Characterization of the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-provoked strong and rapid aversion to unfamiliar foodstuffs in rats

A conspicuous but scantly studied feature of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity is avoidance of unfamiliar foodstuffs, which seems to be one of the very few exquisitely sensitive behavioural effects in adult laboratory animals. Here we characterized this peculiar response further after low doses of TCDD. The time-course of the novelty avoidance, the role of nutriment form and dependence of the aversion on the time lag between TCDD exposure and the presentation of a novel food item was determined using rats with different sensitivities to lethality of TCDD. Rats were offered chocolate, liquid nutriment or familiar feed with an unfamiliar texture and the consumptions were measured for varying periods. Aversion to a novel food item (chocolate) emerged within 5.5h after TCDD exposure. A lag of a week or more between TCDD exposure and the presentation of chocolate abolished the avoidance whereas simultaneous presentation of chocolate with TCDD treatment rendered the rats oblivious to the chocolate's presence for over 40 days. Rats avoided also liquid nutriments when these were coupled with TCDD administration but this faded much sooner than chocolate aversion. Even a change in feed texture at the exposure was able to elicit the response. However, habituation was found to interfere with the aversion. These findings indicate that temporal proximity to TCDD exposure is a requisite for the avoidance response which emerges rapidly and may linger on for extended periods, but is not strictly confined to any specific food type. The molecular mechanisms of this tantalizing behavioural alteration remain to be determined.     

Convulsive and nonconvulsive epilepsy in rats: effects on behavioral response to novelty stress

Behavioral response to a new environment of Wistar and WAG/Rij rats with absence and/or audiogenic seizures (AGSs) was investigated. Behavior was observed in open-field (OF) and light-dark choice (LD) tests. Correlations of test performance with seizure parameters were evaluated. AGS-susceptible Wistar rats exhibited reduced exploration (rearing) in both tests and a tendency toward hyperlocomotion in the OF test. Genetically absence-epileptic WAG/Rij rats demonstrated agitation (increased vertical/horizontal locomotion, enhanced defecation/urination) in the LD test, whereas they exhibited reduced exploration, increased grooming, and hyperlocomotion in the OF test. Anxiety level, as estimated by grooming time in the OF test and latency to first "risk assessment" in the LD test, correlated positively with the propensity for absence seizures in WAG/Rij rats not susceptible to AGSs. It can be concluded that the behavioral response to novelty stress in epileptic subjects depends on the type and severity of seizures.     

Closing the gap between science and policy on air pollution and health

This paper discusses critical issues underlying the interface between air quality science, stakeholder participation, and policy development within the context of the European AIRNET Network multistakeholder project. The paper argues that it is not only the content of air pollution and health issues that stakeholders consider important, but also the process and mechanisms by which the interface operates. A visual representation of the interaction between science, society, and stakeholders in the development, dissemination, and evaluation of effective air quality policy strategies is provided. The paper discusses the role of AIRNET in supporting the Clean Air for Europe (CAFE) program and assesses the AIRNET experience in establishing a network to bridge the gap between air quality policy, stakeholders, the public, and scientific communities.     

Local lactate and histamine changes in small bowel circulation measured by microdialysis in pig hemorrhagic shock

Hemorrhagic shock results in inadequate tissue oxygenation. Plasma lactate (L) can characterize the degree of systemic oxygen debt (OD), but gives no information on local changes. The aim of this study was to characterize different degrees of hemorrhagic shock by microdialysis measurement of L and histamine (H) in small bowel circulation. Thirty-eight pigs were randomized to five groups of increasing OD (< 50 --> 120 ml/kg). The OD was accrued by hemorrhage over 60 min and was followed by retransfusion and observation for 3 days. In parallel to plasma probes, subserosa(ss)-, submucosa(sm)-, and intraluminal(il)-L- and H-probes were obtained by small bowel microdialysis every 30 min for 210 min. Ss- and sm-L increased during hemorrhage from 1.2 +/- 0.06 and 1.18 +/- 0.06 to 2.57 +/- 0.15 and 2.96 +/- 0.27 mmol/L. Highest mean L > 3.5mmol/L resulted 90 and 120 min after induction of hemorrhage. Although ss- and sm- levels hardly differed, il-L was significantly decreased with 0.27 +/- 0.02 mmol/L at 0 min and highest mean il-L at 120 min: 2.45 +/- 0.51 mmol/L. Sm-L was significantly increased after 60, 90, 120, and 150 min of highest hemorrhage severity (OD > 100 mL/kg). In parallel, systemic L increased significantly during hemorrhage and correlated well with the severity of shock. Although systemic H increased significantly during hemorrhage (from 1.3 +/- 0.31 to 15.2 +/- 0.67 ng/mL), H-dialysates showed no effect either over time nor with the degree of hemorrhage. In conclusion, microdialysis allows evaluation of local L changes in small bowel circulation in pig hemorrhagic shock. Sm-L levels appear to correlate with the degree of shock. Local H changes were not observed during hemorrhagic shock in this study.     

Gain optimized cosine transform domain LMS algorithm for adaptive filtering of EEG.

The most common adaptive filtering method is based on the least mean square (LMS) algorithm, which updates the filter coefficients by a gradient based method. The convergence properties of the LMS algorithm can be improved by updating the filter coefficients in the frequency domain. This work presents a new LMS algorithm, which updates the filter coefficients in the cosine transform domain. Instead of a constant gain factor in the coefficient updating the present method uses a time-varying optimized gain factor. This yields a considerably improved convergence performance. The algorithm was applied to the EEG activity analysis of freely behaving rats.     

Wide-band spectral analysis of blood pressure and RR interval variability in borderline and mild hypertension.

The aim of this study was firstly to investigate whether indices of wide-band spectral analysis in borderline hypertensive (BHT) or mildly hypertensive (HT) subjects differ from those in normotensive (NT) subjects, and secondly to assess the predictive value of these indices for future hypertension. Electrocardiogram and intra-arterial 24 h ambulatory blood pressure (BP) were recorded in 32 NT, 29 BHT and 30 HT middle-aged men. From the recordings, a 16 h period was extracted for wide-band spectral analysis. A single spectrum of BP and RR interval (RRI) variability was computed for each period by the fast Fourier transform method. The slopes of the spectra were assessed on a log-log scale by linear fitting of the spectral values. Power spectral densities were calculated over regions of 0-0.003, 0.003-0.04, 0.04-0.15, 0.15-0.40 and 0-0.4 Hz. No between-group differences were found in the slopes of BP and RRI spectra. The between-group differences in spectral powers for BP variability were almost invariably significant. The spectral powers for RRI variability did not show between-group differences. Five years later, 22 NT, 22 BHT and 18 HT subjects were re-assessed using casual BP measurements. In a logistic regression model for the combined group of NT and BHT subjects who became HT (22 of 44) during the five-year period, none of the parameters of wide-band spectrum predicted the development of hypertension. In conclusion, parameters of wide-band spectral analysis may not be useful in predicting future hypertension in NT and BHT subjects. Because the BP level is a major factor influencing BP variability, the between-group differences in wide-band spectral powers in BP may be due to differences in BP level rather than differences in cardiovascular regulatory mechanisms.     

Increased density of H1 histamine receptors in brain regions of rats with absence epilepsy

Inflammation Research -