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PubMed1998

Effect of Fas+ and Fas- target cells on the ability of NK cells to repeatedly fragment DNA and trigger lysis via the Fas lytic pathway.

We and others have recently shown that human NK cells express the Fas ligand (FasL) constitutively and that they can trigger the lysis of Fas positive (Fas+) target cells (TC) by apoptosis. We have also previously demonstrated that NK cells exposed to sensitive TC temporarily lose their ability to lyse sensitive TC via the granule-mediated pathway and that this loss is recovered when inactivated NK cells (NKi) are incubated in medium supplemented with IL-2, IL-12 or IL-15. In this study, we investigated the fate of the Fas-lytic pathway in NK cells exposed to either Fas+ or Fas- TC. To this end, we exposed NK cells to Jurkat (Fas-) or Jurkat (Fas+) TC for up to 6 h, separated NK cells from the TC and assessed the residual lytic activity against K562, a traditional human NK cell target, Jurkat Fas+ and Jurkat Fas- TC. Fas lytic activity was determined in calcium free medium, in the presence or absence of two distinct Fas-blocking monoclonal antibodies and a Fas.Fc fusion protein. In parallel experiments, the extent of DNA fragmentation in the three TCs was also assayed by the JAM test. Our results indicate that: (i) NK cells exposed to susceptible Fas+ TC temporarily lose most of their lytic potential due to the granule-mediated pathway, while only partially losing the Fas-lytic pathway. They also partially lose their ability to fragment DNA. (ii) NK cells exposed to Fas+ TC completely recover the Fas lytic pathway and the ability to fragment DNA via the Fas/Fas ligand when incubated in medium supplemented with IL-2 for 18 h.

Journal Article↗
PubMed2006

Histochemical localization of apoptosis with in situ labeling of fragmented DNA.

Cell death by apoptosis is now recognized widely as an important constituent of cell turnover and disease pathology. Characterized by the cleavage of DNA into oligonucleosome-sized DNA fragments, end-labeling of fragmented DNA often is used as an in situ histological marker of apoptosis. The judicious and appropriate use of this technique therefore provides us with an important tool for assessing cell kinetics. Protocols for both terminal transferase-mediated UTP nick end-labeling, so-called TUNEL, and the combination of TUNEL with immunohistochemical staining are presented here, along with a discussion of its significance and interpretation.

Animals↗
PubMed1994

Distinction of apoptotic and necrotic cell death by in situ labelling of fragmented DNA.

The occurrence and spatial distribution of intracellular DNA fragmentation was investigated by in situ 3' end labelling of DNA breaks in K562 cells treated in such a way to cause either apoptotic or necrotic cell death. The localisation of DNA breaks was examined by confocal laser microscopy and compared with the electron-microscopic appearance of the cells. In addition, the number of cells with fragmented DNA was counted and compared with the number of dead cells, as determined by the nigrosin dye exclusion test. Apoptosis was induced by cultivation of the cells in the presence of actinomycin D. Cells undergoing apoptosis were characterised by massive intracellular DNA fragmentation that was highly ordered into successive steps. Cells in early stages of the apoptotic process had DNA breaks diffusely distributed in the entire nucleus, except the nucleolus, with crescent-like accumulations beyond the nuclear membrane. In the more advanced stages, the nucleus was transformed into many round bodies with intense labelling. Intracellular accumulations of fragmented DNA corresponded exactly to electron-dense chromatin seen in the electron microscope, whereas diffuse DNA breaks had no morphological correlate at the ultrastructural level. In necrosis induced by ionomycin, NaN3, or rapid freezing combined with thawing, no DNA fragmentation occurred at the onset of cell death, but appeared 24 h later. This fragmentation was not characterised by a unique morphology, but represented the breakdown of the chromatin in the configuration remaining after cell death. Therefore, apoptosis is characterised by DNA fragmentation that proceeds in a regular orderly sequence at the beginning of cell death, and can be detected by in situ 3'end labelling of DNA breaks.

Apoptosis↗
PubMed1996

Selecting and amplifying one fragment from a DNA fragment mixture by polymerase chain reaction with a pair of selective primers.

