(Image caption: Alternative mechanisms for driving food consumption. Eating not only is a necessity, it is a learned response to hunger, too. a) In the positive-valance mechanism, hungry animals learn that eating feels good. b) In the negative-valence mechanism, hunger feels bad to animals, and they learn that eating makes these bad feelings dissipate)

Another reason why your diet is doomed – “Hunger” neurons promote negative feelings

Dieting challenges evolution

In its simplest terms, weight loss occurs when the amount of energy consumed in the form of food is less than the amount of energy burned. This can be accomplished by eating less or exercising more. With either approach, the goal is to create a caloric debt that will be resolved by burning stored carbohydrate, protein, or fat. Challenges to losing the holiday weight (alternatively a beer gut, Freshman Fifteen, etc.) are simple: eating feels good and being hungry is uncomfortable. Behaviors that evolved as survival mechanisms to ensure that an animal feeds itself become inconvenient and potentially detrimental side effects in industrialized human populations where cardiovascular disease, diabetes, and obesity, rather than starvation, pose greater risks to long-term survival.

To explain the less commonly researched “discomfort when hungry” phenomenon, researchers at the Howard Hughes Medical Institute (HHMI) Janelia Research Campus hypothesized that specific hypothalamic neurons stimulate food-seeking behaviors to eliminate the negative feelings associated with energy deficit (Betley et al. 2015).

The Hunger Games  – Neural manipulation suggests AGRP signals are negative

Previously demonstrated by other groups, hypothalamic AGRP neurons (agouti-related protein-expressing neurons) fire during energy deficit, such as food restriction, and quickly lead to food-seeking behavior and food-consumption. To determine whether these neurons were associated with positive signals (such as those associated with food reward) versus negative signals (such as those associated with the uncomfortable feelings of hunger), mice either with photoactivatable AGRP neurons (STOCK Agrptm1(cre)Lowl/J 012899 X B6;129S-Gt(ROSA)26Sortm32(CAG-COP4*H134R/EYFP)Hze/J 012569 F1 hybrids) or with virally-transduced AGRP neurons that could be inhibited pharmacologically were subjected to flavor and place preference tests.

In flavor preference tests, AGRP neuron activation reduced an animal’s preference for previously preferred flavored gel compared to unstimulated controls, suggesting that a once tasty flavor was now a less pleasant experience. In contrast, mouse preferences for a preferred gel increased when AGRP neurons in food-restricted mice were pharmacologically inhibited compared to the preferences of untreated controls, suggesting that AGRP inhibition relieved negative feelings. In complementary place preference experiments in which mice were offered two experimental chambers to explore, well-fed mice avoided chambers in which they had previously received AGRP stimulation, indicating AGRP stimulation was undesirable. Similarly, food-restricted mice spent more time in chambers where they had previously received AGRP inhibition, indicating that relief from AGRP simulation was preferred. Together, these results suggest that AGRP neurons stimulate negative signals and generate Pavlovian responses learned through these negative experiences.

AGRP neurons anticipate feeding and turn off

To support their behavioral studies, the HHMI Janelia group performed deep brain imaging in freely-moving AGRP-specific calcium reporter mice using miniature head-mounted fluorescent microscopes. As expected, food-restricted mice showed higher fluorescent signals than mice fed ad libitum, demonstrating that food restriction activates AGRP neurons. Calcium signals quickly diminished when food-restricted mice were allowed to eat. Interestingly, the calcium signals dropped before eating began, including cases where food was visible but not accessible for consumption. In contrast, calcium signals dropped slightly when mice were presented a wooden pellet resembling food, but quickly returned when the mice discovered that the wooden pellet was not food. Together, these experiments indicate that AGRP neuron activity is reduced when feeding cues are present. Further, the rapidity with which the AGRP signals terminate upon feeding or recommence upon presentation with non-food items strengthen the hypothesis that AGRP neurons promote negative, rather than positive, signals.

