bluuebunny/crossref_metadata_2025 huggingface dataset:
Rate of Incorporation of R3hlthymidine In Various Tissues of the Mouse A basis for the evaluation of genotoxic effects of chemicals
Authors: Hellman Björn , Ullberg Sven
Published: May 2008

Abstract. [3H]Thymidine has been extensively used as a selective precursor to DNA in studies on the kinetics of cell proliferation. We have become interested in measuring early inhibition of the DNA synthesis in various organs of intact animals for detecting genotoxic properties of chemicals. Such experiments should, for convenience and to achieve a large capacity, be performed in the simplest way possible.

The present paper deals with some practical aspects on the use of [3H]thymidine in vivo. [6‐3H]Thymidine was injected intraperitoneally in mice and the uptake of radioactivity was evaluated by using whole‐body autoradiography and liquid scintillation spectrometry. Autoradiograms of sections washed with trichloroacetic acid and methanol Were compared with those subjected only to freeze‐drying. Liquid scintillation counting was performed of total, non‐volatile, acid‐insoluble and dNA‐associated radioactivities. A rapid increase of the [3H]thymidine incorporation was seen during the first hour after the injection. Further prolongation of the survival time did not result in any significant increase of the incorporated radioactivity. Moreover, there were only slight differences between the autoradiograms from extracted and non‐extracted sections. Radioactivities asśociated with DNA closely eorrelated to those representing acid‐insoluble material, indicating that acid‐insoluble radioactivity provides a good estimate of the [3H]thymidine incorporation into DNA.
Kinetics of Cell Replacement In the Stratum Granulosum of Mouse Tongue Epithelium
Authors: Hume W. J.
Published: May 2008

Abstract. Sheet preparations of the stratum granulosum from the epithelium of the ventral surface of mouse tongue permit examination of cell replacement of this maturation compartment of the tissue. the cell transit rate/day is related to the cell desquamation rate and the cell production rate. the latter is approximately 6500‐8000 cells/mm2/day, suggesting a 4‐5‐fold greater turnover compared with mouse dorsal skin epithelium. the use of [3H]IUdR and [3H]TdR at different times of day provides evidence for a reutilization of label from [3H]TdR released during nuclear degradation in the stratum granulosum. Flooding with unlabelled thymidine is not effective in suppressing this reutilization.
Cytokinetic Analysis of the Expanding Kupffer‐Cell Population Inrat Liver
Authors: Bouwens L. , Baekeland M. , Wisse E.
Published: May 2008

Abstract. Zymosan stimulation in rats provides a useful model for studying the expansion of the Kupffer‐cell population in liver, which represents the major population of tissue macrophages. This study, using tritiated‐thymidine‐labelling experiments, demonstrates that during population expansion at least 90% of the resident macrophages (Kupffer cells) develop proliferative activity. the mean duration of the cell cycle is estimated to be 52 hr, with an S phase of 7 hr. We have calculated that about 75% of population expansion results from local Kupffer‐cell replication, whereas the remaining growth results from extrahepatic recruitment of macrophage precursors. These findings conflict with a concept of the mononuclear phagocyte system, which states that resident macrophages are (monocyte‐derived) non‐dividing end‐cells.
Methylmercury Effects On Cell Cycle Kinetics
Authors: Vogel D. G. , Rabinovitch P. S. , Mottet N. K.
Published: May 2008

Abstract. Methylmercury (MeHg) effects on cell cycle kinetics were investigated to help identify its mechanisms of action. Flow cytometric analysis of normal human fibroblasts grown in vitro in the presence of BrdU allowed quantitation of the proportion of cells in G1, S, G2 and the next G1 phase. This technique provides a rapid and easily performed method of characterizing phase lengths and transition rates for the complete cell cycle. After first exposure to MeHg the cell cycle time was lengthened due to a prolonged G1. At 3, μm MeHg the G1 phase length was 25% longer than the control. the G1/S transition rate was also decreased in a dose‐related manner. Confluent cells exposed to MeHg and replated with MeHg respond in the same way as cells which have not been exposed to MeHg before replating. Cells exposed for long times to MeHg lost a detectable G1 effect, and instead showed an increase in the G2 percentage, which was directly related to MeHg concentration and length of exposure. After 8 days at 5 μM MeHg, 45% of the population was in G2. the G2 accumulation was reversible up to 3 days, but at 6 days the cells remained in G2 when the MeHg was removed. Cell counts and viability indicated that there was not a selective loss of cells from the MeHg. MeHg has multiple effects on the cell cycle which include a lengthened G1 and decreased transition probability after short term exposure of cycling cells, and a G2 accumulation after a longer term exposure. There were no detectable S phase effects. It appears that mitosis (the G2 accumulation) and probably synthesis of some macromolecules in G1 (the lengthened G1 and lowered transition probability) are particularly susceptible to MeHg.
Analysis of the Changes In the Proportion of Clustered Labelled Cells In Epidermis
Authors: Loeffler M. , Potten C. S. , Ditchfield A. , Wichmannz H.‐E.
Published: May 2008

