Enhanced susceptibility of obese mice to glycidamide-induced sperm chromatin damage without increased oxidative stress.

Diet-induced obesity is known to impair male reproduction and may aggravate the male reproductive toxicity of the food contaminant acrylamide. Exposure of male mice to acrylamide induces paternally mediated pre- and post-implantation losses because of spermatozoal toxicity and these effects are potentiated in mice fed a high-fat diet. Glycidamide - an acrylamide metabolite - is the primary mediator of reproductive effects in males. The mechanisms causing the interaction between diet and acrylamide are not clear. However, diet-induced obesity is associated with oxidative stress in male reproductive tissues which might contribute to increased germ cell susceptibility. In this study, we investigated whether a moderate diet-induced obesity regimen could interfere with glycidamide-induced spermatozoal toxicity and increase oxidative stress. For this purpose, sperm chromatin integrity, oxidised DNA and protein levels, transcript levels of oxidative stress responsive genes and glycidamide-induced DNA and haemoglobin adducts were analysed in samples from male mice exposed to a high-fat diet for 6 weeks in combination with a single glycidamide exposure 7 days prior to sacrifice. We found that glycidamide-induced sperm DNA fragmentation was markedly higher in obese than in lean mice. However, the levels of oxidised DNA and/or protein in blood, liver and testicular tissue was lower in obese than in lean mice. Accompanying the reduced level of oxidised macromolecules, the transcript levels of several oxidative stress-related genes were altered in the liver and testis from obese mice suggesting induction of an antioxidant response in these animals. The haemoglobin-glycidamide adduct levels were higher in obese than in lean animals, whereas obesity did not seem to increase the level of glycidamide-induced DNA adducts. These findings show that a moderate diet-induced obesity regimen may potentiate glycidamide-induced sperm cells toxicity and suggest that the increase in glycidamide-induced sperm toxicity observed in obese mice does not depend on overt oxidative stress.

Impaired sperm chromatin integrity in obese mice.

An increased global prevalence of obesity coincides with an apparent decline in male sperm quality and a possible association between these pathologies has been suggested. In this study, we examined the effects of obesity on sperm chromatin integrity using two mouse models of obesity. In one group of mice, obesity was induced by a high-fat diet (HFD) (diet-induced obesity; DIO model), whereas in the other group, leptin deficiency was used to study the effects of obesity independently of the influence of dietary factors. Sperm chromatin integrity is recognized as an important measure of male infertility, and was analysed by the sperm chromatin structure assay. We found increased sperm DNA fragmentation in both groups of obese mice compared to lean mice, whereas the percentage of immature spermatozoa was not increased by obesity. The DIO model reflects the human condition more closely than the leptin-deficient model and was therefore selected for examination of the transcriptional response of a selection of marker genes in the testis by quantitative real-time PCR. The analysis of transcript levels of the selected testicular marker genes showed moderate, but significant, up-regulation of the Cyp2e1, Cyp19a1, Tnf and Pparg genes in DIO mice compared to lean mice. In conclusion, a clear positive correlation between body mass index and sperm DNA fragmentation was found in two mouse models of obesity. However, the variability in sperm DNA fragmentation within the two groups of obese animals was high. The observed changes in the transcript level of the marker genes suggest that there may be a local response in testicular cells to the HFD regimen with a potential impact on intratesticular signalling and spermatogenesis.

Chronic mucus hypersecretion: prevalence and risk factors in younger individuals.

