Plasticity changes in neuromuscular junction morphology and related regulatory proteins in the hibernating ground squirrel.

Skeletal muscle disuse atrophy can cause degenerative changes in neuromuscular junction morphology. Although Daurian ground squirrels (Spermophilus dauricus) are a natural anti-disuse animal model for studying muscle atrophy during hibernation, little is known about the morphological and regulatory mechanisms of their neuromuscular junctions. Here, we found that morphological indices of the soleus muscle were significantly lower during hibernation (torpor and interbout arousal) compared with pre-hibernation but recovered during post-hibernation. In the extensor digitorum longus muscle, neuromuscular junction morphology did not change significantly during hibernation. Agrin-Lrp4-MuSK is a key pathway for the formation and maintenance of the neuromuscular junction. Our results showed that low-density lipoprotein receptor-associated protein 4 (Lrp4) expression in the soleus (slow muscle) decreased by 46.2% in the interbout arousal group compared with the pre-hibernation group (P = 0.019), with recovery in the post-hibernation group. Compared with the pre-hibernation group, agrin expression in the extensor digitorum longus (fast muscle) increased by 67.0% in the interbout arousal group (P = 0.016). In conclusion, periodic up-regulation in agrin expression during interbout arousal may be involved in the maintenance of neuromuscular junction morphology in the extensor digitorum longus muscle during hibernation. The degenerative changes in neuromuscular junction morphology and the periodic decrease in Lrp4 protein expression in the soleus during hibernation, these changes recovered to the pre-hibernation levels in the post-hibernation group, exhibiting significant plasticity. This plasticity may be one of the important mechanisms for resisting disuse atrophy in hibernating animals.NEW & NOTEWORTHY This study is the first to explore the neuromuscular junction morphology of slow- and fast-twitch muscles in Daurian ground squirrels during different periods of hibernation. Results showed that the neuromuscular junction maintained stable morphology in the extensor digitorum longus muscle. The degenerative changes in neuromuscular junction morphology and the periodic decrease in Lrp4 protein expression in the soleus muscle during hibernation recovered in post-hibernation, exhibiting significant plasticity.

Different fuel regulation in two types of myofiber results in different antioxidant strategies in Daurian ground squirrels (Spermophilus dauricus) during hibernation.

We previously showed that different skeletal muscles in Daurian ground squirrels (Spermophilus dauricus) possess different antioxidant strategies during hibernation; however, the reason for these varied strategies remains unclear. To clarify this issue, we studied REDD1, FOXO4, PGC-1α, FOXO1 and atrogin-1 proteins to determine the potential cause of the different antioxidant strategies in Daurian ground squirrels during hibernation, and to clarify whether different strategies affect atrophy-related signals. Results showed that the soleus (SOL) muscle experienced intracellular hypoxia during interbout arousal, but no oxidative stress. This may be due to increased PGC-1α expression enhancing antioxidant capacity in the SOL under hypoxic conditions. Extensor digitorum longus (EDL) muscle showed no change in oxidative stress, hypoxia or antioxidant capacity during hibernation. The FOXO1 and PGC-1α results strongly suggested differentially regulated fuel metabolism in the SOL and EDL muscles during hibernation, i.e. enhanced lipid oxidation and maintained anaerobic glycolysis, respectively. Atrogin-1 expression did not increase during hibernation in either the SOL or EDL, indicating that protein synthesis was not inhibited by atrogin-1. Thus, our results suggest that different fuel regulation may be one mechanism related to antioxidant defense strategy formation in different kinds of skeletal muscle fibers of Daurian ground squirrels during hibernation.

A Temporal Examination of Cytoplasmic Ca2 + Levels, Sarcoplasmic Reticulum Ca2 + Levels, and Ca2 + -Handling-Related Proteins in Different Skeletal Muscles of Hibernating Daurian Ground Squirrels.

