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At least 685 records · Page 38Linked to original sources
PubMed1978

Compensation of differences in density of radiographs by densitometry.

Radiographs were made of a dried human mandible with variations in kilovolt peak, exposure time, soft-tissue thickness substitutes, and developing time. The densitometric measurements of the image of dental and bony structures were transformed into millimeters of aluminum equivalents by means of densitometric measurements on the penetrometer. Variations in kilovolt peak, exposure time, soft-tissue thickness substitutes, and developing time do not affect the densitometric measurements after transformation, except when radiographs are very dark.

Aluminum↗
PubMed1977

Anatomical studies of simple invertebrate synapses utilizing stage rotation election microscopy and densitometry.

The radial nerve cords of starfish and the central ganglia of a gastropod mollusc were examined for the presence of chemical synapses. No structures with the degree of specialization of synapses in the vertebrate CNS were observed. Presumed chemical synapses, which possessed slight but variable paramembrane densities, were examined with a tilting stage. This showed that such densities were frequently due to overlap of vesicle and axon membrane within the section, which were resolved at the correct angle of tilt. Many structures resembled demonosomes. The necessity for care in interpreting the structure of chemical synapses in vertebrates is emphasized.

Animals↗
PubMed1989

Imaging retinal densitometry with a confocal Scanning Laser Ophthalmoscope.

We describe a novel use of the Scanning Laser Ophthalmoscope (SLO), viz. as an imaging retinal densitometer. In our SLO a helium-neon or an argon laser beam is moved in a raster pattern over the retina; the reflected light is descanned (confocal SLO) and collected by a photomultiplier. Images of the fundus subtending 22 by 18 deg are displayed on a TV monitor. Single frames taken with 514 nm light were stored in a computer in arrays of 256 by 256 pixels and density differences between dark adapted and bleached images were calculated. With a full bleach density differences of about 0.35 were found in the center of the fovea; at retinal eccentricities of 15-20 deg we found 0.15. After selective bleaching with 633 nm light substantial density differences were only seen in the foveal area. We conclude that the confocal SLO is a very suitable instrument for imaging fundus reflectometry.

Densitometry↗
PubMed1989

Use of enzyme-developed immunoblots scanned by densitometry to compare lot-to-lot variability of Russian-thistle extracts.

Two different lots of Russian-thistle extracts from five commercial sources were evaluated by isoelectric focusing, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and immunoblots of Immobilon transfers from these separations. The immunoblots were developed by an enzyme-linked method and scanned with a densitometer. The two lots of a standardized extracts produced scans that suggested uniformity in allergenic components. Several of the nonstandarized extract lots also appeared quite comparable. With further refinement, immunoblotting with densitometric analysis appears to offer an attractive way to standardize allergen extracts.

Allergens↗
PubMed1984

A simplified method for computerized densitometry of complex shapes in 2-deoxyglucose autoradiographs.

A simple, computerized densitometer is described which can be used to measure densities of photographic prints by means of a fiber-optic reflectance densitometric probe coupled to the movable cursor of a digitizing tablet. The cursor, with its attached probe, is moved by hand along a scan trajectory determined by the operator. In its configuration for use with 2-deoxyglucose autoradiographs, the histological section from which the autoradiograph was derived provides architectonic landmarks for guiding the path of the scan. The X, Y and density values taken along a scan line are sequentially stored in the computer memory. Algorithms are presented for plotting densities along unfolded scan lines within layers of structures with complicated shapes, for normalizing non-linearities introduced during photographic processing, for standardizing the data sets with reference to the density of average gray matter in different animals, for calculating total integrated density within defined boundaries along the scan line, for generating averages of multiple scans, and for stacking sequential scans to form pseudo-3-dimensional plots. This system allows densitometric measures to be made from autoradiographs in anatomically defined regions, thereby permitting precise correlation between isotope concentration and histological structure.

Animals↗
PubMed1986

An inexpensive microcomputer digital imaging system for densitometry: quantitative autoradiography of insulin receptors with 125I and LKB Ultrofilm.

