SAMBA, a plant-specific anaphase-promoting complex/cyclosome regulator is involved in early development and A-type cyclin stabilization

The anaphase-promoting complex/cyclosome (APC/C) is a large multiprotein E3 ubiquitin ligase involved in ubiquitin-dependent proteolysis of key cell cycle regulatory proteins, including the destruction of mitotic cyclins at the metaphase-to-anaphase transition. Despite its importance, the role of the APC/C in plant cells and the regulation of its activity during cell division remain poorly understood. Here, we describe the identification of a plant-specific negative regulator of the APC/C complex, designated SAMBA. In Arabidopsis thaliana, SAMBA is expressed during embryogenesis and early plant development and plays a key role in organ size control. Samba mutants produced larger seeds, leaves, and roots, which resulted from enlarged root and shoot apical meristems, and, additionally, they had a reduced fertility attributable to a hampered male gametogenesis. Inactivation of SAMBA stabilized A2-type cyclins during early development. Our data suggest that SAMBA regulates cell proliferation during early development by targeting CYCLIN A2 for APC/C-mediated proteolysis.     

Stroke prevention in atrial fibrillation: current status and emerging therapies

Stroke is the most common cardiovascular disorder after heart disease, with a high mortality and often poor quality of life in survivors. Atrial fibrillation (AF), the most commonly occurring sustained cardiac arrhythmia increases the risk of stroke by five. However, stroke risk is not homogeneous and varies with associated morbidities and risk factors. Risk assessment scores have been developed and according to the calculated level of risk, guidelines recommend treatment with antithrombotic agents, preferably vitamin K antagonists (VKA). Despite these recommendations many patients with AF do not receive adequate thromboprophylaxis. The presence of AF is often not recognized and VKA are underused due to doctor- or patient-related factors and intrinsic disadvantages of these drugs. An awareness campaign for the diagnosis of AF is warranted, highlighting the risk of stroke. Novel anticoagulants that largely overcome many of the limitations of vitamin K antagonists are becoming available.     

Fibrous Component of the Temporomandibular Joint Disk

This article describes the spatial arrangement of collagen fibrils in the articular disk of the normal human temporomandibular joint (TMJ). Disks obtained at necropsy were examined by light microscopy and scanning electron microscopy. Observations by light microscopy showed dense cartilaginous tissue composed of collagen fiber bundles running in all directions. Observations by scanning electron microscopy revealed a network of collagen fibrils which were predominantly organized in bundles. In the surface layers an anteroposterior orientation was detectable. The authors concluded that the fibrous component of the TMJ articular disk is composed of collagen fibrils, organized in a three-dimensional network and able to resist compression forces due to loading.