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Biomedical subjects

F Traganos

Publications and source records attributed to F Traganos.

At least 109 records · Page 6Linked to original sources
PubMed1987

Hyperdiploidy of cultured dermal fibroblasts from patients with aerodigestive squamous carcinoma.

The incidence of hyperdiploidy in monolayer cultures of dermal fibroblasts from 88 patients with squamous carcinoma of the aerodigestive tract was compared with similar cultures from 39 normal subjects using three different techniques; 1) metaphase assay (MA), 2) flow cytometry of stationary cell cultures (FCMs), and 3) flow cytometry of proliferating dividing cell cultures (FCMd). In vitro hyperdiploidy was considered to be present (IVH+): 1) by MA if more than 4% of metaphases were altered, excluding tetraploidy; 2) by FCMs if more than 8% of cells in stationary cultures were hyperdiploid (i.e., DNA index greater than 1), and 3) by FCMd if more than 6% of cells in logarithmic cultures were hypertetraploid (i.e., DNA index greater than 2). There was excellent concordance between the three assays, which assigned cell cultures from 55 of the 88 patients with aerodigestive squamous carcinoma (62%) to the in vitro hyperdiploidy positive (IVH+) category. Cell cultures from all 39 normal individuals were hyperdiploidy negative (IVH-). These data suggest that some substantial proportion of patients with aerodigestive squamous carcinoma may have a genetic predisposition for the disease, which can be identified by these assays. The flow cytometry methods were easier to carry out and may be substituted for the metaphase analyses.

Adolescent↗
PubMed1987

Effects of inhibition of RNA or protein synthesis on CHO cell cycle progression.

Chinese hamster ovary (CHO) cells, synchronized by selective detachment at mitosis, were treated with various concentrations of actinomycin D (AMD) or cycloheximide (CHX) either immediately, or 1, 2, or 3 hr after mitosis. Since the minimum duration of G1 phase in these cultures was 3.4 hr, the addition of RNA or protein synthesis inhibitors took place at the beginning, first third, second third, or end (G1-S boundary) of G1 phase. The kinetics of exit from G1 phase, the rate and extent of traverse of S phase, and the reaccumulation of RNA were estimated under each set of growth conditions by flow cytometry of acridine orange-stained cells. A mathematical model was constructed to describe the trajectories of the cell populations with respect to their increase in RNA and DNA content in the absence or presence of the inhibitor. The chronologic synchrony imposed on the CHO cell population began to decay within 3 hr, resulting in stochastic entrance of cells into S phase in the absence of inhibitor. Addition of AMD or CHX at 0, 1, 2, or 3 hr after mitosis, regardless of the inhibitor concentration, did not provide evidence of a critical restriction point in G1 beyond which cells were committed to enter S phase and were no longer sensitive to moderate suppression of RNA or protein synthesis. The observed kinetics of cell entrance into an traverse of S phase were consistent with an inherently heterogeneous response to serum stimulation occurring at or just after cell division.

Animals↗
PubMed1987

In situ factors affecting stability of the DNA helix in interphase nuclei and metaphase chromosomes.

The data from earlier cytochemical studies, in which the metachromatic fluorochrome acridine orange (AO) was used to differentially stain single vs double-stranded DNA, suggested that DNA in situ in intact metaphase chromosomes or in condensed chromatin of G0 cells is more sensitive to denaturation, induced by heat or acid, than DNA in decondensed chromatin of interphase nuclei. Present studies show that, indeed, DNA in permeabilized metaphase cells, in contrast to cells in interphase, when exposed to buffers of low pH (1.5-2.8) becomes digestible with the single-strand-specific S1 or mung bean nucleases. A variety of extraction procedures and enzymatic treatments provided evidence that the presence of histones, HMG proteins, and S-S bonds in chromatin, as well as phosphorylation or poly(ADP)ribosylation of chromatin proteins, can be excluded as a factor responsible for the differential sensitivity of metaphase vs interphase DNA to denaturation. Cell treatment with NaCl at a concentration of 1.2 N and above abolished the difference between interphase and mitotic cells, rendering DNA in mitotic cells less sensitive to denaturation; such treatment also resulted in decondensation of chromatin visible by microscopy. The present data indicate that structural proteins extractable with greater than or equal to 1.2 N NaCl may be involved in anchoring DNA to the nuclear matrix or chromosome scaffold and may be responsible for maintaining a high degree of chromatin compaction in situ, such as that observed in metaphase chromosomes or in G0 cells. Following dissociation of histones, the high spatial density of the charged DNA polymer may induce topological strain on the double helix, thus decreasing its local stability; this can be detected by metachromatic staining of DNA with AO or digestion with single-strand-specific nucleases.

