Tamoxifen increases the risk of human endometrial cancer and is a potent
carcinogen in rat liver, in which it produces DNA adducts and cytogenetic
damage. Nevertheless its prophylactic use against breast cancer in healthy
women is under investigation in several large trials. To investigate
whether rat hepatocarcinogenicity predicts human hepatocarcinogenicity we
used genetically engineered bacterial and mammalian target cells to
investigate how alpha-hydroxy-tamoxifen, a major phase I metabolite of
tamoxifen, is further metabolised by rat and human phase II enzymes,
sulfotransferases, to mutagenic and DNA- adduct-forming species. We
expressed rat hydroxysteroid sulfotransferase a, a liver-specific enzyme,
and corresponding human sulfotransferase in bacteria (Salmonella
typhimurium) and in a mammalian cell line (Chinese hamster V79 cells) and
tested alpha- hydroxytamoxifen for DNA adduct formation and mutagenicity in
these systems, using unmodified cells as controls. In cells that expressed
rat hydroxysteroid sulfotransferase, alpha-hydroxytamoxifen was mutagenic
and formed the same pattern of DNA adducts as that found in the liver of
tamoxifen-treated rats. Alpha-hydroxytamoxifen was not activated, or was at
least 20 times less active in cells expressing human hydroxysteroid
sulfotransferase. All the other six known human xenobiotic-metabolising
sulfotransferases were also expressed in S. typhimurium. None activated
alpha-hydroxytamoxifen to a mutagen. These results suggest that the risk of
DNA adduct formation, and cancer, in the human liver is low and explain why
tamoxifen is a powerful carcinogen to the rat liver, and why standard
short-term tests fail to detect its mutagenicity.
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Relationships between smoking status and levels of bulky DNA adducts were
investigated in bronchial tissue of lung patients in relation to their
GSTM1 and CYP1A1 MspI genotypes. A total of 150 Hungarian patients
undergoing pulmonary surgery were included in the study, 124 with lung
malignancies and 26 with non-malignant lung conditions. There were
significant relationships between smoking status and bulky DNA adduct
levels, as determined by 32P-post-labelling analysis, in macroscopically
normal bronchial tissues. There was a highly significant difference in the
adduct levels of a combined group consisting of current smokers and
short-term ex-smokers (< or = 1 year abstinence) compared with life-time
non-smokers and long-term ex- smokers (> 1 year abstinence) (P =
0.0001). The apparent half-life was estimated to be 1.7 years for bulky DNA
adducts in the bronchial tissue from ex-smokers. There were no
statistically significant correlations between (i) daily cigarette dose and
DNA adduct levels in current smokers, (ii) DNA adduct level and
histological type of lung cancer, or (iii) GSTM1 and CYP1A1 MspI genotypes
and DNA adduct levels after adjustment for either smoking status or
malignancy. By multiple logistic regression analysis, smoking and GSTM1
null genotype were found to be risk factors for squamous cell carcinoma.
However, bulky DNA adduct levels in bronchial tissue did not appear to be a
statistically-significant risk factor for the major histological types of
lung cancer.
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Metaphyseal growth arrest lines are seen in children who experience significant physical stress such as infection or malnutrition over a sufficient period of time. These lines have not been reported previously in children with psychosocial short stature (PSS). Two boys and a girl with PSS with metaphyseal growth arrest lines on skeletal radiographs at the time of maximal stress in their homes are described. All three had reversible growth hormone insufficiency during admission, which is pathognomic for PSS. Multiple growth arrest lines in the distal end of the radius or vertebrae should alert clinicians to an alternative diagnosis in a child with growth hormone insufficiency. This may provide a clue to the diagnosis of occult PSS. 相似文献
Although intravenous dexamethasone prolongs the analgesic duration of interscalene brachial plexus block, it is uncertain whether this effect can be observed using lower doses of dexamethasone. This study evaluated the impact of intravenous dexamethasone (4 mg and 10 mg) on the analgesic duration of single-shot interscalene block after arthroscopic shoulder surgery. We hypothesized that both doses would prolong the analgesic duration compared with placebo.
Methods
This was a prospective double-blind randomized placebo-controlled study in patients undergoing elective arthroscopic shoulder surgery under regional anesthesia with a single-shot interscalene block (0.5% ropivacaine 20 mL). Patients received dexamethasone 4 mg (D4), dexamethasone 10 mg (D10), or a placebo (normal saline [NS]) intravenously at the time of block completion. The primary outcome was the duration of analgesia, defined as the time from the onset of sensory blockade to the first analgesic request. The primary outcome was first analyzed with a Kruskal-Wallis test and then with a Mann-Whitney test for pairwise between-group comparison.
Results
Sixty-nine patients completed the study. The median [interquartile range] duration of analgesia was significantly different between the three groups (D4, 19.7 [16.9-23.3] hr; D10, 19.1 [11.5-22.8] hr; and NS, 11.8 [9.3-14.0] hr; P = 0.001). This difference was statistically significant for D4 and D10 compared with placebo (median difference [MD], 7.8 hr; 95% confidence interval [CI], 4.6 to 11.1 hr; P < 0.001; and MD, 7.4 hr; 95% CI, 4.2 to 10.5 hr; P = 0.001, respectively) but not for D4 compared with D10 (MD, 0.5 hr; 95% CI, ?2.8 to 3.7 hr; P = 0.38).
Conclusions
Low doses of intravenous dexamethasone (4 mg and 10 mg) significantly prolong the analgesic duration of interscalene block. This trial was registered at ClinicalTrials.gov (NCT02412657).
The heterogeneity and contribution of collagen and elastin to residual stresses have been thoroughly studied, but more recently, glycosaminoglycans (GAGs) also emerged as potential regulators. In this study, the opening angle of aortic rings (an indicator of circumferential residual stresses) and the mural distributions of sulfated GAGs (sGAG), collagen, and elastin were quantified in the ascending, aortic arch and descending thoracic regions of 5- to 6-month-old pigs. The opening angle correlated positively with the aortic ring’s mean radius and thickness, with good and moderate correlations respectively. The correlations between the sGAG, collagen, elastin, and collagen:sGAG ratio and the opening angle were evaluated to identify aortic compositional factors that could play roles in regulating circumferential residual stresses. The total collagen:sGAG ratio displayed the strongest correlation with the opening angle (r = ? 0.715, p < 0.001), followed by the total sGAG content which demonstrated a good correlation (r = 0.623, p < 0.001). Additionally, the intramural gradients of collagen, sGAG and collagen:sGAG correlated moderately with the opening angle. We propose that, in addition to the individual role sGAG play through their content and intramural gradient, the interaction between collagen and sGAG should be considered when evaluating circumferential residual stresses in the aorta.