Antibodies to the Golgi complex and the rough endoplasmic reticulum

Rabbits were immunized with membrane fractions from either the Golgi complex or the rough endoplasmic reticulum (RER) by injection into the popliteal lymph nodes. The antisera were then tested by indirect immunofluorescence on tissue culture cells or frozen, thin sections of tissue. There were may unwanted antibodies to cell components other than the RER or the Golgi complex, and these were removed by suitable absorption steps. These steps were carried out until the pattern of fluorescent labeling was that expected for the Golgi complex or RER. Electron microscopic studies, using immunoperoxidase labeling of normal rat kidney (NRK) cells, showed that the anti-Golgi antibodies labeled the stacks of flattened cisternae that comprise the central feature of the Golgi complex, many of the smooth vesicles around the stacks, and a few coated vesicles. These antibodies were directed, almost entirely, against a single polypeptide with an apparent molecular weight of 135,000. The endoplasmic reticulum (ER) in NRK cells is an extensive, reticular network that pervades the entire cell cytoplasm and includes the nuclear membrane. The anit-RER antibodies labeled this structure alone at the light and electron microscopic levels. They were largely directed against four polypeptides with apparent molecular weights of 29,000, 58,000, 66,000, and 91,000. Some examples are presented, using immunofluorescence microscopy, where these antibodies have been used to study the Golgi complex and RER under a variety of physiological and experimental condition . For biochemical studies, these antibodies should prove useful in identifying the origin of isolated membranes, particularly those from organelles such as the Golgi complex, which tend to lose their characteristic morphology during isolation.     

Annulate lamellae and single pore complexes in normal, SV40-transformed and tumor cells in vitro : A semiquantitative analysis

The frequency with which annulate lamellae (AL) and single cytoplasmic pore complexes appeared in selected groups (normal cell lines, SV40-, Rous sarcoma-, and 6/94 virus-infected cell lines, SV40-transformed cell lines, and both human and mouse tumor cell lines) was observed during standard electron microscopy techniques.All cell lines tested contained single pore complexes in the rough endoplasmic reticulum (RER). Further, it was found that at early passages WI38 cells have more single pore complexes than at later passages. In SV40-infected CV1 cells, the number of pore complexes increased during the infectious cycle, which indicates that the formation of these complexes may not be dependent on nuclear membrane remnants from mitosis. No pore complexes were found during mitosis, i.e., the formation of cytoplasmic pore complexes is by new synthesis or reformation. We speculate that all proliferating cells and germ cells generate pore complexes (similar to nuclear pore complexes) in their cytoplasmic membrane systems. With respect to annulate lamellae, it was found that:

1. (1) In cell lines where AL could be observed, not all cells exhibited AL stacks.

2. (2) “Normal” cells—such as human fetal lung (WI38) and monkey kidney (CV1) cells, mouse macrophages and fibroblasts, and cells from chicken explants—did not have AL stacks, but AL stacks could be induced by exposure to vinblastine.

3. (3) SV40-infected cells did not generate stacks of AL in the cell lines tested.

4. (4) SV40-transformed cells had AL stacks in a few cells or in many, depending on the cell line.

5. (5) The introduction of the SV40-containing chromosome 7 of human transformed LN-SV cells into a cell type that did not express AL formation caused it to form AL.

6. (6) AL were present up to 48 h after enucleation of mouse L cells, that is until the cells show signs of degeneration (which indicates that cellular upkeep of AL may not be dependent on the presence of the nucleus, as was suggested by the simultaneous disappearance of AL at mitosis).

7. (7) All tumor cell lines investigated were found to have AL stacks.

     

Effects of Brefeldin A on the Golgi complex, endoplasmic reticulum and viral envelope glycoproteins in murine erythroleukemia cells

