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Quantification of dendritic and axonal growth after injury to the auditory system of the adult cricket Gryllus bimaculatus.

Pfister A, Johnson A, Ellers O, Horch HW - Front Physiol (2013)

Bottom Line: However, the cues that maintain or influence adult neuronal morphology are less well understood.In males, however, dendritic growth rates were linear, with dendrites growing steadily over time and reaching lengths, on average, twice as long as in females.On the other hand, rates of N5 axonal growth showed no significant sexual dimorphism and were linear.

View Article: PubMed Central - PubMed

Affiliation: Department of Invertebrate Zoology, American Museum of Natural History New York, NY, USA.

ABSTRACT
Dendrite and axon growth and branching during development are regulated by a complex set of intracellular and external signals. However, the cues that maintain or influence adult neuronal morphology are less well understood. Injury and deafferentation tend to have negative effects on adult nervous systems. An interesting example of injury-induced compensatory growth is seen in the cricket, Gryllus bimaculatus. After unilateral loss of an ear in the adult cricket, auditory neurons within the central nervous system (CNS) sprout to compensate for the injury. Specifically, after being deafferented, ascending neurons (AN-1 and AN-2) send dendrites across the midline of the prothoracic ganglion where they receive input from auditory afferents that project through the contralateral auditory nerve (N5). Deafferentation also triggers contralateral N5 axonal growth. In this study, we quantified AN dendritic and N5 axonal growth at 30 h, as well as at 3, 5, 7, 14, and 20 days after deafferentation in adult crickets. Significant differences in the rates of dendritic growth between males and females were noted. In females, dendritic growth rates were non-linear; a rapid burst of dendritic extension in the first few days was followed by a plateau reached at 3 days after deafferentation. In males, however, dendritic growth rates were linear, with dendrites growing steadily over time and reaching lengths, on average, twice as long as in females. On the other hand, rates of N5 axonal growth showed no significant sexual dimorphism and were linear. Within each animal, the growth rates of dendrites and axons were not correlated, indicating that independent factors likely influence dendritic and axonal growth in response to injury in this system. Our findings provide a basis for future study of the cellular features that allow differing dendrite and axon growth patterns as well as sexually dimorphic dendritic growth in response to deafferentation.

No MeSH data available.


Related in: MedlinePlus

Method for finding and placing the midline on tracing images and measurement schematic. (A) Autofluorescent cells at the midline of the prothoracic ganglia were captured in a confocal image. (B) Prior to hand-tracing AN and N5 processes, the midline was approximated by tracing a straight line over the autofluorescent cells. (C) A corresponding image of the ANs and N5 was subsequently captured. The midline was traced onto the AN/N5 image by placing the end-points of the line at the exact coordinates as they appeared on the midline image. The images shown belong to a control cricket. The midline is represented by the dotted line. Scale bars = 20 μm. A schematic highlighting the measurements made in this study is shown in (D). AN dendrites crossing the midline (gray) are represented in the schematic in green. The double-headed arrow (blue) indicates the perpendicular extent measurement. The longest dendrite length was recorded for each animal and is highlighted here in red. All dendrites and their branches were hand-traced (represented by the dashed lines), and the skeletal length measurement is the sum of the lengths of the dashed lines. For simplicity AN dendrites only are represented here but the same methods were used to measure N5 axonal growth across the midline.
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Figure 2: Method for finding and placing the midline on tracing images and measurement schematic. (A) Autofluorescent cells at the midline of the prothoracic ganglia were captured in a confocal image. (B) Prior to hand-tracing AN and N5 processes, the midline was approximated by tracing a straight line over the autofluorescent cells. (C) A corresponding image of the ANs and N5 was subsequently captured. The midline was traced onto the AN/N5 image by placing the end-points of the line at the exact coordinates as they appeared on the midline image. The images shown belong to a control cricket. The midline is represented by the dotted line. Scale bars = 20 μm. A schematic highlighting the measurements made in this study is shown in (D). AN dendrites crossing the midline (gray) are represented in the schematic in green. The double-headed arrow (blue) indicates the perpendicular extent measurement. The longest dendrite length was recorded for each animal and is highlighted here in red. All dendrites and their branches were hand-traced (represented by the dashed lines), and the skeletal length measurement is the sum of the lengths of the dashed lines. For simplicity AN dendrites only are represented here but the same methods were used to measure N5 axonal growth across the midline.

Mentions: AN and N5 growth across the midline were analyzed and quantified “blindly” in coded images using Volocity High Performance 3D Imaging Software (PerkinElmer, Waltham MA, USA). Autofluorescent glial cells collected with 633 nm laser were a reliable marker of the midline, which was represented by a single line running through the glial cells (shown in blue, Figures 2A,B). This line was then transferred, based on coordinate locations, to images of ANs and N5 (Figure 2C).


