Previous studies investigating interactions between spatial attention and numeric stimuli (see SNARC effect) have identified an attentional bias induced by numeric stimuli in accordance with a mental number line model of processing. This processing model attributes orienting effects induced by numeric stimuli to long-term memory structures, such as a left-to-right number system in a given culture. The present study aims to investigate long-term memory may modulate attentional biases induced by the contents in short-term memory. In other words, can simply thinking about number induce spatial biasing effects? In this study, dichotic listening is used to measure of spatial attention in the auditory modality. Subjects were given numeric items to retain in short term memory during the spatial attention task, and prompted to recall the numbers verbally after each trial. Factors of number magnitude, load size, interval size between numbers, and presentation order are analyzed in terms of their effect on auditory spatial orienting. Auditory spatial orienting is assessed through a measure of laterality index – a ratio of left/right ear responses indicating attention as allocated to the left or right side of space. Results demonstrated a clear influence of number magnitude and presentation order on auditory spatial attention, however these effects were highly variable depending on other factors present in each experiment. Overall, results suggest that in addition to SNARC based orienting responses, the orienting effects of items in short term memory on spatial attention may be influenced by novelty, interactions with language, and multiple neural mechanisms responsible for representing quantity information. / acase@tulane.edu

acase@tulane.edu

acase@tulane.edu

Peripheral estradiol treatment enhances hippocampus-dependent memory and morphology in ovariectomized rats. Although these enhancements are traditionally thought to be due to circulating estradiol, recent data suggest these changes are brought on by hippocampus-derived estradiol, the synthesis of which depends on GnRH activity. The goal of the current work is to test the hypothesis that peripheral estradiol affects cognition and the hippocampus through brain-derived estradiol via hippocampal GnRH receptor activity. In Experiment 1, we investigated if peripheral estradiol exerts its effects through regulation of brain-derived estradiol. Intracerebroventricular infusion of letrozole, which prevents the synthesis of estradiol, blocked the ability of peripheral estradiol administration in ovariectomized rats to enhance hippocampus-dependent memory in a radial-maze task and blocked or attenuated estradiol-induced increases in hippocampal synaptic proteins. In Experiment 2, we investigated if peripheral estradiol affects cognition and the hippocampus through hippocampal GnRH receptors. Hippocampal infusion of antide, a long-lasting GnRH receptor antagonist, blocked the ability of peripheral estradiol administration in ovariectomized rats to enhance hippocampus-dependent memory in a radial-maze task and blocked estradiol-induced increases in hippocampal synaptic proteins and aromatase, the final enzyme involved in estradiol synthesis. In Experiment 3A, we investigated whether hippocampal GnRH infusion was sufficient to enhance hippocampus-dependent memory and affect the hippocampus in ovariectomized rats and whether this was dependent on neuroestradiol synthesis. Hippocampal infusion of GnRH enhanced hippocampus-dependent memory in a radial maze task, the effects of which were blocked by letrozole infusion. Unexpectedly, GnRH treatment decreased levels or had no effect on a hippocampal postsynaptic proteins or aromatase. Due to the unexpected molecular results of Experiment 3A, Experiment 3B investigated if shorter treatment of GnRH affects hippocampal proteins differently. As opposed to the 10-12 days of GnRH treatment in Experiment 3A, five days of GnRH treatment increased levels of synaptic proteins via neuroestradiol synthesis as coadministration of letrozole blocked these effects. Results indicate that peripheral estradiol-induced enhancement of cognition and hippocampal morphology is mediated by brain-derived estradiol via hippocampal GnRH receptor activity. / acase@tulane.edu

A growing body of evidence indicates that early life events play a significant role in shaping the behavior and physiology of the adult organism. Repeated maternal separation paradigms, which serve as models for childhood adversity, have yielded permanent physiological, morphological and behavioral changes in adult rats. In studies involving adult animals, a sexually dimorphic pattern has been observed in the cognitive impact of chronic stress paradigms. Male subjects often display cognitive impairments despite a less robust physiological stress response than their female counterparts. Females, on the other hand, often display unaffected or enhanced cognitive functioning. While this effect has been attributed to the neuroprotective effects of estrogen, the present study sought to examine if this dichotomy exists prior to the onset of puberty and thus prior to adult levels of hormones. Male and female Long-Evans rats were separated from the dam and nest for either 15 min (handling) or 180 min (maternal separation) from postnatal days (PND) 2-14. Behavioral testing was carried out between PND 26-39 and included the open field as a measure of anxiety, an object recognition task to assess nonspatial memory, a Y-maze to assess spatial memory, and a water T-maze task to assess learning strategy. No significant effects of sex or treatment were found on the open field. There was also no effect of group or sex on the object recognition test following a 1-hr delay. However, following a 4-hr delay, maternally separated males spent significantly less time with the novel object compared to their handled counterparts, indicating poorer object memory. Meanwhile, maternally separated females spent significantly more time with the novel object as compared to both their handled counterparts and maternally separated males, indicating better object memory. Maternally separated males displayedimpairment on the Y-maze task while maternally separated females showed no effect as compared to controls. All subjects showed a bias toward a response strategy over a place strategy in the water T-maze, perhaps due to age at time of testing. The results of the present study indicate that sex plays a significant role in mediating the cognitive effects of early life stress regardless of the presence of steroid sex hormones. / acase@tulane.edu

