Topographical characterization of the midfacial musculature revealed by means of high-density surface electromyography

This study’s aim was to obtain topographical information of the midfacial musculature and systematically characterize it on a motor unit (MU) level. By means of high density surface electromyography (HDsEMG), motor units’ endplate positions and fiber orientations were examined. Sixteen specially trained, healthy subjects performed selective contraction of midfacial muscles (buccinator (BUC), incisivus (INC), levator anguli oris (LAO), levator labii superioris (LLS), orbicularis oculi (OOC), orbicularis oris pars tangentialis (OOR tan), orbicularis oris pars tangentialis and peripheralis (OOR tan+per), orbicularis oris pars tangentialis and peripheralis and marginalis (OOR tan+per+mar), zygomaticus major (ZYGmaj) and zygomaticus minor (ZYGmin) muscle). Signals were recorded using high-density surface electromyography grids (245 channels). The raw surface electromyography data was decomposed into contributions of single motor units by application of convolution kernel compensation method (CKC). Analysis of decomposed motor unit action potentials (MUAPs) revealed the motor units’ endplate locations and fiber orientations. The results were illustrated in a mean face, which was created by averaging 3D face scan data. A total of 957 MUs were found and assigned to the muscles deliberately contracted during measurement and to levator labii superioris alaeque nasi muscle (LLSan) and nasalis muscle (NAS), which could be distinguished in the analysis as well. OOC and OORmar showed widely distributed endplates on the muscle. A clustering of endplates within individuals but with great variation of the location of clusters between individuals was found for BUC LAO, OORper, OORtan and ZYGmin. A clustering of endplates with similar cluster locations among individuals was found for INC, LLS, LLSan and ZYGmaj. The MUs’ muscle fiber orientations generally conform well to descriptions and drawings in anatomical textbooks and literature. This study’s results contribute to basic anatomical and neurophysiologic knowledge of the facial musculature and may contribute to establish objective electrode placement guidelines or to advance examination methods and (non-)surgical therapies

Irrigation management is a key farmer practice for a better use of nitrate; a case study in an intensive open field endive crop

Trabajo presentado en International Symposium on Plant Nutrition, Fertilization, Soil Management, celebrado en Angers (Francia) del 14 al 20 de agosto de 2022

Characterization of the Primary Photochemistry of Proteorhodopsin with Femtosecond Spectroscopy

Proteorhodopsin is an ion-translocating member of the microbial rhodopsin family. Light absorption by its retinal chromophore initiates a photocycle, driven by trans/cis isomerization, leading to transmembrane translocation of a proton toward the extracellular side of the cytoplasmic membrane. Here we report a study on the photoisomerization dynamics of the retinal chromophore of proteorhodopsin, using femtosecond time-resolved spectroscopy, by probing in the visible- and in the midinfrared spectral regions. Experiments were performed both at pH 9.5 (a physiologically relevant pH value in which the primary proton acceptor of the protonated Schiff base, Asp97, is deprotonated) and at pH 6.5 (with Asp97 protonated). Simultaneous analysis of the data sets recorded in the two spectral regions and at both pH values reveals a multiexponential excited state decay, with time constants of ∼0.2 ps, ∼2 ps, and ∼20 ps. From the difference spectra associated with these dynamics, we conclude that there are two chromophore-isomerizaton pathways that lead to the K-state: one with an effective rate of ∼(2 ps)−1 and the other with a rate of ∼(20 ps)−1. At high pH, both pathways are equally effective, with an estimated quantum yield for K-formation of ∼0.7. At pH 6.5, the slower pathway is less productive, which results in an isomerization quantum yield of 0.5. We further observe an ultrafast response of residue Asp227, which forms part of the counterion complex, corresponding to a strengthening of its hydrogen bond with the Schiff base on K-state formation; and a feature that develops on the 0.2 ps and 2 ps timescale and probably reflects a response of an amide II band in reaction to the isomerization process