SETTING: Chronic mucus hypersecretion (CMH) is a common condition in patients with chronic respiratory diseases. Little is known about the incidence, prevalence and determinants of CMH in younger individuals. OBJECTIVE: To determine prevalence, incidence and risk factors for CMH in a young general population. DESIGN: A cohort of Danish twins (aged 12-41 years) was prospectively examined using questionnaires in 1994 (n = 29 180) and in 2002 (n = 21 130). Prevalence and incidence of CMH were determined, and risk factors for the condition were assessed using logistic regression. RESULTS: Lifetime prevalence of CMH was 8.6% in females and 6.9% in males in 1994, and the cumulative incidence among females and males was respectively 10.7% and 8.7% during the study period. Smoking and asthma were risk factors for CMH, with a dose-response effect of tobacco consumption, and smoking habits also predicting incidence of CMH. CONCLUSION: Among the young, CMH is a condition related to asthma and smoking, with a dose-response relationship with tobacco consumption and a relation between smoking habits and incidence. Female susceptibility to development of CMH was observed, as well as signs of greater susceptibility related to young age.

Rapid decline in 51Cr-EDTA measured renal function during the first weeks following lung transplantation.

We previously described a 54% decline in renal function at 6 months after lung transplantation (LTx). We hypothesized that this decline is a very early event following LTx. Thirty-one consecutive patients (16 females/15 males), mean age 49 (+/-13) years, with emphysema, cystic fibrosis/bronchiectasis or idiopathic pulmonary fibrosis were included in an analysis of renal function before and after LTx. The glomerular filtration rate (GFR) was measured using the (51)Cr-ethylenediaminetetra acetic acid plasma clearance single injection technique (mGFR) at baseline before transplantation and at 1, 2, 3 and 12 weeks postoperatively. Mean mGFR declined from 103 +/- 18 to 65 +/- 22, 53 +/- 16 and 57 +/- 18 mL/min/1.73m(2) at 1-, 3- and 12-weeks post-LTx (p < 0.0001), respectively. In a time-dependent repeated measures ANOVA, risk factors for a decline in mGFR posttransplant included: time (p < 0.0001), acute renal failure within 2 weeks post-LTx (p = 0.0003), use of heart and lung machine (p = 0.04), and the use of ephedrine (p = 0.048), as well as increasing age, older than 18 years at LTx (p = 0.006). These data demonstrate that renal function, measured with an isotope method, decreases dramatically during the first week after LTx.

The efficacy and harm of prostaglandin analogues for IOP reduction in glaucoma patients compared to dorzolamide and brimonidine: a systematic review.

AIM: To systematically review the literature on the efficacy and harm of prostaglandin analogues (PGAs) compared to brimonidine and dorzolamide in treating elevated intraocular pressure (IOP). METHODS: Keywords were searched in major literature databases to identify relevant randomised clinical trials (RCTs) of PGAs for ophthalmic use. The study quality of RCTs was assessed using the Jadad scale. Outcomes assessed included reduction in IOP in individual patients, adverse events (AEs) and withdrawals due to AEs. RESULTS: Eight unique RCTs evaluating a total of 1,722 individuals were included in this systematic review. Analysis did not show a significant reduction in the mean IOP from patients receiving latanoprost compared with those receiving brimonidine (WMD = -1.04; p = 0.30). On the other hand, the latanoprost group showed a significant reduction in mean IOP compared to the dorzolamide group (WMD = -2.64; p<0.00001). The number of ocular AEs (excluding hyperaemia) was significantly higher in the brimonidine group compared with the latanoprost group (RR = 0.66; p = 0.0005). CONCLUSION: Latanoprost was found to be significantly superior to dorzolamide but not brimonidine. However, ocular adverse events were significantly fewer in latanoprost users than in brimonide users. Neither travoprost nor bimatoprost was compared to dorzolamide or brimonidine in the present literature.

Association between obesity and asthma in a twin cohort.

BACKGROUND: Obesity is linked to asthma in a yet poorly understood manner. We examined the relationship between obesity and asthma in a population-based sample of twins. METHODS: From the cohorts born between 1953 and 1982, who were enrolled in The Danish Twin Registry, a total of 29 183 twin individuals participated in a nationwide questionnaire study, where data on height, weight and asthma were collected. Latent factor models of genetic and environmental effects were fitted using maximum likelihood methods. RESULTS: The age-adjusted risk of asthma was increased both in obese females, OR = 1.96 (1.45-2.64), P < or = 0.001 and in obese males, OR = 1.59 (1.08-2.33), P = 0.02. According to best-fitting models, the heritability for obesity was 81% in males and 92% in females, whereas the heritability for asthma was 78% and 68% in males and females respectively. The age-adjusted genetic liabilities to obesity and asthma were significantly correlated only in females, r = 0.28 (0.16-0.38). CONCLUSIONS: Obese subjects have an increased risk for asthma, which in females seems partly because of common genes.

