Diacylglycerol-Stimulated Endocytosis of Transferrin in Trypanosomatids Is Dependent on Tyrosine Kinase Activity

Small molecule regulation of cell function is an understudied area of trypanosomatid biology. In Trypanosoma brucei diacylglycerol (DAG) stimulates endocytosis of transferrin (Tf). However, it is not known whether other trypanosomatidae respond similarly to the lipid. Further, the biochemical pathways involved in DAG signaling to the endocytic system in T. brucei are unknown, as the parasite genome does not encode canonical DAG receptors (e.g. C1-domains). We established that DAG stimulates endocytosis of Tf in Leishmania major, and we evaluated possible effector enzymes in the pathway with multiple approaches. First, a heterologously expressed glycosylphosphatidylinositol phospholipase C (GPI-PLC) activated endocytosis of Tf 300% in L. major. Second, exogenous phorbol ester and DAGs promoted Tf endocytosis in L. major. In search of possible effectors of DAG signaling, we discovered a novel C1-like domain (i.e. C1_5) in trypanosomatids, and we identified protein Tyr kinases (PTKs) linked with C1_5 domains in T. brucei, T. cruzi, and L. major. Consequently, we hypothesized that trypanosome PTKs might be effector enzymes for DAG signaling. General uptake of Tf was reduced by inhibitors of either Ser/Thr or Tyr kinases. However, DAG-stimulated endocytosis of Tf was blocked only by an inhibitor of PTKs, in both T. brucei and L. major. We conclude that (i) DAG activates Tf endocytosis in L. major, and that (ii) PTKs are effectors of DAG-stimulated endocytosis of Tf in trypanosomatids. DAG-stimulated endocytosis of Tf may be a T. brucei adaptation to compete effectively with host cells for vertebrate Tf in blood, since DAG does not enhance endocytosis of Tf in human cells

Effects of straw phonation on choral acoustic and perceptual measures after an acclimation period

A single session of vocalizing through a straw (straw phonation) has been associated with consistent or increased acoustic output and chorister-reported improved choral sound and vocal efficiency. Some choristers, however, report discomfort from the intense pressure of vocalizing through a stirring straw (2.5–3.0 mm opening). It is unclear whether participants acclimate to this pressure over time. Two mixed and two treble choirs sang a unison melody, participated in a straw protocol, and sang the melody again. Choristers used the protocol during warmups in four subsequent rehearsals and repeated the same pretest-posttest protocols on the final day. Survey results indicated (a) at least 89.7% of participants self-reported improved choral sound and more efficient/comfortable individual voicing after the protocols on both data collection days, and (b) participants reported greater impact on their warmup on the final day. Analyses revealed (a) choirs sang with 1.35 to 3.37 dB SPL greater mean spectral energy after the protocols on the first day and 1.63 to 2.65 dB SPL on the final day, and (b) one choir evidenced less change on the final day, one evidenced more change, and two evidenced no statistical difference. These results may represent a modest acclimation effect for choristers using straw phonation

Plasma-Based Forcing Strategies for Control of Crossflow Instabilities

The present work experimentally investigates two forcing strategies toward controlling stationary crossflow instability (CFI) induced transition manifesting on a swept wing at subsonic conditions. The effectiveness of upstream flow deformation (UFD) and the base-flow modification strategies, realized through the application of spanwise-modulated and spanwise-uniform dielectric barrier discharge plasma actuation, respectively, is compared experimentally. Specialized, patterned actuators that generate spanwise-modulated plasma jets have been fabricated using a spray-on technique and positioned near the leading edge. An array of discrete roughness elements (DREs) is installed upstream of the plasma forcing to lock the origin and evolution of the critical stationary CFI vortices in the boundary layer. The impact of the phase relation between the spanwise-modulated plasma jets and the incoming CFI vortices is inspected. Infrared thermography is employed to detect and quantify the transition location. A delay in transition is observed with all tested forcing configurations. However, as the incoming CFI vortices are highly amplified due to the application of DREs, the acquired results suggest that with spanwise-modulated forcing the control mechanism responsible for the observed transition delay is not purely UFD; rather the beneficial effects observed leverage on a combination of direct attenuation of the CFI vortices and localized base-flow modification, depending on the aforementioned phase relation. For all forcing strategies and configurations, a simplified drag reduction efficiency estimation is performed using the experimentally measured transition location and the electrical power use of the actuators. A net gain is found for selected configurations

Swept-wing transition control using DBD plasma actuators

In the present work, laminar flow control, following the discrete roughness elements (DRE) strategy, also called upstream flow deformation (UFD) was applied on a 45◦ swept-wing at a chord Reynold’s number of Rec = 2.1 · 106 undergoing cross-flow instability (CFI) induced transition. Dielectric barrier discharge (DBD) plasma actuation was employed at a high frequency (fac = 10kHz) for this purpose. Specialized, patterned actuators that generate spanwinse-modulated plasma jets were fabricated using spray-on techniques and positioned near the leading edge. An array of DREs was installed upstream of the plasma forcing to lock the origin and evolution of critical stationary CFI vortices in the boundary layer. Two forcing configurations were investigated-in the first configuration the plasma jets were directly aligned against the incoming CF vortices while in the second the CF vortices passed between adjacent plasma jets. Infrared thermography was used to inspect transition location, while quantitative measurements of the boundary layer were obtained using particle image velocimetry. The obtained results show that the plasma forcing reduces the amplitude of stationary CF modes, thus delaying laminar-to-turbulent transition. In contrast to previous efforts [1], the plasma forcing did not introduce unsteady fluctuations into the boundary layer. The mechanism responsible for the observed transition delay appears to leverage more on localised base-flow modification rather than the DRE/UFD control strategy