Cross-calibration of a combined electrostatic and time-of-flight analyzer for energy- and charge-state-resolved spectrometry of tin laser-produced plasma.

We present the results of the calibration of a channeltron-based electrostatic analyzer operating in time-of-flight mode (ESA-ToF) using tin ions resulting from laser-produced plasma, over a wide range of charge states and energies. Specifically, the channeltron electron multiplier detection efficiency and the spectrometer resolution are calibrated, and count rate effects are characterized. With the obtained overall response function, the ESA-ToF is shown to accurately reproduce charge-integrated measurements separately and simultaneously obtained from a Faraday cup (FC), up to a constant factor the finding of which enables absolute cross-calibration of the ESA-ToF using the FC as an absolute benchmark. Absolute charge-state-resolved ion energy distributions are obtained from ns-pulse Nd:YAG-laser-produced microdroplet tin plasmas in a setting relevant for state-of-the-art extreme ultraviolet nanolithography.

Implementation of a multilevel, multicomponent intervention for obesity control in Native American communities (OPREVENT2): challenges and lessons learned.

OPREVENT2 was a multilevel, multicomponent (MLMC) adult obesity prevention that sought to improve access and demand for healthier food and physical activity opportunities in six Native American communities in the Southwest and Midwest. OPREVENT2 worked with worksites, food stores, schools (grades 2-6), through social media and mailings, and with a local community action committee (CAC), in each of the three intervention communities, and was implemented in six phases. We conducted a process evaluation to assess implementation of each intervention component in terms of reach, dose delivered and fidelity. Implementation of each component was classified as high, medium or low according to set standards, and reported back at the end of each phase, allowing for improvements. The school and worksite components were implemented with high reach, dose delivered and fidelity, with improvement over time. The school program had only moderate reach and dose delivered, as did the social media component. The CAC achieved high reach and dose delivered. Overall, study reach and dose delivered reached a high implementation level, whereas fidelity was medium. Great challenges exist in the consistent implementation of MLMC interventions. The detailed process evaluation of the OPREVENT2 trial allowed us to carefully assess the relative strengths and limitations of each intervention component.

[Organophosphorus poisoning: Towards enzymatic treatments]. / Intoxication aux organophosphorés : vers des traitements enzymatiques.

Organophosphorus compounds (OP) are toxic molecules developed as insecticides and chemical warfare nerve agents (CWNAs). Most OP are neurotoxic and act as nervous system disruptors by blocking cholinergic transmission. They are therefore responsible for many poisonings worldwide. OP toxicity may result either from acute or chronic exposure, and their poisoning effect were evaluated using several animal models. These latter were also used for evaluating the efficacy of antidotes. Strategies based on enzymes that can trap (stoichiometric bioscavengers) or degrade (catalytic bioscavengers) OP, were particularly studied since they allow effective decontamination, without toxicity or environmental impact. This review summarizes the results obtained in vivo with enzymes through three levels: prophylaxis, treatment and external decontamination. The efficiency of enzymatic treatments in different animal models is presented and the relevance of these models is also discussed for a better extrapolation to humans.

Implementation of B'More Healthy Communities for Kids: process evaluation of a multi-level, multi-component obesity prevention intervention.

B'More Healthy Communities for Kids was a multi-level, multi-component obesity prevention intervention to improve access, demand and consumption of healthier foods and beverages in 28 low-income neighborhoods in Baltimore City, MD. Process evaluation assesses the implementation of an intervention and monitor progress. To the best of our knowledge, little detailed process data from multi-level obesity prevention trials have been published. Implementation of each intervention component (wholesaler, recreation center, carryout restaurant, corner store, policy and social media/text messaging) was classified as high, medium or low according to set standards. The wholesaler component achieved high implementation for reach, dose delivered and fidelity. Recreation center and carryout restaurant components achieved medium reach, dose delivered and fidelity. Corner stores achieved medium reach and dose delivered and high fidelity. The policy component achieved high reach and medium dose delivered and fidelity. Social media/text messaging achieved medium reach and high dose delivered and fidelity. Overall, study reach and dose delivered achieved a high implementation level, whereas fidelity achieved a medium level. Varying levels of implementation may have balanced the performance of an intervention component for each process evaluation construct. This detailed process evaluation of the B'More Healthy Communities for Kids allowed the assessment of implementation successes, failures and challenges of each intervention component.

