Showing papers on "Ultrastructure published in 1989"

Ultrastructural localization of neuropeptides and GABA in rat dorsal horn: a comparison of different immunogold labeling techniques.:

Abstract: Several immunogold techniques were used to determine the ultrastructural localization of calcitonin gene-related peptide (CGRP), tachykinin, somatostatin, and gamma-amino-butyric acid (GABA) immunoreactivity in the dorsal horn of rat spinal cord. The immunocytochemical reactions were carried out directly on ultrathin sections from non-osmicated frozen tissue, non-osmicated low temperature-embedded (Lowicryl K4M) tissue, and osmicated epoxy-embedded material. Preservation of ultrastructural morphology and immuno-labeling efficiency were compared. Morphology of subcellular organelles was relatively good in ultra-thin frozen sections, which showed the highest immunoreactivity. However, only very small samples of tissue could be examined. Although there was relatively good immunolabeling in the Lowicryl K4M-embedded tissue, the ultrastructure of the neuropil, and particularly that of synapses, was poorly maintained. In contrast, the osmicated epoxy-embedded material offered optimal morphological preservation ...

Intercellular communication between rat anterior pituitary cells.

Abstract: Cell-to-cell communication within the rat anterior pituitary was investigated in 60-day-old male rats with immunohistochemistry, scanning electron microscopy, freeze-fracture electron microscopy, and conventional transmission electron microscopy. A dense cytoreticular network of cytoplasmic processes from the folliculostellate cells was found to contain immunoreactive S-100 protein and was observed throughout the anterior pituitary. Nonimmunoreactive cells, which were granular, were situated in the center of each network. Almost all of the granulated cells were situated in close proximity to the folliculostellate cells. Scanning electron microscopy revealed that the gland consisted of microlobules enclosed by a basal lamina. On the surface of the microlobules were blood vessels whose branches invaded its internal structures. Cytoplasmic processes from folliculostellate cells projected outside the microlobule. Freeze-fracture electron microscopy demonstrated the presence of numerous intramembranous particles on the P-face of the plasma membrane. Scattered on the cell surface were groups of particles forming gap junctions. Meshworks of ridges which were representations of tight junctions were also observed near clusters of microvillous fragments. Clusters of particles forming small gap junctions were located between the meshworks of tight junctions. Small gap junctions were clearly observed by conventional electron microscopy between junctional complexes in a manner similar to that seen by freeze-fracture electron microscopy. Slender cytoplasmic processes of folliculostellate cells came in contact near the basal lamina and were adjoined by small gap junctions. The ratio of nongranular cells which contained gap junctions to those in which the junctions were absent was about 1:1. The size of the gap junctions ranged from 50 nm to 3 microns. No gap junctions were observed along the plasma membranes of the granular cells. The significance of an intercellular communication system within the anterior pituitary gland of the rat is to establish a mechanism for rapid transmission of information in an organ which lacks direct innervation.

Three-dimensional analysis of morphogenesis induced by mating pheromone alpha factor in Saccharomyces cerevisiae.

Abstract: Ultrastructural analyses of cytoplasmic changes in Saccharomyces cerevisiae X2180-1A (MATa) that had been treated with alpha factor were performed by using the freeze-substitution fixation method. After alpha factor treatment, cells exhibited a pointed projection, which is a unique pattern of oriented cell surface growth. The relationship between projection formation and intracellular organelles was examined using serial thin sections and computer-aided three-dimensional reconstructions. Using these analyses membrane vesicles and other organelles were detected, and studies on their dynamic structural reorganization became feasible. Production of membrane vesicles (average 65 nm in diameter) was induced upon exposure of the cells to alpha factor before projection emergence. The total number of membrane vesicles increased at the early stage and decreased at the late stage of projection formation. Three-dimensional analysis indicated that the vesicles were at first dispersed throughout the cell, then accumulated at the site where the projection formed. Morphological changes and multiplication of the Golgi body were seen during the process of projection formation. Other intracellular organelles (nucleus, vacuole, rough endoplasmic reticulum and mitochondria) were also rearranged, showing a polar organization of the cytoplasm during projection formation.

