Colonisation and aflatoxin formation by Aspergillus spp. on brown rices differing in endosperm properties

The use of zebrafish model in prostate cancer therapeutic development and discovery

Zebrafish is now among the leading in vivo model for cancer research, including prostate cancer. They are an alternative economic model being used to study cancer development, proliferation, and metastasis. They can also be effectively utilized for the development of cancer drugs at all levels, including target validation, and high-throughput screening for possible lead molecules. In this review, we provide a comprehensive overview of the role of zebrafish as an in vivo model in prostate cancer research. Globally, prostate cancer is a leading cause of death in men. Although many molecular mechanisms have been identified as playing a role in the pathogenesis of prostate cancer, there is still a significant need to understand the initial events of the disease. Furthermore, current treatments are limited by the emergence of severe toxicities and multidrug resistance. There is an essential need for economical and relevant research tools to improve our understanding and overcome these problems. This review provides a comprehensive summary of studies that utilized zebrafish for different aims in prostate cancer research. We discuss the use of zebrafish in prostate cancer cell proliferation and metastasis, defining signaling pathways, drug discovery and therapeutic development against prostate cancer, and toxicity studies. Finally, this review highlights limitations in this field and future directions to efficiently use zebrafish as a robust model for prostate cancer therapeutics development.

Mycotoxigenic Fungi and Mycotoxins in Agricultural Crop Commodities in the Philippines: A Review

The tropical, warm, and humid conditions that are favorable to the growth and development of mycotoxigenic fungi put the Philippines at a high risk of mycotoxin contamination. To date, seven mycotoxigenic Aspergillus species, four Fusarium species, and one Penicillium species have been isolated from various agricultural crop commodities in the country. There are five mycotoxin groups (aflatoxin, fumonisin, ochratoxin, nivalenol, and zearalenone) that have been detected in both the raw form and the by-products of major crops grown in the country. Since the first scientific report of aflatoxin contamination in the Philippines in 1972, new information has been generated on mycotoxins and mycotoxigenic fungi, but little has been known of other mycotoxins until the last two decades. Further, despite the increase in the understanding of mycotoxigenic fungi and mycotoxins in the country, very limited knowledge exists on practices and measures that control both the fungi and the toxins. This paper reviews the current literature on mycotoxigenic fungi and mycotoxins in the Philippines with emphasis on the last two decades and on other mycotoxins.

Mycotoxin concentrations in rice from three climatic locations in Africa as affected by grain quality, production site, and storage duration

Information on the mycotoxin contamination of rice in Africa is limited although the risk of contamination is high. In this study, domestic milled rice processed by actors using suboptimal methods was purchased and total fumonisin (FUM), zearalenone, and aflatoxin concentrations determined at 0, 90, and 180 days after storage. Three different climatic locations, Cotonou (Benin) in the Guinea savanna, Yaoundé (Cameroon) in the Tropical forest, and N'diaye (Senegal) in the Sahel, were selected as storage sites. Subsets of the samples collected from Glazoue (Benin), Ndop (Cameroon), and Dagana (Senegal) were stored in plastic woven bags under room conditions in the respective sites with or without calcium oxide (burnt scallop shell-BSS, 0.1% w/w) treatment. Multivariance analysis showed that FUM concentration was positively influenced by the duration of storage only while zearalenone concentration was negatively influenced by relative humidity and head rice but positively by impurities. Zearalenone concentration was also influenced by sample collection/storage location, processing type, and duration of storage. Aflatoxin concentration was influenced negatively by storage room temperature and head rice but positively by impurities and chalky grains. In addition, aflatoxin concentration was influenced by collection/storage location and processing type. BSS treatment followed by storage for 6 months had no effect on the concentration of the three assessed mycotoxins. Strategies to reduce the risk of mycotoxin contamination in study sites will include the improvement of physical rice quality through better pre- and postharvest practices and proper packaging of both treated rice and untreated rice in hermetic systems before marketing and storage.

