The pain matrix reloaded: a salience detection system for the body

Neuroimaging and neurophysiological studies have shown that nociceptive stimuli elia salience detection system for the bodycit responses in an extensive cortical network including somatosensory, insular and cingulate areas, as well as frontal and parietal areas. This network, often referred to as the "pain matrix", is viewed as representing the activity by which the intensity and unpleasantness of the perception elicited by a nociceptive stimulus are represented. However, recent experiments have reported (i) that pain intensity can be dissociated from the magnitude of responses in the "pain matrix", (ii) that the responses in the "pain matrix" are strongly influenced by the context within which the nociceptive stimuli appear, and (iii) that non-nociceptive stimuli can elicit cortical responses with a spatial configuration similar to that of the "pain matrix". For these reasons, we propose an alternative view of the functional significance of this cortical network, in which it reflects a system involved in detecting, orienting attention towards, and reacting to the occurrence of salient sensory events. This cortical network might represent a basic mechanism through which significant events for the body's integrity are detected, regardless of the sensory channel through which these events are conveyed. This function would involve the construction of a multimodal cortical representation of the body and nearby space. Under the assumption that this network acts as a defensive system signaling potentially damaging threats for the body, emphasis is no longer on the quality of the sensation elicited by noxious stimuli but on the action prompted by the occurrence of potential threats

Light, the universe and everything – 12 Herculean tasks for quantum cowboys and black diamond skiers

The Winter Colloquium on the Physics of Quantum Electronics (PQE) has been a seminal force in quantum optics and related areas since 1971. It is rather mind-boggling to recognize how the concepts presented at these conferences have transformed scientific understanding and human society. In January 2017, the participants of PQE were asked to consider the equally important prospects for the future, and to formulate a set of questions representing some of the greatest aspirations in this broad field. The result is this multi-authored paper, in which many of the world’s leading experts address the following fundamental questions: (1) What is the future of gravitational wave astronomy? (2) Are there new quantum phases of matter away from equilibrium that can be found and exploited – such as the time crystal? (3) Quantum theory in uncharted territory: What can we learn? (4) What are the ultimate limits for laser photon energies? (5) What are the ultimate limits to temporal, spatial and optical resolution? (6) What novel roles will atoms play in technology? (7) What applications lie ahead for nitrogen-vacancy centres in diamond? (8) What is the future of quantum coherence, squeezing and entanglement for enhanced super-resolution and sensing? (9) How can we solve (some of) humanity’s biggest problems through new quantum technologies? (10) What new understanding of materials and biological molecules will result from their dynamical characterization with free-electron lasers? (11) What new technologies and fundamental discoveries might quantum optics achieve by the end of this century? (12) What novel topological structures can be created and employed in quantum optics

New Technology and Techniques for Needle-Based Magnetic Resonance Image-Guided Prostate Focal Therapy

The most common diagnosis of prostate cancer is that of localized disease, and unfortunately the optimal type of treatment for these men is not yet certain. Magnetic resonance image (MRI)-guided focal laser ablation (FLA) therapy is a promising potential treatment option for select men with localized prostate cancer, and may result in fewer side effects than whole-gland therapies, while still achieving oncologic control. The objective of this thesis was to develop methods of accurately guiding needles to the prostate within the bore of a clinical MRI scanner for MRI-guided FLA therapy. To achieve this goal, a mechatronic needle guidance system was developed. The system enables precise targeting of prostate tumours through angulated trajectories and insertion of needles with the patient in the bore of a clinical MRI scanner. After confirming sufficient accuracy in phantoms, and good MRI-compatibility, the system was used to guide needles for MRI-guided FLA therapy in eight patients. Results from this case series demonstrated an improvement in needle guidance time and ease of needle delivery compared to conventional approaches. Methods of more reliable treatment planning were sought, leading to the development of a systematic treatment planning method, and Monte Carlo simulations of needle placement uncertainty. The result was an estimate of the maximum size of focal target that can be confidently ablated using the mechatronic needle guidance system, leading to better guidelines for patient eligibility. These results also quantified the benefit that could be gained with improved techniques for needle guidance

Antifungal Activity of Cationic Conjugated Polyelectrolytes and Oligomers against Candida albicans

