bluuebunny/crossref_metadata_2025 huggingface dataset:
CYTOKINETIC CHANGES IN THE THYMUS OF TUMOUR‐BEARING AND OF DEXAMETHASONE‐TREATED MICE
Authors: Aherne W. A. , Zaitoun A. M. , Lauder I. , Hull D. L.
Published: May 2008

Changes in the cell population kinetics of the Balb/c mouse thymus were studied (a) during the growth of a syngeneic transplantable sarcoma and (b) following intraperitoneal injection of dexamethasone. The weight of the thymus fell briefly after tumour transplantation, then recovered with overshoot and eventually declined profoundly. After dexamethasone injection the weight of the thymus fell to roughly one‐third of its normal value in 36 hr. Similar cytokinetic changes were observed in both sets of experiments; thymic wasting was accompanied by a small increase in thymocyte cell cycle time, a prolongation of the S‐phase of the cycle, a marked decrease in the thymocyte cell production rate and a marked reduction in the growth fraction of the thymocyte population in the superficial Cortex. It is suggested that thymic atrophy in tumour bearing animals may be a stress phenomenon.
ERYTHROPOIETIN‐INDEPENDENT REGENERATION OF ERYTHROID PROGENITOR CELLS FOLLOWING MULTIPLE INJECTIONS OF HYDROXYUREA
Authors: Wagemaker G. , Visser T. P.
Published: May 2008

It was shown previously that colony formation in vitro by early erythroid progenitor cells (BFUe) requires sequential stimulation with a specific glycoprotein termed BFA and erythropoietin (EP). The action exerted by BFA was characterized as induction of proliferation in BFUe resulting after several cell divisions in EP‐responsive progeny. The present study is directed at detection of EP‐independent regulation of erythroid progenitor cells in vivo.

Haemopoietic regeneration was induced by multiple administrations of hydroxyurea (HU). The femoral regeneration patterns of haemopoietic stem cells (CFUs), granulocyte/macrophage progenitor cells (CFUgm) and erythroid progenitor cells (BFUe, day 3 BFUe and CFUe) were studied in hypertransfused mice in comparison to nontransfused controls. The results show that (1) the phase of exponential regeneration of none of the cell populations studied is affected by hypertransfusion; (2) each of these cell populations exhibit a distinct regeneration pattern, indicating that they behave as separate functional entities; and (3) the three erythroid cell populations are suppressed by hypertransfusion in the post‐exponential phase of regeneration in contrast to CFUs and CFUgm.

The results support a two‐regulator model of erythropoiesis.
THE METAPHASE ARREST TECHNIQUE
Authors: Wright N. A. , Appleton D. R.
Published: May 2008

The accuracy and precision of the stathmokinetic experiment for the determination of cell birth rate are discussed from practical and theoretical viewpoints. Topics covered include the determination of the optimal dosage of the metaphase arresting agent, the times at which observations should be taken and which cells should be counted, the correct method of estimating cell birth rate and the dependence of any derived estimate of the turnover time on the age distribution of cycling cells. Failure to consider any of these points can lead to considerable inaccuracy. It is further shown that the stathmokinetic method is a rather imprecise one for measuring the turnover time and the duration of mitosis.

Data are present comparing the results of using the technique with those obtained from autoradiographic studies.
An In Vitro Model of Hematopoietic Injury In Chronic Hypoplastic Anemia
Authors: Fitchen J. H. , Deregnaucourt Josette , Cline M. J.
Published: May 2008

Mice treated with high‐dose busulfan develop a ‘latent’ form of bone marrow failure characterized by near‐normal peripheral blood counts and marrow cellularity, but marked reductions in marrow pluripotent stem cells (CFUs) and myeloid progenitor cells (CFUc). Spleen cell suspensions from control and ‘latent’ mice were placed in liquid culture in the presence of colony‐stimulating activity. Cells were harvested at intervals up to 14 days and sub‐cultured in agar to assay for CFUc. Baseline splenic CFUc did not differ significantly between control and ‘latent’ mice. Splenic CFUc from control mice increased 50‐fold and reached a peak at day 10 in liquid culture. In contrast, splenic CFUc from ‘latent’ mice increased only 7‐fold and reached a peak at day 3. Our results indicate that although splenic CFUc are present in normal numbers in ‘latent’ mice, their proliferative capacity is markedly reduced, either as the result of defective CFUc self‐renewal or defective feed‐in from CFUs or both.
Variation In G1 Transit Time Relative to the Cycloheximide and Actinomycin D Drug Restriction Points
Authors: Blair O. C. , Roti J. L. Roti
Published: May 2008

The transit time distribution at various points in the cell cycle of synchronized Chinese hamster ovary cells was determined from the mitotic index, [3H]thymidine labeling index and increase in cell number monitored at regular intervals after mitotic selection. Variation in G1 transit time compared with that for the total cell cycle indicates that variation in cell cycle transit time occurs mainly during G1 phase. the cycloheximide (5.0 μg/ml) and actinomycin D (3.0 μg/ml) restriction points occur 0.2 and 1.7 hr prior to entry into S phase, respectively. the transit time distributions are further characterized by the moments of the distributions. the variance (2nd moment about the mean) of the transit time distribution at the actinomycin D restriction point is similar to the variance of the transit time distribution at the G1/S border, thus variation in cell cycle transit time originates earlier than 1.7 hr prior to entry into S phase (i.e., the first 3/4 of G1). If G1 transit time variability and cell cycle control are related, then the results presented here indicate that the major regulatory events do not occur during late G1 phase.
DIFFERENCES AND SIMILARITIES IN ADJUVANT CHEMOTHERAPY IN MOUSE AND MAN
Authors: van Putten L. M. , Gerritsen A. F. C.
Published: May 2008

