Showing papers on "Ultrastructure published in 1992"

Estrogen receptors in dendrites and axon terminals in the guinea pig hypothalamus.

Abstract: The ultrastructural localization of steroid hormone receptors has been made possible by the development of immunocytochemical procedures using monoclonal antibodies. Estrogen receptor-immunoreactivity (ER-IR) in the brain is present most abundantly in neuronal nuclei when observed with light microscopy. However, we have also observed ER-IR in the perikarya and cytoplasmic processes of neurons. To determine the organelles with which the cytoplasmic ER-IR is associated, we developed a technique for ultrastructural visualization of ER-IR. Ovariectomized guinea pigs were perfused, brains vibratome-sectioned, and estrogen receptors immunostained by either an immunoperoxidase-diaminobenzidine technique or by an immunogold-streptavidin procedure, each followed by silver intensification. Electron microscopic analysis confirmed distribution of ER-IR throughout cell nuclei, but ER-IR was also observed in proximal and distal dendrites and rough endoplasmic reticulum. Most surprisingly, however, ER-IR was found in ma...

Epithelial-mesenchymal transformation during palatal fusion: carboxyfluorescein traces cells at light and electron microscopic levels

Abstract: During the fusion of rodent embryo palatal shelves, the cells of the outer epithelial layer slough off, allowing the cells of the medial edge basal layer to form a midline seam that undergoes epithelial-mesenchymal transformation, as judged by electron microscopy and immunohistochemistry. In this study, we analyze the fate of the transformed cells using a lipid soluble dye to label the medial edge epithelium in situ. Prefusion E14 mouse palates were exposed in vitro or in vivo to a fluoresceinated lipid soluble marker, carboxydichlorofluorescein diacetate succinimidyl ester (CCFSE), which localizes in epithelia as a lipid insoluble compound that does not pass into the connective tissue compartment. The midline seam that formed after 24 hours contained labelled epithelial cells that were replaced by individually labelled mesenchymal cells where the seam transformed. By light microscopy, the labelled cells were seen to contain intensely fluorescent bodies that do not react for acid phosphatase. We were able for the first time to identify these structures by electron microscopy as CCFSE isolation bodies. The cells with isolation bodies are clearly healthy and able to participate in subsequent development of the palate. At 4 days after labelling, individual CCFSE containing cells present in the palate mesenchyme occupy both midline and lateral areas and can clearly be classified as fibroblasts by electron microscopy. CCFSE is a far more useful marker than another lipid soluble marker, DiI, for following cells, because the cells can be fixed and identified both at the light and electron microscope levels. Interestingly, if labelled palatal shelves are not allowed to fuse in vitro, the basal epithelial cells do not form mesenchyme after sloughing, indicating that formation of the epithelial midline seam is necessary to trigger its epithelial-mesenchymal transformation.

Giardia lamblia: ultrastructural study of the in vitro effect of benzimidazoles.

Abstract: Axenically grown Giardia lamblia trophozoites treated with low concentrations of the benzimidazole carbamates albendazole and mebendazole detach from glass culture tubes and lose viability. Scanning electron microscopic observations revealed that these drugs produce grotesque modifications of the cell shape of the parasite and disassembly of the adhesive disc. Transmission electron microscopy showed several stages of the fragmentation of adhesive discs with dispersion of microtubules and microribbons in the cytoplasm. Flagella appeared undamaged. In drug-treated trophozoites electron-dense precipitates were selectively deposited on microtubules and microribbons. The results indicate that the antigiardial effect of benzimidazoles is the result of binding to microtubules and subsequent alterations of the cytoskeleton. The electron microscopic observations also suggest that the drugs may bind to microribbon components of the adhesive disc, possibly giardin proteins.

Ultrastructural characterization and three-dimensional reconstruction of isolated maize (Zea mays L.) egg cell protoplasts

Abstract: Isolated egg cell protoplasts ofZea mays L., inbred line A 188, have been studied at the transmission electron microscope level. Their preparation for electron microscopy has been performed by embedding in ultra-low gelling agarose as a preliminary step. Five isolated egg cell protoplasts were serially ultrathin sectioned and studied in detail. One of these protoplasts was reconstructed in three dimensions to provide additional information on its structure. After enzymatic digestion and microdissection, isolated egg cells are true, highly vacuolized protoplasts. The structure of their organelles agrees with in situ observations, indicating an ultrastructural intactness after isolation: the mitochondria are polymorphic, form reticulate networks, and have well developed cristae; the plastids contain starch grains; and the spherical nucleus is euchromatic. As in situ, the organelles of the isolated egg cell protoplasts are aggregated near the nucleus. The complete picture provided by this work should serve as a comparative base for studies on in vitro fertilization products.

