bluuebunny/crossref_metadata_2025 huggingface dataset:
Radioautographic studies on the formation and maturation of bone marrow lymphocytes in mice
Authors: Yoshida Y. , Boku E. , Ohkubo T. , Kamamoto T. , Hiraoka A. , Yamagishi M. , Uchino H.
Published: May 2008

Abstract. DNA labelling by [3H]thymidine and the sandwich radioimmunolabelling method were used to characterize marrow lymphoid cells and to study the kinetics of production and maturation of small lymphocytes in the bone marrow of adult mice. Marrow lymphoid cells consisted of non‐proliferating small lymphocytes, 30–40% of which had detectable surface immunoglobulin (SmIg), and proliferating large lymphoid cells lacking SmIg. Double‐labelling experiments employing [3H]thymidine in vivo followed by sandwich radioimmunolabelling in vitro indicated that marrow small lymophocytes lack detectable SmIg when they are formed but develop SmIg within the first few days after production. Marrow lymphocytopoiesis includes; (1) praliferation of large lymphoid cells, which are presumptive small lymphocyte progenitors, which have a cell cycle time of 14–15 hr, and (2) a 3–5‐day intramyeloid stage when many newly formed small lymphocytes undergo maturational changes towards the B cell lineage.
Characteristics of the Cfu‐S Population In Mice Carrying the SlJ Allele
Authors: Ploemacher R. E. , Brons N. H. C.
Published: May 2008

Abstract Abstract. A tentative characterization of haemopoietic stem cells with respect to their organ distribution, seeding fraction and colony formation in the spleen, radiosen‐sitivity and humoral regulation was attempted in mice heterozygous for the mutant allele SlJ and in their normal littermates. SlJ/+ mice were characterized by a deficient CFU‐s content of the blood and spleen and had slightly lower femoral CFU‐s numbers. This CFU‐s distribution could not be explained by differences in seeding efficiency ‘f’ between CFU‐s of SlJ/+ and +/+ origin in lethally irradiated recipients used in the CFU‐s assay. the seeding fraction of CFU‐s of +/+ origin did not differ in +/+ and SlJ/+ recipients. However, in irradiated SIJ/+ recipient mice a 30% decrease was observed in the number of the colonies derived from splenic and femoral CFU‐s of both +/+ and SlJ/+ origin. the serum level of SHSF (splenic haemopoiesis stimulating factor) was decreased in SlJ/+ mice, but significantly increased in Sl/Sld mice, as compared to their respective normal +/+ littermates. Endogenous colony formation in SlJ/+ spleens was deficient in comparison to that observed in +/+ spleens, and distinct sex differences were observed. However, mutant and normal CFU‐s from spleen and bone marrow had a similar survival following in‐vitro y irradiation.

Femurs and spleens of both SlJ/+ and +/+ origin were implanted into both SlJ/+ and +/+ hosts. Six weeks later the SlJ/+ grafts contained less CFU‐s than the +/+ grafts.

These data show that the splenic stroma of SlJ/+ mice is not defective in its capacity to lodge injected CFU‐s but is deficient in its ability to maintain CFU‐s under ‘steady‐state’ conditions and stimulate their colony formation in a ‘perturbed state’. Some of the characteristics of SlJ/+ mice segregate them from Sl/Sld mice, i.e. a deficient splenic CFU‐s content, normal seeding fractions ‘f’ of CFU‐s from spleen and bone marrow in the presence of an almost compensated anemia, and decreased serum levels of SHSF. the study of the SlJ trait may be a useful extension of the current Sl/Sld model for exploration of hereditary defects in haematopoietic stroma.
Can Nocodazole, an Inhibitor of Microtubule Formation, Be Used to Synchronize Mammalian Cells?
Authors: Nüsse Michael , Egner Hans Joachim
Published: May 2008

Abstract Nocodazole, a temporary inhibitor of microtubule formation, has been used to partly synchronize Ehrlich ascites tumour cells growing in suspension. the gradual entry of cells into mitosis and into the next cell cycle without division during drug treatment has been studied by flow cytometric determination of mitotic cells, analysing red and green fluorescence after low pH treatment and acridine orange staining. Determination of the mitotic index (MI) by this method has been combined with DNA distribution analysis to measure cell‐cycle phase durations in asynchronous populations growing in the presence of the drug. With synchronized cells, it was shown that in the concentration range 0.4–4.0 μg/l, cells could only be arrested in mitosis for about 7 hr and at 0.04 μg/ml, for about 5 hr. After these time intervals, the DNA content in nocodazole‐blocked cells was found to be increased, and, in parallel, the ratio of red and green fluorescence was found to have changed, showing entry of cells into a next cell cycle without division (polyploidization). It was therefore only possible to partially synchronize an asynchronous population by nocodazole. However, a presynchronized population, e.g. selected G1 cells or metabolically blocked G1/S cells, were readily and without harmful effect resynchronized in M phase by a short treatment (0.4 μg/ml, 3–4 hr) with nocodazole; after removal of the drug, cells divided and progressed in a highly synchronized fashion through the next cell cycle.
The Proliferative Status of Microcolony‐Forming Cells In Mouse Small Intestine
Authors: Hendry J. H. , Moore J. V. , Potten C. S.
Published: May 2008