Acridine Orange↗
PubMed1987

Evidence for genetic predisposition for some nasopharyngeal cancers by in vitro hyperdiploidy in human dermal fibroblasts.

A numerical alteration in chromosome complement in human dermal fibroblast cultures, hyperdiploidy with a normal occurrence of tetraploidy (IVH), has been reported to be associated with some hereditary single tumors including squamous carcinoma of the nasopharynx (NPC). Its incidence was compared in cultures derived from 39 NPC patients and 29 clinically normal subjects without a family cancer history by two different methods (percentage of numerically altered metaphases in chromosome preparations from nonconfluent monolayer Petri dish cultures in logarithmic growth, and by the distribution of DNA content of propidium iodide stained cells from plastic flask cultures in stationary growth phase as assayed by flow cytometry) to ascertain its usefulness in identification of such genetic predisposition. Concordance was observed between the two assays. There was a linear relationship between the percentage of hyperdiploid metaphases assayed in the chromosome preparations and the percentage of cells with a DNA index of greater than 1 as determined by flow cytometry. By metaphase assay, none of the 29 normals showed IVH. OF the 39 carcinoma of the nasopharynx patients studied, 19 had IVH and 20 did not. By flow cytometry there were significant differences in the flow cytometry DNA index (p less than 0.001) of IVH-negative (all normals and 20 carcinoma of the nasopharynx patients) and IVH-positive carcinoma of the nasopharynx patients. The percentage of cells with a DNA index of 2 and greater than 1 could be used to distinguish all IVH-negative from the IVH-positive subjects and, thus, were considered to be the parameters of choice in assaying IVH by flow cytometry. None of the subjects studied showed increased in vitro tetraploidy (IVT), which has been associated with some heritable colon cancer syndromes. Irrespective of family cancer history, approximately one-half of the NPC patients (19 of 39) had IVH, which has been reported to be associated with the in vivo expression of certain heritable tumors including carcinoma of the nasopharynx. The average age of carcinoma of the nasopharynx diagnosis was earlier (mean 52 yr) for the IVH-positive group than for the IVH-negative carcinoma of the nasopharynx group (mean 67 yr).

Adult↗
PubMed1987

In vitro evidence for genetic predisposition in some human pancreatic adenocarcinoma.

A numerical alteration in chromosome complement in human dermal fibroblast cultures, hyperdiploidy with a normal occurrence of tetraploidy (IVH) has been reported to be associated with some hereditary single tumors, including pancreatic adenocarcinoma (PaCa). The incidence of IVH was compared in cultures derived from 34 PaCa patients and 39 clinically normal subjects without a family tumor history by three assay systems: (a) percentage of numerically altered metaphases in chromosome preparations (MA); (b) percentage of cells from high-density, stationary cultures with a DNA index (DI) greater than 1 (FCMs); (c) percentage of cells with a DI greater than 2 from cultures of cells undergoing division (FCMd). The last two measurements were obtained by flow cytometric measurement of propidium idodide (PI) stained cells. Concordance was observed between the three assays. There was a linear relationship between the percentage of hyperdiploid metaphases assayed in the chromosome preparation and the percentage of cells with a DI greater than 1 by FCMs and a DI greater than 2 by FCMd. IVH was considered to be present (IVH+) by the MA technique if the percentage of numerically altered metaphases was over 4% exclusive of tetraploids, by the FCMs technique if DI greater than 1 was greater than 10%, and by FCMd if DI greater than 2 was greater than 7%. The assayed group could be divided into two IVH groups on the basis of all three assays, individually or collectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1987

Sensitivity to X-irradiation in relation to cell size of CHO cells synchronized in early G1.

