| 1. |
- Galluzzi, L, et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring cell death in higher eukaryotes.
- 2009
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Ingår i: Cell death and differentiation. - : Springer Science and Business Media LLC. - 1476-5403 .- 1350-9047. ; 16:8, s. 1093-107
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Forskningsöversikt (refereegranskat)abstract
- Cell death is essential for a plethora of physiological processes, and its deregulation characterizes numerous human diseases. Thus, the in-depth investigation of cell death and its mechanisms constitutes a formidable challenge for fundamental and applied biomedical research, and has tremendous implications for the development of novel therapeutic strategies. It is, therefore, of utmost importance to standardize the experimental procedures that identify dying and dead cells in cell cultures and/or in tissues, from model organisms and/or humans, in healthy and/or pathological scenarios. Thus far, dozens of methods have been proposed to quantify cell death-related parameters. However, no guidelines exist regarding their use and interpretation, and nobody has thoroughly annotated the experimental settings for which each of these techniques is most appropriate. Here, we provide a nonexhaustive comparison of methods to detect cell death with apoptotic or nonapoptotic morphologies, their advantages and pitfalls. These guidelines are intended for investigators who study cell death, as well as for reviewers who need to constructively critique scientific reports that deal with cellular demise. Given the difficulties in determining the exact number of cells that have passed the point-of-no-return of the signaling cascades leading to cell death, we emphasize the importance of performing multiple, methodologically unrelated assays to quantify dying and dead cells.
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| 2. |
- Gutierrez, P.J, et al.
(författare)
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Commets on the amplitude-phase relationship of asteroid lightcurves : Effects of topography, surface scattering properties, and obliquity
- 2006
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 454:1, s. 367-377
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We present a theoretical study on the amplitude-phase relationship (APR) for lightcurves of simulated asteroids.Methods. In support of the Rosetta (ESA) mission, we developed a numerical model for the investigation of the light reflectance properties of asteroidal bodies. The code is able to deal with irregular and chemically inhomogeneous surfaces, taking shadowing effects into account. Several standard scattering models have been implemented, which govern local reflectance properties, e. g. the Hapke model and the Lumme-Bowell model. From a kinematic standpoint, the body can move in an arbitrary orbit, and it may rotate in either pure or complex mode with an arbitrary orientation of its angular momentum. As an application of the code, we studied the dependence of the APR on several factors, such as the illumination and observational geometries, overall shape, and large-scale topography, as well as the surface characteristics represented by the parameters in the Hapke and Lumme-Bowell models.Results. In our study, we find that mineralogy, regolith properties, and small-scale surface roughness (i. e., characteristics embodied in the considered surface scattering models), have a negligible effect on the APR. Furthermore, large-scale topography introduces a rather significant dispersion in the APR slope, on the order of 0.010 mag deg(-1). Our simulations suggest that obliquity is the major agent for shaping the APR, causing a 0.020 mag deg(-1) dispersion in the APR slope; the larger the obliquity, the smaller the slope of the APR. For intermediate aspect angles, large obliquities could even lead to an amplitude that decreases with the phase angle.
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| 3. |
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| 4. |
- Saravia, F., et al.
