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At least 163 records · Page 9Linked to original sources
PubMed1991

[Refraction by atrophine cycloplegia].

A new method for refractive measurements with atropine cycloplegia was tested in 90 children with squint. Measurements were taken by an autorefractor (Canon R 10) 90 min after application of 2 atropine eye drops and after 3 days of receiving 1 atropine eye drop 3 times daily, i.e. 9 drops per eye. Results were also compared to conventional "objective" refractometry by means of a hand refractometer (Rodenstock PR 50). According to this method, the total refraction, spherical and cylindric power and the cylinder axis are in agreement with refractive data in 80-90% of the children after 3-day atropinization. The additional cycloplegic effect of atropine given for 3 days is only 0.5 dptr compared to the application of 2 drops on the first day. So for practical purposes the refractive data evaluated after 90-min atropinization can be used as a basis for the prescription of glasses.

Atropine↗
PubMed1992

Characterization of carbonic anhydrase isozyme CA2, which is the CAH2 gene product, in Chlamydomonas reinhardtii.

From high-CO2 (5% CO2) grown unicellular green alga, Chlamydomonas reinhardtii, carbonic anhydrase (CA) was isolated by affinity chromatography and characterized. Isolated CA was identified as an isozyme (CA2) which is the product from the second gene CAH2 by peptide sequencing. The CA2 was inactivated by dithiothreitol. This treatment caused dissociation of CA2 into the large (38 kDa) and small subunits (4243 Da). The molecular mass of the CA2 holoenzyme measured by low-angle laser light-scattering photometry and precision differential refractometry combined with gel-filtration HPLC was 87.9 kDa. These results and gene structure indicate that CA2 is a heterotetramer consisting of two large and two small subunits linked by disulfide bonds like CA1, which is the CAH1 gene product. The specific activity of CA2 purified by anion-exchange HPLC was 3300 units per mg protein, which was approximately 1.6 times higher than that of CA1. Therefore, it was concluded that two structurally related isozymes, CA1 and CA2, are present in the wild type cells of C. reinhardtii and differentially regulated by the atmospheric CO2 concentration.

Amino Acid Sequence↗
PubMed1998

[Construction of a model eye for simulation of Purkinje reflections for determining the radii of curvature and the position of the crystalline lens].

UNLABELLED: Specular reflections at the optical interfaces of the eye, the Purkinje reflections, are used in physiologic optics and ophthalmology for biometric measurements. To date, there is no standard in the measurement of crystalline lens radii of curvature and position. To that end model eyes were designed. MATERIALS AND METHODS: The most important goal was to simulate the Purkinje reflections I, III, and IV, in the human eye as realistically as possible. The casing of the model eye was made of brass; the optical components were made from contact lens material. RESULTS: Several variants of components were manufactured to reproduce the range of variations in human eyes. By combining different components it was possible to vary the radii of curvature of the cornea and of the crystalline lens, axial separations, crystalline lens rotations and decentrations independently and reproducibly. First applications included devices for biometry of the crystalline lens (phacometry), validation of methods for eye alignment measurement, and refractometry. CONCLUSIONS: The properties of the specular reflections of the model eye are very close to the target values in human eyes. One of the advantages of the model eye is the compact design. This model eye is the first measuring standard for phakometry.

Anthropometry↗
PubMed1986

[Studies on the hygiene of arc-welding. (Part 8). Effects of atmospheric conditions on the chemical composition of fumes from low hydrogen welding].

Welding fumes were generated from several kinds of low hydrogen type electrodes which changed the atmosphere with use of various gases, such air, Ar, CO2 and N2, and were collected in water with an impinger. These fumes were analyzed by X-ray refractometry and chemical analysis, and pH of their collecting water was measured. Based on these results, this paper discusses the mechanism of scattering K and Na in fumes from low hydrogen welding which are considered to be the sources of respiratory tract irritation. All sample fumes from low hydrogen welding in several atmospheric conditions contained fluorite (CaF2). The pH of water in which all sample fumes were collected remarkably elevated. Chemical composition ratios of both K2O and Na2O in all sample fumes were larger than those in coating materials. The sample fumes from welding in each of both N2 and CO2 atmosphere showed higher ratios of K2O and Na2O than those in Ar. The conclusions obtained from the discussion are as follows: The potential gradient of the arc becomes larger during welding in the atmosphere with use of N2 or CO2 because the dissociation voltage of N2 and CO2 is very low. Furthermore, fluorite (CaF2) makes the slag more fluid. Then, K and Na become easily dispersed from the arc column of low hydrogen welding.

