bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes In Cell Population Kinetics During Epidermal Carcinogenesis
Authors: Fukuda M. , Okamura K. , Rohrbach R. , Bohm N. , Fujita S.
Published: May 2008

The changes in cell population kinetics in response to a mechanical stimulation by wounding were studied in a hyperplastic epidermis, papilloma and a squamous cell carcinoma of the mouse dorsal skin induced by repeated treatments with 20‐methylcholanthrene.

The Go cell population, which consists of about 66% of the basal cells in the dorsal epidermis of the normal mouse, disappeared in hyperplastic epidermis, papilloma and carcinoma. the zone of proliferating cells enlarged in the papilloma, including several supra‐basal layers, in contrast to its strict localization in the basal layer in hyperplastic epidermis. Proliferating cells were distributed in almost all areas in the carcinoma without localization. the normal responses to wounding were preserved in the hyperplastic epidermis, except for the absence of Go cells, while the papilloma and carcinoma showed no increase in proliferating cells or shortening of the cell cycle time. From the view‐point of cell population kinetics, papilloma and carcinoma are regarded as the tissues in which the flexible control mechanisms of irreversible cell differentiation to mature cells and of the length of cell cycle time are lacking.
Cell Cycle And The Concept Of Physiological Age With Special Reference To Pyruvate Kinase Activity In Wi‐38 Cells
Authors: Steward P. G. , Kapp L. N. , Klevecz R. R.
Published: May 2008

Wi‐38 Cells Were Synchronized By Mitotic Collection And Periodically Assayed For Pyruvate Kinase Activity. The Kinetics Of The Synchronous Cohort Were Determined By Continuous Labelling Index And By Mitotic Index. The Experimental Data Were Analysed By Computer Using A State Vector Model To Yield The Probability Density Functions For Phase Transit Times And For Cell Physiological Ages. Pyruvate Kinase Activity For These Cells As A Function Of Physiological Age Was Then Examined Using The Computer Model. Considering Dna Synthesis, Pyruvate Kinase Activity And Mitosis To Be Markers Of Physiological Age, It Was Found That A Model Which Assumes That A Cohort Of Synchronized Cells Desynchronizes Irreversibly And Uniformly From One Age Marker To The Next Is Incompatible With The Experimental Data. For Example, The Times Over Which Cells Entered The S Phase Were Too Widely Distributed To Be Consistent With The Mitotic Index Data. Also, For Pyruvate Kinase Activity To Be A Function Of Physiological Age Alone, The Cell Ages Were Probably Too Dispersed To Be Compatible With The Experimental Enzyme Data. Alternative Models For Cell Physiological Ageing Are Presented, Which Are Compatible With The Experimental Data.
Kinetic Models of C3h Mouse Mammary Tumor Growth: Implications Regarding Tumor Cell Loss
Authors: Roti J. L. Roti , Bohling V. , Dethlefsen L. A.
Published: May 2008

Three models of tumor cell loss are described. the effects of cell loss on other cellular kinetic parameters are evaluated, and experiments which may distinguish among the models are discussed. Each model is based on a different cell‐loss mechanism, and equations for the cell‐cycle, cell‐frequency distribution, the growth of both the proliferating and non‐proliferating cell population, the growth fraction (GF), and the relative rate of volumetric growth, (dV/dt)/V, are derived.

The following types of data are simulated for each model: the pulse labelling index, the mitotic index, and the labeling index as a function of time after a single or a series of 3H‐TdR injections. the relative volumetric growth rate has the same mathematical form for each model. the PLM curves predicted by each model for the tumor lines studied (S102F and Slow) are not appreciably different. the predicted initial labeling index and mitotic index may differ significantly among the models depending upon the tumor line. the most striking difference among the models lies in the predictions regarding the labeling index as a function of time after a single or after a series of 3H‐TdR injections. These types of labeling experiments should be valuable for distinguishing the different cell‐loss mechanisms in solid tumors.
Species‐Specific Aggregation Factor In Sponges
Authors: Müller W. E. G. , Müller I. , Zahn R. K. , Kurelec B.
Published: May 2008

In dissociated single cells from the sponge Geodia cydonium, DNA synthesis is initiated after incubation with a homologous, soluble aggregation factor. During the DNA‐initiation phase the cyclic AMP‐ and cyclic GMP levels vary drastically; the cyclic AMP content drops from 2.2 pmol/106 cells to 0.3 pmol/106 cells while the cyclic GMP content increases from 0.6 pmol to 3.7 pmol/106 cells. the activity of neither the adenylate cyclase nor of the guanylate cyclase isolated from cells which have been incubated for different periods of time with the aggregation factor, is changed. the soluble as well as the particulate enzyme activities were checked in vitro. the cyclic nucleotide receptors have been isolated from the sponge cells and characterized with respect to their molecular weight, dissociation constant for cyclic AMP or cyclic GMP and intracellular concentration. None of these parameters are altered during aggregation factor‐mediated DNA initiation. From these data it is concluded that the regulation of cyclic nucleotide levels is a consequence of a changed activity of nucleotide cyclases or of phosphodiesterases, but this is presumably not caused by a changed rate of synthesis of nucleotide cyclases or of cyclic nucleotide receptors.
EFFECTS OF HUMAN LEUKOCYTE CONDITIONED MEDIUM ON MOUSE HAEMOPOIETIC PROGENITOR CELLS
Authors: Wagemaker G. , Peters M. Frances
Published: May 2008

