Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SSB”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources
PubMedDate not supplied

Decreased DNA repair capacity in familial, but not in sporadic Alzheimer's disease.

Using the alkaline filter elution technique we determined the induction and disappearance of DNA single-strand breaks (SSB) in freshly isolated peripheral blood lymphocytes (PBL) from 43 Alzheimer's disease (AD) patients and 48 normal, healthy age- and sex-matched control subjects following in vitro exposure to N-ethyl-N-nitrosourea (ENU). The mean percentage SSB disappearance in PBL from control subjects at 1 h after ENU treatment was 41.4 +/- 2.9%; this was not significantly different from that found in samples from AD patients which had no (n = 16) or one (n = 12) first-degree relative with dementia (42.5 +/- 8.2% and 43.0 +/- 4.4%, respectively; p greater than 0.75). However, in PBL of 15 AD patients with at least two first-degree relatives with dementia the mean percentage SSB disappearance was 23.6 +/- 5.8%, which was significantly lower than that found in controls (p less than 0.01) or in the other AD patients (p less than 0.02).

Aged↗
PubMed1992

Induction of DNA breaks in SV40 by heavy ions.

Simian virus (SV40) DNA was used to study the induction of DNA strandbreaks by heavy ions varying in LET. DNA was exposed to X-rays and to accelerated particles either in dilute solution or in the presence of different radical scavengers. Relative proportions of the intact supercoiled DNA, nicked form arising from single strand breaks (SSB) and linear molecules produced by double strandbreaks (DSB) were quantified on the base of their electrophoretic mobility in agarose gels. Cross sections for the induction of SSBs and DSBs were calculated from the slope of dose effect curves. Mercaptoethanol was found to protect more efficiently against DNA strand breakage than Tris. When the biological efficiency, i.e. the number of strand breaks per unit dose and molecule weight was evaluated as a function of LET, curves for SSB induction always showed a continuous decrease. For DSB induction, an increase in the yield of DSBs with a maximum around 500 keV/micrometer was observed in the presence of radical scavenger. This peak of biological efficiency gradually disappeared when the radiosensitivity of the system was increased, and was no longer apparent in the dilute buffer system, where DNA showed a high susceptibility to strand breakage. When the relative biological efficiency was plotted versus LET, the curve for DSB induction observed in a low radical scavenging environment paralleled the curve obtained for SSB induction.

DNA Damage↗
PubMed1983

Single-strand breaks in DNA of various organs of mice induced by styrene and styrene oxide.

Styrene and its metabolite styrene oxide were given i.p. to mice. The induction of single-strand breaks (SSB) in DNA was studied with the DNA unwinding technique. The level of SSB in kidney-DNA was a linear function of the dose for both substances. Styrene and styrene oxide induced an increase in the level of SSB in DNA of kidney, liver, lung, testis and brain 1 h after administration. After 24 h the damage remained on an enhanced level in liver, lung and testis after styrene oxide administration and in all organs except liver after styrene administration.

Animals↗
PubMed1993

Clofibrate enhances the DNA damaging action and cytotoxicity of nitrosoureas.

The ability of N-ethyl-N-nitrosourea (ENU) to produce single strand breaks (SSB) and N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU) to produce SSB and DNA-DNA interstrand cross-links was measured in L1210 cells that had been pretreated with clofibrate (CLO). When ENU was used the SSB frequency rose from 12.4 +/- 1.6/10(6) bases in control cells to 17.3 +/- 1.5/10(6) bases in CLO-treated cells and from 2.8 +/- 0.1/10(6) bases in control cells to 5.5 +/- 0.4/10(6) in CLO-treated cells when BCNU was the damaging agent. Similarly the cross-linking frequency rose from 3.5 +/- 0.1/10(6) bases in control cells to 12.1 +/- 0.5/10(6) bases in CLO-treated cells when BCNU was the cross-linking agent. CLO treatment increased the production of superoxide anion four-fold over the controls and it increased the cytotoxicity of BCNU. Forty-two percent of the control+BCNU cells survived after 24 h whereas only 24% of the CLO+BCNU cells survived. The stimulation of the diffuse condition known as oxidative stress increased the interaction of nitrosoureas with DNA and resulted in increased biological responses, e.g. cytotoxicity.

