Effect of Thyroid Hormone on<i>In Vivo</i>Contractility of the Canine Diaphragm

Miyashita, Akira; Suzuki, Shunsuke; Suzuki, Motoyoshi; Numata, Hiroyuki; Suzuki, Junnichi; Akahori, Tadashi; Ōkubo, Takao

doi:10.1164/ajrccm/145.6.1456

Cited by 10 publications

(13 citation statements)

References 4 publications

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“…We have previously reported that the ∆L/LFRC of Cru and Cos obtained during supramaximal phrenic nerve stimulation reached a plateau on the 14th day after the implantation of the sonomicrometers, and then remained constant for the next 4 weeks [13]. Furthermore, the magnitudes of the shortening were similar to those observed shortly after implantation [13].…”

Section: Critique On Methodologysupporting

confidence: 63%

See 1 more Smart Citation

Patterns of inspiratory muscle shortening during hypoxia and hypercapnia in dogs

Suzuki¹,

Suzuki²,

Akahori³

et al. 1997

Eur Respir J

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The shortening of parasternal intercostal muscles (Para) and crural (Cru) and costal diaphragms (Cos) are not precisely understood. We therefore examined shortening patterns of these inspiratory muscles by using chronically implanted sonomicrometers in dogs.To avoid acute effects of surgery, measurements were performed 3 weeks after implanting the sonomicrometers. Patterns of length changes of Para, Cru, and Cos were measured during hypoxia and hypercapnia under two levels of anaesthesia.Respiratory length change (∆L) was assessed as a percentage change relative to the resting length at functional residual capacity (LFRC). Peak tidal shortening was defined as the maximal change from LFRC (∆L/LFRC). Under light anesthesia, the ∆L/LFRC was the same among the three muscle groups at all tidal volumes (VT). Under deep anaesthesia, the ∆L/LFRC both of Cru and Cos exceeded that of Para. Under light anaesthesia, the maximal shortening velocity ((∆L/LFRC)/∆t ) of Cru was greater than that of Para. Under deep anaesthesia, the (∆L/LFRC)/∆t of Para was exceeded by that both of Cru and Cos. Furthermore, the (∆L/LFRC)/∆t of each inspiratory muscle was greater during hypoxia than during hypercapnia at equal volume.We conclude that: 1) the contribution of the diaphragm to ventilation increases during deep anaesthesia; 2) the muscle shortening velocity during hypoxia or hypercapnia is lower in parasternal intercostal muscles than in the diaphragm; and 3) there is no difference in the shortening pattern between crural and costal diaphragms. Eur Respir J 1997; 10: 430-436 Among the respiratory muscles of the chest wall, the intercostal muscles and the diaphragm act as the major respiratory muscles for breathing. Several reports have suggested that parasternal intercostal muscles (Para) are the primary muscles responsible for expanding the upper rib cage during inspiration [1,2]. The diaphragm is anatomically divided into two muscles, the crural (Cru) and costal parts (Cos) [3]. In animals, the activities of the inspiratory muscles have been studied mainly by electromyography (EMG) [4,5]. These studies have demonstrated that the intercostal muscles, Cru, and Cos are activated differently. On the other hand, studies on the mechanical activities of the inspiratory muscles have focused primarily on their overall movements, i.e. the rib cage and abdominal movements, by inductive plethysmography [6], or the volume-pressure relationships of the rib cage and the diaphragm-abdomen [7]. These studies have suggested that the contribution of the rib cage and diaphragm to ventilation is altered by the magnitude of ventilation or by anaesthesia.Recently, direct measurements of the changes in the lengths of the respiratory muscles have been reported by the use of sonomicrometry [8,9]. This technique allows an accurate measurement of any change in the length of respiratory muscles in vivo. However, EASTON and co-workers [10] found that there was a transient inhibition of diaphragmatic shortening after the upper abdominal surgery require...

