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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 15 (1980), S. 79-101 
    ISSN: 1432-1432
    Keywords: Molecules ; Interstellar ; Chemistry ; Isotopes ; Solar system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The study of interstellar molecules broadly includes two areas of interest. One area uses the unique ability of molecules to act as probes of the physical conditions in the cold, dense, visually opaque component of the interstellar medium. The physical properties of this and other components of the interstellar medium are summarized. The other area deals with the chemistry of interstellar molecules, recent aspects of which are emphasized in this review. Gas-phase chemistry, shock chemistry, and grain surface chemistry are discussed in the context of recent observations. No present observations suggest that surface reactions are relevant, but neither can they be ruled out. Ion-molecule reactions are clearly operative, at least for the simpler species. Chemical isotope fractionation is reviewed, andd it is concluded that the complexities of the chemistry allow no cosmological conclusions to be drawn from observations of deuterium in interstellar molecules, while the presence of13C in interstellar molecules permits an estimate of the12C/13C ratio which is consistent with the current concepts of the nucleosynthesis history of the Galaxy. Possible connections between interstellar molecules and the early molecular history of the solar system are discussed.
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Inorganica Chimica Acta 226 (1994), S. 293-340 
    ISSN: 0020-1693
    Keywords: Chemistry ; Electrochemistry ; Electron transfer ; Metalloproteins ; Redox reactions
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 23 (1977), S. 39-44 
    ISSN: 1432-0827
    Keywords: Dental cementum ; Collagen ; Protein ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Cyanogen bromide (CNBr) peptides were prepared of the insoluble collagen of bovine dental cementum. Following chromatographic separation, the peptides were identified by their amino-acid composition. Type I collagen ([α1(I)]2α2) accounted for more than 90% of the organic matrix, while Type III collagen ([α1(III)]3) was present at a level of approximately 5%. Amino-acid analyses revealed that the CNBr peptides from α1(I) and α2 chains of cementum closely resembled the corresponding peptides from calf skin. The only systematic difference was a higher level of hydroxylation of prolyl and lysyl residues of the cementum peptides.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 7 (1971), S. 150-162 
    ISSN: 1432-0827
    Keywords: Uranium ; Bone ; Distribution ; Fission ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une concentration moyenne de 2.4×10−8 g U/g de cendre a été obtenue à partir de l'os humain normal. La microdistribution de l'uranium dans l'os indique que cet élément est surtout limité à surface de l'endoste et, en particulier, aux surfaces de l'os lamellaire et aux parois des canaux de Havers, ouverts dans l'os corticol. Cette répartition suggère que l'uranium se présente sous une forme chimique impropre à son incorporation dans l'apatite osseux: il ne semble donc pas exister une distribution diffuse significative de l'uranium dans l'os.
    Abstract: Zusammenfassung Eine mittlere Konzentration von 2,4×10−8 g Uran/g Asche wurde in normalen menschlichen Knochen gefunden. Die Feinverteilung von Uran im Knochen zeigt, daß dieses Element hauptsächlich an der endostalen Oberfläche vorkommt, insbesondere an der Oberfläche des trabeculären Knochens und an den Wänden der offenen Haversschen Kanäle im kortikalen Knochen. Diese Verteilung läßt vermuten, daß Uran in einer chemischen Form vorliegt, welche sich für den Einbau in das Knochenapatit nicht eignet. Daraus folgt, daß keine signifikante diffuse Verteilung des Urans innerhalb des Knochens vorliegt.
    Notes: Abstract A mean concentration of 2.4×10−8 g U/g ash has been obtained for normal human bone The microdistribution of uranium in bone indicates that this element is mainly restricted to endosteal surfaces; in particular the surfaces of trabecular bone and the walls of open Haversian canals in cortical bone. This distribution suggests that uranium is present in a chemical form that is not acceptable for incorporation into bone apatite and consequently there does not appear to be a significant diffuse distribution of uranium throughout bone.
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  • 5
    ISSN: 1432-0827
    Keywords: Morphology ; Glycosaminoglycans ; Cartilage ; Chemistry ; Audioradiography ; Healing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Une perte de substance ostéo-cartilagineuse, de taille limitée et identique, est réalisée chez le lapin adulte et la cicatrisation est étudiée histologiquement et par autoradiographie après marquagein vitro au35S-sulfate. Une analyse microchimique est pratiquée pour le contenu et la composition en glycosaminoglycanes. 1. Entre la première semaine et la 4ème et 8ème semaine, un tissu conjonctif non-métachromatique se différencie en un cartilage métachromatique et la quantité de sulfate de chondroitine augmente de façon significative aux dépens des glycoprotéines. 2. Jusqu'à la 4ème semaine, la perte de substance est surtout comblée par de l'os néoformé: après cette période, la région est comblée au delà de la limite de la surface articulaire. 3. Le cartilage hyalin, ressemblant morphologiquement, autoradiographiquement et chimiquement au cartilage articulaire, en ce qui concerne la distribution en glycosaminoglycanes, constitute la surface articulaire de la perte de substance comblée dans un tiers des cas après 8 semaines. Le cartilage hyalin s'observe surtout dans les régions où de l'os néoformé a comblé la cavité médullaire. 4. Dans les deux tiers des cas, après 8 semaines, les surfaces articulaires des zones comblées comportent, non seulement du cartilage, mais aussi du tissu fibreux se formant essentiellement sur les parties latérales et dans les régions, où la cavité médullaire, fliant face, à la surface articulaire, n'a pas été comblée par du tissue osseux. La fraction glycoprotéique augmente par rapport à la fraction chondroitine sulfate. 5. Dans la majorité des cas, après 20 semaines, le cartilage néoformé subit des phénomènes dégénératifs, qui se traduisent par une diminution en chondroitine sulfate.
    Abstract: Zusammenfassung Bei ausgewachsenen Kaninchen wurde ein begrenzter, standardisierter, osteochondraler Defekt hervorgerufen, und das regenerierte Gewebe wurde histologisch und autoradiographisch durch Markierung in vitro mit35S-Sulfat und durch mikrochemische Bestimmung des Gehaltes und der Zusammensetzung der Glykosaminglykane untersucht. Die wichtigsten Befunde waren: 1. Zwischen 1 und 4–8 Wochen veränderte sich nichtmetachromatisches Bindegewebe zu metachromatisch gefärbtem Knorpel, und der Anteil an Chondroitin-Sulfat nahm auf Kosten der Glykoproteine signifikant zu. 2. Bis zu 4 Wochen war der Hauptteil des defekten Gebietes mit neugebildetem Knochen gefüllt; nach dieser Zeit lag dieser Bezirk oberhalb der Verknöcherungsgrenze in Richtung der Gelenkoberfläche. 3. Nach 8 Wochen bestand die Gelenkoberfläche des defekten Gebietes in einem Drittel der Fälle aus hyalinem Knorpel, der morphologisch, autoradiographisch und chemisch dem Gelenkknorpel in Bezug auf die Verteilung von Glykosaminoglykanen glich. Hyaliner Knorpel wurde hauptsächlich an Stellen beobachtet, wo neugebildeter Knochen die Markhöhle geschlossen hatte. 3. Nach 8 Wochen bestand die Gelenkoberfläche des defekten Gebietes in einem Drittel der Fälle aus hyalinem Knorpel, der morphologisch, autoradiographisch und chemisch dem Gelenkknorpel in Bezug auf die Verteilung von Glykosaminoglykanen glich. Hyaliner Knorpel wurde hauptsächlich an Stellen beobachtet, wo neugebildeter Knochen die Markhöhle geschlossen hatte. 4. Nach 8 Wochen bestanden Teile der Gelenkoberfläche des Defektes in zwei Dritteln der Fälle nicht nur aus Knorpel, sondern auch aus fibrösem Gewebe, welches vor allem in den seitlichen Teilen des Defektes und an Stellen vorlag, wo die Markhöhle gegenüber der Gelenkoberfläche nicht mit Knochengewebe verschlossen worden war. Die Glykoproteinfraktion nahm im Vergleich zur Chondroitin-Sulfatfraktion zu. 5. Nach 20 Wochen zeigten sich in den meisten Fällen bei neugebildetem Knorpel degenerative Veränderungen, welche durch eine gewisse Abnahme des Chondroitin-Sulfats wiedergegeben wurden.
    Notes: Abstract A limited, standardized osteochondral defect was created in adult rabbits and the regenerated tissue was examined histologically and autoradiographically after labellingin vitro with35S-sulphate, and microchemically for its content and composition of glycosaminoglycans. The principal findings were: 1. Between 1 week and 4 to 8 weeks, non-metachromatic connective tissue differentiated to metachromatically stained cartilage, and the proportion of the chondroitin sulphate increased significantly at the expense of the glycoproteins. 2. Up to 4 weeks, the major part of the defect area was filled with newly formed bone; after this time, the area lay above the level of the “tidemark”, towards the articular surface. 3. Hyaline cartilage with morphological, autoradiographic and chemical resemblance to the articular cartilage in terms of the distribution of glycosaminoglycans constituted the articular surface of the defect area in one-third of the cases at observation times after 8 weeks. Hyaline cartilage was observed mainly in areas where newly formed bone had closed the medullary cavity. 4. In two-thirds of the cases, after 8 weeks, parts of the articular surface of the defect consisted not only of cartilage but also of fibrous tissue, occurring mainly in the lateral parts of the defect and in areas where the medullary cavity facing the articular surface had not been sealed by bone tissue. The glycoprotein fraction increased relative to the chondroitin sulphate fraction. 5. In most cases after 20 weeks, newly-formed cartilage underwent degenerative changes, which were reflected in some reduction of the chondroitin sulphate.
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  • 6
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    Springer
    Calcified tissue international 10 (1972), S. 82-90 
    ISSN: 1432-0827
    Keywords: Calcium ; Phosphate ; Precipitation ; Kinetics ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé La cinétique de la formation et de la transformation des précipités de phosphate de calcium, obtenus en mélangeant de volumes égaux de solutions à 6×10−3 M de calcium total et/ou phosphate total est étudiée à 25°C. Les solutions de phosphate sont préajustées à un pH de 7.4. Les changements de pH et de turbidité des solutions sont suivis simultanément en fonction du temps. Les précipités sont isolés à des intervalles de temps variables et caractérisés par diverses méthodes physico-chimiques. Initialement un précipité avec un rapport molaire Ca/P de 1.5, amorphe aux rayons X et en diffraction électronique, est formé. Le spectre IR indique la présence de PO 4 3− et de HPO 4 2− . Après une période métastable, on observe la précipitation d'un matériel cristallin dans ou sur la phase amorphe. Vingt quatre heures après préparation de l'échantillon les précipités présentent surtout les caractères du phosphate octocalcique.
    Abstract: Zusammenfassung Die Kinetik der Bildung und Transformation von Calciumphosphat-Niederschlägen wurde bei 25°C untersucht. Es wurden dazu gleiche Volumen von Lösungen gemischt, bei einer Konzentration von 6×10−3M totales Calcium und/oder totales Phosphat. Die Phosphatlösungen wurden zuerst auf pH 7,4 eingestellt. Veränderungen des pH und Trübung der Lösungen wurden gleichzeitig als eine Funktion der Zeit aufgezeichnet. Niederschläge wurden in verschiedenen Zeitintervallen isoliert und mit verschiedenen physiko-chemischen Methoden charakterisiert. Am Anfang wurde ein Niederschlag mit einem molaren Ca/P-Verhältnis von 1,5, im Röntgenbild und in der Elektronendiffraktion amorph, gebildet. Infrarotspektren deuteten die Anwesenheit von PO 4 3− - und HPO 4 2− -Ionen an. Nach einer metastabilen Periode erfolgte ein Niederschlag aus kristallinem Material innerhalb oder auf der amorphen Substanz. 24 Std nach der Herstellung der Proben zeigten die Niederschläge in der Hauptsache die Charakteristiken von Octocalciumphosphat.
    Notes: Abstract The kinetics of the formation and transformation of calcium phosphate precipitates obtained by mixing equal volumes of solutions, 6×10−3 M in total calcium and/or total phosphate was investigated at 25°. The phosphate solutions were preadjusted to pH 7.4. Changes of the pH and turbidity of the solutions were followed simultaneously as a function of time. Precipitates were isolated at various time intervals and characterized by different physicochemical methods. Initially a precipitate with a molar Ca/P ratio of 1.5, amorphous to X-ray and electron diffraction was formed. IR spectra indicated the presence of PO 4 3− and HPO 4 2− ions. After a period of metastability, precipitation of a crystalline material within or upon the amorphous matter occurred. Twenty four hours after sample preparation the precipitates showed mainly the characteristics of octacalcium phosphate.
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  • 7
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    Springer
    Calcified tissue international 14 (1974), S. 3-14 
    ISSN: 1432-0827
    Keywords: Hydroxyapatite ; Mineral ; Phase ; Chemistry ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des diagrammes de phase d'équilibre ont été déterminés pour le système CaO-P2O5-H2O en utilisant des techniques de synthèse hydrothermique au cours de variatio nsde température allant de 300–600° et 2 Kb H2O de pression. De l'hydroxyapatite bien cristallisé a été synthétisé et caractérisé. De faibles variations de paramètres de la maille cristalline, liées à la température de synthèse et composition globale du matériel initial, ont été déterminées. Des conditions chimiques précises sont nécessaires pour obtenir de l'apatite, en tant que seule phase solide en équilibre dans la solution. Les résultats de diagramme de phase d'équilibre sont comparés avec ceux obtenus dans des milieux synthétiques.
    Abstract: Zusammenfassung Es wurden Gleichgewichts-Phasendiagramme für das System CaO-P2O5-H2O bestimmt, indem hydrothermale Synthese-Techniken im Temperaturbereich von 300–600° und bei einem Druck von 2 Kb H2O verwendet wurden. Es wurde gut-kristallisiertes Hydroxyapatit erzeugt und charakterisiert. Es wurden geringe Unterschiede in den Parametern der Zelleinheiten festgestellt, welche von der angewandten Temperatur und der Zusammensetzung des Startmaterials abhingen. Es waren genaue chemische Bedingungen nötig, um Apatit als die einzige feste Phase im Gleichgewicht mit der Lösung zu erhalten. Die Resultate der Gleichgewichts-Phasendiagramme werden mit früheren Untersuchungen mit der Synthesetechnik verglichen.
    Notes: Abstract Equilibrium phase diagrams have been determined for the system CaO-P2O5-H2 using hydrothermal synthesis techniques in the temperature range 300–600° and 2 Kb H2O pressure. Well-crystallized hydroxyapatite has been produced and characterized. Small variations in unit cell parameters dependent on temperature of synthesis and bulk composition of the starting materials have been determined. Precise chemical conditions were required to obtain apatite as the only solid phase in equilibrium with solution. Equilibrium phase diagram results are compared with previous synthetic investigations.
