#cell types

New Post has been published on https://thedigitalinsider.com/brain-pathways-that-control-dopamine-release-may-influence-motor-control/

Brain pathways that control dopamine release may influence motor control

Within the human brain, movement is coordinated by a brain region called the striatum, which sends instructions to motor neurons in the brain. Those instructions are conveyed by two pathways, one that initiates movement (“go”) and one that suppresses it (“no-go”).

In a new study, MIT researchers have discovered an additional two pathways that arise in the striatum and appear to modulate the effects of the go and no-go pathways. These newly discovered pathways connect to dopamine-producing neurons in the brain — one stimulates dopamine release and the other inhibits it.

By controlling the amount of dopamine in the brain via clusters of neurons known as striosomes, these pathways appear to modify the instructions given by the go and no-go pathways. They may be especially involved in influencing decisions that have a strong emotional component, the researchers say.

“Among all the regions of the striatum, the striosomes alone turned out to be able to project to the dopamine-containing neurons, which we think has something to do with motivation, mood, and controlling movement,” says Ann Graybiel, an MIT Institute Professor, a member of MIT’s McGovern Institute for Brain Research, and the senior author of the new study.

Iakovos Lazaridis, a research scientist at the McGovern Institute, is the lead author of the paper, which appears today in the journal Current Biology.

New pathways

Graybiel has spent much of her career studying the striatum, a structure located deep within the brain that is involved in learning and decision-making, as well as control of movement.

Within the striatum, neurons are arranged in a labyrinth-like structure that includes striosomes, which Graybiel discovered in the 1970s. The classical go and no-go pathways arise from neurons that surround the striosomes, which are known collectively as the matrix. The matrix cells that give rise to these pathways receive input from sensory processing regions such as the visual cortex and auditory cortex. Then, they send go or no-go commands to neurons in the motor cortex.

However, the function of the striosomes, which are not part of those pathways, remained unknown. For many years, researchers in Graybiel’s lab have been trying to solve that mystery.

Their previous work revealed that striosomes receive much of their input from parts of the brain that process emotion. Within striosomes, there are two major types of neurons, classified as D1 and D2. In a 2015 study, Graybiel found that one of these cell types, D1, sends input to the substantia nigra, which is the brain’s major dopamine-producing center.

It took much longer to trace the output of the other set, D2 neurons. In the new Current Biology study, the researchers discovered that those neurons also eventually project to the substantia nigra, but first they connect to a set of neurons in the globus palladus, which inhibits dopamine output. This pathway, an indirect connection to the substantia nigra, reduces the brain’s dopamine output and inhibits movement.

The researchers also confirmed their earlier finding that the pathway arising from D1 striosomes connects directly to the substantia nigra, stimulating dopamine release and initiating movement.

“In the striosomes, we’ve found what is probably a mimic of the classical go/no-go pathways,” Graybiel says. “They’re like classic motor go/no-go pathways, but they don’t go to the motor output neurons of the basal ganglia. Instead, they go to the dopamine cells, which are so important to movement and motivation.”

Emotional decisions

The findings suggest that the classical model of how the striatum controls movement needs to be modified to include the role of these newly identified pathways. The researchers now hope to test their hypothesis that input related to motivation and emotion, which enters the striosomes from the cortex and the limbic system, influences dopamine levels in a way that can encourage or discourage action.

That dopamine release may be especially relevant for actions that induce anxiety or stress. In their 2015 study, Graybiel’s lab found that striosomes play a key role in making decisions that provoke high levels of anxiety; in particular, those that are high risk but may also have a big payoff.

“Ann Graybiel and colleagues have earlier found that the striosome is concerned with inhibiting dopamine neurons. Now they show unexpectedly that another type of striosomal neuron exerts the opposite effect and can signal reward. The striosomes can thus both up- or down-regulate dopamine activity, a very important discovery. Clearly, the regulation of dopamine activity is critical in our everyday life with regard to both movements and mood, to which the striosomes contribute,” says Sten Grillner, a professor of neuroscience at the Karolinska Institute in Sweden, who was not involved in the research.

Another possibility the researchers plan to explore is whether striosomes and matrix cells are arranged in modules that affect motor control of specific parts of the body.

“The next step is trying to isolate some of these modules, and by simultaneously working with cells that belong to the same module, whether they are in the matrix or striosomes, try to pinpoint how the striosomes modulate the underlying function of each of these modules,” Lazaridis says.

They also hope to explore how the striosomal circuits, which project to the same region of the brain that is ravaged by Parkinson’s disease, may influence that disorder.

Some common cell types seen/looked for in histology.

Epithelial cells

Epithelial cells form tight cohesive sheets of cells which cover many of the body surfaces, such as the skin or the gut. 

form secretory glands, such as the breast, tear ducts, sweat glands and salivary glands. 

may be just a single cell thick, or may be several cells deep. 

Determines overall shape: cuboidal, columnar or stratified (flattened). 

Endothelial cells

These form a single layer that lines blood or lymphatic vessels.

Muscle cells

Muscle cells fall into three main types.

Striated muscle fibres form the voluntary muscles of the body, i.e. the ones that you can choose to move.

Smooth muscle is a contractile tissue which operates involuntarily. It is found in the gut and around blood vessels and many glands and ducts.

Cardiac muscle is a specialised muscle found only in the heart.

Nerve cells (neurons)

Neurons have long processes (axons) which extend away from the nerve body. They form both the:

central nervous system (CNS), namely the brain, spinal cord and retina of the eye

the peripheral nervous system, which describes any nervous tissue outside the CNS.

