A simplified device for injection of paraffin wax blockades

Microperfusion of renal tubules and microvessels in vivo requires occlusion of the lumen with a reliable blockade. Paraffin wax serves this purpose but requires specialized hydraulic or mechanical devices to stably hold a micropipette while this solid material is extruded through micron-sized tips. This communication describes the construction of a simple and very inexpensive wax injector from commercially available parts. The rear of an aluminum holder is threaded so that a thumbscrew can be used to push a stiff wire into the lumen of a micropipette. A solder cast of the micropipette lumen is employed as a tight-fitting piston to generate the high pressures required for wax extrusion. Several wax injectors can be made at negligible cost. This device has been used in this laboratory to introduce over 1,000 wax blocks into papillary vasa recta.