A unique acid phosphatase location: the transverse tubule of avian fast muscle

Synopsis Acid phosphatase activity was localized cytochemically in the posterior latissimus dorsi muscle of the chicken. Reaction product was observed in three distinct structures: T-tubules, sarcoplasmic reticulum and dense bodies. Examination of cross-and longitudinal sections confirmed that the reaction product was membrane-limited. Acid phosphatase activity was observed in sarcoplasmic reticulum adjacent to the A-I junction and the A-band, in intermyofibrillar dense bodies located along the length of the fibre and in the T-tubules but not in the surface caveolae or in the lateral sacs of the sarcoplasmic reticulum. The uniqueness of the T-tubular localization with respect to cytochemical localizations in other muscles is discussed.     

Effects of colchicine on myofilament arrangement and the lysosomal system in skeletal muscle

Summary Colchicine was intraperitoneally administered chronically to adult male Sprague-Dawley rats. The ultrastructural study of hind-limb muscles revealed that myofilament desorientation resulted. Bundles of myofilaments were found coursing perpendicular or oblique to the longitudinal axis of the muscle fiber. It is concluded that a colchicine-sensitive factor is involved in maintaining normal orientation of myofibrils in mature muscle. Also found in the sarcoplasm of the colchicine treated animals were complex spheromembranous bodies. These bodies enveloped mitochondria or other organelles and appeared to be derived from the sarcoplasmic reticulum. The lysosomal nature of these bodies is indicated by the localization of acid phosphatase activity in them. Acid phosphatase activity was also displayed in the sarcoplasmic reticulum. The spheromembranous bodies seem to be part of a sarcotubulo-lysosomal system in skeletal muscle.This study was supported in part by N.I.H. Grant RR-5576.The author gratefully acknowledges the technical assistance of Mrs. Patricia Driscoll.     

Distribution of Acid Phosphatase in Paramecium caudatum: Its Relations with the Process of Digestion

SYNOPSIS. The distribution of acid phosphatase was investigated at the ultrastructural level in Paramecium caudatum. Acid phosphatase occurs in endoplasmic reticulum, Golgi apparatus, food vacuoles, autophagic vesicles, vacuolar and dense bodies. Some slight deposits are also seen in the mitochondria.
These observations point out that this hydrolase activity is related to digestive processes. The enzyme, originating from the endoplasmic reticulum and Golgi apparatus reaches the food vacuole or autophagic vesicle likely via the reticulum. The digestion of the bacteria or of the enclosed organelle gives rise to electronopaque material which is later found in dense bodies. These dense bodies are likely secondary lysosomes and it is possible that they may fuse with the young food vacuole or with autophagic vesicles.     

Increased autophagy in chloroquine-treated tonic and phasic muscles: An alternative view

Ultrastructural and cytochemical techniques were used to investigate autophagy in the tonic anterior (ALD) and phasic posterior (PLD) latissimus dorsi muscles of the chicken following chloroquine administration. Autophagic vacuoles were seen in the ALD after 1 day of chloroquine administration while no change was seen in the PLD until 3 days. In both muscles, autophagic vacuoles and myeloid bodies were found at the level of the I band. Myeloid bodies usually were found in the longitudinal rows of mitochondria in the ALD muscle. Some, but not all, of the autophagic vacuoles and myeloid bodies were cytochemically acid phosphatase positive, while the portion of the sarcoplasmic reticulum of both muscles which is normally acid phosphatase positive was devoid of activity following chloroquine administration. These observations are discussed in regard to accepted mechanisms of autophagy and the possible inhibition of autophagy in skeletal muscle tissue by chloroquine.     

