Cardiac MRI, is a medical imaging technology for the non-invasive assessment of the function and structure of the cardiovascular system. It is derived from and based on the same basic principles as magnetic resonance imaging (MRI) but with optimization for use in the cardiovascular system. These optimizations are principally in the use of ECG gating and rapid imaging techniques or sequences. By combining a variety of such techniques into protocols, key functional and morphological features of the cardiovascular system can be assessed.
MRI Scan of the Brain
Magnetic resonance imaging (MRI) techniques provide an extremely detailed, 3-D view of a living brain. The technique is critical for identifying abnormalities such as tumors, spotting the warning signs of some brain diseases, and revealing the extent of trauma from strokes.
Source: National Geographic
T cells counter HIV transmission using a surprisingly simple trick: they tie the virions to the cell membrane with an intermembrane protein, appropriately name “tetherin.” When a virion buds from the cell surface, one tetherin domain inserts into the new viral membrane, while another domain stays embedded in the cell’s plasma membrane, preventing the virus particle from diffusing away.
Image: False-colored image of HIV virus particles (yellow and purple) budding from a human T cell (blue) in cell culture. Ultrathin sections (80 nm) were stained with uranylacetate/lead citrate and then imaged with a TEM (Zeiss CEM 902) at 20,000x magnification on negative film (not digital). Learn more about tetherin in Perez-Caballero et al. (2010) and Hinz et al. (2010).
Cocaine blocks the reuptake of all of your neurotransmitters, but it has a certain love for the dopamine pathways in your brain. Since the nerve terminals in your brain can’t get rid of all of that neurotransmitter in the cleft, especially in the mesolimbic reward pathway, you feel euphoric. The other neurotransmitters that aren’t taken back up lead to the other symptoms: increased heart rate, energy levels, blood pressure, agitation, etc.
Magnetic resonance imaging (MRI) of the brain is a safe and painless procedure that uses a magnetic field and radio waves to produce detailed images of the brain and the brain stem. An MRI differs from a CAT scan (also called a CT scan or a computed axial tomography scan) because it does not use radiation.
An MRI scanner consists of a large doughnut-shaped magnet that often has a tunnel in the center. Patients are placed on a table that slides into the tunnel. (Some centers have open MRI machines that have larger openings and are helpful for patients with claustrophobia).
During the exam, radio waves manipulate the magnetic position of the atoms of the body, which are picked up by a powerful antenna and sent to a computer. The computer performs millions of calculations, resulting in clear, cross-sectional black and white images of the body. These images can be converted into three-dimensional (3-D) pictures of the scanned area. This helps pinpoint problems in the brain and the brain stem when the scan focuses on those areas. In some cases, MRI can provide clear images of parts of the brain that can’t be seen as well with an X-ray, CAT scan, or ultrasound, making it particularly valuable for diagnosing problems with the pituitary gland and brain stem.
MRI can detect a variety of conditions of the brain such as cysts, tumors, bleeding, swelling, developmental and structural abnormalities, infections, inflammatory conditions, or problems with the blood vessels. It can determine if a shunt is working and detect damage to the brain caused by an injury or a stroke.
Basilar Artery Aneurysm
A relatively frequent cause of subarachnoid hemorrhage is rupture of a saccular aneurysm. Most aneurysms occur at the bifurcation of large cerebral arteries. Over 90% of aneurysms occur in the circle of Willis and in the proximal middle cerebral artery. An aneurysm is caused by a focal weakening and thinning of the arterial wall. Rupture of an aneurysm can result in subarachnoid hemorrhage but it can also produce intracerebral hemorrhage and necrosis. Vasospasm and hydrocephalus (secondary to obstruction of arachnoid granulations) may be consequences of aneurysmal rupture. Rarely an unruptured aneurysm will reach a size capable of producing a mass effect on the brain.
As a young neurosurgery resident at UCSF in the late ’90s, Dr. Charles Cobbs developed a hunch about brain tumors. It was a theory that he now concedes “was not based on a lot of scientific things.”
Cobbs had observed that his patients diagnosed with malignant glioma - an aggressive brain cancer that leaves victims with a two-year life expectancy - were mostly older, well-educated and from higher socioeconomic backgrounds.
Their “hyper-hygienic” lifestyles had possibly left their immune systems susceptible to more common viruses, such as the human cytomegalovirus, or CMV, a herpes virus so ubiquitous that it infects 4 of 5 Americans.
During off-hours, and without formal research funding, Cobbs and a lab partner analyzed dozens of brain tumor samples: All of them were riddled with CMV.
In 2002, the doctor published his novel finding in a leading medical journal Cancer Research where it was quickly dismissed by many of his peers.
"I was left with a lot of self doubt," said Cobbs, now 45. "My fear was that we’d done something incorrect. But now, my confidence is growing."
