Induction of 8-oxo-7,8-dihydro-2'-deoxyguanosine by ultraviolet radiation in calf thymus DNA and HeLa cells

The levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in purified calf thymus DNA and HeLa cells were measured following exposure to either UVC, UVB or UVA wavelengths. This DNA damage was quantitated using HPLC coupled with an electrochemical detector. The 8-oxodGuo was induced in purified DNA in a linear dose-dependent fashion by each portion of the UV spectrum at yields of 100, 0.46 and 0.16 8-oxodGuo per 10(5) 2'-deoxyguanosine (dGuo) per kJ/m2 for UVC, UVB and UVA, respectively. However, the amount of 8-oxodGuo in HeLa cells irradiated with these UV sources decreased to approximately 2.0, 0.013 and 0.0034 8-oxodGuo per 10(5) dGuo per kJ/m2, respectively. In contrast, the levels of cyclobutyl pyrimidine dimers were similar in both irradiated DNA and cells. Therefore, 8-oxodGuo is induced in cells exposed to wavelengths throughout the UV spectrum although it appears that protective precesses exist within cells that reduce the UV-induced formation of this oxidative DNA damage. Cell survival was also measured and the number of dimers or 8-oxodGuo per genome per lethal event determined. These calculations are consistent with the conclusion that dimers play a major role in cell lethality for UVC- or UVB-irradiated cells but only a minor role in cells exposed to UVA wavelengths. In addition, it was found that the relative yield of 8-oxodGuo to dimers increased nearly 1000-fold in both UVA-irradiated cells and DNA compared with cells subjected to either UVC or UVB. These results are supportive of the hypothesis that 8-oxodGuo, and possible other forms of oxidative damage, play an important role in the induction of biological effects caused by wavelengths in the UVA portion of the solar spectrum.

Induction of ICE and inhibition of c-fos, jun D and zif 268 in 12-month old spontaneously hypertensive rats

A semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay was used to examine ICE, c-fos, jun D and zif 268 mRNA expression in the aortic and renal artery of 12-month old SHRs and wistar rats. Using this assay system, it was observed that the levels of aortic and renal artery expression of ICE were markedly higher in SHRs than in wistar rats. In contrast, the aortic and renal artery expression of immediate early genes (IEGs), c-fos, jun D and zif 268, were significant lower in SHRs than in wistar rats. Thus, our results suggest that differential regulation of death gene ICE and IEGs such as c-fos, jun D and zif 268 might be involved in the mechanism of pathogenesis of hypertension.

Identification of possible reactive oxygen species involved in ultraviolet radiation-induced oxidative DNA damage

We have previously demonstrated that each region of the ultraviolet (UV) spectrum (UVA, UVB, and UVC) induces the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in purified calf thymus DNA and HeLa cells in a fluence-dependent manner. In the present study, we further characterize the possible reactive oxygen species (ROS) that are involved in the induction of 8-oxodGuo by UV radiation. Sodium azide, a singlet oxygen (1O2) scavenger though its quenching effect on HO. was also reported, inhibited 8-oxodGuo production in calf thymus DNA exposed to UVA, UVB, or UVC in a concentration-dependent fashion with maximal quenching effect of over 90% at a concentration of 10 mM. Catalase, at a concentration of 50 U/ml, reduced the yields of UVA- and UVB-induced 8-oxodGuo formation by approximately 50%, but had little effect on UVC-induced 8-oxodGuo production. In contrast, 50 U/ml of superoxide dismutase (SOD) did not affect induction of 8-oxodGuo by any portion of the UV spectrum. Hydroxyl radical (HO.) scavengers mannitol and dimethylsulfoxide (DMSO) moderately reduced the levels of 8-oxodGuo induced by UVA and UVB, but not those by UVC. Instead, mannitol and DMSO enhanced the formation of 8-oxodGuo induced by UVC. These results suggest that certain types of ROS are involved in UV-induced 8-oxodGuo formation with 1O2 playing the predominant role throughout the UV spectrum. Except for UVC, other ROS such as hydrogen peroxide (H2O2) and HO. may also be involved in UVA- and UVB-induced oxidative DNA damage. Superoxide anion appears not to participate in UV-induced oxidation of guanosine in calf thymus DNA, as SOD did not display any quenching effects.

Singlet oxygen involvement in ultraviolet (254 nm) radiation-induced formation of 8-hydroxy-deoxyguanosine in DNA

In the present article, we report that ultraviolet (UV 254 nm) radiation substantially induced the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in purified DNA. The formation of 8-OHdG, a hallmarker of oxidative DNA damage, increased linearly up to 25 kJ/m2 and was dependent on the presence of oxygen in the solution. Deoxygenation by nitrogen significantly reduced the yield of 8-OHdG by UV radiation, whereas oxygenation with 100% oxygen substantially enhanced the yield. The hydroxyl radical (HO.) scavenger dimethysulfoxide (DMSO) dramatically quenched the formation of 8-OHdG by the ionizing radiation and Fenton reaction, but enhanced the formation of UV-induced 8-OHdG. Further studies showed that DMSO and mannitol, two predominant HO. scavengers, enhanced the levels of UV-induced 8-OHdG in a dose-dependent fashion, suggesting that UV-induced 8-OHdG is independent of the generation of HO.. The use of deuterium oxide (D2O), which prolongs the half life of singlet oxygen (1O2), substantially enhanced the yield of 8-OHdG by UV radiation, but not that by Fenton reaction. In contrast, sodium azide, a more and less specific 1O2 quencher, substantially reduced the levels of 8-OHdG by both UV radiation and Fenton reaction, indicating that sodium azide lacks the quenching specificity of 1O2 and HO.. It is proposed that UV induced 8-OHdG proceeds through a singlet oxygen involvement mechanism, rather than the generation of hydroxyl radicals.

