The ultrastructure of the rabbit oocyte at the bilaminar follicle stage]

The electron microscope study of the nucleus and organoids of the rabbit oocytes cytoplasm during growth showed nucleoluslike bodies (RNP-granules) on the lampbrushen chromosomes to reach their maximal size at the stage of bilaminar follicle. The RNP-granules differ from the nucleoli by the time of their occurrence cytochemical characteristics, and by their ultrastructural pattern. Throughout the bilaminar follicle stage four components may be seen in the oocyte nucleolus: a dense fibrillar framework around the vacuoles, islets of the granular mass loosely dispersed, and electron dense fibrillar elements filling up the numberous electrontransparant vacuoles. The nucleolus-like bodies are round in shape and have no vacuoles, consisting to two components only: distinctly outlined granules, and weakly developed fibrillar component. The nuclear envelope is seen blebbing. Separation of two nuclear membranes forms a pocket-like enlargements of the perinuclear space. The pockets are limited by small regions between the adjacent nuclear pores. The outer membrane may bulge producing lacuma and large channels in the cytoplasm, which are interconnected making a closed branched network extending inside of the cytoplasm. The nuclear envelope is suggested to be involved in formation of the endoplasmic reticulum through the blebbing process.     

Electron-microscopic study of the nuclear membrane of the PKEV cells during mitosis. 1. The breakdown of the nuclear membrane (prophase, prometaphase, metaphase)]

An ultrastructural study on dividing PKEV cells provided a possibility to distinguish between certain stages of their desintegration. The changes preceding fragmentation of the nuclear envelope commence with desorganization of its structural components: vanishing of granular peripherial chromatin layer; appearance of the pores without central granules; formation of deep invaginations of the nuclear membranes. The desintegration of the nuclear envelope starts from the disapearance of many pores and the appearance of perforations almost of the same size. Simultaneously, the number of polysomes is reduced on the outer membrane of the nuclear envelope and in the cytoplasm. Specific features of the nuclear envelope being lost it becomes undistinguishable from the reticulum elements. On serial sections, no contacts were observed between chromosomes and membranous elements.     

Freeze-fracture features of epithelioid cells,multinucleated giant cells,and phagocytic macrophages

The freeze-fracture morphology of epithelioid cells, multinucleated giant cells (Langhans' type), and phagocytic macrophages was investigated. The intensely folded and interdigitating surface membranes of epithelioid cells and multinucleated giant cells displayed no specialized areas of cell contact. The size of the intramembranous particles (IMP) and the fact that the area density of IMPs was higher in the cytoplasmic (P) faces than in the external (E) faces of the cell membranes agreed with observations in other eukaryotic cells. The area densities of the IMPs suggest lower transport rates of molecules across the cell membranes of granuloma cells than of certain epithelial cells. Small pits were detected in the surface membranes of the granuloma cells but an extrusion of granules was not observed. The cytoplasmic granules displayed very different sizes and shapes ranging from spherical to rod-shaped. The latter type of granules (probably primary lysosomes) dominated in multinucleated giant cells. The granule membranes were studded with IMPs whose area densities increased with the granule size. Multilamellar bodies with smooth (lipid) fracture faces were found only in phagocytic macrophages. The nuclear pores of the granuloma cells were distributed over the entire surfaces of the nuclei and displayed moderate clustering. The values of the area densities of the nuclear pores were in keeping with the values observed in mammalian and human epithelial or mesenchymal cells, indicating similar exchange rates of molecules between the nucleoplasm and the cytoplasm in these different cell types. In a single phagocytic macrophage the E-face of the inner membrane of the nuclear envelope displayed a network of fine filaments whose nature is at present unknown.     

Fine Structure of Microgametocytes and Macrogametes of Eimeria nieschulzi

SYNOPSIS. An electron microscope study of microgametocytes and macrogametes of Eimeria nieschulzi Dieben, 1924 revealed that they lie within vacuoles bounded by a host unit membrane. The vacuole surrounding the microgametocyte contains granular material. The vacuole around the macrogamete is narrower and contains vesicles and membranes. Micropores were seen on the surface of the plasma membrane of microgametocytes and macrogametes. Microtubules were seen in macrogametes. Young microgametocytes and macrogametes have a similar cytoplasmic matrix, mitochondria and nuclei. Glycogen granules apparently develop around vacuoles in both microgametocytes and macrogametes. Glycogen granules were also seen along the margins of parallel bundles of fibers in microgametocytes. As nuclei of the microgametocyte divide, they move to the periphery of the parasite. Three basal bodies, each with 9 fibers in triplet form, develop in association with each nucleus. Microgametes have 2 free flagella and a central short, attached flagellum. Basal granules lie along the outer fibers of the central flagellum. Each microgamete has an elongate mitochondrion in close contact with the nucleus. In macrogametes wall-forming bodies develop in lacunae in the cytoplasm. Smaller dark bodies with areas of low density were also seen. Wall-forming bodies and dark bodies move to the periphery of mature macrogametes.     

