Biomedical subjects

P Rijken

Publications and source records attributed to P Rijken.

4 recordsLinked to original sources

PubMed2004

Bioavailability of phenolic compounds from olive oil and oxidative/antioxidant status at postprandial state in healthy humans.

Olive oil phenolic compounds are generally believed to have beneficial antioxidant effects, but little is known about characteristics of their postprandial bioavailability in natural olive oil at real-life doses. The aim of the present study was to determine the concentrations of olive oil phenolic compounds in urine collected over 24 h (24-h urine) after a bolus ingestion of 25 ml of olive oil with different phenolic content, and to demonstrate the effect of this real-life olive oil dose on postprandial levels of blood lipids and oxidative stress biomarkers, as well as to examine the beneficial effects of olive oil phenols. Oral fat loads of 25 ml olive oil with high, moderate, and low phenolic content were administered to 12 healthy male volunteers in a randomized, controlled, crossover trial. Tyrosol and hydroxytyrosol were absorbed in a dose-dependent manner according to the phenolic content of the olive oil administered. The administered dose of 25 ml, which is close to that used daily in Mediterranean countries, did not induce significant postprandial lipemia nor did it promote an increase of in vivo oxidation markers. With regard to plasma antioxidant enzymes, glutathione peroxidase activity decreased postprandially after low phenolic content olive oil ingestion; however this was not observed after intake of moderate and high phenolic content olive oils. The phenolic content of the olive oils administered may account for the protection of the endogenous antioxidant defenses at postprandial state after ingestion of moderate and high phenolic content olive oils.

Adult↗

PubMed1999

Ratio-fluorescence microscopy of lipid oxidation in living cells using C11-BODIPY(581/591).

A ratio-fluorescence assay was developed for on-line localization and quantification of lipid oxidation in living cells. The assay explores the oxidative sensitivity of C11-BODIPY(581/591). Upon oxidation, the fluorescence of this fluorophore shifts from red to green. The probe incorporates readily into cellular membranes and is about twice as sensitive to oxidation as arachidonic acid. Using confocal microscopy, the cumene hydroperoxide-induced oxidation of C11-BODIPY(581/591) was visualized at the sub-cellular level in rat-1 fibroblasts. Preloading of the cells with tocopherol retarded this oxidation. The data demonstrate that C11-BODIPY(581/591) is a valuable tool to quantify lipid oxidation and anti-oxidant efficacy in single cells.

Animals↗

PubMed1998

Colonisation of Clostridium in the body is restricted to hypoxic and necrotic areas of tumours.

The use of gene therapy is one of the most recent molecular strategies for the treatment of cancer. It is essential, however, to have an efficient transfer system by which the desired gene can be delivered to the correct environment. The experiments described in this report investigate apathogenic Clostridium as a possible vector to transfer a specific gene product into the extracellular microenvironment of the tumour which is hypoxic/necrotic in parts, using WAG/Rij rats with transplantable rhabdomyosarcomas as a model. Our data show that Clostridium, after systemic administration of at least 10(7) spores, specifically colonises the hypoxic/necrotic areas of our tumour model, the most efficient species being C. acetobutylicum (NI-4082) and C. oncolyticum. Although spores were also detected in normal tissues for up to 4 weeks, they did not germinate in these tissues. We conclude that it seems likely that these bacteria can be used as a selective transfer system into the extracellular environment of tumours which have hypoxic regions. This strategy would be more tumour-specific than various other strategies that are currently being investigated in anti-cancer gene therapy.

Journal Article↗

PubMed1995

The epidermal growth factor.

Epidermal growth factor (EGF) is a single polypeptide of 53 amino acid residues which is involved in the regulation of cell proliferation. Egf exerts its effects in the target cells by binding to the plasma membrane located EGF receptor. The EGF receptor is a transmembrane protein tyrosine kinase. Binding of EGF to the receptor causes activation of the kinase and subsequently receptor autophosphorylation. The autophosphorylation is essential for the interaction of the receptor with its substrates. These bind to the receptor by the so-called SH2 domains. The signal transduction pathways activated by EGF include the phosphatidylinositol pathway, leading to activation of protein kinase C and to increase in the intracellular Ca2+ concentration, and to the ras pathway leading to MAP kinase activation. Recently the cytoplasm has been implicated as playing an important role in EGF induced signal transduction. The EGF receptor has been demonstrated to be an actin-binding protein. In addition EGF causes a rapid actin depolymerisation and the formation of membrane ruffles. In particular these membrane ruffles have been shown to act as the first site of signal transduction after EGF binding, and thus may be considered as signal transduction structures. Finally evidence has been presented suggesting a positive role for EGF and/or the receptor in the nucleus.

Amino Acid Sequence↗