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1.
The in vitro micronucleus technique 总被引:46,自引:0,他引:46
Fenech M 《Mutation research》2000,455(1-2):81-95
The study of DNA damage at the chromosome level is an essential part of genetic toxicology because chromosomal mutation is an important event in carcinogenesis. The micronucleus assays have emerged as one of the preferred methods for assessing chromosome damage because they enable both chromosome loss and chromosome breakage to be measured reliably. Because micronuclei can only be expressed in cells that complete nuclear division a special method was developed that identifies such cells by their binucleate appearance when blocked from performing cytokinesis by cytochalasin-B (Cyt-B), a microfilament-assembly inhibitor. The cytokinesis-block micronucleus (CBMN) assay allows better precision because the data obtained are not confounded by altered cell division kinetics caused by cytotoxicity of agents tested or sub-optimal cell culture conditions. The method is now applied to various cell types for population monitoring of genetic damage, screening of chemicals for genotoxic potential and for specific purposes such as the prediction of the radiosensitivity of tumours and the inter-individual variation in radiosensitivity. In its current basic form the CBMN assay can provide, using simple morphological criteria, the following measures of genotoxicity and cytotoxicity: chromosome breakage, chromosome loss, chromosome rearrangement (nucleoplasmic bridges), cell division inhibition, necrosis and apoptosis. The cytosine-arabinoside modification of the CBMN assay allows for measurement of excision repairable lesions. The use of molecular probes enables chromosome loss to be distinguished from chromosome breakage and importantly non-disjunction in non-micronucleated binucleated cells can be efficiently measured. The in vitro CBMN technique, therefore, provides multiple and complementary measures of genotoxicity and cytotoxicity which can be achieved with relative ease within one system. The basic principles and methods (including detailed scoring criteria for all the genotoxicity and cytotoxicity end-points) of the CBMN assay are described and areas for future development identified. 相似文献
2.
Brozovic G Orsolic N Knezevic F Horvat Knezevic A Benkovic V Sakic K Borojevic N Dikic D 《Journal of applied genetics》2011,52(3):355-361
The aim of this study was to evaluate the genotoxicity of repeated exposure to isoflurane or halothane and compare it with
the genotoxicity of repeated exposure to cisplatin. We also determined the genotoxicity of combined treatment with inhalation
anaesthetics and cisplatin on peripheral blood leucocytes (PBL), brain, liver and kidney cells of mice. The mice were divided
into six groups as follows: control, cisplatin, isoflurane, cisplatin–isoflurane, halothane and cisplatin–halothane, and were
exposed respectively for three consecutive days. The mice were treated with cisplatin or exposed to inhalation anaesthetic;
the combined groups were exposed to inhalation anaesthetic after treatment with cisplatin. The alkaline comet assay was performed.
All drugs had a strong genotoxicity (P < 0.05 vs. control group) in all of the observed cells. Isoflurane caused stronger DNA damage on the PBL and kidney cells,
in contrast to halothane, which had stronger genotoxicity on brain and liver cells. The combination of cisplatin and isoflurane
induced lower genotoxicity on PBL than isoflurane alone (P < 0.05). Halothane had the strongest effect on brain cells, but in the combined treatment with cisplatin, the effect decreased
to the level of cisplatin alone. Halothane also induced the strongest DNA damage of the liver cells, while the combination
with cisplatin increased its genotoxicity even more. The genotoxicity of cisplatin and isoflurane on kidney cells were nearly
at the same level, but halothane caused a significantly lower effect. The combinations of inhalation anaesthetics with cisplatin
had stronger effects on kidney cells than inhalation anaesthetics alone. The observed drugs and their combinations induced
strong genotoxicity on all of the mentioned cells. 相似文献
3.
Modulation of interleukin-12 synthesis by DNA lacking the CpG motif and present in a mycobacterial cell wall complex 总被引:8,自引:0,他引:8
Filion MC Filion B Reader S Ménard S Phillips NC 《Cancer immunology, immunotherapy : CII》2000,49(6):325-334
A mycobacterial cell wall complex prepared from the non-pathogenic microorganism Mycobacterium phlei, where mycobacterial DNA is preserved and complexed to cell wall fragments, possesses anticancer and immunomodulatory activity.
