bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissecting the Hematopoietic Microenvironment
Authors: Wolf N. S.
Published: May 2008

An analysis of the S1/S1d mouse for ferrokinetics and fate of peripheral red blood cells has shown the cause of its anemia to be dual in nature. While the S1/S1d produces red cells at a slightly greater rate than its normal littermate, its bone marrow and spleen appear to be operating near their maximal capacity and will reduce their output if anemic stress is partly relieved. the cause of the moderately high level of erythropoiesis in the S1/S1d is a mean daily loss of 2.5–3.0% of its total blood volume via the intestinal tract.
Dissecting the Hematopoietic Microenvironment
Authors: Wolf N. S.
Published: May 2008

Experiments were carried out with the intent of defining the nature of the microenvironmental defect which severely limits erythropoiesis in the spleen of the S1/S1d mouse. Chimeric spleens, half S1/S1d and half congenic +/+, supported erythropoiesis in the +/+ region but not in the S1/S1d region, regardless of which genotype was the irradiated, marrow‐injected host animal. Implants of normal marrow stroma within the spleens of irradiated S1/S1d mice also supported normal proportions of erythrocytic and granulocytic hematopoiesis. Implants of normal spleen stroma, particularly the capsular portion, into unirradiated S1/S1d mice stimulated erythropoiesis originating from S1/S1d stem cells within and in the immediate vicinity of the implant. the evidence suggests a short range, stromal erythropoietic stimulatory factor which is lacking in the S1/S1d.
Analysis of the Progression of Meiosis In Dispersed Rat Testicular Cells By Flow Cytofluorometry
Authors: LIBBUS B. L. , SCHUETZ A. W.
Published: May 2008

Initiation and progression of meiosis was followed in dispersed rat testicular cells by flow cytofluorometry and cytology. the DNA content of dissociated testicular cells of rats 6–30 days old, killed at daily intervals, was analysed by flow cytofluorometry using propidium iodide as a DNA‐specific and quantitative fluorochrome. Testicular cells of a 6‐day‐old rat showed one peak of fluorescence. A second peak, at twice the modal channel number, appeared in testicular cells of 9‐day‐old animals. the number of cells under this peak increased progressively with age. A third peak, at half the channel number of the original one, appeared at 20 days and accounted for an increasing proportion of cells in testes taken from older rats. Cytological examination of the testicular tissue used for flow cytofluorometric analysis showed that preleptotene spermatocytes first appeared at 8 days after birth. Spermatids were first observed cytologically at 20 days after birth. the close temporal appearance of the fluorescence peaks with that of spermatocytes and spermatids, and the close association of the frequency of diploid and tetraploid cells as derived by flow cytofluorometry and cytology, indicated that the fluorescence peaks correspond—in order of increasing fluorescence—to spermatids, spermatogonia and somatic cells, and to spermatocytes. This conclusion was re‐examined by analysing the ploidy levels of testicular cells of hypophysectomized or estradiol‐treated animals by flow cytofluorometry. There was a loss of the haploid and tetraploid peaks subsequent to hypophysectomy. Estradiol dipropionate‐treated rats, given weekly injections starting at 7 days of age, showed no appearance of the haploid peak and the regression of the tetraploid peak after an initial and transitory appearance.

These results indicate that changes in ploidy levels that accompany the progression of meiosis in the testis were reflected in the sequential appearance of three fluorescence peaks as detected by flow cytofluorometry. the close correlation
Stimulating Factors and Cell Recruitment In Murine Bone Marrow Stem Cells and Emt6 Tumours
Authors: Frindel E. , Guigon M. , Dumenil D. , Fache M. P.
Published: May 2008

The role of a stimulating factor in cell recruitment and the kinetics of its secretion were investigated by in vivo and in vitro techniques. the association of these two methods made it possible to demonstrate that a non‐cycling population liberates a factor which in turn stimulates quiescent bone marrow stem cells into DNA synthesis. Moreover, it seems that undamaged cells are capable of secreting this factor. A stimulating factor responsible for cell recruitment was also demonstrated in an experimental EMT6 tumour and the kinetics of its secretion reported.
Nucleic Acid Profile of the Emt6 Cell Cycle In Vitro
Authors: Watson J. V. , Chambers S. H.
Published: May 2008

Simultaneous RNA and DNA estimations were carried out during the cell cycle of EMT6/M/CC cells growing in vitro following synchronization by mitotic selection. the determinations were performed with a flow cytofluorimeter on individual cells stained with acridine orange. It was found that the RNA content increased during G1 then remained virtually constant between early and mid S phase, but a second increase occurred during late S. the rate of uptake of tritiated uridine paralleled these changes in RNA levels, and it was also found that the rate of uptake in metaphase and anaphase was virtually zero, but a rapid increase occurred in telophase. the increase in DNA during S was approximately linear, and the intermitotic phase and cycle durations were very similar to previously reported results.
Quantitative Description of Cell Cycle Kinetics Under Chemotherapy Utilizing Flow Cytometry
Authors: Kim M. , Wheeler B. , Perry S.
Published: May 2008

