Dietary live yeast and increased water temperature influence the gut microbiota of rainbow trout.

AIMS: The objective was to determine the effects of dietary substitution of fishmeal (FM) with live yeast and increasing water temperature on the diversity and composition of gut microbiota in rainbow trout. METHODS AND RESULTS: Fish were fed either FM or yeast (Saccharomyces cerevisiae) and reared in water temperatures of either 11°C (cold) or 18°C (warm) for 6 weeks. Luminal content and mucosa were collected from the distal gut and the load, diversity and species abundance of yeast and bacteria were analysed using agar plating, MALDI-TOF and rRNA gene amplicon sequencing. Yeast in the gut of fish fed FM were represented by S. cerevisiae, Rhodotorula spp. and Debaryomyces hansenii, while fish fed yeast contained 4-5 log higher CFU per g of yeast that were entirely represented by S. cerevisiae. For gut bacteria, sequencing of 16S rRNA gene amplicons using Illumina MiSeq showed lower bacterial diversity and abundance of lactic acid bacteria, especially Lactobacillus, in fish reared in warm rather than cold water. Fish fed yeast had similar bacterial diversity and lower abundance of Leuconostocaceae and Photobacterium compared with fish fed FM. CONCLUSIONS: Feeding live yeast mainly increased yeast load in the gut, while increased water temperature significantly altered the gut microbiota of rainbow trout in terms of bacterial diversity and abundance. SIGNIFICANCE AND IMPACT OF THE STUDY: Live yeast can replace 40% of FM without disrupting bacteria communities in the gut of rainbow trout, while increased water temperature due to seasonal fluctuations and/or climate change may result in a gut dysbiosis that may jeopardize the health of farmed fish.

Impact of anticipation in dynamical systems.

Many animals, including humans, have predictive capabilities and, presumably, base their behavioral decisions-at least partially-upon an anticipated state of their environment. We explore a minimal version of this idea in the context of particles that interact according to a pairwise potential. Anticipation enters the picture by calculating the interparticle forces from linear extrapolations of the particle positions some time τ in the future. Simulations show that for intermediate values of τ, compared to a transient time scale defined by the potential and the initial conditions, the particles form rotating clusters in which the particles are arranged in a hexagonal pattern. Analysis of the system shows that anticipation induces energy dissipation and we show that the kinetic energy asymptotically decays as 1/t. Furthermore, we show that the angular momentum is not necessarily conserved for τ>0, and that asymmetries in the initial condition therefore can cause rotational movement. These results suggest that anticipation could play an important role in collective behavior, since it may induce pattern formation and stabilizes the dynamics of the system.

Cadmium and mercury exposure over time in Swedish children.

PURPOSE: Knowledge about changes in exposure to toxic metals over time remains very sparse, in particular for children, the most vulnerable group. Here, we assessed whether a reduction in environmental pollution with cadmium (Cd) and mercury (Hg) caused a change in exposure over time. In total, 1257 children (age 4-9) in two towns in Sweden were sampled once in 1986-2013. Blood concentrations of Cd (b-Cd; n=1120) and Hg (b-Hg; n=560) were determined. RESULTS: The median b-Cd was 0.10 (geometric mean 0.10; range 0.010-0.61) µg/L and b-Hg was 0.91 (geometric mean 0.83; range 0.021-8.2) µg/L. Children living close to a smelter had higher b-Cd and b-Hg than those in urban and rural areas. There was no sex difference in b-Cd or b-Hg, and b-Cd and b-Hg showed no significant accumulation by age. b-Cd decreased only slightly (0.7% per year, p<0.001) over the study period. In contrast, b-Hg did show a clear decrease over the study period (3% per year, p<0.001). CONCLUSIONS: The exposure to Cd was very low but still might increase the risk of disease later in life. Moreover, b-Cd only showed a minor decrease, indicating that Cd pollution should be further restricted. b-Hg was relatively low and decreasing, probably because of reduced use of dental amalgam and lower Hg intake from fish. The b-Cd and b-Hg levels decreased much less than the levels of lead in the blood as previously found in the same children.

Stunning fish with CO2 or electricity: contradictory results on behavioural and physiological stress responses.

