bluuebunny/crossref_metadata_2025 huggingface dataset:
ANALYSIS OF THE PROLIFERATION KINETICS OF BURKITT'S LYMPHOMA CELLS
Authors: Woo K. B. , Funkhouser W. K. , Sullivan C. , Alabaster O.
Published: May 2008

The in vitro proliferation kinetics of a cell line derived from a patient with American Burkitt's lymphoma were investigated at three different growth phases: lag (day 1), exponential (day 3) and plateau (day 5). The growth curve, labeling and mitotic indices, percentage labeled mitosis (PLM) curves and DNA content distributions were determined. The data obtained have been analysed by the previously developed discrete‐time kinetic (DTK) model by which a time course of DNA distributions during a 10‐day growth period was characterized in terms of other cell kinetic parameters. The mean cell cycle times, initially estimated from PLM curves on days 1, 3 and 5, were further analysed by the DTK model of DNA distributions and subsequently the mean cell cycle times with respect to DNA distributions during the entire growth period were determined. The doubling times were 39·6, 31·2 and 67·2 hr, respectively, at days 1, 3 and 5. The mean cell cycle time increased from 23·0 to 37·7 hr from day 3 to day 5 mainly due to an elongation of the G1 and G2 phases. A slight increase in the cell loss rate from 0·0077 to 0·0081 fraction/hr was accompanied by a decrease in the cell production rate from 0·0299 to 0·0184 fraction/hr. This calculated cell loss rate correlated significantly with the number of dead cells determined by trypan blue exclusion. Analysis of the number of dead cells in relation to the cell cycle stage revealed that a majority of cell death occurred in G1 (r= 0·908; P < 0·0001). There was a good correlation between the in vitro proliferation kinetics at plateau phase of this Burkitt's lymphoma derived cell line and the in vivo proliferation kinetics of African Burkitt's lymphoma (Iversen et al., 1974), suggesting the potential utility of information obtained by in vitro kinetic studies.
STUDIES ON THE KINETICS OF INITIAL CYCLE PROGRESSION IN VITRO OF ASCITES TUMOUR CELLS SUBSEQUENT TO ISOLATION FROM ASCITES FLUID
Authors: Olivotto M. , Paoletti F.
Published: May 2008

A method is described for determining the duration of cell cycle phases traversed by cells responding to release from proliferation restraint. Experiments have been performed with arrested Yoshida ascites hepatoma cells allowed to re‐enter the growing stage after transfer of cells from the late stage of ascites into an in vitro incubation system. Experimentally, this method requires information on the rate of incorporation of labelled thymidine and on the rate of increase in cell number. The rate of [14C]thymidine incorporation in vitro was shown to be directly proportional to the number of cells synthesizing DNA. This was shown by correlating data from measurements of the rate of thymidine incorporation with those from measurements of the labelling index of the cell population. Theoretically, the method is based on analysis of the region limited by two integral curves, one corresponding to the kinetics of cell entry into and the other to the kinetics of exit from the S‐phase. From data on the actual rate of increase in the total number of cells and data on the S‐phase duration it is possible to obtain information on the cytokinetics of growth resumption by the ascites cell population.
LOCAL MITOGENIC EFFECT OF TISSUE MAST CELL SECRETION
Authors: Franzén L. , Norrby K.
Published: May 2008

The effect of drug‐induced mast cell secretion on proliferation was studied in fibroblast‐like and mesothelial‐like cells in organ‐cultured rat mesentery. Mast cell degranulation achieved by Compound 48/80 was followed by a marked mitogenic reaction in the surrounding tissue cells. The drug itself lacked mitogenic effect on cultured guinea‐pig mesentery, the mast cells of which are unresponsive to the drug, and on a human normal fibroblast‐like cell line. In contrast, histamine at about 10−10 M, a major mast cell component, induced marked mitogenesis in guinea‐pig mesentery without causing degranulation of mast cells.

It is concluded that secreting rat‐tissue mast cells release a mitogenic factor or factors acting locally on nearby tissue cells.
Detailed Kinetic Analysis of Shay Chloroleukaemia Cell Population Propagated In Permanent Suspension Culture In Vitro
Authors: Toivonen H. , Foa P. , Paile W. , Rytömaa T.
Published: May 2008

Detailed kinetic analysis of a growing cell population is difficult, even when assay conditions are nearly ideal. Therefore, it is usually essential to perform several types of experiments and analyse all the results in terms of a mathematical model, the use of which is not limited a priori by a specified application.

In the present study we investigated cell population kinetics using rat chloroleukaemia cells propagated in suspension culture in vitro. the parameters were measured: doubling time of the population, fraction of labelled mitoses, changes in labelling index with time after pulse labelling, continuous labelling and stathmokinetic index. Analysis of the results was based on a computer program CECAM, which is a stochastic model capable of simulating essentially all types of kinetic experiments based on presently known assay techniques.

The results showed that precise and reliable information on cell population kinetics could not be obtained from the analysis of any single type of experimental data. In particular, the technique of labelled mitoses underestimated the duration of the G1 phase, owing to subtle label‐induced changes in population behaviour. These changes could not have been detected with any certainty without rigorous quantitative comparisons with other types of experimental data. As a whole, however, results obtained by the different techniques were in agreement and the kinetic behaviour of chloroleukaemia cells in vitro could be established in detail.

