Basis Of Odour Research Articles

Evaluation of Volatile Compounds in Milks Fermented Using Traditional Starter Cultures and Probiotics Based on Odor Activity Value and Chemometric Techniques.

The volatile components of milks fermented using traditional starter cultures (Streptococcus thermophilus and Lactobacillus bulgaricus) and probiotics (Lactobacillus lactis, Lactobacillus bifidus, Lactobacillus casei, and Lactobacillus plantarum) were investigated by means of gas chromatography-mass spectrometry (GC-MS) combined with simultaneous distillation extraction (SDE). A total of 53 volatile compounds were detected, being 10 aldehydes, 11 ketones, 10 acids, 11 hydrocarbons, 7 benzene derivatives, and 4 other compounds. The starter culture was found to significantly affect the composition of volatile components in the fermented milks. Ketones and hydrocarbons were the dominant compounds in milk before fermentation, while acids were dominant compounds in the fermented samples. Compared with probiotics, there was greater abundance of volatile components in fermented milks with traditional strains. The importance of each volatile compound was assessed on the basis of odor, thresholds, and odor activity values (OAVs). Of the volatile compounds, 31 of them were found to be odor-active compounds (OAV > 1). The component with the highest OAVs in most samples was (E,E)-2,4-decadienal. Heatmap analysis and principal component analysis were employed to characterize the volatile profiles of milks fermented by different starter cultures. The results could help to better understand the influence of starter cultures on the odor quality of milks.

Immunization alters body odor

Infections have been shown to alter body odor. Because immune activation accompanies both infection and immunization, we tested the hypothesis that classical immunization might similarly result in the alteration of body odors detectable by trained biosensor mice. Using a Y-maze, we trained biosensor mice to distinguish between urine odors from rabies-vaccinated (RV) and unvaccinated control mice. RV-trained mice generalized this training to mice immunized with the equine West Nile virus (WNV) vaccine compared with urine of corresponding controls. These results suggest that there are similarities between body odors of mice immunized with these two vaccines. This conclusion was reinforced when mice could not be trained to directly discriminate between urine odors of RV- versus WNV-treated mice. Next, we trained biosensor mice to discriminate the urine odors of mice treated with lipopolysaccharide (LPS; a general elicitor of innate immunological responses) from the urine of control mice. These LPS-trained biosensors could distinguish between the odors of LPS-treated mouse urine and RV-treated mouse urine. Finally, biosensor mice trained to distinguish between the odors of RV-treated mouse urine and control mouse urine did not generalize this training to discriminate between the odors of LPS-treated mouse urine and control mouse urine. From these experiments, we conclude that: (1) immunization alters urine odor in similar ways for RV and WNV immunizations; and (2) immune activation with LPS also alters urine odor but in ways different from those of RV and WNV.

Mate-odour identification by both sexes of Evarcha culicivora, an East African jumping spider

Evarcha culicivora is an unusual salticid spider because each sex actively courts the other and both sexes make distinctive mate-choice decisions. Here we use olfactometer experiments for investigating the ability of each sex to identify potential mates on the basis of odour alone. Test spiders spent more time in the vicinity of opposite-sex conspecific source spiders, regardless of whether or not these source spiders had previously mated, when the alternatives were conspecific individuals of the same sex, juveniles or a control (no odour source). This trend held regardless of the test spider's and source spider's age after reaching maturity and, for male test spiders, it held regardless of the test spider's mating status. However, after females had mated they no longer expressed a preference for male odour.

Is olfactory detection of human cancer by dogs based on major histocompatibility complex-dependent odour components? – A possible cure and a precocious diagnosis of cancer

Given the reports made about dogs detecting cancer on the basis of odour, our hypothesis is that the volatile organic compounds produced by tumours, and detected by dogs, are products of MHC genes. Two lines of evidences support this hypothesis: (1) human body odour is genetically determined by MHC. These antigen molecules (HLA in humans) have soluble and detectable isoforms that are present in body fluids such as blood, urine and sweat; (2) there is a strong association between changes in HLA expression and cancer. Tumour transformation is frequently associated with low classical HLA class I molecules expression, namely HLA-A, HLA-B, and HLA-C. In addition, cancer is associated with high nonclassical HLA class I molecules expression, such as HLA-G and HLA-E. These evidences suggest that these HLA-associated olfactory cues of human cancer could be easily analysed, for example, by the "electronic nose", making possible a very precocious and reliable diagnostic of cancer. Because cancer immunescape mechanism is similar to that observed in the materno-fetal immune tolerance, we propose also that immunomodulatory abortifacients could be a good strategy in cancer treatment.

