bluuebunny/crossref_metadata_2025_split huggingface dataset:
Density Centrifugation of Murine Fibrosarcoma Cells Following In Situ Labelling With Tritiated Thymidine
Authors: Sigdestad C. P. , Grdina D. J. 
Published: May 2008

ABSTRACTMurine fibrosarcoma (FSa) cells form at least five unique subpopulations after centrifugation in linear Renografin density gradients. Each of these subpopulations has been characterized with respect to selected kinetic parameters using pulse‐labelling techniques and flow microfluorometry (FMF) analysis. Tumour‐bearing mice were first injected intraperitoneally with a pulse label of tritiated thymidine ([3H]TdR, 50 μCi). Following 15, 30, 60 min or 24 hr these animals were injected with cold thymidine. Animals were killed, their tumours removed and made into suspension, and separated by density gradient centrifugation. Each gradient was fractionated and the density, cell number, tritium activity, and labelling index (LI) per fraction were determined. These data were then compared to FMF data for selected cell density bands. the results indicated a relatively higher uptake of [3H]TdR in the cells recovered at the lighter (1.06–1.12 g/cm3) as compared to the heavier (>1.12 g/cm3) densities. Following a 30‐min pulse, the LI's of light cells (<1.12 g/cm3) ranged from 25 to 30%, while the heavier cells (>1.12 g/cm3) had LI's between 10 and 15%. the unseparated control cells had an LI of 19%. Comparable results were found at the other times tested. In contrast, the FMF profiles describing the DNA contents of the cells banding in the gradient showed no difference in proportion of S‐phase cells among the separated subpopulations. This lack of correlation between the FMF determination of S‐phase cells and labelling index for the denser cell populations implies that DNA content alone is not an effective measurement of the functional activity of cells in solid tumours. Finally, the relatively reduced uptake of [3H]TdR by these denser cells suggests that they may have resided at relatively large distances from the functional vasculature in the tumour.
Combination of Budr‐Quenched Hoechst Fluorescence With Dna‐Specific Ethidium Bromide Fluorescence For Cell Cycle Analysis With A Two‐Parametrical Flow Cytometer
Authors: Böhmer R.‐M. , Ellwart J. 
Published: May 2008

ABSTRACTStimulated or asynchronous L‐cells were grown in a BUdR‐medium, harvested and stained with a combination of 33258 Hoechst and ethidium bromide for analysis in a FACS II cell sorter. the u.v. laser line served as a light source for exciting the Hoechst fluorescence, the ethidium bromide fluorescence being excited mainly by energy transfer from the Hoechst dye. the quenched Hoechst fluorescence was analysed between 410 nm and 480 nm, the DNA specific EB fluorescence at beyond 630 nm. Thus, not only the actual location of each cell in the cycle could be determined, but also its initial location at time 0 of the experiment, together with its moment of division (BUdR‐quenched Hoechst fluorescence). This method could become a powerful tool in many investigations dealing with cell cycle perturbations in culture.
Cellular proliferation kinetics of the murine sarcoma induced by the Moloney sarcoma virus
Authors: Smadja‐Joffe F. , Bousse‐Kerdiles M. C. Le , Klein B. , Malaise E. P. , Jasmin C. , Degiorgis V. 
Published: May 2008

Abstract. Cell proliferation kinetics of the sarcoma induced by Moloney virus was studied in newborn Swiss OFl mice.After in vivo injection of tritiated thymidine, followed by autoradiography, it was shown that the majority of cells were actively proliferating (labelling index; 31%, growth fraction 78%). The mean cell cycle was 16 hr and cell loss was relatively low (cell loss factor 48%). The study of tumour specific activity with time after a single [in vivo] injection of [3H]dR or [125I]UdR did not demonstrate the same degree of cell loss as that calculated by autoradiography. This result is consistent with a massive reutilization of radioactivity released by normal tissues.
Circadian variations in influx and efflux of the S phase in a partially synchronized cell system Double‐labelling with [3H]thymidine in the epithelium of the hamster cheek pouch
Authors: Møller U. , Keiding N. 
Published: May 2008