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Section: Critique On Methodologysupporting

confidence: 63%

“…Sonomicrometric transducers were implanted in the diaphragm as reported previously [13]. A pair of sonomicrometric transducers (Murata Manufacturing Co., Kyoto, Japan), 2.5-3.0 mm in diameter and covered with epoxy resin, was implanted between the peritoneum and the muscle fibres.…”

Section: Surgical Proceduresmentioning

confidence: 99%

Patterns of inspiratory muscle shortening during hypoxia and hypercapnia in dogs

Suzuki¹,

Suzuki²,

Akahori³

et al. 1997

Eur Respir J

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“…In addition, T 3 treatment of mdx mice increases the size and frequency of lesions in the soleus, but not in fast-twitch muscles. Moreover, the muscle and fiber atrophy that typically accompany the hyperthyroid state often translates into decreased performance, especially in respiratory muscles (Miyashita et al 1992). …”

Section: Discussionmentioning

confidence: 99%

Consequences of thyroxine treatment on diaphragm and EDL of normal and dystrophic hamsters

Singh¹,

Schlenker²,

Singh³

et al. 2004

Can. J. Physiol. Pharmacol.

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Previously administration of thyroxine (T4) to dystrophic hamsters improved ventilation and slowed the progression of the disease. We hypothesized that the normalization of ventilation in these animals was due to T4 improving structural and functional characteristics of the diaphragm. In the present study, contractile characteristics of the diaphragm and the extensor digitorum longus (EDL) from normal and dystrophic hamsters were evaluated after two months of T4 treatment. Compared to their placebo-treated counterparts, diaphragms and EDLs of T4-treated normal hamsters showed increased optimal muscle lengths and twitch tension, decreased contraction times and increased fatigability. T4-treatment in dystrophic hamsters showed only an increase in diaphragmatic twitch tension development. Force-frequency curves before treatment were generally higher for the normal compared to dystrophic diaphragms and EDLs. T4 administration only increased the force in normal diaphragms at the lower frequencies and in the EDLs at the higher frequencies. Although T4 serum levels were increased in both T4-treated groups, triiodothyronine (T3) was much lower in the dystrophic compared to normal hamsters, suggesting that conversion of T4 to T3 was reduced in dystrophic hamsters. We conclude that the limited functional changes in the diaphragms of T4-treated dystrophic hamsters cannot account for the marked improvement in ventilation previously reported.

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“…5) [234] and oxidative modification of myofibrillar proteins contribute to diaphragmatic atrophy [235] and weakness in hyperthyroidism [235,236]. Proteolysis triggered by excess T3 levels [234,236] can be enhanced by administration of glucocorticoids [16].…”

Section: Respiratory Muscle Functionmentioning

confidence: 99%

Endocrinological derangements in COPD

Laghi

Adıgüzel²,

Tobin³

2009

European Respiratory Journal

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Chronic obstructive pulmonary disease (COPD) is no longer considered to affect only the lungs and airways but also the rest of the body. The systemic manifestations of COPD include a number of endocrine disorders, such as those involving the pituitary, the thyroid, the gonads, the adrenals and the pancreas.The mechanisms by which COPD alters endocrine function are incompletely understood but likely involve hypoxaemia, hypercapnia, systemic inflammation and glucocorticoid administration. Altered endocrine function can worsen the clinical manifestations of COPD through several mechanisms, including decreased protein anabolism, increased protein catabolism, nonenzymatic glycosylation and activation of the rennin-angiotensin-aldosterone system.Systemic effects of endocrine disorders include abnormalities in control of breathing, decreases in respiratory and limb-muscle mass and function, worsening of respiratory mechanics, impairment of cardiac function and disorders of fluid balance.Research on endocrine manifestations of COPD embraces techniques of molecular biology, integrative physiology and controlled clinical trials. A sound understanding of the various disorders of endocrine function associated with COPD is prudent for every physician who practices pulmonary medicine.

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Effect of Thyroid Hormone onIn VivoContractility of the Canine Diaphragm

Cited by 10 publications

References 4 publications

Patterns of inspiratory muscle shortening during hypoxia and hypercapnia in dogs

Patterns of inspiratory muscle shortening during hypoxia and hypercapnia in dogs

Consequences of thyroxine treatment on diaphragm and EDL of normal and dystrophic hamsters

Endocrinological derangements in COPD

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