Mapping sheep to human brain: The need for a sheep brain atlas

A brain atlas is essential for understanding the anatomical relationship between neuroanatomical structures. Standard stereotaxic coordinates and reference systems have been developed for humans, non-human primates and small laboratory animals to contribute to translational neuroscience research. Despite similar neuroanatomical and neurofunctional features between the sheep and human brain, little is known of the sheep brain stereotaxy, and a detailed sheep atlas is scarce. Here, we briefly discuss the value of using sheep in neurological research and the paucity of literature concerning the coordinates system during neurosurgical approaches. Recent advancements such as computerized tomography, positron emission tomography, magnetic resonance imaging, functional magnetic resonance imaging and diffusion tensor imaging are used for targeting and localizing the coordinates and brain areas in humans. Still, their application in sheep is rare due to the lack of a 3D stereotaxic sheep atlas by which to map sheep brain structures to its human counterparts. More recently, a T1- and T2-weighted high-resolution MRI 3D stereotaxic atlas of the sheep brain has been generated, however, the journey to create a sheep brain atlas by which to map directly to the human brain is still uncharted. Therefore, developing a detailed sheep brain atlas is valuable for the future to facilitate the use of sheep as a large animal experimental non-primate model for translational neurological research

Cortico-Striatal Spike-Timing Dependent Plasticity After Activation of Subcortical Pathways

Cortico-striatal spike-timing dependent plasticity (STDP) is modulated by dopamine in vitro. The present study investigated STDP in vivo using alternative procedures for modulating dopaminergic inputs. Postsynaptic potentials (PSP) were evoked in intracellularly recorded spiny neurons by electrical stimulation of the contralateral motor cortex. PSPs often consisted of up to three distinct components, likely representing distinct cortico-striatal pathways. After baseline recording, bicuculline (BIC) was ejected into the superior colliculus (SC) to disinhibit visual pathways to the dopamine cells and striatum. Repetitive cortical stimulation (∼60; 0.2 Hz) was then paired with postsynaptic spike discharge induced by an intracellular current pulse, with each pairing followed 250 ms later by a light flash to the contralateral eye (n = 13). Changes in PSPs, measured as the maximal slope normalized to 5-min pre, ranged from potentiation (∼120%) to depression (∼80%). The determining factor was the relative timing between PSP components and spike: PSP components coinciding or closely following the spike tended towards potentiation, whereas PSP components preceding the spike were depressed. Importantly, STDP was only seen in experiments with successful BIC-mediated disinhibition (n = 10). Cortico-striatal high-frequency stimulation (50 pulses at 100 Hz) followed 100 ms later by a light flash did not induce more robust synaptic plasticity (n = 9). However, an elevated post-light spike rate correlated with depression across plasticity protocols (R2 = 0.55, p = 0.009, n = 11 active neurons). These results confirm that the direction of cortico-striatal plasticity is determined by the timing of pre- and postsynaptic activity and that synaptic modification is dependent on the activation of additional subcortical inputs

Understanding the Effects of Repetitive Transcranial Magnetic Stimulation on Neuronal Circuits

Despite the widespread use of repetitive transcranial magnetic stimulation (rTMS) in both research and clinical settings, there is a paucity of evidence regarding the effects of its application on neural activity. Studies investigating the effects of rTMS on human participants (Huang et al., 2005) have shown that patterned trains of rTMS can be used to modulate the sensitivity of motor pathways for a period outlasting the stimulation itself. These changes are often attributed to an rTMS-induced increase in neural plasticity or a change in excitability of the motor pathway. Evidence that rTMS can modify the strength of motor pathways has led to its introduction into stroke rehabilitation research. It is hypothesized that post-stroke, rTMS can enhance plasticity induction within the brain and, when combined with manual therapy, can facilitate surviving neurons assuming the function of those lost to the stroke (Hsu et al., 2012). In practice however, despite a multitude of studies investigating this approach, there remains no convincing evidence that rTMS is capable of promoting sustained long-term improvement in recovery, above the effects of rehabilitation alone (Hsu et al., 2012; Lefaucheur et al., 2014). We are of the opinion that a lack of advancement within the field is due to an incomplete understanding of the effects of TMS on neural elements. Here we discuss some of the existing evidence and propose experimental approaches that may enhance the human application of rTMS

The Utility of Ambulatory Blood Pressure Monitoring for Diagnosing White Coat Hypertension in Older Adults

