scholarly journals CELL POPULATION KINETICS OF AN OSTEOGENIC TISSUE · II

1963 ◽  
Vol 19 (1) ◽  
pp. 33-44 ◽  
Author(s):  
Maureen Owen ◽  
Sheila MacPherson
Keyword(s):  
Cell Division ◽  
Cell Kinetics ◽  
Single Injection ◽  
Tritiated Thymidine ◽  
Cell Types ◽  
Population Kinetics ◽  
Periosteal Surface ◽  
S Period ◽  
Different Cell Types ◽  
Kinetics Of

A study of the cell kinetics on the actively growing periosteal surface of the femur of rabbits aged 2 weeks has been continued. A single injection of tritiated thymidine was given and the rabbits killed from 1 hour to 4 days after injection. The grain count spectra of the different cell types, pre-osteoblast, osteoblast, and osteocyte, have been compared at different times after injection. The results showed evidence for the uptake of thymidine in nuclei which is not associated with cell division. A small percentage of osteoblasts was initially labeled at 1 hour and there was evidence that the majority of these had not divided by 3 or 4 days after injection. Some thymidine-labeled cells had also become osteocytes without division. Furthermore, it appeared that a considerable fraction of the initially labeled pre-osteoblasts did not divide. The S period for the pre-osteoblasts and osteoblasts was measured using a double-labeled thymidine technique.

scholarly journals Chemical and Light Inducible Epigenome Editing

2020 ◽  
Vol 21 (3) ◽  
pp. 998
Author(s):  
Weiye Zhao ◽  
Yufan Wang ◽  
Fu-Sen Liang
Keyword(s):  
Small Molecules ◽  
Expression Patterns ◽  
Cell Types ◽  
Epigenome Editing ◽  
Specific Targeting ◽  
Conditional Control ◽  
Cellular Behaviors ◽  
Different Cell Types ◽  
Kinetics Of ◽  
Epigenetic Research

The epigenome defines the unique gene expression patterns and resulting cellular behaviors in different cell types. Epigenome dysregulation has been directly linked to various human diseases. Epigenome editing enabling genome locus-specific targeting of epigenome modifiers to directly alter specific local epigenome modifications offers a revolutionary tool for mechanistic studies in epigenome regulation as well as the development of novel epigenome therapies. Inducible and reversible epigenome editing provides unique temporal control critical for understanding the dynamics and kinetics of epigenome regulation. This review summarizes the progress in the development of spatiotemporal-specific tools using small molecules or light as inducers to achieve the conditional control of epigenome editing and their applications in epigenetic research.

scholarly journals Phosphorylation and internalization of gp130 occur after IL-6 activation of Jak2 kinase in hepatocytes.

1994 ◽  
Vol 5 (7) ◽  
pp. 819-828 ◽  
Author(s):  
Y Wang ◽  
G M Fuller
Keyword(s):  
Protein Synthesis ◽  
Cell Surface ◽  
De Novo ◽  
Cell Types ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Protein Synthesis Inhibitors ◽  
Different Cell Types ◽  
Kinetics Of

Recent evidence has shown that members of the Jak kinase family are activated after IL-6 binds to its receptor complex, leading to a tyrosine phosphorylation of gp130, the IL-6 signal-transducing subunit. The different members of the IL-6 cytokine subfamily induce distinct patterns of Jak-Tyk phosphorylation in different cell types. Using monospecific antibodies to gp130, Jak2 kinase, and phosphotyrosine, we investigated the kinetics of IL-6 stimulation of members of this pathway in primary hepatocytes. Our findings show that Jak 2 is maximally activated within 2 min of exposure to IL-6, followed by gp130 phosphorylation that reaches its peak in another 2 min then declines to basal level by 60 min. In vitro phosphorylation experiments show that activated Jak 2 is able to phosphorylate both native gp130 and a fusion peptide containing its cytoplasmic domain, demonstrating gp130 is a direct substrate of Jak 2 kinase. Experiments designed to explore the cell surface expression of gp130 show that > or = 2 h are required to get a second round of phosphorylation after the addition of more cytokines. This finding suggests that activated gp130 is internalized from the cell surface after IL-6 stimulation. Additional experiments using protein synthesis inhibitors reveal that new protein synthesis is required to get a second cycle of gp130 phosphorylation indicating gp130 must be synthesized de novo and inserted into the membrane. These findings provide strong evidence that down regulation of the IL-6 signal in hepatocytes involves the internalization and cytosol degradation of gp130.

scholarly journals Efficiencies and kinetics of infection in different cell types/lines by African and Asian strains of Zika virus

2018 ◽  
Vol 91 (2) ◽  
pp. 179-189 ◽  
Author(s):  
Suzane Ramos da Silva ◽  
Fan Cheng ◽  
I‐Chueh Huang ◽  
Jae U. Jung ◽  
Shou‐Jiang Gao
Keyword(s):  
Zika Virus ◽  
Cell Types ◽  
Different Cell Types ◽  
Kinetics Of

scholarly journals Cancer Response to Therapy-Induced Senescence: A Matter of Dose and Timing

