Lymphoid metastasis of rat My2/De leukemia.

By grafting spontaneous leukemia tumor cells, the myeloid My2/De leukemia rat model was established. Death was caused by impaired functions of heavily infiltrated organs. In vitro culturing of tumor cells, blood and bone marrow counts and cytochemic reactions indicated the leukemic the origin resembling human myeoloblastic leukemia. Metastatic spread was followed after i.v. and i.p. injection, and by implantation of leukemia cells under the renal capsule of rats. Primary tumor and metastasis formation was visualized by (18)FDG or (11)C-methionine administration and MiniPET. The accumulation of radiotracers was measured in different organs and expressed as Differential Absorption Ratios (DARs). Subrenal implantation of My2/De cells resulted in their appearance in other abdominal organs and in parathymic lymph nodes. The release of tumor cells from the primary kidney to the peritoneum was mimicked by the i.p. administration of ink particles. Ink particles deposited in the abdominal organs and in the thoracal lymph nodes, preferentially in parathymic lymph nodes, confirming the notion of lymphatic spread of metastasis.

The neuropeptide FMRFamide can protect cells against apoptosis in the snail digestive gland.

FMRFamide-related peptides are widespread neurotransmitters or neurohormones regulating somatic or visceral motor activity. Some recent data indicate that these neuropeptides may be involved in the control of cell proliferation and apoptosis. In this work we investigated the possible effect of FMRFamide on cell viability in an invertebrate-type proliferating tissue. As a model, we used the midintestinal gland of the snail, Helix lucorum Linnaeus. Immunohistochemistry demonstrated the direct innervation of the gland cells by FMRFamide-containing nerve fibers. Midintestinal glands of snails were injected with 50 microM FMRFamide and the control with sterile deionised water or bovine serum albumin (BSA). Injections were administrated 4 times. Transmission electron microscopy, annexin V-labeling, thiazolyl blue (MTT) viability tests and ploidy analyses were carried out to define the viable/dead cell ratio in the tissue samples. FMRFamide increased the MTT-reduction of tissues, reduced the amount of apoptotic nuclei and annexin V-labeled cells. Deionised water or BSA injection induced cell death. Cell cycle analysis revealed that FMRFamide significantly elevated the amount of cells in G0/G1 phase, but did not induce mitosis. We conclude, that the FMRFamide can be a life-signal for cells, protect them from apoptosis without altering mitosis.

Cadmium induced apoptotic changes in chromatin structure and subphases of nuclear growth during the cell cycle in CHO cells.

CHO cells were grown in the presence of 1 mu M CdCl(2) and subjected to ATP-dependent replicative DNA synthesis after permeabilization. By decreasing the density of the cell culture replicative DNA synthesis was diminishing. At higher than 2 x 10(6) cell/ml concentration Cd had virtually no effect on the rate of DNA replication. Growth at higher cell concentrations could be suppressed by increasing Cd concentration. After Cd treatment cells were synchronized by counterflow centrifugal elutriation. Cadmium toxicity on cell growth in early and mid S phase led to the accumulation of enlarged cells in late S phase. Flow cytometry showed increased cellular and nuclear sizes after Cd treatment. As the cells progressed through the S phase, 11 subpopulations of nuclear sizes were distinguished. Apoptotic chromatin changes were visualized by fluorescent microscopy in a cell cycle dependent manner. In the control untreated cells the main transitory forms of chromatin corresponded to those we have published earlier (veil-like, supercoiled chromatin, fibrous, ribboned structures, chromatin strings, elongated prechromosomes, precondensed chromosomes). Cadmium treatment caused: (a) the absence of decondensed veil-like structures and premature chromatin condensation in the form of apoptotic bodies in early S phase (2.2-2.4 average C-value), (b) the absence of fibrous structures, the lack of supercoiled chromatin, the appearance of uncoiled ribboned chromatin and perichromatin semicircles, in early mid S phase (2.5-2.9 C), (c) the presence of perichromatin fibrils and chromatin bodies in mid S phase (2.9-3.2 C), (d) early intra-nuclear inclusions, elongated forms of premature chromosomes, the extrusion and rupture of nuclear membrane later in mid S phase (3.3-3.4 C), (e) the exclusion of chromatin bodies and the formation of clusters of large-sized perichromatin granules in late S phase (3.5-3.8 C) and (f) large extensive disruptions and holes in the nuclear membrane and the clumping of incompletely folded chromosomes (3.8-4. C).

