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Results for “cell proliferation”

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At least 19 recordsLinked to original sources
PubMed1978

Cell proliferation and cell density of mesenchyme in the maxillary process and adjacent regions during facial development in the chick embryo.

Cell proliferation, as measured by DNA labeling indices was analyzed during the early development of the maxillary process. Chick embryos were labeled with [3H]thymidine for 1 h and processed for autoradiography. The percentage of labeled mesenchymal cells was determined within delineated areas in the maxillary processes and in adjacent regions. Analysis of labeling indices in each of the areas at successive stages of development demonstrated a pattern of declining rates of cell proliferation with advancing developmental age. Cell proliferation in adjacent regions declined earlier and, in some instances, faster than it did in the maxillary process. Cell density was measured in the maxillary process and the roof of the stomodeum and was found to be higher in the maxillary process throughout the period studied. Cell density and cell proliferation data were analyzed with reference to the operation of 'density-dependent inhibition' of growth as a regulatory mechanism for the observed changes. 'Density-dependent inhibition' of growth was not a satisfactory explanation for the observed differences between the maxillary process and adjacent regions.

Animals↗
PubMed2024

Transient Zn2+ deficiency induces replication stress and compromises daughter cell proliferation.

Cells must replicate their genome quickly and accurately, and they require metabolites and cofactors to do so. Ionic zinc (Zn2+) is an essential micronutrient that is required for hundreds of cellular processes, including DNA synthesis and adequate proliferation. Deficiency in this micronutrient impairs DNA synthesis and inhibits proliferation, but the mechanism is unknown. Using fluorescent reporters to track single cells via long-term live-cell imaging, we find that Zn2+ is required at the G1/S transition and during S phase for timely completion of S phase. A short pulse of Zn2+ deficiency impairs DNA synthesis and increases markers of replication stress. These markers of replication stress are reversed upon resupply of Zn2+. Finally, we find that if Zn2+ is chelated during the mother cell's S phase, daughter cells enter a transient quiescent state, maintained by sustained expression of p21, which disappears upon reentry into the cell cycle. In summary, short pulses of mild Zn2+ deficiency in S phase specifically induce replication stress, which causes downstream proliferation impairments in daughter cells.

Zinc↗
PubMed1978

The effect of Rauscher murine leukemia virus infection on the hemopoietic system of BALB/c mice. Cell proliferation and cell loss.

Cell proliferation was investigated in normal and Rauscher Leukemia Virus-infected BALB/c mice. Five days after inoculation, islands of leukemic blasts arose in the red pulp, and proliferated as shown by autoradiographic analysis after a pulse of 3H-Thymidine. These cells subsequently infiltrated the whole spleen and 3 weeks after infection about 60% of the spleen consisted of large immature erythroblast-like cells. Repeated injections of 3H-Thymidine led to uniform labeling of 85% of the spleen cells. Cell cycle analysis showed that for bone marrow as well as for spleen cells the total duration of the cell cycle did not differ from the cell cycle times of normal erythroblasts. From the difference between the actual doubling time and the potential doubling time (estimated on the basis of the cell cycle time) it can be calculated that considerable cell loss must occur. This cell loss is only to a minor extent due to the release of blasts into the peripheral blood. Probably cell death and extrusion of nuclei during erythroid differentiation are the main factors involved.

Animals↗
PubMed2023

Transient Zn2+ deficiency induces replication stress and compromises daughter cell proliferation.

Cells must replicate their genome quickly and accurately, and they require metabolites and cofactors to do so. Ionic zinc (Zn2+) is an essential micronutrient that is required for hundreds of cellular processes, including DNA synthesis and adequate proliferation. Deficiency in this micronutrient impairs DNA synthesis and inhibits proliferation, but the mechanism is unknown. Using fluorescent reporters to track single cells via long-term live-cell imaging, we find that Zn2+ is required at the G1/S transition and during S-phase for timely completion of S-phase. A short pulse of Zn2+ deficiency impairs DNA synthesis and increases markers of replication stress. These markers of replication stress are reversed upon resupply of Zn2+. Finally, we find that if Zn2+ is removed during the mother cell's S-phase, daughter cells enter a transient quiescent state, maintained by sustained expression of p21, which disappears upon reentry into the cell cycle. In summary, short pulses of mild Zn2+ deficiency in S-phase specifically induce replication stress, which causes downstream proliferation impairments in daughter cells.

