Double-barrel STA-MCA bypass and partial trapping of a ruptured mycotic MCA aneurysm with flash fluorescence technique

Mycotic brain aneurysms are rare and unusual cerebrovascular lesions arising from septic emboli that degrade the elastic lamina and vessel wall of intracranial arteries, which results in pathologic dilatation. Mycotic aneurysms are nonsaccular lesions that are not often suitable for clipping and instead require bypass, trapping, and flow reversal. This case demonstrates the use of indocyanine green “flash fluorescence” to identify the cortical distribution supplied by an aneurysm’s outflow, facilitating safe treatment with a double-barrel extracranial-intracranial bypass and partial trapping and conversion of a deep bypass to a superficial one. The video can be found here: https://stream.cadmore.media/r10.3171/2021.10.FOCVID21163

Particle size effect on sorting with optical lattice

Transport of mesoscale particles due to driving flow fields or external forces on a periodic surface appears in many areas. Geometrical and physical characteristics of particles affect the velocities of the particles in these periodic landscapes. In this paper, we present a numerical simulation based on solving the Langevin equation for the meso-size particles subjected to the thermal fluctuations in a periodic array of optical traps. We consider the real-size particles which cause the partial trapping of particles in the optical traps. The particles are sorted for the size-dependency of particles’ trajectories. Our results are in good agreement with experiments.

Stability of point spectrum for three-state quantum walks on a line

Evolution operators of certain quantum walks possess, apart from the continuous part, also a point spectrum. The existence of eigenvalues and the corresponding stationary states lead to partial trapping of the walker in the vicinity of the origin. We analyze the stability of this feature for three-state quantum walks on a line subject to homogenous coin deformations. We find two classes of coin operators that preserve the point spectrum. These new classes of coins are generalizations of coins found previously by different methods and shed light on the rich spectrum of coins that can drive discrete-time quantum walks.

Trapping Channel Block of NMDA-Activated Responses By Amantadine and Memantine

Blanpied, Thomas A., Faye Boeckman, Elias Aizenman, and Jon W. Johnson. Trapping channel block of NMDA-activated responses by amantadine and memantine. J. Neurophysiol. 77: 309–323, 1997. We investigated the mechanisms by which the antiparkinsonian and neuroprotective agents amantadine and memantine inhibit responses to N-methyl-d-aspartic acid (NMDA). Whole cell recordings were performed using cultured rat cortical neurons or Chinese hamster ovary (CHO) cells expressing NMDA receptors. Both amantadine and memantine blocked NMDA-activated channels by binding to a site at which they could be trapped after channel closure and agonist unbinding. For neuronal receptors, the IC50s of amantadine and memantine at −67 mV were 39 and 1.4 μM, respectively. When memantine and agonists were washed off after steady-state block, one-sixth of the blocked channels released rather than trapped the blocker; memantine exhibited “partial trapping.” Thus memantine appears to have a lesser tendency to be trapped than do phencyclidine or (5R,10S)-(+)-5m e t h y l - 1 0 , 1 1 - d i h y d r o - 5 H - d i b e n z o [ 1 , d ] c y c l i h e p t e n - 5 , 1 0 - i m i n e(MK-801). We next investigated mechanisms that might underlie partial trapping. Memantine blocked and could be trapped by recombinant NMDA receptors composed of NR1 and either NR2A or NR2B subunits. In these receptors, as in the native receptors, the drug was released from one-sixth of blocked channels rather than being trapped in all of them. The partial trapping we observed therefore was not due to variability in the action of memantine on a heterogeneous population of NMDA receptors in cultured cortical neurons. Amantadine and memantine each noncompetitively inhibited NMDA-activated responses by binding at a second site with roughly 100-fold lower affinity, but this form of inhibition had little effect on the extent to which memantine was trapped. A simple kinetic model of blocker action was used to demonstrate that partial trapping can result if the presence of memantine in the channel affects the gating transitions or agonist affinity of the NMDA receptor. Partial trapping guarantees that during synaptic communication in the presence of blocker, some channels will release the blocker between synaptic responses. The extent to which amantadine and memantine become trapped after channel block thus may influence their therapeutic effects and their modulation of NMDA-receptor-mediated excitatory postsynaptic potentials.