Human odor responses

Wang L, Chen L, Jacob T. Evidence for peripheral plasticity in human odor response. J. Physiol. 2004 554 236-244. 

Particularly alarming are fetal effects of alcohol and drugs on food-related odor responses in humans. Apart from the severe fetal alcohol syndrome, alcohol can affect the chemosensory behavior of a fetus. Alcohol administered to pregnant female rats impaired odor aversions and preferences in their offspring. A... 

There is a large body of research on the effects of food packaging on flavor and odor chemistry of various foods. However, the focus of such research is often targeted toward identifying the chemicals and relative concentrations that occur as a result of food-package interactions. The relationship between food-package interactions and human sensory response has received relatively little scientific attention. 

The relationship between chemical structure and perceived odor has been studied by electrophysiological, chemical-analytical, and psychophysical techniques. Certain odorants in addition to being detected by the olfactory system evoke specific behavioral responses. Recent studies on various mammalian species have attempted to equate specific odor sources with behavioral patterns and to profile the odorants in hopes of Identifying the biologically active components ( ). In addition, studies on human odor suggest similarities in odor sources and types with other mammalian species and also suggest some of these odors may be reflective of internal body processes. 

FIGURE 2 Adverse responses to various pollution levels. A, Pollution level high B, pollution level moderate C, pollution level low. a, One-mile visibility b, 10-mile visibility c, 100-mile visibility d, nasopharyngeal and eye irritation e, material response to acid droplets f, odor response g, 100% crop loss h, rubber cracking 1, zero crop loss j, acute respiratory disease k, livestock flurosis 1, human—chronic respiratory disease, vegetation—decreased yield of fruit and forest, material—corrosion, deterioration, soiling. (From Stern, A. C., Boubel, R. W., Turner, D. B., and Fox, D. L. (1984). Fundamentals of Air Pollution, 2nd ed. Academic Press, Orlando.]... 

Mechanism of action studies were also performed on Culex quinquefasciatus using the same experimental setup. C. quinquefasciatus showed similar results, whereas deet decreased the neuronal response to l-octen-3-ol. However, the investigators proposed that these effects were due to experimental error. They suggested that once deet and l-octen-3-ol were in the same experimental setup, deet would block the effects of l-octen-3-ol. They suggested that deet would mask the effect of human odor and would not directly interfere with the response to a chemical. This masking of l-octen-3-ol, seen with deet, was also observed with two other common insect repellents (IR3535 and picaridin) in Aedes aegypti. ... 

Whatever the physiology of odor perception may be, the sense of smell is keener than that of taste (22). If flavors are classed into odors and tastes as is common practice in science, it can be calculated that there are probably more than 10 possible sensations of odor and only a few, perhaps five, sensations of taste (13,21,35—37). Just as a hereditary or genetic factor may cause taste variations between individuals toward phenylthiourea, a similar factor may be in operation with odor. The odor of the steroid androsterone, found in many foods and human sweat, may eflcit different responses from different individuals. Some are very sensitive to it and find it unpleasant. To others, who are less sensitive to it, it has a musk or sandalwood-like smell. Approximately 50% of the adults tested cannot detect any odor even at extremely high concentrations. It is befleved that this abiUty is genetically determined (38). 

The odor detection-threshold values of organic compounds, water, and mineral oil have been determined by different investigators (Table 2 and 3) and may vary by as much as 1000, depending on the test methods, because human senses are not invariable in their sensitivity. Human senses are subject to adaption, ie, reduced sensitivity after prolonged response to a stimulus, and habituation, ie, reduced attention to monotonous stimulation. The values give approximate magnitudes and are significant when the same techiriques for evaluation are used. Since 1952, the chemistry of odorous materials has been the subject of intense research (43). Many new compounds have been identified in natural products (37—40,42,44—50) and find use in flavors. 

In 1986, the National Geographic Society, in cooperation with the MoneU Center, conducted a worldwide survey of the sense of smell. Over 10 million survey forms were sent to readers of the Society s journal, of which close to 1.5 million forms were completed and returned. With responses to 40 demographic and 42 odor-related questions, the results constitute the largest set of data on human olfaction (4). 

The sensory technique used for assessing human perception of odors is called olfactometry. The basic technique is to present odorants at different concentrations to a panel of subjects and assess their response. The process favored by the U.S. National Academy of Sciences is dynamic olfactometry (16). This technique involves a sample dilution method in which a flow of clean, nonodorous air is mixed with the odorant under dynamic or constant... 

Methyl-2-hexenoic acid (mixture of ll and Z isomers) has been identified as the substance responsible for the odor of human sweat. Synthesize the compound from starting materials having five or fewer carbons. 

Schaal B., Marlier L. and Soussignan R. (1998). Olfactory function in the human fetus evidence from selective neonatal responsiveness to the odor of amniotic fluid. Behav Neurosci 112, 1438-1449. 

Schaal, B., Marlier, L. and Soussignan, R. (1995) Responsiveness to the odor of amniotic fluid in the human neonate. Biol. Neonate 67, 397 106. 

In the same way as volatiles from the whole breast, odorants carried in human colostrum/milk are arousing and attractive to newborns (Mizuno, Mizuno, Shino-hara and Noda 2004 Marlier and Schaal 2005). Interestingly, neonatal responsiveness to these milk cues does not seem to depend on breastfeeding experience as term-born infants exclusively fed formula (Marlier and Schaal 2005), and premature infants (Bingham et al. 2003), react to them in the same way as regularly breast-fed infants. 

Doucet, S., Soussignan, R., Sagot, P., and Schaal, B. (2007b). Human areolar glands emit odorants affecting behaviour and autonomous responses in newborns. Unpublished manuscript. 

Klemm, W.R., Lutes, S.D., Hendrix, D.V. and Warrenburg, S. (1992). Topographical EEG maps of human response to odors. Chemical Senses 17 347-361. 

Predators ignore sea hares because, like other mollusks without shells, they have chemicals that afford them the protection once given by a shell. (We saw earlier that a compound from a tropical sea hare is now a promising anticancer drug.) Many sea hares have an acrid or fetid odor that is distinctly unpleasant to humans. Their egg masses and their skin must be distasteful, because one exploratory bite is enough to convince a would-be assailant to look elsewhere for food. For some species, the deterrents responsible for these properties may come directly from their seaweed diet, but other species seem to synthesize these defenses for themselves. The evidence is mixed and confusing. 

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