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Study Finds No Benefit for Dietary Supplements

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Eating healthy
Credit: iStock/Artfully79

More than half of U.S. adults take dietary supplements [1]. I don’t, but some of my family members do. But does popping all of these vitamins, minerals, and other substances really lead to a longer, healthier life? A new nationwide study suggests it doesn’t.

Based on an analysis of survey data gathered from more than 27,000 people over a six-year period, the NIH-funded study found that individuals who reported taking dietary supplements had about the same risk of dying as those who got their nutrients through food. What’s more, the mortality benefits associated with adequate intake of vitamin A, vitamin K, magnesium, zinc, and copper were limited to food consumption.

The study, published in the Annals of Internal Medicine, also uncovered some evidence suggesting that certain supplements might even be harmful to health when taken in excess [2]. For instance, people who took more than 1,000 milligrams of supplemental calcium per day were more likely to die of cancer than those who didn’t.

The researchers, led by Fang Fang Zhang, Tufts University, Boston, were intrigued that so many people take dietary supplements, despite questions about their health benefits. While the overall evidence had suggested no benefits or harms, results of a limited number of studies had suggested that high doses of certain supplements could be harmful in some cases.

To take a broader look, Zhang’s team took advantage of survey data from tens of thousands of U.S. adults, age 20 or older, who had participated in six annual cycles of the National Health and Nutrition Examination Survey (NHANES) between 1999-2000 and 2009-2010. NHANES participants were asked whether they’d used any dietary supplements in the previous 30 days. Those who answered yes were then asked to provide further details on the specific product(s) and how long and often they’d taken them.

Just over half of participants reported use of dietary supplements in the previous 30 days. Nearly 40 percent reported use of multivitamins containing three or more vitamins.

Nutrient intake from foods was also assessed. Each year, the study’s participants were asked to recall what they’d eaten over the last 24 hours. The researchers then used that information to calculate participants’ nutrient intake from food. Those calculations indicated that more than half of the study’s participants had inadequate intake of vitamins D, E, and K, as well as choline and potassium.

Over the course of the study, more than 3,600 of the study’s participants died. Those deaths included 945 attributed to cardiovascular disease and 805 attributed to cancer. The next step was to look for any association between the nutrient intake and the mortality data.

The researchers found the use of dietary supplements had no influence on mortality. People with adequate intake of vitamin A, vitamin K, magnesium, zinc, and copper were less likely to die. However, that relationship only held for nutrient intake from food consumption.

People who reported taking more than 1,000 milligrams of calcium per day were more likely to die of cancer. There was also evidence that people who took supplemental vitamin D at a dose exceeding 10 micrograms (400 IU) per day without a vitamin D deficiency were more likely to die from cancer.

It’s worth noting that the researchers did initially see an association between the use of dietary supplements and a lower risk of death due to all causes. However, those associations vanished when they accounted for other potentially confounding factors.

For example, study participants who reported taking dietary supplements generally had a higher level of education and income. They also tended to enjoy a healthier lifestyle. They ate more nutritious food, were less likely to smoke or drink alcohol, and exercised more. So, it appears that people who take dietary supplements are likely to live a longer and healthier life for reasons that are unrelated to their supplement use.

While the study has some limitations, including the difficulty in distinguishing association from causation, and a reliance on self-reported data, its findings suggest that the regular use of dietary supplements should not be recommended for the general U.S. population. Of course, this doesn’t rule out the possibility that certain subgroups of people, including perhaps those following certain special diets or with known nutritional deficiencies, may benefit.

These findings serve up a reminder that dietary supplements are no substitute for other evidence-based approaches to health maintenance and eating nutritious food. Right now, the best way to live a long and healthy life is to follow the good advice offered by the rigorous and highly objective reviews provided by the U.S. Preventive Services Task Force [3]. Those tend to align with what I hope your parents offered: eat a balanced diet, including plenty of fruits, veggies, and healthy sources of calcium and protein. Don’t smoke. Use alcohol in moderation. Avoid recreational drugs. Get plenty of exercise.

References:

[1] Trends in Dietary Supplement Use Among US Adults From 1999-2012. Kantor ED, Rehm CD, Du M, White E, Giovannucci EL. JAMA. 2016 Oct 11;316(14):1464-1474.

