The grapefruit flavanone naringin protects against the radiation-induced genomic instability in the mice bone marrow: a micronucleus study

To test the hypothesis that carcinogen exposure and oxidative stress are involved in pancreatic carcinogenesis in susceptible individuals, aromatic DNA adducts and 8-hydroxyguanosine (8-OH-dG) were measured by (32)P-postlabeling and HPLC-EC, respectively, in 31 pancreatic tumors and 13 normal tissues adjacent to the tumor from patients with pancreatic cancer. Normal pancreatic tissues from 24 organ donors, from six patients with non-pancreatic cancers, and from five patients with chronic pancreatitis served as controls. It was found that tissue samples from patients with pancreatic cancer had significantly higher levels of both aromatic DNA adducts and 8-OH-dG compared with control samples. The mean (+/-S.D.) levels of aromatic DNA adducts were 101.8+/-74.6, 26.9+/-26.6, and 11.2+/-6.6 per 10(9) nucleotides in adjacent tissues, tumors, and controls, respectively. The mean (+/-S.D.) levels of 8-OH-dG were 11.9+/-9.6, 10.8+/-10.6, and 6.7+/-4.6 per 10(5) nucleotides in adjacent tissues, tumors, and controls, respectively. Polymorphisms of the CYP1A1, CYP2E1, NAT1, NAT2, GSTM1, MnSOD, and hOGG1 genes were determined in these patients. The level of aromatic DNA adducts was significantly associated with polymorphism of the CYP1A1 gene. No significant correlation was found between the level of 8-OH-dG and the MnSOD, GSTM1, and hOGG1 polymorphisms. However, one novel polymorphism/mutation of the hOGG1 gene was found in a pancreatic tumor. Mutation at codon 12 of the K-ras gene was found in 25 (81%) of 31 pancreatic tumors, including three G-to-A transitions and 22 G-to-T transversions. Patients with the G-to-T mutation had a significantly higher level of aromatic DNA adducts than those with G-to-A or wild-type codon (P=0.02). On the other hand, the K-ras mutation profile was not related to the level of 8-OH-dG. Given the limitation of sample size, these preliminary data lend further support the hypothesis that carcinogen exposure and oxidative stress are involved in pancreatic carcinogenesis.     

Spontaneous oxidative DNA damage in bovine retained and nonretained placental membranes

Retention of fetal membranes (RFM) is believed to be associated with conditions of oxidative stress. In this study, 8-hydroxy-2'-deoxyguanosine (8-OH-dG) was used for the determination of spontaneous oxidative DNA lesions in maternal and fetal parts of bovine retained and nonretained placentas. Placental specimens were collected directly after spontaneous delivery or during cesarean section from cows divided into 6 groups: (A) cesarean section before term without RFM, (B) with RFM, (C) cesarean section at term without RFM, (D) with RFM, (E) spontaneous delivery at term without RFM and (F) with RFM. Isolated DNA was hydrolyzed and analyzed by HPLC; native nucleosides were monitored at 254 nm and 8-OH-dG by electrochemical detection. No significant differences in 8-OH-dG levels between retained and nonretained placental tissues were found in all samples from preterm groups (mean concentrations between 13 and 42 micromol/mol deoxyguanosine (dG)). In the term cesarean section group with RFM a significant increase in 8-OH-dG concentration in DNA from maternal (8-fold) and fetal (18-fold) membranes were detected when compared to the respective nonretained tissues. Also, in the term spontaneous delivery groups maternal nonretained placental tissues showed increased levels of 8-OH-dG in comparison to the respective tissues of the retained placenta group. In placental tissues oxidative DNA lesions appear to be controlled by responsive mechanisms which, possibly following exhaustion, give rise to increased 8-OH-dG levels.     

