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Digitale Medien

New data on the structure and the growth of the osteoderms in the reptile Anguis fragilis L. (Anguidae, Squamata) (1985)

Zylberberg, L. ; Castanet, J.

New York, NY : Wiley-Blackwell

Journal of Morphology 186 (1985), S. 327-342

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ISSN: 0362-2525

Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Medizin

Notizen: Light and electron microscopy shows the osteoderms of Anguis fragilis to be small, flat disks located in the dermis along the adult trunk: microradiography established the extent of the mineralization.Each osteoderm coincides exactly with an epidermal fold forming the keratinized scales characteristic of the skin of reptiles.Sections perpendicular to the surface show two mineralized layers differing in histological and histochemical characteristics and in fine structure, although both contain collagen fibrils. The structure of each layer can be related to that of the surrounding dermis.The outer superficial layer located in the loose dermis contains few collagen bundles that form a discontinuous sheet at the upper surface of the osteoderms. This superficial layer appears to be constituted of units separated by furrows and is composed of woven fibered bone.The basal plate comprises stratified lamellae formed of parallel-oriented collagen fibrils; the fibrils of successive lamellae lie at right angles. The densely packed collagen fibrils of the basal plate are distributed similarly to those of the dense dermis within which it lies. This layer exhibits structural and histochemical characteristics of a lamellar bone.The presence of two different layers in the osteoderms of Anguis fragilis may reflect their mode of formation, which consists of the deposit of mineral crystals in the preexisting dermal tissue. This mineralization process, considered as a “metaplastic ossification,” may reflect the potentiality retained by the dermis of reptiles to form mineralized structures.

Zusätzliches Material: 28 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jmor.1051860309

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Energetic ions upstream of Jupiter's bow shock (1985)

Zwickl, R. D. ; Baker, D. N. ; Krimigis, S. M.

In: Other Sources

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Publikationsdatum: 2019-06-28

Beschreibung: In an analysis of the Jovian ion events, Baker et al. (1984) have found that there appears to be a spectral hardening as the interplanetary magnetic field (IMF) changed orientation from the postnoon to a prenoon connection point. It was also observed that ion events were accompanied by long-period (approximately 10 min) waves whose presence was weakly related to a decrease in the ion anisotropy. The present investigation examines in substantial detail the development of the ion energy spectrum over the full range (approximately 30 keV to approximately 4 MeV). The results of the investigation show that the energy spectra are dominated by heavy ions (presumed to be oxygen and sulfur) at higher (approximately equal to or greater than 300 keV) energies.

Schlagwort(e): LUNAR AND PLANETARY EXPLORATION

Materialart: Journal of Geophysical Research (ISSN 0148-0227); 90; 3947-396

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Digitale Medien

Enterocytic differentiation of a subpopulation of the human colon tumor cell line HT-29 selected for growth in sugar-free medium and its inhibition by glucose (1985)

Zweibaum, Alain ; Pinto, Moïse ; Chevalier, Guillemette ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 122 (1985), S. 21-29

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ISSN: 0021-9541

Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Medizin

Notizen: In order to study the effect of glucose on the differentiation of cultured human colon cancer cells, a subpopulation of HT-29 cells was selected for its capacity to grow in the total absence of sugar. These cells (GIc-cells) exhibit, after confluency, an enterocytic differentiation, in contrast to cells grown with glucose (Glc+ cells), which always remain undifferentiated. The differentiation is characterized by a polarization of the cell layer with apical brush borders and tight junctions, and by the presence of sucrase-isomaltase. The differentiation of Glc-cells is reversible: the addition of glucose to postcon-fluent cultures of Glc- cells results in an inhibiting effect on the expression of sucrase-isomaltase; switching growing cultures of Glc-cells to the Glc+ medium for several passages results in a progressive reversion to the undifferentiated state, which is completed after seven passages. The dedifferentiation process is associated with a parallel, passage-related, increase in the rates of glucose consumption and lactic acid production, and decreases of intracellular glycogen content, which return to the values of the undifferentiated original Glc+ cells. The values of these metabolic parameters are correlated, at each passage, with the degree of dedifferentiation of the cells. When these dedifferentiated cells, after having been cultured in Glc+ medium for 20 passages, are switched back to the Glc- medium, they readily grow without mortality, and reexpress the same enterocytic differentiation as the parent Glc- cells. These results show that the capacity of this subpopulation to grow and differentiate in the absence of sugar is a stable characteristic. They further suggest that glucose metabolism interferes with the program of differentiation of HT-29 cells.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jcp.1041220105

