慢性心衰大鼠心肌细胞内雷尼丁受体及集钙蛋白的表达

目的:研究慢性心衰大鼠心肌细胞内雷尼丁受体(RyR2)及其调节蛋白集钙蛋白的表达,探讨心衰心肌细胞内钙容量降低的机制。方法:雄性SD大鼠被随机分为心衰组和假手术组,运用激光扫描共聚焦显微镜、透射电子显微镜、免疫印迹等方法研究2组大鼠心肌细胞肌浆网内钙容量、心肌细胞超微结构及心肌细胞内肌浆网钙释放通道RyR2和其调节蛋白集钙蛋白表达的变化。结果:慢性心衰大鼠心功能左心室舒张末期压力、左室压力最大上升速率均显著低于假手术组。假手术组大鼠心肌细胞的肌小节完整,肌丝排列整齐,线粒体结构正常;心衰组大鼠部分心肌细胞肌丝溶解,线粒体肿胀,嵴断裂。慢性心衰大鼠心肌细胞肌浆网内钙容量显著低于假手术组。慢性心衰大鼠心肌细胞内RyR2的表达量无明显变化,集钙蛋白表达明显下降。结论:慢性心衰大鼠心肌细胞内集钙蛋白表达下调,可能是导致心肌细胞肌浆网钙容量减少的原因之一。     

葡萄糖-6-磷酸酶在大白鼠心肌细胞超微结构的定位

葡萄糖-6-磷酸酶(G6Pase)是内质网的标志酶,本研究观察了大白鼠左心室心肌细胞的G6Pase的定位。实验结果表明,G6Pase活性遍布于心肌细胞的肌浆网(内质网)腔内,包括肌原纤维之间的肌浆网小管、肌膜下池和核膜。尤其是酶的反应产物在肌原纤维处显示了肌浆网小管的特征性分布:即在A带处肌浆网小管排列紧密形成致密网格,而在I带处排列稀疏,形成多角形大网格。这种排列特点可能和肌肉的舒缩功能有关,在收缩时I带的细丝向A带粗丝处滑动,肌节缩短。在I带处肌浆网小管排列成大网格、稀疏,便于伸长或缩短,是适应性的分布。     

成人房室束、假腱索和节制索的亚显微构造

本文研究了两例成人房室束、假腱索和节制索的亚显微构造。结果表明,在成人房室束、假腱索和节制索中均可见浦肯野细胞,细胞宽而短,肌原纤维和组成肌原纤维的肌丝均较少;核多为一个,核周肌浆中有大量线粒体,核附近偶见高尔基复合体;肌浆中亦见肌浆网、糖原颗粒和溶酶体等。另外在房室束中,还可见一般心肌细胞和介于浦肯野细胞与一般心肌细胞之间的过渡细胞(或称移行细胞)。胶原纤维和毛细血管等分布在几种肌细胞之间。房室束浦肯野细胞的端与端之间有不甚典型的闰盘。相邻并列的过渡细胞之间见两种连接形式:一种是一个过渡细胞的分支与另一个过渡细胞的外侧面形成闰盘样连接;另一种是并列相邻的两个过渡细胞,以短的分支几乎呈直角互相连接。     

毒胡萝卜素诱导成年小鼠心肌细胞凋亡的实验研究

众所周知，心肌细胞的凋亡参与各种心血管疾病发生及发展的过程，而且，机体内有多种参与细胞凋亡的信号传导途径，其中由肌浆网（sarcoplasmic reticulum，SR）应激引起的信号传导径路的激活越来越引起重视。肌浆网是细胞内参与钙转运的细胞器，肌浆网膜上存在的钙泵（Ca^2＋-ATP酶）可促进细胞质钙进入肌浆网；而肌浆网钙泵抑制剂毒胡萝卜素（thapsigargin，TG）可减少钙内流，降低肌浆网的钙容量，升高胞质内Ca^2＋浓度，从而引起肌浆网应激反应，诱导细胞凋亡。     

失血性休克状态下的心肌超微结构

应用家免失血性休克模型观察心肌的超微结构改变。结果发现(1)间盘两侧的心肌纤维呈区带性病变,肌膜呈扇形膨出;Z带互相靠近,肌节缩短;Z带断裂,肌原纤维走向紊乱;线粒体移位至距间盘较远的地区;(2)间盘区以外广大地区心肌纤维显示细胞内水肿;线粒体肿胀,脊破坏减少;肌原纤维灶性溶解;肌浆网小管稀少、断离、扩张及囊泡化等改变。这些改变使心肌的供能装置、收缩结构以及兴奋收缩偶联过程遭到破坏,妨碍心肌收缩功能,从而构成并发急性心功能不全的超微结构基础。     

