Search results for "adenosine triphosphate"
showing 10 items of 232 documents
Neurotransmitters involved in the fast inhibitory junction potentials in mouse distal colon
2003
We investigated, in murine colon circular muscle, the role of adenosine 5′-triphosphate (ATP) and pituitary adenylate cyclase activating peptide (PACAP) as inhibitory neurotransmitters of the fast component of nerve-evoked inhibitory junction potential (fast IJP). Fast IJP was antagonised by apamin or suramin, abolished by desensitisation with the P2Y receptor agonist, adenosine 5′-O-2-thiodiphosphate (ADPβS), unaffected by desensitisation with P2X receptor agonist, α,β-methylene ATP (α,β-meATP), and reduced by PACAP-(6-38), a PACAP receptor antagonist. ATP induced membrane hyperpolarization resistant to tetrodotoxin, Nω-nitro-L-arginine methyl ester (L-NAME) or PACAP-(6-38), but antagonise…
Inhibition of iNOS activity by 1400W decreases glutamate release and ameliorates stroke outcome after experimental ischemia
2005
Background and purpose. It has been shown that the reversed operation of glutamate transporters when ATP levels fall accounts for most glutamate release induced by severe cerebral ischemia. Nitric oxide (NO) is formed after ischemia and causes ATP depletion. Our purpose is to test if NO release from inducible NO synthase (iNOS) after stroke may cause a delayed glutamate release due to ATP depletion that might underlie progression of the ischemic infarct. We have studied the effect of the highly selective inhibitor of iNOS activity 1400W on brain ATP levels, extracellular glutamate, and stroke outcome after transient focal cerebral ischemia in rats. Methods. To induce focal ischemia, the mid…
Quantitative changes of metabolic and bioenergetic parameters in experimental tumors during fractionated irradiation.
1999
Abstract Purpose: Previous studies with rat rhabdomyosarcomas indicate that during fractionated irradiation profound alterations of the tumor microvasculature and the oxygenation status occur when the total dose exceeds 45 Gy. At this dose a destruction which included all structures of the vessels and a significant worsening in tumor oxygenation were found. The aim of the present study was to analyze whether these effects of fractionated irradiation on the microvasculature and on tumor oxygenation also induce changes in the bioenergetic and metabolic status in the tumors during radiation treatment. Methods and Materials: R1H rhabdomyosarcomas of the rat implanted into the flank were irradia…
Blood flow, oxygenation, metabolic and energetic status in different clonal subpopulations of a rat rhabdomyosarcoma.
1998
Differentiation of a tumor plays an important role in terms of biological aggressiveness. The question arises as to whether this is reflected in differences in the metabolic and energetic status of solid tumors. The aim of this study was to analyze the influence of clonal tumor cell differentiation on the microenvironment of rat rhabdomyosarcomas. Two distinct lines of a rhabdomyosarcoma (BA-HAN-1) with different histomorphological properties were used (line F1, co-existence of mononuclear stellate cells and multinuclear myotube-like giant tumor cells; G8, polygonal, mononuclear tumor cells). Solid tumors were grown s.c. on the hind food dorsum of Lewis rats. Tumor oxygenation was measured …
Regulatory properties of 6-phosphofructokinase and control of glycolysis in boar spermatozoa.
2007
Glycolysis is crucial for sperm functions (motility and fertilization), but how this pathway is regulated in spermatozoa is not clear. This prompted to study the location and the regulatory properties of 6-phosphofructokinase (PFK, EC 2.7.1.11), the most important element for control of glycolytic flux. Unlike some other glycolytic enzymes, PFK showed no tight binding to sperm structures. It could readily be extracted from ejaculated boar spermatozoa by sonication and was then chromatographically purified. At physiological pH, the enzyme was allosterically inhibited by near-physiological concentrations of its co-substrate ATP, which induced co-operativity, i.e. reduced the affinity for the …
Anti-B-50 (GAP-43) antibodies decrease exocytosis of glutamate in permeated synaptosomes.
