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Biomedical subjects

E Engel

Publications and source records attributed to E Engel.

At least 19 recordsLinked to original sources
PubMed2005

Ultrafast relaxation in quasi-one-dimensional organic molecular crystals.

We present a comprehensive study of ultrafast relaxation properties of optical excitations in thin films of quasi-1D stacked organic materials PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) and MePTCDI (N,N'-dimethylperylene-3,4,9,10-dicarboximide) over five decades of time. Pump-probe experiments reveal excitonic intraband relaxation time constants of 65 fs for MePTCDI and 100 fs for PTCDA. The initial time-resolved luminescence anisotropy is consistent with the exciton model of Davydov-split states. The subsequent decay of the anisotropy can be explained with a thermally activated exciton hopping process. A full understanding of the pump-probe experiments calls for an explanation beyond the models presently available.

Journal Article↗
PubMed2005

Surface characterization of completely degradable composite scaffolds.

The goal of this study was to characterise the surface properties of completely degradable composite, polylactic acid and calcium phosphate glass, scaffolds. The composite scaffolds are made by solvent casting or phase-separation, using chloroform and dioxane as a solvent respectively. The surface properties were measured on composite films which were made using the same procedure as for the three-dimensional (3D) scaffolds without the pore-creating step. The surface morphology, roughness, wettability and protein adsorption capacity of the films was measured before and after sterilisation with ethylene oxide. The results reveal the influence of solvent type, glass weight content and sterilisation on the wettability, surface energy and protein adsorption capacity of the materials. The addition of glass particles increase the hydrophylicity, roughness and protein adsorption capacity of the surface. This effect, however, depends on the extent of the coating of the glass particles by the polymer film, which is much higher for dioxane films than for chloroform films. This information can be used to interpret and understand the biological behaviour of the 3D scaffolds made of this composite materials.

Adsorption↗
PubMed2005

An iterative sensory procedure to select odor-active associations in complex consortia of microorganisms: application to the construction of a cheese model.

The aim of this study was to develop and validate an iterative procedure based on odor assessment to select odor-active associations of microorganisms from a starting association of 82 strains (G1), which were chosen to be representative of Livarot cheese biodiversity. A 3-step dichotomous procedure was applied to reduce the starting association G1. At each step, 3 methods were used to evaluate the odor proximity between mother (n strains) and daughter (n/2 strains) associations: a direct assessment of odor dissimilarity using an original bidimensional scale system and 2 indirect methods based on comparisons of odor profile or hedonic scores. Odor dissimilarity ratings and odor profile gave reliable and sometimes complementary criteria to select G3 and G4 at the first iteration, G31 and G42 at the second iteration, and G312 and G421 at the final iteration. Principal component analysis of odor profile data permitted the interpretation at least in part, of the 2D multidimensional scaling representation of the similarity data. The second part of the study was dedicated to 1) validating the choice of the dichotomous procedure made at each iteration, and 2) evaluating together the magnitude of odor differences that may exist between G1 and its subsequent simplified associations. The strategy consisted of assessing odor similarity between the 13 cheese models by comparing the contents of their odor-active compounds. By using a purge-and-trap gas chromatography-olfactory/mass spectrometry device, 50 potent odorants were identified in models G312, G421, and in a typical Protected Denomination of Origin Livarot cheese. Their contributions to the odor profile of both selected model cheeses are discussed. These compounds were quantified by purge and trap-gas chromatography-mass spectrometry in the 13 products and the normalized data matrix was transformed to a between-product distance matrix. This instrumental assessment of odor similarities allowed validation of the choice of G312 as the best 10-strain ecosystem.

Cheese↗
PubMed2004

Microstructural, mechanical and citotoxicity evaluation of different NiTi and NiTiCu shape memory alloys.

Transformation temperatures and mechanical properties such as transformation stresses at different temperatures and the superelasticity have been investigated in NiTiCu alloys with various Copper concentrations. The results have been compared with the conventional NiTi alloys. The addition of copper was effective to narrow the stress hysteresis and to stabilize the superelasticity characteristics. Moreover, it produced greater stability on both the transformation temperatures and the forces applied to the different tissues. However, the studies of cell cultured with human fibroblasts showed certain toxicity.

Biocompatible Materials↗
PubMed2004

Detection of cell-free nucleic acids in bronchial lavage fluid supernatants from patients with lung cancer.