Abstract. A new cell kinetic approach is presented from which the duration of the S and G2+ M phases can be estimated. the technique involves an analysis of the spatial distribution of labelled cells in sections or sheets of epithelium (i.e. an analysis of clustered labelled cells). the technique is largely independent of the absolute number of labelled cells and hence is not influenced by factors which affect the absolute number of labelled cells. the technique is described and experimental data from dorsal murine skin are presented. the technique has also been simulated mathematically so that the phase durations and their variances could be estimated. the advantages of the technique are: (1) it is technically simple; (2) it provides at least two independent estimates of the phase durations; (3) unlabelled cells need not be counted (compare with LI or PLM analysis); (4) it is independent of variations in the absolute yield of labelled cells, and (5) it is applicable if the LI is low and the S phase is short (where the PLM technique tends to fail).
Eosinophilic Leucocytes and Phospholipase B of Rat Tissues
Authors: Ottolenghi Athos
Published: May 2008

Abstract. The correlation between the eosinophilic leucocyte population and the phospholipase B activity of rat tissues has been tested with isolated cell preparations from intestine, lung, blood, bone marrow and spleen containing eosinophils in varying proportions and with pure eosinophil fractions separated by centrifugation on discontinuous metrizoate and metrizamide gradients. A uniform value of activity per cell was found in all these tissues extending previous histochemical and biochemical evidence that the eosinophil is the carrier cell for the phospholipase B to all major sites of distribution. the enzyme marker approach has been used for estimating the normal eosinophil population of rat organs and show the distribution pattern of the eosinophils in peripheral organs in the wake of increased production and release from the marrow.
Negative Effect of Iodide On the Survival of Newly Divided Epithelial Cells In Chronically Stimulated Rat Thyroid
Authors: Rognoni J. B. , Penel C. , Golstein J. , Galand P. , Dumont J. E.
Published: May 2008

Abstract. The aim of this work was to investigate some aspects of the thyroid epithelial cell kinetics during the iodide‐induced involution of a hyperplastic goitre in the rat. Rats were made iodine‐deficient for 6 months, and propylthiouracil (PTU) (0.15%) was added to the diet during the last 2 months. Thereafter, rats were refed with iodide and PTU was removed (day 0).

Forty‐eight hours previously, all the rats were injected with tritiated thymidine ([3H]TdR) (1 μCi/g). Some animals were killed 1 hr or 24 hr after [3H]TdR injection (i.e. on day ‐2 and ‐1, day O corresponding to the restoration of a normal iodine diet); the other animals were killed after different delay periods and following L3H]TdR injection. Autoradiography of thyroid sections, iodine determination of plasma iodide and protein‐bound iodine (PBI), and RIA of plasma thyroid stimulatory hormone (TSH) were performed. Plasma TSH concentration was very high on day O of iodide refeeding (3000 ± 330 ng/ml) and remained at this level until day 8. Plasma PBI was very low on day O, remained so until day 4 and greatly increased on day 8. Plasma iodide was also very low on day O, but markedly increased on day 1, then did not vary significantly until day 43 of iodine refeeding. Thyroid weight, elevated on day O, decreased relatively quickly until day 30, then more slowly until day 73.
Infection of Haematopoietic Stem Cells In Mice With Friend Virus Induced Erythroleukaemia
Authors: Johnson Candace S. , Marcelletti John F. , Furmanski Philip
Published: May 2008

Abstract. Animals infected with conventional anaemia (FVA) or polycythemia‐inducing (FVP) strains of the Friend virus develop lethal erythroleukaemia. A variant strain, RFV, induces an initially identical disease except that it spontaneously regresses in 50% of infected mice. to determine whether pluripotent stem cells as measured by spleen colony forming units (CFU‐s) in leukaemic mice are productively infected with virus and whether their infection influences the outcome of the disease, we tested CFU‐s from leukaemic mice for susceptibility to cytotoxicity by monospecific antiviral gp70 antiserum. Spleen CFU‐s from progressively leukaemic (FVP, FVA and RFV) mice were productively infected with virus. CFU‐s in RFV progressors became infected by 40 days post‐virus inoculation. FVA and FVP progressors became infected between 15 and 21 days post virus. Infection of CFU‐s was accompanied by an increase in the proportion of replicating (S phase) CFU‐s in these populations. Spleen CFU‐s from fully regressed RFV regressor mice were uninfected and remained so throughout the course of their disease. Bone marrow CFU‐s in both regressors and progressors remained uninfected and were not induced to increased cell cycling.
Chromatographic Analysis of Gastrin‐Releasing Peptide In Heat‐Inactivated Fetal Calf Serum
Authors: Wiedermann C. J. , Goldman M. E. , Pert C. B.
Published: May 2008

Abstract. Gastrin‐releasing peptide and the carboxyterminal fragments gastrin‐releasing peptide [14‐27] and [18‐27] are found by radioimmunology and high performance liquid chromatography to be present in heat‐inactivated fetal calf sera. Peptides containing the carboxyterminal sequence of gastrin‐releasing peptide are known to display mitogenic activity. Thus, gastrin‐releasing peptide represents a new class of mitogenic factors that are present in heat‐inactivated fetal calf serum.
The Tropic Effect of Intrarectal Deoxycholate On Rat Colorectum Is Unaffected By Oral Metronidazole
Authors: Rainey J. B. , Maeda M. , Williamson R. C. N.
Published: May 2008