Cytochemical studies on peroxisomes in rat and guinea pig myocardium

The enzymatic activity and distribution of peroxisomes (microbodies) in rat and guinea pig hearts were studied cytochemically, by means of oxidation of 3-3'-diaminobenzidine (DAB) and by using B-glycerophosphate and cytidine-5'-monophosphate as substrates. Peroxisomes were localized in proximity to mitochondria and sarcoplasmic reticulum and measured from 0.2 micrometers to 0.5 micrometers in diameter in both animal species. DAB positive bodies were seen both at pH 9.0 and pH 5.0 in rat myocardial cells. However, in guinea pig myocardial cells the reaction was observed only at pH 9.0, or very faintly at pH 5.0. Acid and alkaline phosphatases were not demonstrated in the peroxisomes. Lipid droplets were surrounded by a ring of dense granular reaction product for enzymes, such as acid and alkaline phosphatase, and lipofuscin granules were limited by acid phosphatase or DAB reaction products. The pathophysiological function of peroxisomes is discussed.     

Ultrastructural Localization of Acid Phosphatase in Starved Tokophrya infusionum*

SYNOPSIS. Young organisms of Tokophrya infusionum starved for several hr, are best suited for a study of the fine structure of this organism including the distribution of its organelles. Acid phosphatase was localized by a combined electron microscopy and cytochemical approach using modified Gomori methods. The enzyme was found in small dense bodies, spheroid vesicles, missile-like bodies, rough-surfaced endoplasmic reticulum, residue and autophagic vacuoles. The small dense bodies are thought to be primary lysosomes since electron micrographs show a) a continuity between the membrane of the rough-surfaced endoplasmic reticulum and that of the dense bodies and b) a connection between the contents of both structures when the dense bodies form from the endoplasmic reticulum.     

OBSERVATIONS ON THE FINE STRUCTURE OF PHARYNGEAL MUSCLE IN THE PLANARIAN DUGESIA TIGRINA

Pharyngeal muscle of the planarian Dugesia tigrina was studied by electron microscopy after osmium tetroxide fixation. The muscle cell was observed to contain one myofibril or bundle of myofilaments parallel to its longitudinal axis. The myofilaments were of two types, different in size and distribution. No Z lines or myofilament organization into cross or helical striations were seen. Dense bodies were seen as projections from an invagination of the plasma membrane and as dense lines parallel to the myofilaments. The muscle cells are surrounded by a plasma membrane which is structurally associated with dense body projections, with vesicles and cisternae of sarcoplasmic reticulum, and with synaptic nerve endings. The cell has sarcoplasmic projections perpendicular to its long axis; these projections are seen to contain the nucleus or mitochondria and granules. Mitochondria and granules are also seen in a sarcoplasm rim around the fibril. The dense bodies may serve as attachment for thin myofilaments and function in transmission of stimuli from plasma membrane to the interior of the fibril.     

Intracellular enzymes and their localization in slender and stumpy forms of Trypanosoma brucei rhodesiense

Acid phosphatase and cathepsin D activity is greater in stumpy than in slender forms, especially when estimations are made on a ‘light lysosomal’ fraction. Acid phosphatase is localized in the region of the flagellar pocket in slender forms but is present in lysosomes, phagolysosomes, autophagosomes and rough endoplasmic reticulum of stumpy forms. In stumpy forms dense bodies develop the macrocrystalline structure of peroxisomes. Intense enzyme activity in stumpy forms appears to be associated with absorption of lipid from the plasma by a mechanism similar to but of greater intensity than that described in atheromatous rabbit aorta.     

A phospholamban protein phosphatase activity associated with cardiac sarcoplasmic reticulum