A population of line CHO Chinese hamster cells was synchronized by mitotic selection and allowed to enter early G1, after which the largest and smallest cells in the population were sorted, irradiated, and their viability determined. Despite sizeable differences in volume, metabolic capability and cell cycle progression rates, an equivalent level of survival was obtained for the two populations, indicating that the factors responsible for the volume, metabolic and progression heterogeneity do not contribute greatly to radiation sensitivity.

Animals↗
PubMed1987

In vitro hyperdiploidy in dermal fibroblasts: evidence for genetic predisposition in aerodigestive tract cancer.

A numerical alteration in chromosome complement in human dermal fibroblast cultures, hyperdiploidy with a normal occurrence of tetraploidy (IVH) has been reported (Danes 1984) to be associated with some heritable single tumors including squamous carcinoma of the nasopharynx (Danes 1986). The incidence of IVH was compared in cultures derived from 65 patients with squamous carcinoma in different regions of the aerodigestive tract (ADT) and 32 clinically normal subjects without a family cancer history by 2 different assays, metaphase assay (MA) and flow cytometry (FCM). By MA, none of the 32 normals showed IVH. Of the 65 ADT patients studied, 35 had IVH and 30 did not. By FCM, there were significant differences in the FCM DNA index (p values less than 0.001) of IVH- (all normals and 30 ADT patients) and IVH+ ADT patients. The per cent of cells with a DI of 2 and greater than 1 could be used to distinguish all IVH- from the IVH+ subjects and were thus considered to be the parameters of choice in assaying IVH by FCM. None of the subjects studied showed increased in vitro tetraploidy (IVT) which has been associated with some heritable colon cancer syndromes. Irrespective of family cancer history, approximately half (35/65) of the ADT patients had IVH which has been shown to be associated with the in vivo expression of certain heritable tumors. The average age of squamous carcinoma diagnosis was earlier (mean 50 yrs) for the IVH+ group than for the IVH- ADT group (mean 72 yrs).

Adolescent↗
PubMed1987

DNA topoisomerase II as a potential factor in drug resistance of human malignancies.

The stabilization of the cleavable complex between DNA topoisomerase II and DNA by adriamycin (ADR), as well as by other topoisomerase II-targeted drugs, is an essential step in a process associated with drug cytotoxicity. Unlike many other cell types, ADR does not produce DNA cleavage in the lymphocytes of chronic lymphocytic leukemia (CLL). The CLL lymphocytes have been identified as quiescent cells with an extremely low level of topoisomerase II. The low level of this enzyme could constitute a basis for a new mechanism of drug resistance operating not only in CLL, but perhaps in any slow growing cancer with a large population of quiescent cells. Other factors contributing to drug resistance could include changes in enzyme regulation or processing of the cleavable complex, or the presence of a "mutant" enzyme which renders cancer cells unresponsive to topoisomerase II-targeted drugs. Suggested strategies in drug development, aimed at the topoisomerase II-related drug resistance, could include 1) the selection of topoisomerase I as an alternative target for cancer chemotherapy, 2) the development of ADR analogs which, unlike ADR, stabilize the topoisomerase II-DNA complex with high efficiency, and 3) the search for agents enhancing the SOS-like repair response, presumably triggered by DNA topoisomerase-targeted drugs.

Animals↗
PubMed1987

Cytokinetic effects of bifunctional antitumor intercalator ditercalinium on Friend erythroleukemia cells.

