Involvement of NF-κB and the CX3CR1 Signaling Network in Mechanical Allodynia Induced by Tetanic Sciatic Stimulation / 神经科学通报·英文版

Tetanic stimulation of the sciatic nerve (TSS) triggers long-term potentiation in the dorsal horn of the spinal cord and long-lasting pain hypersensitivity. CX3CL1-CX3CR1 signaling is an important pathway in neuronal-microglial activation. Nuclear factor κB (NF-κB) is a key signal transduction molecule that regulates neuroinflammation and neuropathic pain. Here, we set out to determine whether and how NF-κB and CX3CR1 are involved in the mechanism underlying the pathological changes induced by TSS. After unilateral TSS, significant bilateral mechanical allodynia was induced, as assessed by the von Frey test. The expression of phosphorylated NF-κB (pNF-κB) and CX3CR1 was significantly up-regulated in the bilateral dorsal horn. Immunofluorescence staining demonstrated that pNF-κB and NeuN co-existed, implying that the NF-κB pathway is predominantly activated in neurons following TSS. Administration of either the NF-κB inhibitor ammonium pyrrolidine dithiocarbamate or a CX3CR1-neutralizing antibody blocked the development and maintenance of neuropathic pain. In addition, blockade of NF-κB down-regulated the expression of CX3CL1-CX3CR1 signaling, and conversely the CX3CR1-neutralizing antibody also down-regulated pNF-κB. These findings suggest an involvement of NF-κB and the CX3CR1 signaling network in the development and maintenance of TSS-induced mechanical allodynia. Our work suggests the potential clinical application of NF-κB inhibitors or CX3CR1-neutralizing antibodies in treating pathological pain.

The effects of different doses of oral creatine supplementation on tibial muscle resistence and fatigue in wistar rats / Efeito de diferentes doses de suplementação de creatina na resistência muscular e fadiga em ratos wistar

The aim of the present study was to investigate the effects of different doses of oral creatine supplementation on tibial muscle resistance and fatigue in Wistar rats. The treatment protocols included swimming exercises, supplementation alone (different doses), and supplementation (different doses) + swimming exercises. Analysis of the effect of creatine supplementation on skeletal muscle fatigue was performed using the intensity of muscle contraction to electrical stimulation to evaluate the intensity of muscle contraction, decay time of muscle tetanic contraction to 50% of maximum tension (fatigue), and the area under the curve for the intensity x time ratio, besides AST, LDH, and urea plasmatic analysis. Our results suggest that creatine supplementation seems to be able to produce ergogenic effects on contractile metabolism in the group treated with the dose of 280 mg/kg + swim exercise. This creatine dose presented a statistically significant increase in decay time of muscle tetanic contraction (C280+swim (119±13.1), C500+swim (110±23.6) and C1000+swim (87±15.1)), area under the curve between tetanic contractions, and plasma LDH decrease, when compared to the other doses. These data clearly demonstrate that high doses do not lead to any additional ergogenic effects. We conclude that the dose of 280 mg/kg+swim exercise obtained the best ergogenic effects on tibial muscle resistance and fatigue in Wistar rats.

O objetivo do presente estudo foi investigar os efeitos de diferentes doses de suplementação oral de creatina sobre a resistência e fadiga do músculo tibial em ratos wistar. Os protocolos de tratamento incluíram exercícios de natação, suplementação isolada (doses diferentes) e suplementação (doses diferentes) + exercícios de natação. A análise do efeito da suplementação de creatina na fadiga do músculo esquelético foi realizada utilizando-se a intensidade da contração muscular à uma estimulação elétrica, aferindo a intensidade da contração muscular, tempo de decaimento da contração tetânica do músculo a 50% da tensão máxima (fadiga) e a área sob a curva para a razão de intensidade x tempo, além de análises plasmática de AST, LDH e ureia. Nossos resultados sugerem que a suplementação de creatina parece ser capaz de produzir efeitos ergogênicos no metabolismo contrátil no grupo tratado, com a dose de 280 mg/kg+natação. Esta dose de creatina teve um aumento estatisticamente significativo no tempo de decaimento da contracção tetânica muscular (C280+natação (119±13.1), C500+natação (110±23.6) e C1000+natação (87±15.1)), área sob a curva entre as contrações tetânicas e também diminuição da LDH plasmática quando comparada com as outras doses. Estes dados demonstraram claramente que doses elevadas não conduzem a qualquer aumento adicional de efeitos ergogênicos. Concluimos que a dose de 280 mg / kg + exercício de natação obteve os melhores efeitos ergogênicos sobre a resistência e fadiga do músculo tibial em ratos wistar.

