Co-clustering of Golgi complex and other cytoplasmic organelles to crescentic region of half-moon nuclei during apoptosis

Early apoptosis is defined by stereotypic morphological changes, especially evident in the nucleus, where chromatin condenses and compacts, and assumes a globular, half-moon or crescent-shaped morphology. Accumulating evidence suggests that cytoplasmic organelles such as mitochondria and the Golgi complex are major sites of integration of pro-apoptotic signaling. In this study, cytoplasmic organelles including Golgi complex, mitochondria, endosomes, lysosomes, and peroxisomes were shown to condense at the same unique region adjacent to the crescentic nucleus during a relatively early stage of apoptosis induced by staurosporine or other agents. The co-clustering phenomenon may be caused by shrinkage of cytoplasm during apoptosis although cytoskeletal markers actin and tubulin were not condensed and appeared excluded. These data suggest the co-clustering of cytoplasmic organelles plays an interesting role during the progression of the apoptotic process. It is possible that modification of pro-apoptotic proteins may arise as a result of the interplay of these cytoplasmic organelles.     

LYSOSOMES AND GERL IN NORMAL AND CHROMATOLYTIC NEURONS OF THE RAT GANGLION NODOSUM

The rat ganglion nodosum was used to study chromatolysis following axon section. After fixation by aldehyde perfusion, frozen sections were incubated for enzyme activities used as markers for cytoplasmic organelles as follows: acid phosphatase for lysosomes and GERL (a Golgi-related region of smooth endoplasmic reticulum from which lysosomes appear to develop) (31–33); inosine diphosphatase for endoplasmic reticulum and Golgi apparatus; thiamine pyrophosphatase for Golgi apparatus; acetycholinesterase for Nissl substance (endoplasmic reticulum); NADH-tetra-Nitro BT reductase for mitochondria. All but the mitochondrial enzyme were studied by electron microscopy as well as light microscopy. In chromatolytic perikarya there occur disruption of the rough endoplasmic reticulum in the center of the cell and segregation of the remainder to the cell periphery. Golgi apparatus, GERL, mitochondria and lysosomes accumulate in the central region of the cell. GERL is prominent in both normal and operated perikarya. Electron microscopic images suggest that its smooth endoplasmic reticulum produces a variety of lysosomes in several ways: (a) coated vesicles that separate from the reticulum; (b) dense bodies that arise from focal areas dilated with granular or membranous material; (c) "multivesicular bodies" in which vesicles and other material are sequestered; (d) autophagic vacuoles containing endoplasmic reticulum and ribosomes, presumably derived from the Nissl material, and mitochondria. The number of autophagic vacuoles increases following operation.     

An ultrastructural study of osmiophilia in normal human oesophageal epithelium

Summary Oesophageal biopsies were obtained from patients with normal oesophagi during fibre-optic endoscopy for upper gastro-intestinal symptoms. They were studied with the prolonged osmication technique. The forming face of the Golgi apparatus was demonstrated in the basal and lower prickle cells. These cells also showed osmium deposition in their mitochondria, endoplasmic reticulum, perinuclear cisternae and lysosomes. The capillary endothelial cells also showed osmium deposition in their Golgi apparatus and endoplasmic reticulum.     

Nonuniform distribution of sodium in the rat hepatocyte

The volume of the nucleus, endoplasmic reticulum (including Golgi complex), mitochondria, and cytoplasmic ground substance was measured in rat hepatocytes by stereological methods. The Na content was also measured by flame photometry. Variations in Na content correlated significantly with variations in volume of nucleus and endoplasmic reticulum. From the correlation parameters, Na concentrations were estimated as follows: nucleus, 108 mM; endoplasmic reticulum (ER) (including Golgie complex) 27 mM; cytoplasm (including and remaining organelles) 16 mM.     

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.     

Wandering cells in the nephron of the mudskipper Periophthalmus koelreuteri (Pallas)

Wandering cells that infiltrate between the principal cells of the nephron of the mudskipper Periophthalmus koelreuteri were examined by transmission electron microscope. These cells were found at various levels between the tubule cells and were more abundant in the proximal and collecting segments. These cells have cytoplasmic processes and large spherical nuclei. Their cytoplasm appears electron dense and contains many lysosomes, rough endoplasmic reticulum, free ribosomes, some mitochondria and Golgi profiles. Their ultrastructural features indicate that they may be phagocytic.     

