Showing papers on "Ultrastructure published in 1984"
TL;DR: Observations of hippocampal neurons in dissociated cell culture show that the fundamental differences in form and in the distribution of ribosomes between axons and dendrites can be established in cell culture.
Abstract: We have studied the processes which are elaborated by hippocampal neurons in dissociated cell culture. Nerve cells, which were obtained from fetal rats at 18 to 20 days of gestation, were plated at very low density onto polylysine-treated coverslips and were maintained in serum-free medium. Under such conditions, some cells develop without contacting any neighboring neurons or glial cells. Examples of such isolated cells which had developed for 1 week in culture were studied first by light microscopy, then they were sectioned parallel to the substratum so that all portions of the cell and its processes could be examined by electron microscopy. Dendrites and axons could be clearly distinguished by both light and electron microscopy. Dendrites were rather thick at the base but tapered rapidly to a minimum diameter of about 0.5 micron and contained polyribosomes throughout their length. Axons, which were several times longer than the dendrites, were thinner at the origin, tapered much less, and were essentially ribosome-free. These ultrastructural differences were particularly obvious at branch points, where cytoplasmic organelles tend to accumulate. Clusters of polyribosomes were invariably present at dendritic branch points, but they were never observed at axonal branch points. The axons most commonly arose from the proximal portion of a dendrite rather than directly from the cell body as they typically do in situ. These observations show that the fundamental differences in form and in the distribution of ribosomes between axons and dendrites can be established in cell culture. Contact with afferent fibers or with target cells during the period of process outgrowth is unnecessary for the expression of these features of axonal and dendritic differentiation.
363 citations
01 Jan 1984
TL;DR: A comparison study of the growth and development of collagen fibrils in connective tissue and the structural basis of calcification found elastogenesis in embryonic and post-natal development and the ultrastructural organization of the elastin fibre.
Abstract: 1. Electron microscopy of the collagen fibril.- 2. Growth and development of collagen fibrils in connective tissue.- 3. Collagen distribution in tissues.- 4. Ultrastructural aspects of freeze-etched collagen fibrils.- 5. Electron microscopy of proteoglycans.- 6. Collagen-proteoglycan interaction.- 7. The ultrastructural organization of the elastin fibre.- 8. Elastogenesis in embryonic and post-natal development.- 9. Pathobiology and aging of elastic tissue.- 10. The structural basis of calcification.- 11. Electron microscopy of basal membrane.
168 citations
TL;DR: Pollen grains of Plumbago zeylanica L. were serially sectioned and examined using transmission electron microscopy to determine the three-dimensional organization of sperm cells within the microgametophyte and the quantity of membrane-bound organelles occurring within each cell.
Abstract: Pollen grains of Plumbago zeylanica L. were serially sectioned and examined using transmission electron microscopy to determine the three-dimensional organization of sperm cells within the microgametophyte and the quantity of membrane-bound organelles occurring within each cell. Sperm cells occur in pairs within each pollen grain, but are dimorphic, differing in size, morphology and organelle content. The larger of the two sperm cells (Svn) is distinguished by the presence of a long (approx. 30 μm) projection, which wraps around and lies within embayments of the vegetative nucleus. This cell contains numerous mitochondria, up to two plastids and, infrequently, microbodies. It is characterized by a larger volume and surface area and contains a larger nucleus than the other sperm cell. The second sperm cell (Sua) is linked by plasmodesmata with the Svn, but is unassociated with the vegetative nucleus. It is smaller and lacks a cellular projection. The Sua contains relatively few mitochondria, but numerous (up to 46) plastids and more microbodies than the other sperm. The degree of dimorphism in their content of heritable cytoplasmic organelles must at fertilization result in nearly unidirectional transmission of sperm plastids into just one of the two female reproductive cells, and preferential transmission of sperm mitochondria into the other.
137 citations
TL;DR: The ultrastructure of representative types of ectomycorrhizal root of pine was analysed after collection at different times of year from March to June, indicating that, in contrast to pathogenic attack, no adverse reaction to the fungal presence occurs.
Abstract: Summary
The ultrastructure of representative types of ectomycorrhizal root of pine was analysed after collection at different times of year from March to June, using scanning and transmission electron microscopy. In the Pre-Hartig net zone (PHZ) near the root apex, a well-developed sheath is present in which are incorporated sloughed root cap cells. There is evidence of dissolution of the host cell wall adjacent to fungal elements in some cells. Sheath structure in the Hartig net zone (HZ) is similar to that in the PHZ, but the residual cells here are collapsed root hairs. Glycogen and polyphosphate granules are abundant in the sheath in March but their number declines in later months. The Hartig net is made up of a pseudoparenchyma of infolded fungal elements and the cortical cells adjacent to it are generally living. No basic difference between niycorrhizal and non-mycorrhizal cortical cells was observed, thus indicating that, in contrast to pathogenic attack, no adverse reaction to the fungal presence occurs. Reasons for seasonal changes of storage compounds are discussed.
