Keystone predation and molecules of keystone significance.

Keystone species structure ecological communities and are major determinants of biodiversity. A synthesis of research on keystone species is nonetheless missing a critical component - the sensory mechanisms for behavioral interactions that determine population- and community-wide attributes. Here, we establish the chemosensory basis for keystone predation by sea stars (Pisaster ochraceus) on mussels. This consumer-resource interaction is prototypic of top-down driven trophic cascades. Each mussel species (Mytilus californianus and M. galloprovincialis) secretes a glycoprotein orthologue (29.6 and 28.1 kDa, respectively) that acts, singularly, to evoke the sea star predatory response. The orthologues (named "KEYSTONEin") are localized in the epidermis, extrapallial fluid, and organic shell coating (periostracum) of live, intact mussels. Thus, KEYSTONEin contacts chemosensory receptors on tube feet as sea stars crawl over rocky surfaces in search of prey. The complete nucleotide sequences reveal that KEYSTONEin shares 87% (M. californianus) or 98% (M. galloprovincialis) homology with a calcium-binding protein in the shell matrix of a closely related congener, M. edulis. All three molecules cluster tightly within the Complement Component 1 Domain Containing (C1qDC) protein family; each exhibits a large globular domain, low complexity region(s), coiled coil, and at least four of five histidine-aspartic acid tandem motifs. Collective results support the hypothesis that KEYSTONEin evolved ancestrally in immunological, and later, in biomineralization roles. More recently, the substance has become exploited by sea stars as a contact cue for prey recognition. As the first identified compound to evoke keystone predation, KEYSTONEin provides valuable sensory information, promotes biodiversity, and shapes community structure and function. Without this molecule, there would be no predation by sea stars on mussels.

A multifunctional chemical cue drives opposing demographic processes and structures ecological communities.

Foundation species provide critical resources to ecological community members and are key determinants of biodiversity. The barnacle Balanus glandula is one such species and dominates space among the higher reaches of wave-swept shores (Northeastern Pacific Ocean). This animal produces a cuticular glycoprotein (named "MULTIFUNCin") of 199.6 kDa, and following secretion, a 390 kDa homodimer in native form. From field and lab experiments, we found that MULTIFUNCin significantly induces habitat selection by conspecific larvae, while simultaneously acting as a potent feeding stimulant to a major barnacle predator (whelk, Acanthinucella spirata). Promoting immigration via settlement on the one hand, and death via predation on the other, MULTIFUNCin drives opposing demographic processes toward structuring predator and prey populations. As shown here, a single compound is not restricted to a lone species interaction or sole ecological function. Complex biotic interactions therefore can be shaped by simple chemosensory systems and depend on the multifunctional properties of select bioactive proteins.

Integrating Therapeutic Ultrasound With Nanosized Drug Delivery Systems in the Battle Against Cancer.

Controlled, localized, and timely activation of nanosized drug delivery systems (NSDDSs), using an external stimulus such as therapeutic ultrasound (TUS), can improve the efficacy of cancer treatments compared to either conventional chemotherapy methods or passive NSDDSs alone. Specifically, TUS induces thermal and mechanical effects that trigger drug release from NSDDSs and overcomes drug delivery barriers in tumor microenvironments to allow nanoparticle drug carriers to penetrate more deeply into tumor tissue while minimizing side effects. This review highlights recent advancements, contemplates future prospects, and addresses challenges in using TUS-mediated NSDDSs for cancer treatment, encompassing preclinical and clinical applications.

Effect of Human Umbilical Cord Perivascular Cell-Conditioned Media in an Adult Zebrafish Model of Traumatic Brain Injury.

