Daily number and lengths of activity bursts in rabbit jaw muscles

Muscle activity has predominantly been studied for specific motor tasks not necessarily representative of normal daily behaviour. The few studies that have examined daily muscle use have quantified this by duty time, merging all levels of muscle activity. Muscle activity can also be characterized by the number, duration and level of bursts. The purpose of this study was to characterize, for various levels of muscle activity, the daily masseter and digastric actions in the rabbit. Characterization was realized by quantification of duty time (summed length of all bursts as a percentage of total time), number of bursts and distribution of burst lengths. A telemetric device was implanted in the two muscles of six rabbits, ensuring the recording of their jaw muscle activities while they moved freely. The continuously transmitted signals over 1 day were analysed. The results showed that (i) more than 100,000 bursts per day exceeded the 2% level of the maximum muscle activity in both muscles, whereas fewer than 100 bursts per day exceeded the 90% level; and (ii) the digastric muscle exhibited a significantly higher duty time than the masseter (respectively, 23% and 14% for activities exceeding the 2% level), which was mainly caused by the on average longer burst lengths at the lowest levels. The characterization of muscle activity in daily burst number and distribution of burst lengths exceeding various activity levels provides valuable information on motor control and enables further investigation of the adaptive capacity of muscles.     

Identification,distribution, and myosin subunit composition of type IIX fibers in mouse muscles

The purpose of the present investigation was to study the distribution and subunit composition of type IIX fibers in mouse muscles. The existence of a population of type IIX fibers in fast-twitch muscles of the mouse was shown by mean of immunohistochemistry and gel electrophoresis. In the hindlimb muscles, tibialis anterior (TA) and extensor digitorum longus (EDL), type IIX fibers account for approximately one third of the total fiber number, with the superficial portion of the TA (TAS) being composed exclusively of type IIB and IIX fibers. A similar proportion of IIX fibers was found in diaphragm (DIA) while in tongue muscles approximately 40% of the fibers were IIX. Single fiber gel electrophoresis revealed a significant number of fibers in TAS that contain both IIB and IIX myosin heavy chain (MyHC). This was confirmed with immunohistochemistry, which revealed the presence of fibers with various degrees of staining intensity. This suggests that there may exist a degree of plasticity which results in the conversion of IIX fibers to IIB fibers and vice versa. Analysis of myosin light chain (MyLC) composition of type IIX fibers revealed that the ratio of MyLC3f to MyLC1f was significantly lower than in type IIB fibers. © 1994 John Wiley & Sons, Inc.     

Inactivity-induced modulation of Hsp20 and Hsp25 content in rat hindlimb muscles

Denervation decreases small heat shock protein (HSP) content in the rat soleus muscle; however, it is unknown whether this change is due to inactivity or absence of a nerve-muscle connection. Spinal cord isolation (SI) is a model of inactivity with an intact neuromuscular connection. After 7 days of SI, Hsp20 and Hsp25 levels in the soleus, plantaris, and adductor longus muscles were lower than in control rats, whereas Hsp20 was unchanged and Hsp25 increased in the tibialis anterior. The results for the soleus indicate that these small HSPs respond to inactivity and that this response is not influenced by neural activity-independent factors. Furthermore, the data indicate that these HSPs are impacted to a greater degree in muscles that are predominantly slow or have an antigravity function than in flexor muscles. Understanding the regulation of these HSPs during chronic reductions in neuromuscular activity may have valuable applications for conditions such as spinal cord injury.     

