Angel Medina - Academia.edu (original) (raw)

Papers by Angel Medina

Man and World, 1985

Martin Heidegger qualifies in my view not as a great philosopher but as a "grand" philo... more Martin Heidegger qualifies in my view not as a great philosopher but as a "grand" philosopher. In spite of his penchant for a communion with our intellectual origins he was not a very original thinker. His existen-tial ontology has a tight coherence, but that coherence ...

Nursing philosophy : an international journal for healthcare professionals, 2011

Proceedings of the American Catholic Philosophical Association, 1971

The Journal of Value Inquiry, 1972

Human Studies, 1987

A work like the Essays of Montaigne, written at the threshold of Modern Times, cannot simply be c... more A work like the Essays of Montaigne, written at the threshold of Modern Times, cannot simply be considered, if indeed any book can, as a standard book. Published after the end of an epoch in which each book claimed to be, in itself or in connection with its sources, a full ...

International journal of food microbiology, Jan 29, 2008

Journal of chromatography. B, Analytical technologies in the biomedical and life sciences, 2010

International journal of food microbiology, Jan 2, 2015

Frontiers in Microbiology, 2014

Human Biology - HUM BIOL, 2007

The initial peopling of South America is largely unresolved, in part because of the unique distri... more The initial peopling of South America is largely unresolved, in part because of the unique distribution of genetic diversity in native South Americans. On average, genetic diversity estimated within Andean populations is higher than that estimated within Amazonian populations. Yet there is less genetic differentiation estimated among Andean populations than estimated among Amazonian populations. One hypothesis is that this pattern is a product of independent migrations of genetically differentiated people into South America. A competing hypothesis is that there was a single migration followed by regional isolation. In this study we address these hypotheses using mtDNA hypervariable region 1 sequences representing 21 South American groups and include new data sets for four native Peruvian communities from Tupe, Yungay, and Puno. An analysis of variance that compared the combined data from western South America to the combined data from eastern South America determined that these two regional data sets are not significantly different. As a result, a migration from a single source population into South America serves as the simplest explanation of the data.

Applied and Environmental Microbiology, 2005

Journal of chromatography. A, Jan 12, 2005

Journal of chromatography. A, Jan 21, 2006

International Journal of Food Microbiology, 2005

The natural mycobiota occurring in bee pollen is studied in the present report with special atten... more The natural mycobiota occurring in bee pollen is studied in the present report with special attention to analyze the incidence of fungal species that are potential producers of mycotoxins. A total of 90 ready-to-eat bee pollen samples were analyzed. Eighty-seven samples were collected in stores placed in different Spanish areas and three were from Buenos Aires (Argentina). The statistical results (ANOVA) showed that yeasts and Penicillium spp. were the predominant fungi. With regard to the potential mycotoxin producing species, Penicillium verrucosum, Aspergillus niger aggregate, Aspergillus carbonarius, Aspergillus ochraceus, Aspergillus flavus, Aspergillus parasiticus and Alternaria spp. were found. The last genus was isolated very frequently. The potential ability for producing ochratoxin A (OTA) and aflatoxins B1, B2, G1 and G2 was studied by culturing in vitro the isolates followed by analysis of these mycotoxins in culture extracts by HPLC with fluorescent detection. It was found that 100%, 53.3%, 33.3% and 25% of the isolates of A. carbonarius, A. ochraceus, P. verrucosum and A. niger aggregate, respectively, produced OTA. Moreover, 28.6% of the isolates from the A. flavus plus A. parasiticus group were able to produce aflatoxin B1. Aflatoxin B2 was detected in only 10% of the cultures. Aflatoxins G1 and G2 were not detected in cultures under the assayed conditions. This is the first report carried out on the natural mycobiota occurring in bee pollen in general and on the toxigenic capability of these isolates in particular.

International Journal of Food Microbiology, 2007

Ochratoxin A (OTA) is a mycotoxin produced mainly by several fungal species of the genera Aspergi... more Ochratoxin A (OTA) is a mycotoxin produced mainly by several fungal species of the genera Aspergillus and Penicillium. This mycotoxin has been shown to be nephrotoxic, hepatotoxic, teratogenic and carcinogenic to animals and has been classified as a possible carcinogen to humans. OTA occurs in a variety of foods, including beer and wine. Reports on OTA occurrence in beer indicate that this is a worldwide problem due to the widespread consumption of this beverage. At present, the European Union (EU) has not set a maximum allowable limit (MAL) for this mycotoxin in beer, although there is a limit in barley and malt. Studies carried out in different countries agree in the high proportion of samples contaminated with OTA although levels are, usually, below 0.2 ng/ml. OTA occurrence has been related to the contamination of malt barley with ochratoxigenic species, particularly Penicillium verrucosum. OTA produced in grains is carried to wort and, although fermentation decreases the concentration, the toxin is not eliminated. Reducing the fungal contamination of malt barley is the most promising strategy for reducing OTA in beer. With regard to wine, surveys on the presence of OTA have been conducted worldwide. The proportion of wines in which OTA is detected is very high (above 50%) in some countries (especially in the Mediterranean basin) although only a few wines contained concentrations exceeding the MAL laid down by the EU (2.0 ng/ml). A gradient of concentration is usually recognized; OTA levels decrease in the order red, rosé, and white wine but also with increasing latitude of the producing countries. OTA presence in wines is due to the black aspergilli, mainly A. carbonarius, which can grow on grapes in the vineyards and produce the toxin. At grape crushing, the juice can be contaminated with the toxin which is carried over into wine, where it persists due to its stability. Pre- and post-harvest treatments are being investigated to diminish contamination of wines as much as possible.

