Special secretory cells in the soybean seed coat

Summary The seed coat of soybean (Glycine max L. Merr.) is of physiological interest for synthesis and transport of amino acids and photosynthates during embryo development. A transmission and scanning electron microscopic study to elucidate the structure of the seed coat disclosed a specialized convex area (antipit) appressed to a concave pit in the center of the abaxial surface of the cotyledon. The antipit, which lies on the inner surface of the seed coat at a medial point in the anterior to posterior direction of the seed, contained specialized secretory cells bounded by loose multi-layered cell walls. These cells were rectangular in the developing seed, varied in length, and contributed directly to the convex morphology of the antipit seen on the ventral surface of the seed coat. At maturity these cells assumed the shape of a cone, extending from the aleurone layer in a perpendicular array. The aleurone and cone cells contained numerous Golgi apparatus, laminated rough endoplasmic reticulum, secretory vesicles, and amyloplasts. Secretory vesicles arose directly from tubules of fenestrated trans cisternae of the Golgi apparatus. Mitochondria were clustered with the amyloplasts; stacks of lamellar cisternae of rough endoplasmic reticulum were associated with the nucleus and Golgi apparatus. The cellular contents, the interconnections by plasmodesmata, and the close physical association with the cotyledon suggested that the aleurone and cone cells may be involved in symplastic transport of nutrients for use by the developing embryo.This paper is dedicated to the memory of my parents, Joseph and Theresa Yaklich, who by their example taught me the value of work and the enjoyment of simple things.     

Relationship between the golgi apparatus, gerl, and secretory granules in acinar cells of the rat exorbital lacrimal gland

The method of secretory granuleformation in the acinar cells of the rat exorbital lacrimal gland was studied by electron microscope morphological and cytochemical techniques. Immature secretory granules at the inner face of the Golgi apparatus were frequently attached to a narrow cisternal structure similar to GERL as described in neurons by Novikoff et al. (Novikoff, P. M., A. B. Novikoff, N. Quintana, and J.-J. Hauw. 1971. J. Cell Bio. 50:859-886). In the lacrimal gland. GERL was located adjacent to the inner Golgi saccule, or separated from it by a variable distance. Portions of GERL were often closely paralleled by modified cisternae of rough endoplasmic reticulum (RER), which lacked ribosomes on the surface adjacent to GERL. Diaminobenzidine reaction product of the secretory enzyme peroxidase was localized in the cisternae of the nuclear envelope, RER, peripheral Golgi vesicles, Golgi saccules, and immature and mature secretory granules. GERL was usually free of peroxidase reaction product or contained only a small amount. Thiamine pyrophosphatase reaction product was present in two to four inner Golgi saccules; occasionally, the innermost saccule was dilated and fenestrated, and contained less reaction product than the next adjacent saccule. Acid phosphatase (AcPase) reaction product was present in GERL, immature granules, and, rarely, in the innermost saccule, but not in the rest of the Golgi saccules. Thick sections of AcPase preparations viewed at 100 kV revealed that GERL consisted of cisternal, and fenestrated or tublular portions. The immature granules were attached to GERL by multiple connections to the tublular portions. These results suggest that, in the rat exorbital lacrimal gland, the Golgi saccules participate in the transport of secretory proteins, and that GERL is involved in the formation of secretory granules.     

Endoplasmic Reticulum Formation during Germination of Wheat Seeds : A QUANTITATIVE ELECTRON MICROSCOPE STUDY

This study demonstrates germination-induced ultrastructural changes in wheat (Triticum aestivum L. cv Arthur) aleurone cells. Seeds imbided for 4 hours in water contained endoplasmic reticulum (ER) or ER-like membranes as vesicles or as short segments of membrane associated with the spherosomes on the periphery of aleurone grains. Aleurone cells incubated between 8 and 10 hours contained abundant ER membranes mainly associated with the nuclear envelope and, to a lesser extent, with the spherosomes surrounding the aleurone grain. The membranes located on the periphery of the nucleus occurred as regions of stacked cisternae. When aleurone cells were analyzed by morphometry, the increase in ER during incubation was found to be greater than 2-fold. During the same incubation period, other organelles did not change significantly. The early increase in ER was not affected by gibberellin incubation. Thus, the rapid proliferation of ER observed during the early stages of germination in aleurone cells of wheat is not likely to be controlled directly by gibberellin.     

