Mouse Forestomach Research Articles

FISH analysis of Lactobacillus biofilms in the gastrointestinal tract of different hosts

To investigate the spatial organization of endogenous and exogenously applied Lactobacillus communities at specific locations in the adult gastrointestinal tract of different hosts. Samples of the human, murine and avian gastrointestinal tract of subjects that received or not received a Lactobacillus probiotic were analysed by fluorescence in situ hybridization (FISH) with rRNA-targeted probes. High levels of endogenous lactobacilli were observed on the nonsecretory, stratified squamous epithelia present in the forestomach of mice and crop of chickens, respectively. These epithelial associations showed characteristics of bacterial biofilms, i.e. bacteria attached to a surface and embedded in a matrix of extracellular polymeric substances. In other regions of the analysed intestines, lactobacilli seemed to occur mainly as dispersed bacterial cells or as microcolonies. Exogenous administration of a Lactobacillus probiotic did increase the levels of loosely adherent Lactobacillus cells detected. However, the probiotic strains were unable to establish themselves inside the gastrointestinal biofilms. Gastrointestinal biofilms of lactobacilli occur only in specific niches in certain hosts, such as the murine forestomach and avian crop. Biofilm formation by lactobacilli in specific parts of animal gastrointestinal tracts was documented for the first time by FISH.

Differential Inhibitory Effects of Conjugated Linoleic Acid Isomers on Mouse Forestomach Neoplasia Induced by Benzo(a)pyrene

The differential anticarcinogenic activity of conjugated linoleic acid (CLA) isomers, including c9,t11-CLA, t10,c12-CLA, and t,t-CLA, was examined in a mouse forestomach carcinogenesis regimen induced by benzo(a)pyrene (BP). Female ICR mice (6-7 weeks of age, 26 +/- 1 g) were divided into six groups (30 mice/group, 5 mice/cage): control, linoleic acid, CLA, c9,t11-CLA, t10,c12-CLA, and t,t-CLA. Each mouse was orally given 0.1 mL of sample and 0.1 mL of olive oil on Monday and Wednesday and BP (2 mg in 0.2 mL of olive oil) on Friday. This cycle was repeated four times. Twenty-three weeks later, the experiment was terminated for tumor analysis. t,t-CLA significantly reduced (p < 0.05) both tumor number and tumor size per mouse, relative to CLA and c9,t11-CLA, but similar to t10,c12-CLA. Reduction in tumor incidence by t,t-CLA (84.6%) was similar to that by CLA, c9,t11-CLA, and t10,c12-CLA, but it was significantly reduced (p < 0.05), relative to 100% linoleic acid and control. t,t-CLA elevated the apoptotic index to 35%, relative to 23% for CLA, 21% for c9,t11-CLA, 29% for t10,c12-CLA, 7% for linoleic acid, and 4% for control. t,t-CLA up-regulated the expression of the Bax gene and activated caspase-3 enzymes but down-regulated expression of the Bcl-2 gene. Cytosolic phospholipase A(2) activity was not affected by the CLA isomers tested. These results suggest that t,t-CLA has superior anticarcinogenic potential on BP-induced mouse forestomach neoplasia to CLA, c9,t11-CLA, and t10,c12-CLA, via the induction of apoptosis through mitochondrial dysfunction.

Chemical Carcinogenesis of the Gastrointestinal Tract in Rodents: An Overview with Emphasis on NTP Carcinogenesis Bioassays

Cancers of the stomach and large intestine (LI) are the second and fourth leading causes of human cancer mortality. A review of the National Toxicology Program (NTP) database and the Carcinogenic Potency Database (CPDB) reveals that chemically induced neoplasms of the gastrointestinal tract (GIT) are relatively common. Within the GIT, epithelial tumors of the forestomach in mice and rats and LI of the rat are most common. Generally, there is a high species concordance for forestomach with at least 26 chemicals inducing tumors in both species. Glandular stomach tumors are rare, and the few reported are usually neuroendocrine tumors (carcinoids) originating from the enterochromaffin-like (ECL) cells. Of 290 carcinogenic agents identified by the NTP, 19 (7%) caused intestinal neoplasia, 14 in the rat and 5 in the mouse. Neoplasms occurred in both males and females, exclusively in the small intestine (SI) of the mouse and in the LI or both SI and LI in the rat. Enteric carcinogens (NTP) frequently induced neoplasms at other alimentary sites (oral cavity, esophagus, and stomach). In conclusion, the most common induced GIT tumors are squamous neoplasms of the forestomach, glandular neoplasms of the stomach are rare, and rats appear more prone to developing LI (colorectal) cancer compared to mice.