Gamma irradiation-induced apoptosis in murine pre-B cells prevents the condensation of fibrillar chromatin in early S phase.

Local changes in chromatin structure leading to temporally distinct geometric forms were characterized in nuclei of reversibly permeabilized cells. Reversal of permeabilization was tested by 3H-thymidine incorporation and trypan blue dye exclusion. Apoptotic changes were visualized in a cell cycle dependent manner at the chromatin level by fluorescent microscopy in non-irradiated cells and after 400 rad Co60 irradiation. Fluorescent microscopy of chromatin structures belonging mainly to the interphase of the cell cycle confirmed the existence of specific geometric forms in nuclei of non-irradiated cells. In this control population, the following main transitory forms of condensing chromatin were distinguished: decondensed veil-like structures and fibrous structures in early and mid S phase (2.0-2.5 average C-value), chromatin bodies, semicircles later in mid S phase (3.0-3.5 C), precondensed chromosomes in late S (3.5-3.7 C) and metaphase chromosomes at the end and after S phase (3.7-4.0 C). Our results show that upon gamma-irradiation (a) the cellular and nuclear sizes were increased, (b) the DNA content was lower in each elutriated subpopulation of cells, (c) the progression of the cell cycle was arrested in the early S phase at 2.4 C value, (d) the chromatin condensation was blocked between the fibrillar chromatin and precondensed elongated chromosomal forms, and (e) the number and size of apoptotic bodies were inversely correlated with the progression of the cell cycle, with many small apoptotic bodies in early S phase and less and larger apoptotic bodies in late S phase.

p53 modulates base excision repair activity in a cell cycle-specific manner after genotoxic stress.

To elucidate the nature of the cross-talk between the p53 protein and the DNA repair machinery, we have investigated the relationship between the two throughout the cell cycle. Base excision repair (BER) was analyzed in cell cycle phase-enriched populations of lymphoid cells expressing wild-type p53. Our study yielded the following novel findings: (a) BER exhibited two distinct peaks of activity, one associated with the G0-G1 checkpoint and the second with the G2-M checkpoint; (b) although the overall BER activity was reduced after exposure of cells to 400R, there was an augmentation of the G0-G1-associated BER activity and a reduction in the G2-M-associated BER activity; and (c) modulations in these patterns of BER after genotoxic stress were found to be p53 regulated. p53 protein levels induced after gamma-irradiation were distributed evenly in the various cell cycle populations (analyzed by the PAb-248 anti-p53 monoclonal antibody). However, both the dephosphorylation of serine 376 of p53 (contained in the PAb-421 epitope) and the specific DNA binding activity, as well as apoptosis, were enhanced toward the G2-M populations. Furthermore, inactivation of wild-type p53, mediated by mutant p53 expression, abolished the alterations in the BER pattern and showed no induction of a G2-M-associated apoptosis after gamma-irradiation. These results suggest that after genotoxic stress, stabilized p53 enhances the G0-G1-associated BER activity, whereas it predominantly reduces BER activity at the G2-M-enriched populations and instead induces apoptosis. After genotoxic stress, p53 functions as a modulator that determines the pattern of BER activity and apoptosis in a cell cycle-specific manner.

Subphases of DNA replication in Drosophila cells.

Exponentially growing Drosophila S2 cells in suspension culture were synchronized at low- and high-resolution centrifugal elutriation, and DNA synthesis was measured by [(3)H]-thymidine incorporation throughout the S phase. At low resolution, one repair peak at the G(1)/G(0) border and two replication peaks known as early and late S subphases were observed. At high resolution, six chronologic compartments were distinguished. The distribution of these peaks indicated one repair peak at 2.05 C value, one minor replication peak at 2.43C, and four major subphases of replication corresponding to 2.64C, 2.89C, 3.32C, and 3.60C, representing 6.7%, 3.4%, 15.3%, 20.4%, 32.1%, and 22.0% of the synthetic activity, respectively. The five major peaks of cell growth with 2.32C, 2.56C, 2.85C, 3.18C, and 3.58C values consistently preceded those of replication subphases.