Dantrolene is cytoprotective in two models of neuronal cell death

The neuroprotective effects of dantrolene, an inhibitor of calcium release from intracellular stores, were investigated in a model of cell death induced by calcium release from endoplasmic reticulum in vitro. Thapsigargin (50 nM), a selective inhibitor of endoplasmic reticular Ca(2+)-ATPase, significantly increased the cytosolic Ca2+ concentration to 230% over basal levels, induced DNA fragmentation, and reduced cell viability from 94% in control cells to 41% after a 24-h treatment in GT1-7 hypothalamic neurosecretory cells. Pretreatment with dantrolene for 30 min significantly inhibited elevation of cytosolic Ca2+ levels, DNA fragmentation, and GT1-7 cell death induced by thapsigargin in a dose-dependent manner. To determine if dantrolene would also be protective in an in vivo model of neurodegeneration, it was administered intravenously immediately following a 5-min global cerebral ischemia in gerbils, and the number of intact hippocampal CA1 pyramidal neurons was counted 7 days later. The effects of dantrolene on brain and rectal temperature were monitored in a separate experiment. Dantrolene significantly increased the number of intact CA1 pyramidal neurons from 40% (untreated ischemic animals) to 67 (10 mg/kg), 78 (25 mg/kg), or 83% (50 mg/kg) of values in sham controls (all p < 0.001). No significant changes in brain or rectal temperature were detected for 4 h following 50 mg/kg dantrolene. These results suggest that abnormal Ca2+ release from intracellular stores can induce neuronal death and that such a mechanism may contribute to delayed hippocampal neuronal death after cerebral ischemia. Dantrolene may be a potentially useful drug for neuroprotection after cerebral ischemia.

[A study of 5-fluorouracil on bovine trabecular meshwork cells in vitro]

OBJECTIVE

To determine whether the clinical use of 5-fluorouracil (5-FU) may have any toxic effects on trabecular meshwork cells.

METHODS

Bovine trabecular meshwork (BTM) cells were cultured in vitro. The effects of 5-FU on BTM cells concerning cellular morphology, ultrastructure, vitality and phagocytosis were observed.

RESULT

The safe dosage of 5-FU on BTM cell was 1 x 10-6g.ml-1.

CONCLUSION

Based on the pharmacokinetic data in the rabbit anterior chamber, it is suggested that the 5-FU dosage of conventional use cause no injury to human trabecular meshwork cells.

Lidocaine in the rostroventromedial medulla and the periaqueductal gray attenuates allodynia in neuropathic rats

In the present study we attempted to find out if the rostroventromedial medulla (RVM) or the periaqueductal gray (PAG) might contribute to chronic allodynia induced by unilateral ligation of two spinal nerves in the rat. Lidocaine was microinjected in the RVM or PAG and allodynia was quantitatively determined by measuring the hindlimb withdrawal thresholds to mechanical stimulation of the paw. For comparison, lidocaine was also injected systemically (s.c.). Lidocaine in the RVM produced a dose-related (20 and 40 micrograms) antiallodynic effect. Lidocaine (20 micrograms) in the PAG produced identical antiallodynic effect as in the RVM. With systemic administrations of lidocaine, a considerably higher dose (> > 40 micrograms) was needed to produce a significant antiallodynic effect. Naloxone, an opioid-antagonist (1 mg/kg s.c.), did not attenuate the antiallodynic effect of lidocaine in the RVM. An antiallodynic dose of lidocaine (20 micrograms) in the RVM or the PAG did not influence the withdrawal response in the unoperated hindlimb nor the heat-induced tail-flick reflex. The results indicate that the RVM and the PAG have a facilitatory influence on the spinal segmental mechanisms underlying chronic allodynia. The selective attenuation of allodynia induced by lidocaine in the RVM and the PAG is independent of opiate receptors, and it can not be explained by a systemic spread of the drug.

[Pearl and mother-of-pearl powder in health-care]

Based on pharmacological studies in files, mice and rats, the powder of sea pearl (Pteria martensii), mother-of-pearl and freshwater pearl has been proved to have tonic, anti-aging and anti-radiative actions. The effect of the sea pearl and mother-of-pearl powder is higher than that of freshwater pearl powder.

Non-NMDA glutamate receptor binding in canine brain after global cerebral ischemia and reperfusion

We employed a canine model to test the effects of global cerebral ischemia and reperfusion on binding to alpha-amino-3-hydroxy-5-methyl- 4-isoxazole proprionate (AMPA), kainate (KA), and metabotropic glutamate receptors. Ischemia was induced by 10 min of cardiac arrest, followed by restoration of spontaneous circulation for periods of 0, 0.5, 2, 4, and 24 h. Frozen sections were prepared from parietal and temporal cortex, hippocampus, and striatum, and in vitro autoradiography was performed with one of three radioligands: [3H]AMPA, [3H]KA, or [3H] glutamate (using conditions allowing specific labeling of the metabotropic binding site). In striatum, metabotropic binding was unchanged, whereas AMPA and KA binding decreased by 20-30% at 30 min postischemia, remaining depressed through 24 h. In cortex, AMPA and metabotropic binding were decreased at several time-points after ischemia and recirculation, particularly in parietal cortex, whereas KA binding was unaffected in this tissue. Binding to hippocampal regions was largely unchanged, except for a decrease in KA binding at 2 and 4 h postischemia. These findings contrast with results from parallel studies showing increased striatal binding to NMDA receptors following ischemia. Decreased binding to non-NMDA glutamate receptors in striatum and parietal cortex may serve to protect against damage mediated through these receptors.

A transcription map of the major histocompatibility complex (MHC) class I region

We have applied cDNA hybridization selection to nine YACs spanning 3 Mb of genomic DNA from a region centromeric to HLA-A to the histone cluster that lies telomeric to the human major histocompatibility complex (MHC). In addition to Class I genes and pseudogenes, we describe over 63 genes and 23 additional expressed sequence tags distributed throughout the region. Many of the full-length genes belong to gene families. Prominent among these are a group of genes encoding proteins showing homology to the carboxyl-terminal sequences of butyrophilin and an additional group of zinc finger genes. We also detected several previously undefined genes that are specifically expressed in cells of the immune system, indicating a more complex role of the MHC in the immune response than has been appreciated.

Indonesian Medicinal Plants. XIV. Characterization of 3'-O-Caffeoylsweroside, a new secoiridoid glucoside, and kelampayosides A and B, two new phenolic apioglucosides, from the bark of Anthocephalus chinensis (Rubiaceae)

A new secoiridoid glucoside named 3'-O-caffeoylsweroside (1), and two new phenolic apioglucosides, named kelampayoside A (4) and kelampayoside B (6), together with eleven known compounds (five iridoids and six alkaloids), were isolated from the bark of Anthocephalus chinensis (Rubiaceae), an Indonesian medicinal plant from Sumatra Island, Indonesia. The chemical structures of 1, 4 and 6 have been elucidated respectively as 3'-O-caffeoylsweroside (1), antiarol 1-O-beta-D-apiofuranosyl (1 --> 6)-beta-D-glucopyranoside (4), and antiarol 1-O-beta-D-5"-O-caffeoylapiofuransoyl (1 --> 6)-beta-D-glucopyranoside (6) on the bases of their chemical and physiochemical properties. Among fourteen constituents characterized, cadambine (13), one of the major indole alkaloid constituents of A. chinensis, was shown to exhibit moderate growth-inhibitory activity against the malarial parasite Plasmodium falciparum (a chloroquine-resistant K1 strain) cultured in human erythrocytes.

