A DFT study on the adsorption and dissociation of N-Nitrosodimethylamine on a Ni8 nanocluster.

N-Nitrosodimethylamine (NDMA, ONN(CH3)2) is a highly potent carcinogenic investigated by health authorities in some countries. In this manuscript, density functional theory (DFT) is applied to study the NDMA molecular and dissociative adsorption on a Ni8 nanocluster. Molecular adsorption is two times stronger than the NDMA adsorption on the Ni{111} surface. NDMA dissociative adsorption is found more stable than molecular adsorption by ≈1 eV. To dissociate the NDMA molecule into O and NN(CH3)2 fragments, an activation energy is calculated in 0.954 and 0.810 eV from the two most stable molecular configurations. However, to dissociate the NDMA molecule into ON and N(CH3)2 fragments, a smaller activation energy of 0.654 eV is calculated. With the inclusion of the London dispersion forces (optB88-vdW functional), NDMA molecular interactions are a bit stronger. However, the activation energies are slightly smaller. Meta-GGA functional SCAN has also, been applied. The inclusion of the implicit solvation model displays a NDMA weaker interaction with the Ni8 nanocluster. Dissociative adsorption is more stable than molecular adsorption, but the energy difference is a bit smaller, ≈0.850 eV. Present results show that the Ni8 nanoclusters are promising catalysts to NDMA elimination from water.

Removal of both N-nitrosodimethylamine and trihalomethanes precursors in a single treatment using ion exchange resins.

Drinking water utilities are relying more than ever on water sources impacted by wastewater effluents. Disinfection/oxidation of these waters during water treatment may lead to the formation of several disinfection by-products, including the probable human carcinogen N-nitrosodimethylamine (NDMA) and the regulated trihalomethanes (THMs). In this study, the potential of ion exchange resins to control both NDMA and THMs precursors in a single treatment is presented. Two ion exchange resins were examined, a cation exchange resin (Plus) to target NDMA precursors and an anion exchange resin (MIEX) for THMs precursors control. We applied the resins, individually and combined, in the treatment of surface and wastewater effluent samples. The treatment with both resins removed simultaneously NDMA (43-85%) and THMs (39-65%) precursors. However, no removal of NDMA precursors was observed in the surface water with low initial NDMA FP (14 ng/L). The removals of NDMA FP and THMs FP with Plus and MIEX resins applied alone were (49-90%) and (41-69%), respectively. These results suggest no interaction between the resins, and thus the feasibility of effectively controlling NDMA and THMs precursors concomitantly. Additionally, the effects of the wastewater impact and the natural attenuation of precursors were studied. The results showed that neither the wastewater content nor the attenuation of the precursor affected the removals of NDMA and THMs precursors. Finally, experiments using a wastewater effluent sample showed that an increase in the calcium concentration resulted in a reduction in the removal of NDMA precursors of about 50%.

ß-Amyrin, a pentacyclic triterpene, exhibits anti-fibrotic, anti-inflammatory, and anti-apoptotic effects on dimethyl nitrosamine-induced hepatic fibrosis in male rats.

Hepatic fibrosis is a leading cause of morbidity and mortality worldwide. Attenuation of fibrogenic process can significantly lower the mortality rate. However, pharmaceutical intervention at fibrogenesis stage remains a major task in medicine. So there is a need for a natural compound to treat hepatic fibrosis. This study was outlined to investigate the anti-fibrotic effect of ß-amyrin in dimethylnitrosamine (DMN)-induced hepatic fibrosis male rats. Serum liver function markers (aspartate transaminase, alanine transaminase, alkaline phosphatase and lactate dehydrogenase), oxidative stress markers (malondialdehyde, superoxide dismutase, catalase, glutathione peroxidase, glutathione reduced content and vitamin C), tissue inflammatory marker (tumor necrosis factor α (TNF-α)), apoptosis marker (caspase 3) and fibrolytic marker (tissue inhibitor of metalloproteinase 1 (TIMP-1)) were evaluated before and after ß-amyrin treatment in DMN-induced rat. ß-Amyrin treatment attenuated the altered levels of the serum enzyme markers produced by DMN and caused a subsequent recovery toward normalization. Oxidative stress markers and TNF-α levels were reduced significantly ( p < 0.001) as well as proteins' (caspase-3 and TIMP-1) expression was reduced in ß-amyrin -treated DMN rats. By virtue of ß-amyrin properties of inhibiting oxidative stress, apoptosis, inflammation, and fibrogenesis, it might act as an ideal anti-inflammatory and anti-fibrogenic agent to halt the progression of liver fibrosis to chronicity.