A discrete time cell cycle kinetics model is developed to account for the effects of cytotoxic chemotherapy, particularly including the existence of cells destined to die. A model structure is determined from related experiments, leaving key parameter values undetermined. These values are found by determining the best least squares fit of the predicted to the observed DNA distribution data at a series of time intervals. the numerical methods include separable least squares, linear inequality constrained least squares and the Gauss‐Newton method. This approach is applied to an experiment in which the Ehrlich ascites tumour was given a single dose of bleomycin. the results include several different parameters, including the age response function and a time series of cell age and DNA distributions, which can be used as a basis for further treatment.
Contribution to the Understanding of the Mechanism of Cytokinesis In Plant Cells: the Action of Deoxyguanosine On the Kinetics of A Root Meristem Cell Population
Authors: Lasselain M.‐J. , Pareyre C. , Deysson G.
Published: May 2008

The kinetics of binucleate cells, formed by the action of deoxyguanosine, are studied using three methods: in a population synchronized with hydroxyurea, by autoradiography after pulse‐labelling, and in a sample of a cell population morphologically located at the M‐G1, limit. Deoxyguanosine induces a slowing down in S and G2, independent of the inhibition of cytokinesis. It is only when it takes effect during the G2, stage that deoxyguanosine brings about the formation of binucleate cells.
Dose‐Dependent Cytokinetic Changes Following 1‐β‐D‐Arabinofuranosylcytosine and Hydroxyurea In L1210 and S‐180 In Vivo
Authors: Straus M. J. , Moran Ruth E.
Published: May 2008

DNA synthesis inhibition and recovery in L1210 and S‐180 ascites tumors following 1‐β‐D‐arabinofuranosylcytosine (Ara‐C) and hydroxyurea (HU) were measured autoradiographically as a basis for optimizing drug schedules. Tumor bearing mice, 106 cells day O, were treated on day 4 with 20, 200 or 2000 mg/kg Ara‐C or 50, 300 or 1800 mg/kg HU. At various intervals following drug, [3H]thymidine was administered i.p. and mice were killed 1 hr later. Tumor cells were analyzed for labeling index (LI) and grain count (GC) to determine the percentage of cells in S phase and the distribution of DNA synthesis rates among the labeled cells, respectively. Following each dose of HU, DNA synthesis was inhibited completely. Recovery of LI was rapid and approached control values by 6 hr. Following each dose of Ara‐C, DNA synthesis was inhibited completely for at least 6 hr. Recovery of LI was first noted 6 hr following 20 mg/kg Ara‐C and 9 hr following 200 mg/kg. Following both doses the LI reached 100% of the control value by 26 hr. GC analysis indicated that following Ara‐C treatment, DNA synthesis was reinitiated first with cells with low GC from 6 to 12 hr followed by cells with increasing GC from 12 to 20 hr. the labeling intensity reached control values by 20 hr and an ‘overshoot’ occurred by 26 hr. These data suggest that the recovery of DNA synthesis rate is a gradual process. Survival data for mice receiving two doses of Ara‐C indicated that the optimal interval for retreatment following the lower dose of Ara‐C occurred by 6 hr as compared to 12–16 hr for the higher dose. These times coincided in both instances with recovery of LI to 33–50% of control values. Early recovery of LI may be the best method currently available for estimating the optimal time for retreatment with an S phase specific drug.
Specific Inhibition of Cell Proliferation In the Mouse Intestine By an Aqueous Extract of Rabbit Colon
Authors: Sassier P. , Bergeron M.
Published: May 2008

Aqueous extracts from rabbit colon, kidney, testis and small intestinal mucosa were prepared by homogenization and centrifugation at 105,000 g. After precipitation with ammonium sulphate. the 0–50 fraction (F1) and the supernatant (F2) were collected, dialysed against a phosphate buffer and tested on mice in vivo.

1 hr after a single injection of F1 (15 mg content) from colon, the uptake of tritiated thymidine was decreased in jejunal and colonic DNA in mice. This effect, maximal after 3 hr and totally reversible after 7 hr, was found in neither the kidney nor the testis. the F1 fractions of non‐digestive organs (kidney, testis) were also found to exert a significant inhibition on thymidine incorporation into intestinal DNA in vivo. F1 fractions of intestinal contents, prepared under the same conditions, exerted no significant effects on DNA synthesis in mouse intestine. Conversely, the colon F2 fraction did not inhibit the synthesis of jejunal and colonic DNA in vivo. A slowing of cellular migration was also noticed in the jejunum and colon of mice injected with colon or small intestine F1, as ascertained radioautographically by determining the position of the leading edge of the labelled cells in jejunal or colonic F1‐injected mice.

Our results suggest that the F1 fraction of the aqueous extract of rabbit colon contains one or more substances, which may act either on intestinal DNA synthesis or on the G1‐S transition of the cellular cycle in the mouse intestine. This reversible and tissue‐specific intestinal action appears to inhibit cell proliferation and presents several of the characteristics defining a chalone, as does the action of small intestinal F1 previously reported (Sassier & Bergeron, 1977). However, because of a relative lack of origin specificity of this effect, the physiological significance of our data remains to be ascertained.
The Growth of the Emt6 Tumour In the Lungs of Balb C Mice Following Intravenous Inoculation of Tumour Cells From Culture
Authors: TWENTYMAN P. R.
Published: May 2008

The growth of the EMT6 tumour in the lungs of Balb C mice has been studied following intravenous inoculation of different numbers of tumour cells taken from culture. At various times after injection of cells into mice, cell suspensions have been prepared from pairs of lungs and the number of in vitro colony forming cells assayed by plating into petri dishes. Following intravenous injection of 105 cells, the time required for doubling of the number of clonogenic tumour cells appearing in the cell suspension is around 17 hr until such time that the total tumour cell population per set of lungs reaches 108 cells (at 10–12 days). This doubling time has to be corrected for changes in ability to extract cells from the lungs into the cell suspension at various times and also for possible changes in plating efficiency in vitro. When these correction factors are applied, the most likely value for the doubling time of clonogenic tumour cells in the lungs is in the range 20–24 hr. This is a similar figure to that previously deduced for the EMT6 flank tumour during its microscopic period of growth.