Atropine is more efficient than ZM241385 to reduce a drastic level of fade caused by cisatracurium at 50 Hz / Atropina é mais eficiente que ZM241385 para reduzir o intenso nível de fadiga causada por cisatracurium a 50 Hz

The effects of atropine (non selective muscarinic antagonist) and ZM241385 (A2A receptors antagonist) in the cisatracurium-induced drastic (100%) level of fade at 50 Hz (10 s) (100% Fade) were compared in the phrenic nerve-diaphragm muscle preparations of rats indirectly stimulated at a physiological tetanic frequency (50 Hz). The lowest dose and the instant cisatracurium caused 100% Fade were investigated. Cisatracurium induced 100% Fade 15 min after being administered. Atropine reduced the cisatracurium-induced 100% Fade, but the administration of ZM241385 separately, or combined with atropine, did not cause any effect in the cisatracurium-induced 100% Fade. Data indicate that the simultaneous blockage of M1 and M2 muscarinic receptors on motor nerve terminal by atropine is more efficient than the blockage of presynaptic A2A receptors for a safer recovery of patients from neuromuscular blockade caused by cisatracurium.

Os efeitos de atropina e ZM241385 (antagonistas de receptores A2A) no drástico (100%) nível de fadiga (100% Fadiga) produzido pelo cisatracúrio a 50 Hz (10 s) foram comparativamente investigados em preparações nervo frênico músculo diafragma isolado de ratos indiretamente estimuladas com a frequência fisiológica tetanizante de 50 Hz. A menor dose e o instante no qual cisatracúrio causou 100% Fadiga foram pesquisados. O cisatracúrio induziu 100% Fadiga 15 min depois de ser administrado. A atropina reduziu a fadiga de 100% causada pelo cisatracúrio, mas ZM241385, ou a administração combinada de atropina com ZM241385, não causou qualquer efeito na 100% Fadiga produzida pelo cisatracúrio. Os dados indicam que o bloqueio simultâneo dos receptores muscarínicos M1 e M2 no terminal nervoso motor pela atropina é mais eficiente do que o bloqueio dos receptores pré-sinápticos A2A no auxilio da recuperação mais segura do bloqueio da transmissão neuromuscular causada por cisatracúrio.

Comparison of recovery times from deep neuromuscular blockade between single bolus and continuous infusion of rocuronium

BACKGROUND: To prevent sudden unexpected movement of patients during surgery, muscle relaxants are used to maintain intense neuromuscular blockade.They are administered by intermittent bolus or continuous infusion.Rocuronium is often used for continuous infusion because it is known to lack cumulative effects. The purpose of this study was to compare recovery times from intense neuromuscular block to reappearance of muscle twitches after 0.1 Hz single twitch stimulation. MATERIALS AND METHODS: Seventy five patients were randomized to one of 3 groups.Patients in group 1 were administered a single bolus of rocuronium; groups 2 and 3 were given continuous infusion of rocuronium for 1 and 2 h, respectively.During anesthesia, neuromuscular blockade was monitored by TOF-watch(R) and regulated so as not to exceed more than 5 (PTC) during the infusion. After infusion, PTC was counted every 5 min until single twitch heights had reappeared and the time till the twitch reappeared was calculated. RESULTS: There was a good correlation between the time it took to observe a PTC and the first response of TOF time in each group.In a parallelism test, there were no significant differences. There were also no significant differences in recovery times from PTC to the reappearance of a single twitch between groups. CONCLUSIONS: There are no significant differences in recovery times-from deep neuromuscular blockade to reappearance of single twitch-regardless of the infusion time.When a PTC occurs during deep neuromuscular blockade, it may predict the remaining time of reappearance of a single twitch response.

