scholarly journals The effects of 5α-dihydrotestosterone on the kinetics of cell proliferation in rat prostate

1974 ◽  
Vol 142 (3) ◽  
pp. 483-489 ◽  
Author(s):  
Barry Lesser ◽  
Nicholas Bruchovsky
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cellular Growth ◽  
Velocity Sedimentation ◽  
Growth Fraction ◽  
Subcutaneous Injections ◽  
Daughter Cells ◽  
A Cell ◽  
Rat Prostate ◽  
Kinetics Of

The regenerating rat prostate was used as an experimental model to determine the effects of 5α-dihydrotestosterone on certain parameters of cell proliferation, including the duration of the phases of the cell cycle and the size of the cellular growth fraction. Rats castrated 7 days previously were treated with daily subcutaneous injections of 5α-dihydrotestosterone for 14 days; 48h after the beginning of therapy, cells in the process of DNA synthesis were labelled with a single injection of radioactive thymidine and the progress of these cells through the division cycle was observed. Cell-cycle analysis was performed by fractionating prostatic nuclei according to their position in the cell cycle by using the technique of velocity sedimentation under unit gravity. The results indicate that during regeneration the cell population undergoes 1.8 doublings with a doubling time of 40h, and that the process involves almost four rounds of cell division with a cell-generation time of 20h. The growth fraction at any time is about 0.5, and about half the daughter cells produced do not re-enter the proliferative cycle. All cells present at the start of regeneration eventually undergo at least one division during the course of regeneration, although any given cell can divide from one to four times.

THE EFFECT OF TESTOSTERONE ON CELL PROLIFERATION AND DIFFERENTIATION IN THE SMALL BOWEL

1972 ◽  
Vol 52 (1) ◽  
pp. 161-175 ◽  
Author(s):  
N. A. WRIGHT ◽  
A. R. MORLEY ◽  
D. APPLETON
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Small Bowel ◽  
Cell Kinetics ◽  
Treated Group ◽  
Growth Fraction ◽  
Cell Proliferation And Differentiation ◽  
Proliferation And Differentiation ◽  
Upward Displacement ◽  
Kinetics Of

SUMMARY The action of testosterone on the cell kinetics of the small bowel was studied in the castrated male mouse. The parameters of the cell cycle were measured using the labelled mitoses method. No difference was found between cell cycle parameters in testosterone-treated castrated animals compared with castrated controls. Crypt cell kinetics were studied by measuring the distribution of labelled and mitotic nuclei using a computer programme. The labelling and mitotic indices were significantly raised in the testosterone-treated animals. There was also a significant upward displacement of the cut-off position in the testosterone-treated group, indicating an increase in the size of the proliferative compartment, and thus an increase in growth fraction. This change in growth fraction was confirmed by calculation from the labelled mitoses results, and is considered to be the mechanism by which testosterone stimulates cell proliferation in the small bowel of the castrated mouse. The action of testosterone on the growth fraction may constitute an important component of the general mitogenic effect of the hormone on both target and non-target tissues.

scholarly journals Circ_0084927 promotes cervical carcinogenesis by sponging miR-1179 that suppresses CDK2, a cell cycle-related gene

2020 ◽  
Author(s):  
Xinhua Qu ◽  
Liumei Zhu ◽  
Linlin Song ◽  
Shaohua Liu
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Regulatory Network ◽  
Inhibitory Effect ◽  
Cervical Carcinogenesis ◽  
Activation Assay ◽  
Cell Cycle Related Gene ◽  
Rna Immunoprecipitation ◽  
A Cell ◽  
Brdu Assay