Studies that address fish welfare before slaughter have concluded that many of the traditional systems used to stun fish including CO2 narcosis are unacceptable as they cause avoidable stress before death. One system recommended as a better alternative is electrical stunning, however, the welfare aspects of this method are not yet fully understood. To assess welfare in aquaculture both behavioural and physiological measurements have been used, but few studies have examined the relationship between these variables. In an on-site study aversive behaviours and several physiological stress indicators, including plasma levels of cortisol and ions as well as blood physiological variables, were compared in Arctic char (Salvelinus alpinus) stunned with CO2 or electricity. Exposure to water saturated with CO2 triggered aversive struggling and escape responses for several minutes before immobilization, whereas in fish exposed to an electric current immobilization was close to instant. On average, it took 5 min for the fish to recover from electrical stunning, whereas fish stunned with CO2 did not recover. Despite this, the electrically stunned fish had more than double the plasma levels of cortisol compared with fish stunned with CO2. This result is surprising considering that the behavioural reactions were much more pronounced following CO2 exposure. These contradictory results are discussed with regard to animal welfare and stress physiological responses. The present results emphasise the importance of using an integrative and interdisciplinary approach and to include both behavioural and physiological stress indicators in order to make accurate welfare assessments of fish in aquaculture.

Expression of heat shock protein 27 in gut tissue of growing pigs fed diets without and with inclusion of chicory fiber.

The physiological expression of cytoprotective heat shock protein 27 (Hsp27) in the gut was investigated in eighteen 7-wk-old pigs fed one of 3 fiber-rich diets for 18 d. The diets were a cereal-based control diet and a cereal-based diet with inclusion of either 80 g/kg chicory forage (CF80) or chicory root (CR80). Immunohistochemical staining showed that Hsp27 was expressed in all the samples from ileum and colon. The expression was most intensive in the apical intestinal epitheliums in close contact with luminal contents and lighter in crypt cells. The ileal Peyer's patches showed a strong expression of Hsp27, which was highly correlated with Hsp27 expression in the ileal epithelial cells (P = 0.003). The frequency of ileal Hsp27 expression with the most intensive staining was distributed higher in pigs fed chicory forage diet (CF80, 25%) followed by chicory root diet (CR80, 16.7%) and the control (11.1%). In proximal colon, the frequency of expression showed a similar pattern for the different diets. The intestinal microbiota profile was characterized with the intention to find correlations to heat shock protein (Hsp) expression in pig gastrointestinal (GI) tract and showed that the distal ileum and proximal colon encompass its own unique microbial profile. However, no significant relationship was found between gut microbiota diversity and Hsp27 expression. These indicate that Hsp27 expression in the porcine gut could be associated with specific dietary fiber components but not the overall microbiota diversity.

Long-term lead elimination from plasma and whole blood after poisoning.

OBJECTIVE: Blood lead (B-Pb), one of the most used toxicological biomarker all kind, has serious limitations. Thus, the objective is to evaluate whether plasma lead (P-Pb) is more adequate. METHODS: A long-term follow-up study of five cases of lead poisoning. P-Pb was analysed by inductively coupled plasma mass spectrometry. Kinetics after end of exposure was modelled. RESULTS: P-Pb at severe poisoning was about 20 µg/L; haematological effects at about 5 µg/L. Biological half-time of P-Pb was about 1 month; B-Pb decay was much slower. CONCLUSION: P-Pb is a valuable biomarker of exposure to and risk, particularly at high exposure.

Growth performance, digestibility, and gut development of broiler chickens on diets with inclusion of chicory (Cichorium intybus L.).

A total of 256 broiler chickens (1 d old) were used in a 32-d growth trial to study the effects of chicory (Cichorium intybus L.) forage and root inclusion on growth performance, digestibility, and gut development. The chicory forage originated from 2 harvests (June and September) and was included at 60 and 120 g/kg. The chicory root was included alone at 60 g/kg or together with chicory forage, from both harvests, in equal amounts (60 g/kg). The cereal-based control diet and 7 experimental diets were fed to each of 4 pens of chickens (8 chickens/pen). A higher BW gain and lower feed conversion ratio were found at 13 d of age in chickens fed the 60 g/kg chicory forage diet (P ≤ 0.05), whereas performance did not differ between the control and 60 g/kg chicory root diets. In contrast, a lower performance and digestibility of DM, organic matter, and AME as well as a thinner cecal mucosa layer were found for the 120 g/kg chicory forage diet (P ≤ 0.05). No diet effects on organ parameters or on pH of cecum digesta were detected. The soluble nonstarch polysaccharides fractions of chicory forage did not have any major negative effects on performance and gut development, and chicory forage from the September harvest was seen to have a higher nutritional value than that from the June harvest. Thus, results from the current study suggest that chicory forage is a potentially useful fiber-rich feed ingredient with high palatability for broiler chickens.

