Structure-activity relationships of fumonisins in short-term carcinogenesis and cytotoxicity assays

A short-term rat liver cancer initiation/promotion model was used to monitor the cancer-initiating activity of the mycotoxins fumonisin B1 (FB1), fumonisin B2 (FB2) and fumonisin B3 (FB3) as well as the N-acetyl derivatives of FB1 and FB2, and their respective hydrolysis products the aminopolyols. The induction of resistant hepatocytes, which develop into hepatocyte nodules on selection by the 2-acetylaminofluorene-partial hepatectomy promoting treatment, was taken as the endpoint for cancer initiation. When fed at a level of 1000 mg/kg diet for 21 days, only the fumonisins B were found to initiate cancer. In addition, these mycotoxins caused a marked reduction in the rat body weight during the initiating treatment. Comparative cytotoxicity studies in primary rat hepatocytes indicated that FB2 exhibited the highest cytotoxic effect followed by FB3 and FB1. In general, the fumonisin B mycotoxins exhibited a low cytotoxic effect in hepatocyte cultures, and the concentrations of FB1 and FB2 that caused a 50% (CD50) release of the total lactate dehydrogenase (LDH) were in the order of 2000 and 1000 microM, respectively. The N-acetyl derivatives also exhibited a cytotoxic effect, but were not as cytotoxic as the parent molecules at high concentrations. The respective aminopolyols exhibited a higher cytotoxicity than did the parent compounds, while tricarballylic acid (TCA) exhibited no dose-response effect despite the fact that it had a higher background cytotoxicity compared with the control. The apparent inability of the aminopolyols to act as cancer initiators could be related to a lack in absorption from the gut.(ABSTRACT TRUNCATED AT 250 WORDS)

Fumonisins

Fusarium moniliforme Sheldon is a common fungal contaminant of corn and produces a variety of mycotoxins. Among these are the recently discovered fumonisins, which are now known to cause certain animal diseases, namely leukoencephalomalacia in horses and pulmonary edema in swine. There is a significant association between their presence in corn and human esophageal cancer in southern Africa. Fumonisin B1 causes liver cancer in rats. Five other fumonisins--B2, B3, B4, A1 and A2, have been isolated; the last two are N-acetates of fumonisins B1 and B2 and do not appear to be toxic. Several other Fusarium species are now known to produce fumonisins. Procedures for detection and determination of fumonisins include thin layer chromatography, liquid chromatography (with fluorescence derivatization), post-hydrolysis gas chromatography, immunochemical assay, and mass spectrometry. In addition to their natural occurrence in corn-based animal feeds and in home-grown African corn used for food, fumonisins are frequently found in commercial corn-based foods. Fumonisins are moderately heat-stable. No effective detoxification process has yet been developed for use with fumonisin-contaminated feeds.

Organochlorine and heavy metal contamination in non-viable eggs and its relation to breeding success in a Spanish population of Lesser Kestrels (Falco naumanni)

Residues of organochlorines, polychlorinated biphenyls (PCBs), and heavy metals (mercury, cadmium, lead, copper and zinc) were measured in unhatched eggs of Lesser Kestrels (Falco naumanni) collected in southern Spain in 1988-1991. Although contaminants were detected in all eggs, the amounts were generally below levels known to have negative effects on reproduction. This is consistent with the relatively high hatching rate (about 80%) in the studied population. The nestling mortality was severe, however, apparently due to starvation. It cannot be discounted that pesticides had an indirect effect on the kestrel's breeding success by reducing the populations of prey.

Use and environmental implications of pulp-mill sludge as an organic fertilizer

Pulp-mill sludge is an industrial by-product with a high level of organic matter, which is eventually biodegradable. Since there are few alternatives for its practical use, its utilization as an agricultural fertilizer is proposed. An experiment was carried out during 2 years, with yellow lupin plants (Lupinus luteus L.), in order to define the critical application levels of this material. Biodegradability of the sludge in the soil was also evaluated, as well as its pollutant effects. Results obtained in the first year of the experiment showed that an application rate larger than 50 t ha(-1) of pulp-mill sludge, has a depressive effect on yield. Yet, this effect is completely dissipated in the second year. Finally, it is concluded that, if the use of this organic waste as an agricultural fertilizer is adequately monitored, soil pollution problems should not occur.

Physical and biochemical properties of green banana flour

Banana flour prepared from two cooking banana varieties, namely 'Alukehel' and 'Monthan', were evaluated for their physical and biochemical characteristics. The yields of flour averaged 31.3% for 'Alukehel' and 25.5% for 'Monthan'. The pH of the flour ranged from 5.4 to 5.7. The bulk density and particle size distribution were also measured. The average chemical composition (% dry matter) of the flours were as follows: crude protein, 3.2; crude fat, 1.3; ash, 3.7; neutral detergent fiber, 8.9; acid detergent fiber, 3.8; cellulose, 3.1; lignin, 1.0 and hemicellulose, 5.0. Carbohydrate composition indicated the flour to contain 2.8% soluble sugars, 70.0% starch and 12.0% non-starch polysaccharides. Potassium is the predominant mineral in banana flour. Fresh green banana is a good source of vitamin C, but almost 65% is lost during the preparation of flour. Oxalate content (1.1-1.6%) of banana flour is probably nutritionally insignificant. The overall results are suggestive of the potential of green bananas as a source of flour.

