Ocean Dead Zones, Fossil HIV and Beetle Antibiotics

06 October 2008
Presented by Chris Smith.

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Using your own red blood cells as a Trojan horse to sneak-in chemicals which boost the power of body scans, the spread of ocean dead zones, what a fossil form of HIV can tell us about the origin of AIDS and how beetles create their own antibiotics all feature in this week's Naked Scientists News Flash.  Plus, we get the latest news from the National Cancer Research Institute conference, and discover a 7km train transporting ore across South Africa!

In this episode

Turning blood cells into Trojan Horses

Scientists in Italy have found a way to boost the power of MRI tracer chemicals - by hiding them inside a patient's own cells.

white blood cellsA major problem with contrast agents like iron oxide nanoparticles, which are designed to enhance the signals scanners can pick up from certain tissues is that the agents are rapidly diluted out or picked up and excreted from the body.  Now University of Urbino researcher Mauro Magnani and his team, writing in the Journal of Nanoscience and Nanotechnology, has found a solution.

The researchers first incubate a sample of a patient's red blood cells in a solution containing the nanoparticle-contrast agent.  Crucially the concentration of the solution is adjusted to make it more dilute than blood plasma.  This makes the cells swell up as water moves into them due to the process of osmosis.  As this happens the cell membranes become leaky allowing the iron oxide nanoparticles to enter.  When the concentration is later returned to normal the cells shrink but the nanoparticles remain trapped inside.

The blood can then be re-infused into the patient where the red cells, carrying their contrast cargo, remain in circulation for the rest of their normal lifetime, which can be up to 120 days.  This should enable doctors to make repeated measurements on patients over time, but without needing to top up the contrast.  It could prove useful in spotting signs of internal bleeding, for instance post-surgery.

The italian team have signed a deal with Phillips research to pursue the work, which has not yet been tested on humans although the contrast agent itself has and is safe.

Marine "dead zones" could be even larger than thought

Crabs and other crustaceans in the ocean could be the first to suffocate in the increasing number of marine "dead zones" in the world, areas where there is little or no oxygen. What's more, the extent of oxygen deprivation in the oceans could be much larger than previously thought.

These are the findings of a study from Mediterranean Institute for Advanced Studies in Spain published by Raquel Vaquer-Sunyer and Carlos M. Duarte in the journal PNAS this week which looked at how well different types of bottom-dwelling marine creature can tolerate lowered levels of oxygen in the water in the laboratory.

Picture of the sea floor in the Western Baltic covered with dead or dying crabs, fish and clams killed by oxygen depletion © Kils @ Wikimedia

The researchers searched through hundreds of other previously published studies of two hundred different species to investigate exactly what the threshold level of oxygen is for life in the oceans to be sustained.

What they found was that there is quite a range in the tolerance of different species to restricted oxygen. Some like the American Oyster can put up with virtually no oxygen, while others are much more sensitive - the young larvae of the rock crab will die if there is less than 8.6mg of 02 in every litre of water.

The problem of lowering levels of oxygen in the oceans stems mainly from a process known as eutrophication, which is triggered by nutrients - mostly agricultural fertilisers - washing off land and into coastal waters. Higher levels of nitrates and phosphates cause algal blooms, both of large seaweeds and single celled phytoplankton. When the algae die they sinks to the seabed where bacteria break them down, using up all the oxygen in the water and leading to the so-called "dead zones".

Climate change may also make the problem worse since warmer water holds less oxygen.

A study published earlier this year in the journal Science revealed that there has been an exponential increase since the 1960s in the number of "dead zones" in the world, which currently cover around 245,000 square kilometres.

That study defined dead zones based on a threshold level of around 2 mg of oxygen per litre. What this latest study now suggests is that the threshold could in fact be as high as 4.6 mg of O2 per litre, which would meant the total extent of marine dead zones could be far greater than was previously thought.

All in all, this means that we made need to think again about the health of the oceans and for water quality standards to be set accordingly to tackle the increasing extent of marine dead zones.

Fossil AIDS virus

An international team of scientists have found new evidence pointing to 1908 as the year when HIV was born.  Writing in Nature this week, University of Arizona researcher Mike Worobey describes how he and his colleagues uncovered traces of a fossil form of HIV in tissue samples collected in Africa nearly 50 years ago.

HIV Viruses
HIV viruses in green budding from a lymphocyte © Centers for Disease Control and Prevention

Working with scientists in the Democratic Republic of Congo, which was historically a Belgian colony, the team gained access to a collection of old biopsy specimens and tissue samples dating from 1960.  The material had been chemically "fixed" and embedded in paraffin, which had helped to preserve it in reasonable condition.  The researchers dissolved away the wax and were able to extract genetic material from the samples, which they they then probed for signs of HIV.  In one of the extracts, which was from a lymph node biopsy, they struck gold.  The sample contained a virus frozen in time, giving the researchers a window back in time to the structure of HIV as it was in the 1960s, twenty years before the world even knew it existed.

The team then compared the genetics of the virus with those of another fossil sequence, uncovered several years ago in a blood sample collected in 1959.  The two viruses were significantly different from one another, arguing that HIV had potentially been circulating and evolving in the human population for much longer than thought previously.  According to Mike Worobey, "our best estimate for when HIV entered humans is 1908, but it might have been from 1884 to 1924."  Either way, what's unarguable is that these dates are slap bang in the middle of the time when the first European settlers arrived and founded large cities like Leopoldville (now Kinshasha), and the team suspect that the high population density, debaunchery and risky behaviour that tends to go on in cities was probably the catalyst that unleashed HIV on the human population.

