Prospective Observational Study of Ocular Health in ISS Crews - The Ocular Health Study

The Visual Impairment Intracranial Pressure (VIIP) syndrome is currently NASA's number one human space flight risk. The syndrome, which is related to microgravity exposure, manifests with changes in visual acuity (hyperopic shifts, scotomas), changes in eye structure (optic disc edema, choroidal folds, cotton wool spots, globe flattening, and dilated optic nerve sheaths), and in some cases with documented increased intracranial pressure (ICP) postflight. While the eye appears to be the main affected end organ of this syndrome, the ocular effects are thought to be related to underlying changes in the vascular system and the central nervous system. The leading hypotheses for the development of VIIP involve microgravity-induced head-ward fluid shifts along with a loss of gravity-assisted drainage of venous blood from the brain, leading to cephalic congestion, decreased CSF resorption and increased ICP. Since 70% of ISS crewmembers have manifested clinical signs or symptoms of the VIIP syndrome, it is assumed that the majority have some degree of ICP elevation in-flight compared to the ground. Prolonged elevations of ICP can cause long-term reduced visual acuity and loss of peripheral visual fields, and have been reported to cause mild cognitive impairment in the analog terrestrial population of Idiopathic Intracranial Hypertension (IIH). These potentially irreversible health consequences underscore the importance of identifying the factors that lead to this syndrome and mitigating them

Explaining Africa’s public consumption procyclicality : revisiting old evidence

This paper compiles a novel dataset of time-varying measures of government consumption cyclicality for a panel of 46 African economies between 1960 and 2014. Government consumption has, generally, been highly procyclical over time in this group of countries. However, sample averages hide serious heterogeneity across countries with the majority of them showing procyclical behavior despite some positive signs of graduation from the “procyclicality trap” in a few cases. By means of weighted least squares regressions, we find that more developed African economies tend to have a smaller degree of government consumption procyclicality. Countries with higher social fragmentation and those are more reliant on foreign aid inflows tend to have a more procyclical government consumption policy. Better governance promotes counter- cyclical fiscal policy whileincreased democracy dampens it. Finally, some fiscal rules are important in curbing the procyclical behavior of government consumption.info:eu-repo/semantics/publishedVersio

The Effects of Long Duration Head Down Tilt Bed Rest on Neurocognitive Performance: The Effects of Exercise Interventions

We are conducting ongoing experiments in which we are performing structural and functional magnetic resonance brain imaging to identify the relationships between changes in neurocognitive function and neural structural alterations following a six month International Space Station mission and following 70 days exposure to a spaceflight analog, head down tilt bedrest. Our central hypothesis is that measures of brain structure, function, and network integrity will change from pre to post intervention (spaceflight, bedrest). Moreover, we predict that these changes will correlate with indices of cognitive, sensory, and motor function in a neuroanatomically selective fashion. Our interdisciplinary approach utilizes cutting edge neuroimaging techniques and a broad ranging battery of sensory, motor, and cognitive assessments that will be conducted pre flight, during flight, and post flight to investigate potential neuroplastic and maladaptive brain changes in crewmembers following long-duration spaceflight. Success in this endeavor would 1) result in identification of the underlying neural mechanisms and operational risks of spaceflight-induced changes in behavior, and 2) identify whether a return to normative behavioral function following re-adaptation to Earth's gravitational environment is associated with a restitution of brain structure and function or instead is supported by substitution with compensatory brain processes. Our ongoing bed rest participants are also engaging in exercise studies directed by Dr. Lori Ploutz Snyder. In this presentation, I will briefly highlight the existing literature linking exercise and fitness to brain and behavioral functions. I will also overview the metrics from my study that could be investigated in relation to the exercise and control subgroups

The Effects of Long Duration Bed Rest on Functional Mobility and Balance: Relationship to Resting State Motor Cortex Connectivity

NASA offers researchers from a variety of backgrounds the opportunity to study bed rest as an experimental analog for space flight. Extended exposure to a head-down tilt position during long duration bed rest can resemble many of the effects of a low-gravity environment such as reduced sensory inputs, body unloading and increased cephalic fluid distribution. The aim of our study is to a) identify changes in brain function that occur with prolonged bed rest and characterize their recovery time course; b) assess whether and how these changes impact behavioral and neurocognitive performance. Thus far, we completed data collection from six participants that include task based and resting state fMRI. The data have been acquired through the bed rest facility located at the University of Texas Medical Branch (Galveston, TX). Subjects remained in bed with their heads tilted down 6 degrees below their feet for 70 consecutive days. Behavioral measures and neuroimaging assessments were obtained at seven time points: a) 7 and 12 days before bed rest; b) 7, 30, and 65 days during bed rest; and c) 7 and 12 days after bed rest. Functional connectivity magnetic resonance imaging (FcMRI) analysis was performed to assess the connectivity of motor cortex in and out of bed rest. We found a decrease in motor cortex connectivity with vestibular cortex and the cerebellum from pre bed rest to in bed rest. We also used a battery of behavioral measures including the functional mobility test and computerized dynamic posturography collected before and after bed rest. We will report the preliminary results of analyses relating brain and behavior changes. Furthermore, we will also report the preliminary results of a spatial working memory task and vestibular stimulation during in and out of bed rest

Efecto de la aclimatación precoz sobre metabolitos sanguíneos en pollos de engorde