Ultrastructural evidence for intracellular formation of amyloid fibrils in macrophages.

Abstract: Early amyloid deposition in the spleen was studied by immunoelectron microscopy following the administration of rapid amyloid-inducing agents to mice. Two days after the injection of an amyloidenhancing factor and casein solution, a small amount of amyloid material was observed at the border of the white pulp and the marginal zone (perifollicular area) and also within the white pulp. At this stage, amyloid fibrils were seen mainly in an extracellular distribution along the cytoplasmic processes of reticular cells and also in the cytoplasmic invaginations of macrophages. By immunoelectron microscopy, gold particles labelled fibrillar structures in lysosome-derived organelles in some macrophages as well as dense bodies consisted of a homogeneous, granular matrix not having any recognizable fibrillar structures. Similar immunolabelled organelles were also observed in the amyloid resorption stage, although, at that stage, they commonly contained other phagocytized materials as well. From these findings, we suggest that at least some amyloid fibrils are polymerized in the cytoplasm of the macrophages by the proteolytic cleavage of previously pinocytized serum amyloid A protein (SAA).

Distribution and movement of membrane-associated platelet glycoproteins: use of colloidal gold with correlative video-enhanced light microscopy, low-voltage high-resolution scanning electron microscopy, and high-voltage transmission electron microscopy.

Abstract: Scanning electron microscopy (SEM), especially low-voltage (1 KeV) high-resolution SEM, can be used in conjunction with stereo pair high-voltage (1 MeV) transmission electron microscopy (HVEM) of whole spread cells or thick sections effectively to correlate surface structure with internal structure. Surface features such as microvilli, pits, pseudopodia, ruffles, attached virus, and other surface-related morphologic characteristics can be identified using SEM, while underlying cytoskeletal structure and organelle organization can be viewed by HVEM of the same preparation. However, the need to "prepare" cells for electron microscopy precludes observation in the living state. The use of several types of video-enhanced light microscopy (VLM) permits observation of living cells such that certain surface and internal features can be observed at a relatively high level of resolution or detection. Thus, changes in living cells can be followed, and at appropriate times the cells may be chemically fixed or rapidly frozen and prepared for ultrastructural examination by electron microscopy. We have utilized VLM in conjunction with SEM and HVEM to correlate changes in shape and surface structure with changes in the internal structure of platelets. In addition, we have found it advantageous to use colloidal gold-labeling procedures, because these markers are detectable by all three forms of microscopy. Using this approach we have labeled platelet membrane GPIIb/IIIa, a receptor for RGD-containing adhesive proteins, with gold-fibrinogen or gold-anti-IIb/IIIa. The initial binding and subsequent movement of gold-fibrinogen-IIb/IIIa complexes in living platelets was followed by VLM. The movement of individual labels could be mapped. Subsequent observation by low-voltage (1 KeV) high-resolution SEM and HVEM permits visualization of the same individual receptors tracked by LM. The final position on the membrane or the position-in-transit when fixative was added was determined relative to surface ultrastructure (SEM) and internal, particularly cytoskeletal, ultrastructure (HVEM).

Significance of electron dense microbodies in trap cells of the nematophagous fungus Arthrobotrys oligospora.

Abstract: We have studied the fate of electron dense microbodies in nematode-trapping organs (traps) of the fungus A. oligospora during the initial hours following nematode capture. The interaction studies were performed with isolated traps which had captured a nematode under conditions where the fungal cells had no access to external energy sources. Video enhanced contrast microscopy showed that under these conditions the number of dense bodies present in the trap cell that formed the penetration tube, rapidly decreased. During subsequent penetration and development of the infection bulb this decrease continued while at this time common cell organelles such as mitochondria and vacuoles were formed. This was confirmed by electron microscopy which also revealed that the dense bodies were degraded by means of an autophagic process. The organelles were degraded individually and finally turned into compartments which, based on ultrastructural criteria, were considered vacuoles. Fusion of such vacuoles into larger organelles frequently occurred. The degradation process was initiated early in the interaction since initial stages were already evident within 15 min after capture. Generally it took 1-2 h before the infection bulb had fully developed and trophic hyphae formation started. During this time the original trap cell, characterized by numerous dense bodies, was transformed into an active vegetative hyphal cell containing typical cell organelles such as nuclei, mitochondria, a strongly proliferated endoplasmic reticulum, vacuoles and "normal" microbodies but lacked dense bodies. This disappearance of dense bodies was confined to the cell that penetrated the nematode and--less frequently--its two neighbouring cells in the hyphal loop. In the other cells, constituting the trap, the dense bodies remained unaffected. As will be discussed, the present results support our current view that traps of A. oligospora contribute to the survival of the organism in its natural environment.

