A behavioural analysis of some ventral auditory pathways in the medulla of the rat

Thesis (Ph.D.)--Boston University.Rats were trained on three schedules of reinforcement, a sound aversive schedule, a light aversive schedule and a sound and light discrimination schedule. On the aversive schedules a press response terminated the aversive stimulus. On the discrimination schedule a response in the presence of either stimulus produced food. An auditory threshold was measured on this schedule. Following training the animals received electrolytic lesions in the ventral auditory system of the medulla. Following this they were tested on the behavioral schedules. The brain of each animal was then removed and impregnated with protargol for microscopic examination. Six rats received unilateral lesions, seven received bilateral lesions and six received sham operations. The results were as follows. Of the six animals who received unilateral lesions, one showed a substantial loss of the sound aversive behavior. Of the seven who received bilateral lesions five suffered a loss of the aversive behavior. Of these five, two had a substantial increase in the discriminative threshold. The behavior of the animals who received sham operations was essentially unaffected. There was a consistent relation between extensive damage to the large fiber pathway, the superior olivary pathway and the small fiber pathway and loss of the auditory aversive behavior. Destruction of the superior olivary pathway was not sufficient to produce a loss of the aversive behavior. The suggestion in the literature that the large fiber pathway is responsible for the maintenance of the aversive behavior was confirmed. Destruction of the superior olivary pathway either alone or in combination with destruction of the large fiber pathway did not materially change the auditory discriminative threshold. Destruction of all ventral acoustic pathways caused a loss of both aversive and discriminative auditory behaviors. Dorsal auditory pathways did not by themselves support either behavior. It has not been possible to determine if destruction of the small fiber pathway by itself can cause a loss of discriminative behavior. It was not possible to determine if return of the release response was due to the lesion or due to the loss of the press response

Major Depressive Disorder Among Older African Americans, Caribbean Blacks, And Non‐Hispanic Whites: Secondary Analysis Of The National Survey Of American Life

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98298/1/da22041.pd

NASA's Advanced Radioisotope Power Conversion Technology Development Status

NASA's Advanced Radioisotope Power Systems (ARPS) project is developing the next generation of radioisotope power conversion technologies that will enable future missions that have requirements that cannot be met by either photovoltaic systems or by current radioisotope power systems (RPSs). Requirements of advanced RPSs include high efficiency and high specific power (watts/kilogram) in order to meet future mission requirements with less radioisotope fuel and lower mass so that these systems can meet requirements for a variety of future space applications, including continual operation surface missions, outer-planetary missions, and solar probe. These advances would enable a factor of 2 to 4 decrease in the amount of fuel required to generate electrical power. Advanced RPS development goals also include long-life, reliability, and scalability. This paper provides an update on the contractual efforts under the Radioisotope Power Conversion Technology (RPCT) NASA Research Announcement (NRA) for research and development of Stirling, thermoelectric, and thermophotovoltaic power conversion technologies. The paper summarizes the current RPCT NRA efforts with a brief description of the effort, a status and/or summary of the contractor's key accomplishments, a discussion of upcoming plans, and a discussion of relevant system-level benefits and implications. The paper also provides a general discussion of the benefits from the development of these advanced power conversion technologies and the eventual payoffs to future missions (discussing system benefits due to overall improvements in efficiency, specific power, etc.)

Humanized Mouse Model of Ovarian Cancer Recapitulates Patient Solid Tumor Progression, Ascites Formation, and Metastasis

Ovarian cancer is the most common cause of death from gynecological cancer. Understanding the biology of this disease, particularly how tumor-associated lymphocytes and fibroblasts contribute to the progression and metastasis of the tumor, has been impeded by the lack of a suitable tumor xenograft model. We report a simple and reproducible system in which the tumor and tumor stroma are successfully engrafted into NOD-scid IL2Rγnull (NSG) mice. This is achieved by injecting tumor cell aggregates derived from fresh ovarian tumor biopsy tissues (including tumor cells, and tumor-associated lymphocytes and fibroblasts) i.p. into NSG mice. Tumor progression in these mice closely parallels many of the events that are observed in ovarian cancer patients. Tumors establish in the omentum, ovaries, liver, spleen, uterus, and pancreas. Tumor growth is initially very slow and progressive within the peritoneal cavity with an ultimate development of tumor ascites, spontaneous metastasis to the lung, increasing serum and ascites levels of CA125, and the retention of tumor-associated human fibroblasts and lymphocytes that remain functional and responsive to cytokines for prolonged periods. With this model one will be able to determine how fibroblasts and lymphocytes within the tumor microenvironment may contribute to tumor growth and metastasis, and will make it possible to evaluate the efficacy of therapies that are designed to target these cells in the tumor stroma

Arenavirus budding resulting from viral-protein-associated cell membrane curvature