The pathophysiological events of secondary brain injury contribute to poor outcome after traumatic brain injury (TBI). The neuroprotective effects of mesenchymal cells have been extensively studied and evidence suggests that their effects are mostly mediated through paracrine effects. Human umbilical cord perivascular cells (HUCPVCs) are mesenchymal stem cells with potential therapeutic value in TBI. In this study, we assessed the effect of HUCPVC-conditioned media (CM) in an established adult zebrafish model of TBI induced by pulsed high-intensity focused ultrasound (pHIFU). This model demonstrates similarities to mammalian outcome after TBI. Administration of HUCPVC-CM 1 h postinjury (hpi) resulted in improved outcome after pHIFU-induced TBI. Western blot and immunohistochemistry results demonstrated that the HUCPVC-CM reduced (p < 0.05) reactive astrogliosis at 24 hpi. Moreover, at 24 hpi, the HUCPVC-CM treatment resulted in reduced apoptosis in HUCPVC-CM-treated zebrafish. Behavioral analysis demonstrated improvement in locomotor activity (p < 0.05) and anxiety (p < 0.05) at 6 and 24 hpi following HUCPVC-CM treatment. Overall, HUCPVC-CM treatment improved acute outcome measures in pHIFU-injured zebrafish. Collectively, the data demonstrate a cell-free treatment approach for traumatic brain injuries.

Chemical Ecology of Wave-Swept Shores: the Primacy of Contact Cues in Predation by Whelks.

Wave-swept shores are valuable for developing and testing key ecological principles. A synthesis of research is nonetheless missing a critical component: the chemosensory basis for behavioral interactions that determine population- and community-wide attributes. Chemical signaling environments on wave-swept shores, given their intense, turbulent mixing and complex topographies, would be difficult or impossible to simulate in a laboratory setting. For this reason, appropriately scaled field studies are needed to advance understanding of chemical stimuli and their biotic effects. Here, we performed a field investigation to establish the relative roles of dissolved and contact cues in predation by whelks (Acanthinucella spirata) on barnacles (Balanus glandula), their preferred prey. Experiments tested responses of whelks to seawater drawn above dense prey patches (10,240-12,180 barnacles m-2) and also over adjacent sand flats (no prey present). There was no evidence of waterborne stimuli associated with prey, even when sea states were nearly tranquil. Field trials also tested faux prey, which were constructed from cleaned barnacle shells and flavored gels. Prospective contact cues were presented to whelks at concentrations typical of epidermal tissue and cuticle in live, intact barnacles. These compounds were highly effective inducers of attack behavior and feeding. Selective enzyme degradations showed that the bioactive material was proteinaceous. Moreover, whelks did not distinguish faux barnacles with a single, purified glycoprotein (named "MULTIFUNCin") from live counterparts. Combined field results thus demonstrate the importance of contact cues, and indicate little, if any, effect of waterborne cues on predation by whelks under native conditions. Our findings underscore the need for appropriately scaled field experiments, and highlight surface chemistry as a critical factor that drives trophic interactions on rocky, wave-swept shores.

MULTIFUNCin: A Multifunctional Protein Cue Induces Habitat Selection by, and Predation on, Barnacles.

Foundation species provide critical resources to ecological community members and are major determinants of biodiversity. The barnacle Balanus glandula is one such species and dominates space among the higher reaches on wave-swept shores. Here, we show that B. glandula produces a 199.6-kDa glycoprotein (named "MULTIFUNCin"), and following secretion, a 390-kDa homodimer in its native state. MULTIFUNCin expression is localized in the epidermis, cuticle, and new shell material. Consequently, this molecule can specify upon contact the immediate presence of a live barnacle. Shared, conserved domains place MULTIFUNCin in the α2-macroglobulin (A2M) subgroup of the thioester-containing protein family. Although previously undescribed, MULTIFUNCin shares 78% nucleotide sequence homology with a settlement-inducing pheromone (SIP) of the barnacle, Amphibalanus amphitrite Based on this and further evidence, we propose that the two proteins are orthologues and evolved ancestrally in structural and immunological roles. More recently, they became exploited as chemical cues for con- and heterospecific organisms, alike. MULTIFUNCin and SIP both induce habitat selection (settlement) by conspecific barnacle larvae. In addition, MULTIFUNCin acts as a potent feeding stimulant to major barnacle predators (sea stars and several whelk species). Promoting immigration via settlement on the one hand, and death via predation on the other, MULTIFUNCin simultaneously mediates opposing demographic processes toward structuring both predator and prey populations. As a multifunctional protein cue, MULTIFUNCin provides valuable sensory information, conveys different messages to different species, and drives complex biotic interactions.

