bluuebunny/crossref_metadata_2025_split huggingface dataset:
RADIOTOXICITY OF INCORPORATED [3H]THYMIDINE AS STUDIED BY AUTORADIOGRAPHY AND FLOW CYTOMETRY CONSEQUENCES FOR THE INTERPRETATION OF FLM DATA
Authors: Beck H.‐P. 
Published: May 2008

ABSTRACTThe radiotoxic effects of incorporated [3H]thymidine on proliferation kinetics of flash‐labelled (30 min, 0.3 μCi/ml, 40 Ci/mM) L‐929 cells in vitro were studied by means of autoradiography and flow cytometry. the flow cytometric results obtained by applying the BUdR‐33258 Hoechst technique, using new evaluation procedures, showed that the labelled cells are delayed in their progression through the S and G2+ M phases, leading to mitotic delay. From autoradiographs, the fraction of labelled mitoses was determined and, in addition, the ratio of labelled and of unlabelled mitotic cells to all cells. the radiotoxic effects are not evident from the FLM curve, even if the ratio of labelled mitotic cells to all cells shows a highly distorted shape. A mathematical model has been developed that describes the perturbed cell kinetics due to radiotoxic effects of the incorporated [3H]thymidine. These findings have considerable consequences for the interpretation of autoradiograhic data, especially of labelled mitoses curves.
Cell Cycle Kinetics of Chinese Hamster (Cho) Cells Treated With the Iron‐Chelating Agent Picolinic Acid
Authors: Gurley L. R. , Jett J. H. 
Published: May 2008

ABSTRACTSpontaneously transformed (tumorigenic) Chinese hamster cells (line CHO) do not exhibit picolinic acid‐sensitive G1 and G2 cell cycle arrest points observed in normal and virus‐transformed cells. Rather, picolinic acid arrests CHO cells in S phase only and produces culture growth behaviour similar to that produced by hydroxyurea. Prolonged treatment with picolinic acid permits a slow but significant traverse of cells through S phase. Thus, like hydroxyurea, picolinic acid is not a useful agent for synchronizing exponential CHO cells, but it can be used to resynchronize cultures in early S phase if a previous synchronization procedure (such as isoleucine deprivation) is used. the iron chelating properties of picolinic acid, and the similarities of its effects on cultured cells to those of hydroxyurea and the iron‐chelating drug desferrioxamine, suggest that picolinic acid inhibits DNA synthesis by interfering with the iron‐dependent production of a stable free organic radical which is essential for the ribonucleotide reductase formation of deoxyribonucleotides.
INACCURACY OF ESTIMATIONS OF S PHASE FRACTION BY REDUCTION IN CLONING EFFICIENCY WITH HYDROXYUREA OR TRITIATED THYMIDINE
Authors: Yen A. , Lambek Caryl , Clarkson B. 
Published: May 2008

ABSTRACTThe current hypothesis, that the fractional reduction of cloning efficiency in semi‐solid culture systems induced by pretreatment of the cells with hydroxyurea (HU) or [3H]TdR equals the fraction of cells initially in S phase, is tested. A lymphoblastoid cell line, SK‐L7, with known cell cycle kinetics was exposed to cytotoxic concentrations of HU or suicidal doses of [3H]TdR and then initiated in semi‐solid and liquid culture. Although approximately 0.6 of the initial population was in S, 1‐hr exposures of HU at concentrations of up to 10‐2 M failed to reduce subsequent cloning efficiency. the 1‐hr exposure to HU did not reduce either the immediate cell number or the gross population doubling rate over 24 hr. A 24‐hr exposure to 10‐3 M HU reduced the cloning efficiency by approximately 98%, confirming the drug's cytotoxic capability. [3H]TdR at doses of 100 μCi/ml for 20–40 min reduced the cloning efficiency by approximately 60 and 70%, respectively. Although no cytotoxicity immediately after exposure was observed in either case, gross population doubling rate in liquid culture was reduced. While HU failed to reduce subsequent cloning efficiency, [3H]TdR reduced cloning efficiency by approximately the fraction of initial cells in S. the above hypothesis, therefore, cannot be applied naïvely as a technique for quantitating the fraction of a clonogenic cell population in S phase.
CYTOKINETICS OF TUMOUR AND ENDOTHELIAL CELLS AND VASCULARIZATION OF LUNG METASTASES IN C3H/HE MICE
Authors: Gunduz Nurten 
Published: May 2008