Animals↗
PubMed1994

Effects of VA-045, a novel apovincaminic acid derivative, on age-related impairment evidence in electroencephalograph, caudate spindle, a passive avoidance task and cerebral blood flow in rats.

1. The ability of VA-045 to improve aged-related impairment on electroencephalograph (EEG), caudate spindle, performance on a passive avoidance task and cerebral blood flow (CBF) were evaluated in rats. 2. The cortical EEG of the aged rats showed a higher incidence of spontaneous spindle burst (SSB) than seen in young rats. VA-045 decreased the incidence of SSB in aged rats. In contrast, vinpocetine increased the incidence of SSB in aged rats. 3. Electrical stimulation of the striatum in aged rats lead to a higher incidence of neocortical high voltage spindle (CS) than seen in young rats. In young rats, VA-045 had no effect on the CS, whereas an age-related increase in CS was blocked by VA-045, but was enhanced by vinpocetine. 4. There were no differences in the cortical EEG arousal response elicited by stimulation of the reticular formation of the brain stem in rats of all ages. VA-045 and vinpocetine had no effect on the cortical EEG arousal response in both young and aged rats. 5. VA-045, but not vinpocetine, attenuated the age-related decreased step through latency (STL) on a passive avoidance task. VA-045 and vinpocetine did not enhance the acquisition of learning behavior in a passive avoidance task in young rats. 6. VA-045 increased the cerebral blood flow (CBF) in both young and aged rats and the potency in aged rats was greater than that in young rats. Vinpocetine had no effect on CBF in either young or aged rats. 7. The pharmacological effects of VA-045 on age-related neuronal dysfunction are discussed.

Aging↗
PubMed1987

Enhancement of X ray induced DNA damage by pre-treatment with halogenated pyrimidine analogs.

The use of the halogenated pyrimidine analogs, including bromodeoxyuridine (BrdUrd) and iododeoxyuridine (IdUrd), as potential clinical radiosensitizers is an area of renewed clinical research. Cellular radiation effects of these analogs using clinically achievable steady state plasma levels (10(-7)-10(-5) M) were measured in vitro using exponentially growing Chinese hamster V79 cells. Radiation response was determined by clonogenic survival and by the production of DNA single strand (SSB) and double strand breaks (DSB) using filter elution techniques. Replacement of thymidine in DNA by BrdUrd or IdUrd was also determined. Drug exposure of BrdUrd or IdUrd for two population doublings (17 hr) prior to irradiation resulted in a progressive reduction of n and D0 compared to untreated controls over the drug dose range of 10(-7)-10(-5) M. The percent thymidine replacement increased from 1% at 10(-7) M to 5% at 10(-6) M to 23% at 10(-5) M. Using a 17 hr exposure at 10(-5) of BrdUrd or IdUrd, the production of SSB and DSB was increased by greater than or equal to 2X and greater than or equal to 1.5X respectively. No differences in the kinetics of repair of SSB and DSB were found following 3 hr of post-irradiation repair. We conclude that in this in vitro model, there appears to be a direct relationship between percent thymidine replacement, reduction of radiation survival parameters (n, D0), and the production of DNA strand breaks in the clinically achievable dose range of these halogenated pyrimidine analogs. These filter elution assays may be adapted to in vivo studies and possibly may allow for monitoring of radiation-induced DNA damage and repair in clinical tumor specimens treated with these radiosensitizers.

Animals↗
PubMedDate not supplied

Preferential transfection with M13mp2 RF DNA synthesized in vitro.

