bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method For Measuring the Generation Time and Length of Dna Synthesizing Phase of Clonogenic Cells In A Heterogenous Population
Authors: Wu A. M. 
Published: May 2008

ABSTRACTInformation on the cell cycle of progenitor cells in haemopoietic tissue is useful for understanding population control under physiological and abnormal conditions. Unfortunately, methods that have been developed for measuring cell cycle parameters are applicable only to cells of homogenous populations and not to morphologically non‐recognizable progenitor cells such as colony forming units (CFU) that are present at low frequency in a heterogenous population. to circumvent this difficulty, a method was developed to measure CFU cell cycle parameters based on specific killing of cells in S phase by [3H]thymidine ([3H]TdR). This was done by estimating the number of CFU killed following exposure of the cell suspension to [3H]TdR for various time periods. Since cycling CFU are continuously entering S phase, a linear curve relating the percentage CFU‐kill to the length of exposure of the cells to [3H]TdR in culture can be obtained. the slope of the curve (percentage kill/hr) indicates the rate that CFU enter the S phase and travel through the cell cycle. the inverse of this value will then represent a time period for CFU to move through a complete cell cycle (generation time). the length of S phase can then be obtained by multiplying generation time by the fraction of cells in S phase at time zero. This method has been used to measure generation time and length of S phase of three kinds of haemopoietic progenitor cells: mouse granulocyte‐macrophage CFU, human T lymphocyte CFU and CFU from regenerating mouse spleens. This method should be applicable to any normal or neoplastic clonogenic cell populations and the latter could be either of haematological or of solid tumour origin.
Potential Pitfalls of [3H]Thymidine Techniques to Measure Cell Proliferation
Authors: Maurer H. R. 
Published: May 2008

ABSTRACTPitfalls and artifacts in the use of [3H]thymidine in the measurement of cell proliferation kinetics in vitro and in vivo are reviewed. These pitfalls are of particular significance for the study of inhibitors of cell proliferation including chalones.
REGENERATION OF UTERINE EPITHELIUM AFTER EXPERIMENTAL ABLATION IN THE RAT
Authors: Leroy F. , Lejeune B. , Galand P. 
Published: May 2008

ABSTRACTRegeneration of the uterine luminal epithelium was studied after its mechanical removal in progesterone‐primed rats, leaving one control horn intact. Pulse labelling with [3H]TdR during regeneration, showed a rapid peak of labelling index in remaining glands. A differentiated and highly labelled luminal epithelium reappeared at 34 hr, thereafter showing a rapidly declining LI. After initial depletion, the glandular cell population size was restored within 64 hr, whereas luminal epithelium cell numbers became stabilized at about half normal level. Grain counts after prelabelling showed more rapid dilution in gland cells of stripped uterine horns, indicating accelerated cycling of previously dividing cells. Thymidine labelling indices also showed that, after removal of the epithelium, almost all gland cells became rapidly committed to divide. On average, less than two cell cycles were necessary to restore stable glandular and epithelial population sizes. Numbers of labelled cells were also drastically increased in myometrium and serosa of treated horns. This suggests a non‐specific mechanism for stimulation of mitotic activity after ablation of epithelium.
EVIDENCE OF RAPID AND SLOW PROGRESSION OF CELLS THROUGH G2 PHASE IN MOUSE EPIDERMIS: A COMPARISON BETWEEN PHASE DURATIONS MEASURED BY DIFFERENT METHODS
Authors: Clausen O. P. F. , Thorud E. , Aarnæs E. 
Published: May 2008

ABSTRACTPercentage labelled mitosis (PLM) measurements were initiated at four different times during a 24‐hr period and continued for 24 hr in hairless mouse epidermis. Estimates of G2 and S phase durations (mean TG2 and mean TS) were calculated. A significant number of labelled mitoses (10–20%) was seen after 30 min in all four PLM measurements and the estimated mean TG2 varied from 1.4 to 2.5 hr and was in agreement with values from PLM measurements in other epithelial tissues. These mean TG2 values were much shorter than expected from [3H]TdR double labelling experiments and from a multiparameter cell kinetic study in hairless mouse epidermis and did not reflect the circadian variations seen in these studies. the differences in estimates of phase durations can be explained by postulating two G2 cell populations; one with a rapid and another with a slow rate of cell cycle progression. the cells with the higher rate are mainly registered by the PLM method, whereas those with the lower rate largely escape detection by this method. TG2 estimates from PLM measurements in mouse epidermis therefore do not reflect the phase duration of the entire G2 population. It is also concluded that circadian variations in TS can not be accurately registered by the PLM method.
ANALYSIS OF THE VARIABILITY IN CLEAVAGE TIMES AND DEMONSTRATION OF A MITOTIC GRADIENT DURING THE CLEAVAGE STAGES OF NOTHOBRANCHIUS GUENTHERI
Authors: Van Haarlem R. , Van Wijk R. , Fikkert A. H. M. 
Published: May 2008

