Metabolomic transition trajectory and potential mechanisms of N-nitrosomethylbenzylamine induced esophageal squamous cell carcinoma in rats.

Esophageal squamous cell carcinoma (ESCC) is an environment-relevant malignancy with a high mortality. Nitrosamines, a class of nitrogen-containing environmental carcinogens, are widely suggested as a risk factor for ESCC. However, how nitrosamines affect metabolic regulation to promote ESCC tumorigenesis is largely unknown. In this study, the transition trajectory of serum metabolism in the course of ESCC induced by N-nitrosomethylbenzylamine (NMBA) in rats was depicted by an untargeted metabolomic analysis, and the potential molecular mechanisms were revealed. The results showed that the metabolic alteration in rats was slight at the basal cell hyperplasia (BCH) stage, while it became apparent when the esophageal lesion developed into dysplasia (DYS) or more serious conditions. Moreover, serum metabolism of severe dysplasia (S-DYS) showed more similar characteristics to that of carcinoma in situ (CIS) and invasive cancer (IC). Aberrant nicotinate (NA) and nicotinamide (NAM) metabolism, tryptophan (TRP) metabolism, and sphingolipid metabolism could be the key players favoring the malignant transformation of esophageal epithelium induced by NMBA. More particularly, NA and NAM metabolism in the precancerous stages and TRP metabolism in the cancerous stages were demonstrated to replenish NAD+ in different patterns. Furthermore, both the IDO1-KYN-AHR axis mediated by TRP metabolism and the SPHK1-S1P-S1PR1 axis by sphingolipid metabolism provided an impetus to create the pro-inflammatory yet immune-suppressive microenvironment to facilitate the esophageal tumorigenesis and progression. Together, these suggested that NMBA exerted its carcinogenicity via more than one pathway, which may act together to produce combination effects. Targeting these pathways may open up the possibility to attenuate NMBA-induced esophageal carcinogenesis. However, the interconnection between different metabolic pathways needs to be specified further. And the integrative and multi-level systematic research will be conducive to fully understanding the mechanisms of NMBA-induced ESCC.

Metal ions modify DNA-protecting and mutagen-scavenging capacities of the AV-153 1,4-dihydropyridine.

1,4-Dihydropyridines (1,4-DHP) possess important biochemical and pharmacological properties, including antioxidant and antimutagenic activities. AV-153-Na, an antimutagenic and DNA-repair enhancing compound was shown to interact with DNA by intercalation. Here we studied DNA binding of several AV-153 salts to evaluate the impact of AV-153 modifications on its DNA binding capacity, the ability to scavenge the peroxynitrite, to protect HeLa and B-cells cells against DNA damage. Affinity of the AV-153 salts to DNA measured by a fluorescence assay was dependent on the metal ion forming a salt in position 4 of the 1,4-DHP, and it decreased as follows: Mg > Na > Ca > Li > Rb > K. AV-153-K and AV-153-Rb could not react chemically with peroxynitrite as opposed to AV-153-Mg and AV-153-Ca, the latter increased the decomposition rate of peroxynitrite. AV-153-Na and AV-153-Ca effectively reduced DNA damage induced by peroxynitrite in HeLa cells, while AV-153-K and AV-153-Rb were less effective, AV-153-Li did not protect the DNA, and AV-153-Mg even caused DNA damage itself. The Na, K, Ca and Mg AV-153 salts were also shown to reduce the level of DNA damage in human B-cells from healthy donors. Thus, metal ions modify both DNA-binding and DNA-protecting effects of the AV-153 salts.

Comparative Early Life Stage Toxicity of the African Clawed Frog, Xenopus laevis Following Exposure to Selected Herbicide Formulations Applied to Eradicate Alien Plants in South Africa.

