Electron Lucid Research Articles

Seasonal variations in the morphology of the seminal vesicles of the African straw-coloured fruit bat (Eidolon helvum).

The study investigated seasonal changes in the morphology of the seminal vesicles of Eidolon helvum in a typical African tropical environment. Seminal vesicles of forty-eight bats were examined during the early rainy, late rainy and peak dry seasons, using gross anatomical, histological and ultrastructural techniques. The interlobular connective tissue septa from the external capsule demarcated the glandular parenchyma into numerous lobules of tubulo-alveolar glands. A simple cuboidal epithelium of mono- or bi-nucleated cuboidal cells lined the glandular mucosa during the rainy season. This was replaced by a bistratified cuboidal epithelium, whose upper layer of cells showed evidence of degeneration, during the dry season. The PAS-positive secretory products appeared to be numerous during the rainy season, but few and clumped together during the dry season. The mean gross weight, interlobular septal thickness, acini diameter and epithelial height of the glands varied significantly with season. Ultrastructural features of the secretory cells during the rainy season showed well-developed cytoplasmic organelles, numerous electron lucid secretory vesicles and electron-dense granules. Secretory epithelial cells of the seminal vesicles are very active during the rainy season, while regeneration of degenerated epithelium in preparation for the next reproductive cycle occurs during the dry season.

Light and Electron Microscopic Studies of the Seminal Vesicular Glands of the African Straw-coloured Fruit Bat, Eidolon helvum

Background: Secretions from the seminal vesicular gland enhance the survival and reproductive functions of the spermatozoa. The order Chiroptera has evolved great diversity in their reproductive structure influenced by location, abiotic factors and availability of food. Eidolon helvum is a near threatened tropical African fruit bat and little is known of its reproductive biology. The aim of this study was to highlight the structure, histochemistry and ultrastructure of the seminal vesicular glands of Eidolon helvum. Methods: The paired seminal vesicular glands of 16 adult male Eidolon helvum were obtained in May during the early rainy season in tropical Nigeria. The glands were evaluated grossly, histological and ultrastructurally.Result: The spirally coiled tubular organs were divided into numerous lobules of tubular-alveolar glandular acini lined by simple cuboidal epithelium made up of basal cells and mono or bi-nucleated cuboidal secretory cells. PAS positive secretions projected from the apical surfaces. Principal secretory cells contained numerous rough endoplasmic reticulum, mitochondria, Golgi complexes, electron lucid secretory vesicles, electron dense granules and lysosomes. The unique merocrine and apocrine secretions contributed to the formation of vaginal plugs.

The Sub-microscopic Pathology of Brain Extracellular Space in Some Neuropathological Conditions. A Review

The enlargement and content of perivascular and extracellular spaces in experimental and human material have been reviewed. The human edematous cerebral cortex associated to vascular anomaly, congenital hydrocephalus, brain trauma, and brain tumors were examined by transmission electron microscopy, using cortical biopsies of frontal, parietal, and temporal cortex. In congenital hydrocephalus, the pre-existing extracellular space that features immature cerebral cortex appears notably enlarged and occupied by electron transparent, non-proteinaceous interstitial edema fluid, due to the abnormal accumulation of non-circulating cerebrospinal fluid. In severe human brain trauma associated to subdural or estradural hematomas and brain tumors, the distended extracellular space contains either electron lucid non-proteinaceous edema fluid, and electron dense proteinaceous edema fluid, fibrinoid material, exosomes or extracellular vesicles, extracellular mitochondria, hemorrhagic foci, and non-nervous invading cells, such as phagocytic astrocytes, macrophages, microglia, and monocytes. In brain tumors, the widened extracellular space shows mainly electron dense proteinaceous edema fluid, and bundles of fibrinoid material and extracellular vesicles.

Disentangling the Taxonomy of Rickettsiales and Description of Two Novel Symbionts ("Candidatus Bealeia paramacronuclearis" and "Candidatus Fokinia cryptica") Sharing the Cytoplasm of the Ciliate Protist Paramecium biaurelia.

