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PubMed2000

Promotion of intestinal carcinogenesis by Streptococcus bovis.

The involvement of Streptococcus bovis, an member of the human gut flora, in colorectal neoplastic diseases is an object of controversy. The aim of this study was to determine the effects of S.bovis and of antigens extracted from the bacterial cell wall on early preneoplastic changes in the intestinal tract. Adult rats received i. p. injections of azoxymethane (15 mg/kg body weight) once per week for 2 weeks. Fifteen days (week 4) after the last injection of the carcinogen, the rats received, by gavage twice per week during 5 weeks, either S.bovis (10(10) bacteria) or wall-extracted antigens (100 microg). One week after the last gavage (week 10), we found that administration of either S.bovis or of antigens from this bacterium promoted the progression of preneoplastic lesions through the increased formation of hyperproliferative aberrant colonic crypts, enhanced the expression of proliferation markers and increased the production of IL-8 in the colonic mucosa. Our study suggests that S.bovis acts as a promoter of early preneoplastic lesions in the colon of rats. The fact that bacterial wall proteins are more potent inducers of neoplastic transformation than the intact bacteria may have important implications in colon cancer prevention.

Adenoma↗
PubMed2002

Modifying effects of dietary capsaicin and rotenone on 4-nitroquinoline 1-oxide-induced rat tongue carcinogenesis.

The effects of dietary administration of capsaicin and rotenone on 4-nitroquinoline 1-oxide (4-NQO)-induced tongue tumorigenesis were investigated in male F344 rats. In pilot studies, gavage with capsaicin and rotenone elevated the phase II enzymes glutathione S-transferase (GST) and quinone reductase (QR), in the liver and tongue. Also, a 10 week period of feeding of 500 p.p.m. capsaicin or rotenone together with 4-NQO exposure inhibited the occurrence of tongue dysplasia. Subsequently, a long-term study was conducted to test the protective effects of both compounds on 4-NQO-induced tongue carcinogenesis. One group was treated with 4-NQO alone (20 p.p.m. in drinking water for 8 weeks) and four other groups received the carcinogen treatment plus diets containing 500 p.p.m. test compounds for 10 weeks (initiation phase) or for 28 weeks (post-initiation phase). At the termination of the study (38 weeks), feeding of rotenone during the initiation phase, but not during the post-initiation phase, was found to significantly reduce the incidence of tongue squamous cell carcinoma (53% vs. 16%, 70% reduction, P b=e 0.0250) and severe dysplasia (80% vs. 42%, 70% reduction, P = 0.028). Capsaicin feeding during either the initiation or promotion phase and rotenone feeding during the promotion phase also reduced the frequency of tongue carcinoma without statistical significance. The treatment with two compounds especially rotenone lowered cell proliferation activity in the tongue, elevated phase II enzymes' activities of the liver and tongue, and increased the apoptotic index of tongue carcinoma. Although our results suggest that rotenone feeding during the initiation stage prevented 4-NQO-induced tongue carcinoma, chronic intravenous exposure of rotenone reproduces several features of human Parkinson's disease in rats (Nat. Neurosci., 3, 1301-1306, 2000), suggesting that additional studies to confirm the safety of rotenone are warranted.

4-Nitroquinoline-1-oxide↗
PubMed2001

Proposal of the genus Sphingomonas sensu stricto and three new genera, Sphingobium, Novosphingobium and Sphingopyxis, on the basis of phylogenetic and chemotaxonomic analyses.

Phylogenetic analyses of 16S rRNA gene sequences by distance matrix and parsimony methods indicated that the currently known species of the genus Sphingomonas can be divided into four clusters. Some chemotaxonomic and phenotypic differences were noted among these clusters. Three new genera, Sphingobium, Novosphingobium and Sphingopyxis, are proposed in addition to the genus Sphingomonas sensu stricto. The genus Sphingobium is proposed to accommodate Sphingomonas chlorophenolica, Sphingomonas herbicidovorans and Sphingomonas yanoikuyae. The genus Novosphingobium is proposed for Sphingomonas aromaticivorans, Sphingomonas capsulata, Sphingomonas rosa, Sphingomonas stygia, Sphingomonas subarctica and Sphingomonas subterranea. Sphingomonas macrogoltabidus and Sphingomonas terrae are reclassified in the genus Sphingopyxis. The type species of Sphingobium, Novosphingobium and Sphingopyxis are Sphingobium yanoikuyae, Novosphingobium capsulatum and Sphingopyxis macrogoltabida, respectively.

