bluuebunny/crossref_metadata_2025 huggingface dataset:
RECYCLING OF RESTING CELLS IN THE JB‐1 ASCITES TUMOUR AFTER TREATMENT WITH 1‐β‐D‐ARABINOFURANOSYLCYTOSINE (Ara‐C)
Authors: DOMBERNOWSKY P. , BlCHEL P.
Published: May 2008

Resting cells in tumours present a major problem in cancer chemotherapy.

In the plateau phase of growth of the murine JB‐1 ascites tumour (i.e. 10 days after 2–5 × 106 cells i.p.) large fractions of non‐cycling cells with G1 and G2 DNA content (Q1 and Q2 cells) are present, and the fate of these resting cells was investigated after treatment with l‐β‐d‐arabinofuranosylcytosine (Ara‐C).

The experimental work consisted of growth curves, percentage of labelled mitoses curves after continuous labelling with 3H‐TdR, and cytophotometric determination of single‐cell DNA content in unlabelled tumour cells.

Treatment with an i.p. single injection of Ara‐C 200 mg/kg in the plateau JB‐1 tumour resulted in a significant reduction in the number of tumour cells 1 and 2 days later as compared with untreated controls, while no difference in the number of tumour cells was observed after 3 days. In tumours prelabelled with 3H‐TdR 24 hr before Ara‐C treatment, a significant decrease in the percentage of labelled mitoses was observed 6–8 hr later followed by a return to the initial value after 12 hr, and a new pronounced fall from 20 hr after Ara‐C. The second fall in the percentage of labelled mitoses disappeared when the labelling with 3H‐TdR was continued also after Ara‐C treatment. Cytophotometry of unlabelled tumour cells prelabelled for 24 hr with 3H‐TdR before Ara‐C treatment showed 20 hr after Ara‐C a pronounced decrease in the fraction of Qt cells paralleled by an increase in the fraction of unlabelled cells with S DNA content.

These results indicate recycling of resting cells first with G2 and later with Gx DNA content, which contribute to the regrowth of the tumours.
CHANGES IN THE PROLIFERATION RATE OF MOUSE EPIDERMIS AFTER IRRADIATION: CONTINUOUS LABELLING STUDIES
Authors: Denekamp J. , Stewart F. A. , Douglas B. G.
Published: May 2008

The proliferative response of mouse skin to damage caused by X‐irradiation has been tested by giving repeated injections of tritiated thymidine and scoring the percentage of labelled cells in high resolution autoradiographs. Four, nine and fourteen daily fractions of 300 rads of X‐rays were used and labelling commenced 4 days after the last fraction. The epidermis of the upper surface and the sole of the foot were scored separately and were compared with the skin of unirradiated feet.

In unirradiated skin the proliferation rate of the basal layer cells is more rapid on the sole than on the upper surface. The cell cycle times deduced from continuous labelling curves were 81 hr and 111 hr respectively and the growth fractions were 97% and 85%.

After irradiation with small daily doses the homeostatic response to cell killing was slow. More rapid proliferation occurred after nine fractions in the sole, but was not apparent in the skin of the upper surface until fourteen fractions had been given. After fourteen fractions the cell cycle time was about 24 hr on both surfaces and the growth fraction was about 90%. The initial labelling index after a single thymidine injection was a poor measure of proliferation rate. The delay in the time of onset of faster proliferation is similar, both qualitatively and quantitatively, to that measured previously from the additional dose increments needed if large doses were given at different times after the multifraction treatments (Denekamp, 1973).
FETAL HEMOPOIESIS IN DIFFUSION CHAMBER CULTURES
Authors: Symann Michel , Fontebuoni Anna , Quesenberry Peter , Howard Donald , Stohlman Frederick
Published: May 2008

The growth pattern of fetal liver (FL), normal adult bone marrow (NABM) and regenerating (post Velban treatment) adult bone marrow (RABM) colony forming units (CFU) cultured in diffusion chambers (DC) was studied. When twenty CFU were implanted into DC the recovery of CFU after 4 days with FL, NABM or RABM was 133 ± 7, 19 + 2 and 34 ± 2 CFU, respectively. The transplantation fraction of CFU from NABM decreased from 10‐4% on day 0 to 6–9 % on day 4; that of FL did not change from the initial 6‐2%. The growth rate of CFU derived from FL was substantially greater than that from NABM. The relative growth of FL and RABM CFU was clearly inhibited when the concentration of cells cultured was increased. Spleen colonies from FL cells before culture were larger (P < 0–005) than colonies from NABM but after 7 days of culture there was no difference between the two groups. Histological examination of spleen colonies showed that after DC culture FL and NABM CFU were differentiating along the three normal pathways. These data suggest that intrinsic differences exist between fetal and adult stem cells in the in vivo diffusion chamber culture system.
SOME EFFECTS OF BLEOMYCIN ON THE PROLIFERATION, MATURATION TIME and PROTEIN SYNTHESIS OF HAIRLESS MOUSE EPIDERMIS
Authors: Iversen Olav H. , Clausen Ole P. F. , Iversen Ulla M. , Rohrbach Rolf
Published: May 2008

Hairless mice were given 2 mg Bleomycin i.p. in 1‐0 ml saline on two successive days. By a stathmokinetic method, by micro‐flow fluorometry and by autoradiography certain kinetic parameters were measured during 10 days after the last injection. Cell counts were made and the turnover time of the differentiating cells estimated. Protein synthesis was estimated by the uptake of radioactive histidine, and dry cell mass measured by weighing. Bleomycin affected cell proliferation in the epidermis by depressing biphasically both the number of cells in, and the passage of cells through, the cell cycle phases: S, G2 and M, most probably by directly affecting late Gj cells and cells in mitosis. The time between the two minima of depressed DNA synthesis corresponded to the mean generation time of the basal cells. Histidine uptake and dry cell mass were slightly affected, but the turnover time of the differentiating cells was prolonged.