Cytoplasmic O-glycosylation prevents cell surface transport of E-cadherin during apoptosis.

Cellular adhesion is regulated by members of the cadherin family of adhesion receptors and their cytoplasmic adaptor proteins, the catenins. Adhesion complexes are regulated by recycling from the plasma membrane and proteolysis during apoptosis. We report that in MCF-7, MDA-MB-468 and MDCK cells, induction of apoptosis by agents that cause endoplasmic reticulum (ER) stress results in O-glycosylation of both beta-catenin and the E-cadherin cytoplasmic domain. O-glycosylation of newly synthesized E-cadherin blocks cell surface transport, resulting in reduced intercellular adhesion. O-glycosylated E-cadherin still binds to beta- and gamma-catenin, but not to p120-catenin. Although O-glycosylation can be inhibited with caspase inhibitors, cleavage of caspases associated with the ER or Golgi complex does not correlate with E-cadherin O-glycosylation. However, agents that induce apoptosis via mitochondria do not lead to E-cadherin O-glycosylation, and decrease adhesion more slowly. In MCF-7 cells, this is due to degradation of E-cadherin concomitant with cleavage of caspase-7 and its substrate poly(ADP-ribose) polymerase. We conclude that cytoplasmic O-glycosylation is a novel, rapid mechanism for regulating cell surface transport exploited to down-regulate adhesion in some but not all apoptosis pathways.     

Glycosylated nuclear lectin CBP70 also associated with endoplasmic reticulum and the Golgi apparatus: does the "classic pathway" of glycosylation also apply to nuclear glycoproteins?

The subcellular plurilocalization of some lectins (galectin-1, galectin-3, galectin-10, calreticulin, etc.) is an intriguing problem, implying different partners according to their localization, and involvement in a variety of cellular activities. For example, the well-known lectin, galectin-3, a lactose-binding protein, can act inside the nucleus in splicing events, and at the plasma membrane in adhesion, and it was demonstrated that galectin-3 interacts in the cytoplasm with Bcl-2, an antiapoptotic protein. Some years ago, our group isolated a nuclear lectin CBP70, capable of recognizing N-acetylglucosamine residues. This lectin, first isolated from the nucleus of HL60 cells, was also localized in the cytoplasm. It has been demonstrated that CBP70 is a glycosylated lectin, with different types of glycosylation, comparing cytoplasmic and nuclear forms. In this article, we have studied the localization of CBP70 in undifferentiated HL60 cells by electron microscopy, immunofluorescence analysis, and subcellular fractionation. The results obtained clearly demonstrated that CBP70 is a plurilocalized lectin that is found in the nucleus, at the endoplasmic reticulum, the Golgi apparatus, and mitochondria, but not at the plasma membrane. Because CBP70, a nuclear glycoprotein, was found to be associated also with the endoplasmic reticulum and the Golgi apparatus where the glycosylation take place, it raised the question: where does the glycosylation of nuclear proteins occur?     

Axin expression reduces staurosporine-induced mitochondria-mediated cell death in HeLa cells

Cytoplasmic axin expression frequently produces punctuate structures in cells, but the nature of axin puncta has not been fully elucidated. In an effort to analyze cytoplasmic axin puncta, we established HeLa cells expressing axin in a doxycycline-inducible manner (HeLa-Axin). We observed that axin accumulated in an aggregate-like pattern in perinuclear areas and appeared to be associated with mitochondria, Golgi apparatus, and endoplasmic reticulum (ER), but not lysosomes. Further biochemical analysis suggested that some part of the cytoplasmic axin pool was associated with mitochondria. In addition, mitochondrial proteins [i.e., cytochrome oxidase IV (CoxIV) and cytochrome c] were slightly higher in HeLa-Axin cells than in HeLa-EV cells, suggesting altered mitochondrial degradation. HeLa-Axin cells were then treated with staurosporine (STS) to determine if the mitochondria-induced apoptosis pathway was altered. Compared to STS-treated control cells (HeLa-EV), HeLa-Axin cells had less STS-induced cytotoxicity and reduced caspase-3 activation and PARP cleavage. Given that mitochondria outer membrane potential was unchanged, HeLa-Axin cells might be relatively resistant to STS-mediated mitochondrial damage. Mitochondria associated with axin aggregates were resistant to detergent-mediated permeabilization. These results suggest that axin forms aggregate-like structures in association with mitochondria, which render mitochondria resistant to STS-induced membrane damage and cytotoxicity.     

