bluuebunny/crossref_metadata_2025 huggingface dataset:
Iron deficiency depresses cell proliferation in hamster cheek pouch epithelium
Authors: Ranasinghe A. W. , Johnson N. W. , Scragg M. A.
Published: May 2008

Abstract. Iron deficiency anaemia was induced in hamsters by feeding a low iron diet coupled with weekly bleeding. To assess cell proliferation, the stathmokinetic agent vinblastine sulphate was administered and cell birth rates were calculated from cumulative mitotic indices. The rate was significantly reduced in epithelium from iron‐deficient animals. The uptake of tritiated thymidine ([3H]TdR) was also significantly reduced in these animals. Results of both stathmokinetic and labelling experiments indicate that cell production in the cheek pouch epithelium of iron‐deficient animals is impaired.
Variability of ecdysteroid‐induced cell cycle alterations in Drosophila Kc sublines
Authors: Besson M. T. , Cordier G. , Quennedey B. , Quennedey A. , Delachambre J.
Published: May 2008

Abstract. The cell cycle of two lines isolated from Drosophila Kc cells was followed by flow cytofluorometry and cell counting. The first line is the 8‐9K clone which grew in a medium supplemented with 5% serum; the second, named subline Kc0, grew in a serum‐free medium. The stationary phase is characterized by a G2 cell accumulation: 73% in the 8‐9K clone and 50% in the Kc0 subline.

When the medium was supplemented with the steroid moulting hormone 20‐hydroxyecdysone, more than 90% of 8‐9K cells and 65% of Kc0 cells were progressively arrested in G2. In the continuous presence of 20‐hydroxyecdysone, most of the 8‐9K cells remain G2‐arrested; no massive G2 release into M was observed and only a few cells were able to divide. When treated for only 3 or 7 days, a transient release into M and proliferation occurred after hormone‐free medium renewal, largely masked by G2 cell death. These results are discussed in comparison with other reports on cell cycle alteration induced by ecdysteroids.
Regulation of recovery in the erythroid lineage: model studies
Authors: Tyazhelova V. G.
Published: May 2008

Abstract. Based on data from the literature, the major regulatory features were established for the erythroid population regenerating after perturbation. A mathematical model is proposed which takes into account: (1) the increase in the proliferating CFU‐S due to depopulation of CFU‐S and BFU‐E/8 pools due to increased migration caused by erythropoietin; (2) regeneration of erythroid precursors due to short‐range factors and (3) gradual reduction in the short‐range effects and increase in the humoral influence on BFU‐E/8, BFU‐E/3 and CFU‐E together with short‐range suppression of progenitor differentiation and acceleration of maturation in all subpopulations due to humoral factors. The kinetics of subpopulations as a function of feedback and maturation rate are analysed. The dependence of erythrocyte production on erythrocyte depletion in the blood and on the feedback coefficient is defined.
Cell cycle responses of heterogeneous human colon adenocarcinoma subpopulations to X‐irradiation
Authors: Bliven S. F. , Schneiderman T. E. , Leith J. T.
Published: May 2008

Abstract The cell cycle responses of two exponentially growing subpopulations of cells (clones A and D), originally obtained from a human colon adenocarcinoma to X‐irradiation, were studied using centrifugal elutriation. Cell suspensions were separated by changing counter‐current flow rate while keeping the rotor speed constant (1600 rpm) and the composition of eluted fractions was determined using flow cytometry. The X‐ray sensitivity of unseparated clone D cells was somewhat greater than that of clone A cells (e.g. 10% greater at the 10% level of survival). This difference appeared to be due to a greater value of the α parameter (one‐hit cell killing), using the linear‐quadratic equation in which the relative survival S/S0 = exp – (αD +βD2) with dose (D) in Gy. This finding was confirmed in the cell cycle studies where the α parameter was always greater for the clone D cells than for the clone A cells. The β parameter was essentially the same for both cell lines through the cell cycle.
The effect of haemopoietic stem cell proliferation on the humoral immune response in mice
Authors: Kozlov V. A. , Orlovskaya I. A. , Tsyrlova I. G.
Published: May 2008

Abstract A study was made of the effect of humoral factors, isolated from bone marrow cell (BMC) supernatant fluid and capable of modifying CFU‐S proliferation, on the generation of IgM plaque‐forming cells (PFC) against sheep red blood cells (SRBC) in mice after adoptive transfer. Adoptive transfer of BMC, preincubated with the humoral factor RBME‐III, which stimulates CFU‐S proliferation, was shown to suppress the splenic PFC generation in recipients; treatment of BMC with a further factor NBME‐IV, which inhibits CFU‐S proliferation, was followed by augmentation of PFC generation. Similar effects were obtained while studying the IgM PFC generation in the bone marrow of mice after secondary immunization when relevant factors were injected, in vivo, 24 hr following primary immunization. The results of adoptive transfer experiments indicate that populations of T‐ and B‐cells are not the targets for the action of CFU‐S proliferation regulatory factors. These factors are shown to modulate the erythroid differentiation of CFU‐S. The possibility of quantitative modification of immune response parameters with the help of bone marrow factors that influence the proliferation and differentiation of CFU‐S is discussed.
Oscillations in blood cells as a consequence of suppressed bone marrow cell production
Authors: Tyazhelova V. G.
Published: May 2008