Alphaproteobacteria↗
PubMed1995

Cerebral energy metabolism and immediate early gene induction following severe incomplete ischaemia in transgenic mice overexpressing the human ornithine decarboxylase gene: evidence that putrescine is not neurotoxic in vivo.

Cerebral ischaemia causes activation of ornithine decarboxylase followed by accumulation of putrescine, and these biochemical phenomena have been thought to contribute to the development of neuronal damage. We have used a transgenic mouse line overexpressing the human ornithine decarboxylase gene in their neurons with constitutively high putrescine to study the possible role of putrescine in development of neuronal damage in forebrain ischaemia. An incomplete forebrain ischaemia model was developed in which common carotid arteries were bilaterally occluded and reduction of blood pressure caused by orthostatic reaction was used as a way of decreasing cerebral circulation. Cerebral high-energy metabolites, intracellular pH and lactate were monitored by means of 31P and 1H nuclear magnetic resonance spectroscopy respectively. Incomplete ischaemia for 15 min resulted in severe energy failure, as indicated by an increase in the inorganic phosphate/phosphocreatine ratio, intracellular acidification from a pH of approximately 7.1 to approximately 6.5 and an increase in lactate concentration from < 1 to approximately 10 mmol/kg in both syngenic and transgenic mice. Following deocclusion, recovery of energy metabolites intracellular pH and lactate were identical in both animal groups. Ornithine decarboxylase activity rose 9- and 3-fold in syngenic and transgenic mice respectively 6 h after ischaemia, which was approximately 50-fold greater than the basal level in syngenic mice. In situ hybridization experiments revealed induction of transcription factors c-Fos and zif-268 in the hippocampus, throughout the cerebral cortex and striatum 1-3 h after ischaemia. Messenger RNA of heat shock protein 70 was induced in dentate gyrus and CA3 and CA4 subfields of the hippocampus 1 h after ischaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Inhibition of ornithine aminotransferase by 5-fluoromethylornithine: protection against acute thioacetamide intoxication by elevated tissue ornithine levels.

5-Fluoromethylornithine (5FMOrn) is a selective inactivator of ornithine aminotransferase. Its administration causes a dramatic increase of ornithine concentrations in all tissues. Treatment of mice with 20 mg.kg-1 5FMOrn shortly before or after a lethal dose (600 mg.kg-1, intraperitoneally) of thioacetamide (TAA), followed by a second dose 24 hr later, prevented death of 60% of the mice. Pathologic symptoms of TAA intoxication (liver haemorrhage, elevation of amino acids in blood and tissues, diminution of liver spermidine and spermine concentrations, elevation of the activity of liver enzymes in the plasma) were significantly ameliorated by the treatment. The liver protective action of 5FMOrn is related to the elevation of ornithine concentration, as appears from the fact that other, less selective inactivators of ornithine aminotransferase, also produced some protection against acute intoxication with TAA, but not a structurally related compound with no effect on this enzyme.

Amino Acids↗
PubMed1990

Cure of Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense infections in mice with an irreversible inhibitor of S-adenosylmethionine decarboxylase.