The aim of this study was to determine whether nucleic acids are detectable in cell-free bronchial lavage supernatants, and whether it is possible to find alterations in this DNA and RNA of genes known to be present in lung tumour cells. DNA was isolated from cell-free lavage supernatants from 30 and RNA from 25 lung cancer patients. The DNA was examined for microsatellite alterations (MA) and the RNA analysed for the expression of seven tumour-associated genes. Intact DNA and mRNA could be isolated from all cell-free bronchial lavage supernatants. MA were found in lavage supernatants of 12/30 patients and in lavage cells of 6/30 patients. Altogether alterations were found in 14/30 patients. Analyses of tumour-associated gene expression showed positive results, with at least one marker in the lavage supernatants of all 25 patients. Thus, we could demonstrate, for the first time, that it is possible to isolate intact DNA and RNA from cell-free bronchial lavage supernatants. Their quantity and quality is sufficient for further amplification by polymerase chain reaction (PCR)/reverse transcriptase (RT)-PCR. Altogether, tumour-associated changes were detected in DNA samples from 47% of the patients and in RNA samples from all of the patients analysed.

Aged↗
PubMed2004

Regulation of corpus luteum-function in the bitch.

Functional lifespan of the corpus luteum (CL) in non-pregnant dogs exceeds that of pregnant animals and may last for more than 80 days. Prolactin and LH act luteotropic, however, luteolytic mechanisms are poorly understood. Other than in life stock there is no uterine luteolysine and it was postulated that local paracrine/autocrine mechanisms might play a major role. In following this hypothesis the present investigations have clearly demonstrated that up-regulation of prostaglandin synthesis in the CL as indicated by the expression of cyclo-oxygenase II occurs with its formation and not regression, pointing towards a luteotropic rather than luteolytic action. Throughout dioestrus luteal and other cells of the CL express the oestrogen (ERalpha) and progesterone receptor (PR). While ERalpha expression was not cycle-related, PR concentrations were high in the early and late-luteal phase and a regulatory role of both steroids on CL-function is assumed. As in other species also in the dog the immune system seems to participate in the mechanisms regulating CL-function as an increased presence of lymphocytes within the CL could be detected at the beginning [CD4- CD8-, major histocompatibility complex (MHC)II-antigen expressing cells] and during the latter half of dioestrus (CD8- and MHCII-antigen expressing cells). Thus, leucocyte-derived cytokines may be important and the expression of the mRNA for interleukin (IL)8, IL10, IL12, tumour necrosis factor (TNF)alpha and transforming growth factor (TGF) beta1 was observed throughout dioestrus. Electron microscopy confirmed the slow process of luteolysis; first distinct signs of degeneration were seen on day 60, accompanied by some apoptotic events. From these data it is concluded that luteal regression as monitored by the gradual decrease of systemic progesterone concentrations in the dog is not an actively regulated but rather a permissive process. Immune-mediated events may play a key role. Changes in the vascular supply, as indicated by the expression of endoglin, seem to be of lower importance.

Animals↗
PubMed2004

Detection of tumor-specific mRNA in cell-free bronchial lavage supernatant in patients with lung cancer.

Bronchoscopy is a standard procedure in the workup of patients with suspicious pulmonary lesions. We wondered whether it is possible to isolate malignancy-associated mRNA from cell-free lavage supernatant. Extracellular mRNA from cell-free lavage supernatant of 25 patients with lung cancer (23 with non-small cell lung cancer, 2 with small cell lung cancer) was isolated, reverse-transcribed, and amplified by reverse transcriptase polymerase chain reaction. The quantity and quality of the isolated RNA were checked after cDNA synthesis by amplification with beta-actin-specific primers. Afterwards, a panel of eight genes known to be expressed in lung tumors was used for the detection of tumor-associated mRNA expression in lavage supernatant and serum. mRNA coding for beta-actin could be isolated from lavage supernatant of all 25 patients. In addition, the expression of at least one tumor-associated gene was detectable in all patients. These results show that intact mRNA can be isolated from cell-free lavage supernatant and that its quantity and quality are sufficient for the detection of tumor-associated gene expression alterations. This may open new possibilities for the diagnosis of lung cancer.

Actins↗
PubMed2003

Alendronate and etidronate do not regulate interleukin 6 and 11 synthesis in normal human osteoblasts in culture.

