Preventing long-lasting fear recovery using bilateral alternating sensory stimulation: A translational study.

Posttraumatic stress disorder (PTSD) is a highly debilitating and prevalent psychological disorder. It is characterized by highly distressing intrusive trauma memories that are partly explained by fear conditioning. Despite efficient therapeutic approaches, a subset of PTSD patients displays spontaneous recurrence of traumatic memories after successful treatment. The development of animal behavioral models mimicking the individual variability in treatment outcome for PTSD patients represent therefore an important challenge as it allows for the identification of predicting factors of resilience or susceptibility to relapse. However, to date, only few animal behavioral models of long-lasting fear recovery have been developed and their predictive validity has not been tested directly. The objectives of this study were twofold. First we aimed to develop a simple animal behavioral model of long-lasting fear recovery based on auditory cued fear conditioning and extinction learning, which recapitulates the heterogeneity of fear responses observed in PTSD patients after successful treatment. Second we aimed at testing the predictive validity of our behavioral model and used to this purpose a translational approach based (i) on the demonstration of the efficiency of Eye Movement Desensitization and Reprocessing (EMDR) therapy to reduce conditioned fear responses in PTSD patients and (ii) on the implementation in our behavioral model of an electrical bilateral alternating stimulation of the eyelid which mimics the core feature of EMDR. Our data indicate that electrical bilateral alternating stimulation of the eyelid during extinction learning alleviates long-lasting fear recovery of conditioned fear responses and dramatically reduces inter-individual variability. These results demonstrate the face and predictive validity of our animal behavioral model and provide an interesting tool to understand the neurobiological underpinnings of long-lasting fear recovery.

Persistence of amygdala gamma oscillations during extinction learning predicts spontaneous fear recovery.

Extinction of auditory fear conditioning induces a temporary inhibition of conditioned fear responses that can spontaneously reappear with the passage of time. Several lines of evidence indicate that extinction learning relies on the recruitment of specific neuronal populations within the basolateral amygdala. In contrast, post-extinction spontaneous fear recovery is thought to result from deficits in the consolidation of extinction memory within prefrontal neuronal circuits. Interestingly, recent data indicates that the strength of gamma oscillations in the basolateral amygdala during auditory fear conditioning correlates with retrieval of conditioned fear responses. In the present manuscript we evaluated the hypothesis that post-extinction spontaneous fear recovery might depend on the maintenance of gamma oscillations within the basolateral amygdala by using single unit and local field potential recordings in behaving mice. Our results indicate that gamma oscillations in the basolateral amygdala were enhanced following fear conditioning, whereas during extinction learning gamma profiles were more heterogeneous despite similar extinction learning rates. Remarkably, variations in the strength of gamma power within the basolateral amygdala between early and late stages of extinction linearly predicted the level of post-extinction spontaneous fear recovery. These data suggest that maintenance of gamma oscillations in the basolateral amygdala during extinction learning is a strong predictive factor of long term spontaneous fear recovery.

Comparison between measurements of elasticity and free amino group content of ovalbumin microcapsule membranes: discrimination of the cross-linking degree.

An inverse method is used to characterize the membrane mechanical behavior of liquid filled microcapsules. Cross-linked ovalbumin microcapsules are flowed and deformed into a cylindrical microchannel of comparable size. The deformed shape is compared to predictions obtained numerically when modeling a capsule under the same flow conditions. The unknown shear modulus value corresponds to the best fit. The degree of reticulation is estimated in parallel by determining the free amino groups remaining on the microcapsules after the cross-linking reaction. We characterize microcapsule populations fabricated at different reaction pH (5-8) and times (5-30 min) to study different cross-linking degrees. The capsule shear modulus and the amino groups are nearly constant with the reaction pH for the capsules fabricated after 5 min of reticulation. The shear modulus increases with the reaction time, while the NH(2) content decreases with it. A global increase in shear modulus with pH is also observed, together with an unexpected increase in NH(2) content. The study shows that the inverse method is capable of discriminating between various cross-linking degrees of microcapsules. Moreover, for this type of microcapsules, the mechanical method appears more reliable than the chemical one to obtain an estimation of their cross-linking degree.

Molds in floor dust, building-related symptoms, and lung function among male and female schoolteachers.