Bleomycin thus had a strong long‐lasting inhibitory effect on epidermal cell proliferation and a marked inhibitory effect on epidermal cell maturation in mice.
MODE OF GROWTH OF THE JEJUNAL CRYPT CELLS OF THE RAT: AN AUTORADIOGRAPHIC STUDY USING DOUBLE LABELLING WITH 3H‐ AND 14C‐THYMIDINE IN LOWER AND UPPER PARTS OF CRYPTS
Authors: Burholt Dennis R. , Schultze Brigitte , Maurer Werner
Published: May 2008

The frequency distribution of cells through the mitotic cycle in lower and upper portions of jejunal crypts of the rat was examined by the 3H‐14C‐thymidine double labelling technique. Isolated crypts were cut perpendicular to the longitudinal axis so that the percentage of cells in the lower portion varied from 16 to 74 %. The lower and upper portion of the same crypt were squashed separately on one microscope slide and the number of 3H‐ and 14C‐only labelled cells were scored to determine the flow rate into and out of S for the two portions. The mitotic cycle and its phases of the crypt epithelial cells were also determined.

For lower portions of crypts which contained less than 40 % of the total cell number in that crypt the flow rate into S was about 1–7 times that of the flow rate out of S indicating that nearly every mitosis in this region produced two proliferative daughter cells. As the proportion of cells in the lower part of the crypt increased the quotient of the flow rate into S divided by the flow rate out of S decreased, and approached the steady state value of 1 0 in lower portions containing 60–74 % of the cells. For upper portions of crypts which contained less than 40% of the total crypt cells the flow rate into S was about 0 2 times that of the flow rate out of S, indicating that in this region mitoses predominantly produced non‐proliferative daughter cells. The results obtained were in good agreement with the model of crypt cell proliferation proposed by Cairnie, Lamerton & Steel (1965b).
STUDY OF CELL DEATH IN FRIEND LEUKAEMIA
Authors: Smadja‐Joffe F. , Klein B. , Kerdiles C. , Feinendegen L. , Jasmin C.
Published: May 2008

Cell death of splenic Friend leukaemic cells has been studied in vivo, using 125I‐UdR and 3H‐TdR pulse labelling. The evolution of the splenic specific activity has been measured by autoradiography and external counting during 40 hr after injection of the labelled precursor. These two techniques show the existence of a large reutilization of 3H‐TdR (50%), which is measurable as soon as 7 hr after the injection. The DNA turnover rate is rapid, 83‐8 % of the splenic cellular DNA being renewed per day. These results confirm that most of the cells produced in the Friend leukaemic spleen are rapidly lost; they also demonstrate that this cell loss is mainly due to a massive death, which occurs in proerythroblastic and erythroblastic compartments after one or two cell divisions.

Friend leukaemic cells, which are characterized by a limited capacity of proliferation and a short lifespan, do not appear to be malignant.
DNA TURNOVER AND THYMIDINE RE‐UTILIZATION IN MOUSE TISSUES
Authors: Myers D. K. , Feinendegen L. E.
Published: May 2008

Mice were injected intravenously with tritiated thymidine (TdR) and 125I‐labeled iododeoxyuridine (IUdR) in low doses to provide a simultaneous labeling of tissue DNA with non‐toxic amounts of these two precursors. The total activity per organ and the ratio of the two isotopes was measured in the DNA at various times between 1 and 15 days after the injection. Since TdR from dying cells is re‐utilized more efficiently than IUdR from the same cells, more labeled TdR than IUdR was retained in the tissue DNA in these experiments. From the slopes of the regression lines, the true rate of turnover of replicating tissue DNA and the per cent re‐utilization of TdR were calculated. Re‐utilization of TdR varied from 37 to 60 % in the six tissues examined.
THE INFLUENCE OF DIETARY PROTEIN DEFICIENCY ON HAEMOPOIETIC CELLS IN THE MOUSE
Authors: Bell R. G. , Hazell L. A. , Sheridan J. W.
Published: May 2008

These experiments examined the effect of a diet limited only in protein (4% by weight) on haemopoietic stem cells in mice. This diet places severe restrictions on growth and cell proliferation and this was reflected in lower numbers of colony forming units (CFUs) and in vitro colony forming cells (CFCs). Differences were apparent in the response of different organs to this stress; for instance, the incidence of spleen CFUs fell sharply from around 40/mg spleen tissue to 1 ‐4/mg spleen tissue after 3 weeks on a low protein diet. This selective loss did not occur in bone marrow where total CFUs remained proportional to cellular content. Yet a third pattern was shown by thymus CFUs–although the numbers were low these increased from 16/thymus in normal mice to 132/thymus in deprived mice. This was the only organ examined which showed an increase.