Immunolocalization of venom metalloproteases in venom glands of adult and of newborn snakes of Bothrops jararaca

Using immunoelectronmicroscopy we analyzed qualitative and quantitatively the intracellular distribution of bothropasin, hemorrhagic factor 2 (HF2) and hemorrhagic factor 3 (HF3) in the venom secretory cells from adult snakes in the active (7 days after venom extraction) and in the resting (without venom extraction for 40 days) stages of protein synthesis. Glands from the newborn Bothrops jararaca were also studied. The results lead to the conclusion that all the secretory cells and the secretory pathway in the cells are qualitatively alike in regard to their content of the three metalloproteases. Secretory cells from the resting glands, unlike the active ones and the newborn glands, did not present immunolabeling in the narrow intracisternal spaces of the rough endoplasmic reticulum (RER). The label intensity for bothropasin was greater than that for the other proteins in the adults. HF3 and HF2 labeling densities in the newborn were higher than in the adults and HF3 labeling was not different from that of bothropasin. Co-localization of the three metalloproteases was detected in the RER cisternae of the active gland secretory cells, implying that mixing of the proteases before co-packaging into secretory vesicles occurs at the beginning of protein synthesis in the RER cisternae.     

Fine structure of the sensory epithelium of guinea-pig organ of Corti: Subsurface cisternae and lamellar bodies in the outer hair cells

The fine structure of subsurface cisternae and lamellar bodies in the outer hair cells of the guinea-pig organ of Corti was studied with thin sections and freeze-fracture replicas. Subsurface cisternae in the outer hair cells consist of multilayers along the lateral plasma membrane of the cell. The outermost layer is a flattened cistern in the upper part of the supranuclear region, but comprises a series of tubules in the lower part. Deeper layers are fenestrated cisternae in which disc-like areas are found in the upper part of the supranuclear region. Lamellar bodies consist of concentric layers of fenestrated cisternae and are located in the apical cytoplasm beneath the cuticular plate. They are continuous with the subsurface cisternae. In the supranuclear cytoplasm, bulges of the subsurface cisternae and the lamellar bodies are found. Dilated cisternae are also present. Some dilated cisternae contain many small vesicles, which display acid phosphatase activity. The dilated cisternae are considered as forms of the bulges undergoing transformation into multivesicular bodies. The possible role of the lamellar bodies, and the origin and fate of the subsurface cisternae are discussed.     

The function of the aleurone layer during galactomannan mobilisation in germinating seeds of fenugreek (Trigonella foenum-graecum L.), crimson clover (Trifolium incarnatum L.) and lucerne (Medicago sativa L.): A correlative biochemical and ultrastructural study

Summary The reserve endosperm galactomannans of fenugreek (Trigonella foenum-graecum L.), crimson clover (Trifolium incarnatum L.) and lucerne (Medicago sativa L.) are broken down to free galactose and mannose in dry-isolated endosperms (devoid of embryo) incubated under germination conditions. Breakdown is prevented by inhibition of protein synthesis or of oxidative phosphorylation in the aleurone layer. Resting aleurone cells contain inter alia a large number of ribosomes more or less regularly distributed in the ground plasma. At the onset of germination, before galactomannan breakdown begins, polysomes are formed and seem, at least partly, to become associated with vesicles and flat cisternae both probably newly formed and derived from ER. Concurrently with galactomannan breakdown in the reserve cells, wall corrosion occurs in the aleurone layer, the contents of the aleurone grains disappear and the rough vesicles and cisternae proliferate. Later a large central vacuole is formed which incorporates smaller vacuoles emerging from the cytoplasm, and at the same time the rough ER vesicles and cisternae become highly distended.It is concluded that the cells of the aleurone layer are responsible for the synthesis and secretion into the storage cells of the enzymes necessary for galactomannan degradation. The physiology of galactomannan breakdown is compared and contrasted with that of starch mobilisation in the endosperm of germinating cereal grains.This is part three in a series of papers dealing with galactomannan metabolism. Part two: Planta (Berl.) 100, 131–142 (1971).     

