PCA Muscle Research Articles

Electromyography of the posterior cricoarytenoid muscles: a consensus guideline.

Since the introduction of transcutaneous-transcricoidal needle approaches, electromyography (EMG) of the posterior cricoarytenoid muscle (PCA) became easier to perform and teach. Among the Neurolaryngology working group of the European Laryngological Society, several centers have adopted PCA EMG as part of their routine EMG workup in vocal fold immobility collectively gathering long-term experience. The purpose is to give an update and an extension to already existing guidelines on laryngeal EMG with specific regard to PCA EMG. Consensus of all co-authors is based on continuous exchange of ideas and on joint laryngeal EMG workshop experiences over at least 7years. A Delphi method of consensus development was used, i.e., the manuscript was circulated among the co-authors until full agreement was achieved. Step-by-step instructions on how to perform and interpret PCA EMG are provided. Further research should include the establishment of normal values for PCA and thyroarytenoid muscle (TA) EMG as well as studies on the nature of some unusual activation pattern commonly seen in chronically lesioned PCA.

Functional Evaluation of Larynx Nerve Stimulator With EMG Acquisition Capability and Wireless Connectivity.

Recently, an electrical stimulation of the paralyzed muscle, as a potential therapy for restoring function of a denervated muscle system, has been debated as an innovative treatment in the management of patients with laryngeal paralysis. Numerous studies in acute and chronic animal models have demonstrated that electrical stimulation of the paralyzed posterior cricoarytenoideus muscle (PCA) offers an approach to induce vocal fold abduction and restore ventilation through the glottis. The study aims to test applicability of the controlled opening of the rima glottides via direct electrical stimulation of the posterior cricoarytenoideus muscle. We developed for this purpose a novel instrument system for the controlled larynx nerve stimulation. An acute experiment on the 4 years old pig showed effectiveness of the engineered stimulator. The controlled opening of rima glottidis of both posterior cricoarytenoid muscles and afterwards of both PCA muscle contraction were observed as a result of the electrical stimulation with the applied current in the range of 0.1-3 mA and pulse width of 1 ms and 10 ms. Performed research indicates a large potential of the novel nerve stimulator for the human larynx stimulation.

Olfactory Ecto-Mesenchymal Stem Cells in Laryngeal Nerve Regeneration in Rats

Selective intralaryngeal reinnervation has been shown to be effective in experimental models. This consists of independently reinnerving the adductor and abductor of laryngeal muscles of the larynx, in order to prevent any misalignment of the axonal regrowth, improve the functional recovery and tend toward reduction of synkinesis. The surgical technique remains complex. Current research focuses on simplifying and improving this technique. Olfactory ectomesenchymal stem cells (OEMSC) represent an interesting candidate for cell therapy and could be obtained from olfactory mucosa. Recent reports suggest a neuroregenerative potential in various animal models of central and peripheral nervous systems injuries. The aim of this study was dual: to develop a simple surgical model of selective reinnervation applicable in humans and to evaluate the relevance of OEMSC-based cell therapy for improving axonal guidance. Eight Fisher syngeneic rats were used to carry out the OEMSCs culture. Thirty-four Fisher syngeneic rats were operated on, divided into three groups depending on the transplanting. For all the rats, we have performed a side to end anastomosis of the vagal nerve with the inferior laryngeal nerve by interposition of a nerve graft from the left femoral nerve. Then, the first group didn't have any injection, the second group has an injection of thrombin and the third group has an injection of one million EOMSCs. Three months after surgery, laryngeal muscle activity was evaluated by videolaryngoscopy and electromyography recordings. In order to illustrate the quality of axonal regrowth, a fluorescent tracer was injected into the right posterior crico-arytenoid muscle (PCA) to reveal the cellular bodies of the motoneurons responsible for reinnervation of the PCA in the central nervous system. In our study, no improvement was found during the videolaryngological functional evaluation or with regard to the electrical activity of the PCA muscle. The cells colabelled in retrograde tracing were numerous in all groups, reflecting abnormal axonal regeneration. The interposition of a nerve graft, as side to end anastomosis between the vagus nerve and the inferior laryngeal nerve, filled with OEMSCs, does not provide better reinnervation of a hemilarynx.

