Frequency and Duration Modulate Anticarcinogenic Effects of a Physical Training in the Colon.

Physical exercise has proven protective against colon carcinogenesis. We sought to clarify whether the frequency and duration of physical training were key factors for its anticarcinogenic effects on the colon. Either sedentary or physically trained male Wistar rats (n=82) were either exposed or not to the carcinogen dimethylhidrazine (DMH). The first protocol investigated whether swimming for 60 min in different frequencies modulates antipreneoplastic effects of physical training. Another protocol then explored whether the duration for training 5 times a week impacts on the development of colon preneoplastic lesions. After 8 weeks, serum and colon samples were collected and analyzed afterwards. Swimming once a week for 60 min did not promote those anticarcinogenic effects found in rats trained 5 times weekly. Such weekly sustained physical training not only decreased the development of colon preneoplastic, but also epithelial proliferation, and subepithelial cyclooxygenase 2 (COX-2) expression. Interestingly, a 5 time per week training for less than 60 min was not as protective against colon carcinogenesis as swimming for 90 min. This 90 min training indeed reduced serum cholesterol and triglycerides levels, as well as colonic lipid peroxidation in carcinogen-exposed rats. Our collective data suggest anticarcinogenic effects of physical exercises are potentially promoted when training 5 times a week for at least 60 min.

Pineal gland function is required for colon antipreneoplastic effects of physical exercise in rats.

Light-at-night exposure enhances the risk of cancer. Colon cancer is among the most dangerous tumors affecting humankind. Physical exercise has shown positive effects against colon cancer. Here, we investigated whether pineal gland modulates antipreneoplastic effects of physical exercise in the colon. Surgical and non-surgical pineal impairments were performed to clarify the relationship between the pineal gland activity and manifestation of colonic preneoplastic lesions. Next, a progressive swimming training was applied in rats exposed or not to either non-surgical pineal impairment or carcinogen treatment for 10 weeks. Both surgical and non-surgical pineal impairments increased the development of colon preneoplasia. It was further found that impairing the pineal gland function, higher rates of DNA damage were induced in colonic epithelial and enteric glial cells. Physical exercise acted positively against preneoplasia, whereas impairing the pineal function with constant light exposure disrupts its positive effects on the development of preneoplastic lesions in the colon. This was yet related to increased DNA damage in glial cells and enteric neuronal activation aside from serum melatonin levels. Our findings suggest that protective effects of physical exercise against colon cancer are dependent on the pineal gland activity.

The inflammatory stimulus of a natural latex biomembrane improves healing in mice

The aim of the present study was to compare healing obtained with biomembranes with the natural healing process (sham) using biochemical and immunohistological assays. C57BL/6 mice were divided into 4 groups of 15 mice each and received different subcutaneous implants: natural latex biomembrane (NLB), denatured latex (DL), expanded polytetrafluorethylene (ePTFE), or sham. On the 2nd, 7th, and 14th days post-treatment, 5 mice per group were sacrificed and biopsied for the following measurements: oxidative stress based on malondialdehyde (MDA), myeloperoxidase (MPO) and hydrogen peroxide by the method of ferrous oxidation-xylenol orange (FOX), as well as glutathione and total proteins; histological evaluation to enumerate inflammatory cells, fibroblasts, blood vessels, and collagen, and immunohistochemical staining for inducible nitric oxide synthase, interleukin-1β, vascular endothelial growth factor (VEGF), and transforming growth factor-β1 (TGF-β1). On day 2 post-treatment, NLB stimulated a dense inflammatory infiltrate mainly consisting of polymorphonuclear cells, as indicated by increased MPO (P < 0.05), but oxidative stress due to MDA was not observed until the 7th day (P < 0.05). The number of blood vessels was greater in NLB (P < 0.05) and DL (P < 0.05) mice compared to sham animals on day 14. NLB induced fibroplasia by day 14 (P < 0.05) with low expression of TGF-β1 and collagenesis. Thus, NLB significantly induced the inflammatory phase of healing mediated by oxidative stress, which appeared to influence the subsequent phases such as angiogenesis (with low expression of VEGF) and fibroplasia (independent of TGF-β1) without influencing collagenesis.