ABSTRACTLiving embryos of the annual cyprinodont fish Nothobranchius guentheri were observed under the microscope. Detailed records were made of the time of cell division, disappearance of the nucleus and of the position of each cell within the blastoderm up to and including the sixth cleavage. Combination of these data revealed the presence of a mitotic gradient, a cell division gradient and a gradient of cell cycle duration in the 8‐cell, 16‐cell and 32‐cell stage. Comparison of the variabilities in the duration of the interphase and mitosis reveals that differences between sister cell intercleavage times in the 8‐, 16‐ and 32‐cell stage are, for the most part, due to the variability in the duration of the mitotic process. It is concluded that the DNA‐division cycle is composed of at least two parallel series of events. We found the random transition model of cell cycle control, originally based on the analysis of intermitotic times of mammalian cells in tissue culture, helpful also in analysing intercleavage time variability in embryonic cells.
Clonal Growth of Leukaemic Cells In Vitro
Authors: Preisler H. D. , Epstein J. 
Published: May 2008

ABSTRACTHuman leukaemic cell specimens were obtained from patients and directly plated into soft agar (t= 0) or cultured for 1 week in liquid phase and then plated in soft agar. Growth for 1 week in liquid phase allowed the clonal growth in agar of leukaemic specimens which were unable to clone at t= 0. Clonal growth after liquid culture consisted of the usual leukaemic type of cluster‐colonies, growth of a new type of ‘syncytial’ cell colony or a mixture of colony types. In addition, marrow from a patient with acute lymphocytic leukaemia produced normal‐appearing colonies after 1 week of growth in liquid phase. These studies suggest a similarity in the growth requirements of some leukaemic cells and normal CFUd cells.
The Relationship of G0 to the Cell Cycle of Haemopoietic Spleen Colony‐Forming Cells
Authors: Lord B. I. 
Published: May 2008

ABSTRACTNormal haemopoietic stem cells, defined here as spleen colony‐forming units (CFUs), are slowly proliferating and are generally considered to spend most of their time in the non‐proliferative G0‐state. A series of experiments using various combinations of the stem cell proliferation inhibitor (NBME‐IV) and stimulator (RBME‐III) together with vinblastine as a mitotic blocking agent was designed to determine the location of the G0‐state relative to the cell cycle of the CFUs.From a knowledge of the effects of these agents, the expected results from three different G0‐cell cycle models were charted and compared with the observed proliferative behaviour of the CFUs following these treatments. It was concluded that the out‐of‐cycle G0‐state is located at the end of the G1‐phase of the cycle, so that on receiving a stimulatory signal, the CFUs can rapidly enter the DNA‐synthesis phase.
Cytophotometric Evidence of Non‐S‐Phase Extra‐Dna In Human Neuronal Nuclei
Authors: Böhm N. , Kröner Bärbel , Kaiser Evelyn 
Published: May 2008

ABSTRACTAfter Feulgen staining with acriflavine‐Schiff, the DNA content of glial and neuronal nuclei from various sites of the human CNS (pre‐ and post‐central gyrus, cerebellar cortex and spinal cord) were determined by fluorescence cytophotometry. the specimens were obtained from twelve adult human autopsy cases. Glial cell nuclei always revealed a biomodal DNA distribution pattern with a large 2c and a smaller 4c peak. the 4c peak was most prominent in the cerebellum. A few 8c glial nuclei were found.Neuronal cell nuclei disclosed unimodal DNA histograms with hyperdiploid means in the range 2.2–2.5c (1.8–2.9c for the individual populations). Tetraploid 4c DNA values were not observed, neither in Purkinje cells, nor in pyramidal cells. In eleven out of a total of forty‐four slides the higher DNA means of neuronal nuclei were found to be statistically significant (P < 0.05) when compared with a population of 2c hepatocytes on the same slide.The results indicate the existence of some ‘extra DNA’ in human neuronal cell nuclei, the biological significance of which has still to be elucidated. It is however, suggested that it may play an important role in the functional activity of the CNS.
A Repopulation Assay For B and T Lymphocyte Stem Cells Employing Radiation Chimaeras
Authors: Hunt S. V. , Fowler M. H. 
Published: May 2008

