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The Arterially Perfused Rabbit Papillary Muscle: A Model to Study Electrical Properties in Myocardial Ischemia
Published in Samuel Sideman, Rafael Beyar, Analysis and Simulation of the Cardiac System — Ischemia, 2020
André G. Kléber, Christoph Riegger
Longitudinal tissue resistance, rt, and length constant, λ. — The longitudinal tissue resistance, rt, was obtained from the voltage, Vo, between the two extracellular electrodes (interelectrode distance, Δx) measured during flow of subthreshold current at strength I. A fraction of this current, injected extracellularly at the apical end of the muscle, will flow through the cell membrane into the intracellular space. At a distance of more than about three times the length constant λ, this membrane current becomes neglectable.13,28 In segments remote from the apical end (site of membrane current flow), rt represents the longitudinal tissue resistance, consisting of (intracellular longitudinal resistance) and ro (extracellular longitudinal resistance) in parallel:
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Published in Calver Pang, Ibraz Hussain, John Mayberry, Pre-Clinical Medicine, 2017
Calver Pang, Ibraz Hussain, John Mayberry
The length constant is the distance from the point of origin where the change in membrane potential is equal to 37% of the maximum potential change. The longer the length constant, the further the current can spread, allowing action potentials to propagate faster. Increasing membrane resistance and deceasing internal resistance of the axon can increase length constant.
Computer simulations of an irrigated radiofrequency cardiac ablation catheter and experimental validation by infrared imaging
Published in International Journal of Hyperthermia, 2021
Christian Rossmann, Anjan Motamarry, Dorin Panescu, Dieter Haemmerich
Additionally, a blood velocity boundary condition (uD_in) of 10 cm/s for the blood domain inlet was applied in the model reproducing the experimental conditions (Figure 3(B)), and 0, 0.5, and 25 cm/s were assigned in the second set of computer model studies (Figure 3(A)). The blood flow velocities were selected to simulate the range of velocities typically observed in human hearts [19]. Although the flow rate varies during the cardiac cycle, prior studies in vessels suggest that, due to the long heating duration relative to cardiac cycle length, constant flow velocity can be assumed for the simulation of tissue heat transfer during thermal therapies [32,33].
GlycoVHH: optimal sites for introducing N-glycans on the camelid VHH antibody scaffold and use for macrophage delivery
Published in mAbs, 2023
Loes van Schie, Wander Van Breedam, Charlotte Roels, Bert Schepens, Martin Frank, Ahmad Reza Mehdipour, Bram Laukens, Wim Nerinckx, Francis Santens, Simon Devos, Iebe Rossey, Karel Thooft, Sandrine Vanmarcke, Annelies Van Hecke, Xavier Saelens, Nico Callewaert
The differences in site occupancy (Figure 1C), such as 1) between the Q14N-P15A-G16T and much less efficiently glycosylated G16N-S18T variants – both within loop A-B, and 2) between the P48N-K50T and G49N-E51T variants – both within loop C-C’, suggest that the exact localization of an NXT sequon within a loop of the protein structure is important for N-glycosylation efficiency. Hence, in a third glycoengineering campaign, we performed N-X-T scanning of three selected loops in our benchmark VHH GBP: loop B-C (AHo numbering 27–40), which coincides with CDR1 and contains GBP glycovariant G27N-P30T, loop C-C’ (AHo numbering 47–53), which contains GBP glycovariant P48N-K50T, and loop D-E (AHo numbering 83–88), which contains GBP glycovariant R86N. A first NXT scanning set of GBP glycovariants was generated by introducing an NXT sequon at every single position within the amino acid stretches 27–40 (loop B-C), 48–52 (within loop C-C’) and 83–88 (loop D-E) by mutation of model VHH GBP, while keeping the loop length constant (Supplementary C-A). A second N-X-T scanning set of glycovariants was generated by peptide inserts at several positions within the selected loops. These were short peptides (N-A-T) consisting of an N-glycosylation sequon only, longer peptides (D-N-A-N-A-T) based on a motif frequently occurring in VHH loop D-E, or single or double glycine residues (G-G) flanking the N-glycosylation sequon if the amino acid preceding it was a proline (Supplementary C-A). Upon production in P. pastoris GlycoSwitchM5, VHH glycosylation was evaluated via endoglycosidase treatment and subsequent SDS-PAGE analysis followed either by Coomassie staining or a western blot detecting the C-terminal His6-tag of the VHH (Supplementary C-B and -C). Except for mutant A85N-N87T, which could not be expressed in repeated experiments, all glycovariants were prone to N-glycosylation. Site occupancy varied substantially with the exact position of the sequon (observed in duplicate or triplicate clones per glycovariant). Although the majority of the sites within the selected loop regions showed a high N-glycan site-occupancy (non-glycosylated band barely detectable), some sites (e.g., positions 29 and 46, and a short insert at position 85–86) showed less efficient glycosylation as evidenced by the presence of a lower molecular weight band on SDS-PAGE. Hence, the exact position and/or the local environment of the N-glycosylation sequon again affects N-glycosylation site occupancy.