Abstract A hypothesis is proposed that the oscillations in blood cell numbers are the result of suppressed productivity of the bone marrow and its ability to satisfy both the demands of the erythroid and myeloid cell lines. The hypothesis is used as the basis for a mathematical model which describes the oscillations in all subpopulations of these cell lines. The relationship between the period and amplitude of the oscillations and the extent of suppression of the bone marrow productivity have been explored.
Induction of differentiation in mouse erythroleukaemia cells by the action of papain at the cell surface
Authors: Slosberg E. A. , Scher B. M. , Scher W. , Josephson S. , Waxman S.
Published: May 2008

Abstract The addition of one of several proteases to cultures of mouse erythroleukaemia (MEL) or human K‐562 leukaemia cells can induce a substantial portion of the cells to undergo erythroid differentiation. This effect is due, at least in part, to the proteolytic action of these enzymes. The critical substrate(s) for this proteolytic action is not a component of the medium or a long‐lived substance(s) released from the cells. In order to determine if the substrate(s) is located on the cell surface or intracellularly, a comparison of the ability of non‐immobilized papain and immobilized papain (i.e. covalently linked to Sepharose beads which were larger than the cells) to induce MEL cell differentiation was undertaken. Both papain preparations induced the same level of differentiation. The proteolytic activity of the bead‐linked papain remained associated with the beads. Therefore, proteases induce erythroid differentiation in these cells by acting proteolytically on a substrate(s) that is exterior to the cell.
Cell kinetics and longitudinal bone growth in birds
Authors: Kember N. F. , Kirkwood J. K.
Published: May 2008

Abstract The theory that links cell division in epiphyseal cartilage plates to overall growth of long bones has been extended from linear growth systems to those in which proliferating and hypertrophied cells are not arranged in columns. Consideration has also been given to the analysis of non‐parallel growth systems. The theory is illustrated by examples from the growth of chicken bones.
Suicidal Death of Rat Chloroleukaemia Cells By Activation of the Long Interspersed Repetitive Dna Element (L1rn)
Authors: Servomaa K. , Rytömaa T.
Published: May 2008

Abstract. Rat chloroleukaemia cells, maintained in suspension culture in different media, show rapid exponential growth without cell loss. At about half of the maximal population density the long interspersed repetitive DNA element (L1Rn) is suddenly transcriptionally activated without any obvious exogenous reason. Population growth is then inhibited and, within about 24 h after reaching the maximal density, the population undergoes programmed death (apoptosis). Suicidal cell death is caused by sudden incorporation, apparently by retroposition via an RNA intermediate, of about 300,000 copies of the L1Rn element into random locations in the cell genome, thus creating lethal mutations. the preceding growth inhibition is associated with repression, to an undetectable level, of c‐Ki‐ras expression. Up to the point of massive L1Rn incorporation and cell death, all phenomena are quickly reversible by subculturing; medium change alone is not sufficient. Biological implications of these surprising findings are discussed.
The Spleen Colony Technique. I. Correction For the Overlap Effect and Sources of Error In Cfu‐S Determination
Authors: Znojil V. , Nečas E.
Published: May 2008

Abstract. A linear model for the errors of the ‘spleen colony’ assay for haemopoietic stem cells has been derived. the components emerging from the model are interpreted and practical recommendations given for interpreting measurements made with this assay. the model permits correction for the effect of overlapping colonies and gives average errors for single measurements of the number of CFU‐s. More reliable and more precise information can be obtained using this model.
Effect of Chemical Ablation of Myenteric Neurones On Intestinal Cell Proliferation
Authors: Zucoloto S. , Diaz J. A. , Oliveira J. S. M. , Muccilo G. , Sales Neto V. N. , Kajiwara J. K.
Published: May 2008

Abstract. The duodenum or descending colon of male Wistar rats (average weight 60 g) was treated by a serosal application of a 0.2% solution of benzalkonium chloride (BAC) for 30 min. Control animals were treated with 0.9% (physiological) saline. the rats were allocated to four groups: Group DC (N= 8) in which the duodenum was treated with physiological saline; Group DB (N= 8) in which the duodenum was treated with BAC; Group CC (N= 7) in which the descending colon was treated with physiological saline and Group CB (N= 7) in which the descending colon was treated with BAC. After treatment, the animals were followed up for 5 months. At the end of the experiment, the animals were injected intraperitoneally with vincristine sulphate before sacrifice. Three segments were removed from the duodenum and descending colon for neuronal counting, catecholamine and serotonin measurements and morphokinetic studies of the epithelium. the following results were obtained: (1) there was a significant reduction in neurone number in the myenteric plexus of segments treated with BAC; (2) in the denervated intestinal segments, catecholamine levels were unchanged whereas serotonin levels were increased; (3) epithelial hyperplasia was observed in the denervated duodenum and descending colon; and (4) crypt cell production rate in the duodenum was similar in groups DC and DB but was significantly increased in the descending colon in group CB as compared with controls (CC). the present findings indicate that selective myenteric neuronal denervation caused by benzalkonium chloride plays a causative role in the hyperplasia and crypt cell production rate of the intestinal epithelium (duodenum and descending colon). These changes are probably induced by functional imbalance by the surviving neuronal elements in the gut, implicating neurotransmitters such as acetylcholine, noradrenaline, serotonin, somatostatin and vasoactive intestinal peptide.
Tumour Cell Recruitment of the Jb‐1 and L 1210 Ascites Tumour Determined Directly By Double Labelling With [14C]‐ and [3H]‐Thymidine
Authors: Maurer‐Schultze B. , Kondziella U. , Böswald M.
Published: May 2008