Involvement of the oxytocin gene in the recognition and avoidance of parasitized males by female mice

A major cost of social behaviour is the increased risk of exposure to parasites. Female mice discriminate between uninfected males and males infected with parasites such as the intestinal nematode Heligmosomoides polygyrus, on the basis of social cues, displaying aversive responses to the odours of infected males and preferentially mating with nonparasitized males. Here, using female mice whose gene for the neuropeptide, oxytocin (OT), has been deleted (OT knockout mice, OTKO), we show that at least one normal allele for OT is required for the discrimination, individual recognition and avoidance of H. polygyrus parasitized males on the basis of odour. In an odour choice test, female wild-type (OTWT) and heterozygous (OTHT) mice displayed a marked initial choice for the odours of uninfected males over infected males that were either familiar or novel, whereas the OTKO females showed no consistent initial choice. This was not associated with olfactory deficits because females of all three genotypes distinguished between the odours of uninfected males of varying sexual states. A 1-min exposure to the odours of infected males also induced analgesic responses (i.e. pain inhibition) in OTWT and OTHT females, with the OTKO females displaying a markedly attenuated analgesia. These analgesic responses and the associated behavioural correlates of anxiety/fear facilitate the expression of a reduced interest in and avoidance of parasitized males by females. The OTWT and OTHT, but not the OTKO females, also distinguished between the odours of novel and familiar infected males and modulated their analgesic responses on the basis of prior familiarity, displaying reduced analgesia to familiar males and enhanced analgesia to novel males. Our findings indicate that a normal OT gene is an essential part of the central mechanism whereby females can, on the basis of odour, discriminate between parasitized and nonparasitized males and, thereby, both reduce the transmission of parasites to themselves and select for parasite-free males.

Recognition and avoidance of the odors of parasitized conspecifics and predators: Differential genomic correlates

In many species of animals chemical stimuli are an important source of information about the threats and dangers present in the social and non-social world. Olfactory cues play a fundamental role in modulating social recognition and interactions in a wide variety of mammals. Rodents, in particular, utilize chemical signals, to recognize and avoid conspecifics infected with parasites and other pathogens. Animals also respond to, and utilize, predator odor related information to assess and minimize their risk of predation. In this review, we briefly focus on the relations between odors, parasite recognition and avoidance and consider some of the associated hormonal, neural and genomic mechanisms. We describe how both male and female rodents distinguish between infected and uninfected males on the basis of odors, displaying aversive response to, and avoidance of, the urine odors of infected individuals. We further describe how the recognition and avoidance of the odors of infected individuals involves genes for the neuropeptide, oxytocin, (OT), and estrogenic mechanisms. We show that mice with deletions of the oxytocin gene (OT knockout mice (OTKO)) and mice whose genes for estrogen receptor (ER)-α or ER-β [ER knockout mice (ERKO), αERKO and βERKO] have been disrupted are specifically impaired in their recognition, avoidance, and memory of the odors of infected individuals. We contrast this with the recognition and display of aversive responses to predator (cat) odor that are insensitive to these genetic manipulations. These findings reveal some of the mechanisms associated with the olfactory mediated recognition of parasitized individuals and predators.

Brief exposure to the odour of a parasitized male alters the subsequent mate odour responses of female mice

Parasites can affect mate choice, with females preferentially selecting parasite-free males. Prior exposure to, or experience with, males has also been suggested to influence mate responses. Here, we examined the effects of an immediate, brief (1 or 15 min) pre-exposure to the urinary and associated odours of either an uninfected male house mouse, Mus domesticus , or a male infected with the natural murine nematode parasite, Heligomosomoides polygyrus, on the subsequent responses of female mice to the odours of infected and uninfected males. Using an odour preference test we found that females displayed a marked overall preference for the odours of uninfected males. Pre-exposure to the odours of a parasitized male decreased female preference for nonparasitized males and increased female preference for parasitized males. This ‘prior male’ effect was evident for both the total odour preference and initial odour choice. Females pre-exposed to the odour of a parasitized male displayed decreased choosiness and made no particular initial choice of a male, while still maintaining an overall preference for the odours of uninfected males. These shifts in initial choice and odour preference were not directly associated with either female stress responses or stress-related odour cues of the males. Our findings show that female mice can distinguish between parasitized and nonparasitized males on the basis of odour and suggest that a brief exposure to the odours of infected males influences females' immediate odour preferences, and their subsequent preference for and choice of males. This rapid, infection-associated ‘prior male’ effect may contribute to the reported variations in female mate preference and choice. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour

