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OOPS MALARIA RESEARCH

Ronald Ross won the 1902 Nobel prize for discovering the role of the mosquito in the parasite life cycle, but his later work on mathematical models for the study of its epidemiology was perhaps even more impressive. The Ross malaria model, still referred to, assumes that humans have an equal chance of a mosquito bite, and that infection clearance is unaltered by re-infection. We now know that some people are bitten more often than others, and that repeat infections slow parasite clearance. These and other new data have been incorporated in a mathematical framework to update the Ross model for the twenty-first century. Combined with data on over 90 communities infected by malaria, this reveals that variations in biting and/or susceptibility to infection are key factors determining the prevalence of infection: 20% of people receive 80% of all infections. This finding can be used to direct malaria controls at those most likely to benefit.

(2) When our eyes are presented with incompatible images, our conscious perception fluctuates spontaneously between each monocular view. The nature of the resulting 'binocular rivalry', and how the brain resolves it, is the subject of a long-standing debate that touches on fundamental aspects of human cognition such as attention and selection. Now a neural signature characteristic for binocular rivalry has been identified, at the very earliest stages of visual processing, in the human lateral geniculate nucleus (LGN). This region of the brain contains cells that respond only to stimulation of one or other eye, and the signals in the LGN closely reflect the perceptual dominance seen during binocular rivalry.

(3) Despite the presence of dozens of objects in the environment, our awareness is limited to only three or four objects at any given time. Because of this extreme limitation, we need to be able to control what reaches awareness so that only the most relevant information in the environment consumes this limited mental resource. A study of brain activity in subjects performing a task in which they were asked to 'hold in mind' some of the objects and to ignore other objects has revealed significant variation between individuals in their ability to keep the irrelevant items out of awareness. This shows that our awareness is not determined only by what we can keep 'in mind' but also by how good we are at keeping irrelevant things 'out of mind'. This also implies that an individual's effective memory capacity may not simply reflect storage space, as it does with a hard disk. It may also reflect how efficiently irrelevant information is excluded from using up vital storage capacity.

(4) Many kinds of enzymes need to protect their substrates from unwanted hydrolysis. Koshland proposed more than 40 years ago that these enzymes — he was looking specifically at hexokinase — adopt the catalytically competent conformation only when the appropriate substrates are bound and produce an 'induced fit' conformational change. Later work showed that it is indeed 'induced fit' that stops hexokinase from hydrolysing ATP when there is no glucose about. Structural studies of the large ribosomal subunit now show that a similar fit mechanism operates here too. This provides the answer to the long-standing question of how the nascent peptide in the P site of the ribosome avoids hydrolysis by peptidyl tRNA until the termination step of protein synthesis. This mechanism may well have been available to the ribozymes in an RNA world before proteins came on the scene.

Posted by: happie01 Posts: 48 :: 08-10-2006 :: | Reply to this Message

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OOPS MALARIA RESEARCH

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