A brain embolism can strike suddenly and leave a person severely disabled, but a new US-developed technology used for a year at Hadassah University Medical Center in Jerusalem's Ein Kerem can help. Prof. Jose Cohen, director of the endovascular neurosurgery and invasive neuroradiology unit, is using a kind of miniature "corkscrew" through a catheter in vessels in the brain to extricate the blood clot that clogs them and restore normal circulation. Brain cells are major consumers of oxygen and glucose. When the bloodstream is halted, these cells are irreversibly damaged in less than five minutes. A stroke usually causes a complete cessation of circulation to a relatively small region, where irreversible damage results. But around this region there is an area that continues to be supplied with a small amount of blood. This is called a "twilight zone," and everything is aimed at saving it. The main effort of stroke researchers in the past decade has focused on the search for materials and techniques to slow such peripheral damage until normal blood flow is resumed. About 15,000 Israelis suffer clot-related strokes each year, two-thirds of them over 60. (One of them was then-prime minister Ariel Sharon, who underwent massive surgery that included Cohen.) The rest of the victims are younger, some in their 20s. Of those who survive the initial stroke, about 75% will remain with long-term disability involving movement, feeling, memory or cognition. In some cases the victim may be at risk due to high cholesterol, hypertension and a family history of stroke, but after collapsing, reawakening, feeling weak on one side of the body and having difficulty speaking, the symptoms disappear - only to be followed later by a massive stroke. However, going to a hospital - especially one with a stroke center like Hadassah - at the sign of the first symptom can save lives and prevent permanently disability. While the basic mechanism behind arterial blockage is identical in both stroke and heart attack, advances in treating coronary infarctions did not, until recently, bring about improved treatment of strokes. Today, only one drug called tPA is recognized as useful in increasing blood flow in stroke victims; it can boost the chances for maximal recovery in 33% of victims. But this medication has to be given within three hours of the first symptoms. After that, it is not effective. A few months ago, a group of US researchers reported preliminary results of the "Mercy clot buster," (approved by the US Food and Drug Administration), which pulls the clot out of a vessel like a cork out of a bottle. The catheter is navigated via the blood vessel to the blockage site. As it reaches the clot, the neurosurgeon pushes the hook beyond the end of the catheter, spikes the clot and then pulls it out. In Cohen's attempts to do this on 114 patients, the device succeeded in 61, of whom 20 improved dramatically. Cohen and his colleagues are optimistic about this technology. NEW PLAYER IN FIGHTING VIRUSES A technique for analyzing the function of microRNAs developed by a doctoral student at the Hebrew University of Jerusalem has revealed a new mechanism by which viruses evade the human immune system. The study has major implications. For her work, Naama Elefant, a student of Prof. Hannah Margalit of the HU-Hadassah Medical School, was named one of this year's winners of the Barenholz Prizes for Creativity and Originality in Applied Research. The prize was established by its donor, a leading cancer researcher at the medical school in Jerusalem who is co-developer of the cancer drug Doxil. Elefant's discovery has been declared by Nature Medicine as "one of the 10 notable advances of 2007." MicroRNA genes are very tiny. First discovered in 1993 and at the time considered relatively unimportant, they are now recognized as major players in diverse biological processes. MicroRNAs are important regulators of the production of proteins, which - as the building blocks of cells - must be produced precisely at the right time and place. MicroRNAs latch on to other genes (their targets) and inhibit the production of the protein products of these genes. Hundreds of microRNAs have already been discovered, but the identity of their target genes remains mostly unknown. Elefant developed a computer algorithm that predicts the targets. Her algorithm, named RepTar, searches the thousands of genes in the human genome and through sequence, structural and physical considerations detects matches to hundreds of microRNAs. This technique allowed her to research an interesting group of microRNAs originating in viruses. The presence of microRNAs in viruses raised the intriguing possibility that upon viral infection of a host cell, the virus may use microRNAs as weapons, inhibiting the production of important host proteins. Indeed, the study showed that a viral microRNA inhibits the activity of a gene in the human immune system, making microRNAs important players in the battle between viruses and humans. This was confirmed in collaboration with Prof. Ofer Mandelboim of the same medical school, who showed that this process prevents the recognition of a virus-infected cell by the immune system, thus promoting the virus' survival. Experts say the discovery holds promising therapeutic implications and opens a new direction for anti-viral therapy aimed at inhibiting the viral microRNA. It also offers a possible means of suppressing the immune system in autoimmune diseases and organ transplants by developing synthetic microRNAs that will mimic the action of natural ones.