Candida albicans is a human fungal commensal and an opportunistic pathogen. It is a polymorphic fungus that is able to invade host cells and disseminate through tissues. C. albicans also form biofilms on medical devices and mucosal surfaces, which aid in the development of drug resistance, tissue colonization and evasion of host immunity. Disseminated candidiasis is associated with high mortality rates, especially in immunocompromised hosts. Concern about resistance to current antifungal therapies has led to a push to develop novel, alternative treatments. In this study, we investigated the antifungal activities of two agents: PPE-DABCO, a poly(phenylene ethynylene) (PPE)-based cationic conjugated polyelectrolyte (CPE), and EO-OPE-1 (DABCO), an oligo-phenylene ethynylene (OPE). Both compounds generate singlet oxygen upon UV-irradiation. The effect of both compounds against C. albicans was tested in the dark and with photoactivation using light of the appropriate wavelength for each agent. We demonstrated that both compounds showed enhanced antifungal activity when irradiated with UV-light, reducing the viability of yeast in suspension. Activation of PPE-DABCO with the 405nm confocal laser was also able to significantly reduce the viability of C. albicans yeast and hyphal cells. Furthermore, by limiting the time of exposure to the 405nm laser to 20 minutes, we were able to isolate the effects of photoactivation of PPE-DABCO from effects due to phototoxicity, by assessing the subsequent hyphal growth. Neither dark nor light treatment with either compound was able to prevent the biofilm formation of surviving cells. This study provides evidence that PPE-DABCO and EO-DABCO act as potent antifungal agents upon photoactivation, and photoactivation is necessary to achieve full antifungal efficacy to reduce the viability of yeast and hyphae and prevent morphological transitioning

Optimization of two-photon excited fluorescence for volumetric imaging

Two-photon microscopy is often used in biological imaging due to its optical sectioning and depth penetration capabilities. These characteristics have made two-photon microscopy especially useful for neurobiological studies where imaging a volume at single cell resolution is typically required. This dissertation focuses on the optimization of two-photon excited fluorescence for volumetric imaging of biological samples, with special attention to imaging the mouse brain. Chapter 2 studies wavefront manipulation as a way of optimizing two-photon excited fluorescence. We show, through numerical simulations and experiments, that the magnitude of the two-photon fluorescence signal originating from cell-sized objects can be used as a metric of beam quality. We also show that the cranial window used in mouse experiment is a major source of aberrations, which can readily be represented in the Zernike basis. Finally, we implement a modal wavefront optimization scheme that optimizes the wavefront based entirely on the magnitude of the fluorescence. Along with this scheme, Zernike functions are found to be a useful basis for correcting aberrations encountered in mouse brain imaging while the Hadamard basis is found to be useful for scattering compensation. Corrections performed in mouse brain using Zernike functions are found to be valid over hundreds of microns, allowing a single correction to be applied to a whole volume. Finally, we show that the wavefront correction system can double as a wavefront encoding system for experiments that require custom point-spread-functions. Chapter 3 aims to significantly improve the volume imaging rate of two-photon microscopy. The imaging speed is improved by combining two-photon excitation with scanning confocally-aligned planar excitation microscopy (SCAPE). Numerical simulations, analytical arguments, and experiments reveal that the standard method of combining nano-joule pulses with 80 MHz repetition rates is inadequate for two-photon light-sheet excitation. We use numerical simulations and experiments to explore the possibility of achieving fast volumetric imaging using line and sheet excitation and find that the sheet excitation scheme is more promising. Given that two-photon excitation requires high photon-flux-densities near the focus, achieving high enough fluorescence has to be balanced with restrictions placed by saturation, photodamage, photobleaching and sample heating effects. Finally, we experimentally study light sheet excitation at various pulse repetition rates with femtosecond pulses and find that repetition rates near 100 kHz allow imaging of nonbiological samples of ~200x300x300 μm^3 volume at 20 volumes per second while balancing the above constraints. This work paves the way for achieving fast, volumetric two-photon imaging of the mouse brain

Intracellular delivery by membrane disruption: Mechanisms, strategies, and concepts

© 2018 American Chemical Society. Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, we review techniques for membrane disruption-based intracellular delivery from 1911 until the present. These methods achieve rapid, direct, and universal delivery of almost any cargo molecule or material that can be dispersed in solution. We start by covering the motivations for intracellular delivery and the challenges associated with the different cargo typesñYsmall molecules, proteins/peptides, nucleic acids, synthetic nanomaterials, and large cargo. The review then presents a broad comparison of delivery strategies followed by an analysis of membrane disruption mechanisms and the biology of the cell response. We cover mechanical, electrical, thermal, optical, and chemical strategies of membrane disruption with a particular emphasis on their applications and challenges to implementation. Throughout, we highlight specific mechanisms of membrane disruption and suggest areas in need of further experimentation. We hope the concepts discussed in our review inspire scientists and engineers with further ideas to improve intracellular delivery