[Risk of major lymphoma subtypes and use of mobile phones]. / Rischio dei principali sottotipi di linfoma associato all'uso di apparati di telefonia mobile.

INTRODUCTION: We explored the association between use of mobile phones and lymphoma risk in a case-control study. METHODS: We conducted unconditional logistic regression analysis in 322 lymphoma cases and 446 population controls, adjusting by age, gender and education. RESULTS: Risk of lymphoma (all types; OR = 1.5; 95% CI 1.0 - 2.1), and chronic lymphocytic leukaemia (OR = 1.8; 95% CI 1.0 - 3.4) was elevated in subjects reporting use of mobile phones, but it decreased with duration of use, and years from first purchase. CONCLUSIONS: Our contradictory findings would not support the aetiological nature of the observed associations.

[Assessment of congenital malformation risk in the progeny of the military and civilian personnel of the Salto di Quirra military base: preliminary results]. / Valutazione del rischio di malformazioni congenite nella progenie del personale militare e civile del Poligono Interforze del salto di Quirra: risultati preliminari.

INTRODUCTION: We evaluated the congenital malformation rate in the progeny of the personnel of the Salto di Quirra military base in Sardinia. METHODS: During 2011, we gathered questionnaire information on the reproductive history of 389 employees, more then 99% of those eligible for routine health surveillance. RESULTS: the observed congenital malformation rate (20.1 x 10(-3), 95% CI 6.3 - 33.8) was lower than that reported by the Italian Registries of Congenital Malformations, and it did not vary by exposure to radiofrequency, elf electromagnetic fields, and solvents, and by jobs associated with alleged exposure to nanoparticles or alpha radiation. CONCLUSIONS: Our findings suggest that the documented or alleged occupational exposures among the PISQ workforce did not increase the congenital malformation rate in the progeny.

Liver fibrosis in patients with chronic hepatitis C and persistently normal liver enzymes: influence of HIV infection.

Liver fibrosis progress slowly in patients with chronic hepatitis C and persistently normal alanine aminotransferase (PNALT) compared to subjects with elevated aminotransferases. Differences in liver fibrosis according to human immunodeficiency virus (HIV) status in this population have not been examined. All patients with serum hepatitis C virus (HCV)-RNA and PNALT who underwent liver fibrosis assessment using elastometry since 2004 at three different European hospitals were evaluated. Patients previously treated with interferon were excluded. PNALT was defined as ALT below the upper limit of normality in at least three consecutive determinations within the last 12 months. Fibrosis stage was defined as mild (Metavir F0-F1) if stiffness < or =7.1 kPa; moderate (F2) if 7.2-9.4 kPa; severe (F3) if 9.5-14 kPa, and cirrhosis (F4) if >14 kPa. A total of 449 HIV-negative and 133 HIV-positive patients were evaluated. HIV-negative patients were older (mean age 51.8 vs 43.5 years) and more frequently females (63%vs 37%) than the HIV counterparts. Mean serum HCV-RNA was similar in both the groups (5.9 vs 5.8 log IU/mL). Overall, 78.8% of the HIV patients were on HAART and their mean CD4 count was 525 (+/-278) cells/microL. In HIV-negatives, liver fibrosis was mild in 84.6%; moderate in 8.7%, severe in 3.3% and cirrhosis was found in 3.3%. In HIV patients, these figures were 70.7%, 18.8%, 6%, and 4.5%, respectively. In the multivariate logistic regression analysis, older age (odds ratio or OR: 1.04; 95% confidence interval or CI: 1.02-1.07; P < 0.001) and being HIV+ (OR: 2.6; 95% CI: 1.21-5.85; P < 0.01) were associated with severe liver fibrosis or cirrhosis (F3-F4). Thus, severe liver fibrosis and cirrhosis are seen in 6.6% of the HCV-monoinfected and in 10.5% of HCV-HIV co-infected patients with PNALT. Some degree of liver fibrosis that justifies treatment is seen in 15% of the HCV-monoinfected but doubles to nearly 30% in HIV-HCV co-infected patients with PNALT.

Serum lipoproteins and cancer.

