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Traction force and tension fluctuations in growing axons.

Polackwich RJ, Koch D, McAllister R, Geller HM, Urbach JS - Front Cell Neurosci (2015)

Bottom Line: Actively generated mechanical forces play a central role in axon growth and guidance, but the mechanisms that underly force generation and regulation in growing axons remain poorly understood.The average stress field has strong maxima on the sides of the growth cone, directed inward toward the growth cone neck.Using high time-resolution measurements of the growth cone traction stresses, we show that the stress field is composed of fluctuating local stress peaks, with a large number peaks that live for a short time, a population of peaks whose lifetime distribution follows an exponential decay, and a small number of very long-lived peaks.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and The Institute for Soft Matter Synthesis and Metrology, Georgetown University Washington, DC, USA.

ABSTRACT
Actively generated mechanical forces play a central role in axon growth and guidance, but the mechanisms that underly force generation and regulation in growing axons remain poorly understood. We report measurements of the dynamics of traction stresses from growth cones of actively advancing axons from postnatal rat DRG neurons. By tracking the movement of the growth cone and analyzing the traction stress field from a reference frame that moves with it, we are able to show that there is a clear and consistent average stress field that underlies the complex spatial stresses present at any one time. The average stress field has strong maxima on the sides of the growth cone, directed inward toward the growth cone neck. This pattern represents a contractile stress contained within the growth cone, and a net force that is balanced by the axon tension. Using high time-resolution measurements of the growth cone traction stresses, we show that the stress field is composed of fluctuating local stress peaks, with a large number peaks that live for a short time, a population of peaks whose lifetime distribution follows an exponential decay, and a small number of very long-lived peaks. We show that the high time-resolution data also reveal that the tension appears to vary randomly over short time scales, roughly consistent with the lifetime of the stress peaks, suggesting that the tension fluctuations originate from stochastic adhesion dynamics.

No MeSH data available.


Related in: MedlinePlus

Histogram of lifetimes of stress peaks. Most stress peaks are of short duration, with some longer, and peak lifetimes of about 30–150 s are well-fit with an exponential distribution (red curve). Very short (< 15 s) and very long (>600 s) lived stress peaks are not shown in the histogram. Inset: Log-linear plot of histogram values from t = 30 to t = 150 s, with a least-squares fit (red line) with slope 1/38 s, indicating that the majority of the stress peak lifetimes follow a Poisson distribution with a decay time of about 38 s.
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Figure 5: Histogram of lifetimes of stress peaks. Most stress peaks are of short duration, with some longer, and peak lifetimes of about 30–150 s are well-fit with an exponential distribution (red curve). Very short (< 15 s) and very long (>600 s) lived stress peaks are not shown in the histogram. Inset: Log-linear plot of histogram values from t = 30 to t = 150 s, with a least-squares fit (red line) with slope 1/38 s, indicating that the majority of the stress peak lifetimes follow a Poisson distribution with a decay time of about 38 s.

Mentions: Figure 5 shows the histogram of stress peak lifetimes extracted from all five data sets. There are a large number of very short-lived peaks, followed by an intermediate regime that is well-described by a Poisson distribution (an exponential decay) characterized by a decay time of 38 s (Figure 5, inset), followed by a long tail of very long-lived peaks. The length of the trajectories (1800 s) is sufficiently long that the statistics in the exponentially decaying region are be significantly affected by the finite observation time.


Traction force and tension fluctuations in growing axons.

Polackwich RJ, Koch D, McAllister R, Geller HM, Urbach JS - Front Cell Neurosci (2015)

Histogram of lifetimes of stress peaks. Most stress peaks are of short duration, with some longer, and peak lifetimes of about 30–150 s are well-fit with an exponential distribution (red curve). Very short (< 15 s) and very long (>600 s) lived stress peaks are not shown in the histogram. Inset: Log-linear plot of histogram values from t = 30 to t = 150 s, with a least-squares fit (red line) with slope 1/38 s, indicating that the majority of the stress peak lifetimes follow a Poisson distribution with a decay time of about 38 s.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4624864&req=5

Figure 5: Histogram of lifetimes of stress peaks. Most stress peaks are of short duration, with some longer, and peak lifetimes of about 30–150 s are well-fit with an exponential distribution (red curve). Very short (< 15 s) and very long (>600 s) lived stress peaks are not shown in the histogram. Inset: Log-linear plot of histogram values from t = 30 to t = 150 s, with a least-squares fit (red line) with slope 1/38 s, indicating that the majority of the stress peak lifetimes follow a Poisson distribution with a decay time of about 38 s.
Mentions: Figure 5 shows the histogram of stress peak lifetimes extracted from all five data sets. There are a large number of very short-lived peaks, followed by an intermediate regime that is well-described by a Poisson distribution (an exponential decay) characterized by a decay time of 38 s (Figure 5, inset), followed by a long tail of very long-lived peaks. The length of the trajectories (1800 s) is sufficiently long that the statistics in the exponentially decaying region are be significantly affected by the finite observation time.

Bottom Line: Actively generated mechanical forces play a central role in axon growth and guidance, but the mechanisms that underly force generation and regulation in growing axons remain poorly understood.The average stress field has strong maxima on the sides of the growth cone, directed inward toward the growth cone neck.Using high time-resolution measurements of the growth cone traction stresses, we show that the stress field is composed of fluctuating local stress peaks, with a large number peaks that live for a short time, a population of peaks whose lifetime distribution follows an exponential decay, and a small number of very long-lived peaks.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and The Institute for Soft Matter Synthesis and Metrology, Georgetown University Washington, DC, USA.

ABSTRACT
Actively generated mechanical forces play a central role in axon growth and guidance, but the mechanisms that underly force generation and regulation in growing axons remain poorly understood. We report measurements of the dynamics of traction stresses from growth cones of actively advancing axons from postnatal rat DRG neurons. By tracking the movement of the growth cone and analyzing the traction stress field from a reference frame that moves with it, we are able to show that there is a clear and consistent average stress field that underlies the complex spatial stresses present at any one time. The average stress field has strong maxima on the sides of the growth cone, directed inward toward the growth cone neck. This pattern represents a contractile stress contained within the growth cone, and a net force that is balanced by the axon tension. Using high time-resolution measurements of the growth cone traction stresses, we show that the stress field is composed of fluctuating local stress peaks, with a large number peaks that live for a short time, a population of peaks whose lifetime distribution follows an exponential decay, and a small number of very long-lived peaks. We show that the high time-resolution data also reveal that the tension appears to vary randomly over short time scales, roughly consistent with the lifetime of the stress peaks, suggesting that the tension fluctuations originate from stochastic adhesion dynamics.

No MeSH data available.


Related in: MedlinePlus