Quantification and kinetic study in plasma and tissues of (E)-1,1,4,4-tetramethyl-2-tetrazene, a liquid propellant and a transformation product of 1,1-dimethyl hydrazine.

(E)-1,1,4,4-tetramethyl-2-tetrazene (TMTZ) is formed from the oxidation of the unsymmetrical 1,1-dimethylhydrazine (UDMH) and is used as a storable liquid fuel which can be considered as a new potential propellant for space rocket propulsion. To better understand the toxicological behavior of the compound, an intraperitoneal administration of TMTZ was performed in mice to define its toxicokinetics and tissue distribution. A fully validated liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) assay was developed to determine TMTZ levels in biological samples. Determination of TMTZ was achieved using 50 µL of plasma or tissue solution. Precipitation with ammonium sulfate and acetonitrile was used for sample preparation. Liquid chromatography was performed on an Atlantis HILIC Silica column (Waters; 3 µm, 150 mm × 2.1 mm i.d.). Isocratic elution with a mixture of ammonium acetate buffer (pH 5, 100 mM)/water/acetonitrile (3:2:95, v/v/v) was used. The detection was conducted using an electrospray source in positive ion mode. TMTZ and (15)N2-TMTZ (internal standard) were quantitated in selected reaction monitoring mode using the transition m/z 117→72 and 119→74, respectively. Standard curves exhibited excellent linearity in the range of 10-500 ng/mL for plasma and 50-2000 ng/mL for all tissues (heart, liver, brain, kidney, and lung) analyzed, and acceptable precision and accuracy (<10 %) were obtained. The elimination rate constant strongly suggests that TMTZ was very quickly eliminated from the body. The results of tissue distribution experiments indicated that TMTZ underwent a rapid distribution into limited organs such as the liver, kidney, and brain.

The interplay between QSAR/QSPR studies and partial order ranking and formal concept analyses.

The often observed scarcity of physical-chemical and well as toxicological data hampers the assessment of potentially hazardous chemicals released to the environment. In such cases Quantitative Structure-Activity Relationships/Quantitative Structure-Property Relationships (QSAR/QSPR) constitute an obvious alternative for rapidly, effectively and inexpensively generatng missing experimental values. However, typically further treatment of the data appears necessary, e.g., to elucidate the possible relations between the single compounds as well as implications and associations between the various parameters used for the combined characterization of the compounds under investigation. In the present paper the application of QSAR/QSPR in combination with Partial Order Ranking (POR) methodologies will be reviewed and new aspects using Formal Concept Analysis (FCA) will be introduced. Where POR constitutes an attractive method for, e.g., prioritizing a series of chemical substances based on a simultaneous inclusion of a range of parameters, FCA gives important information on the implications associations between the parameters. The combined approach thus constitutes an attractive method to a preliminary assessment of the impact on environmental and human health by primary pollutants or possibly by a primary pollutant well as a possible suite of transformation subsequent products that may be both persistent in and bioaccumulating and toxic. The present review focus on the environmental - and human health impact by residuals of the rocket fuel 1,1-dimethylhydrazine (heptyl) and its transformation products as an illustrative example.

Efecto del ácido ursodeoxicólico en un modelo experimental de cáncer de colon / Effect of ursodeoxycholic acid in an experimental colon cancer model

Objetivos: analizar si la administración oral del ácido urso -deo xi cólico previene la aparición y desarrollo de carcinogénesiscolónica en ratas.Material y métodos: ciento diez ratas de la raza “Sprague-Dawley” de 10 semanas de vida, de ambos sexos, fueron divididasen 5 grupos: a) 20 ratas control, sin tratamiento; b) 20 ratas, tratadascon ácido ursodeoxicólico (AUDC), a 4 mg/kg/día, juntocon etanol, a 1,23 g/kg peso al día, añadidos al agua de bebida,desde el principio del estudio y durante 24 semanas; c) 30 ratas,18 dosis semanales, de 21 mg/kg peso de dimetilhidracina(DMH) subcutánea, desde el principio del estudio, junto con lasmismas dosis de etanol y AUDC, que en el grupo B; d) 20 ratas,18 dosis semanales subcutáneas de ácido etilen-diamino-tetracético;y e) 20 ratas, tratadas con las mismas dosis de etanol y lasmismas inyecciones de DMH, que el grupo C. El sacrificio de todoslos animales, se llevó a cabo en las semanas 25-27.Resultados: no aparecieron tumores en ausencia de DMH.No se observaron diferencias significativas en el número de ratasque desarrollaron cáncer de colon, ni en el número de neoplasiaspor rata, ni en los hallazgos macro-microscópicos de los tumores,entre los animales del grupo C y del grupo E.Conclusiones: la administración de ácido ursodeoxicólico, enla dosis y tiempo utilizados no modificó la carcinogénesis colónica,usando un modelo dinámico de administración concomitantede inducción tumoral con DMH en ratas

