Starting to breed late in life is a bad idea if you want to maximise the number of offspring that you produce - or so the theory goes.

But doubt has now been cast on this hypothesis - one of the biggest assumptions in behavioural ecology - by researchers from the universities of Bristol and Cape Town and published today in Current Biology.

University of Cincinnati (UC) neuroradiologists believe a brain imaging approach that combines standard magnetic resonance imaging (MRI) scans with specialized contrast-enhanced techniques could lead to more effective diagnoses in patients with difficult-to-detect blood clots in veins of the brain.

James Leach, MD, reports these findings in the April issue of the American Journal of Neuroradiology. This is the first study to correlate the clinical importance of data gleaned from standard MRI scans and detailed contrast-enhanced imaging techniques in patients with chronic thrombosis (blood clots) in veins of the brain.

There are two types of screening programs – proactive and opportunistic. Proactive screening uses population registers to invite people to be screened at regular intervals, while opportunistic screening targets people attending health services for unrelated reasons.

The value of opportunistic chlamydia screening is being called into question.

Seasonal nomadism, migration, and resettlement have always been important for the people living in the northern Polar Regions as these movements are key for their survival. In the past, such movements were usually triggered by the local conditions which their continued existence is affected by activities such as aggregation in temporary winter villages near the sea ice for seal hunting and summer dispersal inland looking for wild reindeer.

Population movements and concentration have, since the 20th century, been more affected by outside factors such as the changes in policies reflecting market or state policies without a local character. The shift is causing damage to the social fabric of these societies.

Virginia Commonwealth University researchers have decoded the genome of a bacteria normally present in the healthy human mouth that can cause a deadly heart infection if it enters the bloodstream.

The finding enables scientists to better understand the organism, Streptococcus sanguinis, and develop new strategies for treatment and infection prevention.

Researchers at Johns Hopkins have discovered how cells fine-tune their oxygen use to make do with whatever amount is available at the moment.

Too little oxygen threatens life by compromising mitochondria that power it, so when oxygen is scarce, cells appear to adjust by replacing one protein with an energy-efficient substitute that "is specialized to keep the motor running smoothly even as it begins to run out of gas," says Gregg Semenza, M.D., Ph.D., a professor of pediatrics and director of the vascular biology program in the Institute for Cell Engineering at Hopkins. "This is one way that cells maintain energy production under less than ideal conditions." A report on the work is in the April 6 issue of Cell.