Succinylcholine-induced phase II block and pharmacodynamics in rat diaphragm

BACKGROUND: Succinylcholine causes phase II block by a large dose or a prolonged exposure. There are rare data in a pharmacodynamics of phase II block. The purpose of this study was to investigate a concentration-response relationship, the occurrence and recovery of phase II block, and to clarify whether pretreatment of succinylcholine potentiates muscle relaxation caused by rocuronium. METHODS: Hemidiaphragm-phrenic nerve preparations were dissected from male Sprague-Dawley rats (150-250 g). Preparations were bathed in Krebs' solution, then maintained at 32oC, and saturated with a mixture of 95% O2 and 5% CO2. Isometric forces made with supramaximal stimulations (0.1 Hz, and 50 Hz for 1.9 s) to the phrenic nerve, were measured with a force transducer, before and after each treatment. Succinylcholine, 10, 20, 40, 60 and 80microM were cumulatively added to the bath. Succinylcholine 80microM (for 100 min) or succinylcholine 300microM (for 20 min) was washed out. After succinylcholine 300microM (for 20 min), or 0microM as pretreatment was washed out, rocuronium, 2, 4, 8, 12, 16, 20microM were cumulatively added to the bath. RESULTS: The potencies of single twitch, peak tetanic tension and tetanic fade for succinylcholine were 36.1, 26.0, 20.7microM. Irrespective of dose or exposure duration, the recovery of muscle relaxation caused by succinylcholine was almost complete around 20 min after succinylcholine was washed out. CONCLUSIONS: Tetanic fade occurred at a lower concentration of succinylcholine than single twitch. The recovery from phase II block was relatively rapid if the concentration of succinylcholine is sufficiently low.

Registro de imunização antitetânica em documentos de mães de uma comunidade carente do Município de São Paulo / Records of anti-tetanic immunization in documents of mothers: a descriptive study

Before the confirmation that, there is as much lack of knowledge among women about the importance of anti-tetanic vaccination during the gestation period, as deficiency in data about this immunization, it was decided to elaborate a research in order to verify and analyze the records of anti-tetanic immunization in documents of groups of 50 Mothers in a poor community of the City of Sao Paulo. This study, descriptive and quantitative, was made in the period from April 2005 to April 2006. There were collected data in records of vaccination and prenatal periods, and also other kinds of records such as social, demographic and obstetric distinctions. The results showed that in 24% of the cases there were flaws in the vaccination scheme. The conclusion is that improving the quality of the records is a must, besides orientating women about the importance of vaccination, what involves the necessity of a closer follow up and assistance during the prenatal period.

Diante da constatação de que existe tanto desconhecimento das mulheres quanto à importância da vacinação antitetânica na gestação quanto deficiência nas anotações dessa imunização, decidiu-se elaborar pesquisa com o objetivo de verificar e analisar o registro da imunização antitetânica nos documentos de um grupo de 50 mães de uma comunidade carente de São Paulo/SP. O estudo, descritivo e quantitativo, foi realizado no período de abril de 2005 a abril de 2006. Foram coletados dados dos registros de vacinação nos documentos de pré-natal e vacinação, além de outros referentes à caracterização sócio-demográfica e obstétrica. Os resultados mostraram que em 24% dos casos ocorreram falhas no esquema vacinal. Conclui-se que é essencial melhorar a qualidade dos registros da assistência pré-natal, além de investir na orientação das mulheres sobre a importância da vacinação, o que implica na necessidade de um seguimento mais próximo, com supervisão e reforço, fundamentais na assistência pré e pós-natal.

