bluuebunny/crossref_metadata_2025_split huggingface dataset:
CELL‐CYCLE ANALYSIS OF PERTURBED CELL POPULATIONS: COMPUTER SIMULATION OF SEQUENTIAL DNA DISTRIBUTIONS
Authors: Gray Joe W. 
Published: May 2008

AbstractA mathematical model is presented that permits simulation of a time sequence of DNA distributions with a single set of cell‐cycle parameters. The method is particularly suited to the quantitative analysis of sets of sequential DNA distributions from perturbed cell populations. The model permits determination of the durations and associated dispersions of the phases of the cell cycle as well as the point in the cell cycle at which the perturbing agent exerts its effect. The mathematical details of the simulation technique are presented, and the technique is applied to the analysis of DNA distributions from perturbed cell populations. Three cell populations are modeled: CHO‐line cells released from a block at the interface of the G1 and S‐phases, 3T3 cells released from a G1‐phase block produced by serum starvation, and S49 mouse lymphoma cells responding to a block in the G1‐phase produced by N6,02′‐dibutyryl adenosine 3′:5′‐cyclic monophosphate (Bt2cAMP).
PERTURBED CELL PROLIFERATION KINETICS OF THE EMT6/M/AC TUMOUR IN MICE TREATED WITH ANTI‐MOUSE LYMPHOCYTE SERUM
Authors: Watson James V. 
Published: May 2008

AbstractThe cell proliferation kinetics of the EMT6/M/AC tumour were determined at two volumes, 6‐3 mm3 and 180 mm3, in mice treated with anti‐mouse lymphocyte serum, AMLS. Comparison of the growth curve with that obtained in non‐AMLS treated animals showed a marked increase in the growth rate at all volumes in the treated group. In contrast, the cell cycle time and the intermitotic phase times were not significantly different in the treated and untreated groups at comparable volumes. The increase in the growth rate in AMLS treated mice was obtained in spite of decreases in both the rate constant for cell production and the growth fraction, and was due to a marked decrease in the rate constant for cell loss.
THE PROLIFERATIVE STATUS OF INTESTINAL EPITHELIAL CLONOGENIC CELLS: SENSITIVITY TO S PHASE SPECIFIC CYTOTOXI CAGENTS
Authors: Boarder T. A. , Blackett N. M. 
Published: May 2008

AbstractHigh concentrations of tritiated thymidine and cytosine arabinoside (Ara‐C) have been used to selectively kill cells in the crypts of Lieberkuhn that are synthesizing DNA. The effect of these agents on the number of regenerating microcolonies seen 3‐J days after a range of radiation doses indicates that a majority of the clono‐genic cells are proliferating rapidly and that the slowly proliferating cells at the base of the crypt do not represent the whole clonogenic population.
RAPID CELL CYCLE ANALYSIS BY MEASUREMENT OF THE RADIOACTIVITY PER CELL IN A NARROW WINDOW IN S PHASE (RCSi)
Authors: Gray J. W. , Carver June H. , George Yolanda S. , Mendelsohn M. L. 
Published: May 2008

ABSTRACTA new rapid method for the cell cycle analysis of asynchronously growing cells is presented. The new method is an alternative to the more time consuming and subjective fraction of labeled mitoses (FLM) method. Like the FLM method, all cells in the S phase of the cell cycle are marked by pulse labeling with a radioactive DNA precursor. The subsequent progress of the cohort of cells thus labeled is monitored through a narrow window in the cell cycle. The window is defined by a narrow range of DNA contents corresponding to cells in mid‐S phase and is designated Si. The cellular DNA content is measured by flow cytometry and the cells in the window Si are selected by electronic cell sorting. The radioactivity per cell in Si (RCSi) is determined by liquid scintillation counting. The duration of S phase and of the total cycle and the dispersions therein are determined from the oscillation of the RCSi values with time. The complete cell cycle analysis can be accomplished in as little as 1 day following the collection of samples.Exponentially growing Chinese hamster ovary (CHO) cells were analyzed according to the RCSi method and the FLM method. It is demonstrated that the two techniques give essentially the same results.
THE KINETICS OF CONTACT INHIBITION IN MAMMALIAN CELLS
Authors: Schmialek P. , Geyer Astrid , Miosga Verena , Nündel M. , Zapf B. 
Published: May 2008

