bluuebunny/crossref_metadata_2025_split huggingface dataset:
ABSENCE OF EFFECT OF MULTIPLE INTRAPERITONEAL INJECTIONS ON CELL PROLIFERATION, AND ESTIMATION OF THE CELL CYCLE TIME IN THE EPITHELIUM OF THE OESOPHAGUS AND FORESTOMACH IN MICE, HAMSTERS AND RATS
Authors: Blenkinsopp W. K. 
Published: May 2008

ABSTRACTCounts of labelled epithelial nuclei in mice given single or multiple injections of tritiated thymidine (to label cells synthesizing deoxyribonucleic acid), either alone or after 24 or 48 hr multiple injections of water, showed that multiple intraperitoneal injections did not disturb normal cell proliferation. The rate of cell proliferation was the same in the epithelium of the oesophagus and forestomach, and in these epithelia there was no difference between mice, hamsters and rats. Cell cycle times were estimated in these epithelia from the number of nuclei labelled in animals given single or multiple injections of tritiated thymidine.
THE COMPARATIVE EFFECT OF BUSULPHAN (‘MYLERAN’) AND AMINOCHLORAMBUCIL ON HAEMOPOIETIC COLONY FORMING UNITS IN THE RAT
Authors: Dunn C. D. R. , Elson L. A. 
Published: May 2008

ABSTRACTUsing the spleen colony assay technique, it has been shown that busulphan (‘Myleran’) in a dose of 10‐2 g/kg (1/2 LD50), causes a marked and prolonged depression (over 90%) in the number of colony forming units per femur (CFU/femur). This depression is apparent before there is any marked reduction of the total cell count per femur and is maximal 2–4 days after an intraperitoneal (i.p.) injection of the drug. It is then followed by a steady recovery, normal values being reached after about 20 days.In contrast, aminochlorambucil (2·5 x 10‐3) g/kg = 1/2 LD50) although producing a rapid fall in the marrow cellularity has no discernable effect on the CFU/femur.If, however, a depression of CFUs is first induced by busulphan and, after allowing time for 50% recovery (13 days), aminochlorambucil is now given, a further severe depression of the CFUs/femur occurs resulting in a considerable prolongation of the neutropenia observed in the blood.The possible implications of this in the mode of action of these two drugs, and in the chemotherapy of leukaemia, are discussed.
STUDIES ON LYMPHOCYTES
Authors: Iorio R. J. , Chanana A. D. , Cronkite E. P. , Joel D. D. 
Published: May 2008

ABSTRACTTritiated thymidine was administered to calves continually for 2 to 8 days via the thymic artery in an attempt to label intensively thymic lymphocytes. Heavily labeled cells which had migrated from the thymus were observed in the spleen, lymph nodes and Peyer's patches. Cell maps were made for the various lymphoid tissues and in all cases the majority of labeled thymic cells were found in the ‘thymus dependent areas’of the spleen and lymph nodes. The number of labeled thymic cells per thousand lymphocytes was highest in the ‘thymus dependent areas’. A few labeled thymic cells were seen in or near the post capillary venules. The labeling pattern in the Peyer's patches was different from that in the spleen and lymph nodes. Labeled thymic cells were not observed in the bone marrow.Heavily labeled cells were not detected in any of the lymphoid tissues of those calves which received continuous intravenous infusion of comparable amounts of tritiated thymidine.
MITOTIC G2 DELAY INDUCED IN SYNCHRONIZED HUMAN KIDNEY CELLS BY UV AND X‐IRRADIATION AND ITS RELATION TO DNA STRAND BREAKAGE, REPAIR AND TRANSCRIPTION
Authors: Scaife J. F. 
Published: May 2008

ABSTRACTSynchronous populations of human kidney T‐cells have been used to investigate the influence of BUdR incorporation into nuclear DNA on mitotic G2 delay produced by UV or X‐irradiation. By this means true G2 delay could be distinguished from a prolongation of the S‐phase. X‐ray induced mitotic delay is only slightly increased in BUdR containing cells. UV induced mitotic delay is appreciably augmented in cells having incorporated BUdR. These cells show extensive single‐strand breaks in their DNA which is fairly rapidly repaired. Transcription and translation are also appreciably reduced following UV in such cells. It is concluded that mitotic inhibition following X‐irradiation is a result of mechanisms other than the damage to and repair of DNA while mitotic inhibition following UV‐irradiation is primarily related to DNA damage and repair. The specific division proteins synthesized in G2 in these cells constitute only a minor component of the total soluble cell proteins.
EPIDERMAL REGENERATION AFTER CELLOPHANE TAPE STRIPPING OF HAIRLESS MOUSE SKIN
Authors: Hennings Henry , Elgjo Kjell 
Published: May 2008