After reaching a total size of 108 tumour cells, the time for doubling of the number of clonogenic tumour cells in the lung increases. During the later stages of tumour growth a good correlation is seen between total lung tumour weight and the number of clonogenic cells present.

For the final 3–4 days of the initial period of rapid tumour growth, it is possible to carry out a haemocytometer count of tumour cells in the lung suspension and hence surviving fraction experiments may be carried out after various forms of treatment. In this way the response to treatment of microscopic tumour foci may be determined.
Characteristic Species Dependent Growth Patterns of Mammalian Neoplasms
Authors: Brunton G. F. , Wheldon T. E.
Published: May 2008

Evidence is presented, arising from an analysis of published data on tumour growth in three species of laboratory animals and in human multiple myeloma supporting a species specific relation between two supposedly independent parameters in the Gompertz equations frequently used to quantify tumour growth curves. This evidence supports the conjecture of Norton et al. (1976), based on their observations of the growth kinetics of a murine melanoma and a rat mammary carcinoma, that such a relation may be a general feature of tumour growth. Published data on the growth of xenografts of human colorectal tumours in immune‐deprived mice suggests that the observed growth relation reflects the ability of a particular species to support a tumour of a certain maximum size. the existence of this relation greatly simplifies the task of predicting complete patterns of undisturbed neoplastic growth in these species.
ANALYSIS OF THE GROWTH KINETICS OF A HUMAN LYMPHOMA CELL LINE
Authors: Drewinko B. , Bobo B. , Roper P. R. , Malahy M. A. , Barlogie B. , Jansson B.
Published: May 2008

The growth kinetics of an established human lymphoma cell line were analyzed by a variety of techniques utilizing various cell inocula (5 x 104 ‐ 5 x 105 cells) dispensed into 60 mm diameter dishes. Techniques included pulse‐labeled mitosis (PLM), continuous labeling with 3H‐TdR, time‐lapse photography (TLP), cell counts by electronic particle counter, and DNA histography obtained by pulse cytophotometry (PCP). There were no significant differences among values determined for any kinetic parameters as a function of cell concentration. the average doubling time of exponentially growing cells, regardless of cell inoculum, was 44.1 hr. the generation time determined by PLM was 31.1 hr with a SD of 4.7 hr. Transit times for each stage were: TG1= 10.6 hr, Ts= 9.9 hr, TG2= 9.9 hr, and Tm= 0.7 hr. Repeated experiments using continuous labeling with 3H‐TdR demonstrated a TG2 of 6.3 hr. the longer value determined by PLM is possibly due to the technical manipulations of this procedure which may delay pulse‐labeled cells from resuming cell cycle transit. Hence, values for cell cycle stages were recalculated to give TG1= 14.1 hr, Ts= 9.9 hr, TG2 = 6.3 hr, and Tm= 0.7 hr. These results were used to compute the size of each cell cycle stage compartment pool and corresponded very closely to values defined directly by PCP. TLP analysis considered only cells that produced colonies of at least thirty‐two cells. Generation times ranged from 8 to 89 hr and showed a positive skewness. the average value measured for 330 divisions was 34.5 hr with a SD of 13.2 hr. Thus, the variance predicted by curve fitting of the PLM data did not correlate with that defined by time‐lapse photography nor did it encompass the range in generation times observed directly by TLP. There was a positive correlation between sister‐sister cell generation times (+0.66) but no relation was noted for mother‐daughter values.
TUMOUR CELL PROLIFERATION IN RELATION TO THE VASCULATURE
Authors: Hirst D. G. , Denekamp J.
Published: May 2008

The proliferation pattern of a transplantable mouse mammary carcinoma has been studied in relation to its macroscopic and microscopic structure. No significant differences were seen in the labelling or mitotic indices or in the percentage labelled mitoses curves for the peripheral 2‐0 mm rim or for the central tumour core.

When these parameters were scored for cells classified according to their position in relation to capillaries or to necrotic regions, marked differences were observed in all the parameters. Higher labelling and mitotic indices and higher grain counts were seen adjacent to the capillaries. These appear to result from a shorter cell cycle duration and a higher growth fraction. The variation in cell cycle is mainly due to a change in the duration of G1.
FLOW CYTOMETRIC CELL CYCLE ANALYSIS USING THE QUENCHING OF 33258 HOECHST FLUORESCENCE BY BROMODEOXYURIDINE INCORPORATION
Authors: Bohmer R. ‐M.
Published: May 2008

Cultures of L cells were grown in medium containing 2.0 mg/l bromodeoxyuridine (BUdR) and stained with the fluorescent dye 33258 Hoechst for flow cytometric analysis. During exposure to BUdR, the cells replace thymidine by BUdR in the newly synthesized DNA. The new DNA is not stainable with 33258 Hoechst, which is highly specific for thymidine. The temporal development of the fluorescence distributions after addition of BUdR to the growth medium has been investigated in the flow cytometer, and the data were used to calculate the mean durations of the phases G1, S and G2+ M in exponentially growing cultures as well as the cycle transit times in synchronized cultures. The percentage of non‐cycling cells was determined in each experiment.
THE DISCRETE–TIME KINETIC MODEL ANALYSIS OF DNA CONTENT DISTRIBUTIONS IN EXPERIMENTAL TUMOUR CELLS
Authors: Woo K. B.
Published: May 2008