Ultrastructural study of M cells from colonic lymphoid nodules obtained by colonoscopic biopsy.

Abstract: The present study was undertaken to investigate ultrastructurally the epithelium covering lymphoid nodules obtained from colonoscopic biopsies of the human colon and rectum. Colonoscopy using the dye spraying contrast, method was performed in nine patients who showed x-ray evidence of lymphonodular hyperplasia. Fifty-two colonoscopical biopsy specimens, of lymphoid nodules were obtained from the ascending, transverse, and descending colon and rectosigmoid region. All specimens were observed by light and electron microscopy. Light microscopy disclosed large lymphoid follicles protruding into the lumen with a “dome-type” configuration. These extended to the lamina propria of the mucosa and were associated with a massive lymphoid aggregation extending as far as the muscularis mucosa from the submucosa. The epithelium covering these nodules contained a few goblet cells and many lymphocytes. Observation of the elevated surface at the apex by scanning electron microscopy revealed M cells with sparse microvilli in the dome epithelium surrounded by crypts. Transmission electron microscopy disclosed M cells enfolding many immature or mature lymphocytes and plasmocytes. The M cells had cytoplasmic microvilli (so-called “microfolds”) on their surfaces, well-developed tubulovesicular systems, and vacuoles in the cytoplasm. The basic structure of the M cells as observed by scanning and transmission electron microscopy was the same as that of M cells in the Peyer's patches of humans and mice. The apical surface of the colonic lymphoid follicles in Crohn's disease patients was associated with erosions observed by scanning electron microscopy. The erosions proved to be the naked surface of the dome after removal of the epithelium and many holes from 2.0 to 6.0 μm in diameter were observed on the naked surface. At high magnification, lymphocytes were seen projecting from holes (18%) on the naked surface of the dome. These ultrastructural findings indicate that human colonic lymphoid follicles are very similar to those seen in other species.

Functional Ultrastructure of the Proximal Tubule

Abstract: The sections in this article are: 1 Location of Proximal Tubule 2 Fixation of Proximal Tubule Cells for Electron Microscopy 3 Ultrastructure of the Mammalian Proximal Tubule Cell 3.1 General Cytology 3.2 Cell Shape 3.3 Segmentation of the Mammalian Proximal Tubule 3.4 Luminal Cell Surface 3.5 Basal and Lateral Cell Surface 3.6 Junctions 3.7 Nucleus 3.8 Mitochondria 3.9 Endoplasmic Reticulum 3.10 Golgi Apparatus 3.11 Vacuolar Apparatus (Lysosomes and Endocytic Vacuoles) 3.12 Peroxisomes 3.13 Cytoskeleton 3.14 Cytoplasmic Ground Substance and Inclusions 4 Structure of Proximal Tubule Cells in Submammalian Species 4.1 Birds 4.2 Reptiles 4.3 Amphibians 4.4 Fishes 5 Ultrastructure of Experimentally Perfused Tubules 6 Quantitative Ultrastructure of Proximal Tubules 7 Transepithelial Transport Routes 7.1 The Transcellular Route 7.2 The Paracellular Route 8 Functions of the Vacuolar Apparatus 8.1 Protein Absorption by the Proximal Tubule Cells 8.2 Transtubular Transport of Proteins 8.3 Basolateral Binding and Uptake of Proteins 8.4 Endocytosis of Nonproteins 8.5 Autophogocytosis 8.6 Lysosomal Accumulation of Metals and Other Substances

Myofibrosarcoma of subcutaneous soft tissue of the cheek.

