<i>In vitro</i> evaluation of antifungal activity of Agave (<i>Agave scabra</i>, Salm Dyck) extracts against post-harvest mushrooms

The agricultural sector, and particularly the horticultural production, has a singular importance in agriculture, considering that it ranks second on agricultural products, nationally and worldwide. Fungal diseases are one of the major causes of vegetable loss during storage, reducing their nutritional value, quality and sale price. Vegetables are usually exposed to diverse treatments with chemical products before storage; as a result, fungal populations develop an increased resistance over time becoming more difficult to control. Because of this, research efforts toward finding more suitable chemicals to control fungal diseases are needed. Natural extracts may be an alternative solve this problem. In the present investigation the fungicidal activity of aqueous and ethanol extracts of Agave scabra was evaluated on the growth of Botrytis cinerea, Mucor sp., Aspergillus niger, Fusarium sp. and Penicillium sp., whose strains were isolated from potato and tomato. To assess their effects, the agar-dilution and agar-well techniques were performed. The ethanol extract was more effective against Botrytis cinerea and Mucor sp. when the agar-well method was used. However, when using the agar-dilution method the ethanol extract of Agave scabra inhibited the growth of Botrytis cinerea, Mucor sp. and Penicillium sp.     

The mycoflora and toxicity of feedstuffs from a production plant in córdoba, Argentina

Feedstuffs used for poultry nutrition in Argentina were analyzed for fungal flora and natural incidence of mycotoxins. Survey of 120 samples of poultry feeds, taken from May 1998 to April 1999, showed the presence of 15 genera of filamentous fungi. The predominant genera wereFusarium spp. andPenicillium ssp., isolated in 67.5 % of the samples, followed byAspergillus spp. (57.5 %). Yeast, were significantly isolated from most of the samples. Species identification was carried down for the toxigenic genera. Fungal total counts of poultry feeds ranged from 2.0 × 10³ to 3.0 × 10⁵ CFU g^-1 The fungal total counts during two months of sampling, were slightly over the limit value of 1 × 105 CFU g^-1, which ensure the hygienic quality of the feed. Potentially toxicogenic species presented moderate mean colony counts. Many of the fungi isolated from poultry feeds are mycotoxin producers. Fumonisins had the highest incidence, and were found in 97 % of the analyzed samples followed by aflatoxin B₁ (46 %), zearalenone (18 %) and deoxynivalenol (6 %). On the co-occurrence of both carcinogenic mycotoxins, all of the FBs contaminated feed samples were co-contaminated with AFB₁. The results show the relevance of the samples screening for viable fungi propagules and the surveillance of their associated mycotoxins in poultry feeds.     

Linkage study on dieldrin resistance and an inversion on the second chromosome of Anopheles stephensi.

In a study on the linkage between the gene for dieldrin resistance and an inversion on the second chromosome in Anopheles stephensi, the two factors were found to assort independently. As dieldrin resistance can be assigned either to the third chromosome, or to a position on the second chromosome more than 50 cross-over units from the inversion.     

The interplay of ubiquitous DNA-binding factors, availability of binding sites in the chromatin, and DNA methylation in the differential regulation of phosphoenolpyruvate carboxykinase gene expression.

We have identified DNA elements in the phosphoenolpyruvate carboxykinase (PEPCK) gene promoter which are bound 'in vivo' by proteins under conditions of basal level gene expression and have evaluated several hypothesis to account for the tissue specific expression of the gene. In vitro DNase I footprinting demonstrated that factors which bind to basal expression elements of the PEPCK promoter, the BSE/CRE and NFI/CCAAT sites, are also present in HTC and XC cells which do not express the PEPCK gene. 'In vivo' DNase I footprinting demonstrated that the BSE/CRE, NFI/CCAAT, and three additional sites are bound by protein in H4IIE cells which express the PEPCK gene but not in the HTC or XC cells. No evidence for a repressor protein or for phased nucleosome binding to the PEPCK promoter in HTC or XC cells could be detected. Genomic sequencing was used to determine if differential methylation of the PEPCK promoter could account for the lack of factor binding in HTC and XC nuclei. None of the 14 cytosine residues in CpG dinucleotides was methylated in H4IIE or rat liver DNA, all were methylated in rat sperm DNA, and 6 were methylated in HTC DNA; including the cytosine at position--90 within the BSE/CRE. Only one cytosine residue, at position--90, was methylated in XC DNA. Treatment of XC cells with 5-azacytidine resulted in loss of methylation at the--90 position yet this was insufficient to allow synthesis of a detectable amount of PEPCK mRNA.     

Isolation and characterization of a cDNA clone for the CCAAT transcription factor EFIA reveals a novel structural motif

Enhancer factor I (EFI) is a trans-acting factor which binds to the Rous sarcoma virus long terminal repeat enhancer and promoter at two inverted CCAAT-box motifs. We demonstrate that two forms of EFI DNA binding activity exist in nuclear extracts of avian cells. One form requires two heterologous components (EFIA)(EFIB) for high affinity, specific DNA binding activity, whereas a second form is not dependent on EFIB for binding and may be composed solely of EFIA, perhaps as a multimer. Both forms give rise to the same mobility shift in gel retardation assays, but the two forms can be separated chromatographically under buffer conditions which stabilize the two DNA binding activities. A cDNA for EFIA has been isolated from a rat liver cDNA expression library. The 1489-base pair EFIA cDNA encodes a 322-amino acid protein which is nearly identical to two previously described human DNA binding proteins. These are dbpB, a DNA binding protein of unknown specificity which binds to the epidermal growth factor receptor enhancer and c-erbB-2 gene promoter (Sakura, H., Maekawa, T., Imamoto, F., Yasuda, K., and Ishii, S. (1988) Gene (Amst.) 73, 499-507), and YB-1, a protein which recognizes the Y-box (inverted CCAAT motif) of the HLA-DR alpha chain gene (Didier, D. K., Schiffenbauer, J., Woulfe, S. L., Zacheis, M., and Schwartz, B. D. (1988) Proc. Natl. Acad. Sci. U. S. A. 85, 7322-7326). EFIA/dbpB/YB-1 share a highly conserved region of 100 amino acids with dbpA, another protein identified by Sakura et al. (1988) which binds to the epidermal growth factor receptor enhancer and c-erbB-2 gene promoter, and with two Xenopus CCAAT binding proteins, FRG Y1 and FRG Y2 (Tafuri, S. R., and Wolffe, A. P. (1990) Proc. Natl. Acad. Sci. U. S. A., in press). This highly conserved domain among all six proteins is presumed to represent or contain a DNA binding domain for the CCAAT motif. In addition, we note that the EFIA/dbpB/YB-1 polypeptide contains a novel arrangement of alternating clusters of positively and negatively charged amino acids not yet reported for any trans-acting factor. The functional significance of this novel structural motif, which is also conserved in dbpA, FRG Y1, and FRG Y2, will be discussed.     

Expression of the cystic fibrosis gene in human development.

The specialised epithelia lining the respiratory tract, pancreatic ducts, male genital ducts and sweat gland ducts are defective in the severe inherited disease, cystic fibrosis (CF). We have looked at the expression of the CF gene in human fetal tissues to throw light on the development of function in specialised ductal epithelia and to determine the age of onset of the CF disease process. The CF gene is already seen to be transcribed in mid-trimester fetal lung, pancreas and male genital ducts. Hence, by this developmental stage, and before they are fully differentiated, these epithelia have the capability to perform important transport functions. Epithelial cell cultures derived from fetal pancreas and male genital ducts maintain expression of the CF gene in vitro and so form good models for analysing CF gene function and differentiation of these specialised epithelia.