Abstract The technique of thymidine (TdR) suicide has been used with the intestinal microcolony assay to demonstrate that in the middle of the light cycle, nearly all intestinal clonogenic cells, in the B6D2F1 mice used in these experiments, were not in S phase. Doses of tritiated thymidine [3H]TdR up to 1 mCi/mouse did not kill a significant fraction of those clonogenic cells which survived a test dose of 12 Gy γ‐rays. This finding supports some data in the literature, but conflicts with others. However, the suicide technique was found in the studies reported here to be very efficient in sterilizing clonogenic cells in the middle of the dark cycle, and also in a regenerating epithelium at day 3 after a dose of 9 Gy. This implies that the technique can discriminate well between populations of clonogenic cells which differ in their content of cells in S phase. the lack of a suicide effect in the middle of the light cycle indicates that the majority of proliferative epithelial cells are not clonogenic.
A Convenient Source of Cfu‐S Inhibitors: the Fetal Calf Liver*
Authors: Guigon M. , Wdzieczak‐Bakala J. , Mary J. Y. , Lenfant M.
Published: May 2008

Abstract The presence of a bone‐marrow stem‐cell inhibitor able to prevent CFU‐s entry into DNA synthesis after cytosine arabinoside (Ara‐C) treatment has been detected in 7‐month‐old fetal calf liver. the inhibitory fraction was obtained through ultrafiltration of a delipidated tissue extract powder and purified by BioGel‐P‐2 chromatography. the elution pattern on Sephadex G10 is similar to that of the bone‐marrow inhibitory extract previously obtained from fetal calf bone marrow. It corresponds to a low‐molecular‐weight molecule (MW > 2000), devoid of species specificity and having no inhibitory effect on GM‐CFC proliferation.
Murine Mammary Tumour Cells In Vitro. I. the Development of A Quiescent State
Authors: Wallen C. Anne , Higashikubo R. , Dethlefsen L. A.
Published: May 2008

Abstract Three mouse mammary tumour lines (66, 67, and 68H) derived from a single mouse mammary tumour were investigated for their growth kinetics and development of quiescent cells in unfed monolayer cultures. All three lines develop pure quiescent populations when grown in unfed plateau cultures. A dramatic cell‐cycle redistribution accompanied the proliferating (P) to quiescent (Q) transition, with the percentage of cells having a G1 DNA content increasing from 50% in the P state to <97% in the Q state. As the cultures progressed from exponential to plateau growth, a decrease of 50% in cellular RNA was observed in all three lines. This property enables the clear identification of P v. Q cells by flow cytometry using the two‐step acridine orange assay. Autoradiographic data verified that these plateau cells were quiescent since >2.5% of the cells incorporated [3H]TdR when labelled for approximately two doubling times. Further comparison of the P and Q cells showed that: (a) the Coulter volume of Q cells was approximately half that of P cells in all three lines; (b) viability, as measured by dye exclusion was >95% in all cultures regardless of their proliferative state; and (c) colony‐forming ability decreased as the cells entered the quiescent state. In each of these cell lines the development of Q‐cell populations was marked by similar changes in all measured parameters. These quiescent tumour cells provide a relatively simple model to evaluate what, if any, important differences exist between the response of P v. Q cells to various therapeutic agents.
Murine Mammary Tumour Cells In Vitro. Ii. Recruitment of Quiescent Cells
Authors: Wallen C. Anne , Higashikubo R. , Dethlefsen L. A.
Published: May 2008

Abstract The development of a pure quiescent (Q) tumour cell population can be induced in three mouse mammary tumour lines (66, 67 and 68H) by nutrient deprivation. When these Q cells were removed from nutrient‐deprived cultures and replated in fresh medium at a lower cell concentration within 72 hr of entering quiescence virtually all of the Q cells could re‐enter the proliferating (P) state. This recruitment was characterized by an increase in cell volume, an increase in total cellular RNA, and a resumption of cell division. the length of the Q to P transition varied among the three cell lines and the depth of the quiescent state depended on the amount of time the cells had been quiescent. Once re‐entry into the P compartment was completed, cell‐cycle times, as estimated by the culture doubling time, were the same as the cells that had not entered the Q state. however, after 72 hr in quiescence, not all of the 66 cells could reattach after trypsinization and of those that could reattach 50% were incapable of either increasing their RNA levels to that of proliferating G1 cells or entering S. Clonogenicity of the nutrient‐deprived Q cells in these lines decreases exponentially from time the cells enter quiescence with approximate half‐times of 32, 34, and 96 hr for the 66, 68H and 67 cells, respectively. Slnce clonogenicity was already declining at a time when all the Q cells could re‐enter the P compartment, the ability of a Q cell to form a colony is not determined solely by its capacity to re‐enter the proliferating compartment.
Growth and Vascular Structure of Human Melanoma Xenografts
Authors: Rofstad Einar K.
Published: May 2008

Abstract The growth and the vascular structure of five human melanomas grown in athymic nude mice were studied. Four growth parameters (tumour volume doubling time, fraction of cells in S‐phase, growth fraction, cell‐loss factor) were analysed against each of four vascular parameters (length of vessels with diameters in the range 5–15 μm, total vessel length, total vessel surface, total vessel volume‐all per unit of histologically intact tumour volume). Statistically significant linear correlations between the parameters were found for any of the combinations. However, there was a consistent trend in the data: the tumour volume doubling time and the cell‐loss factor tended to decrease while the fraction of cells in S‐phase and the growth fraction tended to increase with increasing vascular density, whichever vascular parameter was considered. This finding indicates that the vascular density is among the factors which are decisive for the growth rate of tumours. However, the present work does not exclude the possibility that intrinsic properties of the tumour cells may also be important.
Analysis of X‐Ray‐Induced Cell‐Cycle Perturbations In Mouse Osteosarcoma Cells: A Two‐Signal Cell‐Cycle Model
Authors: van Meeteren A. , van Wijk R. , Stap J. , Deys B. F.
Published: May 2008