In certain circumstances even minute changes in the kinetic parameters of the cells can modify population behaviour drastically. to study these cases adequately the experiments must be designed with utmost care, preferably with the aid of preceding simulations. This is because demonstration of small primary changes in population kinetics may be beyond the limit of detection of any single assay method.
DIFFERENTIATION OF MURINE MARROW MEGAKARYOCYTE PROGENITORS (CFUM): HUMORAL CONTROL IN VITRO
Authors: Freedman M. H. , McDonald T. P. , Saunders E. F.
Published: May 2008

Differentiation of mouse marrow megakaryocyte progenitors (CFUm) was studied in vitro by a colony assay using a plasma clot system. Erythropoietin (EPO) from sheep plasma (6 units/mg protein) in doses from 1 to 5 units/ml induced a linear increase in CFUm to a maximum of 20 colonies/105 cells plated. Human urinary EPO also induced a dose‐responsive increase in CFUm, but the maximum was 9 colonies/105 with 2·0 units/ml of EPO and there was a decrease in colonies above that concentration. Thrombocytopoiesis‐stimulating factor (TSF) derived from human embryonic kidney culture supernatant fluids induced a dose‐responsive increase in CFUm in concentrations from 0·01 to 0·32 mg protein/ml in the absence of added EPO. TSF did not support the growth in vitro of erythroid colonies from mouse marrow (CFUe and BFUe) indicating an absence of EPO activity. In these studies sheep EPO appeared more effective in supporting CFUe growth than human EPO. TSF also had a stimulatory function in megakaryocyte differentiation at a precursor level. Multiple humoral factors play a role in megakaryocytopoiesis in vitro.
Rat C‐6 Glioma Cells Maintained In an Organ Culture System: A Study of Kinetic Parameters
Authors: Halks‐Miller M. , Miller R. G. , Rubinstein L. J.
Published: May 2008

Rat C‐6 glioma cells were grown on a sponge foam matrix in an organ culture system and the cell cycle parameters, including the growth fraction (GF), were assessed after autoradiography. the zones of growth consisted of a compact upper layer (UL) at the gaseous interface, a central necrotic layer and a deeper lower layer (LL) which invaded the matrix. the fraction of continuously labeled mitoses (FCLM) was similar in both the UL and LL cells. the derivatives of the FCLM curves obtained in three experiments gave an average modal TG2 of 5 hr. A mathematical model relating GF, TG2, TC and labeling index as a function of time, LI(t), was devised for cells in a steady state exposed continuously to tritiated thymidine and was applied to data obtained from UL cells. A mean GF of 9% (range: 8–10%) and a mean cell cycle time (TC') of 27 hr (range: 13–47 hr) were obtained. the mean TS was calculated to be 11 hr (range: 8–16 hr) by the method of grain counts per mitotic figure or grain index (GI). Knowledge of TS permitted alternative calculation of the cell cycle time from the equation TS/TC= LI(0)/GF: this gave a mean cell cycle time (TC) of 29 hr (range: 20–45 hr).

Except for the GF, the cell kinetics were comparable to those of the same cell line grown in monolayer culture. the GF in the in vitro system described is in the lower range reported in some human malignant gliomas in vivo.
ON THE DERIVATION OF CELL KINETICS FROM HISTOMORPHOLOGY, OBSERVED IN THE RAT INCISOR ODONTOBLAST
Authors: Michaeli Y. , Pitaru S. , Zajicek G.
Published: May 2008

A method to extract cell kinetic information from histomorphology is presented. Each replicating tissue is essentially an ordered structure with an origin where cells are formed and a periphery toward which they are displaced. the displacement path is called the tissue radius. the tissue variables may be studied in two domains, space and time. the first embraces all the states a cell may assume while the second specifies the cell transition rates. During steady state both domains are related linearly.

These ideas are illustrated in the rat incisor odontoblast population whose life expectation is determined by the tooth wall shape. the odontoblast cell population paves the interior of the tooth wall delimiting a cone‐shaped pulp. Near the root apex the dentine wall is barely visible. As one proceeds distally, the wall thickens while the pulp narrows. Pulp narrowing is associated with odontoblast cell loss whose magnitude may be deduced from the change of the pulp circumference CI(x) (x is the distance from tooth origin). the odontoblast force of mortality μ(x) may be calculated from the instantaneous perimeter change: μ(x) = ‐CI' (x)/CI(x); where CI'(x) stands for the derivative of CI(x). This equation serves for the construction of the odontoblast life table which may be studied in space and time.
Genetic Control of Lipopolysaccharide‐Induced Mobilization of Cfus Dissociation Between Early and Delayed Mobilization of Cfus In Complement C5‐Deficient Mice and Lps Non‐Responder Mice
Authors: BENNER R. , RIJNBEEK A.‐M. , Molendijk W. , Vos O.
Published: May 2008

Lipopolysaccharide (LPS)‐induced mobilization of CFUs from haemopoietic tissues into the circulation has a biphasic pattern. the first rise occurs within 30 min of LPS injection, the second 4–7 days later. This second rise coincides with an increase of the CFUs number in the spleen from about 3000 to about 50,000. We have investigated the relationship between the two peaks by making use of complement C5‐deficient mouse strains and the LPS non‐responder mouse strains C3H/HeJ and C57BL/10ScCr. These latter two strains lack a serologically identifiable structure (‘LPS‐receptor’) which is present in all LPS‐responder strains.

