Comparative subacute effects of dietary raw soya flour on the pancreas of three species, the marmoset, mouse and rat

Characterization and safety evaluation of the impact of hydrocarbon contaminants on ecological receptors

Hydrocarbon-contaminant removal efficiency of Bambara groundnuts and biomagnification was investigated. The crude oil contaminated soil samples in which the plants were established were either un-amended, or amended with NPK, or Urea, or Poultry manure. Amendments improved phytoextraction rates as follows: Urea - 63.37%, NPK - 65.99%, Poultry - manure - 70.04%, for PAH; Urea - 78.80%, NPK - 79.80%, Poultry manure - 87.90%, for BTEX. Hazard characterization from 28-day feeding study revealed negative effects of potentially toxic BTEX and PAH on organ weight, optimum digestibility and animal growth rate. Sleep time decreased with increasing hydrocarbon concentrations probably due to increased liver enzyme activity.

Effects of long term feeding of raw soya bean flour on virus-induced pancreatic carcinogenesis in guinea fowl

The effects of a diet enriched with 25% raw soya bean flour (RSF) on the pancreas and on the avian retrovirus Pts 56-induced pancreatic carcinogenesis in guinea fowl were studied. It has been shown that prolonged RSF feeding of new-hatched virus-infected and uninfected guinea fowl-poults induced enlargement of the pancreas, which was less pronounced when administration of the RSF supplemented diet started at the age of 75 days. Time-dependent multifocal inter- and intralobular hyperplasia of pleomorphic ducts lined by mucin-producing epithelium in the exocrine pancreas of virus-infected guinea fowls fed a RSF supplemented diet was regularly observed. Enlargement of virus-induced ductular neoplasms has been shown only after simultaneous RSF and virus administration.

Influence of heat processing of African yam bean seed (Sphenostylis stenocarpa) flour on the growth and organ weights of rats

The influence of heat processing of African yam bean seed flour on the growth and organ weights of rats was studied. Body weight change, feed utilization and feed conversion ratio were improved by heat processing. All rats significantly (p < or = 0.05) gained weight except those fed raw African yam bean and basal diets (diets 3 and 1 respectively). Raw African yam bean diet decreased the growth of rats and had negative effect on the organ weights especially the pancreas which was enlarged. The results indicate that heat processing improved the growth of rats and organ weights due to heat inactivation of toxic factors especially trypsin inhibitors.

The effect of trypsin inhibitor on the pancreas and small intestine of mice

Pancreatic and intestinal growth rates were measured in mice fed on raw soya-bean flour (RSF) for up to 24 weeks. Control animals were fed on standard chow. The effects of RSF on the mouse pancreas resembled that seen in rats, showing hypertrophy with some hyperplasia. A marked increase in small intestinal weight was also found in mice fed on RSF but not in rats fed on this diet. Histological studies showed an increase in both villous and crypt thicknesses in the small intestine from these mice, and DNA, RNA and protein measurements indicated that the increase in intestinal weight was due to hypertrophy and hyperplasia of the mucosal layer. To determine whether the intestinal growth in mice fed on RSF was purely a response to the trypsin inhibitor (TI) component of the diet, pancreatic and intestinal growth rates were also determined in mice fed on the synthetic trypsin inhibitor camostate, at levels of 0.5 or 2 g/kg in rat chow, for periods of 1-8 weeks. Control animals were fed on standard chow. RSF and 0.5 g camostate/kg had similar trypsin inhibitor activities (measured against bovine trypsin), and both caused similar increases in pancreatic weight, DNA, RNA and protein content. However, 0.5 g camostate/kg did not affect small intestinal weight. Chow containing 2 g camostate/kg contained twice as much TI activity as the RSF diet but produced only a small increase in small intestinal weight at 2 and 8 weeks. This intestinal growth was significantly less than that seen with RSF. The present study shows that, in the mouse, RSF or a diet containing camostate in the appropriate dose produces pancreatic growth comparable to that seen in the rat. RSF also causes intestinal growth, but camostate-containing diets have little or no effect on the growth of the intestine.

Effects of a cholecystokinin receptor antagonist on rat exocrine pancreatic response to raw soya flour

1 Raw soya flour (RSF) in the diet induces pancreatic hypertrophy and hyperplasia in the rat, changes ascribed to production of a high circulating level of cholecystokinin (CCK) due to inhibition of trypsin in the duodenum. Prolonged ingestion results in pancreatic adenomas and carcinomas. 2 L-364, 718, a potent, highly specific CCK antagonist was used to investigate the short-term role of CCK. 3 In rats fed 50% RSF and L-364, 718 5 mg kg-1 p.o. twice daily for 4 d, there was inhibition of pancreatic hypertrophy and hyperplasia, which is further evidence that peripherally-acting CCK plays a major role in the generation of RSF-mediated changes in the pancreas.

