bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE f NUMBER OF PRIMARY TRANSPLANTED SPLENIC COLONY‐FORMING CELLS
Authors: Hendry J. H. 
Published: May 2008

ABSTRACTThe proportion of murine haemopoietic stem cells that settled in the spleen, after transplanting spleen cells into lethally‐irradiated recipient mice, was found by comparing the number of spleen colonies obtained by transplanting a whole spleen with an estimate of the total number of colony‐forming units (CFU) present in the intact spleen. the latter number was estimated assuming that endogenous spleen colonies were produced from surviving spleen‐derived CFU which exhibited the same survival parameters as transplanted CFU.Account was taken of the post‐irradiation loss of CFU from the spleen in the endogenous assay, which was found to be a reasonably constant factor for doses higher than about 100 rad X‐rays.The total measured number of CFU/spleen from transplantation was less than the number calculated in the intact spleen by a factor, the primary f number, of 0.03 ± 0.02.
KINETIC AND HISTOLOGICAL CHANGES OF A SERIALLY TRANSPLANTED MOUSE TUMOUR
Authors: Begg A. C. 
Published: May 2008

ABSTRACTA serially transplanted mouse tumour, NT1, was studied histologically and by autoradiography using tritiated thymidine at three stages in its transplant history: after two, seventeen and twenty‐seven passages. the growth rate of the tumour decreased progressively with increasing passage number, and the mean cycle time of the tumour cells increased from 21 hr to 34 hr between the seventeenth and twenty‐seventh passages. Histologically the tumour changed from having an epithelial structure (second passage), to having a mixed structure with at least two histologically different regions (seventeenth passage), to having a fibrous structure (twenty‐seventh passage). Radiation response experiments were carried out on the second and twenty‐seventh passaged tumours, the results of which are consistent with the kinetic and histological changes.
EFFECTS OF HYDROXYUREA ON THE KINETICS OF COLONY FORMING UNITS OF BONE MARROW IN THE MOUSE
Authors: Vassort F. , Frindel E. , Tubiana M. 
Published: May 2008

ABSTRACTThe number of nucleated bone marrow cells, the number of CFU and the number of DNA‐synthesizing cells in the mouse were studied after injection of hydroxyurea. It was found that one injection provokes a partial synchronization of surviving cells and probably stimulates the transition of CFU from the quiescent to the cycling state. the changes of the proportion of CFU in the S phase makes it possible to estimate approximately a cell cycle duration of about 12 hr.
CHANGES IN THE DNA SYNTHETIC PERIOD DURING THE PHASE OF RAPID GROWTH IN CULTURED DIPLOID FIBROBLASTIC CELLS
Authors: Moore Ruth C. 
Published: May 2008

ABSTRACTThe DNA synthetic period in diploid fibroblastic cell populations was studied during the phase of rapid growth in vitro, using the labelled mitotic wave method and quantitative autoradiography.It was found that the length of the DNA synthetic period increased progressively, from early passage levels, with the number of generations in vitro. the increase was mainly in the time taken to synthesize the first 50%, and especially the first 10%, of DNA.The change was detectable despite the complication due to a low level of tritium incorporation after the removal of tritiated thymidine from the cultures.
INFLUENCE OF METABOLIC DNA ON DETERMINATIONS OF THE CELL CYCLE
Authors: Pelc S. R. 
Published: May 2008

Abstract. Evidence in favour of labelling of DNA in excess of requirements for mitosis was found in adult organs showing no mitosis (heart muscle and brain), in organs with low mitotic indexes (liver, seminal vesicle) and, more recently, in the small intestine of rodents, in bone formation and in growing roots of Vicia faba. A survey of published data showed higher labelling indexes than would be expected from the data for S, M and tc deducted from labelled mitoses curves. to improve the accuracy of the data needed for a complete assessment the duration of mitosis (M) and the proportion of cells which are no longer in the mitotic cycle in the crypts were determined using Colcemid. the fact that all cells in the villi are derived from the crypts and that there is no cell‐loss in the villi was checked by cell‐counts.The results show that 3040%of the labelled nuclei found in crypts of the jejunum of mice at 1 hr after injection of 3H‐thymidine do not proceed to mitosis.The labelling after the last mitosis is interpreted as formation of the metabolic DNA necessary for the function of the differentiated cells in the villi. There is some evidence that metabolic DNA necessary for the processes of mitosis might be lost
KINETICS OF THE INNER ENAMEL EPITHELIUM IN THE ADULT RAT INCISOR DURING ACCELERATED ERUPTION
Authors: Zajicek Gershom , Michaeli Yael , Weinreb Max M. 
Published: May 2008