UNLABELLED: Five hundred and twenty-two teachers from 15 public schools, eight 'water-damaged' schools, and seven 'non-damaged' schools with no visible water damage were included in a cross-sectional design. Mold growth was assessed by recording the amount of dust on the floor and in the air in classrooms and the content of a number of mold species in the dust (CFU/g dust). The evaluation of health symptoms included symptoms recorded by questionnaire and spirometry, bronchial challenge, and CO-diffusion capacity. Nasal lavage fluid was analyzed for IL-8 and ECP. Personal and psychosocial factors were included as confounders. In this study population mucus membrane irritation symptoms (MMI) and general symptoms were reported more frequently by women than by men with odds ratios ranging from 1.4 to 2.1. Women's reports of symptoms from mucous membranes and skin and general symptoms were positively associated with mold exposure. Odds ratio for 'difficult to concentrate' after adjustment for confounders was 11.2 (1.4-90.1, 95% CI) at high levels of mold exposure. None of the lung function tests performed in this study were associated with mold exposure, to the 'water damaged' vs. 'non-damaged' classification, or to the symptoms reported. IL-8 and ECP were not associated either. PRACTICAL IMPLICATIONS: Psychosocial and personal reasons dominate in MMI and general symptoms. Headache and difficulties to concentrate associated with indoor mold exposure, mainly for women. No lung function impairment associated with indoor mold exposure.

Molds in floor dust and building-related symptoms among adolescent school children: a problem for boys only?

UNLABELLED: In this stratified cross-sectional study in eight 'wet' and seven 'dry' schools, 1024 adolescent school children reported potentially building-related symptoms (BRS) in self-administrated questionnaires. From their classrooms dust samples were collected from floors, ventilation ducts, and air; settled dust was collected in cardboard boxes over a period of 5 months. Measurements of temperature, relative humidity and CO2 were performed. BRS were strongly associated with personal factors like recent airway infections, hay fever, asthma and psycho-social work load, but also to molds in floor dust and presence of mechanical ventilation. The association between molds in floor dust and BRS has in stratified analyses shown a strong association among adolescent school boys, and no association among adolescent school girls using multivariable analyses controlling for relevant confounders. In contrast to the menstruating school girls, the symptoms among the small group of not yet menstruating girls were associated with the levels of molds in floor dust. Their symptom prevalences were very similar to those of the boys. This finding makes us suggest a new hypothesis: The higher endogenous estrogen levels of sexually matured adolescent females seems to protect them from the effects of molds in dust, despite their overall higher symptom prevalence. PRACTICAL IMPLICATIONS: In this cross-sectional epidemiological study of adolescent school children we found independent significant positive associations between building-related symptoms and viable molds in floor dust in boys and non-menstruating girls. In contrast, no such associations were seen among menstruating girls. The identification of these two susceptible groups adds further support the relevance of minimizing sources of dust and mold exposure.

The dustfall collector--a simple passive tool for long-term collection of airborne dust: a project under the Danish Mould in Buildings program (DAMIB).

UNLABELLED: A newly developed dustfall device that collects airborne dust by sedimentation has been evaluated in Danish schools. Dust collected over 140 days was compared with airborne dust sampled during single school days and settled floor dust sampled at the end of a school day. Measurements of culturable fungi in air samples corresponded well to those from the dustfall collector in mechanically but not naturally ventilated rooms. Levels of beta(1 --> 3)glucan and culturable fungi in dust from the dustfall collector and settled floor dust did not agree well. Up to 10 times more beta(1 --> 3)glucan per milligram dust was found in the dustfall collectors than in settled floor dust. Only in dust from the dustfall collector was the mass concentration of culturable fungi (cfu/mg) significantly correlated with the degree of dampness. The culturability of fungi in the 140-day dustfall samples tended to be lower than in other types of samples. Nonetheless, the results indicated that the dustfall collector can be used to estimate the median concentration of airborne culturable fungi, provided identical sampling periods are used for all samples. The collector is cost effective and simple to use. PRACTICAL IMPLICATIONS: Traditional ways of assessing exposure to microorganisms by sampling airborne dust or dust from floors have several disadvantages. In the present paper, a new sampler, the dustfall collector, which collects airborne dust by sedimentation over a period of months, is introduced. Tests of this collector indicate that it can be used to estimate the mean concentration of airborne culturable fungi but not beta(1 --> 3)glucan over a long period and that the method can differentiate between buildings with different levels of water damage.

Molds in floor dust and building-related symptoms in adolescent school children.

This stratified cross-sectional epidemiological study included 1053 school children aged 13-17 years. All pupils filled in a questionnaire on building-related symptoms and other relevant health aspects. The following exposure measurements were carried out: room temperature, CO2 level, and relative humidity; building characteristics including mold infestation were assessed, and dust was collected from floors, air, and ventilation ducts during a working day. Dust was examined for endotoxin level, and cultivated for viable molds. We did not find a positive association between building-related symptoms and extent of moisture and mold growth in the school buildings. Five of eight building-related symptoms were significantly and positively associated with the concentration of colony forming units of molds in floor dust: eye irritation, throat irritation, headache, concentration problems, and dizziness. After adjusting for different potentially confounding factors in separate analyses of each symptom, the above-mentioned associations between molds in dust and symptoms were still present, except for concentration problems. However, in none of the analyses was mold exposure the strongest covariate, being secondary to either asthma, hay fever, recent airway infection, or psychosocial factors.