A new method for selecting and amplifying a single DNA fragment from a mixture is proposed. This method is applicable for the rapid classification of DNA fragments from a mixture and for preparation of sequencing templates. DNAs of several to tens of kilobases (kb) are digested with a four-base recognition restriction enzyme to produce smaller fragments. The complementary strand extension reactions are then carried out to produce fluorophore-labeled DNA fragments from the digestion products. These fragments can be rapidly classified according to their terminal-base sequences and their sizes are analyzed by capillary-array gel electrophoresis (CAGE). Electropherograms are used to characterize the fragments and to select polymerase chain reaction (PCR) primers. Any fragment in a digestion mixture can be amplified by PCR with a pair of primers selected from a primer pool by referring to the electropherograms of the fragments. This method was successfully used to compare the electropherograms of two different DNA strands and to sequence a several-kb DNA fragment without subcloning. Combined with CAGE, this method could be used to dramatically simplify DNA fragment analysis.

DNA↗
PubMed1984

Quantitative predictivity of carcinogenicity for four short-term parameters, evaluated in rat liver: alkaline DNA fragmentation, autoradiographic repair, DNA adducts, preneoplastic nodules.

The possibility of the study of a quantitative correlation between short-term tests and carcinogenicity, instead of a qualitative one, is discussed. Four tests related to the target organ, rat liver, were considered: alkaline DNA fragmentation, DNA repair, DNA adducts and the formation of preneoplastic nodules. All the four tests showed a similar level of correlation with carcinogenic potency (r approximately equal to 0.4). With this level of correlation, the dispersion of the data appeared too large to offer a meaningful degree of quantitative predictivity of carcinogenicity, in reference to a single test. It appeared however, that the use of a battery of two or three independent short-term tests, with the above level of simple correlation, could generate a multiple correlation high enough to be potentially useful for some degree of quantitative predictivity of carcinogenic potency.

Amines↗
PubMedDate not supplied

Site-directed insertion of long single-stranded DNA fragments into plasmid DNA.

A new site-directed method for inserting long single-stranded DNA fragments into any region of a duplex vector is described. Its major advantage is independence of the location of the restriction sites. The method involves the assembly of single-stranded DNA fragments by ligation to both ends of the inserted fragments of two cohesive flanks that are complementary to the target region. Short oligonucleotide templates are used to direct the ligation. The resulting fragments, designated further as omega fragments with cohesive flanks, are hybridized with a gapped DNA vector. The heteroduplexes are transformed into Escherichia coli cells without enzymatic filling and sealing of gapped DNA. As a consequence of intracellular repair and heteroduplex resolution, insertion mutants are recovered. To demonstrate the method's efficiency, we inserted a 51-nucleotide synthetic DNA fragment containing a modified glucocorticoid receptor binding site into the region of pBR322, near the transcription starting point of the tet gene. The method we developed makes possible site-directed insertion of synthetic and genome-derived DNA fragments at least 200 nucleotides long.

Base Sequence↗
PubMed1998

Resistance to DNA fragmentation and chromatin condensation in mice lacking the DNA fragmentation factor 45.

The DNA fragmentation factor 45 (DFF45) is a subunit of a heterodimeric nuclease complex critical for the induction of DNA fragmentation in vitro. To understand the in vivo role of DFF45 in programmed cell death, we generated DFF45 mutant mice. DNA fragmentation activity is completely abolished in cell extracts from DFF45 mutant tissues. In response to apoptotic stimuli, splenocytes, thymocytes, and granulocytes from DFF45 mutant mice are resistant to DNA fragmentation, and splenocytes and thymocytes are also resistant to chromatin condensation. Nevertheless, development of the immune system in the DFF45 mutant mice is normal. These results demonstrate that DFF45 is critical for the induction of DNA fragmentation and chromatin condensation in vivo, but is not required for normal immune system development.

Animals↗
PubMed1982

Rapid method for purification of plasmid DNA and DNA fragments from DNA linkers using high-performance liquid chromatography on TSK-PW gel.

High-performance size exclusion chromatography (HPSEC) using TSK-G5000 PW in Tri buffer has been found to be a reliable method for the rapid fractionation of DNA ligation products. Plasmid and fragmented phage DNAs were found to elute in less than 2 min with recoveries greater than 98%. Escherichia coli transfection studies, using plasmid DNA that had been subjected to HPSEC column fractionation, showed high transformation efficiencies. MgCl2, a component of the DNA ligation reaction, was found to produce DNA-column support interactions, which resulted in low DNA recoveries. Such interactions were eliminated by chelation with ethylenediaminetetraacetate prior to chromatography.

Bacteriophages↗
PubMed1999

Detection of fragmented DNA in apoptotic cells embedded in LR white: A combined histochemical (LM) and ultrastructural (EM) study.

