Effect of melatonin on 1,2-dimethylhydrazine-induced intestinal tumors in rats

Fifteen doses of 21 mg/kg body weight of 1,2-dimethylhydrazine (DMH) were injected into 48 female rats at one-week intervals. Controls included 25 animals while 23 received 20 mg/l of melatonin with drinking water, 5 times a week, at night-time, for 6 months, beginning from the day of the first injection. Although malignancies of large bowel developed in all animals, multiple tumors in the melatonin group were significantly fewer than in the rats treated with DMH alone (6,0 and 9,9 respectively; p < 0,001). Similarly, melatonin treatment was followed by a significantly lower frequency of tumor development in the ascending colon as well as fewer multiple neoplasms of the ascending and descending colon. Melatonin was also shown to inhibit carcinogenesis in the small intestine. It is suggested that the antitumor effects of melatonin is due to its antioxidant properties.     

Promotion of colon carcinogenesis through increasing lipid peroxidation induced in rats by a high cholesterol diet

Recent studies suggest a role of the neural cell adhesion molecules L1 and NCAM in mechanisms of memory storage. In the present study we analyzed the effect of continuous intraventricular infusion of polyclonal antibodies directed against L1 (antiL1) or NCAM (antiNCAM) on the performance of male Wistar rats during the acquisition and retention of a spatial learning task (Morris water-maze). In this task animals have to learn the spatial position of a hidden escape platform in a water tank to escape onto it. During acquisition of the task animals with continuous infusion of antiNCAM - but not those infused with antiL1 - showed day-dependent attenuated learning in comparison to controls (P = 0.001). Control animals were either injected with vehicle (PBS) or with polyclonal antibodies raised against liver cell membrane. When the escape platform was removed during the retention test (transfer test), the performance of animals continuously infused with antiL1 as well as those continuously infused with antiNCAM showed an impaired search pattern when compared with the performance of control animals (P = 0.001 and 0.04, respectively). Whereas control animals spent up to 46% of their time searching for the platform in the correct quadrant, the time antiL1- and antiNCAM-infused animals spent in this quadrant was closer to chance level (30.5% and 36.5%), respectively). The present data provide additional support for an involvement of the two adhesion molecules L1 and NCAM in synaptic plasticity underlying memory storage.     

Production of intestinal and other tumors by 1, 2-dimethylhydrazine dihydrochloride in mice. I. A light and transmission electron microscopic study of colonic neoplasms

Single or ten weekly subcutaneous injection(s) of 1, 2-dimethylhydrazine dihydrochloride were administered separately to Swiss mice. The repeated application gave rise mainly to high incidences of tumors in the large intestine. These neoplasms occurred most frequently in the colorectal area and in cecum adjacent to ileum. Light microscopically, these lesions were classified as polypoid adenomas and adenocarcinomas. Most of the adenocarcinomas were highly invasive, although they metastasized rarely. The fine structure of the malignant cells exhibited features typical of columnar absorptive cells. A distinctive alteration was the disorderly arrangement and abnormal size and shape of the microvilli. In addition, the cells exhibited numerous free ribosomes, little RER, priminent Golgi bodies, and uniformly dispersed nuclear chromatin. Morphologically, the intestinal tumors were similar to those found in man. In addition, the repeated administration of 1, 2-DMH also induced significant incidences of neoplasms in blood vessels, lungs, anus, and kidneys while the single application produced tumors in blood vessels and liver. The main hypotheses attempting to explain the selective induction of large intestinal neoplasms are discussed.     

Oxidative stress in diabetic rats induced by streptozotocin: protective effects of melatonin

Two years after Kurt Schneider had finalised his thesis qualifying him as a lecturer at Cologne University, he completed his doctorate dissertation in philosophy, also at Cologne University. His advisor was Max Scheler. Schneider published the results of his researches in a short monograph. It appears that at this time Scheler's phenomenology began to influence psychiatry. However, Kurt Schneider made only passing references to Max Scheler in this regard. Nevertheless, Scheler's influence on Schneider remained noticeable even in his most famous book "Clinical Psychopathology". Years after their academic contacts, Scheler, on several occasions, asked Schneider's advice concerning his psychically disturbed son Wolfgang. Schneider's diagnosis amounted to a case of a severely psychopathic personality. He informed Max Scheler on this and, subsequently, Wolfgang Scheler was interdicted, i.e. legally incapacitated.     