Residue trypsin inhibitor: data needs for risk assessment

Trypsin inhibitor (TI) occurs naturally in many foods from plants, notably soybean protein products. Heat treatment inactivates TI and improves nutritional quality, but residual TI activity of 5 to 20% remains after typical commercial treatments. Chronic feeding of TI or products that contain TI can inhibit trypsin and chymotrypsin, stimulate their secretion, cause hypertrophy and hyperplasia of the pancreas, and lead to adenomas and carcinomas of the exocrine pancreas. In the rat, TI promotes pancreatic carcinogenesis initiated by azaserine. Data needed for possible risk assessment on TI would include 2-year bioassays from animals treated with TI and fed diets carefully controlled for type and amount of fat (which also promotes pancreatic carcinogenesis). The effects of TI on protein nutrition would have to be considered when identifying the maximum tolerated dose. Major reductions in human dietary TI exposure may not be feasible because of the multiple sources of TI, the substantial promotion by other factors such as fat, and the adverse effects of excessive heat on food products. For risk assessment of TI in a particular food, other promotors and the feasibility of decreasing TI intake must be considered.

Changes in numbers of pancreatic acinar cell nuclei and in DNA content during raw soya flour feeding in mice

Nuclei of pancreatic cells were isolated by trypsin-detergent digestion of fresh tissue and stained with propidium iodide, and nuclear DNA was measured by flow cytometry. Samples were isolated from mice fed either chow or raw soya flour (RSF) for periods ranging from 1 day to 48 weeks, beginning at 4 weeks of age. In chow-fed mice, the pancreas contained about 80% diploid (2N) and 20% tetraploid (4N) cells at the start of the study, but tetraploidy gradually increased to about 40% 2 weeks later (6 weeks of age) and remained at this level from that time onwards. Low levels of octaploid nuclei (8N) were also present in some animals after 2 weeks. In RSF-fed mice, about 20% tetraploid nuclei were also present for 1 and 2 days after starting RSF, but by 4 days tetraploidy had increased significantly to 40% and by 14 days had further increased to 50%. This level was significantly higher than that seen in chow-fed animals and was maintained for up to 48 weeks. Significantly higher numbers of octaploid nuclei were also present in the RSF-fed animals. In both chow- and RSF-fed mice, most cells were mononuclear, averaging 70% in chow-fed and 64% in RSF-fed animals. This difference was significant. This study shows that the mouse pancreas differs from the rat pancreas in the absence of a large population of binucleate acinar cells and the presence of considerable nuclear tetraploidy. Raw soya flour feeding leads to significant changes in these features, but in this species these changes do not appear to predispose to neoplasia.

Nutritional toxicology: basic principles and actual problems

Nutritional toxicology is a specialty that combines the backgrounds and research approaches of nutrition and toxicology. Many problems of substantial importance to health and food safety involve interactions of nutrition process and requirement with the effects of toxicological impact. Solution of these problems requires research that meets the procedural and design criteria of experimental nutrition and these of experimental toxicology. The relationships may be described in three basic categories: (1) influence of nutrition on toxicities; (2) influence of toxicants on nutrition; and (3) toxicities of nutrients. Trypsin inhibitor research, an example of diet impacting on toxicological response, illustrates the necessity of controlling nutritional composition aspects that can confound the results. Prolonged acetaminophen administration provides an example of the effects of toxicants on nutritional requirement and function which could be important for persons with marginal sulphur amino acid intake.

Comparison of the effect of lorglumide on pancreatic growth stimulated by camostate in rat and hamster

We conducted a 14 day experiment in which we administered camostate (a trypsin inhibitor) and cholecystokinin alone or in combination with lorglumide, a cholecystokinin receptor antagonist, to both rats and hamsters. Plasma cholecystokinin levels were 21.7 +/- 3.2 pM and 19.6 +/- 2.5 pM with camostate, 16.3 +/- 2.4 pM and 14.8 +/- 2.2 pM with exogenous cholecystokinin, and 3.7 +/- 0.4 pM and 4.2 +/- 1.0 pM in control experiments in rats and hamsters, respectively. Both cholecystokinin and camostate were found to promote pancreatic growth in rats (18 +/- 4 and 111 +/- 7%, respectively) and hamsters (76 +/- 18 and 61 +/- 12%, respectively). Although lorglumide caused a decrease of this effect of camostate in both rats (78 +/- 5%) and hamsters (25 +/- 10%), it only became significant in rats. We therefore conclude that there are important interspecies differences in the role cholecystokinin plays in mediating the trophic effects of trypsin inhibitors on the pancreas.

Pancreatic response in rats and mice to trypsin inhibitors from soy and potato after short- and long-term dietary exposure

The effects on the pancreas of chronic (95 wk) dietary exposure to protease inhibitors from soy and potato were compared in rats and mice. Soy and potato trypsin inhibitor (TI) concentrates were prepared from defatted raw soy flour and potato juice, respectively, by selective precipitation and ultrafiltration. Animals were fed a diet in which casein supplied approximately 20% protein. Each concentrate (less than 1% of the diet) was added to provide 100 and 200 mg of trypsin inhibitor activity per 100 g of diet. In short-term (28 d) experiments in rats, both sources of TI decreased the apparent nutritional quality of casein and produced pancreatic hypertrophy consistent with a hormonally mediated feedback mechanism for pancreatic adaptation to diet that is interactive with the nutritional status of the animal. After long-term feeding (95 wk), soy and potato TI produced dose-related pancreatic pathology in rats consisting of nodular hyperplasia and acinar adenoma, which was typical of that associated with raw soy flour. Although mice responded similarly to rats to soy TI in short-term (28-d) feeding experiments, they were resistant to the formation of these lesions following long-term feeding. This considerable species variation in propensity to develop preneoplastic and neoplastic lesions of the pancreas is not predicted by the short-term hypertrophic and hyperplastic response of the pancreas to TI.