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At least 595 records · Page 33Linked to original sources
PubMed1994

Clinical evaluation of sodium ion selective field effect transistors for whole blood assay.

Sodium ion selective field effect transistors (ISFETs) were evaluated for their performance in measurement of sodium ions in whole blood for 'near patient' analysis in operating theatres and intensive care units. Performance was evaluated in comparison with a standard clinical laboratory sodium/potassium ion analyser (Radiometer KNA1) and with sodium and potassium assays using flame photometry on the plasma from each whole blood specimen. The imprecisions (coefficients of variation) of three ISFETs for sodium ion assay were 1.08, 1.56 and 1.10%, respectively. Robust bivariate linear regression (reweighted least squares preceded by least median of squares) of the ISFET versus KNA1 sodium ion activity yielded a regression coefficient of 1.08 and an intercept of -18.2 mM. The influence of potassium, protein and lipid on the measurement of sodium ions by both ISFETs and the KNA1 was assessed using robust multiple regression (also based on reweighted least squares preceded by least median of squares). In the regression versus flame photometry, protein was found to be more influential for the KNA1 (glass sodium ion selective electrode) than for the ISFET. Potassium had no influence on assays using the ISFET, but had a weak negative influence on assays using the KNA1. Two ISFETs lasted for more than 200 assays each demonstrating their robustness in the assay of whole blood.

Blood Chemical Analysis↗
PubMed1993

Luminance.

Luminance was introduced by the CIE as a photometric analog of radiance. This implies that an additive spectral-luminosity function characterizes the human observer. In practice, many different spectral-sensitivity functions characterize human vision, although few produce the additive spectral-luminosity function V (lambda), which is suitable for use in practical photometry. Methods that give rise to additive spectral-sensitivity functions that most resemble V (lambda) tend to have in common the use of spatial or temporal frequencies that will discriminate against signals from the short-wavelength-sensitive cone pathways or against signals in other chromatic pathways. Some of the difference among results obtained with different techniques seems to reflect the extent to which the methods can bring about changes in the state of chromatic adaptation, but it also seems likely that not all tasks tap the same postreceptoral mechanisms. Psychophysical evidence is equivocal regarding the nature of the postreceptoral mechanisms: some evidence suggests just three mechanisms, one of which has a spectral sensitivity that is like V (lambda); other evidence suggests the existence of multiple mechanisms with different spectral sensitivities. Physiological recordings from neurons in the macaque's visual pathway suggest that the properties of the magnocellular system may be sufficient to account for spectral-sensitivity functions measured with the techniques of heterochromatic flicker photometry, minimally distinct border, and critical flicker fusion. These are the psychophysical methods that yield spectral sensitivities that are most like V (lambda). Other methods of measuring spectral sensitivity seem more likely to depend on signals that travel through the parvocellular system.

Color Perception↗
PubMed1993

Spectral-luminosity functions, scalar linearity, and chromatic adaptation.

We report data for three experiments that assess the effect on the luminosity function of chromatic adaptation arising from the measurement stimuli. First, we report spectral-sensitivity functions (wavelength range, 510-640 nm) measured by heterochromatic flicker photometry for a luminance range of 25-5000 Td. The data were fitted to a linear combination of cone fundamentals. The data narrowed and the fits deteriorated with an increase in luminance level, which indicates that at high luminances chromatic adaptation that is dependent on the spectral composition of the standard and test lights is a factor in spectral-luminosity determination. Second, we report heterochromatic modulation photometry as measured with two spectral lights at constant time-averaged chromaticity and luminance for luminances from 1.6 to 1300 Td. For a time-averaged chromaticity of 570 nm, the red-green ratio of the photometric match was invariant with luminance. For a time-averaged chromaticity of 605 nm, the red-green ratio increased by almost 0.3 log unit for a 2-log-unit increase in luminance, which is indicative of chromatic adaptation to the 605-nm chromaticity. Third, we measured flicker increment detection (wavelength range, 510-640 nm) on 570- and 605-nm backgrounds of 25-5000 Td. The data were fitted to a linear combination of cone fundamentals and showed good fits at all luminances. Fits to the 570-nm-background data set showed little variation in the proportions of the cone fundamentals with luminance. Fits to the 605-nm-background data set required an increased weighting of the middle-wavelength-sensitive cone with luminance. These three experiments indicate that luminance-dependent variation in the spectral-luminosity function as assessed by flicker techniques is caused primarily by chromatic adaptation to the measurement stimuli.

