Biomedical subjects

A J Ramos

Publications and source records attributed to A J Ramos.

At least 37 records · Page 2Linked to original sources

PubMed2004

Incubation time and water activity effects on ochratoxin A production by Aspergillus section Nigri strains isolated from grapes.

AIMS: The objective of this study was to determine the temporal ochratoxin A (OTA) accumulation profile of Aspergillus section Nigri at different water activity (aw) levels. METHODS AND RESULTS: Two Aspergillus carbonarius and two Aspergillus niger aggregate strains isolated from grapes were tested in vitro for OTA accumulation at 25 degrees C on synthetic nutrient medium, over periods of 20 days at different aw levels. Results were modelled by a multiple linear regression and response surface predictive models were obtained. High levels of aw favoured OTA production by these moulds. Maximum amounts of OTA were found at the earlier growth states (5 days for A. carbonarius and 7-13 days for A. niger aggregate). CONCLUSIONS: Provided that A. section Nigri, and mainly A. carbonarius, play the main role in OTA presence in grapes, it would be critical to adjust the harvest and processing time to significantly reduce the chances for OTA accumulation. SIGNIFICANCE AND IMPACT OF THE STUDY: Ochratoxin A production by A. section Nigri has been shown for the first time to occur optimally after as little as 5 days on a grape-like medium.

Aspergillus niger↗

PubMed2004

Impact of essential oils on growth rate, zearalenone and deoxynivalenol production by Fusarium graminearum under different temperature and water activity conditions in maize grain.

AIMS: The effect of five essential oils (oregano, cinnamon, lemongrass, clove and palmarose) on growth rate, zearalenone (ZEA) and deoxynivalenol (DON) production by Fusarium graminearum strains was assessed. METHODS AND RESULTS: The influence of the essential oils was tested on irradiated maize at two concentrations (500 and 1000 mg kg-1), at different water activity (aw) (0.95 and 0.995) and temperature (20 and 30 degrees C) levels. At 0.995 aw all essential oils tested had an inhibitory effect on growth rate of F. graminearum at both temperatures studied. At this aw level, DON production in general was inhibited by all essential oils at 30 degrees C and, although palmarose and clove were the only essential oils with statistically significant inhibitory effect on ZEA production, an inhibitory trend was observed when cinnamon and oregano oils were added to maize grain. CONCLUSIONS: Antifungal and antimycotoxigenic activity of the essential oils assayed was shown to depend on environmental conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: It is apparent that essential oils should be considered as alternative preharvest natural fungicides. Further investigation on natural maize grain might be useful to study the effectiveness of these essential oils in the presence of natural mycoflora of maize grain.

Antifungal Agents↗

PubMed2003

Inhibitory effect of cinnamon, clove, lemongrass, oregano and palmarose essential oils on growth and fumonisin B1 production by Fusarium proliferatum in maize grain.

The effect of cinnamon, clove, oregano, palmarose and lemongrass oils on growth and FB1 production by three different isolates of F. proliferatum in irradiated maize grain at 0.995 and 0.950 aw and at 20 and 30 degrees C was evaluated. The five essential oils inhibited growth of F. proliferatum isolates at 0.995 aw at both temperatures, while at 0.950 aw only cinnamon, clove and oregano oils were effective in inhibiting growth of F. proliferatum at 20 degrees C and none of them at 30 degrees C. Cinnamon, oregano and palmarose oils had significant inhibitory effect on FB1 production by the three strains of F. proliferatum at 0.995 aw and both temperatures, while clove and lemongrass oils had only significant inhibitory effect at 30 degrees C. No differences were found using 500 or 1000 microg essential oil g(-1). At 0.950 aw, none of the essential oils had any significant effect on FB1 production. The results suggest that mainly cinnamon and oregano oils could be effective in controlling growth and FB1 production by F. proliferatum in maize under preharvest conditions.

Cinnamomum zeylanicum↗

PubMed2003

Efficacy of sorbates on the control of the growth of Eurotium species in bakery products with near neutral pH.