Nerves run through virtually all tissues of the body.

Adipose tissue (adipocytes)

This type of cell stores fat, and is found in many tissues, 

 large central vacuole where lipids (fats) are stored.

Leukocytes (white blood cells)

Leukocytes are found in all tissues of the body (not just the blood), where they carry out the function of immune defence.

Lymphoid tissues, such as lymph nodes, tonsils, adenoids and Peyer’s patches (a lymphoid tissue of the intestine), contain highly organised groupings of leukocytes that activate and coordinate the body’s immune response to infection.

Extracellular matrix proteins

Bone, tendons and connective tissues are mostly formed of extracellular matrix proteins.

New Post has been published on https://thedigitalinsider.com/how-jellyfish-regenerate-functional-tentacles-in-days-technology-org/

How jellyfish regenerate functional tentacles in days - Technology Org

At about the size of a pinkie nail, the jellyfish species Cladonema can regenerate an amputated tentacle in two to three days — but how? Regenerating functional tissue across species, including salamanders and insects, relies on forming a blastema, a clump of undifferentiated cells that can repair damage and grow into the missing appendage. Jellyfish and other cnidarians, such as corals and sea anemones, exhibit high regeneration abilities, but how they form the critical blastema has remained a mystery until now.

The emergent model jellyfish Cladonema The jellyfish Cladonema pacificum exhibits branched tentacles that can robustly regenerate after amputation. Image credit: Sosuke Fujita, The University of To

A research team based in Japan has revealed that stem-like proliferative cells — which are actively growing and dividing but not yet differentiating into specific cell types — appear at the site of injury and help form the blastema.

The findings were published in the scientific journal PLOS Biology.

“Importantly, these stem-like proliferative cells in blastema are different from the resident stem cells localized in the tentacle,” said corresponding author Yuichiro Nakajima, lecturer at the Graduate School of Pharmaceutical Sciences at the University of Tokyo. “Repair-specific proliferative cells mainly contribute to the epithelium — the thin outer layer — of the newly formed tentacle.”

The resident stem cells that exist in and near the tentacle are responsible for generating all cellular lineages during homeostasis and regeneration, meaning they maintain and repair whatever cells are needed during the jellyfish’s lifetime, according to Nakajima. Repair-specific proliferative cells only appear at the time of injury.

“Together, resident stem cells and repair-specific proliferative cells allow rapid regeneration of the functional tentacle within a few days,” Nakajima said, noting that jellyfish use their tentacles to hunt and feed.

According to first author Sosuke Fujita, a postdoctoral researcher in the same lab as Nakajima in the Graduate School of Pharmaceutical Sciences, this finding informs how researchers understand how blastema formation differs among different animal groups.

“In this study, our aim was to address the mechanism of blastema formation, using the tentacle of cnidarian jellyfish Cladonema as a regenerative model in non-bilaterians, or animals that do not form bilaterally — or left-right — during embryonic development,” Fujita said, explaining that the work may provide insight from an evolutionary perspective.

Two stem-like cell populations in the regenerating tentacle Resident stem cells (green) and repair-specific proliferative cells (red) contribute to tentacle regeneration in Cladonema. Image credit: Sosuke Fujita, The University of Tokyo

Salamanders, for example, are bilaterian animals capable of regenerating limbs. Their limbs contain stem cells restricted to specific cell-type needs, a process that appears to operate similarly to the repair-specific proliferative cells observed in the jellyfish.

“Given that repair-specific proliferative cells are analogues to the restricted stem cells in bilaterian salamander limbs, we can surmise that blastema formation by repair-specific proliferative cells is a common feature independently acquired for complex organ and appendage regeneration during animal evolution,” Fujita said.

The cellular origins of the repair-specific proliferative cells observed in the blastema remain unclear, though, and the researchers say the currently available tools to investigate the origins are too limited to elucidate the source of those cells or to identify other, different stem-like cells.

Regeneration of the jellyfish tentacle At 72 hours after amputation, the regenerating tentacle of Cladonema is fully functional. Image credit: Sosuke Fujita, The University of Tokyo

“It would be essential to introduce genetic tools that allow the tracing of specific cell lineages and the manipulation in Cladonema,” Nakajima said. “Ultimately, understanding blastema formation mechanisms in regenerative animals, including jellyfish, may help us identify cellular and molecular components that improve our own regenerative abilities.”

Source: University of Tokyo

Chief cells – responsible for intrinsic factor, pepsinogen (Dr. P also said lipase, but pretty sure lipase is mainly coming from the pancreas)

Goblet cells – responsible for mucus

미래에 오신 것을 환영합니다! 우리는 명왕성까지 닿을 수 있었습니다. 그리고 구글 룬(Loon)의 열기구가 스리랑카에 인터넷 서비스를 곧 제공하게 될 것입니다. 이제 여기, 게임 플레이어 여러분들은 새로운 종류(type)의 뉴런을 발견하고 있습니다.

아이와이어의 카운트다운 투 뉴로피아 기간 동안 발견된 뉴런. 파란색 가지 = 혈관

  아이와이어를 통해 가능하게 된 승 디텍터(The Seung Detector), 또는 프린스턴에서는 세포 박물관(The Cell Museum)으로 불리는 새 과학적 도구이자 시각적 플랫폼을 공개 알파 프로토타입으로 배포하게 됨을 기쁘게 알려드리게 되었습니다. museum.eyewire.org에서 탐험해보세요! 여러분이 무엇을 보고 있는지 아시려면 아래 설명을 참고하시면 됩니다.…