Comparison between Intramuscular Multichannel Electrodes and Supramysial Multichannel Electrodes via EMG Measurements for Potential Use as Larynx Stimulation Electrodes: In Vivo Animal Analysis.

One of the most common causes for larynx paralysis is the injury of the recurrent laryngeal nerve which, among others, causes the paralysis of the posterior cricoarytenoideus muscle (PCA). Electrical stimulation of PCA offers an approach to retaining the function of the paralyzed larynx muscle. The study aim was to test the applicability of an intramuscular multichannel array electrode as a measuring electrode for myoelectrical potentials and as a possible electrode for stimulation, e.g., posterior cricoarytenoideus muscle stimulation. For this purpose, two different kinds of electrodes were compared. 42 intramuscular multichannel array electrodes and 11 supramysial multichannel electrodes were implanted into the triceps brachii muscle of rats. The triceps brachii muscle of rats is suitable to serve as a substitute muscle for the human PCA muscle in an in vivo animal model. It has the same striated muscle cells, is of comparable size, and fundamentally serves a similar function to the human PCA muscle during normal respiration. Walking and breathing are circular functions that cause minimal muscle fatigue when carried out steadily. In total, the myoelectrical activity of 6703 steps could be recorded, allowing a comparison and statistical analysis of the EMG amplitudes and EMG activation patterns. Small differences can be detected between the EMG signals of both electrode types which, however, can be explained physiologically. Both electrode types reveal the basic characteristics of the triceps brachii muscle activity, namely the muscle contraction strength and the coordination pattern. This indicates that the intramuscular electrode may be applied for a detailed analysis of the human larynx.

The Posterior Cricoarytenoid Muscle Is Spared from MuRF1-Mediated Muscle Atrophy in Mice with Acute Lung Injury

BackgroundSkeletal muscle wasting in acute lung injury (ALI) patients increases the morbidity and mortality associated with this critical illness. The contribution of laryngeal muscle wasting to these outcomes is unknown, though voice impairments and aspiration are common in intensive care unit (ICU) survivors. We evaluated the intrinsic laryngeal abductor (PCA, posterior cricoarytenoid), adductor (CT, cricothyroid) and limb (EDL, extensor digitorum longus) muscles in a mouse model of ALI.MethodsEscherichia coli lipopolysaccharides were instilled into the lungs of adult male C57Bl6J mice (ALI mice). Limb and intrinsic laryngeal muscles were analyzed for fiber size, type, protein expression and myosin heavy chain (MyHC) composition by SDS-PAGE and mass spectroscopy.ResultsMarked muscle atrophy occurred in the CT and EDL muscles, while the PCA was spared. The E3 ubiquitin ligase muscle ring finger-1 protein (MuRF1), a known mediator of limb muscle atrophy in this model, was upregulated in the CT and EDL, but not in the PCA. Genetic inhibition of MuRF1 protected the CT and EDL from ALI-induced muscle atrophy. MyHC-Extraocular (MyHC-EO) comprised 27% of the total MyHC in the PCA, distributed as hybrid fibers throughout 72% of PCA muscle fibers.ConclusionThe vocal cord abductor (PCA) contains a large proportion of fibers expressing MyHC-EO and is spared from muscle atrophy in ALI mice. The lack of MuRF1 expression in the PCA suggests a previously unrecognized mechanism whereby this muscle is spared from atrophy. Atrophy of the vocal cord adductor (CT) may contribute to the impaired voice and increased aspiration observed in ICU survivors. Further evaluation of the sparing of muscles involved in systemic wasting diseases may lead to potential therapeutic targets for these illnesses.