Findings on the atopic triad from a Danish twin registry.

OBJECTIVE: To estimate to what extent the same genetic and environmental risk factors influence asthma, hay fever and eczema. DESIGN: From the nationwide Danish Twin Registry, twin cohorts born between 1953 and 1982 were contacted for a questionnaire survey, and a total of 29 183 twin individuals (86%) responded. Subjects were classified as cases when responding affirmatively to three questions about the lifetime occurrence of asthma, hay fever and eczema. Variance components twin analysis was conducted using maximum likelihood methods. RESULTS: The phenotypic (within-subject) correlations in liability between the different diseases were 0.57 (95% CI 0.54-0.59) for asthma and hay fever, 0.40 (95% CI 0.36-0.42) for asthma and eczema, and 0.33 (95% CI 0.29-0.36) for hay fever and eczema. Decomposition of these correlations into their genetic and environmental contributions showed that shared genes explained between 70% and 85% of the correlation between the different diseases. The remaining parts were explained by environmental factors shared between the diseases. CONCLUSION: To a large extent, atopic diseases share a common genetic background, although disease-specific genes also play a considerable role. These results can prove informative when counselling families with atopy, and may furthermore be used to guide the search for pleiotropic genes of importance for these diseases.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induces genetic changes in murine intestinal tumours and cells with ApcMin mutation.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is one of the mutagenic heterocyclic amines derived from cooked meat. In previous animal studies, spontaneous tumour formation in B6(Min/+) mice was associated with somatic loss of the wild-type Apc+ allele by loss of the entire chromosome 18 or by recombination. The objective of this study was to examine genetic changes caused by PhIP-exposure in a mouse intestinal cell line and in tumours from hybrid mice by keeping track of the chromosomes carrying the two Apc alleles. We transformed the SV40 T-immortalised intestinal epithelial cell line IMCE, derived from the B6(Min/+) mice by exposure to N-OH-PhIP, and studied the effect on Apc status and chromosome 18. Eighteen transformed cultures were obtained and all of them had retained the Apc+ allele. Five of seven transformed cultures were tumorigenic after implantation in nude mice. Chromosomal analysis of these five cultures and the parent IMCE cell line showed that the IMCE cells were near-tetraploid with an average of 77 chromosomes/cell, while the tumorigenic cell cultures were all triploid to hyper-triploid with a range of 61-69 chromosomes/cell. The number of copies of chromosome 18 was about four in the IMCE line and this copy number was retained in the transformed lines derived from IMCE. Changes in chromosome 18 and Apc during tumour development in vivo were examined in spontaneously formed and PhIP-induced intestinal tumours from two hybrid mice strains, i.e. B6(Min/+) - a murine FAP model - crossed with either AKR/J or A/J. We evaluated the allelic status of Apc, and the heterogenic microsatellite markers D18Mit19 and D18Mit4, located at the upper and lower ends of chromosome 18, respectively. In tumours from untreated animals, instability in the D18Mit19 and Apc was observed. Upon PhIP exposure, the B6(Min/A+) hybrid mouse tumours differed distinctly in genetic profile from those obtained from untreated animals and we detected three genetically different tumour groups, all of which had apparently retained Apc+. One group had allelic balance between the Apc(Min) and Apc+, the second had allelic imbalance between the Apc and D18Mit4 alleles, indicative of chromosomal stability in the first group and instability in the lower end of chromosome 18 in the second group, respectively. The third group showed variable allelic status of the three markers. A similar change in genetic profile was also seen in intestinal tumours of PhIP-exposed B6(Min/AKR+) hybrid mice, but it was less pronounced. Chromosomal breaks and/or recombinational events could be alternative explanations for the observed allelic imbalances in chromosome 18 markers in intestinal tumours from PhIP-exposed mice.