Abstract Background: Cervical cancer (CC) is a highly malignant tumor. Evolving researches on CC have unveiled a concept that circRNA exerts important roles in CC progression. In this study, we mainly explored the role of a novel circRNA, circ_0084927, and its regulatory network in the development of CC.Methods: qRT-PCR was applied to evaluate the expression of circ_0084927, miR-1179 and CDK2 mRNA in CC tissues and cells. Dual-luciferase reporting experiments and RNA immunoprecipitation (RIP) assay were conducted to validate the target relationship of miR-1179 with circ_0084927 and CDK2 mRNA. CCK-8 and BrdU assay was used to evaluate CC cell proliferation. The adhesion and apoptosis phenotypes of CC cells were measured by cell-matrix adhesion and caspase 3 activation assay. Flow cytometry was employed to detect CC cell cycle.Results: Our results indicated that circ_0084927 was up-regulated in CC tissues and cells, and circ_0084927 silence inhibited CC cell proliferation and adhesion, while facilitating apoptosis as well as triggering cell cycle arrest. On the other hand, miR-1179 down-regulation appeared in CC tissues. Additionally, circ_0084927 abolished miR-1179’s inhibitory effects on cell proliferation and adhesion. Our study showed that CDK2 was up-regulated in CC tissues and played a cancer-promoting role. Furthermore, miR-1179 directly targeted CDK2, thereby inhibiting CDK2’s promotion on the malignant phenotypes of CC cells. circ_0084927 revoked the inhibitory effect of miR-1179 on CDK2 by sponging miR-1179.Conclusion: Circ_0084927 promoted cervical carcinogenesis by sequestering miR-1179 that directly targeted CDK2. Our results shed light on the circ_0084927/miR-1179/CDK2 regulatory network that strengthened CC aggressiveness, providing novel candidate targets for CC treatment.

scholarly journals THE TIME OF SYNTHESIS AND THE CONSERVATION OF MITOSIS-RELATED PROTEINS IN CULTURED HUMAN AMNION CELLS

1967 ◽  
Vol 34 (1) ◽  
pp. 97-110 ◽  
Author(s):  
Jesse E. Sisken ◽  
Elaina Wilkes
Keyword(s):  
Time Lapse ◽  
Major Effect ◽  
Human Amnion ◽  
Daughter Cells ◽  
Low Concentrations ◽  
Associated Proteins ◽  
A Cell ◽  
Quantitative Analyses ◽  
Related Proteins ◽  
Kinetics Of

p-Fluorophenylalanine (PFPA), an analogue of phenylalanine which may be incorporated into proteins, increases the duration of mitosis. In the present experiments, based upon quantitative analyses of time-lapse cinemicrographic films, brief treatments of cells with PFPA are shown to affect the duration of metaphase in only those cells which enter division during or shortly after treatment. The offspring of cells with prolonged metaphases also tend to have prolonged metaphases. Analyses of the kinetics of the appearance of prolonged metaphases indicate that some protein specifically associated with mitosis is synthesized primarily during a period which corresponds closely to G2. The manner in which the defect is passed on to daughter cells indicates that the protein involved is conserved and reutilized by daughter cells for their subsequent divisions. Comparable experiments performed with low concentrations of puromycin indicate that the major effect of PFPA is due to its incorporation into protein rather than its ability to inhibit protein synthesis. The fact that puromycin-induced effects can also be passed on to daughter cells is interpreted to mean that cells make only specific amounts of some mitosis-associated proteins and that if a cell "inherits" a deficiency in such protein it is not able to compensate for the deficiency.

scholarly journals The oscillation of mitotic kinase governs cell cycle latches

2021 ◽  
Author(s):  
Bela Novak ◽  
John J Tyson
Keyword(s):  
Cell Cycle ◽  
Negative Feedback ◽  
Molecular Switches ◽  
Feedback Loops ◽  
Yeast Cells ◽  
Cyclin Dependent Kinases ◽  
Mitotic Kinase ◽  
Daughter Cells ◽  
Negative Feedback Loops ◽  
A Cell