The role of the posterior cricoarytenoid muscle in phonation

The posterior cricoarytenoid muscle (PCA) is generally considered to be a respiratory muscle. Indeed, as the sole abductor of the glottis (i.e., the only laryngeal muscle with the capability of opening the true vocal folds), paralysis of the PCA may lead to asphyxiation. While the PCA muscle also appears to play a role in phonation, a consensus has not been reached among voice scientists regarding its precise role in the control of fundamental frequency, phonation threshold pressure, and other phonatory variables. Using a new developed method of graded stimulation to the laryngeal muscles, Chhetri, Neubauer, and Berry (2012) explored the role of the cricothyroid muscle (CT), thyroarytenoid muscle (TA), and the lateral cricoarytenoid and interarytenoid muscle complex (LCA + IA) on fundamental frequency, phonation threshold pressure and glottal posturing. The present study augments the previous study by also investigating the influence of the PCA muscle on these same phonatory variables. Similar to the adductor muscles, it is shown that the PCA muscle introduces new possibilities for achieving multiple phonation types at a given fundamental frequency.

Diffusion of Aniline Blue Injected into Thyroarytenoid Muscle

Objective: Intralaryngeal injection of botulinum toxin into the thyroarytenoid (TA) muscle is one of the methods for the treatment of laryngeal focal dystonia. The side effects and the modification of the laryngeal configuration are probably due to the diffusion of the botulin toxin to nearby structures. Aim: Analyze the diffusion of aniline blue (liquid substance) injected into the TA to the adjacent intrinsic laryngeal muscles. Method: Study Design: Experimental. Eighteen excised cadaveric larynges were analyzed after injection of aniline blue (0.2 mL) into the TA, using the intralaryngeal technique. After fixation by formaldehyde and decalcification using nitric acid, the larynges were sectioned in the coronal plane in 4 slices and the intrinsic muscles analyzed. Results: The aniline blue spread to the lateral cricoarytenoid muscle, the cricothyroid muscle and the posterior cricoarytenoid muscle 94.3%, 42.9%, and 8.6%, respectively. Gender, height, and width of the TA had no effect on the likelihood of diffusion to any of the muscles. Conclusion: The present study showed that, based on the methodology proposed, the diffusion of a solution injected into the TA occurs in almost all cases toward the CAL muscle. The CT muscle was affected in half of the cases. Although rarely, it can also achieve the PCA muscle.

Activity of bilateral posterior cricoarytenoid muscle satellite cell after denervation or reinnervation with ansa in dogs

To investigate the activity of bilateral posterior cricoarytenoid muscle satellite cell after denervation or reinnervation with ansa cervicalis. Twenty four dogs were randomly divided into 3 groups. The bilateral laryngeal recurrent nerves were cut in group one in all dogs. The bilateral laryngeal recurrent nerves were anastomosed with ansa cervicalis after incision in group two in all dogs. The dogs in group three were used as control. Nine weeks after surgery, the electromyography was used to test the regeneration of the nerve. The posterior cricoarytenoid muscles biopsy were collected. The expression of mRNA of Myogenin, Myf5, and Pax7 was assayed by realtime RT-PCR after total RNA isolation. Two dogs died after surgery in incision and anastomose group. The electromyography suggested that the RLN of all dogs had denervated in the incision group and had reinnervated in the anastomose group after 9 weeks. Myogenin mRNA from RLN incision dogs PCA muscles had greater expression versus controls (Z = 1.42, P < 0.01) or anastomosed dogs (Z = 1.38, P < 0.01). Myf5 mRNA expression from RLN incision dogs PCA muscles had significant increase versus control dogs (Z = 1.66, P < 0.01) or anastomosed dogs (Z = 1.69, P < 0.01). Pax7 mRNA expression from RNL incision dogs had significant increase compared with control (Z = 1.66, P < 0.01) or anastomosed animals (Z = 1.42, P < 0.05). There was no significant difference in Myogenin (Z = 1.34, P > 0.05), Myf5 (Z = 0.54, P > 0.05) and Pax (Z = 0.54, P > 0.05) mRNA expression between controls and anastomosed animals. The bilateral denervation of RLN cause significantly increasing in dog PCA muscle satellite cell proliferation and differentiation. The bilateral reinnervation of RLN cause PCA muscle satellite cell come back nonproliferative, quiescent state in dog.