NCA对受磷蛋白敲除小鼠心肌兴奋-收缩偶联的作用

 目的: 硝酰基(HNO)在轻微增加细胞内钙的基础上可以显著增加心肌肌丝对钙离子的反应性。本研究中,我们应用崭新的HNO供体乙酸1-亚硝基环己酯(NCA)来观察HNO对受磷蛋白敲除(PLB-KO)小鼠心室梳状肌的作用。方法: 小鼠右心室的完整梳状肌被连接在张力换能器与刺激电极之间,肌小节长度设定在2.2~2.3μm之间,K-H液表面灌流后,Fura-2经玻璃微电极负载进行离子透入法检测[Ca²⁺]_i,同时测定心肌收缩张力的变化。结果: PLB-KO小鼠心室梳状肌比野生型(WT)小鼠具有更高的钙瞬变及收缩力,同时展示负性收缩力-收缩频率相关性(FFR)。NCA(2.5μmol/L)在不同浓度细胞外钙([Ca²⁺]_o)条件下增加PLB-KO及WT小鼠心肌收缩力,但并不影响PLB-KO小鼠的负性FFR。稳态条件下2组小鼠去肌膜梳状肌的收缩力-钙离子相关性无显著性差异,NCA则增加去肌膜梳状肌的钙离子的反应性。结论: NCA提供的HNO通过增加PLB-KO及WT小鼠心肌肌丝对钙离子的反应性而增强心肌收缩力;心肌细胞内钙瞬变的增加伴随收缩力的增强表明HNO可改善钙离子活性,进一步证实HNO作为正性肌力药物的作用效果。     

大白鼠肥大心肌细胞的超微结构及细胞化学研究

结扎大白鼠腹主动脉,使其狭窄,造成心脏负荷增加,饲养7周后,引起左心室心肌肥大。电子显微镜下,肥大的心肌细胞核大,核染色质淡,核仁大;核糖体和粗面内质网增生;高尔基体数目增多,体积增大,线粒体、溶酶体等也增多。对照组心肌细胞核相对较小,粗面内质网稀少,高尔基体亦小。本实验还采用细胞化学G6Pase和TPPase,分别显示肌浆网和高尔基体形态。肥大的心肌细胞除了肌浆网小管有酶反应外,增生的粗面内质网腔内有G6Pase反应产物。在肥大心肌细胞高尔基体显示了TPPase反应,更证实了高尔基体体积增大以及数目增多。本实验动物的心肌细胞,正处在工作负荷增加,蛋白质合成旺盛的心肌细胞肥大代偿期。     

犬肌硬膜桥的扫描电子显微镜观察

目的 扫描电子显微镜下观察犬寰枕间隙肌硬膜桥与硬脊膜及寰枕后膜的连接方式。方法 取6份犬枕下寰枕间隙组织进行扫描电子显微镜观察,记录并拍摄犬头后小直肌肌硬膜桥纤维与寰枕后膜及硬脊膜纤维的连接关系,分析肌硬膜桥与寰枕后膜及硬脊膜的纤维连接形式。结果 于寰枕间隙,肌硬膜桥纤维存在于头后小直肌与寰枕后膜,及寰枕后膜与硬脊膜之间。由犬头后小直肌腹侧发出的肌硬膜桥纤维平行排列,以锐角汇入寰枕后膜,并延续为寰枕后膜背侧浅层;寰枕后膜腹侧发出的与硬脊膜连接的肌硬膜桥纤维分成多束,束外有被膜包裹,内部纤维平行排列。寰枕后膜与硬脊膜之间的肌硬膜桥纤维最终以“编织”的方式汇入硬脊膜浅层,参与硬脊膜的构成。结论 肌硬膜桥纤维与硬脊膜纤维以编织的方式相连接,提示肌硬膜桥纤维可以有效地传递拉力。     

成人房室结的超微结构

目的　探讨正常成人房室结的超微结构特征。方法　利用透射电镜观察正常成年人房室结的细胞及其构筑。结果　正常成人房室结主要由起搏细胞 (P细胞 )和心肌细胞构成 ,移行细胞较少。P细胞位于心肌细胞之间 ,成群存在。P细胞多为椭圆或柱状 ,细胞核相对较大 ,细胞器较少。移行细胞的形态和结构介于P细胞和心肌细胞之间。心肌细胞较多 ,相互平行排列 ,与P细胞无特化连接。结论　成人房室结的起搏细胞较少 ,普通心肌细胞较多 ,有心肌化的倾向。     

