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Bernhard J Müller, Günter Mistlberger, Ingo Klimant
In this contribution, we present new insights and a critical discussion in the optical detection of saxitoxin using fluorophores with crown ethers. Fluorescence enhancement is caused by the reduction of photoinduced electron transfer upon complexation with the analyte. Our attempts to improve this detection method neither did yield a functioning sensor nor were the attempts to reproduce published data in this area successful. Due to the fact that only low concentrations of saxitoxin are available, multiple surrogates were investigated at high concentrations...
2018: Monatshefte Für Chemie
Christian C Petersen, Ralph E Mistlberger
The mechanisms that enable mammals to time events that recur at 24-h intervals (circadian timing) and at arbitrary intervals in the seconds-to-minutes range (interval timing) are thought to be distinct at the computational and neurobiological levels. Recent evidence that disruption of circadian rhythmicity by constant light (LL) abolishes interval timing in mice challenges this assumption and suggests a critical role for circadian clocks in short interval timing. We sought to confirm and extend this finding by examining interval timing in rats in which circadian rhythmicity was disrupted by long-term exposure to LL or by chronic intake of 25% D2O...
June 1, 2017: Journal of Biological Rhythms
Brianne A Kent, Ralph E Mistlberger
Alzheimer's disease (AD) is the most common cause of dementia and currently there are no effective disease-modifying treatments available. Hallmark symptoms of AD include impaired hippocampus-dependent episodic memory and disrupted sleep and circadian rhythms. The pathways connecting these symptoms are of particular interest because it is well established that sleep and circadian disruption can impair hippocampus-dependent learning and memory. In rodents, these procedures also markedly suppress adult hippocampal neurogenesis, a form of brain plasticity that is believed to play an important role in pattern separation, and thus episodic memory...
April 2017: Frontiers in Neuroendocrinology
Denise M Weisgerber, Maria Nikol, Ralph E Mistlberger
Sleep deprivation (SD) impairs vigilance and increases the risk of driving accidents during the commute home after night work. Bright light (BL) can enhance alertness and cognitive performance. We examined the effects of BL (5600 lux) versus dim light (DL, 35 lux) at the end of a night awake on driving performance. METHODS: Subjects (N = 19, 22.8 ± 4 ya) completed three conditions, counterbalanced for order at >1 week intervals. The two overnight SD conditions began in the lab at usual bedtime...
February 2017: Sleep Medicine
J M Henn, B Mistlberger
We compute the three-loop four-gluon scattering amplitude in maximally supersymmetric Yang-Mills theory, including its full color dependence. Our result is the first complete computation of a nonplanar four-particle scattering amplitude to three loops in four-dimensional gauge theory and consequently provides highly nontrivial data for the study of nonplanar scattering amplitudes. We present the amplitude as a Laurent expansion in the dimensional regulator to finite order, with coefficients composed of harmonic polylogarithms of uniform transcendental weight, and simple rational prefactors...
October 21, 2016: Physical Review Letters
Emily Cole, Ralph E Mistlberger, Devon Merza, Lianne J Trigiani, Dan Madularu, Amanda Simundic, Dave G Mumby
Circadian time-place learning (TPL) is the ability to remember both the place and biological time of day that a significant event occurred (e.g., food availability). This ability requires that a circadian clock provide phase information (a time tag) to cognitive systems involved in linking representations of an event with spatial reference memory. To date, it is unclear which neuronal substrates are critical in this process, but one candidate structure is the hippocampus (HPC). The HPC is essential for normal performance on tasks that require allocentric spatial memory and exhibits circadian rhythms of gene expression that are sensitive to meal timing...
December 2016: Neurobiology of Learning and Memory
Amy L Hall, Andrea N Smit, Ralph E Mistlberger, Glenn J Landry, Mieke Koehoorn
INTRODUCTION: Shift work is a common working arrangement with wide-ranging implications for worker health. Organisational determinants of shift work practices are not well characterised; such information could be used to guide evidence-based research and best practices to mitigate shift work's negative effects. This exploratory study aimed to describe and assess organisational-level determinants of shift work practices thought to affect health, across a range of industry sectors. METHODS: Data on organisational characteristics, shift work scheduling, provision of shift work education materials/training to employees and night-time lighting policies in the workplace were collected during phone interviews with organisations across the Canadian province of British Columbia...