Risk factors for asthma in young adults: a co-twin control study.

BACKGROUND: The liability to asthma is influenced both by genetic and environmental factors. The objective of this study was to identify risk factors for asthma in young adult twin pairs during an 8-year period. METHODS: From the birth cohorts 1953-1982 of the Danish Twin Registry, 6,090 twin pairs who were initially unaffected with respect to asthma at a nationwide questionnaire-based study in 1994 participated in a similar follow-up study in 2002. Subjects were regarded incident asthma cases when responding affirmatively to the question 'Do you have, or have you ever had asthma'? in 2002. Pairs in which only one twin developed asthma -- discordant pairs -- were identified and conditional logistic regression was applied to detect effects of risk factors. RESULTS: A total of 126 monozygotic (MZ) and 273 dizygotic (DZ) discordant twin pairs were identified. In MZ twins hay fever (OR = 3.16, 95% CI: 1.29-7.73, P = 0.007) and exercise (OR for inactivity = 0.35, 95% CI: 0.13-0.91, P = 0.023) were significantly associated with asthma, whereas in DZ twins, hay fever (OR = 2.44, 95% CI: 1.44-4.13, P = 0.001), eczema (OR = 1.96, 95% CI: 1.02-3.78, P = 0.040), female sex (OR between males and females = 0.54, 95% CI: 0.36-0.80, P = 0.002), and increasing levels of body mass index (BMI; OR per unit = 1.11, 95% CI: 1.02-1.20, P = 0.009) were significant predictors of asthma. CONCLUSIONS: Hay fever, eczema, female sex, exercise and increasing levels of BMI were risk factors for asthma in young adults. The different risk profile observed in MZ twins compared with DZ twins may reflect an underlying genetic vulnerability shared between those risk factors and asthma.

Automated external defibrillators for home use.

The Philips HeartStart Home Defibrillator is an automated external defibrillator (AED) that is approved for home use by untrained users. Most cardiac arrests occur in the home, so a rapid response with cardiopulmonary resuscitation (CPR) and defibrillation is critical for survival. No prospective studies demonstrate that the use of AEDs in the home by untrained persons improves health outcomes. Further investigation is needed to determine the benefit and harm of AEDs in the home.

Intestinal tumorigenesis in multiple intestinal neoplasia mice induced by the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine: perinatal susceptibility, regional variation, and correlation with DNA adducts.

In our previous experiments, multiple injections with the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were used to induce intestinal tumors in C57BL/6J-multiple intestinal neoplasia (Min)/+ mice. To define the period of highest susceptibility to PhIP perinatally, we first determined the effect of a single s.c. injection. Ten or 50 mg/kg PhIP increased the number and diameter of small intestinal tumors dose-dependently in 3-day-old Min/+ mice. In the colon, only 50 mg/kg PhIP increased the incidence and number of tumors. The number of dysplastic aberrant crypt foci decreased from weeks 7 to 11. In the same period, an increase in the number of tumors was seen, indicating that over time the dysplastic aberrant crypt foci develop into tumors. Min/+ mice were then exposed in utero through their dams being given one s.c. injection of 50 mg/kg PhIP 3 days before giving birth or were exposed directly to the same dose on day 3, 12, or 36 after birth. Remarkably, the most susceptible period for tumorigenesis in the small intestine was between days 3-12 after birth, whereas in the colon it was from day 3 before to day 3 after birth. Furthermore, we examined whether the formation of DNA adducts determined after 24 h could explain the observed time-dependent and regional susceptibility to PhIP. A higher level of PhIP-DNA adducts was found after exposure on day 12 after birth, compared with day 36 after birth, in all parts of the small intestine but not in the colon, which was in close accordance with the numbers of tumors present. The levels of PhIP-DNA adducts along the intestines were highest in the middle and distal parts of the small intestine, where tumor numbers were also the highest. In conclusion, Min/+ mice are most susceptible to intestinal tumor induction by PhIP from day 3 before to day 12 after birth, and this susceptibility could at least partly be explained by the formation of PhIP-DNA adducts.