Inner enamel epithelial (IEE) cell production was compared in accelerated and normal eruption (control). Each group consisting of thirty rats received 1 μCi/g tritiated thymidine. The animals were sacrificed at short time intervals up to 14 hr after injection. The excised incisors were cut mid‐sagittally and processed autoradiographically.The fast growing incisor produces twice as many cells as the control. Increased cell production is achieved in two ways: proliferative pool expansion (by 25.5%) and generation time (tc) shortening to 16 hr (tc= 23 hr in the control). Generation time shortening resulted mainly from a diminution in tg1= 8.6 hr (tg1= 14.1 hr in the control) and ts which equaled 5.5 hr (ts= 7 hr in control). Mitotic times which equaled 0.4 hr and tg2, 1.5 hr were identical in both groups.The eruption/IEE cell production ratio equals 1.1 in both groups.
THE SYNTHESIS OF PHOSPHOLIPIDS IN THE NUCLEUS AND NUCLEAR MEMBRANE OF SYNCHRONIZED HeLa CELLS
Authors: Pegoraro Luigi , Galanti Norbel , Stein Gary , Baserga Renato 
Published: May 2008

HeLa cells were synchronized by a double thymidine block and pulse labeled at different stages of the cell cycle with 3H‐choline. The specific activity of phospholipids extracted from the cell, the nucleus and the nuclear membrane showed a progressive increase from S to G1; the incorporation of choline into phospholipids of asynchronous cells showed a specific activity intermediate between the values of S and G1 cells. Similar results were obtained when 32phosphorus was used as a precursor instead of choline. Thin layer chromatographic analysis of phospholipids extracted from cells in S and from cells in G1 failed to show any difference in the distribution of radioactivity among the various phospholipid classes.Choline uptake by HeLa cells in different phases of the cell cycle did not show significant variations. However, during the synchronization process, shortly after the addition of excess thymidine, an increased uptake of choline by cells and an increased incorporation of choline into phospholipids were found. The results indicate that some of the changes occurring in phospholipids synthesis may not be cell cycle dependent, but may be the effect of the synchronizing process.
REGULATION AND KINETICS OF SPERMATOGONIAL PROLIFERATION IN ARENICOLA MARINA (ANNELIDA, POLYCHAETA) I. THE ANNUAL CYCLE OF MITOTIC INDEX IN THE TESTIS
Authors: Olive P. J. W. 
Published: May 2008

The annual variation in the mitotic index of the testis of Arenicola marina after 48 hr treatment with colchicine has been determined. This mitotic index in the population is distributed log‐normally. The mean mitotic index is low in winter but increases during the spring to a maximum in early summer. The mean mitotic index remains high until September when it decreases temporarily. There is a second minor increase in the mean mitotic index prior to spawning.Decerebration of animals prior to the spring increase in the mitotic index did not prevent this increase occurring in decerebrate animals maintained in the laboratory. Removal of the coelomic gametes was effective in stimulating the testicular mitotic index only when performed during the period of low mitotic activity in early autumn.
REGULATION AND KINETICS OF SPERMATOGONIAL PROLIFERATION IN ARENICOLA MARINA (ANNELIDA, POLYCHAETA) II. KINETICS
Authors: Olive P. J. W. 
Published: May 2008

The rate of accumulation of mitoses in the testis of Arenicola marina has been estimated by the colchicine method. The rate is low in February but increases during spring to a maximum in June. The rate remains high during July and August but decreases in September. A second temporary and minor rise was observed in October or November prior to spawning.The rate of accumulation of mitoses (with respect to the duration of metaphase arrest) is logarithmic from February to June, but is arithmetic during the latter part of the reproductive cycle (July‐October). The transition from one phase to the next coincides with the initiation of spermatocyte release from the testis into the coelom.The rate of accumulation of mitoses has also been recorded in testes cultured in vitro. The rate in vitro does not differ from that in vivo in May when the rate is high, but in September when the rate in vivo is depressed, culture in vitro significantly increases the mitotic rate.The cell cycle time of the proliferating spermatogonia has been estimated by a modified per cent labelled mitosis technique. The cell cycle time is unusually long (in excess of 20 days) and the G2 period is at least 5 days. It is suggested that the testis of A. marina is an exponentially growing cell population from February until early June when coelomic spermatocytes first appear. The rate of cell release then temporarily exceeds the rate of renewal: eventually they become equal and the testis remains in steady state until September when the mitotic rate is depressed due to the presence of maturing spermatocytes. The depression of the mitotic rate in September is achieved by the arrest of spermatogonia in G2. Explanting the gonads in organ culture removes the inhibition and causes an increased flow of cells from G2 into mitosis.
OBSERVATIONS ON HUMAN MONOCYTE KINETICS AFTER PULSE LABELING
Authors: Whitelaw D. M. 
Published: May 2008