[2] Association among dietary supplement use, nutrient intake, and mortality among U.S. adults. Chen F, Du M, Blumberg JB, Ho Chui KK, Ruan M, Rogers G, Shan Z, Zeng L, Zhang. Ann Intern Med. 2019 Apr 9. [Epub ahead of print].

[3] Vitamin Supplementation to Prevent Cancer and CVD: Preventive Medication. U.S. Preventive Services Task Force, February 2014.

Links:

Office of Dietary Supplements (NIH)

Healthy Eating Plan (National Heart, Lung, and Blood Institute/NIH)

National Health and Nutrition Examination Survey (Centers for Disease Control and Prevention, Atlanta)

U.S. Preventive Services Task Force (Rockville, MD)

Fang Fang Zhang (Tufts University, Boston)

NIH Support: National Institute on Minority Health and Health Disparities


An Indisposable Idea from a Disposable Diaper

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3D Silver Nanostructures
Caption: 3D silver nanostructures created using implosion fabrication. Credit: Daniel Oran, Massachusetts Institute of Technology

Using a screwdriver on the tiny microcircuits arrayed inside a computer hard drive can be a real eye strain. Even more challenging is building the microcircuits or other electronic components at the nanoscale, one-billionth of a meter or less.

That’s why researchers are always on the lookout for new tools to help them work on such a minute scale. But some of these incredibly tiny tools and scaffolds can derive from very unexpected sources.

As published in the journal Science, an NIH-funded team has developed a technique called implosion fabrication to build impressively small and intricate components on the nanoscale [1]. Its secret ingredient: water-swollen gels that you’d find in a baby’s disposable diaper.

A baby’s disposable diaper? If that sounds familiar, my blog highlighted a related technique called expansion microscopy a few years ago that uses water-swollen gels that are generated from a compound used in diapers called sodium polyacrylate.

The previously-reported microscopy technique, from the lab of Edward Boyden, Massachusetts Institute of Technology, Cambridge, embeds biological samples in a fine web of sodium polyacrylate. When water is added, the gel expands, blowing up the specimen to 100 times its original size. This groundbreaking technique, called expansion microscopy, has enabled labs around the world to use conventional microscopes for high-resolution, nanoscale imaging.

In the latest work, Boyden’s team, including co-first authors Daniel Oran and Samuel Rodriques, asked a simple question: What would happen if they applied the sample preparation technique used for expansion microscopy—only in reverse?

To find out, Boyden’s team created millimeter-sized blocks of the super-absorbent sodium polyacrylate diaper compound. After using a nifty trick for attaching molecular anchors in a 3D pattern, they dehydrated the gel and voila! The structures imploded and shrank down to one-thousandth their original size, while holding their 3D shape.

During the process, they can add to the anchors a range of functional molecules or elements. These include DNA, nanoparticles, semiconductors, or almost anything that’s needed.

While more work is needed to perfect the new technique, the researchers have already shown it can create objects one cubic millimeter in size, engineered to include intricate details down to about 50 nanometers. For comparison, a virus is about 30 to 50 nanometers.

These latest findings come as a reminder that advances in biomedicine often lead in wonderful and unexpected new directions. Out of the NIH-funded efforts related to The Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative, members of the Boyden Lab wanted to see the brain better using basic microscopes. Now, we have a widely-applicable promising new approach to nanofabrication.

Reference:

[1] 3D nanofabrication by volumetric deposition and controlled shrinkage of patterned scaffolds. Oran D, Rodriques SG, Gao R, Asano S, Skylar-Scott MA, Chen F, Tillberg PW, Marblestone AH, Boyden ES. Science. 2018 Dec 14;362(6420):1281-1285.

Links:

Size of the Nanoscale (Nano.gov)

Synthetic Neurobiology Group, Ed Boyden (MIT, Cambridge, MA)

The Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative (NIH)

NIH Support: Common Fund; National Institute of Mental Health; National Institute of Biomedical Imaging and Bioengineering; National Human Genome Research Institute; National Institute on Drug Abuse; National Institute of Neurological Disorders and Stroke


New Target for Cancer Immunotherapy: Exosomes

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It was once a central tenet of biology that RNA molecules did their work inside the cell. But it’s now clear that RNA molecules are also active outside the cell, with potentially major implications for our health. To learn more about these unrecognized roles, the NIH Common Fund has launched the Extracellular RNA (exRNA) Communication Program.

