Halothane induces calcium release from human skinned masseter muscle fibers

BACKGROUND: An increase in masseter muscle tone in response to halothane or succinylcholine anesthesia (or both) can be observed in healthy persons. Thus the authors compared the fiber-type halothane and succinylcholine sensitivities in human masseter and vastus lateralis muscles. METHODS: Masseter and vastus lateralis muscle segments were obtained from 13 and 9 healthy persons, respectively. After chemical skinning of a single fiber and loading the sarcoplasmic reticulum with Ca++ 0.16 microM solution, halothane (0.5-4 vol% bubbled in the incubating solution), succinylcholine (0.1 microM to 10 mM), or both sensitivities were defined as the concentration inducing more than 10% of the maximum tension obtained by application of 16 microM Ca++ solution. The myofilament response to Ca++ was studied with and without halothane by observing the isometric tension of skinned masseter fibers challenged with increasing concentrations of Ca++. Muscle fiber type was determined by the difference in strontium-induced tension measurements. RESULTS: A significant difference in halothane sensitivity was found between type 1 masseter fibers (0.6+/-0.2 vol%; mean +/- SD) versus type 1 (2.7+/-0.6 vol%) and type 2 vastus lateralis muscle (2.5+/-0.4 vol%). Succinylcholine did not induce Ca++ release by the sarcoplasmic reticulum. In the masseter muscle, 0.75 vol% halothane decreased the maximal activated tension by 40% but did not change the Ca++ concentration that yields 50% of the maximal tension. CONCLUSIONS: The very low halothane threshold for Ca++ release from the masseter muscle usually could be counteracted by a direct negative inotropic effect on contractile proteins. However, halothane may increase the sensitivity of the sarcoplasmic reticulum Ca++ release to succinylcholine-induced depolarization, leading to an increase in masseter muscle tone.     

The incidence of masseter muscle rigidity after succinylcholine in infants and children

To determine whether the incidence of masseter muscle rigidity is affected by the anaesthetic induction sequence, we prospectively studied for ten months the anaesthetic course in 5,641 infants and children who received muscle relaxation to facilitate tracheal intubation. The anaesthetic induction sequence consisted of intravenous sodium thiopentone (STP) 5 mg · kg^?1 alone, halothane induction alone 1–4%, or halothane followed by STP. Inhalational inductions with halothane included nitrous oxide and oxygen. Tracheal intubation was facilitated by either intravenous succinylcholine (Sch) at least 1.5 mg · kg^?1 or by a non-depolarizing muscle relaxant. The induction sequence and all episodes of MMR were recorded. Ninety percent of the patients received Sch and 10% received a non-depolarising agent. Of those who received Sch, 88% (5,064 patients) were anaesthetised with STP and 12% (607 patients) were anaesthetised with halothane alone or halothane followed by STP Masseter muscle rigidity was defined clinically by the transient inability to distract the mandible from the maxilla such that the mouth could not be opened or could only be opened with force. No children anaesthetised with STP followed by Sch developed MMR. One child (0.9%) developed MMR after halothane and Sch and two developed MMR after halothane, STP and Sch (0.4%). The incidence of MMR after Sch was less with STP than with halothane alone or with halothane and STP (P < 0.025). The peak CPK values in the three children who developed MMR were 17,580 IU · L^?1 after halothane and Sch, and 7,280 IU·^?1 and 3,273 IU ·^?1 after halothane, STP and Sch. There was no evidence of MH reactions in these patients. No child developed malignant ventricular arrhythmias or cardiac arrest after Sch or a non-depolarising neuromuscular relaxant. There were no episodes of succinylcholine apnoea. We conclude that MMR is less likely to occur following STP and Sch than after halothane and Sch.     

