Rat Bioassay Research Articles

Effects of Co-administration of Antioxidants and Arsenicals on the Rat Urinary Bladder Epithelium

Oxidative stress has been increasingly recognized as a possible mechanism in the toxicity and carcinogenicity of various chemicals, including arsenic. Therefore, treatment with antioxidants may afford a protective effect against arsenic-induced cytotoxicity and carcinogenesis. Dimethylarsinic acid (DMAV) has been shown to be a bladder carcinogen in rats when administered at high doses (100 ppm) in the diet or in the drinking water. The main purpose of the present study was to evaluate the effects of co-administration of antioxidants with arsenicals on the rat urinary bladder epithelium in vitro and in vivo. In a previous experiment, treatment with 1000 ppm melatonin for two weeks did not inhibit cell proliferation induced in the rat urothelium by 100 ppm DMAV. In the current study, we examined the effects of five antioxidants that act via different mechanisms, on the in vitro cytotoxicity of various arsenicals, for the purpose of determining which antioxidants might have protective effects against arsenic-induced cytotoxicity. The antioxidants that inhibited cytotoxicity in vitro were then studied also in vivo. Melatonin showed slight inhibition of the cytotoxicity of arsenite, but had no effect on the other arsenicals. N-acetylcysteine (NAC) inhibited the cytotoxicity of monomethylarsonous acid (MMAIII), DMAV, dimethylarsinous acid (DMAIII), and trimethylarsine oxide (TMAO). Vitamin C inhibited cytotoxicity induced by arsenate, arsenite, MMAIII) and DMAIII. Tiron and Trolox had no effect on the cytotoxicity of any arsenical. The in vitro inhibitory effects of NAC and vitamin C on DMAV and on DMAIII, suggested that these antioxidants might afford preventive effects on DMAV-induced bladder cytotoxicity and carcinogenesis in rats. To test this hypothesis, a 10-week rat bioassay was conducted. Melatonin was also included to clarify the results of the previous two-week experiment. The sodium salt of vitamin C (Na-Asc), but not melatonin or NAC, inhibited the proliferative effects of DMAV on the bladder epithelium in rats. These results suggest that oxidative stress is at least in part involved in DMAV-induced rat bladder toxicity and proliferation, and therefore, vitamin C may afford inhibitory effects in DMAV-induced bladder carcinogenesis in rats. Microarray analysis of DMAV-responsive genes revealed that DMAV did not have a consistent modifying effect on gene expression in the rat bladder epithelium, suggesting that proteins and/or lipids may be the targets of damage by DMAV-induced oxidative stress.

The routine use of a new formulation of follitropin alfa (FbM) for follicular development for IVF. A large multicenter observational study in the UK

Until recently recombinant hFSH has been filled and released by bioactivity using in-vivo rat bioassay. The availability of an improved method of size exclusion highly precise liquid chromatography (SE-HPLC) enables the quantification of r-hFSH protein content filled by mass (FbM), in which 75IU FSH-activity corresponds to 5.5 mcg of r-hFSH protein. This new formulation of r-hFSH monodose also contains methionine, Tween, and 10% overfill that in combination provides more accurate and precise control over the actual dose delivered to the patient.

Bioactivation, toxicokinetics and acute effects of chloroform in Fisher 344 and Osborne Mendel male rats.

Chloroform has been regarded as a renal carcinogen, based on results obtained with Osborne Mendel (OM) rats. Fisher 344 (F344) rats, considered representative of OM rats on the basis of comparable acute toxic effects, have been used in most of the studies aimed to elucidate the mechanisms of kidney tumour induction. In the present work, in vitro and in vivo chloroform bioactivation in the liver and kidney of F344 and OM rats has been reported, as well as additional toxicokinetics and acute toxicity information. Complete similarity of chloroform metabolism and toxicokinetics was evidenced in the two rat strains. Chloroform metabolism was fully saturated at the OM rat bioassay doses (90-180 mg kg(-1) body wt.), working at a maximal rate of 40-50 micro mol (14)CO(2) expired kg(-1) h(-1). No acute hepatotoxicity, nephrotoxicity or consequent cell proliferation was evidenced at 180 mg kg(-1) body wt. chloroform. In the rat liver, phosgene was confirmed as the major metabolite. Renal microsomes from both F344 and OM rats in vitro were unable to produce any oxidative metabolite; at variance, adducts due to oxidative and reductive metabolites were detected in vivo. Our results indicated the presence in the rat kidney of electrophilic metabolites other than phosgene, representing either oxidative metabolites formed elsewhere and sufficiently stable to be transported to the kidney or electrophilic metabolites secondary to the formation of reductive radicals. Therefore, the rat kidney represents a suitable model to study the toxicological effects, including genotoxicity, of chloroform metabolites in the absence of cytotoxic effects produced by phosgene formed in situ.