Abstract: A low grade soft tissue sarcoma from the naso-labial fold and designated as myofibrosarcoma (sarcoma of myofibroblasts) is described using standard light microscopy techniques, immunohistochemistry and electron microscopy. Pink fibrillated cytoplasm, regarded as one of the typical histological features of leiomyosarcoma, was not obvious but immunostaining for alpha-smooth muscle actin was positive suggesting smooth muscle differentiation. By electron microscopy, tumour cells contained abundant rough endoplasmic reticulum cisternae and a large Golgi body; there were modest but numerous bundles of fine filaments with focal densities. A conventional lamina was lacking but the cell surface was characterised by fibronexus junctions in which there was a conspicuous extracellular, fibronectin-containing fibril, apparently mediating contact between cell and matrix. The tumour cells therefore showed myofibroblastic differentiation. The cell surfaces showed strong immunoreactivity with an anti-fibronectin antibody. Myofibrosarcoma is not a widely recognised entity and this case is only the 7th example to be documented in detail by means of both immunohistochemistry and ultrastructure. The combination of electron microscopy for detecting the fibronexus junction and immunostaining for fibronectin at the cell periphery is suggested as potentially useful for distinguishing myofibrosarcoma from leiomyosarcoma.

Internal reproductive system in adult males of the genus Camponotus (Hymenoptera: Formicidae: Formicinae)

Abstract: Descriptions are provided of the histology and ultrastructure of the male internal reproductive tracts from three species of Camponotus, representing three subgenera. This study is the first to provide ultrastructural information on the testes (including spermatogenesis and spermiogenesis), seminal vesicles, and accessory glands in ants. Testes contain about ten follicles each, and each follicle is capable of producing hundreds of cysts in which spermatozoa develop. Structural evidence of meiosis in late pupal testes includes cytoplasmic bridges between spermatocytes, centriole elimination, and fusion of mitochondria. Developing spermatids are in close contact with cyst cells in the region of the acrosome. Mature spermatozoa are similar in ultrastructure to those described previously for two other subfamilies of ants (Myrmicinae and Dolichoderinae). The ultrastructure of the seminal vesicle suggests that it is not merely a passive organ for sperm storage. Large numbers of both mitochondria and membranous whorls suggest a pH-regulating and/or hormonal function. The accessory gland is made up of secretory cells that contain a diversity of secretory granules. SDS-PAGE reveals several proteins found in the accessory glands but absent in the adjacent genitalia. Preliminary analyses indicate that carbohydrate is an important component of accessory gland secretions.

Human meibomian glands: the ultrastructure of acinar cells as viewed by thin section and freeze-fracture transmission electron microscopies.

Abstract: Heightened interest in meibomian glands dysfunction prompted the authors to examine the ultrastructure of the glandular epithelium in specimens of surgical origin, by thin section and freeze-fracture electron microscopies. In meibomian glands, the morphology and ultrastructure of acinar cells varies considerably according to their stage of holocrine differentiation. This study shows close interdependence between fat droplets and Golgi apparatus or endoplasmic reticulum. As the cells initiate their differentiation, the smooth endoplasmic reticulum and the Golgi apparatus become prominent and the first small lipid droplets appear in the cytoplasm. When fractured through a plane close to their surface, lipid droplets appear onion-like structured, ie made up of a variable number of irregular shaped concentric lamellae. This lamellar organization suggests that membranes are not only involved in synthesis, but also that some of their components are incorporated in the fat droplets. The authors conclude that human meibomian glands are a holocrine glandular complex that, despite great differences in type and location, present basic similarities with sebaceous glands.

Sperm cells in pollen tubes ofNicotians tabacum L.: three-dimensional reconstruction, cytoplasmic diminution, and quantitative cytology

Abstract: The organization of the sperm cells and vegetative nucleus (male germ unit) ofNicotiana tabacum was examined 18 h after semivivo pollination using transmission electron microscopy, computerassisted serial section reconstruction and quantitative cytology. Based on a measurement of 11 cellular parameters in nine reconstructed sperm cell pairs, there are no statistically significant differences between the two cells. The Svn is characterized by a strapshaped cytoplasmic extension that is physically associated with the surface of the vegetative nucleus. The nucleus is located adjacent to the sperm crosswall, with sperm organelles being distributed between the nucleus and the extension. The Sua is a tapered cell with cytoplasmic areas at both poles and deep axial invaginations near the crosswall. This cell has a centrally-located nucleus and a largely polar distribution of organelles. Three mechanisms for cytoplasmic diminution were observed that appear to contribute actively to the loss of cytoplasmic volume and organelles: (1) enucleated cytoplasmic body production in the Sua; (2) vesiculation at the tip of the cytoplasmic projection of the Svn; and (3) vesicle-containing body accumulation in the periplasm of both the Svn and Sua.

The fine structure of the follicular cells in growing and atretic ovarian follicles of the domestic goose.

