How MRI Scanner Works

The MRI Scanner

Magnetic Resonance Imaging (MRI) takes advantage of the fact that the nucleus of a hydrogen atom (a single proton) behaves like a weak compass needle. In the presence of a strong magnetic field, the hydrogen atoms will align themselves, but a radio signal of the correct resonant frequency will cause them to deflect slightly. When the signal is removed, the atoms return to their equilibrium state and emit a radio signal of their own. An MRI scanner can detect these signals and use them to map the distribution of molecules with lots of hydrogen atoms – ie, water and fat. In this way, it can create detailed images of the inside of the body.

A. Scanning table

The patient can only be scanned from inside the magnetic coil, so a motorised table slides them in and out.

B. RF system

An antenna produces a radio signal to ‘nudge’ the hydrogen nuclei and listento the answering radio wave they emit.

C. Liquid helium

Liquid helium is pumped through an enclosing jacket to cool the superconducting magnets almost to absolute zero.

D. Main magnet

Superconducting magnetic coils produce a magnetic field of 1.5 teslas – that’s about 300times stronger than a fridge magnet.

E. Patient

The high magnetic fields mean that patients with cochlear implants, pacemakers or embedded shrapnel usually can’t be scanned.

F. Gradient system

A second coil distorts the main magnetic field so that the resonant frequency of the protons varies according to position.

HOW GUT BACTERIA COULD EFFECT BRAIN AND BODY

Research published in the open access journal Microbiome sheds new light on how gut bacteria may influence anxiety-like behaviors. Investigating the link between gut bacteria and biological molecules called microRNAs (miRNAs) in the brain; researchers at the APC Microbiome Institute at University College Cork, which is funded by Science Foundation Ireland, found that a significant number of miRNAs were changed in the brains of microbe-free mice. These mice are reared in a germ-free bubble and typically display abnormal anxiety, deficits in sociability and cognition, and increased depressive-like behaviors.

Dr Gerard Clarke, the corresponding author said: “Gut microbes seem to influence miRNAs in the amygdala and the prefrontal cortex. This is important because these miRNAs may affect physiological processes that are fundamental to the functioning of the central nervous system and in brain regions, such as the amygdala and prefrontal cortex, which are heavily implicated in anxiety and depression.”

miRNAs are short sequences of nucleotides (the building blocks of DNA and RNA), which can act to control how genes are expressed. miRNA dysregulation or dysfunction is believed to be an underlying factor contributing to stress-related psychiatric disorders, neurodegenerative diseases and neurodevelopmental abnormalities. miRNA changes in the brain have been implicated in anxiety-like behaviors.

Dr Clarke said: “It may be possible to modulate miRNAs in the brain for the treatment of psychiatric disorders but research in this area has faced several challenges, for example, finding safe and biologically stable compounds that are able to cross the blood-brain barrier and then act at the desired location in the brain. Our study suggests that some of the hurdles that stand in the way of exploiting the therapeutic potential of miRNAs could be cleared by instead targeting the gut microbiome.”

The researchers found that levels of 103 miRNAs were different in the amygdala and 31 in the prefrontal cortex of mice reared without gut bacteria (GF mice) compared to conventional mice. Adding back the gut microbiome later in life normalized some of the changes to miRNAs in the brain.

The findings suggest that a healthy microbiome is necessary for appropriate regulation of miRNAs in these brain regions. Previous research demonstrated that manipulation of the gut microbiome affects anxiety-like behaviors but this is the first time that the gut microbiome has been linked to miRNAs in both the amygdala and prefrontal cortex, according to the authors.

The researchers used next-generation-sequencing (NGS) to find out which miRNAs were present in the amygdala and the prefrontal cortex of groups of 10-12 control mice with a normal gut microbiota, GF mice and ex-GF mice – which had been colonized with bacteria by housing them with the control mice – and adult rats whose normal microbiota had been depleted with antibiotics.

They found that depleting the microbiota of adult rats with antibiotics impacted some miRNAs in the brain in a similar way to the GF mice. This suggests that even if a healthy microbiota is present in early life, subsequent changes in adulthood can impact miRNAs in the brain relevant to anxiety-like behaviors, according to the authors.

