The relationship between the levels of DNA-hydrocarbon adducts and the formation of sister-chromatid exchanges in Chinese hamster ovary cells treated with derivatives of polycyclic aromatic hydrocarbons

The frequencies of the induction of sister-chromatid exchanges and the levels of deoxyribonucleoside-hydrocarbon adducts formed in Chinese hamster ovary cells that had been treated with either dihydrodiols or a diol-epoxide derived from polycyclic aromatic hydrocarbons were determined. Up to 6-fold increases in the incidence of these exchanges were observed when the cells were treated either with the dihydrodiols, trans-3,4-dihydro-3,4-dihydroxy-7-methylbenz[a]anthracene,trans-7,8-dihydro-7,8-dihydroxybenzo[a]pyrene or the diol-epoxide, (±)-r-7, t-8dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a] pyrene but when the cells were transferred to media free of these compounds, there were rapid reductions in the frequency of these exchanges. When the exchanges were induced by the diol-epoxide, the decreases in frequency were paralleled by decreases in the levels of deoxyribonucleoside-diol-epoxide adducts that were present in hydrolysates of DNA isolated from the cells. There thus appears to be a close relationship between the frequency of sister-chromatid exchanges and the levels of deoxyribonucleoside-diol-epoxide adduct formation.     

Influence of both coculture and BrdU on NOR activity of mouse,rat and human cells

Summary The coculture of mouse PG19 cells with human MGC cells can significantly suppress nucleolar organizer region (NORs) activity of both PG19 and MGC cells. 5-bormodeoxyuridine (BrdU) can also significantly suppress the NOR activity of rat RC cells, human MGC and Hela cells, and mouse PG19 cells: i.e. the average number of Ag-NORs and the number of chromosomes bearing Ag-NORs per cell decrease significantly. The degree of the suppression increases with increase in both BrdU concentration in the culture medium and BrdU treatment time. The suppressed NOR activity of the PG19 cells can gradually be restored when the BrdU-treated cells are transferred into BrdU-free medium for 50 h. In PG19 cells deoxycytidine (dC) can reverse the suppression of NOR activity caused by BrdU. Coculture plus BrdU treatment suppress the NOR activity of PG19 cells more severely than BrdU treatment alone. In coculture medium containing 30 g BrdU/ml, dC can also reverse the suppression of the NOR activity of PG19 cells but not that of the MGC cells. The degree of the reversion in the coculture plus BrdU treatment is significantly lower than that found with BrdU-treatment alone.     

Free Radical Mediated Cytotoxicity of Desferrioxamine

Toxic effects of desferrioxamine (DFO) upon cell growth were assayed with continuous bromodeoxyur-idine (BrdU) labeling and bivariate ethidium bromide/Hoechst 33258 Row cytometry. At 5% oxygen DFO caused a dose-dependent inhibition of cell growth. which was potentiated at 20% oxygen. and by cumene hydroperoxide but not by paraquat. An irreversible arrest in the GZ phase of the cell cycle was the cell-kinetic mechanism underlying this growth inhibition. The G2 arrest was not dependent upon the BrdU concentration in the medium, thus ruling out a direct attack of a free radical on thymidine residues. The observed cytotoxicity of DFO cautions against its use in the treatment of conditions of elevated oxidative stress.     

Replication banding in the chromosomes of the European eel (Anguilla anguilla)

The chromosomes of the European eel Anguilla anguilla have been analyzed with a replication banding technique from lymphocyte cultures treated with 5-BrdU. This technique allows us to identify with high resolution the individual chromosome pairs and to differentiate classes of chromatin by the order of replication. The replication banding obtained on the chromosomes of European eel can be related with the structural bands described in this species.     

Origin and clonal relationship of common inhibitory motoneurons CI1 and CI3 in the locust CNS

In the primordial thoracic ganglia of locust embryos, the bromodeoxiuridine (BrdU) technique for labelling proliferating cells and their progeny was combined with intracellular dye injection to investigate the origin and the clonal relationship of common inhibitory motoneurons. Common inhibitors 1 (CI₁) and 3 (CI₃) were found to be siblings, that is, they are produced by the division of one ganglion mother cell. This ganglion mother cell results from the first division of neuroblast 5–5, at about 30% of embryonic development. A large portion, at least, of the ganglion mother cells produced by subsequent divisions of neuroblast 5–5 give rise to interneurons with contralaterally ascending or descending axons and GABA-like immunoreactivity. Thus, CI₁ and CI₃ are more closely related to putative inhibitory interneurons than they are to other, that is, excitatory, motoneurons. Consistent with this, the CI somata are associated with cell bodies of putative inhibitory interneurons rather than with clusters of excitatory motoneuron somata. These results elicit speculations regarding the evolutionary origin of inhibitory motoneurons. 1994 John Wiley & Sons, Inc.     

