http://hdl.handle.net/10339/25960 Fri, 24 May 2013 02:06:28 GMT 2013-05-24T02:06:28Z http://hdl.handle.net/10339/37413 Neural temporal dynamics of stress in comorbid major depressive disorder and social anxiety disorder Waugh, Christian E.; Hamilton, J. Paul; Chen, Michael C.; Joormann, Jutta; Gotlib, Ian H. BACKGROUND: Despite advances in neurobiological research on Major Depressive Disorder and Social Anxiety Disorder, little is known about the neural functioning of individuals with comorbid depression/social anxiety. We examined the timing of neural responses to social stress in individuals with major depression and/or social anxiety. We hypothesized that having social anxiety would be associated with earlier responses to stress, having major depression would be associated with sustained responses to stress, and that comorbid participants would exhibit both of these response patterns. METHODS: Participants were females diagnosed with pure depression (n = 12), pure social anxiety (n = 16), comorbid depression/social anxiety (n = 17), or as never having had any Axis-I disorder (control; n = 17). Blood oxygenation-level dependent activity (BOLD) was assessed with functional magnetic resonance imaging (fMRI). To induce social stress, participants prepared a speech that was ostensibly to be evaluated by a third party. RESULTS: Whereas being diagnosed with depression was associated with a resurgence of activation in the medial frontal cortex late in the stressor, having social anxiety was associated with a vigilance-avoidance activation pattern in the occipital cortex and insula. Comorbid participants exhibited activation patterns that generally overlapped with the non-comorbid groups, with the exception of an intermediate level of activation, between the level of activation of the pure depression and social anxiety groups, in the middle and posterior cingulate cortex. CONCLUSIONS: These findings advance our understanding of the neural underpinnings of major depression and social anxiety, and of their comorbidity. Future research should elucidate more precisely the behavioral correlates of these patterns of brain activation. Provisional PDF; fully formatted PDF in production - August 2012 Fri, 01 Jun 2012 00:00:00 GMT http://hdl.handle.net/10339/37413 2012-06-01T00:00:00Z http://hdl.handle.net/10339/37411 Corazonin Neurons Function in Sexually Dimorphic Circuitry That Shape Behavioral Responses to Stress in Drosophila Zhao, Yan; Bretz, Colin A.; Hawksworth, Shane A.; Hirsh, Jay; Johnson, Erik C. All organisms are confronted with dynamic environmental changes that challenge homeostasis, which is the operational definition of stress. Stress produces adaptive behavioral and physiological responses, which, in the Metazoa, are mediated through the actions of various hormones. Based on its associated phenotypes and its expression profiles, a candidate stress hormone in Drosophila is the corazonin neuropeptide. We evaluated the potential roles of corazonin in mediating stress-related changes in target behaviors and physiologies through genetic alteration of corazonin neuronal excitability. Ablation of corazonin neurons confers resistance to metabolic, osmotic, and oxidative stress, as measured by survival. Silencing and activation of corazonin neurons lead to differential lifespan under stress, and these effects showed a strong dependence on sex. Additionally, altered corazonin neuron physiology leads to fundamental differences in locomotor activity, and these effects were also sex-dependent. The dynamics of altered locomotor behavior accompanying stress was likewise altered in flies with altered corazonin neuronal function. We report that corazonin transcript expression is altered under starvation and osmotic stress, and that triglyceride and dopamine levels are equally impacted in corazonin neuronal alterations and these phenotypes similarly show significant sexual dimorphisms. Notably, these sexual dimorphisms map to corazonin neurons. These results underscore the importance of central peptidergic processing within the context of stress and place corazonin signaling as a critical feature of neuroendocrine events that shape stress responses and may underlie the inherent sexual dimorphic differences in stress responses. Mon, 01 Feb 2010 00:00:00 GMT http://hdl.handle.net/10339/37411 2010-02-01T00:00:00Z http://hdl.handle.net/10339/37410 Perinatal Androgens