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  • 1990-1994  (78)
  • 1970-1974  (17)
  • 1960-1964  (8)
  • Chemistry  (99)
  • Ascidians
  • Microvilli
  • Morphogenesis
  • 1
    Electronic Resource
    Electronic Resource
    Cytoplasmic filaments and morphogenesis: Effects of cytochalasin B on contractile epidermal cells (1972)
    Springer
    Cell & tissue research 132 (1972), S. 167-192 
    Details
    ISSN: 1432-0878
    Keywords: Microfilaments ; Contractility ; Morphogenesis ; Ascidians ; Cytochalasin B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary During tail resorption in Distaplia occidentalis the caudal epidermis contracts to 8.5% of its initial length in about 6 minutes and forces the axial complex (muscle, notochord and nerve cord) into a coiled configuration in the trunk. The contraction of the caudal epidermal cells is accompanied by rapid alignment of arrays of circa 50 Å (diameter) filaments parallel to the axis of contraction in the apical cytoplasm of each epidermal cell. Normal metamorphosis (including tail resorption) can be instantly induced by treating tadpole larvae with 0.5% dimethylsulfoxide. Cytochalasin B, (CCB) 〉 0.25 μg/ml rapidly inhibits contraction of the caudal epidermis. The tail stops shortening, then partly re-extends. When CCB is removed by washing immediately after relaxation, tail resorption resumes. Cytochalasin B reversibly disrupts the organization of central and subterminal arrays of apical filaments in the contractile caudal epidermal cells. Membrane associated filaments near the junctional complexes are not disrupted by 0.25–1.0 μg/ml of CCB. This suggests that CCB does not degrade the filaments into subunits. It is more likely that CCB blocks contraction by disrupting the binding forces between overlapping filaments and facilitates the disorganization of unattached filaments. A second type of filament with a fusiform configuration has been detected in the epidermal cells after CCB treatment. The possibility that these are myosinoid proteins is considered. The data presented in this paper strengthen the hypothesis that the filaments in the epidermal cells are part of a contractile apparatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307009
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  • 2
    Electronic Resource
    Electronic Resource
    Patterns of morphogenesis mediated by dynamic microvilli: Chaetogenesis in Nereis vexillosa (1974)
    Springer
    Cell & tissue research 151 (1974), S. 141-157 
    Details
    ISSN: 1432-0878
    Keywords: Setae ; Polychaeta ; Microvilli ; Morphogenesis ; Chaetogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pattern of morphogenesis of the chitinous compound (jointed) setae of the larvae of polychaete Nereis vexillosa Grube was deduced from electron-microscopic analyses of many stages of secretion. Each seta is secreted over a period of three days within an epidermal follicle consisting of several lateral cells and a basal cell (chaetoblast). The configuration of the apical surface of the chaetoblast changes continuously during secretion. Secreted setal material is polymerized into longitudinally oriented setal filaments, probably by enzymes located on the surfaces of microvilli of the chaetoblast. As a result of this process the setae lengthen by basal appositional growth. We infer that the precise size and shape of each complex seta (a characteristic of the species and the age of the worm) is controlled by sequential modulations of the number, size, shape, arrangement and orientation of the microvilli of the chaetoblast. Each seta embodies a cryptic record of the activities of the chaetoblast on which it formed. The genetic and epigenetic mechanisms involved in chaetogenesis are problematic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222219
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  • 3
    Electronic Resource
    Electronic Resource
    Cephalopod integument: The ultrastructure of Kölliker's organs and their relationship to setae (1974)
    Springer
    Cell & tissue research 151 (1974), S. 293-308 
    Details
    ISSN: 1432-0878
    Keywords: Integument ; Octopus ; Setae ; Secretion ; Microvilli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Kölliker's tufts are transient epidermal bristles found on the external surfaces of late embryonic and juvenile octopods. The structure and growth of Kölliker's tuft is remarkably similar to that of polychaete setae. Each tuft is a fasicle of approximately 1500 distally tapered cannular rodlets located in an epidermal follicle composed of several lateral follicular cells and a single basal chaetoblast. The base of the follicle is associated with obliquely striated dermal muscle fibers. Together these elements comprise Kölliker's organ. The rodlets, composed of longitudinally oriented filaments, are separated basally from one another by a layered meshwork of interstitial filaments. Microvilli on the apical concave surface of the scyphate chaetoblast insert into the base of each rodlet. We infer that the tuft elongates by basal appositional growth and that glycoprotein secreted by the follicle cells is organized into filaments by the apical plasmalemma of the chaetoblast. Each microvillus serves as a template for the formation of a rodlet, therefore the number, size, shape, distribution and dynamic activity of the microvilli determine the morphology of the tuft.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224540
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  • 4
    Electronic Resource
    Electronic Resource
    Transcellular emigration of blood cells during ascidian metamorphosis (1970)
    Springer
    Cell & tissue research 107 (1970), S. 157-173 
    Details
    ISSN: 1432-0878
    Keywords: Ascidians ; Metamorphosis ; Blood cells ; Epidermis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary During the first 10 minutes after the onset of metamorphosis in the ascidian Amaroucium constellatum there is a massive emigration of blood cells (granulocytes) from the hemocoel, across the epidermis, into the tunic. Electron microscopy has been employed to extend some of the classical observations of the last century. The new findings are compatible with the hypothesis that the blood cells follow a transcellular pathway. Our interpretation is as follows: an emigrating cell enters the basal part of an epidermal cell and becomes enclosed within a vacuole. The vacuole and the blood cell move to the apex of the epidermal cell. The vacuole fuses with the plasmalemma releasing the blood cell into the tunic. Blood cells can therefore pass through the epidermis without leaving a hole and without rupturing intercellular junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335222