Ultrastructural cytochemical and autoradiographic demonstration of nonspecific esterase(s) in guinea pig basophils

We used ultrastructural autoradiographic and cytochemical methods to localize esterase activities in unstimulated guinea pig basophils and in basophils undergoing degranulation or recovery from degranulation. We used tritium-labeled diisopropylfluorophosphate (DFP) as a probe for serine enzymes and localized this probe by ultrastructural autoradiography to cytoplasmic granules of immature or mature unstimulated basophils, as well as to granules released by degranulating basophils. Ultrastructural cytochemistry using alpha naphthyl acetate (ANA) as substrate localized nonspecific esterase activity to extruded granules, either within the interiors of degranulation sacs or within granules completely separated from degranulating basophils. Extruded granules retained their esterase activity for as long as 24 hr after antigen-induced degranulation. The plasma membranes of unstimulated or degranulating basophils, as well as of basophils recovering from degranulation, displayed prominent cell surface ANA esterase ectoenzyme activity. Lipid bodies, organelles present in the cytoplasm of both control and recovering basophils, were also alpha naphthyl acetate esterase (ANAE)-positive. Thus, cytochemical and autoradiographic techniques localized esterase and/or [3H]-DFP-binding activities to cytoplasmic granules, lipid bodies, and cell surface of basophils, and these enzyme activities persisted during both degranulation and recovery from degranulation.     

Cyanophilic bodies in cervico-vaginal smears.

Thirty-six out of 171 (21%) cervico-vaginal smears that manifested pronounced squamous epithelial atrophy contained cyanophilic bodies about the size and shape of parabasal cells. These cyanophilic bodies have been misinterpreted as cancer cells. Patients whose smears contained cyanophilic bodies were likely to be elderly, at least ten years postmenopausal, and free of any gynecologic symptoms or abnormalities except those associated with previous surgery. Smears which contained cyanophilic bodies also contained numerous parabasal cells in various stages of degeneration, objects which closely resembled trichomonads, and a heavy background of granular material. A morphologic continuum existed between all of these elements. The conclusion, therefore, is that cyanophilic bodies, spurious trichomonads and the granular material are all derived from degenerating parabasal cells. It is suggested that cyanophilic bodies develop because of the diminished efflux of exfoliated epithelial cells and mucus associated with squamous epithelial atrophy. The ensuing stagnation of parabasal cells allows them to degenerate to an advanced degree. It appears that as some of the parabasal cells degenerative, their nuclear chromatin becomes widely dispersed throughout the cytoplasm, thereby forming cyanophilic bodies.     

Ultrastructure of the nuclear apparatus of the infusorian Loxodes magnus. I. The macronuclei, macronuclear anlagen and the interphasic micronuclei]

The nuclear apparatus of Loxodes magnus Stokes (Holotricha) consists of numerous macronuclei which belong to the diploid type and never divide, and of numerous micronuclei. No nuclear groups exist; individual nuclei often lie in cytoplasmic islets surrounded by large lacunae of the smooth endoplasmic reticulum. Interphasic micronuclei have two-membraned envelopes with numerous pores, usually lined at the cytoplasmic side with a layer of vacuoles, channels, or flattened vesicles of the smooth endoplasmic reticulum. The chromatin of the micronuclei consists of anastomosing threads, 0.1--0.2 mum wide, between which several nucleolus-like bodies of microfibrillar structure occur. Adult macronuclei have a similar nuclear envelope and a similar system of vacuoles, channels, and flattened agranular cisternae outside it. The macronucleus contains a single large composite nucleolus with 3 or 4 fibrillar cores inside the common granular cortex. The fibrillar cores are pierced by channels containing nucleolar organizers in the form of strands of condensed chromatin. The peripheral zone of the macronucleus is filled with decondensed chromatin fibrils and contains a number of small chromocenters and several aggregates of RNP granules. No protein inclusions (spheres) have been observed in Loxodes macronuclei. The macronuclear anlagen, developing in the cycle of every cell division, show progressive decondensation of the chromosomes and formation of several nucleoli, each with its own organizer. Later on, the nucleoli fuse into a single nucleolus. The small chromocentres are the last to form.     