Abstract. Tumour cell recruitment of the JB‐1 and L 1210 ascites tumour has been demonstrated directly by a double‐labelling method with [14C]‐ and [3H]‐thymidine (TdR). After [14C]‐labelling of all proliferating tumour cells by multiple injections of [14C]TdR, recruitment of resting cells was stimulated by removal of the majority of tumour cells, i.e. by maximum aspiration of ascitic fluid. the number of recruited resting cells in the remaining tumour that re‐enter the cell cycle after stimulation was demonstrated directly by a single injection of [3H]TdR given at different times after stimulation. the increase in the percentage of purely [3H]‐labelled cells, i.e. recruited cells, with increasing time after stimulation, shows that recruitment is not a synchronous but a continuous process, the maximum of which occurs earlier in the case of the L 1210 than the JB‐1 tumour. This suggests that there seems to be a relationship between the time required for maximum recruitment and the corresponding cell cycle parameters of the unperturbed tumour. There is a transitory increase of the growth fraction to about 100% and a considerable shortening of the cycle time at the maximum of recruitment.
Double Labelling With Bromodeoxyuridine and (3H)‐Thymidine of Proliferative Cells In Small Intestinal Epithelium In Steady State and After Irradiation
Authors: Chwalinski S. , Potten C. S. , Evans G.
Published: May 2008

Abstract. The simultaneous immunohistochemical detection of bromodeoxyuridine (BrdU) and [3H]‐thymidine ([3H]TdR), by conventional autoradiography, was performed on the mouse small intestine (ileum). Proliferation was studied under normal conditions as well as after 3 Gy of γ‐rays. the BrdU method in conjunction with [3H]TdR autoradiography appears to be reliable and useful for the study of cell kinetics especially in disturbed states, on condition that [3H]TdR is delivered to the animals before BrdU. It has been found that cells in the crypt are delayed by irradiation in their progression through the cell cycle predominantly in late S phase. the cells at the bottom of the crypt are more affected than the more differentiated but proliferating cells in the upper part of the crypt.
The Labelling Index Is Not Always Reliable. Discrepancies Between the Labelling Index and the Mitotic Rate In the Rat Corneal Epithelium After Intraperitoneal and Topical Administration of Tritiated Thymidine and Colcemid
Authors: Haaskjold E. , Refsum S. B. , Bjerknes R. , Paulsen T. O.
Published: May 2008

Abstract. Many cell kinetic studies are based on the assumption that tritiated thymidine injected into an animal is available for incorporation into DNA for only a short time, and that it labels all cells in the S phase. the present study indicates that this is not the fact for the rat corneal epithelium. the labelling index (LI) declines considerably from the limbal area to the central cornea, while the mitotic rate is almost constant all over the corneal epithelium. the LI should therefore not be used as the only criterion in the assessment of proliferation rate.
Method For Probing Cells In Radiation‐Induced G2Arrest: Demonstration of Potentially Lethal Damage Repair
Authors: Rowley R. , Egger M. J.
Published: May 2008

Abstract. Chinese hamster ovary cells were arrested in the G2 phase of the cell cycle by X‐irradiation. When subsequently treated with 5 mM caffeine the arrested population progressed into mitosis as a synchronous cohort where it was harvested by mitotic cell selection. This procedure provides a means to isolate cell populations treated in G2, for the investigation of G2 arrest. Comparisons were made of the number of cells retrieved from G2 arrest with the number suffering arrest, as determined by flow cytometry and by matrix algebraic simulations of irradiated cell progression. the retrieved population was not significantly less than expected for doses up to 3.5 Gy, indicating that the retrieval process does not favour the isolation of any population subset below this dose. Cell populations retrieved from arrest at varying intervals (0‐3 h) after irradiation (0‐3.5 Gy) showed an increase in survival with increase in interval, consistent with repair of potentially lethal damage. the repair curves (surviving fraction us time) were each described by a single exponential. G2 cells that were brought to mitosis without a period of arrest exhibited the same radiation response as cells irradiated in mitosis.
Early Plasma Cell Recruitment In Multiple Myeloma Following Chemotherapy
Authors: Ucci G. , Riccardi A. , Dörmer P. , Danova M. , Luoni R.
Published: May 2008

Abstract. Therapy‐induced modifications of bone marrow plasma cell kinetics were studied in three patients with myelomatosis. the investigation was performed prior to and 15 d after termination of a course of aggressive chemotherapy. an increase in the labelling index (40‐212% of pretreatment values) with a corresponding reduction of Ts (5‐34%) was observed in all cases. As a consequence of this combined variation, the fractional turnover rate (which represents the percentage of cells produced per unit time) was the parameter with the highest increment (54‐276%). These results indicate that plasma cell recruitment occurs soon after chemotherapy and is characterized by a shorter S phase and a higher number of DNA‐synthesizing cells.
The Spleen Colony Technique. Iii. Comparison of the Overlap Effect and of Errors In Cfu‐S Determination and the [3H]‐Thymidine Suicide Data For Several Strains of Mice
Authors: Znojil V. , Necas E.
Published: May 2008