After injection of eleven different mouse strains with LPS, the numbers of circulating CFUs increased rapidly in all strains, except in the C5‐deficient A/J, AKR/J, DBA/2J and B10.D2/oSn mice. On the other hand, the delayed LPS‐induced accumulation of CFUs in blood and spleen occurred in all mouse strains tested, including the C5‐deficient strains, but not in the LPS non‐responder strains C3H/HeJ and C57BL/10ScCr. These results show that (a) early LPS‐induced mobilization of CFUs is dependent on the availability of C5, in contrast to the delayed CFUs accumulation in blood and spleen, (b) the presence of the LPS receptor is not required for early CFUs mobilization by LPS and (c) recognition of the mobilizing agent by a specific receptor is required for the delayed accumulation of CFUs in blood and spleen.
Post‐Irradiation Thymocyte Regeneration After Bone Marrow Transplantation I. Regeneration and Quantification of Thymocyte Progenitor Cells In the Bone Marrow
Authors: Boersma W. , Betel I. , Daculsi R. , van der Westen G.
Published: May 2008

Growth kinetics of the donor‐type thymus cell population after transplantation of bone marrow into irradiated syngeneic recipient mice is biphasic. During the first rapid phase of regeneration, lasting until day 19 after transplantation, the rate of development of the donor cells is independent of the number of bone marrow cells inoculated. the second slow phase is observed only when low numbers of bone marrow cells (2.5 × 104) are transplanted. the decrease in the rate of development is attributed to an efflux of donor cells from the thymus because, at the same time, the first immunologically competent cells are found in spleen. After bone marrow transplantation the regeneration of thymocyte progenitor cells in the marrow is delayed when compared to regeneration of CFUs. Therefore, regenerating marrow has a greatly reduced capacity to restore the thymus cell population. One week after transplantation of 3 × 106 cells, 1% of normal capacity of bone marrow is found. It is concluded that the regenerating thymus cells population after bone marrow transplantation is composed of the direct progeny of precursor cells in the inoculum.
Haematopoiesis In Mice Heterozygous For the W Trait: Defective Formation of Transient Endogenous Spleen Colonies
Authors: Wiktor‐Jedrzejczak W. , Szczylik C. , Górnas P. , Sharkis S. J. , Ahmed A.
Published: May 2008

It has been determined that W/+ and Wv/+ heterozygous mice, as compared with normal +/+ homozygous littermates, form significantly lower numbers of transient 5‐day endogenous spleen colonies in response to X‐irradiation. This defect was evident for doses of irradiation between 2–6 Gy (200–600 rad) and was associated with a slightly increased radiosensitivity of the assayed precursor cells (TE‐CFU) in W heterozygotic mice. Moreover, the defect was transplantable, i.e., intrinsic to the marrow cells and not to the microenvironment, and was not associated with a similar decrease in cells which form erythropoietic bursts in vitro (BFUe). This study provides a cellular basis for increased radiosensitivity of W/+ and Wv/+ mice and suggests that the ‘W’ mutation is semi‐dominant, both with respect to the white spotting and TE‐CFU formation.
Leukocyte Mobilization In Mice By Polyanions Decline of Leukocyte Mobilizing Capacity After Transplantation of Lymphoma
Authors: Benner R. , Nikkels P. G. J. , van Oudenaren A. , Wolters E. A. J.
Published: May 2008

The leukocyte mobilizing polyanions dextran sulphate (DS) and polymethacrylic acid (PMAA) were administered to AKR and (C57BL × CBA) F1 mice at various times after transplantation of syngeneic lymphoma cells. In nonleukaemic mice DS and PMAA increased the number of circulating leukocytes 3–4‐fold. the extent of leukocyte mobilization in leukaemic mice depended on the interval between transplantation of the lymphoma cells and injection of the polyanion. During the development of leukaemia in AKR as well as in (C57BL × CBA) F1 mice the capacity to react upon injection of polyanions with leukocyte mobilization gradually decreased. For DS, this decrease started before the number of leukocytes increased in the peripheral blood. On the other hand, the capacity for PMAA‐induced leukocyte mobilization was fully preserved for several more days. In heavily leukaemic mice neither DS nor PMAA could further increase the number of peripheral blood leukocytes. In such mice the distribution pattern of leukaemic blast cells, small lymphocytes, granulocytes and monocytes was also hardly or not affected by injection of the polyanion.
Decreased Sensitivity to Hydroxyurea and to [3H]Thymidine Suicide In the Middle of the S Phase
Authors: Nečas E. , Poňka P. , Neuwirt J.
Published: May 2008

Pluripotent haemopoietic stem cells (CFUs) move synchronously through the cell cycle in hydroxyurea‐treated mice in a cohort 1–2 hr broad. Ten to fifteen hours after hydroxyurea they pass through S phase. DNA synthesis appears to be depressed 5–10 times when the cells are in the middle part of the S phase but does not seem to be completely interrupted. High concentrations of [3H]thymidine must be used for ‘suicide’ in order to achieve lethality for the cells with depressed DNA synthesis. At the time when DNA synthesis is depressed, the sensitivity of the cells to hydroxyurea also decreases. This may lead to a significant underestimation of the S phase fraction by the hydroxyurea method, because CFUs with low DNA synthesis rate are resistant to hydroxyurea although being in S phase.
SUPPRESSION OF SERUM OR LIVER CYTOSOL‐INDUCED G1‐S BLOCK IN BABY RAT HEPATOCYTES BY A PROTEASE ANTAGONIST: THE KUNITZ FACTOR
Authors: Nadal C. , Le Rumeur E.
Published: May 2008