ABSTRACTThe repopulation of the peripheral lymphoid compartment of lethally‐irradiated rats reconstituted with lymphopoietic stem cells was studied. Cell lineages were traced by using genetic markers of cell surface molecules: immunoglobulin allotype for B lymphocytes and peripheral T cell alloantigen for T lymphocytes. Provided the markers had been bred on to a genetic background congenic with the hosts, they conferred neither an advantage nor disadvantage in competition with unmarked cells. the degree of chimaerism measured the lymphopoietic activity of the restorative inoculum. the most potent activity was found in foetal liver and spleen; next was infant spleen and bone marrow; then young adult bone marrow. Peripheral lymphoid tissues showed very little activity and thymus cells were inert. This tissue distribution, the stability of the chimaerism and the substantial expansion of numbers from the injected cells all point to the assay measuring an early stem cell.The overlap of subpopulations of lymphocytes in the rat thoracic duct was studied. A method for the conjugation of fluorescein to antibodies while they are attached to immuno‐adsorbent affinity columns is also described.
KINETICS OF TISSUE PROLIFERATION IN COLORECTAL MUCOSA DURING POST‐NATAL GROWTH
Authors: Maskens A. P. , Dujardin‐Loits Rose‐Marie 
Published: May 2008

ABSTRACTThe main developmental event in the colorectal mucosa during post‐natal growth is a dramatic increase in the number of crypts of Lieberkühn, resulting from a longitudinal fission of pre‐existing crypts. In the present study, the kinetic aspects of this process have been analysed, using extensive gland and cell counts involving the entire colon and rectum of 24 male BD IX rats distributed into four age groups.The number of crypts was found to rise from an average 4652 to 423,800 between birth and adulthood; the corresponding ratios of bifurcating glands were 13.55 and 0.67%, respectively. Crypt production attained its maximum 18 days after birth with an hourly increment of 519 units. the time spent by replicating glands in the bifurcating stage (‘fission time’) averaged 6.9–10.5 hr.The mean number of epithelial cells per crypt rose from 249 in 4‐day old rats to 635 in adults. the estimated total number of epithelial cells in the colon and rectum was one million in newborns and 248 million in adults. the increment in cell number peaked 3 weeks after birth with a value of 310,000/hr. During the first few days after birth, all cells produced in the epithelium were retained. Cell loss thereafter rapidly progressed, reaching 70% of the cell production in 3‐week old animals.
Polyploidy In the Murine Colonic Pericryptal Fibroblast Sheath
Authors: Neal J. V. , Potten C. S. 
Published: May 2008

ABSTRACTThe cause of the apparently paradoxical occurrence of relatively high levels of labelling and low levels of mitotic activity in the pericryptal fibroblast sheath (PCFS) was investigated. Analysis of the distribution of grain densities over epithelial cells and the PCFS in the colon demonstrated that, although the former had a unimodal peak, the PCFS had a multi‐peak distribution. the PCFS nuclei with the higher grain densities gradually disappeared with time, due not to proliferation but to lateral migration into the lamina propria. Photodensitometric analysis confirmed the existence of polyploid cells in the colonic PCFS, but not in the epithelium.
EFFECTS OF ENVIRONMENTAL TEMPERATURE ON HAEMOPOIETIC STEM CELLS IN THE TAILS OF MICE
Authors: Littleton R. J. , Zebro T. , Wright E. A. 
Published: May 2008

ABSTRACTUsing the endogenous spleen colony assay method of Till & McCulloch (1963), the numbers of haemopoietic stem cells present in the bone marrow in the tails of mice were estimated under different environmental temperatures. Compared to animals kept at 22–26°C, mice transferred to and kept at 36.5°C showed a doubling of colony‐forming units in the tail in 1–4 weeks. Exposing them to 8°C caused a significant depopulation to approximately one‐third in 3–4 weeks. By transferring the mice from one temperature extreme to another these changes could be reversed. Tail marrow depleted of viable stem cells by X‐irradiation was repopulated within approximately 3 weeks in animals kept at room temperature or above but this process was inhibited in the cold.
Rat Serum Factors Inhibiting the G1‐S Transition In Hepatocytes
Authors: Nadal C. , Le Rumeur E. , Boffa G. A. 
Published: May 2008