Removal of N-nitrosodimethylamine precursors with powdered activated carbon adsorption.

The main objective of this study was to examine the roles of powdered activated carbon (PAC) characteristics (i.e., surface chemistry, pore size distribution, and surface area) in the removal of N-nitrosodimethylamine (NDMA) formation potential (FP) in surface and wastewater-impacted waters. Also, the effects of natural attenuation of NDMA precursors in surface waters, NDMA FP concentration, and carbon dose on the removal of NDMA FP by PAC were evaluated. Finally, the removal of NDMA FP by PAC at two full-scale DWTPs was monitored. Wastewater-impacted and surface water samples were collected to conduct adsorption experiments using different PACs and activated carbon fibers (ACFs) with a wide range of physicochemical characteristics. The removal efficiency of NDMA FP by PAC was significantly higher in wastewater-impacted than surface waters. Adsorbable NDMA precursors showed a size distribution in the waters tested; the adsorbable fraction included precursors accessing the pore size regions of 10-20 Å and <10 Å. Basic carbons showed higher removal of NDMA FP than acidic carbons on a surface area basis. The overall removal of NDMA FP by PAC on a mass basis depended on the surface area, pore size distribution and pHPZC. Thus, PACs with hybrid characteristics (micro and mesoporous), higher surface areas, and basic surface chemistry are more likely to be effective for NDMA precursor control by PAC adsorption. The application of PAC in DWTPs for taste and odor control resulted in an additional 20% removal of NDMA FP for the PAC doses of 7-10 mg/L. The natural attenuation of NDMA precursors through a combination of processes (biodegradation, photolysis and adsorption) decreased their adsorbability and removal by PAC adsorption.

Cost of the Cervical Cancer Screening Program at the Mexican Social Security Institute / Costo del Programa de Detección Oportuna de Cáncer Cervical en el Instituto Mexicano del Seguro Social

Objective. To estimate the annual cost of the National Cervical Cancer Screening Program (CCSP) of the Mexican Institute of Social Security (IMSS). Materials and methods. This cost analysis examined regional coverage rates reported by IMSS. We estimated the number of cytology, colposcopy, biopsy and pathology evaluations, as well as the diagnostic test and treatment costs for cervical intraepithelial neoplasia grade II and III (CIN 2/3) and cervical cancer. Diagnostic test costs were estimated using a micro-costing technique. Sensitivity analyses were performed. Results. The cost to perform 2.7 million cytology tests was nearly 38 million dollars, which represents 26.1% of the total program cost (145.4 million). False negatives account for nearly 43% of the program costs. Conclusion. The low sensitivity of the cytology test generates high rates of false negatives, which results in high institutional costs from the treatment of undetected cervical cancer cases.

Objetivo. Estimar el costo anual del Programa Nacional de Detección Oportuna de Cáncer Cervical en el Instituto Mexicano del Seguro Social (IMSS). Material y métodos. Este análisis de costos examinó las distintas coberturas por región reportadas por el IMSS. Se estimó el número de citologías, colposcopías, biopsias y evaluaciones de patología y los costos de pruebas de diagnóstico y de tratamientos por neoplasia cervical intraepitelial de grado II y III (NIC 2/3) y cáncer cervical. Los costos de las pruebas de diagnóstico se estimaron utilizando una técnica de microcosteo. Se llevó a cabo un análisis de sensibilidad. Resultados. El costo de realizar 2.7 millones de citologías fue de 38 millones de dólares, lo que representa 26.1% del costo total del programa (145.4 millones). Los falsos negativos corresponden a casi 43% de los costos del programa. Conclusiones. La baja sensibilidad de la citología genera un alto número de falsos negativos que resultan en costos elevados para la institución por el tratamiento de estos casos no detectados.