DNA from a number of prokaryotes has been found to modulate the immune system and to induce cytokine synthesis. We have therefore
determined whether the DNA associated with this complex has the ability to induce the synthesis of interleukin-12 (IL-12),
a potent anticancer cytokine. Mycobacterial DNA complexed with cell wall fragments or DNA purified from M. phlei induced IL-12 synthesis by murine and human monocytes and macrophages in vitro, and was capable of inducing IL-12 synthesis
in vivo in mice following i.p. administration. Neutralization of DNA with cationic liposomes or digestion with DNase I significantly
decreased the ability of the cell wall complex to induce IL-12. CpG methylation of DNA extracted from these cell walls or
from M. phlei did not affect the induction of IL-12 synthesis by monocytes and macrophages. In contrast, CpG methylation of DNA from Escherichia coli abolished its ability to induce IL-12 synthesis. These results demonstrate that unmethylated CpG motifs present in M. phlei DNA are not a prerequisite for the induction of IL-12 synthesis. The size of the mycobacterial DNA, in the range of 5 bp
to genomic DNA, did not influence its capacity to induce IL-12. Our results emphasize that M. phlei DNA associated with the cell wall complex makes a significant contribution to the overall immunomodulatory and anticancer
activity of this mycobacterial cell wall preparation and that these activities are not correlated with the presence of CpG
motifs.
Received: 23 November 1999 / Accepted: 28 March 2000 相似文献
4.
The terminal DNA sequence requirements for piggyBac transposable element excision were explored using a plasmid-based assay in transfected, cultured insect cells. A donor plasmid
containing duplicate 3′piggyBac terminal inverted repeats was constructed that allowed individual nucleotides or groups of nucleotides within one of the
3′ repeats to be mutated. The relative extent of excision using the mutated end versus the wild-type end was then assayed.
Removal of even one of the terminal 3′ G nucleotides from the piggyBac inverted repeat, or removal of the dinucleotide AA from the flanking TTAA target site prevents excision of piggyBac at the mutated terminus. Incorporation of an asymmetric TTAC target site at the 3′ end does not prevent excision from the
mutated end. Thus, both piggyBac DNA and flanking host DNA appear to play crucial roles in the excision process.
Received: 9 July 1996 / Accepted: 6 May 1997 相似文献
5.
A gene transfer system for Rhodococcus opacus PD630 based on electroporation was established and optimized employing the Escherichia coli-Rhodococcus shuttle vectors pNC9501 and pNC9503 as well as the E. coli-Corynebacterium glutamicum shuttle vector pJC1 as suitable cloning vectors for R. opacus PD630, resulting in transformation efficiencies up to 1.5 × 105 CFUs/μg plasmid DNA. Applying the optimized electroporation protocol to the pNC9501-derivatives pAK68 and pAK71 harboring
the entire PHB synthesis operon from Ralstonia eutropha and the PHA synthase gene phaC1 from Pseudomonas aeruginosa, respectively, recombinant PHA biosynthesis was established in R. opacus PD630 and the TAG-negative mutant ROM34. Plasmid pAK68 enabled synthesis and accumulation of poly(3HB) in R. opacus PD630 and ROM34 during cultivation under storage conditions from 1% (w/v) gluconate, of poly(3HB-co-3HV) from 0.2% (w/v) propionate and of poly(3HV) from 0.1% (w/v) valerate. Under storage conditions, recombinant strains
of PD630 and ROM34 harboring pAK71 were able to synthesize and accumulate PHA of the medium chain length hydroxyalkanoic acids
3HHx, 3HO, 3HD and 3HDD from 0.1% (w/v) hexadecane or octadecane and a copolyester composed of 3HHp, 3HN and 3HUD from 0.1%
(w/v) pentadecane or heptadecane. In the recombinant strains of PD630 and ROM34, the thiostrepton-induced overexpression of
a 20 kDa protein was observed with its N-terminus exhibiting a homology of 60% identical amino acids to TipA from Streptomyces lividans.
Received: 13 March 1999 / Received revision: 18 May 1999 / Accepted: 21 May 1999 相似文献
6.