Canine cardiac sarcoplasmic reticulum vesicles contain intrinsic phospholamban protein phosphatase activity, which is also effective in dephosphorylating phosphorylase a. The phosphatase associated with sarcoplasmic reticulum membranes was solubilized with Triton X-100 and subjected to chromatography on Mono Q HR 5/5 and polylysine-agarose. A single peak of phosphatase activity was eluted from each column and it was coincident for both phospholamban and phosphorylase a, used as substrates. Thermal denaturation of the enzyme resulted in progressive and coincident loss of both phospholamban and phosphorylase a phosphatase activities. Enzymic activity was partially inhibited by protein phosphatase inhibitor 1. Migration of the enzyme during sucrose density gradient ultracentrifugation corresponded to a globular protein with an apparent Mr of 46,000. This enzyme preparation could dephosphorylate both the calcium-calmodulin-dependent as well as the cAMP-dependent sites on phospholamban. Thus, dephosphorylation of phospholamban by this sarcoplasmic reticulum-associated phosphatase may participate in modulating sarcoplasmic reticulum function in cardiac muscle.     

Comparative study of the ring glands from wild type and 1(2)gl mutant drosophila melanogaster

Structural and functional changes have been correlated during metamorphic degeneration of a single muscle fiber, the plantar retractor of G. mellonella, its axon, and their junctions to determine which features persist as long as muscle contractility. Changes commence simultaneously in muscle and nerve near cuticular attachments, and spread towards the center. Alterations associated with the muscle, including appearance of collapsed tracheoles and mitochondria with dense bodies, begin late in the last larval instar. Within 12 hours after pupal ecdysis some tracheolar withdrawal occurs, sarcoplasmic reticulum becomes reduced, and many mitochondria have dense bodies, dense membranes, or are enlarged. By 17–19 hours primary myofilaments and striations begin to disappear, microtubules and autophagic vacuole-like bodies appear, and phagocytes invade the muscle. It remains partially contractile upon electrically stimulating its nerve, the ventral nerve, until these changes spread throughout the fiber. Neuromuscular junction changes, including appearance of dense mitochondria and isolation bodies, begin late in the last larval instar. Junctions become fewer, and none remain in those muscle areas where tracheoles, sarcoplasmic reticulum, and primary myofilaments have disappeared. Preliminary studies on nerve discharge activity to the muscle suggest that nerve silence occurs at approximately the time when the muscle loses all contractility. In some axons isolation bodies appear and neurotubules are lost, other axons remain unchanged, and new ones develop later in the pupal state. Phagocytes invade the neural lamella and it disappears in the late pupa, but it reappears in the adult. The adult ventral nerve has over three times more axons and a thinner layer of glial cells than the larval nerve.     

The pedal muscle of the land snail Megalobulimus oblongus (Gastropoda, Pulmonata): an ultrastructure approach

M. Cristina Faccioni-Heuser, Denise M. Zancan, Christiane Q. Lopes and Matilde Achaval. 1999. The pedal muscle of the land snail Megalobulimus oblongus (Gastropoda, Pulmonata): an ultrastructure approach. — Acta Zoologica (Stockholm) 80: 325–337
The ultrastructure of the pedal muscle of the Megalobulimus oblongus is described. This muscle consists of transverse, longitudinal and oblique bundles ensheathed in collagenous tissue. Each muscle cell is also ensheathed by collagen. The smooth muscle cells contain thin and thick filaments; the thin filaments are attached to dense bodies. These cells contain a simple system of sarcoplasmic reticulum, subsarcolemmal caveolae and mitochondria with dense granules in the matrix, and glycogen. Three types of muscle cells were identified. Type A cells exhibited densely packed myofilaments, abundant glycogen rosettes, numerous mitochondria and sarcoplasmic reticulum profiles. Type B cells exhibited scanty glycogen and mitochondria, few cisternae of sarcoplasmic reticulum and large intermyofibrillar spaces. Type C cells exhibited intermediate characteristics between type A and type B cells. Neither nexus nor desmosomes were observed between the muscle cell membranes. The muscle contains well developed connective tissue and blood vessels. These structures and the distribution of muscle cells are probably involved in the muscular-hydrostat system. The muscle is richly innervated, having neuromuscular junctions with clear and electron-dense synaptic vesicles. The clear vesicles probably contain acetylcholine because the axons to which they are connected arise from acetylcholinesterase positive neurones of the pedal ganglion. The other vesicles may secrete monoamines such as serotonin and/or neuropeptides such as substance P.     