Graptopetalum paraguayense ameliorates chemical-induced rat hepatic fibrosis in vivo and inactivates stellate cells and Kupffer cells in vitro.

BACKGROUND: Graptopetalum paraguayense (GP) is a folk herbal medicine with hepatoprotective effects that is used in Taiwan. The aim of this study was to evaluate the hepatoprotective and antifibrotic effects of GP on experimental hepatic fibrosis in both dimethylnitrosamine (DMN)- and carbon tetrachloride (CCl(4))-induced liver injury rats. METHODS: Hepatic fibrosis-induced rats were fed with the methanolic extract of GP (MGP) by oral administration every day. Immunohistochemistry, biochemical assays, and Western blot analysis were performed. The effects of MGP on the expression of fibrotic markers and cytokines in the primary cultured hepatic stellate cells (HSCs) and Kupffer cells, respectively, were evaluated. RESULTS: Oral administration of MGP significantly alleviated DMN- or CCl(4)-induced liver inflammation and fibrosis. High levels of alanine transaminase, aspartate transaminase, bilirubin, prothrombin activity and mortality rates also decreased in rats treated with MGP. There were significantly decreased hydroxyproline levels in therapeutic rats compared with those of the liver-damaged rats. Collagen I and alpha smooth muscle actin (α-SMA) expression were all reduced by incubation with MGP in primary cultured rat HSCs. Furthermore, MGP induced apoptotic cell death in activated HSCs. MGP also suppressed lipopolysaccharide-stimulated rat Kupffer cell activation by decreasing nitric oxide, tumor necrosis factor-α and interleukin-6 production, and increasing interleukin-10 expression. CONCLUSIONS: The results show that the administration of MGP attenuated toxin-induced hepatic damage and fibrosis in vivo and inhibited HSC and Kupffer cell activation in vitro, suggesting that MGP might be a promising complementary or alternative therapeutic agent for liver inflammation and fibrosis.

Diferenciação de células-tronco em hepatócitos e desenvolvimento de modelo pré-clínico de fibrose hepática para ensaios de terapia celular / Mesenchymal stem cell differentiation in hepatocytes and development of pre-clinic model of hepatic fibrosis for cellular therapy assays

Este trabalho teve como objetivo desenvolver um protocolo para a diferenciação in vitro de células-tronco mesenquimais (CTM) em hepatócitos e a padronização de um modelo animal de fibrose hepática induzida por dimetilnitrosamina (DMN) para ensaios pré-clínicos de transplante de CTM. CTM isoladas de fontes variadas apresentaram morfologia fibroblastóide e aderência ao plástico e o padrão de marcadores de superfície celular esperado na análise por citometria de fluxo. A capacidade de diferenciação osteogênica e adipogênica dessas células foi comprovada pelas colorações de vermelho de alizarina, oil red e azul de toluidina, respectivamente, confirmando, que as células isoladas para este estudo se comportaram como CTM conforme proposto pela Sociedade Internacional de Pesquisa em Células-tronco. A diferenciação hepática foi avaliada quanto à morfologia e capacidade das células diferenciadas de estocar glicogênio confirmada por PAS (ácido periódico-Schiff), de sintetizar albumina confirmada por imunofluorescência, além da capacidade de expressar genes hepato-específicos verificada por ensaios de PCR em tempo real. Com base na literatura para diferenciação hepática, diferentes protocolos de um, dois e três passos foram testados. CTM humanas mostraram capacidade de produzir e estocar glicogênio e de sintetizar albumina, apenas quando diferenciadas com protocolos de três etapas, porém sem uma expressão aumentada dos genes hepato-específicos albumina, α-fetoproteína e c-Met. Uma etapa de diferenciação endodérmica, previamente aplicada à diferenciação hepática, aumentou a capacidade de produzir e estocar glicogênio das CTM diferenciadas. Para a padronização do modelo de fibrose hepática induzida por DMN, foram realizados experimentos de dose-resposta e foi verificado o efeito da hepatectomia em modelos mistos DMN/hepatectomia. A injúria hepática e o efeito do transplante de CTM foram avaliados por análise macroscópica dos fígados, histologia das biópsias de fígados corados com HE e tricromo de Masson e parâmetros bioquímicos séricos. Alterações macroscópicas, histológicas e nos níveis séricos de fosfatase alcalina indicam a indução da fibrose hepática nos ratos Wistar tratados com DMN na dose de 10 µg/g de peso animal por três dias consecutivos durante quatro semanas, mas não observamos nenhum efeito induzido pela hepatectomia. Porém, este modelo com DMN se mostra semelhante a estágios iniciais de uma fibrose hepática. O transplante de 1 x 107 CTM de veia de cordão umbilical humano (VCUH) no modelo de injúria hepática induzida por DMN não resultou em melhora da fibrose, diminuição dos níveis séricos de fosfatase alcalina e nem em ganho de peso dos animais quando comparados aos animais tratados com PBSA após a injúria hepática (grupo placebo). Em conjunto, esses resultados sugerem que CTM humanas se diferenciam após tratamentos mais complexos, onde os indutores hepatogênicos são sequencialmente adicionados ao meio de modo a mimetizar a sinalização durante o desenvolvimento embrionário. O transplante de CTM de VCUH parece não ter efeito positivo em um modelo pré-clínico de injúria hepática similar a estágios iniciais de fibrose. Financiado por CNPq (573578/2008-7) e FAPESP (2007/54260-2)

