PAHs and star formation in the HII regions of nearby galaxies M83 and M33

We present mid-infrared (MIR) spectra of HII regions within star-forming galaxies M83 and M33. Their emission features are compared with Galactic and extragalactic HII regions, HII-type galaxies, starburst galaxies, and Seyfert/LINER type galaxies. Our main results are as follows: (i) the M33 and M83 HII regions lie in between Seyfert/LINER galaxies and HII-type galaxies in the 7.7/11.3 - 6.2/11.3 plane, while the different sub-samples exhibiting different 7.7/6.2 ratios; (ii) Using the NASA Ames PAH IR Spectroscopic database, we demonstrate that the 6.2/7.7 ratio does not effectively track PAH size, but the 11.3/3.3 PAH ratio does; (iii) variations on the 17 $\mu$m PAH band depends on object type; however, there is no dependence on metallicity for both extragalactic HII regions and galaxies; (iv) the PAH/VSG intensity ratio decreases with the hardness of the radiation field and galactocentric radius (Rg), yet the ionization alone cannot account for the variation seen in all of our sources; (v) the relative strength of PAH features does not change significantly with increasing radiation hardness, as measured through the [NeIII]/[NeII] ratio and the ionization index; (vi) We present PAH SFR calibrations based on the tight correlation between the 6.2, 7.7, and 11.3 $\mu$m PAH luminosities with the 24 $\mu$m luminosity and the combination of the 24 $\mu$m and H$\alpha$ luminosity; (vii) Based on the total luminosity from PAH and FIR emission, we argue that extragalactic HII regions are more suitable templates in modeling and interpreting the large scale properties of galaxies compared to Galactic HII regions.Comment: 26 pages, 24 figures, 6 tables. Accepted for publication in MNRA

The Predictive Nature of Individual Differences in Early Associative Learning and Emerging Social Behavior

Across the first year of life, infants achieve remarkable success in their ability to interact in the social world. The hierarchical nature of circuit and skill development predicts that the emergence of social behaviors may depend upon an infant's early abilities to detect contingencies, particularly socially-relevant associations. Here, we examined whether individual differences in the rate of associative learning at one month of age is an enduring predictor of social, imitative, and discriminative behaviors measured across the human infant's first year. One-month learning rate was predictive of social behaviors at 5, 9, and 12 months of age as well as face-evoked discriminative neural activity at 9 months of age. Learning was not related to general cognitive abilities. These results underscore the importance of early contingency learning and suggest the presence of a basic mechanism underlying the ontogeny of social behaviors

Influence of Postnatal Glucocorticoids on Hippocampal-Dependent Learning Varies with Elevation Patterns and Administration Methods

Recent interest in the lasting effects of early-life stress has expanded to include effects on cognitive performance. An increase in circulating glucocorticoids is induced by stress exposure and glucocorticoid effects on the hippocampus likely underlie many of the cognitive consequences. Here we review studies showing that corticosterone administered to young rats at the conclusion of the stress-hyporesponsiveness period affects later performance in hippocampally-mediated trace eyeblink conditioning. The nature and even direction of these effects varies with the elevation patterns (level, duration, temporal fluctuation) achieved by different administration methods. We present new time course data indicating that constant glucocorticoid elevations generally corresponded with hippocampus-mediated learning deficits, whereas acute, cyclical elevations corresponded with improved initial acquisition. Sensitivity was greater for males than for females. Further, changes in hippocampal neurogenesis paralleled some but not all effects. The findings demonstrate that specific patterns of glucocorticoid elevation produced by different drug administration procedures can have markedly different, sex-specific consequences on basic cognitive performance and underlying hippocampal physiology. Implications of these findings for glucocorticoid medications prescribed in childhood are discussed

Variations in Effects of Elevated Corticosterone Related to Drug Delivery Method: Plasma Concentration, Dentate Gyrus Neurogenesis, and Development of Trace Eyeblink Conditioning

