Miniaturization of an Anoikis assay using non-adhesive micromolded hydrogels

Anoikis is a specific form of apoptosis resulting from the loss of cellular attachment to extracellular matrix or other cells. Challenges in simulating these conditions in vitro make it difficult to generate a controlled, efficient assay to study anoikis. We developed a microscale method for analysis and quantification of anoikis using micromolded, non-adhesive hydrogels. These hydrogels allow for isolation and observation of single, unattached cells in an ordered array, and controlled distribution. Cell distributions resulting from multiple seeding densities were compared to a mathematical probability model. Normal human fibroblasts, human umbilical vein endothelial cells, and Mandin-Darby canine kidney epithelial cells were seeded at low densities of approximately one cell/well. Because the hydrogel is made of non-adhesive agarose, attachment was negligible. Survival was monitored using fluorescent microscopy, and quantified by image analysis. The attachment and proliferative potential of cells after being held in a non-adherent environment was assessed with a companion attachment assay. The data from both methods revealed that cells were able to survive much longer than expected without attachment. When tested with H35 rat hepatoma cells we showed that single cancer cells could grow into three-dimensional spheroids, demonstrating the utility of this method in understanding the role of anoikis in cancer

Measurement of Particle Production and Inclusive Differential Cross Sections in pbar{p} Collisions at sqrt{s}=1.96 TeV

21 pages, 10 figuresWe report a set of measurements of particle production in inelastic pbar{p} collisions collected with a minimum-bias trigger at the Tevatron Collider with the CDF II experiment. The inclusive charged particle transverse momentum differential cross section is measured, with improved precision, over a range about ten times wider than in previous measurements. The former modeling of the spectrum appears to be incompatible with the high particle momenta observed. The dependence of the charged particle transverse momentum on the event particle multiplicity is analyzed to study the various components of hadron interactions. This is one of the observable variables most poorly reproduced by the available Monte Carlo generators. A first measurement of the event transverse energy sum differential cross section is also reported. A comparison with a Pythia prediction at the hadron level is performed. The inclusive charged particle differential production cross section is fairly well reproduced only in the transverse momentum range available from previous measurements. At higher momentum the agreement is poor. The transverse energy sum is poorly reproduced over the whole spectrum. The dependence of the charged particle transverse momentum on the particle multiplicity needs the introduction of more sophisticated particle production mechanisms, such as multiple parton interactions, in order to be better explained

A Measurement of the t-tbar Cross Section in p-pbar Collisions at sqrt(s) = 1.96 TeV using Dilepton Events with a Lepton plus Track Selection

43 pages, 22 figures; Submitted to Phys. Rev. DThis paper reports a measurement of the cross section for the pair production of top quarks in ppbar collisions at sqrt(s) = 1.96 TeV at the Fermilab Tevatron. The data was collected from the CDF II detector in a set of runs with a total integrated luminosity of 1.1 fb^{-1}. The cross section is measured in the dilepton channel, the subset of ttbar events in which both top quarks decay through t -> Wb -> l nu b where l = e, mu, or tau. The lepton pair is reconstructed as one identified electron or muon and one isolated track. The use of an isolated track to identify the second lepton increases the ttbar acceptance, particularly for the case in which one W decays as W -> tau nu. The purity of the sample may be further improved at the cost of a reduction in the number of signal events, by requiring an identified b-jet. We present the results of measurements performed with and without the request of an identified b-jet. The former is the first published CDF result for which a b-jet requirement is added to the dilepton selection. In the CDF data there are 129 pretag lepton + track candidate events, of which 69 are tagged. With the tagging information, the sample is divided into tagged and untagged sub-samples, and a combined cross section is calculated by maximizing a likelihood. The result is sigma_{ttbar} = 9.6 +/- 1.2 (stat.) -0.5 +0.6 (sys.) +/- 0.6 (lum.) pb, assuming a branching ratio of BR(W -> ell nu) = 10.8% and a top mass of m_t = 175 GeV/c^2