Promotion of the mediterranean diet incancer long-survivors by means of the Med-Food Anticancer Program: a pilot study.

BACKGROUND: The intervention "Med-Anticancer Food Program" has proven to be effective in promoting the Mediterranean Diet, significantly increasing the Mediterranean Adequacy Index in healthy subjects. There are no studies that have investigated the effectiveness of this intervention in individuals who have had a diagnosis of cancer. OBJECTIVE: To perform a pilot study to assess the opportunity of employing the methodology of the Med-Anticancer Food Program in order to encourage "long-term cancer survivors" to adhere to the Mediterranean Diet, as well as healthy people, and this in order to apply the program to larger groups. METHODS: From the residents' register of Foggia, a city in southern Italy, forty adults of both sexes, over 25 years of age, were recruited at random and assigned (1:1) as follows: - Twenty healthy subjects to the intervention-1 group - Twenty long-term cancer survivors to the intervention-2 group. The Med-Anticancer Food Program was applied to both groups with an articulated intervention 11 weeks long, followed by a 52-week period of follow up. By means of a food diary of the last 3 days, the Mediterranean Adequacy Index values were calculated before intervention (T0), after a period of 11 weeks of interventions (T1) and at the end of the 52 weeks of follow-up period (T2). The H0 hypothesis of the study was that there are no differences between the two interventions in reaching by T1, and maintaining at T2, values of Mediterranean Adequacy Index around 7, considered the optimum for adherence to the Mediterranean diet. RESULTS: Out of the subjects assigned to the intervention-1 group (n = 20), 11 subjects have completed the 52-months follow-up (55.0% ); for intervention-2, 16 (80%) out of 20 have completed it. The average age of subjects was 52.1 years. The Mediterranean Adequacy Index, of intervention-1 group significantly increased from 2.8 (T0) to 9.2 (T1) and to 9.0 (T2) (p <0.0001); whereas, in the intervention-2 group, Mediterranean Adequacy Index moved from 2.4 (T0) to 10.2 (T1) and to 9.3 (T2) (p <0.0001). The difference of Mediterranean Adequacy Index between the two study groups at T1 and T2 was not significant. Such non-significance persists also after the stratification by sex and age obtained with Mantel-Haenszel procedure. The performance of the values of the laboratory parameters considered (folic acid, total cholesterol, alkyl resorcinol) was similar in the subjects of both intervention 1 and 2, without any difference, while considered at a basal level T0, at T1 and at the end of the follow-up period (T2). CONCLUSIONS: The results of our work suggest the feasibility of conducting the Med-Anticancer Food Program in long-term cancer survivors. The results of the pilot study show that such intervention, carried on a small number of long term cancer survivors, is adequate to assess its feasibility but, due to the limited size of our study, a confirmation is required through larger nutritional prevention intervention studies.

Differential modification of genetic susceptibility to childhood eczema by two probiotics.

BACKGROUND: In a double-blind, randomized, placebo-controlled birth cohort, we have recently shown a beneficial effect of Lactobacillus rhamnosus HN001 (HN001) for the prevention of eczema in children through to 6 years of age but no effect of Bifidobacterium animalis subsp lactis HN019 (HN019). OBJECTIVE: Among this cohort of children, we aim to investigate whether these probiotics could modify the expression of genetic predisposition to eczema conferred by genetic variation in susceptibility genes. METHODS: Thirty-three eczema susceptibility SNPs (in eleven genes) were genotyped in 331 children of European ancestry. RESULTS: Children who carried a genetic variant that put them at a high risk of developing eczema were less likely to develop eczema if they had been randomized to the HN001 intervention group compared to those in the placebo group. HN019 was also able to protect against the effects of some SNPs. As well as modifying genetic susceptibility to childhood eczema, HN001 was also found to modify genetic susceptibility to eczema severity and atopy risk. CONCLUSION AND CLINICAL RELEVANCE: This is the first study to show an effect of a probiotic on reducing eczema risk amongst those with particular eczema-associated genotypes. Our findings suggest that Lactobacillus rhamnosus HN001 may be particularly effective in preventing eczema in children with specific high-risk genotypes.

Randomized, controlled nutrition education trial promotes a Mediterranean diet and improves anthropometric, dietary, and metabolic parameters in adults.