The effects of a return to a high protein (18 %) diet showed that the spleen was the most responsive organ. By day 5 after the return to 18% protein the spleen contained as many CFUs per million cells as the bone marrow. During this time the content of CFU in the spleen had increased some 50‐fold whereas bone marrow CFUs only doubled. The spleen assumes the major reconstitutive role during the refeeding process.
THE MIGRATION OF LYMPHOCYTES ACROSS SPECIALIZED VASCULAR ENDOTHELIUM
Authors: Ford W. L. , Sedgley M. , Sparshott S. M. , Smith M. E.
Published: May 2008

Lymphocytes were exposed in vitro to either trypsin or neuraminidase. The ability of the treated cells to migrate into tissues was measured (a) by i.v. injection into intact recipients and (b) by vascular perfusion through an isolated lymph‐node preparation. The localization of trypsinized cells in the lymph‐nodes of recipients was deficient when compared to untreated lymphocytes and there was a surplus of trypsinized cells in the blood. Trypsinized cells migrated into the isolated nodes in reduced numbers. By contrast, neuraminidase treated lymphocytes were markedly deficient in the blood of recipients early after injection; their localization in the spleen and lymph‐nodes was also deficient but they were in surplus in the liver. Moreover they migrated into the isolated nodes in slightly increased numbers. By 24 hr after injection the perturbed localization pattern produced by either enzyme was partly restored to normal. In conclusion, trypsin interfered with the capacity of lymphocytes to migrate into lymph‐nodes but neuraminidase did not; the latter promoted the hepatic sequestration of cells and the reduced localization in the blood and tissues was a consequence of this. The hypothesis that lymphocytes adhere to specialized endothelia in lymph‐nodes because of specific glycoside sequences on their surface lacks experimental support.
THE EFFECTS OF COLCEMID ON MOUSE BONE MARROW
Authors: Shackney Stanley E. , Bunn Paul A. , Ford Sharon S.
Published: May 2008

Following Colcemid administration, mitoses accumulate preferentially in the subendosteal region of the bone marrow of the mouse. This finding suggests that the most rapidly proliferating cells are localized to the subendosteal region, and complements previous radioautographic studies which have demonstrated a corresponding labelling gradient in the marrow. Quantitative estimates of cell cycle time by the stathmokinetic method were precluded by the presence of significant Colcemid induced interphase cell loss. Colcemid also affected cell differentiation in the marrow. Following Colcemid administration there was a fall in mature granulocytes in the marrow, and a concommitant rise in marrow megakaryocytes.
CELL CYCLE KINETICS IN AN IN VITRO TUMOR MODEL
Authors: Durand RalphE.
Published: May 2008

Cell cycle kinetic parameters of multicell spheroids in vitro have been estimated using thymidine labeling techniques and autoradiography. Both the mitotic index and thymidine labeling index decreased in larger spheroids, whereas the duration of the cell cycle, as determined by two independent methods utilizing labeled mitoses or labeled cells, was essentially independent of spheroid size or age. These results suggest that the tumor‐like growth exhibited by spheroids is the result of a decreasing growth fraction and a large apparent cell loss, rather than a general elongation of the cell cycle.
INNER ENAMEL EPITHELIUM CELL PRODUCTION RATES
Authors: Bar‐Lev Moshe , Zajicek Gershom , Michaeli Yael , Weinreb Max M.
Published: May 2008

Crowning of all four rat incisors slows down their eruption rate, leading to a diminution of cell production by the inner enamel epithelium (IEE). The production rate by 100 progenitor cells is dominated as production rate %. The normal IEE in rats weighing 200 g produces daily 67 cells %. In the crowned incisor this rate drops to 15 cells % while during accelerated eruption the IEE produces daily 152 cells %. In all three conditions the ratio between eruption rate and IEE cell production rate remains unchanged and an eruption of 6.4 μm reflects a production of 1 cell % by the IEE.

A method which relates labelled cell displacement along the IEE with its cell production rate is described and its applicability to other cell renewal systems discussed.
HYDROXYUREA: USE IN DETERMINING THE DURATION OF G2 IN TETRAHYMENA
Authors: WORTHINGTON D. H. , NACHTWEY D. S.
Published: May 2008

Observation of division of individual cells in microdrops, plus autoradiographic studies using tritiated thymidine and standard cell cycle analysis techniques, reveal that hydroxyurea (10 DIM) reversibly arrests the normal progression of exponentially growing Tetrahymena pyriformis through the initial 92 % of S‐phase while not affecting cells in the terminal 8 % and in G2 and division. Thus the fraction of the population of cells that is in G2 can be approximately determined by the fraction of the population able to divide in the presence of hydroxyurea. This fraction can be related to the approximate duration of G2 by calculations which compensate for the age gradient.
AUTORADIOGRAPHIC STUDY OF TYPE II‐CELL HYPERPLASIA IN LUNGS OF MICE CHRONICALL EXPOSED TO URETHANE
Authors: Kauffman Shirley L.
Published: May 2008

Hyperplasia of pulmonary alveolar epithelium was induced by exposure of adult mice to 0–1% urethane in drinking water, and their lungs were analysed using combined autoradiographic and morphometric methods. The response of pulmonary epithelium showed three phases: an initial one of 3 weeks in which the number of type II cells was consistently low and, after a transient decrease in 3H‐thymidine labeling index, the latter steadily increased. Degenerating or dead type II cells were found, consequently this period was considered one in which cell death was disproportionately increased over cell production. Between the 3rd and 6th weeks the number of type II cells doubled, and thereafter increased at a slower rate. The 3H‐thymidine labeling index reached its peak at 6 weeks. The third phase was marked by a decline in labeling index which returned to near‐normal levels by the 16th week. The number of type II cells declined slowly after the 10th week and was still elevated at the end of the observation period. Tumors consisting of type II cells continued to arise even during the period of declining labeling index.

