bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spermatogonial Multiplication In the Chinese Hamster. Iv. Search For Long Cycling Stem Cells
Authors: Lok D. , Jansen M. T. , de Rooij D. G. 
Published: May 2008

ABSTRACT In the Chinese hamster, 17 days, i. e. one cycle of the seminiferous epithelium, after two injections of [3H]TdR given 24 hr apart, labelled cells were found among all types of spermatogonia, including stem cells (As). These labelled As spermato‐gonia derive from one or more self‐renewing divisions of the stem cells that originally incorporated [3H]TdR. In the steady state, half of the divisions of the As will be self‐renewing and the other half will give rise to Apr spermatogonia that will ultimately become spermatozoa. Theoretically, the labelling index (LI) after 17 days will be similar to that after 1 hr, and in this study twice as high as for the 1‐hr interval since only one injection was given. However, experimental values only half that of the theoretical LI were found after 17 days. the following causes for the loss of labelled stem cells are discussed: (1) dilution of label because of division; (2) influx of unlabelled components of false pairs (i. e. newborn stem cells that still have to migrate away. mostly during G1, from their sister cells and are scored as Apr spermatogonia) between 1 hr and 17 days; (3) the existence of long‐ and short‐cycling stem cells, probably combined with preferential differentiation of the short‐cycling elements; (4) selective segregation of DNA at stem cell mitosis; and (5) irradiation death of radiosensitive labelled stem cells.As it is not impossible that factors 1, 2, 4 and 5 together account for the total loss of labelled stem cells, LI results do not provide evidence for the existence of separate classes of short‐ and long‐cycling stem cells.The distributions of the LIs of the As, Apr and Aal spermatogonia over the stages of the epithelial cycle at 17 days are similar to those at 1 hr after injection. Hence the regulatory mechanisms that govern the stimulation and inhibition of proliferation of As that give rise to new As for the next epithelial cycle are similar to those of the As that will divide into Apr spermatogonia during the same epithelial cycle.Grain counts revealed that more [3H]TdR is incorporated into As, Apr and Aal spermatogonia that are in S phase during epithelial stages X‐IV than in stages V‐IX.
Survival and Repopulation of Irradiated ‘Pre‐Cfu‐C’ In Mice
Authors: Aizawa Shin , Amaki Ichita , Miyanomae Takeshi , Tsurusawa Masahito , Mori Kazuhiro J. 
Published: May 2008

ABSTRACT Supernatants of murine bone‐marrow cultures contain a colony‐promoting factor (CPF) which increases the number of granulocyte and macrophage colonies in semi‐solid agar cultures in the presence of colony‐stimulating factor (CSF). Incubation of bone‐marrow cells with CPF results in an increase in the number of granulocyte/macrophage progenitor cells (CFU‐c) and the CPF‐responsive cells may be younger than the CFU‐c.We have investigated the radiosensitivity and the pattern of the recovery after irradiation of CPF‐responsive cells. We found that the radiosensitivity of CPF‐responsive cells was significantly lower than those of CFU‐c. burst‐forming units‐erythroid (BFU‐e) and pluripotent stem cells in vivo (CFU‐s) and in vitro (CFU‐mix). the CPF‐responsive cells remained subnormal even at 28 days after irradiation of the mice, a time when the CFU‐s and CFU‐c had recovered completely.Therefore the CPF‐responsive cells may constitute a separate compartment, namely ‘pre‐CFU‐c’, in the maturation sequence of granulopoiesis, and this maturation of the ‘pre‐CFU‐c’ to CFU‐c seems to be highly stimulated after irradiation to counterbalance the influx from CFU‐s.
A Study of the Proliferative Response of Rabbit T Cells Using the Brdu‐Hoechst Method
Authors: Roholl Paul J. M. , Distel Ben 
Published: May 2008