兔下颌角截骨后咬肌适应性变化

目的通过对兔下颌角弧形截骨后咬肌相关指标测定，研究咬肌在骨架缩短后的变化规律。方法3个月龄雌性新西兰大白兔25只，行左侧下颌角弧形截骨，右侧不手术作为自身对照。2、4、8、12和24周分别处死5只动物，双侧咬肌总量称重。取双侧下颌角中点浅部咬肌，行HE、ATP酶染色。结果左侧咬肌重量减轻与右侧差异显著，肌小节长度2周和4周术侧缩短，8周后恢复正常；部分肌纤维Ⅰ型向Ⅱ型转化；Ⅰ、Ⅱ型肌纤维面积左侧较右侧减小。结论兔下颌角截骨术后肌小节长度、肌纤维转型、咬肌细胞面积发生相应变化，表明下颌骨架缩短后咬肌发生适应性的改建。     

The effects of masseter muscle paralysis on facial bone growth

BACKGROUND: Understanding the effects of muscle function on facial bone growth may help us treat children with facial anomalies. Facial bone growth is known to be a result of both genetic and epigenetic influences. One of the main epigenetic factors controlling growth is thought to be muscle action. The purpose of this study was to establish a model of single facial muscle paralysis and to identify the effects masseter muscle paralysis has on mandible and zygoma growth. METHODS: Twenty New Zealand white rabbits were divided into control, paralysis, and sham groups. Masseter muscle paralysis was achieved with botulinum toxin A (BTX). Computed tomographic and single-photon emission computed tomography (SPECT) scans and cephalometric measurements were performed. Masseter weights and mandible and zygoma volumes, shapes, and metabolism were measured. RESULTS: Eighteen animals completed the study. Significant decreases in zygoma and mandible volumes with minimal changes in shape were seen on the paralyzed sides. SPECT showed a decrease in bone production in both zygomas and mandibles on the paralyzed sides. CONCLUSIONS: An animal model has been created in which the effects of single muscle paralysis on bone growth can be studied. Masseter muscle function may be responsible in maintaining mandible and zygoma volume by controlling bone production. Masseter function alone has less influence on mandible and zygoma shape.     

The effect of muscle relaxants on masseter tone. An experimental study in an MH-susceptible swine model]

Malignant hyperthermia (MH) may occur, when a genetically predisposed individual or pig (MHS) is exposed to triggering agents. The increase in free, ionized sarcoplasmic calcium inducing the vicious circle of MH is believed to result from calcium-induced release with volatile anaesthetics, and from depolarization-induced calcium release with succinylcholine (SCH). The administration of SCH to susceptible humans or pigs frequently produces an increase in masticatory muscle tone. This hitherto ill-defined phenomenon is referred to as "masseter spasm" (MS). We have attempted to elucidate the pathophysiology of MS in a porcine model. METHODS. After the protocol had been approved by the state authorities, 6 MHS pigs were investigated. The pigs were mixed breeds (German Landrace and Dutch Pietrain) and were 9 +/- 1 weeks old with an average body weight of 25.5 kg. Premedication consisted of intramuscular injection of azaperone, 7.5 mg.kg-1. Anaesthesia was induced with piritramide, 1.2 mg.kg-1, administered via a cannulated ear vein. Subsequent to laryngoscopic endotracheal intubation, neuromuscular blockade was achieved with 4 mg pancuronium. Ventilation was set at 12 breaths per minute and adjusted to maintain an end-tidal CO2 concentration of 4.7% by adapting the tidal volume (PhysioFlex). Anaesthesia was maintained with piritramide, 2.25 mg.kg-1.h-1, pancuronium, 0.4 mg.kg-1.h-1, and N2O (60% in O2). Instrumentation included an arterial line, a central venous line, and a fiberoptic pulmonary artery catheter (Oximetrix). Masticatory muscle tone (MMT) was assessed with an intermolar balloon, connected to a pressure transducer and calibrated to zero prior to SCH administration. As a reference variable for effects produced by SCH, intraocular pressure (IOP) was measured manometrically in the anterior chamber. After stabilization of haemodynamic variables, the neuromuscular blockade was allowed to wear off. After recovery of the evoked masseter electromyogram, a paralyzing dose of pancuronium was administered (0.5 mg.kg-1). When paralysis was complete, SCH was administered (1.5 mg.kg-1), followed a few minutes later by dantrolene infusion (5 mg.kg-1 over 10 min). RESULTS. The administration of SCH was followed by clinically unequivocal MH episodes in all pigs, indicated by an increase in oxygen uptake (VO2; PhysioFlex; Fig. 1) and end-tidal CO2 concentration and a decrease in oxygen saturation of mixed venous blood (svO2; Fig. 2). Despite complete neuromuscular blockade (monitored with EMG), SCH produced an increase in MMT in all pigs which was reversed by dantrolene (Fig. 3). The time course of MMT paralleled that of IOP, suggesting a similar underlying mechanism. DISCUSSION. Succinylcholine is a trigger of MH in susceptible individuals; onset of the syndrome may be associated with "masseter spasm". SCH increases extraocular muscle tone, probably by means of stimulating multiply innervated fibers; the resulting IOP increase is not prevented by competitive neuromuscular blockade. The existence of multiple innervated fibers has also been shown in muscle spindles in the deep layers of the masseter, with their stimulation resulting in elevation of the jaw. We speculate that the increases in MMT and IOP observed in this study reflect the same process, i.e. a motor response, initiated by SCH-induced stimulation of the intramyocellular contractile system of multiply innervated muscle fibers, that is independent of neuromuscular transmission. Triggering of MH with SCH despite complete neuromuscular blockage suggests a mechanism other than depolarization-induced calcium increase. And, for the semantics, according to neurological terminology MS should be referred to as contracture not as spasm.     