A mathematical model of errors of the spleen colony technique is applied to data obtained from four mouse strains and F1 hybrids. the variance of the colony counts was close to the Poisson distribution in inbred mice and F1 hybrids. However, it should be checked regularly. the magnitude of the error in CFU‐s determination and of the estimations of the S phase fraction was derived, and is presented relative to the mean colony counts for all mouse strains studied. the optimum spleen colony counts are generally higher than those which are commonly used. However, the utilization of the optimum spleen colony counts requires a correction for the effect of colony overlap.
Cytostatic and Cytotoxic Effects of Pannon (P‐30 Protein), A Novel Anticancer Agent
Authors: Darzynkiewicz Z. , Carter S. P. , Mikulski S. M. , Ardelt W. J. , Shogen K.
Published: May 2008

P‐30 Protein is a novel protein, of molecular weight approximately 15 kD, obtained from the extract of a vertebrate tissue showing in vivo antitumour activity. Cytostatic and cytotoxic effects of this product in its purified form (P‐30 Protein) or in partially purified extracts (Pannon) were studied in vitro on human leukaemic HL‐60, human submaxillary carcinoma A‐253, human colon adenocarcinoma Colo 320 CM and murine erythroleukaemia (Friend leukaemia) cell lines. of these cells, HL‐60, A‐253 and Colo 320 CM were sensitive and Friend leukaemia resistant to this agent. the effects were time‐ and concentration‐dependent. During the initial 24–48 h of treatment, a slowdown in cell proliferation was apparent but cell death was not extensive. After 24–48 h, there was a reduction in the proportion of cells in S phase of the cell cycle and the cells became preferentially arrested in G1 phase. the G1 cells showed high heterogeneity with respect to RNA content and some cells were characterized by very low RNA content. Progressive cell death occurred in cultures maintained with Pannon for up to 7 d in proportion to its concentration. Reductions of 50 and 90% in clonogenicity of A‐253 cells were observed during their growth in the presence of 0.13 and 1.5 μg/ml of this protein, respectively. Exponentially growing cells were more sensitive to Pannon compared with cells from confluent cultures. Colonies of A‐253 cells growing in the presence of Pannon were much smaller in size compared with control colonies, indicating that the rate of proliferation of clonogens is reduced by this agent. It appears that P‐30 Protein induces cytostatic effects via modulation of cell transition to quiescence or differentiation. the mechanism of its cytotoxic activity is unclear.
A mathematical model of erythropoiesis in mice and rats Part 3: Suppressed erythropoiesis
Authors: Wulff H. , Wichmann H. E. , Pantel K. , Loeffler M.
Published: May 2008

Abstract A mathematical model of erythropoietic cell production and its regulation process has been proposed in a preceding paper. It is primarily based on the assumption that the number of cell divisions taking place in the CFU‐E and erythropoietic precursor stages can be regulated depending on the oxygen supply to the tissue. Here we provide evidence that this model adequately describes situations of suppressed erythropoiesis. In detail this implies a quantitative description of the following processes: (1) changes in tissue oxygen tension (PtO2) due to increase in red cell numbers (red cell transfusion, posthypoxia), decrease in plasma volume (dehydration) or increase in atmospheric oxygen pressure (hyperoxia), (2) PtO2 dependent reduction of erythropoietin (EPO) production, (3) dose‐response of reduced EPO‐levels on erythropoietic amplification (omission of three to five mitoses).

Model simulations are compared to experimental data obtained from red cell transfusion, posthypoxia, hyperoxia and dehydration. A satisfactory agreement suggests that the model adequately describes and correlates different ways to suppress erythropoiesis. It quantifies the role and relative contribution of the haematocrit, haemoglobin concentration, atmospheric oxygen pressure, tissue oxygen pressure and plasma volume as triggers in erythropoietic suppression under various conditions. In conjunction with the preceding two papers it could be shown that one unique set of model parameters is sufficient to describe erythropoiesis in steady state, stimulation and suppression. Limitations of the model are discussed and experiments for a more detailed investigation of the feedback mechanisms are proposed.
Action of cortisol on the proliferation of rainbow trout fibroblasts
Authors: Lee L. E. J. , Bols N. C.
Published: May 2008

Abstract The effect of cortisol on the proliferation of the rainbow trout fibroblast cell line, RTG‐2, was examined in synchronous and asynchronous cultures. When the transition from G1 to S was synchronized by restoring serum to serum‐deprived cultures, the addition of cortisol at the time of serum restoration delayed the entry of cells into S phase. However, if cortisol was added 24 h after serum restoration, at the G1/S transition point, the subsequent peak of DNA synthesis was unaffected. In asynchronous cultures cortisol inhibited [3H]‐thymidine and [3H]‐uridine but not [3H]‐leucine incorporation into acid‐insoluble material. If the exogenous nucleoside concentration was raised, [3H]‐thymidine but not [3H]‐uridine incorporation continued to be inhibited by cortisol. This suggested that cortisol's effect on [3H]‐thymidine incorporation reflected a change in entry into S phase and not just on thymidine uptake and metabolism. Cortisol inhibited the proliferation of RTG‐2 in asynchronous cultures. At 1000 ng/ml of cortisol a reduction in cell number became apparent before the RTG‐2 cultures were confluent, whereas at 100 ng/ml the reduction only became evident in confluent cultures. The synthetic antiglucocorticoid, RU 486, which acts at the level of the corticosteroid receptor, blocked the growth inhibition by cortisol. These results suggest that cortisol regulates rainbow trout fibroblast proliferation via the corticosteroid receptor and that the G1/S transition is one point at which this regulation occurs.
Cyclin/PCNA immunostaining as an alternative to tritiated thymidine pulse labelling for marking S phase cells in paraffin sections from animal and human tissues
Authors: Galand P. , Degraef C.
Published: May 2008