Age-dependent increase of indigenous DNA adducts in rat brain is associated with a lipid peroxidation product

Indigenous DNA adducts (I-compounds) are considered to be a biomarker of aging tissues. Thus far, few studies have been conducted to investigate the accumulation patterns of I-compounds in the brain during aging. Particularly, identities of age-dependent I-compounds have largely remained unknown. In the current study, we have determined the amounts of I-compounds in the brains of male Fischer 344 rats at ages 1, 6, 12, 18, and 24 months using a 32P-postlabeling technique. The results indicate that I-compounds increase in the rat brain age dependently from 6 to 24 months of age. Total I-adduct levels (central and upper cutouts) increase 3.5-fold from 6 to 24 months. Contrary to the results of other investigators, brains of 1-month-old rats contain the highest level of I-compounds, which may be due to the hypermetabolic status during the infant period. In an effort to characterize I-compounds, different deoxynucleosides were coincubated with malondialdehyde (MDA). The results show that only deoxyguanosine (dGMP)-MDA adducts overlap with I-compounds of the rat brain DNA adducts map. A total of five dGMP-MDA adducts have been identified as responsible for I-compounds in brain tissues. It is known that brain tissue contains high levels of lipids that are susceptible to oxygen free radicals and that MDA is the most abundant and genotoxic product of lipid peroxidation. The present study provides supporting evidence that lipid peroxidation and its product (MDA) may play an important role in endogenous brain DNA modification, which may partly contribute to cerebral aging and age-related degenerative disorders of the brain. The accumulation of I-compounds with aging may serve as an index of indirect oxidative damage to DNA as evidenced by the presence of MDA-DNA adducts.

[Inhibitory effects of gypenoside on rat heart and brain Na+, K+(-)ATPase activity]

The effects of gypenoside (Gyp) on the microsomal Na+, K(+)-ATPase from rat hearts and brains were investigated in comparison with ginsenoside (Gin). The results showed that Gyp could inhibit the enzyme activity rapidly and reversibly in vitro. The inhibition was in a concentration-depend manner. The IC50 of Gyp for the heart and brain was 58.79 +/- 8.05 mg/L and 52.07 +/- 6.25 mg/L, respectively. Kinetic analysis revealed that Gyp was an incompetitive inhibitor of ATP. These results suggest that the positive inotrope effect and the inhibition of CNS by Gyp are related to the in hibitory action of Gyp on the actiyily of Na+, K(+)-ATPase from hearts or brains.

The preventive and therapeutic potential of the squalene-containing compound, Roidex, on tumor promotion and regression

Recent scientific evidence has shown free radicals or reactive oxygen species (ROS) to play an important role in the initiation and progression of cancer. Many radical scavengers have also been found to help reduce the attacks by these ROS. Interestingly, the ROS scavengers that have been investigated are naturally occurring compounds such as vitamins C and E. Roidex is a formulation of squalene, vitamin e, and aloe vera. It was our goal to investigate whether Roidex was able to prevent the development of chemically induced cancer and to cause regression of any tumors already formed in a mouse skin model. In the prevention study, skin tumors were initiated in 50 female CD-1 mice with 7,12-dimethylbenz[a]-anthracene (DMBA) and promoted with 12-O-tetradecanoylphorbol-13-acetate (TPA). The mice were treated with either mineral oil, 5% squalene, or Roidex. At the end of the prevention study, there was a 33.34% incidence to tumors (multiplicity of 1.40) in the mineral oil-treatment group, 26.67% (multiplicity of 0.467) in the 5% squalene and Roidex groups, respectively. The tumor regression study involved the selection of mice with tumors and possible regression of these tumors with Roidex treatment. There was a regression of 33.34% of the tumors in the Roidex-treated group (39 tumors to 26 tumors) compared to the non-treated group whose tumors regressed only 3.44% (29 tumors to 28 tumors).

Intraoperative use of mitomycin in trabeculectomy

Mitomycin (0.2 mg/ml) was applied intraoperatively to 26 glaucomatous patients (33 eyes) during conventional trabeculectomy procedure. Most of them were considered to be at high risk of surgical failure. The conjunctival flap was fornix-based in 9 patients (11 eyes). The success rate was 84.8% without any serious side effect.

Expression of mesenger RNA for transforming growth factor-beta 1 in bovine trabecular meshwork

PURPOSE

To investigate the relationship between transforming growth factor-beta 1 (TGF-beta 1) and primary open-angle glaucoma, we have determined whether trabecular tissues have the expression of messenger RNA for TGF-beta 1.

METHODS

Total RNA of 24 newborn bovine trabecular tissue were extracted by Guanidine isothiocyanate method. The TGF-beta 33 plasmid was brought into E. colibacillius HB101 and amplificated. After Bam HI endolase degradation and label with alpha-32p-dATP the RNA was hybridized with the cDNA (complementary DNA) probe and examined by autoradiography.

RESULTS

The presence of mRNA for TGF-beta 1 in bovine trabecular meshwork was confirmed.

CONCLUSIONS

The TGF-beta 1 present in normal aqueous humor must be at least partly derived from the trabecular meshwork. It offered a basis for understanding the relationship between abnormal synthesis, activation and clearance of TGF-beta 1 and the pathogenesis of primary open-angle glaucoma (POAG) in molecular biology.

Inhibition of UV light- and Fenton reaction-induced oxidative DNA damage by the soybean isoflavone genistein

We have investigated the effect of the soybean isoflavone genistein on 8-hydroxy-2'-deoxyguanosine (8-OHdG) formation in calf thymus DNA exposed to either UV irradiation or the Fenton reaction system. Under the conditions used we observed that UV light and the Fenton reaction significantly increase 8-OHdG formation in DNA. Co-incubation with genistein inhibits the formation of 8-OHdG induced by either UV light irradiation or the Fenton reaction in a dose-dependent manner. The quenching effect of genistein on 8-OHdG formation induced by UV light is much more potent than that by the Fenton reaction, suggesting that the mechanisms of 8-OHdG formation may differ between the two systems. We further compared the antioxidant activities and quenching effect on 8-OHdG formation of genistein with biochanin A. Genistein potently scavenges both hydrogen peroxide in the medium and superoxide anion generated by xanthine/xanthine oxidase, whereas biochanin A has either a weak or no scavenging effect on these reactive oxygen species. However, both genistein and biochanin A display a similar quenching effect on UV light-induced 8-OHdG formation. These results suggest that the quenching effect of genistein and biochanin A on UV light-induced 8-OHdG formation is different from their ability to scavenge hydrogen peroxide and superoxide anion. The potent inhibition of UV light-induced oxidative DNA damage by genistein suggests its potential anticarcinogenic role in photocarcinogenesis.

