Biomedical subjects

L Pastoriza

Publications and source records attributed to L Pastoriza.

8 recordsLinked to original sources

PubMed2001

An empirical model for describing the effects of nitrogen sources on nisin production.

AIMS: A study on the effects of tryptone and yeast extract on nisin production by Lactococcus lactis was carried out using a second order rotatable factorial design. METHODS AND RESULTS: The results show that both ingredients increased nisin production, although a small decrease in nisin levels was noted at high tryptone concentrations. In view of the low vitamin content of tryptone, the amino acids present in both tryptone and yeast extract may be responsible for these observations. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The observed response suggests that maintaining tryptone concentrations in the centre of the domain and increasing the concentration of yeast extract would be ideal conditions for nisin production. However, when the economic aspects are considered, it appears that low concentrations of yeast extract and reasonably high concentrations of tryptone are optimal.

Anti-Bacterial Agents↗

PubMed2001

Joint effect of nisin, CO2, and EDTA on the survival of Pseudomonas aeruginosa and Enterococcus faecium in a food model system.

A study on the joint effect of either nisin or Nisaplin, headspace CO2 levels, and EDTA on the survival of Pseudomonas aeruginosa and Enterococcus faecium was carried out in a water-soluble fish muscle extract at 3 degrees C using a second-order rotatable factorial design. E. faecium was completely deactivated by all processing after 2 days of storage. In contrast, P. aeruginosa was much less susceptible to treatments, and cell death was satisfactorily described by two models. Nisin increased cell death, whereas Nisaplin (commercial form of nisin) was not suitable, as it caused undesirable interference, presumably due to its co-compounds. Interactions between Nisaplin or nisin and either EDTA or CO2 were found to be nonstatistically significant. Factors that could account for this unexpected lack of synergism are discussed. However, a statistically significant positive interaction was found between CO2 and EDTA. This finding could allow CO2 levels to be decreased and hence to reduce the main disadvantages of CO2 application, namely, exudation and acidification.

Animals↗

PubMed2000

Inhibition of formaldehyde production in frozen-stored minced blue whiting (Micromesistius poutassou) muscle by cryostabilizers: an approach from the glassy state theory.

Adding maltodextrins to minced blue whiting muscle inhibited formaldehyde production during storage at -10 and -20 degrees C. Sucrose, however, was effective only at -20 degrees C. These results were not proportional to the difference between the storage temperature and the ice-melting onset (T(m)'), and freeze-concentration had to be considered. In the face of serious limitations to do this, resource was made to the state diagram for the sucrose-water binary system and the percentage variation of the ice-melting endotherm area of the different samples. A higher T(m)' and a lower freeze-concentration would account for the inhibiting effects of maltodextrins, whereas sucrose, despite diminishing T(m)', had an effect nearly as great as maltodextrins at -20 degrees C but had hardly any at -10 degrees C. The reason for this seems to lie in a lower freeze-concentration of solutes in the unfrozen water phase. Similarly, the differences found between sucrose and maltodextrins, as well as among maltodextrins, were also explained in terms of T(m)' and freeze-concentration.

Animals↗

PubMed2000

Dose-response relationships. A model for describing interactions, and its application to the combined effect of nisin and lactic acid on Leuconostoc mesenteroides.

As well as producing bacteriocins, many lactic bacteria produce other potentially toxic compounds or growth inhibitors, especially lactic acid, which may interfere in the assays commonly used to quantify these peptides. A systematic set of modifications is proposed which, when applied to the logistical equation, enable it to describe the combined (but not additive) effects of two or more active principles. The general model thus derived is applied to the interaction of nisin and lactic acid on Leuconostoc mesenteroides.

Anti-Bacterial Agents↗

PubMed1999

Induction of lung fibrosis in the mouse by intratracheal instillation of fluorescein isothiocyanate is not T-cell-dependent.

