Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Photometry”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources
PubMed2001

Reference ranges of electrolyte and anion gap on the Beckman E4A, Beckman Synchron CX5, Nova CRT, and Nova Stat Profile Ultra.

The widespread use of ion-selective electrode causes the reference range of the anion gap (AG) to be lowered from 8-16 to 3-11 mmol/l. The use of the outdated reference range (8-16 mmol/l) leads to the misinterpretation of the value of the anion gap. To interpret the anion gap accurately, one must use an analyzer-specific reference range. This study established the reference ranges of the electrolyte and anion gap in four ion-selective electrode analyzers. We collected clotted and lithium-heparinized blood from 124 healthy volunteers. We determined the electrolyte in the Beckman E4A (serum), Beckman Synchron CX5 (serum), and Nova CRT (serum and plasma). The anion gap was calculated from the formula: [Na(+)-(Cl(-)+HCO3(-))]. Blood sodium, potassium and bicarbonate were determined using the Nova Stat Profile Ultra. We used the plasma chloride from the Nova CRT to calculate the value of the anion gap in the Nova Stat Profile Ultra. We established the reference ranges using the non-parametric percentile estimation method. Accuracy and precision of the electrolyte performances obtained from all analyzers were acceptable. Reference values of serum and plasma sodium, potassium, and chloride were similar in all analyzers. The value of blood sodium obtained from the Nova Stat Profile Ultra was slightly higher than the values for the serum and plasma sodium obtained from the other analyzers. The bicarbonate ranges obtained from the Nova analyzers were higher than the values obtained from the Beckman analyzers. For the anion gap, the reference ranges in this study were low but similar to other studies (3-11 mmol/l) using ion-selective electrode. However, our reference ranges were lower than the previous reference ranges obtained from the continuous-flow analyzer (8-16 or 9-18 mmol/l) incorporated with flame photometry and colorimetry techniques.

Anions↗
PubMed2002

Decreased anion gap in polyclonal hypergammaglobulinemia.

OBJECTIVES: The anion gap has proved a valuable tool in the diagnosis of various forms of acid-base disorders, although the importance of slight rises in the anion gap remains unclear. The concept of the anion gap is often misunderstood and misapplied. The relationship between gammaglobulins and the serum anion gap has not received much attention except for reports of a narrowing of the gap associated with certain monoclonal immunoglobulin G gammopathies. We present patients with polyclonal gammopathy, the magnitude of which correlated strongly and negatively with the anion gap. DESIGN: The anion gap can be readily calculated from routine laboratory data, and anion gap was calculated as ([Na] +[K])- ([Cl] + [HCO3]). SUBJECTS: Serum anion gaps were determined in 206 patients with polyclonal hypergammaglobulinemia and 63 healthy subjects. MEASUREMENTS: Serum sodium and potassium ions concentration were determined by flame photometry. Serum bicarbonate level was measured as total carbon dioxide content. Serum chloride level was determined by chlorimetric titration with silver ions. RESULTS: All patients with polyclonal hypergammaglobulinemia had a statistically significant reduction in their mean serum anion gaps (6.4 +/- 1.2 mmol/L) when compared with normal control volunteers (15.3 +/- 2.4 mmol/L), p < 0.05. CONCLUSIONS: Our results show a negative correlation between serum anion gap and gammaglobulins concentration.

Acid-Base Equilibrium↗
PubMed1977

Clinical evaluation of the Technico Stat/Ion system.

1. We describe our evaluation of the Technicon Stat/Ion, an instrument which performs sodium, chloride and bicarbonate analysis simultaneously. 2. All four of the assays resulted in linear response over the entire clinical range with insignificant carryover between specimens. 3. Precision studies for within-run variation were: sodium 0.3 percent, potassium 0.7 percent, chloride 0.5 percent and bicarbonate 1.6 percent. Day-to-day precision was similar to the within-run precision. 4. Comparison methods for sodium, potassium, chloride and bicarbonate utilizing flame photometry, chloridometry and titration of released carbon dioxide respectively showed the following linear regression and correlation coefficients: sodium y=0.96+5.5 (a=0.988) potassium y=1.01x+0.0 (a=.996) chloride y=0.99x+1.0 (a=.993)bicarbonate y=1.0x+1.2 (alpha=.969).

Autoanalysis↗
PubMed1999

Monocytic cells secrete factors that evoke excitatory synaptic activity in rat hippocampal cultures.

