Fungal contamination and selected mycotoxins in pre- and post-harvest maize in Honduras

Sixty nine samples of maize were collected from pre-harvest standing crops and on-farm storage facilities from 52 smallholder farms located within 4 regions of Honduras during October 1992 and November 1993. Samples were visually assessed for insect damage and fungal spoilage, and the mycoflora quantified on artificial media. The major components of the ear rot complex were:Fusarium moniliforme, F. moniliforme var.subglutinans, Penicillium species,Stenocarpella maydis, S. macrospora andAcremonium spp. Representative samples were also assayed for mycotoxin content. Fumonisin B₁ was detected in all 24 samples tested at levels of between 68–6,555 (µg/kg), and aflatoxin was detected in 2 samples heavily contaminated withAspergillus flavus. Moniliformin and tenuazonic acid were not detected in the samples tested. The implications of these findings for human and livestock health risk are discussed, together with possible strategies for controlling these pathogens.     

High-Density Lipoprotein Aggregated by Oxidation Induces Degeneration of Neuronal Cells

Abstract: We have previously reported that high-density lipoprotein (HDL) exhibits antineuritogenic effects on chicken cerebral cells in culture. In the present study, we show the effects of HDLs, oxidized by UV irradiation or heating, on chicken cerebral neurons in culture. Both treatments produced several physical and chemical changes in the HDLs, i.e., formation of lipid peroxides, enlargement of HDL diameters, an increased exposure of the tryptophan groups of the apolipoprotein A-I to a more hydrophilic environment, formation of bityrosines, and cross-linking of apolipoprotein A-I. When these treatments were performed in the absence of EDTA, most of the modifications described above were more intense and HDLs formed a macroaggregate that displays a rosette-like structure. The aggregated HDLs produced neurodegeneration and death when added to both undifferentiated and differentiated cerebral neurons in culture. This process was accompanied by the disorganization of the cellular microtubular cytoskeleton and hyperphosphorylation of the microtubule-associated protein tau. Native HDL or HDLs treated in the presence of EDTA inhibited the neuritogenesis of undifferentiated neurons but did not show any significant effect on the differentiated neurons in culture. The effects on the cellular cytoskeleton and morphology of aggregated HDLs recall those of the fibrillar β-amyloid peptide. The present results suggest that aggregated HDLs could participate in neurodegeneration associated with oxidative stress in the CNS.     

Attenuating mutations in the poliovirus 5' untranslated region alter its interaction with polypyrimidine tract-binding protein.

Mutations in the 5' untranslated regions (5'-UTRs) of all three serotypes of the Sabin vaccine strains are known to be major determinants of the attenuation phenotype. To further understand the functional basis of the attenuation phenotype caused by mutations in the 5'-UTR, we studied their effects on viral replication, translation, and the interaction of the viral RNA with cell proteins. A mutation at base 472 (C472U), which attenuates neurovirulence in primates and mice, was previously found to reduce viral replication and translation in neuroblastoma cells but not in HeLa cells. This mutation reduced cross-linking of the poliovirus 5'-UTR to polypyrimidine tract-binding protein (pPTB) in neuroblastoma cells but not in HeLa cells. These defects were absent in a neurovirulent virus with C at nucleotide 472. When C472U and an additional mutation, G482A, were introduced into the 5'-UTR, the resulting virus was more attenuated, had a replication and translation defect in both HeLa cells and neuroblastoma cells, and cross-linked poorly to pPTB from both cell types. A neurovirulent revertant of this virus (carrying U472C, G482A, and C529U) no longer had a replication defect in HeLa and SH-SY5Y cell lines and cross-linked with pPTB to wild-type levels. The results suggest that the attenuating effects of the mutation C472U may result from an impaired interaction of the 5'-UTR with pPTB in neural cells, which reduces viral translation and replication. Introduction of a second mutation, G482A, into the 5'-UTR extends this defect to HeLa cells.     