Prejunctional Phenomenon during Succinylcholine Onset in Cats / 대한마취과학회지

BACKGROUND: Succinylcholine (Sch) has been generally reported not to produce tetanic stimulation fade on train of four in phase I block, except phase II block. But, the prejunctional phenomenon of Sch during onset is rarely reported these days, and so we investigated whether the prejunctional phenomenon of Sch during onset exists in cats. METHODS: We checked train of four ratios (TOF-R) and tetanic fade ratios (TF-R) by using a nerve stimulator before and after 50microgram/kg of Sch less than ED95 was administered, and during recovery in anesthetized cats. We analyzed TOF-R and TF-R before drug administration as a control and during onset and recovery time in order to estimate the statistic significance of fade. RESULTS: TOF fade and tetanic stimulation during the onset of Sch appeared like those in the partial block of nondepolarizing neuromuscular blockades TOF-R and TF-R during Sch onset compared with those in control and recovery time of Sch had statistical significance (P <0.05). CONCLUSIONS: The prejunctional phenomenon appeared only during Sch onset in cats and then disappeared during recovery to the control level.

The effect of the exhaustive enduring exercise training on the amount of the skeletal muscle protein and isometric tetanic force of rats / 体力科学

A study was conducted to examine the effects of exhaustive enduring exercise training on the skeletal muscle of rats. Twenty-six male Wistar rats were divided into 3 groups : an exhaustive training group (EE), a free-eating control group (Co), and a pair weight group in which body weight was matched to EE (PW) . The rats in EE were forced to run on a treadmill with an inclination of 0-3°, 6 days/week for 4 weeks. At first the rats ran at a constant speed for 60 min. Then we gradually added 2 m/min to the basic speed every minute until they were exhausted. The treadmill speed was 20 m/min during the first, 30 m/min during the second, 35 m/min during the third, and 40 m/min during the final week. The muscle wet weight, the quantity of the muscle protein and the isometric tetanic force were measured with the soleus and extensor digitorum longus (EDL) . Food restriction induced significant decreases in EDL weight. Exhaustive enduring exercise training induced noteworthy decreases in soleus weight, but remarkable gains in EDL weight. It also induced significant changes of the quantity of the muscle protein in the two muscles, which corresponded to the changes in muscle weight. The isometric tetanic force of both muscles was not affected by food restriction. The isometric tetanic force showed a significant decreases in EDL in EE comparison Co. The isometric tetanic force of the soleus did not show a significant decreases. However, its degree of decrease corresponded to that of the muscle protein. These findings illustrate that exhaustive endurance exercise training induces degradation of the soleus and hypertrophy of the EDL. However, it also decrease the muscle force which generats the capacity of the two muscles. We think that this phenomenon depends on the skeletal muscle characteristics, such as fiber type, and eccentric or concentric contraction.

Changes of Length and Active Force of the Soleus Muscle According to the Position of Ankle Joint in Rabbit / 대한정형외과연구학회지

The dynamic performance of a skeletal muscle depends on the length-force and force-velocity relationships. The length-force relationship of muscle was described by Blix for the first time. The contractile elements of muscles produce the active length-force curve. The objective of this study is to determine the length-force relationship of the rabbit's soleus muscle and changes of tetanic force according to the position of ankle joint. The amount of excursion of the soleus muscle for full range of motion of the ankle joint was 25 mm. The ratio of excursion compared to the length of neutral position was 24%. That means that the soleus muscle has large amount of excursion that is responsible for producing active force throughout the whole range of ankle motion. The length at which active force of the muscle is maximal is called optimum length(Lo). The ratio of the optimum length compared to the length of neutral position was 98%. This means that the active force of the soleus muscle was maximal at the position of slight plantarflexion(about 2 degrees of plantarflexion). The value of the tetanic force was 3.1kg/cm2 in average, and the active length-force curve showed asymmetrical shape. The effective range is a length change from minimal point of zero active force to maximal point of zero active force. In this study, the minimal point of zero active force was 11mm shorter and maximal point of zero active force was 13mm longer than optimum length. Therefore, the effective range was 24mm. Active force increased abruptly at which muscle length was 90% of neutral length. At that point, active force was less than 20% of maximal tetanic force.

