An ultrastructural study of larval settlement in the sea anemone Urticina crassicornis (Cnidaria,Actiniaria)

Laboratory-reared larvae of the sea anemone Urticina (= Tealia) crassicornis have been examined by electron microscopy prior to and following settlement on algal substrata. At 18 days postfertilization, the free-swimming planula larva measures about 600 μm long. A stomodaeal invagination occurs at the narrow end of the larva and connects with a solid mass of endoderm in the core region. The endoderm possesses septa with well-developed myonemes and is situated subjacent to a thin sheet of mesoglea. The uniformly ciliated ectoderm that constitutes the outer layer of the larva contains: (1) spirocysts, (2) nematocysts, (3) mucus, (4) three types of membrane-bound granules, (5) a basiepithelial nerve plexus, and (6) a few nongranular cells that may represent sensory neurons. Within several minutes after the introduction of the algal substratum, the planula characteristically directs its broadened aboral end toward the alga and secretes a refractile sheet of material. As the aboral end attaches to the substratum, the larva becomes noticeably shorter along its oral-aboral axis, presumably owing to the contractions of myonemes that are located within the endodermal septa. All three types of granules and the ectodermal mucoid substances are exocytosed during settlement, but spirocysts and nematocysts characteristically remain undischarged. Ovoid, PAS⁺ granules are believed to be at least partly responsible for adhesion, since these granules are concentrated at the aboral end prior to settlement and are somewhat similar in ultrastructure to putative viscid granules produced by other species. Contrary to a previous report based on light microscopy, no discrete sensory organ is evident in serial sections of the aboral ectoderm. The ability of planulae to detect suitable substrata appears to depend instead on sparsely distributed sensory cells that occur throughout the larval ectoderm.     

Ultrastructural and tissue-culture studies on the role of fibronectin,collagen and glycosaminoglycans in the migration of neural crest cells in the fowl embryo

Summary The initial migration of neural crest (NC) cells into cell-free space was studied by transmission electron microscopy at trunk levels of fowl embryos, some of which were fixed in the presence of ruthenium red. Migrating NC cells occurred in zones which contained fewer ruthenium-red stained 15–40 nm diameter granules than other regions. The ruthenium-red stained granules were linked by similarly stained thin ( 3 nm diameter) microfibrils. The granules resemble proteoglycan and the microfibrils may be hyaluronate. NC cells contacted thicker ( 10 nm diameter) fibrils and interstitial bodies, which did not require ruthenium red for visualization. Cytoplasmic microfilaments were sometimes aligned at the point of contact with the extracellular fibrils, which may be fibronectin and collagen.Phase-contrast time-lapse videotaping and scanning electron microscopy showed that NC cells of the fowl embryo in vitro migrated earlier and more extensively on glass coated with fibronectin-rich fibrous material and adsorbed fibronectin molecules than on glass coated with collagen type I (fibres and adsorbed molecules). NC cells became completely enmeshed in fibronectin-rich fibres, but generally remained on the surface of collagen-fibre gels. When given a choice, NC cells strongly preferred fibronectin coatings to plain glass, and plain glass to dried collagen gels. NC cells showed a slight preference for plain glass over glass to which collagen was adsorbed. Addition to the culture medium of hyaluronate (initial conc. 20 mg/ml), chondroitin (5 mg/ml) and fully sulphated chondroitin sulphate and dermatan sulphate (up to 10 mg/ml) did not drastically alter NC cell migration on fibronectin-rich fibrous substrates. However, partially desulphated chondroitin sulphate (5mg/ml) strongly retarded the migration of NC cells.The in vivo and in vitro studies suggest that fibronectin may dictate the pathways of NC cell migration by acting as a highly preferred physical substrate. However, the utilization of these pathways may be reduced by the presence of proteoglycans bearing undersulphated chondroitin sulphate.Abbreviations NC neural crest - ECM extracellular material - GAG glycosaminoglycan - FN fibronectin - CIG cold insoluble globulin - TEM transmission electron microscopy - SEM scanning electron microscopy - DMEM-H HEPES buffered Dulbecco's modified Eagle's medium - FCS foetal calf serum - CEE chick embryo extract - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis - PBS phosphate-buffered saline     

The effects of colchicine on the ultrastructure of the dental epithelium and odontoblasts of teleost tooth buds

