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At least 145 records · Page 8Linked to original sources
PubMed1985

High performance liquid chromatographic separation of diacylglycerol acetates to quantitate disaturated species of lung phosphatidylcholine.

A high-performance liquid chromatographic (HPLC) separation of diacylglycerol acetates to quantitate disaturated species of lung phosphatidylcholine (PC) was studied. The diacylglycerol acetates were applied on a reversed phase column, eluted by an isocratic solvent, acetonitrile/isopropanol/water (35:15:1, v/v/v) at a flow rate of 1 ml/min, and detected by differential refractometry (RI). This isocratic HPLC method was useful to separate disaturated species from the others of lung PC. The quantitative analysis of the molecular species separated by HPLC was studied by RI detection. Chromatograms obtained by RI detection and radioactivity determination of diacylglycerol [3H]acetates prepared by [3H]acetic anhydride were almost identical. The RI detector responded in the same degree for different authentic standards of diacylglycerol acetates. The detection limit with RI detection was about 30 nmoles. Molecular species of PCs from human lung and carcinoma tissues were analyzed by this HPLC method. The contents of disaturated species were very similar to those reported previously. These results indicate that RI detection is very useful in the nmole range for the quantitative analysis among the molecular species containing disaturated species.

Acetates↗
PubMed2000

Correlation among refractive, keratometric and topographic astigmatism after myopic photorefractive keratectomy.

BACKGROUND: Photorefrative keratectomy can be used to flatten the curvature of the anterior cornea and reduce the myopic refraction of the eye. This leads to unphysiological topographical changes of the cornea and may alter the conditions for examinations of corneal surface topography. The purpose of this study was to check for mutual agreement of three different methods of assessment of astigmatism before and after myopic photorefractive keratectomy (PRK). PATIENTS AND METHODS: Forty-seven eyes of 28 patients (age 32.7+/-6.6 years) following PRK using an 193-nm excimer laser were included in this study. 37 eyes were treated for pure myopia (-4.9+/-2.4 D) and 10 eyes for myopic astigmatism (sphere -2.0 to -7.0 D, cylinder -1.0 to -3.0 D). Preoperatively and at 18 months postoperatively, subjective refractometry, keratometry and topography analysis were performed. The axes of topographic and keratometric cylinder were standardized periodically (180 degrees) with respect to the refractive cylinder axis. RESULTS: Pre- and postoperatively, the absolute astigmatism values correlated highly significantly between all three methods (P< or =0.001). The mean refractive cylinder was 0.65+/-0.61 D preoperatively and 0.46+/-0.41 D postoperatively (P=0.2). The mean keratometric astigmatism was 1.14+/-0.64 D before and 0.94+/-0.50 D after PRK treatment (P=0.2). Among the three methods, the mean topographic astigmatism was the highest (P<0.001) preoperatively (1.31+/-0.56 D) and postoperatively (1.21+/-0.52 D) (P=0.3). In eyes treated for pure myopia, no difference between pre- and postoperative refractive, keratometric and topographic astigmatism was detected (P>0.5). The axes of both topographic and keratometric astigmatism correlated highly significantly with the refractive cylinder axis (R> or =30.9, P<0.0001). CONCLUSION: Up to 2 years after myopic PRK, the difference between refractive and keratometric astigmatism does not differ from the preoperative value, indicating an even corneal surface. The absolute astigmatism values and the cylinder axis correlated well between subjective and objective methods of astigmatism assessment. Thus, objective measurements may be helpful in determining the cylinder component of best spectacle correction after PRK. However, topographic analysis overestimates astigmatism values systematically before and after PRK.

Adult↗
PubMed1998

Sensitivity of the MTI photoscreener for amblyogenic factors in infancy and early childhood.