The inflammatory stimulus of a natural latex biomembrane improves healing in mice.

The aim of the present study was to compare healing obtained with biomembranes with the natural healing process (sham) using biochemical and immunohistological assays. C57BL/6 mice were divided into 4 groups of 15 mice each and received different subcutaneous implants: natural latex biomembrane (NLB), denatured latex (DL), expanded polytetrafluorethylene (ePTFE), or sham. On the 2nd, 7th, and 14th days post-treatment, 5 mice per group were sacrificed and biopsied for the following measurements: oxidative stress based on malondialdehyde (MDA), myeloperoxidase (MPO) and hydrogen peroxide by the method of ferrous oxidation-xylenol orange (FOX), as well as glutathione and total proteins; histological evaluation to enumerate inflammatory cells, fibroblasts, blood vessels, and collagen, and immunohistochemical staining for inducible nitric oxide synthase, interleukin-1ß, vascular endothelial growth factor (VEGF), and transforming growth factor-ß1 (TGF-ß1). On day 2 post-treatment, NLB stimulated a dense inflammatory infiltrate mainly consisting of polymorphonuclear cells, as indicated by increased MPO (P < 0.05), but oxidative stress due to MDA was not observed until the 7th day (P < 0.05). The number of blood vessels was greater in NLB (P < 0.05) and DL (P < 0.05) mice compared to sham animals on day 14. NLB induced fibroplasia by day 14 (P < 0.05) with low expression of TGF-ß1 and collagenesis. Thus, NLB significantly induced the inflammatory phase of healing mediated by oxidative stress, which appeared to influence the subsequent phases such as angiogenesis (with low expression of VEGF) and fibroplasia (independent of TGF-ß1) without influencing collagenesis.

Effects of the levonorgestrel-releasing intrauterine system on cell proliferation, Fas expression and steroid receptors in endometriosis lesions and normal endometrium.

BACKGROUND: The objectives of this study were: (i) to evaluate the effects of the levonorgestrel-releasing intrauterine system (LNG-IUS) on both proliferation and apoptosis markers and hormone receptors of the eutopic and ectopic endometrium of women experiencing pain related to endometriosis and (ii) to compare the results with those obtained with GnRH agonist (GnRHa) injections. METHODS: Pre- and post-treatment endometrium and endometriosis specimens were obtained from 22 women experiencing pain related to endometriosis who were treated with LNG-IUS (n = 11) or GnRHa (n = 11) for 6 months. Changes in the expression of proliferating cell nuclear antigen, Fas, progesterone receptor (PRA) and estrogen receptor alpha (ER-alpha) were analyzed by immunohistochemistry. RESULTS: The cell proliferation index was significantly reduced in the epithelium and stroma of both the eutopic and the ectopic endometrium after treatment with the LNG-IUS and GnRHa. Only LNG-IUS users showed an increased H-score for Fas in the epithelium of the eutopic and ectopic endometrium (P < 0.05). Expression of ER-alpha and PRA by the glandular epithelium was lower in the eutopic endometrium after both treatments, but this reduction was noted in the ectopic endometrium only after LNG-IUS treatments (P < 0.05). No difference was detected between groups for any of the markers. CONCLUSIONS: LNG-IUS reduced both cell proliferation and the expression of PRA and ER-alpha and increased Fas expression in the eutopic and ectopic endometrium of patients with endometriosis. Some of these actions were not observed with GnRHa.

