Cellijnen en Salmonella

In human gastrointestinal disease caused by Salmonella, transepithelial migration of neutrophils follows the attachment of bacteria to epithelial tissue. This migration of neutrophils is stimulated by the release of chemokines, including interleukin-8 (Il -8), from the epithelial cells. We have developed an in vitro model system (human epithelial monolayers, among which Caco-2 cells grown on microtiter multiwell plates) for studying host-pathogen interactions. After infection with different pathogens we measured Il-8 production during time. Results showed that Il-8 release was time related and varied with the pathogen. Salmonella enteritidis (Se) did induce the highest response. Subsequently, three doses of this Se strain were used and the Il-8 response was measured at different time points. Caco-2 cells remained intact over a period of 24h, the production of Il-8 increased in time and was found to be Se dose-dependent. Other tested epithelial monolayers, such as HT29 colon cancer cells, gave similar results.Infectie met Salmonella kan gepaard gaan met de invasie van darmepitheelcellen. De aan de invasie voorafgaande aanhechting leidt reeds tot de transmigratie van witte bloedcellen (neutrofielen) vanuit de bloedbaan naar het epitheelweefsel. De migratie wordt gestimuleerd door de productie van chemokines, waaronder interleukine-8 (Il-8) door epitheelcellen. Wij hebben een in vitro model systeem ontwikkeld (humaan epitheelweefsel gekweekt in microtiterplaten) waarin gastheer - pathogeen interacties kunnen worden bestudeerd. Epitheelcellen zijn gedurende een uur blootgesteld aan verschillende pathogene micro-organismen, waarna de Il-8 response is gemeten. Als controle zijn meegenomen een Escherichia coli stam zonder LPS en een probiotische Lactobacillus. De resultaten laten zien dat de IL-8 productie per pathogeen varieert, waarbij Salmonella enteritidis de hoogste respons geeft. In vervolgexperimenten zijn drie concentraties S. enteritidis gebruikt, waarna de respons gedurende 24 uur is gemeten. De gebruikte cellijn bleek na 24 uur nog intact, de Il-8 productie correleerde met de doses, en nam toe in de tijd. Hieruit kan geconcludeerd worden dat het door ons ontwikkelde model gebruikt kan worden voor het bestuderen van factoren die van invloed zijn op dosis-respons relaties. De respons betreft dan prikkeling van het immuunsysteem ten gevolge van adhesie en invasie van darmepitheelcellen door salmonellae. Tenslotte wordt een benaderingwijze voorgesteld om resultaten van in vitro dosis-respons experimenten te vertalen naar de mens

Large magnetoresistance using hybrid spin filter devices

A magnetic "spin filter" tunnel barrier, sandwiched between a non-magnetic metal and a magnetic metal, is used to create a new magnetoresistive tunnel device, somewhat analogous to an optical polarizer-analyzer configuration. The resistance of these trilayer structures depends on the relative magnetization orientation of the spin filter and the ferromagnetic electrode. The spin filtering in this configuration yields a previously unobserved magnetoresistance effect, exceeding 100%.Comment: 3.5 pages, 3 figures, submitted to Appl. Phys. Let

Monolayer resolved oscillating hyperfine fields in epitaxial face-centered-tetragonal Co(001) films

Ultrahigh-quality thin fct-Co films grown on Cu(001) were studied by 59Co NMR. The influence of the spin-dependent electron scattering at the interfaces is obsd. for at least four Co at. layers from the interface with monolayer resoln. An oscillatory effect on the Co hyperfine field with a period of several monolayers is measured, corresponding to the oscillating conduction electron polarization. The observation is exclusively possible in this system due to its very narrow resonance lines, corresponding to a virtually perfect Co structure. [on SciFinder (R)

Electric-field gradients in thin face-centered-tetragonal Co films observed by nuclear magnetic resonance

Thin tetragonally strained fcc-Co films grown epitaxially on Cu(001) single crystals have been investigated by 59Co nuclear magnetic resonance (NMR). The ultrahigh structural quality and the homogeneity of the strain result in the direct NMR observation of electric-field gradients, which is unique in thin films. The structural quality and the homogeneity and size of the strain are analyzed by means of the very small NMR linewidths, the hyperfine field anisotropies, and the uniform electric-field gradients. A quantitative agreement with the observed strain is found. The strain, and thus the tetragonal distortion, in the films is found to be surprisingly stable, showing less than 10% strain relief for 80 ML Co films

In Which Situations Do Adolescents Seek Parental Support and What Do They Need?

Throughout development, the conditions that elicit children’s support seeking behaviour change hand in hand with maturation and changing developmental tasks. Little is known about the situations in which adolescents need support or about which parental behaviours elicit adolescents’ sense of being supported. In the current study, adolescents living in the Netherlands (N = 98, Mage = 15.5, SD = 1.16, range = 14–18 years) filled in online questionnaires in which they were asked to recall autobiographical support-related memories (ASMs) separately for both parents. Support from both parents was most frequently needed in case of concerns about competence. Loss or illness of close others or pets elicited primarily a need for maternal support whereas family conflicts and practical problems most frequently elicited a need for paternal support. Additionally, parent behaviour reported in times of distress was most frequently related to comforting and facilitating support seeking. These behaivours were rated as satisfying and sufficiently supportive for the reported distress. These results confirm the importance of parental support in adolescence. Clinical implications of these findings and directions for future research are discussed

Prediction of biopore- and matrix-dominated flow from X-ray CT-derived macropore network characteristics

Peer reviewedPublisher PD