[Decontamination of organophosphorus compounds: Towards new alternatives]. / La décontamination des organophosphorés : vers de nouvelles alternatives.

Organophosphorus coumpounds (OP) are toxic chemicals mainly used for agricultural purpose such as insecticides and were also developed and used as warfare nerve agents. OP are inhibitors of acetylcholinesterase, a key enzyme involved in the regulation of the central nervous system. Chemical, physical and biological approaches have been considered to decontaminate OP. This review summarizes the current and emerging strategies that are investigated to tackle this issue with a special emphasis on enzymatic remediation methods. During the last decade, many studies have been dedicated to the development of biocatalysts for OP removal. Among these, recent reports have pointed out the promising enzyme SsoPox isolated from the archaea Sulfolobus solfataricus. Considering both its intrinsic stability and activity, this hyperthermostable enzyme is highly appealing for the decontamination of OP.

[Knowledge transfer and implementation of clinical practice guidelines. Experience of the Canadian Hypertension Education Program]. / Le transfert des connaissances et la mise en oeuvre de lignes directrices de pratique Expérience du Programme d'Education Canadien sur l'Hypertension.

For the last 10 years, the update of guidelines for the treatment of hypertension in Canada is part of an annual process. This national strategy called the Canadian Hypertension Education Program (CHEP) has an organizational structure which allows not only to revise guidelines using an evidence-based scientific process but also to facilitate the implementation and the dissemination of the recommendations to the various healthcare professionals (doctors, pharmacists, nurses, etc.). As part of this process, the CHEP is also measuring different outcomes which could estimate the impact of its interventions. Recent data clearly show an improvement of the screening of hypertension as well as the quality of antihypertensive treatment (increase in the number of new prescriptions and of the percentage of subjects treated with 2 antihypertensive agents or more) in Canada. Finally, recent Canadian data showing a reduction of the cardiovascular complications attributable to hypertension suggest a possible link of causality with the implementation of the CHEP. This article will describe the functioning of the CHEP with its various strategies aiming at a better management of hypertension in Canada.

Hepatocarcinogenesis by diethylnitrosamine in rats fed high dietary levels of lipotropes.

The effects of high dietary levels of lipotropes on the carcinogenic activity of diethylnitrosamine (DENA) in rats were studied. All animals given DENA, with or without a dietary supplement, developed hepatocellular carcinomas. The mean survival times of all groups of rats dying with hepatocellular carcinomas after DENA treatment were determined. Choline, betaine, and folic acid consistently exerted no significant effect on those mean survival times. In rats receiving approximately equal to 2 mg DENA/day, methionine administration led to a slight but significant increase in the mean survival time of the carcinogen-treated rats, whereas vitamin B12 significantly lowered the survival time; neither substance altered the mean survival times of those treated with only 1.0 mg DENA/day. On the other hand, ethanolamine decreased the mean survival times of rats given 1.0 mg DENA daily, but had no effect on animals receiving 2 ml/day of carcinogen. Dimethylthetin (sulfur analogue of betaine), methotrexate, lecithin, and cephalin exerted no effect on the carcinogenic activity of DENA. The administration of dimethylthetin and betaine along with DENA led to markedly increased liver weights in animals dying of hepatocellular carcinomas, when compared to liver weights of animals treated with DENA alone.

Selection of carcinogens and related compounds tested for mutagenic activity.