Bisphosphonates exert a potent inhibitory effect on bone resorption. Several studies have been performed, with contradictory results, to ascertain whether the effect of bisphosphonates on osteoclasts could be produced, at least in part, by modulation of the synthesis of resorption-promoting factors by osteoblasts. The aim of this study was to evaluate the effect of etidronate (10-4-10-9 M) and alendronate (10-7-10-12 M) on the production of IL-6 and IL-11 using human osteoblast cultures. Cytokines were quantified by ELISA, and mRNA expression was tested. Treatment with alendronate and etidronate had no effect on the synthesis of IL-6 or IL-11, and IL-6 and IL-11 mRNA levels. These results were obtained both in nonstimulated cultures and in cultures stimulated by means of TNF-a, IL-1b, and TNF-a+IL-1b, with or without FCS. In conclusion, a possible indirect osteoclast-mediated effect of alendronate and etidronate on bone resorption would not be exerted through reduction in osteoblastic synthesis of IL-6 and IL-11.

Aged↗
PubMed2002

Relativistic density functional calculations for Pt2.

First full-relativistic density functional calculations with the extension of the spin-polarization functional for the relativistic density functional theory in their collinear and noncollinear form are presented here for the molecular system Pt2. The agreement with experiment is very good.

Journal Article↗
PubMed2002

Regional differences of H+, HCO3-, and CO2 diffusion through native porcine gastroduodenal mucus.

Gastroduodenal mucus may play a critical role in defending the epithelium from luminal acid and in the creation of a microenvironment suitable for H. pylori. We measured transmucus permeation of H+, HCO3-, and CO2 with an in vitro perfusion chamber through freshly harvested or partially purified porcine gastric mucin. pH and CO2 concentrations were measured with selective ion electrodes; HCO3- and CO2 concentrations were derived. Viscosity was measured by rotational microviscometry. Mucin viscosity was directly related to concentration. There was a large variation in viscosity among native mucus from antrum, corpus, and duodenum. The highest viscosity was found in the antral mucus; duodenal mucus had the lowest. Diffusion coefficients of duodenal mucus for H+ and HCO3- were significantly lower than those from corpus and antrum. CO2 diffusion coefficients were invariant. In conclusion, despite large variations in viscosity, antral and corpus gastric mucus were similar in terms of ion diffusion. Surprisingly, the low viscosity duodenal mucus was a more potent barrier to ion diffusion than was gastric mucus. Consequently, duodenal mucus may play a more important role in inhibiting ion diffusion than its gastric counterpart.

Animals↗
PubMed2002

Human-osteoblast proliferation and differentiation on grit-blasted and bioactive titanium for dental applications.

Physico-chemical and topographical surface quality of commercially pure titanium (c.p. Ti) dental implants is one of the most influencing factors in the improvement of their osseointegration. In this sense, previously, a two-step method (2S) for obtaining bioactive blasted-rough titanium surfaces was developed for improving short-term (due to its bioactivity) and long-term (due to its roughness) osseointegration. This 2S-method consists of: (1) Grit blasting on titanium surface in order to roughen it, and (2) thermo-chemical (TCh) treatment in order to obtain a bioactive surface with bone-bonding ability. The aim of the present work is to evaluate the in vitro human-osteoblast response (proliferation, differentiation - ALP activity- and cell morphology-studied by environmental scanning electron microscopy) of rough c.p. Ti (grit blasted), bioactive c.p. Ti (thermo-chemically treated) and rough-bioactive c.p. Ti (2S-treated). Different grit materials (Al(2)O(3) and SiC) have been used in order to investigate their influence. The results showed that cell adhesion was statistically higher for the rough and bioactive surfaces, whatever the grit used. Cells proliferated very well on all the c.p. Ti surfaces. If comparing groups with and without TCh (all other treatments being equal) the ALP was always higher in the groups with TCh, indicating stimulation of osteoblast differentiation because of TCh, more significantly in the groups that were first blasted. Those ALP results were accompanied by a decrease in the value of proliferation, which shows the good behavior of the cells. This results suggest that a rough and bioactive-titanium surface obtained by 2S-treatment enhances adhesion and differentiation activity of human osteoblasts cells.

Journal Article↗
PubMed2001

Breaking Abbe's diffraction resolution limit in fluorescence microscopy with stimulated emission depletion beams of various shapes.

We report on the generation of various hole-centered beams in the focal region of a lens and investigate their effectiveness to break the diffraction barrier in fluorescence microscopy by stimulated emission. Patterning of the phase of the stimulating beam across the entrance pupil of the objective lens produces point-spread-functions with twofold, fourfold, and circular symmetry, which narrow down the focal spot to 65-100 nm. Comparison with high-resolution confocal images exhibits a resolution much beyond the diffraction barrier. Particles that are only 65-nm apart are resolved with focused light.

Journal Article↗
PubMed2001

Investigation of the correlation potential from Kohn-Sham perturbation theory.