Several studies have shown that uptake of a Mediterranean diet could prevent many chronic diseases, such as cancer. However, the effectiveness of Mediterranean diet promotion interventions has not been well researched. The aim of this study was to evaluate the effectiveness of a nutrition education intervention for promoting the Mediterranean diet, by assessing changes in anthropometric, physical activity, dietetic and metabolic parameters in healthy adult subjects, before and after the intervention. Eighty participants, both sexes, aged 51-59 years, were randomly assigned in a 1:1 ratio to the intervention or the control group. The intervention group participated in the Med-Food Anticancer Program (MFAP), designed to promote a Mediterranean diet. This was organized into 15 weeks of intensive training and 10 weeks of consolidation. Participants of the two groups were assessed at baseline (T0) and after 25 weeks (T1) for anthropometric, physical activity, dietetic, and metabolic parameters. The hypothesis was that subjects participating in MFAP would show an improvement in these parameters. The primary endpoint was an improvement of the Mediterranean Adequacy Index (MAI), calculated by dividing the percentage of total energy from typical Mediterranean food groups by the percentage of total energy from non-typical Mediterranean food groups. At T1, the intervention group showed a significant decrease in body weight (-8.3%, P = 0.045), body mass index (-12.4%, P = 0.05), cheese (53.0%, P < 0.0001) and meat (-49.3%, P = 0.005) intake, fasting glycaemia (-9.2%, P = 0.012), and fasting insulin (-32.6%, P = 0.014), C-Reactive Protein (-34.0%, P = 0.005). They showed a significant increase in MAI (+213, P < 0.0001), physical activity (expressed in steps per day, +200.4%, P < 0.0001), fruit (+38.8, P < 0.0001), vegetables (29.3%, P < 0.0001), and dietary fiber (+38.6%, P = 0.04) intake. In contrast, the control group presented non-significant variations in measured parameters, for exception of cheese intake (+18.2%, P < 0.0001). The MFAP was found to promote uptake of the Mediterranean diet, and improve anthropometric, physical activity, dietary, and metabolic parameters in healthy subjects.

[Nutrition prevention intervention for cancers: "Med-Food Anticancer Program"]. / L'intervento di prevenzione nutrizionale dei tumori: "Med-Food Anticancer Program".

Several studies recommend the Mediterranean diet and daily physical activity to prevent cancer development. These recommendations, however must be transformed into public health structured programmes, so that they assume operational effectiveness. The aim of the diet and lifestyle intervention called Med-Food Anticancer Program (MFAP) is to promote the Mediterranean diet and physical activity in the adult population. In particular; the target for participants in the intervention is the increased consumption of legumes, fish, whole grain bread and cereals, fruits and vegetables, and the decreased consumption of meat, cheese and foods of animal origin. At the same time, it is recommended to make at least ten thousand steps a day. Two studies have shown the effectiveness of MFAP.

Training the teachers for improving primary schoolchildren's fruit and vegetables intake: a randomized controlled trial.

Effectiveness comparison of different school-based nutrition education interventions to improve fruit and vegetable (F&V) consumption in schoolchildren not yet well researched. We evaluated the effectiveness of two school-based interventions promoting fruit and vegetable intake among Italian schoolchildren. In this randomized intervention trials, the first intervention was conducted by schoolteachers who attended a nutritionist-led training course (group-1), the second intervention conducted by schoolteachers who performed a self-training course (group-2). Thirty-two second to fifth-grade elementary classes enrolling 96 schoolteachers and 813 schoolchildren were randomized, and assigned to the two different nutrition education interventions. 804 students completed the study. By the end of the study, the group-1 (n = 409) followed by the teachers who attended a nutritionist-led course successfully increased the consumption of fruit and vegetables: in 183 (44.7%) and 157 (38.3%) schoolchildren respectively; the group-2 (n = 395) with teachers who performed a self-training course reported an increased consumption of fruit and vegetables in 81 (20.5%) and 76 (19.2%), respectively. This study indicates that a school-based nutrition education conducted by teachers who attended a nutritionist-led training course has a significant impact on primary school-age children's F&V intake.

PTPN2 but not PTPN22 is associated with Crohn's disease in a New Zealand population.

Recent genome-wide association studies have provided evidence for the involvement of the genes PTPN2 and PTPN22 in the pathogenesis of Crohn's disease (CD). We investigated whether genetic variants in these genes were associated with CD in a New Zealand population. Single-nucleotide polymorphisms (SNPs) rs2542151 (PTPN2) and rs2476601 (PTPN22) were genotyped in 315 CD cases and 481 controls. In this sample, we were able to confirm an association between CD and PTPN2 (genotypic P = 0.019 and allelic P = 0.011), and phenotypic analysis showed an association of this SNP with late age at first diagnosis, inflammatory and penetrating CD behaviour, requirement of bowel resection and being a smoker at diagnosis. There was no evidence for an association with PTPN22.