1999
Abstract The involvement of the protein kinase C substrate, B-50 (GAP-43), in the release of glutamate from small clear-cored vesicles in streptolysin-O-permeated synaptosomes was studied by using anti-B-50 antibodies. Glutamate release was induced from endogenous as well as 3 H -labelled pools in a [Ca2+]-dependent manner. This Ca2+-induced release was partially ATP dependent and blocked by the light-chain fragment of tetanus toxin, demonstrating its vesicular nature. Comparison of the effects of anti-B-50 antibodies on glutamate and noradrenaline release from permeated synaptosomes revealed two major differences. Firstly, Ca2+-induced glutamate release was decreased only partially by anti…
Changes in microregional perfusion, oxygenation, ATP and lactate distribution in subcutaneous rat tumours upon water-filtered IR-A hyperthermia
1995
The effect of hyperthermia on microcirculatory and metabolic parameters in s.c. DS-sarcomas of different sizes on the hind foot dorsum of SD-rats was investigated. Hyperthermia was carried out using a novel water-filtered, infrared-A radiation technique. Heating was performed at a rate of 0.5 degrees C/min until 44 degrees C was achieved in the tumour centre, which was maintained for 60 min. Using a multichannel laser Doppler flowmeter, red blood cell flux could be assessed continuously and at several sites within the tumour tissue simultaneously. Substantial inter-site variations in laser Doppler flux (LDF) were observed during hyperthermia which were independent of tumour size, site of me…
Metabolic pathways of 4-bromo-2,5-dimethoxyphenethylamine (2C-B): analysis of phase I metabolism with hepatocytes of six species including human
2004
Abstract 4-Bromo-2,5-dimethoxyphenethylamine (2C-B) is a psychoactive designer drug of abuse that is sold under the street names “Venus”, “Bromo”, “Erox”, “XTC” or “Nexus”. Concern has been raised because only little is known about its toxicity and metabolism in humans. In the present study we incubated 2C-B with human, monkey, dog, rabbit, rat and mouse hepatocytes to identify the metabolites formed and to determine possible toxic effects as evidenced by an ATP assay. Our data allow construction of the main metabolic pathways of 2C-B. Oxidative deamination results in the 2-(4-bromo-2,5-dimethoxyphenyl)-ethanol (BDMPE) and 4-bromo-2,5-dimethoxyphenylacetic acid (BDMPAA) metabolites. Additio…
Mitochondrial reactive oxygen species are obligatory signals for glucose-induced insulin secretion.
2009
OBJECTIVE—Insulin secretion involves complex events in which the mitochondria play a pivotal role in the generation of signals that couple glucose detection to insulin secretion. Studies on the mitochondrial generation of reactive oxygen species (ROS) generally focus on chronic nutrient exposure. Here, we investigate whether transient mitochondrial ROS production linked to glucose-induced increased respiration might act as a signal for monitoring insulin secretion. RESEARCH DESIGN AND METHODS—ROS production in response to glucose was investigated in freshly isolated rat islets. ROS effects were studied using a pharmacological approach and calcium imaging. RESULTS—Transient glucose increase …
Nitrergic and purinergic interplay in inhibitory transmission in rat gastric fundus.
2007
Summary 1 This study was undertaken to analyse the involvement of ATP in non-adrenergic non- cholinergic (NANC) relaxation and possible interplay between nitrergic and purinergic systems in rat gastric fundus. 2 Experiments were performed in vitro on strips of longitudinal muscle from rat gastric fundus, recording the mechanical activity as changes in isometric force. In addition, NO release induced by different experimental conditions was assayed. 3 Under NANC conditions in serotonin-precontracted strips, electrical field stimulation (EFS) elicited a tetrodotoxin (TTX)-sensitive relaxation accompanied by nitric oxide (NO) release. This effect was antagonized by pretreatment with the NO …