The Kunitz factor did not modify hepatocyte synchronization obtained in baby rats after inflammatory stimulation but abolished the G1‐S block induced by adult rat serum or liver cytosol. This effect was dose‐dependent. the Kunitz factor was only active during the hour preceding serum or liver cytosol injection.
An Improved Sum‐Of‐Normals Technique For Cell Cycle Distribution Analysis of Flow Cytometric Dna Histograms
Authors: Jett J. H. , Gurley L. R.
Published: May 2008

An improved method for determining the fraction of cells in the G1, S and G2+ M phases of the life cycle, from DNA distributions of S phase rich cultures, is presented. Picolinic acid synchronized cell cultures were used to demonstrate the usefulness of the technique for the cell cycle distribution analysis. the algorithm presented quantifies DNA histograms from FCM analyses using an extension of the previously reported ‘sum of discrete normal curves’ technique. It alleviates problems encountered with earlier methods by extending the contribution of the S phase cells to the distribution under the G1 and G2+ M peaks; at the same time it allows more of the descriptive parameters to be determined from the individual histograms. the fractions of cells in the G1, S, and G2+ M phases of the life cycle obtained by this method compare favourably with autoradiographic analyses and other analytical results.
REGULATION OF HUMAN MYELOPOIESIS BY PROSTAGLANDIN E AND LACTOFERRIN
Authors: Pelus L. M. , Broxmeyer H. E. , Moore M. A. S.
Published: May 2008

Studies on human myeloid stem cell proliferation indicate that progenitor cell populations committed to monocytoid differentiation are preferentially inhibited by prostaglandin E (PGE). the addition of PGE but not PGF to day 7 CFUGM cultures upon initiation results in the dose‐dependent inhibition of total colony and cluster formation. Morpholigical analysis of proliferating clones demonstrates that the effect of PGE on total colony and cluster formation results from the selective inhibition of monocyte‐macrophage colony forming cells. Mixed monocytoid/neutrophil colony formation was markedly less sensitive and neutrophil and eosinophil colony formation essentially insensitive to the inhibitory effects of PGE. the inhibition of monocytoid colony formation by PGE1 extends equally well to day 13 CFUGM, but not to CFUGM in suspension culture. the observed effects of PGE1 on monocytoid committed pre‐CFUGM and day 7 and day 14 CFUGM indicate that sensitivity to inhibition by PGE increases with progenitor cell maturity. Specificity analysis indicates that prostaglandins of the E series (PGE1, PGE2) are by far the most active naturally occurring prostanoate compounds inhibiting CFUGM proliferation.

The addition of iron saturated lactoferrin to liquid cultures of human peripheral blood monocytes, inclusion into mononuclear cell feeder layers or addition to agar cultures proliferating in response to endogenously produced CSFs, results in the equivalent inhibition of CSFs necessary for day 7 and day 14 monocytoid and/or neutrophil and eosinophil colony and cluster formation.

These results indicate roles for PGE and lactoferrin in myeloid stem cell regulation in vitro and suggest that they may serve as physiological regulators of granulocyte and monocyte proliferation.
The Effect of X‐Irradiation On Cell Loss In Five Solid Murine Tumours, As Determined By the 125Iudr Method
Authors: Kelley S. D. , Kallman R. F. , Rapacchietta Diane , Franko A. J.
Published: May 2008

The rate of cell loss in irradiated RIF‐1, EMT6, KHJJ, B16 and KHT tumours was studied using the 125IUdR loss technique. Administration of 125IUdR preceded localized tumour irradiation by 2 days. Loss of tumour radioactivity was measured for 6–8 days after irradiation. the blood flow to some tumours was occluded during, and for 30 min following, injection of the label to measure the amount of radioactivity entering the tumour as a result of reutilization of label from the gut epithelia and influx of labelled host cells. Irradiation did not significantly alter the amount of radioactivity entering these clamped tumours during the 8–10 days after injection of 125IUdR. This permitted comparison of irradiated and control groups based on the loss of radioactivity from the non‐occluded tumours. Irradiation of RIF‐1, EMT6, KHJJ or B16 tumours with doses of 600, 1400, 2400 or 4400 rads produced no significant increase in the rate of loss of tumour radioactivity. This suggested that, in the population of labelled cells, cell lysis following irradiation proceeded slowly. In contrast, KHT tumours showed a significant increase in loss rate following each radiation dose, although the increase was dose‐independent. In all tumour systems, the constant rate of cell loss after radiation appeared to coincide with published reports of tumour growth responses after irradiation. the present data suggest that the manner of expression of radiation‐induced cell killing results from the cellular proliferative status, i.e. whether a cell is cycling or non‐cycling.
Production of presumptive humoral haematopoietic regulators in canine cyclic haematopoiesis
Authors: Dunn C. D. R. , Jones J. B. , Lange R. D. , Wright E. G. , Moore M. A. S.
Published: May 2008

Abstract. Conditioned media (CM) were prepared according to previously published techniques from the bone marrow of dogs with cyclic haematopoiesis (CH). CM prepared from day 9 marrows inhibited mouse bone marrow CFU‐s proliferation rate while CM from day 10 marrows were stimulatory and also contained an erythroid stimulating factor which appeared to be erythropoietin. In addition a highly significant trend from CM containing CFU‐s inhibitory materials to media with CFU‐s stimulatory activity was observed through cycles day 1 to 8. These studies further support the concept that CH is due to a defect in factors controlling stem cell proliferation and suggest that a major event occurs in CH dog marrow on days 9 and/or 10 of the cycle.