Exogenous glucocorticoids are commonly used in modern medications even though adverse effects on hippocampal-dependent learning and memory have been reported. Studies examining the effects of glucocorticoids on the developing brain and behavior report inconsistent results. Such studies require a reliable, long-term method of drug administration, and recent reports have questioned the reliability of available drug delivery methods in mice. In our laboratory, variable behavioral results using trace eyeblink conditioning (EBC) suggest that we may be having similar problems in developing rat pups.To better understand this issue, we conducted a detailed time-course assessment of blood plasma concentrations of corticosterone (CORT) to compare 3 common methods of administration starting on postnatal day 15 in Long-Evans rat pups: s.c. pellet (35 mg, 21-day slow-release), s.c.injection (twice daily, 3 days, 20 mg/kg), and s.c. osmotic mini-pump (release rate 1μL/hr), with appropriate vehicle controls for each. For CORT plasma assays, blood samples were taken over the course of 7 days for pellets and over 3 days for injections and minipumps. Additionally, some of the animals in each group received three daily intraperitoneal injections of BrdU (50 mg/kg) on postnatal days 16-18, in order to study possible CORT effects on neurogenesis. Ten days after the last BrdU injection, brains were harvested. Coronal sections containing dorsal hippocampus were collected, immunostained and scanned with a confocal microscope. Stereological analysis focused on quantifying newly generated neurons using the Rare Events Protocol.Trace EBC was impaired by pellets and minipumps but facilitated by injections. Pellets produced peak plasma CORT elevations up to 3800 ng/ml at 4 hours post-surgery and returned to baseline within 5 days. Injection produced a peak plasma elevation of CORT of up to 2000 ng/ml at 1 hour after each injection, which returned to baseline within 4 hours, producing a fluctuating pattern of elevations. Minipumps produced peak CORT elevation of 527 ng/ml 1 hour after surgery, which corresponded with surgical stress-related elevation in control animals. CORT elevation then dropped to a relatively steady level for the next 3 days at 200-300 ng/ml. These findings suggest that the different peak levels and elevation patterns of these three CORT delivery methods are likely to yield differences in behavioral outcomes. However, the total number of newly generated neurons in the days immediately following CORT administration, and their density in dorsal dentate gyrus, were not significantly influenced by the elevated CORT, regardless of delivery method

Variations in Effects of Elevated Corticosterone Related to Drug Delivery Method: Plasma Concentration, Dentate Gyrus Neurogenesis, and Development of Trace Eyeblink Conditioning

Exogenous glucocorticoids are commonly used in modern medications even though adverse effects on hippocampal-dependent learning and memory have been reported. Studies examining the effects of glucocorticoids on the developing brain and behavior report inconsistent results. Such studies require a reliable, long-term method of drug administration, and recent reports have questioned the reliability of available drug delivery methods in mice. In our laboratory, variable behavioral results using trace eyeblink conditioning (EBC) suggest that we may be having similar problems in developing rat pups.To better understand this issue, we conducted a detailed time-course assessment of blood plasma concentrations of corticosterone (CORT) to compare 3 common methods of administration starting on postnatal day 15 in Long-Evans rat pups: s.c. pellet (35 mg, 21-day slow-release), s.c.injection (twice daily, 3 days, 20 mg/kg), and s.c. osmotic mini-pump (release rate 1μL/hr), with appropriate vehicle controls for each. For CORT plasma assays, blood samples were taken over the course of 7 days for pellets and over 3 days for injections and minipumps. Additionally, some of the animals in each group received three daily intraperitoneal injections of BrdU (50 mg/kg) on postnatal days 16-18, in order to study possible CORT effects on neurogenesis. Ten days after the last BrdU injection, brains were harvested. Coronal sections containing dorsal hippocampus were collected, immunostained and scanned with a confocal microscope. Stereological analysis focused on quantifying newly generated neurons using the Rare Events Protocol.Trace EBC was impaired by pellets and minipumps but facilitated by injections. Pellets produced peak plasma CORT elevations up to 3800 ng/ml at 4 hours post-surgery and returned to baseline within 5 days. Injection produced a peak plasma elevation of CORT of up to 2000 ng/ml at 1 hour after each injection, which returned to baseline within 4 hours, producing a fluctuating pattern of elevations. Minipumps produced peak CORT elevation of 527 ng/ml 1 hour after surgery, which corresponded with surgical stress-related elevation in control animals. CORT elevation then dropped to a relatively steady level for the next 3 days at 200-300 ng/ml. These findings suggest that the different peak levels and elevation patterns of these three CORT delivery methods are likely to yield differences in behavioral outcomes. However, the total number of newly generated neurons in the days immediately following CORT administration, and their density in dorsal dentate gyrus, were not significantly influenced by the elevated CORT, regardless of delivery method