Effect of cadmium on the relationship between replicative and repair DNA synthesis in synchronized CHO cells.

Repair and replicative DNA synthesis were measured at different stages of the cell cycle in control and cadmium-treated Chinese hamster ovary (CHO-K1) cells. Cells were synchronized by counterflow centrifugal elutriation. Elutriation resulted in five repair and four replication subphases. On Cd treatment, repair synthesis was elevated in certain subphases. Replicative subphases were suppressed by Cd treatment, with some of the peaks almost invisible. The number of spontaneous strand breaks measured by random oligonucleotide primed synthesis assay showed a cell-cycle-dependent fluctuation in control cells and was greatly increased after Cd treatment throughout the S phase. Elevated levels of the oxidative DNA damage product, 8-oxodeoxyguanosine, were observed after Cd treatment, with the highest level in early S phase, which gradually declined as damaged cells progressed through the cell cycle.

Relationship of repair and replicative DNA synthesis to cell cycle in Chinese hamster ovary (CHO-K1) cells.

To strengthen the causal association between repair and replicative DNA synthesis, we have simultaneously measured the two types of DNA synthesis in a cell cycle-dependent manner. Synchrony was obtained by counterflow centrifugal elutriation of logarithmic-phase Chinese hamster ovary (CHO) cells kept in suspension cultures. A comparison of cell cycle profiles of ATP-dependent replicative and ATP-independent repair synthesis in permeable cells shows opposite trends. The rates of repair synthesis and replication are inversely correlated.

Analysis of 5'-termini of early intermediates of Okazaki fragments accumulated in thymocytes after emetine treatment of mice.

Nascent Hg-DNA synthesized by the incorporation of Hg-dCTP in reversibly permeable cells of murine thymocytes has been characterized earlier. Here we describe the analysis of 5' ends of oligonucleotides isolated from thymocytes 48 hr after a single dose of emetine administration to mice. This small-molecular-weight population of nascent DNA shorter than Okazaki fragments was absent in control cells. More than 90% of the terminally 32P-labeled oligonucleotides carried a terminally phosphorylated RNA moiety at the 5' end, as demonstrated by alkaline hydrolysis. The size of the short nascent DNA fragments carrying RNA primers ranged between 9 and 50 nucleotides with an average chain length of 15 nucleotides. These oligomers are regarded as the precursors of the Okazaki fragments.

Multiple subphases of DNA replication in Chinese hamster ovary (CHO-K1) cells.

Replicative DNA synthesis has been measured throughout the S phase in synchronized populations of Chinese hamster ovary cells. When exponentially growing, cells in suspension cultures were subjected to counterflow centrifugal elutriation and the resolution power was increased the biphasic replication profile has been resolved and multiple subphases were distinguished. These replication peaks, termed replication checkpoints, are distributed evenly throughout the S phase. The replication checkpoints have been characterized by their average C values corresponding to 2.05, 2.12, 2.2, 2.45, 2.6, 2.8, 2.95, 3.15, 3.3, 3.45, and 3.85.

Elevated nascent DNA content of peripheral blood mononuclear cell compartment in lymphoma patients.

The kinetics of DNA synthesis and the DNA pattern of isolated peripheral blood mononuclear cells from control subjects and lymphoma patients prior to drug treatment were studied as a possible tool in the early diagnosis of lymphoma. Thymidine and [H3]-dTTP incorporation represented the measure of replicative DNA synthesis in permeable murine thymocytes and HT-168 human melanoma cells as described earlier. The kinetic parameters of nucleotide incorporation were compared with the ploidity parameters of the Feulgen-stained smears examined by the DNASK TV-cytophotometric system. For better evaluation and visualization of the S-phase population, the method of silver impregnation of the Nucleolar-Organizer-Region in combination with the Feulgen technique was used. Significant differences were observed among the five determined parameters of healthy and lymphoma patients. Our results allow to explain some of the facts related to T-cell function deficiency in lymphoma.