To explore the possible mechanism of the sarcoplasmic reticulum (SR) in the maintenance of cytoplasmic calcium (Ca2+) homeostasis, we studied changes in cytoplasmic Ca2+, SR Ca2+, and Ca2+-handling proteins of slow-twitch muscle (soleus, SOL), fast-twitch muscle (extensor digitorum longus, EDL), and mixed muscle (gastrocnemius, GAS) in different stages in hibernating Daurian ground squirrels (Spermophilus dauricus). Results showed that the level of cytoplasmic Ca2+ increased and SR Ca2+ decreased in skeletal muscle fiber during late torpor (LT) and inter-bout arousal (IBA), but both returned to summer active levels when the animals aroused from and re-entered into torpor (early torpor, ET), suggesting that intracellular Ca2+ is dynamic during hibernation. The protein expression of ryanodine receptor1 (RyR1) increased in the LT, IBA, and ET groups, whereas the co-localization of calsequestrin1 (CSQ1) and RyR1 in GAS muscle decreased in the LT and ET groups, which may increase the possibility of RyR1 channel-mediated Ca2+ release. Furthermore, calcium pump (SR Ca2+-ATPase 1, SERCA1) protein expression increased in the LT, IBA, and ET groups, and the signaling pathway-related factors of SERCA activity [i.e., ß-adrenergic receptor2 protein expression (in GAS), phosphorylation levels of phospholamban (in GAS), and calmodulin kinase2 (in SOL)] all increased, suggesting that these factors may be involved in the up-regulation of SERCA1 activity in different groups. The increased protein expression of Ca2+-binding proteins CSQ1 and calmodulin (CaM) indicated that intracellular free Ca2+-binding ability also increased in the LT, IBA, ET, and POST groups. In brief, changes in cytoplasmic and SR Ca2+ concentrations, SR RyR1 and SERCA1 protein expression levels, and major RyR1 and SERCA1 signaling pathway-related factors were unexpectedly active in the torpor stage when metabolic functions were highly inhibited.

Remarkable Homeostasis of Protein Sialylation in Skeletal Muscles of Hibernating Daurian Ground Squirrels (Spermophilus dauricus).

As the most common post-translational protein modification, glycosylation is intimately linked to muscle atrophy. This study aimed to investigate the performance of protein glycosylation in the soleus muscle (SOL) in Daurian ground squirrels (Spermophilus dauricus) and to determine the potential role of protein glycosylation in the mechanism underlying disuse muscle atrophy prevention. The results showed that (1) seven glycan structures comprising sialic acid α2-3 galactose (SAα2-3Gal) were altered during hibernation; (2) alterations in the SAα2-3Gal structure during hibernation were based on changes in the expression levels of beta-galactoside alpha-2 and 3-sialyltransferases; and (3) α2-3-linked sialylated modifications of heat shock cognate 70 and pyruvate kinase and expression of 14-3-3 epsilon protein were oscillatorily changed during hibernation. Our findings indicate that the skeletal muscles of hibernating Daurian ground squirrels maintain protein sialylation homeostasis by restoring sialylation modification during periodic interbout arousal, which might protect the skeletal muscles against disuse atrophy.

Different fuel regulation in two types of myofiber results in different antioxidant strategies in Daurian ground squirrels (Spermophilus dauricus) during hibernation.

We previously showed that different skeletal muscles in Daurian ground squirrels (Spermophilus dauricus) possess different antioxidant strategies during hibernation; however, the reason for these varied strategies remains unclear. To clarify this issue, we studied REDD1, FOXO4, PGC-1α, FOXO1, and atrogin-1 proteins to determine the potential cause of the different antioxidant strategies in Daurian ground squirrels during hibernation, and to clarify whether different strategies affect atrophy-related signals. Results showed that the soleus (SOL) muscle experienced intracellular hypoxia during interbout arousal, but no oxidative stress. This may be due to increased PGC-1α expression enhancing antioxidant capacity in the SOL under hypoxic conditions. Extensor digitorum longus (EDL) muscle showed no change in oxidative stress, hypoxia, or antioxidant capacity during hibernation. The FOXO1 and PGC-1α results strongly suggested differentially regulated fuel metabolism in the SOL and EDL muscles during hibernation, i.e., enhanced lipid oxidation and maintained anaerobic glycolysis, respectively. Atrogin-1 expression did not increase during hibernation in either the SOL or EDL, indicating that protein synthesis was not inhibited by atrogin-1. Thus, our results suggest that different fuel regulation may be one mechanism related to antioxidant defense strategy formation in different kinds of skeletal muscle fibers of Daurian ground squirrels during hibernation.