P. K. Mishra S. Khan A. Bhargava H. Panwar S. Banerjee S. K. Jain K. K. Maudar 《Cell biology and toxicology》2010,26(3):279-291
Implications of environmental toxins on the regulation of neutrophil function are being significantly appraised. Such effects
can be varied and markedly different depending on the type and extent of chemical exposure, which results in direct damage
to the immune system. Isocyanates with functional group (–NCO), are considered as highly reactive molecules with diverse industrial
applications. However, patho-physiological implications resulting from their occupational and accidental exposures have not
been well delineated. The present study was carried out to assess the immunotoxic response of isocyanates and their mode of
action at a molecular level on cultured human neutrophils isolated from healthy human volunteers. Studies were conducted to
evaluate both dose- and time-dependent (n = 3) response using N-succinimidyl N-methylcarbamate, a chemical entity that mimics the effects of methyl isocyanate in vitro. Measure of apoptosis through annexin-V-FITC/PI
assay, active caspase-3, apoptotic DNA ladder assay and mitochondrial depolarization; induction of oxidative stress by CM-H2DCFDA and formation of 8′-hydroxy-2′-deoxyguanosine; and levels of antioxidant defense system enzyme glutathione reductase,
multiplex cytometric bead array analysis to quantify the secreted cytokine levels (interleukin-8, interleukin-1β, interleukin-6,
interleukin-10, interferon-γ, tumor necrosis factor, and interleukin-12p70) parameters were evaluated. Our results demonstrate
that isocyanates induce neutrophil apoptosis via activation of mitochondrial-mediated pathway along with reactive oxygen species
production; depletion in antioxidant defense states; and elevated pro-inflammatory cytokine response. 相似文献
7.
Population dynamics of ammonia-oxidizing bacteria (AOB) in a full-scale aerated submerged biofilm reactor for micropolluted
raw water pretreatment was investigated using molecular techniques for a period of 1 year. The ammonia monooxygenase (amoA) gene fragments were amplified from DNA and RNA extracts of biofilm samples. Denaturing gradient gel electrophoresis (DGGE)
profile based on the amoA messenger RNA approach exhibited a more variable pattern of temporal dynamics of AOB communities than the DNA-derived approach
during the study. Phylogenetic analysis of excised DGGE bands revealed three AOB groups affiliated with the Nitrosomonas oligotropha lineage, Nitrosomonas communis lineage, and an unknown Nitrosomonas group. The population size of betaproteobacterial AOB, quantified with 16S ribosomal RNA gene real-time polymerase chain
reaction assay, ranged from 6.63 × 105 to 2.67 × 109 cells per gram of dry biofilm and corresponded to 0.23–1.8% of the total bacterial fraction. Quantitative results of amoA gene of the three specific AOB groups revealed changes in competitive dominance between AOB of the N. oligotropha lineage and N. communis lineage. Water temperature is shown to have major influence on AOB population size in the reactor by the statistic analysis,
and a positive correlation between AOB cell numbers and ammonia removal efficiency is suggested (r = 0.628, P < 0.05). 相似文献
8.
Daniela Guicking Brigitte Fiala Frank R. Blattner Ferry Slik Maryati Mohamed Kurt Weising 《Tree Genetics & Genomes》2011,7(3):573-585
Macaranga (Euphorbiaceae) has received much ecological and evolutionary research attention as a genus that includes some of the most
conspicuous pioneer trees of Southeast Asian tropical rainforests and because of its manifold associations with ants, including
about 30 species that are obligate ant-plants (myrmecophytes). We used sequence data from three chloroplast DNA loci (ccmp5,
ccmp6, atpB-rbcL) to assess phylogeographical patterns in species of Macaranga, section Pruinosae, sampled from various regions of Borneo and the Malay Peninsula. Forty-nine chloroplast DNA haplotypes (HT) were identified
among 768 specimens from five species, Macaranga gigantea (N = 329; 23 HT), Macaranga pearsonii (N = 347; 21 HT), Macaranga puberula (N = 24; 4 HT), Macaranga hosei (N = 48; 6 HT), and Macaranga pruinosa (N = 20; 5 HT). Forty-one haplotypes were species-specific, whereas eight haplotypes were shared by two, three, or four species
and occupied internal positions in a parsimony network. Population genetic parameters based on haplotype frequencies proved
to be in a similar range in the non-myrmecophytic M. gigantea and in the ant-associated M. pearsonii, which have overlapping distributions in northern and eastern Borneo. A comparison of G
ST and N
ST values revealed a strong phylogeographic structure in both species, whereas colonization pathways suggested by the network
topology were different. Both species exhibited similar levels of haplotypic diversity and moderate to high levels of population
differentiation. There were no obvious indications for an influence of the symbiotic ant partners on the population structure
of their host plants. 相似文献
9.
