Cm38: a new antimicrobial peptide active against Klebsiella pneumoniae is homologous to Cn11.

Antimicrobial peptides (AMPs) represent a large and ubiquitous group of peptides. The current crisis in antibiotic therapy has led to an intensified search for new antimicrobial agents. In this regard, scorpion venom constitutes a rich source of biologically active peptides including AMPs. In the present study, the purification of a novel peptide with antimicrobial activity against the Gram-negative bacteria Klebsiella pneumoniae is described. This antimicrobial peptide, named Cm38, was purified from Centruroides margaritatus scorpion venom using a two-step chromatographic strategy using C8 and C18 columns. This toxin inhibits the proliferation of the Gram-negative bacteria Klebsiella pneumoniae with a Minimal Inhibitory Concentration (MIC) of 64 µM. An analysis of the N-terminal sequence of Cm38 revealed a close structural relationship to Cn11, a Na+-channel modulator toxin previously isolated from Centruroides noxius scorpion venom. Therefore, to test Cm38 for effects on ion channels, we measured its effects on action potential firing in cultured dorsal root ganglion neurons. Cm38 depolarized and increased action potential firing in a subset of neurons tested. The present work reports a new peptide related to Cn11 with antimicrobial properties that is also active in neurons.

Bioacumulation of cyanotoxins in Hypophthalmichthys molitrix (silver carp) in Paranoá Lake, Brasilia-DF, Brazil.

Three individuals of silver carp (Hypophthalmichthys molitrix) were collected biweekly from Paranoá Lake (DF, Brazil) for analysis of microcystin (MC) concentrations in their muscle and liver tissue. Analysis by high performance liquid chromatography and mass spectrometry revealed MC masses and fragmentation patterns that were identified as MC-LR (995.04 m/z), MC-LA (909.01 m/z) and an unknown MC (987.07 m/z). Concentrations were calculated as MC-LR equivalents using a calibration curve prepared with a standard of MC-LR. May/06 was the month with the highest MC-LR equivalent concentrations in muscle and liver (3.83 ± 2.78, and 12.94 ± 10.51 µg g(-1), respectively). Our results show that during the drought months (April-September), consumption of fish with these MC concentrations would result in exposure to MCs that greatly exceed the World Health Organization's recommended tolerable daily intake limit of 0.04 µg MC kg(-1) body weight.

Genotoxicity in Oreochromis niloticus (Cichlidae) induced by Microcystis spp bloom extract containing microcystins.

Studies of genotoxicity in fish caused by cyanobacterial extracts containing microcystins (MCs) can be useful in determining their carcinogenic risk due to a genotoxic mechanism. An extract of cyanobacterial Microcystis ssp, containing MC-LR and -LA from a bloom collected in a eutrophic lake, showed genotoxicity to Oreochromis niloticus. DNA damage (comet assay) was significantly induced in peripheral erythrocytes with both tested concentrations of 6.90 µg kg(-1) bw and 13.80 µg kg(-1) bw through intraperitoneal injection (ip). There was no micronucleus induction after ip injection at concentrations of 6.90 µg kg(-1) bw and 13.80 µg kg(-1) bw. Body exposure resulted in micronucleus induction and DNA damage only at the highest tested concentrations of 103.72 µg L(-1). Thus, comet assay and ip injection revealed the highest levels of the genotoxicity of MCs. Apoptosis-necrosis test carried out at concentrations of 6.90 µg kg(-1) bw and 13.80 µg kg(-1) bw revealed that at low concentrations more apoptosis than necrosis occurred. At higher concentrations more necrosis than apoptosis occurred.

Amarelinha do Amapá: a carotenoid-rich cassava cultivar.

Eight cassava (Manihot esculenta Crantz) cultivars, of which four are indigenous to the Amazon region, along with an interspecific hybrid, were assessed for their carotenoid content. They were propagated and are maintained in the living Manihot collection at the University of Brasília. The cultivar "Amarelinha do Amapá", which was collected from the State of Amapá, was found to have a very high content of beta-carotene: 27 mg per 100 mg, which is more than 50-fold higher than in other cassava cultivars. This cultivar, which also has excellent palatability, could be an important source of beta-carotene for cassava breeding.

Cassava diversity in Brazil: the case of carotenoid-rich landraces.

In Brazil, the center of cassava origin, cassava landraces have acquired through their domestication a large diversity in relation to many economic traits such as high content of carotenoids and excellent palatability among other characters. One of these clones, which has been grown by indigenous Brazilian farmers and is now being maintained in the University of Brasília gene bank, showed a high level of lycopene content (5 mg/kg viz. a viz. zero in common cultivars, and 12-20 mg/kg in tomato, a lycopene-rich vegetable). A second landrace called UnB 400 had a high content of beta-carotene, which reached 4 mg/kg.