Olfactory preference for mother over home nest shavings by newborn rats

The developmental course and behavioral processes by which infant rats come to prefer one of two prominent natural odors within their rearing environment, those of their mother and home nest shavings, was studied. Pups as young as 4–5 days and as old as 9–10 days prefer their mother's odor over that of their home nest shavings in a two-choice test chamber; pups deprived overnight prior to testing express that preference more strongly than nondeprived littermates when the mother is awake, but not when anesthetized. Encountering maternal and shavings odors in a two-choice paradigm engages a behavioral sequence that progresses from arousal and active sampling of both odors during the establishment of preference to increased mouthing after the choice has been made. A .5°C thermal gradient augments the maternal preference response from 4–5 days of age on, and is necessary to it in 2-day-olds. One-day-old pups do not express a preference for their mothers in our test apparatus on the basis of odor even with the addition of a .5°C thermal gradient, suggesting that preference for the odor of mother over home shavings may be acquired between 1 and 2 days of age. © 1998 John Wiley & Sons, Inc. Dev Psychobiol 33: 5–20, 1998

Olfactory preference for mother over home nest shavings by newborn rats

The developmental course and behavioral processes by which infant rats come to prefer one of two prominent natural odors within their rearing environment, those of their mother and home nest shavings, was studied. Pups as young as 4-5 days and as old as 9-10 days prefer their mother's odor that of their home nest shavings in a two-choice test chamber; pups deprived overnight prior to testing express that preference more strongly than nondeprived littermates when the mother is awake, but not when anesthetized. Encountering maternal and shavings odors in a two-choice paradigm engages a behavioral sequence that progresses from arousal and active sampling of both odors during the establishment of preference to increased mouthing after the choice has been made. A .5 degrees C thermal gradient augments the maternal preference response from 4-5 days of age on, and is necessary to it in 2-day-olds. One-day-old pups do not express a preference for their mothers in our test apparatus on the basis of odor even with the addition of a .5 degrees C thermal gradient, suggesting that preference for the odor of mother over home shavings may be acquired between 1 and 2 days of age.

Acylation of (+) -2-Pinene, (-) -2 (10) -Pinene and (+) -1-p-Menthene by Synthetic Zeolite Catalysts

Examination was made of acylation reactions of (+) -2-pinene (1), (-) -2 (10) -pinene (2) and (+) -1-p-menthene (3) with acid anhydrides (acetic anhydride and propionic anhydride) in the presence of synthetic zeolites and the following results were obtained. With US-Y type zeolites, (4) (13) were obtained from (1) (3) as the main products, respectively and evaluated on the basis of odor ; (9) emitted odors that would qualify them as flavor agents. The antimicrobial activity of acylated compounds (4) (13) toward Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Aspergillus niger and Penicillium citrinum was also examined and it was found that compound (7) (at 100 μg/mL) derived from (1) and (2), completely inhibited the growth of B. subtilis.

Discrimination by female mice between the odours of parasitized and non-parasitized males

The detection and avoidance of parasitized males has been proposed to be a component of female mate choice. We investigated whether or not female laboratory mice, Mus musculus domesticus, could discriminate between parasitized and non-parasitized males on the basis of odour. Female mice were given a choice between the urine and other odorous secretions of either a male mouse sub-clinically infected for five days with the naturally occurring, enteric, single host, protozoan parasite, Eimeria vermiformis, or an uninfected male. Females showed a marked preference for the odours of non-parasitized male mice over those of the parasitized males; as measured by number of investigations, time spent per investigation, and total investigation time of the odours in a choice situation. Female mice also displayed an overwhelming initial, or first choice, preference for the odours of the non-parasitized male mice over those of the parasitized males. These observations show that female mice can distinguish between the odours of parasitized and non-parasitized males, and discriminate against parasitized males on the basis of odour. We suggest that the detection and avoidance of infected males by female mice through odour cues may function to reduce parasite transmission and potentially serve as a component of female mate selection or choice.

