pH Effects on fluorescence of umbelliferone

Fink, David W.; Koehler, W

doi:10.1021/ac60291a034

Cited by 143 publications

(115 citation statements)

References 19 publications

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“…Determination of coumarin and its hydroxylated metabolite 7-hydroxycoumarin (CYP2A6 activity) was carried out at room temperature, at a flow rate of 0.4 ml/min, using an isocratic mobile phase consisting of 30% acetonitrile and 70% water. 7-Hydroxycoumarin was monitored using fluorescence detection at excitation and emission wavelengths of 325 nm and 452 nm, respectively, while coumarin was monitored using UV detection at 325 nm (Fink & Koehler, 1970). Supernatants were diluted 1:100 with water and 5 ml dilute sample were injected into the chromatograph.…”

Section: Methodsmentioning

confidence: 99%

The role of selected cytochrome P450 enzymes on the bioactivation of aflatoxin B1 by duck liver microsomes

Diaz¹,

Murcia²,

Cepeda³

et al. 2010

Avian Pathology

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A study was conducted to determine the cytochrome (CYP) P450 enzymes responsible for the bioactivation of aflatoxin B1 (AFB1) into its epoxide form (AFBO) in duck liver microsomes. Six male and six female 6-week-old Pekin ducks were used. The biochemical toxicology strategies applied included the use of selective inhibitors, prototype substrate activity for specific human P450s, correlation between aflatoxin bioactivation and enzymatic activity of prototype substrates, and the expression of specific CYP450 enzymes using antibodies against human CYP450s. Enzymatic activity was detected for the duck orthologues CYP1A1/2, CYP2A6 and CYP3A4 but not for the CYP2D6 orthologue. Immunoreactive proteins for CYP1A1, CYP2A6 and CYP3A4 were also detected. Inhibition studies suggested that the duck turkey CYP2A6 orthologue and, to a lesser extent, the CYP1A1 orthologue are involved in the bioactivation of AFB1. Correlation studies, however, suggest that CYP3A4, CYP2A6 and CYP1A1/2 are all involved in AFBO formation. The finding that four CYP enzymes may be involved in AFB1 bioactivation in ducks could explain the high sensitivity of this species to AFB1. Further studies are needed to fully elucidate the phase I hepatic metabolism of AFB1 in ducks, the only poultry species that develops hepatic cancer from AFB1 exposure.

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Section: Methodsmentioning

confidence: 99%

The role of selected cytochrome P450 enzymes on the bioactivation of aflatoxin B1 by duck liver microsomes

Diaz¹,

Murcia²,

Cepeda³

et al. 2010

Avian Pathology

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show abstract

“…In the present study, we have investi gated regional changes of brain tissue pH in various degrees of incomplete ischemia correlating with re gional changes of energy metabolism in normally fed mongolian gerbils following acute unilateral oc clusion of the common carotid. Regional changes of brain tissue pH were measured semiquantita tively using the umbelliferone technique (Fink and Koehler, 1970;Sundt et a\. , 1978;Welsh et aI.…”

mentioning

confidence: 99%

Brain Tissue Acidosis and Changes of Energy Metabolism in Mild Incomplete Ischemia—Topographical Study

