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PubMed1997

DNA damage, gadd153 expression, and cytotoxicity in plateau-phase renal proximal tubular epithelial cells treated with a quinol thioether.

2-Bromo-bis-(glutathion-S-yl)hydroquinone [2-Br-bis-(GSyl)HQ] causes DNA single-strand breaks (SSB), causes growth arrest, induces the expression of gadd153 (a gene inducible by growth arrest and DNA damage), and decreases histone H2B mRNA in log-phase renal proximal tubular epithelial cells (LLC-PK1). Renal epithelial cells in vivo normally exhibit a low mitotic index, therefore experiments in both plateau- and log-phase cells are necessary for a comprehensive understanding of the stress response to 2-Br-bis-(GSyl)HQ. In the present article we demonstrate that not all features of the stress response in log-phase cells are reproduced in plateau-phase cells. Thus, although 2-Br-bis-(GSyl)HQ causes concentration and time-dependent increases in DNA SSB, and increases the expression of gadd153, histone H2B mRNA levels are unaltered in plateau-phase cells. The relationship between reactive oxygen species, DNA damage, gene expression, and cytotoxicity was also investigated. Our findings suggest that (i) 2-Br-bis-(GSyl)HQ-mediated DNA damage in LLC-PK1 cells is mediated by the generation of H2O2; (ii) DNA damage, either directly or indirectly, contributes to cell death; and (iii) DNA damage, either directly or indirectly, provides the initial signal for gadd153 expression. In addition, DNA repair is rapid in LLC-PK1 cells, and the DNA-repair inhibitors 1-beta-D-arabinofuranosylcytosine and hydroxyurea have no effect on the amount of DNA SSB. Although the addition of 3-aminobenzamide following 2-Br-bis-(GSyl)HQ exposure has no effect on the removal of DNA SSB, it causes a slight but significant increase in gadd153 expression and cell viability, indicating that activation of poly(ADP-ribose)polymerase may exacerbate toxicity. Finally, aurintricarboxylic acid did not prevent DNA SSB or cytotoxicity in 2-Br-bis-(GSyl) HQ-treated LLC-PK1 cells, implying that activation of endonucleases does not play a role in these processes.

Animals↗
PubMed1995

Fluorescence recovery assay: a continuous assay for processive DNA polymerases applied specifically to DNA polymerase III holoenzyme.

A continuous assay was developed for processive DNA polymerases. The specific enzyme used to develop the assay was the most processive polymerase known, Escherichia coli DNA polymerase III holoenzyme. The assay was based upon the recovery of the intrinsic fluorescence of single-stranded DNA binding protein (SSB) as it was displaced from the DNA template during DNA synthesis. The intrinsic fluorescence of SSB was quenched by as much as 80% when it bound to single-stranded DNA. As the DNA was replicated, SSB was displaced and recovered its fluorescence. The amount of fluorescence recovered was directly proportional to the amount of DNA synthesized and was used to quantitate the rate of DNA synthesis. However, since 50 to 60 nucleotides must be replicated for every SSB tetramer released, the assay is expected to work best for processive DNA polymerases. The only requirement for using this assay with other DNA polymerases is that they be able to synthesize DNA on a template coated with SSB. The replication SSBs do not pose an obstacle to the assay because they all appear to have intrinsic fluorescence that is sensitive to their ssDNA-bound state.

Bacterial Proteins↗
PubMed1994

Cigarette tar promotes neutrophil-induced DNA damage in cultured lung cells.

We have investigated the ability of aqueous cigarette tar extracts to promote human polymorphonuclear leukocyte (PMNL)- and hydrogen peroxide (H2O2)-induced DNA single-strand breaks (DNA-SSB) in cultured human lung cells. Tar extract itself did not cause any DNA-SSB formation, whereas PMNL (activated with phorbol myristate acetate (PMA)) and H2O2 both caused a small but significant DNA-SSB formation on their own. On the other hand, if cells were first treated with tar extract and then exposed to PMA-activated PMNL or H2O2, the DNA-SSB formation increased considerably. Pretreatment with iron-loaded tar extracts caused a greater increase after PMNL exposure than pretreatment with regular tar extracts. No DNA-SSB formation was found if catalase was present during the PMNL exposure, indicating that H2O2 was important for the PMNL-induced DNA damage. These findings suggest that cigarette tar promotes neutrophil-induced DNA damage in human lung cells and that this effect can be further potentiated by iron. This can be of importance in explaining the carcinogenic effects of cigarette smoking and the increased risk of lung cancer among asbestos workers and iron miners who smoke.