ABSTRACTIn the past 10 years, the number of endosymbionts described within the bacterial order Rickettsiales has constantly grown. Since 2006, 18 novel Rickettsiales genera inhabiting protists, such as ciliates and amoebae, have been described. In this work, we characterize two novel bacterial endosymbionts from Paramecium collected near Bloomington, IN. Both endosymbiotic species inhabit the cytoplasm of the same host. The Gram-negative bacterium “Candidatus Bealeia paramacronuclearis” occurs in clumps and is frequently associated with the host macronucleus. With its electron-dense cytoplasm and a distinct halo surrounding the cell, it is easily distinguishable from the second smaller symbiont, “Candidatus Fokinia cryptica,” whose cytoplasm is electron lucid, lacks a halo, and is always surrounded by a symbiontophorous vacuole. For molecular characterization, the small-subunit rRNA genes were sequenced and used for taxonomic assignment as well as the design of species-specific oligonucleotide probes. Phylogenetic analyses revealed that “Candidatus Bealeia paramacronuclearis” clusters with the so-called “basal” Rickettsiales, and “Candidatus Fokinia cryptica” belongs to “Candidatus Midichloriaceae.” We obtained tree topologies showing a separation of Rickettsiales into at least two groups: one represented by the families Rickettsiaceae, Anaplasmataceae, and “Candidatus Midichloriaceae” (RAM clade), and the other represented by “basal Rickettsiales,” including “Candidatus Bealeia paramacronuclearis.” Therefore, and in accordance with recent publications, we propose to limit the order Rickettsiales to the RAM clade and to raise “basal Rickettsiales” to an independent order, Holosporales ord. nov., inside Alphaproteobacteria, which presently includes four family-level clades. Additionally, we define the family “Candidatus Hepatincolaceae” and redefine the family Holosporaceae.IMPORTANCE In this paper, we provide the characterization of two novel bacterial symbionts inhabiting the same Paramecium host (Ciliophora, Alveolata). Both symbionts belong to “traditional” Rickettsiales, one representing a new species of the genus “Candidatus Fokinia” (“Candidatus Midichloriaceae”), and the other representing a new genus of a “basal” Rickettsiales. According to newly characterized sequences and to a critical revision of recent literature, we propose a taxonomic reorganization of “traditional” Rickettsiales that we split into two orders: Rickettsiales sensu stricto and Holosporales ord. nov. This work represents a critical revision, including new records of a group of symbionts frequently occurring in protists and whose biodiversity is still largely underestimated.

Ultrastructure of Gametocyst of Parasitic Protozoan, Nematopsis sp. in Black Tiger Shrimp Penaeus monodon from the Gulf of Thailand

Ultrastructure of gametocyst of Nematopsis sp., a protozoa parasite of black tiger shrimp Penaeus monodon from the Gulf of Thailand is described. Ball-shaped gametocysts of about 110–160 µm diameter were found in close contact with the intestinal wall of shrimps. Surface of the gametocyst cyst wall or capsule is wrinkled with a circular bare area at one pole that contains a central pore 4–5 µm in diameter. The interior of the gametocyst is composed of numerous gymnospores and membranous sacs. Gymnospores varied in size with an average diameter of 6–8 µm. Ball-shaped gymnospores were composed of numerous, radially arranged, cone shaped sporozoites. Average width and length of sporozoites were 0.8–1.2 µm and 3–5 µm, respectively, with their rostral part pointing outward and caudal part, inward connecting to the residual cytoplasm in the centre of a gymospore. The rostral part of the sporozoite contains an oval nucleus, rough endoplasmic reticulum, mitochondria and a group of secretory granules. Membranous sacs were composed of two types of globular granules; large electron lucid granules and small dense granules.

