Search

Babesia microti can lead to severe babesiosis in immunosuppressed populations, but due to high numbers of asymptomatic cases, clinical reporting is unable to define its geographic distribution. Although Lyme disease caused by Borrelia burgdorferi is endemic throughout Pennsylvania (PA), human babesiosis is under recognized, despite sharing the same vector and primary reservoir host. Ixodes ticks are known to carry B. microti throughout PA, but information about pathogen prevalence in small mammal reservoirs remains limited. Characterizing B. microti prevalence in these small mammals can elucidate mechanisms of pathogen spread and define geographic areas where humans are at risk of infection. We tested 692 small mammals across eight contiguous counties in central PA for molecular evidence of B. microti and B. burgdorferi. In total, six different small mammal species were collected. The overall prevalence of B. microti was 32% with similar rates observed across all counties. Surprisingly, this was higher than the prevalence of B. burgdorferi at 21%. In fact, high rates of B. microti were found in all six species, and both pathogens were identified in 11% of mammals tested. The prevalence of B. microti was highest in Myodes gapperi (southern red-backed vole) at 39% despite Peromyscus leucopus (white-footed mouse) being considered the primary reservoir host for B. microti. In conclusion, B. microti has a high prevalence across multiple small mammal species throughout central PA. This prevalence is greater than B. burgdorferi despite a much higher incidence of Lyme disease compared to babesiosis in PA. Although it remains unknown how the prevalence of B. microti in small mammal hosts corresponds to human infection rates, the high pathogen prevalence of B. microti suggests that it is an emerging pathogen in this area. Currently, babesiosis is not a reportable disease in PA, and additional studies are warranted to evaluate its clinical significance in this geographic region.

Animal discrimination training and testing often are used to assess animal behavioral flexibility and capabilities. GO-NOGO discrimination, in particular, has been used extensively, across a multitude of species and experimental paradigms. In its typical form, GO-NOGO discrimination learning is assessed by the magnitude of, and rate of acquisition of, discrimination capability, which is nominally low at the start of training, and through experience, is improved as a function of the reward schedule employed. Discrimination performance in this task is normally reported via a single empirical metric, as the percentage of stimulus-response trials which included a ‘correct’ response. However, this view of discrimination as a singular skill masks the considerable differences which exist in GO and NOGO responses (which typically require an action, and a suppression of action, respectively). To investigate the potential for these two responses to be learned independently and via different mechanisms, we performed operant training of adult zebra finches (Taeniopygia guttata) in a GO-NOGO auditory discrimination task. We demonstrate that correct responsiveness to GO and NOGO stimuli was learned via different overall performance trajectories, with performance on GO and NOGO trials emerging independently both within and between training sessions. We propose that this differential learning derives from a combination of response generalization and response modal form. These data suggest that response action and suppression are subserved by different neural circuits, and further indicate that consideration of discrimination tasks as univariate problems masks underlying complexity by obscuring their individual components.

Amphibian ventral epithelia can perform significant Na+ transport, as characterized in the now-classic two-membrane model first demonstrated by Ussing and colleagues. This transport is normally demonstrated by using short-circuit current (Isc) to negate transport-generated potentials across epithelia suspended in Ussing chambers. While this model and method have been supported through decades of experimentation, the exact relationship between the transport current and the epithelial potential generated is often ignored, as potentials typically are treated as a factor to be systematically eliminated. Here, leopard frog (Rana spp.) ventral epithelium were utilized in Ussing chambers for tests of specifically how the relationship between epithelial potentials and transport currents depends upon external medium ionic content. Stable skin potentials were recorded using 300 mOsm NaCl; potentials were then reduced to 0 mV via Isc in order to estimate the magnitude of the ionic transport current. A subset of the epithelia prepared was then tested in one or more alternative ionic solutions (300 mOsm KCl, NaHCO3, and CaCl2). While identifiable skin potentials were detected in all solutions tested, only in NaCl were the magnitudes of the epithelial potential and short-circuit current statistically significantly related. Detectable skin potentials in non-Na+-containing solutions indicates the existence of non-Na+ electrogenic activity in this tissue, whose presence explains the relatively poor ability of transport current magnitudes to explain the magnitudes of observed skin potential. Estimates of molecular transport rates for Na+ exceed 4 x 1014 molec sec-1 cm-1, demonstrating the enormous osmoregulatory challenge faced by fresh water amphibians in maintaining ionic homeostasis.

Physical exercise is well-understood to provide significant health benefits, through physiological adaptations induced by the repeated exertion stress exercise imposes on our systems. Chief among these are cardiovascular adaptations to exercise, including adjustments of cardiac parameters such as stroke volume, heart rate, and maximal cardiac output. It is commonly assumed that aerobic forms of exercise provide greater cardiovascular benefits than do non-aerobic forms of exercise. To test this assumption, exercise habits and resting heart rate were examined in a large population of healthy young adults. 90% of subjects reported regular physical exercise, with aerobic exercise constituting 64% of all exercise hours. Subjects with a history of smoking exhibited higher resting heart rates than those with no smoking history, an effect which was due primarily to a reduction in exercise hours by smokers than due to a smoking habit itself. While both total exercise amount and aerobic exercise amount were significantly and negatively related to resting heart rate, total exercise amount was a better overall predictor of resting heart rate than was aerobic exercise amount. All forms of exercise were associated with cardiovascular health, with cardiovascular benefits accruing according to the amount of exercise performed, even in optimally healthy young adults.