Abstract. By means of a double‐labelling experiment, circadian variations in the kinetic parameters of the S phase of the hamster cheek pouch epithelium were studied. The evaluation of the experiment included a recently developed correction for deviations from the strict pulse interpretation of the labelling technique.Pronounced circadian variations were found in S phase influx and efflux; the diurnal mean of both was estimated as 0.5%/hr, when based on measurements of all nucleated epithelial cells. Variations in S phase influx seem mainly responsuble for the diurnal variation in cell proliferation, although diurnal variation in DNA synthesis rate, and thus in mean transit time, was also found. The increases in LI and influx were closely correlated and related to the beginning of the dark period.A circadian variation in cell number was also observed.
The spatial organization of the hierarchical proliferative cells of the crypts of the small intestine into clusters of ‘synchronized’ cells
Authors: Potten C. S. , Chwalinski S. , Swindell R. , Palmer M. 
Published: May 2008

Abstract. A statistical analysis of the distribution of [3H]TdR‐labelled cells in longitudinal and transverse sections of crypts from the ileum of the mouse, indicated that there was a strong tendency for labelled or unlabelled cells to be associated in short vertical runs and lateral clumps, suggesting the presence of clusters of labelled cells on the sides of the crypts. A model is discussed for the cellular spatial organization of the crypt that proposes a vertical alignment of the cells within branches of the proliferative cell lineage. The model would predict vertical alignment of partially synchronized cells as well as some lateral clumping.In the present studies mitoses were not observed at higher levels in the crypt than labelled (S phase) cells. This observation would be predicted by the non‐random spatial organization suggested by the model.The model would also make certain predictions concerning cell migration. These are discussed in relation to cell migration studies which include evidence that migration continues in the absence of mitotic activity.
The kinetics of villus cell populations in the mouse small intestine
Authors: Wright N. A. , Irwin M. 
Published: May 2008

Abstract. The cell population kinetics of the villus epithelium of the mouse have been analysed with respect to the size, flux and time. Microdissection methods were employed to measure the villus cell population size and yielded reproducible, precise results. There was a proximodistal negative size gradient in villus cell population and, in those villi of normal morphology, there was a good correlation with the usual morphometric estimators such as height and row count, although correlation was improved by a product variable consisting of a height multiplied by a width parameter.Flux onto the villus is the product of the crypt cell production rate, which was measured by a metaphase arrest method using vincristine and crypt microdissection, and the crypt:villus ratio; net villus influx was maximum proximally in the bowel, where the largest villi were found, and decreased distally. The distribution of transit times of labelled cells to the crypt: villus junction and to the villus tip was measured, allowing the measurement of the median villus transit time.Comparison of the measured villus transit time with the theoretical transit time calculated from the villus influx and population size gave results consistent with a steady state hypothesis. It was found, at each level of the small intestine studied, that the number of epithelial cells on the villus was equivalent to the total number of crypt cells associated with the villus.
The kinetics of villus cell populations in the mouse small intestine
Authors: Wright N. A. , Al‐Nafussi A. 
Published: May 2008

Abstract. Cytosine arabinoside was used to kill large numbers of proliferating crypt cells in the mouse small intestine, and the recovery sequence was analysed in terms of the villus population size, the crypt population size, the crypt:villus and the net villus cell influx; because the crypt:villus ratio changed considerably, it was found appropriate to express the crypt population in terms of the crypt cell mass per villus in order to relate it to the villus cell population.All parameters measured showed a series of damped oscillations over the experimental period, and analysis of the relationship between the several population changes strongly suggest that negative feedback control mechanisms are responsible for the response pattern. The importance of measuring the correct kinetic parameters in growth control studies on renewing epithelia is stressed.
Self‐replication of somatostatin cells in the antral mucosa of rodents
Authors: Lehy T. 
Published: May 2008