Bronchi↗
PubMed1993

Two mutant RecA proteins possessing pH-dependent strand exchange activity exhibit pH-dependent presynaptic filament formation.

In previous studies it was shown that the mutant RecA proteins, [G160N]RecA and [H163A]RecA, are unable to catalyze ATP-dependent DNA strand exchanges at pH 7.5, but are active at pH 6.0 to 6.8. Here, we have used electron microscopy to follow the assembly of these mutant proteins onto single-stranded DNA at pH 7.5 and pH 6.2. In the absence of ATP, the filaments formed by the mutant proteins were similar to those formed by the wild-type protein, at both pH 7.5 and pH 6.2. In the presence of ATP, however, the filaments formed by the wild-type protein at pH 7.5 were extended and were stable in the presence of saturating SSB protein, whereas the filaments formed by the mutant proteins were shorter and unstable in the presence of SSB protein. At pH 6.2, in contrast, the filaments formed by the mutant proteins in the presence of ATP were of the same contour length as the wild-type RecA protein filaments and were stable in the presence of SSB protein. In the presence of the non-hydrolyzable ATP analog, ATP gamma S, and SSB protein, the mutant proteins formed full-length filaments at pH 7.5 that had a helical periodicity identical with that of the wild-type filaments (and characteristic of the strand exchange-active open conformational state); if SSB protein was omitted, the mutant protein filaments still exhibited the open helical periodicity, but were shorter and of highly variable length, presumably because of an improper threading of the ssDNA into the mutant filament. To account for these results, we propose that: (1) the mutant proteins are unable to isomerize efficiently to the open conformational state at pH 7.5 in the presence of ATP, but are able to do so in the presence of ATP gamma S; this indicates that the mechanistic defect is related to ATP hydrolysis rather than ATP binding; and (2) the mutant proteins are able to isomerize to the open conformational state in the presence of ATP at pH 6.2, indicating that protonation of the mutant filaments is sufficient to relieve the mechanistic deficiency.

Adenosine Triphosphate↗
PubMed2001

Overexpression, rapid isolation, and biochemical characterization of Escherichia coli single-stranded DNA-binding protein.

Escherichia coli (E. coli) single-stranded binding protein (SSB) is a valuable protein for various biotechnical applications, such as PCR and DNA sequencing. Here we describe an efficient expression and purification scheme where the tendency of SSB to aggregate at low salt concentration and high protein concentration is avoided. The method contains fewer steps of purification and results in high protein yield, compared to previous published protocols. In our protocol, cells are harvested after cultivation overnight and SSB is isolated by ammonium sulfate precipitation followed by anion-exchange chromatography. The yield from a 2-liter fed-batch fermentor is 2 g protein, which is higher than all production methods for SSB earlier reported. Moreover, the two classical isolation steps combined in the purification scheme are robust, cost-efficient, and suitable for scaling up. The resulting SSB is pure and a correctly folded tetramer with an apparent binding to single-stranded DNA with a K(D) of 10(-8) M, as determined by surface plasmon resonance.

Amino Acid Sequence↗
PubMed1994

Determination of DNA single-strand breaks in lymphocytes of smokers and nonsmokers exposed to environmental tobacco smoke using the nick translation assay.

The detection of DNA single-strand breaks (SSB) in human mononucleated white blood cells (MWBC) using a modified version of the nick translation assay is presented. This assay allows rapid and sensitive examination of SSB using only 5 ml heparinized blood for an eightfold determination. The assay was standardized by incubation of MBWC in vitro with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a known genotoxic agent. In vitro incubation of MWBC with MNNG induced a dose-dependent increase in DNA-SSB at doses between 5 and 500 microM MNNG. The detection limit for the assay was 5 microM MNNG. To assess the suitability of this assay to detect SSB in vivo a controlled study was performed in which volunteer smokers (n = 5), nonsmokers (n = 5) exposed to environmental tobacco smoke (ETS), and nonsmokers controls (n = 5) were compared. The study lasted 4 experimental days, 2 control and 2 exposure days. On control days (days 1 and 3) smokers and nonsmokers sat in an unventilated 45 m3 room for 8 h. On the exposure days (days 2 and 4) each of the five smokers smoked 24 cigarettes in 8 h, while the five nonsmokers were exposed to the ETS generated by the smoking volunteers. High exposure to tobacco smoke was confirmed by dosimetry of carboxyhemoglobin (CO-Hb), plasma nicotine and cotinine levels. Blood was drawn before and after each exposure on all 4 experimental days for determination of DNA-SSB in lymphocytes immediately after isolation of blood cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Stimulation-induced behavioral inhibition: a new model for understanding physical violence.

