bluuebunny/crossref_metadata_2025 huggingface dataset:
Decrease in the ability of CFU‐s in shielded marrow to be recruited into cell cycle after multiple irradiations: experimental results and computer simulations
Authors: Sainteny F. , Guiget M. , Mary J. Y.
Published: May 2008

Nine doses of 1.5 Gy given to mice with one shielded leg result in very similar perturbations in shielded marrow (CFU‐s kinetics whatever the source of radiation (X or γ rays). At the time of the ninth irradiation, the size of the shielded CFU‐s compartment is reduced to 75% of control level. After 15 min it decreases to 47% and, 1 day later, remains below the pre‐ninth irradiation level (62% of control level) in spite of two significant peaks of CFU‐s in DNA synthesis, at 1 and 8 hr after the ninth irradiation. For acceptable fitting to experimental data, computer simulations make it necessary to assume that a fraction of shielded marrow CFU‐s is not capable of entering the cell cycle after the treatment. This is not explainable by defects in the stimulators of CFU‐s proliferation secreted by shielded haemopoietic tissue because their production and their efficacy are demonstrated to be normal after the nine exposures. the incomplete recovery of the shielded CFU‐s pool from porliferating CFU‐s can be attributed to a loss in CFU‐s by differentiation at birth.
Proliferation Kinetics of A Human Malignant Melanoma Serially Grown In Nude Mice
Authors: Spang‐Thomsen M. , VindelØv Lars L.
Published: May 2008

The technique of labelled mitoses and flow cytometric DNA analysis were used to determine the proliferation kinetics of a human malignant melanoma grown in nude mice. the effect of tumour volume and of long‐term serial transplantation on the kinetic parameters was investigated.

The results showed that the cell loss factor, which was the dominant factor in the growth of this melanoma, increased from 52 to 69% with increasing tumour size, whereas the calculated growth fraction showed no systematic changes. the cell generation time increased from 34 to 44 hr with tumour size, mainly due to a prolongation of the G1, duration time, whereas no significant changes occurred in the duration of the S and G2, phases of the cell cycle. the stability of the investigated tumour characteristics indicated that the kinetics of this melanoma remained unchanged during more than sixty serial transplantations in nude mice. the methods applied are suitable for a detailed description of tumour growth kinetics, since they provide complementary results.
Comparative Investigations On the Effect of Different Dose Schedules of the Phase‐Specific Drug Vincristine (Vcr) On the Proliferation Kinetics of A Solid Experimental Tumour
Authors: de Lacroix W. Féaux , Mallmann H.
Published: May 2008

The aim of the present investigation was to study the effect of a high bolus injection (1 × 2.1 mg) of vincristine (VCR) during the phase of tumour growth retardation at the 14th day after transplantation and to compare the findings with the results of single (1 × 0.35 mg) and repeated (6 × 0.35 mg) applications of this cytostatic drug. Furthermore, an attempt was made to induce a synchronization of tumour cell proliferation. It was found that the effect on the volume growth was very pronounced after the high bolus injection and the repeated application of vincristine compared with the single low dose of the cytostatic drug. A synchronization of the tumour cell proliferation by flow out of the mitotic block could not be demonstrated. On the other hand a modest simultaneous recruitment of previously non‐cycling tumour cells into the cell cycle occurred in the periphery of the tumour after the high bolus injection. the repeated application and the high bolus injection of VCR increased the cytostatic effect, especially in the tumour centre, related to the more slowly proliferating tumour cell compartment.
Pattern of Dna Synthesis and Its Effect On the Classification of Cells By Flow Cytometry
Authors: Culpin D. , Morris V. B.
Published: May 2008

A flow cytometer produces a DNA distribution which contains information about the proportions of cells in various phases of the cell cycle. In this report we show that the form assumed for the rate of DNA synthesis in a cell plays an important part in the estimation of those proportions. We compare three forms for the rate of DNA synthesis, one of which is derived from knowledge of the mechanism of DNA replication, and find that they give substantially different estimates of the proportions of cells in the G1 and G2+ M phases.
Clonal Attenuation In Chick Embryo Fibroblasts Experimental Data, A Model and Computer Simulations
Authors: Angello J. C. , Prothero J. W.
Published: May 2008

When cells from mass cultures of chick embryo fibroblasts are grown at very low density, some cells yield large clones while others produce smaller clones, and some cells fail to divide at all. the distribution of clone sizes is related to the number of population doublings which the donor mass culture has undergone: the more doublings which have occurred, the smaller the average clone size. In this report we describe a model which analyses this phenomenon, referred to as ‘clonal attenuation’, in detail.

The model is based on the concept that a cell with hypothetically unlimited replicative potential—i.e. a ‘stem’ cell—can become ‘committed’ to a programme of limited replicative potential. This event is assumed to be stochastic and to have a fixed probability per stem cell division. the parameters of the model are: Pc, the probability of commitment; N, the number of differentiative divisions; and Tc, the cell‐cycle times. By computer simulation, it is shown that Pc increases roughly exponentially at each successive stem cell division. According to the model, when the daughter of a stem cell becomes committed, its progeny proceed through N obligatory divisions before becoming terminally differentiated (post‐mitotic). the best‐fit value of N was found to be seven.

