Formation and persistence of O6-(2-hydroxyethyl)-2′-deoxyguanosine in DNA of various rat tissues following a single dose of N-nitroso-N-(2-hydroxyethyl)urea. An immuno-slot-blot study

Rabbit antibodies against O6-(2-hydroxyethyl)-2′-deoxyguanosine (O6-HEdG) were used to develop a highly sensitive immuno-slot-blot assay for this promutagenic base which enabled the quantitation of ≥ 3.6 μmol O6-HEdG/mol deoxy-guanosine, corresponding to ≥ 5 fmol in a 3-μg DNA sample. This assay was used to study DNA hydroxyethylation by N-nitroso-N-(2-hydroxyethyl)urea (HENU) in adult male F344 rats. Initial amounts of O6-HEdG 2 h after a single i.v. dose of 50 mg/kg were highest in kidney (81 μmol O6HEdG/mol deoxyguanosine), followed by lung and liver (67 and 55 μmol/mol dG respectively). Formation of O6-HEdG in cerebral DNA was considerably lower (18 μmol O6-HEdG/mol deoxyguanosine), probably reflecting delayed crossing of the blood—brain barrier by HENU due to its hydrophilicity. The formation of O6-HEdG in liver and kidney was strictly proportional to dose over a range of 5-50 mg HENU/kg. Repair of O6-HEdG was very rapid in liver (apparent half-life, 12 h), and somewhat slower in kidney and lung (approximate half-life, 40 h and 48 h respectively). In contrast, 62% of the initial amount of O6-HEdG in cerebral DNA was still present after 7 days. Saturation of the hepatic O6-alkyl-guanine-DNA alkyltransferase by pretreatment with N-nitrosodimethylamine (20 mg/kg) almost completely inhibited the removal of O6-HEdG, indicating that O6-HEdG is predominantly repaired by this repair enzym

p53 mutations in phenacetin-associated human urothelial carcinomas

Chronic abuse of the analgesic drug phenacetin is associated with an increased risk of development of transitional cell carcinomas of the urinary tract. It is unclear whether phenacetin acts through chronic tissue damage (phenacetin nephropathy) or via a genotoxic metabolite causing promutagenic DNA lesions. In the present study, we investigated 15 urothelial carcinomas from 13 patients with evidence of phenacetin abuse. Tumors were screened for p53 mutations in exons 5-8 by single-strand conformation polymorphism (SSCP) analysis, followed by direct sequencing of PCR-amplified DNA. p53 Mutations were detected in 8/14 primary tumors (57%). All except one were missense mutations located in exon 5 (three mutations), exon 6 (one), exon 7 (two) and exon 8 (one). The type of mutation varied, with a preference for CpG sites. A frameshift mutation resulting from the insertion of a single cytosine at codons 151/152 was detected in a bladder tumor and its lung metastasis. Urothelial carcinomas located in the renal pelvis and in the ureter of the same patient exhibited two different mutations, strongly suggesting that they developed independently. Another patient had tumors in the renal pelvis and bladder, both of which contained the same p53 mutation, indicating intracavitary metastatic spread. This demonstrates that screening of p53 mutations allows the clonal origin of tumors in patients with multiple primary and metastatic lesions to be determined. None of the tumors investigated contained mutations in codons 12, 13 or 61 of H-ras or K-ras protooncogene

Genetic amplification and the individuation of the parent-child relationship across adolescence

