Fast Protein Liquid Chromatography (FPLC)

Doel van dit onderzoek is: Het beoordelen omtrent de mogelijke toepassing van FPLC bij het kwaliteitsonderzoek in land- en tuinbouwprodukten. De FPLC apparatuur werd gedurende één week door de fabrikant (Pharmacia) beschikbaar gesteld. In deze korte periode werd de apparatuur gebruikt om een indruk te verkrijgen omtrent de mogelijke bruikbaarheid bij het vleesspeciesonderzoek en bij het onderscheiden van verse en bebroede onbevruchte eieren aan de hand van het eiwitpatroon. De bruikbaarheid van FPLC bij het speciesonderzoek lijkt goed, aangezien tussen waterige extracten van diverse vleessoorten een duidelijk verschil waarneembaar is. Naast het identificeren van vlees moet het mogelijk zijn om in mengsels van rund- en varkenseiwit (gehakt) de afzonderlijke percentages te bepalen. Bij bebroede eieren werd een component, in kleine concentratie, waargenomen, die mogelijk een afbraakprodukt van albumine is. De mogelijkheid om deze component te gebruiken om bebroede eieren te identificeren moet nader onderzocht worden

Dissecting magnetar variability with Bayesian hierarchical models

Neutron stars are a prime laboratory for testing physical processes under conditions of strong gravity, high density, and extreme magnetic fields. Among the zoo of neutron star phenomena, magnetars stand out for their bursting behaviour, ranging from extremely bright, rare giant flares to numerous, less energetic recurrent bursts. The exact trigger and emission mechanisms for these bursts are not known; favoured models involve either a crust fracture and subsequent energy release into the magnetosphere, or explosive reconnection of magnetic field lines. In the absence of a predictive model, understanding the physical processes responsible for magnetar burst variability is difficult. Here, we develop an empirical model that decomposes magnetar bursts into a superposition of small spike-like features with a simple functional form, where the number of model components is itself part of the inference problem. The cascades of spikes that we model might be formed by avalanches of reconnection, or crust rupture aftershocks. Using Markov Chain Monte Carlo (MCMC) sampling augmented with reversible jumps between models with different numbers of parameters, we characterise the posterior distributions of the model parameters and the number of components per burst. We relate these model parameters to physical quantities in the system, and show for the first time that the variability within a burst does not conform to predictions from ideas of self-organised criticality. We also examine how well the properties of the spikes fit the predictions of simplified cascade models for the different trigger mechanisms.Comment: accepted for publication in The Astrophysical Journal; code available at https://bitbucket.org/dhuppenkothen/magnetron, data products at http://figshare.com/articles/SGR_J1550_5418_magnetron_data/129242

Quantitative methods for differentiation of vegetable and animal proteins in foods II

Op verzoek van de Nederlandse delegatie van het Codex Committee on vegetable proteins (CXVP) is een tweede "working paper" over de differentiatie van plantaardige en dierlijke eiwitten in voedingsmiddelen samengesteld. Deze "working paper" is een vervolg op de eerste van november 1981 over hetzelfde onderwerp (RIKILT- verslag 82.43). Ze beschrijft welke vooruitgang het kwantitatieve onderzoek van eiwitten van plantaardige en dierlijke oorsprong gedurende de afgelopen twee jaar heeft gemaakt

Optical emission spectroscopy of metal-halide lamps: Radially resolved atomic state distribution functions of Dy and Hg

Absolute line intensity measurements are performed on a metal-halide lamp. Several transitions of atomic and ionic Dy and atomic Hg are measured at different radial positions from which we obtain absolute atomic and ionic Dy intensity profiles. From these profiles we construct the radially resolved atomic state distribution function (ASDF) of the atomic and ionic Dy and the atomic Hg. From these ASDFs several quantities are determined as functions of radial position, such as the (excitation) temperature, the ion ratio Hg^+/Dy^+, the electron density, the ground state, and the totaldensity of Dy atoms and ions. Moreover, these ASDFs give us insight about the departure from equilibrium. The measurements show a hollow density profile for the atoms and the ionization of atoms in the center. In the outer parts of the lamp molecules dominate

Het aantonen van bebroede eieren in eiprodukten aan de hand van het 3-hydroxyboterzuurgehalte

De ontwikkeling van een enzymatische en een gaschromatografische methode voor het aantonen van 3-hydroxyboterzuur is in het kort beschreven. Beide methoden zijn gelijkwaardig gebleken