Medium conditioned by human peripheral blood leukocytes (HLCM) was studied for its in vitro effects on haemopoietic progenitor cells (CFU‐s and CFU‐c) present in mouse bone marrow. HLCM has poor colony stimulating activity in semi‐solid cultures of mouse bone marrow cells. but invariably increases the number of colonies obtained in the presence of plateau levels of semi‐purified colony stimulating factor (CSF). In liquid cultures, HLCM appears to contain a potent initiator of DNA synthesis in CFU‐s. an activity which coincides with an increased CFU‐s maintenance and causes a three‐ to four‐fold increase in CFU‐c number. It is apparent from this study that HLCM, in addition to stimulating colony formation in cultures of human bone marrow cells, has a profound in vitro effect on primitive haemopoietic progenitor cells of the mouse, which cannot be attributed to CSF.
The Proliferative Status And Clonogenic Capacity Of Tumour Cells In A Transplantable Rhabdomyosarcoma Of The Rat Before And After Irradiation With 800 Rad Of X‐Rays
Authors: Hermens A. F. , Barendsen G. W.
Published: May 2008

R‐1 Rhabdomyosarcomas Transplantable In The Inbred Strain Of Wag/Rij Rats Were Labelled Semicontinuously With 3H‐Tdr And Subsequently Irradiated With X‐Rays In Order To Estimate The Rate Of Recruitment Of Q Into P Cells And To Obtain More Insight Into The Importance Of Hypoxia With Respect To The P And Q Status Of Clonogenic Cells. Labelling Was Performed By Giving Animals From One To A Total Number Of Up To Seven Intraperitoneal Injections With 3H‐Tdr Within 30 Hr. Half Of The Number Of Tumours Received An Acute Dose Of 800 Rad Of 300 Kv X‐Rays At 45 Min After Completion Of The Last Labelling In Order To Reduce The Fraction Of Well Oxygenated Cells Among The Surviving Clonogenic Cells To Less Than 1%; Labelled Control Tumours Were Sham Irradiated. Fractions Of Labelled Tumour Cells, LiTumour’Were Evaluated From Autoradiographs Prepared From Sections Of Tumours That Were Fixed 15 Min After Irradiation: Fractions Of Labelled Cell Foci, LiFo, Were Determined In Autoradiographs Prepared From Cultures Of Cells Isolated From The Remaining Parts Of The Tumours.

Analysis Of The Variation In LiTumour As A Function Of Time And Of The Number Of Injections Showed That The Rate Of Recruitment Of Q Cells Into P Cells Is Most Likely Less Than 1%/Hr. Comparison Of Data On LiFo Derived For Irradiated And Non‐Irradiated Tumours Indicates That Clonogenic Q Cells Are More Frequently Present Among Cells Which Survived The Dose Of 800 Rad Of X‐Rays. These Results Suggest That, In R‐1 Tumours Of About 800 Mm3 The Clonogenic Q Cell Population Contains A Larger Fraction Of Hypoxic Cells Than The Fraction Of Hypoxic Cells Present In The Clonogenic P Cell Population.

Several factors are discussed which complicate the analysis and may influence the results, e.g. reutilization of labelled debris of dead cells from irradiated tumours.
Changes In Stem Cell Compartments In Mice After Hydroxyurea
Authors: Nečas E. , Poňka P. , Neuwirt J.
Published: May 2008

Hydroxyurea injection kills only approximately 10% of CFU, which are in the S phase of the cell cycle. In mice given a single injection of hydroxyurea CFUs in the femur decreased only about 50% in 2–4 days after hydroxyurea, and then started to return to normal levels with an overshoot evident after the eighth day after hydroxyurea. CFUs in spleens of mice given a single injection of hydroxyurea show an evident overshoot as early as 3 days after the drug, reaching levels which are about 300% of normal. CFUs from blood disappear rapidly, but equally rapidly return to normal values followed by a significant overshoot. the radioresistance of mice increased up to 4 days after hydroxyurea.
Chalone Inhibition of Granulocyte Colony Growth In Agar: Kinetic Quantitation By Capillary Tube Scanning
Authors: Maurer H. R. , Henry R. , Maschler R.
Published: May 2008

Mouse bone marrow cells were seeded into capillary tubes containing agar with colony stimulating factor. the development of myelomonocytic clusters and colonies was followed by daily tube scanning using their light scattering properties. Three kinetic scanning parameters were determined and the significance of different threshold settings was evaluated; viz. the number of signals, the mean signal height and the signal integrals. the inhibitory effect of two extracts with known granulocyte chalone activity which had been prepared from human peripheral leukocytes and rat bone marrow cells, was followed with the scanning method. A continuous reduction of clusters and colony formation and their growth throughout the incubation period was observed which suggested a sustained retardation of proliferation of both the stem cells committed for myelomono‐poiesis and their progeny.
Differential Radiation Response Amongst Proliferating Epithelial Cells
Authors: Potten C. S. , Al‐Barwari S. E. , Searle J.
Published: May 2008

Tissue irradiation results in both reproductive and histologically evident cell death. the correlation between these is poor. Irrespective of dose and fraction sterilized, many cells behave as if unirradiated (cell cycle and maturation activity). the fraction of histologically observable dead cells is usually less than 0.1, with most in the intestine being positioned in the presumptive stem cell region. the data strongly suggest different epithelial sub‐populations with differing radioresponses. These may be the stem and differentiated proliferative cells.
ANALYSIS OF GROWTH OF TETRAPLOID NUCLEI IN ROOTS OF VICIA FABA
Authors: Bansal J. , Davidson D.
Published: May 2008

