Effects of arsenate, chromate, and sulfate on arsenic and chromium uptake and translocation by arsenic hyperaccumulator Pteris vittata L.

We investigated effects of arsenate (AsV), chromate (CrVI) and sulfate on As and Cr uptake and translocation by arsenic hyperaccumulator Pteris vittata (PV), which was exposed to AsV, CrVI and sulfate at 0, 0.05, 0.25 or 1.25 mM for 2-wk in hydroponic system. PV was effective in accumulating large amounts of As (4598 and 1160 mg/kg in the fronds and roots at 0.05 mM AsV) and Cr (234 and 12,630 mg/kg in the fronds and roots at 0.05 mM CrVI). However, when co-present, AsV and CrVI acted as inhibitors, negatively impacting their accumulation in PV. Arsenic accumulation in the fronds was reduced by 92% and Cr by 26%, indicating reduced As and Cr translocation. However, addition of sulfate increased uptake and translocation of As by 26-28% and Cr by 1.63 fold. This experiment demonstrated that As and Cr inhibited each other in uptake and translocation by PV but sulfate enhanced As and Cr uptake and translocation by PV.

Optimum P levels for arsenic removal from contaminated groundwater by Pteris vittata L. of different ages.

Optimization of arsenic uptake by Pteris vittata may reduce the remediation time and cost of arsenic-contaminated groundwater. This greenhouse experiment evaluated the effects of five doses of P (0, 150, 300, 450 and 600 microM P) and two fern ages (45 and 90 d old) on the effectiveness of arsenic removal using 18 L of contaminated groundwater per plant. Arsenic-depletion was monitored weekly over a period of 74 d. It took 38 d for 45-d ferns in the no P treatment to deplete the arsenic to the target concentration of 10 microg L(-1) from 126 microg L(-1). During the 74-d study, the best treatment for 90-d ferns was at 150 microM of P, reducing the arsenic concentration to 12 microg L(-1). Because arsenic uptake and removal is inversely related to the P-status, P-free Hoagland solution would maximize arsenic uptake in a short term. However, on a long-term basis, ministering the 0.2-strength Hoagland solution at 150 microM P may be an effective approach for maximizing plant biomass production and arsenic removal.

Timing of phosphate application affects arsenic phytoextraction by Pteris vittata L. of different ages.

The effects of timing in phosphate application on plant growth and arsenic removal by arsenic hyperaccumulator Pteris vittata L. of different ages were evaluated. The hydroponic experiment consisted of three plant ages (A45d, A90d and A180d) and three P feeding regimens (P200+0, P134+66 and P66+134) growing for 45 d in 0.2-strength Hoagland-Arnon solution containing 145 microg L(-1) As. While all plants received 200 microM P, P was added in two phases: during acclimation and after arsenic exposure. High initial P-supply (P200+0) favored frond biomass production and plant P uptake, while split-P application (P134+66 and P66+134) favored plant root production. Single P addition favored arsenic accumulation in the roots while split-P addition increased frond arsenic accumulation. Young ferns (A45d) in treatment P134+66 were the most efficient in arsenic removal, reducing arsenic concentration to below 10 microg L(-1) in 35 d. The results indicated that the use of young ferns, coupled with feeding of low initial P or split-P application, increased the efficiency of arsenic removal by P. vittata.

Phytoextraction by arsenic hyperaccumulator Pteris vittata L. from six arsenic-contaminated soils: Repeated harvests and arsenic redistribution.

This greenhouse experiment evaluated arsenic removal by Pteris vittata and its effects on arsenic redistribution in soils. P. vittata grew in six arsenic-contaminated soils and its fronds were harvested and analyzed for arsenic in October, 2003, April, 2004, and October, 2004. The soil arsenic was separated into five fractions via sequential extraction. The ferns grew well and took up arsenic from all soils. Fern biomass ranged from 24.8 to 33.5 g plant(-1) after 4 months of growth but was reduced in the subsequent harvests. The frond arsenic concentrations ranged from 66 to 6,151 mg kg(-1), 110 to 3,056 mg kg(-1), and 162 to 2,139 mg kg(-1) from the first, second and third harvest, respectively. P. vittata reduced soil arsenic by 6.4-13% after three harvests. Arsenic in the soils was primarily associated with amorphous hydrous oxides (40-59%), which contributed the most to arsenic taken up by P. vittata (45-72%). It is possible to use P. vittata to remediate arsenic-contaminated soils by repeatedly harvesting its fronds.