The effectiveness of adjuvant chemotherapy is easily demonstrated in many mouse models, whereas in man the response is good but far less spectacular. With the aid of a mathematical model the following variables in which differences may exist between mouse and man were tested:

1. Uniformity of tumour load in population

2. Cell kinetic factors in drug sensitivity

3. Variation of drug sensitivity among tumours

4. Drug penetration into tumour

5. Tumour antigenicity

6. Variation in growth rate among tumours

It is concluded that factors 1 and 3 are responsible for the difference. Mouse models are more sensitive by selection of an effective drug and an optimal tumour load. Other factors seem not to affect the results.
Changes In the Proliferation Characteristics of A Solid Transplantable Tumour of the Mouse With Time After Transplantation
Authors: de Lacroix W. Féaux , Lennartz K. J.
Published: May 2008

The aim of the present investigation was to study changes in cell proliferation kinetics with time after transplantation in a solid transplantable mammary carcinoma of the C3H mouse. From growth curves and tumour doubling times, three different experimental times were chosen; the exponential phase of growth on the 7th day post‐transplantation, during the phase of retardation on the 21st day after transplantation and in the stationary phase of growth on the 30th day after transplantation. It was found that the cell loss factor contributed primarily to the retardation of volume growth. the lowering of the growth fraction played a minor part in the delay of growth while the duration of cell cycle was not prolonged before the plateau phase of growth on the 30th day after transplantation was reached.
RADIOTOXICITY OF INCORPORATED [3H]THYMIDINE AS STUDIED BY AUTORADIOGRAPHY AND FLOW CYTOMETRY CONSEQUENCES FOR THE INTERPRETATION OF FLM DATA
Authors: Beck H.‐P.
Published: May 2008

The radiotoxic effects of incorporated [3H]thymidine on proliferation kinetics of flash‐labelled (30 min, 0.3 μCi/ml, 40 Ci/mM) L‐929 cells in vitro were studied by means of autoradiography and flow cytometry. the flow cytometric results obtained by applying the BUdR‐33258 Hoechst technique, using new evaluation procedures, showed that the labelled cells are delayed in their progression through the S and G2+ M phases, leading to mitotic delay. From autoradiographs, the fraction of labelled mitoses was determined and, in addition, the ratio of labelled and of unlabelled mitotic cells to all cells. the radiotoxic effects are not evident from the FLM curve, even if the ratio of labelled mitotic cells to all cells shows a highly distorted shape. A mathematical model has been developed that describes the perturbed cell kinetics due to radiotoxic effects of the incorporated [3H]thymidine. These findings have considerable consequences for the interpretation of autoradiograhic data, especially of labelled mitoses curves.
Cell Cycle Kinetics of Chinese Hamster (Cho) Cells Treated With the Iron‐Chelating Agent Picolinic Acid
Authors: Gurley L. R. , Jett J. H.
Published: May 2008

Spontaneously transformed (tumorigenic) Chinese hamster cells (line CHO) do not exhibit picolinic acid‐sensitive G1 and G2 cell cycle arrest points observed in normal and virus‐transformed cells. Rather, picolinic acid arrests CHO cells in S phase only and produces culture growth behaviour similar to that produced by hydroxyurea. Prolonged treatment with picolinic acid permits a slow but significant traverse of cells through S phase. Thus, like hydroxyurea, picolinic acid is not a useful agent for synchronizing exponential CHO cells, but it can be used to resynchronize cultures in early S phase if a previous synchronization procedure (such as isoleucine deprivation) is used. the iron chelating properties of picolinic acid, and the similarities of its effects on cultured cells to those of hydroxyurea and the iron‐chelating drug desferrioxamine, suggest that picolinic acid inhibits DNA synthesis by interfering with the iron‐dependent production of a stable free organic radical which is essential for the ribonucleotide reductase formation of deoxyribonucleotides.
INACCURACY OF ESTIMATIONS OF S PHASE FRACTION BY REDUCTION IN CLONING EFFICIENCY WITH HYDROXYUREA OR TRITIATED THYMIDINE
Authors: Yen A. , Lambek Caryl , Clarkson B.
Published: May 2008

The current hypothesis, that the fractional reduction of cloning efficiency in semi‐solid culture systems induced by pretreatment of the cells with hydroxyurea (HU) or [3H]TdR equals the fraction of cells initially in S phase, is tested. A lymphoblastoid cell line, SK‐L7, with known cell cycle kinetics was exposed to cytotoxic concentrations of HU or suicidal doses of [3H]TdR and then initiated in semi‐solid and liquid culture. Although approximately 0.6 of the initial population was in S, 1‐hr exposures of HU at concentrations of up to 10‐2 M failed to reduce subsequent cloning efficiency. the 1‐hr exposure to HU did not reduce either the immediate cell number or the gross population doubling rate over 24 hr. A 24‐hr exposure to 10‐3 M HU reduced the cloning efficiency by approximately 98%, confirming the drug's cytotoxic capability. [3H]TdR at doses of 100 μCi/ml for 20–40 min reduced the cloning efficiency by approximately 60 and 70%, respectively. Although no cytotoxicity immediately after exposure was observed in either case, gross population doubling rate in liquid culture was reduced. While HU failed to reduce subsequent cloning efficiency, [3H]TdR reduced cloning efficiency by approximately the fraction of initial cells in S. the above hypothesis, therefore, cannot be applied naïvely as a technique for quantitating the fraction of a clonogenic cell population in S phase.
CYTOKINETICS OF TUMOUR AND ENDOTHELIAL CELLS AND VASCULARIZATION OF LUNG METASTASES IN C3H/HE MICE
Authors: Gunduz Nurten
Published: May 2008

