Effect of vegetable and carotenoid consumption on aberrant crypt multiplicity, a surrogate end-point marker for colorectal cancer in azoxymethane-induced rats

Epidemiological studies indicate that increased vegetable consumption reduces the risk of colorectal cancer mortality. In the present study we have investigated the effect of consumption of standard diets supplemented with freeze-dried vegetables (peas, spinach, sprouts and broccoli) and carotenoids (all-trans beta-carotene and palm oil carotenoid extract) on surrogate end-point markers for colorectal cancer in an azoxymethane-induced rat model. Mean aberrant crypt multiplicity was reduced (19%) by the pea-supplemented diet only (P < 0.05). The vegetable-induced effect was more apparent in aberrant crypt foci with higher multiplicity. Intervention with diets supplemented with peas, spinach, sprouts and a mix of all vegetables reduced the number of foci with >2 aberrant crypts/focus by 37, 26, 23 and 26%, respectively (P < 0.05). Even more pronounced effects were observed in foci with >3 aberrant crypts/focus, with reductions of approximately 50% in the pea and spinach intervention groups. All-trans beta-carotene and palm oil-derived carotenoids, supplied at similar doses to those expected in the vegetable diets, inhibited ACM only marginally. Aberrant crypt foci formation in groups fed a sprout-supplemented diet prior to or following azoxymethane treatment was similar, indicating that this effect is due to inhibition of promotion rather than initiation of colorectal carcinogenesis. Vegetable and carotenoid consumption did not affect in situ proliferation of colonic crypt cells, as assessed by semi-automated image analysis of bromodeoxyuridine (BrdU)-positive nuclei. BrdU-negative nuclei of colonic crypt cells were reduced slightly in the combined vegetable groups, as compared with the control (P < 0.05). These data: (i) are in line with epidemiological evidence regarding beneficial effects of vegetable consumption on colorectal carcinogenesis; (ii) indicate that consumption of several types of vegetables inhibits early post-initiation events in colorectal carcinogenesis; (iii) suggest that the vegetable-induced effect is more pronounced in advanced lesions; (iv) indicate that the carotenoid content of the vegetables (alpha- and beta-carotene) contributes only marginally to the vegetable-induced effects.

The association of increasing dietary concentrations of fish oil with hepatotoxic effects and a higher degree of aorta atherosclerosis in the ad lib.-fed rabbit

The long-term effects of consumption of marine long-chain n-3 polyunsaturated fatty acids (PUFA) on atherosclerosis in the rabbit were examined. Female Dutch rabbits were fed purified diets, containing 40 energy% total fat, for a period of 2.5 years. To study the dose response relationship between fish oil intake and atherosclerosis, four diets were formulated with fish oil levels being 0, 1, 10 and 20 energy%. A fifth and sixth group were fed an alpha-linolenic acid-(C18:3, n-3) and linoleic acid-(C18:2, n-6) rich diet, respectively. Every 6 weeks, blood samples were taken for determination of clinical chemical parameters, triacylglycerol and total cholesterol levels. Feeding 10 and 20 energy% fish oil containing diets, resulted in an increase of liver enzymes (AST, ALT and ALP). Histological evaluation of the liver also revealed adverse effects of fish oil containing diets. Triacylglycerol blood levels were similar in all groups, and remained constant throughout the study. Total cholesterol levels in blood was significantly lower in the animals fed a linoleic acid-rich diet, as compared with the other five groups. An n-3 long-chain PUFA concentration dependent increase in aorta plaque surface area was observed in the fish oil groups. A significant positive relationship was found between the group mean score for severity of liver pathology and the aorta plaque surface area. These results indicate that the long-chain n-3 polyunsaturated fatty acids in fish oil may be hepatotoxic to the herbivorous rabbit, which may interfere with the outcome of atherosclerosis studies. This finding necessitates the exclusion of liver pathology in experimental studies on atherosclerosis in animal models.

Rat odontogenic tumors associated with disturbed tooth eruption

Most odontogenic tumors occurring in rats have the appearance of immature or mature odontomas. The present brief paper describes two spontaneously occurring odontogenic lesions in rats; both had the appearance of complex odontomas. One was associated with a lesion that had the appearance of an odontogenic fibroma; the other occurred concomitant with a lesion that had the appearance of a cementoblastoma. Their possible relationship with disturbed eruption due to malocclusion is discussed.

Review article. The rat incisor in toxicologic pathology

Microscopic examination of the incisors of rats and mice may reveal toxicologically significant changes. First, the incisor morphology reflects the nutritional status of the animal: fluctuations of mineral metabolism and vitamin availability are disclosed by the rodent incisors, because the incisors continue to grow during life. Similarly, direct or indirect changes of mineral metabolism by a test substance are reflected in the morphological appearance of the incisor dentin. In addition, hormonal disturbances may give rise to typical structural alterations of the incisor in the test animal. Certain chemicals may have deleterious effects upon the odontogenic tissues, resulting in tooth malformation and malocclusion and eventually in odontomas. Apparent nasal tumors may turn out to be of dental origin. Nasal luminal masses that are discussed within this scope are dental malformation, dental callus, and true odontogenic tumors. According to our experience, odontogenic tumors might possibly develop within the scope of a reaction to mechanical tooth trauma as well. In carcinogenicity studies, this consideration deserves attention when evaluating treatment-related putative odontogenic tumors.