ELECTRON MICROSCOPIC RADIOAUTOGRAPHIC DETECTION OF SITES OF PROTEIN SYNTHESIS AND MIGRATION IN LIVER

The sites of synthesis of proteins and their subsequent migration in rat liver have been studied during a 75 min period after labeling of liver-slice proteins by exposure to leucine-H³ for 2 min. Incorporation of the label into protein began after 1 min and was maximal by 4 min. Electron microscopic radioautography showed that synthesis of proteins in hepatocytes occurs mainly on ribosomes, particularly those in rough endoplasmic reticulum and, to some extent, in nuclei and mitochondria. Most of the newly formed proteins leave the endoplasmic reticulum in the course of 40 min, and concurrently labeled proteins appear in Golgi bodies, smooth membranes, microbodies, and lysosomes. A likely pathway for the secretion of some or all plasma proteins is from typical rough endoplasmic reticulum to a zone of reticulum which is partially coated with ribosomes, to the Golgi apparatus, and thence to the cell periphery. The formation of protein by reticuloendothelial cells was measured and found to be about 5% of the total protein formed by the liver.     

Ultrastructure of the pineal organ of the killifish,Fundulus heteroclitus,with special reference to the secretory function

Summary The pineal organ of the killifish, Fundulus heteroclitus, was investigated by electron microscopy under experimental conditions; its general and characteristic features are discussed with respect to the photosensory and secretory function. The strongly convoluted pineal epithelium is usually composed of photoreceptor, ganglion and supporting cells. In addition to the well-differentiated photosensory apparatus, the photoreceptor cell contains presumably immature dense-cored vesicles (140–220 nm in diameter) associated with a well-developed granular endoplasmic reticulum in the perinuclear region and the basal process. These dense-cored vesicles appear rather prominent in fish subjected to darkness. The ganglion cell shows the typical features of a nerve cell; granular endoplasmic reticulum, polysomes, mitochondria and Golgi apparatus are scattered in the electron-lucent cytoplasm around the spherical or oval nucleus. The dendrites of these cells divide into smaller branches and form many sensory synapses with the photoreceptor basal processes. Lipid droplets appear exclusively in the supporting cell, which also contains well-developed granular endoplasmic reticulum and Golgi apparatus. Cytoplasmic protrusions filled with compact dense-cored vesicles (90–220 nm in diameter) are found in dark-adapted fish. The origin of these cytoplasmic protrusions, however, remains unresolved. Thus, the pineal organ of the killifish contains two types of dense-cored vesicles which appear predominantly in darkness. The ultrastructural results suggest that the pineal organ of fish functions not only as a photoreceptor but also as a secretory organ.We thank Dr. Grace Pickford for the fishes.     

Tubular lysosomes in rat and gerbil pinealocytes

Ultracytochemical demonstration of acid phosphatase (AcPase) in pinealocytes of rat and Mongolian gerbil (Meriones unguiculatus) has revealed an existence of tubular lysosomes (30-200 nm in diameter and more than 5 micron long) in their cytoplasm. The tubular lysosomes arise by bulging from GERL cisternae (Golgi apparatus, endoplasmic reticulum, lysosomes) and spread throughout the whole cell body without forming an anastomosing network. Numerous varicosities are characteristic for the tubular lysosomes whose similarity with grumose bodies has lead to conclusion that the vermiculate variety of the latter are almost certainly tubular lysosomes. The role of these organelles is unknown. Their possible engagement in a rapid cytoplasmic remodelling of the pinealocyte body in answer to various stimuli has been discussed.     

