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A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavior of the receiving individuals. There are alarm pheromones, food trail pheromones, sex pheromones, and many others that affect behavior or physiology. Pheromones are used by many organisms, from basic unicellular prokaryotes to complex multicellular eukaryotes. Their use among insects has been particularly well documented. In addition, some vertebrates, plants and ciliates communicate by using pheromones. The ecological functions and evolution of pheromones are a major topic of research in the field of chemical ecology.
The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory (smell) sense organ located in the soft tissue of the nasal septum, in the nasal cavity just above the roof of the mouth in various tetrapods. The name is derived from the fact that it lies adjacent to the unpaired vomer bone in the nasal septum. It is present and functional in all snakes and lizards, and in many mammals, including cats, dogs, cattle, pigs, and some primates. Some humans may have physical remnants of a VNO, but it is vestigial and non-functional.
The olfactory bulb is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OFC) and the hippocampus where it plays a role in emotion, memory and learning. The bulb is divided into two distinct structures: the main olfactory bulb and the accessory olfactory bulb. The main olfactory bulb connects to the amygdala via the piriform cortex of the primary olfactory cortex and directly projects from the main olfactory bulb to specific amygdala areas. The accessory olfactory bulb resides on the dorsal-posterior region of the main olfactory bulb and forms a parallel pathway. Destruction of the olfactory bulb results in ipsilateral anosmia, while irritative lesions of the uncus can result in olfactory and gustatory hallucinations.
The house mouse is a small mammal of the order Rodentia, characteristically having a pointed snout, large rounded ears, and a long and almost hairless tail. It is one of the most abundant species of the genus Mus. Although a wild animal, the house mouse has benefited significantly from associating with human habitation to the point that truly wild populations are significantly less common than the semi-tame populations near human activity.
Androstenone (5α-androst-16-en-3-one) is a 16-androstene class steroidal pheromone. It is found in boar's saliva, celery cytoplasm, and truffle fungus. Androstenone was the first mammalian pheromone to be identified. It is found in high concentrations in the saliva of male pigs, and, when inhaled by a female pig that is in heat, results in the female assuming the mating stance. Androstenone is the active ingredient in 'Boarmate', a commercial product made by DuPont sold to pig farmers to test sows for timing of artificial insemination.
Allelic exclusion is a process by which only one allele of a gene is expressed while the other allele is silenced. This phenomenon is most notable for playing a role in the development of B lymphocytes, where allelic exclusion allows for each mature B lymphocyte to express only one type of immunoglobulin. This subsequently results in each B lymphocyte being able to recognize only one antigen. This is significant as the co-expression of both alleles in B lymphocytes is associated with autoimmunity and the production of autoantibodies.
The Lee–Boot effect is a phenomenon concerning the suppression or prolongation of oestrous cycles of mature female mice, when females are housed in groups and isolated from males. It is caused by the effects of an estrogen-dependent pheromone, possibly 2,5-dimethylpyrazine, which is released via the urine and acts on the vomeronasal organ of recipients. This pheromone lowers the concentration of luteinizing hormone and elevates prolactin levels, synchronising or stopping the recipient's cycle. This effect goes some way to explain why spontaneous pseudopregnancy can occur in mice. The same response is invoked from isolated females when brought into contact with urine-soaked bedding from other females' cages. The adrenal glands are required for production of the urine pheromone which is responsible for this effect.
The Monell Chemical Senses Center is a non-profit independent scientific institute located at the University City Science Center campus in Philadelphia, Pennsylvania. Monell conducts and publishes interdisciplinary basic research on taste, smell, and chemesthesis.
In the context of human evolution, human vestigiality involves those traits occurring in humans that have lost all or most of their original function through evolution. Although structures called vestigial often appear functionless, a vestigial structure may retain lesser functions or develop minor new ones. In some cases, structures once identified as vestigial simply had an unrecognized function. Vestigial organs are sometimes called rudimentary organs. Many human characteristics are also vestigial in other primates and related animals.
Danielle Renee Reed is an American geneticist employed at the Monell Chemical Senses Center in Philadelphia, Pennsylvania. She is most notable for her papers regarding genetic variation in taste and obesity in mice and humans.
Dr. Gary K. Beauchamp was the director and president of the Monell Chemical Senses Center from August 1990 to September 2014.