Effect of dietary genistein on antioxidant enzyme activities in SENCAR mice

Dietary administration of the soybean isoflavone genistein (50 and 250 ppm) for 30 days significantly increases the activities of antioxidant enzymes in various organs of SENCAR mice. Feeding a 250-ppm genistein diet to SENCAR mice significantly increases the activities of catalase in small intestine, liver, and kidney, the activities of superoxide dismutase and glutathione peroxidase in skin, and the activity of glutathione reductase in skin and small intestine. Feeding 50 ppm genistein to SENCAR mice results in elevated catalase activity in the small intestine and increases glutathione-S-transferase activities in skin, small intestine, liver, kidney, and lung. Dietary genistein's greatest enhancement of antioxidant enzyme activities occurred in skin and small intestine. Our results suggest that dietary genistein enhances the activities of antioxidant enzymes in various organs, which may be a mechanism(s) of genistein's chemopreventive action.

Inhibitory effect of genistein on a tumor promoter-induced c-fos and c-jun expression in mouse skin

The effects of genistein, a soybean isoflavone, on 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced expression of c-fos and c-jun in CD-1 mouse skin have been investigated. A promoting dose (8.5 mu mol) of TPA significantly increases transcript levels of c-fos, and 2.7 and 3.2 kb c-jun mRNA in mouse skin by 7.0-, 3.2-, and 1.7-fold, respectively. Topical application of genistein 30 min before TPA treatment inhibits TPA-induced expression of these protooncogenes. Suppression of c-fos was more pronounced than that of c-jun, and at a dose of 10 mu mol genistein, TPA-induced c-fos expression was almost completely diminished. Genistein exhibited only a weak suppressive effect on TPA-induced c-jun mRNA expression. Effect of application time of genistein on TPA-induced c-fos expression was also investigated. The results showed that topical application of 10 mu mol genistein 30 min prior to, simultaneously, and 30 min after tumor promoter treatment can equally suppress TPA-induced c-fos expression. The mechanism by which genistein inhibits TPA-induced proto-oncogene expression is unknown. However, it appears that the inhibition of c-fos expression by genistein is independent of the protein kinase C (PKC) activation pathway because of its weak suppressive effect on PKC activity. It is hypothesized that the inhibitory effect of genistein on TPA-induced c-fos expression may be through the modulation of mitogen-activated protein (MAP) kinase in vivo.

Effects of caloric restriction on age-related oxidative modifications of macromolecules and lymphocyte proliferation in rats

Decreased immune function associated with aging has been demonstrated in both humans and animals. We hypothesize that reactive oxygen species (ROS)-mediated damage to biological macromolecules may contribute to compromised immune response during aging. In this study, we compared the levels of lipid peroxidation and oxidatively modified proteins in plasma and splenocytes, and the mitogen-induced T lymphocyte proliferation in ad lib-fed (AL) and caloric restricted (CR) Fischer 344 x BNF1 male rats at the ages of 5, 18, and 31 months. The results show that AL rats exhibit an age-related decrease in proliferative response of splenic lymphocytes to phytohemagglutinin (PHA) and concanavalin A (Con A). This functional decline in T-lymphocytes during aging is inversely correlated to the levels of both lipid peroxidation and protein carbonyl in the plasma and splenic lymphocytes. Caloric restriction, however, can partially reverse the age-dependent decrease in T lymphocyte proliferation and significantly reduce lipid peroxidation and protein carbonyl contents in plasma and splenocytes. The above observations support the hypothesis that the age-associated declines in immune function are related to the oxidative modification of biological macromolecules, which in turn may lead to enzyme inactivation, membrane disruption, and cell senescence. One of the mechanisms by which caloric restriction reverses declined immune function in aged rats is hypothesized to be through reduction in ROS production and thereby protection of cellular macromolecules against oxidative damage.

A simplified approach for isolating oligo(dT) primed cDNA clones with probes generated by cDNA selection

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Unidirectional valve patch for repair of cardiac septal defects with pulmonary hypertension

BACKGROUND

Congenital septal defects with a large left-to-right shunt often cause pulmonary hypertension, which complicates surgical repair of the defects.

METHODS

Twenty-four patients with congenital cardiac septal defects and severe pulmonary hypertension had operation to close the septal defect using a unidirectional valve patch during a 3-year period. The ratio of systolic pulmonary artery pressure to systolic arterial blood pressure was near to or more than 1.0 in all patients.

RESULTS

Two patients died in the hospital after operation, and there have been no deaths during intermediate term follow-up. Mean pulmonary artery pressure decreased from 80 +/- 12 mm Hg to 56 +/- 18 mm Hg. The ratio of pulmonary artery pressure to systemic arterial pressure dropped from 1.1 +/- 0.1 mm Hg to 0.7 +/- 0.1 mm Hg. The unidirectional valve patch functioned allowing right to left shunting in 4 patients with a systolic pulmonary artery pressure more than systolic arterial blood pressure immediately after closure of a septal defect. The patch sealed or was effectively closed by the third postoperative day. There was impressive improvement in symptoms and exercise tolerance after operation during the 3-month to 3-year (mean, 1.1 year) follow-up period.

CONCLUSIONS

The unidirectional valve patch is useful for management of patients having operation to close cardiac septal defects in the presence of severe pulmonary hypertension.

Psychoactive substance use in three sites in China: gender differences and related factors

One year prevalence rates for psychoactive substance use are reported based on a community survey in Hunan, Helongjiang and Jiangsu. Data were gathered on more than 14,000 respondents (15-65 years old). The drinking rates ranged from 58.3% to 82.6% for men and from 16.3% to 31.4% for women. Smoking rates ranged from 64.9% to 68.1% for men and from 0.1% to 20.5% for women. Most drinkers were light users and most smokers were heavy users. Illicit drug use was found in the Hunan site. For both frequency and quantity of psychoactive substance use, women are lighter consumers than males (except for the use of minor tranquillizers and analgesics). Psychosocial factors related to drinking and smoking are also investigated in this study.