Acid phosphatase activity in normal and sarcolytic myotubes in muscle anlagen of the human hand

Summary During physiological embryonic and fetal sarcolysis, regressive changes occur in the affected myotubes in the muscle anlagen of the human hand. These result in the fragmentation and destruction of myotubes and phagocytosis of most of the fragments. To assess the extent of participation of autophagia in the course of such changes, the acid phosphatase activity in the myotubes was studied light microscopically and electron microscopically. By the Gomori method, a low activity of acid phosphatase was found in normal myotubes, which was confined to some vesicles of the Golgi apparatus and membranes of tubules and vesicles evidently belonging to the sarcoplasmic reticulum. The acid phosphatase activity was elevated in sarcolytic myotubes. The enzyme was localized in dense bodies (lysosomes) and on membranes of various vacuoles. The azo-coupling reaction carried out using the semipermeable-membrane technique revealed a much higher activity of acid phosphatase than did the Gomori method, particularly in sarcolytic myotubes. The activity was concentrated in a narrow strip on their periphery and in their center. In electronograms of sarcolytic myotubes, vacuoles were found in places where high acid phosphatase activity was found. At times, the reaction was rather diffuse in some sarcolytic myotubes. The reaction was weaker in normal myotubes.From these findings it may be concluded that a rise of acid phosphatase activity occurs in sarcolysis, indicating an activation of autophagia in myotubes. By the action of their own hydrolases, the myotubes disintegrate and are phagocytized by macrophages.     

Ultrastructure of muscle cells in Siboglinum fiordicum (Pogonophora)

Two different muscle types are found in the body of Siboglinum fiordicum: body wall muscle and blood vessel muscle. Both are of a myomesothelial type. The myofibrils of the body wall muscle are non-striated and consist of thick and thin myofilaments. Scattered dense bodies and attachment plaques are described. The sarcoplasmic reticulum forms a three-dimensional network in the myofibrils and only peripheral couplings are observed. The thick filaments are of a paramyosin type and have a diameter ranging from 400-1500 A. The blood vessels muscle is non-striated, but sometimes a sarcomere-like organization has been observed. Both thick and thin filaments are present. The thick filaments have a diameter of 250-400 A and lack transverse striations. Dense bodies and attachment of plaques are few. The sparse sarcoplasmic reticulum is restricted to the myofibril periphery where it makes peripheral couplings with sarcolemma. The luminal surface of the vessels is lined by a basal lamina with collagen-like inclusions. No endothelium is found. The body wall muscle and the blood vessel muscle are compared with other muscle types described in invertebrates.     

The phospholamban phosphatase associated with cardiac sarcoplasmic reticulum is a type 1 enzyme.

Canine cardiac sarcoplasmic reticulum vesicles contain intrinsic protein phosphatase activity, which can dephosphorylate phospholamban and regulate calcium transport. This phosphatase has been suggested to be a mixture of both type 1 and type 2 enzymes (E. G. Kranias and J. Di Salvo, 1986, J. Biol. Chem. 261, 10,029-10,032). In the present study the sarcoplasmic reticulum phosphatase activity was solubilized with n-octyl-beta-D-glucopyranoside and purified by sequential chromatography on DEAE-Sephacel, polylysine-agarose, heparin-agarose, and DEAE-Sephadex. A single peak of phosphatase activity was eluted from each column and it was coincident for both phospholamban and phosphorylase a, used as substrates. The partially purified phosphatase could dephosphorylate the sites on phospholamban phosphorylated by either cAMP-dependent or calcium-calmodulin-dependent protein kinase(s). Enzymatic activity was inhibited by inhibitor-2 and by okadaic acid (I50 = 10-20 nM), using either phosphorylase a or phospholamban as substrates. The sensitivity of the phosphatase to inhibitor-2 or okadaic acid was similar for the two sites on phospholamban, phosphorylated by the cAMP-dependent and the calcium-calmodulin-dependent protein kinases. Phospholamban phosphatase activity was enhanced (40%) by Mg2+ or Mn2+ (3 mM) while Ca2+ (0.1-10 microM) had no effect. These characteristics suggest that the phosphatase associated with cardiac sarcoplasmic reticulum is a type 1 enzyme, and this activity may participate in the regulation of Ca2+ transport through dephosphorylation of phospholamban in cardiac muscle.     

