Sense of smell and organ--论文代写范文精选

人类VNO可能作为信息素探测器。然而,到目前为止,没有证据表明人类VNO嗅觉系统是相互连接的。缺乏证据表明,否有这样一个东西作为人类信息素，在过去,造成了相当大的科学争论。下面的essay代写范文进行详述。

Abstract 
The vomeronasal organ 
The vomeronasal organ (VNO), also termed Jacobson’s organ, is a special part of the olfactory system(s) and can be found in most tetrapods at least in the embryonic stages. In most mammals, it is located above the hard palate on both sides of the nasal septum and consists of a pair of blind-ended tubes that open into the nasal cavity. In some mammals, it is connected to the oral cavity by the nasopalatine duct. Receptor cells in the epithelium of the mammalian VNO are not equipped with cilia [24, 25, 26] and their axons extend to an “accessory” olfactory bulb, that projects directly into the limbic system, bypassing the thalamus, and thus cortical integration. Simply put, the VNO is representative of an accessory olfactory system [27] that directly translates olfactory cues into neuroendocrine responses. In the past, the VNO was believed to exist only in lower mammals, and only at embryonic stages in primates. However, recent data have shown that the VNO also exists in adult humans [28]. Monti-Bloch and Grosser [29] found the adult human VNO responds to picogram amounts of human skin pheromones with depolarization. These fi ndings suggest, that the human VNO may function as a pheromone detector as it does in other mammals. However, so far there is no evidence that the human VNO is connected to a functional accessory olfactory system. This lack of evidence, in the past, has caused considerable scientifi c debate about whether or not there is such a thing as a human pheromone.

Pheromones 
The term “pheromone” comes from the ancient Greek words “pherein”: to carry, and “hormon”: to excite. Karlson and Luscher [30] introduced this term in 1959. Pheromones are referred to as ecto-hormones: chemical messengers that are transported outside the body that have the potential to evoke certain responses, such as physiological (e.g., hormonal) or behavioral changes in a conspecifi c. Thus, pheromones play an important role in inter-individual communication, and are known to do so in species from single-celled yeasts to primates, despite different manifestations of what might be considered “behavior”. Pheromones can be divided into at least two classes, according to the physiological effects they cause in the recipient: “signal” and “primer” pher omones [31]. Signal pheromones cause short-term changes, such as the release of neurotransmitters that can directly modify the recipient’s behavior. For example, Moss and Dudley [32] suggest that a fraction of the GnRH molecule functions directly as a neurotransmitter in rats to elicit a behavioral effect (i.e., lordosis). 

This behavioral effect is characteristic of a “signal” pheromone, which activates a response. Primer pheromones evoke long lasting changes in the body by infl uencing the hypothalamic-pituitary-gonadal axis, which allows both for organizational and activational effects of primer pheromones. Primer pheromones are believed to exert their affect by altering the hypothalamic secretion of GnRH. Hypothalamic GnRH triggers the secretion of gonadotrophic hormones from the pituitary. The gonadotropins follicle stimulating hormone (FSH), and LH affect gonadal hormone secretion. In females, FSH stimulates follicle maturation in the ovaries and the secretion of estrogens; LH stimulates the ovarian theca cells to produce androgens, which diffuse to the granulosa cells of the ovarian follicle, where they are converted to estrogens, and LH also stimulates the growth of the corpus luteum and secretion of progesterone. 

In males, FSH stimulates spermatogenesis and probably affects T production and secretion by acting indirectly on an as-yet-unidentifi ed Sertoli cell protein [33]. In males, the LH/FSH ratio controls T production by Leydig cells in the testes. Sex steroid hormones like T and E alter neurotransmission by infl uencing synaptogenesis, synaptolysis, and apoptosis during development. GnRH pulsatility is unequivocally required for LH release (see [34]), and GnRH pulsatility is directly associated with changes in LH and in FSH pulsatility that are manifest in LH/FSH ratios, which modulate steroidogenesis. 

Thus, LH and the LH/FSH ratio are human measures of GnRH pulsatility and so are T and E levels, though these measures are less direct. The effect of primer pheromones on GnRH allows pheromones to infl uence LH/FSH ratios and the production of T and E, or simply put, primer pheromones infl uence the entire hypothalamic-pituitary-gonadal axis, which infl uences behavior by altering neuroanatomy and thus neurotransmission. The odors produced by humans are a function of the location on the body where the odor is being produced. The amount of available oxygen as well as water and skin gland secretions determine the type and number of cutaneous fl ora, which are present on different body areas. Moist areas of the body, such as the mouth, axillae, genital region, and feet, support greater varieties and numbers of bacteria because they are occluded, or are moist because of their function (e.g., mouth, vaginal barrel). The type and density of cutaneous microorganisms on different areas of the body interacting with skin and other glandular secretions give rise to a variety of odors from various body sites.