Monocyte kinetics were studied in seven hematologically normal individuals using in vivo pulse labeling with tritiated thymidine. Although occasional labeled cells appear in the peripheral blood within 4 or 5 hr of the administration of label, a significant outflow from the marrow begins 13–26 hr later. This interval is occupied by the G2 and M phases of the mitotic cycle since mitotic cells are not observed in the peripheral blood. The duration of the DNA synthesis phase of monocytes is measured at 34 hr ≈ 1.8 hr. Cells do not enter this phase while circulating since exposure of circulating cells to tritiated thymidine does not result in any uptake. If monocytes are not ‘end’cells which have completed their mitotic activity before leaving the marrow they must at least be inhibited from further proliferative activity until they are permanently sequestered in other tissues.The generation time is probably not less than 40 hr and data derived from the mean grain counts of labeled cells suggest that it is often more than 70 hr. The total daily output of monocytes in man is 9.4 × 108 cells per 24 hr ≈ 3.3 × 108.Cells leave the bloodstream with a half‐time of about 71 hr thereby proving themselves to be considerably more durable than neutrophils which have a half‐life in the neighborhood of 6 hr.
RELATION BETWEEN THE CIRCADIAN RHYTHMS OF MITOTIC RATE AND CHOLESTEROL‐7α‐HYDROXYLASE ACTIVITY IN THE REGENERATING LIVER
Authors: Van Cantfort Jacques J. , Barbason Hervé R. 
Published: May 2008

The evolution of mitoses and cholesterol‐7α‐hydroxylase activity were studied in parallel in the regenerating liver after a partial hepatectomy performed at two different hours of the nycthemeral period, i.e. 10 a.m. and 8 p.m.The mitotic index was used to assess the function of cell division while cholesterol‐7α‐hydroxylase activity was taken as a test of the tissue‐specific function. The results showed a different evolution of these two functions according to the time of the surgery. The data indicated that a mutually exclusive relationship took place between the function of cell‐division and the tissue‐specific function.These observations suggested that, during liver regeneration, the derepression of the genes coding the enzymes of these two different functions takes place in a complementary fashion, at two different phases of the nycthemeral period.
MULTIPLICATION OF HAEMOPOIETIC COLONY FORMING UNITS (CFU) IN MICE AFTER X‐IRRADIATION AND BONE MARROW TRANSPLANTATION
Authors: Vos O. 
Published: May 2008

Kinetics of the multiplication of haemopoietic CFUs was studied in lethally irradiated mice receiving various numbers of syngeneic bone marrow cells. After transplantation of a small number of bone marrow cells, the growth rate of CFU in femoral bone marrow appeared to decrease after about 10 days after transplantation, before the normal level of CFU in the femur was attained. In the spleen it was found that the overshoot which was observed about 10 days after transplantation of a large number of bone marrow cells is smaller or absent when a small number of cells is transplanted. Experiments dealing with transplantation of 50 x 106 bone marrow cells 0, 4 or 10 days after a lethal irradiation indicated that the decline in growth rate of CFUs about 10 days after irradiation could not be attributed to environmental changes in the host.The results are explained by the hypothesis that a previous excessive proliferation of CFUs diminishes the growth rate thereafter. This hypothesis is supported by experiments in which 50 x 106 bone marrow cells derived from normal mice or from syngeneic chimaeras were transplanted. The slowest growth rate was observed when bone marrow that had been subjected to the most excessive proliferation in the weeks preceding the experiment was transplanted.
CELL POPULATION KINETICS OF PLUCKED AND UNPLUCKED MOUSE SKIN I. UNIRRADIATED SKIN
Authors: Hegazy M. A. H. , Fowler J. F. 
Published: May 2008