The dissociation between the proliferative response which was reversible, and the neoplastic response which was not, supports the assumption that the major part of the observed population growth or hyperplasia induced by urethane was a form of regeneration repair secondary to cell death and may be unrelated to tumor growth.
A STABLE ISOTOPE METHOD FOR MEASUREMENT OF THYMIDINE INCORPORATION INTO DNA
Authors: Heck Henry d'A. , McReynolds James H. , Anbar Michael
Published: May 2008

A method has been developed for the measurement of DNA synthesis in vivo using the incorporation of multilabeled, non‐radioactive thymidine. Simultaneous intraperitoneal injection of hexalabeled thymidine and tritiated thymidine into a normal adult rat resulted in the incorporation of both labeled nucleosides into the DNA of cells undergoing replication. The DNA of several tissues and organs was analysed, including liver, thymus, spleen, bone marrow, and small intestine. Following extraction with hot trichloroacetic acid, acid hydrolysis, and thin‐layer chromatography of the hydrolysates, the isotopic compositions of the thymine products were determined by field ionization mass spectrometry and by scintillation counting. The relative incorporation of radioactive and stable isotope‐labeled thymidine was similar in all tissues, and corresponded to the ratio of the two labeled nucleosides in the injected material. These results indicate the feasibility of utilizing thymidine multilabeled with stable isotopes for measurement of cellular proliferation rates in conjunction with cancer therapy.
THE APPLICATION OF AGE DISTRIBUTION THEORY IN THE ANALYSIS OF CYTOFLUORIMETRIC DNA HISTOGRAM DATA
Authors: Watson James V.
Published: May 2008

Age distribution theory has been employed in a model to analyse a variety of histograms of the DNA content of single cells in samples from experimental tumours growing in tissue culture. The method has produced satisfactory correspondence with the experimental data in which there was a wide variation in the proportions of cells in the intermitotic phases, and generally good agreement between the 3H‐thymidine labelling index and the computed proportion in S phase. The model has the capacity to analyse data from populations which contain a proportion of non‐cycling cells. However, it is concluded that reliable results for the growth fraction and also for the relative durations of the intermitotic phase times cannot be obtained for the data reported here from the DNA histograms alone. To obtain reliable estimates of the growth fraction the relative durations of the phase times must be known, and conversely, reliable estimates of the relative phase durations can only be obtained if the growth fraction is known.
CYTOKINETICS OF RAT TRACHEAL EPITHELIUM STIMULATED BY MECHANICAL TRAUMA
Authors: Gordon Ronald E. , Lane Bernard P.
Published: May 2008

Mild abrasion of rat tracheal epithelium results in irreversible damage to the superficial cells and stimulates the viable basal cells to participate in a nearly synchronous wave of DNA synthesis and mitosis. For the growth population as a whole, DNA synthesis started at 14 hr after injury and persisted for 16 hr. The duration of S in individual cells was determined autoradiographically by identifying the time at which a second pulse of DNA precursor (14C‐TdR) was no longer incorporated by cells labelled with 3H‐TdR at the onset of S. S was found to be 8–9 hr long. It was also determined that cells entering S at later times synthesized DNA for the same 8–9 hr period. TG2 was calculated to be 21/2–31/2 hr by subtraction of Ts and 1/2TM from the period from onset of DNA synthesis to metaphase. By making a second denuding lesion adjacent to the first injury, the cells were stimulated through at least another period of S. At the peak of the second wave of DNA synthesis (50 hr after injury) 14C‐TdR was present in the same cells which had incorporated 3H‐TdR administered at the mid‐point of the preceding synthetic phase. The 28‐hr interval between these two peaks of synthesis is the measure of cell cycle duration for these regenerating tracheal epithelial cells.
FASTING AND REFEEDING: CELL KINETIC RESPONSE OF JEJUNUM, ILEUM AND COLON
Authors: Hagemann Ronald F. , Stragand James J.
Published: May 2008

Following a period of fasting, feeding a normal diet results in a burst of DNA synthesis in the crypts of the colonic epithelium. This is due largely to a prompt entry of cells, blocked in G1, into S. Peak levels of S cellularity exceed 4 times the fasting, and 2 times the normal fed, control values. Refeeding a low residue diet (soluble casein, glucose and corn oil) results in a return to control levels of proliferative activity, but no hyperplasia.

However, in jejunum and ileum, refeeding is followed by a return to near control levels of proliferation with only a slight overshoot in S phase cellularity.

During the fasting period, the ileal crypt proliferative compartment (Pc‐zone) and total crypt cellularity decline significantly. These changes are accompanied by an increase in the total cycle time, due to an equivalent lengthening of the G1 and S phases. Following refeeding, there is a reduction in the cycle time and a gradual return to the control values for the Pc‐zone size and cellularity.

In the colon, fasting has no effect on the Pc‐zone size or total crypt cellularity. There is an approximate doubling of the cycle time due solely to an increase in G1. Following refeeding there is an increase in the Pc‐zone size and crypt cellularity and a marked shortening of the cycle time.

Evidence that a G1 cycle blockade is induced in the colon by fasting is given by a lengthening of the G1 period and by stathmokinetic studies employing vincristine.
PROLIFERATION OF ERYTHROID AND GRANULOCYTE PROGENITORS IN THE SPLEEN AS A FUNCTION OF STEM CELL DOSE
Authors: Hasthorpe S. , Hodgson G.
Published: May 2008

A study of the kinetics of cellular proliferation, in the morphologically unrecognizable haemopoietic progenitor cell compartment, as a function of injected CFU‐S dose has been carried out in the spleens of lethally X‐irradiated mice using 3H‐TdR labelling. Amplification in this proliferating cell compartment was observed to decline as CFU‐S dose increased. The number of divisions in the differentiated line arising from CFU‐S up to the first appearance of recognizable erythroid precursors were calculated to be 9.2, 12.5, 15 and 17 for the 2, 0.35, 0.05 and 0.007 femur equivalent doses respectively. The growth of cell populations arising from CFU‐S was biphasic, with a rapid initial phase having a doubling time of about 6.3 hr, and a slow phase of doubling time around 1 day. Analysis of the rapid phase by the FLM method gave a cycle time of 5.6 hr. Recognizable labelled erythroid precursors were detected at the same time as, or just after, the change in slope of the growth curve. Significant numbers of proliferating (labelled) granulocytes only appeared in the spleens of animals receiving the higher marrow doses (2 and 0.35 femur). The erythroid to granulocyte ratio was also a decreasing function of marrow dose.
FATE OF THYMOCYTES: STUDIES WITH 125I‐IODODEOXYURIDINE AND 3H‐THYMIDINE IN MICE
Authors: Joel D. D. , Chanana A. D. , Cottier H. , Cronkite E. P. , Laissue J. A.
Published: May 2008

