Showing papers on "Ultrastructure published in 1983"

Comparison of nonciliated tracheal epithelial cells in six mammalian species: ultrastructure and population densities.

Abstract: Three types of nonciliated epithelial cells in mammalian conducting respiratory airways are thought to be secretory: mucous (goblet) cells, serous epithelial cells, and Clara cells. Mucous and serous cells are considered to be the secretory cells of the trachea. Clara cells are considered to be the secretory cells of the most distal conducting airways or bronchioles. To ascertain if mucous and serous epithelial cells are common to the tracheal epithelium of mammalian species, we characterized the ultrastructure and population densities of tracheal epithelial cells in six species:- hamster (H), rat (Rt), rabbit (Rb), cat (C), Bonnet monkey (M. radiata) (B), and sheep (S). Following fixation by airway infusion with glutaraldehydelparaformaldehyde, tracheal tissue was processed for light and electron microscopy (EM.) by a selective embedding technique. Tracheal epithelium over cartilage was quantitated by light microscopy and characterized by transmission EM. Mucous cells were defined by abundant large nonho...

Electron microscopy of gas space (aerenchyma) formation in adventitious roots of Zea mays L. subjected to oxygen shortage.

Abstract: This paper examines the ultrastructure of cortical cells in maize root tips during the early stages in lysigenous aerenchyma formation, promoted by oxygen-deficient nutrient solution. The aim was to determine whether changes in fine structure were compatible with oxygen starvation as the primary cause of cell degeneration and death. There was an initial collapse of some cortical cells, indicating loss of turgor, and the cytoplasm became more electron dense. Mitochondria and endoplasmic reticulum appeared normal at this early stage though the tonoplast lost its integrity. Subsequently the cytoplasm became less electron dense than surrounding healthy cells, and underwent further degeneration while the plasmalemma retracted from the cell wall. Cell walls remained unaltered until this stage, but some then became thin and electron transparent. No cells of the stele were found to degenerate. These observations, which do not readily accord with the hypothesis that oxygen starvation was the cause of cell death, are compared with detailed studies of cell degeration in other cell types. An alternative mechanism for the stimulation of cortical cell lysis in poorly oxygenated roots involving the hormone ethylene, is discussed.

Ultrastructure of trout spermatozoa: Changes after dilution and deep-freezing

Abstract: Trout spermatozoa taken from the testis, vas deferens and ejaculate are described at the ultrastructural level. The morphology of the spermatozoa head, changes in the middle-piece structure, and the relationship between the centrioles and the flagellum were studied under consideration of their role in the reproduction of this species. Morphological changes observed after dilution of the spermatozoa in freshwater or saline and subsequent freezing deserve attention in connection with certain manipulations used in fish farms and laboratories.

Isolation and ultrastructural characterization of secretory mutants of Tetrahymena thermophila

Abstract: Isolation of 14-secretory mutants (exo-) of Tetrahymena thermophila and ultrastructural characterization (freeze-fracture and thin-section) of two of these (SB255 and SB258) are described. The site of secretion is marked by an intramembrane particle array, the rosette, beneath which the secretory organelle rests. Using Alcian Blue (8GS) as a secretagogue, a screening procedure for exo- cells was developed. Of the resulting 14 clones isolated, 10 are stable and have a tight mutant phenotype. Two of these, SB255 and SB258, lack assembled rosettes. Electron microscopy shows that SB255 has a reduced total number of mucocysts, whereas SB258 appears to have the normal number. This study demonstrates a useful eukaryotic model with which to study by genetic dissection the regulatory mechanisms involved in membrane events in secretion.

The ultrastructure of the amebocyte-producing organ in Biomphalariaglabrata

Abstract: The amebocyte-producing organ (APO) in normal and echinostome-sensitized Biomphalariaglabrata was studied at the ultrastructural level The APO in unexposed snails consists of small clusters of primary ameboblasts resting on the epithelial cells lining the pericardium The ameboblasts are held in a loose reticulum formed by extensions from smooth muscle and few fibroblastic cells Secondary ameboblasts and amebocytes constitute further stages of this cell line Amebocytes, resembling cells in the snail's circulation, appear in the blood sinus coursing through the interior of the APO Exposure of snails to echinostome miracidia results in significant morphological changes in the organ Large clusters of primary and and secondary ameboblasts appear, many of these cells undergoing mitosis Fully activated APOs consist of masses of cells loosely arranged in zones of progressive maturation Blood cells in activated APOs were significantly larger than those seen in normal APOs

Ultrastructural evidence of continued reorganization at the aging (11-26 months) rat soleus neuromuscular junction.