Formation of the oxidative damage marker 8-hydroxy-2'-deoxyguanosine from the nucleoside 2'-deoxyguanosine: parameter studies and evidence of Fe(II) binding

High-performance liquid chromatography (HPLC) with UV absorption detection was employed to measure the amounts of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) produced from the nucleoside 2'-deoxyguanosine (dG) under varying reaction conditions using iron and H(2)O(2). The results indicate that 8-OH-dG produced from the reaction of iron and H(2)O(2) with dG can undergo reaction with free (i.e., unchelated) Fe(III) and that adding the chelating agent ethylenediaminetetraacetic acid (EDTA) after the reaction prevents this from occurring. It also appears that the free radical species generated by iron-EDTA chelates in pH 7.4 N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) (Hepes) buffer is either not formed or unstable in unbuffered aqueous solution. Finally, 8-OH-dG levels are significantly larger when Fe(II) is allowed to bind to the nucleoside dG prior to addition of H(2)O(2). However, production of 8-OH-dG from unbound Fe(II) is also relevant. The results of this work show that differing reaction conditions in vivo, especially at the cellular level, will affect significantly the measured yields of 8-OH-dG. These results also have implications for studies involving DNA and the ability to distinguish between 8-OH-dG produced from free iron and iron bound to both phosphate groups and the DNA base guanine.     

Reversal by nickel(II) of inhibitory effects of some scavengers of active oxygen species upon hydroxylation of 2'-deoxyguanosine in vitro.

Effects of ethanol (EtOH), mannitol (Man), L-histidine (His) and glutathione (GSH) on the oxidation of 2'-deoxyguanosine (dG) to its 8-hydroxy derivative (8-OH-dG) with H2O2 plus L-ascorbic acid (Ascb) in the absence and presence of Ni(II) were investigated in order to unveil the nature of active oxygen species involved in that oxidation. In the absence of Ni(II), production of 8-OH-dG was inhibited by His much greater than GSH greater than or equal to GSSG (oxidized glutathione) much greater than EtOH, but not by Man. The latter tended to enhance the production of 8-OH-dG. In the presence of Ni(II), the inhibition by His, GSH and GSSG, but not EtOH, was prevented. The results indicate involvement of a 'crypto-hydroxyl' radical as the dG oxidizing species in both the absence and presence of Ni(II). Also, the results provide evidence that Ni(II) complexes with His, GSH and GSSG may lack antioxidant capacity. Moreover, the Ni(II) complex with His was found capable of enhancing 8-OH-dG production by the Ascb+H2O2 system to a greater extent than Ni(II) alone. Likewise, although to a lesser extent, the formation of 8-OH-dG was enhanced by the combination of Ni(II) and Man which do not form complexes at pH 7.4. Since His is a major Ni(II) carrier in animal tissues, the dG oxidation enhancing capacity of the Ni(II) complex with His may contribute to the toxic and carcinogenic effects of Ni(II).     

Lipid peroxidation products mediate the formation of 8-hydroxydeoxyguanosine in DNA.

Membrane lipid peroxidation processes yield products that may react with DNA to cause oxidative modifications. We have investigated this possibility and have found that calf thymus DNA exposed to autooxidized lipids causes the formation of 8-hydroxy-2'-deoxyguanosine (8-OH-dG). 8-OH-dG formation in DNA was measured using high-pressure liquid chromatography with electrochemical detection. Methyl linolenate oxidized for different lengths of time was exposed to DNA. The amount of 8-OH-dG formed in DNA was proportional to the amount of lipid peroxidation as measured by the thiobarbituric reactive substances present. The formation of 8-OH-dG in DNA by autooxidized methyl linolenate was dependent on the presence of the transition metal ions Cu or Fe and was inhibited by various scavengers, including superoxide dismutase and catalase. This implicates the involvement of oxygen free radicals in the process. Liposomes formed from phosphatidylcholine (82%) and methyl arachidonate (18%) were peroxidized for different lengths of time and then exposed to DNA. 8-OH-dG was formed in DNA by exposure to Cu(II) and peroxidized liposomes. Under these conditions, Fe(III) was slightly less effective than Cu(II) in mediating 8-OH-dG formation. These observations clearly show that 8-OH-dG formation in DNA may result from processes that may occur during intracellular lipid peroxidation.     