A list of 102 chemicals was prepared for subsequent mutagenesis assays in a National Cancer Institute program to determine the extent of correlation between carcinogenesis and mutagenesis in standardized assays. The chemicals were divided into five major categories: 37 aromatic amines, 11 polycyclic aromatic hydrocarbons, 8 nitrosamines and nitrosamides, 16 alkylating agents, and a miscellaneous category consisting of 11 heterocyclic compounds, 7 amides, ureas and acylating agents, 5 antimetabolites, 4 inorganic chemicals, and 3 promoters. The chemicals were further described as procarcinogens (requiring metabolic activation to exert their biologic activities), ultimate carcinogens (direct-acting chemicals not requiring metabolic activation), and noncarcinogens (compounds shown to be inactive in one or more adequate carcinogenicity tests). An extensive bibliography documents the selection and categorization of the compounds.

Evaluation of the mutagenicity and DNA-modifying activity of carcinogens and noncarcinogens in microbial systems.

The mutagenicity of 99 chemicals was determined in a standard Salmonella typhimurium assay with the use of strains TA1535 and TA1538; the DNA-modifying capacity was determined with normal and DNA polymerase-deficient Escherichia coli strains. The following categories of chemicals were studied: alkylating agents (15); nitrosamines, hydrazines, and related substances (8); heterocyclics (10); aromatic amines (36); polycyclic aromatic hydrocarbons (11); amides, ureas, and acylating agents (7); antimetabolites (5); inorganics (4); and promoters (3). Of the substances studied, 21 were known noncarcinogens, 21 were ultimate carcinogens, and 45 were procarcinogens. Of the noncarcinogens, 35, 30, and 25% were positive in the Salmonella, E. coli, and both systems, respectively. All of the ultimate carcinogens were detectable as mutagens of DNA-modifying agents; 79, 100, and 79% gave positive tests in the Salmonella, E. coli, and both systems, respectively. Of the procarcinogens 72% were identifiable by these procedures: 52, 67, and 48% in the Salmonella, E. coli, and both assays, respectively. A tabulation of the combined data for ultimate carcinogens and procarcinogens indicates that 77% of the carcinogens gave positive results: 61, 74, and 59% in the Salmonella, E. coli, and both assays, respectively. We suggest that, for prescreening procedures with microbial assays, S. typhimurium strains TA98 and TA100 be included and the standard E. coli DNA polymerase-deficient assay be run in tandem with the Salmonella mutagenicity assay. When the standard E. coli DNA polymerase-deficient assay does not give interpretable results because of the lack of zones of growth inhibition, a modified assay with the use of liquid suspension should be performed.

Initial National Cancer Institute studies on mutagenesis as a prescreen for chemical carcinogens: an appraisal.

The efficacy of several in vitro and in vivo assays to detect carcinogens from a list of compounds was evaluated. Salmonella and polymerase A-deficient Escherichia coli in vitro were the most effective systems studied. Together they detected 82% of the organic carcinogens tested. Potential prescreening systems, which were thought to be currently insufficiently sensitive for the routine screening of potential carcinogens, included a) the development of resistance to thymidine overloading, methotrexate, and cytosine arabinoside by L5178y cells, b) Saccharomyces cerevisiae D3, c) the intraperitoneal host-mediated assay, and d) thymidine uptake as a reflection of DNA repair.

Profound postinitiation enhancement by short-term severe methionine, choline, vitamin B12, and folate deficiency of hepatocarcinogenesis in F344 rats given a single low-dose diethylnitrosamine injection.

