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"Smell"
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The hidden power of smell : how chemicals influence our lives and behavior
The main purpose of the book is to provide insight into an area that humans often take for granted. There are wonderful and exciting stories of organisms using chemical signals as a basis of a sophisticated communication system. In many instances, chemical signals can provide more detailed and accurate information than any other mode of communication, yet this world is hidden from us because of our focus on visual and auditory signals. Although we have a diversity of senses available to us, humans are primarily auditory and visual animals. These stimuli are sent to the more cognitive areas of our brain where they are immediately processed for information. We use sounds to communicate and music to excite or soothe us. Our vision provides us with communication, entertainment, and information about our world. Even though our world is dominated by other stimulus energies, we have chosen, in an evolutionary sense, either auditory or visual signals to carry our most important information. This is not the case for most other organisms. Chemical signals, mediated through the sense of smell and taste, are typically more important and are used more often than other sensory signals. The world of communication using chemicals is an alien world for us. We are unaware of how important chemical signals are to other organisms and we often overlook the influence of chemical signals in our own life. Part of this naivete about chemical signals is due to our cultural focus on visual and auditory signals, but a larger part of our collective ignorance is the lack of information about chemical communication in both popular and scientific writings. The popular press and popular writings virtually ignore the chemical senses, especially in regard to their role or influence for humans and our human culture.
Book
Rotten green tests in Java, Pharo and Python
Rotten Green Tests are tests that pass, but not because the assertions they contain are true: a rotten test passes because some or all of its assertions are not actually executed. The presence of a rotten green test is a test smell, and a bad one, because the existence of a test gives us false confidence that the code under test is valid, when in fact that code may not have been tested at all. This article reports on an empirical evaluation of the tests in a corpus of projects found in the wild. We selected approximately one hundred mature projects written in each of Java, Pharo, and Python. We looked for rotten green tests in each project, taking into account test helper methods, inherited helpers, and trait composition. Previous work has shown the presence of rotten green tests in Pharo projects; the results reported here show that they are also present in Java and Python projects, and that they fall into similar categories. Furthermore, we found code bugs that were hidden by rotten tests in Pharo and Python. We also discuss two test smells —missed fail and missed skip —that arise from the misuse of testing frameworks, and which we observed in tests written in all three languages.
Journal Article
Smell and taste recovery in coronavirus disease 2019 patients: a 60-day objective and prospective study
The long-term recovery rate of chemosensitive functions in coronavirus disease 2019 patients has not yet been determined.
A multicentre prospective study on 138 coronavirus disease 2019 patients was conducted. Olfactory and gustatory functions were prospectively evaluated for 60 days.
Within the first 4 days of coronavirus disease 2019, 84.8 per cent of patients had chemosensitive dysfunction that gradually improved over the observation period. The most significant increase in chemosensitive scores occurred in the first 10 days for taste and between 10 and 20 days for smell. At the end of the observation period (60 days after symptom onset), 7.2 per cent of the patients still had severe dysfunctions. The risk of developing a long-lasting disorder becomes significant at 10 days for taste (odds ratio = 40.2, 95 per cent confidence interval = 2.204-733.2, p = 0.013) and 20 days for smell (odds ratio = 58.5, 95 per cent confidence interval = 3.278-1043.5, p = 0.005).
Chemosensitive disturbances persisted in 7.2 per cent of patients 60 days after clinical onset. Specific therapies should be initiated in patients with severe olfactory and gustatory disturbances 20 days after disease onset.
Journal Article
Genetic variation in a human odorant receptor alters odour perception
The scent of androstenone
In humans, there is considerable variation between individuals in both their sensitivity to certain smells and their subjective experience of them. A new study is the first to show that genetic variation in a single human odorant receptor correlates with perceptual variation. OR7D4, an odorant receptor, is selectively activated
in vitro
by androstenone, a testosterone metabolite thought by some to be a candidate human pheromone. Variations in the gene encoding OR7D4 affected how the subjects thought the androstenone smelt — some found it pleasant, others offensive, to others it was odourless — and also how intense that smell was.
In humans, there is considerable variation between individuals in their sensitivity to certain smells and their subjective experience of them. This paper identifies a potential genetic source of variability in perception of odorous steroids. OR7D4, an odorant receptor, is selectively activated
in vitro
by androstenone and variants of the gene are associated with differences in psychophysical performance in human subjects
Human olfactory perception differs enormously between individuals, with large reported perceptual variations in the intensity and pleasantness of a given odour. For instance, androstenone (5α-androst-16-en-3-one), an odorous steroid derived from testosterone, is variously perceived by different individuals as offensive (“sweaty, urinous”), pleasant (“sweet, floral”) or odourless
1
,
2
,
3
. Similar variation in odour perception has been observed for several other odours
4
,
5
,
6
. The mechanistic basis of variation in odour perception between individuals is unknown. We investigated whether genetic variation in human odorant receptor genes accounts in part for variation in odour perception between individuals
7
,
8
. Here we show that a human odorant receptor, OR7D4, is selectively activated
in vitro
by androstenone and the related odorous steroid androstadienone (androsta-4,16-dien-3-one) and does not respond to a panel of 64 other odours and two solvents. A common variant of this receptor (OR7D4 WM) contains two non-synonymous single nucleotide polymorphisms (SNPs), resulting in two amino acid substitutions (R88W, T133M; hence ‘RT’) that severely impair function
in vitro
. Human subjects with
RT
/
WM
or
WM
/
WM
genotypes as a group were less sensitive to androstenone and androstadienone and found both odours less unpleasant than the
RT
/
RT
group. Genotypic variation in OR7D4 accounts for a significant proportion of the valence (pleasantness or unpleasantness) and intensity variance in perception of these steroidal odours. Our results demonstrate the first link between the function of a human odorant receptor
in vitro
and odour perception.
Journal Article