The effects of sorbic acid and potassium sorbate on growth of different Eurotium isolates when added to a bakery product analogue were tested under different environmental conditions. Water activity of the products was adjusted to values in the range of 0.75-0.90, and storage temperatures were in the range of 15-30 degrees C. Preservatives were added in concentrations ranging from 0.025% to 0.2%. It was observed that 0.025% and 0.05% concentrations always enhanced the isolates growth, while 0.1% had little preservative effect. Finally, even the highest concentration (0.2%) was not suitable as it only controlled fungal growth under certain water activity and temperature levels. It was concluded that these weak-acid preservatives are not useful when added to bakery products with near to neutral pH.

Bread↗

PubMed2003

SEM study of water activity and temperature effects on the initial growth of Aspergillus ochraceus, Alternaria alternata and Fusarium verticillioides on maize grain. Scanning electron microscopy.

A scanning electron microscopy (SEM) study of the effect of water activity (a(w)), temperature and fungal interactions on the very early phases of Aspergillus ochraceus, Alternaria alternata and Fusarium verticillioides development on maize grains was carried out. Germination and growth of individual fungal strains were assayed at 0.92, 0.95 and 0.98 a(w), and 20 and 30 degrees C. Hyphal lengths were measured on micrographs taken by SEM at different periods of incubation. A. alternata had the highest linear growth at 0.98 a(w), and was the only species able to grow under all conditions tested, whereas A. ochraceus was not able to germinate at 0.92 a(w) at any temperature assayed. F. verticillioides demonstrated a different behaviour depending on growth temperature. Fungal interactions were studied at 0.95a(w) and 30 degrees C. A. ochraceus germination was inhibited when it was co-inoculated with one or two of the other species. A. alternata showed an increased growth rate when growing together with the other fungi, whereas growth of F. verticillioides was significantly inhibited when paired with A. ochraceus.

Alternaria↗

PubMed2003

Influence of hepatitis C virus coinfection on failure of HIV-infected patients receiving highly active antiretroviral therapy to achieve normal serum beta2microglobulin levels.

The influence of hepatitis C virus (HCV) coinfection on the kinetics of serum beta2microglobulin levels in HIV-infected patients undergoing highly active antiretroviral therapy was analyzed. After 96 weeks of therapy, beta2microglobulin levels declined significantly both in 24 HCV seronegative and 16 HCV-infected individuals. Throughout the follow-up period, HCV-infected patients showed higher beta2microglobulin values than non-HCV-infected patients. These results show that HCV infection precludes immune deactivation in HIV-infected patients undergoing highly active antiretroviral therapy.

Antiretroviral Therapy, Highly Active↗

PubMed2003

Antifungal activity of volatile compounds generated by essential oils against fungi commonly causing deterioration of bakery products.

AIMS: To investigate the volatile fractions of 16 essential oils for activity against the more common fungi causing spoilage of bakery products, Eurotium amstelodami, E. herbariorum, E. repens, E. rubrum, Aspergillus flavus, A. niger and Penicillium corylophilum. METHODS AND RESULTS: The study applied 50 microl of pure essential oils in a sterilized filter paper, were carried out at pH 6 and at different water activity levels (0.80-0.90). First, a wheat flour based agar medium was used, where cinnamon leaf, clove, bay, lemongrass and thyme essential oils where found to totally inhibit all microorganisms tested. These five essential oils were then tested in sponge cake analogues, but the antifungal activity detected was much more limited. CONCLUSION: Five essential oils showed potential antifungal capacity against all species tested, over a wide range of water availability. Their activity, however, seems to be substrate-dependent. More research is needed to make them work in real bakery products, as in the preliminary study limited effectiveness was found. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential of the cinnamon leaf, clove, bay, lemongrass and thyme essential oils against species belonging to Eurotium, Aspergillus and Penicillium genus has been demonstrated.

Agar↗

PubMed2003

Modified atmosphere packaging for prevention of mold spoilage of bakery products with different pH and water activity levels.

