“You have to eat something”. Everybody knows this sentence from his/her mother/grandmother. And it is actually true. Starvation is life-threatening. So no wonder that the human body takes this matter quite serious and responds with some emergency plans for energy conservation, like e.g. reduction of metabolism and body temperature. But starvation induced reduction in body temperature can not only be found in humans and other mammals but also in ectotherms, such as mosquitoes, cockroaches, and rainbow trout. What about Drosophila (fruit flies)? Yujiro Umezaki, et al. tested if Drosophila also shows starvation-induced body temperature reduction and if so, how they control it. Drosophila are so small, that their body temperature is mainly regulated by the ambient temperature. The small flies actively move to temperature regimes which suits their needs. Yujiro Umezaki, et al. showed, that starvation results in a lower preferred temperature in Drosophila. This process is like other starvation-induced behaviors controlled by the insulin/insulin-like growth factor (IGF) signaling pathway. (It is the same pathway we had in the last paper of the day, for the longevity and egg quality in C.elegans). To make a long story short: Starvation in Drosophila results in an increased expression of insulin-like peptide 6 (Ilp6) in the fat body (fly liver and adipose tissues). Ilp6 then alternates the “warm sensing” (TrpA1) channels of the temperature controlling neurons (anterior cells), so that the “too warm” threshold is decreased. Therefore, the preferred temperature is lower. What is most interesting, and the taking-home message for today is that the IGF signaling pathway is well conserved in vertebrates and invertebrates. It has been shown that starvation-induced decrease in body temperature in mice is controlled by IGF receptors, and Drosophila Ilp6 is functionally and structurally similar to IGFs. Therefore, it seems like the mechanism underlying the starvation-induced reduction in body temperature may be evolutionarily conserved between different species. So your body response to starving is not so different from the body response in Drosophila.
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Life as a female moth is hard. Sitting alone in the dark, you are listening to the ultrasonic sounds of the night. Is this the attractive call of a male moth? If so, go ahead and make some love. But be careful. Bats are out there. You can hear their ultrasonic sounds which they use for echolocation. So you should be sure that the singing male moth is worth the risk. Is it the Romeo of your dreams or just a little wimp? The answer lies in the song, the environment temperature and your perception. The lesser wax moth (Achroia grisella) belongs to the group of insects which choose their partner mainly by their acoustic performance, like you know it from crickets and grasshoppers. A healthy male moth is supposed to produce louder songs with higher frequencies, compared to his old/weak rivals. However, there is the problem of the environmental temperature which can make the process of finding a partner a little bit more tricky. As cold blooded animals, the muscle performance of the male (and so its song quality) is enhanced with increasing temperatures. Therefore, in grasshoppers, not only the male song changes with increasing temperature but also the preferred song of the female is temperature dependent. This temperature coupling of “producer” and “receiver” ensures that the female is able to identify the males of the right species at different temperatures. (Here I would like to refer to the great work of my former colleague F.A. Römschied https://elifesciences.org/articles/02078 ). But is this temperature coupling, which can be found in many different acoustic species, really the result of the evolutionary need to find the right partner or is it just a lucky coincidence, that the female perception changes with temperature? This is the question of a paper from Greefield and Medlock in 2007. They point out that temperature coupling just makes sense when you (1) have a narrow range of “attractive songs” for females which selects against faster and slower rates and you (2) have other acoustic species around, which you have to distinguish. Therefore, in their paper, they focus on the lesser wax moth, which does not fulfill these criteria. Female moth prefer any songs above a certain frequency and their habitat is lacking any other acoustic species (besides the bats with low frequency sounds). Moreover, the female acceptance threshold for acceptance is much lower than the male song rates. Therefore, temperature effects on male song rates does not conflict with the moth concept of “the fastest and loudest song is the most attractive one”. Nevertheless, male song rate and female acceptance threshold do exhibit parallel increases with elevated temperature. But why, when there is no evolutionary benefit? Greefield and Medlock show that male and female thermal effects are genetically correlated. Of course that genetic coupling could be there, because evolution selected for parallel temperature effects in female and male. However, as evolutionary benefit of thermal coupling is hard to explain in this case, it could also be, that the thermal coupling is just a coincidence because the same genes can control different properties in different tissues like the song production with the wings in the male and the song perception in the female. So the main message of the paper is, that when there is thermal coupling between the sexes, you should not automatically assume that it is based on an evolutionary need to adapt sound and sound preference but it could also just be that sound production and sound perception are two temperature dependent processes which are controlled by the same genes. Appel and Cocroft (2014) published a paper in which title they claimed that “plants respond to leaf vibrations caused by insect herbivore chewing”. In their study, the plant defence mechanism (production of toxins) which is normally activated by the feeding caterpillars, could also be activated by appropriate application of acoustic vibration directly to a leaf. That means that the acoustic vibrations are either directly transmitted through the leaf tissue or (even more interesting) are transmitted through the air and detected by plant “ears” (antenneas). If the latter is true, plants could “hear” if a neighbour plant is attacked, just by detecting the chewing sound waves of the caterpillars. Is that possible? “Yes it is possible” says the paper from Shaobao Liu et al. (2017). They analyzed if the Arabidopsis trichomes (hair cells) which has several mechanosensory functions, could additionally work as acoustic detectors. For that they analyzed geometry, mass and stiffness of the trichomes and showed theoretically that their primary modal frequencies would be able to resonate when exposed to acoustic waves with the frequencies similar to chewing caterpillar. In easy words: theoretically the trichomes could work like ears for the plant and detect chewing sounds. "Arabidopsis Leaf Trichomes as Acoustic Antennae."
