today I learned

Vapor Detection and Discrimination with a Panel of Odorant Receptors

Model diagram to show that the authors measured the amount of luminescence (glow) over time in the cells, and then they used the area under the curve (AUC) as the number they reported to determine response to the odorants.

Today I learned: that scientists have been trying to create artificial “noses”. Traditionally, dogs and other animals have been trained to identify specific smells like cancer, drugs, toxins, etc. But recent research is trying to design these artificial systems that could act as a way to screen for many odors at once. This groups of scientists used cells grown in the lab that have an olfactory receptor (OR) and proteins inside the cell that cause the cell to light up when an odorant (chemical that has a smell) is recognized by the OR. This works because in mammals, when an OR recognizes an odorant, that OR then becomes “activated” and transmits a signal into the cell. The cell then passes that message along to another cell, which passes it onto the area of the brain that processes these signals and tells us what we are smelling. They used seven odorants — ranging from those that smell like cloves to those that smell like banana — and tested them with many different ORs to see how much the cells lit up. With this they were able to identify specifically which ORs responded to which smells and how sensitively they could respond. This system can be used to help create systems that can discriminate between odorants, even if they look very similar in structure.

Reference: Kida, Hitoshi, et al. “Vapor Detection and Discrimination with a Panel of Odorant Receptors.” Nature Communications, vol. 9, no. 1, 2018, doi:10.1038/s41467-018-06806-w.

Baleen Whale Cortisol Levels Reveal a Physiological Response to 20th Century Whaling

Today I learned: whaling in the 20th century indirectly stressed out many different species of whales. A group of scientists looked at the earplugs of three different types of baleen whales: fin, humpback, and blue. A whale earplug is a collection of ear wax that has alternating lines that tell the age of a whale (like tree rings do) and store both endogenous (i.e. hormones) or exogenous (i.e. pollutants) chemicals. Because of this, they could measure the amount of cortisol, a stress hormone, in each whale during many different years. They found that when whaling numbers peaked, there was also a peak in the average cortisol levels. Interestingly, when whaling decreased during World War II, they still saw slightly higher cortisol levels, which suggests that wartime noises (i.e. submarines, bombing/explosions, planes, etc.) also increased the stress in the whales. The sharp drop in cortisol levels in the 1970s was connected to the start of the Marine Mammal Protection Act that put a moratorium on whaling. However, cortisol levels have been slowing increasing since then, indicating that other stressors are present (i.e. increased sea temperatures, over-fishing, and noise).

Graph showing that when whaling numbers peak, there is a peak in cortisol levels

The graph shows that from 1900-2000, when whaling numbers (blue) increased, there was also an increase in cortisol levels (black). Highlighted in grey is a period corresponding to WWII where the whaling numbers were low, but cortisol was still high. Also shown is a red line to indicate when the Marine Mammal Protection Act went into effect in 1972 to emphasize the sharp drop in cortisol levels that followed.

Reference: Trumble, Stephen J., et al. “Baleen Whale Cortisol Levels Reveal a Physiological Response to 20th Century Whaling.” Nature Communications, vol. 9, no. 1, 2018, doi:10.1038/s41467-018-07044-w.


Modern Slavery and the Race to Fish

Today I learned: about 32% of wild-caught fish that is eventually sold in the US is illegally caught. Because of how fish are caught, and then distributed, it is really hard to track which shipments come from ships/fishery sectors that abuse their labor force. Additionally, labor accounts for 30–50% of fishing costs and many fishing sectors are seeing falling profit returns, prompting many countries to cut costs and resort to unethical conditions to make a profit. A group of researchers from Canada and Australia looked at a few different metrics to try and identify which countries were more likely to have poor worker conditions. The authors found that a country’s Global Slavery Index (GSI), the percent of unreported fish caught, the value of the fish caught, and the amount of distant-water fishing best predicted the countries that had modern slavery in the fishing industry. While an obvious step to reduce the unethical conditions includes more oversight on the ships themselves, more research has to be done to understand how the current problems affect fisheries policy.