This report concerns the effects of Brefeldin A (BFA): i) on the Golgi complex and the ER of retrovirus-transformed murine erythroleukemia (MEL) cells and, ii) on the viral proteins these cells express. Golgi complexes were extensively disorganized by BFA. Within 5 min, most stacked cisternae were converted to vesicles scattered throughout the centrosphere region. By 30 min, the Golgi complexes were completely disassembled. Only clusters of small vesicles ("Golgi remnants") persisted in the vicinity of the centrioles and microtubule-organizing centers. Some of these small vesicles had a simple coat structure on their membranes. Over the next 1 to 2 h of BFA treatment, the number of vesicles in the Golgi area decreased concomitantly with the expansion of a predominantly smooth membrane portion of the ER, consisting of a network of dilated tubules in continuity with regular RER cisternae, annulate lamellae and the nuclear envelope. By electron microscopy, viral glycoproteins appeared to accumulate on the membranes of this network, and immature virions were found to bud preferentially into its cisternal space. Viral accumulations increased with time under BFA. The rest of the RER appeared normal, apparently unaffected by the drug. Preferential virion budding suggests that this expanding network is a chemically differentiated part of the ER. By immunofluorescence, antibodies to viral envelope proteins gave a punctate staining at the surface of control cells, presumably in the areas of virion budding, whereas relatively large intracellular masses of antigens were found in BFA-treated cells. We assume that these masses represent the differentiated parts of the ER. Taken together, these findings suggest that BFA blocks intracellular transport of newly synthesized cellular and viral proteins immediately distal to the distinct compartment of the ER in which virion budding preferentially occurs. BFA effects are rapidly and fully reversible. Within 1 min of the removal of the drug, stacks of Golgi cisternae began to reappear in the vicinity of the centrioles, and by 30 min, Golgi complexes regained their normal structural appearance.     

The Giant Stacked Rough Endoplasmic Reticulum and Its Activity During Cotton Microspore Development

The giant stacked rough endoplasmic reticulum(S-RER)is discovered in the study of cotton microsporogenesis. These giant S-RER are randomly dispersed in the outerpart of the microspore cytoplasm and are easily visualized ,because they have sufficient number and are large enough for examination under light microscope. The diameters of those stacks attain to a range of 2.0—4.5μm. Specific characteristics of S-RER vary with the developmental stage and metabolic state, but they may be included into two main types :one is small and simple, the other is large and complex. The giant stacks may be composed of more than 50 parallel cisternae. Of course, between the main types there are many transitional forms. In addition, a few special configurations of S-RER was observed which the cisternae always become vesicularized at the peripheral portion of the stacks occurring near the plasma membrane (PM). In this case,the S-RER itself may be further lost its own structural property,instead of substituted a lot of small vesicles at its original site. It may also be called vesicular RER. Those vesicles derived from RER cisternae bear ribosomes on the outer surface. On the other hand,vesicles as a major vesicle may be directly formed at the ends of RER cisternae, which, in fact, serve as transition elements. The dynamic activities of those vesicles during the spore metabolic processes are conducted via two pathways operative:(1)the vesicles detach from the RER end and migrate towarss PM,then the vesicle membrane fuses with PM and the contents of the vesicles are discharged, (2) vesicles fuse together among themselves to form provacuolar bodies in the outer part of the spore cytoplasm. Several provacuolar bodies may further converge more and more to form small vacuoles. From the data studied the following conclusions may be drawn: (1)although the S-RER presented during cotton microsporogenesis is much the same as that in mature pollen grains of some plants,yet in this study S-RER always shows functional activities. So that S-RER is not limitted to represent an inactive RER configuration. (2)During the development of cotton microspore,the enlargement of the cell size is bound to follow a rapid increase and great extension of the vacuoles. It indicates that a rapid synthesis of endomembrane materials must be involved in the growth of microspore. The supply of membrane materials is one of the important functions of S-RER.     

High-resolution calcium mapping of the endoplasmic reticulum-Golgi-exocytic membrane system. Electron energy loss imaging analysis of quick frozen-freeze dried PC12 cells.

The calcium pools segregated within the endoplasmic reticulum, Golgi complex, exocytic, and other organelles are believed to participate in the regulation of a variety of cell functions. Until now, however, the precise intracellular distribution of the element had not been established. Here, we report about the first high-resolution calcium mapping obtained in neurosecretory PC12 cells by the imaging mode of the electron energy loss spectroscopy technique. The preparation procedure used included quick freezing of cell monolayers, followed by freeze-drying, fixation with OSO4 vapors, resin embedding, and cutting of very thin sections. Conventional electron microscopy and high-resolution immunocytochemistry revealed a high degree of structural preservation, a condition in which inorganic elements are expected to maintain their native distribution. Within these cells, calcium signals of nucleus, cytosol, and most mitochondria remained below detection, whereas in other organelles specific patterns were identified. In the endoplasmic reticulum, the distribution was heterogeneous with strongly positive cisternae (more often the nuclear envelope and stacks of parallel elements that are frequent in quick frozen preparations) lying in the proximity of or even in direct continuity with other, apparently negative cisternae. The Golgi complexes were labeled strongly and uniformly in all cisternae and part of their vesicles, with no appreciable differences along the cis-trans axis. Weaker or negative signals were recorded from the trans-Golgi network elements and from scattered vesicles, whereas in contrast secretion granules were strongly positive for calcium. These results are discussed in relation to the existing knowledge about the mechanisms of calcium transport in the variations organelles, and about the processes and functions regulated by organelle lumenal calcium in eukaryotic cells.     