Influence of Postnatal Glucocorticoids on Hippocampal-Dependent Learning Varies with Elevation Patterns and Administration Methods

Recent interest in the lasting effects of early-life stress has expanded to include effects on cognitive performance. An increase in circulating glucocorticoids is induced by stress exposure and glucocorticoid effects on the hippocampus likely underlie many of the cognitive consequences. Here we review studies showing that corticosterone administered to young rats at the conclusion of the stress-hyporesponsiveness period affects later performance in hippocampally-mediated trace eyeblink conditioning. The nature and even direction of these effects varies with the elevation patterns (level, duration, temporal fluctuation) achieved by different administration methods. We present new time course data indicating that constant glucocorticoid elevations generally corresponded with hippocampus-mediated learning deficits, whereas acute, cyclical elevations corresponded with improved initial acquisition. Sensitivity was greater for males than for females. Further, changes in hippocampal neurogenesis paralleled some but not all effects. The findings demonstrate that specific patterns of glucocorticoid elevation produced by different drug administration procedures can have markedly different, sex-specific consequences on basic cognitive performance and underlying hippocampal physiology. Implications of these findings for glucocorticoid medications prescribed in childhood are discussed

Variations in Effects of Elevated Corticosterone Related to Drug Delivery Method: Plasma Concentration, Dentate Gyrus Neurogenesis, and Development of Trace Eyeblink Conditioning

Exogenous glucocorticoids are commonly used in modern medications even though adverse effects on hippocampal-dependent learning and memory have been reported. Studies examining the effects of glucocorticoids on the developing brain and behavior report inconsistent results. Such studies require a reliable, long-term method of drug administration, and recent reports have questioned the reliability of available drug delivery methods in mice. In our laboratory, variable behavioral results using trace eyeblink conditioning (EBC) suggest that we may be having similar problems in developing rat pups.To better understand this issue, we conducted a detailed time-course assessment of blood plasma concentrations of corticosterone (CORT) to compare 3 common methods of administration starting on postnatal day 15 in Long-Evans rat pups: s.c. pellet (35 mg, 21-day slow-release), s.c.injection (twice daily, 3 days, 20 mg/kg), and s.c. osmotic mini-pump (release rate 1μL/hr), with appropriate vehicle controls for each. For CORT plasma assays, blood samples were taken over the course of 7 days for pellets and over 3 days for injections and minipumps. Additionally, some of the animals in each group received three daily intraperitoneal injections of BrdU (50 mg/kg) on postnatal days 16-18, in order to study possible CORT effects on neurogenesis. Ten days after the last BrdU injection, brains were harvested. Coronal sections containing dorsal hippocampus were collected, immunostained and scanned with a confocal microscope. Stereological analysis focused on quantifying newly generated neurons using the Rare Events Protocol.Trace EBC was impaired by pellets and minipumps but facilitated by injections. Pellets produced peak plasma CORT elevations up to 3800 ng/ml at 4 hours post-surgery and returned to baseline within 5 days. Injection produced a peak plasma elevation of CORT of up to 2000 ng/ml at 1 hour after each injection, which returned to baseline within 4 hours, producing a fluctuating pattern of elevations. Minipumps produced peak CORT elevation of 527 ng/ml 1 hour after surgery, which corresponded with surgical stress-related elevation in control animals. CORT elevation then dropped to a relatively steady level for the next 3 days at 200-300 ng/ml. These findings suggest that the different peak levels and elevation patterns of these three CORT delivery methods are likely to yield differences in behavioral outcomes. However, the total number of newly generated neurons in the days immediately following CORT administration, and their density in dorsal dentate gyrus, were not significantly influenced by the elevated CORT, regardless of delivery method