Single-strand DNA binding protein (SSB) from Escherichia coli abolishes transfection of E.coli by viral M13mp2 DNA at levels that inhibit transfection by M13mp2 replicative form (RF) DNA by approx. 25%. Synthesis of M13mp2 RF DNA (SS leads to DS) has been carried out using DNA polymerase I (Klenow fragment) and a unique 15-nucleotide primer. A time course for in vitro synthesis showed that the increase in transfection in the presence of SSB paralleled DNA synthesis after an initial lag period for transfection. Digestion of replication products with restriction endonucleases and S1 endonuclease indicates that only those molecules that are fully or almost fully duplex transfect competent cells in the presence of SSB.

Base Composition↗
PubMed1990

Evidence for AP site formation related to DNA-oxygen alkylation in CHO cells treated with ethylating agents.

DNA single-strand breaks (ssb) induced by N-ethyl-N-nitrosourea (ENU) in CHO cells are quickly resealed within 10 min after treatment. This rapid repair kinetics is not explained by the rate of base excision repair which removes the main ethyl products with a half-life in the order of hours. We have explored the potential use of methoxyamine (MX), a chemical that reacts at neutral pH with AP sites in DNA in vitro, to clarify the origin of ENU-induced ssb. The presence of 50 mM MX during cell treatment with diethyl sulfate (DES) caused selective inhibition of the repair of AP sites generated during base excision repair and inhibited alkaline cleavage at these sites. The treatment of CHO cells with ENU in the presence of MX clearly showed that the burst of ssb observed immediately after treatment was due to AP site formation. Plasmid DNA treated in vitro with ENU did not present AP endonuclease-sensitive sites; therefore, the AP sites produced in CHO cells by ENU treatment are not due to the chemical hydrolysis of a very unstable ethyl adduct but rather are intermediates of an as yet undefined enzymatic pathway. This process occurs specifically after treatment with SN1-type ethylating agents (ENU and N-ethyl-N'-nitro-N-nitrosoguanidine) suggesting an association between this phenomenon and DNA-oxygen alkylation. We suggest that these breaks are generated by a mechanism of O6-ethylguanine processing without removal of the modified base.

Animals↗
PubMed1995

Detection of single-strand breaks and formamidopyrimidine-DNA glycosylase-sensitive sites in DNA of cultured human fibroblasts.

Under oxidative stress 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG), a damaged base with mutagenic potential, and single-strand breaks (SSB) are formed in DNA. Both lesions are frequently used as a parameter for oxidative damage of DNA. Here we report on results from the evaluation of a modified nick translation assay, where 8-oxodG and SSB formation in cellular DNA of cultured human fibroblasts were simultaneously detected. The assay is based on a method previously described by others, with several modifications in reaction conditions and type of substrate. We used formamidopyrimidine-DNA glycosylase (FPG) in our assay in order to measure the formation of FPG-sensitive lesions (which include 8-oxodG) in DNA of human fibroblasts in response to ionising radiation. The quantification of the DNA damage was based on calibration experiments with plasmid DNA pUC19. Dose-response curves of SSB and FPG-sensitive lesion formation in human fibroblasts VH-10 were established. A very low background level of 8-oxodG was detected in unirradiated fibroblasts (approx. 500 residues per cell).

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1992

Affinity of SSB/La nuclear antigen to small nuclear ribonucleic acids.

Anti-SSB/La antibody is one kind of antinuclear antibody and is found predominantly in patients with Sjögren's syndrome and systemic lupus erythematosus. SSB/La antigen is present in the nucleus as ribonucleoprotein in particle form and is composed of peptide and RNAs. SSB/La antigen can be partially purified through several sequential procedures including salt fractionation and ion exchange chromatography. SSB/La antigen is capable of binding to 4 RNAs from uninfected KB cells and 6 RNAs from Epstein-Barr virus transformed WiL2 cells. These RNAs can bind to SSB/La peptide in vitro and form ribonucleoprotein complexes which could be reprecipitated by anti-SSB/La antibody. SSB/La associated RNAs are labile and subjected to degradation easily. Anti-SSB/La antibody may be a useful probe to investigate the potential role of Epstein-Barr virus involvement in cutaneous pathology.