Abstract Paraffin sections from animal or human tissues fixed in different fixatives were submitted to immunostaining with the mouse monoclonal antibody 19A2, developed by Ogata et al. (1987a) against cyclin/PCNA. Detection of the bound antibody was performed by the indirect method with biotinylated sheep antibody and streptavidin‐biotin‐peroxidase complexes. No, or faint, nuclear staining was seen in material fixed in ethanol, Bouin, Bouin‐Hollande, Carnoy or formaldehyde, whereas readily detectable immunocytochemical reaction was constantly observed over nuclei of methanol‐fixed tissues. Hydrolysis with 2 N HCl prior to immunocytochemistry (as currently performed to render incorporated BrdU accessible to antibodies) somewhat improved the results with Bouin or Carnoy and markedly augmented the intensity of the peroxidase reactions in formaldehyde and in methanol‐fixed tissues.

The distribution of the positive nuclei in the two latter cases coincided with the proliferative compartment. On the other hand, double labelling with [3H]‐thymidine and with the cyclin/PCNA antibody revealed that in methanol‐fixed tissues the cyclin/PCNA labelling index did not differ by more than 6% from the [3H]‐thymidine index. Besides the two labels overlapped in a proportion of labelled cells that was in reasonable agreement with expectation considering cells flow in and out of S phase since the time of [3H]‐thymidine injection. This indicates that both labels recognize the same cells in this material. In contrast, in formaldehyde‐fixed tissues, the cyclin/PCNA labelling index markedly exceeded the [3H]‐thymidine labelling index. From this it is concluded that cyclin/PCNA immunostaining can be used:

 In formaldehyde‐fixed tissues (including existing material stored as paraffin blocks): for defining and mapping the proliferative (or germinative) compartment.

 In methanol‐fixed tissues as a substitute to the [3H]‐thymidine autoradiographic labelling index.

From this, a method is proposed (derived from classical ‘double‐labelling’technique) for measuring S phase duration in tissues fixed at a known interval time after a single labelling with [3H]‐thymidine (or BrdU) and submitted to cyclin/PCNA immunocytochemical detection and to autoradiography (or to BrdU immunostaining).
Circadian synchronization of liver regeneration in adult rats: the role played by adrenal hormones
Authors: Barbason H. , Bouzahzah B. , Herens Ch. , Marchandise J. , Sulon J. , Cantfort J. van
Published: May 2008

Abstract The role played by the adrenal hormones in the regulation of liver proliferation in adult rats was investigated under various experimental conditions.

In untreated control groups, cell growth was very low and endogenous corticosterone levels showed a clearly‐defined circadian rhythm with a peak in the evening. Adrenalectomy depressed the level of endogenous corticosterone immediately and the growth rate of the liver increased significantly. We were able to prevent this effect by repeated injections of corticosterone at physiological doses.

After a 1/3 hepatectomy and a sham‐operation, the corticosterone blood level maintained its normal circadian pattern with the exception of a transient increase during the first two post‐operative hours. After a hepatectomy of this kind, a negative correlation was found to exist between the adrenal hormone level and the waves of DNA synthesis; the subsequent mitoses appeared in two successive circadian waves of decreasing amplitude, a maximum value being reached in the morning. In rats submitted to a 1/3 hepatectomy and an adrenalectomy simultaneously, the endogenous corticosterone level fell significantly after a post‐operative peak. The regenerating pattern was completely different from that induced by 1/3 hepatectomy alone. The rise in the labelling index began earlier and rose to significantly higher values; it was then followed by a single large mitotic wave without any circadian rhythm.

These results favour the hypothesis that adrenal hormones have a significant effect on the negative control of liver regeneration. Circadian changes in the corticosterone level were responsible for the nycthemeral pattern observed in the regenerating liver after a partial hepatectomy. The results show a marked inhibition of the G1‐S transition, particularly in the evening, when the endogenous corticosterone concentration was at its highest. Also discussed is the relationship between corticoids and ‘chalones’, which synergetically inhibit the passage from G0 into the cell cycle.
Tracer dose and availability time of thymidine and bromodeoxyuridine: application of bromodeoxyuridine in cell kinetic studies
Authors: Böswald M. , Harasim S. , Maurer‐Schultze B.
Published: May 2008