Liu, Shaobao, et al. Biophysical Journal 113.9 (2017): 2068-2076. In order to explore the temporary representation of visual and spatial information, Adrian X. Ellis, Sergio Della Sala and Robert H. Logie (1995) published a paper in which they summed up all evidences for visuo-spatial working memory. Visual and spatial information about the environment are needed for planning interactions “and for predictions as to the outcome of external events and of our own actions”. Therefore it is somehow connected to the planning of movement and working memory. Indeed, there are studies based on dual task interference techniques showing that the control and/or production of movement is overlapping to some extent with the cognitive functions required for mental imaging task. Doing a movement task parallel to a mental imaging task decreases the performance of the mental imaging more as a comparable not-mental-imaging second task. That sounds all quite complicated. Lets just focus on the point that somehow planning movement and mental imaging are connected because “production of a movement to a target clearly requires some representation of where the target is in relation to the body or limb involved”. However, as the review paper of Ellis et al. points out: the visual-spatial representation does not have to be conscious. Unilateral spatial neglect is a neuropsychological condition in which a person fails to attend to the side opposite a brain lesion. Studies showed that people with the unilateral neglect fail to see differences between the picture of a chimeric animal (where front part of an animal is connected to a back part of a different animal… see example) and the picture of the same animal without any chimeric modulation, as long as the wrong “back” part is on the site they fail to attend to. In the example picture this means a person which neglect the left side will not be able to point out any difference between this picture and the picture of just a lying cat. However, if you ask the person which picture looks more like a fish, there is a large chance the person is showing to the chimeric picture. That shows that the visual-spatial representation does not have to be conscious in order to do a controlled (planned) movement like pointing to a certain picture. The conclusion of Ellis et al. is that “clearly the relationship between implicit processing, planning of action and the nature of the representation in working memory is an area that is ripe for further exploration.” Indeed, it seems like there was further exploration of this topic after this paper (in 1995). At least there was a book published about the visuo-spatial working memory in 2014 (Robert H. Logie, Psychology Press). So it seems like the visuo-spatial working memory theory still holds. "The Bailiwick of visuo-spatial working memory: evidence from unilateral spatial neglect"
Adrian X. Ellis, Sergio Della Sala and Robert H. Logie Cognitive Brain Research 3.2 (1996): 71-78. We do it every day… we like it when it is the coffee in the morning and don’t like it when it is a sweating person in the full subway. Our olfactory system detects all the pleasant and unpleasant odours of our environment for 24h every day of our life. However, what seems so simple in our daily life is quite hard to rebuild with electronic-chemical devices, so called electronic noses. In order to smell something, different kinds of odourant molecules needs to be detected and their relative amounts decide about the flavour they are creating. Julian W. Gardner and Philip N. Bartlett published 1994 a review about the history electronic noses. The first electronic noses were already build in the early 60’s but it needed further 20 years in order to improve an intelligent design for odour detection and the first conference for electronic noses was held in 1990. In the human nose, G-binding proteins act as chemosensory receptors in the olfactory cells. The binding of the odour molecules with the receptors triggers a second-messenger signal cascade which ends up in the creation of action potential which are transferred by nerve cells to the brain. In the electronic nose, inorganic semiconducting materials such as oxides and catalytic metals have been used as sensors for odour molecules. For example, the electronic nose of Wilkens and Hatman (1964) was based on redox reactions of the odourants at an electrode. The sensors are enough for odour detection, but for odour classification, the electric signal created by the receptors needs to be analysed by the usage of pattern recognition (PARC) engine or supervised learning artificial networking technique. The main problems in building electronic noses are the conflicts between sensitivity, selectivity and life duration. The sensitivity of the sensors depends on environmental properties such as temperature and humidity. Moreover, it is difficult to distinguish between the different odour molecules and reactive species decrease the life time of the sensors. However, the receptor cells in the human nose also have a low sensitivity, low specificity and short life duration (22 days). It is the subsequent neuronal processing which increases the sensitivity (by three orders magnitude) and offers us the probability to distingue between several thousand odours. So the solution for the electronic nose problems is not located in the odour sensors but the computation network behind it. A brief history of electronic noses
Julian W. Gardner and Philip N. Bartlett Sensors and Actuators B: Chemical 18.1 (1994): 210-211. |
IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
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