BACKGROUND AND AIMS: In haematological and solid tumours the blood lipoprotein profile has been reported to be altered; while decreased levels of total cholesterol and increased values of triglycerides have been observed. The mechanism and meaning of these changes are, however, not fully understood. The aim of the present study was to determine relationships between cancer progression and serum lipoproteins. METHODS AND RESULTS: We performed a case-control study. We included cancer patients admitted to the 1st Division of Medical Oncology, Businco Hospital of Cagliari, Italy, between 1984 and 1998; 519 patients with any type of solid tumours and 928 healthy controls. We considered total cholesterol (C), high-density lipoprotein (HDL)-C, low-density lipoprotein (LDL)-C, triglycerides and apolipoprotein A-1; other parameters examined were glycaemia, insulinaemia, body mass index (BMI), homeostasis model assessment-estimated insulin resistance (HOMA-IR), C reactive protein (CRP) and tumour necrosis factor-alpha (TNF-alpha). In the cancer group HDL-C and apolipoprotein A-1 were lower (p<0.05) and triglycerides were higher (p<0.05) than in controls; HDL-C (mg/dl) females: 48 vs. 64; males, 40 vs. 52; Apo-A-1 (mg/dl) females: 125 vs. 173; males, 120 vs. 152; triglycerides (mg/dl) females: 133 vs. 96; males, 152 vs. 117. Glucose (mg/dl) was lower in the cancer group (p<0.05); females, 72.3 vs. 80.0; males, 75.7 vs. 78.4. CONCLUSION: Using multivariate analysis we were able to rule out cardiovascular and inflammatory diseases as causes of low HDL-C, and also demonstrate that these alterations can be shown as a specific consequence of the presence of a malignant tumour with a diagnostic and prognostic significance.

Mycobacterium tuberculosis and whole-genome sequencing: how close are we to unleashing its full potential?

BACKGROUND: Nearly two decades after completion of the genome sequence of Mycobacterium tuberculosis (MTB), and with the advent of next generation sequencing technologies (NGS), whole-genome sequencing (WGS) has been applied to a wide range of clinical scenarios. Starting in 2017, England is the first country in the world to pioneer its use on a national scale for the diagnosis of tuberculosis, detection of drug resistance, and typing of MTB. AIMS: This narrative review critically analyses the current applications of WGS for MTB and explains how close we are to realizing its full potential as a diagnostic, epidemiologic, and research tool. SOURCES: We searched for reports (both original articles and reviews) published in English up to 31 May 2017, with combinations of the following keywords: whole-genome sequencing, Mycobacterium, and tuberculosis. MEDLINE, Embase, and Scopus were used as search engines. We included articles that covered different aspects of whole-genome sequencing in relation to MTB. CONTENT: This review focuses on three main themes: the role of WGS for the prediction of drug susceptibility, MTB outbreak investigation and genetic diversity, and research applications of NGS. IMPLICATIONS: Many of the original expectations have been accomplished, and we believe that with its unprecedented sensitivity and power, WGS has the potential to address many unanswered questions in the near future. However, caution is still needed when interpreting WGS data as there are some important limitations to be aware of, from correct interpretation of drug susceptibilities to the bioinformatic support needed.

Estimates of Environmental Exposure to Radiofrequency Electromagnetic Fields and Risk of Lymphoma Subtypes.

We investigated the association between environmental exposure to radiofrequency electromagnetic fields (RF-EMF) and risk of lymphoma subtypes in a case-control study comprised of 322 patients and 444 individuals serving as controls in Sardinia, Italy in 1998-2004. Questionnaire information included the self-reported distance of the three longest held residential addresses from fixed radio-television transmitters and mobile phone base stations. We georeferenced the residential addresses of all study subjects and obtained the spatial coordinates of mobile phone base stations. For each address within a 500-meter radius from a mobile phone base station, we estimated the RF-EMF intensity using predictions from spatial models, and we performed RF-EMF measurements at the door in the subset of the longest held addresses within a 250-meter radius. We calculated risk of lymphoma and its major subtypes associated with the RF-EMF exposure metrics with unconditional logistic regression, adjusting by age, gender and years of education. In the analysis of self-reported data, risk associated with residence in proximity (within 50 meters) to fixed radio-television transmitters was likewise elevated for lymphoma overall [odds ratio = 2.7, 95% confidence interval = 1.5-4.6], and for the major lymphoma subtypes. With reference to mobile phone base stations, we did not observe an association with either the self-reported, or the geocoded distance from mobile phone base stations. RF-EMF measurements did not vary by case-control status. By comparing the self-reports to the geocoded data, we discovered that the cases tended to underestimate the distance from mobile phone base stations differentially from the controls ( P = 0.073). The interpretation of our findings is compromised by the limited study size, particularly in the analysis of the individual lymphoma subtypes, and the unavailability of the spatial coordinates of radio-television transmitters. Nonetheless, our results do not support the hypothesis of a link between environmental exposure to RF-EMF from mobile phone base stations and risk of lymphoma subtypes.