Adaptation, Ocular↗
PubMed1992

Achromatic form perception is based on luminance, not brightness.

Two figures were examined, one a subjective disk and the other a cup whose shape was revealed by shadows. The figures were presented in a single color on a background of a different color, and the observers adjusted the radiance of one color until, in the first case, the vividness of the subjective contour reached a minimum (minimum subjective contour) or, in the second case, the impression of depth that is due to shadows disappeared (shadow disappearance). The results for these two tasks followed the data for minimum flicker matches (made with the same stimuli) much more closely than those for direct brightness matching. We therefore claim that achromatic form perception in general and subjective contour and shadow perception in particular are based on the intensity dimension measured by flicker photometry, not on that measured by brightness matching. Finally, in agreement with these findings, bleaching of short-wavelength sensitive cones did not affect settings for subjective contours, shadows, or flicker photometry but did affect brightness matching.

Color Perception↗
PubMed1994

Concanavalin-A-extractable non-mucous glycoprotein concentrations in gallbladder bile of cholesterol gallstone patients.

BACKGROUND: The relationship between protein concentrations and the nucleation activity of bile in cholesterol gallstone patients has already been investigated. Nucleation promoters are mucins and concanavalin A (Con-A)-extractable glycoproteins. Nucleation inhibitors are apolipoproteins. We wanted to investigate whether a change in concentration of apolipoprotein A-I (Apo A-I) or Con-A in the bile of cholesterol stone carriers is dependent on the nucleation time. METHODS: Total protein was measured by fluorescence photometry, and Con-A-extractable glycoproteins were separated by their affinity to lectins and measured by photometry. Apolipoproteins were measured by radioactive competitive protein binding assay. RESULTS: The protein concentrations in our bile samples were 2.41 +/- 1.08 mg/ml for the whole group, 2.73 +/- 1.07 mg/ml for a nucleation time less than 3 days, and 2.04 +/- 1.00 for a longer nucleation time. The concentration of the Con-A fraction accounted for 0.289 +/- 0.096 mg/ml, 0.306 +/- 0.081 mg/ml, and 0.274 +/- 0.109, respectively. The Apo A-I concentration was 52 +/- 64 micrograms/ml; 50 +/- 56 micrograms/ml for a nucleation time less than 3 days and 85 +/- 133 micrograms/ml for a longer nucleation time. CONCLUSIONS: Obviously, individual protein fractions have an effect on the nucleation behaviour of gallbladder bile in cholesterol gallstone patients.

Apolipoprotein A-I↗
PubMed2001

Relationship between aqueous humor protein level and outflow facility in patients with uveitis.

PURPOSE: To determine whether there is a relationship between the aqueous humor protein level and outflow facility in patients with uveitis. METHODS: Aqueous humor protein levels were determined by laser flare photometry, and outflow facility was determined by Schiotz tonography. RESULTS: Thirty patients with uveitis and 10 control subjects were studied. Outflow facility was lower in patients with uveitis (0.21 +/- 0.12 microl/min x mm Hg) than in control subjects (0.33 +/- 0.05 microl/min x mm Hg, P < 0.001). Patients with uveitis and laser flare photometry results (flare) more than 20 photon units/msec (n = 21) had a lower outflow facility (0.17 +/- 0.07 microl/min x mm Hg) than patients with uveitis and flare less than 20 photon units/msec (n = 9, 0.32 +/- 0.14 microl/min x mm Hg, P = 0.004). Furthermore, no difference was identified between outflow facility in patients with active uveitis (those who had anterior chamber cells) and flare less than 20 photon units/msec and outflow in control subjects. In patients with uveitis, there was a linear correlation between flare and outflow facility (r = -0.50, P = 0.005). There was no relationship between flare measurements and either intraocular pressure or aqueous humor cell levels when scored with a clinical, semiquantitative system. CONCLUSIONS: Outflow facility is significantly reduced in patients with uveitis who have high aqueous humor protein levels. Outflow facility appears to be normal in patients with active uveitis whose flare levels are low, and therefore the association between flare and outflow facility does not appear to be an indirect reflection of elevated anterior chamber cells. It is possible that elevated aqueous humor protein levels contribute to the development of uveitic glaucoma in some individuals by decreasing aqueous humor outflow facility, although a causal relationship cannot be established on the basis of this study.