Exposure to cadmium and persistent organochlorine pollutants and its association with bone mineral density and markers of bone metabolism on postmenopausal women.

Environmental contaminants such as cadmium and persistent organochlorine pollutants have been proposed as risk factors of osteoporosis, and women may be at an increased risk. To assess associations between exposure to cadmium and two different POPs (2,2',4,4',5,5'-hexachlorobiphenyl CB-153, 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene p,p'-DDE), on one hand, and bone effects, on the other, in a population-based study among postmenopausal (60-70 years) Swedish women with biobanked blood samples. The study included 908 women and was designed to have a large contrast of bone mineral densities, measured with a single photon absorptiometry technique in the non-dominant forearm. Biochemical markers related to bone metabolism were analyzed in serum. Exposure assessment was based on cadmium concentrations in erythrocytes and serum concentrations of CB-153 and p,p'-DDE. Cadmium was negatively associated with bone mineral density and parathyroid hormone, positively with the marker of bone resorption. However, this association disappeared after adjustment for smoking. The major DDT metabolite (p,p'-DDE) was positively associated with bone mineral density, an association which remained after adjustment for confounders, but the effect was weak. There was no evidence that the estrogenic congener (CB-153) was associated with any of the bone markers. In conclusion, no convincing associations were observed between cadmium and POPs, on one hand, and bone metabolism markers and BMD, on the other.

Does gold concentration in the blood influence the result of patch testing to gold?

BACKGROUND: We have recently found a correlation between contact allergy to gold sodium thiosulphate (GSTS) and gold concentration in the blood (B-Au) in a stented population: the higher the B-Au, the stronger the patch-test reaction. OBJECTIVES: To further investigate the correlation between B-Au and patch-test reactivity to gold. METHODS: In this provocation control cross-over trial of 24 patients with dermatitis with a known contact allergy to gold, the patients were randomized into two groups where one was topically provoked to gold (15 mg GSTS) and one to the control. All patients were simultaneously patch tested with GSTS in 10 aqueous dilutions (1.1 mg GSTS). Patch-test readings were performed and blood was drawn. After 6 weeks, the experiment was repeated and the group that had previously been provoked with gold was now provoked with the control and vice versa. RESULTS: B-Au was higher after gold provocation whereas no treatment effect was discerned for minimal eliciting concentration (MEC) or summarized test score (STS). Instead, significant differences in period effect were observed implying higher B-Au and STS and lower MEC on test occasion II. The most likely explanation is the increased B-Au and /or booster effect from test occasion I. There was a correlation between B-Au and MEC: the higher the B-Au, the lower the MEC. CONCLUSIONS: The correlation between B-Au and MEC indicates that the B-Au is of importance for the skin reactivity to gold.

Gene divergence and pathway duplication in the metabolic network of yeast and digital organisms.

We have studied the metabolic gene-function network in yeast and digital organisms evolved in the artificial life platform Avida. The gene-function network is a bipartite network in which a link exists between a gene and a function (pathway) if that function depends on that gene, and can also be viewed as a decomposition of the more traditional functional gene networks, where two genes are linked if they share any function. We show that the gene-function network exhibits two distinct degree distributions: the gene degree distribution is scale-free while the pathway distribution is exponential. This is true for both yeast and digital organisms, which suggests that this is a general property of evolving systems, and we propose that the scale-free gene degree distribution is due to pathway duplication, i.e. the development of a new pathway where the original function is still retained. Pathway duplication would serve as preferential attachment for the genes, and the experiments with Avida revealed precisely this; genes involved in many pathways are more likely to increase their connectivity. Measuring the overlap between different pathways, in terms of the genes that constitute them, showed that pathway duplication also is a likely mechanism in yeast evolution. This analysis sheds new light on the evolution of genes and functionality, and suggests that function duplication could be an important mechanism in evolution.

The emergence of overlapping scale-free genetic architecture in digital organisms.