Collectively, these results indicate that energy homeostasis depends, in part, on alleviating negative signals produced during hunger. Findings from this study corroborate the negative emotions people experience when dieting and point to alternative avenues to regulate food intake. The negative-valence mechanism that AGRP neurons utilize contrasts with the majority of hunger-associated neurons previously studied, which stimulate reward pathways and result in positive feelings when hunger is satisfied. Certainly, then, fine control of energy homeostasis is accomplished by possessing both kinds of neurons.

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Several hours had passed since they stormed out of the house in opposite directions. The night chill had a soothing effect on Marcello and after wandering in the deserted streets of Valence he finally turned back. He grabbed the ice cream on his way and texted Ronnie. It didn’t take him long to find her, sitting at the beach.

“Hey,” he said as he sat down next to her.

Dmitri Mendeleev’s 182nd Birthday

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Date: February 8, 2016

Around 400 BC, the ancient Greeks organized the worldly elements into four groups: air, water, earth, and fire. In the seventeenth century, Robert Boyle explained the material world in terms of elements, mixtures, and compounds. And in 1869, Dmitri Mendeleev made sense of the 56 elements known at the time, showing how they related to each other in a distinct pattern. His periodic table let elements fall into “periods” according to atomic mass and valence (the power that determines how they combine). 

Scholars had attempted to organize the elements into a table before, but Mendeleev’s work extended beyond mere chart-making. Mendeleev used the logic of his table to argue for the existence of yet-to-be discovered elements (like gallium and germanium), and even to predict their behaviors. Some of these predictions were wrong, but the basic principles behind his periodic organization continue to stand at the foundation of modern chemistry. The periodic table of the elements (now with 118 elements and counting) adorns science classrooms worldwide.

In the final illustration, artist Robinson Wood imagines Mendeleev in the act of setting down the logic of his table (which reportedly came to him in a dream). Today, on Mendeleev’s 182nd birthday, we celebrate how this visionary helped us order and understand our world. 

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The Doodle Team’s early explorations for today’s illustration highlight (1) the element named after Mendeleev (mendelevium), and (2) the work Mendeleev did at his famous desk (where he was often photographed).


Location: Global

Tags: Birthday, Sciences, chemistry, Periodic Law, elements, atomic

rutiilus asked:

Looks like [ the most flawless] cinnamon roll but could actually kill you [+ raise you, and kill you again].

        Even you, Teller? Can you at least explain to
          me what this means? Is it flawless when the
          frosting is evenly spread upon the top or is it
          more a matter of shapeliness? I don’t eat them
          so I’m unsure what constitutes their appearance

Reese had intended to avoid Anderson Island, or well, anywhere outside of Valence until she went back to work, but she’d be going back to Vixen tomorrow, and to be honest, Valence was suffocating her. She adored the women she’d come to see as mothers to her. They just were so into everything. They’d demanded every detail about her bruise, and had filled her small house with more food than she could handle. She appreciated their kindness, and loved the way they made her feel as though she belonged, but she needed a little space.

She pulled Laurent’s jacket on. It was a nice jacket, warm, and well, she liked it. She wasn’t going to Vixen, and she didn’t intend to really seek anyone out so she figured nothing would come of it. She got Livia’s stroller ready, glad that it was cold but not quite so snowy. The little one was bundled up and ready herself. The drive was short enough. Reese parked her car, got the stroller out, and then Livia. She settled Livia in the stroller, leaning down to kiss her. “How about a walk through the park, hm?” She asked, grinning at the little one. 

She covered her bruise as best she could, but it still could be seen, much more than Reese wanted. She just prayed she wouldn’t end up on TMI. She walked, pushing Livia in the stroller, until she came to a bench that was cleared off. She moved to sit down, the stroller in front of her. She reached for the story book she’d brought, flipping it open and reading. “It was time for spring vacation. Olivia decided that she and her family ought to spend a few days in Venice.” She read, continuing the story. She looked up after a few minutes, nearly halfway through when she noticed the other. 

“Enjoying the story?” She asked, smiling. 


Mécaniques Discursives at Lux Valence

projet réalisé en collaboration avec Yannick Jacquet