Effects of maternal exposure to cow's milk high or low in isoflavones on carcinogen-induced mammary tumorigenesis among rat offspring

We investigated whether maternal exposure during pregnancy to cow's milk containing endogenous estrogens and insulin-like growth factor 1 (IGF-1) and either high or low levels of isoflavones from dietary legumes (HIM and LIM, respectively) affected carcinogen-induced mammary carcinogenesis in female rat offspring. Pregnant Sprague-Dawley rats were given HIM, LIM, or tap water (control) from gestational day (GD) 11 until birth; hereafter all rats received tap water. Mammary tumorigenesis was induced by administrating 7,12-dimethylbenz[a]anthracene (DMBA) on postnatal day 50. No differences in maternal serum estradiol (P = 0.19) and IGF-1 levels (P = 0.15) at GD 19 or birth weight among the milk and water groups were seen, but estradiol, and IGF-1 levels and birth weight were numerically higher in the LIM group than in the HIM group. Puberty onset occurred earlier in the LIM offspring than in controls (P = 0.03). Although the high isoflavone content seemed to prevent the effect on circulating estradiol and IGF-1 levels and advanced puberty onset seen in the LIM group, HIM increased DMBA-DNA adducts in the mammary gland and tended to increase mammary tumorigenesis. In contrast, offspring exposed to LIM in utero, did not exhibit increased breast cancer risk, despite having higher estradiol and IGF-1 environment and consequently earlier puberty onset. These results indicate that the phytochemical content in the cow's milk, consumed by a pregnant dam, determines how milk affects the offspring.     

Variation in PAH‐related DNA adduct levels among non‐smokers: The role of multiple genetic polymorphisms and nucleotide excision repair phenotype

Polycyclic aromatic hydrocarbons (PAHs) likely play a role in many cancers even in never‐smokers. We tried to find a model to explain the relationship between variation in PAH‐related DNA adduct levels among people with similar exposures, multiple genetic polymorphisms in genes related to metabolic and repair pathways, and nucleotide excision repair (NER) capacity. In 111 randomly selected female never‐smokers from the Golestan Cohort Study in Iran, we evaluated 21 SNPs in 14 genes related to xenobiotic metabolism and 12 SNPs in eight DNA repair genes. NER capacity was evaluated by a modified comet assay, and aromatic DNA adduct levels were measured in blood by 32 P‐postlabeling. Multivariable regression models were compared by Akaike's information criterion (AIC). Aromatic DNA adduct levels ranged between 1.7 and 18.6 per 10⁸ nucleotides (mean: 5.8 ± 3.1). DNA adduct level was significantly lower in homozygotes for NAT2 slow alleles and ERCC5 non‐risk‐allele genotype, and was higher in the MPO homozygote risk‐allele genotype. The sum of risk alleles in these genes significantly correlated with the log‐adduct level (r = 0.4, p < 0.001). Compared with the environmental model, adding Phase I SNPs and NER capacity provided the best fit, and could explain 17% more of the variation in adduct levels. NER capacity was affected by polymorphisms in the MTHFR and ERCC1 genes. Female non‐smokers in this population had PAH‐related DNA adduct levels three to four times higher than smokers and occupationally‐exposed groups in previous studies, with large inter‐individual variation which could best be explained by a combination of Phase I genes and NER capacity.     

Synthetic somatostatin analog (octreotide) suppresses daytime growth hormone secretion equivalently in young and older men: preserved pituitary responsiveness to somatostatin's inhibition in aging

OBJECTIVE: To gain greater insight into the mechanisms controlling the low daytime rate of growth hormone (GH) secretion in older men. DESIGN: We conducted a randomized, controlled study of GH secretion during inhibition by octreotide, a somatostatin analog. PARTICIPANTS: Nine young (35-44 years) and ten older (62-79 years) healthy men participated. INTERVENTION: Octreotide versus nothing, while subjects were on a standardized diet. MEASUREMENTS: All subjects were assessed on two separate occasions: baseline and at time of the intervention of octreotide (100 microg subcutaneously); the order of the intervention was randomly assigned. Octreotide was administered at 8:00 a.m. Venous sampling was performed every 10 minutes for 8 hours (8:30 a.m. to 4:30 p.m.). To estimate the joint parameters of pulsatile and basal (between secretory pulses) GH secretion, we used an ultrasensitive chemiluminescence-based GH assay and multiparameter deconvolution analysis. RESULTS: Compared with baseline, octreotide markedly reduced mean (8-hour) serum GH concentrations in both young (0.585+/-0.255 microg/L vs 0.070+/-0.029 microg/L; P = .008) and older (0.397+/-0.107 microg/L vs 0.087+/-0.027 microg/L; P = 0.005) men. In younger men, octreotide decreased the serum GH concentration primarily by suppressing the mass of GH released per secretory pulse (2.4+/-0.9 microg/L vs 1.0+/-.7 microg/L; P = .015) and the interpulse (basal) rate of GH release (0.0014+/-0.0003 microg/L/min vs 0.0006+/-0.0002 microg/L/min; P = .051). In older men, octreotide also restrained the mass of GH per secretory pulse (1.5+/-0.4 microg/L vs 0.4+/-0.1 microg/L; P = .028) and lowered basal GH release (0.0014+/-0.0003 microg/L/min vs 0.0004+/-0.0001 microg/L/min; P = .007). There were no significant differences when the older men were compared with the young controls. CONCLUSIONS: Our data suggest that the daytime relative GH deficiency seen in older men is not a result of excessive pituitary susceptibility to the inhibitory capabilities of somatostatin, but more likely reflects impoverished endogenous GHRH drive and/or heightened release of brain somatostatin.     

