Behavior, synaptic mitochondria, and microglia are differentially impacted by chronic adolescent stress and repeated endotoxin exposure in male and female rats.

Early life adversity and chronic inflammation have both been associated with cognitive impairment and neural compromise. In this study, we investigated the interactions between a history of chronic adolescent stress (CAS) and repeated endotoxin exposure on behavior, synaptic mitochondria, and microglia in adult male and female Wistar rats. Adult rats from chronic stress and control conditions were exposed to either repeated endotoxin (lipopolysaccharide; LPS) or saline injections every 3 days for 9 weeks. In both sexes, repeated LPS, regardless of stress history, impaired working memory in the Y maze. Regarding spatial memory, LPS impaired function for females; whereas, CAS altered function in males. Although males had an increase in anxiety-like behavior shortly after CAS, there were no long-term effects on anxiety-like behavior or social interaction observed in males or females. Stress did not alter synaptic mitochondrial function in either sex. Repeated LPS altered synaptic mitochondrial function such that ATP production was increased in females only. There were no observed increases in IBA-1 positive cells within the hippocampus for either sex. However, LPS and CAS altered microglia morphology in females. Impact of repeated LPS was evident at the terminal endpoint with increased spleen weight in both sexes and decreased adrenal weight in males only. Circulating cytokines were not impacted by repeated LPS at the terminal endpoint, but evidence of CAS effects on cytokines in females were evident. These data suggest a long-term impact of chronic stress and an impact of repeated endotoxin challenge in adulthood; however, not all physiological and behavioral metrics examined were impacted by the paradigm employed in this study and the two environmental challenges rarely interacted.

Chronic adolescent stress causes sustained impairment of cognitive flexibility and hippocampal synaptic strength in female rats.

Females that experience chronic stress during development, particularly adolescence, are the most vulnerable group to stress-induced disease. While considerable attention has been devoted to stress-induced manifestation of anxiety, depression, and PTSD, evidence indicates that a history of chronic stress is also a risk factor for cognitive decline and dementia - with females again in a higher risk group. This interplay between sex and stress history indicates specific mechanisms drive neural dysfunction across the lifespan. The presence of sex and stress steroid receptors in the hippocampus provides a point of influence for these variables to drive changes in cognitive function. Here, we used a rodent model of chronic adolescent stress (CAS) to determine the extent to which CAS modifies glutamatergic signaling resulting in cognitive dysfunction. Male and female Wistar rats born in-house remained non-stressed (NS), unmanipulated aside from standard cage cleaning, or were exposed to either physical restraint (60 min) or social defeat (CAS) each day (6 trials each), along with social isolation, throughout the adolescent period (PND 35-47). Cognition was assessed in adult (PND 80-130) male and female rats (n = 10-12) using the Barnes Maze task and the Attention Set-Shift task. Whole hippocampi were extracted from a second cohort of male and female rats (NS and CAS; n = 9-10) and processed for RNA sequencing. Brain tissue from the first cohort (n = 6) was processed for density of glutamatergic synaptic markers (GluA1, NMDA1a, and synaptophysin) or whole-cell patch clamping (n = 4) to determine glutamatergic activity in the hippocampus. Females with a history of chronic stress had shorter latencies to locate the goal box than NS controls during acquisition learning but showed an increased latency to locate the new goal box during reversal learning. This reversal deficit persisted across domains as females with a history of stress required more trials to reach criterion during the reversal phases of the Attention Set-Shift task compared to controls. Ovariectomy resulted in greater performance variability overall during reversal learning with CAS females showing worse performance. Males showed no effects of CAS history on learning or memory performance. Bioinformatic prediction using gene ontology categorization indicated that in females, postsynaptic membrane gene clusters, specifically genes related to glutamatergic synapse remodeling, were enriched with a history of stress. Structural analysis indicated that CAS did not alter glutamate receptor density in females. However, functionally, CAS females had a decreased AMPA/NMDA-dependent current ratio compared to controls indicating a weakening in synaptic strength in the hippocampus. Males showed only a slight change in density of NMDA1a labeling in the CA3 region with a history of stress. The data observed here suggest that females are at risk for impaired cognitive flexibility following a history of adolescent stress, possibly driven by changes in glutamatergic signaling.

Chronocoulometry for quantitative control of mass removal in micro-structures and sensors.

In this work, tungsten wires have been etched in a KOH electrolyte solution. Based on the oxidation state of the electrolytic dissolution reaction's product and time integration of the Faradaic current produced during the reaction, this method is capable of providing a direct measurement of the change in mass of a structure from anodic dissolution. To assess the application of this process for controlled mass removal spanning sub-micrograms to milligrams, two experimental studies and accompanying uncertainty analyses have been undertaken. In the first of these, 5 tungsten wires of length 30 mm were used to remove mass values ranging from 50 to 350 µg. Uncertainty estimates indicate relative combined standard uncertainties of less than 0.3% in the mass changes determined from the measurement of Faradaic current. Comparison of the mass change determined using the electrolytic method, and using a precision ultra-microbalance agreed within this uncertainty. The charge-based method was then applied to modify the dynamic characteristics of a quartz tuning fork oscillator. In these experiments, tungsten fiber attached to one tine of the oscillator was etched in 5 µg increments up to 120 µg of total removed mass. In general, frequency shifts of 2.8 Hz · µg(-1) were observed, indicating sub-microgram resolution for the characterization of probes based on frequency shift and charge-based mass measurement. Taken together, this study provides the basis for a precision method for determining changes in mass based on electrical measurements from an electrochemical system. The utility of this technique is demonstrated through controlled modification of the dynamic properties of a mechanical oscillator.