Air Pollutants, Occupational↗
PubMed1988

Relative density of urine: methods and clinical significance.

The physical properties and chemical composition of urine are highly variable and are determined in large measure by the quantity and the type of food consumed. The specific gravity is the ratio of the density to that of water, and it is dependent on the number and weight of solute particles and on the temperature of the sample. The weight of solute particles is constituted mainly of urea (73%), chloride (5.4%), sodium (5.1%), potassium (2.4%), phosphate (2.0%), uric acid (1.7%), and sulfate (1.3%). Nevertheless, urine osmolality depends only on the number of solute particles. The renal production of maximally concentrated urine and formation of dilute urine may be reduced to two basic elements: (1) generation and maintenance of a renal medullary solute concentration hypertonic to plasma and (2) a mechanism for osmotic equilibration between the inner medulla and the collecting duct fluid. The interaction of the renal medullary countercurrent system, circulating levels of antidiuretic hormone, and thirst regulates water metabolism. Renin, aldosterone, prostaglandins, and kinins also play a role. Clinical estimation of the concentrating and diluting capacity can be performed by relatively simple provocative tests. However, urinary specific gravity after taking no fluids for 12 h overnight should be 1.025 or more, so that the second urine in the morning is a useful sample for screening purposes. Many preservation procedures affect specific gravity measurements. The concentration of solids (or water) in urine can be measured by weighing, hydrometer, refractometry, surface tension, osmolality, a reagent strip, or oscillations of a capillary tube. These measurements are interrelated, not identical. Urinary density measurement is useful to assess the disorders of water balance and to discriminate between prerenal azotemia and acute tubular necrosis. The water balance regulates the serum sodium concentration, therefore disorders are revealed by hypo- and hypernatremia. The disturbances are due to renal and nonrenal diseases, mainly liver, cardiovascular, intestinal, endocrine, and iatrogenic. Fluid management is an important topic of intensive care medicine. Moreover, the usefulness of specific gravity measurement of urine lies in interpreting other findings of urinalysis, both chemical and microscopical.

Biophysical Phenomena↗
PubMed1975

Estimation of protein content in the plasma of young chickens by a refractometric method.

This study was conducted to evaluate a refractometric method for determination of protein content of chicken plasma. Comparison of the results obtained with the refractometric and the Lowry methods indicated that refractometry, when used with due caution in a typical laboratory situation, provided a simple, fast, inexpensive and valid method for determining the protein content of plasma from young chickens.

Animals↗
PubMed1982

Colostrum deficiency in mule deer fawns: identification, treatment and influence on neonatal mortality.

Glutaraldehyde coagulation test, zinc sulfate turbidity test, and total protein refractometry were adapted for use in detecting failure of passive transfer of colostral immunoglobulins to mule deer fawns (Odocoileus hemionus). The results of all three tests were similar. Serum total protein concentration was directly correlated to gamma globulin concentration and gave the best indication of morbidity and mortality. Thirteen of 13 fawns with serum total protein concentrations of 5 g/dl or less at 1 to 7 days of age developed diarrhea and died before 17 days of age. Only 1 of 14 fawns having a serum protein concentration above this level became sick and died. Seven of 13 fawns that had serum total protein concentrations of 5 g/dl or less, and that had already developed diarrhea, were given 20 ml of plasma per kg body weight. Although this increased their serum gamma globulin concentrations 0.3 g/dl, none survived. Administration of bovine colostrum to one fawn increased its serum gamma globulin concentration suggesting that mule deer fawns are able to absorb gamma globulins from bovine colostrum.

Animals↗
PubMedDate not supplied

Changes in the lymphocyte cytoplasmic refractive index following typhoid vaccination.

The refractive index of the circulating blood lymphocytes (LCRI) of healthy young adults vaccinated with typhoid vaccine has been measured by immersion refractometry and phase contrast microscopy. A rise in the LCRI preceeds the rise in the antibody titre by two to three days. A more pronounced rise also occurred in one patient prior to a rejection crises following a kidney transplant.

Adolescent↗
PubMed1975

[Some quantitative characteristics of the frog retinal rod outer segments].

Retinal rod outer segments in frogs were studied by means of light microscopy, refractometry, microspectrophotometry, and electron microscopy. Analysis of the data obtained shows that an unidentified substance, which makes up about 50% of outer segment dry weight, is lost during routine biochemical investigations. The protein parts of the rhodopsin molecules make up 85% of the outer segments proteins and 25% of outer segment dry weight. Rhodopsin molecules can be arranged in a square array with a unit cell side of about 7 nm on one side of each disk membrane. Lipids in a single membrane occupy only 2 nm, and disk membranes are strongly hydrated.

