Bacterial bioshield could keep HIV at bay
A LIVING microbicide reduces HIV-like infection in monkeys, and might one day provide women with long-lasting defence against the virus.
Dean Hamer of the National Institutes of Health in Bethesda, Maryland, and colleagues engineered naturally occurring vaginal bacteria to produce the anti-HIV protein cyanovirin-N.
They applied a gel containing the bacteria to the vaginas of rhesus macaques before infecting them by the same route with a hybrid of SIV and HIV. The engineered bacteria cut the infection rate by 63 per cent (Mucosal Immunology, DOI: 10.1038/mi.2011.30).
Human females have 10 times as much of the bacteria as female macaques, so the engineered bacteria could reduce infection rates even more dramatically, says Hamer. Clinical tests could begin in a few years after safety testing.
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Gastric bypass creates a healthier appetite
Here's a piece of good news for people who have had a gastric bypass – not only will you eat less, you may also start to eat more healthily.
The most common form of bariatric – anti-obesity – surgery is the "Roux-en-Y" gastric bypass, which involves stapling the stomach so a small pouch is made at the top, which is then connected directly to the small intestine. This bypasses most of the stomach and the duodenum so the patient feels full quicker .
The vertical-banded gastroplasty is an alternative technique which reduces the volume of the stomach without bypassing any part of the intestine, restricting how much the patient can eat at any one time.
After people undergo gastric bypass operations, it is not uncommon for them to report that their eating habits have changed. To investigate these claims,Carel le Roux and colleagues from Imperial College London asked 16 people who had undergone either type of bariatric surgery six years before to fill in a survey about their dietary preferences after the operation.
People who had had a gastric bypass reported eating a lower proportion of fat after surgery than those with a vertical-banded gastroplasty.
Low-fat rats
To find out why this was so, the team carried out either a gastric bypass or a sham operation on 26 rats.
They found the rats with the gastric bypass ate less and regained less weight after recovering from the surgery than the others. In just 10 days after the operation, the gastric bypass rats had, on average, increased the proportion of low-fat food in their diets by a factor of four.
In a separate experiment, researchers gave other post-operative rats sugar water while infusing corn oil directly into their stomachs. This meant that their digestive system encountered fat but the animals had not tasted it. The bypass rats learned to avoid the water nevertheless, but the sham-operated rats did not. This suggests that the preference for low-fat food may have been a result of the bypass rats finding it harder to digest high-fat food after the operation, rather than it somehow affecting their sense of taste.
It's their hormones
Le Roux's team also found that levels of hormones which promote satiety – such as glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) – were higher in rats with a gastric bypass after eating than in the sham-operated rats.
"After gastric bypass operations in both humans and rats these hormones are greatly elevated," says le Roux. "GLP-1 may be important when it comes to food preferences." The hormone, which promotes insulin production, is already used to treat diabetes. "We are currently doing studies to see if it can be used to tackle obesity" says le Roux.
"A gastric bypass is a free injection of GLP-1," says bariatric surgeon Richard Welbourn, a member of the Royal College of Surgeons in the UK, who was not involved in the study.
"When patients say 'I don't like fatty foods any more,' we can now say this effect has a real physiological basis," says Welbourn. "Gastric bypass is a profoundly effective operation. We're operating on the gut, but we're changing the brain."
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IVF success rates boosted by a bed of nails
SOME recent newborns conceived through IVF may owe their existence to the fact that they spent their first few days resting on a bed of nails.
In vitro fertilisation occurs in a dish. After a few days of culturing, the fertilised egg is implanted into the uterus. But, clearly, a dish is an unnatural environment for a fertilised egg to spend its first days, says Gary Smith at the University of Michigan, Ann Arbor.
"The idea is to ask how embryos develop in the body and copy that in the laboratory," he says. His team has focused on mimicking the pulses of nutrient-rich fluid sent washing over the embryo by muscle contractions within the fallopian tubes.
To do this, they created a plastic chip containing a small well to house the embryo. The bottom of the well sits in a network of 30-micrometre-deep channels filled with a nutrient and hormone-rich medium. Underneath these channels is a flexible polymer, and beneath this an array of moveable pins taken from an electronic Braille display (see diagram) . The pins can be made to move up and down, pushing up the flexible polymer and squeezing the channels to send pulses of medium washing over the embryo.
To find out whether their device offered advantages over dish culture, Smith's team recruited 25 women who were undergoing IVF treatment. Each woman produced between eight and 20 eggs that were successfully fertilised in the lab. The group then put roughly half of these 315 embryos in the new system to culture, and half in the traditional static system.
Two days later, the group looked at markers of embryo quality, such as the number of cells. The results suggest that the new system boosts embryo quality: 39 per cent of embryos cultured this way were graded as top quality compared with 29 per cent of those in a dish. The team also found that a zygote's chance of developing into a good quality embryo - a step below top quality but still suitable for implantation - was 1.6 times higher if it had been cultured on a bed of pins.
The top quality embryos from both systems were implanted into the women, some of whom went on to have successful pregnancies, which were not tracked. "The general consensus is that this system will translate into better pregnancy rates, but we need to study these [pregnancies] before recommending the system," says Smith, who presented the findings at the European Society of Human Reproduction and Embryology annual meeting in Stockholm, Sweden, this month.
The moving pins may be crucial, says Michele Boiani, an embryologist at the Max Planck Institute for Molecular Biomedicine in Münster, Germany. Boiani recalls once driving a number of mouse embryos to another lab. "The 'highway mouse embryos' developed better than the ones I had left as controls in the static incubator," he says.