ABSTRACTTo elucidate the process of contact inhibition in mammalian cells, we investigated the kinetics of growth arrest in [3H]thymidine labelled embryonic chinese hamster (Cricetulus griseus L.) cells after the addition of various concentrations of unlabelled cells. It was observed that after the contact inhibition concentration had been reached, the cells grew undisturbed for one more generation. In the following 24 hr the concentration fell back to the level at the beginning of the experiment and stayed there.
SPECIFIC INHIBITION OF CELL PROLIFERATION IN THE MOUSE INTESTINE BY AN AQUEOUS EXTRACT OF RABBIT SMALL INTESTINE
Authors: Sassier P. , Bergeron M. 
Published: May 2008

ABSTRACTAn aqueous extract was prepared from the mucosa of rabbit small intestine by homogenization and centrifugation at 105,000 g. After precipitation with ammonium sulfate, the 0–50 fraction (F1) and the supernatant (F2) were collected, dialysed against a phosphate buffer and tested on rats in vitro and mice in vivo.The F1 fraction was found to inhibit thymidine incorporation into rat intestinal DNA in vitro, but this effect was not found to be tissue specific (liver, kidney).Two hours after a single injection of F1 (10 mg protein content), the uptake of tritiated thymidine was decreased in jejunal and colonic DNA in mice. This effect was maximal between 2 and 4 hr and totally reversible after 7 hr; this effect was found in neither the kidney nor the testis. A slowing of cellular migration was also noticed in the jejunum and the colon.Conversely, the F2 fraction did not inhibit the synthesis of jejunal and colonic DNA either in vitro or in vivo.Our results suggest that the F1 fraction of the aqueous extract of rabbit small intestine contains one or more substances which may act either on intestinal DNA synthesis or on the G1–S transition of the cellular cycle in the mouse intestine. This reversible and specific intestinal action appears to inhibit cell proliferation and presents several of the characteristics defining a chalone.
PLANNING THE SUICIDE EXPERIMENTS
Authors: Hazout S. , Valleron A.‐J. 
Published: May 2008

ABSTRACTSuicide experiments involve a great degree of uncertainty in the counting of cell colonies. This work studies from a statistical point of view the precision of the estimation as a function of the number of experimental units which are used. Assuming that the colony numbers in recipients follow a Poisson distribution, we give the necessary number of recipients (a) to determine with a given accuracy the percentage of DNA synthesizing cells (S cells), (b) to test whether or not a cell population is quiescent, and (c) to compare the percentages of S cells in two cell populations.
CELL LOSS FROM SEVERAL TYPES OF SOLID MURTNE TUMOUR: COMPARISON OF 125I‐IODODEOXYURIDINE AND TRITIATED THYMIDINE METHODS
Authors: Begg A. C. 
Published: May 2008

