Evidence That Estrogen Hastens Epiphyseal Fusion and Cessation of Longitudinal Bone Growth by Irreversibly Depleting the Number of Resting Zone Progenitor Cells in Female Rabbits

With age, growth plate cartilage undergoes programmed senescence, eventually causing cessation of bone elongation and epiphyseal fusion. Estrogen accelerates this developmental process. We hypothesized that senescence occurs because progenitor cells in the resting zone are depleted in number and that estrogen acts by accelerating this depletion. To test this hypothesis, juvenile ovariectomized rabbits received injections of estradiol cypionate or vehicle for 5 weeks, and then were left untreated for an additional 5 weeks. Exposure to estrogen accelerated the normal decline in growth plate height and in the number of proliferative and hypertrophic chondrocytes. Five weeks after discontinuation of estrogen treatment, these structural parameters remained advanced, indicating an irreversible advancement in structural senescence. Similarly, transient estrogen exposure hastened epiphyseal fusion. Estrogen also caused a more rapid decline in functional parameters of growth plate senescence, including growth rate, proliferation rate, and hypertrophic cell size. However, in contrast to the structural parameters, once the estrogen treatment was discontinued, the growth rate, chondrocyte proliferation rate, and hypertrophic cell size all normalized, suggesting that estrogen has a reversible, suppressive effect on growth plate function. In addition, estrogen accelerated the normal loss of resting zone chondrocytes with age. This decrease in resting zone cell number did not appear to be due to apoptosis. However, it was maintained after the estrogen treatment stopped, suggesting that it represents irreversible depletion. The findings are consistent with the hypothesis that estrogen causes irreversible depletion of progenitor cells in the resting zone, thus irreversibly accelerating structural senescence and hastening epiphyseal fusion. In addition, estrogen reversibly suppresses growth plate function.

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Analysis of Association between Morphometric Parameters of Growth Plate and Bone Growth of Tibia in Mice and Humans

Cartilage ◽

10.1177/1947603519900800 ◽

2020 ◽

pp. 194760351990080 ◽

Cited By ~ 1

Author(s):

Kimberly Wilson ◽

Yu Usami ◽

Danielle Hogarth ◽

Amanda L. Scheiber ◽

Hongying Tian ◽

...

Keyword(s):

Growth Rate ◽

Growth Plate ◽

Linear Correlation ◽

Bone Growth ◽

Plate Height ◽

Total Height ◽

Tibia Bone ◽

Proliferation Activity ◽

Tibia Length ◽

Plate Width

Objective The purposes of this study are to evaluate which growth plate parameters are associated with bone growth in mice and to compare the mouse results with those in humans. Design The sagittal sections of the proximal growth plate of the mouse tibia from neonate to young adult stages were subjected to histomorphometric and functional analyses. The radiographic images of tibias of human patients until puberty were analyzed to obtain the tibia length and the proximal growth plate height. It was found that a linear correlation best modeled the relationship between the growth plate variables with the tibia growth rate and length. Results In mice, total height, resting zone height, combined height of the proliferation and prehypertrophic zones, proliferation activity, and the total width of tibia growth plate showed high linear correlation with tibia bone length and bone growth rate, but the hypertrophic zone height and the growth plate area did not. In both mice and humans, the total growth plate width of tibia was found to have the strongest correlation with tibia length and growth rate. Conclusions The results validated that growth plate total height, the height of the resting zone and cell proliferation activity are appropriate parameters to evaluate the balance between growth plate activity and bone growth in mice, consistent with previous reports. The study also provided a new growth plate parameter candidate, growth plate width for growth plate activity evaluation in both mouse and human tibia bone.

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Faculty Opinions recommendation of Growth rate and cell size modulate the synthesis of, and requirement for, G1-phase cyclins at start.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1023340.270674 ◽

2005 ◽

Author(s):

Frederick R Cross

Keyword(s):

Growth Rate ◽

Cell Size ◽

G1 Phase

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Catch-Up Growth after Hypothyroidism Is Caused by Delayed Growth Plate Senescence

Endocrinology ◽

10.1210/en.2007-0993 ◽

2008 ◽

Vol 149 (4) ◽

pp. 1820-1828 ◽

Cited By ~ 32

Author(s):

Rose Marino ◽

Anita Hegde ◽

Kevin M. Barnes ◽

Lenneke Schrier ◽

Joyce A. Emons ◽

...

Keyword(s):

Growth Rate ◽

Growth Inhibition ◽

Growth Plate ◽

Bone Growth ◽

Structural Characteristics ◽

Linear Growth Rate ◽

Growth Plate Chondrocytes ◽

Growth Plates ◽

Catch Up ◽

Growth Inhibiting

Catch-up growth is defined as a linear growth rate greater than expected for age after a period of growth inhibition. We hypothesized that catch-up growth occurs because growth-inhibiting conditions conserve the limited proliferative capacity of growth plate chondrocytes, thus slowing the normal process of growth plate senescence. When the growth-inhibiting condition resolves, the growth plates are less senescent and therefore grow more rapidly than normal for age. To test this hypothesis, we administered propylthiouracil to newborn rats for 8 wk to induce hypothyroidism and then stopped the propylthiouracil to allow catch-up growth. In untreated controls, the growth plates underwent progressive, senescent changes in multiple functional and structural characteristics. We also identified genes that showed large changes in mRNA expression in growth plate and used these changes as molecular markers of senescence. In treated animals, after stopping propylthiouracil, these functional, structural, and molecular senescent changes were delayed, compared with controls. This delayed senescence included a delayed decline in longitudinal growth rate, resulting in catch-up growth. The findings demonstrate that growth inhibition due to hypothyroidism slows the developmental program of growth plate senescence, including the normal decline in the rate of longitudinal bone growth, thus accounting for catch-up growth.

