Monday, 20 August 2018

Stem Cells Enclosed in a Hydrogel May Help Damaged Muscles

Stem cells produce the specialized cells that our body needs. Researchers at the Georgia Institute of Technology have discovered that stem cells known as muscle satellite cells (MuSCs) may help people with certain skeletal muscle injuries or illnesses when administered in a hydrogel. The research was done in mice, but it may apply to humans as well.

Muscles of the head
Patrick J. Lynch, CC BY 2.5
Problems With Muscle Regeneration

When skeletal muscles in elderly people are seriously injured, the tissue often fails to regenerate properly. The muscles of people with Duchenne muscular dystrophy degenerate and become weak due to a genetic problem. In both of these cases, injecting MuSCs into damaged or weakened muscles to replace missing tissue sounds like a great idea. It presents challenges, however. The cells must stay alive in the body, attach to the right area, and then produce new muscle cells.

Muscular Dystrophy

The term “muscular dystrophy” refers to a group of diseases in which muscles degenerate. Unfortunately, the diseases are progressive. The muscles become weaker as their mass decreases. The illnesses are caused by a genetic problem. Duchenne muscular dystrophy or DMD is the most common disorder in the group.

DMD starts in childhood and generally occurs in boys. It’s a sex-linked disease, which means that it’s controlled by a gene on the sex chromosomes. It’s possible for a girl to get the disease, but the condition is rare in females. There is no cure for the disorder at the moment. Doctors have methods to help people deal with DMD, though.

The lifespan of patients with DMD is increasing due to better treatments. The weakening of respiratory muscles eventually results in the death of many patients, however. Due to the gene problem, the patients lack a protein called dystrophin. This protein protects muscle cells. Gene therapy is an active area of research for the disorder.

Inflammation

Under normal conditions, temporary inflammation in the body is useful. Cells of the immune system and the chemicals that they release repair the damaged area and destroy pathogens. After the area has been repaired, inflammation subsides. Extreme or chronic inflammation can be harmful, however. The excessive or continued production of inflammatory chemicals can create pain and damage tissue. The immune system is very active in the damaged and inflamed muscles found in elderly people with serious injuries. Inflammation is also involved in DMD. In both cases, the immune system attacks and destroys any stem cells that are injected.

Skeletal muscle
Bruce Blaus, CC BY 3.0
Benefits of the Hydrogel

The researchers have created a hydrogel to enclose muscle stem cells. The gel consists of a net of molecules suspended in water. The net forms a matrix that traps and protects the stem cells.

In mice with a condition resembling the two illnesses described above, the gel was injected directly into muscles that weren’t regenerating. The gel protected the stem cells from inflammatory chemicals and stopped them from being destroyed. In addition, the stem cells were able to heal the damaged tissue. Without the hydrogel, only 1% to 20% of the injected stem cells survived and many of the surviving cells were weak.

The researchers say that the stem cells multiply within the biocompatible and biodegradable hydrogel that they’ve created. When the gel attaches to tissues it hardens and forms a glue that holds the cells in place. The “glue” gradually disintegrates, leaving the healthy stem cells attached to the damaged area. The stem cells then divide and form new muscle cells.

A Potential Treatment

Regenerating the damaged muscle cells of elderly people could be very useful for mobility and quality of life. Regenerating the diaphragm (the main muscle of respiration) could be a life saver for people with Duchenne muscular dystrophy. The hydrogel treatment is not ready for clinical trials in humans yet, but the researchers are working towards this goal.

One problem is that the muscle stem cells may have to come from someone with healthy muscles. With a few exceptions, when cells from another person’s body are placed in our own, the immune system attacks and destroys the cells. This means that researchers will have to solve the donor cell rejection problem in humans before the treatment can be tested. The results of their research could be very worthwhile, though.

References

Facts about muscular dystrophy from the Mayo Clinic
Duchenne muscular dystrophy information from the Muscular Dystrophy Association
A matrix delivers healing stem cells from the ScienceDaily new service




Thursday, 12 July 2018

A Mediterranean Diet May Help People With Osteoporosis

Osteoporosis is a condition in which bone loss is so severe that it increases the risk of a fracture. Bone mass naturally decreases as we age, but osteoporosis is not an inevitable result of this process. It’s a common disorder, however. For those who have the condition, slowing the rate of bone loss or even better building bone would be very helpful. Some interesting research from the University of East Anglia in Britain has shown that a Mediterranean diet appears to reduce bone loss in people who have osteoporosis.