Viral replication occurs within cells, with release (and onward infection) primarily achieved through two alternative mechanisms: lysis, in which virions emerge as the infected cell dies and bursts open; or budding, in which virions emerge gradually from a still living cell by appropriating a small part of the cell membrane. Virus budding is a poorly understood process that challenges current models of vesicle formation. Here, a plausible mechanism for arenavirus budding is presented, building on recent evidence that viral proteins embed in the inner lipid layer of the cell membrane. Experimental results confirm that viral protein is associated with increased membrane curvature, whereas a mathematical model is used to show that localized increases in curvature alone are sufficient to generate viral buds. The magnitude of the protein-induced curvature is calculated from the size of the amphipathic region hypothetically removed from the inner membrane as a result of translation, with a change in membrane stiffness estimated from observed differences in virion deformation as a result of protein depletion. Numerical results are based on experimental data and estimates for three arenaviruses, but the mechanisms described are more broadly applicable. The hypothesized mechanism is shown to be sufficient to generate spontaneous budding that matches well both qualitatively and quantitatively with experimental observations

Local Convergence and Global Diversity: From Interpersonal to Social Influence

Axelrod (1997) showed how local convergence in cultural influence can preserve cultural diversity. We argue that central implications of Axelrod's model may change profoundly, if his model is integrated with the assumption of social influence as assumed by an earlier generation of modelers. Axelrod and all follow up studies employed instead the assumption that influence is interpersonal (dyadic). We show how the combination of social influence with homophily allows solving two important problems. Our integration of social influence yields monoculture in small societies and diversity increasing in population size, consistently with empirical evidence but contrary to earlier models. The second problem was identified by Klemm et al.(2003a,b), an extremely narrow window of noise levels in which diversity with local convergence can be obtained at all. Our model with social influence generates stable diversity with local convergence across a much broader interval of noise levels than models based on interpersonal influence.Comment: 20 pages, 3 figures, Paper presented at American Sociological Association 103rd Annual Meeting, August 1-4, 2008, Boston, MA. Session on Mathematical Sociolog

The faint young Sun problem

For more than four decades, scientists have been trying to find an answer to one of the most fundamental questions in paleoclimatology, the `faint young Sun problem'. For the early Earth, models of stellar evolution predict a solar energy input to the climate system which is about 25% lower than today. This would result in a completely frozen world over the first two billion years in the history of our planet, if all other parameters controlling Earth's climate had been the same. Yet there is ample evidence for the presence of liquid surface water and even life in the Archean (3.8 to 2.5 billion years before present), so some effect (or effects) must have been compensating for the faint young Sun. A wide range of possible solutions have been suggested and explored during the last four decades, with most studies focusing on higher concentrations of atmospheric greenhouse gases like carbon dioxide, methane or ammonia. All of these solutions present considerable difficulties, however, so the faint young Sun problem cannot be regarded as solved. Here I review research on the subject, including the latest suggestions for solutions of the faint young Sun problem and recent geochemical constraints on the composition of Earth's early atmosphere. Furthermore, I will outline the most promising directions for future research. In particular I would argue that both improved geochemical constraints on the state of the Archean climate system and numerical experiments with state-of-the-art climate models are required to finally assess what kept the oceans on the Archean Earth from freezing over completely.Comment: 32 pages, 8 figures. Invited review paper accepted for publication in Reviews of Geophysic

Appraisals of emotion-eliciting events: Testing a theory of discrete emotions.

A recent theory Why 1 Two individuals will feel the same emotion to the extent that their appraisals of a situation are the same. Two individuals with different appraisals, or the same individual with different appraisals at different times, will feel different emotions. Thus, by identifying emotion-causing patterns of appraisal, such theories may be able to explain how an infinite variety of situations can elicit the same emotion and may also be able to explain the apparent variability across people and over time in emotional responses to the same event. The challenge for appraisal theorists is to specify the patterns of appraisal that can produce particular emotions. In the present generation of appraisal theories, Roseman (1979) proposed that five appraisals influence emotions: (a) motivational state: whether an individual's motive in a given situation is aversive (a punishment that he or she seeks to avoid) or appetitive (a reward that he or she seeks to attain), (b) situational state: whether the motivational state (the punishment or reward) is present or absent in the situation to which the individual is reacting, (c) probability: whether the occurrence of an outcome is uncertain or certain, (d) legitimacy: whether a negative outcome is deserved or a positive outcome is deserved in the situation, and (e) agency: whether an outcome is caused by impersonal circumstances, some other person, or the self. In testing this theory, Roseman (1983) found that each of the five appraisals had a significant effect on emotion ratings and that the overall pattern of relationships between particular combinations of appraisals and particular emotions corresponded significantly to theoretical predictions. Post hoc analyses suggested that the effects of the motivational state and situational state appraisals (interacting to determine whether an outcome was appraised as negative vs. positive), and of probability, con-