Platelet-activating factor acetylhydrolase isoforms I and II in human uterus. Comparisons with pregnant uterus and myoma

The concentrations of platelet-activating factor (PAF) that possesses the ability to stimulate myometrial contraction are partially regulated by intracellular type of platelet-activating factor acetylhydrolase (PAF-AH) in many tissues. Tissue cytosol contains at least two intracellular PAF-AH, isoforms I and II. To examine the relationship between the activity and isoforms of intracellular PAF-AH in human uterine myometrium and myoma, we assayed the PAF-AH activity and identified the PAF-AH isoforms I and II by Western blot analysis. The intense bands of the alpha2 and ss subunits of PAF-AH isoform I were detected in nonpregnant uterus; however, the specific bands of the alpha1 subunit of PAF-AH isoform I and the PAF-AH isoform II were extremely weak. The levels of the alpha2 and ss subunits and PAF-AH activity in pregnant uterus (37-39 wk gestation) were significantly lower than those in nonpregnant uterus. On the other hand, the level of ss subunit and the PAF-AH activity in myoma were significantly higher than those in nonpregnant uterus. No significant difference was found in the expression of the PAF-AH isoform II among three tissues. These results indicate that the change in the PAF-AH activity observed in pregnant uterus and myoma are due to the lower or higher protein expression of the PAF-AH isoform I, especially the alpha2 and/or ss subunits. The decrease of the uterine PAF-AH activity in the late stage of pregnancy may facilitate the action of PAF to stimulate myometrial contraction.     

Age-associated accumulation of 8-hydroxydeoxyguanosine in mitochondrial DNA of human diaphragm

This is the first report that age-associated accumulation of 8-hydroxydeoxyguanosine (8-OH-dG) does occur in human mitochondrial DNA (mtDNA) in muscle of diaphragm. We extracted mtDNA from human diaphragm muscles from differing age groups, and determined the amount of 8-OH-dG by ultramicro-high performance liquid chromatography/mass-spectrometry system. With the same specimen, multiple deletions of mtDNA were detected by electrophoresis after amplification by the polymerase chain reaction method. In subjects below age 55, the level of 8-OH-dG in mtDNA was below 0.02% of the total deoxyguanosine (dG), whereas, in subjects over age 65, the level of 8-OH-dG increased with age at a rate of ca. 0.25% per 10 years, reaching 0.51% at age 85. Moreover, a concomitant increase in multiple deletions was detected with the increase in age. These results suggest that, in younger diaphragms, replication of mtDNA dilutes out 8-OH-dG being not detectable. In the elderly subjects aged over 65, the replication rate might be slowed down leading to the accumulation of 8-OH-dG in mtDNA, which would accelerate the age-associated multiple deletions of mtDNA observed among the subjects.     

Prenatal Stress Causes Oxidative Damage to Mitochondrial DNA in Hippocampus of Offspring Rats

Mitochondrion, the primary source of reactive oxygen species (ROS), is also the target of ROS. 8-Hydroxy-2′-deoxyguanosine (8-OH-dG) is the major end-product of damaged DNA caused by ROS. In our previous studies, we showed that prenatal stress (PNS) preferentially caused cognitive dysfunction and increased ROS in the hippocampus of female offspring rats. The present study aimed to determine 8-OH-dG level of mitochondria in order to elucidate the mechanism of hippocampal pyramidal neuronal damage and cognitive dysfunction induced by PNS. Pregnant rats were divided into two groups: control group (undisturbed) and PNS group (exposed to a restraint stress for 7 days at the late stage of gestation). Offspring rats were divided into four groups: female-control group, male-control group, female-stress group, male-stress group and used at 30-day-old after their birth. The content of 8-OH-dG was determined by high performance liquid chromatography-electrochemical detection (HPLC-ECD). The results showed that the contents of 8-OH-dG in female and male prenatal stressed offspring were significantly higher than that in their respective controls (P < 0.001). 8-OH-dG level was significantly higher in the female-stress group than in the male-stress group (P < 0.05), whereas there was no any gender-dependent difference in the control groups. These results suggest that accumulation of oxidative mitochondrial DNA damage may play an important role in PNS-induced cognitive dysfunction in female offspring rats. Special issue article in honor of Dr. Akitane Mori.     

