Sex differences in behavior and pro-inflammatory cytokine mRNA expression following stressor exposure and re-exposure.

Stressful events promote a wide range of neurotransmitter and neuroendocrine changes, which likely serve in an adaptive capacity. However, with repeated stressor exposure, behavioral disturbances, such as anxiety and depression, may develop. Moreover, re-exposure to a stressor for some time following an initial aversive experience may instigate especially pronounced neurochemical variations that favor the emergence of depression and anxiety. These outcomes may stem from any number of neurobiological changes, but increasing attention has focused on the potential contribution of inflammatory factors, such as cytokines. Given the distinct differences in stressor responsiveness that have been reported between males and females, alongside a much higher rate of mood disorders in females, we sought to examine whether repeated exposure to stressors would differentially influence elevated plus-maze behavior in male and female CD-1 mice, and whether such changes would be paralleled by variations of pro-inflammatory mRNA cytokine expression within the prefrontal cortex (PFC) and the hippocampus. In males, the sensitization of interleukin (IL)-1ß was evident in both brain regions in those mice that had initially been stressed and then 6 weeks later re-exposed to a stressor exhibiting higher IL-1ß expression than did mice stressed on only a single occasion. Females demonstrated higher baseline expression of cytokine expression within the hippocampus, but neither a single exposure nor re-exposure stressor treatment produced significant cytokine elevations. In the PFC an acute stressor treatment increased IL-1R expression, but otherwise had little effect. In a plus-maze test, stressed male mice displayed markedly reduced latencies to the open arms that was evident in a test 6 weeks later irrespective of whether mice were re-exposed to a stressor, whereas in females this outcome was less evident. These studies are consistent with the perspective that female mice are relatively resilient toward stressor-induced cytokine elevations even though in humans females are generally more prone to developing mood disturbances.

The bioactivity and ion release of titanium-containing glass polyalkenoate cements for medical applications.

The ion release profiles and bioactivity of a series of Ti containing glass polyalkenoate cements. Characterization revealed each material to be amorphous with a T(g) in the region of 650-660°C. The network connectivity decreased (1.83-1.35) with the addition of TiO(2) which was also evident with analysis by X-ray photoelectron spectroscopy. Ion release from cements were determined using atomic absorption spectroscopy for zinc (Zn(2+)), calcium (Ca(2+)), strontium (Sr(2+)), Silica (Si(4+)) and titanium (Ti(4+)). Ions such as Zn(2+) (0.1-2.0 mg/l), Ca(2+) (2.0-8.3 mg/l,) Sr(2+) (0.1-3.9 mg/l), and Si(4+) (14-90 mg/l) were tested over 1-30 days. No Ti(4+) release was detected. Simulated body fluid revealed a CaP surface layer on each cement while cell culture testing of cement liquid extracts with TW-Z (5 mol% TiO(2)) produced the highest cell viability (161%) after 30 days. Direct contact testing of discs resulted in a decrease in cell viability of the each cement tested.

Comparison of two methods for estimating the sensation level of amplified speech.

Several methods have been proposed to estimate the sensation level (SL) at which children receive amplified speech from their hearing aids. The present study compared the SL estimates obtained with two such methods: (1) a sound field aided audiogram approach, and (2) an electroacoustic approach that incorporated the use of a probe tube microphone system (Seewald, Ross, & Stelmachowicz, 1987). Sound field aided thresholds were obtained for 13 hearing-impaired subjects at eight audiometric frequencies. For the electroacoustic approach, in situ thresholds were obtained using a button-type hearing aid receiver attached to a custom earmold. Real ear aided responses were measured using a 70 dB RMS speech-weighted composite noise signal (Frye, 1986). A comparison of the frequency-specific SL estimates derived from the two different methods revealed that the sound field aided audiogram approach yielded higher SL estimates for 74% of the individual comparisons. A detailed analysis of the findings obtained from two subjects suggested that when the results of the two methods did not agree, the differences were due to an interaction between signal level and the unique input/output characteristics of the subjects' hearing aids. A precautionary measure is suggested for those who wish to use sound field aided threshold data to estimate the SLs at which children receive amplified conversational speech.