Hemodynamics in Ruptured Intracranial Aneurysms

Incidental detection of unruptured intracranial aneurysms (UIA) has increased in the recent years. There is a need in the clinical community to identify those that are prone to rupture and would require preventive treatment. Hemodynamics in cerebral blood vessels plays a key role in the lifetime cycle of intracranial aneurysms (IA). Understanding their initiation, growth, and rupture or stabilization may identify those hemodynamic features that lead to aneurysm instability and rupture. Modeling hemodynamics using computational fluid dynamics (CFD) could aid in understanding the processes in the development of IA. The neurosurgical approach during operation of IA allows direct visualization of the aneurysm sac and its sampling in many cases. Detailed analysis of the quality of the aneurysm wall under the microscope, together with histological assessment of the aneurysm wall and CFD modeling, can help in building complex knowledge on the relationship between the biology of the wall and hemodynamics. Detailed CFD analysis of the rupture point can further strengthen the association between hemodynamics and rupture. In this chapter we summarize current knowledge on CFD and intracranial aneurysms

2.4-Å structure of the double-ring Gemmatimonas phototrophica photosystem.

Phototrophic Gemmatimonadetes evolved the ability to use solar energy following horizontal transfer of photosynthesis-related genes from an ancient phototrophic proteobacterium. The electron cryo-microscopy structure of the Gemmatimonas phototrophica photosystem at 2.4 Å reveals a unique, double-ring complex. Two unique membrane-extrinsic polypeptides, RC-S and RC-U, hold the central type 2 reaction center (RC) within an inner 16-subunit light-harvesting 1 (LH1) ring, which is encircled by an outer 24-subunit antenna ring (LHh) that adds light-gathering capacity. Femtosecond kinetics reveal the flow of energy within the RC-dLH complex, from the outer LHh ring to LH1 and then to the RC. This structural and functional study shows that G. phototrophica has independently evolved its own compact, robust, and highly effective architecture for harvesting and trapping solar energy

2.4-Å structure of the double-ring Gemmatimonas phototrophica photosystem.

Phototrophic Gemmatimonadetes evolved the ability to use solar energy following horizontal transfer of photosynthesis-related genes from an ancient phototrophic proteobacterium. The electron cryo-microscopy structure of the Gemmatimonas phototrophica photosystem at 2.4 Å reveals a unique, double-ring complex. Two unique membrane-extrinsic polypeptides, RC-S and RC-U, hold the central type 2 reaction center (RC) within an inner 16-subunit light-harvesting 1 (LH1) ring, which is encircled by an outer 24-subunit antenna ring (LHh) that adds light-gathering capacity. Femtosecond kinetics reveal the flow of energy within the RC-dLH complex, from the outer LHh ring to LH1 and then to the RC. This structural and functional study shows that G. phototrophica has independently evolved its own compact, robust, and highly effective architecture for harvesting and trapping solar energy

Horizontal transfers of two types of puf operons among phototrophic members of the Roseobacter clade

The Roseobacter clade represents one of the most important bacterial groups in marine environments. While some of its members are heterotrophs, many Roseobacter clade members contain bacterial photosynthetic reaction centers. We investigated the phylogeny of pufL and pufM genes encoding the L and M subunits of reaction centers using available genomic data and our own cultured species. Interestingly, phylogeny of pufL and pufM genes largely deviated from 16S rRNA-based phylogeny. The sequences split into two clearly distinct clades. While most of the studied species contained pufL and pufM sequences related to those found in Roseobacter litoralis, some of the marine species contained sequences related to the freshwater Rhodobacter species. In addition, genomic data documents that Roseobacter-type centers contain cytochrome c subunits (pufC gene product), whereas Rhodobacter-type centers incorporate PufX proteins. This indicates that the two forms of the reaction centers are not only distinct phylogenetically, but also structurally. The large deviation of pufL and pufM phylogeny from 16S phylogeny indicates multiple horizontal transfers of the puf operon among members of the order Rhodobacterales