Abstract. The present experiments with [14C]‐thymidine (TdR) and [3H]‐bromo‐deoxyuridine (BrdU) using mouse jejunal crypt cells show that the upper limit of the tracer dose of TdR is about 0.5 µg g body weight‐1 and that of BrdU is about 5·0 µg g body weight‐1. Applying these doses, the proportions of the endogenous DNA synthesis attributed to the exogenous DNA precursor are 2% and 9% respectively. For [3H]‐TdR doses commonly used in cell kinetic studies this proportion is only 0‐1‐1.0%, a negligible quantity that does not influence the endogenous DNA synthesis. The maximum availability time of tracer doses of TdR as well as BrdU is 40 to 60 min, the majority of the precursors being incorporated after 20 min. The availability time is the same for TdR doses exceeding the tracer dose by a factor of 80, whereas it is prolonged in the case of BrdU doses exceeding the tracer dose by a factor of 50. BrdU is suitable to replace radioactively labelled TdR in short term cell kinetic studies, i.e. determination of the labelling index or of the S phase duration by double labelling. However, more studies are needed to elucidate how far BrdU can replace TdR in long term studies as shown by differences between the fraction of labelled mitoses (FLM) curves of a human renal cell carcinoma measured with BrdU and [3H]‐TdR.
Influence of hydrocortisone on the survival and cluster and colony forming characteristics of normal human granulocyte‐macrophage progenitors
Authors: Pasquale D. , Chikkappa G.
Published: May 2008

Abstract. This study was performed to determine the colony and cluster forming ability of granulocyte‐macrophage (CFU‐GM) progenitors of normal human blood low density cells cultured in a liquid culture system in the presence and absence of physiological doses of hydrocortisone (He). The CFU‐GM recovered from the liquid cultures were assayed in soft agar medium. The results of the assays indicated that time‐related development of clusters and colonies over 1‐16 days, proliferative responsiveness to a source of colony stimulating activity, number of cells developed per colony, and the cellular composition of clusters and colonies produced from CFU‐GM recovered from 14‐day‐old liquid cultures with 1·0 µM. He, were all similar to those that developed from the normal human blood low density cells. However, a higher fraction of the CFU‐GM in day 14 liquid cultures with 1·0 µM He were in DNA synthesis phase compared with the CFU‐GM from the peripheral blood. This study confirmed the results of previous studies showing lower numbers of recognizable neutrophilic granulocytes and improved survival/proliferation of CFU‐GM at day 14 in liquid cultures with 1·0 µM He compared with cultures without He. The present results suggest that the normal human blood CFU‐GM which persists and proliferates under the influence of He in a liquid culture system is similar in ontogeny to the blood CFU‐GM, and that the recovery of CFU‐GM from liquid cultures under the influence of He appears to be exerted through stimulation of proliferation and controlled differentiation.
Quantitative contribution of factors regulating rat colonic crypt epithelium: role of parenteral and enteral feeding, caloric intake, dietary cellulose level and the colon carcinogen DMH
Authors: Cameron I. L. , Ord V. A. , Hunter K. E. , Nguyen M. Van , Padilla G. M. , Heitman D. W.
Published: May 2008

Abstract. To elucidate the role and quantitative contribution of several exogenous factors which may regulate colon crypt mitotic activity, proliferative zone height (PZH) and crypt height, groups of rats were subjected to various feeding regimens both with and without treatment with the colon carcinogen, 1,2‐dimethylhydrazine (DMH). The rats were divided into two major groups and one group was given eight weekly injections of DMH base at 9·5 mg kg‐1 body weight. Throughout this period and for two additional weeks the rats were isocalorically fed either a defined nutritionally complete diet with different levels of dietary cellulose or they were parenterally (i.v.) fed a nutritionally complete liquid formula with different caloric levels. The rats were then injected with colchicine 3 h prior to sacrifice to arrest and to collect dividing cells at metaphase. The results of multiple regression analysis of all data were interpreted to indicate that parenteral feeding caused dramatic suppression of the colon crypt height (CH) and of the number of metaphase figures per crypt (MC). Increased cellulose intake stimulated CH but suppressed MC. The CH was also stimulated by DMH. CH was positively correlated to PZH and MC. The MC was suppressed by cellulose intake and negatively correlated to PZH but was positively correlated to CH. The PZH was positively correlated to CH. These findings were related to the role of luminal food, functional workload, kcal intake and treatment with DMH on the measured colon crypt parameters. A quantitative assessment of factors that regulate the measured colonic crypt parameters was accomplished.
A mathematical model of erythropoiesis in mice and rats. Part 4: Differences between bone marrow and spleen
Authors: Pantel K. , Loeffler M. , Bungart B. , Wichmann H. E.
Published: May 2008

Abstract. In a preceding analysis we hypothesized that the most important parameter controlled by erythropoietic regulation in vivo is the degree of amplification (number of cell divisions) in the CFU‐E and erythroblast cell stages. It was concluded that erythropoetic amplification in vivo is controlled according to a sigmoidal dose‐response relationship with respect to the control parameter which is the haematocrit (or haemoglobin concentration). Here, this hypothesis is extended to include the differences in murine bone marrow and splenic erythropoiesis that are described and quantified by different dose‐response relationships. Comparing several sets of experimental data with mathematical model simulations, this approach leads to the following conclusions: (i) in the unperturbed normal steady state at least one extra erythropoietic cell division takes place in the spleen compared with the bone marrow; (ii) a strong erythropoietic stimulus, such as severe bleeding or hypoxia, can induce five to six additional cell divisions in the spleen but only two to three additional divisions in the bone marrow; this results in a considerable increase in the spleen's contribution to erythropoiesis from about 10% in normal animals to over 40% during strong stimulation; (iii) under erythropoietic suppression, such as red cell transfusion, a similar number of cell divisions is skipped in both organs and the splenic contribution to erythropoiesis remains unchanged. In conclusion, the concept that bone marrow and spleen microenvironments differ in the dose‐response relationship for erythropoietic regulation provides an explanation for the changing contribution of splenic murine erythropoiesis following a variety of experimental treatments.
A relationship found between intra‐oral sites of 4NQO reductase activity and chemical carcinogenesis
Authors: Booth D. R.
Published: May 2008