Intestinal tumours induced by the food carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in multiple intestinal neoplasia mice have truncation mutations as well as loss of the wild-type Apc(+) allele.

C57BL/6J-Min/+ (multiple intestinal neoplasia) is a murine model for familial adenomatous polyposis (FAP), where the mice are heterozygous for a nonsense Apc(Min) (adenomatous polyposis coli) mutation, and therefore develop numerous spontaneous adenomas in the small intestine and colon. Neonatal exposure of Min/+ mice to the food carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) (eight subcutaneous injections of 25 or 50 mg/kg PhIP to pups or 50 mg/kg PhIP to lactating dams) markedly increased (2--9-fold) the number of intestinal tumours, especially in the small intestine. We examined whether the Apc gene was affected in small intestinal and colonic tumours induced by PhIP. In spontaneous tumours formed in these mice, the main mechanism for tumour induction is loss of the wild-type Apc(+) allele, i.e. loss of heterozygosity (LOH). Also in the PhIP-induced tumours, this is a major mechanism, since large fractions of PhIP-induced tumours had LOH in APC: However, mechanisms other than LOH must also prevail, since a lower frequency of LOH was found in the small intestinal tumours from male mice exposed to PhIP either via breast milk (65%) or by direct injection (68%), compared with the untreated controls (92%). Tumours that had retained the wild-type Apc(+) allele were further analysed for presence of truncated Apc proteins with in vitro synthesized protein (IVSP) assay. Truncated Apc proteins, indicating truncation mutations in exon 15 of the Apc gene, were detected in 20% (8 of 40) of the tumours not showing LOH from the small intestine after PhIP exposure, all in segment 2 (codons 686--1217). Seventeen percent (2 of 12) of the colonic tumours had a truncated Apc protein in segment 3 (codons 1099--1693). Importantly, no truncated proteins were detected in tumours from unexposed mice with apparently retained wild-type Apc(+) allele. These results show that PhIP induces intestinal tumours in the Min/+ mice both by causing LOH and truncation mutations in the wild-type Apc(+) allele.

Qualitative and quantitative relationship between dysplastic aberrant crypt foci and tumorigenesis in the Min/+ mouse colon.

The multiple intestinal neoplasia (Min)/+ mouse, which harbors only one functional allele of the Apc gene, is susceptible to environmental factors that disrupt this gene and subsequently trigger Apc-driven tumorigenesis in the colon. Aberrant crypt foci (ACF) are assumed to be preneoplastic lesions in colon carcinogenesis. Recently, we reported the absence of "classical" ACF in the colon of untreated Min/+ mice. Instead we identified flat dysplastic lesions, which we denoted ACF(Min) (J. E. Paulsen et al., Scand. J. Gastroenterol., 35: 534-539, 2000). In contrast to the classical type, ACF(Min) are not elevated above the surrounding mucosa, and their detection is totally dependent on methylene blue staining and transillumination. In the present study, we treated Min/+ mice with 5 mg/kg body weight azoxymethane (AOM) at weeks 1 and 2 and demonstrated induction of both types of lesions. However, only ACF(Min) appeared to be associated with the development of adenomas. Monocryptal ACF(Min), large ACF(Min), and adenomas showed a uniform histopathological picture of dysplasia and cytoplasmic overexpression of beta-catenin, indicating a qualitative relationship between these lesions. Also a quantitative relationship was suggested because the dramatic decrease in ACF(Min) number from week 7 to 11 was paralleled by a reciprocal increase in tumor number, indicating fast-crypt multiplication of ACF(Min). In AOM-treated +/+ (wild-type) littermates, a low number of ACF(Min) and tumors with the same characteristics as in Min/+ mice was seen. In contrast to ACF(Min), histopathological and immunohistochemical examination of classical ACF showed normal or hyperplastic crypts with normal levels of beta-catenin expression. In AOM-treated Min/+ mice, the number of classical ACF was virtually constant from week 7 to 11, and only a modest increase of crypt multiplicity was observed. The number of AOM-induced classical ACF at week 11 was not different in Min/+ mice and +/+ mice. In conclusion, we identified two distinct populations of altered crypts in the colon of Min/+ mice after AOM treatment. The ACF(Min), which resemble the dysplastic ACF described previously, clearly showed a continuous development from the monocryptal stage to adenoma, and they were characterized by fast-growing crypts with altered control of beta-catenin. In contrast, the classical ACF, which resemble the hyperplastic ACF described previously, were characterized by slow-growing crypts with normal beta-catenin expression, and they were probably not related to tumorigenesis.