Purification and characterization of phospholamban phosphatase from cardiac muscle

A protein phosphatase which dephosphorylates phospholamban was purified from canine cardiac cytosol. Purification involved sequential chromatography on DEAE-Sephacel, polylysine-agarose, heparin-agarose, Mono Q HR 10/10, and Superose 6. The enzyme was composed of three subunits with Mr = 63,000, 55,000, and 38,000, and it could dephosphorylate the sites on phospholamban phosphorylated by either cAMP-dependent or calcium-calmodulin-dependent protein kinase. Phospholamban phosphatase activity was enhanced 12-, 9-, and 3-fold by the divalent cations Mg2+, Mn2+, and Ca2+, respectively. The phosphatase was inhibited by PPi, ATP, NaF, and Pi and the degree of inhibition was different with each compound. The substrate specificity of the purified phosphatase for cardiac phosphoproteins was determined using troponin I, phospholamban, and highly enriched sarcolemmal and sarcoplasmic reticulum preparations, phosphorylated by the cAMP-dependent protein kinase. The phosphatase exhibited the highest activity with phospholamban as substrate. Thus, dephosphorylation of phospholamban by this phosphatase may participate in regulation of sarcoplasmic reticulum function in cardiac muscle.     

Ultrastructure of atrial and ventricular myocardium in the pike Esox lucius L. and mackerel Scomber scombrus L. (Pisces)

Summary Atrial and ventricular muscle in the pike and mackerel hearts consists of narrow, branching cells. The atrial cells in the two species are similar whereas the ventricular cells differ. The sarcolemma is attached to the Z and M lines of the sarcomere. Intercalated discs are common, and the transverse parts display desmosomes and intermediate junctions. Nexuses are uncommon and only occur in the longitudinal parts of the intercalated discs. The sarcoplasmic reticulum forms a regular hexagonal network on the myofibrillar surface. Subsarcolemmal cisternae form peripheral couplings at the I-A level. Junctional processes are usually inconspicuous, but an electron dense substance is present between the sarcolemma and the Junctional sarcoplasmic reticulum. Specific heart granules are common in atrial cells of both species and in ventricular cells of the pike, but are very scarce in mackerel ventricular muscle.This work was supported by grants from the Norwegian Research Council for Sciences and the Humanities     

Determination of calcium transport and phosphoprotein phosphatase activity in microsomes from respiratory and vascular smooth muscle.

1. Calcium transport into microsomal vesicles of respiratory (tracheal) smooth muscle was characterized. This calcium transport was ATP dependent and stimulated by the presence of the oxalate ion. The magnitude of transport was similar to that reported for microsomes from other types of smooth muscle. 2. Bovine and rabbit, heavy and light microsomes were isolated from respiratory (tracheal) and vascular (aortic) smooth muscle. Preincubation of these vesicles with cyclic AMP and protein kinase did not alter the transport of calcium into the vesicles. There uas no evidence of phosphate incorporation into microsomal membrane proteins. Similar results were obtained if phosphorylase b kinase replaced the combination of cyclic AMP and protein kinase during the preincubation. 3. The phosphoprotein phosphatase activity of cardiac sarcoplasmic reticulum and smooth muscle microsomes was determined. The activity of this enzyme was found to be several-fold less in the cardiac sarcoplasmic reticulum than in various smooth muscle microsome preparations.     