Intrinsic denervation of the colon is associated with a decrease of some colonic preneoplastic markers in rats treated with a chemical carcinogen

Denervation of the colon is protective against the colon cancer; however, the mechanisms involved are unknown. We tested the hypothesis that the denervated colonic mucosa could be less responsive to the action of the chemical carcinogen dimethylhydrazine (DMH). Three groups of 32 male Wistar rats were treated as follows: group 1 (G1) had the colon denervated with 0.3 mL 1.5 mM benzyldimethyltetradecylammonium (benzalkonium chloride, BAC); G2 received a single ip injection of 125 mg/kg DMH; G3 was treated with BAC + the same dose and route of DMH. A control group (Sham, N = 32) did not receive any treatment. Each group was subdivided into four groups according to the sacrifice time (1, 2, 6, and 12 weeks after DMH). Crypt fission index, ß-catenin accumulated crypts, aberrant crypt foci, and cell proliferation were evaluated and analyzed by ANOVA and the Student t-test. G3 animals presented a small number of aberrant crypt foci and low crypt fission index compared to G2 animals after 2 and 12 weeks, respectively. From the second week on, the index of ß-catenin crypt in G3 animals increased slower than in G2 animals. From the 12th week on, G2 animals presented a significant increase in cell proliferation when compared to the other groups. Colonic denervation plays an anticarcinogenic role from early stages of colon cancer development. This finding can be of importance for the study of the role of the enteric nervous system in the carcinogenic process.

Intrinsic denervation of the colon is associated with a decrease of some colonic preneoplastic markers in rats treated with a chemical carcinogen.

Denervation of the colon is protective against the colon cancer; however, the mechanisms involved are unknown. We tested the hypothesis that the denervated colonic mucosa could be less responsive to the action of the chemical carcinogen dimethylhydrazine (DMH). Three groups of 32 male Wistar rats were treated as follows: group 1 (G1) had the colon denervated with 0.3 mL 1.5 mM benzyldimethyltetradecylammonium (benzalkonium chloride, BAC); G2 received a single ip injection of 125 mg/kg DMH; G3 was treated with BAC + the same dose and route of DMH. A control group (Sham, N = 32) did not receive any treatment. Each group was subdivided into four groups according to the sacrifice time (1, 2, 6, and 12 weeks after DMH). Crypt fission index, ss-catenin accumulated crypts, aberrant crypt foci, and cell proliferation were evaluated and analyzed by ANOVA and the Student t-test. G3 animals presented a small number of aberrant crypt foci and low crypt fission index compared to G2 animals after 2 and 12 weeks, respectively. From the second week on, the index of ss-catenin crypt in G3 animals increased slower than in G2 animals. From the 12th week on, G2 animals presented a significant increase in cell proliferation when compared to the other groups. Colonic denervation plays an anticarcinogenic role from early stages of colon cancer development. This finding can be of importance for the study of the role of the enteric nervous system in the carcinogenic process.

Trypanosoma cruzi infection and/or administration of the nonsteroidal anti-inflammatory nimesulide increase the number of colonic crypts overexpressing metallothioneins in rat colon carcinogenesis.

Trypanosoma cruzi infection and nonsteroidal anti-inflammatory drugs inhibit colorectal carcinogenesis by mechanisms not completely known and metallothionein proteins (MTs) may be involved in this process. Sixty-six male Wistar rats weighing 90 to 120 g were randomly divided into seven groups (GI to GVII). GI, GII and GIII animals were subcutaneously infected with 200,000 trypomastigote forms of the Y strain of T. cruzi. After 8 weeks, GI, GII, GIV, and GVI were injected with one weekly subcutaneous dose of 12 mg/kg dimethylhydrazine for 4 weeks. In sequence, GI, GIV and GV were treated with nimesulide (10 mg/kg per dose, five times per week for 8 weeks). Groups I, III, IV, and VI had 12 animals, and each of the other groups had 6 animals. All the animals were euthanized 8 weeks after the last dimethylhydrazine injection. The colons were fixed and processed for MT immunohistochemistry. The index of MT-overexpressing colonic crypts (MTEC) was estimated as the percentage of MT-stained crypts in relation to the total number of crypts scored. Five hundred crypts per animal were scored. Data were analyzed by the Kruskal-Wallis test followed by the Dunn test. There was an increase in MTEC index in the groups either infected with T. cruzi or treated with nimesulide or both infected and treated when compared to control (401, 809, and 1011%, respectively). We suggest that the increased formation of MTEC may be related to the protection against carcinogenesis provided both by T. cruzi infection and nimesulide.