Succession following the catastrophic eruption of Ksudach volcano (Kamchatka, 1907)

Ksudach Volcano, southern Kamchatka Peninsula, erupted in 1907 and impacted over 2000 km² of forests with air-fall pumice deposits. We identified three impact zones. In Zone I, deposits deeper than 100 cm destroyed all vegetation. Two early successional stages occur, a lichen-dominated desert and isolated patches of a pioneer herb stage. Zone II is defined by pumice deposits 30 to 100 cm deep. Deposits of 70 to 100 cm destroyed all vegetation, but left scattered snags. Here primary succession dominates recovery, but its rate varies. Isolated trees survived in deposits of 30 to 70 cm and primary and secondary successional stages form a complex mosaic termed an intermediate succession. In Zone II, the primary stages found in Zone I are joined by a dwarf shrub-herb stage and a secondary birch forest stage. Zone III occurs where thinner deposits permitted some vegetation to survive in all locations. Secondary succession dominates in deposits of 10 to 30 cm. Trees suffered damage, but survived deposits of 20 to 30 cm, while other vegetation layers were eliminated. Deposits of 10 to 20 cm eliminated mosses and lichens and but only reduced the number of dwarf shrubs and herbs. Deposits of less than 10 cm damaged herb, moss and lichen layers but did not eliminate any species. All sampled vegetation remains in a pre-climax state, having yet to recover fully from earlier eruptions. Reconstructed vegetation maps for before 1907 and for ca. 1925 are compared to the map of vegetation in 1994. Based on degree of soil formation, vegetation recovery and colonization rates at different pumice depths, and the current vegetation, we estimate that full recovery of the soil-vegetation system will take more than 2000 years.     

Contribution to the determination of the chemotherapeutic drug G1 in biological fluids

A sensitive gas chromatographic method for the quantitative determination of the new antibacterial and antifungal drug G1, 1-(5-bromofuran-2-yl)-2-bromo-2-nitroethene, has been optimized. The method involves a fast and single extraction step from spiked serum and urine samples. The G1 drug was quantified using an internal standard method and by means of a nitrogen-selective detector. The results are statistically significant and show that mean levels of G1 as low as 1 μg ml⁻¹ can be measured accurately.     

p95vav associates with the nuclear protein Ku-70.

The proto-oncogene vav is expressed solely in hematopoietic cells and plays an important role in cell signaling, although little is known about the proteins involved in these pathways. To gain further information, the Src homology 2 (SH2) and 3 (SH3) domains of Vav were used to screen a lymphoid cell cDNA library by the yeast two-hybrid system. Among the positive clones, we detected a nuclear protein, Ku-70, which is the DNA-binding element of the DNA-dependent protein kinase. In Jurkat and UT7 cells, Vav is partially localized in the nuclei, as judged from immunofluorescence and confocal microscopy studies. By using glutathione S-transferase fusion proteins derived from Ku-70 and coimmunoprecipitation experiments with lysates prepared from human thymocytes and Jurkat and UT7 cells, we show that Vav associates with Ku-70. The interaction of Vav with Ku-70 requires only the 150-residue carboxy-terminal portion of Ku-70, which binds to the 25 carboxy-terminal residues of the carboxy SH3 domain of Vav. A proline-to-leucine mutation in the carboxy SH3 of Vav that blocks interaction with proline-rich sequences does not modify the binding of Ku-70, which lacks this motif. Therefore, the interaction of Vav with Ku-70 may be a novel form of protein-protein interaction. The potential role of Vav/Ku-70 complexes is discussed.     

Effect of blue-green light on growth rate and chemical composition of three diatoms

The diatomsChaetoceros sp.,Skeletonema costatum andThalassiosira pseudonana were grown with different irradiances of white and of blue-green light, and with a mixture of blue-green plus 6.5 mol m^–2 s^–1 of white light. Exponential growth rates were higher in mixed blue for the first two, whileT. pseudonana grew faster in white light but, in all cases, mean cell division rates did not differ with increasing irradiances. Harvesting in stationary, rather than in late exponential growth phase, resulted in higher protein contents forChaetoceros sp. andS. costatum, but forT. pseudonana the highest value was in the exponential phase. The highest protein content was in blue-green light for the three species and it increased with irradiance. As to other fractions, the three strains showed different responses, related to quality and quantity, as well as to culture ages.     

Production of polyhydroxyalkanoates by Azotobacter chroococcum H23 in wastewater from olive oil mills (alpechin)

We describe the production of large amounts of homo- and copolymers of polyhydroxyalkanoates (PHAs) by Azotobacter chroococcum strain H23 when growing in culture media amended with alpechin. A. chroococcum grown on NH₄⁺-medium supplemented with alpechin formed PHAs up to 50% of the cell dry weight after 24h. The results show that alpechin supports the growth of strain H23 and also that this waste could be utilized as a carbon source. Production of PHAs by using alpechin looks promising, since the use of inexpensive feed-stocks for PHAs is essential if bioplastics are to become competitive products.