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P.0025 Preliminary results of growth rate profiling of induced pluripotent stem cells and neuronal progenitor cells from Attention-Deficit Hyperactivity Disorder

European Neuropsychopharmacology ◽

10.1016/j.euroneuro.2021.10.033 ◽

2021 ◽

Vol 53 ◽

pp. S19-S20

Author(s):

C.M. Yde Ohki ◽

M. Rickli ◽

L. Grossmann ◽

C. Döring ◽

A.M. Werling ◽

...

Keyword(s):

Stem Cells ◽

Attention Deficit Hyperactivity Disorder ◽

Growth Rate ◽

Induced Pluripotent Stem Cells ◽

Progenitor Cells ◽

Attention Deficit ◽

Pluripotent Stem Cells ◽

Hyperactivity Disorder ◽

Neuronal Progenitor ◽

Induced Pluripotent

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Covariation of metabolic rates and cell size in coccolithophores

Biogeosciences ◽

10.5194/bg-12-4665-2015 ◽

2015 ◽

Vol 12 (15) ◽

pp. 4665-4692 ◽

Cited By ~ 15

Author(s):

G. Aloisi

Keyword(s):

Growth Rate ◽

Environmental Change ◽

Cell Size ◽

Environmental Conditions ◽

Laboratory Experiments ◽

Opposite Effect ◽

Cell Structure ◽

Metabolic Rates ◽

The Future ◽

Phytoplankton Group

Abstract. Coccolithophores are sensitive recorders of environmental change. The size of their coccosphere varies in the ocean along gradients of environmental conditions and provides a key for understanding the fate of this important phytoplankton group in the future ocean. But interpreting field changes in coccosphere size in terms of laboratory observations is hard, mainly because the marine signal reflects the response of multiple morphotypes to changes in a combination of environmental variables. In this paper I examine the large corpus of published laboratory experiments with coccolithophores looking for relations between environmental conditions, metabolic rates and cell size (a proxy for coccosphere size). I show that growth, photosynthesis and, to a lesser extent, calcification covary with cell size when pCO2, irradiance, temperature, nitrate, phosphate and iron conditions change. With the exception of phosphate and temperature, a change from limiting to non-limiting conditions always results in an increase in cell size. An increase in phosphate or temperature (below the optimum temperature for growth) produces the opposite effect. The magnitude of the coccosphere-size changes observed in the laboratory is comparable to that observed in the ocean. If the biological reasons behind the environment–metabolism–size link are understood, it will be possible to use coccosphere-size changes in the modern ocean and in marine sediments to investigate the fate of coccolithophores in the future ocean. This reasoning can be extended to the size of coccoliths if, as recent experiments are starting to show, coccolith size reacts to environmental change proportionally to coccosphere size. The coccolithophore database is strongly biased in favour of experiments with the coccolithophore Emiliania huxleyi (E. huxleyi; 82 % of database entries), and more experiments with other species are needed to understand whether these observations can be extended to coccolithophores in general. I introduce a simple model that simulates the growth rate and the size of cells forced by nitrate and phosphate concentrations. By considering a simple rule that allocates the energy flow from nutrient acquisition to cell structure (biomass) and cell maturity (biological complexity, eventually leading to cell division), the model is able to reproduce the covariation of growth rate and cell size observed in laboratory experiments with E. huxleyi when these nutrients become limiting. These results support ongoing efforts to interpret coccosphere and coccolith size measurements in the context of climate change.

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Numerical Simulation of Conical Pick Cutting Arc Rock Plate Fracture Based on ANSYS/LS-DYNA

Advances in Materials Science and Engineering ◽

10.1155/2020/6563520 ◽

2020 ◽

Vol 2020 ◽

pp. 1-16 ◽

Cited By ~ 1

Author(s):

Zhiwen Wang ◽

Qingliang Zeng ◽

Zhenguo Lu ◽

Lirong Wan ◽

Xin Zhang ◽

...

Keyword(s):

Numerical Simulation ◽

Cutting Force ◽

Structural Parameters ◽

Cutting Parameters ◽

Rock Breaking ◽

Central Axis ◽

Plate Height ◽

Conical Pick ◽

Cutting Angle ◽

Cutting Point

The new method of rock breaking based on the combination of circular sawblade and conical pick was proposed to improve the effectiveness of hard rock breaking. The numerical simulation method was applied to research the conical pick cutting arc rock plate by ANSYS/LS-DYNA. The conical pick cutting arc rock plate numerical simulation model was established to research the influence of arc rock plate structural parameters and cutting parameters on cracks formation and propagation of the arc rock plate and the cutting force in the process of conical pick cutting arc rock plate. The amount of cracks is positively correlated with arc rock plate thickness, the cutting speed, and distance of cutting point to arc rock plate central axis and negatively correlated with the cutting angle. The mean peak cutting force is positively correlated with the thickness of arc rock plate and the distance of cutting point to arc rock plate central axis; however, it is negatively correlated with the arc rock plate height and width and cutting angle of conical pick. The simulation results can be used to predict the conical pick work performance with various cutting parameters and structural parameters.

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