下颌骨截骨术后咬肌变化的研究

目的 观察下颌角截骨术后咬肌形态的动态变化.方法 采集120例下颌骨截骨受术者术前及术后3、6、12个月时头颅CT数据,并进行三维重建,通过软件平台设定合适的阈值范围,分割出咬肌组织.经过断层叠加创建咬肌的三维分割体,由软件输出咬肌体积等三维信息.再选定3处横截面,即A平面:过咬合平面水平,下颌升支前后缘中点的平面;B平面:A平面上1cm;C平面:A平面下1cm.在各横截面上测量咬肌的面积和厚度,观察咬肌在不同水平上的面积、厚度随时间的变化趋势.结果 咬肌体积与横截面面积的变化趋势基本相同,体积在术后3、6、12个月时分别缩小至术前的82.02%、77.00%和80.43%,术后各时期体积均明显小于术前(P＜0.05).A、B、C 3个平面咬肌面积的变化:A平面在术后3、6、12个月分别缩小至术前的85.81%、78.86%和81.56%,B平面分别萎缩至术前的80.94%、75.03%和77.04%,而C平面近似原下颌角角区下降最多,分别为13.46%、11.48%和13.89%.各测量数值与术前比较均有显著差异(P＜0.05,P＜0.05,P＜0.01).咬肌厚度的变化:A平面在术后3、6、12个月时分别缩小16.54%、15.85%、4.69%,术后12个月时与术前比较无明显差异.而B、C平面在各随访时间的厚度与术前比较均有显著差异(P＜0.05).结论 下颌角截骨术使咬肌发生了自行萎缩,原下颌角角区(C平面)的咬肌萎缩最为明显.因此在下颌骨截骨的术前的预测中应考虑到咬肌的萎缩,以更好地指导手术.     

Histochemical study of adrenergic nerve fibers in the skeletal muscle of the rat]

The distribution of adrenergic nerve fibers in the vessels, nerves, and skeletal muscles of the rat was studied by the glyoxylic acid fluorescence method and by electron microscopy. The changes in catecholamine fluorescence were investigated after decentralization, lumbar sympathectomy, and femoral nerve ligation. Catecholamine fluorescence was mainly localized in the arteries, and arterioles in the perimysium of the skeletal muscle. Sometimes, a spot-shaped catecholamine was seen in the metarteriole and capillary. Adrenergic nerve fibers ran parallel with femoral nerve fibers. After lumbar sympathectomy catecholamine fluorescence disappeared, the fluorescence in the quadriceps femoris muscle did not disappear even after ligation of the femoral nerve. Unmyelinated nerve fibers were identified adjacent to the capillary, whereas adrenergic nerve fibers were seen approaching to the quadriceps femoris muscle within a gap of 300 nm.     