Simultaneous HPLC analysis of 8-hydroxydeoxyguanosine and 7-methylguanine in urine from humans and rodents

With a recently developed high-performance liquid chromatography (HPLC) method based on anion exchange chromatography, precise fraction collection, and reversed-phase chromatography, the oxidative DNA damage marker 8-hydroxydeoxyguanosine (8-OH-dG) was measured in human urine samples. The HPLC analysis was further modified to measure 8-OH-dG in rat and mouse urine samples. In addition, the urinary RNA degradation product 7-methylguanine (m7Gua) was analyzed simultaneously. The correlation coefficient (r) for the correlation between urinary creatinine and m7Gua was 0.9 for rats and 0.8 for humans and mice. Levels of 8-OH-dG in relation to urinary creatinine were compared and found to be similar for humans and rats and twice as high for mice. Urinary levels of m7Gua, as normalized to creatinine, were several-fold higher in rodents as compared with human levels, thereby correlating with the higher resting metabolic rate of rodents. The presented results show that 8-OH-dG and m7Gua can be analyzed simultaneously and reliably in urine from humans and rodents. In addition, m7Gua may be used as a reliable marker instead of creatinine for the normalization of 8-OH-dG in urine from rats and mice and also may be used in addition to normalization with creatinine in measurements of 8-OH-dG in human urine samples.     

Further evidence that oxidative stress may be a risk factor responsible for the development of atherosclerosis

There are numerous data suggesting that oxidative stress may be involved in the development of atherosclerosis. Therefore, in the present study we measured the amount of 8-hydroxy-2'-deoxyguanosine (8-OH-dG), one of the typical biomarkers of oxidative stress, in DNA isolated from lymphocytes of the patients and in the control group. Levels of antioxidant vitamins (A, C, and E) and intracellular labile iron pool (LIP), which can influence oxidative stress, were also determined. Blood samples were obtained from a control group of 55 healthy persons and from 43 atherosclerotic patients. 8-OH-dG and the vitamin levels were measured by high-performance liquid chromatography. Labile iron pool in lymphocytes was analyzed by fluorescent assay. The levels of 8-OH-dG and LIP were significantly higher and vitamin C concentration was significantly lower in the patient group than in the control group. The rest of the analyzed parameters do not significantly differ between the groups. A lower concentration of vitamin C and higher levels of labile iron pool in a group of atherosclerotic patients when compared with the control group may lead to oxidative stress, which is manifested by a higher level of 8-OH-dG in blood lymphocytes. All these factors may create an environment that promotes the development of atherosclerosis.     

Oxidative DNA damage in tissues of English sole (Parophrys vetulus) exposed to nitrofurantoin

Juvenile English sole were exposed intramuscularly to nitrofurantoin (NF) and the levels of 8-hydroxy-2′deoxyguanosine (8-OH-dG) in liver, kidney and blood were determined using reversed-phase HPLC with electrochemical detection. Identification and quantitation of the 8-OH-dG in the samples was accomplished by comparison with standard 8-OH-dG, which was characterized by UV spectroscopy and fast-atom bombardment mass spectrometry. The levels of hepatic 8-OH-dG increased (r² = 0.59, P = 0.015) with the dose of NF (0.10 – 10 mg NF/kg fish). In kidney and blood, however, the levels of 8-OH-dG were significantly higher than controls only at the highest dose tested. The level of binding in liver ranged from 0.37 to 0.76 fmol 8-OH-dG/μg DNA. The levels of hepatic 8-OH-dG reached a maximum (approx. 1 fmol 8-OH-dG/μg DNA) between 1 and 3 days after exposure, followed by a decrease to control levels (approx. 0.25 fmol 8-OH-dG/μg DNA) at 5 days post-exposure. These data demonstrate the first direct evidence for the formation of oxidized DNA bases resulting from the metabolism of a nitroaromatic compound by fish.     