Cortical thymocytes of young adult mice were labeled in situ with radioactive DNA precursors. As a result of cell emigration and cell death, total thymic radioactivity decreased within 8 days to 10% or less of that present on day 1. Accumulation of thymic migrants in peripheral lymphoid organs was estimated by computing the net thymus‐derived radioactivity in these tissues. Thymic cell death was assessed by comparing values obtained with 125I‐UdR to those acquired with 3H‐TdR. The results indicate that cortical thymocytes migrate to the spleen, mesenteric lymph node, femurs and intestine; nevertheless, only a small fraction of the activity originally present in the thymus was recovered in these organs; the vast majority of newly formed cortical thymocytes apparently die after a relatively short life span. Exclusive of the fraction which dies in situ, evidence for thymocyte death is seen in bone marrow; however, most migrants appear to terminate in the intestine.
NUCLEIC ACID CONTENT OF HeLa S3 CELLS DURING THE CELL CYCLE: VARIATIONS BETWEEN CYCLES
Authors: Thilly W. G. , Arkin D. I. , Wogan G. N.
Published: May 2008

The process of continuous resynchronization with excess thymidine provides sufficient cell material for accurate chemical determination of DNA and RNA in HeLa S3 cells at hourly intervals during the cell cycle. Total DNA is constant during the non‐S phase portion of the cell cycle but varies widely among cycles of synchronous growth. Total cellular RNA content increases linearly in the G1 phase and accelerates to a higher linear rate of accumulation, which remains constant during most of the S and G2 phases. The ratios of early and late cycle rates of RNA accumulation are not constant among cycles.
PROPERTIES OF THE H‐4‐II‐E TUMOR CELL SYSTEM
Authors: Evans M. J. , Kovacs C. J.
Published: May 2008

Growth and cell proliferation kinetics of hepatoma H‐4‐II‐E and its tissue culture derivative have been studied to establish the characteristics of an in vivo—in vitro solid tumor model. The H‐4‐II‐E line, originating from the Reuber H‐35 hepatoma, can be maintained and studied either in cell culture or as a transplantable solid tumor in ACI male rats. In addition it allows for the in vitro assay of cell survival following treatment of animal tumors in situ. In vivo, hepatoma H‐4‐II‐E is a rapidly growing tumor with a mean doubling time of 49.2 hr. The cell cycle time is 39.1 hr with a cell loss factor of 0.32. Retrospective examination of tumor specimens obtained during the establishment of the H‐4‐II‐E tumor system demonstrates that both structural as well as cell population changes have occurred. The biological characteristics of the primary tumor (H‐35) and an early intermediate stage (H‐35tc2) are compared with H‐4‐II‐E and the histopathological, growth and cell kinetic changes are discussed.
METHODS FOR DETERMINING THE PROLIFERATION KINETICS OF CELLS BY MEANS OF 5‐BROMODEOXYURIDINE
Authors: Pera F. , Mattias P. , Detzer K.
Published: May 2008

After treatment of cells with 5‐bromodeoxyuridine (BUdR), the percentage of completely BUdR‐labelled interphase nuclei is greater the longer the BUdR treatment. The labelling effect is visible after staining with the fluorochrome 33258 Hoechst and with Giemsa. Various formulae and a nomogram are presented by means of which the percentage of cells in S period, duration of the S period and the whole cell cycle can be determined by examination of a single preparation or by comparison of several preparations. The methods are tested using cell cultures of Microtus agrestis and compared with autoradiographic methods after labelling with 3H‐thymidine.
THE ROLE OF ERYTHROPOIETIN IN REGULATION OF POPULATION SIZE AND CELL CYCLING OF EARLY AND LATE ERYTHROID PRECURSORS IN MOUSE BONE MARROW
Authors: Iscove N. N.
Published: May 2008

This study was designed to determine the stage in haemopoietic cell differentiation from multipotential stem cells at which erythropoietin becomes physiologically important. The responses of haemopoietic precursor cells were monitored in the bone marrow of mice under conditions of high (after bleeding) and low (after hypertransfusion) ambient erythropoietin levels. The number of relatively mature erythroid precursors (CFU‐E), detected by erythroid colony formation after 2 days of culture, increased three‐fold in marrow by the fourth day after bleeding, and decreased three‐fold after hypertransfusion. Assessed by sensitivity to killing by a brief exposure to tritiated thymidine (3H‐TdR) in vitro, the proliferative activity of CFU‐E was high (75% kill) in untreated and bled animals, and was slightly lower (60% kill) after hypertransfusion. The responses of more primitive erythroid progenitors (BFU‐E), detected by erythroid colony formation after 10 days in culture, presented a contrasting pattern. After hypertransfusion they increased slightly, while little change was noted until the fourth day after bleeding, when they decreased in the marrow. The same response pattern was observed for the progenitors (CFU‐C) detected by granulocyte/macrophage colony formation in culture. The sensitivity of BFU‐E to 3H‐TdR was normally 30%, and neither increased after bleeding nor decreased after hypertransfusion. However, in regenerating marrow the 3H‐TdR sensitivity of BFU‐E increased to 63%, and this increase was not affected by hypertransfusion. These results are interpreted as indicating (1) that physiological levels of erythropoietin do not influence the decision by multipotential haemopoietic stem cells to differentiate along the erythroid pathway as opposed to the granulocyte/macrophage pathway; (2) that early erythroid‐committed progenitors themselves do not respond to these levels of erythropoietin, but rather are subject to regulation by erythropoietin‐independent mechanisms; and (3) that physiological regulation by erythropoietin commences in cells at a stage of maturation intermediate between BFU‐E and CFU‐E.
THE EFFECT OF E TYPE PROSTAGLANDINS ON THE PROLIFERATION OF HAEMOPOIETIC STEM CELLS IN VIVO
Authors: Gidȧli J. , Fehėr I.
Published: May 2008