Ultrastructural characterization of the interphase nucleus of Gonyostomum semen.

The interphase nucleus of the chloromonadophycean alga, Gonyostomum semen (Ehrenberg) Diesing, has a highly distinctive appearance. Interphase chromatin is readily distinguishable in both light and electron microscope preparations. It extends throughout the neucleus and frequently makes contact with the nucleoli and with the nuclear envelope. Among the chromatin filaments are large numbers of 35-46 nm diameter granules which occur singly or in clusters. The nucleoli are characteristically located in the posterior half of the nucleus and are composed of granular and non-granular components. Nuclear pores occur in slight depressions of the nuclear surface; their lumen has a diameter of approximately 75 nm and contains electron-dense material. The chromatin and the large numbers of nuclear granules are unusual and warrant further investigation.     

ULTRASTRUCTURE OF CARPOSPOROGENESIS IN THE PARASITIC RED ALGA FAUCHEOCOLAX ATTENUATA SETCH. (RHODYMENIALES,RHODYMENIACEAE)

Carpospore differentiation in Faucheocolax attenuata Setch. can be separated into three developmental stages. Immediately after cleaving from the multinucleate gonimoblast cell, young carpospores are embedded within confluent mucilage produced by gonimoblast cells. These carpospores contain a large nucleus, few starch grains, concentric lamellae, as well as proplastids with a peripheral thylakoid and occasionally some internal (photosynthetic) thylakoids. Proplastids also contain concentric lamellar bodies. Mucilage with a reticulate fibrous substructure is formed within cytoplasmic concentric membranes, thus giving rise to mucilage sacs. Subsequently, these mucilage sacs release their contents, forming an initial reticulate deposition of carpospore wall material. Dictyosome vesicles with large, single dark-staining granules also contribute to wall formation and may create a separating layer between the mucilage and carpospore wall. During the latter stages of young carpospores, starch is polymerized in the perinuclear cytoplasmic area and is in close contact with endoplasmic reticulum. Intermediate-aged carpospores continue their starch polymerization. Dictyosomes deposit more wall material, in addition to forming fibrous vacuoles. Proplastids form thylakoids from concentric lamellar bodies. Mature carpospores are surrounded by a two-layered carpospore wall. Cytoplasmic constituents include large floridean starch granules, peripheral fibrous vacuoles, mature chloroplasts and curved dictyosomes that produce cored vesicles which in turn are transformed into adhesive vesicles. Pit connections remain intact between carpospores but begin to degenerate. This degeneration appears to be mediated by microtubules.     

Zoosporulation in Labyrinthula sp.; an Electron Microscope Study1

SYNOPSIS. Zoosporulation in Labyrinthula sp. in monoxenic culture was initiated by aggregation of spindle cells into reticulate sori. The spindle cells then changed into rounded or oval cells and formed, de novo, 2 pairs of centrioles at opposite sides of each nucleus. A pair of granular aggregates (protocentrioles) ～ 240 mμ in diameter served as precursor bodies during centriole formation. Spindle microtubules around the prophase nucleus connected the pairs of centrioles but were not found in the nucleoplasm until nuclear envelope fragmentation occurred. Prophase nuclei of uninucleated sporangia contained synaptinemal complexes; therefore, meiosis is presumed to occur. The envelope fragments moved toward the centrioles and regrouped to form the nuclear membranes of the daughter cells. Alternating nuclear and cytoplasmic divisions subdivided the preparation into 8 cells which differentiated into laterally biflagellated zoospores. Flagellar development involved growth of the kinetosome microtubules into a bud which formed over the kinetosome tangential to the cell surface. Kinetosomes were derived directly from centrioles with little differentiation other than addition of an electron-dense core to the lumen of the centriole. Zoospore ultrastructure included a stigma comprised of a row of electron-dense granules located slightly under the plasmalemma and posterior to the pair of kinetosomes. A single row of 17–21 microtubules lay parallel to the stigma granules, one or more being connected to the anterior kinetosome. A striated fiber apparatus similar to that found in some phytoflagellates connected the midregions of the kinetosomes. Fibers 1.0–1.2 μ long were attached to the plasmalemma around the base of the anterior flagellum. Zoospores settled on the substrate and differentiated directly into spindle cells. Since synaptinemal complexes were observed the planonts are probably haploid zoospores and probably not gametes since planogametic copulation was not observed.     