AbstractCon‐A‐ and PHA‐induced proliferation of cells from rabbit thymus, spleen and mesenteric lymph node was studied with the DNA‐fluorescent probe 33258 Hoechst. the fluorescence of this probe is quenched when 5‐bromo‐2′‐deoxy‐uridine is incorporated into nascent DNA during the S phase. Fluorescence decreased with increasing content of newly formed DNA per cell. Proliferation kinetics and the number of Con‐A‐ and PHA‐reactive cells (C+ and P+ cells) were determined cytofluorometrically.Lymphocytes from control and dexamethasone (DX)‐treated animals start their proliferation early: after 42 hr about 25% of the control and the majority of the DX‐resistant cells finished their second cell division.Small numbers of C+ (12.0%) and P+ (3.5%) cells were found in control thymus, while these percentages were enhanced in DX thymus: 32.5 and 27.0% respectively; 50% of the spleen T cells in control and DX animals are C+ or P+ and 75% of the lymph‐node T cells are C+ (after DX 45%) and 50% are P+ (after DX also 50%).It is concluded that in thymus and lymph nodes, a steroid sensitive (Ss) C+P‐, and in lymph nodes a Ss C+P+ cell pool is present. A mitogen non‐proliferative cell pool (C‐P‐) is present in control and DX thymus.
Mitotic and Labelling Activity In Normal Human Epidermis In Vivo
Authors: Camplejohn R. S. , Gelfant S. , Chalker D. , Sittampalam Y. 
Published: May 2008

AbstractLabelling and mitotic indices were studied in the epidermis of twenty‐eight young men. A mean labelling index of 5.5% was found from the whole study and a mean mitotic index of 0.06%. Mitotic index particularly was extremely variable; indices between 0.002 and 0.438% were found in individual biopsies. In the first two of three experiments in which mitotic index at 09.00 hours was compared with that at 15.00 hours, significant differences were found (15.00 hours > 09.00 hours by a factor of 2.6, P < 0.001). However, in the third such experiment no such difference was found, suggesting that the timing and occurrence of diurnal rhythms of mitotic activity may not be consistent in normal human epidermis. In the one experiment in which it was investigated, a significantly higher mitotic index was found at 21.00 hours compared to 09.00 and 15.00 hours. Labelling index did not vary significantly at 09.00, 15.00 or 21.00 hours. However, labelling index did show a significant pattern of change over a 12‐month period in two groups of subjects; peaks of labelling were seen in July and troughs in January. Very high ratios of labelled: mitotic cells were found, the median ratio for the whole study being ninety‐eight labelled: one mitotic cell. This finding supports the possibility that not all labelled cells subsequently go on to divide in normal human epidermis.
Subpopulations of Slowly Cycling Cells In S and G2 Phase In Mouse Epidermis
Authors: Clausen O. P. F. , Aarnæs E. , Kirkhus B. , Pedersen S. , Thorud E. , Bolund L. 
Published: May 2008

AbstractEvidence has been presented supporting the existence of heterogeneity in cell‐cycle progression in mouse epidermis, the present study was undertaken to characterize this heterogeneity in more detail. Hairless mice were continuously labelled with tritiated thymidine every 4 hr for 4 days. Basal cell suspensions were prepared from slices of mouse skin at intervals during the experiment and subjected to DNA flow cytometry. Cell‐cycle analysis was combined with sorting of cells from windows in G1, S and G2, phase, and the proportion of labelled cells within each window was determined in autoradiographs. Reanalysis and resorting to control the purity of sorted fractions were performed.Computer simulations of the data were made using a mathematical model assuming different S and G2 phase characteristics. A good fit to the data was only obtained when heterogeneity in mouse epidermal cell‐cycle progression was assumed, indicating the existence of slowly traversing, distinct subpopulations of cells in G2 and S phase. These cells are assumed to contribute to about 40% of all cells in S phase and to about 70% of all in G2 phase. the estimated residence times in the resting states were 38 and 32 hr in S and G2 phase, respectively. Two‐parameter sorting based on DNA and light scatter indicated that slowly cycling cells were larger than the average. There is no evidence of significant subpopulations of permanently non‐proliferating keratinocytes in any of the cell‐cycle phases.
Cell‐Cycle Analysis Using A Monoclonal Antibody to Brdurd
Authors: Dean Phillip N. , Dolbeare Frank , Gratzner Howard , Rice Glenn C. , Gray Joe W. 
Published: May 2008