DNA adducts,genetic polymorphisms,and K-ras mutation in human pancreatic cancer

To test the hypothesis that carcinogen exposure and oxidative stress are involved in pancreatic carcinogenesis in susceptible individuals, aromatic DNA adducts and 8-hydroxyguanosine (8-OH-dG) were measured by ³²P-postlabeling and HPLC–EC, respectively, in 31 pancreatic tumors and 13 normal tissues adjacent to the tumor from patients with pancreatic cancer. Normal pancreatic tissues from 24 organ donors, from six patients with non-pancreatic cancers, and from five patients with chronic pancreatitis served as controls. It was found that tissue samples from patients with pancreatic cancer had significantly higher levels of both aromatic DNA adducts and 8-OH-dG compared with control samples. The mean (±S.D.) levels of aromatic DNA adducts were 101.8±74.6, 26.9±26.6, and 11.2±6.6 per 10⁹ nucleotides in adjacent tissues, tumors, and controls, respectively. The mean (±S.D.) levels of 8-OH-dG were 11.9±9.6, 10.8±10.6, and 6.7±4.6 per 10⁵ nucleotides in adjacent tissues, tumors, and controls, respectively. Polymorphisms of the CYP1A1, CYP2E1, NAT1, NAT2, GSTM1, MnSOD, and hOGG1 genes were determined in these patients. The level of aromatic DNA adducts was significantly associated with polymorphism of the CYP1A1 gene. No significant correlation was found between the level of 8-OH-dG and the MnSOD, GSTM1, and hOGG1 polymorphisms. However, one novel polymorphism/mutation of the hOGG1 gene was found in a pancreatic tumor. Mutation at codon 12 of the K-ras gene was found in 25 (81%) of 31 pancreatic tumors, including three G-to-A transitions and 22 G-to-T transversions. Patients with the G-to-T mutation had a significantly higher level of aromatic DNA adducts than those with G-to-A or wild-type codon (P=0.02). On the other hand, the K-ras mutation profile was not related to the level of 8-OH-dG. Given the limitation of sample size, these preliminary data lend further support the hypothesis that carcinogen exposure and oxidative stress are involved in pancreatic carcinogenesis.     

No measurable increase in thymidine glycol or 8-hydroxydeoxyguanosine in liver DNA of rats treated with nafenopin or choline-devoid low-methionine diet

Male rats were treated for 2 months with 1000 ppm nafenopin in the diet or for 4 or 7 days with a choline-devoid low-methionine diet. DNA was isolated from the livers and analyzed for the presence of cis-thymidine glycol-3'-phosphate (cis-dTGp) by 32P-postlabeling and for the level of 8-hydroxy-deoxyguanosine (8-OH-dG) by electrochemical detection (ECD). In no DNA sample was the level of cis-dTGp above the limit of detection of 1 modified thymidine per 10(6) nucleotides. With 8-OH-dG, a background level of this modification of 20 8-OH-dG per 10(6) nucleosides was found in liver DNA of control rats, which was not affected by either treatment. It is postulated for thymidine glycol that a potential increase was below the limit of detection or was rapidly repaired in vivo and that the steady-state level of endogenous 8-hydroxydeoxyguanosine appears not to be influenced by the treatments chosen.     

Oxidative DNA damage in tissues of English sole (parophrys vetulus) exposed to nitrofurantoin

Juvenile English sole were exposed intramuscularly to nitrofurantoin (NF) and the levels of 8-hydroxy-2′deoxyguanosine (8-OH-dG) in liver, kidney and blood were determined using reversed-phase HPLC with electrochemical detection. Identification and quantitation of the 8-OH-dG in the samples was accomplished by comparison with standard 8-OH-dG, which was characterized by UV spectroscopy and fast-atom bombardment mass spectrometry. The levels of hepatic 8-OH-dG increased (r² = 0.59, P = 0.015) with the dose of NF (0.10 – 10 mg NF/kg fish). In kidney and blood, however, the levels of 8-OH-dG were significantly higher than controls only at the highest dose tested. The level of binding in liver ranged from 0.37 to 0.76 fmol 8-OH-dG/μg DNA. The levels of hepatic 8-OH-dG reached a maximum (approx. 1 fmol 8-OH-dG/μg DNA) between 1 and 3 days after exposure, followed by a decrease to control levels (approx. 0.25 fmol 8-OH-dG/μg DNA) at 5 days post-exposure. These data demonstrate the first direct evidence for the formation of oxidized DNA bases resulting from the metabolism of a nitroaromatic compound by fish.     

