Validation of a radioimmunoassay procedure for N,N'-diacetylbenzidine, a metabolite of the chemical carcinogen benzidine, in urine.

The biaryl amine benzidine has been reported to produce tumors of the bladder in both man and animals. We have developed and validated a radioimmunoassay (RIA) procedure for monitoring potential human exposure to benzidine through detection in urine samples of one of its known urinary metabolites. The antibody used in the assay was produced in rabbits and is specific for N,N'-diacetylbenzidine (N,N'-DAB). At a 1/15000 initial dilution, this antiserum bound 50% of an iodinated tracer [125I]-N4'-[4-hydroxyphenethylaminohemisuccinyl]-4-acetamido-4-aminobiphenyl. One hundred pg (0.373 pmol) of N,N'-DAB displaced 50% of the tracer initially bound to the antiserum. The validity of the RIA procedure was established by the parallelism exhibited between the standard curve and aliquots of spiked human urine samples. The RIA has good spiked human urine samples. The RIA has good sensitivity (average minimal detectable dose less than 10 pg) and reproducibility (within-and between-assay coefficients of variation at midrange of the standard curve were 3.94 and 12.48, respectively). A series of 109 randomly selected human urine control samples were analyzed and a nonspecific interference of 0.52 +/- 0.04 ng of N,N'-DAB/mL urine was found.

Spontaneous diabetes mellitus in the New Zealand white rabbit: history, classification, and genetic analysis.

A colony of NZW rabbits was developed in which 18 of 126 members exhibited overt symptoms of diabetes mellitus. On the basis of total body weight measurements, obesity does not appear to play a primary role in the development or manifestation of the syndrome. The relatively high frequency of occurrence of spontaneous diabetes mellitus in this colony seems to suggest a unique genetic predisposition of these rabbits, yet analysis of glucose tolerance of colony animals indicates no clear genetic mode of transmittance of the trait. Rather, data suggest a possible interaction of as yet undefined genetic and/or environmental influences as being responsible for the disease state. Regressions of k-value on age indicate an early predetermination of glucose intolerance in the rabbits. In addition to a planned program of breeding, investigations of dietary intake and possible relationships of the diabetic condition to bacterial or viral infections appear to be initial areas indicative of further study.

Development of a radioimmunoassay procedure for 4-acetamidobiphenyl, a metabolite of the chemical carcinogen 4-aminobiphenyl, in urine.

The synthetic chemical 4-aminobiphenyl (4-ABP) has been shown to be a bladder carcinogen in both man and animals. A valid radioimmunoassay for a metabolite of 4-ABP has been developed as a means to monitor potential human exposure to 4-ABP. The antibody was produced by the immunization of two female New Zealand White rabbits and was found to be highly specific for 4-acetamidobiphenyl (4-AABP), the acetylated metabolite of 4-ABP. At an initial dilution of 1/5000, the antisera bound 45% of the [125I]-labeled derivative of 4-ABP. This derivative was prepared by coupling 4-hemisuccinamidobiphenyl (4-HSBP) with tyramine, and then radioiodinating this compound using the enzymatic lactoperoxidase method. The dose of 4-acetamidobiphenyl which would displace 50% of the labeled hapten initially bound to the antiserum, was about 1 ng (4.8 pmol). Scatchard analysis of the standard curve binding data indicated the presence of at least two populations of binding sites. The equilibrium association constant for the higher binding affinity component was 2.8 x 10(8) Liters/mole. A series of 210 randomly selected human urine control samples were analyzed and a nonspecific background contribution of 1.67 +/- 0.07 ng (mean + S.E.) of "4-acetamidobiphenyl"/mL urine was found.

Use of a programmable desk-top calculator for the statistical quality control of radioimmunoassays.

We have developed an interactive statistical quality-control system for the small- to medium-sized radioimmunoassay laboratory, which can be used in a programmable desk-top calculator instead of the medium- or large-scale computer systems usually required. The design of this quality-control system is modeled after the suggestions of Rodbard and has three components. The first component evaluates the relationship between the measured response variable of the radioimmunoassay and the precision (or variance) of these measurements. This derived relationship is then used in the second component of the system as the basis for the weighting function used to calculate an interative, weighted, least squares regression of the logit-log transformation of the dose-response curve. The third component uses the quality-control parameters statistically calculated from the linearized dose-response curve to monitor whether the assay is "in-control". The calculator tabulates the means and confidence limits for the various parameters and can plot the statistical quality-control charts. The major benefit of this statistical quality-control system is that it allows the real-time computation and plotting of quality-control data with a programmable desk-top calculator.

Effects of amygdaloid lesions on reproductive function of grouped caged mice.

Amygdalotomized, sham-operated and intact wild-derived house mice of both sexes were group-caged (8-10) or singly caged for 3 weeks. The weights of ovaries (p is less than 0.05) and uteri (p is less than 0.01) were less in intact and sham-operated grouped females compared to singly caged intact and amygdalotomized females. The weight of the reproductive organs in amygdalotomized grouped female mice was not different from singly caged controls. Body weights among amygdalotomized grouped females were heavier (p is less than 0.05) than singly caged controls. Seminal vesicle weights of intact and sham-operated grouped males were less (p is less than 0.05) than that of singly caged controls and grouped amygdalotomized males. Plasma LH values from the various groups coincided with the morphological data. These results support the hypothesis that increased population density impairs reproductive function in mammals. Perhaps the effects of decreased pituitary-gonadal function associated with overcrowding are mediated via amygdalar nuclei.

Radioimmunoassays for monitoring exposure to potential carcinogens.

As the numbers and production of environmental pollutants and hazardous industrial compounds increase, the necessity for monitoring the environment and workplace to avoid or to limit human exposure to toxic substances becomes more urgent. In support of the occupational safety program at the National Center for Toxicological Research, very sensitive and specific radioimmunoassays for measuring two known animal carcinogens, 2-acetylaminofluorene and diethylstilbestrol and their metabolites were developed. Radioimmunoassay (RIA) techniques offer unique advantages over ixisting methodologies in the field of toxicology; these include exquisite specificity and sensitivity, simplicity in sample handling and rapid analysis. These RIAs are currently being used for monitoring possible human exposure to carcinogenic compounds.