bluuebunny/crossref_metadata_2025_split huggingface dataset:
CONTROL OF GRANULOCYTE PRODUCTION
Authors: Rytöaa T. , Kiviniemi Kyllikki 
Published: May 2008

ABSTRACTIt has previously been demonstrated that granulocyte production is controlled by a humoral feedback mechanism based on at least two tissue‐specific substances, granulocytic chalone and antichalone. It is now shown that the action of these regulators is almost instantaneous, reversible, short‐term, and at least in the case of chalone, followed by an overshoot during recovery.It is also shown that both substances operate primarily, if not solely, in a phase prior to DNA synthesis: chalone prevents and antichalone promotes the entry of precursor cells into the DNA synthesis phase. These actions are based on a switch mechanism, apparently involving transient change in the synthesis of a short‐living RNA.In addition to these results, a dose‐effect relationship is obtained for chalone, and continuous production of the inhibitor in mature granulocytes is indicated.
SEMIQUANTITATIVE CELL CYCLE MODEL FOR SLOW GROWING ESCHERICHIA COLI
Authors: Simon Z. 
Published: May 2008

ABSTRACTA cell cycle model for Escherichia coli is discussed. It is assumed that the DNA synthesis starts when a threshold dTTP concentration is reached, that the dTTP synthesis is subject to product inhibition and that the duration of DNA replication is given by the time necessary to synthesize the required quantity of dTTP. The model is compared with data for slow growth rates. The constancy of cell volume and of the quotient of presynthetic period per generation cycle is reproduced by the model. The calculated upper limit for the cell volume and lower limit for the quotient are about ten times higher and lower respectively than the real values.
THE EFFECT OF CELL CROWDING ON THE IN VITRO REACTIVITY OF NORMAL AND ABNORMAL HUMAN LYMPHOCYTES
Authors: Watkins Sylvia M. , Moorhead John F. 
Published: May 2008

ABSTRACTThe effects of cell crowding on the blastogenic response to phytohaemagglutinin in in vitro cultures of lymphocytes from both normal subjects and from patients with lymphoproliferative disorders were studied. Moderate degrees of cell crowding resulted in enhancement of blast transformation; however, further increases in the degree of crowding produced relative or absolute inhibition of blast transformation, an effect which was more marked in the normal controls than in the lymphoproliferative group. The significance of these findings is discussed.
THE RATE OF DECAY OF THE DOSE EQUIVALENT OF RADIATION INDUCED SUB‐LETHAL DAMAGE
Authors: Liversage W. E. 
Published: May 2008

ABSTRACTExisting experimental data relating to the rate of recovery of the dose equivalent of sub‐lethal damage are analysed. A precise determination of the half‐life of the dose equivalent is found to be impossible, but all the evidence reviewed suggests that it is of the order of 1 or 2 hr for mammalian systems irradiated at normal body temperature and that, in such systems, little error is produced in dosage calculations by assuming a value of 1.5 hr to be applicable, as originally suggested by Lajtha & Oliver (1961).
HEPATOCYTIC PROLIFERATION IN NORMAL RATS AFTER MULTIPLE EXCHANGE TRANSFUSIONS WITH BLOOD FROM PARTIALLY HEPATECTOMIZED RATS
Authors: Grisham J. W. 
Published: May 2008

ABSTRACTEither three or four (but not one or two) consecutive exchange transfusions (75–85% washout of blood) of rats with intact livers, utilizing blood from donors partially hepatectomized 24 hr earlier, results in increased incorporation of 3H‐thymidine into hepatic DNA and hepatocytic nuclei 20 hr after the first transfusion. Exchange transfusion with blood from sham‐hepatectomized animals does not produce this effect.
A DELAY IN THE G2 PERIOD OF CULTURED HUMAN LEUCOCYTES AFTER TREATMENT WITH RUBIDOMYCIN (DAUNOMYCIN)
Authors: Brehaut Loreen A. 
Published: May 2008

ABSTRACTHuman leucocytes were cultured for 3 days at 37°C, and during this time treated with rubidomycin (also known as daunomycin) for periods up to 48 hr. The effects of this treatment were studied by examining mitotic indices, uptake of 3H‐thymidine, and patterns of DNA content (measured by microdensitometry on Feulgen‐stained cells). A low concentration of rubidomycin (0.1 μg/ml) caused accumulation of cells in the G2 period, which in turn resulted in a decrease in the mitotic index. A secondary effect was a slight drop in 3H‐thymidine uptake after 12 hr. Higher doses (up to 10 μg rubidomycin per ml) caused an inhibition of DNA synthesis, with accumulation of unlabelled cells between G2 and G2. The probable mode of action of rubidomycin, as presented by earlier authors, is the intrusion of the drug molecule between DNA strands, forming a complex with DNA, and hindering its normal folding. This is discussed with respect to the present findings.
RADIOAUTOGRAPHIC STUDIES OF THE STEM CELL IN THE THYMUS OF THE IRRADIATED RAT
Authors: Everett N. B. , Tyler Ruth W. 
Published: May 2008