The rise in pesticides application has increased the need for better understanding of their ecological impacts. The global amphibian declines, for example, have been positively correlated with pesticides use. The differential susceptibility in the developmental stages of amphibians to chemical substances are still largely unknown. We examined the 96-h differential toxicity responses of embryos, premetamorphic and transitional larval stage of Xenopus laevis, to six formulated aquatic herbicide products containing the active ingredients of diquat dibromide (Midstream), glufosinate ammonium (Basta), imazapyr (Arsenal), and three glyphosate formulations (Roundup, Kilo Max, and Environ Glyphosate). The results showed the premetamorphic stage as the most sensitive to the herbicides toxicity. This study confirmed that the developmental stage at which amphibian are exposed to contaminants is critical to their survival and that the chemical contamination hypothesis of the global decline of amphibians should continue to be considered. This establishment of the premetamorphic larval as sensitive toxicity representative for all developmental stages of X. laevis means that this stage could be used more extensively in pesticides toxicity assessments.

Herbicide Toxicity Testing with Non-Target Boreal Plants: The Sensitivity of Achillea millefolium L. and Chamerion angustifolium L. to Triclopyr and Imazapyr.

Terrestrial plant toxicity tests were conducted to determine the sensitivity of two boreal plants, yarrow (Achillea millefolium L.) and fireweed (Chamerion angustifolium L.), to the herbicides imazapyr and triclopyr. Both plants are common non-target species on northern powerline rights-of-way where the impacts of proposed herbicide applications are of concern. In the vegetative vigour test, triclopyr foliar spray caused extensive damage to A. millefolium at <50% of the maximum field application rate (inhibition concentration (IC)50 = 1443.8 g a.i. ha-1) and was lethal to C. angustifolium at the lowest dose tested (1210.9 g a.i. ha-1). Both species demonstrated extremely high sensitivity to imazapyr foliar spray: IC50s = 8.29 g a.i. ha-1 and 4.82 g a.i. ha-1 (<1.5% of the maximum field rate). The seedling emergence and seedling growth tests were conducted in the organic horizon of five boreal soils. Few differences in herbicide bioavailability between soils were detected. Triclopyr limited growth of A. millefolium, C. angustifolium and standard test species Calamagrostis canadensis at low levels (most IC50 estimates between 2-20 µg g-1). For imazapyr, IC50 estimates could not be calculated as there was >75% inhibition of endpoints at the lowest doses of ~2 µg g-1. A foliar application of triclopyr or imazapyr for woody species control would likely cause significant damage to boreal non-target plants. The high sensitivity of both species to herbicide residues in soil indicates long term impacts are dependent on herbicide degradation rates in northern conditions. A. millefolium performed well and is recommended for use in toxicity testing relevant to boreal regions.

6-Benzylidene-2-[4-(pyridin-3-ylcarboxy)benzylidene]cyclohexanones: A novel cluster of tumour-selective cytotoxins.

Novel cytotoxins 3-5 containing the 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore are disclosed. The compounds in series 3 and 5 have the potential to liberate niacin which may reduce some of the side effects of antineoplastic compounds. 3a-c emerged as the most potent cytotoxic compounds with IC50 values in the low micromolar range against human Molt4/C8 and CEM CD4+ T-lymphocytes as well as murine L1210 leukemia cells. QSAR studies revealed that cytotoxic potencies were negatively correlated with the magnitude of the Hammett sigma values of the aryl substituents. The compounds 3a-e displayed tumour-selective toxicity against human HL-60, HSC-2, HSC-3 and HSC-4 neoplasms as compared to human HGF, HPC and HPLF nonmalignant cells. A representative potent compound 3a caused PARP1 cleavage and G0/G1 cell cycle arrest in HSC-2 cells. These compounds are well tolerated in mice at doses up to and including 300mg/kg of the compounds and no mortalities were noted after 4h. The stability studies undertaken did not reveal that a representative compound 3a underwent hydrolysis to the related phenol 2a. Some guidelines for further analog development of the novel esters 3 were made.

Imazapyr+imazapic herbicide determines acute toxicity in silver catfish Rhamdia quelen.