Quantification of the specific membrane capacitance of single cells using a microfluidic device and impedance spectroscopy measurement.

The specific membrane capacitance (SMC) is an electrical parameter that correlates with both the electrical activity and morphology of the plasma membrane, which are physiological markers for cellular phenotype and health. We have developed a microfluidic device that enables impedance spectroscopy measurements of the SMC of single biological cells. Impedance spectra induced by single cells aspirated into the device are captured over a moderate frequency range (5 kHz-1 MHz). Maximum impedance sensitivity is achieved using a tapered microfluidic channel, which effectively routes electric fields across the cell membranes. The SMC is extracted by curve-fitting impedance spectra to an equivalent circuit model. From our measurement, acute myeloid leukemia (AML) cells are found to exhibit larger SMC values in hypertonic solutions as compared with those in isotonic solutions. In addition, AML cell phenotypes (AML2 and NB4) exhibiting varying metastatic potential yield distinct SMC values (AML2: 16.9 ± 1.9 mF/m(2) (n = 23); NB4: 22.5 ± 4.7 mF/m(2) (n = 23)). Three-dimensional finite element simulations of the microfluidic device confirm the feasibility of this approach.

Electronic detection of dielectrophoretic forces exerted on particles flowing over interdigitated electrodes.

Dielectric particles flowing through a microfluidic channel over a set of coplanar electrodes can be simultaneously capacitively detected and dielectrophoretically (DEP) actuated when the high (1.45 GHz) and low (100 kHz-20 MHz) frequency electromagnetic fields are concurrently applied through the same set of electrodes. Assuming a simple model in which the only forces acting upon the particles are apparent gravity, hydrodynamic lift, DEP force, and fluid drag, actuated particle trajectories can be obtained as numerical solutions of the equations of motion. Numerically calculated changes of particle elevations resulting from the actuation simulated in this way agree with the corresponding elevation changes estimated from the electronic signatures generated by the experimentally actuated particles. This verifies the model and confirms the correlation between the DEP force and the electronic signature profile. It follows that the electronic signatures can be used to quantify the actuation that the dielectric particle experiences as it traverses the electrode region. Using this principle, particles with different dielectric properties can be effectively identified based exclusively on their signature profile. This approach was used to differentiate viable from non-viable yeast cells (Saccharomyces cerevisiae).

Dielectric response of particles in flowing media: the effect of shear-induced rotation on the variation in particle polarizability.

When particles in liquid suspensions flow through channels and pipes in a laminar fashion, the resulting parabolic velocity profile gives rise to shear, which induces the particles to rotate. If flowing suspensions containing dielectric particles are immersed in an external electric field, the anisotropic polarization induced in rotating nonspherical particles will vary with the orientation of the particle with respect to the external field; what results is an uncertainty in experimental measurements that involve particle polarization. The present study establishes the limits of this uncertainty and shows that departure from spherical symmetry in individual particles can lead to a significant overlap in measurements attempting to discriminate between particle subpopulations in suspensions. For example, the uncertainty in signal amplitude for a population of activated T-lymphocytes can be as high as 20%. Such concerns arise in applications like field-flow fractionation, dielectrophoretic sorting of particles, flow impedance measurements and cytometry, and, most recently, isodielectric separation, all of which are used to separate particles in a flow based on their dielectric response. This paper considers axisymmetric particles as the first departure from the approximation of spherical symmetry, shows how to calculate an estimate of the size of the population overlap, and suggests possible strategies to minimize it.