Epidermal tissue homeostasis: apoptosis and cell emigration as mechanisms of controlled cell deletion in the epidermis of the toad, Bufo bufo.

Abstract: In normal, non-expanding toad epidermis more cells are produced than needed to replace cells lost by moulting. By implication, cell deletion additional to moulting must take place. This paper deals with the mechanisms by which the “surplus” of cells is deleted, taking advantage of the fact that the ratio between cell birth rate (K b) and the rate of desquamation (K d), which in normal toads is 2 to 3, can be manipulated. In toads deprived of the pars distalis of the pituitary gland it is decreased to 0.2 to 0.3, and in toads with hydrocortisone pellets implanted into the subcutaneous lymph space it is increased to 7 to 10. Thus, structures candidates for the morphological manifestation of the deletion process should occur rarely in toads in which the pars distalis has been removed and frequently in toads with hydrocortisone pellets implanted. Categorization and enumeration of such structures by light microscopy in the epidermis from operated, normal, and hormone-treated toads were performed. The incidence of structures referred to as “dark cells” and “omega-figures” were found to correlate relatively well with the K b/Kd-ratio. A subsequent ultrastructural analysis — on a cell-by-cell basis — of “dark cells” showed these to reflect various stages of apoptosis. The duration of the apoptotic process was calculated to be approximately 7 h. Light- and electron microscopy of “omega-figures” combined with histochemical observations of PSA-lectin binding were interpreted as reflecting a release of cells from the basal epidermis and their final elimination within the dermis. It is concluded (i) that apoptosis is an important mechanism of controlled cell deletion, (ii) that emigration to, and elimination in, the dermis is a possible deletion mechanism, and (iii) that necrosis is unlikely to play a role in controlled cell deletion.

Influence of pH extremes on sporulation and ultrastructure of Sarcina ventriculi.

Abstract: Distinct morphological changes in the ultrastructure of Sarcina ventriculi were observed when cells were grown in medium of constant composition at pH extremes of 3.0 and 8.0. Transmission electron microscopy revealed that at low pH (less than or equal to 3.0) the cells formed regular packets and cell division was uniform. When the pH was increased (to greater than or equal to 7.0), the cells became larger and cell division resulted in irregular cells that varied in shape and size. Sporulation occurred at high pH (i.e., greater than or equal to 8.0). The sporulation cycle followed the conventional sequence of development for refractile endospores, with the appearance of a cortex and multiple wall layers. The spores were resistant to oxygen, lysozyme, or heating at 90 degrees C for 15 min. Spores germinated within the pH range of 4.6 to 7.0.

An ultrastructural study of spore wall morphogenesis in equisetum arvense

Abstract: Observation en microscopie electronique a transmission de la structure fine des parois sporales

Variation in the ultrastructure of the biflagellate motile cells of six unicellular genera of the chlamydomonadales and chlorococcales (chlorophyceae), with emphasis on the flagellar apparatus