Abstract: The structure of follicular layer of growing and atretic follicles in the ovary of the domestic goose, was studied by electron microscopy In small follicles, the wall is lined with a narrow layer of tightly packed small, cuboidal cells separated from the thecal tissue by the basal lamina During growth, they transform into tall, columnar cells arranged in a single row The cells display several peculiar ultrastructural features First, annulate lamellae are commonly observed Second, cytoplasmic dense-cored granules accumulate in close association with fenestrated cisternae and networks of tubuli derived from the RER They consist of spheres and strands of amorphous substance of unknown origin Third, the cells contain many transosomes, a unique organelle of the avian follicle cell consisting of a dense plaque associated with ribosome-like particles The mature forms of transosomes are located at the tips of lateral and apical cell projections, while bodies thought to be their precursors, are found in the apical cytoplasm In follicles larger than 8 mm in diameter, most of the transosomes and their precursors have disappeared Follicular atresia occurs in all of the size-classes of follicles investigated A loss of transosomes (in follicles up to 8 mm in diameter) and an accumulation of lipid droplets are the first atretic events detectable by electron microscopy Morphologic features, including deep nuclear indentations, accumulation of lipid droplets frequently encireled by membrane whorls, dilation and disintegration of RER cisterns, swelling of mitochondria and accumulation of dense irregular masses of unknown origin in the cytoplasm, are taken as evidence for advanced degradation We conclude that necrosis is the dominant type of cell death of the follicular cells during atresia However, a small fraction of cells, characterized by dark condensed cytoplasm, seems to die by apoptosis

Ultrastructure of root cortical cells parasitized by the ring nematodeCriconemella xenoplax

Abstract: Individuals of the plant-parasitic nematodeCriconemella xenoplax, monoxenically cultured on root expiants of clover, carnation, and tomato, fed continuously for up to 8 days from single cells in the outer root cortex. Individual cortical cells parasitized by nematodes were modified into discrete “food cells” in all hosts examined. The nematode's stylet penetrated between epidermal cells and frequently through a subepidermal cortical cell. Electron-transparent callose-like material continuous with the cell wall enveloped the portion of the stylet that traversed subepidermal cortical cells. Food cells were typically located in the first or second cell layers of the cortex. The stylet penetrated 5–6 μm through the wall of the food cell without penetrating the plasma membrane. Electron-transparent callose-like deposits formed between the invaginated plasma membrane and stylet, except at its aperture. The plasma membrane of the food cell was appressed tightly to the wall of the stylet aperture creating a 130–160 nm hole in the membrane. This opening provided continuity between the lumen of the stylet and the food cell cytosol for ingestion of nutrients by the nematode. Ribosomes were dissociated from the cisternae of the endoplasmic reticulum in food cells and accumulated with other cell organelles in a zone of modified cytoplasm around the stylet. A fibrillar material appeared to form a barrier in the cytosol around the stylet aperture that limited movement of cell organelles toward the aperture. Electron-dense secretory components were secreted into the food cell by the nematode. Clusters of putative nematode secretory components consisting of 20–40 nm diameter, electron-dense particles were dispersed in the densely particulate zone of cytoplasm around the stylet tip. The cytosol immediately around the stylet aperture in the center of the modified cytoplasm was finely granular.

Metamorphosis of calcareous sponges I. Ultrastructure of free-swimming larvae

Abstract: Summary Free-swimming larvae of two calcareous sponges were studied by electron microscopy. The larvae are composed of four kinds of cells, namely flagellated cells, granular cells, four cruciform cells, and several yolk-containing cells. In the anterior hemisphere of the larvae, the columnar flagellated cells are arranged in a single layer. Their nucleus and Golgi apparatus are located in close proximity to the flagellar rootlets. There are granular cells in the posterior hemisphere of the larvae. They have a nucleus with a nucleolus, large phagosomes, well-developed Golgi apparatus, and numerous RER cisternae. There is a cruciform cell in each quadrant of the larvae. From its characteristic arrangement of organelles, it is suggested but not concluded that the cruciform cells participate in photoreception. The yolk-containing cells are, most probably, nutritive cells derived from the mother sponge. The roles of these four kinds of cells in habitat selection and metamorphosis are discussed.