Time course of twitch potentiation after tetanic nerve and direct stimulations in the thumb adduction in man / 体力科学

Effects of various tetanic stimulation frequencies (50 Hz, 100 Hz and 200 Hz) on the time course of twitch potentiation were examined in the adduction of human pollicis. Isometric twitch tension curve and surface electromyogram were recorded immediately after (1 sec) the 10 sec-tetanus and at intervals of lOsec (up to 300sec) . The stimulating methods were by nerve and direct stimulations in order to examine the role of nerve on the post-tetanic potentiation. The results were summarized as follows :<BR>1) The greatest potentiation was observed immediately after the tetanus. The potentiation decreased rapidly in the period of 60 sec after the tetanus. Then, the potentiation continued to decrease at the low frequency (50 Hz) ; however, it tended to level off at the high frequencies (100 Hz and 200 Hz) .<BR>2) The time course of twitch potentiation by the nerve stimulation was larger than that by the direct stimulation. This result suggests that nerve has a factor which enhances potentiation. The duration of the potentiation varied according to the stimulation frequencies by the nerve stimulation. It seems that this phenomenon was strongly influenced by the nerve.<BR>3) The degree of increase in twitch tension tended to depend greatly on the peak rate of force development. This result suggests that the increase in twitch tension was closely related to the intensity of the active state.<BR>4) Time course of time to peak tension relatively corresponded to the half relaxation time. It seems possible for the duration of the active state to be related to calcium uptake at the sarcoplasmic reticulum.<BR>5) The coupling efficiency by the direct stimulation tended to be smaller than that by the nerve stimulation after 10 sec. This result suggests that the stimulating nerve possesses a factor which prolongs the period of potentiation.

Assessment of the Optimal Interval of Tetanic Stimulation for Post-Tetanic Count / 대한마취과학회지

Post-tetanic count(PTC) was a known monitoring method to evaluate intense neuromuscular blockade of peripheral muscles. It has been reported that intermittent tetanic stimulation(50 Hz for 5 sec.) every 6 to 10 min. during intense nondepolarizing neuromuscular blockade did not influence the recovery of neuromuscular transmission. However, the relatively frequent use of tetanic stimulation might be possible to influence the recovery of neuromuscular blockade and the repeated stimuli might result in a false recovery state. The purpose of this study was to determine the best interval time of tetanic stimulation for evaluation of the correct PTC. Sixty adult patients undergoing stomach operations were randomly allocated to three groups according to the interval of tetanic stimulation ; group 1 (6 min. n=20), group 2 (8 min. n=20) and group 3 (10 min. n=20). In all cases, Anesthesia was maintained with 50% nitrous oxide, 50% oxygen and 1-2% enflurane following induction of anesthesia with thiopental sodium 3-5 mg/kg. Neuromuscular block was achieved by intravenous pancuronium bromide 0.13 mg/kg before application of ulnar nerve stimuli using Myotest MKII. The adduction force of the resultant thumb twitch was measured by the acceleration of a small piezo-electric ceramic wafer with electrodes of Mini-accelograph and recorded by Datascope 2200 I After 1 Hz single twitch stimulation, a tetanic stimulus(50 Hz) was applied for 5 sec. Three seconds later, the single twitch stimulation was again applied for 1 min. followed by 1 min. of TOF stimulation. This pattem of tetanic stimulation was continued by the interval of 6, 8 and 10 min. The results were as follows: 1. The continuance (which was the percentage when PTC was continuously increased, not intermittently reduced) was 73.7% in group 1 and 2, but 100% in group 3 and there were statistically significance. 2. In the regression analysis between FI'C and time from PTC1, we yielded the following equations ; Y=10+3.5X (r(2)=0.71) for group 1, Y=8.6+4.1X (r(2)=0.78) for group 2 and Y=9.8+5.7X (r(2)=0.69) for group 3. The slope and intercept of the line of group 3 showed significantly different to that of group 1 and 2 (p<0.001). The more frequent tetanic stimulation reduced the time to arrive the same PTC. 3. The time from PTCl to TOFl was 51.6+/-3.9 min. in group 1, 65+/-5 min. in group 2 and 69+/-4.3 min. in group 3. There were no statistically significance, but they had trend to reduce by more frequent tetanic stimulation. 4. PTC was 12.9+/-0.9 in group 1, 14.9+/-1.5 in group 2 and 13.2+/-0.8 in group 3 when TOF1 was appeared, and 38.3+/-2.3 in group 1, 33.3+/-2.3 in group 2 and 32.4+/-2.6 in group 3 when the second response to TOF stimulation(TOF2) was recorded(meanSEM). There were no statistically significance. With the above results the authors concluded that 10 min. will be the optimal interval of the tetanic stimulation for the correct PTC, and recognized that the interval of tetanic stimulation was not related to the time from PTC1 or PTC at TOF twitches.