Abstract: The ultrastructural features of the biflagellate motile cells of six different species of the Chlorophyceae, namely Dunaliella lateralis (Polyblepharidaceae, Chlamydomonadales), Chlorococcum hypnosporum, Spongiochloris spongiosa, Protosiphon botryoides (Chlorococcaceae, Chlorococcales), Tetracystis aeria and Pseudotetracystis terrestris (Tetracystidaceae, Chlorococcales), were examined with an emphasis on the flagellar apparatus (FA). They have different vegetative characteristics, such as, being motile or nonmotile, variations in chloroplast morphology, possession of one or more nuclei, and reproductive features such as formation of tetrahedral tetrads, and naked or walled zoospores. Ultrastructural differences amongst reproductive cells of the six species include variations in cell surface structure, basal body to basal body angle, beamlike extensions of the distal fiber, extensive connections of the proximal sheath between basal bodies, two-membered rootlets, striated microtubule-associated components, two-membered rootlet-nucleus and/or mitochondria connections, X-membered rootlets, connections of rootlets and basal bodies, rhizoplasts and accessory basal bodies. All six species possess pyrenoids penetrated by thylakoid membranes, and the FA typical of the Chlorophyceae (sensu Mattox and Stewart, 1984). These six species should be divided into two groups. The first includes D. lateralis, C. hypnosporum, and T. aeria, in which accessory basal bodies are present, the basal body to basal body angle is relatively fixed, and a cell wall or surface coat is present. The second group includes Ps. terrestris, S. spongiosa, and Pr. botryoides, in which accessory basal bodies are absent, the basal body to basal body angle is variable and the zoospores are naked. THE UNICELLULAR green algae are common to freshwater and soil environments. In the past, vegetative morphology and reproductive features as recognized by light microscopy have been used in taxonomy (e.g., Starr, 1955; Bold, 1970). More recently, however, observations with the transmission electron microscope (TEM) on the processes of mitosis and cytokinesis, and flagellar apparatus features, have changed our traditional concepts of green algal taxonomy and phylogeny. These ultrastructural studies have strongly indicated that the use of traditional morphological features alone have led to unnatural taxonomies and that many of these features probably occurred in parallel among separate evolutionary lines (for

Ultrastructure of the embryonic dorsal organ of Orchestia cavimana (crustacea, amphipoda); with a note on localization of chloride and on the change in calcium-deposition before the embryonic moult.

Abstract: The transitory dorsal organ of Orchestia cavimana appears simultaneously with the development of the germ layer and is gradually reduced during the last 2–3 days of embryonic development. It represents the only direct connection of the embryo with the chorion or—after the embryonic moult—with the embryonic envelope. The shape is hemispherical and it consists of about 50 bottle-shaped cells, arranged radially around a centre. This centre is filled with different kinds of extracellular material which forms a central plug apically and a central cone below it. The bottle-shaped cells taper apically. The neck region of these cells is characterized by numerous microvilli which project into the intercellular space. This space is filled with an electron dense substance and is in contact with the central cone. In the basal neck region numerous mitochondria are associated with the microvilli. The high density of mitochondria is characteristic for the nuclear region. The cytoplasm of the basal region below the nucleus contains numerous calcium granules. Evidence for the concentration of chloride in the apical dorsal organ is shown. Before the embryonic moult and during the duplication of the egg-volume the number of calcium granules in the dorsal organ and the integument is reduced. Simultaneously calcium granules appear in the now visible periembryonic space. This suggests that part of the calcium is shifted into this space. The function of the dorsal organ is discussed. Besides the probable main function—transport activity of ions—its role before and during embryonic moult and its part in the utilisation of yolk are discussed.

Toxic effects of organophosphates on nerve cell growth and ultrastructure in culture

Abstract: Organophosphates (OP) comprise one of the major classes of pesticides in use today. It is well accepted that the primary site of action of the OPs is at cholinergic synapses. However, it has been suggested that OPs may have direct neural effects as well. In this study, cultured chick dorsal root ganglia (DRG) were used to study the effect of fenthion (FEN), an OP pesticide, on isolated nerve cell growth and ultrastructure. Light microscopic evaluation revealed a dose-response relationship between the concentration of FEN (10(-2) M to 10(-5) M) and severity of morphologic changes. Cultured explants were treated with a lower concentration of FEN (10(-6) M) and morphologic alterations were compared to those observed in explants treated with 10(-6) M paraoxon, a more acutely toxic OP, or 10(-6) M neostigmine, a non-OP inhibitor of acetyl-cholinesterase. Based on both light and electron microscopy, neostigmine had no observed effect on cell morphology except for an inhibition of the extension of neurites by DRG cells. In contrast, explants treated with OPs exhibited a significant alteration in cell morphology. Initial lesions were observed first in the neurites and pseudopodia and consisted of vacuolization, loss of tubular structures, retraction of pseudopodia, and cell membrane disruption at the growth cone. Lipid accumulations were observed within the cytoplasm of treated cells. The effects of paraoxon on DRG cell morphology were significantly more severe than the effects of FEN, and lipid vacuoles observed in paraoxon-treated cells were several times larger than those observed in FEN-treated cells (5-10 microns in diameter vs. 0.5-1.0 microns in diameter). Results show that OPs have a direct effect on DRG nerve cells in culture, consistent with an alteration in cell membrane integrity. Cultured DRG cells can be useful in the evaluation of toxicologic effects.