Home bedding modifies ultrasonic vocalization of infant bank voles

Bank vole,Clethrionomys glareolus, pups, similar to many other infant rodents, emit ultrasonic vocalizations when they are removed from the nest and cooled. Infants exposed to bedding from their home cage produced fewer and shorter calls than infants tested without bedding. Sound frequencies were significantly higher in infants exposed to home bedding than in other experimental groups. These results provide evidence that infant bank voles are able to identify the presence of home bedding, probably on the basis of odor. This appears to be the first report of shifts in frequency of pup ultrasonic calls in response to olfactory cues.

Honey bee, , nestmate discrimination: hydrocarbon effects and the evolutionary implications of comb choice

Comb wax in honey bee colonies serves as a source and medium for transmission of recognition cues. Worker honey bees learn the identity of their primary nesting material, the wax comb, within an hour of emergence. In an olfactometer, bees discriminate between combs on the basis of odour; they prefer the odours of previously learned combs. Representatives of three of the most common compound classes in bee's wax were surveyed for effects on nestmate discrimination behaviour. Hexadecane, octadecane, tetracosanoic acid and methyl docosanoate make worker honey bees less acceptable to their untreated sisters. Other similar compounds did not have this effect. These findings support the hypothesis that nestmate recognition in honey bees is mediated by many different compounds, including some related to those found in comb wax.

Honey bee, Apis mellifera, nestmate discrimination: hydrocarbon effects and the evolutionary implications of comb choice

Comb wax in honey bee colonies serves as a source and medium for transmission of recognition cues. Worker honey bees learn the identity of their primary nesting material, the wax comb, within an hour of emergence. In an olfactometer, bees discriminate between combs on the basis of odour; they prefer the odours of previously learned combs. Representatives of three of the most common compound classes in bee's wax were surveyed for effects on nestmate discrimination behaviour. Hexadecane, octadecane, tetracosanoic acid and methyl docosanoate make worker honey bees less acceptable to their untreated sisters. Other similar compounds did not have this effect. These findings support the hypothesis that nestmate recognition in honey bees is mediated by many different compounds, including some related to those found in comb wax.

Role of flower and pollen aromas in host-plant recognition by solitary bees.

The means by which newly emerged pollen-specific (oligolectic) solitary bees locate their appropriate pollen host plant is not clearly understood. To evaluate the role of flower and pollen odors in this recognition process, preference tests were performed on foraging-inexperienced and, for comparison, field-experienced individuals of the solitary bee Colletes fulgidus longiplumosus. The bees were presented with a choice of four plant species, offered in the form of aromas from flowers, whole pollen, pollenkitt, and internal pollen lipids. Observed feeding-attempt response patterns suggest: 1) that bees can distinguish between plant species on the basis of odors from flowers, whole pollen, and pollenkitt, 2) inexperienced bees show a preference for the pollen on which they were reared as larvae, and 3) chemicals eliciting feeding responses to pollen appear to be contained in the pollenkitt. Feeding responses by experienced bees differ from those of inexperienced bees in ways which indicate that the insects' odor-based search image of the host plant becomes modified by foraging experience.

Odor-guided behavior in mammals.

The odor-guided behaviors selected for presentation in this paper encompass the major areas of animal behavior, and illustrate the important principal that complex relations exist between odor-guided behaviors, hormonal state, and experiential factors. Clearly, experiences with odors at several life stages results in profound influences upon later behaviors, including those related to eating, mating, fighting, and nesting. Interestingly, only brief social encounters are needed in rats to induce such phenomena as ultrasonic calling to conspecific estrous females or their odors, preferences for estrous over non-estrous odors, and the short-term modification of feeding behaviors. Although the mechanisms behind these intriguing phenomena are poorly understood, it is noteworthy that rats can learn relatively complex concepts on the basis of odors, rivaling even the ability of our own species to learn analogous tasks by visual cues. Despite the fact that close relationships can be demonstrated between odor-guided behaviors and variables such as endocrine state and sexual experience, caution is warranted in assuming that simple causal relations exist between such variables. In normally cycling women, for example, the correlation between olfactory sensitivity and plasma levels of estradiol during the menstrual cycle is relatively high; however, attenuation of the cyclical estradiol fluctuations by oral contraceptives does not eliminate the olfactory fluctuations, suggesting the relation is not causal. In house mice, social experience can override hormonal factors in their odor-guided urine marking and submissive behaviors. Thus, even though androgen titer usually correlates with such measures, a mouse made subordinant in a social encounter will not exhibit scent marking even when its circulating testosterone is maintained at a high level by a silastic implant. Further reason for caution comes from studies that suggest olfactory input influences the endocrine systems of sexually experienced and sexually inexperienced animals in different ways. For example, in sexually experienced male rats, anosmia decreases testosterone and estradiol levels and increases corticosterone levels, whereas in sexually inexperienced ones it has no significant influence on the levels of these steroids. Taken together, such observations suggest that the causal bases of a number of the odor-guided behaviors described in this paper are complex.(ABSTRACT TRUNCATED AT 400 WORDS)