BACKGROUND: Many psychological traits become increasingly influenced by genetic factors throughout development, including several which might intuitively be seen as purely environmental characteristics. One such trait is the parent-child relationship, which is associated with a variety of socially significant outcomes, including mental health and criminal behavior. Genetic factors have been shown to partially underlie some of these associations, but the changing role of genetic influence over time remains poorly understood. METHOD: Over 1,000 participants in a longitudinal twin study were assessed at three points across adolescence with a self-report measure regarding the levels of warmth and conflict in their relationships with their parents. These reports were analyzed with a biometric growth curve model to identify changes in genetic and environmental influences over time. RESULTS: Genetic influence on the child-reported relationship with parent increased throughout adolescence, while the relationship’s quality deteriorated. The increase in genetic influence resulted primarily from a positive relation between genetic factors responsible for the initial relationship and those involved in change in the relationship over time. In contrast, environmental factors relating to change were negatively related to those involved in the initial relationship. CONCLUSIONS: The increasing genetic influence appears due to early genetic influences having greater freedom of expression over time, while environmental circumstances were decreasingly important to variance in the parent-child relationship. We infer that the parent-child relationship may become increasingly influenced by the particular characteristics of the child (many of which are genetically-influenced), gradually displacing the effects of parental or societal ideas of child-rearing

Modulation of N-nitrosomethylbenzylamine bioactivation by diallyl sulfide in vivo

Diallyl sulfide (DAS), a major component of garlic oil, is an inhibitor of tumorigenesis by various metabolcally activated carcinogens. In rats, pretreatment with DAS has been observed to suppress completely the induction of oesophageal neoplasms by N-nitrosomethylbenzylamine (NMBzA) (Wargovich et al. (1988) Cancer Res., 48, 6872-6875). This communication reports the effects of DAS on overall NMBzA metabolism and on DNA methylation of NMBzA in vivo under conditions equivalent to a single treatment of the chemoprevention assay. Male Fischer 344 rats received a single i.g. dose of DAS (200 mg/kg body wt) followed by an s.c. injection of [methyl-14C]NMBzA (3.5 mg/kg). In controls, exhalation of 14CO2 was complete within 5 h (t½max = 1.2 h). with 50% of the injected radioactivity recovered as 14CO2. When DAS was given 3 h prior to [methyl-14C]NMBzA, 49% of the injected radioactivity was released within 10 h (t½max = 3 h). When DAS was administered 18 h before the carcinogen, 42% of [methyl-14C]NMBzA was converted to 14CO2, with exhalation complete after 6 h (t½max = 1.8 h). We further examined the effects of acute doses of 10—200 mg/kg of DAS on DNA methylation by a single dose of NMBzA (3.5 mg/kg; survival time, 6 h) administered 3 h later. At 200 mg/kg, DAS inhibited the formation of O6-methyldeoxyguanosine (O6-MEdG) in oesophagus (−26%), nasal mucosa (−51%), trachea (−68%) and lung (−78%). In liver, levels of 7-MEdG were reduced by 43%. Decreases in DNA methylation were proportional to dose for >25 mg/kg of DAS in oesophagus, liver and nasal mucosa, for 25—200 mg/kg in trachea and 10—50 mg/kg in lung. The dose—activity relationship for inhibition by DAS of DNA methylation by NMBzA suggests that short-term modulation of carcinogen bioactivation in situ contributes to but may not be sufficient for the chemoprevention of nitrosamine tumorigenesis by DAS. Diallyl sulfide (DAS), a major component of garlic oil, is an inhibitor of tumorigenesis by various metabolcally activated carcinogens. In rats, pretreatment with DAS has been observed to suppress completely the induction of oesophageal neoplasms by N-nitrosomethylbenzylamine (NMBzA) (Wargovich et al. (1988) Cancer Res., 48, 6872-6875). This communication reports the effects of DAS on overall NMBzA metabolism and on DNA methylation of NMBzA in vivo under conditions equivalent to a single treatment of the chemoprevention assay. Male Fischer 344 rats received a single i.g. dose of DAS (200 mg/kg body wt) followed by an s.c. injection of [methyl-14C]NMBzA (3.5 mg/kg). In controls, exhalation of 14CO2 was complete within 5 h (t½max = 1.2 h). with 50% of the injected radioactivity recovered as 14CO2. When DAS was given 3 h prior to [methyl-14C]NMBzA, 49% of the injected radioactivity was released within 10 h (t½max = 3 h). When DAS was administered 18 h before the carcinogen, 42% of [methyl-14C]NMBzA was converted to 14CO2, with exhalation complete after 6 h (t½max = 1.8 h). We further examined the effects of acute doses of 10—200 mg/kg of DAS on DNA methylation by a single dose of NMBzA (3.5 mg/kg; survival time, 6 h) administered 3 h later. At 200 mg/kg, DAS inhibited the formation of O6-methyldeoxyguanosine (O6-MEdG) in oesophagus (−26%), nasal mucosa (−51%), trachea (−68%) and lung (−78%). In liver, levels of 7-MEdG were reduced by 43%. Decreases in DNA methylation were proportional to dose for >25 mg/kg of DAS in oesophagus, liver and nasal mucosa, for 25—200 mg/kg in trachea and 10—50 mg/kg in lung. The dose—activity relationship for inhibition by DAS of DNA methylation by NMBzA suggests that short-term modulation of carcinogen bioactivation in situ contributes to but may not be sufficient for the chemoprevention of nitrosamine tumorigenesis by DA