Animals↗
PubMed1976

Objective evaluation of experimental ocular irritation.

After topically administered nitrogen mustard the irritative effect on the pupil, intraocular pressure, protein concentration of the aqueous humor and on the vessels of the iris and conjunctiva was quantified. The protein level in aqueous was determined by refractometry. The degree of hyperemia of conjunctiva and iris was determined by measuring the amount of Evans blue dye present in the tissue minutes after intravenous administration. A reproducible relationship was obtained using these methods to evaluate the degree of irritation produced by nitrogen mustard.

Animals↗
PubMed1990

[Aberrometry in the diagnosis of eye diseases].

Four methods (by means of Smirnova-Korniushina's aberrometer; with the help of aberroscope--Cherning's lattice; by presenting a figure of a cross; and by automatic refractometry through different portions of the pupil) were used for studying aberration of the optic system of the eye in 490 persons. Among them, 37 were healthy persons, 27--patients with ametropia of moderate degree, 24--with high myopia, 9--with astigmatism above 3.0 D, 16--with monocular diplopia, 327--with keratoconus, 7--with scars of the cornea, 21--with initial cataract, 47--after keratotomy. In norm and in ametropia to 6.0 D, a histogram of refraction distribution by the pupil has a small disperse and a pronounced peak, the Cherning's lattice is straight. In high myopia, the disperse of refraction increases, the peak is slightly pronounced, the lattice is curved along the margins. In astigmatism, the disperse of refraction is great, but there can be peaks. The whole lattice is curved. In monocular diplopia, two more peaks can be seen on the histogram. The lattice is greatly curved. In keratoconus, aberrometry without correction is possible only at the initial stage and shows a rather mixed picture. The histogram of refraction represents a low irregular row. In aberroscopy, the bands are greatly curved, frequently overstep the bounds of the frame that itself looses a form of a circle, becomes oval or polygonal. Contact correction improves the aberration picture considerably. In scars of the cornea, the lattice is distorted and infrequently repeats their forms. In initial cataract, the course of the bands becomes interrupted and rounded spots appear between them.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Effect of interleukin-2 on microvascular liquid and protein transport in the rat small intestine.

Interleukin-2 (IL-2), a glycoprotein lymphokine derived from activated T-lymphocytes displays potent anti-cancer properties but its therapeutic use has been limited by generalized tissue swelling. To shed light on the mechanism underlying this potentially life-threatening edematogenic syndrome, recombinant IL-2 or an equal volume of control solution (excipient or 5% dextrose) was administered to 88 adult, male Sprague-Dawley rats. Initially, rats were injected with 50,000 Cetus units (equal to 300,000 I.U.) of IL-2 intraperitoneally, either one-time ("acute" rats) or every eight hours for two or seven days ("chronic" rats). Thereafter, under pentobarbital anesthesia, the main mesenteric lymph duct was isolated, incised, and measurements made of intestinal lymph flow (JV) and the total protein content and protein fractions in lymph (L) and plasma (P) (refractometry and agarose gel electrophoresis, respectively). Final measurements were also carried out after superior mesenteric vein constriction to assess filtration-independent L/P total protein "washdown." After IL-2, JV and protein clearance (JV x L/P) were increased (p less than 0.001) while lymph and plasma total protein content and protein fractionation were unchanged. Protein washdown was also maintained. These data are not only inconsistent with bulk "plasma leak" from damaged capillaries, but in conjunction with previously demonstrated increased cardiac output and reduced systemic vascular resistance after IL-2 administration, the findings favor augmented microvascular surface exchange area from increased capillary perfusion as the primary mechanism underlying increased transcapillary liquid and protein flux. This conclusion conforms to the rapid reversal of edema in patients after cessation of IL-2 therapy.

Animals↗
PubMed1987

Clinical pathologic alterations in horses during a water deprivation test.