Abstract: Ultrastructural remodeling, with evidence of focal deafferentation and reinnervation, occurs within normal young adult rat soleus neuromuscular junctions (Cardasis and Padykula, 1981). This may be related to normal variations in function. Recognition of this plasticity provides a basis for analysis of aging changes in junctional ultrastructure. Thirty soleus junctions were studied between 11 and 26 months of life. In these junctions, compared to younger ones (3-5 months) synaptic sites with the conventional ultrastructure become increasingly sparse. There is an increase in extent and frequency of exposed junctional folds, of intervention of Schwann cell cytoplasm between axon and junctional folds, and of numbers of lysosomes in all cytoplasmic profiles. Often primary clefts are shallow or missing, and secondary folds are widened and contain collagen. Features limited largely to these older junctions include highly pleomorphic myonuclei, deeply invaginated by myofibrils, and an increase in cellular profiles between basal lamina and sarcolemma. The identity of these profiles is unknown. At other locations within many of the same endplates, small intact terminals are associated with larger expanses of junctional folds, and several small terminals occur within the same primary cleft. Such terminals frequently contain dense-cored vesicles. These observations suggest continuation of some terminal axonal regeneration. Thus, the ultrastructure of these aging neuromuscular junctions reveals the same degenerative and regenerative events suggested by the ultrastructure of younger junctions, but suggests a shift in the balance between them.

Microglandular adenosis of the breast. A clinicopathologic study of 11 cases with ultrastructural observations.

Abstract: The clinical and pathologic features of 11 examples of microglandular adenosis of the breast are presented. Microglandular adenosis is a rare, benign lesion that is easily confused with carcinoma. It is characterized by a concentrated proliferation of round glands with open lumens in a densely homogeneous stroma that clearly delineates microglandular adenosis from the adjacent uninvolved breast. The glands are lined by a single layer of cells with distinctly vacuolated or granular cytoplasm. Ultrastructurally, the single layer of epithelial cells lacks cytoplasmic protrusions and is surrounded by a thick multilayered basement membrane. Light- and electron-microscopic features that help distinguish microglandular adenosis from well-differentiated (tubular) carcinoma and sclerosing adenosis, entities with which it is easily confused, are discussed.

Identification and in situ localization of the "thymic nurse cell" in man.

Abstract: The observation of the "thymic nurse cell" (TNC), a reticuloepithelial cell with intracytoplasmic lymphocytes, in suspension of murine thymic tissue prompted us to investigate the existence of this cell in cell suspension, as well as in tissue sections of the human thymus. TNC-like cells were enriched in suspension by enzymatic disintegration of thymic tissue and 1 X G sedimentation over 50% fetal calf serum gradients. TNC-like cells were negative for lysosomal enzymes: in this respect, as well as in light microscopic morphology, the cells were different from tissue macrophages with intracytoplasmic lymphocytes. In electron microscopy, TNC-like cells showed reticuloepithelial characteristics. In 1-micron tissue sections, clusters of lymphocytes with a possible reticuloepithelial nucleus were observed close to blood capillaries in the cortical area. Ultrastructural analysis confirmed the epithelial nature of this cell, as well as its location adjacent to blood capillaries. We concluded that there is in situ existence of TNC in man. This observation enables studies on the role of TNC in intrathymic T cell maturation.

Macular pucker. II. Ultrastructure.

Abstract: Twenty symptom-producing epimacular membranes removed during vitreous surgery were examined by light microscopy, scanning and transmission electron microscopy. These membranes contain cells of glial and pigment epithelial origin, but one also finds myofibroblasts and fibroblasts which cannot be identified morphologically as to their origin. The membranes can be classified into two types. Membranes in one group are composed of numerous alternating layers of collagen and cells and some internal limiting lamina. The second type of membrane is generally composed of a single layer of cells with large sheets of internal limiting lamina from the retinal surface and little if any collagen. Both types of membranes have cells on the retinal side of the removed internal limiting lamina, presumably derived from neurosensory retina.

Ultrastructure of the branchial epithelium of an amphibious brackish-water crab

Abstract: The ultrastructure of the branchial epithelium of the amphibious brackish-water crab Uca mordax (Smith) was investigated in relation to adaptation to the salinity of the medium. No distinct differences were observed in the epithelial structure of animals adapted to either 100% sea water or to 1% sea water. Thus any interpretation of the significance of particular structures in relation to specific transport processes should be regarded with caution. Apart from strict epithelial cells, pillar cells and glycogen (presumed) storage cells were found. The epithelial cells showed very well-developed apical microvilli or lamellae and basal interdigitations with adjacent cells. Well-developed junctional complexes were seen (band desmosomes, septate desmosomes, gap junctions). The cells are extremely rich in mitochondria. Microtubules, peroxisome-like bodies, multivesicular bodies and near-nuclear Golgi complexes were present.