A sponge cake analog was used to study the influence of pH, water activity (aw), and carbon dioxide (CO2) levels on the growth of seven fungal species commonly causing bakery product spoilage (Eurotium amstelodami, Eurotium herbariorum, Eurotium repens, Eurotium rubrum, Aspergillus niger, Aspergillus flavus, and Penicillium corylophilum). A full factorial design was used. Water activity, CO2, and their interaction were the main factors significantly affecting fungal growth. Water activity at levels of 0.80 to 0.90 had a significant influence on fungal growth and determined the concentration of CO2 needed to prevent cake analog spoilage. At an aw level of 0.85, lag phases increased twofold when the level of CO2 in the headspace increased from 0 to 70%. In general, no fungal growth was observed for up to 28 days of incubation at 25 degrees C when samples were packaged with 100% CO2, regardless of the aw level. Partial least squares projection to latent structures regression was used to build a polynomial model to predict sponge cake shelf life on the basis of the lag phases of all seven species tested. The model developed explained quite well (R2 = 79%) the growth of almost all species, which responded similarly to changes in tested factors. The results of this study emphasize the importance of combining several hurdles, such as modified atmosphere packaging, aw, and pH, that have synergistic or additive effects on the inhibition of mold growth.

Ascomycota↗

PubMed2002

Risk assessment of the use of sub-optimal levels of weak-acid preservatives in the control of mould growth on bakery products.

The hurdle technology approach was used to prevent fungal growth of common contaminants of bakery products including isolates belonging to the genera Eurotium, Aspergillus and Penicillium. Several levels (0.003%, 0.03% and 0.3%) of calcium propionate, potassium sorbate and sodium benzoate were assayed on a model agar system in a full-factorial experimental design in which the other factors assayed were pH (4.5, 6 and 7.5) and a(w) (0.80, 085, 0.90 and 0.95). Potassium sorbate was found to be the more suitable preservative to be used in combination with the common levels of pH and a(w) in Spanish bakery products. Sub-optimal concentrations (0.003% and sometimes 0.03%) led to an enhancement of fungal growth. None of the preservatives had a significant inhibitory effect at neutral pH.

Antifungal Agents↗

PubMed2002

Mortality due to liver failure and impact on survival of hepatitis virus infections in HIV-infected patients receiving potent antiretroviral therapy.

The aim of the present study was to examine the causes of death, the mortality attributable to liver failure, and the impact of hepatitis virus infections on the survival of a cohort of HIV-infected patients before and after the extensive use of highly active antiretroviral therapy (HAART). Liver disease associated with hepatitis C virus (HCV) seems to be accelerated in patients infected with the human immunodeficiency virus (HIV). On the other hand, the effect of HCV on HIV progression was controversial before the introduction of HAART. However, the last study to report changes in mortality due to liver failure was published in 1997, and the impact of HCV carriage on the survival of HIV-infected patients receiving HAART needs to be clarified. In this investigation, 492 patients who were prescribed antiretroviral drugs between April 1989 and September 2000 were included in the study cohort. The median duration of follow-up of the cohort was 1,392 days. HCV infection was present in 323 (68%). Mortality attributable to AIDS decreased from 4.5 to 1.8 per 100 persons per year. Mortality due to liver failure increased from 0.3 to 0.5 per 100 persons per year ( P<0.01). The survival of patients with and without HCV infection was similar ( P=0.8). Although liver failure is an increasing cause of death among HIV-infected patients receiving HAART, HCV infection has still no impact on the survival of HIV-infected patients.

AIDS-Related Opportunistic Infections↗

PubMed2002

Combined effects of weak acid preservatives, pH and water activity on growth of Eurotium species on a sponge cake.

The combined effects of weak acid preservatives (sorbate, benzoate and propionate), pH (6.0, 7.5) and water activity (a(w)) levels (0.80, 0.85, 0.90) on growth of four Eurotium species isolated from bakery products on a sponge cake analogue were studied. Even though it is universally known that these preservatives are much more effective at lower pH values, we chose a 6-7.5 level to correlate with the pH of the Spanish cake product studied. In general, 0.3% doses of all three preservatives were effective only when they were applied at pH 6.0 and at 0.80-0.85 a(w). Potassium sorbate was clearly the most effective in inhibiting growth of all isolates. Under the conditions tested, application of all three preservatives added at 0.03% acted as growth promoter of all isolates rather than having a preservative effect.