Microglia- and macrophage-induced neuronal death may underlie a number of neurodegenerative diseases. The effects of factors secreted by monocytic cells were studied on glutamatergic synaptic transmission between cultured rat hippocampal neurons. Conditioned media from differentiated human U937 cells was collected after 24 h and applied to neurons (0.5%-30% dilution). Unactivated U937 cells spontaneously released factors that when applied to neuronal cultures evoked bursts of action potentials and elicited neuronal death (29+/-4%). Conditioned media collected from U937 cells evoked intracellular calcium ([Ca(2+)](i)) spiking (0.5%-2% dilution) and at higher concentrations evoked sustained increases in intracellular calcium (3%-30% dilution), as measured by indo-1-based photometry in single neurons. Activation of the U937 cells with zymosin A (500 microg/ml) enhanced the potency of the conditioned media to increase intraneuronal [Ca(2+)](i) as indicated by a leftward shift in the concentration-response curve. Selective antagonists to voltage-gated Na(+) and Ca(2+) channels and NMDA-gated channels (tetrodotoxin, nimodipine, and (+/-)-2-amino-5-phosphonopentanoic acid, respectively) blocked the calcium transients elicited by unactivated and zymosin -A-treated conditioned media. This pharmacologic profile is consistent with U937-released factors that excite the synaptic network that forms between cultured hippocampal neurons.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1998

The influence of phenobarbital on cytochromes and reactive oxygen species in erythropoietin producing HepG2 cells.

Light absorption photometry of HepG2 cells treated with phenobarbital for enhancing the content of cytochrome P-450 and the synthesis of erythropoietin revealed an influence on all cytochromes detectable in the wavelength range between 400 and 620 nm. No correlation was found between specific changes of cytochrome P-450 absorption and increased EPO synthesis as proposed earlier by Fandrey et al. (Life Sci. (1990) 47, 127-134). In the present study, however, the increased erythropoietin synthesis could be related to a decreased intracellular hydroxyl radical level described as crucial for the oxygen regulated gene expression (Kietzmann et al., Biochem. J. (1998) 335, 425-432; Porwol et al., Eur. J. Biochem. (1998) 256, 16-23).

Cytochrome P-450 Enzyme System↗
PubMedDate not supplied

Comparison of diclofenac and fluorometholone in preventing cystoid macular edema after small incision cataract surgery: a multicentered prospective trial.

PURPOSE: To compare a nonsteroidal topical solution (0.1% diclofenac) to a steroidal topical solution (0.1% fluorometholone) in preventing cystoid macular edema (CME) and disruption of the blood-aqueous barrier. METHODS: A multicentered, prospective clinical trial was performed on eyes undergoing phacoemulsification followed by implantation of a foldable acrylic intraocular lens by the envelope technique. The presence and degree of cystoid macula edema (CME) was determined by fluorescein angiography. A breakdown of the blood-aqueous barrier was determined by laser flare-cell photometry. RESULTS: Five weeks after surgery, CME was present in 3 of 53 eyes (5.7%) receiving diclofenac and in 29 of 53 eyes (54.7%) receiving fluorometholone. This difference was statistically significant (P < .001). The amount of flare in the anterior chamber at 3 days, 1, 2, 5, and 8 weeks after surgery was also significantly lower (P < .01-P < .001) in the diclofenac group. The degree of flare at 3 days, 1, 2, 5, and 8 weeks after surgery was significantly higher in eyes with CME (P < .001). CONCLUSIONS: These findings suggest that diclofenac effectively prevents CME following cataract surgery and that CME is closely related to the breakdown of the blood-aqueous barrier.

Aged↗
PubMed1975

Thin-layer chromatographic determination of barbiturates and phenytoin in serum and blood.

A method is described for the measurement of blood, serum and/or plasma levels of hexobarbital, phenobarbital, cyclobarbital and phenytoin by ultraviolet reflectance photometry on thin-layer chromatograms. The lowest concentrations measured were 0.3-0.7 mug/ml. The accuracy was similar to that of gas chromatographic procudures. For phenytoin determinations 5-(p-methylphenyl)-5-phenylhydantoin may be used as internal standard. The method has been applied to clinico-pharmacological assays, to the measurement of cyclobarbital elimination in man following a therapeutic dose, and to the study of phenobarbital kinetics in rats using serial blood samples.

Animals↗
PubMed2003

Determination of total petroleum hydrocarbons in soil by dynamic on-line supercritical fluid extraction with infrared photometric detection.