Structure and ultrastructure of the oesophagus in sea-water and fresh-water teleosts (Pisces)

Abstract: The oesophageal epithelium of eleven sea-water and four fresh-water teleosts was studied by light and electron microscopy. In sea-water species, the three main regions from pharynx to stomach are: a thick stratified pharyngeal epithelium with complex foldings and numerous mucous cells, and a simple microvillous columnar epithelium in the middle and posterior part. In fresh-water species, foldings are simple, the first two regions occupy the whole length, and no microvillous epithelium is observed. The adaptation from fresh-water to sea-water is characterized by the development of the third, microvillous epithelium. Different microridge cells appear in the mucous region of fresh-water and sea-water Anguilla anguilla oesophagus. The ultrastructure of the microvillous epithelium suggests an active transport of ions along the lateral membranes with water recycling in frequently dilated intercellular spaces.

Structure of the piriform cortex of the opossum. II. Fine structure of cell bodies and neuropil.

Abstract: The fine structure of cell bodies and neuropil in the piriform cortex of the opossum has been examined. A close similarity in ultrastructure of many features has been demonstrated between this pylogenetically old cortex in a primitive mammal and the neocortex of higher mammals. Cell bodies of pyramidal cells are very similar to those in the neocortex: The nucleus is pale with a smooth surface, the cytoplasm has a modest number of organelles, and the soma receives a small number of exclusively symmetrical synapses. Semilunar cells, which have apical but no basal den-drites, are very similar to pyramidal cells in ultrastructure of their cell bodies. Two populations of neurons with nonpyramidal ultrastructural features have been distinguished: (1) cells in layer III that closely resemble the well-known large multipolar cells in neocortex by virtue of a large number of symmetrical and asymmetrical somatic synapses and long cisterns of rough endoplasmic reticulum (ER); and (2) large cells in layer I with very few somatic synapses, a large number of mitochondria, and short cisterns of rough ER that may correspond to cells with somatic appendages described with the Golgi method. Large numbers of profiles are found in all layers that contain round vesicles and make asymmetrical synapses onto dendritic spines, and occasionally, dendritic shafts. Theseprofileshavedistinctly different morphological features in layer Ia, in which olfactory bulb afferents are concentrated, and in layers Ib, II, and III, which contain terminals of association and commis-sural fibers. A smaller number of profiles containing pleomorphic vesicles make symmetrical contacts onto initial segments, dendritic shafts, cell bodies, and occasionally, dendritic spines. Most dendritic spines in all layers are small to medium in size (0.3–1.2 μm) and presumably originate from pyramidal cells. In layer Ia, however, large, flattened spines are also present which appear to originate from semi-lunar cells. In layer III, and to a lesser extent other layers, large irregular spines are present that may be branched appendages on dendrites of complex appendage cells (Haberly, 1983).

Ultrastructure of cartilage from young adult sea lamprey, Petromyzon marinus L: a new type of vertebrate cartilage.

Abstract: Ultrastructural observations of cartilage from adult sea lamprey, Petromyzon marinus, reveal a highly cellular cartilage with an unusual extracellular matrix. The avascular cartilage is surrounded by a vascular perichondrium, which consists of dense connective tissue containing fibroblasts, collagen fibrils, and microfibrils. The cells (chondrocytes) vary in morphology in different parts of the cartilage in a way that may reflect their state of activity. Chondrocytes within the peripheral cartilage contain tubulo-vesicular structures along the cell surface, an extensive lamellar rough endoplasmic reticulum, and a well-developed Golgi complex with associated vesicles and vacuoles. The presence of material within the Golgi elements that resembles components of the extracellular matrix suggests the involvement of the peripheral chondrocytes in the synthesis and secretion of the matrix components. Chondrocytes within the central cartilage are hypertrophied and contain a pale cytoplasm with a reduced number of organelles that are widely spaced throughout the cell. The appearance of the organelles within these cells suggests that they are not as actively involved in the production of the matrix as those of the peripheral cartilage. The extracellular matrix consists of a dense network of randomly arranged, branched, noncollagenous matrix fibrils 15-40 nm in diameter and varying amounts of electron-dense matrix granules. Due to the unique nature of its extracellular matrix, the cartilage of the lamprey cannot be likened to any of the known vertebrate cartilages and, therefore, must be considered a new type of vertebrate cartilage.

