Random initialisation of the excitation-emission matrix fluorescence spectral variables in constraint fashion for subsequent multivariate curve resolution alternating least square analysis on a peculiarly designed calibration set: Simultaneous sensing of nine polycyclic aromatic hydrocarbons in water samples.

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Random initialisation of the excitation-emission matrix fluorescence spectral variables in constraint fashion for subsequent multivariate curve resolution alternating least square analysis on a peculiarly designed calibration set: Simultaneous sensing of nine polycyclic aromatic hydrocarbons in water samples.

Spectrochim Acta A Mol Biomol Spectrosc. 2018 Nov 05;204:354-361

Authors: El Kurdi R, Kumar K, Patra D

Abstract
Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and mutagenic in nature therefore their sensing in water sample is an important analytical task. In the present work, a novel approach that is based on the random initialisation of the excitation-emission matrix fluorescence (EEMF) spectral variables in constraint fashion for subsequent multivariate curve resolution alternating least Square (MCR-ALS) analysis is introduced for simultaneously sensing the complex dilute aqueous mixture of PAHs. The usefulness of the proposed analytical approach is successfully demonstrated by applying it intentionally on a calibration set that is peculiar in many senses. The peculiarity mainly arises because the designed (i) the calibration set consist of nine PAHS having significant spectral overlap, (ii) the concentration of each PAH in different samples are kept constant and (iii) any two samples differ only in the presence and absence of the PAHs. The proposed approach is found to make precise and accurate estimation of each of the nine PAHs without involving any pre-separation. In summary, the proposed approach provides a simple and cost-effective procedure for simultaneous sensing of several PAHs in water samples. The proposed approach could be very useful in developing countries.

PMID: 29957414 [PubMed - indexed for MEDLINE]

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Brain responses to anticipation and consumption of beer with and without alcohol.

Brain responses to anticipation and consumption of beer with and without alcohol.

Chem Senses. 2018 Nov 13;:

Authors: Smeets PAM, de Graaf C

Abstract
Beer is a popular alcoholic beverage world-wide. Non-alcoholic beer is increasingly marketed. Brain responses to beer and non-alcoholic beer (NA-beer) have not been compared. It could be that the flavor of beer constitutes a conditioned stimulus associated with alcohol reward. Therefore, we investigated whether oral exposure to NA-beer with or without alcohol elicits similar brain responses in reward-related areas in a context where regular alcoholic beer is expected. Healthy men (n=21) who were regular beer drinkers were scanned using functional MRI. Participants were exposed to word cues signaling delivery of a 10-ml sip of chilled beer or carbonated water (control) and subsequent sips of NA-beer with or without alcohol or water (control). Beer alcohol content was not signaled. The beer cue elicited less activation than the control cue in the primary visual cortex, supplementary motor area (reward-related region) and bilateral inferior frontal gyrus/frontal operculum. During tasting, there were no significant differences between the 2 beers. Taste activation after swallowing was significantly greater for alcoholic than for NA-beer in the inferior frontal gyrus/anterior insula and dorsal prefrontal cortex (superior frontal gyrus). This appears to be due to sensory stimulation by ethanol rather than reward processing. In conclusion, we found no differences in acute brain reward upon consumption of NA-beer with and without alcohol, when presented in a context where regular alcoholic beer is expected. This suggests that in regular consumers beer flavor rather than the presence of alcohol is the main driver of the consumption experience.

PMID: 30423017 [PubMed - as supplied by publisher]

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Rapid detection of taste and odor compounds in water using the newly invented chemi-ionization technique coupled with time-of-flight mass spectrometry.

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Rapid detection of taste and odor compounds in water using the newly invented chemi-ionization technique coupled with time-of-flight mass spectrometry.

Anal Chim Acta. 2018 Dec 04;1035:119-128

Authors: Zhang H, Ma P, Shu J, Yang B, Huang J

Abstract
Taste and odor (T&O) compounds are widespread in water environments and have attracted considerable public attention. Nowadays, the standard detections of these chemicals rely mainly on off-line methods such as GC-MS or evaluation by trained analysts' senses. In this study, we report a method for the rapid detection of T&O compounds in water by exploiting a newly invented chemi-ionization source, in combination with headspace vapor measurement at room temperature. The calibrated limits of detection (LODs) of 2-methylbutyraldehyde, methyl tert-butyl ether (MTBE), methyl methacrylate (MMA), 2-isobutyl-3-methyoxypyrazine (IBMP), and 2-isopropyl-3-methoxypyrazine (IPMP) are in the range of 3.5-50.2 ng L-1, and the estimated LODs of 2-methylisoborneol (2-MIB) and geosmin (GSM) are 0.25 and 0.77 ng L-1, respectively. The calibration results reveal that the instrumental LODs for 2-methylbutyraldehyde, MTBE, MMA, β-cyclocitral, 2-MIB, and GSM are 1-2 orders of magnitude better than the odor thresholds of humans. The accuracy, precision, recovery, and linearity (R2) of the method are tested. Water samples from city tap water and three rivers in Beijing are assessed using this technique, and the typical T&O compositions are observed with concentrations ranging from 0.2 to 297 ng L-1. The new ultra-sensitive rapid detection method shows comparable sensitivities to the existing off-line technique and displays great potential for real-time detection of T&O pollution in water environments.

PMID: 30224129 [PubMed - indexed for MEDLINE]

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Selective effects of temperature on the sensory irritation but not taste of NaCl and citric acid.

Selective effects of temperature on the sensory irritation but not taste of NaCl and citric acid.