Aims: the present study was designed to examine the effect ofursodeoxycholic acid as chemoprotective agent in experimentalcolon carcinogenesis in rats.Material and methods: one hundred and ten 10-week-old,Sprague-Dawley rats were divided into five groups: group A (20),no treatment. Group B (20), receiving daily both ursodeoxycholicacid (UDCA) 4 mg/kg of body weight and ethanol 1.23 g/kg ofbody weight added to the drinking water from the beginning ofthe study through 24 weeks. Group C (30), receiving 18 weeklydoses of dimethylhydrazine (DMH) 21 mg/kg of body weight subcutaneouslyfrom the beginning of the study, with the same dosesof UDCA and ethanol as in group B. Group D (20), ethylen-diamin-tetracetic acid solution alone for 18 weeks. Group E (20),receiving the same doses of ethanol plus DMH injections as ingroup C. All experimental animals were sacrificed after 25-27weeks.Results: no tumors developed in dimethylhydrazine-freegroups. No significant differences in number of tumor-free animals,number of tumors per rat, and macro-microscopic tumorfindings were seen between animals in group C and animals ingroup E.Conclusions: we concluded that such an ursodeoxycholicacid supplementation did not modify colorectal carcinogenesis usinga dynamic DMH-induced model in rats

A preliminary assessment of the potential environmental and human health impact of unsymmetrical dimethylhydrazine as a result of space activities.

A preliminary assessment of the potential environmental and human health impact of UDMH as a result of space activities has been carried out applying a theoretical approach in comparison with selected experimental data. The theoretical framework includes QSAR, ADME and PASS modelling as well as studies on the possible atmospheric dispersion of UDMH as calculated applying the OML-Multi model. The possible impact on the environment and the human health has been elucidated and it has been concluded that UDMH especially inside the fall region of burned-out rocket stages constitute a significant threat to both environmental and human health, the latter as a results of the carcinogenic, mutagenic, convulsant, teratogenic and embryotoxic characteristics of UDMH in addition to the general toxic characteristics of the compound.

Efecto de la desfuncionalización colónica en un modelo experimental de cáncer de colon / Effect of defunctionalization on colon carcinogenesis in the rat

Objetivo: examinar el efecto de la ausencia fecal en la aparicióny desarrollo de la carcinogénesis colónica en ratas de ambossexos.Material y métodos: ciento treinta y ocho ratas “Sprague-Dawley” de 10 semanas de vida, de ambos sexos, divididas en5 grupos: A) 20 ratas, sin tratamiento; B) 26 ratas, con una desfuncionalizacióncolónica; C) 30 ratas, 18 dosis semanales de 21mg/kg peso de dimetilhidracina (DMH) desde el principio del estudio;D) 20 ratas, 18 semanas con ácido etilen-diamino-tetracético;y E) 42 ratas, igual técnica quirúrgica que B, y las mismas inyeccionesque C. El sacrificio tuvo lugar a las 25-27 semanas. Se estudióla incidencia de tumores colorrectales, su localización y loshallazgos anátomo-patológicos, comparando entre grupos.Resultados: la ausencia de carcinógeno no desarrolló tumores.No hubo diferencias significativas entre el número total de tumoresinducidos ni en el promedio de tumores por rata entre lasratas C y las E. La ausencia fecal provocó unos tumores de menortamaño (p = 0,007), los cuales presentaron estirpes más glandulares(p = 0,00009), mejor diferenciadas (p = 0,0054) y menos invasivas(p = 0,015). Así mismo, la ausencia fecal modificó tanto elpredominio natural de los machos sobre las hembras para desarrollarun mayor número de tumores colónicos DMH-inducidos(p = 0,025), como el predominio en el colon derecho de los carcinomasmucinosos DMH-inducidos (p = 0,0065).Conclusiones: la desfuncionalización colónica en ratas provocaen los segmentos desfuncionalizados una alteración de lospatrones de la carcinogénesis DMH-inducida

