scholarly journals Anatomy of Cowper’s gland in humans suggesting a secretion and emission mechanism facilitated by cooperation of striated and smooth muscles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Satoru Muro ◽  
Janyaruk Suriyut ◽  
Keiichi Akita
Keyword(s):  
Smooth Muscle ◽  
Striated Muscle ◽  
Three Dimensional ◽  
Smooth Muscles ◽  
Levator Ani ◽  
Striated Muscles ◽  
External Urethral Sphincter ◽  
Macroscopic Anatomy ◽  
Dimensional Reconstruction ◽  
Perineal Muscle

AbstractThis study presents the detailed anatomy of the Cowper’s gland in humans. Elucidating the mechanism of secretion and emission of the Cowper’s gland requires analysis of the muscles around the Cowper’s gland. We hypothesized that the Cowper’s gland involves not only smooth muscle but also the striated muscles of the pelvic floor. Here, we provide comprehensive and three-dimensional anatomy of the Cowper’s gland and its surrounding structures, which overcomes the current local and planar understanding. In this study, seven male corpses of body donors were used to conduct macroscopic anatomy, histology, and three-dimensional reconstruction. The Cowper’s gland was surrounded laterally and posterosuperiorly by striated and smooth muscles, respectively. The striated muscle bundle was connected from the superficial transverse perineal muscle, levator ani, and external anal sphincter to the external urethral sphincter (rhabdosphincter). The smooth muscle was part of the deep transverse perineal muscle and entered between the bilateral Cowper’s glands and lobules. Our findings indicate that the secretion and emission of the Cowper’s gland in humans are carried out through the cooperation of striated and smooth muscles.

scholarly journals An invertebrate smooth muscle with striated muscle myosin filaments

2015 ◽  
Vol 112 (42) ◽  
pp. E5660-E5668 ◽  
Author(s):  
Guidenn Sulbarán ◽  
Lorenzo Alamo ◽  
Antonio Pinto ◽  
Gustavo Márquez ◽  
Franklin Méndez ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Actin Filaments ◽  
Striated Muscle ◽  
Smooth Muscles ◽  
Structural Similarity ◽  
Striated Muscles ◽  
Muscle Tissues ◽  
Myosin Filaments ◽  
Muscle Myosin ◽  
Surprising Finding

Muscle tissues are classically divided into two major types, depending on the presence or absence of striations. In striated muscles, the actin filaments are anchored at Z-lines and the myosin and actin filaments are in register, whereas in smooth muscles, the actin filaments are attached to dense bodies and the myosin and actin filaments are out of register. The structure of the filaments in smooth muscles is also different from that in striated muscles. Here we have studied the structure of myosin filaments from the smooth muscles of the human parasite Schistosoma mansoni. We find, surprisingly, that they are indistinguishable from those in an arthropod striated muscle. This structural similarity is supported by sequence comparison between the schistosome myosin II heavy chain and known striated muscle myosins. In contrast, the actin filaments of schistosomes are similar to those of smooth muscles, lacking troponin-dependent regulation. We conclude that schistosome muscles are hybrids, containing striated muscle-like myosin filaments and smooth muscle-like actin filaments in a smooth muscle architecture. This surprising finding has broad significance for understanding how muscles are built and how they evolved, and challenges the paradigm that smooth and striated muscles always have distinctly different components.

scholarly journals Three-dimensional reconstruction of caldesmon-containing smooth muscle thin filaments.

1993 ◽  
Vol 123 (2) ◽  
pp. 313-321 ◽  
Author(s):  
P Vibert ◽  
R Craig ◽  
W Lehman
Keyword(s):  
Smooth Muscle ◽  
Three Dimensional ◽  
Smooth Muscles ◽  
Smooth Muscle Contraction ◽  
Structural Basis ◽  
Actin Monomer ◽  
Thin Filaments ◽  
Outer Domain ◽  
Dimensional Reconstruction

Caldesmon is known to inhibit actomyosin ATPase and filament sliding in vitro, and may play a role in modulating smooth muscle contraction as well as in diverse cellular processes including cytokinesis and exocytosis. However, the structural basis of caldesmon action has not previously been apparent. We have recorded electron microscope images of negatively stained thin filaments containing caldesmon and tropomyosin which were isolated from chicken gizzard smooth muscle in EGTA. Three-dimensional helical reconstructions of these filaments show actin monomers whose bilobed shape and connectivity are very similar to those previously seen in reconstructions of frozen-hydrated skeletal muscle thin filaments. In addition, a continuous thin strand of density follows the long-pitch actin helices, in contact with the inner domain of each actin monomer. Gizzard thin filaments treated with Ca2+/calmodulin, which dissociated caldesmon but not tropomyosin, have also been reconstructed. Under these conditions, reconstructions also reveal a bilobed actin monomer, as well as a continuous surface strand that appears to have moved to a position closer to the outer domain of actin. The strands seen in both EGTA- and Ca2+/calmodulin-treated filaments thus presumably represent tropomyosin. It appears that caldesmon can fix tropomyosin in a particular position on actin in the absence of calcium. An influence of caldesmon on tropomyosin position might, in principle, account for caldesmon's ability to modulate actomyosin interaction in both smooth muscles and non-muscle cells.