15-week long school-based nutritional education program to promote Italian primary schoolchildren's fruit and vegetable intake.

A short-version (15-week long) of school-based nutrition education program called "Bring Fruit to School" to enhance primary schoolchildren's fruit and vegetable (F&V) intake was evaluated. We recruited 199 primary schoolchildren from 8 classes (grade 2-5). The primary end-point was an increase in the children's F&V intake. The intervention period lasted 15 weeks, and was divided into three phases: weeks 1-5, weeks 6-10 and weeks 11-15. The F&V intake of the schoolchildren was also monitored in a subsequent follow-up period (16th-32nd week). By week 15, 92 (46.2%, P < .001) schoolchildren increase fruit intake and 91 (45.7%, P < .001) increase vegetable intake. The F&V intake increased during the intervention period and was constant in follow-up. The BFtS program is an effective means to promote primary schoolchildren's F&V intake, and was implemented in Italy by the Food and Nutrition Service of Foggia's Local Health Authority. It could be extended to many other countries by local nutrition agencies, such as associations for nutrition.

Gender-stratified analysis of DLG5 R30Q in 4707 patients with Crohn disease and 4973 controls from 12 Caucasian cohorts.

BACKGROUND: DLG5 p.R30Q has been reported to be associated with Crohn disease (CD), but this association has not been replicated in most studies. A recent analysis of gender-stratified data from two case-control studies and two population cohorts found an association of DLG5 30Q with increased risk of CD in men but not in women and found differences between 30Q population frequencies for males and females. Male-female differences in population allele frequencies and male-specific risk could explain the difficulty in replicating the association with CD. METHODS: DLG5 R30Q genotype data were collected for patients with CD and controls from 11 studies that did not include gender-stratified allele counts in their published reports and tested for male-female frequency differences in controls and for case-control frequency differences in men and in women. RESULTS: The data showed no male-female allele frequency differences in controls. An exact conditional test gave marginal evidence that 30Q is associated with decreased risk of CD in women (p = 0.049, OR = 0.87, 95% CI 0.77 to 1.00). There was also a trend towards reduced 30Q frequencies in male patients with CD compared with male controls, but this was not significant at the 0.05 level (p = 0.058, OR = 0.87, 95% CI 0.74 to 1.01). When data from this study were combined with previously published, gender-stratified data, the 30Q allele was found to be associated with decreased risk of CD in women (p = 0.010, OR = 0.86, 95% CI 0.76 to 0.97), but not in men. CONCLUSION: DLG5 30Q is associated with a small reduction in risk of CD in women.

Dopamine transporter (DAT1/SLC6A3) polymorphism and the association between being born small for gestational age and symptoms of ADHD.

Being small for gestational age (SGA) has been established as a risk factor for Attention Deficit Hyperactivity Disorder (ADHD). Likewise, several molecular genetic studies have found a link between DAT1 and ADHD. This study investigated whether SGA moderates the effect of dopamine transporter gene variants on the risk of ADHD. A total of 546 children of European descent were genotyped at age 11 for seven DAT1 SNPs (rs6347, rs11564774, rs40184, rs1042098, rs2702, rs8179029 and rs3863145). The Strengths and Difficulties Questionnaire was used to measure symptoms of ADHD at ages 3.5, 7 and 11. We found significant gene-environment interactions between birth weight and DAT1 SNPs (rs6347, rs40184, rs1042098, rs3863145) on ADHD symptoms at 3.5 years only. Results suggest that genotypic variation of DAT1 may confer a relative protective effect against ADHD in SGA individuals. This study supports the idea that being born SGA moderates the effect of the DAT1 gene on ADHD symptoms in the preschool years and may help to explain some of the heterogeneity in ADHD outcomes.

Heterocyclic amine content of cooked meat and risk of prostate cancer.

