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PubMed1978

Lectin binding to mosquito Aedes aegyptii and human KB cells: structural comparisons of membrane oligosaccharides.

High capacity adsorbents for lectins, including Lotus tetragonolobus L-fucose-binding protein, were readily prepared by conjugation of monosaccharides with commercially available, epoxy-activated Sepharose. Purified, radioiodinated lectins were bound to cells of the mosquito Aedes aegyptii and of human KB tumour. Relative to human KB cells, mosquito cells bound less of lectins specific for the sugars (L-fucose and D-galactose) that are terminal residues in many mammalian glycoproteins, whereas the number of binding sites of lectins specific for core-region sugars (D-mannose and 2-acetamido-2-deoxy-D-glucose) were similar. Neuraminidase, which greatly enhanced binding of peanut agglutinin or soybean agglutinin to human KB cells, had negligible effects on binding of these lectins to mosquito cells. The comparative structures of surface oligosaccharides of mosquito and KB cells are discussed in relation to the lectin-binding studies.

Aedes↗
PubMed1992

[The endothelial cell: a cell structurally simple but functionally very complex].

Vascular endothelium is morphologically similar to a simple squamous epithelium that lines the internal surface of vessels. These cells, even if structurally simple, are functionally very complex. They regulate vascular tone by producing vasodilators such as prostacyclin and nitric oxide and vasoconstrictors such as endothelin. In addition, endothelial cells express activators and inhibitors of coagulation, fibrinolysis and platelet aggregation. Alterations of the functional equilibrium of endothelial cells might be related to the development of many cardiovascular diseases.

Amino Acid Sequence↗
PubMed1995

Mechanotransduction in vertebrate hair cells: structure and function of the stereociliary bundle.

The mechanosensitive hair cells of the vertebrate acousticolateralis system have an apical bundle of stereocilia, deflections of which control the opening of mechano-electrical transduction channels and thus generate receptor potentials in the cell below. This review describes current theories of hair cell function in the light of recent immunocytochemical and ultrastructural findings; in particular, the location and operation of the transduction channels are considered. The most widely accepted hypothesis of mechanotransduction by hair cells is that fine extracellular links that run between the tips of shorter stereocilia and the sides of taller ones operate the transduction channels. However, the fact that the transduction channels are amiloride sensitive has led to labeling experiments using antibodies to the amiloride-sensitive epithelial Na+ channel from kidney which suggest that the mechanotransduction channels may not be directly associated with the tip links. Instead, they appear to be located near a junctionlike structure at the point of contact between the shorter and taller stereocilia. The implications of these findings for the tip link hypothesis are discussed.

Animals↗
PubMed1982

Hyperoxic-induced alterations in lung cell structure and function. Effects on cellular cyclic AMP content and comparison to alterations produced by exogenous cyclic AMP.

Hyperoxic exposure in vitro of two lung-derived cell types (the epithelial-derived L2 cells and WI-38 fibroblasts) inhibits cellular replication, produces striking morphologic changes and may result in cell death; these effects have been observed consistently in other cell types. Hyperoxic exposure of L2 cells is associated with an increase in cellular cyclic AMP content (cellular cyclic AMP content 454 +/- 115 fmol/micrograms DNA in cells exposed to pO2 677 Torr for 96 h compared to 136 +/- 17 fmol/microgram DNA in air-grown cells). Hyperoxic exposure of WI-38 fibroblasts is not associated with increased cyclic AMP content. Although cultivation of L2 cells in the presence of exogenous dibutyryl cyclic AMP does inhibit replication and produce morphologic alterations, similar effects are produced by sodium butyrate alone. Hyperoxic exposure alters cyclic AMP metabolism in some cell types, but the structural and functional alterations observed in L2 cells and WI-38 fibroblasts following hyperoxic exposure are not produced by changes in cellular cyclic AMP content.

Anaerobiosis↗
PubMed2001

Development of retinal ganglion cell structure and function.