The Mediterranean Diet
G.steph.rocket, via Wikimedia Commons, CC BY-SA 4.0 License

Functions and Activities of Bone


Bone forms the skeleton that enables us to move and protects our organs. It also stores minerals (including calcium and phosphorus) and releases them when necessary. Red bone marrow makes and releases our blood cells. Yellow bone marrow stores and releases lipids.

Bone is not a static material. It’s continually being made and broken down according to stresses on the skeleton and the chemical needs of the body. Osteoblasts are cells that build bone; osteoclasts are cells that break it down. The stimulation of these cells and control of bone deposition and breakdown is a complex process affected by many factors. Some important facts about the process are already known, however.

As we age, the breakdown of bone tends to exceed its deposition. Exercises to strengthen bones can help to keep them strong. If you already have osteoporosis, make sure that you check with your doctor before doing strength-building exercises. Some of them can do more harm than good for someone who has the condition. Eating a nutritious diet that includes sufficient calcium and vitamin D is another step that can be helpful for building bone. Calcium is an essential component of bones. Vitamin D is needed in order for calcium to be absorbed through the lining of the intestine.

Common locations and effects of osteoporosis
Bruce Blaus, via Wikimedia Commons, CC BY-SA 4.0 license

The Mediterranean Diet


The Mediterranean diet is the traditional one followed by people in the Mediterranean region. In its earlier form it consisted of unrefined grains, legumes or pulses, vegetables, fruits, fish, some chicken, some cheese, yogurt, and eggs, nuts, olive oil, and moderate amounts of wine. Today the diet is often modified by modern food choices to a greater or lesser extent, even in the region where it originated. With the exception of the wine, which is controversial with respect to its effects on our health, the Mediterranean diet closely resembles ones often recommended by nutritionists.

The Research Study


1142 people between the ages of 65 and 79 participated in the study. Half of the subjects followed a Mediterranean diet and the others didn’t. People were assigned to the groups on a random basis. The special diet followed by people in the study was “rich in fruit, vegetables, nuts, unrefined cereals, olive oil, and fish”. The bone density of subjects was measured at the start of the study and after twelve months.

The researchers found that the diet had no noticeable effect on the bones of people with normal bone density. The density decreased by the amount expected over a twelve-month interval. In the people who had osteoporosis at the start of the study and who followed the Mediterranean diet, however, the density of the femoral neck increased over the twelve-month period. The femoral neck is located in the hip joint and is a common site of fracture in people with osteoporosis. On the other hand, the diet had no effect on the density in the lumbar region or at other sites. In people with osteoporosis who didn't follow the Mediterranean diet, density of the femoral neck decreased.

The researchers say that they were impressed that a noticeable effect on bone density could be found after only twelve months. They would like to see the results of a longer experiment in order to discover more about how it affects both people with osteoporosis and those without and to see if other sites in the body are eventually influenced by the diet.

A Healthy Diet


As the researchers say, the Mediterranean diet has already been shown to have health
benefits and to reduce the risk of some serious diseases, including cardiovascular problems, cancer, Parkinson's disease, and Alzheimer's disease. It seems like a good idea to follow it even before we find out more about its effects on bone density. The only precaution that a person starting the diet should take is to do some research about the health effects of drinking wine. The latest studies suggest that it has harmful effects as well as potentially helpful ones.

References


Osteoporosis facts from Osteoporosis Canada

Mediterranean diet information from the Mayo Clinic

The Mediterranean Diet and bone loss from the ScienceDaily news service

Monday, 22 January 2018

The Persian Shallot and Multidrug-Resistant Tuberculosis

The Persian shallot is a plant that is greatly appreciated for its culinary and ornamental benefits. It may also have important medical uses. It's classified in the same genus as the onion and has the scientific name Allium stipitatum. The plant is native to Asia and grows from a bulb with a strong flavour. Researchers have discovered that the plant contains chemicals that may be useful in fighting tuberculosis, or TB.

