Method for the determination of immune complexes by reaction with polyethylene glycol

A study of circulating immune complexes was carried out using a reaction with polyethylene glycol. The method turned out to be simple, highly sensitive and affordable for any clinical laboratory with a photoelectric colorimeter. Analysis of the survey data of 115 healthy donors, 63 patients with rheumatoid arthritis and 16 patients with systemic lupus erythematosus made it possible to establish the level of circulating immune complexes in health and disease. The circulating immune complexes were studied in patients with rheumatism and chronic tonsillitis. To assess the results of the reaction, human aggregated gamma globulin (manufactured by Kazan NIIEM) was used.

Collaborative Study of Rapid Methods for Alkaline Phosphatase in Milk and Cream

Determination of alkaline phosphatase activity in milk and cream by the modified Scharer rapid test with use of photoelectric colorimeter for measuring absorbance was collaboratively studied. Milk samples (skim milk. milk and cream) with and without added raw milk were sent to 12 collaborators to be tested by (a) the modified Scharer rapid test using commercial standards and phenol standards for comparing colors, (b) the rapid colorimetric test and (c) the Rutgers method. The latter method was used for comparison only. In the modified Scharer rapid test, based on the category of standards, 73.3% of the samples using the commercial standards and 71.6% of the samples using phenol standards were correctly diagnosed. When the scoring was based on positive or negative, 98.4 and 92.6% of the samples were correctly diagnosed. Results with the phenol standards were significantly lower than those observed with the commercial standards. There were no false-positive results, as all incorrect readings were below limit of detection. Most of the errors occurred when the expected value was 1.0 μg phenol/ml. Results were 100% correct for the Rutgers method, but there are only two choices for this method, and they correspond to positive or negative. Compared to the theoretical values, data obtained by the colorimetric method ranged from 1.5 to 18.1% high, with a coefficient of variation of 4.4 to 13.4%. These variations were assumed satisfactory considering the levels at which phosphatase was tested.

Rapid Colorimetric Test for Alkaline Phosphatase in Dairy Products

The Scharer rapid test for measuring alkaline phosphatase activity in milk and milk products was modified to include a photoelectric colorimeter in place of visual observation of color. Dairy products containing various amounts of added enzyme (3–15 μg phenol/ml or g) were prepared for analysis as per standard methods and analyzed by the rapid colorimetric test. A linear relationship was found between the percent of raw milk added and the enzyme activity with a correlation coefficient (r) range of 0.963 to 1.000. Hydrolysis of the substrate (disodium phenyl phosphate) by the surviving enzyme in different dairy products was similar. Recovery of the added enzyme varied, depending on the nature of the product. The method is quantitative, reproducible, and can be used as a rapid confirmatory procedure. Similarly, this method was applied to differentiating residual and reactivated enzyme in milk, cream and buttermilk. Compared to the Scharer rapid and the Rutgers visual methods, this test was more reliable in borderline cases because it eliminated the bias encountered in visual examination. A method was developed to analyze alkaline phosphatase in casein.

Rapid Methods for Differentiating Reactivated from Residual Phosphatase in Milk and Cream: Collaborative Study

Three methods for differentiating reactivated from residual phosphatase in milk and cream were collaboratively tested using both magnesium acetate and magnesium chloride for reactivating phosphatase. The methods evaluated were the modified Scharer rapid test, the rapid colorimetric test, and the Rutgers method. Nine collaborators tested 6 unknown milk samples containing reactivated and/or residual phosphatase, and 16 collaborators tested 6 unknown cream samples containing reactivated and/or residual phosphatase. Results indicated that use of magnesium acetate in place of magnesium chloride for reactivating phosphatase improved test results. Visual tests (modified Scharer rapid and Rutgers) predicted correct results when the samples contained high levels of reactivated or residual phosphatase. In borderline cases where the reactivated phosphatase contents of the undiluted control sample and the diluted sample containing Mg were very close, the test results of the visual methods were significantly different from 100% correct results at the α = 0.05 level. Use of a photoelectric colorimeter or its equivalent for measuring the absorbance in conjunction with the modified Scharer rapid test improved results considerably. The modified Scharer rapid test was adopted official first action.

A comparison of quantitative methods for measuring yeast flocculation

Two quantitative objective methods for measuring flocculation of a yeast culture were com pared and correlated with subjective estimation by eye. One method involved counting in a haemocytometer the number of free cells (i.e., cells not found in flocs) and then the total number of cells after complete deflocculation by pronase. The number of cells in flocs was derived by subtracting the number of free cells from the total number of cells. The other method made use of the decrease in turbidity of a flocculated culture on standing. Gross flocs settled to the bottom of a tube within 5 min. The decrease in turbidity was measured by a photoelectric colorimeter. The difference in turbidity readings between 0 and 5 min was assumed to represent the turbidity component due to cells in flocs. The methods were appropriately applicable to monitoring the time course of sex-directed flocculation of the fission yeast Schizosaccharomyces pombe. A culture at maximum flocculation contained 500 gross flocs ml−1 which represented up to 70% of the total number of cells. A typical primary floc occupied a volume of 1 × 10−4 ml and contained 1 × 105 cells.