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At least 487 records · Page 27Linked to original sources
PubMed1985

Direct measurement of lateral transport in membranes by using time-resolved spatial photometry.

Spatially resolving light detectors allow, with proper calibration, quantitative analysis of the variations in two-dimensional intensity distributions over time. An ultrasensitive microfluorometer was assembled by using as a detector a microchannel plate-intensified video camera. The camera was interfaced with a software-based digital video analysis system to digitize, average, and process images and to directly control the timing of the experiments to minimize exposure of the specimen to light. The detector system has been characterized to allow its use as a photometer. A major application has been to perform fluorescence recovery after photobleaching measurements by using the camera in place of a photomultiplier tube (video-FRAP) with the goal of detecting possible anisotropic diffusion or convective flow. Analysis of the data on macromolecular diffusion in homogenous aqueous glycol solutions yielded diffusion constants in agreement with previous measurements. Results on lipid probe diffusion in dimyristoylphosphatidylcholine multibilayers indicated that at temperatures above the gel-to-liquid crystalline phase transition diffusion is isotropic, and analysis of video-FRAP data yielded diffusion coefficients consistent with those measured previously by using spot photobleaching. However, lipid probes in these multibilayers held just below the main phase transition temperature exhibited markedly anisotropic diffusive fluxes when the bleaching beam was positioned proximate to domain boundaries in the P beta' phase. Lipid probes and lectin receptor complexes diffused isotropically in fibroblast surface membranes with little evidence for diffusion channeled parallel to stress fibers. A second application was to trace the time evolution of cell surface reactions such as patching. The feasibility of following, on the optical scale, the growth of individual receptor clusters induced by the ligand wheat germ agglutinin was demonstrated.

Animals↗
PubMed1991

Molecular weight determination of phospholamban oligomer in the presence of sodium dodecyl sulfate: application of low-angle laser light scattering photometry.

The number of polypeptides constituting the oligomeric structure of canine phospholamban (a putative regulator of Ca(2+)-ATPase of cardiac sarcoplasmic reticulum) stable even in the presence of sodium dodecyl sulfate was estimated through determination of the molecular weight of the oligomer. Owing to the small molecular size, the low UV-absorptivity and the limited availability, the molecular weight determination required very sophisticated application of the following technique, used as the only recourse: low-angle laser light scattering measurement combined with high-performance gel chromatography. The molecular weight of phospholamban oligomer was found to be 30,400 and the number of subunits was concluded to be five after correction for the dependence of the apparent molecular weights on the protein concentration.

Animals↗
PubMed1996

Experimental correspondence between spore dosimetry and spectral photometry of solar ultraviolet radiation.

The biologically effective dose of solar UV radiation was estimated from the inactivation of UV-sensitive Bacillus subtilis spores. Two types of independent measurements were carried out concurrently at the Aerological Observatory in Tsukuba: one was the direct measurement of colony-forming survival that provided the inactivation dose per minute (ID/min) and the other was the measurement of the spectral irradiance by a Brewer spectrophotometer. To obtain the effective spectrum, the irradiance for each 1 nm wavelenght interval from 290 to 400 nm was multiplied with the efficiency for inactivation derived from the inactivation action spectrum of identically prepared spore samples. Integration of the effective spectrum provided the estimate for ID/min. The observed values of ID/min were closely concordant with the calculated values for the data obtained in four afternoons in 1993. The average ratio (+/- SD) between them was 1.24 (+/- 0.16) for 14 data points showing high inactivation rates (> 0.05 ID/min). Considering difficulties in the absolute dosimetry of UV radiation, the concordance was satisfactory and improved credibility of the two types of monitoring systems of biologically effective dose of solar UV radiation.

Bacillus subtilis↗
PubMed1998

Photometry and spectroscopy of the GRB 970508 optical counterpart

An optical transient within the error box of the gamma ray burst GRB 970508 was imaged 4 hours after the event. It displayed a strong ultraviolet excess, and reached maximum brightness 2 days later. The optical spectra did not show any emission lines, and no variations on time scales of minutes were observed for 1 hour during the decline phase. According to the fireball and afterglow models, the intensity should rise monotonically before the observed optical maximum, but the data indicate that another physical mechanism may be responsible for the constant phase seen during the first hours after the burst.

Journal Article↗
PubMed1961

The determination of magnesium in biological materials by flame photometry.

A method is described for the measurement of magnesium in biological materials and has been applied to the Unicam flame spectrophotometer SP 900. Samples were diluted in 10 mM strontium ethylenedinitrolo tetraacetate (EDTASr), 10 mM potassium carbonate, giving final magnesium concentrations of about 0.1 to 0.2 mM. The EDTASr almost eliminated the depression of magnesium emission by interfering anions. The potassium carbonate slightly depressed both magnesium emission and flame background, which were then virtually unaffected by further addition of cations. Spectral interference by sodium was controlled by including 14 mM sodium chloride in the plasma standards and making small corrections (usually under 2%) on the basis of the plasma sodium level. The urine standards contained no sodium, but a small correction (usually about 2%) was made on the basis of the urine sodium level. There was insufficient sodium in faeces to cause spectral interference. Using the diluent described, added magnesium was satisfactorily recovered from plasma deproteinized with perchloric acid, urine, and faeces. When different volumes of identical samples of plasma and urine were analysed, the magnesium found was proportional to the volume of sample diluted. The plasma magnesium levels reported for a small group of healthy people were similar to those found by previous workers.