DNA adduct levels and intestinal lesions in congenic rapid and slow acetylator syrian hamsters admi food mutagens 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) or 2-amino-3-methylimidazo[4,5-f]quinoline (IQ).

Epidemiological studies indicate that rapid acetylators with a high intake of well-done red meat have an increased risk of colorectal cancer. Arylamine N-acetyltransferase enzymes (E.C. 2.3.1.5) activate carcinogenic heterocyclic amines found in the crust of fried meat via O-acetylation of their N-hydroxylamines to reactive intermediates that bind covalently to DNA and produce mutations. Syrian hamsters as well as humans express two N-acetyltransferase isozymes (NAT1 and NAT2) which differ in substrate specificity and genetic control. Nucleic acid substitutions in the NAT2 gene segregate individuals into rapid, intermediate and slow acetylator phenotypes. In the present paper, we examined the role of the polymorphic NAT2 acetylator genotype in carcinogenesis induced by the food mutagens 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) or 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) by comparing Syrian hamster lines congenic at the NAT2 locus. No differences were found between rapid and slow acetylator congenic hamsters in levels of intestinal PhIP-DNA adducts. In contrast to previous studies in rats, no carcinogen-related induction of the preneoplastic lesions aberrant crypt foci or tumors was found in the intestines of rapid and slow acetylator congenic Syrian hamsters administered PhIP or IQ.

Identification and quantification of aberrant crypt foci in the colon of Min mice--a murine model of familial adenomatous polyposis.

Min mice are heterozygous for a nonsense mutation in the murine adenomatous polyposis coli (APC) gene and spontaneously develop multiple intestinal neoplasms similar to the familial adenomatous polyposis (FAP) syndrome in humans. Aberrant crypt foci (ACF) are assumed to be preneoplastic lesions in both murine and human colon carcinogenesis and have been observed in FAP patients. Light microscopic examination of the colonic mucosa of 42 Min mice did not show even a single 'classical' ACF on the basis of previously defined criteria, specifying that they are elevated above the surrounding mucosa. However, in Min mice we discovered aberrant crypt foci of a different type, which we denoted ACF(Min). In contrast to the classical type, ACF(Min) were not elevated above the surrounding mucosa, their detection was totally dependent on methylene blue staining and transillumination, and they could not be identified with scanning electron microscopy. Histopathologic examination of ACF(Min) showed dysplastic crypts, similar to those found in larger lesions--that is, microadenomas in the Min mouse. The number of ACF(Min) increased up to the age of 6 weeks and then seemed to remain at a constant level of approximately four per colon. In conclusion, by transillumination of whole-mount preparations stained with methylene blue, we have identified and quantified small microscopic lesions that may be precursors of colonic adenomas in Min mice.

The drinking water chlorination by-products 3,4-dichloro-5-hydroxy-2[5H]-furanone(mucochloric acid) and 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone do not induce preneoplastic or neoplastic intestinal lesions in F344 rats, balb/ca mice or C57bl/6J-min mice.

