A commentary on the segmental motor system of the turtle: Implications for the study of its cellular mechanisms and interactions

Callister, Robert J.; Laidlaw, Douglass H.; Stuart, Douglas G.

doi:10.1002/jmor.1052250206

Cited by 16 publications

(8 citation statements)

References 115 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…24,50) with little change in expiratory and inspiratory duration (50). In this study, VT and frequency decreased in spinalized turtles while breathing 6 -8% CO 2 , whereas only VT decreased with 2% CO 2 (Fig. 3).…”

Section: Hypercapnic Responses Are Attenuated In Spinalized Turtlessupporting

confidence: 49%

“…4, C1 and C2). There were no hypercapnia-induced changes in singlet frequency at 2-6% CO 2 (Fig. 4C1).…”

Section: Spinalization Reduced Episodic Breathing and Increased Singlmentioning

confidence: 89%

“…3, A1 and A2). Thus breathing frequency was significantly lower compared with preinjury levels during hypercapnic challenges at 2, 6, and 8% CO 2 (Fig. 3, A1 and A2).…”

mentioning

confidence: 85%

See 2 more Smart Citations

Spinal cord injury-induced changes in breathing are not due to supraspinal plasticity in turtles (Pseudemys scripta)

Johnson¹,

Creighton²

2005

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

Johnson, Stephen M., and Robert J. Creighton. Spinal cord injury-induced changes in breathing are not due to supraspinal plasticity in turtles (Pseudemys scripta). Am J Physiol Regul Integr Comp Physiol 289: R1550 -R1561, 2005. First published August 11, 2005; doi:10.1152/ajpregu.00397.2005-After occurrence of spinal cord injury, it is not known whether the respiratory rhythm generator undergoes plasticity to compensate for respiratory insufficiency. To test this hypothesis, respiratory variables were measured in adult semiaquatic turtles using a pneumotachograph attached to a breathing chamber on a water-filled tank. Turtles breathed room air (2 h) before being challenged with two consecutive 2-h bouts of hypercapnia (2 and 6% CO 2 or 4 and 8% CO2). Turtles were spinalized at dorsal segments D8-D10 so that only pectoral girdle movement was used for breathing. Measurements were repeated at 4 and 8 wk postinjury. For turtles breathing room air, breathing frequency, tidal volume, and ventilation were not altered by spinalization; single-breath (singlet) frequency increased sevenfold. Spinalized turtles breathing 6 -8% CO 2 had lower ventilation due to decreased frequency and tidal volume, episodic breathing (breaths/episode) was reduced, and singlet breathing was increased sevenfold. Respiratory variables in sham-operated turtles were unaltered by surgery. Isolated brain stems from control, spinalized, and sham turtles produced similar respiratory motor output and responded the same to increased bath pH. Thus spinalized turtles compensated for pelvic girdle loss while breathing room air but were unable to compensate during hypercapnic challenges. Because isolated brain stems from control and spinalized turtles had similar respiratory motor output and chemosensitivity, breathing changes in spinalized turtles in vivo were probably not due to plasticity within the respiratory rhythm generator. Instead, caudal spinal cord damage probably disrupts spinobulbar pathways that are necessary for normal breathing.control of breathing; respiration; reptile; chelonian; episodic breathing IN RESPONSE TO INJURY, THE central nervous system undergoes morphological and physiological changes to compensate for loss of function, such as altered gene expression, neuronal reorganization, and altered synaptic plasticity. Likewise, after incomplete spinal cord injury, remaining descending spinal pathways and spinal motor networks undergo reorganization and neuroplasticity to compensate for loss of function (6,20,51). Because respiratory dysfunction is the leading cause of death in spinal cord-injured patients (9, 59), understanding the mechanisms by which the respiratory control system undergoes compensatory plasticity may lead to novel therapeutic strategies for reducing respiratory complications and subsequent morbidity.After spinal cord injury, breathing pattern is altered to maintain adequate ventilation (V E). For example, high cervical spinal cord injury compromises synaptic drive to phrenic and intercostal motoneurons in mammals, r...