Novel findings on ultrastructural protection of skeletal muscle fibers during hibernation of Daurian ground squirrels: Mitochondria, nuclei, cytoskeleton, glycogen.

We examined ultrastructure protective phenomena and mechanisms of slow and fast muscles in hibernating Daurian ground squirrels (Spermophilus dauricus). Some degenerative changes such as slightly decreased sarcomere length and vacuolization occurred in hibernation, but periaxonal capsular borders in intrafusal fibers remained distinct and the arrangement of extrafusal fibers and Z-lines unscathed. In soleus samples, the number of glycogenosomes more than tripled during hibernation. The expression of phosphorylated glycogen synthase remained unaltered while that of glycogen phosphorylase decreased during hibernation. The number of extensor digitorum longus glycogenosomes decreased and the expression of phosphorylated glycogen synthase decreased, while glycogen phosphorylase expression remained unaltered. The nuclei number remained unchanged. Kinesin and desmin, preventors of nuclear loss and damage, were maintained or just slightly reduced in hibernation. The single-fiber mitochondrial concentration and sub-sarcolemmal mitochondrial number increased in both muscle types. The expression of vimentin, which anchors mitochondria and maintains Z-line integrity, was increased during and after hibernation. Also, dynamin-related protein 1, mitochondrial fission factor, and adenosine triphosphate synthase were elevated in both muscle types. These findings confirm a remarkable ultrastructure preservation and show an unexpected increase in mitochondrial capacity in hibernating squirrels.

Muscle-specific activation of calpain system in hindlimb unloading rats and hibernating Daurian ground squirrels: a comparison between artificial and natural disuse.

To determine whether the regulation of calpain system is involved in non-hibernators and hibernators in disused condition, the soleus (SOL) and extensor digitorum longus (EDL) muscles were used for investigating the muscle mass, the ratio of muscle wet weight/body weight (MWW/BW), fiber-type distribution, fiber cross-sectional area (CSA), and the protein expression of MuRF1, calpain-1, calpain-2, calpastatin, desmin, troponin T, and troponin C in hindlimb unloading rats and hibernating Daurian ground squirrels. The muscle mass, MWW/BW, and fiber CSA were found significantly decreased in SOL and EDL of hindlimb unloading rats, but unchanged in hibernating ground squirrels. The MuRF1 expression was increased in both SOL and EDL of unloading rats, while it was only increased in SOL, but maintained in EDL of hibernating ground squirrels. The expression levels of calpain-1 and calpain-2 were increased in different degrees in unloaded SOL and EDL in rats, while they were maintained in EDL and even reduced in SOL of hibernating ground squirrels. Besides, the expression of calpastatin was decreased in unloaded rats, but increased in hibernating ground squirrels. The desmin expression was decreased in unloaded rats, but maintained in hibernating squirrels. Interestingly, the levels of troponin T and troponin C were decreased in both SOL and EDL of unloaded rats, but increased in hibernating ground squirrels with muscle-type specificity. In conclusion, differential calpain activation and substrate-selective degradation in slow and fast muscles are involved in the mechanisms of muscle atrophy of unloaded rats and remarkable ability of muscle maintenance of hibernating ground squirrels.

A dramatic blood plasticity in hibernating and 14-day hindlimb unloading Daurian ground squirrels (Spermophilus dauricus).

We compared the effects of hibernation inactivity and 14-day hindlimb unloading in non-hibernating period on biochemical, rheological, and hematological parameters of blood in Daurian ground squirrels (Spermophilus dauricus). Twenty-four squirrels were randomly divided into four groups: control (CON), hibernation (HIB), post-hibernation (POST), and 14-day hindlimb unloading (HU). The results showed that serum enzymes (L-lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase) activities decreased in HIB, POST, and HU squirrels compared with CON. Total protein (including albumin and globulin) maintained in HIB but decreased in HU compared with CON. Total cholesterol and high-density lipoprotein-cholesterol increased in HIB but maintained in HU and POST compared with CON. Meanwhile, serum creatinine decreased and urea increased in HU compared with CON. All blood ions concentrations were unchanged in HIB, POST, and HU squirrels compared with CON except calcium which increased in HIB compared with CON, and phosphorus which increased in HIB and POST compared with CON. Most of detected serum biochemical analytes in POST recovered to the CON level. Blood viscosity, which was unchanged in all shear rates in HU, increased in HIB and recovered in POST in lower shear rates compared with CON. Erythrocyte and corpuscular volume decreased in HIB and HU but maintained in POST compared with CON. All the routine hematological parameters recovered in POST as compared with CON except platelet, which decreased in HIB and POST but maintained in HU compared with CON. In conclusion, our results suggested a remarkable ability to maintain blood homeostasis in hibernating squirrels.