Growth of nuclei of a marked population of cells was determined from G1 to prophase in roots of Vicia faba. the cells were marked by inducing them to become tetraploid by treatment with 0.002% colchicine for 1 hr. Variation in nuclear volume is large; it is established in early G1 and maintained through interphase and into prophase. One consequence of this variation is that there is considerable overlap between volumes of nuclei of different ages in the cell cycle; nuclear volume, we suggest, cannot be used as an accurate indicator of the age of the cell in its growth cycle. Nuclei exhibit considerable variation in their growth rate through the cell cycle. of the marked population of cells, about 65% had completed a cell cycle 14–15 hr after they were formed. These tetraploid nuclei have a cell cycle duration similar to that of fast cycling diploid cells of the same roots. Since they do complete a cell cycle, at least 65% of the nuclei studied must come from rapidly proliferating cells, showing that variability in nuclear volumes must be present in growing cells and cannot be attributed solely to the presence, in our samples, of non‐cycling cells.
A Stochastic Model For Cell Populations With Circadian Rhythms
Authors: Hopper J. L. , Brockwell P. J.
Published: May 2008

A mathematical model for cell kinetics, based on a random walk, is developed. the model allows variations with time of the rates of passage of proliferating cells through the four phases of the mitotic cycle. Circadian variations in the mitotic and labelling indices of the Syrian hamster cheek pouch epithelium have previously been observed, and the random walk model has been used to simulate this phenomenon. Assuming that all basal cells are proliferative and that these cells leave the basal layer randomly throughout the mitotic cycle to become differentiated cells, it was found that the experimentally observed circadian rhythms of the mitotic and labelling indices could be reproduced in the model by postulating a circadian rhythm in the rate of passage of cells through the G1 and S phases only. Moreover, the growth activity of cells in both the G1 and S phases appears to reach a peak during the dark hours of the light‐dark cycle, and to fall off rapidly in the early hours of daylight. the postulate of Møller, Larsen & Faber (1974) that injection of the animals with tritiated thymidine causes a shortening of the G2 phase duration has been qualitatively confirmed by using the random walk model to simulate the FLM and MI curves after injection with tritiated thymidine.
FAILURE TO FIND A HUMORAL FACTOR WHICH INFLUENCES THE COMPENSATORY RESPONSE AFTER RESECTION OF THE RAT SMALL BOWEL
Authors: Kirchner F. R. , Osborne J.W.
Published: May 2008

Small bowel resection was performed in one parabiont of a parabiotic rat pair to determine whether there was a ‘humoral’ or other circulating factor present which could influence the compensatory response seen in the remainder of the small bowel. Following intestinal resection in one parabiont, there was an increase in DNA synthesis in the intestine of that member provided at least 40% of the small intestine was removed. the compensatory response seen in a resected animal was not observed in its parabiotic partner, even though an attempt was made to make the potentially responding animal more sensitive to the influence of any circulating ‘factors’ by resecting its intestine as well.

The results obtained are in disagreement with the one closely related report in the literature; it is suggested that there is no good evidence for the existence of a resection‐induced circulating factor with the capability of crossing a vascular anastomosis and controlling proliferation of small intestinal epithelium.
Endogenous Thymic Factors Regulating Cell Proliferation and Analysis of Their Mechanism of Action
Authors: Blazsek I. , Gaál D.
Published: May 2008

Endogenous factors inhibiting the proliferation of T‐lymphocytes were investigated which may function as modulators of T‐lymphocyte production within the thymus. an extract from calf thymus (T4) enriched in lymphocyte chalone arrests rat thymocytes at the G1 S boundary and in the S phase of the cell cycle in short‐term cultures. It also inhibits the proliferative response of human peripheral blood lymphocytes to PHA‐P in a time‐dependent manner, as well as the spontaneous proliferation of in vitro cultured human chronic leukaemic lymphoblasts. This crude extract contains two active moities which can be isolated by molecular filtration on Sephadex G‐75 column.

A species non‐specific, cell line selectivity inhibitory effect is characteristic of the high molecular weight fraction (mol. wt. > 40,000). This activity is resistant to moderate heat treatment and trypsin but is sensitive to mild alkaline hydrolysis and to RNase A digestion. About ten protein components and a toluidine blue positive substance can be detected by analytical polyacrylamide gel electrophoresis. the active inhibitor, a proposed protein‐RNA complex, might be identical with the chalone.

The low molecular weight, non‐dialysable factor (T4–4) inhibits [3H]thymidine incorporation into acid insoluble DNA in a cell non‐specific manner. A possible relationship between the two activities is discussed.
Cell Proliferation In Emt6 Tumors Treated With Single Doses of X‐Rays Or Hydroxyurea. I. Experimental Results
Authors: Rockwell Sara , Frindel Emilia , Valleron A. J. , Tubiana M.
Published: May 2008

EMT6 mouse mammary tumors were treated in vivo with 5 mg/mouse of hydroxyurea (HU) or 300 rads of X‐rays. the proliferation of the tumor cells was followed for 28 hr after treatment. Changes in the 3H‐TdR labeling index, the mitotic index, the specific activity of the 3H‐TdR‐labeled DNA, and the proportion of suspended, clonogenic cells in the S phase of the cell cycle were examined and compared. Evidence was found for reassortment of the surviving cells in treated tumors into partially synchronous cohorts. the partial synchrony in the proliferation of the surviving cells was not accurately predicted by the changes in the labeling index and the mitotic index. the changes in DNA specific activity proved unacceptable as an indicator of cell proliferation in solid EMT6 tumors treated with low doses of radiation or HU.
Cell Kinetics In the Erythroid Compartment of Guinea Pig Bone Marrow: A Model Based On 3H‐Tdr Studies
Authors: Prothero J. , Starling M. , Rosse C.
Published: May 2008