103 citations
TL;DR: Almost complete restoration of epidermal function was achieved after transplantation of PEC onto adult syngeneic mice and, although keratinocytes in primary culture differ considerably from those in vivo, they have not irreversibly lost the capacity for complete differentiation.
93 citations
TL;DR: The three-dimensional organization of cortices isolated from unfertilized and fertilized Strongylocentrotus purpuratus eggs has been examined and it has been found that when moderate shear forces are used, the isolated unfertile egg cortex, in addition to cortical granules, contains acidic vesicles and an elaborate network of rough endoplasmic reticulum.
89 citations
TL;DR: It is shown that in the midgut of the insect Manduca sexta, distinct ultrastructural changes accompany loss of potassium transport activity during a larval molt and in the prepupal stage.
Abstract: The general organization of arthropod epithelia is compared to that of vertebrates. It is suggested that although ciliated epithelia, stratified epithelia and in some cases continuous muscle sheaths do not occur in arthropods, they have certain analogous structures which carry out the same functions. For example, the arthropod cuticle is compared to the squamous layer of vertebrate stratified epithelia, and complex arthropod basement membranes are compared to the muscle and connective tissue sheaths of certain vertebrate epithelia. The cellular organization of transporting epithelial cells is then discussed, with particular reference to elaboration of plasma membranes, and similarities and differences between vertebrates and arthropods, and between insects and crustaceans are pointed out. Specializations peculiar to insect cells are described, including the insertion of mitochondria into apical membrane microvilli, and the presence along this membrane of small particles called portasomes believed to be involved in active transport. Finally, it is shown that in the midgut of theinsect Manduca sexta , distinct ultrastructural changes accompany loss of potassium transport activity during a larval molt and in the prepupal stage. The ultrastructural changes which occur include a proliferation of the basement membrane and muscle tissue underlying the epithelium, and a change in the morphology of the potassium transporting goblet cells. Possible correlations between ultrastructural changes and loss of transport activity are discussed.
83 citations
TL;DR: The results suggest the possibility that the different collagen types are synthesized by the same cells and that the variation in cellular morphology could be associated with the changes in the type of collagen synthesized.
Abstract: Osteogenic tissue formed in vivo in diffusion chambers inoculated with a suspension of marrow cells contains both bone and cartilage. Observations by transmission electron microscopy on the transitional zone between these tissues showed a mixture of osseous and cartilaginous features in both matrix and cells. Two forms of collagen, morphologically consistent with Types I and II, are found in intimate association within the same intercellular septa. The results suggest the possibility that the different collagen types are synthesized by the same cells and that the variation in cellular morphology could be associated with the changes in the type of collagen synthesized. This unique characteristic of calcified tissues formed in diffusion chambers is probably the result of isolation from direct blood circulation, mechanical stress, and cellular mechanisms of tissue breakdown.
72 citations
Journal Article•
TL;DR: The present demonstration that the A and S cells are ultrastructurally totally different cells, together with the fact that intermediate types of cells do not exist, may support the interpretation that type A and type S synoviocytes represent two distinct cell types with distinct and different functions.
63 citations
57 citations
TL;DR: Changes in germ cell structure have been related to some of the characteristic features of spermatogenesis in guppy, e.g. the large number of sPermatogonial generations and the complexity of s permiogenesis.
Abstract: The structure of guppy (Poecilia reticulata) spermatogonia and spermatocytes has been studied using electron microscopy. The spermatogonia, situated at the apex of the seminiferous tubule, are almost all surrounded by a network of Sertoli cells; they have very diffuse chromatin and one or two large nucleoli. The cytoplasm contains relatively few organelles, although annulate lamellae are found. The mitochondria have few cristae and are concentrated at one pole of the cell; they are sometimes found with intermitochondrial cement. These spermatogonia are separated from each other, having no intercellular bridges or inclusion in Sertoli cells, and are relatively undifferentiated; they correspond to stem cells. The spermatogonia beneath the apex are organized into cysts. First-generation spermatogonia are more dense and heterogeneous, their nuclei becoming smaller and their chromatin becoming denser during successive generations. In spermatocytes, the synaptinemal complex exists as a modified form until metaphase. The concentration of organelles in the cytoplasm increases and the organelles become more diversified as spermatogenesis progresses. Many cytoplasmic bridges are observed (several per cell), indicating that the cells remain in contact after several divisions. These changes in germ cell structure have been related to some of the characteristic features of spermatogenesis in guppy, e.g. the large number of spermatogonial generations and the complexity of spermiogenesis.