ELECTRON MICROSCOPE STUDIES ON DEVELOPING CRAYFISH OOCYTES WITH SPECIAL REFERENCE TO THE ORIGIN OF YOLK

The endoplasmic reticulum is composed, in places, of stacks of parallel cisternae which are limited by membranes having great numbers of ribosomes attached to their outer surface. These are connected with other cisternae of similar structure but with fewer ribosomes and without preferred orientation. The latter extend in all directions from the stacked cisternae, branching and anastomosing freely so that the entire system of membrane-limited cisternae appears interconnected; a morphological condition suitable to serve as the basis for an active transport system. Within the stacked cisternae appear granules about 40 to 60 mµ in diameter. These are thought to represent the precursors of proteinaceous yolk, and the hypothesis is advanced that most of the intracisternal granules are synthesized here, possibly under the influence of the ribosomes. They then "flow" into and along the unoriented cisternae to regions where they collect, expand the cisternae, and undergo transformation into finely granular, relatively large proteinaceous yolk bodies. The mitochondria are somewhat pleomorphic, often show atypical cristae, and frequently contain a few dense granules. Lipid is abundant. Other cytoplasmic components are illustrated.     

Ultrastructural study on nuclear-cytoplasmic relationships in oocytes of the African lungfish,Protopterus aethiopicus

Summary Growing oocytes of Protopterus, like those of some amphibians and teleosts, show an impressive development of the nucleolar apparatus. Numerous nucleolus-like bodies establish close spatial relationships with the nuclear envelope by extending pedicels and streams of finely dispersed material towards the inner membrane.At such contact points, gaps in the perinuclear cistern are more frequent than elsewhere along the nuclear boundary. Expansion of the outer nuclear membrane gives rise to blebs, with or without visible content, and these become pinched off to form small vesicles in the perinuclear cytoplasm.Small, electron dense aggregates, indistinguishable from nucleolar material occur on both sides of the nuclear envelope opposite to each other, some being connected by a slender portion of the same material within a nuclear pore. Such accumulations are interpreted as detached parts of nucleolar bodies in transit to cytoplasmic sites where they presumably participate in the biogenesis of ribosomes. At the height of nucleolar emission, nucleoplasm and perinuclear cytoplasm are so rich in small electron dense particles that they are almost indistinguishable from each other.At this stage of massive transport, the route provided by the nuclear pores seems to be insufficient and another, more spacious, gateway may be in operation. The latter involves direct passage of material across the nuclear membranes preferentially where these form blebs.This view is supported not only by the overt spatial relationships between nucleolar pedicels and blebs, but by the occurrence within perinuclear lacunae and blebs of particles that seem to be derived from nucleolar bodies. Furthermore, frequent interruptions in the nuclear membranes preferentially located where they expand into outpocketings suggest that at these sites temporary gateways may exist in the living cell that permit easy access of intranuclear components to the cytoplasm.Supported by grants AM-3984, NB-00840, and NB-05219 from the U.S.P.H.S.     

The Fine Structure of the Macrogametocytes of Adelina tribolii Bhatia, 1937 (Eucoccidia, Telosporea) from the Fat Body of the Beetle Tribolium castaneum Hbst.

SYNOPSIS. Macrogametocytes of the coccidium Adelina tribolii Bhatia, 1937 are described from the time when they settle in the fat body of the host and form periparasitic vacuoles around them to the stage of microgametocyte occurrence and the beginning of syzygy formation.
The macrogametocyte is surrounded by a 2-layered pellicle 50 mμ thick. Its continuity is interrupted by one or several micropores 40 mμ across and 86 mμ deep.
The cytoplasm of the parasite contains numerous vesicles and lamellae of rough and smooth endoplasmic reticulum. Mitochondria of various sizes have short tubules. The macrogametocyte contains a variable number of dark bodies 1.4-2.4 μ in diameter. It also contains several vacuoles up to 1.2 μ which are covered with a 3-layered membrane and enclose a granular material.
In old macrogametocytes in syzygy multivesicular bodies develop which measure up to 2.4 by 1.6 μ. Several smaller vacuoles containing granular material are also a constituent of the electrondense basic substance of these corpuscles.
Paraglycogen granules 1.4 by 0.9 A occur in old macrogametocytes and are situated inside the vacuoles which are not bordered by a membrane. The numbers and size of these granules increase with the age of the parasite. The Golgi complex lies close to the nucleus.
The nucleus, 6-8.5 μ in diameter, is in the center of the macrogametocyte and contains a large eccentric nucleolus. The nuclear membrane is 2-layered and has many pores.     