Nimodipine Improves Reinnervation and Neuromuscular Function after Injury to the Recurrent Laryngeal Nerve in the Rat

Injury of the recurrent laryngeal nerve (RLN) is associated with a high degree of neuronal survival, but leads to various levels of vocal fold motion impairment or laryngeal synkinesis, which has been attributed to misdirected reinnervation of the target muscles in the larynx or aberrant, competing reinnervation from adjacent nerve fibers. The aim of the present study was to evaluate the impact of the regeneration-promoting agent nimodipine on reinnervation and neuromuscular function following RLN crush injury. Sixty adult rats were randomized into nimodipine-treated or untreated groups and then underwent RLN crush injury. Reinnervation of the posterior cricoarytenoid muscle (PCA) was assessed by electrophysiological examination, retrograde tracing of lower motor neurons before and after injury, and quantification of neuromuscular junctions in the PCA muscle. At 6 weeks after injury, the nimodipine-treated animals showed significantly enhanced neuromuscular function and also demonstrated a higher number of motor neurons in the brain stem that had reinnervated the PCA, compared to the untreated animals. The somatotopic organization of ambiguus motor neurons innervating the larynx was similar before injury and after reinnervation. Nimodipine improves regeneration and neuromuscular function following RLN injury in the adult rat, and could be of use in future strategies following RLN injury.

Contribuição ao estudo anatômico da inervação dos músculos cricoaritenóideos posterior e lateral

A problemática da inervação laríngea tem motivado o aparecimento de grande número de pesquisas, especialmente àquelas relacionadas ao nervo laríngeo recorrente (NLR). As numerosas variações anatômicas, a importante aplicação cirúrgica e ainda as dificuldades na comprovação funcional dos ramos nervosos para laringe tornam este assunto intrigante e desafiador. Diante disto, o presente estudo objetiva a investigação minuciosa dos ramos do nervo laríngeo recorrente (NLR), destinados aos músculos cricoaritenóideos posterior (CAP) e lateral (CAL). FORMA DE ESTUDO: Experimental. MATERIAL E MÉTODO: Foram realizadas dissecções bilaterais, ao microscópio cirúrgico, de 20 laringes de adultos, de ambos os sexos, referentes às regiões posterior e posterolateral da laringe. RESULTADOS: Encontraram-se diferenças morfológicas nos ramos do NLR que alcançam os músculos CAP e CAL, observando-se inervação unipedicular, bipedicular e tripedicular. Encontraram-se, também, fibras do músculo CAP dispostas obliquamente às do feixe principal, em forma de um "aqueduto", sob o qual passa o NLR. CONCLUSÕES: O nervo laríngeo recorrente (NLR) penetra na laringe sob a sua margem inferior, atrás da articulação cricotireoidea; a inervação característica de ambos os músculos (CAP e CAL) é predominantemente bipedicular; o mencionado "aqueduto", formado por um feixe de fibras do CAP, seria uma variação anatômica pouco estudada.

Synaptology and ultrastructural characteristics of laryngeal cricothyroid and posterior cricoarytenoid motoneurons in the nucleus ambiguus of the rat.

