The Evolution of Ventriculoperitoneal Shunt Valves and Why They Fail.

This article reviews the historical progression of ventriculoperitoneal shunt valve designs with the goal of providing an understanding of their functionality and failure mechanisms. While shunting is the predominant treatment for hydrocephalus, the statistics of overall shunt failure remain high, and valve failure is responsible for a significant percentage of revision surgeries. Therefore, this review spans valve evolution from an engineering perspective with an emphasis on discussing potential failure mechanisms and patient-specific valve selection.

Investigation of stent retriever removal forces in an experimental model of acute ischemic stroke.

Introduction: Mechanical thrombectomy becomes more complex when the occlusion occurs in a tortuous cerebral anatomy, increasing the puncture to reperfusion time and the number of attempts for clot removal. Therefore, an understanding of stent retriever performance in these locations is necessary to increase the efficiency and safety of the procedure. An investigation into the effects of occlusion site tortuosity, blood clot hematocrit, and device geometry was conducted to identify their individual influence on stent retriever removal forces.

Direct and indirect selection in a proofreading polymerase.

The traits that affect evolvability are subject to indirect selection, as these traits affect the course of evolution over many generations rather than the direct replicative fitness of an individual. However, the evolution of evolvability-determining traits is often difficult to study because putative evolvability alleles often have confounding direct fitness effects of unknown origin and size. Here, we study theoretically and experimentally the evolution of mutation rates in proofreading polymerases with orthogonal control of direct and indirect selection.

Abundance measurements reveal the balance between lysis and lysogeny in the human gut microbiome.

The human gut contains diverse communities of bacteriophage, whose interactions with the broader microbiome and potential roles in human health are only beginning to be uncovered. Here, we combine multiple types of data to quantitatively estimate gut phage population dynamics and lifestyle characteristics in human subjects. Unifying results from previous studies, we show that an average human gut contains a low ratio of phage particles to bacterial cells (~1:100), but a much larger ratio of phage genomes to bacterial genomes (~4:1), implying that most gut phage are effectively temperate (e.