Abstract. The possibility that antral somatostatin cells have a self‐replicating activity has been studied in three species of rodents: mice, rats and guinea‐pigs, after a flash tritiated thymidine injection. The immunocytochemical staining of somatostatin cells, using specific antiserum, was combined with radioautographic procedures. The labelling index for somatostatin cells–and for gastrin cells indentified on serial sections–was established after counting a large number of cells at the optical microscope level, on parallel tissue strips removed throughout the entire antrum.A significant percentage of the somatostatin cell population synthesized DNA. Values were similar for the three species of rodents ranging from 0.8 to 1.1%, that is slightly higher than the percentage of labelled gastrin cells, which was 0.6–0.7%. After a 36‐hr continuous infusion of radioactive precursor in one rat, the labelling index observed remained low; 2.33% for somatostatin cells and 1.68% for gastrin cells. Colchicine injection in mice allowed the observation of mitotic figures in well differentiated somatostatin cells. Four hours after that injection, the mitotic index was estimated roughly at 0.3%.Thus, evidence has been presented that in rodents a fraction of the antral somatostatin cell population is capable of dividing, similar to the situation in gastrin cells.
The proliferative response of rat liver parenchymal cells after partial hepatectomy A methodological study comparing flow cytometry of nuclear DNA content and in vivo and in vitro uptake of thymidine
Authors: Digernes V. , Brønstad G. , Sand T.‐E. , Christoffersen T. 
Published: May 2008

Abstract. DNA synthesis in rat hepatocytes, from livers regenerating after 70% hepatectomy, was assessed by flow cytometric determination of nuclear DNA content and by incorporation of [3H]thymidine. Parenchymal liver cells were isolated by collagenase perfusion and low‐speed centrifugation. Nuclei from the isolated cells were prepared for flow cytometry by a treatment with detergent, pepsin and RNase, and stained with ethidium bromide. Parallel samples of cells were incubated with [3H]thymidine and analysed for rate of incorporation of radioactivity into DNA and for labelling index determination.The flow cytometric measure of the replicative response, i.e. the presence of cells with S‐phase DNA content within the diploid and tetraploid cell populations, was compared with the incorporation of [3H]thymidine. For each of fourteen animals, including two control rats and twelve partially hepatectomized animals killed either before (at 13 hr after hepatectomy), at the onset (16 and 18 hr) or at the peak (24 hr) of regenerating activity, a fairly good correlation was found between the different methods. Satisfactory resolution of the flow cytometric detection of S‐phase cells was indicated by a sorting experiment using an Ortho (system 50‐H) cell sorter which demonstrated that after [3H]thymidine injection in vivo 88% of the diploid and 84% of the tetraploid S‐phase nuclei were labelled, while labelling in the G1‐fractions was only 2 and 7%, respectively.
Non‐Exponential Growth By Mammalian Cells In Culture
Authors: Skehan Philip , Friedman Susan J. 
Published: May 2008

AbstractThe concept of exponential growth by mammalian cells in culture is based upon the apparent linearity of semilogarithmic data plots. This method of graphical analysis is known to be an unreliable test of the exponential hypothesis. We have re‐examined the question of growth exponentiality using the more sensitive method of Smith plots, in which specific growth rate is plotted against either time or density on transformed graphical coordinates which linearize the mathematical expression of the growth hypothesis being tested. With exponential growth, data points fall on a horizontal straight line when specific growth rate is plotted against time or density. Using both our own and literature data, we have performed Smith plot analyses on the growth of 125 different mammalian and avian cell lines. of these, only eleven exhibited an exponential phase. the remaining cell lines all had non‐exponential growth patterns. the most common of these consisted of an initial period of growth acceleration followed by a later phase of deceleratory growth. A smaller number of lines exhibited deceleratory kinetics at all times after plating. We conclude that mammalian cell growth in culture is predominantly non‐exponential, and that the apparent exponentiality of semilogarithmic data plots is usually a methodological artifact.
On the Equivalence of Mathematical Models For Cell Proliferation Kinetics
Authors: Sundareshan Malur K. , Fundakowski Richard 
Published: May 2008

AbstractVarious types of mathematical models, such as partial differential equations, ordinary differential equations and difference equations, are available in the literature to describe the kinetics of cell proliferation, and different studies of cell kinetic phenomena have been conducted using these models. This paper discusses the equivalence between the different models identifying the conditions and approximations under which one type of models may be derived from another. Such an equivalence study is highly useful for an integration of the diverse results that have been obtained using different models in order to gain a more complete understanding of cell kinetic phenomena.
Cell‐Cycle‐Dependent and ‐Independent Damage to Rat Haemopoiesis By Hydroxyurea
Authors: Dörmer P. , Böhmer R.‐M. 
Published: May 2008

