bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell‐Cycle‐Dependent and ‐Independent Damage to Rat Haemopoiesis By Hydroxyurea
Authors: Dörmer P. , Böhmer R.‐M.
Published: May 2008

The 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

Erythropoiesis 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

Chinese 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

Labelling 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

In 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

With 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.
Effect of Medium Osmolality On the Growth of Murine Continuous Marrow Cultures
Authors: Tennant G. B. , Bailey‐Wood R. , Dallimore C. M.
Published: May 2008

The effect of medium osmolality was examined in primary, continuous bone‐marrow cultures established from to strain mice. the non‐adherent cell population increased exponentially between weeks 2 and 5 and thereafter declined steadily. the number of CFU‐GM followed a similar pattern but showed greater variability. the optimum osmolality in 4 week old cultures was found to be about 345 mosmol/kg which was higher than the plasma osmolality (n= 20; mean = 323.3 mosmol/kg; range = 313–331). Maximum non‐adherent cell numbers were found at about 345 mosmol/kg (better than half‐maximum between 320 and 370 mosmol/kg). CFU‐GM numbers in the culture supernatant were maximal at about 355 mosmol/kg (better than half‐maximum between 320 and 400 mosmol/kg). an adherent layer developed over a wider range of osmolality than supported granulopoiesis (better than half‐maximum between 258 and 402 mosmol/kg). It was necessary to increase the osmolality of Fischer's medium in order to obtain maximum growth.
Use of A Mouse Chimaeric Model to Study Cell Migration Patterns In the Small Intestinal Epithelium
Authors: Wilson T. J. G. , Ponder B. A. J. , Wright N. A.
Published: May 2008

The pattern of cells migration in the small intestinal epithelia of a RIII/⇒ro C57BL/6J mouse aggregation chimaera is demonstrated using Dolichos biflorus agglutinin‐peroxidase (DBA) conjugate as a strain‐specific marker. Using serial tangential sections of heterogeneously stained villi and plotting the distribution of labelled/unlabelled cells with a drawing tube, and by three‐dimensional reconstruction with the aid of computer graphics, we show the migration pathway to be in tight cohorts of similar DBA‐peroxidase staining type, which move upwards in straight lines. There is little cell mixing either on the villus or along the crypt‐villus junctions. Our observations also show for the first time that a single crypt can feed cells to more than one villus. They also suggest that either cell loss is not confined to the villus tips but can take place from the villus sides, or that there is marked asynchrony of cell production between crypts.
Combined Effects of Aphidicolin and Retinoic Acid On Proliferation and Differentiation of Human Leukaemic (HL‐60) Cells
Authors: Chou R. H. , Chervenick P. A.
Published: May 2008

The relationships between replicative DNA synthesis and retinoic acid (RA)‐induced differentiation of human promyelocytic leukaemic (HL‐60) cells are evaluated with the use of Aphidicolin, a specific and reversible inhibitor of DNA polymerase alpha (α). Addition of a sublethal concentration of Aphidicolin (0.4 μM) in culture for 3 days suppresses DNA synthesis to a similar level of the resting stage (day 8) in control cultures. DNA synthesis is reactivated to the level observed in the growing stage of control cultures once Aphidicolin is removed after 3 days in culture. the level of DNA synthesis at the early stage of RA‐induction (day 3) is suppressed by only 17% when compared to control cultures. the inhibitory effect of Aphidicolin on DNA synthesis in both control cultures and RA‐induced cell cultures is similar. However, no reactivation of DNA synthesis is observed after removal of Aphidicolin on day 3 from RA‐induced cell cultures. Flow cytometric analysis of DNA content on day 3 reveals that cells accumulate in G1 and early S phases of the cell cycle after exposure to Aphidicolin with or without RA. of interest is the fact that, while Aphidicolin alone did not induce cells to differentiate, neither did it interfere with RA‐induced cell differentiation (the rate of RA‐induced cell differentiation in the presence of Aphidicolin is similar to that of RA‐treated cultures in the absence of Aphidicolin). These results suggest that the combined use of Aphidicolin and RA may inhibit leukaemic cell proliferation more effectively without causing severe cytotoxicity and without interfering with RA‐induced cell differentiation.
Oestradiol is effective in stimulating 3H‐Thymidine Incorporation But Not On Proliferation of Breast Cancer Cultured Cells
Authors: Jozan S. , Gay G. , Marques B. , Mirouze A. , David J. F.
Published: May 2008