Adult↗
PubMed2005

Luminous efficiency and the measurement of daytime displays, signals, and visors.

PURPOSE: Measurements concerning the usability or safety of optical equipment are based on assumptions regarding luminous efficiency. The current luminous efficiency functions are derived from human sensitivity experiments taken at low light levels compared with the outdoor daytime environment. The amount of error induced by extrapolating from low light level data to high light level applications is not known. We sought to determine whether standard luminous efficiency curves CIE V(lambda) and CIE Heterochromatic Brightness Matching are appropriate for measuring day-use optical equipment such as display phosphors, lasers, LEDs, and laser eye protection, which are becoming more common in aviation. METHODS: Flicker photometry and successive heterochromatic brightness matching were used to measure changes in luminance efficiency functions with increasing levels (1, 10, 100, and 1000 fL) of light adaptation. RESULTS: Luminous efficiency was found to depend on both the method and the reference intensity with which the measurements were taken. For heterochromatic brightness matching, luminous efficiency increased for longer wavelengths as reference intensity increased. Peak luminous efficiency shifted from approximately 540 nm to greater than 600 nm with increasing intensity. Peak luminous efficiency was constant for flicker photometry across all intensities, but the function narrowed slightly at 100 fL. CONCLUSION: Luminous efficiency curves measured at high reference intensities are substantially different from the standard luminous efficiency functions. Caution should be used when measuring spectrally narrow and bright sources such as lasers and LEDs with a V(lambda) corrected photometer because the measured luminance may correlate poorly with perceived brightness.

Adult↗
PubMed1990

Electrode measurement of glucose and urea in undiluted samples.

The development of ion-selective electrodes (ISEs) for electrolyte measurements necessitates a re-evaluation of the biological and clinical interpretation of a result. In pathological situations (e.g., hyperlipidemia and hyperproteinemia) direct potentiometry is the method of choice for ion measurements in blood. However, the "plasma water effect" exists also in normal samples, requiring new reference values for physiological ranges. A compromise between medical and instrumentation workers retained the old reference values (flame photometry for Na+ and K+) by introducing correction factors into the ISE instruments, so that the results for direct ISE and flame photometry are the same for "normal" samples. Analyses of "abnormal" samples will reveal biases between the two methods. Now, a new generation of electrodes for assaying additional metabolites reopens the issue. Although classical methods measure a quantity of substance in a predetermined volume of sample, the majority of the substance is usually in the aqueous phase, and the volumes occupied by lipid and protein are not taken into consideration. In evaluating the NOVA 12 instrument (NOVA Biomedical), using electrodes for direct measurement in serum or plasma of Na, K, Cl, total CO2, urea, and glucose, we have demonstrated the inadequacy of classical measurements of urea and glucose, especially in pathological situations characterized by a large variation in the plasma water fraction.

Analysis of Variance↗
PubMed1989

[Assessment of an extraction-photometric method of determining mercury in urine].

Experimental trials of the extraction photometry of the urine mercury have shown that this method is not sensitive enough to detect the mercury concentrations in human urine in health. Even if the mercury concentrations are detectable with this method, the results are unrepeatable because of the inadequacy of the extraction technique. This makes extraction photometry unacceptable for measuring the urine mercury concentrations at clinical laboratories.

Humans↗
PubMed1989

Enzymatic determination of potassium in serum.