Chem Senses. 2018 Nov 12;:

Authors: Nachtigal D, Andrew K, Green BG

Abstract
This study investigated the effect of temperature on taste and chemesthetic sensations produced by the prototypical salty and sour stimuli NaCl and citric acid. Experiment 1 measured the perceived intensity of irritation (burning, stinging) and taste (saltiness, sourness) produced on the tongue tip by brief (3 sec) exposures to suprathreshold concentrations of NaCl and citric acid at 3 different temperatures (12, 34, 42°C). No significant effects of temperature were found on the taste or sensory irritation of either stimulus. Experiment 2 investigated the potential effects of temperature on sensory irritation at peri-threshold concentrations and its sensitization over time. Measurements were again made on the tongue tip at the same 3 temperatures. Heating was found to enhance the perception of irritation at peri-threshold concentrations for both stimuli, whereas cooling suppressed sensitization of irritation for NaCl but not for citric acid. These results (i) confirm prior evidence that perception of suprathreshold salty and sour tastes are independent of temperature; (ii) demonstrate that heat has only weak effects on sensory irritation produced by brief exposures to NaCl and citric acid; and (iii) suggest that sensitization of the irritation produced by NaCl and citric acid occur via different peripheral mechanisms that have different thermal sensitivities. Overall the results are consistent with involvement of the heat-sensitive channel TRPV1 in the sensory irritation of both stimuli together with one or more additional channels (e.g. ASIC, ENaC, TRPA1) that are insensitive to heat and may possibly be sensitive to cooling.

PMID: 30418541 [PubMed - as supplied by publisher]

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Experience-Dependent c-Fos Expression in the Mediodorsal Thalamus Varies with Chemosensory Modality.

Experience-Dependent c-Fos Expression in the Mediodorsal Thalamus Varies with Chemosensory Modality.

Chem Senses. 2018 Nov 02;:

Authors: Fredericksen KE, McQueen KA, Samuelsen CL

Abstract
The mediodorsal thalamus is a higher-order thalamic nucleus critical for many cognitive behaviors. Defined by its reciprocal connections with the prefrontal cortex, the mediodorsal thalamus receives strong projections from chemosensory cortical areas for taste and smell, gustatory cortex and piriform cortex. Recent studies indicate the mediodorsal thalamus is involved in experience-dependent chemosensory processes, including olfactory attention and discrimination and the hedonic perception of odor-taste mixtures. How novel and familiar chemosensory stimuli are represented within this structure remains unclear. Here, we compared the expression of c-Fos in the mediodorsal thalami of rats familiar with an odor, a taste, or an odor-taste mixture with those that sampled the stimuli for the first time. We found that familiar tastes or odor-taste mixtures induced significantly greater c-Fos expression in the mediodorsal thalamus than novel tastes or odor-taste mixtures, whereas novel odors induced greater c-Fos expression than familiar odors. These experience-dependent and modality-specific differences in c-Fos expression may relate to the behavioral relevance of the chemosensory stimulus, including odor neophobia. In a two-bottle brief-access preference task, rats preferred water to isoamyl acetate-odorized water over multiple days. However, after experience with isoamyl acetate mixed with sucrose (odor-taste mixture), the preference for water was eliminated. These findings demonstrate that experience with chemosensory stimuli modulates responses in the mediodorsal thalamus, suggesting this structure plays an integral role in communicating behaviorally relevant chemosensory information to higher-order areas to guide food-related behaviors.

PMID: 30388214 [PubMed - as supplied by publisher]

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Vapor detection and discrimination with a panel of odorant receptors.

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Vapor detection and discrimination with a panel of odorant receptors.

Nat Commun. 2018 Nov 01;9(1):4556

Authors: Kida H, Fukutani Y, Mainland JD, de March CA, Vihani A, Li YR, Chi Q, Toyama A, Liu L, Kameda M, Yohda M, Matsunami H

Abstract
Olfactory systems have evolved the extraordinary capability to detect and discriminate volatile odorous molecules (odorants) in the environment. Fundamentally, this process relies on the interaction of odorants and their cognate olfactory receptors (ORs) encoded in the genome. Here, we conducted a cell-based screen using over 800 mouse ORs against seven odorants, resulting in the identification of a set of high-affinity and/or broadly-tuned ORs. We then test whether heterologously expressed ORs respond to odors presented in vapor phase by individually expressing 31 ORs to measure cAMP responses against vapor phase odor stimulation. Comparison of response profiles demonstrates this platform is capable of discriminating between structural analogs. Lastly, co-expression of carboxyl esterase Ces1d expressed in olfactory mucosa resulted in marked changes in activation of specific odorant-OR combinations. Altogether, these results establish a cell-based volatile odor detection and discrimination platform and form the basis for an OR-based volatile odor sensor.

PMID: 30385742 [PubMed - in process]

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Biological preparedness and resistance to extinction of skin conductance responses conditioned to fear relevant animal pictures: A systematic review.

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Biological preparedness and resistance to extinction of skin conductance responses conditioned to fear relevant animal pictures: A systematic review.

Neurosci Biobehav Rev. 2018 Oct 28;:

Authors: Åhs F, Rosén J, Kastrati G, Fredrikson M, Agren T, Lundström JN

Abstract
Preparedness theory is one of the most influential ideas in explaining the origin of specific phobias. The theory proposes that fear conditioning is selective to animals that have posed a threat to survival throughout human evolution, and that acquired fear memories to such threats are resistant to extinction. We reviewed fear conditioning studies testing whether autonomic responses conditioned to pictures of snakes and spiders show greater resistance to extinction than neutral cues. We identified 32 fear conditioning experiments published in 23 studies including 1887 participants. Increased resistance to extinction of conditioned responses to snake and spider pictures was found in 10 (31%) of the experiments, whereas 22 (69%) experiments did not support the hypothesis. Thus, the body of evidence suggests that preparedness theory does not explain the origin of specific phobias.

PMID: 30381252 [PubMed - as supplied by publisher]

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