Wu's Method Research Articles

A picric acid blood-sugar method after zinc precipitation.

Abstract The Myers-Bailey modification of the Lewis-Benedict picric acid method of blood-sugar estimation has been further modified to include zinc as a protein precipitant. In the present study the zinc precipitation was found to remove on the average 21 mg. of nonglucose reducing substances. Thus modified the method appears to give results which approach the values for the true sugar content of the blood. The figures reported are still a little higher than those obtained by the Folin- Wu method on the zinc filtrate, but the agreement with the Benedict copper method (II) is close. Certain advantages of the picric acid method of blood-sugar estimation are discussed.

A Note on the Distillation of Ammonia in the Folin and Wu Method for the Determination of Urea in Blood

A simple modification of the distillation procedure in the Folin and Wu method for the routine determination of urea in blood has proved extremely helpful for our hospitals. The changes proposed resulted from an attempt to overcome the trouble which some workers, particularly students and others of little experience in the laboratories, had encountered with the distillation process of the original method. The principal causes of difficulty were (1) frothing in the distillation tube with the carrying over of some of the contents, (2) sucking back of the distillate, and (3) blowing out of the distillate from the receiving tube by steam as a result of too rapid distillation. Elimination as far as possible of these potential sources of error in the original procedure has met with considerable success. We have abandoned the use of the loosely fitting rubber stopper on the long arm of the bent glass tubing to hold the 25 cc. graduated receiving test tube* in position. Instead, we place this test tube in a 600 cc. beaker filled with cold water and bring it into place for distillation by raising the beaker so that the end of the glass tubing comes well below the surface of the 0.05 normal hydrochloric acid in the receiving test tube. The beaker is held in position during the distillation by a wooden block of suitable size.

Plasma protein fractions in normal pregnancy, labor, and puerperium

A cumulative study has been made of the various protein fractions in the blood plasma of normal nonpregnant, pregnant, parturient, and puerperal women, using the Wu method of analysis. It was hoped to relate the changes in some one fraction, globulin or fibrin particularly, with the changes in watery dilution of the blood during the reproductive cycle. The curve developed for fibrin corresponds rather closely with that for plasma volume percentage, and it is suggested that perhaps the dilution of the plasma may be directly related to the increase of fibrin, although it is thought that other factors may have a rôle. The cause of the fibrin increase is admitted to be unknown, but not much consideration is given to the idea that it may be the result of a mild gestational injury to the liver. The accurate relationship between the rise in fibrin and the increased sedimentation rate of the blood cells, in the absence of any similar changes in the globulin fraction, leads us to agree with those who believe that the latter is the result of the former, the increased agglutination of the red cells into rouleaux being an intermediate and necessary stage for the increase in sinking velocity. There is a rise of globulin on the third day after delivery which may be directly associated with the onset of milk secretion.

The determination of galactose in the presence of glucose

Folin and Wu's method for blood-sugar has been adapted to the determination of galactose glucose mixtures. The method is based on the fact that copper solutions of different alkalinities give different reduction values for galactose, but the same for glucose. It was also found that Bertrand's as well as the Myer-Benedict method give the same reduction values for glucose and galactose. The use of the latter methods in combination with that of Folin and Wu is unsatisfactory due to errors that may be introduced by the discrepancies for glucose values obtained on the same blood.