A new N-nitroso compound, N-2-methylpropyl-N-1-methylacetonyl-nitrosamine, in moldy millet and wheat flour

A new N-nitroso compound, N-2-methylpropyl-N-1-methylacetonyl-nitrosamine (MAMPNA), was found in millet and wheat flour inoculated with Fusarium moniliforme Sheldon, a common species of fungi occurring in foods in Linxian County, after 8-day incubation and an addition of a small amount of NaNO2. The compound has been identified by GC-MS and confirmed by synthesized MAMPNA. The present paper reports the isolation and detection of MAMPNA in moldy foods, and discusses the role of the fungus in processes of nitrosamine formation and possible biosynthetic approach of the new compound.

Influence of pN2 and pD2 on HD formation by various nitrogenases

Formation of HD from D2 has been demonstrated with nitrogenase preparations from Azotobacter vinelandii, Clostridium pasteurianum, Klebsiella pneumoniae, and Azospirillum sp. We conclude that the formation of HD from D2 is a general property of nitrogenases. However, the nitrogenases differ in their Ki values for D2 (N2 fixation) and in their rates of catalyzing HD formation; among the nitrogenases tested, C. pasteurianum nitrogenase had the lowest activity for formation of HD. When contaminating N2 was removed from the atmospheres above reaction mixtures, less than 1% of the total electron flux in the system was directed to HD formation; hence, we doubt that N2-independent HD formation is significant. A working hypothesis is suggested that operates without invoking an N2-independent reaction for forming HD.

Characterization of human cells persistently infected with cytomegalovirus and exposed to a chemical carcinogen

A non-productive, persistent human cytomegalovirus (CMV) infection was developed in human embryo lung (LU) cells by initially using supraoptimal temperatures to restrict the replication of a recent CMB isolate (76-24). Although CMV replication was observed in some cells within a few weeks of shifting the cultures to 37 degrees C and subculturing, CMV cytopathic effects and infectious CMV were not detected with further subculturing during the next 5 weeks. CMV-specific nuclear antigens were, however, observed in most cells (designated LU-76-24) for 38 additional culture passages made during the following 12 months. Although the LU-76-24 cells were morphologically distinct from LU cell cultures carried in parallel as controls, the LU-76-24 were contact-inhibited in spite of a somewhat disoriented growth pattern. Treatment of LU-76-24 cells with 0.05 microgram/ml of the chemical carcinogen 4-nitroquinoline 1 oxide (NQO) induced a lytic CMV infection from which a clone of cells (designated LUC-NQO) was isolated. No effect was seen when LU cells were treated with the same dose of NQO. LUC-NQO cells were morphologically altered from LU-76-24 cells and had lost contact inhibition. Even though CMV-specific nuclear antigens were observed in LUC-NQO cells, infectious CMV was not detected in lysates of these cells, nor was CMV rescued by co-cultivation of these cells with susceptible cells or by induction with 5-iodo-2'-deoxyuridine. LUC-NQO, but not LU or LU-76-24 cells, plated with good efficiency in semi-solid medium. The results indicate that long-term, non-productive, persistent CMV infections can be established in vitro and suggest that such cells may be more susceptible than non-infected cells to the action of chemical carcinogens.

Herpes virus inactivation by chemical carcinogens: differential inactivation of herpes simplex viruses by 4-nitroquinoline 1-oxide and related compounds

Treatment of stocks of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) with the chemical carcinogen 4-nitroquinoline 1-oxide (NQO) resulted in inactivation of virus infectivity at rates which were directly dependent on the concentration of NQO and interval of exposure to NQO. HSV-1 strains were more sensitive than HSV-2 strains to inactivation by NQO, although survival curves of both HSV types were multicomponent. Exposure of HSV-2 to a related group of chemicals suggested that the structural specificity required for inactivation of this virus was similar to that established by previous in vivo carcinogenicity tests.

Effect of six herpes simplex virus isolates on chromosomes of rabbit and hamster cell cultures

The chromosome effect of 6 herpes simplex virus isolates in rabbit kidney (RK) and hamster embryo (HE) cell cultures was variable. However, each virus isolate produced similar rates of altered metaphases in RK and HE cell cultures 4 and 8 h after infection. The observations suggest an inverse relationship between frequency of chromosome aberrations and previously reported ability to biochemically transform rodent cells.

Inactivation of human cytomegalovirus by the chemical carcinogen 4-nitroquinoline 1-oxide

The infectivity of cytomegalovirus (CMV), strain Davis, was inactivated by 4-nitroquinoline 1-oxide (NQO). A series of survival curves indicates that the rate of inactivation was directly dependent on the concentration of NQO over a range of 5 to 200 microgram/ml. At concentrations of I microgram/ml or less, inactivation of virus stock was not observed and at concentrations in excess of 200 microgram/ml, the cellular toxicity of residual NQO prevented quantification of the relatively low surviving infectivity. At a concentration of 200 microgram/ml NQO or less, the loss of virus infectivity could be clearly shown to result from the interaction of NQO with virus and not with cells, since the addition of similar doses of NQO to assay cells simultaneously with virus did not adversely affect the sensitivity of the assay cells to measure virus infectivity. Similarly, the dimethylsulphoxide carrier at concentrations of 5% or less was shown to have a negligible effect on both virus infectivity and on the sensitivity of human skin muscle cells to assay virus infectivity. NQO inactivation of virus infectivity appeared to depend very little on white light, since the kinetics of inactivation in the presence and in the absence of white light were similar.

Demonstration of oncogenic potential of mammalian cells transformed by DNA-containing viruses following photodynamic inactivation

The oncogenic properties of hamster embryo cells transformed by herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) and SV40 virus following photodynamic inactivation using neutral red were determined by subcutaneous inoculation into newborn Syrian hamsters. Cells transformed by all three viruses produced palpable tumors after different latent periods. Histopathological examination showed that HSV-2 tumors were fibrosarcomas and metastases were often seen in the lungs. HSV-2 primary tumors were reinoculated subcutaneously into weanling hamsters; they developed palpable tumors within 2 weeks. HSV-specific antigens were detected in the cytoplasm and/or on the surface of both the HSV-1 and HSV-2 tumor-cell cultures by the indirect immunofluorescence technique. The same method revealed SV40 tumor antigen in the nuclei of the SV40 tumor cells. Sera from HSV or SV40 tumor-bearing hamsters gave positive reactions when tested against HSV-infected hamster cells or SV40-infected monkey cells, respectively. These results demonstrate that herpes simplex virus and SV40, whose infectivity was lost following photodynamic inactivation, retained the virus genetic information necessary for transformation of normal cells to an oncogenic phenotype.