We have studied the evolution of genetic architecture in digital organisms and found that the gene overlap follows a scale-free distribution, which is commonly found in metabolic networks of many organisms. Our results show that the slope of the scale-free distribution depends on the mutation rate and that the gene development is driven by expansion of already existing genes, which is in direct correspondence to the preferential growth algorithm that gives rise to scale-free networks. To further validate our results we have constructed a simple model of gene development, which recapitulates the results from the evolutionary process and shows that the mutation rate affects the tendency of genes to cluster. In addition we could relate the slope of the scale-free distribution to the genetic complexity of the organisms and show that a high mutation rate gives rise to a more complex genetic architecture.

Iron status influences trace element levels in human blood and serum.

Food is the main source of trace elements for the general population. The gastrointestinal absorption of certain trace elements, e.g., cadmium, is strongly influenced by iron (Fe) status. This factor may also be relevant for the bioavailability of other trace elements. Therefore, we investigated relationships between Fe status indicators and trace element concentrations in blood and serum of 234 boys and girls at ages 15 and 17 years. Fe status was measured using serum ferritin (S-Ft), soluble transferrin receptor in serum (sTfR), and the ratio sTfR/S-Ft. The trace elements we investigated were, in blood, cadmium, cobalt, copper, zinc, selenium, rubidium, mercury, and lead, and, in serum, cobalt, copper, zinc, selenium, rubidium, tungsten, mercury, and lead. We found inverse correlations between Fe status and blood cadmium, blood or serum cobalt, or blood copper. There were positive correlations between Fe status and mercury concentrations. Selenium was positively correlated with sTfR. The relationships between Fe status and lead were equivocal. There were fewer correlations for serum than for blood, but the inverse relationships between Fe status and cobalt were equally strong in serum and blood. We found only occasional, and perhaps spurious, correlations with zinc, rubidium, and tungsten. In conclusion, previous indications that cadmium, cobalt, and copper are absorbed by transport mechanisms similar to that of Fe are supported by this study. Strong positive correlations between Fe status and mercury concentrations remain to be explained.

War of attrition with implicit time cost.

In the game-theoretic model war of attrition, players are subject to an explicit cost proportional to the duration of contests. We construct a model where the time cost is not explicitly given, but instead depends implicitly on the strategies of the whole population. We identify and analyse the underlying mechanisms responsible for the implicit time cost. Each player participates in a series of games, where those prepared to wait longer win with higher certainty but play less frequently. The model is characterized by the ratio of the winner's score to the loser's score, in a single game. The fitness of a player is determined by the accumulated score from the games played during a generation. We derive the stationary distribution of strategies under the replicator dynamics. When the score ratio is high, we find that the stationary distribution is unstable, with respect to both evolutionary and dynamical stability, and the dynamics converge to a limit cycle. When the ratio is low, the dynamics converge to the stationary distribution. For an intermediate interval of the ratio, the distribution is dynamically but not evolutionarily stable. Finally, the implications of our results for previous models based on the war of attrition are discussed.

Comparative cytotoxicity of deoxynivalenol, nivalenol, their acetylated derivatives and de-epoxy metabolites.

The cytotoxicity of the de-epoxy metabolites of trichothecenes nivalenol (NIV) and deoxynivalenol (DON) was determined and compared with the cytotoxicity of the respective toxin with an intact epoxy group and their acetylated derivatives. The cytotoxic effects was determined by using the 5-bromo-2'-deoxyuridine (BrdU) incorporation assay assessing DNA-synthesis. The toxicity of NIV and DON expressed as the concentration inhibiting 50% of the DNA synthesis (IC(50)), was occurring at similar micromolar concentrations (1.19+/-0.06 and 1.50+/-0.34 microM). The toxicity of fusarenon X (4-acetyl NIV) in the assay was similar to the toxicity of NIV, and the toxicity of 15-AcDON was equal to the toxicity of DON. 3-AcDON was less toxic than DON and 15-AcDON. The IC(50) value for de-epoxy DON was 54 times higher in the assay than the IC(50) for DON, while the IC(50) of de-epoxy NIV was 55 times higher than the IC(50) for NIV. The results verify previous findings that the de-epoxidation is a detoxification reaction.

A rapid and sensitive cytotoxicity screening assay for trichothecenes in cereal samples.