Chemical characterization and protein quality evaluation of leaf protein concentrates from Glyricidia sepium and Leucaena leucocephala

SummaryLeaves and leaf protein concentrates (LPCs) from leaves of Glyricidia sepium and Leucaena leucocephala were analysed for chemical constituents. The protein quality of the LPC, with or without dl‐methionine supplementation, was estimated by using sixty weanling albino rats. Glyricidia leaves contained higher crude protein and lower crude fibre than L. leucocephala leaves, while the ash values were identical. In the LPCs, crude protein showed a good balance of amino acids and nutritionally important minerals. The gross energy (GE) was only enhanced in the LPC of Glyricidia and, although tannin content was reduced in the LPCs, the phytate concentration increased. The rat bioassay did not suggest that, even when supplemented with dl‐methionine, Glyricidia or Leucaena LPC would support rat growth when used as the sole sources of dietary protein. Based on the analytical and bioassay data, the nutritional potentials and limitations of these under‐utilized protein resources are discussed.

Nutritional Status of the Protein of Corn-Soy Based Extruded Products Evaluated by Rat Bioassay

A rat bioassay was conducted to preclinically evaluate nutritional quality of two supplementary foods (SFs) developed based on corn and soy blends for feeding preschool children. The SFs prepared by extrusion cooking and subsequently modified to taste either sweet or salty provide 395 +/- 2 kcal of energy and 20 +/- 2 g protein per 100 g of food. The proximate constituents and energy contents of SFs were within the ranges prescribed for processed weaning foods and could satisfactorily meet the requirements of preschool children. Groups of male weanling rats were fed SFs for 4 weeks to evaluate the protein quality. The body weight gain of rats fed with SFs were significantly higher than those fed with skimmed milk powder (SMP) diet as control. The protein efficiency ratio and net protein utilization results of SFs were not significantly different (p > 0.05) from values of control group. It is inferred that these SFs were nutritionally comparable to SMP.

Characteristic Expression Profiles Induced by Genotoxic Carcinogens in Rat Liver

When applied in toxicological studies, the recently developed gene expression profiling techniques using microarrays, which brought forth the new field of toxicogenomics, facilitate the interpretation of a toxic compound's mechanism of action. In this study, we investigated whether genotoxic carcinogens at doses known to induce liver tumors in the 2-year rat bioassay deregulate a common set of genes in a short-term in vivo study and, if so, whether these deregulated genes represent defined biological pathways. Rats were dosed with the four genotoxic hepatocarcinogens dimethylnitrosamine (4 mg/kg/day), 2-nitrofluorene (44 mg/kg/day), aflatoxin B1 (0.24 mg/kg/day), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK, 20 mg/kg/day). After treatment for up to 14 days, the expression profiles of the livers were analyzed on Affymetrix RG_U34A microarrays. Among the significantly upregulated genes were a set of target genes of the tumor suppressor protein p53, indicating a DNA damage response. Such a response was expected and, therefore, confirmed the validity of our approach. In addition, the gene expression changes suggest a specific detoxification response, the activation of proliferative and survival signaling pathways, and some cell structural changes. These responses were strong throughout the 14 day time course for 2-nitrofluorene and aflatoxin B1; in the case of dimethylnitrosamine and NNK, the effects were weakly detectable at day 1 and then increased with time. For dimethylnitrosamine and aflatoxin B1, which caused observable inflammation in vivo, we found a corresponding upregulation of inflammatory genes at the same time points. Thus, by the toxicogenomic analysis of short-term in vivo studies, we identified genes and pathways commonly deregulated by genotoxic carcinogens, which may be indicative for the early events in tumorigenesis and, thus, predictive of later tumor development.