and Adult Behavior Vary with Nestling Social System in Siblicidal Boobies Müller, Martina S.; Brennecke, Julius F.; Porter, Elaine T.; Ottinger, Mary Ann; Anderson, David J. BACKGROUND: Exposure to androgens early in development, while activating adaptive aggressive behavior, may also exert long-lasting effects on non-target components of phenotype. Here we compare these organizational effects of perinatal androgens in closely related Nazca (Sula granti) and blue-footed (S. nebouxii) boobies that differ in neonatal social system. The older of two Nazca booby hatchlings unconditionally attacks and ejects the younger from the nest within days of hatching, while blue-footed booby neonates lack lethal aggression. Both Nazca booby chicks facultatively upregulate testosterone (T) during fights, motivating the prediction that baseline androgen levels differ between obligately siblicidal and other species. METHODOLOGY/PRINCIPLE FINDINGS: We show that obligately siblicidal Nazca boobies hatch with higher circulating androgen levels than do facultatively siblicidal blue-footed boobies, providing comparative evidence of the role of androgens in sociality. Although androgens confer a short-term benefit of increased aggression to Nazca booby neonates, exposure to elevated androgen levels during this sensitive period in development can also induce long-term organizational effects on behavior or morphology. Adult Nazca boobies show evidence of organizational effects of early androgen exposure in aberrant adult behavior: they visit unattended non-familial chicks in the colony and direct mixtures of aggression, affiliative, and sexual behavior toward them. In a longitudinal analysis, we found that the most active Non-parental Adult Visitors (NAVs) were those with a history of siblicidal behavior as a neonate, suggesting that the tendency to show social interest in chicks is programmed, in part, by the high perinatal androgens associated with obligate siblicide. Data from closely related blue-footed boobies provide comparative support for this interpretation. Lacking obligate siblicide, they hatch with a corresponding low androgen level, and blue-footed booby adults show a much lower frequency of NAV behavior and a lower probability of behaving aggressively during NAV interactions. This species difference in adult social behavior appears to have roots in both pleiotropic and experiential effects of nestling social system. CONCLUSIONS/SIGNIFICANCE: Our results indicate that Nazca boobies experience life-long consequences of androgenic preparation for an early battle to the death. Sun, 01 Jun 2008 00:00:00 GMT http://hdl.handle.net/10339/37410 2008-06-01T00:00:00Z http://hdl.handle.net/10339/37408 Yeast Sex: Surprisingly High Rates of Outcrossing between Asci Murphy, Helen A.; Zeyl, Clifford W. BACKGROUND: Saccharomyces yeasts are an important model system in many areas of biological research. Very little is known about their ecology and evolution in the wild, but interest in this natural history is growing. Extensive work with lab strains in the last century uncovered the Saccharomyces life cycle. When nutrient limited, a diploid yeast cell will form four haploid spores encased in a protective outer layer called the ascus. Confinement within the ascus is thought to enforce mating between products of the same meiotic division, minimizing outcrossing in this stage of the life cycle. METHODOLOGY/PRINCIPLE FINDINGS: Using a set of S. cerevisiae and S. paradoxus strains isolated from woodlands in North America, we set up trials in which pairs of asci were placed in contact with one another and allowed to germinate. We observed outcrossing in ~40% of the trials, and multiple outcrossing events in trials with three asci in contact with each other. When entire populations of densely crowded asci germinated, ~10–25% of the resulting colonies were outcrossed. There were differences between the species with S. cerevisiae having an increased tendency to outcross in mass mating conditions. CONCLUSIONS/SIGNIFICANCE: Our results highlight the potential for random mating between spores in natural strains, even in the presence of asci. If this type of mating does occur in nature and it is between close relatives, then a great deal of mating behavior may be undetectable from genome sequences. Sat, 01 May 2010 00:00:00 GMT http://hdl.handle.net/10339/37408 2010-05-01T00:00:00Z