Morphological diversity of pedicels in phoretic deutonymphs of Uropodina mites (Acari: Mesostigmata)

The pedicel is a structure that connects the phoretic deutonymph of Uropodina mites with its carrier and enables dispersal. The shapes, lengths and diameters of pedicels formed by Uropoda orbicularis, Trichouropoda ovalis, Uroobovella pulchella and Uroobovella nova were studied by scanning and light microscopy. Pedicels of U. orbicularis and T. ovalis have the shape of a straight stalk. In U. pulchella, the pedicel is extremely short, irregularly shaped and composed of homogeneous material. The longest pedicel is found in U. nova and it may be helically coiled in this species. The length of the pedicel is positively correlated with deutonymph body size between species, but not within species. Pedicels of U. orbicularis and U. pulchella have the largest diameter. The pedicel diameter in U. orbicularis and T. ovalis is inversely proportional to its length, but not in U. nova and U. pulchella. The constituent of pedicel stems in U. pulchella is homogeneous, whereas in U. orbicularis and T. ovalis it contains a bundle of tightly packed fibres. In U. nova coiled pedicels are comprised of two layered materials of different electron density, one of which is electron lucid and located peripherally. Hypotheses on the origin of the pedicel are proposed.

Alterations in granule matrix and cell surface of focal adhesion kinase-deficient mast cells.

Focal adhesion kinase (FAK) is a nonreceptor protein tyrosine kinase that plays an important role in many cellular processes and is tyrosine phosphorylated after FcepsilonRI aggregation in mast cells. In mice, null mutation of the fak gene results in a lethal phenotype in which the embryos fail to develop past day 8.5 of gestation. To study the role of FAK in these mast cells, 8.5-day embryos were isolated and placed in culture with IL-3 and stem cell factor (SCF). Although FAK was not required for the development of mast cells in culture, the FAK(-/-) embryo-derived mast cells had several distinct characteristics. Compared with the controls, the mast cells that lack FAK were less metachromatic and by electron microscopy had granules that appeared largely electron lucid, although their histamine content was unchanged. The FAK-deficient mast cells had a reduction in the content of chondroitin/dermatan sulfate, the major glycosaminoglycan component of the granular matrix. The FAK-deficient cells had fewer microvilli that were fused with each other, giving the cell surface a ruffled appearance. There was also a 3-fold increase in the number of cells highly expressing beta(7) integrin. However, signal transduction from the high affinity IgE receptor for the secretion of histamine was similar in the wild-type, heterozygote, and the FAK-deficient cells. The FcepsilonRI-induced tyrosine phosphorylation of paxillin, Crk-associated tyrosine kinase substrate (CAS), and mitogen-activated protein kinase proteins was independent of FAK. These results indicate that FAK plays a role in regulating the glycosaminoglycan content of the secretory granules and influences the cell surface morphology of mast cells.

Nucleolar ultrastructure in bovine nuclear transfer embryos.