Tetramethylpyrazine ameliorated disuse-induced gastrocnemius muscle atrophy in hindlimb unloading rats through suppression of Ca2+/ROS-mediated apoptosis.

The purpose of this study was to examine the possible mechanism underlying the protective effect of tetramethylpyrazine (TMP) against disuse-induced muscle atrophy. Sprague-Dawley rats were randomly assigned to receive 14 days of hindlimb unloading (HLU, a model of disuse atrophy) or cage controls. The rats were given TMP (60 mg/kg body mass) or vehicle (water) by gavage. Compared with vehicle treatment, TMP significantly attenuated the loss of gastrocnemius muscle mass (-33.56%, P < 0.01), the decrease of cross-sectional area of slow fiber (-10.99%, P < 0.05) and fast fiber (-15.78%, P < 0.01) during HLU. Although TMP failed to further improve recovery of muscle function or fatigability compared with vehicle treatment, it can suppress the higher level of lactate (-22.71%, P < 0.01) induced by HLU. Besides, TMP could effectually reduce the increased protein expression of muscle RING-finger protein 1 induced by HLU (-14.52%, P < 0.01). Furthermore, TMP can ameliorate the calcium overload (-54.39%, P < 0.05), the increase of malondialdehyde content (-19.82%, P < 0.05), the decrease of superoxide dismutase activity (21.34%, P < 0.05), and myonuclear apoptosis (-78.22%, P < 0.01) induced by HLU. Moreover, TMP significantly reduced HLU-induced increase of Bax to B-cell lymphoma 2 (-36.36%, P < 0.01) and cytochrome c release (-36.16%, P < 0.05). In conclusion, TMP attenuated HLU-induced gastrocnemius muscle atrophy through suppression of Ca2+/reactive oxygen species increase and consequent proteolysis and apoptosis. Therefore, TMP might exhibit therapeutic effect against oxidative stress, cytosolic calcium overload, and mitochondrial damage in disuse-induced muscle atrophy.

iTRAQ-based proteomic analysis of myofibrillar contents and relevant synthesis and proteolytic proteins in soleus muscle of hibernating Daurian ground squirrels (Spermophilus dauricus).

BACKGROUND: Daurian ground squirrels (Spermophilus dauricus) deviate from significant increase of protein catabolism and loss of myofibrillar contents during long period of hibernation inactivity. METHODS: Here we use iTRAQ based quantitative analysis to examine proteomic changes in the soleus of squirrels in pre-hibernation, hibernation and post-hibernation states. The total proteolysis rate of soleus was measured by the release of the essential amino acid tyrosine from isolated muscles. Immunofluorescent analysis was used to determine muscle fiber cross-sectional area. Western blot was used for the validation of the quantitative proteomic analysis. RESULTS: The proteomic responses to hibernation had a 0.4- to 0.8-fold decrease in the myofibrillar contractile protein levels of myosin-3, myosin-13 and actin, but a 2.1-fold increase in myosin-2 compared to pre-hibernation group. Regulatory proteins such as troponin C and tropomodulin-1 were 1.4-fold up-regulated and 0.7-fold down-regulated, respectively, in hibernation compared to pre-hibernation group. Moreover, 10 proteins with proteolytic function in hibernation, which was less than 14 proteins in the post-hibernation group, were up-regulated relative to the pre-hibernation group. The total proteolysis rates of soleus in hibernation and post-hibernation groups were significantly inhibited as compared with pre-hibernation group. CONCLUSION: These findings suggest that the myofibrillar remodeling and partial suppression of myofibrillar proteolysis were likely responsible for preventing skeletal muscle atrophy during prolonged disuse in hibernation. This is the first study where the myofibrillar contents and relevant synthesis and proteolytic proteins in slow soleus was discussed based on proteomic investigation performed on wild Daurian ground squirrels. Our results lay the foundation for further research in preventing disuse-induced skeletal muscle atrophy in mammals.

