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1.
Enhancement of the photodynamic antitumor effect by streptococcal preparation OK-432 in the mouse carcinoma 总被引:3,自引:0,他引:3
Uehara M Sano K Wang ZL Sekine J Ikeda H Inokuchi T 《Cancer immunology, immunotherapy : CII》2000,49(8):401-409
Biological response modifier antitumor effects are enhanced by the activation of the host defense mechanisms. We have investigated
the antitumor effect of photodynamic therapy (PDT) and/or local administration of a biological response modifier, the streptococcal
preparation OK-432, on transplanted NR-S1 mouse squamous cell carcinoma. Hematoporphyrin oligomers (20 mg/kg body weight)
were used to photosensitize PDT. A pulsed Nd:YAG dye laser, tuned at 630 nm, was used as the light source. The laser power
was 15 mJ cm−2 pulse−1, and the irradiation time was 40 min. The photosensitizer was injected intraperitoneally 48 h before laser irradiation. Where
used, OK-432 was injected into the tumor either 3 h prior to PDT or immediately afterwards. The antitumor effects were evaluated
48 h after each protocol by (a) estimating the area of tumor necrosis (%) in hematoxylin/eosin-stained specimens, and (b)
bromodeoxyuridine immunohistochemistry. Furthermore, the tumor sizes were evaluated 3, 7 and 10 days after each protocol,
and the survival time after each protocol was evaluated as well. The anti-tumor effect of PDT was enhanced by administration
of OK-432 3 h before PDT, whereas the administration of OK-432 immediately after PDT did not potentiate a PDT antitumor effect.
Treatment with OK-432 alone had little effect on tumors. Photodynamic therapy in combination with local administration of
OK-432 3 h before PDT is considered to be a useful treatment modality.
Received: 23 July 1999 / Accepted: 31 May 2000 相似文献
2.
The possible ameliorative effects of quercetin on soybean [Glycine max (L.) Merr.] leaves exposed to UV-B radiation were conducted in greenhouse. The symmetrical leaves supplied with quercetin
solution (0.2%, 1%) were exposed to UV-B radiation (0, 3.5, 6.5 kJ m−2 d−1). 0.2% quercetin ameliorated leaf photosynthesis, improved leaf water content (LWC), and decreased lipid oxidation. The unfavorable
effect on photosynthetic parameter was displayed in 1% quercetin treatment. The effect of quercetin on phenylalanine ammonia
lyase (PAL) activity varied with the quercetin concentration, UV-B radiation intensity and leaf development. In the later
development polyphenol oxidase (PPO) activity was increased significantly by quercetin treatments. We suggested that quercetin
with suitable concentration could serve as UV-B protective agent partly due to its antioxidant capacity. 相似文献
3.
Vasin MV Ushakov IB Kovtun VIu Komarova SN Semenova LA Koroleva LV Galkin AA Afanas'ev RV 《Radiatsionnaia biologiia, radioecologiia / Rossi?skaia akademiia nauk》2011,51(2):247-251
Experiments on mice-hybrids F1(CBA x C57B1/6) have detected a favorable effect of the associated application of quercetin (30-60 minutes before y-exposure of an animal) and a radioprotectant of urgent action indralin (in the case of its application after y-exposure) on a post-irradiation repair of the hematopoietic tissue in acute radiation sickness after y-exposure at a non-lethal dose of 6.7 Gy, which manifested itself in the accelerated formation of endogenous spleen colonies and spleen mass recovery, as well as in the lesser degree of leukopenia on the 12th and the 16th day after acute radiation injury. Quercetin per se did not have a radio-protective effect. 相似文献
4.
The effect of soluble glucan derivates on spleen colony-forming units in sublethally irradiated mice
A. Líšková J. Wagnerová L. Červeňáková A. Krištofová M. Ferenčík 《Folia microbiologica》1990,35(4):353-362
We examined the effects of 5 soluble derivatives of yeast glucan on the formation of exogenous (CFU-S) and endogenous (E-CFU)
colony-forming units in the spleens of sublethally irradiated (60Co, 6.5–7.0 Gy) mice of two inbred strains. For the estimation of CFU-S, glucans were administered intravenously either to
donors or recipients of spleen cells 24 h prior to irradiation or removal of the spleen. The number of CFU-S was increased
when both the donors and recipients were treated with glucan; the highest increase was obtained with glucans S, P and K. All
glucan preparations increased significantly also the number of E-CFU even when administered 90 min after irradiation. There
exist differences in the response to the stimulatory effect of glucans among individual mouse strains. Thus, for example,
the stimulatory effect of glucan KM on the E-CFU number was significantly more pronounced in strain A/Ph than in strain C57B1/6. 相似文献
5.