Trypanosoma cruzi infection and/or administration of the nonsteroidal anti-inflammatory nimesulide increase the number of colonic crypts overexpressing metallothioneins in rat colon carcinogenesis

Trypanosoma cruzi infection and nonsteroidal anti-inflammatory drugs inhibit colorectal carcinogenesis by mechanisms not completely known and metallothionein proteins (MTs) may be involved in this process. Sixty-six male Wistar rats weighing 90 to 120 g were randomly divided into seven groups (GI to GVII). GI, GII and GIII animals were subcutaneously infected with 200,000 trypomastigote forms of the Y strain of T. cruzi. After 8 weeks, GI, GII, GIV, and GVI were injected with one weekly subcutaneous dose of 12 mg/kg dimethylhydrazine for 4 weeks. In sequence, GI, GIV and GV were treated with nimesulide (10 mg/kg per dose, five times per week for 8 weeks). Groups I, III, IV, and VI had 12 animals, and each of the other groups had 6 animals. All the animals were euthanized 8 weeks after the last dimethylhydrazine injection. The colons were fixed and processed for MT immunohistochemistry. The index of MT-overexpressing colonic crypts (MTEC) was estimated as the percentage of MT-stained crypts in relation to the total number of crypts scored. Five hundred crypts per animal were scored. Data were analyzed by the Kruskal-Wallis test followed by the Dunn test. There was an increase in MTEC index in the groups either infected with T. cruzi or treated with nimesulide or both infected and treated when compared to control (401, 809, and 1011 percent, respectively). We suggest that the increased formation of MTEC may be related to the protection against carcinogenesis provided both by T. cruzi infection and nimesulide.

Hypolipemic and antioxidant activities from Tamarindus indica L. pulp fruit extract in hypercholesterolemic hamsters.

Dietary modifications may significantly reduce cardiovascular disease (CVD) risk factors, including cholesterol and atherosclerosis. The present study addressed the effects of the crude extract from the pulp fruit of Tamarindus indica L. on lipid serum levels and early atherosclerotic lesions in hypercholesterolemic hamsters in vivo, and the extract's antioxidant action, in vitro. Animals were fed on either chow or atherogenic diet during 10 weeks and concomitantly received either water or T. indica L. extract for drinking. Treatment of hypercholesterolemic hamsters with the T. indica pulp fruit extract (5%) led to a decrease in the levels of serum total cholesterol (50%), non-HDL cholesterol (73%) and triglyceride (60%), and to an increase of high-density lipoprotein (HDL) cholesterol levels (61%). In vitro, the extract presented radical scavenging ability, as assessed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radicals assays, and led to decreased lipid peroxidation in serum, as assessed by the thiobarbituric acid reactive substances (TBARS) assay. In vivo, the extract improved the efficiency of the antioxidant defense system, as assessed by the superoxide dismutase, catalase and glutathione peroxidase activities. Together these results indicate the potential of tamarind extracts in diminishing the risk of atherosclerosis development in humans.

p63 correlates with both BRCA1 and cytokeratin 5 in invasive breast carcinomas: further evidence for the pathogenesis of the basal phenotype of breast cancer.

AIMS: To study the expression of p63, cytokeratin (CK) 5 and CK8/18 in invasive ductal carcinomas and their relationship with BRCA1 and other pathological and immunohistochemical features of clinical significance. METHODS AND RESULTS: Immunohistochemistry with the antibodies p63, CK5, CK8/18, BRCA1, oestrogen receptor, progesterone receptor, p53, c-erbB-2 and Ki67 was performed in 102 formalin-fixed paraffin-embedded samples of invasive ductal carcinomas. The CK5+ cases were submitted to a double-immunolabelling study with p63. There was a strong relationship between CK5 and p63 expression and both markers were associated with hormonal receptor-negative high-grade carcinomas with high proliferative rate. Furthermore, there was coexpression of CK5 and p63 in neoplastic cells, indicating that p63, like CK5, is a marker of the basal phenotype of breast cancer. There was a strong relationship between reduced expression of BRCA1 with both p63 and CK5 expression as well as an inverse correlation between p63 and CK8/18 expression, suggesting that loss of p63 expression is required for the transition between a basal to a luminal phenotype of breast carcinoma. CONCLUSIONS: Since p63 is thought to be a marker of stem cells and may act as an oncogene, our data support the idea that BRCA1 acts as stem cell regulator.

