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  • 1
    Electronic Resource
    Electronic Resource
    Choanocyte-like cells in the digestive system of the starfish Marthasterias glacialis (Echinodermata) (1991)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 208 (1991), S. 215-225 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Two types of choanocyte-like cells have been found in the digestive tract of the starfish. Type I choanocytes are in the lining epithelium of all organs of the digestive system. These are narrow, columnar cells strongly anchored basally and expanded apically into a protuberance projecting into the lumen. A prominent flagellum surrounded by microvilli projects from the center of this protuberance. Apical cytoplasm contains numerous mitochondria, secondary lysosomes, and multivesicular bodies. A distinctive characteristic of these cells is a filament bundle that traverses the length of the cell from its region of attachment on the rootlet of the flagellar basal body to its terminus on the basal plasma membrane. Between the attenuated basal ends of type I cells are the nerve fibers of an intraepithelial nerve plexus. Thickness of the plexus is correlated with the quantity of type I cells in the epithelium.Type II choanocytes are in the cuboidal coelomic epithelium that forms the outer layer of digestive tract organs. These cells are smaller than those of type I, and they have an apical collar surmounted by a ring of 13 microvilli. Within the collar is a cup-shaped depression with a central flagellum. Coated vesicles, secondary lysosomes, and phagocytic infoldings are observed in and near the collar cytoplasm. Filament bundles similar to those in type I choanocytes are also observed in coelomic epithelial cells that are sufficiently tall. Injection of peroxidase into the stomach and ferritin into the coelom results in phagocytic uptake of these macromolecules by type I and type II choanocytes, respectively.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052080207
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  • 2
    Electronic Resource
    Electronic Resource
    Steric inhibition of cytoplasmic dynein and kinesin motility by MAP2 (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 1-16 
    Details
    ISSN: 0886-1544
    Keywords: cytoplasmic dynein ; kinesin ; microtubules ; motility ; MAPs ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using several in vitro motility assays, we found that motility driven by the microtubule (MT) motors, kinesin and cytoplasmic dynein, could be inhibited by MAP2 but not by tau protein or the MT-binding proteolytic fragment of MAP2.In MT gliding assays, even the presence of one MAP2 molecule per sixty-nine tubulin dimers caused an inhibition of about 75% of MT motility at low concentrations of both motors. The percent inhibition of motility decreased with increasing concentration of either motor, suggesting that the inhibition was the result of competition for access to the MT surface. The decrease in the number of moving MTs with MAP2 was correlated with an increase in the frequency of release of moving MTs from the motor-coated glass. In assays of in vitro vesicular organelle motility and formation of ER networks, the presence of MAP2 inhibited small vesicle movements and to a lesser extent ER network formation.To determine if competition for specific sites on the MT or coating of the MT surface inhibited motility, we used tau protein and the chymotryptic MT-binding fragments of MAP2 to coat MTs. No inhibition was observed and there was even an increase in the number of attached and moving MTs in the gliding assay with tau-coated MTs. Because MAP2, tau and the chymotryptic MT-binding fragments of MAP2 bind to the same domain on tubulin, masking of the MT surface sites does not appear responsible for the inhibition of motility by MAP2. Rather, we suggest that the sidearm of MAP2 interfered with the interaction of motors with MTs and caused a dramatic increase in the rate of MT release. In vivo, MAP2 could play a major role in the generation of cellular polarity even at substoichiometric levels by inhibiting transport on microtubules in specific domains of the cytoplasm. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970240102
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  • 3
    Electronic Resource
    Electronic Resource
    In vitro depolymerization dynamics of brain endogenous microtubules (1990)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 43 (1990), S. 281-291 
    Details
    ISSN: 0730-2312
    Keywords: tubulin ; microtubule depolymerization ; glycerol stabilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A subcellular fraction containing fragments of endogenous microtubules stabilized in 50% glycerol was separated by diferential centrifugation of rat brain homogenates. The pellets were suspended in glycerol-deficient media, and microtubule depolymerization was monitored by measuring the decrease of sedimentable tubulin. Concomitantly, the number and size of microlubules in the suspensions were followed via electron microscopy. Depolymerization was accompanied by a proportional decrease in the number of microtubules, whereas the average size did not change significantly. After approximately 20 min, a subpopulation of microtubules became stable and did not suffer further depolymerization. These results indicate that upon dilution some microtubules completely depolymerize, whereas others remain stable in the glycerol-deficient medium. The degree of depolymerization depended on both the volume of the resuspension media and on the final glycerol concentration. The results suggest that the depolymerization of the remaining microtubules is prevented by stabilizing factors released from depolymerizing microtubules. Tubulin dimers are not one of these factors, since depolymerization was not altered by the addition ofcolchicine or by changing the concentration of free tubulin in the medium.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240430308
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  • 4
    Electronic Resource
    Electronic Resource
    Preservation of antigenic reactivity after cryofixation, cryosubstitution, and cryoembedding in Lowicryl HM23: Application to alcohol dehydrogenase in Drosophila fat body (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 24 (1993), S. 453-454 
    Details
    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070240511
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  • 5
    Electronic Resource
    Electronic Resource
    Distribution of filipin-sterol complexes in the plasma membrane of stallion spermatozoa during the epididymal maturation process (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 28 (1991), S. 158-168 
    Details
    ISSN: 1040-452X
    Keywords: Sperm membrane ; Sperm cholesterol ; Spermatic maturation ; Freeze-fracture and stallion spermatozoa ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The presence and distribution of cholesterol in mature and immature epididymal spermatozoa was analyzed using filipin as a cytochemical tool in freeze-fracture replicas and thin section preparations. The polyenic-antibiotic filipin formed complexes with 3,β-OH sterols, producing characteristic protrusions, or pits, that were heterogeneously distributed in the plasma membrane of stallion spermatozoa, revealing a specific organization in a functionally specialized area of the gamete. The acrosomal region of the sperm head presented a significantly higher density of filipin sterol complexes than the postacrosomal region, which was usually free of these complexes. The plasma membrane of the flagellum also showed filipin sterol complexes randomly distributed in freeze-fracture replicas. The strong filipin labeling observed in the membrane of spermatozoa obtained from the caput region of the epididymis decreased significantly during epididymal passage. The significance of these changes is not completely understood, but they might contribute to establishing the molecular organization necessary for sperm transit and storage in the epididymis as well as to development of motile spermatozoa that are able to fertilize the oocyte and induce normal embryonic development.