Spring constant calibration of atomic force microscopy cantilevers with a piezosensor transfer standard.

We describe a method to calibrate the spring constants of cantilevers for atomic force microscopy (AFM). The method makes use of a "piezosensor" composed of a piezoresistive cantilever and accompanying electronics. The piezosensor was calibrated before use with an absolute force standard, the NIST electrostatic force balance (EFB). In this way, the piezosensor acts as a force transfer standard traceable to the International System of Units. Seven single-crystal silicon cantilevers with rectangular geometries and nominal spring constants from 0.2 to 40 Nm were measured with the piezosensor method. The values obtained for the spring constant were compared to measurements by four other techniques: the thermal noise method, the Sader method, force loading by a calibrated nanoindentation load cell, and direct calibration by force loading with the EFB. Results from different methods for the same cantilever were generally in agreement, but differed by up to 300% from nominal values. When used properly, the piezosensor approach provides spring-constant values that are accurate to +/-10% or better. Methods such as this will improve the ability to extract quantitative information from AFM methods.

Liquid ammonia mediated metathesis: synthesis of binary metal chalcogenides and pnictides.

Addition of stoichiometric amounts of low valent metal halides to liquid ammonia solutions of disodium chalcogenide (Na(2)E; E = S, Se, Te) afforded a range of both crystalline (PbE (E = S, Se, Te), TlE (E = S, Se), Tl(5)Te(3), Ag(2)E (E = S, Se, Te)) and X-ray amorphous (MS (M = Ni, Cu, Zn, Cd, Hg), M(2)E(3) (M = Ga, In; E = S, Se, Te), HgE (E = Se, Te), CuE (E = S, Se, Te), Cu(2)S) metal chalcogenides in good yield (95%). Reactions between metal halides and sodium pnictides (Na(3)Pn; Pn = As, Sb) in liquid ammonia also afforded X-ray amorphous material (M(3)Pn(2), M = Zn, Cd; MPn, M = Fe, Co, Ni) in good yield (95%). Isolation of the metal chalcogenides and pnictides was achieved through washing with CS(2) and distilled water. All reactions were complete within 36 h. Products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDXA), electron probe analysis, FT-IR spectroscopy, Raman spectroscopy, microanalysis, and band gap measurements. Annealing amorphous material at 250-300 degrees C for 48 h induced sufficient crystallinity for analysis by X-ray powder diffraction.

Effects of videotaped violence on hypermnesia for imaginally encoded concrete and abstract words.

To assess whether increased arousal would differentially affect hypermnesia (enhanced recall) for imaginally encoded concrete and abstract words, two sets of materials (a violent videotape for high arousal and a bird-nest-building videotape for low arousal) were interpolated at four different points in a memory experiment. A pilot experiment measuring the change in heart rate before and after the viewing of two sets of materials confirmed the relationship between self-reported arousal and physiological state. Evidence suggests that only when arousing materials are experienced during the retention interval will hypermnesia be inhibited. In all conditions, concrete words were recalled at twice or more the rate of abstract words.

Hypermnesia for high-imagery words: the effects of interpolated tasks.

The purpose of this study was to determine whether hypermnesia (improved net recall over time) can be differentially affected by manipulating the nature of tasks performed during the intervals between successive recall trials. In Experiment 1, all subjects were asked to imaginally encode separate words and were tested three times for recall. The control group (no interpolated task) produced the hypermnesia effect. Both groups performing interpolated tasks showed significantly lower recall. A second experiment was conducted in order to replicate these results and to examine the effects of intertest rehearsal on hypermnesia. In Experiment 2, subjects were asked to encode pairs of words using interactive-imagery instructions. Six different interpolated task conditions were employed, varying in the degree to which subsystems of working memory were used. Groups performing imaginal interpolated tasks showed no hypermnesia, whereas those performing nonimaginal tasks did. These findings suggest that access to working memory (see Baddeley, 1986) is not necessary for hypermnesia.

Antileukotoxin antibody produced in the bovine lung after aerosol exposure to viable Pasteurella haemolytica.

Experiments were performed to determine the in vivo immunogenicity of Pasteurella haemolytica leukotoxin. Calves were exposed twice to aerosol mists of viable P haemolytica, using a treatment regimen previously shown to induce a resistant state. Pulmonary lavage fluids and serum samples from these calves were assayed for leukotoxin-neutralizing antibodies. Before aerosol exposure, neutralizing antibody titers were routinely found in serum samples, but were not detectable in pulmonary lavage concentrates before exposure. After aerosol exposure, titers of toxin-neutralizing immunoglobulin (Ig)A and IgG antibodies were found in pulmonary lavage concentrates and were accompanied by increased serum toxin neutralization titers.

The use of imagery by intelligent and by creative schoolchildren.

Two studies focusing on differences in thinking strategies between intellectually gifted and creative children were undertaken. In the first study (N = 29), ethnographic techniques of observation along with testing and problem-solving interviews were used in a regular classroom. Three subjects (one high IQ and high creativity, one high IQ and low creativity, and one low IQ and high creativity) were identified for intensive observation. In the second study, testing procedures and problem-solving interviews were completed with 30 children who were placed in a gifted program within an urban school system. Both studies produced evidence supporting the link between imaging abilities and creative thinking.