ABSTRACTA detailed study of the cellular proliferation kinetics in interfollicular plucked and unplucked mouse skin has been made in Swiss albino mice, using tritiated thymidine autoradiography. Diurnal variations in mitotic and labelling indices were demonstrated in both systems.The mean cell cycle times for unplucked and plucked skin were estimated by four different methods and found to be 100 ± 10 and 47 ± 3 hr respectively. Most of the difference was due to the shortening of G1 phase after plucking. Repeated labelling at intervals shorter than the DNA synthesis times resulted in all the basal layer cells becoming labelled, so that the growth fraction was unity, in unplucked and plucked skin.A well‐defined second wave of labelled mitoses was seen at about 100 hr after labelling the unplucked (i.e. normal) mouse skin.A double labelling technique using 14C‐TdR and 3H‐TdR with a single layer of emulsion gave reasonable values for the duration of the DNA synthesis phase.
THE EFFECT OF METHYL CCNU (NSC‐95441) ON THE CELLULAR KINETICS OF NORMAL AND LEUKEMIC MURINE TISSUES IN VIVO
Authors: Young Robert C. 
Published: May 2008

ABSTRACTThe effect of MeCCNU on the cellular kinetics of normal and leukemic murine tissues is examined in vivo. A prolongation in the S phase is noted after doses of MeCCNU as low as 4 mg/kg, and this prolongation persists for approximately 4 hr after the dose. No persistent alteration in the growth fraction is produced by MeCCNU. The generation time of the cells regrowing after MeCCNU is slightly prolonged, compared to normal L1210 leukemia. Simultaneous studies on ascites tumor, normal bone marrow, and normal gastrointestinal mucosa, using the in vivo uptake of 3H‐thymidine into DNA, have shown a differential effect on the tumor and normal tissues.
KINETICS OF MURINE HAEMOPOIETIC CELL PROLIFERATION IN DIFFUSION CHAMBERS
Authors: Bøyum Arne , Breivik Harald 
Published: May 2008

ABSTRACTMurine bone marrow cells were cultured in cell impermeable diffusion chambers in the abdominal cavities of mice. The kinetics of granulocyte and macrophage formation were studied by stathmokinetic and autoradiographic techniques. During the period of most rapid growth of proliferative granulocytes, their generation time and its different phases were: tc∽ 8 hr, tG1∽ 1·5 hr, ts∽ 5·5 hr, tG2∽ 0·7 hr and tM∽ 0·25 hr.The generation time of macrophages and their precursors was approximately 8 hr. Formation of macrophages was significantly reduced when chamber inoculum was increased, as judged by 3H‐TdR labelling index.
A MATHEMATICAL MODEL OF THE CELL CYCLE OF L5178Y
Authors: Roti Roti J. L. , Okada S. 
Published: May 2008

ABSTRACTGiven the starting cell cycle age distribution and the growing conditions, the model developed through modification of Hahn's vector analysis predicts the age distribution of the population after a growth period. The model was able to simulate changes in growth and the per cent of cells in each stage of the cell cycle for cells growing in excess thymidine, in colcemid, in normal medium, and after successive treatments of these drugs, specifically the chemical synchronization method of L5178Y cells.
CYTOKINETICS OF THE S‐180 ASCITES TUMOR SYSTEM
Authors: Schiffer L. M. , Nelson Janet S. R. , Dilettuso Barbara , Migliorato Dolores , Randolph William 
Published: May 2008

ABSTRACTThe cytokinetics of the S‐180 mouse ascites tumor system was determined on Days 2, 4, 6 and 9 of growth. Studies included volume tumor growth, per cent labeled mitoses curves, and repeated injections of tritiated thymidine. It was possible to extrapolate the cytokinetic compartment values to Day 0 of growth. Results indicate that the growth fraction of the S‐180 system remains close to 1 throughout its growth, with progressive lengthening of G1, S and G2 times. Cell loss is minimal through 6 days but becomes significant thereafter. A theoretical growth curve constructed from cytokinetic values is similar to the actual volume growth curve.
HYDROXYUREA EFFECTS IN THE C3H MOUSE II. MAMMARY TUMOR CELL KINETICS
Authors: Dethlefsen Lyle A. , Riley Reba M. 
Published: May 2008

ABSTRACTThe cellular kinetics of C3H mouse mammary tumors were studied following a single dose (3 mg/g body weight) of hydroxyurea (HU). This dose was large enough to cause a significant perturbation in the growth curves of these tumours. This was accomplished by labeling the cells with tritiated 5‐iodo‐2′‐deoxyuridine and performing detailed autoradiographic analysis. This dose of HU caused a temporary inhibition in growth and completely inhibited DNA synthesis for 4–5 hr. The HU‐killed cells (pyknotic and karyorrhectic) reach a maximum around 10–12 hr and are apparently all removed in about 1 day. Tumors from a fast‐growing line (S102F) showed some evidence for cell synchrony upon recovery from HU inhibition but desynchronization occurred within one cell cycle. The cell generation time was not decreased during the acute recovery phase, but the growth fraction shifted from 0·6 to 1·0, and the data suggested that the normal flow of cells from the proliferating pool to the degenerate pool was temporarily interrupted. The cellular kinetic parameters have probably returned to normal by 48 hr after the HU injection.
LOCAL AND SYSTEMIC CONTROL OF GRANULOCYTIC AND MACROPHAGE PROGENITOR CELL REGENERATION AFTER IRRADIATION
Authors: Chan S. H. , Metcalf D. 
Published: May 2008