A model of lung metastases was developed using intravenous injection of tumour cell aggregates of spontaneous C3H/He mammary tumours in syngeneic mice. the growth rate of lung tumours decreased with increasing tumour volume, with mean host survival of 46 days. the cytokinetics of individual tumours ranging between 0.004 and 4.2 mm3 in volume were studied. the labelling index (LI) ranged between 12 and 17%, the DNA synthesis time (Ts) being 9–10 hr. the growth fraction (GF) ranged between 26 and 38%. the cell cycle time (Tc) was found to be 18–19 hr. the LI and the GF decreased with increasing tumour volume doubling time (Td). No correlation was found between the tumour volume and Tc. the LI of endothelial cells within these tumours, ranging between 0.004 and 4.2 mm3 in volume was 14–15% and endothelial cell proliferation was not affected by tumour growth.

Vascular parameters were also determined for these tumours as a function of tumour volume. Vascular volume increased with increasing tumour size while the percentage of capillary vessels decreased. the cellular volume to capillary volume ratio increased with increasing tumour volume. Necrosis was observed in 0.27 mm3 tumours and increased with increasing tumour size.

The results from these studies suggested that the age‐dependent decrease in proliferative activity of tumour cells growing in the lung is related to change in effective vascularity.
DETERMINATION OF STEADY STATE GENERATION TIME DISTRIBUTIONS FROM LABELLED MITOSIS EXPERIMENTAL DATA
Authors: Palsson B. , Himmelstein K. J.
Published: May 2008

The proper application of detailed deterministic cell kinetic models depends on the way in which cells are assigned their generation times. A method is presented for the determination of population generation time distributions from labelled mitoses experiments. the model assumes that the generation time of each new cell is a function of both the steady‐state generation time distribution function of the population, and also the generation time frequency‐function of the previous generation of cells. This approach is applied to two different cell types to successfully simulate extended labelled mitoses curves using a population balance model with constant maturation rates.
A Mathematical Model For Analysing Cellular Age‐Response Functions In Terms of Physiological Age
Authors: Valleron A.‐J. , Rockwell Sara
Published: May 2008

A mathematical model is presented which facilitates the analysis of cellular age‐response functions in terms of the physiological ages of the cells. Age‐response functions are generally determined by obtaining synchronous cohorts of cells and measuring the sensitivity of the cohorts to the treatment agent at different times after selection (i.e., at several different chronological ages). the model described here uses data on the [3H]TdR labelling patterns of the cell population to determine the distribution of physiological ages for the cohorts at the times of treatment. the age‐response function data are then analysed in terms of the physiological ages of the cells. the compartments used in the analysis may be chosen according to the biology of the system and the wishes of the experimenters and not imposed by the variability of the phase durations. the application of the model is illustrated using the age‐response functions for EMT6 cells exposed to radiation and HeLa cells exposed to hydroxyurea.
Clonal Variation In Proliferation Rate of Cultures of Gpk Cells
Authors: Riley P. A. , Hola M.
Published: May 2008

Pedigrees of twenty‐six clones of a line of keratocytes derived from guinea‐pig ear epidermis (GPK cells) were analysed from time‐lapse film. the mean interdivision time (IDT) for the culture was 1143 φ 215 (SD) min. the mean generation rates (mean reciprocal interdivision times) of clones varied over a range of 3.93–10.2 × 10‐4/min and the standard deviation of the clonal mean generation rates was 16.8% of the average value. Transient intraclonal variations in IDT due to mitoses in a plane perpendicular to the substratum were observed. the data were also analysed on the basis of cell location in sixteen equal zones (quadrats) of the filmed area. the mean generation rate of quadrats was 8.73 x 10‐4/min (SD = 4.9%). the spatial distribution showed some clustering of cells. the mean local density of the clones (2.25 φ 0.62 cells/10‐4 cm2) was significantly higher than the quadrat density (1.76 φ 0.8 cells/10‐4 cm2). There was no significant correlation between clonal density and mean generation rates, whereas for quadrats a significant negative correlation was found (P= 2.7%). the results support the proposition that cell lineage is the major determinant of the proliferation rate of subconfluent cultures.
Laser Flow Cytofluorometric Analysis of Htc Cells Synchronized With Hydroxyurea, Nocodazole and Aphidicolin
Authors: Miller‐Faurès A. , Michel N. , Aguilera A. , Blave A. , Miller A. O. A.
Published: May 2008

The technique of laser flow cytofluorometry has been used to monitor the arrival in G1 and the subsequent progression through the cell cycle of HTC cells accumulated in metaphase with colcemid alone or after treatment with hydroxyurea and Nocodazole. Under the experimental conditions used in this study, the latter procedure gives much better results, avoiding in particular the extensive formation of micronucleated cells. Aphidicolin, an inhibitor of DNA polymerase, in combination with Nocodazole, provides a useful method to tightly synchronize these cells at the G1/S border.
Bone Marrow Response to Damage Induced By Hydroxyurea Or Colchicine
Authors: Nečas E.
Published: May 2008

The extent of bone marrow damage caused by the administration of single or repeated doses of either hydroxyurea (1000 mg/kg b.w.) or colchicine (1 mg/kg b.w.) are comparable. This conclusion is based on serial studies of bone marrow cellularity and of the CFUc numbers in the bone marrow. the proliferation response of the pluripotential haemopoietic stem cells, determined by the cells forming colonies in the spleen of lethally irradiated mice (CFUs) markedly differs if the bone marrow damage is caused by hydroxyurea or colchicine. While hydroxyurea administration stimulates a large proportion of the resting G0 cells into the cell cycle, the damage induced by colchicine is followed by only a mild increase in the CFUs proliferation rate.

