Lab notes: What’s making children die of diarrhoea, how smoking alters DNA and more

Vaccines are the key to preventing childhood diarrhoea

Childhood diarrhoea, the second leading cause of death among children younger than five, seems to be overwhelmingly caused by pathogens like bacteria, parasites and viruses, according to a new global study.

An international collaboration of researchers reassessed more than thousand samples from the Global Enteric Multicentre Study or GEMS to find that pathogens caused more than 89% of all childhood diarrhea cases as opposed to the previously estimates 51%. The finding is important because it identifies where treatment for childhood diarrhea should be focused. Other causes of childhood diarrhea include food poisoning, food allergies, irritable bowel disease and celiac disease.

The analysis of samples from Bangladesh, India, Pakistan, the Gambia, Kenya, Mali, and Mozambique showed that the most common diarrhoea infections were caused by Shigella and rotavirus, followed by adenovirus, enterotoxin-producing E coli, Cryptosporidium, and Campylobacter. The six pathogens contributed to more than 77% of all diarrhoea. More than half the children assessed in the study who carried diarrhea-causing pathogens suffered form more than one infection.

Every year, half a million children under the age of five die of diarrhoea. The disease is managed mainly through rehydration and providing zinc supplements. Antibiotics are give only to those with signs of dysentery and cholera.

The better way to fight the disease is prevention through vaccination. Oral vaccines for rotavirus already exist and are being administered in many countries through public health programmes. The authors of the study, which has been published in The Lancet, say that their findings highlight the need to now prioritise vaccines for Shigella and enterotoxin-producing E coli. Another challenge is to find suitable treatments for multiple infections causing diarrhea.

Smoking scars DNA

Researchers have now found that smoking alters a smoker’s DNA, inactivating genes or changing molecular machinery. Some of the changes were reversed after the subject had quit smoking for about five years. Others lasted up to 30 years. These changes in molecular machinery were found to lead to cancer and other diseases.

The findings by a team of scientists from Harvard Medical School published in the journal Circulation: Cardiovascular Genetics showed that smoking had an effect on genome-wide methylation. DNA methylation is mechanism used by cells to control gene expression and to switch certain genetic functions “on” or “off”. The team examined blood samples of 16,000 people who had taken part in medical studies. some as far back as 1971 and all who had filled out surveys about their lifestyles and habits. The analysis showed a pattern of methylation changes in smokers that affected 7,000 genes or a third of the human genome. The most significant methylation sites were linked to genes with associations to cardiovascular diseases and certain cancers.

Many changes reverted to normal in smokers who had quit for about five years but changes in 19 genes, including the one linked to lymphoma lasted 30 years.

How to grow human lung tissue

There may be hope on the horizon for smokers who have damaged their lungs irreparable. Scientists have managed to grow three-dimensional lung-like tissues in a laboratory.

A team of researcher at the University of California, Los Angeles coated tiny gel beads with stem cells derived from adult lungs. These cells then assembled themselves into the shapes of air sacs found in human lungs. While no one has built fully functional lungs yet, this experiment showed that it is possible to create lung cells arranged in the same spatial way as they do naturally in the human body, the researchers said.

The team will use this artificially grown lung tissue to stud diseases like idiopathic pulmonary fibrosis, a chronic lung disease characterised by scarring of the lungs making it thick and stiff and resulting in shortness of breath and lack of oxygenation in the brain and body. The study was published in the journal Stem Cells Translational Medicine.