Diagram showing that the more that the US, Western European, and Scandinavian countries import fish from high slavery-risk countries, the more likely that the domestic supply contains illegally caught fish

River plots showing that when the US (left) and Western European and Scandinavian countries (right) import fish from high slavery risk countries (yellow, orange, and red), the domestic supply contains fish caught under unethical conditions. (Figure adapted from Tickler et al.)

Reference: Tickler, David, et al. “Modern Slavery and the Race to Fish.” Nature Communications, vol. 9, no. 1, 2018, doi:10.1038/s41467-018-07118-9.

Distinct Patterns of Brain Activity Mediate Perceptual and Motor and Autonomic Responses to Noxious Stimuli

experimental set-up showing that the scientists randomized the time between laser pulses and how strong the pulses were. Perception (how it felt), motor (reaction time), and autonomic (skin conductance) responses were measured after laser pulses.

Experimental design from Tiemann et al.

Today I learned: a group of scientists figured out that distinct brain responses are involved in mediating our response to pain (noxious stimulus) via motor (movement), perceptual (feeling), and autonomic (unconscious body reactions like signal conducting) responses. To figure out this stimulus-brain-outcome relationship they measured motor (reaction times), perceptual (pain rating 0-100), autonomic (skin conductance), and brain (brain waves) responses to a series of random laser pulses (varied in both the time between pulses and the intensity of the pulses). As expected, more intense laser pulses caused the participants to have a faster reaction time, a higher pain rating, and stronger skin conductance measurements. But what was really interesting about this study was that they found that of the four brain waves they measured, not all were responsible for every response. Rather, each brain wave was involved in mediating either only one or two of the responses to the laser pulses. And contrary to what most people would expect, the earliest brain waves were not involved in the perception response, which means that you don’t need to consciously perceive the painful stimulus in order to have a motor or autonomic response.

Reference: Tiemann, Laura, et al. “Distinct Patterns of Brain Activity Mediate Perceptual and Motor and Autonomic Responses to Noxious Stimuli.” Nature Communications, vol. 9, no. 1, 2018, doi:10.1038/s41467-018-06875-x.

Oxygen Depletion of Pacific Ocean During Glacial Period

Today I learned: scientists figured out the oxygen levels in the waters off of Central America from 40,000 years ago. Before this study, people had thought that during the last glacial period (~110,000-15,000 years ago), oxygen levels in the oceans were higher because cold water can hold onto oxygen better. But this group was able to use a type of fossilized plankton that only takes up a type of nutrient in oxygen-rich conditions to determine that the deeper waters of the eastern Pacific Ocean were actually oxygen-depleted during this time. Typically, oxygen levels in oceans increase as you go deeper, but Hoogakker et al. found that there was no increase from shallow to deeper waters. Because the Pacific Ocean is the biggest sink (or storer) of carbon, holding about 50% of the total oceanic amount, this group suggested that the Pacific Ocean played an important role in the amount of carbon dioxide in the atmosphere during the glacial period and the transition period that followed.


Reference: Hoogakker, Babette A. A., et al. “Glacial Expansion of Oxygen-Depleted Seawater in the Eastern Tropical Pacific.” Nature, vol. 562, no. 7727, 2018, pp. 410–413., doi:10.1038/s41586-018-0589-x.

Dandelion Flight

image of a single dandelion with the two vortices of air above it

Dandelion seed with air vortex above filaments (taken from Cummins et al, 2018).

Today I learned: two years ago scientists finally figured out the secret to dandelion flight. A group from the UK found a new type of air movement (an air bubble/vortex that stays right above each seed, but doesn’t interact with it) that keeps dandelion seeds afloat. Each seed basically acts like a disk with a lot of holes in it that allows air to flow through. They also showed that the seeds can stay afloat so well and travel so far because of the structure of the seeds. Dandelion seeds are lightweight and plumed, which means that they can create air drag while still providing stability. So the next time you blow on a dandelion puff, you can think of each seed as a little parachute being carried by the wind. 


Reference: Cummins, Cathal, et al. “A Separated Vortex Ring Underlies the Flight of the Dandelion.” Nature, vol. 562, no. 7727, 2018, pp. 414–418., doi:10.1038/s41586-018-0604-2.