Determination of fungal spore release from wet building materials.

The release and transport of fungal spores from water-damaged building materials is a key factor for understanding the exposure to particles of fungal origin as a possible cause of adverse health effects associated to growth of fungi indoors. In this study, the release of spores from nine species of typical indoor fungi has been measured under controlled conditions. The fungi were cultivated for a period of 4-6 weeks on sterilized wet wallpapered gypsum boards at a relative humidity (RH) of approximately 97%. A specially designed small chamber (P-FLEC) was placed on the gypsum board. The release of fungal spores was induced by well-defined jets of air impacting from rotating nozzles. The spores and other particles released from the surface were transported by the air flowing from the chamber through a top outlet to a particle counter and sizer. For two of the fungi (Penicillium chrysogenum and Trichoderma harzianum), the number of spores produced on the gypsum board and subsequently released was quantified. Also the relationship between air velocities from 0.3 to 3 m/s over the surface and spore release has been measured. The method was found to give very reproducible results for each fungal isolate, whereas the spore release is very different for different fungi under identical conditions. Also, the relationship between air velocity and spore release depends on the fungus. For some fungi a significant number of particles smaller than the spore size were released. The method applied in the study may also be useful for field studies and for generation of spores for exposure studies.

Exposure-response relationship between gastrointestinal problems among waste collectors and bioaerosol exposure.

OBJECTIVES: A high frequency of gastrointestinal problems has previously been reported for waste collectors. The present study relates the gastrointestinal problems to measurements of the bioaerosols that waste collectors are exposed to during work. METHODS: A job-exposure matrix was constructed from a combination of questionnaire data and field measurements. The questionnaire data were collected from 1747 male waste collectors and a comparison group of 1111 male municipal workers. Moreover a total of 189 full-shift personal samples was collected. The samples were used for characterizing the bioaerosol exposure described by viable fungi, total count of fungal spores, microorganisms, and endotoxins. RESULTS: In a multivariate analysis, high exposure to endotoxins was associated with nausea [prevalence proportion ratio (PPR) 1.60], and the risk of reporting nausea decreased with decreasing exposure so that workers with low exposure had the fewest reports (PPR 1.39) in the comparison with the unexposed group. High exposure to endotoxins was also associated with reports of diarrhea (PPR 5.60), and the risk of reporting diarrhea decreased with decreasing exposure so that the workers with low exposure had the fewest reports (PPR 3.02). The same pattern existed for exposure to fungi, for which high exposure resulted in the most reports (PPR = 4.59), and for diarrhea, for which low exposure resulted in the fewest reports (PPR = 3.15). CONCLUSIONS: An exposure-response relationship was found between nausea and endotoxin exposure and between diarrhea and exposure to both endotoxins and viable fungi.

Endotoxin potency in the A549 lung epithelial cell bioassay and the limulus amebocyte lysate assay.

The purpose of this study was to elucidate to what extent the potency of endotoxins measured by the limulus amebocyte lysate (LAL) assay is reflected in the potency in an in vitro assay based on release of interleukin-8 (IL-8) from a lung epithelial cell line, A549. Lipopolysaccharides (LPS) from Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enteritidis and detoxified LPS from E. coli were applied in serial dilutions in the LAL assay and in the A549 bioassay. Also 19 organic dust samples from waste recycling plants were tested. The A549 cells were incubated for 24 h with LPS or dust, and the IL-8 secretion was determined by ELISA. The method for evaluation of the LAL assay showed linearity for the four endotoxins. Using the slope as a measure of the potency factor (PF), LPS from E. coli and S. enteritidis was about four times more potent than that for LPS from K. pneumoniae and P. aeruginosa. In the A549 bioassay each of the different types of endotoxin had characteristic and very different dose-response curves. The potency of the LPS, in the A549 bioassay, ranked as follows K. pneumoniae > P. aeruginosa > E. coli > or = S. enteritidis. The content of endotoxin in the dust samples did not correlate with their potency in the A549 bioassay. The present study indicates a poor correlation between the potency of endotoxin in the LAL assay compared with the A549 bioassay. The lack of correlation when organic dust samples are tested may reflect the fact that these samples contain biological active compounds, which are non-reactive in the LAL-assay but stimulate IL-8 secretion from epithelial cells.

Endotoxin and microorganisms in percolate derived from compostable household waste.

Health related problems among Danish garbage collectors have been reported. Separated compostable household waste was analyzed for endotoxin and microorganisms in an experimental study. Aerosols and liquid (percolate) from the waste were sampled over two 14-day periods during storage in containers.