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  • 8
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    Calcified tissue international 13 (1973), S. 259-270 
    ISSN: 1432-0827
    Keywords: Fluorapatite ; Exchange ; Chemistry ; Crystallography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un échantillon minéral provenant de Burgess, Canada s'est révélé être un speciment exceptionnellement pur de fluoroapatite après analyse chimique et cristallographique. La composition globale de cet échantillon est la suivante: $$(Ca^2 )9.98(Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )0.02(PO_4^{3 - } )5.98(HCO_3^ - ,CO_3^{2 - } )0.02(F^ - )2$$ . L'axe cristallographique C est de 6.865 A et l'axe a de 9.374 A. Des expériences d'échanges réalisés à l'aide de45Ca,32P et18F indiquent la présence de gros cristallites de surface spécifique de l'ordre de 1 m2/g. Il apparait que l'interprétation physique des processus d'échange ne nécessite pas l'existence de compartiments séparés, avec chacun son propre facteur cinétique, les échanges semblent être simplement liés à un changement exponentiel dans l'énergie libre de la réaction. Pour la réaction suivante: $$(Ca)_5 (PO_4 )_3 OH solide + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F solide + (OH^ - )$$ , la constante thermodynamique de 101.26 a été calculée, suggérant que le fluorapatite se forme toujours aux dépens de l'hydroxyapatite dans des conditions physiologiques. Cette transformation se continue en abaissant le pH.
    Abstract: Zusammenfassung Eine Mineralprobe aus Burgess, Kanada, erwies sich nach chemischer und kristallographischer Analyse als außergewöhnlich reines Fluorapatit. Die Gesamtzusammensetzung entspricht: $$(Ca^{2 + } )_{9,98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0,02} (PO_4^{3 - } )_{5,98} (HCO_3^ - ,CO_3^{2 - } )_{0,02} (F^ - )_2 $$ . Die kristallographische c-Achse wurde bestimmt und ergab 6,865 Å, und die a-Achse ergab 9,374 Å. Austauschwerte, welche durch Anwendung von45Ca,32P und18F erhalten wurden, deuteten auf große Kristalliten mit einer spezifischen Oberfläche von ca. 1 m2/g. Die Befunde deuten darauf hin, daß für die physikalische Erklärung des Austauschvorganges keine separaten Kompartimente mit eigenen kinetischen Faktoren nötig sind, sondern daß der Austausch mit dem exponentiellen Wechsel in der freien Energie der Reaktion in einfacher Beziehung steht. Für die Reaktion $$(Ca)_5 (PO_4 )_3 OH_{in fester Form} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{in fester Form} + (OH^ - )$$ wurde als thermodynamische Konstante 101,26 errechnet, was darauf deutet, daß unter physiologischen Bedingungen immer Fluorapatit auf Kosten von Hydroxyapatit entsteht. Diese Umwandlung wird erhöht, wenn das pH erniedrigt wird.
    Notes: Abstract A mineral specimen from Burgess, Canada, proved upon chemical and crystallographic analyses to be an exceptionally pure sample of fluorapatite. The over-all composition corresponds to $$(Ca^{2 + } )_{9.98} (Sr^{2 + } ,Na^ + ,K^ + ,Mg^{2 + } )_{0.02} (PO_4^{3 - } )_{5.98} (HCO_3^ - ,CO_3^{2 - } )_{0.02} (F^ - )_2 $$ . The crystallographic c-axis was determined to be 6.865 Å, and the a-axis 9.374 A. Exchange data obtained by employing45Ca,32P, and18F indicate the presence of large crystallites with a specific surface of the order of 1 m2/g. It is indicated that the physical interpretation of the exchange process does not require the existence of separate departments, each with its own kinetic factor, but that the exchange may be simply related to the exponential change in the free energy of the reaction. For the reaction $$(Ca)_5 (PO_4 )_3 OH_{solid} + (F^ - ) \rightleftarrows (Ca)_5 (PO_4 )_3 F_{solid} + (OH^ - )$$ the thermodynamic constant has been calculated to be 101.26, implying that fluorapatite always will form at the expense of hydroxyapatite under physiologic conditions. This transformation will be furthered by lowering the pH.
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  • 9
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    Calcified tissue international 23 (1977), S. 87-94 
    ISSN: 1432-0827
    Keywords: Calcium ; Osteoporosis ; Lactation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The calcium homeostatic mechanism was challenged in adult female rats by feeding them a calcium-deficient diet containing oxalate, and by subjecting them to pregnancy and lactation. The regimen caused a substantial weight loss, especially in those animals which reared their young well. Severe hypocalcaemia was observed in the lactating rats. Serum-P was slightly elevated. The content of hydroxyproline in serum was considerably elevated, reflecting the degree of calcium deprivation. Serum proteins were least influenced. The calcium depriving regimen reduced the growth of long bones, but did not stop it. The ash content of the bones was considerably reduced, the degree of reduction depended on the degree of calcium deprivation. Ash as percentage of total bone organ was reduced, but not to the same extent as total ash. Analyses of different parts of femur showed that the proximal and distal parts had lost more bone mineral than the diaphyseal shaft. The ash content of cortical bone tissue from the femur was estimated by a volumetric method. No differences were observed between test groups and controls, indicating that no measurable amounts of bone mineral had been removed from the walls of the vascular canals or by osteocytic osteolysis. Planimetric determinations on cross sections from femora disclosed that a great amount of bone had been removed from the endosteal surface of the diaphysis, while the periosteal surface demonstrated reduced bone apposition.
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  • 10
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    Calcified tissue international 12 (1973), S. 125-136 
    ISSN: 1432-0827
    Keywords: Mineralization ; Molt ; Isopod ; Chemistry ; Light microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Au cours de la phase inhabituelle de mue d'un isopode d'eau courante,Lirceuts brachyrus, la moitié postérieure de l'exosquelette est éliminée 24 heures avant la moitié antérieure. A ce stade, une reminéralisation se développe dans la partie postérieure alors que la partie antérieure est dans un stade de pré-mue. Le pourcentage de différence en calcium dans les deux moitiés à mi-mue et mue complète est respectivement de 22% (p〈0.01) et 33% (p〈0.01), indiquant une complexation du calcium pendant la mue. La rapidité de la reminéralisation est illustrée par le fait que le contenu minéral total double dans la partie postérieure entre la mi-mue et la mue totale et dans la partie antérieure entre la fin de la mue et un jour après. Le carbonate de calcium, sous forme de calcite, a pu être identifié par diffraction électronique de coupes fines des téguments.
    Abstract: Zusammenfassung Während der ungewöhnlichen Häutungssequenz des Frischwasser-IsopodenLirceus brachyurus (Harger) wird die hintere Hälfte des äußeren Skeletts 24 Std vor der vorderen Hälfte abgestoßen. In der halbgehäuteten Phase erfolgt Remineralisation im hinteren Teil, während der vordere Teil in einem Vorhäutungszustand ist. Der prozentuale Unterschied des Calciums in den zwei Hälften bei Halb- und Vollhäutungszustand ist 22% (p〈0,01) bzw. 33% (p〈0,01), was andeutet, daß Calcium während der Häutung abgesondert wird. Die Geschwindigkeit der Remineralisation erhellt aus der Tatsache, daß sich der Gesamtmineralgehalt im hinteren Teil zwischen Halt- und Vollhäutung, in der vorderen Hälfte jedoch zwischen Endhäutung und einem Tag nach der Häutung verdoppelt. Calciumcarbonat in kristalliner Calcitform wurde mittels Elektronendiffraktion von dünnen Hautschnitten nachgewiesen.
    Notes: Abstract During the unusual molt sequence of the fresh-water isopod,Lirceus brachyrus (Harger), the posterior half of the exoskeleton is shed 24 hours before the anterior half. At the half-molt stage, occurs in the posterior part while the anterior portion is in a pre-molt condition. The percentage difference in calcium in the two halves at half-molt and full-molt is22 (p〈0.01) and33 (p〈0.01) respectively, an indication that calcium is sequestered during The rapidity of remineralization is illustrated by the fact that the total mineral content doubles in the posterior part between half and full molt and in the anterior half between the end of molt and one day after ecdysis. Calcium carbonate in the calcite cystalline form was demonstrated by electron diffraction of thin sections of the integument.
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  • 11
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    Calcified tissue international 16 (1974), S. 145-152 
    ISSN: 1432-0827
    Keywords: EHDP ; Bone ; Chemistry ; Serum ; Rabbits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on bone and serum chemistry were investigated in adult rabbits. EHDP was administered by subcutaneous injection at doses of 0.25, 2.5 and 10 mg/kg body weight/day for of 28 days. Blood samples were obtained weekly from each rabbit and serum levels of total calcium, ionized calcium, inorganic phosphate and alkaline phosphatase were determined. At the end of the treatment period all rabbits were sacrificed and the tibiae removed for chemical analysis and histological evaluation. The effect of EHDP administration on serum chemistry was both dose- and time-related. The highest of the three doses, 10 mg/kg/day, resulted in a time-related decrease in total serum calcium. This dose also caused a rapid but transient reduction in serum ionized calcium. The effect of EHDP on serum inorganic phosphate was biphasic. Administration of 2.5 mg/kg/day resulted in a time-related elevation in this parameter, whereas the 10 mg/kg/day dose resulted in a time-related hypophosphatemic response. There were no significant drug-related changes in tibial fat-free dry weight, ash weight, total calcium or total phosphorus values. However, administration of 2.5 and 10 mg/kg/day EHDP resulted in increased osteoid tissue as measured histologically. These results are compared with data from other EHDP studies, and discussed in relation to the maturity and growth-state of the experimental animals.
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  • 12
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    Calcified tissue international 8 (1971), S. 197-210 
    ISSN: 1432-0827
    Keywords: Fluorescence ; Calcium ; Collagen ; Chemistry ; Bone ; Dentine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des composants fluorescents de l'os et la dentine sont séparés des hydrolysats alcalins de leur marice sur des colonnes Sephadex C25 CM d'échange cationique. Les concentrations en fluorescence et le spectre d'excitation (λ max 330 nm) et d'émission (λ max 395 nm) sont les mêmes que ceux observés au niveau des matrices intactes et gélatinisées. Les paramètres de fluorescence ne sont pas altérés par hydrolyse. La filtration sur gel à l'aide de colonnes Sephadex G 10 perment de différencier le matériel isolé en deux composants, ayant la même fluorescence et la même absorption UV. La fluorescence est indépendante de pH de 3.5–9.5. Des études de dialyse et de filtration sur gel de matrices gélatinisées indiquent une association étroite du matériel fluorescent avec les chaines polypeptidiques de collagène.
    Abstract: Zusammenfassung Fluorescierende Bestandteile aus Knochen und Dentin wurden in Sephadex C25 CM Kationen-Austauschersäulen von alkalischen Hydrolysaten ihrer Matrices getrennt. Die Fluorescenzintensitäten sowie die Erregungs- (λ max 330 nm) und Emissions- (λ max 395 nm) Spektren waren dieselben wie bei intakten und gelatinisierten Matrices. Die Fluorescenzparameter wurden durch die Hydrolyse nicht verändert. Eine Gelfiltration über Sephadex-G10-Säulen trennte das isolierte Material in 2 Komponenten auf, welche gleiche Fluorescenz- und UV-Absorptionseigenschaften zeigten. Im pH-Bereich zwischen 3,5 und 9,5 war die Fluorescenz unabhängig vom pH. Dialysierversuche sowie Gelfiltrationsexperimente mitden gelatinisierten Matrices zeigten eine starkgefügte Bindung des fluorescierenden Materials mit den Polypeptidketten des Kollagens.
    Notes: Abstract Fluorescent components in bone and dentine were separated from alkaline hydrolysates of their matrices on Sephadex C25 CM cationic exchange columns. The fluorescence levels, and the excitation (λ max 330 nm) and emission (λ max 395 nm) spectra, were the same as those observed in the intact and gelatinised matrices. The fluorescence parameters were unaltered by the hydrolysis procedure. Gel filtration on Sephadex G. 10 columns further resolved the isolated material into two components with the same fluorescence and UV absorption properties. The fluorescence was independent of pH over the range 3.5–9.5. Dialysis and gel filtration studies on the gelatinised matrices indicated a firmly-bonded association of the fluorescent material with the collagen polypeptide chains.
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    Pure and applied geophysics 118 (1980), S. 128-151 
    ISSN: 1420-9136
    Keywords: Galactic cosmic rays ; Solar proton events ; Particle precipitation ; Chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An assessment is made of the relative contribution of certain classes of energetic particle precipitation to the chemical composition of the middle atmosphere with emphasis placed on the production of odd nitrogen and odd hydrogen species and their subsequent role in the catalytic removal of ozone. Galactic cosmic radiation is an important source of odd nitrogen in the lower stratosphere but since the peak energy deposition occurs below the region where catalytic removal of O3 is most effective, it is questionable whether this mechanism is important in the overall terrestrial ozone budget. The precipitation of energetic solar protons can periodically produce dramatic enhancement in upper stratospheric NO. The long residence time of NO in this region of the atmosphere, where catalytic interaction with O3 is also most effective, mandates that this mechanism be included in future modelling of the global distribution of O3. Throughout the mesosphere the precipitation of energetic electrons from the outer radiation belt (60°≲Λ≲70°) can sporadically act as a major local source of odd hydrogen and odd nitrogen leading to observable O3 depletion. Future satellite studies should be directed at simultaneously measuring the precipitation flux and the concomitant atmosphere modification, and these results should be employed to develop more sophisticated models of this important coupling.
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    Calcified tissue international 10 (1972), S. 171-197 
    ISSN: 1432-0827
    Keywords: Amorphous ; Crystalline ; Calcium phosphate ; Chemistry ; Composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des échantillons non lavés de phosphate de calcium amorphe (ACP) contiennent une fraction labile, non remplaçable, riche en phosphate acide avec un rapport Ca/P faible: cette fraction est perdue de façon irréversible au cours du lavage. De l'ACP frais, précipité entre pH 6.6–10.6, varie dans un rapport molaire Ca/P de 1.18 à 1.50 et dans un rapport HPO 4 2− /P total de 33.0% à 10.1%. A pH 7.40, de l'ACP frais a un rapport molaire Ca/P de 1.36±0.02 et contient 22.8 (±2.2)% HPO 4 2− . Les résultats obtenus avec du précipité non lavé ne peuvent s'expliquer par du Ca2+ emprisonné et de l'HPO 4 2− ou du Na+, Cl− et CO 3 2− exogènes. Les phosphates de calcium amorphes constituent une classe de sels ayant des caractères chimiques variables et des propriétés physiques identiques, comparables au verre. Le CaHPO4·xH2O non cristallin peut être un ACP, surtout au cours des phases précoces de formation. A des pH physiologiques, l'ACP se transforme en petits cristaux applatis contenant de fortes quantités de phosphate acide facilement remplaçable. Le fait de laver la couche de surface produit un changement chimique dans les nouveaux cristaux: des cristaux non lavés donnent des diagrammes de diffraction d'apatite peu cristallins, ainsi que des spectres infra-rouges peu nets, intermédiaires entre des apatites et du phosphate octocalcique. Des explications structurales sont proposées et les compositions minérales amorphe/cristalline de l'os et du cartilage sont recalculées.