Antibodies, Antinuclear↗
PubMedDate not supplied

L-histidine-mediated enhancement of hydrogen peroxide-induced cytotoxicity: relationships between DNA single/double strand breakage and cell killing.

Results presented in this study demonstrate an association between the L-Histidine-mediated enhancement of H2O2-induced cytotoxicity and the formation of DNA double strand breakage (DSB), whereas no relationship exists between the increased cytotoxic response and DNA single strand breakage (SSB). Indeed, the higher lethality and the production of DNA DSB occurred in oxidatively-injured cells regardless of whether the exposure to L-Histidine was performed before or during challenge with the oxidant. In fact, the increased level of DNA SSB detected in cells simultaneously exposed to the oxidant and the amino acid was not observed in cells pre-treated with L-Histidine and then challenged with hydrogen peroxide. Further experiments have demonstrated an association between the kinetics of DNA DSB formation and the enhancement of the cytotoxic response. In conclusion, intracellular L-Histidine seems to mediate the formation of DNA DSB and the increased growth-inhibitory response elicited by the oxidant. In addition, these results suggest that the enhancement of DNA SSB is produced by the extracellular/plasma membrane fraction of the amino acid and not causally related to the L-Histidine-mediated increase of the growth-inhibitory response to H2O2-treated cells.

Animals↗
PubMed2006

The role of reactive oxygen species in the herbicide acetochlor-induced DNA damage on Bufo raddei tadpole liver.

After exposure of Bufo raddei tadpoles to acetochlor (ACETO) for 14 days, malondialdehyde (MDA) and DNA-single strand break (DNA-SSB) in livers were analyzed. An enhanced accumulation of MDA suggests that ACETO causes oxidative stress, and the significant increase in the level of DNA-SSB indicates that ACETO induces DNA damage in a dose-dependent manner as well. On the basis of the fact that oxidative stress is caused by excessive production of reactive oxygen species (ROS), and the present results, we speculate that ACETO-induced DNA damage may be a consequence of the generation of ROS. To evaluate this hypothesis, tadpoles were treated with ROS scavenger, N-acetyl-L-cysteine (NAC) or melatonin (MEL), prior to ACETO exposure. The decrease of DNA-SSB level and the increase of total antioxidant capability (TAC) show that ACETO-caused DNA damage can be attenuated by NAC and MEL. In addition, a negative correlation was observed between the extent of DNA damage and the level of TAC in tadpole liver. In conclusion, the results suggest that ACETO-induced DNA damage is mediated by ROS.

Acetylcysteine↗
PubMed2006

Real-time observation of RecA filament dynamics with single monomer resolution.

RecA and its homologs help maintain genomic integrity through recombination. Using single-molecule fluorescence assays and hidden Markov modeling, we show the most direct evidence that a RecA filament grows and shrinks primarily one monomer at a time and only at the extremities. Both ends grow and shrink, contrary to expectation, but a higher binding rate at one end is responsible for directional filament growth. Quantitative rate determination also provides insights into how RecA might control DNA accessibility in vivo. We find that about five monomers are sufficient for filament nucleation. Although ordinarily single-stranded DNA binding protein (SSB) prevents filament nucleation, single RecA monomers can easily be added to an existing filament and displace SSB from DNA at the rate of filament extension. This supports the proposal for a passive role of RecA-loading machineries in SSB removal.

Binding Sites↗
PubMed2005

Genetic polymorphisms and possible gene-gene interactions in metabolic and DNA repair genes: effects on DNA damage.