骨骼肌肌球蛋白重链与不同类型训练的影响

背景：研究表明,快肌和慢肌的最大缩短速度存在差异, 这主要由于快慢肌所表达的MHC类型不同,引起肌球蛋白ATPase 活性差异的缘故。目的：介绍不同运动条件下骨骼肌纤维肌球蛋白重链组成变化的研究内容,理解运动训练与骨骼肌收缩性能的关系。方法：应用计算机检索PubMed与Medline springlink数据库1990-01/2009-10有关骨骼肌肌球蛋白重链的文章,检索词为“skeletal muscle”、“myosin heavy chain”、“training”,限定语言种类为English。同时计算机检索中国期刊全文数据库2000-01/2009-10期间的相关文章,检索词为“骨骼肌,肌球蛋白重链,训练”,限定文章语言种类为中文。纳入标准：不同运动形式对骨骼肌肌球蛋白重链的影响。排除标准：重复或类似的同一研究。结果与结论：肌球蛋白的形态学特征：快慢肌中含有不同类型肌球蛋白重链。运动对肌球蛋白重链的影响：耐力训练可引起肌球蛋白重链由快向慢转变,但受训练时间、强度以及年龄因素的影响;抗阻力量训练使得快型肌球蛋白重链升高,同时也受训练强度、时程的影响;减少活动大多会引起慢型肌球蛋白重链向快型肌球蛋白重链转化。抗阻力量训练可引起骨骼肌肥大表现为肌纤维肌球蛋白重链增多,以及肌纤维的转化表现为MHC-Ⅱx(以前称Ⅱb MHC)向MHC-Ⅱa转化,低氧训练可以引起慢型肌球蛋白重链向快型方向转化,减少活动方式多数会引起慢型肌球蛋白重链向快型肌球蛋白重链方向转化。     

Absence of developmental and unconventional myosin heavy chain in human suprahyoid muscles

Introduction: Contradictory reports of the myosin heavy chain (MHC) composition of adult human suprahyoid muscles leave unresolved the extent to which these muscles express developmental and unconventional MHC. Methods: By immunohistochemistry, separation sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE)‐Coomassie, separation SDS‐PAGE‐Western blot, and mRNA PCR, we tested for conventional MHCI, MHCIIA, MHCIIX, developmental MHC embryonic and MHC neonatal, and unconventional MHC alpha‐cardiac, MHC extraocular, and MHC slow tonic in adult human anterior digastric (AD), geniohyoid (GH), and mylohyoid (MH) muscles. Results: By separation SDS‐PAGE‐Coomassie and Western blot, only conventional MHC are present. By immunohistochemistry all muscle fibers are positive for MHCI, MHCIIA, or MHCIIX, and fewer than 4 fibers/mm² are positive for developmental or unconventional MHC. By PCR, mRNA of MHCI and MHCIIA dominate, with sporadically detectable MHC alpha‐cardiac and without detectable mRNA of other developmental and unconventional MHC. Conclusions: We conclude that human suprahyoid muscles AD, GH, and MH are composed almost exclusively of conventional MHC isoforms. Muscle Nerve 49:534–544, 2014     

Reduced jaw opening from paradoxical activity of mandibular elevator muscles treated with botulinum toxin

The aim of the study was the effect of injections with botulinum toxin A (BTX-A) on reduced jaw opening, caused by paradoxical, antagonistic activity of jaw elevator muscles after brain stem lesions. The study included a male (51 years) and a female (69 years) patient. Subjective assessment, clinical recordings, muscle blocks and electromyography (EMG) were used to diagnose paradoxical activity, and to plan, guide and evaluate the treatment. The paradoxical innervation pattern was unilateral in the male and bilateral in the female. The paradoxical activity during jaw opening amounted to 24-109% of the level during maximum biting, and bursts of paradoxical activity were also present during chewing. EMG-guided blocks and later BTX-A injections of the affected muscles increased the opening by 9-23 mm from pre-treatment values of 15-18 mm, and normalized chewing. The study proved BTX-A to be an effective treatment for reduced jaw opening caused by paradoxical activity. Treatment was optimized by EMG evaluation of the current activity of the jaw elevator muscles, permitting individual treatment plans with longer intervals between BTX-A injections and lower doses than with conventional treatment for oromandibular dystonia. Thus the treatment only had to be repeated one to two times per year to maintain acceptable jaw mobility.     