Yamaguchi M Hamamoto R Uchiyama S Ishiyama K 《Molecular and cellular biochemistry》2007,303(1-2):83-88
The effect of various flavonoids, which are present in food and plants, on bone calcium content and osteoclastogenesis were
investigated to compare action of flavonoid on bone formation and bone resorption in vitro. Rat femoral-diaphyseal (cortical
bone) and -metaphyseal (trabecular bone) tissues were cultured for 48 h in Dulbecco’s modified Eagle’s medium (high glucose)
supplemented with antibiotics and bovine serum albumin. Amoung quercetin, myricetin, kaempferol, isorhamnetin, curcumin, hesperidin,
or astaxanthin in the range of 10−7–10−5 M, culture with quercetin (10−6 or 10−5 M) caused a significant increase in diaphyseal calcium content. Such an effect was not seen in other compounds. Mouse bone
marrow cells were cultured for 7 days in the presence of parathyroid hormone (PTH; 10−7 M), a bone-resorbing factor, in vitro. Culture with PTH caused a significant increase in osteoclast-like cell formation. This
increase was significantly inhibited in the presence of quercetin, myricetin, kaempferol, isorhamnetin, or curcumin in the
range of 10−8–10−6 M. Such an effect was not seen in the case of hesperidin or astaxanthin. In addition, culture with PTH (10−7 M) caused a significant decrease in diaphyseal calcium content. This decrease was completely prevented in the presence of
quercetin, myricetin, kaempferal, or isorhamnetin of 10−6 M. This study demonstrates that various flavonoids have a potent inhibitory effect on osteoclastogenesis and bone resorption
rather than bone formation in vitro. Among various flavonoids, quercetin had a stimulatory effect on bone formation and an
inhibitory effect on bone resorption in vitro. 相似文献
6.
We investigated the immunological responses induced by human interferon β (IFNβ) gene transfer in human gliomas produced
in the brains of nude mice. A suspension of human glioma U251-SP cells was injected into the brains of nude mice. The IFNβ
gene was transferred by intratumoral injection with cationic liposomes or cationic liposomes associated with anti-glioma monoclonal
antibody (immunoliposomes). When intratumoral injection of liposomes or immunoliposomes containing the human IFNβ gene was
performed every second day for a total of six injections, starting 7 days after tumor transplantation, complete disappearance
of the tumor was observed in six of seven mice that had received liposomes and in all seven mice receiving immunoliposomes.
In addition, experimental gliomas injected with immunoliposomes were much smaller than those injected with ordinary liposomes
following delayed injections beginning 14 days after transplantation. An immunohistochemical study of the treated nude mouse
brains revealed a remarkable induction of natural killer (NK) cells expressing asialoGM1 antigen. To investigate the significance
of NK cells in the antitumor effect, we injected liposomes or immunoliposomes containing the human IFNβ gene into tumors in
nude mice depleted of NK cells by irradiation and anti-asialoGM1 antibody administration. The antitumor effect of the liposomes
or immunoliposomes was abolished. Subsequent subcutaneous glioma challenge of the nude mice after intracerebral tumor implantation
and gene transfer resulted in no subcutaneous tumor growth. These results suggest that the induction of NK cells is important
in the cytocidal effect of liposomes or immunoliposomes containing the human IFNβ gene upon experimental gliomas.
Received: 10 February 1998 / Accepted: 1 September 1998 相似文献
7.