The simulations also reveal that the absolute number of stem cells in the total population increases for most of the lifespan of the culture. When Pc becomes much greater than 0.5, the number of stem cells declines rapidly to zero, and the culture nears senescence.

Sensitivity analysis shows that Pc can assume only a limited range of values at each stem‐cell division.
Kinetics of Micronucleus Expression In Synchronized Irradiated Chinese Hamster Ovary Cells
Authors: Brock William A. , Williams Marcia
Published: May 2008

The kinetics of expression of radiation‐induced micronuclei (MN) in synchronized Chinese hamster cells (CHO) was examined. the purpose of the study was to determine if the cell cycle distribution of a population significantly influences the levels of radiation induced MN, thereby obscuring the exact quantification of the radiation effect. Cells were synchronized by centrifugal elutriation, irradiated, and then different phases of the cell cycle were examined for: cell cycle progression, division probability, and temporal expression of MN. the results demonstrate that the time interval for maximal MN expression is long enough that the position of cells in the cell cycle and radiation induced division delays do not prevent the majority of cells from completing their first post‐irradiation mitosis, therefore, expressing MN. By following the progression of synchronized cell populations by flow cytometry and also examining the time of division of individual cells for 24 hr after irradiation, we observed that the maximum number of cells from all phases of the cell cycle are in their first post‐irradiation interphase at that time, thus explaining the MN results.
A Novel Approach to the Study of Kinetically Changing Cell Populations
Authors: Sheridan J. W.
Published: May 2008

A method is described for estimating changes in cell cycle times during periods of rapid change in proliferation rate. This method, which depends upon the interpretation of pre‐ and post‐velocity sedimentation fractionation continuous thymidine labelling patterns, exploits the relationship between sedimentation rate and cell cycle location. By this means, cycle times can be estimated under conditions that are difficult (if not impossible) to analyse by FLM methods.
Self‐Renewal Capacity and Clonal Succession of Haemopoietic Stem Cells In Long‐Term Bone Marrow Culture
Authors: Chertkov J. L. , Drize Nina J. , Gurevitch Olga A. , Udalov G. A.
Published: May 2008

Abstract. The CFU‐s proliferative potential varied greatly during long‐term cultivation. Most of the CFU‐s in the cultures were represented by cells with low renewal capacity. Pre‐CFU‐s cells capable of producing multipotential colonies in methylcellulose, which contained CFU‐s with a high proliferative potential, were identified in the culture. In cultivation of a mixture of cells of different karyotype their ratio changed rapidly from week to week. the findings were consistent with the hypothesis that haemopoietic stem cells are maintained in the culture by the products of a small number of clones which arise and decline in succession, and that pre‐CFU‐s, but not the CFU‐s themselves, are clonogenic progenitors.
Epidermal Tissue Homeostasis
Authors: Budtz Povl E.
Published: May 2008

Abstract. Following removal of the pars distalis of the pituitary gland in toads, epidermal efflux from the stratum corneum recruitment cell pool (i.e. production of corneal layers) is greatly increased. In this investigation the cell birth rate is studied by means of the metaphase arrest technique, as a function of time after pars distalis ablation. the method allows assessment of the total cell production over 14 days after the operation, to be compared with the total efflux and changes in the epidermal cell pool size.

Whereas in intact toads the rate of cell production exceeds that of cell loss by moulting by a factor of 2.7, the ‘surplus’ of cells neither being used for formation of corneal layers nor permanently accommodated within the living epidermis, a ‘balance sheet’ of efflux and influx indicates that following pars distalis ablation all cells produced are also used for the (excessive) formation of corneal cell layers.

The observations lend further support to the hypothesis that controlled cell deletion is a tissue homeostatic mechanism complementary to controlled cell divisions.
In Vitro Thymidine Labelling In Human and Porcine Growth Plates
Authors: Thurston M. N. , Kember N. F.
Published: May 2008

Abstract. An in vitro technique has been used to label dividing cells in the growth plates of human bones with tritiated thymidine. the patterns of labelling in autoradiographs of human plates are described and values given for the labelling index, the number of cells in the proliferation zones and the heights of hypertrophied cells. In two of the four subjects no labelled cells were found in the growth plates and possible causes for these failures are discussed. In vitro labelling data on five porcine growth plates are also presented for comparison with the human data. In both structure and cell kinetics the epiphyseal cartilage plate in the pig is intermediate between the human and rodent plates.
Migration of Fibroblastoid Stromal Cells In Murine Blood
Authors: Piersma A. H. , Ploemacher R. E. , Brockbank K. G. M. , Nikkels P. G. J. , Ottenheim C. P. E.
Published: May 2008

Abstract. This paper describes the kinetics of fibroblastic colony forming units (CFU‐f) in murine blood after phenylhydrazine‐induced haemolytic anaemia and their subsequent migration into haemopoietic organs. Murine blood contained 5.3 φ 0.8 CFU‐f per 106 nucleated cells. Absence of particle ingestion and factor VIII‐related antigen in addition to the enzyme pattern in CFU‐f‐derived cells confirmed that these cells did not have a macrophage‐like or endothelial nature. Phenylhydrazine treatment of mice resulted in a 3‐fold increase in blood CFU‐f numbers which was accompanied by increases in blood cellularity and granulocyte‐macrophage progenitor numbers. When both partners of CBA/N and CBA/T6T6 mice in parabiosis had been treated with phenylhydrazine, spleens and femoral bone marrow of both mice were shown to contain partner‐derived CFU‐f. These data suggest that circulating CFU‐f represent a stromal cell population which can migrate into haemopoietic organs.
Effects of Hydroxyurea On the Mitotic Activity and the G2 Phase In Hairless Mouse Epidermis
Authors: Iversen Olav Hilmar , Harket Gunvald , Rabe Ragnar
Published: May 2008

