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L G Littlefield

Publications and source records attributed to L G Littlefield.

At least 55 records · Page 3Linked to original sources
PubMed1984

Evaluations of cellular proliferation and chromosome breakages after in vitro exposure of human lymphocytes to calcium or zinc DTPA.

The analysis of mitotic indices (MI) and chromosome breakages in metaphases of 50-hr lymphocyte cultures exposed to the calcium or zinc chelates of diethylenetriamine pentaacetic acid (DTPA) demonstrated: (1) an 80% reduction in MI in cultures from three women but no reduction in those from two men after in vitro exposure to CaDTPA in concentrations as low as 10 micrograms/ml culture medium, and complete suppression of mitoses in cultures from men and women after exposure to 40 micrograms/ml CaDTPA; (2) minor suppression in MI in cultures from women and none in those from men after exposure to 40 or 80 micrograms/ml ZnDTPA; (3) no ring or dicentric chromosomes in 1700 metaphases from DTPA-treated cultures. Likewise, in other experiments we observed no differences in the frequency or distributions of rings and dicentrics in lymphocyte cultures from two persons after in vitro exposure to 250-R 60Co gamma radiation in the presence or absence of 10 micrograms/ml CaDTPA or 10 or 80 micrograms/ml ZnDTPA. These data indicate that while accurate estimates of the frequencies of radiation-induced rings and dicentrics in lymphocytes can be made in actinide-contaminated persons undergoing DTPA chelation therapy, blood samples for cytogenetic cultures should not be obtained from chelated patients until the compound has been cleared from the blood plasma.

Calcium↗
PubMed1983

SCE evaluations in human lymphocytes after G0 exposure to mitomycin C. Lack of expression of MMC-induced SCEs in cells that have undergone greater than two in vitro divisions.

We conducted a series of experiments designed to determine whether DNA damage induced in G0 lymphocytes by mitomycin C (MMC) would be expressed as sister-chromatid exchanges during the second and third post-treatment cell cycles. Lymphocytes from normal donors were exposed to MMC for 2 h prior to culture in the presence of phytohemagglutinin. MMC-treated and control cells were subsequently exposed to bromodeoxyuridine (BrdUrd) for the entire culture period (i.e. 48 h or 72 h) or for the terminal 24 h of 72-h cultures. We observed a 3-4-fold increase in SCEs in MII metaphases from lymphocytes treated with MMC and cultured in the presence of BrdUrd for the entire culture period. In contrast, in replicate cultures of MMC-treated lymphocytes that were exposed to BrdUrd for the terminal 24 h only, the SCE frequency in uniformly harlequinized metaphases was not significantly different from that observed in control cultures. We interpret these data as providing evidence that MMC-induced lesions (or alterations) in the DNA of G0 lymphocytes are probably expressed as SCEs during the first period of mitogen-induced DNA synthesis, and that these lesions do not persist and give rise to SCEs in subsequent cell divisions.

Antibiotics, Antineoplastic↗
PubMed1982

SCE frequencies in rabbit lymphocytes as a function of time after an acute dose of cyclophosphamide.

Following acute and chronic exposures to various chemicals in vivo, the average SCE frequency in human and rabbit lymphocytes has generally been shown to decrease with time posttreatment. The rate of this decline varies, however, and little data have been published pertaining to the decrease in SCEs soon after exposure. To gain more information about the immediate decline in SCEs with time, we injected rabbits with a single dose of 35 mg/kg cyclophosphamide (CP) and determined SCE levels in circulating lymphocytes at various times 5 h to 2 weeks after treatment. We observed a rapid decline in SCE frequencies within 5 days, and by 10 days post-exposure the SCE levels were back to control values. The distribution of SCEs among cells and the number of circulating lymphocytes were also analyzed at each time. Within 2-3 days posttreatment we observed a rapid loss of cells with high SCE levels concomitantly with a rapid decline in circulating lymphocytes and a decrease in the average SCE frequency. When the number of lymphocytes began to increase, the number of cells with normal SCE values also increased. By 10-11 days after CP, the lymphocyte count had recovered, the SCE frequency had returned to control levels, and the distribution of SCEs among cells was almost identical to the control distribution. These data, in addition to published information on rabbit lymphocyte lifespan, suggest that the decline in SCE levels with time posttreatment is a function of lymphocyte turnover.

Animals↗
PubMed1982

Establishment of two parental cell lines and three clonal cell strains from rat colonic carcinoma.

Two epithelial cell lines were established from separate pools of cells that were harvested by a sequential proteolytic treatment of a single specimen of rat transplantable colonic carcinoma. The cells were small (10-micrometer diameter) and cuboidal and displayed desmosomes and light junctions. Both cell lines grew rapidly with population-doubling times of 20 to 22 hr, were near diploid in chromosome number, contained A-2 and B-7 marker chromosomes, and were tumorigenic in rats. Each was distinguishable from the other by the shape of its cell clusters in monolayer culture, its serum requirement for growth, its modal chromosome number, and its karyotypic alterations. Undifferentiated cells, cystic cells, and vacuolated cells, but not mature mucous cells, were observed in monolayer cultures. Clonal cell strains mimic the morphological and growth properties of their respective parental cell line but display unique karyotypic alterations in addition to the A-2 and B-7 marker chromosomes.