AbstractThe flow cytometric measurement of DNA distributions of cells has many applications in biomedical research. Phase fractions estimated (calculated) from such distributions are used to study the growth characteristics of various types of cells, particularly when the cells have been exposed to perturbing agents such as chemotherapeutic drugs. For more than 10 years many methods for resolving DNA distributions into the three cell subpopulations (G1, S and G2, + M) have been reported in the literature. A new method of analysis utilizing a monoclonal antibody to bromodeoxyuridine (BrdUrd) has been developed (Gratzner, 1982; Dolbeare et al., 1983) which makes it possible in most cases to accurately determine phase fractions without resorting to mathematical models. the procedure involves the incorporation of BrdUrd by growing (DNA synthesizing) S phase cells, labelling the BrdUrd with a fluorescent monoclonal antibody, and the bivariate measurement of the antibody and of total DNA content, the latter through propidium‐iodide staining. the resulting bivariate distributions clearly and simply resolve the three subpopulations. This paper describes the method and illustrates its use in the analysis of various fractions of elutriated exponentially growing Chinese hamster ovary (CHO) cells.
Endogenous Regulation of Endothelial Cell Proliferation
Authors: Sorgente Nino , Bullard Debra L. , Jakovljevic Ljiljana , Dorey Kathleen 
Published: May 2008

AbstractBovine aortic endothelial cells (BAEC) in culture have the ability to regulate their own proliferation. We have found that a fraction below 100,000 daltons obtained from the media of confluent cultures of BAEC inhibits tritiated thymidine [3H]TdR incorporation as well as their proliferation. the inhibition is dose‐ and time‐dependent; maximum inhibition of [3H]TdR incorporation occurs 8 hr after cells are released from synchronization and the inhibitory fraction is added. Inhibition is evident at concentrations as low as 50 μg/ml and reaches a maximum at 600 μg/ml. the blockage of [3H]TdR incorporation is reflected in the inhibition of cell proliferation. In the presence of 400 μg of endogenous inhibitor per ml of media, added at the time of plating, the average population doubling time increases from 19 to 41 hr. These findings indicate that, in culture, BAEC can regulate their own proliferation by synthesizing an endogenous inhibitor(s) of proliferation.
Different Sensitivities of Granulocyte‐Macrophage and Erythroid Progenitor Cells of Normal Human Bone Marrow to S‐Phase‐Specific Agents
Authors: Kubota Kazuo , Preisler Harvey D. , Costanzo Catherine 
Published: May 2008

AbstractThe extraordinary sensitivity of early erythroid progenitor cells (BFU‐e) of normal human bone marrow to tritiated thymidine ([3H]TdR) was studied. While exposure of bone‐marrow cells to [3H]TdR for 1 hr resulted in the death of only 40% of the granulocyte‐macrophage progenitor cells (CFU‐c), 90% of BFU‐e were killed. Experiments in which normal bone‐marrow cells were mixed with bone‐marrow cells which had been exposed to [3H]TdR demonstrated that the excessive killing of BFU‐e by [3H]TdR reflected carry‐over of the [3H]TdR by the exposed cells. A carry‐over effect was not observed for CFU‐c, suggesting the presence of a fundamental difference in the metabolism of TdR between CFU‐c and BFU‐e. There was a suggestion of a carry‐over effect regarding two other S‐phase‐specific agents, hydroxyurea and 1‐β‐D‐arabinofuranosylcytosine.
Cell Kinetic Studies In the Epidermis of Mouse. Iii. the Percent Labelled Mitosis (Plm) Technique
Authors: Potten C. S. , Wichmann H. E. , Dobek K. , Birch J. , Codd T. M. , Horrocks L. , Pedrick M. , Tickle S. P. 
Published: May 2008