ABSTRACTA model of lung metastases was developed using intravenous injection of tumour cell aggregates of spontaneous C3H/He mammary tumours in syngeneic mice. the growth rate of lung tumours decreased with increasing tumour volume, with mean host survival of 46 days. the cytokinetics of individual tumours ranging between 0.004 and 4.2 mm3 in volume were studied. the labelling index (LI) ranged between 12 and 17%, the DNA synthesis time (Ts) being 9–10 hr. the growth fraction (GF) ranged between 26 and 38%. the cell cycle time (Tc) was found to be 18–19 hr. the LI and the GF decreased with increasing tumour volume doubling time (Td). No correlation was found between the tumour volume and Tc. the LI of endothelial cells within these tumours, ranging between 0.004 and 4.2 mm3 in volume was 14–15% and endothelial cell proliferation was not affected by tumour growth.Vascular parameters were also determined for these tumours as a function of tumour volume. Vascular volume increased with increasing tumour size while the percentage of capillary vessels decreased. the cellular volume to capillary volume ratio increased with increasing tumour volume. Necrosis was observed in 0.27 mm3 tumours and increased with increasing tumour size.The results from these studies suggested that the age‐dependent decrease in proliferative activity of tumour cells growing in the lung is related to change in effective vascularity.
DETERMINATION OF STEADY STATE GENERATION TIME DISTRIBUTIONS FROM LABELLED MITOSIS EXPERIMENTAL DATA
Authors: Palsson B. , Himmelstein K. J. 
Published: May 2008

ABSTRACTThe proper application of detailed deterministic cell kinetic models depends on the way in which cells are assigned their generation times. A method is presented for the determination of population generation time distributions from labelled mitoses experiments. the model assumes that the generation time of each new cell is a function of both the steady‐state generation time distribution function of the population, and also the generation time frequency‐function of the previous generation of cells. This approach is applied to two different cell types to successfully simulate extended labelled mitoses curves using a population balance model with constant maturation rates.
A Mathematical Model For Analysing Cellular Age‐Response Functions In Terms of Physiological Age
Authors: Valleron A.‐J. , Rockwell Sara 
Published: May 2008

ABSTRACTA mathematical model is presented which facilitates the analysis of cellular age‐response functions in terms of the physiological ages of the cells. Age‐response functions are generally determined by obtaining synchronous cohorts of cells and measuring the sensitivity of the cohorts to the treatment agent at different times after selection (i.e., at several different chronological ages). the model described here uses data on the [3H]TdR labelling patterns of the cell population to determine the distribution of physiological ages for the cohorts at the times of treatment. the age‐response function data are then analysed in terms of the physiological ages of the cells. the compartments used in the analysis may be chosen according to the biology of the system and the wishes of the experimenters and not imposed by the variability of the phase durations. the application of the model is illustrated using the age‐response functions for EMT6 cells exposed to radiation and HeLa cells exposed to hydroxyurea.
Clonal Variation In Proliferation Rate of Cultures of Gpk Cells
Authors: Riley P. A. , Hola M. 
Published: May 2008

ABSTRACTPedigrees of twenty‐six clones of a line of keratocytes derived from guinea‐pig ear epidermis (GPK cells) were analysed from time‐lapse film. the mean interdivision time (IDT) for the culture was 1143 φ 215 (SD) min. the mean generation rates (mean reciprocal interdivision times) of clones varied over a range of 3.93–10.2 × 10‐4/min and the standard deviation of the clonal mean generation rates was 16.8% of the average value. Transient intraclonal variations in IDT due to mitoses in a plane perpendicular to the substratum were observed. the data were also analysed on the basis of cell location in sixteen equal zones (quadrats) of the filmed area. the mean generation rate of quadrats was 8.73 x 10‐4/min (SD = 4.9%). the spatial distribution showed some clustering of cells. the mean local density of the clones (2.25 φ 0.62 cells/10‐4 cm2) was significantly higher than the quadrat density (1.76 φ 0.8 cells/10‐4 cm2). There was no significant correlation between clonal density and mean generation rates, whereas for quadrats a significant negative correlation was found (P= 2.7%). the results support the proposition that cell lineage is the major determinant of the proliferation rate of subconfluent cultures.
Laser Flow Cytofluorometric Analysis of Htc Cells Synchronized With Hydroxyurea, Nocodazole and Aphidicolin
Authors: Miller‐Faurès A. , Michel N. , Aguilera A. , Blave A. , Miller A. O. A. 
Published: May 2008