In February, brain cancer researchers at Duke University Medical Center published the first peer-reviewed report that confirmed Cobbs’ discovery, followed by two reports from independent labs at the M.D. Anderson Cancer Center at University of Texas in Houston and the Karolinska Institute in Stockholm, Sweden. And this month, the National Brain Tumor Society is sponsoring a first-of-its-kind gathering in Boston of the world’s top virologists and glioma experts to examine the possible link between CMV and the deadly brain tumors that are diagnosed in 10,000 Americans every year.
"His discovery opens the door and has broad implications in this field," said Dr. Duane Mitchell, a Duke University Medical Center researcher who is conducting vaccine trials based on Cobb’s findings. “And the door has just been opened.”
A blueprint for restoring touch with a prosthetic hand
New research at the University of Chicago is laying the groundwork for touch-sensitive prosthetic limbs that one day could convey real-time sensory information to amputees via a direct interface with the brain.
he research, published early online in theProceedings of the National Academy of Sciences, marks an important step toward new technology that, if implemented successfully, would increase the dexterity and clinical viability of robotic prosthetic limbs.
"To restore sensory motor function of an arm, you not only have to replace the motor signals that the brain sends to the arm to move it around, but you also have to replace the sensory signals that the arm sends back to the brain," said the study’s senior author, Sliman Bensmaia, PhD, assistant professor in the Department of Organismal Biology and Anatomy at the University of Chicago. "We think the key is to invoke what we know about how the brain of the intact organism processes sensory information, and then try to reproduce these patterns of neural activity through stimulation of the brain.”
Bensmaia’s research is part of Revolutionizing Prosthetics, a multi-year Defense Advanced Research Projects Agency (DARPA) project that seeks to create a modular, artificial upper limb that will restore natural motor control and sensation in amputees. Managed by the Johns Hopkins University Applied Physics Laboratory, the project has brought together an interdisciplinary team of experts from academic institutions, government agencies and private companies.
Bensmaia and his colleagues at the University of Chicago are working specifically on the sensory aspects of these limbs. In a series of experiments with monkeys, whose sensory systems closely resemble those of humans, they indentified patterns of neural activity that occur during natural object manipulation and then successfully induced these patterns through artificial means.
The first set of experiments focused on contact location, or sensing where the skin has been touched. The animals were trained to identify several patterns of physical contact with their fingers. Researchers then connected electrodes to areas of the brain corresponding to each finger and replaced physical touches with electrical stimuli delivered to the appropriate areas of the brain. The result: The animals responded the same way to artificial stimulation as they did to physical contact.
Next the researchers focused on the sensation of pressure. In this case, they developed an algorithm to generate the appropriate amount of electrical current to elicit a sensation of pressure. Again, the animals’ response was the same whether the stimuli were felt through their fingers or through artificial means.
Finally, Bensmaia and his colleagues studied the sensation of contact events. When the hand first touches or releases an object, it produces a burst of activity in the brain. Again, the researchers established that these bursts of brain activity can be mimicked through electrical stimulation.
The result of these experiments is a set of instructions that can be incorporated into a robotic prosthetic arm to provide sensory feedback to the brain through a neural interface. Bensmaia believes such feedback will bring these devices closer to being tested in human clinical trials.
"The algorithms to decipher motor signals have come quite a long way, where you can now control arms with seven degrees of freedom. It’s very sophisticated. But I think there’s a strong argument to be made that they will not be clinically viable until the sensory feedback is incorporated,” Bensmaia said. “When it is, the functionality of these limbs will increase substantially.”
The Defense Advanced Research Projects Agency, National Science Foundation and National Institutes of Health funded this study. Additional authors include Gregg Tabot, John Dammann, Joshua Berg and Jessica Boback from the University of Chicago; and Francesco Tenore and R. Jacob Vogelstein from the Johns Hopkins University Applied Physics Laboratory.
Human serum albumin is the most abundant protein in human blood plasma. Albumin constitutes about half of the blood serum protein, and transports hormones, fatty acids, and other compounds, buffers pH, and maintains osmotic pressure, among other functions.
Albumin is synthesized in the liver as preproalbumin, which has an N-terminal peptide that is removed before the nascent protein is released from the rough endoplasmic reticulum. The product, proalbumin, is in turn cleaved in the Golgi vesicles to produce the secreted albumin.
The reference range for albumin concentrations in serum is approximately 35 - 50 g/L (3.5 - 5.0 g/dL), and it has a serum half-life of approximately 20 days.
It may look like a burnt log, but it’s actually one of the oldest-known human brains, preserved for 4,000 years after being “scorched and boiled in its own juices.”
“The level of preservation in combination with the age is remarkable,” Frank Rühli at the University of Zurich, Switzerland told New Scientist, adding that most archaeologists simply don’t even look for brain matter. “”If you publish cases like this, people will be more and more aware that they could find original brain tissue too.”
The brain was found in Seyitömer Höyük, a bronze-age settlement in Turkey, yet analysis of the brain showed that the man had actually died in the mountains. (Photo: Journal of Comparative Human Biology)
A service that digitally weaves together the DNA of prospective parents to check for potential disease in thousands of “virtual babies” is set to launch in the US by December.