Bone marrow transplantation studies (Dale & Graw, 1974; Weiden et al., 1974; Jones et al., 1975b) have indicated that canine cyclic haematopoiesis (CH) is probably due to a disorder in the multipotential stem cells. Morphological evidence (Scott et al., 1973) and the almost synchronous cycling of CFU‐e, CFU‐c and diffusion chamber progenitor cells (DCPC) (DUM et al., 1977, 1978a, b) lend support to such a theory. However, efforts to identify the mechanisms controlliig multipotential stem cell proliferation in dogs have been handicapped by the lack of suitable techniques to study these cells in the canine. Recently, Wright and co‐workers (Wright & Lord, 1978, 1979; Wright et al., 1979; Lord et al., 1979), on the basis of previous observations (Frindel et al., 1976; Frindel & Guigon, 1977), described the preparation of species non‐specific, bone marrow conditioned media (CM) which are capable of influencing the proliferation rate of murine colony forming units‐spleen (CFU‐s). The studies now reported were designed to determine if CM prepared from canine CH marrow would influence the proliferation rate of murine bone marrow CFU‐s. The results indicate that a major event, possibly related to the in vivo control of stem cell proliferation in dogs with CH, occurs on days 9–10 of the cycle; day 1 being the first day when the peripheral blood neutrophil count falls below‐1600 mm3.
Effects of cytosine arabinoside and daunorubicin on survival and cell cycle progression of chinese hamster ovary cells
Authors: Fried J. , Perez A. G. , Doblin J. , Clarkson B. D.
Published: May 2008

Abstract. Kinetic and cytotoxic effects of cytosine arabinoside (Ara‐C) and daunorubicin (DNR) on exponentially growing Chinese hamster ovary (CHO) cells were measured by flow cytometry and by a colony‐forming assay, respectively. With Ara‐C alone, increasing drug concentrations between 10‐7 M, for up to 27 hr, were associated with increased inhibition of cell progression through the S phase. Even at the very toxic concentration of 10‐4 M, however, cells were able to enter and progress slowly through S. DNR, which appears to enter these cells relatively slowly, was highly toxic even at 2 times 10‐7 M. It decreased the rate of progression through S phase and caused cells to accumulate in G2, except at the highest concentration (2 times 10‐5 M), at which progression was inhibited throughout the cycle. Simultaneous exposure of the cells to Ara‐C and DNR yielded cell cycle distributions similar to those of the former drug alone. When cells were exposed to a non‐lethal dose of Ara‐C and to a dose of DNR which was lethal to a fraction of the cell population (or conversely), either simultaneously or separated by a drug‐free interval, small, but in some cases significant, drug interactions were observed. These effects were not caused by druginduced redistribution of cells within the cell cycle, but may have been related to the effects of the non‐lethal drug on DNA synthesis rate.
A comparative study on wound‐healing in neonatal and adult mouse epidermis in vivo
Authors: Bertsch S. , Marks F.
Published: May 2008

Abstract. A cut made into the back skin of either newborn or adult mice evokes, at both ages, a hyperproliferative response in the epidermis. Differences in the reaction of neonatal as compared with adult epidermis are found in the spatial distribution of proliferative activity as well as in its time course. The response in adult mouse epidermis is inhibited by local application of indomethacin, whereas the response of the newborn epidermis is not.
Subclassification of cells in S phase in a partially synchronized cell system
Authors: Møller U. , Keiding N. , Engel F.
Published: May 2008

Abstract. A circadian dependent delay in the incorporation of [3H]TdR into DNA, presumably due to variations in the intracellular pool of [3H]TdR derivatives, was found. It seems reasonable to relate this effect to a circadianally varying age distribution of cells in S phase.

At any given time the S phase cells showed large variations in DNA synthesis rate, but it was still possible to identify a mean diurnal variation in the DNA synthesis rate.

Differences in the ability of S phase cells to incorporate [3H]TdR are also discussed in relation to flow cytometrical measurements, and this contributes to the understanding of the commonly observed phenomenon that flow cytometry estimates of S‐fractions are higher than those obtained with autoradiography.
A comparison of mathematical methods for the analysis of DNA histograms obtained by flow cytometry
Authors: Baisch H. , Beck H.‐P. , Christensen I. J. , Hartmann N. R. , Fried J. , Dean P. N. , Gray J. W. , Jett J. H. , Johnston D. A. , White R. A. , Nicolini C. , Zeitz S. , Watson J. V.
Published: May 2008

Abstract. Twelve methods for analysing FCM‐histograms were compared using the same set of data. Some of the histograms that were analysed were simulated by computer and some were taken from experiments. Simulated data were generated assuming asynchronously growing cell populations and (i) measurement coefficients of variation (CV) from 2 to 16%; (ii) constant measurement CV or CV's increasing from G1 to G2 phase, and (iii) varying fractions of cells in each phase. Simulated data were also generated assuming synchronous cell populations in which a block in early S phase was applied and released. DNA histograms were measured for L‐929 cells at various times after mitotic selection. Labelling indices were also measured for these cells at the same time.

