Hypersensitivity of Bloom's syndrome fibroblasts to N-ethyl-N-nitrosourea

Fibroblast cells from two Japanese patients with Bloom's syndrome (BS) and normal donors were studied for the inactivation of colony-forming ability and the induction of sister-chromatid exchanges (SCEs) after N-ethyl-N-nitrosourea (ENU) treatment. The reduction of ENU-induced SCEs as a function of post-treatment incubation time was also compared between BS and normal fibroblasts. BS cells were approximately 4 times more sensitive than normal cells to the lethal effect of ENU and remarkably hypersensitive to the SCE induction by ENU. The post-treatment incubation of ENU-treated normal cells in the fresh medium resulted in a time-dependent decrease of the SCE level until 6 h after which time the SCE level remained the plateau of about 50% of the initial level. In contrast, the ENU-induced SCEs in BS cells decreased much more slowly with post-treatment incubation time and its half life was 24 h. These results collectively support the view that BS cells may be defective in the rapid repair of certain type(s) of DNA damages induced by ENU.     

Sister-chromatid exchanges induced by ultraviolet light in Bloom's syndrome fibroblasts

The relationships between the cytotoxic effect of ultraviolet light and the UV-induced sister-chromatid exchanges (SCEs) were compared among fibroblast cell strains from two unrelated Bloom's syndrome (BS) patients, one xeroderma pigmentosum (XP) patient belonging to complementation group A and two unrelated normal controls. The "net" induced SCEs as a function of UV fluence, obtained by subtracting spontaneous SCEs from observed SCEs, were much higher in both BS cells and XP group A cells than in normal cells. The relative efficiency of induced SCE, defined as the "net" induced SCEs as a function of surviving fraction after UV irradiation, was higher in BS cells than in normal and XP cells, and there was essentially no difference between XP and normal cells. These results imply that in addition to the extremely high frequency of spontaneous SCEs, the increased efficiency in UV induction of SCEs may reflect the intrinsic defect(s) in BS cells.     

Biotransformation of 1-nitropyrene and 2-nitrofluorene to novel metabolites, the corresponding formylamino compounds, in animal bodies

The present study provides the first evidence that nitropolycyclic aromatic hydrocarbons such as 1-nitropyrene and 2-nitrofluorene are metabolized to the corresponding formylamino compounds in animal bodies. The study shows that the formation of such novel metabolites, 1-formylaminopyrene and 2-formylaminofluorene, is due to N-formylation of the nitroreduction products, 1-aminopyrene and 2-aminofluorene, by liver formamidase in the presence of N-formyl-L-kynurenine.     

Potentiation of harringtonine cytotoxicity by calcium antagonist diltiazem and biscoclaurine alkaloid cepharanthine in adriamycin-resistant P388 murine leukemia and K562 human leukemia cells

Harringtonine showed cross resistance in adriamycin-resistant murine leukemia P388 (P388/ADM) and human leukemia K562 (K562/ADM) cells. The relative resistance of the P388/ADM and K562/ADM cells to harringtonine was about 7 and 40, respectively. Calcium influx blockers, diltiazem and the biscoclaurine alkaloid cepharanthine enhanced the cytotoxicity of harringtonine in P388/ADM and K562/ADM cells. The extent of enhancement was different for the two drugs, and up to a 9- to 10-fold increase in harringtonine cytotoxicity occurred in P388/ADM cells, and 14- to 22-fold enhancement in K562/ADM cells with diltiazem or cepharanthine. Harringtonine resistance of P388/ADM was circumvented completely, and the resistance of K562/ADM was circumvented partially, by diltiazem or cepharanthine. The mechanism of enhanced cytotoxicity by diltiazem and cepharanthine is probably inhibition of active efflux of harringtonine in P388/ADM and K562/ADM cells.     

Instability of Mex- phenotype in human lymphoblastoid cell lines

Three lymphoblastoid cell lines (LCLs) had extremely low activities of O6-alkylguanine-DNA alkyltransferase (O6-AGT), and were classified as Mex-. They were highly sensitive to cell killing by 1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosoure a hydrochloride (ACNU), whereas NMO2, a Mex+ LCL with a high O6-AGT activity, was resistant to the agent. Small fractions of these Mex- LCLs survived the treatment with 10 micrograms/ml of ACNU for 24 h, and the surviving cells were found to be resistant to subsequent treatments with the agent. In addition, they contained O6-AGT activities comparable to that of NMO2 and were therefore regarded as Mex+. These results suggest that the Mex- phenotype in LCLs is unstable.     