ABSTRACTAfter repeated applications of cellophane tape to the dorsal skin of hairless mice, the proliferative response in the treated epidermis was estimated by three different methods. The mitotic rate was determined in the interfollicular epidermis using the Colcemid technique, and the DNA synthetic activity was estimated after 3H‐thymidine injection by counting labelled interfollicular cells in autoradiographs and by determining the specific activity of epidermal DNA.An initial 40–50% inhibition of DNA synthesis and mitosis was followed by an increase in the labelling index and the mitotic rate 8–10 hr after tape stripping. By 24 hr, peak values 5–6 times the controls were attained for both parameters. The labelling index and the mitotic rate were nearly normal at 3–4 days, but a second small peak was seen on day 5. Normal values were found on days 6 and 8. A similar pattern of response was found biochemically, but the peak of DNA specific activity was much broader and the extent of the increase was only about half as great as the increase in the labelling index. Possible reasons for these differences are discussed.
EFFECT OF HAIR PLUCKING ON THE KINETICS OF METHYLCHOLANTHRENE‐INDUCED SKIN TUMOURS IN MICE
Authors: Hegazy M. A. , Fowler J. F. 
Published: May 2008

ABSTRACTBoth the latent period and the volume doubling time of 20‐methylcholanthrene‐induced tumours in the skin of SAS/TO mice have been found to be longer for plucked skin than for unplucked skin, even though the cell cycle time of the basal layer cells of the epithelium is much shorter after plucking (50 ± 4 hr) than in unplucked skin (110 ± 10 hr).
ON THE EXISTENCE OF A Go‐PHASE IN THE CELL CYCLE
Authors: Burns F. J. , Tannock I. F. 
Published: May 2008

ABSTRACTThe model is based on the assumption that the cell cycle contains a Go‐phase which cells leave randomly with a constant probability per unit time, γ. After leaving the Go‐phase, the cells enter the C‐phase which ends with cell division. The C‐phase and its constituent phases, the‘true’G1‐phase, the S‐phase, the G2‐phase and mitosis are assumed to have constant durations of T, T1Ts, T2 and Tm, respectively. For renewal tissue it is assumed that the probability per unit time of being lost from the population is a constant for all cells irrespective of their position in the cycle.The labelled mitosis curve and labelling index for continuous labelling are derived in terms of γ, T, and Ts. The model generates labelled mitosis curves which damp quickly and reach a constant value of twice the initial labelling index, if the mean duration of the Go‐phase is sufficiently long. It is shown that the predicted labelled mitosis and continuous labelling curves agree reasonably well with the experimental curves for the hamster cheek pouch if T has a value of about 60 hr. Data are presented for the rat dorsal epidermis which support the assumption that there is a constant probability per unit time of a cell being released from the Go‐phase.
THE EFFECTS OF LOW CONCENTRATIONS OF ACTINOMYCIN D ON THE PROGRESS OF CELLS THROUGH THE CELL CYCLE
Authors: Rickinson A. B. 
Published: May 2008

ABSTRACTThe progress of L‐cells through the cell cycle in asynchronous and in synchronous culture has been studied at a concentration of actinomycin D which mediates an apparently‘nucleolar‐specific’inhibition of RNA synthesis. Under such conditions, cells may be blocked or seriously delayed in the G1 and G2 phases of the cycle whilst the processes of DNA synthesis and mitosis once initiated, can still occur at control rates. The results show that the sensitivity of a cell to these blocks depends critically upon the position of that cell within the cycle at the time of drug addition. The possible mechanisms of the drug's action are discussed.
THE EFFICIENCY OF THE ASSAY FOR HAEMOPIETIC COLONY FORMING CELLS
Authors: Lahiri S. K. , Keizer H. J. , Putten L. M. van 
Published: May 2008

ABSTRACTThe quantitative efficiency of the spleen colony assay in mice is discussed in the light of recent findings on the kinetics of colony forming cells. Arguments are presented showing that the f factor, the 2 hr CFU recovery fraction in the spleen, markedly over‐estimates the assay efficiency which is the ratio of the numbers of colony forming units and colony forming cells.
EFFECTS OF SHORT‐TERM CULTURE ON POPULATIONS OF HEMOPOIETIC PROGENITOR CELLS FROM MOUSE MARROW
Authors: McCulloch E. A. , Till J. E. 
Published: May 2008