The potential promoting and/or complete carcinogenic activity of a methyl group-deficient (MD) diet lacking methionine, choline, vitamin B12, and folate on liver tumor induction in weanling male F344/NCr rats was examined. Each of 50 rats per group received one injection 20 mg diethylnitrosamine [(DENA) CAS: 55-18-5; N-nitrosodiethylamine]/kg body weight at 4 weeks of age, and then each was maintained on a methyl group-adequate (MA) diet for 52 weeks (groups 2 and 5) or on an MD diet for 15 weeks followed by the MA diet for 37 weeks (group 4). Controls received injections of saline and were maintained on the same two respective diet regimens (groups 1 and 3, respectively). Histologic results from sacrifices at 6, 10, 15, 22, 39, and 52 weeks revealed early development of foci of eosinophilic gamma-glutamyltransferase (GGT)-positive hepatocytes by week 6 in DENA-MD diet-treated rats, with subsequent development of a diffuse hyperplasia of hepatocytes, oval cell proliferation, cholangiofibrosis, nodular cirrhosis, and neoplastic nodule (NN) formation and, at 52 weeks, hepatocellular carcinomas (HCC) in 13 of 15 rats. Similar but significantly fewer lesions were observed at slightly later sacrifice times in the livers of saline-MD diet-treated rats, with development of NN in 5 of 12 rats and an HCC in 1 of 12 rats at 52 weeks. DENA-treated rats on MA diets developed relatively few GGT-positive foci, and none developed any neoplastic lesions. Except for basophilic foci, areas and foci of cellular alteration containing glycogen-rich hepatocytes frequently exhibited diminished uptake of injected iron and decreased glucose-6-phosphatase and ATPase contents focally or throughout. This study indicates that a relatively brief exposure of both untreated and DENA-treated weanling rats to a severely MD diet produces classical preneoplastic and neoplastic lesions in their livers.

Mutagenic activity of chemical carcinogens and related compounds in the intraperitoneal host-mediated assay.

The mutagenic activities of 79 carcinogens, noncarcinogens, and structurally related compounds toward Salmonella typhimurium strains TA1530, TA1535, and TA1538 and toward Saccharomyces cerevisiae D3 were investigated in the intraperitoneal host-mediated assay. Fewer than half of the carcinogens were mutagenic toward the Salmonella strains. The insensitivity of the system was most marked with the aromatic amine and polycyclic hydrocarbon procarcinogens. Under the test conditions, fewer than 10% of the carcinogens showed clear mutagenic activity toward S. cerevisiae D3. However, none of the noncarcinogens was significantly mutagenic toward either S. typhimurium or S. cerevisiae D3. Overall, the intraperitoneal host-mediated assay does not seem suitable for routine preliminary screening of large numbers of potential carcinogens. The median lethal doses to mice of 46 compounds were determined.

Hepatic DNA methylation and liver tumor formation in male C3H mice fed methionine- and choline-deficient diets.

The effects of the chronic administration of methyl-deficient, amino acid-defined diets on liver tumor formation were examined in male weanling C3H/HeN mice previously treated with a single ip injection of 0 or 150 mg diethylnitrosamine/kg body weight [(DENA) CAS: 55-18-5]. Five diets were used: diet 1, adequate; diet 2, devoid of both methionine and choline; diet 3, devoid of methionine only; diet 4, devoid of choline only; and diet 5, devoid of methionine, choline, folic acid, and vitamin B12. Equimolar homocystine replaced methionine in all methionine-devoid diets. All diets were administered for 1 year. No hepatocellular carcinomas and only 3 liver adenomas were seen among the 129 animals at risk in the 5 groups that had received no DENA. Among the DENA-treated groups fed diets 1-4, the incidence of hepatocellular carcinomas in the mice at risk averaged 40%, with no significant differences noted among groups. A relatively low incidence of liver carcinomas (10%) was seen among DENA-treated mice subsequently fed diet 5; it could be ascribed to the enhanced mortality seen in these animals due to the dietary deficiencies. Lung tumors were seen in 44% of the DENA-treated mice surviving more than 35 experimental weeks and in only 2.5% of the corresponding DENA-untreated animals. Feeding diet 2, deficient in methionine and choline, to male C3H mice for 5-20 weeks decreased the hepatic ratio of S-adenosylmethionine (CAS: 29908-3-0) to S-adenosylhomocysteine (979-92-0) relative to that observed in mice fed the adequate diet 1. The 5-methyldeoxycytidine [(5-MC) CAS: 838-07-3] contents of liver DNA in animals fed diet 2 for 5, 10, and 20 weeks, however, were not significantly different from the corresponding levels in diet 1-fed mice. The results indicate that a methionine- and choline-deficient dietary regimen that lowers the 5-MC levels in DNA and enhances liver tumor formation in male F344 rats does not do so in male C3H mice.