Evaluated the effect of early acclimatization in blood metabolites and productivity during the stage of completion of broilers (Gallus gallus domesticus L.). We used three hundred ninety six chickens a day of the Cobb 500 line, randomly assigned into three treatments: T1, birds acclimated to the 5, 10 and 15 days of those exposed 6 hours at temperatures between 38 and 40 °C, T2, birds acclimated on day 5, with a 24 hours exposure at temperatures between 38 and 40 °C. T3, birds without acclimatization. Determined: metabolites in blood (glucose, urea nitrogen, creatinine, cholesterol, triglycerides, magnesium, calcium and phosphorus). Blood samples were performed collected at the 38 and 45 days of age. Acclimation does not affect (p>0.05) the variables: glucose (38 days), calcium, phosphorus, magnesium, cholesterol and triglycerides (45 days); cholesterol and phosphorus (38 days) was lower (p<0.05) in all the treatments. Treatments with acclimatization early (without taking into account the heat index) adversely affected the phosphorus and positively cholesterol and glucose levels. If levels of magnesium, calcium, triglycerides, remained constant despite the treatments. Creatine and urea nitrogen, had low values in all evaluated groups. Treatment of acclimatization which offered the best results was carried out the five day with 24 hours of exposure.  Se evaluó el efecto de la aclimatación precoz en metabolitos sanguíneos y la productividad durante la etapa de finalización de pollos de engorde (Gallus gallus domesticus L.). Se utilizaron 396 pollos de un día de la línea Cobb 500, asignados aleatoriamente en tres tratamientos: T1, aves aclimatadas a los 5, 10 y 15 días de edad, expuestas 6 horas a temperaturas de entre 38 y 40°C, T2, aves aclimatadas el día 5, con una exposición de 24 horas a temperaturas de entre 38 y 40°C. T3 aves sin aclimatación. Se determinó: metabolitos en sangre (glucosa, nitrógeno ureico, creatinina, colesterol, triglicéridos, magnesio, calcio y fósforo). Las muestras de sangre se recolectaron a los 38 y 45 días de edad. La aclimatación no afecto (p>0,05) las variables: glucosa (38 días), calcio, fósforo, magnesio, colesterol y los triglicéridos (45 días); el colesterol y fósforo (38 días) fue menor (p<0,05) en todos los tratamientos. Los tratamientos con aclimatación precoz (sin tener en cuenta el índice de calor) afectaron negativamente el fósforo y positivamente los niveles colesterol y glucosa. Los niveles de calcio, magnesio, triglicéridos, permanecieron constantes pese a los tratamientos. La creatinina y el nitrógeno ureico, presentaron valores bajos en todos los grupos evaluados. El tratamiento de aclimatación que ofreció los mejores resultados fue el realizado el día cinco con 24 horas de exposición. &nbsp

Random multi-hopper model: super-fast random walks on graphs

We develop a mathematical model considering a random walker with long-range hops on arbitrary graphs. The random multi-hopper can jump to any node of the graph from an initial position, with a probability that decays as a function of the shortest-path distance between the two nodes in the graph. We consider here two decaying functions in the form of Laplace and Mellin transforms of the shortest-path distances. We prove that when the parameters of these transforms approach zero asymptotically, the hitting time in the multi-hopper approaches the minimum possible value for a normal random walker. We show by computational experiments that the multi-hopper explores a graph with clusters or skewed degree distributions more efficiently than a normal random walker. We provide computational evidences of the advantages of the random multi-hopper model with respect to the normal random walk by studying deterministic, random and real-world networks

The Cortico-Limbo-Thalamo-Cortical Circuits: An Update to the Original Papez Circuit of the Human Limbic System

The Papez circuit, first proposed by James Papez in 1937, is a circuit believed to control memory and emotions, composed of the cingulate cortex, entorhinal cortex, parahippocampal gyrus, hippocampus, hypothalamus, and thalamus. Pursuant to James Papez, Paul Yakovlev and Paul MacLean incorporated the prefrontal/orbitofrontal cortex, septum, amygdalae, and anterior temporal lobes into the limbic system. Over the past few years, diffusion-weighted tractography techniques revealed additional limbic fiber connectivity, which incorporates multiple circuits to the already known complex limbic network. In the current review, we aimed to comprehensively summarize the anatomy of the limbic system and elaborate on the anatomical connectivity of the limbic circuits based on the published literature as an update to the original Papez circuit

The Impact of 6 and 12 Months in Space on Human Brain Structure and Intracranial Fluid Shifts

As plans develop for Mars missions, it is important to understand how long-duration spaceflight impacts brain health. Here we report how 12-month (n = 2 astronauts) versus 6-month (n = 10 astronauts) missions impact brain structure and fluid shifts. We collected MRI scans once before flight and four times after flight. Astronauts served as their own controls; we evaluated pre- to postflight changes and return toward preflight levels across the 4 postflight points. We also provide data to illustrate typical brain changes over 7 years in a reference dataset. Twelve months in space generally resulted in larger changes across multiple brain areas compared with 6-month missions and aging, particularly for fluid shifts. The majority of changes returned to preflight levels by 6 months after flight. Ventricular volume substantially increased for 1 of the 12-month astronauts (left: +25%, right: +23%) and the 6-month astronauts (left: 17 ± 12%, right: 24 ± 6%) and exhibited little recovery at 6 months. Several changes correlated with past flight experience; those with less time between subsequent missions had larger preflight ventricles and smaller ventricular volume increases with flight. This suggests that spaceflight-induced ventricular changes may endure for long periods after flight. These results provide insight into brain changes that occur with longduration spaceflight and demonstrate the need for closer study of fluid shift

Procyclicality or Reverse Causality?

There is a large literature showing that fiscal policy is either acyclical or countercyclical in industrial countries and procyclical in developing countries. Most of this literature is based on OLS regressions that focus on the correlation between a fiscal variable (usually the budget balance or expenditure growth) and either GDP growth or some measure of the output gap. This paper argues that such a methodology does not permit the identification of the effect of the business cycle on fiscal policy and hence cannot be used to estimate policy reaction functions. The paper proposes a new instrument for GDP growth and shows that, once GDP growth is properly instrumented, procyclicality tends to disappear