Abstract. Intrarectal administration of sodium deoxycholate (SDC) enhances experimental colorectal carcinogenesis, an effect that is partly vitiated by oral metronidazole. the effect of topical SDC with or without concurrent metronidazole on colorectal cell proliferation was explored in male Sprague‐Dawley rats (n= 30) allocated to five groups. Two groups received thrice weekly intrarectal instillations of 1 ml N saline or 1 ml 0.12 m SDC. A third group received SDC plus metronidazole 22.5 mg/kg/day in the drinking water. Controls had no instillations or metronidazole alone. At time of killing (10 weeks), crypt cell production rate (CCPR) was determined by the stathmokinetic technique for four large‐bowel segments. Saline had no significant effect on colorectal CCPR but SDC produced increases throughout, varying from 53% in the proximal colon to 222% in the rectum (P < 0.01). Metronidazole did not reduce this effect, although given alone it reduced colonic CCPR by 40 to 50%. the direct tropic effect of bile acids could largely explain their cocarcinogenic properties. Since metronidazole does not prevent this increase in cell proliferation, its mildly protective role against cancer may reflect the presence of fewer anaerobes capable of degrading bile acids to carcinogenic metabolites.
Distribution of Interdivisional Times In Proliferating and Differentiating Friend Murine Erythroleukaemia Cells
Authors: Axelrod David E. , Haider Fatema R. , Tate Ann C.
Published: May 2008

Abstract. The interdivisional times of Friend murine erythroleukaemia cells which are growing continuously, or during terminal erythroid differentiation after exposure to dimethyl sulphoxide (DMSO), were determined by time lapse video photography. the median interdivisional times were found to increase from 11.75 hr before exposure to DMSO, to 24.0 hr at 72 hr after exposure. This increase in median interdivisional time was accompanied by an increase in heterogeneity of interdivisional times (%CV= 8‐5 → 40.8), by an increase in the similarity of sister interdivisional times (ryy= 0.622 → 0.925), and by a decrease in the fraction of cells observed to divide (F= 1. 0 → 0.807). Cells exposed to DMSO for 72 hr can be induced to divide at least once with nearly normal interdivisional times, if they are resuspended at a tenfold higher cell concentration. Computer simulations of cell cycle regulation, based on the opposing reactions model of Murphy, generate interdivisional time distributions which resemble the experimental data better than the single transition probability model of Smith and Martin.
Cell Position Dependence of Labelling Thymidine Nucleotides Using the De Novo and Salvage Pathways In the Crypt of Small Intestine
Authors: Chwalinski S. , Potten C. S.
Published: May 2008

Abstract. About twice as much tritiated thymidine ([3H]TdR) is taken up by cells at the bottom of the crypt of the small intestine as by the rapidly cycling mid‐crypt cells. However, the uptake of tritiated deoxyuridine ([3H]UdR) is even throughout the crypt.

Exogenous thymidine is incorporated about four times and eight times more efficiently than deoxyuridine by the cells in the mid‐crypt and cells at the bottom of the crypt, respectively. However all S phase cells in the crypt appear to be capable of using either precursors, i.e. either the de novo or salvage pathway.

Since methotrexate (1 or 5 mg/kg) inhibits (at 5 mg/kg completely) the uptake of [3H]UdR, but has no effect on [3H]TdR uptake, the de novo and salvage pathways appear to be independent. Within the precision of the methods used in the experiments the 3 hr inhibition of the de novo pathway of deoxythymidylic acid (dTMP) synthesis by methotrexate does not produce any increase in utilization of the salvage pathway measured by incorporation of [3H]TdR into DNA. the increased efficiency of thymidine utilization by crypt base cells is not attributable to (i) differences in accessibility of thymidine; (ii) differences in the rate of DNA synthesis or (iii) the size of the nuclei.
A trophic effect of epidermal growth factor (EGF) on rat colonic mucosa in organ culture
Authors: Finney K. J. , Ince P. , Appleton D. R. , Sunter J. P. , Watson A. J.
Published: May 2008

Abstract. The development of an organ‐culture system for rat colonic mucosa has enabled a direct assessment of the effect of epidermal growth factor (EGF) on cell division. An augmented mitotic index (AIm) has been employed to identify changes in cell proliferation.

Explants of colonic mucosa from four animals were maintained in a medium containing serum for five days. On the fifth day of culture, half of the explants received fresh medium containing EGF (40 ng/ml) and the remainder (controls) fresh medium only. At 6,12,24 and 48 hr thereafter groups of both experimental and control explants received the metaphase‐arresting drug vincristine (4 μg/ml) for 3 hr prior to fixation. The proportions of vincristine‐arrested metaphases within the explants were determined. Analysis of the data indicates that when serum is present exogenous EGF exerts a trophic effect which increases with time (P < 0.001).

In a second experiment colonic explants from four animals were maintained for five days in a serum‐free medium and were then divided into groups, each of which received one of a range of concentrations of EGF. The AIm was determined for each group after 36 hr. It was found that increasing concentrations of EGF produce a small but significant increase in cell proliferation (P < 0.01). This effect, however, was less pronounced than that seen when serum was present.

These results suggest that EGF has a trophic action on the colon and interacts with additional factors found in serum.
Flow cytometric analysis of the recruitment of G0 cells in human epidermis in vivo following tape stripping
Authors: Boezeman J. B. M. , Bauer F. W. , de Grood R. M.
Published: May 2008

Abstract. Tape stripping of human skin elicits a proliferative response of a synchronously‐dividing group of cells. The progress of this cohort of cells has been monitored using two windows in the cell cycle, one located in mid‐S phase and the other centred around G2+ M. The cellular DNA is measured with flow cytometry, the windows are defined by two ranges in the DNA histogram.