ABSTRACT The effects of X‐irradiation on mouse osteosarcoma cells have been studied by time‐lapse cinematography and the resulting pedigrees have been analysed statistically. It is shown that the irradiation treatment causes three types of cell kinetic lesions: cell death (disintegration), cell sterilization (failure to divide) and proliferation delay. the first two lesions are the most important with regard to survival of the irradiated cell in a clonal assay. of these two lesions, sterilization appears to be highly correlated for sister cells, while this is not true for cell disintegration. This indicates that cell survival in a clonal assay may be a function of the ratio of the incidences of these two types of lesions. the X‐ray‐induced proliferation delay was studied in terms of intermitotic time distributions, mother‐daughter correlation and sibling correlation in relation to the current cell‐cycle phase at the time of treatment. This analysis shows that the effects of irradiation on these cell‐cycle characteristics is highly cellcycle‐dependent. A qualitative model to account for the observations is presented.
Evaluation of the Effects of Pentagastrin, Gastrin and Pancreatic Glucagon On Cell Proliferation In the Rat Gastrointestinal Tract
Authors: Fatemi S. H. , Cullan G. E. , Sharp J. G.
Published: May 2008

ABSTRACT The effects of six injections of a range of doses (100–1000 μg/kg bodyweight) of pentagrastrin and single injection of a range of doses of porcine gastrin (10–40 μg/kg bodyweight) and pancreatic glucagon (25–100 μg/kg bodyweight) on cell proliferation in the intestine of fasted rats has been investigated. the end‐point employed included the measurement of 14C leucine incorporation and thymidine‐derived tritium content of the body of the stomach, duodenum, jejunum, ileum and colon. the carbon 14 and tritium content per μg of tissue in triplicate samples of fifty individually dissected crypts of glands were determined. From these data and the wet weight of the washed, blotted, intestinal segments, values for crypts/μg tissue and crypts/segment were calculated. the results demonstrated that pentagastrin at physiological doses decreased cell proliferation slightly in stomach, while gastrin and glucagon were without effect. In the small intestine, pentagastrin and gastrin were without significant effect with the exception that they increased the weight of the duodenum. In contrast, a high physiological dose of glucagon increased DNA and protein synthesis throughout the small bowel, but particularly in the ileum. Pharmacological doses of pentagastrin and all doses of gastrin appeared to increase cell proliferation in the colon although the possibility could not be excluded that this was due to stimulation of precursor uptake. Gastrin also increased colonic weight. Glucagon had no effects in the colon. These observations are compatible with the hypothesis that (i) the primary effects of gastrin and pentagastrin on the proximal intestine are as secretogogues and effects on cell proliferation may be secondary, (ii) gastrin and pentagastrin at physiological levels do not stimulate small intestinal cell proliferation, however glucagon does, and (iii) gastrin at physiological levels and pentagastrin at pharmacological levels may stimulate cell proliferation in the colon.
Spermatogonial Multiplication In the Chinese Hamster. Iv. Search For Long Cycling Stem Cells
Authors: Lok D. , Jansen M. T. , de Rooij D. G.
Published: May 2008

ABSTRACT In the Chinese hamster, 17 days, i. e. one cycle of the seminiferous epithelium, after two injections of [3H]TdR given 24 hr apart, labelled cells were found among all types of spermatogonia, including stem cells (As). These labelled As spermato‐gonia derive from one or more self‐renewing divisions of the stem cells that originally incorporated [3H]TdR. In the steady state, half of the divisions of the As will be self‐renewing and the other half will give rise to Apr spermatogonia that will ultimately become spermatozoa. Theoretically, the labelling index (LI) after 17 days will be similar to that after 1 hr, and in this study twice as high as for the 1‐hr interval since only one injection was given. However, experimental values only half that of the theoretical LI were found after 17 days. the following causes for the loss of labelled stem cells are discussed: (1) dilution of label because of division; (2) influx of unlabelled components of false pairs (i. e. newborn stem cells that still have to migrate away. mostly during G1, from their sister cells and are scored as Apr spermatogonia) between 1 hr and 17 days; (3) the existence of long‐ and short‐cycling stem cells, probably combined with preferential differentiation of the short‐cycling elements; (4) selective segregation of DNA at stem cell mitosis; and (5) irradiation death of radiosensitive labelled stem cells.

As it is not impossible that factors 1, 2, 4 and 5 together account for the total loss of labelled stem cells, LI results do not provide evidence for the existence of separate classes of short‐ and long‐cycling stem cells.

The distributions of the LIs of the As, Apr and Aal spermatogonia over the stages of the epithelial cycle at 17 days are similar to those at 1 hr after injection. Hence the regulatory mechanisms that govern the stimulation and inhibition of proliferation of As that give rise to new As for the next epithelial cycle are similar to those of the As that will divide into Apr spermatogonia during the same epithelial cycle.

Grain counts revealed that more [3H]TdR is incorporated into As, Apr and Aal spermatogonia that are in S phase during epithelial stages X‐IV than in stages V‐IX.
Survival and Repopulation of Irradiated ‘Pre‐Cfu‐C’ In Mice
Authors: Aizawa Shin , Amaki Ichita , Miyanomae Takeshi , Tsurusawa Masahito , Mori Kazuhiro J.
Published: May 2008

ABSTRACT Supernatants of murine bone‐marrow cultures contain a colony‐promoting factor (CPF) which increases the number of granulocyte and macrophage colonies in semi‐solid agar cultures in the presence of colony‐stimulating factor (CSF). Incubation of bone‐marrow cells with CPF results in an increase in the number of granulocyte/macrophage progenitor cells (CFU‐c) and the CPF‐responsive cells may be younger than the CFU‐c.

