Repeated histamine inhalation tests in asthmatic patients

Histamine inhalation tests were performed in 12 asthmatic patients using a 2-min tidal breathing inhalation technique. The tests were repeated on separate days with 30-, 60-, and 120-min intervals between inhalation tests. On another day the inhalation tests were repeated four times with 40-min intervals between tests. The geometric mean provocative concentrations of histamine needed to cause a 20% fall in forced expiratory volume in 1 sec (PC₂₀) for the group on the latter study day were 1.67, 1.57, and 1.55 mg/ml (p > 0.25) indicating no change in sensitivity to inhaled histamine with repeated testing. The results suggest that cumulative dose-response curves for drugs potentially affecting the airways or antagonizing histamine can be constructed within 1 day using histamine inhalation tests. The data also suggested that an individual PC₂₀result may be sensitively assessed by comparing it to a ±2 SD range from the mean of a series of control or placebo PC₂₀ values.     

Inhaled verapamil in histamine-induced bronchoconstriction

Fifteen asthmatic subjects participated in a double-blind trial comparing the protective effects of inhaled verapamil, salbutamol, and saline against inhaled histamine. Inhaling verapamil between four repeated histamine inhalation tests produced no significant protection against histamine-induced bronchoconstriction, while there was significant protection with salbutamol (p < 0.001). Inhaling verapamil before a single inhalation test produced limited but significant protection (p < 0.05) compared with a saline control in eight asthmatic subjects. This small protective effect in the two-treatment study of eight asthmatics suggests that either the protective effect of verapamil is variable among subjects or a preceding histamine inhalation test blocks the verapamil effect.     

Sister chromatid exchange in normal and Ph1-positive leukemic cells after mitomycin-C treatment in vitro

The sister chromatid exchange (SCE) frequency was investigated in normal bone marrow and Ph1-positive cells of chronic myelocytic leukemia (CML) patients with and without mitomycin-C (MMC) treatment in vitro. Even though the spontaneous SCE frequency was found to be significantly lower in CML cells, the absolute SCE values after MMC treatment did not differ between leukemic and normal cells, and this seems to indicate an equilization of SCE rates. However, the fact that leukemic cells with lower spontaneous SCE rates need a further increase of SCE to reach values equal to those of normal cells might indicate a somewhat higher susceptibility of leukemic cells to DNA damage by MMC. This interpretation appears to be confirmed by the fact that the inhibition of cellular proliferation at higher MMC doses considerably reduced the number of leukemic cells that was able to divide twice during a given culture time.     

Sister chromatid exchange levels and cell cycle time in human bone marrow cells and lymphocytes

The frequency of sister chromatid exchange (SCE) and the cell-cycle-specific pattern of mitoses were analyzed at the same time in normal bone marrow cells and lymphocytes of six healthy donors. The SCE frequency was found to be significantly higher in lymphocytes. The cell-cycle-specific pattern revealed significantly shorter cell cycle times for normal bone marrow cells as compared with those of phytohemagglutinin (PHA) stimulated lymphocytes. Chromosomes of bone marrow metaphases displayed a more contracted morphology.     

Sister chromatid exchange: Variation by age,sex, smoking,and breast cancer status

Variation in sister chromatid exchange (SCE) frequency in lymphocytes of 125 persons was compared using a multivariate general linear model. The study was performed to determine whether SCE frequency differs with respect to age, sex, smoking, and breast cancer status. Study subjects were divided into: members of two branches of families having an excess of cancer (primarily breast) including a brother and sister in one family who developed nonbreast malignancies within 1 yr of the study; women in both families successfully treated for breast cancer (all at least 5 yr posttreatment); and women from the general population with confirmed breast cancer.Controls consisted of spouses who married into the high-risk kindreds, hospital personnel, and others (primarily tradesmen without history of occupational exposure). Results show that: (1) Women with active breast cancer have a significantly higher mean SCE frequency than control women or women greater than 5 yr posttreatment for breast cancer; (2) Cigarette smokers show a significantly higher number of SCEs than was observed in nonsmokers; (3) The increase in SCE level in smokers is dose-related to exposure as measured by cumulative pack-years; (4) SCE values in both high-risk families are not significantly different from controls; (5) Neither the age nor sex of the individual affects SCE frequency; and (6) The observed distribution of exchanges agrees with that expected based on the proportion of the genome represented by each chromosome group.     