Animals↗
PubMed1981

Cytogenetic effects of cis-platinum(II)diamminedichloride in vivo.

The chemotherapeutic agent cis-platinum(II)diamminedichloride (cis-PDD) has been shown to be mutagenic, teratogenic, and carcinogenic. We determined the cytogenetic effects of cis-PDD on human and rabbit lymphocytes in vitro and on rabbit marrow cells, lymph node cells, and lymphocytes in vivo. Lymphocyte cultures from two humans and one rabbit were treated in vitro with cis-PDD. For in vivo studies, five New Zealand white rabbits were given iv injections of cis-PDD. Posttreatment blood samples were withdrawn for analysis and rabbits were sacrificed at either 6 or 24 hr for cytogenetic analysis of marrow and node cells. Sister chromatid exchange (SCE) analysis of human and rabbit metaphases from lymphocytes treated in vitro showed that rabbit lymphocytes are more sensitive to SCE induction by cis-PDD. Significant increases in SCE were observed in lymphocyte cultures obtained as early as 1 hr post treatment from injected rabbits. Analysis of node, marrow, and lymphocyte metaphases from injected rabbits showed a high number of chromosome aberrations in these cells with bone marrow showing a delayed response to treatment. These results indicate that cis-PDD is clastogenic in hematopoietic tissues in vivo and that SCE methodology may be useful in monitoring patients receiving cis-PDD therapy.

Animals↗
PubMed1981

Physical, chemical, and biological factors affecting sister-chromatid exchange induction in human lymphocytes exposed to mitomycin C prior to culture.

In experiments to assess the effects of several biological, chemical, and physical variables on sister-chromatid exchange (SCE) induction in cultured lymphocytes exposed to mitomycin C (MMC) before PHA stimulation we observed: (1) high SCE frequencies in female cells, and normal SCE frequencies in Y-bearing metaphases in mixed cultures containing equal numbers of MMC-treated female lymphocytes and untreated male lymphocytes; (2) small, but statistically significant, decreases in SCEs with increasing pH after G0 exposure in the pH range 6.6-7.6; (3) pronounced reductions in MMC-induced SCEs in lymphocytes exposed at 4 degrees C vs. 37 degrees C. In other studies, SCE induction was evaluated in cultures exposed during G0 to MMC concentrations ranging from 0.25 to 2.5 microgram/ml for varying time intervals ranging from 5 min to 24 h. For all concentrations tested SCE induction varied as a linear function of G0 exposure time. To compare SCE induction between cultures, we calculated the mean frequencies of SCEs induced per metaphase/unit dose MMC/unit G0 exposure time (SCE/microgram/h). A mean frequency of 20.7 +/- 4.8 SCE/microgram/h was observed for 41 lymphocyte cultures suggesting that a single term adequately describes the rate of SCE induction following G0 exposure to a 10-fold range in concentration of MMC for time intervals of 30 min to 24 h.

Cells, Cultured↗
PubMed1981

Evaluation of chemically induced cytogenetic lesions in rabbit oocytes. I. The test system and the effects of streptonigrin.

An appropriate method for evaluating transmissible genetic damage in female germ cells is presented. Analysis of karyotype preparations from preimplantation (6- day) rabbit embryos for consistent structural chromosome abnormalities is described as a sensitive way in which these determinations can be made. A table prepared from summarized research reports shows that less than 1 in 2000 rabbit blastocysts karyotyped thus far has a consistent structural chromosome abnormality. In the new data presented in this study, none of the 90 control blastocysts karyotyped had consistent structural chromosome abnormalities while 13 of 278 from female rabbits treated with streptonigrin (NSC-45383) before conception did. These findings demonstrate that karyotype analysis for consistent chromosome lesions in preimplantation rabbit embryos from females exposed to chemical clastogens can serve as a sensitive and quantitative means of estimating effects on oocytes. The results of the study also show that the consistent structural chromosome lesions in the blastocyst karyotypes are what would be predicted from the mode of action of streptonigrin and the segregation of chromosomes during meiosis. The relative efficiency of this system based on the rabbit as compared to another recently described system bases on the hamster is also discussed.

Animals↗
PubMed1981

Analysis of mutagen-induced chromosome damage in a primate species (Saguinus oedipus oedipus) at risk for spontaneous adenocarcinoma of the colon.

A high incidence of adenocarcinoma of the colon (greater than 16%) has been observed at necropsy in the South American primate, Saguinus oedipus oedipus (S. oedipus), while the disease has not been found in tamarins of the closely related species, Saguinus fuscicollis spp, housed in the same research colony. Cytogenetic analyses in cultured lymphocytes from 10 S. oedipus and 10 S. fuscicollis illigeri (S. fuscicollis) demonstrated no differences in the average frequencies of spontaneous or mitomycin C (MMC)-induced sister chromatid exchanges (SCEs) between animals of the two species. However, highly significant variability in MMC-induced chromosome lesions was observed between the individual S. oedipus, with one animal exhibiting increased sensitivity for both SCEs and chromosome breakages. At present we do not know the relationship, if any, between increased sensitivity to mutagen-induced cytogenetic lesions in specific S. oedipus tamarins and the increased risk for colon cancer that has been documented in this primate species. However, our cytogenetic findings in this one S. oedipus are similar to data obtained in evaluations of persons with several autosomal recessive conditions in which there is a genetic predisposition for developing malignancies.