Origin of replication of the Bacillus subtilis chromosome: in vitro approach to the isolation of early replicating segments.

We have developed a permeable cell system for the study of the molecular mechanisms involved in the control and initiation of DNA replication at the origin of the Bacillus subtilis chromosome. Our system take advantage of the synchronous initiation of DNA replication that occurs in outgrowing B. subtilis spores and the curtailment of DNA elongation by novobiocin. Early replicating DNA sequences were identified by the use of 5-mercury-dCTP as substrate, which allows the isolation of nascent DNA chains by affinity chromatography on thiol agarose. The average size of the isolated nascent DNA was 1,000 bp, and more than 80% of the nascent DNA chains had RNA primers at their 5' end. The study of the temporal order of chromosome replication near the origin using this experimental system showed that a segment containing recF and gyrB replicated earlier than a segment containing gyrA and part of the rRNA operon (rrnO). This observation is in agreement with previous in vivo data on the replication of origin region and supports the conclusion that the major activity in our in vitro system was the faithful replication of the ori region.

Effect of mercury substitution of DNA on its susceptibility to cleavage by restriction endonucleases.

Mercurated DNA was synthesized in vitro by substituting Hg-dCTP or Hg-dUMP for dCTP in one strand of M13mp8DNA in a DNA polymerase I reaction. Restriction enzymes, including Sma I, Pst I, Bam HI, Hind III, and Hinc II, were completely inactive when their recognition sites were fully substituted with Hg-dCMP, while Hg-dUMP containing DNA was hydroxlyzed to some extent. Under conditions favoring star activities, or when DNA was substituted with a low level of mercury-nucleotide, DNA was cleaved by restriction enzymes. Susceptibility to degrading and synthesizing enzymes and insensitivity to restriction endonucleases of fully mercurated DNA makes mercuration an attractive molecular "tag" for in vitro manipulation and selective isolation of Hg-DNA.

Formation of leucyl-leucine-O-methylester in leucine-O-methylester treated cells.

Porcine polymorphonuclear cells (PMN) and murine macrophages (M phi) were treated in vitro with Leu-OMe or Leu-Leu-OMe (1.5-5.0 mM) for various periods of time. It was found that the Leu-OMe and Leu-Leu-OMe entered cells rapidly, concomitantly the intracellular leucine accumulated. The methyl derivative diffused faster than Leucine due to its lipophylic character. The Leucine-O-methylesters hydrolysed rapidly as a consequence of the esterase and peptidase activities. The cells treated with Leu-OMe accumulated a high amount of Leucine and some Leu-Leu-OMe too. It was found that the formation of the didpeptide-methylester is not a spontaneous process, rather an enzymatic one. The Leu-OMe treated cells serve as a model which can be used to investigate the effect of the amino acid metabolism and the formation of dipeptides intracellularly and extracellularly.

Oncogene expression in thymocytes after emetine treatment of mice.

Emetine (33 mg/kg IP) was used as an immunosuppressive agent to inhibit thymic development. The specific and reversible effect of emetine on the macromolecular biosynthesis of thymocytes provided an in vivo model to investigate cellular differentiation. Cortical cells emigrated upon emetine administration at the early stage of inhibition of macromolecular synthesis, followed by a repopulation stage and differentiation of the thymus. Early events of differentiation were measured by the gene expression of oncogenes showing a gradual decrease of c-myc mRNA level, a temporary decline in c-fos mRNA which was reversed at t = 72 h after emetine treatment. The two-fold increase in mRNA synthesis of c-src oncogene after emetine treatment was paralleled by a fivefold rise in total tyrosine kinase activity. The concomitant appearance of an M(r) = 60,000 protein a t = 96 h after emetine treatment may be an indication of the involvement of specific proteins in thymic development.

Cytometric analysis of DNA replication inhibited by emetine and cyclosporin A.