Oxidative damage elicited by imbalance of free radical scavenging enzymes is associated with large-scale mtDNA deletions in aging human skin

Mitochondrial DNA (mtDNA) mutations and impaired respiratory function have been demonstrated in various tissues of aged individuals. We hypothesized that age-dependent increase of ROS and free radicals production in mitochondria is associated with the accumulation of large-scale mtDNA deletions. In this study, we first confirmed that the proportion of mtDNA with the 4977 bp deletion in human skin tissues increases with age. We then investigated the 8-hydroxy-2'-deoxyguanosine (8-OH-dG) content in skin tissues and lipid peroxides content of the skin fibroblasts from subjects of different ages. The results showed an age-dependent increase of 8-OH-dG level in the total DNA of skin tissues of the subjects above the age of 60 years. The specific content of malondialdehyde, an end product of lipid peroxidation, was also found to increase with age. On the other hand, we examined the enzyme activities of Cu, Zn-superoxide dismutase (Cu,Zn-SOD), Mn-superoxide dismutase (Mn-SOD), catalase, and glutathione peroxidase (GPx) in the skin fibroblasts. The activities of Cu,Zn-SOD, catalase and glutathione peroxidase were found to decrease with age. However, the activity of Mn-SOD was increased with age before 60 years but was decreased thereafter. Moreover, the activity ratios of Mn-SOD/catalase and Mn-SOD/GPx exhibited the same pattern of change with age. This indicates that free radical scavenging enzymes can effectively dispose of ROS and free radicals before 60 years of age. However, elevated oxidative stress caused by an imbalance between the production and removal of ROS and free radicals occurred in skin fibroblasts after 60 years of age. Taken together, we suggest that the functional decline of free radical scavenging enzymes and the elevation of oxidative stress may play an important role in eliciting oxidative damage and mutation of mtDNA during the human aging process.     

Ultrasound characteristics of uterine myoma before and after uterine artery embolization

The diagnosis and treatment of uterine leiomyoma are topical problems of modern gynecology and radiodiagnosis. Organ-saving treatments for uterine myoma, one of which is uterine artery embolization, are gaining wide acceptance now. The objective of the study was to increase the informative value of ultrasound study to predict the uterine myoma after uterine artery embolization. One hundred uterine myoma patients aged 20 to 52 years were examined. Small pelvic Doppler ultrasonography was carried out in all the patients. The reduction of myomatous nodules was estimated after uterine artery embolization. The decrease in uterine myoma sizes was found to be due to the reduction in their vascularization and the occurrence of ischemia with degeneration in the myoma. Ultrasonography was found to be most accessible and informative in the prognostic and postoperative evaluation of the efficiency of X-ray endovascular treatment for uterine myoma.     

Left ventricular interstitial 8-hydroxy-deoxyguanosine concentration following myocardial ischemia and reperfusion in anesthetized rats

Summary

The effect of myocardial ischemia and reperfusion on left ventricular interstitial 8-hydroxydeoxyguanosine (8-OH-dG), a possible biomarker for in vivo oxidative deoxyribonucleic acid damage, in anesthetized rats was investigated. A microdialysis probe was implanted. Levels of 8-OH-dG in microdialysates were analyzed via an on-line high performance liquid chromatography system equipped with an electrochemical detector. Myocardial ischemia for 10 or 20 min, induced by clamping of the left anterior descending coronary artery, did not affect 8-OH-dG levels. However, reperfusion following either 10-min or 20-min ischemia significantly increased 8-OH-dG levels in collected microdialysates. Reperfusion-induced increases in 8-OH-dG levels were more prominent in the 20 min ischemia group (as high as 3.5 fold relative to basal levels) than in the 10 min ischemia group as high as 2.0 fold relative to basal levels). In conclusion, we observed that left ventricular interstitial 8-OH-dG concentration increased following myocardial ischemia and reperfusion in anesthetized rats. These results suggest that 8-OH-dG might be a useful biomarker for oxidative damage following myocardial ischemia and reperfusion.     