Methyl groups in carcinogenesis: effects on DNA methylation and gene expression.

Lipotrope-deficient (methyl-deficient) diets cause fatty livers and increased liver-cell turnover and promote carcinogenesis in rodents. In rats prolonged intake of methyl-deficient diets results in liver tumor development. The mechanisms responsible for the cancer-promoting and carcinogenic properties of this deficiency remain unclear. The results of the experiments described here lend support to the hypothesis that intake of such a diet, by causing depletion of S-adenosylmethionine pools, results in DNA hypomethylation, which in turn leads to changes in expression of genes that may have key roles in regulation of growth. In livers of rats fed a severely methyl-deficient diet (MDD), lowered pools of S-adenosylmethionine and hypomethylated DNA were observed within 1 week. The extent of DNA hypomethylation increased when MDD was fed for longer periods. The decreases in overall levels of DNA methylation were accompanied by simultaneous alterations in gene expression, yielding patterns that closely resembled those reported to occur in livers of animals exposed to cancer-promoting chemicals and in hepatomas. Northern blot analysis of polyadenylated RNAs from livers of rats fed control or deficient diets showed that, after 1 week of MDD intake, there were large increases in levels of mRNAs for the c-myc and c-fos oncogenes, somewhat smaller increases in c-Ha-ras mRNA, and virtually no change in levels of c-Ki-ras mRNA. In contrast, mRNAs for epidermal growth factor receptor decreased significantly. The elevated levels of expression of the c-myc, c-fos, and c-Ha-ras genes were accompanied by selective changes in patterns of methylation within the sequences specifying these genes. Changes in DNA methylation and in gene expression induced in livers of rats fed MDD for 1 month were gradually reversed after restoration of an adequate diet. In hepatomas induced by prolonged dietary methyl deficiency, methylation patterns of c-Ki-ras and c-Ha-ras were abnormal. Although human diets are unlikely to be as severely methyl deficient as those used in these experiments, in some parts of the world intake of diets that are low in methionine and choline and contaminated with mycotoxins, such as aflatoxin, are common. Even in industrialized nations, deficiencies of folic acid and vitamin B12 are not uncommon and are exacerbated by some therapeutic agents and by substance abuse. Thus, it seems possible that interactions of diet and contaminants or drugs, by inducing changes in DNA methylation and aberrant gene expression, may contribute to cancer causation in humans.

Bioassay of alkyl halides and nucleotide base analogs by pulmonary tumor response in strain A mice.

The production of lung adenomas in strain A mice following multiple injections of 17 alkyl halides and of 3 base analogs was investigated. A slight but significant increase in the average number of lung tumors per mouse was noted following the administration of methyl iodide, n- and i-propyl iodide, sec- and tert-butyl chloride, i-, sec-, and tert-butyl bromide, and n- and sec-butyl iodide. The administration of comparable doses of ethyl bromide, ethyl iodide, n-butyl chloride, benzyl chloride, and 1-chloromethylnaphthalene to mice resulted in no significant increase in the frequency of lung tumors over that seen in vehicle-treated control mice. n-Butyl bromide and tert-butyl iodide similarly appeared to have no significant effect on the lung tumor frequency, but these compounds were too toxic to be tested at the high dosages used with the other alkyl halides. 5-Iodo-, 5-bromo-, and 5-fluorodeoxyuridine also appeared to have no significant effect on the lung tumor frequency. These results indicate that a high proportion of low-molecular-weight alkyl halides may be weakly carcinogenic and provide evidence supporting an electrophilic hypothesis of carcinogenesis.