The laryngeal motoneurons innervating the cricothyroid muscle (CT) are located in the semicompact formation just ventral to the rostral part of the compact formation of the nucleus ambiguus. The motoneurons innervating the posterior cricoarytenoid muscle (PCA) are located in the loose formation. We retrogradely labeled the CT and the PCA motoneurons using cholera toxin subunit B-conjugated horseradish peroxidase, and determined the ultrastructure and synaptic organization of these neurons. The CT and the PCA motoneurons had the appearance of alpha-motoneurons, i.e., large, oval or polygonal cells containing well-developed organelles and a prominent spherical nucleus. Two kinds of neurons were recognized among the PCA motoneurons. The one (PCA-A) was significantly smaller than the other (PCA-B). The average number of axosomatic terminals in a section was significantly largest in the PCA-B (56.6), smaller in the PCA-A (36.0), and smallest in the CT (32.3) neurons. Most of the axosomatic terminals (64.7%) contained pleomorphic vesicles and made symmetric synaptic contacts (Gray's type II) with the PCA-A neurons, while more than 60% contained round vesicles with asymmetric synaptic contacts (Gray's type I) in the CT (69.5%) and the PCA-B (60.6%) neurons. A few terminals associated with subsurface cisterns were present on all laryngeal motoneurons. These results indicated that the CT motoneurons may receive mostly excitatory terminals, whereas the PCA muscle may be regulated by neurons having many inhibitory terminals, and neurons having many excitatory terminals.

Human posterior cricoarytenoid muscle compartments. Anatomy and mechanics.

To document the presence and functional significance of distinct anatomical compartments in the human posterior cricoarytenoid muscle (PCA). Anatomic study of human cadaver larynges. Seventeen fresh larynges, harvested at autopsy from 8 men and 9 women, with no history of laryngeal disease or surgery. Twenty-three PCA muscles from 12 human cadaver larynges were dissected. Computed tomographic scanning and rigid body mechanical analysis were used to compute 3-dimensional motion with simulated individual contraction of PCA compartments in 5 fresh larynges. Discrete medial and lateral bellies with different orientations of muscle fibers were found in every muscle. The 2 bellies insert on opposing aspects of the muscular process of the arytenoid. Very little linear translation was effected by either muscle. The axes of rotation attributable to the 2 bellies differed significantly, with the medial belly effecting rotation about a more vertical axis. The axis of rotation for the lateral muscle belly was nearer the anterior posterior axis than that of the medial belly. These data indicate that PCA muscle contraction results in arytenoid rotation about a variable oblique axis without significant lateral gliding. There are 2 bellies within the human PCA muscle with differing mechanical actions on the cricoarytenoid joint.

Mechanism of the differential sensitivity in the rat adductor and abductor laryngeal muscles to a non-depolarizing neuromuscular blocker

We have compared the neuromuscular blocking effects of tubocurarine at pre- and postsynaptic sites in the lateral cricoarytenoid muscle (LCA) (one of the adductor muscles of the vocal cords) and in the posterior cricoarytenoid muscle (PCA) (sole abductor muscle of the vocal cords) of the rat. Fine wire electrodes were inserted into both muscles and evoked compound electromyographic (EMG) responses measured by supramaximal stimulation of the recurrent laryngeal nerves. End-plate potentials (EPP), mean quantal content and carbachol sensitivity to tubocurarine in both muscles were measured using intracellular microelectrodes. Tubocurarine produced a concentration-dependent reduction in the EMG responses, EPP amplitude, mean quantal content and carbachol sensitivity. The LCA muscle was more resistant to tubocurarine than the PCA muscle in EPP amplitude, mean quantal content and carbachol sensitivity, suggesting unequal pre- and postsynaptic sensitivity for inhibition of elicited acetylcholine release, reduction in EPP amplitude and loss of evoked muscle action potentials. Examination of muscle fibre composition demonstrated that the LCA muscle contained a significantly higher fraction of slow twitch muscle fibres than PCA muscle. However, the sizes of the fibres were similar in both muscles. We conclude that the mechanism of unequal sensitivity to a non-depolarizing neuromuscular blocker in the LCA and PCA muscles may be explained by differential sensitivities at the pre- and postsynaptic sites of the neuromuscular junction.

Laryngeal electromyography with separated surface electrodes in patients with multiple system atrophy presenting with vocal cord paralysis.

