SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Valve

56

Limited information is available regarding genetic contributions to valvular calcification, which is an important precursor of clinical valve disease.

Concepts: Check valve, Valve

28

Reoperation for failing stentless aortic valve replacement is a technically demanding procedure that has traditionally been tackled in one of two ways: either root replacement or the more conservative option of implanting a stented valve within the valve. We sought to determine the relative operative risks, follow-up status and medium to long-term survival of these two methods.

Concepts: Valve Corporation, Valve, Derivative, Left ventricle, Aortic insufficiency, Aortic valve replacement, Aortic valve

28

Object Overdrainage of CSF remains an unsolved problem in shunt therapy. The aim of the present study was to evaluate treatment options on overdrainage-related events enabled by the new generation of adjustable gravity-assisted valves. Methods The authors retrospectively studied the clinical course of 250 consecutive adult patients with various etiologies of hydrocephalus after shunt insertion for different signs and symptoms of overdrainage. Primary and secondary overdrainage were differentiated. The authors correlated the incidence of overdrainage with etiology of hydrocephalus, opening valve pressure, and patient parameters such as weight and size. Depending on the severity of overdrainage, they elevated the opening pressure, and follow-up was performed until overdrainage was resolved. Results The authors found 39 cases (15.6%) involving overdrainage-related problems-23 primary and 16 secondary overdrainage. The median follow-up period in these 39 patients was 2.1 years. There was no correlation between the incidence of overdrainage and any of the following factors: sex, age, size, or weight of the patients. There was also no statistical significance among the different etiologies of hydrocephalus, with the exception of congenital hydrocephalus. All of the “complications” could be resolved by readjusting the opening pressure of the valve in one or multiple steps, avoiding further operations. Conclusions Modern adjustable and gravity-assisted valves enable surgeons to set the opening pressure relatively low to avoid underdrainage without significantly raising the incidence of overdrainage and to treat overdrainage-related clinical and radiological complications without surgical intervention.

Concepts: Valve, Etiology, Medicine, Shunt, Surgery, Cerebrospinal fluid, Hydrocephalus

27

To test the ability of a model-based segmentation of the aortic root for consistent assessment of aortic valve structures in patients considered for transcatheter aortic valve implantation (TAVI) who underwent 256-slice cardiac computed tomography (CT).

Concepts: Aortic valve, Valve, Left ventricle, Radiography, Radiology, Aorta, Computed tomography angiography, Medical imaging

18

Endobronchial valves (EBV) have been successfully used in patients with severe heterogeneous emphysema to improve lung physiology. Limited available data suggests that EBVs are also effective in homogeneous emphysema.

Concepts: Valve Corporation, Valve, Lung

3

Little is known about the association between bicuspid aortic valve (BAV) morphologic findings and the degree of valvular dysfunction, presence of aortopathy, and complications, including aortic valve surgery, aortic dissection, and all-cause mortality.

Concepts: Check valve, Degree of a polynomial, The Association, Valve, Aortic insufficiency, Aortic valve, Aortic dissection, Bicuspid aortic valve

3

Water samples of the Drinking Water Supply System (DWSS) of the city of Braunschweig were analysed for its Legionella species composition using genus-specific PCR amplicons and single-strand conformation polymorphism (SSCP) fingerprint analyses based on 16S rRNA genes. These analyses comprised the whole supply chain including raw water, treatment process and large-scale storage, and a seasonal study of finished drinking water sampled monthly from cold and hot tap water. Treatment of raw water had a major impact on Legionella species by reducing their diversity and abundances. The Legionella species composition of the tap water was highly distinct from that of both source waters. In cold water, 8-14 different phylotypes of Legionella (PTLs) were observed per sample with relative abundances ranging from >1% to 53%. In hot water, L. pneumophila was present during all seasons at high relative abundances (8-40%) accompanied by 5-14 other PTLs of which 6 PTLs were in common with cold water. This thermophilic Legionella community, including L. pneumophila, was able to grow in the hot water above 50 °C. Such thermophilic Legionella populations are of general relevance for drinking water management and public health, but also for the ecology and evolution of the genus Legionella.The ISME Journal advance online publication, 3 November 2015; doi:10.1038/ismej.2015.199.

Concepts: Water, Ribosomal RNA, Valve, 16S ribosomal RNA, Tap water, Water quality, Drinking water, Water supply

3

During January 2014, an industrial solvent contaminated West Virginia’s Elk River and 15% of the state population’s tap water. A rapid in-home survey and water testing was conducted two weeks following the spill to understand resident perceptions, tap water chemical levels, and premise plumbing flushing effectiveness. Water odors were detected in all 10 homes sampled before and after premise plumbing flushing. Survey and medical data indicated flushing caused adverse health impacts. Bench-scale experiments and physiochemical property predictions showed flushing promoted chemical volatilization, and contaminants did not appreciably sorb into crosslinked polyethylene (PEX) pipe. Flushing reduced tap water 4-methylcyclohexanemethanol (4-MCHM) concentrations within some but not all homes. 4-MCHM was detected at unflushed (<10 to 420 µg/L) and flushed plumbing systems (<10 to 96 µg/L) and sometimes concentrations differed among faucets within each home. All waters contained less 4-MCHM than the 1,000 µg/L Centers for Disease Control drinking water limit but one home exceeded the 120 µg/L drinking water limit established by independent toxicologists. Nearly all households refused to resume water use activities after flushing because of water safety concerns. Science based flushing protocols should be developed to expedite recovery, minimize health impacts, and reduce concentrations in homes when future events occur.

Concepts: Tap water, Sink, Water supply, Water quality, Drinking water, Valve, Water pollution, Water

3

Owing to a considerable shift toward bioprosthesis implantation rather than mechanical valves, it is expected that patients will increasingly present with degenerated bioprostheses in the next few years. Transcatheter aortic valve-in-valve implantation is a less invasive approach for patients with structural valve deterioration; however, a comprehensive evaluation of survival after the procedure has not yet been performed.

Concepts: Valve

2

Two-pore domain (K2P) K(+) channels are major regulators of excitability that endow cells with an outwardly rectifying background “leak” conductance. In some K2P channels, strong voltage-dependent activation has been observed, but the mechanism remains unresolved because they lack a canonical voltage-sensing domain. Here, we show voltage-dependent gating is common to most K2P channels and that this voltage sensitivity originates from the movement of three to four ions into the high electric field of an inactive selectivity filter. Overall, this ion-flux gating mechanism generates a one-way “check valve” within the filter because outward movement of K(+) induces filter opening, whereas inward movement promotes inactivation. Furthermore, many physiological stimuli switch off this flux gating mode to convert K2P channels into a leak conductance. These findings provide insight into the functional plasticity of a K(+)-selective filter and also refine our understanding of K2P channels and the mechanisms by which ion channels can sense voltage.

Concepts: Biology, Electric charge, Inductor, Ion, Magnetic field, Potassium channel, Valve, Electromagnetism