Influence of botulinum toxin on rabbit jaw muscle activity and anatomy

Introduction: Muscles can adapt their fiber properties to accommodate to new conditions. We investigated the extent to which a decrease in muscle activation can cause an adaptation of fiber properties in synergistic and antagonistic jaw muscles. Methods: Three months after the injection of botulinum toxin type A in one masseter (anterior or posterior) muscle changes in fiber type composition and fiber cross‐sectional areas in jaw muscles were studied at the microscopic level. Results: The injected masseter showed a steep increase in myosin type IIX fibers, whereas fast fibers decreased by about 50% in size. Depending on the injection site, both synergistic and antagonistic muscles showed a significant increase in the size of their fast IIA fibers, sometimes combined with an increased number of IIX fibers. Conclusion: Silencing the activity in the masseter not only causes changes in the fibers of the injected muscle but also leads to changes in other jaw muscles. Muscle Nerve, 2012     

Limited expression of slow tonic myosin heavy chain in human cranial muscles

Recent reports of slow tonic myosin heavy chain (MHCst) in human masticatory and laryngeal muscles suggest that MHCst may have a wider distribution in humans than previously thought. Because of the novelty of this finding, we sought to confirm the presence of MHCst in human masticatory and laryngeal muscles by reacting tissue from these muscles and controls from extraocular, intrafusal, cardiac, appendicular, and developmental muscle with antibodies (Abs) ALD-58 and S46, considered highly specific for MHCst. At Ab dilutions producing minimal reaction to muscle fibers positive for MHCI, only extraocular, intrafusal, and fetal tongue tissue reacted with Ab S46 had strong immunoreaction in an appreciable number of muscle fibers. In immunoblots, Ab S46, but not Ab ALD-58, labeled adult extraocular muscles; no other muscles were labeled with either Ab. We conclude that, in humans, Ab S46 has greater specificity for MHCst than does Ab ALD-58. We suggest that reports of MHCst in human masticatory and laryngeal muscles reflect false-positive identification of MHCst due to cross-reactivity of Ab ALD-58 with another MHC isoform.     

Alterations in contractile properties and expression of myofibrillar proteins in wobbler mouse muscles

The purpose of this study was to characterize the alterations in muscle contractile (tension-pCa relationship) and biochemical (myosin heavy and light chains, troponin C content) properties in a hereditary motoneuron disease. The study was performed on wobbler mouse mutants which presented a neuronal degeneration. The time course of the disease was followed at 5 and 7 weeks in sternocleidomastoid (SCM) and soleus muscles. The wobbler disease was found to induce a shift from fast to slow myosin heavy-chain isoform expression in SCM and soleus muscles. The analysis of the myosin light-chain (MLC) composition revealed, for the SCM muscles, the appearance of the slow isoforms at 5 weeks and an increase in the regulatory MLC2 content at 7 weeks. A significant increase in the slow troponin C isoform content was found in both types of wobbler muscles at 7 weeks. The wobbler soleus and SCM muscles presented an age- and fiber-type-related atrophy, characterized by a decline in absolute maximal tension and fiber diameter. A decrease in calcium sensitivity was observed at 7 weeks for the soleus fibers and at both 5 and 7 weeks for the SCM. The results indicated fast-to-slow changes in contractile and biochemical properties of the wobbler soleus and SCM muscles, which occurred during the motoneuron degeneration process previously described in the wobbler pathology.     

Phenotypic conversion of distinct muscle fiber populations to electrocytes in a weakly electric fish

In most groups of electric fish, the electric organ (EO) derives from striated muscle cells that suppress many muscle phenotypic properties. This phenotypic conversion is recapitulated during regeneration of the tail in the weakly electric fish Sternopygus macrurus. Mature electrocytes, the cells of the electric organ, are considerably larger than the muscle fibers from which they derive, and it is not known whether this is a result of muscle fiber hypertrophy and/or fiber fusion. In this study, electron micrographs revealed fusion of differentiated muscle fibers during the formation of electrocytes. There was no evidence of hypertrophy of muscle fibers during their phenotypic conversion. Furthermore, although fish possess distinct muscle phenotypes, the extent to which each fiber population contributes to the formation of the EO has not been determined. By using myosin ATPase histochemistry and anti-myosin heavy chain (MHC) monoclonal antibodies (mAbs), different fiber types were identified in fascicles of muscle in the adult tail. Mature electrocytes were not stained by the ATPase reaction, nor were they labeled by any of the anti-MHC mAbs. In contrast, mature muscle fibers exhibited four staining patterns. The four fiber types were spatially arranged in distinct compartments with little intermixing; peripherally were two populations of type I fibers with small cross-sectional areas, whereas more centrally were two populations of type II fibers with larger cross-sectional areas. In 2- and 3-week regenerating blastema, three fiber types were clearly discerned. Most (> 95%) early-forming electrocytes had an MHC phenotype similar to that of type II fibers. In contrast, fusion among type I fibers was rare. Together, ultrastructural and immunohistochemical analyses revealed that the fusion of muscle fibers gives rise to electrocytes and that this fusion occurs primarily among the population of type II fibers in regenerating blastema. J. Comp. Neurol. 399:20–34, 1998. © 1998 Wiley-Liss, Inc.     