The Ryanodine Receptor/Calcium Release Channel and its Interaction Partners

1998 ◽  
Vol 4 (S2) ◽  
pp. 968-969
Author(s):  
Terry Wagenknecht ◽  
Montserrat Samso
Keyword(s):  
Calcium Release ◽  
Striated Muscle ◽  
Ryanodine Receptors ◽  
Three Dimensional ◽  
Structural Complexity ◽  
Body Representation ◽  
Calcium Release Channel ◽  
Release Channel ◽  
Fk506 Binding Protein ◽  
Dimensional Reconstruction

Ryanodine receptors (RyRs) function as the major intracellular calcium release channels in striated muscle, where they also play a central role in excitation-contraction (e-c) coupling, the signal transduction process by which neuron-induced depolarization of the muscle plasma membrane leads to release of Ca from the sarcoplasmic reticulum. Structurally, RyRs are the largest ion channels known, being composed of 4 identical large subunits (565 kDa). In situ, RyRs interact with numerous proteins that are essential for e-c coupling or regulation thereof. Some of these ligands include calmodulin, a 12-kDa FK506-binding protein (FKBP, an immunophi1 in), calsequestrin, triadin, and the dihydropyridine receptor (DHPR).Detergent-solubilized, purified RyRs appear to retain their native structure as assessed by electron cryo-microscopy, and are amenable to three-dimensional reconstruction by single-particle image processing techniques. In Fig. 1, a solid-body representation of the reconstructed skeletal muscle RyR shows the structural complexity that is revealed at moderate resolutions (3-4 nm).

The Sarcoplasmic Reticulum of Smooth Muscle Fibers

1982 ◽  
Vol 37 (5-6) ◽  
pp. 481-488 ◽  
Author(s):  
L. Raeymaekers
Keyword(s):  
Smooth Muscle ◽  
Calcium Oxalate ◽  
Striated Muscle ◽  
Smooth Muscles ◽  
Morphological Characterization ◽  
Calcium Oxalate Crystals ◽  
Additional Amount ◽  
Skinned Smooth Muscle ◽  
Ca Uptake

Abstract The ability of the sarcoplasmic (endoplasmic) reticulum (SR, ER) of smooth muscle cells to accumulate Ca was demonstrated by measuring the uptake of 45Ca in fibers which were chemically skinned with saponin, and by electron cytochemistry of the accumulated Ca. The Ca uptake was dependent on ATP and it was stimulated by oxalate, as it is the case in SR of striated muscle. Electron microscopy of the skinned smooth muscle preparations revealed the presence of calcium oxalate deposits in the reticulum. The SR vesicles were isolated from several smooth muscles. The purification was carried out by taking advantage of the density increase of the SR vesicles after loading with calcium in the presence of oxalate. Among the muscles investigated the smooth muscle of the pig stomach was found to be the most suitable and it was selected for further biochemical and morphological characterization of the SR vesicles. These vesicles, which contain calcium oxalate crystals, were able to accumulate an additional amount of Ca. The Ca uptake was supported by several energy yielding substrates. Their order of potency was ATP > dATP ≃ UTP > ITP > GTP ≃ CTP. The rate of Ca uptake was two orders of magnitude slower than that in SR of skeletal muscle. The measurement of the level of phosphorylated Ca transport intermediate showed that this difference is due to smaller number of calcium transport sites per vesicle. The distribution of intramembrane particles in freeze-fractured specimens is in agreement with this conclusion.

The Three Dimensional Organization of Smooth Muscle: Information from Serial Section Reconstructions

1998 ◽  
Vol 4 (S2) ◽  
pp. 438-439
Author(s):  
R.A. Horowitz ◽  
C.M. Powers ◽  
P. Valero ◽  
R. Craig
Keyword(s):  
Smooth Muscle ◽  
Three Dimensional ◽  
Smooth Muscles ◽  
General Applicability ◽  
The Past ◽  
Myosin Filaments ◽  
Rabbit Portal Vein ◽  
Tension Generation ◽  
Parallel Arrays

Smooth muscle is a machine consisting of working and supporting elements whose structure and 3D organization must be elucidated for the mechanics of shortening and tension generation to be understood. Based on longitudinal and serial transverse sections of rabbit portal vein it was suggested that the contractile elements of smooth muscle formed “mini-sarcomeres”, analogous to skeletal muscle, containing parallel arrays of 3-5 myosin filaments 1.6-2.2 um long. Observations at the light microscopic level were consistent with this idea. The past decade has seen little further investigation into the in situ ultrastructure of this or other smooth muscles, and the general applicability of these findings remains unknown. We have taken advantage of recent methodological advances, which can provide full 3D computer representations of cellular organization based on EM data, using guinea pig taenia coli muscle as a model system.Serial transverse sections (Fig 1) were used to generate 3D reconstructions of the organization of the myosin filaments and their relation to dense bodies, actin bundles, mitochondria and other organelles.