Cancers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 484
Author(s):  
Maria Patrizia Mongiardi ◽  
Manuela Pellegrini ◽  
Roberto Pallini ◽  
Andrea Levi ◽  
Maria Laura Falchetti
Keyword(s):  
Wound Healing ◽  
Growth Factors ◽  
Cell Division ◽  
Stromal Cells ◽  
Cell Types ◽  
Response To Therapy ◽  
Matrix Remodeling ◽  
Aggressive Cancer ◽  
Secretory Phenotype ◽  
Different Cell Types

Cellular senescence participates to fundamental processes like tissue remodeling in embryo development, wound healing and inhibition of preneoplastic cell growth. Most senescent cells display common hallmarks, among which the most characteristic is a permanent (or long lasting) arrest of cell division. However, upon senescence, different cell types acquire distinct phenotypes, which also depend on the specific inducing stimuli. Senescent cells are metabolically active and secrete a collection of growth factors, cytokines, proteases, and matrix-remodeling proteins collectively defined as senescence-associated secretory phenotype, SASP. Through SASP, senescent cells modify their microenvironment and engage in a dynamic dialog with neighbor cells. Senescence of neoplastic cells, at least temporarily, reduces tumor expansion, but SASP of senescent cancer cells as well as SASP of senescent stromal cells in the tumor microenvironment may promote the growth of more aggressive cancer subclones. Here, we will review recent data on the mechanisms and the consequences of cancer-therapy induced senescence, enlightening the potentiality and the risk of senescence inducing treatments.

scholarly journals Roles of Actin in the Morphogenesis of the Early Caenorhabditis elegans Embryo

2020 ◽  
Vol 21 (10) ◽  
pp. 3652
Author(s):  
Dureen Samandar Eweis ◽  
Julie Plastino
Keyword(s):  
Cell Division ◽  
Caenorhabditis Elegans ◽  
Asymmetric Cell Division ◽  
Cell Types ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Asymmetric Cell Divisions ◽  
C Elegans ◽  
Asymmetric Divisions ◽  
Different Cell Types

The cell shape changes that ensure asymmetric cell divisions are crucial for correct development, as asymmetric divisions allow for the formation of different cell types and therefore different tissues. The first division of the Caenorhabditis elegans embryo has emerged as a powerful model for understanding asymmetric cell division. The dynamics of microtubules, polarity proteins, and the actin cytoskeleton are all key for this process. In this review, we highlight studies from the last five years revealing new insights about the role of actin dynamics in the first asymmetric cell division of the early C. elegans embryo. Recent results concerning the roles of actin and actin binding proteins in symmetry breaking, cortical flows, cortical integrity, and cleavage furrow formation are described.

Energetics of muscle contraction: the whole is less than the sum of its parts

2002 ◽  
Vol 30 (2) ◽  
pp. 227-231 ◽  
Author(s):  
M. J. Kushmerick ◽  
K. E. Conley
Keyword(s):  
Oxidative Phosphorylation ◽  
Supply And Demand ◽  
Lactate Production ◽  
Cell Types ◽  
Individual Values ◽  
Muscle Energetics ◽  
Modular Units ◽  
Small Set ◽  
Different Cell Types ◽  
Kinetics Of

Understanding muscle energetics is a problem in optimizing supply of ATP to the demands of ATPases. The complexity of reactions and their fluxes to achieve this balance is greatly reduced by recognizing constraints imposed by the integration of common metabolites at fixed stoichiometry among modular units. ATPase is driven externally. Oxidative phosphorylation and glycogenolysis are the suppliers. We focus on their regulation which involves different controls, but reduces to two principles that enable facile experimental analysis of the supply and demand fluxes. The ratio of concentration of phospho-creatine (PCr) to ATP, not their individual values, sets the range of achievable concentrations of ADP in resting and active muscle (at fixed pH) in different cell types. This principle defines the fraction of available flux of oxidative phosphorylation utilized (at fixed enzyme activities). Then the kinetics of PCr recovery defines the kinetics of oxygen supply and substrate utilization. The second principle is the constancy of PCr and H+ (lactate) production by glycogenolysis due to the coupling of ATPase and glycolysis. This principle enables glycogenolytic flux to be measured from intracellular proton loads. Further simplification occurs because the magnitude of the interacting fluxes and metabolite concentrations are specified within narrow limits when both the resting and active fluxes are quantified. Thus there is a small set of rules for assessing and understanding the thermodynamics and kinetics of muscle energetics.