    Abstract: Zusammenfassung Ungewaschene Proben von amorphem Calciumphosphat (ACP) enthalten eine unersetzliche labile Fraktion, welche reich an saurem Phosphat ist und ein niederes Ca/P-Verhältnis hat und welche während des Waschprozesses unwiderruflich verloren geht. Natives ACP, welches im pH-Bereich 6,6–10,6 ausgefällt wurde, variierte im molaren Ca/P-Verhältnis zwischen 1,18 und 1,50 und in HPO 4 2− /totales P zwischen 33,0 und 10,1%. Bei pH 7,40 hatte natives ACP ein molares Ca/P-Verhältnis von 1,36±0,02 und enthielt 22,8 (±2,2)% HPO 4 2− . Die Werte beim ungewaschenen Niederschlag rühren weder von aus dem Überstand aufgenommenem Ca2+ und HPO2−, noch von außen kommendem Na+, Cl− und CO 3 2− her. Die amorphen Calciumphosphate werden als eine Klasse von Salzen erkannt, welche veränderliche chemische, aber identische glasartige physicochemische Eigenschaften haben. Nicht kristallines CaHPO4·xH2O kann auch ein ACP sein, besonders in den frühen Bildungsstadien. Bei physiologischem pH verwandelt sich ACP in kleine plattenförmige Kristalle, welche große Mengen von leicht ersetzbarem saurem Phosphat enthalten. Das Waschen dieser Oberflächenschicht erzeugte chemische Veränderungen in den resultierenden Kristallen; ungewaschene Kristalle zeigten ein Diffraktionsmuster, das nur schwach demjenigen des kristallinen Aspatites glich, aber ein schlecht aufgelöstes Infrarotspektrum, welches zwischen Apatit und Octocalciumphosphat war. Es werden strukturelle Erklärungen für alle diese Phenomena diskutiert, und revidierte amorph/kristalline Mineralzusammensetzungen von Knochen und Knorpel wurden neu berechnet.
    Notes: Abstract Unwashed samples of amorphous calcium phosphate (ACP) contain an irreplaceable labile fraction, rich in acid phosphate and low in Ca/P ratio, which is irreversibly lost during the washing process. Native ACP precipitated in the pH range 6.6–10.6 varied in Ca/P molar ratio from 1.18 to 1.50 and in HPO 4 2− /total P from 33.0% to 10.1%. At pH 7.40, native ACP had a Ca/P molar ratio of 1.36±0.02 and contained 22.8 (±2.2)% HPO 4 2− . Unwashed precipitate data could not be attributed to either trapped supernatant Ca2+ and HPO 4 2− or extraneous Na+, Cl−, and CO 3 2− . The amorphous calcium phosphates are recognized as a class of salts having variable chemical but identical glass-like, physicochemical properties. Non-crystalline CaHPO4·xH2O may also be an ACP, especially during early formative stages. At physiological pH, ACP transforms to small platy crystals containing large amounts of readily-replaceable acid phosphate. Washing this surface layer produced chemical alterations in the resultant crystals; unwashed crystals had poorly-crystalline apatitic diffraction patterns but exhibited poorly-resolved infrared spectra intermediate between apatite and octacalcium phosphate. Structural explanations for all these phenomena are discussed, and revised bone and cartilage amorphous/crystalline mineral compositions have been re-calculated.
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    Calcified tissue international 23 (1977), S. 13-17 
    ISSN: 1432-0827
    Keywords: Dental calculus ; Glycopeptide ; Chemistry
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    Topics: Biology , Medicine , Physics
    Notes: Summary A method is described for the isolation and purification of a sulphated glycopeptide from human supragingival calculus. The compound was isolated after using EDTA treatment, 2 M CaCl2 extraction, proteolytic digestion, ethanol precipitation, and finally purified by DEAE cellulose chromatography. It migrated as a single component on cellulose acetate electrophoresis, and chemical and infrared spectral analysis showed the presence of covalently attached sulphate groups. The sulphated glycopeptide was distinguished from being a sulphated glycosaminoglycan.
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    ISSN: 1432-0827
    Keywords: Bacterial amphophile ; Purification ; Chemistry ; Resorption ; Ca influx ; Cyclic AMP
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    Topics: Biology , Medicine , Physics
    Notes: Summary The bone resorptive factor and amphipathic antigen (AcA) previously identified by us in preparations fromActinomyces viscosus have been partially purified, characterized chemically, and compared. They elute at the same location on chromatography with Ac 22. The fatty acid composition of AcA and the bone resorptive factor is the same. Some differences in carbohydrate composition are observed. TheActinomyces factor does not affect calcium influx or cyclic AMP in isolated bone cells. Therefore it is concluded that AcA stimulates resorption either by gaining entrance into bone cells or by way of a yet undetermined second messenger.
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    Calcified tissue international 8 (1971), S. 228-236 
    ISSN: 1432-0827
    Keywords: Skin ; Calcinosis ; Keratin ; Chemistry ; X-ray diffraction
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    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des études histologiques antérieures ont montré que le follicle pileux est particulièrement susceptible de se calcifier, lorsque la peau de rats hypercalcémiques est lésée. Des analyses chimiques et par diffraction aux rayons X du follicule ont confirmé ce résultat. — En se basant sur l'augmentation du calcium et du phosphore, les calcifications débutent dans le tissue folliculaire 6–12 h après une blessure d'intensité moyenne de la peau de rats, ayant reçu du dihydrotachysterol (DHT), et 24–48 h après une blessure similaire chez des rats non injectés. Les diagrammes de diffraction aux rayons X sont diffus. Trois heures après la blessure, on note une augmentation du calcium du tissu folliculaire qui ne semble pas en rapport avec le DHT qui traduit probablement une liaison de calcium plutôt qu'un dépot minéral.
    Abstract: Zusammenfassung Frühere histologische Untersuchungen haben gezeigt, daß der Haarfollikel besonders anfällig für Verkalkungen ist, wenn die Haut von hypercalcämischen Ratten verletzt wird. Dieses Resultat wurde nun durch direkte chemische Bestimmungen und Röntgendiffraktions-analysen von Follikelgewebe bestätigt. Aufgrund der erhöhten Calcium- und Phosphatwerte kann gesagt werden, daß nach einer leichten Quetschung der Haut von Ratten, die mit Dihydrotachysterol (DHT) behandelt wurden, im Haarfollikelgewebe nach 6–12 Std Mineral-ablagerungen stattfanden, wogegen Kontrollratten mit der gleichen leichten Hautverletzung diese Ablagerungen erst nach 24–48 Std zeigten. Röntgendiffraktionsanalysen ergaben ein diffuses Apatit-Muster. Innerhalb 3 Std nach der Verletzung wurde ein Anstieg des Calcium-gehaltes im Follikelgewebe beobachtet, der nicht im Zusammenhang mit der DHT-Behandlung stand, also nicht eine Mineralablagerung, sondern eher eine Bindung von Calcium widerspiegelte.
    Notes: Abstract Previous histological investigations have shown that the hair follicle is particularly susceptible to mineralization when the skin of hypercalcaemic rats is injured. Direct chemical and X-ray diffraction analyses of follicle tissue have now confirmed this finding. As judged by increases in both calcium and phosphorus, mineral deposits began to form in hair follicle tissue 6–12 h after a mild crush injury to the skin of rats dosed with dihydrotachysterol (DHT), and 24–48 h after a similar injury to the skin of non-dosed rats. X-ray diffraction gave a diffuse apatite pattern. Within 3 h of injury there was a rise in the calcium content of follicle tissue which was not related to DHT-dosing and which was probably a reflection of calcium binding rather than mineral deposition.
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    Calcified tissue international 8 (1971), S. 304-319 
    ISSN: 1432-0827
    Keywords: Chemistry ; Calcium ; Phosphate ; Solubility ; Computer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Un programme d'ordinateur a été mis au point pour calculer les activités ioniques du calcium et l'orthophosphate dans un grand nombre de solutions. Dans le cas de solutions synthétiques, les calculs sont vérifiés en comparant les valeurs de pH, obtenues par ordinateur, avec celles observées expérimentalement. Des essais de ce type, avec des solutions possèdant des concentrations de calcium et d'orthophosphate trouvées dans les liquides biologiques et à des valeurs de pH variant de 3.00 à 10.00, indiquent que le programme est adapté pour des applications biologiques. Le programme n'est pas effectif pour des solutions, dans les lesquelles l'ion bromure est la source principale de la force ionique, sans doute, par manque d'équation étendue de Debye-Hückel dans ces circonstances. Aucune formation de complexe de phosphate de sodium n'a été notée à des concentrations biologiques normales.
    Abstract: Zusammenfassung Es wurde ein Computer-Programm ausgearbeitet, um die Ionenaktivitäten von Calcium und Orthophosphat in einer breiten Varietät von Lösungen zu berechnen. Die Berechnungen wurden bei synthetischen Lösungen durch Vergleiche zwischen den auf diese Weise errechneten pH-Werten und den experimentell gefundenen kontrolliert. Diese Art Kontrollen mit Calcium-und Orthophosphatkonzentrationen, wie sie in biologischen Flüssigkeiten gefunden werden, und mit pH-Werten zwischen 3,0 und 10,0 wies darauf hin, daß das Programm für biologische Anwendungen geeignet war. Das Programm konnte nicht benützt werden für solche Lösungen, bei welchen hauptsächlich das Bromidion zur Einstellung der Ionenstärke verwendet wurde, vermutlich weil die erweiterte Debye-Hückel-Gleichung unter diesen Umständen nicht anwendbar ist. Die Bildung eines Natriumphosphat-Komplexes unter normalen biologischen Konzentrationen konnte nicht nachgewiesen werden.
    Notes: Abstract A computer program has been designed to calculate the ionic activities of calcium and orthophosphate in a wide variety of solutions. In the case of synthetic solutions the calculations were checked by comparing the computed pH values with those observed experimentally. Tests of this type with solutions having the concentrations of calcium and orthophosphate found in biological fluids and with pH values ranging from pH 3.0–10.0 indicated that the program was suitable for biological applications. The program was not effective for solutions in which the bromide ion was a principal source of ionic strength probably because of the failure of the extended Debye-Hückel equation under those circumstances. No evidence for the formation of any sodium phosphate complex at normal biological concentrations could be found.
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    ISSN: 1432-0975
    Keywords: Key words Otolith ; Chemistry ; ICP-MS ; Stock discrimination ; Epinephelus striatus
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    Topics: Biology , Geosciences
    Notes: Abstract  We examined the utility of otolith minor and trace element chemistry, assayed with inductively coupled plasma mass spectrometry (ICP-MS), as a means of delineating population structure in the Nassau grouper (Epinephelus striatus). We characterized the elemental composition of otoliths collected in 1993 from three locations in Exuma Sound, Bahamas and from Glover Reef, Belize in 1995. A single location in Exuma Sound was sampled in 1994 to test temporal variability in otolith composition. Five elements (Ca, Zn, Sr, Ba and Pb) were routinely detected, at levels significantly above background, by solution-based ICP-MS. Results from analysis of variance of elemental data, expressed as a ratio to Ca, indicated that there were no significant differences among the Exuma locations for any element, but significant variability was found between Glover Reef and the pooled Exuma localities for Zn/Ca, Sr/Ca and Ba/Ca ratios. Significant inter-annual differences at one Exuma Sound location was restricted to Ba/Ca ratios. Discriminant function analysis correctly classified 86% and 95% of the Belize and pooled Exuma sites, respectively. Otoliths from Belize were characterized by low Zn/Ca and high Ba/Ca and Pb/Ca ratios compared to otoliths from fish collected in Exuma Sound. Although differences in Ba levels may be related to upwelling at Glover Reef, more data are needed to definitely link otolith composition with regional differences in water chemistry.
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    Accreditation and quality assurance 5 (2000), S. 409-413 
    ISSN: 1432-0517
    Keywords: Key words Metrology ; Comparisons ; Chemistry ; Standards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  After stressing the importance in the modern world of accurate and reproducible measurements, the actions taken by the Bureau International des Poids et Mesures to set up, together with the regional metrology organizations, a series of key comparisons are described. They are the technical foundation of a mutual recognition of national measurement standards arrangement prepared in conjunction with the National Metrology Institutes (NMIs). This arrangement also includes the recognition of calibration and measurement certificates issued by these institutes. Then, the consequences of this arrangement for trade are described. The case of chemical analysis is illustrated by the application of the Kyoto protocol on the reduction of greenhouse gases. But the global workload to be taken up by the International Committee of Weights and Measures, its Consultative Committee for Amount of Substance and the NMIs is huge.
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    Aquatic sciences 51 (1989), S. 108-128 
    ISSN: 1420-9055
    Keywords: Chemistry ; mountain lakes ; silica ; acidity ; sediment
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    Topics: Biology
    Notes: Abstract Alpine lakes in siliceous catchments of Tyrol and Carinthia (Austria) show signs of acidification. About 9% of the studied lakes have no alkalinity, more than 20% are below pH 6. About two thirds of all lakes have acid neutralizing capacities below 100 μeq 1−1. In spite of moderate precipitation acidity, some lakes show considerable concentrations of dissolved reactive aluminum during or shortly after snowmelt. High altitude lakes of the Alps are definitely more acidic than high mountain lakes in remote areas. Large differences in water and soil chemistry of nearby situated lakes were attributed to heterogeneities of bedrock geology. Paleolimnological investigations on former pH values of five lakes, based on diatom assemblages in the sediment, showed different developments: recent and past acidification, stable conditions, and alkalinization.