A model of steady‐state erythropoiesis in the guinea pig is described. the model incorporates an unidentified progenitor compartment, as well as compartments representing proerythroblasts, basophilic, polychromatic and orthochromatic cells. A computer representation of the model permits a simulation of the labeling curves obtained in pulse and intermittent labeling regimes. It was found that a reasonable fit to the data can be achieved when the parameters for the various compartments are essentially identical. the results of a preliminary sensitivity analysis, carried out by perturbing the duration of S phase from the best fit value, are reported. the fit achieved to the data supports the hypothesis underlying the model that each compartment corresponds to one generation and that the flux within and between compartments is sequential.
THE RELATIONSHIP BETWEEN STEM CELL SEEDING EFFICIENCY AND POSITION IN CELL CYCLE
Authors: Monette F. C. , DeMello J. B.
Published: May 2008

The seeding efficiency of colony‐forming cells from normal, regenerating and velocity‐sedimented cycling and non‐cycling narrow preparations was compared. Colony‐forming cells in cycle were found to exhibit a 50% reduction in splenic seeding when compared to normal marrow or sedimented non‐cycling cells. The results of this study indicate that the spleen colony assay underestimates the total number of colony‐forming cells by a fraction which is directly related to the number of cells in cycle.
IN VIVO EFFECTS OF 5‐FLUOROURACIL AND FTORAFUR[1‐(TETRAHYDROFURAN‐2‐YL)‐5‐FLUOROURACIL] ON MURINE MAMMARY TUMORS AND SMALL INTESTINE
Authors: Pallavicini Maria G. , Cohen A. M. , Dethlefsen L. A. , Gray J. W.
Published: May 2008

The in vivo anti‐tumour and toxic effects of ftorafur (FT) and 5‐fluorouracil (FU) were studied in the C3H mouse. On a molar basis, FU was two to three times more potent than FT with respect to growth inhibition of murine mammary adenocarcinomas. However, FT produced less host toxicity than FU when both drugs were compared at dose levels which produced equivalent anti‐tumor effects. The differences between FT and FU with respect to tumor growth inhibition and host toxicity were reflected in their ability to suppress deoxyuridine incorporation into tumor cell and intestinal DNA, respectively.

Flow cytometry (FCM) studies indicated that FT and FU were capable of producing pertubations in the DNA distribution of tumour cells. Both drugs induced an initial accumulation of cells in S phase following their administration at equivalent anti‐tumour dose levels. At later intervals, an apparent block of cell progression at the G1/S boundary was observed.

Drug‐induced perturbations in the DNA distribution of tumour cells as detected by FCM correlated with results obtained by classical autoradiographic techniques using tritiated thymidine. Both procedures showed that tumor cells were capable of moving through S phase even in the presence of an apparently near complete inhibition of deoxyuridine incorporation into DNA. That such cells were, in fact, capable of synthesizing DNA at moderate rates was shown by their ability to incorporate 32P into DNA. The possible relationship of these findings to the therapeutic and toxic activities of FT and FU is discussed.
DNA FLOW CYTOMETRY OF ISOLATED KERATINIZED EPITHELIA: A METHODOLOGICAL STUDY BASED ON ULTRASONIC TISSUE DISAGGREGATION
Authors: Møller Ulla , Larsen J. K.
Published: May 2008

Ultrasonication of keratinized, stratified, squamous epithelium, which had been separated from underlying tissue by means of acetic acid, resulted in disaggregation of all cellular layers in the epithelium, giving a suspension of single nuclei with mitoses preserved. This suspension was treated with RNAse and ethidium bromide for analysis by flow cytometry. From the resulting DNA histogram the G1, S and G2+ M fractions were estimated using the computer program of Fried (1976). Treatment with dithiothreitol before sonication increased the yield of nuclei in suspension and decreased the amount of debris and clumps, thereby suppressing overestimation of small S fractions.

This method of preparation prior to DNA flow cytometry was useful for the study of the hamster cheek pouch epithelium and of normal and pathological human epidermis.
ESTIMATION OF EFFECTIVE EOSINOPOIESIS AND BONE MARROW EOSINOPHIL RESERVE CAPACITY IN NORMAL MAN
Authors: Walle A. J. , Parwaresch M. R.
Published: May 2008

The eosinophil reserve capacity of the post‐mitotic granulocyte compartment in the bone marrow and the effective eosinopoiesis in three haematologically normal men have been quantified by means of kinetic parameters of [3H]thymidine flash‐labelled peripheral blood eosinophils.

From (a) the time of the appearance in the blood of labelled eosinophils after the tracer injection, (b) the inflow characteristics of the labelled eosinophils in the blood and (c) the magnitude of the eosinophil granulocyte pool in the venous blood, the effective eosinopoiesis (i.e. the eosinophil turnover) was calculated to range between 0.014 and 0.031 × 109 cells/kg body weight per day (mean 0.22 × 109 cell/kg per day). The post‐mitotic eosinophil reserve capacity of the bone marrow ranged from 0.09 to 0.20 × 109 cells/kg body weight (mean 0.14 × 109 cells/kg). The large reserve pool and the high turnover rate may contribute to sudden rises of the peripheral blood oesinophil counts in some cases of eosinophilia.
THE EFFECT OF TEMPERATURE ON THE TURNOVER OF TASTE BUD CELLS IN CATFISH
Authors: Raderman‐Little R.
Published: May 2008

Renewal of taste bud cells on the barbels of channel catfish was studied. Groups of catfish, held in and acclimitized to 14°C, 18°C, 22°C and 30°C dechlorinated tap water were injected with [3H]thymidine (3.0 μCi/g body weight intraperitoneally). Barbels were sampled at various times after injection and prepared for light microscope autoradiography. Results show that epithelial cells surrounding the taste buds divide and some of their daughter cells migrate into the taste buds. The time at which 50% of the labelled cells have degenerated is taken as the average turnover time or average life span of the taste bud cells. The average life span as well as the time spent inside the taste buds is highly temperature‐dependent. At 14°C, 18°C, 22°C and 30°C the average life span is on the order of 40, 30, 15 and 12 days respectively. Further studies indicate that both light and dark staining cells of the taste bud were labelled.
STUDIES ON THE MECHANISM OF HAEMOPOIETIC STEM CELL (CFUs) MOBILIZATION
Authors: Wilschut Ina J. C. , Erkens‐Versluis Mieke E. , Ploemacher R. E. , Benner R. , Vos O.
Published: May 2008