Secretory granule ultrastructure of teleost inner dental epithelial (IDE) cells has been reported to be similar to procollagen granules of other cells synthesizing collagen. This study describes the ultrastructure of secretory products in odontogenic cells during enameloid matrix formation in cichlids after inhibition of granule secretion with colchicine. Thirty-six fish were injected with 0.1 mg colchicine, then three were killed first at 2-hr intervals for 12 hr, then daily for 5 days. Tooth buds were processed for transmission electron microscopy, and ultrastructural alterations were assessed for each post-injection interval. Four hours post-injection, IDE cells contained increased numbers of secretory granules, lightly stained granules, dilated cisternae of the granular endoplasmic reticulum, and intercellular amorphous material. After 6 hr, the IDE intercellular amorphous material additionally contained electron dense deposits, and after 8 hr, the intercellular material had fibers similar in appearance to enameloid collagen. No ultrastructural changes were detected in odontoblasts that were in close proximity to the enameloid matrix. Only odontoblasts synthesizing predentin were affected by colchicine, and the observed alterations were similar to those seen in IDE cells. It is concluded that IDE cells synthesize and secrete ectodermal enameloid matrix collagen.     

Ultrastructure of endocrine cells in the stomach of two teleost fish Perca fluviatilis L. and Ameiurus nebulosus L.

Summary In the gastric mucosa of two teleost species, the perch (Perca fluviatilis) and the catfish (Ameiurus nebulosus) three endocrine cell types were found, located predominantly between the mucoid cells of the gastric mucosa. A fourth cell type is present in the gastric glands of catfish. Each cell type was defined by its characteristic secretory granules. Type-I cells were predominant in both fish. These cells contained round or oval granules with a pleomorphic core. The average diameter of granules was 400 nm for the perch and 270 nm for the catfish. Type-II cells of both species displayed small, highly osmiophilic granules about 100 nm in diameter. The secretory granules of type-III cells (260 nm in the perch and 190 nm in the catfish) were round or slightly oval in shape and were filled with a finely particulate electron-dense material. Type-IV cells of the catfish were found in the gastric glands only. Their cytoplasm was filled with homogeneous, moderately electron-dense granules averaging 340 nm in diameter. The physiological significance of these different morphological types of gastric endocrine cells requires further investigation.     

Electron-microscope studies of Drosophila salivary-gland chromosomes

Summary The submicroscopic structure of the chromosomes of the larval salivary gland cells inDrosophila melanogaster has been studied by means of electron microscopy of thin sections.The three fixatives used were buffered 1% osmium tetroxide, unbuffered Zenker's solution, and buffered formaldehyde in concentrations of 0·1% and 1·0%. It was found that formalin preserves the fine structure of the chromosomes better than the other fixatives.Nucleoprotein is present in the chromosome in the form of granules 200 Å to 300 Å in diameter. The granules are connected together by strands of protein approximately 100 Å in diameter. The length of the strands between successive granules in the banded areas is 100 Å to 300 Å and in the interband regions it is 700 Å to 900 Å.Heterochromatin differs from euchromatin in the absence or reduction in the amount of strand material.The nucleolus is composed of an aggregate of granules 300 Å to 600 Å in diameter contained in an amorphous matrix. Within the nucleolus are a series of canals containing material similar in appearance to that of the euchromatic band material.Submicroscopic granules are also present in the karyoplasm and in the cytoplasm surrounding the nuclear membrane. The cytoplasmic granules are more densely distributed near the nuclear membrane.A model for chromosome structure is proposed.The Applied Fisheries Laboratory is operated by the University of Washington under Contract No. AT(45-1)540 with the United States Atomic Energy Commission.     

Ultrastructure of Cysts of Naegleria spp: A Comparative Study*

SYNOPSIS. Ultrastructure of cysts of Naegleria gruberi, Naegleria fowleri, and Naegleria jadini was compared by transmission electron microscopy. Pores in the cyst wall were observed in all 3 species. In N. gruberi they were surrounded by a collar and sealed with a relatively large mucoid plug; no such collar was seen around the pores in the other 2 species, in which the plug was smaller than that in N. gruberi. An electron-dense plaque serving as an additional pore closure was present in all 3 species. In N. gruberi, the cyst wall consisted of an inner thick and an outer thin layer; however, only the inner component was present in cysts of N. fowleri and N. jadini, which had a smooth appearance. At the ultrastructural level, excystment of N. fowleri involved digestion of the mucoid plug and emergence of the trophozoite through the pore. Some digestion of the cyst wall also appeared to take place during excystment.     