COTTON EMBRYOGENESIS: THE EARLY DEVELOPMENT OF THE FREE NUCLEAR ENDOSPERM

An electron microscope study was made of the central cell and the development of the free nuclear endosperm surrounding the zygote and synergids during the first three days after pollination. The cytoplasm of the central cell, concentrated around the partially-fused polar nuclei, contains many ribosomes, mitochondria and large, dense, starch-containing plastids, some dictyosomes and lipid bodies, and long, single cisternae of rough endoplasmic reticulum (RER) that frequently terminate in whorls. Dense, core-containing microbodies are closely associated with the RER. After fertilization the cytoplasm of the 2-and 4-nucleate endosperm shows an increase in number of dictyosomes, and in amount of RER which becomes stacked in arrays of parallel cisternae. Cup-shaped plastids are associated with many long, helical polysomes. Perinuclear aggregates of dense, granular material also appear after fertilization. Granular aggregates and helical polysomes disappear after the first few divisions of the primary endosperm nucleus. During the second and third days of development there is an increase in dictyosome number and RER proliferation, and endosperm nuclei become deeply lobed. Concurrently, there is a sharp decline in the starch and lipid reserves of the central cell and elaborate transfer walls are formed at the micropylar end of the embryo sac and on the outer surface of the degenerating synergid. The transfer walls contain groups of small, membrane-bound vesicles, and are associated with large numbers of mitochondria and with the smooth endoplasmic reticulum.     

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.     

Asymmetrical microtubule capping structures in frog palate cilia

The three-dimensional ultrastructure of the Golgi apparatus in milk secreting epithelial cells of bovine mammary gland was explored. From computer-aided reconstructions of serial thin sections, it was determined that the Golgi apparatus was composed of a single set of stacked cisternae. The three-dimensional shape of the dictyosome varied from cell to cell, but the overall shape was that of a hollow cone, cylinder, or bowl. The cis and trans surfaces of the dictyosome were arranged in three-dimensional space such that the cis face was located on the outer surface of the hollow structure and the trans face on the inner surface. The cytoplasmic channel (secretory channel) that traversed the longitudinal axis of the hollow dictyosome contained secretory vesicles. Densely stacked cisternae of rough endoplasmic reticulum surrounded the dictyosome, and microvesicles appeared to fuse with, or bud from, cisternae of both organelles. These findings suggest that Golgi apparatus of the lactating epithelial cell is highly organized and that the Golgi apparatus and secretory channel are essentially an independent compartment within the cell.     

Liver ultrastructure and a new cell type in the Japanese newt, Cynops pyrrhogaster.

The liver of the Japanese newt, Cynops pyrrhogaster, has been investigated using light, scanning, and transmission electron microscopy. Hepatic parenchyma was composed of clusters and cords or tubules of polyhedral cells separated by a sinusoidal net. Hepatocytes had spherical, euchromatic nuclei with one or more nucleoli and stacked mitochondria with sparse cristae and dense bodies. Rough endoplasmic reticula formed peribiliary stacks and diffusely scattered vesicles and tubules. Smooth endoplasmic reticula were more pronounced in glycogen-rich hepatocytes. Most hepatocytes contained peroxisomes, Golgi complexes and large numbers of fat droplets within the cytoplasm along with glycogen. Some cells were mainly glycogen-storing and contained few or no fat droplets. A special feature of the newt liver was biliary atresia. Bile canaliculi had short, stout microvilli which were entirely atretic in some canaliculi. Canaliculi were sealed off by junctional complexes including zonulae occludentes and maculae adherentes. The latter showed extraordinary wider desmosomal gaps in the vicinity of the atretic bile canaliculi. The sinusoid wall was non-distinctive and contained fenestrated endothelial cells connected to Kupffer cells by zonulae occludentes. A distinctive new cell type (OG cell) was observed in the newt liver. These cells were found individually or in small clusters in proximity with the sinusoidal surfaces. They had small nuclei, a paucity of cytoplasmic organelles, but numerous, unique, osmiophilic granules of two distinct types. Less numerous Type I granules contained homogeneous electron-dense material, and a predominant Type II granule contained circumferentially arranged subparticulation. Granules of both types were detected within the cytoplasm of endothelial cells and within sinusoids together with blood elements. The function of this secretory type cell remains obscure, though it may represent a stage of melanophore.     