Staphylococcal endo-beta-N-acetylglucosaminidase inhibits response of human lymphocytes to mitogens and interferes with production of antibodies in mice.

The effect of a bacteriolytic enzyme, the endo-beta-N-acetylglucosaminidase excreted by Staphylococcus aureus (SaG) on the response of human lymphocytes to mitogens and on the immune response in mice has been studied. SaG inhibited incorporation of [3H]thymidine into TCA-precipitable material by human peripheral lymphocytes stimulated either by phytohemagglutinin or by concanavalin A, as well as formation of cytoplasmic immunoglobulin-containing cells by B lymphocytes treated with pokeweed mitogen. In all cases the level of inhibition first increased with the SaG concentrations reaching values of over 80% at an enzyme concentration of 100 micrograms/ml, and then decreased. Heat-inactivated SaG as well as SaG treated with both polyclonal and monoclonal specific antibodies or enzyme inhibitors such as chitotriose or hydrolyzed peptidoglycan had no effect on lymphocyte response to mitogens. In mice, SaG at a dose of 300 micrograms per mouse was found to cause a fourfold decrease in the anti-BSA antibody titer and an approximately 70-75% reduction in the immunoglobulin-containing cells in the spleens of mice injected with sheep red blood cells. SaG also completely abolished the enhancing effect of adjuvants such as muramyldipeptide, Freund's complete adjuvant, and Escherichia coli lipopolysaccharide. When SaG was injected into mice together with S. aureus peptidoglycan hydrolyzed either by SaG or by human lysozyme, the inhibitory effect on both production of anti-BSA circulating antibodies and appearance of Igc cells in the spleens of mice injected with sheep red blood cells was enhanced. As we know that (a) human tissues contain endo-beta-N-acetylglucosaminidases; (b) other human hexosaminidases (lysozymes) have previously been shown to interfere with the functions of immunocompetent cells; and (c) products of hexosaminidase hydrolysis of peptidoglycan (muropeptides) known to modulate immune response are ordinarily found in the urine of healthy persons, the possibility that hexosaminidases play a major role in the regulation of the immune response is raised and discussed.

Mycobacterium tuberculosis and whole genome sequencing: a practical guide and online tools available for the clinical microbiologist.

Whole genome sequencing (WGS) has the potential to revolutionize the diagnosis of Mycobacterium tuberculosis infection but the lack of bioinformatic expertise among clinical microbiologists is a barrier for adoption. Software products for analysis should be simple, free of charge, able to accept data directly from the sequencer (FASTQ files) and to provide the basic functionalities all-in-one. The main aim of this narrative review is to provide a practical guide for the clinical microbiologist, with little or no practical experience of WGS analysis, with a specific focus on software products tailor-made for M. tuberculosis analysis. With sequencing performed by an external provider, it is now feasible to implement WGS analysis in the routine clinical practice of any microbiology laboratory, with the potential to detect resistance weeks before traditional phenotypic culture methods, but the clinical microbiologist should be aware of the limitations of this approach.

2-Substituted penems with amino acid-related side chains: synthesis and antibacterial activity of a new series of beta-lactam antibiotics.

A new series of 6-(hydroxyethyl)penems 2-substituted with amino acid-related side chains was synthesized. The nature of the amino acyl derivative proved to be crucial both from a synthetic point of view, as beta-lactam ring opening can compete with C-2 nucleophilic substitution, and for antibacterial activity. Primary amino acid amides emerged as the most suitable side chains for enhancing permeability through a Gram-negative outer membrane. In vitro activity of the new 2-[(aminoamido)methyl]penems 3a-u was influenced by the nature and position of the amide moiety, the ring size for cyclic amides, and the configuration of the amino acid. Compounds bearing amides derived from small N-methyl amino acids (such as 3a) or from cyclic amino acids (such as prolinamide 3p and 4-hydroxyprolinamide 3r) showed broad spectrum in vitro activity against both Gram-positive and Gram-negative microorganisms.