Impairments of mitochondrial genome are associated with a wide spectrum of degenerative diseases, development of tumors, aging,
and cell death. We studied the content of mitochondrial DNA (mtDNA) with mutations and the total content of mutations in the
brain and the spleen of mice subjected to X-ray irradiation at a dose of 1–5 Gy at 8–28 days after treatment. In these mice,
we studied the number of mutant copies of extracellular mtDNA (ec-mtDNA) and its total content in blood plasma. We estimated
mutations in control and irradiated mice using cleavage of heteroduplexes prepared by hybridization of PCR amplicons of mtDNA
(D-loop region) mediated by CEL-I endonuclease, an enzyme that specifically cleaves unpaired bases. Changes in the total number
of mtDNA copies relative to nuclear DNA were assessed by real time PCR using the ND-4 and GAPDH genes, respectively. We found that the number of mutant mtDNA copies was significantly increased in the brain and the spleen
of irradiated mice and reached the maximum level at the eighth day after treatment; it then decreased by the 28th day after
treatment. In nuclear genes similar to mutagenesis, mutagenesis of mtDNA in the brain and spleen tissues linearly depended
on irradiation dose. In contrast to mutant nuclear genes, most mutant mtDNA copies were eliminated in the brain and spleen
tissues, whereas the total content of mtDNA did not change within 28 days after irradiation. Our data show that, during this
period, a high level of ec-mtDNA with mutations was observed in DNA circulating in blood plasma with the maximum level found
at the 14th day. We suppose that mutant mtDNA copies are eliminated from cells of animals subjected to irradiation during
the posttreatment period. Higher content of ec-mtDNA in blood plasma can be considered as a potential marker of radiation
damage to the body. 相似文献
8.
J C Marsh D R Boggs P A Chervenick G E Cartwright M M Wintrobe 《Journal of cellular physiology》1968,71(1):65-75
A variety of erythropoietic stimuli influenced the number of endogenous spleen colonies in irradiated mice and the number of transplantable colony forming cells in the spleen and marrow of unirradiated mice. Bleeding was the most effective stimulus. Bleeding before irradiation resulted in a 30-fold increase in endogenous spleen colonies and in increases in spleen weight, spleen iron and iododeoxyuridine uptake and volume of packed red cells ten days after irradiation. Bleeding unirradiated mice produced a 10-fold increase in the number of transplantable colony forming cells in the spleen and a slight decrease in the total number in the humerus. Bleeding before irradiation resulted in a significant reduction in 30-day post irradiation deaths, an effect abolished by splenectomy. Plasma from bled mice induced an increase in endogenous colonies when injected before irradiation into normal mice. Injection of erythropoietin, testosterone or testosterone plus cobalt induced effects which were, in general, qualitatively similar to those of bleeding, although they were less effective quantitatively. Except for a slight effect induced by ten injections of erythropoietin, post-irradiation stimulation in normal mice proved ineffective. Erythropoietin increased colony numbers and spleen iron uptake when given after irradiation to hypertransfused mice. The results of these studies do not support the concept that the colony forming cell and the erythropoietin sensitive cell are separate entities. 相似文献
9.
E G Kurella V V Mal'tseva L S Seslavina S L Stvolinski? 《Biulleten' eksperimental'no? biologii i meditsiny》1991,112(7):52-53
It was shown that intake of carnosine in a dose of 50-100 mg/kg of body weight before X-ray irradiation resulted in an increase of the survival of experimental mice. The protective effect of carnosine was manifested, when it was injected either before or after irradiation, but the effect was more pronounced in the case of shortening time between irradiation and injection. An enhancement of colony forming index of bound cells in spleen was also observed simultaneously with protective action of carnosine. These effects are supposed to be the result of immunomodulating activity of carnosine. 相似文献
10.
Four experiments were conducted to quantify the reported attenuation by microwave (MW) irradiation of ethanol-induced hypothermia. In one experiment rats were irradiated (continuous wave 2.45 GHz, specific absorption rate = 0.3 W/kg) or sham irradiated for 45 min, injected with 3.6 g/kg, 20% (v/v) ethanol (EtOH) or saline (NaCl) i.p.. Colonic temperature was monitored at 20-min intervals for 2 h. This procedure was repeated for 8 days to determine the rate of tolerance development to the hypothermic effect of ethanol. While MW irradiation did significantly attenuate EtOH-induced hypothermia, it did not enhance or retard the rate of tolerance development. To determine the duration of irradiation necessary to attenuate EtOH-induced hypothermia, groups of rats were irradiated or sham irradiated for 5, 15, 30, or 60 min prior to EtOH injection and subsequent temperature measurements. The attenuation was apparent only after 60 min of irradiation. To determine the duration of the attenuation effect after irradiation, rats were injected with EtOH or NaCl at 0, 30, 60, 120, or 480 min after 45 min of irradiation or sham irradiation. The attenuation effect was apparent among rats injected 0 to 30 min after irradiation and for the first 40 min for groups injected at 120 min. Additional rats were injected with NaCl or 0.9, 1.8, or 2.7 g/kg of EtOH i.p. following 45 min of irradiation or sham irradiation to determine if the attenuation effect depends on the dose of EtOH administered. Attenuation of EtOH-induced hypothermia was more apparent at lower doses of EtOH than at higher doses. These results indicate that the effect is an acute response to irradiation, and rule out several other potential explanations. 相似文献
11.