DNA staining methods based on aspecific interactions with dye molecules have been replaced by an immunofluorescent approach to measure DNA replication. Biotin-11-dUTP was incorporated into permeable thymocytes isolated after emetine or cyclosporin A treatment of mice. Active sites of DNA replication were amplified based on biotin-avidin interaction and verified under fluorescent microscope. Cytometry of fluorescent images allow the direct measurement of replicating DNA without aspecific detection of total cellular DNA. Cytometric analysis of replication revealed that emetine acts at the early S phase, while cyclosporin A blocks in vivo DNA synthesis at mid S phase.

[DNA-based diagnosis]. / DNS diagnosztika.

DNA diagnostics is rapidly developing and gaining ground especially in the identification of genetic, malignant and infectious diseases as well as in the identification of individuals by means of DNA finger-printing. Present review deals with these and with the technical aspects of DNA diagnostics. The rapidly expanding field of diagnostics is contrasted by gene therapy which is recently not yet adaptable for human use.

Early replication signals in nuclei of Chinese hamster ovary cells.

DNA replication sites generally known as replicon domains were resolved as individual replication signals in interphase nuclei of permeabilized Chinese hamster ovary cells by immunofluorescent microscopy. Biotin-11-dUTP was utilized as a tool to label newly replicated DNA in permeable cells and to study the distribution of nascent DNA in pulselabel and in pulsechase experiments. Active sites of DNA replication were visualized in exponentially growing cells and in synchronized cultures throughout the S phase. Fluorescent images of replication sites were analyzed by standard fluorescence microscopy and in three dimensions by confocal laser scanning microscopy. The rapid increase in number of discrete foci of newly replicated DNA is an indication that DNA synthesis starts at limited number of sites in mammalian nuclei rather than at thousands of foci at the same time.

Rec mutants of Escherichia coli deficient in subunits of rec BC (D) complex.

The inactivation of rec BC (D) DNase upon chromatography on DEAE-cellulose was observed. Simultaneously DNA-stimulated ATPases (I and II) and DNase activities on single- and double-stranded DNA substrates were measured in Escherichia coli rec+ and rec- cell extracts. Normal levels of ATPase I and II were detected in rec+ cells. Rec A- cells were lacking DNA dependent ATPase I, while rec B single and rec BC double mutants were defective in DNA dependent ATPase II, the second major enzyme of this type. Rec B and C mutations did not change DNase activities. Rec A mutation significantly increased DNase activity on linear single-stranded substrate.

Cellular regulation of ADP-ribosylation of proteins. III. Selective augmentation of in vitro ADP-ribosylation of histone H3 in murine thymic cells after in vivo emetine treatment.

Thymic cells were isolated at intervals of between 0 and 144 h from mice that received one intraperitoneal injection of emetine (33 mg/kg), and thymus weight, incorporation of [14C]leucine into proteins and [3H]thymidine into DNA in intact thymic cells, as well as initial rates of protein ADP-ribosylation in permeabilized cells [A. Sóoki-Tóth, F. Asghari, E. Kirsten, and E. Kun (1987) Exp. Cell Res. 170, 93] were simultaneously monitored. The effect of emetine as an inhibitor of protein synthesis [F. Antoni, N. G. Luat, I. Csuka, I. Oláh, A. Sóoki-Tóth, and G. Bánfalvi (1987) Int. J. Immunopharmacol. 9, 333] corresponds to the induction of sequential cellular events, such as cell exit and remigration, by other antimitotic agents [C. Penit and F. Vasseur (1988) J. Immunol. 140, 3315] and produces an activation of proliferation of cells reentering into this organ. Proliferation, as demonstrated by a large increase in DNA synthesis and entrance into S phase, was kinetically related to an apparent increase in poly(ADP-ribose) polymerase activity in thymic cells and a highly significant in vitro ADP-ribosylation of histone H3. Since no DNA fragmentation occurred in thymic cells, as tested by a fluorometric technique [C. Birnboim and J. J. Jevac (1981) Cancer Res. 41, 1889], it is probable that a selective activation of poly(ADP-ribose) polymerase may have been induced in cells that undergo differentiation and proliferation while repopulating the thymus.