Detection of S-Phase Cells in Smear Cytology Using in Vitro Bromodeoxyuridine Labeling

A technique Is described for rapid detection of S-pha?e cells of tumor tissues in smear specimens using bromodeoxyuridine (BrdU) immunostaining. Mouse NR-S1 tumors and human tumor specimens were prepared for smear cytology after incubation in RPMI 1640 culture medium containing 200 μM BrdU at 37 °C under 3 atm for 1 hr. Samples were fixed in 70% ethanol for 30 min and used immediately or air dried for 30 min. Samples were then denatured in either 4 N HC1 or 0.07 N NaOH to prepare partially single-stranded DMA. Fixation with air drying for 30 min followed by 30 min in 70% ethanol and 1 min denaturation with 0.07 N NaOH resulted in satisfactory staining quality. Cultured tumor specimens were processed for routine paraffin sections after smears were made for cytology. The labeling indices of the smear specimens and of the paraffin sections gave similar results. This technique should be useful in evaluating the cell proliferative potential of tumor tissue in smear cytology without processing paraffin sections.     

促黄体素释放激素类似物(LH-RH-A)对妊娠大鼠子宫代谢的直接作用

本实验结果表明,胚泡着床点对~3H-尿嘧啶和~3H-亮氨酸的摄取明显高于非着床点子宫部位。LH-RH-A可显著抑制胚泡着床点对这两种同位素的摄取;且对非着床子宫组织也有抑制作用,但抑制程度较弱。进一步证实,着床的胚泡确能产生一种或几种因子,对子宫内膜的分化起重要作用;同时证实,LH-RH-A可通过对RNA和蛋白质合成的抑制作用而直接影响妊娠大鼠子宫的代谢,对胚泡着床点部位的影响尤为明显。     

The paramedial neurosecretory cells of the suboesophageal ganglion of the cricket,Teleogryllus commodus (Walk.)

Summary Ovariectomy, performed immediately after the final hatch, caused a reduction of stainable (neurosecretory?) material in the paramedial neurosecretory cells (PNC) (A-type) of the suboesophageal ganglion in 10 day-old females of Teleogryllus commodus (Walk.). A concomitant increase in nuclear volume and in the incorporation of ³⁵S-cysteine indicates increased synthesis of neurosecretory material. From these findings it is concluded that more stainable material is secreted in the cerebral neurohaemal organ after Ovariectomy. A functional relationship between the PNC and the ovaries is suggested.     

Sister chromatid exchange studies for monitoring DNA damage and repair capacity after cytostatics in vitro and in lymphocytes of leukaemic patients under cytostatic therapy.

The effect of various cytostatic drugs was studied on the frequency of sister chromatid exchanges (SCEs) in vitro and in PHA-stimulated lymphocytes of leukaemic patients under cytostatic therapy. The lymphocyte system is a sensitive one for the detection of DNA damage after administration of cytostatic drugs in vitro. Mitomycin C, busulphan, vincristine, chlorambucil, cytosine arabinoside, cyclophosphamide and lycurim were tested. All except cyclophosphamide induced high frequencies of SCEs in the first mitosis after their administration. The experiments with PHA-stimulated lymphocytes in vivo from patients treated with cytostatics showed that cytosine arabinoside, in combination with thioguanine, did not induce higher frequencies of SCEs, whereas in patients who were treated with cyclophosphamide alone or in combination with other cytostatic drugs, there was a higher incidence of SCEs during treatment. About 10 days after the termination of the treatment the elevated freuqencies of SCEs returned to the initial level. After administration of some mutagens, especially alkylating agents in vivo, the lymphocyte system can be used to assess induced DNA repair by continuously monitoring for SCEs.     

Mutation to ouabain-resistance in Chinese hamster cells: induction by ethyl methanesulphonate and lack of induction by ionising radiation

The spontaneous frequency of mutants resistant to growth inhibition by ouabain (OUAR mutants) was found to be about 5:10(-5) per viable cell in uncloned cultures of Chinese hamster V79-4 cells. In freshly-isolated clones or cultures started from a few cells this frequency was initially reduced to about 1.10(-6) in 1 mM ouabain. No increase in the frequency of OUAR mutants was found in cultures treated with gamma-rays despite exploration of such variables as radiation dose, ouabain concentration, post-treatment interval before selection, cell density in selective medium, and clonal state of the cells at the time of adding ouabain (in situ vs. respreading method). A similar negative result was found for accelerated helium ions, for which the mutagenic effectiveness per unit dose has been shown to be about 10 times higher than gamma-rays for the induction of thioguanine-resistant mutants in these cells. Some evidence was found for an interaction between cellular radiation damage and ouabain-resistance, which may lead to a reduction in the survival of OUAR mutants in irradiated populations, but this damage seemed insufficient to account for inability to detect radiation-induced OUAR mutants. Reproducibly large increases in the frequency of OUAR mutants were found in cultures treated with various concentrations of ethyl methanesulphonate (EMS) by respreading cells in 1 mM ouabain for up to 8 days after EMS treatment. The concentration-OUAR mutant induction curve was approximately linear with low EMS concentrations. Recent evidence is reviewed in support of the suggestion, made in earlier studies, that ionising radiation is unable to induce OUAR mutants because of the severity of the genetic damage it causes.