Stable atrogin-1 (Fbxo32) and MuRF1 (Trim63) gene expression is involved in the protective mechanism in soleus muscle of hibernating Daurian ground squirrels (Spermophilus dauricus).

Understanding the mechanisms that protect against or limit muscle atrophy in hibernators during prolonged inactivity has important implications for its treatment. We examined whether external factors influence the pathways regulating protein synthesis and degradation, leading to muscle atrophy prevention in Daurian ground squirrels (Spermophilus dauricus). We investigated the effects of 14-day hindlimb-unloading (HU) in different seasons and two-month hibernation on the soleus (SOL) muscle wet mass, muscle-to-body mass ratio, fiber cross sectional area (CSA), fiber distribution and muscle ultrastructure. We also measured changes in the protein expression and activation states of Akt, mTOR and FoxO1 and the mRNA expression of atrogin-1 and MuRF1. Compared with the control groups, autumn and winter HU significantly lowered SOL muscle wet mass and muscle-to-body mass ratio, decreased type I and II fiber CSA and induced ultrastructural anomalies. However, these measured indices were unchanged between Pre-hibernation and Hibernation groups. Furthermore, phosphorylation levels of Akt and mTOR significantly decreased, while the phosphorylation level of FoxO1 and mRNA expression of atrogin-1 and MuRF1 increased after HU. During hibernation, the phosphorylation levels of Akt and mTOR significantly decreased, but the phosphorylation level of FoxO1 and mRNA expression of atrogin-1 and MuRF1 remained unchanged. Overall, our findings suggest that disuse and seasonality may not be sufficient to initiate the innate protective mechanism that prevents SOL atrophy during prolonged periods of hibernation inactivity. The stable expression of atrogin-1 and MuRF1 may facilitate to prevent SOL atrophy via controlling ubiquitination of muscle proteins during hibernation.

[Effect of two Pi deficiency syndrome models on the configuration and function of the skeletal muscle in mice].

OBJECTIVE: To observe the relation between Pi deficiency syndrome (PDS) and the configuration and functions of extensor digitorum longus (EDL)and soleus (SOL). METHODS: Totally 36 ICR mice were randomly divided into 3 groups according to weight matching principle, the control group, the exhausted group, and the rhubarb group, 12 in each group. Two PDS models were established by either purgation with rhubarb diarrhea (as Group A) or exhausted swimming plus sleep deprivation (as Group B).The cross sectional area (CSA) of type I and II fibers of extensor digitorum longus (EDL) and soleus (SOL), relative proportions of type I and II fibers were measured by m-ATPase histochemical method. The isotonic contraction and the maximum tetanus contraction of EDL and SOL were detected by PowerLab system. RESULTS: Compared with the control group, the body weight, body temperature, and the general health condition of PDS model rats obviously decreased; the spleen index and the thymus index were also lower; the maximal isotonic contraction and the maximum tetanus contraction obviously decreased; the cross section areas of EDL and SOL were reduced with loosely arranged cells. In EDL, the proportion of type I fibers was added and the proportion of type II fibers was lowered. In SOL, there was no change in the proportion of type I and type II fibers. CONCLUSIONS: EDL and SOL were obviously atrophied in the two PDS model mice. The type I fibers of SOL was more significantly atrophied in Group B.

Changes in calpains and calpastatin in the soleus muscle of Daurian ground squirrels during hibernation.