This month, members of this research consortium described their latest progress in unraveling the secrets of exRNA in a group of 18 papers in the Cell family of journals. And it’s not just RNA that the consortium is studying, it’s also proteins. Among the many exciting results just published is the serendipitous discovery that proteins carried inside tiny, bubble-like vesicles, called exosomes, may influence a cancer’s response to immunotherapy [1]. The work sheds light on why certain cancers are resistant to immunotherapy and points to new strategies for unleashing the immune system in the fight against cancer.

The new findings center on a type of immunotherapy drugs known as checkpoint inhibitors. They are monoclonal antibodies produced by industry that can boost the immune system’s ability to attack and treat cancer.

One of those antibodies specifically targets a protein, called PD-1, on the surface of certain immune cells. When PD-1 binds a similarly named protein, called PD-L1, on the surface of another cell, the interaction prevents immune cells from attacking. Some tumors seem to have learned this and load up on PD-L1 to evade the immune system.

That’s where checkpoint inhibitors come in. By blocking the interaction between PD-1 and PD-L1, the treatment removes a key check on the immune system, allowing certain immune cells to wake up and attack the tumor.

Checkpoint inhibitors work better in some cancer types than in others. In melanoma, for example, up to about 30 percent of patients respond to checkpoint inhibitor therapy. But in prostate cancer, response rates are in the single digits.

Researchers led by Robert Blelloch, a member of the exRNA consortium and a scientist at the University of California, San Francisco, wanted to know why. He and his team looked for clues in RNA within the cells taken from immunotherapy-resistant prostate cancers.

As published in Cell, the researchers got their first hint of something biologically intriguing in an apparent discrepancy in their data. As they expected from prior work, PD-L1 protein was present in the treatment-resistant cancers. But the PD-L1 messenger RNAs (mRNA), which serve as templates for producing the protein, told an unexpected story. The resistant cancer cells made far more PD-L1 mRNAs than needed to produce the modest levels of PD-L1 proteins detected inside the cells.

Where was the missing PD-L1? Blelloch’s team found it in exosomes. The cancer cells were packaging large quantities of the protein inside exosomes and secreting them out of the cell to other parts of the body.

In additional studies with a mouse model of prostate cancer, the researchers found that those PD-L1-packed exosomes travel through the blood and lymphatic systems to lymph nodes, the sites where immune cells become activated. Once there, PD-L1-laden exosomes put the immune system to sleep, preventing certain key cells from locating and attacking the cancer, including the primary tumor and places where it may have spread.

In important follow up studies, the researchers edited two genes in cancer cells to prevent them from producing exosomes. And, in the absence of exosomes, the cells no longer formed tumors. Importantly, both edited and unedited cells still produced PD-L1, but only those that exported PD-L1 in exosomes disarmed the immune system. Studies in a mouse model of immunotherapy-resistant colorectal cancer yielded similar results.

The new evidence suggests that blocking the release of PD-L1 in exosomes, even temporarily, might allow the immune system to launch a successful and sustained attack against a cancer.

Blelloch notes that many intriguing questions remain. For example, it’s not yet clear why antibodies that target PD-L1 on cancer cells don’t disable PD-L1 found in exosomes. The good news is that the new findings suggest it may be possible to find small molecules that do target PD-L1-packed exosomes, unleashing the immune system against cancers that don’t respond to existing checkpoint inhibitors. In fact, Blelloch’s team is already screening for small molecules that might fit the bill.

Since its launch about five years ago, the exRNA Communication Program has published an impressive 480 peer-reviewed papers, including the latest work in the Cell family of journals. I’d encourage readers to click on some of the other excellent work. I hear that another batch of papers will be published later this year.

Reference:

[1] Suppression of exosomal PD-L induces systemic anti-tumor immunity and memory. Poggio M, Hu T, Pai CC, Chu B, Belair CD, Chang A, Montabana E, Lang UE, Fu Q, Fong L, Blelloch R. Cell. 2019 Apr 4;177(2):414-427.