The authors note that the exact mechanism by which the gut microbiota is able to influence the miRNAs in the brain remains unclear. Even though the study shows that effects of the microbiota on miRNAs are present in more than one species (mice and rats), further research into the possible.connection between gut bacteria, miRNAs and anxiety-like behaviors is needed before the findings can be translated to a clinical setting.

Dr Clarke said: “This is early stage research but the possibility of achieving the desired impact on miRNAs in specific brain regions by targeting the gut microbiota – for example by using psychobiotics – is an appealing prospect.”

Source:
https://www.biomedcentral.com/about/press-centre/science-press-releases/25-08-17

Journal article:
https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-017-0321-3

#infopraphic via The Huffington Post

#gutbacteria #miRNAs #gutmicrobiota #anxiety #prefrontalcortex #amygdala #neuroscience

A Rapid Eye Movement Test That Could Help Diagnose Autism Disorders

Neuroscientists at the University of Rochester have masterminded a rapid eye movement test that can detect abnormalities in the cerebellum (Latin for "little brain") that also appear to be a marker for certain autism spectrum disorders (ASD).

Their paper, "Eye Movements, Sensorimotor Adaptation and Cerebellar-Dependent Learning in Autism: Toward Potential Biomarkers and Subphenotypes," was published online July 12, 2017 in the European Journal of Neuroscience. >>
http://onlinelibrary.wiley.com/doi/10.1111/ejn.13625/full

In a series of experiments, the authors of this study had individuals with and without ASD track a visual target as it zoomed around to different locations on a screen. As participants' eyes darted across the screen chasing a target, the researchers were tracking their rapid eye movements (also known as "saccades"). Saccades are the synchronized rapid movements both eyes make as your gaze and attention quickly shifts from one point of focus to another.

“These finding suggest that assessing the ability of people to adapt saccade amplitudes is one way to determine whether this function of the cerebellum is altered in ASD,” said Edward Freedman, Ph.D. an associate professor in the URMC Department of Neuroscience and co-author of the study.
“If these deficits do turn out to be a consistent finding in a sub-group of children with ASD, this raises the possibility that saccade adaptation measures may have utility as a method that will allow early detection of this disorder.”

► Learn more>> https://www.urmc.rochester.edu/news/story/5102/eye-test-could-help-diagnose-autism.aspx

► Image credit: 8thstar/CC 3.0>> https://commons.wikimedia.org/wiki/Human_eye#/media/File:A_blue_eye.jpg

Quantum Chemistry Solves The Question of Why Life Needs So Many Amino Acids

Quantum Chemistry Solves The Question of Why Life Needs So Many Amino Acids

A flexible approach to life.

DAVID NIELD

3 FEB 2018

One of the oldest and most fundamental questions in biochemistry is why the 20 amino acids that support life are all needed, when the original core of 13 would do – and quantum chemistry might have just provided us with the answer.

According to new research, it's the extra chemical reactivity of the newer seven amino acids that make them so vital to life, even though they don't add anything different in terms of their spatial structure.

Quantum chemistry is a way of taking some of the principles of quantum mechanics – describing particles according to probabilistic, wave-like properties – and applying them to the way atoms behave in chemical reactions.

The international team of scientists behind the new study used quantum chemistry techniques to compare amino acids found in space (and left here by meteorite fragments) with amino acids supporting life today on Earth.

"The transition from the dead chemistry out there in space to our own biochemistry here today was marked by an increase in softness and thus an enhanced reactivity of the building blocks," says one of the researchers, Bernd Moosmann from Johannes Gutenberg University Mainz in Germany.

It's the job of amino acids to form proteins, as instructed by our DNA. These acids were formed right after Earth itself came into being, about 4.54 billion years ago, and so represent one of the earliest building blocks of life.

However, why evolution decided that we needed 20 amino acids to handle this genetic encoding has never been clear, because the first 13 that developed should have been enough for the task.

The greater "softness" of the extra seven amino acids identified by the researchers means they are more readily reactive and more flexible in terms of chemical changes.

If you were representing the amino acids as circles, they could be drawn as multiple concentric circles representing differing energy levels, rather than one single circle of the same chemical hardness and energy level – kind of like in the photo below.

                                                                                                       (Michael Plenikowski)

                                                              

Having determined the hypothesis through quantum chemistry calculations, the scientists were able to back up their ideas with a series of biochemical experiments.