This study aimed to develop an in vitro differentiation protocol of mesenchymal (MSC) stem cells to hepatocytes and to standardize an animal model for hepatic fibrosis induced by dimethylnitrosamine (DMN) for preclinical transplant assays of MSC. MSC isolated from various sources presented fibroblastoid morphology, plastic adherence, and the expected pattern of cell surface markers by flow cytometry analysis. The capacity of osteogenic, adipogenic and chondrogenic differentiation of these cells was confirmed by alizarin red, oil red and toluidine blue staining, respectively, confirming that the cells isolated for this study behave as MSC, as proposed by the International Society for Stem Cell Research. Hepatogenic differentiation was evaluated by analysis of cell morphology, capacity to store glycogen confirmed by PAS (periodic acid-Schiff), albumin synthesis confirmed by immunofluorescence, as well as hepatic-specific gene expression verified by real time PCR assays. Based on the published literature on hepatic differentiation, several protocols of one, two, and three steps were tested. Human MSC differentiated solely when treated in a three step-protocol, showing the ability to produce and store glycogen and synthesize albumin; however the expression of hepatic-specific genes such as albumin, α-fetoprotein and c-Met was not increased. An endoderm differentiation stage, added to the hepatic differentiation protocol, increased the capacity to produce and store glycogen of differentiated MSC. In order to standardize the model of liver fibrosis induced by DMN, dose-response experiments were performed and the effect of hepatectomy in mixed models DMN/hepatectomy was observed. Severity of liver injury and the effect of cell transplantation were evaluated by macroscopic analysis of the livers, histology of liver biopsies stained with HE and Masson's trichrome, and evaluation of serum biochemical parameters. The macroscopic and histological observations, and altered alkaline phosphatase serum levels indicated the success in inducing liver fibrosis in DMN-treated rats at a dose of 10 µg/g of animal weight for three consecutive days, during four weeks, without any additional effect upon hepatectomy. Transplanting 1 x 107 umbilical cord MSC in the model of liver injury induced by DMN did not result in improvement of the fibrosis, decrease of alkaline phosphatase serum levels, or in weight gain of the treated animals compared to animals treated with PBSA after liver injury (placebo group). Together, these results suggest that human MSC are capable of differentiating to hepatocyte-like cells after more complex protocols, where hepatogenic inducers are sequentially added to the medium in order to mimic signaling that occurs during fetal development. Transplantation of undifferentiated umbilical cord MSC did not have any positive effect in a preclinical liver injury model characterized by an early stage of fibrosis. Supported by CNPq (573578/2008-7) and FAPESP (2007/54260-2)

Expression and distribution of connexin 32 in rat liver with experimentally induced fibrosis / Expressão e distribuição da conexina 32 em fígados de ratos com fibrose induzida experimentalmente