Biological sciences↗
PubMed1976

Chromatin structure and function in proliferating cells.

The conclusions that we would like to draw from this review are the following: (a) Chromatin structure and function are exceedingly sensitive to changes in the proliferative state of a cell. Differences can be detected between cells in mitosis, G1 and S, and even between G0 and G1 cells. (b)These differences are very unlikely to be artifactual, since similar changes can also be demonstrated in intact nuclei. (c) Some of these differences can be abolished by extraction of chromatins with low concentrations of salt. (d) Differences between chromatins of normal and neoplastic cells can also be detected, but they are largely related to differences in the extent of cell proliferation. (e) A number of laboratories have been very busy in trying to elucidate chromatin structure with different technologies. Sometimes a change in a macromolecule cause by a physiological stimulus can tell us as much about its structure as a thousand instruments. The changes occuring in chromatin of proliferating cells could perhaps be profitably used to know more about chromatin structure.

Animals↗
PubMed1979

Cell proliferation and cortical cell production in relation to wool growth.

The relationship of wool growth to cell proliferation in the follicle bulb and to the subsequent migration and growth of the fibre cortical cells was investigated in 10 Peppin Merino sheep. These sheep had been maintained on a low, medium or high level of nutrient intake to ensure a wide range in wool growth. The number and mitotic activity of the germinal cells in the follicle bulb were determined after administration of colchicine. Cortical cell size was measured following isolation of the fibre cells by acid-treatment of wool. The average fibre production of the follicle varied from 4.1 x 10(4) to 13.2 x 10(4) micron3/day in these sheep. There were also substantial differences between sheep in the mitotic activity of the germinal cells in the bulb, the rate of cell proliferation being highly correlated with the average daily fibre production of the follicle (r = + 0.88, n = 10). However, the size of the germinal cell population differed from sheep to sheep and was not closely related to the level of fibre production (r = + 0.48, n = 10). The average turnover time of these cells was inversely related to fibre production and varied from 41.6 to 19.4 h (r = -0.82, n = 10). Multiple regression analysis of the data showed that the average daily fibre production of the follicle was largely determined by the number of germinal cells present in the bulb and their rate of proliferation (R = +0.95, n = 10). Variations in cell turnover time and in cortical cell size were not significant in influencing the rate of fibre production. In these sheep, the average cortical cell varied in size from 658 to 1279 micron 3 and the positive correlation (r = + 0.83, n = 10) found between cell size and fibre production is considered to merely reflect an allometric relationship. The proportion of germinal cells contributing to the fibre cortex was found to be small and variable, ranging from 9.4 to 17.8%. Furthermore, this proportion was not related to the nutritional level of these sheep, and it is thought that the variability in the distribution of cells to the fibre may be attributed to genetic differences between sheep.

Animals↗
PubMed1977

Autoradiographic demonstration of proliferating cells in cerebrospinal fluid.

The proliferative activity of cells, isolated from 82 human CSF specimens, was examined by 3H-thymidine autoradiography. High labelling indices (LI) were found in acute viral meningitis (up to 8 per cent) and radiculitis (up to 6 per cent). CSF cell proliferation was also shown in the subacute stages of viral diseases and in other inflammatory processes (LI ranging from 0.5 per cent to 3 per cent). Most of the cells labelled from these CSF specimens were large lymphocytes, "lymphoid cells" and plasmacytes. Their presence in CSF is presumed to indicate an immune reaction. By the demonstration of a proliferative activity of these cells, aseptic inflammatory processes can be differentiated from "unspecific" pleocytosis. Because of a correlation between the LI of CSF cells and the stages of some inflammations, this method is suggested for an assessment of pregression or remission of chronic processes, e.g. "chronic meningitis" and multiple sclerosis. It can also be used in experimental research: the same type of mononuclear cells was labelled after having been cultured for 23 hours prior to the incubation with 3H-thymidine. Proliferating tumor cells as well as proliferating non-neoplastic mononuclear cells were demonstrated in CSF from various neoplastic diseases. In the clinical diagnosis of these processes, the method is of limited value. It proved very useful, however, for an assessment of the therapeutic effects of intrathecal cytostatic therapy. CSF specimens from non-inflammatory and non-neoplastic diseases regularly contained very few proliferating cells (LI: less than 0.1).