孕鼠肝内胆汁淤积症对母鼠和胎鼠心脏的影响

目的探讨孕鼠肝内胆汁淤积症对母鼠和胎鼠心脏的影响。方法应用雌、孕激素建立妊娠肝内胆汁淤积大鼠模型,光镜和电镜观察母鼠和胎鼠心脏的病理改变。结果（1）胆淤组和对照组比较,孕鼠血清丙氨酸转氨酶（ALT）、门冬氨酸转氨酶（AST）、总胆汁酸（TBA）的差异有显著性（P〈0．01）。（2）胆淤组孕鼠肝脏光镜下见部分肝细胞有颗粒样变性和空泡变性,电镜下见肝组织中毛细胆管扩张,毛细胆管及肝细胞内见高电子致密物沉积。（3）胆淤组孕鼠胎盘光镜下见部分滋养细胞颗粒样变性和空泡变性。（4）胆淤组孕鼠心脏光镜下见心肌组织中局灶性心肌细胞颗粒样变性。（5）胆淤组胎鼠心脏光镜下见心肌组织中心肌细胞广泛空泡变性;电镜下见胎鼠心肌细胞内高电子致密物沉积,部分肌丝断裂,肌节模糊,细胞内线粒体水肿,脱髓鞘样改变。结论孕鼠肝内胆汁淤积症时高胆汁酸血症对母鼠和胎鼠心肌细胞均有明显的毒性作用,尤其以胎鼠心肌细胞病变更为严重。     

Development of the excitation-contraction coupling apparatus in skeletal muscle: peripheral and internal calcium release units are formed sequentially

Summary The development of calcium release units and of transverse tubules has been studied in skeletal muscle fibres from embryonal and newborn chicken. Three constituents of calcium release units: the tetrads, the feet and an internal protein directly associated with junctional surface of the sarcoplasmic reticulum are visualized by various electron microscope techniques. Evidence in the literature indicates that the three components correspond to the voltage sensors, the sarcoplasmic reticulum calcium release channels and the calcium binding protein calsequestrin respectively.We recognize two stages at which important events in membrane morphogenesis occur. The first stage coincides with early myofibrillogenesis (starting at approximately embryonal day E5.5), and it involves the assembly of calcium release units at the periphery of the muscle fibre in which feet and the internal protein are identified. Groups of tetrads also are present at very early stages and their disposition indicates a relation to the feet of peripheral couplings. Thus three major components of the excitation-contraction coupling pathway are in place as soon as myofibrils develop. The density of groups of tetrads in the surface membrane of primary and secondary fibres is similar, despite differences in developmental stages. The second stage involves the formation of a complex transverse tubule network and of internal sarcoplasmic reticulum-transverse tubule junctions, while peripheral couplings disappear. This stage starts abruptly (between E15 and E16) and simultaneously in primary and secondary fibres. It coincides with the myotube-to-myofibre transition. The two stages are separated by a relatively long intervening period (between E9 and E16). During the latter part of this period some primitive transverse tubules appear, and form junctions with the sarcoplasmic reticulum, but they remain strictly located at the periphery of the fibre and are not numerous. Finally, after the second stage there is a prolonged (up to 4 weeks) period of maturation, during which density of free sarcoplasmic reticulum increases, triads acquire a location at the A-I junction and fibre type differences appear. We conclude that a system for calcium uptake, storage and release exists at the periphery of the myotube during early myogenesis. The complexity of the system and its ability to deliver calcium through the entire fibre develop in parallel to the formation of myofibrils.     

Structure and molecular organisation of the sarcoplasmic reticulum of skeletal muscle fibers

Activation of muscle contraction is a rapid event that is initiated by depolarization of the plasma membrane and transverse (T) tubules, which following transduction in the interior of the muscle cell, activate the release of calcium from the sarcoplasmic reticulum (SR). Pioneer studies using electron microscopy defined the organization of the sarcoplasmic reticulum and the details of the junctions between sarcoplasmic reticulum and T tubules, which are essential for translating the electrical signal on the plasma membrane to calcium release from the sarcoplasmic reticulum. Molecular biology and biochemistry studies have revealed the presence of several proteins located on the sarcoplasmic reticulum, some of which participate together with the ryanodine receptors to the assembly of a large multi-protein complex, while others, like the calcium pumps, have independent localization and activities. As a whole, the current view of this system contemplates the existence of a high level of structural organization in the sarcoplasmic reticulum with respect to the localization of ryanodine receptors and other proteins. In this review we shall summarize studies on the expression and possible functional significance of the ryanodine receptor type 3 in mammalian skeletal muscles and recent studies aimed to dissect the mechanisms that establish the organization of the SR in striated muscles.     