Protective effect of melatonin against hippocampal DNA damage induced by intraperitoneal administration of kainate to rats

The pineal hormone melatonin protects neurons in vitro from excitotoxicity mediated by kainate-sensitive glutamate receptors and from oxidative stress-induced DNA damage and apoptosis. Intraperitoneal injection on kainate into experimental animals triggers DNA damage in several brain areas, including the hippocampus. It is not clear whether melatonin is neuroprotective in vivo. In this study, we tested the in vivo efficacy of melatonin in preventing kainate-induced DNA damage in the hippocampus of adult male Wistar rats. Melatonin and kainate were injected i.p. Rats were killed six to 72 h later and their hippocampi were examined for evidence of DNA damage (in situ dUTP-end-labeling, i.e. TUNEL staining) and for cell viability (Nissl staining). Quantitative assay was performed using computerized image analysis. At 48 and 72 h after kainate we found TUNEL-positive cells in the CA1 region of the hippocampus; in the adjacent sections that were Nissl-stained, we found evidence of cell loss. Both the number of TUNEL-positive cells and the loss of Nissl staining were reduced by i.p. administration of melatonin (4 x 2.5 mg/kg; i.e. 20 min before kainate, immediately after, and 1 and 2 h after the kainate). Our results suggest that melatonin might reduce the extent of cell damage associated with pathologies such as epilepsy that involve the activation of kainate-sensitive glutamate receptors.     

Attenuation by genistein of sodium-chloride-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats

The effects of prolonged administration of genistein, a tyrosine-kinase inhibitor, on sodium-chloride-enhanced induction of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine, and the labeling and apoptotic indices and vessel counts in the gastric mucosa and gastric cancers, were investigated in Wistar rats. After 25 weeks of the carcinogen treatment, rats were fed chow pellets containing 10% sodium chloride and were given s.c. injections of genistein at dosages of 15 mg/kg or 30 mg/kg body weight every other day. In week 52, the incidence of gastric cancers was significantly greater in rats fed sodium chloride than in untreated control rats. Prolonged administration of genistein at a dosage of 30 mg/kg, but not 15 mg/kg, body weight significantly reduced the incidence of gastric cancers, which was increased by oral treatment with sodium chloride. Genistein at the higher dose significantly decreased the labeling index and vessel counts of the antral mucosa and the gastric cancers (which were increased by treatment with sodium chloride) and significantly increased the apoptotic index of the antral mucosa and the cancers (which was lowered by the treatment with sodium chloride). These findings suggest that genistein attenuates gastric carcinogenesis promoted by sodium chloride, by inducing increased apoptosis and lower cell proliferation and angiogenesis of antral mucosa and gastric cancers.     

Inhibitory effect of combined treatment with the aromatase inhibitor exemestane and tamoxifen on DMBA-induced mammary tumors in rats

The antitumor effect of exemestane (FCE 24304), an irreversible aromatase inhibitor, given alone or in combination with tamoxifen, was investigated in rats with 7,12-dimethylbenzanthracene (DMBA)-induced mammary tumors. The compounds were given once daily, 6 days a week for 4 weeks. Exemestane, given at the dose of 20 mg/kg/day s.c., induced 26% complete (CR) and 18% partial (PR) tumor regressions, compared to 0% CR and 6% PR observed in controls. Tamoxifen, given at 1 mg/kg/day p.o., induced 16% CR and 13% PR. The combined treatment caused 41% CR and 16% PR, thus resulting in a higher antitumor effect than either single treatment. The appearance of new tumors was reduced by each single treatment and almost totally prevented by the combined treatment. Serum prolactin (PRL) levels, assayed 4 h after the last dose, were unchanged in the group treated with the combination, whereas tamoxifen alone caused a slight increase of serum PRL. These results indicate that estrogen deprivation through aromatase inhibition and estrogen receptor antagonism causes a better inhibition of DMBA-induced mammary tumors than either treatment modality alone.     