Allium stipitatum by KENPEI, CC BY-SA 3.0 License

The Persian Shallot

The Persian shallot has a basal group of strap-shaped leaves and a tall flowering stalk that extends far above the ground. The pretty star-shaped flowers are white to lilac in colour. They're borne in an umbel, which is a structure consisting of multiple flowers emerging from a common point. Although an individual flower of a shallot is small, the umbel as a whole is large and attractive. The plant is sold by nurseries for ornamental use. The bulb is a popular food in Iran.

Tuberculosis

Tuberculosis is an infectious disease caused by a bacterium named Mycobacterium tuberculosis. The bacterium is best known for its effects on the lungs, but it may also affect other parts of the body. The patient experiences a cough and releases sputum, which is a mixture of mucus from the lungs and saliva from the mouth. The sputum may be bloody. There may be additional symptoms, including chest pain, fever, fatigue, and unexpected weight loss.

TB may be serious. In some cases it's a latent (hidden and dormant) condition due to the inactivity of the bacteria in the body. In other cases the bacteria become active and the person develops symptoms of the disease.

Tuberculosis is generally treated by a mixture of antibiotics. These often need to be taken for months in order to be effective. A worrying trend is the development of antibiotic resistance in M. tuberculosis. Antibiotics that once killed bacteria quickly now either take longer to work or are ineffective. This is not only unfortunate for the patient but also a problem for the community because tuberculosis is infectious. It's spread by droplets of liquid released during coughing and sneezing. Antibiotic resistance is becoming a serious problem in many other bacterial infections besides TB.

As many as 50 million people worldwide are currently infected with multi-drug resistant TB, which means it's vital to develop new antibacterials. Quote from Dr. Sanjib Bhakta of the University of London

Possible symptoms of tuberculosis by Mikael Haggstrom, public domain image
It should be noted that the symptoms mentioned above are not unique to tuberculosis and that a patient may not experience all of them. Anyone who suspects that they have the disease or who has unexplained symptoms should visit a doctor.

Potentially Useful Compounds in the Persian Shallot

We need to find new ways to fight bacteria, including the species that causes tuberculosis. The Persian shallot may be very useful in improving the action of some present antibiotics used to treat TB.

A team of researchers from British universities recently studied chemicals found in an extract from Persian shallot bulbs. They made synthetic copies of some of the chemicals. When used with antibiotics, four of the synthetic chemicals increased the effectiveness of the antibiotics in killing multidrug-resistant tuberculosis bacteria. The addition of one of the synthetic chemicals "inhibited growth of the isolated TB cells by more than 99.9%". The shallot chemicals appear to interfere with activities in the bacteria that protect them from antibiotics.

The results described above sound fantastic, but they were done with isolated cells in lab equipment. The chemicals may not be so effective inside the human body. Absorption, dilution, and inactivation may all be a problem for medicinal drugs that enter the body. It's possible that the chemicals could be useful, however. The researchers hope to use the synthesized  chemicals as templates for new drugs that will be effective in humans.

Medicines From Plants

Plants are a wonderful resource. Many pharmaceutical drugs originally came from nature. Conservation of wild plants is important for many reasons. One of these is the likelihood of finding medicinal chemicals inside them. These may become increasingly important if antibiotic resistance spreads, as it's doing at the moment.

References

Information about Allium stipitatum from the Royal Horticultural Society, or RHS
Onions could hold key to fighting antibiotic resistance from the Medical Xpress news site
Facts about tuberculosis from the National Institutes of Health, or NIH



Tuesday, 21 November 2017

Cinnamon: A Delicious Spice, Cinnamaldehyde, and Obesity

Cinnamon is shown on the right and star anise on the left.
Public domain photo by Couleur

A Versatile Spice


Cinnamon is a delicious addition to foods and drinks. The spice may have an interesting benefit beyond flavour enhancement. Cinnamaldehyde is the main chemical responsible for the flavour and aroma of cinnamon. Researchers have discovered that the substance may play a role in the fight against obesity. This could be great news. Care is necessary when using cinnamon, however. The spice is widely accepted as being safe for human consumption when used in culinary amounts. It may not be a good idea to eat huge amounts of cinnamon in an attempt to promote weight loss, though, as described below.

A Delicious Addition to Food and Drinks


Even without health benefits, cinnamon is a lovely spice. It's a great addition to many foods, including those of some traditional fall and winter celebrations. Apple and pumpkin pies, mincemeat, rolls and toast, Christmas cakes and puddings, eggnog, coffee, and tea are all enhanced by the addition of the spice. Cinnamon works well in both sweet and savoury dishes. I nearly always have some in my kitchen.

