Peripheral, but not central, axotomy induces neuropilin-1 mRNA expression in adult large diameter primary sensory neurons.

Neuropilin-1 (NP-1) is a component of the receptor for semaphorin3a (Sema3a), a member of a large family of molecules with widespread expression and demonstrable influence (via their ability to repel growing axons) on nervous system development. Recent studies have shown that some types of adult mammalian neurons retain the capacity to respond to Sema3a, particularly in relation to neuronal injury and regeneration. Although variations in expression of Sema3a mRNA have been revealed in neurons in both the central and peripheral nervous systems in this context, relatively little is known about NP-1 expression patterns. In this study we investigated the expression of NP-1 mRNA in adult dorsal root ganglion (DRG) neurons in intact and lesioned animals. We compared the effect of unilateral lesioning of the sciatic nerve or unilateral dorsal rhizotomy at lumbar levels L4/5, and bilateral dorsal funiculus lesioning at thoracic levels T10/11 on NP-1 mRNA expression in the cell bodies of lumbar DRGs. A significantly increased level of NP-1 mRNA expression was detected only following sciatic nerve lesioning (P < 0.001), but not after rhizotomy or dorsal funiculus lesioning. Furthermore, this upregulation was mainly confined to large diameter neurons of DRGs at lumbar levels L4/5, which provide the main sensory contribution to the sciatic nerve. These results suggest a role for NP-1 in the axonal response to peripheral nerve injury, which may be specific to a particular subset of primary sensory neurons.

Phlebitis associated with peripheral cannulae.

Observation of the cannula is imperative in detecting early signs of phlebitis. To maintain high standards of cannula care, nurse education is important, along with regular auditing of the incidence of phlebitis. Careful consideration should be given to the size of cannula used and the position in which it is sited. Use of Vialon cannulae may be preferable to Teflon.

Minimisation of sensitivity losses due to the use of gradient pulses in triple-resonance NMR of proteins.

The use of pulsed field gradients in multiple-pulse NMR experiments has many advantages, including the possibility of obtaining excellent water suppression without the need for selective presaturation. In such gradient experiments the water magnetization is dephased deliberately; exchange between the saturated protons of the solvent water and the NH protons of a protein transfers this saturation to the protein. As the solvent is in large excess and relaxes relatively slowly, the result is a reduction in the sensitivity of the experiment due to the fact that the NH proton magnetization is only partially recovered. These effects can be avoided by ensuring that the water magnetization remains intact and is returned to the +z-axis at the start of data acquisition. General procedures for achieving this aim in any triple-resonance experiment are outlined and two specific examples are given. Experimental results confirm the sensitivity advantage of the modified sequences.

Improving solvent suppression in jump-return NOESY experiments.

The problems associated with solvent suppression in jump-return NOESY spectra and in particular the difficulties experienced with using short mixing times are examined. It is shown that the degree of water suppression depends critically on the extent of radiation damping of the water magnetisation during the mixing time of the NOESY sequence. A new jump-return NOESY sequence is proposed which incorporates field gradients and which achieves good levels of water suppression for all values of the mixing time, and for all increments of the NOESY experiment.