Involvement of FADD and caspase-8 signalling in detachment-induced apoptosis

AbstractDetachment of most untransformed adherent cells from the extracellular matrix promotes apoptosis, in a process termed anoikis [1,2]. The death signalling mechanisms involved in this process are not known, although adhesion or transformation by ras oncogenes have been shown to protect epithelial cells from apoptosis through activation of phosphatidylinositol 3-kinase and protein kinase B (PKB/Akt) [3]. Here we show that detachment-induced apoptosis (anoikis) is blocked by the expression of a dominant-negative form of FAS-associated death domain protein (FADD) in a number of untransformed epithelial cell lines. Because the soluble extracellular domains of the death receptors CD95, DR4 and DR5 failed to block anoikis, we conclude that ligand-dependent activation of these death receptors is not involved in this process. Detachment induced strong activation of caspase 8 and caspase 3. Detachment-induced caspase-8 activation did not require the function of downstream caspases but was blocked by overexpression of the anti-apoptotic proteins Bcl-2 or Bcl-XL. We propose that caspase-8 activation is the initiating event in anoikis, which is subsequently subject to a positive-feedback loop involving mitochondrial events

Tutkimus ekstrinsisten koheesioelementtien käyttöön koheesiivisessa murtumassa

Fracture of quasi-brittle materials such as sea ice can be simulated using cohesive crack model. The model can be applied to finite-element method using cohesive elements, which can be divided into intrinsic and extrinsic types. Extrinsic type elements are better suited for simulations where the crack path is not known. One such application is ice-structure interaction simulation, where intact ice sheet breaks against an offshore structure. In this work the use of cohesive elements is studied, with focus in fracture of sea ice. A state-of-the-art review on cohesive fracture modelling and cohesive elements is conducted. As a computational part extrinsic cohesive fracture model for sea ice is developed for use in ice-structure interaction simulations. The model is based on earlier fracture model used in simulations of ice-structure interaction. This thesis also includes a study on cohesive fracture modelling using commercial finite-element software Abaqus as an alternative for in-house created codes. At the time Abaqus only includes intrinsic elements, but extrinsic element could be added as user-created element. Creating such elements is challenging and time-consuming, and the study results in Abaqus not being a feasible alternative for ice-structure interaction simulation. As a result of this work an improved version of the 2-D cohesive crack model is created. The model improves on the original model by in shear dominated cases. Wide variety of tests were conducted using MATLAB to compare the performance between the two models. The new model is found to be better compared to the original model in shear dominated cases, while performing equally well in tensile cases.Jään kaltaisten kvasihauraiden materiaalien murtumista voidaan mallintaa koheesiivista särömallia käyttäen. Malli voidaan liittää osaksi elementti-menetelmää käyttäen koheesiivisia elementtejä, jotka voidaan jakaa intrinsisiin ja ekstrinsisisiin malleihin. Ekstrinsinen malli soveltuu paremmin jään murtumisen kaltaisiin tapauksiin, jossa särön kulkureittiä ei tiedetä etukäteen. Yksi tällainen sovelluskohde on jään ja rakenteen välisen vuorovaikutuksen mallintaminen, jossa jäälautta murtuu meriteknistä rakennetta vasten. Tässä työssä tutkitaan koheesiivisten elementtien käyttöä. Työ sisältää kattavan kirjallisuuskatsauksen koheesiivisen murtuman mallintamisesta ja koheesiivisten elementtien käytöstä. Työn laskennallisessa osiossa kehitetään ekstrinsinen koheesiivinen murtumismalli merijäälle, jota voidaan käyttää jään ja rakenteen välisen vuorovaikutuksen mallintamisessa. Malli perustuu aiemmassa tutkimuksessa kehitettyyn murtumismalliin jota myös käytetään jään ja rakenteen vuorovaikutuksen simuloinnissa. Tässä työssä tutkitaan myös koheesiivisen murtuman mallintamista kaupallisella Abaqus-elementtimenetelmäohjelmistolla vaihtoehtona itse tehdyille laskenta-malleille. Tällä hetkellä Abaqus sisältää ainoastaan intrinsisiä elementtejä, mutta ekstrinsisiä elementtejä voidaan lisätä käyttäjän itse tekemillä elementeillä. Omien elementtien kehittäminen on kuitenkin haastavaa ja aikaa vievää. Tutkimuksen tuloksena todetaan ettei Abaqus ole käyttökelpoinen vaihtoehto jään ja rakenteen välisen vuorovaikutuksen simuloinnissa. Työn tuloksena kehitettiin paranneltu versio kaksiulotteisesta koheesiivisesta särömallista, joka toimii alkuperäistä mallia paremmin leikkaussuuntaisissa kuormitustapauksissa. Mallien toimintaa verrattiin MATLAB ohjelmistolla toteutetuilla testeillä. Uusi malli toimii alkuperäistä mallia paremmin leikkaus-kuormitustapauksissa, ja pärjäten yhtä hyvin vetokuormitustapauksissa