ABSTRACTThe method of measuring tumour cell loss rates in situ following radioactivity loss after a single injection of 125I‐iododeoxyurudine (125I‐UdR) was tested for its accuracy in five different types of murine tumour. To achieve this the method was compared with two others: (1) using 125I‐UdR, but excising tumours before the radioactivity determinations, with or without extracting DNA; (2) using tritiated thymidine and autoradiography. A third method was used on three of the tumours, in which 125I‐UdR‐labelled tumours were grown in unlabelled hosts, followed by whole body counting of the tumour‐bearing mice.In two of the tumours an increase was observed in total tumour radioactivity with time after 125I‐UdR injection. This prevented the estimation of cell loss parameters in these tumours. Approximately half the increase was due to reutilization of 125I‐UdR supplied from tissues within the mouse; approximately a third to an influx of labelled inflammatory cells (probably in response to infection accompanying ulceration of overlying skin); and the remainder to an increase in non‐DNA radioactivity. In these tumours cell loss rates could be obtained from the whole body counting technique in which influxes of labelled cells and reutilizable radioactivity were eliminated.A comparison of either 125I‐UdR technique with the 3H‐TdR technique showed good agreement of the cell loss factors for the low cell loss tumours. However, for tumours with high cell loss factors the 125I‐UdR technique gave lower values for cell loss. This implied that reutilization of 125I‐UdR within the tumour (i.e. from internal, not external sources) occurred in the high cell loss tumours.It is concluded that equating radioactivity loss with cell loss after an injection of 125I‐UdR is reasonable for some tumours, but will result in significant underestimates in others. For high cell loss tumours the 3H‐TdR technique will give the
CELL LOSS FROM THREE ESTABLISHED LINES OF THE C3H MOUSE MAMMARY TUMOR: A COMPARISON OF THE 125I‐UdR AND THE 3H‐TdR‐AUTORADIOGRAPHIC METHODS
Authors: Dethlefsen L. A. , Sorenson J. , Snively J. 
Published: May 2008

ABSTRACTThe125I‐UdR method for measuring cell loss from solid tumors has been re‐evaluated. The rate of tumor cell loss from three established lines (S102F, S102S and Slow) of the C3H mouse mammary tumor was determined by the 125I‐UdRmethod and the results were compared to the estimates for cell loss as determined by the combined approach of cellular 3H‐TdR autoradiography and volumetric growth‐rate determinations. This detailed comparison shows that the two methods complement each other but cannot substitute for one another because they give different quantitative information. The combined approach measures the flow of viable cells, as determined morphologically, from the proliferating compartment to the quiescent compartment, the quiescent compartment out of the tumor, etc., but does not evaluate the flow of degenerate cells or acellular (necrotic) debris. In contrast, the 125I‐UdR method indicates the net flow of intact cells and/or dead cells as well as debris from the tumor as the I25l‐labeled material is lost from the tumor, but gives limited internal information. Thus, depending on the specific experiment, an investigator could choose one or the other of the methods to answer the question. Perhaps both would be desirable at times; however, in most cases, one could not substitute one method for the other. The data from the Slow tumors also indicate that in certain tumors, the quantitative information from the 125I‐UdR method may be quite limited, i.e. the confidence limits within an experiment as well as the replication error between experiments may be high.
GRAIN COUNT THRESHOLD DEPENDENCE OF FLM CURVE PATTERN AND CELL CYCLE PARAMETERS OF HEPATOCYTES IN VIVO
Authors: Wirsching Rainer , Rabes Hartmut M. 
Published: May 2008

ABSTRACTFLM curves from hepatocytes of regenerating rat liver in vivo were compared at different grain count thresholds. Estimates of cell cycle phases derived from curves with thresholds decreasing from 15 to 1 grain (background 0.2 grains per nuclear area) revealed a prolongation of ts from 6.6 to 9.5 hr, at the expense of tG2M, and tG1, whereas tc remained constant. A similar pattern was observed in FLM curves at various threshold levels for hepatocytes localized in subunits of the liver lobule along the vascular axis from afferent to efferent pole. The shapes of these FLM curves indicated an intralobular gradient of reutilizable labelled material.The use of two different threshold levels is crucial for proper selection of FLM curves to evaluate cell cycle phases in regenerating rat liver: first, a threshold to exclude the autoradiographic background, and a second one to avoid errors due to reutilization of labelled DNA precursors. Each threshold has its own implications for the estimation of cell cycle phases.
Effect of Myleran On Murine Hemopoiesis
Authors: Delmonte L. , Williams N. , Moore M. A. S. 
Published: May 2008

