scholarly journals Cytokinetic analysis of the impaired proliferative response of peripheral lymphocytes from aged humans to phytohemagglutinin.

1979 ◽  
Vol 149 (5) ◽  
pp. 1029-1041 ◽  
Author(s):  
R R Tice ◽  
E L Schneider ◽  
D Kram ◽  
P Thorne
Keyword(s):  
Cell Cycle ◽  
Staining Technique ◽  
Cell Entry ◽  
Differential Staining ◽  
Cycle Duration ◽  
Computer Simulation Model ◽  
Peripheral Lymphocytes ◽  
Lymphocyte Cultures ◽  
Aged Individual ◽  
Successive Generations

The effect of donor age on the rate of cell entry into the proliferating pool and subsequent cell cycle duration for peripheral lymphocytes stimulated by phytohemagglutinin (PHA) were examined by using the bromodeoxyuridine incorporation-differential staining technique. Distribution curves for the appearance of metaphase cells in successive generations as a function of culture time were obtained and analyzed both graphically and by a computer simulation model. Peripheral lymphocytes from aged individuals (approximately 75 yr) were stimulated by PHA at approximately one-half of the rate of peripheral lymphocytes from young individuals (approximately 21 yr). Subsequent cell-cycle durations were estimated to range from 10.0 to 25.0 h for aged individual lymphocyte cultures and 10.6-15.6 h for young individual lymphocyte cultures. The possible significance of these findings to aging in general is discussed.

scholarly journals Positive Feedback Between PU.1 and the Cell Cycle Controls Myeloid Differentiation

Science ◽  
2013 ◽  
Vol 341 (6146) ◽  
pp. 670-673 ◽  
Author(s):  
Hao Yuan Kueh ◽  
Ameya Champhekar ◽  
Stephen L. Nutt ◽  
Michael B. Elowitz ◽  
Ellen V. Rothenberg
Keyword(s):  
Cell Cycle ◽  
Cell Fate ◽  
Positive Feedback ◽  
Regulatory Gene ◽  
Control Cell ◽  
Stem Cell Differentiation ◽  
Myeloid Differentiation ◽  
Cycle Duration ◽  
Gene Circuits ◽  
Cell Cycles

Regulatory gene circuits with positive-feedback loops control stem cell differentiation, but several mechanisms can contribute to positive feedback. Here, we dissect feedback mechanisms through which the transcription factor PU.1 controls lymphoid and myeloid differentiation. Quantitative live-cell imaging revealed that developing B cells decrease PU.1 levels by reducing PU.1 transcription, whereas developing macrophages increase PU.1 levels by lengthening their cell cycles, which causes stable PU.1 accumulation. Exogenous PU.1 expression in progenitors increases endogenous PU.1 levels by inducing cell cycle lengthening, implying positive feedback between a regulatory factor and the cell cycle. Mathematical modeling showed that this cell cycle–coupled feedback architecture effectively stabilizes a slow-dividing differentiated state. These results show that cell cycle duration functions as an integral part of a positive autoregulatory circuit to control cell fate.

Genome in toto

Genome ◽  
1999 ◽  
Vol 42 (2) ◽  
pp. 361-362 ◽  
Author(s):  
Alexander E Vinogradov
Keyword(s):  
Cell Cycle ◽  
Genome Evolution ◽  
Genome Size ◽  
Cycle Duration ◽  
Noncoding Dna ◽  
Cell Cycle Duration ◽  
The Relationship

At a certain temperature, which is a compromise for temperatures at which the species are adapted, the relationship between genome size and cell cycle duration during synchronous cleavage divisions can be very strong (r = 1.00, P < 0.01) in four closely related frogs, suggesting a functional dependence.Key words: genome size, genome evolution, genome cytoecology, noncoding DNA, cell cycle duration.

The preimplantation pig embryo: cell number and allocation to trophectoderm and inner cell mass of the blastocyst in vivo and in vitro

Development ◽  
1988 ◽  
Vol 102 (4) ◽  
pp. 793-803 ◽  
Author(s):  
V.E. Papaioannou ◽  
K.M. Ebert
Keyword(s):  
Inner Cell Mass ◽  
Cell Mass ◽  
Staining Technique ◽  
Cell Number ◽  
Total Cell ◽  
Differential Staining ◽  
Morphological Development ◽  
Total Cell Number

Total cell number as well as differential cell numbers representing the inner cell mass (ICM) and trophectoderm were determined by a differential staining technique for preimplantation pig embryos recovered between 5 and 8 days after the onset of oestrus. Total cell number increased rapidly over this time span and significant effects were found between embryos of the same chronological age from different females. Inner cells could be detected in some but not all embryos of 12–16 cells. The proportion of inner cells was low in morulae but increased during differentiation of ICM and trophectoderm in early blastocysts. The proportion of ICM cells then decreased as blastocysts expanded and hatched. Some embryos were cultured in vitro and others were transferred to the oviducts of immature mice as a surrogate in vivo environment and assessed for morphology and cell number after several days. Although total cell number did not reach in vivo levels, morphological development and cell number increase was sustained better in the immature mice than in vitro. The proportion of ICM cells in blastocysts formed in vitro was in the normal range.