This is a kinetic assay for measuring K+ in serum, based on the activation of pyruvate kinase (EC 2.7.1.40) by K+. We eliminated interference from Na+ and NH4+ ions, which also activate this enzyme, by including Na+-binding and NH4+-consuming reagents in the reaction mixture. The assay was developed with and evaluated in the Cobas Fara centrifugal analyzer (and has been used in other kinetic analyzers). Within-run and between-run CVs were less than 1.4% and less than 1.6%, respectively. The reaction rate per millimole of K+ per liter (0.05 delta A/min) was more than double that of the reagent blank (0.02 delta A/min). Results correlated well with those by flame photometry, and interference from bilirubin, hemoglobin, lipids, heparin, and other cations was negligible. This method, in conjunction with a previous method we have reported in which beta-galactosidase is used for measuring Na+ in serum, offers a practical alternative to the use of ion-selective electrodes and flame photometry for measuring these clinically important monovalent cations in high-throughput or "stat" biochemical analyzers.

Ammonia↗
PubMed1989

[Pseudohyponatremia and anion gap changes in multiple myeloma].

Pseudo-hyponatremia is a rare condition characterized by a decrease in plasma sodium concentration associated with a normal or increased effective plasma osmolarity. We present the case of a 62 year old woman with multiple myeloma (IgG) who had a plasma sodium of 84.5 mEq/l (as measured with flame photometry) and an anion gap of -8.8 mEq/l. However, when determined with an ion-selective electrode, plasma sodium was 135 mEq/l. The patient was treated with chemotherapy and did not receive sodium. One week later, plasma sodium--again measured by flame photometry--was 134 mEq/l and the anion gap 4.0 mEq/l. The pathophysiological and clinical aspects of pseudo-hyponatremia and the anion gap are discussed.

Acid-Base Equilibrium↗
PubMed1988

New perspectives in diagnosis of hemostasis disorders.

The classical coagulation analyses are performed either by using manual methods or by means of various instruments with a different degree of automation. The introduction of chromogenic peptide substrates which can be split by thrombin has led to the development of photometric assays for PT and aPTT determination independent from the fibrinogen concentration and from its conversion to fibrin. After that, turbidimetric methods for the determination of fibrinogen, thrombin time and batroxobin time have been set up allowing the use of photometry for the determination of the most important hemostaseological parameters. For such purposes a new analytical system (ChromoTimeSystem, Behringwerke AG, Marburg/FRG) based on a special instrument and reagents for chromogenic and turbidimetric methods for coagulation and fibrinolysis has been developed. The ChromoTimeSystem allows to perform by photometry all important tests for coagulation and fibrinolysis. The analytical characteristics of this new system are presented.

Blood Coagulation Disorders↗
PubMed1985

[Lithium in the therapy of hematologic diseases in childhood].

The literature as well as the author's data of this topic are reviewed. Lithium stimulates myelopoesis in vitro, especially via CSF-production. This effect is associated with a modulation of cyclic nucleotides. Lithium stimulates leukemic cell lines too. However, according to epidemiological data lithium does not play an etiological role in leukemia. Furthermore, lithium does not stimulate several tumor cell lines in culture. The effect of cytostatic drugs as well as remission rates are not lessened by lithium. In spite of increased production the functions of the granulocytes are not impaired. Because of the wide range of serum level variation serum level determinations are mandatory. To treat hematological disorders a serum level between 0.7 and 1.2 mmol/l should be achieved. Flame emission photometry and atomic absorption photometry are equivalent methods for determination of the serum level. CNS, thyroid gland, kidney, electrolyte balance, gastrointestinal tract have to be monitored for side effects. Lithium therapy has not be given in pregnancy and to breast feeding mothers. In neutropenia with increased susceptibility to infections lithium therapy including serum level monitoring can be given. Lithium reduces leukopenia and infections following cytotoxic chemotherapy for solid tumors. Current pediatric studies are investigating whether patients with chemotherapy induced neutropenia benefit from this effect in terms of increased and prolonged remission rates.

Anemia, Aplastic↗
PubMed1984

Color contrast perimetry.