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4

Digitale Medien

Neutral amino acid transport in embryonal carcinoma cells (1985)

Zuzack, John S. ; Tasca, Richard J. ; DiZio, Stephen M.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 122 (1985), S. 379-386

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ISSN: 0021-9541

Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Medizin

Notizen: Neutral amino acid transport was characterized in the pluripotent embryonal carcinoma (EC) cell line, OC15. Ten of the thirteen amino acids tested are transported by all three of the major neutral amino acid transport systems - A, L, and ASC - although one system may make a barely measurable contribution in some cases. The characterization of N-methyl-aminoisobutyric acid (meAIB) transport points to this model amino acid as a definitive substrate for System A transport by OC15 cells. Thus, high concentrations of meAIB can be used selectively to block System A transport, and the transport characteristics of meAIB represent system A transport. Kinetic analysis of System A, with a Km = 0.79mM and Vmax = 14.4 nmol/mg protein/5 min, suggests a single-component transport system, which is sensitive to pH changes. While proline transport in most mammalian cells is largely accomplished through System A, it is about equally divided between Systems A and ASC in OC15 cells, and System A does not contribute at all to proline transport by F9 cells, an EC cell line with limited developmental potential. Kinetic analysis of System L transport, represented by Na+-independent leucine transport, reveals a high-affinity, single-component system. This transport system is relatively insensitive to pH changes and has a Km = 0.0031 mM and Vmax = 0.213 nmol/mg protein/min. The putative System L substrate, 2-aminobicyclo-[2,2,1]heptane-2-carboxylic acid (BCH), inhibits Systems A and ASC as well as System L in OC15 cells. Therefore, BCH cannot be used as a definitive substrate for System L in OC15 cells. Phenyialanine is primarily transported by Na+ -dependent Systems A and ASC (83% Na+-dependent; 73% System ASC) in OC15 cells, while it is transported primarily by the Na+-independent System L in most other cell types, including early cleavage stage mouse embryos and F9 cells. We have also found this unusually strong Na+-dependency of phenyl-alanine transport in mouse uterine blastocysts (82% Na+-dependent). There is no evidence for System N transport by OC15 cells, since histidine is transported primarily by a Na+-independent, BCH-inhibitable mechanism.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jcp.1041220307

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5

Digitale Medien

Lectin-induced blockage of developmental processes in preimplantation mouse embryos in vitro (1985)

Zuzack, John S. ; Tasca, Richard J.

New York, NY : Wiley-Blackwell

Gamete Research 12 (1985), S. 275-290

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ISSN: 0148-7280

Schlagwort(e): lectins ; preimplantation mouse embryos ; glycoconjugates ; Life and Medical Sciences ; Cell & Developmental Biology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie

Notizen: This study attempts to assess the developmental importance of cell surface glycoconjugates of preimplantation mouse embryos. This was done by incubating early embryos in various lectins and analyzing subsequent development. If specific cell surface glycoconjugates (lectin receptors) are linked to specific developmental processes, such as cell division, compaction, and blastocyst formation, then different lectins should block these different developmental processes. The results show that wheat-germ agglutinin (WGA; N-acetyl-D-glucosamine-specific) at 50 μg/ml prevents the cell division of four-cell embryos. However, this effect of WGA occurs only in embryos with intact zonae pellucidae. Concanavalin A (Con A; α-D-glucose and α-D-mannose-specific) treatment, 20 μg/ml, of four-cell or early eight-cell embryos prevents compaction, the first major change in cell shape in early mouse embryogenesis. Divalent succinly Con A does not affect development, suggesting that the Con A effect is due to crosslinking of cell surface glycoconjugates. Exposure of four-cell or early eight-cell embryos to 10 μg/ml Lotus Tetragonolobus puprureas agglutinin (LTA; α-L-fucose-specific) or 25 μg/ml Limulus polyphemus agglutinin (LPA; sialic acid-specific) allows compaction or development to the morula stage, but blocks blastocyst formation. All lectins tested retard cell division to some extent. Late morulae and early blastocysts are more resistant than earlier stages to all of the lectins studied. This study demonstrates that very low concentrations of these lectins affect different developmental processes, presumably based upon their sugar specificities.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/mrd.1120120306