ABSTRACTRadioautographic evidence is presented which characterizes the marrow derived stem cell which promotes thymic recovery following irradiation in the rat. These immigrant cells are similar in morphology to blood monocytes and have been called monocytoid, meaning monocyte‐like in appearance. The typical cell had abundant pale staining cytoplasm and a nucleus with many invaginations and folds and a fine chromatin structure. There was no prominent nucleolus. The majority of these cells entered the thymus of the irradiated rat via the blood vessels into the septa and made their way through the connective tissue to the outer cortex. Three distinct morphological cell types appeared to be derived from the immigrant cells. These were fibrocyte‐like cells which were located within the septa, macrophages located mainly within the medulla and septa, and large blast cells within the cortex, which proliferated giving rise to large thymocytes. The blast cells were characterized as having abundant moderately basophilic (and pyroninophilic) cytoplasm with a distinct cytoplasmic boundary, a large nucleus which still had invaginations and folds, a loose chromatin structure and one or more very prominent nucleoli. They were located in groups primarily within the outer cortex and often adjacent to blood vessels. They were found to be highly susceptible to damage in smear preparations. In contrast, their progeny, the large thymocytes were not highly susceptible to damage in smear preparations but teased out as large round cells with a highly basophilic rim of cytoplasm. The large thymocytes were precursors to medium and small cells.A radioautographic technique for 1 μ tissue sections is also described.
KINETIC PROPERTIES OF HAEMOPOIETIC STEM CELLS
Authors: Lajtha L. G. , Pozzi Laura v. , Schofield R. , Fox Margaret 
Published: May 2008

ABSTRACTA comparison of the exocolonizing and autorepopulating tests for haemopoietic stem‐cell assay indicate that the ‘overshoot’in splenic colony formation, observed 12–14 days after 150 rad total‐body radiation (TBR), only occurs with the auto‐repopulation assay. The explanation is that the priming dose of 150 rad increases the absolute seeding rate of stem cells from the marrow. A seeding rate significantly greater than normal can ‘take’only if the spleen is available—it can expand and accommodate stem cells while the bone marrow cannot. If, however, the absolute number of colony‐forming cells are decreased in the femur, a relative increase in seeding rate can take place even in the splenectomized animal. Evidence is presented concerning the different turnover states of exo‐ and autorepopulating stem cells (CFU) and those responsible for erythropoietic response (ERC), and the precursors of agar colony‐formers.
THE EFFECT OF X‐RAY INDUCED SYNCHRONY ON TWO‐DOSE CELL SURVIVAL EXPERIMENTS
Authors: Young Judith M. , Fowler John F. 
Published: May 2008

ABSTRACTCalculations were made based on experimental data of the variation in radiosensitivity and in cell cycle delay with age in Chinese hamster cells (Sinclair, 1967, 1968). The computed syntheses included: (a) single‐dose survival curves; (b) splitdose recovery curves, the pattern of survival; and (c) two‐dose survival curves, the shape of the second survival curve. It is clear that, after an initial dose, changes occur in the subsequent dose‐response curve which depend upon size of dose and time after irradiation. Following rapid and apparently complete repair of sublethal injury, these changes can be attributed to progression of a partially synchronized population through phases of varying radiosensitivity. These changes may be small in some systems, but important in others. The concept of equal dose‐increments after each of several dose fractions is an over‐simplification and must be used with care.
THE EFFECT OF HYDROCORTISONE ON HeLa CELL GROWTH
Authors: Kollmorgen G. M. , Griffin M J. 
Published: May 2008

ABSTRACTHeLa Chessen cells have a doubling time of 18 hr when grown in MEM containing 10% calf serum and antibiotics. When hydrocortisone (1.7 μg/ml) is added to exponentially distributed cells in log growth in this medium, a new pattern of growth begins to emerge after 10–12 hr. This pattern is characterized by a transitional state lasting for about 6 hr, and then a new doubling time of about 35 hr is maintained thereafter. Hydrocortisone removes about 5% of the cells from the proliferative pool and extends the generation time of proliferating cells to about 30 hr. The extension of the generation cycle appears to occur almost entirely in late G1.Cells grown as clones (average 6 cells/clone) prior to the addition of hydrocortisone, undergo these changes with doses as low as 0.00017 μg/ml of medium. When the average clone size is 1.5 cells per clone, the drug concentration must be 0.017 μg/ml or higher to initiate this response.The HeLa S3 strain continues to grow with an 18‐hr doubling time in the presence of hydrocortisone after a temporary delay in growth occurring between the 12th and 16th hour.
GRAFT SIZE CONSIDERATIONS IN THE KINETICS OF SPLEEN COLONY DEVELOPMENT
Authors: Schofield R. , Lajtha L. G. 
Published: May 2008