The oocyte of a new world marsupial, Monodelphis domestica: structure, formation, and function of the enveloping mucoid layer

Ovulated oocytes of the gray short-tailed opossum Monodelphis domestica are surrounded by a thin zona pellucida and are devoid of a cumulus oophorus. In the ampulla of the oviduct, oocytes acquire a thick mucoid layer composed of concentrically arranged fibrillar material. Exocytosis by the secretory cells of the oviductal epithelium occurs in the region of the oviduct adjacent to the egg. This suggests that the oocyte-zona-mucus layer complex may influence the oviductal epithelium to secrete. During secretion, fibrillar contents of the secretion granules appear to be transformed into membranous material which presumably becomes fibrillar again as it is incorporated into the forming mucoid layer. Spermatozoa (which are known to pair in the cauda epididymis) are found in pairs and with intact acrosomes in the mucoid layer of fertilized eggs. This suggests that spermatozoa of Mondelphis remain paired until they reach the zona pellucida and that the acrosome functions in zona binding and/or penetration.     

Fine structure of syzygial articulations before and after arm autotomy in florometra serratissima (Echinodermata: Crinoidea)

Summary About 1 s after appropriate stimulation, arms of Florometra serratissima break at articulations called syzygies that are specialized for autotomy. The fine structure of unreacted and of newly broken syzygies is described. The unreacted syzygy includes (1) ligament fibers consisting of collagen fibrils interconnected by interfibrillar strands and (2) axons filled with presumed neurosecretory granules. The newly broken syzygy includes (1) ruptured ligament fibers consisting of swollen collagen fibrils associated with interfibrillar globules and (2) axons containing few presumed neurosecretory granules, some of which are fixed in the act of exocytosis; moreover, the calcareous skeleton adjacent to the broken syzygy is partly eroded. The observations before and after breaking suggest that the autotomy mechanism may comprise the following sequence of events: rapid neural transmission from stimulation site to syzygy triggers a massive exocytosis of granules from presumed neurosecretory axons; the released neurosecretions (which could include chelating agents, strong acids, proteolytic enzymes or enzyme activators) etch the skeleton and lower the tensile strength of the ligament fibers by weakening the collagen fibrils and/or the interfibrillar material; breakage of the ligament fibers, the major connective tissue of the articulation, is quickly followed by rupture of all the other tissues at the syzygy.     

In situ Imaging of Pea Starch in Seeds

A method has been developed for the in situ imaging of starch in dry seeds by exploiting the tight packing of the starch and protein storage reserves within the cells of the embryo. The method can be adapted to prepare seed samples which are suitable for light microscopy (birefringence and iodine staining), scanning electron microscopy and atomic force microscopy. Its potential for imaging the internal structure of starch granules without any prior isolation process is demonstrated for round smooth peas. Using a standard ultramicrotome, thin sections were cut directly from selected regions of dry pea seeds and examined by light microscopy before and after hydration. The sectioning procedure left a planed surface with the internal structure of the starch granules exposed. This material was examined by scanning electron microscopy and atomic force microscopy directly or after controlled hydration. In the hydrated pea samples, the growth ring structure and blocklet sub-structure of individual starch granules within the seed were visualised directly by atomic force microscopy. Furthermore, the effects of hydration and staining were monitored and have been used to introduce contrast into the images. The observations have revealed new information on the blocklet distribution within pea starch granules and the physical origins of the growth ring structure of the granules: the blocklet distribution suggests that the granules contain alternating bands with different levels of crystallinity, rather than alternating amorphous and crystalline growth rings.     

The Histochemistry and Fine Structure of the Nutritional Reserves in the Fin Rays of a Lancelet,Branchiostoma lanceolatum (Cephalochordata = Acrania)

Abstract Adults of the European lancelet were collected at Banyuls-sur-Mer (Mediterranean France) in mid-spring, shortly before the onset of the breeding season. The dorsal and ventral fin rays were studied by light microscopic histochemistry and by transmission electron microscopy (TEM). Each fin ray is a mass of extracellular material that accumulates beneath the mesothelium of a fin box coelom. The fin ray material is rich in lipids, proteins, and neutral mucopolysaccharides. TEM reveals no lipid droplets in this material, which consists entirely of a packed mass of 15–20 nm granules of medium electron density. It is likely that these granules consist of glycoproteins or glycolipoproteins. Our results are consistent with the proposal of Azariah (1965, Journal of the Marine Biological Association of India 7: 459–661) that lancelet fin rays are nutritional reserves supporting gametogenesis during the breeding season.     

