Freshwater shrimps (Macrobrachium depressimanum and Macrobrachium jelskii) as biomonitors of Hg availability in the Madeira River Basin, Western Amazon.

Total mercury (THg) concentrations measured in two freshwater shrimp species (Macrobrachium depressimanum and Macrobrachium jelskii) showed a relationship with the location of artisanal and small-scale gold mining (ASGM) from the Madeira River Basin, Western Amazon. Between August 2009 and May 2010, 212 shrimp samples were collected in the confluence of the Madeira River with three of its tributaries (Western Amazon). THg concentration was quantified in the exoskeleton, hepatopancreas and muscle tissue of the shrimps by cold vapor atomic absorption spectrophotometry. There were no significant differences between the two shrimp species when samples came from the Madeira River, but Hg concentrations were significantly lower in a tributary outside the influence of the gold mining area. Average THg concentrations were higher in the hepatopancreas (up to 160.0 ng g-1) and lower in the exoskeleton and muscle tissue (10.0-35.0 ng g-1 and < 0.9-42.0 ng g-1, respectively). Freshwater shrimps from the Madeira River respond to local environmental levels of Hg and can be considered as biomonitors for environmental Hg at this spatial scale. These organisms are important for moving Hg up food webs including those that harbor economic significant fish species and thus enhancing human exposure.

Spatial-temporal dynamics and sources of total Hg in a hydroelectric reservoir in the Western Amazon, Brazil.

Damming rivers to construct hydroelectric reservoirs results in a series of impacts on the biogeochemical Hg cycle. For example, modifying the hydrodynamics of a natural watercourse can result in the suspension and transport of Hg deposits in the water column, which represents an exposure risk for biota. The objective of this study was to evaluate the influences of seasonality on the dispersion of total Hg in the Hydroelectric Power Plant (HPP)-Samuel Reservoir (Porto Velho/Brazil). Sampling campaigns were performed during the three following hydrological periods characteristic of the region: low (Oct/2011), ebbing (May/2012), and high (Feb/2013) water. Sediment profiles, suspended particulate matter (SPM), and aquatic macrophytes (Eicchornia crassipes and Oryza spp.) were collected, and their Hg concentrations and isotopic and elemental C and N signatures were determined. The drainage basin significantly influenced the SPM compositions during all the periods, with a small autochthonous influence from the reservoir during the low water. The highest SPM Hg concentrations inside the reservoir were observed during the high water period, suggesting that the hydrodynamics of this environment favor the suspension of fine SPM, which has a higher Hg adsorption capacity. The Hg concentrations in the sediment profiles were ten times lower than those in the SPM, indicating that large particles with low Hg concentrations were deposited to form the bottom sediment. Hg concentrations were higher in aquatic macrophyte roots than in their leaves and appeared to contribute to the formation of SPM during the low water period. In this environment, Hg transport mainly occurs in SPM from the Jamari River drainage basin, which is the primary source of Hg in this environment.

A dual role of 20-hydroxyecdysone in the control of protein synthesis related to DNA puff activity in the anterior region of Bradysia hygida (Diptera, Sciaridae) salivary gland.

During the last 30 h of the larval stage, the salivary glands of Bradysia hygida show the amplification of some genes, resulting in the formation of two successive groups of DNA puffs, which direct the synthesis of two different sets of polypeptides. Incubation of anterior (S1) salivary gland regions, at age E7, beginning of first group of DNA puffs activity, in culture medium for 2 to 10 h results in a decrease in the synthesis of the polypeptides characteristic of this period. However, during subsequent incubation (from E7 to E7+12 h-24 h), when the second group of DNA puffs is active, S1 regions were able to synthesize some polypeptides characteristic of this period. The role of 20-OH ecdysone was studied, in vitro and in vivo, during these two periods of protein synthesis in S1 regions. The presence of the hormone was shown to be necessary to maintain, in vitro, the synthesis of the first set of polypeptides and was strongly inhibitory, in vitro and in vivo, to the synthesis of the second set of polypeptides. Thus, it is likely that the activity of the two distinct groups of DNA puffs is under opposite 20-OH-ecdysone control mechanisms.

Thyroid peroxidase in dyshormonogenetic goiters with organification and thyroglobulin defects.

Thyroid peroxidase (TPO) iodide and guaiacol oxidation activities were evaluated in eight dyshormonogenetic goiters. Two of these had a defective thyroglobulin; the TPO iodide oxidation (431 and 316 U/g ptn) and iodination (31 and 8.6 nmol I/mg ptn) activities were within the normal ranges. The goiters from two siblings with positive perchlorate iodide discharge tests also had normal TPO iodide oxidation (602 and 299 U/g ptn) and iodination activities (44 and 11 nmol I/mg ptn). No TPO iodide oxidation activity was found in the goiters from the other four patients with positive perchlorate iodide discharge tests, and TPO iodide oxidation inhibitory activities were detected in both their TPO and thyroglobulin preparations. Three of them had some TPO guaiacol oxidation activity and did not inhibit normal guaiacol oxidation. The TPO preparation immunoblot of these three goiters showed a faintly visible band of normal 100 kDa TPO. However, in the other patient no guaiacol oxidation activity was detected, and only two bands of low-molecular-weight TPO (72 and 43 kDa) were found, again showing that iodine organification defects in dyshormonogenetic goiters can be due to either qualitative or quantitative TPO defects. The TPO inhibition diminished when iodide was increased in the assay, but was not altered by increasing cofactor (H2O2). Our results, so far, suggest that the TPO-inhibitory substance may interact reversibly with a specific iodide site on the enzyme or with the oxidized form of iodide, and/or could bind free iodide, making it unavailable for enzymatic oxidation.

Ependymal astrocytoma: subependyoma or subependymal glomerate astrocytoma.

The histological study of four cases and one by electron microscopy of subependyomomas allowed us to obtain morphostructural characteristics of ependymocytes and astrocytes. Comparing these findings to those of the present day literature, we propose to name these tumours ependymal astrocytomas.