Drosophila Histone Deacetylase-3 Controls Imaginal Disc Size through Suppression of Apoptosis

Histone deacetylases (HDACs) execute biological regulation through post-translational modification of chromatin and other cellular substrates. In humans, there are eleven HDACs, organized into three distinct subfamilies. This large number of HDACs raises questions about functional overlap and division of labor among paralogs. In vivo roles are simpler to address in Drosophila, where there are only five HDAC family members and only two are implicated in transcriptional control. Of these two, HDAC1 has been characterized genetically, but its most closely related paralog, HDAC3, has not. Here we describe the isolation and phenotypic characterization of hdac3 mutations. We find that both hdac3 and hdac1 mutations are dominant suppressors of position effect variegation, suggesting functional overlap in heterochromatin regulation. However, all five hdac3 loss-of-function alleles are recessive lethal during larval/pupal stages, indicating that HDAC3 is essential on its own for Drosophila development. The mutant larvae display small imaginal discs, which result from abnormally elevated levels of apoptosis. This cell death occurs as a cell-autonomous response to HDAC3 loss and is accompanied by increased expression of the pro-apoptotic gene, hid. In contrast, although HDAC1 mutants also display small imaginal discs, this appears to result from reduced proliferation rather than from elevated apoptosis. The connection between HDAC loss and apoptosis is important since HDAC inhibitors show anticancer activities in animal models through mechanisms involving apoptotic induction. However, the specific HDACs implicated in tumor cell killing have not been identified. Our results indicate that protein deacetylation by HDAC3 plays a key role in suppression of apoptosis in Drosophila imaginal tissue

Smoking, occupational exposures and lymphocyte DNA damage in Chinese workers

published_or_final_versionCommunity MedicineDoctoralDoctor of Philosoph

X-ray Micro CT Based Characterization of Pore-Throat Network for Marine Carbonates from South China Sea

The pore-throat network of rock exerts a vital influence on the permeability and mechanical properties of the rock. Resorting to X-ray micro-CT scanning, the present work investigates the pore-throat structure of marine biogenic carbonate samples from the South China Sea and compares them to terrigenous sedimentary sandstone. With the help of the maximum ball (MB) algorithm, the pore-throat networks inside representative elementary volumes of rock samples are revealed by stick-and-ball diagrams, which enables quantitative analyses afterwards. Higher and more deviant cross sectional porosity was observed for the carbonate samples compared to the sandstone sample, indicating relatively heterogeneous pores in the carbonate. Over 85% of pores in the carbonate samples were classified as mesopores. Irregular triangular cross sections can be inferred for the pores and throats of the carbonate. The type of rock and the porosity seem to have little effect on the shapes of the pores and throats. In the studied carbonate, the average volume of the throat was approximately one order of magnitude smaller than the average volume of a pore. The distribution of throat radius differed significantly between the studied carbonate samples. The average coordination number of the carbonate was measured to be 1

Numerical simulation of the wave-induced dynamic response of poro-elastoplastic seabed foundations and a composite breakwater

In this study, an integrated numerical model FSSI-CAS 2D (previously known as POROWSSI 2D) is developed for the problem of wave-elasto-plastic seabed-structure interactions, where the Volume Average Reynolds Average Navier-Stokes (VARANS) equation is taken as the governing equation for wave motion and porous flow in porous medium; the dynamic Biot's equation known as "u - p" is taken as the governing equation for the dynamics of porous seabed soil under wave loading. The Pastor-Zienkiewicz Mark III proposed by Pastor et al. (1990) [45] is used to describe the dynamic behaviour of poro-elasto-plastic seabed under wave loading. This developed integrated numerical model is validated by a centrifuge test conducted by Sassa and Sekiguchi (1999) [30]. The developed integrated numerical model is applied to investigate the wave-induced dynamic response of a composite breakwater and its elasto-plastic seabed foundation. The numerical results indicate that the pore pressure in an elasto-plastic seabed builds up under wave loading, leading to the reduction of the contact effective stresses between soil particles. The residual liquefaction occurs when the effective stresses decrease to a value approaching zero. The wave-induced residual liquefaction in seabed is progressive downward. A parameter considering the cohesion and friction angle of soil is defined to evaluate the residual liquefaction potential. Analysis results illustrate that the friction angle of soil has significant effect on the soil liquefaction; and Nevada dense sand becomes liquefied if the defined parameter exceeded 0.86. Parametric study shows that wave characteristics and soil properties have significant effects on the wave-induced progressive residual liquefaction in loose elasto-plastic seabed foundation. (C) 2014 Elsevier Inc. All rights reserved

A 3-D semi-coupled numerical model for fluid-structures-seabed-interaction (FSSI-CAS 3D):model and verification

In this study, a semi-coupled 3-D numerical model for fluid-structures-seabed-interaction is developed. The dynamic Biot's equation known as "u-p" approximation, and modified Navier-Stokes equation in which the linear drag force between the flowing pore water and the solid matrix of porous medium is included, is respectively adopted as the governing equation in the soil sub-model and the wave sub-model. A coupling algorithm is developed to integrate the two sub-models together, in which non-match mesh and non-match time scheme are used based on the shepherd interpolation method. The data exchange is implemented at the interface between fluid domain and seabed/marine structures domain adopting the coupling algorithm. Finally, the developed 3-D numerical model is validated by an analytical solution and a laboratory wave flume test.No Full Tex

AE Test of Calcareous Sands with Particle Rushing

The particle of calcareous sands was forced to crush, then the energy from the crushing was released by the form of sound waves. Therefore the AE technique was used to detect the calcareous sands AE signal when it crushed. by to study the AE characteristics, the mechanics of calcareous sands was studied. Study showed that: (1) there was the AE activities on the low confining pressure condition at the beginnig of test, (2) there was more and more AE activities with the continuing of test until to the end, (3) the calcareous sands’ AE activities was on the whole testing, (4) the calcareous sands’ particle crushing and mutual friction played different roles for its AE activities. Then the AE model based on the calcarous sands’ particle crushing was discussed