Palytoxin toxicity after acute oral administration in mice

The acute oral toxicity of palytoxin (PLTX), a highly toxic compound associated with seafood intoxication in tropical and subtropical areas, was investigated in mice. After gavage administration (300–1697μg/kg) to groups of five female CD-1 mice, signs of toxicity and lethality were recorded for 24h. The LD50 was 767μg/kg (95% confidence limits: 549–1039μg/kg) and the main symptoms observed were scratching, jumping, respiratory distress and paralysis. Hematoclinical analyses showed increased levels of creatine phosphokinase and lactate dehydrogenase at doses of 600μg/kg and above, and aspartate transaminase at 848μg/kg and above. Histological analysis revealed acute inflammation of the forestomach in mice surviving up to 24h after administration (424–1200μg/kg). Other histological alterations were observed in the liver and pancreas, while cardiac and skeletal muscle cells revealed only ultrastructural alterations visible by transmission electron microscopy. Ultrastructural and hematoclinical findings suggest an involvement of skeletal and/or cardiac muscle as targets of PLTX, according to the observed human symptoms. A NOEL of 300μg/kg can be estimated from this acute oral toxicity study.

Daily gavage with corn oil is a causative factor for proliferative lesions of the forestomach in B6C3F1 mice

Daily gavage with corn oil is a causative factor for proliferative lesions of the forestomach in B6C3F1 mice

Screening and identification differentially displayed genes in fore stomach carcinoma of mice

Objective To screen and identify key genes differentially displayed in mouse fore stomach carcinoma, in order to elucidate the molecular mechanism underlying carcinogenesis.

4-1BB (CD137) Ligand Enhanced Anti-Tumor Immune Response against Mouse Forestomach Carcinoma In Vivo

Cancer occurrence and development has been demonstrated to be associated with escape from immune surveillance, and low costimulatory molecules expression has been considered as one of the important reasons for cancer evading the immune system. 4-1BB (CD137) is a costimulatory molecule expressed on the surface of activated T cells. Interaction of 4-1BB with its natural ligand (4-1BBL) expressed on antigen presenting cells (APCs) has been shown to amplify T-cell mediated immunity. We therefore examined whether murine cancer cells expressing 4-1BBL could produce anti-tumor effects in inoculated mice. Mouse forestomach carcinoma (MFC) cells were transfected with 4-1BBL gene (MFC/4-1BBL). The proliferation of the transduced cells in vitro was not different from that of parental cells. However, MFC/4-1BBL cells developed small tumors and induced higher cytotoxicity of tumor infiltration lymphocyte (TIL). Production of cytokines (IFN-gamma, TNF-alpha and IL-2) in serum and cytotoxic T lymphocyte (CTL) activity of splenocytes from mice immunized with mitomycin C (MMC)-treated MFC/4-1BBL cells were significantly higher than that from mice immunized with MMC-treated parental MFC and MFC/pMKITneo cells. These results suggest that modification of cancer cells with 4-1BBL gene can produce anti-tumor immune responses.

Depletion of CD4(+)CD25(+) regulatory T cells can promote local immunity to suppress tumor growth in benzo[a]pyrene-induced forestomach carcinoma.