Ditercalinium (NSC 335153) is a novel 7H-pyridocarbazole dimer in which the two monomers are joined by a rigid bis(ethylpiperidinyl)-linking chain producing a molecule capable of bisintercalation into DNA with extremely high affinity. The effect of ditercalinium on cell proliferation and its interaction with DNA in situ has been investigated in the Friend leukemia cell system. Ditercalinium caused an inhibition of cell growth at 0.5 microM and cell death at 2.5 microM. However, both the cytokinetic and cytotoxic effects became evident only after 1-2 days of continuous drug exposure. In contrast, monointercalators generally affect cell growth within several hours of administration. Furthermore, whereas most intercalators arrest cells in G2 phase, ditercalinium demonstrated no cell cycle phase specificity. In fact, a stathmokinetic experiment, in which vinblastine was used to prevent cell division in exponentially growing Friend leukemia cell cultures, demonstrated that ditercalinium effectively "froze" cells in position throughout the cell cycle, in a dose-dependent fashion. By determining the sensitivity of DNA in situ in fixed Friend leukemia cells to acid-induced denaturation, it was apparent that ditercalinium, rather than stabilizing DNA as do monointercalators, increased the sensitivity of DNA in situ to denaturation induced by acid. It appears, therefore, that the cytokinetic effects and interaction with chromatin of an agent that has the ability to bisintercalate into DNA are qualitatively different from those induced by classical monointercalating drugs.

Animals↗
PubMed1986

Changes in thymocyte proliferation at different stages of viral leukemogenesis in AKR mice.

Proliferation in total populations of thymocytes from control AKR mice or AKR mice injected intrathymically with MCF 69L1 virus was measured by flow cytometry of acridine orange-stained cells. Cell sorting experiments showed that the majority subpopulations of small cortical and medullary thymocytes in control mice were noncycling and were predominantly in the Go phase of the cell cycle. Of the 15 to 20% cycling thymic lymphoblasts, approximately 50% were in the G1 phase, 35% were in the S phase, and 15% were in the G2 + M phases of the cell cycle. Cycling cells appeared to consist of a major subpopulation with low RNA content and a minority subpopulation with high RNA content. In virus-injected mice, no changes in cell cycling were observed at stage I of leukemogenesis (30 to 40 days postinjection), at which time infection of thymocytes by MCF virus is maximum and constant but no clonality is evident. Thus, MCF virus infection of thymocytes per se does not appear to alter cell proliferation. Increased cell cycling and a shift in cell cycle distribution to more cells in G1 was observed at stage II of leukemogenesis (50 to 60 days postinjection), at which time a clonally expanded cell population is known to emerge in thymuses of injected mice. Acridine orange staining resolved these novel cycling cells from subpopulations of normal thymic lymphoblasts on the basis of intermediate RNA content. The transition from stage II to stage III (50 to 60 days postinjection) was accompanied by the outgrowth of a major cycling population with a distinct, often increased, RNA content. As a result, the residual "normal" background of cycling cells often observed in stage II was markedly reduced or completely absent by stage III. Populations of cycling blasts from mice with frank leukemia differed from those at stage III by a variability in mean RNA content and in cell cycle distribution indicative of individual tumor heterogeneity. In addition, thymomas often contained multiple populations of cycling blasts that could be resolved by their discrete RNA distributions. Simultaneous staining of DNA and RNA by acridine orange appears particularly well-suited for studying a heterogeneous population of cycling and noncycling cells represented by mouse thymus. This method has permitted a rapid and quantitative analysis of cell cycle parameters at progressive stages of viral leukemogenesis in AKR mice.

AKR murine leukemia virus↗
PubMed1986

A standardized assay to identify colon cancer genotypes by in vitro tetraploidy in human dermal fibroblasts.

