Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Cumbal Volcano Hydrothermal system Gases Fumaroles Springs Geochemistry Isotopes  (1)
  • Zirkadianer Rhythmus  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Der Hautarzt 50 (1999), S. 5-11 
    ISSN: 1432-1173
    Keywords: Schlüsselwörter Melatonin (N-Acetyl-5-Methoxytryptamin) ; Zirkadianer Rhythmus ; Schlaf-Wach-Rhythmus ; Radikalfänger ; Key words Melatonin (N-acethyl-5-methoxytryptamin) ; Circadian rhythm ; Daily sleep induction ; ageing ; Free radical scavenger
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Melatonin (N-acetyl-5-methoxytryptamine) is a hormone with multiple functions in humans, produced by the pineal gland and stimulated by β-adrenergic receptors. Serum melatonin levels exhibit a circadian rhythm with low levels during the day, rise in the evening and maximum levels at night between 2 and 4 a.m.. Melatonin participates in the regulation of several physiological processes such as seasonal biological rhythm, daily sleep induction, aging and modulation of immunobiological defence reactions. Furthermore, melatonin has a highly lipophilic molecular structure facilitating penetration of cell membranes and serving as an extra- and intracellular free radical scavenger. Melatonin seems to quench mainly hydroxyl radicals, the most damaging of all free radicals. Melatonin may play a role in the etiology and treatment of several dermatoses e.g. atopic eczema, psoriasis and malignant melanoma. The influence of melatonin on hair growth is another aspect. Topical application of melatonin inhibits the development of UV-erythema. Penetration through skin after topical application and oral bioavailability auxit further investigations on the pharmacokinetic and pharmacodynamic actions of melatonin.
    Notes: Zusammenfassung Melatonin (N-Acetyl-5-Methoxytryptamin) ist ein unter dem Einflußβ-adrenerger Rezeptoren von der Glandula pinealis produziertes und sezerniertes Hormon mit vielfältigem Wirkungsspektrum. Die Ausschüttung des Hormons folgt einem zirkadianen Rhythmus mit niedrigen, gleichmäßigen Spiegeln tagsüber und einem abendlichen Ansteigen und nächtlichen Peak zwischen 2.00 und 4.00 Uhr. Melatonin beeinflußt den saisonalen Biorhythmus, den Schlaf-Wach-Rhythmus, den Alterungsprozeß und moduliert immunbiologische Abwehrfunktionen. Zusätzlich besitzt Melatonin unabhängig von einem Rezeptorsystem durch seine starken lipophilen Eigenschaften die Fähigkeit, frei durch Zellmembranen zu diffundieren und im extra- wie intrazellulären Raum als Radikalfänger zu wirken. Die Affinität zu dem stark schädigenden Hydroxylradikal ist besonders groß. In der Dermatologie ergeben sich für Melatonin Perspektiven bei einigen Hauterkrankungen wie zum Beispiel dem atopischen Ekzem, der Psoriasis und dem malignen Melanom. Der Einfluß von Melatonin auf das Haarwachstum ist ein weiterer Aspekt. In topischer Anwendung hat Melatonin eine suppressive Wirkung auf die Ausbildung eines UV-Erythems. Über die Penetrationseigenschaften durch die Haut und die orale Verfügbarkeit liegen einige Erkenntnisse vor, die durch weitere Untersuchungen der Pharmakokinetik und Pharmakodynamik ergänzt werden können.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-0819
    Keywords: Cumbal Volcano Hydrothermal system Gases Fumaroles Springs Geochemistry Isotopes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract. We present chemical and isotopic data for fumarolic vapor and thermal spring discharges from Cumbal Volcano, SW Colombia. In 1988 Cumbal showed signs of apparent reactivation. Gases and steam condensates were sampled from summit fumaroles (83–375°C) of Cumbal in 1988–1996 and discharges from thermal springs (15–37°C) on its flanks in 1995–1996. Based on relative CO2, total S (H2S+SO2), and HCl contents, fumarolic discharges are principally magmatic in composition. Fumarolic steam condensates (1993–1996) have δ18O values of –11.4 to +2.5‰ and δD values of –91 to –43‰. δ18O and δD compositions indicate mixing between local meteoric and magmatic waters. 3He/4He ratios in 1993–1996 samples (5.3–7.9 Rcor) are consistent with addition of mantle-derived helium. δ13CCO2 values for 1996 samples (–6.7 to –5.0‰) likely indicate contribution of marine-carbonate, organic sediment, and mantle-derived CO2. δ34SStotal compositions (–4.6 to +5.6‰) of 1988–1996 fumarolic discharges have magmatic signatures and may reflect cycles of deposition and remobilization of native sulfur. Thermal waters are acid-sulfate or bicarbonate in composition. Relative concentrations of chemical constituents of thermal waters imply that the composition of waters is controlled by absorption of magmatic volatiles into shallow ground- and surface waters, dilution with meteoric waters along flow paths, and dissolution of host rocks. δ18O and δD compositions are consistent with a meteoric origin of waters. δ34SStotal values for thermal spring gas discharges (9.6–10.5‰) suggest deposition of δ34S-depleted sulfur minerals along flow paths. Chemical and isotopic compositions of 1988–1995 fumarolic discharges provide evidence for input of magmatic volatiles into the Cumbal hydrothermal system. From 1995 to 1996, geochemical data show increasing hydrothermal signatures, suggesting a decline in magmatic volatile input.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...