ABSTRACTThe technique of laser flow cytofluorometry has been used to monitor the arrival in G1 and the subsequent progression through the cell cycle of HTC cells accumulated in metaphase with colcemid alone or after treatment with hydroxyurea and Nocodazole. Under the experimental conditions used in this study, the latter procedure gives much better results, avoiding in particular the extensive formation of micronucleated cells. Aphidicolin, an inhibitor of DNA polymerase, in combination with Nocodazole, provides a useful method to tightly synchronize these cells at the G1/S border.
Bone Marrow Response to Damage Induced By Hydroxyurea Or Colchicine
Authors: Nečas E. 
Published: May 2008

ABSTRACTThe extent of bone marrow damage caused by the administration of single or repeated doses of either hydroxyurea (1000 mg/kg b.w.) or colchicine (1 mg/kg b.w.) are comparable. This conclusion is based on serial studies of bone marrow cellularity and of the CFUc numbers in the bone marrow. the proliferation response of the pluripotential haemopoietic stem cells, determined by the cells forming colonies in the spleen of lethally irradiated mice (CFUs) markedly differs if the bone marrow damage is caused by hydroxyurea or colchicine. While hydroxyurea administration stimulates a large proportion of the resting G0 cells into the cell cycle, the damage induced by colchicine is followed by only a mild increase in the CFUs proliferation rate.The seeding efficiency of the spleen colony technique has been determined after both hydroxyurea and colchicine administration. This parameter, important for the estimation of the number of the pluripotential haemopoietic stem cells in blood forming organs, is significantly affected by hydroxyurea administration, but also by repeated injections of colchicine. Following a single dose of hydroxyurea, the time‐course of the CFUs numbers, which were corrected for the change in the seeding efficiency, shows an overshoot occurring after 18–20 hr. At the other time periods, the number of pluripotential haemopoietic stem cells is little affected by a single hydroxyurea injection. This poses a question about the nature of the stimulus, which after hydroxyurea administration triggers the CFUs from the resting G0 state into the cell cycle. There is evidence that this stimulus is probably not represented by the damage caused to the various intensively proliferating cell populations of the bone marrow. This evidence is based on experiments which show that colchicine induced damage, of a degree similar to that after hydroxyurea, does not stimulate the CFUs proliferation rate to an extent comparable to hydroxyurea.The possibility that colchicine could block CFUs in the G0 state or that it could interfere with the progress of CFUs through the G1 and S phases of the cell cycle have been ruled out by experiments which demonstrated that colchicine (1 mg/kg b.w.), administered 10 min before hydroxyurea, does not reduce the number of CFUs triggered into the cell cycle as the consequence of hydroxyurea administration.
Proliferation In Liquid Culture of Myeloid Progenitor Cells From the Blood of Normals and Patients With Aplastic Anaemia
Authors: Fitchen J. H. , Deregnaucourt Josette , Cline M. J. 
Published: May 2008

ABSTRACTWe studied myeloid progenitor cells (CFUc) from peripheral blood mononuclear leukocytes (MNL) of normals and patients with severe aplastic anaemia (AA). Baseline CFUc averaged 4.4 φ 1.5 (range 0–17)/106 MNL in fifteen normals and 0 φ 0/106 MNL in six patients with severe AA (P > 0.05). to assess CFUc proliferative capacity, 107 MNL were put into liquid culture in Marbrook chambers with colony‐stimulating activity and sub‐cultured in agar at intervals up to 10 days. CFUc from normal MNL increased from 44 φ 15/chamber at Day 0 to 156 φ 33/chamber at peak value (P > 0.02). In contrast, CFUc from AA MNL remained undetectable throughout the period of liquid culture (AA peak v. normal peak; P > 0.001). These results indicate a marked decrease in circulating CFUc in patients with severe AA, and a profound abnormality in CFUc proliferation in vitro. This abnormality could be due to defective replication of CFUc, a lack of feed‐in from more primitive precursors, or both.
EFFECT OF TRITIATED THYMIDINE ON THE KINETICS AND VIABILITY OF 9L CELLS IN VITRO
Authors: Wiezsaecker M. , Hoshino T. , Kobayashi S. 
Published: May 2008

ABSTRACTThe colony‐forming efficiency of 9L rat gliosarcoma cells was unaffected by treatment with 0.1 μCi/ml of [3H]TdR. However, when cells were treated with 1 or 10 μCi/ml of [3H]Tdr, cell growth was reduced and cell survival decreased.When monolayer 9L cells were treated with 1 μCi/ml of [3H]TdR for up to 72 hr, approximately 5% survived, which is closely related to the percentage of non‐cycling cells in this system. When cells were treated with 10 μCi/ml of [3H]TdR for 72 hr, less survival was observed. the additional cell kill observed may be induced by [3H]TdR released from doomed cells into petri dishes during the incubation period of the colony‐formation assay.
Mitotic Rate of Rat Thyroid Follicular Cells In Vivo In Response to A Single Injection of Thyrotropin (Tsh)
Authors: Redmond Olga , Tuffery A. R. 
Published: May 2008