Virus-neuron interactions in the mouse brain infected with Japanese encephalitis virus

The virus-host interactions between Japanese encephalitis (JE) virus and mouse brain neurons were analyzed by electron microscopy. JE virus replicated exclusively in the rough endoplasmic reticulum (RER) of neurons. In the early phase of infection, the perikaryon of infected neurons had relatively normal-looking lamellar RER whose cisternae showed focal dilations containing progeny virions and characteristic endoplasmic reticulum (ER) vesicles. The reticular RER, consisted of rows of ribosomes surrounding irregular-shaped, membrane-unbounded cisternae and resembled that observed in JE-virus-infected PC12 cells, were also seen adjacent to the lamellar RER. The appearance of the reticular RER indicated that RER morphogenesis occurred in infected neurons in association with the viral replication. The fine network of Golgi apparatus was extensively obliterated by fragmentation and dissolution of the Golgi membranes and their replacement by the electron-lucent material. As the infection progressed, the lamellar RER was increasingly replaced by the hypertrophic RER which had diffusely dilated cisternae containing multiple progeny virions and ER vesicles. The Golgi apparatus, at this stage, was seen as coarse, localized Golgi complexes near the hypertrophic RER. In the later phase of infection, RER of infected neurons showed a degenerative change, with the cystically dilated cisternae being filled with ER vesicles and virions. Small, localized Golgi complexes frequently showed vesiculation, vacuolation, and dispersion. The present study, therefore, indicated that during the viral replication the normal lamellar RER which synthesized neuronal secretory and membrane proteins was replaced by the hypertrophic RER which synthesized the viral proteins. The hypertrophic RER eventually degenerated into cystic RER whose cisternae were filled with viral products. The constant degenerative change which occurred in the Golgi apparatus during the viral replication suggested that some of the viral proteins transported from RER to the Golgi apparatus were harmful to the Golgi apparatus and that increasing damage to the Golgi apparatus during the viral replication played the principal role in the pathogenesis of JE-virus-infected neurons in the central nervous system.     

The fine structure and phosphatase cytochemistry of the Golgi complex and associated structures in the Sertoli cells of Syrian hamsters

The Golgi complex in the Sertoli cell of the Syrian hamster is well developed and consists of stacks of cisternae and associated vesicles. The inner- and outermost cisternae of the Golgi stacks are usually moderately dilated and exhibit numerous fenestrations. The middle portions of the intermediate cisternae are greatly flattened and not fenestrated, but toward the periphery these cisternae gradually become dilated and show a few fenestrations. On the inner aspect of the Golgi stacks the following structures are seen frequently: (1) one or two series of linearly arrayed circular profiles some of which are interconnected by tubules; (2) networks of anastomosing tubules with circular or oval meshes (800 to 1200 A in diameter); and/or (3) irregularly disposed tubules. The circular profiles and tubules are approximately 450 A in diameter. Acid phosphatase activity was localized in these anastomosing tubules when the tissues were incubated for more than one hour in a modified Gomori's medium (Barka and Anderson, 1963). Strong thiamine pyrophosphatase activity was demonstrated in the inner one to three cisternae of the Golgi stacks but not in the associated tubules. The system of the Golgi associated tubules is morphologically and histochemically distinct from the Golgi stacks and is probably equivalent to the Golgi-endoplasmic reticulum-lysosome system (GERL) in other cell types. The three dimensional aspects of the GERL-equivalent system are discussed.     