Increased tetraploidy in dermal fibroblast cultures (IVT), which is a putative biomarker for genetic predisposition to colon cancer, was assayed by two different methods: by per cent of tetraploid metaphases in chromosome preparations from non-confluent monolayer petri dish cultures in logarithmic growth (MA); by flow cytometry (FCM) distribution of DNA content of propidium iodide stained cells from plastic flask cultures in stationary growth phase. The assayed cultures were derived from split thickness skin biopsies from two clinical groups: 11 normal individuals without a family history of colon cancer and 17 clinically affected individuals with autosomal dominant polyposis coli cancer syndrome (6 with colonic adenomatosis, i.e. familial polyposis coli (FPC) and 11 also having extracolonic lesions, i.e. the Gardner syndrome, (GS). Concordance was observed between the two assays. There was a linear relationship between the per cent of tetraploid metaphases assayed in the chromosome preparations and the per cent of cells with a DNA index (DI) of precisely 2, or of all cells with a DI greater than 1 as determined by FCM. In comparisons between the clinical groups, there was significant differences in the FCM DNA index (p values less than 0.001) of IVT- (normals and IVT- FPC) and IVT+ individuals (IVT+ GS and those FPC with IVT). The per cent of cells with a DI of 2 and greater than 1 could be used to distinguish all IVT- individuals (normals and IVT- FPC) from IVT+ FPC individuals. However, only by per cent of cells with a DI greater than 1 could all the individual GS affecteds be distinguished from IVT- individuals. Thus, the per cent of cells with a DI greater than 1 is considered to be the parameter of choice to be used in assaying IVT by flow cytometry.

Adenomatous Polyposis Coli↗
PubMed1986

Expression of murine gamma fetal antigen in adult hematopoietic tissue and during induced differentiation of Friend erythroleukemia cells.

Quantitative analysis of extracts of various normal adult CD-1 mouse tissues indicated that the serologically defined murine gamma fetal antigen (gamma-FA) was expressed at high levels in hematopoietic tissue in general and in bone marrow (BM) in particular. Metabolic labeling of isolated BM cells indicated that the BM was a site of gamma-FA synthesis in the adult animal. The size(s) of the antigen immunoprecipitated from labeled BM cells (35 and 27 kilodaltons) with anti-gamma-FA serum correlated well with molecular weight estimates of fibrosarcoma-fetal mouse-associated gamma-FA, as determined by molecular sieve chromatography. For ascertainment of the relationship between hematopoietic cell differentiation and gamma-FA content, a multiparameter flow cytometric approach was used to evaluate gamma-FA levels in Friend erythroleukemia (FL) cells as a function of growth state (blast or dimethyl sulfoxide-differentiated) and cell-cycle compartment. Differentiated G1-arrested FL cells (G1D) possessed significantly lower gamma-FA-associated immunofluorescence as compared to control cells in the G0-G1 substate. Remaining S- and G2 + M-phase cells in differentiated populations demonstrated an even greater reduction in gamma-FA content relative to control cells in the corresponding cell-cycle phases. The available data support the tentative classification of gamma-FA as a murine differentiation antigen.

Actins↗
PubMed1985

Denaturation and condensation of DNA in situ induced by acridine orange in relation to chromatin changes during growth and differentiation of Friend erythroleukemia cells.

DNA in situ is progressively denatured when the cells or nuclei are treated with increasing concentration of acridine orange (AO). This transition can be monitored by flow cytometry as a decrease in green fluorescence. The complexes of denatured DNA and AO undergo immediate condensation and aggregation; this step is manifested by appearance of red luminescence and formation of precipitates that can be detected by electron microscopy. The precipitates form preferentially in heterochromatin as well as in ribosomes and polysomes. Their formation and further aggregation affects cellular light scatter properties in both the forward and right-angle direction. The AO-induced DNA denaturation and condensation was studied in nuclei of Friend erythroleukemia cells from exponentially growing, differentiated or quiescent cells. The DNA in nuclei of quiescent cells, from plateau-phase cultures, was the most sensitive to denaturation; it denatured (measured by changes in luminescence) at an AO concentration between 50 and 80 microM with the midpoint of the transition (Cd) at 70 microM. DNA in nuclei of differentiated cells (dimethyl-sulfoxide-induced erythroid differentiation) was more resistant (Cd = 77-83 microM), whereas DNA in exponentially growing cells was the most resistant (Cd = 86 microM). Extraction of proteins with 0.1 M HCl at 0 degree C abolished the differences between the cells and shifted the transition to a lower AO concentration (Cd = 46 microM). For comparison, the midpoint transitions representing condensation of free, nucleic acids measured as light scatter changes occurred at 13, 22, 31 and 53 microM of AO, for rRNA, tRNA, and denatured and native-calf thymus DNA, respectively. Denaturation and condensation of DNA, which can be induced by AO either in isolated nuclei or viable permeabilized or fixed cells provides a new approach to discriminate cell subpopulations with different chromatin structure by flow cytometry. The molecular mechanisms of this phenomenon are discussed.