The application of a bioassay for toxicity screening of cereal samples has been studied. The sensitive Swiss mouse 3T3 fibroblasts (3T3 cells) were used to determine the cytotoxicity of Fusarium trichothecenes T-2 toxin (T-2), HT-2 toxin (HT-2), deoxynivalenol (DON) and nivalenol (NIV) in cereal samples. Clean-up of the sample extracts was performed using the MycoSep #225 column and the cytotoxic effects of the samples were determined using the 5-bromo-2'-deoxyuridine (BrdU) bioassay assessing DNA-synthesis. Trichothecene-free samples of wheat, wheat bran and barley had no toxic effect on the 3T3 cells at sample concentrations up to 400 mg/ml cell culture medium while a few oat samples had an inhibiting effect on the DNA-synthesis. IC(50) values (50% response compared with untreated cells) of trichothecene-free wheat and oats spiked with T-2, HT-2, DON and NIV were similar to IC(50) values of pure toxins. A cytotoxicity screening of 33 different cereal samples showed that all samples contaminated with a trichothecene concentration higher than the IC(50) values of T-2, HT-2, DON and NIV had a clear inhibiting effect on DNA-synthesis of the 3T3 cells. The culture of 3T3 cells on microtiter plates in combination with the simple and rapid sample clean-up using the MycoSep #225 column provides a sensitive and easy method for the screening of trichothecenes in cereal samples.

Yearly measurements of blood lead in Swedish children since 1978: an update focusing on the petrol lead free period 1995-2001.

BACKGROUND AND AIMS: To assess blood lead concentrations (B-Pb) in children not exposed to petrol lead. In a previous paper we reported the results for the period 1978-94 (2441 children measured). A substantial decrease of B-Pb was found, which reflected a beneficial effect of gradual banning of petrol lead. Since 1994, petrol sold in Sweden has not contained lead. METHODS: In the south of Sweden, each year from 1995 to 2001, B-Pb was measured in 329 boys and 345 girls, aged 7-11 years. RESULTS: The geometric mean (GM) of B-Pb was 21 (range 6-80) microg/l. There was no consistent change of B-Pb from 1995 to 2001. Children living near a lead smelter had raised B-Pb (GM 24 microg/l, range 11-80). Passive smoking, but not age and sex, influenced B-Pb significantly. CONCLUSIONS: B-Pb in Swedish children, no longer exposed to petrol lead, seems to have stabilised at an average level close to 20 microg/l (provided there is no nearby industrial lead emission).

Portal net appearance of amino acids in growing pigs fed a barley-based diet with inclusion of three different forage meals.

The net absorption of amino acids (AA) in young pigs fed a barley-based control diet (C) and diets where barley was replaced by 200 g/kg fresh weight of dried lucerne (Medicago sativa; L20), white clover (Trifolium repens; W20) or perennial ryegrass (Lolium perenne; PR20) meal was studied. Castrated male pigs were fitted with permanent catheters in the hepatic portal vein and mesenteric artery, and the hepatic portal net absorption of AA was estimated from the porto-arterial plasma concentration differences and the hepatic portal-vein blood flow. In general, the essential AA (EAA) concentrations in the hepatic portal vein reached peak levels 90 min after feeding and thereafter exhibited a transient decline. Maximum porto-arterial differences were reached between 1 and 3 h postprandially for most of the AA. The cumulative net absorption of non-essential AA (NEAA) and EAA did not differ significantly between the barley-based diet and diets W20 and PR20. Due to a lower intake of AA on diet L20, the cumulative net absorption of NEAA and EAA was significantly (P < 0.05) lower than diet C. With the exceptions of the EAA arginine, cystine and valine, and the NEAA glutamic acid + glutamine and glycine, there were no significant differences in the absorption coefficients for the EAA and NEAA between the diets. In addition, the pattern of the total EAA in the mixture absorbed postprandially did not differ significantly between the diets. The present study gives support to the contention that the replacement of barley AA with forage meal AA in a barley-based diet for growing pigs should be expected to result in minor differences in the net portal flux of AA.

Effect of exposure to dietary nivalenol on activity of enzymes involved in glutamine catabolism in the epithelium along the gastrointestinal tract of growing pigs.