Herpes simplex virus 1 envelopment follows two diverse pathways

Herpesvirus envelopment is assumed to follow an uneconomical pathway including primary envelopment at the inner nuclear membrane, de-envelopment at the outer nuclear membrane, and reenvelopment at the trans-Golgi network. In contrast to the hypothesis of de-envelopment by fusion of the primary envelope with the outer nuclear membrane, virions were demonstrated to be transported from the perinuclear space to rough endoplasmic reticulum (RER) cisternae. Here we show by high-resolution microscopy that herpes simplex virus 1 envelopment follows two diverse pathways. First, nuclear envelopment includes budding of capsids at the inner nuclear membrane into the perinuclear space whereby tegument and a thick electron dense envelope are acquired. The substance responsible for the dense envelope is speculated to enable intraluminal transportation of virions via RER into Golgi cisternae. Within Golgi cisternae, virions are packaged into transport vacuoles containing one or several virions. Second, for cytoplasmic envelopment, capsids gain direct access from the nucleus to the cytoplasm via impaired nuclear pores. Cytoplasmic capsids could bud at the outer nuclear membrane, at membranes of RER, Golgi cisternae, and large vacuoles, and at banana-shaped membranous entities that were found to continue into Golgi membranes. Envelopes originating by budding at the outer nuclear membrane and RER membrane also acquire a dense substance. Budding at Golgi stacks, designated wrapping, results in single virions within small vacuoles that contain electron-dense substances between envelope and vacuolar membranes.     

The presence of vasoactive intestinal polypeptide (VIP)-like-immunoreactive nerve fibres and VIP-receptors in the pineal gland of the Mongolian gerbil (Meriones unguiculatus)

Summary The photocytes and other endodermal cells composing the wall of the meridional canals of the comb-jelly, Mnemiopsis leidyi, were investigated by transmission electron microscopy. Although many of these cells possess distinctive features such as a ciliary apparatus, lysosome-like bodies or vacuoles, they share with photocytes the presence of a network of rough endoplasmic reticulum (RER) whose cisternae enwrap large mitochondria and are aligned along the subsurface of the plasma membrane. A stereological analysis of organelle content in photocytes confirms the prominence of the RER in these cells and a shift of RER from mitochondria to plasma membrane subsurface in photocytes induced to luminesce by the mitochondrial inhibitor dinitrophenol. Photocytes and other endodermal cells of the meridional canals are interconnected by numerous gap junctions which, among photocytes, often form symmetrical triads with cortical cisternae and mitochondria. The gap junctions and RER/mitochondria assemblages are interpreted as possible substrates for, respectively, conduction of luminescence excitation along the canals and for excitation-luminescence coupling. Neuntes occasionally make synapses with photocytes and other endodermal cells lying adjacent to the mesoglea.     

Immunolocalization of the oligosaccharide trimming enzyme glucosidase II

We used immunoelectron microscopy to localize glucosidase II in pig hepatocytes. The enzyme trims the two inner alpha 1,3-linked glucoses from N-linked oligosaccharide precursor chains of glycoproteins. Immunoreactive enzyme was concentrated in rough (RER) and smooth (SER) endoplasmic reticulum but not detectable in Golgi apparatus cisternae. Transitional elements of RER and smooth membraned structures close to Golgi apparatus cisternae contained labeling for glucosidase II. Specific labeling was also found in autophagosomes. These results indicate strongly that glucosidase II acts on glycoproteins before their transport to, and processing in Golgi apparatus cisternae, and suggest that an important transitional region for glucosidase II exists between RER and Golgi apparatus cisternae. Degradation in autophagolysosomes could form a normal catabolic pathway for glucosidase II.     

Remodeling of the rough endoplasmic reticulum during stimulation of procollagen secretion by ascorbic acid in cultured chondrocytes. A biochemical and morphological study

The cellular and molecular mechanisms regulating the reversible accumulation of nonhelical, underhydroxylated procollagen in the rough endoplasmic reticulum (RER) remain obscure. To clarify these mechanisms, we isolated chondrocytes from chick vertebral cartilage and kept them in scorbutic monolayer cultures. By Day 9 of culture, the chondrocytes had accumulated a large amount of underhydroxylated Type II procollagen in their RER. Within 1 h of ascorbate treatment, the accumulated procollagen was hydroxylated; this was accompanied by a slight stimulation of procollagen secretion and was followed by a marked stimulation starting between 2 and 3 h of treatment. Secretion of the accumulated procollagen was completed by about 24 h of treatment. Strikingly, the marked stimulation of procollagen secretion at 2-3 h of treatment was associated with marked remodeling of the RER. This organelle came to consist of a few, unusually large cisternae ("sacs") and many flat cisternae while the RER in untreated cells consisted of uniform, oval cisternae. The RER remodeling was accompanied by a comparable redistribution of the accumulated Type II procollagen stored in it. The RER sacs and flat cisternae invariably communicated directly and were still detectable by 8 h but not by 24 h of treatment. RER remodeling and procollagen redistribution also occurred in untreated chondrocytes that had been shifted to 23 degrees C for 2-3 h. Together, the data indicate that folding of the accumulated procollagen molecules into their normal helical configuration is followed by procollagen redistribution within, and remodeling of, the RER. These processes may have a role in stimulating procollagen export from the RER and secretion.     

