Biomedical subjects

E Van Bavel

Publications and source records attributed to E Van Bavel.

5 recordsLinked to original sources

PubMed2004

Influence of polymer matrix and adsorption onto silica materials on the migration of alpha-tocopherol into 95% ethanol from active packaging.

In this study, the effect of polymer materials with different polarity, namely low density polyethylene (LDPE) and ethylene vinyl acetate (EVA), on the migration behaviour of alpha-tocopherol from active packaging was investigated. The antioxidant was also adsorbed onto silica materials, namely SBA-15 (Santa Barbara-15) and Syloblock, in order to protect the antioxidant during extrusion and to ensure a controlled and sufficient release during the shelf-life of the food product. Migration experiments were performed at 7.0 +/- 0.5 degrees C and 95% ethanol was used as fatty food simulant. All films contained a high concentration of alpha-tocopherol, approximately 2000 mg kg(-1), to obtain an active packaging. Polymer matrix had a small influence on the migration profile. The migration of 80% of total migrated amount of antioxidant was retarded for 2.4 days by using LDPE instead of EVA. When alpha-tocopherol was adsorbed onto both silica materials, the migration of 80% of total migrated amount of antioxidant was retarded for 3.4 days in comparison to pure alpha-tocopherol. No difference was seen between the migration profiles of alpha-tocopherol adsorbed onto both silica materials. In the case of pure alpha-tocopherol, 82% of the initial amount of alpha-tocopherol in the film migrated into the food simulant at a rather fast migration rate. In the case of adsorption on silica materials, a total migration was observed. These antioxidative films can have positive food applications.

Adsorption↗

PubMed2002

Plugged hexagonal templated silica: a unique micro- and mesoporous composite material with internal silica nanocapsules.

We describe in this paper the development of plugged hexagonal templated silicas (PHTS) which are hexagonally ordered materials, with internal microporous silica nanocapsules; they have a combined micro- and mesoporosity and a tuneable amount of both open and encapsulated mesopores and are much more stable than other tested micellar templated structures.

Journal Article↗

PubMed2001

Endothelial function in myometrial resistance arteries of normal pregnant women perfused with syncytiotrophoblast microvillous membranes.

OBJECTIVE: To investigate the effects of syncytiotrophoblast microvillous membranes (STBM) in concentrations, found in vivo in women with pre-eclampsia, on endothelial function in isolated resistance arteries. SETTING: Department of Obstetrics and Gynaecology, Huddinge University Hospital, Stockholm. SAMPLE: Twenty-nine myometrial resistance arteries isolated from biopsies of healthy term pregnant women, obtained during caesarean section. METHODS: The myometrial arteries were mounted in a pressure arteriograph and perfused intraluminally for three hours with STBM (20 to 2000ng/mL) or with erythrocyte membranes or physiological salt solution as controls, all substituted with 0.5% bovine serum albumin. Bradykinin concentration-response curves were performed before and after perfusion. MAIN OUTCOME MEASURES: The bradykinin concentrationresponse curves were fitted to the Hill equation and maximal dilation and the pEC50 values were determined from these fits. Differences within groups were analysed with a paired Student's t test. Electron microscopic evaluation of the endothelium was performed. RESULTS: Neither STBM nor erythrocyte membrane perfusion affected maximal dilation or the pEC50 values of the bradykinin concentration-response curves at any concentration. Examination by electron microscopy showed no obvious damage to the endothelium after perfusion with STBM or erythrocyte membranes. CONCLUSION: Perfusion with STBM in concentrations up to 100 times those reported in pre-eclampsia has no significant effect on bradykinin-mediated dilation in isolated myometrial arteries.

Adult↗

PubMed1987

Ionic channels and membrane hyperpolarization in human macrophages.

Microelectrode impalement of human macrophages evokes a transient hyperpolarizing response (HR) of the membrane potential. This HR was found to be dependent on the extracellular concentration of K+ but not on that of Na+ or Cl-. It was not influenced by low temperature (12 degrees C) or by 0.2 mM ouabain, but was blocked by 0.2 mM quinine or 0.2 mM Mg2+-EGTA. These findings indicate that the HR in human macrophages is caused by the activation of a K+ (Ca2+) conductance. Two types of ionic channels were identified in intact cells by use of the patch-clamp technique in the cell-attached-patch configuration, low and high-conductance voltage-dependent K+ channels. The low-conductance channels had a mean conductance of 38 pS with Na+-saline and 32 pS with K+-saline in the pipette. The high-conductance channels had a conductance of 101 and 114 pS with Na+- and K+-saline in the pipette, respectively. Cell-attached patch measurements made during evocation of an HR by microelectrode penetration showed enhanced channel activity associated with the development of the HR. These channels were also high-conductance channels (171 pS with Na+- and 165 pS K+-saline in the pipette) and were voltage dependent. They were, however, active at less positive potentials than the high-conductance K+ channels seen prior to the microelectrode-evoked HR. It is concluded that the high-conductance voltage-dependent ionic channels active during the HR in human macrophages contribute to the development of the HR.

Cell Membrane↗

PubMed1984

Oscillatory hyperpolarizations and resting membrane potentials of mouse fibroblast and macrophage cell lines.

L cells (a mouse fibroblast cell line) and macrophages have been reported to exhibit slow oscillatory hyperpolarizations and relatively low membrane potentials, when measured with glass micro-electrodes. This paper describes the role of micro-electrode-induced leakage in these oscillations for L cells and a mouse macrophage cell line (P388D1). Both L cells and macrophages showed fast negative-going peak-shaped potential transients upon micro-electrode entry. This shows that the micro-electrode introduces a leakage conductance across the membrane. The peak values of these fast transients were less negative for L cells (-17 mV) than for macrophages (-39 mV), although their sustained resting membrane potentials were about equal (-13 mV). This indicates that the pre-impaled membrane potential of macrophages is more negative than that of L cells. Ionophoretic injection of Ca2+ into the P388D1 macrophages showed the existence of a Ca2+ -dependent hyperpolarizing conductance presumed to be involved in the oscillatory hyperpolarizations of L cells and macrophages. Cells increased in size by X-ray irradiation to reduce membrane input resistances were still found to be susceptible to micro-electrode-induced leakage. Impalement transients upon entry of a second electrode during a hyperpolarization evoked by a first electrode, were often step-shaped instead of peak-shaped due to the high membrane conductance associated with hyperpolarization. Since peak-shaped impalement transients were always seen with the first impalement both in oscillating and non-oscillating cells, oscillatory hyperpolarizations cannot be regarded as spontaneously occurring in the unperturbed cells but are induced by micro-electrode penetration. Since the hyperpolarizing response can be evoked by ionophoretic injection of Ca2+, and oscillatory as well as single hyperpolarizing responses are absent in a Ca2+ -free medium, it is concluded that the Ca2+ needed intracellularly to activate the hyperpolarizing responses enters the cell via the leakage pathway introduced by the measuring electrode.

Animals↗