Disruption of paired-associate learning in rat offspring perinatally exposed to dioxins

The prevalence of cognitive abnormalities in children has partly been ascribed to environmental chemical exposure. Appropriate animal models and tools for evaluating higher brain function are required to examine this problem. A recently developed behavioral test in which rats learn six unique flavor-location pairs in a test arena was used to evaluate paired-associate learning, a hallmark of the higher cognitive function that is essential to language learning in humans. Pregnant Long-Evans rats were dosed by gavage with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) at a dose of 0, 200, or 800 ng/kg (referred as Control, TCDD-200, TCDD-800, TBDD-200, or TBDD-800, hereafter) on gestational day 15, and the offspring was tested during adulthood. Paired-associate learning was found to be impaired in the TCDD-200 and TBDD-200 groups, but not in either group exposed to 800 ng/kg, the observations of which were ensured by non-cued trials. As for the emotional aspect, during habituation, the TCDD-200 and TBDD-200 groups showed significantly longer latencies to enter the test arena from a start box than the Control, TCDD-800, and TBDD-800 groups, suggesting that the TCDD-200 and TBDD-200 groups manifested anxiety-like behavior. Thus, both the chlorinated dioxin and its brominated congener affected higher brain function to a similar extent in a nearly identical manner. Use of the behavioral test that can evaluate paired-associate learning in rats demonstrated that in utero and lactational exposure to not only TCDD but also TBDD perturbed higher brain function in rat offspring in a nonmonotonic manner

Predissociation mechanism of acetylene A1AU state1.2

[1] Chem. Phys. Lett., 150, 380 (1988) pbaOs6d@JPNTOHOK [2] J. Chem. Phys., 92, 959 (1990)Author Institution: Department of Chemistry Faculty of Science, Tohoku UniversityThe fluorescence excitation spectrum, the MPI spectrum and the absorption spectrum of acetylene were observed for the $\bar{A}^{1}A_{u}\leftarrow \bar{X} ^{1}\Sigma^{+}_{g}$ band system in a static gas cell and in a supersonic jet. A sudden and drastic decrease in fluorescence quantum yield, $\Phi_{r}$ was found between the $V_{4}K_{2} (46339cm^{-1})$ and $2^{1}V^{3}K^{0} (46673cm^{-1})$ sublevels. The decrease in $\Phi_{f}$ is concluded to be due to the predissociation into $C_{2}H+H$. J dependence of $\Phi_{f}$ was found for the V4K1 vibronic sublevel, while it is absent for the level lying above $V_{4}K_{1}$. From the observed J. dependence, the predissociation mechanism was concluded to be vibrational predissociation by tunneling through a potential barrier. Deuterium effect on the predissociation of acetylene is also discussed

Automated test of behavioral flexibility in mice using a behavioral sequencing task in IntelliCage

There has been a long-standing need to develop efficient and standardized behavioral test methods for evaluating higher-order brain functions in mice. Here, we developed and validated a behavioral flexibility test in mice using IntelliCage, a fully automated behavioral analysis system for mice in a group-housed environment. We first developed a "behavioral sequencing task" in the IntelliCage that enables us to assess the learning ability of place discrimination and behavioral sequence for reward acquisition. In the serial reversal learning using the task, the discriminated spatial patterns of the rewarded and never-rewarded places were serially reversed, and thus, mice were accordingly expected to realign the previously acquired behavioral sequence. In general, the tested mice showed rapid acquisition of the behavioral sequencing task and behavioral flexibility in the subsequent serial reversal stages both in intra- and inter-session analyses. It was found that essentially the same results were obtained among three different laboratories, which confirm the high stability of the present test protocol in different strains of mice (C57BL/6, DBA/2, and ICR). In particular, the most trained cohort of C57BL/6 mice achieved a markedly rapid adaptation to the reversal task in the final phase of the long-term serial reversal test, which possibly indicated that the mice adapted to the "reversal rule" itself. In conclusion, the newly developed behavioral test was shown to be a valid assay of behavioral flexibility in mice, and is expected to be utilized in tests of mouse models of cognitive deficits

Stretch-bend combination polyads in the Ã1Au [A tilde superscript 1 A subscript u] state of acetylene, C2H2 [C subscript 2 H subscript 2]