This article describes a video digitizing system designed for measuring film optical density. The system, which is based on a 6-bit (64 gray level) digitizer, solid state video camera, and Apple II microcomputer, digitizes a rectangular area selected by the operator and converts the gray level values into preselected standard units. In order to develop autoradiographic standard curves for quantitative autoradiography with 125I-insulin, liver slices labeled with 125I-insulin and plastic sections containing known amounts of tritium were apposed to the same sheet of LKB Ultrofilm for exposures of 1-7 days. The results indicate that 3H plastic standards can be used to calibrate QAR of 125I-labeled ligands with LKB Ultrofilm. The Apple system was also used to measure binding of 125I-insulin to the external plexiform layer (EPL) in slices of the rat olfactory bulb. Results suggest that the EPL has two binding sites for insulin, a high affinity site with Kd = 1.0 X 10(-8) M and a low affinity site having a Kd = 1.4 X 10(-5) M.

Animals↗
PubMed1988

The analytic and functional accuracy of a video densitometry system.

Applications using radiotracers and quantitative film autoradiography are increasing dramatically in the neurosciences. Microcomputer-based image analyzing systems with video input have been developed to provide rapid quantification of autoradiographic images on relatively inexpensive systems. However, there has been some question as to whether such systems can reliably produce high levels of densitometric accuracy, especially when compared to mechanical scanners which are standard in research requiring extreme fidelity of measurement. We report methods and results from tests done to determine the analytical and functional accuracy of the Drexel Unix-based Microcomputer image Analysis System (DUMAS), which is a video densitometric system designed to provide quantitative data from autoradiograms. Analytical accuracy was determined by measuring photometric uniformity, the optical density transfer function, temporal stability, geometric uniformity, and flare. In addition, data are provided on the resolution of the system at several magnifications. Functional accuracy, the accuracy of the estimates of mean isotope concentrations in diverse neural structures, was determined by comparing the results obtained on the DUMAS system with the results from analyzing the same [14C]2-deoxyglucose images with two different Optronics P1000 systems. Our results show that, provided care is taken in the choice of a camera and a light source, the analytic accuracy of videodensitometry is high. Its functional accuracy is also high in that measurements of radioisotope concentrations in diverse neural structures made on the DUMAS system agree closely with the measurements from a properly adjusted Optronics P1000 system. The rapidity and economy of videodensitometry is not, therefore, obtained at the sacrifice of densitometric accuracy. Given adequately tested hardware and provided that suitable checks on instrument calibration and adjustment are made, the errors in autoradiographic quantification due to the image analyzing system itself are minor in comparison to other sources of error, including, as we show, variations in the user's delineation of the boundaries of neural structures.

Autoradiography↗
PubMed1993

A comparative study of vertebrate eye lens crystallins using isoelectric focusing and densitometry.

1. The crystallin proteins of numerous species belonging to different classes of vertebrates have been studied. 2. Species-specific crystallin patterns are revealed which unequivocally characterize the different species. 3. A marked variability in the number and percentage of alpha-, beta- and gamma-crystallins were found in the various species. 4. The gamma-crystallin family, with a meagre number of common bands, has proved to be most representative of the species. The beta-crystallins, with their greater number of common bands, have been best preserved throughout vertebrate evolution. 5. From the similarity coefficient matrix a dendrogram is drawn up, a visual phylogenetic summary of the interrelationships between the vertebrates considered. 6. In the Discussion, other aspects are considered, such as lens morphology, functionality, animal age, post-synthetic modifications and genetic factors.

Animals↗
PubMed1992

Combined thin-layer chromatography-photography-densitometry for the quantification of ifosfamide and its principal metabolites in urine, cerebrospinal fluid and plasma.

A method has been devised for the determination of the anticancer drug ifosfamide and its principal metabolites in urine, plasma and cerebrospinal fluid (CSF). The urine and CSF samples are absorbed onto Amberlite XAD-2 eluting the compounds of interest with methanol. Plasma is deproteinated using cold acetonitrile and centrifuged to yield a clear supernatant. The eluate and supernatant are analyzed by thin-layer chromatography, with spot visualization using 4-(4-nitrobenzyl)pyridine. The plates are photographed for subsequent densitometeric analysis. The intra-assay coefficient of variation for each compound in both urine and plasma was less than 10% and the lower limit of detection was 1 microgram/ml. The method provides a means of determining the full spectrum of metabolic products of ifosfamide in patients and will allow detailed investigation of variability in metabolism and pharmacokinetics of this drug.