Fine structure of the dorsal epithelium of the tongue of the freshwater turtle, Geoclemys reevesii (Chelonia, Emydinae)

Abstract: Scanning electron microscopy shows that lingual papillae occur all over the dorsal surface of the tongue of the freshwater turtle, Geoclemys reevesii. The surface of each papilla is composed of compactly distributed hemispherical bulges, each composed of a single cell. Microvilli are widely distributed over the surface of cells. Histological examination reveals that the connective tissue penetrates deep into the center of papillae and that the epithelium is stratified columnar. Under the transmission electron microscope, the cells of the basal and the deep intermediate layers of the epithelium appear rounded. A large nucleus lies in the central area of each cell. The cytoplasm contains mitochondria, endoplasmic reticulum and free ribosomes. The cell membrane form numerous processes. The shallow intermediate layer contains two types of cell. The cytoplasm of the first has numerous fine granules, in addition to mitochondria, ribosomes, and endoplasmic reticulum. The other type of cell contains highly electron-dense granules. The surface layer shows two cell types. One type consists of typical mucous cells. The other type of cell contains fine, electron-lucent granules. The latter cells lie on the free-surface side, covering the mucous cells, and have microvilli on their free surfaces.

Physiological and ultrastructural effects of fumonisin on jimsonweed leaves

Abstract: The physiological and ultrastructural effects of fumonisin B1, a phytotoxin obtained from Fusarium moniliforme, on jimsonweed (Datura stramonium L.) were studied. When fumonisin B1 was applied at concentrations of 3 to 1000 μg/mL (4.1 to 1388 μM) to jimsonweed leaves, effects such as electrolyte leakage, autolysis, and photobleaching of tissues were noted in less than 12 h after exposure to light (480 μmol∙m−2∙s−1, PAR) at 25 °C. The degree of damage was directly proportional to the concentration and duration of exposure in all cases. Chlorophyll reduction from 5 to 73% occurred after 48 h in the light. In darkness, electrolyte leakage above control levels was noted only in treated samples after 72 h. However, when these dark-treated samples were subsequently placed in the light, electrolyte leakage occurred in 12 h. Ultrastructural damage in mesophyll palisade cells exposed to 500 μg/mL fumonisin B1 began at 6 h and intensified after 12 h. Cytoplasmic degeneration occurred first, followed by disruption o...

Nervous System of the Tornaria Larva (Hemichordata: Enteropneusta). A Histochemical and Ultrastructural Study

Abstract: Transmission electron microscopy (TEM) and histochemical approaches were used to investigate the topology and ultrastructure of the nervous system of the tornaria larva of an enteropneust, Balanoglossus proterogonius. Cholinesterase activity was detected in the epithelium of the pre- and postoral ciliary bands. Groups of catecholamine-containing cells (CA) were detected at the anterior tip of larva, in the ventral epidermis behind the mouth, and in the stomach wall near its junction with the intestine. Single CA neurons were detected in the telotroch epithelium. Axon tracts are described in ciliary band epithelia. At the base of the aboral plate, epithelial nerve cells form a ganglion-like cluster. Single neuron-like cells and single axons and axonal tracts were found in the epithelium of digestive tract. The data were compared with ones from the literature and with those obtained from other marine invertebrate larvae. The properties of the neural elements and their possible functions are discussed.

Macrophage development: I. Rationale for using Griffonia simplicifolia isolectin B4 as a marker for the line.

Abstract: The isolectin B4 of Griffonia simplicifolia (GSA I-B4) binds to cell membrane glycoconjugates bearing terminal alpha-D-galactose, which macrophages possess. We have investigated the merits of its use as a marker for cells of this lineage when examining the early origin of macrophage populations in rat embryos, the stages and time scale of transformation from precursor forms to active, matured cells, and the response of precursors and macrophages to colony-stimulating blood factors, the last two studies conducted in organ cultures of prenatal lungs. In the present instance, GSA I-B4 was used either coupled with fluorescein (FITC) for light microscopy of living and fixed cells, or with peroxidase for light or electron microscopy. Control incubations of lung culture-derived macrophages proved that staining resulted from specific binding to galactosyl units on the cell membrane, since it was competitively inhibited by alpha-D-galactose. The lectin binds to few cells in 14-day prenatal lung explants but to a great many macrophages that subsequently develop in the cultures, indicating that it can be relied on for quantitative studies on population growth; however, it is important to provide reagents with good access to the cells. Apart from macrophages and their precursors, virtually no cells in prenatal lung cultures bind this lectin. Granulocytes of adult blood are GSA positive, but they are not yet present in 14-day prenatal explants and do not develop subsequent to culturing; hence they are not a source of confusion for experimental studies using this system. Precursors of granulocytes begin to appear in rat embryos around day 13 and have GSA-positive cell membranes, but like definitive granulocytes they also have conspicuous peroxidase-positive lysosomal granules which serve to distinguish them from early macrophages, particularly when cells are studied at an ultrastructural level. With these objections cleared away, GSA I-B4 emerges as a valuable means to mark cells of the macrophage line, mature or immature.