To elucidate the distribution of CD4(+)CD25(+) regulatory T cells (Tregs) in different lymphoid tissues and its local enhancement on tumor growth before and after depletion of CD4(+)CD25(+) Tregs. Female ICR mice were gavaged with benzo[a]pyrene (BaP) to induce forestomach carcinoma. CD4(+)CD25(+) Tregs were intraperitoneally depleted with monoclonal antibody PC61. These mice were divided into BaP-only, BaP + IgG, BaP + PC61, and control groups. The forestomach of mice was dissected for histological analysis, and tunnel test was performed for apoptosis of tumor cells. CD4(+)CD25(+) Tregs were sorted from different lymphoid tissues and expression of Foxp3, IL-10, and chemokine receptors was analyzed by flow cytometry, semi-quantitative and real-time polymerase chain reaction. The mice gavaged with only BaP showed increased forestomach papilloma and carcinoma at wk 16 and 32. The proportion of CD4(+)CD25(+) Tregs was significantly higher in peri-stomach regional lymph nodes than in other lymphoid tissues. These CD4(+)CD25(+) Tregs in regional lymph nodes expressed higher levels of Foxp3 and IL-10, enriched in the CD62L-subset, and CCR1 and CCR5 chemokine receptors. In mice gavaged with BaP + PC61, the number of tumor nodules and tumor volume decreased significantly with massive infiltrating cells and apoptosis of tumor cells. In the draining regional lymph nodes, the number of CD4(+)CD25(+) Tregs also decreased significantly. Inducible and activated CD4(+)CD25(+) Tregs in the draining regional lymph nodes suppress host local immunity during tumor growth. Depletion of CD4(+)CD25(+) Tregs can promote host local immunity to suppress tumor growth.

Neuromedin U can exert colon‐specific, enteric nerve‐mediated prokinetic activity, via a pathway involving NMU1 receptor activation

The neuromedin U (NMU) receptors, NMU1 and NMU2, are expressed in the gut but their functions are unclear. This study explores the role of NMU in gastrointestinal motility. The effects of NMU were examined in the forestomach and colon isolated from NMU2R wild-type and NMU2R-/- (knockout) mice, looking for changes in muscle tension and in nerve-mediated responses evoked by electrical field stimulation (EFS), and in models of peristalsis in mouse colon and faecal pellet transit in guinea-pig colon. In the mouse forestomach, NMU (1 nM-10 microM) concentration-dependently induced muscle contraction, in the presence of tetrodotoxin and atropine, in preparations from both wild-type and NMU2R-/- mice (pEC50: 7.9, 7.6, Emax: 0.26, 0.20g tension, respectively, n=8 each concentration). The same concentrations of NMU had no consistent effects on the responses to EFS (n=8). In the mouse colon, NMU (0.1 nM-1 microM) had no significant effect on baseline muscle tension (n=8), but concentration-dependently potentiated EFS-evoked contractions in preparations from both wild-type and NMU2R-/- mice, pEC50: 8.1, 7.8, Emax: 24%, 21%, respectively, n=6-11. NMU (0.01 nM-0.1 microM, n=5-7) concentration-dependently decreased the interval between waves of peristalsis in the mouse colon (pEC50: 8.8) and increased the rate at which a faecal pellet moved along the guinea-pig colon. These results demonstrate that NMU exerts colon-specific, nerve-mediated, prokinetic activity, via a pathway involving activation of NMU1 receptors. This suggests that this receptor may represent a molecular target for the treatment of intestinal motility disorders.

Expression of PCNA, AKP and ACP during development of mouse fore stomach carcinoma

To find out the relationship of the expressions of proliferating cell nuclear antigen (proliferating cell nuclear antigen, PCNA), alkaline phosphotase (alkaline phosphotase, AKP) and acid phosphotase (acid phosphotase, ACP) with the development of mouse fore stomach cancerization. The animal models, including the various stages during the development of NIH mouse fore stomach carcinoma, were made by N-Nitrososarcosineethylester (N-Nitrososarcosineethylester, NSEE). The mice were sacrificed on the 14th, 28th, 42nd, 56th, 70th and 84th days respectively after mice were irrigated with NSEE. The fore stomach was taken out and dissected. The methods of histopathology, immunohistochemistry and isoenzyme electrophoresis were adopted to study the dynamic changes of cell shape and expression of PCNA, AKP and ACP. On the 42nd and 56th days after NSEE treatment, the expression of PCNA increased gradually along with the cancerization. Comparing with the control, there were significant differences (P<0.05). On the 70th and 84th days, the expression of PCNA increased further (compared with the control P<0.01). The activity of AKP increased gradually along with the cancerization. On the 14th, 28th, 42nd and 56th days, there were significant differences (P<0.05); on the 70th and 84th days, the activity of AKP increased further (P<0.01). The activity of ACP also increased on the 14th, 28th, 42nd and 56th days, and there were significant differences on the 70th days (P<0.05) and on the 84th days (P<0.01) compared with the control. During the carcinogenesis of NIH mouse fore stomach, the expressions of PCNA, AKP and ACP increased gradually and were consisted with the changes of cell shapes.