ABSTRACTThe mitotic rate of thyroid follicular cells was assessed by a stathmokinetic method at intervals from 15 min to 24 hr after a single injection of 1 iu/kg of thyrotropin (TSH). the mitotic rate was increased 15 min after TSH and remained elevated for 3 hr. Two further peaks of mitotic activity were present at 9 hr and 24 hr after TSH. Serum TSH concentrations were increased from 5 min to 3 hr with a maximum at 1 hr.
Evidence for discrete cell kinetic subpopulations in mouse epidermis based on mathematical analysis
Authors: Potten C. S. , Wichmann H. E. , Loeffler M. , Dobek K. , Major D. 
Published: May 2008

Abstract. Continuous (repeated) labelling studies in mouse epidermis indicate that nearly all cells are labelled after about 100 hr. Percentage labelled mitoses studies ([3H]TdR at 15.00 and 03.00 hours) have a first peak that does not reach 100% and has a half‐width of about 10 hr. Small second and third peaks can be detected at about 90 and 180 hr, respectively. The changes with time in the number of labelled cells show a difference dependent on the time of day of [3H]TdR administration. Both curves show an early doubling in labelled cells which then decline, forming a peak of labelled cells. A second peak occurs at about 120 hr. This is followed by a progressive decline with no further peaks until values of about 1% labelling are obtained at 340 hr.These experiments have been investigated mathematically. A computer programme has been devized that permits all three types of experiments to be analysed simultaneously. More importantly, it can analyse situations with a heterogeneity in cell cycle parameters in all proliferative subpopulations.Various models for epidermal cell replacement have been considered. The data as a whole can best be explained if the basal layer contains at least two distinct subpopulations of cells and an exponentially decaying post‐mitotic population with a half‐life of about 30 hr. The proliferative sub‐populations must be characterized by near integer differences in the length of cycle, the precursor (stem) compartment having the longer cycle. An inverse relationship is required for the length of S, i.e. the shortest time for the stem cells.A full range of cell kinetic parameters can be calculated and are tabulated for the most appropriate model system which is one involving three transit proliferating subpopulations.
[3H]thymidine labels less than half of the DNA‐synthesizing cells in the mouse tumour, carcinoma NT
Authors: Hamilton E. , Dobbin J. 
Published: May 2008

Abstract. We have studied carcinoma NT, a transplantable mouse adenocarcinoma of spontaneous origin. Cells labelled with [3H]thymidine ([3H]TdR) were restricted to a narrow zone around the periphery of this tumour and were also found in rings up to 50 μm wide, around isolated blood vessels in the central necrotic area. Labelling with [3H]deoxyuridine ([3H]UdR), another DNA synthesis precursor, produced a very different pattern. The labelled zone around the periphery was much wider than with [3H]TdR, and [3H]UdR labelled cells were found up to 110 μm from isolated vessels. [3H]iododeoxyuridine ([3H]IUdR) gave the same pattern of labelling as [3H]UdR. In the heavily labelled zone, within 1 mm of the tumour periphery, the labelling index (LI) was 51% after [3H]UdR or [3H]IUdR injection, and only 36% with [3H]TdR.The data show that at least half of the DNA‐synthesizing cells in this tumour did not incorporate [3H]TdR. Previous workers reported cell loss factors for carcinoma NT of 60% calculated from [3H]TdR labelling data and 30% from the rate of loss of [125I]UdR. The present work suggests that calculations based on [125I]UdR data are more likely to be accurate for carcinoma NT than those using [3H]TdR data.
The effect of environmental stress stimuli on cell division in rat palatal epithelium
Authors: Fisker A. V. , østergaard E. , Karring T. 
Published: May 2008