Total petroleum hydrocarbons (TPHs) in soil are determined by on-line dynamic supercritical fluid extraction (SFE) using infrared filter photometry detection. The filter photometer was constructed in the laboratory using a tungsten lamp, an optical notch filter that selects the C-H stretching vibration of the extracted organics, an optical chopper with demodulation electronics, and a PbSe detector. A modified high-pressure fiber optic flow cell was used to couple the SFE system to the photometer. Quantitation of TPHs was accomplished through the construction of calibration curves of integrated absorbance of C-H stretching (over time) versus concentration. Our studies show that the sensitivity of this system is affected by both the optical path length in the high-pressure cell and the SFE fluid flow-rate, and detection limits for TPHs are in the mid part-per-million range. The results of the application of this on-line SFE-IR instrument to the determination of TPHs in real-world samples show good agreement with those obtained from standard Soxhlet extraction-IR methods.

Calibration↗
PubMed1997

Methods for the determination of nitrite by high-performance liquid chromatography with electrochemical detection.

A review on the use of high-performance liquid chromatography coupled with electrochemical detection (HPLC-ED) for the measurement of nitrite (NO2-) and nitrate (NO3-) is presented. HPLC-ED has been used for the determination of NO2- and NO3- in food, biological and environmental samples. Analysis of the current literature indicates that the measurement of NO2- and NO3- by the HPLC-ED procedure is more sensitive, selective and faster than methods based on UV absorption, photometry, fluorometry or chemiluminescence.

Chromatography, High Pressure Liquid↗
PubMed1987

Time course of response of individual messenger RNAs in the rat heart to T3.

The time course of response of specific mRNAs following administration of triiodothyronine (T3) to hypothyroid rats was examined. We were particularly interested in identifying mRNAs showing a rapid response. Hypothyroid rats were injected with 0.2 mg of T3/100 g body wt and total cardiac RNA was prepared 0.5, 1, 2, 3, 5, 12 and 24 h later. RNA was translated in vitro in the presence of [35S]-methionine, the labeled peptides separated by two-dimensional electrophoresis and quantitated by digital matrix photometry. Of a total of 427 translational products 13 were identified to be selectively responsive to thyroid hormone. A specific mRNA coding for a protein designated as spot 72b (Mr 81,600, pI 5.34) was observed to show the most rapid response to T3. Administration of T3 to the hypothyroid animal resulted in an increase in the level of spot 72b by 2.6-fold within 1 h. The lag time between injection of T3 and response of other specific mRNA species varied between 5 to 24 h. These results demonstrate the diversity of response of individual cardiac mRNAs. The specific T3 responsive mRNA species described in the heart have not been demonstrated in other tissues indicating that induction of distinctive mRNA species is highly tissue specific. Relatively late responses may represent indirect effects of T3 mediated by interaction with other hormonal or metabolic signals. The rapid induction of spot 72b suggests it may result from the interaction of T3 with the nuclear receptor leading to a direct effect on the expression of this gene in the heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Subclinical mastitis among HIV-infected and uninfected Zimbabwean women participating in a multimicronutrient supplementation trial.

Subclinical mastitis, defined as raised milk sodium/potassium (Na/K) ratio is common and associated with poor infant growth and increased mother-to-child HIV transmission. In 1996-97, we conducted a randomized controlled trial of multiple micronutrient supplementation, at recommended daily allowance levels, from 22 to 35 weeks gestation until 3 months post-partum, on the prevalence and severity of subclinical mastitis among 84 HIV-infected and 83 HIV-uninfected lactating Zimbabwean women and on their infants' growth. Spot milk samples collected before 4.5 months post-partum were analysed for Na/K ratio by flame photometry. There was no significant difference in prevalence of subclinical mastitis between HIV-infected and HIV-uninfected women. After controlling for infant age at time of sampling, micronutrient-supplemented HIV-infected women had non-significantly (P = 0.08) lower geometric mean Na/K ratio (0.43, 95% CI 0.35-0.51) than HIV-infected women given placebo (0.51, 95% CI 0.42-0.61). Micronutrient supplementation had no effect on the prevalence of subclinical mastitis among HIV-uninfected women (odds ratio [OR] = 1.26, 95% CI 0.45-3.51, P = 0.80) but induced a borderline decrease in prevalence (OR = 2.82, 95% CI 0.96-8.26, P = 0.07) among HIV-infected women. Infant weight between 1.5 and 4.5 months was lower in women with higher milk Na/K ratio. Thus, the importance of subclinical mastitis for infant growth suggests that further investigations to decrease the condition, perhaps using higher micronutrient doses, are warranted.