When recording the activity of the posterior cricoarytenoid muscle (PCA) with surface electrodes, there is contamination from the surrounding muscles such as the cricopharyngeal muscle. We therefore devised a new oesophageal catheter electrode of the separate type, having three individual surface electrodes for the PCA, cricopharyngeal muscle and diaphragm. The records obtained with this catheter demonstrated satisfactory separation between PCA and cricopharyngeal muscle activities. We used this catheter in patients with multiple system atrophy presenting with vocal cord paralysis, who were awake or asleep. There were two interesting electromyographical findings, which were inspiratory activity of the adductor muscle (the thyroarytenoid muscle) and fade-out of the abductor muscle, that is, PCA activity during sleep. Although vocal cord paralysis is one of the most serious life-threatening complications, the precise mechanism has not been clarified. We believe that our catheter may be useful in investigating the mechanism of vocal cord paralysis which could cause sudden death in neurodegenerative disorders, including multiple system atrophy.

内喉頭筋運動ニューロンの再支配について

Reinnervation and subsequent paradoxical movements of the motor nerve after injury is well known in the facial nerve, ocular nerve, peroneal nerve, etc. as well as the recurrent laryngeal nerve (RLN). Way of the experimental injury to the RLN at a level below 15 mm from the lower margin of the cricoid cartilage was accomplished two different methods : one to be neurorrhaphy under microscope after transection of the nerve and the other to be freezing by ophthalmological forceps at a temperature below 80 degrees for five minutes. This latter procedure allows the Schwann sheathe and perineurium to remain intact but damages the endoneurium. Movements of the pathological vocal fold were observed macroscopically and monitored regularly by electromyogram (EMG) from one week to nine months. Redistribution of the motoneuron originating from regrowth of the nerve fiber around the injured RLN was histologically verified by horseradish peroxidase (HRP) at the time of the EMG monitorings. The target muscles for observatory analyses were determined to be the posterior cricoarytenoid muscle (PCA) and thyroarytenoid muscle (TA). Monitoring of these muscles between the adductor and abductor is essential in order to assess the paradoxical movement after regrowth of nerve fibers. It was suggested that following transection of the nerve sprouting began three months later than it did in the group that underwent freezing injury two weeks after trial when the distribution rate was calculated in the nucleus ambiguus of the medulla oblongata. Furthermore, the numbers of sprouting fibers increased at one point beyond the normal level (in our study) of 90 six months after injury and gradually normalized in both groups at the 9 months. The rate of excessive growth in the first transected group was superior to the second freezing group. This result suggests that the rate of paradoxical movement following misdirected reinnervation is greater in the transected group than in the freezing group. This was verified by monitoring of the EMG. In both groups, HRP stained target neuron cells affecting the PCA muscle were observed in the localized control dorsoventral area at the more cephalad site. However, aberrant motoneurons also appeared out of the normal area and in the caudal and ventral regions (TA motoneuron). This also suggests paradoxical movement after reinnervation of nontarget organs.

Muscle Transfer for Laryngeal Paralysis: Restoration of Inspiratory Vocal Cord Abduction by Phrenic-Omohyoid Transfer

Omohyoid muscle transfer to the denervated posterior cricoarytenoid muscle (PCA) was performed in three monkeys. The transposed omohyoid muscle was reinnervated by the phrenic nerve by performing nerve anastomosis prior to muscle transfer. The muscles were sutured over the denervated ipsilateral PCA muscle to allow for neurotization of the denervated PCA muscle in such a way as to reproduce the directional vector of PCA contraction, eg, to mimic the directional pull of the PCA muscle. The muscle flaps were found to be long enough to reach the contralateral PCA muscle, confirming that the technique might be used ultimately for bilateral simultaneous PCA reinnervation. Each animal achieved reinnervation. The superiorly based omohyoid muscle flap was found to more closely emulate the size and orientation of the underlying PCA muscle. Electromyography, videolaryngoscopy, and histologic examination were used to confirm the results. The procedure has the potential for PCA muscle replacement in long-standing cases of paralysis with PCA denervation atrophy as well as for reinnervating a denervated PCA muscle.