Microvascular changes in rat glomeruli as a consequence of small differences in selenium exposure

This paper evaluates the effect of small differences in selenium exposure, within the safe range, on the glomerular vascular tufts of rats fed high-sucrose diets. In the first experiment male Wistar rats were housed in galvanized cages and were provided sucrose-based diets to induce a mild chronic insult to the microcirculation. One group of rats received the diet prepared to contain 0.10 mg Se/kg and another group 0.21 mg Se/kg. To assure that the galvanized metal cages were not influencing the results of the experiment this protocol was repeated in a second experiment wherein rats were housed in stainless steel cages. The levels of Se used supported normal activity of the long-term indicator of Se sufficiency, erythrocyte glutathione peroxidase. In both experiments rats fed diets containing 0.21 mg Se/kg had larger Bowman's capsules (P < 0.01) and vascular tufts (P < 0.01). Vascular tufts from these rats also contained a higher proportion of open capillary lumen (P < 0.01), contained less cytoplasmic and extracellular material (P < 0.001), and had larger nuclei (P < 0.001) than those fed 0.10 mg Se/kg. A third study was designed to determine if the selenium-dependent differences in nuclear size were indicative of this being a site of incorporation. Year-old rats subjected to the same protocol as those in the second experiment were given 75Se, by injection into the femoral vein, to label the sites of incorporation. Glomeruli were purified and subjected to subcellular fractionation. Ninety percent of the radioactivity was associated with the crude nuclear fraction. Purification of the crude nuclear fraction demonstrated that the radioactivity was associated with the nuclei.

Brain acetylcholinesterase activity and optomotor behavior in bluegills, Lepomis macrochirus exposed to different concentrations of diazinon

Organophosphorus pesticides inhibit acetylcholinesterase (AChE) activity to varying degrees in different species of fish. Estimation of AChE activity is a useful tool for establishing the degree of pollution caused by these pesticides. Behavioral changes are very good and sensitive indicators of any chemical pollution. Changes in the optomotor behavior are easily quantifiable. Therefore estimation of AChE activity and changes in the optomotor response are taken as criteria to study the effects of different concentrations (15, 30, 45, 60 and 75 micrograms/l) of diazinon, an organophosphorus compound, in bluegill Sunfish, Lepomis macrochirus. The fish were exposed for a period of 24 hours. In this study, AChE activity showed a significant decline above an exposure concentration of 45 micrograms/l exposure concentration. In the case of optomotor behavior, a decline in the scores of the "following" responses of the fish was noticed from an exposure concentration of 30 micrograms/l. It seems that a behavioral bioassay is more sensitive than other types of testing.

Temperature-modulated aflatoxin B1 hepatic disposition and formation and persistence of DNA adducts in rainbow trout

Previous work showed that the incidence of chemically induced tumors in fish increased with environmental temperature. The present study assessed genotoxicity as a mechanism to explain such results. Rainbow trout (2 g) were acclimated to 10 or 18 degrees C for 1 month and then immersed in 0.1 ppm [3H]aflatoxin B1 (AFB1) solutions for 30 min at their respective acclimation temperatures, or at 14 degrees C. The total radioactivity in liver immediately after immersions was 50% higher for 18- than 10 degrees C-acclimated and exposed fish. Conversely, adduction of [3H]AFB1 to hepatic DNA of 10 degrees C-acclimated fish was higher than that of 18 degrees C-acclimated fish after exposure. A similar DNA adduction result was observed after [3H]AFB1 immersion concentrations were varied to achieve similar hepatic [3H]AFB1 equivalents. After acute shifts in temperature (10 to 14 degrees C or 18 to 14 degrees C), no differences were found in hepatic [3H]AFB1 equivalents. However, adduction of [3H]AFB1 to hepatic DNA was higher for 10- than for 18 degrees C-acclimated fish 1 day after exposures at 14 degrees C. This was probably explained by effects of temperature acclimation on the status of the membrane-bound cytochrome P-450 system, affecting its competition with a detoxifying cytosolic enzyme. After [3H]AFB1 immersions at respective acclimation temperatures, or acute temperature shifts to 14 degrees C, DNA adducts were less persistent in fish maintained for 21 days at 18 degrees C than at 10 degrees C. Our data demonstrated that temperature-modulated AFB1 genotoxicity occurred via three mechanisms: hepatic disposition and formation and persistence of DNA adducts.

