Perinatal Asphyxia Reduces Dentate Granule Cells and Exacerbates Methamphetamine-Induced Hyperlocomotion in Adulthood

Background: Obstetric complications have been regarded as a risk factor for schizophrenia later in life. One of the mechanisms underlying the association is postulated to be a hypoxic process in the brain in the offspring around the time of birth. Hippocampus is one of the brain regions implicated in the late-onset dopaminergic dysfunction associated with hypoxic obstetric complications. Methodology/Principal Findings: We used an animal model of perinatal asphyxia, in which rat pups were exposed to 15 min of intrauterine anoxia during Cesarean section birth. At 6 and 12 weeks after birth, the behavior of the pups was assessed using a methamphetamine-induced locomotion test. In addition, the histopathology of the hippocampus was examined by means of stereology. At 6 weeks, there was no change in the methamphetamine-induced locomotion. However, at 12 weeks of age, we found an elevation in methamphetamine-induced locomotor activity, which was associated with an increase of dopamine release in the nucleus accumbens. At the same age, we also found a reduction of the dentate granule cells of the hippocampus. Conclusions/Significance: These results suggest that the dopaminergic dysregulation after perinatal asphyxia is associated with a reduction in hippocampal dentate granule cells, and this may partly contribute to the pathogenesis of schizophrenia.浜松医科大学学位論文　医博第548号(平成２１年３月１８日

Ultrasonic contact pulse transmission for elastic wave velocity and stiffness determination: Influence of specimen geometry and porosity

AbstractElasticity determination by means of ultrasonic pulse transmission requires experimental realization of non-dispersive, i.e. frequency-independent, wave propagation, be it in form of bulk waves propagating in an (approximately) infinite medium, or of extensional waves propagating through a 1D bar system. While it is conceptually known that wavelengths need to tend towards zero (as compared to the specimen dimensions perpendicular to the pulse propagation direction) in the 3D case, and towards infinity in the 1D case, we here report on a new systematic experimental assessment of the influence of the sample geometry on wave type: tests on solid isotropic aluminum samples reveal that the extensional (or bar) wave propagation mode requires transmission of truly slender samples (required slenderness ratio of 20 or larger for wavelengths equal to the wave travel distance; this minimum slenderness ratio is increasing with increasing travel distance-over-wavelength ratio). After a transition zone with dispersive wave propagation, non-dispersive bulk waves are detected once the slenderness ratio is reduced to 5 or lower (at wavelengths equal to the wave travel distance; this maximum slenderness ratio is increasing with increasing travel distance-over-wavelength ratio). On the other hand, it is conceptually known from continuum mechanics that the wavelength needs to be larger than the investigated material volume or representative volume element (RVE), as to reveal the material’s elastic properties, while corresponding quantitative data are rare. As a remedy, we here report on new experiments on transversely isotropic, porous aluminum samples, which reveal that minimum pore dimension-over-wavelength ratios of 1 and 10, respectively, relate to detection of normal and shear stiffnesses, respectively, of the solid material between the pores, while these ratios need to be smaller than 0.01 and 0.1, as to detect the normal and shear stiffnesses of the overall porous materials. The latter can be quantified through various homogenization techniques