The growth of numerous human oestrogen target cell lines is said to have been stimulated by oestradiol. We studied the action of this hormone on the growth of two human cancer cell lines originating from endometrium (GUS), and from breast (FAM). Oestradiol was inactive on endometrial cell multiplication as well as on their tritiated thymidine uptake, but in FAM breast cancer cells, we noticed a discrepancy between tritiated thymidine uptake and actual cell proliferation: there was a 40% increase in DNA precursor uptake, but no change in either the number of cells or in their DNA content, both of which were verified by two different methods. Therefore, an actual increased nuclear (autoradiographic) uptake of thymidine did take place in oestrogenized cells, associated with an increase of incorporation into DNA (a rise of radioactivity in the acid‐insoluble materials), but finally there was no greater total DNA increase in the whole treated population than in control cells.

Then we examined the metabolism of tritiated thymidine in oestradiol‐treated FAM cells. We extracted the radioactive thymine nucleotides and characterized them chromatographically: the oestradiol caused an increase in the labelling of deoxythymine monophosphate (TMP). How these results are consistent with both unmodified cell count and whole DNA content is discussed.
Two‐Dimensional Diffusion Limited System For Cell Growth
Authors: Hlatky L. , Alpen E. L.
Published: May 2008

Abstract. A new cell system, designed to supplement multicellular spheroids as tumour analogues, was analysed theoretically and experimentally. This ‘sandwich’ system is a single layer of cells, subject to self‐created gradients of nutrients and metabolic products. Due to these gradients the sandwich system develops a border of viable cells and an inner region of necrotic cells corresponding to the viable rim and the necrotic center of a spheroid. However, sandwiches differ from spheroids in several ways. All the cells in the sandwich can be microscopically viewed during the entire experiment. In sandwiches there is no three‐dimensional cell to cell contact. Also, the gradients are less steep in our sandwich system, so the width of the viable region in a sandwich is about 10 times as large as the width of the viable rim in a spheroid. Indeed, in sandwiches the experimenter has some control over the steepness of the gradients and thus can vary the width of this viable border. We used DNA labelling studies and flow cytometry along with visual observation to analyse the system. Our experiments show that the observed cell necrosis, similar to that found in spheroids, is due to diffusion limitations. the results are consistent with the idea that oxygen deprivation stops cell cycling and, when extreme and prolonged, leads to necrosis. the possibility that substances other than oxygen are involved is not excluded by the data. the data also suggests that in the final, near‐equilibrium state the average overall oxygen consumption rate for the viable sandwich population may be about one‐quarter of that for an exponentially growing population of the same cell line.
The Sensitivity of G0‐State Haemopoietic Spleen Colony‐Forming Cells to A Stimulus For Proliferation
Authors: Lord B. I.
Published: May 2008

Haemopoietic spleen colony‐forming units (CFU‐s) close to the axis (axial CFU‐s) of the long bones have a high probability of self‐renewal. They are pluripotent cells and are largely in a Go‐State. By contrast, CFU‐s close to the bone surface (marginal CFU‐s) have a lower probability of self‐renewal and are probably more mature, though still pluripotent. Most CFU‐s proliferation arises in this zone. As a consequence, marginal CFU‐s tend to have shorter Go histories than do axial CFU‐s. Femoral marrow was, therefore, divided into axial and marginal populations and the sensitivity of the CFU‐s to an endogenous CFU‐s‐specific proliferation‐stimulating factor was assessed and compared by the tritiated thymidine suicide technique. It was found that axial CFU‐s are considerably more resistant to stimulation than are marginal CFU‐s in that larger doses for longer periods of exposure are required to increase the proliferative activity of the cells. This behaviour is consistent with the suggestion that cells with a low division probability exist in deeper levels of the quiescent Go‐state. Although this hypothesis was developed from the behaviour of cells maintained in culture under sub‐optimal physiological conditions, this phenomenon appears, in vivo, to be a characteristic of the stem cell population of haemopoietic tissue; their high resistance to stimulation maintaining the axial CFU‐s in a quiescent state.
Kinetic and Physical Studies of Cell Death Induced By Chemotherapeutic Agents Or Hyperthermia
Authors: Dyson J. E. D. , Simmons Deena M. , Daniel Jill , McLaughlin J. M. , Quirke P. , Bird C. C.
Published: May 2008