We have investigated the radiosensitivity and the pattern of the recovery after irradiation of CPF‐responsive cells. We found that the radiosensitivity of CPF‐responsive cells was significantly lower than those of CFU‐c. burst‐forming units‐erythroid (BFU‐e) and pluripotent stem cells in vivo (CFU‐s) and in vitro (CFU‐mix). the CPF‐responsive cells remained subnormal even at 28 days after irradiation of the mice, a time when the CFU‐s and CFU‐c had recovered completely.

Therefore the CPF‐responsive cells may constitute a separate compartment, namely ‘pre‐CFU‐c’, in the maturation sequence of granulopoiesis, and this maturation of the ‘pre‐CFU‐c’ to CFU‐c seems to be highly stimulated after irradiation to counterbalance the influx from CFU‐s.
A Growth Curve of Cell Numbers In the Neural Retina of Embryonic Chicks
Authors: Morris Valerie B. , Cowan Richard
Published: May 2008

ABSTRACT The growth of cell numbers in a normal embryonic population of ncural retinal cells is described. the numbers were estimated from a time shortly after the neural retina first becomes recognizable to a time when numbers of retinal cells have become steady. Cell numbers were estimated in preparations of an entire neural retina dispersed into a suspension of single nuclei which were then counted in a Coulter counter. the growth curve of the In numbers of cells has three phases of growth: an exponential phase during which there is steady‐state exponential growth, a differentiative phase during which cell proliferation ceases and an end phase when no further change in cell numbers can be detected. the variances of the In numbers of cells were highest during the exponential phase. the variances decreased during the differentiative phase and were at their lowest during the end phase. For variances to decrease requires mechanisms which control the final numbers of cells in the neural retina very precisely. the implications of mechanisms which operate by controlling cell lineages are explored.
A Study of the Proliferative Response of Rabbit T Cells Using the Brdu‐Hoechst Method
Authors: Roholl Paul J. M. , Distel Ben
Published: May 2008

Con‐A‐ and PHA‐induced proliferation of cells from rabbit thymus, spleen and mesenteric lymph node was studied with the DNA‐fluorescent probe 33258 Hoechst. the fluorescence of this probe is quenched when 5‐bromo‐2′‐deoxy‐uridine is incorporated into nascent DNA during the S phase. Fluorescence decreased with increasing content of newly formed DNA per cell. Proliferation kinetics and the number of Con‐A‐ and PHA‐reactive cells (C+ and P+ cells) were determined cytofluorometrically.

Lymphocytes from control and dexamethasone (DX)‐treated animals start their proliferation early: after 42 hr about 25% of the control and the majority of the DX‐resistant cells finished their second cell division.

Small numbers of C+ (12.0%) and P+ (3.5%) cells were found in control thymus, while these percentages were enhanced in DX thymus: 32.5 and 27.0% respectively; 50% of the spleen T cells in control and DX animals are C+ or P+ and 75% of the lymph‐node T cells are C+ (after DX 45%) and 50% are P+ (after DX also 50%).

It is concluded that in thymus and lymph nodes, a steroid sensitive (Ss) C+P‐, and in lymph nodes a Ss C+P+ cell pool is present. A mitogen non‐proliferative cell pool (C‐P‐) is present in control and DX thymus.
Mitotic and Labelling Activity In Normal Human Epidermis In Vivo
Authors: Camplejohn R. S. , Gelfant S. , Chalker D. , Sittampalam Y.
Published: May 2008

Labelling and mitotic indices were studied in the epidermis of twenty‐eight young men. A mean labelling index of 5.5% was found from the whole study and a mean mitotic index of 0.06%. Mitotic index particularly was extremely variable; indices between 0.002 and 0.438% were found in individual biopsies. In the first two of three experiments in which mitotic index at 09.00 hours was compared with that at 15.00 hours, significant differences were found (15.00 hours > 09.00 hours by a factor of 2.6, P < 0.001). However, in the third such experiment no such difference was found, suggesting that the timing and occurrence of diurnal rhythms of mitotic activity may not be consistent in normal human epidermis. In the one experiment in which it was investigated, a significantly higher mitotic index was found at 21.00 hours compared to 09.00 and 15.00 hours. Labelling index did not vary significantly at 09.00, 15.00 or 21.00 hours. However, labelling index did show a significant pattern of change over a 12‐month period in two groups of subjects; peaks of labelling were seen in July and troughs in January. Very high ratios of labelled: mitotic cells were found, the median ratio for the whole study being ninety‐eight labelled: one mitotic cell. This finding supports the possibility that not all labelled cells subsequently go on to divide in normal human epidermis.
Subpopulations of Slowly Cycling Cells In S and G2 Phase In Mouse Epidermis
Authors: Clausen O. P. F. , Aarnæs E. , Kirkhus B. , Pedersen S. , Thorud E. , Bolund L.
Published: May 2008

Evidence has been presented supporting the existence of heterogeneity in cell‐cycle progression in mouse epidermis, the present study was undertaken to characterize this heterogeneity in more detail. Hairless mice were continuously labelled with tritiated thymidine every 4 hr for 4 days. Basal cell suspensions were prepared from slices of mouse skin at intervals during the experiment and subjected to DNA flow cytometry. Cell‐cycle analysis was combined with sorting of cells from windows in G1, S and G2, phase, and the proportion of labelled cells within each window was determined in autoradiographs. Reanalysis and resorting to control the purity of sorted fractions were performed.