Physical violence is widely considered to result from action carried out with the intention of causing injury; that is, from aggression. However, the "hypothesis" of aggression is inapplicable in all but a few instances as well as inappropriate for many destructive, rage-associated responses directed at inanimate objects. This paper outlines a new perspective on physical violence, reinterpreting many behaviors hitherto labeled aggressive as stimulation-seeking behaviors (SSBs) above an arbitrary level of intensity. It is further proposed that: 1) physical violence is a by-product of SSB, driven in part by brain catecholaminergic (CA) systems, and the direct result of exchanges of energy that exceed the body's tolerance threshold; 2) allegedly discrete categories of motor-motivational behavior represent overlapping bands of intensity on a continuous spectrum of SSB; and 3) the sensory input derived from SSB is fed back into the central nervous system where it activates brain serotonergic and/or cholinergic systems, which in turn inhibit CA systems, resulting in a general state of behavioral quiescence. In addition to accounting for a number of previously unexplained observations, the model suggests that physical violence could be prevented by providing groups at high risk with extensive opportunities for therapeutic sensory stimulation to substitute for that derived from excessive SSB. For people at especially high risk, portable devices could be developed that would allow the user to self-administer desired levels of sensory stimulation at moments of intense anger, thereby preventing potentially dangerous outbursts of SSB prior to the onset of the behavior.

Aggression↗
PubMed2000

DNA single-strand breaks are increased in muscle diseases with rimmed vacuoles.

Some pathological similarities between Alzheimer's disease and muscle diseases with rimmed vacuoles (RV) have been pointed out. For example, several pathological hallmark proteins have been reported to be immunopositive in the lesions of both diseases. Since apoptotic processes or primary DNA damage are suggested to play a role in the pathomechanism of Alzheimer's disease, we examined DNA double-strand breaks (DSB) and single-strand breaks (SSB) in the muscle biopsy specimens of several diseases, including muscle diseases with RV. Although no DSB-positive myonuclei were detected in any muscles examined, the number of SSB-positive myonuclei markedly increased in the muscles from cases with polymyositis and muscle diseases with RV. In polymyositis, SSB-positive myonuclei were observed in regenerating fibers and muscle fibers in the vicinity of inflammatory infiltrates, suggesting that the increase of SSB is due to muscle fiber regeneration following necrosis and inflammation. In muscle diseases with RV, however, SSB-positive myonuclei were observed in small angulated fibers and in morphologically normal fibers, regardless of necrosis, regeneration or inflammation. These findings suggest that muscle diseases with RV may share a common pathological process involving DNA damage.

Adolescent↗
PubMed1985

Nuclear localization of a lactic dehydrogenase with single-stranded DNA-binding properties.

In the preceding article [1] we identified the 34 kD single-stranded DNA-binding (ssb) protein, whose synthesis is inhibited in PC12 cells concomitantly with nerve growth factor (NGF)-induced mitotic arrest, with the enzyme lactic dehydrogenase (LDH-ssb protein). Localization studies performed with antibodies raised against the LDH-ssb protein demonstrate the presence of a pool of this protein in the nucleus of several cell types. The nuclear association of this protein is sensitive to DNase treatment of the cells and quantitative electron microscopy confirms that the LDH-ssb protein is located close to chromatin structures. These results point to a possible involvement of the LDH-ssb protein in some nuclear function(s).

Animals↗
PubMed1985

Variability in the nucleic acid binding site size and the amount of single-stranded DNA-binding protein in Escherichia coli.

The Escherichia coli single-stranded DNA binding protein (SSB), essential for DNA replication, recombination and repair, can undergo a thermally induced irreversible conformational change which does not eliminate its biological activity, but changes the number of nucleotides it covers (binding site size) when binding to a single-stranded nucleic acid lattice. The binding site size of native and conformationally changed SSB was also found to be a function of the molecular mass of the polynucleotide, an observation which is unusual for single-stranded DNA binding proteins and will greatly affect the affinity relationship of this protein for nucleic acids. A radioimmunoassay used to quantitate in SSB level in cells revealed the number of SSB tetramers to be larger than initial estimates by a factor of as much as six. All these data suggest that the biological role of SSB and its mechanism of action is by far more complex than originally assumed.