Reversal by 5-azacytidine of the S-adenosyl-L-methionine-induced inhibition of the development of putative preneoplastic foci in rat liver carcinogenesis.

The development of gamma-glutamyltranspeptidase (GGT)-positive foci, in Wistar rats, initiated with diethylnitrosamine and subjected to selection according to 'resistant hepatocyte' protocol, was coupled, 7 weeks after initiation, with liver DNA hypomethylation and with a fall in S-adenosylmethionine/S-adenosylhomocysteine (SAM/SAH) ratio, and in 5-methylthio-adenosine (MTA) content. A 15-day treatment with SAM, started 1 week after selection, caused a dose-dependent decrease in the development of GGT-positive foci, recovery of liver SAM/SAH ratio and MTA level, and liver DNA methylation. A 12-day treatment with 20 mumol/kg per day of 5-azacytidine (AzaC), starting 1 week after selection, enhanced growth of GGT-positive foci, caused strong DNA hypomethylation, and partially counteracted the inhibition of GGT-positive foci growth, without affecting recovery of SAM/SAH ratio and MTA level, induced by SAM. These results suggest a role of DNA methylation in the antipromoting effect of SAM.

Evaluation of bactericidal activity of cefotaxime and other beta-lactams by a novel method.

In previous studies on Streptococcus faecium we proposed that the minimum beta-lactam concentration killing 99.9% of a bacterial population within 3 hours be defined as the minimum directly bactericidal concentration (MDBC) of that drug. In the present study we first evaluated the kinetics of cellular killing by various beta-lactams as related to penicillin-binding-protein (PBP) binding in Escherichia coli DC2, a hyperpermeable mutant. We concluded that in E. coli the MDBC for beta-lactams coincides with the minimum concentration capable of saturating PBPs 1b, 2 and 3. Of the antibacterial drugs we studied, cefsulodin, mecillinam and aztreonam had a much greater affinity for one essential PBP (PBP 1b, 2 and 3, respectively) than for all others, whereas cefotaxime had close affinities for all the above PBPs. MDBC values of greater than 500, 500, greater than 50, 10 and 1.5 mg/L were obtained for cefsulodin, mecillinam, aztreonam, ampicillin and cefotaxime, respectively. On the basis of the pharmacokinetic properties of these drugs, our results indicate that mecillinam, ampicillin and cefsulodin may be bactericidal in urine but not at other body sites; aztreonam is probably bactericidal in urine and blood, but not elsewhere; and cefotaxime is bactericidal in all the biological fluids we studied.

Inhibition of bacterial cell surface extension by various means causes blocking of macromolecular synthesis.

It has been suggested that, in rod-shaped bacteria, two sites for peptidoglycan assembly exist: one which is responsible for septum formation and the other, for lateral wall extension. The balance between the activities of these two sites enables bacteria to conserve their own morphology during cell growth. The effect of specifically inhibiting septum formation by different means (antibiotics and/or mutations), upon cell surface extension and macromolecular synthesis in rod-shaped and coccoid bacteria of various species, was studied. Inhibition of either cell wall expansion or macromolecular synthesis did not occur when septum formation was impaired in both rod-shaped bacteria and cocci possessing the two sites for peptidoglycan assembly, whereas a rapid and complete block of such synthesis was caused by inhibiting both sites in rod-shaped bacteria, or septum formation in cocci which possess only this site. These data indicate that bacteria possess a control mechanism that prevents macromolecular synthesis when envelope extension is inhibited.

Detection of bacterial phosphatase activity by means of an original and simple test.

A new test for the detection of bacterial phosphatase activity has been devised. The test is performed using agar media containing both methyl green (MG) and phenolphthalein diphosphate (PDP); in these media phosphatase-producing strains grow deep-green-stained colonies whereas non-producing strains do not. A total of 739 different strains were tested, including 593 staphylococci, 95 micrococci, 11 streptococci, 10 corynebacteria, 14 enterobacteria, and 16 candidae. All strains found phosphatase-positive according to the conventional phosphatase test displayed deep-green-stained colonies on MG-PDP media, whereas all phosphatase-negative strains showed unstained colonies on the same media. The main advantages of the present phosphatase test as compared with other conventional ones are that it is more simple to perform, it can reveal the phosphatase activity of colonies grown in deep agar, and can be incorporated into commercial multitest kits.

Intrinsic penicillin resistance in enterococci.