An ultrastructural and histochemical study of oogenesis in the trichostrongylid nematode Heligmosomoides polygyrus

Oogenesis in trichostrongylids has been examined for the first time in a light and electron microscopic investigation of Heligmosomoides polygyrus. The female reproductive tract is a single straight tube containing small oogonia (6 micron in diameter), which are arranged in a rosette pattern around a central rachis at the anterior end of the tract. Developing oocytes separate from the rachis and pass posteriorly in single file down the growth zone. Oocytes increase rapidly in volume due to the accumulation of cytoplasmic inclusion granules. These granules are of 3 types. Type 1 granules are amorphous and probably consist primarily of lipoprotein. Type 2 granules are large lipid inclusions and type 3 granules are electron-dense lipoprotein yolk bodies, which are probably used for energy reserves in the developing embryo. Histochemical studies show a more intense reaction for DNA in the nuclei of oogonia than in the nuclei of oocytes. There is a strong reaction for RNA in the nucleoli and in the cytoplasm of oogonia and oocytes. Ultrastructural studies indicate that this RNA is probably in the form of rRNA in the abundant ribosomes. Mature oocytes are cylindrical (60 X 70 micron), have a distinct nucleus with nuclear pores, and the cytoplasm is filled with inclusion granules and ribosomes but contains only small amounts of glycogen. Prior to fertilization the plasma membrane of oocytes acquires a flocculent coat. These oocytes contain 6 distinct bivalent chromosomes in diakinesis. Thus the major changes that occur in developing germ cells are 2-fold: nuclear changes that prepare the chromosomes for fertilization by initiating reduction division, and cytoplasmic changes that involve the synthesis and storage of inclusion granules.     

Localization of AU-rich element-containing mRNA in cytoplasmic granules containing exosome subunits

Eukaryotic mRNAs can be degraded in either decapping/5'-to-3' or 3'-to-5' direction after deadenylation. In yeast and mammalian cells, decay factors involved in the 5'-to-3' decay pathway are concentrated in cytoplasmic processing bodies (P bodies). The mechanistic steps and localization of mammalian mRNA decay are still not completely understood. Here, we investigate functions of human mRNA decay enzymes in AU-rich element (ARE)-mediated mRNA decay (AMD) and find that the deadenylase, poly(A) ribonuclease PARN, and enzymes involved in the 5'-to-3' and 3'-to-5' decay pathways are required for AMD. The ARE-containing reporter mRNA accumulates in discrete cytoplasmic granular structures, which are distinct from P bodies and stress granules. These granules consist of poly(A)-specific ribonuclease, exosome subunits, and decay-promoting ARE-binding proteins. Inhibition of AMD increases accumulation of ARE-mRNA in these granules. We refer to these structures as cytoplasmic exosome granules and suggest that some AMD may occur in these granules.     

Ultrastructural changes in the spermatid nuclear envelope of Periplaneta americana during spermiogenesis

The nuclear envelope in the earliest stage of spermatid development possesses double membranes with pores aggregated in certain areas and arranged in a hexagonal pattern. The convex face of the outer nuclear membrane is relatively smooth and the convex face of the inner nuclear membrane carries many particles which are arranged in net-like pattern. In the later developmental stages, nuclear pores were not observed, the convex face of the inner nuclear membrane being covered with densely packed particles and the convex face of the outer nuclear membrane having a rough appearance. During the final stage of spermatid development, the cross-fractured face of the nucleus reveals the profiles of the nuclear fibres, the granular appearance of the convex face of the outer nuclear membrane, and the convex face of the inner nuclear membrane carrying more densely packed particles.     

Amblyospora sp. (Microspora, Amblyosporidae) infecting nerve ganglia of Culex pipiens (Diptera, Culicidae) from Egypt.