In this review, we summarize the main stages of structural and functional development of retinal ganglion cells (RGCs). We first consider the various mechanisms that are involved in restructuring of dendritic trees. To date, many mechanisms have been implicated including target-dependent factors, interactions from neighboring RGCs, and afferent signaling. We also review recent evidence showing how rapidly such dendritic remodeling might occur, along with the intracellular signaling pathways underlying these rearrangements. Concurrent with such structural changes, the functional responses of RGCs also alter during maturation, from sub-threshold firing to reliable spiking patterns. Here we consider the development of intrinsic membrane properties and how they might contribute to the spontaneous firing patterns observed before the onset of vision. We then review the mechanisms by which this spontaneous activity becomes correlated across neighboring RGCs to form waves of activity. Finally, the relative importance of spontaneous versus light-evoked activity is discussed in relation to the emergence of mature receptive field properties.

Animals↗
PubMed2004

Ex-vivo study of flow dynamics and endothelial cell structure during extended hypothermic machine perfusion preservation of livers.

Liver transplantation is often the only effective treatment for end stage liver diseases resulting from cirrhosis, hepatitis, progressive jaundice, and biliary atresia. Hypothermic machine perfusion (HMP) preservation may enhance donor pool by extending preservation time and reclaiming marginal donor livers including those from non-heart beating donors (NHBD), as demonstrated in the kidney. However, current HMP protocols have not been successful in improving extended preservation of livers and the major cause of preservation injury remains unknown. An intravital microscopy study was conducted to understand the flow dynamics of sinusoidal perfusion during 24h HMP with cold modified University of Wisconsin (UW) solution. Fluorescein isothiocynate (FITC) labeled albumin was utilized to visualize microvascular space and FITC labeled red blood cells (RBCs) were used to visualize flow dynamics during HMP. A heterogeneous flow pattern with regions of red cell stasis was observed after 24-h HMP. To examine the cause of red cell stasis, intravital and confocal microscopy studies of endothelial cells (ECs) structure labeled with DiI acetylated low-density lipoprotein (DiI acLDL) were conducted. These studies suggest that morphological changes in EC structures occurred during 24h HMP, which may cause obstruction to the sinusoidal flow. Histological findings confirm these results. As a result, heterogeneous flow pattern, red cell stasis, and edema occur, which may lead to the failure of these tissues following extended HMP.

Adenosine↗
PubMed1988

Glycopeptides from murine teratocarcinoma cells: structure of the determinants recognised by Griffonia simplicifolia agglutinin I and by sera from patients with ovarian germ cell tumors.

High-molecular-weight glycopeptides synthesised by teratocarcinoma OTT6050 bear the binding site for Griffonia simplicifolia agglutinin I and are recognised by antibodies in the sera of patients with ovarian germ cell tumors. Digestion of the glycopeptides with endo-beta-D-galactosidase C abolished the lectin binding activity and the antigenic activity. Since the product of the enzymic digestion is alpha-D-Gal-(1----3)-D-Gal, it is concluded that the disaccharide structure is involved in the lectin binding site and the antigenic site.

Animals↗
PubMed2003

The pyramidal neuron in occipital, temporal and prefrontal cortex of the owl monkey (Aotus trivirgatus): regional specialization in cell structure.

Recent studies have revealed marked regional variation in pyramidal cell morphology in primate cortex. In particular, pyramidal cells in human and macaque prefrontal cortex (PFC) are considerably more spinous than those in other cortical regions. PFC pyramidal cells in the New World marmoset monkey, however, are less spinous than those in man and macaques. Taken together, these data suggest that the pyramidal cell has become more branched and more spinous during the evolution of PFC in only some primate lineages. This specialization may be of fundamental importance in determining the cognitive styles of the different species. However, these data are preliminary, with only one New World and two Old World species having been studied. Moreover, the marmoset data were obtained from different cases. In the present study we investigated PFC pyramidal cells in another New World monkey, the owl monkey, to extend the basis for comparison. As in the New World marmoset monkey, prefrontal pyramidal cells in owl monkeys have relatively few spines. These species differences appear to reflect variation in the extent to which PFC circuitry has become specialized during evolution. Highly complex pyramidal cells in PFC appear not to have been a feature of a common prosimian ancestor, but have evolved with the dramatic expansion of PFC in some anthropoid lineages.

