Evidence that myosin light chain phosphorylation regulates contraction in the body wall muscles of the sea cucumber

Nephtys lacks circular body-wall muscles. The chief antagonists of the longitudinal muscles are the dorso-ventral muscles of the intersegmental body-wall. The worm is restrained from widening when either set of muscles contracts by the combined influence of the ligaments, some of the extrinsic parapodial muscles, and possibly, to a limited extent, by the septal muscles. Although the septa are incomplete, they can and do form a barrier to the transmission of coelomic fluid from one segment to the next under certain conditions, particularly during eversion of the proboscis. Swimming is by undulatory movements of the body but the distal part of the parapodia execute a power-stroke produced chiefly by the contraction of the acicular muscles. It is suspected that the extrinsic parapodial muscles, all of which are inserted in the proximal half of the parapodium, serve to anchor the parapodial wall at the insertion of the acicular muscles and help to provide a rigid point of insertion for them. Burrowing is a cyclical process involving the violent eversion of the proboscis which makes a cavity in the sand. The worm is prevented from slipping backwards by the grip the widest segments have on the sides of the burrow. The proboscis is retracted and the worm crawls forward into the cavity it has made. The cycle is then repeated. Nephtys possesses a unique system of elastic ligaments of unusual structure. The anatomy of the system is described. The function of the ligaments appears to be to restrain the body-wall and parapodia from unnecessary and disadvantageous dilatations during changes of body-shape, and to serve as shock-absorbers against the high, transient, fluid pressures in the coelom, which are thought to accompany the impact of the proboscis against the sand when the worm is burrowing. From what is known of its habits, Nephtys is likely to undertake more burrowing than most other polychaetes.

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Myosin Light Chain Phosphorylation during Regional Myocardial Ischemia

Advances in Myocardiology ◽

10.1007/978-1-4757-4441-5_45 ◽

1983 ◽

pp. 479-487

Author(s):

P. Cummins ◽

D. M. Yellon ◽

D. J. Hearse

Keyword(s):

Myocardial Ischemia ◽

Light Chain ◽

Myosin Light Chain ◽

Myosin Light Chain Phosphorylation ◽

Regional Myocardial Ischemia

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Arteriolar vasodilation involves actin depolymerization

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00723.2017 ◽

2018 ◽

Vol 315 (2) ◽

pp. H423-H428

Author(s):

Philip S. Clifford ◽

Brian S. Ferguson ◽

Jeffrey L. Jasperse ◽

Michael A. Hill

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Sodium Nitroprusside ◽

Light Chain ◽

Myosin Light Chain ◽

Muscle Relaxation ◽

Nitric Oxide Donor ◽

Smooth Muscle Relaxation ◽

Myosin Light Chain Phosphorylation ◽

Actin Depolymerization

It is generally assumed that relaxation of arteriolar vascular smooth muscle occurs through hyperpolarization of the cell membrane, reduction in intracellular Ca2+ concentration, and activation of myosin light chain phosphatase/inactivation of myosin light chain kinase. We hypothesized that vasodilation is related to depolymerization of F-actin. Cremaster muscles were dissected in rats under pentobarbital sodium anesthesia (50 mg/kg). First-order arterioles were dissected, cannulated on glass micropipettes, pressurized, and warmed to 34°C. Internal diameter was monitored with an electronic video caliper. The concentration of G-actin was determined in flash-frozen intact segments of arterioles by ultracentrifugation and Western blot analyses. Arterioles dilated by ~40% of initial diameter in response to pinacidil (1 × 10−6 mM) and sodium nitroprusside (5 × 10−5 mM). The G-actin-to-smooth muscle 22α ratio was 0.67 ± 0.09 in arterioles with myogenic tone and increased significantly to 1.32 ± 0.34 ( P < 0.01) when arterioles were dilated with pinacidil and 1.14 ± 0.18 ( P < 0.01) with sodium nitroprusside, indicating actin depolymerization. Compared with control vessels (49 ± 5%), the percentage of phosphorylated myosin light chain was significantly reduced by pinacidil (24 ± 2%, P < 0.01) but not sodium nitroprusside (42 ± 4%). These findings suggest that actin depolymerization is an important mechanism for vasodilation of resistance arterioles to external agonists. Furthermore, pinacidil produces smooth muscle relaxation via both decreases in myosin light chain phosphorylation and actin depolymerization, whereas sodium nitroprusside produces smooth muscle relaxation primarily via actin depolymerization. NEW & NOTEWORTHY This article adds to the accumulating evidence on the contribution of the actin cytoskeleton to the regulation of vascular smooth muscle tone in resistance arterioles. Actin depolymerization appears to be an important mechanism for vasodilation of resistance arterioles to pharmacological agonists. Dilation to the K+ channel opener pinacidil is produced by decreases in myosin light chain phosphorylation and actin depolymerization, whereas dilation to the nitric oxide donor sodium nitroprusside occurs primarily via actin depolymerization. Listen to this article’s corresponding podcast at https://ajpheart.podbean.com/e/vascular-smooth-muscle-actin-depolymerization/ .

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Distribution of Saponins in the Sea Cucumber Holothuria lessoni; the Body Wall Versus the Viscera, and Their Biological Activities

Marine Drugs ◽

10.3390/md16110423 ◽

2018 ◽

Vol 16 (11) ◽

pp. 423 ◽

Cited By ~ 7

Author(s):

Yadollah Bahrami ◽

Wei Zhang ◽

Christopher M. M. Franco

Keyword(s):

High Performance ◽

Sea Cucumber ◽

Body Wall ◽

Biological Activities ◽

Folk Medicine ◽

Pharmaceutical Products ◽

The Body ◽

Triterpene Glycosides ◽

Partition Chromatography ◽

Wide Range

Sea cucumbers are an important ingredient of traditional folk medicine in many Asian countries, which are well-known for their medicinal, nutraceutical, and food values due to producing an impressive range of distinctive natural bioactive compounds. Triterpene glycosides are the most abundant and prime secondary metabolites reported in this species. They possess numerous biological activities ranging from anti-tumour, wound healing, hypolipidemia, pain relieving, the improvement of nonalcoholic fatty livers, anti-hyperuricemia, the induction of bone marrow hematopoiesis, anti-hypertension, and cosmetics and anti-ageing properties. This study was designed to purify and elucidate the structure of saponin contents of the body wall of sea cucumber Holothuria lessoni and to compare the distribution of saponins of the body wall with that of the viscera. The body wall was extracted with 70% ethanol, and purified by a liquid-liquid partition chromatography, followed by isobutanol extraction. A high-performance centrifugal partition chromatography (HPCPC) was conducted on the saponin-enriched mixture to obtain saponins with a high purity. The resultant purified saponins were analyzed using MALDI-MS/MS and ESI-MS/MS. The integrated and hyphenated MS and HPCPC analyses revealed the presence of 89 saponin congeners, including 35 new and 54 known saponins, in the body wall in which the majority of glycosides are of the holostane type. As a result, and in conjunction with existing literature, the structure of four novel acetylated saponins, namely lessoniosides H, I, J, and K were characterized. The identified triterpene glycosides showed potent antifungal activities against tested fungi, but had no antibacterial effects on the bacterium Staphylococcus aureus. The presence of a wide range of saponins with potential applications is promising for cosmeceutical, medicinal, and pharmaceutical products to improve human health.

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