The morphology,occurrence, and distribution of dilated cisternae of the endoplasmic reticulum in tissues of plants of theCruciferae

Summary Morphology, occurrence, and distribution of dilated cisternae of the endoplasmic reticulum (ER) were studied by electron microscopy. The cisternae which contained an electron-dense matrix were intimately associated with the granular ER membranes appearing as tubular necks at the edges of the ER profiles. After budding off from the ER the cisternae still had ribosomes attached to the outside of the bounding membranes. The accumulations were variable in shape, being 0.4 to 1.5 in width and 4 to 5 in length.The cisternae were found to be unique for plants of theCruciferae and could not be observed in species from related families such asPapaveraceae andResedaceae.The dilated cisternae were a common component of the cytoplasm in root tips, stems, and leaves. In meristematic cells the number of accumulations was small but increased in older differentiating cells of the root cap. The similarity to microbodies described by previous authors from other plants is discussed.     

Electron microscopic and cytochemical studies of the mouse subcommissural organ

Summary In mice most of the ependymal cells of the subcommissural organ (SCO cells) are densely packed with dilated cisternae of the endoplasmic reticulum (ER) containing either finely granular or flocculent materials. The well developed supra-nuclear Golgi apparatus consists of stacks of flattened saccules and small vesicles; the two or three outer Golgi saccules are moderately dilated and exhibit numerous fenestrations; occasional profiles suggesting the budding of coated vesicles and formation of membrane-bound dense bodies from the ends of the innermost Golgi saccules are seen. A few coated vesicles and membrane-bound dense bodies of various sizes and shapes are also found in the Golgi region.The contents of the dilated ER cisternae are stained with periodic acid-silver methenamine techniques. In the Golgi complex the two or three inner saccules are stained as deeply as the dense bodies, and the outer saccules are only slightly stained. The stained contents of ER cisternae are more electron opaque than those of the outer but less opaque than those of the inner Golgi saccules and the dense bodies.Acid phosphatase activities are localized in the dense bodies, some of the coated vesicles in the Golgi region, and in the one or two inner Golgi saccules.On the basis of these results the following conclusions have been reached: (1) In mouse SCO cells the finely granular and the flocculent materials in the lumen of ER cisternae contain a complex carbohydrate(s) which is secreted into the ventricle to form Reissner's fiber; (2) the secretory substance is assumed to be synthesized by the ER and stored in its cisternae, and the Golgi apparatus might play only a minor role, if any, in the elaboration of the secretory material; (3) most of the dense bodies in the mouse SCO cells are lysosomal in nature instead of being so-called dark secretory granules.Sponsored by the National Science Council, Republic of China.     

Polysomes and intracisternal accumulations in enucleate sieve elements of rice (Oryza sativa L.)

Polysomes in sieve elements of rice (Oryza sativa L.) were studied with the electron microscope. The polysomes were found on the rough endoplasmic reticulum (ER) present in immature sieve elements and also on the cisternae of aggregated ER in the parietal layer of mature, enucleate sieve elements. In the immature sieve elements the ER cisternae existed as narrow profiles while in the mature sieve elements the ER cisternae were considerably dilated and contained a fibrillar material and, occasionally, electron-opaque inclusions. In addition to the aggregated ER, single profiles of ER were found applied to the lateral walls and also the sieve plates. These cisternae also bore ribosomes and were separated from the plasmalemma by a narrow, dense space. In the mature sieve elements much of the surface of the ER membranes was covered with polysomes. The dimensions of the polysomes are described and the possibility that they contribute to the formation of the fibrillar material in the intracisternal space is discussed.Abbreviations ER endoplasmic reticulum     

Fine structural and cytochemical studies on the hamster subcommissural organ

The subcommissural organ (SCO) of the golden hamster (Mesocricetus auratus) was studied by conventional electron microscopy, freeze-fracture technique, zinc-iodide-osmium (ZIO) and acid phosphatase cytochemical reactions. The ultrastructure of hamster SCO cells shows a few flattened cisternae of rough endoplasmic reticulum (ER) without dilated ones in the cytoplasm. The Golgi apparatus is very well developed. Freeze-fracture studies also indicate only short profiles of flattened ER in the cytoplasm endorsing the absence of dilated ER cisternae. After the treatment with ZIO mixture, reaction products were observed over flattened cisternae of the ER and the nuclear envelope. The Golgi apparatus was also reactive toward the ZIO mixture. Acid phosphatase activities are localized in the inner one or two saccules of the Golgi apparatus and dense bodies. From these results we suggest that (1) hamster SCO cells do not accumulate secretory material in the cytoplasm in the form of discrete secretory granules or dilated cisternae of ER, and (2) hamster SCO cells may possess extremely high secretory activity or may not be actively involved in secretory function at all as in rats or other rodents.     

