How marijuana clouds the memory

THE link between marijuana and memory loss is well known, but now scientists have found exactly how the drug causes forgetfulness.

Marijuana impairs users' working memory - the ability to retain and use information over short periods of time - a major downside of the medical use of marijuana.

The researchers say the discovery, published in the scientific journal Cell yesterday, could help scientists create medical marijuana that does not impact on a person's memory while still treating their pain.

They said the knowledge of how memory was affected could also be applied to other cells, to help other memory-loss concerns. "We may find a way to deal with working memory problems in Alzheimer's," the researchers said.

French and Canadian neuroscientists found that marijuana users suffered memory loss because the main psychoactive ingredient, THC, affects the support cells of neurons, known as astroglial cells, but not the neurons themselves, as previously thought.

"We have found that the starting point for this phenomenon - the effect of marijuana on working memory - is the astroglial cells," study researcher Giovanni Marsicano said.

The researchers made the discovery after initially investigating why receptors that respond to both THC and signals naturally produced in the brain were found on astroglial cells.

"The study shows that one of the most common effects of cannabinoid intoxication is due to activation of astroglial CB1Rs (cell receptors)," the researchers say.

University of Adelaide pharmacologist Associate Professor Rod Irvine said the effect of marijuana on short-term memory loss was related to dosage. "The heavier the use, the more likely it is to have an impact on memory," he said. "It's probably not going to have an effect on light or occasional users."

Australians are among the world's biggest potheads. A study released late last year found that as many as 14.8 per cent of people aged 15 to 64 had used the drug at least once in the previous year.

Marijuana is not prescribed for medicinal use in Australia, but Prof Irvine said it was a common excuse for many recreational users of the drug.

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World’s first biodegradable joint implant grows new joints

Joint replacements have a big history of failure so we can only hope that this version works well

Joint implants should always be made of materials like titanium, so they can last the lifetime of the patient ... right? Well, not according to researchers at Finland's Tampere University of Technology. They've developed a product known as RegJoint, which is reportedly the world's first biodegradable joint implant. Unlike permanent implants, it allows the patient's bone ends to remain intact, and it creates a new joint out of their own tissue.

In arthritic joints, the cartilage that protects the connecting ends of the bones has become compromised. This allows the bones themselves to grate against one another, causing pain and reducing the joint's range of movement. A traditional permanent implant replaces the ends of the affected bones with low-friction man-made material.

RegJoint, however, takes a different approach.

The implant has been in development since the mid 90s, and is intended for use in the small finger and toe joints of osteoarthritis and rheumatoid arthritis patients. It is made from a polylactide copolymer, and is inserted within the joint capsule of the affected digit.

Once in place, it reduces pain by acting as a cushioning spacer between the exposed bone ends, while also also restoring a reasonable range of movement, and keeping the already-compromised cartilage from being damaged further. Additionally, however, it triggers the body to produce new fibrous tissue, which proceeds to gradually replace the implant. According to the university, all that's left eventually is a fully-functioning "neojoint," made from the body's own cells.

Recently, RegJoint received CE Mark approval, which will allow it to be sold within Europe - it has already been used in over 200 patients, in clinical trials. Assisting in its development were Conmed Linvatec Biomaterials and Scaffdex Ltd., which is now bringing the implant to market.

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