ABSTRACTThe kinetics of spleen colony development has been studied after the injection of 106, 105 and 3 × 104 bone marrow cells. The results indicate that:

The CFU population growth rate is independent of cell dose until the logarithmic growth phase is passed. Slowing of growth was seen by day 12 after the highest dose, by day 15 after the median dose, but was not observed during the period of observation after the low dose.
The growth rate of CFU per colony is independent of cell dose, but the curves are not identical. The differences between the curves leads to the conclusion that there is a dose‐dependent delay in the commencement of CFU proliferation. The delay is roughly equal to one cell cycle time between the medium and high inoculum groups and also between the medium and low inoculum groups.
The number of cells per colony is graft size dependent, the doubling times, where these can be roughly assessed, being inversely related to the graft size. From the average number of cells per colony on day 6 it is calculated that the mean doubling time in the early stages of colony development is less than 7 hr.
The proportion CFU:colony cells is dose dependent with the highest inoculum having the highest proportion and the low inoculum group having the lowest proportion.
CYCLES OF REDUPLICATION IN MEGAKARYOCYTE NUCLEI
Authors: Goyanes‐Villaescusa Vicente 
Published: May 2008

ABSTRACT1. Estimates of the number of dividing megakaryocytes with mitotic apparatus have been obtained in intact and in phenylhydrazine‐papain treated rats.2. In treated rats chromosome morphology was studied using colchicine and hypotonic treatment.3. In bone marrow smears and in cultures two systems for nuclear reduplication were demonstrated: C‐mitosis, and multipolar mitosis without cytokinesis.4. In phenylhydrazine‐papain treated rats, the mitotic index of each bone marrow cell series was greatly increased.
ANALYSIS OF THE KINETICS OF GRANULOSA CELL POPULATIONS IN THE MOUSE OVARY
Authors: Hartmann Niels Rudolph , Pedersen Torben 
Published: May 2008

ABSTRACTThe kinetics of granulosa cell populations in two types of follicles in ovaries of 28‐day‐old Bagg mice are investigated. The analysis includes estimations of mean values and standard deviations of the transit times (TG1, TS, TG2 and TC), the doubling time TD, and the proliferative fraction p.First the percentage of labelled mitosis curve (PLM‐curve) and the continuous labelling curve (CL‐curve) are estimated. Then a hypothesis concerning the cell kinetics of the granulosa cells in the two follicle types is set up. The normal distribution is chosen to simulate the probability density functions of the transit times. On the basis of the hypothesis mathematical expressions for the PLM‐ and CL‐curves are worked out. By fitting the calculated PLM‐curve to the experimental one it is possible to estimate mean values and standard deviations of TG1, TS>, and TG2. As a test of the hypothesis the CL‐curve is calculated by means of the estimated parameter values and compared to the experimental one. The calculated PLM‐ and CL‐curves are found to be in good agreement with the experimental data as far as both follicle types are concerned.It is concluded that the method is a useful procedure. The choice of a normal distribution does not imply a significant limitation of the method in these investigations. Moreover it is concluded that the hypothesis is plausible. This means, e.g., that the proliferative fraction is unity in the two follicle types and that there is no cell loss from the cell systems.
RENEWAL OF GOBLET AND PANETH CELLS IN THE SMALL INTESTINE
Authors: Cairnie A. B. 
Published: May 2008

ABSTRACTSingle and repeated injections of 3H‐thymidine were used to demonstrate that both Paneth and goblet cells in the small intestine of the rat undergo renewal but do not themselves proliferate. Goblet cells are renewed much faster than Paneth cells and probably migrate with the columnar cells from the crypts to the villi. Attempts were made to identify the proliferative precursors.
EFFECTS OF BACTERIAL ENDOTOXIN ON HEMOPOIETIC COLONY‐FORMING CELLS IN THE SPLEENS OF NORMAL MICE AND MICE OF GENOTYPE S1/S1
Authors: McCulloch E. A. , Thompson M. W. , Siminovitch L. , Till J. E. 
Published: May 2008