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6

Digitale Medien

Purification of human DNA (cytosine-5-)-methyltransferase (1985)

Zucker, Keith E. ; Riggs, Arthur D. ; Smith, Steven S.

New York, N.Y. : Wiley-Blackwell

Journal of Cellular Biochemistry 29 (1985), S. 337-349

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ISSN: 0730-2312

Schlagwort(e): DNA methyltransferase ; 5-methylcytosine ; hydrophobic interaction chromatography ; maintenance methylase ; Life and Medical Sciences ; Cell & Developmental Biology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Chemie und Pharmazie , Medizin

Notizen: We have developed a facile procedure for the purification of DNA methyltransferase activity from human placenta. The procedure avoids the isolation of nuclei and the dialysis and chromatography of large volumes. A purification of 38,000-fold from the whole cell extract has been achieved. The procedure employs ion exchange, affinity, and hydrophobic interaction chromatography coupled with preparative glycerol gradient centrifugation. A protein of 126,000 daltons was found to copurify with the activity and was the major band seen in the most highly purified material after SDS gel electrophoresis. This observation, coupled with an observed sedimentation coefficient of 6.3S, suggests that the enzyme is composed of a single polypeptide chain of this molecular weight. Hemimethylated DNA was found to be the preferred substrate for the enzyme at each stage in the purification. The ratio of the activity of the purified product on hemimethylated to that on unmethylated M13 duplex DNA was about 12 to 1. Thus, the purified activity has the properties postulated for a maintenance methyltransferase. The availability of highly purified human DNA methyltransferase should facilitate many studies on the structure, function, and expression of these activities in both normal and transformed cells.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jcb.240290407

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7

Digitale Medien

NMR-Untersuchungen an 1,2-Bis(alkylphosphino)-benzenen und ihren Anionen (1985)

Zschunke, A. ; Riemer, M. ; Leissring, E. ; [weitere]

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 525 (1985), S. 35-40

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ISSN: 0044-2313

Schlagwort(e): Chemistry ; Inorganic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: NMR-Studies of 1,2-Bis(alkylphosphino)benzenes and their Anions7Li, 13C, and 31P magnetic resonance spectroscopy, including studies of spin-lattice relaxation times, have been used to investigate the structure of 1,2-bis-(alkylphosphino)benzenes and their dilithiated species in THF and Et2O solutions. A phosphorus inversion barrier of 100-110 kJ/mol has been determined for the diastereomeric bisphosphines. The chemical shifts of the diphosphides demonstrate the delocalization of the negative charge of the anions in the aromatic ring. 7Li-31P-nuclear spin couplings and T1 measurements for 13C nuclei indicate that all lithiated species are dimers with intermolecular P-Li-P-bridges.

Notizen: 7Li-, 13C- und 31P-NMR, einschließlich Spin-Gitter-Relaxationszeitmessungen, wurden zur Strukturaufklärung von 1,2-Bis(alkylphosphino)benzenen und ihren dilithiierten Spezies in THF und Et2O-Lösungen angewendet. An den diastereomeren Bisphosphinen läßt sich eine Phosphorinversionsbarriere von 100-110 kJ/mol bestimmen. Die chemischen Verschiebungen der Diphosphide demonstrieren die Delokalisierung der negativen Ladung des Anions in den aromatischen Ring.7Li-31P-Kernspinkopplungen und T1-Messungen der 13C-Kerne zeigen, daß alle lithiierten Spezies unter Ausbildung intermolekularer P-Li-P-Brücken dimer vorliegen.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/zaac.19855250606

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The interplanetary micrometeoroid flux and lunar primary and secondary microcraters (1985)

Zook, H. A. ; Fechtig, H. ; Lange, G. ; [weitere]