Ultrastructural and Histochemical Study of the Neuromuscular Junctions in the Denervated Intrinsic Laryngeal Muscle of the Cat

Morphological changes and acetylcholinesterase (AchE) activity in the neuromuscular junctions (NMJ) of the normal and denervated posterior cricoarytenoid muscle (PCA muscle) of the cat were studied. Two days after denervation, the nerve terminals at the NMJ had almost disappeared. Six weeks after denervation, intensity of AchE activity at the former junctional site (FJS) was unchanged histochemically. At this stage, primary synaptic clefts were distorted and the Schwann's cells covered the FJS. Fourteen weeks after denervation, AchE activity at the FJS had decreased in contrast to that of the non-affected side. Calcitonin gene-related peptide (CGRP) was also investigated at the NMJ of the normal PCA muscles immunocytochemically. The present study shows that CGRP coexists with Ach in the nerve terminals of the PCA muscles and may be involved in the regulation of the contractile function of the intrinsic laryngeal muscle.

A targeted problem and its solution: A new method of needle‐electrode placement in the posterior cricoarytenoid muscle for electromyography

In 1979 the authors developed a new method of needle-electrode placement in the posterior cricoarytenoid muscle (PCA) for electromyography. The PCA muscle is easily reached by inserting a needle electrode through the cricothyroid membrane at the midline and penetrating the lamina of the cricoid cartilage in the subglottic cavity. Access to the PCA muscle for electrode insertion was best afforded by a percartilaginous approach. This report details the new technique used at our laboratory. To our knowledge, this is the first report of needle-electrode placement in the PCA muscle by a percartilaginous approach. This new electrode insertion technique has been applied to more than 100 dogs for research purposes and to 1200 patients with laryngeal motor disorders for clinical diagnosis. This is a simple technique requiring the usual skills. Reliable electromyographic recordings have been obtained by this new method. No untoward effects, such as hematoma or infection from repeated placements were observed in approximately 3200 examinations performed to date. It is reasonable to assume that the percartilaginous route for electrode insertion in the PCA muscle is feasible in man. Techniques of electrode placement in the intrinsic laryngeal muscles are reviewed and compared.

Zur Spontandegeneration im M. posticus

The intrinsic muscles of the larynx were prepared in 265 forensic postmortems (death by strangulation: 73; other violent deaths: 93, natural death: 79, others: 20) for a histological examination. Muscle-fiber alterations were found in the (macroscopically normal) PCA muscle in most cases where the persons were of middle age or older. There were abnormalities such as rows or clumps of nuclei (also inside muscle fibers), the accumulation of lipofuscin pigment, focal or total necrosis of muscle fibers with or without predominant histiocytic infiltration, atrophic muscle cells, and fibrosis. The changes were mostly mild (normal muscle cells predominated) but clearly visible. If there had been acute damage to the larynx (for instance, death some time after attempted strangulation), these preexistent alterations must be taken into consideration when interpreting the microscopical findings.

Histochemical study of acetylcholine receptors at the neuromuscular junctions of the cat posterior cricoarytenoid muscle using erabutoxin B

Acetylcholine receptors (AchRs) at the neuromuscular junctions of the cat posterior cricoarytenoid muscle (PCA muscle) were demonstrated by using erabutoxin b (Eb) which has a curare-like action. Eb is one of the short-chain neurotoxins which is obtained from Laticauda-semifasciata. At the light microscopic level, the localization of the neuromuscular junctions was detected on the muscle fiber by rhodamine-labeled Eb (TMR-Eb) under a fluorescein microscopy. For the electron microscopy horseradish peroxidase-labeled Eb (HRP-Eb) was used. After incubation with HRP-Eb conjugate the tissue was fixed in a mixture of paraformaldehyde and glutaraldehyde, then embedded in Epon. The reaction products were largely restricted to the postsynaptic membrane at the neuromuscular junction. Acetylcholinesterase (AchE) activity was also demonstrated electron microscopically by Karnovsky's and Lewis' methods respectively. The reaction products were localized at the subneural apparatus of the neuromuscular junction. Both these results were compared.