Effects of Hypodynamia-Hypokinesia on the Muscle Spindle Discharges of Rat Soleus Muscle

2003 ◽  
Vol 89 (6) ◽  
pp. 3000-3007 ◽  
Author(s):  
Laurent De-Doncker ◽  
Florence Picquet ◽  
Julien Petit ◽  
Maurice Falempin
Keyword(s):  
Soleus Muscle ◽  
Dorsal Root ◽  
Weight Bearing ◽  
Muscle Spindles ◽  
Linear Range ◽  
Fiber Types ◽  
Vibration Sensitivity ◽  
Afferent Fibers ◽  
Rat Soleus Muscle ◽  
Static Sensitivity

The aim of this study was to determine whether Ia and II fiber discharges of soleus muscle spindles were modified after a 14-day period of hypodynamia (absence of weight bearing) and hypokinesia (reduction of motor activity). Fifty-one and 38 afferent fibers were studied, respectively, in control and hypodynamia-hypokinesia (HH) groups. Under deep anesthesia (pentobarbital, 30 mg/kg), a L3–L6 laminectomy was performed. Unitary potentials from the L5 dorsal root were recorded in response to ramp-and-hold stretches applied at two stretch amplitudes (3 and 4 mm) and four stretch velocities (6, 10, 15, and 30 mm/s) and to sinusoidal stretches applied at four stretch amplitudes (0.12, 0.25, 0.5, and 1 mm) and six stretch frequencies (0.5, 1, 2, 3, 6, and 10 Hz). In both animal groups, the Ia fibers showed higher dynamic index values, smaller linear range, and higher vibration sensitivity than the II fibers. They also exhibited a pause in their discharges during the stretch release contrary to II fibers, which displayed no pause in their responses. After HH, our results showed that for both fiber types all parameters measured under ramp-and-hold stretches (except the static sensitivity) were significantly increased and under sinusoidal stretches, the vibration sensitivity increased, and the response amplitude only increased at 0.12-mm stretch amplitude. The linear range of Ia afferents was limited to 0.12 mm, whereas it was unchanged for the II fibers. After HH, the stretches could be better transmitted to the muscle spindles, probably resulting from changes in passive mechanical properties of the soleus.

Characterization of Spindle Afferents in Rat Soleus Muscle Using Ramp-and-Hold and Sinusoidal Stretches

2003 ◽  
Vol 89 (1) ◽  
pp. 442-449 ◽  
Author(s):  
Laurent De-Doncker ◽  
Florence Picquet ◽  
Julien Petit ◽  
Maurice Falempin
Keyword(s):  
Conduction Velocity ◽  
Soleus Muscle ◽  
Muscle Length ◽  
Muscle Spindles ◽  
Linear Range ◽  
Fiber Types ◽  
First Response ◽  
Rat Soleus Muscle ◽  
The Right ◽  
Response Group

The discharge properties of 51 afferents were studied in the rat soleus muscle spindles. Under deep anesthesia using a pentobarbital sodium solution (30 mg/kg), a laminectomy was performed and the right L4 and L5 dorsal and ventral roots were transected near their entry into the spinal cord. In situ, the minimal ( L min) muscle length [3 ± 0.08 (SE) cm] of the soleus was measured at full ankle extension. Unitary potentials from the L5dorsal root were recorded in response to ramp-and-hold stretches applied at 3 mm (S3) and 4 mm (S4) amplitudes and four stretch velocities (6, 10, 15, and 30 mm/s), sinusoidal stretches performed at four amplitudes (0.12, 0.25, 0.5, and 1 mm) and six stretch frequencies (0.5, 1, 2, 3, 6, and 10 Hz), and vibrations applied at 50-, 100-, and 150-Hz frequencies. These two kinds of stretches were performed at three different muscle lengths ( L min+10%, L min+15%, and L min+20%), whereas vibrations were applied at L min+20% muscle length. Conduction velocity of the fibers was calculated but did not allow to discriminate different fiber types. However, the mean conduction velocity of the first fiber group (43.3 ± 0.8 m/s) was significantly higher than that of the second fiber group (33.9 ± 0.9 m/s). Three parameters allowed to differentiate the responses of primary and secondary endings: the dynamic index (DI), the discharge during the stretch release from the ramp-and-hold stretches, and the linear range and the vibration sensitivity from sinusoidal stretches. The slope histogram of the linear regression based on the DI and the stretch velocity was clearly bimodal. Therefore the responses were separated into two groups. During the stretch release at a velocity of 3 mm/s, the first response group ( n = 26) exhibited a pause, whereas the second ( n = 25) did not. The linear range of the second ending group (0.12–1 mm) was broader than that of the first (0.12–0.25 mm). The first ending group showed a higher sensitivity to high-vibration frequencies of small amplitude than the second. In comparison with the literature, we can assert that the first and the second ending groups corresponded to the primary and secondary endings, respectively. In conclusion, our study showed that in rat soleus muscle spindles, it was possible to immediately classify the discharge of Ia and II fibers by using some parameters measured under ramp-and-hold and sinusoidal stretches.