Trends of accuracy of clinical diagnoses of the basic cause of death in a university hospital.

AIMS: To determine the agreement between clinical and necropsy diagnoses of the basic cause of death, and to compare the results with those obtained in a previous study carried out at the same university hospital. METHODS: In total, 4828 necropsies, performed between 1990 and 1995 in the University Hospital of the Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil, were reviewed. Examinations were concluded at the macroscopic part of the necropsy in nearly 35% of the cases. Statistical analysis was carried out using the kappa coefficient comparing the clinical diagnosis and the diagnosis obtained after necropsy. The jackknife method was used to identify comparable kappa values for the comparison of the two periods. RESULTS: Compared with the 1978-80 period, a significant increase in diagnostic agreement was seen for the group submitted to complete necropsy, whereas no similar increase was detected when only the macroscopic step was analysed. CONCLUSIONS: There was a discrete tendency to an improved correlation between clinical and postmortem data stated by full necropsy analysis. The findings show that microscopic analysis remains important to confirm the cause of death in many cases. Diagnostic discrepancies remained high, and therefore complete necropsy continues to be an essential instrument for the assessment of clinical diagnosis.

Does the correlation between EBNA-1 and p63 expression in breast carcinomas provide a clue to tumorigenesis in Epstein-Barr virus-related breast malignancies?

Several investigators have identified Epstein-Barr virus (EBV) particles in breast carcinomas, a fact that supports a role for EBV in mammary tumorigenesis. The possible mechanism involved in this process is not clear. The present study was carried out in an attempt to determine whether there is a relationship between latent infection with EBV and p53 and p63 expression in breast carcinomas. Immunohistochemistry developed with 3.3-diaminobenzidine tetrahydrochloride was performed in 85 formalin-fixed paraffin-embedded breast carcinomas using anti-EBV EBNA-1, anti-p63, anti-p53, anti-estrogen receptor (ER) and anti-progesterone receptor (PR) antibodies. The cases were selected to represent each of the various histologic types: intraductal carcinoma (N = 12), grade I invasive ductal carcinoma (N = 15), grade II invasive ductal carcinoma (N = 15), grade III invasive ductal carcinoma (N = 15), tubular carcinoma (N = 8), lobular carcinoma (N = 10), and medullary carcinoma (N = 10). The ductal breast carcinomas were graded I, II and III based on the Scarff-Bloom and Richardson grading system modified by Elston and Ellis. One slide containing at least 1000 neoplastic cells was examined in each case. ER, PR, p63, p53 and EBNA-1 were positive in 60, 40, 11.8, 21.2 and 37.6 percent of carcinomas, respectively. There was a correlation between EBNA-1 and p63 expression (P < 0.001), but not between EBNA-1 and p53 (P = 0.10). These data suggest a possible role for p63 in the mammary tumorigenesis associated with Epstein-Barr virus infection.

Does the correlation between EBNA-1 and p63 expression in breast carcinomas provide a clue to tumorigenesis in Epstein-Barr virus-related breast malignancies?