Dilated Endoplasmic Reticulum Cisternae in Differentiating Xylem of Minor Veins of Mimosa pudica L. Leaf

The differentiating tracheary elements in the xylem of minorveins in Mimosa pudica L. contain, as is usual, complete nucleateprotoplasts. Within the latter, dictyosomes with associatedvesicles and endoplasmic reticulum (ER) are prominent components.The ER cisternae show an uncommon feature of developing voluminousdilations accumulating finely fibrous material. Similar dilatedER cisternae occur in parenchyma cells associated with the trachearyelements. Most of the dilated cisternae are elongated, taperingat both ends, and almost circular in transections. They varyin size. The largest measured was 10 µm long and 3 µmwide. In the tracheary elements the cisternae break down asthe protoplast disintegrates. For a time, mature cells containfibrous material, apparently the product of the dilated cisternae,at least in part. In the parenchyma cells the dilated cisternaeare released into the vacuoles after the associated trachearyelements reach maturity. They become structurally modified anddisintegrate. The timing in the appearance and disintegrationof the dilated ER cisternae suggests that these structures havesome function with reference to the differentiation of trachearyelements in the xylem.     

Three dimensional visualization of the Golgi apparatus and endoplasmic reticulum in the subcommissural organ cells with high voltage electron microscopy

Fine structure and stereo-images of the Golgi apparatus and endoplasmic reticulum (ER) in the subcommissural organ (SCO) cells were visualized by the application of zinc-iodide osmium tetroxide (ZIO) impregnation, conventional electron microscopy and high voltage electron microscopy (HVEM). The Golgi apparatus in the SCO cells of rats, gerbils and hamsters consisted of flattened saccules stacked in parallel array. It showed a selective staining toward ZIO mixture and might form a complex network of tubular structures because of the presence of numerous fenestrations in the flattened Golgi saccules. The cytoplasm of the SCO cells in the rat and gerbil was crowded by dilated cisternae of the ER with a few flattened profiles. In the hamster SCO cells, however, the dilated cisternae of the ER were not observed. Flattened cisternae of ER in all species studied showed a positivity for ZIO impregnation and formed a complex tubular network, whereas dilated cisternae of the ER in the rats and gerbils did not show any reactivity. It was thus determined that the observation of thin and thick sections selectively stained with appropriate reagent for defined cellular organelles under conventional electron microscopy and HVEM offered valuable information about three-dimensional organization of the cell. A definite species-specific variation of SCO ultrastructure and cytochemistry was also demonstrated.     

Plasticity of the endoplasmic reticulum in three cell types of slugs poisoned by molluscicides

Summary In three cell types of slug tissue-the crypt, mucous and storage cell-ultrastructural alterations of the endoplasmic reticulum (ER) can be induced by oral application of the pesticides Cloethocarb, metaldehyde, or Dimilin. In the crypt cells of the hepatopancreas, the narrow-luminar cisternae of the rough endoplasmic reticulum which are parallelly arranged in controls get slightly dilated, vesiculated and form circular arrays. Intermediate stages between narrow luminar, vesiculated and circularly arranged ER can be observed. In the mucous cells of the skin and the stomach, the wideluminar cisternae of the rough endoplasmic reticulum the lumen of which contains tubular-like structures become heavily dilated. Also in this cell type, intermediate stages between dilated cisternae without tubular-like structures and non-dilated cisternae can be observed. In the storage cells of the crop, in which lipid storage is reduced after molluscicide application, the formation of a special type of ER characterized by locally enlarged ER-cisternae, broken through by several cytoplasmic strings, becomes obvious.     

Ultrastructure ofPapaver somniferum cells culturedin vitro and treated with fungal homogenate eliciting alkaloid production

Summary Cells of poppy (Papaver somniferum L.) which had been grownin vitro, treated with autoclavedBotrytis homogenate for 24 hours, and which had responded with browning and drastic sanguinarine accumulation, did not show lysis but presented an ultra-structure as known for parenchyma cells. The only change observed was the occurrence of electron-dense droplets in vacuoles dotting the tonoplast, stacking of the ER, and dilation of cisternae. At places where the cisternae were dilated the membranes were free of ribosomes. Sanguinarine accumulation appears not to require structural cell differentiation.NRCC #24164.     