Unequal impact of short-term testosterone repletion on the somatotropic axis of young and older men

The present clinical study compares the impact of low- and high-dose parenteral testosterone (T) supplementation on daily GH secretory patterns and serum IGF-I, IGFBP-1, and IGFBP-3 concentrations in healthy older (60-82 yr) and young (20-40 yr) men. To this end, we administered three consecutive weekly injections of randomly ordered saline and either a low (100 mg) or a high (200 mg) dose of testosterone enanthate im; namely, saline (n = 17, young and n = 16, older), a low dose (n = 8 young, n = 8 older) and a high dose (n = 9 young, and n = 8 older) of androgen. To monitor somatotropic-axis responses, blood was sampled every 10 min for 24 h for later chemiluminescence-based assay of serum GH, RIA of serum IGF-I, and immunoradiometric assay of serum IGFBP-1 and IGFBP-3 concentrations. Data were analyzed via a nested analysis of covariance statistical design. At baseline (saline injection), older, compared with young, men maintained: 1) similar serum total T, IGFBP-1, and IGFBP-3 but reduced IGF-I concentrations, namely, mean (+/- SEM) IGF-I 160 plus or minus 15 vs. 280 plus or minus 18 microg/liter, (P < 0.001); 2) reduced GH secretory burst mass (0.68 +/- 0.09 vs. 1.2 +/- 0.20 microg/liter, P = 0.031); 3) more disorderly GH release patterns (approximate entropy 0.501 +/- 0.058 vs. 0.288 +/- 0.021, P < 0.001); and 4) blunted 24-h rhythmic GH output (nyctohemeral amplitude 0.25 +/- 0.05 vs. 0.47 +/- 0.08 microg/liter, P = 0.025). Serum T concentrations (ng/dl) did not differ in the two age groups supplemented with either a low dose [550 +/- 50 (young) and 544 +/- 128 (older)] and high [1320 +/- 92 (young) and 1570 +/- 140 (older)] dose of T. The 100-mg dose of androgen exerted no detectable effect on GH secretion in either age cohort but increased the serum IGF-I concentration in young men by 20% (P = 0.00098). The 200-mg dose of T failed to alter daily GH production in young volunteers but in older men stimulated: 1) a 2.03-fold rise in the mean (24-h) serum GH concentration (P = 0.0053, compared with the response to saline); 2) a 1.20-fold increase in basal (nonpulsatile) GH production (P = 0.039); 3) a 2.15-fold amplification of GH secretory burst mass (P = 0.0020); 4) a 2.17-fold elevation of the Mesor of nyctohemeral GH output (P = 0.025); 5) a 1.79-fold enhancement in GH approximate entropy (P = 0.0003); and 6) a 40% increase in the fasting serum IGF-I concentration (P = 0.000005). Multivariate statistical analysis indicated that following high-dose T administration, the E2 increment significantly predicted the IGF-I increment in both age groups combined (P = 0.003); T dose positively forecast the serum total IGF-I concentration (P = 0.0031); and age and T dose jointly determined serum LH concentrations (P = 0.031). In summary, neither a physiological nor a pharmacological dose of T administered parenterally for 3 wk augments daily GH secretion in eugonadal young men. In contrast, a high dose of aromatizable androgen significantly amplifies 24-h basal, pulsatile, entropic, and nyctohemerally rhythmic GH production and elevates the serum IGF-I concentration in older men. The mechanistic basis for the foregoing age-related distinction in GH/IGF-I axis responsivity to T is not known.     

Changes in the compound action current amplitudes in relation to the conduction velocity and functional recovery in the reconstructed peripheral nerve.