The kinetics of three physical parameters: cell density, relative cytoplasmic viscosity and DNA stability to denaturation have been measured during the period preceding cell death induced by hyperthermia, methylprednisolone and a series of cancer chemotherapeutic agents. This series of measurements employed cultured human lymphoblastoid cells as an experimental system to establish the changes that can be observed in the early stages of cell death, prior to applying such measurements to tissue biopsies from solid human tumours. Cell death, induced by hyperthermia up to 43°C, methylprednisolone, vincristine, 5‐fluorouracil, BCNU and melphalan, showed essentially identical and reproducible changes corresponding to those which characterize programmed cell death (apoptosis). Such changes could also be observed following hyperthermia above 43°C, but reproducibility was poor and increasing damage to the cell membranes was evident. In cells treated with adriamycin or methotrexate, cell sub‐populations showing an increase in cell density were not detected. Measurements of DNA stability were readily performed by flow cytofluorometry thus allowing rapid quantitation of the fraction of cells in the early stages of cell death. Modified flow cytometric instrumentation would further allow measurement of cytoplastic viscosity as an additional parameter to indicate entry into programmed cell death. This suggests that these measurements could readily be applied to cell suspensions derived from tumour tissue biopsies for a more accurate assessment of tumour growth rate, and to allow monitoring of response to therapy in sequential tumour biopsies.
Rate of Loss of Tritiated Thymidine Label In Basal Cells In Mouse epithelial tissues
Authors: Bickenbach J. R. , McCutecheon J. , Mackenzie I. C.
Published: May 2008

A subpopulation of epithelial cells which retains a tritiated thymidine label (termed label‐retaining cells, LRCs) has been previously demonstrated in skin and oral mucosae of mice and hamsters. to examine the rate of decrease in the number of LRCs and the changes in degree of labelling, young mice were labelled with tritiated thymidine and the rate at which label was diluted from basal keratinocytes assessed for up to 90 days. the number of LRCs in each tissue examined decreased from 15 to 90 days after labelling with the epidermal tissues maintaining a higher percentage of LRCs than the oral mucosae. Grain counts for LRCs in each tissue at each time period indicated that the number of silver grains overlying LRCs also decreased with time. the observed decrease in numbers of LRCs and the change in their degree of labelling with time suggest that such cells divide slowly, a property associated with stem cells.
Sleep Deprivation Alters the Cell Population Kinetics In the Jejunum of the Male Syrian Hamster (Mesocricetus auratus)
Authors: Jazwinska Elizabeth C.
Published: May 2008

The proliferative and functional units of the jejunum were studied every 3 hr during 24 hr in groups of control and sleep‐deprived hamsters. Peaks in kinetic parameters were evident during the sleep period in control hamsters; in the absence of sleep, peak values were significantly reduced. Sleep deprivation was associated with reduction of G2 to M flux and reduction of the circadian rhythm in mitotic index from 74% to 25%. the reduction in the number of cells passing through M was reflected by a drop in labelling index 9 hr later. These findings are consistent with the theory that sleep promotes restorative processes.
Growth Regulation In Multilayered Cultures of Human Diploid Fibroblasts: the Roles of Contact, Movement and Matrix Production
Authors: Bard Jonathan , Elsdale Tom
Published: May 2008

Abstract. Early subcultures of human embryonic lung fibroblasts are exceptional, as they grow far beyond confluence before growth ceases: the stationary dish may well contain 3‐10 monolayer equivalents. Maximal growth rates, however, occur at about one‐sixth confluence when doubling times are 15‐20 hr; a density at which cell contacts begin to become frequent. the fact that a slowing down of growth is first apparent at such low densities argues against this regulation being due to diffusion effects. Confirmation of the role of short‐range or contact interactions in growth regulation comes from an experiment using mixed cultures of fibroblasts: this shows that growth inhibition is not carried by medium‐borne influences but depends on short‐range (<1 mm) interactions. Evidence that cells can escape the effects of such contact interactions and so divide comes from time‐lapse studies of dense cultures: there is a burst of motility soon after a fresh‐medium change, which is followed by a burst of mitosis × 20 hr later. A medium change to conditioned medium supplemented with 10% foetal calf serum leads to neither the burst of motility nor the subsequent burst of mitosis, although this medium is better able to support the growth of sparse cells than is fresh medium. Data are also presented to show that the amount of collagen deposited in superconfluent cultures affects their growth: the stimulation of collagen production with ascorbic acid leads to an unexpectedly low stationary cell density and rather less movement in the culture. This result suggests that the collagen stabilizes cell contacts that are responsible for growth inhibition. the question of why these cells grow more slowly as density increases cannot be answered directly by these experiments; nevertheless, the results suggest that cell contact affects the permeability of the cell membrane to medium.
Growth Characteristics of Human Melanoma Multicellular Spheroids In Liquid‐Overlay Culture: Comparisons With the Parent Tumour Xenografts
Authors: Rofstad Einar K. , Wahl Anne , Davies Catharina de L. , Brustad Tor
Published: May 2008