Myrosin cells and dilated cisternae of the endoplasmic reticulum in the order Capparales

Ultrastructural results for different types of protein–rich cells in five families generally accepted as Capparalean (Brassicaceae, Capparaceae, Resedaceae, Tovariaceae and Moringaceae) and two others (Gyrostemonaceae and Bataceae) considered by some workers to be Capparalean, support their alignment in the order Capparales. The term myrosin cell is used for those protein–rich cells which are typically idio–blastic and characterized by a homogenous, granular proteinaceous material in the vacuole and a cytoplasm which is filled with an extensive rough endoplasmic reticulum. This idioblastic myrosin cell type is characteristic for the Brassicaceae, Capparaceae, Tovariaceae, Moringaceae and Gyrostemonaceae. The guard cells of stomata may appear as myrosin cells, in which case they are termed guard–cell myrosin cells; they are found in the Resedaceae, Tovariaceae and Bataceae. Other proteinaceous cells are those with protein–rich dilated cisternae (DC) of the endoplasmic reticulum (ER). One type is the organelle–like DC, utricular or irregular dilations of the ER, filled with protein and ribosome–studded. Utricular DC are characteristic for the Brassicaceae and Capparaceae. Another type of DC is represented by protein–containing vacuoles derived from the ER, protein–rich ER–dependent vacuoles; these are found in the Brassicaceae, Capparaceae, Resedaceae, Tovariaceae and Gyrostemonaceae. The myrosin cells and cells with protein–rich dilated cisternae are here regarded as taxonomic criteria for the order Capparales.     

Effects of brefeldin A on the Golgi apparatus, the nuclear envelope, and the endoplasmic reticulum in a green alga,Scenedesmus acutus

Summary The effects of brefeldin A (BFA) on the structure of the Golgi apparatus, the nuclear envelope, and the endoplasmic reticulum (ER), and on the thiamine pyrophosphatase (TPPase) activity in these organelles were examined in a green alga,Scenedesmus acutus, to obtain evidence for the existence of a retrograde transport from the Golgi apparatus to the ER via the nuclear envelope. InScenedesmus, Golgi bodies are situated close to the nuclear envelope throughout the cell cycle and receive the transition vesicles not directly from the ER, but from the nuclear envelope. BFA induced the disassembly of Golgi bodies and an increase in the ER cisternae at the trans-side of decomposed Golgi bodies in interphase cells and multinuclear cells before septum formation. The accumulated ER cisternae connected to the nuclear envelope at one part. TPPase activity was detected in all cisternae of Golgi bodies, but not in the nuclear envelope or the ER in nontreated cells. On the contrary, in BFA-treated cells, TPPase activity was detected in the nuclear envelope and the ER in addition to the decomposed Golgi bodies. When septum-forming cells were treated with BFA, the disassembly of Golgi bodies was less than that in interphase cells, and TPPase activity was detected in the Golgi cisternae but not in the nuclear envelope or the ER. These results suggest mat BFA blocks the anterograde transport from the nuclear envelope to the Golgi bodies but does not block the retrograde transport from the Golgi bodies to the nuclear envelope in interphase and multinuclear cells.Abbreviations BFA brefeldin A - ER endoplasmic reticulum - TPPase thiamine pyrophosphatase     

STRUCTURE AND DEVELOPMENT OF SIEVE ELEMENTS IN THE LEAF OF ISOETES MURICATA

Leaf tissue of Isoetes muricata Dur. was fixed in glutaraldehyde and postfixed in osmium tetroxide for electron microscopy. The very young sieve elements can be distinguished from contiguous parenchyma cells by their distinctive plastids and the presence of crystalline and fibrillar proteinaceous material in dilated cisternae of the rough ER. During differentiation, the portions of ER enclosing this proteinaceous substance become smooth surfaced and migrate to the cell wall. Along the way they apparently form multivesicular bodies which then fuse with the plasmalemma, discharging their contents to the outside. At maturity, the sieve element contains an elongate nucleus, which consists of dense chromatin material, and remnants of the nuclear envelope. In addition, the mature sieve element is lined by a plasmalemma and a parietal, anastomosing network of smooth ER. Both plastids and mitochondria are present. P-protein is lacking at all stages of development. Tonoplasts are. not discernible in mature sieve elements. The end walls of mature sieve elements contain either plasmodesmata or sieve pores or both, but only plasmodesmata occur in the lateral walls.     