Hairless mice were given 5 mg hydroxyurea (HU) intraperitoneally (i.p.) followed by 0.15 mg Colcemid® at various times after HU. the animals were killed at 2 and 4 hr after Colcemid, the epidermal mitotic counts in dorsal skin were determined and the mitotic rates calculated. These were compared with the normal mitotic rates, and the ratios between the results from HU‐treated and ‐untreated animals were calculated. Hydroxyurea caused a considerable reduction in the mitotic rate with a trough at 6 hr, followed by a wave of increased mitotic rate with a peak at 14 hr, followed by a secondary drop at 20 hr, and then a return to normal.

Another group of mice were given HU only, and the fraction of epidermal cells in G2 was measured by flow cytometry. From these animals, without previous injection of Colcemid, we also determined the mitotic counts and calculated the mitotic durations. Cells piled up in G2 for the first 6 hr after HU injection, then the G2 compartment was emptied. the results are discussed in relation to previous results from this department showing the effect of the same dose of HU on DNA synthesis in the same mouse strain. It is concluded that HU not only blocks or retards DNA synthesis in epidermal cells, but also affects the movement of cells through G2 and M. the cell kinetic effects of HU thus seem to be very complex.
Proliferation of Cardiomyocytes and Interstitial Cells In the Cardiac Muscle of the Mouse During Pre‐ and Postnatal Development
Authors: Cluzeaut Françoise , Maurer‐Schultze Brigitte
Published: May 2008

Proliferation of cardiomyocytes and interstitial cells in the cardiac ventricle of the mouse during pre‐ and postnatal development was studied. Furthermore, the number of cardiomyocyte and interstitial cell nuclei per unit area was determined on histological sections.

The labelling index of cardiomyocytes decreases from 23% on day 14 of gestation to about zero at 3 weeks after birth. the number of cardiomyocyte nuclei per unit area increases up to day 16 of gestation and then continuously declines. This coincides with the concept that the increase in size of the heart during early fetal life is mainly due to hyperplasia, while during late fetal life and after birth it is mainly, and during adult life exclusively, due to hypertrophy of cardiomyocytes. Proliferation of interstitial cells continues up to 5 days after birth and then decreases. the ratio of cardiomyocytes to interstitial cells decreases by a factor of about 10 between day 14 of gestation and 3 weeks after birth.
A Modified Harlequin Stain For Cell Kinetics
Authors: Pincu Madeleine , Kimme‐Smith Carolyn , Norman A.
Published: May 2008

Lymphocytes cultured with 4 × 10‐4 m bromodeoxyuridine (BrdU) and stained by the harlequin procedure show wide variations in the colour and texture of their interphase nuclei. We demonstrate that we are able, by inspection, to identify four sets of nuclei: small dark nuclei (D) in cells that have not transformed in response to mitogenic stimulation; red nuclei (R) in transformed cells that have not synthesized DNA in culture; speckled nuclei (S)—red speckles on a bluish background—in cells that are synthesizing DNA for the first time in culture; blue nuclei (B) in cells that have completed one or more cycles of DNA synthesis. By using this modified harlequin stain to score the fraction of proliferating cells, and using the modified or conventional harlequin stain to determine the relative frequencies of mitotic cells in the first, second, or later divisions, we are able to estimate the fraction of lymphocytes in the original blood sample that can divide in culture. In addition, we show that the technique lends itself to automation. For this we have digitized black and white video images of the cells and extracted features based on the distribution of optical densities in the nuclei. Discriminant analysis carried out on these descriptors resulted in the correct classification of the three major groups R, S and B with an accuracy of 80.3%, 58.5% and 85.1%, respectively.
Synchronization of the Human Promyelocytic Cell Line HL 60 By Thymidine
Authors: Mortensen Børge T. , Hartmann Niels R. , Christensen Ib J. , Larsen Jørgen K. , Kristensen Tom , Wieslander Steen B. , Nissen Nis I.
Published: May 2008

Cultures of the promyelocytic cell line HL 60 were synchronized with thymidine. A concentration of 0.05 mM thymidine and an exposure time of 24 hr was found optimal for blocking about 90% of the cells in S phase. Following release from the thymidine block the cell cultures were followed intermittently over 40 hr for fluctuation in cell numbers, labelling with radioactive thymidine and nuclear DNA distributions.

