Purification, Characterisation and Crystallisation From a Range of Rhodospirillineae Pigment-Protein Complexes

A range of photosynthetic integral membrane pigment-protein complexes were purified from several species of purple bacteria. The light-harvesting complexes that were isolated were the RC-LHI conjugate (also called the core conjugate) and the B800-850 peripheral light-harvesting complex (LHII). Uniform growth and protein purification protocols were established for each species. The stability of the RC-LHI conjugates was species dependent. The most stable cores were obtained from Rp. acidophila, Rp. cryptolactis and Rp. palustris. The least stable RC-LHI conjugates were from R. centenum and Rh. sphxieroides. Biochemical analysis of the RC-LHI conjugate foimd that all the species investigated had a similar RC:BChla ratio of approximately -1:30. An experimentally determined extinction coefficient for BChl a at 880nm (which is used to calculate the RC:BChl a ratios) for each species was obtained and found to lie within the range of 100-120 mM cm-1. When the RC:BChl a ratios were recalculated using the experimentally determined extinction coefficients the average RC:BChl a ratio increased to -1:34. The purified membrane proteins were then screened to see if suitable crystals could be obtained for structural analysis. Two Dimensional and Three Dimensional crystallisation techniques were utilised and the results compared. 2D arrays of the RC-LHI conjugate from Rp. palustris and Rp. acidophila were obtained. Initial image analysis the Rp. acidophila RC-LHI conjugate suggests a hexagonal lattice with a centre-to-centre distance of approximately 115+/-5A, gamma =12

Oh, Behave! Behavior as an Interaction between Genes & the Environment

This lesson is designed to teach students that behavior is a trait shaped by both genes and the environment. Students will read a scientific paper, discuss and generate predictions based on the ideas and data therein, and model the relationships between genes, the environment, and behavior. The lesson is targeted to meet the educational goals of undergraduate introductory biology, evolution, and animal behavior courses, but it is also suitable for advanced high school biology students. This lesson meets the criteria for the Next Generation Science Standard HS-LS4, Biological Evolution: Unity and Diversity (NGSS Lead States, 2013)

Brainstem Cholinergic Modulation of Muscle Tone in Infant Rats

In week-old rats, lesions of the dorsolateral pontine tegmentum (DLPT) and nucleus pontis oralis (PnO) have opposing effects on nuchal muscle tone. Specifically, pups with DLPT lesions exhibit prolonged bouts of nuchal muscle atonia (indicative of sleep) and pups with PnO lesions exhibit prolonged bouts of high nuchal muscle tone (indicative of wakefulness). Here we test the hypothesis that nuchal muscle tone is modulated, at least in part, by cholinergically mediated interactions between these two regions. First, in unanesthetized pups, we found that chemical infusion of the cholinergic agonist carbachol (22 mM, 0.1 µL) within the DLPT produced high muscle tone. Next, chemical lesions of the nucleus pontis oralis (PnO) were used to produce a chronic state of high nuchal muscle tone, at which time the cholinergic antagonist scopolamine (10 mM, 0.1 µL) was infused into the DLPT. Scopolamine effectively decreased nuchal muscle tone, thus suggesting that lesions of the PnO increase muscle tone via cholinergic activation of the DLPT. Using 2-deoxyglucose (2-DG) autoradiography, metabolic activation throughout the DLPT was observed after PnO lesions. Finally, consistent with the hypothesis that PnO inactivation produces high muscle tone, infusion of the sodium channel blocker, lidocaine (2%), into the PnO of unanesthetized pups produced rapid increases in muscle tone. We conclude that, even early in infancy, the DLPT is critically involved in the regulation of muscle tone and behavioral state and that its activity is modulated by a cholinergic mechanism that is directly or indirectly controlled by the PnO

The Development of Sleep-Wake Rhythms and the Search for Elemental Circuits in the Infant Brain

Despite the predominance of sleep in early infancy, developmental science has yet to play a major role in shaping concepts and theories about sleep and its associated ultradian and circadian rhythms. Here we argue that developmental analyses help us to elucidate the relative contributions of the brainstem and forebrain to sleep-wake control and to dissect the neural components of sleep-wake rhythms. Developmental analysis also makes it clear that sleep-wake processes in infants are the foundation for those of adults. For example, the infant brainstem alone contains a fundamental sleep-wake circuit that is sufficient to produce transitions among wakefulness, quiet sleep, and active sleep. In addition, consistent with the requirements of a flip-flop model of sleep-wake processes, this brainstem circuit supports rapid transitions between states. Later in development, strengthening bidirectional interactions between the brainstem and forebrain contribute to the consolidation of sleep and wake bouts, the elaboration of sleep homeostatic processes, and the emergence of diurnal or nocturnal circadian rhythms. The developmental perspective promoted here critically constrains theories of sleep-wake control and provides a needed framework for the creation of fully realized computational models. Finally, with a better understanding of how this system is constructed developmentally, we will gain insight into the processes that govern its disintegration due to aging and disease

