Search Results - (Author, Cooperation:E. Appel)

2015-03-31

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Coculture Techniques ; *Electrons ; Ferrosoferric Oxide/*metabolism ; Geobacter/growth & development/*metabolism ; Iron/*metabolism ; Light ; *Magnetite Nanoparticles ; Oxidation-Reduction ; Rhodopseudomonas/growth & development/*metabolism

1365-246X

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Magnetostratigraphic age dating has been carried out on sandstones of a well exposed continuous 5500 m thick Miocene-Pleistocene section in the Surai Khola area (West Nepal). The section is situated in the Siwalik Range which consists of molasse sediments from the Himalaya. Progressive demagnetization and isothermal remanence experiments prove that haematite is the carrier of the characteristic remanent magnetization (ChRM) throughout the entire section. The final polarity sequence is based on 436 samples, of which 233 have normal and 203 reverse polarity. Antiparallel mean directions of the normally and reversely polarized samples indicate that the ChRM is of primary origin. Comparison of the polarity sequence with a standard polarity time-scale yields a time period for the section between chron 1r or chron 2r (Matuyama) and probably chron 5AB (between 1–2 Myr and about 13 Myr).

Electronic Resource

1365-246X

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Palaeomagnetic investigations have been carried out on Tethyan sediments from the NW Zanskar Range (33.9°N, 76.5°E). A total of 455 oriented samples from 41 sites were drilled from four stratigraphic units of Middle Cretaceous to Early Eocene age (Shillakong Formation, Marpo Limestone/Spanboth Formation, Stumpata Quartzarenite/Spanboth Formation, Kong Formation).A characteristic remanence (ChRM) could be isolated for 27 sites (254 specimens) through detailed thermal and alternating field demagnetization and multicomponent analysis. All the ChRM directions identified are similar, irrespective of geological age. They fail the fold test and yield an overall in situ mean direction of D= 336.6°/I=+39.6° with α95= 5.9° and k= 22.9. This corresponds to a palaeopole position at 66.5°N, 323.5°E (N-pole). Isothermal remanence (IRM) acquisition and thermal demagnetization of a saturation IRM identify pyrrhotite as the dominant ferrimagnetic mineral and carrier of the ChRM. The pyrrhotite remanence is probably a thermoremanent magnetization acquired when the temperature of low-grade metamorphism decreased below about 300°C.The ChRM directions are thus clearly secondary in origin, and a negative conglomerate test carried out on the Kong Formation demonstrates that remanence acquisition post-dates the Early Eocene. The mean ChRM inclination suggests that the remanence was acquired at about 20°N. Cooling events in the higher Himalayan crystallines indicate an Oligocene age for this remanence acquisition. The mean ChRM declination shows a counterclockwise rotation of 23.4° since remanence acquisition. Assuming remanence acquisition at about 30 Myr ago, a slight counterclockwise rotation of about 10° relative to the stable Indian Plate can be concluded. This does not fit with the general pattern of palaeomagnetic results from neighbouring areas within the western syntaxis of the Himalaya, from which a clockwise rotation relative to the stable Indian Plate is expected for the Zanskar Range.

Electronic Resource

1365-246X

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

The remanent magnetization of Palaeozoic and Mesozoic carbonates from the Tibetan Sedimentary Series (TSS) of the Manang area north of the Annapurna Range (north central Nepal) has been investigated. the TSS forms part of the tectonic unit between the Indian-Eurasian plate boundary in the north and the Main Central Thrust (MCT) in the south.Apart from a present field direction, three remanence components have been separated: a normal polarity, post-folding remanence (negative fold test) is carried by pyrrhotite (the core corrected mean direction for five sites with 47 specimens from Silurian/Devonian rocks is decl. = 312.9°, incl. = 58.3°α95= 17.6°, K= 19.8). the origin of this component is not understood.A more precisely determined, reversed polarity, post-folding remanence (99 per cent negative fold test) is also carried by pyrrhotite (the core corrected mean direction for 12 sites with 229 specimens from Carboniferous/Triassic rocks is decl. = 196.4°, incl. = -65.9°, α95= 3.2°, k = 183).One site of Lower Carinan age shows—in addition to the pyrrhotite component— a second, stable remanence direction carried by magnetite. the fold test is 99 per cent positive and there is a high probability that the remanence is of detrital origin (the bedding corrected direction for one site with 40 specimens is decl. =334.3°, incl. = -54.1°, α95= 4.2°, k = 30.2, palaeolatitude 34.6°S).The direction of the magnetite component coincides with other Triassic palaeodirection data from the literature and the inclination suggests a palaeoposition of the TSS at the northern margin of India at this time. the northern extent of India in the Triassic cannot be reconstructed from the data because of the strong anticlockwise rotation (48°) of stable India since this time.The inclination of the reverse polarity pyrrhotite component is 19° steeper than expected from the maximum northern position of the area. This suggests a regional northward tilt along the MCT which is supported by steep inclinations found in other areas.Declination data for the reverse polarity pyrrhotite component and for the magnetite component deviate clockwise from expected values for the area by 23°-34° (calculated from the Indian APWP). Utilizing Klootwijk, Conaghan & Powell's (1985) rotational underthrusting model, the minimum magnitude of continental underthrusting between the TSS and stable India at the longitude of central Nepal (84°E) has been calculated from the declination of our reverse polarity pyrrhotite component. A possible range of 520–1100 km results from consideration of different tectonic models.