The Method of Recording on the Response Using the Simple Tactile Neuromuscular Monitor / 대한마취과학회지

Recently, since muscle relxants has been used routinely, it is very important to understand the state of muscle relaxation during and after anethesia for safe anesthesia. But it is difficult that all patients have the opportunity to be helped by the auto-recording neuromuscular monitor, because of high in price. Therefore, many anesthesiologists have been using the simple tactile neuromuscular monitor for the evaluation of muscle relaxation, but there are many difference to evaluate for the reponse of muscle contraction by tactile or visual sensation. This study was designed to investigate the method of recording on the response of nerve stimulation from simple tactile neuromuscular monitor. The pressure generated from moving of thumb connected with finger ring lock syringe by ulnar nerve stimulation was transmitted to the invasive blood pressure monitor through the arterial pressure transducer. As a result, this method could record the response of single twitch stimulation, train-of-four stimulation, tetanic stimulation, post-tetanic count and double-burst stimulation displaying in the invasive blood pressure monitor, and was exellent in recording compared with auto-record- ing neuromuscular monitor.

Relationship between the Change of PTC and the Response of Endotracheal Intubation after Vecuronium Induction / 대한마취과학회지

The relationship between the post-tetanic count(PTC) and the response of tracheal intubation after vecuronium-induced neuromuscular blockade was studied in 99 cases who were ASA 1 or 2 adult patients. All patients were premedicated with glycopyrrolate 0.2mg and hydroxizine 1 mg/kg IM 1 hour before induetion, and were inducted with pentothal sodium Smg/kg and O2- N2O(50%) enflurane(2%). The patients were randomly divided to two groups according to dose of vecuronium applied after inducion ; 0.08 mg/kg(n=54) group and 0.12 mg/kg(n=45) group. Neuromuscular blockade was monitored by stimulation of the ulnar nerve at the wrist with single twitch using INNERVATOR(Fisher and Paykel Co.). Post tetanic count(PTC) was counted at different times, i.e., 0, 10, 20, 25, 30 and 35 seconds, 9 persons respectively at each time, after disappearance of single twitch. Tracheal intubation was performed immediately after counting of PTC. The response of tracheal intubation was appreciated based on vocal cord reflex, coughing or barking and patient movement. The time from administration of vecuronium to disappearance of single twitch was 167.8+/-23.4 seconds in 0.08mg/kg group and 163.7+/-51.1 seconds in 0.12mg/kg group and there was no statistical difference. After complete disappearance of single twitch, the PTC was zero at 35 seconds in 0.08 mg/kg group and at 25 seconds in 0. 12 mg/kg group. While the PTC was lowering, the lower intubation condition score should be expected, but the 0 of PTC did not coin-cided with the 0 of intubation condition score. However, the 0 of PTC did not always indicated that response to tracheal intubation could be disappear completely. Profound neuromuscular blockade did not reduce the hemodynamic responses to tracheal intubation.