ABSTRACTWe have studied the response of progenitor cells in mouse marrow to short‐term cultivation in cell culture. In the presence of a feeder layer of mouse renal tubules, the number of granulocyte progenitors able to form colonies in cell culture showed a net increase. No such increase in numbers of stem cells detected by the spleen colony assay was observed under the same conditions, although there was some stimulation of uptake of tritiated thymidine into these cells. A rapid decrease in the numbers of both types of progenitor cells occurred in the cultures in the absence of a feeder layer. However, when marrow cell populations that had been cultivated for 2 days in the absence of a feeder layer were transplanted into irradiated mice, the surviving stem cells detected by the in vivo assay showed a prolonged phase of rapid growth, resulting in a more pronounced ‘overshoot’ in the growth curve.
CARTILAGE CELL PROLIFERATION IN THE TAIL‐VERTEBRAE of NEW‐BORN RATS
Authors: Dixon B. 
Published: May 2008

ABSTRACTCartilage cell proliferation has been studied in the tail‐vertebrae of new‐born rats. At 1 day the median cycle time for cartilage cells was about 22 hr; G1+ 1/2M, S, and G2+ 1/2M being 6.8 ± 2.5, 11.6 ± 2.2, and 4.6 ± 2.0 hr respectively. At 7‐10 days, cell proliferation is confined mainly to the lower half of the epiphysis. Here cycle times are longer, about 3 1/2 days in the most active region. Differences in cycle times appear to be due to either a lengthening of G1 or the entry of cells into a resting state. Changes in cartilage cell kinetics are discussed in relation to the structure and function of the epiphysis.
THE RELATIONSHIP BETWEEN CELL MATURATION and PROLIFERATION IN the ERYTHROID SYSTEM of the RAT
Authors: Hanna I. R. A. , Tarbutt R. G. 
Published: May 2008

ABSTRACTCalculations have been made of the change with time in the tritiated thymidine labelling index of erythroid cells in normal and anaemic rats, on the basis of two different models of the erythroid system. In the first model it is assumed that cells pass from one stage of maturation to the next at all phases of the cell cycle, whereas in the second model the cells can only progress to the next stage when they reach a certain point in the cell cycle. the changes in labelling index predicted on the basis of these two models are markedly different, especially in the non‐dividing stages of the system, and the change in labelling index as a function of time therefore provides an experimental method for distinguishing between the two models. the experimental data favours the model in which cells cross compartmental boundaries at all stages of maturation. Some important consequences of this model are discussed.
THE INFLUENCE of A LOW ENVIRONMENTAL TEMPERATURE ON the STEM CELL POPULATION of the BONE MARROW and INTESTINAL MUCOSA
Authors: Baker D. G. , Carsten A. L. , Hopper A. F. 
Published: May 2008

ABSTRACTProtracted exposure of rats to a low environmental temperature (2° C) resulted in almost a two‐fold increase in the number of colony forming units per femur. Following a dose of Vinblastine, return of CFUs in the bone marrow to the pretreatment level was more rapid in the cold exposed rats than in rats at a 25° C environment. the cell cycle time of the cells in the intestinal crypt was reduced for the cold exposed rats. These observations are thought to be the basis for the increased radioresistance and/or more rapid recovery from whole body irradiation previously reported.
ANOMALOUS STIMULATION OF PROTEIN SYNTHESIS: EVIDENCE FOR TRANSLATIONAL CONTROL IN PRIMARY CELLS
Authors: Christopher C. W. , Ishikawa Kiichi , Amos Harold 
Published: May 2008

ABSTRACTChick cells in primary culture synthesize protein at an accelerated rate following recovery from prolonged (2‐12 hr) inhibition of protein synthesis. This ‘overshoot’ is followed by a return to the normal rate of synthesis.Both actinomycin and fluorophenylalanine provided during the recovery period enhance the ‘overshoot’ and prevent the return to normal.The results are consistent with the proposal that protein synthesis is restricted by an inhibitor or ‘governor’, itself a protein of relatively short half life.Neither L nor HeLa cells demonstrate an ‘overshoot’ during the recovery phase.
THE TECHNIQUE OF LABELLED MITOSES: ANALYSIS BY AUTOMATIC CURVE‐FITTING
Authors: Steel G. G. , Hanes S. 
Published: May 2008