Human body odor 
In humans, pheromone production is primarily linked to the apocrine glands of the skin, but also is linked to other glandular secretions and to skin fl ora present in moist areas of the body, like the axillae, mouth, feet, and genitals. For example, concentrations of C2-C5 aliphatic acids that are secreted from the vaginal barrel, and that have been referred to as “copulins,” vary with menstrual cycle phase. The odor of the copulins and its behavioral effects also appear to vary with the menstrual cycle. Thus, copulins are also referred to as pheromones [35, 36]. In suffi cient quantity, pheromones are consciously detected as natural human body odor. Apocrine glands are found in areas that include the genital area, around the navel, on the chest, breasts, and areola, and are concentrated in the axillae. 

Like ecrine (watery sweat) glands and sebaceous (sebumsecreting) glands, apocrine glands are associated with hairs. The high concentration of apocrine glands found in the armpits led to the term: “axillary organ”, which is considered an independent “organ” of human odor production. Apocrine glands have a tubular, coiled structure and are about 2 mm in diameter [37]. Human apocrine glands develop in the embryo, but become functional only with the onset of puberty [38]. This link between apocrine gland function and puberty refl ects that function is closely linked to levels of sex steroid hormones that increase with the onset of adrenarche and puberty. Freshly produced apocrine secretion has no odor [39], and is transformed into odorous products by microorganisms (see [40] for review). 

For reasons that remain unclear, humans produce a relatively high amount of odor production, when compared to other primates. The odors of the skin, the saliva, urine and, genital secretions, contribute to the amount and hedonic quality that is characteristic of natural human body odor. In this regard, we note that any odor, even the scent of rose, becomes aversive when it is produced in suprathreshold quantities. Thus, though pheromonal communication typically occurs without consciousness, pheromones, when produced in high concentration, may still have both conscious and aversive effects on others.

Human pheromones 
By defi nition a human pheromone elicits changes in the physiology and/or behavior of a conspecifi c. Stern and McClintock [41] showed that the phero mones of women regulate ovulation in other women, presumably by affecting levels of LH and FSH. Berliner, Monti-Bloch, Jennings-White and Diaz-Sanchez [42] suggest that a progesteronic pheromone alters LH pulsatility in men. These studies show that human pheromones, or that a putative human pheromone, elicit change in hormones. Similarly, Juette [43] showed that an aqueous mixture of fi ve ovulatory fatty acids evoked increased saliva T levels in men, and produced better judgments of female photos and of female voices than in controls. 

Thus, both physiology (i.e., T levels) and behavior (i.e., judgment) were affected. The putative human pheromone androstadione also has been shown to elicit physiological (i.e., hormonal) and behavioral (i.e., mood) changes [44, 23]. Shinohara, Morofushi, Funabashi, and Kimura [45] showed that axillary pheromones from women either in the follicular or in the ovulatory phase of the menstrual cycle differentially modulate pulsatile LH pulse frequency in other women, a hormonal effect. Preti, Wysocki, Barnhart, Sonheimer and Leyden [46] recently showed that male axillary extracts effect LH and mood in female recipients, and suggested that the LH response may be used to determine precisely what compound is involved in this pheromonal effect, which is a typical mammalian female response to pheromones from a male conspecifi c [14]. Minimally, human pheromones appear to alter both physiology and behavior in other humans. It is still unknown how many different pheromones are produced in human axillae, but some of them have been investigated in recent years. 

Most studies focused on the 16-androstenes, metabolites of the characteristically male sexual hormones, the androgens, which are secreted by the apocrine glands. Dorfman [47] assumes that the 16-androstenes develop with the metabolism of testosterone. Two of these androstenes, the alcohol 5-androst-16en-3ol (androstenol) and the ketone 5α-androst-16en-3-one (androstenone) have odorous characteristics that bear a similarity to the smell of male axillae. Androstenol has a musk-like scent, while androstenone smells urinous. It is important to note that the odors arise only via the activity of microorganisms [48]. Among these microorganisms are the aerobic bacteria Corynebacterium ssp., which transform the odorless precursors androstadienol and androstadienone, into the odorous 5α-androstenone [49]. 

If the axillae are treated with antibacterial detergents, the production of androstenone decreases signifi cantly [50]. Male axillary sweat contains approximately fi ve times more androstenone than female sweat [51]. This sex difference can be explained by sexually dimorphic levels of blood androgens, and by sex differences in the colonization of microorganisms. For example, Jackman and Noble [52] investigated the axillary bacteria of 163 male and 122 female subjects and were able to show that in most men the axillae were dominated by the bacteria Corynebacteria ssp., whereas in women they found the bacteria Micrococcaceae. Other putative human pheromones, whether secreted primarily in the axillae, or in other areas, can be expected to be identifi ed upon the examination of sexually dimorphic adrenal hormone metabolites, and with the identifi cation of other sexually dimorphic microorganism colonization.

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