scholarly journals Lateral Root Priming Synergystically Arises from Root Growth and Auxin Transport Dynamics

2018 ◽  
Author(s):  
Thea van den Berg ◽  
Kirsten H. ten Tusscher
Keyword(s):  
Cell Cycle ◽  
Root Growth ◽  
Lateral Root ◽  
Root Formation ◽  
Growth Dynamics ◽  
Root Tip ◽  
Cycle Duration ◽  
Elongation Zone ◽  
Lateral Root Formation ◽  
Cell Cycle Duration

AbstractThe root system is a major determinant of plant fitness. Its capacity to supply the plant with sufficient water and nutrients strongly depends on root system architecture, which arises from the repeated branching off of lateral roots. A critical first step in lateral root formation is priming, which prepatterns sites competent of forming a lateral root. Priming is characterized by temporal oscillations in auxin, auxin signalling and gene expression in the root meristem, which through growth become transformed into a spatially repetitive pattern of competent sites. Previous studies have demonstrated the importance of auxin synthesis, transport and perception for the amplitude of these oscillations and their chances of producing an actual competent site. Additionally, repeated lateral root cap apoptosis was demonstrated to be strongly correlated with repetitive lateral root priming. Intriguingly, no single mutation has been identified that fully abolishes lateral root formation, and thusfar the mechanism underlying oscillations has remained unknown. In this study, we investigated the impact of auxin reflux loop properties combined with root growth dynamics on priming, using a computational approach. To this end we developed a novel multi-scale root model incorporating a realistic root tip architecture and reflux loop properties as well as root growth dynamics. Excitingly, in this model, repetitive auxin elevations automatically emerge. First, we show that root tip architecture and reflux loop properties result in an auxin loading zone at the start of the elongation zone, with preferential auxin loading in narrow vasculature cells. Second, we demonstrate how meristematic root growth dynamics causes regular alternations in the sizes of cells arriving at the elongation zone, which subsequently become amplified during cell expansion. These cell size differences translate into differences in cellular auxin loading potential. Combined, these properties result in temporal and spatial fluctuations in auxin levels in vasculature and pericycle cells. Our model predicts that temporal priming frequency predominantly depends on cell cycle duration, while cell cycle duration together with meristem size control lateral root spacing.

scholarly journals Effects of cell cycle variability on lineage and population measurements of mRNA abundance

2020 ◽  
Author(s):  
Ruben Perez-Carrasco ◽  
Casper Beentjes ◽  
Ramon Grima
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Negative Binomial ◽  
Eukaryotic Cell ◽  
Cycle Duration ◽  
Cell Cycle Duration ◽  
Monotonically Decreasing Function ◽  
Binomial Mixture ◽  
A Cell ◽  
The Mean

AbstractMany models of gene expression do not explicitly incorporate a cell cycle description. Here we derive a theory describing how mRNA fluctuations for constitutive and bursty gene expression are influenced by stochasticity in the duration of the cell cycle and the timing of DNA replication. Analytical expressions for the moments show that omitting cell cycle duration introduces an error in the predicted mean number of mRNAs that is a monotonically decreasing function of η, which is proportional to the ratio of the mean cell cycle duration and the mRNA lifetime. By contrast, the error in the variance of the mRNA distribution is highest for intermediate values of η consistent with genome-wide measurements in many organisms. Using eukaryotic cell data, we estimate the errors in the mean and variance to be at most 3% and 25%, respectively. Furthermore, we derive an accurate negative binomial mixture approximation to the mRNA distribution. This indicates that stochasticity in the cell cycle can introduce fluctuations in mRNA numbers that are similar to the effect of bursty transcription. Finally, we show that for real experimental data, disregarding cell cycle stochasticity can introduce errors in the inference of transcription rates larger than 10%.

scholarly journals A simplified method for differential staining of aborted and non-aborted pollen grains

2010 ◽  
Vol 1 (2) ◽  
pp. 13 ◽  
Author(s):  
Ross Peterson ◽  
Janet P. Slovin ◽  
Changbin Chen
Keyword(s):  
Mercuric Chloride ◽  
Chloral Hydrate ◽  
Pollen Grains ◽  
Staining Technique ◽  
Field Studies ◽  
Differential Staining ◽  
Practical Applications ◽  
Time Period ◽  
Simplified Method ◽  
Pollen Vitality

The ability to use chemical staining to discriminate aborted from non-aborted pollen grains has well-known practical applications in agriculture. A commonly used technique for assessing pollen vitality, Alexander’s stain, uses chloral hydrate, phenol and mercuric chloride, all of which are highly toxic. We describe here an improved pollen staining technique that avoids the use of a regulated chemical chloral hydrate and two extremely toxic chemicals mercuric chloride and phenol, and requires a much shorter time period for sample preparation and staining. This simplified method is very useful for field studies without high-end equipments such as fluorescence microscopes. Samples can be collected and fixed in the fields and examined in a simple laboratory that has light microscopes.

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