A. Ben-Amotz Boris Rachmilevich Simon Greenberg Mordechai Sela Zeev Weshler 《Radiation and environmental biophysics》1996,35(4):285-288
β-Carotene and other carotenoids are reported to be potent free radical quenchers, singlet oxygen scavengers, and lipid antioxidants.
Whole-body irradiation is known to cause an immunosuppression effect in mammals through the possible initiation and production
of reactive oxygen species. We decided to test the possible antioxidative effect against whole-body irradiation of a natural
β-carotene, composed of equal amounts of the all-trans and 9-cis isomers, obtained from the unicellular alga Dunaliella bardawil. Rats were fed on ground commercial food enriched with natural β-carotene (50 mg/kg diet). On completion of 1 week with β-carotene, the rats were exposed to a single dose of 4 Gy whole-body irradiation, after which their livers and blood were
removed for β-carotene and retinol analysis in comparison with control livers of animals irradiated or not, or supplemented with β-carotene after irradiation. A normal increase in body weight with no ill effects was noted in the groups of rats whose diet
was supplemented by β-carotene before and after irradiation, compared with the reduction in the specific growth rate in the group of rats irradiated
without β-carotene. Liver β-carotene and retinol decreased significantly after irradiation compared with the rats which were not irradiated. This decrease
was not shown in rats fed β-carotene prior to irradiation, and the effect of irradiation was partially cured by supplementation with β-carotene after irradiation. High-pressure liquid chromatography (HPLC) analysis of the irradiated animals showed a selective
decline in 9-cis β-carotene and in retinol over all-trans β-carotene and retinyl esters. These results suggest that 9-cis β-carotene and retinol protect in vivo against the cellular damage by free radicals induced after whole-body irradiation.
Received: 14 May 1996 / Accepted in revised form: 24 June 1996 相似文献
12.
13.
Vicentini FT Casagrande R Verri WA Georgetti SR Bentley MV Fonseca MJ 《AAPS PharmSciTech》2008,9(2):591-596
The purpose of this study was to develop a lyotropic liquid crystalline formulation using the emulsifier vitamin E TPGS and
evaluate its behavior after incorporation of a flavonoid, quercetin. The physical (macro and microscopic), chemical (determination
of quercetin content by the HPLC method) and functional (determination of quercetin antioxidant activity by DPPH• assay) stability of the lamellar liquid crystalline formulation containing flavonoid was evaluated when stored at 4 ± 2 °C;
30 ± 2 °C/70 ± 5% RH (relative humidity) and 40 ± 2 °C/70 ± 5% RH during 12 months. The lamellar liquid crystalline structure
of the formulation was maintained during the experiment, however chemical and functional stability results showed a great
influence of the storage period in all conditions tested. A significant decrease in quercetin content (approximately 40%)
was detected during the first month of storage and a similar significant loss in antioxidant activity was detected after 6 months.
The remaining flavonoid content was unchanged during the final 6 months of the experimental period. The results suggest possible
interactions between quercetin and the liquid crystalline formulation, which could inhibit or reduce the quercetin activity
incorporated in the system. In conclusion, the present study demonstrated that incorporation of quercetin (1%) did not affect
the liquid crystalline structure composed of vitamin E TPGS/IPM/PG–H2O (1:1) at 63.75/21.25/15 (w/w/w). Nevertheless, of the total quercetin incorporated in the system only 60% was free to act as an antioxidant. 相似文献
14.
M. G. Lomaeva G. V. Vasil’eva L. A. Fomenko V. N. Antipova A. I. Gaziev V. G. Bezlepkin 《Russian Journal of Genetics》2011,47(10):1221-1226
The level of genome instability (GI) was studied in the progeny of female mice exposed in the preconceptional period to radiation
doses of 0.5, 1, and 2 Gy in comparison to that in the progeny of the same parent pairs born before irradiation of the females.
To assess the level of genome instability, we analyzed polymorphism of DNA fragments from postmitotic (blood and brain) and
proliferating (spleen and tail tip) tissues amplified by AP-PCR (PCR amplification with an arbitrary primer). It was found
that polymorphism of the spectrum of AP-PCR products, which is a multilocus genetic marker (MGM), in the genome of somatic
cells in the progeny of female mice exposed to 2 Gy was higher than in the progeny of male mice exposed to the same doses.