Abstract. The effect on cell proliferation of procedures commonly used in studies in laboratory animals was examined in the palatal epithelium of rats. Groups of rats were exposed to ether anaesthesia, immobilization in the supine position or to cage change. Animals left undisturbed in the cages during the experiment were used as controls. At intervals of 30 min, four animals of each group were killed and histological sections of the palatal mucosa were prepared. The number of prophases, metaphases and ana/telophases in the epithelium was counted and related to 1 mm2 of the surface. Thirty minutes after the various procedures the number of metaphases and ana/telophases were extremely low. After a further 30 min a high number of prophases was observed. The number of metaphases rose within the following 30 min, during which time the number of ana/telophases also reached a maximum.These observations indicate that the environmental stimuli have blocked the entrance of cells into mitosis and have resulted in an accumulation of cells, which, following the raising of the blockade, pass through the various stages of the mitotic phase. In studies of cell population kinetics the blockade of cell division as a result of environmental stress stimuli may lead to misleading results.
Effects of retinoic acid on cell proliferation and cell differentiation in a rat tracheal epithelial cell line
Authors: Klann R. C. , Marchok Ann C. 
Published: May 2008

Abstract. The effects of 3.3 times 10‐7 M to 3.3 times 10‐5 M all‐trans‐retinoic acid (vitamin‐A acid) on the total cell population dynamics of 165 S, a keratinizing epithelial cell line from carcinogen‐exposed rat trachea, were studied. During the first 6 days of culture, cells accumulated on the dish in the presence of the vitamin to twice the density of controls. [3H]thymidine incorporation into DNA and percentage of [3H]thymidine‐labelled cells in autoradiographs were stimulated in a dose‐dependent fashion to a maximum of 25‐ and 34‐fold, respectively. Exfoliation of cells from the cultures was also enhanced 2–3‐fold, resulting in nearly twice the total number of cells (attached plus exfoliated) in the presence of the vitamin.During 19 days of culture, retinoic acid maintained a higher level of [3H]thymidine incorporation and cell exfoliation in 165 S cells so that by day 19, total cell production was more than three times that seen in controls. At this time, vitamin‐treated cultures showed a reduced cell saturation density compared to controls. The higher final cell density in the control cultures was a result of multilayering and papillary formation which did not occur in the presence of retinoic acid. The papillae in control cultures stained specifically with Rhodamine B or with the eosin and orange G components of the Papanicolaou method. A count of the number of eosin and orange G positive cells in the attached and exfoliated cell compartments showed an 8‐fold reduction of keratinization in retinoic acid‐exposed cultures. Our results show that retinoic acid is a growth stimulant in these cell cultures, causing increased cell proliferation and exfoliation accompanied by inhibition of keratinization.
Characteristics of the Cfu‐S Population In Mice Carrying the SlJ Allele
Authors: Ploemacher R. E. , Brons N. H. C. 
Published: May 2008

Abstract Abstract. A tentative characterization of haemopoietic stem cells with respect to their organ distribution, seeding fraction and colony formation in the spleen, radiosen‐sitivity and humoral regulation was attempted in mice heterozygous for the mutant allele SlJ and in their normal littermates. SlJ/+ mice were characterized by a deficient CFU‐s content of the blood and spleen and had slightly lower femoral CFU‐s numbers. This CFU‐s distribution could not be explained by differences in seeding efficiency ‘f’ between CFU‐s of SlJ/+ and +/+ origin in lethally irradiated recipients used in the CFU‐s assay. the seeding fraction of CFU‐s of +/+ origin did not differ in +/+ and SlJ/+ recipients. However, in irradiated SIJ/+ recipient mice a 30% decrease was observed in the number of the colonies derived from splenic and femoral CFU‐s of both +/+ and SlJ/+ origin. the serum level of SHSF (splenic haemopoiesis stimulating factor) was decreased in SlJ/+ mice, but significantly increased in Sl/Sld mice, as compared to their respective normal +/+ littermates. Endogenous colony formation in SlJ/+ spleens was deficient in comparison to that observed in +/+ spleens, and distinct sex differences were observed. However, mutant and normal CFU‐s from spleen and bone marrow had a similar survival following in‐vitro y irradiation.Femurs and spleens of both SlJ/+ and +/+ origin were implanted into both SlJ/+ and +/+ hosts. Six weeks later the SlJ/+ grafts contained less CFU‐s than the +/+ grafts.These data show that the splenic stroma of SlJ/+ mice is not defective in its capacity to lodge injected CFU‐s but is deficient in its ability to maintain CFU‐s under ‘steady‐state’ conditions and stimulate their colony formation in a ‘perturbed state’. Some of the characteristics of SlJ/+ mice segregate them from Sl/Sld mice, i.e. a deficient splenic CFU‐s content, normal seeding fractions ‘f’ of CFU‐s from spleen and bone marrow in the presence of an almost compensated anemia, and decreased serum levels of SHSF. the study of the SlJ trait may be a useful extension of the current Sl/Sld model for exploration of hereditary defects in haematopoietic stroma.