ABSTRACTSpleen colony forming cells (CFU‐S) and agar‐gel colony forming cells (CFU‐C) are separate but heterogeneous cell populations, as measured by buoyant density. Myleran (MY) abrogated the major (lighter density) components of the CFU‐S and CFU‐C compartments, thus shifting the surviving CFU‐S and CFU‐C density profiles into the higher density region. the normal spleen colony erythrocytic: granulocytic (E:G) ratio profile showed three density regions with different distributions of erythroid and granulocytic colonies. the preponderantly erythrocytic colony‐generating CFU‐S of the intermediate density regions were eradicated by MY. Comparison of the density distribution of erythrocytic and granulocytic colony‐generating CFU‐S of normal bone marrow showed that the erythrocytic CFU‐S profile paralleled that of total CFU‐S, while most of the granulocytic CFU‐S were contained in the major (and lowest density) peak. MY eradicated the two main (and lowest density) peaks of CFU‐S; surviving CFU‐S occurred preponderantly in a minor (higher density) peak which has a high potential for generating erythrocytic colonies.
An Iron Requirement For the Synchronous Progression of Colonic Cells Following Fasting and Refeeding
Authors: Stragand J. J. , Hagemann R. F. 
Published: May 2008

ABSTRACTEvidence is presented to show dietary iron to be a major co‐factor in the colonic hyperplasia observed following fasting and refeeding. the iron component serves to remove a fasting induced colonic G1 cycle block and produce the resultant synchronous progression of cells through the cycle. Deleting iion from the refed diet results in no colonic hyperplasia and/or synchronous progression of cells. the results are discussed from the viewpoint of colonic steady state cell renewal and as a possible tool for the study of in vivo steady state cell renewal.
Pluripotent (Cfu‐S) and Granulocyte‐Committed (Cfu‐C) Stem Cells In Intact and 89Sr Marrow‐Ablated S1/S1D Mice
Authors: Adler S. S. , Trobaugh F. E. 
Published: May 2008

ABSTRACTPeripheral blood values, femur cell counts, spleen weights, pluripotent (CFU‐S) and granulocyte progenitor cell (CFU‐C) concentrations and total content of spleens and femurs have been evaluated in intact (non‐marrow‐ablated) and 89Sr marrow‐ablated S1/S1d and +/+ mice. 89Sr‐irradiated mice were studied 6 and 11 days after the administration of 89Sr. In intact S1/S1d mice the femur CFU‐S concentration, total femur CFU‐S, femur CFU‐C concentration and total femur CFU‐C were 84, 54, 105 and 68% that of +/+ mice femurs respectively; the respective values for the spleens of S1/S1d mice were 40,46,61 and 69%. These are the first simultaneous determinations of CFU‐S and CFU‐C concentrations, and content of spleens and marrows, of S1/S1d and +/+ mice. In 89Sr marrow‐ablated mice, 11 days after injection of the radionuclide: (a) the total content of marrow CFU‐C and CFU‐S was about 1% of that found in the marrows of intact mice for both +/+ and S1/S1d groups; (b) the spleens of +/+ mice increased in weight to 162% of the control, but the spleens of S1/S1d mice did not increase in weight; and (c) the spleens of +/+ mice had a total content of CFU‐C and CFU‐S of 800% and 260% of the control, respectively, whereas the respective values for the S1/S1d mice were 120% and 76% of the control. Thus the S1/S1d spleen fails to compensate for marrow ablation by housing additional CFU‐S and has an impaired ability to compensate by housing additional CFU‐C.
Removal of the Horny Layer Does Not Stimulate Cell Proliferation In Neonatal Mouse Epidermis
Authors: Bertsch S. , Marks F. 
Published: May 2008