The fractions of cells in the G1, S, and (G2+ M) phases were calculated by each analytical method and compared with the actual fractions used for simulation, or in case of experimental data, with autoradiographic results. Generally, all methods yielded reasonably accurate fractions of cells in each phase with relative errors in the range of 10–20%. However, most methods tended to overestimate G1 fractions and underestimate S fractions. In addition, variations in the shape of the S phase distribution often caused considerable errors. Phase fractions were also calculated for histograms of kinetically perturbed populations, simulated as well as experimental The errors were only slightly larger than for histograms from asynchronously growing cell populations.
Quantitative aspects of granulocytic progenitor cell (CFUc) mobilization from extravascular sites in dogs using dextran sulphate (DS)
Authors: Nothdurft W. , Steinbach K. H. , Ross W. M. , Fliedner T. M.
Published: May 2008

Abstract. The relationship between the increase in the blood CFUc concentration after intravenous injection of dextran sulphate (DS) and the pre‐existing levels of spontaneously circulating CFUc was studied in dogs. After 15 mg DS/kg body weight the CFUc numbers per ml blood rose by a factor of 3.7 over the pre‐injection values, from 78 ± 11 (SEM) to 359 ± 50, in normal dogs, and increased by a factor of 3.9 in 0.84‐Gy‐r‐irradiated animals which had a reduced initial CFUc concentration per ml, from 35 ± 8 to 116 ± 43. The injection of 20 mg DS/kg body weight into unirradiated dogs caused an increase, by a factor of 11.5, of the pre‐injection CFUc concentration, from 101 ± 20 to 921 ± 106. On the basis of the mobilization curves for individual dogs, a significant correlation was found between the normal blood CFUc value and the number of CFUc mobilized by DS for both dose levels. From the descending part of the mobilization curves obtained after 15 mg DS/kg body weight, kinetic parameters of canine circulating CFUc were derived. The mean blood transit time (τ) was 1.4 ± 0.5 hr and the half time (T/2) was 1.0 ± 0.4 hr.
Continuous maturation of proliferating erythroid precursors
Authors: Mackey M. C. , Dörmer P.
Published: May 2008

Abstract. This study examines published steady state cell kinetic (mitotic and DNA synthesis phase) data from the recognizable proliferating erythroid precursors in humans, rats, and guinea‐pigs, and human neutrophilic precursors, for consistency with a continuous maturation‐proliferation model of the cell cycle. We find that these data are completely consistent with the hypothesis that maturation between morphological compartments may take place at any point in the cell cycle. A number of compartmental parameters are derived under this assumption.
On the existence of non‐cycling germinative cells in human epidermis in vivo and cell cycle aspects of psoriasis
Authors: Gelfant Seymour
Published: May 2008

Abstract. This report deals with the controversies of whether all germinative epidermal cells in human epidermis are in the cycling state and whether stimulated hyperproliferation of psoriatic epidermis is due to a shortening of the cell cycle time or to a recruitment of non‐cycling germinative epidermal cells. Experiments were performed on human subjects in vivo. Continuous infusion of [3H]thymidine for 8½ days indicated that 40% of germinative epidermal cells reside in the non‐cycling state. Proliferative stimulation by tape stripping indicated recruitment of non‐cycling (G0) germinative epidermal cells in both normal and psoriatic skin, and a prolongation (rather than a shortening) of cell cycle traverse in activated psoriatic epidermal cells.
Cell kinetic studies on the JB‐1 ascites tumour of the mouse
Authors: Müller V. O. , Friede H. , Schultze Brigitte
Published: May 2008

Abstract. The FLM method, modified by double labelling with [3H]‐ and [14C]‐thymidine, has been applied to the 4‐day old JB‐1 ascites tumour of the mouse. It results in well separated waves of purely [3H]‐ and purely [14C]‐labelled mitoses, which show a remarkable asymmetry with long tails to the right. The following values for the mean transit times of the cells have been derived from this FLM curve, for a tumour age of 4–6 days: TC= 32.5 hr, TS= 16.7 hr, TG1= 3.7 hr, TG1= 11.0 hr and TM= 1.1 hr. A further evaluation of the FLM curve, however, is difficult, due to the non‐stationary growth of the tumour.

A number of other experimental findings (growth curve, decrease of the labelling and mitotic index with increasing tumour age, two single‐labelled FLM curves starting 4 and 6 days after tumour inoculation) indicate that the cell cycle time increases during the experimental period of the double‐labelled FLM curve (about 2 days). A lengthening of the cycle time should result in an increasing enlargement of the areas under the waves of the modified FLM curve. However, such an increase in area has not been found; the areas are constant.

All the results of the present cell kinetic studies would be consistent if it were postulated that the cell cycle time lengthens with increasing tumour age up to about 4 days after inoculation, then remains relatively constant at between 4 and 6 days and thereafter increases again. Short‐term double labelling experiments suggest that this is actually the case. Under the assumption of nearly constant phase durations during the 5th and 6th day of tumour growth further conclusions can be drawn from the modified FLM curve. In particular, it follows that the transit times of the cells through successive cycle phases are uncorrelated and the variances of the transit times through a cycle phase are proportional to the duration of this phase.
Evidence for the pulmonary origin of alveolar macrophages
Authors: Tarling J. D. , Coggle J. E.
Published: May 2008

Abstract. This paper supports the hypothesis that some form of pulmonary alveolar macrophage (PAM) production occurs within the lung in the normal steady state. The study involved monitoring the change in number of labelled PAMs following two modes of irradiation‐the first with the thorax being irradiated and the rest of the mouse shielded, the second with the thorax shielded and the body irradiated. Also measurements of monocyte and PAM numbers after a single bone marrow irradiation were carried out. Finally, the labelling indices of monocytes in both control and thorax irradiated mice were measured.