Olanzapine, an atypical antipsychotic, alleviates symptoms of schizophrenia while producing fewer side effects compared to first generation antipsychotics. However, chronic usage remains problematic due to the propensity of olanzapine to induce weight gain and metabolic disturbances. Moreover, the cellular mechanisms underlying the metabolic side effects are poorly understood. The central nervous system (CNS) exerts both hormonal and neuronal control over whole body homeostasis. The dorsal motor nucleus of the vagus (DMV) participates in this regulation through modulation of the parasympathetic outflow to subdiaphragmatic organs. We hypothesized that olanzapine disrupts neurotransmission of the DMV, and thus contributes to the dysregulation of metabolism. We used whole-cell patch-clamp recordings from female C57BL/6J to assess the effect of olanzapine on DMV neurons. First, we investigated the effect of acute olanzapine administration on the activity of DMV neurons. Acute application of 10 µM olanzapine on DMV neurons induced both pre- and postsynaptic effects. Voltage-clamp recordings revealed that, in 5 out of 9 DMV neurons, excitatory inputs to DMV neurons were significantly increased by 71.6 ± 22.1%. In addition, in current-clamp mode, olanzapine induced a robust hyperpolarization from -49.00 ± 0.64 mV to -60.82 ± 2.78 mV. The hyperpolarization suppressed action potential firing. As a next step, we investigated the subchronic effect of olanzapine on the activity of DMV neurons. Daily subcutaneous injections were made for 20 days (5 mg/kg/day of olanzapine and vehicle). We did not find significant differences in body weight, blood glucose, and insulin or leptin levels. Subchronic administration of olanzapine generated presynaptic changes in DMV neurons. In treated animals, additional infusion of 10 µM olanzapine on DMV neurons significantly reduced excitatory neurotransmission by 41.0 ± 3.1% in 10 out of 17 neurons. Our findings indicate that olanzapine directly modulates the neuronal activity in DMV neurons, and could thus contribute to the metabolic disturbances seen in long-term treatments. / acase@tulane.edu

Inflammation is a driving force behind various lethal pathological conditions, including atherosclerosis and cancer metastasis. Inflammatory mediators are keys that unlock the immune response via triggering interactions of leukocytes and vascular endothelial cells. Oxidized low density lipoprotein (OxLDL), lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-α), and histamine are all strong activators of the inflammatory response, and they can be simultaneously produced during various inflammatory disorders. This study focuses on investigating the cooperative effect of TNF-α and histamine, as well as OxLDL and histamine on monocyte-endothelium interactions. Furthermore, the roles of LPS-activated monocytes and histamine in interactions of breast cancer cells with vascular endothelium are also explored. The results suggest that: 1) TNF-α and histamine have a synergistic effect on monocyte-endothelium interactions; 2) histamine cooperatively works with OxLDL to induce monocyte recruitment on endothelial cells; 3) OxLDL treated macrophages and mast cells respectively release TNF-α and histamine, which in turn synergistically increase the capture of monocytes by endothelial cells; 4) LPS activated monocytes secret TNF-α to activate endothelial cells and assist in adhesion of carcinoma cells to activated vascular endothelium; 5) exposure of activated endothelial cells to histamine exaggerates the carcinoma cell arrest, especially in the presence of LPS activated monocytes. In summary, this study implies that an increased risk of atherogenesis may be among the population affected by allergy or asthma and having lipid rich diet that leads to the production of TNF-α and OxLDL in body. It also highlights that the mechanism by which Gram-negative bacterial infection increases a risk of breast cancer metastasis through the cardiovascular system, and shows the necessity to develop better approaches for preventing this infection after surgical resection or before histamine combined IL-2 immune therapy in order to reduce a risk of cancer metastasis. / acase@tulane.edu

