ABSTRACT
A outbreak of disease with symptoms of evisceration and skin ulteration led to mass mortality in sea cucumber Apostichopus japonicus cultivated in indoor ponds near the Dalian coast from December 2004 to April 2005. Spherical virus particles with a diameter of 75-200 nm were found in the cytoplasm of cells in the water-system, the alimentary canal and in the respiratory trees of the diseased and dying sea cucumber individuals by electron microscopic observation of ultrathin sections. Examination by negative stained samples revealed that all the diseased sea cucumbers were infected by the virus, while the healthly ones cultivated outside the contagious area were not. Two bacterial strains were also isolated from the diseased animals. When exposed to a medium containing the virus particles, regardless of whether the bacterial suspension was added,healthy sea cucumbers exhibited identical disease symptoms as the ones in the indoor ponds, and had a mortality of 90%-100%. However, when exposed to a medium in which there was only one of the two bacterial strains, 30%-80% of the sea cucumbers were infected and nearly 20% died. Negative staining showed that the viral particles were detected only in the bodies of the tested animals that were exposed to the viral medium. Histopathologically, the diseased sea cucumbers are characterized by karyopycnosis, and disintegration of the endoplasmic reticula and mitochondria in the epithelial cells in the water-system, the respiratory tree and the alimentary canal.
ABSTRACT
To study the effects of different post design on retention. 27 simulated tooth roots made of PMMA were divided into three groups, then manufactured the cement-expanded composite screw post-core system (CECSP), cement screw post-core system (CSP) and cast metal post-core system (CMP). The root and post-core system was tensiled by the speed of 10 mm/min on the Instron 4302 and recorded the retention force. It appeared significantly different between retention force of CECSP and CSP and CAM (P < 0.05). As a result, the retention mechanical properties of CECSP was much better than those of cement screw post-core system and cast metal post-core system. Therefore, it is possible to find a new way for restoration of endodontically treated teeth.