Claims dealing with the precipitation in the syringe and infusion route obstruction during continuous subcutaneous insulin infusion (CSII) have increased since the supply of bufferedfast acting human insulin preparation was withdrawn from the Japanese market. When the precipitations encountered in the syringes at our institution were examined under a microscope, they were found to be a conglomerate of amorphous particles such as are seen in isoelectric precipitation. The pH of the insulin solution was found to be slightlydiminished. When the CSII syringe and catheter were examined for dissolution of zinc into the insulin solution the zinc ion content was found to be slightly increased. No bufered fast-acting human insulin preparation is currently available in Japan. It is known that, depending on the preservative, the solubility of insulin decreases in response to an increasing concentration of zinc ions in the insulin solution. The present study suggests that the occurrence of precipitation during CSII may be associated with the dissolution of acidic substances and zinc ions from the syringe and catheter used in CSII.
It has been reported that impairment of glycogen synthase, the key enzyme in glycogen synthesis, could be a genomic marker of NIDDM. Groop et al. identified a polymorphism by Xbal digestion of the glycogen synthase gene. We studied 55 unrelated patients with NIDDM and 40 unrelated nondiabetic subjects with no family history of NIDDM. Using PCR on genomic DNA from the leukocytes of these subjects, we amplified a region of the genomic DNA encompassing the Xbal new cleavage site (an intron 302 base pairs upstream from position 1970 of cDNA) with sense and anti-sense primers;5'CTCTCCGACCTTCTGGACTG3'(1935-1954) and 5'GCTCGTAGGTGAAGTGCTCT3'(2014-2033), respectively. The Xbal new cleavage site in the PCR fragment was found in one of 40 non-diabetic subjects and none of the 55 patients with NIDDM. Therefore, Xbal polymorphism of the glycogen synthase gene is rare in Japanese and can not be used as a genomic marker for Japanese NIDDM.