Sarcoplasmic Reticulum Function in Smooth Muscle

2010 ◽  
Vol 90 (1) ◽  
pp. 113-178 ◽  
Author(s):  
Susan Wray ◽  
Theodor Burdyga
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Physiological Activity ◽  
Smooth Muscles ◽  
Outward Current ◽  
Integrated Approach ◽  
Transient Outward Current ◽  
Coupling Mechanism ◽  
Striated Muscles ◽  
Development And Aging

The sarcoplasmic reticulum (SR) of smooth muscles presents many intriguing facets and questions concerning its roles, especially as these change with development, disease, and modulation of physiological activity. The SR's function was originally perceived to be synthetic and then that of a Ca store for the contractile proteins, acting as a Ca amplification mechanism as it does in striated muscles. Gradually, as investigators have struggled to find a convincing role for Ca-induced Ca release in many smooth muscles, a role in controlling excitability has emerged. This is the Ca spark/spontaneous transient outward current coupling mechanism which reduces excitability and limits contraction. Release of SR Ca occurs in response to inositol 1,4,5-trisphosphate, Ca, and nicotinic acid adenine dinucleotide phosphate, and depletion of SR Ca can initiate Ca entry, the mechanism of which is being investigated but seems to involve Stim and Orai as found in nonexcitable cells. The contribution of the elemental Ca signals from the SR, sparks and puffs, to global Ca signals, i.e., Ca waves and oscillations, is becoming clearer but is far from established. The dynamics of SR Ca release and uptake mechanisms are reviewed along with the control of luminal Ca. We review the growing list of the SR's functions that still includes Ca storage, contraction, and relaxation but has been expanded to encompass Ca homeostasis, generating local and global Ca signals, and contributing to cellular microdomains and signaling in other organelles, including mitochondria, lysosomes, and the nucleus. For an integrated approach, a review of aspects of the SR in health and disease and during development and aging are also included. While the sheer versatility of smooth muscle makes it foolish to have a “one model fits all” approach to this subject, we have tried to synthesize conclusions wherever possible.

Isometric and isotonic contractions in airway smooth muscle

1977 ◽  
Vol 55 (4) ◽  
pp. 833-838 ◽  
Author(s):  
N. L. Stephens ◽  
W. Van Niekerk
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Striated Muscle ◽  
Smooth Muscles ◽  
Active Tension ◽  
Vitro Model ◽  
Tension Curves ◽  
Isotonic Contractions ◽  
Develop Tension

Canine tracheal smooth muscle was used as an in vitro model of smooth muscle in intrapulmonary airways to determine whether active tension curves derived from isometric and isotonic muscles are similar, and thus resemble striated muscle in this respect. Isometric, isotonic after-loaded, and isotonic free-loaded contractions elicited at different lengths and loads, were analysed. The data demonstrate that length–tension (L–T) diagrams are different in these various types of contractions for electrically and carbachol driven tracheal smooth muscles strips. In general, at any given length active tension is less in isotonic and free-loaded modes of contraction as compared with isometric. We conclude that the ability to actively develop tension at a given length in airway smooth muscle depends on the mode of contraction.

Mechanics and energetics of myosin molecular motors from nonpregnant human myometrium

2011 ◽  
Vol 111 (4) ◽  
pp. 1096-1105 ◽  
Author(s):  
Edouard R. Lecarpentier ◽  
Victor A. Claes ◽  
Oumar Timbely ◽  
Abdelilah Arsalane ◽  
Jacques A. Wipff ◽  
...  
Keyword(s):  
Rate Constants ◽  
Molecular Motors ◽  
Muscle Tension ◽  
Three Dimensional ◽  
Smooth Muscles ◽  
Load Level ◽  
Mechanical Activity ◽  
Human Myometrium ◽  
Striated Muscles ◽  
Tension Peak