DISTRIBUTION OF PHOSPHATASES IN THE GOLGI REGION AND ASSOCIATED STRUCTURES OF THE THORACIC GANGLIONIC NEURONS IN THE GRASSHOPPER, MELANOPLUS DIFFERENTIALIS

The neuronal perikarya of the grasshopper contain sudanophilic lipochondria which exhibit an affinity for vital dyes. These lipochondria are membrane-delimited and display acid phosphatase activity; hence they correspond to lysosomes. Unlike those of most vertebrates, these lysosomes also hydrolyze thiamine pyrophosphate and adenosine triphosphate. Like vertebrate lysosomal "dense bodies," they are electron-opaque and contain granular, vesicular, or lamellar material. Along with several types of smaller dense bodies, they are found in close spatial association with the Golgi apparatus. The Golgi complexes are frequently arranged in concentric configurations within which these dense bodies lie. Some of the smaller dense bodies often lie close to or in association with the periphery of dense multivesicular bodies. Further, bodies occur that display gradations in structure between these multivesicular bodies and the dense lysosomes. Acid phosphatase activity is present in the small as well as the larger dense bodies, in the multivesicular bodies, and in some of the Golgi saccules, associated vesicles, and fenestrated membranes; thiamine pyrophosphatase is found in both the dense bodies and parts of the Golgi complex. The close spatial association of these organelles, together with their enzymatic similarities, suggests the existence of a functional or developmental relationship between them.     

Fine structure of fast-twitch and slow-twitch guinea pig muscle fibers

The guinea pig soleus muscle is a convenient model for the study of slow-twitch intermediate (STI) fiber ultrastructure because it is composed entirely of fibers of this class. Such fibers were compared with fast-twitch red (FTR) and fast-twitch white (FTW) fibers from the vastus lateralis muscle. FTW fibers are characterized by small, sparse mitochondria, a narrow Z line and, an extensive sarcoplasmic reticulum arranged primarily in longitudinal profiles at the A band and with numerous expansions at the I band. Abundant mitochondria with a dense matrix and subsarcolemmal and perinuclear aggregations are typical of FTR fibers. These fibers contain a plexus of sarcoplasmic reticulum at the A band and a less extensive network at the I band. The Z lines are wider (890 ± 74 Å) than those of FTW fibers (582 ± 62 Å). STI intermediate fibers are distinguished from other types by wide Z lines (1205 ± 58 Å), a faint M band, and a less extensive sarcoplasmic reticulum. Compared to FTR fibers, STI fiber mitochondria are usually smaller with less notable subsarcolemmal accumulations. FTW fibers have a more limited capillary supply, rarely contain lipid inclusions, and thus may be restricted to phasic activity. Extensive capillarity, mitochondrial and lipid context, and fast contraction times indicate possible phasic and tonic roles for FTR fibers. STI fibers, characterized by numerous lipid inclusions, extensive capillarity, relatively numerous mitochondria, but slow contraction-relaxation cycles, are morphologically suited for tonic muscle activity.     

可口革囊星虫肾管肌组织的结构特征

采用显微及亚显微技术观察了可1：7革囊星虫肾管肌组织的结构特征。肾管肌组织位于柱状上皮层下,由纵肌及环肌组成。肌细胞（肌纤维）呈长梭形,核位于细胞边缘并明显突向细胞外基质中,核周围有较多线粒体及少量内质网。肌纤维表面有许多囊状或指状突起的肌质囊,内含肌浆、光面内质网、线粒体及糖原颗粒。肌质囊之间的肌膜内面具膜相关电子致密斑。肌纤维内含粗、细两种肌丝,细肌丝围绕在粗肌丝周围,在肌丝之间分布有糖原颗粒、线粒体及胞质致密体。线粒体及糖原为肌纤维的代谢提供能量,肌组织的收缩对促进肾管的过滤排泄及繁殖时配子进入肾管可能起重要作用。