Het schrijven van RIKILT rapporten en wetenschappelijke artikelen

Dit raport is samengesteld door de werkgroep "Herziening rapportindeling RIKILT'', Duidelijk ingedeelde rapporten, voorzien van een abstract, verhogen de leesbaarheid en de bekendheid. De aanbevelingen die hier gegeven worden zijn gebaseerd op internationale afspraken. Verder zijn er nog aanvullende richtlijnen gegeven voor zover dat nodig was, zodat dit rapport alle informatie bevat voor het schrijven van een RIKILT rapport. Voor het schrijven van wetenschappelijke artikelen is volstaan met het geven van richtlijnen. Doorgaans is het de regel dat ieder tijdschrift en/of uitgever zijn eigen richtlijnen heeft, waaraan de schrijver zich houden moet

Collagen reorganization at the tumor-stromal interface facilitates local invasion

BACKGROUND: Stromal-epithelial interactions are of particular significance in breast tissue as misregulation of these interactions can promote tumorigenesis and invasion. Moreover, collagen-dense breast tissue increases the risk of breast carcinoma, although the relationship between collagen density and tumorigenesis is not well understood. As little is known about epithelial-stromal interactions in vivo, it is necessary to visualize the stroma surrounding normal epithelium and mammary tumors in intact tissues to better understand how matrix organization, density, and composition affect tumor formation and progression. METHODS: Epithelial-stromal interactions in normal mammary glands, mammary tumors, and tumor explants in three-dimensional culture were studied with histology, electron microscopy, and nonlinear optical imaging methodologies. Imaging of the tumor-stromal interface in live tumor tissue ex vivo was performed with multiphoton laser-scanning microscopy (MPLSM) to generate multiphoton excitation (MPE) of endogenous fluorophores and second harmonic generation (SHG) to image stromal collagen. RESULTS: We used both laser-scanning multiphoton and second harmonic generation microscopy to determine the organization of specific collagen structures around ducts and tumors in intact, unfixed and unsectioned mammary glands. Local alterations in collagen density were clearly seen, allowing us to obtain three-dimensional information regarding the organization of the mammary stroma, such as radiating collagen fibers that could not have been obtained using classical histological techniques. Moreover, we observed and defined three tumor-associated collagen signatures (TACS) that provide novel markers to locate and characterize tumors. In particular, local cell invasion was found predominantly to be oriented along certain aligned collagen fibers, suggesting that radial alignment of collagen fibers relative to tumors facilitates invasion. Consistent with this observation, primary tumor explants cultured in a randomly organized collagen matrix realigned the collagen fibers, allowing individual tumor cells to migrate out along radially aligned fibers. CONCLUSION: The presentation of these tumor-associated collagen signatures allowed us to identify pre-palpable tumors and see cells at the tumor-stromal boundary invading into the stroma along radially aligned collagen fibers. As such, TACS should provide indications that a tumor is, or could become, invasive, and may serve as part of a strategy to help identify and characterize breast tumors in animal and human tissues

NOX4-dependent ROS production by stromal mammary cells modulates epithelial MCF-7 cell migration

BACKGROUND: The influence of the stromal microenvironment on the progression of epithelial cancers has been demonstrated. Unravelling the mechanisms by which stromal cells affect epithelial behaviour will contribute in understanding cellular malignancy. It has been proposed that redox environment has a role in the acquisition of malignancy. In this work, we studied the influence of epithelial cells on the stromal redox status and the consequence of this phenomenon on MCF-7 cell motility. METHODS: We analysed in a co-culture system, the effect of RMF-EG mammary stromal cells on the migratory capacity of MCF-7 cell line. To test whether the NOX-dependent stromal redox environment influences the epithelial migratory behaviour, we knocked down the expression of NOX4 using siRNA strategy. The effect of TGF-b1 on NOX4 expression and activity was analysed by qPCR, and intracellular ROS production was measured by a fluorescent method. RESULTS: Migration of MCF-7 breast epithelial cells was stimulated when co-cultured with RMF-EG cells. This effect depends on stromal NOX4 expression that, in turn, is enhanced by epithelial soluble factors. Pre-treatment of stromal cells with TGF-b1 enhanced this migratory stimulus by elevating NOX4 expression and intracellular ROS production. TGF-b1 seems to be a major component of the epithelial soluble factors that stimulate NOX4 expression. CONCLUSIONS: Our results have identified that an increased stromal oxidative status, mainly provided by an elevated NOX4 expression, is a permissive element in the acquisition of epithelial migratory properties. The capacity of stromal cells to modify their intracellular ROS production, and accordingly, to increase epithelial motility, seems to depend on epithelial soluble factors among which TGF-b1 have a decisive role.This work was supported by the grant (1080196 to JM) from the Fondo Nacional de Ciencia y Tecnologı´a (FONDECYT) of Chile