BACKGROUND: Screening for amblyogenic factors in infancy by pediatricians is unsatisfactory, as they hardly ever detect ametropia or microstrabismus. As photoscreening seems to be a helpful method to detect even small squint angles and refractive errors, we tested the MTI photoscreener for its sensitivity with respect to amblyogenic factors. PATIENTS AND METHODS: One hundred and twelve children aged 6-48 months were first examined with the MTI photoscreener. Then each child underwent complete medical examination by an ophthalmologist and an orthoptist. The examination included the Hirschberg test (corneal reflex evaluation), the Brückner test (fundus red reflex), and, where possible, the Lang stereotest, the cover test and visual acuity assessment, as well as a motility test, biomicroscopy, ophthalmoscopy in mydriasis and refractometry in cycloplegia. Exclusion criteria were any organic pathological results, manifest strabismus, ametropia > or = 2 D and astigmatism > or = 1 D. An orthoptist, a pediatrician and two ophthalmologists independently evaluated the Polaroid pictures according to the criteria given in the handbook of the MTI photoscreener. RESULTS: For 10 children the evaluation with the MTI photoscreener was not possible despite the fact that photographs were retaken several times. Thirteen photographs showing obvious pathologic findings despite their poor quality were included. Eighty-three of the remaining 102 children failed the eye examination according to the above-mentioned criteria. The mean sensitivity of the MTI photoscreener was determined to be 82.8%. The ability to correctly identify the absence of any amblyogenic factors (specificity) was 61.8%. CONCLUSIONS: Sensitivity was high when compared to the usually low detection rate during pediatric examinations. Due to the low specificity, effectiveness was poor. Therefore an ophthalmological examination should be included in the preventive screening during infancy and early childhood.

Amblyopia↗
PubMed1983

Chromatographic analysis of sugars in physiological fluids by postcolumn reaction with cuprammonium: a new and highly sensitive method.

A new highly sensitive method of high-performance liquid chromatographic analysis has been used to separate mono-, di-, and oligosaccharides present in jejunal aspirates from experimentally perfused animals. The sugars in the column eluant are detected at 280 to 310 nm after reaction with cuprammonium. No reaction coil is required between the column and uv detector because the reaction is virtually instantaneous. This technique is more sensitive than differential refractometry, so that it is possible to detect 2.5 nmol (450 ng) of glucose routinely, compared to a minimum detection limit of 100 nmol (18 micrograms) using a commercial refractive index detector. Using a suitable postcolumn pump, the technique is not sensitive to changes in solvent composition, as with gradient elution, and is applicable to analysis of other cis-cis glycols.

Ammonia↗
PubMed1980

Further characterization and N-terminal sequence of cobra venom phospholipase A2.

N-terminal amino acid sequence data on cobra venom phospholipase A2 (Naja naja naja) demonstrate the absence of histidine at positions 10 and 20, in contrast to most other Naja enzymes. The presence of three tryptophans was demonstrated by p-toluenesulfonic acid hydrolysis, and the location of two of these at positions 18 and 19 parallels other Naja phospholipase A2 sequences. Based on the amino acid composition of the enzyme, the theoretical E278 0.1% should be 2.2, which is consistent with dry weight determinations, refractometry and amino acid analysis. Unusually high reactivity of the enzyme toward the protein assay of Lowry et al. gives an erroneously low E278 0.1% value of 1.45 when compared to bovine serum serum albumin as a protein standard. Using an E278 0.1% of 2.2, this enzyme is inactivated by the active site reagent p-bromophenacyl bromide with a stoichiometry of 1 mol reagent per mol enzyme. Chromatography on Affi-Gel Blue provides further purification of this phospholipase A2.

Acetophenones↗
PubMed1989

Functional morphology of accommodation in the raccoon.

The raccoon (Procyon lotor) is a small carnivore which eats in the upright position, using hand- and finger-like front paws and digits to wash, hold and examine its food at close range. These anatomic and behavioral characteristics prompted structural and functional studies of the accommodative capability of this species. By light and electron microscopy, we observed a prominent ciliary smooth muscle and zonular apparatus. When stimulated by carbachol or pilocarpine, the muscle and zonular apparatus exhibited a shift from longitudinal to reticular or circular orientation of some ciliary muscle bundles, anterior movement of the muscle as a whole, and more oblique crossing of the zonular fiber bundles in the zonular plexus. Maximum carbachol-induced accommodative amplitude measured by coincidence refractometry ranged from 3 to 19 diopters in these 1 to 9 yr old animals, with no definite age-accommodation relationship. A-scan ultrasonographic biometry showed that during accommodation the lens thickened very little, if at all, but moved anteriorly, while the apparent cornea to retina distance increased slightly. The raccoon thus exhibits the greatest accommodative capability of any non-primate terrestrial mammal so far studied.

Accommodation, Ocular↗
PubMed1977

Characterization of functionally distinct lymphoid and myeloid cells from human blood and bone marrow. I. Separation by a buoyant density gradient technique.