Quantitative risk analyses for RCF: survey and synthesis

Refractory ceramic fiber (RCF) is a high-temperature insulating fiber used principally in industrial applications. Epidemiological studies on occupationally exposed cohorts have not indicated that exposure leads to fibrosis, increased lung cancer, or mesothelioma. However, inhalation bioassays with rats and hamsters have shown that these animals can develop each of these endpoints when exposed to high levels of RCF-particle mixtures. This work summarizes relevant quantitative risk analyses based upon analysis of the rat bioassay studies, which lead to predicted unit risks that range nearly three orders of magnitude. Additionally, we identify key assumptions that affect the risk estimates and provide additional estimates using the benchmark dose methodology favored by the U.S. EPA in cases where mechanistic models are inadequate or not available. We show that a key determinant of risk is how lung burdens are normalized (e.g., in terms of the number of fibers per square centimeter of lung surface or the number of fibers per milligram dry lung) for species conversion. Plausible values of unit potency/risk range from 1.4 × 10 −4 to 7.2 × 10 −4, neglecting any allowance for the effects of particulate material in the RCF tested in the bioassay experiments.

Pregnancy interceptive activity of Melia azedarach Linn. in adult female Sprague-Dawley rats

Ethanolic extract of the root of Melia azedarach Linn. (family: Meliaceae) collected from the Institute campus intercepted pregnancy in 60% and 75% adult female rats when administered at 250 and 500 mg/kg daily doses, respectively, on Days 1–10 post-coitum by the oral route. On fractionation, the activity was localized in the chloroform fraction of the ethanolic extract, which showed 80–100% activity at 250 mg/kg daily dose in repeat tests. In animals that became pregnant, there was also a significant reduction in mean number of implantations and all the implantations exhibited signs of resorption. Of the four major compounds isolated in sufficient quantity and characterized from the active chloroform fraction, two compounds showed only marginal (50%) contragestational effect. Further exploration of the active chloroform fraction, which is also devoid of estrogen agonistic activity at the contraceptive dose in immature rat bioassay, is being undertaken to identify and characterize the active principle(s).

Possible role of new pressor protein in hypertensive anephric hemodialysis patients.

Unexplained hypertension was observed in three anephric children on hemodialysis. We investigated the possible involvement of a novel hypertensive extra-renal enzyme new pressor protein (NPP), related to coagulation beta-FXIIa. Currently, NPP activity can only be determined by a rat bioassay model. On study day 1, pre dialysis, patients 1, 2, and 3 were hypertensive and their plasmas raised rat systolic blood pressure (SBP) by 45, 34, and 9 mmHg, respectively. Post dialysis, patients 1 and 2 reached their estimated dry body weight and their systemic pressures dropped, while patient 3 remained hypertensive and hypervolemic. Their post-dialysis plasmas raised rat SBP by 22, 14, and 9 mmHg, respectively. On day 2, similar relationships between patient SBP, volume status, and plasma NPP-like activity in rats were observed. The characteristic rat BP responses, lack of inhibition by captopril (ruling out a renin-mediated effect), and inhibition by soybean trypsin inhibitor support co-identity with NPP. Plasma FXIIa (combined alpha-FXIIa and beta-FXIIa) was measured by immunoassay and found to be elevated in all patients. This investigation suggests that there is high endogenous NPP activity in the plasmas of these hypertensive hemodialysis patients, it changes with SBP and fluid volume, and is a possible contributor to their hypertension. Further studies are required to examine the wider applicability of these novel findings.

Plasma homocysteine and glycine are sensitive indices of folate status in a rodent model of folate depletion and repletion.