The beneficial effect of antihypertensive medication on reducing the risk of cardiovascular disease (CVD) events is supported by data from randomized controlled trials of older adults with hypertension. However, in clinical practice, overtreatment of hypertension in older adults may lead to side effects and an increased risk of falls. The diagnosis and treatment of hypertension is primarily based on blood pressure measurements obtained in the clinic setting. Ambulatory blood pressure monitoring (ABPM) complements clinic blood pressure by measuring blood pressure in the out-of-clinic setting. ABPM can be used to identify white coat hypertension, defined as elevated clinic blood pressure and non-elevated ambulatory blood pressure. White coat hypertension is common in older adults but does not appear to be associated with an increased risk of CVD events among this population. Herein, we review the current literature on ABPM in the diagnoses of white coat hypertension in older adults, including its potential role in preventing overtreatment

The X-ray Remnant of SN1987A

We present high resolution Chandra observations of the remnant of SN1987A in the Large Magellanic Cloud. The high angular resolution of the Chandra X-ray Observatory (CXO) permits us to resolve the X-ray remnant. We find that the remnant is shell-like in morphology, with X-ray peaks associated with some of the optical hot spots seen in HST images. The X-ray light curve has departed from the linear flux increase observed by ROSAT, with a 0.5-2.0 keV luminosity of 1.5 x 10^35 erg/s in January 2000. We set an upper limit of 2.3 x 10^34 ergs/s on the luminosity of any embedded central source (0.5 - 2 keV). We also present a high resolution spectrum, showing that the X-ray emission is thermal in origin and is dominated by highly ionized species of O, Ne, Mg, and Si.Comment: 16 pages, 3 figures, Accepted for publication in ApJ Letter

Exposure to Household Air Pollution from Biomass Cookstoves and Levels of Fractional Exhaled Nitric Oxide (FeNO) among Honduran Women

Household air pollution is estimated to be responsible for nearly three million premature deaths annually. Measuring fractional exhaled nitric oxide (FeNO) may improve the limited understanding of the association of household air pollution and airway inflammation. We evaluated the cross-sectional association of FeNO with exposure to household air pollution (24-h average kitchen and personal fine particulate matter and black carbon; stove type) among 139 women in rural Honduras using traditional stoves or cleaner-burning Justastoves. We additionally evaluated interaction by age. Results were generally consistent with a null association; we did not observe a consistent pattern for interaction by age. Evidence from ambient and household air pollution regarding FeNO is inconsistent, and may be attributable to differing study populations, exposures, and FeNO measurement procedures (e.g., the flow rate used to measure FeNO)

Differences in night-time and daytime ambulatory blood pressure when diurnal periods are defined by self-report, fixed-times, and actigraphy: Improving the Detection of Hypertension study

To determine whether defining diurnal periods by self-report, fixed-time or actigraphy produce different estimates of nighttime and daytime ambulatory blood pressure (ABP)

Exposure to Household Air Pollution from Biomass Cookstoves and Blood Pressure Among Women in Rural Honduras: A Cross‐Sectional Study

Growing evidence links household air pollution exposure from biomass cookstoves with elevated blood pressure. We assessed cross‐sectional associations of 24‐hour mean concentrations of personal and kitchen fine particulate matter (PM2.5), black carbon (BC), and stove type with blood pressure, adjusting for confounders, among 147 women using traditional or cleaner‐burning Justa stoves in Honduras. We investigated effect modification by age and body mass index. Traditional stove users had mean (standard deviation) personal and kitchen 24‐hour PM2.5 concentrations of 126 μg/m3 (77) and 360 μg/m3 (374), while Justa stove users’ exposures were 66 μg/m3 (38) and 137 μg/m3(194), respectively. BC concentrations were similarly lower among Justa stove users. Adjusted mean systolic blood pressure was 2.5 mm Hg higher (95% CI, 0.7‐4.3) per unit increase in natural log‐transformed kitchen PM2.5 concentration; results were stronger among women of 40 years or older (5.2 mm Hg increase, 95% CI, 2.3‐8.1). Adjusted odds of borderline high and high blood pressure (categorized) were also elevated (odds ratio = 1.5, 95% CI, 1.0‐2.3). Some results included null values and are suggestive. Results suggest that reduced household air pollution, even when concentrations exceed air quality guidelines, may help lower cardiovascular disease risk, particularly among older subgroups