Imazapyr (IMY) and imazapic (IMI) are imidazolinone herbicides which have been associated in a commercial formulation (Kifix(®)). To date, there are no studies on the toxicity of an IMY+IMI herbicide in fish. This work aimed to assess the acute toxicity (24 and 96 h) of IMY+IMI (0, 0.488 and 4.88 µg/L) towards Rhamdia quelen through hematological, biochemical, immunological, ionoregulatory and enzymatic indexes. Red blood cell count was lower at 4.88 than at 0.488 µg/L (24 and 96 h); mean corpuscular volume was lower than control at both concentrations (24 h) and at 0.488 µg/L (96 h); lymphocytes declined at 4.88 µg/L comparing to control (96 h); and monocytes increased at 4.88 µg/L (96 h) in comparison with the respective control and with 4.88 µg/L at 24h. Aspartate aminotransferase was higher at 0.488 µg/L (96 h) than the respective control and the respective concentration at 24 h; uric acid reduced at 4.88 µg/L comparing with 0.488 µg/L (96 h); and cortisol was lower at 4.88 µg/L compared to 0.488 µg/L and control (96 h). Herbicide exposure lowered plasma bactericidal activity at both concentrations (24 h) and at 0.488 µg/L (96 h); and plasma complement activity declined at 4.88 µg/L comparing with 0.488 µg/L and control (96 h), and was lower at all concentrations at 96 h than at 24 h. Plasma K(+) levels were higher at 4.88µg/L than in the remaining groups (24 and 96h); and Na(+) levels decreased at 4.88 µg/L compared to control (96 h). Na(+)/K(+)-ATPase and H(+)-ATPase activities in gills were lower at 4.88 µg/L comparing with control (24 h) and with the respective concentration at 96 h; and AChE activity in brain was higher at 0.488 and 4.88 µg/L than control (24 h) and the respective concentrations at 96 h, while in muscle it was higher at 0.488 and 4.88 µg/L than control (96 h) and the respective concentrations at 24 h. The present findings demonstrate that, despite IMY+IMI targets the animal-absent AHAS enzyme, such formulation displayed an acute toxic effect upon R. quelen homeostasis by impacting on vital functions such as immune defense, metabolism, ionoregulation and neurotransmission.

Nanoparticles Based on Chitosan as Carriers for the Combined Herbicides Imazapic and Imazapyr.

The use of lower concentrations and fewer applications of herbicides is one of the prime objectives of the sustainable agriculture as it decreases the toxicity to non-targeted organisms and the risk of wider environmental contamination. In the present work, nanoparticles were developed for encapsulation of the herbicides imazapic and imazapyr. Alginate/chitosan and chitosan/tripolyphosphate nanoparticles were manufactured, and their physicochemical stability was evaluated. Determinations were made of the encapsulation efficiency and release kinetics, and the toxicity of the nanoparticles was evaluated using cytotoxicity and genotoxicity assays. The effects of herbicides and herbicide-loaded nanoparticles on soil microorganisms were studied in detail using real-time polymerase chain reactions. The nanoparticles showed an average size of 400 nm and remained stable during 30 days of storage at ambient temperature. Satisfactory encapsulation efficiencies of between 50 and 70% were achieved for both types of particles. Cytotoxicity assays showed that the encapsulated herbicides were less toxic, compared to the free compounds, and genotoxicity was decreased. Analyses of soil microbiota revealed changes in the bacteria of the soils exposed to the different treatments. Our study proves that encapsulation of the herbicides improved their mode of action and reduced their toxicity, indicating their suitability for use in future practical applications.

Characterization of the anxiolytic and sedative profile of JM-20: a novel benzodiazepine-dihydropyridine hybrid molecule.

OBJECTIVES: The aim of this study was to investigate the effects of oral administration of a novel benzodiazepine derivative, JM-20, on the neurological behavior of different rodent models, focusing on the GABAergic effect. We have also investigated the acute toxicity of oral administration of JM-20 in mice. METHODS: Mice or rats received oral administration of JM-20 at 2, 4, 8, and 10 mg/kg to evaluate the sedative/hypnotic, anxiolytic, and anticonvulsant effects, as well as the influence on the stereotyped behavior induced by amphetamine. Diazepam (DZP) was used as a positive control. In addition, the mice received a single oral JM-20 dose of 2000 mg/kg to evaluate the acute toxicity. RESULTS: In a dose-dependent manner, JM-20 (i) increased the number of crossings and decreased the number of rearings in the open-field test; (ii) decreased the aggressive behavior of socially-isolated mice; and (iii) increased the latency period for tonic seizure's onset and the percentage of survival of animals with seizures. Moreover, JM-20 increased the sleeping time induced by barbiturates and the time spent and the number of entries in the open arms of the elevated plus-maze test. In the JM-20 toxicity test, no mortality was observed and only minor signs of toxicity associated with sedation were detected. CONCLUSIONS: These results indicate that JM-20 has an anxiolytic profile similar to DZP and its dihydropyridine moiety did not appear to interfere with the GABAergic activity associated with benzodiazepine. Furthermore, JM-20 did not show significant acute toxic effects in mice.