Folate deficiency in the livers of diethylnitrosaminetreated rats.

The effects of diethylnitrosamine on the metabolism of folic acid and related compounds in rat liver were investigated. The administration, in the drinking water, of diethynitrosamine to rats for 3 weeks led to decreased hepatic levels of folate, S-adenosylmethionine, and 5-methyltetrahydrofolate:homocysteine methyltransferase. Liver methylenetetrahydrofolate reductase levels were unaffected by administration of diethylnitrosamine. The polyglutamate fraction of hepatic folates obtained from rats treated with diethylnitrosamine for 3 weeks prior to injection with [3H]folate contained less radioactivity than did the polyglutamate fraction obtained from the livers of control rats treated with [3H]folate alone. Similarly, the polyglutamate folate fraction of rat livers that were simultaneously perfused with both diethylnitrosamine and [3H]folate contained less label than the polyglutamate fraction of rat livers perfused with [3H]folate only. Livers perfused with [2-14C]histidine and diethylnitrosamine produced more formiminoglutamate and less CO2 than livers treated with [2-14C]histidine only. The changes noted in the hepatic folate metabolism of diethylnitrosamine-treated rats resemble those seen in the livers of methyl-deficient rats.

The effects of a marginally lipotrope-deficient diet on the hepatic levels of S-adenosylmethionine and on the urinary metabolites of 2-acetylaminofluorene in rats.

Hepatic levels of S-adenosylmethionine (AdoMet), of glutathione, and of the microsomal enzymes p-nitroanisole demethylase and benzo(a)pyrene hydroxylase were measured in male and female rats fed a diet marginally deficient in choline and methionine and void of folic acid (lipotrope deficient) or an adequate diet for 0 to 14 weeks with and without added 2-acetylaminofluorene (AAF). The urinary metabolites of AAF were determined throughout the experimental period. After 2 to 4 weeks of dietary administration, the hepatic AdoMet levels were 43% lower in male rats fed the lipotrope-deficient diet than in male rats fed the lipotrope-adequate diet; no differences were found in hepatic AdoMet of females fed the lipotrope-deficient or lipotrope-adequate diets for 2 to 14 weeks. Administration of AAF to lipotrope-deficient female rats for 2 weeks led to a transient decrease in hepatic levels of AdoMet. The administration of AAF for 2 to 14 weeks did not significantly affect hepatic AdoMet in female rats fed the lipotrope-adequate diet or in male rats fed either diet. Female rats fed the lipotrope-deficient diet and treated with AAF excreted decreased proportions of N-hydroxy-2-acetylaminofluorene and increased proportions of 5-hydroxy-2-acetylaminofluorene in their urine. However, the urine of lipotrope-deficient male rats treated with AAF contained increased proportions of N-hydroxy-2-acetylaminofluorene and decreased levels of 5-hydroxy-2-acetylaminofluorene. The urinary excretion of 7-hydroxy-2-acetylaminofluorene by male and female lipotrope-deficient rats treated with AAF was generally similar to that in lipotrope-adequate rats. The lipotrope-deficient diet did not appear to alter the hepatic levels of glutathione, p-nitroanisole demethylase, or benzo(a)pyrene hydroxylase activity was lower in the livers of lipotrope-deficient male rats treated with AAF for 8 to 14 weeks than in the livers of lipotrope-deficient rats not receiving the carcinogen. The altered metabolism of AAF correlated well with the previously reported effects of a marginal lipotrope deficiency on AAF carcinogenesis.

Effects of calcium and magnesium acetates on the carcinogenicity of cadmium chloride in Wistar rats.