The paramedial neurosecretory cells of the suboesophageal ganglion in the cricket,Teleogryllus commodus (Walk.)

Summary The paramedian neurosecretory cells (PNC) (A-type) in the suboesophageal ganglion of the cricket, Teleogryllus commodus (Walk.), have been studied by electron microscopy. In control animals (10 day-old virgin females) three different cell stages could be distinguished: Stage 1 shows a variable content of elementary granules and characteristics of actively synthesising cells. Stage 2 is characterised by the presence of numerous fusion bodies, which are formed by the coalescence of elementary granules, presumably for storage purposes. In stage 3 granules are degraded in lysosomes (?). While the production of material rich in cysteine increases after ovariectomy (Dürnberger et al., 1978), the fine structure of the cells is essentially unchanged. The only noted differences are an increased lysosomal synthetic activity and the existence of stages intermediate between 2 and 3, which were never found in control animals. The functional significance of the different stages is discussed.     

The morphology of the cement gland apparatus of Larval Pterophyllum scalare Cuv. & Val. (Cichlidae,Teleostei)

Summary The cement gland apparatus of newly hatched Pterophyllum scalare Cuv. & Val. was examined by histology, scanning and transmission electron microscopy. The whole organ is composed of three pairs of endoepithelial, ductless glands, which cause prominent elevations on the larval head and are found in a specific arrangement. Each single gland is represented by an aggregation of elongated, tubular secretory cells surrounding a pyriform acinus. It overlies a basal lamina and is covered by the outer layer of the bilaminar embryonic epidermis.Two different types of secretory cells can be distinguished. One type is restricted to the bottom of the cavity. It is characterized by multiform cytoplasmic protrusions, which project into the gland's cavity. The secretory granules contain a network of light filamentous material. The second type constitutes the side wall of the acinus. It does not develop any protrusions. The contents of the secretory granules is of very high and homogeneous electron density. The mechanism of extrusion is discussed for both cell types. All secretory cells show a strong PAS-reaction. In SEM a circular microridge pattern with attached mucus globules can be recognized on the larval epithelial surface.Dedicated to Prof. Dr. H. Leonhardt on the occasion of his 60th birthday     

Interaction of collagen with hydrophobic protein granules in the egg capsule of the dogfish scyliorhinus canicula

The egg capsule of the dogfish is a composite material containing collagenous fibrils and 2 mum spherical hydrophobic protein granules. The latter appear to owe much of their hydrophobicity to an exceptionally high tyrosine content (approximately 20% of total amino acid residues). The hydrophobic component appears to form as an emulsion in the secretory granules of the D and E zone gland cells of the nidamental gland. Droplets of the hydrophobic material appear to become coated with remarkably regular layers of radially-arranged collagen molecules which form a series of concentric, evenly spaced layers around each hydrophobic granule. Numerous disclinations were seen where the layers around adjacent granules interfered with one another. The layers are thought to represent a lamellar liquid crystalline phase previously described for this collagen (Knight et al., 1993). The fine structural appearance of the concentric layers and evidence for radial arrangement of collagen molecules within them is compatible with the suggestion that the layers are built from a dumbbell-shaped unit approximately 35 nm long with hydrophobic groups concentrated at the ends. This unit may represent a dumbbell-shaped molecule or an oligomer of two or more molecules lying parallel with one another in a head-to-tail arrangement. Such a unit can be readily incorporated into models for the micellar, hexagonal columnar and final fibrillar phases previously described for this collagen (Knight et al., 1993). Evidence from the TEM study of stretched egg capsule wall suggests that there is a mechanical interaction between the hydrophobic granules and the collagen fibrils in the fully formed material. We suggest that the radial, concentric layered arrangement of collagen molecules is established by hydrophobic interactions within the liquid crystalline material and locked into place by oxidative covalent cross-linking to give a 3-dimensional cross-linked meshwork of collagen fibrils and hydrophobic granules. The latter arrangement helps to account for the high tensilestrength and toughness of this material.     