Cinnamon is a great addition to Christmas foods.
Public domain photo by Couleur

Harvesting Cinnamon


Cinnamon is obtained from the inner bark of certain tree species in the genus Cinnamomum. Cinnamomum cassia is the most common species used commercially and produces the type of cinnamon sold in most grocery stores. Spice made from this tree is sometimes known as cassia instead of cinnamon. Cinnamomum verum is called Ceylon cinnamon or “true” cinnamon and is generally more expensive, at least where I live.

The wet, inner bark of a cinnamon tree curls as it dries, forming shapes known as quills. The quills are cut into shorter sections to be sold as sticks or ground into a powder. Removing the bark from part of the tree has to be done carefully in order for the tree to survive. The cambium, or the layer that produces new bark, must be left in place.

After about two years of harvest, cinnamon trees are often coppiced. Coppicing is a technique in which a tree is cut down to a short stump. The stumps grow new shoots. In the case of cinnamon, these can eventually be used to harvest spice. Coppicing allows cultivated trees to live for a long time. It works with many tree species, but not all of them.

Cinnamaldehyde


In its pure form, cinnamaldehyde is a thick yellow liquid at room temperature. Previous research has shown that the chemical appears to reduce both obesity and high blood sugar in mice. New research from the University of Michigan has added to the evidence. This research is especially interesting because it involved cells donated by human volunteers, though it wasn’t done in the human body. The donated cells were fat cells, or adipocytes.

The scientists found that cinnamaldehyde activated adipocyte genes and enzymes involved in thermogenesis, or the process of heat production from chemicals. The cinnamaldehyde triggered the production of heat from the lipid (fat) molecules in the adipocytes. During this process, the fat molecules broke down.

Cinnamon and tea is a lovely combination.
Public domain photo by George Hodan

Safety of Cinnamaldehyde


Concentrated cinnamaldehyde is a skin irritant, and the chemical is toxic in large doses. Quote from the National Center for Biotechnology Information

Cinnamaldehyde is used as a fungicide and an insecticide. The safety of cinnamaldehyde as an obesity treatment—if in fact it works in the intact body—is currently unknown. The concentrated chemical is dangerous, as the quote above states. More research is needed to understand the action and safety of different concentrations of the substance in the human body. One question that needs to be answered is whether deliberately stimulating thermogenesis in adipocytes with cinnamaldehyde is safe.

Using the Spice


It's unlikely that the ingestion of a single, specific substance will completely solve a weight problem. The usual recommendations of health experts to eat a healthy diet and exercise regularly are important. It’s also important for people who are very overweight or out of shape to see a doctor before starting an exercise program and to start the program gently. It might be a good idea to also use cinnamon liberally (but not excessively), though. The addition of the spice to a wide variety of food would certainly be enjoyable for many people. It might also be a helpful addition to a healthy lifestyle with respect to losing weight.


References


Cinnamon turns up the heat on fat cells from the Medical Xpress news site

Cinnamaldehyde information from the National Center for Biotechnology Information

Friday, 21 July 2017

The Potential Role of Cows in Preventing HIV Infections

The HIV virus is a nasty entity that attacks the immune system and stops it from doing its job. The infection can be deadly. Fortunately, the disease can be controlled, provided patients have access to antiretroviral therapy and follow its protocol correctly. The therapy inhibits or slows the replication of the virus. The therapy isn’t available everywhere in the world, however. People are still dying from AIDS, the end stage of the infection. It would be wonderful to stop the disease before it starts. The impressive immune system of cows may enable us to create a vaccine and/or new treatments for the disorder.


The green particles are HIV virions, or individual virus particles.
The blue object is a white blood cell.
Public domain photo from the CDC

Effects of HIV


The HIV or Human Immunodeficiency Virus destroys cells called helper T cells or CD4 cells. The latter name arises from the fact that the cells have a protein called CD4 on their membrane. Helper T cells are essential for activating other cells that either directly or indirectly destroy invading viruses, bacteria, and fungi.

As the viral disease progresses, so many CD4 cells are destroyed in the patient that their body can no longer fight infections or the types of cancer that are caused by an infection. Eventually the immune system is in such a weakened condition that is person is said to have AIDS, or Acquired Immunodeficiency Syndrome.