Hydroxylation and deglycosylation of 2'-deoxyguanosine in the presence of magnesium and nickel

Nickel (Ni), a carcinogenic and genotoxic metal, has been shown to enhance deglycosylation and hydroxylation of 2'-deoxyguanosine (dG) that has been caused by ascorbic acid and H2O2. There is evidence that Mg is a competitive antagonist of the toxicological effects of Ni. A factorial design was used to examine the interactive influence of Mg and Ni on the deglycosylation and hydroxylation of dG under a range of pH conditions in which ascorbate (Ascb) and H2O2 were added. Formation of guanine (Gu) (deglycosylation) and 8-hydroxy-2'-deoxyguanosine (8-OH-dG) (hydroxylation) appeared in large amounts in samples in which both H2O2 and Ascb were present. The largest amounts of Gu appeared where both Ni or magnesium (Mg) were present. When Mg alone was present, the amounts of Gu was intermediate between these two. Slightly less 8-OH-dG was formed where only Mg was present. The reaction mixtures were more sensitive to the pH than to the respective presence or absence of metals. At slightly acid or neutral pH (6.2-7.0) large amounts of both Gu and 8-OH-dG were formed. Gu formation decreased dramatically between pH 7.0 and 7.2. There was no 8-OH-dG formed at pH 7.8 and only small amounts at pH 7.6. The formation of 8-OH-dG was generally less where Mg was present. When Ni was absent, 8-OH-dG formation was greater in the pH 6.8 mixtures. The formation of Gu and 8-OH-dG from 2'-deoxyguanosine are directly a function of pH. Slight changes in pH greatly effected the formation of these biomarkers of oxidatively damaged DNA. Additional research is needed to determine if this is a cause or effect, i.e. does pH enhance toxicity conditions, thus permitting formation of 8-OH-dG, or does pH permit the reaction to proceed.     

子宫动脉栓塞治疗子宫肌瘤伴月经过多的临床研究

目的：回顾分析24例子宫肌瘤伴月经过多患者入介治疗疗效和子宫动脉栓塞安全性。方法：选择24例子宫肌瘤伴月经过多患者进行子宫肌瘤供血动脉的栓塞。结果：插管栓塞动脉率100％,随访20年。治疗后1月,24例患者经月经明显减少,B超随访,3个月子宫肌瘤体积平均缩小30％,随访2年,其中2例行腹腔镜下子宫肌瘤经阴道摘除术,6例子宫肌瘤消失,16例子宫肌瘤体积平均缩小80％,结论：子宫肌瘤行介入治疗疗效肯定,对粘膜下子宫肌瘤及子宫肌瘤伴月经过多患者尤为适宜。     

Melatonin reduces the increase in 8-hydroxy-deoxyguanosine levels in the brain and liver of kainic acid-treated rats

In the present study, the effect of melatonin on oxidative DNA damage induced by kainic acid (KA) treatment was investigated. 8-hydroxy-deoxyguanosine (8-OH-dG) is a main product of oxidatively damaged DNA and was used as the endpoint in these studies. The levels of 8-OH-dG were found to be elevated in the hippocampus and frontal cortex of rats treated with KA. These elevated levels were significantly reduced in animals that were co-treated with melatonin. Thus, there was no difference in 8-OH-dG levels in the brain of control rats compared to those treated with KA (10 mg/kg) plus melatonin (10 mg/kg). The levels of 8-OH-dG also increased in the liver of rats treated with KA. This rise in oxidatively damaged DNA was also prevented by melatonin administration. Melatonin's ability to reduce KA-induced increases in neural and hepatic 8-OH-dG levels presumably relates to its direct free radical scavenging ability and possibly to other antioxidative actions of melatonin.