The ability of protaglandins E1 and E2 to stimulate the proliferation of haemopoietic stem cells (CFUs) was studied in vivo. PGE2, in a dose range of 10‐4 to 10‐1μg/g body weight and PGE1 in a dose range of 10‐5 to 10‐1μg/g body weight, produced a rapid cycling wave of CFUs. The increase in the number of CFUs in S phase was not followed by a rise in the femoral CFUs content, and except for a transient increase in femoral CFUc level, no increase in differentiation was found either. Therefore, it is proposed that haemopoiesis after PG‐induced CFU stimulation is ineffective. PGE2 did not stimulate regeneration of CFUs in a perturbed state (after sublethal irradiation). All these findings support the idea that PGEs might represent potent stimulators of the haemopoietic stem cells acting in physiological doses. However, if acting concurrently with physiological control systems PGs lead to ineffective haemopoiesis (under normal conditions) or do not exert any measurable effect (after sublethal irradiation).
THE EFFECT OF TRANSPOSITION TO JEJUNUM ON EPITHELIAL CELL KINETICS IN AN ILEAL SEGMENT
Authors: Rijke R. P. C. , Hanson W. R. , Plaisier H. M.
Published: May 2008

Epithelial cell kinetics were studied in an ileal segment after transposition to proximal jejunum. The number of cells per villus column in the transposed ileum increased after 4‐7 days to reach values normal for jejunum after 14‐30 days. This increase was accompanied by a simultaneous increase in the number of cells per crypt column up to 130% of values in jejunum and ileum in situ. The percentage of labelled crypt cells, after labelling with 3H‐thymidine, and the relative size of the proliferative cell compartment in the crypt in the transposed ileum did not differ from values in the ileum in situ at any time interval after surgery. The total proliferative activity per crypt, which was determined by scintillation counting of isolated crypts after 3H‐thymidine labelling, increased two‐fold from 7 days after surgery. Cell migration studies showed that the increase in the number of villus cells was probably not caused by a change in the life span of the epithelial cells. It seems that the increase in the number of villus cells in ileal epithelium after transposition to proximal jejunum is brought about by an enlargement of the crypt, while the relative size of the proliferative cell compartment in the crypt remains unchanged.
CELL CYCLE CHARACTERISTICS OF SYNCHRONIZED AND ASYNCHRONOUS POPULATIONS OF HUMAN CELLS AND EFFECT OF COOLING OF SELECTED MITOTIC CELLS
Authors: Pettersen E. O. , Bakke O. , Lindmo T. , Oftebro R.
Published: May 2008

The method of synchronizing cells by means of mitotic selection has been adapted to the human line NHIK 3025. Increase in cell number as a function of time in asynchronous and synchronous populations was studied as well as mitotic index as a function of time after selection of synchronized populations. Phase durations of the cell cycle of synchronous populations were determined by 3 H‐thymidine incorporation and scintillation counting. The relative phase durations of exponentially growing asynchronous populations were determined by mathematical analysis of DNA‐histograms recorded by flow cytofluorimetry. Both the generation time and the various phase durations of the cell cycle were found to be the same in asynchronous and synchronous populations. It was found that NHIK 3025 cells are damaged by cooling to 4 and 0°C so that cooling of selected cells in order to increase the yield would reduce the quality of the synchronized populations.
CIRCADIAN RHYTHMS OF PRESUMPTIVE STEM CELLS IN THREE DIFFERENT EPITHELIA OF THE MOUSE
Authors: Potten Christopher S. , Al‐Barwari Shlemon E. , Hume William J. , Searle Jeffrey
Published: May 2008

Variation in the percentage of labelled cells (LI), mitoses (MI) and apoptosis (AI: i.e. shrinkage necrosis) have been studied throughout a 24 hr period (40 min after labelling with 3H‐TdR) for tongue epithelium, epidermis and intestinal epithelium in the mouse. A room with reversed light cycle was used to obtain data for half of the 24 hr period. All three tissues showed marked variations in LI with peak values between 24.00 and 03.00 hours. In the intestine a maximum value for MI was observed 3‐6 hr after that for LI and with a maximum value for AI slightly later.

In all three epithelia the circadian rhythm was most striking in cells at positions which can be correlated with presumptive stem cell activity; e.g. in the crypts the labelling and mitotic peaks reflecting a circadian rhythm were most clearly distinguishable at the basal part of the crypts. These observations are discussed in relation to the validity of various proliferative models.
AN EXTENDED TRANSITION PROBABILITY MODEL OF THE VARIABILITY OF CELL GENERATION TIMES
Authors: Svetina S.
Published: May 2008

The transition probability model of variability of cell generation times is extended so that the rate constant for the transition from the A‐state to the B‐phase of the cell cycle depends on time which a particular cell has already spent in the A‐state. A specific time dependence of this rate constant is introduced. It is determined by the value of one constant which is then an additional parameter of the model. The corresponding cell population kinetics are calculated and compared to existing experimental evidence. The model accounts satisfactorily for the generation time distribution function and for the shortening of the G1 phase of binucleate cells. The time dependence of the transition probability is related to the cell kinetics of an hypothetical cell constituent. A possible relationship is proposed between the chemical parameters within the cell and the parameters of the cell population kinetics.
SERIAL TRANSPLANTATION, HISTOLOGY AND CELLULAR KINETICS OF A RAT ADENOCARCINOMA
Authors: Moore J. V. , Dixon B.
Published: May 2008

Data are reported on the growth, histology and cell population kinetics of a spontaneous mammary tumour in the rat at the 1st and 35‐40th transplantation generation. With serial transplantation subcutaneously in isologous animals, the macroscopic growth characteristics of the tumour did not alter. The tumour had a volume doubling time of approximately 1.6 days at 400 mm3, increasing to about 7 days at 20,000 mm3.