BACKGROUND: Some epidemiologic studies have described positive associations between prostate cancer risk and meat consumption, but underlying mechanisms have not been identified. Heterocyclic amines are mutagens formed during the cooking of meat. Well-done meat has been associated with increased risks of colorectal and breast cancers in humans. This study examined associations between prostate cancer risk and 1) estimated daily intake of heterocyclic amines from cooked meat and 2) level of cooked-meat doneness. METHODS: A population-based, case-control study involving 317 case patients with prostate cancer and 480 age-matched control subjects was carried out in Auckland, New Zealand. Levels of meat doneness and daily intake of heterocyclic amines were determined from self-reported dietary data and experimentally measured heterocyclic amine levels in locally sourced meat samples cooked under controlled conditions to varying degrees of doneness. RESULTS: The heterocyclic amines found in the highest concentrations in meat samples were 2-amino-1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine (IFP) and 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) from well-done chicken and pork and very well-done beefsteak. Meat doneness was weakly and inconsistently associated with prostate cancer risk for individual types of meat, but increased risk was observed for well-done beefsteak (relative risk = 1.68; 95% confidence interval = 1.02-2.77; two-sided P for trend =.03). A weak positive gradient of increased risk was associated with estimated daily exposure to IFP but not with the other major heterocyclic amines. CONCLUSIONS: Meat doneness and estimated intake of heterocyclic amines from cooked meat were not clearly associated with prostate cancer risk.

Comparison of the mutagenic and clastogenic activity of amsacrine and other DNA-intercalating drugs in cultured V79 Chinese hamster cells.

The acridine derivative amsacrine (m-AMSA) is used clinically for the treatment of acute leukemias. The mutagenic activity of this drug has been evaluated at the 6-thioguanine (6-TG) and ouabain resistance loci in cultured Chinese hamster fibroblasts (V79-171b cell line). m-AMSA was found to have weak but significant mutagenic activity at the 6-TG but not at the ouabain resistance locus, after either 1- or 45-hr exposures at concentrations causing up to 90% cell kill. Two other intercalating agents with antitumor activity, Adriamycin and actinomycin D, provided essentially identical results. All three drugs were potent inducers of micronuclei in V79-171b cells, indicating high clastogenic activity. For these intercalating agents, the yield of 6-TG-resistant mutants was approximately 100-fold lower than that for ethyl methanesulfonate after exposures causing equivalent toxicity or equivalent chromosome breakage. The acridine half-mustard ICR-191 resembled ethyl methanesulfonate rather than the other intercalating agents in providing a high yield of 6-TG-resistant mutants relative to its clastogenic activity. The tumor-inactive intercalator 9-aminoacridine demonstrated only low clastogenic activity with a lack of significant mutagenic activity at toxic concentrations. These results suggest that, for m-AMSA, Adriamycin, and actinomycin D, both cell killing and mutagenesis could be direct consequences of chromosome breakage, while 9-aminoacridine may kill cells by a different mechanism. In view of its mutagenic and clastogenic activity at clinically achievable exposures and the similarity of its genotoxic properties to Adriamycin, m-AMSA should be considered a potential carcinogen.

A quinazoline-based HDAC inhibitor affects gene expression pathways involved in cholesterol biosynthesis and mevalonate in prostate cancer cells.

Chronic inflammation can lead to the development of cancers and resolution of inflammation is an ongoing challenge. Inflammation can result from dysregulation of the epigenome and a number of compounds that modify the epigenome are in clinical use. In this study the anti-inflammatory and anti-cancer effects of a quinazoline epigenetic-modulator compound were determined in prostate cancer cell lines using a non-hypothesis driven transcriptomics strategy utilising the Affymetrix PrimeView® Human Gene Expression microarray. GATHER and IPA software were used to analyse the data and to provide information on significantly modified biological processes, pathways and networks. A number of genes were differentially expressed in both PC3 and DU145 prostate cancer cell lines. The top canonical pathways that frequently arose across both cell lines at a number of time points included cholesterol biosynthesis and metabolism, and the mevalonate pathway. Targeting of sterol and mevalonate pathways may be a powerful anticancer approach.

Mutagenic properties of topoisomerase-targeted drugs.

Topoisomerases maintain DNA structure by relieving torsional stress occurring in DNA during transcription, replication and cell division. Topoisomerases are of two main types, causing transient breaks in one (type I) or both (type II) and strands of DNA, and a number of clinical anticancer drugs are thought to act by inhibiting religation of these transient breaks. Topoisomerase II appears to have a close association with the SMC (stable maintenance of chromosomes) family of proteins involved in organisation of the chromatin in a series of loops on the proteinaceous chromosomal scaffold. Inhibition of topoisomerase II function can result in deletions of such loops, probably mediated by reciprocal exchange of topoisomerase subunits. Disruption of topoisomerase I and/or II function during DNA replication results in smaller DNA deletions and other mutations, probably arising from non-homologous recombination. Inhibition of topoisomerase II action during mitosis and meiosis can cause incomplete separation of chromatids and chromosomes, with the consequent production of genomic mutations. Topoisomerase-mediated mutagenicity is important because it can lead not only to drug resistance but also to drug-induced secondary cancers. Mutagenicity of topoisomerase-directed agents has been underestimated in the past, since these drugs are not usually capable of reacting covalently with DNA and usually have low mutagenicity in microbial assays.