AbstractFull PLM curves have been obtained for four sites in the mouse. the first peaks have been analysed by computer and the duration of the G2+ M and S phases determined together with their standard deviations. the full curves showed a general similarity for all four sites with no clear second peak. the data are compared with the published data for mouse and human epidermis using the in vivo PLM technique. the timing and shape of the first peak can vary considerably even for one site in mice. Hence, both G2+ M and S can vary in their durations. Cells labelled at one time of day exhibit different kinetic properties to those labelled at another time of day. the duration of G2+ M is shortest in dorsum labelled at 03.00 hours (3.2 hr) and longest in tail (up to 7.5 hr). the S‐phase is shortest in dorsum (6.3–7.2 hr) and longest in tail or ear (13.3–14.1 hr). There is also a very large standard deviation in tail and foot. There is little general variability when the psoriatic human data are considered, which is surprising. the general variability amongst the data from experimental mice might also be expected amongst humans which might make comparisons between the cell kinetics of normal and diseased skin difficult.
Effects of Pulse Labelling With Tritiated Thymidine On the Circadian Rhythmicity In Epidermal Cell‐Cycle Distribution In Mice
Authors: Clausen O. P. F. , Kirkhus B. 
Published: May 2008

AbstractThe influence of pulse labelling with 50 °Ci tritiated thymidine ([3H]TdR) (2 μCi/g) on epidermal cell‐cycle distribution in mice was investigated. Animals were injected intraperitoneally with the radioactive tracer or with saline at 08.00 hours, and groups of animals were sacrificed at intervals during the following 32 hr. Epidermal basal cells were isolated from the back skin of the animals and prepared for DNA flow cytometry, and the proportions of cells in the S and G2 phases of the cell cycle were estimated from the obtained DNA frequency distributions. the proportions of mitoses among basal cells were determined in histological sections from the same animals, as were the numbers of [3H]TdR‐labelled cells per microscopic field by means of autoradiography.The results showed that the [3H]TdR activity did not affect the pattern of circadian rhythms in the proportions of cells in S, G2 and M phase during the first 32 hr after the injection. the number of labelled cells per vision field was approximately doubled between 8 and 12 hr after tracer injection, indicating an unperturbed cell‐cycle progression of the labelled cohort. In agreement with previous reports, an increase in the mitotic index was seen during the first 2 hr.These data are in agreement with the assumption that 50 °Ci [3H]TdR given as a pulse does not perturb cell‐cycle progression in mouse epidermis in a way that invalidates percentage labelled mitosis (PLM) and double‐labelling experiments.
Cell Population Kinetics and Dna Content During Thyroid Carcinogenesis
Authors: Christov Konstantin 
Published: May 2008