CYST FORMATION IN THE FRESHWATER DINOFLAGELLATE CERATIUM HIRUNDINELLA (DINOPHYCEAE)1

Cyst formation in Ceratium hirundinella (O. F. Müll.) Bergh was studied by light and electron microscopy, using material from several lakes and reservoirs and also laboratory cultures. Cells preparing to encyst build up large quantities of starch and lipid and at the same time reduce their other cell components. The cyst is released from the theca as a naked cell bounded by a double membrane. The most commonly found cyst deposits a layer of electron-dense granules containing silicon on the outer membrane and lays down a cellulose-like material between the two membranes. Cysts without the electron-dense granules are commonly formed in cultures but rarely found in lakes. These cysts appear less resistant to decay and do not show the reorganization of cell contents for dormancy. It is suggested that C. hirundinella has both a resting cyst, forming part of the life cycle, and a temporary cyst stage.     

Exocytosis of cortical granules from activated oocytes of the toad,Bufo arenarum

Summary Observation of the cortical region of oocytes of Bufo arenarum by transmission electron microscopy reveals modifications on their surface and in the contents of the cortical granules (CG) during activation. In non-activated oocytes only amorphous cortical granules (ACG) can be observed. Activated oocytes display ACG, intermediate cortical granules containing both amorphous and membranous material (ICG), and a third type containing only membranous material (MCG). During exocytosis, CG release their contents into the perivitelline space, where the amorphous and membranous materials are found. The three types of CG found during oocyte activation suggest transformation of ACG to MCG and indicate that the different components of the cortical granules, when released into the perivitelline space, might play different roles in prevention of polyspermy.Members of the Scientific Research Career of CONICET, R. Argentina.     

Light and electron microscopy of the leucocytes of Crassostrea virginica (Mollusca: Pelecypoda)

Summary The fine structure of oyster leucocytes resembles to a great extent, that of typical eucaryotic cells. Organelles which have been described for the first time in this report are light granules, dense granules, protocentriole and X structure. Light microscopy reveals two morphological types of oyster leucocytes: agranular and granular. Based upon nuclear morphology and cytoplasmic compositions revealed in electron microscopy, at least three types of agranular and one type of granular cells are recognized.In the Giemsa-stained preparations, granular leucocytes exhibit three distinct types of cytoplasmic granules: refractile, dark blue, and pink, which presumably correspond to light granules Type A, B, and C seen in the electron micrographs. A granular leucocyte may contain one or more types of granules. Cytochemical investigations show that oyster leucocytes contain at least three hydrolytic enzymes: non-specific esterases, acid, and alkaline phosphatase. The latter two enzymes constitute 63% of the enzyme activity detected. These intracellular enzymes may be associated with the light granules and/or lysosome-like bodies.It is also demonstrated that the granular leucocyte population is significantly higher (P<0.001) in the oysters experimentally infected with Bacillus mycoides (72.19±4.71%) as contrasted with that of the controls (37.18±4.48%).Leucocytes in progressive stages of degeneration are also described.Contribution No. 71 from Marine Research Laboratory, University of Connecticut.The initial phase of this investigation was carried out at the Department of Zoology, Rutgers, The State University, New Brunswick, New Jersey, and supported by Public Health Service Research Grant AI-00781 from the National Institute of Allergy and Infectious Diseases of the National Institute of Health, awarded to Dr. L. A. Stauber. Supported by a grant from the University of Connecticut Research Foundation and Faculty Summer Fellowship to S. Y. Feng.     

SYNTHESIS, MIGRATION, AND RELEASE OF PRECURSOR COLLAGEN BY ODONTOBLASTS AS VISUALIZED BY RADIOAUTOGRAPHY AFTER [3H]PROLINE ADMINISTRATION