SummaryIn order to transmit a eukaryotic cell’s genome accurately from mother cell to daughter cells, it is essential that the basic events of the cell division cycle (DNA synthesis and mitosis) occur once and only once per cycle, i.e., that a cell progresses irreversibly from G1 to S to G2 to M and back to G1. Irreversible progression through the cell cycle is assured by a sequence of ‘latching’ molecular switches, based on molecular interactions among cyclin-dependent kinases and their auxiliary partners. Positive feedback loops (++ or −−) create bistable switches with latching properties, and negative feedback loops drive progression from one stage to the next. In budding yeast (Saccharomyces cerevisiae) these events are coordinated by double-negative feedback loops between Clb-dependent kinases (Clb1-6) and their antagonists (APC:Cdh1 and Sic1). If the coordinating signal is compromised, either by deletion of Clb1-5 proteins or expression of non-degradable Clb2, then irreversibility is lost and yeast cells exhibit multiple rounds of DNA replication or mitotic exit events (Cdc14 endocycles). Using mathematical modelling of a stripped-down control network, we show how endocycles arise because the switches fail to latch, and the gates swing back and forth by the action of the negative feedback loops.

Growth Fraction of Colorectal Carcinoma (Ki67): A Comparative Study

1992 ◽  
Vol 7 (2) ◽  
pp. 93-96 ◽  
Author(s):  
A. Benetti ◽  
A. Berenzi ◽  
P. Grigolato
Keyword(s):  
Monoclonal Antibody ◽  
Cell Proliferation ◽  
Colorectal Carcinoma ◽  
Nuclear Antigen ◽  
Growth Fraction ◽  
Immunoperoxidase Technique ◽  
Ki67 Staining ◽  
A Cell ◽  
Colorectal Adenocarcinomas ◽  
Age And Sex

We studied the growth fraction of55 resected colorectal adenocarcinomas by means of a three-step immunoperoxidase technique (avidin-biotin-peroxidase) using the monoclonal antibody Ki67 directed against a cell proliferation-associated nuclear antigen. The percentage of Ki67-positive cells was evaluated independently by two observers, and a Ki67 score was obtained for each case. No correlation was observed between Ki67 staining and patient's age and sex, tumor size and localization or grading and staging according to Dukes’ method (modified by Astler-Coller and Turnbull). The growth fraction showed extreme heterogeneity in the cases examined, within each grade of differentiation.

c-Jun N-terminal kinase/c-Jun inhibits fibroblast proliferation by negatively regulating the levels of stathmin/oncoprotein 18

2010 ◽  
Vol 430 (2) ◽  
pp. 345-354 ◽  
Author(s):  
Yvonne Y. C. Yeap ◽  
Ivan H. W. Ng ◽  
Bahareh Badrian ◽  
Tuong-Vi Nguyen ◽  
Yan Y. Yip ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cellular Proliferation ◽  
Cell System ◽  
Tumour Suppressor Protein ◽  
Oncoprotein 18 ◽  
A Cell ◽  
Cancer Types ◽  
Type C ◽  
Interfering Rna

The JNKs (c-Jun N-terminal kinases) are stress-activated serine/threonine kinases that can regulate both cell death and cell proliferation. We have developed a cell system to control JNK re-expression at physiological levels in JNK1/2-null MEFs (murine embryonic fibroblasts). JNK re-expression restored basal and stress-activated phosphorylation of the c-Jun transcription factor and attenuated cellular proliferation with increased cells in G1/S-phase of the cell cycle. To explore JNK actions to regulate cell proliferation, we evaluated a role for the cytosolic protein, STMN (stathmin)/Op18 (oncoprotein 18). STMN, up-regulated in a range of cancer types, plays a crucial role in the control of cell division through its regulation of microtubule dynamics of the mitotic spindle. In JNK1/2-null or c-Jun-null MEFs or cells treated with c-Jun siRNA (small interfering RNA), STMN levels were significantly increased. Furthermore, a requirement for JNK/cJun signalling was demonstrated by expression of wild-type c-Jun, but not a phosphorylation-defective c-Jun mutant, being sufficient to down-regulate STMN. Critically, shRNA (small hairpin RNA)-directed STMN down-regulation in JNK1/2-null MEFs attenuated proliferation. Thus JNK/c-Jun regulation of STMN levels provides a novel pathway in regulation of cell proliferation with important implications for understanding the actions of JNK as a physiological regulator of the cell cycle and tumour suppressor protein.