Differential expression of acetohydroxyacid synthase genes in sunflower plantlets and its response to imazapyr herbicide.

Acetohydroxyacid synthase (AHAS) catalyzes the first reaction in branch chain amino acids biosynthesis. This enzyme is the target of several herbicides, including all members of the imidazolinone family. Little is known about the expression of the three acetohydroxyacid synthase genes (ahas1, ahas2 and ahas3) in sunflower. The aim of this work was to evaluate ahas gene expression and AHAS activity in different tissues of sunflower plantlets. Three genotypes differing in imidazolinone resistance were evaluated, two of which carry an herbicide resistant-endowing mutation known as Ahasl1-1 allele. In vivo and in vitro AHAS activity and transcript levels were higher in leaves than in roots. The ahas3 transcript was the less abundant in both tissues. No significant difference was observed between ahas1 and ahas2 transcript levels of the susceptible genotype but a higher ahas1 transcript level was observed in leaves of genotypes carrying Ahasl1-1 allele. Similar transcript levels were found for ahas1 and ahas2 in roots of genotypes carrying Ahasl1-1 allele whereas higher ahas2 abundance was found in the susceptible genotype. Herbicide treatment triggered tissue-specific, gene and genotype-dependent changes in ahas gene expression. AHAS activity was highly inhibited in the susceptible genotype. Differential responses were observed between in vitro and in vivo AHAS inhibition assays. These findings enhance our understanding of AHAS expression in sunflower genotypes differing for herbicide resistance and its response to herbicide treatment.

Impact of the ahas transgene and of herbicides associated with the soybean crop on soil microbial communities.

Although Brazil has recently reached the position as the second largest producer of genetically modified soybean [Glycine max (L.) Merr.], there are few reports on the effects of transgenic crops and the associated use of specific herbicides on soil microbial communities, both under the edaphoclimatic conditions in Brazil, and in other producer regions in the southern hemisphere. The aim of this study was to evaluate the effects of transgenic soybean containing the ahas gene conferring resistance to herbicides of the imidazolinone group, and of the herbicides associated with transgenic soybeans on the soil microbial community. Twenty field experiments were carried out during three growing seasons (summer of 2006/2007, short-season of 2007 and summer of 2007/2008), in nine municipalities located in six Brazilian states and in the Federal District. The experiments were conducted using a completely randomized block design with four replicates and three treatments: (1) conventional (non-transgenic) soybean cultivar Conquista with conventional herbicides (bentazone + acifluorfen-sodium and other herbicides, depending on the level of infestation in each region); (2) near-isogenic transgenic Cultivance (CV127) containing the ahas gene, with conventional herbicides; (3) transgenic Cultivance with specific herbicide of the imidazolinone group (imazapyr). As the objective of the study was to verify impacts of the transgene and herbicides on the soil microbial community of the whole area and not only a punctual rhizospheric effects, samples were taken at the 0-10 cm layer prior to cropping and at R2 soybean growth stage, between plant rows. Quantitative (microbial biomass C and N, MB-C and MB-N) and qualitative (DGGE of the 16S rDNA region) parameters of soil microbial community were evaluated. No qualitative or quantitative differences were found that could be attributed to the transgene ahas. A comparison of Cultivance soybean with conventional and imidazolinone-group herbicides applications also failed to reveal differences that could be attributed to the specific use of imazapyr, even after three consecutive croppings at the same site. Finally, no differences were detected between conventional (Conquista and conventional herbicides) and transgenic soybean managements (Cultivance and imazapyr). However, marked differences were observed in MB-C and MB-N between the different sites and times of year and, for the 16S rDNA-DGGE profiles, between different sites. In conclusion, microbial community evaluations were found to be sensitive and viable for monitoring different technologies and agricultural management methods, but no differences could be attributed to the ahas transgene for three consecutive cropping seasons.