The elaboration of dentin collagen precursors by the odontoblasts in the incisor teeth of 30–40-g rats was investigated by electron microscopy, histochemistry, and radioautography after intravenous injection of tritium-labeled proline. At 2 min after injection, when the labeling of blood proline was high, radioactivity was restricted to the rough endoplasmic reticulum, indicating that it is the site of synthesis of the polypeptide precursors of collagen, the pro-alpha chains. At 10 min, when the labeling of blood proline had already declined, radioactivity was observed in spherical portions of Golgi saccules containing entangled threads, and, at 20 min, radioactivity appeared in cylindrical portions containing aggregates of parallel threads. The parallel threads measured 280–350 nm in length and stained with the low pH-phosphotungstic acid technique for carbohydrate and with the silver methenamine technique for aldehydes (as did extracellular collagen fibrils). The passage of label from spherical to cylindrical Golgi portions is associated with the reorganization of entangled into parallel threads, which is interpreted as the packing of procollagen molecules. Between 20 and 30 min, prosecretory and secretory granules respectively became labeled. These results indicate that the cylindrical portions of Golgi saccules transform into prosecretory and subsequently into secretory granules. Within these granules, the parallel threads, believed to be procollagen molecules, are transported to the odontoblast process. At 90 min and 4 h after injection, label was present in predentin, indicating that the labeled content of secretory granules had been released into predentin. This occurred by exocytosis as evidenced by the presence of secretory granules in fusion with the plasmalemma of the odontoblast process. It is proposed that pro-alpha chains give rise to procollagen molecules which assemble into parallel aggregates in the Golgi apparatus. Procollagen molecules are then transported within secretory granules to the odontoblast process and released by exocytosis. In predentin procollagen molecules would give rise to tropocollagen molecules, which would then polymerize into collagen fibrils.     

An ultrastructural study of byssus stem formation in Mytilus californianus

In Mytilus californianus, root lamellae of the byssus stem are formed by two morphologically distinct exocrine cell types. Type 1 cells contain large ellipsoid granules which are ultrastructurally identical to those of the collagen gland associated with byssus thread formation: these granules are secreted only at the base of the stem generator. Type 2 cells contain small cylindroid granules which are secreted only from the lateral surfaces of generator septa. The resultant matrix is biphasic because the two secretions are incompletely mixed. Lamellar sheets of matrix are propelled outward by the action of cilia and are molded into a cylinder at the neck region of the stem. However, the stem retains a lamellar pattern. Byssus threads are attached to the stem by flattened rings formed from thread material which is secreted into the cervical crevice surrounding the neck. The microanatomy of the stem forming region is described and a new term, “stem generator,” is proposed for this organ.     

Morphological characterization of female accessory sex glands of Eupolybothrus fasciatus (Newport) (Chilopoda Lithobiomorpha)

The female reproductive system of Eupolybothrus fasciatus (Newport) (Chilopoda Lithobiomorpha) includes three types of well-developed accessory glands, viz. large glands, small glands, and the periatrial gland. External morphology and the ultrastructural organization of these glands have been investigated by light and electron microscopy. The small and large glands are paired and have coiled ducts that open, respectively, into and externally to the genital atrium. By contrast, the periatrial gland is unpaired and is located on the ventral wall of the atrium into which it opens via several small canals. Ultrastructural features show that all three glands consist of two different types of cells: secretory cells and ductule cells. The secretary cells contain prominent secretory granules and are similar to a class of insect epidermal gland cells (class 3) organized as acini surrounding an extracellular lumen into which microvilli project. The granules, which have different morphological features in each gland, could be responsible for important differential functions such as producing a sexual attractant, providing a coating material that protects eggs laid on the ground, and contributing to a fluid that digests spermatophores. © 1996 Wiley-Liss, Inc.     

The Golgi apparatus in epidermal mucoid and ellipsoid-vacuolate cells ofAeolidia papillosa andCoryphella rufibranchialis (Nudibranchia)

Summary The epidermal cell layer of the apical end of the ceras was investigated in two species of aeolid nudibranchs. Based on cellular inclusions, mostly two cell types were found: mucoid and ellipsoid-vacuolate cells. Mucoid cells ofCoryphella rufibranchialis have large heterogeneous and fibrillar secretory granules whereas inAeolidia papillosa, the granules are homogeneous, but vary in electron density from one cell to another. Ellipsoid-vacuolate cells contained large quantities of small vacuoles with an included ellipsoidal structure. Both species contained very numerous ellipsoid-vacuolate cells. Secretory granules and ellipsoid-vacuoles appear to arise from the Golgi apparatus and these contents stain with PAS, suggesting a polysaccharide composition. Mucoid cells contained both secretory granules and ellipsoid-vacuoles which may arise from the same Golgi apparatus.