Induction of resistance to 6-thioguanine and cytarabine by a range of anticancer drugs in Chinese hamster AA8 cells.

A mutagenicity assay using AA8 Chinese hamster cells has been used to explore the potential of some currently used clinical anticancer drugs to induce cells resistant to 6-thioguanine and cytarabine. Preliminary experiments gave evidence of a "low dose" and "high dose" resistance to cytarabine, and subsequent work considered only the latter of these events. When ethyl methane sulphonate was used as a reference mutagen, induced resistance to cytarabine developed substantially later and at a lower frequency than resistance to 6-thioguanine. Of the clinical drugs tested, carmustine showed the highest ability to induce either 6-thioguanine or cytarabine resistant cells. Bleomycin, daunomycin and amsacrine showed moderate ability, while vincristine was essentially inactive in these assays. Such information could potentially be used in selecting new drug combinations or timing of drug administration in cancer chemotherapy.

Protection by inhibitors of multidrug resistance against mitochondrial mutagenesis in Saccharomyces cerevisiae.

A number of inhibitors thought to act on the drug efflux mechanism of multidrug-resistant cells have been tested for their ability to inhibit the induction of respiration-deficient (petite) colonies of the yeast Saccharomyces cerevisiae by mitochondrial mutagens. The mutagens tested were 3,6-diamino-9-(4-[(methylsulphonyl)aminophenyl]amino) acridine (an antitumour compound related to both amsacrine and proflavine), ethidium bromide, quinolinium dibromide (NSC 176319, a non-intercalative DNA binding antileukaemia agent) and rhodamine 123. The inhibitors tested included verapamil, perhexiline, chlorpromazine, trifluoperazine, reserpine, chloroquine, quinacrine, tamoxifen, clomiphene, cyclosporin A, valinomycin, amphotericin B and Tween 80. Several of these agents protected against mitochondrial mutagenesis, the most active being verapamil, reserpine, chloroquine, cyclosporin A and Tween 80. The correspondence between activity against multidrug resistance and activity in the yeast system strongly implies some degree of similarity in mechanisms for drug efflux from multidrug-resistant cells and drug uptake into the mitochondria of yeast. Agents protecting against the uptake of drugs into mitochondria of mammalian cells may have use in minimizing the long-term toxicity of anticancer drugs mediated by mitochondrial drug retention.

Genetic toxicology of tricyclic carboxamides, a new class of DNA binding antitumour agent.

(N-[2-(Dimethylamino)ethyl]acridine-4-carboxamide (acridine carboxamide; NSC 601316) is an acridine-derived experimental antitumour agent with curative properties against Lewis lung carcinoma in mice. Although it intercalates into DNA and also appears to interact with topoisomerase II, its DNA binding properties appear distinct from other acridine derivatives such as the clinical antitumour drug, amsacrine. The mutagenic properties of acridine carboxamide, together with three related compounds containing either 9-aminoacridine or phenazine chromophores, were studied at the 6-thioguanine and ouabain loci in cultured V79 Chinese hamster fibroblasts. Each compound, when tested at concentrations causing up to 90% kill, had weak but significant activity at the 6-thioguanine but not at the ouabain locus. All drugs were potent inducers of micronuclei, indicating high clastogenic activity. There was a highly significant relationship between mutation frequency (as resistance to 6-thioguanine) and either cytotoxicity (measured as D37 in a clastogenicity assay) or clastogenicity. A broader range of compounds was also tested for microbial mutagenicity. In Salmonella typhimurium strains, none were mutagenic in TA98, TA100 or TA102 but several were mutagenic in TA1537, a frameshift tester strain. Some drugs also caused 'petite' mutagenesis in Saccharomyces cerevisiae. In general, compounds with the phenazine chromophore, which has no positive charge, were the most mutagenic in these systems. However, activity was not related to mammalian mutagenicity or antitumour effect. The results suggest that in mammalian cells, the cytotoxicity, clastogenicity and mutagenic activity of these drugs are mediated by similar mechanisms to those for amsacrine analogues, probably involving the enzyme DNA topoisomerase II.