Hemangioma of the masseter muscle: report of a case

This condition constitutes 0.8% of all hemangiomas, 14% in the head and neck [1]. Skeletal muscle involvement was first described in 1843 by Liston [2]. The rarity of these tumors and the difficulty with diagnosis often leads to incomplete excision [3]. These are congenital lesions consisting of mesodermal nests of vasoformative tissue that gives rise to the vascular tree [4]. They may be exacerbated by trauma and reproductive hormones [3, 5]. They can resolve spontaneously [3, 4, 6]. They present as a palpable, rubbery mass in 98% of cases [4]. Occasionally, they are compressible and pulsate. Conventional X-rays show phleboliths, MRI scanning gives good soft tissue definition, but angiography reveals the vascular nature of the tumor [7]. Irradiation cautery, sclerosants, lasers, steroids and surgical excision have been used for treatment [3, 4, 6, 8, 12]. Total excision is the treatment of choice [4, 6, 10, 13, 14].     

Myosin heavy chain mRNA isoforms in masseter muscle before and after orthognathic surgery.

OBJECTIVES: Orthognathic surgery leads to changed jaw position and force vector of mastication to which the muscles must adapt. The aim of the present study was to determine the relative expression of myosin heavy chain (MyHC) messenger RNA (mRNA) isoforms in different types of human masseter muscle fiber under consideration of change in the number of occlusal contacts before and 6 months after surgery. STUDY DESIGN: Muscle biopsies were taken from the anterior and posterior parts of both sides in 30 patients with prognathic and retrognathic mandibles. Specific mRNA MyHC analysis was made by real-time polymerase chain reaction to quantify the isoforms I, IIa, and IId/x. RESULTS: There was a shift in the relative content from type I (46% before, 37% after) to type IIa (29% before, 42% after). This shift correlates with number of teeth in occlusion. CONCLUSIONS: Correlation between isoform shift and number of teeth in occlusion indicates higher mastication force which stabilizes the treatment result.     

Superficial tendoplasty after injury of the intrinsic muscle]

In 6 fingers of two injured patients, after the lesion of the intrinsic musculature of the finger with three phalanges Bunnell's sublime tendoplasty has been performed by the authors. Satisfactory functional results have been obtained, therefore the method is recommended by the authors for the treatment of similar lesions.     

Propofol reduces succinylcholine induced increase of masseter muscle tone

Purpose

Succinylcholine is known to increase the tone of the masseter muscles. As excessive jaw tension may complicate rapid sequence induction, we investigated three induction techniques, all including the use of succinylcholine, with respect to masseter muscle tone, neuromuscular blockade, intubation conditions, and time course of intubation.

Methods

Sixty adult patients were allocated to one of three induction groups: Group THIO received 5 mg · kg^?1 thiopentone, Group THIO/ATR received 5 mg · kg^?1 thiopentone plus 0.05 mg · kg^?1 atracurium for precurarization, and Group PROP received 2.5 mg · kg^?1 propofol. All patients received 3 μg · kg^?1 fentanyl and 1.5 mg · kg^?1 succinylcholine. Time for induction of anaesthesia was recorded, and, after inserting a Grass Force Transducer between upper and lower incisors, jaw tone and the time course of jaw tension was recorded before and after the administration of succinylcholine.

Results

No differences in the onset of sleep were observed among the three groups (Group THIO 33 ± 2 sec: THIO/ATR 30 ± 2 sec: PROP 35± 2 sec, mean ± SE). Masseter preloads following induction of anaesthesia were similar in all three groups (THIO 16.4 ± 2.1 N: THIO/ATR 15.1 ± 2.0 N: PROP 12.7 ± 1.6 N). However, after administration of succinylcholine, the increase in masseter tone was less in Groups PROP (5.0 ±1.1 N) and THIO/ATR (6.4 ± 2.1 N) than in Group THIO (12.4 ± 3.0 N;P < 0.05).

Conclusion

Jaw tension after administration of succinylcholine is influenced by the choice of induction agent. The increase of masseter muscle tone is lower following propofol or thiopentone/atracurium induction than with thiopentone alone.     