[Effect of RU486 on metabolism of glycosaminoglycans in the cultured calf trabecular meshwork cells]

The trabecular meshwork from newborn bovine eyes was used for cell culture and subculture to the third passage. Then the concentrations of RU486, a corticosteroid antagonist, in the medium were made to be 50, 100 and 200 micrograms/ml and 3H-glycosamine was introduced as the radioactive precursor. After extraction and purification, an aliquot of glycosaminoglycans (GAGs) was used for cellulose acetate electrophoresis, sequential degradation by different enzymes and radioactivity determination by scintillation counting to determine the total amount of GAGs and the amounts of constituents, such as hyaluronic acid (HA), etc. In the control group, the total amount of GAGs was 980 DPM/micrograms cell prot (disintegration per minute/micrograms cell protein) and HA accounted for 17.8%, while in the medium of 50 micrograms/ml and 100 micrograms/ml RU486, HA was increased to 50.1% and 46.1%, respectively. In the medium of 200 micrograms/ml RU486, the total amount of GAGs was decreased to 695 DPM/micrograms cell prot. The results were consistent with the theory of pharmacology and pharmacodynamics. It is possible that the corticosteroid antagonist can be used to reverse the pathogenesis of primary open-angle glaucoma.

Differential expression of glial fibrillary acidic protein (GFAP) in the retinae and visual cortices of rats with experimental renal hypertension

To examine the expression of the GFAP protein in the retina and visual cortex under normal and pathological conditions, hypertension was induced in adult male Sprague-Dawley rats by applying silver clips onto renal arteries and the change in GFAP expression was followed by Western blotting and immunocytochemical staining. One week after operation when the induced hypertension was at the initial stage, GFAP expression in the retina was reduced to half of the sham control. By 4 weeks, when consistent hypertension was developed, a further decrease in the level of GFAP expression in the retina to one third of the sham control was observed. Immunocytochemical staining showed that the number of GFAP-positive cells in the nerve fiber layer of the retina of the hypertensive rat was reduced to less than one third of the sham control. However, similar changes in GFAP expression in the visual cortex of hypertensive rats were not observed. This study represents the first report to date on GFAP expression in the retina and visual cortex and includes discussion of the possible mechanisms through which GFAP expression is mediated.

[Investigation of the contamination of air and environment in the blood dialysis department]

As the blood dialysis has been applied more widely, the hygenic state of air and furniture surfaces in blood dialysis room and that of dialysis fluid would diretly affect the incidence of nosocomial infections. The results of investigation in three hospital dialysis units showed that: With people walking around, the number of air microbes presented a kenetic variation, ranged from 410 to 1755CFU/m3. That number was positively related to the number of dust particles in the air, which carring certain amount pathogenic of conditional-pathogenic microbes, among which, fungi, Stap. aureus and Pseud. aruginosa acount for 8.38%, 2.99% and 1.39% respectively. Physical of chemical disinfection treatment showed prompt effects (P < 0.01). The thermogenic reaction and infections in dialysis patients were mainly due to microbes containminated in the water for dialysis. Some of these microbes may produce intracellular or and exo-toxin and thermogenic factors. The microbes in dialysis machines could 100% be killed immediately after disinfecting the dialysis tubes with 5% available chlorine. But the germ numer could rise again as the time streched. Our results suggested that certain monitoring and disinfectious procedures must be carried out in hospital critical departments so as to reduce nosocomial infection cases.

Effect of left ventricular hypertrophy secondary to chronic pressure overload on transmural myocardial 2-deoxyglucose uptake. A 31P NMR spectroscopic study

BACKGROUND

This study tested the hypothesis that 31P nuclear magnetic resonance (NMR)-detectable 2-deoxyglucose (2DG) uptake is increased in chronically pressure-overloaded hypertrophied left ventricular myocardium.

METHODS AND RESULTS

31P NMR spectroscopy was used to determine the transmural distribution of high-energy phosphate levels and 2-deoxyglucose-6-phosphate (2DGP) accumulation during intracoronary infusion of 2DG (15 mumol.kg body wt-1.min-1) in eight normal dogs and in eight dogs with severe left ventricular hypertrophy (LVH) produced by ascending aortic banding. The ratio of LV weight to body weight was 8.25 +/- 0.65 g/kg in the LVH group compared with 4.35 +/- 0.11 g/kg in the normal group (P < .01). Myocardial ATP content was decreased by approximately 40% and phosphocreatine (PCr) by approximately 60% in LVH hearts. ATP values were transmurally uniform in LVH and normal hearts, whereas PCr was lower in the subendocardium (Endo) than the subepicardium (Epi) of both groups. The PCr/ATP ratio was lower in LVH hearts (1.72 +/- 0.05, 1.64 +/- 0.07, and 1.53 +/- 0.10 in Epi, midwall, and Endo, respectively) compared with normal hearts (2.36 +/- 0.05, 2.09 +/- 0.06, and 1.96 +/- 0.06; each P < .01 normal versus LVH). Arterial blood levels of glucose, insulin, and free fatty acids were comparable between groups, whereas arterial lactate and norepinephrine levels were significantly higher in the LVH group. 2DG infusion did not affect systemic hemodynamics or myocardial high-energy phosphate or inorganic phosphate levels in either group. At the end of 60 minutes of 2DG infusion, there was no detectable accumulation of 2DGP in the normal hearts. However, seven of the eight LVH hearts showed time-dependent accumulation of 2DGP, which was linearly related to the severity of hypertrophy (r = .90 for subendocardial 2DGP versus LV weight/body weight). A transmural gradient of 2DGP was present, with greatest accumulation in the subendocardium (3.3 +/- 1.6, 5.8 +/- 2.3, and 7.9 +/- 2.2 mumol/g in Epi, midwall, and Endo of the LVH hearts, respectively; P < .05 Epi versus Endo).

CONCLUSIONS

The pressure-overloaded hypertrophied left ventricle demonstrated increased accumulation of 2DGP detected with 31P NMR spectroscopy. Accumulation of 2DGP was positively correlated with the degree of hypertrophy and was most marked in the subendocardium.