Dr. Alexander Bachmanov studied veterinary medicine at the Saint Petersburg Veterinary Institute, Russia (1977-1982), received his Ph.D. in biological sciences from the Pavlov Institute of Physiology in Saint Petersburg, Russia in 1990. He completed postdoctoral fellowships at the Physiological Laboratory at Cambridge University in 1993 and at the Monell Chemical Senses Center, Philadelphia, Pennsylvania, in the United States from 1994 to 1997. He later joined Monnell's faculty.
George Preti was an analytical organic chemist who worked at the Monell Chemical Senses Center in Philadelphia, Pennsylvania. For more than four decades, his research focused on the nature, origin, and functional significance of human odors. Dr. Preti's laboratory has identified characteristic underarm odorants, and his later studies centered upon a bioassay-guided approach to the identification of human pheromones, odors diagnostic of human disease, human malodor identification and suppression and examining the “odor-print” of humans.
Dr. Morley Richard Kare (1922–1990) was a physiologist and biologist.
Dr. Michael G. Tordoff is a psychobiologist working at the Monell Chemical Senses Center. His research deals with the genetics and physiology of taste and nutrition. His early work addressed (a) how and what animals learn about the value of their food, (b) how artificial sweeteners influence appetite and body weight, (c) how salt intake is regulated, and (d) how dietary calcium influences salt intake. Recently, he has been investigating calcium taste and appetite. He is the primary proponent of the notion that calcium is a basic taste, equivalent to sweet, sour, salty, and bitter.
Major urinary proteins (Mups), also known as α2u-globulins, are a subfamily of proteins found in abundance in the urine and other secretions of many animals. Mups provide a small range of identifying information about the donor animal, when detected by the vomeronasal organ of the receiving animal. They belong to a larger family of proteins known as lipocalins. Mups are encoded by a cluster of genes, located adjacent to each other on a single stretch of DNA, that varies greatly in number between species: from at least 21 functional genes in mice to none in humans. Mup proteins form a characteristic glove shape, encompassing a ligand-binding pocket that accommodates specific small organic chemicals.
The Bruce effect, or pregnancy block, is the tendency for female rodents to terminate their pregnancies following exposure to the scent of an unfamiliar male. The effect was first noted in 1959 by Hilda M. Bruce, and has primarily been studied in laboratory mice. In mice, pregnancy can only be terminated prior to embryo implantation, but other species will interrupt even a late-term pregnancy.
Vomeronasal receptors are a class of olfactory receptors that putatively function as receptors for pheromones. Pheromones have evolved in all animal phyla, to signal sex and dominance status, and are responsible for stereotypical social and sexual behaviour among members of the same species. In mammals, these chemical signals are believed to be detected primarily by the vomeronasal organ (VNO), a chemosensory organ located at the base of the nasal septum.
The Great Pheromone Myth is a book on pheromones and their application to chemosensation in mammals by Richard L. Doty, director of the University of Pennsylvania's Smell and Taste Center in Philadelphia. Doty argues that the concept of pheromone introduced by Karlson and Lüscher is too simple for mammalian chemonsensory systems, failing to take into account learning and the context-dependence of chemosensation. In this book, he is especially critical of human pheromones, arguing that not only are there no definitive studies finding human pheromones, but that humans lack a functional vomeronasal organ to detect pheromones. Its publication received coverage in the news media, especially concerning its arguments that human pheromones do not exist.
No study has led to the isolation of true human sex pheromones, although various researchers have investigated the possibility of their existence.
References
- ↑ Wysocki, Charles; Lepri, J. (1991), "Consequences of removing the vomeronasal organ", The Journal of Steroid Biochemistry and Molecular Biology, 39 (4B), Philadelphia: 661–9, doi:10.1016/0960-0760(91)90265-7, PMID 1892795 [ dead link ]
- ↑ Wysocki, Charles; Yamazaki, Kunio; Curran, M; Wysocki, LM; Beauchamp, GK (2004), "Mice (Mus musculus) lacking a vomeronasal organ can discriminate MHC-determined odortypes", Hormones and Behavior, 46 (3), Philadelphia: 241–6, doi:10.1016/j.yhbeh.2004.02.010, PMID 15325225 [ dead link ]