Quantification of dendritic and axonal growth after injury to the auditory system of the adult cricket Gryllus bimaculatus.

Pfister A, Johnson A, Ellers O, Horch HW - Front Physiol (2013)

Method for finding and placing the midline on tracing images and measurement schematic. (A) Autofluorescent cells at the midline of the prothoracic ganglia were captured in a confocal image. (B) Prior to hand-tracing AN and N5 processes, the midline was approximated by tracing a straight line over the autofluorescent cells. (C) A corresponding image of the ANs and N5 was subsequently captured. The midline was traced onto the AN/N5 image by placing the end-points of the line at the exact coordinates as they appeared on the midline image. The images shown belong to a control cricket. The midline is represented by the dotted line. Scale bars = 20 μm. A schematic highlighting the measurements made in this study is shown in (D). AN dendrites crossing the midline (gray) are represented in the schematic in green. The double-headed arrow (blue) indicates the perpendicular extent measurement. The longest dendrite length was recorded for each animal and is highlighted here in red. All dendrites and their branches were hand-traced (represented by the dashed lines), and the skeletal length measurement is the sum of the lengths of the dashed lines. For simplicity AN dendrites only are represented here but the same methods were used to measure N5 axonal growth across the midline.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750946&req=5

Figure 2: Method for finding and placing the midline on tracing images and measurement schematic. (A) Autofluorescent cells at the midline of the prothoracic ganglia were captured in a confocal image. (B) Prior to hand-tracing AN and N5 processes, the midline was approximated by tracing a straight line over the autofluorescent cells. (C) A corresponding image of the ANs and N5 was subsequently captured. The midline was traced onto the AN/N5 image by placing the end-points of the line at the exact coordinates as they appeared on the midline image. The images shown belong to a control cricket. The midline is represented by the dotted line. Scale bars = 20 μm. A schematic highlighting the measurements made in this study is shown in (D). AN dendrites crossing the midline (gray) are represented in the schematic in green. The double-headed arrow (blue) indicates the perpendicular extent measurement. The longest dendrite length was recorded for each animal and is highlighted here in red. All dendrites and their branches were hand-traced (represented by the dashed lines), and the skeletal length measurement is the sum of the lengths of the dashed lines. For simplicity AN dendrites only are represented here but the same methods were used to measure N5 axonal growth across the midline.
Mentions: AN and N5 growth across the midline were analyzed and quantified “blindly” in coded images using Volocity High Performance 3D Imaging Software (PerkinElmer, Waltham MA, USA). Autofluorescent glial cells collected with 633 nm laser were a reliable marker of the midline, which was represented by a single line running through the glial cells (shown in blue, Figures 2A,B). This line was then transferred, based on coordinate locations, to images of ANs and N5 (Figure 2C).

Bottom Line: However, the cues that maintain or influence adult neuronal morphology are less well understood.In males, however, dendritic growth rates were linear, with dendrites growing steadily over time and reaching lengths, on average, twice as long as in females.On the other hand, rates of N5 axonal growth showed no significant sexual dimorphism and were linear.

View Article: PubMed Central - PubMed

Affiliation: Department of Invertebrate Zoology, American Museum of Natural History New York, NY, USA.

ABSTRACT
Dendrite and axon growth and branching during development are regulated by a complex set of intracellular and external signals. However, the cues that maintain or influence adult neuronal morphology are less well understood. Injury and deafferentation tend to have negative effects on adult nervous systems. An interesting example of injury-induced compensatory growth is seen in the cricket, Gryllus bimaculatus. After unilateral loss of an ear in the adult cricket, auditory neurons within the central nervous system (CNS) sprout to compensate for the injury. Specifically, after being deafferented, ascending neurons (AN-1 and AN-2) send dendrites across the midline of the prothoracic ganglion where they receive input from auditory afferents that project through the contralateral auditory nerve (N5). Deafferentation also triggers contralateral N5 axonal growth. In this study, we quantified AN dendritic and N5 axonal growth at 30 h, as well as at 3, 5, 7, 14, and 20 days after deafferentation in adult crickets. Significant differences in the rates of dendritic growth between males and females were noted. In females, dendritic growth rates were non-linear; a rapid burst of dendritic extension in the first few days was followed by a plateau reached at 3 days after deafferentation. In males, however, dendritic growth rates were linear, with dendrites growing steadily over time and reaching lengths, on average, twice as long as in females. On the other hand, rates of N5 axonal growth showed no significant sexual dimorphism and were linear. Within each animal, the growth rates of dendrites and axons were not correlated, indicating that independent factors likely influence dendritic and axonal growth in response to injury in this system. Our findings provide a basis for future study of the cellular features that allow differing dendrite and axon growth patterns as well as sexually dimorphic dendritic growth in response to deafferentation.

No MeSH data available.


Related in: MedlinePlus