Links:

Video: Unlocking the Mysteries of RNA Communication (Common Fund/NIH)

Immunotherapy to Treat Cancer (National Cancer Institute/NIH)

Blelloch Lab (University of California, San Francisco)

NIH Support: Common Fund; National Cancer Institute; National Center for Advancing Translational Sciences; National Heart, Lung, and Blood Institute; National Institute on Drug Abuse


A CRISPR Approach to Treating Sickle Cell

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Unedited and edited sickle cells
Caption: Red blood cells from patient with sickle cell disease. The cells were differentiated from bone marrow with unedited and edited hematopoietic stem cells, and the red arrows show the sickled cells. Credit: Wu et al. Nature Medicine. March 25, 2019

Recently, CBS’s “60 Minutes” highlighted the story of Jennelle Stephenson, a brave young woman with sickle cell disease (SCD). Jennelle now appears potentially cured of this devastating condition, thanks to an experimental gene therapy being tested at the NIH Clinical Center in Bethesda, MD. As groundbreaking as this research may be, it’s among a variety of innovative strategies now being tried to cure SCD and other genetic diseases that have long seemed out of reach.

One particularly exciting approach involves using gene editing to increase levels of fetal hemoglobin (HbF) in the red blood cells of people with SCD. Shortly after birth, babies usually stop producing HbF, and switch over to the adult form of hemoglobin. But rare individuals continue to make high levels of HbF throughout their lives. This is referred to as hereditary persistence of fetal hemoglobin (HPFH). (My own postdoctoral research in the early 1980s discovered some of the naturally occurring DNA mutations that lead to this condition.)

Individuals with HPFH are entirely healthy. Strikingly, rare individuals with SCD who also have HPFH have an extremely mild version of sickle cell disease—essentially the presence of significant quantities of HbF provides protection against sickling. So, researchers have been exploring ways to boost HbF in everyone with SCD—and gene editing may provide an effective, long-lasting way to do this.

Clinical trials of this approach are already underway. And new findings reported in Nature Medicine show it may be possible to make the desired edits even more efficiently, raising the possibility that a single infusion of gene-edited cells might be able to cure SCD [1].

Sickle cell disease is caused by a specific point mutation in a gene that codes for the beta chain of hemoglobin. People with just one copy of this mutation have sickle cell trait and are generally healthy. But those who inherit two mutant copies of this gene suffer lifelong consequences of the presence of this abnormal protein. Their red blood cells—normally flexible and donut-shaped—assume the sickled shape that gives SCD its name. The sickled cells clump together and stick in small blood vessels, resulting in severe pain, anemia, stroke, pulmonary hypertension, organ failure, and far too often, early death.

Eleven years ago, a team led by Vijay Sankaran and Stuart Orkin at Boston Children’s Hospital and the Dana-Farber Cancer Institute discovered that a protein called BCL11A seemed to determine HbF levels [2]. Subsequent work showed the protein actually works as a master mediator of the switch from fetal to adult hemoglobin, which normally occurs shortly after birth.

Five years ago, Orkin and Daniel Bauer identified a specific enhancer of BCL11A expression that could be an attractive target for gene editing [3]. They could knock out the enhancer in the bone marrow, and BCL11A would not be produced, allowing HbF to stay switched on.

Because the BCL11A protein is required to turn off production of HbF in red cells. the researchers had another idea. They thought it might be possible to keep HbF on permanently by disrupting BCL11A in blood-forming hematopoietic stem cells (HSCs). The hope was that such a treatment might offer people with SCD a permanent supply of healthy red blood cells.

Fast-forward to the present, and researchers are now testing the ability of gene editing tools to cure the disease. A favorite editing system is CRISPR, which I’ve highlighted on my blog.

CRISPR is a highly precise gene-editing tool that relies on guide RNA molecules to direct a scissor-like Cas9 enzyme to just the right spot in the genome to correct the misspelling. The gene-editing treatment involves removing bone marrow from a patient, modifying the HSCs outside the body using CRISPR gene-editing tools, and then returning them back to the patient. Preclinical studies had shown that CRISPR can be effective in editing BCL11A to boost HbF production.

But questions lingered about the editing efficiency in HSCs versus more common, shorter-lived progenitor cells found in bone marrow samples. The efficiency greatly influences how long the edited cells might benefit patients. Bauer’s team saw room for improvement and, as the new study shows, they were right.

