Roy D. Robinson

DNA cytometry and chromosome 9 aberrations by fluorescence in situ hybridization of irrigation specimens from bladder cancer patients

OBJECTIVES To determine the sensitivity and specificity of combining fluorescence in situ hybridization (FISH) measurement of chromosome 9 and DNA cytometry of bladder irrigation specimens in the detection of bladder cancer. METHODS Bladder irrigation specimens were obtained from 37 normal control patients and 317 bladder cancer patients during cystoscopic examinations. Bladder cancer patients were sampled in the absence of observable tumor (256 specimens) and concurrently with tumor (204 specimens). Chromosome 9 copy number was determined on a cellular basis by FISH, and cellular DNA content was determined by Feulgen DNA staining and image cytometry. RESULTS Sensitivity of chromosome 9 FISH was 42% for all tumors and was not correlated to transitional cell carcinoma tumor grade, while the sensitivity of DNA cytometry was 55% and improved with increasing grade from 38% for grade 1 to 90% for grade 3 tumors. The results of FISH and DNA cytometry were combined, resulting in specificity of 92% and sensitivity of 69% for grade 1, 76% for grade 2, and 97% for grade 3 tumors. CONCLUSIONS The lack of increase with grade in the percentage of positive specimens by FISH supports the hypothesis that chromosome 9 aberrations are critical events in bladder tumorigenesis for many patients. These data demonstrate the presence of cells in irrigation specimens with specific genomic lesions of chromosome 9 and DNA content. Combining FISH on chromosome 9 and DNA cytometry provides an increase in sensitivity to transitional cell carcinoma over either test alone.

Are Developmental Changes in Methylmercury Metabolism and Excretion Mediated by the Intestinal Microflora

Methylmercury, unlike mercuric mercury, is rapidly and almost completely absorbed from the mammalian gut, hence the body burden of mercury after exposure to methylmercury is related to the rate of mercury excretion. By comparison to adult mice, sucking mice excrete very little mercury after methylmercury exposure until the 16th-18th postnatal days, when there is an abrupt increase in fecal mercury excretion coinciding with the time of weaning. Several explanations of this developmental change in mercury elimination can be proposed, including an increase in biliary secretion of mercury compounds at weaning, changes in binding of mercury to gut contents or ohanges in the rate of demethylation of methylmercury by the intestinal microflora. It is probable that more than one of these factors are responsible but evidence is presented here to support the view that bacterial demethylation plays an important role. It is known that the majority of mercury in feces, after methylmercury exposure of adult animals, is in the mercuric form and that there is an increase in the amount of mercuric mercury in young mice at weaning when the rate of mercury elimination increases. The major changes in intestinal flora which occur during weaning are reflected in an increase in the ability of the gut contents of weaned mice to demethylate methylmercury in vitro. Similarly, feces from neonatal and preweaned human infants show negligible rates of methylmercury demethylation in vitro by comparison to weaned infants and adults. Further evidence for the implication of the gut flora in determining rates of mercury excretion has been obtained by modification of the gut flora by diet and antibiotics. We conclude that the conversion of methylmercury to the poorly absorbed mercuric mercury by the intestinal flora is a major factor determining excretion rate and therefore body burden of mercury after methylmercury exposure.