Benzo(a)pyrene binding to DNA in organ cultures of human endometrium.

Benzo(a)pyrene was found to bind to DNA in human endometrial tissue in vitro. Among specimens from 41 individuals examined, there was a 70-fold range in the observed specific activities of carcinogen binding to DNA. To determine whether this interindividual variability was correlated with the hormonally determined state of differentiation of the endometrial tissue, this population was subdivided to separate postmenopausal patients from premenopausal patients; among premenopausal patients, further division was made according to location within the menstrual cycle. Tissue obtained late in the proliferative phase or early in the secretory phase of the menstrual cycle had the highest mean specific activity of benzo(a)pyrene binding. In spite of the relatively small group sizes, the observed difference between this and the level of benzo(a)pyrene binding in the mid- and late secretory phases was statistically significant. The average binding level among the small number of patients studied who had entered a natural menopause was lower than the average binding for any of the subgroups of premenopausal patients and significantly lower than the mean for the whole population of premenopausal patients.

Optimization of diagnostic discrimination applied to the amniotic fluid lecithin/sphingomyelin ratio.

An unrecognized disparity frequently separates the intuitive reliance placed on laboratory information by those who produce it and those who use it. To harmonize these dissimilar perceptions requires quantitative measures of the information contained in laboratory data. The assay of the lecithin/sphingomyelin ratio in amniotic fluid is used as an example to analyze the discriminatory ability of a test. This assay can be optimized from the different viewpoints of sensitivity, specificity, diagnostic effectiveness or value. In each case test results are interpreted in the light of different factors and so the optimal decision threshold to separate positive from negative results may vary. Appreciation of this concept would endow the interpretation of laboratory tests with the same flexibility traditionally available to other clinical information.

Clostridium difficile peritonitis in a neonate. A case report.

We describe a case of fatal peritonitis due to Clostridium difficile in a neonate. Although the patient had several clinical features that were compatible with the diagnosis of neonatal necrotizing enterocolitis, examination of the bowel at laparotomy disclosed that a mesenteric band caused the patient's underlying disease. Postmortem histopathologic tests revealed gram-positive rods in the wall of the small intestine. Clostridium difficile was the only organism recovered from an antemortem culture of peritoneal fluid and was also recovered from a postmortem blood culture.

Inhibition of binding of benzo(a)pyrene to DNA by 7,8-benzoflavone in organ cultures of human bronchus.

Levels of binding of exogeneously added benzo(a)pyrene to DNA in organ culture were examined in nine specimens of normal human bronchus obtained by bronchoscopy of tumor patients. The specimens were divided into two portions and incubated with [3H]benzo(a)pyrene in the absence or presence of 2 microM 7,8-benzoflavone for 24 h. 7,8-benzoflavone inhibited [3H]benzo(a)pyrene-DNA binding from 24 to 60%. Generally, the levels of binding of [3H]benzo(a)pyrene to DNA in the presence of 7,8-benzoflavone were relatively low and closely bracketed the mean value for the nine specimens. This appears to indicate that there are at least two components to [3H]benzo(a)pyrene-DNA binding catalyzed by the human bronchus. One component is quite variable in activity and is sensitive to inhibition by 7,8-benzoflavone, and may be an environmentally induced activity. The second component is lower in activity, and may be a constitutive portion of the mixed-function oxidase.

Evaluation of two photometers used in enzyme-linked immunosorbent assays.

The performance of two commercially available high-speed photometers, designed for through-the-plate reading, was evaluated. Linearity of instrumental reading and reproducibility of same-day and 2-day measurements were assessed by least-squares analysis and analysis of variance, respectively. For both instruments, the photometric error was on the order of thousandths of an absorbance unit and was much smaller than the error of the currently available enzyme-linked immunosorbent assays.

Relative frequency of Clostridium difficile in patients with diarrheal disease.

We have studied 161 patients with diarrheal disease to determine the frequency with which Clostridium difficile occurs in such patients. C. difficile or its toxin or both were detected in stools from 19 patients (11.9%), 17 of whom had previously received antimicrobial agents. Enteric pathogens other than C. difficile were recovered less frequently, with Salmonella sp., Giardia lamblia, and Campylobacter fetus being recovered from 4.1, 2.5, and 1.3%, respectively, of the patients studied. These data suggest that C. difficile may be frequently encountered in specimens obtained from patients with diarrhea who receive antibiotics and may play a role in diarrheal disease in such patients.

Evaluation of the Titertek Multiskan for determining minimal inhibitory concentration endpoints.

A commercially available through-the-plate reading photometer (Titertek Multiskan, Flow Laboratories, McLean, Va.) was used to determine microdilution minimal inhibition concentrations (MICs) for 190 clinical isolates of bacteria (115 gram-negative rods and 75 gram-positive cocci). The performance of the instrument was evaluated by comparing its MIC readings to those that were visually determined. The MICs determined by the instrument were identical to those determined visually for 94% of the gram-negative rods and 89% of the gram-positive cocci tested. Of the MICs determined by the instrument, 99% was within one dilution of the MICs determined visually.