Computer simulations of the data were made using a mathematical model assuming different S and G2 phase characteristics. A good fit to the data was only obtained when heterogeneity in mouse epidermal cell‐cycle progression was assumed, indicating the existence of slowly traversing, distinct subpopulations of cells in G2 and S phase. These cells are assumed to contribute to about 40% of all cells in S phase and to about 70% of all in G2 phase. the estimated residence times in the resting states were 38 and 32 hr in S and G2 phase, respectively. Two‐parameter sorting based on DNA and light scatter indicated that slowly cycling cells were larger than the average. There is no evidence of significant subpopulations of permanently non‐proliferating keratinocytes in any of the cell‐cycle phases.
Cell‐Cycle Analysis Using A Monoclonal Antibody to Brdurd
Authors: Dean Phillip N. , Dolbeare Frank , Gratzner Howard , Rice Glenn C. , Gray Joe W.
Published: May 2008

The flow cytometric measurement of DNA distributions of cells has many applications in biomedical research. Phase fractions estimated (calculated) from such distributions are used to study the growth characteristics of various types of cells, particularly when the cells have been exposed to perturbing agents such as chemotherapeutic drugs. For more than 10 years many methods for resolving DNA distributions into the three cell subpopulations (G1, S and G2, + M) have been reported in the literature. A new method of analysis utilizing a monoclonal antibody to bromodeoxyuridine (BrdUrd) has been developed (Gratzner, 1982; Dolbeare et al., 1983) which makes it possible in most cases to accurately determine phase fractions without resorting to mathematical models. the procedure involves the incorporation of BrdUrd by growing (DNA synthesizing) S phase cells, labelling the BrdUrd with a fluorescent monoclonal antibody, and the bivariate measurement of the antibody and of total DNA content, the latter through propidium‐iodide staining. the resulting bivariate distributions clearly and simply resolve the three subpopulations. This paper describes the method and illustrates its use in the analysis of various fractions of elutriated exponentially growing Chinese hamster ovary (CHO) cells.
Endogenous Regulation of Endothelial Cell Proliferation
Authors: Sorgente Nino , Bullard Debra L. , Jakovljevic Ljiljana , Dorey Kathleen
Published: May 2008

Bovine aortic endothelial cells (BAEC) in culture have the ability to regulate their own proliferation. We have found that a fraction below 100,000 daltons obtained from the media of confluent cultures of BAEC inhibits tritiated thymidine [3H]TdR incorporation as well as their proliferation. the inhibition is dose‐ and time‐dependent; maximum inhibition of [3H]TdR incorporation occurs 8 hr after cells are released from synchronization and the inhibitory fraction is added. Inhibition is evident at concentrations as low as 50 μg/ml and reaches a maximum at 600 μg/ml. the blockage of [3H]TdR incorporation is reflected in the inhibition of cell proliferation. In the presence of 400 μg of endogenous inhibitor per ml of media, added at the time of plating, the average population doubling time increases from 19 to 41 hr. These findings indicate that, in culture, BAEC can regulate their own proliferation by synthesizing an endogenous inhibitor(s) of proliferation.
Different Sensitivities of Granulocyte‐Macrophage and Erythroid Progenitor Cells of Normal Human Bone Marrow to S‐Phase‐Specific Agents
Authors: Kubota Kazuo , Preisler Harvey D. , Costanzo Catherine
Published: May 2008

The extraordinary sensitivity of early erythroid progenitor cells (BFU‐e) of normal human bone marrow to tritiated thymidine ([3H]TdR) was studied. While exposure of bone‐marrow cells to [3H]TdR for 1 hr resulted in the death of only 40% of the granulocyte‐macrophage progenitor cells (CFU‐c), 90% of BFU‐e were killed. Experiments in which normal bone‐marrow cells were mixed with bone‐marrow cells which had been exposed to [3H]TdR demonstrated that the excessive killing of BFU‐e by [3H]TdR reflected carry‐over of the [3H]TdR by the exposed cells. A carry‐over effect was not observed for CFU‐c, suggesting the presence of a fundamental difference in the metabolism of TdR between CFU‐c and BFU‐e. There was a suggestion of a carry‐over effect regarding two other S‐phase‐specific agents, hydroxyurea and 1‐β‐D‐arabinofuranosylcytosine.
Aspects of Statistics In Studies of Cell Proliferation
Authors: Appleton David R.
Published: May 2008

Statistical methods such as regression analysis are often used to estimate cell kinetic parameters, such as cell birth rate or tumour growth rate. the standard errors which the statistical procedures provide may be considerable underestimates of the true uncertainty surrounding the parameter of interest.
Cell Kinetic Studies In the Epidermis of Mouse. Iii. the Percent Labelled Mitosis (Plm) Technique
Authors: Potten C. S. , Wichmann H. E. , Dobek K. , Birch J. , Codd T. M. , Horrocks L. , Pedrick M. , Tickle S. P.
Published: May 2008

Full PLM curves have been obtained for four sites in the mouse. the first peaks have been analysed by computer and the duration of the G2+ M and S phases determined together with their standard deviations. the full curves showed a general similarity for all four sites with no clear second peak. the data are compared with the published data for mouse and human epidermis using the in vivo PLM technique. the timing and shape of the first peak can vary considerably even for one site in mice. Hence, both G2+ M and S can vary in their durations. Cells labelled at one time of day exhibit different kinetic properties to those labelled at another time of day. the duration of G2+ M is shortest in dorsum labelled at 03.00 hours (3.2 hr) and longest in tail (up to 7.5 hr). the S‐phase is shortest in dorsum (6.3–7.2 hr) and longest in tail or ear (13.3–14.1 hr). There is also a very large standard deviation in tail and foot. There is little general variability when the psoriatic human data are considered, which is surprising. the general variability amongst the data from experimental mice might also be expected amongst humans which might make comparisons between the cell kinetics of normal and diseased skin difficult.
Effects of Pulse Labelling With Tritiated Thymidine On the Circadian Rhythmicity In Epidermal Cell‐Cycle Distribution In Mice
Authors: Clausen O. P. F. , Kirkhus B.
Published: May 2008