We developed an improved method for the detection of double-strand DNA breaks in apoptotic cells at both the light (LM) and electron microscopic (EM) levels using a modification of the TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick end-labeling (TUNEL) technique. Cultured rat cerebellar granule cells were exposed to low potassium conditions to induce apoptosis. Twenty-four hr after treatment, one group of cells was fixed in situ with 4% paraformaldehyde and labeled for DNA fragmentation characteristic of apoptosis. Apoptotic cells were visualized with diaminobenzidine (DAB) and viewed by LM. The second group of cells was detached from the culture dish, pelleted, fixed with a 4% paraformaldehyde and 0. 2% glutaraldehyde mixture, and embedded in LR White. For LM, the modified TUNEL technique was performed on 1.5-microm LR White sections and apoptotic cells were visualized using an enzymatic reaction to generate a blue precipitate. For EM, thin sections (94 nm) were processed and DNA fragmentation was identified using modified TUNEL with streptavidin-conjugated gold in conjunction with in-depth ultrastructural detail. Alternate sections of cells embedded in LR White can therefore be used for LM and EM TUNEL-based detection of apoptosis. The present findings suggest that the modified TUNEL technique on LR White semithin and consecutive thin sections has useful application for studying the fundamental mechanism of cell death. (J Histochem Cytochem 47:561-568, 1999)

Animals↗
PubMed1998

Inhibition of apoptosis-associated DNA fragmentation activity in nonapoptotic cells: the role of DNA fragmentation factor-45 (DFF45/ICAD).

We have investigated the mechanism whereby nuclear DNA fragmentation activity emerging during early apoptosis is inhibited during normal cell life. In a cell-free system, cytosol fractions from diverse nonapoptotic human cell lines (Jurkat T-cell leukemia, HeLa carcinoma, SK-N-MC neuroblastoma, and WI-38 embryonic lung fibroblast) potently neutralized the nuclear DNA fragmentation activity of cytosol from apoptotic anti-Fas treated Jurkat cells. Recombinant human DNA fragmentation factor 45 kDa subunit (DFF45/ICAD), an inhibitor of the caspase-activated DNase DFF40/CAD, substituted for healthy cytosol in inhibiting DNA fragmentation. An antiserum against human DFF45 detected 44 and 34 kDa proteins (major and minor, respectively) in the cytosols but not in the nuclear or membrane fractions of various cultured human cells. Cytosols depleted of DFF45/ICAD by immunoadsorption had little or no inhibitor of nuclear DNA fragmentation activity and no caspase-activated DNA fragmentation activity. We conclude that immunoreactive DFF45/ICAD is the principal inhibitor of apoptotic DNase activity in the cytosol of healthy cells.

Adenocarcinoma↗
PubMed1995

Microwave-enhanced in situ end-labeling of fragmented DNA: parametric studies in relation to postmortem delay and fixation of rat and human brain.

In situ end-labeling (ISEL) identifies DNA fragmentation in apoptotic or necrotic nuclei in tissue sections. However, application of ISEL on human brain requires conservation of DNA integrity during the postmortem delay (PMD) and good accessibility of fragmented DNA after (prolonged) tissue fixation. We therefore investigated ISEL in relation to PMD and fixation in rat and human brain. Application on a unilateral lesion model in perfused rat brain revealed that prolonged post-fixation strongly diminished ISEL results. However, microwave pre-treatment can counteract these masking effects without inducing nonspecific labeling contralaterally. On the other hand, in briefly post-fixed, perfused brain or immersion-fixed rat and human PMD brain, microwave pre-treatment was deleterious and induced strong nonspecific labeling. In young rat brain, PMD did not influence the low numbers of apoptotic nuclei until 24 hr PMD, when massive nuclear labeling occurred. In human cortex, DNA fragmentation patterns were independent of duration of fixation or PMD and were already present from 4.25 hr PMD onwards. Our data suggest that ISEL on human brain represents antemortem DNA damage rather than PMD artifacts. Furthermore, microwave pre-treatment appears beneficial only in particular fixation conditions.

Aged↗
PubMed1991

Streptozocin- and alloxan-induced H2O2 generation and DNA fragmentation in pancreatic islets. H2O2 as mediator for DNA fragmentation.

