RESUMEN
A new setup for high precision, automated secondary pH measurements together with a reference measurement procedure has been developed and tested in interlaboratory comparisons using buffers pH 4.005, pH 7.000, and pH 10.012 at 25 °C and 37 °C. Using primary buffers as standards, a standard uncertainty in pH better than 0.005 can be reached. The central measuring device is a one piece, thermostatted cell of PFA (perfluoroalkoxy) with a built-in Hamilton(®) Single Pore™ Glass electrode. Due to its flow-through principle this device allows pH measurements with low consumption of measurement solutions. The very hydrophobic and smooth PFA as construction material facilitates complete emptying of the cell. Furthermore, the tempering unit affords very precise temperature control and hence contributes to the low target uncertainty of the produced secondary buffer solutions. Use of a symmetric measurement sequence and the two point calibration was sufficient to reach high precision and accuracy.
RESUMEN
Mast cell proliferation has been reported in peripheral nerves of streptozotocin diabetic rats. We examined the question by light microscopy using morphometric techniques including estimation of shape and size. After 4 weeks of diabetes the mast cell area in transverse sections was 32.7 +/- 7.0 microns 2 vs. 22.5 +/- 5.4 microns 2 in controls (P less than 10(2)). Mast cell profiles approximated to ellipses in longitudinal sections, the long diameter being 11.4 +/- 1.2 microns vs. 14.0 +/- 1.0 microns in controls (P less than 10(4)). Correspondingly, the profile number was increased (30 +/- 6%) in longitudinal sections and decreased in transverse sections (11 +/- 16%). The present study does not provide evidence for mast cell proliferation in peripheral nerves in experimental diabetes, and, furthermore, underlines the need of evaluation of dimensions in studies of particle numbers.