Abstract. Topical application on rat oral mucosa of the chemical 4‐nitroquinoline 1‐oxide (4NQO) has been shown to produce squamous cell carcinomas on the posterior tongue and/or the posterior hard palate. 4NQO is broken down in vivo by a diaphorase, 4NQO reductase (E.C.1.6.99.2), to produce an active molecule believed to be responsible for carcinogenesis. It has been shown that there are higher concentrations of 4NQO reductase in oesophageal mucosa compared with elsewhere in the gastrointestinal tract. The purpose of these experiments was to compare the distribution of certain diaphorases in the oral mucosa. Samples of rat tongue and cheek epithelia were homogenized, then ultracentrifuged to provide mixed cytosol and microsome fractions from the epithelial cells. A spectrophotometer was used to measure the variation in absorbance at 340 nm of NADH consumed by reduction of 4NQO by enzymes present in the tissue extracts. A histochemical technique was used to compare the activity of NADH diaphorase, NADP diaphorase and glucose‐6‐phosphate dehydrogenase at different sites of the oral mucosa. Statistical analysis showed that there were significant (P < 0–01) differences between the activities of all three enzymes at different sites of the oral mucosa. In each case, a higher activity was found at the sites of high incidence of squamous cell carcinoma. A lower activity was found at sites where carcinomas did not occur.
Characterization of bone‐derived chondrogenesis‐stimulating activity on embryonic limb mesenchymal cells in vitro
Authors: Gawande S. R. , Tuan R. S.
Published: May 2008

Abstract. Demineralized bone matrix contains factors which stimulate chondrogenesis and osteogenesis in vivo. A water‐soluble extract of bone has been shown to stimulate chondrogenesis in vitro in embryonic limb mesenchymal cells (Syftestad, Lucas & Caplan, 1985). The aim of this study was to analyse the cellular mechanism of the bone‐derived chondrogenesis‐stimulating activity, with particular attention on how normal requirements for chondrogenesis may be altered. The effects of bovine bone extract (BBE) on chondrogenesis in vitro were studied using micromass cultures of chick limb bud mesenchyme isolated from embryos at Hamburger‐Hamilton (HH) stage 23/24, an experimental system which is capable of undergoing chondrogenic differentiation. Bovine diaphyseal long bones were demineralized and extracted with guanidine‐HCl to prepare BBE (Syftestad & Caplan, 1984). High‐density mesenchyme cultures (30 times 106 cells/ml) were exposed to different doses of BBE (0–01‐1‐0 mg ml‐1) and chondrogenesis was quantified based on cartilage nodule number and [35S]sulphate incorporation. BBE was tested on micromass cultures of varying plating densities (2–30 times 106 cells/ml), on cultures of ‘young’ limb bud cells (HH stage 17/18), and on cultures enriched with chondroprogenitor cells obtained from subridge mesoderm. Since poly‐L‐lysine (PL) has recently been shown (San Antonio & Tuan, 1986) to promote chondrogensis, PL and BBE were introduced together in different doses, in the culture medium, to determine if their actions were synergistic. Our results show that BBE stimulates chondrogenesis in a dose‐dependent manner and by a specific, direct action on the chondroprogenitor cells but not in normally non‐chondrogenic, low density or ‘young’ limb bud cell cultures. The effects of PL and BBE are additive and these agents appear to act by separate mechanisms to stimulate chondrogenesis; PL primarily enhances nodule formation, and BBE appears to promote nodule growth.
Mathematical model analysis of mouse epidermal cell kinetics measured by bivariate DNA/anti‐bromodeoxyuridine flow cytometry and continuous [3H]‐thymidine labelling
Authors: Aarnæs E. , Kirkhus B. , Clausen O. P. F.
Published: May 2008

Abstract. In a previous study the epidermal cell kinetics of hairless mice were investigated with bivariate DNA/anti‐bromodeoxyuridine (BrdU) flow cytometry of isolated basal cells after BrdU pulse labelling. The results confirmed our previous observations of two kinetically distinct sub‐populations in the G2 phase. However, the results also showed that almost all BrdU‐positive cells had left S phase 6–12 h after pulse labelling, contradicting our previous assumption of a distinct, slowly cycling, major sub‐population in S phase. The latter study was based on an experiment combining continuous tritiated thymidine ([3H]TdR) labelling and cell sorting. The purpose of the present study was to use a mathematical model to analyse epidermal cell kinetics by simulating bivariate DNA/BrdU data in order to get more details about the kinetic organization and cell cycle parameter values. We also wanted to re‐evaluate our assumption of slowly cycling cells in S phase.

