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        PRIONS? Are they crunchy, fried snacks? Or, one of those gaudy clothes turned out by fashion designers? Wait, before letting the imagination run riot, look at the dictionary. The word has two meanings - a) An infective protein in human cells causing brain diseases, and b) A rare bird from Arctic regions seen in Tasmania.

But it is the human prions that should interest us all for at stake is the health of millions of youth and adults worldwide. For insightful views on a range of neuro-degenerative diseases caused by self-mutating prions, one has to listen to Nobel Laureate Professor Stanley B Prusiner from the University of California, San Francisco (UCSF) whose more than two decades of research on prions, a term he coined in 1982, fetched him the coveted prize for Medicine in 1997.         Prions are single proteins without nucleic acid and they are completely different from other pathogens like virus, bacteria and fungi, Prusiner says at an interactive meet before he delivered the 27th T S Srinivasan endowment lecture in Chennai yesterday. They can manifest as genetic illness in humans that is spontaneous, sporadic and infectious in nature.         Humans are struck by three prion diseases - Creutzfeldt-Jakob disease (CJD), its two variants Gerstmann - Straussler - Schienker (GSS) and Familial Insomnia (FI), besides Kuru found in cannibals. After the raging epidemic of Mad Cow Disease - bovine spongiform encephalopathy (BSE) - that began from Britain to spread across Europe, the CJD variants that appeared in teenagers and young adults in 1995 created a big scare in the UK, he informs.

Stanley B Prusiner

        But first more on MCD. This prion disease affected cattle in late 1970s due to three main reasons. High cost of energy (hit by oil crisis) needed to rear cattle; parts of sheep offal as feedstock for cattle; price rise of meat cholesterol used in cattle rearing with the cost of organic solvents going up. All these coincident amplified the spontaneous cases of BSE that broke across the cattle farms in the UK, Prusiner explains. The transmission of MCD from cows to humans created a health panic in Europe in early 1990s disrupting the process of safe blood supply. Both CJD and MCD prions have identical effects on 'bovinised' and humanised mice, thus showing the pathology of different prions have the same genetic mapping.

        The rogue protein is capable of stimulating and converting normal-shaped proteins continuously, which over time affects the nervous system which is vulnerable to prions. 'We are yet to understand fully the evolutionary process of prions in human cells. At present clinical trials for treatment is underway at UCSF, even as search is on to find a reliable therapy and drug for such degenerative illnesses,' he explains. However, it is widely understood alpha and beta changes of helices (molecular layers) of proteins created prions which once formed siphoned off healthy proteins into misshapen state in a continuous process.

        Dr Krishnamoorthy Srinivas, chairman, Institute of Neurological Sciences, VHS, Adyar, informs the discovery of prions and the disease creating mechanism opened a window for treatment and cure of such neurological disorders. Drawing a parallel between Alzheimers, Parkinson's and prion diseases, Dr Srinivas explained all the three neuro disorders affected the aged populace with memory loss and slow onset of cognitive impairment.