January 2017: Occupational and Environmental Medicine
T Dattolo, C P Coomans, H C van Diepen, D F Patton, S Power, M C Antle, J H Meijer, R E Mistlberger
Circadian rhythms in mammals are regulated by a system of circadian oscillators that includes a light-entrainable pacemaker in the suprachiasmatic nucleus (SCN) and food-entrainable oscillators (FEOs) elsewhere in the brain and body. In nocturnal rodents, the SCN promotes sleep in the day and wake at night, while FEOs promote an active state in anticipation of a predictable daily meal. For nocturnal animals to anticipate a daytime meal, wake-promoting signals from FEOs must compete with sleep-promoting signals from the SCN pacemaker...
February 19, 2016: Neuroscience
Charalampos Anastasiou, Claude Duhr, Falko Dulat, Franz Herzog, Bernhard Mistlberger
We present the cross section for the production of a Higgs boson at hadron colliders at next-to-next-to-next-to-leading order (N^{3}LO) in perturbative QCD. The calculation is based on a method to perform a series expansion of the partonic cross section around the threshold limit to an arbitrary order. We perform this expansion to sufficiently high order to obtain the value of the hadronic cross at N^{3}LO in the large top-mass limit. For renormalization and factorization scales equal to half the Higgs boson mass, the N^{3}LO corrections are of the order of +2...
May 29, 2015: Physical Review Letters
Mateusz Michalik, Andrew D Steele, Ralph E Mistlberger
Restricted daily feeding schedules induce circadian rhythms of food-anticipatory activity (FAA) in mice and other species. The entrainment pathway(s) and location(s) of circadian oscillators driving these rhythms have not been definitively established. An important role for dopamine signaling and the dorsal striatum is suggested by a confluence of observations, including shifting of FAA rhythms by dopamine receptor agonists and attenuation by antagonists and D1 receptor knockout (D1R KO). The dopamine reward system exhibits sexual dimorphisms in structure and function; if FAA rhythms are regulated by this system, then FAA may also be sexually dimorphic...
June 2015: Behavioral Neuroscience
Hanna Opiol, Ilya Pavlovski, Mateusz Michalik, Ralph E Mistlberger
Rats readily learn to anticipate a reward signaled by an external stimulus. Anticipatory behaviors evoked by conditioned stimuli include 50 kHz ultrasonic vocalizations (USVs), a proposed behavioral correlate of positive affect and activation of midbrain dopamine pathways. Rats can also anticipate a reward, such as food, provided once daily, without external cueing. Anticipation of a daily reward exhibits formal properties of a circadian rhythm. The neural circuits that regulate the timing and amplitude of these rhythms remain an open question, but evidence suggests a role for dopamine...
May 1, 2015: Behavioural Brain Research
Andrew D Steele, Ralph E Mistlberger
Dopamine neurons in the midbrain have a central role in generating cycles of biological activity with periods as short as 4 hours and as long as 100 hours.
2015: ELife
Danica F Patton, Angela M Katsuyama, Ilya Pavlovski, Mateusz Michalik, Zachary Patterson, Maksim Parfyonov, Andrea N Smit, Elliott G Marchant, Seung Hwan Chung, John Chung, Alfonso Abizaid, Kai-Florian Storch, Horacio de la Iglesia, Ralph E Mistlberger
Circadian clocks in many brain regions and peripheral tissues are entrained by the daily rhythm of food intake. Clocks in one or more of these locations generate a daily rhythm of locomotor activity that anticipates a regular mealtime. Rats and mice can also anticipate two daily meals. Whether this involves 1 or 2 circadian clocks is unknown. To gain insight into how the circadian system adjusts to 2 daily mealtimes, male rats in a 12∶12 light-dark cycle were fed a 2 h meal either 4 h after lights-on or 4 h after lights-off, or a 1 h meal at both times...
2014: PloS One
G Mistlberger, M Pawlak, E Bakker, I Klimant
We introduce here a dynamic optode for buffer capacity sensing based on photochromic spiropyran (Sp). It represents the first reversible optical sensor for buffer capacity. Sensing was possible using a non-equilibrium readout mode, a novelty for photoswitchable optical ion sensors. In addition to the buffer capacity, the final point of each measurement sequence provides the pH of the solution.