TL;DR: Groups of mitochondria are located in between the hyphae, suggesting a strong association between the host and the endophyte for energy supply and amino acid production and the consequences of the inability to separate the mitochondria from the vesicle clusters in nodule homogenates in physiological studies have been discussed.
Abstract: The fine structures of the microsymbiont inside the root nodules ofDatisca cannabina have been studied by light, by transmission- and by scanning-electron microscopy. The endophyte is prokaryotic and actinomycetal in nature. The hyphae are septate and branched, diameter 0.3–0.5 μm. The tips of hyphae are swollen to form electron-dense, clubshaped to filamentous vesicles, ranging in diameter: 0.4–1.4 μm. The endophyte penetrates through walls of the cortial cells. The infected zone is kidney shaped and confined to one side of the acentric stele. The orientation of infection is reversed from other actinorhizae exceptCoriaria. The hyphae are near the host cell wall and vesicles are directed towards the central vacuole. Vesicles are aseptate and no collapsing of the vesicle cell wall (void area) has been observed. Vesicle clusters structures are globular with an opening at one side of the cluster. The host cell is multinucleate or contains a lobed nucleus. Groups of mitochondria are located in between the hyphae, suggesting a strong association between the host and the endophyte for energy supply and amino acid production. The consequences of the inability to separate the mitochondria from the vesicle clusters in nodule homogenates in physiological studies have been discussed.
Journal Article•
TL;DR: The ultrastructure of the rat pineal gland was studied from 75 days until 10 months of age and there was a clear increase in the number of dense bodies or lysosomes in the Type I pinealocyte.
Abstract: The ultrastructure of the rat pineal gland was studied from 75 days until 10 months of age. Type I pinealocytes of young adults showed nuclei with dispersed chromatin, numerous infoldings of the nuclear envelope and well developed nucleoli. The cytoplasm displayed many mitochondria and clusters of smooth endoplasmic reticulum. With increasing age, there was a clear increase in the number of dense bodies or lysosomes in the Type I pinealocyte. The changes in the Type II pinealocytes with age were mainly in nuclear shape and in the appearance of lipofuscin granules.
TL;DR: Based on magnified electron micrographs of normal and inverted statocytes a morphometrical analysis of the distribution and redistribution of amyloplasts, nuclei, mitochondria, vacuoles and ER was made, and the only significant difference was found in the redistribution ofAmyloplast between aux-1 and the gravitropical normal types.
Abstract: The root anatomy and ultrastructure of the agravitropic Arobidopsis thaliana L. mutants Dwf and aux-1 were compared with the gravitropic mutant aux-2 and the wild type (WT) in an attempt to find an explanation for the lack of response to gravity. No differences were found in the organization of the root cap. The central part of the cap (columella) contains 5 storeys of developing, functioning and degenerating statocytes. Their ultrastructure is very similar in all four types of plant. Particular attention was paid to the distribution of rough endoplasmic reticulum (ER). Both in the WT and the mutants the ER is concentrated in the distal part at the "floor" of the cell. Light micrographs were used to compare the sedimentation rates of movable cell structures in normal and agravitropic root statocytes. A longitudinal movement of amyloplasts and nuclei was observed when the roots were inverted. In WT and aux-2 the rates were on average 6.3 micrometers h-1 (amyloplasts) and 2.1 micrometers h-1 (nucleus). In aux-1 the sedimentation rates were significantly lower: 2.4 and 0.6 micrometers h-1, respectively. Based on magnified electron micrographs of normal and inverted statocytes a morphometrical analysis of the distribution and redistribution of amyloplasts, nuclei, mitochondria, vacuoles and ER was made. The only significant difference was found in the redistribution of amyloplasts between aux-1 and the gravitropical normal types.
TL;DR: Eighteen two- to four-cell embryos, cultured in vitro for 32–65 hr after insemination, were examined by transmission electron microscopy to assess their normality and developmental potential.
Abstract: Eighteen two- to four-cell embryos, cultured in vitro for 32–65 hr after insemination, were examined by transmission electron microscopy to assess their normality and developmental potential. These stages are now being widely used for embryo transfer in in vitro fertilization clinics. They were obtained by inseminating preovulatory oocytes aspirated at laparoscopy, with or without ovarian stimulation, by methods which have yielded normal pregnancies. The organization of seven embryos was apparently normal and their blastomeres had cellular organelles usually present in fertilized ova. Details of their ultrastructure including subtle changes observed on prolonged culture are described. Other embryos showed some normal and obvious abnormal features, such as partial fragmentation and multinucleated blastomeres, or evidence of degeneration.