The histology, however, changed dramatically from that of a well differentiated papillary adenocarcinoma with a well defined vascular pattern and minimal necrosis to become by the 35th generation a poorly differentiated pleomorphic cellular tumour in which stromal elements and associated vascular supply were minimal and necrosis prominent. These changes were not manifested in the median cycle time of its cells, 16–18 hr, but by an increase in the growth fraction from 0.36 to 0.59 with a commensurate increase in the cell loss factor from 0.04 to 0.30.
AN IN VIVO STATHMOKINETIC STUDY OF CELL PROLIFERATION IN HUMAN GASTRIC CARCINOMA AND GASTRIC MUCOSA
Authors: Wright Nicholas A , Britton David C. , Bone George , Appleton David R.
Published: May 2008

Cell production rates were studied in a group of eleven patients with carcinoma of the stomach using an in vivo technique with vincristine. In normal pyloric mucosa estimates ranged from 8 to 15 cells/1000 cells/hr, and in the carcinomas from 3 to 24 cells/1000 cells/hr. Because of the very large variation in the data, comparison between individual tumours and normal mucosa is not regarded as being worth while at this stage. The implications of these results for previous human in vivo stathmokinetic experiments are also discussed.
REGULATION OF MATURATION RATE OF MOUSE GRANULOCYTES
Authors: Bbenestad Haakon , Rytömaa Tapio
Published: May 2008

Regenerating mouse bone marrow cells were cultured i.p. in diffusion chambers (DC) to study factors affecting the maturation rate of granulocyte precursors. One day after exposing 3‐day‐old DC cultures to 3H‐thymidine the cultures were harvested, and labelled proliferative and non‐proliferative granulocytes were counted in radioautographs. The relative maturation rate—defined as the fraction of proliferative precursors maturing into the non‐proliferative compartment per unit time—could be increased by different experimental procedures that inhibit cell production. Inhibition was obtained (a) by increasing culture cellularity; (b) by implanting DC into normal rats or rats with huge s.c. chloroma tumours rather than into mice; and (c) by treating the cells with leucocyte extracts (granulocyte chalone) during the last day of culture. Furthermore, a sudden inhibition of rapidly proliferating granulocytes by leucocyte extracts resulted in an increase (apparently transient) in the absolute number of labelled non‐proliferative granulocytes. Such an increase was not detected in experiments involving a stronger or sustained inhibition of granulopoiesis, evidently because the size of the precursor population had been markedly reduced.
COMPARISON OF GROWTH CHARACTERISTICS OF EXPERIMENTAL TUMOURS AND DERIVED CELL CULTURES
Authors: Barendsen G. W. , Janse H. C. , Deys B. F. , Hollander C. F.
Published: May 2008

Cells from seven different rat tumours and a mouse sarcoma have been transplanted in syngeneic animals and were cultured in vitro. Tumours produced by inoculation of cultured cells in animals have been compared with the primary tumours. For the transplanted tumours, volume doubling times, Td, have been compared with doubling times, Td(cult), of cell numbers in cultures. Volume doubling times of the transplanted tumours generally decrease with increasing volume. At volumes of about 0.5 cm3, Td values range from 2.2 days to 10 days, while Td(cult) values ranged from 11 to 24 hr. A systematic correlation between Td and Td(cult) could not be established. During sequential transplantation of the tumours for many generations, as well as during continuous propagation of derived cell cultures, significant changes occurred which resulted in a decrease in the expression of differentiation characteristics in tumours.
REPLICON NUMBER AND GROWTH RATE IN FATHEAD MINNOW CELLS CULTURED AT 14 AND 34°C
Authors: Grabar F. , Flickinger R. A.
Published: May 2008

DNA fiber autoradiography was performed on cells of the fathead minnow cultured at 14 and 34°C. Replicon growth rates were found to be about twice as fast at the higher temperature, but there was no appreciable difference in the number of replicons.
The Circadian Variations In the Eithelial Growth of the Hamster Cheek Pouch: Quantitative Analysis of Dna Distributions*
Authors: Møller U. , Larsen J. K.
Published: May 2008

The pronounced diurnal rhythm in DNA distribution of the hamster check pouch epithelium both in the S fraction and in the (G2+ M) fraction was compared with previous studies of the changes in tritiated thymidine labelling index and mitotic activity. the DNA distributions were obtained by flow cytometry after ultrasonic disaggregation of the isolated epithelium into a suspension of single nuclei. the DNA distributions were analysed with the computer program of J. Fried (1976) and by planimetry. the S fraction was higher than the autoradiographic labelling index during the whole 24 hr period. Only the computer fitted S fraction and the labelling index had the same difference between maximal and minimal values, and maxima at the same time of day. the DNA distributions showed a diurnal release of G1 cells into S phase proceeding through (G2+ M) phase and returning to G1 phase within a 24 hr period.
Cell Proliferation and Ageing In Mouse Colon
Authors: Hamilton Elizabeth
Published: May 2008

The descending colon of 4 month and 2 year old mice was exposed to 1250 rad X‐rays. This killed most of the epithelial cells. the surviving cells formed new crypts and surface epithelium in animals of both ages. Not all the crypts were replaced. the irradiated area contained no more than 80% of the control number of crypts per section for at least 6 weeks after irradiation. In the young mice new crypts were much larger and the labelling index (LI) was much higher than in unirradiated animals during the first week after irradiation. In the old mice the overshoot in LI and crypt size began later and continued longer than in young animals. This may be because the control of cell proliferation was much less precise in old than in young mice.