Nuclear transfer experiments in mammals have attempted to reprogram a donor nucleus to a state equivalent to the zygotic one. Reprogramming of the donor nucleus is, among other features, indicated by a synthesis of ribosomal RNA (rRNA). The initiation of rRNA synthesis is simultaneously reflected in nuclear morphology as a transformation of the nucleolus precursor body into a functional rRNA synthesising nucleolus with a characteristic ultrastructure. We examined nucleolar ultrastructure in bovine in vitro produced (control) embryos and in nuclear transfer embryos reconstructed from a MII phase (nonactivated) or S phase (activated) cytoplasts. Control embryos were fixed at the two-, four-, early eight- and late eight-cell stages; nuclear transfer embryos were fixed at 1 and 3 hr post fusion and at the two-, four-, and eight-cell stages. Control embryos possessed a nucleolar precursor body throughout all three cell cycles. In the eight-cell stage embryo, a primary vacuole appeared as an electron lucid area originating in the centre of the nucleolar precursor body. In nuclear transfer embryos reconstructed from nonactivated cytoplasts, the nuclear envelope was fragmented or completely broken down at 1 hr after fusion and, by 3 hr after fusion, it was restored again. At this time, the reticulated fibrillo-granular nucleolus had an almost round shape. The nucleolar precursor body seen in the two-cell stage nuclear transfer embryos consisted of intermingled filamentous components and secondary vacuoles. A nucleolar precursor body typical for the two-cell stage control embryos was never observed. None of the reconstructed embryos of this group reached the eight-cell stage. Nuclear transfer embryos reconstructed from activated cytoplasts, in contrast, exhibited a complete nuclear envelope at all time intervals after fusion. In the two-cell stage nuclear transfer embryo, the originally reticulated nucleolus of the donor blastomere had changed into a typical nucleolar precursor body consisting of a homogeneous fibrillar structure. A primary vacuole appeared in the four-cell stage nuclear transfer embryos, which was one cell cycle earlier than in control embryos. Only nuclear transfer embryos reconstructed from activated cytoplasts underwent complete remodelling of the nucleolus. The reorganisation of the donor nucleolar architecture into a functionally active nucleolus was observed as early as in the four-cell stage nuclear transfer embryo. These ultrastructural observations were correlated with our autoradiographic data on the initiation of RNA synthesis in nuclear transfer embryos.

Detection of Penicillin‐binding Proteins in the Endosymbiont of the Trypanosomatid Crithidia deanei

ABSTRACT. Growth by serial transfers of the trypanosomatid Crithidia deanei in culture medium containing 1 mg/ml of the β‐lactam antibiotics ampicillin or cephalexin resulted in shape distortion of its endosymbiont. The endosymbiont first appeared as filamentous structures with restricted areas of membrane damage. An increase of electron lucid areas was also observed in the endosymbiont matrix. The continuous treatment with β‐lactam antibiotics, resulted in endosymbiont membranes fragmentation; and later on the space previously occupied by the symbiont was identified as an electron lucid area in the host cytoplasm. The putative targets of β‐lactam antibiotic were two membrane‐bound penicillin‐binding proteins (PBPs) detected in the Sarkosyl‐soluble fraction of purified symbionts labeled with [3H]‐benzylpenicillin. The apparent molecular weight of the proteins were 90 kDa (PBP1) and 45 kDa (PBP2). PBP2 represented 85% of the total PBP content in the membrane fraction of the endosymbionts. Competition experiments using the tested antibiotics and [3H]‐benzylpenicillin showed that ampicillin and cephalexin have half saturating concentrations considerably higher than [3H]‐benzylpenicillin and indicated that PBP1 is the probable lethal target of the antibiotics tested. These results suggest that a physiologically active PBP is present in the cell envelope of C. deanei endosymbionts and may play important roles in the control of processes such as cell division and shape determination.

Intercellular lamellar lipids in plantar stratum corneum.

Plantar stratum corneum was examined by means of transmission electron microscopy after conventional osmium fixation and after fixation with ruthenium tetroxide. The latter fixative was used in order to reveal the possible existence of lamelarly ordered lipids in the intercellular space, as has previously been demonstrated for non-palmo-plantar stratum corneum. A major part of the plantar stratum corneum intercellular space was occupied by extracellular parts of desmosomes. In specimens fixed with ruthenium tetroxide the intercellular space not occupied by desmosomes was found to contain multiple alternating electron dense and electron lucid bands, suggestive of membraneous structures. This pattern appeared to be similar to that previously described for non-palmo-plantar stratum corneum. It is suggested that the intercellular lipids of palmo-plantar stratum corneum may be qualitatively similar to the intercellular lipids of non-palmo-plantar stratum corneum. The lower lipid content, expressed as weight per unit weight of tissue, in palmo-plantar stratum corneum as compared to non-palmo-plantar stratum corneum may be related to the fact that a larger portion of the intercellular space of the former tissue is occupied by desmosomes. The relatively high water permeability of palmo-plantar stratum corneum implies that desmosomes, i.e. non-lipid regions of the intercellular space, may have a high water permeability and hence could establish a hydrophilic route through the stratum corneum.