Abstract. The growth characteristics of multicellular spheroids, derived from human melanoma xenografts and cultivated in liquid‐overlay culture, were studied and compared with those of the parent tumours. Six of the seven melanomas investigated formed spheroids, which grew exponentially up to a volume of 1‐2 × lo7 pm3 (a diameter of 270‐340 μ) before the growth rate tapered off. the morphology of the spheroids varied considerably among the melanomas; some spheroids grew as densely packed, spherical structures of cells whereas others were loosely packed and showed an irregular shape. Central necrosis developed when the spheroids attained a diameter of 150‐200, μ. the histological and cytological appearance of the spheroids was remarkably similar to that of the parent xenograft in five of the six cases. the sixth melanoma contained two subpopulations with distinctly different DNA content, one of which was predominant in the spheroids, the other in the tumours. This gave rise to clear histological and cytological differences. the volume‐doubling time of the spheroids during the exponential growth phase ranged from 1.7 → 0.2 to 2.7 + 0.4 days and the fraction of cells in S from 13 → 1 to 28 → 2%. the volume‐doubling time decreased with increasing fraction of cells in S, indicating that the differences in growth rate were due mainly to differences in the growth fraction or to differences in the duration of G,. the spheroid volume‐doubling times did not correlate with those of the parent xenografts (Td= 4.2‐22.5 days at V= 200 mm3), possibly because the cell loss factors of the xenografts were large and varied among the melanomas. the fractions of cells in G1/G0, S and G2+ M in the spheroids and the xenografts did not correlate either, but were found to be within the same narrow ranges in the spheroids and the xenografts—i.e. 50‐80% (G1/Go), 10‐30% (S) and 10‐20% (G2+ M).
Rate and Time of Dna Synthesis of Human Leukaemic Blasts In Bone Marrow and Peripheral Blood
Authors: Ucci Giovanni , Riccardi Alberto , Dörmer Peter , Danova Marco
Published: May 2008

Abstract. We have evaluated DNA synthesis rate (S rate) and time (Ts) and tritiated thymidine labelling index (LI) of peripheral blood (PB) and/or bone marrow (BM) leukaemic blasts (Bl) in nineteen cases of acute leukaemia (twelve non‐lymphoblastic, AnLL, and seven lymphoblastic, ALL), in one case of non‐Hodgkin's leukaemic lymphoma and in a case of plasma cell leukaemia.

The LI of PB‐BI was significantly lower than that of BM‐Bl (range 0.1‐6.2% and 1.9‐19.5%, respectively; P < 0.01). the S rate was higher for PB‐Bl than for BM‐Bl (range 3.5‐11‐3 and 2.5‐9.5 mol × 10‐18/min; P < 0.02) and the Ts of PB‐Bl was shorter than that of BM‐Bl (range 7.6‐22.1 and 10.8‐34.7 hr, respectively; P < 0.02). In eight cases where S rates of both BM‐Bl and PB‐Bl were available, a linear correlation (r= 0.82; P < 0.01) was found between the two parameters. This suggests that the DNA synthetic rate is a property of the leukaemic cell line in individual patients and differs from case to case. It further indicates that the environmental influences on the DNA synthesis rate in BM or PB are always of the same order of magnitude. From the results of this study we speculate that the DNA synthesis rate of leukaemic blasts is slowed down in the BM by environmental factors such as cell density.
A Cytokinetic Study of Small‐Intestinal and Colonic Mucosa After Resection of 70% of the Small Intestine
Authors: Senior P. V. , Pritchett C. J. , Sunter J. P. , Appleton D. R. , Watson A. J.
Published: May 2008

Abstract. Pulse‐labelling with tritiated thymidine and a fraction of labelled mitoses experiments have been performed in order to investigate the proliferative changes induced at various sites in the hyperplastic small‐intestinal mucosa of rats previously subjected to resection of 70% of the small intestine. Proliferative activity in the colon was also studied.