Objective: to examine the effect of fecal absence on experimentalcolon carcinogenesis in both male and female rats.Material and methods: a total of 138 10-week-old Sprague-Dawley, male and female rats were divided into five groups: A) 20rats, no treatment; B) 26 rats, colonic defunctionalization; C) 30rats, 18 weekly doses of dimethylhydrazine (DMH), 21 mg/kgbody weight each, from the beginning of the study; D) 20 rats,ethylen-diamine-tetraacetic acid for 18 weeks; and E) 42 rats,same surgical procedure as rats in group B plus DMH injections atthe same doses as rats in group C. Animals were sacrificed after25-27 weeks. Number of tumors, their location, and pathologicalfindings were all compared between groups.Results: no tumors developed in the dimethylhydrazine-freegroups. No differences were obtained either in number of tumorsor tumors per rat for group C as compared to group E. Fecal absencewas associated with smaller-sized tumors (p = 0.007),greater numbers of non-mucinous tumors (p = 0.00009), betterdifferentiation (p = 0.0054), and lesser penetration into the wall(p = 0.015) for group E as compared to group C. In the dimethylhydrazinegroup, fecal absence altered the number of tumors developingin males as compared to female rats (p = 0.025). Moreover,this fecal absence showed no inhibitory effect on rightcolonic tumors (p = 0.0065).Conclusions: fecal absence alters the DMH-carcinogenic patternin the defunctionalized colon when using an experimentalmodel in both male and female rats

Anticarcinogenic effects of curry leaves in dimethylhydrazine-treated rats.

Curry leaves are one of the spices used in Indian dishes for aroma and preservation. There are no reports on the antioxidant properties of curry leaves. In this study, the antioxidant potential of curry leaves in rats treated with a known chemical carcinogen, dimethylhydrazine hydrochloride (DMH) was investigated. Food intake was reduced in the rats fed curry leaf-supplemented diet but the body and the organ weights were not affected. Vitamin A content in the liver was significantly increased whereas glutathione (GSH) content was not altered. A 50% reduction was seen in the micronuclei induced by DMH and a 30% reduction in the activity of gamma-glutamyl transpeptidase when the rats were fed a curry leaf-supplemented diet. These results indicate that curry leaves have high potential as reducer of the toxicity of DMH.

Inhibition of 1,2-dimethylhydrazine-induced oxidative DNA damage by green tea extract in rat.

Following subcutaneous injection of 1,2-dimethylhydrazine (DMH), which is carcinogenic to rat colon and liver, to Sprague-Dawley rats, a significant increase of 8-hydroxydeoxyguanosine (8-OHdG) was observed in the DNA of colonic mucosa and liver. The 8-OHdG formation reached the maximal level at about 24 h after the DMII injection. On the other hand, no increase of 8-OHdG was observed in the DNA of the kidney. Drinking green tea extract (GTE) for ten days prior to the DMH injection significantly inhibited the formation of 8-OHdG in the colon. These findings demonstrate that DMH causes oxidative damage to the DNA of its target organ, and that GTE protects colonic mucosa from this oxidative damage.

A possible explanation for the differential cancer incidence in the intestine, based on distribution of the cytotoxic effects of carcinogens in the murine large bowel.