Enhancement by the tricyclic antidepressant, desipramine, of experimental carcinogenesis in rat colon induced by azoxymethane

The effects of the tricyclic antidepressant drug desipramine on the incidence, number and histology of colon tumors induced by azoxymethane (AOM), and on the serum norepinephrine (NE) concentration and the labeling index of colon mucosa were investigated in Wistar rats. Rats were treated s.c. with 7.4 mg AOM/kg body wt once a week for 10 weeks, and also s.c. with 10 mg desipramine hydrochloride (desipramine)/kg body weight until the end of the experiment. Treatment with desipramine significantly increased the incidence, but not the number, of colon tumors in week 35. However, it did not influence the location and the histological appearance of the colon tumors or the histological types of colon adenocarcinomas. Furthermore, it significantly increased the serum NE level and the labeling index of colon mucosa during and after AOM treatment. These findings indicate that desipramine enhanced the development of colon tumors and that its effect may be related to its effect in increasing proliferation of colon epithelial cells.     

Prevention of N-methylnitrosourea-induced colon carcinogenesis in F344 rats by lycopene and tomato juice rich in lycopene

A liquid chromatographic/tandem mass spectrometric (LC/MS/MS) assay was developed for the quantitative determination of olanzapine (LY170053, OLZ) in human plasma and serum. Bond Elut C2 solid-phase extraction cartridges (single cartridge or 96-well format), in conjunction with a positive pressure manifold, were used to extract OLZ and its internal standard, LY170222, from the biological matrix. Chromatographic resolution of OLZ from endogenous plasma interferences and its metabolites was accomplished with a MetaChem monochrom HPLC (4.6 x 150 mm, dp 5 microns). Detection was effected with a Perkin-Elmer SCIEX API III Plus mass spectrometer using positive ion atmospheric pressure chemical ionization and a multiple reaction monitoring protocol. The linear dynamic range was from 250 pg ml-1 to 50 ng ml-1 of human plasma/serum using a 0.5 ml aliquot. The inter-day precision (relative standard deviation) and accuracy (relative error) in plasma ranged from 6.26 to 7.66% and from -3.54 to 7.52%, respectively. The intra-day precision and accuracy in serum ranged from 3.46 to 8.76% and from -8.06 to 12.46%, respectively. This assay is sensitive and selective, and will be used to support both human clinical and toxicological analyses. Furthermore, using the 96-well solid-phase extraction format, sample preparation can be easily automated.     

Anticarcinogenic effect of palustran on development of tumors induced by 3-(1-alpha-L-arabinopyranosyl)-1-methyl-1-nitrosourea (AMNU) in rats

Clinical manifestations of superior sagittal sinus (SSS) thrombosis are nonspecific but characterized by headache, papilledema, seizures, focal deficits, progressive coma and death. Recurrent transient focal neurologic deficit is an extremely rare manifestation in superior sagittal sinus thrombosis and the mechanism is unknown. A 45-year-old man presented with headache for two weeks and four episodes of transient (5-10 minutes) right or left hemiparesis for two days. Magnetic resonance image and transfemoral cerebral angiography revealed superior sagittal sinus thrombosis with numerous prominent collateral venous channels. There was no parenchymal lesion. After four days of heparinization, no further transient focal neurologic deficits developed. Follow-up angiography showed partial recanalization of the SSS. Possible mechanism of transient ischemic attacks in this patient is thought to be a transient functional disturbance due to a temporal reduction of tissue perfusion in the process of operating fully-enough collateral channels.     