A structural analog, 5'-([(Z)-4-amino-2-butenyl]methylamino)-5'-deoxy adenosine (MDL 73811), of decarboxy S-adenosyl-L-methionine, the product of the reaction catalyzed by S-adenosyl-L-methionine (AdoMet) decarboxylase (DC), was found to inhibit Trypanosoma brucei brucei AdoMet DC. The inhibition was time dependent (tau 50, 0.3 min), exhibited pseudo-first-order kinetics (Ki, 1.5 microM), and was apparently irreversible. The natural substrate of the reaction, AdoMet, protected the enzyme from inactivation, suggesting that MDL 73811 was directed at the enzyme active site and was probably catalytically activated. Administration of MDL 73811 to T. b. brucei-infected rats resulted in rapid inhibition of AdoMet DC activity, a decrease in spermidine, and an increase in putrescine in the trypanosomes isolated from treated rats. Treatment of T. b. brucei-infected mice with MDL 73811 (20 mg/kg of body weight intraperitoneally twice daily for 4 days) resulted in cures of the trypanosome infections. Additionally, drug-resistant T. brucei rhodesiense infections in mice were cured by either a combination of MDL 73811 (50 mg/kg intraperitoneally three times per day for 5 days) and relatively low oral doses of alpha-difluoromethylornithine or MDL 73811 (50 mg/kg per day for 7 days) administered alone in implanted miniosmotic pumps. These data suggest that MDL 73811 and, perhaps, other inhibitors of AdoMet DC have potential for therapeutic use in various forms of African trypanosomiasis.

Adenosylmethionine Decarboxylase↗
PubMed2006

The immunomodulatory benzodiazepine Bz-423 inhibits B-cell proliferation by targeting c-myc protein for rapid and specific degradation.

Myc proteins regulate cell growth and are oncogenic in many cancers. Although these proteins are validated molecular anticancer targets, new therapies aimed at modulating myc have yet to emerge. A benzodiazepine (Bz-423) that was discovered in efforts to find new drugs for lupus was found recently to have antiproliferative effects on Burkitt's lymphoma cells. We now show that the basis for the antiproliferative effects of Bz-423 is the rapid and specific depletion of c-myc protein, which is coupled to growth-suppressing effects on key regulators of proliferation and cell cycle progression. c-Myc is depleted as a result of signals coupled to Bz-423 binding its molecular target, the oligomycin sensitivity-conferring protein subunit of the mitochondrial F(1)F(o)-ATPase. Bz-423 inhibits F(1)F(o)-ATPase activity, blocking respiratory chain function and generating superoxide, which at growth-inhibiting concentrations triggers proteasomal degradation of c-myc. Bz-423-induced c-myc degradation is independent of glycogen synthase kinase but is substantially blocked by mutation of the phosphosensitive residue threonine 58, which when phosphorylated targets c-myc for ubiquitination and subsequent proteasomal degradation. Collectively, this work describes a new lead compound, with drug-like properties, which regulates c-myc by a novel molecular mechanism that may be therapeutically useful.

B-Lymphocytes↗
PubMed2003

A review of chemotherapeutic approaches to the treatment of cryptosporidiosis.

This review focuses on chemotherapies used against the parasite, Cryptosporidium parvum, the causative agent of cryptosporidiosis. Populations at risk from severe morbidity or mortality from cryptosporidiosis are discussed with particular reference to those infected with HIV. The review then examines chemotherapies used in the clinical setting, as well as a number of in vitro and in vivo experimental studies. It begins with a discussion of the targets within Cryptosporidium that have been the foci of past treatments and then examines novel target sites that may present an exploitable alternative. Some of the novel target sites discussed include the recently discovered apicomplexan plastid and its associated pathways. Lastly, the review examines tubulin as a potential anticryptosporidial target in view of the fact that it has been exploited successfully for almost 50 years for the treatment of helminthiasis. The review concludes with a five-year outlook on the future of anticryptosporidial drug design.

Animals↗
PubMed2000

Ornithine aminotransferase, a potential target for the treatment of hyperammonemias.