In the progenies of female mice born before and after irradiation, tissue-specific variations in the level of DNA polymorphism
were detected. The maximum value of this polymorphism (with respect to the frequency of “nonparental bands”) was determined
for peripheral blood DNA in comparison with the other tissues. Estimations of the MGM polymorphism with the AP-PCR method
demonstrate an increased level of genome instability in somatic cells of offsprings from female mice exposed to a single acute
dose of X-rays (0.5, 1, and 2 Gy) in the preconceptional period. Radiation-induced transgenerational genome instability with
an increase in the dose of preconceptional irradiation of female mice was more pronounced in DNA of the postmitotic tissues
(blood and brain DNA) than in DNA of the proliferating tissues (spleen and tail tip epithelium). 相似文献
15.
Mice were injected with serotonin (0.5 and 2.0 mg/mouse) 15 min before and immediately after irradiation (4.5 and 7.0 Gy). With the preparation administered prior to irradiation one could observe an increase in the quantity of CFUc survived (endo- and exo-test), acceleration of restoration of cellularity (in the bone marrow) and growth of the spleen weight. The acceleration of restoration of the bone-marrow cellularity was also noted when serotonin was administered after irradiation. The post-irradiation effect of serotonin was also detected in cells in vitro. It is concluded that the radiomodifying effect of serotonin on the haemopoietic system is due to a decrease in the number of damaged cells and increase in the rate of reproduction of intact cells. 相似文献
16.
H. Marvanová 《Folia microbiologica》1969,14(6):566-570
The effect of thymectomy + irradiation and of bursectomy + irradiation on the rejection of skin grafts and injected homologous
spleen cells was studied. Prolonged skin graft survival was found in thymectomized and irradiated chickens. Bursectomy together
with irradiation and isolated irradiation did not affect the rejection of these grafts. Surgical operations together with
irradiation had no effect on the rejection of an allogenein cellular graft. In one-day-old recipients, survival of the cells
was prolonged in all the birds, while in 12-day-old recipients the cells were rejected at the normal time by both bursectomized
and thymectomized birds. The possible explanations of these results are discussed.
Dedicated to Academician Ivan Málek on the occasion of his 60th birthday 相似文献
17.
J. Wagnerová A. Líšková L. Červeňáková T. Trnovec M. Ferenčík 《Folia microbiologica》1991,36(2):198-204
We examined the effect of soluble derivatives of yeast glucan on the humoral immune response of various strains of inbred
mice after administration of different doses according to various schedules. Glucan was injected i.v. or s.c. in a single
dose or repeatedly. The immune response was examined by determining the titres of serum hemagglutinins against sheep erythrocytes
(SRBC-Ab). The immunoadjuvant effect of glucan derivatives depends on the inbred strain used, on the dose of glucan, mode
and time of administration with respect to antigen injection. The results have shown that the stimulatory effect of glucan
derivatives occurred already after a single injection, the optimum dose being 10–20 mg/kg. Intravenous injection was more
efficient than the subcutaneous one. In some cases, a slight increase of the spleen mass was observed.
Translated by I. Miler 相似文献
18.
Chang PY Doppalapudi R Bakke J Puey A Lin S 《Radiation and environmental biophysics》2007,46(2):113-118
We are using a plasmid-based transgenic mouse mutation model system to evaluate the effectiveness of aluminum or low-density
polyethylene (LDPE) shielding after 250 MeV/u protons or 1 GeV/u iron ion irradiation. Transgenic mice, with multiple copies
of the plasmid pUR288 lacZ transgene integrated into the genome of every cell of the animal, were either irradiated or sham-treated. Multiple endpoints,
including early cytogenetic damage in erythrocytes at 48 h after exposure, chromosome aberrations in bone marrow lymphocytes,
and lacZ mutant frequencies (MF) in brain and spleen tissues were measured in the same animals. The frequency of total circulating
reticulocytes (fRET) dropped precipitously at 48 h after 2 Gy of proton irradiation. The average level of micronucleated reticulocytes
(fMN–RET) was fivefold higher in the irradiated samples relative to the controls at the same time point. There was an increase
in total chromosome aberrations in bone marrow lymphocytes at 8 weeks after proton irradiation but this increase was not statistically
significant relative to the controls. Evaluation of the lacZ MF in the brain and spleen tissues showed that proton irradiation induced a twofold increase in MF in each tissue. Similar
samples were collected from animals that were shielded from the proton beam by aluminum. Compared to the unshielded treatment
group, we noted no difference in fRET, fMN–RET, chromosome aberrations in lymphocytes and lacZ MF in brain and spleen tissues obtained from these animals. In a separate study, animals were exposed to high-energy iron
ions with or without 10 or 15 cm LDPE. Using the same approach, we noted a precipitous drop in fRET, and an elevation in fMN–RET
within 48 h after 1 Gy of iron ions. Total chromosome aberrations in bone marrow lymphocytes were slightly elevated but not
significant at 8 weeks after iron ion exposure. Shielding animals with 10 or 15 cm of polyethylene appeared to have no effect
on the level of RET, MN–RET or chromosome aberrations in these animals. LacZ MF in brain and spleen tissues increased 1.5–2-fold above control levels after 1 Gy iron ions at 8 weeks after treatment.