There has been significant interest in developing dry adhesives mimicking the gecko adhesive system, which offers several advantages compared to conventional pressure sensitive adhesives. Specifically, gecko adhesive pads have anisotropic adhesion properties: the adhesive pads (spatulae) stick strongly when sheared in one direction but are non-adherent when sheared in the opposite direction. This anisotropy property is attributed to the complex topography of the array of fine tilted and curved columnar structures (setae) that bear the spatulae. In this thesis, easy, scalable methods, relying on conventional and unconventional techniques are presented to incorporate tilt in the fabrication of synthetic polymer-based dry adhesives mimicking the gecko adhesive system, which provide anisotropic adhesion properties. In the first part of the study, the anisotropic adhesion and friction properties of samples with various tilt angles to test the validity of a nanoscale tape-peeling model of spatular function are measured. Consistent with the Peel Zone model, samples with lower tilt angles yielded larger adhesion forces. Contact mechanics of the synthetic array were highly anisotropic, consistent with the frictional adhesion model and gecko-like. Based on the original design, a new design of gecko-like dry adhesives was developed which showed superior tribological properties and furthermore showed anisotropic adhesive properties without the need for tilt in the structures. These adhesives can be used to reversibly suspend weights from vertical surfaces (e.g., walls) and, for the first time to our knowledge, horizontal surfaces (e.g., ceilings) by simultaneously and judiciously activating anisotropic friction and adhesion forces. Furthermore, adhesion properties between artificial gecko-inspired dry adhesives and rough substrates with varying roughness are studied. The results suggest that both adhesion and friction forces on a rough substrate depends significantly on the geometrical parameters of the substrate. The results in this study may be helpful for understanding how geckos overcome the influence of natural surface roughness. The novel designs of our dry adhesives open the way for new gecko-like adhesive surfaces and articulation mechanisms that do not rely on intensive nanofabrication. / acase@tulane.edu

The understory insectivore guild is disproportionately affected by deforestation, and knowing the underlying mechanisms is critical to effective conservation. I investigated demographic, ecological, and behavioral responses of Chestnut-backed Antbird (Myrmeciza exsul) populations (a persistent understory insectivore) to a fragmented Costa Rican rainforest landscape where many ecologically similar species have declined. I estimated demographic rates to parameterize population models in three habitats differentially affected by forest fragmentation: contiguous, peninsular, and fragment. Models indicated that M. exsul are declining in the peninsula (λ=0.83), but increasing in fragments (λ=1.41). Sensitivity analyses suggested that population growth was most sensitive to adult survival and nesting success, suggesting these two variables as potentially important explanatory demographic parameters in this landscape. I studied nest predation using digital video and quantified breeding success and population density in each site. Nest predation rate was so high in the peninsula that few nests fledged any young, much lower in the fragments, and intermediate in the contiguous forest, inversely tracking M. exsul population density and corroborating population growth rate findings. Using 22,000 hours of active nest video recordings, one primary predator emerged, the bird-eating snake (Pseustes poecilonotus), responsible for 80% of nest attacks. Pseustes’ prevalence in the peninsula where predation rates were highest implies possible predation-limitation. Populations both declining and growing locally provided unique insights into the mechanisms of change in a deforestation-impacted landscape, but represent only some fragmentation consequences. Therefore, I reviewed regional studies to assess other potential contributions to understory insectivorous bird decline in the Sarapiquí. Empirical studies supported effects of habitat area loss, dispersal limitation, reduced microhabitat availability, and low physiological tolerances to changing climates. / acase@tulane.edu

The use of ethanol as an additive to gasoline fuel is becoming a common phenomenon. It helps solve the energy crisis and environmental issues that fossil fuel has brought about. However, when dissolved in motor oil, ethanol would dilute motor oil and drastically change its lubrication properties, in the same manner as gasoline dilution. Since ethanol has higher boiling point than gasoline, it takes longer time to be cooked away from the oil, causing more severe changes to motor oil properties. In this work, a new analytical method is presented to study the behaviour of ethanol/oil system. Seven motor oil formulations provided by Italian group E.n.i. are tested regarding their performance in resisting ethanol dilution. The tests are conducted in microcapillaries within which ethanol droplet dissolves in motor oil phase under 40oC or 60oC. Mathematical model is developed to study the shrinkage kinetics of ethanol droplets. And, the mass transfer coefficients of ethanol transporting to different oil formulations are obtained. Similar experiments are conducted on hexadecane and new and used Shell SAE 5W-30 motor oil to discover the difference between motor oil and pure hydrocarbon and the difference between new motor oil and used motor oil. It was found through hexadecane tests and Shell motor oil tests that hydrocarbons with shorter chain length were less capable of resisting ethanol dilution; old motor oil are slower in dissolving ethanol than new oil; and, suspected ethanol-soot complex may form in old motor oil, which might corrode engine parts. / acase@tulane.edu