The connexin 32 (Cx32) is a protein that forms the channels that promote the gap junction intercellular communication (GJIC) in the liver, allowing the diffusion of small molecules through cytosol from cell-to-cell. Hepatic fibrosis is characterized by a disruption of normal tissue architeture by cellular lesions, and may alter the GJIC. This work aimed to study the expression and distribution of Cx32 in liver fibrosis induced by the oral administration of dimethylnitrosamine in female Wistar rats. The necropsy of the rats was carried out after five weeks of drug administration. They presented a hepatic fibrosis state. Sections from livers with fibrosis and from control livers were submitted to immunohistochemical, Real Time-PCR and Western-Blot analysis to Cx32. In fibrotic livers the Cxs were diffusely scattered in the cytoplasm, contrasting with the control livers, where the Cx32 formed junction plaques at the cell membrane. Also it was found a decrease in the gene expression of Cx32 without reduction in the protein quantity when compared with controls. These results suggest that there the mechanism of intercellular communication between hepatocytes was reduced by the fibrotic process, which may predispose to the occurrence of a neoplastic process, taken in account that connexins are considered tumor suppressing genes.(AU)

A conexina 32 (Cx32) é uma proteína que constitui os canais que promovem as comunicações intercelulares via junções comunicantes (CIJC) no fígado, permitindo difusão de pequenas moléculas citoplasmáticas de uma célula à outra. A fibrose hepática caracteriza-se pela alteração da arquitetura normal do fígado e podem alterar as CIJCs. O objetivo deste trabalho foi estudar a expressão e distribuição de Cx32 na fibrose hepática. O objetivo do presente trabalho foi estudar a expressão e distribuição da Cx32 em fígados com fibrose induzida pela administração oral de dimetilnitrosamina em fêmeas de ratos Wistar. A necropsia foi realizada após cinco semanas da última administração da droga e observou-se um quadro de fibrose hepática. Amostras dos fígados com fibrose e de animais controle foram submetidas à análise imunoistoquímica, por Real Time-PCR e por Western-Blot verificando-se a presença de Cx32 difusa e dispersa no citoplasma dos fígados com fibrose. No grupo controle a Cx32 localizou-se na membrana citoplasmática com a formação de placas juncionais. O fígado com fibrose também revelou diminuição da expressão gênica de Cx32, embora sem a redução da quantidade do produto protéico, quando comparado ao grupo controle. Estes resultados sugerem que o mecanismo de comunicação intercelular entre os hepatócitos reduziu-se durante o processo fibrótico, o que pode predispor a ocorrência de processos neoplásicos, uma vez que as conexinas são consideradas genes supressores de tumores.(AU)

Expression and distribution of connexin 32 in rat liver with experimentally induced fibrosis / Expressão e distribuição da conexina 32 em fígados de ratos com fibrose induzida experimentalmente

The connexin 32 (Cx32) is a protein that forms the channels that promote the gap junction intercellular communication (GJIC) in the liver, allowing the diffusion of small molecules through cytosol from cell-to-cell. Hepatic fibrosis is characterized by a disruption of normal tissue architeture by cellular lesions, and may alter the GJIC. This work aimed to study the expression and distribution of Cx32 in liver fibrosis induced by the oral administration of dimethylnitrosamine in female Wistar rats. The necropsy of the rats was carried out after five weeks of drug administration. They presented a hepatic fibrosis state. Sections from livers with fibrosis and from control livers were submitted to immunohistochemical, Real Time-PCR and Western-Blot analysis to Cx32. In fibrotic livers the Cxs were diffusely scattered in the cytoplasm, contrasting with the control livers, where the Cx32 formed junction plaques at the cell membrane. Also it was found a decrease in the gene expression of Cx32 without reduction in the protein quantity when compared with controls. These results suggest that there the mechanism of intercellular communication between hepatocytes was reduced by the fibrotic process, which may predispose to the occurrence of a neoplastic process, taken in account that connexins are considered tumor suppressing genes.