Effect of moderate protein-deficiency on ultrastructure in parotid and submandibular acinar cells in the adult rat.

Powdered diets, of three different levels of protein, were given to groups of adult male rats for 21 days. Two diets with reduced protein content, 5% or 10% casein, were given to experimental rats. A diet with an adequate protein content, 20% casein, was given to controls. A reference group of rats was fed a standard pellet diet for the same period. At the end of the experimental period, the parotid and the submandibular glands were removed and subjected to electron microscopy. The zymogen granules of acinar cells in the parotid glands from the rats receiving the 5% protein diet had lost their normal opaqueness and turned electron lucid whereas parotid glands from the rats fed the 20%, the 10%, and the standard pellet diet exhibited normal acinar cells. The ultrastructure of submandibular acinar cells was not affected in any dietary group.

Epididymal white adipose tissue after cold stress in rats II. Mitochondrial changes

We have previously shown that after severe cold stress of rats the epididymal white adipose tissue (WAT) acquires many of the morphological characteristics (innervation, vascularization, appearance of adipocytes) of brown adipose tissue (BAT). In the present study, the mitochondrial characteristics have been analyzed. Mitochondria from the epididymal fat pad of cold-stressed rats become enlarged and had a volume 1.7 times greater than that in the control group (0.5 μm3 in the experimental versus 0.3 μm3 in the control group). The mitochondria occupied about 60% of the cytoplasm (14% in the control group), thus approaching the highest value reported for any cell. The straight or slightly wavy cristae completely traversed the width of the mitochondria and occupied an area of 26 μm2/1 μm3 of mitochondrion in the experimental adipose tissue (7 μm2 in the control group) and 15 μm2/1 μm3 of cytoplasm (1.4 μm2 in the control). The mitochondrial matrix became electron lucid and could contain lamellar whorls, as could the surface of the mitochondria. These mitochondria of epididymal WAT resembled, both morphologically and morphometrically, mitochondria in the BAT of cold-exposed rodents. In the epididymal mitochondria, immunoelectron microscopy did not reveal the presence of the BAT-specific uncoupling protein thermogenin, nor could the slot-blot technique detect thermogenin mRNA. We conclude that even under these extreme conditions of cold stress, WAT cannot adopt the thermogenin-dependent thermogenesis of BAT. The dramatic mitochondriogenesis can be interpreted only as being indicative of an extremely high metabolism in the tissue, thus placing unprecedented pressure on the energy turnover capacity of the cell.

Ultrastructure of changes at the surface during the early development phases of Taenia ovis cysticerci in vitro

Harris A., Heath D. D., Lawrence S. B. and Shaw R. J. 1987. Ultrastructure of changes at the surface during the early development phases of Taenia ovis cysticerci in vitro. International Journal for Parasitology 17: 903–910. Transmission and scanning electron microscopy and conventional, interference, and u.v. light microscopy were used to examine the epithelial membrane and underlying cytoplasm during the early development of Taenia ovis cysticerci in vitro. For 2 h after activation of the oncosphere, blebs of plasma membrane containing cytoplasm and secretory granules were released. Two h later the surface area of the plasma membrane had increased by the elaboration of microvilli. Microvilli increased in length and number for 48 h. Synthesis of granules was observed in two of the four lobes of the penetration glands for at least 4 h in vitro. Granules were present in the surface epithelium 4 h after activation. At 24 h granules remaining in the epithelium were electron lucid. In the presence of heat inactivated serum from sheep immunised against T. ovis oncospheres, an electron dense material was precipitated on and between microvilli within 24–48 h of culture. Material in this position reacted positively with fluorescein-labelled antisheep IgG. When metacestodes became motile after 4–5 days, microvilli were sloughed and replaced by a form of microtriche.

