Photon Shot Noise Limits on Optical Detection of Neuronal Spikes and Estimation of Spike Timing

AbstractOptical approaches for tracking neural dynamics are of widespread interest, but a theoretical framework quantifying the physical limits of these techniques has been lacking. We formulate such a framework by using signal detection and estimation theory to obtain physical bounds on the detection of neural spikes and the estimation of their occurrence times as set by photon counting statistics (shot noise). These bounds are succinctly expressed via a discriminability index that depends on the kinetics of the optical indicator and the relative fluxes of signal and background photons. This approach facilitates quantitative evaluations of different indicators, detector technologies, and data analyses. Our treatment also provides optimal filtering techniques for optical detection of spikes. We compare various types of Ca2+ indicators and show that background photons are a chief impediment to voltage sensing. Thus, voltage indicators that change color in response to membrane depolarization may offer a key advantage over those that change intensity. We also examine fluorescence resonance energy transfer indicators and identify the regimes in which the widely used ratiometric analysis of signals is substantially suboptimal. Overall, by showing how different optical factors interact to affect signal quality, our treatment offers a valuable guide to experimental design and provides measures of confidence to assess optically extracted traces of neural activity

First scattered light images of debris disks around HD 53143 and HD 139664

We present the first scattered light images of debris disks around a K star (HD 53143) and an F star (HD 139664) using the coronagraphic mode of the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST). With ages 0.3 - 1 Gyr, these are among the oldest optically detected debris disks. HD 53143, viewed ~45 degrees from edge-on, does not show radial variation in disk structure and has width >55 AU. HD 139664 is seen close to edge-on and has belt-like morphology with a dust peak 83 AU from the star and a distinct outer boundary at 109 AU. We discuss evidence for significant diversity in the radial architecture of debris disks that appears unconnected to stellar spectral type or age. HD 139664 and possibly the solar system belong in a category of narrow belts 20-30 AU wide. HD 53143 represents a class of wide disk architecture with characteristic width >50 AU.Comment: 7 pages, 3 figure

Development of a Sustainable Community‐Based Dental Education Program

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153534/1/jddj002203372011758tb05148x.pd

Influence of Community‐Based Dental Education on Dental Students’ Preparation and Intent to Treat Underserved Populations

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153622/1/jddj002203372012765tb05286x.pd

Anti-Salmonella lacatic acid bacteria from porcine intestinal sources

The aim of this study was to isolate lactic acid bacteria (LAB) with anti-Salmonella activity from the porcine gastrointestinal tract (GIT) and to characterise these for potentially probiotic properties using in vitro assays. Porcine caecal and faecal samples were screened for the presence of anti-Salmonella LAB; the ten most promising isolates belonged to the genera Lactobacillus and Pediococcus. The LAB exhibited large variation in their ability to survive in simulated gastric juice at pH 1.85. While Lactobacillus acidophilus species survived at up to 80% for 30 min, Lb. pentosus species declined to less than 0.001%. All isolates tolerated porcine bile at a concentration of 0.3%, with some capable of growth in the presence of up to 5% bile. The ability of the LAB isolates to prevent Salmonella invasion of intestinal epithelial cells varied, with reductions of 55% (Lb. acidophilus spp.) to 82% (Lb. salivarius spp.) observed. The data demonstrates that some porcine intestinal LAB isolates may offer potential as probiotics for the reduction of Salmonella carriage in pigs

The identification and neurochemical characterization of central neurons that target parasympathetic preganglionic neurons involved in the regulation of choroidal blood flow in the rat eye using pseudorabies virus, immunolabeling and conventional pathway tracing methods