Biotransformation of 2-, 3-, and 4-methoxy-amphetamines by Cunninghamella echinulata

1. Three methoxyamphetamine analogues have been incubated with Cunninghamella echinulata under different environmental and nutrient conditions. 2. The biotransformation of 4-methoxyamphetamine was inhibited by cobalt; the carbon source and other trace metals had no effect. The rate of biotransformation of 4-methoxyamphetamine and formation of 4-hydroxyamphetamine was greater in cultures incubated on 30 degrees angle brackets rather than flat. 3. Carbon monoxide, ethanol and quinidine had a significant effect on methoxyamphetamine metabolism. 4. Metabolism was influenced by the position of the methoxy side-chain and substrate concentration. In day 7 samples the relative order for biotransformation was 3- greater than 4- greater than 2-methoxyamphetamine. 5. O-Demethylation was the major metabolic route in the biotransformation of 4-methoxyamphetamine but occurred to a lesser extent with 3-methoxyamphetamine, and was only a trace pathway with 2-methoxyamphetamine. N-acetylation was a trace pathway.

[The quantification of toxaphene residues in fish oils]

When quantified by HPGC-ECD and HPGC-NCI-SIM commercially available standards of the insecticide Toxaphene show different detector responses, primarily depending on the percentage of chlorine in the mixtures. To obtain accurate results, residues of Toxaphene in environmental samples should be quantified by using a standard with a similar or nearly similar detector response. If this is not possible, any standard may be used but the results of the samples must be corrected afterwards. By comparing different integration methods, it can be seen that the best results are obtained by integrating as many single-peak areas as possible. Quantification by integration of the bulge formed by raising the baseline, which can be observed in many gas chromatograms of Toxaphene standards, should be avoided because this hump is caused by degradation of chlorobornanes under higher temperatures. The extent of this bulge depends both on temperature and the percentage of chlorine, the latter being generally lower in the samples as a result of transformation processes under environmental conditions. Therefore integration of the bulge or the whole area leads to lower results.

[Results of a monitoring program for the determination of the intake of copper, lead, cadmium, zinc and nickel with food]

A monitoring programme was developed for the evaluation of the intake of Cu, Pb, Cd, Zn, and Ni with food in a part of Sachsen-Anhalt. The results of this programme did not show great differences compared to the values found in other countries. The weekly intake of the elements with food have been published for this highly industrialised region during the period 1985-1989.

Occurrence of some mycotoxins (aflatoxin, ochratoxin A, citrinin, zearalenone and vomitoxin) in various Egyptian feeds

Ninety five samples of various Egyptian feedstuffs were investigated for the aflatoxin B1, B2, G1, and G2 means thin layer chromatography (TLC). Out of these samples 44.2% were positive (maize, rice crack, rice germ, rice germ cake, rice bran, wheat bran, cotton seed, cotton seed cake, peanut, and mixed feed for broilers, egg production, calf fattening and milk production). High percentage (90.5%) of the positive samples were contaminated with less than 100 ppb total aflatoxins. Peanut from "Ismailia" showed the highest contamination-mean of 400 ppb aflatoxin B1. The contamination relationship between kernels and shell of the same pods of the peanut was 1:7. The lowest contamination-mean was 5 ppb B1 in soya bean samples. All samples of horse bean and fish meal were negative. Aflatoxin B1 was present alone so frequently (in 76.2% of the positive samples). The relationship between the concentrations of aflatoxins B2:G1:B1 was 1:2.3:22.4. 51 different samples of foods and feeds from various Egyptian regions were collected and investigated for the nephrotoxic mycotoxin ochratoxin A means TLC. Twelve samples (23.5%) from them were designated as positive samples. The positive samples belonged to white maize, wheat, wheat bran, beans, rice germ, rice germ cake, broilers feed, egg production feed, and milk production feed; whereas the yellow maize (hybrid), soya beans, wheat soya meal, rice crack, cotton seed, cotton seed cake, and fish meal samples were negative. The contamination range was from 4 ppb to 577 ppb with an average of 58.2 +/- 22.9 ppb. Half of the positive samples was contaminated with 10-100 ppb whereas 41.7% from the positive samples had less than 10 ppb and 8.3% only had more than 100 ppb. Citrinin is existing in Egyptian food and feedstuffs. Out of 52 different samples--from various Egyptian regions-15.4% were positive. These were rice bran, rice germ, maize (white), wheat bran, cotton seed cake and fish meal. The highest contamination was in fish meal (40-70 ppb) whereas the lowest was in wheat bran (3 ppb). Mean of the contamination level was 25.9 +/- 3.4 ppb with a range of 3-70 ppb. For the first time in the Egyptian foods and feeds will be informed about the presence of the mycotoxin zearalenone with a high concentration. From several Egyptian places, 64 samples were collected (4 samples for each food or feed stuff).(ABSTRACT TRUNCATED AT 400 WORDS)