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Biomedical subjects

J L Li

Publications and source records attributed to J L Li.

At least 145 records · Page 8Linked to original sources
PubMed1986

A new subtype of a natural viral inhibitor (CVI) that is stable in the gastrointestinal tract.

A virus inhibitor found in gastric secretions and in extracts from gastrointestinal tissues is described. The inhibitor shares a number of characteristics with the recently described contact-blocking virus inhibitor (CVI), which is produced by unstimulated cells in culture, and occurs naturally in some body fluids. The new inhibitor, which we have designated gastrointestinal-CVI (GI-CVI) is similar to the originally described CVI in its resistance to denaturation by acid and alkali, stability at 100 degrees C, and broad antiviral action. GI-CVI can be distinguished from the previously described material by its resistance to proteolytic inactivation and enhanced heat stability, however. This new virus inhibitor has been found in significant titers in gastrointestinal secretions and tissue extracts from three mammalian species.

Animals↗
PubMed1986

Synthesis of nitrosomethylisoamylamine from isoamylamine and sodium nitrite by fungi.

Nitrosomethylisoamylamine (NMIA), a carcinogenic N-nitroso compound was synthesized from isoamylamine (IAA) in a glucose-ammonium nitrate medium after several days' incubation with fungi and subsequent nitrosation with sodium nitrate. The nitrosamine was not produced by control reactions which lacked either IAA or fungi. The yield of NMIA varied with the length of incubation after inoculation with the fungi, and with the concentrations of IAA and NaNO2, the duration of nitrosation, the pH of the medium and the species of the fungi. The optimum conditions for the formation of the nitrosamine are reported.

Amines↗
PubMed1986

Nephrotoxicity and renal cell carcinoma after use of iron- and aluminum-nitrilotriacetate complexes in rats.

Wistar male rats were tested for nephrotoxicity and carcinogenicity after administration of ferric nitrilotriacetate [(NTA) CAS: 139-13-9] (Fe-NTA) [No. of rats (n) = 24] and Al-NTA (n = 24). The control rats were given AlCl3 (n = 10), NTA (n = 10), and saline (n = 10). Sublethal doses of Fe-NTA [5-7 mg Fe/kg (body wt)] and Al-NTA [1.5-2.0 mg Al/kg (body wt)] were chosen and injected ip for 3 months. AlCl3 and NTA were given in equivalent doses and saline was given in equivalent volumes. All the rats given Fe-NTA or Al-NTA had a depressed weight gain, polyuria, and glucosuria from the 1st week. Histologically, acute tubular necrosis and regenerating epithelial cells were observed. Regenerative atypical epithelial cells in the renal cortex were seen at the termination of Fe-NTA or Al-NTA administration. Control rats had no remarkable changes. After 1 year, primary renal cell carcinoma and metastases to liver, lung, and peritoneum were observed only in Fe-NTA-treated rats (14 of 18 surviving rats). On the contrary, there were no tumors in Al-NTA-treated rats (none of 12 surviving rats). The results suggest that nephrotoxicity and renal cell carcinoma are two independent phenomena from Al-NTA treatment and that a long-term sublethal dose of Al-NTA is not related to renal carcinogenicity.

Acetates↗
PubMed1985

Synthesis of methylisoamylnitrosamine from isoamylamine by fungi (Fusarium moniliforme).

Methylisoamylnitrosamine, a carcinogenic N-nitroso compound, has been formed in glucose ammonium nitrate medium containing 150 mg of isoamylamine (a primary amine) inoculated with a common fungus (Fusarium moniliforme Sheldon), to which 400 mg NaNO2 are added after incubation for 7-8 days at 28 degrees C. No such compound has been found in control samples without fungi or isoamylamine. This paper reports a method of experimental synthesis of the nitrosamine by F. moniliforme strains 82-01 and 83-01, using isoamylamine and NaNO2, as well as the analysis of the compound by GC/MS and GC/TEA.

Amines↗
PubMed1984

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.

Chromatography, Thin Layer↗
PubMed1983

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.

Anaerobiosis↗
PubMed1982

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.

4-Nitroquinoline-1-oxide↗
PubMed1981

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.

4-Nitroquinoline-1-oxide↗
PubMed1980

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.

Animals↗
PubMed1979

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.

4-Nitroquinoline-1-oxide↗