7,12-dimethylbenz[a]anthracene induces oxidative DNA modification in vivo

Initiation and promotion are major stages in the multistage carcinogenesis process. Formation of initiating carcinogen-DNA base adducts leads to heritable genetic changes, but the tumor-promoting events induced by complete carcinogens have not, as yet, been elucidated. Oxidant production and oxidative DNA damage induced by phorbol esters (i.e., 12-O-tetradecanoyl-phorbol-13-acetate) are associated with tumor promotion, while antioxidants and inhibitors of oxidative DNA damage suppress promotion and carcinogenesis. Our goal was to establish whether a carcinogen that requires oxidative metabolism for its activity can also induce oxidant production and DNA base oxidation. We found that topical treatment of SENCAR mice with 7,12-dimethylbenz[a]anthracene, which induces tumors in 40-50% of the mice, also causes hydrogen peroxide production and formation of oxidized bases (i.e., 8-hydroxyl-2'-deoxyguanosine and 5-hydroxymethyl-2'-deoxyuridine) in epidermal DNA. The levels of oxidized bases were of comparable magnitude to those mediated by the potent tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. The oxidized bases persisted over several weeks in epidermal DNA. These oxidative events appear to be temporally associated with inflammatory responses that include edema and polymorphonuclear leukocyte infiltration, which remained elevated over longer periods of time and at higher levels than those induced by phorbol ester. Because these processes are usually associated with tumor promotion, our results support the conjecture that oxidative events may be involved in what is operationally referred to as the tumor promotion process by 7,12-dimethylbenz[a]anthracene.

[Constituents of the petroleum ether and ethyl acetate extract fractions from Dracaena cochinensis (Lour.) S.C. Chen]

Six constituents have been isolated from the petroleum ether and ethyl acetate extract fractions of Dracaena cochinensis. Their structures have been identified as 1,2,4,5-tetrachloro-3,6- dimethoxy-benzene,docosyl alcohol, octadecyl acetate, eicosyl acetate, resveratrol and 4',7-dihydroxy-flavone on the basis of physical, chemical and spectral deta. Of these compounds 1,2,4,5-tetrachloro-3,6-dimethoxy-benzene is a new one.

In vivo formation of DNA-adducts in mouse skin DNA by tamoxifen

Tamoxifen (TAM)-induced DNA adduct formation in mouse skin was determined by a nuclease P1-enhanced 32P-postlabelling technique. Topical application of TAM significantly induced a number of DNA-adducts in mouse skin in a dose- and time-dependent manner. When SENCAR mice were topically treated with different doses of TAM for 6 h, total DNA adduct levels in skin were increased by 2.5- (1 mumol TAM), 4.5- (5 mumol TAM) and 4.8-fold (10 mumol TAM), respectively. In addition, at least four novel DNA adducts were observed. Time-course studies showed that TAM-induced DNA adducts reach a peak at 6 h post-treatment. However, the pattern of TAM-induced DNA adducts was different from that induced by DMBA (a potent skin carcinogen). TAM has been found to form DNA-adducts in the liver and kidney of rodents. Our work confirms the genotoxic effects observed by other investigators by showing that TAM also causes DNA-adducts formation in mouse skin. Since TAM is widely used for the treatment of breast cancer and currently for chemo-prevention trials, further studies should be conducted to assess the potential risk of long-term use of TAM in humans.

Role of vasogenic edema and tissue cavitation in ischemic evolution on diffusion-weighted imaging: comparison with multiparameter MR and immunohistochemistry

PURPOSE

To examine the mechanisms of further evolution that occurs from the early to late phase after initial changes in diffusion-weighted imaging after cerebral ischemia.

METHODS

Sprague-Dawley rats were subjected to middle cerebral artery occlusion. Diffusion-, proton density-, T1- and T2-weighted imaging were performed on days 0, 2, and 6. Histologic examination (IgG, glial fibrillary acidic protein, and cresyl violet staining) was done after scanning.

RESULTS

Apparent diffusion coefficients (ADCs) in the ischemic hemisphere were significantly decreased on day 0. Thereafter, ADCs increased over time and became significantly higher than the contralateral side by day 6. Changes in basal ganglia occurred more rapidly than in cortex. Proton density-, T1-, and T2-weighted scans showed maximal changes on day 2. From day 0 to day 2, there are significant correlations between changes in ADC and changes in T1-weighted signals and T2-weighted signals. Histologic exam showed early neuronal injury on day 0, intense gliotic activity and protein leakage associated with infarction and edema on day 2, and cavitation in severely infarcted areas on day 6.

CONCLUSION

After initial reduction of ADC, the subsequent increase in ADC values on day 2 may be associated with vasogenic edema and cell lysis. Later elevations in ADC may be related to cavitation of infarcted tissue.

A search for genes from the dark band regions of human chromosome 21

As part of an effort to isolate genes from the entire long arm of human chromosome 21, we performed cDNA selection with 15 YACs from the regions of the pericentromeric heterochromatin and the two Giemsa dark bands of this chromosome using cDNA libraries from six different tissues. Nine of these YACs mapped to the Giemsa dark band, 21q21. The 9 YACs cover approximately 6 Mb of DNA, representing 15% of 21q and a significant portion of the 12-15 Mb estimated to be within this band. Several lines of evidence from analysis of the selected cDNA libraries suggest that this region of 21q has very few single-copy transcribed sequences. An EcoRI library was constructed with DNA from 1 of the 9 YACs. Grail analysis of the sequences of both ends of 24 YAC-specific clones from this EcoRI library revealed no potential exons. In contrast to these results, the selected cDNA libraries of a control YAC from the human MHC region in 6p21.3 as well as those from most of the other 21q YACs consisted largely of YAC-specific single-copy cDNA clones. Given the success of the cDNA selection method for finding a large number of genes in YACs from other chromosomal regions, these results suggest that the 6 Mb of DNA in the dark band 21q21 contains few single-copy sequences expressed in this tissue set. In contrast, selected cDNA libraries from the pericentromeric region, the telomeric border of the dark band 21q21, and the dark band 21q22.2 yielded more than 30 new ESTs.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-adrenergic receptor function in cultured AT-1 cardiomyocytes

AT-1 cells are highly differentiated, contracting cardiomyocytes derived from atrial tumours in transgenic mice. The aim of this study was to characterize beta-adrenergic receptor function and associated intracellular calcium regulation in AT-1 cells. Equilibrium binding experiments with [3H]-CGP-12177 showed a Kd = 0.30 +/- 0.08nM and a Bmax = 2.25 +/- 0.47 fmol/10(5) cells. Competition binding experiments with CGP-20712A showed presence of predominantly beta 1-adrenoreceptors. S-(-)propranolol, atenolol and R-(+)propranolol showed a competitive inhibition of binding with successively lower affinity. Isoproterenol, 2 microM, for 48 hours down-regulated the number (p < 0.05) of beta-adrenergic receptors/cell by about 50%; 10 microM for one hour increased the cAMP concentration (p < 0.05) by about 100%. Cytosolic [Ca2+] was measured flourimetrically in spontaneously and synchronously beating AT-1 cells. The resting cytosolic concentration was 94 +/- 10 nM. The observed sinusoidal Ca2+ oscillation frequency increased after addition of 10 microM isoproterenol (p < 0.02). This effect was antagonized by 10 microM alprenolol (p < 0.01). In conclusion, AT-1 cells have functional beta-adrenoreceptor signalling pathways and constitute an important tool in cardiac biology.