Along the way the team determined that the extra amino acids – particularly methionine, tryptophan, and selenocysteine – could well have evolved as a response to increasing levels of oxygen in the biosphere in the planet's youngest days.

Peering so far back in time is difficult, as the first organic compounds never left fossils behind for us to analyse, but this may have been part of the process that kicked off the formation of life on Earth.

As the very earliest living cells tried to deal with the extra oxidative stress, it was a case of survival of the fittest. The cells best able to cope with that additional oxygen – through the protection of the new amino acids – were the ones that lived on and flourished.

"With this in view, we could characterise oxygen as the author adding the very final touch to the genetic code," says Moosmann.

The research has been published in PNAS.

                                                     --by Sciencealert.com

 Increased brain acidity in psychiatric disorders

Your body’s acid/alkaline homeostasis, or maintenance of an adequate pH balance in tissues and organs, is important for good health. An imbalance in pH, particularly a shift toward acidity, is associated with various clinical conditions, such as a decreased cardiovascular output, respiratory distress, and renal failure. But is pH also associated with psychiatric disorders?

Researchers at the Institute for Comprehensive Medical Science at Fujita Health University in Japan, along with colleagues from eight other institutions, have identified decreased pH levels in the brains of five different mouse models of mental disorders, including models of schizophrenia, bipolar disorder, and autism spectrum disorder. This decrease in pH likely reflects an underlying pathophysiology in the brain associated with these mental disorders, according to the study published August 4th in the journal Neuropsychopharmacology.

While post-mortem studies have shown that the brains of patients with the abovementioned mental disorders tend to have a lower pH than those of controls, this phenomenon has been considered to be the result of secondary factors associated with the diseases rather than a primary feature of the diseases themselves. Secondary factors that confound the observation of a decreased brain pH level include antipsychotic treatments and agonal experiences associated with these disorders.

Dr. Miyakawa and his colleagues performed a meta-analysis of existing datasets from ten studies to investigate the pH level of postmortem brains from patients with schizophrenia and bipolar disorder. They observed that patients with schizophrenia and bipolar disorder exhibited significantly lower brain pH levels than control participants, even when potential confounding factors were considered (i.e., postmortem interval, age at death, and history of antipsychotic use). “These factors may not be major factors causing a decrease in pH in the postmortem brains of patients with schizophrenia and bipolar disorder,” Miyakawa explains.

The researchers then conducted a systematic investigation of brain pH using five mouse models of psychiatric disorders, including models for schizophrenia, bipolar disorder, and autism spectrum disorders. All of the mice used in the study were drug-naive, with equivalent agonal states, postmortem intervals, and ages within each strain. The analyses revealed that in all five mouse models, brain pH was significantly lower than that in the corresponding controls. In addition, the levels of lactate were also elevated in the brains of the model mice, and a significant negative correlation was found between brain pH and lactate levels. The increase in lactate may explain the decreased brain pH levels, as lactate is known to act as a strong acid.

Miyakawa suggests that, “while it is technically impossible to completely exclude confounding factors in human studies, our findings in mouse models strongly support the notion that decreased pH associated with increased lactate levels reflects an underlying pathophysiology, rather than a mere artifact, in at least a subgroup of patients with these mental disorders.”

Changes in the brain pH level have been considered an artifact, therefore substantial effort has been made to match the tissue pH among study participants and to control the effect of pH on molecular changes in the postmortem brain. However, given that decreased brain pH is a pathophysiological trait of psychiatric disorders, these efforts could have unwittingly obscured the specific pathophysiological signatures that are potentially associated with changes in pH, such as neuronal hyper-excitation and inflammation, both of which have been implicated in the etiology of psychiatric disorders. Therefore, the present study highlighting that decreased brain pH is a shared endophenotype of psychiatric disorders has significant implications on the entire field of studies on the pathophysiology of mental disorders.

This research raises new questions about changes in brain pH. For example, what are the mechanisms through which lactate is increased and pH is decreased? Are specific brain regions responsible for the decrease in pH? Is there functional significance to the decrease in brain pH observed in psychiatric disorders, and if so, is it a cause or result of the onset of the disorder? Further studies are needed to address these issues.