Carbonates↗
PubMed2001

[Application possibilities of dynamic laser light scattering photometry for the examination of poly(ethylene glycol) suppositories].

Status epilepticus is one of the most common neurologic emergencies in children, adolescents, and young adults. The advantage of diazepam suppository in medicinal therapy appears mainly in treatment of childhood epilepsy. A hydrophilic suppository base was investigated in solution by dynamic light scattering and results were compared to those of the membrane diffusion experiments measuring diazepam solubilization. According to the dynamic laser light scattering photometric measurements, the good solubilization effect of the macrogol mixture (5% Polysorbatum 20, 10% Macrogolum 400, 85% Macrogolum 1540) is explained by the formation of small, tight micellas. As the Polysorbatum 20 tenside resulted in the significant decrease (p < 0.05) of the formation of great micellas, its use led to the formation of small, tight, almost monodisperse micellas of 40-50 nm in the aqueous solution of the macrogol mixture.

Diazepam↗
PubMed1998

[In vivo ICG fluorescence photometry for quantification of warm ischemia damage of to the liver in a rat model].

The clearance of indocyanine green (ICG) from the peripheral blood has been used for the study of hepatic function in clinical and experimental investigations. We describe a method of simultaneous, semiquantitative measurement of the kinetics of ICG in the peripheral blood, liver, kidney and bile system following intraoperative bolus injection. The method is based on the fluorescence of ICG in the near infrared spectrum. Using this method, we have recognized a temporary extrahepatic storage of ICG within the kidney. Our first results prove changes in the ICG-metabolism fifteen minutes after reperfusion following a 30-minute hepatic ischemia and partial liver resection in the rat.

Animals↗
PubMed1998

[A fluorescence photometry study on the suberinite in the shallow burial peat].

A detailed study of the suberinite in the shallow burial peat from Zhenan basin, western Yunnan, has been carried out. The study has revealed that the suberinite is the most unstable maceral among all the stable macerals. It may be oxidized and/or decomposed, resulting in changes in the structure and, especially optical feature. The fluorescence light of the suberinite that has not been oxidized and decomposed is green with I546 ranging from 1.5 to 2.0; and the fluorescence spectrum has one peak: lambda(max) ranging from 480 to 510nm; Q500/650 ranging from 0.12 to 0.26; semi-wave width averaging 150nm. Nevertheless, those suberinites that are oxidized and/or decomposed give off yellow or yellowish brown fluorescent light and the I546 reduces to less than 1, even to 0.05 lambda(max) increases from 580 to 610nm; Q500/560 from 2.75 to 3.31. With illuminating time going by, the fluorescence feature of the suberinite could be changed, mainly in the fluorescence intensity and fluorescence spectrum. The suberinite that has been not oxidized and/or decomposed changes negetively in fluorescence intensity and its fluorescence spectrum moves towards red light wavelength. Nevertheless those suberinites that have been oxidized and/or decomposed change positively in fluorescence intensity and the fluorescent spectrum moves towards blue light wavelength.

English Abstract↗
PubMed1990

[Single cell fluorescence photometry for quantification of antigens on alveolar macrophages].

The quantitation of cell surface antigens on alveolar macrophages (AM) using flow-cytometry is complicated by strong autofluorescence and wide variation of cell- size and autofluorescence. Therefore a microscope-fluorometric method was developed which allows simultaneous assessment of fluorescence of fluorochrome-labelled monoclonal antibodies and size in individual cells. Autofluorescence of smokers AM was found to be variable and considerably stronger than autofluorescence of nonsmokers AM. By means of a multi step determination of autofluorescence and specific fluorescence using different filter combinations of the microscope fluorometer density of membrane bound HLADR-antigens could be efficiently determined also in strongly autofluorescent smoker AM.

Antigens, Surface↗
PubMed1988

[Simultaneous photometry of the DNA and silver-grain count in liver cells labelled with 3H-thymidine or 3H-leucine].

A modified method was proposed for reflected light simultaneous measurement of DNA content and of the silver grain number in the nucleus or cytoplasm of the same cell. Specimens-smears of isolated liver cells incorporated 3H-thymidine and 3H-leucine were prepared on coverslips and after processing were mounted on the slide glasses with smeared side facing downwards to avoid the influence of grains on DNA content measurements. To decrease the background, label measurements were carried out in polarized light. It was shown that the intensity of 3H-leucine incorporation in hepatocytes increases proportionally with cell ploidy degree.

Animals↗