How Many Ways Through the Golgi Maze?

The secretory route in eukaryotic cells has been regarded as one common pathway from the endoplasmic reticulum (ER) through the Golgi cisternae to the trans Golgi network where recognition, sorting and exit of cargo molecules are thought to occur. Morphologically, the ribosome-coated ER is observed throughout the cytoplasm, while the Golgi apparatus usually is confined to a perinuclear position in mammalian cells. However, Golgi outposts have been observed in neuronal dendrites and dispersed Golgi elements in skeletal muscle myofibers. In insects, like in Drosophila melanogaster imaginal disc cells and epidermal cells of Tobacco and Arabidopsis leafs, individual Golgi stacks are distributed throughout the cytoplasm. Golgi stacks do not only differ in their intracellular localization but also in the number of stacks from one to several hundreds. Each stack consists of closely aligned, flattened, membrane-limited cisternae. The number of cisternae in a Golgi stack is also variable, 2-3 in some ciliates, 10 in many plant cell types and up to 30 in certain euglenoids. The yeast Saccharomyces cerevisiae has a Golgi structure of minimal complexity with scattered solitary cisternae. It is assumed that the number of Golgi cisternae reflects the overall complexity of the enzymatic reactions that occur in their lumen, while the number of stacks reflects the load of macromolecules arriving at the cis side. In this review, we will focus on how the available morphological and biochemical data fit with the current view of protein sorting in the secretory pathway, particularly in polarized cells like neuronal and epithelial cells.     

Cytochemical studies on the internal polarity of the golgi apparatus and the relationship between this organelle and GERL

Summary Cytochemical studies were performed to clarify the occurrence of an internal polarity of the Golgi apparatus and the relationship between this organelle and GERL in many kinds of cells having different morphologies and functions. The fine structural localizations of thiamine pyrophosphatase (TPPase) and acid phosphatase (AcPase) were examined in anterior pituitary cells, thyroid epithelial cells, gastric chief and parietal cells, duodenal absorptive epithelial cells, hepatocytes, adrenal cortical and medullary cells of mice, and thyroid epithelial cells of domestic fowls. TPPase activity is usually localized in the cisternae of 1–3 stacks and vesicles on the trans-side of the Golgi apparatus of all the cells examined, and in some immature secretory granules of anterior pituitary cells and of gastric chief cells. Rigid lamellae and multivesicular bodies are rarely positive to this reaction, in several kinds of cells. AcPase activity was usually demonstrable in the cisternae of 1–3 stacks and vesicles on the trans-side of the Golgi apparatus, and also in rigid lamellae, coated vesicles, multivesicular bodies and lysosomes in all varieties of cells studied. Some immature secretory granules are positive to the AcPase reaction in anterior pituitary cells and gastric chief cells. The areas positive for both enzyme activities were partially or almost completely overlapping in all the cells examined, though there were minor variations among them. The grades of overlap are classified into three types. Prolonged osmication was performed on thyroid epithelial cells, duodenal absorptive epithelial cells, hepatocytes, adrenal cortical cells, Leydig cells, the epithelial cells of the vas deferens and the theca cells of mice. Cisternae of 1–3 stacks on the cis-side of the Golgi apparatus of all the cells examined were stained with osmium tetroxide. In all these cells we observed that the Golgi apparatus has an internal polarity and that GERL is a part of this organelle in cytochemical respects.This study was supported by grants from the Japan Ministry of Education     

The rough endoplasmic reticulum and the Golgi apparatus visualized using specific antibodies in normal and tumoral prolactin cells in culture