scholarly journals CELL POPULATION KINETICS OF AN OSTEOGENIC TISSUE · I

1963 ◽  
Vol 19 (1) ◽  
pp. 19-32 ◽  
Author(s):  
Maureen Owen
Keyword(s):  
Cell Proliferation ◽  
Cell Population ◽  
Tritiated Thymidine ◽  
Point Of View ◽  
Haversian Canal ◽  
Main Site ◽  
Rate Of Increase ◽  
Periosteal Surface ◽  
Kinetics Of ◽  
Rate Of Movement

Cell proliferation on the actively growing periosteal surface of the femur of rabbits aged 2 weeks has been investigated using autoradiographic techniques. Injections of tritiated glycine and tritiated thymidine were given simultaneously and the animals sacrificed at intervals from 1 hour to 5 days after injection. The glycine labeled the position of the bone surface at the time of injection and the thymidine labeled the cells which were synthesising DNA. The rate of increase in the cell population was determined by counting the number of cells beyond the glycine label at different times after injection. The cell kinetics of the fibroblast-pre-osteoblast-osteoblast-osteocyte system has been studied. The fibroblasts are relatively unimportant from the point of view of increase in the cell population. The main site of cell proliferation is the layer of pre-osteoblasts on the periosteal surface. The rate of movement of cells from the pre-osteoblast to the osteoblast and osteocyte compartments has been measured. The incorporation of osteoblasts into the bone is not a random process, but it appears that the osteoblast must spend a certain time on the periosteal surface before becoming either an osteocyte or a relatively inactive osteoblast lining an haversian canal. It was estimated that, on an average, an osteoblast produces 2 or 3 times its own volume of matrix during its most active period on the periosteal surface.

DNA Polymerase in Avian Erythroid Cells

1972 ◽  
Vol 11 (3) ◽  
pp. 785-798
Author(s):  
A. F. WILLIAMS
Keyword(s):  
Cell Division ◽  
Dna Synthesis ◽  
Dna Polymerase ◽  
Cell Types ◽  
Polymerase Activity ◽  
Erythroid Cells ◽  
Isolated Nuclei ◽  
Dividing Cells ◽  
Different Cell Types

The level and properties of DNA polymerase activity assayable in extracts of avian erythroid cells was studied. The enzyme was detectable in the dividing cells (erythroblasts) of the erythropoietic series and also the immature non-dividing erythrocytes. It could not be assayed in mature erythrocytes. Investigations showed that activity began to decline at the time of the last cell division of the erythroid series. Properties of the enzyme did change in different cell types; however, the changes did not correlate with cessation of DNA synthesis. Some preliminary results on DNA synthesis by isolated nuclei are also reported and these showed that only nuclei from erythroblasts could synthesize DNA in vitro in the absence of primer.

scholarly journals CELL POPULATION KINETICS OF EXCISED ROOTS OF PISUM SATIVUM

1965 ◽  
Vol 27 (1) ◽  
pp. 179-189 ◽  
Author(s):  
Jack Van't Hof
Keyword(s):  
Cell Population ◽  
Mitotic Cycle ◽  
Sucrose Concentration ◽  
Tritiated Thymidine ◽  
Cycle Duration ◽  
Population Kinetics ◽  
Pea Roots ◽  
Mitotic Figures ◽  
Kinetics Of ◽  
Subsequent Rise

The cell population kinetics of excised, cultured pea roots was studied with the use of tritiated thymidine and colchicine to determine (1) the influence of excision, (2) the influence of sucrose concentration, (3) the average mitotic cycle duration, and (4) the duration of mitosis and the G1, S, and G2 periods of interphase.1 The results indicate that the process of excision causes a drop in the frequency of mitotic figures when performed either at the beginning of the culture period or after 100 hours in culture. This initial decrease in frequency of cell division is independent of sucrose concentration, but the subsequent rise in frequency of division, after 12 hours in culture, is dependent upon sucrose concentration. Two per cent sucrose maintains the shortest mitotic cycle duration. The use of colchicine indicated an average cycle duration of 20 hours, whereas the use of tritiated thymidine produced an average cycle duration of 17 hours.

scholarly journals When fate follows age: unequal centrosomes in asymmetric cell division

2014 ◽  
Vol 369 (1650) ◽  
pp. 20130466 ◽  
Author(s):  
Jose Reina ◽  
Cayetano Gonzalez
Keyword(s):  
Stem Cells ◽  
Cell Division ◽  
Strong Correlation ◽  
Molecular Mechanisms ◽  
Asymmetric Cell Division ◽  
Current Knowledge ◽  
Cell Types ◽  
Functional Implications ◽  
Different Cell Types ◽  
Review Current

A strong correlation between centrosome age and fate has been reported in some stem cells and progenitors that divide asymmetrically. In some cases, such stereotyped centrosome behaviour is essential to endow stemness to only one of the two daughters, whereas in other cases causality is still uncertain. Here, we present the different cell types in which correlated centrosome age and fate has been documented, review current knowledge on the underlying molecular mechanisms and discuss possible functional implications of this process.

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