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.     

棉花花粉水合和萌发时超微结构的变化：着重论述内质网和被膜小泡

棉花(Gossypium hirsutum L.)花粉在授粉后水合至萌发时期的营养细胞中贮藏的大量淀粉粒和脂体被动用。超微结构的观察表明,首先是造粉质体中的淀粉粒降解,尔后是脂体。在花粉水合至萌发时期,营养细胞中内质网和高尔基体十分活跃,并含丰富的被膜小泡。内质网的构型发生明显的变化:花粉刚水合时内质网潴泡高度扩张,不同程度扩张的内质网潴泡连续成网状并折迭形成许多囊袋状结构单位,其中包含造粉质体、脂体和被膜小泡群;其后,内质网潴泡形成的囊袋状结构消失,变为分支互通的网状结构;至萌发时,内质网潴泡略为扩张,有些连续成简单的网状,有些呈游离的囊泡状。被膜小泡始终是成群地分布,并与脂体联结,当脂体降解时一些被膜小泡与之融合。根据棉花花粉在水合至萌发时期,营养细胞质中存在独特形态的内质网系统和含丰富的被膜小泡,它们的动态行为及与淀粉和脂体的转化和降解之间的密切关系,讨论了这两种细胞器可能的功能。     

Cytological differentiation in the uropygial gland.

Ultrastructural changes were studied in the cells undergoing secretory differentiation in zone I of the tubules of the uropygial gland of White Plymouth Rock chickens. A layer of basal cells and four secretory stages are recognized as the cells migrate from the periphery to the lumen of tubules and progressively elaborate a secretion product. Basal cells, containing rough endoplasmic reticulum and free ribosomes, rest on the basement membrane and are the source from which secretory cells arise. Dilated perinuclear cisternae and the proliferation of smooth endoplasmic reticulum in the form of vesicles, invaginated sacs and cusp-shaped cisternae indicate the onset of lipgenesis in stage I cells. The perinuclear cisternae are more dilated and the endoplasmic reticulum is composed on saccules and cisternae in stage II cells. Stage III cells are characterized by concentric lamellae of endoplasmic reticulum surrounding secretory droplets. Dilated cisternae of endoplasmic reticulum and secretory droplets both contain a reticular substance. The perinuclear cisternae of stage III cells have returned to normal dimensions. Large mature lucent secretory droplets, lined with electron-dense material, fill the cytoplasm ostage IV cells which degenerate and release their secretory product into the tubule lumen. Spherical membrane-bound compartments containing a mottled substance of moderate electron density occur in basal cells and all subsequent secretory stages. These mottled bodies are surrounded by saccules of endoplasmic reticulum in stage II cells and are intimately associated with secretory droplets in stage III cells, but there is no evidence that they give rise to secretory droplets and their role in secretory differentiation is unknown.     

Mast cells of lymph hearts during ontogenesis of frogs Rana temporaria

Electron microscopic observations of the lymph hearts of tadpoles and yearling frogs of Rana temporaria showed that mast cells (MCs) were present not only between muscle fibers (population of resident MCs), but in the cavities of lymph heart (population of circulating MCs), too. There were some differences in the ultrastructure of the resident MCs at each studied stage of larval development. The first recognizable MCs were revealed in the lymph hearts at premetamorphosis (stages 39-41). MCs presented as mononuclear relatively small and slightly elongated cells with a few immature secretory granules and numerous free ribosomes, polysomes and short cisternae of rough endoplasmic reticulum (RER) in the cytoplasm. Chromatin of their nuclei was poorly condensed; the Golgi apparatus was moderately developed. At pro-metamorphosis (stages 44-45), we revealed MCs at different levels of their differentiation. Some MCs demonstrated an active process of granulogenesis in their cytoplasm. Among densely packed cytoplasmic organelles, immature secretory granules were closely associated with cisternae of RER and free ribosomes. Other MCs appeared as more differentiated cells. They were characterized by a predominantly heterochromatic nuclei and cytoplasm filled with polymorphic and heterogeneous granules. MCs also showed a reduction in the number of free ribosomes and cisternae of RER in the cytoplasm. On the contrary, the Golgi apparatus was well developed. Stacks of Golgi cisternae, detaching vacuoles, and progranules occupied the perinuclear region. The majority of the outlines above ultrastructural features of differentiated MCs were typical for MCs of yearling frogs. At metamorphic climax (stages 52-53), MCs often tightly contacted with macrophages. We did not reveal apoptotic MCs. However, some MCs exhibited morphological features typical for programmed necrosis-like death, which was characterized by mitochondria swelling, dilatation of cisternae of RER and nuclear envelope, plasma membrane rupture and subsequent loss of intracellular contents. Electron microscopical immunocytochemistry revealed the localization of atrial natriuretic peptide (ANP), substance S (SP) and heat shock protein (Hsp70) in the secretory granules of the resident and circulating MCs at different stages of tadpole development and in yearling frogs.     

