Effect of oxygen carriers in microbial and plant cell cultures.

Dissolved oxygen concentration is one of the most limiting factors in aerobic cultures, due to the poor solubility of oxygen in aqueous media. In many processes, the microorganisms growth and production can be affected as a result of insufficient oxygen supply to the broths [1, 2]. To increase oxygen solubility, some methods can be used, such as the increment of aeration or agitation rates or decrease of the solution temperature.

Effect of polyunsaturated fatty acids (PUFAs) on the proliferation and extracellular matrix mineralization and gene expression of gilthead seabream skeletal cell lines

The aquaculture industry aims at replacing significant amounts of marine fish oil by vegetable oils in fish diet. Dietary lipids have been shown to alter the fatty acid composition of bone compartments, which would impact the local production of factors controlling bone formation. Knowledge on the mechanisms underlying the nutritional regulation of bone metabolism is however scarce in fish. Two in vitro bone-derived cell systems developed from seabream (an important species for aquaculture in the Mediterranean region) vertebra, capable of in vitro mineralization and exhibiting prechondrocyte (VSa13) and pre-osteoblast (VSa16) phenotype, were used to assess the effect of certain polyunsaturated fatty acids (PUFAs; arachidonic (AA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids) on cell proliferation, extracellular matrix (ECM) mineralization and gene expression. While all PUFAs promoted morphological changes in both cell lines, VSa16 cell proliferation appeared to be stimulated by PUFAs in a dose dependent manner until 100M, whereas proliferation of VSa13 cells was impaired at concentrations above 10M. AA, EPA and DHA inhibited VSa13 ECM mineralization, alone and in combination, while VSa16 ECM mineralization was only inhibited by AA and EPA. DHA had the opposite effect, increasing mineralization almost by 2 fold. When EFAs were combined, DHA apparently compensated for the inhibitory effect of AA and EPA. Expression of marker genes for bone and lipid metabolisms has been investigated by qPCR and shown to be regulated in pre-osteoblasts exposed to individual PUFAs. Our results show that PUFAs are effectors of fish bone cell lines, altering cell morphology, proliferation and mineralization when added to culture medium. This work also demonstrates the suitability of our in vitro cell systems to get insights into mineralization-related effects of PUFAs in vivo and to evaluate the replacement of fish oils by vegetable oil sources in fish feeds.

The response of watercress (Nasturtium officinale) to vacuum impregnation: Effect of an antifreeze protein type I

The setting up of methodologies that reduce the size of ice crystals and reduce or inhibit the recrystalli- sation phenomena could have an extraordinary significance in the final quality of frozen products and consequently bring out new market opportunities. In this work, the effect of an antifreeze protein type I (AFP-I), by vacuum impregnation (VI), on frozen watercress was studied. The VI pressure, samples’ weight, Hunter Lab colour, scanning electron microscopy (SEM), and a wilting test were analysed in this work. The water intake of watercress samples augmented with vacuum pressure increase. The results also showed that, independently from the vacuum pressure used, the Lab colour parameters between raw and impregnated samples were maintained, showing no significant differences (P > 0.05). A VI of 58 kPa, during 5 min, allowed impregnating the AFP-I solution (0.01 mg ml-1) into the water- cress samples. The scanning electron microscopy (SEM) analysis showed the AFP-I impregnated frozen samples with better cell wall definition and rounded cell shape with smaller ice crystals compared with the control samples. The wilting test results corroborated that AFP-I is a valuable additive, since the leaves impregnated with AFP-I showed higher turgidity compared to the control samples. The present findings will help to better understand the effect of AFP-I, particularly, on frozen water- cress microstructure and its importance as valuable food additive in frozen foods and mainly in leafy vegetables.

Role of insulin and insulin-like peptides in bone formation: identification of bone-specific target genes and regulatory mechanisms, and characterization of the insulin-mimetic effect of vanadium

Tese de Doutoramento em Biologia, Especialidade em Biologia Molecular, Universidade do Algarve, 2008