In the distal ileum there is a significant reduction in cell cycle time (Tc) of cells at all levels within the crypt and the growth fraction falls. In the jejunum and proximal ileum the crypts contain an increased number of proliferating cells, but as the size of the maturation zone is also increased, there is no significant alteration in the relative number of proliferating cells per crypt. Nor does the distribution of proliferating cells in these crypts seem to alter. There is no general reduction in Tc at these sites, but there does appear to be a significant reduction in Tc on the part of the cells in the stem‐cell zone at the crypt base.

In neither proximal nor distal colon was there any significant proliferative change apparent after small‐intestinal resection.
Values of Growth Fraction and Cell Loss Factor of Sixty‐Five Tumours Re‐Examined
Authors: Knolle H.
Published: May 2008

Abstract. It has been shown that the mathematical evaluation of data from many cell kinetic experiments, published up to 1977, was rather inaccurate. the discrepancies between published values of growth fraction (GF) and the cell loss factor ø, and the results of new calculations based on the same values of LI, Td, Tc, TG1, Ts and TG2, are sometimes surprising. Using a suitable approximation of ex ‐ 1, the known formulae for GF and ø are replaced by simpler ones of sufficient accuracy. This may help to avoid computational errors in future cell kinetic studies of tumours.
Haematological Cell Proliferation and Differentiation Responses to Perturbations of Polyamine Biosynthesis
Authors: O'Conor G. Thomas. , McCann Peter P. , Wharton William W. , Niskanen Eero
Published: May 2008

Abstract. Combined administration of methylglyoxal‐bis‐guanylhydrazone (MGBG) (25 mg/kg) with difluoromethylornithine (DFMO), or MGBG alone at a higher dose (50 mg/kg), to mice resulted in a decreased white cell count (WBC) in the peripheral blood while DFMO or MGBG alone at a lower dose (25 mg/kg) had no effect. As expected, DFMO alone increased the number of colony forming units spleen (CFU‐s), colony forming units diffusion chamber granulocyte (CFU‐dg) and colony forming units culture (CFU‐c) in the bone marrow. MGBG treatment led to an increase in CFU‐dg alone. Combined treatment seemingly had no effect on marrow stem cells. Total tibial and differential counts were not affected by any of the treatments. Cell proliferation in diffusion chamber cultures, as judged by CFU‐dg colony formation, was impaired by MGBG alone or in combination with DFMO, at dose levels which had no effect or increased the precursor cell number in the bone marrow. This effect was partially reversed with either putrescine or spermidine. Determination of intra‐cellular polyamine concentrations, demonstrated decreased putrescine and spermidine levels after DFMO administration. As expected, MGBG treatment resulted in decreased spermidine and spermine levels, concomitant with an increase in putrescine. In mice which received both agents, rather than only MGBG, after 3 days higher intracellular polyamine concentrations were observed. After 11 days, however, there was no significant difference between the two groups.
The distribution and kinetics of nuclei in rat osteoclasts
Authors: Ries William L. , Gong Joseph K. , Gunsolley John C.
Published: May 2008

Abstract. Osteoclast development and growth were studied by determining the number of labelled nuclei in osteoclasts of different sizes (based on the number of nuclei per osteoclast, N/O) and the number of osteoclasts with labelled nuclei at various intervals after tritiated thymidine ([3H]TdR) injection in young rats. The osteoclast smears were made from the cellular periosteum of the proximal tibia. The frequency distribution of the N/O osteoclasts types in the smears had profiles similar to that of in situ osteoclasts in whole mounts of proximal tibia, which indicates that the osteoclast population of the smears was representative of that on the bone surface. A vast majority of the osteoclasts had a 1–6 N/O, and a number of the cells had as many as 26 or more nuclei. Furthermore, profiles of N/O frequency distributions were similar over the course of the study. Nuclei with [3H]TdR label were initially observed in osteoclasts between 4 and 12 hr after isotope injection. However, fusion of labelled nuclei to osteoclasts continued for at least 150 hr. In general, the labelled osteoclasts exhibited a significantly larger number of nuclei than the unlabelled osteoclasts. The probability of an osteoclast incorporating one or more labelled nuclei increased with time after injection and with an increase in N/O. Labelling intensity decreased with time post injection and with an increase in N/O. The data suggest that turnover of nuclei is more rapid in osteoclasts with high N/O values.
Cytokinetic studies on the switch from glucose to uridine metabolism, and vice versa, of Ehrlich ascites tumour cells in vitro
Authors: Löffler M. , Wenzel A. , Schneider F.
Published: May 2008

Abstract. Glucose is normally required as the energy source and for the proliferation of neoplastic cells. For Ehrlich ascites tumour cells, kept under glucose‐free culture conditions, this requirement was alleviated by uridine, indicating that the supply of ribose is obligatory for sustaining growth capacity.