The mathematical model shows a good fit to the experimental BrdU data initiated either at 08.00 hours or 20.00 hours. Simultaneously, it was also possible to obtain a good fit to our previous continuous labelling data without including a sub‐population of slowly cycling cells in S phase. This was achieved by improving the way in which the continuous [3H]TdR labelling was simulated. The presence of two distinct sub‐populations in G2 phase was confirmed and a similar kinetic organization with rapidly and slowly cycling cells in G1 phase is suggested. The sizes of the slowly cycling fractions in G1 and G2 showed the same distinct circadian dependency. The model analysis indicates that a small fraction of BrdU labelled cells (3–5%) was arrested in G2 phase due to BrdU toxicity. This is insignificant compared with the total number of labelled cells and has a negligible effect on the average cell cycle data. However, it comprises 1/3 to 1/2 of the BrdU positive G2 cells after the pulse labelled cells have been distributed among the cell cycle compartments.
Synchrony of bone marrow proliferation and maturation as the origin of cyclic haemopoiesis
Authors: Schmitz S. , Loeffler M. , Jones J. B. , Lange R. D. , Wichmann H. E.
Published: May 2008

Abstract.Cyclic haemopoiesis in Grey Collie dogs is characterized by stable oscillations in all haemopoietic lineages. It is proposed that in these animals, in contrast to normal animals, the maturation process of haemopoietic (in particular granuloid) cells from the primitive progenitors to the functional cells is characterized by an abnormally strong synchrony. It is conjectured that the marrow maturation time has a very small variance compared with non‐cyclic normal dogs. With a mathematical model of haemopoiesis it is shown that small fluctuations are amplified via regular feedback processes such that stable granuloid oscillations are established. Erythroid oscillations are induced indirectly by granuloid feedback to the stem cell pool. The model calculations further show that the synchrony hypothesis of bone marrow maturation can quantitatively explain the following experimental results: (1) the maintenance of stable cycles of granuloid and erythroid bone marrow and blood cells with a period of approximately 14 d; (2) the disappearance of granuloid and erythroid cycles during the administration of the colony stimulating factor rhG‐CSF; (3) the reappearance of oscillations when the administration of CSF is discontinued; (4) the cessation of cycles during endotoxin application; and (5) the persistence of cycles during erythroid manipulations (bleeding anaemia, hypoxia, hypertransfusion). We therefore conclude that cyclic haemopoiesis is not caused by a defect in the regulatory control system but by an unusual maturation process.
The effects of the platinum anti‐tumour agents on renal cell kinetics and the response to a second cytotoxic agent
Authors: Ewen C. , Hendry J. H.
Published: May 2008

Abstract. Following 15 mg kg‐1 cisplatin to mice, the labelling index (LI) in the kidney decreased from 0–4% to & lt;0–01% at 1–3 d, increased to 1–9% at day 16 and returned to control levels by day 30. Cytotoxicity was assessed by counts of viable tubule cross‐sections and recovery was incomplete up to 14 months after treatment.

Cisplatin treatment impaired the regeneration response to a dose of 16 mg kg‐1 uranyl nitrate (UN) given 14 d after cisplatin when assessed by an increase in LI and sub‐capsular tubule count. However, there was recovery with greater time intervals. At nine months after cisplatin there was no difference in response to UN of controls and mice previously treated by cisplatin.

Prior treatment with paraplatin or iproplatin at LD50 doses produced not only no histopathological changes but also no impairment of the subsequent responses to UN.
Cell inactivation and cell cycle inhibition as induced by extreme hypoxia: the possible role of cell cycle arrest as a protection against hypoxia‐induced lethal damage
Authors: Åmellem ø , Pettersen E. O.
Published: May 2008

Abstract. Cycling mammalian cells that are rendered extremely hypoxic 4 ppm O2 tend to accumulate in a pre‐DNA‐synthesis stage. It is not clear whether or not this is the result of an active regulation by the cells. In the present study we have rendered cells, synchronized by mitotic selection, extremely hypoxic over a relatively long period of time (up to 48 h). We have recorded cell cycle progression during hypoxia as well as cell inactivation depending on where in the cell cycle the cells were located when the hypoxic treatment was started. Three main conclusions are drawn: 1 the cell cycle arrest in late‐G1 is complete even during a long‐lasting (24 h) hypoxic treatment; 2 while cells in early‐ and mid‐S are completely arrested and quickly inactivated under hypoxic conditions, cells in late‐S, G2 and mitosis are able to continue cell cycle progression and divide; 3 whether the cells are located in G2, mitosis or early‐G1 at the onset of hypoxia, they were able to survive relatively long‐lasting hypoxic treatment. The present results are in favour of the view that the pre‐DNA‐synthetic arrest induced by extreme hypoxia may function to rescue the cells from severely damaging effects that would appear if the cells were able to initiate DNA synthesis.
Diversity of penetration of anti‐cancer agents into solid tumours
Authors: Simpson‐Herren L. , Noker P. E.
Published: May 2008

Abstract. Failure of anti‐cancer agents to reach all clonogenic cells at cytotoxic concentrations is recognized as an important form of resistance in solid tumours. Subcutaneously implanted mammary adenocarcinoma 16/C was used to evaluate the intratumour distribution of five alkylating, bioreductive alkylating and intercalating agents and two radiation sensitizers. The agents were classified according to their in vivo distribution in well‐ and poorly‐perfused tumour regions, as delineated by lissamine green. The classifications were: (1) distribution in direct proportion to the vascular supply; (2) uniform distribution to well‐ and poorly‐perfused tumour regions; and (3) preferential retention in the poorly‐perfused tumour regions. Our current state of knowledge did not allow reliable prediction of the classification based on chemical structure or mechanism of action.