Adult↗
PubMed2000

In vitro effects of different steroid hormones on superoxide anion production of human neutrophil granulocytes.

Neutrophil granulocytes play an important role in atherogenesis also through their free radical generation. According to recent studies, a point of action by which estrogens can provide protection against atherosclerosis is their inhibiting effect on superoxide anion production. The aim of our study was to test whether this means a common effect of steroids on superoxide production, or whether various steroid hormones have different action on superoxide generation of human granulocytes. Neutrophils were separated from the blood samples of twelve healthy volunteers. Isolated cells were incubated with different concentrations (10(-9), 10(-8), 10(-7) M) of hydrocortisone, aldosterone, cortexolone, 17-beta-estradiol, progesterone, and testosterone. Superoxide anion production was determined by photometry using the reduction of ferricytochrome-C. Compared to that of control cells neutrophils incubated with 17-beta-estradiol, progesterone, testosterone and hydrocortisone showed significantly reduced superoxide production. No significant alteration of superoxide anion production was found after the incubation of cells with aldosterone and cortexolone. It is concluded that similarly to estradiol other sex steroids and cortisol can inhibit the free radical production of human granulocytes, but mineralocorticoid aldosterone and Reichstein's substance S do not show such activity. Our results provide new evidence supporting the theory that certain types of steroid hormones have antioxidant capacity. This may give further reasons for investigating the molecular background of the existence or absence of this property and thus might lead to the development of new free radical scavengers.

Adult↗
PubMed2002

Opsin gene and photopigment polymorphism in a prosimian primate.

A recent genetic investigation found some species of prosimian to have an opsin gene polymorphism [Nature 402 (1999) 36]. In the present study the functional implications of this finding were explored in a correlated investigation of opsin genes and spectral sensitivity measurements of a diurnal prosimian, Coquerel's sifaka (Propithecus verreauxi coquereli). Spectra recorded using electroretinogram (ERG) flicker photometry reveal a cone photopigment polymorphism paralleling an opsin gene polymorphism detected by molecular methods. This species has two middle-to-long-wavelength cone pigments with peak sensitivities of about 545 and 558 nm and a short-wavelength-sensitive cone with a peak at about 430 nm. The distribution of these pigments among animals predicts the presence of both dichromatic and trichromatic forms of color vision.

Animals↗
PubMed2002

Individual differences in chromatic (red/green) contrast sensitivity are constrained by the relative number of L- versus M-cones in the eye.

Many previous studies have shown that the relative number of long-wavelength-selective (L) versus medium-wavelength-selective (M) cones in the eye influences spectral sensitivity revealed perceptually. Here, we hypothesize that the L:M cone ratio should also influence red/green chromatic contrast sensitivity. To test this, in each subject we derived an estimate of L:M ratio based on her red/green equiluminance settings (obtained with heterochromatic flicker photometry), and measured both red/green chromatic and luminance contrast sensitivity at different spatial and temporal frequencies. Factor analysis was applied to the data in order to reveal covariance between conditions. As expected, chromatic and luminance contrast sensitivity were found to be independent of one another, and no relationship was observed between L:M ratio and luminance contrast sensitivity. However, a significant relationship was observed between L:M ratio and chromatic contrast sensitivity, wherein subjects possessing the most symmetrical L:M cone ratios (i.e., near 1:1) appear to possess the relatively greatest chromatic contrast sensitivity. This relationship can be accounted for by a simple model based on the notion of random L- and M-cone inputs to the center and surround receptive fields of chromatic (L-M) mechanisms.

Adolescent↗
PubMed2003

Cone pigment variations in four genera of new world monkeys.

Previous research revealed significant individual variations in opsin genes and cone photopigments in several species of platyrrhine (New World) monkeys and showed that these in turn can yield significant variations in color vision. To extend the understanding of the nature of color vision in New World monkeys, electroretinogram flicker photometry was used to obtain spectral sensitivity measurements from representatives of four platyrrhine genera (Cebus, Leontopithecus, Saguinus, Pithecia). Animals from each genus were found to be polymorphic for middle to long-wavelength (M/L) sensitive cones. The presence of a short-wavelength sensitive photopigment was established as well so these animals conform to the earlier pattern in predicting that all male monkeys are dichromats while, depending on their opsin gene array, individual females can be either dichromatic or trichromatic. Across subjects a total of five different M/L cone pigments were inferred with a subset of three of these present in each species.

Adaptation, Ocular↗
PubMed2003

Senescence of the temporal impulse response to a luminous pulse.

