Muscle Fiber-Type Distribution Pattern in the Human Cricopharyngeus Muscle

Grabscheid Voice Center, Department of Otolaryngology, The Mount Sinai Medical Center, New York, New York 10029-6574, USA.
Dysphagia (Impact Factor: 2.03). 02/2002; 17(2):87-96. DOI: 10.1007/s00455-001-0108-2
Source: PubMed


Our previous studies described that the human cricopharyngeus (CP) is composed of two neuromuscular compartments (NMCs), horizontal and oblique. The present study was designed to explore the differences in muscle fiber-type distribution between the NMCs within the human CP and to examine the oxidative capacity of the muscle fibers. Seven adult human CP muscles obtained from autopsies were stained for myofibrillar ATPase, reduced nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR), and succinic dehydrogenase (SDH) to analyze enzyme-histochemical fiber-type characteristics. Notable findings obtained from this study are as follows: (1) Different NMCs within the human CP contained different percentages of muscle fiber types. The horizontal CP (CPh) contained more slow-twitch fibers than the oblique CP (CPo). (2) Each of the NMCs was dividable histochemically into two layers or subcompartments: a slow fiber-type inner layer and a relatively fast fiber outer layer. (3) As a whole, type I fibers had higher levels of NADH-TR and SDH than type II fibers. However, in both type I and II muscle fiber types, different patterns of oxidative enzyme activity were seen. Histochemically defined fiber layers of the CP are not seen in other mammals, suggesting that CP function is more specialized in humans.

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    • "In our study, the proportion and distribution of muscle fiber types were identified by NADH-TR staining. In general, type I fibers (slow twitch-oxidative) are stained darker when stained with NADH-TR; type II fibers, including type IIa fibers (fast twitch-oxidative-glycolytic) and type IIb fibers (fast twitch-glycolytic) are stained somewhat moderately and weakly, respectively (Mu and Sanders, 2002). The tibialis anterior of 46-d-old broilers consists of types I, IIa, and IIb fibers (Figure 1a), but the pectoralis major mainly consists of type IIb fibers (Figure 1b). "
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    ABSTRACT: The effect of transport stress on blood metabolism, glycolytic potential, and meat quality in broilers was investigated. Arbor Acres chicks (n = 360, 1 d old, males) were randomly allotted to 1 of 5 treatments: unstressed control, 45-min (short-term) transport with 45-min (short-term) recovery, 45-min transport with 3-h (long-term) recovery; 3 h (long-term) transport with 45-min recovery, and 3-h transport with 3-h recovery. Each treatment consisted of 6 replicates with 12 birds each. On d 46, all birds (except the control group) were transported according to a designed protocol. Transport time affected plasma glucose level (P < 0.05) and glycogen level (P = 0.06) in breast muscle as well as the area (P < 0.01) and density (P < 0.01) of IIa fibers. Glucose concentration increased slightly during the first 45 min of transport and then decreased dramatically in the long-term transported broilers (P < 0.05). Long-term transport decreased the concentration of breast glycogen (P = 0.06) and affected the size of IIa fibers in tibialis anterior by decreasing the area (P < 0.01) with an increase in density (P < 0.01). However, a long-term recovery after transport contributed to the homeostasis of blood corticosterone (CORT, P = 0.05) and low levels of glycogen (P < 0.05), lactate (P < 0.01), and glycolytic potential (P < 0.01) in thigh muscles. Interactions existed between transport and recovery time on area (P < 0.05) and density (P < 0.01) of IIa fibers. Furthermore, plasma nonesterified fatty acids increased significantly in the 3-h transport with 3-h recovery group (P < 0.05) in comparison with the control. These results suggested that transport induced the release of plasma CORT and glycopenia, which affected the contractive status of muscle fibers by changing their area and density, and enhanced glycolysis and even lipolysis. A long-term recovery after transport was beneficial in lowering plasma CORT levels and reducing muscle glycolysis, which might improve broiler meat quality.
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    ABSTRACT: The inferior pharyngeal constrictor (IPC) muscle functions during swallowing, respiration, and vocalization. The most-caudal portion of the IPC is believed to be part of the functional upper esophageal sphincter (UES). We hypothesized that the caudal fibers of the human IPC may have enzyme-histochemical characteristics similar to those of the cricopharyngeus muscle, a major component of the UES. In this study, human IPC muscles obtained from autopsy were studied using Sihler's stain to examine innervation patterns, and using myofibrillar ATPase, NADH tetrazolium reductase (NADH-TR), and succinic dehydrogenase (SDH) techniques to investigate the distribution and oxidative capacity of the slow- (type I) and fast- (type II) twitch fibers in the muscle. The results showed that the human IPC consists of at least two neuromuscular compartments (NMCs): rostral and caudal. Each of the NMCs was innervated by a separate nerve branch derived from the pharyngeal branch of the vagus nerve. The rostral NMC is faster (39% type I, 61% type II) than the caudal NMC (70% type I, 30% type II). In addition, two histochemically-delineated fiber layers were identified in the human IPC: a slow inner layer (SIL) with predominantly type I fibers (66%), and a fast outer layer (FOL) with predominantly type II fibers (62%) (P < 0.01). However, the dimensions of both fiber layers and proportions of the muscle fiber types varied with the NMCs. Specifically, the ratio of the thickness of the SIL to FOL was approximately 2:1 for the caudal NMC and approximately 1:2 for the rostral NMC, respectively. In the SIL the type I fibers accounted for 84% for the caudal NMC and 69% and 44% for the lower and upper portions of the rostral NMC. In contrast, the type II fibers in the FOL accounted for 46% for the caudal NMC and 67% and 74% for the lower and upper portions of the rostral NMC, respectively (P < 0.01). The caudal NMC of the IPC shared histochemical characteristics with the cricopharyngeus muscle, in that it contained predominantly slow oxidative fibers. Overall, the caudal NMC and the SIL in the IPC had high NADH-TR and SDH activities. However, different patterns of oxidative enzyme activity were identified in both type I and type II fibers. This study provided histochemical evidence for the concept that the caudal NMC within the IPC contributes to the functional UES. In addition, the two histochemically-defined fiber layers in the IPC may be a specialized adaptation in humans to enable different upper-airway functions during respiration, swallowing, and speech.
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    ABSTRACT: Cricopharyngeus (CP) muscle spasm can lead to severe dysphagia. Myotomy of the CP muscle was the treatment of choice. Recently, botulinum toxin type A (BtxA) has been used for CP spasm. It usually brings improvement in deglutition but most patients require reinjection in 3-5 months. We report a 35-year-old man who had an arteriovenous malformation hemorrhage in the brain stem resulting in CP spasm and consequently severe dysphagia. He received BtxA injection and deglutition and nutrition remained good one year after treatment. A literature review analyzing 28 patients and our patient showed negative correlations between age and BtxA dose and between age and duration. Efficacy was positively correlated with duration and BtxA dose was positively correlated with pretreatment severity. In conclusion, physicians would use higher doses on patients with more severe cases but use lower doses on older patients. Those who obtained better post-treatment results would enjoy longer effective duration. Thus, the effective duration of the BtxA is multifactorial.
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