Automated muscle fiber type population analysis with ImageJ of whole rat muscles using rapid myosin heavy chain immunohistochemistry

Introduction: Skeletal muscle consists of different fiber types which adapt to exercise, aging, disease, or trauma. Here we present a protocol for fast staining, automatic acquisition, and quantification of fiber populations with ImageJ. Methods: Biceps and lumbrical muscles were harvested from Sprague‐Dawley rats. Quadruple immunohistochemical staining was performed on single sections using antibodies against myosin heavy chains and secondary fluorescent antibodies. Slides were scanned automatically with a slide scanner. Manual and automatic analyses were performed and compared statistically. Results: The protocol provided rapid and reliable staining for automated image acquisition. Analyses between manual and automatic data indicated Pearson correlation coefficients for biceps of 0.645–0.841 and 0.564–0.673 for lumbrical muscles. Relative fiber populations were accurate to a degree of ± 4%. Conclusions: This protocol provides a reliable tool for quantification of muscle fiber populations. Using freely available software, it decreases the required time to analyze whole muscle sections. Muscle Nerve 54 : 292–299, 2016     

Myosin heavy chain isoform expression in human extraocular muscles: longitudinal variation and patterns of expression in global and orbital layers

Introduction: We investigated the distribution of myosin heavy chain (MyHC) isoforms along the length of the global and orbital layers of human extraocular muscles (EOMs). Methods: Whole muscle tissue extracts of human EOMs were cross‐sectioned consecutively and separated into orbital and global layers. The extracts from these layers were subjected to electrophoretic analysis, followed by quantification with scanning densitometry. Results: MyHC isoforms displayed different distributions along the lengths of EOMs. In the orbital and global layers of all EOMs except for the superior oblique muscle, MyHCeom was enriched in the central regions. MyHCIIa and MyHCI were most abundant in the proximal and distal ends. Conclusions: A variation in MyHC isoform expression was apparent along the lengths of human EOMs. These results provide a basis for understanding the molecular mechanisms underlying the functional diversity of EOMs. Muscle Nerve, 2012     

Effects of exercise and creatine on myosin heavy chain isoform composition in patients with Charcot-Marie-Tooth disease

It is not known whether myosin heavy chain (MHC) content changes in response to exercise training or creatine supplementation in subjects with Charcot-Marie-Tooth disease (CMT). Based on previous data, we hypothesized that resistance exercise and creatine would increase the percentage of type I MHC composition in the vastus lateralis muscle and that myosin isoform changes would correlate with improved chair rise-time in CMT subjects. To test this hypothesis, 18 CMT subjects were randomly assigned to either a placebo or creatine group. All subjects performed a 12-week, home-based, moderate-intensity resistance training program. Chair rise-time was measured before and after the training program. Muscle biopsies were obtained from the vastus lateralis before and after the 12-week program. Gel electrophoresis showed a significant decrease (approximately 30%) in MHC type I in CMT subjects given creatine supplementation when compared with placebo. There was a nonsignificant increase in both MHC type IIa (approximately 23%) and MHC type IIx (approximately 7%) in CMT subjects given creatine. Reduced MHC type I content and increased MHC type IIa content correlated with faster chair rise-times (i.e., improved muscle performance). The training-induced change in MHC IIa content was inversely correlated with chair rise-time in CMT subjects given creatine. When the two subject groups were combined, there was a linear, negative relationship between the change in MHC type IIa content and chair rise-time after training and a positive relationship between the training-induced change in MHC type I content and chair rise-time. These data suggest that improved function (chair rise-time) was associated with a lower level of MHC type I and increased MHC type IIa composition. Furthermore, the data are consistent with the hypothesis that creatine supplementation alters MHC composition in CMT patients undergoing resistance training and that MHC changes associated with creatine supplementation can improve muscle function.     