The cohort can be described as the recruitment of cells from a pre‐existing G0 compartment which consists of 76% of all proliferative cells. The duration of the S phase is calculated to be 10.2 hr and G2+ M phase 5.1 hr. The cell cycle time of 39 hr for normal human keratinocytes derived from these figures is in line with recent values obtained by different techniques.
Modulation of in vitro thymidine incorporation into crypt cells from the murine small intestine
Authors: Speekenbrink A. B. J. , Parrott D. M. V.
Published: May 2008

Abstract. A method is described for the isolation of enriched populations of crypt cells from the murine small intestine. The method was developed to study the response of cells to various stimuli in vitro. The properties of the isolated cell preparations varied with the state of the intestinal mucosa of the mice from which they were isolated. Thus we could distinguish between cells from lactating and non‐lactating mice. Polyamines, which are putative modulators of crypt cell division, failed to stimulate [3H]TdR incorporation in vitro. Lymphocyte culture supernatants suppressed [3H]TdR incorporation at dilutions of 1:4 to 1:64. Supernatants of 12‐O‐tetradecanoylphorbol‐13‐acetate‐stimulated EL‐4 cells and of mixed lymphocyte cultures failed to stimulate [3H]TdR incorporation of any dilution. Supernatants of concanavalin A‐stimulated spleen cells gave less suppression of [3H]TdR incorporation than those of unstimulated spleen cells and stimulated incorporation at dilutions of 1:64 and 1:128. Phytohaemagglutinin stimulated [3H]TdR incorporation at high concentrations, whereas concanavalin A (con A) had no effect. This study shows that the isolated murine crypt cells may have the potential to provide a useful in vitro model for crypt cell responses to stimuli.
Mechanism of inhibition of junctional communication between animal cells by phorbol ester
Authors: Pitts J. D. , Burk R. R.
Published: May 2008

Abstract. The tumour promotor 4β‐phorbol 12‐myristate 13‐acetate (TPA) reduces the rate of junction formation between V79 Chinese hamster lung cells in culture but not between BHK21/13 Syrian hamster fibroblasts. TPA may act on all cells but only affect junction formation in those situations where the rate of junction formation is already low.
Determination of proliferative parameters from growth curves
Authors: Cowan R. , Morris V. B.
Published: May 2008

Abstract.Data on total cell numbers and proportions of non‐proliferative cells during the development of a tissue can be obtained by experiment. This paper shows, via a simple mathematical model, that data collected over a period of time determine the time profile of two proliferative parameters. These are the rate per proliferative cell per day at which cells divide and the average number of proliferative daughters which result from the division of a proliferative cell. One dataset alone does not provide sufficient information to determine either time profile. The findings are applicable where there is no significant cell death during the growth period. The mathematical model is fitted to data from chick neural retina.
Cell population kinetics in pig epidermis: further studies
Authors: Morris G. M. , Hopewell J. W.
Published: May 2008

Abstract. The cell population kinetics of the epidermis were studied in 4‐month‐old pigs. Mitotic figures were confined to the basal cell (L1) and the first suprabasal cell layer (L2). The mitotic index (MI) was 0.17 ± 0.04% for L1 and 0.08 ± 0.03% for L2. Labelled nuclei were distributed throughout the viable epidermis, the majority (79.1 ± 1.1%) were in L1 with 19.5 ± 1.2% in L2. The labelling indices (LI) in layers L1 and L2 were 7.1 ± 0.4% and 3.4 ± 0.1%, respectively. After labelling with two injections of tritiated thymidine [3H]TdR separated by 90 min, the LI increased to 8.2 ± 0.3% in L1 and to 4.0 ± 0.2% in L2. This increased labelling confirmed that cell proliferation occurs in both layers, L1 and L2, of the epidermis.

The cell production rate (K) in L1 and L2 had an upper limit of 10.7 ± 1.0 and 6.2 + 1.8 cells per 1000 cells per hour respectively. The cell flow rate per hour (cell flux), into and out of the DNA synthesis phase (S), and the duration of DNA synthesis were determined from double‐labelling studies with [3H]TdR and [14C]TdR. The cell flux into and out of S was identical and was calculated as 0.6 ± 0.1%/hr (L1) and 0.5 ± 0.1%/hr (L2). Values for tS varied from 8 to 10 hr. The cell turnover times (tT) were in the range 89–129 hr and 180–261 hr for L1 and L2, respectively.

Log normal curves were fitted to the fraction labelled mitoses data for L1 and L2. Values for tS for cells in L1 and L2 were 9.8 hr and 11.9 hr, respectively. tG2+ 1/2tM was 7.2 hr in L1 and 9.1 hr in L2.
Long duration of mitosis and consequences for the cell cycle concept, as seen in the isthmal cells of the mouse pyloric antrum. I. Identification of early and late steps of mitosis
Authors: El‐Alfy M. , Leblond C. P.
Published: May 2008

Abstract. In this series of two articles, the duration of mitosis and that of the cell cycle were examined in a group of proliferating cells located in the mouse pyloric antrum and known as isthmal cells. However, before measuring the duration of mitosis, as described in the second article, it is necessary to identify the early and late steps of the mitotic process. This is attempted in the present article, in which the four phases of mitosis and the interphase are described in semithin (0.5 μm thick) Epon serial sections stained with hemalun. The frequency of these phases is then estimated.

The beginning of prophase is indicated by the appearance in the nucleus of numerous 0.2‐0.3 μm thick basophilic threads. The threads gradually increase in thickness to become the typical chromosomes (about 0.7‐μm thick) observed at the end of prophase. Metaphase and anaphase show no remarkable features. At telophase, chromosomes separate from one another, gradually acquire pale segments along their length eventually to look like rows of alternating dark and light patches, and finally vanish.