A method was developed to analyse and characterize FMF measurements of DNA content distribution, utilizing the discrete time kinetic (DTK) model for cell kinetics analysis. The DTK model determines the time sequence of the cell age distribution during the proliferation of a tumor cell population and simulates the distribution pattern of the DNA content of cells in each age compartment of the cell cycle. The cells in one age compartment are distributed and spread into several compartments of the DNA content distribution to allow for different rates of DNA synthesis and instrument dispersion effects. It is assumed that the DNA content of cells in each age compartment has a Gaussian distribution. Thus, for a given cell age distribution the DNA content distribution depends on two parameters of the cells in each age compartment: the average DNA content and its coefficient of variation. As the DTK model generates the best fit DNA content distribution to the FMF measurement data, it enables one to estimate specific values of these two parameters in each stage of the cell cycle and to determine the fraction of cells in each cycle phase. The method was utilized to fit FMF measurements of DNA content distributions and to analyse their relationship to the cell kinetic parameters, namely cell loss rate, cell cycle times and growth fraction of exponentially growing Chinese hamster ovary cells in vitro and, also, with a wide range of coefficients of variation, of the L1210 ascites tumour during the growth period.
AN EXAMINATION OF SOME BASIC ASSUMPTIONS OF DNA DISTRIBUTION ANALYSIS USING BIOLOGICAL DATA
Authors: Brunsting A. , Collins J. M. , Kane F. R. , Bagwell C. B.
Published: May 2008

An examination is made of how the observed DNA distributions spread from their original biological distributions. Using distributions from testicular and hepatic tissue we find that the current assumptions for DNA distribution analysis need re‐examination and suggest how this might be done.
LABELLING INDEX OF HUMAN SQUAMOUS CELL CARCINOMAS
Authors: Chavaudra N. , Richard J. M. , Malaise E. P.
Published: May 2008

In vivo and in vitro labelling has been compared in sixteen human solid squamous cell carcinomas (ENT). The median in vivo/in vitro LI ratio was 1·2, but for two‐thirds of the patients it was only 1·1, suggesting a slight LI underestimation in vitro. Two factors can possibly explain the divergences: heterogeneity from one biopsy to another in the same tumour, and lower mean grain count in the deep cell layers of the in vitro labelled tumour samples. Therefore, the fact we did not find a good agreement between in vivo and in vitro data for one‐third of the tumours points out that one must be cautious in considering in vitro LI as a valid result for a given patient. However, even if the in vitro LI leads to a certain underestimate, it can provide useful data.
EFFECT OF AN INHIBITING FACTOR ISOLATED FROM RAT LIVER ON DNA POLYMERASES IN REGENERATING RAT LIVER
Authors: Pietu G. , Munsch N. , Mousset S. , Frayssinet C.
Published: May 2008

We partially purified an inhibitory factor (LIF), isolated from 105,000 g supernatant of a saline adult rat liver homogenate. LIF stopped in vitro cell multiplication by blocking the G1—S transition, and reduced in vivo [3H]thymidine incorporation into liver DNA in two‐thirds hepatectomized rats. This reduction in DNA synthesis was observed at 24 hr after hepatectomy, even when the LIF was injected before the beginning of the S phase, 10 hr after hepatectomy, i.e. when DNA polymerase activity had not yet increased. Under these experimental conditions, LIF in vivo treatment prevented α DNA polymerase activity from increasing after partial hepatectomy, so that enzyme activity at 24 hr in LIF‐treated rats decreased compared to the controls. No direct inhibitory effect of LIF on α DNA polymerase was detected. LIF did not affect β DNA polymerase.

These results suggest that LIF plays a part in controlling liver growth.
CELL POPULATION KINETIC PROFILE OF THE MOUSE THYMUS, AND THE CHANGES INDUCED BY PREDNISOLONE
Authors: Zaitoun A. M. , Lauder I. , Aherne W. A.
Published: May 2008

The cell population kinetic parameters of the thymus in BALB/c mice have been estimated using stathmokinetic and [3H]TdR techniques in both control animals and animals treated with prednisolone. FLM data were analysed by computer using the Gilbert program. The study showed that prednisolone had an inhibitory effect mainly in the DNA synthesis phase and in G1. Stathmokinetic data also showed a decrease in the cell birth rate and an increase in the apparent cell cycle time (or potential doubling time) after treatment. The labelling index, the mitotic index and the growth fraction were also decreased. The study also shows a good agreement between the data obtained by stathmokinetic and [3H]TdR techniques.
A NEW METHOD FOR THE ESTIMATION OF CELL CYCLE PHASES
Authors: Zajicek G. , Michaeli Y. , Regev J.
Published: May 2008

A method is described, which is applicable to cell renewal systems with an anatomical structure in which all cell locations may be uniquely mapped. Its use is demonstrated on the rat incisor inner enamel epithelium, which forms a one cell thick column in the sagittally sectioned tooth. Cells born in the apical part of the column migrate toward the distal end of the tooth, where they mature. As the cells migrate along the column, they traverse the various cell cycle phases.

The present study has been designed to estimate the probability of a cell being in a given phase; all cells touching the basement membrane were numbered, and the number of cells separating any two cells was taken as a measure of distance. Since generally all cells move in one direction (lateral cell migration may occur), it is possible to solve the problem with the aid of functions describing the renewal counting stochastic process in which cell distance serves as an independent variable.

