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Bone-marrow cells from a patient with Bloom’s syndrome cultured for 48 h in the presence of BudR exhibited a striking increase in the number of sister chromatid exchanges (SCEs) in comparison to that in the marrow cells of a patient with treated polycythemia vera (PV). Thus, it appears that an increased incidence of SCE in Bloom’s syndrome occurs in various differentiated types of cells, not just blood lymphocytes, and constitutes the syndrome’s most characteristic cytogenetic feature. In contrast, the incidence of SCE was not increased in marrow cells and lymphocytes of the particular PV patient studied here, whose cells did exhibit increased numbers of chromatid and chromosome gaps and breaks, presumably as result of the patient’s earlier treatment. An increased frequency of SCE was demonstrated in Bloom’s syndrome lymphocytes using both a technique based on BudR incorporation and one based on labeling with tritiated deoxycytidine. This observation constitutes evidence against the increase of SCE being due to an unusual reaction to BudR. By conventional cytogenetic techniques, chromosome instability, including chromatid and chromosome breaks, but no homologous chromatid interchanges were also recognized in Bloom’s syndrome bone-marrow cells incubated in vitro (without BudR) for either 1.5 or 46 h. This observation points to the existence of chromosome instability in vivo.

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When Bloom syndrome (BS) cells labeled with bromodeoxyuridine (BrdUrd) for one round of DNA replication were fused with nonlabeled normal cells, the hybrid cells had a normal level of sister chromatid exchange (SCE) at the first mitosis after fusion. However, when normal cells treated with mitomycin C (MC) were fused with nontreated normal cells, the MCinduced SCE was not affected by fusion with normal cells. Single and twin SCEs were analyzed in the Colcemid-induced endoreduplicated normal and BS lymphoid B cells from diplochromosomes. In normal cells, the same number of SCEs occurs in each of the two cell cycles; the SCE ratio of single (6.30 SCEs per cell) to twin (2.92 SCEs per cell) was 2:1 on the endoreduplicated-cell basis, showing 1:1 on the diploid-cell basis. In BS cells, the SCE ratio of single (144.8 SCEs per cell) to twin (5.9 SCEs per cell) was 25:1 on the endoreduplicated-ceIl basis and was 12:1 on the diploid-cell basis. These studies strongly suggest that most of the BS SCEs occur during the second cell cycle when BrdUrd-containing DNA is used as template for replication and that the normal level of BS SCE observed at the first mitosis of the hybrid cells is the result of SCE inhibition resulting from the fusion with normal cells.The increased rate of sister chromatid exchange (SCE) in Bloom syndrome (BS) cells has bemen well established (1-3), though neither the mechanism leading to nor the biological significance of SCE is known. Normalization of the SCE frequency in BS cells by cell fusion with eudiploid cells by using polyethylene glycol and dimethyl sulfoxide techniques has been reported (4-6). When BS cells labeled with bromodeoxyuridine (BrdUrd) for one round of DNA replication were fused with nonlabeled normal cells, the hybrid cells had a normal level of SCE at the first mitosis after fusion (6). However, recent studies of single and twin SCEs in endoreduplicated normal cells also have shown that an equal number of SCEs occur in each of the two cell cycles of growth required for their demonstration (7, 8). On the basis of these data, a 50% reduction in BS chromosome SCE frequency could theoretically be expected to be observed one cell cycle after fusion. However, a clearcut normalized level of SCE was observed; therefore, the theoretical half reduction was clearly inconsistent with the exact data of ref. MATERIALS AND METHODSA permanent BS lymphoid B-cell line (EBV-BS1I2), which retained its original increased SCE in 100% of the cells, and a normal B-cell line (EBV-NL) were established from a patient with BS and from a normal subject by using Epstein-Barr virus (EBV) (9, 10). To induce endoreduplication of human cells, we used the spindle inhibitor Colcemid technique (8). The method involved the 8-hr treatment with Colcemid (0.1 ug/ml; Difco) in the middle of BrdUrd incubation-that is, between 22 and 30 hr during the late part of first mitosis. After such an intervening treatment, the Colcemid-containing medium was discarded, and the cells were reincubated in fresh medium cont...

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ABSTRACT. A 4-year-old male Shiba dog initially presented with pain of an undetermined origin and hypersensitivity to touch. Seven days later, the dog developed ataxia, hind-leg weakness and knuckling. The dog died on 20 days after presentation. Postmortem examination revealed a mass in the body of thoracic vertebra. Histopathologically, the mass consisted of granulomatous inflammation, including fungal organisms that were immunohistochemically positive for Candida albicans. Similar granulomatous lesions were observed in the systemic lymph nodes, kidneys, pancreas, spleen, prostate gland, thyroid glands and heart. This case was diagnosed as systemic candidiasis with spondylitis.