The objectives of the current studies included the characterization of the temporal changes in indices of folate status and amino acid concentrations during both folate depletion and repletion phases. In trial 1, a 6 week folate depletion protocol was employed, using 60 weanling rats assigned to receive an amino acid-defined diet with or without 1 mg/kg folic acid. A 4 week folate depletion period was judged to be optimal on the basis of the development of nadirs in both plasma and hepatic folate stores and elevated (>6-fold relative to folate-adequate controls) concentrations of plasma homocysteine and glycine. In trial 2, 54 weanling rats, previously maintained on a folate-devoid diet for 4 weeks, were assigned to receive 0.25 mg/kg folate as either crystalline folic acid or folate from a folate-enriched egg yolk powder. Both forms of folate supported similar rates of gain, increases in plasma and hepatic folate stores, and reductions in plasma glycine concentrations, whereas the folate in egg yolk powder lowered plasma homocysteine concentrations further than the crystalline folic acid (P < 0.05). These data support the use of both plasma glycine and homocysteine as sensitive response criteria for folate status in a rat bioassay of folate depletion and repletion and establish appropriate temporal end-points for such studies.

Concordance of Rat- and Human-Based Risk Estimates for Particle-Related Lung Cancer

In this study we use existing data in both rats and humans exposed to respirable, poorly soluble particles to compare the dose–response relationships for lung cancer. Exposure–response data for lung cancer were available in both species for crystalline silica and in rats for coal dust and titanium dioxide. Tumorigenic doses (TDs) associated with specified levels of excess risk (e.g. 1%) were computed, using multistage models in rats and relative rate models in humans. The rat-based and human-based TDs for crystalline silica are reasonably concordant (i.e. TD ratios near 1.0) for several dose metrics, including average internal dose in the lungs. The rat-based TDs associated with a 1% excess risk of lung cancer (TD 1 ) (extrapolated to humans, assuming a 45 yr working lifetime exposure) are point estimates from 0.007 to 0.24, 2 to 91 and 1.7 to 444 mg/m3, respectively, for crystalline silica, coal and titanium. The rat-based TD 1 values for silica, coal and titanium dioxide are consistent with the relative toxicity of these airborne particulates and with results from epidemiological studies. These findings provide some support for the continued use of risk assessment models based on rat bioassay data for particulates when human data are not available.

The role of transgenic mouse models in carcinogen identification.

In this article, we examine existing data on the use of transgenic mouse models for identification of human carcinogens. We focus on the three most extensively studied of these mice, Trp53+/-, Tg/AC, and RasH2, and compare their performance with the traditional 2-year rodent bioassay. Data on 99 chemicals were evaluated. Using the International Agency for Research on Cancer/Report on Carcinogens determinations for the carcinogenicity of these chemicals to humans as the standard for comparison, we evaluated a variety of potential testing strategies ranging from individual transgenic models to combinations of these three models with each other and with traditional rodent assays. The individual transgenic models made the "correct" determinations (positive for carcinogens; negative for noncarcinogens) for 74-81% of the chemicals, with an increase to as much as 83% using combined strategies (e.g., Trp53+/- for genotoxic chemicals and RasH2 for all chemicals). For comparison, identical analysis of chemicals in this data set that were tested in the 2-year, two-species rodent bioassay yielded correct determinations for 69% of the chemicals. However, although the transgenic models had a high percentage of correct determinations, they did miss a number of known or probable human carcinogens, whereas the bioassay missed none of these chemicals. Therefore, we also evaluated mixed strategies using transgenic models and the rat bioassay. These strategies yielded approximately 85% correct determinations, missed no carcinogens, and cut the number of positive determinations for human noncarcinogens in half. Overall, the transgenic models performed well, but important issues of validation and standardization need further attention to permit their regulatory acceptance and use in human risk assessment.