The influence of pulse labelling with 50 °Ci tritiated thymidine ([3H]TdR) (2 μCi/g) on epidermal cell‐cycle distribution in mice was investigated. Animals were injected intraperitoneally with the radioactive tracer or with saline at 08.00 hours, and groups of animals were sacrificed at intervals during the following 32 hr. Epidermal basal cells were isolated from the back skin of the animals and prepared for DNA flow cytometry, and the proportions of cells in the S and G2 phases of the cell cycle were estimated from the obtained DNA frequency distributions. the proportions of mitoses among basal cells were determined in histological sections from the same animals, as were the numbers of [3H]TdR‐labelled cells per microscopic field by means of autoradiography.

The results showed that the [3H]TdR activity did not affect the pattern of circadian rhythms in the proportions of cells in S, G2 and M phase during the first 32 hr after the injection. the number of labelled cells per vision field was approximately doubled between 8 and 12 hr after tracer injection, indicating an unperturbed cell‐cycle progression of the labelled cohort. In agreement with previous reports, an increase in the mitotic index was seen during the first 2 hr.

These data are in agreement with the assumption that 50 °Ci [3H]TdR given as a pulse does not perturb cell‐cycle progression in mouse epidermis in a way that invalidates percentage labelled mitosis (PLM) and double‐labelling experiments.
Aspects of Statistics In Studies of Cell Proliferation Iii. Alternative Models Give Different Results
Authors: Appleton David R.
Published: May 2008

Alternative models for the analysis of the spatial distribution of cells in an intestinal crypt cross‐section are discussed. It is shown that different, though reasonable, models lead to different conclusions.
Cell Population Kinetics and Dna Content During Thyroid Carcinogenesis
Authors: Christov Konstantin
Published: May 2008

The proliferation kinetics and DNA content of thyroid follicular cells in rats were studied by autoradiography and cytophotometry. Continuous treatment of animals with methylthiouracil (MTU) results in hyperplasia followed by tumour growth in the thyroid gland. the mitotic index (MI) increases from 0.006 ± 0.002% in controls to 0.13 ± 0.06% in hyperplasia and to 0.09 ± 0.03% in malignant cells. the same is true for the labelling index (LI) which rises from 0.08 ± 0.003% in controls to 1.4 ± 1.1% in hyperplasia and to 1.0 ± 0.6% in follicular adenomas. the S‐phase duration (Ts) is shortened from 8.0 ± 1.2 hr in controls to 6.0 ± 1.4 hr in animals treated for 9 months with MTU and prolonged to 15.4 ± 2.1 hr in papillary carcinomas. In all MTU‐treated animals a decrease in the value of the potential population doubling time (TPD) and thyroid weight doubling time (TD) was observed. the cell loss factor (ø) decreases in animals treated for 3 months with MTU and increases during the stage of tumour growth in the gland (animals treated 12–15 months with MTU). DNA measurements in the nuclei of hyperplastic and neoplastic thyroid tissues reveal cells with values exceeding that in control animals. However, no difference was found in the DNA content between thyroid adenomas and carcinomas, nor between thyroid hyperplasia and neoplasia.

During the last decade numerous autoradiographic studies have been performed on the cell population kinetics of benign and malignant tumours in animals and man (Steel, 1977; Tubiana & Malaise, 1977). It has been established that cell proliferation is an important parameter in both the initiation and promotion phases of carcinogenesis (Oehlert, 1973; Berenblum, 1979). Cell kinetic studies during carcinogenesis have predominantly dealt with the liver (Rajewsky, 1967; Chernozemski & Warwick, 1970), skin (Raick, 1974), the mammary gland (Bresciani, 1965; Nagasawa, Yanai & Nagigushi, 1976b), the uterine cervix (Nagasawa, Matsuura & Tojo, 1976a) and intestinal cells (Tutton & Barka, 1966; Pozharisski, Klimashewski & Gushin, 1977). Information on the changes in cell population kinetics during thyroid carcinogenesis is still incomplete. Data reported in the literature are mainly devoted to the short‐term effects of goitrogens and radiation factors (Santler, 1957; Sheline, 1969; Philip, Crooks & MacGregor, 1969; Wynford‐Stringer & Williams, 1982; Redmond & Tuffery, 1981).