In a 96‐hr culture experiment with mouse‐derived cells, the increase in cell number from cultures supplemented with 5 mM uridine was 50–70%, whilst lactate production was 5% that of controls. An increase in the number of multinucleate cells was observed from cell‐smears; DNA histograms indicated the presence of cells with a DNA content higher than 4c and an increased portion of cells in G2 phase. For precise determination of changes in cell cycle distribution on transfer of cells from glucose‐supplemented to glucose‐free conditions, the progression of phase‐accumulated cells (by centrifugal elutriation) was monitored by DNA distribution analysis; G2 cells continued the cycle at a rate comparable to controls but were delayed, in the following cycle, predominantly in S and G2 phases. This was also observed with G1 cells from a G1‐accumulated fraction in the first cycle.

The addition of glucose to cells kept for some hours in glucose‐free, uridine‐supplemented medium resulted in an immediate increase in mitotic index (amplification by the colcemid method).

The results are interpreted and support our concept that the delivery of compounds, necessary for normal growth, i.e. hexoses for glycoproteins and glycolipids, are limited as a consequence of the ‘metabolic channelling’ of pentose from uridine in Ehrlich ascites tumour cells. Therefore, the constantly lowered growth‐rate in uridine‐supplemented cells observed with long‐term culture experiments could reflect an adaption of growth‐cycle to these limitations.
Growth in solid heterogeneous human colon adenocarcinomas: comparison of simple logistical models
Authors: Michelson S. , Glicksman A. S. , Leith J. T.
Published: May 2008

Abstract. Three models of simple logistical growth were used to describe volumetric growth in heterogeneous tumours. Two clonal subpopulations (designated as clone A and clone D) originally obtained from a human colon adenocarcinoma were used to produce solid xenograft tumours in nude mice. Volumetric growth of tumours produced from pure cells alone was compared to that produced from 50% A:50% D, 88% A:12% D, and 9% A:91% D admixtures. Gompertzian analysis of the in vivo growth data indicated significant differences in both the initial growth rates and final asymptotic limiting volumes of the pure versus the admixed tumours. Verhulstian and modified Verhulstian models were also used to derive regression curves from the same data. The fit of the curves was compared with each other using standard (Akaike, 1974; Schwartz, 1978) information criteria. In four of the five tumour populations the Gompertz equation fitted best. Only in the 88% A:12% D tumours did the modified Verhulst model fit best. The deviations from the regression curves, the residuals, for all three models were systematically distributed. These systematic errors are likely to be the result of using simplified logistical models to describe the growth kinetics of interacting populations in heterogeneous tumours.
Evidence for arrested G2 cell subpopulation in rat liver inducible to mitosis
Authors: Gómez‐Lechón J. , Castell J. V.
Published: May 2008

Abstract The intraperitoneal administration of several substances (biliverdin, heat‐killed bacteria and diatomaceous earth) to rats caused the prompt appearance of a mitotic wave in the liver. Autoradiographic analysis of livers of treated animals showed no evidence of [3H]‐thymidine uptake by mitotic hepatocytes. In addition, livers from xenobiotic‐treated rats showed a very low thymidine kinase activity, close to that found in normal livers. This excludes the possibility that non‐cycling cells move to mitosis through the S phase. The results suggest that mitosis could be derived from a hepatocyte subpopulation arrested in the G2 phase of the cell cycle, which is stimulated to divide by the xenobiotics.
Proliferation kinetics of human B‐ and T‐lymphocytes
Authors: Miller K.
Published: May 2008

Abstract Human peripheral blood B‐ and T‐lymphocytes, highly purified by immunological methods, were supplemented with γ‐irradiated unseparated autologous mononuclear cells to restore helper functions and stimulated with pokeweed mitogen and phytohaemagglutinin, respectively. Proliferation kinetics of the cell populations were investigated using 5‐bromodeoxyuridine (BrdU) labelling of the cell cultures and chromosome preparation at different times after stimulation. The percentages of metaphase cells having replicated for one, two or three generations in the presence of BrdU were determined following sister chromatid differential staining. In all donors, the changes in these percentages were faster in B‐ than in T‐lymphocytes, indicating a longer cell cycle time in the latter population.
Proportions of Mitotic and Apoptotic Cells In A Range of Untreated Experimental Tumours
Authors: Sarraf C. E. , Bowen I. D.
Published: May 2008