Influence of chronic stretching upon rat soleus muscle during non-weight-bearing conditions

1994 ◽  
Vol 429 (2) ◽  
pp. 274-279 ◽  
Author(s):  
Damien Leterme ◽  
Corinne Cordonnier ◽  
Yvonne Mounier ◽  
Maurice Falempin
Keyword(s):  
Soleus Muscle ◽  
Weight Bearing ◽  
Rat Soleus Muscle

Distribution of myosin heavy chain isoforms in non-weight-bearing rat soleus muscle fibers

1996 ◽  
Vol 81 (6) ◽  
pp. 2540-2546 ◽  
Author(s):  
Robert J. Talmadge ◽  
Roland R. Roy ◽  
V. Reggie Edgerton
Keyword(s):  
Myosin Heavy Chain ◽  
Soleus Muscle ◽  
Heavy Chain ◽  
De Novo ◽  
Weight Bearing ◽  
Muscle Fibers ◽  
Myosin Heavy Chain Isoforms ◽  
Hindlimb Suspension ◽  
Type I ◽  
Rat Soleus Muscle

Talmadge, Robert J., Roland R. Roy, and V. Reggie Edgerton.Distribution of myosin heavy chain isoforms in non-weight-bearing rat soleus muscle fibers. J. Appl. Physiol. 81(6): 2540–2546, 1996.—The effects of 14 days of spaceflight (SF) or hindlimb suspension (HS) (Cosmos 2044) on myosin heavy chain (MHC) isoform content of the rat soleus muscle and single muscle fibers were determined. On the basis of electrophoretic analyses, there was a de novo synthesis of type IIx MHC but no change in either type I or IIa MHC isoform proportions after either SF or HS compared with controls. The percentage of fibers containing only type I MHC decreased by 26 and 23%, and the percentage of fibers with multiple MHCs increased from 6% in controls to 32% in HS and 34% in SF rats. Type IIx MHC was always found in combination with another MHC or combination of MHCs; i.e., no fibers contained type IIx MHC exclusively. These data suggest that the expression of the normal complement of MHC isoforms in the adult rat soleus muscle is dependent, in part, on normal weight bearing and that the absence of weight bearing induces a shift toward type IIx MHC protein expression in the preexisting type I and IIa fibers of the soleus.

Differential response of macrophage subpopulations to soleus muscle reloading after rat hindlimb suspension

1994 ◽  
Vol 77 (1) ◽  
pp. 290-297 ◽  
Author(s):  
B. A. St Pierre ◽  
J. G. Tidball
Keyword(s):  
Soleus Muscle ◽  
Weight Bearing ◽  
Recovery Process ◽  
Wistar Rat ◽  
Hindlimb Suspension ◽  
Muscle Necrosis ◽  
Macrophage Subpopulations ◽  
Rat Soleus Muscle ◽  
Developmental Myosin Heavy Chain ◽  
Immunohistochemical Techniques

The hypothesis that distinct populations of macrophages are associated with muscle necrosis and regeneration was examined in Wistar rat soleus muscle after 10 days of hindlimb suspension and 2, 4, and 7 days after the resumption of weight bearing. Necrosis was identified using histological features, such as muscle fiber infiltration, and regeneration was identified using immunohistochemical techniques for developmental myosin heavy chain (dMHC). Light-microscopic observations show that necrotic fibers in 2-day reloaded soleus muscle were invaded by ED1+ and Ia+ macrophages. The number of invaded fibers in muscles reloaded for 2 days increased to 2.8/mm2 compared with 0.2/mm2 in age-matched normal muscle but returned to control values by the 4th day of resumed weight bearing. In the interstitial spaces of 2-day recovery muscle, ED1+ and Ia+ macrophages numbered 369 and 332/mm2, respectively, compared with 12 and 72/mm2, respectively, in control soleus. After 7 days of reloading, the number of ED1+ cells was similar to that of control. Ia+ macrophages decreased to 240/mm2 at 4 days but after 7 days rose above control values to 429/mm2. ED2+ macrophages in 4- and 7-day reloaded soleus increased 70–80% in the interstitial spaces compared with control but were not observed to infiltrate necrotic muscle fibers at any time points. Immunohistochemistry and immunoblots using a monoclonal anti-dMHC antibody demonstrate a greater proportion of myofibers expressing dMHC isoforms after 4 and 7 days of reloading. These findings indicate that macrophage subpopulations are associated with distinct stages during the recovery process from hindlimb suspension: ED1+ macrophages are associated with muscle necrosis, whereas ED2+ cells are associated with muscle regeneration.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogenetic, gravity-dependent development of rat soleus muscle

2001 ◽  
Vol 280 (4) ◽  
pp. C1008-C1016 ◽  
Author(s):  
Yoshinobu Ohira ◽  
Takato Tanaka ◽  
Tomoo Yoshinaga ◽  
Fuminori Kawano ◽  
Takeshi Nomura ◽  
...  
Keyword(s):  
Soleus Muscle ◽  
Weight Bearing ◽  
Postnatal Period ◽  
Hindlimb Unloading ◽  
Full Weight Bearing ◽  
Type I ◽  
Myosin Isoforms ◽  
Normal Transition ◽  
Postural Muscle ◽  
Rat Soleus Muscle

We tested the hypothesis that rat soleus muscle fiber growth and changes in myosin phenotype during the postnatal, preweaning period would be largely independent of weight bearing. The hindlimbs of one group of pups were unloaded intermittently from postnatal day 4 to day 21: the pups were isolated from the dam for 5 h during unloading and returned for nursing for 1 h. Control pups were either maintained with the dam as normal or put on an alternating feeding schedule as described above. The enlargement of mass (∼3 times), increase in myonuclear number (∼1.6 times) and myonuclear domain (∼2.6 times), and transformation toward a slow fiber phenotype (from 56 to 70% fibers expressing type I myosin heavy chain) observed in controls were inhibited by hindlimb unloading. These properties were normalized to control levels or higher within 1 mo of reambulation beginning immediately after the unloading period. Therefore, chronic unloading essentially stopped the ontogenetic developmental processes of 1) net increase in DNA available for transcription, 2) increase in amount of cytoplasm sustained by that DNA pool, and 3) normal transition of myosin isoforms that occur in some fibers from birth to weaning. It is concluded that normal ontogenetic development of a postural muscle is highly dependent on the gravitational environment even during the early postnatal period, when full weight-bearing activity is not routine.

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