A conexina 32 (Cx32) é uma proteína que constitui os canais que promovem as comunicações intercelulares via junções comunicantes (CIJC) no fígado, permitindo difusão de pequenas moléculas citoplasmáticas de uma célula à outra. A fibrose hepática caracteriza-se pela alteração da arquitetura normal do fígado e podem alterar as CIJCs. O objetivo deste trabalho foi estudar a expressão e distribuição de Cx32 na fibrose hepática. O objetivo do presente trabalho foi estudar a expressão e distribuição da Cx32 em fígados com fibrose induzida pela administração oral de dimetilnitrosamina em fêmeas de ratos Wistar. A necropsia foi realizada após cinco semanas da última administração da droga e observou-se um quadro de fibrose hepática. Amostras dos fígados com fibrose e de animais controle foram submetidas à análise imunoistoquímica, por Real Time-PCR e por Western-Blot verificando-se a presença de Cx32 difusa e dispersa no citoplasma dos fígados com fibrose. No grupo controle a Cx32 localizou-se na membrana citoplasmática com a formação de placas juncionais. O fígado com fibrose também revelou diminuição da expressão gênica de Cx32, embora sem a redução da quantidade do produto protéico, quando comparado ao grupo controle. Estes resultados sugerem que o mecanismo de comunicação intercelular entre os hepatócitos reduziu-se durante o processo fibrótico, o que pode predispor a ocorrência de processos neoplásicos, uma vez que as conexinas são consideradas genes supressores de tumores.

CYP2A6/2A7 and CYP2E1 expression in human oesophageal mucosa: regional and inter-individual variation in expression and relevance to nitrosamine metabolism.

Oesophageal cancer is one of the most common and lethal malignancies in the world. Despite many efforts, treatment is still ineffective for most cases; thus, the development of preventive strategies is crucial for decreasing the burden presented by this disease. Environmental factors, particularly nitrosamines, are thought to be involved in the genesis of oesophageal tumours, and knowledge about the expression of enzymes capable of activating pre-carcinogens in human oesophagus is very important for the development of preventive measures. We analysed the expression of CYP1A1, CYP1A2, CYP2A6/2A7, CYP2E1 and CYP3A4 mRNA in oesophageal mucosa of 50 patients by semi-quantitative RT-PCR. In five patients, who suffered from squamous cell carcinoma, we measured Nnitrosodimethylamine and N-nitrosodiethylamine metabolism in normal and tumorous tissue. CYP2A6/2A7 mRNA was expressed in 61% and CYP2E1 mRNA in 96% of the patients, but in the latter a lower degree of inter-individual variation was observed. These enzymes were expressed either in the distal or middle portions of the oesophagus of 90% of the patients. CYP1A1, CYP1A2 and CYP3A4 mRNA expression was not detected in any portion of the oesophagus. Oesophageal microsomes activated N-nitrosodimethylamine with a low degree of inter-individual variation and microsomes prepared from the tumour of a patient who strongly expressed CYP2A6/2A7 mRNA activated N-nitrosodiethylamine. We conclude that the human oesophagus expresses CYP2A6/2A7 and CYP2E1 and can activate nitrosamines. Notably, the expression of these enzymes is preferentially localized to the most common sites where tumours arise.

Alcohol induction of liver nuclear ethanol and N-nitrosodimethylamine metabolism to reactive metabolites.

In previous studies from our laboratory we reported the presence in highly purified liver nuclei, free of contamination with other organelles, of an ethanol metabolizing system (NEMS) able to lead to acetaldehyde and 1-hydroxyethyl free radicals (1HEt). In the present study we tested whether this NEMS is inducible by chronic alcohol administration to rats and whether these nuclei also have increased ability to bioactivate N-nitrosodimethylamine (NDMA). Sprague Dawley male rats (125-150g) were fed with a nutritionally adequate liquid diet containing alcohol to provide 36% of total energy (standard Lieber-De Carli rat diet), for 28 days. Controls received an isocaloric diet without alcohol. Animals were sacrificed, livers were excised and microsomes and purified nuclear fractions were prepared. Both microsomes and nuclei from treated animals had significantly increased ability compared to controls, to biotransform ethanol to acetaldehyde using NADPH as cofactor under an air atmosphere. Both organelles also exhibited significantly increased capacity compared to controls, to bioactivate NDMA to formaldehyde and to reactive metabolites that bind covalently to proteins. Nuclear preparations from control animals were also able to metabolize NDMA to formaldehyde and reactive metabolites. Results indicate that liver nuclei may have a CYP2E1 able to bioactivate both NDMA and EtOH and that these processes are being induced by chronic alcohol drinking. The bioactivation of these xenobiotics to reactive metabolites in the neighborhood of nuclear proteins and DNA might have significant toxicological implications.