Ascomycota↗

PubMed2001

Effect of water activity and temperature on growth of three Penicillium species and Aspergillus flavus on a sponge cake analogue.

This study compared the effect of temperature and water activity and their interactions on the rate of mycelial growth of Penicillium aurantiogriseum, P. chrysogenum, P. corylophilum and Aspergillus flavus on a sponge cake analogue. As expected, growth rates showed dependence on a(w), and temperature. However, no significant differences were observed in the growth rates of different isolates. The minimum a(w) values for growth of the Penicillium spp. was 0.85-0.90. A. flavus was able to grow at 0.90 a(w) when the temperature was above 15 degrees C. This study has shown that fungal growth by these species on a sponge cake analogue, with a composition similar to usual bakery products, is prevented if the a(w) is kept at < 0.85.

Aspergillus flavus↗

PubMed2001

Increased nitric oxide synthase activity in a model of serotonin depletion.

Serotonin (5HT) containing cell bodies are localized in mesencephalic and rhombencephalic raphe nuclei. It has been proposed that 5HT could be involved in neuronal development and plasticity. In the central nervous system, nitric oxide (NO) has been postulated as a neurotransmitter and neuromodulator, and has been implicated in neurotoxicity as well as in neuroprotection. Using the nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) technique, NO synthesizing neurons were described in raphe nuclei. By immunohistochemistry, nitric oxide synthase (NOS) was found colocalized with 5HT in some dorsal raphe nucleus (DRN) neurons. In a model of inhibition of 5HT synthesis produced by daily administration of parachlorophenilalanine during 14 days, we have studied the relationship between 5HT and NO systems after 5HT depletion by histochemical and immunocytochemical methods. After the treatment, we observed an important reduction of 5HT immunostaining in the DRN and enhanced NOS activity demonstrated by NADPH-d technique, especially in the dorsomedial and ventromedial subgroups. In spite of the increased NOS activity, we could not observe significant changes in the NOS-immunoreactivity in the DRN after 5HT depletion. These results could indicate that 5HT depletion is concomitant with changes in NOS activity without affecting NOS expression in the DRN.

Animals↗

PubMed2001

[Natural contamination with mycotoxins in forage maize and green coffee in Nayarit State (Mexico)].

The presence of mycotoxins in forage maize (zearalenone, fumonisin B1, T-2 toxin and diacetoxyscirpenol) and green coffee (ochratoxin A) from Nayarit State (Mexico) has been studied. All maize samples analyzed showed fumonisin B1 contamination, with an average concentration of 2,541 microg/kg. Fifteen percent of the samples contained zearalenone, with an average concentration of 1,610 microg/kg. Only one sample showed T-2 toxin contamination (7 microg/kg), and no diacetoxyscirpenol was detected. Sixty-seven per cent of green coffee samples were contaminated with ochratoxin A, with an average concentration of 30.1 microg/kg. This is the first study about mycotoxins developed in Nayarit and it has shown that mycotoxin contamination is a real problem in both foodstuffs studied.

English Abstract↗

PubMed2000

Neuroglial interactions in a model of para-chlorophenylalanine-induced serotonin depletion.

Serotonin (5HT) is involved in the development and plasticity of the CNS through the release of S-100beta, a glial trophic factor which stabilizes synapses and neuronal cytoskeleton and promotes neuronal development. S-100beta is released from glial cells after activation of glial 5HT(1A) receptors. We present in this paper the effects upon neurons and glia of a 5HT depletion induced by 14 days of treatment with para-chlorophenylalanine (PCPA) in adult rats. S-100beta, 5HT, 5HT-transporter (5HT-T) and neurofilaments (Nf-200 and Nf-68) expressions were studied by immunohistochemistry and image analysis in striatum, hippocampus, parietal and frontal cortex. Immediately after ending PCPA treatment we found increased intracellular S-100beta immunoreactivity in glial cells, reduced 5HT immunolabelling, reduced density of 5HT-T, Nf-200 and Nf-68 fibers and morphological alterations in neuronal cytoskeleton. One week after PCPA treatment S-100beta immunoreactivity decreased towards control levels, 5HT was normalized in dorsal raphe nucleus, but not in innervation areas; 5HT-T, Nf-200 and Nf-68 fiber densities increased but some neuronal cytoskeletal alterations were still present in striatum. Two weeks after PCPA treatment S-100beta had returned to control levels in most studied regions; 5HT immunoreactivity was normalized, meanwhile 5HT-T, Nf-200 and Nf-68 fiber densities increased reaching values over the control level. We propose that S-100beta could be accumulated in glial cells during the 5HT depletion period, to be released once 5HT levels have recovered. Neuronal cytoskeletal alterations and reduced fiber density may be the expression of decreased extracellular availability of S-100beta. Conversely, increased 5HT-T, Nf-200 and Nf-68 expressions, once S-100beta is normalized, may be the biological response to the growth factor release.