An impulse response function (IRF) to a luminous pulse was derived for 70 normal observers ranging in age from 16 to 86 years. Thresholds were measured for two pulses separated by interstimulus intervals from 6.7 to 180 ms. The pulses had a spatial Gaussian shape (+/-1SD=2.3 degrees diam) and were presented as increments on a 10 cd/m(2) background, having the same chromaticity as the pulse. A spatial 4-alternative forced-choice method was combined with a staircase procedure. Retinal illuminance was equated individually by heterochromatic flicker photometry and control of pupil area. Each IRF was measured four times, in separate sessions, for each observer. IRFs calculated from the threshold data revealed significant age-related changes in the response amplitude of both excitatory and inhibitory phases. In general, there were no significant changes in the time to the first peak or in the first zero crossing. For 12 of 20 observers over 60 years of age, however, the amplitude of the second (inhibitory) phase was reduced relative to the excitatory phase so their IRFs were quite slow and long. Control conditions with three pseudophakic observers and two normal observers with induced blur demonstrated that age-related changes in the IRF under these conditions cannot be ascribed to optical factors. The data suggest that the human visual system generally maintains a stable speed of response to a flash until at least about 80 years of age, even while there are senescent reductions in response signal amplitude.

Adolescent↗
PubMed1998

Temporal analysis of the chromatic flash VEP--separate colour and luminance contrast components.

Temporal analysis of the chromatic flash visual evoked potential (VEP) was studied in human subjects with normal and anomalous colour vision using a deterministic pseudo-random binary stimulus (VERIS). Five experiments were carried out on four normal subjects investigating heterochromatic red-green exchange and single colour/achromatic (either red/grey or green/grey) exchange over a wide range of luminance ratios for the two stimuli, the effects of lowered mean luminance on the chromatic VEP and the effects of colour desaturation at constant mean luminance and constant luminance contrast. Finally, the performance of three dichromats, a protanope and two deuteranopes, on heterochromatic exchange VEP and on colour desaturation were investigated. In contrast to the chromatic electroretinogram, which shows great symmetry with respect to luminance ratio on opposite sides of the isoluminant point, the chromatic VEP demonstrated a distinct asymmetry when the colours exchanged included red. On the red side of isoluminance (red more luminant than green), a wave with longer latency and altered waveform became dominant. The effects of green stimulation were indistinguishable from those of achromatic stimulation at the same luminance contrast over the whole range of chromatic contrast and for all levels of desaturation studied. Desaturation of red with constant luminance contrast (desaturated red/grey stimulation) resulted in a systematic alteration in the evoked waveform. Subtraction of the achromatic first- and second-order responses from responses recorded in the red desaturation series resulted in remarkably uniform waveforms, with peak amplitudes growing linearly with saturation. The absence of interaction between achromatic and coloured components for all (including the most intense colour) stimulus parameters used suggests that the generators of these components are separate. Recordings from the dichromats showed that the contrast response minimum shifted from the point of photopic isoluminance to the point of zero cone contrast (at the silent substitution point) for the remaining cone type. The waveforms recorded with a series of luminance ratios were much simpler than those recorded from trichromats and symmetrical with respect to their isoluminant points. Despite the indication of the presence of L cones of apparently normal spectral sensitivity in the deuteranopes (on the basis of flicker photometry), there was no evidence for a red-sensitive component in the desaturation or heterochromatic stimulation series. The results are discussed in terms of the possibility of separate generation of chromatic and achromatic contributions to the VEP.

Color Perception↗
PubMed1977

Lactate dehydrogenase content related to cross-sectional area in muscle fibres.

Cross-sectional areas and lactate dehydrogenase activity were determined of separate muscle fibres of mouse rectus femoris muscle in both ventral and dorsal parts of the muscle. The lactate dehydrogenase activity was measured quantitatively by microscope photometry using a tetrazolium staining in absence or presence of either vitamin K3 or phenazine methosulfate. If the observations are restricted to a relatively small area of the muscle cross section, one can distinguish categorically narrow ("red") and broad ("white) fibres with average values for cross sectional area and LDH content that depend on the part of the muscle chosen (higher LDH and smaller area in ventral part). However, if these data from the different parts or from the whole muscle are added together, no categorical distinction between the fibre types is allowed. On the basis of the observations a categorical division of muscle fibres within relatively large muscle areas or in a whole muscle is rather dubious. A relation is suggested between the subjective impression of different muscle fibre types in a field of observation with the number of motorunits present in that field.

Animals↗