Streptozocin (STZ) and alloxan (ALX) exhibit the most potent diabetogenicity and are used for induction of experimental diabetes mellitus. An understanding of the mechanisms of action of the typical diabetogenic agents is important for elucidating the causes of diabetes. Okamoto proposed a model in which DNA fragmentation plays an important role in the development of diabetes. DNA fragmentation supposedly results from the accumulation of superoxide or hydroxyl radicals. However, direct evidence for this accumulation is lacking. With isolated rat pancreatic islets in vitro, we demonstrated that STZ and ALX stimulated H2O2 generation and caused DNA fragmentation. Addition of STZ or ALX resulted in an increase in H2O2 generation. On DNA analysis, when incubated without STZ or ALX, DNA sedimented as a single peak; when incubated with STZ or ALX, DNA sedimented slower as a broad peak and was fragmented. Graded doses of STZ and ALX stimulated H2O2 generation and induced DNA fragmentation; their effects on H2O2 generation and DNA fragmentation were evident at a concentration of 0.1 mM and were maximal at 1 mM. Administration of STX or ALX to rats in vivo stimulated H2O2 generation and caused DNA fragmentation in pancreatic islets. H2O2 itself also induced DNA fragmentation. These findings may support Okamoto's proposal that STZ and ALX induce diabetes through the following biochemical events: STZ and ALX----H2O2 generation----DNA fragmentation----beta-cell destruction. This study may constitute the first demonstration of STZ- and ALX-stimulated H2O2 generation, which probably acts as a mediator of STZ- and ALX-induced DNA fragmentation.

Alloxan↗
PubMed1990

Cytochalasin B induces cellular DNA fragmentation.

Cellular DNA fragmentation can be induced in many biological instances without plasma membrane damage. The fungal metabolite, cytochalasin B, is capable of modifying numerous cellular functions related to DNA synthesis. In this work it is demonstrated that cytochalasin B is capable of inducing DNA fragmentation in a number of cells lines. This DNA fragmentation occurs before plasma membrane lysis and over a period of hours. Cytochalasin E and villin, agents that act on the microfilaments, also induce DNA fragmentation. Phorbol dibutyrate, a diacylglyceral analog, is able to inhibit cytochalasin B-induced DNA fragmentation in a dose-dependent fashion. These findings support the interpretation that cytochalasin B is inducing DNA fragmentation via its effect on the actin filaments.

Actins↗
PubMed1995

In situ detection of fragmented DNA (TUNEL assay) fails to discriminate among apoptosis, necrosis, and autolytic cell death: a cautionary note.

Detection of DNA fragments in situ using the terminal deoxyribonucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end labeling (TUNEL) assay is increasingly applied to investigate active cell death (apoptosis). We studied the specificity of the assay in well-defined models of apoptosis and necrosis as well as in postmortem autolysis in rat liver. During involution of liver hyperplasia, which follows stopping treatment with the hepatomitogens cyproterone acetate (CPA) or nafenopin (NAF), numerous apoptotic hepatocytes could be observed with TUNEL-positive chromatin residues. A similar TUNEL-positive reaction appeared in necrotic hepatocytes after a cytotoxic dose of carbon tetrachloride (CCl4) or N-nitrosomorpholine (NNM). Also, in insufficiently fixed, autolytic livers TUNEL-positive nuclei were observed. Thus, DNA fragmentation is common to different kinds of cell death; its detection in situ should not be considered a specific marker of apoptosis.

Animals↗
PubMedDate not supplied

[Interaction of EcoRII restriction and modification enzyme with synthetic DNA fragments. IV. DNA duplexes with phosphoamide and pyrophosphate internucleotide bonds--the substrates for the study of single-strand breaks].

A set of DNA duplexes with repeated EcoRII, EcoRI and AluI restriction endonuclease recognition sites in which EcoRII scissile phosphodiester bonds were replaced by phosphoramide or uncleavable pyrophosphate bonds have been synthesized. Endonuclease EcoRII was found not to cleave the substrate at the phosphoramide bond. The substrates containing non-nydrolysable pyrophosphate or phosphoramide bonds in one of the chains of EcoRII recognition sites were used to show that this enzyme is able to catalyze single-strand scissions. These scissions occur both in dA- and dT-containing chains of the recognition site. Endonuclease EcoRII interacts with both strands of the DNA recognition site, each of them being cleaved independently on the cleavage of the other. Synthesized DNA-duplexes are cleaved specifically by EcoRI and AluI endonucleases, this cleavage being retarded if the modified bonds are in the recognition site (EcoRI) or flank it (AluI). For EcoRII and AluI this effect is more pronounced in the case of substrates with pyrophosphate bonds than with the phosphoramide ones.

Autoradiography↗