Membrane ultrastructure of alkaliphilic Bacillus species studied by rapid-freeze electron microscopy.

Abstract: Cells of Bacillus firmus OF4 and Bacillus alcalophilus were examined by rapid-freeze freeze-fracture and freeze-substitution electron microscopy. No special vesicular structures linked to growth at alkaline pH were found, either within or associated with the cytoplasmic membrane. The cytoplasmic membranes of the alkaliphilic bacilli and the neutrophilic Bacillus subtilis BD99 were indistinguishable. Distinctive intramembrane particle rings, presumed to be flagellar structures on the basis of distribution and morphological characteristics, were found in all of these species. These observations indicate that the adaptations required to effect oxidative phosphorylation and flagellar rotation at extreme alkaline pH occur without gross morphological rearrangement.

Replication of dengue viruses in mosquito cell cultures--a model from ultrastructural observations.

Abstract: Mosquito cell cultures infected with human sera from dengue-1 and dengue-2 outbreaks, started in Rio de Janeiro by 1986 and 1990 respectively, were examined by electron microscopy at different times post the infection of cell cultures. More information was obtained about cell penetration of virus particles in the presence or not of antibodies, their pathway inside the cells, replication mode and exit. Infectiveness of the virus at those different stages can only be attributed to the particles appearing inside the trans-Golgi vesicles; most of all newly formed virus particles remain inside the RER-derived cell vesicles or inside lysosomes, even during cell lysis. Groups of larges particles, 65-75 nm in diameter at dengue-2 infections, persist during cell passage. The large amounts of smooth membrane structures, as vesicles or tabules inside the RER are attributed to a cell response to viral infection.

Ultrastructure of the Spermatozoon of the Tuatara (Sphenodon punctatus) and Its Relevance to the Relationships of the Sphenodontida

Abstract: Spermatozoa of the New Zealand tuatara , Sphenodon punctatus punctatus (Gray), are described from light and electron microscopic observations and compared with spermatozoa of other living ‘reptiles’ (Chelonia, Crocodilia, Squamata), birds and mammals. Mature Sphenodon spermatozoa consist of an acrosomal complex (length 4 µm), elongate, helical nucleus (54-56 µm), a relatively short midpiece (7-8 µm), elongate principal piece (74-78 µm) and short end piece (2-4 µm). The acrosomal vesicle and underlying subacrosomal material form a double, curved, conical sheath around the nucleus anteriorly. Two parallel, loosely helical, endonuclear canals each containing perforatorial material, extend posteriorly from the apex of the nucleus to at least 2.5 µm below the base of the acrosomal complex. Rings of several spherical mitochondria are stacked around the elongate distal centriole to form the midpiece. Each mitochondrion has concentric cristae surrounding a dense central body. Proximal and distal centrioles, although differing markedly in length, are similar in having triplets with an open C tubule. Nine peripheral fibres are intimately associated with the triplets of the distal centriole. A well developed annulus defines the posterior extremity of the midpiece. The principal piece consists of a 9 + 2 axoneme (accompanied anteriorly by nine peripheral fibres) surrounded by a highly electron-dense fibrous sheath and the plasma membrane. Absence of a penis in Sphenodon has not resulted in recognizable modifications of the spermatozoon. Sphenodon shares many spermatozoal features here interpreted as plesiomorphies with crocodiles and turtles, particularly the latter group, but exhibits none of the advanced character states (apomorphies) diagnostic of the Squamata. These data not only underscore the primitive status of living tuatara (recently questioned in the literature) but also militate against a close, sister-group relationship between the Sphenodontida and Squamata.