Immunofluorescent labeling of synaptic vesicle protein 2 (SV2) and confocal microscopy were employed to assess the role of synapse density in the functioning of the avian song system. Synapse density in premotor nuclei HVC and RA was measured, in both sexes of two species characterized by male-only singing behavior: the zebra finch Taeniopygia guttata, which sings a single, stereotyped song, and the Carolina wren Thryothorus ludovicianus, which sings a large repertoire of different songs. Multiple levels of analyses demonstrate overall similarity of synapse density between nuclei HVC and RA, suggesting that synapse density is regulated uniformly across these regions within individuals. Male zebra finches and male Carolina wrens have equivalent synapse densities, suggesting a common pattern of masculinized development despite dramatic behavioral differences. Female Carolina wrens have synaptic density similar to that of males of both species, while female zebra finches exhibit greater synaptic densities in both regions than do male zebra finches or both sexes of wrens. Prior reports implicate testosterone as a regulator of synapse density in this system; sex differences in circulating or neural testosterone may contribute to the sexual dimorphism of synapse density observed here. Interspecific comparison of song system synapse density in nonsinging females suggests that synapse density in female songbirds may be a particularly labile trait.

Scaling of avian brain:body mass throughout the diversification of the class was investigated by analysis of a large collection of adult brain and body masses. Linear regression model analysis of whole-class brain:body scaling resulted in scaling exponents ranging from 0.574 to 0.609, values which exclude several prior empirical and theoretical estimates. Taxonomic level-specific analysis of brain:body scaling was performed by major-axis regression of trait variances partitioned among levels of taxonomic distinction. Brain:body scaling exponents varied markedly among avian orders, but were not easily related to ecological differences among taxa. Avian brain:body scaling exhibited a partial taxon-level effect, in that scaling exponents vary with the taxonomic level of investigation. However, scaling exponents were greatest at the family level, a pattern not consistent with prior ontogenetic or genetic covariance models of trait diversification. Instead, it is suggested that initial diversification among birds was largely through body size diversification, while later diversification of families within orders contained a relatively greater degree of brain size diversification. Avian developmental mode, known to influence avian brain size at hatching, was associated with relatively little variance in adult brain mass. Avian brain:body diversification has occurred relatively uniformly in precocial taxa, while diversification within altricial taxa is marked by a relatively high degree of brain mass diversification among families within orders.

Sexual and interspecific differences in the size of passerine bird song repertoires are related to differences in the size of song-control regions (SCR) within the brain. Most species of Thryothorus wrens (family Certhiidae) are known to duet, and, in both sexes, song repertoire sizes are related to the size of the SCR. However, one member of this genus, the Carolina wren T. ludovicianus, is very sexually dimorphic in its singing behavior: Males develop large song repertoires, whereas females do not sing. In this study, Nissl staining was used to investigate whether the marked gender difference in the behavior of this species is related to sexual dimorphism of the SCR. Carolina wren males, as predicted, possess the largest premotor song nuclei within the genus; these nuclei could not be identified within Nissl-stained female tissue. The cellular bases for gender differences in SCR morphology also were examined: Males and females differed strongly in the size and density of neurons making up the regions in which SCRs exist in the male forebrain. Interspecific comparison provided no evidence for a decoupling of behavioral and neural evolution within this clade. Male Carolina wrens possess the largest song repertoires and SCRs within the genus, whereas females of this species represent the opposite behavioral and neural extremes of this songbird group. These results are consistent with the hypothesis that the size of the passerine song repertoire is limited by the amount of neural tissue devoted to singing.

The fates of 12 1 nests of Northern Cardinals (Cardinalis cardinalis) in south- western Ohio were determined in 199 1 and 1992. Success rate was only 1 So/o, estimated by the Mayfield method. All failed nests were known or suspected to have heen preyed upon. Several hypotheses to explain differences between the location of successful and failed nests were tested. None of those considered explained why the contents of particular nests were taken. We propose that a high incidence of predation by a rich guild of nest predators precludes the existence of predictably safe nest sites for cardinals. Instead, cardinals appear simply to be well-adapted to renest rapidly in response to the near randomness of nest predation. A similar adaptation may characterize many passerines.

