No abstract available

[en] In severe nutriment conditions, the social amoeba Dictyostelium discoideum enters a particular life cycle where it forms multicellular patterns to achieve aggregation. Extensively observed from an initial dispersed state, its developmental program can usefully be studied from a confined population to implement theoretical developments regarding biological self-organization. The challenge is then to form a cell assembly of well-defined geometrical dimensions without hindering cell behavior. To achieve this goal, we imposed transient constraints by applying temporary external magnetic gradients to trap magnetically labeled cells. Deposits of various numbers of cells were geometrically characterized for different magnetic exposure conditions. We demonstrated that the cell deposit was organized as a three-dimensional (3D) structure by both stacking layers of cells and extending these layers in the substrate plane. This structure evolves during the aggregation phase, forming periodic aggregative centers along the linear initial pattern

[en] The effect was followed up of ionizing radiation of 20, 25, 30, 32, 35, 40 and 50 krad on the virulence and the immunigenic properties of B.ovis. The experiments were carried out with 22 sheep (20 test and 2 donor) according to the rate of treatment into 7 test groups with a total of 17 animals, and 1 control with 3 sheep. One month after infection with irradiated blood reinfection was carried out of 8 animals (of different groups) that had recovered, using virulent untrated blood. The titer of the antibodies in the remaining sheep was followed up by means of the complement fixation test. It was found that irradiation at 20 - 25 krad lowered the virulence of the Babesia organisms, but these could provoke the disease in an acute form and cause death. The animals that survived after being infected with the indicated doses developed a comparatively good immunity. It is considered that the most appropriate dose of irradiation is 30 krad. 32 and 35 krad do not kill Babesiae; the parasites thus irradiated, however, cannot protect the animals ar reinfection. It has been found that Babesiae irradiated at the rates of 40 and 450 krad do not cause an infection process, and at reinfection the animals respond almost in the same way as the controls. (author)

No abstract available

[en] A digital holographic microscope is employed to measure the 3D motion of free-swimming microorganisms. The focus function used to quantify image sharpness provides a better depth-directional accuracy with a smaller depth-of-focus compared with the intensity method in determining the depth-directional position of spherical particles of various diameters. The focus function is then applied to measure the 3D positions of free-swimming microorganisms, namely dinoflagellates C. polykrikoides and P. minimum. Both automatic segmentation and proper selection of a focus function for a selected segment are important processes in measuring the positional information of two free-swimming microorganisms of different shapes with various width-to-length ratios. The digital holographic microscopy technique improved in this work is useful for measuring 3D swimming trajectories, velocities and attitudes of hundreds of microorganisms simultaneously. It also exhibits exceptional depth-directional accuracy

No abstract available

[en] We consider reshaping an obstacle virtually by using transformation optics in acoustic and electromagnetic scattering. Among the general virtual reshaping results, the virtual minification and virtual magnification in particular are studied. Stability estimates are derived for scattering amplitude in terms of the diameter of a small obstacle, which implies that the limiting case for minification corresponds to a perfect cloaking, i.e., the obstacle is invisible to detection

[en] The shape and motion of cells can yield significant insights into the internal operation of a cell. We present a simple, yet versatile, framework that provides multiple metrics of cell shape and cell shape dynamics. Analysis of migrating Dictyostelium discoideum cells shows that global and local metrics highlight distinct cellular processes. For example, a global measure of shape shows rhythmic oscillations suggestive of contractions, whereas a local measure of shape shows wave-like dynamics indicative of protrusions. From a local measure of dynamic shape, or boundary motion, we extract the times and locations of protrusions and retractions. We find that protrusions zigzag, while retractions remain roughly stationary along the boundary. We do not observe any temporal relationship between protrusions and retractions. Our analysis framework also provides metrics of the boundary as whole. For example, as the cell speed increases, we find that the cell shape becomes more elongated. We also observe that while extensions and retractions have similar areas, their shapes differ

No abstract available

[en] The aim of this study was to investigate the influence of electromagnetic radiation of a Digital Global System for Mobile Communication mobile telephone (900MHz) on Entameba histolytica (E.histolytica) and Entamoeba dispar (E.dispar) (cysts or trophozites, or both) in a 24-hour period. This study was carried out from April 2004 to May 2004 at the Department of Parasitology, Medical Faculty of Dokuz Eylul University in Izmir, Turkey. The cultivated isolate tubes, which were exposed to electromagnetic fields at 37C, were evaluated as study group, whereas the tubes without exposure were assessed as control group. Finally, only living parasites in all tubes were counted using a hemacytometer. The effect of the temperature was evaluated for both control and study groups. The influence of electromagnetic field and temperature were assessed separately for the study group. The parasite number of E.histolytica decreased after exposure at 37C and room temperature (p=0.009) compared to the decrease in the control group (p=0.009). The parasite number of dispar also decreased after exposure at 37C and room temperature (p=0.009). In comparison to control tubes, this was a significant decrease (p=0.008). In the case of exposure of E. histolytica the results did not reveal any significant difference between temperature degrees to magnetic field (p=0.459) and E.dispar (p=0.172).Our findings show that exposure to electromagnetic field for a certain period of time may cause damage that can lead to death in single-cell organisms. (author)