Giant mitochondria in the mature egg cell of Pelargonium zonale

Abstract: Giant mitochondrial nuclei (known as nucleoids or mt-nuclei), which contain extremely large amounts of DNA, were studied in thin sections of the mature egg and proembryo (2 and 6 days after double fertilization) ofPelargonium zonale. Samples were embedded in Technovit 7100 resin, stained with 4′,6-diamidino-2-phenylindole (DAPI) and examined by immuno-gold electron microscopic cytochemistry. The egg cell contained giant mitochondria (either long and stretched or cup-shaped) which contained a large amount of DNA (more than 4 megabase pairs). However, the other cells, such as synergids, the central cell and nucellus contained small spherical mitochondria. Giant mitochondria in the egg cell were often found to make mitochondria complexes due to the grouping of cupule-shaped mitochondria. Immuno-gold electron microscopic cytochemistry revealed that the mitochondrial DNA is localized in the electron transparent of the giant mitochondria. Apparently, the large mitochondria in the egg cell divided in stages to form small, spherical mitochondria during the early stages of embryogenesis and the DNA content in individual large mitochondrion also decreased significantly. The amount of mitochondrial DNA reached approximately 800 kbp in the globular embryo 6 days after double fertilization. The formation of giant mitochondria in mature eggs has significant aspects after double fertilization.

Olfactory epithelium in young adult and aging rats as seen with high-resolution scanning electron microscopy.

Abstract: The present study uses mainly scanning electron microscopy to demonstrate the three-dimensional internal cell structures of rat olfactory epithelial cells. The aldehyde-prefixed osmium-DMSO-osmium (AODO) method devised by Tanaka and Mitsushima (1984) was applied to the present study to disclose intracellular structures such as endoplasmic reticulum, mitochondria, Golgi apparatus, and lysosomes. The spatial distribution pattern of these structures in olfactory and supporting cells is discussed, paying special attention to the formation of lipofuscin-like granules present in aged rats.

Structure of protein bodies and elemental composition of phytin from dry germ of maize (Zea mays L.)

Abstract: Protein bodies (PBs) from the epidermis and cortex of the radicle, as well as from coleorhizal and scutellar parenchyma of dry maize seeds were studied with the emphasis on presence and elemental composition of globoid crystals. PBs with variable structure were found in investigated tissues. Radicular epidermis was the only investigated tissue containing structurally uniform populations of PBs. They were filled by a homogeneous matrix without globoid crystals or their remnants. PBs structure and amount of proteinaceous matrix varied in the same cell of coleorhiza and scutellum. In the case of radicular cortex, the structure of PBs differed between analyzed individuals. Globoid crystals of various sizes were found in PBs from scutellum, coleorhiza, and from inner layers of radicular cortex. The largest globoid crystals (up to 2.0 μ in diameter) were seen in the scutellum. Energy-dispersive X-ray microanalysis revealed the presence of P,K. Mg, and some traces of Fe and Zn in the majority of globoid crystals from the scutellum. Globoid crystals from coleorhiza and radicular cortex were rich in Zn and Ca. The presence of considerable Zn was usually accompanied by high Ca, at the expense of K and Mg. As EDX analyses revealed significant differences in Zn and Zn/P values between analyzed tissues, it is probable that the majority of Zn is preferably accumulated in globoid crystals of some tissues of maize germ.

An electron microscope study of resin production and secretion by the glands of seedlings of Betula pendula Roth.

Abstract: summary Transmission and scanning electron microscopy were used to study the ultrastructure and secretory processes of resin glands on shoot stems of Betula pendula seedlings during seasonal growth. The multicellular peltate glands possess a cortex of columnar cells surrounding a parenchymal medulla differing from the stem parenchyma below. Myelin-like deposits comprising concentric layers of membranes and osmiophilic substances accumulate mainly in the cortical cells, while only the medullar cells have chloroplasts. Both of these deposits appear to be synthesized, initially, in the endoplasmic reticulum. The myelin-like material is believed to consist of steroidal triterpenoids in cytoplasmic membranes, and the osmiophilic deposits to represent phenolics. Studies of glands of different ages suggest that the electron-transparent resin ultimately exported is formed by combining the two initial products. In the cortical cells the secretion first accumulates in vesicles that fuse with larger ones and the periplasmatic space. From the latter the secretion diffuses through the cell wall and the resin is finally deposited in the subcuticular space. Secretion vesicles, but no periplasmatic deposits were seen in the medullar cells. At the end of seasonal growth the cortical cells are markedly vacuolate and appear to have lost their organelles. Some of the cells accumulate an electron-opaque material not seen earlier. The medullar cells of the glands are suberized before winter dormancy, but usually later than in the surrounding stem bark.