scholarly journals Temporal integration of mitogen history in mother cells controls proliferation of daughter cells

Science ◽  
2020 ◽  
Vol 368 (6496) ◽  
pp. 1261-1265 ◽  
Author(s):  
Mingwei Min ◽  
Yao Rong ◽  
Chengzhe Tian ◽  
Sabrina L. Spencer
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Mother Cell ◽  
Protein Production ◽  
Temporal Integration ◽  
Protein Translation ◽  
Cycle Phase ◽  
Daughter Cells ◽  
Mother Cells ◽  
Multicellular Organisms

Multicellular organisms use mitogens to regulate cell proliferation, but how fluctuating mitogenic signals are converted into proliferation-quiescence decisions is poorly understood. In this work, we combined live-cell imaging with temporally controlled perturbations to determine the time scale and mechanisms underlying this system in human cells. Contrary to the textbook model that cells sense mitogen availability only in the G1 cell cycle phase, we find that mitogenic signaling is temporally integrated throughout the entire mother cell cycle and that even a 1-hour lapse in mitogen signaling can influence cell proliferation more than 12 hours later. Protein translation rates serve as the integrator that proportionally converts mitogen history into corresponding levels of cyclin D in the G2 phase of the mother cell, which controls the proliferation-quiescence decision in daughter cells and thereby couples protein production with cell proliferation.

Tubulin post-translational modifications and the construction of microtubular organelles in Trypanosoma brucei

1988 ◽  
Vol 90 (4) ◽  
pp. 577-589 ◽  
Author(s):  
R. Sasse ◽  
K. Gull
Keyword(s):  
Cell Cycle ◽  
Trypanosoma Brucei ◽  
Mitotic Spindle ◽  
Post Translational Modification ◽  
Post Translational Modifications ◽  
Alpha Tubulin ◽  
Daughter Cells ◽  
A Cell ◽  
Microtubular Organelles ◽  
Tubulin Content

We have used specific monoclonal antibodies to facilitate a study of acetylated and tyrosinated alpha-tubulin in the microtubule (MT) arrays in the Trypanosoma brucei cell. Acetylated alpha-tubulin is not solely located in the stable microtubular arrays but is present even in the ephemeral microtubules of the mitotic spindle. Moreover, there is a uniform distribution of this isoform in all arrays. Studies of flagella complexes show that acetylation is concomitant with assembly of MTs. There is no subsequent major modulation in the content of acetylated alpha-tubulin in MTs. Conversely, polymerizing flagellar MTs have a high tyrosinated alpha-tubulin content, which is subsequently reduced to a basal level at a discrete point in the cell cycle. The MTs of the intranuclear mitotic spindle appear never to contain tyrosinated alpha-tubulin, suggesting that they are actually constructed of detyrosinated alpha-tubulin or that detyrosination is extremely rapid at this time in the cell cycle. T. brucei therefore, represents a cell type with extremely active mechanisms for the post-translational modification of alpha-tubulin. Our analyses of the timing of acquisition and modulation in relation to MT construction in T. brucei, suggest that acetylation and detyrosination of alpha-tubulin are two independently regulated post-translational modifications, that are not uniquely associated with particular subsets of MTs of defined lability, position or function. Post-assembly detyrosination of alpha-tubulin may provide a mechanism whereby the cell could discriminate between new and old MTs, during construction of the cytoskeleton through the cell cycle. However, we also suggest that continuation of detyrosination, allows the cell, at cell division, to partition into daughter cells two equivalent sets of cytoskeletal MTs.