The morphological pathway for mouse forestomach cancer

We analyzed the morphological changes accompanying the development of cancer in the mouse forestomach. The main aim of the study was to evaluate whether cancer in this area of the stomach arises de novo or undergoes a series of precancerous changes. Tumors were induced by the 1,2-dimethylbenz(a)antracene (DMBA) at a total dose of 4 mg/mouse. The suspected areas of the stomach were studied morphologically in 79 mice. Benign tumors (squamous-cell papillomas) and malignant tumors (squamous-cell carcinomas) were found in 40 mice. Tumors arose in all cases together with differential changes in the forestomach epithelium. These changes were seen as irregular diffuse hyperplasia or focal proliferation, with or without differential signs of dysplasia. Destruction of the basal epithelial membrane indicated transformation of the process into malignant invasive carcinoma. Thus, in chemically induced cancer of the forestomach, squamous-cell carcinoma develops as the final stage of morphologically recognizable precancerous changes in the epithelial layer. De novo formation of such tumors in the forestomach was not observed.

A High-Molecular-Mass Surface Protein (Lsp) and Methionine Sulfoxide Reductase B (MsrB) Contribute to the Ecological Performance of Lactobacillus reuteri in the Murine Gut

Members of the genus Lactobacillus are common inhabitants of the gut, yet little is known about the traits that contribute to their ecological performance in gastrointestinal ecosystems. Lactobacillus reuteri 100-23 persists in the gut of the reconstituted Lactobacillus-free mouse after a single oral inoculation. Recently, three genes of this strain that were specifically induced (in vivo induced) in the murine gut were identified (38). We report here the detection of a gene of L. reuteri 100-23 that encodes a high-molecular-mass surface protein (Lsp) that shows homology to proteins involved in the adherence of other bacteria to epithelial cells and in biofilm formation. The three in vivo-induced genes and lsp of L. reuteri 100-23 were inactivated by insertional mutagenesis in order to study their biological importance in the murine gastrointestinal tract. Competition experiments showed that mutation of lsp and a gene encoding methionine sulfoxide reductase (MsrB) reduced ecological performance. Mutation of lsp impaired the adherence of the bacteria to the epithelium of the mouse forestomach and altered colonization dynamics. Homologues of lsp and msrB are present in the genomes of several strains of Lactobacillus and may play an important role in the maintenance of these bacteria in gut ecosystems.

In vivo metabolism and kinetics of ethylene glycol monobutyl ether and its metabolites, 2-butoxyacetaldehyde and 2-butoxyacetic acid, as measured in blood, liver and forestomach of mice

Ethylene glycol monobutyl ether (EGBE) causes forestomach hyperplasia and neoplasia in mice when administered chronically by inhalation.The study was initiated to test the physiologically based pharmacokinetic (PBPK) model prediction that 2-butoxyacetaldehyde (BAL), a transient, labile intermediate in the oxidation of EGBE to butoxyacetic acid (BAA), is unlikely to achieve concentrations sufficient to cause DNA damage in target tissues.Male and female B6C3F1 mice were administered a high oral dose of EGBE (600 mg kg−1), and tissues were collected at 5, 15, 45 and 90 min following the dose. The tissues were processed for determination of EGBE, BAL and BAA by gas chromatography-mass spectrometry.BAL was detected at low concentrations in all tissues sampled and at all time points following EGBE administration (about 0.3–33 μM). BAL concentrations were highest in the initial samples (5 min) in all tissues and declined from that point.BAL concentrations in liver and forestomach tissues corresponded to the peak concentrations predicted by an already published PBPK model, and are higher than BAL concentrations that could be achieved by inhalation exposure to EGBE.Mouse inhalation exposure to EGBE is therefore unlikely to generate BAL concentrations in tissues sufficient to initiate a carcinogenic response.

Interactive effects of nrf2 genotype and oltipraz on benzo[a]pyrene-DNA adducts and tumor yield in mice.