Both the number of monocytes and PAMs, along with the labelling indices of monocytes and PAMs after irradiation, indicate the independence of PAMs from a monocyte precursor population, and also provide evidence for a pulmonary origin of PAMs.
A model for the growth of multicellular spheroids
Authors: Landry J. , Freyer J. P. , Sutherland R. M.
Published: May 2008

Abstract. Based on biological observations and the basic physical properties of tri‐dimensional structures, a mathematical expression is derived to relate the growth rate of multicellular spheroids to some easily measurable parameters. This model involves properties both of the individual cells and of the spheroid structure, such as the cell doubling time in monolayer, the rate of cell shedding from the spheroid and the depth of the external rim of cycling cells. The derived growth equation predicts a linear expansion of the spheroid diameter with time. The calculated growth rate for a number of spheroid cell types is in good agreement with experimental data. The model provides a simple and practical view of growth control in spheroids, and is further adapted to include parameters presumably responsible for the growth saturation in large spheroids.
Stem cell (CFU‐s) proliferation in sublethally irradiated mice
Authors: Nečas E.
Published: May 2008

Abstract. The proliferation rate of haemopoietic stem cells (CFU‐s) was followed after sublethal total body irradiation with 1.5 Gy. The [3H]‐thymidine suicide technique was used to measure the CFU‐s proliferation rate. The measurements extended from 10 min after irradiation up to 21 days. The CFU‐s did not enter the DNA synthesis period (S‐phase) shortly after irradiation, as had been previously suggested, but did so only with a delay of 14–16 hr. A large scatter of results was explained by an oscillatory pattern in CFU‐s proliferation. The CFU‐s prepared for cell division in synchronized waves, with a period of 20–22 hr.
Time‐dependent effects of removal of the pars distalis of the pituitary gland on toad epidermal cell and tissue kinetic parameters
Authors: Budtz Povl E.
Published: May 2008

Abstract. Amphibian moulting and its hormonal control has been extensively studied, but the possible influence of hormones on epidermal proliferation has been less investigated. In the present contribution to studies on the control of epidermal homeostasis, the proliferative pattern of the toad epidermis following ablation of the pars distalis of the pituitary gland is analysed by an investigation of the changes in the epidermal cell number, metaphase index and [3H]thymidine incorporation at various times after the operation.

During the first 24 hr after pars distalis ablation, labelling index (LI) increased concurrently with an initial decrease in the metaphase index (MI), followed by an increase. During the same period of time the mean grain count (MGC) and the grain distribution pattern also changed. From 24 hr to 7 days after operation, MI, LI, and MGC were significantly lower than those of controls, but increased to control levels at 14 days after the operation. Phase durations and their possible changes were not measured directly, but data showed that the S‐phase duration (Ts) and the mitotic duration (TM) must have changed in relation to each other during the experiment. Assuming that the MGC is a rough estimate of the DNA‐synthesis rate, the compatibility of a postulated change in phase duration with the observed MGC was analysed. This analysis revealed that TS and TM could have decreased up to 18 hr after the operation, whereas these phase durations, after 24 hr and during the rest of the experiment, increased compared to those of controls. Even with these possible changes in phase durations, and in the absence of direct assessment of cell division rates, the observed cell kinetic parameters appeared incompatible with an increased rate of proliferation. This was surprising since the efflux of cells from the living, subcorneal epidermis to the stratum corneum was significantly increased after pars distalis ablation, without a concurrent decrease in the stratum corneum recruitment cell pool (SCRP‐number of subcorneal epidermal cells per mm surface). Possible reasons for the discrepancy between the expected increase in proliferation following pars distalis ablation, and the failure to demonstrate this, are discussed.
Synchronization of mammalian cells by selection and additional chemical block studied by DNA distribution analysis and BrdUrd‐Hoechst 33258‐technique
Authors: Nüsse Michael
Published: May 2008

Abstract. Ehrlich ascites tumour cells growing in vitro in suspension culture were separated according to volume by the technique of velocity sedimentation in a zonal rotor with a reorienting gradient. Using DNA distribution analysis the sedimentation pattern of the cells could be analysed in detail. With appropriate conditions it was possible to separate pure G1 cells. Samples could also be obtained which were enriched in S or G2 + M cells. The main limitation of the selection in this type of rotor was the reorientation of the gradient which caused disturbances during deceleration of the rotor. The synchronous growth of selected G1 cells has been studied in detail to investigate the reasons for the rather poor synchrony of these cells. The poor synchrony was found to be caused mainly by the small volume of the selected G1 cells compared with the normal volume of G1 cells in an asynchronous population. The synchronization of these cells could be essentially improved by a short treatment with excess thymidine causing a metabolic block at the G1/S border. The duration of this treatment could be minimized using DNA distribution analysis of growing cells after releasing of the block. The durations of the cell cycle phases in synchronized cells agreed with the values calculated in asynchronous cells by DNA distribution analysis and the BrdUrd‐Hoechst 33258‐technique.
Human colorectal tumours in short‐term organ culture A stathmokinetic study
Authors: Pritchett C. J. , Senior P. V. , Sunter J. P. , Watson A. J. , Appleton D. R. , Wilson R. G.
Published: May 2008

Abstract. Short‐term organ culture, using a technique to preserve epithelial/stromal interaction and metabolism, is a useful technique for carrying out kinetic studies on human colorectal carcinoma and adjacent normal mucosa, providing initial perturbations of proliferative indices are allowed to settle. Tumours require 3.0 μg/ml vincristine for complete metaphase arrest compared with mucosa, which needs 0.5 μg/ml, a 6‐fold difference. Using a stathmokinetic technique, the birth rate of tumour cells is 10.21 cells/1000 cells per hr, compared with 7.73 cells/1000 cells per hr for mucosa, a statistically significant difference (P < 0.01).
Proliferative Response and Renewal of Hepatic Function Following Cocaine Administration In Mice
Authors: Padilla George M. , Kloss Michelle W. , Rauckman Elmer J. , Rosen Gerald M.
Published: May 2008