To produce lasting HbF production, it’s important to edit as many HSCs as possible. But it turns out that HSCs are more resistant to editing than other types of cells in bone marrow. With a series of adjustments to the gene-editing protocol, including use of an optimized version of the Cas9 protein, the researchers showed they could push the number of edited genes from about 80 percent to about 95 percent.

Their studies show that the most frequent Cas9 edits in HSCs are tiny insertions of a single DNA “letter.” With that slight edit to the BCL11A gene, HSCs reprogram themselves in a way that ensures long-term HbF production.

As a first test of their CRISPR-edited human HSCs, the researchers carried out the editing on HSCs derived from patients with SCD. Then they transferred the editing cells into immune-compromised mice. Four months later, the mice continued to produce red blood cells that produced high levels of HbF and resisted sickling. Bauer says they’re already taking steps to begin testing cells edited with their optimized protocol in a clinical trial.

What’s truly exciting is that the first U.S. human clinical trials of such a gene-editing approach for SCD are already underway, led by CRISPR Therapeutics/Vertex Pharmaceuticals and Sangamo Therapeutics/Sanofi. In January, CRISPR Therapeutics/Vertex Pharmaceuticals announced that the U.S. Food and Drug Administration (FDA) had granted Fast Track Designation for their CRISPR-based treatment called CTX001 [4].

In that recent “60 Minutes” segment, I dared to suggest that we now have what looks like a cure for SCD. As shown by this new work and the clinical trials underway, we in fact may soon have multiple different strategies to provide cures for this devastating disease. And if this can work for sickle cell, a similar strategy might work for other genetic conditions that currently lack any effective treatment.

References:

[1] Highly efficient therapeutic gene editing of human hematopoietic stem cells. Wu Y, Zeng J, Roscoe BP, Liu P, Yao Q, Lazzarotto CR, Clement K, Cole MA, Luk K, Baricordi C, Shen AH, Ren C, Esrick EB, Manis JP, Dorfman DM, Williams DA, Biffi A, Brugnara C, Biasco L, Brendel C, Pinello L, Tsai SQ, Wolfe SA, Bauer DE. Nat Med. 2019 Mar 25.

[2] Human fetal hemoglobin expression is regulated by the developmental stage-specific repressor BCL11A. Sankaran VG, Menne TF, Xu J, Akie TE, Lettre G, Van Handel B, Mikkola HK, Hirschhorn JN, Cantor AB, Orkin SH.Science. 2008 Dec 19;322(5909):1839-1842.

[3] An erythroid enhancer of BCL11A subject to genetic variation determines fetal hemoglobin level. Bauer DE, Kamran SC, Lessard S, Xu J, Fujiwara Y, Lin C, Shao Z, Canver MC, Smith EC, Pinello L, Sabo PJ, Vierstra J, Voit RA, Yuan GC, Porteus MH, Stamatoyannopoulos JA, Lettre G, Orkin SH. Science. 2013 Oct 11;342(6155):253-257.

[4] CRISPR Therapeutics and Vertex Announce FDA Fast Track Designation for CTX001 for the Treatment of Sickle Cell Disease, CRISPR Therapeutics News Release, Jan. 4, 2019.

Links:

Sickle Cell Disease (National Heart, Lung, and Blood Institute/NIH)

Cure Sickle Cell Initiative (NHLBI)

What are Genome Editing and CRISPR-Cas9? (National Library of Medicine/NIH)

Could Gene Therapy Cure Sickle Cell Anemia? (CBS News)

Daniel Bauer (Dana-Farber Cancer Institute, Boston)

Somatic Cell Genome Editing Program (Common Fund/NIH)

NIH Support: National Heart, Lung, and Blood Institute; National Institute of General Medical Sciences; National Institute of Allergy and Infectious Diseases; National Institute of Diabetes and Digestive and Kidney Diseases


The Brain Ripples Before We Remember

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Ripple brain
Credit: Thinkstock

Throw a stone into a quiet pond, and you’ll see ripples expand across the water from the point where it went in. Now, neuroscientists have discovered that a different sort of ripple—an electrical ripple—spreads across the human brain when it strives to recall memories.

In memory games involving 14 very special volunteers, an NIH-funded team found that the split second before a person nailed the right answer, tiny ripples of electrical activity appeared in two specific areas of the brain [1]. If the volunteer recalled an answer incorrectly or didn’t answer at all, the ripples were much less likely to appear. While many questions remain, the findings suggest that the short, high-frequency electrical waves seen in these brain ripples may play an unexpectedly important role in our ability to remember.