Source:
https://www.eurekalert.org/pub_releases/2017-08/fhu-iba080717.php

Journal article:
https://www.nature.com/articles/npp2017167

#psychiatricdisorders #phbalance #schizophrenia #bipolardisorder

SENSATIONAL CELLS

THE HUMAN CELL ATLAS IS INITIALLY

FOCUSED ON FIVE TYPES OF CELL…

BRAIN

The brain is probably the most complex organ in                   
the body, made up of more than 86 billion nerve                     
cells (neurons). By mapping all the patterns of                       
gene activity in different brain cells, researchers                     
hope to understand how neurons wire up and                         
communicate, and what goes wrong in psychiatric                 
and neuro degenerative illnesses.                                             

IMMUNE SYSTEM

There are hundreds of types of cell in the immune
system alone, each with distinct roles in spotting
and responding to infections or disease. Analysing
each cell type will reveal the changes that happen
as the immune system fires into action, and will
shed light on autoimmune conditions and
allergies.

EPITHELIAL CELLS

Epithelial cells are one of the most versatile cell

types. They make the linings of our organs,
ranging from the tubes of the gut to the delicate air
sacs of the lungs. Establishing how epithelial cells
carry out such a diverse range of roles will explain
how organs grow and are affected by diseases
such as cancer

PLACENTA AND FOETUS

Studying these tissues will reveal how we grow

and develop in the womb, and how a healthy
placenta develops to provide oxygen and
nutrients. This will give us vital clues for
understanding what has gone wrong in babies
who are born with developmental disorders, or
when a pregnancy ends in miscarriage or stillbirth.

CANCER

By analysing gene activity in single cancer cells,
researchers hope to identify the changes that
trigger the growth and spread of tumours. They
are also searching for clues to explain how these
rogue cells can develop resistance to therapy, with
the aim of finding ways to prevent the disease
coming back again after treatment.

What Happens when We Vomit:

Why hummingbirds are so big-hearted

BIRDS fly better if they have big hearts. The best flyers, like hovering hummingbirds, have the largest. When a hummingbird hovers, it beats its wings in a figure-of-eight pattern up to 80 times per second, much like a helicopter. This is energetically costly, says Roberto Nespolo at the Austral University of Chile. But most birds don’t fly this way. Some flap their wings up and down, like geese. Others, like eagles, soar on updraughts of hot air, while some ground-dwellers, like pheasants, undergo only short bouts of flapping.
In theory, birds using more costly forms of flying should have larger hearts. The bigger the heart, the more blood a bird can pump to its flight muscles. To find out, Nespolo and his team grouped 915 bird species by flight type and compared their hearts. Hummingbirds had the biggest hearts for their body size, at 3 per cent of their mass. In contrast, a pelican’s heart is just 0.8 per cent of its mass. The sizes of birds’ hearts matched their flight mode. The optimal size for hovering was 2.43 times that for flapping and 3 times higher than gliding (Journal of Experimental Biology, DOI:10.1242/jeb.162693). It is surprising that flapping fliers had similar hearts to gliders, says Rebecca Kimball at the University of Florida. “I would have assumed that flapping flight would have required a lot more energy.”

-----NEW SCIENTIST DECEMBER 2018

COULD JUPITER BECOME A STAR?

Jupiter is often called a ‘failed star’ because, although it is mostly hydrogen like most normal stars, it is not massive enough to commence thermonuclear reactions in its core and thus become a ‘real star’. But the term ‘failed star’ is a bit of a misnomer. Theoretically, any object at all could be made into a star, simply by adding enough matter to it. With enough mass, the internal pressure and temperature of the object will reach the threshold needed to start thermonuclear reactions. That threshold is the least for the simplest element, hydrogen. In order to turn Jupiter into a star like the Sun, for example, you would have to add about 1,000 times the mass of Jupiter. But, to make a cooler ‘red dwarf’, you would only need to add about 80 Jupiter masses. Although the exact numbers are still a bit uncertain, it is possible that a ‘brown dwarf’ could still form (in which deuterium, rather than hydrogen, fuses in the star’s core) with only about 13 Jupiter masses. So, Jupiter cannot and will not spontaneously become a star, but, if a minimum of 13 extra Jupiter-mass objects happen to collide with

it, there is a chance it will.