Animals↗
PubMed1987

Isolation and culture of ram rete testis epithelial cells: structural and biochemical characteristics.

Cultures of rete testis epithelial cell-enriched preparations from testes of adult rams have been investigated, and some of their properties have been determined. In monolayers, the cells form mosaic-like borders, and retain many ultrastructural features characteristic of rete epithelial cells in situ, including an indented nucleus with prominent heterochromatin clumps, short rod-shaped or round mitochondria that are easily distinguished from the elongated mitochondria of Sertoli cells, the presence of desmosomes, and few if any lipid droplets or vacuoles. Unlike Sertoli cell-enriched aggregates in culture, rete testis epithelial cell preparations do not form cytoplasmic extensions, and no associated germ cells are present. Rete cells in culture express cytokeratin and vimentin in the cytoskeleton, whereas Sertoli cells prepared from testes of adult rams contain vimentin but not cytokeratin. Both rete cells and Sertoli cells stain positively for laminin but not for fibronectin, Collagen Type I, or Collagen Type III. The rete cells synthesize and secrete several proteins into the culture medium, evident in gel electrophoresis patterns of radiolabeled proteins. This pattern is similar, but not identical, to that secreted by Sertoli cell-enriched preparations. Rete cells in culture in the presence of serum continue to undergo mitotic division, but Sertoli cells do not. A variety of criteria were employed to estimate the relative numbers of Sertoli cells present in the rete testis epithelial cell-enriched preparations from testes of adult rams, including morphological and ultrastructural differences between the two cell types, and the presence of desmosomal proteins and cytokeratin in rete cells but not in Sertoli cells. The relative number of fibroblast-like cells was determined by measuring the expression of fibronectin and Collagen Type I, and an immunocytochemical probe for the detection of Factor VIII was used to estimate the degree of contamination by vascular endothelial cells. Using these markers, we determined that the rete testis epithelial cell-enriched preparations were about 93% pure. Primary cultures under defined conditions contained relatively few Sertoli cells (0.4%), but were contaminated to a larger extent by fibroblast-like cells (approximately 4%) and by endothelial cells (about 3%). The possible functions of rete testis epithelial cells are discussed herein.

Animals↗
PubMed1983

Correlation of parietal cell structure and function.

The apical surface of the gastric parietal cell is greatly expanded (5-10-fold) during maximal HCl secretion, as compared to the resting cell. The membrane recycling hypothesis has been proposed to account for the extensive, functionally related, rearrangement of cell membranes. Cytoplasmic membranes within the resting cell, the tubulovesicles, contain the H+/K+-ATPase. Fusion of tubulovesicles with the apical plasma membrane occurs when the cells are stimulated, thus providing the increased surface area and proper disposition of the H+ pump enzyme. Microfilaments, composed of actin and other regulatory proteins, serve to direct the reordering of the apical surface during stages of the secretory cycle. Cell fractionation of resting oxyntic mucosa reveals that virtually all of the H+/K+-ATPase activity is associated with light microsomal membrane vesicles, presumably derived from tubulovesicles. Although the enzyme from resting tissue is fully competent (e.g. ATP-driving pump, H+-K+ exchange), the microsomal vesicles lack an endogenous pathway to provide rapid access for K+ to its intravesicular activity site. In stimulated stomach, there is a redistribution of H+/K+-ATPase to a larger, denser membrane fraction, the so-called stimulation-associated vesicles. Morphological features and chemical content (e.g. microfilament proteins) suggest that the stimulation-associated vesicles are derived from the expanded apical surface of the stimulated oxyntic cell. A KCl cotransport system has been identified in the stimulation-associated membranes, which operates in parallel with the ATP-driven H+-K+ exchange pump. These two transport systems operate in concert within the apical membrane to provide the machinery for net HCl transport by the parietal cell.

Actins↗
PubMed1997

The chloride cell: structure and function in the gills of freshwater fishes.