ABSTRACTAn improved method is described for the analysis of data obtained by the technique of labelled mitoses. It is a development of the method described by Barrett (1966) in which theoretical curves are computed on the basis of a model which assumes that the phases G1, S and G2 are described by independent log‐normal distributions; the analysis consists in finding a form of this model which gives a labelled mitoses curve which is the best fit to the available data. This fitting procedure has now been made automatic. No comprehensive indication of the goodness of fit can be given, although in the analysis of over fifty sets of data the method appears to have worked well.A supplementary computer program is described which, on the basis of three separate assumed modes of cell loss, calculates the form of the age distributions and theoretical continuous labelling curves. This allows growth fraction to be calculated in a way which takes account of the distribution of phase durations and the non‐rectangular age distributions of expanding cell populations. It also gives an opportunity to study the implications of continuous labelling data as regards the mode of cell loss.A comparison is made between the present method of labelled mitoses curve analysis and the empirical rules which have often been used.
KINETICS OF THE INNER ENAMEL EPITHELIUM IN THE ADULT RAT INCISOR
Authors: Zajicek Gershom , Bar‐Lev Moshe 
Published: May 2008

ABSTRACTThe inner enamel epithelium (IEE) in the model consists of a 1500 cell matrix. Cells formed on the apical side of the matrix proliferate and migrate towards its incisal (or distal) end, where they are shed. the continuous cell supply is maintained by two types of cell: (a) the blasts, which preserve their physical position in the matrix. Upon division, the blast yields one blast, occupying the space of the mother cell, and a migrating metablast. (b) the metablasts, which divide while migrating along the matrix. Each blast division forms a metablast clone whose size depends on the number of divisions its members undergo. the metablasts finally mature and cease to divide.Each cell is described by three attributes which change with time: age, label content and the number of divisions it underwent since the metablast clone was formed. (This attribute is set to zero in the blasts.)The system is governed by the following parameters: (a) the size of the blast compartment. (b) the number of divisions a metablast clone undergoes in its life time. (c) the lengths of the phases in the cell cycle. (d) the length of the time unit. (e) Degree of variation in the system (noise).In the experiments described only one set of parameters was used: tc= 22 hr, tG1= 12.5 hr, ts= 7 hr, tG2= 2 hr, tm= 30 min, variation = 20%.The model mimics well experimental results reported before, such as the migration rate of labelled cells on the IEE axis and labelled mitosis curve. It predicts new facts like changes in the grain count and labelled cell index with time.
NATURAL VARIATION IN THE S‐PHASE OF RENEWING EPITHELIA OF THE POUCHLESS OPOSSUM, MARMOSA MITIS
Authors: Thrasher J. D. , Berg N. B. , Hauber E. 
Published: May 2008

ABSTRACTThe sites of cell proliferation and the duration of the S‐phases in epithelia (tongue, stomach, duodenum, jejunum, ileum and descending colon) of the pouchless opossum, Marmosamitis, have been studied following the injection of tritiated thymidine. the sites of cell proliferation in these epithelia are not significantly different than those reported for rodent tissues. On the other hand, measurements of the mean duration of DNA synthesis revealed great variability in this phase: tongue (12.8 hr), stomach (>14.0 hr), duodenum (8.5 hr), jejunum (8.6 hr), ileum (9.7 hr) and descending colon (11‐3 hr). In addition, the values obtained for the mean duration of t2 (G2+2/1M) are fairly constant among the various epithelia. It is concluded that the times obtained for the average duration of the S‐phases are longer and more variable in M. mitis than similar observations reported on renewing epithelia of eutherian mammals.
THE RELATIONSHIP BETWEEN SPLEEN COLONY PRODUCTION AND SPLEEN CELLULARITY
Authors: Lord B. I. 
Published: May 2008

ABSTRACTThe fraction, f, of injected spleen colony‐forming cells which can be recovered from the spleen of a radiated mouse has been determined at various times up to 24 hr following the initial cell injection. the cellularity of the spleen at the time of assay was also measured and compared with the calculated f number. the linear relationship between these two parameters indicated that over the period of 2‐24 hr the number of CFU/106 spleen cells was constant, both falling in a parallel fashion. A further experiment using non‐irradiated W/Wv mice in which the spleen size did not change showed the same f number at the end of this period as at 2 hr. It is concluded that CFU are expelled from the spleen during its post‐irradiation contraction thus leading to the apparent fall in f number. It is also concluded that a more realistic f number is obtained by assaying the splenic CFU content 24 hr after the primary cell transfer rather than 2 hr.
PROLIFERATION KINETICS IN EPITHELIUM OF GUINEA‐PIG COLON
Authors: Sawicki W. , Rowiński J. , Blaton Olena 
Published: May 2008