A variety of substances can mobilize haemopoietic stem cells (CFUs) into the peripheral blood. In this study the involvement of the complement system in the mobilization process was investigated. Pretreatment of mice with the complement‐activating factor of cobra venom (CoF), which lowered the serum C3 levels to 10–25% of the normal value, could completely prevent CFUs mobilization induced by high doses of CoF, endotoxin (ET) from Salmonella typhosa, inulin, zymosan and the proteolytic enzymes proteinase and trypsin. On the other hand, mobilization induced by the polyanions dextran sulphate and the copolymer of polymethacrylic acid and styrene could not be prevented, or at least affected only slightly.

There appears to be a relationship between the extent of decomplementation by CoF and the extent of CFUs mobilization induced by ET.

The results indicate that certain agents mobilize CFUs via the complement system, whereas other agents induce CFUs mobilization independent of the availability of complement components.
FUNCTIONAL CELL COMPARTMENTS IN A RAT MODEL FOR HUMAN ACUTE MYELOCYTIC LEUKAEMIA
Authors: Hagenbeek A. , Martens A. C. M.
Published: May 2008

Functional cell compartments were studied in a rat model for human acute myelocytic leukaemia (AML). This was done by tracing the distribution of injected 51Chromium‐labelled leukaemic cells in the body. It was concluded that two functional compartments can be distinguished in acute leukaemia, i.e., a rapidly exchangeable pool of cells (including the circulating blood pool, the marginal noncirculating blood pool and the rapidly exchangeable tissue pool; RETP) and a slowly exchangeable tissue pool (SETP). The sizes of these various compartments were roughly quantified at various stages of the disease by calculations based on the principle of isotope dilution and organ weight measurements. As the leukaemia progresses, the size of the SETP increases significantly relative to the size of the RETP. Simultaneously, the exchange rates of leukaemic cells between the organs and the blood decrease. The blood transit time of leukaemic cells was also significantly prolonged, as is the case in human AML.
LIPOPROTEIN INHIBITOR OF BQNE MARROW CELLS IN TUMOR‐BEARING RATS
Authors: Zucker S. , Michael Miriam S. , Lysik Rita M. , Glucksman M. J. , Reese J. , Rudin A. , DiStefano J.
Published: May 2008

The role of a plasma inhibitor of erythropoiesis is evaluated in rats with Walker‐256 carcinoma (W‐256). Plasma from tumor‐bearing rats was treated by gel filtration chromatography (Sephadex G‐150) and fractions were combined into four pools on the basis of mol. wt. Inhibitory activity was assayed by adding an aliquot of the plasma fractions to normal rat marrow cells which were cultured for 24 hr with and without erythropoietin. 59Fe‐heme synthesis, [3H]thymidine DNA synthesis, and 14C‐leucine protein synthesis were studied. The results indicated that cultures containing the high mol. wt. pool (>400,000 daltons) had significantly decreased heme, DNA and protein synthesis. This inhibitor also diminished the response to erythropoietin in polycythemic mice. The lower mol. wt. pool stimulated heme synthesis in vitro. To identify the inhibitor further, plasma lipo‐protein classes were isolated by density gradient ultracentrifugation. The very low density lipoprotein (VLDL) and chylomicron fractions markedly inhibited DNA, protein and heme synthesis. Low density and high density lipoprotein fractions were inactive. A lipoprotein inhibitor of erythropoiesis was also identified in cancerous ascitic fluid, and to a lesser degree, in normal rat plasma. We suggest that this VLDL inhibitor of marrow erythropoiesis is a contributing factor in the anaemia of cancer.
SPERMATOGONIAL CHALONE(S): EFFECT ON THE PHASES OF THE CELL CYCLE OF TYPE A SPERMATOGONIA IN THE RAT
Authors: Irons Margaret J. , Clermont Y.
Published: May 2008

Adult rats with X‐irradiated testes were used to analyze the effect of the spermatogonial chalone(s) on the phases of the cell cycle of type A spermatogonia. Twelve days after irradiation, the animals were used in two experiments designed to test the existence of hypothetical G2 and S phase chalones. For the G2 assay, rats injected twice with testicular extract (Group I), liver extract (Group II) or physiological saline (Group III) were killed 10 hr after the initial injection. Mitoses of type A, Intermediate and type B spermatogonia were counted in whole mounts of dissected seminiferous tubules. To test for an S phase inhibitor, two groups of rats were given multiple injections of either testicular extract (Group IV) or saline solution (Group V). Twenty‐two hr after the first injection they were injected with [3H]thymidine and killed 2 hr later. Silver grains over labelled type A nuclei were counted in radioautographed sections of testes from these animals. The average grain counts were identical in Groups IV and V, indicating that the testicular extract did not affect type A spermatogonia during the S phase. Counts of type A mitoses in Groups I, II and III revealed that in the animals injected with the testicular extract (Group I) the number of divisions was 50% lower than in the control groups (Groups II and III). In contrast, mitotic activity of differentiating spermatogonia (In + B) was similar in all three groups of animals. This result is attributed to a testicular chalone which specifically inhibits type A spermatogonia during the G2 phase of the cell cycle. Indirect evidence for a G1 spermatogonial chalone is also presented, as a result of an analysis of published data (Clermont & Mauger, 1974).
CELL PROLIFERATION OF CARCINOMA IN BILHARZIAL BLADDER: AN AUTORADIOGRAPHIC STUDY
Authors: Awwad H. K. , Hegazy M. , Ezzat S. , El‐Bolkainy N. , Burgers M. V.
Published: May 2008

The rate of cell production in thirty‐five cases of carcinoma in Bilharzial bladder was evaluated from the labelling index after in vitro incubation with [3H]TdR. Squamous cell carcinoma was the most frequent histological type in this series and had a median LI of 8.0% which corresponds to a potential doubling time of 5.9 days. In squamous cell tumours the LI increased with the histological grade. Transitional cell tumours had a somewhat greater LI.