The new study, published in Science, builds on brain recording data compiled over the last several years by neurosurgeon and researcher Kareem Zaghloul at NIH’s National Institute of Neurological Disorders and Stroke (NINDS). Zaghloul’s surgical team often temporarily places 10-to-20 arrays of tiny electrodes into the brains of a people with drug-resistant epilepsy. As I’ve highlighted recently, the brain mapping procedure aims to pinpoint the source of a patient’s epileptic seizures. But, with a patient’s permission, the procedure also presents an opportunity to learn more about how the brain works, with exceptional access to its circuits.

One such opportunity is to explore how the brain stores and recalls memories. To do this, the researchers show their patient volunteers hundreds of pairs of otherwise unrelated words, such as “pencil and bishop” or “orange and navy.” Later, they show them one of the words and test their memory to recall the right match. All the while, electrodes record the brain’s electrical activity.

Previously published studies by Zaghloul’s lab [2, 3] and many others have shown that memory involves the activation of a number of brain regions. That includes the medial temporal lobe, which is involved in forming and retrieving memories, and the prefrontal cortex, which helps in organizing memories in addition to its roles in “executive functions,” such as planning and setting goals. Those studies also have highlighted a role for the temporal association cortex, another portion of the temporal lobe involved in processing experiences and words.

In their data collected in patients with epilepsy, Zaghloul’s team’s earlier studies had uncovered some telltale patterns. For instance, when a person correctly recalled a word pair, the brain showed patterns of activity that looked quite similar to those present when he or she first learned to make a word association.

Alex Vaz, one of Zaghloul’s doctoral students, thought there might be more to the story. There was emerging evidence in rodents that brain ripples—short bursts of high frequency electrical activity—are involved in learning. There was also some evidence in people that such ripples might be important for solidifying memories during sleep. Vaz wondered whether they might find evidence of ripples as well in data gathered from people who were awake.

Vaz’s hunch was correct. The reanalysis revealed ripples of electricity in the medial temporal lobe and the temporal association cortex. When a person correctly recalled a word pair, those two brain areas rippled at the same time.

Further analysis showed that the ripples appeared in those two areas a few milliseconds before a volunteer remembered a word and gave a correct answer. Your brain is working on finding an answer before you are fully aware of it! Those ripples also appear to trigger brain waves that look similar to those observed in the association cortex when a person first learned a word pair.

The finding suggests that ripples in this part of the brain precede and may help to prompt the larger brain waves associated with replaying and calling to mind a particular memory. For example, hearing the words, “The Fab Four” may ripple into a full memory of a favorite Beatles album (yes! Sgt. Pepper’s Lonely Hearts Club Band) or, if you were lucky enough, a memorable concert back in the day (I never had that chance).

Zaghloul’s lab continues to study the details of these ripples to learn even more about how they may influence other neural signals and features involved in memory. So, the next time you throw a stone into a quiet pond and watch the ripples, perhaps it will trigger an electrical ripple in your brain to remember this blog and ruminate about this fascinating new discovery in neuroscience.

References:

[1] Coupled ripple oscillations between the medial temporal lobe and neocortex retrieve human memory. Vaz AP, Inati SK, Brunel N, Zaghloul KA. Science. 2019 Mar 1;363(6430):975-978.

[2] Cued Memory Retrieval Exhibits Reinstatement of High Gamma Power on a Faster Timescale in the Left Temporal Lobe and Prefrontal Cortex. Yaffe RB, Shaikhouni A, Arai J, Inati SK, Zaghloul KA. J Neurosci. 2017 Apr 26;37(17):4472-4480.

[3] Human Cortical Neurons in the Anterior Temporal Lobe Reinstate Spiking Activity during Verbal Memory Retrieval. Jang AI, Wittig JH Jr, Inati SK, Zaghloul KA. Curr Biol. 2017 Jun 5;27(11):1700-1705.e5.

Links:

Epilepsy Information Page (National Institute of Neurological Disorders and Stroke/NIH)

Brain Basics (NINDS)

Zaghloul Lab (NINDS)

NIH Support: National Institute of Neurological Disorders and Stroke; National Institute of General Medical Sciences


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