Mathematical evaluation of the results revealed a cycling time of 18.6 hr and a duration of specific cell phases of 8.6 hr, 7.1 hr and 2.9 hr for G1, S and G2+ M, respectively. the doubling time was 26 hr and the growth fraction was estimated as 1.
Growth Rate Regulation and Random Transition A study performed on embryonal carcinoma cell lines. I.
Authors: Sennerstam R. , Strömberg J. O.
Published: May 2008

Abstract. Analyses of cell‐cycle characteristics of the three embryonal carcinoma (EC) cell lines F9, PCC3 N/1 and PCC4 Azal, have been performed. the three lines reflect successive stages in early mouse embryogenesis as regards cell surface antigens and cell‐cycle characteristics. In an attempt to understand changes in cell‐cycle characteristics occurring during early embryogenesis, the two‐random transition probability (TP) model was applied to the EC‐cell system—and particularly to the F9 line. By utilizing an intraclonal heterogeneity in intermitotic times found in these EC lines, a growth‐regulating point was introduced as a modification of the two‐random TP model. the modified model was found to be very useful when demonstrating the cell‐cycle growth kinetics of the F9 line. the model is used in an accompanying paper to extend the analysis of cell‐cycle characteristics in undifferentiated EC cells.
Effect of diabetes on the rhythm of r[3H]thymidine incorporation in Con‐A‐stimulated mice splenocytes
Authors: Prunet J. , Panijel J.
Published: May 2008

Abstract. The chronogram of hyperglycaemia in alloxan‐induced diabetic DBA/2 mice (living under conditions standardized for light‐synchronized periodicity and fed ad libitum) presented an ultradian rhythm (during spring) different from the circadian blood glucose chronogram of normal control mice.

Simultaneously, the [3H]hymidine ([3H]TdR) incorporation chronogram of diabetic mouse splenocytes, stimulated or unstimulated with Concanavalin‐A (Con‐A), was changed and unbalanced, compared to that of normal control mice.

Previous experiments showed that the [3H]TdR incorporation chronogram of stimulated or non‐stimulated splenocytes of normal DBA/2 mice presented seasonal variations. They were characterized generally by an ultradian rhythm. Yet, during spring, they exhibited a circadian rhythm because one phase was advanced and superimposed on the other, the latter being typically unvarying.

It seems probable that the unbalanced rhythm of [3H]TdR incorporated in diabetic mouse splenocytes, stimulated or not, was responsible for a dysfunction of that population in diabetes.
Urothelial Proliferation In Growing Mice
Authors: Jost S. P. , Potten C. S.
Published: May 2008

Abstract. Developing murine urothelium undergoes pronounced proliferation until at least 10 days after birth. Thereafter, both mitotic and [3H]TdR‐labelling indices fall sharply with age. the ratio of labelling to mitotic indices also alters dramatically during development, which is probably due to both endoreduplication and changes in the relative durations of the DNA synthesis and mitotic phases. This ratio reaches stability at 5 weeks of age. the adult labelling and mitotic indices were 0.11 and 0.019% respectively, indicating a very slow turnover.
Retention of Labelled Dna Precursor By Murine Cells After A Single Administration of Tritium Labelled Thymidine
Authors: Miller Richard C. , Riley Edgar F.
Published: May 2008

Abstract. The central zone of the rat lens epithelium, extending half way from the centre to the periphery of a whole mount preparation, normally has less than 1% of the cells in the cell cycle at any given time. Mechanical wounding initiates a burst of proliferation in the central zone. DNA synthesis begins 14 hr after wounding followed by mitosis 10 hr later. When [3H]TdR was applied at 2 hr prior to S phase, some moderately heavy and some light labelling was observed after the onset of S phase. When [3H]TdR was applied 5 hr before S phase (9 hr after wounding), all the cells were lightly labelled. Only small amounts of the label were available to these cells 5 hr after application. It is significant that there was labelling in this group because it indicates the persistence of relatively small intracellular pools of [3H]TdR for several hours after the initial ‘pulse’ labelling of cells. Determinations of the duration of S phase were based on the assumption that pulse labelling may be affected by the persistence of the pools of [3H]TdR and consequent light labelling of the cells.
Analysis of the Length of S‐Phase Required to Show Sister Chromatid Differential Staining
Authors: Crossen Peter E. , Gerner Eugene W. , Bell Carl W. , Trent Jeffrey M.
Published: May 2008

Abstract. In vitro studies of BrdU‐dependent sister chromatid differential staining typically employ two cycles of BrdU incorporation. Experiments are described which determined the actual fraction of both S‐phases that the rat embryonic fibroblasts (Rat‐1) cells had to traverse in order to show distinctive differential staining. Following synchronization of cells by a combination of serum deprivation and hydroxyurea blockage, sister chromatid differential staining, labelling index, mitotic index, and per cent DNA replication are determined. Results indicate that only ≤50% of the first S‐phase is necessary in order to show distinctive differential staining. the importance of this finding to studies of cellular proliferation using BrdU incorporation is discussed.
Mitogenic Activity of Snake Venom Lectins
Authors: Mastro Andrea M. , Hurley David J. , Winning Richard K. , Filipowski Richard , Ogilvie Mary L. , Gartner T. Kent.
Published: May 2008

Abstract. Five lactose‐inhibitable lectins have been isolated from snake venoms. These five share certain biochemical properties but are not identical (Gartner, Stocker & Williams, 1980; Gartner & Ogilvie, 1984). In this study the lectins were tested for their ability to stimulate lymphocytes to undergo DNA synthesis. We found that three of the lectins were comparable in mitogenic activity to the T cell lectin, concanavalin A (Con A). the mitogenic activity was blocked by lactose, a sugar which also blocks the haemagglutination activity of these lectins. Although mitogenic response appeared to be due to T cells, it depended on the presence of accessory cells in the culture. This requirement for macrophages could be replaced by the phorbol ester tumour promoter, 12‐o‐tetradecanoylphorbol‐13‐acetate (TPA).
Dynamics of Cell Kinetic Parameters During 9l Spheroid Growth
Authors: Sweigert Susan E. , Alpen Edward L.
Published: May 2008