The present study was carried out to investigate if changes in the cell population kinetics and DNA content occur during thyroid carcinogenesis, as well as if thyroid adenomas and carcinomas differ in their proliferative potential and DNA content.
Aspects of Statistics In Studies of Cell Proliferation
Authors: Appleton David R.
Published: May 2008

Computer simulation of an experiment can help to reveal how effective that experiment might be in estimating cell kinetic parameters, or in elucidating the nature of a proliferative response to a perturbation of the steady state, such as a carcinogenic or therapeutic treatment. Writing a simulation also clarifies one's thoughts about possible mechanisms of the proliferative response.
Cell‐Cycle‐Specific Activity of Cyclic Nucleotide Phosphodiesterase In Physarum polycephalum
Authors: Kupetz I. S. , Jeter J. R.
Published: May 2008

The cell‐cycle‐related activities of the cAMP‐ and cGMP‐dependent phosphodiesterases of Physarum polycephalum were assayed. the activities of plasmodial homogenate and of selected subcellular fractions were measured. the results suggested the presence of both cAMP‐ and cGMP‐dependent phosphodiesterase in the isolated nuclei of P. polycephalum. In addition, they reveal that the cAMP‐ and cGMP‐dependent phosphodiesterase activities of the subcellular fractions fluctuate throughout the cell cycle. the whole‐cell homogenates exhibit no cell‐cycle‐related changes in the presence of 5 × 10‐4 m cGMP. Kinetic data suggest the presence of multiple phosphodiesterase activities in the homogenate and its particulate fractions for the cGMP‐dependent enzyme. Multiple cAMP activities are also suggested for the particulate fractions. the Km values indicate that the substrate affinities of the phosphodiesterases from P. polycephalum are similar to those found previously in mammalian systems.
On the Role of Microfilaments In Cell‐Shape‐Mediated Growth Control of Lens Epithelial Cells
Authors: Iwig M. , Glaesser D.
Published: May 2008

With regard to the fact that, in anchorage‐dependent lens epithelial cells, DNA synthesis can be switched on and off by cell flattening and cell rounding, respectively, the state of the microfilaments has been followed by labelling actin with FL‐phalloidin during cell‐shape alterations. Cell flattening proved to be accompanied by both a structural organization of actin filaments into stress fibres and an enlargement of the area of the cell nucleus. Cell rounding, on the other hand, caused the microfilament bundles to disappear and the area of the nucleus to become smaller. From the time course of the inhibition of DNA synthesis by cytochalasin B, it was inferred that functionally intact microfilaments are required for the entrance of the cells into DNA synthesis but not for the maintenance of ongoing DNA synthesis. the assumption has been made that the tension, generated by microfilaments during cell spreading, will affect the state of the plasma membrane as well as the shape and the structure of the nucleus, which in turn seems to be preparatory for cells to enter the cycle.
Testicular Morphology and Cell Proliferation Kinetics of Immature Germ Cells and Sertoli Cells In Suckling Undernourished Rats
Authors: Bansal‐Rajbanshi Mridula , Mathur Meera
Published: May 2008

Undernutrition during suckling was induced in newborn rats by increasing the litter size to sixteen pups to be fed by one mother. Animals reared in litters of eight served as controls. Undernourished animals showed retarded body and testicular growth during a suckling period of 22 days. Sequential morphogenesis of the testis was not altered up to 15 days of age. However, certain morphological alterations in Sertoli cells and Leydig cells were observed from 15 days onwards. Cell generation cycle of spermatogonial germ cells and supporting cells (future Sertoli cells) on day 9 showed marked prolongation of DNA synthetic phase (S), unaltered post‐DNA synthetic phase (G2) and total cycle (Tc) and shortening of the pre‐DNA synthetic phase (G1) indicating a depression in DNA synthesis in undernutrition.
Effect of Haemopoietic Stem‐Cell Proliferation Regulators On Early and Late Spleen Colony‐Forming Cells
Authors: Wright E. G. , Lorimore S. A. , Lord B. I.
Published: May 2008

An inhibitor and stimulator of CFU‐s proliferation can be obtained from haemopoietic tissue containing, respectively, relatively quiescent CFU‐s (e.g. normal bone marrow) and proliferating CFU‐s (e.g. regenerating bone marrow). Their effects on the proliferative behaviour of steady‐state and regenerating marrow CFU‐s, which produce colonies 7, 10 and 12 days post‐transplantation have been investigated.

The results demonstrate changing sensitivities of CFU‐s to inhibitor and stimulator as they progress through a developmental age structure. ‘Older’ CFU‐s (producing early spleen colonies) are more sensitive to stimulator, ‘Younger’ CFU‐s (producing late spleen colonies) are more sensitive to inhibitor.
Basal‐Cell Subpopulations and Cell‐Cycle Kinetics In Human Epidermal Explant Cultures
Authors: Jensen P. K. A. , Pedersen S. , Bolund L.
Published: May 2008

Cultured human epidermal cells were studied by cell sorting and autoradiography after different 3H‐thymidine (3H‐dThd)‐labelling procedures and after labelling with DNA precursors that are incorporated via salvage or de novo pathways. It was shown that 3H‐dThd incorporation was the best measure of the rate of DNA replication. Dose‐response experiments with pulse and continuous labelling revealed that all S‐ and G2‐phase cells were cycling, whereas some 20% of the cells stayed in G1‐phase for long periods of time. Most, if not all of these cells were probably non‐proliferating differentiated keratinocytes. At least two subpopulations of S‐phase cells could be discriminated on the basis of the rate of incorporation of DNA precursors. the difference in precursor incorporation did not seem to be caused by differences in nucleotide metabolism but rather to reflect true differences in the rate of DNA replication. Continuous labelling experiments showed that these subpopulations also were apparent in the G1‐ and G2‐phases. Studies of the grain‐count distribution revealed that cells that appeared to move rapidly through the S‐phase moved slowly through the G2‐phase, and vice versa. Cells stained with acridine orange were subjected to a two‐parameter analysis in the cell sorter by simultaneous measurement of the DNA and RNA fluorescence. Autoradiography of sorted cells revealed that, on average, cells with low RNA contents incorporated 3H‐dThd at a higher rate than cells with high RNA contents.
Estimation of Circadian Variations In Cell Cycle Phase Durations In Murine Epidermal Basal Cells
Authors: Thorud Erik , Aarnæs Erik , Clausen Ole Petter F. , Bjerknes Rolf , Anker Peder
Published: May 2008