Mechanical properties of spontaneously contracting isolated nonpregnant human myometrium (NPHM) were investigated throughout the whole continuum of load from zero load up to isometry. This made it possible to assess the three-dimensional tension-velocity-length (T-V-L) relationship characterizing the level of contractility and to determine crossbridge (CB) kinetics of myosin molecular motors. Seventy-seven muscle strips were obtained from hysterectomy in 42 nonpregnant patients. Contraction and relaxation parameters were measured during spontaneous mechanical activity. The isotonic tension-peak velocity (T-V) relationship was hyperbolic in 30 cases and nonhyperbolic in 47 cases. When the T-V relationship was hyperbolic, the Huxley formalism could be used to calculate CB kinetics and CB unitary force. At the whole muscle level and for a given isotonic load level, part of the V-L phase plane showed a common pathway, so that a given instantaneous length corresponded to only one possible instantaneous velocity, independent of time and initial length. At the molecular level, rate constants for CB attachment and detachment were dramatically low, ∼100 times lower than those of striated muscles, and ∼5 to 10 times lower than those of other smooth muscles. The CB unitary force was ∼1.4 ± 0.1 pN. NPHM shared similar basic contractile properties with striated muscles, reflected in the three-dimensional T-V-L relationship characterizing the contractile level. Low CB attachment and detachment rate constants made it possible to generate normal CB unitary force and normal muscle tension in NPHM, even though it contracted extremely slowly compared with other muscles.

Extractability and properties of the contractile proteins of vertebrate smooth muscle

1973 ◽  
Vol 265 (867) ◽  
pp. 169-181 ◽  
Keyword(s):  
Smooth Muscle ◽  
Ionic Strength ◽  
Striated Muscle ◽  
Smooth Muscles ◽  
Contractile Proteins ◽  
Biosynthetic Activity ◽  
Salting Out ◽  
Low Ionic Strength ◽  
The Comparative Study ◽  
Muscle Myosin

The vertebrate smooth muscles differ from the striated ones by their larger extracellular space, the smaller size of their cells and their high content in extracellular components. Furthermore, the smooth muscle cell is a bifunctional biological unit able to carry on also an important biosynthetic activity. The contractile proteins of vertebrate smooth muscle are extractable at low ionic strength contrarily to those of striated muscle. The partition of the salt extractable nitrogen between the low and high ionic strength extracts is very different in these two cases. Acidification of low ionic strength extracts of vertebrate smooth muscle at pH 5 allows precipitation of the contractile proteins quantitatively together with a large amount of contaminants typical of the smooth muscles. Comparison of the contractile proteins of vertebrate smooth muscle with their striated counterparts shows that actin is a very constant component of the contractile machinery, that tropomyosin holds an intermediate position, while myosin is the most variable. The smooth muscle myosin differs not only by some general properties as salting-out range and thermostability, but also by the behaviour of various parts of the molecule. The globular head has a different ATPase activity and is responsible for the very peculiar immunological behaviour of this myosin. The point along the myosin rod which is attacked by trypsin is much more resistant to proteolysis. The light meromyosin is more soluble and differs very much in amino acid composition. The comparative study of myosin reveals only minor variations from one species to the other but more or less wide ones within each species according to the type of muscle examined.

scholarly journals Digestive and respiratory tract motor responses associated with eructation

2013 ◽  
Vol 304 (11) ◽  
pp. G1044-G1053 ◽  
Author(s):  
Ivan M. Lang ◽  
Bidyut K. Medda ◽  
Reza Shaker
Keyword(s):  
Respiratory Tract ◽  
Striated Muscle ◽  
Smooth Muscles ◽  
Upper Esophageal Sphincter ◽  
Gastric Distension ◽  
Thoracic Esophagus ◽  
Striated Muscles ◽  
Motor Responses ◽  
Esophageal Sphincter ◽  
Secondary Peristalsis

We studied the digestive and respiratory tract motor responses in 10 chronically instrumented dogs during eructation activated after feeding. Muscles were recorded from the cervical area, thorax, and abdomen. The striated muscles were recorded using EMG and the smooth muscles using strain gauges. We found eructation in three distinct functional phases that were composed of different sets of motor responses: gas escape, barrier elimination, and gas transport. The gas escape phase, activated by gastric distension, consists of relaxation of the lower esophageal sphincter and diaphragmatic hiatus and contraction of the longitudinal muscle of the thoracic esophagus and rectus abdominis. All these motor events promote gas escape from the stomach. The barrier elimination phase, probably activated by rapid gas distension of the thoracic esophagus, consists of relaxation of the pharyngeal constrictors and excitation of dorsal and ventral upper esophageal sphincter distracting muscles, as well as rapid contraction of the diaphragmatic dome fibers. These motor events allow esophagopharyngeal air movement by promoting retrograde airflow and opening of the upper esophageal sphincter. The transport phase, possibly activated secondary to diaphragmatic contraction, consists of a retrograde contraction of the striated muscle esophagus that transports the air from the thoracic esophagus to the pharynx. We hypothesize that the esophageal reverse peristalsis is mediated by elementary reflexes, rather than a coordinated peristaltic response like secondary peristalsis. The phases of eructation can be activated independently of one another or in a different manner to participate in physiological events other than eructation that cause gastroesophageal or esophagogastric reflux.

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