Abstract. Cell population kinetics were followed in 9L tumour spheroids as they grew from aggregates of about 80 μm in diameter to over 800 μm. the kinetic parameters measured were cell cycle time, spheroid‐doubling time, and growth fraction; from these the cell loss factor ø was calculated. the rate of cell shedding from the surface was also measured, so that the contribution of shedding to the overall cell loss could be evaluated. the major findings include significant elongation of the cell cycle, a low rate of cell death in spheroids below 500 μ in diameter, and a relatively high GF in large spheroids. the results also indicated that 9L spheroid kinetic parameters may be strongly influenced by the culture methodology.
Evidence For Cell Generation Controlled Proliferation In the Small Intestinal Crypt
Authors: Meinzer H. P. , Sandblad B.
Published: May 2008

Abstract. In this paper we discuss the hypothesis that cell proliferation is controlled by the number of generations after leaving an ‘eternal’ stem cell. the theory is based on a simulation of the kinetic behaviour of cells in the intestinal crypts. There is evidence of three, four and five generations of cells which are allowed to enter mitosis in the lower and upper part of the normal intestinal tract, and in some disease states, respectively. We suggest an internal proliferation control: some kind of knowledge that cells carry from generation to generation. It is an open question what sets and changes the generation counter: internal genetic information or external influences such as growth factors or chalones.

The geometric shape of the epithelial tissue in the intestinal tract can be understood as the steady state of a highly dynamic process. Age and death are determined from the beginning; cell‐cell interaction or communication is not necessary and can be neglected. Our theory will be illustrated using the intestinal crypts as they are easily accessible, of a simple structure and completely described in the literature.
Effects of Puromycin, Cycloheximide and Noradrenaline On Cell Migration Within the Crypts and On the Villi of the Small Intestine
Authors: Kaur P. , Potten C. S.
Published: May 2008

Abstract. The normal process of cell migration, occurring as part of the replacement scheme within the small intestinal epithelium, was investigated extensively. the effects of puromycin, cycloheximide and noradrenaline on the movement of tritiated thymidine ([3H]TdR) prelabelled crypt or villus cells have been studied. These studies have led to the formulation of a model for the mechanism of cell migration, postulating that the crypts and villi behave as separate units, with regard to cell migration, in addition to their distinct structural and functional properties. It is proposed that crypt cell migration is an active process requiring protein synthesis and protein glycosylation, whilst movement of villus epithelial cells is passive, depending on the continued contraction of smooth muscle cells in the lamina propria.
Role of splenic stroma in the action of bacterial lipopolysaccharides on radiation mortality: a study in mice carrying the Slj allele
Authors: Ploemacher R. E. , Brons N. H. C.
Published: May 2008

Abstract. Slj/+ mice display a slight macrocytic anaemia due to a defect in their haemopoietic organ stroma. They have a deficient endogenous spleen colony (CFU‐end) formation following sublethal doses of gamma‐radiation compared with their normal +/+ littermates, which is likely to be due to the low pre‐irradiation CFU‐S content of the Slj/+ spleen. CFU‐S in these congenic mice do not differ in their sensitivity to gamma‐irradiation or stem cell‐activating factor.

While injection of +/+ mice with 10 μg of lipopolysaccharide‐W (LPS) one day prior to irradiation led to a substantial increase in their survival, the survival of Slj/+ mice was only slightly increased. Irradiation induced a similar dose‐related reduction in the numbers of CFU‐S in the spleen and femora of LPS‐injected Slj/+ mice compared to similarly treated +/+ mice when measured directly after irradiation. At Day 9 after irradiation, injection of LPS led to a significantly higher CFU‐end formation and higher numbers of CFU‐S and nucleated cells in the Slj/+ spleens compared to LPS‐injected +/+ mice. No such differences in the radioprotective effect of LPS were observed in the +/+ and Slj/+ mice with respect to the splenic and femoral 59Fe‐incorporation and the femoral CFU‐S numbers at Day 9.

These data strongly suggest a contribution by immigrating CFU‐S to the CFU‐S numbers and endogenous colony formation in at least the Slj/+ spleen after LPS injection and subsequent sublethal irradiation. The observations also imply that the splenic organ stroma may play a mediatory role in the radioprotective action of LPS. In addition, the data represent an extreme example of a lack of correlation between animal survival and haemopoietic parameters. Caution should be taken when applying endogenous colony counts as a means of screening potential anti‐radiation drugs.
Cell kinetics of hypoxic cells in a murine tumour in vivo: flow cytometric determination of the radiation‐induced blockage of cell cycle progression
Authors: Rutgers Derk H. , Niessen Dorien P. P. , van der Linden Pieter M.
Published: May 2008

Abstract. Cells from the small cell population of viable cells in the large necrotic centre of murine M8013 tumours were investigated with respect to their cell kinetics. Flow cytometry (FCM) of this part of subcutaneously transplanted tumours revealed the presence of tumour cells with G1, S and G2 + M phase DNA‐contents. These severely hypoxic cells could have stopped cell cycle progression due to the nutritional deprivation, irrespective of their position within the cell cycle.