We investigated in a central European population, the association between genetic polymorphisms in several genes coding for xenobiotic metabolizing enzymes (CYP1A1, CYP2E1, EPHX1, GSTP1, GSTM1 and GSTT1) and in DNA repair genes (XPD, XPG, XPC and XRCC1) and the levels of single-strand breaks (SSBs) and SSB endonuclease III sensitive sites (endoIII sites) in peripheral blood lymphocytes. No significant differences in the mean levels of SSBs and endoIII sites after stratification for main confounders and occupational exposure were observed in the studied population. Significantly higher levels of SSBs were observed in individuals bearing the wild-type alleles (AA) (0.75+/-0.51SSB/10(9)Da) and heterozygous (AC) genotypes (0.67+/-0.49SSB/10(9)Da) compared to those with homozygous XPD (CC) genotype (0.43+/-0.28SSB/10(9)Da, P=0.033). A moderate increase in the levels of SSBs was also found in individuals with the homozygous XPG exon 15 wild type (GG) and heterozygous (GC) genotypes in comparison to those with the homozygous (CC) genotype (P=0.066) and in individuals with low activity EPHX1 genotype in comparison to those with high activity genotype. Nevertheless, these differences were not statistically significant. No other significant association was found. When gene-gene interactions were evaluated, a combination of EPHX1 activity genotypes with that of either XPD or XPG significantly (P=0.003 and 0.016, respectively) modulated SSB levels resulting in a three-fold difference between the "protective" and the "adverse" genotype-combinations. Almost three-fold differences in SSB levels were found between the "protective" and the "adverse" genotype-combinations of EPHX1 activity genotype and GSTM1 or GSTT1 genotypes, respectively. In conclusion, our results suggest a relation between markers of genotoxicity and polymorphisms in genes coding for xenobiotic metabolizing and DNA repair enzymes as well as a modulating effect of combinations of these polymorphisms.

Adult↗
PubMed2004

[Congenital heart block associated with maternal anti SSA/SSB antibodies :a report of four cases].

Congenital heart block (CHB) associated with maternal anti-SSA/SSB antibodies: a report of four cases. CHB detected in utero is strongly associated with maternal antibodies to SSA (Ro) and SSB (La). Their pathogenic role in the development of CHB has been established in several studies. The mothers of affected infants frequently had autoimmune disease (systemic lupus erythematosus, Sjögren's syndrome) or were entirely asymptomatic. It is very difficult to identify pregnant asymptomatic mothers carrying anti-SSA/SSB antibodies. We report four cases of infants born to asymptomatic mothers with anti-SSA/SSB antibodies, three of them developed isolated congenital cardiac heart block and one with no evidence of CHB. All three CHB are detected during pregnancy between 16 and 24 weeks of gestation. All maternal sera contained antibodies to SSA alone or the both SSA and SSB. Three of four subsequent pregnancies were complicated by heart block. One child affected died in utero. While the two other newborns with CHB required pacemaker insertion during the first 3 months of life. Although the association of anti-SSA/SSB with CHB is widely accepted, the precise mechanism by which these antibodies cause cardiac conduction abnormalities remains to be defined. Antibodies to SSA/SSB have been proposed to be a serologic marker for neonatal lupus syndrome and CHB. Fetal and neonatal diseases are presumed to be due to the transplacental passage of these IgG autoantibodies from the mother into the fetal circulation. Since these antibodies may have a pathogenic role in CHB, screening of infants with isolated CHB or neonatal lupus and their mothers for the presence of anti-SSA and anti-SSB is strongly recommended.

Adult↗
PubMed2005

Expression and purification of the SsbB protein from Streptococcus pneumoniae.