Antibodies directed against membrane components of dog pancreas rough endoplasmic reticulum (A-RER) and rat liver Golgi apparatus (A-Golgi) (Louvard, D., H. Reggio, and G. Warren, 1982, J. Cell Biol. 92:92-107) have been applied to cultured rat prolactin (PRL) cells, either normal cells in primary cultures, or clonal GH3 cells. In normal PRL cells, the A-RER stained the membranes of the perinuclear cisternae as well as those of many parallel RER cisternae. The A-Golgi stained part of the Golgi membranes. In the stacks it stained the medial saccules and, with a decreasing intensity, the saccules of the trans side, as well as, in some cells, a linear cisterna in the center of the Golgi zone. It also stained the membrane of many small vesicles as well as that of lysosomelike structures in all cells. In contrast, it never stained the secretory granule membrane, except at the level of very few segregating granules on the trans face of the Golgi zone. In GH3 cells the A-RER stained the membrane of the perinuclear cisternae, as well as that of short discontinuous flat cisternae. The A-Golgi stained the same components of the Golgi zone as in normal PRL cells. In some cells of both types the A-Golgi also stained discontinuous patches on the plasma membrane and small vesicles fusing with the plasma membrane. Immunostaining of Golgi membranes revealed modifications of membrane flow in relation to either acute stimulation of PRL release by thyroliberin or inhibition of basal secretion by monensin.     

The Ultrastructural Evidence on the Origin of Protein Bodies in the Rough Endoplasmic Reticulum of Developing Cotyledons of Soybean

The process of protein body formation from rough endoplasmicreticulum (RER) in cotyledon cells of soybean has been followed.From about 43 d after flowering (DAF), the lumen of some partsof RER cisternae was dilated and filled gradually with proteinaceousmaterial. This kind of dilated RER expanded further to formlong and irregularly shaped protein bodies (PBs), and the latterdivided into smaller spherical protein bodies in mature seedsat 63 DAF. From these results and our previous observations,we draw the conclusion that there are two pathways of proteinbody formation in developing cotyledon cells in soybean. Duringthe early stage, vacuoles in the cells were filled with proteinaceousmaterial and turned into protein bodies. During the late stage,some of the dilated RER with storage proteins developed intoPBs A few vacuoles can also form PBs at this late stage. Inaddition, some fibre structures, 7–8 nm in width, wereseen to be oriented in parallel in longitudinal sections ofRER cisternae in cotyledon cells at 45 DAF. Soybean, protein body, ER origin, storage protein     

Disruption of endoplasmic reticulum to Golgi transport leads to the accumulation of large aggregates containing beta-COP in pancreatic acinar cells.

When transport between the rough endoplasmic reticulum (ER) and Golgi complex is blocked by Brefeldin A (BFA) treatment or ATP depletion, the Golgi apparatus and associated transport vesicles undergo a dramatic reorganization. Because recent studies suggest that coat proteins such as beta-COP play an important role in the maintenance of the Golgi complex, we have used immunocytochemistry to determine the distribution of beta-COP in pancreatic acinar cells (PAC) in which ER to Golgi transport was blocked by BFA treatment or ATP depletion. In controls, beta-COP was associated with Golgi cisternae and transport vesicles as expected. Upon BFA treatment, PAC Golgi cisternae are dismantled and replaced by clusters of remnant vesicles surrounded by typical ER transitional elements that are generally assumed to represent the exit site of vesicular carriers for ER to Golgi transport. In BFA-treated PAC, beta-COP was concentrated in large (0.5-1.0 micron) aggregates closely associated with remnant Golgi membranes. In addition to typical ER transitional elements, we detected a new type of transitional element that consists of specialized regions of rough ER (RER) with ribosome-free ends that touched or extended into the beta-COP containing aggregates. In ATP-depleted PAC, beta-COP was not detected on Golgi membranes but was concentrated in similar large aggregates found on the cis side of the Golgi stacks. The data indicate that upon arrest of ER to Golgi transport by either BFA treatment or energy depletion, beta-COP dissociates from PAC Golgi membranes and accumulates as large aggregates closely associated with specialized ER elements. The latter may correspond to either the site of entry or exit for vesicles recycling between the Golgi and the RER.     

Dispersion of cisternae of rough endoplasmic reticulum in aging CNS neurons: a strictly linear trend.

Dispersion of cisternae of rough endoplasmic reticulum (RER) in aging rats has been determined quantitatively for mitral cells of the olfactory bulb and Purkinje cells of the cerebellum using a recently published morphometric technique (Cruz Orive, '76). In both cell types dispersion of cisternae occurred throughout the period studied and in a linear fashion. The observed RER dispersion cannot be attributed to a decrease in the total amount of RER, since the total amount of RER was constant in Purkinje cells and increased in mitral cells during the age studied.     