Animal evolutionary history has progressed, in fits and starts, over several billions of years of changing environmental conditions on this planet. Ancient environments were strikingly different from modern conditions, and, in some cases, have left a permanent stamp on animal (including human) anatomy and physiology. Recently Lassek and Gaulin (2011) assessed the role which dietary fatty acids may play in shaping human cognitive performance, and in doing so, provide an intriguing glimpse into the evolution of animal nervous systems. Using a large sample of American children aged 6–16 from the Third National Health and Nutrition Examination Survey [Center for Disease Control (CDC), 1988–1994], Lassek and Gaulin explored the statistical relationships between human cognitive performance (assessed via standardized math and reading tests) and dietary components, while controlling for other measures of subjects’ social and environmental backgrounds (including lead exposure, family size and income, ethnicity). They found that dietary fatty acids, particularly n − 3 (“omega-3”) and n − 6 forms, were positively and negatively related, respectively, to cognition scores in both male and female children. The benefits of dietary n − 3 fatty acids were especially important for cognition in female children (Lassek and Gaulin, 2011). Both n − 3 and n − 6 fatty acids are essential nutrients that must be obtained from dietary sources, and our Western diets are known to have relatively low n − 3:n − 6 ratios (Blasbalg et al., 2011). Why their opposite utility? And why of differential importance for males and females? Lassek and Gaulin (2011) suggest explanations which are rooted in our evolutionary past. Our nervous systems contain a predominance of n − 3 fatty acids, which Lassek and Gaulin (2011) hypothesize is due to the fact that animal neurons first evolved in an environment rich in n − 3 fatty acids but limiting in n − 6 fatty acids. Under these conditions, n − 3 fatty acids became, and remain, critical for complete nervous development. Lassek and Gaulin cite corroborative evidence for the ability of n − 6 fatty acids to compete with n − 3 fatty acids for enzymatic access, suggesting that this competition is a direct mechanism for the differential utility of dietary n − 3 and n − 6 forms. Dietary intake of n − 3 fatty acids is shown by Lassek and Gaulin to be especially important for females, which they suggest is due to the fact that female children must partition their dietary intake of these essential nutrients for both their own use as well as toward fat stores for later use as a nutritive source for the provisioning of developing offspring. Here, too, an ancient evolutionary shaping of our animal parental roles continues to represent itself in our utilization of dietary components, with implications for cognitive performance. It is well understood that n − 3 fatty acids are profoundly bio-active in neural as well as other tissues, with influence on cell membrane fluidity (Fernstrom, 1999; Schmitz and Ecker, 2008, and others), oxidative capacity (example in Maillet and Weber, 2007), and gene expression (recently reviewed in Bordoni et al., 2006). Their direct effects on the genesis, viability, and connectivity of neural tissues have also been demonstrated repeatedly in animal studies (as cited by Lassek and Gaulin, 2011), and their dietary importance to the neural development of human infants is also known (Hoffman et al., 2009; Leung et al., 2011; Muhlhausler et al., 2011; Salvig and Lamont, 2011). Lassek and Gaulin (2011) now add to this body of knowledge by demonstrating the importance of dietary n − 3 fatty acids beyond infancy into childhood and adolescence, and also provide evidence and explanation for the differential importance of dietary fatty acids for female children. In doing so, they highlight the need for more stringent consideration of n − 3 dietary requirements during childhood as well as the need for more specific research on the mechanisms by which these essential nutrients influence human cognition. In using their evolutionary perspective, they also provide an important reminder of the need to consider evolutionary constraint in the shaping of our marvelously complex, yet very biologically, nervous systems – in many ways, we (still) are what we eat.

For many songbirds, the vocal repertoire constitutes acoustically distinct songs that are flexibly used in various behavioral contexts. To investigate how these different vocalizations are represented in the song neural system, we presented multiple song stimuli while performing extracellular recording in nucleus HVC in adult male song sparrows Melospiza melodia, a species known for its complex vocal repertoire and territorial use of song. We observed robust auditory responses to natural song stimuli in both awake and anesthetized animals. Auditory responses were selective for multiple songs of the bird's own repertoire (BOR) over acoustically modified versions of these stimuli. Selectivity was evident in both awake and anesthetized HVC, in contrast to auditory selectivity in zebra finch HVC, which is apparent only under anesthesia. Presentation of multiple song stimuli at different recording locations demonstrated that stimulus acoustic features and local neuronal tuning both contribute to auditory responsiveness. HVC auditory responsiveness was broadly distributed and nontopographic. Variance in auditory responsiveness was greater among than within HVC recording locations in both anesthetized and awake birds, in contrast to the global nature of auditory representation within zebra finch HVC. To assess the spatial consistency of auditory representation within HVC, we measured the repeatability with which ensembles of BOR songs were represented across the nucleus. Auditory response ranks to different songs were more consistent across recording locations in awake than in anesthetized animals. This spatial reliability of auditory responsiveness suggests that sound stimulus acoustic features contribute relatively more to auditory responsiveness in awake than in anesthetized animals.

A Ruby-throated Hummingbird (Archilochus colubris) that had become entangled and died in the flowers of a common burdock (Arctium minus) was found 12 August 1999 in Cambria County, Pennsylvania.