The average axon diameter in the proximal segment of a transected and reconstructed peripheral nerve will decrease shortly after the transection and increase again when the regenerating axons make contact with their targets. The magnetically recorded nerve compound action current (NCAC) amplitude and the conduction velocity (CV) are directly related to the axon diameters. In this experiment, the peroneal nerve was unilaterally transected and reconstructed in 42 rabbits. After 3, 4.5, 6, 8, 12, 20, and 36 weeks of regeneration time, hind leg motor function recovery, NCAC amplitude, and CV(1st peak) were studied. Our results demonstrate a significant decrease in signal amplitude and CV in the first 8 weeks after reconstruction. These decreases are related (P < 0.05). After 8 weeks of regeneration time, motor function and the CV of the recorded signals start to recover, but the signal amplitudes do not. Based on the correlation of the CV and signal amplitude with axon diameter, they would both be expected to increase with recovering function. As an explanation for this lack of increase of signal amplitude, we suggest that, at the same time as some axons reach their target organs and start to mature, a number of the axons which have not reached a proper target organ will lose their signal-conducting capability. This will cause a decrease in compound signal amplitude, which cancels out the expected increase in NCAC amplitude, due to axonal maturation.     

The effect of intrahypothalamic administration of sodium pentobarbital on eating behaviour and feed intake in chickens

Injection of sodium pentobarbital solutions were carried out in chickens, through permanently implanted cannulas in the brain. Chickens with cannulas implanted in the third ventricle, above the hypothalamic ventromedial area, responded with immediate increase in feed intake and vigorous pecking behaviour which lasted from 10–60 min. Chickens with cannulas implanted in the posterior lateral hypothalamus showed no changes in their feed intake or eating behaviour after sodium pentobarbital injection. The results with chickens correspond to those obtained with rats, cats and dogs.     

Impact of multiple genetic polymorphisms on effects of a 4-week blueberry juice intervention on ex vivo induced lymphocytic DNA damage in human volunteers

Consumption of fruits and vegetables has been associated with a decrease in cancer incidence and cardiovascular disease, presumably caused by antioxidants. We designed a human intervention study to assess antioxidative and possible anti-genotoxic properties of fruit-borne antioxidants. We hypothesized that individuals bearing genetic polymorphisms for genes related to quercetin metabolism, benzo[a]pyrene metabolism, oxidative stress and DNA repair differ in their response to DNA protective effects of increased antioxidant intake. In the present study, 168 healthy volunteers consumed a blueberry/apple juice that provided 97 mg quercetin and 16 mg ascorbic acid a day. After a 4-week intervention period, plasma concentrations of quercetin and ascorbic acid and trolox equivalent antioxidant capacity (TEAC) were significantly increased. Further, we found 20% protection (P < 0.01) against ex vivo H(2)O(2)-provoked oxidative DNA damage, measured by comet assay. However, the level of ex vivo induced benzo[a]pyrene-diol-epoxide (BPDE)-DNA adducts was 28% increased upon intervention (P < 0.01). Statistical analysis of 34 biologically relevant genetic polymorphisms revealed that six significantly influenced the outcome of the intervention. Lymphocytes from individuals bearing variant genotype for Cyp1B1 5 seemed to benefit more than wild-types from DNA damage-protecting effects upon intervention. Variants for COMT tended to benefit less or even experienced detrimental effects from intervention. With respect to GSTT1, the effect is ambiguous; variants respond better in terms of intervention-related increase in TEAC, but wild-types benefit more from its protecting effects against oxidative DNA damage. We conclude that genotyping for relevant polymorphisms enables selecting subgroups among the general population that benefit more of DNA damage-modulating effects of micronutrients.     

New methods for assessing male germ line mutations in humans and genetic risks in their offspring

Germ line mutations resulting from chemical or radiation exposure are a particular problem in toxicology as they affect not only the exposed generation but also an infinite number of generations thereafter. Established methods to show that these mutations occur in an F1 or subsequent population require the use of a large number of progeny for statistical significance. Consequently, many thousands of animals have been used in the past. Such a use is no longer considered desirable and is also very expensive. Several new molecular techniques (including analysis of tandem repeats and randomly amplified polymorphic DNA) now provide alternative methods of assessment, which also allow the quantification of individual mutations in individual sperm cells. These can also be applied to human offspring, making extrapolation obsolete. The downside of these methods is that they effectively determine the mutation rate in certain regions of DNA and the relevance of these to diseases, particularly cancer, is not always apparent. Therefore, it must be assumed that an increase in mutation rates in these selected regions correlates with altered phenotype. However, disease types linked to changes in tandem repeat length indicate that these may act as relevant markers for the development of phenotypes. Further research and evaluation are required to more closely link changes in DNA with altered phenotype and validate the use of tandem repeats and randomly amplified polymorphic DNA in transgenerational genotoxicity testing. This paper introduces and compares recently developed methods to assess mutations in sperm due to stem cell damage.