Animals↗

PubMed2000

The effect of fungal competition on colonization of maize grain by Fusarium moniliforme, F. proliferatum and F. graminearum and on fumonisin B1 and zearalenone formation.

The effect of water activity (0.98, 0.95, 0.93) and temperature (15, 25 degrees C) on fungal growth and toxin production from interactions between isolates of Fusarium moniliforme and F. proliferatum producing fumonisin, and an isolate of F. graminearum producing zearalenone, incubated at the same time on irradiated maize grains were determined in vitro. Populations (CFUs) of F. moniliforme and F. proliferatum were reduced to a greater or lesser extent by the presence of F. graminearum under all conditions tested, while that the presence of F. moniliforme or F. proliferatum had a minor inhibitory effect on fungal populations of F. graminearum. Fumonisin B, production by F. proliferatum was inhibited under all conditions tested, while fumonisin B1 production by F. moniliforme was inhibited at 15 degrees C and enhanced at 25 degrees C in the presence of F. graminearum. The level of zearalenone was not significantly modified in the presence of F. moniliforme and F. proliferatum under the conditions tested.

Analysis of Variance↗

PubMed2000

Effect of modified atmosphere packaging and water activity on growth of Eurotium amstelodami, E. chevalieri and E. herbariorum on a sponge cake analogue.

The combined effects of water activity (aw), oxygen (O2) and carbon dioxide (CO2) levels on growth variables of three species of Eurotium (two isolates of each) on a sponge cake analogue were studied. The use of a multivariate statistical method (PLS) for the analysis of data showed that in general, the fungi had the same behaviour, according to their growth responses, to changes in the three tested factors. However, the maximal growth of E. herbariorum was somewhat more affected by the O2 level at lower CO2 levels. On the other hand, CO2, aw and the interaction between CO2 and O2 were found to be the most significant factors describing growth variables. In addition, the model found in this study had a good predictive power. There was a positive correlation between the CO2 concentration in the bags and the lag phase, and a negative correlation between the growth rate and maximum mycelial growth. In general, no isolates were able to growth when CO2 concentrations were higher than 60% under anaerobic conditions. At lower values of CO2, aw and O2 influenced growth variables. Low levels of O2 (0.02-0. 5%) did not affect the growth variables studied when levels of CO2 in the bags were high. However, when the CO2 concentration decreased, the different O2 levels had an influence on the growth variables, i. e., a small difference in the concentration of O2 can allow fungi to grow.

Animals↗

PubMed2000

[Emerging mycotoxin control. Current limits and regulations].

Emerging mycotoxins are of a great importance due to their high occurrence in foods and feeds and their implication in pathologies. There is a need to control them both in pre- and post-harvest. However, the increasing drawbacks of chemical decontamination methods, makes the use of preventive methods more attractive. These are based on avoiding growth of mycotoxigenic fungi and mycotoxin accumulation in these substrates (by using reduced aw levels, and modifying other storage conditions) and the early detection of these mycotoxins by using simple and fast analysis techniques. At the same time, it is important to know the effect that industrial processing has on mycotoxin concentration in foods and feeds, because it may reduce the toxin content. Finally, maximum limits of mycotoxin concentration should be established for both foods and feeds.

English Abstract↗