Ornithine-delta-aminotransferase (OAT) (EC 2.6.1.13) is a pyridoxal-5' phosphate dependent mitochondrial matrix enzyme. It controls the L-ornithine (Orn) level in tissues by catalysing the transfer of the delta-amino group of Orn to 2-oxoglutarate. The products of this reaction are L-glutamate-gamma-semialdehyde and L-glutamate. Among the compounds known to inhibit (or inactivate) OAT, only L-canaline and (SS)-5-(fluoromethyl)ornithine [(SS)-5FMOrn] are selective for OAT. Treatment of laboratory animals with 5FMOrn causes a dramatic accumulation of Orn in most tissues and organs, and the enhanced formation of urea due to saturation of ornithine:carbamoyltransferase with its substrate. The enhancement of urea formation by increased endogenous levels of Orn is comparable with that produced by large doses of Orn and arginine, a treatment known to enhance the detoxification of ammonia. However, protection to lethal doses of ammonium salts by exogenous Orn is rapidly fading. In contrast, inactivation of OAT by a small dose of 5FMOrn renders a long-lasting protective effect against various forms of hyperammonemic states. Among these the reduction of ammonia concentrations in blood and tissues, and the reduction of the pathologic excretion of orotic acid to normal levels in mice with hereditary defects of the urea cycle, were most impressive. In human hereditary OAT deficiency the elevated intraocular concentrations of Orn are considered to be a cause of gyrate atrophy. This is presumably the reason, why OAT has not been considered as a therapeutically useful target. Chronic inactivation of OAT by repeated administration of 5FMOrn, caused elevated intraocular Orn concentrations, but this treatment had no effect on the function and histology of the visual system, or the behaviour of adult mice. The confirmation of this and related observations in higher species will show, whether OAT inactivation has potentials in the treatment of hyperammonemic states.

Ammonia↗
PubMed2006

The use of anticancer drugs in antiparasitic chemotherapy.

Many similarities exist between cancer cells and parasites. A potentially lucrative starting point for the discovery of novel drugs to combat parasites is to examine available compounds developed against cancer for antiparasitic properties. Here, we review the use of current and promising anticancer agents for treating major human parasitic diseases.

Antineoplastic Agents↗
PubMed1999

Biogenic amines and sensory changes associated with the microbial flora of Mediterranean gilt-head sea bream (Sparus aurata) stored aerobically at 0, 8, and 15 degrees C.

Changes in the concentrations of tyramine, agmatine, putrescine, cadaverine, spermidine, tryptamine, spermine, histamine, and trimethylamine were studied in parallel with the development of the microbial population during the storage of Mediterranean gilt-head sea bream (Sparus aurata) at three temperatures (0, 8, 15 degrees C). Changes in sensory scores were also recorded. Pseudomonads and H2S-producing bacteria were the dominant microorganisms. Enterobacteriaceae and lactic acid bacteria were also present in the fish microflora. Among the biogenic amines, putrescine and cadaverine were detected when pseudomonads exceeded 10(6) to 10(7) CFU/g. Histamine was produced only in samples stored at 15 degrees C. Tyramine, tryptamine, agmatine, and trimethylamine were absent regardless of the storage temperature.

Aerobiosis↗
PubMed2000

Influence of environmental stimulation on neurogenesis in the adult insect brain.

Mushroom bodies are the main integrative structures of insect brain. They receive sensory information from the eyes, the palps, and the antennae. In the house cricket, Acheta domesticus, a cluster of mushroom body neuroblasts keeps producing new interneurons during an insect's life span. The aim of the present work is to study the impact of environmental stimuli on mushroom body neurogenesis during adulthood. Crickets were reared either in an enriched environment, where they received complex environmental and congeneric stimulations or isolated in small cages and deprived of most visual, auditory, and olfactory stimuli. They then were injected with a S-phase marker, 5-bromo, 2'-deoxyuridine (BrdU) and sacrificed at different periods of their life. Neurogenesis and cell survival were estimated by counting the number of BrdU-labeled cells in the mushroom bodies. Environmentally enriched crickets were found to have an increased number of newborn cells in their mushroom bodies compared with crickets housed in cages with an impoverished environment. This effect of external factors on neurogenesis seems to be limited to the beginning of imaginal life. Furthermore, no cell loss could be detected among the newborn neurons in either environmental situation, suggesting that cell survival was not affected by the quality of the environment. Considering vertebrate studies which showed that enriched environment increases hippocampal cell survival and improves animal performances in spatial learning tests, we suggest that the increased number of interneurons produced in an integrative brain structure after exposure to enriched environment could contribute to adaptive behavioral performances in adult insects.

Acoustic Stimulation↗