Dripping Dendrites

While all cells in the body hold the same genome, only a particular set of its genes get turned on in various cells; each type of neuron switches on a gene set that defines its character.

In this picture, a gene called JAM-B had been switched on, which then turned on a fluorescent protein to reveal a small group of brain cells. The resulting image shows that all of the neurons’ projections called dendrites are aligned in the same direction; moreover, these retinal neurons are known to detect only objects moving in an upward direction.

Pictured above is the cross-section of the hippocampus of a mouse. This photograph brilliantly displays the inner workings of the neurons in our brain’s memory center, as the somas of each individual neuron can be seen as small circles scattered throughout. The hippocampus is visible directly below the outer layer of the cerebral hemispheres, otherwise known as the neocortex.

A scanning electron microscope (SEM) image zooms in on the baroque branching structures that send blood to the human brain’s cortex. The vessels are organized such that the large blood vessels surround the surface of the brain (top of image), sending thin, dense projections down into the depths of the cortex (bottom of image).

This 1875 drawing showing a dog’s olfactory bulb was completed using a staining method named after Camillo Golgi in which certain chemicals are injected into nervous tissue so they can be seen. Some say its application to the study of brain tissue represents the beginning of modern neuroscience.

Dead Sea Microbe’s Fluorescent Protein Sheds Light on Brain Activity

A fluorescent protein derived from a Dead Sea microbe could be a novel way to track electrical signals in the brain, researchers say. It’s noninvasive and nontoxic, so it could enable neuron tracking without harming the neurons.

Neurons communicate via chemical and electrical signals, and monitoring these channels could help neuroscientists understand brain function and degenerative diseases. But tracking electrical impulses is tricky. Molecular tags can be slow and even toxic to cells, which must be exposed to light for the fluorescence to work. And piercing a neuron with an electrode will damage and kill them. But a new fluorescent protein appears to track these synaptic action potentials without toxic side effects. It is derived from the Dead Sea bacteria Halorubrum sodomense.

The protein was previously used to dampen overly active neurons, but in a new study, researchers at Harvard used it as a super-fast voltage sensor, reports Technology Review. A team led by biophysicist Adam Cohen used archaerhodopsin-3, or Arch, as an electrical sensor. They determined that an electrical potential could change the protein’s color, which could then be detected, serving as an electricity monitor.

The team used a virus to add the Arch protein into rat hippocampal neurons in a petri dish. Using laser light (and watching through a CCD), the researchers were able to map neuronal activities at sub-millisecond time scales, they write.

It worked faster and with a better resolution than sodium-ion monitoring, as well as other fluorescent compounds like jellyfish protein, they added. Next, they plan to use Arch to measure neuronal activity in live animals, starting with zebrafish and the worm C. elegans, Tech Review says.

“Microbial rhodopsin [protein]–based voltage indicators promise to enable optical interrogation of complex neural circuits and electrophysiology in systems for which electrode-based techniques are challenging,” the authors say.

Cilia On Brain Cells Linked to Obesity

Tiny hairy projections on brain cells may play a big role in obesity and appetite regulation, new research suggests.

These structures, called cilia, are present on almost every cell of the body. New research shows that the cilia on appetite-regulating brain cells ultimately control whether our bodies get the signal. When defective, the teensy hair-like structures don’t seem to alert the body it’s eaten enough, leading to overeating and obesity.

“Obesity is a growing problem on the rise in the country, and we’ve found … that problems with the small cell appendage called the cilia can lead to overeating,” study researcher Nicolas Berbari, of the University of Alabama at Birmingham, told LiveScience.

The cilia on our neurons (also called primary cilia) are one of two cilia types, the other being the more well known motile cilia.

“Very little has been known about what the neuronal cilia are actually doing,” said study researcher Bradley Yoder, of the University of Alabama at Birmingham. “Most neurobiologists aren’t even aware that there are cilia on neurons.”

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evanthehawk:

The human brain has a huge number of synapses. Each of the 10¹¹ (one hundred billion) neurons has on average 7,000 synaptic connections to other neurons. It has been estimated that the brain of a three-year-old child has about 10¹⁵ synapses (1 quadrillion). This number declines with age, stabilizing by adulthood. Estimates vary for an adult, ranging from 10¹⁴ to 5 x 10¹⁴ synapses (100 to 500 trillion).^[11]