The seeding efficiency of the spleen colony technique has been determined after both hydroxyurea and colchicine administration. This parameter, important for the estimation of the number of the pluripotential haemopoietic stem cells in blood forming organs, is significantly affected by hydroxyurea administration, but also by repeated injections of colchicine. Following a single dose of hydroxyurea, the time‐course of the CFUs numbers, which were corrected for the change in the seeding efficiency, shows an overshoot occurring after 18–20 hr. At the other time periods, the number of pluripotential haemopoietic stem cells is little affected by a single hydroxyurea injection. This poses a question about the nature of the stimulus, which after hydroxyurea administration triggers the CFUs from the resting G0 state into the cell cycle. There is evidence that this stimulus is probably not represented by the damage caused to the various intensively proliferating cell populations of the bone marrow. This evidence is based on experiments which show that colchicine induced damage, of a degree similar to that after hydroxyurea, does not stimulate the CFUs proliferation rate to an extent comparable to hydroxyurea.

The possibility that colchicine could block CFUs in the G0 state or that it could interfere with the progress of CFUs through the G1 and S phases of the cell cycle have been ruled out by experiments which demonstrated that colchicine (1 mg/kg b.w.), administered 10 min before hydroxyurea, does not reduce the number of CFUs triggered into the cell cycle as the consequence of hydroxyurea administration.
Proliferation In Liquid Culture of Myeloid Progenitor Cells From the Blood of Normals and Patients With Aplastic Anaemia
Authors: Fitchen J. H. , Deregnaucourt Josette , Cline M. J.
Published: May 2008

We studied myeloid progenitor cells (CFUc) from peripheral blood mononuclear leukocytes (MNL) of normals and patients with severe aplastic anaemia (AA). Baseline CFUc averaged 4.4 φ 1.5 (range 0–17)/106 MNL in fifteen normals and 0 φ 0/106 MNL in six patients with severe AA (P > 0.05). to assess CFUc proliferative capacity, 107 MNL were put into liquid culture in Marbrook chambers with colony‐stimulating activity and sub‐cultured in agar at intervals up to 10 days. CFUc from normal MNL increased from 44 φ 15/chamber at Day 0 to 156 φ 33/chamber at peak value (P > 0.02). In contrast, CFUc from AA MNL remained undetectable throughout the period of liquid culture (AA peak v. normal peak; P > 0.001). These results indicate a marked decrease in circulating CFUc in patients with severe AA, and a profound abnormality in CFUc proliferation in vitro. This abnormality could be due to defective replication of CFUc, a lack of feed‐in from more primitive precursors, or both.
EFFECT OF TRITIATED THYMIDINE ON THE KINETICS AND VIABILITY OF 9L CELLS IN VITRO
Authors: Wiezsaecker M. , Hoshino T. , Kobayashi S.
Published: May 2008

The colony‐forming efficiency of 9L rat gliosarcoma cells was unaffected by treatment with 0.1 μCi/ml of [3H]TdR. However, when cells were treated with 1 or 10 μCi/ml of [3H]Tdr, cell growth was reduced and cell survival decreased.

When monolayer 9L cells were treated with 1 μCi/ml of [3H]TdR for up to 72 hr, approximately 5% survived, which is closely related to the percentage of non‐cycling cells in this system. When cells were treated with 10 μCi/ml of [3H]TdR for 72 hr, less survival was observed. the additional cell kill observed may be induced by [3H]TdR released from doomed cells into petri dishes during the incubation period of the colony‐formation assay.
Mitotic Rate of Rat Thyroid Follicular Cells In Vivo In Response to A Single Injection of Thyrotropin (Tsh)
Authors: Redmond Olga , Tuffery A. R.
Published: May 2008

The mitotic rate of thyroid follicular cells was assessed by a stathmokinetic method at intervals from 15 min to 24 hr after a single injection of 1 iu/kg of thyrotropin (TSH). the mitotic rate was increased 15 min after TSH and remained elevated for 3 hr. Two further peaks of mitotic activity were present at 9 hr and 24 hr after TSH. Serum TSH concentrations were increased from 5 min to 3 hr with a maximum at 1 hr.
A long‐lived thymidine pool in epithelial stem cells
Authors: Hume W. J. , Potten C. S.
Published: May 2008

Abstract. The labelling index (LI) of the individual basal cell positions of the anterior column of mouse tongue filiform papillae was assessed with time after an injection of [3H]TdR at 12.00 hours (the minimum point in the circadian LI rhythm). An initial doubling of the LI in the stem cell zone due to cell division was followed by a second rise of 14–16% 16 hr after injection and this occurred even in the presence of vincristine. Although the uptake of [3H]TdR and the initial LI doubling were largely prevented by a preceding injection of hydroxyurea, the 14–16% LI rise was still observed. The possible explanations are discussed, the favoured one being that an average of one of the six or seven cells (the stem cell) in each stem cell zone can store [3H]TdR in a long‐lived precursor pool for at least 16 hr before being utilized for DNA synthesis. This complements previously published work which suggested that one cell in each stem cell zone may selectively segregate DNA at mitosis.
Velocity sedimentation profiles of normal and regenerating primitive erythroid burst‐forming units: relation to phase of cell cycle and growth in vitro
Authors: Koury M. J. , Krantz S. B.
Published: May 2008