An Effective Model for Engaging Faculty and Undergraduate Students in Neuroscience Outreach with Middle Schoolers

Engaging undergraduate students in science outreach events is critical for improving future communication between scientists and community members. Outreach events are opportunities for faculty and undergraduates to utilize active learning strategies to engage non-scientists in scientific questions and principles. Through careful design of outreach events, undergraduate students can practice science communication skills while reaching populations of the public that remain underserved and underrepresented in scientific fields. Here we describe a classroom outreach event designed to give a broad overview of the field of neuroscience to middle school students of all backgrounds by delivering the content in school, during school hours. Through a variety of active learning strategies, middle school students learned about basic structures of the brain and their corresponding functions. Additionally, these students participated in demonstrations during which they generated and tested their own hypotheses and learned about sensory transmission and responses. We designed the lesson to meet the educational goals for middle school students, fulfilling the criteria for the Next Generation Science Standard MS-LS1-8 (NGSS Lead States, 2013). We evaluated the impact of the event on both undergraduate student instructors and middle school participants. Our results demonstrate that these outreach events effectively deliver new content to middle school students while also reinforcing the importance and value of outreach to undergraduate instructors

Lesions of the Intergeniculate Leaflet Lead to a Reorganization in Circadian Regulation and a Reversal in Masking Responses to Photic Stimuli in the Nile Grass Rat

Light influences the daily patterning of behavior by entraining circadian rhythms and through its acute effects on activity levels (masking). Mechanisms of entrainment are quite similar across species, but masking can be very different. Specifically, in diurnal species, light generally increases locomotor activity (positive masking), and in nocturnal ones, it generally suppresses it (negative masking). The intergeniculate leaflet (IGL), a subdivision of the lateral geniculate complex, receives direct retinal input and is reciprocally connected with the primary circadian clock, the suprachiasmatic nucleus (SCN). Here, we evaluated the influence of the IGL on masking and the circadian system in a diurnal rodent, the Nile grass rat (Arvicanthis niloticus), by determining the effects of bilateral IGL lesions on general activity under different lighting conditions. To examine masking responses, light or dark pulses were delivered in the dark or light phase, respectively. Light pulses at Zeitgeber time (ZT) 14 increased activity in control animals but decreased it in animals with IGL lesions. Dark pulses had no effect on controls, but significantly increased activity in lesioned animals at ZT0. Lesions also significantly increased activity, primarily during the dark phase of a 12:12 light/dark cycle, and during the subjective night when animals were kept in constant conditions. Taken together, our results suggest that the IGL plays a vital role in the maintenance of both the species-typical masking responses to light, and the circadian contribution to diurnality in grass rats

Melanopsin-Containing ipRGCs Are Resistant to Excitotoxic Injury and Maintain Functional Non-Image Forming Behaviors After Insult in a Diurnal Rodent Model

Intrinsically photosensitive retinal ganglion cells (ipRGCs) are critical for the light signaling properties of non-image forming vision. Melanopsin-expressing ipRGCs project to retinorecipient brain regions involved in modulating circadian rhythms. Melanopsin has been shown to play an important role in how animals respond to light, including photoentrainment, masking (i.e., acute behavioral responses to light), and the pupillary light reflex (PLR). Importantly, ipRGCs are resistant to various forms of damage, including ocular hypertension, optic nerve crush, and excitotoxicity via N-methyl-D-aspartic acid (NMDA) administration. Although these cells are resistant to various forms of injury, the question still remains whether or not these cells remain functional following injury. Here we tested the hypothesis that ipRGCs would be resistant to excitotoxic damage in a diurnal rodent model, the Nile grass rat (Arvicanthis niloticus). In addition, we hypothesized that following insult, grass rats would maintain normal circadian entrainment and masking to light. In order to test these hypotheses, we injected NMDA intraocularly and examined its effect on the survivability of ipRGCs and RGCs, along with testing behavioral and functional consequences. Similar to findings in nocturnal rodents, ipRGCs were spared from significant damage but RGCs were not. Importantly, whereas image-forming vision was significantly impaired, non-image forming vision (i.e, photoentrainment, masking, and PLR) remained functional. The present study aims to characterize the resistance of ipRGCs to excitotoxicity in a diurnal rodent model

The quantum query complexity of certification

We study the quantum query complexity of finding a certificate for a d-regular, k-level balanced NAND formula. Up to logarithmic factors, we show that the query complexity is Theta(d^{(k+1)/2}) for 0-certificates, and Theta(d^{k/2}) for 1-certificates. In particular, this shows that the zero-error quantum query complexity of evaluating such formulas is O(d^{(k+1)/2}) (again neglecting a logarithmic factor). Our lower bound relies on the fact that the quantum adversary method obeys a direct sum theorem.Comment: 8 pages; Updated to reflect changes in final journal version and to point out that the main result only applies for k>