Temperature-dependent differences between readily releasable and reserve pool vesicles in chromaffin cells

AbstractStatistical differences between amperometric traces recorded from chromaffin cells using K+ and Ba2+ secretagogues support the assertion that readily releasable pool (RRP) and reserve pool (RP) vesicles can be probed with pool-specific secretagogues. Release from the RRP was evoked by K+ while release from the RP was evoked by Ba2+. Similar temperature-dependent changes in spike area and half-width for both pools suggest that the content of RRP and RP vesicles is similar and packaged in the same way. Differences between the vesicle pools were revealed in the temperature dependence of spike frequency. While the burst spike frequency of the RRP, which is comprised of pre-docked and primed vesicles, increased 2.8% per °C, the RP spike frequency increased 12% per °C. This difference is attributed to a temperature-dependent mobilization of the RP. Furthermore, the RP exhibited more foot events at room temperature than the RRP but this difference was not apparent at 37 °C. This trend suggests that RP vesicle membranes have a compromised surface tension compared to RRP vesicles. Collectively, the changes of release characteristics with temperature reveal distinctions between the RRP and the RP

Vesicular Ca2+-induced secretion promoted by intracellular pH-gradient disruption

The actions of the protonophore CCCP on intracellular Ca2+ regulation and exocytosis in chromaffin cells have been examined. Simultaneous fura-2 imaging and amperometry reveal that exposure to CCCP not only perturbs mitochondrial function but that it also alters vesicular storage of Ca2+ and catecholamines. By disrupting the pH gradient of the secretory vesicle membrane, the protonophore allows both Ca2+ and catecholamine to leak into the cytosol. Unlike the high cytosolic Ca2+ concentrations resulting from mitochondrial membrane disruption, Ca2+ leakage from secretory vesicles may initiate exocytotic release. In conjunction with previous studies, this work reveals that catalytic and self-sustained vesicular Ca2+-induced exocytosis occurs with extended exposure to weak acid or base protonophores

Exploring inflammatory disease drug effects on neutrophil function

Combined use of a novel platform and traditional approaches yield new insight into drug effects on neutrophil function

Influence of the Spatial Distribution of Cationic Functional Groups at Nanoparticle Surfaces on Bacterial Viability and Membrane Interactions

While positively charged nanomaterials induce cytotoxicity in many organisms, much less is known about how the spatial distribution and presentation of molecular surface charge impact nanoparticle–biological interactions. We systematically functionalized diamond nanoparticle surfaces with five different cationic surface molecules having different molecular structures and conformations, including four small ligands and one polymer, and we then probed the molecular-level interaction between these nanoparticles and bacterial cells. Shewanella oneidensis MR-1 was used as a model bacterial cell system to investigate how the molecular length and conformation of cationic surface charges influence their interactions with the Gram-negative bacterial membranes. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) demonstrate the covalent modification of the nanoparticle surface with the desired cationic organic monolayers. Surprisingly, bacterial growth-based viability (GBV) and membrane damage assays both show only minimal biological impact by the NPs functionalized with short cationic ligands within the concentration range tested, yet NPs covalently linked to a cationic polymer induce strong cytotoxicity, including reduced cellular viability and significant membrane damage at the same concentration of cationic groups. Transmission electron microscopy (TEM) images of these NP-exposed bacterial cells show that NPs functionalized with cationic polymers induce significant membrane distortion and the production of outer membrane vesicle-like features, while NPs bearing short cationic ligands only exhibit weak membrane association. Our results demonstrate that the spatial distribution of molecular charge plays a key role in controlling the interaction of cationic nanoparticles with bacterial cell membranes and the subsequent biological impact. Nanoparticles functionalized with ligands having different lengths and conformations can have large differences in interactions even while having nearly identical zeta potentials. While the zeta potential is a convenient and commonly used measure of nanoparticle charge, it does not capture essential differences in molecular-level nanoparticle properties that control their biological impact

Nanoscale battery cathode materials induce DNA damage in bacteria

The increasing use of nanoscale lithium nickel manganese cobalt oxide (LixNiyMnzCo1−y−zO2, NMC) as a cathode material in lithium-ion batteries poses risk to the environment. Learning toxicity mechanisms on molecular levels is critical to promote proactive risk assessment of these complex nanomaterials and inform their sustainable development. We focused on DNA damage as a toxicity mechanism and profiled in depth chemical and biological changes linked to DNA damage in two environmentally relevant bacteria upon nano-NMC exposure. DNA damage occurred in both bacteria, characterized by double-strand breakage and increased levels of many putative chemical modifications on bacterial DNA bases related to direct oxidative stress and lipid peroxidation, measured by cutting-edge DNA adductomic techniques. Chemical probes indicated elevated intracellular reactive oxygen species and transition metal ions, in agreement with DNA adductomics and gene expression analysis. By integrating multi-dimensional datasets from chemical and biological measurements, we present rich mechanistic insights on nano-NMC-induced DNA damage in bacteria, providing targets for biomarkers in the risk assessment of reactive materials that may be extrapolated to other nano–bio interactions

Chronic Exposure to Complex Metal Oxide Nanoparticles Elicits Rapid Resistance in Shewanella Oneidensis MR-1

Engineered nanoparticles are incorporated into numerous emerging technologies because of their unique physical and chemical properties. Many of these properties facilitate novel interactions, including both intentional and accidental effects on biological systems. Silver-containing particles are widely used as antimicrobial agents and recent evidence indicates that bacteria rapidly become resistant to these nanoparticles. Much less studied is the chronic exposure of bacteria to particles that were not designed to interact with microorganisms. For example, previous work has demonstrated that the lithium intercalated battery cathode nanosheet, nickel manganese cobalt oxide (NMC), is cytotoxic and causes a significant delay in growth of Shewanella oneidensis MR-1 upon acute exposure. Here, we report that S. oneidensis MR-1 rapidly adapts to chronic NMC exposure and is subsequently able to survive in much higher concentrations of these particles, providing the first evidence of permanent bacterial resistance following exposure to nanoparticles that were not intended as antibacterial agents. We also found that when NMC-adapted bacteria were subjected to only the metal ions released from this material, their specific growth rates were higher than when exposed to the nanoparticle. As such, we provide here the first demonstration of bacterial resistance to complex metal oxide nanoparticles with an adaptation mechanism that cannot be fully explained by multi-metal adaptation. Importantly, this adaptation persists even after the organism has been grown in pristine media for multiple generations, indicating that S. oneidensis MR-1 has developed permanent resistance to NMC

Recommendations for Nanomedicine Human Subjects Research Oversight: An Evolutionary Approach for an Emerging Field

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96363/1/j.1748-720X.2012.00703.x.pd

Present and Future of Surface-Enhanced Raman Scattering.

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article