Ultrastructure of the dinoflagellate Polykrikos. I. Development of the nematocyst-taeniocyst complex and morphology of the site for extrusion

Abstract: Development of the nematocyst-taeniocyst complex in the four-zooid stage of a dinoflagellate, Polykrikos kofoidi, was studied by electron microscopy. We observed the following stages: formation of large spherical bodies in islets of cytoplasm containing extensive rough endoplasmic reticulum and Golgi complexes; differentiation of an anlage of first the nematocyst and then the taeniocyst into a tandem pair; and, maturation of the complex into a nematocyst with operculum and capsule, and a taeniocyst with head, neck and body. In the intermediate stages of dinoflagellate cnidogenesis the structurally elaborate pattern of development differed from that of coelenterate nematocysts but in certain features the mature organelles of both groups were similar. Nematocyst-taeniocyst complexes migrated into chutes on zooids and four near the junction of the annulus and sulcus at the flagellar bases. The specialized chute was partially lined by thimble-shaped organelles of unknown function. The taeniocyst protruded from the surface in association with a striated fibre whose structure and position were those of a trigger to discharge the two organelles. We found no cytostome in this holozoic colony; the structure of the chute suggested that it might also function as a cytostome.

An ultrastructural study of the tracheal epithelium of the guinea-pig with special reference to the ciliary structure.

Abstract: The ultrastructure of the normal guinea-pig tracheal mucosa has been characterised by transmission and scanning electron microscopy. The pseudostratified epithelium was composed of basal cells, goblet cells, ciliated cells and intermediate cells. Interepithelial granulocytes and lymphocytes were occasionally seen. Regional variations in the distribution of goblet cells and ciliated cells were noted, and the continual turnover of the epithelial cells was manifested in the findings of proliferating, differentiating and exfoliating cells. The function of the numerous microvilli extending into the lumen remains unknown, although the bundles of actin filaments in their core and the anionic properties of their surface suggest a dual function, as motile processes and as sites of re-absorption of excess fluid. Numerous microtubules criss-cross the apex of the ciliated cell. It is suggested that they are an integrated part of the cytoskeleton and/or are involved in some kind of intracytoplasmic transport. Other microtubules are attached to the basal feet and penetrate deep into the cytoplasm; their function has yet to be elucidated. A possible role may be that they, alone or in conjunction with the microfilaments (actin) of the cell cytoplasm, constitute a contractile mechanism responsible for the synchronous beating of the cilia in a given cell. Only in rare cases have the basal bodies developed striated rootlets. Morphological evidence from the current study, that the ciliary crown is in physical contact with the superficial mucus layer, supports the hypothesis that this structure serves as a special device for pushing the mucus forward.

Ultrastructure and staining properties of aortic microfibrils (oxytalan).

Abstract: Microfibrils are the insoluble, 10- to 12-nm components of the extracellular matrix that are involved in elastogenesis. Reports of their ultrastructure vary: they have been described as tubular and beaded and as nontubular filaments that are devoid of any periodicity. Ultrastructurally, microfibrils resemble oxytalan fibers that have been observed in peridontal membranes, skin, and other locations. Whether microfibrils have the staining characteristics of oxytalan is difficult to determine in tissues because available light microscopic stains also stain elastin. Calf aortic smooth muscle cells grown in media without added ascorbate provide a unique model for examining the ultrastructure and staining characteristics of chemically defined microfibrils. Microfibrils are the predominant insoluble extracellular protein in such cultures, which do not deposit collagen or elastin. These studies demonstrate that microfibrils are tubular structures with 10- and 12-nm striations and have the same staining characteri...

Uterine glands of the pig during pregnancy. An ultrastructural and cytochemical study.