Acridine Orange↗
PubMed1985

Effect of N-(4-hydroxyphenyl)retinamide on murine mammary tumor cells in culture.

The effects of N-(4-hydroxyphenyl)retinamide (HPR), a synthetic analogue of vitamin A, on cell morphology, cell cycle kinetics, cytoplasmic matrix, and expression of murine mammary tumor virus (MuMTV) in MuMTV-infected murine mammary tumor cells (GR-3A) were determined. Cellular uptake of HPR was rapid and linear, with zero-order kinetics, during the first 30 minutes of incubation. Flow cytometric analysis of cells treated with nontoxic levels of HPR (10 microM) for 48 hours revealed a reduction in percent cells in the DNA synthetic (S) phase of the cell cycle with a concomitant increase in percent cells in the G1 phase of the cell cycle. Dexamethasone-stimulated MuMTV expression was not affected after 48 hours of HPR exposure, whereas the virus expression was significantly reduced in cells treated with HPR for seven days. The reduction in MuMTV expression was preceded by changes in cell morphology (decreased cell-cell contact and reduced cell flattening) and altered F-actin aggregation. Continuous exposure to HPR (10 microM) for 14 days resulted in reduced cell proliferation rates and decreased cell plating efficiency of GR-3A cells. Taken together, these results indicate that HPR is rapidly incorporated into GR-3A cells and that the effects of HPR on cell profileration, cytoskeletal organization, and cell morphology appear to precede the effects of this retinoid on the expression of the etiological agent of murine mammary tumorigenesis, MuMTV.

Actin Cytoskeleton↗
PubMed1985

Kinetic analysis of drug-induced G2 block in vitro.

The data on cell-cycle effects of two prospective antitumour agents, (+)-1,2,-bis(3,5-dioxopiperazine-1-yl)propane (soluble ICRF; NSC 169780) and 1,4-bis(2'chloroethyl)-1,4-diazabicyclo [2.2.1] heptane diperchlorate (CBH; NSC 57198) were used to determine whether a modified stathmokinetic experiment could predict the effects of continuous, long-term (0-48 hr) drug exposure in an in vitro L1210 murine leukaemia cell system. Generally, continuous drug exposure of exponentially growing cells does not provide sufficient quantitative information concerning cell-cycle-phase-specific mechanisms of drug action. Alternatively, stathmokinetic experiments, which are usually limited to some fraction of one cell doubling time, provide little information about long-term drug effects. By using mathematical models constructed for this purpose, however, stathmokinetic data can predict the overall proportion of cells affected by a drug though failing to discern between various kinds of drug action (e.g. reversible v. irreversible block, blocking v. killing action, etc.), especially when it occurs in G2 phase. In addition, it can be shown that for at least one of the drugs (soluble ICRF) the stathmokinetic experiment fails to predict 'after-effects' of drug treatment which extend into the following cell cycle(s). It also becomes clear that the degradation of exponential growth characteristics of quickly dividing cells during long-term, continuous drug exposure makes prediction of cell-cycle kinetic perturbations uncertain when derived from short-duration stathmokinetic experiments. However, with care, the joint application of 'short term' (e.g. stathmokinesis) and 'long term' (e.g. continuous exposure) techniques allow adequate quantitative insight into drug-perturbed cell-cycle kinetics. The applicability of modelling techniques is discussed: in the present instance it is limited to lower drug concentrations. For higher drug concentrations, effects like increased ploidy, ineffective division, etc., make it impossible in the present study to obtain a clear picture of the kinetics.