Beetles use antibiotics to protect their food

Beetles use an antibiotic new to science to protect their fungal food stores from attack by other fungal invaders.  That's according to a new study published this week in the journal Science by a team of researchers led by Jarrod Scott from the University of Wisconsin Madison.

Southern pine beetles are a major pest in the southern United States where they infest pine trees and cause millions of pounds of damage.  The adult beetles dig tunnels under the bark of pine trees, and infest them with a particular strain of fungi, called Entomocorticium, which they carry in a special pouch called a mycanjium.  The beetles then harvest the fungus to feed to their growing larvae.

It was already known that the Entomocorticium fungus the beetles carefully farm can be outcompeted by another fungus called Ophiostoma, which disrupts the development of young beetles because they don't have enough food.  What Scott and his team have discovered is that the beetles play host to two types of bacteria that produce antibiotics which keeps the invading fungus at bay, but which leave the beneficial food fungus alone.

Using a scanning electron microscope they scrutinised the beetles and their homes and it was noticed that the tunnels dug by the beetles in the pine bark were filled with a type of bacteria called actino-bacteria that no-one had noticed before.  The researchers  also found the bacteria inside the mycanjium pouches of the adult beetles, where they carry the food fungi.  They tested the effects of the bacteria and showed that the invading fungus is 20 times more susceptible to it than the food fungus.

This is the first time that beetle has been shown to seek out the help of not just the food fungus but also the bacteria to protect it. 
Back in 2006, leaf cutter ants were discovered to do something very similar, using home-made antibiotics to protect the colonies of fungus that grow on leaf clippings inside their nests.  Future research targeting the bacteria and antibiotics used by the Southern Pine Beetles could provide a brand new way of dealing with the pest beetle and others like it.

13:17 - News from the NCRI Conference

This weekend saw the National Cancer Research Institute conference in Birmingham, and our very own Kat Arney went along to bring us all the latest news from the front line in the war against cancer...

News from the NCRI Conference
Kat Arney

Kat - I'm here at the NCRI conference, that's the National Cancer Research Institute which is an organisation which brings together all the funders of cancer research here in the UK. That's people like the government, charities all sorts of organisations that are funding cancer research.  The conference is really a fantastic opportunity to showcase what's going on in the world of cancer research. We've got everyone from people doing the really fundamental lab research. We had a talk this afternoon from Professor Tony Kouzarides from Cambridge University who's looking right at the sort of molecular post-it notes that are put on our DNA that are important in cancer. Right now we're sat above the lecture theatre and there's someone talking about the importance of dying with dignity when people come to the end of their journey with cancer. There's going to be everything from the very basic research through to the much more quality of life, patient care areas.

Normal (left) versus cancerous (right) mammography image.Chris - What's the problem with the UK allegedly not doing so well with the cancer stakes compared with the rest of Europe?

Kat - Exactly. The first lecture today was from Professor Michel Coleman from the London School of Hygiene and Tropical Medicine. He's one of the world's leading epidemiologists. That's someone who studies the statistics and the populations to do with cancer and he was pointing out there have been a lot of studies. These Eurocare studies that have shown that Britain pretty much is one of the sick men in Europe. In terms of football league tables we're drifting towards the relegation zone. This is happening for a number of reasons. For a start the Eurocare studies are using relatively old data. In fact, here in the UK around the year 2000, 2002 we brought in a cancer plan. We are turning around what we're doing but it has shown that the UK has been falling behind. It's not actually what people think. It's not about access to drugs. It's actually really to do with early detection. That was one of the most interesting results hat he showed. When you look at five year survival rates across Europe (this is the standard bench mark that people use for how many people survive that long). If you take out from those statistics all the people who die from cancer within a year, that's people who die from very late/very advanced tumours, if you take those people out of the equation Britain comes back in line with the European average. This tells us that in fact in Britain our major problem is diagnosing cancer early.

Chris - Why is that?

Kat - There's a number of reasons. It's obviously a problem with just educating people. We need to get more information out there about what the symptoms of cancer are and that people should not just get the stiff upper lip and think it'll probably go away if I ignore it. Go to the doctor. There's also an issue with educating the GPs as well to spot when someone presenting with certain symptoms may have cancer. You'd think well cancer is a relatively common disease but actually GPs may only see six to ten patients a year who actually do have cancer in a list of 2-3000 patients. It's not really that common for each GP so we need to do more in education for GPs and the public. Also more in things like CT scanning, MRI scanning to try and get cancer detected as early as possible.

Chris - Also in the news this week is a story about how computers can help to read mammograms which might help to bring out the prediction and detection rates.

Kat - Exactly and this ties in to the whole early detection thing. In the Uk we have a fantastic system of breast screening run by the NHS and it does save thousands of lives. It invites all women in their fifties from fifty to seventy to go for a mammogram every three years. Every mammogram is read by two doctors; two radiologists look at it, look for any dodgy spots and decide whether to call the woman back or not. Now what these researchers, led by Professor Fiona Gilbert at the University of Aberdeen, have shown is that you can use one doctor and a computer-aided detection system. How this works is the computer system scans through the mammogram, spots anything that it thinks looks suspicious and then the doctor looks at it and goes, ' Yep, that looks dodgy...no, that's just an area of fluff or whatever.' Then you only need to have one doctor's time per mammogram. Basically you're holding the workload for doctors. This is really important because in some areas of the country we're seeing screening - the interval of screening is meant to be 3 years - but we're seeing it drift out to three and a half, four years. There simply aren't the resources. This could be a really great way to get more women screened and to help ease the pressure on screening services.

Chris - Which would be very good for affecting that diagnosis detection problem.

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