Changes in ultrastructure of Golgi apparatus during the cell cycle in a synchronous culture of Catharanthus roseus

Abstract: summary Changes in the ultrastructure of the Golgi apparatus during the cell cycle were investigated using a highly synchronized cell division system in a Catharanthus roseus (L.) G. Don suspension culture. During the G2 phase and cytokinesis, diameters of the dictyosomes and the number of cisternae significantly increased. Electron micrographs of cells in cytokinesis suggested that dictyosomes were dividing into two. Numerous secretory vesicles were associated with the dictyosomes in cells of the second G1 phase, the time when cell wall synthesis is most active. Structural changes in the Golgi apparatus are discussed in relation to the cell cycle and changes in cell wall synthesis.

Effects of vitamin A on growth and differentiation of human tracheobronchial epithelial cell cultures in serum-free medium.

Abstract: Differentiating epithelial cell cultures from human tracheobronchial epithelium have been propagated in serum-free medium. The major objective of this study was to examine the trophic effects of vitamin A on cell multiplication and morphology of the tracheal cell cultures. The cellular responses were analyzed in terms of growth kinetics, morphological and ultrastructural alterations and secretion of glycoconjugates. Cell cultures in control medium exhibited characteristics of epithelial cells including microvilli on cell surfaces, desmosomes between cells, and numerous secretory vesicles in the cytoplasm. Vitamin A at 10(−6) M and 10(−7) M inhibited cell replication and enhanced the secretion of [3H]glucosamine-labeled glycoconjugates. Further, vitamin A increased the production of plasma membrane vesicles and acquisition by the cells of a highly secretory ultrastructure. This in vitro model of human epithelial cells will be important in the investigation of various aspects of growth and differentiation.

Lungs of the gecko Rhacodactylus leachianus (Reptilia: Gekkonidae): a correlative gross anatomical and light and electron microscopic study.

Abstract: The lungs of the New Caldeonian gecko Rhacodactylus leachianus were examined by means of gross dissection and light and electron microscopy. This tropical species, which is the largest living gecko, possesses two simple, single-chambered lungs. Right and left lungs are of similar size and shape. The lung volume (27.2 ml.100 g-1) is similar to that of the tokay (Gekko gecko) but differs in that the gas exchange tissue is approximately homogeneously distributed, and the parenchymal units (ediculae) are very large, approximately 2 mm in diameter. The parenchymal depth varies according to the location in the lung, being deepest near the middle of the lung and shallowest caudally. Scanning and transmission electron microscopy reveal an unusual distribution of ciliated cells in patches on the edicular walls as well as on the trabeculae. Secretory cells are very numerous, particularly in the bronchial epithelium, where they greatly outnumber the ciliated cells. The secretory cells form a morphological continuum characterized by small secretory droplets apically and large vacuoles basally. This continuum includes cells resembling type II pneumocytes but which are devoid of lamellar bodies. Type I pneumocytes similar to those of other reptiles cover the respiratory capillaries, where they form a thin, air-blood barrier together with the capillary endothelial cells and the fused basement laminae. The innervation, musculature, and vascular distribution in R. leachianus are also characterized. Apparent simplification of the lungs in this taxon may be related to features of its sluggish habits, whereas peculiarities of cell and tissue composition may reflect demands of its mesic habitat.

