A brief elevation of serum amyloid A is sufficient to increase atherosclerosis

Serum amyloid A (SAA) has a number of proatherogenic effects including induction of vascular proteoglycans. Chronically elevated SAA was recently shown to increase atherosclerosis in mice. The purpose of this study was to determine whether a brief increase in SAA similarly increased atherosclerosis in a murine model. The recombination activating gene 1-deficient (rag1^−/−) × apolipoprotein E-deficient (apoe^−/−) and apoe^−/− male mice were injected, multiple times or just once respectively, with an adenoviral vector encoding human SAA1 (ad-SAA); the injected mice and controls were maintained on chow for 12–16 weeks. Mice receiving multiple injections of ad-SAA, in which SAA elevation was sustained, had increased atherosclerosis compared with controls. Strikingly, mice receiving only a single injection of ad-SAA, in which SAA was only briefly elevated, also had increased atherosclerosis compared with controls. Using in vitro studies, we demonstrate that SAA treatment leads to increased LDL retention, and that prevention of transforming growth factor beta (TGF-β) signaling prevents SAA-induced increases in LDL retention and SAA-induced increases in vascular biglycan content. We propose that SAA increases atherosclerosis development via induction of TGF-β, increased vascular biglycan content, and increased LDL retention. These data suggest that even short-term inflammation with concomitant increase in SAA may increase the risk of developing CVD.     

Behavioral “bycatch” from camera trap surveys yields insights on prey responses to human‐mediated predation risk

Human disturbance directly affects animal populations and communities, but indirect effects of disturbance on species behaviors are less well understood. For instance, disturbance may alter predator activity and cause knock‐on effects to predator‐sensitive foraging in prey. Camera traps provide an emerging opportunity to investigate such disturbance‐mediated impacts to animal behaviors across multiple scales. We used camera trap data to test predictions about predator‐sensitive behavior in three ungulate species (caribou Rangifer tarandus; white‐tailed deer, Odocoileus virginianus; moose, Alces alces) across two western boreal forest landscapes varying in disturbance. We quantified behavior as the number of camera trap photos per detection event and tested its relationship to inferred human‐mediated predation risk between a landscape with greater industrial disturbance and predator activity and a “control” landscape with lower human and predator activity. We also assessed the finer‐scale influence on behavior of variation in predation risk (relative to habitat variation) across camera sites within the more disturbed landscape. We predicted that animals in areas with greater predation risk (e.g., more wolf activity, less cover) would travel faster past cameras and generate fewer photos per detection event, while animals in areas with less predation risk would linger (rest, forage, investigate), generating more photos per event. Our predictions were supported at the landscape‐level, as caribou and moose had more photos per event in the control landscape where disturbance‐mediated predation risk was lower. At a finer‐scale within the disturbed landscape, no prey species showed a significant behavioral response to wolf activity, but the number of photos per event decreased for white‐tailed deer with increasing line of sight (m) along seismic lines (i.e., decreasing visual cover), consistent with a predator‐sensitive response. The presence of juveniles was associated with shorter behavioral events for caribou and moose, suggesting greater predator sensitivity for females with calves. Only moose demonstrated a positive behavioral association (i.e., longer events) with vegetation productivity (16‐day NDVI), suggesting that for other species bottom‐up influences of forage availability were generally weaker than top‐down influences from predation risk. Behavioral insights can be gleaned from camera trap surveys and provide complementary information about animal responses to predation risk, and thus about the indirect impacts of human disturbances on predator–prey interactions.     

Measurement of Contractile Stress Generated by Cultured Rat Muscle on Silicon Cantilevers for Toxin Detection and Muscle Performance Enhancement

Background

To date, biological components have been incorporated into MEMS devices to create cell-based sensors and assays, motors and actuators, and pumps. Bio-MEMS technologies present a unique opportunity to study fundamental biological processes at a level unrealized with previous methods. The capability to miniaturize analytical systems enables researchers to perform multiple experiments in parallel and with a high degree of control over experimental variables for high-content screening applications.

Methodology/Principal Findings

We have demonstrated a biological microelectromechanical system (BioMEMS) based on silicon cantilevers and an AFM detection system for studying the physiology and kinetics of myotubes derived from embryonic rat skeletal muscle. It was shown that it is possible to interrogate and observe muscle behavior in real time, as well as selectively stimulate the contraction of myotubes with the device. Stress generation of the tissue was estimated using a modification of Stoney''s equation. Calculated stress values were in excellent agreement with previously published results for cultured myotubes, but not adult skeletal muscle. Other parameters such as time to peak tension (TPT), the time to half relaxation (½RT) were compared to the literature. It was observed that the myotubes grown on the BioMEMS device, while generating stress magnitudes comparable to those previously published, exhibited slower TPT and ½RT values. However, growth in an enhanced media increased these values. From these data it was concluded that the myotubes cultured on the cantilevers were of an embryonic phenotype. The system was also shown to be responsive to the application of a toxin, veratridine.

Conclusions/Significance

The device demonstrated here will provide a useful foundation for studying various aspects of muscle physiology and behavior in a controlled high-throughput manner as well as be useful for biosensor and drug discovery applications.     

Calcium plays a central role in the sensitization of TRPV3 channel to repetitive stimulations

Transient receptor potential channels are involved in sensing chemical and physical changes inside and outside of cells. TRPV3 is highly expressed in skin keratinocytes, where it forms a nonselective cation channel activated by hot temperatures in the innocuous and noxious range. The channel has also been implicated in flavor sensation in oral and nasal cavities as well as being a molecular target of some allergens and skin sensitizers. TRPV3 is unique in that its activity is sensitized upon repetitive stimulations. Here we investigated the role of calcium ions in the sensitization of TRPV3 to repetitive stimulations. We show that the sensitization is accompanied by a decrease of Ca(2+)-dependent channel inhibition mediated by calmodulin acting at an N-terminal site (amino acids 108-130) and by an acidic residue (Asp(641)) at the pore loop of TRPV3. These sites also contribute to the voltage dependence of TRPV3. During sensitization, the channel displayed a gradual shift of the voltage dependence to more negative potentials as well as uncoupling from voltage sensing. The initial response to ligand stimulation was increased and sensitization to repetitive stimulations was decreased by increasing the intracellular Ca(2+)-buffering strength, inhibiting calmodulin, or disrupting the calmodulin-binding site. Mutation of Asp(641) to Asn abolished the high affinity extracellular Ca(2+)-mediated inhibition and greatly facilitated the activation of TRPV3. We conclude that Ca(2+) inhibits TRPV3 from both the extracellular and intracellular sides. The inhibition is sequentially reduced, appearing as sensitization to repetitive stimulations.     

Efficient inhibition of germination of coat-deficient bacterial spores by multivalent metal cations, including terbium (Tb³+)

Release of dipicolinic acid (DPA) and its fluorescence with terbium (Tb(3+)) allow rapid measurement of the germination and viability of spores of Bacillus and Clostridium species. However, germination of coat-deficient Bacillus spores was strongly inhibited by Tb(3+) and some other multivalent cations. Tb(3+) also inhibited germination of coat-deficient Clostridium perfringens spores.