Sister chromatid exchange (SCE) frequency and high-frequency cells (HFCs) were analyzed in 50 storage battery plant workers
with mean blood lead level (BLL) of 40.14±9.99 μg/dL. The mean BLL in the control group (n=30) was 9.77±1.67 μg/dL. This difference in mean BLLs between control and exposed group was statistically significant (p<0.05) and reflects clearly the lead exposure in the workers. Urinary aminolevulinic acid (U-ALA) was also determined in both
control (3.37±0.89 mg ALA/g creatinine) and exposed groups (12.39±6.18 mg ALA/g creatinine) and U-ALA excretion was statistically
higher (p<0.05) in lead-exposed workers. The relationship between biomarkers of lead exposure/effect and HFC percentage was higher
than the relationship between biomarkers of lead exposure/effect and SCE frequency. Accordingly, HFC analysis seemed to be
more sensitive than the SCE analysis as a cytogenetic biomarker for lead exposure. Additionally, the statistically significant
correlation (r
2=0.880, p<0.01) between U-ALA excretion and HFC percentage in lead-exposed workers supported the probability of ALA mediated indirect
mechanism for lead genotoxicity. 相似文献
10.
Wei Dai Linglin Fu Huahua Du Huitao Liu Zirong Xu 《Biological trace element research》2010,136(1):71-78
In order to investigate the effects of montmorillonite (MMT) on reducing dietary lead (Pb) toxicity to tilapia (Oreochromis niloticus), 240 fish were randomly divided into four treatments denominated as follows: control treatment (fed with a basal diet),
MMT treatment (fed with a basal diet added with 0.5% MMT), Pb treatment (fed with a basal diet added with 100 mg Pb per kilogram
dry weight (dw)), and Pb + MMT treatment (fed with a basal diet added with 100 mg Pb per kilogram dw and 0.5% MMT). Changes
in Pb accumulation, oxidative stress, and DNA damage in tilapia were measured after 60 days. DNA damage was assessed using
comet assay. The results showed that MMT supplemented in diet significantly reduced Pb accumulation in kidney and blood of
tilapia exposed to dietary Pb (P < 0.05). Malondialdehyde level decreased insignificantly while levels of total antioxidant capacity and glutathione (GSH),
activities of glutathione peroxidase, and superoxide dismutase increased insignificantly in kidney of tilapia in Pb + MMT
treatment as compared to Pb treatment (P > 0.05). Significant decreases in tail length, tail DNA, tail moment, and Olive tail moment of peripheral blood cells in
Pb + MMT treatment were observed when compared with Pb treatment (P < 0.05). The results indicated that dietary MMT supplementation could alleviate dietary Pb toxicity to tilapia effectively. 相似文献
11.
S. S. Sudge K. B. Bastawde D. V. Gokhale U. R. Kalkote T. Ravindranathan 《Applied microbiology and biotechnology》1998,49(5):594-599
About 1000 bacterial colonies isolated from sea water were screened for their ability to convert dl-5-phenylhydantoin to d(−)N-carbamoylphenylglycine as a criterion for the determination of hydantoinase activity. The strain M-1, out of 11 hydantoinase-producing
strains, exhibited the maximum ability to convert dl-5-phenylhydantoin to d(−)N-carbamoylphenylglycine. The strain M-1 appeared to be a halophilic Pseudomonas sp. according to morphological and physiological characteristics. Optimization of the growth parameters revealed that nutrient
broth with 2% NaCl was the preferred medium for both biomass and enzyme production. d-Hydantoinase of strain M-1 was not found to be inducible by the addition of uracil, dihydrouracil, β-alanine etc. The optimum
temperature for enzyme production was about 25 °C and the organism showed a broad pH optimum (pH 6.5–9.0) for both biomass
and hydantoinase production. The organism seems to have a strict requirement of NaCl for both growth and enzyme production.
