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At least 217 records · Page 12Linked to original sources
PubMed1983

Clinical applications of fluorometry.

An instrument has been developed that measures in ten seconds the level of fluorescein along a scanning line from the retina to the cornea. With spatial resolving power of 1.1 mm in the eye, concentrations of 1 X 10(-8) gr/ml fluorescein and higher are detectable. In this way an indication of the integrity of the blood-ocular barriers is achieved. In uveitis the dysfunction is mainly localised at the blood-aqueous barrier while in diabetic retinopathy the blood-retinal barrier is predominantly affected. Sources of error are discussed.

Adult↗
PubMedDate not supplied

Glycolysis in heart failure: a 31P-NMR and surface fluorometry study.

Glycolysis is slow in the heart, especially in the cardiomyopathic heart. Glycolysis is partially rate-limited by phosphofructokinase (PFK), an enzyme which is inhibited by calcium (Ca2+)i and hydrogen ions (H+)i and activated by cAMP. (H+)i and (Ca2+)i are augmented in cardiomyopathy. With glucose as the only substrate (NADH)/(NAD) the phosphorylation potential and developed pressure were significantly lower, and concentrations of phosphomonoester sugars and hydrogen ions (H+)i were significantly higher in isolated cardiomyopathic hearts as compared to healthy hamster hearts. Pyruvate lowered diastolic (Ca2+)i in cardiomyopathic hamster hearts. With pyruvate as the substrate (NADH)/(NAD), the phosphorylation potential and developed pressure increased significantly and concentrations of phosphomonoester sugars (PME), (H+)i and diastolic (Ca2+)i decreased significantly in myopathic hamster hearts. The results suggest that late heart failure in the myopathic hamster is associated with calcium and/or hydrogen ion-induced inhibition of glycolysis.

Animals↗
PubMed1985

Muscle fluorometry: a determination of the depth of penetration.

Fluorometric recordings of NADH (nicotinamide adenine dinucleotide) were made on rabbit papillary muscles. The specimens were placed between the UV light source and a small window of the detection stage. As the muscle was moved over the window in a transverse direction, simultaneous measurements could be taken of transmitted UV light and fluorescent light for various thicknesses of tissue. It is concluded that a muscle thickness of 0.65 mm is optimal before absorption of the incident light decreases the fluorescence signal.

Animals↗
PubMed2006

Applying Pulse Amplitude Modulation (PAM) fluorometry to microalgae suspensions: stirring potentially impacts fluorescence.

The use of microalgae suspensions in PAM-fluorometers such as the Water-PAM (Walz GmbH, Germany) presents the problem of maintaining a homogeneous sample. The Water-PAM is marketed with an optional accessory for stirring the sample within the cuvette while in the emitter-detector (ED) unit. This stirring device can help to prevent cells from settling out of suspension over the time-course of chlorophyll-a fluorescence measurements. The ED unit was found to provide a vertically heterogeneous light environment and, therefore, cells within a single sample can exist in different quenched states. Enhancing cell movement by stirring was found to substantially influence measured fluorescence yield while performing induction curve and rapid light curve analyses. This is likely to result from relatively unquenched cells outside the main light-path moving into a higher light region and thus emitting disproportionately more fluorescence than quenched cells. Samples containing cells with high sinking rates or motile species may encounter similar (but reduced) problems. This effect can be mitigated by: (a) reducing analysis time to minimise the distance cells can sink/swim during the measurement procedure and avoiding the necessity of stirring; (b) limiting the proportion of sample outside the light path by minimising sample volume or; (c) by activating the stirrer only for short periods between saturation pulses and allowing enough time after stirring for quenching to stabilise before activation of the saturation pulse. Alternatively, modifications to the instrument providing a vertical dimension to the LED-array could resolve the issue by providing a more homogeneous light environment for the sample.

Chlorophyll↗
PubMed1983

Picomole quantitation of ammonia by flow-through fluorometry.

A new fiber optic fluorometer has been used to measure picomole amounts of ammonia. The method is based on the enzymatic conversion of alpha-ketoglutaric acid and ammonium ion to glutamate with associated oxidation of NADH. The decrease in NADH fluorescence is used to quantify sample ammonia content. The method is rapid and reproducible and is capable of resolving differences as small as 0.3 pmol between samples containing 0-7 pmol.

Ammonia↗
PubMed1990

Flow injection fluorometry of protein using hypochlorite-thiamine reagent.

This paper describes a flow injection protein assay based on the formation of N-chlorides. Thiamine, which gives fluorescent thiochrome on reaction with N-chlorides, is used as a reagent. The protein sample is first mixed with the carrier solution containing sodium hypochlorite to chlorinate peptide bonds. The fluorescence reagent, containing thiamine and sodium nitrite, is then delivered to the mixture; the sodium nitrite decomposes active chlorine. The assay is sensitive, reproducible, and linear over a range from 20 ng to 2 micrograms of bovine serum albumin. The fluorescence intensity reflects the correct amount of protein because the thiochrome formed is proportional to the number of peptide bonds.

Dose-Response Relationship, Drug↗
PubMed1991

Correction for incomplete labeling in the measurement of distance distributions by frequency-domain fluorometry.

Measurements of time-resolved fluorescence are now being used to recover conformational distributions of biological macromolecules. The fluorescence data of the donor are easily corrupted by incomplete labeling of the macromolecules by the acceptor. In the present paper we describe a general procedure to correct for incomplete acceptor labeling in the determination of distance distributions from frequency-domain measurements of the donor fluorescence decay kinetics. The method can also be used to determine the extent of acceptor labeling. Simulated data were used to determine the effect of incomplete labeling on resolution of the distance distribution and the effect on the recovered distributions if one fails to account for incomplete labeling by the acceptor. The expressions and implemented algorithm were verified using known mixtures of donor-control and donor-acceptor pair molecules, which simulated the presence of a donor population lacking the acceptor. Finally, we present data on the distance distributions between two labeled sites in myosin S1 (Cys-697 to Cys-707) where it was not possible to obtain complete labeling of the acceptor site.

Algorithms↗