We investigated changes in muscle mass, calpains, calpastatin and Z-disk ultrastructure in the soleus muscle (SOL) of Daurian ground squirrels (Spermophilus dauricus) after hibernation or hindlimb suspension to determine possible mechanisms by which muscle atrophy is prevented in hibernators. Squirrels (n=30) were divided into five groups: no hibernation group (PRE, n=6); hindlimb suspension group (HLS, n=6); two month hibernation group (HIB, n=6); two day group after 90±12 days of hibernation (POST, n=6); and forced exercise group (one time forced, moderate-intensity treadmill exercise) after arousal (FE, n=6). Activity and protein expression of calpains were determined by casein zymography and western blotting, and Z-disk ultrastructure was observed by transmission electron microscopy. The following results were found. Lower body mass and higher SOL muscle mass (mg) to total body mass (g) ratio were observed in HIB and POST; calpain-1 activity increased significantly by 176% (P=0.034) in HLS compared to the PRE group; no significant changes were observed in calpain-2 activity. Protein expression of calpain-1 and calpain-2 increased by 83% (P=0.041) and 208% (P=0.029) in HLS compared to the PRE group, respectively; calpastatin expression increased significantly by 180% (P<0.001) and 153% (P=0.007) in HIB and POST, respectively; the myofilaments were well-organized, and the width of the sarcomere and the Z-disk both appeared visually similar among the pre-hibernation, hibernating and post-hibernation animals. Inhibition of calpain activity and consequently calpain-mediated protein degradation by highly elevated calpastatin protein expression levels may be an important mechanism for preventing muscle protein loss during hibernation and ensuring that Z-lines remained ultrastructurally intact.

Peanut Allergy, Allergen Composition, and Methods of Reducing Allergenicity: A Review.

Peanut allergy affects 1-2% of the world's population. It is dangerous, and usually lifelong, and it greatly decreases the life quality of peanut-allergic individuals and their families. In a word, peanut allergy has become a major health concern worldwide. Thirteen peanut allergens are identified, and they are briefly introduced in this paper. Although there is no feasible solution to peanut allergy at present, many methods have shown great promise. This paper reviews methods of reducing peanut allergenicity, including physical methods (heat and pressure, PUV), chemical methods (tannic acid and magnetic beads), and biological methods (conventional breeding, irradiation breeding, genetic engineering, enzymatic treatment, and fermentation).

[Effects of tetramethylpyrazine on nitric oxide synthase activity and calcium ion concentration of skeletal muscle in hindlimb unloading rats].

OBJECTIVE: To explore the effects of tetramethylpyrazine on the nitric oxide synthase activity and calcium ion concentration in skeletal muscle fiber and decipher the possible mechanisms of anti-muscle atrophy function of tetramethylpyrazine in hindlimb unloading rats. METHODS: Hindlimb unloading (HLU) rats were used as a muscle atrophy model to study the activity of nitric oxide synthase by colorimetry. The concentration of intracellular calcium ion was measured by laser scanning confocal microscope. A total of 18 female rats were randomly divided into 3 groups: control (CON), hindlimb unloading with water (HLU + W) and hindlimb unloading with tetramethylpyrazine (HLU + Tmp) (n = 6 each). RESULTS: (1) Compared with CON, the activity of nitric oxide synthase decreased by 28% in HLU + W (P < 0.05) and decreased by 46% in HLU + Tmp (P < 0.01). The activity of nitric oxide synthase less decreased in HLU + Tmp than that in HLU + W, but it was not statistically significant (P > 0.05). (2) Compared with CON, the concentrations of intracellular calcium ion in HLU + W and HLU + Tmp increased by 330% and 86% respectively (P < 0.01). Compared with HLU + W, the concentration of intracellular calcium ion decreased by 130% in HLU + Tmp (P < 0.01). CONCLUSION: The activity of nitric oxide synthase decreases and the concentration of calcium ion increases in hindlimb unloading rats. And tetramethylpyrazine may suppress the calcium ion overloading but not the activity of NOS associated with disuse muscular atrophy.

[Effects of simulated weightlessness on emotional behaviour in rats].

OBJECTIVE: To study the influence of 14- day simulated weightlessness on emotional behaviour in rats. METHODS: Sixteen from twenty male SD rats were selected and assigned to a 2-group design: the control group and the tail suspension (TS) group (n = 8). The essay deployed typical methods for assessing emotional activity in the current, including food-intake and body weight variation, open field testing, sucrose preference testing and the evaluation of emotional arousal level to test emotional behavior. RESULTS: 1. After 14- day simulated weightlessness for rats, their food-intake and body weight increase were less than those in the control group. 2. The ability of movement reduced in rats, the number of locomotion was significantly lower than that in the control group (P < 0.05) and the frequency of self-grooming was significantly higher than that in the control group(P <0.01. 3. A higher level of emotionality in TS group was recorded. 4. Sucrose preference was not observed in TS group. CONCLUSION: It demonstrated depression, anxiety and nervous symptom occurred in the TS rats with a certain degree of nervous reaction but no anhedonia.

