Biology and management of Bemisia whitefly vectors of cassava virus pandemics in Africa.

Cassava mosaic disease and cassava brown streak disease are caused by viruses transmitted by Bemisia tabaci and affect approximately half of all cassava plants in Africa, resulting in annual production losses of more than $US 1 billion. A historical and current bias towards virus rather than vector control means that these diseases continue to spread, and high Bemisia populations threaten future virus spread even if the extant strains and species are controlled. Progress has been made in parts of Africa in replicating some of the successes of integrated Bemisia control programmes in the south-western United States.

Spatio-temporal patterns of genetic change amongst populations of cassava Bemisia tabaci whiteflies driving virus pandemics in East and Central Africa.

The greatest current threat to cassava in sub-Saharan Africa, is the continued expansion of plant virus pandemics being driven by super-abundant populations of the whitefly vector, Bemisia tabaci. To track the association of putatively genetically distinct populations of B. tabaci with pandemics of cassava mosaic disease (CMD) and cassava brown streak disease (CBSD), a comprehensive region-wide analysis examined the phylogenetic relationships and population genetics of 642 B.

Hyperventilation following head injury: effect on ischemic burden and cerebral oxidative metabolism.

Objective: To determine whether hyperventilation exacerbates cerebral ischemia and compromises oxygen metabolism (CMRO2) following closed head injury.

Design: A prospective interventional study.

Setting: A specialist neurocritical care unit.

Does induced hypertension reduce cerebral ischaemia within the traumatized human brain?

Recent changes in published guidelines for the management of patients with severe head injury are based on data showing that aggressive maintenance of cerebral perfusion pressure (CPP) can worsen outcome due to extracranial complications of therapy. However, it remains unclear whether CPP augmentation could reduce cerebral ischaemia, a finding which might prompt the search for CPP augmentation protocols that avoid these extracranial complications. We studied 10 healthy volunteers and 20 patients within 6 days of closed head injury.

Measuring TMS stimulus/response characteristics from both hemispheres simultaneously for proximal and distal upper limb muscles.

The different types of magnetic stimulators available commercially permit preferential activation of an area of cortex confined to one hemisphere. Stimulating bilaterally may be a desirable means, however, of obtaining information from each hemisphere simultaneously at rest or during a motor task. The aims of this study were to validate and optimize this method by comparing the biophysical and the physiologic features of biphasic with monophasic stimulation from a circular coil.

Acquisition and expression of proximal and distal upper limb stimulus-response curves to transcranial magnetic stimulation.

Motor cortex stimulus-response (S/R) curves are an indication of cortical excitability and are of relevance to topographical mapping. The aims of this study were to compare two different methods of collecting data to construct a S/R curve for transcranial magnetic stimulation (TMS) in the upper limbs, to identify reliable summary statistics for the S/R curve, and to determine whether S/R curves predicted motor threshold. Motor evoked potentials (MEP) were obtained from biceps brachii (BB) and abductor pollicis brevis (APB) muscles at rest with a circular coil centered at the vertex.

How well do we understand the neural origins of the fMRI BOLD signal?

The successful use of functional magnetic resonance imaging (fMRI) as a way of visualizing cortical function depends largely on the important relationships between the signal observed and the underlying neuronal activity that it is believed to represent. Currently, a relatively direct correlation seems to be favoured between fMRI signals and population synaptic activity (including inhibitory and excitatory activity), with a secondary and potentially more variable correlation with cellular action potentials.