When prophases and telophases are defined in this manner, the enumeration of isthmal cells yields a high proportion of prophases (28%) and telophases (31%), but a low proportion of metaphases (1%) and anaphases (0.3%). Forty per cent of the cells are in interphase.
Prolongation of cell cycle transit time and the presence of non‐cycling cells in human lymphoblastoid cells cultured under adverse conditions
Authors: Villiers C. L. , Adam F. K. A. , Miller N. , Brown D. , Hughes‐Jones N. C.
Published: May 2008

Abstract. The growth characteristics of B lymphocytes infected with Epstein‐Barr virus (lymphoblastoid cells) have been investigated by flow cytometric analysis of DNA content and by estimation of cell culture doubling times. It was found that the manipulative procedures involved in the cell cycle analysis resulted in a slowing of the growth rate. This slowing of growth was brought about by the prolongation of cell cycle transit times and by the entry of cells into a short‐lived non‐cycling pool. The entry of a proportion of the cells into the non‐cycling pool may be the normal response of lymphoblastoid cells to non‐optimal conditions. The non‐cycling cells survived in culture with a T1/2 of approximately 30–60 hr and continued to secrete immunoglobulin. Their surface transferrin receptors were considerably reduced, which suggests that the failure to divide may have resulted from a failure of growth factor receptors to reach a threshold value following mitosis.
Simultaneous staining of exponentially growing versus plateau phase cells with the proliferation‐associated antibody Ki‐67 and propidium iodide: analysis by flow cytometry
Authors: Baisch H. , Gerdes J.
Published: May 2008

Abstract. The antibody Ki‐67, which detects proliferating cells, was used in combination with propidium iodide, a DNA‐specific dye. The double‐staining method allowed discrimination of cells in the phases of the cell cycle as well as the recognition of Ki‐67 staining characteristics. Suspension cultures of U937 cells were measured in exponential growth and plateau phase in nutritional deprivation. The fraction of Ki‐67 positive cells was nearly 100% 2 days after dilution and 46% 7 days after dilution of the cultures. Stathmokinetic measurements with colchicine and flow cytometry measurements with the BrdU‐Hoechst technique yielded close to 100% proliferation at day 2 but only 18% and 6%, respectively, at day 7. The discrepancy between Ki‐67 results and the results of the two other methods is considered to be a characteristic of nutritionally deprived cells.
Stem cell maintenance and commitment to differentiation in long‐term cultures of murine marrow obtained from different spatial locations in the femur
Authors: Lorimore S. A. , Wright E. G.
Published: May 2008

Abstract. Murine bone marrow was separated into axial and marginal fractions in order to investigate the ability of cells from different spatial locations in the marrow to establish long‐term cultures. The maintenance of haemopoiesis was significantly poor in long‐term cultures of marginal marrow compared with axial or control (unfractionated marrow) cultures. Using techniques to further fractionate the axial or marginal marrow by depleting either stromal or haemopoietic cells, it was possible to investigate the relative importance of stromal and haemopoietic cell components. In the combinations studied, the more important determinant of effective in vitro haemopoiesis was the source of the haemopoietic cells rather than the stroma. The most effective stem cell maintenance and commitment to differentiation was observed when the source of the haemopoietic population was axial marrow. The data are consistent with axial marrow being a source of ‘high quality’ stem cells and this quality being an intrinsic property of the cells rather than one imposed by the stromal environment.
Cell cycle related [3H]thymidine uptake and its significance for the incorporation into DNA
Authors: Naito K. , Skog S. , Tribukait B. , Andersson L. , Hisazumi H.
Published: May 2008

Abstract. Cellular uptake of [3H]thymidine ([3H]TdR) and incorporation into DNA of Ehrlich ascites tumour cells were studied in relation to the cell cycle by measuring the activity in the acid‐soluble and insoluble parts of the cell material. Cells were synchronized at various stages of the cell cycle using centrifugal elutriation. The degree of synchrony of the various cell fractions was measured by flow‐cytofluorometric DNA analysis. From the cellular uptake, the TdR triphosphate (dTTP) concentration of a mean cell in an unseparated cell population was calculated to be 20 × 10‐18 mol/cell. The pool activity of G1 cells was unmeasurable but rose to maximum values at the border of the G1‐S phase. It decreased again during G2. The [3H]TdR incorporation into DNA was low during early S phase, reached a maximum value at two‐thirds of the S phase and decreased again during late S phase. These changes in DNA synthesis were not due to changes in the dTTP pool being a limiting factor. During maximum DNA synthesis, 10%× min‐1 of the dTTP pool was utilized, at which time the pool size also decreased by about 30%. Changes in pool size during the cell cycle have to be taken into account when the results of incorporation of radioactive TdR into DNA are discussed.
Measurement of the transit time for cells through the epidermis and stratum corneum of the mouse and guinea‐pig
Authors: Potten C. S. , Saffhill R. , Maibach H. I.
Published: May 2008