Abstract. The primitive burst‐forming unit‐erythroid (BFU‐e) derived from normal and regenerating murine bone marrow was examined by velocity sedimentation at unit gravity. An increase in the modal sedimentation velocity and the percentage of rapidly sedimenting BFU‐e was found in regenerating marrow as compared to normal marrow. Neither hypertransfusion‐induced plethora nor administration of erythropoietin (Ep) during regeneration altered the changes from normal in the velocity sedimentation profile observed during regeneration. Separated marrow cells were pooled as rapidly sedimenting and slowly sedimenting and then examined for percentage of BFU‐e in DNA synthesis and growth response in vitro to increasing concentrations of a partially purified Ep preparation. The percentage of BFU‐e in DNA synthesis as determined by tritiated thymidine killing does not correspond to the BFU‐e growth response to Ep in vitro. No difference in growth was noted between BFU‐e from rapidly and slowly sedimenting normal marrow cells despite an increased percentage in DNA synthesis of normal BFU‐e which sedimented rapidly. No significant difference in the percentage of BFU‐e in DNA synthesis was found between the rapidly and slowly sedimenting subpopulations of regenerating BFU‐e, but the latter had a reduced growth response to low concentrations of Ep.
Isolation of rat intestinal crypt cells
Authors: Lawson A. J. , Smit R. A. , Jeffers N. A. , Osborne J. W.
Published: May 2008

Abstract. A technique is presented which yields single cells and intact crypts in suspension from unfixed rat intestinal mucosal epithelium. Everted lengths of intestine were digested by 27 mM sodium citrate in phosphate‐buffered saline (pH = 7.3) at 37°C. Mucosal cells were dislodged by vibratory stress (hand vortexing) following incubation for prescribed intervals at 37°C in 1.5 mM ethylenediamine tetraacetic acid (EDTA) and 0.5 mM dithiothreitol (dtt). Alkaline phosphatase determinations, phase microscopy, and in vivo and in vitro evaluations of tritiated thymidine ([3H]TdR) incorporation were performed on isolated intestinal cells. Data indicate that cells were sequentially derived from villus tip to crypt base as judged by cellular morphology, alkaline phosphatase activity/mg protein and radioactivity per μg protein. Upon completion of the intestinal cell isolation assay, scanning electron microscopy of the remaining intestine revealed that approximately 95% of the crypt openings were vacant; the villi were totally denuded; the supporting structures, including the lamina propria, appeared intact. In vitro radiolabelling of intestinal cell fractions enriched with crypts revealed a linear incorporation of [3H]TdR from 0–60 min which was strongly influenced by the presence of foetal calf serum (FCS). Measurements of the compensatory response of the mucosa to resection of 70% of the small bowel indicated that the mucosal cell separation is capable of detecting alterations in crypt cell proliferation. Previously, such alterations were monitored by other methods utilizing microdissection procedures or stathmokinetic agents.
Tracheal epithelium: cell kinetics and differentiation in normal rat tissue
Authors: Donnelly Grace M. , Haack D. G. , Heird Connie S.
Published: May 2008

Abstract. The fate of [3H]thymidine ([3H]Tdr) pulse‐labelled cells was followed in tracheal epithelium of young male rats. The time course for cell differentiation, and the relation of events to tissue composition were studied. In vivo labelling and light microscope autoradiography of epoxy embedded sections were used. Labelled and total nuclei for each cell type, and combinations of labelled cells which were adjacent to one another, were tallied. Hierarchical analyses of variance were performed on the several data sets. All cell types, except ciliated, were labelled at 1 hr. A few labelled ciliated cells were seen 24 hr post‐label. The frequency of labelled intermediate cells peaked at day 2; goblet and ciliated cells at day 3. No significant changes occurred in the labelling index, but at 24 hr the frequency of adjacent labelled cells (ALC) had increased > 5‐fold, and changes had occurred in patterns of ALC combinations. The labelled ciliated cells which were seen at 24 hr were adjacent to labelled intermediate cells. No labelled basal‐ciliated cell combinations were seen at any time. Data indicated that ciliated cells can develop from S‐phase intermediate cells within 24 hr, and neither basal nor superficial goblet cells are progenitors of ciliated cells. It is proposed that both superficial goblet cell and ciliated cell development is preceded by two divisions: a basal cell division followed by an intermediate cell division.
Cell kinetics of lithium‐induced granulopoiesis
Authors: Gallicchio V. S. , Chen M. G.
Published: May 2008

Abstract. Lithium has been shown to be an effective inducer of granulopoiesis. The mechanism of lithium action has been shown to influence CFU‐s and CFU‐c proliferation, increase colony‐stimulating factor (CSF) production and reduce erythropoiesis. We report here evidence to show that lithium recruits CFU‐c that are not normally in the cell cycle into active DNA synthesis, as measured by hydroxyurea and tritiated thymidine suicide techniques. Furthermore, lithium action is shown to be time‐dependent, since the delay addition of lithium for 5 min to normal bone marrow removes the enhancement usually seen when lithium is given at time zero. The implications of these lithium‐induced effects are described.
Acinar cell proliferation in the parotid and submandibular salivary glands of the neonatal rat
Authors: Klein R. M.
Published: May 2008