Chromatography, Thin Layer↗
PubMed1990

Thin-layer chromatography and densitometry in drug assay: comparison of methods for monitoring valproic acid in plasma.

A thin-layer chromatographic (TLC) method is described for the assay of the anti-epileptic drug, valproic acid, in plasma. The use of high-performance (HPTLC) plates gave sensitive detection limits (4.87 micrograms ml-1) for derivatives of valproic acid and the reproducibility on the same or different plates was good. Comparison with high-performance liquid chromatography showed a similar performance of plate and column.

Chromatography, High Pressure Liquid↗
PubMed2004

Relationship among densitometry, bone histomorphometry, and histologic stage in idiopathic myelofibrosis.

Idiopathic myelofibrosis (IMF) induces dramatic changes in bone. Bone remodeling and densitometric alterations in a series of nine patients with IMF and their relationship with the histologic stage of the disease were assessed. Patients were included at diagnosis and a bone marrow biopsy, dual-energy X-ray absorptiometry, and transiliac bone biopsy for histomorphometric analysis were performed. Five cases were classified as IMF histologic stage 1, one as stage 2, and three as stage 3. Compared with 40 age- and sex-matched controls, the following histomorphometric parameters were significantly higher in our patients: bone volume (BV/TV), osteoblast surface (Ob.S/BS), eroded surface (ES/BS), osteoclast surface (Oc.S/BS), osteoclast number (N.Oc/TA), mineralizing surface (MS/BS), reversal period (Rv.P), and remodeling period (Rm.P). Mineral apposition rate (MAR) and erosion depth (E.Depth) were significantly decreased (P < 0.05 for all comparisons). Bone mineral density (BMD) measurements showed high values for patient age and sex both at femur neck (Z score range +0.19 to +7) and total femur (Z score range -0.09 to +6.48). When densitometric values were analyzed according to IMF histologic stage, patients in stages 1 and 2 had significantly lower BMD values than to those in stage 3 (P = 0.024). In conclusion, patients with IMF present a characteristic bone histomorphometric pattern with increased bone volume and bone cells but low apposition and decreased erosion depth, suggesting a positive balance in bone remodeling units. This balance would produce the increase in bone mass observed in this disease. Given the increase in BMD observed with more advanced stages of IMF, this noninvasive method could be useful tool for assessing IMF progression.

Biomechanical Phenomena↗
PubMed2005

Application of first-derivative, ratio derivative spectrophotometry, TLC-densitometry and spectrofluorimetry for the simultaneous determination of telmisartan and hydrochlorothiazide in pharmaceutical dosage forms and plasma.

Four sensitive methods are described for the direct determination of telmisartan (TELM) and hydrochlorothiazide (HCT) in combined dosage forms without prior separation. The first method is a first derivative spectophotometry (1D) using a zero- crossing technique of measurement at 241.6 and 227.6 nm for TELM and HCT, respectively. The second method is the first derivative of ratio spectrophotometry (1DD) where the amplitudes were measured at 242.7 nm for TELM and 274.9 nm for HCT. The third method is based on TLC separation of the two drugs followed by the densitometric measurements of their spots at 295 and 225 nm for TELM and HCT, respectively. The separation was carried out on silica gel 60 F254 using butanol: ammonia 25% (8:2 v/v) as mobile phase. The fourth method is spectrofluorimetric determination of TELM, depending on measuring the native fluorescence of the drug in 1 M sodium hydroxide at lambda excitation 230 nm and emission at 365 nm. The proposed methods were applied successfully for the determination of the two drugs in bulk powder and in pharmaceutical formulations. The spectrofluorimetric method was utilized for the analysis of TELM in human plasma.

Benzimidazoles↗
PubMed2004

Fast determination of colchicine by TLC-densitometry from pharmaceuticals and vegetal extracts.