AbstractThe proliferation kinetics and DNA content of thyroid follicular cells in rats were studied by autoradiography and cytophotometry. Continuous treatment of animals with methylthiouracil (MTU) results in hyperplasia followed by tumour growth in the thyroid gland. the mitotic index (MI) increases from 0.006 ± 0.002% in controls to 0.13 ± 0.06% in hyperplasia and to 0.09 ± 0.03% in malignant cells. the same is true for the labelling index (LI) which rises from 0.08 ± 0.003% in controls to 1.4 ± 1.1% in hyperplasia and to 1.0 ± 0.6% in follicular adenomas. the S‐phase duration (Ts) is shortened from 8.0 ± 1.2 hr in controls to 6.0 ± 1.4 hr in animals treated for 9 months with MTU and prolonged to 15.4 ± 2.1 hr in papillary carcinomas. In all MTU‐treated animals a decrease in the value of the potential population doubling time (TPD) and thyroid weight doubling time (TD) was observed. the cell loss factor (ø) decreases in animals treated for 3 months with MTU and increases during the stage of tumour growth in the gland (animals treated 12–15 months with MTU). DNA measurements in the nuclei of hyperplastic and neoplastic thyroid tissues reveal cells with values exceeding that in control animals. However, no difference was found in the DNA content between thyroid adenomas and carcinomas, nor between thyroid hyperplasia and neoplasia.During the last decade numerous autoradiographic studies have been performed on the cell population kinetics of benign and malignant tumours in animals and man (Steel, 1977; Tubiana & Malaise, 1977). It has been established that cell proliferation is an important parameter in both the initiation and promotion phases of carcinogenesis (Oehlert, 1973; Berenblum, 1979). Cell kinetic studies during carcinogenesis have predominantly dealt with the liver (Rajewsky, 1967; Chernozemski & Warwick, 1970), skin (Raick, 1974), the mammary gland (Bresciani, 1965; Nagasawa, Yanai & Nagigushi, 1976b), the uterine cervix (Nagasawa, Matsuura & Tojo, 1976a) and intestinal cells (Tutton & Barka, 1966; Pozharisski, Klimashewski & Gushin, 1977). Information on the changes in cell population kinetics during thyroid carcinogenesis is still incomplete. Data reported in the literature are mainly devoted to the short‐term effects of goitrogens and radiation factors (Santler, 1957; Sheline, 1969; Philip, Crooks & MacGregor, 1969; Wynford‐Stringer & Williams, 1982; Redmond & Tuffery, 1981).The present study was carried out to investigate if changes in the cell population kinetics and DNA content occur during thyroid carcinogenesis, as well as if thyroid adenomas and carcinomas differ in their proliferative potential and DNA content.
Aspects of Statistics In Studies of Cell Proliferation
Authors: Appleton David R. 
Published: May 2008

AbstractComputer simulation of an experiment can help to reveal how effective that experiment might be in estimating cell kinetic parameters, or in elucidating the nature of a proliferative response to a perturbation of the steady state, such as a carcinogenic or therapeutic treatment. Writing a simulation also clarifies one's thoughts about possible mechanisms of the proliferative response.
Cell‐Cycle‐Specific Activity of Cyclic Nucleotide Phosphodiesterase In Physarum polycephalum
Authors: Kupetz I. S. , Jeter J. R. 
Published: May 2008

AbstractThe cell‐cycle‐related activities of the cAMP‐ and cGMP‐dependent phosphodiesterases of Physarum polycephalum were assayed. the activities of plasmodial homogenate and of selected subcellular fractions were measured. the results suggested the presence of both cAMP‐ and cGMP‐dependent phosphodiesterase in the isolated nuclei of P. polycephalum. In addition, they reveal that the cAMP‐ and cGMP‐dependent phosphodiesterase activities of the subcellular fractions fluctuate throughout the cell cycle. the whole‐cell homogenates exhibit no cell‐cycle‐related changes in the presence of 5 × 10‐4 m cGMP. Kinetic data suggest the presence of multiple phosphodiesterase activities in the homogenate and its particulate fractions for the cGMP‐dependent enzyme. Multiple cAMP activities are also suggested for the particulate fractions. the Km values indicate that the substrate affinities of the phosphodiesterases from P. polycephalum are similar to those found previously in mammalian systems.
On the Role of Microfilaments In Cell‐Shape‐Mediated Growth Control of Lens Epithelial Cells
Authors: Iwig M. , Glaesser D. 
Published: May 2008