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  • 5
    Electronic Resource
    Electronic Resource
    Design and Synthesis of Novel Opiate Antagonists with LH-Stimulating Properties (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 326-336 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Opiate antagonists stimulate the release of LH and might, therefore, contribute to an innovative therapy for the treatment of numerous clinical syndromes characterized by hypofunction of the HHG axis. The purpose of this work was to design and synthesize pure opiate antagonists useful for this therapy. Me, Et, Pr, and PhCH2 groups were introduced at the crucial 14β-position of morphines and morphinans via a hetero-Diels-Alder key step starting from thebaine derivative 1 and tested for opiate antagonism and LH-stimulating activity. Me-, Et-, and Pr-substituted compounds 11a-c were stronger antagonists than naltrexone, whereas Pr and PhCH2 substituents in 11c, 11d, 9d, 9d3, 9d4, and 9d5 led to orally active LH stimulators. Based on our finding that the μ-antagonists 12 and 11b5 showed no LH stimulation, we conclude that a combination of both μ-and χ-antagonism is necessary for potent LH stimulation.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730212
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of membrane matrix on the transport of potassium ions (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 2855-2859 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1974.070180926
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  • 7
    Electronic Resource
    Electronic Resource
    Excited states of CF4 plasma for polymerization of TMPTA monomer (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 323-328 
    Details
    ISSN: 0887-624X
    Keywords: CF4 plasma ; trimethylolpropane triacrylate ; excited states ; plasma induced polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The F and CF2-CF2+ excited states have been detected by emission spectroscopy in CF4RF plasmas used for TMPTA polymerization. These excited states are related through electron collision to F and CF2 ground states. The temporal variation of the F and CF2-CF2+ radiative states near the substrate reveals that the F atoms disappear first by incorporation in the monomer during the polymerization phase and, then, by a third body recombination process enhanced by the polymer surface. The CF2-CF2+ radiative states are varying as the inverse of the F states indicating a strong destruction mechanism of CF2 radicals by F atoms.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300217
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  • 8
    Electronic Resource
    Electronic Resource
    Polymer drying. VII. 1H-NMR studies of evaporation from liquid saturated poly(styrene-co-divinylbenzene) (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1155-1161 
    Details
    ISSN: 0887-624X
    Keywords: adsorption ; desorption ; association ; polystyrene ; NMR ; polymer transitions ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Composition-studies were carried out in which samples of films composed of poly(styrene-co-divinylbenzene) particles enmeshed by poly(tetrafluoroethylene) fibers were saturated with dichloromethane and then allowed to evaporate at 23°C to virtual dryness as the 1H-NMR signals and residual weight of sorbed liquid were monitored. The correlations, of 1H-NMR line-widths with the corresponding log of the number, αt of residual sorbed molecules per monomer unit show that sharp changes occur as αt passes through αG the composition that exists when all the liquid not sorbed (i.e., not present within the liquid-saturated particles), has been eliminated, and again as αt passes through αg the composition that exists when the particles attain the rigidity characteristic of the glassy state. Correlation of the corresponding T1 relaxation times with log αt show that sharp changes occur when αt becomes equal first to α′s and then to α′g the compositions that exist respectively when, firstly, all the sorbed liquid not immobilized by adsorption to the polymer chains within the particles has been eliminated, and then when the desorption of immobilized liquid from the chains causes the composition to begin to undergo transition from its rubbery state to its glassy state.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300622
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of polarity of the medium on the stereospecific polymerization of propylene by ansa-zirconocene catalyst (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2049-2056 
    Details
    ISSN: 0887-624X
    Keywords: metallocenes ; olefin polymerizations ; Ziegler-Natta catalysts ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Propylene was polymerized with rac-ethylene-bis (1-η5-indenyl)dichlorozirconium/methylaluminoxane in solvents of different polarity. The poly (propylene) formed was separated by solvent extraction; 13C-NMR and DSC measurements were made on the polymer fractions. The poly(propylene) in each solvent fraction has its characteristic molecular weight steric pentad distributions, melting transition temperature, and enthalpy for fusion irrespective of the polymerization medium. The results suggest that the medium dielectric constant does not affect the polymerization rate or the intrinsic stereoselectivity, propagation and chain transfer rates a given catalytic species but can alter the occurrence of steric insertion errors through shifting of distributions of the propagating species producing poly(propylenes) of different stereoregularities. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321106
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  • 10
    Electronic Resource
    Electronic Resource
    CO2/CH4 separation by facilitated transport in amine-polyethylene glycol mixtures (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 1135-1145 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this work, the separation of carbon dioxide from methane by reactive liquid membranes consisting of the secondary amines, diethanolamine, and diisopropanolamine in polyethylene glycol with an average molecular weight of 400 was studied. A mathematical model was developed to describe the transport process. This model employs the zwitterion mechanism for the CO2 amine reaction kinetics. Membrane flux experiments utilizing a flat plate device were carried out to verify the model predictions. It was found that large permeabilities and separations were achieved for low CO2 feed concentrations. The results also show that DEA based solutions give better separation than DIPA based solutions.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390706
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