Colchicine, (S)-N-(5,6,7,9-tetrahydro-1,2,3,10-tetramethoxy-9-oxobenzo-(a(-heptalen-7-yl)-acetamide, is the main alkaloid contained in Colchicum autumnale (meadow saffron). There are known colorimetric, spectrophotometric, volumetric, potentiometric, voltametric, gravimetric and various chromatographic methods for quantitative determination of colchicine, each of them presenting a series of advantages and disadvantages. As an alternative, we proposed the use of a densitometric determination for colchicine allowing the determination of this alkaloid from pharmaceutical products, as well from seeds of meadow saffron. The total alkaloid extract was separated by Thin-Layer Chromatography using Silicagel 60F(254) layers and a mixture of chloroform:acetone:diethylamine (5:4:1) as mobile phase. The same conditions were used for the determination from pharmaceutical products. Densitometric measurements were carried out at the absorption maximum (350 nm) of colchicine, the determinations being made by reflectance and by fluorescence. The peaks were optimized regarding to their area and shape by varying four scanning parameters (slit width and height, number of measurements and scanning speed). We established the calibration plot using pure colchicine in the range 50-600 ng mL(-1). The proposed method could be widely used in the pharmaceutical industry for the quick and accurate quantitative determination of colchicine because it eliminates the interferences given by other bioactive or degradation compounds. The method was characterized by validation parameters (linearity, accuracy, fidelity, sensitivity) and it was established its performances in comparison with an HPLC method and an official quantitative determination from the Romanian Pharmacopoeia X edition respectively.

Chromatography, Thin Layer↗
PubMed2005

High-throughput film-densitometry: an efficient approach to generate large data sets.

A film-handling machine (robot) has been built which can, in conjunction with a commercially available film densitometer, exchange and digitize over 300 electron micrographs per day. Implementation of robotic film handling effectively eliminates the delay and tedium associated with digitizing images when data are initially recorded on photographic film. The modulation transfer function (MTF) of the commercially available densitometer is significantly worse than that of a high-end, scientific microdensitometer. Nevertheless, its signal-to-noise ratio (S/N) is quite excellent, allowing substantial restoration of the output to "near-to-perfect" performance. Due to the large area of the standard electron microscope film that can be digitized by the commercial densitometer (up to 10,000 x 13,680 pixels with an appropriately coded holder), automated film digitization offers a fast and inexpensive alternative to high-end CCD cameras as a means of acquiring large amounts of image data in electron microscopy.

Automation↗
PubMed2005

Blood volume measurement: The comparison of pulse dye densitometry and Dill and Costill's methods.

In many clinical situations, it is crucial to determine circulating blood volume (BV) easily and to repeat this measurement. The Dye DensitoGram Analyzer (DDG, Nihon Kohden Corp) measures semi-automatically BV, using an injection of IndoCyanine Green (ICG, 10 mg), and avoiding intermittent blood samples. The DDG was used during a 90-day microgravity simulation by Head-Down-Tilt bed rest (HDT) to measure BV and compared with the calculation of the plasma volume (PV) variations according to Dill and Costill's formula (DC). Seventeen healthy volunteers were included: 8 control subjects (Co) and 9 subjects submitted to a resistive exercise counter-measure (CM). Measurements were performed, one day before HDT, on days 3 and 90 of HDT and on day 9 after HDT. A double measurement of the BV was performed to assess the repeatability of this method. On the last day of HDT a significant decrease (p < 0.05) in the PV was noted with the DDG (Co: -12.3+/-5.7%, CM: -9.0+/-5.3%) and DC; (Co: -4.7+/-1.8%, CM: -6.8+/-2.5%). A good repeatability of the technique was shown with a low intrasubjects coefficient of variation (4.95+/-0.95%) and an acceptable intersubjects coefficient of variation (15.30+/-1.13%). No correlation was noted between DDG and DC (r2 = 0.27). The DDG gives a good repeatability, not affected by the microgravity exposure. Thanks to its capacity to measure accurately the BV within 7-10 min, this device presents major advantages for clinical use and research purpose.

Adult↗