线粒体在细胞凋亡中的介导作用

线粒体是细胞内产生能量的重要细胞器,被认为是细胞生存与死亡的调节中心。Bcl-2家族蛋白、内质网和溶酶体能引起线粒体膜通透性的改变,造成线粒体功能损伤,诱导细胞凋亡。本文主要综述线粒体在Bcl-2家族蛋白、内质网和溶酶体诱导细胞凋亡中作用的研究进展。     

Fine structure of spermatogonia and primary spermatocytes in rabbits

Summary The fine structure of rabbit Spermatogonia and primary spermatocytes in meiotic prophase has been studied with different methods of preparation, including a technique for acid phosphatase activity. The spermatogonial cytoplasm is rich in free ribosomes and containes moderate amounts of vesicular, smooth-surfaced endoplasmic reticulum and mitochondria, a simple Golgi-apparatus, some micropinocytotic vesicles, and occasional multivesicular bodies, vacuoles and dense bodies with acid phosphatase activity. The large type A Spermatogonia have a prominent nucleolus and their mitochondria sometimes form clusters with a dense intermitochondrial substance, similar to that in spermatocytes.The nucleus and cytoplasm of primary spermatocytes increase markedly in volume and density during meiotic prophase. The Golgi apparatus enlarges and becomes more differentiated and finally forms small proacrosome granules. The endoplasmic reticulum produces numerous small, mainly smooth vesicles and might also be the source of a new organelle: numerous piles of narrow cisternae with opaque contents. These piles disintegrate late in prophase. The mitochondria become aggregated in clusters with dense intermitochondrial substance and their internal structure is characterized by highly dilated cristae and small particles, interpreted as mitochondrial ribosomes, in the matrix. The role of these structures in the formation of new mitochondria is discussed. The clusters of mitochondria finally disperse and their cores of dense intermitochondrial substance, possibly containing ribonucleoprotein, coalesce into a large chromatoid body similar to that in spermatids. Micropinocytosis and a few lysosomes occur in most spermatocytes. The pachytene nuclei show prominent nucleoli and a distinct sex vesicle without any synaptinemal complex.The importance for spermatid differentiation of some events taking place in the cytoplasm of primary spermatocytes is emphasized.Financial support for this study was received from the Swedish Medical Research Council.     

Studies on the polymorphic spermatozoa of a marine snail. 2. Genesis of the eupyrene sperm

Spermiogenesis of the eupyrene sperm in the snail, Fusitriton oregonensis, was studied with light and electron microscopes. Endoplasmic reticulum, which encircles the nucleus in each spermatid, appears to connect with the Golgi body and to interconnect between adjacent spermatids via cytoplasmic bridges. It is suggested that as the Golgi body migrates around the nucleus the endoplasmic reticulum may circulate with it. The alignment of the proacrosome with the nucleus is effected by a 180° rotation of the Golgi body, after which it separates and migrates posteriorly with the residual cytoplasm. Each sperm possesses a well-developed intracellular digestive system as indicated by multivesicular bodies, residual bodies, and myeloid figures. Autophagy begins in the residual cytoplasm before it is released from the middle piece. Microtubules are found outside the nucleus and mitochondria during the final stages of spermiogenesis, when elongation is almost complete. These microtubules appear to be involved in the final shaping and twisting process, in which torsion is locked in the nucleus and the mitochondria spiral around the axoneme. The annulus attaches the distal centriole to the plasma membrane in the early spermatid and as flagellar production begins they move towards the implantation fossa at the base of the nucleus. There are two centrioles in the early spermatid, the distal centriole and procentriole. The small procentriole fuses with the distal centriole in the intranuclear canal to form the centriolar cap of the basal body. This cap is pushed through the end of the nuclear tube and is separated from the subacrosomal space by only the nuclear membranes.     

Transport and secretion of truncated T cell receptor beta-chain occurs in the absence of association with CD3

The T cell receptor (TCR) beta-chain is produced in the endoplasmic reticulum where it associates with the TCR alpha-chain and the members of the CD3 complex to form the complete receptor. When the other chains of the complex are not available, the beta-chain is rapidly degraded within the endoplasmic reticulum. When incomplete TCR.CD3 complexes are formed, they are transported through the Golgi apparatus and degraded in lysosomes. In this study, a truncated form of the TCR beta-chain has been made by removal of the transmembrane and cytoplasmic segments. Unlike the normal beta-chain, the truncated molecule is stable and is transported through the Golgi apparatus and secreted. This process occurs at a similar rate in both T and B cells, indicating that it is not affected by the presence or absence of CD3 components. These data suggest that an element in the transmembrane or cytoplasmic region of the beta-chain confers sensitivity to the degradative control mechanisms that regulate TCR expression.     