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    Astrophysics and space science 224 (1995), S. 81-84 
    ISSN: 1572-946X
    Keywords: Chemistry ; Depletions ; Shocks ; IRAS 05338-0624 ; NGC 1333 IRAS 4
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    Topics: Physics
    Notes: Abstract High resolution interferometer and single-dish observations of young, deeply embedded stellar systems reveal a complex chemistry in the circumstellar environments of low to intermediate mass stars. Depletions of gas-phase molecules, grain mantle evaporation, and shock interactions actively drive chemical processes in different regions around young stars. We present results for two systems, IRAS 05338-0624 and NGC 1333 IRAS 4, to illustrate the behavior found and to examine the physical processes at work.
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    Astrophysics and space science 216 (1994), S. 153-154 
    ISSN: 1572-946X
    Keywords: Chemistry ; Molecular Hydrogen ; Cloud Models
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    Topics: Physics
    Notes: Abstract Observations of the CO J=1-0 line are commonly used as a tracer for molecular material in clouds. The ratio of the H2 column density to the integrated intensity of this line,X, is often taken to be constant, despite theoretical and observational uncertainty. We have tried to identify how this ratio depends on cloud parameters, testing a simple theoretical argument suggesting its invariance with respect to density. The apparent constancy can be understood if clouds are clumpy on scales of Av ≈ 1-2 mag.
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    Astrophysics and space science 233 (1995), S. 125-137 
    ISSN: 1572-946X
    Keywords: Interstellar Medium ; Dark Clouds ; Chemistry ; Bistability ; C-shock Waves
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    Topics: Physics
    Notes: Abstract Shock waves perturb the chemical state of the interstellar gas. We consider the effects of C-shocks on the composition of molecular clouds, for a range of values of the pre-shock gas density and magnetic induction. The time required to re-establish equilibrium in the post-shock gas depends on the initial conditions and can become very large. The significance of the two known chemical phases of dark clouds and of bistability is considered in this context.
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    Astrophysics and space science 233 (1995), S. 161-164 
    ISSN: 1572-946X
    Keywords: Stars ; Chemistry ; Diffusion
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    Topics: Physics
    Notes: Abstract We have assessed the role of diffusion in determining chemical abundances in molecular interface regions. Chemical models have been developed which include the appropriate diffusion terms and that are appropriate to a narrow diffusion region (∼0.01pc) that may exist at the interface between a dark core and a hot, shocked T-Tauri wind. We have assumed pressure balance throughout and have calculated the chemical abundances as functions of time and position through the interface. The results show that significant enhancements of detectable molecules/transitions are expected (e.g. CO J=6→5, OH and CH). Using a realistic value of the diffusion coefficient a diffusive region of dimension 0.01pc may be established within about 104 years. In general it seems likely that diffusion processes are highly significant on these and smaller lengthscales.
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    Boundary layer meteorology 85 (1997), S. 197-222 
    ISSN: 1573-1472
    Keywords: Turbulence ; Chemistry ; Closure ; Convective boundary layer
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    Topics: Geosciences , Physics
    Notes: Abstract We study the interactions of chemistry and turbulent mixing of tracersin the convective boundary layer with a second-order closure model,including higher order chemistry terms. In order to limit the number of predictive equations we prescribe the profiles for ¯w¯Θ, ¯w¯θ ¯θ and the lengthscale l. However, for model validation we treat temperature and humidity asinert tracers, and compare the results with profiles observed during theAir Mass Transformation Experiment, and with similarity expressions for thesurface layer. We find good agreement of the mean profiles, but the (co-)variances are slightly underpredicted. Furthermore, the model usesdiagnostic equations expressing third moments of concentration in terms ofsecond moments and their vertical derivatives. They are compared withlarge-eddy model results, showing good agreement and, therefore, thesimplifications are justified. The model is applied to the transport of two gases subject to one bimolecular reaction. The importance of concentration correlations on themean transformation rate is studied. For two gases diffusing in oppositedirections we find for moderate and fast chemistry a 50% and90% decreased transformation rate due to the negatively correlatedconcentrations. These values are similar to large-eddy results of Schumannand Sykes et al. For two bottom-up tracers we find that the covariance ofboth reactive species is either positive or negative, increasing or reducingthe effective transformation rate depending on the Damköhler number (the ratio of the turbulent and the chemistry timescale). A significantdirect influence of chemistry on the flux divergence is found in bothcases. According to the model the effective transport to mid-levels of theboundary layer is increased when two reactive tracers diffuse in oppositedirections, and decreased in the case of two bottom-up tracers.
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    Earth, moon and planets 88 (2000), S. 35-58 
    ISSN: 1573-0794
    Keywords: Chemistry ; interplanetary dust particles (IDPs) ; Leonids ; meteor trails ; meteoroids ; meteors ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The cometary Leonid meteoroids represent a size range in between largest carbon-richIDPs and the smallest CI meteorites. Their dustball structure and chemistry offer anopportunity to constrain hierarchical dust accretion inferred from petrologic studies ofaggregate and cluster IDPs. The Leonid shower meteoroids of known ``comet ejection''ages provide an opportunity to study space weathering of cometary dust over periodsof up to several hundred years. The meteors and aggregate and cluster IDPs displaycontinuous thermal modification of organics and volatile element (Na, K-bearing phases), that occur as discrete minerals and amorphous solids each different response during kinetically controlled ablation. Leonid meteoroids are not excessively Na-rich. The occurrences of Leonid meteors can now be accurate predicted and combined withknowledge better models for the settling rates, collections of surviving dust becomea comet nucleus-sampling mission.
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    Journal of science education and technology 5 (1996), S. 193-201 
    ISSN: 1573-1839
    Keywords: Chemistry ; chemistry education ; multiple intelligences ; imagery ; visual-spatial thinking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Natural Sciences in General , Technology
    Notes: Abstract Chemistry has evolved from a science dominated by mathematics into a science highly dependent on spatial-visual intelligence. Yet the chemical content of introductory courses remains taught essentially the same as 40–50 years ago. Chemistry, today, is recognized by chemists as the molecular science. Yet, school chemistry is alienated from that perception. Thanks to the computer, young people are more comfortable with visual imaging than their instructors were at the same age. Thus the time is rife to reinvigorate chemistry education by means of the visual-spatial approach, an approach wholly in conformance with the way modern chemistry is thought about and practiced.
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    Pharmacy world & science 8 (1986), S. 245-251 
    ISSN: 1573-739X
    Keywords: Analysis ; Antineoplastic agents ; Biosynthesis ; Botany ; Chemistry ; Cytotoxins ; Eupatorium cannabium ; Sesquiterpenes
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A review onEupatorium cannabinum L. is given, including botany, history and constituents. The sesquiterpene lactones are discussed in more detail, covering their biosynthesis, isolation, analysis and biological activity. Special attention is paid to the cytotoxic and antitumour activities of the sesquiterpene lactones.
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    Pharmacy world & science 9 (1987), S. 305-314 
    ISSN: 1573-739X
    Keywords: Atrial natriuretic factor ; Blood pressure ; Chemistry ; Diuresis ; Homeostasis ; Kidney ; Muscle, smooth ; Natriuresis ; Receptors, endogenous compounds ; Renin-angiotensin system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is now known that cardiac atria play an important role in blood pressure and volume regulation. Mechanical distension of the atria results in the release of a potent diuretic and natriuretic agent or agents termed the atrial natriuretic factor (ANF). Several structurally related forms of ANF exist in man and it is thought that these represent precursory forms of a single optimally active molecule and/or the presence of more than one form of active ANF. The chemical structure of ANF between different mammalian species is similar. ANF receptors have been identified in kidney, brain, vascular endothelial and smooth muscle cells, tracheal and bronchial smooth muscle and the adrenal glands of many mammalian species, including man. This would suggest that ANF influences blood pressure and volume homoeostasis by affecting any one of a number of biochemical or physiological mechanisms via different target tissues. ANF is now considered a potentially valuable therapeutic agent for the treatment of hypertension and congestive heart failure. Synthesis of potent receptor antagonists could be extremely useful in the treatment of various clinical situations which are produced or complicated by endogenously produced ANF, such as chronic orthostatic hypotension.
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    Pharmacy world & science 10 (1988), S. 93-95 
    ISSN: 1573-739X
    Keywords: Anthracyclines ; Chemistry ; Drug stability ; Mitomycins
    Source: Springer Online Journal Archives 1860-2000
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    Pharmacy world & science 10 (1988), S. 101-116 
    ISSN: 1573-739X
    Keywords: Chemistry ; Chromatography ; Etoposide ; Immunoassay ; Metabolism ; Podophyllotoxin ; Pharmacokinetics ; Teniposide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Etoposide (VP 16-213) and teniposide (VM 26) are semisynthetic epipodophyllotoxin derivatives active against a variety of tumours. The clinical efficacy has led to an increasing interest in these compounds. This review presents information on the mechanism of action, biochemical pharmacology, bioanalysis, metabolism and pharmacokinetics of etoposide and teniposide.
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    Pharmacy world & science 13 (1991), S. 109-118 
    ISSN: 1573-739X
    Keywords: Chemistry ; Consumer product safety ; Drug packaging ; Environmental pollution ; Plasticizers ; Polyvinyls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this report the state of the art with respect to PVC as pharmaceutical packaging material is described. A general introduction into the applications of PVC is followed by a description of its production process. The metabolic effects of the monomer of PVC, vinyl chloride and of the most commonly used plasticizer diethylhexylphthalate are mentioned. Special attention is given to the pharmaceutical properties of plasticized PVC bags in comparison to other plastics and the environmental aspects of waste PVC disposal. Although there are emotional and political queries regarding the future use of PVC as a (pharmaceutical) packaging material, we conclude that there is no scientific justification for a total or partial ban of PVC. PVC will remain a fact of life as a cheap, versatile, high-performance and well-investigated plastic material for medical and pharmaceutical applications, to be replaced by newer plastics only for certain well-defined indications where the requirements of the plastic to be used are so specific that it will economically and technically be justified to use another polymer. Community and hospital pharmacists have to be prepared for a role in intake of waste plastic disposables, probably against deposit money, in order to fulfil the logistics needed for recycling.
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  • 34
    ISSN: 1573-739X
    Keywords: Antimalarials ; Artemisia annua L ; Artemisinin ; Biosynthesis ; Chemistry ; Clinical trials ; Pharmacology ; Phytochemistry ; Sesquiterpenes ; Toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Artemisinin, a sesquiterpene lactone endoperoxide isolated fromArtemisia annua L., and a number of its semisynthetic derivatives have shown to possess antimalarial properties. They are all eflective againstPlasmodium parasites that are resistant to the newest and commonly used antimalarial drugs. This article gives a survey of the literature dealing with artemisinin-relaled antimalarial issues that have appeared from the end of 1989 up to the beginning of 1994. A broad range of medical and pharmaceutical disciplines is covered, including phytochemical aspects like the selection of high-producing plants, analytical procedures, and plant biotechnology. Furthermore, the organic synthesis of artemisinin derivatives is discussed, as well as their mechanism of action and antimalarial activity, metabolism and pharmacokinetics, clinical studies, sideeffects and toxicology, and biological activities other than antimalarial activity.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 225-242 
    ISSN: 0886-1544
    Keywords: spermatozoa ; calcium ion transport ; motility regulation ; cholinergic agonists ; ouabain ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Behavioral responses of mature spermatozoa treated with neurotropic factors suggest that calcium entry and intracellular transport may be regulated by a cholinergic mediated program. To test the validity of this proposed mechanism, the effect of several agents on Ca distribution in the sperm cell was examined cytochemically.Sites of Ca accumulation were visualized in thin sections of bull spermatozoa by the application of a modification of Gomori's histochemical procedure for phosphatases. Intact bull sperm cells incubated at room temperature in a buffered balanced salt solution containing 5 mM/liter of CaCl2 showed small, randomly scattered deposits of the reaction product. Similarly treated sperm cells, plasmolyzed in hypoosmotic KCl, revealed a greatly increased amount of deposit associated with the cell membranes (mitochondrial surfaces and plasmalemma), the axonemal complex components, and satellite fibers adjacent to the outer dense fibers. Preincubation of intact cells in nicotine or eserine considerably enhanced the entry of calcium into the cell and its association with the membranes and other intracellular organelles. Decamethonium, an irreversible depolarizer and blocker of cholinergic receptors, interfered with the uptake and intracellular distribution of the calcium. Ouabain, the digitalis glycoside that decreases progressive motility of bull sperm and inhibits Na-, K-ATPase, appears to block Ca efflux, causing an intense accumulation of electron-opaque particles in the plasma membrane while smaller numbers of particles are distributed sparsely throughout the cell interior.The cytochemical results showing enhanced calcium entry in the presence of cholinergic agents, depressed intracellular calcium in cells treated with cholinergic receptor blocker, and intense accumulation of calcium within the cell membrane in the presence of ouabain are consistent with spermatozoan behavioral responses to these agents. These observations support the concept that neurotropic factors may be involved in regulating transmembrane and intracellular transport of ions in control of sperm cell function.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 309-315 
    ISSN: 0886-1544
    Keywords: tropomyosin ; avian muscular dystrophy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The isotype pattern of tropomyosin was investigated in normal and dystrophic avian pectroal muscle using two-dimensional gel electrophoresis. Previous reports have shown that adult pectoral muscle of chickens contains only the α-subunit of tropomyosin and a breast-type troponin-T (TN-T), whereas pectoral fetal muscle contains both α- and β-tropomyosin and leg-type TN-T. The change from the fetal to the adult forms begins shortly after hatching. It has been previously reported that avian dystrophic pectoral muscle contains both the leg- and breast-type TN-T; we show that in avian dystrophic muscle there is also persistent expression of the β-subunit of tropomyosin.