Kinetic analysis of the growth of bone marrow mononuclear phagocytes in long term cultures

Contains fulltext : 4427.pdf (publisher's version ) (Open Access

Development of a novel evaluation method for air particles using surface plasmon resonance spectroscopy analysis

The aim of this study was to develop a novel evaluation method for air particles using surface plasmon resonance spectroscopy (SPR) analysis. An L1 sensor chip modified with immobilized liposome was used as a model of the membrane of epithelial cells in organs of respiration. A test suspension of dispersed air particles was flowed onto the sensor chip. The interaction between the surface of the sensor chip and particulates in the sample solution was detected by SPR. It is deduced that the SPR measurement provides information about the adsorption/desorption behavior of the particles on the membrane. Environmentally certified reference materials, diesel particulate matter, vehicle exhaust particulates, urban particulate matter, coal fly ash, and rocks, were used as air particulate samples. Filtrates of suspensions of these samples were analyzed by SPR. Each sample revealed characteristic SPR sensor-gram patterns. For example, diesel particulate matter strongly interacted with the lipid bilayer, and was hardly dissociated. On the other hand, coal fly ash and rock particles interacted poorly with the membrane. The presented method could be used to evaluate or characterize air particles.ArticleANALYST. 138(18):5437-5443 (2013)journal articl

Elucidating the mechanism of ferrocytochrome c heme disruption by peroxidized cardiolipin

The interaction of peroxidized cardiolipin with ferrocytochrome c induces two kinetically and chemically distinct processes. The first is a rapid oxidation of ferrocytochrome c, followed by a slower, irreversible disruption of heme c. The oxidation of ferrocytochrome c by peroxidized cardiolipin is explained by a Fenton-type reaction. Heme scission is a consequence of the radical-mediated reactions initiated by the interaction of ferric heme iron with peroxidized cardiolipin. Simultaneously with the heme c disruption, generation of hydroxyl radical is detected by EPR spectroscopy using the spin trapping technique. The resulting apocytochrome c sediments as a heterogeneous mixture of high aggregates, as judged by sedimentation analysis. Both the oxidative process and the destructive process were suppressed by nonionic detergents and/or high ionic strength. The mechanism for generating radicals and heme rupture is presented

Is diagnosing exposed dentine a suitable tool for grading erosive loss?

Quantifying tooth wear in general and erosion in particular mostly is made by distinguishing between lesions restricted to enamel and lesions reaching the underlying dentine. Various scores for grading have been used, but in all systems, higher scores are given in cases of exposed dentine, thus, indicating a more severe stage of the condition. Clinical diagnosis of exposed dentine is made by assessing changes in colour or optical properties of the hard tissues. This paper aims to review the literature and discuss critically problems arising form this approach. It appears that classifying the severity of erosion by the area or depth of exposed dentine is difficult and poorly reproducible, and taking into account the variation of enamel thickness, the amount of tissue lost often is not related simply to the area of exposed dentine. There has still been very little longitudinal investigation of the significance of exposed dentine as a prognostic indicator. Further work and discussion is needed to reevaluate the explanative power of current grading procedures