Nanobody-mediated macromolecular crowding induces membrane fission and remodeling in the African trypanosome.

The dense variant surface glycoprotein (VSG) coat of African trypanosomes represents the primary host-pathogen interface. Antigenic variation prevents clearing of the pathogen by employing a large repertoire of antigenically distinct VSG genes, thus neutralizing the host's antibody response. To explore the epitope space of VSGs, we generate anti-VSG nanobodies and combine high-resolution structural analysis of VSG-nanobody complexes with binding assays on living cells, revealing that these camelid antibodies bind deeply inside the coat. One nanobody causes rapid loss of cellular motility, possibly due to blockage of VSG mobility on the coat, whose rapid endocytosis and exocytosis are mechanistically linked to Trypanosoma brucei propulsion and whose density is required for survival. Electron microscopy studies demonstrate that this loss of motility is accompanied by rapid formation and shedding of nanovesicles and nanotubes, suggesting that increased protein crowding on the dense membrane can be a driving force for membrane fission in living cells.

Atlas of voluntary facial muscle activation: Visualization of surface electromyographic activities of facial muscles during mimic exercises.

Complex facial muscle movements are essential for many motoric and emotional functions. Facial muscles are unique in the musculoskeletal system as they are interwoven, so that the contraction of one muscle influences the contractility characteristic of other mimic muscles. The facial muscles act more as a whole than as single facial muscle movements. The standard for clinical and psychosocial experiments to detect these complex interactions is surface electromyography (sEMG). What is missing, is an atlas showing which facial muscles are activated during specific tasks. Based on high-resolution sEMG data of 10 facial muscles of both sides of the face simultaneously recorded during 29 different facial muscle tasks, an atlas visualizing voluntary facial muscle activation was developed. For each task, the mean normalized EMG amplitudes of the examined facial muscles were visualized by colors. The colors were spread between the lowest and highest EMG activity. Gray shades represent no to very low EMG activities, light and dark brown shades represent low to medium EMG activities and red shades represent high to very high EMG activities relatively with respect to each task. The present atlas should become a helpful tool to design sEMG experiments not only for clinical trials and psychological experiments, but also for speech therapy and orofacial rehabilitation studies.

Facial muscle activation patterns in healthy male humans: a multi-channel surface EMG study.

In order to accurately characterize essential muscle activity during facial movements a new surface EMG (SEMG) technique was introduced and applied. Results represent reference data of healthy persons for future diagnostic purposes. In 30 healthy males monopolar electromyograms of the facial muscles were simultaneously recorded from 48 bilateral-symmetrically applied small surface electrodes while performing 29 facial movements of high clinical relevance. Mean SEMG amplitudes were quantified by power spectral analysis, normalized and presented as movement-related SEMG profiles. The mean SEMG amplitudes increased significantly in response to facial movements. Critical values of the movement-related SEMG amplitude increase were ascertained, valid for 90% of all examined subjects. The mean SEMG amplitudes differed between the performed facial movements, the examined muscles, and intramuscularly between lateral-medial and superior-inferior electrode positions, but not systematically between right and left side of face. The results show that the interplay between individual facial muscles and intramuscularly between their functional subunits is more differentiated than was previously estimated. With the presented facial SEMG technique the produced SEMG profiles are highly relevant for better planning of facial movement restoration. Based on the established reference data, this method can be used to objectively evaluate a facial paresis and to monitor changes during the course of disease and treatment. To easily apply the method, a reduction of electrode positions is intended after the clinical evaluation.