The method predicts labelled cell and mitotic rates which agree with those estimated in the usual way. It was then utilized to estimate the fraction of cells in G2.
FURTHER STUDIES ON MOBILIZATION OF CFUs
Authors: Vos O. , Wilschut Ina J. C.
Published: May 2008

Mobilization of CFUs from haemopoietic tissues into circulation was studied after injection of different bacterial lipopolysaccharides (LPS), zymosan, phytohaemagglutinin (PHA), concanavalin A (Con A), trypsin and di‐isopropyl‐fluorophosphate‐inhibited trypsin. All bacterial LPS used gave an increase of CFUs in the peripheral blood at 1 h after i.v. injection. Some variation in activity could not be excluded. As with Salmonella typhosa LPS, zymosan gave an increase in circulating CFUs during the first few hr and a second peak a few days later. After injection of zymosan as well as S. typhosa LPS the second peak in the blood was accompanied by a large increase in CFUs numbers in the spleen. PHA gave an immediate mobilization of CFUs, but the mobilization after injection of Con A during the first few hr occurred more slowly. After injection of S. typhosa LPS, zymosan and PHA the blood C3 level was found to be depressed considerably. This might indicate that the complement system is involved in the early mobilization of CFUs.

Dexamethasone, a synthetic hormone which has been reported to give sequestration of several cell types in the bone marrow, did not inhibit the early and late mobilization of CFUs which normally occurs after injection of S. typhosa LPS.
CIRCADIAN RHYTHMS IN MOUSE EPIDERMAL BASAL CELL PROLIFERATION
Authors: Clausen O. P. F. , Thorud E. , Bjerknes R. , Elgjo K.
Published: May 2008

Several kinetic parameters of basal cell proliferation in hairless mouse epidermis were studied, and all parameters clearly showed circadian fluctuations during two successive 24 hr periods. Mitotic indices and the mitotic rate were studied in histological sections; the proportions of cells with S and G2 phase DNA content were measured by flow cytometry of isolated basal cells, and the [3H]TdR labelling indices and grain densities were determined by autoradiography in smears from basal cell suspensions. The influx and efflux of cells from each cell cycle phase were calculated from sinusoidal curves adapted to the cell kinetic findings and the phase durations were determined.

A peak of cells in S phase was observed around midnight, and a cohort of partially synchronized cells passed from the S phase to the G2 phase and traversed the G2 phase and mitosis in the early morning. The fluctuations in the influx of cells into the S phase were small compared with the variations in efflux from the S phase and the flux through the subsequent cell cycle phases. The resulting delay in cell cycle traverse through S phase before midnight could well account for the accumulation of cells in S phase and, therefore, also the subsequent partial synchrony of cell cycle traverse through the G2 phase and mitosis. Circadian variations in the duration of the S phase, the G2 phase and mitosis were clearly demonstrated.
NON‐RANDOM ASSOCIATION OF MITOTIC CELLS FROM CULTURED HUMAN LYMPHOCYTE SUSPENSIONS
Authors: Fitzgerald P. H.
Published: May 2008

By using chromosome markers in two separate cell lines of a human dispermic chimera, it was shown that 4.9% of metaphases in suspensions of PHA‐cultured lymphocytes were paired because of non‐random factors. A similar amount of metaphase pairing occurred in cultured lymphocytes of normal donors, and evidence from the relative mitotic cycles of the paired cells indicated that some of this pairing was non‐random. Such non‐random pairing could be a source of bias in cell kinetic and other studies involving metaphase cells in lymphocyte cultures.
INTERFERENCE OF SEX‐RELATED FACTORS IN THE RESPONSE OF LIVER CELLS TO EXPERIMENTAL MITOTIC STIMULI
Authors: Lombard M.‐N. , Nadal C. , Fiszer‐Szafarz B. , Rumeur E. Le , Zajdela F.
Published: May 2008

Stimulation of liver cell multiplication was obtained under two different experimental conditions.

A single injection of casein solution resulted in (a) an identical synchronized mitotic wave response in 10‐day old male and female rats and (b) a significantly lower response in adult male rats compared to females, a difference which was reduced by castration of males at birth but essentially maintained if animals were operated when 10 days old.

Partial hepatectomy shortly after puberty resulted in active hepatocyte multiplication occurring 3 hr earlier in females than in males. This difference was suppressed when females were ovariectomized at birth and significantly reduced when they were spayed at a later age. Hepatocytes of castrated females entered actively into S phase 2 hr later than the sham‐operated controls. Unilateral ovariectomy on the other hand indicated that during compensatory and/or hyper‐compensatory activity of the single ovary there was a maximum difference between the male and female rate of [3H]thymidine uptake in liver nuclei 20 hr after hepatectomy. A further kinetic study (t= 25, 30, 40, 65, 90 hr) indicated no significant sex‐related difference in the number of S phases per 10,000 cells.

The DNA content of regenerating versus control livers was comparable in both sexes at t= 22 and 90 hr but higher in females at t= 40 and 65 hr.

