Faculty Bibliography

Treatment of cultured mouse macrophages with either of two different vanadium compounds was shown to affect the production/release of two major immunoregulatory cytokines. The pentavalent vanadium compound ammonium metavanadate was shown previously to disrupt cell-mediated immunity at the earliest stages of an in vivo anti-Listerial response, in that mice treated with vanadium displayed decreased accessory cell recruitment and numbers of activated macrophages at infection sites. To determine whether these effects were due to vanadium-induced alterations in the production of biologically-active mediators, mouse macrophage-like WEHI-3 cells were treated in vitro with ammonium metavanadate or vanadium pentoxide prior to stimulation with lipopolysaccharide endotoxin (LPS). After stimulation, monokine (tumor necrosis factor-alpha and interleukin-1) and prostaglandin E2 (PGE2) activities were assessed. Both vanadium compounds decreased recovered monokine activities; measured TNF alpha concentrations were also reduced. Spontaneous release of the IL-1/TNF-regulating prostanoid PGE2 was significantly increased by the highest concentration of vanadate tested, although LPS-stimulated PGE2 production was unaffected by either compound. These results indicate that, in vitro, pentavalent vanadium can interfere with immunoregulatory mediators critical for maintaining host immunocompetence

The purpose of this study is to present three patients with multifocal primary neuroblastoma, to review the literature, and describe the radiographic findings. SUBJECTS AND METHODS: Three children with multifocal neuroblastoma have been identified. The case histories and imaging findings in these patients are reviewed. RESULTS: Two children had synchronous and one child had metachronous multifocal primary neuroblastoma. The primary tumors were both in the abdomen in one patient, both in the chest in another patient, and in the chest and abdomen in the third patient. Evidence for multifocal origin of these tumors, rather than metastatic spread, is presented. CONCLUSION: Multifocal primary neuroblastomas can occur. The tumors maybe synchronous or metachronous. Awareness of this disorder may prevent errors in diagnosis and staging. Although not identified in our patients there is a strong familial incidence of neuroblastomas in those patients with multifocal tumors.

Chromium, like many transition metal elements, is essential to life at low concentrations yet toxic to many systems at higher concentrations. In addition to the overt symptoms of acute chromium toxicity, delayed manifestations of chromium exposure become apparent by subsequent increases in the incidence of various human cancers. Chromium is widely used in numerous industrial processes, and as a result is a contaminant of many environmental systems. Chromium, in its myriad chemical forms and oxidation states, has been well studied in terms of its general chemistry and its interactions with biological molecules. However, the precise mechanisms by which chromium is both an essential metal and a carcinogen are not yet fully clear. The following review does not seek to embellish upon the proposed mechanisms of the toxic and carcinogenic actions of chromium, but rather provides a comprehensive review of these theories. The chemical nature of chromium compounds and how these properties impact upon the interactions of chromium with cellular and genetic targets, including animal and human hosts, are discussed

Ammonium metavanadate yielded a dose-dependent increase in mutation frequency at the V79 hprt locus following a 24-h exposure period in serum-free F12 medium. Vanadate also increased the mutation frequency of V79 cells by exposure of cells in salts-glucose medium, but these effects were not as striking, or as dose-dependent as they were in serum-free F12 medium. Ammonium metavanadate enhanced the mutation frequency in a V79 variant containing a transfected bacterial gpt gene. These cells are known to be more responsive to oxidative type mutations, and to mutations involving deletions. Although the absolute level of mutations was greater in these cells with ammonium metavanadate, so was the background, and these cells did not exhibit an enhanced mutagenic response to vanadate when compared to the wild-type V79 cells. The vanadate results were compared to a positive control potassium chromate, which exhibited a dose-dependent increase in mutation frequency. Ammonium metavanadate induced DNA-protein crosslinks formation in both Chinese hamster ovary and human MOLT4 cells, and the role of these relatively unrepaired genetic lesions in the mutations produced by vanadate and chromate are discussed

