Examining the Effect of Public Hiking Trail Use on Soil Loss and Stream-Bottom Embeddedness in First-Order Vermont Streams

Erosion of public hiking trails is a key management issue in Vermont. Previous studies have suggested a link between outdoor recreational land use, soil erosion, and diminished stream health. Trail development, maintenance, and use in Vermont is regulated through a series of state and local regulations. This study investigated the relationship between hiking trail character (trail age, visitation rate, and trail-stream crossings) and soil loss on trails and the relationship between soil loss, stream-bottom embeddedness, and stream health. Nine paired trail-stream sites and one undeveloped forested stream site (control) were monitored to determine stream-bottom embeddedness, macroinvertebrate community composition, and soil incision on trails. Regression analysis was performed to determine the relationships present between trail characteristics, soil loss, and embeddedness. The results did not indicate any significant relationships between trail character, soil loss, and embeddedness. Stream-bottom embeddedness was significantly negatively related to stream gradient, indicating that natural geography has more impact than recreational land use on sediment dynamics in forested streams. None of the stream sites were impaired, as indicated by macroinvertebrate community composition. The results of this study may suggest that current trail regulations are effective in minimizing the impact of public hiking trail construction and use on trail-adjacent streams. Future work could focus on monitoring trails throughout their lifespan to better understand the long-term effects of trail use on the surrounding landscape. Future studies could also examine which methods are most effective in measuring soil loss on hiking trails and sediment dynamics in headwater streams

The ruminant sorting mechanism protects teeth from abrasives

Dental wear due to ingestion of dust and grit has deleterious consequences. Herbivores that could not wash their food hence had to evolve particularly durable teeth, in parallel to the evolution of dental chewing surface complexity to increase chewing efficacy. The rumen sorting mechanism increases chewing efficacy beyond that reached by any other mammal and has been hypothesized to also offer an internal washing mechanism, which would be an outstanding example of an additional advantage by a physiological adaptation, but in vivo evidence is lacking so far. Here, we investigated four cannulated, live cows that received a diet to which sand was added. Silica in swallowed food and feces reflected experimental dietary sand contamination, whereas the regurgitate submitted to rumination remained close to the silica levels of the basal food. This helps explain how ruminants are able to tolerate high levels of dust or grit in their diet, with less high-crowned teeth than nonruminants in the same habitat. Palaeo-reconstructions based on dental morphology and dental wear traces need to take the ruminants’ wear-protection mechanism into account. The inadvertent advantage likely contributed to the ruminants’ current success in terms of species diversity

Characterization of a porcine model of atrial arrhythmogenicity in the context of ischaemic heart failure

Atrial fibrillation (AF) is a major healthcare challenge contributing to high morbidity and mortality. Treatment options are still limited, mainly due to insufficient understanding of the underlying pathophysiology. Further research and the development of reliable animal models resembling the human disease phenotype is therefore necessary to develop novel, innovative and ideally causal therapies. Since ischaemic heart failure (IHF) is a major cause for AF in patients we investigated AF in the context of IHF in a close-tohuman porcine ischaemia-reperfusion model. Myocardial infarction (AMI) was induced in propofol/fentanyl/ midazolam-anaesthetized pigs by occluding the left anterior descending artery for 90 minutes to model ischaemia with reperfusion. After 30 days ejection fraction (EF) was significantly reduced and haemodynamic parameters (pulmonary capillary wedge pressure (PCWP), right atrial pressure (RAP), left ventricular enddiastolic pressure (LVEDP)) were significantly elevated compared to age/weight matched control pigs without AMI, demonstrating an IHF phenotype. Electrophysiological properties (sinus node recovery time (SNRT), atrial/AV nodal refractory periods (AERP, AVERP)) did not differ between groups. Atrial burst pacing at 1200 bpm, however, revealed a significantly higher inducibility of atrial arrhythmia episodes including AF in IHF pigs (3/15 vs. 10/16, p = 0.029). Histological analysis showed pronounced left atrial and left ventricular fibrosis demonstrating a structural substrate underlying the increased arrhythmogenicity. Consequently, selective ventricular infarction via LAD occlusion causes haemodynamic alterations inducing structural atrial remodeling which results in increased atrial fibrosis as the arrhythmogenic atrial substrate in pigs with IHF