The irradiation was repeated, in an attempt to age prematurely the epithelial cells by increasing the number of divisions they underwent. the overshoot in LI and cells per crypt was smaller after a second dose than after the first in both young and old mice. There was almost no overshoot after a third dose was given to young mice.

Increasing the number of divisions undergone by the surviving epithelial cells did not change the timing of repopulation in young mice compared to that found in old mice. Little evidence was found for the presence of a limited proliferative lifespan in colon epithelial cells.
SPECIFICITY of EPIDERMAL CHALONE EXTRACTS FOR HUMAN EPIDERMOID TUMOUR CELLS IN VITRO: A PRELIMINARY REPORT
Authors: KORSGAARD R. , IVERSEN O. H. , ISAKSSON‐FORSÉN G. , BURTON D. R.
Published: May 2008

In order to test the mitosis‐inhibiting effect and the tissue specificity of the epidermal G2 chalone for tumour cells, extracts from hairless mouse epidermis were tested in short‐term tissue cultures of cells from human respiratory tract epidermoid carcinomas and adenocarcinomas. the chalone inhibited strongly the mitotic activity in two cases of histologically proven epidermoid carcinoma, and had no effect in two cases of adenocarcinoma. In one case of a supposed epidermoid carcinoma, the chalone had no effect. Revision of the histology, and the result of autopsy 11 months later, showed that in this case the lesion in the lung had been a poorly differentiated metastasis from an adenocarcinoma of the ovary. Liver extracts produced in the same way as the epidermal extracts showed no mitotic inhibition in any of the cultures. These results indicate that epidermal G2 chalone produced from mouse skin is tissue specific for human epidermoid tumour cells, and also indicate that a chalone test might be used as a diagnostic tool for poorly differentiated carcinomas to see whether they are of epidermoid origin or not.
The Proliferative State of Clonogenic Cells In the Lewis Lung Tumour After Treatment With Cytotoxic Agents
Authors: Bateman A. E. , Steel G. G.
Published: May 2008

The proportion of clonogenic cells from the Lewis lung carcinoma which are in S‐phase of the cell cycle has been measured as the fraction killed by a short exposure to hydroxyurea in vitro. Estimates of the proportions of Sphase cells before and 30 min after doses of γ‐radiation of 1000–2000 rad suggest no alternation in the cell cycle age distribution due to these doses of radiation. As the survivors of these high doses of radiation are predominantly hypoxic, the results imply that hypoxic cells have the same cell cycle age distribution as oxygenated cells in Lewis lung tumours. After treatment with cyclophosphamide or CCNU, the proportion of S‐phase cells among the survivors exceeds the faction of S‐phase cells in untreated populations. This increase is consistent with a relative resistance of S‐phase cells to alkylating agents and nitrosoureas.
Cell Kinetics and the Control of Growth In Long Bones
Authors: Kember N. F.
Published: May 2008

The cell kinetics of the cartilage growth plate are outlined and discussed in terms of the probable levels of control on the system. Possible mechanisms of growth control at the cellular level are examined for (i) the rate of cell division in the proliferation zone, (ii) the command to differentiate that limits the size of the proliferation zone and (iii) the ageing process in the cartilage plate. the evidence of cell kinetics does not point unequivocally to any particular mechanism.
Erythrokinetics In Mice Bearing Tumours In Either Preirradiated Or Unirradiated Tissue
Authors: JIRTLE R. L. , CLIFTON K. H.
Published: May 2008

Experiments were designed to clarify the causes of anaemia in hosts bearing tumours in either unirradiated or preirradiated tissue. Isotopic methods are described which enable the estimation of erythrocyte destruction and production rates, and the potential red cell life spans in tumour‐bearing animals. In this experimental system, anaemia (a) is in large part due to accelerated random erythrocyte loss, (b) is exacerbated as tumours grow by a progressive reduction in the potential erythrocyte life span due to intrinsic erythrocyte defects, (c) is accompanied by an increase in erythrocyte production of six‐ to ten‐fold and (d) is postponed in onset and decreased in magnitude by preirradiation of the tumour transplant site.
The Measurement of Cell Turnover Rates Using Stable Isotope‐Labelled Thymidine: Experiments On the Small Intestine and On A Transplantable Lymphatic Tumour of the Mouse
Authors: Heck H. d'A. , Dyer R. L. , Anbar M. , Becker F. A.
Published: May 2008

Multilabelled, non‐radioactive thymidine and tritiated thymidine were incorporated simultaneously into the DNA of a rapidly‐growing, transplantable mouse lymphoma and the DNA of mouse small intestine by a single intraperitoneal injection of both labelled nucleosides. Mice were killed at selected times during the next 7 days, and the specific activities of the tissues and extracted DNA and the 132/126 mass ratio of thymine isolated from the DNA were determined by scintillation counting and by field ionization mass spectrometry respectively. the rates of decrease of the concentrations of tritiated and stable isotope‐labelled thymine in the DNA of the tumour or of the intestine were essentially identical. These results indicate the feasibility of using thymidine multilabelled with stable isotopes for measurement of cell turnover rates in conjunction with cancer therapy.