Electronic Resource

0018-7143

Biology

0018-7143

Biology

0012-821X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Geosciences

Physics

Electronic Resource

0031-9201

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Geosciences

Physics

Electronic Resource

0031-9201

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Geosciences

Physics

Electronic Resource

0031-9201

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Geosciences

Physics

Electronic Resource

0031-9201

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Geosciences

Physics

Electronic Resource

0031-9201

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Geosciences

Physics

Electronic Resource

0031-9201

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Geosciences

Physics

Electronic Resource

0304-8853

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

0029-554X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Energy, Environment Protection, Nuclear Power Engineering

Physics

Electronic Resource

1432-2048

Springer Online Journal Archives 1860-2000

Biology

Zusammenfassung 1. Durch Anwendung des Boysen Jensenschen Versuchsprinzips ließ sich zeigen, daß die geotropische Induktion bei Haferkeimlingen eine transversale Wuchsstoffverlagerung in der Spitze verursacht. Die Versuchspflanzen wurden am Gipfel 2 mm tief eingeschnitten und die Spalthälften durch ein eingesetztes Glimmerplättchen voneinander getrennt gehalten. 2. Bringt man die so vorbereiteten Koleoptilen im Wasserbad in geotropische Reizlage, so krümmen sie sich erheblich stärker auf, wenn der Spalt in der Vertikalebene liegt als bei dessen Horizontalstellung, in der er die Wuchsstoffverschiebung blockiert (2 Std-Reaktionswerte: 19,0 bzw. 10,80). 3. Werden die Pflanzen in gleicher Weise in einem 10−6 mol IES-Bad exponiert, so entwickelt sich die geotropische Aufkrümmung bei beiden Stellungen des Spaltes stärker als im Wasser. Andererseits macht sich jetzt die Wirkung der Querblockierung viel weniger bemerkbar (2 Std-Reaktionswerte: 24,6 bzw. 20,30). Daraus ist zu schließen, daß die Reizlage auch in der Basis eine Polarisierung induziert, welche die Ober- und Unterhälfte des Organs auf gleiche Auxinzufuhr verschieden stark reagieren läßt. 4. Zum direkten Nachweis der transversalen Wuchsstoffverschiebung in der geotropisch induzierten Spitze wurde durch 2 Einschnitte eine ihrer Symmetriehälften entfernt. In den entstandenen Winkel wurde zur Aufnahme des von der Längsschnittfläche abgegebenen Wuchsstoffs ein Agarwürfel eingesetzt. Nach 90 min langem Kontakt wurde der Auxingehalt der Würfel mit dem Wentschen Krümmungstest ermittelt. Es ergab sich, daß die verbliebene Spitzenhälfte in Vertikalstellung seitlich fast keinen Wuchsstoff ausscheidet; in der Horizontallage dagegen wird nach unten eine Auxinmenge abgegeben, die annähernd 10−7 mol IES entspricht.

Electronic Resource

1432-1041

Sympathetic activity ; plasma catecholamine concentration ; dopamine-β-hydroxylase activity ; graded physical exercise ; heart rate ; man