The effects of calcium and magnesium acetates on the formation of injection site and testicular tumors in male Wistar rats over 2 years following s.c. injections of cadmium chloride (CdCl2) were determined. The rats (25/group) received a single s.c. dose of CdCl2 (0.02 or 0.04 mmol/kg; 0.9% NaCl solutions). Calcium and magnesium acetates were administered as 3% dietary supplements for 2 weeks prior to and 2 weeks after the CdCl2 injection, or as three daily s.c. injections (0.16 mmol calcium acetate per kg, 4 mmol magnesium acetate per kg; 0.9% NaCl solutions) at the same site as CdCl2 on the day before, the day of, and the day after CdCl2 dosing. Control groups were given 0.9% NaCl solution instead of CdCl2 plus s.c. or dietary calcium and magnesium acetates. In rats given injections of CdCl2 alone, the final tumor yields were 33 and 34% of rats at risk at the injection site (mostly fibrosarcomas) and 86 and 85% of rats at risk in the testes (mostly interstitial cell tumors), respectively, for the low- and high-CdCl2 doses. In control rats, the corresponding tumor yields were 0% at the site of 0.9% NaCl solution injection and 30% in the testes. Dietary calcium and magnesium acetates or s.c. calcium acetate did not affect significantly the tumor yields and latent periods. Simultaneous injections of magnesium acetate at the same site completely prevented the development of injection site tumors for both CdCl2 doses but had no effect on the final yields of testicular tumors. CdCl2 injection also caused significant elevation of incidence of the pancreatic islet cell tumors (8.5 versus 2.2%) regardless of any other experimental treatment. These results provide further evidence that the divalent carcinogenic metals may exert their activity through an antagonism with the physiologically essential divalent metals.

Inhibition by magnesium and calcium acetates of lead subacetate- and nickel acetate-induced lung tumors in strain A mice.

The ability of the physiologically essential divalent metals calcium and magnesium to inhibit the tumorigenic activities of lead and nickel towards the lungs of strain A mice was investigated. The tumorigenic salts lead(II) subacetate and nickel(II) acetate were injected i.p. at their maximal tolerated doses (0.04 mmol/kg/injection of each metal) for a total of 24 injections, whenever possible. Calcium(II) acetate and magnesium(II) acetate were administered in the same preparation along with the lead and nickel salts at molar doses of approximately 1, 3, 10, and 30 times the maximal tolerated dose of the tumorigen. The animals were sacrificed 30 weeks after the first injection, and the lung tumors were counted. The lead and nickel salts, administered alone, each produced a significant increase in the observed number of lung adenomas per mouse. When administered with any of the doses of calcium acetate or magnesium acetate tested, neither lead subacetate nor nickel acetate showed any significant tumorigenic activity. Calcium acetate alone (total dose, 11 mmol/kg of body weight) appeared to yield a significant rise in lung adenomas observed. The results indicate an antagonism between magnesium and calcium and the tumorigenic metals nickel and lead.

Altered cobalamin distribution in rat hepatomas and in the livers of rats treated with diethylnitrosamine.

The distribution of cobalamin cofactors was investigated in the livers and tumors of rats bearing transplanted Morris 7777 or 7800 hepatomas, in the livers of rats treated with the hepatocarcinogen diethylnitrosamine, and in normal rats. There was a significant increase in the proportion of methylcobalamin both in livers and tumors from rat bearing the hepatomas 7777 and 7800 compared to the proportion of methylcobalamin in the livers of normal rats. The total cobalamin content of the hepatomas was significantly lower than that of host or control livers. Similarly, the total cobalamin content of the livers from the tumor-bearing rats was less than that in control animals. The administration to rats of an acute dose of diethylnitrosamine led to an 84% increase in the hepatic concentration of methylcobalamin. Chronic administration of diethylnitrosamine slightly increased the hepatic methylcobalamin concentration, but this was not statistically significant. Liver weight was reduced, and the hepatic content of total cobalamin fell to 55% of that in control animals.