Abstract. The quantitative aspect of apoptosis in experimental tumours is often neglected. In this study, the apoptotic and mitotic indices for a range of tumours have been determined at light microscope level. It has been found that the apoptotic levels fall into a consistent range for all tumour types and agree well with those described by previous workers. It is suggested that these might be basic parameters of tumour expansion, as relevant to growth kinetics as mitotic levels.
Non‐Circadian Rhythm In Proliferation of Haematopoietic Stem Cells
Authors: Nečas E. , Znojil V.
Published: May 2008

Abstract. The proportion of haematopoietic stem cells (CFU‐s) engaged in DNA synthesis was determined by means of the [3H]‐thymidine ([3H]TdR) suicide technique during recovery of bone marrow from the damage caused by a sublethal total body irradiation. In contrast with previous reports the [3H]TdR suicide rate was not permanently increased. It was observed that CFU‐s passed through S phase in synchronous waves, following a dose of irradiation of 1.5 Gy. After a dose of 2.6 Gy, there was only one initial wave of increased CFU‐s sensitivity to the action of [3H]TdR. Following the depression occurring 26 hr after the irradiation with 2.6 Gy, the proportion of CFU‐s killed by the [3H]TdR was permanently increased until 5‐6 days after irradiation. Thereafter large differences in the [3H]TdR suicide data were observed among individual mice. Evidence was obtained that individual mice, which had been irradiated by a dose of 2.6 Gy 8‐9 days before, had identical values of the CFU‐s [3H]TdR suicide rate in the bone marrow from different bones of the lower extremities. the recurrence of the synchronous waves in CFU‐s passage through the cell cycle was recorded when the CFU‐s population regenerated to only about 10% of its normal value. These waves were obviously not related to a particular time of the day and, consequently, they did not represent the circadian rhythm. It is concluded that the synchronous waves in which CFU‐s proliferation occurred reflected the action of the control mechanism on CFU‐s proliferation. This mechanism should be endowed with an important systemic component besides locally operating factors.
Simulation of Cfu‐S Kinetics After Irradiation
Authors: Hauser F. , Nečas E.
Published: May 2008

Abstract. A simulation model of the CFU‐s population is used to interpret data from experimental studies of bone marrow recovery after irradiation. the model includes an original hypothesis that the proliferation rate in the CFU‐s population depends on the number of DNA‐synthesizing CFU‐s. It is assumed that the DNA‐synthesizing CFU‐s produce a factor in the presence of which CFU‐s enter the resting state Go after mitosis and remain there for prolonged periods of time. the model can adequately reproduce complex CFU‐s kinetics observed after severe damage caused by irradiation with a unique set of parameters.
Comparative Analysis of Different Approaches to Investigate Cell Kinetics
Authors: Silvestrini R. , Costa A. , Veneroni S. , Del Bino G. , Persici P.
Published: May 2008

Abstract. The potential of different methods to investigate proliferative activity of cell populations was analysed for non‐Hodgkin's lymphomas. Cells in S phase and all cycling cells were determined on cell suspensions obtained from fresh lymph node material by [3H]‐thymidine autoradiography ([3H]TdR LI), a monoclonal antibody to bromodeoxyuridine (BrdU LI), and the monoclonal antibody Ki67. A good correlation was observed between the values of [3H]TdR LI and BrdU LI (rs= 0.90; P < 0.01), [3H]TdR LI and S phase (rs= 0.62; P < 0.01) and [3H]TdR LI and Ki67 (rs= 0.64; P < 0.01) in individual lymphomas. Using the median values obtained from the different approaches as cut‐off points to define slowly and rapidly proliferating tumours, the best agreement was observed between [3H]TdR LI and BrdU LI (91%) and poorer agreements, even though statistically significant, were observed between [3H]TdR LI and S phase (73%) or Ki67 (76%). In conclusion, the kinetic information derived from different approaches was more or less concordant and newly proposed approaches should be directly and carefully verified for their prognostic relevance before using them as alternatives to conventional methods.
Local Re‐Utilization of Thymidine In Normal Mouse Tissues As Measured With Iododeoxyuridine
Authors: Quackenbush R. C. , Shields A. F.
Published: May 2008