The cancer chemopreventive actions of oltipraz (4-methyl-5-[2-pyrazinyl]-1,2-dithiole-3-thione) have been primarily associated with the induction of phase 2 detoxifying enzymes through transcriptional activation of the antioxidant response element (ARE) in the promoter regions of these genes. The transcription factor Nrf2 has been shown to bind to and activate AREs. Previously, we demonstrated that nrf2-deficient mice had low basal expression of phase 2 enzymes and were substantially more susceptible to benzo[a]pyrene (B[a]P)-induced neoplasia of the forestomach than wild-type. Moreover, loss of Nrf2 abrogated the chemopreventive action of oltipraz, when administered 48 h before B[a]P, an interval allowing maximal induction of many phase 2 enzymes. Oltipraz also inhibits some cytochrome P450s involved in the bioactivation of B[a]P. In the present study we observed that oltipraz had no protective effect on tumor burden in the forestomach of nrf2-deficient mice when administered 1 h before B[a]P, a timeline that selectively optimizes for possible inhibitory effects on cytochrome P450s. To evaluate the role of nrf2 genotype on B[a]P disposition, levels of B[a]P-DNA adducts were measured as tetrols released from DNA isolated from target (forestomach) and non-target tissues (liver) of wild-type and nrf2-deficient mice treated with either vehicle or oltipraz 1 or 48 h before B[a]P. Levels of B[a]P-DNA adducts in forestomach were significantly higher in nrf2-deficient compared with wild-type mice. Oltipraz treatment at 1 or 48 h before B[a]P had no protective effect on forestomach tetrol levels in nrf2-deficient mice, whereas a significant reduction was observed in wild-type mice treated with oltipraz 48 h, but not 1 h, before carcinogen. Combining all treatments and genotypes, there was a strong correlation (R(2) = 0.91) between levels of B[a]P-DNA adducts in forestomach and subsequent yield of tumors. In contrast to the results in forestomach, nrf2 genotype did not modify hepatic B[a]P-DNA adduct levels while both oltipraz treatments were protective, suggesting that Nrf2-independent mechanisms (e.g. P450 inhibition) for oltipraz can also occur in vivo in some tissues.

Inhibition of nitrosodiethylamine-induced hepatocarcinogenesis by dietary turmeric in rats

Turmeric, widely used in food and medicine has been shown to prevent benzo(a)pyrene [B(a)P] or dimethylbenz(a)anthracene (DMBA)-induced forestomach, skin and mammary tumors in mice and/or rats. In this study we examine the modulatory effects of turmeric on nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in rats. Female Wistar rats were administered NDEA (200 ppm) through drinking water (5 days per week) for 4 weeks. Control and/or NDEA-treated rats received 0, 0.2, 1.0 or 5.0% turmeric diet (w/w) either before (2 weeks), during (4 weeks) and after NDEA exposure (10 weeks) or starting from 24 h after NDEA exposure for 10 weeks. NDEA-treated rats receiving 1 or 5% turmeric before, during and after carcinogen exposure showed significant decrease in number of gamma glutamyl transpeptidase (GGT) positive foci measuring >500 or >1000 μm and decrease in the incidence of NDEA-induced focal dysplasia (FD) and hepatocellularcarcinomas. Decrease in the number of GGT positive foci measuring >1000 μm was also observed in NDEA-treated rats receiving 0.2% turmeric, although no decrease in tumor incidence was noted. On the other hand, similar levels of turmeric treatment (0.2, 1 and 5%) after exposure to NDEA did not show any protective effects. The underlying mechanism(s) of chemoprevention of NDEA-induced hepatocarcinogenesis need to be explored.

Critical role of allyl groups and disulfide chain in induction of Pi class glutathione transferase in mouse tissues in vivo by diallyl disulfide, a naturally occurring chemopreventive agent in garlic.

