Resolution In Mice Research Articles

Effects of Positron Range and Annihilation Photon Acolinearity on Image Resolution of a Compton PET

In order to assess the effects of positron range and acolinearity on image resolution of a Compton PET scanner designed for sub-millimeter resolution in mice, Monte Carlo simulations were performed using EGS4 code. The PET device consists of a BGO ring (17.6 cm dia., 16 cm length, and 2 cm thickness segmented into 3 mm times 3 mm times20 mm crystals) surrounding a concentric position-sensitive silicon ring (4 cm dia. times4 cm long times1.6 cm thick segmented into 16 layers of 0.3 mm times0.3 mm times1 mm elements) for the scatter detector. For each detected event, interaction position was obtained from the silicon pad in which a single Compton scatter occurs and the BGO crystal which has maximum energy deposited. Acolinearity was considered in sampling the direction vector of annihilation photon pairs. The cusp-like distribution of positron range in water was added in sinogram. An intrinsic detector resolution of 230 mum FWHM is obtained. By considering positron range and acolinearity, the overall image resolutions of 18F, 11C, 13N, and 15O point sources in water are 360, 440, 490, and 550 mum FWHM, respectively. Image quality was evaluated with 2-D images of cylindrical source for each positron emitter in a water cylinder reconstructed with filtered back projection (FBP). Monte Carlo simulation indicates the blurring effect from positron range of various isotopes dominates the image resolution of the Compton PET instrument. A negligibly small effect on resolution was introduced from acolinearity due to the small diameter of the silicon detector.

1012. Non-Invasive Imaging of Airways and Other Organs at High Resolution in Mice

1012. Non-Invasive Imaging of Airways and Other Organs at High Resolution in Mice

We-P14:451 Dietary iron overlod in rats strongly affects lipid parameters

Fibrosis is the result of the abnormal accumulation of the extracellular matrix and ineffective clearance of fibroplasia. CD4+CD25+Foxp3+ regulatory T cells (Tregs) are immunosuppressive lymphocytes that are highly expressed in the fibrotic tissues and peripheral blood of patients with cirrhosis or hepatocellular carcinoma. The role of Tregs in the progression of liver fibrosis is not well understood. Our experiments reveal that abundant of Tregs was scattered around sites of fibroplasia. Conversely, the depletion of Tregs promoted the resolution of liver fibrosis. As a consequence of Tregs depletion, the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) was altered; mmp9 and timp1 were reduced, whereas mmp2 and mmp14 were enhanced. The mmp9/timp1, mmp13/timp1, and mmp14/timp2 ratios were significantly increased in association with fibrosis resolution. Kupffer cells (KCs) are the main source of MMP. We observed that when KCs were cocultured with Tregs, the Tregs were able to inhibit MMP expression of KCs even at a low ratio; and anti–transforming growth factor-β (TGF-β) significantly reversed the inhibition of Tregs on MMP. Meanwhile, we also found that after Tregs depletion, TGF-β levels decreased in the mice liver, unlike in fibrosis. Furthermore, double depletion of both KCs and Tregs did not cause fiber resolution in mice. Thus, our results demonstrate that the persistence of liver cirrhosis is maintained by increased Tregs in the sites of fibroplasia and the subsequent regulation of the MMP/TIMP balance and that the suppression of KC-mediated MMP expression contributed to the regulatory process.

The genetic basis of family conflict resolution in mice.

Asymmetries in the costs and benefits of parental investment for mothers, fathers and offspring result in family conflict over the production and provisioning of young. In species where females provide most resources before and after birth, the resolution of this conflict may be influenced by genes expressed in mothers and by maternally and paternally inherited genes expressed in offspring. Here we disentangle these effects by means of reciprocal mating and cross-fostering of litters between two strains of mice that differ with respect to the typical resolution of family conflict. We find that differences in litter size between these two strains are determined by paternal genotype, whereas differences in provisioning are under maternal control, showing that there is antagonistic coadaptation of maternal and paternal effects on distinct life-history traits. Maternal provisioning is also influenced by the type of foster offspring. Contradictory to theoretical expectations, however, we find no evidence for a negative correlation across strains between maternal provisioning and offspring demand. Instead, we show that there is positive coadaptation such that offspring obtain more resources from foster mothers of the same strain as their natural mother, irrespective of their father's strain.

Sex-specific differences in meiotic chromosome segregation revealed by dicentric bridge resolution in mice.

The meiotic properties of paracentric inversion heterozygotes have been well studied in insects and plants, but not in mammalian species. In essence, a single meiotic recombination event within the inverted region results in the formation of a dicentric chromatid, which usually breaks or is stretched between the two daughter nuclei during the first meiotic anaphase. Here, we provide evidence that this is not the predominant mode of exchange resolution in female mice. In sharp contrast to previous observations in other organisms, we find that attempts to segregate the dicentric chromatid frequently result not in breakage, stretching, or loss, but instead in precocious separation of the sister centromeres of at least one homolog. This often further results in intact segregation of the dicentric into one of the meiotic products, where it can persist into the first few embryonic divisions. These novel observations point to an unusual mechanism for the processing of dicentric chromosomes in mammalian oogenesis. Furthermore, this mechanism is rare or nonexistent in mammalian spermatogenesis. Thus, our results provide additional evidence of sexual dimorphism in mammalian meiotic chromosome behavior; in "stressful" situations, meiotic sister chromatid cohesion is apparently handled differently in males than in females.