Effects of the herbicide imazapyr on juvenile Oregon spotted frogs.

Conflict between native amphibians and aquatic weed management in the Pacific Northwest is rarely recognized because most native stillwater-breeding amphibian species move upland during summer, when herbicide application to control weeds in aquatic habitats typically occurs. However, aquatic weed management may pose a risk for aquatic species present in wetlands through the summer, such as the Oregon spotted frog (OSF, Rana pretiosa), a state endangered species in Washington. Acute toxicity of herbicides used to control aquatic weeds tends to be low, but the direct effects of herbicide tank mixes on OSFs have remained unexamined. We exposed juvenile OSFs to tank mixes of the herbicide imazapyr, a surfactant, and a marker dye in a 96-h static-renewal test. The tank mix was chosen because of its low toxicity to fish and its effectiveness in aquatic weed control. Concentrations were those associated with low-volume (3.5 L/ha) and high-volume (7.0 L/ha) applications of imazapyr and a clean-water control. Following exposure, frogs were reared for two months in clean water to identify potential latent effects on growth. Endpoints evaluated included feeding behavior, growth, and body and liver condition indices. We recorded no mortalities and found no significant differences for any end point between the herbicide-exposed and clean-water control frogs. The results suggest that imazapyr use in wetland restoration poses a low risk of direct toxic effects on juvenile OSFs.

Niacin reduces plasma CETP levels by diminishing liver macrophage content in CETP transgenic mice.

The anti-dyslipidemic drug niacin has recently been shown to reduce the hepatic expression and plasma levels of CETP. Since liver macrophages contribute to hepatic CETP expression, we investigated the role of macrophages in the CETP-lowering effect of niacin in mice. In vitro studies showed that niacin does not directly attenuate CETP expression in macrophages. Treatment of normolipidemic human CETP transgenic mice, fed a Western-type diet with niacin for 4 weeks, significantly reduced the hepatic cholesterol concentration (-20%), hepatic CETP gene expression (-20%), and plasma CETP mass (-30%). Concomitantly, niacin decreased the hepatic expression of CD68 (-44%) and ABCG1 (-32%), both of which are specific markers for the hepatic macrophage content. The decrease in hepatic CETP expression was significantly correlated with the reduction of hepatic macrophage markers. Furthermore, niacin attenuated atherogenic diet-induced inflammation in liver, as evident from decreased expression of TNF-alpha (-43%). Niacin similarly decreased the macrophage markers and absolute macrophage content in hyperlipidemic APOE*3-Leiden.CETP transgenic mice on a Western-type diet. In conclusion, niacin decreases hepatic CETP expression and plasma CETP mass by attenuating liver inflammation and macrophage content in response to its primary lipid-lowering effect, rather than by attenuating the macrophage CETP expression level.

Effects of herbicides on Behr's metalmark butterfly, a surrogate species for the endangered butterfly, Lange's metalmark.

Lange's metalmark butterfly, Apodemia mormo langei Comstock, is in danger of extinction due to loss of habitat caused by invasive exotic plants which are eliminating its food, naked stem buckwheat. Herbicides are being used to remove invasive weeds from the dunes; however, little is known about the potential effects of herbicides on butterflies. To address this concern we evaluated potential toxic effects of three herbicides on Behr's metalmark, a close relative of Lange's metalmark. First instars were exposed to recommended field rates of triclopyr, sethoxydim, and imazapyr. Life history parameters were recorded after exposure. These herbicides reduced the number of adults that emerged from pupation (24-36%). Each herbicide has a different mode of action. Therefore, we speculate that effects are due to inert ingredients or indirect effects on food plant quality. If these herbicides act the same in A. mormo langei, they may contribute to the decline of this species.

Functionalized (poly(ɛ-caprolactone))2-poly(ethylene glycol) nanoparticles with grafting nicotinic acid as drug carriers.