Perturbation theory on the basis of the Kohn-Sham Hamiltonian leads to an implicit density functional for the correlation energy E(c). In this contribution we investigate the corresponding correlation potential v(c). It is shown that for finite systems the v(c) obtained by direct application of the optimized potential method diverges in the asymptotic region. The presence of unoccupied states, inherent in any perturbative form of E(c), is identified as the origin of this unphysical behavior. An approximate variational procedure is developed in order to avoid this difficulty. The potential resulting from this method qualitatively reproduces the shell structure of the exact atomic v(c).

Journal Article↗
PubMed2001

Determination of taste-active compounds of a bitter Camembert cheese by omission tests.

The taste-active compounds of a Camembert cheese selected for its intense bitterness defect were investigated. The water-soluble fraction (WSE) was extracted with pure water and fractionated by successive tangential ultrafiltrations and nanofiltration. The physicochemical assessment of these fractions led to the construction of a model WSE which was compared by sensory evaluation to the crude water-soluble extract, using a panel of 16 trained tasters. As no significant difference was perceived, this model WSE was then used directly or mixed with other cheese components for omission tests. Among the main taste characteristics of the WSE (salty, sour, umami and bitter), bitterness was found to be due to small peptides whose mass distribution was obtained by RPHPLC-MS (400-3000 Da) and whose taste properties are discussed.

Amino Acids↗
PubMed2001

Evolution of the composition of a selected bitter Camembert cheese during ripening: release and migration of taste-active compounds.

The aim of this study was to add to the understanding of changes in taste that occur during the ripening of a bitter Camembert cheese by the evolution of its composition. Physicochemical analyses were performed on rind, under-rind, and center portions of a Camembert cheese selected for its intense bitterness. At each of the six steps of ripening studied organic acids, sugars, total nitrogen, soluble nitrogen, phosphotungstic acid soluble nitrogen, non-protein nitrogen, Na, K, Ca, Mg, Pi, Cl, and biogenic amines were quantified in each portion. Changes in cheese composition seemed to mainly result from the development of Penicillium camemberti on the cheese outer layer. Migration phenomena and the release of potentially taste-active compounds allowed for the evolution of saltiness, sourness, and bitterness throughout ripening to be better understood. Apart from taste-active compounds, the impact of the cheese matrix on its taste development is discussed.

Carbohydrates↗
PubMed2001

Evolution of the taste of a bitter Camembert cheese during ripening: characterization of a matrix effect.

The objective of this study was to characterize the effect of ripening on the taste of a typically bitter Camembert cheese. The first step was to select a typically bitter cheese among several products obtained by different processes supposed to enhance this taste defect. Second, the evolution of cheese taste during ripening was characterized from a sensory point of view. Finally, the relative impact of fat, proteins, and water-soluble molecules on cheese taste was determined by using omission tests performed on a reconstituted cheese. These omission tests showed that cheese taste resulted mainly from the gustatory properties of water-soluble molecules but was modulated by a matrix effect due to fat, proteins, and cheese structure. The evolution of this matrix effect during ripening was discussed for each taste characteristic.

Cheese↗
PubMed2001

Nitric oxide up-regulates ferritin mRNA level in snail neurons.

We cloned and sequenced the ferric ion-binding protein, ferritin, from the nervous system of the pulmonate snail, Helix pomatia. Helix H-ferritin cDNA contains a 519-bp open reading frame (ORF) and predicts an iron-responsive element (IRE) at the 5'-untranslated region (5'-UTR) of the ferritin mRNA. The deduced amino acid sequence revealed 86% similarity with Lymnaea stagnalis ferritin and about 70% similarity with vertebrate H-ferritin. While secreted ferritin isoforms contain a signalling sequence at their N-terminal end, Helix ferritin does not contain this sorting signal indicating that it is restricted to the cytoplasm. The amino acid ligands at positions Glu25, Tyr30, Glu59, Glu60, His63, Glu105 and Gln139 indicate an active ferroxidase site in Helix ferritin. In situ hybridization visualized ferritin mRNA in neuronal cell bodies but not in the neuropil. In contrast, ferritin-immunoreactive protein was localized in cell bodies and neurites. We further demonstrate that the NO donors S-nitroso-N-acetylpenicillamine (SNAP), or hydroxylamine (HA), increase the intracellular ferritin mRNA level by about 55%. In conclusion, our findings show that Helix neurons express an intracellular H-ferritin isoform and suggest that iron and NO metabolism are coupled.

Amino Acid Sequence↗