The HIV virus is transmitted by the transfer of specific body fluids from an infected person to an uninfected one. The CDC article in the “References” section below has more information about transmission.

The Controlled and the Uncontrolled Virus


For people who have access to proper therapy, an HIV infection is no longer an automatic death sentence. The therapy must be followed carefully and consistently, however.
"Today, someone diagnosed with HIV and treated before the disease is far advanced can live nearly as long as someone who does not have HIV." Quote from the CDC, or the Centers for Disease Control and Prevention

HIV is a horrible virus if it's not controlled, not only because of its dangerous effects but also because the active virus is so hard for the body to fight. The virus often mutates (changes genetically), even while it’s inside a patient's body. The mutation gives the virus new characteristics. This makes it difficult for the patient to create effective antibodies. Antibodies are proteins that attack harmful viruses and bacteria.

A very small number of patients manage to create antibodies that attack parts of the virus that are unaffected by mutations. This is the case even if the patients don’t receive antiviral therapy. The antibodies that they create are said to be “broadly neutralizing” because they attack many different versions, or strains, of HIV.

Cow Antibodies


Researchers have discovered that cows—or at least four of them—also make broadly neutralizing antibodies to the HIV virus. In addition, some of these antibodies appear and work in weeks instead of the years required in the human body. Specifically, the researchers found that after the cows were exposed to proteins from the HIV virus, the antibodies that they made were able to neutralize 26% of HIV strains within 42 days and 96% of them within 381 days.

"From the early days of the epidemic, we have recognized that HIV is very good at evading immunity, so exceptional immune systems that naturally produce broadly neutralizing antibodies to HIV are of great interest - whether they belong to humans or cattle." Quote from Dr. Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases

Cows don't experience HIV infections in their normal lives. The researchers suspect that because the digestive tract of cows is exposed to so many bacteria in their diet, the animals have developed the ability to produce a wide variety of antibodies relatively rapidly. Their ability may help us to obtain new chemicals to fight the HIV virus in humans and perhaps to create a vaccine to prevent the infection.

References


HIV information from the CDC

HIV antibody production in cows

Tuesday, 11 July 2017

Human Herpesvirus 6 and Multiple Sclerosis: A Possible Link

Human herpesvirus 6 (HHV-6) is a very common virus. Researchers estimate that more than 80% of us were exposed to the virus in childhood, usually without realizing it. The immune system can generally fight the active form of HHV-6, but the virus has a technique to avoid complete destruction. It has the ability to become latent. This means that it’s present in our cells but is hiding from the immune system and is apparently inactive. Researchers think that the latent virus isn’t completely inactive, however, and that it may be involved in some cases of multiple sclerosis.
Illustration by LadyofHats, public domain license

Multiple sclerosis or MS is a demyelinating disorder. Myelin is a fatty material that covers and insulates the nerves. For an unknown reason, in MS patients the immune system destroys myelin surrounding the nerve cells in the brain and spinal cord. This disrupts the flow of nerve impulses through the body and can cause a wide variety of debilitating symptoms, including muscle weakness, coordination problems when moving, and problems with sensation.

As long ago as 2003, researchers found latent HHV-6 in the brain cells of people with severe multiple sclerosis. HHV-6 may not be a direct cause of MS, but it’s thought that the virus prevents the body from repairing loss of myelin. When myelin is damaged in our body, oligodendrocyte progenitor cells normally migrate to the injured area and produce oligodendrocytes. These cells then make myelin to repair the injury. This process may not happen in someone with MS.

HHV-6 becomes latent by incorporating its own DNA into the DNA of its host. The virus then produces a protein called U94. This protein helps the virus to remain in the DNA and prevents it from being detected by the immune system. Researchers from the University of Rochester in the United States have discovered that when the HHV-6 virus is present in the DNA of human oligodendrocyte progenitor cells placed in lab animals, the U94 protein that’s made prevents the cells from migrating to nerves with injured myelin. As a result, the myelin of the animals disappears and the nerves are damaged.