On the other hand, MF in tissues harvested from shielded animals appeared to be lower than their unshielded litermates, suggesting
the polyethylene shielding was effective in reducing the iron-induced genomic damage in tissues. Although shielding may be
effective, in some cases, in reducing the physical dose of particle radiation, our cytogenetic results showed that the biological
impact of the particle beam remain unchanged. On the other hand, reduction in transgene MF in tissues from LDPE-shielded animals
but not in the aluminum-shielded animals strongly suggests that careful consideration of the biological endpoints used is
necessary in the evaluation of the efficacy of the selected shielding material. 相似文献
19.
Greice S. Borghetti Ivana S. Lula Ruben D. Sinisterra Valquiria L. Bassani 《AAPS PharmSciTech》2009,10(1):235-242
The present study was designed to investigate the influence of operating conditions (temperature, stirring time, and excess
amount of quercetin) on the complexation of quercetin with β-cyclodextrin using a 23 factorial design. The highest aqueous solubility of quercetin was reached under the conditions 37°C/24 h/6 mM of quercetin.
The stoichiometric ratio (1:1) and the apparent stability constant (Ks = 230 M−1) of the quercetin/β-cyclodextrin complex were determined using phase-solubility diagrams. The semi-industrial production
of a 1:1 quercetin/β-cyclodextrin solid complex was carried out in aqueous solution followed by spray-drying. Although the
yield of the spray-drying process was adequate (77%), the solid complex presented low concentration of quercetin (0.14%, w/w) and, thus, low complexation efficiency. The enhancement of aqueous solubility of quercetin using this method was limited
to 4.6-fold in the presence of 15 mM of β-cyclodextrin. Subsequently, an inclusion complex was prepared via physical mixture
of quercetin with β-cyclodextrin (molar ratio of 1:1 and quercetin concentration of 23% (w/w)) and characterized using infrared spectroscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy,
and scanning electron microscopy analyses. The enhancement of aqueous solubility of quercetin using this method was 2.2-fold,
similar to that found in the complex prepared in aqueous solution before the spray-drying process (2.5-fold at a molar ratio
of 1:1, i.e., 6 mM of quercetin and 6 mM of β-cyclodextrin). 相似文献
20.
The protective effect of fruits and vegetables against cancer is well established. It is believed that this effect is mediated by antioxidants and decreased oxidative damage to DNA. However, the identity of the antioxidant(s) responsible is not clear. Moreover, a potentially damaging pro-oxidant effect of some antioxidants has been reported. In this study the ex vivo effects of several dietary antioxidants, including quercetin, various catechins, ascorbic acid and f -tocopherol, were investigated, at concentrations up to 200 u w M, using the single cell gel electrophoresis (comet) assay for DNA damage. Lymphocytes from three healthy subjects were pre-incubated with these antioxidants, and the comet assay was performed on treated, untreated, challenged and unchallenged cells in parallel, oxidant challenge being induced by 5 u min exposure to hydrogen peroxide (final concentrations H 2 O 2 : 30, 45, or 60 u w M). Results using this ex vivo cellular assay showed protection by some antioxidants (quercetin, caffeic acid), no effect by some (catechin, epicatechin, catechin gallate, epicatechin gallate) and an apparently damaging effect by others (epigallocatechin, epigallocatechin gallate). Damage may have been caused by production of H 2 O 2 from these polyphenolics. Neither ascorbic acid nor f -tocopherol protected or damaged DNA. Further study of the role of quercetin and caffeic acid in DNA protection is needed. 相似文献