Binding Sites↗
PubMed1982

A CHO-cell strain having hypersensitivity to mutagens, a defect in DNA strand-break repair, and an extraordinary baseline frequency of sister-chromatid exchange.

A mutant of CHO cells (strain EM9) previously isolated on the basis of hypersensitivity to killing by ethyl methanesulfonate (EMS) is approx. 10-fold more sensitive than the parental line, AA8, to killing by both EMS and MMS. It is also hypersensitive to killing by other alkylating agents (ethyl nitrosourea and N-methyl-N'-nitro-N-nitrosoguanidine), X-rays, and ultraviolet radiation. The production and repair of DNA single-strand breaks (SSB) were studied using the technique of alkaline elution of DNA from filters. After exposure to 4 Gy of X-rays at 0 degrees C and subsequent incubation at 25 degrees C, SSB were repaired within 12 min in AA8, but little repair occurred in EM9. Similarly, with doses of EMS or MMS that produced comparable numbers of SSB in AA8 and EM9 at the end of a 10-min exposure, repair of SSB occurred more rapidly in AA8 than in EM9, suggesting that individual SSB are longer lived in EM9. EM9 was found to be hypersensitive also to the induction of mutations and sister-chromatid exchanges (SCE) by EMS; per unit dose the mutant had twice as many mutations to thioguanine resistance, 3 times as many mutations to azaadenine resistance, and a 7-fold enhancement in SCE, compared to AA8. Moreover, the baseline frequency of SCE in the mutant was extraordinarily high, i.e., 8.6 +/- 0.6 vs. 107 +/- 5 SCE/cell for AA8 and EM9, respectively, with 10 microM BrdUrd in the medium. The high SCE frequency in EM9 did not vary significantly with BrdUrd concentration over the range examined from 2.5 to 20 microM, and the percentage of 5-bromouracil substitution in the DNA was the same in EM9 and AA8 under these conditions. These data, however, do not rule out the possibility that the high SCE frequency in EM9 is a consequence of an altered sensitivity to incorporated BrdUrd. Thus, EM9 may carry a pleiotropic mutation affecting some function in DNA replication and/or DNA repair and causing the variety of phenotypic properties described in this study.

Animals↗
PubMed1983

Induction of single-strand breaks plus alkali-labile bonds by N-nitrosoureas in rat tissues in vivo: ethylnitrosourea versus benzylnitrosourea.

Alkaline sucrose sedimentation procedures were used to quantitate the amount of single-strand breaks plus alkali-labile bonds (SSB + ALB) induced and repaired following a single intraperitoneal injection of the neurocarcinogen N-ethyl-N-nitrosourea (ENU) and its non-neurocarcinogenic analog N-benzyl-N-nitrosourea (BNU) in the brain, liver and kidney of female Sprague-Dawley rats. SSB + ALB were measured and used as an indicator of apurinic/apyrimidinic sites, phosphotriesters and in situ breaks. ENU induced a dose-dependent increase in the number of SSB + ALB at the doses studied (0, 0.39, 0.77, 1.54 mmoles/kg) in all 3 tissues. At 1 h postinjection with 0.77 mmoles/kg of these compounds there were 50-70% fewer breaks induced by BNU than ENU. The SSB + ALB induced by ENU persisted over a 7-day period, while those induced by BNU did not. Thus, these studies showed that 2 homologues of nitrosoureas, ENU and BNU, exhibited different potentials to induce and to persist SSB + ALB in vivo.

DNA↗
PubMed1989

Production of DNA single-strand breaks in unstimulated splenocytes by dimethylnitrosamine.

In an attempt to elucidate the mechanism whereby primary hepatocytes, but not liver S9 homogenates, generate immunosupprssive metabolites of dimethylnitrosamine (DMN), the production of DNA single-strand breaks (SSB) in unstimulated splenocytes was investigated with alkaline-elution analysis. Both hepatocytes and S9 homogenates induced SSB in cultured splenocytes by DMN - minimum detectable doses with the two metabolic activation systems (MAS) were 1 microM and 5 mM, respectively. DNA elution profiles were linear in splenocytes co-cultured with DMN and hepatocytes and convex in splenocytes incubated with DMN and S9 homogenates. Aminoacetonitrile (AAN; 10 mM), a DMN demethylase inhibitor, reversed SSB in splenocytes when incubated with either MAS. Addition of exogenous calf-thymus DNA to the hepatocyte co-culture medium did not affect the production of SSB. Rocking the hepatocyte-splenocyte cultures changed the elution profile from linear to convex. All of these treatments have been previously shown to block the immunosuppression by DMN in the hepatocyte co-culture system. These results indicate that the immunosuppression by DMN is not related to DNA damage, as measured by the production of SSB, and suggest that the metabolism of DMN to intermediates capable of producing genotoxicity and immunotoxicity may be qualitatively and/or quantitatively different.

