RESUMO
The majority of patients with obesity, insulin resistance, and metabolic syndrome have hypertension, but the mechanisms of hypertension are poorly understood. In these patients, impaired sodium excretion is critical for the genesis of Na(+)-sensitive hypertension, and prior studies have proposed a role for the epithelial Na(+) channel (ENaC) in this syndrome. We characterized high fat-fed mice as a model in which to study the contribution of ENaC-mediated Na(+) reabsorption in obesity and insulin resistance. High fat-fed mice demonstrated impaired Na(+) excretion and elevated blood pressure, which was significantly higher on a high-Na(+) diet compared with low fat-fed control mice. However, high fat-fed mice had no increase in ENaC activity as measured by Na(+) transport across microperfused cortical collecting ducts, electrolyte excretion, or blood pressure. In addition, we found no difference in endogenous urinary aldosterone excretion between groups on a normal or high-Na(+) diet. High fat-fed mice provide a model of metabolic syndrome, recapitulating obesity, insulin resistance, impaired natriuresis, and a Na(+)-sensitive elevation in blood pressure. Surprisingly, in contrast to previous studies, our data demonstrate that high fat feeding of mice impairs natriuresis and produces elevated blood pressure that is independent of ENaC activity and likely caused by increased Na(+) reabsorption upstream of the aldosterone-sensitive distal nephron.
Assuntos
Pressão Sanguínea/efeitos dos fármacos , Canais Epiteliais de Sódio/metabolismo , Resistência à Insulina , Obesidade/metabolismo , Sódio/farmacologia , Aldosterona/urina , Animais , Ritmo Circadiano , Dieta Hiperlipídica , Túbulos Renais Coletores/efeitos dos fármacos , Túbulos Renais Coletores/metabolismo , Masculino , Síndrome Metabólica/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Natriurese , Néfrons/efeitos dos fármacos , Néfrons/metabolismo , Obesidade/etiologia , Sódio/urina , Sódio na Dieta/efeitos adversosRESUMO
Many studies investigating cue competition have focused on the blocking effect. We investigated the blocking effect with pigeons using a landmark-based spatial search task in both a touchscreen preparation (Exp. 1a) and an automated remote environmental navigation apparatus (Exp. 1b). In Phase 1, two landmarks (LMs: A and Z) appeared on separate trials as colored circles among a row of eight (touchscreen) or six (ARENA) identical response units. Subjects were rewarded for pecking at a target response unit to the right of LM A and to the left of an extraneous LM, Z. During the blocking trials in Phase 2, LM X was presented in compound with a second LM (A) that had been previously trained. On control trials, LM Y was presented in compound with LM B and a target in the same manner as in the trials of AX, except that neither landmark had previously been trained with the target. All subjects were then tested with separate trials of A, X, B, and Y. Testing revealed poor spatial control by X relative to A and Y. We report the first evidence for a spatial-blocking effect in pigeons and additional support for associative effects (e.g., blocking) occurring under similar conditions (e.g., training sessions, spatial relationships, etc.) in 3-D and 2-D search tasks.
Assuntos
Aprendizagem por Discriminação/fisiologia , Percepção Espacial/fisiologia , Comportamento Espacial/fisiologia , Animais , Comportamento Animal/fisiologia , Columbidae , Sinais (Psicologia)RESUMO
Consumers actively look to and expect businesses to engage in charitable donation activities. While past research has demonstrated the strategic benefits that corporate social responsibility (CSR) affords to firms, little is known about the way consumers apply subjective (or objective) ethical standards for corporate donations. Our research focuses on the way expectation standards of CSR are applied to luxury (versus non-luxury) companies. Do consumers hold a belief that luxury firms are expected to donate more? Four experimental studies find robust and converging evidence that consumers do not hold luxury firms to a higher standard; instead, they take on the normative belief that companies are obligated to donate equal amounts. This reference-independence holds stable across different product categories (Studies 1a and 1b), perspectives (Study 2), and attempts to alter the belief (Study 3). However, individual differences do exist among consumers regarding the level of donation expected, particularly for materialists and spendthrifts. Specifically, moderation analyses reveal that materialists and spendthrifts (compared to non-materialists and tightwads) expect higher levels of corporate donations regardless of the type of firm (i.e., luxury vs. non-luxury). This research extends the discussion of subjective ethical beliefs in the context of luxury CSR.
Assuntos
Comércio , Motivação , Responsabilidade Social , Organizações , Obrigações MoraisRESUMO
The goal of three experiments was to study whether rats are aware of the difference between absence of events and lack of evidence. We used a Pavlovian extinction paradigm in which lights consistently signaling sucrose were suddenly paired with the absence of sucrose. The crucial manipulation involved the absent outcomes in the extinction phase. Whereas in the Cover conditions, access to the drinking receptacle was blocked by a metal plate, in the No Cover conditions, the drinking receptacle was accessible. The Test phase showed that in the Cover conditions, the measured expectancies of sucrose were clearly at a higher level than in the No Cover conditions. We compare two competing theories potentially explaining the findings. A cognitive theory interprets the observed effect as evidence that the rats were able to understand that the cover blocked informational access to the outcome information, and therefore the changed learning input did not necessarily signify a change of the underlying contingency in the world. An alternative associationist account, renewal theory, might instead explain the relative sparing of extinction in the Cover condition as a consequence of context change. We discuss the merits of both theories as accounts of our data and conclude that the cognitive explanation is in this case preferred.