This review focuses on the structure and function of the branchial chloride cell in freshwater fishes. The mitochondria-rich chloride cell is believed to be the principal site of trans-epithelial Ca2+ and Cl- influxes. Though currently debated, there is accruing evidence that the pavement cell is the site of Na+ uptake via channels linked electrically to an apical membrane vacuolar H(+)-ATPase (proton pump). Chloride cells perform an integral role in acid-base regulation. During conditions of alkalosis, the surface area of exposed chloride cells is increased, which serves to enhance base equivalent excretion as the rate of Cl-/HCO3- exchange is increased. Conversely, during acidosis, the chloride cell surface area is diminished by an expansion of the adjacent pavement cells. This response reduces the number of functional Cl-/HCO3- exchangers. Under certain conditions that challenge ion regulation, chloride cells proliferate on the lamellae. This response, while optimizing the Ca2+ and Cl- transport capacity of the gill, causes a thickening of the blood-to-water diffusion barrier and thus impedes respiratory gas transfer.

Acid-Base Equilibrium↗
PubMed1997

Gastric oxyntic cell structure as related to secretory activity.

The oxyntic, or parietal cell has two characteristic membrane systems. The mammalian intracellular canaliculi are specialized networks of narrow channels lined with numerous microvilli. The other common to all oxyntic cells is the tubulovesicles, a system of tubules and vesicles. The tubulovesicular compartment is drastically depleted during maximal gastric acid secretion and this is coincident with an increase in the cell surface membrane area. A plausible explanation of this process is the fusion and transfer of tubulovesicular membranes to the plasma membrane. However, for many years there was no convincing evidence of the connections between these two membrane systems. How the tubulovesicular membranes transform into plasma membrane without demonstrable connections has been an enigma to electron microscopists. Recent ultra-high resolution scanning electron microscopic observation on the rat oxyntic cell treated with aldehyde-osmium-aldehyde method revealed that in the resting stage, the tubulovesicles were isolated spherical vesicles. But after tetragastrin stimulation, they were interconnected by slender connecting tubules forming a tubulovesicular network. Then this network was fused to the intracellular canaliculus at relatively few points. These connections between the tubulovesicles and luminal surface membrane was also demonstrated in the frog oxynticopeptic cells. In this review, these membrane transformations as well as changes of the H+/K(+)-ATPase, the lectin binding glycocalyx and the cytoskeleton during secretion will be illustrated and discussed.

Actins↗
PubMed1981

Changes in ERG b-wave and Müller cell structure induced by alpha-aminoadipic acid.

The role of the Müller cell in the generation of the ERG b-wave was studied in the skate eye by examining the effects of a gliotoxic agent (alpha-aminoadipic acid; alpha-AAA) on retinal structure and function. Superfusing the eyecup for 1 h in 50 mM alpha-AAA resulted in the loss of the b-wave and extensive damage to glial cells, i.e. disruption of the cells' plasma membranes, and a marked loss of cytoplasmic substance. Of the other retinal elements, only the horizontal cells showed some signs of injury in alpha-AAA. On returning the retina to a normal Ringer solution, the widespread loss of cytoplasmic electron density persisted, but the Müller cell membranes appeared to have undergone repair, and the b-wave recovered fully its normal amplitude and waveform.

Adipates↗
PubMed1972

New centrifugation technique for isolating enzymes from large cell structures: isolation and characterization of two Bacillus subtilis autolysins.

Bacillus subtilis cell walls can be centrifuged through a linear gradient of 0 to 2 m LiCl and 10 to 25% sucrose so that different autolysins are removed by different salt concentrations and banded in separate positions as the walls pass through the gradient. Using this technique we have found that B. subtilis cell walls are isolated with two autolytic enzymes attached. One autolysin, a glycosidase, can be eluted from walls with 0.5 m LiCl, has a pH optimum between 5 and 8, is relatively heat-sensitive, and has a molecular weight of 60,000. The other autolysin, an alanine amidase, can be eluted from walls with 1.5 m LiCl, has a pH optimum around 8, is relatively heat-stable, has a molecular weight of 35,000, and is present in quantities ten times greater than the glycosidase.

Alanine↗
PubMed2004

New SPUDT cell structures.