Circadian variations in the proliferative activity of squamous epithelia are well known. However, circadian variations in the duration of the various cell cycle phases (S, G2 and mitosis) have been disputed. the percent labelled mitoses method, which is traditionally used to obtain duration of cell cycle phases, is poorly suited for identification of circadian variations. Therefore methods combining changes in compartment size (cell cycle phase) and cellular flux through the compartments have been used. Three different methods using such data are presented. These incorporate various simplifying assumptions that cause methodological errors. Limits for use of the different methods are indicated. the use of all three methods gives comparable and pronounced circadian variations in the duration of S and G2 phase. These results are also compatible with circadian variations in the mitotic duration, but they may also represent artefacts due to sensitivity to model errors.
Mathematical Model of Acute Myeloblastic Leukaemia: an Investigation of the Relevant Kinetic Parameters
Authors: Djulbegović Benjamin , Svetina Saša
Published: May 2008

A simple model of acute myeloblastic leukaemia (AML) development is introduced, explicitly including cell growth, cell differentiation and cell‐cell interaction. Each of these processes is described by a single model parameter. It is hypothesized that the leukaemic cell is characterized by an alteration of only one of these processes. the kinetic behaviour of the AML system is examined separately for possible alterations of each of the three parameters describing the three processes involved. It is shown that, on the basis of the existing data on AML kinetics, the alteration of the growth and cell‐cell interaction parameters can be eliminated as a possible source of AML. Thus kinetic data support the modification of the differentiation process as the origin of the AML state. Further, the growth characteristics of normal and leukaemic cells in the presence of each other are analysed. It is shown how the initial growth of leukaemic cells depends on the difference in the differentiation of normal and leukaemic cells and how the same difference determines the decay of normal cells in the presence of the predominantly leukaemic population. Correlations between the kinetic parameters of the normal and leukaemic populations are suggested to characterize the leukaemic state.
Effect of Vinblastine On the Cell Cycle and Migration of Ameloblasts of Mouse Incisors As Shown By Autoradiography Using 3H‐Thymidine
Authors: Mercedes Maria , Samperiz Fernandez , Blumen Guilherme , Merzel Jose
Published: May 2008

Abstract. The effects of vinblastine on the cell cycle and the migration of ameloblasts were studied in the lower incisors of mice by labelling the cells with 3H‐thymidine ([3H]TdR) and radioautography. A group of mice received 2 μg/g of body weight vinblastine intraperitoneally and 6 hr after these animals and those of a control group were injected with 1μCi/g body weight of [3H]TdR, and sacrificed at time intervals from 0.75 hr to 15 days.

The generation time of ameloblasts in the progenitor compartment was 14.8 hr in animals treated with vinblastine and 17 hr in the controls, using the FLM curve method; with the grain dilution method the duration was respectively 29.25 hr and 25.96 hr. the thymidine labelling index of the treated animals was 50% higher than the controls. the velocity of ameloblast migration, determined either by the displacement of the most incisally labelled cell or by the grain dilution method, was lower in the experimental group (2.48 cell positions/hr and 9.18 μ/hr respectively) as compared with the control (3.21 cell positions/hr and 18.88 μm/hr respectively).

The results on the ameloblast production rate are contradictory but the slowing down in the velocity of cell migration is compatible with a decrease of the rate of cell production in the progenitor compartment as a vinblastine effect.
Epidermal Tissue Homeostasis
Authors: Budtz Povl E.
Published: May 2008

Abstract. Toad epidermis is a suitable model for studies on tissue homeostasis because cell pool size, influx into and efflux from the cell pool can be easily determined. the cell pool size was obtained by cell counting on photomicrographs, the influx (cell birth rate) was assessed by the metaphase‐arrest technique, and the efflux (cell loss by moulting) assessed by counting the number of cells in the corneal layer and recording of intermoult periods. the importance of the methods for assessing these parameters per square unit of skin surface is emphasized.

These parameters were studied in eight groups of ten adult male toads sacrificed at various hours of the day. There were minor variations in the cell birth rate, fluctuating around a mean of 26 cells/mm2/hr (obtained at the metaphase collection period from 11.00‐14.00 hours). By summation of the cell productions during the eight metaphase collection periods of 3 hr, and extrapolation to an intermoult period (time between two moults), a calculated cell production of about 6340 cells/mm2 in 10.3 days was obtained, whereas the cell loss at each moult was only 2370 cells/mm2. Thus the cell production rate exceeds the rate of cell loss through moults by a factor of 2.7. Arguments are presented that the ‘surplus’ of cells produced cannot be permanently accommodated within the living epidermis. Consequently a cell deletion rate beyond that by moulting of about 4000 cells/mm2 in 10.3 days or 16 cells/mm2/hr can be calculated.

These results are discussed in relation to current concepts of tissue homeostatic mechanism(s). the results are consistent with the hypothesis that controlled cell deletion may be a tissue homeostatic mechanism complementary to controlled cell divisions.
Analysis of Cell Types Identifiable In Air‐Dried Cell Preparations of Human Testis
Authors: Curtis D.
Published: May 2008

Abstract. The mixed cell population of the testicular epithelium has been studied in air‐dried cell preparations obtained from a testicular biopsy. Observed cell types are defined, quantified and assigned to cell stages of the spermatogenic cycle. Studies with tritiated thymidine helped to categorize the spermatogonial cell types. Variation in cell size within cell categories, variation in frequency of cells in different categories within individuals, and variation in frequency of cells within categories between individuals were subjected to quantitative analysis.