ABSTRACTMultiple doses of S. typhosa endotoxin caused an increase in the number of hemopoietic stem cells present in mouse marrow and spleen that could be detected using the spleen‐colony assay. This increase was inhibited by Colcemid, and by the genetically‐determined defect in hemopoiesis in mice of genotype S1/S1d. However, the defect in S1/S1d hosts did not prevent an endotoxin‐induced increase in the number of cells capable of forming colonies in cell culture. The results support the view that bacterial endotoxin acts, via a genetically‐controlled regulatory mechanism, to stimulate the proliferation of hemopoietic stem cells in the spleen.
ERYTHROPOIETIN SENSITIVITY OF RAT BONE MARROW CELLS SEPARATED BY VELOCITY SEDIMENTATION
Authors: McCool Dorothy , Miller R. J. , Painter R. H. , Bruce W. R. 
Published: May 2008

ABSTRACTRat bone marrow cells have been separated on the basis of their sedimentation at unit gravity. The cell population most responsive to erythropoietin in vitro was found to have a sedimentation velocity of about 6.6 mm/hr. In the process of becoming hemoglobin‐synthesizing cells, it undergoes cell division and its sedimentation velocity decreases to 3.9 mm/hr and then to 2.1 mm/hr, the sedimentation velocity of mature red blood cells.
SOME COMPARISONS OF THE KINETIC PROPERTIES OF FEMORAL AND SPLENIC HAEMOPOIETIC STEM CELLS
Authors: Guzman E. , Lajtha L. G. 
Published: May 2008

ABSTRACTA slightly different radiosensitivity is confirmed between colony forming units (CFU) in the femur as opposed to those of the spleen. The recovery pattern of the CFU in the femur and in the spleen following sublethal doses of radiation can be markedly different, depending on the radiation dose, particularly concerning the postirradiation ‘dip’. The turnover state of splenic CFU appears to be greater in normal animals than that of the femoral CFU. Hypertransfusion doubles the splenic CFU by the fourth day, while only marginally affecting femoral CFU. Erythropoietin, while increasing the CFU turnover significantly in both femur and spleen of the polycythaemic animal, also increases femoral but not splenic CFU.
PROTEIN SYNTHESIS IN EHRLICH ASCITES CELLS
Authors: Frindel E. , Baserga R. , Brigham P. 
Published: May 2008

ABSTRACTRapidly dividing Ehrlich ascites cells have a higher rate of protein synthesis than slowly‐growing cells. This is true whether protein synthesis is measured in vivo or in a cell‐free amino acid incorporating system. A lack of endogenous messenger RNA or a ribosomal defect in stationary cells is suggested as a likely cause of the decreased rate of protein synthesis.The soluble proteins synthesized by rapidly‐dividing cells are qualitatively different from those synthesized by slowly‐growing cells. The latter also have a larger intracellular pool of several amino acids and a slower protein turnover than rapidly‐dividing cells.
KINETICS OF A DRUG SENSITIVE CLONE OF HeLa CELLS
Authors: Nias A. H. W. , Fox Margaret , Fox B. W. 
Published: May 2008

ABSTRACTDrug sensitive clones have been isolated from a population of HeLa cells after treatment with methyl methane sulphonate (MMS). One of these clones has now been studied in more detail and some possible mechanisms of drug sensitivity have been related to the proliferation kinetics of the cells of this clone. The cell cycle is elongated and labelling techniques show this elongation to be confined to the G1 phase. Synchronized cultures have shown that the G1 phase is more sensitive to MMS than the S phase. These observations provide some explanation for the drug sensitivity of this clone of cells.
ANTIBODY‐PRODUCING CELLS: ANALYSIS AND PURIFICATION BY VELOCITY SEDIMENTATION
Authors: Phillips R. A. , Miller R. G. 
Published: May 2008

ABSTRACTVelocity sedimentation cell separation is a simple and reproducible method for obtaining highly enriched populations of viable antibody‐producing cells. Using suspensions of spleen cells prepared from mice immunized with sheep erythrocytes, fractions containing up to 2% 19S‐PFC and 25% 7S‐PFC can be obtained. Granulocytes constitute almost all of the remaining cells in these fractions.The sedimentation profile of 7S‐PFC is very broad in comparison with that of cell populations known to be homogeneous in size (e.g. mouse erythrocytes). Analysis of the profile of 7S‐PFC at different times after immunization suggests that the heterogeneity arises largely from the doubling in cell volume as a cell moves from one mitosis to the next. Early in the immune response, when the majority of the PFC are proliferating, the variation in sedimentation velocities is consistent with such a two‐fold variation in cell volume. Late in the response, when most PFC have stopped proliferating, the sedimentation profile is more homogeneous. This analysis suggests that the fractionation procedure is sensitive enough to separate PFC according to their position in the cell cycle.Sedimentation velocities were also measured for several other classes of cells found in spleen. Comparison of these values shows that sedimentation velocity is a useful parameter for characterizing different types of cells.
THE USE OF 59Fe UPTAKE FOR THE EVALUATION OF CELL PROLIFERATION IN SPLEEN COLONIES
Authors: Siracusa G. , Silini G. , Bricanti G. 
Published: May 2008