Acetonitriles↗
PubMed1988

Benzo[a]pyrene- and formaldehyde-induced DNA damage and repair in rat tracheal epithelial cells.

The single and combined effects of 2 environmental carcinogens, benzo[a]pyrene (BAP) and formaldehyde (HCHO), on cell growth and DNA damage were assessed in a rat tracheal epithelial cell line, C18. Treatment of C18 cells with HCHO for 90 min reduced the calculated growth index at the highest concentration tested, 400 microM, while no growth effects were observed with BAP treatments. Combination treatments reduced the growth index to 75% of control values. Alkaline elution analysis of C18 cell DNA detected both DNA-protein crosslinks (DPC) and single-strand breaks (SSB) as a result of HCHO treatment, while BAP caused only SSB. HCHO-induced SSB were repaired within 2 h, whereas BAP-induced SSB persisted for at least 48 h. Combination treatment of cells with BAP followed by HCHO enhanced the number of SSB, but reduced DPC. The results are discussed in reference to earlier work which demonstrated the interaction in vivo between BAP and HCHO with respect to their carcinogenicity in rat tracheal implants.

Animals↗
PubMed1995

In vitro and in vivo generation of reactive oxygen species, DNA damage and lactate dehydrogenase leakage by selected pesticides.

Reactive oxygen species may be involved in the toxicity of various pesticides and we have, therefore, examined the in vivo effects of structurally dissimilar polyhalogenated cyclic hydrocarbons (PCH), such as endrin and chlordane, chlorinated acetamide herbicides (CAH), such as alachlor, and organophosphate pesticides (OPS), such as chlorpyrifos and fenthion, on the production of hepatic and brain lipid peroxidation and DNA-single strand breaks (SSB), two indices of oxidative stress and oxidative tissue damage. The selected pesticides were administered p.o. to female Sprague-Dawley rats in two 0.25 LD50 doses at 0 h and 21 h and killed at 24 h. In a parallel set of experiments, we have determined the in vitro effects of these pesticides on the DNA-SSB and enhanced lactate dehydrogenase leakage (LDH) from neuroactive PC-12 cells in culture. In vitro production of reactive oxygen species by these pesticides was also assessed by determining the enhanced chemiluminescence responses of hepatic and brain homogenates. Following treatment of rats with endrin, chlordane, alachlor, chlorpyrifos and fenthion, increases of 2.8-, 3.0-, 4.2-, 4.3- and 4.8-fold were observed in hepatic lipid peroxidation, respectively, while at these same doses, increases in lipid peroxidation of 2.4-, 2.1-, 3.6-, 4.6- and 5.3-fold, respectively, were observed in brain homogenates. Increases of 4.4-, 3.9-, 1.6-, 3.0- and 3.5-fold were observed in hepatic DNA-SSB following treatment of the rats with endrin, chlordane, alachlor, chlorpyrifos and fenthion, respectively, while at these same doses, increases of 1.9-, 1.7-, 2.2-, 1.4-, 1.4-fold, respectively, were observed in brain nuclear DNA-SSB. Following in vitro incubation of hepatic and brain tissues with 1 nmol/ml of each of the five pesticides, maximum increases in chemiluminescence occurred within 4-7 min of incubation and persisted for over 10 min. Increases of 3.0-, 2.7-, 3.6-, 4.9- and 4.4-fold were observed in chemiluminescence following in vitro incubation of the liver homogenates with endrin, chlordane, alachlor, chlorpyrifos and fenthion, respectively, while increases of 1.7-, 1.8-, 2.0-, 3.4- and 3.7-fold, respectively, were observed in the brain homogenates. Increases of 2.2-, 2.3-, 2.9-, 2.9- and 3.4-fold were observed in the chemiluminescence responses in the liver homogenates of the animals treated with endrin, chlordane, alachlor, chlorpyrifos and fenthion, respectively, while increases of 1.8-, 2.0-, 3.2-, 2.9- and 2.4-fold, respectively, were observed in the brain homogenates. Cultured neuroactive PC-12 cells were incubated with the pesticides and the release of the enzyme lactate dehydrogenase (LDH) into the media as an indicator of cellular damage and cytotoxicity was examined. Maximal release of LDH from cultured PC-12 cells was observed at 100 nM concentrations of the pesticides. Increases of 2.3-, 2.5-, 2.8-, 3.1 and 3.4-fold were observed in LDH leakage following incubation of the PC-12 cells with endrin, chlordane, alachlor, chlorpyrifos and fenthion, respectively. Following incubation of the cultured PC-12 cells with 100 nM concentrations of these same pesticides, increases in DNA-SSB of 2.5-, 2.2-, 2.1-, 2.4- and 2.5-fold, respectively, were observed. The results clearly demonstrate that these different classes of pesticides induce production of reactive oxygen species and oxidative tissue damage which may contribute to the toxic manifestations of these xenobiotics. Reactive oxygen species may serve as common mediators of programmed cell death (apoptosis) in response to many toxicants and pathological conditions.