Inhibitory effect of progesterone on androgen-induced lordosis in ovariectomized rats

The role of family history as a risk factor of coronary heart disease was explored in the first-degree relatives of 121 female and 586 male survivors of a recent acute myocardial infarction and in those of 130 control women. It was significantly more common for female patients than male patients to have first-degree relatives with coronary artery disease before the age of 65 (76% vs 62%, P = 0.0026). For the sisters of the female patients the cumulative risk of coronary heart disease by the age of 65 years was almost twice that of the sisters of the male patients (25.9% vs 15.8%, P = 0.0123). The risk for the brothers of the females did not significantly differ from that of the brothers of the male patients, but it was 3.5 times that of the brothers of the controls. Thus, while a history of coronary heart disease in first-degree relatives is a risk factor for the disease, the risk is greater in women than in men.     

No involvement of APC gene mutations in ulcerative colitis-associated rat colon carcinogenesis induced by 1-hydroxyanthraquinone and methylazoxymethanol acetate

In 1992, 1531 women aging 25-45 years from 5 urban and rural regions were interviewed about infertility and subfecundity within the German part of a study by the European community. 1248 of them had a positive reproductive history with 3018 pregnancies. 400 (= 13.25%) occurred during contraception. This affected 296 women (= 19.6% of all women). Smoking seems to have a promotion effect. The risk of ectopic pregnancies seems to be higher in contraceptive users. The highest fetal loss was found in women using an IUD. There were no differences in the course and outcome of pregnancy between users and nonusers of contraceptives. About 40% of the women in the corresponding group reported an irregular application of the contraceptive technique.     

Protective effect of melatonin in a non-septic shock model induced by zymosan in the rat

N-acetyl tyrosine (NAT) is hydroxylated by mushroom tyrosinase and the N-acetyl dopa formed is oxidized by the enzyme to N-acetyl dopaquinone (lambda max = 390 +/- 10 nm). H2O2 and NH2OH each shortened the lag period of NAT hydroxylation by the enzyme. H2O2 had an effect on the changes with time in the spectrum of product(s) formed and on the spectrum of the final product(s) obtained when NAT was hydroxylated by mushroom tyrosinase, in a manner suggesting that H2O2 converts N-acetyl dopaquinone to a pink-violet product(s) (lambda max = 490 nm), whereas such a product(s) was not formed in the absence of H2O2. A pink-violet product(s) (lambda max 490 +/- 20 nm) was also formed when NAT was hydroxylated by mushroom tyrosinase in the presence of NH2OH or para amino benzoic acid (PABA), probably as a result of an interaction between N-acetyl dopaquinone and NH2OH or PABA forming mono- or di-oximes. Kojic acid (5-hydroxy-2-hydroxymethyl)-4H-pyran-4-one) inhibited effectively the rate of NAT hydroxylation by mushroom tyrosinase in the absence or presence of H2O2. When NAT was oxidized by the enzyme in the absence of kojic acid, N-acetyl dopaquinone was formed at once and a shoulder at 490-530 nm appeared later. Under identical conditions but in the presence of kojic acid, a yellow product(s), characterized by a peak at 320 +/- 10 nm, was detected, suggesting that N-acetyl dopaquinone oxidizes kojic acid to the yellow product(s). Maltol (3-hydroxy-2-methyl-4H-pyran-4-one), a gamma-pyrone derivative structurally related to kojic acid, also inhibited the rate of NAT hydroxylation by mushroom tyrosinase. The addition of maltol at the plateau phase of the reaction resulted in an immediate decline in absorbance at 400 nm, suggesting that maltol conjugates with N-acetyl dopaquinone, yielding a product(s) characterized by a lower extinction coefficient at 400 nm than that of N-acetyl dopaquinone alone. The final brown-red product(s) formed when NAT was hydroxylated by mushroom tyrosinase was bleached in the presence of ascorbic acid or H2O2.     