Labelling methods, used to disclose the cell kinetics of this cell population, are hampered by the absence of a transport system in these large necrotic areas. Therefore, FCM was used to monitor radiation‐induced changes in the cell cycle distribution. From this investigation it was concluded that hypoxic cells in the necrotic centre of the M8013 tumour progress through the cell cycle. As well as a cell population with a cell cycle time (Tc) of approximately 84 hr, a subpopulation with a Tc of approximately 21 hr occurred.
A new in vitro assay for cell motility and proliferation
Authors: Benestad H. B. , Saxholm H. J. K. , Siebke E. M.
Published: May 2008

Abstract. We have described and characterized a new micropore membrane assay for migration and proliferation of cells of various tumourigenic potential. The assay was developed to facilitate analysis of some aspects of cancer invasion and metastasis. Tumorigenic and non‐tumorigenic C3H/10 T1/2 cells grow in and migrate out of a culture chamber during a 1–11 day period, the shorter periods are used for chambers with 6 μm thick polycarbonate membranes, the longer ones for 140 μ m thick cellulose nitrate membranes. Cell growth within the chambers, in their micropore membranes and on the outside of the membranes, was assessed with microscopy, electronic cell counting, flow cytometry of propidium iodide (PI) stained cells, and 3H‐thymidine ([3H]TdR) incorporation. A complete retrieval of intact cells that have traversed the membraneous chamber wall is possible, and these cells can be recultured or used in other studies. The tumorigenic cells had a steeper growth curve in vitro than the non transformed cells, but the relative sizes of the emigrated subpopulations were not significantly different. The subpopulation of tumorigenic cells that emigrated spontaneously from the chambers was less able than the subpopulation retained to populate secondary chamber cultures, suggesting that the clonogenic (stem) tumour cells are ‘slow movers’.
Cell kinetics of mouse kidney using bromodeoxyuridine incorporation and flow cytometry: preparation and staining
Authors: Wilson G. D. , Soranson J. A. , Lewis A. A.
Published: May 2008

Abstract. The kidney is recognized as a dose‐limiting tissue by certain radiation treatments. The relationship between the onset of compensatory proliferation in response to irradiation and the expression of functional damage is difficult to study because of the low cell turnover in slowly proliferating tissues. We report on a method to obtain a suitable cell preparation from mouse kidney for study by flow cytometry using the recently developed staining techniques for bromodeoxyuridine incorporation. The labelling index of 0.3% in untreated mouse kidney was easily measured because large numbers of cells could be analysed rapidly. We show that compensatory proliferation after unilateral nephrectomy remains elevated for up to 3 weeks after surgery. Using the BrdU/FCM technique we were able to measure the duration of the S phase in normal and nephrectomized kidneys which we found to be 8.5 hr in both cases. The estimates of potential doubling time were similar to the time scale observed to elapse before functional damage is observed in normal kidneys and those in which damage is precipitated by surgery.
Implications of disaggregation procedures on biological representation of human solid tumours
Authors: Costa A. , Silvestrini R. , Bino G. Del , Motta R.
Published: May 2008

Abstract. This study was designed to define some biological aspects of cell suspensions, obtained by mechanical or enzymatic disaggregations, and to verify whether single cell suspensions are representative of original solid tumours. The study was performed on a series of 25 human solid tumours including breast carcinoma, ovarian carcinoma and malignant melanoma. A higher cell viability and a loss of aneuploid subpopulations, or a lower fraction of aneuploid cells, were observed in enzymatically‐released samples than in samples obtained by the mechanical procedure. Moreover, the proliferative activity, which was generally similar for the cell suspensions obtained by the two disaggregation procedures, was always markedly lower in the cell suspensions than in solid samples from the same tumour. In conclusion, the results from this study indicate that many changes, such as selective release of cell populations from the tumour matrix, damage and destruction of aneuploid and proliferating cells can be induced to various extents by different disaggregation procedures.
Chemoattraction enrichment of Thymus‐homing bone marrow cells
Authors: Haar J. L. , Grogan W. McLean , Popp J. D. , Taubenberger J. K.
Published: May 2008

Abstract. It has been reported that a population of cells from mouse bone marrow migrates to supernatant made from the incubation of minced fragments of new‐born mouse thymuses and that the migrated population is enriched for immature lymphoid cells. In the present study, we show that this method enriches for thymic‐homing cells. Migration‐enriched cells were labelled with fluorescein isothiocyanate (FITC) and were injected into the tail veins of lethally irradiated mice. Cell suspensions of the thymuses from these experimental mice had 8.1 ± 1.8% fluorescing cells compared to control mice given equal numbers of non‐migration‐enriched FITC labelled cells which had 2.4 ± 1.7% positive cells.
Bone marrow osteogenic stem cells: in vitro cultivation and transplantation in diffusion chambers
Authors: Friedenstein A. J. , Chailakhyan R. K. , Gerasimov U. V.
Published: May 2008