A buoyant density gradient procedure for mammalian cell separation is described. Gradients of Ficoll and Hypaque in balanced salt solution were used in a zonal rotor to separate distinct leukocyte populations from human peripheral blood and bone marrow. This method possesses the advantages of uniform osmolarity, density determination by refractometry, ease of preparation of gradient solutions, large sample capacity, and low viscosity with consequent ease of sterilization. Granulocyte-monocyte colony-forming units (CFU-C) from blood and bone marrow banded as a homogeneous peak with a density of 1.056 g cm-3 on steep gradients. Recovery of CFU-C was 36% with a 7- to 9-fold enrichment on shallow gradients. Both fractionated and unfractionated peripheral blood cells were stimulated by phytohemagglutinin (PHA), Concanavalin A (Con A), and allogeneic lymphocytes. In contrast, cells from unfractionated bone marrow and cells from the light density fraction of marrow were inhibited by Con A and responded variably to PHA.

Blood Cells↗
PubMed1982

Chromatic dispersion of the ocular media.

Measurements of chromatic dispersion of aqueous and vitreous humors, cornea and lens of the eye are sparse and incomplete. The wavelength variation in refractive index of the ocular media of cow, pig, frog (Rana pipiens), chicken, rock bass (Ambloplites rupestris), albino rat and cat as well as human lenses was determined by means of Abbe and Pulfrich refractometry. While the humors are somewhat less dispersive than water, the cornea is more dispersive at short wavelengths. In general, the lens is significantly more dispersive than water with dispersion increasing asymptotically at the blue end of the spectrum. The exaggerated dispersion taking place at short wavelengths should be taken into account in calculations of chromatic aberration.

Adolescent↗
PubMed1983

Longitudinal chromatic aberration of the vertebrate eye.

A recent study involving Abbe and Pulfrich refractometry analyses the dispersion of the human lens and the ocular media of a number of vertebrates. In general, the lens and, to a lesser extent, the cornea, are more dispersive than expected at wavelengths below 500 nm. The dispersion findings of this study were used in conjunction with reduced eye parameters of a number of vertebrates to calculate the longitudinal chromatic aberration of rock bass, frog, chicken, rat, cat, pig, cow, and human eyes. The calculated chromatic aberration of the human eye is greater than values reported earlier, because of the exaggerated dispersion of the lens at short wavelengths. While the values calculated for the additional species studies may be larger in some instances than expected, presumably due to lens dispersion as well, chromatic aberration is not large enough to account for the hyperopia found by retinoscopic study of small eyes.

Animals↗
PubMed1985

A schematic eye for the mouse, and comparisons with the rat.

The thicknesses and spheric and aspheric curvatures of the optic components were measured from cross-sections of frozen eyes of C57B1/6J mice. The equivalent refractive index of the crystalline lens was obtained from its back-vertex power in albumin. Refractive indices of the cornea, aqueous and vitreous humors were obtained by refractometry or interferometry at four wavelengths across the visible spectrum. The measurements parallel earlier ones on the hooded rat. The eyes of the mouse and rat differ mainly in size, by a linear scale factor of 1.9-2.0, and only slightly in refractive index. Thus refraction, chromatic aberration, and retinal illumination are easily compared in the two species. An analysis of the contribution of each optical surface to refraction may facilitate extrapolation to other strains of mice. Chromatic aberration is discussed with respect to depth of field and the retinoscopy artefact.

Animals↗
PubMed1985

The magnitude of longitudinal chromatic aberration of the human eye between 458 and 633 nm.

The longitudinal chromatic aberration (LCA) of the human eye was determined between wavelengths 458 and 633 nm for ten observers by incorporating Argon and Helium-Neon Lasers into a Badal optometer system such that tonic (or "dark focus") resting positions of accommodation could be measured under darkroom conditions. A mean chromatic range of 1.87 D was found between 488 and 633 nm. The range increased slightly to 1.91 D when the experiment was repeated under cycloplegia on a subset of three subjects. Additional wavelengths (458 and 476 nm) for a further subset (four subjects) increased the range to 2.65 D. This magnitude of LCA would support recent predictions based on Abbe and Pulfrich refractometry analyses of the dispersion of the human crystalline lens and ocular media.

Accommodation, Ocular↗
PubMed1981

Solution characterization of starch nicotinates with different degrees of esterification.

A series of starch-nicotinic acid copolymers with a degree of esterification ranging from about 15% to about 90% was prepared, and the stability in solution of two representative samples of the series was tested. The variation of some physico-chemical characteristics in the series was examined by solubility tests, viscometry and refractometry, and found to be not simply correlatable to the nicotinylation degree.