The effect of feeding regimen on apparent and true ileal nitrogen digestibility for rats fed diets containing different sources of protein

AbstractA standard protocol is required for carrying out routine ileal nitrogen (N) digestibility rat bioassays. The aim of this study was to determine the effects of feeding regimen on ileal N digestibility in rats fed diets containing different protein sources and chromic oxide as an indigestible marker. The experimental design was seven diets (protein‐free (PF), enzyme‐hydrolysed casein (EHC), lactalbumin (LAC), wheat gluten (GLU), fish fillets (FIS), soy protein isolate (SOY), zein) by three feeding regimens (frequent, meal, ad libitum) with 10 rats per diet. In frequent feeding, food was provided for eight 10 min periods between 09:00 and 16:00; in meal feeding, food was provided for one 3 h period at 09:00; in ad libitum feeding, food was available at all times. Rats were fed for 8 days, killed and digesta were collected from the terminal 20 cm of the ileum. The diets and freeze‐dried digesta were then analysed for N and chromium (Cr). There were statistically significant effects of feeding regimen on ileal digesta weight, ileal N/Cr ratio and apparent (AND) and true (PF TND, EHC TND) N digestibility. Mean N digestibilities, averaged over four dietary treatments (LAC, GLU, FIS, SOY), for the frequent, meal and ad libitum feeding regimens respectively were: AND, 88.8, 90.4, 85.8; PF TND, 94.9, 96.4, 97.0; EHC TND, 92.7, 94.0, 95.6. Although the N digestibilities were higher for rats on meal feeding compared with frequent feeding, the only statistically significant differences were for the lactalbumin treatment, and these were small in absolute terms. This study demonstrated that meal feeding was suitable and frequent feeding was unnecessary for most protein sources tested, and that ad libitum feeding was not ideal because of the smaller and more variable quantities of digesta collected and the more variable ileal N/Cr ratios.© 2002 Society of Chemical Industry

Respiratory hypersensitivity to trimellitic anhydride in Brown Norway Rats: a comparison of endpoints

A rat bioassay has been developed to provide an objective approach for the identification and classification of respiratory allergy using trimellitic anhydride (TMA), which is a known respiratory tract irritant and asthmagen. Particular emphasis was placed on the study of route-of-induction-dependent effects and their progression upon inhalation challenge with TMA (approximately 23 mg m(-3) for a duration of 30 min), which included analysis of specific and non-specific airway hyperreactivity and pulmonary inflammation initiated and sustained by immunological processes. Refinement of the bioassay focused on procedures to probe changes occurring upon challenge with TMA or methacholine aerosols using physiological, biochemical and immunological procedures. Following challenge with TMA, the rats sensitized to TMA showed marked changes in peak inspiratory and expiratory air flows and respiratory minute volume. In these animals, a sustained pulmonary inflammation occurred, characterized by specific endpoints determined in bronchoalveolar lavage (lactate dehydrogenase, protein, nitrite, eosinophil peroxidase, myeloperoxidase). When compared with the naive controls, lung weights were increased significantly, as were the weights of lung-associated lymph nodes following inhalation induction and auricular lymph nodes following topical induction. The extent of changes observed was equal or more pronounced in animals sensitized epicutaneously (day 0:150 microl vehicle/50% TMA on each flank, day 7; booster administration to the skin of the dorsum of both ears using half the concentration and volume used on day 0) when compared with rats sensitized by 5 x 3 h day(-1) inhalation exposures (low dose: 25 mg TMA m(-3), high dose: 120 mg TMA m(-3)). In summary, the findings support the conclusion that the Brown Norway rat model is suitable for identifying TMA as an agent that causes both an immediate-type change of breathing patterns and a delayed-type sustained pulmonary inflammatory response. However, it remains unresolved whether the marked effects observed in the topically sensitized rats are more related to a route-of-induction or dose-dependent phenomenon.

SHORT-TERM INHALATION TOXICITY OF POLYISOCYANATE AEROSOLS IN RATS: COMPARATIVE ASSESSMENT OF IRRITANT-THRESHOLD CONCENTRATIONS BY BRONCHOALVEOLAR LAVAGE