TL;DR: Ultrastructure of the glands revealed a well‐differentiated epithelium with basement membrane, desmosomes and the presence of microvilli with core rootlets, glycocalyx, and intracytoplasmic R‐bodies, indicating the glandular epithelia was of the „intestinal type.
Abstract: This report is the first description of the ultrastructure of the glandular elements in a so-called glandular Schwannoma (malignant peripheral nerve sheath tumor with glandular elements) The appearance of this uncommon tumor was typical by light microscopy Electron microscopy of the sarcomatous component revealed features consistent with Schwann cell origin Ultrastructure of the glands revealed a well-differentiated epithelium with basement membrane, desmosomes and the presence of microvilli with core rootlets, glycocalyx, and intracytoplasmic R-bodies No cilia or blepharoplasts were present, arguing against ependymal origin of these glands The microvilli with core rootlets, the glycocalyx and the R-bodies indicate the glandular epithelium was of the "intestinal type" The basis for the presence of such epithelium in Schwann cell neoplasms is uncertain, but pathologic induction-interaction between neural crest and mesenchyme may be the most plausible explanation
TL;DR: It is postulated, that the dark secretory granules are prestages of the actual secretory product presenting as lightgranules and that dark and light granules do not represent different secretory capacities of the cell.
Abstract: Light- and electron microscopic studies of recent years have definitely concluded that the epithelium of the middle ear is a modified respiratory epithelium with ciliated and secretory cells including goblet cells. Goblet cells are secretory cells completely filled with secretory granules. Secretory cells and ciliated cells are both derived from the basal cell. The subepithelial layer which consists of loose connective tissue is a structure of just as great importance as the epithelial layer. It is still not clear whether the dark granulated cell is the site of production of the serous middle ear effusion or whether it merely represents an immature stage of the mucigen-producing cell.
TL;DR: Differences in the ultrastructure of the type species of the genusDunaliella, D. salina, has been reinvestigated in an attempt to clarify the relationships between Dunaliella and spermatozopsis, and justify distinction between the two taxa at generic level.
Abstract: The ultrastructure of the type species of the genusDunaliella, D salina, has been reinvestigated in an attempt to clarify the relationships betweenDunaliella andSpermatozopsis Dunaliella salina differs in the following ultrastructural characters fromSpermatozopsis (as exemplified byS similisPreisig etMelkonian): presence of a distinctive surface coat covering the plasmalemma; presence of a prominent pyrenoid (with pairs of thylakoids partially entering the pyrenoid matrix); dictyosomes parabasal; endoplasmic reticulum closely underlying the plasmalemma around most of the cell; contractile vacuoles absent; cell form ovoid to elongated and not spirally twisted; mitochondrial profiles near the flagellar apparatus Differences in the ultrastructure of the flagellar apparatus: basal body angle more or less fixed; distal connecting fibre cross-striated; system II fibre (rhizoplast) present, associated with mitochondrial profile; system I fibre underlying two-stranded microtubular root; mating structure present These ultrastructural differences justify distinction between the two taxa at generic level The problematical status of “freshwater” species ofDunaliella is briefly discussed
TL;DR: The morphognomy of the secretory granules of the major endocrine cell types is qualitatively similar to that of mammals and whether or not the quantitative and/or associative differences contribute to the marked metabolic differences between reptiles and mammals, remains to be determined.
Abstract: Insulin, glucagon, somatostatin, and pancreatic polypeptide (PP) were localized in the pancreas of the common garter snake, Thamnophis sirtalis, by light and transmission electron microscopic (TEM) immunocytochemistry. Colloidal gold-protein A was used for TEM localization and the peroxidase--antiperoxidase complex technique was used for light microscopy. The glucagon-containing A cells and the insulin-positive B cells were the most numerous cell types. The somatostatin-containing D cells made up about 15% of the endocrine cells. PP-positive F cells were a minor cell type. The only topographic arrangement of the cells within the endocrine-rich areas that was apparent was the peripheral localization of the D and F cells. Cells of a specific cell type were sometimes grouped together. At the electron microscopic (EM) level, the gold particles (indicating the presence of hormone) were localized nearly exclusively over the secretory granules of the reactive cells. The alpha-granules were the largest found and were predominantly electron dense with a moderately electron-dense periphery. PP-containing granules were the smallest. The somatostatin-reactive delta-granules were round and moderately electron opaque. The beta-granules were heterogeneous in appearance. The morphognomy of the secretory granules of the major endocrine cell types is qualitatively similar to that of mammals. Whether or not the quantitative and/or associative differences contribute to the marked metabolic differences between reptiles and mammals, remains to be determined.