International Journal of Food Microbiology, 2006

The present work deals with the toxigenic mycobiota occurring in Spanish malting barley and the c... more The present work deals with the toxigenic mycobiota occurring in Spanish malting barley and the capability for producing mycotoxins by several important toxigenic fungi. One hundred and eighty seven samples of malting barley were gathered from Spanish breweries before processing. One hundred and fifty kernels per sample were surface-sanitized with a 2% sodium hypochlorite solution and incubated on three culture media. The most abundant fungi were species of Alternaria, Aspergillus, Penicillium and Fusarium, which were present in 93%, 82.3%, 57.8% and 27.8% of the samples, respectively. To evaluate their mycotoxin producing potential a number of isolates belonging to each genus, except Penicillium, were randomly selected and incubated on culture media known to be appropriate for production of mycotoxins. Alternariol and alternariol monomethyl ether were produced by 26.7% of Alternaria spp. isolates (all belonged to Alternaria alternata). All tested isolates of F. verticillioides produced fumonisin B1 (FB1) and 61.3% of them produced fumonisin B2 (FB2), whereas FB1 was synthesized by 83.3% and FB2 by 77.8% of F. proliferatum isolates. Twenty percent of the isolates of the Aspergillus flavus/A. parasiticus group had the capability to produce aflatoxin B1 and aflatoxin B2. Thirty out of 34 isolates of F. graminearum produced deoxynivalenol and zearalenone whereas the other 4 isolates produced nivalenol. Ochratoxin A was detected in 75% and 15% of isolates of Aspergillus section Nigri and A. ochraceus, respectively. This is the first survey carried out in Spain on the toxigenic mycobiota contaminating malting barley in breweries and the mycotoxin producing capacity of several species. The information obtained is useful for assessing the risk of mycotoxins in beer.

Systematic and Applied Microbiology, 2004

International Journal of Biological Macromolecules, 2004

The capacity of bee pollen as a substrate for production of ochratoxin A (OTA) by a strain of Asp... more The capacity of bee pollen as a substrate for production of ochratoxin A (OTA) by a strain of Aspergillus ochraceus was studied. For control purposes corn, wheat and rice grains, and eleven liquid media were assayed. They were Yeast Extract Sucrose broth (YES), YES supplemented with 0.05, 0.1, 0.5, 1 and 5% bee pollen, YES supplemented with 0.5% peptone, 50% must, Wickerham medium, Aflatoxin Production medium and Coconut Broth Medium. Cultures were maintained at 28 C for 4 weeks and were analyzed every seven days for OTA by liquid chromatography with fluorescence detection. OTA production in bee pollen was significantly (P < 0.01) higher than production in corn, wheat and rice grains regardless of incubation time. With regard to liquid cultures, OTA accumulation in YES supplemented with 5% bee pollen was significantly higher than in pollen-free liquid cultures. A positive correlation between the proportion of pollen added to YES medium and OTA level was observed. This is the first report concerning the use of bee pollen as a substrate to stimulate OTA production. On the basis of the preliminary results obtained in this study it can be hypothesized that bee pollen may constitute an important risk factor concerning the presence of OTA in the diet of consumers of that nutritious food.

Journal of Chromatography A, 2004

Ochratoxin A (OTA) is a mycotoxin produced by some species of Aspergillus and Penicillium verruco... more Ochratoxin A (OTA) is a mycotoxin produced by some species of Aspergillus and Penicillium verrucosum. It has been found in foods and feed all over the world. There is a great concern about OTA because it is nephrotoxic and probably, carcinogenic to humans. Most of analytical methods developed for OTA in wine, beer and other products are based on LC with fluorescence detection (LC–FLD). In the present work, various procedures for extraction and/or clean-up for determination of OTA in musts, wine and beer by LC–FLD were compared: (1) dilution with polyethylen glycol 8000 and NaHCO3 solution and clean-up an on immunoaffinity column (IAC); (2) extraction with chloroform and IAC clean-up; solid-phase extraction (SPE) on (3) reversed-phase (RP) C18; (4) RP phenylsilane and (5) Oasis HLB cartridges. SPE on phenylsilane and Oasis HLB have not been reported for OTA analysis in beverages. The same LC–FLD conditions and concentration ratio were used. The former procedure was simple, rapid and provided flat baselines, free from most impurity peaks, high OTA recoveries and quite repeatable results. RP C18 using methanol–acetic acid (99.5:0.5) as elution solvent provided good recoveries and precision, thus becoming a cheaper but interesting alternative at 0.1–1 ng/ml spiking levels. Oasis HLB cartridges were usually better than phenylsilane. Possible binding of OTA to proteins or other components was tested by acid treatment before extraction but no significant differences with controls appeared.