Bioactivation of N-nitrosomethylbenzylamine and N-nitrosomethyl-amylamine in oesophageal papillomas

Oesophageal papillomas were induced in male F344 rats by continuous exposure to N-nitrosomethylbeazylamine (NMBZA) and N-nitrosomethyl(2-methylbutyl)ainine in the drinking water at concentrations of 10 and 19.5 p.p.m. respectively. After 81-141 days animals received a single i.p. chasing dose of NMIBZA (0.1 mmol/kg), [14C-methyl]NMBZA or N-nitroso[14C-methyl]amylamine and were killed 6 h later. Induced papillomas (3-9 per animal) were analysed by autoradlography and by immunohistochemistry using a polyclonal antibody to O6-methyldeoxyguanosine Both techniques revealed the presence of high levels of alkylation products in all papillomas investigated. Immunohistochemical staining of O6-methyldeoxyguanosine was largely restricted to nudei of the basal layer and of epithelial cells with incipient keratinization. These findings demonstrate that NMBZA and N-nitrosomethylamylamine and probably related methyl alkylnitrosamines are effectively bioactivated in premalignant lesions, indicating that during chronic exposure papifiomas can acquire additional mutations that are likely to play a major role in tumour progressio

Randomised controlled trial of integrated care to reduce disability from chronic low back pain in working and private life

Objective To evaluate the effectiveness of an integrated care programme, combining a patient directed and a workplace directed intervention, for patients with chronic low back pain

Electronic Band Structure of the Two-Dimensional Surface-State Bands of the (1×1) and (1×2) Phases of Bi/GaSb(110)

The surface-state bands of the (1×1) and (1×2) phases of Bi/GaSb(110) have been probed using angle-resolved ultraviolet photoemission spectroscopy with synchrotron radiation. Four Bi-induced surface-state bands have been identified for both the (1×1) and the (1×2) phases. The bands with the lowest binding energies (SI and SII) have been attributed to intrachain bonding in the Bi overlayer and the higher-binding-energy bands (SIII and SIV) to overlayer states involved in the back bonding of the overlayer to the substrate. Based on initial-state dispersion measurements, we conclude that the Bi chains in the epitaxial overlayer remain intact throughout the phase transition. We propose a model for the overlayer structure of the (1×2) phase of Bi/GaSb(110)

A theoretical analysis of Ballistic Electron Emission Microscopy: k-space distributions and spectroscopy

We analyze BEEM experiments. At low temperatures and low voltages, near the threshold value of the Schottky barrier, the BEEM current is dominated by the elastic component. Elastic scattering by the lattice results in the formation of focused beams and narrow lines in real space. To obtain the current injected in the semiconductor, we compute the current distribution in reciprocal space and, assuming energy and $k_{\parallel}$ conservation. Our results show an important focalization of the injected electron beam and explain the similarity between BEEM currents for Au/Si(111) and Au/Si(100).Comment: 17 pages, 5 figures (postscript), Latex, APS, http://www.icmm.csic.es/Pandres/pedro.htm. Appl. Surf. Sci. (in press