Changes in the activity of enzymes involved in oxidative metabolism of glutamine, and in protein content, in the epithelial tissue along the gastrointestinal (GI) tract of growing pigs exposed to nivalenol (NIV) in the diet were investigated. The epithelial tissue was taken from the stomach, small intestine and colon of three groups of animals fed diets without NIV (control), with inclusion of 2.5 mg NIV/kg diet (low dose) and with inclusion of 5.0 mg NIV/kg diet (high dose). The activities of glutaminase, glutamate dehydrogenase, oxoglutarate dehydrogenase, isocitrate dehydrogenase and alanine aminotransferase were determined. In the control pigs the activities of oxoglutarate dehydrogenase and alanine aminotransferase were higher (P < 0.05) in the epithelium of the small intestine as compared with the stomach and colon, while there were no differences in the activities of glutaminase, glutamate dehydrogenase and isocitrate dehydrogenase. With increasing inclusion of NIV in the diet the activity of oxoglutarate dehydrogenase decreased (P < 0.05) in the epithelium of the small intestine and colon, and the activity of alanine aminotransferase tended (P = 0.07) to increase in the epithelium of the small intestine. The activities of glutaminase, glutamate dehydrogenase and isocitrate dehydrogenase remained unaffected by the inclusion of NIV in the diet. In the control pigs the protein content in the epithelium of the small intestine was higher (P < 0.05) than in the stomach and colon, while there were no effects of NIV inclusion in the diet on the protein content. It can be concluded from the present study that the epithelial tissue of the small intestine and colon of pigs exposed to a diet containing NIV will have a reduced enzymatic capacity to utilise alpha-ketoglutarate in the tricarboxylic acid cycle (TCA-cycle), suggesting an impaired energy supply to these organs.

Activities of enzymes involved in glutamine metabolism in connection with energy production in the gastrointestinal tract epithelium of newborn, suckling and weaned piglets.

Changes in the activity of enzymes involved in glutaminolysis and energy metabolism in the entire gastrointestinal (GI) tract of developing piglets are presented for the first time. The activities of glutaminase, glutamate dehydrogenase, oxoglutarate dehydrogenase, isocitrate dehydrogenase and alanine aminotransferase in the epithelium along the gastrointestinal tract from newborn, suckling (2-4 weeks old) and weaned (9 weeks old) piglets were investigated. The activity of glutaminase in the epithelium from the small intestine and colon was higher (p < 0.05) in weaned piglets than in newborn and suckling piglets. In addition, glutamate dehydrogenase and alanine aminotransferase activities in the small intestinal epithelium were higher (p < 0.05) for weaned piglets than for newborns. The activity of oxoglutarate dehydrogenase in the epithelium of the small intestine was significantly lower in newborn and suckling piglets compared with weaned individuals. The activity of isocitrate dehydrogenase in the epithelium along the gastrointestinal tract was higher (p < 0.05) for suckling and weaned piglets than for newborn piglets. The present data indicate that the utilization of substrates for energy production differs markedly between the stomach, small intestine and colon of growing piglets. Also, the capacity of enzymes in the epithelium of the GI tract to utilize acetyl-CoA as an energy substrate in the tricarboxylic acid cycle increased with piglet age. The epithelium of the GI tract of the newborn, suckling and weaned piglets showed a high capacity to metabolize alpha-ketoglutarate.

Cytotoxicity of four trichothecenes evaluated by three colorimetric bioassays.

The application of cell culture technique for screening of low concentrations of Fusarium mycotoxins was examined. Three colorimetric bioassays were used to determine the cytotoxicity of the trichothecenes T-2 toxin (T-2), HT-2 toxin (HT-2), deoxynivalenol (DON) and nivalenol (NIV) to 3T3 mouse fibroblasts (3T3 cells). The bioassays assess DNA synthesis (incorporation of 5-bromo-2'-deoxyuridine; BrdU), metabolic activity (cleavage of 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyltetrazolium bromide; MTT) and cell membrane damage (release of lactate dehydrogenase; LDH), respectively. The BrdU bioassay was the most sensitive and the IC50 values (50% response compared to untreated cells) of T-2, HT-2, DON and NIV were 4.6, 13, 263 and 365 ng/ml, respectively. At the same toxin concentrations used in the BrdU bioassay, only T-2 and HT-2 were toxic enough to obtain IC50 values using the MTT bioassay. The IC50 values for T-2 and HT-2 were 12 and 68 ng/ml, respectively. When determined by the LDH bioassay, the IC50 values of T-2 and HT-2 were 18 and 42 ng/ml, respectively. At the tested concentrations, DON and NIV had a minor effect on the 3T3 cells when evaluated by the MTT and LDH bioassays. The BrdU bioassay in combination with 3T3 cells was found to be a suitable method for determination of trichothecene-induced toxicity at low concentrations.