Penicillin resistance development in enterococci has been associated with overproduction of a low-affinity penicillin-binding protein (PBP) that is a normal component of the PBP pattern of these bacteria and is apparently able to substitute the functions of the other PBPs. In resistant mutants of Enterococcus hirae ATCC 9790 the low-affinity PBP (PBP5) overproduction was associated with a deletion in a genetic element, located 1 kb upstream of the pbp5 gene, which negatively controlled PBP5 synthesis. Hypersusceptibility to penicillin was associated with a point mutation in the pbp5 gene, which causes premature termination of translation. Structural homologies between low-affinity PBPs of the different enterococcal species have been suggested by cross-reactivity of antibodies raised against E. hirae PBP5 with PBP5 of Enterococcus faecium and Enterococcus faecalis. Acquisition of a high-level ampicillin resistance in E. faecium was associated with overproduction of PBP5, which, compared with PBP5 of moderately resistant strains, appeared to be modified in its penicillin-binding capability. The modified phenotype of PBP5 was found to be associated to some amino acid substitutions in the region between the SDN and KTG motifs. In particular, the substitution converting a polar residue (T) in a nonpolar one (A or I) could play an important role in remodeling the penicillin-binding domain and determining the decrease in penicillin affinity.

Diffusion of carbapenems through the outer membrane of enterobacteriaceae and correlation of their activities with their periplasmic concentrations.

Scarce information is available on the real mechanism by which carbapenemes penetrate in Enterobacteriaceae, although a considerable amount of evidence suggests that in many species of this family the lack of certain outer membrane proteins is associated with the acquisition of resistance to these antibiotics. The existance of specific pathways for the carbapenems has never been demonstrated, although at times it has been postulated in both wild and mutant strains, on the basis of evident discordances between permeability patterns and suceptibility data. By using the Zimmerman and Rosselet technique, which requires the strain under investigation to harbor a suitable beta-lactamase, the permeability of intact Escherichia coli and Enterobacter cloacae cells to meropenem and imipenem was investigated by transferring a constructed vector carrying the carbapenem hydrolyzing CphA metallo-beta-lactamase gene into the parental strains and their porin-deficient mutants. Reduced amounts of nonspecific porins significantly reduced the penetration of both carbapenems. The virtual absence of porins caused the MICs of meropenem to increase, mostly in Enterobacter cloacae, while it did not affected the MICs of imipenem. No evidence of specific porin pathways of the type described in Pseudomonas aeruginosa was found.

Evaluation of in vitro antimicrobial activity of lomefloxacin against staphylococci, enterococci, Enterobacteriaceae, and Pseudomonas aeruginosa.

In vitro antimicrobial activity of lomefloxacin and other antibiotics (norfloxacin, beta-lactams, cotrimoxazole, netilmicin, and miokamycin) was evaluated against 317 clinical isolates including Staphylococcus aureus, enterococci, Enterobacteriaceae, and Pseudomonas aeruginosa. Lomefloxacin showed a high in vitro activity against a wide variety of bacterial species. Against Enterobacteriaceae, lomefloxacin displayed the highest activity (MIC90S, less than or equal to 1 microgram/ml), and it was usually more active than ampicillin and netilmicin, and often more active than cotrimoxazole. Lomefloxacin showed a good antimicrobial activity also against both methicillin-susceptible and methicillin-resistant S. aureus, as it was able to inhibit 90% of staphylococcal strains at a concentration less than or equal to 2 micrograms/ml. Against enterococci and P. aeruginosa, lomefloxacin was usually less active (MIC90S, 8 micrograms/ml). As compared to norfloxacin, lomefloxacin displayed an overall similar activity against staphylococci and enterococci, but appeared less active against Gram-negative bacteria. Bactericidal activity of lomefloxacin against E. coli, when assayed by a novel method, proved to be high, and results indicate that an oral dose of 200 mg of lomefloxacin should exert a very high bactericidal activity against E. coli in urinary tract infections, even in those sustained by large bacterial populations.

Analysis of the Salmonella fim gene cluster: identification of a new gene (fimI) encoding a fimbrin-like protein and located downstream from the fimA gene.