Abstract. Fibroblast colonies (clones) were obtained by explantation of bone marrow single‐cell suspensions and were used to establish multicolony and single‐colony derived fibroblast cultures by successive passaging of either pooled or individual colonies. When transplanted in diffusion chambers after 20–30 cell doublings in vitro, the descendants of fibroblast colony‐forming cells (FCFC), whether grown from single or pooled colonies, retained the ability for bone and cartilage formation. The content of osteogenic precursors in the cultured progeny significantly outnumbered the initiating FCFC. Thus the high proliferative potential of bone marrow FCFC and their ability to serve as common precursors of bone and cartilage‐forming cells makes them probable candidates for the role of osteogenic stem cells.
Proliferation kinetics of plasma cells and of normal haemopoietic cells in multiple myeloma
Authors: Ucci G. , Riccardi A. , Dörmer P. , Danova M. , Luoni R. , Montecucco C. M. , Ciotti R. , Girino M.
Published: May 2008

Abstract. DNA synthesis time (Ts) and 3H thymidine (TdR) labelling index (LI) of bone marrow (BM) myelomatous plasma cells (PC) and of the residual haemopoietic cell population (RHCP) were measured by in vitro quantitative 14C‐TdR autoradiography in five patients with multiple myeloma (MM) in different phases of disease (three at presentation and two at relapse) and in one patient with solitary extra‐osseous myeloma. One other patient with plasma cell leukaemia (PCL) was studied during an initial relapse phase and later during the leukaemic terminal phase. PC Ts was 18.8 ± 3.7 (from 13.3 to 25.0) hr and PC LI was 2.5 ± 1.8%; (from 1.0 to 6.3%). In the case of PCL, circulating PC had a Ts of 14.4 hr and a LI of 3.1. From these experimental measurements, the fractional turnover rate (FTR—percentage of cells produced per unit time) and the potential doubling time (Td) of BMPC were calculated assuming that all BMPC were in a steady‐state at the time of the study. BMPC FTR was 3.53 ± 2.3% cells per day (from 1.2 to 6.72) and BMPC Td was 46.8 ± 27.5 days (from 15.0 to 75.4). Comparison with results obtained in BM blasts of children with acute lymphoblastic leukaemia (ALL) indicated that BMPC had a lower proliferative activity (P < 0.001), although BMPC Ts was not significantly different. In two patients a tumour doubling time of 6 and 13 months was determined by clinical follow up. Comparison of this parameter with Td showed a cell loss factor of more than 90% in both patients.

Kinetic data relative to RHCP showed slight variations with respect to those found in normal subjects, with a general tendency towards a prolongation of Ts and a reduction of LI.
Comparison of growth and cell proliferation kinetics during mouse molar odontogenesis in vivo and in vitro
Authors: Ahmad N. , Ruch J. V.
Published: May 2008

Abstract. The growth of embryonic first lower mouse molars in vitro was slow and reduced in comparison with in vivo development: the volume of teeth removed on day 15 and 16 of gestation and cultured for 6 days did not exceed the volume reached at day 18 in vivo. The volume of teeth removed on day 17 and 18 and cultured for 6 days either remained constant or decreased. The appearance of post‐mitotic odontoblasts and ameloblasts was delayed in vitro. This behaviour might be correlated with a lengthening of the cell cycle (Tc). In vitro, the average durations of Tc (established by the percentage labelled mitoses technique) were 17.4–20.2 hr and 19.1–19.4 hr for pre‐odontoblasts and pre‐ameloblasts respectively. In vivo, the corresponding Tc values were 13.9 hr and 13.5 hr. The coordination of mitotic activities of pre‐odontoblasts and pre‐ameloblasts existing in vivo was maintained in vitro, and therefore seemed to require intra‐dental control mechanisms. Non‐specific extra‐dental serum factors may affect the duration of Tc.
Sensitivity to X‐irradiation in relation to cell size of CHO cells synchronized in early G1
Authors: Tobey R. A. , Crissman H. A. , Wilder M. E. , Traganos F. , Darzynkiewicz Z.
Published: May 2008

Abstract. 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.
A technique to analyse the emerging zonality of heterogeneous solid tumours
Authors: Michelson S. , Leith J. T. , Glicksman A. S.
Published: May 2008

Abstract A technique to analyse the time‐dependent emergence of homogeneous regions composed of cells from a single clone within an artificial (clonally) heterogeneous tumour is described. Neoplasms were grown in vivo as xenografts made from varying proportions of the dichotomous subpopulations (Clones A and D). They were sampled frequently for volume and composition. A variable number of tumour cross‐sections were taken as part of the sampling technique. The random subsamples obtained from each cross‐section were enzymatically disaggregated into single cells. From the single cell disaggregates the composition of the tumours was estimated. An estimator for the global proportion of cells was then calculated from all the single cell disaggregates. Time‐dependent changes in the overall composition of the tumour requires that a time‐dependent estimate of the global proportions of the subpopulations be calculated from each sample. Analysis of the sample proportions results in a statistic which can be tested for goodness‐of‐fit against a standardized normal variate as a test of emerging zonality.

Data from three artificial admixtures were examined. The results show that ‘zonality’, i.e. regions composed primarily of single subpopulations, emerges in all cases. However, the rate at which the zones emerge appears to depend on the ‘compositional stability’.