In: Other Sources

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Publikationsdatum: 2011-08-19

Beschreibung: It is proposed that considerable care is required to properly interpret either spacecraft in situ data or lunar crater data as well as near-earth data; in the case of the former, complications may arise which may be attributed to secondary lunar ejecta impacts, in the latter, they may result from impacting earth-orbiting debris. Experimental evidence suggests that most impact pits on lunar rocks with pit diameters smaller than 7 micrometers have been generated by lunar secondary ejecta impacts and not by primary meteoroid impacts. It is also found that lunar crater production rates are more accurate when deduced from meteoroid space experiments and not from solar flare track ages. It is concluded that in so far as all of the above qualifications are taken into account, a self-consistent meteoroid flux versus mass distribution is obtained.

Schlagwort(e): LUNAR AND PLANETARY EXPLORATION

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Digitale Medien

Study on the equilibrium in the MBr2—CH3OH—H2O System (M = Sr2+, Ba2+) at 25° C (1985)

Zlateva, I. ; Stoev, M.

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 525 (1985), S. 199-204

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ISSN: 0044-2313

Schlagwort(e): Chemistry ; Inorganic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Untersuchung der Gleichgewichte in den Systemen MBr2—CH3OH—H2O (M = Sr2+, Ba2+) bei 25°CUntersucht wird die Dehydratation in den Dreistoffsystemen MBr2—CH3OH—H2O (M = Sr2+, Ba2+) bei 25°C mit Hilfe physikochemischer Analysen. Es wurden Kristallisationsfelder der Kristallhydrate SrBr2 · H2O und BaBr2 · H2O gefunden. Die Löslichkeitskurven weisen auf Komplexbildungsprozesse hin. Es werden Schlußfolgerungen über die Dehydratation und Solvatbildung in den Dreistoffsystemen vom Typ MBr2—CH3OH—H2O bei 25°C mit Mg2+, Ca2+, Sr2+ und Ba2+-Ionen gezogen.

Notizen: The dehydration processes in the three-component system MBr2—CH3OH—H2O (M = Sr2+, Ba2+) have been studied at 25°C by physico-chemical analyses. Crystallization fields for the lower crystal hydrates SrBr2 · H2O and BaBr2 · H2O have been found. The solubility curves exhibit complex-formation processes. The dehydration and solvation processes in three-component system such as MBr2—CH3OH—H2O at 25°C with M = Mg2+, Ca2+, Sr2+, Ba2+ have been discussed in general terms.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/zaac.19855250623

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Digitale Medien

Study on the equilibrium in the MCl2—CH3OH—H2O System (M = Sr2+, Ba2+) at 25°C and 50°C (1985)

Zlateva, I. ; Stoev, M.

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 525 (1985), S. 205-213

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ISSN: 0044-2313

Schlagwort(e): Chemistry ; Inorganic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Untersuchung der Gleichgewichte in den Systemen MCl2—CH3OH—H2O (M = Sr2+, Ba2+) bei 25° und 50°CDie Untersuchungen über das System MCl2—CH3OH—H2O bei 25°C und 50°C (M = Sr2+, Ba2+) zeigen, daß die Dehydratation in Wasser-Methanol-Systemen stufenweise verläuft, so daß bei 25°C in Abhängigkeit vom Molverhältnis des Lösungsmittelgemisches sämtliche existierenden niedrigeren Kristallhydrate entstehen können.Dehydratation und Solvatbildung in den Dreistoffsystemen MCl2—CH3OH—H2O (M = Mg2+, Ca2+, Sr2+, Ba2+) werden mit den entsprechenden in Bromidsystemen verglichen.

Notizen: Studies on the equilibrium in the system MCl2—CH3OH—H2O at 25°C and 50°C (M = Sr2+, Ba2+) show that the dehydration in the water-methanol systems proceeds stepwise and all possible lower crystal hydrates may be obtained at 25°C depending on the molar ratio for the mixed solvent. The dehydration and solvation processes in the three-component system MCl2—CH3OH—H2O (M = Mg2+, Ca2+, Sr2+, Ba2+) have been considered in general and compared with those in the bromide system.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/zaac.19855250624

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