We have shown previously that the chemoprotective activity of diallyl disulfide (DADS), a naturally occurring anticancer agent in garlic, against benzo[a]pyrene (BP)-induced forestomach carcinogenesis in mice correlates strongly with its inductive effects on the expression of Pi class glutathione (GSH) transferase mGSTP1-1. The present structure-activity relationship studies were designed to define the role of allyl groups and the disulfide chain in mGSTP1-inducing activity of DADS. Hepatic mGSTP1 mRNA levels rose rapidly upon treatment of mice with DADS, reached a maximum between 12 and 24 h (< or =5.7-fold induction) and fell to control levels by 48 h after DADS treatment. Induction of mGSTP1 mRNA in the forestomach was maximal between 6 and 12 h after DADS treatment (< or =4.7-fold induction). The mGSTP1 mRNA expression was either unaltered (liver) or moderately increased (forestomach) upon treatment of mice with dipropyl disulfide (DPDS), which is a naturally occurring saturated analog of DADS. These results indicated that the allyl groups are critical for the mGSTP1-inducing activity of DADS. A statistically significant increase in the expression of mGSTP1 mRNA was also observed in the liver and forestomach of mice treated with diallyl monosulfide (DAMS), albeit to a much lesser extent compared with DADS. These results indicated that the oligosulfide chain length in garlic organosulfides (OSCs) is equally important for their mGSTP1-inducing activity. The role of the disulfide chain in DADS-mediated induction of mGSTP1 was further investigated by testing a pair of alkadienes (1,7-octadiene and 1,8-nonadiene) having structural similarity to DADS. Both DADS and the alkadienes carry allyl groups at both ends of a linear molecule and the distance between the allylic carbon atoms is similar in both compounds, but the central disulfide chain of DADS is replaced with an alkyl chain in the alkadienes. The alkadienes were either ineffective or moderately active in increasing mGSTP1 expression. In conclusion, the results of the present study clearly indicate that the presence of terminal allyl groups as well as the central disulfide chain is required for maximum induction of mGSTP1 in vivo by garlic-derived OSCs.

The development of forestomach tumours in the mouse following exposure to 2-butoxyethanol by inhalation: studies on the mode of action and relevance to humans

2-Butoxyethanol, a forestomach carcinogen in mice exposed by inhalation, has been shown to enter the forestomach as a result of grooming and ingestion of material condensed on the skin and fur during exposure. The material entering the stomach concentrates in the forestomach region and persists for at least 48 h post-exposure. Mice given single oral doses of either 2-butoxyethanol or 2-butoxyacetic acid, daily for 10 days, developed a marked hyperkeratosis in the forestomach. 2-Butoxyacetic acid was more potent than 2-butoxyethanol, the NOEL for the former being 50 mg/kg and for the latter, 150 mg/kg. Although a dose dependent increase in cell replication was also seen with both chemicals, the results were confounded by a high labelling rate in the controls. There was no evidence of significant binding of radiolabelled 2-butoxyethanol to proteins in stomach tissues. 2-Butoxyethanol was metabolised in vitro in both mouse and rat forestomach and glandular stomach fractions by alcohol dehydrogenases forming 2-butoxyacetaldehyde which was rapidly converted by aldehyde dehydrogenases to 2-butoxyacetic acid. There was a marked species difference in alcohol dehydrogenase activity between rats and mice with the maximum rates up to one order of magnitude greater in mouse than rat. The alcohol and aldehyde dehydrogenases were heavily concentrated in the stratified squamous epithelium of the forestomach of both rats and mice whereas in the glandular stomach the distribution was more diffuse. In human stomach both enzymes were evenly distributed throughout the epithelial cells of the mucosa. It is concluded that 2-butoxyethanol is ingested following inhalation exposure and concentrates in the forestomach where it is metabolised to 2-butoxyacetic acid which causes cellular damage, increased cell replication and hyperkeratosis. These changes are believed to lead to the tumours seen in mice exposed to 2-butoxyethanol for a lifetime. Differences in structure and enzyme distribution between the rodent and human stomach suggest that the responses seen in the mouse are unlikely to occur in humans.

The forestomach of rats and mice, an effective device supporting digestive metabolism in muridae (review)