Ultrastructural analysis of spermiogenesis in Admetus pomilio (Arachnida, amblypygi).

The mature spermatozoon of Admetus pomilio is a spherical cell containing nucleus and tightly coiled flagellum. In early spermatids the Golgi apparatus forms the acrosomal vesicle and at the opposite side the distal centriole gives rise to the axonemal complex of the sperm tail. As the nucleus elongates, chromatin forms twisted filaments and the spermatid nucleus takes on a helical form. Microtubules are juxtaposed with the nucleus envelope, which is separated from a central chromatin mass by an electron lucid region. A long perforatorium, located on the border of the chromatin mass, runs helically in the nucleus from the centriolar region to subacrosomal space. During tail elongation, the anterior part of the axoneme is surrounded by a long, spiral mitochondrial sheath. In the late spermatid, chromatin filaments appear twisted and become aggregated. The nucleus and flagellum undergo further contortions in which the nucleus coils and the flagellum winds up into the body of the cell and coils in a regular fashion. The mitochondrial sheath surrounds about 2/3 of the 9 + 3 axoneme. These features of spermatid ultrastructure resemble those in the primitive Liphistiomorpha.

Electron microscopy of fat-storing cells in liver diseases with special reference to cilia and cytoplasmic cholesterol crystals.

Two hundred and ten fat-storing cells in the liver of patients with liver diseases were examined electron microscopically, and 5 of them were found to project a single cilium from the perinuclear region to the space of Disse. Three cilia were in the space between a hepatocyte and their own cell body, and 2 were between a sinusoidal endothelial cell and their own cell body. In cross sections of the cilium, the axoneme consisted of 9 pairs of microtubules arranged in a cylinder and lacked a central pair of microtubules ("9 + 0" pattern). Arms and spokes were also absent in the axoneme. Therefore, the single cilium of fat-storing cells was considered to be immotile. Some fat-storing cells from a patients with alcoholic liver cirrhosis contained an angular electron lucid inclusion, which was identical to cholesterol ester crystals, suggesting the presence of disturbed cholesterol metabolism.

Formation of the odontostyle during molting of the nematode Xiphinema americanum (Nematoda: Dorylaimoidea)

A light and transmission electron microscope study was made of the feeding apparatus of the nematode Xiphinema americanum Cobb, 1913, during molting. The odontostyle, the anterior part of the feeding stylet, is formed by two cells in the slender esophagus, one located posterior to the other. A deep cylindrical invagination develops into the posterior (odontostyle) cell, while the anterior cell extends a tubular sheath around the invagination and forming odontostyle. The odontostyle cell produces a shorter forward-projecting sleeve inside and sealed to the sheath by a junctional complex. Dense granules produced from Golgi complexes in the odontostyle cell are exocytosed into the extracellular pocket thus formed. Granules coalesce in this mold to form the extracellular odontostyle. The invagination and sheath deepen posteriorly as formation proceeds, reaching down to the looped esophagus as the odontostyle nears completion. During the posterior shift to the storage site, the odontostyle contracts and becomes electron lucid. In the following intermolt storage period, it remains extracellular, surrounded by the odontostyle cell. It is suggested that changes in shape of the anterior and odontostyle cells, and movement of these cells are largely responsible for movement of the odontostyle in the esophagus.

Fine structure of sensory tubes on the antennule of Conchoecia spinirostris (Ostracoda, Crustacea). A new type of sensillum in crustaceans.