Ontogeny of substance P-, CGRP-, and VIP-containing nerve fibers in the amphibian carotid labyrinth of the bullfrog,Rana catesbeiana

Summary The ontogeny of substance P, CGRP (calcitonin gene-related peptide), and VIP (vasoactive intestinal polypeptide) containing nerve fibers in the carotid labyrinth of the bullfrog, Rana catesbeiana, was examined by the peroxidase-antiperoxidase method. The time of appearance of these three peptides was different for each. First, CGRP fibers appeared in the wall of the carotid arch and external carotid arteries, and in a thin septum between these two arteries at an early stage of larval development (stage III). At stage V, substance P immunoreactive fibers appeared, and VIP fibers were detected at the early metamorphic stage (stage XXII). Up to the completion of metamorphosis, the number of these fibers remained low. From 1 to 5 weeks after metamorphosis, substance P, CGRP, and VIP fibers increased in number to varying degrees. By 8 weeks after metamorphosis, the distribution and abundance of these fibers closely resembled those of the adults. Some CGRP and VIP immunoreactive glomus cells were found at the stages immediately before and after the completion of metamorphosis. These findings suggest that substance P, CGRP, and VIP fibers during larval development and metamorphosis may be nonfunctional, and start to participate in vascular regulation only after metamorphosis. The transient CGRP and VIP in some glomus cells may be important for the development of the labyrinth, or may take part in vascular regulation through the close apposition of the glomus and smooth muscle cells (g-s connection).     

Epstein-Barr virus (EBV) and human hematopoietic cell lines: a review.

Two facts need to be pointed out to help explain why the history of Epstein-Barr virus (EBV) research has been inseparable from that of the studies with human hematopoietic cell lines of neoplastic and non-neoplastic origin. One is that Burkitt lymphoma (BL) cell lines, EBV-positive or-negative, can be established in culture quite easily. Thus, the BL cell lines which Epstein established were indeed some of the first hematopoietic as well as virus-carrying cell lines of human neoplastic origin. The other is that EBV-positive B-cell lymphoblastoid cell lines (B-LCL) of normal origin can be grown from samples of sero-positive individuals. B-LCL were often mistakenly regarded as being of neoplastic origin, but are almost always of normal cell origin. Very rarely, however, B-LCL with the same clonal markers as those of neoplastic cells have also been obtained. While the development of B-LCL has been referred to as the in vitro viral immortalization of human B cells and as a phenomenon representing the potential oncogenicity of EBV, the phenotypic and genotypic differences between B-LCL and EBV-carrying BL cells are obvious, indicating that the development of B-LCL per se does not prove the oncogenic activity of EBV. Two EBV-derived antigens, EBNA2 and latent-infection membrane protein (LMP), which are strongly expressed by B-LCL but not by BL cells, have recently been detected in EBV-positive proliferative B cells in patients with organ transplants, suggesting that the proliferating of B-LCL-like cells may take place as an initial step of the multi-step in vivo oncogenesis of EBV.(ABSTRACT TRUNCATED AT 250 WORDS)     

Utility of the hot-wire spirometer

A comparative study has been carried out to investigate the performance of the hot-wire spirometer and the Rollingseal spirometer; the reproducibility of the data generated by an individual examiner; and the validity of data obtained by an "inexperienced examiner" using the hot-wire spirometer. The following results were obtained: 1. The experimental data given by the hot-wire spirometer were about 5-6% higher for FVC and FEV1, and about 10-12% higher for PFR, V50, and V25, respectively, when compared to the data generated by the Rollingseal spirometer. 2. The reproducibility of the data produced by the hot-wire spirometer operated by an "experienced examiner" was good, as the percent difference was about +/- 3%. 3. Reliable data were obtained with the spirometer even by an "inexperienced examiner" if he/she has gone through an on-site training concerning instrumentation and measurement methods for spirography.     

Effects of silver ion on the calcium-induced calcium release channel in isolated sarcoplasmic reticulum

Ag+-induced Ca2+ release in isolated sarcoplasmic reticulum (SR) was studied by the stopped flow method monitoring chlortetracycline fluorescence change. After improving the experimental procedure, the initial rate of Ca2+ release could be determined more precisely than before. Micromolar concentrations of Ag+ specifically enhanced Ca2+ efflux from heavy fraction of SR vesicles (HSR). This specific effect was referred to as Ag+-induced calcium release. The Ag+-induced Ca2+ efflux was activated by caffeine and ATP, but was inhibited by Mg2+ and procaine. Further, Ag+ enhanced the Ca2+-induced Ca2+ release over the whole range of Ca2+ concentrations, similarly to ATP. Parallel to Ca2+ efflux, Mg2+ efflux, measured by the same method, was also activated by Ag+. Choline permeability determined by the light scattering method was also activated by Ag+. The results suggest that Ag+ binds to the activation site of the Ca2+-induced Ca2+ release channel and opens the channel. The Ag+ binding site is different from the Ca2+ binding site but similar to the ATP binding site.