Occurrence of unusual heterogeneous lipid-containing granule-storing cells in the main excretory duct epithelium of the male mouse submandibular gland

Summary The fine structure of the main excretory duct epithelium of the male mouse submandibular glands was investigated by scanning and transmission electron microscopy. Three principal cell-types were observed: type I and II, and basal cells. This epithelium was characterized by the presence of intercellular canaliculi. Type-I cells were the most numerous. They had an abundance of mitochondria, well-developed Golgi apparatus, a few electron-lucent lipid-containing granules and poorly developed basal infoldings. These cells were also characterized by many glycogen granules throughout the cytoplasm and abundant smooth endoplasmic reticulum in the apical cytoplasm. Type-II cells were the second most numerous. Their most characteristic feature was the presence of abundant heterogeneous lipid-containing granules having acid phosphatase activity at the periphery. They were concentrated in the infra- and supranuclear cytoplasm. The granules may be derived from mitochondrial transformation and seem to be a special kind of secondary autolysosome. Type-II cells also contained abundant mitochondria throughout the cytoplasm, much smooth endoplasmic reticulum in the apical cytoplasm, a well developed Golgi apparatus adjacent to the heterogeneous lipid-containing granules and no basal infoldings. Basal cells were situated adjacent to the basal lamina. They had a large nucleus and the cytoplasm was filled with glycogen granules.     

Golgi apparatus and golgi zone

The author of this paper has attempted to clarify some problems concerning the nomenclature of Golgi apparatus and Golgi zone. The actual aim of this paper is to summarize — while using the more safe nomenclature—the existing knowledge about the functional relations between nucleus and cytoplasm arising from the study of the juxtanuclear zone by electron microscopy. Some observations lead to the assumption that the juxtanuclear zone is the place where cell components are formed or transformed. Considering its temporary character in proliferating cells and taking into account the connections with endoplasmic reticulum and the presence of pores, the nuclear membrane remains apparently a barrier restraining the spontaneous movement of substances and of cell components respectively between cytoplasm and karyoplasm that can be seen e.g. in the grouping of cytoplasmic formations in the juxtanuclear zone. In plant cells, within the zone mentioned agglomerations of different cell formations have been found, either the Golgi apparatus or mitochondria, secretion granules, lipid inclusions, vacuoles or plastids. Such a gathering of cytoplasmic material has been observed especially in young embryonic cells or in cells with retarded or stopped metabolism. The older and/or intensively active cells would then absolve an expansion of the cytoplasmic material into the whole cell. Similar formative mechanisms, now available for study during some ontogenic phases or at definite functional states only, could be effective even in the course of phylogenesis. From this point of view some of the formations described could be regarded as a kind of atavisms.     

Colleters in Bathysa nicholsonii K. Schum. (Rubiaceae): ultrastructure, secretion protein composition, and antifungal activity

Colleters are secretory structures well distributed in many organs of Angiosperms. Ultrastructurally, the colleters secretory cell presents an enhanced endoplasmic reticulum, Golgi apparatus, and mitochondria. Secretion synthesis, transportation, and passage through outer cell wall is poorly characterized. This study characterized the anatomy and ultrastructure of BATHYSA NICHOLSONII (Rubiaceae) colleters and evaluated the presence of protein in the secretion and its antifungal property. Samples were collected and prepared according to usual techniques in light and electron microscopy, electrophoresis, and fungal growth inhibition assay. Colleters are of a standard type, cylindrical and elongated, formed by one secretory epidermal palisade layer, and a central axis formed by parenchymatic cells and a vascular trace. Epidermal cells have dense cytoplasm with abundant ribosome, a nucleus, enhanced endoplasmic reticulum and Golgi apparatus. The outer cell wall presented morphologically distinct layers. The presence of secretory cavities was noted in all outer cell wall extents. Secretion preparations analyzed by SDS-PAGE showed that B. NICHOLSONII secretion is a mixture of proteins with molecular masses covering a range of approximately 66 to 24 kDa. This preparation presented an inhibitory effect on the fungi spore growth.