The object of this study was to compare the relative potency of respirable aerosols of the aliphatic hexamethylene 1,6-diisocyanate homopolymer of the isocyanurate type (HDI-IC) and the aromatic polymeric methylenediphenyl-4,4'-diisocyanate (pMDI) to elicit early changes in bronchoalveolar lavage fluid (BALF). The validity of the concentration × time (C × t) concept was addressed in rats exposed to concentrations from 3.4 to 58.1 mg pMDI/m 3 and exposure durations of 6 h to 23 min, respectively (C × t ≈ 1200 mg/m 3 -min). One additional group of rats was exposed to 2.7 mg MDA/m 3 for 1 × 6 h, a putative product of hydrolysis of pMDI. In rats repeatedly exposed to 12.9 mg pMDI/m 3 (6 h/day, 5 days/wk for 14 days), cumulative exposure-related changes were examined. Results show that total protein and angiotensin-converting enzyme (ACE) in BALF were among the most sensitive endpoints to probe early effects caused by exposure to irritant polyisocyanate aerosols. In the repeated-exposure study, BALF protein was maximal after the first exposure day. Based on these most sensitive endpoints in BALF, a benchmark no-effect threshold concentration of 0.5 and 3 mg/m 3 was estimated for the pMDI and HDI-IC aerosol, respectively. The slope of the concentration-effect curve was steeper following exposure to HDI-IC than to pMDI. These estimated acute no-observed-effect levels (NOELs) were almost identical to those observed in longer term inhalation studies using conventional endpoints. It is concluded that pulmonary irritation caused by polyisocyanate aerosols can readily be quantified in an acute rat bioassay by the analysis of total protein in BALF.

The effect of a Tropaeolum speciosum oil supplement on the nervonic acid content of sphingomyelin in rat tissues

The lipids of Tropaeolum speciosum (T. speciosum) are a rich source of naturally occurring nervonic acid (24:1n-9). We report that adding a T. speciosum oil supplement to a semi-purified diet significantly increased the amount of 24:1n-9 in liver and heart, but not brain, sphingomyelin (SM) of young rats. The bioavailability of 24:1n-9 from the lipids of T. speciosum was similar to that of 24:1n-9 ethyl ester in this rat bioassay.

Effect of soaking, germination, autoclaving and cooking on chemical and biological value of guar compared with faba bean.

Raw, soaked, germinated, autoclaved and cooked both of guar and faba bean were chemically and biologically evaluated. Crude protein, crude fiber and ash contents of guar and faba bean decreased as a result of all treatments with the exception of protein content in both germinated guar and faba bean. A slight decrease in lipid content was noticed during germination, while there were no changes in lipids after soaking, autoclaving and cooking. Protein content of guar was higher than of faba bean, and showed higher values for all amino acids than faba bean protein except for lysine and tryptophan. Germination caused a slight increase in total essential amino acids, while soaking caused a slight decrease in both of guar and faba bean. There was a slight decrease in the mineral contents by the heat processes with the exception of Mg and Mn for guar and Na, Mn for faba bean due to the cooking process. Germinated guar and faba bean showed noticeable decrease in Na, K, Cu, Mn and Mg and a slight increase in Fe and Zn than the raw materials. Germination was more effective in reducing phytic acid than heat treatment, and therefore it improves the nutritional quality of both guar and faba bean. Protein efficiency ratio (PER), true digestibility (DT) and biological value (BV) were estimated in all treatments under study using rat bioassay procedures. Data revealed pronounced improvements of the nutritive value as a result of all processes under study especially germination being the most effective.

The effects of ad libitum overfeeding and moderate and marked dietary restriction on age-related spontaneous pancreatic islet pathology in Sprague-Dawley rats.