The fine structure and possible functions of scolex gland cells inTrilocularia acanthiaevulgaris (Cestoda, tetraphyllidea)

Abstract: The ultrastructure of the scolex glands ofTrilocularia acanthiaevulgaris is described with the aid of transmission electron microscopy. The syncytial scolex gland cells exhibit an ultrastructure which is typical of secretory cells, in that they contain extensive and distended cisternae of granular endoplasmic reticulum (GER), numerous Golgi complexes and secretory vesicles. The vesicles are transported via microtubule-lined ducts to the apex of the scolex where they are released from the tegumental surface by an eccrine process. The secretion is often accumulated in reservoirs created by a lateral swelling of the ducts. Cytochemical studies show that the secretion has a glycoprotein nature. It is suggested that the secretion probably acts as an adhesive, aiding attachment of the worm to the host mucosa. This may be more important in juvenile worms which have less well-developed scoleces.

Wax lipid secretion and ultrastructural development in the egg-waxing (Gene's) organ in ixodid ticks.

Abstract: Gene's organ, the egg-waxing organ of ticks, performs an essential function in females by coating the eggs with a waterproofing layer during oviposition, which prevents desiccation of the embryo, ensuring its viability. The organ is a target for control agents and a potential site of virus replication involving trans-oval transmission of arboviruses. The organ is a complex dermal gland, developed to an elaborate degree. The external appendage, the horns, is an evertable balloon-like cuticular sac which manipulates the eggs and coats them in wax. Wax passes through pores in the cuticle from the internal, sub-cuticular lumen. Gene's organ develops in synchrony with oogenesis and oviposition. This paper describes the development of the gland cells and formation of the intra-cuticular lumen and its ultrastructure during engorgement and oviposition in ixodid ticks. The structural basis for wax secretion in Gene's organ is also described.

Changes in the Anterior Midgut Cells of Adult Female Rhodnius prolixus (Hemiptera: Reduviidae) after Feeding

Abstract: The anterior midgut (crop) cells of Rhodnius prolixus Stl undergo several modifications following a blood meal. The basal plasma membrane is highly folded, and within 2 h of feeding these folds separate so that a large surface area of membrane is exposed for rapid transport of water across the epithelium. On the apical cell surface, extracellular membrane layers are produced, but their extensive proliferation is not seen. In contrast to other midgut regions, no well-defined post-bloodmeal modifications to the lysosomes or rough endoplasmic reticulum are observed. Intracellular spherites are present only in crop cells of Rhodnius and are considered to be reservoirs of inorganic ions retained during diuresis. Large quantities of lipidlike inclusions are also found in the crop cells, many more than in other midgut regions. The crop ultrastructure is related to its functions in rapid diuresis of water from the midgut lumen, in mineral ion regulation, in digestion of some nonprotein components, and as a nutrient storage organ. Differences between the ultrastructure of the anterior and posterior midgut cells are attributed to their different functions during digestion.

Annual changes in the number, testosterone content and ultrastructure of glandular tissue cells of the testis in the marbled newt Triturus marmoratus.

Abstract: The testes of 8 specimens of Triturus marmoratus were collected during each month of 1987 and processed for electron microscopy and light microscopy demonstration of testosterone (T) following the ABC (avidin-biotin peroxidase complex) method According to their staining affinity for anti-T antibodies, the glandular tissue cells were classified as T-, T+, T++, and T and the annual changes in the numbers of these cell populations, as well as in the volume occupied by the glandular tissue, were calculated The volume occupied by the glandular tissue increases from September to December; it begins to decrease in April and disappears from June to August The glandular tissue is formed from the interstitial cells that surround the lobules containing differentiating germ cells During the spermatogenic process, the interstitial cells do not show staining affinity for anti-T antibodies In August-September, the interstitial cells around the lobules that have completed spermatogenesis become positively stained (T+) and form the glandular tissue when the spermatozoa leave the testis The numbers of intensely stained cells in the glandular tissue (T++ and T ) increase from September to November; begin to decrease in December; disappear in January-February; increase again in March and decrease again in April until they disappear in June-September The interstitial cells, before their transformation in glandular tissue, are ultrastructurally similar to fibroblasts After their transformation these cells increase in size and develop abundant smooth endoplasmic reticulum, mitochondria with tubular cristae and lipid droplets This morphological pattern is maintained in the glandular tissue from September to April in spite of the changes in staining affinity during this period