Mutagenicity of benzo(a)pyrenyl-1-sulfate in the Ames test.

Comparison of the mutagenicity of nine isomeric benzo(a)pyrenyl [B(a)P] phenols conjugated with either sulfate or glucuronide was carried out using strain Salmonella typhimurium TA98. Of the nine conjugates tested, only B(a)P-1-sulfate was mutagenic. Accordingly, the mutagenicity of B(a)P-1-sulfate was compared with that of B(a)P and 1-hydroxybenzo(a)pyrene [B(a)P-1-OH] in the presence and absence of rat lung S9 and Aroclor-induced liver S9 with and without an NADPH-generating system. B(a)P-1-sulfate was slightly mutagenic, whereas B(a)P and the 1-hydroxy derivative were nonmutagenic when S9 fractions and NADPH were omitted. Addition of induced liver S9 with NADPH caused mutagenicity with B(a) -1-OH greater than B(a)P greater than B(a)P-1-sulfate. B(a)P-1-sulfate was the only mutagenic species when lung S9 was added. This mutagenicity did not require NADPH. Sodium sulfite, an inhibitor of arylsulfatase, decreased the mutagenicity of B(a)P-1-sulfate. These data suggest that a unique mutagenic species is generated from B(a)P-1-sulfate via arylsulfatase in rat lung.     

Conjugation of benzo(a)pyrene 7,8-dihydrodiol-9,10-epoxide in infant Swiss-Webster mice.

Benzo(a)pyrene 7,8-dihydrodiol-9,10-epoxide (BPDE), accepted as the ultimate carcinogen of benzo(a)pyrene, has a very short half-life in aqueous solutions yet induces lung tumors when injected into infant mice. To evaluate the possibility that metabolites of BPDE, principally in the form of stable conjugates, contribute to binding to DNA in peripheral tissues, infant mice were injected i.p. with 39 nmol (+/- ) anti-BPDE. One h after injection, 5% of the dose was recovered in serum and appeared mostly as conjugated metabolites (54% as glucuronides and 16% as glutathione conjugates). Amounts of direct acting electrophiles in serum estimated by trapping with DNA comprised less than 0.02% of the injected dose. No more than 10% of the radioactivity in extracts of liver, lung, and kidney was recovered as BPDE. Glutathione conjugates predominated in the liver and lung, whereas glucuronides were the major metabolites in kidney. Radioactivity bound to DNA in liver, lung, and kidney was 21.5, 42.7, and 7.8 pmol/mg, respectively. Despite the rapid conversion of BPDE to stable conjugates, 32P-postlabeling profiles of DNA adducts in lung closely resembled that noted after addition of BPDE directly to lung homogenate. Thus, the reactive intermediate as well as stable conjugates of BPDE may be transported to target tissues where they initiate tumors.     

Radiological images on personal computers: Introduction and fundamental principles of digital images

This series of articles will explore the issues related to displaying, manipulating, and analyzing radiological images on personal computers (PC). This first article discusses the digital image data file, standard PC graphic file formats, and various methods for importing radiological images into the PC.     

A simple and versatile harvesting device for processing radioactive label incorporated into and-or released from cells in microculture

The difficulty with microculture systems is not in growing small numbers of cells in the wells of microtiter plates, but in harvesting, washing and processing these cells or their supernatants for radioactive counting. The logistical advantage of microculture techniques has prompted development of a simplified and versatile microculture harvesting device which can process cell precipitates as well as cell supernatants, can be made by any machine shop, and has proven extremely useful in a laboratory of immunology.     

Oxidative stress occurs in perfused rat liver at low oxygen tension by mechanisms involving peroxynitrite

Ethanol increases free radical formation; however, it was recently demonstrated that it also causes extensive hypoxia in rat liver in vivo. To address this issue, it was hypothesized that peroxynitrite formed in normoxic periportal regions of the liver lobule has its reactivity enhanced in hypoxic pericentral regions where the pH is lower. Via this pathway, peroxynitrite could lead to free radical formation in the absence of oxygen. Livers from fed rats were perfused at low flow rates for 75 min. Under these conditions, periportal regions were well oxygenated but pericentral areas became hypoxic. Low-flow perfusion caused a significant 6-fold increase in nitrotyrosine accumulation in pericentral regions. During the last 20 min of perfusion, the spin-trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone was infused and adducts were collected for electron-spin resonance analysis. A six-line radical adduct signal was detected in perfusate. Direct infusion of peroxynitrite produced a radical adduct with identical coupling constants, and a similar pattern of nitrotyrosine accumulation was observed. Retrograde perfusion at low rates resulted in accumulation of nitrotyrosine in periportal regions. Although the magnitude of the radical in perfusate was increased by ethanol, it was not derived directly from it. Both nitrotyrosine accumulation and radical formation were reduced by inhibition of nitric oxide synthase with N-nitro-L-arginine methyl ester, but not with the inactive D-isomer. Radical formation was decreased nearly completely by superoxide dismutase and N-nitro-L-arginine methyl ester, consistent with the hypothesis that the final prooxidant is a derivative from both NO. and superoxide (i.e., peroxynitrite). These results support the hypothesis that oxidative stress occurs in hypoxic regions of the liver lobule by mechanisms involving peroxynitrite.     

Antitumor effects of GBS toxin: a polysaccharide exotoxin from group Bβ-hemolytic streptococcus

A group B streptococcus (GBS) isolated from human neonates diagnosed with sepsis and respiratory distress (early-onset disease) produces a polysaccharide exotoxin (GBS toxin) that, when infused in sheep, causes lung pathophysiology similar to that seen in humans. Histological studies have demonstrated that GBS toxin induces a strong inflammatory response in the lung, with pulmonary sequestration of granulocytes and extensive capillary endothelial damage. The susceptibility of humans to GBS toxin is age-dependent and limited to about 4 days after birth. It is rarely evident thereafter. This suggests that the binding of GBS toxin to the target endothelium occurs via specific components in the developing lung endothelial cells of the newborn that are later lost. We report here that GBS toxin can also bind to developing endothelium associated with neoplasia and induce an inflammatory response. GBS toxin was shown by immunohistochemistry to bind to capillary endothelium of human large-cell carcinomas. In nude mice bearing human tumor xenografts, intravenously administered GBS toxin caused tumor necrosis and hemorrhagic lesions, and substantially inhibited the rate of growth of the tumors. In BALB/c mice bearing Madison lung tumors, GBS toxin induced an inflammatory response resulting in marked changes in tumor morphology, including vasodilation, endothelial and tumor cell necrosis, invasion of lymphocytes and macrophages, and capillary thrombosis. In these tumor models, no evidence of toxicity to the vasculature of other tissues was observed. The reported pathophysiology of GBS in human neonates, the lack of disease in non-neonates colonized with GBS, and these results suggest that GBS toxin may have potential as a well tolerated agent in cancer therapy of some human tumors.Abbreviations GBS group BStreptococcus - PBS phosphate-buffered saline This work was supported in part by a grant from the March of Dimes Foundation