Abstract. Although the rat salivary glands are deficient in acini at birth, acinar cells proliferate rapidly during the early post‐natal period. The pattern of acinar cell proliferation was analysed in the parotid and submandibular glands of neonatal rats from day of birth until day 34. Mitotic and [3H]thymidine ([3H]TdR) labelling indices of the two glands show distinctly different patterns. Analysis of cell division in the rat parotid gland demonstrated a peak of mitotic index at 14 days (2.9 ± 0.4%) and labelling index at 16 days (25.2 ± 2.1%). Submandibular gland acinar cell proliferation reaches a zenith between 7–8 days; labelling index (14.2 ± 1.1%) and mitotic index (2.3 ± 0.3%). Cell proliferation decreases rapidly in both glands after reaching a peak in activity. Gland size increases more rapidly in the submandibular gland which correlates with the earlier shift from cell proliferation to differentiation which occurs in this organ. Circadian rhythms of [3H]TdR incorporation were also investigated in this study. A circadian rhythm of [3H]TdR incorporation into DNA occurs at 15 days after birth with a peak at 06.00 hours in both glands and a trough occurring at 15.00 hours in parotid gland and 18.00 hours in the submandibular gland. Determination of specific activity of DNA (ct/min per μg DNA) on days 8, 10, 12, 13, 14, 15, and 16 after birth at 06.00 and 15.00 hours indicated that a circadian rhythm in [3H]TdR incorporation into DNA began on day 14. The developmental switch from suckling to solid food may be an initiating factor in the sychronization of the circadian rhythm in cell proliferation.
Kinetics of protein and DNA synthesis studied by mathematical modelling of flow cytometric protein and DNA histograms
Authors: Lindmo T.
Published: May 2008

Abstract. Mathematical models for histograms of cellular protein content as measured by flow cytometry were developed, based on theoretical protein distributions. These were derived from the age distribution of cells and the accumulation function for cellular protein content as a function of age within the cell cycle. A model assuming an exponential age distribution and an exponential protein. accumulation function was found to give the best representation of protein histograms of exponentially growing NHIK 3025 cells. This is in good agreement with the known kinetic behaviour of such cells. By the combined use of the protein histogram model and a similar model for DNA content, and assuming linear DNA accumulation during S, the fraction of cells in S, as a function of cellular protein content, was simulated. This function showed good agreement with values of the [3H]TdR labelling index scored in cells sorted by flow cytometry from 5‐channel intervals of the protein histogram. The protein and DNA histogram models were combined into a two‐dimensional model for correlated protein/DNA measurements. Comparison between simulated data and experimentally derived two‐dimensional protein/DNA histograms gave further support to the cell kinetic assumptions underlying the models, but also identified some minor deviations which could not be recognized in the analysis of the one‐dimensional histograms.
Image analysis for the automated estimation of clonal growth and its application to the growth of smooth muscle cells
Authors: Gavino V. C. , Milo G. E. , Cornwell D. G.
Published: May 2008

Abstract. Image analysis was used for the automated measurement of colony frequency (f) and colony diameter (d) in cultures of smooth muscle cells, Initial studies with the inverted microscope showed that number of cells (N) in a colony varied directly with d: log N= 1.98 log d ‐ 3.469 Image analysis generated the complement of a cumulative distribution for f as a function of d. The number of cells in each segment of the distribution function was calculated by multiplying f and the average N for the segment. These data were displayed as a cumulative distribution function. The total number of colonies (fT) and the total number of cells (NT) were used to calculate the average colony size (NA). Population doublings (PD) were then expressed as log2NA. Image analysis confirmed previous studies in which colonies were sized and counted with an inverted microscope. Thus, image analysis is a rapid and automated technique for the measurement of clonal growth.
Stem cell (CFUs) proliferation inhibitor in blood of mice injected with hydroxyurea
Authors: Nečas E.
Published: May 2008

Abstract. Analysis of the mouse haemopoietic stem cell (CFUs) kinetics after hydroxyurea administration has provided an in vivo assay suitable for detection of factors which inhibit recruitment of non‐proliferating G0‐CFUs into cell cycle, or transit of CFU's through the G1 phase. Using this assay, it has been demonstrated that plasma obtained from mice which had received hydroxyurea approximately 12–14 hr previously, possesses a factor which inhibited the triggering of CFUs into the cell cycle. The appearance of this CFUs proliferation inhibitor occurred at a time when 60–70% of the CFUs were synchronized in the S phase of the cell cycle, as a consequence of hydroxyurea action. Some basic properties of the inhibitor were investigated.
Kinetics and cellularity of erythroblasts in the growing rat
Authors: Dörmer P. , Militzer H. , Dahr P. , Ruppelt W.
Published: May 2008

Abstracts. Parameters of recognizable erythroid cell proliferation were measured in four groups of normal rats weighing 50, 100, 150 and 300 g in order to provide a comprehensive set of data suitable for a re‐investigation of erythropoietic models. Total erythroblast cellularity was measured by the 59Fe technique, DNA synthesis time by quantitative 14C‐autoradiography, and the erythrocyte production rate was derived from the increase with time of the erythrocyte labelling index after repeated injections of 3H‐leucine. Furthermore, the relative erythroblast density was determined in the various morphological compartments. From the total erythroid cell mass in DNA synthesis and the absolute erythrocyte production rate, figures were derived for the mean DNA synthesis time of erythroid cells and compared with the directly measured ones. The discrepancies in all weight groups between direct and indirect determination of DNA synthesis time were considerable. In a previous study re‐evaluation of comparable data in literature had revealed comparable inconsistencies. Since a critical discussion of possible errors in the experimental techniques does not indicate data acquisition to be the principal source of disagreement it is concluded that the type of model applied to describe how cells pass the boundaries of morphological cell compartments is of high significance. Models based on a sequential flux of cells through the individual compartments are inadequate for evaluation of the presented set of data.
Evidence for discrete cell kinetic subpopulations in mouse epidermis based on mathematical analysis
Authors: Potten C. S. , Wichmann H. E. , Loeffler M. , Dobek K. , Major D.
Published: May 2008