The mystery of the unstained Golgi complex cisternae

The Champy-Maillet OsKI reaction has been used upon Golgi complexes to show two kinds of staining. It stains material being processed as it passes along the secretory pathway of the rough endoplasmic reticulum (RER) and Golgi cisternae (GC) up to crystallization in secretory vesicles. It also stains separately the environment within parts of the GC. This GC staining may occur in all compartments (transition vesicles, saccules, condensing vacuoles), but it is characteristically missing from any one of them. The unstained cisternae may be explained if outer saccules are made from either stained or unstained transition vesicles, both of which occur. The presence of empty, unstained transition vesicles is dictated by the surface to volume ratios of microvesicles in relation to saccules. Most transition vesicles must return their membrane to the endoplasmic reticulum, but from time to time it is presumed that they fuse to make a saccule. Saccules, stained and unstained, then mature through the stack. OsKI reactions with tissues and test molecules suggest that in the RER and GC the stain detects labile--S . S--bridges before they lock the tertiary configuration of proteins.     

Early Stages in Wheat Endosperm Formation and Protein Body Initiation

The early stages of endosperm formation and protein body initiationare described for hard red winter wheat using light and transmissionelectron microscopy. Two days after flowering (DAF) the endospermwas a thin layer of coenocytic cytoplasm lining the embryo sac.By 4 DAF the endosperm had cellularized and completely filledthe embryo sac. Enough differentiation had occurred by 6 DAFto distinguish cells destined to become the aleurone layer,sub-aleurone region and central endosperm. Protein bodies wereinitiated at about 6–7 DAF and were first found near theGolgi apparatus. Wheat was ready for combine harvest at 34 DAF.Enlargement of the small protein bodies near the Golgi apparatusoccurred by several mechanisms: (1) fusion with one or moreof the dense Golgi vesicles or fusion with other protein bodies,(2) fusion with small electron-lucent Golgi-derived vesicles,(3) pinocytosis of a portion of the adjacent cytoplasm intothe developing protein body and (4) fusion of large proteinbodies with one another at later stages of grain development.Of the four mechanisms described, the pinocytotic vesicles andfusion of protein bodies were the most frequent and consistentprocesses observed. Direct connections between rough endoplasmicreticulum (RER) and protein bodies were not observed. The resultssuggest a rôle for the Golgi apparatus in the initiationof protein bodies. Also, the lack of RER derived vesicles suggestsa soluble mode of secretion of storage proteins involved inthe enlargement of protein bodies. Triticum aestivum, wheat endosperm, protein bodies Golgi apparatus     

Accumulation of Metabolites during Seed Development in Trifolium repens L.

Metabolite deposition during seed development was examined histochemicallyin Trifolium repens by light- and fluorescence microscopy. Allendosperm haustorium at the chalazal pole of the embryo sacand wall protrusions in cell walls of the suspensor and theembryo sac suggest that transfer of metabolites from maternalto offspring tissue takes place primarily at these sites. Thisis further supported by prominent cutinization of the interpolarregion of the embryo sac wall, accumulation of starch in integumentaltissue at the embryo sac poles, and breakdown of interpolarendothelial cells. Decomposition of osteosclereid starch isfollowed by accumulation in the cellular endosperm and subsequentlyin the embryo parallel to endosperm degradation. The starchaccumulates gradually inward from the subepidermal cells ofthe embryo to the stele. Protein bodies are formed in the vacuolesalong the tonoplast, later to be cut off in vesicles releasedinto the cytoplasm. At maturity the embryo is packed with proteinand starch, but without lipid reserves. Phytin is observed inthe protein bodies. The mature embryo is surrounded by a proteinand starch containing aleurone layer which originates from theendosperm.Copyright 1994, 1999 Academic Press White clover, protein, starch, cuticle, embryo sac wall     

Cytopathology of PC12 cells infected with Japanese encephalitis virus.