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary In 11 healthy untrained volunteers the increase in plasma dopamine-β-hydroxylase (DBH) activity during graded physical exercise has been examined as a true measure of increased activity of the sympathetic nervous system. The correlation between DBH activity, catecholamine concentration (CA) in plasma and heart rate was studied. When work on an electrically braked bicycle ergometer was gradually increased from 12.5 to 100, 200 and 300 watts there was a linear increase in DBH activity and heart rate; the increase in CA concentrations followed an exponential function. The peak values for DBH activity and CA concentration in plasma after the 300 watt work load (as percentages of the resting levels) were 130±3% and 820±71%, respectively; the adrenaline concentration in plasma increased only to 150±19% (p〉0.05). There were significant correlations between heart rate and work load, DBH and work load and log CA and work load. The data imply direct correlations between heart rate and DBH, heart rate and log CA and DBH and log CA. The exponential increase in noradrenaline concentration in plasma might be due either to a greater net “overflow” from sympathetic nerve endings, and/or to increased secretion by the adrenal medulla. In the latter case, the release of noradrenaline would not be accompanied by secretion either of adrenaline or DBH. After work ceased there were sharp falls in heart rate and CA concentration, which indicate an immediate drop in sympathetic activity. DBH activity in plasma returned to normal very slowly; it reached half maximum values after 20 – 22 min. It is concluded that increased sympathetic activity in man can be estimated in vivo as changes in DBH and/or CA concentration in plasma. In contrast, a rapid decrease in sympathetic activity is directly reflected only by a rapid fall in the plasma concentrations of CA.

Electronic Resource

1432-1041

Oxyfedrine ; norephedrine ; man ; urinary excretion ; sympathomimetic

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary After oral administration of oxyfedrine to healthy volunteers, norephedrine was identified in the urine by thin layer chromatography and gas liquid chromatography and mass spectrography. 30 hours after single oral doses of 8, 16 or 24 mg of oxyfedrine, about 4, 8 and 9 mg, respectively, of norephedrine were found in the urine, i.e. on a molar base 75–100% of the dose was excreted as norephedrine. The peak of excretion occurred within 2–4 hours after administration of the drug. No accumulation of oxyfedrine and/or its metabolite was observed after administration of 16 mg of oxyfedrine t.i.d. for three days. It could not be decided whether oxyfedrine was metabolized to norephedrine by liver enzymes, as in rats, or was spontaneously degraded to norephedrine, e.g. in duodenal fluid before absorption. 30–150 min after oral oxyfedrine (24 mg) norephedrine was demonstrable in duodenal fluid. Thus, in addition to the directβ-sympathomimetic effects of oxyfedrine, it may also have indirect sympathomimetic effects because of the noradrenaline-releasing properties of its metabolite norephedrine.

Electronic Resource

1432-1041

mental stress ; sympathetic activation ; delayed auditory feedback ; plasma norepinephrine ; plasma epinephrine ; plasma dopamine-beta-hydroxylase

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary Using delayed auditory feedback (delay 0.175 s) a standardized form of mental stress was investigated in 8 healthy male volunteers. After a resting period and a period of undelayed reading, the volunteers were exposed for 5 min to the DAF stress. During the DAF period heart rate increased by 10% and systolic and diastolic blood pressure increased by 9% and 18%, respectively. As a measure of acute sympathetic activation, plasma concentrations of norepinephrine and epinephrine rose by 68% and 49%, respectively. The activity of dopamine-β-hydroxylase in plasma was increased by 25%. From these results it can be concluded that the DAF procedure provides a suitable method for inducing a standardized mental stress in normal subjects, which can be measured as changes in biochemical and cardiovascular variables.

Electronic Resource

1432-1041

amezinium ; sympathomimetic effects ; catecholamines ; echocardiography ; systolic time intervals ; orthostatic stress ; inhibition of noradrenaline uptake

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary The cardiovascular effects of the sympathomimetic agent amezinium were investigated in a double-blind, placebo-controlled, randomized trial in six volunteers. Before and 2 h after oral administration of amezinium 30 mg or placebo the cardiovascular responses to orthostatic stress, induced by 80° passive head-up tilt, were assessed by recording blood pressure, systolic time intervals, and echocardiogram. Plasma catecholamines were also determined. After amezinium treatment, the average supine systolic blood pressure was increased by +30 mm Hg and after tilting it remained above both the pre-treatment and placebo values. Compared to placebo, amezinium elicited only minor changes in heart rate and diastolic blood pressure. The effect of amezinium on the pre-ejection period corrected for heart rate (PEPc) and mean velocity of fiber shortening (VCFmean) indicated positive inotropic properties. Its effects were distinctly more pronounced during tilt than with the subjects supine. Plasma concentrations of noradrenaline and adrenaline were not influenced by amezinium during rest or tilt. From these results and previous research it is concluded that amezinium induces its sympathomimetic effects by preferentially inhibiting the re-uptake of noradrenaline which is released by the drug itself, or by sympathetic activation during tilt. This mechanism of action might explain the pronounced sympathomimetic effects of the drug, especially during orthostatic stress.

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