Several investigators have identified Epstein-Barr virus (EBV) particles in breast carcinomas, a fact that supports a role for EBV in mammary tumorigenesis. The possible mechanism involved in this process is not clear. The present study was carried out in an attempt to determine whether there is a relationship between latent infection with EBV and p53 and p63 expression in breast carcinomas. Immunohistochemistry developed with 3.3-diaminobenzidine tetrahydrochloride was performed in 85 formalin-fixed paraffin-embedded breast carcinomas using anti-EBV EBNA-1, anti-p63, anti-p53, anti-estrogen receptor (ER) and anti-progesterone receptor (PR) antibodies. The cases were selected to represent each of the various histologic types: intraductal carcinoma (N=12), grade I invasive ductal carcinoma (N=15), grade II invasive ductal carcinoma (N=15), grade III invasive ductal carcinoma (N=15), tubular carcinoma (N=8), lobular carcinoma (N=10), and medullary carcinoma (N=10). The ductal breast carcinomas were graded I, II and III based on the Scarff-Bloom and Richardson grading system modified by Elston and Ellis. One slide containing at least 1000 neoplastic cells was examined in each case. ER, PR, p63, p53 and EBNA-1 were positive in 60, 40, 11.8, 21.2 and 37.6% of carcinomas, respectively. There was a correlation between EBNA-1 and p63 expression (P<0.001), but not between EBNA-1 and p53 (P=0.10). These data suggest a possible role for p63 in the mammary tumorigenesis associated with Epstein-Barr virus infection.

No reduction with ageing of the number of myenteric neurons in benzalkonium chloride treated rats.

The number of myenteric neurons may be reduced by topical serosal application of benzalkonium chloride (BAC). We studied the effects of ageing in the population of neurons that survive after the application of BAC. Ten treated and ten control animals were killed at intervals of 2, 6, 12 and 18 months after the surgery. We performed myenteric neurons counting in serially cut histological preparations of the descending colon. The control animals revealed a continuous loss of myenteric neurons number with increasing of age. Interestingly, contrary to control animals, the BAC-treated rats presented no neuron loss with ageing at any experimental time. The reasons for their survival with ageing could be related to a neuroplasticity phenomenon.

NK1.1+ cells and T-cell activation in euthymic and thymectomized C57Bl/6 mice during acute Trypanosoma cruzi infection.

Natural killer (NK) cells may provide the basis for resistance to Trypanosoma cruzi infection, because the depletion of NK1.1 cells causes high levels of parasitemia in young C57Bl/6 mice infected with T. cruzi. Indeed, NK1.1 cells have been implicated in the early production of large amounts of interferon (IFN)-gamma, an important cytokine in host resistance. The NK1.1 marker is also expressed on special subpopulations of T cells. Most NK1.1+ T cells are of thymic origin, and their constant generation may be prevented by thymectomy. This procedure, by itself, decreased parasitemia and increased resistance in young mice. However, the depletion of NK1.1+ cells by the chronic administration of a monoclonal antibody (MoAb) (PK-136) did not increase the parasitemia or mortality in thymectomized C57Bl/6 mice infected with T. cruzi (Tulahuen strain). To study the cross-talk between NK1.1+ cells and conventional T cells in this model, we examined the expression of activation/memory markers (CD45RB) on splenic CD4+ and CD8+ T cells from young euthymic or thymectomized mice with or without depletion of NK1.1+ cells and also in aged mice during acute infection. Resistance to infection correlated with the amount of CD4+ T cells that are already activated at the moment of infection, as judged by the number of splenic CD4+ T cells expressing CD45RB(-). In addition, the specific antibody response to T. cruzi antigens was precocious and an accumulation of immunoglobulin (Ig)M with little isotype switch occurred in euthymic mice depleted of NK1.1+ cells. The data presented here suggest that NK1.1+ cells have important regulatory functions in euthymic, but not in thymectomized mice infected with T. cruzi. These regulatory functions include a helper activity in the generation of effector or activated/memory T cells.

Topical application of benzalkonium chloride to the stomach serosa increases gastric emptying time, acid secretion, serum gastrin and size of the mucosa.