Co-expression in CHO cells of two muscle proteins involved in excitation-contraction coupling

Summary Ryanodine receptors and dihydropyridine receptors are located opposite each other at the junctions between sarcoplasmic reticulum and either the surface membrane or the transverse tubules in skeletal muscle. Ryanodine receptors are the calcium release channels of the sarcoplasmic reticulum and their cytoplasmic domains form the feet, connecting sarcoplasmic reticulum to transverse tubules. Dihydropyridine receptors are L-type calcium channels that act as the voltage sensors of excitation-contraction coupling: they sense surface membrane and tranverse tubule depolarization and induce opening of the sarcoplasmic reticulum release channels. In skeletal muscle, ryanodine receptors are arranged in extensive arrays and dihydropyridine receptors are grouped into tetrads, which in turn are associated with the four subunits of ryanodine receptors. The disposition allows for a direct interaction between the two sets of molecules.CHO cells were stably transformed with plasmids for skeletal muscle ryanodine receptors and either the skeletal dihydropyridine receptor, or a skeletal-cardiac dihydropyridine receptor chimera (CSk3) which can functionally substitute for the skeletal dihydropyridine receptor, in addition to plasmids for the ₂, and subunits. RNA blot hybridization gave positive results for all components. Immunoblots, ryanodine binding, electron microscopy and exposure to caffeine show that the expressed ryanodine receptors forms functional tetrameric channels, which are correctly inserted into the endoplasmic reticulum membrane, and form extensive arrays with the same spacings as in skeletal muscle. Since formation of arrays does not require coexpression of dihydropyridine receptors, we conclude that self-aggregation is an independent property of ryanodine receptors. All dihydropyridine receptor-expressing clones show high affinity binding for dihydropyridine and immunolabelling with antibodies against dihydropyridine receptor. The presence of calcium currents with fast kinetics and immunolabelling for dihydropyridine receptors in the surface membrane of CSk3 clones indicate that CSk3-dihydropyridine receptors are appropriately targeted to the cell's plasmalemma. The expressed skeletal-type dihydropyridine receptors, however, remain mostly located within perinuclear membranes. In cells coexpressing functional dihydropyridine receptors and ryanodine receptors, no junctions between feet-bearing endoplasmic reticulum elements and surface membrane are formed, and dihydropyridine receptors do not assemble into tetrads. A separation between dihydropyridine receptors and ryanodine receptors is not unique to CHO cells, but is found also in cardiac muscle, in muscles of invertebrates and, under certain conditions, in skeletal muscle. We suggest that failure to form junctions in co-transfected CHO cell may be due to lack of an essential protein necessary either for the initial docking of the endoplasmic reticulum to the surface membrane or for maintaining the interaction between dihydropyridine receptors and ryanodine receptors. We also conclude that formation of tetrads requires a close interaction between dihydropyridine receptors and ryanodine receptors.     

A correlated thin-section and freeze-fracture analysis of guinea pig adrenocortical cells

Comparison of the fine structural features of guinea pig adrenocortical cells as seen in thin sections with those revealed by freeze-fracture confirms the structural appearance of steroid-secreting cells as interpreted from thin sections and reveals significant new features of the membranous organelles. Smooth-surfaced endoplasmic reticulum appears as a network of tubules, interwoven or in parallel, and as cisternae, fenestrated and non-fenestrated. These elements are tightly packed in the deeper cortical cells, excluding other organelles from their domain. Tubules and fenestrated cisternae possess randomly distributed intramembranous particles on their PF faces, while closely packed non-fenestrated cisternae possess aggregates of particles interspersed with aparticulate regions on their PF faces. These differences in particle distribution suggest functional specialization among the various forms of reticulum. Mitochondria appear as elongated structures of varying shape. Freezefracture reveals that all their cristae have circular origins from the inner membrane. Sinuous tubules, which appear as tubules in section, and straight tubules, which appear as lamellae in section, arise from single sites. Flattened sac-like cristae may have multiple circular origins. Definite contact points seen between inner and outer membranes may facilitate passage of molecules, including steroids, into the mitochondrial compartments. Lysosomes and peroxisomes, which are easily identified in thin sections with the aid of cytochemistry, are difficult to identify with certainty by freezefracture. Single membrane-bound granules of slightly smaller diameter than mitochondria may represent lysosomes. Smaller granules interconnected with the tubular reticulum, as well as dilated regions of this organelle, may represent peroxisomes. Plasma membranes show no indication of tight junctions but do have abundant gap junctions which show a zonal differentiation: small gap junctions throughout the cortex, medium-sized regularly shaped gap junctions in zona fasciculata externa, and large irregular gap junctions in zona fasciculata interna and zona reticularis. The large junctions cover planar areas as well as surfaces of projections of one cell into another. Such junctions may allow passage of ions as well as of low-molecular-weight substances between the cells, facilitating or even amplifying the response to trophic hormone stimulation.     