Skeletal muscle is protected from disuse in hibernating dauria ground squirrels.

The purpose of this study is to test the hypothesis that muscle fibers are protected from undue atrophy in hibernating dauria ground squirrels (Spermophilus dauricus, Brandt). Muscle mass, fiber cross sectional area (CSA, video analysis) and fiber type distribution (m-ATPase staining) were determined in extensor digitorum longus (EDL) muscle from non-hibernating control animals (Pre-H), from animals who hibernated for one (H1) or two (H2) months, and from animals 2-4days after arousal (Post-H; N=8 each). Muscle wet weight decreased less than body weight in hibernating animals, resulting in a steady increase in muscle-to-body mass ratio (+37% in Post-H compared to Pre-H, p<0.001). In the Pre-H group, Type I (6.3±2.0%) and II (93.7±2.0%) fiber CSAs were 1719±201 and 2261±287µm(2), respectively. There was a tendency (n.s.) of larger CSA of type I in hibernators compared to pre-H. In the Post-H group, fiber CSA and type distribution were not different from Pre-H. We are the first to report data on EDL fiber type distribution and confirm a protective effect that prevents muscle atrophy in spite of prolonged disuse during hibernation in dauria ground squirrels.

[Effect of Ligusticum and its two main components on muscle atrophy in a hind limb unloaded rat model].

OBJECTIVE: To study the effects of Ligusticum and its two components (Sodium Ferulate and Ligustrazine as main efficacy components in Ligusticum for invigorating blood circulation) on muscle atrophy in a hind limb unloaded rat model. METHODS: The tail-suspended rats were subjected to a 14-days disuse, immunohistochemistry and hemorheology were used to study the effects of medicines on soleus muscle. RESULTS: Compared with HLU+ W: (1) The CSA of soleus type I fibers in HLU + SfH and HLU+ TmpH increased by 37.3% and 39.4% respectively (P < 0.05). (2) Expression level of MHC II were inhibited in all treatment groups (P < 0.01). (3) Expression of MHC II in nuclear bag 2 fiber were altered from positive to negative. (4) The blood viscosity in low shear rates decreased obviously (P < 0.01), even near to control. CONCLUSION: Ligusticum and its two main efficacy components (Sodium Ferulate and Ligustrazine) can prevent soleus atrophy induced by disuse, and Sodium Ferulate and Ligustrazine in high dose showed most efficacy.

[Effects of Ligustrazine and Radix Astragali on activities of myosin adenosine triphosphatase of soleus muscle and muscle atrophy in tail-suspended rats].

OBJECTIVE: To study the effects of Ligustrazine (Lig) and Radix Astragali (Rad) on activities of myosin adenosine triphosphatase (mATPase) of soleus muscle and atrophy in tail-suspended rat. METHOD: Weightlessness was simulated by tail suspension in female rats. The activities of mATPase of intrafusal and extrafusal fibres in soleus muscle were detected by method of Ca2(+)-ATPase. RESULT: 1) Compared with tail-suspended (TS) group, the percentage of type II fibres of SOL in both Ligustrazine (Lig) group and Rad group decreased distinctly. Furthermore, the percentage of type I and type II fibres of SOL in Rad group showed no difference with control (CON) group. 2) The type I CSA of Lig group was markedly larger than that in TS group, and there was no difference as compared with that of CON group. CSA of type I, II and average CSA of Rad group were remarkably larger than those in TS group, and there were no difference as compared with those of CON group. 3) mATPase activities of intrafusal fibres in both Lig group and Rad group were approximate to that of CON group. CONCLUSION: Lig and Rad are both able to effectively prevent muscle atrophy caused by tail suspension, restrain the slow-twitch muscle transform to fast-twitch muscle and control the increase of mATPase activities caused by weightlessness.