Extended effect after a single dose of type A botulinum toxin for asymmetric masseter muscle hypertrophy

Facial asymmetry can either be physiological or pathological and is a common cosmetic concern. A 35-year-old Indian male presented with broad appearing lower face and prominent left jaw since adolescence. Parotid enlargement and other local disorders were ruled out. Ultrasonographic thickness of right masseter muscle was 13 mm while that of left was 14.9 mm, in unclenched state. Type-A botulinum toxin (T-ABT) was injected, evenly at five points, in both muscles within the “safe zone”. Using a 29 gauge needle, 15 and 25 international units were delivered to right and left masseters, respectively. Six months post — injection, a reduction of 2.9 mm and 4.4 mm was observed along with a reduced external facial asymmetry. At 24 months, patient maintains a satisfactory facial contour with no significant early or late post-injection complications. Intra-massteric injection of T-ABT can be used effectively as a primary or adjunct procedure for holistic oculo-facial sculpting.KEY WORDS: Botulinum toxin, extended volume reduction, facial asymmetry, masseter hypertrophy     

山羊下颌角截骨术后咬肌再附着过程中胶原变化的观察

目的:观察不同术式下颌角截骨术后山羊咬肌再附着过程,并与正常咬肌附着进行比较,探讨下颌角截骨术后咬肌-下颌骨再愈合过程对口腔咀嚼功能恢复的影响。方法:以16只成年山羊为研究对象,随机分入A、B、C、D四组,每组4只。A组:随机取一侧行下颌角弧形截骨术;B组:随机取一侧行下颌角弧形截骨术 咬肌部分切除术;C组:随机取一侧行下颌骨外板取出术;D组:随机取一侧行下颌骨嚼肌剥离术。分别于术后1月、2月、3月、6月于各组咬肌再附着区行组织学观察及骨膜厚度测量。结果:术后3个月前,各实验组界面愈合有一定差别,恢复程度依次为咬肌剥离组,去下颌骨外板组,去下颌角组,去下颌角及咬肌组,术后3个月后各实验组肌骨界面恢复情况无明显差别,术后6月各组肌-骨界面结构类似于正常咬肌附着。骨膜厚度测量结果,咬肌剥离组在术后2月时基本恢复正常厚度,其余实验组在术后6月时恢复正常厚度。结论:下颌角截骨术后2个月,咬肌-下颌骨附着初步重建,术后3个月,建立较牢固的肌骨附着,术后6个月,肌骨附着基本恢复正常。间接说明下颌角截骨术后3月,患者可逐渐恢复正常的咀嚼活动。     

Zymographic and ultrastructural evaluations after low-level laser irradiation on masseter muscle of HRS/J strain mice

Low-level laser therapy (LLLT) has been widely used in the treatment of the stomatognathic system dysfunction; however, its biological effect remains poorly understood. This study evaluated the effect of LLLT (GaAlAs, 780 nm, 20 J/cm², 40 mW) on masseter muscle of HRS/J mice after different numbers of laser irradiations (three, six, and ten) for 20 s in alternate days. Three experimental groups were defined according to the number of laser irradiations and three control groups (n?=?5) were used. On the third day after the last irradiation, all animals were killed and the masseter muscle was removed and processed for the following analysis: (a) transmission electron microscopy, (b) zymography, (c) immunohistochemistry for vascular endothelial growth factor (VEGF) and VEGFR-2. The results showed: (a) with six laser applications, a dilation of T tubules, and sarcoplasmic reticulum cistern, increased pinocytosed vesicles in the endothelium; with ten laser applications, few pinocytic vesicles in the endothelium and condensed mitochondria. (b) Under the conditions of this study, the synthesis of other matrix metalloproteinases was not observed, only the MMP-2 and -9. (c) After ten laser irradiations, immunostaining was observed only for VEGFR-2. We conclude that after six laser applications, ultrastructural changes may facilitate the Ca⁺² transfer to cytosol and increase the fluid transport from one surface to another. The ultrastructural changes and no immunostaining for VEGF with ten applications may decrease the metabolic activity as well as damage the angiogenic process, suggesting that an effective number of laser applications may be less than ten, associating to this therapy a better cost–benefit.