A species of Amblyospora-infecting neurones of Culex pipiens is described. Diplokaryotic meronts, which divided by binary fission, were distinguished at the electron microscope level by their unthickened plasma membranes. Sporonts with an electron-dense surface coat gave rise to eight uninucleate sporoblasts within a sporophorous vesicle, cytoplasmic division occurring at the quadrinucleate or octonucleate stages. Indications that nuclear fusion and chromosome reorganization occurred in merogony and sporogony were obtained by light microscopy but meiosis was not detected at the ultrastructural level. Spores were typical of Amblyospora, being ovoid when fresh, truncate when stained, and having an exospore of two membranous layers subtended by a thick amorphous layer, an electron-lucent endospore, an anisofilar polar filament, and a polaroplast comprised of an anterior region of close-packed lamellae and a posterior region of expanded sacs. The metabolic products in the sporophorous vesicle took the form of large globules, small globules with electron-dense borders, and fine granules. These were depleted in mature sporophorous vesicles, though a surface layer of fine granules on the spores may have been derived from them. Many stages were degenerate and it is suggested that C. pipiens may be an accidental host in which the parasite could develop suboptimally in nervous tissue only. Infections in larvae hatched from eggs in the laboratory indicate that vertical transmission occurs.     

The Eyes of Mesostoma ehrenbergi (Focke, 1836) (Platyhelminthes,Rhabdocoela). Fine Structure and Photoreceptor Membrane Turnover

Abstract Each pigment-cup eye of Mesostoma ehrenbergi consists of two photoreceptor cells, the anterior cell being bilobate. the posterior almost linear, and of a multicellular pigment cup. The nuclei of the photoreceptor cells are located inside the medial region of the brain. Thin cytoplasmic photoreceptor projections provided with neurosecretory-like granules are interposed between the inner surface of the eye cup and the distal extremity of the microvilli. The breakdown and renewal of microvillar membranes was analysed. Membrane turnover is a continuous process. At dusk and during the night abscission of photoreceptive membranes occurs. At dawn the membrane fragments are degraded to granular material, which is then endocytosed into the submicrovillar cytoplasm as coated vesicles. These vesicles form multivesicular bodies. The degradation of multivesicular body content occurs during the following light hours. The dark period is correlated with membrane synthesis for elongation of reticular membranes, which are converted into ellipsoid bodies. The formation of new microvillar membranes occurs at the base of the microvillar border, and involves the fusion with the old microvillar membranes of small vesicles detached from the tubular endoplasmic membranes and from the flattened concentric cisternae of ellipsoid bodies. The correlations with daily cycles of other invertebrates are discussed.     

DNA fluorescent stain accumulates in the Golgi but not in the kinetosomes of amitochondriate protists.

Hindgut symbiotic trichomonads (uninucleate Caduceia versatilis, and multinucleate Stephanonympha sp. and Snyderella tabogae) from the dry-wood-eating termite Cryptotermes cavifrons (Kalotermitidae) accumulate DAPI (4,6diamidino-2-phenylindole) in the membranous sacs of the Golgi complex. This form of Golgi complex, typical of protists in the class Parabasalia, is called a parabasal body. Trichomonads contain organellar systems, mastigonts, that consist of four undulipodia (e.g. eukaryotic flagella and cilia), axostylar microtubules, a parabasal body and other structures. These cells bear from one (in the case of Caduceia) to hundreds (in the case of Snyderella) of mastigonts. These features are characteristic of their protist class (Parabasalia). The nuclei of all three species stained with DNA-specific stains: DAPI, SYTOX, acridine orange, propidium iodide, ethidium bromide and Feulgen, at optimal concentrations, but kinetosomes failed to stain at all. The nuclei, parabasal bodies and symbiotic bacteria (but no microtubular structures) fluoresced in glutaraldehyde-fixed cells stained with 1.45 microM DAPI. Parabasal bodies of Snyderella and Caduceia treated to remove lipids with Triton X-100, or treated with 5% trichloroacetic acid, lacked DAPI-fluorescence. I conclude that DNA, present as expected in nuclei and bacterial symbionts, is absent from and not associated with calonymphid kinetosomes. The reason for DNA-RNA stain accumulation in the Golgi cistemae is not clear.     

The fine structure of the granular amebocytes of the Pacific oyster, Crassostrea gigas

Oyster granular amebocytes were characterized by electron microscopy to be of two types. Acidophiles contained relatively small, spherical, amorphous, osmiophilic cytoplasmic granules with a maximum dimension of 0.4–0.56 μ. Basophiles contained large, cytoplasmic granules, approximately 0.7–1.2 μ in diameter. The granules resembled hollow, spherical structures in which an outer membrane and a layer of closely associated granular material enclosed an electron-transparent interior.