Abstract. Continuous (repeated) labelling studies in mouse epidermis indicate that nearly all cells are labelled after about 100 hr. Percentage labelled mitoses studies ([3H]TdR at 15.00 and 03.00 hours) have a first peak that does not reach 100% and has a half‐width of about 10 hr. Small second and third peaks can be detected at about 90 and 180 hr, respectively. The changes with time in the number of labelled cells show a difference dependent on the time of day of [3H]TdR administration. Both curves show an early doubling in labelled cells which then decline, forming a peak of labelled cells. A second peak occurs at about 120 hr. This is followed by a progressive decline with no further peaks until values of about 1% labelling are obtained at 340 hr.

These experiments have been investigated mathematically. A computer programme has been devized that permits all three types of experiments to be analysed simultaneously. More importantly, it can analyse situations with a heterogeneity in cell cycle parameters in all proliferative subpopulations.

Various models for epidermal cell replacement have been considered. The data as a whole can best be explained if the basal layer contains at least two distinct subpopulations of cells and an exponentially decaying post‐mitotic population with a half‐life of about 30 hr. The proliferative sub‐populations must be characterized by near integer differences in the length of cycle, the precursor (stem) compartment having the longer cycle. An inverse relationship is required for the length of S, i.e. the shortest time for the stem cells.

A full range of cell kinetic parameters can be calculated and are tabulated for the most appropriate model system which is one involving three transit proliferating subpopulations.
[3H]thymidine labels less than half of the DNA‐synthesizing cells in the mouse tumour, carcinoma NT
Authors: Hamilton E. , Dobbin J.
Published: May 2008

Abstract. We have studied carcinoma NT, a transplantable mouse adenocarcinoma of spontaneous origin. Cells labelled with [3H]thymidine ([3H]TdR) were restricted to a narrow zone around the periphery of this tumour and were also found in rings up to 50 μm wide, around isolated blood vessels in the central necrotic area. Labelling with [3H]deoxyuridine ([3H]UdR), another DNA synthesis precursor, produced a very different pattern. The labelled zone around the periphery was much wider than with [3H]TdR, and [3H]UdR labelled cells were found up to 110 μm from isolated vessels. [3H]iododeoxyuridine ([3H]IUdR) gave the same pattern of labelling as [3H]UdR. In the heavily labelled zone, within 1 mm of the tumour periphery, the labelling index (LI) was 51% after [3H]UdR or [3H]IUdR injection, and only 36% with [3H]TdR.

The data show that at least half of the DNA‐synthesizing cells in this tumour did not incorporate [3H]TdR. Previous workers reported cell loss factors for carcinoma NT of 60% calculated from [3H]TdR labelling data and 30% from the rate of loss of [125I]UdR. The present work suggests that calculations based on [125I]UdR data are more likely to be accurate for carcinoma NT than those using [3H]TdR data.
Changes in cell kinetics associated with differentiation of a human promyelocytic cell line (HL60)
Authors: Fibach E. , Treves A. , Peled T. , Rachmilewitz E. A.
Published: May 2008

Abstract. Terminal cell differentiation results in an irreversible arrest in the G1 phase of the cell cycle and loss of the capacity for cell renewal. In the murine erythroleukaemia cell line (MELC), commitment to erythroid differentiation was found also to be preceded by an early, transient, phase of inhibition of growth due to prolongation of the G1 phase. We determined the effect of differentiation‐inducing agents on the growth kinetics of a human promyelocytic cell line (HL60) which undergoes differentiation into mature granulocyte. At concentrations of inducers optimal for cell differentiation, an early, transient stimulation of cell multiplication was found. DNA synthesis was enhanced in HL60 cells as early as 5 hr after exposure to inducer. Nevertheless, HL60 cell maturation eventually also resulted in a loss of the multiplication ability. The duration of exposure to inducer required for irreversible loss of the potential for self‐renewal was determined by the fall in the cloning efficiency of induced cells; the results indicate that it preceded the switch‐off of the replication mechanism; the majority of the cells lost their ability to form large colonies at the time of peak DNA synthesis and were able to complete an additional two to three cell cycles at a rate similar to uninduced cells. These changes occurred before HL60 cells became committed and might play a pivotal role in the process of cell differentiation.
Structural and functional significance of association of a low molecular weight chalone from JB‐1 ascites tumours with high molecular weight factors
Authors: Barfod N. M. , Schjerbeck Pia
Published: May 2008

Abstract. The cell‐specific inhibitory (chalone) activity of JB‐1 ascites tumour cell proliferation has been purified using five different procedures. By combining (1) molecular weight estimations based on ultrafiltration and gel chromatography, and (2) partitioning in organic solvent and ion exchangers, it is concluded that the active factor associates, in a complex manner, with various other components involving both hydrophobic and ionic forces. The active factor appears to be a slightly acidic, hydrophobic peptide (molecular weight 500–1000 D). When assessing the activity in vivo, it appears to be highly dependent on associated serum factors. Thus, the chalone studied appears to interact both structurally and functionally with various associated factors which affect its physicochemical behaviour and biological activity.
Analysis of regenerating hepatic cell replication in vivo by differential chromatid staining
Authors: Kato H. , Reff M. , Schneider E. L.
Published: May 2008

