Standard Dose-response Curve Research Articles

A Rat Bioassay for Measuring the Comparative Availability of Carbohydrates and Its Application to Legume Foods, Pure Carbohydrates and Polyols

An assay was developed to evaluate the bioavailability of dietary carbohydrate by slope-ratio analysis of weight gain and plasma ketones of rats fed a carbohydrate-free diet supplemented with glucose as a standard and selected food items, pure carbohydrates and polyols. The diet was based on 35% food grade oleic acid, 12% casein protein supplemented with methionine (0.3%) and arginine (0.2%), 7.5% soybean oil, 37% cellulose, minerals and vitamins. Glucose, as the reference standard, or test materials were incorporated in the diet by replacing equi-energetic amounts of oleic acid and adjusting cellulose to equalize total weight. Optimal levels of protein (casein) and triglyceride (soybean oil) in the basal diet were defined as those levels above which additional protein or fat would serve only to provide endogenous glucose from their glucogenic amino acids and glycerol constituents. A standard dose-response curve was obtained by feeding diets containing 0%, 1% and 2% glucose. Similar dose response curves were obtained by feeding test materials. Under these experimental conditions, additional glucose or additional protein were growth stimulating and casein had approximately 50% of the value of an equal weight of glucose, which was consistent with its content of glucogenic amino acids. The specific carbohydrate value of a food was estimated in the assay by subtracting the calculated glucogenic value of its digestible protein from the total response. The apparent availability of the carbohydrates (i.e., nitrogen-free extract) in soybean meal, lima bean (Phaseolus lumatus), and chick pea (Cicer arietinum) were 35, 70, and 80%, respectively, as available as glucose. Galactose, a 1:1 mixture of galactose + glucose, fractose and starch were as available as glucose. Lactose, ribose, sorbitol, and xylitol were 50 to 65% as available as glucose while mannitol and inulin were not available to a significant extent. Possible metabolic bases for these differences are discussed.

Purification and Physical Characterization of Human Alpha‐fetoprotein from Cord Blood and from Ascites Fluid of Individuals with Hepatocellular Carcinoma

Human alpha‐fetoprotein (HuAFP) was isolated from cord blood and ascites fluid of individuals with hepatocellular carcinoma. The purification procedures employed antibody‐affinity chromatography and preparative polyacrylamide gel electrophoresis (Prep PAGE). Final yields of HuAFP averaged 40% and demonstrated 99.8% purity.Physicochemical studies of HuAFP from cord blood showed a molecular weight of 70.000, pl = 4.85, Stokes radius of 2.699 nm, and valence of (H*/mol) of 11.0. Similar studies of HuAFP from ascites fluid from individuals with hepatocellular carcinoma showed a molecular weight of 69.000, pl = 4.80, Stokes radius of 2.798 nm. and valence of (H*/mol) of 12.2. These AFP molecules isolated from separate origins demonstrated no significant physicochemical or antigenic differences. Assessment of potency and purity of these preparations were made by Lowry protein analyses, radioimmunoassay (RIA) to AFP and albumin. PAGE, SDS‐PAGE, and isoelectric focusing patterns on polyacrylamide gel electrophoresis.The sensitivity of the RIA for human AFP was increased by the use of high affinity goat anti‐AFP. To minimize non‐specific serum effects, human serum, from which AFP had been specifically removed by affinity chromatography was added to each tube in the standard dose response curve. The sensitivity of the assay was 0.7 ng/ml.

The effects of busulphan on the chromosomes of normal human lymphocytes

In vitro exposure of human lymphocytes to busulphan (BUS) produced an increase in chromosome aberrations and in sister-chromatid exchange (SCE) frequency. The distribution of chromosome breaks throughout the karyotype was non-random and they occurred mainly in the G-negative bands. Certain bands had a marked susceptibility to BUS and comparisons with the human chromosome-break distributions reported for a number of drugs revealed that some of these bands were equally susceptible to other alkylating agents. Both the number of chromosome gaps and breaks and the SCE frequency increased with BUS concentration, but only the SCE dose-response was a clearly defined linear relationship. Therefore a standard SCE dose-response curve was constructed for future comparison with the results of similar investigations of patients on BUS therapy.

The effects of busulphan on the chromosomes of normal human lymphocytes

In vitro exposure of human lymphocytes to busulphan (BUS) produced an increase in chromosome aberrations and in sister-chromatid exchange (SCE) frequency. The distribution of chromosome breaks throughout the karyotype was non-random and they occurred mainly in the G-negative bands. Certain bands had a marked susceptibility to BUS and comparisons with the human chromosome-break distributions reported for a number of drugs revealed that some of these bands were equally susceptible to other alkylating agents. Both the number of chromosome gaps and breaks and the SCE frequency increased with BUS concentration, but only the SCE dose-response was a clearly defined linear relationship. Therefore a standard SCE dose-response curve was constructed for future comparison with the results of similar investigations of patients on BUS therapy.