The Gram positive bacterium, Streptococcus pneumoniae, has two genes, designated ssbA and ssbB, which are predicted to encode single-stranded DNA binding proteins (SSB proteins). We have shown previously that the SsbA protein is similar in size and in biochemical properties to the well-characterized SSB protein from Escherichia coli. The SsbB protein, in contrast, is a smaller protein and has no counterpart in E. coli. This report describes the development of an expression system and purification procedure for the SsbB protein. The ssbB gene was amplified from genomic S. pneumoniae DNA and cloned into the E. coli expression vector, pET21a. Although, we had shown previously that the SsbA protein is strongly expressed from pET21a in the E. coli strain BL21(DE3)pLysS, no expression of the SsbB protein was detected in these cells. However, the SsbB protein was strongly expressed from pET21a in the Rosetta(DE3)pLysS strain, a derivative of BL21(DE3)pLysS which supplies the tRNAs for six codons that are used infrequently in E. coli. The differential expression of the two SSB proteins in the parent BL21(DE3)pLysS strain was apparently due to the presence of two rare codons in the ssbB gene sequence that are not present in the ssbA sequence. Using the Rosetta(DE3)pLysS/pETssbB expression system, a protocol was developed in which the SsbB protein was purified to apparent homogeneity. DNA binding assays confirmed that the purified SsbB protein had single-stranded DNA binding activity. The expression and purification procedures reported here will facilitate further investigations into the biological role of the SsbB protein.

Bacterial Proteins↗
PubMed2004

Biflavonoids from Brazilian pine Araucaria angustifolia as potentials protective agents against DNA damage and lipoperoxidation.

A biflavonoid fraction (BFF) obtained from Araucaria angustifolia needles was effective to quench singlet oxygen (1O2), to protect plasmid DNA against single strand break (ssb) caused by 1O2 or Fenton reaction and to inhibit Fenton or UV radiation-induced lipoperoxidation in phosphatidylcholine liposomes. The activity of the biflavonoid fraction (BFF) was compared with quercetin, rutin (flavonoids), ginkgetin, amentoflavone (biflavonoids), alpha-tocopherol and Trolox. The BFF displayed a higher quenching rate constant compared to flavonoids and biflavonoids and protected against ssb induced by 1O2. Although the BFF was not as efficient as either flavonoids, alpha-tocopherol or Trolox in protection against ssb induced by Fenton-reaction or lipoperoxidation, these scavenging properties suggest that BFF is still an excellent candidate for successful employment as an antioxidant and photoprotector.

Brazil↗
PubMed2004

Sensitivity of the FPG protein towards alkylation damage in the comet assay.

The comet assay (single cell gel electrophoresis) is widely used for the evaluation of DNA-damaging effects in genotoxicity testing and population monitoring. In its standard version at pH >13, DNA double strand breaks (DSB), DNA single strand breaks (SSB) and alkali-labile sites (ALS) lead to increased DNA migration. At reduced pH (12.5-12.1) the expression of ALS as SSB can be eliminated and the effect of SSB only can be identified. Specific endonucleases have been used to characterize specific classes of DNA damage. The formamido pyrimidine glycosylase (FPG) protein has been used to assess oxidative DNA base damage because it detects 8-OH guanine and other oxidatively damaged purines. Here, we show that the FPG protein also detects alkylation damage with high sensitivity in the comet assay. Human whole blood, isolated lymphocytes and V79 cells were treated with alkylating agents and post-incubated with FPG. FPG strongly enhanced MMS- and EMS-induced DNA damage but had no significant effect on ENU-induced DNA damage, indicating that the amount of N-7 guanine alkylation is responsible for the observed effect. Reducing the pH during alkali unwinding and electrophoresis to 12.5 to avoid the contribution of ALS to the comet assay effects, strongly decreased the sensitivity of the comet assay with and without FPG treatment and prevented DNA migration. We conclude that enhanced DNA effects in the comet assay by FPG after exposure to genotoxins with unknown mode of action should not directly be regarded as evidence for the presence of oxidative damage. Furthermore, reducing the pH leads to a considerable loss in sensitivity and should not be used in biomonitoring and other applications which require a sensitive protocol.

Alkylation↗