Heterogeneity of T-tubule geometry in vertebrate skeletal muscle fibres

Summary Average dimensions of transverse tubules were obtained from electron micrographs of thin sections of mammalian and amphibian skeletal muscle fibres and the effect of transverse tubule geometry on the electrical characteristics of the fibres has been considered. The preparations examined were toad sartorius, mouse soleus, rat extensor digitorum longus, soleus and sternomastoid muscles. The T-tubule dimensions varied considerably between the different preparations and the average volume to surface ratio of the transverse tubule in amphibian fibres (8.1 nm) was generally greater than that in mammalian fibres (3.0–6.2 nm). The small volume to surface ratio of the mammalian transverse tubule would tend to reduce the electrical space constant of the transverse tubule system and reduce the rate of cross-sectional activation of the fibres during a twitch contraction. The area of transverse tubule membrane in junctional contact with the sarcoplasmic reticulum was determined and was found to be greater in mammalian fibres than in amphibian fibres. The relative areas of junctional contact, along a unit length of transverse tubule, were the same in rat extensor digitorum longus and soleus fibres.     

Cytological studies of muscle dedifferentiation and differentiation during limb regeneration of the newt Triturus

During limb regeneration of the newt Triturus, muscle first dedifferentiates giving rise to mesenchymal cells which, subsequently, differentiate to reform normal muscle. In dedifferentiating muscle, myofibrils and elements of the sarcoplasmic reticulum decrease gradually in number. Myofilaments become less distinct and seem to be supplanted by zones of amorphous material. Large masses of glycogen accumulate in dedifferentiating cells and mitochondria show a transient enlargement. In the later stages of dedifferentiation, glycogen decreases in amount while cytoplasmic ribosomes and cisternae of rough-surfaced endoplasmic reticulum appear. Mesenchymal cells are formed by disappearance of all traces of myofilaments, by further elaboration of rough endoplasmic reticulum, and increase in number of Golgi complexes. During the earliest stages of differentiation, muscle has less endoplasmic reticulum and many more free ribosomes which occur in clusters or linear chains. Thin (?70 A) and thick (?135 A) filaments appear in the cytoplasm, often in association with ribosomal olusters, and shortly thereafter aggregate into small fibrils. In early fibrils, the thin filaments overlap the thick to produce I and A bands and the free ends of the thin filaments converge and cross to mark the site of the Z line. Fibrils enlarge by addition of filaments along their sides and at their ends. In larger fibrils, the H band and M line are apparent. Initially, the transverse tubular system develops by the confluence of vesicular inpocketings of the surface plasma membrane. The smooth sarcoplasmic reticulum is continuous with rough-surfaced membranous cisternae. Some of the smooth tubules, probably sarcoplasmic reticulum, contain intracisternal masses of dense granular material and are situated adjacent to the Z line. When dense material occurs in the membranous structures, material of similar density and texture appears within the adjacent Z line. Normal muscle fibers are formed by fusion of myoblasts, increase in number and size of myofibrils, organization of transverse tubules and sarcoplasmic reticulum into triads, loss of ribosomes, and appearance of glycogen.     

BASAL CELL ADENOMA WITH PARALLEL TUBULES IN STROMAL CELLS OF THE PAROTID GLAND

A case of basal cell adenoma in the right parotid region of a 51 years old male was reported. The tumor measured 2.5 cm x 3 cm, was spherical and covered with a fibrous capsule. Histologically, it was a tubular monomorphic adenoma with scant edematous interstitial tissue. The stromal cells stained positively by the PAP method using anti-S-100 protein serum. Electron microscopically, the tumor cells forming tubules had many microvilli at the luminal surface, many filaments in the cytoplasm and well developed des-mosomes in the intercellular junctions. Ordinary intracellular organelles of the tumor cells were small in number, and their nuclei were oval with shallow indentation. In the dilated rough endoplasmic reticulum of the stromal cells, many straight parallel tubules were found. The tubules measured from 15 nm to 25 nm thick and 3.5 γm long in the longitudial sections and from 25 nm to 30 nm in diameter with electron lucent core and poor coat in the cross sections. Other cell organelles of the stromal cells were small in number, and filaments and dense attachments were found in the ectoplasm. Around the stromal cells there was a discontinous basement membrane. ACTA PATHOL. JPN. 34 : 1449–1458. 1984.     