Abstract. Thymidine (TdR) and its analogue, iododeoxyuridine (IdUdr), were used to quantitate nucleoside re‐utilisation in vivo. Significantly different results are obtained, however, depending upon what form of isotopically labelled iododeoxyuridine is used. No measurable local thymidine re‐utilization was found in mouse thymus, spleen or bone marrow when the retention of [3H]IdUdR was compared with [14C]TdR. On the other hand, significant differences were found between the retention of [125I]IdUdR and [3H]IdUdR, which is attributed to de‐iodination of iododeoxyuridine. Some thymidine re‐utilization was found in duodenum using both [3H]IdUdR and [125I]IdUdR. Information on the in vivo distribution of TdR and the contention that a large degree of TdR re‐utilization in the thymus is evidence of extensive cell death must be re‐interpreted in the light of these results. In addition, evidence for little or no local re‐utilization in some tissues will greatly simplify the use of [11C]TdR as an imaging agent for measuring tissue proliferation in vivo with positron emission tomography (PET).
The Cell Cycle Time In Intestinal Crypts By Simulation of Flm Experiments
Authors: Meinzer H. P. , Chen W. , Sandblad B. , Wright N.
Published: May 2008

Abstract. A computer program is developed that permits simulation of the dynamic behaviour of cells in intestinal crypts (Meinzer & Sandblad, 1985). Here we present the simulation of FLM data which is compared with the experimental findings of Al‐Dewachi et al. (1974). the phase durations and total cycle times of cells in the jejunal crypts of rats were calculated. Additionally, the influence of various control parameters on the simulation output is discussed, e.g. the standard errors of phase times and the grain dilution at mitosis.
Cell Cycle Redistribution of Cultured Cells After Treatment With Chemical Radiation Protectors
Authors: Sigdestad C. P. , Guilford W. , Perrin J. , Grdina D. J.
Published: May 2008

The effect of two radioprotective agents (WR‐1065 and WR‐151326) was tested for their ability to modify cell cycle progression. Each protector was administered at a concentration of 4 mmol to exponentially growing cultures of V79 cells for periods of time up to 3 h. Under these conditions no cell toxicity was observed. At selected times up to and after removal of the protector, aliquots of cells were removed, counted and fixed in cold 70% ethanol. the cells were stained with DAPI in a 0.1% citrate solution and DNA histograms were obtained using a PARTEC PAS‐II flow cytometer. the coefficient of variation of the G1 peaks obtained for unperturbed cell samples routinely ranged from 1.5 to 2.5%. During exposure, both radioprotectors effectively perturbed cell cycle progression, as characterized by a build‐up of cells in S and G2 phases. After the protectors were removed, cells began to redistribute throughout the cell cycle. Twelve hours were required before cells exposed to WR‐1065 approached levels commensurable with controls. In contrast, cells treated with WR‐151236 required about 24 h to redistribute to control levels. These data demonstrate that different thiol‐containing radioprotective compounds can differentially affect the progression and redistribution of exposed cells.
A mathematical model of erythropoiesis in mice and rats Part 1: Structure of the model
Authors: Loeffler M. , Pantel K. , Wulff H. , Wichmann H. E.
Published: May 2008

Abstract A mathematical model has been developed which describes the regulation of erythropoiesis in mice and rats. The main model assumptions are: (1) Regulation is mediated by erythropoietin (EPO). (2) The production of EPO depends exponentially on the tissue oxygen pressure (e.g. in the renal production sites). (3) There are sigmoidal dose‐response curves relating the EPO concentration in the plasma to the mitotic activity of CFU‐E and proliferative erythropoietic precursors. For maximum stimulation two to four additional mitoses may occur, while for an absent stimulus three to five mitoses may be omitted. (4) The normal precursor transit time of three to four days may be shortened by more than 50% during maximum stimulation. (5) The erythrocytes have a normal lifespan of 42–56 days, which may be reduced to 15–20 days under erythropoietic stimulation.

Among these assumptions, the dose‐response relationships between EPO and the mitotic activity of CFU‐E and the proliferative erythropoietic precursors are the most important hypotheses of the model. This is the first of a series of three papers and gives a description of the mathematical formalism and the parameters used. In the subsequent papers computer simulations on erythropoietic stimulation and suppression are presented.