Chromosomal breakage and sister chromatid exchange in peripheral blood lymphocytes and lymphoblastoid cell lines in the X-linked lymphoproliferative syndrome

The frequencies of chromosomal aberrations and sister chromatid exchange (SCE) were measured in lymphoblastoid cell lines (LCLs) and in phytohemagglutinin (PHA)- and pokeweed mitogen (PWM)-stimulated lymphocytes from males with X-linked lymphoproliferative (XLP) syndrome, their obligate carrier mothers, and control subjects. We observed an increased frequency of chromosomal aberrations including increased polyploidy in LCLs derived from families with XLP with time in culture. The SCE rate in LCLs (mean of 3.89 SCEs per cell) was much lower than that in PHA- or PWM-stimulated lymphocytes: PWM-stimulated lymphocytes showed 9.58 SCEs per cell and PHA-stimulated cells had 11.38 SCEs per cell. A greater number of chromosomal gaps and breaks in the D-group chromosomes of LCLs of affected males and carrier females were identified compared to the number expected, based on chromosomal length and the number of aberrations seen in PHA-stimulated cell cultures. No differences in the frequency of SCEs or chromosomal aberrations were found in control subjects and affected males or carrier females in the peripheral lymphocytes stimulated by PHA. Phenotypes of XLP appear to arise from failure of immune responses to Epstein-Barr virus (EBV) and not from intrinsic chromosomal breakage or instability.     

Phentolamine increases neuronal binding and retrograde transport of dopamine beta-hydroxylase antibodies

When 125I-labelled antibodies against dopamine beta-hydroxylase (DBH) were injected into the anterior eye chamber of guinea-pigs they bound to sympathetic nerve terminals, were internalized into the axons and retrogradely transported to the ipsilateral superior cervical ganglion (SCG). This process was demonstrated to depend on specific binding sites since neutralized antibodies were not taken up and transported. The alpha-receptor antagonist phentolamine caused a 2.5-fold increase in binding in the iris and a 2.1-fold increase in accumulation of [125I]anti-DBH in the SCG. The results demonstrate that retrograde axonal transport of synaptic vesicle components is coupled to their turnover in nerve terminals.     

Sister chromatid exchange in malignant lymphomas

Sister chromatid exchange (SCE) was evaluated in peripheral lymphocytes from 20 untreated patients with malignant lymphomas: 6 with Hodgkin's disease (HD), 14 with non-Hodgkin lymphoma (NHL), and 5 with lymphadenitis. The mean SCE frequency (+/- SE) was: 11.2 +/- 0.6, 11.0 +/- 0.6, and 7.2 +/- 0.3 for HD, NHL, and lymphadenitis patients, respectively, and 8.7 +/- 0.2 for the control group. No differences in SCE score were observed in HD and NHL. These results allowed us to consider both groups (HD and NHL) as a single neoplastic population (mean +/- SE, 11.0 +/- 0.4). No significant differences were found between the lymphadenitis and control groups. On the other hand, significantly higher SCE scores were seen in neoplastic populations than in the control and lymphadenitis groups (p less than 0.001 and p less than 0.01, respectively). When SCE was compared by chromosome number and group between neoplastic patients and controls, a higher SCE frequency was observed in chromosomes #1, #2, #3, and B, C + X, E, F chromosome groups than in controls. SCE levels were significantly higher in lymphoma patients in all chromosome numbers and groups mentioned than in patients with lymphadenitis. It is suggested that the high SCE rate in the malignant lymphoma population is possibly related to an increased chromosomal instability.     

Elevated sister chromatid exchange rate in lymphocytes of the European eel (Anguilla anguilla) with cauliflower tumor

Sister chromatid exchange (SCE) frequency and chromosomal aberration were studied in cultured lymphocytes from the European eel (Anguilla anguilla) with cauliflower tumors. SCE was significantly increased in the affected fishes compared with normal controls, whereas chromosomal aberration did not. In comparison to normal cells, the lymphocytes responding to phytohemagglutinin M (PHA-M) in cultures from tumorous eels showed no evidence of cell cycle retardation. A possible mechanism for elevation of SCE and the significance of this finding relation to the etiology were discussed.     