Abstract A new approach to determine the transit time through the epidermis is presented, involving a gentle washing of the skin surface to collect the loosely attached surface corneocytes. This, it is believed, will be less likely to stimulate the system than tape‐stripping or scraping. Radioactively labelled thymidine and iododeoxyuridine have been used to label cells in the basal layer and various labelled amino acids (glycine, cystine and methionine) have been used to label the metabolically viable cell layers (up to and including the granular layer). The resulting changes in surface radioactivity levels have been interpreted to provide a basal to surface transit time of 8–9.5 days for hairless and haired mouse epidermis and about 13.5 days for guinea‐pigs. The basal to granular layer transit time, which probably includes some basal layer residence time, is about 4.5 days in the mouse and 8 days in the guinea‐pig. The granular to surface time in mice is about 5 days. The results also suggest that when nuclear and cytoplasmic organelles are degraded in the granular layer, material is released that can diffuse rapidly through the stratum corneum to the surface. Some of this can be shown by chromatography to be thymidine. Hence, the stratum corneum is pervious to molecules such as nucleosides. This rapid diffusion outwards through the skin can also be detected shortly after injecting [125I]‐iododeoxyuridine.
In vitro effect of a glycopeptide acting in vivo on hepatocyte cell cycle
Authors: Lombard M.‐N. , Nadal C. , Monnot M.‐J.
Published: May 2008

Abstract A factor specifically inhibiting the hepatocyte cell cycle in vivo was found to block the G1‐S transition of liver cells in vitro. It proved to be non‐toxic in our culture conditions, as judged by the reversibility of the effect on cell proliferation. It was not active on DNA synthesis in fibroblastic cell lines (3T3).
A modification of the grain count halving method for detailed analysis of cell kinetic parameters
Authors: Bassukas I. D. , Maurer‐Schultze B.
Published: May 2008

Abstract A modification of the conventional grain count halving (GCH) method is presented. By determining the decrease of the mean grain number of all interphase cells in addition to that of all labelled interphase cells on the same autoradiographs, the potential doubling time Tpot (or the cell production rate kp) can be obtained in one and the same experiment. Thus the modified GCH method provides not only the cycle time of the cell population studied but also the growth fraction and, with additional cytofluorometric measurements, the duration of all cycle phases. By evaluating the cell production rate and the growth fraction this method leads to more reliable cell kinetic data of experimental tumours and human tumours growing in nude mice. In contrast to other cell kinetic methods, the modified GCH method can also be applied in special cases to human tumours in vivo, since only few points of measurement are needed. A comparison of the cell kinetic results obtained by the modified GCH method with those derived from the fraction of labelled mitoses method, both applied to allotransplants of the adenocarcinoma EO 771 in nude mice, shows good agreement.
The kinetics of pre‐antral follicle development in ovaries of CBA/Ca mice during the first 14 weeks of life
Authors: Faddy M. J. , Telfer E. , Gosden R. G.
Published: May 2008

AbstractThe kinetics of ovarian follicle growth and death have been estimated in virgin inbred mice using a compartmental model and data obtained from differential follicle counts in histologically sectioned ovaries. The results showed that both growth and death rates are dependent on stage of development, defined by the compartments, and age, indicated in the model by step functions with transitions at 20 and 60 days of age. During the initial phase of postnatal ovarian development, large numbers of follicles disappeared from the non‐growing reserve as a result of the combined effects of follicle death and recruitment into the growing population. The reduced death rate after 20 days led to a secondary peak in the numbers of follicles at intermediate stages. In contrast to these fluctuations, the number of large follicles, including pre‐ovulatory types, were remarkably constant after this age and the rate of outflow stabilized at two to three follicles per day after an initially high value. This rate is sufficient for the normal ovulation rate in a 4‐day oestrous cycle with a small surplus of follicles undergoing atresia. The rates of migration through successive stages of development decreased during ageing as large follicles began to emerge at the approach of puberty: this result may indicate that the recruitment of small growing follicles is influenced by a feedback effect.
Population dynamics of the murine lymphokine activated killer system: precursor frequency and kinetics of maturation and renewal
Authors: Owen‐Schaub L. B. , III G. P. Hemstreet , Hemingway L. L. , Abraham S. R. , DeBault L. E.
Published: May 2008

Abstract The proliferation kinetics and population renewal of recombinant interleukin‐2 (rIL‐2)‐induced murine lymphokine activated killers (LAK) arising from splenic precursors was studied. Extensive proliferation has been shown to accompany the de novo generation of LAK cytotoxicity. In this report, a thymidine ‘hot pulse’ suicide technique was employed to examine the sensitivity of LAK progenitors during various time periods following culture initiation. Hot pulse during the first 24 hr of culture resulted in a 30–35% reduction in lytic activity when assayed on day 5. Pulse periods between days 1 and 4 resulted in almost complete inhibition (90–95%) of lytic function when assayed on day 5. Proliferation of LAK progenitors was documented by limiting dilution analysis comparison of splenic precursors and functionally mature LAK cultures. These studies showed a 75‐ to 80‐fold enrichment of LAK progenitors after 3 days culture in rIL‐2. By flow cytometric cell cycle analysis, we demonstrated that the number of cells in the S/G2/M phase increased with the length of rIL‐2 culture and represented approximately 40% of the cells by day 4. Finally, we used the rate of decay of lytic activity following irradiation as a factor to define the mean life span of a cytotoxic effector in the absence of cellular input. An exponential decrease to approximately 50% of controls was observed within 8–9 hr after irradiation. Taken together, these results suggest that the LAK system is highly dynamic and requires continuous cellular proliferation for its maintenance.
Cycle reset in a melanoma cell line caused by cooling
Authors: Dewey D. L.
Published: May 2008