show abstract

Section: Hypercapnic Responses Are Attenuated In Spinalized Turtlessupporting

confidence: 49%

“…4, C1 and C2). There were no hypercapnia-induced changes in singlet frequency at 2-6% CO 2 (Fig. 4C1).…”

Section: Spinalization Reduced Episodic Breathing and Increased Singlmentioning

confidence: 89%

See 1 more Smart Citation

Spinal cord injury-induced changes in breathing are not due to supraspinal plasticity in turtles (Pseudemys scripta)

Johnson¹,

Creighton²

2005

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

show abstract

“…In general, many molecular, cellular, and neural network properties and mechanisms have been subject to evolutionary conservation in both vertebrates and invertebrates (Pearson, 1993;Fetcho, 1992;Callister et al, 1995;. With this principle in mind, we have compared, in the Discussion, the present results with those reported previously for (1) turtle MNs and INs (Hounsgaard and Kjaerulff, 1992) in analogous in vitro slice preparations, (2) lamprey MNs and INs in an in vitro SC preparation (Buchanan, 1993), and (3) cat MNs in the intact in vivo cord (for reviews, see Burke, 1981;Binder et al, 1996).…”

mentioning

confidence: 99%

Properties of spinal motoneurons and interneurons in the adult turtle: Provisional classification by cluster analysis

et al. 1998

Self Cite

View full text Add to dashboard Cite

The purpose of the present study was to compare, in motoneurons (MNs) vs. interneurons (INs), selected passive, transitional, and active (firing) properties, as recorded in slices of lumbosacral spinal cord (SC) taken from the adult turtle. The cells were provisionally classified on the basis of (1) the presence (in selected INs) or absence (MNs and other INs) of spontaneous discharge, (2) a cluster analysis of selected properties of the nonspontaneously firing cells, (3) a comparison to previous data on turtle MNs and INs, and (4) a qualitative comparison of the results with those reported for other vertebrate species (lamprey, cat). The provisional nomenclature accommodated properties appropriate for solely MNs (Main MN group) vs. nonspontaneously firing INs (Main IN-N) vs. spontaneously firing INs (IN-S) and for neurons with two degrees of intermediacy between the Main MN and the Main IN-N groups (Overlap MN, Overlap MN/IN). Morphological reconstructions of additional cells, which had been injected with biocytin during the electrophysiological tests, were shown to provide clear-cut support for the provisional classification procedure. The values for the measured parameters in the 96 tested cells covered the spectrum reported previously across adult vertebrate species and were robust in measurements made on different SC slices up to 5 days after their removal from the host animal. The interspecies comparisons permitted the predictions that (1) our Main MN and Overlap MN cells would be analogous to two MN types that innervate fast-twitch and slow-twitch skeletomotor muscle fibers, respectively, in the cat, and (2) the MNs in our Overlap MN/IN group probably innervate slow (nontwitch, tonic) muscle fibers whose presence has recently been established in the turtle hindlimb. In summary, the results bring out the utility of the SC slice preparation of the turtle for study of spinal motor mechanisms in adult tetrapod vertebrates, particularly as an adjunct to the in vivo cat, because of the ease with which robust measurements can be made of the active properties of both MNs and INs.

show abstract

“…4.6, and 4.7), NADH-diaphorase activity, and alpha-glycerophosphate dehydrogenase (␣-GPDH) activity. These markers provide an indirect assessment of contraction speed (SO Ͻ FOG/Fg), oxidative capacity (SO/FOG Ͼ Fg), and glycolytic (anaerobic) capacity (SO Ͻ FOG/Fg), respectively (for relevant references, see Callister et al, 1995). In addition, it was necessary to identify slow-tonic fibers whose staining with the above markers is identical to that of twitch SO fibers.…”