Epidemiological studies indicate an association between exposure to chlorinated drinking water and risk of intestinal cancer. In order to study this experimentally, we have examined the effects of 3,4-dichloro-5-hydroxy-2[5H]-furanone (mucochloric acid, MCA) and 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX), mutagenic and genotoxic compounds in drinking water, on aberrant crypt foci and tumours in the intestines of male F344 rats and Balb/cA mice, and C57BL/6J-Min (multiple intestinal neoplasia)/+ mice of both sexes, in six independent experiments. In some experiments the effects of MCA and MX on aberrant crypt foci induced by the colon carcinogens 1,2-dimethylhydrazine or its metabolite azoxymethane were also studied. Neither MCA nor MX alone induced aberrant crypt foci or intestinal tumours when given in drinking water. With this route of exposure neither MCA nor MX, when given in combination with 1,2-dimethylhydrazine or azoxymethane, had any effect on the induction or growth of the aberrant crypt foci. Drinking water exposure of MX did not affect the number or growth of aberrant crypt foci or intestinal tumours in the Minl+ mice. When administered intrarectally MCA had a weak inducing effect on aberrant crypt foci in the colons of Balb/cA mice. Exposure to MCA and MX intrarectally apparently promoted the growth of aberrant crypt foci both in rats and mice, increasing the crypt multiplicity, aberrant crypts/aberrant crypt foci. Based on an overall evaluation of these experiments, the intestinal tract, at least in rats and mice, seems not to be a main target organ for effects of MCA or MX on preneoplastic or neoplastic development.

[Chlorination of drinking water--possible cancer risk from a by-product]. / Klorering av drikkevann--mulig kreftrisiko av et biprodukt.

In a recent study, 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX; CAS no 77439-76-0) which is formed during chlorination of water containing organic substances, was found to be carcinogenic in the rat, at multiple sites in both sexes. MX is known as a potent bacterial mutagen. Epidemiological studies have suggested an association between chlorinated water consumption and a moderate increase in the risk of cancer. Although MX is a strong mutagen in prokaryotes, its genotoxic effects in mammalian cells are not so large, and more variable results are obtained. Very low concentrations of MX are found in drinking water (ng/L), whereas the genotoxic and carcinogenic effects in experimental animals of this compound are detectable at relatively high doses (mg/kg body weight). Relative to the risk for infectious diseases from the consumption of contaminated drinking water, the possible cancer risk associated with MX exposure appears to be low. Even so, efforts should be made to reduce disinfection byproduct formation by removing organic matter before chlorination.

Neonatal exposure to the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine via breast milk or directly induces intestinal tumors in multiple intestinal neoplasia mice.

We examined whether the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) could increase intestinal tumorigenesis in neonatal C57BL/6J-Min/+ mice, a murine model for familial adenomatous polyposis. Min/+ mice are heterozygous for a nonsense mutation in the adenomatous polyposis coli gene and spontaneously develop multiple intestinal adenomas, primarily in the small intestine. Neonatal Min/+ mice (3-6 days old) were exposed to PhIP via breast milk from lactating dams given 8 s.c. injections of 50 mg/kg PhIP three times a week or to 8 s.c. injections of 25 or 50 mg/kg PhIP directly, over the same period. At the age of 11 weeks, the number, diameter and location of the intestinal tumors were scored. Remarkably, a 2- to 4-fold increase in the number of small intestinal tumors was seen in Min/+ mice exposed to PhIP via breast milk (P < 0.001). To our knowledge, this is the first time PhIP has been reported to induce tumors following exposure via breast milk from PhIP-exposed dams. Upon direct exposure to 50 mg/kg PhIP, a 6- to 9-fold increase in the number of small intestinal tumors was observed (P < 0.001). The diameter of the PhIP-induced small intestinal tumors was slightly increased (P < 0.001). In the colon, a 3- to 4-fold increase in the number of tumors was seen in Min/+ mice exposed to PhIP via breast milk (P = 0. 004). Direct exposure to 50 mg/kg PhIP caused a 2- to 6-fold increase in the number of colonic tumors (P = 0.014). The PhIP-induced colonic tumors were located more distally and displayed a smaller diameter than the tumors from the controls (P < 0.05). In contrast to a previous study, where PhIP showed only a moderate tumorigenic effect in adult Min/+ mice, the present study demonstrates a strong tumorigenic effect of PhIP in neonatally exposed Min/+ mice, even after exposure via breast milk from PhIP-exposed dams.