Potential antitumor agents. 33. Quantitative structure--activity relationships for mutagenic activity and antitumor activity of substituted 4'-(9-acridinylamino)methanesulfonanilide derivatives.

A series of substituted 4'-(9-acridinylamino)methanesulfonanilide (AMSA) derivatives have been tested for mutagenicity using Salmonella typhimurium strain TA 1537 and for antitumor activity against the L1210 leukemia in mice. Two measures of mutagenic activity were determined and quantitative structure--activity relationships (QSAR) developed for them. M50, the percentage of drug-induced mutant colonies observed at the concentration providing 50% inhibition of bacterial growth, is a measure of mutagenic efficiency. The lowest molar drug concentration (1/C) needed to induce a fixed proportion of revertants (chosen as 50 per 10(8) bacteria) is a measure of mutagenic effectiveness. The two measures of antitumor activity modeled were ILSmax (the percent increase in life span observed for each derivative at its LD10 dose), a measure of tumor cell selectivity, and 1/D40 (the dose of drug to provide an ILS of 40%), a measure of dose potency. These measures of bioactivity were intercompared and modeled in terms of a number of drug physicochemical properties. The results show that drug lipophilic/hydrophilic balance is the dominant factor in determining both mutagenic and antitumor activity, although other factors are involved. The two different types of activity can be readily separated in the AMSA drug series by appropriate choice of substituent and adjustment of overall drug lipophilic/hydrophilic balance.

Topoisomerase II enzymes and mutagenicity.

Topoisomerase II (topo II) enzymes maintain DNA structure by relieving torsional stress occurring in double-strand DNA during transcription and replication. Topo II causes transient breaks in both strands of DNA, allowing passage of one double helix through another, and probably acts as a structural protein in interphase cells, playing a role in the organisation of mitotic and meiotic chromosomes. A number of clinical anticancer drugs are thought to act on topo II enzymes to stabilise DNA-drug-topo II ternary complexes known as "cleavable complexes." These complexes may lead to illegitimate recombination events, as well as to the formation of other DNA lesions. Topo II-mediated genotoxicity is strongly dependent on the cell cycle status of the target cells. It is now apparent that some dietary components and environmental chemicals may act on topo II. Since the structural features of chemicals that lead to topo II interaction are not clear, it is currently not possible to predict such activity from chemical structure. For many years, the central dogma of chemical carcinogenesis has been that the most carcinogenic chemicals are those that can form a covalent bond with DNA, either directly or after metabolic activation. Topo II-directed drugs are not usually capable of forming covalent bonds with DNA and tend to have low mutagenicity in microbial assays. However, topo II-directed agents are potent cancerogens, inducing characteristic cytogenetic modifications. It is important to define the most sensitive tests to identify topo II-directed mutagens and to develop appropriate strategies for genotoxicity testing of such chemicals.

Meiotic recombination and germ cell aneuploidy.

Data on human trisomic conceptuses suggest that the extra chromosome commonly has a maternal origin, and the amount and position of crossing-over on nondisjoined chromosomes is commonly altered. These observations may provide important clues to the etiology of human germ cell aneuploidy, especially in regard to evaluating whether environmental factors play a role. There is concordance of effects of environmental agents on fungi, plants, and animals, which suggests that the overall process of meiosis is well conserved and that chemical and physical agents can affect meiotic recombination, leading to aneuploidy. It seems likely that meiosis in humans will fit the general pattern of meiosis in terms of sensitivity to radiation and chemicals. Thus studies on other organisms provide some insight into the procedures necessary for obtaining useful human data. For example, frequencies of spontaneous meiotic recombination are not uniform per physical length in Drosophila, and different regions of a chromosome respond differently to treatment. Treatments that relieve constraints on the distribution of meiotic exchange, without changing greatly the overall frequency of exchange, may increase the number of univalents and give the impression that there are chromosome-specific responses. Recombination studies that monitor one or a few relatively short genetic regions may also give a false impression of the effects of a treatment on recombination. In addition, meiotic mutants in Saccharomyces and Drosophila highlight a number of processes that are important for production of an exchange event and the utility of that event in the proper segregation of both homologues and sisters. They also suggest that tests for pairing at pachytene, chiasmata at diplotene, and genetic crossing-over may give different results.