    Additional Material: 23 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080280209
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  • 6
    Electronic Resource
    Electronic Resource
    IGF-I and the IGF-I receptor in development of nonmammalian vertebrates (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 35 (1993), S. 427-433 
    Details
    ISSN: 1040-452X
    Keywords: Chick embryos ; Organogenesis ; δ-crystallin gene ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Extracellular signals are likely to be involved in the control of growth and differentiation during embyrogenesis of vertebrates. These signals include, among others, several members of the insulin family: insulin-like growth factor (IGF)-I, IGF-II, and insulin. In the chick embryo, maternal IGF-I is stored in the yolk. In addition, the embryonic IGF-I gene is expressed very early and in late development in multiple tissues. We have used reverse-transcribed (RT) RNA and amplification by the polymerase chain reaction (PCR) to detect IGF-I gene expression. IGF-I was preferentially expressed in cephalic regions during late neurulation and early organogenesis. During late organogenesis, in some tissues, such as the eye lens, IGF-I gene expression is compartmentalized to a subset of cells, the epithelial cells. In these lens cells, IGF-I stimulates transcription of the δ-crystallin gene. Competence to respond to IGF-I exists in multiple cell types, since, based on binding studies, receptors for IGF-I are widespread in the gastrulating and neurulating embryo. Target tissues in which an autocrine/paracrine role for IGF-I appears more likely are the developing eye lens and retina, which are avascular organs rich in IGF-I receptors. In late development, IGF-I may have an additional endocrine role, with an impact on the general growth of the chick embryo. In embryos developed ex ovo, that show growth retardation after day 10 of embyrogenesis, IGF-I serum levels are very low. By day 8, expression of IGF-I mRNA in these embryos is markedly reduced in multiple tissues. Future studies in which IGF-I and its receptor are overexpressed or abolished should clarify the function of this growth factor in development. © 1993 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080350418
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  • 7
    Electronic Resource
    Electronic Resource
    TGF-β receptors (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 32 (1992), S. 99-104 
    Details
    ISSN: 1040-452X
    Keywords: Betaglycan ; Binding proteins ; Cell surface proteins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The nature and role of cell surface proteins that bind members of the TGF-β family has been investigated. TGF-β, activins, and BMPs each bind to receptors of 55 kDa (type I) and 70 kDa (type II). In the TGF-β system, these receptors are implicated in the mediation of multiple responses. A member of the type II receptor family has been cloned that encodes four alternatively spliced versions of a transmembrane serine/threonine kinase receptor related to the recently cloned mouse activin receptor and C-elegans daf-1 gene. Inhibitors of serine/threonine kinase activity block transcriptional and growth inhibitory responses to TGF-β. In addition to the signaling receptors, many cell types express the TGF-β binding proteoglycan betaglycan. Betaglycan has been purified, molecularly cloned, and shown to bind TGF-β via its core protein and basic fibroblast growth factor via its heparan sulfate chains. In addition to receptors I and II and betaglycan, some cells express a newly identified set of membrane proteins that specifically bind either TGF-β1 or TGF-β2. Three of the four isoform-restricted binding proteins are bound to the membrane via phospholipid anchors. Like betaglycan, these proteins might function to regulate the interaction between TGF-β and their target cells. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080320204
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  • 8
    Electronic Resource
    Electronic Resource
    Surface expression and distribution of Fc receptor III (CD 16 molecule) on human natural killer cells and polymorphonuclear neutrophils (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 28 (1994), S. 277-285 
    Details
    ISSN: 1059-910X
    Keywords: NK cells ; Neutrophils ; Fcγ receptor ; Immunogold ; SEM ; Backscattered electron imaging ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Human natural killer cells and polymorphonuclear neutrophils constitutively express the low-affinity IgG Fc receptor (FcγRIII, CD16 molecule). To investigate cell surface morphology, antigenic receptor density, and topographical distribution of FcγRIII on the plasma membrane of natural killer cells and polymorphonuclear neutrophils, conventional scanning electron microscopy (SEM), flow cytometry, and immunoscanning electron microscopy were used. FcγRIII was detected with an indirect immunogold labeling procedure, and receptors were visualized in the backscattered and secondary electron imaging mode of SEM. Natural killer cells showed a cell surface