The fimA gene coding for the major component (fimbrin) of type 1 fimbriae was mapped within the Salmonella typhi fim gene cluster, and its nucleotide sequence determined. The deduced amino acid sequence of S. typhi fimbrin is highly homologous to that of S. typhimurium type 1 fimbrin and showed similarity to that of other enterobacterial type 1 fimbrins. Downstream of fimA, an open reading frame was found, named fimI, able to encode a fimbrin-like protein. The fimI product could represent the counterpart, in type 1 fimbriae, of the PapH protein involved in cell anchoring and length modulation of Escherichia coli Pap pili. This genetic organization was found to be common to other Salmonella serovars, including S. typhimurium and S. choleraesuis.

Identification of an Escherichia coli periplasmic acid phosphatase containing of a 27 kDa-polypeptide component.

An acid phosphatase containing a 27-kDa polypeptide component has been identified in Escherichia coli by means of a zymogram technique. The enzyme is secreted in the periplasmic space and is able to hydrolyze several organic phosphate esters, but not diesters, showing preferential activity on p-nitrophenyl phosphate and other phenolic phosphate esters. Production of the enzyme apparently occurs only in cells growing on carbon sources other than glucose.

fimA-folD genes linkage in Salmonella identifies a putative junctional site of chromosomal rearrangement in the enterobacterial genome.

Analysis of the Salmonella chromosomal region located upstream of the fimA gene (coding for the major type 1 fimbrial subunit) showed a close linkage of this gene to the folD gene (coding for the enzyme 5,10-methylenetetrahydrofolate dehydrogenase/5,10-methenyltetrahydrofolate cyclohydrolase), indicating that the fim gene cluster of Salmonella, unlike that of Escherichia coli, has no regulatory genes located upstream of fimA and apparently terminates with this gene. The respective locations of the fim and folD genes in the E. coli and Salmonella genetic maps suggests that the fimA-folD intergenic region of Salmonella encompasses a junctional site of a genetic rearrangement that probably originated from the different chromosomal location of the fim genes in these species.

Comparative effects of L-methionine, S-adenosyl-L-methionine and 5'-methylthioadenosine on the growth of preneoplastic lesions and DNA methylation in rat liver during the early stages of hepatocarcinogenesis.

Male Wistar rats, initiated with diethylnitrosamine (DENA), were subjected to a selection treatment, according to the "resistant hepatocyte" model, followed or not followed by phenobarbital (PB). Rats received, for 3 weeks after selection, 4 i.m. doses (96 mmol/kg) of L-methionine, S-adenosyl-L-methionine (SAM), or 5'-methylthioadenosine (MTA), a SAM catabolite formed during polyamine synthesis or by spontaneous splitting of SAM at physiologic temperature and pH. They were then killed. In some rats, SAM and MTA treatments were started 20 weeks after initiation. The animals were killed 3 weeks later and persistent (neoplastic) nodules (PN) were collected. Some rat groups received 1/2 and 1/4 of the above SAM and MTA doses, or 1/8 of the above MTA dose. SAM and MTA, but not methionine, caused a dose-dependent decrease in number and surface area of gamma-glutamyltranspeptidase (GGT)-positive foci, and in labeling index (LI) of focal cells, coupled with remodeling. SAM and MTA liver contents, SAM/S-adenosylhomocysteine (SAH) ratio and overall methylation of liver DNA were low during the development of GGT-positive foci. SAM, but not methionine, caused a dose-dependent recovery of SAM content and DNA methylation, and a partial reconstitution of liver MTA pool. Exogenous MTA only induced the reconstitution of MTA pool, without affecting SAM level and DNA methylation. Recovery of SAM and MTA pool and DNA methylation was found in the rats subjected to SAM plus MTA, indicating the absence of inhibition of DNA methyltransferases in vivo by MTA. MTA also inhibited liver reparative growth in partially hepatectomized rats, without modifying SAM content and DNA methylation of regenerating liver (RL). A high activity of ornithine decarboxylase (ODC) was found in the liver, during the development of preneoplastic foci, and in PN. This activity was inhibited by SAM and MTA treatments. Although MTA was more effective than SAM, the decrease in ODC activity was coupled with a larger fall in DNA synthesis in SAM-treated than in MTA-treated rats. Thus the antipromotion effect of SAM could not merely depend on its (spontaneous) transformation into MTA. Although MTA production may play a role in the SAM antipromotion effect, other mechanisms could be involved. A role of DNA methylation in the inhibition of growth by SAM is suggested. MTA is a potential chemopreventive agent for liver carcinogenesis.