Subtidal benthic heterogeneity: flow environment modification and impacts on marine algal community structure and morphology.

The shallow subtidal zone of rocky coastlines is a highly dynamic environment characterized by micro- and macroscopic benthic structures that alter the ambient flow environment, creating "flow microhabitats." We examined the impact of macroscopic benthic structure on the maximum flow speeds and the corresponding macroalgal community cover and morphological diversity observed in response to microhabitats in both exposed and sheltered near-shore sites. Flow speeds were reduced by a factor of 2 within crevices and also in the flow-shadow of protruding rock substrate when compared to neighboring unobstructed planar microhabitats. Algal communities within crevices and in the wake of protrusions were found to have greater cover of foliose red algal species compared to horizontal microhabitats in exposed sites, but reduced cover of these species in sheltered sites. The morphologies of two rhodophytes common to all microhabitats, Chondracanthus spinosus and Pterocladiella capillacea, were examined at both exposed and sheltered sites. Exposed horizontal morphotypes of both species were generally smaller and streamlined, whereas thalli from within crevices and in the wake of protrusions were larger and bushier. We conclude that algal cover and morphology is affected by the alteration in flow around both protruding bodies and crevices when compared to unobstructed sites.

A microwave interferometric system for simultaneous actuation and detection of single biological cells.

In biomedical applications ranging from the study of pathogen invasion to drug efficacy assays, there is a growing need to develop minimally invasive techniques for single-cell analysis. This has inspired researchers to develop optical, electrical, microelectromechanical and microfluidic devices for exploring phenomena at the single-cell level. In this work, we demonstrate an electrical approach for single-cell analysis wherein a 1.6 GHz microwave interferometer detects the capacitance changes (DeltaC) produced by single cells flowing past a coplanar interdigitated electrode pair. The experimental and simulated capacitance changes generated by yeast cells are in close agreement. By using the capacitance changes of uniform polystyrene spheres (diameter = 5.7 microm) for calibration purposes, we demonstrate a 0.65 aF sensitivity in a 10 ms response time. Using an RC circuit, a low frequency sinusoidal potential is simultaneously superimposed on the electrode pair to generate a dielectrophoretic force that translates cells. Specifically, when yeast cells suspended in a solution of 90 ppm NaCl in deionized water are exposed to 10 kHz and 3 MHz potentials (ranging from 1-3 V(pp)), they experience negative and positive dielectrophoresis, respectively. The corresponding changes in cell elevation above the interdigitated electrodes are detected using the asymmetry of the capacitance signature produced by the cell. Cell elevation changes can be detected in less than 80 ms. The minimum detectable change in elevation is estimated to be 0.22 microm. This approach will have applications in rapid single-cell dielectrophoretic analysis, and may also prove useful in conjunction with impedance spectroscopy.

Effect of the finite extinction ratio of an electro-optic modulator on the performance of distributed probe-pump Brillouin sensor systems.

The effect of the finite extinction ratio of an electro-optic modulator (EOM) on the Brillouin frequency measurement of a distributed Brillouin-based fiber optic sensor is studied. An EOM with a finite extinction ratio limits the application of Brillouin optical time domain analysis in a distributed Brillouin-based fiber optic sensor. This results in confusion in specifying the location of the strained region and in error in detecting the Brillouin frequency and hence in strain and temperature measurement.

Distributed brillouin scattering sensor for discrimination of wall-thinning defects in steel pipe under internal pressure.

A distributed Brillouin scattering sensor has been employed to identify several inner wall cutouts in an end-capped steel pipe by measuring the axial and hoop strain distributions along the outer surface of the pipe. The locations of structural indentations that constitute 50-60% of the inner pipe wall are found and distinguished by use of their corresponding strain-pressure data. These results are quantified in terms of the fiber orientation, defect size and depth, and behavior relative to those of unperturbed pipe sections.