morphology compatible with lymphocytic differentiation characterized by microvilli and microridges. Polymorphonuclear neutrophils showed surface features characterized by ridges with folds and scattered short microvilli. Natural killer cells displayed a lower cell labeling density, whereas polymorphonuclear neutrophils showed a high level of expression of FcγRIII on the plasma membrane by quantitative analysis with SEM in the backscattered electron imaging mode. Flow cytometry analysis confirmed these findings. Analysis of the topographical distribution of FcγRIII antigenic receptor sites by SEM in the backscattered and secondary electron imaging modes showed that FcγRIII on natural killer cells are randomly distributed, whereas FcγRIII are located on ridges and folds of the plasma membrane of polymorphonuclear neutrophils. These observations suggest that natural killer cells and polymorphonuclear neutrophils differ in their levels of expression and topographic distribution of FcγRIII on the plasma membrane. This different spatial distribution of FcγRIII would provide morphological evidence of certain cellular functions mediated by natural killer cells and polymorphonuclear neutrophils. © 1994 Wiley-Liss, Inc.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070280404
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  • 9
    Electronic Resource
    Electronic Resource
    Mechanical stimulation of skeletal muscle generates lipid-related second messengers by phospholipase activation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 155 (1993), S. 63-71 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Repetitive mechanical stimulation of cultured avian skeletal muscle increases the synthesis of prostaglandins (PG) E2 and F2α which regulate protein turnover rates and muscle cell growth. These stretch-induced PG increases are reduced in low extracellular calcium medium and by specific phospholipase inhibitors. Mechanical stimulation increases the breakdown rate of 3H-arachidonic acid labelled phospholipids, releasing free 3H-arachidonic acid, the rate-limiting precursor of PG synthesis. Mechanical stimulation also increases 3H-arachidonic acid labelled diacylglycerol formation and intracellular levels of inositol phosphates from myo-[2-3H]inositol labelled phospholipids. Phospholipase A2 (PLA2), phosphatidylinositol-specific phospholipase C (PLC), and phospholipase D (PLD) are all activated by stretch. The stretch-induced increases in PG production, 3H-arachidonic acid labelled phospholipid breakdown, and 3H-arachidonic acid labelled diacylglycerol formation occur independently of cellular electrical activity (tetrodotoxin insensitve) whereas the formation of inositol phosphates from myo-[2-3H]inositol labelled phospholipids is dependent on cellular electrical activity. These results indicate that mechanical stimulation increases the lipid-related second messengers arachidonic acid, diacylglycerol, and PG through activation of specific phospholipases such as PLA2 and PLD, but not by activation of phosphatidylinositol-specific PLC. © 1993 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041550109
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  • 10
    Electronic Resource
    Electronic Resource
    Human Interleukin-3 inhibits the binding of granulocyte-macrophage colony-stimulating factor and interleukin-5 to basophils and strongly enhances their functional activity (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 145 (1990), S. 69-77 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The human T cell-derived cytokines interleukin (IL)-3, granulocyte-macrophage colony-stimulating factor (CM-CSF), and IL-5 were examined for their ability to bind specifically to human basophils and to regulate their function. Scatchard analysis of equilibrium binding studies showed that IL-3 and GM-CSF, bound to basophils with apparent dissociation constants (KD) = 8 × 10-11M and 3.9 × 10-11M, respectively. Specificity studies under conditions that prevent receptor internalization showed that the binding of IL-3, GM-CSF, and IL-5 was not inhibited by tumor necrosis factor (TNF)-α, IL-1β, interferon (IFN)-γ, or G-CSF. However, receptors for IL-3, GM-CSF, and IL-5 interacted with each other on the basophil membrane, showing a unique spectrum of cross-reactivity, with IL-3 competing for GM-CSF and IL-5 binding, whereas GM-CSF and IL-5 showed little or no competition for IL-3 binding. In order to relate the binding properties of these cytokines to function, they were tested for their ability to influence basophil histamine release in an IgE/anti-IgE-dependent system. We found a hierarchy in the stimulation of basophil with the order of potency being IL-3 〉GM-CSF 〉IL-5. In addition, IL-3 stimulated larger amounts of histamine release than GM-CSF or IL-5. The observation that IL-3 interacts with receptors for GM-CSF and IL-5 may have a bearing on its stronger functional effects and suggests a major role for IL-3 in the pathogenesis of hypersensitivity syndromes.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041450111
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