This study compared the effects of ad libitum (AL) overfeeding and moderate or marked dietary restriction (DR) on aged-related degenerative and proliferative changes of the endocrine pancreas in Sprague-Dawley (SD) rats. SD rats were fed Purina Certified Rodent Diet AL (group 1), DR at 72-79% of AL (group 2), DR at 68-72% of AL (group 3) or DR at 47-48% of AL (group 4) for 106 weeks. Interim necropsies were performed at 13, 26, and 53 weeks, after a 7-day 5-bromo-2-deoxyuridine (BrdU)-filled minipump implantation. Before each necropsy, glucose and serum insulin levels were measured. In addition to the routine histopathologic examination performed in both sexes, determination of 9 pancreatic islet stereologic parameters was done in males at 13, 26, and 53 weeks. In AL-fed rats, early changes in the islet morphology occurred, which resulted in a high incidence of islet fibrosis, focal hyperplasias and adenomas by two years. DR was dose-proportionally associated with decreased glucose and serum insulin levels, and delayed the onset, and decreased the incidence and severity of islet fibrosis and hyperplasia. Results of the stereology supported the histopathologic and clinical chemistry findings. It demonstrated that, compared to AL-fed rats, DR-fed rats had smaller pancreas, smaller pancreatic islets, smaller insulin secreting cell volumes, a lower degree of islet fibrosis and a lower islet cell BrdU labeling index, which correlated with a lower incidence of islet adenoma and carcinoma at study termination. Moderate and marked degrees of DR delayed the onset and severity of islet hyperplasia and fibrosis in a temporal- and dose-related manner. In contrast to marked DR, which dramatically prevented these changes, moderate DR delayed but not prevented onset of islet tumors. These findings support the concept that moderate DR results in a better-controlled animal model with a lower incidence or delayed onset of chronic spontaneous endocrine diseases in the rat bioassay.

Rat kidney pathology induced by chronic exposure to fumonisin B1 includes rare variants of renal tubule tumor.

The carcinogenicity of fumonisin B1 (FB1), a worldwide contaminant of corn produced by Fusaria species of fungi, has been tested recently in 2-year feeding studies in Fischer F344 rats and B6C3F1 mice. Inclusion of FB1 at 50 and 80 ppm in the diet induced liver tumors in female mice, and at 50 and 150 ppm induced renal tumors in male rats (22). In the present study, the kidneys from the rat bioassay were examined to characterize the various histopathological changes associated with renal tumor induction. In all high-dose (150 ppm) and mid-dose (50 ppm) male rats, and to a lesser extent in high-dose (100 ppm) female rats, there was evidence of sustained nephrotoxicity manifested as basophilia, apoptosis, cell regeneration, and simple tubule hyperplasia, affecting proximal convoluted tubules in the deep cortex, extending into the outer region of the outer stripe of outer medulla. A further alteration consisted of sporadic areas of interstitial hyalinization in deep cortex, suggestive of expanded basement membrane, coupled with tubule atrophy. The continued presence of nephrotoxicity throughout chronic exposure to FB1 suggested that renal tumor development may have been an outcome of sustained cell loss and compensatory regeneration. In some cases, preneoplastic tubules or incipient renal tumors presented an immature or fetal form in association with interstitial hyalinization. The renal tubule tumors induced by FB1 were typified by a rare, highly malignant, anaplastic variant capable of growth by infiltration. Of the 10 renal tubule tumors diagnosed in the mid-dose males, and the 16 in the high-dose males, 8 and 10, respectively, were graded as carcinomas. Anaplastic variants represented 50% of the mid-dose carcinomas and 80% of the high-dose carcinomas. One of the anaplastic carcinomas in a mid-dose male was a true sarcomatoid phenotype not previously recorded in the rodent. Metastatic invasion of the lung occurred with 25% of the mid-dose carcinomas and 50% of the high-dose carcinomas. It was speculated that FB1 may have been influencing the growth characteristics of the induced renal tumors via its inhibitory action on the synthesis of sphingolipids, which in turn, participate in regulating cell contact, growth, and differentiation, or alternatively by affecting cell adhesion molecules.

Biochemical and technological studies on the production of isolated guar protein.

Guar seeds contain 32% crude protein. Therefore, attempts were made to prepare protein isolates from guar seed flour (GSF) by extraction in different media (distilled water, salt solution, alkali solution alone or in combination) followed by a precipitation at acid pH. From the four technologies adopted, mixed salt-alkali solution was found to be the most satisfactory for extraction of protein from GSF. The highest amount of product was obtained in the mixed technology along with the highest amount of protein (87.5%). Protein isolates were also nutritionally evaluated following well-established rat bioassay procedures in a comparative study with casein as standard. The protein isolates are rich in lysine but poor in sulphur-containing amino acids such as methionine and cysteine. Protein isolates obtained by mixed salt-alkali solution showed high water and oil absorption as well as good emulsifying and foaming stability. The results indicate that protein isolates can be used as a supplementary source of protein in different food industries.