Systems of mate selection in a cockroach species with male dominance hierarchies

The system of mate selection in the cockroach, Nauphoeta cinerea, was studied experimentally. The dominant male in a group mates more often than expected if random mating were occurring. The presence of a female usually does not result in changes in the dominance hierarchy, but the frequency of certain behavioural patterns in intermale interactions changes after introduction of the female. Females can discriminate between dominant and non-dominant males on the basis of odour. The experimental approach to this question is somewhat confounded by turning tendencies of the females; data are presented relating female choice to turning tendency.

Discrimination among colony mates' anogenital odors by guinea pigs (Cavia porcellus).

Controversy exists in the literature regarding whether odor is used by guinea pigs in detection of physiological estrus in female counterparts. Three experiments are presented which used an aversively motivated learning task to examine the ability of adult guinea pigs to discriminate among odors from non-specific anogenital swabbings of colony mates. The first and second experiments examined the ability of male and female guinea pigs to discriminate among odors of colony mates controlled for age and sex. Both males and females were able to discriminate among individual animals on the basis of odor. Since individual animals could be discriminated, the third experiment, examining detection of physiological estrus, tested the ability of males and females to discriminate preserved odor samples from the same female during conditions of estrus and nonestrus. Both males and females were able to discriminate between the conditions. Results are discussed with reference to the involvement of odor in the social behavior of guinea pigs.

Appetitive Learning in 1-Day-Old Rat Pups

One-day-old rat pups learned to probe upward into a terry-cloth-covered paddle when they were rewarded with small infusions of milk into their mouths. In the presence of two paddles, discriminable on the basis of odor and position in the test container, the pups learned to probe into the paddle that provided them with milk. These experiments demonstrate (i) that milk may serve as a reinforcer to deprived rat pups and (ii) that pups as young as 1 day are capable of appetitive learning.

Snake Species Discrimination and the Role of Olfactory Cues in the Snake-Directed Behavior of the California Ground Squirrel

This experiment had two objectives. One was to seek evidence for greater caution by California ground squirrels (Spermophilus beccheyi) when interacting with venonnous rattlesnakes (Crotalus viridis), their most important snake predator, than when interacting with nonvenomous gopher snakes (Pituophis melanoleucus), their second-most important snake predator. The second was to examine the role of olfaction in mediating snake-directed behavior by these squirrels, since matry squirrel-snake encounters occur in burrows where visual cues are unavailable. In an illuminated room, we videotaped the responses by eight freely moving ground squirrels to the two snake species; the snakes were presented in large, transparent plastic bags that were either sealed (odor unavailable) or perforated (odor available). The results confirmed our predictions that the squirrels should behave more cautiously toward rattlesnakes than toward gopher snakes, and that olfaction is an important mediator of snake-directed behavior. Although the squirrels approached the two snake species equally often, they attended more to the rattlesnake than to the gopher snake, but remained farther away from the rattlesnake. When snake odor was available, the squirrels spent more time attending to the snakes, approached the snakes more frequently, approached the snakes in elongate postures more often and sand kicked more at the snakes. We proposed the following. 1. The antipredator strategy of snake harassment by California ground squirrels is sensitive to risk, exhibiting attenuation where risk is higher. 2. Olfaction is likely to be even more important during squirrel-snake encounters in the dark, especially in burrows. 3. The ability to recognize snakes on the basis of odor may not depend on prior experience with snakes, and may circumvent difficulties associated with visual detection of snakes.