Olfactory masking has been used to erase the unpleasant sensation in human cultures for a long period of history. Here, we show a positive correlation between the human masking and the odorant suppression of the transduction current through the cyclic nucleotide–gated (CNG) and Ca2+-activated Cl− (Cl(Ca)) channels. Channels in the olfactory cilia were activated with the cytoplasmic photolysis of caged compounds, and their sensitiveness to odorant suppression was measured with the whole cell patch clamp. When 16 different types of chemicals were applied to cells, cyclic AMP (cAMP)-induced responses (a mixture of CNG and Cl(Ca) currents) were suppressed widely with these substances, but with different sensitivities. Using the same chemicals, in parallel, we measured human olfactory masking with 6-rate scoring tests and saw a correlation coefficient of 0.81 with the channel block. Ringer's solution that was just preexposed to the odorant-containing air affected the cAMP-induced current of the single cell, suggesting that odorant suppression occurs after the evaporation and air/water partition of the odorant chemicals at the olfactory mucus. To investigate the contribution of Cl(Ca), the current was exclusively activated by using the ultraviolet photolysis of caged Ca, DM-nitrophen. With chemical stimuli, it was confirmed that Cl(Ca) channels were less sensitive to the odorant suppression. It is interpreted, however, that in the natural odorant response the Cl(Ca) is affected by the reduction of Ca2+ influx through the CNG channels as a secondary effect. Because the signal transmission between CNG and Cl(Ca) channels includes nonlinear signal-boosting process, CNG channel blockage leads to an amplified reduction in the net current. In addition, we mapped the distribution of the Cl(Ca) channel in living olfactory single cilium using a submicron local [Ca2+]i elevation with the laser photolysis. Cl(Ca) channels are expressed broadly along the cilia. We conclude that odorants regulate CNG level to express masking, and Cl(Ca) in the cilia carries out the signal amplification and reduction evenly spanning the entire cilia. The present findings may serve possible molecular architectures to design effective masking agents, targeting olfactory manipulation at the nano-scale ciliary membrane.
We investigated malodorous compounds on clothes in daily use and identified, for the first time, middle-chain fatty acids responsible for the malodour often described as 'wet and dirty dust-cloth-like'. Application of a preparative fraction collector and gas chromatography-mass spectrometry of the acidic volatile fraction carefully isolated from used clothes revealed the newly identified odorants responsible for unpleasant odours. In particular, the olfactory threshold of 4-methyl-3-hexenoic acid (4M3H), which has the 'wet and dirty dust-cloth-like' odour, was found to be the lowest among the detected fatty acids. Although 4M3H was present in trace amounts in the clothes tested (up to 5 mg/50 g cloth), an aroma extract dilution analysis revealed that it contributed the highest to the overall strength of malodour on them. In addition, quantitative analysis of the detected fatty acids in the clothes revealed a correlation between the logarithm of several fatty acid concentrations (their amount in the clothes) and the overall odour intensity. In particular, 4M3H showed a high correlation value (r = 0.72, p < 0.05). These results provide proof that these odorants can be used as indicators to assess the effectiveness of detergents and to develop a new deodorant technology.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is highly contagious and continues to spread worldwide. To avoid the spread of infection, it is important to control its transmission routes. However, as methods to prevent airborne infections are lacking, people are forced to take measures such as keeping distance from others or wearing masks. Here, we evaluate the antiviral activity of propylene glycol (PG), which is safe, odorless, and volatile. PG showed pronounced antiviral activity against the influenza virus (IAV) at concentrations above 55% in the liquid phase. Given its IAV inactivation mechanism, which involves increasing the fluidity of the viral membrane, PG is expected to have a broad effect on enveloped viruses. PG showed antiviral activity against SARS-CoV-2. We also developed a system to evaluate the antiviral effect of PG in spray and volatilized forms. PG was found to be effective against aerosol IAV in both forms; the effective PG concentration against IAV in the vapor phase was 87 ppmv (0.27 mg/L). These results demonstrate that PG is an effective means for viral inactivation in various situations for infection control. This technology is expected to control the spread of current and future infectious diseases capable of causing outbreaks and pandemics.
Phenols are a group of odorous components that are released from rotten human urine. Just after urination, the most abundant urinary phenols exist in odorless conjugates with glucuronic acid or sulfate. In this study, we analyzed these two types of conjugates in rotten human urine using LC-MS/MS and found that only the glucuronic acid conjugates (glucuronides) underwent degradation. This suggested that suppression of glucuronide degradation would effectively reduce urinary odor generation. Thus, about 200 fragrance chemicals were examined in an attempt to find an inhibitor of the bacterial enzyme involved in glucuronide degradation ( β-glucuronidase). Macrocyclic compounds, such as 8-cyclohexadecen-1-one, exhibited strong inhibitory activity against β-glucuronidase and were effective at reducing urinary odor generation.
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