Arsenic chemistry in the rhizosphere of Pteris vittata L. and Nephrolepis exaltata L.

This greenhouse experiment evaluated the influence of arsenic uptake by arsenic hyperaccumulator Pteris vittata L. and non-arsenic hyperaccumulator Nephrolepis exaltata L. on arsenic chemistry in bulk and rhizosphere soil. The plants were grown for 8 weeks in a rhizopot with a soil containing 105 mg kg(-1) arsenic. The soil arsenic was fractionated into five fractions with decreasing availability: non-specifically bound (N), specifically bound (S), amorphous hydrous-oxide bound (A), crystalline hydrous-oxide bound (C), and residual (R). P. vittata produced larger plant biomass (7.38 vs. 2.32 mg plant(-1)) and removed more arsenic (2.61 vs. 0.09 mg pot(-1) arsenic) than N. exaltata. Plant growth reduced water-soluble arsenic, and increased soil pH (P. vittata only) in the rhizosphere soil. P. vittata was more efficient than N. exaltata to access arsenic from all fractions (39-64% vs. 5-39% reduction). However, most of the arsenic taken up by both plants was from the A fraction (67-77%) in the rhizosphere soil, the most abundant (61.5%) instead of the most available (N fraction).

Local invasiveness of ameloblastoma. Role played by matrix metalloproteinases and proliferative activity.

AIMS: Ameloblastoma is an odontogenic neoplasm characterized by local invasiveness and recurrence. In this study we analysed the role played by matrix metalloproteinases (MMPs) in the local invasiveness of ameloblastoma. We also attempted to establish a relationship between the presence of MMPs and the proliferative activity of ameloblastoma cells. METHODS AND RESULTS: Immunohistochemistry was carried out to detect different MMPs in formalin-fixed paraffin-embedded samples of human ameloblastoma. Immunohistochemistry, however, does not establish whether a given MMP is latent or active. To address this point, we carried out biochemical methods, namely zymography and Western blotting. Our results showed expression of latent and active forms of MMPs 1, 2 and 9 in ameloblastoma. These enzymes may digest bone matrix and release mitogenic factors, which would increase tumour proliferation. This possibility prompted us to study the proliferation of ameloblastoma cells located in close proximity to bone. Silver-stained nucleolar organizer region morphometry revealed that ameloblastoma cells in the vicinity of bone show increased proliferation, when compared with controls. CONCLUSIONS: Our results suggest an interdependent mechanism involving MMPs and proliferation of ameloblastoma cells, which may contribute to the local invasiveness of this tumour.

Preliminary analysis of microsatellite markers derived from sugarcane expressed sequence tags (ESTs)

Expressed sequence tags (ESTs) in the sugarcane (Saccharum spp) database (SUCEST) were electronically searched and 402 microsatellites identified. Various dinucleotide and trinucleotide simple sequence repeat (SSR) motifs were found, with these being more frequently observed in ESTs obtained from flower cDNA libraries. PCR primers were designed for 20 of these SSRs and were tested on eight sugarcane genotypes, the sequences of these primers and a list of known sugarcane genes containing SSR motifs being presented in this paper. Polymorphisms were evident both at the cultivar level and between Saccharum species. These results show that EST-derived SSRs in Saccharum species are useful because they are polymorphic and transferable. The large number of microsatellites that will eventually be available from the SUCEST database (containing 295,000 submitted reads) will have many potential applications in linkage mapping and the planning of crosses.

Fratura com afundamento craniano em crianças com menos de dois anos de idade / Depressed skull fractures in children under 2 years of age

As fraturas com afundamento da calota craniana (FAC) säo relativamente frequentes e seu tratamento neurocirúrgico está bem estabelecido, porém pouca atençäo tem sido dada a esta patologia na faixa etária de 0 a 2 anos de idade. Este estudo baseia-se na análise retrospectiva de 43 pacientes com FAC e idade entre 0 e 2 anos. As principais causas da FAC foram as quedas, seguidas pelos atropelamentos. A maioria apresentava FAC tipo I, isto é, aquela na qual o osso deprimido permanece conectado à calota craniana. Tratamento cirúrgico foi instituído em 69,8 por cento dos casos. A incidência de lesöes encefálicas associadas foi mais baixa do que a relatada na literatura