[Heterocyclic amines in cooked meat]. / Heterosykliske aminer i stekt kjøtt.

The age adjusted incidence of cancer has increased on average 1% annually since the beginning of this century, and cancer is now one of the most prevalent causes of death. Diet is suggested to be responsible for about 30-70% of all cancer cases. The heterocyclic amines (HCA) produced during processing of meats and fish at temperatures above 150 degrees C are candidate dietary causes. Amounts in food range from less than 1 ng/g in cooked meat or fish up to over 300 ng/g in well done flame grilled chicken breast meat. The most important parameters determining HCA amounts are cooking temperature and cooking time. 20 different HCAs are identified from cooked or grilled meats and fish. HCAs are causing cancer in various organs in mice, rats and cynomolgus monkeys. It is of interest to note that in rats, PhIP, the most abundant heterocyclic amine in cooked food, causes colon, prostate and mammary cancer, which are the most prevalent cancers in humans. Epidemiological studies show a correlation between intake of red meat and colon, mammary and prostate cancer. Based on the adverse effects of HCA, a reduced intake is recommended and practical advice on how this can be done is given.

A fish oil derived concentrate enriched in eicosapentaenoic and docosahexaenoic acid as ethyl ester suppresses the formation and growth of intestinal polyps in the Min mouse.

We examined whether the n-3 polyunsaturated fatty acid ethyl ester enriched fish oil K85 (54.4% of eicosapentaenoic acid and 30.3% of docosahexaenoic acid as ethyl esters) could inhibit the intestinal tumorigenesis in Min mice, a murine model of familial adenomatous polyposis (FAP). Min mice that are heterozygous for a nonsense mutation in the Apc gene, develop spontaneously multiple intestinal neoplasms, primarily in the small intestine. K85 was dissolved in corn oil (vehicle) and mixed into the AIN-76A diet. The total oil content (K85 + corn oil) was 12% in all diets. The various experimental diets contained 0 (vehicle control), 0.4, 1.25 or 2.5% of K85. In the small intestine, the mean number of tumors/mouse was 105 +/- 18 (SEM) in control males and 70 +/- 11 in control females. Dietary K85 treatment reduced the number of small intestinal tumors: in males, the maximum reduction was 66% (P = 0.002) with 0.4% of K85; and in females, the maximum reduction was 48% (P = 0.043) with 2.5% of K85, but the inhibition was only slightly increased from 0.4% to 2.5% of K85. The mean tumor diameter was 1.33 +/- 0.08 mm in control males and 1.06 +/- 0.08 in control females, and the diameter ranged from <0.1 mm (monocryptal adenomas) to 4 mm. The small intestinal tumor diameter was reduced by K85 in a dose-dependent manner: in males, with a maximum reduction of 26% (r = -0.64, P = 0.004); and in females, with a maximum reduction of 38% (r = -0.61, P < 0.004). In the large intestine, the mean number of tumors/mouse was 1.0 +/- 0.5 in males and 0.8 +/- 0.2 in females. Although K85 treatment tended to reduce the number and diameter of the large intestinal tumors, these effects did not reach statistical significance. Aberrant crypt foci not elevated from the flat mucosa (ACF(Min)) occurring in the colon of Min mice were also scored. The mean number of ACF(Min)/colon (3.8 +/- 0.9) and the crypt multiplicity (1.49 +/- 0.28) in females were reduced by 73% (P = 0.03) and 60% (P = 0.048) with 2.5% of K85, respectively, whereas no significant effect could be observed in the males.