ABSTRACTAn attempt was made to detect the serum factors inhibiting the G1‐S transition in synchronized, baby rat hepatocytes. In untreated adult rat serum, this inhibitory activity was always linked to high molecular weight (HMW) compounds. Incubation of serum with trypsin or chymotrypsin resulted in the formation of a low molecular weight (LMW) G1‐S inhibitory factor. the same result was obtained with fractions from adult rat liver but not with kidney or spleen fractions. Separation of the LMW factor by ultrafiltration increased its specific activity by about 103. the active period in the cell cycle of both the LMW and HMW factors was the same: the late G1 phase. However, the activity of the LMW factor was not blocked by the Kunitz factor. an enzymatic transformation of the HMW factor might be induced by liver cell membrane‐bound proteases and constitute a mechanism regulating hepatocyte proliferation.
Dna Synthesis and Cell Generation Pattern of Chronic Lymphatic Leukaemia Lymphocytes Stimulated By Phytohaemagglutinin
Authors: Matera L. , Cordero A. , Piazza A. , Giovinazzo B. , Pegoraro L. 
Published: May 2008

ABSTRACTA detailed analysis of the cell recruitment and of the cell generation pattern of normal lymphocytes and chronic lymphatic leukaemia (CLL) lymphocytes, simulated by phytohaemagglutinin (PHA), was performed by the bromodi‐oxyuridine (BUdR) Hoechst technique.It was found that in normal cultures the majority of cells divide two or three times, producing an early peak of DNA synthesis, while only a few cells grow exponentially and pass through many rounds of replication. On the contrary, the majority of CLL responsive cells grow exponentially, producing a delayed peak of DNA synthesis, while cells which divide only two or three times are scarce or absent. No difference in the minimal cell cycle length of the normal and the CLL exponentially growing population was found. In addition, a cell population recruited into cycle for the first time 5–6 days following PHA stimulation was observed in normal cultures but not in CLL cultures.
Cell Kinetic Characteristics In Different Parts of Multicellular Spheroids of Human Origin
Authors: Wibe E. , Lindmo T. , Kaalhus O. 
Published: May 2008

ABSTRACTThe growth fraction, the cell cycle time, and the duration of the individual cell cycle phases were determined as a function of distance from the surface of multicellular spheroids of the human cell line NHIK 3025. the techniques employed were percentage of labelled mitoses and labelling index measurements after autoradiography and flow cytometric measurements of DNA histograms. to separate cell populations from the different parts of the spheroid, fractionated trypsinization was employed.The results were compared with corresponding values in NHIK 3025 cell populations grown as monolayer cultures. While practically all cells in exponentially growing monolayer populations are proliferating, the growth fraction was between 0.6 and 0.7 in the outer parts of the spheroid. the inner region was mainly occupied by a necrotic mass. the proliferating fraction of the recognizable cells in the inner region was slightly below 0.5. the mean cell cycle time of NHIK 3025 cells in monolayer culture is 18 hr. the mean cell cycle time of proliferating cells in the periphery of the spheroid was 30 hr, compared to 41 hr in the inner region (150 μm from the spheroid surface). All phases of the cell cycle were prolonged compared to populations of exponentially growing monolayer cells. Within each part of the spheroid the distribution of cell cycle times was considerably broadened compared with monolayer populations.
Analysis of the effect of hydroxyurea on stem cell (CFU‐s) kinetics
Authors: Neĉas E. , Hauser F. 
Published: May 2008

Abstract. Hydroxyurea induces profound changes in the pluripotential haemopoietic stem cell (CFU‐s) kinetics. The main feature of these changes is a synchronous entry of resting Go CFU‐s into the cell cycle. The analysis of the passage of the CFU‐s cohort through the cell cycle has been largely based on the examination of the fraction of CFU‐s which synthesize DNA in the S phase of the cell cycle. This analysis has, however, been hampered by the fact that both the sensitivity of the S phase CFU‐s to hydroxyurea and their sensitivity in the [3H] thymidine suicide technique vary as the cells pass through the S phase. Methods which overcome these difficulties have been used in the experiments presented in this paper.It was demonstrated that hydroxyurea kills only about 80% of the S phase CFU‐s. The sensitivity to hydroxyurea gradually decreases as the cells approach the middle part of the S phase and increases again as the cells enter the late portions of the S phase.The degree of CFU‐s synchrony at the point of entry into and exit from, the S phase has been established. Mathematical analysis of the available data suggests that CFU‐s pass through the S phase with a mean transit time of 4–79 hr (standard deviation, 1.45 hr).Hydroxyurea, administered in vivo, blocks CFU‐s in the late G1 phase. The duration of this G1‐S block, induced by a dose of 1000 mg of hydroxyurea per kg body weight, is approximately 2 hr. The CFU‐s in the middle of the S phase, which survive hydroxyurea administration, are also blocked in their passage through the S phase. These cells, however, seem to finish the S phase with a delay of approximately 2 hr.
The regulation of bone marrow‐derived mononuclear phagocyte differentiation and mobilization in syngeneic and allogeneic YAC‐lymphoma‐bearing mice
Authors: Bursuker I. , Goldman R. 
Published: May 2008

