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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.


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N5 axonal skeletal length increased significantly over time after deafferentation, while the longest axon and perpendicular extent of N5 axons did not. (A) N5 axonal maximum perpendicular extent and (B) longest axon showed no significant change over the deafferentation time period while (C) skeletal length increased significantly in a linear fashion. N5 growth patterns did not differ between males (blue) and females (red). Black data points represent means, and error bars represent standard error of the mean. The shaded gray area indicates the 95% confidence interval. Female N5 control (n = 6), 30 h (n = 9), 3 days (n = 6), 5 days (n = 9), 7 days (n = 5), 14 days (n = 3), and 20 days (n = 10). Male N5 control (n = 9), 30 h (n = 7), 3 days (n = 4), 5 days (n = 9), 7 days (n = 7), 14 days (n = 9), and 20 days (n = 7). See Table 2 for regression equations and statistics.
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Figure 4: N5 axonal skeletal length increased significantly over time after deafferentation, while the longest axon and perpendicular extent of N5 axons did not. (A) N5 axonal maximum perpendicular extent and (B) longest axon showed no significant change over the deafferentation time period while (C) skeletal length increased significantly in a linear fashion. N5 growth patterns did not differ between males (blue) and females (red). Black data points represent means, and error bars represent standard error of the mean. The shaded gray area indicates the 95% confidence interval. Female N5 control (n = 6), 30 h (n = 9), 3 days (n = 6), 5 days (n = 9), 7 days (n = 5), 14 days (n = 3), and 20 days (n = 10). Male N5 control (n = 9), 30 h (n = 7), 3 days (n = 4), 5 days (n = 9), 7 days (n = 7), 14 days (n = 9), and 20 days (n = 7). See Table 2 for regression equations and statistics.

Mentions: As previously noted, and as seen in the results of our present study, N5 axonal processes cross the midline in control animals far more frequently and more extensively than do AN-2 dendrites (Schmitz, 1989). However, N5 maximum perpendicular extent and longest axon did not change significantly after deafferentation over time (Figures 4A,B; Table 2), and there were no significant differences between males and females either specifically at the end-point of 20 days (Figures 4A,B; Table 2) or overall for data pooled over all time periods (Kruskal–Wallis tests, each df = 96, each p > 0.26). In contrast, N5 skeletal length increased linearly until day 20 for gender-pooled data (although not for male and female data analyzed separately: Figure 4C, Table 2) with no significant difference between skeletal length in males and females either at the end-point of 20 days (Table 2) or overall for data pooled over all time periods (Kruskal–Wallis test, df = 96, p = 0.93).


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)

N5 axonal skeletal length increased significantly over time after deafferentation, while the longest axon and perpendicular extent of N5 axons did not. (A) N5 axonal maximum perpendicular extent and (B) longest axon showed no significant change over the deafferentation time period while (C) skeletal length increased significantly in a linear fashion. N5 growth patterns did not differ between males (blue) and females (red). Black data points represent means, and error bars represent standard error of the mean. The shaded gray area indicates the 95% confidence interval. Female N5 control (n = 6), 30 h (n = 9), 3 days (n = 6), 5 days (n = 9), 7 days (n = 5), 14 days (n = 3), and 20 days (n = 10). Male N5 control (n = 9), 30 h (n = 7), 3 days (n = 4), 5 days (n = 9), 7 days (n = 7), 14 days (n = 9), and 20 days (n = 7). See Table 2 for regression equations and statistics.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: N5 axonal skeletal length increased significantly over time after deafferentation, while the longest axon and perpendicular extent of N5 axons did not. (A) N5 axonal maximum perpendicular extent and (B) longest axon showed no significant change over the deafferentation time period while (C) skeletal length increased significantly in a linear fashion. N5 growth patterns did not differ between males (blue) and females (red). Black data points represent means, and error bars represent standard error of the mean. The shaded gray area indicates the 95% confidence interval. Female N5 control (n = 6), 30 h (n = 9), 3 days (n = 6), 5 days (n = 9), 7 days (n = 5), 14 days (n = 3), and 20 days (n = 10). Male N5 control (n = 9), 30 h (n = 7), 3 days (n = 4), 5 days (n = 9), 7 days (n = 7), 14 days (n = 9), and 20 days (n = 7). See Table 2 for regression equations and statistics.
Mentions: As previously noted, and as seen in the results of our present study, N5 axonal processes cross the midline in control animals far more frequently and more extensively than do AN-2 dendrites (Schmitz, 1989). However, N5 maximum perpendicular extent and longest axon did not change significantly after deafferentation over time (Figures 4A,B; Table 2), and there were no significant differences between males and females either specifically at the end-point of 20 days (Figures 4A,B; Table 2) or overall for data pooled over all time periods (Kruskal–Wallis tests, each df = 96, each p > 0.26). In contrast, N5 skeletal length increased linearly until day 20 for gender-pooled data (although not for male and female data analyzed separately: Figure 4C, Table 2) with no significant difference between skeletal length in males and females either at the end-point of 20 days (Table 2) or overall for data pooled over all time periods (Kruskal–Wallis test, df = 96, p = 0.93).

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