Dimetilnitrosamina y antioxidantes: cáncer vesicular experimental / Dimethylnitrosamine and antioxidants: experimental gallbladder neoplasms

Este tipo de estudio tiene especial interés para Chile dado el notable incremento de este cáncer, el cual se mantiene hasta la actualidad (1.628 muertes y tasa de 11,5 por 100.000 en 1995). La especie usada fue el hamster (Mesocricetus auratus) y un carcinógeno, la dimetil nitrosamina, fue administrado por vía oral, en una dosis establecida. Se formaron 3 grupos de 20 animales cada uno, por un tiempo que alcanza los seis meses. El primer grupo se organizó como control. El grupo control ha tenido muertes espontáneas después del primer año de vida y no ha mostrado ningún cáncer vesicular. Los otros dos grupos tienen muy poco tiempo de evolución para extraer conclusiones en relación a cáncer, pero habría un efecto protector de los antioxidantes

Pharmacokinetic parameters determined from the clastogenic activity of ethylnitrosourea and dimethylnitrosamine in mice in vivo.

The latency period (LP) and the time of effective activity (TEA) of ethylnitrosourea (ENU) and dimethylnitrosamine (DMN) were inferred by comparing their kinetics of micronucleated polychromatic erythrocytes (MN-PCE) formation with the kinetics induced by radiation. The results indicate that LP and TEA vary between ENU and DMN. For ENU, these parameters are very similar to radiation indicating a rapid distribution, reaction and elimination. DMN presents a very long LP which agrees with the requirement of mutagen activation. The kinetics of MN-PCE production caused by DMN showed two peaks; this could be due to the presence of two different metabolites, two types of lesions in DNA or two mechanisms of MN-PCE formation. These hypotheses do not exclude each other. The data presented here support the conclusion that the comparison of MN-PCE-formation kinetics induced by chemical agents with that caused by radiation permits one to estimate the LP and the TEA, and provide information on the possible mechanism of action of chemical mutagens.

Dietary nitrosodimethylamine and the risk of lung cancer: a case-control study from Uruguay.

Evidence from animal studies indicates that various N-nitroso compounds are carcinogenic. We investigated whether consumption of nitrosodimethylamine (NDMA) and foods and beverages containing NDMA are carcinogenic for the lung. In a hospital-based case-control study in Uruguay, dietary intake of NDMA and its food sources was measured in 320 cases of lung cancer and 320 controls afflicted with diseases not related with tobacco use and diet. After adjusting for tobacco smoking and total energy intake, NDMA displayed a significant dose-response pattern, with a 3-fold increase in risk for the higher category of intake. The risks were slightly more elevated for adenocarcinoma of the lung. Also, salted meat consumption and beer intake were associated with an increased risk of lung cancer.

Estimation of the fraction of the dose of N-nitrosodimethylamine metabolized to methylamine in rats.

Despite many years of research on the metabolism of N-nitrosodimethylamine (NDMA) in rats, the significance of enzymatic denitrosation as a pathway remains unclear. To assess the role of this pathway of metabolism in rats, animals were administered NDMA by intravenous infusion at two infusion rates until steady state was achieved and the concentrations of NDMA (Css,NDMA) and methylamine (MA) (Css,MA), a product of the enzymatic denitrosation pathway, were determined in plasma. The clearance of NDMA (ClNDMA) from plasma was determined by dividing the infusion rate by Css,MA. The plasma clearance of MA (ClNDMA) was determined in a separate experiment. The fraction of the dose of NDMA metabolized by enzymatic denitrosation (fm) was calculated using the equation fm = (Css,MA*ClMA)/(Css,NDMA*ClNDMA). By this method it was estimated that 29% of the dose of NDMA was metabolized via the enzymatic denitrosation pathway. Thus enzymatic denitrosation is an important pathway in the metabolism of NDMA in rats.