AbstractWith regard to the fact that, in anchorage‐dependent lens epithelial cells, DNA synthesis can be switched on and off by cell flattening and cell rounding, respectively, the state of the microfilaments has been followed by labelling actin with FL‐phalloidin during cell‐shape alterations. Cell flattening proved to be accompanied by both a structural organization of actin filaments into stress fibres and an enlargement of the area of the cell nucleus. Cell rounding, on the other hand, caused the microfilament bundles to disappear and the area of the nucleus to become smaller. From the time course of the inhibition of DNA synthesis by cytochalasin B, it was inferred that functionally intact microfilaments are required for the entrance of the cells into DNA synthesis but not for the maintenance of ongoing DNA synthesis. the assumption has been made that the tension, generated by microfilaments during cell spreading, will affect the state of the plasma membrane as well as the shape and the structure of the nucleus, which in turn seems to be preparatory for cells to enter the cycle.
Testicular Morphology and Cell Proliferation Kinetics of Immature Germ Cells and Sertoli Cells In Suckling Undernourished Rats
Authors: Bansal‐Rajbanshi Mridula , Mathur Meera 
Published: May 2008

AbstractUndernutrition during suckling was induced in newborn rats by increasing the litter size to sixteen pups to be fed by one mother. Animals reared in litters of eight served as controls. Undernourished animals showed retarded body and testicular growth during a suckling period of 22 days. Sequential morphogenesis of the testis was not altered up to 15 days of age. However, certain morphological alterations in Sertoli cells and Leydig cells were observed from 15 days onwards. Cell generation cycle of spermatogonial germ cells and supporting cells (future Sertoli cells) on day 9 showed marked prolongation of DNA synthetic phase (S), unaltered post‐DNA synthetic phase (G2) and total cycle (Tc) and shortening of the pre‐DNA synthetic phase (G1) indicating a depression in DNA synthesis in undernutrition.
Effect of Haemopoietic Stem‐Cell Proliferation Regulators On Early and Late Spleen Colony‐Forming Cells
Authors: Wright E. G. , Lorimore S. A. , Lord B. I. 
Published: May 2008

AbstractAn inhibitor and stimulator of CFU‐s proliferation can be obtained from haemopoietic tissue containing, respectively, relatively quiescent CFU‐s (e.g. normal bone marrow) and proliferating CFU‐s (e.g. regenerating bone marrow). Their effects on the proliferative behaviour of steady‐state and regenerating marrow CFU‐s, which produce colonies 7, 10 and 12 days post‐transplantation have been investigated.The results demonstrate changing sensitivities of CFU‐s to inhibitor and stimulator as they progress through a developmental age structure. ‘Older’ CFU‐s (producing early spleen colonies) are more sensitive to stimulator, ‘Younger’ CFU‐s (producing late spleen colonies) are more sensitive to inhibitor.
Basal‐Cell Subpopulations and Cell‐Cycle Kinetics In Human Epidermal Explant Cultures
Authors: Jensen P. K. A. , Pedersen S. , Bolund L. 
Published: May 2008

AbstractCultured human epidermal cells were studied by cell sorting and autoradiography after different 3H‐thymidine (3H‐dThd)‐labelling procedures and after labelling with DNA precursors that are incorporated via salvage or de novo pathways. It was shown that 3H‐dThd incorporation was the best measure of the rate of DNA replication. Dose‐response experiments with pulse and continuous labelling revealed that all S‐ and G2‐phase cells were cycling, whereas some 20% of the cells stayed in G1‐phase for long periods of time. Most, if not all of these cells were probably non‐proliferating differentiated keratinocytes. At least two subpopulations of S‐phase cells could be discriminated on the basis of the rate of incorporation of DNA precursors. the difference in precursor incorporation did not seem to be caused by differences in nucleotide metabolism but rather to reflect true differences in the rate of DNA replication. Continuous labelling experiments showed that these subpopulations also were apparent in the G1‐ and G2‐phases. Studies of the grain‐count distribution revealed that cells that appeared to move rapidly through the S‐phase moved slowly through the G2‐phase, and vice versa. Cells stained with acridine orange were subjected to a two‐parameter analysis in the cell sorter by simultaneous measurement of the DNA and RNA fluorescence. Autoradiography of sorted cells revealed that, on average, cells with low RNA contents incorporated 3H‐dThd at a higher rate than cells with high RNA contents.