Search Results - (Author, Cooperation:D. Saur)

2011-10-29

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; Cell Lineage ; Cell Movement ; Clone Cells/cytology/physiology ; Gene Knock-In Techniques ; Interneurons/*cytology/*physiology ; Mice ; Mitosis ; Neocortex/*cytology/embryology ; *Neural Inhibition ; Neural Stem Cells/*cytology/physiology ; *Neurogenesis ; Neuroglia/cytology/physiology ; Preoptic Area/cytology/embryology ; Telencephalon/*cytology/embryology

1440-1681

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

1. In order to investigate purinergic effects on rat ileal smooth muscle, we used α,β-methylene ATP (α,β-MeATP), ATP, ADP and UTP. α,β-Methylene ATP and ATP were the only agonists that caused a concentration-dependent inhibition of carbachol-precontracted smooth muscle. The inhibitory effect of α,β-MeATP was completely blocked by pyridoxalphosphate-6-azophenyl-2′,4′-disulphonic acid (3 × 10–5 mol/L), a selective antagonist of the P2X 〉 〉 P2Y receptor.2. Using reverse transcription–polymerase chain reaction we demonstrated the presence of both, P2X and P2Y receptor mRNA within the rat ileal longitudinal muscle/myenteric plexus layer preparation.3. The α,β-MeATP-induced inhibition was blocked in a concentration-dependent manner in the presence of the K+ channel blocker apamin, but was unaffected by other K+ channel blockers, such as charybdotoxin (10–7 mol/L), 4-aminopyridine (10–4 mol/L), glibenclamide (10–5 mol/L) and tetraethylammonium (10–3 mol/L).4. The α,β-MeATP-induced inhibition was unaffected by pretreatment with atropine (10–6 mol/L), phentolamine (10–6 mol/L), propranolol (10–6 mol/L), nitrendipine (10–7 mol/L), pertussis toxin (10–6 mol/L) NG-nitro- L-arginine (3 × 10–4 mol/L) and tetrodotoxin (10–6 mol/L), excluding an involvement of adrenergic, cholinergic, neural, nitrinergic or G-protein involvement in purinergic-mediated inhibition.5. In order to investigate whether the internal Ca2+ stores participated in the inhibitory effect observed, we depleted internal Ca2+ stores with cyclopiazonic acid, a specific Ca2+-ATPase inhibitor. The inhibitory effect of α,β-MeATP was completely abolished after depletion of the intracellular Ca2+ stores.6. This is in contrast with the effects seen for neurotensin, where neurotensin-induced inhibition was unchanged after depletion of intracellular Ca2+ stores, suggesting at least two different pathways of apamin-sensitive non-adrenergic, non-cholinergic inhibition in rat ileal smooth muscle.7. According to our results, the inhibitory effect of α,β-MeATP in rat ileum longitudinal smooth muscle is mediated via a P2 purinoceptor, most likely a P2X receptor, involves G-protein-independent activation of an apamin-sensitive K+ channel and requires filled intracellular Ca2+ stores.

Electronic Resource

0368-1874

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0368-1874

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0022-0728

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0022-0728

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

1600-079X

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The aim of the present study was to investigate the effects of melatonin on non-adrenergic, non-cholinergic (NANC) relaxant neurotransmission in the gastrointestinal tract, which is mainly mediated by nitrergic and peptidergic mechanisms. Melatonin (10−7–10−3 M) had no effect on the basal tonus of the rat gastric fundus smooth muscle. Relaxant responses following electrical stimulation(40 V; 0.5 ms pulse duration; 10 s stimulation duration) under NANC conditions on a 5-hydroxytryptamine (5-HT, 10−7 M) contraction plateau were elicited at frequencies in the range of 0.5–16 Hz. Melatonin significantly reduced these inhibitory NANC responses (16 Hz without melatonin: –103 ± 6.3%; melatonin 10−5 M: –80.4 ± 7.5%; melatonin 10−4 M: –39.1 ± 17.1%). Intracellular recording was carried out in a mouse colonic preparation. Electrical neural stimulation of the mouse colonic neurons caused biphasic intracellular hyperpolarization in smooth-muscle cells. The initial fast component is apamin-sensitive, and the following slow component is dependent on nitrergic mechanisms, as it is abolished in the presence of NG-nitro-L-arginine (L-NNA). Melatonin significantly reduced the nitric oxide-dependent slow component of neurally transmitted hyperpolarization, whereas the initial fast component was left unchanged. In a synaptosomal preparation of the enteric nervous system of rat intestine, enzymatic nitric oxide synthase (NOS) activity was significantly reduced by melatonin at concentrations ranging from 10−7 to 10−4 M (basal preparation including cofactors: 61.2 ± 9.4 fmol/mg; melatonin 10−4 M: 39.2 ± 6.9 fmol/mg). Reverse transcriptase-polymerase chain reaction (RT-PCR) studies were conducted to investigate the melatonin receptors (mt1, MT2 and MT3) present in the esophagus, stomach and ileum of the rat. The presence of mt1 mRNA expression alone, but not of mRNA expression for MT2 or MT3, was demonstrated in the tissues. In conclusion, this study demonstrates that melatonin reduces the functional inhibitory NANC response. It shows that this effect may be the result of a reduction of the nitrergic component of the smooth-muscle inhibitory junction potential (IJP) and related to direct inhibition of NOS activity in enteric synaptosomes. The presence of mt1 receptor transcripts adds supportive evidence for a possible physiological role of melatonin within the enteric nervous system.