Elevated sister chromatid exchange and cell cycle analysis in bone marrow in childhood ALL

Sister chromatid exchange (SCE) frequencies were analyzed in both stimulated and unstimulated bone marrow samples from eight patients recently found to have childhood acute lymphocytic leukemia (ALL). Six of the patients had elevated SCE frequencies in stimulated marrow when compared to control values. In unstimulated marrow, all four patients had elevated SCE frequencies. These data agree with peripheral leukocyte findings in ALL. Cell cycle analysis revealed no significant differences between the patient marrows and the control marrows. Since no correlation between cell cycle distribution and SCE frequency was found, it is suggested that the differences in SCE observed may be related to the type of proliferating cell.     

Some comments on sister chromatid exchange (SCE) in human neoplasia

The incidence of sister chromatid exchange (SCE) in bone marrow cells and/or lymphocytes of patients with various leukemias and the effects of drugs on the SCE incidence in the cells of patients with leukemia or cancer are presented and discussed. The possible use of SCE for screening antileukemic drugs, mutagenic and/or carcinogenic agents and susceptible human populations is presented.     

Cancer in relatives of patients with aplastic anemia

The risk of cancer was examined among family members of 9 patients with Fanconi's anemia. Seven cancers of diverse types were observed, as compared with the 10.4 expected (P > 0.05). In addition, the study of relatives of 60 patients with acquired aplastic anemia showed no unusual distribution of cancers by site and age at diagnosis. In particular, no relative in either series had acute leukemia. Methodologic issues complicate the interpretation of several published reports of excess cancers among heterozygotes of Fanconi's anemia, ataxia-telangiectasia, and xeroderma pigmentosum.     

Sister chromatid exchanges induced by nitrogen mustard in Fanconi's anemia. Application to the detection of heterozygotes and interpretation of the results

Nitrogen mustard-induced SCE were studied on Fanconi's anemia (FA) patients, FA parents, and control lymphocyte cultures. When low doses of nitrogen mustard were added at the time cultures were initiated, a distinction could be made between FA heterozygotes and controls. In FA heterozygotes increase of SCE levels higher than that observed in controls was found, thus allowing the recognition of heterozygotes. FA cells appeared to be more sensitive to nitrogen mustard than FA heterozygous and control cells. The data argues in favor of an excision-repair defect, and is discussed in the light of possible repair and SCE production mechanisms.     

Evidence that the replication point is the site of sister chromatid exchange

DNA synthesis in Chinese hamster cells was blocked partially by treating the cells with either fluorodeoxyuridine (FUdR) or cycloheximide (CHM) for various lengths of time. Analyses of the population kinetics and measurement of incorporation of labeled nucleosides during the FUdR block strongly suggested that the number of growing points was accumulated by the treatment while the rate of chain growth was greatly reduced. No evidence for such an accumulation was obtained in the CHM-treated cells. To study the relation between DNA replication and sister chromatid exchange (SCE), bromodeoxyuridine-labeled cells were exposed to blue fluorescent light while DNA synthesis was blocked. The frequency of SCE induced by the light treatment appeared to increase as the number of growing points increased, implying that the site of exchange is confined to the replication forks. The induction of SCE by fluorescent light was inhibited completely by CHM-treatment. The reason for this finding remains to be elucidated.     

Inherited aplastic anemia with abnormal clones in bone marrow and increased endoreduplication in peripheral lymphocytes

Cytogenetic studies in peripheral blood and bone marrow cells from a female patient (aged 31 years) with inherited aplastic anemia and without other congenital anomalies are reported. Endoreduplication was increased in stimulated peripheral lymphocytes in several investigations. Chromosome breaks were shown to be near the control frequency, although chromatid exchange figures and dicentrics were present. Cytogenetic analysis was extended to the three children of our patient. Abnormal clones were detected in bone marrow preparations of our patient in all cytogenetic investigations. At the first examination, two of these clones were prevalent, with their karyotypes being 48,XX,+9,+16 and 46,XX,dup(1)(q24→q32),t(17;?)(p12–13;?). The prevailing karyotype after 2 years was 46,XX,t(17;?)(p12–13;?). Involvement of chromosomes #1 and #17 is discussed, taking into account data from the literature concerning several human neoplasias.     