Abstract: The ultrastructure of the porcine uterine glands is described from material taken from 11 pregnant pigs at exactly known stages of gestation (day 30; 58; 80; 100; 110). Fixation was performed by perfusion via a branch of the uterine artery and the tissue was routinely processed for electron microscopy. Additionally, cytochemical studies (phosphotungstic acid reaction for glycoproteins, according to Rambourg 1967; acid phosphatase reaction; ultrastructural localization of cellular iron, according to Parmley et al. 1978) were performed. On day 30 of pregnancy the uterine glands are coiled, simple tubular glands with a narrow lumen. The epithelial lining is simple columnar and consists basically of two cell types, ciliated cells and secretory cells. The secretory activity of the glandular epithelium is low; only a few secretory granules are present in the supranuclear cytoplasm. At midpregnancy the ultrastructure of the glands has significantly changed and the cells now show all the characteristics of high secretory activity: numerous parallel cisternae of rough endoplasmic reticulum, an extensively developed Golgi apparatus and many secretory granules which give a positive reaction for acid phosphatase and glycoproteins. The lumina of the glands are significantly enlarged and filled with a great amount of a granular, acid phosphatase-positive material. In the last third of pregnancy, only minor changes in the ultrastructure of the uterine glands are observed. The secretory activity is still high. The amount of rough endoplasmic reticulum has further increased and parallel arrays of cisternae occupy a considerable part of the supranuclear cytoplasm. The importance of the uterine secretion for embryonic nutrition and development is only partly understood. One of the secreted glycoproteins, uteroferrin, is believed to play an important role in the iron transfer from mother to fetus. From midpregnancy onward, a special cell type, the "granule laden cell" is found scattered between normal secretory cells of the uterine glands. Contrary to the opinion of Perry and Cromby (1982), we could demonstrate that these cells frequently extend to the lumen of the gland; hence the term "basal cell" seems inappropriate for this cell type.

Cytochemical Detection of Polysaccharides and the Ultrastructure of the Cell Coat of Zoospores of Chytriomyces Aureus and Chytriomyces Hyalinus

Abstract: The formation and structure of cell coats on zo6spores of Chytriomyces aureus and C. hyalinus are described from an ultrastructural and cytochemical study. After zoospore initials are cleaved, but before organelles are organized into the arrangement found in free-swimming zoospores, dictyosomal vesicles deposit a cell coat on the outer surface of the plasma membrane. In free-swimming zoospores, the cell coat covers all of the zoospore except the flagellar sheath. The inner layer of the cell coat is homogeneously dense and is covered with an outer layer of helically arranged spines. Both layers of the cell coat stain with the silver methenamine technique for polysaccharides, as do glycogen and fibril-containing vesicles in the cytoplasm. Sodium bisulfite and hydrogen peroxide controls confirm the polysaccharide specificity of the reaction in glycogen deposits, vesicles, and the outer layer of the cell coat. Use of the sulfhydryl blocking agent, iodoacetate, demonstrates sulfhydryl-containing compounds in the inner layer of the cell coat.

The fine structure of epidermal lines on arms and head of postembryonic Sepia officinalis and Loligo vulgaris (Mollusca, Cephalopoda).

Abstract: The structure and cell types of the epidermal lines that are found on the surface of the head and arms of Sepia officinalis and Loligo vulgaris, were investigated by light- and transmission electron microscopy. The lines consist of ciliated cells and non-ciliated, accessory cells. The axon of the ciliated cell and the ultrastructure of the latter indicate that this element is sensory; therefore, the epidermal lines of cephalopods may be regarded as a type of sensory organ.

Comparative ultrastructure of the inner capsule of the muscle spindle and the tendon organ

Abstract: The ultrastructure of inner capsule cells of the vertebrate muscle spindle was studied by transmission electron microscopy and compared with that of homologous cells in the tendon organ. Aside from variations in their complexity and pattern of organization, cells of the inner capsule in these two sensory receptors exhibited marked similarities in fine structure. The virtual absence of basal lamina in the region of the nucleated soma as well as on the branching cytoplasmic extensions of these cells was noted. In the inner capsule of both end organs, three kinds of intercellular specialization were encountered. Cell processes were typically linked together at multiple sites by intermediate junctions. In addition, focal points of membrane fusion between two or more cellular profiles were identified as tight junctions. In more extensive regions of plasma membrane overlap, gap junctions were also discerned. It seems probable that these sites along the inner capsule represent areas of mechanical and electrical linkage, enabling contiguous cells to function as a synchronous unit. Tight junctions may also provide the inner capsular sheath with specific permeability-barrier characteristics. Elements of the Golgi complex and associated presecretory vesicles and cytoplasmic granules were prominent. Their presence implicates these cells in the elaboration of the paracellular connective-tissue matrix occupying the intracapsular spaces of both receptors. The close resemblance of these cells to endoneurial fibroblasts of peripheral nerve and to hyalocytes of the vitreous body is emphasized. It is likely that, regardless of species examined, cells of the inner capsule in both receptors play an overall protective role in the formation, maintenance and regulation of their luminal paracellular contents.