Pulmonary fibrosis is the pathological result of a diverse group of insults. Common features of this group of diseases include chronic inflammation and immune cell activation. The pathogenesis of pulmonary fibrosis is not well defined and the prognosis is poor, highlighting the need for good animal models to elucidate the cellular and molecular events that lead to pulmonary fibrosis. This paper provides insight on a newly described model of pulmonary fibrosis using a single intratracheal challenge with fluorescein isothiocyanate (FITC). Balb-c and C57BL6 mice given intratracheal FITC develop acute lung injury followed by chronic inflammation. Significant increases in lung collagen content compared to saline-treated mice are noted at day 21 after inoculation. T-cell-deficient animals develop similar increases in lung collagen content compared to immunocompetent controls despite the abrogation of specific anti-FITC serum antibodies. Thus, the induction of fibrosis in FITC-challenged mice is not dependent on T cell immunity. Persistent chronic inflammation and acute lung injury may be the inciting events for the development of lung fibrosis in this model.

Animals↗

PubMed1999

Effect of various cryostabilizers on the production and reactivity of formaldehyde in frozen-stored minced blue whiting muscle.

The production of formaldehyde in frozen-stored minced blue whiting muscle was described by a rectangular hyperbolic model, and the effectiveness of each cryostabilizer is discussed in terms of its parameters. The maltodextrins assayed noticeably inhibited formaldehyde production, this effect being greater at -20 degrees C than at -10 degrees C. Sucrose was only effective at -20 degrees C. It seems that these compounds act by restricting molecular diffusion. The effect of each cryostabilizer on formaldehyde binding was closely regulated by its effect on production. This is discussed in terms of the binding equation parameters. The binding of formaldehyde during frozen storage was dependent on protein rearrangements leading to reactive groups becoming available. The constraints of cryostabilizers on molecular diffusion reduced the exposure of these groups. Consequently, the interpretation of formaldehyde reactivity was biased, leading to conclusions different from those that would be obtained from a study done under standard conditions.

Animals↗

PubMed1999

A method for bacteriocin quantification.

Different aspects of the most commonly used assay methods in the study of bacteriocins were examined. The conditions under which extraction and incubation (including exposure time) take place were analysed, and several different formal models that are usually employed to calculate ID50 were compared. As an alternative designed to overcome the problems which characterize the response of micro-organisms that are sensitive to bacteriocins, an operative procedure in a liquid medium and a modified re-parameterized logistic equation is proposed. When applied to the inhibition of Leuconostoc mesenteroides by nisin, the model allows an optimal experimental procedure to be defined.

Animals↗

PubMed1995

Changes in lipids of whole and minced rayfish (Raja clavata) muscle during frozen storage.

The effects of the storage temperature (-18 degrees C and -40 degrees C) and the addition of butylhydroxytoluene (BHT) on the different classes of lipids (phospholipids, triacylglycerides, free fatty acids, sterols and sterol esters plus waxes) and the fatty acid composition of minced (8 and 12 mm) and whole rayfish wing muscle stored for 1 year in the frozen state were studied. The phospholipid content decreased significantly and the free fatty acid content increased significantly at both storage temperatures, but more pronounced, at -18 degrees C. Significant differences were found between phospholipid and free fatty acid contents of the minced and the whole samples, which again were more pronounced at -18 degrees C. A significant increase of the major fatty acids (22:6n-3 and 16:0) was observed after 1 year in the frozen state. Significant differences were also obtained between the samples stored at -18 degrees C and at -40 degrees C; the lower the storage temperature, the higher their content. The polyunsaturated fatty acid (PUFA) content increased significantly in all the samples. Significant differences were found between the samples stored at -18 degrees C and at -40 degrees C. The lower the temperature, the higher the PUFA content. Non-significant differences were observed between the 8-mm and the 12-mm minced samples. Non-significant differences were found between the samples stored in the presence and in the absence of BHT. Mincing hastened hydrolytic and oxidative processes, which were slowed down at the lower storage temperature. Nonetheless, non-significant differences were found between both particle sizes.

Animals↗