AbstractThe generally accepted cell‐killing effect of hydroxyurea (HU) on S‐phase cells, as well as its potential to arrest cells at the G1/S boundary, hardly explain its benefit for application in human chronic myelogenous leukaemia. Studies were therefore performed in rat haemopoiesis in order to quantify the cell‐killing effect on various phases of the cell cycle. For this purpose, the [3H]thymidine ([3H]TdR) labelling index and the specific activity of [3H]TdR in the DNA‐synthesizing fraction of cells were determined after a non‐cytoreductive dose of 25 mg/kg HU, as well as a medium cytoreductive dose of 100 mg/kg. Furthermore, flow cytometric DNA histograms and absolute as well as differential cell counts of femoral bone marrow were performed after 100 mg/kg HU.The results indicate a predominant cell kill in G1 encompassing almost all 2c cells in the proliferative pool, while the S‐phase fraction is not even reduced to half its initial value. the specific activity of [3H]TdR in cells synthesizing DNA, as well as the labelling index after HU show an initial dip and a tendency to recovery, as has been observed in many other cell systems. Instead of a complete restoration, however, there is a second depression of these parameters lasting for at least one cell cycle. the results are interpreted as a partly cell‐cycle‐dependent and partly independent action of HU in this cell system. the independent component may be attributed to the repeatedly described direct interference of HU with DNA. In rat haemopoiesis, therefore, this direct effect of HU on the DNA strands appears to be much more pronounced than in cell‐culture systems and other mammalian tissues. In view of these findings, some caution should be taken in using HU for the determination of the S‐phase fraction by way of a suicide experiment.
Cell Kinetic Behaviour of A Synchronized Population of Erythroid Precursor Cells in vitro
Authors: Nijhof W. , Wierenga P. K. , Pietens J. , Bloem R. 
Published: May 2008

AbstractErythropoiesis in vitro was studied with practically pure erythroid progenitor cells: CFU‐E (colony‐forming‐units‐erythroid). the isolation of CFU‐e from spleens of thiamphenicol pretreated anaemic mice with the combined methods of centrifugal elutriation and Percoll density gradient centrifugation was monitored by flow cytometry. the ultimate CFU‐e preparation with a density of 1.070 g/ml contained a high percentage of cells in the S phase of the cell cycle (80%). CFU‐e occasionally found at a lower density of 1.065 g/ml were predominantly in the G2, + M and G1 phases.When CFU‐e were cultured, the number of cells in the distinctive phases of the cell cycle changed periodically, so the cells were partly synchronized. Four periods up to 27 hr were observed by flow cytometrical screening of the cultured cells at hourly intervals. Cell‐cycle times between 6 and 7 hr were found for all erythroid cell divisions. This was in agreement with results obtained from colony growth curves. Without the addition of erythropoietin cells start to degenerate after the second cell division. This experimental approach can be used for the cell kinetic modelling of erythropoiesis.
Effect of Mitochondrial Inhibitors On Metaphase‐Telophase Progression and Nuclear Membrane Formation In Chinese Hamster Cells
Authors: Chai Lee S. , Schumer Joan M. , Sandberg Avery A. 
Published: May 2008

AbstractChinese hamster Don cells in log‐phase were exposed to Colcemid during the G2 period with and without a combination of divalent cation chelators and mitochondrial inhibitors. Isolated metaphase cells were incubated as follows: (i) without Colcemid but with other agents and the progression was monitored from metaphase (M) to telophase (Tel) and to cell division; (ii) with Colcemid and other agents and the rate of micronuclei formation in the absence of anaphase was studied. Both EDTA and EGTA accelerated the progression from M to Tel, but did not affect the overall rate of cell division. Chloramphenicol (CAP), an inhibitor of mitochondrial protein synthesis, blocked the effect of the chelators and also retarded the progression. an inhibitor of mitochondrial respiration, Antimycin A (AA), also retarded the progression in the absence of the chelators and prevented the promoting effect of the chelators. A stimulator of ATPase for ATP breakdown. 2,4‐dinitrophenol (DNP), accelerated the M to Tel progression.Chloramphenicol (CAP) and AA, as well as DNP, appeared to have little effect on the formation of micronuclei in the presence of Colcemid. EGTA, which affects cell surface Ca2+, stimulated the formation of micronuclei. This study indicates that Ca2+ ions and mitochondrial function are involved in the regulation of a certain segment of mitosis beyond metaphase, with Ca2+ sequestration in the mitochondria and chelation of Ca2+ by EGTA as dominant factors.
Cell Kinetic Studies of Chick Brain Cells In Culture: an Autoradiographic Study With [3H]‐ and [14C]‐Thymidine
Authors: Barakat I. , Korr H. , Schultze‐Maurer B. , Sensenbrenner M. 
Published: May 2008