Infection of a clonal rat pheochromocytoma cell line, PC12, with Japanese encephalitis (JE) virus produced successively higher titers of virus in the culture fluid during the 72-h experimental period. In electron microscopical observation, JE virus entered PC12 cells by direct penetration through the plasma membrane at 2 min postinoculation (p.i.) and caused marked cellular hypertrophy and extensive proliferation of the cellular secretory system including rough endoplasmic reticulum (RER) and Golgi complexes starting 24 h p.i. The proliferating RER of the virally infected cells contained progeny virions and characteristic endoplasmic reticulum vesicles in its cisternae, and the proliferating Golgi complexes contained virions in their saccules. These findings indicated that the proliferation of the cellular secretory system occurred in association with viral replication and maturation in the system. Seventy-two hours p.i., the cellular secretory system of infected PC12 cells showed degenerative changes with vesiculation, disorganization, and dispersion of the Golgi complexes and fragmentation, focal cystic dilation, and dissolution of the RER in the same manner as those seen in the secretory system of JE-virus-infected neurons in the mouse brain. Thus, JE-virus-infected PC12 cells seem to be a suitable neurogenic cell line for the study of the pathogenic mechanism of JE virus. At the same time, the virally infected cells seem to offer an interesting cell model for the study of the morphogenesis of the cellular secretory system.     

Nucellar degeneration inCortaderia (Gramineae)

Summary Vigorous degradation of nucellar tissue in the apomictic grassCortaderia jubata is associated with early degeneration of the megaspore mother cell and the subsequent enlargement of several cells to form somatic embryo sacs. Nucellar degeneration is recognised by the separation of the nuclear membranes, at first along only small sectors of the nucleus, and the appearance within the enlarging perinuclear space of vesicles formed by blebbing of both the inner and outer membranes of the nuclear envelope. Invaginations of the bounding membrane of the dilating RER are responsible for many single-membrane-bound vesicles lying in cisternae throughout the cytoplasm. Eventually the nucleus, enclosed mainly in the inner nuclear membrane, and the cytoplasm, are subject to extensive vesicularization. An electron opaque substance is present in the perinuclear space, in the ER, in vacuoles, and outside the plasmalemma adjacent to the degenerating cell wall, and is similar to a substance which appears on the inner and outer membrane surfaces of mitochondria during later stages of cell degeneration. It is suggested that the genesis and growth of embryo sacs inC. jubata are linked with a programmed nucellar cell autolysis.     

A post-embedding immunoelectron-microscopic demonstration of apolipoprotein-B-containing lipoprotein particles in hepatocytes of fetal rats

We used the protein-A gold technique to demonstrate the presence of apolipoprotein-B in ultrathin sections of fetal rat liver tissue. It was possible to show for the first time that the electron-dense, osmiophilic particles with diameters of 20-40 nm located within the RER cisternae and Golgi complexes of fetal rat hepatocytes contain apolipoprotein-B components and therefore are lipoproteins. After specific labelling an accumulation of gold label was observed on the RER cisternae, Golgi cisternae and the Golgi-associated secretory vesicles of hepatocytes. The specificity of this labelling pattern was assessed by comparison with cytochemical controls. Our qualitative findings were confirmed by a quantitative analysis of the mean labelling intensity (mean number of gold particles per square micron of the surface area of a particular cellular compartment) on the RER, Golgi complexes, mitochondria, nuclei and the remaining cytoplasm of hepatocytes. It is concluded that the hepatocytes of fetal rats are capable of forming apolipoprotein-B-containing lipoprotein particles. With respect to the size-distribution pattern of the observed intra-hepatic lipoprotein particles, we suggest that the hepatocytes of fetal rats produce lipoproteins of the low- and very low-density-lipoprotein type.