The choroidal blood vessels of the eye provide the main vascular support to the outer retina. These blood vessels are under parasympathetic vasodilatory control via input from the pterygopalatine ganglion (PPG), which in turn receives its preganglionic input from the superior salivatory nucleus (SSN) of the hindbrain. The present study characterized the central neurons projecting to the SSN neurons innervating choroidal PPG neurons, using pathway tracing and immunolabeling. In the initial set of studies, minute injections of the Bartha strain of the retrograde transneuronal tracer pseudorabies virus (PRV) were made into choroid in rats in which the superior cervical ganglia had been excised (to prevent labeling of sympathetic circuitry). Diverse neuronal populations beyond the choroidal part of ipsilateral SSN showed transneuronal labeling, which notably included the parvocellular part of the paraventricular nucleus of the hypothalamus (PVN), the periaqueductal gray, the raphe magnus (RaM), the B3 region of the pons, A5, the nucleus of the solitary tract (NTS), the rostral ventrolateral medulla (RVLM), and the intermediate reticular nucleus of the medulla. The PRV+ neurons were located in the parts of these cell groups that are responsive to systemic blood pressure signals and involved in systemic blood pressure regulation by the sympathetic nervous system. In a second set of studies using PRV labeling, conventional pathway tracing, and immunolabeling, we found that PVN neurons projecting to SSN tended to be oxytocinergic and glutamatergic, RaM neurons projecting to SSN were serotonergic, and NTS neurons projecting to SSN were glutamatergic. Our results suggest that blood pressure and volume signals that drive sympathetic constriction of the systemic vasculature may also drive parasympathetic vasodilation of the choroidal vasculature, and may thereby contribute to choroidal baroregulation during low blood pressure

Application of Probiotic Bacteria to Functional Foods

End of Project ReportProbiotic cultures are described as live microbial feed supplements that improve intestinal microbial balance and are intended for maintenance of health or prevention, rather than the curing of disease. The demand for probiotic foods is increasing in Europe, Japan and the U.S. reflecting the heightened awareness among the public of the relationship between diet and health. Traditionally, the most popular food delivery systems for these cultures have been freshly fermented dairy foods, such as yogurts and fermented milks, as well as unfermented milks with cultures added. However, in the development of functional foods, the technological suitability of probiotic strains poses a serious challenge since their survival and viability may be adversely affected by processing conditions as well as by the product environment and storage conditions. This is a particular concern, given that high levels (at least 107 per gram or ml) of live micro-organisms are recommended for probiotic products. In previous studies (see DPRC No. 29) the successful manufacture of probiotic Cheddar cheese harbouring high levels (>108 cfu/g) of the probiotic Lactobacillus paracasei NFBC 338 strain was reported. Hence, the overall objective of these studies was to continue the development and evaluation of Functional Foods containing high levels of viable probiotic bacteria, with particular emphasis on overcoming the technological barriers and the identification of strains suited to particular applications, such as incorporation into Cheddar cheese and spray-dried powders.Department of Agriculture, Food and the Marin

Aspirin reduces lipopolysaccharide induced pulmonary inflammation in human models of ARDS

International audienc

Modeling the distributions of tegu lizards in native and potential invasive ranges

Invasive reptilian predators can have substantial impacts on native species and ecosystems. Tegu lizards are widely distributed in South America east of the Andes, and are popular in the international live animal trade. Two species are established in Florida (U.S.A.)-Salvator merianae (Argentine black and white tegu) and Tupinambis teguixin sensu lato (gold tegu)-and a third has been recorded there-S. rufescens (red tegu). We built species distribution models (SDMs) using 5 approaches (logistic regression, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy) based on data from the native ranges. We then projected these models to North America to develop hypotheses for potential tegu distributions. Our results suggest that much of the southern United States and northern México probably contains suitable habitat for one or more of these tegu species. Salvator rufescens had higher habitat suitability in semi-arid areas, whereas S. merianae and T. teguixin had higher habitat suitability in more mesic areas. We propose that Florida is not the only state where these taxa could become established, and that early detection and rapid response programs targeting tegu lizards in potentially suitable habitat elsewhere in North America could help prevent establishment and abate negative impacts on native ecosystems.Fil: Jarnevich, Catherine S.. U.s. Geological Survey; Estados UnidosFil: Hayes, Mark A.. Cherokee Nation Technologies; Estados UnidosFil: Fitzgerald, Lee A.. Department Of Wildlife And Fisheries Sciences; Estados UnidosFil: Yackel Adams, Amy A.. U.s. Geological Survey; Estados UnidosFil: Falk, Bryan G.. U.s. Geological Survey; Estados Unidos. National Park Service; Estados UnidosFil: Collier, Michelle A. M.. National Park Service; Estados Unidos. U.s. Geological Survey; Estados UnidosFil: Bonewell, Lea` R.. U.s. Geological Survey; Estados UnidosFil: Klug, Page E.. U.s. Geological Survey; Estados Unidos. U.S. Department of Agriculture APHIS, Wildlife Services, National Wildlife Research Center, North Dakota Field Station; Estados UnidosFil: Naretto, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; ArgentinaFil: Reed, Robert N.. U.s. Geological Survey; Estados Unido