The optimum pH and temperature of enzyme activity were 9–9.5 and 30 °C respectively. The biotransformation under the alkaline
conditions allowed the conversion of 80 g l−1
dl-5-phenylhydantoin to 82 g l−1
d(−)N-carbamoylphenylglycine within 24 h with a molar yield of 93%.
Received: 15 September 1997 / Received revision: 5 January 1998 / Accepted: 6 January 1998 相似文献
12.
Carruyo I Fernández Y Marcano L Montiel X Torrealba Z 《Biological trace element research》2008,125(3):276-285
The present study determines lead content in onion root tip cells (Allium cepa L.), correlating it with its toxicity. The treatment was carried at 25 ± 0.5°C using aqueous solutions of lead chloride at
0.1, 0.25, 0.50, 0.75, and 1 ppm for 12, 24, 48, and 72 h. For each treatment, a control where the lead solution was substituted
by distilled water was included. After treatment, the meristems were fixed with a mixture of alcohol–acetic acid (3:1) and
colored according to the technique of Feulgen. Lead content was quantified by graphite furnace absorption atomic spectrometry.
The lead content in the roots ranged from 3.25 to 244.72 μg/g dry weight, with a direct relation with the concentration and
time of exposure. A significant negative correlation was presented (r = −0.3629; p < 0.01) among lead content and root growth increment, and a positive correlation (r = 0.7750; p < 0.01) with the induction of chromosomic aberrations. In conclusion, lead is able to induce a toxic effect in the exposed
roots, correlated with its content. 相似文献
13.
Nitrosamines are stable compounds, biologically and chemically inert unless activated. In biological systems, N-nitrosodiethylamine (NDEA) can be activated by a variety of enzymes, leading to aldehydes and/or intermediates which are
themselves alkylating agents. Additionally, it has been shown that NDEA causes reactive oxygen species (ROS) production and
induces mutagenicity. The cell defense seeks to neutralize ROS that escape the primary defense mechanisms (antioxidants) by
DNA-repair mechanisms. NDEA is present at low concentrations in major dietary sources, like cured meats, salami, millet flour,
and dried cuttlefish, where NDEA mutagenicity has been detected. These facts lead us to evaluate vitamin E as a ROS scavenger,
in Escherichia coli mutants system, against genotoxicity induced by NDEA at low concentrations under exogenous metabolic activation. Statistical
analysis were performed in order to compare the effects of NDEA-induced genotoxicity (a) between the mutants and the wild-type
strains, at the same metabolic activation conditions and, (b) between the same strains in the presence or in the absence of
vitamin E (150 μM). The indirect evaluation of ROS production by NDEA metabolizing shows that vitamin E protects E. coli cells proficient or deficient in the DNA-repair genes from cytotoxic effects. Our results underscore the role of scavenger
molecules such as vitamin E in the diet, avoiding lesions induced by NDEA at low concentrations, via ROS, that could be repaired
by nucleotide excision repair and base excision repair proteins. 相似文献
14.
R. P. Wilson B. Alvarrez L. Latorre D. Adelung B. Culik R. Bannasch 《Polar Biology》1998,19(6):407-413
The movements of gentoo penguins (Pygoscelis papua) in Antarctica were studied by equipping a total of 37 birds captured at Ardley Island, South Shetlands between December
1991 and May 1996 with position-determining devices. Information on area usage was derived from 20 of these devices and covered
the incubation period (N = 3 birds), the chick-rearing period (N = 14 birds) and the over-wintering period (N = 3 birds). During incubation birds only ventured further than 50 km from the colony 20% of the time and no individual ranged
further than 200 km from the colony. In contrast, no individuals attending chicks ranged further than 16 km from the colony.
During winter the maximum distance ranged from the colony was 268 km. Mean distances between the birds and the colony were
80, 81 and 127 km. Individual birds tended to associate with one spot, making short (10 day) forays away before returning
to nodal areas. The ranging capacity of gentoo penguins appears considerably less than that of sympatric congeners and may
reflect the ability of gentoo penguins to dive deeper and thus exploit prey not accessible to congeners.
Received: 1 October 1997 / Accepted: 3 February 1998 相似文献
15.
Limited information is available on the potential risk of degradation products of metal-on-metal bearings in joint arthroplasty.