AbstractLabelling index, S‐phase duration and cell‐cycle time of proliferating brain cells from 6‐day‐old chick embryos in culture were investigated autoradiographically after labelling with [3H]‐ and/or [14C]‐thymidine. the dissociated cells were cultured in the absence or in the presence of brain extract from 8‐day‐old chick embryos. Cultures contained essentially two cell types, which could be easily distinguished by the size of their nuclei: small nuclei identified as belonging to precursor cells of neurons and large nuclei corresponding to astroglial cells. the labelling index of astroglial cells (16.4%) was about 2 times higher than that of the neuronal cells (9.9%). Under the influence of brain extract the labelling index of neuroblasts was nearly doubled while that of the astroglial cells remained nearly unchanged. From double‐labelling experiments with [3H]‐ and [14C]‐thymidine, the same S‐phase duration of about 7 hr was found for both cell types cultured with or without brain extract. A cell‐cycle duration of 39 hr for neuronal and of 29 hr for astroglial cells was found. the cycle times remained constant under the influence of brain extract. From the measured data mentioned above, a growth fraction of 50% (neuroblasts) and 68% (astroglial cells) was calculated in control cultures without brain extract. After addition of brain extract, the growth fraction increased for both cell types (neuroblasts: 92%; astroglial cells: 80%). the results demonstrate that more cells proliferate in the presence of brain extract, but the durations of the S‐phase and the cell cycle remain unchanged.
Feedback Regulation of the Proliferation of the Undifferentiated Spermatogonia In the Chinese Hamster By the Differentiating Spermatogonia
Authors: de Rooij D. G. , Lok D. , Weenk D. 
Published: May 2008

AbstractIn the seminiferous epithelium the differentiating spermatogonia proliferate following a very strict synchronous pattern, and undergo the S phase during parts of particular epithelial stages. the undifferentiated spermatogonia do not divide synchronously and display maximum proliferative activity in stages XI‐III. Hence the S‐phase‐specific cytotoxic agent Ara‐C kills different proportions of these two cell types dependent on the epithelial stage. We have studied the effect of several combinations of degrees of cell loss to both compartments on proliferation of the undifferentiated spermatogonia.It was found that when the differentiating spermatogonia are removed, the proliferation of the undifferentiated spermatogonia is not inhibited at epithelial stage III, as seen in controls. However, when the undifferentiated spermatogonia were already arrested in G1, removal of the differentiating spermatogonia did not evoke proliferation again. When the population of undifferentiated spermatogonia was reduced in an area where the differentiating spermatogonia were left intact, the inhibition of the proliferation of undifferentiated spermatogonia took place around stage III as usual.It is concluded that in the normal adult seminiferous epithelium, the length of the period of active proliferation of the undifferentiated spermatogonia is regulated by negative feedback from the differentiating spermatogonia.
Alterations In Metaphase Durations In Cells Derived From Human Tumours
Authors: Sisken J. E. , Bonner Susan V. , Grasch Sally D. , Powell Deborah E. , Donaldson E. S. 
Published: May 2008

AbstractWith the use of time‐lapse cinemicrography, we previously found that metaphase durations were significantly prolonged in SV40‐transformed human fibroblasts when compared to untransformed controls. This was consistent with some earlier reports and suggested that prolonged metaphases could account for high metaphase/prophase ratios and possibly, in part, for increased mitotic indices seen in advanced tumours. However, there are inconsistencies in the literature and no comparable data available from malignant carcinomas. Presented in this paper are data from two cervical dysplasias, two cases of carcinoma in situ, nine malignant carcinomas and several other types of human cells. the results show that mean metaphase durations were prolonged in cells derived from most of the carcinomas but not from the other cell types. On the other hand, cytokinesis appears to progress more rapidly than normal in most of the tumour‐derived cells. These and other findings indicate that the changes are a result of some metabolic alteration common to many but not all tumour cells. For reasons presented, we suggest as a working hypothesis that the alterations may be due to changes in calcium regulation, possibly resulting from alterations in mitochondrial metabolism.