March 11, 2015: Chemical Communications: Chem Comm
Christian C Petersen, Danica F Patton, Maksim Parfyonov, Ralph E Mistlberger
Rats can anticipate a daily feeding time. This has been interpreted as a rhythm controlled by food-entrainable circadian oscillators, because the rhythm persists during several cycles of total food deprivation and fails to track mealtimes if the feeding schedule deviates substantially from 24. These and other properties distinguish anticipation of daily meals from anticipation of food rewards provided at intervals in the seconds-to-minutes range, suggesting distinct mechanisms. It has been reported that rats can anticipate meals at long, but noncircadian, intervals if they are required to work for food, and that anticipation of daily meals, expressed in operant behavior, shows the scalar property, a hallmark of timing intervals in the seconds-to-minutes range...
December 2014: Behavioral Neuroscience
Christian M Gallardo, Martin Darvas, Mia Oviatt, Chris H Chang, Mateusz Michalik, Timothy F Huddy, Emily E Meyer, Scott A Shuster, Antonio Aguayo, Elizabeth M Hill, Karun Kiani, Jonathan Ikpeazu, Johan S Martinez, Mari Purpura, Andrea N Smit, Danica F Patton, Ralph E Mistlberger, Richard D Palmiter, Andrew D Steele
Daily rhythms of food anticipatory activity (FAA) are regulated independently of the suprachiasmatic nucleus, which mediates entrainment of rhythms to light, but the neural circuits that establish FAA remain elusive. In this study, we show that mice lacking the dopamine D1 receptor (D1R KO mice) manifest greatly reduced FAA, whereas mice lacking the dopamine D2 receptor have normal FAA. To determine where dopamine exerts its effect, we limited expression of dopamine signaling to the dorsal striatum of dopamine-deficient mice; these mice developed FAA...
2014: ELife
Günter Mistlberger, Gastón A Crespo, Eric Bakker
This review provides an overview of the key aspects of designing ionophore-based optical sensors (IBOS). Exact response functions are developed and compared with a simplified, generalized equation. We also provide a brief introduction into less established but promising working principles, namely dynamic response and exhaustive exchange. Absorbance and fluorescence are the main optical readout strategies used in the evaluation of a sensor response, but they usually require a robust referencing technique for real-world applications...
2014: Annual Review of Analytical Chemistry
Christian M Gallardo, Cynthia T Hsu, Keith M Gunapala, Maksim Parfyonov, Chris H Chang, Ralph E Mistlberger, Andrew D Steele
In rodents, daily feeding schedules induce food anticipatory activity (FAA) rhythms with formal properties suggesting mediation by food-entrained circadian oscillators (FEOs). The search for the neuronal substrate of FEOs responsible for FAA is an active area of research, but studies spanning several decades have yet to identify unequivocally a brain region required for FAA. Variability of results across studies leads to questions about underlying biology versus methodology. Here we describe in C57BL/6 male mice the effects of varying the 'dose' of caloric restriction (0%, 60%, 80%, 110%) on the expression of FAA as measured by a video-based analysis system, and on the induction of c-Fos in brain regions that have been implicated in FAA...
2014: PloS One
Ian C Webb, Michael C Antle, Ralph E Mistlberger
Circadian rhythms in most mammals are synchronized to local time by phase and period resetting actions of daily light-dark cycles on a retino-recipient, light-entrainable circadian pacemaker, the suprachiasmatic nucleus (SCN). The SCN receives input from other brain regions, some of which mediate the phase and period resetting actions of behavioral arousal on circadian rhythms. We review historical milestones in the discovery of so-called "nonphotic" circadian clock resetting induced by environmentally stimulated arousal, or by feedback from clock-controlled rest-activity cycles...
June 2014: Behavioral Neuroscience
Xiaojiang Xie, Gastón A Crespo, Günter Mistlberger, Eric Bakker
Biological light-driven proton pumps use light to move protons across a cell membrane, creating a proton gradient. Although photochromic compounds such as spiropyrans can reversibly convert between two structures with differing pKa values, spiropyrans have not been used to generate either a light-driven proton pump or an electrical current. Here, we report an artificial light-harvesting system based on a supported liquid membrane doped with a spiropyran. Irradiating the membrane with ultraviolet light induces a ring-opening reaction, converting spiropyran to merocyanine, whereas irradiation with visible light induces the reverse reaction...
March 2014: Nature Chemistry
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