Animals↗
PubMed1985

Effects of new N-alkyl analogues of adriamycin on in vitro survival and cell cycle progression of L1210 cells.

The effects of N-benzyladriamycin-14-valerate (AD198) and N,N-dimethyladriamycin-14-valerate (AD199), two novel lipophilic N-alkyl derivatives of Adriamycin (ADR), on cell growth and cell cycle distribution were investigated in L1210 cells grown in suspension. Following a 1-h exposure to the drug levels selected, growth inhibition was noticeable in all cultures for most or all of the observation period of 96 h. With flow cytometry, an asynchronous cell population was measured with respect to cellular DNA, RNA, and light scatter (size) properties following a 1-h incubation with the various ADR analogues. In addition, flow cytometric techniques were utilized to determine whether drug treatment altered the sensitivity of DNA in situ to acid-induced denaturation or to binding by small DNA-intercalating dyes. Unlike the parent compound ADR or its DNA-nonbinding derivative N-trifluoroacetyladriamycin-14-O-hemiadipate (AD143), the N-alkyl derivatives AD198 and AD199 only slightly affected L1210 cell cycle traverse over the first 5 h posttreatment. However, by 24 h, AD199 (0.62 micrograms/ml) caused an S- and G2 + M-phase accumulation which became more dramatic at 48 and 72 h. AD198 (3.27 micrograms/ml) also caused an accumulation of cells predominantly in G2 + M phase at longer culture times (48 to 96 h). The two half-substituted congeners N-benzyladriamycin (AD288) and N,N-dimethyladriamycin (AD280) affected L1210 cell cycle traverse over a similar time scale at concentrations of 12.3 and 4.17 micrograms/ml, respectively. AD280 blocked cells in G1 and G2 + M whereas AD288 caused predominantly a G2 + M accumulation. While neither ADR nor AD143 interfered appreciably with binding and fluorescence of the intercalating dye acridine orange, all of the N-alkyl analogues tested reduced the fluorescence signal of acridine orange-stained L1210 cells by 26 to 60%. This effect lasted, with decreasing intensity, for at least 48 h following a 1-h exposure to the drugs. In addition, while ADR appeared to stabilize DNA in situ against acid-induced denaturation, all N-alkyl derivatives, to varying degrees, tended to increase DNA denaturability. Thus alkylation at the glycoside amine combined with the lipophilic 14-valerate side chain function accounts for several new biochemical and biological properties of AD198 and AD199, relative to ADR.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Analysis of a cell cycle model based on unequal division of metabolic constituents to daughter cells during cytokinesis.

We demonstrate that the unequal division of RNA during cytokinesis explains the dispersion of cell generation times in CHO cell cultures. Experimental cytometric results reported previously serve as a basis for a probabilistic model of cytokinesis. Unequal RNA division to daughter cells, together with two simple laws of RNA production, are used as a source of randomness within the cell cycle. The model reproduces the experimental growth of the CHO cell population, including the observed variability in RNA content. The model has stabilizing properties which explain why a cell population with increased RNA content characteristics, a few cell cycles, to the original pattern. Other cell cycle characteristics, like sister-to-sister and mother-to-daughter generation time correlations implied by the model, are close to their experimental analogs. The conceptual basis of the model is general enough to include unequal division of factors other than RNA (cell mass, cell proteins, etc.) as sources of generation time variability. It seems that the observed dispersion of cell generation times, explained previously in the terms of random transitions in some part of the cell cycle (the Smith & Martin A and B state hypothesis), can be reduced to the single random event of unequal division. This supplies a new convenient tool in the investigation of cell cycle kinetics.

Animals↗