(författare)
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Differences in boar sperm head shape and dimensions recorded by computer-assisted sperm morphometry are not related to chromatin integrity
- 2007
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Ingår i: Theriogenology. - : Elsevier. - 0093-691X .- 1879-3231. ; 68:2, s. 196-203
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Tidskriftsartikel (refereegranskat)abstract
- Although sperm head shape and relative dimensions are considered reliable indicators of sperm quality, their quantification is most often operator-driven, e.g., subjective. Artificial insemination semen doses from 35 mature stud boars of known fertility and belonging to three breeds and two hybrid breeds (Duroc, Large White, Landrace, respectively, Yorker and Risco) were used in this study. Sperm samples were extended to 100 x 10(6) Cells per mL and 10 mu L of the sperm suspension used to made smears which, stained, were examined using phase contrast microscopy interfaced with an automated sperm morphology analyzer (ASMA, 2 ISAS (R)). Each sperm head was measured for four primary parameters [area (A) mu m(2), perimeter (P) mu m, length (L) mu m, width (M mu m], and four derived parameters of head shape [(L/W, (4 pi A/P-2), ((L - W/(L + M), (pi LW/4A)]. Definition of head size was statistically performed. The threshold for each class was established on the basis of the area values, considering the 25th percentile as small and the 75th percentile as large spermatozoa. In a second step, sperm head shape was determined as normal, elliptic, abnormal (rugose) contour, long or irregular and percentiles set as above to define spermatozoa with normal values for each shape parameter. Significant differences were found among breeds in the size of morphologically normal spermatozoa, which were significantly larger and more elliptic (P less than 0.001) in the Duroc breed. Sperm chromatin integrity was studied using the SCSA-assay, with significant differences observed in the degree of fragmentation intensity (DFI) although this value was consistently low in all animals studied. The hereby-validated ASMA was able to determine significant differences in sperm shape and dimensions among breeds, which were not accompanied by deviations in chromatin structure neither within nor between fertile AI-boars. (c) 2007 Elsevier Inc. All rights reserved.
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| 5. |
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| 6. |
- Nunez, A. J., et al.
(författare)
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Toughening of wood particle composites - Effects of sisal fibers
- 2006
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 101:3, s. 1982-1987
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Tidskriftsartikel (refereegranskat)abstract
- Sisal fibers were added to wood particle composites to enhance their toughness. The selected matrix was a commercial styrene diluted unsaturated polyester thermoset resin. Fracture tests were carried out using single-edge notched beam geometries. Stiffness, strength, critical stress intensity factor K-IQ, and work of fracture W-f of notched specimens were determined. The incorporation of sisal fibers into wood particle composites significantly changed the fracture mode of the resulting hybrid composite. For the neat matrix and the wood particle composites, once the maximum load was reached, the crack propagated in a catastrophic way. For hybrid composites, fiber bridging and pull-out were the mechanisms causing increased crack growth resistance. Addition of a 7% wt of sisal fibers almost doubled the K-IQ value of a composite containing 12% wt of woodflour. Moreover, the W-f increased almost 10-fold, for the same sample. In general, the two composite toughness parameters K-IQ and W-f increased when the fraction of sisal fibers was increased.
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| 7. |
- Nunez, Eugenia, et al.
(författare)
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Morphology, crystallization and melting of single crystals and thin films of star–branched polyesters with poly(epsilon-caprolactone) arms as revealed by atomic force microscopy.
- 2008
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Ingår i: Journal of Macromolecular Science, Part B. - : Informa UK Limited. - 0022-2348 .- 1525-609X. ; 47:3, s. 589-607
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Tidskriftsartikel (refereegranskat)abstract
- The morphology and thermal stability of different sectors in solution- and melt-grown crystals of star-branched polyesters with poly(epsilon-caprolactone) (PCL) arms, and of a reference linear PCL, have been studied by tapping-mode atomic-force microscopy (AFM). Real-time monitoring of melt-crystallization in thin films of star-branched and linear PCL has been performed using hot-stage AFM. A striated fold surface was observed in both solution- and melt-grown crystals of both star-branched and linear PCL. The presence of striations in the melt-grown crystals proved that this structure was genuine and not due to the collapse of tent-shaped crystals. The crystals of the star-branched polymers had smoother fold surfaces, which can be explained by the presence of dendritic cores close to the fold surfaces. The single crystals of linear PCL grown from solution showed earlier melting in the {100} sectors than in the {110} sectors, whereas no such sectorial dependence of the melting was found in the solution-grown crystals of the star-branched polymers. The proximity of the dendritic cores to the fold surface yields at least one amorphous PCL repeating unit next to the dendritic core and more nonadjacent and less sharp chain folding than in linear PCL single crystals; this evidently erased the difference in thermal stability between the {110} and {100} sectors. Melt-crystallization in thin polymer films at 53-55 degrees C showed 4 times faster crystal growth along b than along a, and more irregular crystals with niches on the lateral faces in star-branched PCL than in linear PCL. Crystal growth rate was strictly constant with time. Multilayer crystals with central screw dislocation (growing with or without reorientation of the b-axis) and twisting were observed in both classes of polymers.
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| 8. |
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