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Qualitative alteration of peripheral motor system begins prior to appearance of typical sarcopenia syndrome in middle-aged rats.

Tamaki T, Hirata M, Uchiyama Y - Front Aging Neurosci (2014)

Bottom Line: Muscle tenderness in passive stretching was also measured as stretch absorption ability, associated with histological quantitation of muscle connective tissues.These findings are likely to be closely related to significant losses in fast-type MUs, muscle strength and contraction velocity, which could be a causative factor in falls in the elderly.Thus, prevention should be started in middle age that could be retained relatively higher movement ability.

View Article: PubMed Central - PubMed

Affiliation: Muscle Physiology and Cell Biology Unit, Tokai University School of Medicine Isehara, Japan ; Division of Basic Clinical Science, Department of Regenerative Medicine, Tokai University School of Medicine Isehara, Japan.

ABSTRACT
Qualitative changes in the peripheral motor system were examined using young, adult, middle-aged, and old-aged rats in order to assess before and after the appearance of sarcopenia symptoms. Significant loss of muscle mass and strength, and slow-type fiber grouping with a loss of innervated nerve fibers were used as typical markers of sarcopenia. Dynamic twitch and tetanus tension and evoked electromyogram (EEMG) were measured via electrical stimulation through the sciatic nerve under anesthesia using our force-distance transducer system before and after sciatectomy. Digital and analog data sampling was performed and shortening and relaxing velocity of serial twitches was calculated with tension force. Muscle tenderness in passive stretching was also measured as stretch absorption ability, associated with histological quantitation of muscle connective tissues. The results indicated the validity of the present model, in which old-aged rats clearly showed the typical signs of sarcopenia, specifically in the fast-type plantaris muscles, while the slow-type soleus showed relatively mild syndromes. These observations suggest the following qualitative alterations as the pathophysiological mechanism of sarcopenia: (1) reduction of shortening and relaxing velocity of twitch; (2) decline of muscle tenderness following an increase in the connective tissue component; (3) impaired recruitment of motor units (MUs) (sudden depression of tetanic force and EEMG) in higher stimulation frequencies over 50-60 Hz; and (4) easy fatigability in the neuromuscular junctions. These findings are likely to be closely related to significant losses in fast-type MUs, muscle strength and contraction velocity, which could be a causative factor in falls in the elderly. Importantly, some of these symptoms began in middle-aged rats that showed no other signs of sarcopenia. Thus, prevention should be started in middle age that could be retained relatively higher movement ability.

No MeSH data available.


Related in: MedlinePlus

Comparison of fiber-type components in PLT muscle between adult and middle-aged rats. Whole PLT sections were stained for ATPase (preincubation, 4.6); thus, the darkest staining represents Type I, medium Type IIb, and light Type IIa (C). This is likely to give the impression that the distribution of Type I fibers is slightly higher in middle-aged rats (B) than in adult rats (A). Differences were significant when calculated per unit area (section) for Type I and Type IIb (D), thus confirming the histochemical changes from fast- to slow-type fibers. Bars in (A,B) = 1 mm, (C) = 100 μm. *P < 0.05.
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Figure 8: Comparison of fiber-type components in PLT muscle between adult and middle-aged rats. Whole PLT sections were stained for ATPase (preincubation, 4.6); thus, the darkest staining represents Type I, medium Type IIb, and light Type IIa (C). This is likely to give the impression that the distribution of Type I fibers is slightly higher in middle-aged rats (B) than in adult rats (A). Differences were significant when calculated per unit area (section) for Type I and Type IIb (D), thus confirming the histochemical changes from fast- to slow-type fibers. Bars in (A,B) = 1 mm, (C) = 100 μm. *P < 0.05.

Mentions: With regard to the decline in shortening-relaxing velocity in the middle-aged group without an apparent decrease in muscle mass, we further examined muscle fiber type distribution in PLT muscles (Figure 8). For this analysis, the old-aged group was eliminated because they showed significant decreases in muscle mass and increases in Type I fibers with typical grouping (Figure 3), and this corresponded to the literature (Kung et al., 2014). Therefore, advanced analysis was performed between the adult and middle-aged groups. In the ATPase (pH 4.6) staining of whole cross-sections, dark-brown Type I fibers were impressively higher in middle-aged than in adult rats, whereas Type IIa (relative white in C) and IIb (light-brown in C) fibers were similar (Figures 8A vs. B). However, when these distributions were calculated, there were significant increases in Type I and decreases in Type IIb fibers, and non-significant changes in Type IIa fibers were observed in the middle-aged group (Figure 8D). Thus, the shift from Type IIb to Type I fibers appears to begin in middle-aged rats, corresponding to the results of twitch-shortening and -relaxing velocity (Figure 7A), while muscle mass was maintained (Figure 5).