                                           Possible symptoms of multiple sclerosis 
                               Illustration by Mikael Haggstrom, public domain license

The discovery about the possible relationship between the virus and MS is interesting, but there are some questions that need to be answered. 
  • One question is whether the inability of oligodendrocyte progenitor cells to migrate when they are infected by the virus is true in human cells as well as in the cells of lab animals. 
  • Another is whether the latent virus is harmful in people with MS or whether it needs to become active in order to be harmful. 
  • Yet another topic to investigate is the location of the virus in the bodies of healthy people and in the bodies of those with MS. 
  • We also need to know how the body of people with MS responds to the latent and active virus compared to the body of someone without MS. 
It certainly seems that the potential link between human herpesvirus 6 and multiple sclerosis should be investigated further. It’s sad that we still don’t know the cause or causes of the disorder. Understanding how the disease arises could enable us to treat it better and perhaps prevent it. 

References

The possible role of HHV-6 in multiple sclerosis
Facts about multiple sclerosis

Tuesday, 6 June 2017

Modified Vancomycin: Preventing Antibiotic Resistance in Bacteria

Vancomycin is an antibiotic that is prescribed to treat some potentially serious bacterial infections. For many years, it's been a powerful ally in our fight against disease. In recent times, however, it's lost some of its effectiveness. Bacteria are developing resistance to many of our current antibiotics, including vancomycin. In what could be a very significant discovery, scientists have found a way to modify the vancomycin molecule so that it becomes effective again.


Methicillin-resistant Staphylococcus aureus or MRSA is 
   being absorbed by a white blood cell in this colorized photo.
Vancomycin is used to treat MRSA. (Public domain photo)


The Importance of Antibiotics


Antibiotics are chemicals made by bacteria or fungi in order to attack other organisms. Their discovery was a wonderful time in history. Some very serious and previously fatal diseases were able to be cured by the chemicals. We are currently experiencing the reverse situation, however. As antibiotics stop working due to bacterial resistance, the spectre of untreatable diseases is reappearing.



How Do Bacteria Become Resistant to Antibiotics?


Antibiotic resistance in bacteria develops because of the genetic variability of the individuals in a species. Some individuals in a species of bacteria may contain a gene (or genes) that prevents them from being harmed by a particular antibiotic. When other members of the population are killed by the medication, the resistant ones survive. When they reproduce, they pass on the gene for resistance to some of their offspring. Over time, the population as a whole may become resistant to the antibiotic.



Vancomycin and Its Action


Vancomycin has been prescribed for over sixty years. It was discovered in 1953 in a soil sample from Borneo and is made by a bacterium named Amycolatopsis orientalis. It's prescribed as a treatment for some serious conditions that other antibiotics can no longer cure. Vancomycin may have some major side effects, however. These effects don't always occur, but if they do, they may include hearing and kidney problems.


All forms of vancomycin—natural and modified—work by interfering with the process in which bacteria produce their cell wall. The wall surrounds the cell membrane and has protective functions. Vancomycin does its job by binding to protein fragments (peptides) in the cell wall. Peptides and proteins consist of a chain of amino acids.


Unmodified vancomycin binds to two copies of an amino acid called D-alanine that end some of the peptides in bacterial cell walls. This stops the wall from being assembled and kills the bacteria. Many of the once-susceptible bacteria have now evolved to have a D-alanine paired with a D-lactic acid combination at the end of their peptides instead of a double D-alanine combination, however. Natural vancomycin can't bind with this combination and is therefore rendered ineffective.



Modified Vancomycin


A group of scientists at The Scripps Research Institute in the United States has made modifications to the vancomycin molecule to restore its effectiveness. The first modification was the creation of a form that can bind with with a D-alanine—D-lactic acid pair in a bacterium's cell wall. Other scientists created two additional modifications to the structure of the antibiotic. One prevents the cell wall from being made while the other causes the wall to burst. The Scripps team has now created vancomycin with all three modifications. This means that the altered antibiotic prevents bacteria from making their cell wall in a total of three different ways.


Resistance should be much less likely to develop when the new version of vancomycin is used. If any bacteria become resistant to one of the antibiotic's new abilities, they should be unable to resist the other two, perhaps for a long time into the future.


Animal and human trials are needed before the modified vancomycin can be prescribed by doctors. The information announced so far is both hopeful and exciting, however. We badly need either new antibiotics or old ones that work successfully again. 



References


A modified antibiotic in the fight against drug resistance from The Guardian newspaper


The creation of a more effective antibiotic from sciencemag.org