Fungicidal and anti-aflatoxigenic effects of the essential oil of Cymbopogon citratus (DC.) Stapf. (lemongrass) against Aspergillus flavus Link. isolated from stored rice

AIMS

To develop a natural fungicide against aflatoxigenic fungi, to protect stored rice, using the essential oil of lemongrass.

METHODS AND RESULTS

Aspergillus flavus Link. was isolated from stored rice and identified as an aflatoxigenic strain. Lemongrass oil was tested against A. flavus and the test oil was fungistatic and fungicidal against the test pathogen at 0.6 and 1.0 mg ml(-1), respectively. Aflatoxin production was completely inhibited at 0.1 mg ml(-1). The results obtained from the thin layer chromatographic bioassay and gas chromatography indicated citral a and b as the fungicidal constituents in lemongrass oil. During the fumigant toxicity assay of lemongrass oil, the sporulation and the mycelial growth of the test pathogen were inhibited at the concentrations of 2.80 and 3.46 mg ml(-1), respectively.

CONCLUSION

Lemongrass oil could be used to manage aflatoxin formation and fungal growth of A. flavus in stored rice.

SIGNIFICANCE AND IMPACT OF THE STUDY

Currently, fungicides are not used to control fungal pests or mycotoxin production on stored rice. Rice treated with the essential oil of lemongrass could be used to manage fungal pests as well as the insect pests in stored rice. The essential oil is chemically safe and acceptable to consumers, as synthetic chemical fungicides can cause adverse health effects to consumers.

Storage fungi and seed health of rice: a study in the Philippines

Fifty seed samples of different rice varieties stored in warehouses for varying periods (1-28 months) were collected and screened for their fungal flora, using standard blotter and agar plate methods, resulting in the isolation of 36 fungal forms. The samples were also studied for moisture content, germinability, and seedling abnormalities. Significant correlations were found among the numbers of fungi, storage period, and germinability. Fourteen samples, seven each of IR64 and IR66 were studied with regard to moisture content, germination test, abnormal seedlings, speed of germination, conductance of leachates, total dehydrogenase activity, total free amino acids, total soluble sugar, fat acidity, gelatinization temperature, gel consistency, amylose content, translucency, and per cent whiteness. Significant relationships were found between the fungi and the parameters studied.

Natural occurrence of toxigenic fungi and mycotoxins in rice bran

Thirty four samples of rice bran, of which 9 were from raw (untreated) rice (RR) and 25 from parboiled rice (PbR) were collected from commercial rice mills in and around Madras and analysed for storage mycoflora and mycotoxins. Fungi of the Aspergillus flavus group were present in 29 of the 34 samples (8 from RR and 21 from PbR) in quantities ranging from less than 1-432 thousand propagules/g, though not always as the dominant mycoflora. Fungal numbers were usually higher in RR than in PbR samples. Five of the 9 RR samples and 6 of the 25 PbR samples were positive for aflatoxins. Among 29 isolates of A. flavus obtained from the bran samples, 16 isolates -6 from RR bran and 10 from PbR bran - were found to be toxigenic in vitro. Some isolates of A. candidus also seemed to produce aflatoxin and other fluorescent substances.

Stimulation by Hyphopichia burtonii and Bacillus amyloliquefaciens of aflatoxin production by Aspergillus flavus in irradiated maize and rice grains

Aspergillus flavus was grown on maize and rice extract agars and on irradiated viable cracked maize and rice grains, either in pure culture or in dual culture with wild strains of either Hyphopichia burtonii or Bacillus amyloliquefaciens. Aflatoxin production by A. flavus and its growth and interactions with the other microorganisms were studied at three water activities (aw) (0.98, 0.95, and 0.90) and two temperatures (25 and 16 degrees C). Both H. burtonii and B. amyloliquefaciens markedly stimulated growth and aflatoxin production by A. flavus on cracked maize, especially at 25 degrees C and 0.95 and 0.98 aw. No aflatoxin was detected in pure cultures of A. flavus on cracked rice after 12 days of incubation at 25 degrees C, but some was produced by mixed cultures at 16 degrees C and 0.98 aw. The morphological interactions among A. flavus, H. burtonii, and B. amyloliquefaciens were also examined on maize and rice extract agars under similar controlled conditions.