A method for color perimetry is proposed in which colored test objects are presented in a white surround, so that the luminance of the object and its surround are identical. The color of the test object then may be varied in its degree of saturation, while maintaining a constant luminance. A color video instrument controlled by a microcomputer is used as a tangent screen. Foveally viewed, colored test objects are adjusted initially in luminance by heterochromatic flicker photometry to match the luminance of a white background at 100 apostilb. The relative foveal scotoma for blue light requires that test objects large enough to include the perifoveal retina be used for flicker photometry of blue test objects. Due to the progressively increasing threshold for luminance contrast detection in extrafoveal retina, differences in luminance between the colored objects and the white surrounding, as the test objects are moved into the extrafoveal visual field, appear to remain subthreshold. Test object detection can thus be expected to be a perimetric measure of color contrast detection, relatively unaffected by luminance contrast detection. This strategy should simplify the use of colored objects for clinical perimetric testing and should provide a specific test of color vision in the extrafoveal visual field.

Adult↗
PubMed1982

Sodium measurements in multiple myeloma: two techniques compared.

Sodium was determined by flame photometry and by direct potentiometry in 56 serum or plasma samples from 24 patients with multiple myeloma or macroglobulinemia. We observed differences between the two techniques as large as 17 mmol/L (12%). The flame-photometric values decreased relative to the direct-potentiometric values as protein increased or water content decreased. Moreover, the two sodium measurements could not be interconverted simply on the basis of correcting for protein or water content. There was significantly lower residual variance (p less than 0.005) when the direct-potentiometric sodium values were compared with the osmolality (corrected for the influence of glucose and urea nitrogen) than when the flame-photometric values for sodium were so compared. We conclude that direct potentiometric measurements of sodium in patients with multiple myeloma gives clinically relevant results but flame photometry does not. Clearly, the method by which sodium is measured in patients with multiple myeloma must be considered if results are to be interpreted correctly.

False Negative Reactions↗
PubMed1978

[The microscopy fluorometry (author's transl)].

The microscope photometry and the method of continuously recording photometry help in the exemplification of the temporal development of virus multiplication and in providing information on the localization of the antigen in cells. Furthermore an automatic fluorometric microscope photometer (AFM) is described. By this method, the titre and that dilution required for the complete detection of antigens can be determined and an objective comparison of the various conjugate specimens is possible.

Antigens↗
PubMed1982

Potentiometric analysis for sodium and potassium in biological fluids.

Results obtained with a potentiometric analyzer, NOVA 1, specific for sodium and potassium, were compared with those by flame photometry. Both instruments showed linearity within a physiological range of sodium and potassium concentrations and had similar precisions. Volume displacements from addition of albumin or Intralipid to aqueous samples yielded the predicted lower flame-photometric results because of the relative decrease in sample water. There may be a small interaction between sodium and albumin. Physiological measurements on plasma from uremic patients showed no change after dialysis that could be ascribed to a decrease in interaction of these ions with creatinine and urea. Potentiometric values for sodium and potassium did not differ significantly, whether measured in cerebrospinal fluid or in the corresponding plasma. Results for urine were the same potentiometrically and by flame photometry.

Humans↗
PubMed1980

[Changes in succinate dehydrogenase activity in the cerebral cortex as an effect of aminazin (histochemical and electron-cytochemical study)].

The activity and localization of succinate dehydrogenase (SDH) in the cortex of rats was studied before and after aminazin administration (15 mg/kg). Changes in the enzyme activity according to photometry occurred in 2 directions: a general drop in the activity of neurons and neuropile, a decrease in the amount of neurons reacting to SDH. Ultrastructurally the enzyme was detectable in the mitochondria of the cell body, adjacent processes and in the processes of cells circumscribing the vessels. In most of the neuropile mitochondria the product of the reaction was not found. Under the influence of aminazin there appeared dark neurons not containing organellas with products of reaction. There were also light neurons in the mitochondria without products of reaction and lipofucsin granules containing products of reaction. The above-mentioned changes permit to explain the drop in the SDH activity, found on photometry of histochemical changes.

Animals↗