New York start-up Genepeeks will initially focus on donor sperm, simulating before pregnancy how the genetic sequence of a female client might combine with those of different males. Donors that more often produce “digital children” with a higher risk of inherited disorders will be filtered out, leaving those who are better genetic matches.
Everything happens in a computer, but experts have raised ethical questions.
"We are just in the business right now of giving prospective mothers, who are using donor sperm to conceive, a filtered catalogue of donors based on their own underlying genetic profile. We are filtering out the donor matches with an elevated risk of rare recessive paediatric conditions" Genepeeks co-founder Anne Morriss told BBC News.
She was motivated in part by her own experience of starting a family. Her son was conceived with a sperm donor who happened to share with Morriss the gene for an inherited disorder called MCADD. MCADD (medium-chain acyl-CoA dehydrogenase deficiency) prevents those affected from converting fats to sugar. It can be fatal if it is not diagnosed early. Luckily, in Ms Morriss’s case, the condition was picked up in newborn screening tests.
"My son has a pretty normal life" Ms Morriss said, "but about 30% of children with rare genetic diseases don’t make it past the age of five."
Genepeeks has formalised a partnership with a sperm bank - the Manhattan Cryobank - and has a patent pending on the DNA screening technology. The start-up benefits from the rapid pace of change in genetic technology. Indeed, six months ago, Genepeeks’ founders decided it was able to use a superior system for DNA analysis (called “targeted exon sequencing”) than the one originally envisaged - a result, says Anne Morriss, of falling costs and increased flexibility.
For couples planning babies, other companies already screen one or both partners for genes that could cause disease if combined with a similar variant - so-called “carrier screening”.
One academic who studies the use of genetic technology commented: “This is like that, but ramped up 100,000 times.”
Ms Morriss’s business partner, Prof Lee Silver, a geneticist and expert on bioethics at Princeton University, New Jersey, told BBC News: “We get the DNA sequence from two prospective parents. We simulate the process of reproduction, forming virtual sperm and virtual eggs. We put them together to form a hypothetical child genome. Then we can look at that hypothetical genome and - with all the tools of modern genetics - determine the risk that the genome will result in a child with disease. We’re looking directly for disease and not carrier status. For each pair of people that we’re going to analyse, we make 10,000 hypothetical children.”
The process will be run for the client and each potential donor one by one, scanning for some 600 known single-gene recessive conditions. In this way, the highest-risk pairings can be filtered out.
Anne Morriss added: “At this stage our clients won’t be receiving any genetic information back. We’re very much focused on the practical utility of helping prospective parents who want to protect their future kids, giving them the option of additional analysis to what is currently being offered in the industry.”
But the company’s founders have plans to expand the screening beyond single-gene recessive disorders to more complex conditions in which multiple genes play a part. Indeed, going to the trouble of simulating thousands of digital children deliberately lays the ground for this: “[It’s] impossible to get towards an accurate risk calculation in any other way” said Anne Morriss.
And in a video produced by the company, Prof Silver says: “My hope for the future is that any people who want to have a baby can use this technology to greatly reduce the risk of disease being expressed in their child.”
To some, such a prospect might appear like a step towards designer babies - until now the preserve of science fiction literature and films such as Gattaca, which envisaged a future of genetic “haves” and “have-nots”.
Bio-ethicists approached by the BBC said Genepeeks was a logical outcome of the increasing demand for more information when making reproductive decisions. However, some raised potential concerns about risk communication and the expansion of screening beyond rare single-gene disorders. But they suggested there were few, if any, regulatory barriers.
One ethicist told BBC News: “The biggest question for me, just from the outset, is the understanding of uncertainty. Even people who have been doing genomics for years still have a hard time figuring out exactly what a risk for a particular genetic predisposition really means for a family. Gene-environment interactions can lead to people either having disease or not having disease.”
Dr Ewan Birney, associate director of the European Bioinformatics Institute in Hinxton, UK, echoed the point: “It’s good that they’re focusing on the carrier status of these rare Mendelian disorders where it’s potentially more clear-cut. That said, these things are more complex than they first seem. I’m sure the scientists appreciate that complexity. But when transmitting that complexity to everyday people, these things can sound more absolute than they really are. The thing I would want to stress here is just how complex this is. It’s great that people are thinking of using this technology in lots of different ways, but our knowledge gap is very large.”
Risk communication to clients was, said Anne Morriss, “absolutely critical to anyone in this industry”. ”We have to be crystal clear about what we’re testing for, what risks we’re helping to reduce; that there’s no guarantee you won’t give birth to a sick child” she said.
Prof Mildred Cho, associate director of the Stanford Center for Biomedical Ethics in California, raised questions over whether the sperm donor should also receive information about their genome gleaned from the screening process. ”Unlike hair colour, occupation or family history - those are things the donor already knows - the thing that’s different about this that I see is it could create information that the donor doesn’t already have. It also has implications for the donor’s other biological family members.”
This week it also emerged that California-based consumer genetics company 23andMe had submitted the patent on a DNA analysis tool for planning a child.