Kim

Handa

Ishikawa

et al. 1985

J Cereb Blood Flow Metab

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Summary: Regional changes of brain tissue pH and its correlation to energy metabolism were studied in various degrees of incomplete ischemia for 5 and 60 min in the unilateral common carotid occlusion of normally fed mongolian gerbils. The degree of ischemia was evaluated by the severity of neurological deficits following 60 min of occlusion, and animals were divided into three groups: symptomatic, borderline, and asymptomatic. Changes of NADH and ATP distribution corresponded well to the degree of ischemia. On the other hand, acidosis devel oped more clearly and extended in wider areas than the The brain is highly dependent on a continuous supply of glucose and oxygen to maintain neuronal function. Thus, the brain tissue is vulnerable to ischemia for lack of energy substrate and oxygen. Although it is evident that permanent breakdown of energy metabolism following ischemia causes irre versible brain tissue damage, energy failure during ischemia does not always result in permanent damage. Experimental studies have demonstrated a better recovery of energy metabolism (Hossmann and Kleihues, 1973; Nordstrom and Siesjo, 1978; Rehncrona et aI., 1980) following complete than in complete ischemia in spite of a similar perturbation of brain energy state. Thus, it seems clear that en ergy failure during ischemia is not a limiting factor for the functional and the structural damage during the postischemic reperfusion period. Instead, other possible factors such as formation of free radicals (Flamm et aI. , 1978), accumulation of free fatty acids (Bazan, 1970), and postischemic hypoperfu sion (Paschen et aI. , 1983) lactic acidosis following severe incomplete ischemia as an important factor of irreversible brain tissue damage (Rehncrona et aI. , 1980(Rehncrona et aI. , , 1981 Kalimo et aI. , 1981; Plum et aI. , 1983). However, development of lactic acidosis and its correlation to the changes of energy state in mild incomplete ischemia, which is not detrimental enough to cause irreversible cell damage, have not been well discussed (Ginsberg et a\. , 1983). In the present study, we have investi gated regional changes of brain tissue pH in various degrees of incomplete ischemia correlating with re gional changes of energy metabolism in normally fed mongolian gerbils following acute unilateral oc clusion of the common carotid. Regional changes of brain tissue pH were measured semiquantita tively using the umbelliferone technique (Fink and Koehler, 1970;Sundt et a\. , 1978; Welsh et aI. , 1982;Csiba et a\. , 1983). Regional changes of the redox state of brain tissue were assessed using NADH fluorescence histochemistry (Welsh and Rieder, 1978), and regional changes of ATP using the luci ferine luciferase bioluminescent method (Kogure and Alonso, 1978). MATERIALS AND METHODSForty-six mongolian gerbils of either sex, weighing 50-80 g, were used in this study. The animals were allowed REGIONAL METABOLISM AND pH IN CEREBRAL ISCHEMIA 433 FIG. 1. Ultraviolet light reflectance (UV), regional NADH fluorescence (NADH), regional ATP...

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“…Umbelliferone possesses the additional property of act ing as a pH indicator (Fink and Koehler, 1970). Thus at 340-nm excitation the dye behaves isobestically, and the emitted signal is proportional to the dye concentration and is independent of the environmental pH.…”

Section: Umbelliferone As a Ph Indicatormentioning

confidence: 99%

Digital Imaging of Umbelliferone Clearance: A Method for Repeated Measurements of Cerebral Cortical Blood Flow with High Temporal and Spatial Resolution

Kirkpatrick

Bucknall

Naylor

et al. 1994

J Cereb Blood Flow Metab

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Summary:We have developed a procedure for digital im aging of the exposed cerebral cortex during elution of a fluorescent dye. This avoids disturbing the cortex and has provided a method for the repeated estimation of regional CBF (rCBF) with a high topographical resolution. Under varying conditions of MABP and arterial blood gases, grey-level images of the exposed cortex irradiated with ultraviolet light (340 or 370 nm) were digitised (8 bits) at 15-s intervals after the injection of 1-2 ml of saturated umbelliferone solution into the lingual or external carotid artery of anaesthetised cats and rabbits. Specifically de signed software allowed (a) regions of interest (ROIs) in the exposed cortex to be defined that were automatically applied to the sequence of images in a selected clearance and (b) solution of the initial slope equation for rCBF from the decay in grey-level fluorescence by exponential regression. Separate software that solved the equation at the level of a single pixel allowed a pseudocolour map of cortical rCBF to be generated. The method registers the cerebrovascular responses of autoregulation and CO2 reactivity and can detect tran sient changes in rCBF induced by direct cortical stimu lation. Early experience suggests potential use of the method for the monitoring of changes in regional rCBF during ischaemia and for sequential measurement of changes in cortical perfusion in any study where a high topographical resolution is needed.

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pH Effects on fluorescence of umbelliferone

Cited by 143 publications

References 19 publications

The role of selected cytochrome P450 enzymes on the bioactivation of aflatoxin B1 by duck liver microsomes

The role of selected cytochrome P450 enzymes on the bioactivation of aflatoxin B1 by duck liver microsomes

Brain Tissue Acidosis and Changes of Energy Metabolism in Mild Incomplete Ischemia—Topographical Study

Digital Imaging of Umbelliferone Clearance: A Method for Repeated Measurements of Cerebral Cortical Blood Flow with High Temporal and Spatial Resolution

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