Effect of selective and non-selective muscarinic blockade on baclofen inhibition of gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats

The effects of baclofen, a gamma-amino-n-butyric acid receptor B agonist, on gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine and how its effects are influenced by selective (M1) and non-selective (M1 and M2) pharmacological blockade of muscarinic receptors were investigated in inbred Wistar rats. Rats were given s.c. injections of 8 mg/kg body wt baclofen with and without 0.5 mg/kg body wt atropine (non-selective M1 and M2 muscarinic receptor antagonist) or 1.0 mg/kg body wt pirenzepine (selective M1 muscarinic receptor antagonist) every other day after a 25 week carcinogen treatment. At week 52 baclofen significantly decreased the incidence of gastric cancers. Concomitant treatment with atropine significantly attenuated the inhibition by baclofen of gastric carcinogenesis, but combined use with pirenzepine had no significant effect on the inhibition by baclofen of gastric carcinogenesis. Baclofen also significantly decreased the labeling index of the antral mucosa. Baclofen plus atropine attenuated the decrease in the labeling index of the antral mucosa due to baclofen, but baclofen plus pirenzepine had no significant effect on the labeling index. These results suggest that the inhibition of gastric carcinogenesis by baclofen is mediated through muscarinic receptors and M2 receptors, but not M1 receptors, are involved in this response.     

Inhibitory effect of sarcophytol A on pancreatic carcinogenesis after initiation by N-nitrosobis(2-oxypropyl)amine in Syrian hamsters

Sarcophytol A (SaA), a cembrane-type diterpene, inhibits pancreatic carcinogenesis induced by N-nitrosobis(2-oxypropyl)amine (BOP) in hamsters. The experimental groups received two injections of BOP at 70 mg/kg dose, followed 2 weeks later by a 20 mg/kg dose injection, and were fed a basal diet or 0.01 and 0.05% SaA diets starting 1 week after the second injection of BOP. Control groups were injected with normal saline and fed the basal diet or the 0.05% SaA diet. All animals were killed 30 weeks after the start of the experiments. Seventeen BOP-treated hamsters fed the basal diet developed pancreatic tumors (77.3%) while only 12 of 21 hamsters fed the 0.01% SaA diet (57.1%) and 12 of 23 hamsters fed the 0.05% SaA diet (52.2%) developed pancreatic tumors. Pancreatic lesions included ductal hyperplasia, atypical ductal hyperplasia, and carcinoma in situ. Microscopic invasive carcinoma induced by BOP and the incidence of larger pancreatic tumors in hamsters were significantly higher in hamsters fed the basal diet than in hamsters fed the SaA diet (p < 0.05). The proliferating cell nuclear antigen (PCNA) labeling index of pancreatic carcinoma in BOP-treated hamsters fed the basal diet was 41.2 +/- 13.4%, whereas BOP-treated hamsters fed 0.01 and 0.05% SaA diets yielded PCNA indexes of 26.8 +/- 8.3 and 28.4 +/- 7.0%, respectively. k-ras mutation was detected in 40% of cancers in both groups. No pancreatic tumors developed in saline-treated groups, and no differences in body weights or histological findings in their organs, including the pancreas, were observed in either group. These findings suggest that SaA not only inhibits BOP-induced pancreatic carcinogenesis in hamsters, but also provides antipromotion and antiprogression effects on these tumors, even when SaA commences 1 week after the initiation of pancreatic carcinogenesis.     

Increased expression of inducible and endothelial constitutive nitric oxide synthases in rat colon tumors induced by azoxymethane

Nitric oxide (NO) is an important bioregulatory mediator involved in a variety of biological processes under both physiological and pathological conditions. To assess whether NO production is altered in colon carcinogenesis, the expression levels and localization of two isoforms of NO synthase, inducible NO synthase (iNOS) and endothelial constitutive NO synthase (eNOS), were examined by immunoblot and immunohistochemical methods in normal colonic mucosa and colon carcinomas induced by azoxymethane in male F344 rats. All colon carcinoma tissues examined were found to have an increased expression of iNOS and eNOS proteins as compared to normal colonic mucosa. In particular, the pronounced staining of iNOS protein localized to the luminal surface of carcinoma epithelial cells was not detectable in normal colon epithelium. The neovasculature in tumor tissues also demonstrated intense eNOS immunoreactivity in endothelial cells. These findings indicate that NO production is markedly elevated in azoxymethane-induced rat colon carcinomas, suggesting that regulatory pathways involving this mediator have some biological relevance to colon carcinogenesis in this model.     

