospholipids was observed. Intestinal content of rats with normal and diverted bile secretion was submitted to the same in vitro incubation, and the enzyme was more stable in the segments containing biliary phospholipids. This suggests that the interaction between the bile lipoprotein complex, colipase and lipase in the presence of bile salts could have an important role in the intestinal lumen by retaining the enzyme activity.     

Dioxins and furans in cow milk and dairy products: A review of the scientific literature

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are a group of persistent organic pollutants with well-known toxic effects and potential carcinogenicity. Human exposure to PCDD/Fs is mainly through food, including dairy products. The scientific information on the concentrations of PCDD/Fs in milk and dairy products is here reviewed. It also includes the intake of PCDD/Fs through the consumption of these products. PCDD/Fs concentrations in milk and dairy products are currently decreasing. A similar trend is also noted for their contributions to the total dietary intake of PCDD/Fs. No significant health risks due to exposure to PCDD/Fs through the consumption of dairy products are expected.