Abstract. YAC‐lymphoma inoculation (ip) into syngeneic A/J mice results in a massive in situ proliferation of the lymphoma cells, with non‐significant increases in the peritoneal macrophage population, and also in a remarkable and progressive increase in the bone marrow precursor cells forming both macrophage and fibroblastoid colonies in vitro. In the allogeneic situation (BALB/c mice), YAC‐lymphoma cells proliferate to a limited extent before tumour regression. These processes (i.e. proliferation and regression) were accompanied by a progressive increase in the peritoneal macrophage population, which declined to normal after tumour regression. Macrophages accumulating at the regression stage exhibited in vitro cytolytic activity towards YAC‐lymphoma cells and cytostatic activity towards unrelated cells. No correlation was observed between the limited asynchronous increase in the bone marrow level of precursor cells for in vitro differentiating macrophage and fibroblastoid colonies, on one hand, and macrophage accumulation at the tumour site in BALB/c mice on the other. Conditioned media from in vitro proliferating YAC‐lymphoma cells exhibited high colony‐stimulating activity for macrophage colony formation in vitro. Bone marrow cells taken from YAC‐lymphoma inoculated A/J mice expressed potent tumorogenic potential at early stages after tumour inoculation. At day 2 after tumour inoculation the bone marrow cells were already tumorogenic and concomitantly expressed augmented levels of macrophage and fibroblastoid colony‐forming capacity.The results indicate an inter‐relationship between tumour growth and mononuclear phagocyte differentiation and proliferation.
Proliferation kinetics of endothelial and tumour cells in three mouse mammary carcinomas
Authors: Hirst D. G. , Denekamp J. , Hobson B. 
Published: May 2008

Abstract. An autoradiographic study of three corded mouse tumours is reported. The proliferation characteristics of both tumour cells and endothelial cells were studied. The doubling time of these three tumours differed by a factor of 2.6 but there was only a small difference in the intermitotic time. All three tumours showed a very high cell loss factor (˜0.80) and the differences in growth rate resulted mainly from differences in the growth fraction.The endothelial cell proliferation rates differed markedly in the three tumours, with labelling indices ranging from 18% in the faster tumours to 4.5% in the slowest. The potential doubling times for endothelium, calculated from these values, were much slower than the tumour cell cycle time or the tumour potential doubling time, but were two to four times faster than the volume doubling time of the tumour.It appears likely that the endothelial proliferation rate influences the growth fraction, but similar high cell loss factors can occur in tumours with a four‐fold difference in endothelial cell production rates. Inadequate branching of blood vessels seems likely to be at least as important as inadequate production of endothelial cells. It is not possible to determine whether slow tumour cell production evokes a slower endothelial growth or vice versa.
A comparative investigation of the antimitotic action of 2‐mercaptoethanol and colcemid on V‐79 Chinese hamster cells
Authors: Speit G. , Speit Dorothee , Vogel W. 
Published: May 2008

Abstract. The current study was performed to characterize the antimitotic action of 2‐mercaptoethanol (MET) on mammalian cells.At concentrations of 2.5 × 10‐2 M, MET arrests V‐79 Chinese hamster cells in metaphase. Smaller concentrations (from 5 × 10‐3 M) only produce a mitotic block after several hours, only arresting those mitoses which have gone through one cell cycle in the presence of MET. The accumulation of mitoses by MET is smaller in comparison with colcemid, explained by an effect reducing the number of cells which enter mitosis. In contrast to colcemid, MET‐concentrations which do not lead to a mitotic block cause a delay in proliferation. It was shown, by means of the BUdR‐labelling method that cells in the presence of colcemid concentrations which arrest mitosis again enter interphase and become polyploid, whereas MET leads to an irreversible arrest of mitosis and does not produce polyploidy in V‐79 cells.