Robustness studies show that the technique is robust with respect to the global estimator of the proportion.
Sensitivity of flow cytometric data to variations in cell cycle parameters
Authors: Ubezio P. , Rossotti A.
Published: May 2008

Abstract We investigated to what extent flow cytometric DNA histograms are informative of cell cycle parameters. We created a computer program to simulate cell cycle progression in a generic and flexible way. Various scenarios, characterized by different models and distributions of cell cycle phase transit times, have been analysed in order to obtain the percentages of cells in the different cell cycle phases during exponential growth and their time course after mitotic block.

Cell percentages during exponential growth were insensitive to intercell variability in phase transit times and thus can be employed to estimate the relative mean phase transit times, even in the presence of non‐cycling cells. However, this information is ambiguous if re‐entry of such cells into the cycling status is permitted. The stathmokinetic outline gives the mean phase transit times, but also provides information about the spread, but not the form, of the phase transit time distributions, being particularly sensitive to the spread of G1 phase duration. The stathmokinetic outline also helps distinguish between scenarios considering only cycling cells, those forecasting a fraction of definitively non‐cycling cells and those admitting a Go status with first‐order output kinetics.
A study of cell migration in the adrenal cortex of the rat using bromodeoxyuridine
Authors: McNicol A. M. , Duffy A. E.
Published: May 2008

Abstract Bromodeoxyuridine (BrdU) was administered by a single intraperitoneal injection to immature (14 days) male and female and adult male Sprague‐Dawley rats. Animals were killed at intervals from 2 hr to 28 days following injection. Labelled cells in the adrenal cortex were identified by an indirect immunoperoxidase technique using a monoclonal antibody to BrdU. At 2 hr, labelling was maximal in the outer zona fasciculata and zona glomerulosa in both prepubertal and adult rats. The numbers of immunopositive cells were greater in the 14 day rats. In both groups, the front of immunopositive cells moved deeper into the cortex with time. These results support the centripetal migration theory of adrenal growth.
Psoriasis: hyperproliferation cannot induce characteristic epidermal morphology
Authors: Heenen M. , Galand P. , de Maertelaer V. , Heenen P. H.
Published: May 2008

Abstract A mathematical model of cell renewal in epidermis is proposed for describing how psoriatic lesions might develop, based on available cell kinetic data for normal and psoriatic epidermis. Our simulations clearly demonstrate that an increase in the turnover rate in the germinative cell population cannot alone induce the typical psoriatic tissue architecture (i.e. increased number of germinative cells). Two perturbations are needed to account for the morphology of clinically‐stable psoriatic lesions. The first corresponds to a temporary disturbance of the steady state of the germinative layer, resulting in limited growth of this compartment; the second perturbation corresponds to a reduction in transit time in the differentiated compartment. Moreover, our simulation, based on a widely‐accepted hypothesis of homeostatic control of tissue kinetics, demonstrates that the primary cause of typical psoriatic morphology is probably an alteration in epidermal maturation. In this view, depletion of differentiated cells at the surface is the stimulus for the increased cell production rate in the germinative population.
Analysis of the growth kinetics of murine erythroleukaemia cells following commitment to terminal differentiation
Authors: Fibach E.
Published: May 2008

Abstract Differentiation of murine erythroleukaemia cells by various inducers involves a step of irreversible commitment, after which the presence of the inducer is not required for completion of the process. Some cells become partially committed and give rise to differentiated as well as undifferentiated progeny. Commitment occurs asynchronously; under suboptimal inducing conditions, such as low concentration of inducer or short duration of exposure, both committed and uncommitted cells co‐exist. In the present study the growth of these subpopulations was compared. Murine erythroleukaemia cells were exposed to the inducer hexamethylene‐bisacetamide for 24 hr, then the inducer was removed by washing and the rate of proliferation of committed and uncommitted cells was measured. Commitment was scored by cloning the cells in inducer‐free semi‐solid medium and determining the cellular composition of the colonies with respect to haemoglobin content. The results indicated that following removal of the inducer the rate of proliferation was retarded similarly for both committed and uncommitted cells. Partially committed cells disappeared rapidly due to assymetrical cell division into fully committed and uncommitted cells. Both committed and uncommitted cells resumed logarithmic growth at 53 hr, but while uncommitted cells continued this pace until saturation was achieved, committed cells stopped multiplying earlier as a result of terminal differentiation.
An Autoradiographic Study of the Developing Parietal Cell Population In Neonatal Pigs
Authors: Darzynkiewicz Zbigniew , Tudor E. McI. , Hopper J. L. , Hannah† M. C.
Published: May 2008

Abstract. Autoradiographic labelling using tritiated thymidine ([3H]TdR) was used to examine the pattern of development of gastric parietal cells in newborn pigs. Specific objectives were to establish sites in the gland where cells with a characteristic parietal cell morphology first appear, the extent of their migration or displacement, and the kinetics of any development and migration that occurs. Five newly‐born littermate piglets were given a virtually continuous label of [3H]TdR over 24 hr, sacrificed at 1, 3, 5, 7 and 10 days thereafter, and samples of the gastric mucosa taken. the percentage of labelled parietal cells as a function of position in the oxyntic gland was measured for each pig. A generalized log linear model was fitted to the data using the statistical package GLIM, confirming a significant trend for labelled cells to occupy higher sites in the oxyntic gland as the time since labelling of cells increased. Goodness of fit tests showed that the trend effect was highly unlikely to be due to the variability of cell distribution from animal to animal. the dynamics of the parietal cell population and the strengths of GLIM for analysing cell labelling data are discussed.