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Actual Concentration (actual + concentration)
Selected AbstractsChanges in the levels of indoleamine phytochemicals during véraison and ripening of wine grapesJOURNAL OF PINEAL RESEARCH, Issue 1 2010Susan J. Murch Abstract:, Melatonin and serotonin have previously been described in mature wine grapes and finished wines, but the metabolism of these signalling molecules in the development of wine grapes has not previously been investigated. We harvested wine grapes at different stages of development from lag phase through véraison from eight different commercial vineyards representing a diversity of growing conditions, management practices, merlot varietals and localized ecosystems to determine whether different patterns in melatonin and serotonin can be found in wine grapes during seed development and berry maturation. Melatonin was detected in 45% of the fully developed purple, postvéraison grapes but only found in 23% of prelag phase samples. However, the actual concentration of melatonin was highest in wine grapes harvested at the early stage of véraison when the seed is developing. Serotonin was not detected in any of the prelag phase grapes but was consistently detected in 30,35% of grapes harvested during the véraison transition at consistent levels of about 8,10 ,g/g. Interestingly, the nitrogen storage compound ,-aminobutyric acid was also found at about 115 ,g/g in 77% of early stage green grapes and declined in both prevalence and concentration with ripening. Together, these data are indicative of a potential role for these molecules in the development and maturation of wine grapes. [source] ECL Cell Histamine Mobilization Studied byGastric Submucosal Microdialysis in Awake Rats:Methodological ConsiderationsBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 2 2003Peter Ericsson They secrete histamine in response to circulating gastrin. Gastric submucosal microdialysis has been used to study ECL-cell histamine mobilization in awake rats. In the present study we assess the usefulness and limitations of the technique. Microdialysis probes were implanted in the gastric submucosa. Histological analysis of the stomach wall around the probe revealed a moderate, local inflammatory reaction 1,2 days after implantation; the inflammation persisted for at least 10 days. Experiments were conducted 3 days after the implantation. The "true" submucosal histamine concentration was determined by perfusing at different rates (the zero flow method) or with different concentrations of histamine at a constant rate (the no-net-flux method): in fasted rats it was calculated to be 87±5 (means±S.E.M.) nmol/l and 76±9 nmol/l, respectively. The corresponding histamine concentrations in fed rats were 93±5 and 102±8 nmol/l, respectively. With a perfusion rate of 74 ,l/hr the recovery of submucosal histamine was 49%, at 34 ,l/hr the recovery increased to 83%. At a perfusion rate below 20 ,l/hr the microdialysate histamine concentration was close to the actual concentration in the submucosa. The ECL-cell histamine mobilization was independent of the concentrations of Ca2+ in the perfusion medium (0,3.4 mmol/l Ca2+). In one experiment, histamine mobilization in response to gastrin (10 nmol/kg/hr subcutaneously) was monitored in rats pretreated with prednisolone (60 mg/kg) or indomethacin (15 mg/kg). The two antiinflammatory agents failed to affect the concentration of histamine in the microdialysate either before or during the gastrin challenge, which was in accord with the observation that the inflammatory reaction was modest and that inflammatory cells were relatively few around the probe and in the wall of the probe. In another experiment, rats were given aminoguanidine (10 mg/kg) or metoprine (10 mg/kg) 4 hr before the start of gastrin infusion (5 nmol/kg/hr intravenously). Metoprine (inhibitor of histamine N-methyl transferase) did not affect the microdialysate histamine concentration, while aminoguanidine (inhibitor of diamine oxidase) raised both basal and gastrin-stimulated histamine concentrations. We conclude that microdialysis can be used to monitor changes in the concentration of histamine in the submucosa of the stomach, and that the inflammatory reaction to the probe is moderate and does not affect the submucosal histamine mobilization. [source] An introduction to enantiomers in psychopharmacologyHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue S2 2001Brian E. Leonard Abstract There is growing scientific, clinical, commercial and regulatory recognition that enantiomers offer benefits over racemates in the management of psychiatric diseases as well as in clinical medicine generally. However, relatively few studies consider enantiomers' individual characteristics. This review considers some of the clinical benefits associated with using stereochemically pure drugs in psychiatric conditions other than depression. A review of the evidence shows that enantiomers offer four main benefits. Firstly, using a single enantiomer may allow a reduction in total dose, while maintaining or improving outcomes. For example, (+)-nefopam's antinociceptive activity is greater than that produced by both the racemate and (,)-nefopam, but with the same level of acute toxicity. Thus, a single enantiomer may offer greater efficacy, dose for dose, than the racemate. Secondly, assessing dose,response relationships is simpler. There is no reason to suppose that a racemate will necessarily contain the isomers' optimum therapeutic ratio, that one of the isomers will be inactive or that the enantiomers' dose,response curves will coincide. For example, the dose,response relationship for the induction of catalepsy in the rat by thioridazine suggested that the racemate was around 12 times more potent than (+)-thioridazine and three times more potent than (,)-thioridazine, when considering the actual concentrations in the striatum. Thirdly, using a single enantiomer may reduce pharmacokinetic and pharmacodynamic variability between patients. For example, the coefficients of variation for some of methadone's pharmacokinetic parameters may reach 70%, which might have clinical consequences. Finally, using a single enantiomer may reduce toxicity arising from the therapeutically inactive stereoisomer. For example, the single enantiomers of bupivacaine and ropivacaine are significantly less cardiotoxic than their respective racemates. This review illustrates why stereochemistry should be considered when assessing the toxicology, pharmacokinetics, metabolism and efficacy of a racemate. Indeed, the differences may be so marked that achiral analyses may be misleading, and clinicians should consider prescribing an enantiomer whenever possible. In many cases, prescribing a single enantiomer improves the benefit:risk ratio. Finally, there is no reason to suppose that a racemate's characteristics will apply to the constituent enantiomers. Copyright © 2001 John Wiley & Sons, Ltd. [source] Approach to estimation of absorption of aliphatic hydrocarbons diffusing from interior materials in an automobile cabin by inhalation toxicokinetic analysis in ratsJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2010Toshiaki Yoshida Abstract The interior air of an automobile cabin has been demonstrated in our previous studies to be contaminated by high concentrations of a large variety of aliphatic hydrocarbons diffusing from the interior materials. In the present study, the amounts of seven selected aliphatic hydrocarbons absorbed by the car driver were estimated by evaluating their inhalation toxicokinetics in rats. Measured amounts of the substances were injected into a closed chamber system in which a rat had been placed, and the concentration changes in the chamber were examined. The toxicokinetics of the substances were evaluated based on concentration,time courses using a nonlinear compartment model. Their absorption amounts in humans at the levels of actual concentrations in the cabins without ventilation were extrapolated from the results found with the rats. The absorption amounts estimated for a driver during a 2,h drive were as follows: 6,µg/60,kg of human body weight for methylcyclopentane (interior concentration 23,µg/m3 as median value in previous study), 5,µg for 2-methylpentane (36,µg/m3), 13,µg for n- hexane (65,µg/m3), 51,µg for n- heptane (150,µg/m3), 26,µg for 2,4-dimethylheptane (97,µg/m3), 17,µg for n- nonane (25,µg/m3) and 49,µg for n- decane (68,µg/m3). An inverse relationship was found between the exposure and absorption among the substances (e.g. between n-decane and 2,4-dimethylheptane). These findings suggest that not only the exposure concentrations but also the absorption amounts should be taken into account to evaluate the health effects of exposure to low concentrations of volatile compounds as environmental contaminants. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||