Clinical Study of Post - tetanic Count ( PTC ) during Vecuronium - induced Intense Neuromuscular Blockade / 대한마취과학회지

Vecuronium induced intense neuromuscular blockade was evaluated in 40 USA class l, ll adult patients using the post tetanic count (PTC) and train-of-four(TOF) methods. All patients were anesthetized with thiopental sodium, nitrous oxide(50%), and enflurane(1~2%). Neuromuscular monitoring commended immediately after administration of thiopental sodium. The ulnar nerve was stimulated using surface electrodes and the mechanical response of the adductor policis muscle recorded using the Acclograph, neuromuscular transmission monitor. TOF nerve stimulation was used every 15s. After supramaximal stimulation was achieved a bolus of vecuronium 0.1mg/kg was injected intravenously. The traches was intubated when TOF response was depressed to 95% or above to control twitch height and the lungs ventilated with a tidal volume of 10ml/kg and a rate of 14 b.p.m. The patients were allocated randomly to two groups of 20 patients each. Patients in control group were allowed to recover TOF response spontaneously, and in PTC group were applied tetanic stimulation(50Hz for 5s) at 7 minutes intervals during no TOF response. In PTC group, the tetanic stimulation was preceded by a 30s period of 1Hz stimulation on each occasion, which was continued after the 3s pause. Duration of no TOF response in each group, and relationship between first post tetanic twitch height of PTC and time to first reaction to TOF nerve stimulation in PTC group were measured. In the results, duration of no TOF response was shortened by tetanic stimulation(p<0.01). There was a close inverse correlation between first post tetanic twitch height or PTC and time to first reaction to TOF nerve stimulation (p<0.01). It was concluded that PTC method appeared to be a valuable supplement to TOF nerve stimulation in assessment and trend for vecuronium induced intense neuromusclular blockade.

Variation of sarcomere length, sarcomere number and tetanic tension of skeletal muscle during postnatal growth in mice / 体力科学

The purpose of present study was to investigate the relationship between the increase of sarcomere length, sarcomere number and tetanic tension of the extensor digitorum longus muscles during postnatal growth in mice. The following results were obtained ; 1) The cross-sectional area, length of muscle and fiber length increased rapidly up to 7th week. 2) The sarcomere number increased up to 9 th week, 3) The tetanic tension per cross-sectional area decreased significantly in 7 th week, 4) The maximum value of sarcomere length which was obtained at middle region of the fiber correlated significantly with the tetanic tension per cross-sectional area (the correlation coefficient : r=-0.675) . These observations suggest that the local expansion of sarcomere length during postnatal growth affects the tension development.

Contractile properties of skeletal muscle during postnatal growth in mice: Related to morphological changes / 体力科学

The variation of lengths, cross-sectional areas, weights, tetanic tensions, and passive tensions in extensor digitorum longus muscles in mice were investigated during postnatal growth. The increase of tetanic tension was discussed in relation to morphological changes of muscle. The muscle lengths were measured at right angle of articulatio genus and talocruralis (L<SUB>0</SUB>) . Following results were obtained: 1) The length, cross-sectional area and weight of muscle increased rapidly up to 7 th weeks, and tetanic tension developed significantly in 2 nd to 5 th week. 2) The muscle length (ML), muscle cross-sectional area (MCA) and muscle weight (MW) correlated significantly with the measured tetanic tension (TT) at L<SUB>0</SUB> (the correlation coefficient r=0.852, 0.886 and 0.903 in ML, MCA and MW respectively) . 3) TT/MCA and TT/MW decreased in 7 th to 8 th week. 4) The passive tension at 130% L<SUB>0</SUB>per MCA showed maximum values in 8 th and 9 th weeks. 5) Relative muscle endurance were reduced in 2 nd to 4 th week and reached to steady level after 4 th week. These observations suggest that the functional development of muscle is late for morphological one and/or rapid morphological increment affects the contractile properties of muscle.