Most Cones Don’t Really See Color

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Astronomers Discover an Entirely New Kind of Galaxy

Astronomers at the University of Minnesota Duluth and the North Carolina Museum of Natural Sciences have identified a new class of ring galaxy. Named PGC 1000714, it features an elliptical core with not one, but two outer rings. It’s the only known galaxy of its kind in the known universe.

(Image caption: The synapses of pyramid cells in the cerebral cortex form functional groups. Some of the related synapses are shown in green in the reconstruction. Credit: © MPI of Neurobiology / Scheuss)

Neurons form synapse clusters

The cerebral cortex resembles a vast switchboard. Countless lines carrying information about the environment, for example from the sensory organs, converge in the cerebral cortex. In order to direct the flow of data into meaningful pathways, the individual pyramidal cells of the cerebral cortex act like miniature switchboard operators. Each cell receives information from several thousand lines. If the signals make sense, the line is opened, and the information is relayed onward. Scientists at the Max Planck Institute of Neurobiology in Martinsried have now shown for the first time that contact points between specific neuron types are clustered in groups on the target neuron. It is probable that signals are coordinated with each other in this way to make them more “convincing”.

The cells of the cerebral cortex have a lot to do. They process various types of information depending on the area in which they are located. For example, signals from the retina arrive in the visual cortex, where, among other things, the motion of objects is detected. The pyramidal cells of the cerebral cortex receive information from other cells through thousands of contact points called synapses. Depending on where, how many and how often synapses are activated, the cell relays the signal onward – or not.

Information is passed on in the form of electrical signals. The neurobiologists were able to measure these signals at various contact points of the neuron. “The exciting thing is that the signals that a cell receives from, say, ten simultaneously active synapses can be greater than the sum of the signals from the ten individual synapses,” says Volker Scheuss, summarizing the basis of his recently published study. “However, until now it was unclear whether this phenomenon can be explained by a specific arrangement of synapses on pyramidal cells.”

By combining modern methods, the neurobiologists in Tobias Bonhoeffer’s Department have analysed the arrangement of synapses. They were able to selectively activate a specific type of pyramid cell in brain slices from mice using optogenetics. Thanks to simultaneous “calcium imaging”, they were then able to observe and record the activity of individual synapses under a two-photon microscope. In this way, they succeeded in showing for the first time how synapses are arranged with respect to each other.

The result of such synapse mapping analysed with a newly developed algorithm was clear: The synapses of pyramidal cells form clusters consisting of 4 to 14 synapses arranged within an area of less than 30 micrometres along the dendrite. “The existence of these clusters suggests that the synapses interact with each other to control the strength of the combined signal,” explains Onur Gökçe, author of the study. This is the first anatomical explanation for the disproportionate strength of clustered synapse signals in comparison to the individual signals – a finding known from activity measurements. The observation in layer 5 pyramidal cells was of particular interest, as the activity of these cells oscillates synchronously. “This rhythmic activity, which probably influences the processing of visual information, could synchronously activate synapse clusters, thus boosting the overall signal received,” says Scheuss.

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This year’s Halloween special wraps up the chemistry behind making a mummy: http://wp.me/p4aPLT-26m

A special organic dye, Nile Red in different solvents.

From left to right I dissolved equal amounts of Nile Red (a dye) in different solvents. The solvents were: methanol, diisopropyl ether, hexane, n-propanol, tetrahydrofuran, toluene, ethanol, acetone.

Depending on the solvents polarity, the dye dissolved to give different colored solutions (upper image), this is called solvatochromism. It is the ability of a chemical substance to change color due to a change in solvent polarity.

Under UV light, these solutions emitted different colors (bottom pics), this is called solvatofluorescence. The emission and excitation wavelength both shift depending on solvent polarity, so it fluoresces with different color depending on the solvent what it’s dissolved in.

Nile Red is a quite expensive dye, which costs a bit over 1000 USD/gram, therefore I had to make it. The purification of the raw material was posted HERE. 

To help the blog, donate to Labphoto through Patreon: https://www.patreon.com/labphoto

Memory Competition

Most of the brain contains cells that no longer divide and renew. However, the dentate gyrus, nestled within the memory-forming centre of the brain (the hippocampus) is one of the few sites where new cells continue to form throughout life. As a person ages, there is an ever-increasing struggle for these new dentate gyrus neurons (coloured pink) to integrate with existing older neurons (green) because the latter already has well-established connections. This may be why learning and memorisation becomes more difficult as a person gets older. Scientists have now found that by temporarily reducing the number of dendritic spines – branches of neurons that form connections with other neurons – in the mature cells, the new cells have a better chance of functionally integrating. Indeed, in live mice, briefly eliminating dendritic spines boosted the number of integrated new neurons, which rejuvenated the hippocampus and improved the animals’ memory precision.

Written by Ruth Williams

Image courtesy of Kathleen McAvoy

Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, USA

Copyright held by original authors

Research published in Neuron, September 2016

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Brain Parasites: part II.

Taenia solium:

The pork tapeworm, Taenia solium, is the most harmful tapeworm in humans. Taenia solium infection is acquired either from human feces that contains Taenia solium eggs or from uncooked pork which contains larval cysts. If larvae are ingested, they mature into adults in the small intestine. This infection type is called taeniasis and is often asymptomatic. If eggs are ingested, the resulting disease is cysticercosis. It gets its name from larval Taenia solium called cysticercus. Both diseases are common in Africa, Asia, South America and Southern Europe. Taeniasis is rare in Muslim countries since people there do not consume pork.

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Dancing Flames - Aluminium’s reactivity 

aluminium’s protective oxide layer can make it difficult to see its true reactivity in the context of metals reacting with aqueous solutions. (Do not try to recreate experiment without the presence of a trained professional)

Procedure:

Dissolve copper(II) chloride in the hydrochloric acid and set the solution aside. Take a piece of aluminium foil approximately the width of the base of the conical flask and approximately 20 cm long. Roll it loosely just enough to be able to fit through the neck of the flask – use a splint or spatula to gently push it home so it lies on its side on the base of the flask. Have a source of ignition nearby with some splints. Pour the solution inside the flask and swirl the flask gently to get the reaction going. 

After a few seconds, the mixture will begin to react vigorously and produce hydrogen gas. Hold the lit splint by the opening of the flask and the gas will ignite. If you have timed it right, the flame will sink back into the flask and dance inside above the reaction with an eerie green color from the copper.

Reaction:

2Al(s) + 3CuCl2(aq) → 2AlCl3(aq) + 3Cu(s)

2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g)

The primary objective here is to show how reactive aluminium is. The aluminium oxide layer protects the metal beneath from further reaction with air, water or acid. But chloride ions can ligate aluminium ions at the metal–oxide interface and break down the protective layer, allowing the reaction to proceed. -rsc

Giffed by: rudescience  From: This video