A possible early postnatal interference of certain hormonal mechanisms in the receptivity to mitotic stimuli is postulated and discussed.
ALTERATION OF NEONATAL RAT PAROTID GLAND ACINAR CELL PROLIFERATION BY GUANETHIDINE‐INDUCED SYMPATHECTOMY
Authors: Klein R. M.
Published: May 2008

Newborn rats were injected with guanethidine‐sulfate (20 μg/g body weight) every 48 hr from 12 hr after birth until day 14 (eight injections per animal). The guanethidine treatment resulted in an 86% absolute reduction in cell number in the superior cervical ganglia of 15 day old rats. The cells which remained after guanethidine treatment showed destruction of mitochondria and an extensive decrease in endoplasmic reticulum. Chemical sympathectomy with guanethidine induced a 3.1 hr lengthening of the acinar cell generation cycle time (17.4 hr to 20.5 hr), resulting from a longer G1 period (6.9 hr in the control group as compared to 10.5 hr in the guanethidine‐treated group), as well as a decrease in the mean percentage of [3H]thymidine‐labeled acinar cells (22.3 ± 0.5% to 19.3 ± 0.5%) and mean acinar cell mitotic index (2.6 ± 0.2% to 2.1 ± 0.1%). A circadian rhythm was found to exist in parotid gland acinar cell mitotic activity of 15 day old rats and the amplitude of the rhythm was reduced from 26.5% to 14.9% in guanethidine‐treated rats. This study indicates that the diminution of sympathetic influence on the developing parotid gland results in a slight, but significant alteration in acinar cell proliferation.
LOW LEVEL INCORPORATION OF TRITIATED THYMIDINE INTO THE NUCLEAR DNA OF PURKINJE NEURONS OF ADULT MICE
Authors: Cameron I. L. , Pool Mary R. H. , Hoage T. R.
Published: May 2008

Adult mice were pulse labeled with tritiated thymidine [3H]TdR and killed 9 hr later. A low level incorporation of [3H]TdR into the nuclear DNA of Purkinje neurons was found in autoradiographs. Enzymatic digestions with DNase and with RNase in combination with autoradiographic grain counts indicate that a portion of nuclear DNA is not stable in the Purkinje nucleus. These results are discussed in light of reports of the stable nature of DNA in Purkinje neurons of adult mice.
ON THE PROGENITOR CELL MIGRATION VELOCITY
Authors: Zajicek G. , Michaeli Y. , Regev J.
Published: May 2008

An attempt is presented to extract cell kinetic information from histomorphological features. It is applicable to rapidly proliferating tissues like the intestinal epithelium. Each replicating tissue has an origin where cells are formed and a periphery toward which cells migrate. The migration path along which they move is denominated as tissue radius on which all cell positions are mapped. Cell migration on the radius is associated with cell proliferation at tissue origin. Each mitosis there is associated with the displacement of all cells distal to it by one cell position. The more mitoses positioned between a cell and tissue origin, the greater its migration velocity. It is possible therefore to derive the cell migration velocity v(x) from the cumulative mitotic distribution on the radius, N(x). v(x) = N(x)/tm (tm= mitotic time). In this form v(x) represents also cell production at any point on the radius and may serve for the computation of other cell kinetic parameters like generation time.

These arguments are illustrated on the rat incisor tooth inner enamel epithelium which has been studied in the normal and rapidly erupting tooth.
LIMITATIONS IN THE USE OF [3H]THYMIDINE INCORPORATION INTO DNA AS AN INDICATOR OF EPIDERMAL KERATINOCYTE PROLIFERATION IN VITRO
Authors: Davison P. , Liu S. , Karasek M.
Published: May 2008

The validity of using the incorporation of [3H]thymidine into DNA as an indicator of epidermal keratinocyte proliferation in vitro has been investigated. Other parameters of cell proliferation, direct count of cell number and measurement of DNA content, consistently fail to correlate with changes in [3H]thymidine incorporation into DNA in primary and first passage cultures of rabbit and human epidermal keratinocytes. Maximum incorporation of [3H]thymidine precedes the active growth period by three days. Incorporation declines markedly during the proliferative period. Thymidine kinase activity decreases during the proliferative growth phase.

Incorporation of another pyrimidine nucleotide precursor, [14C]aspartic acid, suggests that in epidermal keratinocytes in vitro the extent of utilization of the salvage and the de novo pathways may be inversely related. In such cases [3H]thymidine incorporation into TCA precipitable material fails to reflect accurately cell proliferation.
VARIABILITY OF CELL GENERATION TIMES IN A HEPATOMA CELL PEDIGREE
Authors: Van Wijk R. , Van De Poll K. W.
Published: May 2008

Time‐lapse cinematographic analysis of a clone of HTC rat hepatoma cells showed variations in interdivision time within the clone. A positive correlation was found between the interdivision times of mother and daughter cells. The variability of the differences between interdivision times of cells of sister, cousin, second cousin or second‐second cousin relationship was calculated. The proportion of cells with large differences in intermitotic times was found to increase with decreasing relationship. The clonal division pattern observed suggests strongly that ‘inherited’factors govern the process leading to cell division but that their effects can be modified.
CELL‐PRODUCTION RATES ESTIMATED BY THE USE OF VINCRISTINE SULPHATE AND FLOW CYTOMETRY I. AN IN VITRO STUDY USING MURINE TUMOUR CELL LINES
Authors: Barfod I. H. , Barfod N. M.
Published: May 2008

A method for the evaluation of cell‐production rates is described which combines flow cytometry (FCM) and the stathmokinetic method.

By means of FCM it is possible to estimate the distribution of cells with G1, S and (G2+ M) DNA content in a population. As this method gives the relative (G2+ M) DNA content of cells within the cell cycle, it may be possible to evaluate cell‐production rates by this technique.