Acetamides↗
PubMed1993

Effects of age and ethanol on DNA single-strand breaks and toxicity induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone or n-nitrosodimethylamine in hamster and rat liver.

The effects of age and ethanol exposure on liver DNA single-strand breaks (SSB) and liver cell injury induced in hamsters and rats by a single equimolar dose (0.39 mmol/kg) of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) or N-nitrosodimethylamine (NDMA) were investigated. NNK induced more DNA SSB (by 10-50%) than NDMA in the liver of adult hamsters and rats, but similar differences were not observed in newborn animals. Nitrosamine-induced hepatic DNA damages was compared in newborn and adult animals. While newborn hamsters were less sensitive to NNK-induced DNA damage than adult hamsters, newborn rats were more sensitive to NDMA-induced DNA damage than adult rats. In utero ethanol exposure did not alter significantly the induction of hepatic DNA SSB by NNK or NDMA compared to newborn hamsters and rats. Interestingly, species differences in the extents of NNK-induced hepatic DNA SSB and toxicity were observed in ethanol-consuming adult hamsters and rats. Ethanol treatment of hamsters caused a significant reduction (by 35%) of the frequency of hepatic DNA SSB and a 3.5-fold enhancement of hepatotoxicity induced by NNK.

Age Factors↗
PubMed1995

DNA single-strand breaks in postischemic gerbil brain detected by in situ nick translation procedure.

Using an in situ nick translation procedure, DNA single-strand breaks (SSB) in postischemic gerbil hippocampus were investigated after 15-min forebrain ischemia followed by 0-4h of recirculation. In the control group, increased SSB were noticed in the ependymal cell layer and the dentate gyrus. After 15-min ischemia without recirculation, no remarkable changes in SSB were observed. However, after 1 h of recirculation, a marked increase in SSB was recognized throughout the hippocampus, especially in the cells in CA1 subfield and the dentate gyrus. After 4 h of recirculation, SSB decreased to a level near that of the control group. The results of the present study indicate that ischemic insults may injure intranuclear DNA during postischemic recirculation periods. Although many factors may be involved, activated endonuclease due to an intracellular Ca2+ rise, free radicals, and postischemic hyperthermia appear to be involved in this phenomenon.

Animals↗
PubMed1984

Effects of BSO and DEM on thiol-level and radiosensitivity in HeLa cells.

Reduction of the intracellular GSH and NPSH levels in HeLa cells by BSO and DEM treatments was determined. The effect of a 16 to 22 hr incubation with BSO at 37 degrees C, resulting in a depletion of GSH and NPSH to about 10 and 50%, respectively, and the effect of a 50 min incubation with DEM resulting in a reduction of GSH and NPSH to about 30 and 60%, respectively, on radiation sensitivity were studied. As parameters for radiation damage, single and double strand DNA breaks (ssb and dsb) and cell killing were used. Furthermore, repair of ssb and dsb were followed in the first 30 to 120 min after radiation, respectively. BSO and DEM treatment gave a small sensitization for the 3 types of radiation damage (ssb, dsb and cell killing) in aerobic condition. In hypoxic condition the sensitizing effect of both compounds on dsb was larger than the effect on ssb. Pretreatment with BSO and DEM had no influence on repair of ssb and dsb when cells were irradiated in air, but when cells were irradiated in hypoxia, repair was somewhat inhibited after pretreatment with DEM. It can be postulated that a reduction of the intracellular GSH level by BSO and DEM treatment affects cellular radiosensitivity both by a competitive mechanism between GSH and O2 and by inhibition of enzymatic repair of DNA breaks, the latter only in the case of DEM treatment.

Buthionine Sulfoximine↗