Abstract. The cell cycle of mouse hepatic cells was examined in vivo following partial hepatectomy, by differential chromatid staining in the presence of non‐inhibitory concentrations of bromodeoxyuridine (BrdU). Using this technique, distribution curves were obtained for the appearance of metaphase cells in successive generations, and mean cell cycle time (11 hr) was determined. Cell cycle times derived with this technique are several‐fold faster than previous reports of regenerating liver which used radionucleotide labelling.
The effect of environmental stress stimuli on cell division in rat palatal epithelium
Authors: Fisker A. V. , østergaard E. , Karring T.
Published: May 2008

Abstract. The effect on cell proliferation of procedures commonly used in studies in laboratory animals was examined in the palatal epithelium of rats. Groups of rats were exposed to ether anaesthesia, immobilization in the supine position or to cage change. Animals left undisturbed in the cages during the experiment were used as controls. At intervals of 30 min, four animals of each group were killed and histological sections of the palatal mucosa were prepared. The number of prophases, metaphases and ana/telophases in the epithelium was counted and related to 1 mm2 of the surface. Thirty minutes after the various procedures the number of metaphases and ana/telophases were extremely low. After a further 30 min a high number of prophases was observed. The number of metaphases rose within the following 30 min, during which time the number of ana/telophases also reached a maximum.

These observations indicate that the environmental stimuli have blocked the entrance of cells into mitosis and have resulted in an accumulation of cells, which, following the raising of the blockade, pass through the various stages of the mitotic phase. In studies of cell population kinetics the blockade of cell division as a result of environmental stress stimuli may lead to misleading results.
Radiotoxicity of incorporated [3H]thymidine Consequences for the interpretation of FLM data of irradiated cell populations
Authors: Beck H.‐P.
Published: May 2008

Abstract. Problems in the interpretation of FLM data of externally irradiated cell populations are mainly due to the interference of radiation effects with radiotoxic effects originating from incorporated [3H]thymidine. These problems were investigated using L‐929 cells flash labelled in vitro with [3H]thymidine (30 min, 0.3 μCi/ml, 40 Ci/mM) and irradiated with 2 Gy of 200 kV X‐rays; the fractions of labelled mitoses and the index of labelled and of unlabelled mitoses were determined. The results showed that the FLM is not an adequate parameter to quantify the early cell kinetic changes in irradiated cell populations.
Effects of retinoic acid on cell proliferation and cell differentiation in a rat tracheal epithelial cell line
Authors: Klann R. C. , Marchok Ann C.
Published: May 2008

Abstract. The effects of 3.3 times 10‐7 M to 3.3 times 10‐5 M all‐trans‐retinoic acid (vitamin‐A acid) on the total cell population dynamics of 165 S, a keratinizing epithelial cell line from carcinogen‐exposed rat trachea, were studied. During the first 6 days of culture, cells accumulated on the dish in the presence of the vitamin to twice the density of controls. [3H]thymidine incorporation into DNA and percentage of [3H]thymidine‐labelled cells in autoradiographs were stimulated in a dose‐dependent fashion to a maximum of 25‐ and 34‐fold, respectively. Exfoliation of cells from the cultures was also enhanced 2–3‐fold, resulting in nearly twice the total number of cells (attached plus exfoliated) in the presence of the vitamin.

During 19 days of culture, retinoic acid maintained a higher level of [3H]thymidine incorporation and cell exfoliation in 165 S cells so that by day 19, total cell production was more than three times that seen in controls. At this time, vitamin‐treated cultures showed a reduced cell saturation density compared to controls. The higher final cell density in the control cultures was a result of multilayering and papillary formation which did not occur in the presence of retinoic acid. The papillae in control cultures stained specifically with Rhodamine B or with the eosin and orange G components of the Papanicolaou method. A count of the number of eosin and orange G positive cells in the attached and exfoliated cell compartments showed an 8‐fold reduction of keratinization in retinoic acid‐exposed cultures. Our results show that retinoic acid is a growth stimulant in these cell cultures, causing increased cell proliferation and exfoliation accompanied by inhibition of keratinization.
Growth characteristics of human melanoma xenografts
Authors: Rofstad E. K. , Fodstad ø. , Lindmo T.
Published: May 2008

Abstract. The growth of twelve human malignant melanomas in athymic nude mice was studied. Gompertz curves were fitted to volumetric growth data. DNA histograms were obtained with flow cytometry. Each of the twelve melanomas exhibited a characteristic growth pattern, indicating that inherent properties of the tumours are important for the growth control. The theoretical maximum volumes (Vmax) ranged from 208 to 12,900 mm3, the volume doubling times (Td) from 2.8 to 15.3 days (V= 50 mm3) and from 3.8 to 64.6 days (V= 200 mm3), and the fraction of cells in S from 5 to 21%. Tumours with short Td were characterized by a higher growth fraction and probably by a lower cell loss factor than those with long Td. The growth was also influenced by the nude mouse host, as indicated by the values for Vmax which were similar to those reported for mouse tumours (geometric mean = 8100 mm3), but considerably lower than the volumes of many tumours in man. Also the Td‐values for the xenografts were generally lower than those reported for tumours in man, presumably due to a lower cell loss factor. During serial transplantation the growth rate of one of the melanomas increased abruptly, probably because of both an increased growth fraction and a reduced cell loss factor. The latter result demonstrates the necessity of keeping basic biological parameters of xenografts under observation during serial transplantation.