Electronic Resource

1618-2650

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Summary The UV-photolytic decomposition of some tensides and complexones has been investigated using the DPASV peak of indium as an indicator. The results show that UV-irradiation alone can completely decompose these compounds at lower concentrations within a short time. Higher concentrations need an additional oxidising agent.

Electronic Resource

1618-2650

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Summary Various simultaneous effects of humic acids on the current and potential of differential pulse anodic stripping peaks of copper, lead, cadmium and zinc in weakly alkaline and acidic (pH 2) solutions have been investigated and interpreted with regard to metal complexation and the adsorption of humic acid on the mercury electrode. The applicability of the standard additions method for metal quantitation and the experimental conditions for UV-photolysis with a high-pressure mercury lamp have been examined in model as well as real water samples.

Electronic Resource

1618-2650

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Abstract Ligand competition coupled with differential pulse anodic stripping voltammetry has been investigated for the determination of copper, lead and cadmium. Ethylenediamine displaces humic acid in its metal complexes forming kinetically labile compounds. It also eliminates interferences associated with the oxidation of copper. This enhances the sensitivity of the determination of the metals over a wide range of humic acid concentration (up to 30 mg/l). The procedure has been applied to the determination of heavy metals in a real water sample.

Electronic Resource

1618-2650

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Abstract A flow-through cell with integrated hanging mercury drop electrode for voltammetric, inverse voltammetric, adsorptive voltammetric, and chronoamperometric methods is described. HMDE droplets are automatically formed and renewed. By optimizing the flow-channel the sensitivity could be increased approximately five times in comparison with batch methods using the same deposition conditions.

Electronic Resource

1618-2650

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Zusammenfassung Es wird eine Anordnung zur inversen Voltammetrie beschrieben, bei der sämtliche Arbeitsgänge (Elektrodenformierung, Entlüftung, Elektrolyse und Aufnahme der Stromspannungskurve) programmgesteuert durchgeführt werden.

Summary A device for inverse voltammetry is described. Formation of the electrode, deaeration, electrolysis, and registration of the stripping process are directed by a programming unit.

Electronic Resource

1618-2650

Best. von Nickel ; Polarographie ; Extraktion

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Zusammenfassung Zur Bestimmung des Nickels in wäßrigen Lösungen im ppb-Bereich wird das NiHeptoxim ausgeschüttelt und die extrahierte Verbindung in einer Grundlösung aus Toluol/Methanol/LiCl mit der differentiellen Pulse-Polarographie bestimmt. Arbeitsbedingungen für die Bestimmung des Nickels neben einem großen Überschuß an Co, Fe und Neutralsalzen werden angegeben. Die Bestimmungsgrenze liegt im Bereich von 1–2 ppb Ni.

Summary The analysis of aqueous solutions of nickel in the ppb-region is possible by extracting Niheptoxime-chelate and subsequent differential pulse polarographic determination of the extracted compound in a supporting electrolyte of toluene/methanol/ LiCl. Working conditions for the determination of Ni in presence of a large amount of Co, Fe and inert salts are given. The limit of determination is in the range of 1–2ppb Ni.

Electronic Resource