The aim of this study was to investigate the cytotoxicity and genotoxicity of orthopedic-related cobalt nanoparticles on human
T cells in vitro. T cells were collected using magnetic CD3 microbeads and exposed to different concentrations of cobalt nanoparticles
and cobalt chloride. Cytotoxicity was evaluated by methyl thiazolyl tetrazolium and lactate dehydrogenase release assay. Cobalt
nanoparticles dissolution in culture medium was determined by inductively coupled plasma-mass spectrometry. To study the probable
mechanism of cobalt nanoparticles effects on T cells, superoxide dismutase, catalase, and glutathione peroxidase level was
measured. Cobalt nanoparticles and cobalt ions could inhibit cell viability and enhance lactate dehydrogenase release in a
concentration- and time-dependent manner (P < 0.05). The levels of cobalt ion released from cobalt nanoparticles in the culture medium were less than 40% and increased
with cobalt nanoparticles concentration. Cobalt nanoparticles could induce primary DNA damage in a concentration-dependent
manner, and the DNA damage caused by cobalt nanoparticles was heavier than that caused by cobalt ions. Cobalt nanoparticles
exposure could significantly decrease superoxide dismutase, catalase, and glutathione peroxidase activities at subtoxic concentrations
(6 μM, <CC50). These findings suggested that cobalt nanoparticles could generate potential risks to the T cells of patients suffer from
metal-on-metal total hip arthroplasty, and the inhibition of antioxidant capacity may play important role in cobalt nanoparticles
effects on T cells. 相似文献
16.
Sherri M. Jones Timothy A. Jones Roshni Shukla 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(6):631-638
Short-latency vestibular-evoked potentials to pulsed linear acceleration were characterized in the quail. Responses occurred
within 8 ms following the onset of stimuli and were composed of a series of positive and negative peaks. The latencies and
amplitudes of the first four peaks were quantitatively characterized. Mean latencies at 1.0 g ms−1 ranged from 1265 ± 208 μs (P1, N = 18) to 4802 ± 441 μs (N4, N = 13). Amplitudes ranged from 3.72 ± 1.51 μV (P1/N1, N = 18) to 1.49 ± 0.77 μV (P3/N3, N = 16). Latency-intensity (LI) slopes ranged from −38.7 ± 7.3 μs dB−1 (P1, N = 18) to −71.6 ± 21.9 μs dB−1 (N3, N = 15) and amplitude-intensity (AI) slopes ranged from 0.20 ± 0.08 μV dB−1 (P1/N1, N = 18) to 0.07 ± 0.04 μV dB−1 (P3/N3, N = 11). The mean response threshold across all animals was −21.83 ± 3.34 dB re: 1.0 g ms−1 (N = 18). Responses remained after cochlear extirpation showing that they could not depend critically on cochlear activity.
Responses were eliminated by destruction of the vestibular end organs, thus showing that responses depended critically and
specifically on the vestibular system. The results demonstrate that the responses are vestibular and the findings provide
a scientific basis for using vestibular responses to evaluate vestibular function through ontogeny and senescence in the quail.
Accepted: 18 January 1997 相似文献
17.
Unsurprisingly, survey results indicate that Texas biology and biological anthropology faculty with expertise in an evolutionary
area strongly support teaching “just evolution” (100%; N = 54) and not creationism/intelligent design. Importantly, they do not think that religious faith is incompatible with acceptance
of evolutionary biology (91%; N = 55), even though 50% (N = 52) describe themselves as “not at all religious.” As school boards nationwide debate science standards, it is important
that faculty with relevant expertise have a voice. Biological anthropologists should not be overlooked as a public resource
in these debates. 相似文献
18.