Esters↗
PubMed1982

Estimation of molecular weights of membrane proteins in the presence of SDS by low-angle laser light scattering combined with high-performance porous silica gel chromatography. Confirmation of the trimer structure of porin of the E. coli outer membrane.

An assessment study was carried out to evaluate the performance of the low-angle laser light-scattering technique combined with high-performance porous silica gel chromatography in the presence of sodium dodecyl sulfate and precision differential refractometry. It was found that the combined technique is highly promising as a reliable method for determining the molecular weight of a membrane protein solubilized by the surfactant. As a test, molecular weights of porin forming the permeability channel of the outer membrane of E. coli B in an oligomeric form were measured before and after heat treatment, which is known to cause dissociation. The results obtained indicate that the porin oligomer is a trimer with stoichiometric composition.

Chromatography, High Pressure Liquid↗
PubMed1983

Determination of molecular weight of membrane proteins by the use of low-angle laser light scattering combined with high-performance gel chromatography in the presence of a non-ionic surfactant.

An assessment study was carried out to evaluate the performance of the low-angle laser light scattering technique combined with high-performance gel chromatography in the presence of a nonionic surfactant, octaethyleneglycol n-dodecyl ether, precision differential refractometry and ultraviolet photometry. It was found that the combined technique is highly promising as a method for the determination of the molecular weight of a membrane protein solubilized by the surfactant. For trial, molecular weights of the following membrane proteins of Escherichia coli, both solubilized in oligomeric forms, were measured; porin that forms the transmembrane diffusion pore in the outer membrane, and lambda-receptor protein that facilitates the diffusion of maltose-maltodextrins across the outer membrane. The result obtained indicates that both porin and lambda-receptor protein exist as trimers in the surfactant solution.

Bacterial Outer Membrane Proteins↗
PubMed1986

A comparison of three methods for determining the concentration of rat urine.

The concentrations of 78 rat urines were compared using osmometry, refractometry and test strips for specific gravity. Test strip specific gravity values are a guide to urine concentration; where small changes of urine concentration are expected, the test strips should not be a replacement for more accurate methods such as osmometry.

Animals↗
PubMed1989

A field lab method to determine urine concentration in small mammals.

1. The concentrations of 136 urine samples from four species of small mammals were compared using osmometry, refractometry and a colorimetric test for urea concentration. 2. To obtain a wide range of concentrations (430-3950 mOsm/kg), urine samples were collected under normal and dehydration conditions. 3. Regression analyses of paired values indicate that measurements of total solids concentration (refractometric method) permit evaluations of urine osmolality and estimations of the concentration of urea with a high degree of confidence.

Animals↗
PubMed1981

Dilatometric, refractometric and viscometric study of lysozyme-cation interaction.

The interaction between hen egg-white lysozyme and Cu(II) or Co(II) cations has been studied by dilatometry, equilibrium dialysis-differential refractometry and viscometry at different metal cation concentrations. Delta V isotherms in copper and cobalt solutions have been obtained from dilatometry. Preferential adsorption parameters and specific viscosity have been determined from refractometric and viscosimetric measurements. It has been observed that this interaction produces structural alterations in lysozyme. The magnitude of these conformational changes depends on the metal ion and protein concentration. The results obtained using the three techniques are in good agreement.

Animals↗
PubMed1997

Assay of synovial fluid parameters: hyaluronan concentration as a potential marker for joint diseases.

Synovial fluids from the knees of patients with degenerative joint disease (n = 29), osteoarthritis (n = 16), diabetic arthropathy (n = 12), gout (n = 7) and acute inflammatory joint disease (n = 7) were investigated by high-performance size-exclusion chromatography combined with multiangle laser light scattering detection and differential refractometry. These data were compared with the viscosities of the same samples measured by rotation viscometry with one low shear rate, as well as with C reactive protein. The median value of the weight-average molecular weight of hyaluronan in synovial fluids, which differed less than the viscosity of these groups, varied between 1.09 x 10(6) g/mol (range 0.849-1.63 x 10(6) g/mol) (acute-inflammatory joint disease) and 1.91 x 10(6) g/mol (range 1.06-3.48 x 10(6) g/mol) (degenerative joint disease). The correlation between viscosity and hyaluronan concentration was much better than between viscosity and weight-average molecular weight. Changes in C reactive protein concentration were correlated with the disease activity. The concentration of hyaluronan was significantly higher in the cases of degenerative joint disease and diabetic arthropathy. These results suggest that synovial fluid concentration of hyaluronan is appropriate as a prognostic value in the evaluation of different kinds of joint diseases.

Biomarkers↗