Qualitative alteration of peripheral motor system begins prior to appearance of typical sarcopenia syndrome in middle-aged rats.

Tamaki T, Hirata M, Uchiyama Y - Front Aging Neurosci (2014)

Comparison of fiber-type components in PLT muscle between adult and middle-aged rats. Whole PLT sections were stained for ATPase (preincubation, 4.6); thus, the darkest staining represents Type I, medium Type IIb, and light Type IIa (C). This is likely to give the impression that the distribution of Type I fibers is slightly higher in middle-aged rats (B) than in adult rats (A). Differences were significant when calculated per unit area (section) for Type I and Type IIb (D), thus confirming the histochemical changes from fast- to slow-type fibers. Bars in (A,B) = 1 mm, (C) = 100 μm. *P < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4214197&req=5

Figure 8: Comparison of fiber-type components in PLT muscle between adult and middle-aged rats. Whole PLT sections were stained for ATPase (preincubation, 4.6); thus, the darkest staining represents Type I, medium Type IIb, and light Type IIa (C). This is likely to give the impression that the distribution of Type I fibers is slightly higher in middle-aged rats (B) than in adult rats (A). Differences were significant when calculated per unit area (section) for Type I and Type IIb (D), thus confirming the histochemical changes from fast- to slow-type fibers. Bars in (A,B) = 1 mm, (C) = 100 μm. *P < 0.05.
Mentions: With regard to the decline in shortening-relaxing velocity in the middle-aged group without an apparent decrease in muscle mass, we further examined muscle fiber type distribution in PLT muscles (Figure 8). For this analysis, the old-aged group was eliminated because they showed significant decreases in muscle mass and increases in Type I fibers with typical grouping (Figure 3), and this corresponded to the literature (Kung et al., 2014). Therefore, advanced analysis was performed between the adult and middle-aged groups. In the ATPase (pH 4.6) staining of whole cross-sections, dark-brown Type I fibers were impressively higher in middle-aged than in adult rats, whereas Type IIa (relative white in C) and IIb (light-brown in C) fibers were similar (Figures 8A vs. B). However, when these distributions were calculated, there were significant increases in Type I and decreases in Type IIb fibers, and non-significant changes in Type IIa fibers were observed in the middle-aged group (Figure 8D). Thus, the shift from Type IIb to Type I fibers appears to begin in middle-aged rats, corresponding to the results of twitch-shortening and -relaxing velocity (Figure 7A), while muscle mass was maintained (Figure 5).

Bottom Line: Muscle tenderness in passive stretching was also measured as stretch absorption ability, associated with histological quantitation of muscle connective tissues.These findings are likely to be closely related to significant losses in fast-type MUs, muscle strength and contraction velocity, which could be a causative factor in falls in the elderly.Thus, prevention should be started in middle age that could be retained relatively higher movement ability.

View Article: PubMed Central - PubMed

Affiliation: Muscle Physiology and Cell Biology Unit, Tokai University School of Medicine Isehara, Japan ; Division of Basic Clinical Science, Department of Regenerative Medicine, Tokai University School of Medicine Isehara, Japan.

ABSTRACT
Qualitative changes in the peripheral motor system were examined using young, adult, middle-aged, and old-aged rats in order to assess before and after the appearance of sarcopenia symptoms. Significant loss of muscle mass and strength, and slow-type fiber grouping with a loss of innervated nerve fibers were used as typical markers of sarcopenia. Dynamic twitch and tetanus tension and evoked electromyogram (EEMG) were measured via electrical stimulation through the sciatic nerve under anesthesia using our force-distance transducer system before and after sciatectomy. Digital and analog data sampling was performed and shortening and relaxing velocity of serial twitches was calculated with tension force. Muscle tenderness in passive stretching was also measured as stretch absorption ability, associated with histological quantitation of muscle connective tissues. The results indicated the validity of the present model, in which old-aged rats clearly showed the typical signs of sarcopenia, specifically in the fast-type plantaris muscles, while the slow-type soleus showed relatively mild syndromes. These observations suggest the following qualitative alterations as the pathophysiological mechanism of sarcopenia: (1) reduction of shortening and relaxing velocity of twitch; (2) decline of muscle tenderness following an increase in the connective tissue component; (3) impaired recruitment of motor units (MUs) (sudden depression of tetanic force and EEMG) in higher stimulation frequencies over 50-60 Hz; and (4) easy fatigability in the neuromuscular junctions. These findings are likely to be closely related to significant losses in fast-type MUs, muscle strength and contraction velocity, which could be a causative factor in falls in the elderly. Importantly, some of these symptoms began in middle-aged rats that showed no other signs of sarcopenia. Thus, prevention should be started in middle age that could be retained relatively higher movement ability.

No MeSH data available.


Related in: MedlinePlus