Effects of pH on nonenzymatic oxidation of phenylhydroquinone: potential role in urinary bladder carcinogenesis induced by o-phenylphenol in Fischer 344 rats

o-Phenylphenol (OPP) and its sodium salt (SOPP) are broad spectrum fungicides and antibacterials to which humans are frequently exposed. Both OPP and SOPP have been found to cause cancer in the urinary bladder of male F344 rats at high doses, and the metabolite phenylhydroquinone (PHQ) is believed to play a key role in the carcinogenicity of these compounds. Tumor formation in the treated animals has also been shown to be significantly influenced by urinary pH. To provide additional insights into the mechanisms of OPP carcinogenesis, we have investigated the autoxidation of PHQ over the pH range commonly found in the urine of OPP- and SOPP-treated rats. Over the pH range studied (6.3-7.6), a curvilinear relationship between rate of PHQ oxidation and pH was observed. Phenylbenzoquinone (PBQ) was formed during the autoxidation of PHQ, with a formation yield of 0.92 +/- 0.02. In addition, the effects of PBQ and oxygen concentrations on PHQ autoxidation and the nonenzymatic conversion of PBQ to PHQ were also studied. Our data indicate that the production of reactive metabolites from PHQ involves a pH-independent (i.e., oxygen-dependent) and a pH-dependent pathway and that the rate of pH-dependent PHQ autoxidation was found to be enhanced by the presence of PBQ. A reaction mechanism has been formulated to explain the experimental data observed, with ionization of PHQ semiquinone being identified as a key step in reactive species production for the pH-dependent pathway. By combining data from OPP animal carcinogenicity studies with the proposed reaction pathway, a good correlation between the proposed formation of reactive species and bladder lesions was observed. These results indicate that the pH-dependent autoxidation of free PHQ metabolite in the urine may potentially be responsible for the tumorigenic effects of OPP and SOPP observed in the rat bladder.     

Inhibitory effect of selenium on biliary secretion of methyl mercury in rats

The inhibitory effect of sodium selenite on biliary secretion of methyl mercury was examined in rats. The biliary secretion of methyl mercury in rat treated with 1 mumol/kg of methyl mercury was significantly decreased by administration of selenite at doses of 0.05 mumol/kg or higher. In rats given 10 mumol/kg of methyl mercury, marked depression of biliary secretion of mercury was observed when selenite was injected at a dose of 0.2 mumol/kg. On the other hand, secretion of substantial amounts of selenium was observed when biliary secretion of mercury was depressed. When the concentration of selenium in the bile was higher than 5 nmol/ml, biliary secretion of mercury was markedly depressed independently of the dose of methyl mercury administered (1 mumol/kg or 10 mumol/kg). These results suggest that the degree of inhibitory effect of selenite may be determined by the selenium concentration in the liver or the bile after treatment with selenite rather than the molar ratio of the dose of methyl mercury and selenite. We concluded that the decrease in biliary secretion of methyl mercury induced by selenite may result from inhibition of pathway for secretion of methyl mercury from liver to bile rather than the direct formation of a complex between methyl mercury and selenium. Methyl mercury has been considered to be secreted from liver to bile as a complex with glutathione (GSH). However, administration of selenite did not affect biliary secretion of GSH or hepatic glutathione S-transferase activity. Moreover, gel filtration of liver cytosol demonstrated that the distribution pattern of hepatic methyl mercury between macromolecules and GSH was not significantly changed by administration of selenite. These results suggest that selenite does not affect complex formation of methyl mercury with GSH at least in the liver. Selenite might specifically inhibit the activity of the canalicular transporter(s) which transport complexes of methyl mercury and GSH from the liver to bile.