ABSTRACTA technique of 59Fe uptake in the spleen of irradiated bone‐marrow‐transplanted mice has been applied to the study of some kinetic parameters of the erythroid spleen nodule cells. Measurements of the doubling time of this population have been obtained together with estimates of radioactivity disappearance from the spleen, owing to a release of nodule cells into the blood stream. The kinetics of expansion of the erythroid cell compartment is compared with the pattern of increase of the colony‐forming cells in the spleen. The expansion of the erythroid cell population seems to be the result of at least two processes: an increase in the number of differentiating cells and the release of mature cells into the blood stream. It is suggested that more refined attempts to evaluate kinetic parameters of the spleen nodule cell population should allow for these factors.
CELL CYCLE CHARACTERISTICS OF HUMAN SOLID TUMORS IN VIVO
Authors: Young Robert C. , DeVita Vincent T. 
Published: May 2008

ABSTRACTThe duration of the DNA synthetic phase of solid tumors in six patients was determined in vivo by local injections of tritiated thymidine into tumor nodules on the skin and serial biopsies of the lesions. Labeled mitosis curves constructed from the data obtained revealed a distinct wave of labeled mitoses but no evidence of a second wave of DNA synthesis in all six patients. The duration of S phase was 24, 22 and 24 hr in the three patients with malignant melanomas and 19, 22 and 24 hr in the three patients with breast cancer. The method is relatively simple and requires much lower doses of tritiated thymidine; reproducible data are obtainable in patients with solid tumors in a much shorter period of time than with previous experiments.
STUDIES ON LYMPHOCYTES
Authors: Ruchti C. , Cottier H. , Cronkite E. P. , Jansen C. R. , Rai Kanti R. 
Published: May 2008

ABSTRACTContinuous extracorporeal irradiation of the circulating blood (ECIB) of from 3 to 501/2 hr duration was used to study in the calf the differential depletion of lymphocytes from spleen, lymph nodes and thymus as compared to blood and thoracic duct lymph. The cell content of tissues was measured by planimetry and/or test point analysis. Lymphocyte depletion by ECIB from various lymphoreticular organs, and from different areas within a given organ, was less than in the circulating blood or the thoracic duct lymph and varied from one site of a lymphoreticular organ to another. The degree of depletion with time followed an exponential function with at least two components. The first component corresponded to a relatively rapid fall and the second to a very slow reduction in lymphocyte content. The former is related to the elimination of an easily mobilizable pool of lymphocytes while the latter corresponds to a more sessile mass of lymphocytes which exchange with blood lymphocytes very slowly. Elimination of the easily mobilizable pool of lymphocytes by ECIB from all tissues studied was observed within 10–15 hr, indicating that the rate of exchange with blood is similar for this group of cells in various lymphoreticular tissues. The size, however, of the easily mobilizable vs the more sessile pools of lymphocytes may vary considerably, the best estimates for the former being as follows (in per cent of total lymphocyte mass): lymph node medulla, less than 10%; lymph node cortex plus paracortical zone, 18% (depletion mainly paracortical); red pulp of the spleen, 37%; densely populated white pulp of the spleen, 55%; and loosely populated white pulp of the spleen, 60%. In comparison, the approximate fractions of lymphocytes originating fromthe easily mobilizable pools in various lymphoreticular tissues plus the cells already circulating a t the onset of EClB correspond to 64% for the thoracic duct lymph and 78% for the circulating blood respectively. These findings are discussed in relation to production, recirculation and life span of lymphocytes, and immune reactions.
OPTIMIZED PARAMETERS FOR THE MITOTIC CYCLE
Authors: Barrett John C. 
Published: May 2008

ABSTRACTA method is described for the maximum likelihood estimation of the six parameters representing the means and standard deviations of the phases G1, S and G2 of the mitotic cycle. The likelihood is not explicitly formulated but is computed by the Monte Carlo program which evaluates the percentage of mitotic cells labelled with 3H‐thymidine. The method is applied to data obtained from an experiment performed with transplanted Marshall rat mammary tumours.