The ability of four mutagenic/carcinogenic chemicals administered as single doses to induce a programmed form of cell death (apoptosis) in the BDF1 mouse large bowel was studied and compared with a previous study on the small intestine using the same mice. The number of apoptotic cells was counted following treatment with the direct-acting agents N-nitroso-N-methylurea (NMU) and N-nitroso-N-ethylurea (NEU) and two agents which require metabolic activation 1,2-dimethylhydrazine (DMH) and N-nitrosodimethylamine (NDMA). DMH (80 mg/kg) was the most effective at inducing acute cell death and this was closely followed by NMU (200 mg/kg). The least effective agent in the large bowel was NDMA. The peak yield of apoptosis occurred between 4 h (NEU) and 8 h (DMH) after treatment. An analysis of the changing shapes of the frequency plots of apoptosis at each cell position in the crypt at various times after exposure permits an estimate to be made of the position in the crypt of the primary target cells for the cytotoxic action at time t = 0. For the agents studied, this is in the range of the 5th to the 10th position from the base of the crypt. This distribution for the target cells for apoptotic cell death is not coincident with that for the presumptive stem cells, which is at cell position 1 or 2. Comparisons with results previously obtained in the small intestine (ileum) of the same mice show that the relative cytotoxic effectiveness of the four agents differs. Furthermore, the position of the target cells is at about the 4th position from the bottom of the crypt in the ileum, and here the distribution is coincident with that presumed for the stem cells. Our interpretation of the data is that damaged cells in the stem cell region of the small bowel are removed by the activation of a cell suicide programme, which effectively removes potentially harmful genetic alterations. In contrast, in the large bowel, cell death is not initiated particularly strongly in the stem cell region but tends to occur higher in the crypt. The absence of this selective deletion process may result in the perpetuation of deleterious mutations in the colonic stem cell population and this may explain in part, the higher incidence of cancers observed in the large bowel.

Cytochrome P450 activity and distribution in the human colon mucosa.

Enzymatic activity associated with the mixed-function oxidase system was determined in microsomes prepared from the mucosal cells extracted from normal human colons. A high activity toward nitrogen oxidation reactions was observed. 1,2-Dimethylhydrazine, a colon-specific carcinogen, was metabolized at a higher rate in vitro by human colon microsomes as compared with the rat, and exhibited a km ten-fold lower, 1.03 mmol/l versus 9.68 mmol/l, respectively. This activity was inhibited by classic cytochrome P450 inhibitors; 70% inhibition was achieved using 70 mmol/l metyrapone (2-methyl-1,2-di-3-pyridyl-1-propanone), 20 mmol/l; SKF-525A (diethylaminoethyl-2,-2-diphenylvalerate HCl), or 350 mumol/l n-octylamine. These data suggest the presence of a stable, active mixed-function oxidase system in the human colon mucosa which has a preferential activity toward nitrogenous compounds and provides a mechanism for the activation of carcinogens. Its distribution in the colon appears to parallel the reported incidence of human colonic carcinomas.

Free radical activation of monomethyl and dimethyl hydrazines in isolated hepatocytes and liver microsomes.

Isolated hepatocytes and liver microsomes incubated with monomethyl-1,1 dimethyl- and 1,2 dimethyl-hydrazines produced free radical intermediates which were detected by ESR spectroscopy by using 4-pyridyl-1-oxide-t-butyl nitrone (4-POBN) as spin trapping agent. The spectral features of the spin adducts derived from all three hydrazine derivatives corresponded to the values reported for the methyl free radical adduct of 4-POBN. In the microsomal preparations inhibitors of the mixed function oxidase system and the destruction of cytochrome P450 by pretreating the rats with CoCl2 all decreased the free radical formation. Methimazole, an inhibitor of FAD-containing monoxygenase system, similarly decreased the activation of 1,1 dimethyl-hydrazine, but not that of monomethyl- and 1,2 dimethyl-hydrazines. The addition to liver microsomes of physiological concentrations of glutathione (GSH) lowered by approx. 80% the intensities of the ESR signals. Consistently, incubation of isolated hepatocytes with methyl-hydrazines decreased the intracellular GSH content, suggesting that GSH can effectively scavenge the methyl free radicals. The results obtained suggest that methyl free radicals could be the alkylating species responsible for the toxic and/or carcinogenic effect of methyl-hydrazines.

Dependence of 1,2-dimethylhydrazine metabolism on its treatment schedule.

The content of cytochromes P-450 and b5 in rat liver microsomes, as well as the extent of labeling of nucleic acids and proteins of the liver and kidneys and of mucosa from different intestinal segments, was studied in rats injected daily or once a week subcutaneously with similar total doses of 1,2-dimethyl-hydrazine (SDMH) and in untreated rats. Daily SDMH administrations led to a decrease in cytochrome P-450 activity. Pretreatment of rats with unlabelled SDMH resulted in decreased labeling of DNA, RNA, proteins, and acid-soluble fractions after [3H]SDMH injection. A more pronounced effect was found after the daily treatment.