Section: Tissue Processingmentioning

confidence: 99%

Slow-tonic muscle fibers and their potential innervation in the turtle,Pseudemys (Trachemys)scripta elegans

et al. 2005

Self Cite

View full text Add to dashboard Cite

A description is provided of the ratio of slow-tonic vs. slow- and fast-twitch fibers for five muscles in the adult turtle, Pseudemys (Trachemys) scripta elegans. The cross-sectional area of each fiber type and an estimation of the relative (weighted) cross-sectional area occupied by the different fiber types are also provided. Two hindlimb muscles (flexor digitorum longus, FDL; external gastrocnemius, EG) were selected on the basis of their suitability for future motor-unit studies. Three neck muscles (the fourth head of testo-cervicis, TeC4; the fourth head of retrahens capitus collique, RCCQ4; transversalis cervicis, TrC) were chosen for their progressively decreasing oxidative capacity. Serial sections were stained for myosin adenosine triphosphatase (ATPase), NADH-diaphorase, and alpha-glycerophosphate dehydrogenase (alpha-GPDH). Conventional fiber-type classification was then performed using indirect markers for contraction speed and oxidative (aerobic) vs. glycolytic (anaerobic) metabolism: i.e., slow oxidative (SO, including slow-twitch and possibly slow-tonic fibers), fast-twitch, oxidative-glycolytic (FOG), and fast-twitch glycolytic (Fg) fibers. Slow-tonic fibers in the SO class were then revealed by directing the monoclonal antibody, ALD-58 (raised against the slow-tonic fiber myosin heavy chain of chicken anterior latissimus dorsi), to additional muscle cross sections. All five of the tested muscles contained the four fiber types, with the ATPase-stained fibers including both slow-tonic and slow-twitch fibers. The extreme distributions of SO fibers were in the predominately glycolytic TrC vs. the predominately oxidative TeC4 muscle (TrC-SO, 9%; FOG, 20%; Fg, 71% vs. TeC4-SO, 58%: FOG, 16%; Fg, 25%). Across the five muscles, the relative prevalence of slow-tonic fibers (4-47%) paralleled that of the SO fibers (9-58%). TeC4 had the highest prevalence of slow-tonic fibers (47%). The test muscles exhibited varying degrees of regional concentration of each fiber type, with the distribution of slow-tonic fibers paralleling that of the SO fibers. In the five test muscles, fiber cross-sectional area was usually ranked Fg > FOG > SO, and slow-twitch always > slow-tonic. In terms of weighted cross-sectional area, which provides a coarse-grain measure of each fiber type's potential contribution to whole muscle force, all five muscles exhibited a higher Fg and lower SO contribution to cross-sectional area than suggested by their corresponding fiber-type prevalence. This was also the case for the slow-twitch vs. slow-tonic fibers. We conclude that slow-tonic fibers are widespread in turtle muscle. The weighted cross-sectional area evidence suggested, however, that their contribution to force generation is minor except in highly oxidative muscles, with a special functional role, like TeC4. There is discussion of: 1) the relationship between the present results and previous work on homologous neck and hindlimb muscles in other nonmammalian species, and 2) the potential motoneuronal innervation of slow-tonic fibers ...

show abstract

A commentary on the segmental motor system of the turtle: Implications for the study of its cellular mechanisms and interactions

Cited by 16 publications

References 115 publications

Spinal cord injury-induced changes in breathing are not due to supraspinal plasticity in turtles (Pseudemys scripta)

Spinal cord injury-induced changes in breathing are not due to supraspinal plasticity in turtles (Pseudemys scripta)

Properties of spinal motoneurons and interneurons in the adult turtle: Provisional classification by cluster analysis

Slow-tonic muscle fibers and their potential innervation in the turtle,Pseudemys (Trachemys)scripta elegans

Contact Info

Product

Resources

About