Abstract When cells in culture are released from G0 into cycle by diluting into fresh medium there is a delay of many hours before they re‐enter the cycle and start DNA synthesis. A mouse melanoma cell line designated HP2 has been used to investigate the effects of non‐standard temperatures between the time of plating and DNA synthesis. When the cells were incubated in a 5% CO2 box at 8°C for periods during the G0‐G1 transition there was an extra delay before the start of S, approximately equal to the time that the cells were held at 8°C and independent of the time when the cold pulse was administered. When the cells were cooled to 25°C the delay was longer than the time for which the cells had been kept at 25°C, and this extra delay was also dependent on the point in G0‐G1 when the cells were cooled, as though the cells could be reset to an earlier time by this treatment. It is suggested that a labile substance required for progression is destroyed faster than it is made at 25°C but at 8°C the rate of destruction is very low. Another phenomenon noted during these cooling experiments was that the peak height of the S phase profile, as measured by frequent pulse‐thymidine incorporation experiments, was substantially higher for cells which had been cooled at a later stage in the G0‐G1 transition, even though the overall times at 37°C and at the colder temperature were identical. By varying the temperature of the cold pulse it was possible to separate the change in the peak height and the delay as separate entities.
Cell Kinetic Study of Human Carcinomas Using Bromodeoxyuridine
Authors: Kikuyama Shigehiro , Kubota Tetsuro , Watanabe Masahiko , Ishibiki Kyuya , Abe Osahiko
Published: May 2008

Abstract. Cell kinetics in human malignant tumours were studied in vivo using bromodeoxyuridine (BrdU) and immunohistochemistry. BrdU was administered to twenty‐four patients with gastric cancer at a dose of 1 g pre‐operatively. Specimens were obtained during the operation, fixed in 70% ethanol and embedded in paraffin. BrdU‐incorporating cells were detected by immunohistochemical staining using anti‐BrdU monoclonal antibody. the labelling index (LI), determined by counting tumour cells microscopically, ranged from 4.0 to 41.4%. the LI was higher at the site of invasion than in the central area of the tumour, but no correlation was found between histological differentiation and LI. the LI of stage I gastric cancer was statistically lower than that of stage II, III and IV gastric cancers (P < 0.005). This technique, which is less cumbersome and time‐consuming than using radioactive isotopes of thymidine, appears to be useful for studying cell kinetics of human malignant tumours.
Commitment to Ploidy Conversion of 3y1 Cells During Metaphase Arrest By Colcemid
Authors: Okuda A. , Kimura G.
Published: May 2008

Abstract. Diploid rat 3Y1 fibroblasts proliferate to a saturation density, where they are arrested with a 2N DNA content. After treatment to induce ploidy conversion, the conversion rate can be estimated by determining the fraction of cells with a 4N DNA content in the confluent culture using flow cytometry. Using this method it was found that during mitotic inhibition with colcemid, 3Y1 cells were converted to tetraploids with a high efficiency (above 80%); the optimum colcemid concentration and exposure period were 40 ng/ml and 8 hr, respectively. When metaphase cells were reseeded with 40 ng/ml of colcemid, they delayed anchorage to a dish; 6 hr was required for complete adhesion (in the absence of colcemid only 1 hr was required). When reseeded metaphase cells were exposed to 40 ng/ml of colcemid for 5 hr followed by its removal, a greater fraction of the cells anchored to the substratum were converted to tetraploids, whereas most of the floating cells were not. A greater fraction of the anchored cells had formed nuclei, whereas most of the floating cells preserved condensed metaphase chromosomes. These results indicate that the cells which have formed nuclear structure without chromosome separation during mitotic inhibition are irreversibly committed to ploidy conversion, with restoration of anchorage.
A Kinetic Method to Determine the Cell Cycle Times of Chick Skin Fibroblast Subpopulations
Authors: Angello J. C.
Published: May 2008

Abstract. We have inferred, from computer simulations of clonal growth data, mean cell cycle time (Tc) for putative subpopulations of fibroblastic cells having unique replicative potentials. the growth kinetics of chick embryo fibroblast clones can be accounted for if it is assumed that: (1) there is a transient, and rather substantial, decline in mean Tc (from 34 to 12 hr) immediately following the commitment of a ‘stem’ cell daughter to a limited replicative lifespan; (2) the mean Tc increases progressively (from 12 to 48 hr) as ‘committed’ cells exhaust their remaining replicative potential; and (3) the daughters of committed cells may occasionally become abruptly post‐mitotic.
The Cell Cycle of Spermatogonial Colony Forming Stem Cells In the Cba Mouse After Neutron Irradiation
Authors: Bootsma A. L. , Davids J. A. G.
Published: May 2008

Abstract. In the CBA mouse testis about 10% of the stem cell population is highly resistant to neutron irradiation (Do, 0.75 Gy). Following a dose of 1.50 Gy these cells rapidly increase their sensitivity towards a second neutron dose and progress fairly synchronously through their first post‐irradiation cell cycle. From experiments in which neutron irradiation was combined with hydroxyurea it appeared that in this cycle the S‐phase is less radiosensitive (Do, 0.43 Gy) than the other phases of the cell cycle (Do, 0.25 Gy). From experiments in which hydroxyurea was injected twice after irradiation the speed of inflow of cells in S and the duration of S and the cell cycle could be calculated. Between 32 and 36 hr after irradiation cells start to enter the S‐phase at a speed of 30% of the population every 12 hr. At 60 hr 50% of the population has already passed the S‐phase while 30% is still in S. the data point to a cell cycle time of about 36 hr, while the S‐phase lasts 12 hr at the most.
Growth of Im‐9 Human Lymphoblasts In Serum‐Free Medium: Stimulation By Glucocorticoids
Authors: Straus D. S.
Published: May 2008