Induction and reduction of sister chromatid exchange by CCNU in human lymphocytes in vitro

Sister chromatid exchange (SCE) was studied in human lymphocytes treated with 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in vitro. A dose-dependent increase of SCE was observed in cells exposed to 10(-5) - 10(-4) M CCNU. The maximal increase was 25-35 SCEs/cell over the control level, which is similar to the increase found in patients treated with CCNU in vivo. In the presence of rat liver microsomes (S-9 fraction) the frequency of CCNU-induced SCE was slightly higher than in parallel cultures without S-9, suggesting that microsomal metabolism may enhance the rate of decomposition of CCNU into reactive products. The CCNU-induced increase of SCE was greater in cells treated for longer time periods (up to 70 hr) than in cells subjected to a 1-hr treatment. This effect was most pronounced at higher concentrations of the drug (5 X 10(-5) M). The frequency of CCNU-induced SCE was also found to be dependent on the time of treatment in the cell cycle. A treatment for 1 hr during early G1-phase (about 20 hr before the first S-phase) gave rise to a higher increase of SCE than a 1 hr treatment immediately before or during the first or second S-phase. Thus, the CCNU-induced DNA damage leading to SCE seems to persist and may even increase during the prereplicative phase of the cell cycle. After replication in BrdUrd-free medium, the frequency of CCNU-induced SCEs decreased to the control level. The present results, taken together with other studies of strand break and cross-link formation by CCNU in mammalian cells in vitro, suggest that the major SCE-inducing damage by CCNU is DNA interstrand cross-links. These lesions then appear to be slowly removed, if at all, during the prereplicative phase of the cell cycle, and to disappear during or after replication in BrdUrd-free medium in vitro.     

Temperature-dependence of sister chromatid exchange: An implication for its mechanism

To obtain some insight into the mechanism for spontaneous sister chromatid exchange (SCE), the effect of temperature on the incidence of SCE was studied by culturing Chinese hamster cells at various temperatures. The frequency of SCE increases fivefold when the incubation temperature was raised from 31 to 42°C; this increase was strictly temperature dependent. An Arrhenius plot of the SCE frequency indicated that the formation of SCE was enhanced greatly when the temperature was raised above 39°C. Cell growth at temperatures higher than 39°C also caused a marked elongation of the DNA synthetic phase. A working hypothesis was proposed that spontaneous SCE might result from a cooperative of processes involved in repair of spontaneous DNA damage and DNA replication.     

Inhibition of bromodeoxyuridine-associated sister chromatid exchanges in Bloom's syndrome cells with cycloheximide

Effects of cycloheximide (CH) and deoxycytidine (dC) on the frequency of sister chromatid exchanges (SCEs) in normal and Bloom's syndrome (BS) cells labeled with bromodeoxyuridine (BrdU) during first, second, and third cell cycles were evaluated using endomitotic and three-way differentiation analyses. When CH at 0.2 and 2.0 ng/ml was added to normal and BS cultures of BrdU-labeled endomitoses, the rate of single SCEs was significantly decreased in BS cells, though the rate of reduction in single SCEs was slight in normal cells. No significant change was detected in the twin SCE rate. In BS cells, treatment with CH at 0.2 and 2.0 ng/ml produced significant reductions in SCEs in both the second (SCE2) and third (SCE3) cell cycles, sometimes reaching the normal level. Treatment with dC at 13 and 26 micrograms/ml resulted in almost no significant changes in rates of SCE during first, second, and third cell cycles. When CH was added to BrdU-labeled normal and BS cell cultures, the cell growth rates improved from 35% to 70% over the control level in the BS cells, though in normal cells, the addition of CH resulted in a close-dependent lower cell growth rate. Deoxycytidine did not noticeably affect the cell growth rates in BrdU-labeled normal and BS cultures. The finding that the reduction of BrdU-induced SCEs in BS is paralleled by cell growth improvement is of special interest.     

Evidence for an indirect effect of radiation on mammalian chromosomes. III. UV- and x-ray-induced sister chromatid exchanges in heterokaryons

The hypothesis that chromosomes may be damaged indirectly by radiation was examined by assaying sister chromatid exchange, (SCE) frequency in heterokaryons between irradiated and unirradiated mouse and Chinese hamster cells. One cell line was UV or x irradiated, then fused to unirradiated BrdU-labeled cells of the other line; SCEs in the unirradiated set were scored in heterokaryons. A dose-dependent increase was consistently observed; the magnitude of which suggested that 25% of UV-induced and up to 60% of x-ray-induced SCEs are indirectly induced. Medium transfer experiments, cell mixing, and fusion with irradiated chick erythrocyte ghosts suggested that unirradiated chromosomes in heterokaryons are damaged by a stable, nondiffusible cytoplasmic component contributed by the irradiated cell.