Kinetics of in vitro ageing of mouse embryo fibroblasts

1984 ◽  
Vol 65 (1) ◽  
pp. 163-175
Author(s):  
C. Karatza ◽  
W.D. Stein ◽  
S. Shall
Keyword(s):  
Cell Cycle ◽  
Growth Rate ◽  
Mouse Embryo ◽  
Growth Pattern ◽  
Cell Strain ◽  
Growth Fraction ◽  
Cycle Duration ◽  
Cell Cycle Duration ◽  
Kinetics Of

The kinetics of ageing of normal mouse embryo fibroblast cells in culture have been determined. The growth pattern during every passage was established. It was observed that the growth pattern was not exponential, but that the growth rate declined progressively both within and with every passage. We also estimated the cell cycle parameters using the Fraction of Labelled Mitoses method at every passage. We found that the cell cycle duration was constant throughout the lifespan of this cell strain; the median value of the cell cycle duration was found to be 15.5 +/− 0.5 h (S.D., n = 8). From these two sets of observations we infer that the fraction of dividing cells declines smoothly from the beginning of the culture. Our data exclude quite positively any description of ageing of the fibroblast population in terms of a catastrophe or any abrupt change in the population. Our data are also inconsistent with a linear decline in growth fraction. On the contrary, we observed that there was a gradual and smooth decline in the growth rate of the strain, due to a smoothly declining growth fraction. This smooth change in the growth behaviour of this cell strain is accurately described by the mortalization theory of Shall & Stein in which the single parameter gamma (gamma), describes the change in reproductive potential over the entire lifespan. The parameter gamma describes the rate at which the doubling time of the culture increases. It is the number of generations at which half of the newborn cells are themselves reproductively sterile. Our present data provided an estimate of gamma for this cell strain, which was consistent during the entire lifespan of the strain; the best estimate of gamma for this cell strain was 20.3 +/− 0.6 generations (S.D., n = 19).

scholarly journals Antibody microinjection reveals an essential role for human polo-like kinase 1 (Plk1) in the functional maturation of mitotic centrosomes.

1996 ◽  
Vol 135 (6) ◽  
pp. 1701-1713 ◽  
Author(s):  
H A Lane ◽  
E A Nigg
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Regulation ◽  
Fundamental Aspect ◽  
Early Prophase ◽  
Functional Maturation ◽  
A Cell ◽  
Gamma Tubulin ◽  
Cycle Regulation ◽  
Kinetics Of

Mammalian polo-like kinase 1 (Plk1) is structurally related to the polo gene product of Drosophila melanogaster, Cdc5p of Saccharomyces cerevisiae, and plo1+ of Schizosaccharomyces pombe, a newly emerging family of serine-threonine kinases implicated in cell cycle regulation. Based on data obtained for its putative homologues in invertebrates and yeasts, human Plk1 is suspected to regulate some fundamental aspect(s) of mitosis, but no direct experimental evidence in support of this hypothesis has previously been reported. In this study, we have used a cell duplication, microinjection assay to investigate the in vivo function of Plk1 in both immortalized (HeLa) and nonimmortalized (Hs68) human cells. Injection of anti-Plk1 antibodies (Plk1+) at various stages of the cell cycle had no effect on the kinetics of DNA replication but severely impaired the ability of cells to divide. Analysis of Plk1(+)-injected, mitotically arrested HeLa cells by fluorescence microscopy revealed abnormal distributions of condensed chromatin and monoastral microtubule arrays that were nucleated from duplicated but unseparated centrosomes. Most strikingly, centrosomes in Plk1(+)-injected cells were drastically reduced in size, and the accumulation of both gamma-tubulin and MPM-2 immunoreactivity was impaired. These data indicate that Plk1 activity is necessary for the functional maturation of centrosomes in late G2/early prophase and, consequently, for the establishment of a bipolar spindle. Additional roles for Plk1 at later stages of mitosis are not excluded, although injection of Plk1+ after the completion of spindle formation did not interfere with cytokinesis. Injection of Plk1+ into nonimmortalized Hs68 cells produced qualitatively similar phenotypes, but the vast majority of the injected Hs68 cells arrested as single, mononucleated cells in G2. This latter observation hints at the existence, in nonimmortalized cells, of a centrosome-maturation checkpoint sensitive to the impairment of Plk1 function.

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