Alternate disposition of tetrads in peripheral couplings of skeletal muscle

Summary The sarcoplasmic reticulum forms junctions with the surface membrane (peripheral couplings), which are structurally and functionally equivalent to the junctions between sarcoplasmic reticulum and transverse tubules (triads and dyads). Feet (ryanodine receptors, or sarcoplasmic reticulum calcium release channels) are disposed in arrays in the junctional sarcoplasmic reticulum membrane. Tetrads (groups of four dihydropyridine receptors, each called a unit) are disposed in ordered arrays in junctional domains of transverse tubules and surface membrane. We measured three parameters of tetrad arrays in peripheral couplings from three different species: (1) the centre-to-centre distances between tetrads (intertetrad spacing); (2) the angle between lines joining tetrad units and those joining the centres of tetrads (skew angle); (3) the centre-to-centre distance between tetrad units (intratetrad spacing). These measurements are compared with those predicted from models of feet and tetrad arrays. Intratetrad spacings and skew angles are consistent with an interaction of tetrads with alternate feet and with a location of tetrad units over feet subunits. The slightly larger size of the intratetrad spacing relative to the distance between feet subunits indicates that tetrads may be larger than feet, despite the fact that the molecular weight of DHPRs is less than that of feet subunits. This is offered as a possible explanation for the association of tetrads with alternate feet. Arrays of tetrads tend to be incomplete in images from freeze-fractures, due to lack of some of the units composing the tetrads. Since it is not possible to establish which units are actually absent and which are missing from the images due to fracturing problems, the average ratio between DHPRs and feet cannot be accurately determined.     

Differential response of the membrane systems involved in excitation–contraction coupling to early and later postnatal denervation in rat skeletal muscle

We compared the morphological features of the membrane systems involved in excitation–contraction (E–C) coupling during early postnatal development stages in rat skeletal muscles (tibialis anterior) denervated either at birth or 7 days after birth. Four obvious structural changes are observed in the arrangement of the transverse (T) tubule network and the disposition of triads following early postnatal denervation: (1) an increase in the longitudinal segments of the T tubule network, (2) changes in the direction and disposition of triads, (3) the appearance of caveolae clusters, (4) the appearance of pentads and heptads (i.e. a close apposition of two or three T tubule elements with three or four elements of terminal cisternae of sarcoplasmic reticulum). The increased presence of longitudinal T tubules parallels the loss of cross striations, and this in turn is due to misalignment of the myofibrils. The clusters of caveolae appear almost exclusively in muscle fibres denervated at birth, and pentads and heptads are more frequently observed in muscles denervated at 7 days. The differential growth of muscle fibres in response to denervation leads to the formation of abnormal membrane systems involved in the E–C coupling with very unique morphological features, which differ from the case of denervation in adult muscle fibres.     

Basal cell adenoma with parallel tubules in stromal cells of the parotid gland

A case of basal cell adenoma in the right parotid region of a 51 years old male was reported. The tumor measured 2.5 cm x 3 cm, was spherical and covered with a fibrous capsule. Histologically, it was a tubular monomorphic adenoma with scant edematous interstitial tissue. The stromal cells stained positively by the PAP method using anti-S-100 protein serum. Electron microscopically, the tumor cells forming tubular had many microvilli at the luminal surface, many filaments in the cytoplasm and well developed desmosomes in the intercellular junctions. Ordinary intracellular organelles of the tumor cells were small in number, and their nuclei were oval with shallow indentation. In the dilated rough endoplasmic reticulum of the stromal cells, many straight parallel tubules were found. The tubules measured from 15 nm to 25 nm thick and 3.5 micrometers long in the longitudinal sections and from 25 nm to 30 nm in diameter with electron lucent core and poor coat in the cross sections. Other cell organelles of the stromal cells were small in number, and filaments and dense attachments were found in the ectoplasm. Around the stromal cells there was a discontinuous basement membrane.