Adenocarcinoma↗
PubMed1981

Factors affecting the sensitivity of rabbit lymphoid and bone marrow cells to Streptonigrin-induced chromosome aberrations.

In previous cytogenetic studies of rabbits injected with the clastogen, streptonigrin (SN), we observed a higher incidence of chromosome aberrations in lymph node cells than in marrow cells recovered 6 h after treatment. In this study we examined several factors that may be responsible for this difference in the incidence of lesions. Results from SN pulse-treated lymphoid and marrow cultures demonstrated that the responses were different in vitro also. In addition, at higher doses of SN, lymphoid cells displayed a greater sensitivity to the drug when treated during DNA synthesis; marrow cells showed no differences in sensitivity throughout the cell cycle. Analysis of the percentage of lymph node and marrow metaphases labeled following 2, 4, or 6 h of culture in the presence of tritiated thymidine indicated that G2 was less than 2 h in lymph node cells and approximately 4 hr in marrow cells. From these data we conclude that the difference in the incidence of lesions 6 hr after an in vivo SN exposure. However, our data also indicate that lymph node cells are innately more sensitive to the induction of lesions than are marrow cells.

Animals↗
PubMed1981

Chromosomal radiation sensitivity in ataxia telangiectasia long-term lymphoblastoid cell lines.

Elevated frequencies of spontaneous chromosome breakage and hypersensitivity to radiation induced chromosome damage are characteristic findings in cultured lymphocytes and skin fibroblasts of patients with ataxia telangiectasia (AT). To determine whether long-term AT lymphoblastoid cells (B-lymphocytes) which do not express spontaneous chromosomal instability, exhibit increased chromosomal radiation sensitivity, four AT lymphoblastoid cell lines were exposed to various doses of 250 kVp X-rays during G2. At doses of 25 and 50 rad, the AT cells exhibited a 2-3 fold increase in radiation damage relative to that observed in B-cell lines or PHA stimulated lymphocytes from normal donors, while at 100 rad, the AT cells demonstrated approximately 1.5 times more lesions. These findings suggest that the genetic (or other) factors responsible for increased chromosomal radiation sensitivity in AT lymphocytes and fibroblasts also operate in long-term lymphoblastoid AT cells.

Ataxia Telangiectasia↗
PubMed1980

The effect of washing lymphocytes after in vivo treatment with streptonigrin on the yield of chromosome and chromatid aberrations in blood cultures.

Cytogenetic analyses of cultured blood lymphocytes from streptonigrin-treated female rabbits demonstrated that the yield of chemically-induced chromatid aberrations, expecially exchanges, is influenced by the method of blood handling before in vitro culture. When blood cells from treated animals were washed with tissue-culture medium before culture, chromatid breaks were observed at the same level as in the controls, and no chromatid exchanges were found. However, when duplicate aliquots of blood were inoculated directly into culture medium, without washing, elevated levels of chromatid breaks were observed and chromatid exchanges were found. These findings indicate that the clastogen, streptonigrin, was carried into the culture medium with the blood-cell inoculum.

Animals↗
PubMed1980

Sister chromatid exchange and mitotic stimulation in lymphocytes from four species of the genus Saguinus.

Lymphocytes from 18 tamarins of four species were cultured in bromodeoxyuridine (BrdUrd) supplemented medium, stained by a fluorescence plus Giemsa (FPG) method, and evaluated for both sister chromatid exchange (SCE) and mitotic stimulation. The overall SCE frequency was found to be 7.02 +/- 3.45 per cell with individual cells containing from zero to 33 spontaneous SCEs. As a measure of mitotic stimulation a total of 3,200 metaphases from the 18 animals were evaluated for the number of DNA replications in vitro by the FPG differential chromatid staining.

Animals↗
PubMed1979

Sister-chromatid exchanges in human lymphocytes exposed during Go to four classes of DNA-damaging chemicals.

Human lymphocytes were treated prior to mitogenic stimulation with varying concentrations of 6 cytostatic drugs representing 4 classes of DNA-damaging chemicals. Afterwards the cells were washed to remove residual chemical and cultured in the presence of bromodeoxyuridine for analysis of sister-chromatid exchanges (SCEs). A dose-related increase in SCEs was observed in cells exposed during Go to the alkylating chemicals mitomycin C, chlorambucil, and thiotepa, while significant increases in SCEs were not noted in cultures exposed to methotrexate, cytarabine, or bleomycin. These findings suggest that not all classes of clatogenic chemicals which induce SCEs in proliferative cells substituted with BUdR are capable of inducing long-lived lesions in the DNA of Go lymphocytes that can lead to SCE formation.

Bleomycin↗