Nicotinic acid was grafted on (poly(ɛ-caprolactone))(2)-poly(ethylene glycol) copolymers that were used for the preparation of nanoparticles with the objectives to monitor particle size and to optimize the drug loading capacity as well as the release profile of the particles. Increasing amounts of grafting nicotinic acid increased the particle size as a result of an enhanced hydrophobicity of the copolymer. Ibuprofen and indomethacin with two different molecular characteristics were selected as model drugs to be bound to the nanoparticles. The presence of grafting nicotinic acid enhanced the loading capacity for both drugs compared to the nanoparticles without nicotinic acid. However, no correlation between amount of grafting nicotinic acid and loading capacity was observed. The release characteristic of both drugs was fitted to the Higuchi model indicating Fickian diffusion. The release characteristic of indomethacin mainly depended on the crystalline property of the copolymer whereas that of ibuprofen was additionally influenced by the hydrogen bonding between drug and grafted copolymer.

Seeing red: flushing out instigators of niacin-associated skin toxicity.

The use of niacin to improve plasma lipid levels and reduce risk of myocardial infarction is limited by noxious skin effects that result from stimulation of G protein-coupled receptor 109A (GPR109A) in skin immune cells. Niacin causes vasodilation, manifest as rubor (redness) of the head and neck, providing a visible sign associated with other, more bothersome skin complaints. The working theory is that niacin provokes Langerhans cells to produce prostaglandin D2 (PGD2), stimulating vascular DP1 receptors to cause vasodilation. In this issue of the JCI, Hanson and colleagues raise a serious challenge to this paradigm in showing that the major player in vasodilation is the keratinocyte, which produces PGE2, stimulating EP2/4 receptors, shifting the role of the Langerhans/PGD2/DP1 pathway to that of an accomplice. They also show that the antipsoriasis drug monomethyl fumarate, itself a GPR109A agonist, provokes vasodilation through the same cells. These efforts bring us one step closer to solving a key limitation of an important cardioprotective drug and reveal that the skin response to niacin is much more complicated than previously thought.

Nicotinic acid- and monomethyl fumarate-induced flushing involves GPR109A expressed by keratinocytes and COX-2-dependent prostanoid formation in mice.

The antidyslipidemic drug nicotinic acid and the antipsoriatic drug monomethyl fumarate induce cutaneous flushing through activation of G protein-coupled receptor 109A (GPR109A). Flushing is a troublesome side effect of nicotinic acid, but may be a direct reflection of the wanted effects of monomethyl fumarate. Here we analyzed the mechanisms underlying GPR109A-mediated flushing and show that both Langerhans cells and keratinocytes express GPR109A in mice. Using cell ablation approaches and transgenic cell type-specific GPR109A expression in Gpr109a-/- mice, we have provided evidence that the early phase of flushing depends on GPR109A expressed on Langerhans cells, whereas the late phase is mediated by GPR109A expressed on keratinocytes. Interestingly, the first phase of flushing was blocked by a selective cyclooxygenase-1 (COX-1) inhibitor, and the late phase was sensitive to a selective COX-2 inhibitor. Both monomethyl fumarate and nicotinic acid induced PGE2 formation in isolated keratinocytes through activation of GPR109A and COX-2. Thus, the early and late phases of the GPR109A-mediated cutaneous flushing reaction involve different epidermal cell types and prostanoid-forming enzymes. These data will help to guide new efficient approaches to mitigate nicotinic acid-induced flushing and may help to exploit the potential antipsoriatic effects of GPR109A agonists in the skin.

Safety of an oxygen-coordinated niacin-bound chromium(III) complex (NBC): II. Developmental toxicity study in rats.