ABSTRACTMechanical treatment of newborn mouse back skin by removal of the horny layer does not stimulate DNA synthesis and mitotic activity. These results are discussed in connection with recent experiments with newborn and adult mouse epidermis, and reveal further evidences for the ontogenetic development of an endogenous growth control (chalones).
EFFECT of DOUBLE PARTIAL HEPATECTOMIES AT VARIOUS INTERVALS ON [3H]THYMIDINE INCORPORATION INTO RAT LIVER DNA
Authors: Honda S. , Hirose S. 
Published: May 2008

ABSTRACTAt various intervals after a 34% hepatectomy, another 34% (50% of the remnant) hepatectomy was performed on rats, and the [3H]thymidine incorporation into the DNA of remaining liver cells was measured 24 hr after the first operation. the values of [3H]thymidine incorporation into liver DNA of rats hepatectomized doubly (34% and 34%) at 6, 8 and 10 hr intervals were greater than the sum of the value of rats which received a single 34% hepatectomy at the start and those of rats which received a single 68% hepatectomy at 6, 8 and 10 hr, respectively.
QUANTIFICATION OF ENTRY INTO AND EXIT FROM THE CELL CYCLE IN HUMAN LYMPHOCYTE CULTURES
Authors: Dorian R. , Bernheim J. L. , Mendelsohn J. 
Published: May 2008

ABSTRACTA mathematical model is presented for the analysis of transition between cycling and non‐cycling compartments by cells responding to a growth stimulus. the cellular age distribution as a function of time is derived from sequential [3H]thymidine pulse labeling indices. Rates of entry into and exit from the cycling compartment are determined on the basis of labeling indices obtained after instantaneous and long duration [3H]thymidine pulses. Analysis of an experiment involving sequential measurements over the whole lifespan of a human lymphocyte culture stimulated by phytohemagglutinin is presented as an example of the application of this method.
A SIMPLE METHOD FOR PRODUCING DIFFERENT GROWTH FRACTIONS IN VITRO FOR USE IN ANTI‐CANCER DRUG STUDIES
Authors: Barranco S. C. , Bolton W. E. , Novak J. K. 
Published: May 2008

ABSTRACTA simple technique has been used experimentally to produce in vitro Chinese hamster ovary cells with growth fractions ranging from 0 to 100%. Known numbers of exponentially growing and plateau‐phase tissue culture cells were mixed in various proportions to yield the desired final growth fraction. Cells attach to the culture flask surface within 1 hr of mixing. Treatment at that time with the nitrosourea compounds, CCNU and MeCCNU, resulted in differential drug survival sensitivities that were dependent upon the growth fraction of the population treated.
FAILURE TO IDENTIFY A SPERMATOGONIAL CHALONE IN ADULT IRRADIATED TESTES
Authors: Cunningham G. R. , Huckins Claire 
Published: May 2008

ABSTRACTThe adult irradiated rat testis was used as a model system to confirm the existence of a spermatogonial chalone. Rats were given 330 rad whole body 60Co irradiation, a dose which selectively destroys most of the spermatogonial population except for the radioresistant As stem cells. 11 days after irradiation, when spermatogonial numbers were minimal, the rats were injected with a testicular or liver extract prepared from normal adult rats, or with saline. Each group received a total of four injections given at 4 hr intervals. 2 hr before death, the animals were injected with [3H]TdR. Testicular DNA was isolated and the incorporation of [3H]TdR was determined. The mean ± s.e. ct/min per μg DNA in rats given testicular extract (9·38 ± 0·94) was no different than in those receiving liver extract (10·43 ± 2·01) or saline (7·23 ± 0·69). Autoradiographic studies indicated that variability in counts within or between groups could be attributed to variations in the number of pre‐leptotene spermatocytes which incorporated [3H]TdR for the meiotic divisions. Quantitatively, there were no differences between groups in terms of the numbers of A spermatogonia, their labelling indices, or mitotic activity. Therefore, the presence of a spermatogonial chalone could not be demonstrated using crude extracts from normal testes in this irradiated model.
REGENERATIVE PROLIFERATION OF MOUSE EPIDERMAL CELLS FOLLOWING APPLICATION OF A SKIN IRRITANT (CANTHARIDIN)
Authors: Clausen O. P. F. 
Published: May 2008