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    Cell Motility and the Cytoskeleton 2 (1982) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 2 (1982), S. 287-308 
    ISSN: 0886-1544
    Keywords: actin-binding protein ; Dictyostelium ; cytoskeleton ; amoeboid movement ; calcium ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A protein from Dictyostelium discoideum with an apparent subunit molecular weight of 95,000 daltons (95K protein) was previously identified as an actin-binding protein ‘Hellewell and Taylor, 1979’. In this paper, we present a method for purifying the protein, and characterize some important aspects of its structure and function. Purification of the 95K protein is achieved by fractionation with ammonium sulfate followed by chromatography on DEAE-cellulose, gel filtration on 6% agarose, and final purification on hydroxyapatite. The 95K protein is a dimer, composed of apparently identical subunits. It is a rod-shaped molecule, 38 nm in length, with a Stokes radius of 74 Å. In these structural properties, the 95K protein is similar to muscle and nonmuscle α-actinins. The 95K protein and filamin are equally competent, when compared on a weight basis, to enhance the apparent viscosity of actin as determined by falling ball viscometry. The apparent viscosity of mixtures of the 95K protein and actin is dramatically reduced at pH greater than 7.0 or free ‘Ca2+’ greater than 10-7 M. We also examine the mechanism by which calcium regulates the interaction of the 95K protein and actin. A change in free ‘Ca2+’ induces no detectable change in the quaternary structure of the 95K protein. Our experiments indicate that the 95K protein does not dramatically alter the length distribution of actin filaments in the presence of micromolar free ‘Ca2+’. A large fraction of the 95K protein cosediments with actin in the presence of low free ‘Ca2+’ (ca. 3 × 10-8M), but not in the presence of high free ‘Ca2+’ (ca. 4 × 10-6M). We conclude that increased free ‘Ca2+’ inhibits gelation of actin by the 95K protein by reducing the affinity of the 95K protein for actin. We propose that 95K protein is an important component of the cytoskeletal/contractile system in D. discoideum amoebae.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 343-354 
    ISSN: 0886-1544
    Keywords: NBD-phallacidin ; actin ; ocular tissues ; wound repair ; stress fibers ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fluorescent derivative of the actin-binding toxin phallacidin, 7-nitrobenz-2-oxa-1,3 diazole phallacidin, has been used to cytologically demonstrate the presence of actin in lens epithelium, corneal endothelium, and retinal pigment epithelium. In these noninjured tissues, no stress fibers are observed and fluorescence is confined mainly to an area at or near the cell membrane, although some diffuse cytoplasmic staining can also be seen. However, following injury to either the lens epithelium or corneal endothelium of rats and frogs, stress fibers are detected, but only in those cells that migrate into the wound area. Cells on the periphery of each tissue do not partake in would repair and thus maintain their normal appearance. After the tissue has regenerated, stress fibers disappear, and those cells involved in the injury response return to their normal morphology.When rabbit corneal endothelium is placed in tissue culture, stress fibers are observed as the cells migrate away from the initial explant. Upon reaching confluency, these cells spread out and each is surrounded by thick actin-containing bands. Furthermore, they exhibit some stress cables within their cytoplasm. This is in contrast to their appearance in vivo where stress fibers are absent and fluorescence is limited to a region near the cell membrane.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 369-383 
    ISSN: 0886-1544
    Keywords: motility ; flagella ; cilia ; microtubules ; Gregarines ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The male gametes of the parasitic protozoan, Lecudina tuzetae, have a motile flagellum with a “6 + O” ultrastructure ‘Schrével and Besse, 1975’. These gametes were isolated from the cysts in which they develop and were observed and photographed under a variety of conditions. The flagella beat continuously, without stopping and starting, with a beat period of about 2 sec. They can beat in solutions whose viscosities are greater than 0.5 Nsm-2 (l Nsm-2 = 103 cP). The waveform can be approximated by a series of helical arcs and interconnecting straight regions that travel from the base to the tip. The helical regions have a radius of curvature of 3.2 μm and subtend a final angle of 1.7 radians. The straight portions are 2.0 μm in length. There are two sets of opposing bends, but they do not originate in the same plane. The resulting waveform is an approximately helical coil, with a pitch of 9.8 μm, a pitch angle of 0.6 radian and a peak-to-peak amplitude of 2.3 μm. The sense of the coil is left handed. The axoneme twists during beating. The main differences between the movement of this flagellum and that of typical 9 + 2 flagella are a low beat frequency and three-dimensional bends that produce relatively little forward movement of the cell. Twisting is discussed as a means of discriminating between some types of models of flagellar motility.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 429-443 
    ISSN: 0886-1544
    Keywords: 21S dynein ; tubulin ; binding stoichiometry ; ATP sensitivity ; binding cooperativity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The binding properties of Tetrahymena 21S dynein to doublet A and B subfiber microtubules were analyzed by both a turbidimetric assay (Δ A350 nm) and electron microscopy. KCl-extracted, sucrose-gradient, purified 21S dynein binds to each of the two kinds of axonemal microtubules in both ATP-insensitive and ATP-sensitive modes, even though only a single type of binding occurs to each of the subfibers in situ. Total dynein bound to axonemal microtubules is a composite of binding that is sensitive to dissociation by ATP and binding that is insensitive to ATP. Each exhibits a different binding profile. Total binding exhibits a sigmoid profile (h = 1.93) and saturates at 1.49 mg D/mg T. ATP-sensitive binding likewise exhibits a sigmoid profile (h = 2.66) but saturates at 1.06 mg D/mg T. Binding occurs with a similar affinity for both A and B subfibers. The Hill coefficient (h) for ATP-sensitive binding implies positive cooperativity between binding events. ATP-insensitive binding was studied independently in 20 μM ATP, 10 μM vanadate, which blocks ATP-sensitive binding. ATP-insensitive binding exhibits a hyperbolic profile (h = 1.0) and likewise occurs along each of the two kinds of axonemal tubules. Binding saturates at 0.87 mg D/mg T. The binding data suggest that the tubulin dimer has conserved both ATP-sensitive and ATP-insensitive binding sites for 21S dynein, even though the sites may not be expressed in vivo.
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    Cell Motility and the Cytoskeleton 2 (1982), S. i 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 43
    ISSN: 0886-1544
    Keywords: flagella ; cilia ; trachea ; microtubules ; crowns ; microtubule assembly ; caps ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distal tips of the central pair and A-microtubules are capped in mammalian and avian tracheal cilia. The capping structures are similar to those found in protozoan cilia and flagella [Dentler, 1981], and consist of a central microtubule cap that links the central microtubules to the membrane or to the ciliary crown and A-microtubule plugs that insert into the lumen of each of the A-microtubule plugs is bound to the central microtubule cap by distal filaments. The ends of the central and outer doublet microtubules are tightly bound to the cap in both intact and in demembranated and reactivated tracheal cilia. Analysis of the displacement of the microtubule tips in cilia fixed at various bend angles revealed that the displacements of A-microtubules are only partially in agreement with those predicted by the sliding filament model [Satir, 1968]. These results are discussed with respect to the regulation of microtubule sliding in capped cilia and the role of the microtubule capping structures in microtubule assembly.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 19-24 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Cell Motility and the Cytoskeleton 1 (1981), S. 329-347 
    ISSN: 0886-1544
    Keywords: actin ; microfilaments ; heavy meromyosin ; mammary gland ; secretion ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytochalasin B, a microfilament-altering drug, inhibits lactose synthesis in lactating guinea pig mammary gland [Biochim. Biophys. Acta 392:20, 1975] but not primarily by inhibiting glucose transport [Eur. J. Cell Biol. 20:150, 1979]. In order to study the possible role of microfilaments in lactose synthesis and secretion, we isolated both the alveolar (milk-secreting) and myoepithelial (contractile) cells from lactating mammary gland. Light microscopy shows that the alveolar cell fraction (viability approximately 71%) is homogenous and that the cells retain strong polarity of secretory structures in the apical region. Two proteins were extracted from the alveolar cell fraction. One (mol wt 42,000) comigrates with skeletal muscle actin on SDS-PAGE gels. The other, a high-molecular-weight (180,000) protein (HMWP) may be analogous to actin-binding protein or clathrin. An extract from the myoepithelial cell fraction also contains a protein that comigrates with actin but no HMWP. Whole tissue extract contains the 42K protein, and a 185K HMWP. Examination of the alveolar cell extract by electron microscopic (EM) negative staining revealed meshworks of multistranded, interconnecting filaments, with attached globular structures (100-200 A) (possibly the HMWP) and single filaments (40-60 A diameter) branching off. To localize these filamentous structures in situ, whole tissue was glycerinated and incubated with rabbit skeletal muscle heavy meromyosin (HMM). Masses of filaments in myoepithelial cells served as convenient standards for HMM decoration. Decorated filaments have cross-arms or projections, unlike the narrow, smooth filaments of control tissue. Decorated filaments in alveolar cells are located beneath the plasma membrane, in close association with secretory vacuoles, and near the Golgi apparatus; filaments near the latter two are often oriented perpendicular to the plasma membrane. Microvesicles are embedded in meshworks under the plasmalemma and near the Golgi apparatus. Intermediate-sized (85-115 A diameter), non-decorated filaments diverge from the meshworks of decorated filaments. Microvesicles are associated with intermediate-sized filaments as well. The association of actin-like filaments with secretory vacuoles and microvesicles and their location in areas of the cell concerned with biosynthetic activities suggest a possible function in the intracellular transport of secretory products.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 165-168 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 2 (1982), S. 199-204 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 2 (1982), S. 71-75 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 3 (1983), S. 93-103 
    ISSN: 0886-1544
    Keywords: bacterial motility ; flagella ; sheathed flagella ; complex flagella ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Although bacterial flagellar sheaths were observed over 30 years ago, they may still be characterized as structures in search of a function. In addition to true sheaths, bacterial flagella may possess other adornments that cause an increase in the organelle's cross-sectional diameter. These “complex flagella” are sharply differentiated from sheathed flagella. Immunological and chemical distinctions have been found between flagellar sheaths, flagellar cores, and LPS layers inferred to be the sheath sensu stricto. Although complex flagella may serve as specific receptors for flagellotropic phages or in allowing for more efficient swimming in viscous environments, similar functions have not yet been attributed to true sheaths. It is postulated that flagellar sheaths may allow for specific interaction between a bacterium and a surface. In addition, there is a problem as to the relationship between a rapidly rotating flagellum and the sheath.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 113-121 
    ISSN: 0886-1544
    Keywords: coelomocytes ; filopodia ; whole cell translocation ; video microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have utilized a video-enhanced contrast system coupled to a DIC-equipped microscope to examine the motility of both whole coelomocytes and individual filopodia. When the cells are left in diluted coelomic fluid, they exhibit a fibroblast-like mode of translocation across the substrate. These cells extend lamellipodia at their advancing margin and develop retraction fibers at the trailing edge. Filopodia are actively extended from the lamellipodia of the advancing margin. Cells that are washed free of the coelomic fluid and placed in an isotonic buffer lose their ability to translocate. Filopodia on these stationary cells are seen to undergo a series of waving and bending motions. These motions are rapid and result in a filopodium folding back upon itself only to reextend later. Both forms of motility are discussed in light of the existing structural and biochemical knowledge of this and other cell types.
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    Cell Motility and the Cytoskeleton 1 (1981), S. 387-397 
    ISSN: 0886-1544
    Keywords: birefringence ; polarizing microscope ; sea urchin egg ; cortex ; mitosis ; cleavage ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Birefringence (BR) at the cell surface of fertilized eggs of the sand-dollar, Clypeaster japonicus, during mitosis and cleavage was determined with a photoelectric BR detection apparatus [Hiramoto et al, 1981a]. The cortex of about 2 μm thickness is birefringent positive with respect to the normal to the cell surface. The hyaline layer is negatively birefringent. The halo-layer consisting of a row of microvilli surrounding the egg is positively birefringent in normal Ca-free sea water, while it is negatively birefringent in Ca-free sea water with high refractive index. The BR of the cortex gradually increases over the entire surface during mitosis until the onset of cleavage. The BR of the cortex at the polar region reaches a maximum shortly after the onset of cleavage and then decreases, while the BR of the cortex at the equatorial region begins to decrease shortly before the onset of cleavage, reaches a minimum shortly after the cleavage starts, and then increases again as the cleavage furrow advances. The coefficient of birefringence of the cortex is about 2.5 × 10-5 at the maximum. The BR change of the cortex during mitosis and cleavage is interpreted as a passive deformation caused by the constriction of the contractile ring as well as an active structural change of the cortex occurring in the dividing cell.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 213-226 
    ISSN: 0886-1544
    Keywords: microtubules ; fertilization ; cell division ; sea urchin ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The microtubule-containing structures that appear in eggs during fertilization and cell division in the sea urchins Lytechinus variegatus and Arbacia punctulata were detected by antitubulin immunofluorescence microscopy of detergent extracted cytoskeletal preparations. The extraction buffer, which is composed of 0.55 mM MgCl2, 10 mM EGTA, 25 mM MES, 25% glycerol, 1% Nonidet P-40, and 25 μM PMSF, pH 6.7, allows for dramatically improved fluorescent images compared to those obtained using conventional staining procedures, with residual background staining being reduced to near zero.The immunofluorescent images obtained using this technique provide information on several motile events that occur during the first cell cycle. This technique demonstrates that all of the cytoplasmic microtubules are associated with the incorporated sperm's centrioles during female pronuclear migration. This changes during the centration of the male and female pronuclei at which time a monastral array of microtubules forms in the egg's cytoplasm. A large proportion of the monastral microtubules do not appear to be associated with the centrioles. At prophase and early metaphase, the centrioles are the dominant microtubule organizing centers (MTOCs) consistent with mitotic theories that the kinetochore catches, but does not initiate, microtubules. Observations of intercentriolar distances show that there are three stages of pole separation during the first cell cycle. The initial separation occurs during pronuclear centration, the second during the streak stage, and the final one during the late stages of mitosis. At telophase, polar microtubules appear to extend into the cortex supporting the cell surface at all regions except the presumptive cleavage site.