ABSTRACTAgar cultures of C57BL bone marrow cells were used to determine colony stimulating factor (CSF) and serum CSF‐inhibitor levels in C57BL and BALB/c mice following irradiation. Whole‐body irradiation caused an acute, dose‐dependent, rise in serum CSF levels and fall in CSF‐inhibitor levels. The regeneration of granulocytic and macrophage progenitor cells (in vitro CFCs) in the femur after 250 rads whole‐body irradiation was preceded or paralleled by a fall in serum CSF‐inhibitors and a dramatic rise in the capacity of bone‐adherent cells in the marrow (‘stromal cells’) to produce material with colony‐stimulating activity. No comparable changes were observed in the activity of marrow haemopoietic cells during regeneration or in the lungs or spleen. A similar rise in the activity of bone‐adherent cells was observed in shielded femurs during regeneration of in vitro CFCs.Regeneration of granulocytic and macrophage progenitor cells following irradiation may be regulated by fluctuations in circulating CSF‐inhibitor levels and local production of CSF within the marrow cavity.
THE PROLIFERATION OF LYMPHOID CELLS IN GUINEA‐PIG BONE MARROW
Authors: Miller S. C. , Osmond D. G. 
Published: May 2008

ABSTRACTA double isotope DNA labelling method has been used to determine the duration of DNA synthesis (S) in bone marrow lymphoid cells classified by their nuclear diameters in smears. Incorporation of 3H‐thymidine was confined almost entirely to marrow lymphoid cells of 8·0‐15·0 μm nuclear diameter (large lymphoid cells). After exposure to 3H‐thymidine in vivo and 14C‐thymidine 40‐104 min later in vitro, the proportion of cells labelled with 3H alone to those labelled with 14C(±3H) in radioautographic smears, plotted against time indicated the efflux from S per hour. Collectively, 28·3 ± 1·1% of all large lymphoid cells were in S and the efflux from S was 15·1% per hour. With decreasing cell size (nuclear diameter) the efflux fell progressively from 28·3% per hour (11·0 μm) to 9·2% per hour (8·0‐8·9 μm) and the proportion of cells in S declined from 54·9 ± 2·3% to 14·8 ± 1·6%. Influx into S, measured in vitro by reversing the sequence of isotopes, closely resembled the corresponding efflux values in vivo relative to cell size. Most DNA synthesizing marrow large lymphoid cells belonged to a subgroup with deeply basophilic cytoplasm. The results demonstrate that basophilic large lymphoid cells in the marrow are actively proliferating and have a mean S phase duration of 6·6 hr. The largest marrow lymphoid cells (11·0 μm) proliferate most rapidly (S phase, 3·5 hr; maximum cell cycle time, 6·4 hr) while S duration is prolonged progressively to 10·9 hr for the smaller cells (8·0‐8·9 μm).
INCREASE OF DNA POLYMERASE ACTIVITY FIRMLY BOUND TO NUCLEI DURING THE DNA SYNTHETIC PHASE OF THE CELL CYCLE
Authors: Furlong N. B. , Novak W. B. , Stubblefield T. E. 
Published: May 2008

ABSTRACTDNA polymerase activities were measured on nuclear and supernatant fractions obtained from hamster fibroblast cells (the Don‐C clone) grown in tissue culture and mitotically synchronized by selective removal of cells arrested in metaphase following a brief exposure to colcemid. A reproducible fraction (5–10%) of the polymerase activity was found to remain bound in the nuclear pellet after repeated cycles of freezing and thawing. The specific activity of this firmly‐bound nuclear DNA polymerase was found to increase during S‐phase in proportion to DNA synthesis. The bulk of this activity, after extraction in 1 m salt, exhibited an S value of 8·7 on neutral high salt sucrose gradients and was 24 times more active with poly dA. dT10 as template than with heat denatured DNA. The rest of the cellular DNA polymerase activity showed no significant variation correlated with the cell cycle. This activity also had an S value from 8 to 9 but it was only 2·8 times more active with the homopolymer template than with heat denatured DNA. DNA polymerase activity similar to the firmly‐bound activity was found in extracts prepared from metaphase chromosomes.