Rotational analyses are reported for a number of newly-discovered vibrational levels of the S1-trans [S subscriopt 1 -trans](Ã1Au) [A tilde superscript 1 A subscript u] state of C2H2 [C subscript 2 H subscript 2]. These levels are combinations where the Franck–Condon active v2' [v subscript 2 prime] and v3' [v subscript 3 prime] vibrational modes are excited together with the low-lying bending vibrations, v4' [v subscript 4 prime] and v6' [v subscript 6 prime]. The structures of the bands are complicated by strong a- and b-axis Coriolis coupling, as well as Darling–Dennison resonance for those bands that involve overtones of the bending vibrations. The most interesting result is the strong anharmonicity in the combinations of v3' [v subscript 3 prime] (trans bend, ag [a subscript g]) and v6' [v subscript 6 prime] (in-plane cis bend, bu [b subscript u]). This anharmonicity presumably represents the approach of the molecule to the trans–cis isomerization barrier, where ab initio results have predicted the transition state to be half-linear, corresponding to simultaneous excitation of v3' [v subscript 3 prime] and v6' [v subscript 6 prime]. The anharmonicity also causes difficulty in the least squares fitting of some of the polyads, because the simple model of Coriolis coupling and Darling–Dennison resonance starts to break down. The effective Darling–Dennison parameter, K4466 [K subscript 4466], is found to increase rapidly with excitation of v3' [v subscript 3 prime], while many small centrifugal distortion terms have had to be included in the least squares fits in order to reproduce the rotational structure correctly. Fermi resonances become important where the K-structures of different polyads overlap, as happens with the 2131B1 [2 superscript 1 3 superscript 1 B superscript 1] and 31B3 [3 superscript 1 B superscript 3] polyads (B = 4 or 6). The aim of this work is to establish the detailed vibrational level structure of the S1-trans [S subscript 1 -trans] state in order to search for possible S1-cis [S subscript 1 -cis] (1A2) [(superscript 1 A subscript 2)] levels. This work, along with results from other workers, identifies at least one K sub-level of every single vibrational level expected up to a vibrational energy of 3500 cm−1 [cm superscript -1].United States. Dept. of Energy (Grant DE-FG0287ER13671)Natural Sciences and Engineering Research Council of Canada (NSERC)National Science Council of Taiwa

Neurocognitive and physical functioning in the Seveso Women's Health Study

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is neurotoxic in animals but few studies have investigated its effects on the human brain. Related dioxin-like compounds have been linked to poorer cognitive and motor function in older adults, with effects more pronounced in women, perhaps due to the loss of neuro-protective estrogen in menopause. On 10 July 1976, a chemical explosion in Seveso, Italy, resulted in one of the highest known residential exposures to TCDD. In 1996, we initiated the Seveso Women's Health Study, a retrospective cohort study of the health of the women who were newborn to 40 years old in 1976. Here, we investigate whether TCDD exposure is associated with physical functioning and working memory more than 20 years later. Individual TCDD concentration (ppt) was measured in archived serum collected soon after the explosion. In 1996 and 2008, we measured physical functioning (n=154) and working memory (n=459), respectively. We examined associations between serum TCDD and motor and cognitive outcomes with multivariate linear regression and semi-parametric estimators. A 10-fold increase in serum TCDD was not associated with walking speed (adjusted β=0.0006ft/s, 95% Confidence Interval (CI): -0.13, 0.13), upper body mobility (adjusted β=-0.06, 95% CI: -0.36, 0.23), or manual dexterity (adjusted β=0.34, 95% CI: -0.65, 1.33). We observed an inverted U-shaped association in grip strength, with poorer strength in the lowest and highest TCDD exposure levels. There was no association between TCDD and the Wechsler digit and spatial span tests. Neither menopause status at assessment nor developmental timing of exposure modified associations between TCDD and working memory. Our findings, in one of the only studies of TCDD's effects on neuropsychological and physical functioning in women, do not indicate an adverse effect on these domains, with the exception of a U-shaped relationship with grip strength. Given the limited assessment and relative youth of the women at this follow-up, future work examining additional neuropsychological outcomes is warranted