ABSTRACT Experiments were undertaken to investigate the hepatic, temporal and spatial sequence of events following a single injection of cocaine, a known hepatotoxin. Centrilobular necrosis was induced in male mice (DBA/2Ha) 24 hr post‐injection (PI). the time course of hepatic damage was monitored by assaying microsomal cytochrome P450 content, the activity of microsomal FAD‐containing monooxygenase (FAD‐M) and by determining the levels of serum glutamic pyruvic transaminase (SGPT). Kinetics of the onset of DNA synthesis were determined by autoradiography of thin liver sections and the incorporation of 3H‐methyl thymidine into perchloric‐acid‐precipitable material. There was no increase in the labelling index (LI) and thymidine (TdR) incorporation in the first 24 hr PI. the LI rose to 14.6% and TdR incorporation showed a 5‐fold increase over control values 48 hr PI. Both indices declined slightly at 72 hr PI and returned to control values by 96 hr PI. In contrast, the cytochrome P450 content declined by 69%, the FAD‐M activity dropped by 40% and the SGPT levels showed an 18‐fold increase at 24 hr PI, coincident with cytological signs of necrosis. Although the patterns of recovery differed between these selected enzymes, normal values were attained by 96 hr PI. These results demonstrate that cell damage and hepatic dysfunction precede the onset of DNA synthesis and subsequent proliferation.
Cell Synchrony Techniques. I. A Comparison of Methods
Authors: Grdina David J. , Meistrich Marvin L. , Meyn Raymond E. , Johnson Tod S. , Whitel R. Allen
Published: May 2008

Abstract Selected cell synchrony techniques, as applied to asynchronous populations of Chinese hamster ovary (CHO) cells, have been compared. Aliquots from the same culture of exponentially growing cells were synchronized using mitotic selection, mitotic selection and hydroxyurea block, centrifugal elutriation, or an EPICS V cell sorter. Sorting of cells was achieved after staining cells with Hoechst 33258. After synchronization by the various methods the relative distribution of cells in G1 S, or G2+ M phases of the cell cycle was determined by flow cytometry. Fractions of synchronized cells obtained from each method were replated and allowed to progress through a second cell cycle. Mitotic selection gave rise to relatively pure and unperturbed early G1 phase cells. While cell synchrony rapidly dispersed with time, cells progressed through the cell cycle in 12 hr. Sorting with the EPICS V on the modal G1 peak yielded a relatively pure but heterogeneous G1 population (i.e. early to late G1). Again, synchrony dispersed with time, but cell‐cycle progression required 14 hr. With centrifugal elutriation, several different cell populations synchronized throughout the cell cycle could be rapidly obtained with a purity comparable to mitotic selection and cell sorting. It was concluded that, either alone or in combination with blocking agents such as hydroxyurea, elutriation and mitotic selection were both excellent methods for synchronizing CHO cells. Cell sorting exhibited limitations in sample size and time required for synchronizing CHO cells. Its major advantage would be its ability to isolate cell populations unique with respect to selected cellular parameters.
A Comparison of Low and High Dose‐Rate Radiation For Recipient Mice In Spleen‐Colony Studies
Authors: Lord B. I. , Hendry J. H. , Keene J. P. , Hodgson B. W. , Xu C. X. , Rezvani M. , Jordan T. J.
Published: May 2008

Over the last 15 years, endogenous spleen‐colony formation in our mice, following lethal irradiation, has increased to an unacceptable level. It has been found necessary, therefore, to introduce a new method of preparing recipient mice for spleen‐colony studies. Irradiation with low dose‐rate 60Cobalt γ rays has been compared with high dose‐rate linear accelerator electrons, and their effects on endogenous spleen colony formation compared with earlier X and γ ray dose‐response data. It was found that a large dose (13.5 Gy) of γ rays results in fewer endogenous colonies than 8.5 Gy of electrons, yet because of its low dose rate (14.1 × 10−3 Gy/min) it has a marked sparing of the intestinal tissue as measured by the intestinal microcolony technique. This in turn permits better survival and, therefore, a ‘healthier’ animal for spleen‐colony work. Exogenous colony formation is also lower in the low dose‐rate, γ‐irradiated recipients and this is shown to be due to a reduced spleen‐seeding efficiency.

It is concluded that very low dose‐rate radiation is preferable for haemopoietic ablation, that a mouse colony requires constant monitoring for changes of endogenous spleen‐colony formation and that the spleen‐seeding efficiency of CFU‐s depends on the irradiation technique used‐there is no absolute value for a given strain of mouse.
Delay In Entry Into S Phase After Heat Shock
Authors: Dewey D. L. , Holden J. L.
Published: May 2008

Synchronized cells of the Harding Passey melanoma grown in culture were given a heat shock treatment of 44° C for 36 min. Thymidine incorporation was measured at frequent intervals after heat shock to determine the time of onset of the next DNA synthetic period.

If the heat shock was given at the end of G1, the following S was delayed by 20 hr. Heating at other times in the cell cycle resulted in an even longer interval before the onset of S. the end of G1 was also the most resistant to hyperthermic killing and to the effect of heat on the magnitude of thymidine incorporation in the following S. Heating the cells a second time did not repeat the effect of the first treatment unless the second heat shock treatment was at a considerably higher temperature. Thus thermotolerance to heat shock killing also applies to cell‐cycle delay.