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    Cell Motility and the Cytoskeleton 3 (1983) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 3 (1983), S. 273-280 
    ISSN: 0886-1544
    Keywords: Chlamydomonas flagellar collars ; Chlamydomonas cell wall ; mating in Chlamydomonas ; cell wall proteins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The flagella of Chlamydomonas reinhardtii protrude through the cell wall via short, tunnel-like openings that are lined with 11 nm × 500 nm fibers arranged in parallel array. These cylindrical collections of fibers presumably permit free movement of the flagella within the cell wall. In this report electron-microscopic evidence is presented showing that during the initial stages of the mating reaction intact collars slip off of the ends of the flagella when cell wall loss occurs. Electrophoretic analysis of isolated collars reveals one major protein and several minor species.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 333-347 
    ISSN: 0886-1544
    Keywords: Caenorhabditis elegans spermatozoa ; cell motility ; electron microscopy ; cell-substrate contact ; 2-nm filaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The locomotion of C. elegans spermatozoa resembles, in many respects, the crawling movements of other eukaryotic cells. However, these sperm contain surprising little actin, which plays no apparent role in this cell's motility. Electron microscopy has revealed that crawling spermatozoa retain a strict morphological polarity so that the organelle-filled cell body is separated from the pseudopod by an array of cytoplasmic laminar membranes. When sperm crawl only the pseudopod contacts the substrate; the cell body is either pulled behind or carried on top of the rear portion of the pseudopod. Fingerlike projections which extend forward from the leading edge of the pseudopod initiate contact with the substrate. The underside of the pseudopod exhibits areas of close (40 nm separation) membrane-substrate association with intervening areas of wide (up to 300 nm) membrane-substrate gaps. The pseudopod cytoplasm contains 2-nm filaments but no filamentous actin has been observed. These 2-nm filaments were detected in thin sections of crawling cells and in negative-stained remnants of spermatozoa disrupted by either hypotonic buffer on Triton X-100. The filaments are found both free in the cytoplasm and closely associated with the cytoplasmic face of the plasma membrane and are usually oriented along the long axis of the cell. Neither the identity nor the function of these filaments has been established although their location and orientation suggest that they may be involved in generating propulsion.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 349-361 
    ISSN: 0886-1544
    Keywords: myosin phosphorylation ; actin polymerization ; chemotactic factors ; leukocytes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Changes in the state of polymerization of actin and phosphorylation of myosin have been observed in polymorphonuclear leukocytes (PMNs) soon after the addition of the chemotactic peptide N-formylnorleucylleucylphenylalanine. At a time when the cells are observed to extend many ruffles or lamellipodia from their surface, the fraction of the cellular actin present in a monomeric form is decreased by about 25% as assayed by the ability of the G-actin to inhibit DNAase. These changes are temporally correlated with an increase in the staining by nitrobenzooxadiazole (NBD)-phallacidin, a probe that binds F-actin selectively. The NBD-phallacidin staining is observed in the surface ruffles. When the peptide concentration is decreased by addition of a tenfold excess of buffer, cells withdraw their surface ruffles and form blebs. These changes correlate with an increase in the G-actin levels detected with the DNAase inhibition assay. An increase in phosphorylation of the 20,000-dalton light chain of myosin is also observed in leukocytes stimulated by addition of chemotactic peptide. These observations of changes in cytoskeletal proteins of PMNs provide a beginning for further studies on the regulation of cell motility by chemotactic factors.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 391-397 
    ISSN: 0886-1544
    Keywords: focal contacts ; microfilaments ; microinjection ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The role of structural elements in the organization and maintenance of focal contacts was studied by microinjecting into tissue culture cells specific probes which interfere with filamentous actin or with vinculin: actin interaction. Injection of actin capping proteins from Physarum and brain resulted in breakdown of microfilament bundles starting at their distal ends and in loss of focal contacts. This process was fully reversible. Injection of a high affinity antibody against chicken gizzard vinculin led to partial breakdown of microfilament bundles concomitant with disruption of focal contacts with vinculin remaining at the plasma membrane. This process was irreversible.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 431-438 
    ISSN: 0886-1544
    Keywords: myotendinous junction ; laminin ; type IV collagen ; heparan sulfate proteoglycan ; alpha actinin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The muscle-tendon junction of murine skeletal muscles has been analyzed by a variety of extraction techniques, by myosin subfragment-1 binding experiments, and by ultrastructural immunocytochemistry. The results indicate that the muscle-tendon junction is composed of four distinct domains: an intracellular domain, the internal lamina; a domain connecting the internal lamina with the lamina densa of the external lamina, the connecting domain; the lamina densa; and a domain which attaches the lamina densa to the collagen fibers, the matrix. Each of these domains is distinct with respect to position, three-dimensional organization, and molecular composition, and is therefore considered to have a unique role in the transmission of contractile force.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 463-483 
    ISSN: 0886-1544
    Keywords: intracellular matrix ; extracellular matrix ; covalently cross-linked matrix ; ε-(γ-glutamic) lysine bonds ; skeletal muscle ; titin ; covalently cross-linked collagen ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When skeletal, cardiac, and smooth muscle is exhaustively extracted with a protein-unfolding reagent such as 6 M guanidine HCl and a disulfide-reducing reagent such as 5% β-mercaptoethanol, a tissue ghost remains intact and retains the characteristic shape and dimensions of the tissue before extraction. In the case of chicken pectoral muscle, the tissue ghost contains 1% of the original muscle proteins. Guanidine HCl extraction followed by collagenase treatment of glycerol-extracted chicken pectoral muscle releases a clean preparation of elongated structures containing 0.2% of the original protein and representing the covalently cross-linked remnants of the muscle fibers. The material of these muscle fiber ghosts extends throughout the interior of the cell. Antibodies raised against the tissue ghosts of smooth muscle cross-react with glycerol extracted skeletal myofibrils, forming a banding pattern which coincides with the banding pattern observed when myofibrils are reacted with antibodies against titin. Titin, a large and soluble protein found in skeletal muscle, cross-reacts with our antigizzard antibody. However, amino acid analysis of the muscle fiber ghosts indicates that titin cannot be the only subunit of the insoluble polymer, but that one or more proteins with a very high glycine and alanine content and a very low basic and acidic amino acid content must also form part of the covalently cross-linked matrix. The possibility is presented that this matrix may be the basis of the superthin 2-3-nm filaments which have been observed in a variety of cell types.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 513-524 
    ISSN: 0886-1544
    Keywords: fertilization ; actin ; microfilaments ; sea urchin ; cell division ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The sea urchin egg at fertilization is an ideal model in which to study actin-mediated surface activity. Electron microscopy of unfertilized eggs demonstrates the presence of thousands of well-arrayed short microvilli, which appear supported by cytochalasin-sensitive actin oligomers as detected with rhodamine-labeled phalloidin staining of permeabilized eggs. At insemination, the previously short microvilli elongate and cluster around the successful sperm during incorporation. Phalloidin staining demonstrates a tremendous recruitement of polymerized actin into the site of sperm incorporation, resulting in the formation of the fertilization cone. Fertilization of cytochalasin-treated eggs results in the normal activation of the metabolic and bioeletric events, but sperm incorporation does not occur since the localized actin assembly required for fertilization cone formation is precluded. After sperm incorporation, the entire fertilized surface is restructured, as a result of a massive polymerization of actin to produce a burst in microvillar elongation. Addition of cytochalasin to eggs immediately following sperm incorporation demonstrates the recruitment of actin assembly for the proper progression through the first cell cycle. During normal cell divison, the egg surface retains the long microvilli. The furrow which forms at cytokinesis does not appear as a unique new structure, but rather as a reorganization of the cortical microfilaments. Quantitative fluorescence microscopy argues against an increase in microfilaments during early cytokinesis. At the latest stages of cytokinesis, a thickening of the cortical actin is noted, which could possibly be interpreted as a contractile ring. A minor basal level of actin assembly with numerous nucleation sites in unfertilized eggs and a tremendous but localized assembly of microfilaments surrounding the sperm during incorporation, followed by a massive global microfilament assembly event to elongate the fertilized egg microvilli resulting later in the reorganization of these microfilaments to produce the forces necessary for cytokinesis, highlight the utility of the study of sea urchin eggs at fertilization for understanding actin-membrane interactions.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 553-565 
    ISSN: 0886-1544
    Keywords: microfilaments ; cytoskeleton ; simian virus 40 ; cell adhesion ; cell surface ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to assess the role of cytoskeletal structure in modulating cell surface topography during cell transformation, cytoskeletal organization of 3T3 mouse cells transformed with a tsA mutant of simian virus 40 (SV40) was studied in detail by correlative light and electron microscopy. Detergent-extracted, criticalpoint dried whole cells observed in the electron microscope were seen to contain well-organized microfilament bundles (stress fibers) traversing the longitudinal axis of cells grown at the restrictive temperature (39°C). When grown at the permissive temperature (32°C), cells prepared in this manner were not observed to contain such structures. However, when semithin sections (0.5 μm) were viewed by transmission electron microscopy at 120 kV, short microfilament bundles were seen in 32°C-grown cells. There was an alteration in the morphology of these structures at sites of attachment to the substratum (focal contacts), and they were shorter in length than microfilament bundles of 39°C-grown cells. A difference was also observed between the two phenotypes in the layer of microfilaments associated with the dorsal cell surface. Since it is this layer that directly determines cell surface architecture, it is proposed that changes in microfilament bundle-generated surface tension are responsible for alterations of this layer, leading to an altered cell surface morphology. Tension may be modified by disturbances in focal contacts (or adjacent regions) or altered actin-associated protein(s).
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    Cell Motility and the Cytoskeleton 3 (1983), S. 609-622 
    ISSN: 0886-1544
    Keywords: erythrocyte membrane ; surface elastic shear modulus ; membrane viscosity ; hereditary disorders of blood ; membrane yield ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Measurements of the mechanical properties of the erythrocyte membrane provide a direct assessment of the proper function of its structural components. To assess the effects of alterations in molecular structure on membrane mechanical properties, measurements have been performed on cells from six individuals whose membranes contain inherited, biochemically characterized structural defects. Because the contribution of the memmbrane skeleton to the mechanical behavior of the membrane is most evident in shear deformation, mechanical experiments were performed to measure the material constants which characterize the response of the membrane to shear force resultants. The surface elastic shear modulus characterizes the elastic response of the membrane; the yield shear resultant is the maximum shear force resultant which the membrane can support elastically; and the plastic viscosity coefficient characterizes the rate of membrane deformation when the elastic limit has been exceeded.Generally, it was found that when the molecular defect is found to occur in a region of the skeleton which is stress-supporting, the maximum elastic strength of the membrane is reduced. However, the magnitude of the reduction can be quite different for membranes having similar or even identical defects. In some cases the differences can be attributed to the removal of the most fragile cells of the population by the spleen, but other results indicate that the biochemical description of the defects may be incomplete. These results emphasize the need for further refinements both in the biochemical characterization of membrane skeleton structure and in the description and measurement of membrane mechanical properties.
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    Cell Motility and the Cytoskeleton 4 (1984), S. 129-135 
    ISSN: 0886-1544
    Keywords: amoeboid motion ; chemoattractants ; chemotaxis ; Dictyostelium ; filopodia ; folic acid ; pterins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Living vegetative D. discoideum amoebae were studied to determine whether their filopodia respond to folic acid, a chemoattractant for these cells. Exponentially growing amoebae (ca. 10 μm diameter) exhibit 5-30 μm long filopodia; at stationary phase, aggregation competent amoebae have numerous multibranched filopodia up to 100 μm long. Folic acid was observed to stimulate production, elongation, and branching of filopodia with its effects progressively changing as the amoebae approach aggregation. Filopodial construction was also found to be dependent upon Mg2+ levels. The significance of these results is discussed with respect to progressive changes within the vegetative phase as well as to the mechanisms of amoeboid movement, pseudopodial activity, and chemotaxis.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 649-655 
    ISSN: 0886-1544
    Keywords: axonal transport ; lymphocyte capping ; spectrin ; fodrin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fodrin is an actin/calmodulin-binding protein with similarities to spectrin (erythrocytes) and TW 260/240 (brush border). It is concentrated beneath the plasma membranes of neurons and other cells. We have observed translocations of fodrin in both neurons and lymphocytes. Newly synthesized, radiolabeled fodrin moves down axons at a maximum velocity (about 50 mm/day) that is slower than the most rapidly axonally transported proteins (group I). A portion of fodrin appears to move more slowly at velocities (1-10 mm/day) resembling those of actin and myosin (group IV) and tubulin and neurofilament proteins (group V). In lymphocytes, when certain surface antigens are induced by cross-linking agents to migrate to one pole of the cell and form a cap, fodrin redistributes beneath the membrane and forms a subcap. The movements of fodrin in lympohocyte capping and in the axonal transport of group IV polypeptides have certain similarities. In both cases, the redistribution of fodrin is accompanied by concomitant redistributions of actin, myosin, and calmodulin, and both processes proceed at similar velocities. We consider the possibilities that these two processes are related, both being driven by a submembrane force-generating system comprising in part actin, myosin, and fodrin, and that fodrin serves to link various organelles or proteins to this system.
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    Cell Motility and the Cytoskeleton 4 (1984), S. 1-5 
    ISSN: 0886-1544
    Keywords: motility ; power output ; muscle ; flagella ; cytokinetic furrow ; mitotic spindle ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cellular motile systems as diverse as muscle and the mitotic spindle have been compared by their specific power output: the maximum power they develop per unit of engine volume. Striated muscles and flagella have high specific output; their performance is comparable to that of typical automobile engines. The cytokinetic furrow and the mitotic spindle have very much lower specific power output. The furrow's output is 7,000 times lower than muscle and the spindle's is 300,000 times lower. Different macromolecules have been used to generate power in systems with similar output (muscles and flagella) and, conversely, the same macromolecular motor has been used in systems with very different output (muscles and cytokinetic furrows). The common feature amid this diversity is adaptation to a particular biological role, which specific power output reflects very well. High values are found where a powerful, compact engine should be advantageous, while low values are found where precision, not power, matters most.