Autoradiography↗
PubMed1978

[Curve of labeled mitoses with different states of cell proliferation kinetics. V. Effect of the circadian rhythm of cell proliferation on the shape of the labeled mitosis curve].

The influence of the diurnal rhythm in cell proliferation processes on the behavior of labeled mitoses curve (LMC) is under investigation. The mathematical model predicts that LMC observed following 3H-thymidine administration to experimental animals at different day-times can differ greatly even when temporal parameters of the mitotic cycle remain unchanged. The analysis of the experimental data on the hamster's cheek pouch epithelium suggests that diurnal differences in LMCs cannot be explained in certain cases by the influences of transient processes in cell kinetics only, and therefore the existence of a slight trend in prolongation of periods of the mitotic cycle cannot be completely excluded.

Animals↗
PubMed1979

[Cell proliferation and migration in the roof of the mesencephalon (tectum) in Xenopus laevis tadpoles and adult frogs normally and in brain injury. II. Cell proliferation and differentiation of the tectum in frogs].

The proliferation and directions of cell differentiation in tectum opticum were studied in the young frogs under the conditions of normal development and upon brain trauma by means of 3H-thymidine autoradiography. The same types of cells were shown to be able of proliferation in both the cases: cells of the ventricle zone and glioblasts (gliocytes) in all other tectum layers. A study of directions of the tectum proliferating cells' differentiation in the frogs has shown that the proliferating cells differentiate mainly in the ependyme tanicytes in the ventricle layer 1 and gliocytes in the other tectum layers. The trauma did not change the direction of proliferating cells' differentiation towards the formation of neurons. The complete regeneration is observed in the tectum layer 1 only.

Animals↗
PubMed1978

Polyclonal activation of human B lymphocytes in vitro by pokeweed mitogen: a simple technique for the simultaneous assessment of cell proliferation, generation of plasma cells, plaque-forming cells and immunoglobulin production.

A simple technique has been worked out for the simultaneous assessment of cell proliferation, generation of plasma cells, plaque-forming cells and immunoglobulin production from single cultures of 1 X 10(6) human peripheral blood lymphocytes stimulated with pokeweed mitogen (PWM). Kinetic studies showed that number of cells, thymidine incorporation rate, number of plaque-forming cells against fluorescein-isothiocyanate-haptenated sheep erythrocytes and concentration of IgM and IgG in the supernatant peaked on the average between day 5 and 7 of culture. This technique is particularly suitable for the analysis of hypogammaglobulinaemias in infancy.

Adult↗
PubMed1977

Gastric mucosal cell proliferation and immunoglobulin-containing cells in Ménétriér's Disease.

The amount of immunoglobulin-containing cells in gastric mucosa from 6 patients with Ménétriér's disease was estimated. Furthermore, the rate of gastric epithelial cell proliferation was sutdied in 4 of the patients. Fluorescent antisera specifically reacting with IgA, IgG and IgM were applied, and accordingly the cells were differentiated and quantitated. Other biopsies were labelled in vitro with 3H-thymidine and autoradiographs were prepared. The percentage of DNA-synthesising cells in the progenitor cell region was estimated. The number of IgM-containing cells in the gastric fundic mucosa was markedly increased, while the rate of epithelial cell proliferation was increased in 2 cases and within normal range in the remaining 2 patients.

Adult↗
PubMed1979

Immunoregulation of localized and disseminated murine myeloma: antigen-specific regulation of MOPC-315 stem cell proliferation and secretory cell differentiation.