The objective of the present study was to evaluate the teratogenic potential of a novel oxygen-coordinated niacin-bound chromium complex (NBC) in Sprague-Dawley rats. Due to its potential to affect fat synthesis and reduce food intake, processes which are often crucial in normal fetal development, this teratology study was undertaken as part of a multi-generation reproductive investigation. The animals in this study were selected randomly after weaning from each F(2b) litter of the F1 generation from the two-generation reproductive toxicity study. To start the teratology study, Sprague-Dawley rat pups ( approximately 30/sex/group) from the F(2b) generation were allowed to grow up to 10-12 weeks of age before mating. The rats in treatment group were exposed directly to NBC through feed. The dietary exposure levels were the same as those employed for the two-generation reproductive toxicity study, viz. 4, 15, or 60 ppm. Following mating at maturity, the pregnant rats were observed daily for clinical signs of adverse effects, and body weight and feed consumption were recorded. On the day 20th of the gestation, animals were subjected to a necropsy and caesarean section to examine the uterus, ovaries and fetuses for assessment of different parameters of pregnancy and embryo-fetal defects. In this study, no indications of maternal toxicity, adverse effects on the parameters evaluated for the gravid uteri, external abnormalities in the fetuses, soft tissue abnormalities in the fetuses, or skeletal abnormalities in the fetuses were noted. Based on the results of this developmental toxicity study, NBC was found to benon-teratogenic in Sprague-Dawley rat, at the dietary exposure levels of 4, 15, and 60 ppm, equivalent to the dose levels of 0.50, 2.0, or 8.0mg/kg/day, respectively.

Safety of a novel oxygen-coordinated niacin-bound chromium(III) complex (NBC): I. Two-generation reproduction toxicity study.

The objective of this study was to evaluate the effects of a novel oxygen-coordinated niacin-bound chromium(III) complex (NBC) on the reproductive systems of male and female rats, the postnatal maturation and reproductive capacity of their offspring, and possible cumulative effects through multiple generations. Sprague-Dawley rats were maintained on feed containing NBC at dose levels of 0, 4, 15, or 60ppm for 10weeks prior to mating, during mating, and, for females through gestation and lactation, across two generations. For the parents (F(0) and F(1)) and the offspring (F(1) and F(2a)), reproductive parameters such as fertility and mating, gestation, parturition, litters, lactation, sexual maturity and development of offspring were assessed. Results from the current study indicated that dietary exposure of NBC to parental male and female rats of both (F(0) and F(1)) the generations during the premating and mating periods, for both sexes, and during gestation and lactation in case of female rats, did not cause any significant incidence of mortality or abnormal clinical signs. Compared to respective controls, NBC exposure did not affect reproductive performance as evaluated by sexual maturity, fertility and mating, gestation, parturition, litter properties, lactation and development of the offspring. Based on the findings of this study, the parental as well as the offspring no-observed-adverse-effect level for NBC was determined to be greater than 60ppm in diet or equivalent to 7.80 and 8.31mg/kg body weight/day in male and female rats, respectively.

[Effects of excess nicotinic acid on growth and the urinary excretion of B-group vitamins and the metabolism of tryptophan in weaning rats].

To determine the tolerable upper intake level of nicotinic acid in humans, we investigated the effects of excess nicotinic acid administration on body weight gain, food intake, and urinary excretion of water-soluble vitamins and the metabolism of tryptophan in weaning rats. The weaning rats were freely fed a niacin-free 20% casein diet (control diet) or the same diet with 0.1%, 0.3% or 0.5% nicotinic acid for 23 days. The excess nicotinic acid intake did not affect body weight gain, food intake, serotonin contents in the brain, stomach and small intestine, or the urinary excretions of water-soluble vitamins. Although excess nicotinic acid did not affect the upper part of the tryptophan-nicotinamide pathway, 0.5% nicotinic acid diet increased the urinary excretion of quinolinic acid. The diet containing more than 0.3% nicotinic acid also increased the urinary excretion of nicotinic acid, which is usually below the limit of detection. As determined from the results of body weight gain and food intake as indices for apparent adverse effects, the no-observed-adverse-effect-level (NOAEL) for nicotinic acid was 0.5% in diet, corresponding to 450 mg/kg body weight/day. As judged from in increase of urinary quinolinic acid and nicotinic acid as indices of metabolic change, NOAEL was 0.1% in diet, corresponding to 90 mg/kg body weight/day, and the lowest-observed-adverse-effect-level (LOAEL) was 0.3% in diet, corresponding to 270 mg/kg body weight/day.