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    Cell Motility and the Cytoskeleton 4 (1984), S. 76-76 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 2 (1982), S. 73-82 
    ISSN: 0886-1544
    Keywords: desmids ; videomicrography ; photokinesis ; photophobic response ; photophosphorylation ; photosynthesis ; phototaxis ; uncouplers ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of the uncouplers CCCP and DNP on photokinesis, phototaxis, and the photophobic response in the desmid Cosmarium have been studied both in population systems and by videomicrographic, single-cell analysis. Light-dependent motility is specifically inhibited by both uncouplers, indicating that photokinesis is driven by photophosphorylation. In population experiments, phototaxis and accumulations in light traps due to photophobic responses are inhibited by drug concentrations comparable to those that inhibit photokinesis. Analysis of single-cell behavior demonstrated, however, that neither photophobic responses elicited by an increase in light intensity (step-up response) nor by a decrease (stepdown response) are inhibited, as long as the reduced motility allows the organisms to cross a light--dark border. Phototactic orientation is not impaired by DNP in the single cell analysis, but CCCP significantly reduced the degree of orientation. The results indicate that, although chlorophyll is the photoreceptor for all three photoresponses, at least the photophobic response is independent of both the photosynthetic electron transport chain and photophosphorylation.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 91-92 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 2 (1982) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 2 (1982), S. 93-101 
    ISSN: 0886-1544
    Keywords: cell motility ; singlet microtubules ; dynein ; coccid insect ; aflagellate spermatozoa ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this report we demonstrate that in the coccid insects Pseudococcus, Phenacoccus, and Planococcus the whole spermatozoon is made up by a nuclear central core surrounded by two complete and one incomplete turns of concentric microtubule palisades. Microtubules of the outer row are linked by a system of short projections 6 nm long; those of the inner row are linked to each other by similar arms; a second system of 6 nm arms links the tubules of each inner row to those of the respective outer row. All these systems of arms are longitudinally spaced every ∼ 12 nm. The motility of this spermatozoon is due to waves progressing from the posterior extremity to the anterior one. By SDS polyacrylamide gel electrophoresis a group of high molecular weight polypeptides is detected, one of which migrates in coincidence with the A dynein band from sea urchin sperm. Our data suggest that occurrence in coccid spermatozoon of a motility due to singlet tubules-dynein interaction.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 103-113 
    ISSN: 0886-1544
    Keywords: actin ; cleavage ; fluorescein-labeled phalloidin ; microinjection ; phalloidin ; sand dollar eggs ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Effects of microinjection of phalloidin on fertilization and cleavage of sand dollar (Clypeaster japonicus and Scaphechinus mirabilis) eggs were studied. The drug, previously injected into unfertilized eggs, showed no effect on the elevation of the fertilization membrane upon insemination up to an intracellular concentration of 50 μM. However, the movement of the egg pronucleus to the sperm pronucleus was inhibited and the fusion of pronuclei did not occur. The subsequent development no longer took place. When phalloidin was injected into fertilized eggs, the thickness of the cortical layer increased and the microvilli became conspicuous. Both nuclear division and cleavage were inhibited at the intracellular concentration of more than 20 μM, though the latter seemed to be more sensitive to phalloidin than the former.Fluorescein-labeled phalloidin (FL-phalloidin) was injected into eggs in order to investigate F-actin localization by fluorescence microscopy. In both unfertilized and fertilized eggs, FL-phalloidin was localized in the cortical layer within 1 min after injection. It was also localized in the cortical layer as radially oriented rodlike structures when injected into fertilized eggs before the disappearance of the nuclear membrane. No distinct fluorescence was detected in the mitotic apparatus or in the cleavage furrow. FL-phalloidin redistributed gradually into egg cytoplasm. In unfertilized eggs, fluorescent rods were found especially in the egg pronucleus 30 min after injection.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 131-147 
    ISSN: 0886-1544
    Keywords: higher land plant contractile system ; actin activation of myosin ; S-1 decoration of actin ; polymerization of actin ; calcium sensitivity of actomyosin interaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This paper describes the initial isolation of actin- and myosin-like proteins from the cytoplasm of the endocarp tissue cells of the fruit of the tomato, Lycopersicon esculentum. Low ionic strength buffers extracted the 42,000 molecular weight tomato actin in the depolymerized form. Tomato actin can be polymerized in 0.1 M KCl, 2 mM MgCl2 to form 6 nm diameter filaments resembling rabbit skeletal muscle F-actin in their ultrastructure and pattern of decoration with rabbit myosin subfragment-1 (S-1). Tomato F-actin activates the low ionic strength Mg2+ ATPase of rabbit S-1 up to ten-fold. High ionic strength extracts of tomato yield a myosinlike enzyme whose ATPase activity in 0.5 M KCl is maximal in the presence of K+-EDTA and is repressed in the presence of Mg2+. The column-purified enzyme forms a complex with rabbit F-actin, which can be dissociated by Mg2+ ATP. The low ionic strength Mg2+ ATPase of tomato myosin can be activated ten-fold by rabbit actin and up to nineteen-fold by tomato actin. No activation of the tomato myosin by rabbit F-actin occurs in the absence of free calcium ions.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 149-161 
    ISSN: 0886-1544
    Keywords: cell locomotion ; gastrulation ; contact paralysis ; collagen substratum ; serum factors ; morphogenetic movements ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Prospective mesodermal cells of Xenopus laevis gastrulae showed substantial locomotion in vitro, averaging 4.3 μM/min, when dissociated and cultured on a glass surface coated with collagen and fetal bovine serum. The cell translocate by making lamellipodia and filopodia whereas the main cell body remains rounded. When two mesodermal cells made contact with each other, they showed contact paralysis of lamellipodial activity. In contrast, when mesodermal cells contact ectodermal cells, contact paralysis does not occur. Rather, migrating mesodermal cells continue to translocate. The locomotion in vitro appears to mimic that in vivo during gastrulation, because of the similarities of the rate of movement and the cell shape in culture and in embryos. Neither prospective ectodermal cells from gastrulae nor prospective mesodermal cells from blastulae showed locomotion under the same culture conditions.
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    Cell Motility and the Cytoskeleton 5 (1985), S. 251-263 
    ISSN: 0886-1544
    Keywords: Chlamydomonas ; movement ; flagellar beat ; stigma ; high-speed microcinematography ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using high-speed microcinematography (100-500 f/s) the movement of Chlamydomonas reinhardtii mutant 622 E has been studied with frame-by-frame analysis. The stigma lies in the cell equator, displaced out of the flagellar plane anticlockwise by an angle of about 45°. During forward movement the cells rotate anticlockwise about their long axis with a frequency of 1.4-2 Hz (maximum 2.5 Hz). The rotation is caused by a lateral component of 3-dimensional beating of the flagella during the effective strokes. The helical swimming path is a result of an unequal flagellar beating. This is normally synchronous, but synchrony is interrupted from time to time by an additional beat of the outward directed flagellum, in our study one after about every twenty beats on average. These results are discussed and compared with the results published by other groups.
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    Cell Motility and the Cytoskeleton 5 (1985) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 5 (1985), S. 377-392 
    ISSN: 0886-1544
    Keywords: newt ; lung ; cilia ; beat frequency ; waveform ; models ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Highly coupled newt lung ciliated cell models were used to study the effects of MgATP concentration on ciliary beat frequency and waveform. Models were prepared from ciliated lung cells of the newt Taricha granulosa by trypsin dissociation of the epithelium, demembranation with Triton X-100, and reactivation with MgATP, as described previously [Weaver and Hard, 1985]. Beat frequencies were measured stroboscopically. Ciliary waveforms of reactivated models and intact mucociliary epithelial sheets were determined by single frame analysis of high-speed movies. Waveform parameters calculated included the durations of the effective and recovery strokes, the angular velocities of the ciliary base and tip, the position of the bend along the ciliary shaft during the recovery stroke, the velocity of recovery stroke bend propagation, and the ratio of the duration of recovery stroke bend propagation to the duration of the recovery stroke itself. We found that beat frequency varied biphasically in response to MgATP at 21°C, as shown previously for isolated, individual, newt lung axonemes. Apparent Fmax (maximum beat frequency) and Km values of 25 Hz and 0.14 mM, and 35 Hz and 0.47 mM, respectively, were obtained for each linear segment of the biphasic double reciprocal plot. Demembranation did not alter either ciliary waveform or the pattern of coordination. In this system, metachrony is antilaeoplectic and ciliary waveform appears to be regulated independent of beat frequency.
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    Cell Motility and the Cytoskeleton 5 (1985), S. 507-527 
    ISSN: 0886-1544
    Keywords: axonal transport ; microtubules ; organelles ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A model for fast axonal transport is developed in which the essential features are that organelles may interact with mechanochemical cross-bridges that in turn interact with microtubules, forming an organelle-engine-microtubule complex which is transported along the microtubules. Computer analysis of the equations derived to describe such a system show that most of the experimental observations on fast axonal transport can be simulated by the model, indicating that the model is useful for the interpretation and design of experiments aimed at clarifying the mechanism of fast axonal transport.
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    Cell Motility and the Cytoskeleton 6 (1986), S. 1-1 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 6 (1986), S. 25-34 
    ISSN: 0886-1544
    Keywords: respiratory cilia ; dynein ; ATPases ; porcine trachea ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Milligram amounts of mammalian ciliary axonemes were isolated from porcine tracheas. These were reactivated upon addition of ATP, indicating intact functional capability with a mean beat frequency at 37°C of 8.2 Hz. Electron microscopy showed typical ultrastructure of the isolated demembranated axonemes. Electrophoresis into polyacrylamide gradient gels containing sodium dodecyl sulfate revealed reproducible protein profiles from ten different tracheal preparations. Four major protein bands were observed in the 300-330 K molecular weight region, as well as tubulin at 51-54K. Extraction of the isolated tracheal axonemes with 0.6M KCl removed the outer dynein arms seen in electron microscopic cross-section of axonemes, preferentially solubilized two of the high molecular weight proteins at 320 and 330 K, and resulted in a three- to four-fold increase in ATPase specific activity. Sedimentation of the dialyzed salt extract on a 5-30% sucrose density gradient and subsequent fractionation yielded two peaks of ATPase activity. The faster migrating, 19S major ATPase peak correlated with the 320 and 330 K proteins, and two other proteins at 81 and 67 K. The slower sedimenting, 12S minor ATPase peak corresponded to a 308 K protein and two smaller proteins at 33 and 48 K. Thus, the outer dynein arm of tracheal cilia appeared to be associated with at least two high molecular weight proteins. These results demonstrate that adequate quantities of functionally intact axonemes can be reproducibly isolated from porcine tracheas, allowing further fractionation and analysis of mammalian cilia.
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    Cell Motility and the Cytoskeleton 6 (1986) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 81
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    Keywords: contractile system ; microfilaments ; microtubules ; endoplasmic reticulum ; ciliophora ; oligotrichina ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Tontonia appendiculariformis is a marine planktonic ciliate with a long tail. The tail can contract rapidly, becoming transformed into an oval mass one-twentieth of its original length. The highly complex ulrastructure of the tail is described here in detail. A large part of the volume of the tail contains numerous more or less parallel membranous tubes. The membrane of the tubes has numerous invaginations and is probably derived from the smooth endoplasmic reticulum. This tubular material forms a continuous layer around the tail, interrupted in only one region, which contains cilia. Associated with the cilia are basal fibres with a periodically banded appearance. The tubular layer forms several folds separated by hyaloplasm containing many mitochondria. The pellicle of the tail is thrown into numerous pleats. It comprises a perilemma, a plasmalemma, and complex alveoli, but epiplasm and microtubules are absent. The alveoli appear to form septa within the folds of the layer of membranous tubes. In the region where the tail is attached to the body of the ciliate there are conspicuous bundles of microtubules and microfilaments. The membranous tubes and septa appear to be connected to small bundles of microfilaments, which presumably represent the contractile material. However, we consider the membranous tubes as potentially active in producing the change in shape. Although the structure of the tail of Tontonia is unique, there are certain similarities to the stalk of the Tintinnina and also to the motile extension of the dinoflagellate Erythropsidinium.
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    Cell Motility and the Cytoskeleton 6 (1986), S. 249-255 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 83
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    Cell Motility and the Cytoskeleton 6 (1986), S. 229-236 
    ISSN: 0886-1544
    Keywords: α-helix ; filament motility ; filament contractility ; filament sliding ; microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The twisting behavior of α helices has hardly been considered hitherto with regard to the function of proteins. The well-known electrostatic repulsion between the highly charged side chains, which depends on their interaction with ions, is absolutely connected with torsional rotations of the helix as long as its hydrogen bonds hold. This means a direct transformation of chemical into mechanical energy. However, the stability of a twisted single α helix with charged side chains is low in an aqueous environment. It may easily ball up to form a globular molecule with nonhelical regions of the polypeptide chain. This corresponds to a primitive contraction that obviously occurs with spasminlike proteins that contain strongly twisted filaments as Salisbury [J. Submicrosc. Cytol. 15:105-110, 1983] has shown. Steps that increase the stability and rigidity of α helical filaments are (1) the formation of coiled-coils, (2) self-intertwining (“telephone cord phenomenon”) or intertwining with other coiled-coils as shown with the intermediate filaments, and (3) association with cytoskeletal elements (microfilaments, protofilaments of microtubules) that contain globular subunits. These coarser elements are rotated by winding and unwinding of the smaller helical molecules and thus transmit the torsion produced in the α helices to the microscopic level by the sliding (screwing) motion and the shearing effect that is connected with the waves of a rotating helix. Particles are transported if connected to the helical side arms. Since the displacement of the side arms seems to occur along the single protofilaments of a microtubule, a rotation of these protofiiaments is suggested. The bidirectional transport of particles along single microtubules may be explained by the association of left- and right-handed helices with the protofilaments. According to the models, parallel and antiparallel sliding of neurofilaments and neurotubules is suggested.
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    Cell Motility and the Cytoskeleton 6 (1986), S. 256-272 
    ISSN: 0886-1544
    Keywords: ciliary motility ; cAMP regulation ; swimming speed ; membrane potential ; detergent models ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The membrane potential of Paramecium controls the frequency and direction of the ciliary beat, thus determining the cell's swimming behavior. Stimuli that hyperpolarize the membrane potential increase the ciliary beat frequency and therefore increase forward swimming speed. We have observed that (1) drugs that elevate intracellular cyclic AMP increased swimming speed 2-3-fold, (2) hyperpolarizing the membrane potential by manipulation of extracellular cations (e.g., K+) induced both a transient increase in, and a higher sustained level of cyclic AMP compared to the control, and (3) the swimming speed of detergent-permeabilized cells in MgATP was stimulated 2-fold by the addition of cyclic AMP. Our results suggest that the membrane potential can regulate intracellular cAMP in Paramecium and that control of swimming speed by membrane potential may in part be mediated by cAMP.
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    Cell Motility and the Cytoskeleton 2 (1982), S. 191-194 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 86
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    Cell Motility and the Cytoskeleton 5 (1985), S. 529-543 
    ISSN: 0886-1544
    Keywords: actin ; regulatory protein ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have isolated a 30,000-dalton protein from Dictyostelium which cosedimented with and affected the low shear viscosity of actin. At low concentrations, this protein increased the low shear viscosity to greater than that of the actin control, whereas higher concentrations decreased viscosity. The viscosity decrease correlated with the formation of actin filament bundles, as seen electron microscopically. This protein resembled a previously reported actin-binding protein from Dictyostelium [Fechheimer and Taylor, 84, J Biol Chem 259:4514] in electrophoretic mobility, Stokes radius, and ability to crosslink filaments, but was shown to be different by peptide mapping, lack of immunologic crossreactivity, and lack of sensitivity to calcium.
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    Cell Motility and the Cytoskeleton 5 (1985), S. 545-557 
    ISSN: 0886-1544
    Keywords: neutrophils ; cytoskeleton ; actin polymerization ; NBDphallacidin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The studies presented here characterize a simple, quantitative NBDphallacidin extraction assay for determining the F-actin content of fMLP-activated neutrophils. The NBDphallacidin extraction assay is based upon the specificity of NBDphallacidin binding to F-actin and the solubility of NBDphallacidin in methanol. Cells are fixed, permeabilized, and stained with NBDphallacidin; the cells are then pelleted, the bound NBDphallacidin is extracted into methanol, and the RFI (excite 465; emit 535) of the solution is determined. Binding of NBDphallacidin to neutrophils is saturable and 90% of bound NBDphallacidin is displaced by nonfluorescent phalloidin. The extraction of bound NBDphallacidin into methanol is complete and the excitation/emission characteristics of NBDphallacidin are not altered by extraction. The assay is relatively inexpensive, applicable to the study of cells in suspension or on substratum, allows kinetic studies with 5-10s time resolution, and is not affected by the shape of the cell or the distribution of the probe. We used the NBDphallacidin extraction assay to study the kinetics of fMLP-induced change in the F-actin content of neutrophils and the effect of tBOC peptide, an inhibitor of fMLP binding, on these changes. The extraction assay reveals a rapid, sequential fMLP-induced increase followed by a decrease in F-actin content. The tBOC peptide inhibits fMLP-induced actin polymerization. Addition of tBOC during fMLP-induced polymerization or at times when F-actin content is maximal enhances F-actin depolymerization. The rate of F-actin depolymerization is ≥ fourfold faster in the presence than in the absence of tBOC. The results show that (1) The NBDphallacidin extraction assay is useful for studying the kinetics of change in F-actin content of nonmuscle cells; (2) fMLP receptor occupancy is required for fMLP-dependent polymerization but not depolymerization; and (3) both the actin polymerizing and depolymerizing processes are active in the cell within 5 s after fMLP stimulation. Implications of these observations for understanding the observed increase and, then, decrease in F-actin content of fMLP-activated cells are discussed.