Conquering the Jet Lag Era: Experiences from Virtual Interdisciplinary Collaboration across Continents

Mit der Ausschreibung International Virtual Academic Collaboration (IVAC) verfolgt der Förderträger DAAD die Ziele, die Studienangebote an deutschen Hochschulen und deren ausländischen Kooperationshochschulen zu flexibilisieren und den Studierenden einen erweiterten Zugang zur internationalen Hochschulbildung zu ermöglichen. In dem geförderten Projekt Collaborative International, Intercultural & Interdisciplinary Learning (COIIIL) zwischen den Partnerinstitutionen Technische Universität Dresden, Stellenbosch University, Shiraz University und Bucknell University wurden diese Ziele adressiert

X-Box Binding Protein 1 Is Essential for the Anti-Oxidant Defense and Cell Survival in the Retinal Pigment Epithelium

Damage to the retinal pigment epithelium (RPE) is an early event in the pathogenesis of age-related macular degeneration (AMD). X-box binding protein 1 (XBP1) is a key transcription factor that regulates endoplasmic reticulum (ER) homeostasis and cell survival. This study aimed to delineate the role of endogenous XBP1 in the RPE. Our results show that in a rat model of light-induced retinal degeneration, XBP1 activation was suppressed in the RPE/choroid complex, accompanied by decreased anti-oxidant genes and increased oxidative stress. Knockdown of XBP1 by siRNA resulted in reduced expression of SOD1, SOD2, catalase, and glutathione synthase and sensitized RPE cells to oxidative damage. Using Cre/LoxP system, we generated a mouse line that lacks XBP1 only in RPE cells. Compared to wildtype littermates, RPE-XBP1 KO mice expressed less SOD1, SOD2, and catalase in the RPE, and had increased oxidative stress. At age 3 months and older, these mice exhibited apoptosis of RPE cells, decreased number of cone photoreceptors, shortened photoreceptor outer segment, reduced ONL thickness, and deficit in retinal function. Electron microscopy showed abnormal ultrastructure, Bruch's membrane thickening, and disrupted basal membrane infolding in XBP1-deficient RPE. These results indicate that XBP1 is an important gene involved in regulation of the anti-oxidant defense in the RPE, and that impaired activation of XBP1 may contribute to RPE dysfunction and cell death during retinal degeneration and AMD

Laminar shear stress modulates the activity of heterologously expressed P2X4 receptors

AbstractP2X4 receptors are involved in mechanotransduction processes, but it is unknown whether or not P2X4 receptors form mechanosensitive ion channels. This study questioned, whether laminar shear stress (LSS) can modulate P2X4 receptor activity. Mouse P2X4 receptor was cloned and heterologously expressed in Xenopus laevis oocytes. In two-electrode-voltage-clamp experiments the application of ATP (100μM) produced a transient inward current that was decreased by about 50% upon a second ATP application, corresponding to the desensitization behavior of P2X4 receptors. In P2X4 expressing oocytes LSS (shear forces of ~5.1dynes/cm2) did not produce any effect. However, LSS modulated the response of P2X4 to ATP. With LSS (~5.1dynes/cm2) the desensitization of the current due to the second ATP application was diminished. Ivermectin (IVM), a compound which stabilizes the open state of P2X4 receptors, mimicked the effect of LSS (~5.1dynes/cm2), since there was no additional effect of LSS after pre-incubation with IVM detected. This indicates that LSS like IVM stabilizes the open state of the receptor, although the particular mechanism remains unknown. These data demonstrate that LSS modulates the activity of P2X4 receptors by eliminating the desensitization of the receptors in response to ATP probably by stabilizing the open state of the channel