Some anti-allergic and anti-inflammatory actions of 2-N-carboxamidinonormianserin (FCC5)

The aims of these studies were to examine the effects of FCC5 (2-carboxamidino-1,2,3,4,10,14b-hexahydrodibenzo (c,f) pyrazino (1,2,-a) azepine HCl), an analogue of mianserin, on immediate type hypersensitivity reactions in-vitro. The actions of FCC5 were examined on the Schultz-Dale reaction of guinea-pig ileum and on histamine and leukotriene release from human- and guinea-pig-sensitized lung fragments. FCC5 (applied topically) was assessed for anti-inflammatory activity in-vivo against phorbol-12-myristate-13-acetate (PMA)-induced oedema in the mouse ear. FCC5 (IC50 = 0.17 microM) was a potent inhibitor of the Schultz-Dale reaction in-vitro, as assessed by a concentration-dependent attenuation of egg albumin-induced contractions of sensitized guinea-pig isolated ileum. Using human and guinea-pig isolated sensitized lung fragments, FCC5 (1-100 microM) attenuated antigen-induced release of sulphidopeptidoleukotrienes and histamine. FCC5 (50 micrograms topically) resembled mianserin and indomethacin in attenuating PMA-induced mouse ear inflammation. These properties together with previously published evidence of long lasting antihistamine properties in-vivo, suggest that FCC5 has therapeutic potential as an anti-allergic agent, especially in pathological conditions where an inflammatory component is present.

Antioxidant and antipromotional effects of the soybean isoflavone genistein

Antioxidant and antipromotional effects of the soybean isoflavone genistein have been studied in HL-60 cells and the mouse skin tumorigenesis model. Effects of structure-related flavone/isoflavones on hydrogen peroxide (H2O2) production by 12-O-tetradecanoylphorbol-13-acetate (TPA)-activated HL-60 cells and superoxide anion (O2-) generation by xanthine/xanthine oxidase were compared. Of tested isoflavones, genistein is the most potent inhibitor among TPA-induced H2O2 formation by (dimethyl sulfoxide) DMSO-differentiated HL-60 cells, daidzein is second, and apigenin and biochanin A show little effect. In contrast, genistein, apigenin, and prunectin are equally potent in inhibiting O2- generation by xanthine/xanthine oxidase, with daidzein showing a moderate inhibitory effect and biochanin A exhibiting no effect. These results suggest that the antioxidant properties of isoflavones are structurally related and the hydroxy group at Position 4' is crucial in both systems. Dietary administration of 250 ppm genistein for 30 days significantly enhances the activities of antioxidant enzymes in the skin and small intestine of mice. Further studies show that genistein significantly inhibits TPA-induced proto-oncogene expression (c-fos) in mouse skin in a dose-dependent manner. In a two-stage skin carcinogenesis study, low levels of genistein (1 and 5 mumol) significantly prolong tumor latency and decrease tumor multiplicity by approximately 50%. We conclude that genistein's antioxidant properties and antiproliferative effects may be responsible for its anticarcinogenic effect. Its high content in soybeans and relatively high bioavailability favor genistein as a promising candidate for the prevention of human cancers.

[A morphological study of experimental corneal neovascularization]

Corneal neovascularization (CNV) was induced by alkali burn injuries in 20 rabbit corneas. The process of CNV was observed with biomicroscopy in vivo and histologically by light and electron microscopy. At 8 hours after injury, an obvious acute inflammatory response as evidenced by infiltration of neutrophils had already occurred in the pericorneal limbal area. Many neutrophils in the extravascular space contained abundant intracytoplasmic phagolysosomes. The vascular sprouts appeared 2 days after injury. The infiltration of neutrophils and their debris were visible around newly formed blood vessels in the cornea. The results suggest that there be the participation and an inductive action of neutrophils in the pathogenesis of CNV.

Clinical significance of multiple hypothalamic-pituitary functions assessment in patients with Turner's syndrome

Hypothalamic-pituitary functions in 26 cases of Turner syndrome were assessed with a combined stimulation test. The results showed that the peak GH levels of 12 cases were less than 10 micrograms/L; 3 patients were demonstrated as having an even TSH response, while another one with a delayed TSH peak, and other 4 had high basal values and consistent exaggerated TSH responses to TRH; all patients showed increased basal and peak LH and FSH levels but 5, whose LH and FSH secretion patterns were similar to normal. 12 cases have been treated with individualized protocols and followed up for 12 months or more, of them the growth velocity all increased, especially those with hypothyroidism or with a BA less than 13. It is suggested that multiple functions of hypothalamic-pituitary axis in Turner patients be evaluated as early as possible, in order that proper treatment could be adopted and their growth and development improved.

The cloning and expression of a human creatine transporter

A human creatine transporter (hCRT-BS2M) cDNA clone was isolated from a human brainstem/spinal cord using a PCR and phage plaque hybridization based technique. This clone included an open reading frame of 1,905 base pairs(bp) within a 2,283bp cDNA. Northern blot hybridization detected the expression of corresponding mRNAs most prominently in the skeletal muscle, heart and kidney. Peptide sequence analysis of the hCRT-BS2M protein product revealed 12 putative transmembrane domains. The predicted protein sequence further demonstrates that the hCRT-BS2M has highly conserved amino acid identity with the other members of the sodium dependent plasma membrane transporter family. Transient expression of the hCRT-BS2M in COS-7 cells demonstrates sodium dependent [14C]creatine uptake with a KM value of 14.9 +/- 3.0 microM (n = 5) that is attenuated by creatine and selective structural analogues of creatine.