In all histological types the LI was significantly greater in the deep infiltrating parts of the tumour than in the superficial parts. The discrepancy between the estimated potential doubling time and the growth rate normally attributed to such tumours suggests the existence of an extensive cell loss factor. Areas of focal or diffuse mucosal hyperplasia were associated with increased LI.
CYTOTOXIC EFFECTS OF COLCEMID OR HIGH SPECIFIC ACTIVITY TRITIATED THYMIDINE ON CLONOGENIC CELL SURVIVAL IN B6CF1 MICE
Authors: Hanson W. R. , Fry R. J. M. , Sallese A. R.
Published: May 2008

High specific activity tritiated thymidine (HSA‐[3H]TdR) and colcemid were given in cytotoxic doses and regimens to B6CF1/Anl mice. The number of cells per intestinal crypt was reduced by the S‐phase‐specific HSA‐[3H]TdR and the metaphase blocking and cytotoxic effect of multiple injections of colcemid. In 50‐day old mice, the cytotoxic effect of multiple injections of colcemid reduced both the number of cells per crypt and the clonogenic cell survival. However, the number of surviving intestinal clonogenic or stem cells, assayed by the micro‐colony technique, did not change in 110–130‐day old mice. These data suggest that most of the cells at risk from these cytotoxic agents are not clonogenic in adult 110–130‐day old mice but are the cells in amplification division. However, since the stem cells of young mice are more susceptible to colcemid, they are apparently in a more rapid cell cycle than those of older mice. The clonogenic cell survival measured in 110–130‐day old mice after a single radiation dose of 14 Gy (1400 rad) responded in a non‐linear way to increasing time of continuous colcemid cytotoxicity. These data suggest that the intestinal stem cells can respond to amplification compartment cell death by a shortening of their cell cycle and thus, over time, the number of stem cells at risk to colcemid cytotoxicity increases.
CELL PROLIFERATION KINETICS OF EPIDERMIS AND SEBACEOUS GLANDS IN RELATION TO CHALONE ACTION
Authors: Laurence Edna B. , Spargo D. J. , Thornley A. L.
Published: May 2008

Median S‐phase lengths of pinna epidermis and sebaceous glands, and of epithelia from the oesophagus and under surface of the tongue of Albino Swiss S mice were estimated by the percentage labelled mitoses method (PLM). The 18.4 and 18.8 hr for the median length of S‐phase for pinna epidermis and sebaceous glands respectively made it possible for these two tissues to be used experimentally for testing tissue specificity in chalone assay experiments. The 10.0 and 11.5 hr for oesophagus and tongue epithelium respectively made experimental design for chalone assay difficult when pinna epidermis was the target tissue.

The results of the Labelling Index measured each hour throughout a 24‐hr period showed no distinct single peaked diurnal rhythm for pinna epidermis and sebaceous glands. Instead a circadian rhythm with several small peaks occurred which would be expected if an S‐phase of approximately 18 hr was imposed on the diurnal rhythm. This indicates that there may be very little change in the rate of DNA synthesis.

The results are given for the assay in vivo of purified epidermal G1 and G2 chalones, and the 72–81% ethanol precipitate of pig skin from which they could be isolated. These experiments were performed over a time period which took into account the diurnal rhythm of activity of the mice as well as the S‐phase lengths. Extrapolating the results with time of action of the chalone shows that the G1 chalone acts at the point of entry into DNA synthesis and that the S‐phase length was approximately 17 hr for both the pinna epidermis and sebaceous glands. This may be a more correct value since the PLM method overestimates the median S‐phase length as it is known that in pinna skin the [3H]TdR is available to the tissues for 2 hr and true flash labelling does not take place. The previous reports that epidermal G1 chalone acts some hours prior to entry into S‐phase resulted from experiments on back skin where the S‐phase is shorter and there is a pronounceddiurnal rhythm which could mask the chalone effect. The epidermal G, chalone had no effect on DNA synthesis even at different times in the circadian rhythm.

Thus the circadian rhythms and S‐phase lengths of the test tissues need to be considered when experiments are performed with chalones. Ideally, the target tissues selected for cell line specificity tests should have the same cell kinetics for the easier and more accurate assessment and interpretation of results. When the tissues have markedly different cell kinetics, experimental procedures and results need to be evaluated accordingly. The point of action of G, chalone can only be assessed if the effect is measured over the peak of incorporation of 13H]TdR into DNA.