DNA--protein complexes isolated from CHO cells treated with at least 10-30 microM potassium chromate exhibited an alteration in the degradation of the DNA by restriction enzymes compared to DNA--protein complexes isolated from untreated cells. This alteration in restriction enzyme digestion of DNA--protein complexes induced by chromate was shown to depend upon the binding of trivalent chromium to the DNA and upon the protein associated with the DNA, since both EDTA pretreatment and protease K reversed the inhibition of restriction enzyme degradation of the DNA. The inhibition of restriction enzyme degradation of DNA--protein complexes may be utilized as an indirect way to detect DNA--protein complexing induced by chromate and perhaps other agents

Transfer of a normal Chinese hamster X chromosome (carried in a mouse A9 donor cell line) to a nickel-transformed Chinese hamster cell line with an Xq chromosome deletion resulted in senescense of these previously immortal cells. At early passages of the A9/CX donor cells, the hamster X chromosome was highly active, inducing senescence in 100% of the colonies obtained after its transfer into the nickel-transformed cells. However, senescence was reduced to 50% when Chinese hamster X chromosomes were transferred from later passage A9 cells. Full senescing activity of the intact hamster X chromosome was restored by treatment of the donor mouse cells with 5-azacytidine, which induced demethylation of DNA. These results suggest that a senescence gene or genes, which may be located on the Chinese hamster X chromosome, can be regulated by DNA methylation, and that escape from senescence and possibly loss of tumor suppressor gene activity can occur by epigenetic mechanisms

Actin was found to be the major protein crosslinked to the DNA of intact Chinese hamster ovary cells that were treated with either potassium chromate (hexavalent) or cis-diamminedichloroplatinum(II) (cis-platinum). This protein was identified as actin by its mol. wt (45 kd), its isoelectric point (pI = 5.4), positive reactivity with an actin antibody, and by protease mapping. Additionally, a purified actin standard migrated to the same location in a two-dimensional gel system as p45. Actin comprised approximately 20% of the protein component in chromate-induced DNA-protein crosslinks. In addition, to actin, several other major proteins (e.g. 53 kd, pI = 5.2, 50 kd, pI = 9) were crosslinked to DNA following exposure to cis-platinum or chromate. These proteins were abundant in the nuclear matrix fraction. Hexavalent chromate is the toxicologically active form because it is readily taken up into cells by an anion transport system. In contrast, trivalent chromium is considerably less toxic because it cannot enter the cell; however, most of the hexavalent form is eventually reduced to the trivalent form inside the cell. Previous studies have suggested that the trivalent form of chromium participates in complexing DNA with proteins. DNA-protein crosslinks were formed in isolated nuclei or in mixtures of purified DNA and protein incubated with trivalent chromium. However, the formation of these complexes required at least 16 h of incubation to exchange the parent compound ligands. Hexavalent chromate did not form these complexes in vitro under similar conditions. Incubation of trivalent chromium with purified actin and DNA resulted in DNA-actin crosslinks as detected by an electrophoretic mobility different from that of either free actin or DNA when the complex was transferred from a gel to nitrocellulose and stained for protein. These studies describe a new technique for detecting DNA-protein complexes and demonstrate that actin-DNA structures in intact cells create sites that selectively react with metal DNA-protein crosslinking agents

Detoxification of aflatoxin contaminated foods has been a continuing challenge for the food industry. This article examines primarily the detoxification of aflatoxin B₁ in foods and feeds. The sensitivity of aflatoxins to physical or chemical treatments is affected by many factors including moisture content, location of the toxins in the food, forms of the food, and interactions of the toxins with food components. Thus, it is important to understand these factors before a specific detoxification method can be recommended. In addition, the use of any applicable treatment conditions should not cause undesirable alterations to the nutritional and organoleptic qualities of the foods. The combined use of physical and chemical treatment procedures appear to provide a better prospect than the use of only a single treatment procedure. A reevaluation of the present processing conditions may shed light on the development of modified procedures to effectively degrade aflatoxins in foods, while still achieving other processing objectives.

The formation and identification of DNA-protein crosslinks are usually detected by filter binding assays such as alkaline elution. We describe a modified blotting method to selectively identify DNA-protein complexes (DPCs) formed in vitro by either Cr3+ ion or formaldehyde. This protocol allows DPC formation in vitro to be assayed with various chemical agents, requires minimal usage of radioactivity, and is performed in a shorter time frame than that commonly used to resolve DPCs from free proteins and unbound DNA