Efecto del carcinogeno dimetilnitrosamina sobre el rinon del vison / Efect of carcinogen dimethylnitrasamine on the kidney of mink

Visones de un criadero que recibian alimentos, sobre la base de restos de pescado, evidenciaron un significativo aumento en su mortalidad, presencia de canceres hepaticos y alteraciones renales revelables histologicamente. Esos efectos fueron atribuibles a presencia, en el alimento, de dimetilnitrosamina (NDMA), en concentraciones 1,8 ug/g. En este trabajo se estudia en detalle el efecto de la NDMA sobre el rinon del vison. Visones que fueron tratados ip con NDMA(7 mg/kg en sol. fis.), mostraron dano evidenciable ultraestructuralmente en la corteza renal. El dano fue mayor en los tubulos proximales, que en los distales, pero era de naturaleza similar. Las celulas epiteliales tubulares de los animales intoxicados mostraron: a)Condensacion de la cromatina nuclear y dilatacion de la membrana perinuclear. b)Marcada hinchazon mitocondrial y ruptura de sus crestas con perdida de contenida de la matriz mitocondrial. c)Despegue de ribosomas y dilatacion del reticulo endoplasmico. d)Aumento del numero y tamano de las vacuolas autofagicas. e)Aparicion de gotas lipidicas en el citiplasma. En contraste con lo previamente establecido, para el caso de cancer hepatico del vison, el mecanismo del dano renal por NDMA no se pudo correlacionar directamente con la union de metabolitos reactivos de esta a proteinas o acidos nucleicos o la biotransformacion microsomal o mitocondrial de la NDMA o formaldehido. No obstante, el rinon biotransforma la NDMA a CO2, pero lo hace 3-4 veces menos intensamente que el rinon de rata. Los resultados sugeririan la presencia, en el caso del dano renal por NDMA, de mecanismos distintos de accion, a los habitualmente aceptados como responsables del dano hepatico o el renal en otras especies. Alternativamente, el dano renal puede deberse a dano hepatico concomitante

Efecto del carcinogeno dimetilnitrosamina sobre el rinon del vison / Efect of carcinogen dimethylnitrasamine on the kidney of mink

Visones de un criadero que recibian alimentos, sobre la base de restos de pescado, evidenciaron un significativo aumento en su mortalidad, presencia de canceres hepaticos y alteraciones renales revelables histologicamente. Esos efectos fueron atribuibles a presencia, en el alimento, de dimetilnitrosamina (NDMA), en concentraciones 1,8 ug/g. En este trabajo se estudia en detalle el efecto de la NDMA sobre el rinon del vison. Visones que fueron tratados ip con NDMA(7 mg/kg en sol. fis.), mostraron dano evidenciable ultraestructuralmente en la corteza renal. El dano fue mayor en los tubulos proximales, que en los distales, pero era de naturaleza similar. Las celulas epiteliales tubulares de los animales intoxicados mostraron: a)Condensacion de la cromatina nuclear y dilatacion de la membrana perinuclear. b)Marcada hinchazon mitocondrial y ruptura de sus crestas con perdida de contenida de la matriz mitocondrial. c)Despegue de ribosomas y dilatacion del reticulo endoplasmico. d)Aumento del numero y tamano de las vacuolas autofagicas. e)Aparicion de gotas lipidicas en el citiplasma. En contraste con lo previamente establecido, para el caso de cancer hepatico del vison, el mecanismo del dano renal por NDMA no se pudo correlacionar directamente con la union de metabolitos reactivos de esta a proteinas o acidos nucleicos o la biotransformacion microsomal o mitocondrial de la NDMA o formaldehido. No obstante, el rinon biotransforma la NDMA a CO2, pero lo hace 3-4 veces menos intensamente que el rinon de rata. Los resultados sugeririan la presencia, en el caso del dano renal por NDMA, de mecanismos distintos de accion, a los habitualmente aceptados como responsables del dano hepatico o el renal en otras especies. Alternativamente, el dano renal puede deberse a dano hepatico concomitante