The results of the effects of skin extracts are analysed in relation to changes in the availability of i3H]TdR for the incorporation into DNA and to the possibility of there being two distinct populations of proliferating cells.
ANALYSIS OF INTESTINAL CELL PROLIFERATION AFTER GUANETHIDINE‐INDUCED SYMPATHECTOMY
Authors: Klein R. M.
Published: May 2008

Neonatal administration of guanethidine‐sulfate results in an alteration of the cell proliferative pattern of the small intestinal epithelium of the young adult rat. Sympathectomy with guanethidine has previously been shown to depress mitotic, labelling, and total cellular migration indices while increasing the generation cycle time (TC) of small intestinal crypt cells as measured by a stathmokinetic method. The present study showed that the G1, S and G2 phases of the crypt cell cycle are altered by sympathectomy, G1 accounting for most of the increase in TC. In addition, the percentage of [3H]‐thymidine labelled crypt cells is reduced and the duration of crypt cell transit is lengthened by guanethidine‐induced sympathectomy.
CELL‐PRODUCTION RATES ESTIMATED BY THE USE OF VINCRISTINE SULPHATE AND FLOW CYTOMETRY
Authors: Barfod I. H. , Barfod N. M.
Published: May 2008

A new method for the evaluation of cell production rates combining flow cytometry (FCM) and the stathmokinetic method using vineristine sulphate (VS) has been used for the analysis of three aneuploid ascites tumours at different stages of growth. Using this technique it was possible to estimate the well‐known decrease in cell production rates of ageing ascites tumours. The percentage of normal host cells in the aneuploid tumours studied was easily determined by FCM prior to the calculation of the tumour cell‐production rates. A correlation was found between the percentage of tumour cells in the S phase and the tumour cell‐production rate. This correlation is probably explained by the gradual transfer of proliferating cells in S phase to resting G1 and G2 phases with increasing tumour age.
KINETICS OF HUMAN LYMPHOCYTE RESPONSES IN VITRO: THE PHASE OF EXPONENTIAL GROWTH
Authors: Hanrahan L. R. , O'Leary J. J. , Mehta C. , Rosenberg A.
Published: May 2008

The kinetics of thymidine uptake in human peripheral lymphocytes stimulated by allogenic cells, antigen E (ragweed allergen) and a variety of mitogens can generally be divided into four consecutive phases. First, a lag period with no increase in thymidine uptake, then a short period of rapid change in uptake, followed by a log‐linear growth period and finally a decay phase. In this report we examine in detail the characteristics of the third, log‐linear growth phase. Since, as discussed in the preceding paper, thymidine uptake is proportional to the number of cells acumulating thymidine, we can calculate from the log‐linear growth period an apparent doubling time. We show that for five different stimulating agents the cells reach a log‐linear growth phase of varying length and that the doubling times show little variation. This invariance indicates that, despite possible variation in cell death and recruitment rates, the rate of proliferation is in all cases dominated by the generation time of human lymphocytes.
DYNAMIC HISTOLOGY OF A RAT HEPATOMA AND THE RESPONSE TO 5‐FLUOROURACIL*
Authors: Moore J. V. , Hopkins H. A. , Looney W. B.
Published: May 2008

The cellular response of the rat hepatoma 3924A to a single intraperitoneal injection of 5‐fluorouracil has been measured in respect of the spatial relationship of the cells to the tumour microvasculature. In this tumour the parenchyma is arranged in cords approximately 150 μm thick around central capillaries. For untreated tumours, those cells at distances less than 80 μm from the capillary had a mean [3H]TdR labelling index of 39% and a mitotic index of 2·1%, while for those cells more than 80 μm away the values were 14% and 0·8% respectively. Two days after 150 mg/kg of 5‐fluorouracil, mean cord thickness was reduced by 25% and did not recover to the control level until 11 days after treatment. This was also true for the mitotic index. Recovery of the labelling index was complete 2 days earlier. Although absolute values of parameters were different in the populations adjacent to and remote from the capillary, the time course of recovery was similar, with a ‘growth spurt’ 7 to 9 days after treatment. The results from this histologically‐based assay have been compared with those from biochemical/biophysical assays that sample the overall tumour population.
PROLIFERATION STUDIES OF THE ENDOTHELIAL AND SMOOTH MUSCLE CELLS OF THE MOUSE MESENTERY AFTER IRRADIATION
Authors: Hirst D. G. , Denekamp Juliana , Hobson B.
Published: May 2008

A continuous labelling technique was employed to study the effects of external β‐radiation on the proliferation of endothelial cells and smooth muscle cells in the mesenteric arterioles of mice. Labelled and non‐labelled cells of either type were determined by autoradiographic techniques in control animals and at different times (3, 12 and 48 weeks) after single doses of 20 and 45 Gy (2000 and 4500 rads). The fraction of cells labelled, even after 7 days of repeated injections was very low in all instances.

Calculations showed very long turnover times for the two cell populations in control animals (>2 years for endothelium and >3 years for smooth muscle). After 20 and 45 Gy, no significant increase in endothelial proliferation was seen except at 3 weeks. No significant increase in labelling was observed in smooth muscle at any time after irradiation.

These labelling data have been compared with the pattern of cell depletion of the irradiated endothelium. It was concluded that the depletion was much earlier than expected for a slowly proliferating tissue, if all the cells were cycling very slowly. Such an early depletion is, however, consistent with cell death resulting from a small proportion of the cells having a short cell cycle. The recovery of the endothelial cell numbers between 9 and 12 months was not accompanied by a rise in the fraction of labelled cells. It is suggested that repopulation may occur from outside the treated area.
ANALYSIS OF INTESTINAL CELL PROLIFERATION AFTER GUANETHIDINE‐INDUCED SYMPATHECTOMY
Authors: Klein R. M.
Published: May 2008