Level of independence of motor unit properties from neuromuscular activity

Neuromuscular activity was eliminated in the tibialis anterior muscle of adult cats for 6 months by spinal isolation (Sl), i.e., complete spinal cord transections at T-12–13 and at L-7–S-1, plus bilateral dorsal rhizotomy between the two transection sites. One motor unit from each muscle was isolated using ventral root teasing procedures and physiologically tested. The fibers belonging to each motor unit were visualized in PAS-staired sections by the loss of glycogen following prolonged repetitive stimulation. Qualitatively, the normal enzymatic interrelationships among fibers identified by myosin heavy chain composition were unchanged by SI. Generally, each motor unit from SI cats were of a single myosin immunohistochemical type. The same physiological motor unit types that typify control muscles were found in SI cats. In Sl compared to control cats, there was approximately a 10% increase in the number of muscle fibers expressing fast myosin. Mean fiber activity levels of ATPase and SDH for a given fiber type (based on MHC antibody reactions) decreased by approximately 10% and 25%, whereas GPD activity increased approximately 35%. It is concluded that differential levels or patterns of activity are not essential to maintain the range of histochemical and physiological motor unit types found in the tibialis anterior of normal adult cats. © 1994 John Wiley & Sons, Inc.     

Quality of care in psychiatry is related to research activity

BackgroundThe top biomedical research institutions have traditionally been assumed to provide better medical treatment for their patients. However, this may not necessarily be the case. Low-to-moderate negative associations between research activity and the quality-of-care provided by clinical departments have been described. We aimed to examine this relationship in the psychiatric units of the largest hospitals in Spain.MethodsScientific publications for 50 hospitals were retrieved from the Web of Science (2006–2015), and quality of mental healthcare data were gathered from Spanish National Health System records (2008–2014). Spearman-rank correlation analyses (adjusting for number of beds and population) were used to examine the associations between research data and quality-of-care outcomes in psychiatry. Stepwise regression models were built in order to determine the predictive value of research productivity for healthcare outcomes.ResultsWe found a positive association between research activity indicators (i.e., number of publications, number of citations, cumulative impact factor, and institutional H-index) and better quality-of-care outcomes in psychiatry (i.e., number of readmissions, transfers, and discharges from hospital). In particular, a higher research activity predicted a lower level of readmissions for individuals with psychoses (p = 0.025; R = 0.317), explaining 8.2% of the variance when other factors were accounted for.ConclusionsHigher research activity is associated with better quality of mental healthcare in psychiatry. Our results can inform decision-making in clinical and research management settings in order to determine the most appropriate quality measures of the impact of research on the prognosis of individuals with psychiatric conditions.     

Cortical cholinergic activity is related to the novelty of the stimulus

A number of studies have related cholinergic activity to the mediation of learning and memory. However, the acetylcholine (ACh) participation has been recently implicated in the early stages of memory formation but not during retrieval. The aim of the present study is to evaluate ACh release in the insular cortex (IC) during presentation of different taste stimuli and during their re-exposition by means of the free-moving microdialysis technique. We evaluated the changes in ACh release when a novel taste, saccharin or quinine was presented to the rat and after several presentations of saccharin. Unilateral microdialysis was performed in the IC 1 h before and 1 h after the presentation of: (1) a familiar stimulus (water), (2) a novel taste (quinine), (3) another novel taste (saccharin), (4) a second presentation, (5) a third presentation, and (6) a fourth presentation of saccharin. The volume consumed by the animals was registered as a behavioral parameter. The ACh levels from the microdialysis fractions were analyzed by an HPLC-ED system. Biochemical results showed a significant increment in the cortical ACh release induced by a novel stimulus compared with the release observed during the presentation of a familiar stimulus. The ACh release observed after several presentations of the stimuli decreased to the same levels as those produced by the familiar taste, indicating an inverse relationship between familiarity and cortical ACh release. These results suggest that the cholinergic system plays an important role in the identification and characterization of different kinds of stimuli.     