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    Cell Motility and the Cytoskeleton 6 (1986), S. 48-55 
    ISSN: 0886-1544
    Keywords: vinculin ; actin ; adhesion plaques ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Vinculin was purified from chicken gizzard by a modification of the method of Feramisco and Burridge [1980; J Biol Chem 255:1194]. Vinculin did not alter the viscosity of actin as measured in an Ostwald viscometer, nor did it affect actin polymerization as measured with the fluorescent NBD-actin assay. Sedimentation experiments demonstrated that vinculin did not bind to actin, and electron microscopy of negatively stained specimens indicated that vinculin did not aggregate actin filaments into bundles. These results suggest that vinculin, by itself, does not interact with actin at least under commonly used conditions to assay actin-protein interactions in vitro.
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    Cell Motility and the Cytoskeleton 6 (1986), S. 35-47 
    ISSN: 0886-1544
    Keywords: microbeam ; microtubules ; nucleus ; cytoskeleton ; motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: During hyphal tip growth in the fungus Basidiobolus magnus, nuclei normally maintain a constant distance from the advancing cell apex by continuously migrating forward. It is not known whether the mechanism that produces nuclear movement also mediates nuclear positioning, or whether these two processes are under separate control. By irradiating small cytoplasmic regions with an ultraviolet microbeam, the coordination between movement and positioning could be disrupted. Regardless of the distance of the target from the nucleus, anterior irradiations (those ahead of the nucleus) caused the nucleus to stop or move backwards, whereas posterior (behind the nucleus) irradiations caused an acceleration in the nuclear velocity. The nucleus retained its ability to move following irradiation, so there was only loss of control over normal positioning. These results suggest that movement and positioning are mediated by different mechanisms. Quantitative microtubule analysis demonstrated that microtubules in the target region had been depolymerized, but in other regions of the cell they were apparently normal. We suggest that the depolymerization of microtubules affects nuclear movement by altering the tensile strength of the cytoplasm, and that cytoskeletal tension mediate nuclear positioning.We also found that accelerated nuclear movement could occur when most of the microtubules surrounding the nucleus were depolymerized. A comparison of the microtubule population surrounding the nucleus in unirradiated versus irradiated cells suggested that microtubules move with nuclei. Therefore, the nucleus does not appear to move via a direct interaction with microtubules.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 167-184 
    ISSN: 0886-1544
    Keywords: saltatory organelle movements ; ciliary movement ; dynein ; vanadate ; microinjection ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To test the idea that saltatory organelle movements of nonmuscle cells might be driven by microtubule-dynein interactions, we microinjected vanadate into several different types of cultured cell. Solutions of sodium metavanadate made up in a simple buffered salt solution were pressure microinjected into fully spread cells in an open-topped culture chamber placed on the stage of an inverted microscope. The cells were observed by oil-immersion phase-contrast optics and results were recorded on movie film. Vanadate, at 10-5-10-2 M, microinjected into cultured chick embryo fibroblasts, failed to inhibit organelle movements. To test the effectiveness of vanadate's inhibitory action under living cell conditions, ciliated epithelial cells were micro-injected. In these cells even the smallest microinjection of 5 × 10-5 M vanadate caused an immediate cessation of ciliary beating. Moreover, in cells that were well spread it was found that whereas vanadate, at 5 × 10-5 × 10-3M, inhibited ciliary motion, it failed to inhibit organelle saltations in the same cell. To determine whether vanadate would inhibit a living actin-myosin system, myocardial cells were also microinjected. Following microinjection of 5 × 10-5 and 5 × 10-4M vanadate a temporary tonic contraction (which also occurred following microinjection of buffer alone) was followed by regular beating. Taken together these results demonstrate that in living cell systems microtubule-dynein interactions are as sensitive to vanadate inhibition as they are in demembranated model systems, and that a working actin-myosin system in a living muscle cell does not share this great sensitivity. In light of the pronounced differential inhibitory effects of vanadate on the movements of cilia and organelles, our results suggest that saltatory organelle movements in chick embryo fibroblasts and rabbit oviduct epithelial cells are unlikely to be brought about by microtubule-dynein interactions.
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    Cell Motility and the Cytoskeleton 3 (1983) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 92
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    Cell Motility and the Cytoskeleton 3 (1983), S. 247-259 
    ISSN: 0886-1544
    Keywords: spermatozoa ; Ciona ; axoneme ; quiescence ; twist ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A simple planar model of sliding can predict the amount of sliding required to form a certain degree of bend. The accuracy of this prediction relies on the assumptions that no twists occur in the axoneme and that no sliding occurs at the base. However, previous studies indicated that twists may occur.This paper explores a new method for quantitating and analyzing twists. Preliminary results using this method showed that there were twists. In order to control for possible artifacts due to fixation and other preparative procedures, the characteristic S-shaped quiescent state of Ciona spermatozoa was studied.Analyses of platinum replicas of those flagella in which this waveform is well preserved suggest that most, if not all, of the twists observed are due to the artifact of a curved shape settling onto a surface. Detailed analyses indicate that if twists do occur in quiescent sperm, they are probably less than 0.4 radian. Since axonemes are evidently easily twisted in rigor, and even after fixation, caution should be exercised in interpretation of axonemal twists.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 261-271 
    ISSN: 0886-1544
    Keywords: chromosome movement ; meiosis ; spermatocytes ; prophase ; nuclear envelope ; aster ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Association of bivalent chromosomes with the astral centers and nuclear envelope was analyzed in crane-fly spermatocytes during the final hours of diakinesis. In contrast to other systems in which movement of chromosomes during diakinesis correlates with the clustering of bivalents near the astral centers, such clustering is not prevalent in crane-fly spermatocytes. Polarization indices of bivalents calculated 5 to 10 minutes before the end of diakinesis provided evidence for polarization of only a fraction of all bivalents. Similar results were obtained in a large number of fixed cells in which asters and chromosomes were preferentially stained. Ultrastructural analysis of cells in late diakinesis revealed significant contact between bivalents and the nuclear envelope in all 46 cells that were analyzed. The extent of contact in some cells was greater than in others. Sites of contact included the telomeric ends of bivalents, and in some cases the distribution of contact sites suggested the possible involvement of centromeres in chromosome-nuclear envelope association. The results are consistent with the hypothesis that a dynamic interaction between chromosomes and nuclear envelope may exist during late prophase, when the movement of chromosomes is known to occur.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 283-305 
    ISSN: 0886-1544
    Keywords: taxol ; microtubules ; intermediate filaments ; fibroblasts ; epithelial cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Taxol promotes microtubule (MT) assembly in vitro and induces the reorganization of the cytoskeleton into unusual MT arrays in cultured cells. The possibility that taxol also has an indirect effect on intermediate filaments (IF) was investigated. In baby hamster kidney (BHK-21) and human skin (ENSON) fibroblasts treated with 1-10 μM taxol for 1-24 h, the drug induces changes which are similar to those produced by colchicine. These include a loss of major cellular extensions, a redistribution of organelles to a perinuclear location, and an inhibition of locomotion. Saltatory particle movements are not inhibited, however. Ruffling and filopod formation continue, indicating that cells are viable up to 24 h.Polarized light microscopy of living fibroblasts treated with taxol reveals the presence of perinuclear birefringent material which has been examined by immunofluorescence. In control cells, IF and MT radiate from a juxtanuclear region and extend to the cell periphery. In taxol-treated cells, MT and IF are excluded from cell margins, forming large central bundles.In the epithelial cell lines PtK2 and PAM, the keratin system of IF does not become redistributed; in PtK2, however, a second fibroblastlike system of IF does become redistributed to a perinuclear position during taxol treatment.Ultrastructural analyses show that taxol-treated fibroblasts contain parallel arrays of cross-bridged MT-IF as well as bundles of MT exclusive of IF. Epithelial cells contain a predominance of IF-free MT bundles which are organized into hexagonally packed arrays. In these bundles MT frequently exhibit hooks or other incomplete MT profiles and are linked by filamentous material.
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    Cell Motility and the Cytoskeleton 7 (1987) 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Cell Motility and the Cytoskeleton 3 (1983), S. 375-382 
    ISSN: 0886-1544
    Keywords: actin ; spectrin ; band 4.1 ; cytochalasins ; erythrocyte ; brain ; actin-membrane attachment ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A complex of proteins with properties similar to those of erythrocyte spectrinband 4.1-actin complex has been idientified in a preparation derived from bovine brain. The complex has an apparent sedimentation coefficient of about 26S, and contains brain spectrin (also called fodrin) and actin as major components. The actin in the complex is in the oligomeric form, which nucleates assembly of actin filaments that grow from the “barbed” end. The complex cross-links actin filaments, resulting in an increase in low-shear viscosity. Whether the complex contains a protein analogous to erythrocyte band 4.1 is not known. However, it can be demonstrated that brain spectrin has the capability to interact with band 4.1 in a way which increases its ability to cross-link actin filaments.
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    Cell Motility and the Cytoskeleton 3 (1983), S. 405-417 
    ISSN: 0886-1544
    Keywords: vinculin ; focal contacts ; microfilaments ; transformation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Talin is a recently identified cytoskeletal protein with a polypeptide molecular weight of 215,000 daltons. In cultured fibroblasts talin has been localized by immunofluorescence in adhesion plaques (focal contacts), in the ruffling membranes and leading lamellae of the cell periphery, and in fibrillar patterns that align with microfilament bundles and/or with cell surface fibronectin. These cellular locations suggest that the protein could function either in the attachment of microfilaments to the plasma membane or in the organization of microfilaments close to membrane attachment sites. Cell transformation by viruses such as Rous sarcoma virus disrupts the normal organization of talin, and in most transformed cells talin appears distributed diffusely through the cytoplasm. In a few cells talin is detected in doughnut-shaped aggregates, as a ring surrounding a central core of actin. The significance of these structures is uncertain, but in some cells the individual structures will condense to form much larger aggregates with a striking appearance when viewed by immunofluoresence microscopy.
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    Cell Motility and the Cytoskeleton 6 (1986), S. 640-648 
    ISSN: 0886-1544
    Keywords: cell model ; lamellipodia ; phosphorylation ; Ca2+-dependent contraction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Permeabilized cell models of muscle and nonmuscle cells have proven useful for examining the regulation of actin, myosin, and other cytoskeletal proteins during cell contraction. Upon addition of Ca2+ and ATP, glycerinated chick embryonic skin fibroblasts retract their tails and lamellipodia. Ca2+-independent contractions are obtained by preincubation of cell models in Ca2+ ATPγS, followed by EGTA and ATP addition, or by addition of trypsin-treated myosin light chain kinase that no longer requires Ca2+ for reactivation. By pretreating cells before glycerination with colchicine, it is possible to study lamellipodial contraction independent of tail contraction. Similar responses to ATPγS pretreatment and unregulated myosin light chain kinase are observed in cells that only contain lamellipodia. SDS-PAGE electrophoresis of glycerinated fibroblasts incubated in ATPγ35S and Ca2+ shows that only two major proteins are thiophosphorylated, and that one of them, a band that comigrates with the 20K MW light chain of myosin, is thiophosphorylated in a Ca2+-dependent manner. Since the rate of tail contraction is several-fold faster after Ca2+ and ATPγS pretreatment or incubation in excess myosin light chain kinase, myosin light chain phosphorylation may be a rate-limiting step during contraction.
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  • 99
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We present a high-resolution electron microscopic study of the sidearms on microtubules and vesicles that are suggested to form the crossbridges which produce the microtubule-based vesicle transport in squid axoplasm. The sidearms were found attached to the surfaces of the anterogradely transported vesicles in the presence of ATP. These sidearms were made of one to three filaments of uniform diameter. Each filament measured 5-6 nm in width and 30-35 nm in length. The filaments in some of the sidearms had splayed apart by pivoting at their base, thereby assuming a “V” shape. The spread configuration illustrated the independence of the individual filaments. The filaments in other sidearms were closely spaced and oriented parallel to each other, a pattern called the compact configuration. In axoplasmic buffer containing AMP-PNP, structures indistinguishable from the filaments of the sidearms on the vesicles were observed attached to microtubules. Pairs of filaments, thought to represent the basic functional unit, were observed attached to adjacent protofilaments of the microtubules by their distal tips. These data support a model of vesicle movement in which a pair of filaments within a sidearm forms two crossbridges and moves a vesicle by “walking” along the protofilaments of the microtubule.
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    Cell Motility and the Cytoskeleton 7 (1987), S. 31-38 
    ISSN: 0886-1544
    Keywords: microtubule assembly ; proleolysis ; Vinca drugs ; Zn2+-induced assembly ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Limited proteolysis of tubulin with subtilisin results in cleavage of both the α and β subunits, releasing small peptides from the C-terminal ends. At 37°C the digested tubulin assembles into polymorphic structures: microtubules with attached ribbons in the presence of GTP, rings in the presence of GDP, and protofilament spirals in the presence of vinblastine. Undigested tubulin does not assemble under these conditions. Rings and Vinca-induced spiral structures are assembled from undigested tubulin only when microtubule-associated proteins, high Mg2+ concentrations, or polycations are present. Thus, cleavage with subtilisin affects assembly in a manner similar to the addition of these agents. It appears that binding of positively charged substances may act by neutralizing the charge on the highly acidic C-terminal regions of the α- and β-subunits, while cleavage with subtilisin produces the same effect by removing these peptides. Undigested and subtilisin-digested tubulin form sheets of protofilaments in the presence of Zn2+, which indicates that the binding sites for the 2-3 Zn2+ ions necessary to induce sheet formation do not reside in the C-terminal regions of the monomers.
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