Rats were treated with guanethidine‐sulphate every 48 hr from birth until 15 days and then maintained until young adulthood. Sympathectomy was verified by dissection and light microscopic preparation of the superior cervical and coeliac ganglia which showed at least a 78% reduction in the number of perikarya. The effect of the chemical sympathectomy was a decrease in the amplitude of the circadian mitotic rhythm from 44·7 to 27·1%, 67·0 to 25·3% and 54·9 to 24·7%, in the duodenum, jejunum, and ileum, respectively. The shape of the mitotic index curve was altered and the mean mitotic index was significantly decreased (P < 0·01) in all three segments of the small intestine. The mean mitotic index of control intestinal epithelium was 3·2 ± 0·1%, 3·6 ± 0·1% and 4·0 ± 0·1% in the duodenum, jejunum, and ileum, respectively, and 2·3 ± 0·1%, 2·4 ± 0·1%, and 2·5 ± 0·1% in guanethidine‐treated rats. Stathmokinetic estimates of cycle time were obtained by use of the metaphase arrest agent, colchicine. The longest cell generation cycle time (Tc) and lowest mitotic index occurred between 12.00 and 16.00 hours and the shortest Tc and highest mitotic index occurred between 00.00 and 04.00 hours, in all three segments of the small intestine. Guanethidine‐treatment lengthens Tc throughout the small intestinal epithelium and reduces the range of variation in Tc over a 24‐hr period. It is suggested that norepinephrine depletion induced by guanethidine may be the cause of the inhibition in circadian periodicity and that norepinephrine and the sympathetic nervous system may be essential for the maintenance of circadian rhythms in mitotic activity.
COMPARISON OF DNA RENEWAL IN GERM‐FREE AND CONVENTIONAL MICE USING [125I]IODODEOXYURIDINE AND [3H]THYMIDINE
Authors: Webb P. , Chanana A. D. , Cronkite E. P. , Laissue J. A. , Joel D. D.
Published: May 2008

Germ‐free (GF) and conventional (CV) C3H mice received a single injection of 1 μCi [3H]thymidine and 3 μCi [125I]iododeoxyuridine to provide simultaneous labeling of DNA with the two precursors. Thymus, spleen, mesenteric lymph nodes, bone marrow (femora), small intestine, colon and skin were examined for total organ activity and rate of DNA renewal 1–8 days after injection. Precursor incorporation, assayed on day 1, was lower in the thymus, mesenteric lymph nodes and femora (and, to a lesser extent, in the spleen and colon) of GF mice as compared to CV animals. The opposite was observed in the small intestine and skin, i.e. total organ activity was higher in GF animals. Differences in precursor incorporation were partly due to differences in organ weights between the two groups of mice.

In comparison to CV animals, DNA renewal rates were diminished in the mesenteric lymph nodes, bone marrow, colon (following a 3‐day plateau) and spleen of GF mice. Little, if any, difference was observed between the two groups with respect to the rate of DNA turnover in the thymus and skin. Radioactivity of the small intestine remained constant for 2 days. Thereafter intestinal activity in GF mice declined at an initial slow rate between days 2 and 5 followed by a rapid decrease between days 5 and 8. In CV mice the first phase of activity loss was short with the rapid decline in intestinal activity beginning on day 3.

From the slopes of the regression lines, the percentage thymidine reutilization was estimated. Reutilization varied from 0 to 63% in the various organs examined, with the greatest difference between GF and CV mice occurring in the mesenteric lymph nodes.
VARIABILITY OF SHORT‐TERM CULTURES OF HeLa S‐3 CELLS: CHANGES IN DNA DISTRIBUTIONS AND RATES OF DNA SYNTHESIS
Authors: Collins J. M. , Berry D. E. , Bagwell C. B.
Published: May 2008

DNA distributions of HeLa S‐3 cells in spinner culture exhibit significant time—dependent changes. The major differences appear to occur in the S‐phase region. Significant changes in the rates of DNA synthesis in several S‐phase subcompartments correlated well with the changes in the DNA distributions. It is proposed that fluctuations in these rates of DNA synthesis are a reflection of the inherent instability of these abnormal, heteroploid cells.
THE EFFECT OF PARTIAL BODY IRRADIATION ON HAEMOPOIETIC STEM CELL MIGRATION
Authors: Croizat H. , Frindel E. , Tubiana M.
Published: May 2008

Data obtained after various types of partial body irradiation support the concept of a small rapidly exchangeable pool of CFUs, which seems to be exhausted rapidly after irradiation. The depletion of this pool is the most plausible explanation for the decrease in stem cell migration observed 3 hr after exposure in C3H mice. After partial body irradiation the size of the rapidly mobilizable pool is reduced in proportion to the areas of bone marrow irradiated. When only one marrow area is shielded, the recovery of this pool does not occur during the first 24 hr after exposure.
DETERMINING THE LABELING INDEX IN AUTORADIOGRAPHY
Authors: Schoenfeld D. , Kallman R. F.
Published: May 2008

A method is proposed for estimating the labeling index in autoradiographs. It is based on a model for the frequency distribution of grain counts for those cells which have few grains. The method does not require extensive grain counting and provides reasonable estimates even when the background level is high. It is particularly suited for experiments where tumor cells, labeled in vivo, are, autoradiographed after being cultured in vitro.
PERITONEAL EXUDATE MONONUCLEAR PHAGOCYTE COLONY‐FORMING CELLS: THEIR PROLIFERATIVE STATE IN VIVO AND SENSITIVITY TO CYTOTOXIC AGENTS
Authors: Lin H.‐S.
Published: May 2008

We investigated the proliferative state of peritoneal exudate macrophage colony‐forming cells (PE‐CFC) by exposing them to [3H]thymidine with a high specific activity in vitro and by administering cytosine arabinoside and methotrexate in vivo. Since [3H]TdR had no appreciable killing effect on PE‐CFC and since the drug treatment caused no reduction in the appearance of PE‐CFC, we concluded that the majority of PE‐CFC, if not all, are not in active cell cycle. The production of PE‐CFC was, however, suppressed by the administration of nitrogen mustard, cyclophosphamide, BCNU and vinblastine.