Assuntos
Extinção Psicológica , Animais , Condicionamento Clássico , Sinais (Psicologia) , Aprendizagem por Discriminação , Feminino , Ratos/psicologia , Ratos Long-Evans/psicologiaRESUMO
We achieve tunneling spin injection from Co into single layer graphene (SLG) using TiO2 seeded MgO barriers. A nonlocal magnetoresistance (ΔR(NL)) of 130 Ω is observed at room temperature, which is the largest value observed in any material. Investigating ΔR(NL) vs SLG conductivity from the transparent to the tunneling contact regimes demonstrates the contrasting behaviors predicted by the drift-diffusion theory of spin transport. Furthermore, tunnel barriers reduce the contact-induced spin relaxation and are therefore important for future investigations of spin relaxation in graphene.
RESUMO
A. P. Blaisdell, K. Sawa, K. J. Leising, and M. R. Waldmann (2006) reported evidence for causal reasoning in rats. After learning through Pavlovian observation that Event A (a light) was a common cause of Events X (an auditory stimulus) and F (food), rats predicted F in the test phase when they observed Event X as a cue but not when they generated X by a lever press. Whereas associative accounts predict associations between X and F regardless of whether X is observed or generated by an action, causal-model theory predicts that the intervention at test should lead to discounting of A, the regular cause of X. The authors report further tests of causal-model theory. One key prediction is that full discounting should be observed only when the alternative cause is viewed as deterministic and independent of other events, 2 hallmark features of actions but not necessarily of arbitrary events. Consequently, the authors observed discounting with only interventions but not other observable events (Experiments 1 and 2). Moreover, rats were capable of flexibly switching between observational and interventional predictions (Experiment 3). Finally, discounting occurred on the very first test trial (Meta-Analysis). These results confirm causal-model theory but refute associative accounts.
Assuntos
Aprendizagem por Associação , Condicionamento Clássico , Resolução de Problemas , Animais , Comportamento Apetitivo , Formação de Conceito , Sinais (Psicologia) , Tomada de Decisões , Feminino , Rememoração Mental , Motivação , Ratos , Ratos Long-Evans , Inibição Reativa , Enquadramento Psicológico , Transferência de ExperiênciaRESUMO
We investigated extinction and spontaneous recovery of spatial associations using a landmark-based appetitive search task in a touchscreen preparation with pigeons. Four visual landmarks (A, B, C, and D) were separately established as signals of a hidden reinforced target among an 8 × 7 array of potential target locations. The target was located above landmarks (LM) A and C and below B and D. After conditioning, A and B were extinguished. Responding to A and C was assessed on probe tests 2 days following extinction, whereas, B and D were tested 14 days after extinction. We observed spontaneous recovery from spatial extinction following a 14-day, but not a 2-day, postextinction retention interval. Furthermore, by plotting the spatial distribution of responding across the X and Y axes during testing, we found that spontaneous recovery of responding to the target in our task was due to enhanced spatial control (i.e., a change in the overall distribution of responses) following the long delay to testing. These results add spatial extinction and spontaneous recovery to the list of findings supporting the assertion that extinction involves new learning that attenuates the originally acquired response, and that original learning of the spatial relationship between paired events survives extinction. (PsycINFO Database Record
Assuntos
Comportamento Animal/fisiologia , Columbidae/fisiologia , Reforço Psicológico , Percepção Espacial/fisiologia , Comportamento Espacial/fisiologia , Animais , Extinção Psicológica/fisiologia , Aprendizagem Espacial/fisiologiaRESUMO
INTRODUCTION: To construct a trainer that would achieve the equivalent goals of the Fundamentals of Laparoscopic Surgery (FLS) trainer at an economical cost. A validation study comparing our homemade (HM) trainer vs the FLS trainer was performed. A literature search as well as a price comparison with other commercially available laparoscopic trainers is presented. METHODS: The HM laparoscopic trainer was constructed using a prefabricated hard plastic frame with a vinyl plastic sheet affixed as the roof. A row of light-emitting diode lights and a charge-coupled device camera were mounted on the inside roof of the frame. Electrical wires were spliced to supply power to both the light-emitting diode lights and the camera. The charge-coupled device camera was connected to a liquid crystal display screen which was affixed directly across from the user. Subjects were prospectively randomized to perform the 5 tasks put forth by the McGill Inanimate System for Training and Evaluation of Laparoscopic Skills on both the HM trainer and the FLS trainer (pegboard transfer, pattern cut, placement of ligating loop, extracorporeal knot suture, and intracorporeal knot suture). Simple paired t test was performed to compare times between the trainers. SETTING: The construction of the trainer and the validation study were performed at the Central Michigan University College of Medicine Department of Simulation. PARTICIPANTS: Subjects consisted of third- and fourth-year medical students (n = 30). RESULTS: A laparoscopic trainer box was constructed and assembled in 2 hours. The HM trainer cost $309 representing a cost savings of $1371. Results of the validation study demonstrated no statistical difference in times to complete 3 out of the 5 tasks as well as no difference in total time to complete all 5 tasks (p value< 0.05). CONCLUSION: Valid laparoscopic simulators can be constructed at an economical cost.
Assuntos
Simulação por Computador , Desenho de Equipamento , Laparoscopia/educação , Laparoscopia/instrumentação , Competência Clínica , Humanos , Análise e Desempenho de Tarefas , Interface Usuário-ComputadorRESUMO
Laser driven plasma light sources offer highly intense output in the UV-visible region combined with a source size as small as 100 µm. In order to effectively use the small source size in high brightness applications, a stigmatic monochromator and focusing system must be used. Here we describe a simple brightness preserving optical system that should be useful across a broad range of applications. The output flux of this system is between 6 × 10(11) ph∕s and 4 × 10(12) ph∕s with a spectra resolution of 1.7 nm and field spot size of 0.1 mm from the UV to the VIS spectra range.