Changing ultrastructure of thyrotrophs in the rat anterior pituitary after thyroidectomy as studied by immuno-electron microscopy and enzyme cytochemistry

Summary The characteristic ultrastructure of thyrotrophs of the rat anterior pituitary was observed by immuno-electron microscopy and enzyme cytochemistry with increasing time after thyroidectomy (TX). The rough endoplasmic reticulum (ER) became dilated, the intracisternal granules reacted to serum raised against thyroid stimulating hormone (TSH) around 21 days after TX, and lysosomes and peculiar structures with positive acid phosphatase activity were present. The administration of thyroxine (T₄) to the thyroidectomized rats resulted in the reformation of secretory granules, a reduction of dilated cisternae of rough ER and the activation of the lysosomal systems. Morphological features indicating that the TX-cells might be derived from growth hormone (GH) cells or cells other than TSH cells, previously suggested by some researchers, were not recognized in the present study. The amount of serum and pituitary TSH was measured by radioimmunoassay (RIA), and correlated well with the morphological changes. These results indicate that the TX-cells are hypertrophied hyperfunctioning TSH cells that have been affected by the lack of negative feedback of thyroid hormone.     

Ultrastructural evidence of endoplasmic reticulum changes during the maturation of the olive pollen grain (Olea europaea L., Oleaceae)

Characteristic features of rough endoplasmic reticulum (rER) distribution and proliferation were noted during olive pollen (Olea europaea L.) development, suggesting the physiological significance of this organelle. Initially scarce in the young microspore, ER increases as cytoplasmic vacuoles form. At the vacuolated microspore stage the cytoplasm contains numberous polysomes and elongated rER cisternae arranged preferentially in stacks, with an average intracisternal width of 0.07 µm. Stacks persist in the bicellular pollen grain but consist of fewer, shorter, dilated cisternae (mean intracisternal width 0.1 µm) containing a considerable electron-dense matrix. Cisternae in the mature grain are fragmented, leaving behind an ER of swollen pockets. Pockets of ER containing a material of greater electron density are evenly deposited along the plasmalemma, in close relation with it. A dense material is seen in the tubules of the apertural region, which was lacking in earlier stages. Our results show that ER may be involved in protein transport to the intine.     

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     

Neurosecretion of the mediodorsal cells of the central nervous system of the snail Helisoma duryi

Summary The neurosecretory mediodorsal cells that produce a putative growth hormone of the snail Helisoma duryi were studied in fast-growing virgin snails and in slow-growing reproducing snails. There are about 60 mediodorsal cells in clusters on each side of the cerebral commissure of the central nervous system, and they contain dense-cored granules which are 100–200 nm in diameter. The cells of virgin snails have dense Golgi bodies, scattered ER cisternae, and few granules, while those of reproducing snails have pale Golgi bodies, stacked ER cisternae, and numerous granules. Thus the mediodorsal cells of the virgin snails appear to be more active synthetically than those of the reproducing snails. The cells near the endocrine dorsal bodies contain many dorsal body precesses in their membrane interdigitations. There are junction-like interactions between some of the interdigitations. Gap junction-like contacts are seen between mediodorsal cells and glial cells. The axon endings of the mediodorsal cells at the neurohemal area in the labial nerve show more release profiles in virgin snails than in reproducing snails. A daily pattern of release has been observed in reproducing snails, and rates of release are higher in the evening than in the morning.     

FINE STRUCTURE AND HISTOCHEMISTRY OF VESICLE CELLS OF THE RED ALGA ANTITHAMNION DEFECTUM (CERAMIACEAE)1

The ultrastructure and histochemistry of the refractile, vesiculate cells (“blasenzellen,”“cellules secretrices,”“gland cells”) of Antithamnion defectum Kylin were examined. The refringent vacuolar contents disclosed two components of differing density: an electron opaque, proteinaceous matrix material surrounding cores of irregularly shaped, less opaque material. The cores contain less protein and more unknown material than the matrix. Part or all of the vacuolar material is synthesized by abundant rough endoplasmic reticulum (ER) and deposited in smooth surfaced cisternae that swell to form vesicles. Mitochondria are usually associated with stacks of the swelling cisternae. The vesicles enlarge by continued deposition of synthesized material and coalescence with other vesicles. All vesicles eventually coalesce to form the mature vacuole. A crystalline array of fibrils develops in the cytoplasm during later stages of vacuole enlargement. The crystal contains a sulfated, acidic polysaccharidic material. The chloroplasts, if present, and nucleus degenerate at vacuole maturity. Active release of the vacuolar material does not occur, and organelles for extracellular secretion are not present. Structural evidence suggests a storage, rather than secretory, function for the cells.     