In the present study it was found that administration of a metaphase‐arresting (stathmokinetic) agent, vincristine sulphate (VS), to asynchronous cell populations of three different murine tumour cell lines in vitro increased the peak representing cells with (G2+ M) DNA content as the number of mitotic (M) cells increased during the period of treatment.

The accumulation of mitotic cells was determined by cell counts on smears under the microscope and compared with the increase in the (G2+ M) DNA peak measured by FCM as a function of time after the administration of VS. Good agreement was obtained between the cell‐production rates as estimated by FCM and by mitotic counts in all three cell lines investigated.
KINETICS OF HUMAN LYMPHOCYTE RESPONSES IN VITRO: DETERMINATION OF CLONE SIZE AND INITIAL RATE OF ENTRY INTO DNA SYNTHESIS
Authors: O'Leary J. J. , Hanrahan L. R. , Mehta C. , Rosenberg A.
Published: May 2008

In this third paper on the kinetics of lymphocyte stimulation we present a simple stochastic model for the entry of mitogen stimulated human lymphocytes into the proliferative cycle. The model is based on the assumption that responder ‘recruitment’ is a process of simple exponential decay. The model can be applied to the initial rapid rise in thymidine uptake after stimulation and successfully predicts the behavior of colchicine inhibited mitogen responses. Application of the model allows the estimation of the following constants; the size of the responding clone, the rate of entry of committed cells into the initial cell cycle, the duration of the lag period before uptake of thymidine increases above background and the average duration of thymidine uptake in responding lymphocytes (Ts).

If we analyze the experimental results of mitogen stimulation experiments in these terms we can show that the first three constants are sensitive functions of both the dose of mitogen and the source of the responding lymphocytes. The most interesting finding may be the fact that low doses of mitogen seem to decrease the rate of entry of committed lymphocytes into cell cycle. This would imply that the rate determining step in this process is not of an all or none type.
KINETICS OF CELL PROLIFERATION IN THE PRE‐IMPLANTED MOUSE EMBRYO IN VIVO AND IN VITRO
Authors: Streffer C. , van Beuningen D. , Molls M. , Zamboglou N. , Schulz S.
Published: May 2008

The cell proliferation of pre‐implanted mouse embryos was investigated after development in vivo and in vitro. The studies were started at the pronuclear stage, 2 h post conception (p.c.) and continued until the hatching of blastocysts, 120–144 h p.c.

The number of cell nuclei, the DNA content of each nucleus, the mitotic index and the labelling index were determined. From these data it was possible to calculate the length of the cell generation cycle and its various phases. With the exception of the first cell cycle the S‐phase was constant. The G1‐ as well as the G2‐phase varied in length during the different cell cycles.

From 31–72 h p.c. the increase in cell number was exponential. After cultivation in vitro this increase was smaller than in vivo. At later periods the proliferation rate decreased with proceeding development. In late blastocysts most of the cells were in the G1‐phase. The development of the embryos was somewhat faster in vivo than in vitro. But in principle conditions were comparable.
EFFECT OF BLEOMYCIN ON MOUSE HAEMOPOIETIC COLONY FORMING CELLS IN CULTURE (CFUc)
Authors: Briganti G. , Levi G. , Spalletta E. , Galloni L. , Mauro F.
Published: May 2008

The kinetics of CFUc studied by hydroxyurea and endotoxin treatments indicate that this cell population is proliferating actively (some 50% in S‐phase). This fact implies a peculiar response to (BLM) treatment with Bleomycin, a drug which appears to be proliferation—dependent. The dose—response has a steep initial slope resulting in a low extrapolation number (n= 0·66; D37 = 960 ± 70 mg BLM/kg body weight). The steep initial slope is confirmed by split‐dose experiments resulting in a potentiation effect by fractionation. Further evidence for the dependence of the action of this drug upon the proliferative state of the cell population is derived from time—response studies after single doses of BLM.
EXISTENCE OF AN ENDOGENOUS INHIBITOR OF DNA SYNTHESIS IN RABBIT SMALL INTESTINE SPECIFICALLY EFFECTIVE ON CELL PROLIFERATION IN ADULT MOUSE INTESTINE
Authors: Sassier P. , Bergeron M.
Published: May 2008

Aqueous extracts from rabbit organs were prepared by homogenization and centrifugation at 105,000 g. After precipitation with ammonium sulphate, the 0–50 fraction was separated by ultrafiltration through Amicon XM 100 and XM 300 membranes yielding two filtrate fractions (U1 and U2) and one retentate fraction (U3). Only U1 and U3 inhibited thymidine incorporation into DNA. After a single injection of U1 from rabbit small intestine, the uptake of tritiated thymidine was decreased in mouse jejunal and colonic DNA. This effect, totally reversible after 7 hr, was found in neither the kidney nor the testis. The U1 fractions of colon and non‐digestive organs (kidney, testis) were found not to exert a significant inhibition on thymidine incorporation into intestinal DNA in vivo. The U3 fraction from rabbit small intestine also decreased the uptake of tritiated thymidine in mouse jejunal and colonic DNA in vivo. However, this inhibition was irreversible and not tissue‐specific.

Slowing of cell migration was also noticed in the jejunum of mice injected with U1 or U3, as ascertained radioautographically by determining the position of the leading edge of the labelled cells in U1‐ or U3‐injected mice compared with controls. A decrease of mitotic activity in U1‐ and U3‐injected mice was recorded 8·5 hr after a single injection of small intestinal fractions.