TL;DR: It is concluded that the macaque extrapulmonary airway epithelium differs from published descriptions of laboratory rodents in both cell types present and relative abundance of those cell types.
Abstract: Since there are major differences between the airway epithelium of man and that of common laboratory species, the tracheobronchial epithelium of the bonnet macaque was characterized to evaluate its usefulness as a model for study of human conducting airways. This study compared the light microscopic, scanning electron microscopic, and ultrastructural appearance of epithelium from the posterior membranous and anterior cartilaginous trachea and mainstem bronchus. Population densities, epithelial volumetric densities, and frequency distributions of cross-sectional areas of nuclei were determined for cell types present on electron micrographs. Four epithelial cell types were distinguished by ultrastructural criteria. Basal cells were 31% of the population and were similar to those described in other species. Ciliated cells were also similar to those of other species and composed 41% of the population; their nuclei were larger than those of other cell types. Mucous goblet cells had large numbers of secretory granules with electron-dense cores and a lucent periphery. They were only 8% of the population by nuclear count but composed 20% of the epithelial volume. The fourth cell type had multiple small vesicles containing small amounts of granular material and was termed a "small mucous granule cell." Small mucous granule cells (16% of the population) were present in greater numbers than mucous goblet cells but were a smaller proportion of the epithelial volume (8%). While population densities of cell types determined from transmission electron micrographs did not vary between sample sites, scanning electron microscopy demonstrated longitudinal streaks of secretory cells in the posterior trachea suggesting that regional differences in epithelial organization exist. We conclude that the macaque extrapulmonary airway epithelium differs from published descriptions of laboratory rodents in both cell types present and relative abundance of those cell types. Although detailed quantitative studies of human extrapulmonary airways are not available, the primate airways resemble those of man in both the types of cells present and the complexity of pseudostratification.
TL;DR: A pathotype of A. alternata with selective pathogenicity to rough lemon produces two or more substances with selective toxicity to the host, and nearly 100% were affected at 6 h.
Abstract: A pathotype of A alternata with selective pathogenicity to rough lemon produces two or more substances with selective toxicity to the host The major toxin was extracted from culture fluids with ethyl acetate and purified by several different chromatographic procedures Toxin (10 ng/mL, 25 μL) was applied to leaves; within 24 h, water congestion and veinal necrosis were evident The first toxin-induced change detected by electron microscopy was in the mitochondria; toxin at 1 μg/mL caused swelling, reduction in numbers and vesiculation of cristae, and decreases in electron density of the matrix At 1 h after toxin treatment, the percentages of affected mitochondria in cells of several tissues were 18 in bundle sheaths, 9 in mesophyll cells adjacent to bundle sheath, and 9% in mesophyll cells remote from sheath The number of affected mitochondria increased with time, until nearly 100% were affected at 6 h No effects on other organelles were evident at 6 h No ultrastructural changes were evident in cell
TL;DR: Progressive changes in the ultrastructure of the larval fat body of Drosophila melanogaster were studied during the third instar, and morphological evidence indicated D granules have the unusual characteristic of forming in the intercellular space before entering the cytoplasm.
Abstract: Progressive changes in the ultrastructure of the larval fat body of Drosophila melanogaster were studied during the third instar In addition to electron microscopy, light microscopy and morphometric stereology were employed to evaluate the tissue at five 12-hr intervals: 48, 60, 72, 84, and 96 hr after hatching from the egg Lipid and glycogen were found stored throughout the instar, whereas protein is stored in the form of cytoplasmic granules mainly during the final 24 hr The cells increased in cross-sectional area, and there was a concomitant increase in the relative amounts of these substances Based on morphological characteristics there were three types of protein granules which we called dense granules (D), heterogeneous granules (H), and autophagic vacuoles The morphology, size range, time of appearance, and changes in frequency of these granules suggested that the H type arose from D granules, and that the autophagic vacuoles were derived from D and H types Morphological evidence indicated D granules have the unusual characteristic of forming in the intercellular space before entering the cytoplasm
TL;DR: Examination of the explants showed a homogeneous layer of odontoblasts attached to the dentinal surface, which had a normal structure and nuclear polarity similar to that seen in vivo.
TL;DR: The morphology and the ultrastructure of the Lymphocystis disease virus (LDV) strain Leetown, a fish iridovirus, was studied by electron microscopy.