Golgi structure in three dimensions: functional insights from the normal rat kidney cell

Three-dimensional reconstructions of portions of the Golgi complex from cryofixed, freeze-substituted normal rat kidney cells have been made by dual-axis, high-voltage EM tomography at approximately 7-nm resolution. The reconstruction shown here ( approximately 1 x 1 x 4 microm3) contains two stacks of seven cisternae separated by a noncompact region across which bridges connect some cisternae at equivalent levels, but none at nonequivalent levels. The rest of the noncompact region is filled with both vesicles and polymorphic membranous elements. All cisternae are fenestrated and display coated buds. They all have about the same surface area, but they differ in volume by as much as 50%. The trans-most cisterna produces exclusively clathrin-coated buds, whereas the others display only nonclathrin coated buds. This finding challenges traditional views of where sorting occurs within the Golgi complex. Tubules with budding profiles extend from the margins of both cis and trans cisternae. They pass beyond neighboring cisternae, suggesting that these tubules contribute to traffic to and/or from the Golgi. Vesicle-filled "wells" open to both the cis and lateral sides of the stacks. The stacks of cisternae are positioned between two types of ER, cis and trans. The cis ER lies adjacent to the ER-Golgi intermediate compartment, which consists of discrete polymorphic membranous elements layered in front of the cis-most Golgi cisterna. The extensive trans ER forms close contacts with the two trans-most cisternae; this apposition may permit direct transfer of lipids between ER and Golgi membranes. Within 0.2 microm of the cisternae studied, there are 394 vesicles (8 clathrin coated, 190 nonclathrin coated, and 196 noncoated), indicating considerable vesicular traffic in this Golgi region. Our data place structural constraints on models of trafficking to, through, and from the Golgi complex.     

荔枝雄花性别决定过程中细胞超微结构的变化

荔枝雄花雌蕊原基在大孢子母细胞减数分裂后开始衰退.内质网历经增生扩展,穿壁相连,同心缠绕,多条平行弯曲,不规则堆叠.内质网和高尔基体产生许多囊泡,囊泡在细胞内含物的降解和运输过程中起着重要的作用.线粒体在雌蕊原基细胞衰败的前、中期数量增加,后期分批降解.过氧化物酶体在雌蕊原基细胞衰败的中期紧挨核短暂出现.细胞核的染色质凝集断裂;核周腔扩大,形成胀泡;染色质趋边,外泄.细胞原生质表现出有序的、在膜包裹下的降解,首先是核糖体,而后依次是:过氧化物酶体、内质网、高尔基体、线粒体、核.雌蕊原基的衰败历程可能是一种程序性细胞死亡的过程.     

Light and electron microscope observations on the gastric mucosa of the frog (Rana esculenta)

Summary The structure of the frog gastric and esophageal mucosa was studied in the course of a complete hibernation period and compared with that in summer frogs (see preceding article).It appeared that especially chief cells and parietal cells are liable to cytoplasmic remodelling. Thus, in chief cells the rough endoplasmic reticulum (RER) undergoes disorganization, the number of free ribosomes increases and the Golgi system becomes transformed into a compact vesicular structure. The number of pepsinogen granules in chief cells of late winter frogs is only 20% of that in frogs studied at the onset of hibernation. The loss of pepsinogen granules is at least partly due to autophagy. In addition, lysosomes are involved in focal degradation of the cytoplasm, which may ultimately result in complete degeneration of some chief cells. The presence of zymogen granules containing fibrocyte-like cells in the tunica propria proved heterophagocytosis by these cells.In parietal cells, the area occupied by smooth endoplasmic reticulum becomes reduced. The basal cytoplasm of both chief cells and parietal cells contains numerous lipid droplets, which, in contrast to those in summer frogs, are continuous with RER cisternae. The juxtaposition of lipid droplets and mitochondria seen in summer frogs is eventually lost in hibernating animals.Apart from the appearance of supra-nuclear lipid droplets, the mucous cells of the surface epithelium show no striking alterations. However, in the glandular pits both surface mucous cells and mucous neck cells contain less mucous granules than in summer frogs.The results are discussed in connection with parallel biochemical work and available literature, and in the light of our previous studies on the exocrine pancreas in hibernating frogs.