ABSTRACTThe strong skin irritant cantharidin dissolved in benzene was applied to the back of hairless mice. Single cell suspensions of epidermal basal cells were obtained and flow microfluorometric measurements of cellular DNA content were made. Smears were made for autoradiography, and the [3H]TdR labelling index (LI) and mean grain count (MGC) were assessed up to 3 days after cantharidin application.Three successive peaks of cells with S phase DNA content accompanied by three LI peaks were observed. The first two peaks were follwed by peaks of cells in G2 phase, indicating that after the acute cell injury caused by cantharidin the cells traversed the cell cycle in partial synchrony through two subsequent cell cycles, each of 10–12 hr duration. During this phase of rapid proliferation the LI reached the proportion of cells in S phase, contrary to what is observed in untreated mouse epidermis, where the labelled cells contribute to about half the proportion of cells with S phase DNA content. The first two peaks of cells in S phase and LI coincided with an increased MGC, whereas the third peak was accompanied by a MGC significantly below control values. This indicates that this latter peak is due to a longer DNA synthesis time rather than to a partially synchronized and increased cell proliferation. The duration of the G1, S and G2 phases seems to be reduced initially in rapidly proliferating epidermis.
VIABILITY OF THE CERVICAL EPITHELIUM DURING CARCINOGENESIS IN MICE
Authors: Rubio C. A. , Skoog L. , Fox C. H. 
Published: May 2008

ABSTRACTAutoradiograms of histological specimens from the cervix of seventy‐five mice were analysed after in vivo injection with an RNA precursor. All nucleated, non‐pyknotic cells and some mitotic figures were labelled, which suggested that the tissue was metabolically active (i.e. viable). Only the uppermost epithelial pyknotic cells were devitalized, as deduced by the morphological appearance of the cells and by the absence of label. The viability of the whole epithelium suggests that the previously reported focal distribution of proliferating and non‐proliferating areas in the cervical epithelium of mice is a genuine phenomenon.
TESTOSTERONE‐INDUCED CELL PROLIFERATION IN THE ACCESSORY SEX GLANDS OF MICE AT VARIOUS TIMES AFTER CASTRATION
Authors: Alison M. R. , Wright N. A. 
Published: May 2008

ABSTRACTThe proliferative response to testosterone in the accessory sex glands (seminal vesicle and coagulating gland) of castrated male Balb/c mice has been examined by pulse and continuous thymidine‐labelling experiments, and by the fraction of labelled mitoses technique. Progressive reductions in cellularity followed castration, and by varying the time elapsing between castration and the initiation of testosterone treatment, it was clear that the size of the response depended upon the number of cells in the tissue, relative to the normal complement.Interpretation of FLM data was difficult in periods where proliferative rates changed rapidly. We have attempted to explain the cell kinetic events by postulating a G0 compartment, from which cells are stimulated to enter the proliferative cycle before subsequently returning to an out of cycle state. It was thought unlikely that substantial changes in cell cycle time occurred.In both the accessory sex glands, the overall form of the continuous thymidine labelling curves showed that most proliferative cells entered DNA synthesis in a shorter time after stimulation at 14 days after castration than they did at 3 days after castration. The data were not consistent with cells moving deeper into G0 with time after castration. In the seminal vesicle almost all epithelial cells were potentially proliferative by 3 days after castration. In the coagulating gland only 30% were potentially proliferative at 3 days, increasing to 85% at 14 days after castration. However, such proportional increases represented much smaller changes in terms of absolute numbers of cells, because of a concomitant decline in cellularity from 3 to 14 days after castration.