Summary The forestomach of rats and mice adapts the digestive regime of rats and mice from “food intake in bulks” to a “steady state digestion”. It stores well chewed and salivated food in amounts as needed for one to three hours or longer. The forestomach supplies its content for further digestion independently from its filling degree but in relation to the host's actual energy need during the light period or lipid metabolism during the dark period. Postprandial hyperglycemia and glycogen increase in the liver is lacking. Animals ingest most of their daily food during darkness. Meal frequency increases while the amount of food stored in the forestomach is hardly influenced. However, extremely high food demand or limitation of feeding time leads to increased filling per meal of the forestomach by four times and more, but in relation to “eating for calories”. The brain's appetite-regulating-network and signals which mechanically record the distension of the forestomach-stomach-cavity determine the ingested volume. In leptin-deficient Lep ob /Lep ob mice the filling volume of the forestomach per meal increases up to five times during the night and twice during the day. The frequency of meals declines. Emptying of the forestomach is controlled by a local feed back loop between duodenal reabsorption and the tension of the forestomach muscle fibres linked by humoral signals such as secretin and cholecystokinin. During storage in the forestomach food pap is subjected to digestion of starch, fat and chitin, but none of cellulose or protein can be observed. Microorganisms are without significance for the forestomach's function as shown in germ-free animals. Lactobacillae dominate in the variety of organisms lodged there. They are authochthonous and attached to the surface of the wall as dense carpets. Their lactic acid may have preservation effect on the food stored.

Mechanism(s) of turmeric-mediated protective effects against benzo(a)pyrene-derived DNA adducts

The effects of turmeric feeding before and after benzo(a)pyrene [B(a)P] exposure on the levels of B(a)P-derived DNA adducts were studied in tissues of Swiss mice employing 32P-postlabelling analysis. A reduction in the levels of B(a)P-derived DNA adducts in liver, lung, and forestomach was observed in animals pre-treated with 0.2 or 1% turmeric diet and exposed to B(a)P by oral intubation when compared to animals receiving standard laboratory diet and B(a)P. The observed decrease was not due to dilution caused by nascent DNA synthesis. Comparative evaluation of levels of B(a)P-derived DNA adducts in tissues of animals shifted to 0.2 or 1% turmeric diet after 24 h of oral intubation of B(a)P with those continued on standard laboratory diet did not suggest enhanced disappearance/repair of B(a)P-derived DNA adducts due to exposure to turmeric. Further, pre-treatment of mice with 1% turmeric diet significantly reduced the B(a)P-induced increase in activity of cytochrome P450 (CYP450) isozymes CYP 1A1 and 1A2 in liver, lung, and forestomach of mice. In addition, hepatic glutathione S-transferase (GST) was found to be elevated in turmeric pre-treated mice. Thus turmeric-mediated decrease in induction of phase-I enzymes in liver, lung, and forestomach of mice and enhancement of hepatic GST appear to play an important role in reducing the B(a)P-induced DNA damage in target and non-target tissues.

Comparative carcinogenicity of 1,3-butadiene, isoprene, and chloroprene in rats and mice

1,3-Butadiene, isoprene (2-methyl-1,3-butadiene), and chloroprene (2-chloro-1,3-butadiene) are high-production-volume chemicals used mainly in the manufacture of synthetic rubber. Inhalation studies have demonstrated multiple organ tumorigenic effects with each of these chemicals in mice and rats. Sites of tumor induction by these epoxide-forming chemicals were compared to each other and to ethylene oxide, a chemical classified by the National Toxicology Program (NTP) and by the International Agency for Research on Cancer (IARC) as carcinogenic to humans. For this group of chemicals, there are substantial species differences in sites of neoplasia; neoplasia of the mammary gland is the only common tumorigenic effect in rats and mice. Within each species, there are several common sites of tumor induction; these include the hematopoietic system, circulatory system, lung, liver, forestomach, Harderian gland, and mammary gland in mice, and the mammary gland and possibly the brain, thyroid, testis, and kidney in rats. For studies in which individual animal data were available, mortality-adjusted tumor rates were calculated, and estimates were made of the shape of the exposure–response curves and ED10 values (i.e. exposure concentrations associated with an excess risk of 10% at each tumor site). Most tumorigenic effects reported here were consistent with linear or supralinear models. For chloroprene and butadiene, the most potent response was for the induction of lung neoplasms in female mice, with ED10 values of 0.3 ppm. Based on animal cancer data, isoprene and chloroprene are listed in the NTP's Report on Carcinogens (RoC) as reasonably anticipated to be a human carcinogen. Butadiene is listed in the RoC as known to be a human carcinogen ‘based on sufficient evidence of carcinogenicity from studies in humans, including epidemiological and mechanistic information’, with support from experimental studies in laboratory animals. Epidemiology data for isoprene and chloroprene are not considered adequate to evaluate the potential carcinogenicity of these agents in humans.