Our results suggest that U1 and U3 from rabbit small intestine contain one or more substances which may act on the G1—S transition of the cell cycle in the mouse intestine. However, only the effect of U1 is reversible and tissue specific. Our data suggest the existence of a factor, having a low molecular weight, which regulates intestinal cell proliferation.
A SIMPLIFIED METHOD OF DNA DISTRIBUTION ANALYSIS
Authors: Dean P. N.
Published: May 2008

Current methods of analysing DNA distributions utilize complex mathematical expressions that require the use of large non‐linear curve fitting methods and, consequently, large computers. This paper presents a new method of analysing DNA distributions of asynchronously growing or mildly perturbed cells. The S phase fraction is obtained by fitting a second degree polynomial to that part of the distribution, mid S phase, which is not influenced by either the G1 or the G2+ M peaks. The method is simple and fast, it exceeds the accuracy of other methods and it can be used on a large desk calculator or mini‐computer.
A CRITICAL REVIEW OF THE USE OF VINCRISTINE (VCR) AS A TUMOUR CELL SYNCHRONIZING AGENT IN CANCER THERAPY
Authors: Camplejohn R. S.
Published: May 2008

Vincristine (VCR) has been used clinically in so‐called ‘tumour cell synchronization therapy schedules'. These schedules are based on the assumption that cells, arrested in metaphase by low doses of VCR, subsequently re‐enter the proliferative cycle synchronously. However, the evidence that tumour cell synchrony can be achieved under clinical conditions or that ‘cell synchronization therapy schedules’ yield a better therapeutic response than other efficient combination schemes, is scanty. Further, even in experimental systems, the efficacy of VCR as a cell synchronizing agent is disputed. Indeed, in some systems, cells arrested in metaphase by low doses of VCR, do not re‐enter a normal proliferative cycle at all following arrest. In addition, the complex nature of the VCR—tumour interaction and the heterogeneous nature of the tumour cell populations against which it is used augurs badly for the successful application of cell synchronization therapy schedules.
RENEWAL OF TASTE BUD CELLS IN RAT CIRCUMVALLATE PAPILLAE
Authors: Farbman A. I.
Published: May 2008

The life span of taste bud cells in rat circumvallate papillae was measured by autoradiography after labeling them with a pulse of [3H]thymidine. Specimens of circumvallate papillae were taken daily 1·5‐18·5 days after the isotope was administered; thereafter, specimens were taken on alternate days until 25·5 days. For each time interval, the number of labeled cell nuclei was counted in 200‐450 taste buds and plotted as the ratio of labeled cells/taste bud v. time after injection of [3H]TdR. In all, 6958 taste buds were counted.

The total number of labeled cells (dark plus light) per taste bud reached peaks at 6·5, 13·5 and 20·5 days. The curve for the number of labeled dark cells/bud had essentially the same shape as that for total cells. The number of labeled light cells/bud reached a modest peak at 6·5 days and slowly declined to a plateau for the remainder of the experiment. The data show that an average of 2 days elapsed after injection before labeled dark cells entered the bud and they spent an average of 7 days in the non‐proliferating taste bud compartment; thus, the life span of the dark cell was 9 days. The life span of the light cell was difficult to estimate quantitatively, but this cell type was labeled at a much slower rate than dark cells and is assumed to have a significantly longer tenure in the taste bud.
A COMPARISON OF IN VIVO AND IN VITRO STATHMOKINETIC METHODS FOR THE STUDY OF CELL PROLIFERATION IN HAMSTER ORAL EPITHELIA
Authors: Scragg Margaret A. , Johnson N. W.
Published: May 2008

Mitotic indices (MI) expressed as numbers of metaphase figures per 100 basal cells in the cheek pouch and palatal epithelium of the Syrian hamster following metaphase arrest with vinblastine sulphate (VLB) were compared using in vivo and in vitro techniques. The MI in vivo 4 1/2 hr after intraperitoneal injection of 4 mg VLB/kg body weight was 2·69 ± 0·37 for cheek pouch and 12·08 ± 1·09 for palate. MI in vitro was measured using small tissue explants cultured for 4 hr in medium supplemented with VLB at concentrations ranging from 6‐600 μg/ml. The maximum MI for cheek pouch epithelium in vitro (2·7) did not differ significantly from that observed in vivo (P > 0·50) and was obtained in the presence of 12–30 μg VLB/ml, a concentration comparable with that used in vivo. In contrast, the maximum MI for palate epithelium in culture (5·6) was significantly lower than that in vivo (P < 0·001) and was only achieved in the presence of extremely high concentrations of VLB. Possible reasons are discussed for the discrepancy between the MI for palatal epithelium in vivo and in vitro.
FEEDBACK INHIBITION OF HEPATIC DNA SYNTHESIS
Authors: Schulte‐Hermann R. , Schmitz E.
Published: May 2008

α‐Hexachlorocyclohexane (α‐HCH) and some other xenobiotic inducers were used to elicit adaptive increases in mono‐oxygenase activity, size and DNA content of rat liver. After elimination of the inducers, organ size and mono‐oxygenase activity returned to normal whereas the DNA content of the liver remained increased. Upon renewed treatment with an inducer the adaptive responses uncoupled. While mono‐oxygenase induction and liver enlargement did occur, DNA replication was largely suppressed. These findings show that in the hyperplastic state the liver is resistant to stimulation of DNA synthesis by the inducers. It is concluded that the DNA content of the liver (or the number of liver cells) is controlled by a feedback system which monitors an excess of DNA (cells) and suppresses cell replication if the content of DNA exceeds the normal level. Organ mass has little, if any, effect on the operation of this feedback system.