In addition to setae, the first antennae of Conchoecia spinirostris also bear soft sensory tubes (female: 4 tubes + 1 seta; male: 2 tubes + 3 setae). These tubes were examined electron microscopically. Each tube is divided into 4 regions: the stem, the bulbous region, the main region, and the tip. A tube contains 40--60 multiciliated dendrites, some hypodermal cells, and nonneuronal cells, and it has a specialized cuticle. Each dendrite develops within the tube, on the terminal 5--8 micron of its inner dendritic segment, approx. 25 cilia in a 9 X 2 + 0 pattern, whose rootlets are absent or only poorly developed. Each cilium splits up into 9 ramifications which extend into the tip. These ramifications partly take a spirallike course and form a ring in the distal main part beneath the cuticle. Their membranes often dilate into spindleshaped swellings. In the center of the middle and distal parts of the main region approx. 7 dendrites without cilia are located, one of them reaches into the tip. The poreless cuticle is extremely delicate and electron lucid. In contrast to the cuticle of the setae it is elastic and soft. Special substructures are described. The tubes are completely covered by a filamentous surface coat. Because of the structure and the thin walled nature of the cuticle, permeability for dissolved substances is assumed. The ciliary ramifications are likely to represent the receptive apparatus. The sensory tubes are interpreted as chemoreceptors. They can best be compared with the chemoreceptors of certain crustaceans, but differ strongly from the types of sensilla found in insects.

Ultrastructure of microfilament bundles in baby hamster kidney (BHK-21) cells. The use of tannic acid.

After standard glutaraldehyde-osmium tetroxide fixation procedures, the majority of microfilament bundles in BHK-21 cells exhibit relatively uniform electron density along their long axes. The inclusion of tannic acid in the glutaraldehyde fixation solution results in obvious electron density shifts along the majority of microfilament bundles. Striated patterens are frequently observed which consist of regularly spaced electron dense (D) and electron lucid (L) bands. A striated pattern is also observed along many BHK-21 stress fibers after processing for indirect immunofluorescence utilizing BHK-21 myosin antiserum. A direct correlation of these periodicities seen by light and electron microscope techniques is impossible at the present time. However, comparative measurements indicate that the overall patterns seen in the immunofluorescence and electron microscope preparations are similar. The ultrastructural results provide an initial clue for the ultimate determination of the supramolecular organization of contracile proteins other than actin within the microfilament bundles of non-muscle cells.

Some ultrastructural features of acinic cell carcinoma

The ultrastructure of an acinic cell carcinoma, occurring in the left parotid gland of a 52-year-old woman and causing a total facial nerve paralysis, is described. Histologically the tumour consisted of numerous granulated cells arranged around lumen-like openings and resembling a secretory system. Furthermore, areas with agranulated cells growing in a solid pattern were also encountered. In the electron microscope the cytoplasmic granules of the tumour cells displayed a varied appearance. Granules of a dense homogeneous type, as well as granules with a more electron lucid appearance were observed. Furthermore, numerous cytoplasmic granules displayed a bipartite structure with a dense central and a more electron lucid outer zone. In specimens primarily fixed in OSO4 or KMnO4 the granules displayed a 'leached out' appearance. The membrane-bounded of the tumour cells also showed a strong positive staining with the periodic acid-chromic silver technique of Rambourg et al. (1969). Other characteristic ultrastructural features of the tumour cells studied were: Smooth cell surfaces, the presence of subplasmalemmal bands of electron dense material, desmosome-like attachment areas between cells and grossly altered mitochondria.

Ultrastructural cytochemistry of the secretory granules of the hamster submandibular gland

The ultrastructure and cytochemistry of the secretory granules of the male hamster submandibular salivary gland were studied; After fixation in glutaraldehyde followed by osmium tetroxide the granules exhibit a characteristic bipartite substructure, with an electron lucid crescenteric rim and a more dense central core. A differentiation into two regions of the granules could also be visualized in specimens primarily fixed in Millonig's osmium tetroxide or in potassium permanganate. The electron lucid peripheral portion of the membrane bounded secretory granules further displays a strong positive reaction after staining of ultrathin sections with the periodic acid-chromic acid-(PA-CrA)-silver technique. The strong periodate reactivity of the rim relative to the core, suggests a difference in mucin composition of the two granule regions. With the PA-CrA-silver straining technique a positive reaction was also observed within the Golgi apparatus of the acinar cells.