Autoradiographic analysis of L- and N-type voltage-dependent calcium channel binding in canine brain after global cerebral ischemia/reperfusion

Binding of antagonists to L- and N-type voltage-dependent calcium channels (VDCC) was measured in canine brain following global ischemia and reperfusion. Ischemia was induced by 10 min cardiac arrest, followed by restoration of spontaneous circulation for periods of up to 24 h. Binding of [3H]PN200-110 and [125I]omega-conotoxin GVIA to frozen sections from hippocampus, striatum, parietal cortex and temporal cortex was analyzed using quantitative receptor autoradiography. The binding patterns of the two radioligands were similar in cortex and striatum, but differed in hippocampus. In the latter tissue, [125I]omega-conotoxin GVIA binding was dense over synaptic regions, especially the presynaptic polymorph layer of the dentate gyrus, but was virtually absent over cell body layers. In contrast, [3H]PN200-110 binding was more homogenously distributed, with highest binding in the molecular layer of the dentate gyrus. The binding of [125I]omega-conotoxin GVIA was not different from sham controls at any time point following cardiac arrest. [3H]PN200-110 binding was decreased in each region immediately following ischemia, recovering within 30 min of recirculation. These findings are in contrast to earlier findings of rapid increases in L-type VDCC binding to membrane fractions obtained from cortex and striatum in this model, and suggest that the previously detected increases may be due to a redistribution of channels from subcellular compartments to the plasma membrane during ischemia.

Effect of norfloxacin and clonidine on human trabecular meshwork cells in vitro

We evaluated the effect of norfloxacin and clonidine on the morphology, DNA synthesis and phagocytic activity of cultured human trabecular meshwork cells in the 3rd-5th generations. Exposure to norfloxacin at a concentration of 1.5 x 10(-4) g ml-1 for 6 h led to retraction of cytoplasmic processes and rounding of cell profile, and exposure for 48 h caused cell death. Exposure to clonidine at 1.0 x 10(-3) g ml-1 for 12 h caused cell degeneration, and exposure for 72 h led to cell death. The morphologic changes were dose-time dependent. Tritiated thymidine incorporation was determined as an index of DNA synthesis, which was significantly inhibited by 1.5 x 10(-5) g ml-1 norfloxacin or 1.0 x 10(-3) g ml-1 clonidine, but obviously enhanced by 1.0 x 10(-4) and 1.0 x 10(-5) g ml-1 clonidine. Both drugs inhibited phagocytosis of latex microspheres in a dose-dependent mode. According to the presented results and the pharmacokinetic data reported in the literature, we suggest that the topical use of norfloxacin should not be too frequent or continued too long, especially when the corneal epithelium was not intact; clonidine has no deleterious effect on trabecular cells in its conventional use.

Genes in one megabase of the HLA class I region

To define the gene content of the HLA class I region, cDNA selection was applied to three overlapping yeast artificial chromosomes (YACs) that spanned 1 megabase (Mb) of this region of the human major histocompatibility complex. These YACs extended from the region centromeric to HLA-E to the region telomeric to HLA-F. In addition to the recognized class I genes and pseudogenes and the anonymous non-class-I genes described recently by us and others, 20 additional anonymous cDNA clones were identified from this 1-Mb region. We also identified a long repetitive DNA element in the region between HLA-B and HLA-E. Homologues of this element were located at several sites in the human genome outside of the HLA complex. The portion of the HLA class I region represented by these YACs shows an average gene density as high as the class II and class III regions. Thus, the high gene density portion of the HLA complex is extended to more than 3 Mb.

Intravitreal pharmacokinetics of liposome-encapsulated amikacin in a rabbit model

BACKGROUND

Intravitreal injection of antibiotics has become a standard therapy for bacterial endophthalmitis. The duration of effective antimicrobial levels in the vitreous after single injection, however, may not be long enough to get optimal response. The authors prepared liposome-encapsulated amikacin for prolonging the duration of intravitreal therapeutic concentrations and investigated the intravitreal pharmacokinetics of the liposomes and amikacin in phosphate buffer solution (PBS) as control.

METHODS

The liposome-encapsulated amikacin was prepared by reverse-phase evaporation method. The intravitreal pharmacokinetics of the liposomes was compared with amikacin in PBS by fluorescence polarization immunoassay. Albino rabbits were randomly distributed into 12 groups. Rabbits in groups 1 to 6 and in groups I to VI (control groups) received an intravitreal injection of the liposome-encapsulated amikacin and amikacin in PBS, respectively.

RESULTS

The encapsulation rate of amikacin was 91%. The time of 50% spontaneous degradation (half-life) of the liposomes in PBS (38 degrees C, pH 7.4) was 47.6 days, and the time of 50% release (half-life) of the drug from the liposomes in PBS was 84.8 hours. The vitreous amikacin concentrations in groups 1 to 6 were significantly greater (P < 0.05) than those in control groups I to VI in every time interval, except in groups 1 to 3 at 1 hour after injection. The difference was particularly obvious in the endophthalmitis groups. The clearance of encapsulated amikacin in vitreous appeared to be related to the state of blood-ocular barrier and to the structural integrity of vitreous. The distribution, the absorption, and the elimination of encapsulated amikacin in vitreous showed the first-order kinetics.

CONCLUSION

The liposome-encapsulated amikacin prolonged half-life of the drug in vitreous. The results of the pharmacokinetic analysis suggested that in endophthalmitis, especially in severe cases, the liposomes may be preferable to conventional preparation.

Relationship of oxidative events and DNA oxidation in SENCAR mice to in vivo promoting activity of phorbol ester-type tumor promoters

Reactive oxygen species (ROS) have been implicated as being involved in tumor promotion processes. However, the mechanism by which ROS modulate tumor promotion has not as yet been elucidated. In this report, we show that phorbol ester-type tumor promoters (12-O-tetradecanoylphorbol-13-acetate [TPA], mezerein and 12-O-retinoylphorbol-13-acetate [RPA]), which vary in their in vivo potencies, also differ in their effect on formation of hydrogen peroxide (H2O2) and oxidation of normal bases to 5-hydroxymethyl-2'-deoxyuridine [HMdU] and 8-hydroxyl-2'-deoxyguanosine [8-OHdG] in the DNA of SENCAR mouse epidermis, though they are equipotent in causing infiltration of polymorphonuclear leukocytes (PMNs). Treatment of SENCAR mice with the chemopreventive agents (-)-epigallocatechin gallate or tamoxifen (6.5 nmol) prior to application of TPA (6.5 nmol) diminished PMN infiltration, and formation of H2O2, HMdU and 8-OHdG. These results strengthen the evidence that ROS are involved in tumor promotion, and that generation of ROS and the subsequent oxidative DNA modification are related to the tumor-promoting potencies of the different phorbol ester-type promoters.