AN ELECTRON MICROSCOPE STUDY OF THE GLAND CELLS OF THE MINK ENDOMETRIUM

Portions of mink endometrium in delayed implantation, early postimplantation, and pseudo pregnancy were fixed in buffered osmium tetroxide with sucrose, or potassium permanganate. After rapid dehydration the portions of endometrium were embedded in either methacrylate or epoxy resin. Examination of the cells from the body of the glands of the endometrium of delayed implantation revealed the presence of prominent terminal bars, numerous secretion granules, and membrane discs in the apical region of the cell. In the supranuclear and infranuclear regions, mildly dilated cisternae of the endoplasmic reticulum were present, and in many cells unusually large mitochondria were seen. Numerous changes were noted in the gland cells of the post implantation stage. The endoplasmic reticulum in the basal region was extensively dilated, and the nuclei were situated more centrally. Giant mitochondria were no longer present. The large secretion granules were not present, but smaller granules were seen, especially in the Golgi region. Some of the Golgi cisternae were dilated and the pattern of parallel membranes was consequently less distinct. It is suggested that gland cells in the postimplantation and pseudopregnancy stages exhibit evidence of greater secretory activity than those in the delayed implantation stage.     

Ultrastructure of meristematic epidermal cells of maize root under water deficit conditions

Summary Structural components of meristematicZea mays primary root epidermal cells were observed after osmotic stress of the nutrient medium (12.5 atm.) and after rehydration. After non-lethal osmotic stress (24 hours), aggregation of nuclear chromatin, parallel ER arrangement, and reduction of mitochondrial cristae were found. Increased number of Golgi cisternae indicated vesicle production inhibition, and microtubules were absent in treated cells, although plastid structure remained unchanged. After lethal osmotic stress (48 hours), fragmentation of cytoplasmic membranes and a more severe structure damage of all cellular components occurred. Structure of the nucleus, mitochondria, Golgi apparatus and microtubules reappeared in the cells after rehydration. The only new feature of these cells was occurrence of smooth ER, which may indicate that the ER system has acquired a different function in regenerated cells.     

ULTRASTRUCTURE OF THE SECRETORY DUCTS OF RHUS GLABRA L.

The infrastructure and development of the secretory ducts were studied in the secondary phloem of Rhus glabra L. The ducts were found to develop schizogenously. The electron microscope observations may explain the view of several previous authors of schizo-lysigenous development of the duct lumen in the Anacardiaceae. The secreted material consists of lipophilic and polysaccharide substances. The electron micrographs suggest that the lipophilic substances arise in plastids, ER cisternae, Golgi vesicles, and mitochondria. The polysaccharide constituents apparently originate from the outer wall layers of the epithelial cells. The wall layers facing the lumen of the duct disintegrate and form, together with the secreted osmiophilic droplets, the gum-resin. Numerous microtubules were found along walls of the epithelial cells.     

ONTOGENY,HISTOCHEMISTRY AND FINE STRUCTURE OF CELLULAR INCLUSIONS IN VEGETATIVE CELLS OF ANTITHAMNION DEFECTUM (CERAMIACEAE,RHODOPHYTA)1

The ultrastructure and histochemistry of developing and mature cell inclusions in vegetative cells of Antithamnion defectum Kylin were examined. Those studied were chloroplast inclusions, cytoplasmic crystals and spherical bodies within the vacuole. Chloroplasts of mature vegetative cells contain an interthylakoidal, apparently noncrystalline deposit of undetermined chemical identity. The bodies are parallel to the long axis of the plastid, are square (0.13 μm) in cross-section, and up to 3 μm long. Spherical vacuolar bodies (0.5–1.5 μum diam) are formed during early stages of vacuole formation by accumulation of protein deposits in swelling endoplasmic reticulum (ER) cisternae. Swelling of smooth ER contiguous to the ER containing the deposits results in the vacuole enclosing the spherical bodies. In mature cells, vesicles appear to be secreted into the preformed vacuole. Cytoplasmic proteinaceous crystalloids develop without a bounding membrane and may serve as protein reserves.