Time course of inflammatory cytokines in acute ischemic stroke patients and their relation to inter-alfa trypsin inhibitor heavy chain 4 and outcome

Background:

Biomarker for prognosis of stroke is urgently needed for the management of acute ischemic stroke (AIS) patients.

Objective:

To evaluate the course of inflammatory cytokines in AIS patients and its comparison with inter-alfa trypsin inhibitor heavy chain 4 (ITIH4) and outcome after AIS.

Materials and Methods:

A panel of 12 inflammatory cytokines and ITIH4 were estimated in serial blood samples collected at admission, 24 h, 48 h, 72 h, 144 h and at discharge of AIS patients (n = 5).

Results:

Out of the 12 cytokines, only interleukin (IL)-2, tumor necrosis factor-alfa (TNF-α), IL-10, IL-6, IL-1B and IL-8 were in the measurable range of the kit (10 pg/mL). We found high IL-2 at admission, which decreased (P < 0.05) in the follow-up samples. TNF-α initially increases (P < 0.05) at 24 h followed by gradual decrease (P < 0.05) after 72 h. IL-10 decreases initially (P < 0.05) till 72 h as compared with its level at admission and then increases (P < 0.05) after 144 h. Similarly, ITIH4 was down-regulated in the early 72 h followed by further increase with improvement of the patient. ITIH4 correlates with IL-10 and computed tomography scan infarct volume. Serum IL-6, IL-1B and IL-8 increased in the AIS patients, but did not show any pattern.

Conclusions:

Serial measurement of IL-10, IL-2 and TNF-α and ITIH4 may be useful for the follow-up of clinical outcome after AIS.     

Innervation is required to stabilize and amplify creatine kinase activity in regenerated extensor digitorum longus muscles of rats

Neural control of creatine kinase (CK, adenosine 5′-triphosphate creatine phosphotransferase: EC 2.7.3.2) was investigated by measuring enzymatic activity and isoenzymatic representation of CK in extensor digitorum longus (EDL) muscles of adult rats during and after regeneration. Experimental models were ischemized EDLs, reversibly or permanently denervated. Results showed that, during regeneration, CK in muscle fibers was likewise modified in both reversibly and permanently denervated EDLs. After regeneration a clear dichotomy was observed between the regenerated EDLs which were innervated and recovering CK activity, and those in which innervation was prevented and were rapidly losing activity. Further to investigate the neural influence on CK turnover, merely denervated agematched EDLs were analysed and found to lose CK activity rapidly. The major conclusions are that during regeneration muscle CK is autonomously expressed, but following regeneration neural influence becomes an absolute requirement for stabilization and amplification of CK.     

Long-latency reflexes in contracted hand and foot muscles and their relations to somatosensory evoked potentials and transcranial magnetic stimulation of the motor cortex.

OBJECTIVE: The cortical relay time (CRT) for V2 of long-latency reflexes (LLRs) in the contracted thenar and short toe flexor muscles was studied. METHODS: LLRs and somatosensory evoked potentials (SEPs) were studied by electrical stimulation of the median or posterior tibial nerve. The CRT for V2 was calculated by subtracting the onset latency of cortical potentials in SEPs and that of motor evoked potentials (MEPs) by transcranial magnetic stimulation (TMS) from the onset latency of V2 in eight healthy subjects. RESULTS: The CRT for the thenar muscles was 11.4+/-0.9 ms (mean +/- SD), as the onset latency was 48.8+/-1.4 ms for V2, 16.0+/-1.2 ms for N20 and 21.3+/-1.1 ms for MEP, respectively. The CRT for the short toe flexor muscles was 3.0+/-1.3 ms, as the onset latency was 80.5+/-4.5 ms for V2, 35.3+/-1.8 ms for P38 and 42.2+/-2.0 ms for MEP, respectively. CONCLUSION: Significantly longer CRT for V2 for the thenar muscles (P<0.001, paired Student's t test) may indicate more synaptic relays as compared to that for the short toe flexor muscles.