Abstract. The IM‐9 human B‐lymphoblast cell line grows well in a completely defined serum‐free medium containing insulin, transferrin, low density lipoprotein and oleic acid in complex with fatty acid‐free bovine serum albumin. Growth of the IM‐9 cells is stimulated by addition of physiological concentrations of hydrocortisone to this medium. the order of growth stimulatory potency of several steroids is dexamethasone > hydrocortisone > aldosterone, whereas testosterone does not stimulate growth of the IM‐9 cells. This order of potency suggests that the effect is mediated by binding to glucocorticoid receptors. Growth of the IM‐9 cells is also stimulated by the neuropeptide substance P. the defined serum‐free medium described in this report will be useful for further studies of the biological responses of the IM‐9 cells to other hormones in the absence of interference from hormones and growth factors present in serum.
Acute and Subacute Effects of Thiamine Deficiency On the Morphometry and Cell Kinetics of Jejunal and Ileal Epithelial Cells
Authors: Cipriano T. C. , Zucoloto S. , Muccilot G. , Kajiwara J. K.
Published: May 2008

Abstract. The effects of acute and subacute thiamine deficiency on jejunal and ileal epithelial cells were studied in rats, using crypt and villus cell population, crypt cell production per crypt (CCPC), crypt growth fraction (Ip) and crypt cell cycle time (Tc) as parameters. In acute thiamine deficiency there was marked jejunal hypoplasia of the crypt and villus, but in the ileum there was hypoplasia only of the crypt. the jejunal epithelium of the subacute thiamine deficiency (STD) group showed no morphometric changes. In contrast, in the ileal epithelium of STD rats there was decreased crypt depth and villus cell population. Thiamine deficiency had no significant effect on CCPC, Ip and Tc.
Intestinal Crypt Proliferation. Ii. Computer Modelling of Mitotic Index Data Provides Further Evidence For Lateral and Vertical Cell Migration In the Absence of Mitotic Activity
Authors: Loeffler M. , Potten C.S. , Paulus U. , Glatzer J. , Chwalinski S.
Published: May 2008

Abstract. The position‐dependent mitotic index before, and 1, 2 and 3 h after vincristine was scored. the accumulation of cells in mitosis leads to an increase in the mitotic index from 0.06 to 0.34 at crypt positions 8‐12. Surprisingly, the leading edge of the position‐related mitotic index distribution moves to higher crypt positions although cell division was stopped. In addition, the vertical clustering of mitotic figures in sections was recorded. the data were examined using a previously described computer crypt model. We conclude: the average mitotic phase duration is about 0.7 h (40 min) and varies little with cell position; the geometrical correction factor for overscoring mitoses in crypt sections is about 0.6‐0.7 and adjacent cell columns can merge. Lateral cell displacement after mitosis, as predicted in a previous model analysis, would be a mechanism to counteract other forces that tend to reduce the crypt circumference. In the normal steady state merging and expansion processes would just balance each other. This would not follow if one mechanism was blocked. Thus we propose a new concept in which the crypt geometry would be dynamically determined by cell proliferative activity in connection with lateral positioning of new cells on one hand and contracting forces on the other hand.
Epidermal Tissue Homeostasis.
Authors: Budtz P. E.
Published: May 2008

Abstract. It has previously been shown that in toad epidermis the cell birth rate (Kb) exceeds the rate of cell loss through moulting (Kb) and that the ‘surplus’ of cells seems to be removed in a controlled manner. Assuming that the epidermis is non‐expanding, a Kb/Kd ratio > 1 indicates that cell deletion additional to desquamation takes place. In normal toads this ratio is 2‐3. Following implantation of hydrocortisone pellets into intact toads (release rate, 18 μ/g toad/d), the Kb/Kd ratio, over a period of 14 d of hormone treatment, had increased to about 7, due mainly to an increased Kb and to a lesser extent to a decreased Kd. No change in the epidermal cell pool size had taken place. It was previously shown that, following removal of the pars distalis of the pituitary gland, the Kb/Kd ratio decreased with time, due to a decreasing Kb and an increasing Kd, eventually leading to a decreased epidermal cell pool size. In this paper it is shown that, in pars distalisectomized toads with hydrocortisone pellets implanted, the Kb/Kd ratio is restored to control levels by a restoration of the Kb as well as the Kd. the results differ from those of previous studies in which ACTH or adrenocortico‐steroids were administered discontinuously (by injection). Thus, by experimental manipulation, different Kb/Kd ratios can be obtained: low (< 1, pars distalis ablation), medium (2‐3, normal toads) and high (7, hydrocortisone implantation). the potentiality of this unique situation in analysing the important question of how the ‘surplus’ cells are deleted is discussed.
Mathematical Analysis of Haemopoietic Grafted Cell Renewal and Migration Through the Allogeneic Or Syngeneic Mouse Host
Authors: Spach C. , Motta R.
Published: May 2008

Abstract. A mathematical analysis of results from kinetic studies of 125‐iododeoxyuri‐dine uptake and loss in almost all the lymphoid and non‐lymphoid organs of mice is described. Applied to data gathered from a graft‐versus‐host reaction experiment, this analysis affords quantitative precision on the differential effects of organ alloantigens on the proliferating grafted cells. It is shown that, depending on the organ and the post‐graft period, cell growth can be ascribed to alloantigen‐driven cell renewal or to alloantigen‐driven trapping or sequestration. Possible applications of the present approach in graft rejection monitoring are discussed.