ABSTRACTThe distribution of mitotic, DNA synthesizing and mature goblet cells along crypts of different length, situated in various regions of the colonic wall circumference, was determined. the distribution of proliferating cells can be approximated by a normal curve, and the distribution of mature goblet cells by an exponential curve. Some of the parameters of the distributions, different for various crypt classes, are shown to have common values when normalized by dividing them by the crypt length in a given class. the results are considered as indicating the manifestation of two levels of control of proliferation: one establishing the common pattern of the distributions along different crypts, and the second causing the differences in distributions depending on the region of the colonic wall.
INCORPORATION OF TRITIATED THYMIDINE INTO THE SKIN AND HAIR FOLLICLES
Authors: Potten Christopher S. , Jessup Barbara A. , Croxson Mary B. 
Published: May 2008

ABSTRACTThe incorporation of tritiated thymidine into the skin has been studied after the initiation of new hair growth by plucking. Techniques are described whereby the incorporation into hair follicles and into the basal layer of the epidermis can be studied independently. Fluctuations are observed in the levels of incorporation in both cell populations through the hair growth cycle. These fluctuations show great regularity. the early fluctuations have been attributed to synchronous progression of cells through the cell division cycle. the significance of the fluctuations is discussed with particular reference to (I) possible persistence of cell cycle synchrony, (II) regulatory feedback mechanisms controlling DNA synthesis, perhaps through specific mitotic inhibitors, (III) the existence of Go, G1 and G2 cell sub‐populations.
A QUANTITATIVE STUDY OF THE MITOTIC ACTIVITY IN THE SUBEPENDYMAL PLATE OF ADULT RATS
Authors: Hopewell J. W. 
Published: May 2008

ABSTRACTA quantitative study of the mitotic activity of the cells of the subependymal layer in the rat brain has shown that mitotic activity decreases with the increase in age of the animals. Mitotic activity is still found in rats 16 months old and in the case of animals of two strains of rats, of this age, the mitotic count is significantly higher in males than in females.The relationship between a reduced rate of brain growth and the decline in mitotic activity and the significance and importance of the higher mitotic count in the subependymal plate of 16‐month‐old males compared with similar females is discussed.
THE APPLICATION OF AGE RESPONSE FUNCTIONS TO THE OPTIMIZATION OF TREATMENT SCHEDULES
Authors: Steward Palmer G. , Hahn George M. 
Published: May 2008

ABSTRACTA computer‐based technique is described for calculating the survival of normal and malignant cell populations during and after chemotherapy or radiotherapy. For exponentially growing cells, cell sensitivity as a function of the position in the cell cycle (age response function) is considered and survival calculated by means of a method discussed previously (Hahn, 1966; Hahn & Kallman, 1967). It is shown how the age response function is obtained from experimental data. Two examples of the application of the computer‐based technique are given. As one example, the technique is used to ‘optimize’ the scheduling of fractionated irradiations to differentially kill one cell line over another using as a basis for optimization differences in their age response functions. the second example illustrates the use of the technique to determine the relative advantage of different chemotherapy protocols. Here the survival of cycling and noncycling bone marrow stem cells, and resistant and sensitive malignant cells, is calculated. It is suggested that the technique may have direct relevance for the chemotherapy of some leukemias.
THE VALIDITY OF AUTORADIOGRAPHIC LABELING
Authors: Moffatt D. J. , Youngberg S. P. , Metcalf W. K. 
Published: May 2008

ABSTRACTAs part of an experimental evaluation of autoradiographs after administration of 3H‐thymidine to rats, we estimated the background distribution of silver grains. the mean level was within normally accepted limits. the distribution of non‐isotope induced grains was such that the validity of all labeling studies which do not evaluate background must be subject to question.
PERIODICITY OF DNA SYNTHETIC ENZYMES DURING THE HeLa CELL CYCLE
Authors: Brent T. P. 
Published: May 2008

ABSTRACTThe levels of the deoxynucleoside phosphokinases have been determined during the cell cycle in synchronous cultures of HeLa cells. Deoxycytidine and thymidine phosphokinases showed temporally similar periodic fluctuations while the purine deoxynucleoside phosphokinases showed a constant high activity. Experiments with metabolic inhibitors suggest that the observed rise in thymidine phosphokinase activity is directly due to the enzyme's biosynthesis.