Caffeine potentiates the lethal effects of ultraviolet and ionising radiation on wild-type Schizosaccharomyces pombe cells. In previous studies this was attributed to the inhibition by caffeine of a novel DNA repair pathway in S. pombe that was absent in the budding yeast Saccharomyces cerevisiae. Studies with radiation-sensitive S. pombe mutants suggested that this caffeine-sensitive pathway could repair ultraviolet radiation damage in the absence of nucleotide
excision repair. The alternative pathway was thought to be recombinational and to operate in the G2 phase of the cell cycle. However, in this study we show that cells held in G1 of the cell cycle can remove ultraviolet-induced lesions in the absence of nucleotide excision repair. We also show that
recombination-defective mutants, and those now known to define the alternative repair pathway, still exhibit the caffeine
effect. Our observations suggest that the basis of the caffeine effect is not due to direct inhibition of recombinational
repair. The mutants originally thought to be involved in a caffeine-sensitive recombinational repair process are now known
to be defective in arresting the cell cycle in S and/or G2 following DNA damage or incomplete replication. The gene products may also have an additional role in a DNA repair or damage
tolerance pathway. The effect of caffeine could, therefore, be due to interference with DNA damage checkpoints, or inhibition
of the DNA damage repair/tolerance pathway. Using a combination of flow cytometric analysis, mitotic index analysis and fluorescence
microscopy we show that caffeine interferes with intra-S phase and G2 DNA damage checkpoints, overcoming cell cycle delays associated with damaged DNA. In contrast, caffeine has no effect on
the DNA replication S phase checkpoint in reponse to inhibition of DNA synthesis by hydroxyurea.
Received: 16 June 1998 / Accepted: 13 July 1998 相似文献
19.
Goulart Vincius D. L. R. Teixeira Camila P. Young Robert John 《European Journal of Wildlife Research》2010,56(4):641-649
In this study, we investigated what problems urban marmosets (Callithrix penicillata) face in a city environment through the analysis of responses to callouts (N = 348) made by the environmental police of Belo Horizonte, Minas Gerais, Brazil, in the period from 2002 to 2007. Our objective
was to characterise the problems faced by the marmosets and human city dwellers. The environmental police responded to two
types of callouts: (1) solicitation whereby a person called them to report a problem (N = 218); and (2) the report of a hurt or injured animal (N = 127). On average, one callout per week was made in relation to urban marmosets. We found no time of year effects in relation
to callouts, or any effect of gender or age of the person making the callout (P > 0.05). Furthermore, we found no environmental (e.g. percentage of “green area”) or socioeconomical variables (e.g. salary
levels) of the city’s administrative regions associated with callouts (P > 0.05). The majority of callouts resulted in the attempt to capture marmosets (N = 345), and usually, only one animal was captured (N = 309). Many of these animals were released into city forest fragments (N = 146). Some sick animals were sent to veterinary clinics (N = 25) whereas others or confiscated animals were sent to the government’s wildlife processing centre (N = 143). From this data, we were able to make a series of recommendation about how the management of urban marmosets could
be improved. 相似文献
20.
Kazimirova A Magdolenova Z Barancokova M Staruchova M Volkovova K Dusinska M 《Mutation research》2012,748(1-2):42-47
The in vitro genotoxicity of PLGA-PEO (poly-lactic-co-glycolic acid-polyethylene oxide copolymer) nanoparticles was assessed in TK6 cells using the comet assay as well as cytokinesis-block micronucleus (CBMN) assay. The cells were exposed to 0.12-75μg/cm2 of PLGA-PEO nanoparticles during 2 and 24h for analysis in the comet assay, and to 3-75μg/cm2 of these nanoparticles during 4, 24, 48 and 72h, respectively, for analysis in the CBMN assay. Two different protocols for treatment with cytochalasin B were used. We found that PLGA-PEO was neither cytotoxic (measured by relative cell growth activity and cytokinesis-block proliferation index (CBPI)), nor did it induce DNA strand-breaks (detected by the comet assay) or oxidative DNA lesions (measured by the comet assay modified with lesion-specific enzyme formamidopyrimidine-DNA-glycosylase). There were no statistically significant differences in the frequencies of micronucleated binucleated cells (MNBNCs) between untreated and treated cells in either of the conditions used. This suggests that PLGA-PEO did not have potential genotoxicity. However, using two experimental protocols of the micronucleus assay, PLGA-PEO nanoparticles showed a weak but significant increase in the level of MN in mononucleated cells, in cells treated for 48h with PLGA-PEO nanoparticles when cytochalasin B was added for the last 24h (1st protocol), and in cells treated for 24h with PLGA-PEO nanoparticles followed by washing of NPs and addition of cytochalasin B for another 24h (2nd protocol). It remains unclear whether the increase of MNMNC after treatment with PLGA-PEO nanoparticles is the effect of a possible, weak aneugenic potential or early effect of these particles, or due to another reason. These results suggest that aneugenicity in addition to clastogenicity may be considered as an important biomarker when assessing the genotoxic potential of polymeric nanoparticles. 相似文献