Tumor development, MOPC-315 stem cells, and M315-secretory cells were quantitated in carrier-primed BALB/c mice that had been challenged subcutaneously or i.v. with mixtures of TNP-carrier and TNP-binding MOPC-315 cells. We observed that tumor incidence, myeloma stem cells, and secretory myeloma cells were: i) suppressed in mice in whom carrier-specific suppressor T cells had previously been induced and ii) initially ehnahced in mice with carrier-specific helper T cells. The early enhancement in mice with carrier-specific helper T cells was followed by progressively declining myeloma stem cell frequencies and regression of established tumors. These studies demonstrate that T cell-derived immunoregulators of host origin can be focused onto localized and disseminated malignant B cells and specifically regulate the expansion and differentiation of the neoplastic clone.

Animals↗
PubMed1979

Lymphocyte subpopulations in man: suppression of PWM-induced B-cell proliferation by infectious mononucleosis T cells.

The in vitro polyclonal pokeweed mitogen (PWM)-induced activation of human B lymphocytes is enhanced by addition of autologous or allogeneic irradiated T cells. This model for B/T-cell cooperation may be used to define and describe the balance between T helper and T suppressor phenomena. The present study investigates the helper and suppressor capacities of mononuclear cells isolated from peripheral blood of infectious mononucleosis patients during the acute disease and the reconvalescence period. During the acute disease we found a functional lack of T helper capacity; furthermore, the T cells were able to suppress the PWM and T-cell-dependent B-cell proliferation of healthy donor cells. The suppression was non-cytotoxic; i.e. not due to destruction of the responder cells. This phenomenon of non-cytotoxic suppression was found for all seven patients studied and disappeared during the reconvalescence period, indicating that the T lymphocytosis seen in infectious mononucleosis includes an expansion of T suppressor cells.

Adolescent↗
PubMed1977

The effects of neuraminidase and galactose oxidase on murine lymphocytes. I. Evidence for the differential delivery of signal(s) leading to cell proliferation and the differentiation of cytotoxic T cells.

The sequential treatment of normal C57BL/6 mouse spleen cell populations with neuraminidase (NA) and galactose oxidase (GO) resulted in cell proliferation, but not in the differentiation of cytotoxic T cells. In contrast, C57BL/6 spleen cells derived from animals primed 5 to 8 months earlier with alloantigen (P815 mastocytoma cells of the DBA/2 strain) both proliferated and demonstrated T cell-mediated cytotoxicity after NAGO stimulation. T cells differentiating into cytotoxic cells after NAGO treatment demonstrated properties similar to alloantigen-specific 'memory' T cells. These were: 1) cytotoxicity developed only from 'primed' cell populations, 2) cytotoxicity developed within 24 hr after NAGO treatment, 3) DNA synthesis was not required for the differentiation of cytotoxic cells during the first 24 hr of culture but both DNA synthesis and cell proliferation were required for the cytotoxicity developing after 24 hr, and 4) all cytotoxicity induced by NAGO showed specificity for the priming alloantigen. It was found, furthermore, that cytotoxicity could be induced at much lower GO concentrations than needed for increased DNA synthesis. We interpret this finding as an indication that NAGO can differentially deliver two 'signals' to T lymphocytes: one leading to cell proliferation, the other causing the differentiation of memory T cells into cytotoxic effectors.

Animals↗
PubMed1979

A simple reliable system for studying antigen-specific murine T cell proliferation.

Antigen-specific T cell proliferation can be readily elicited from the popliteal lymph node cells of mice which have received immunizations of antigen in the hind footpads. The advantages of our system over other published methods are (i) simplicity in method and materials, (ii) much improved reproducibility, (iii) negligible concomitant B cell proliferation, (iv) large degrees of antigen specific proliferation with very low background, and (v) complete dependence of the response on accessory cells or macrophages. These results were brought about by proper immunization procedures for mice and judicious choice of culture conditions. Our data show that the system is very suitable for the study of macrophage-T cell interaction in the induction of T cell proliferation as well as the genetic basis of responsiveness or non-responsiveness to protein and polypeptide antigens.

Animals↗