AIM: In the present study we evaluated the effects of gastric myenteric denervation using benzalkonium chloride (BAC) on the time for gastric emptying, as well as gastric secretion, and mucosal epithelial cell size and population in rats. METHODS AND RESULTS: Wistar rats were treated with topical serosal application of BAC to the stomach. Control animals received saline. Ninety days after surgery, gastric emptying time, gastric acid secretion and serum gastrin levels were studied. Next, the animals were sacrificed and the stomachs were removed, fixed in formalin and histologically processed for histomorphometry of the height, area and volume of the glandular portion, and volume and population of mucous, chief, parietal, G- and labelled cells. BAC animals showed a significant delay in gastric emptying and an increase in gastric acid secretion and serum gastrin levels. These animals also presented a significant reduction of myenteric neuron number, hypertrophy of parietal and chief cells, hyperplasia of G cells and an increase in the gastric mucosa area. CONCLUSION: The absence of the myenteric plexus seems to protect the stomach from the hyperplastic effects of hypergastrinemia. Gastric food stasis may act as a factor triggering morphological and functional alterations of the gastric epithelium. Although gastric food stasis is a common finding in medical practice, its physiopathological consequences are poorly understood and have not been frequently discussed in the literature.

Chronic Trypanosoma cruzi infection associated with low incidence of 1,2-dimethylhydrazine-induced colon cancer in rats.

Experimental data have demonstrated that chronic infection with intracellular parasites may enhance resistance against some types of tumour. This phenomenon has not yet been demonstrated for experimental Trypanosoma cruzi chronic infection. This study investigated the effect of a specific colon cancer inducing drug, 1,2-dimethylhydrazine (DMH), on chronically T.cruzi infected Wistar rats. Infection was obtained by inoculation of 10(5) tripomastigote forms by subcutaneous (s.c.) route. Acute phase of the infection was monitored every other day by examination of a blood smear from each animal until negativation. In the early chronic phase of the infection, colon adenocarcinoma was induced by weekly s.c. injections of DMH at a dose of 20 mg/kg body weight for 12 weeks. 102 animals were divided in four test groups: 39 infected rats received DMH (group 1); 32 non-infected rats received DMH (group 2); 16 infected rats and 15 non-infected animals were used as control groups. Animals were killed 6 months after the first dose of DMH. The whole colon was removed and prepared for light microscopic examination. Twelve animals from group 1 and 22 from group 2 had colon adenocarcinomas, the proportion of cancer being 30.7 and 68.7%, respectively (chi(2) = 10.16; P < 0.05). The relative risk of having a colon tumor in infected animals (group 1) was 0.45 (IC 95% 0.26-0.76), which is a protective risk compared with non-infected animals. These findings show that chronic infection with T.cruzi is associated with a lower incidence of DMH-induced colon cancer in rats.

Endocrine cells in the denervated intestine.

This study deals with the effects of myenteric denervation of the proximal jejunum on endocrine cell population of the crypt-villus unit, 5 months after treatment with benzalkonium chloride (BAC). Male Wistar albino rats weighing on average 100 g were allocated to two groups: the BAC group - the proximal jejunal serosa was treated with 2 mM BAC for 30 min, and the control group - treated with saline solution (0,9% NaCl). There was a significant reduction in neurone number in the jejunal myenteric plexus of the BAC group and the endocrine cell population (serotoninergic and argyrophilic cells) was significantly increased in this intestine segment. In conclusion, the present findings provide further evidence that the myenteric denervation induced by BAC may lead to the development of a local imbalance of the neurotransmitters, with a consequent induction of enteroendocrine cell (argyrophilic and serotoninergic cells) hyperplasia in the crypt and villus.

Immunolocalisation of myosin-V in the enteric nervous system of the rat.

We show here the localisation of myosin-V in whole mount preparations of the mucous-submucous and the muscular layers of rat small intestine by using an affinity purified antibody specific to the tail domain of myosin-V. Myosin-V immunostaining was intense in the submucous and myenteric nervous plexuses, allowing the visualisation of neuronal cell bodies and fibres. Western blots of total muscle layers homogenates detected with the same antibody revealed a single band of the expected size for myosin-V. Understanding the cellular localisation and function of this class of myosin is an important challenge and the accessibility and simplicity of the enteric nervous system as compared to the central nervous system, makes the digestive tract an attractive model for studying possible functional roles of myosin-V in neurotransmission and neuroplasticity.