The present paper describes single-phase unidirectional transducers (SPUDT) cells with all fingers wider than lambda/8 while maintaining the unidirectional effect. The first solution is related to a SPUDT consisting of lambda/4 and lambda/2 wide fingers arranged in two tracks. Each track has no significant unidirectional effect. Both tracks form a waveguide, and the waveguide coupling generates the interaction of the tracks. As a result of that interaction, a unidirectional effect arises as verified by experiment. This transducer type is called double-track (DT) SPUDT. A second solution is suggested that includes, in contrast to distributed acoustic reflection transducer (DART), electrode width control (EWC), and Hunsinger cells, SPUDT cell fingers with one and the same width only. Cell types with lambda/6, lambda/5, and lambda/3 wide fingers called uniform width electrode (UWE) cells are considered. One of these cell types, including exclusively lambda/5 wide fingers, is experimentally investigated and a unidirectional effect is found. Moreover, a filter example using the lambda/5 cell type has been designed for reducing SPUDT reflections. The echo suppression expected could be verified experimentally. No waveguide coupling is required for this cell type.

Journal Article↗
PubMed1988

Extrinsic determinants of retinal ganglion cell structure in the cat.

The degree to which a retinal ganglion cell's environment can affect its morphological development was studied by manipulating the distribution of ganglion cells in the developing cat retina. In the newborn kitten there is an exuberant ganglion cell projection from temporal retina to the contralateral lateral geniculate nucleus (LGNd) (Leventhal et al., 1988) and from nasal retina to the ipsilateral LGNd. Neonatal, unilateral optic tract section results in the survival of many of these ganglion cells (Leventhal et al., 1988). The morphology of ganglion cells which survive in regions of massively reduced ganglion cell density was studied. As reported previously (Linden and Perry, 1982; Perry and Linden, 1982; Ault et al., 1985; Eysel et al., 1985), we found that the dendritic fields of all types of ganglion cells on the border of an area depleted of ganglion cells extended into the depleted area. The cell bodies and dendritic fields of alpha and beta cells within depopulated areas, as well as on the borders of the depopulated areas, were larger than normal. The dendritic fields of these cells also exhibited abnormal branching patterns. For alpha and beta cell types the relative increase in size tended to be greatest where the relative change in density was the greatest. In fact, isolated beta cells within the cell-poor area centralis region resembled normal central alpha cells in the cell-rich region of the area centralis in the same retina. Interestingly, in the same regions of reduced density where alpha and beta cells were dramatically larger than normal, the cell body and dendritic field sizes of other cell types (epsilon, g1 and g2 were unchanged. These results indicate that neuronal interactions during development contribute to the morphological differentiation of retinal ganglion cells and that different mechanisms mediate the morphological development of different classes of cells in cat retina.

Animals↗
PubMed1993

Immunophenotypic properties and estrogen dependency of budding cell structures in the developing mouse mammary gland.

The initial phase of growth of the parenchymal component of the mouse mammary gland is ductal clongation, which is mainly accomplished by proliferating cells in a specialized structure termed end bud. End buds are composed of multiple layers of epithelial cells (so called body cells) which are capped by a single layer of morphologically unique cells termed cap cells. We sought to examine the interrelationship between cap cells and other epithelial cell subclasses using a variety of antibodies to different keratin proteins and also antibodies to vimentin, actin and collagen IV. An extensive immunohistochemical characterization of the epithelial components of the developing and differentiating mammary gland demonstrated that cap cells were devoid of any immunohistochemically-detectable keratins but were positive for collagen IV. In contrast, the majority of cells in the end bud along with the luminal epithelial and myoepithelial cells were keratin positive. The body cells of the end bud were the only cells which were positive for antibody to keratin 6, a keratin which previously has been reported to be expressed in proliferating mammary epithelial cells. In addition, estrogen receptor was localized only to epithelial cells of ducts, alvcoli and body cells of end buds, but not to cap cells or myoepithelial cells. We interpret these results to suggest that cap cells are not totpotent stem cells but rather cells specialized in paving the way for ductal elongation as well as serving as precursors to myoepithelial cells.

Actins↗