A 72-hour water deprivation test was performed in 12 horses to determine clinical pathologic changes. Reference values for electrolyte (X) clearance, expressed as a percentage of creatinine clearance (CLCR; %CLCRX), were also determined. A comparison was made between urine concentration measurement techniques. Results of %CLCRX determination in 12 horses before water deprivation were 0.034 +/- 0.095 %CLCRNa, 42.4 +/- 9.8 %CLCRK, 0.352 +/- 0.190 %CLCRCl, and 0.710 +/- 0.250 %CLCRP. During water deprivation, there was individual variation for electrolyte clearances, but Na excretion increased significantly (P less than 0.01) at 24 and 48 hours. After 48 hours' water deprivation, %CLCRNa decreased significantly, but was still greater than the initial clearance. Plasma protein was a better indicator of water deprivation (dehydration) in the horse than was PCV. Electrolyte concentrations in serum and urine were determined. Little significant (P less than 0.01) change in acid-base values was noticed after 72 hours' water deprivation. Urine osmolality (as determined by osmometry) was compared with sp gr (determined by refractometry) in determining urine concentration. Initially, sp gr correlated well with urine osmolality determinations, but this correlation decreased after 48 hours.

Animals↗
PubMed1985

Immunoglobulin transfer and weight gains in suckled beef calves force-fed stored colostrum.

Concentrations of immunoglobulins and total proteins in second-day post-partum serum samples of 62 beef calves from multiparous dams were measured by zinc sulphate turbidity, electrophoresis, radial immunodiffusion and refractometry. These results, together with health records and weight gains, were used to evaluate the practice of routinely force-feeding 1 L of stored colostrum to suckled beef calves immediately after birth. There was no apparent benefit from such force-feeding. It did not result in greater 48-hour serum immunoglobulin levels, nor did it improve weight gains at 42 days. None of the calves required treatment for neonatal disease, but one force-fed calf died from inhalation of regurgitated colostrum.

Animals↗
PubMed1971

Quantitation of serum lipoproteins by electrophoresis on agarose gel: standardization in lipoprotein concentration units (mg-100 ml) by comparison with analytical ultracentrifugation.

Lipoprotein electrophoresis on agarose gel has been modified to allow estimation of the absolute quantity of each fraction. The reproducibility of the method is illustrated by 12 determinations in a single day on serum from one normal subject: mean total dye uptake was 302 +/- 9 (sd "corrected dye units," and the percentages of beta-, pre-beta, and alpha-lipoprotein were 56.1 +/- 0.9, 29.1 +/- 0.4, and 14.8 +/- 0.7, respectively. Reproducibility over a period of 8 months was also demonstrated. Serum lipoproteins of five normal and 15 hyperlipidemic individuals determined by this technique were compared with values obtained by analytical ultracentrifugation. The correlation coefficients were: 0.993 for pre-beta-LP vs. VLDL, 0.978 for beta-LP vs. LDL, and 0.867 for alpha-LP vs. HDL. Lipoprotein values obtained by paper electrophoresis were also correlated with those of the analytical ultracentrifuge, but to a lesser degree (r = 0.956, 0.691, and 0.786, respectively). Values for LDL and VLDL which were measured by refractometry after preparative ultracentrifugation were very similar to those obtained from the analytical ultracentrifuge. Serum triglyceride concentration was highly correlated (r = 0.972) with the agarose values for pre-beta-LP; serum cholesterol concentration was correlated (r = 0.673) with beta-LP. It is proposed that the standard curves of the comparisons with the analytical ultracentrifugal values be used to convert the corrected dye units of electrophoresis on agarose gel to mg/100 ml of specific lipoprotein.

Adult↗
PubMed1978

An interlaboratory comparison of serum total protein analyses.

An analysis of the 1976 CAP Comprehensive Chemistry Survey of total serum proteins is presented. More than 2,000 laboratories contributed data in this survey. Estimation of total serum protein concentration by the biuret reaction remains the most widely used technic, followed by refractometry. Precision and accuracy data for a number of analytic systems and methods are presented. Precisions for the entire group are nearly comparable. A negative bias for total protein concentration was shown by the SMAC.

Blood Chemical Analysis↗
PubMed1982

The use of the laser light scattering for the molecular weight determination of membrane proteins in surfactants.

A method is described for the determination of the molecular weight of the protein moiety of protein surfactant complexes using of low angle laser light (633 nm) scattering in combination with high performance porous silica gel chromatography, precision differential refractometry and differential UV absorption was described. The calibration curves in sodium dodecyl sulfate (SDS) and in a non-ionic surfactant, octaethyleneglycol dodecyl ether, using several reference proteins yielded linear lines. Molecular weight of porin oligomers and monomers, an intrinsic membrance protein that forms the permeability channel in the outer membrane of Escherichia coli, were calculated and were found to be 109,000 and 36,300, respectively in SDS and that of oligomers in octaethy leneglycol dodecyl ether was 114,200. Similarly, the molecular weights of maltoporin oligomers and monomers, which form maltose-maltodextrin specific channels, appeared to be 148,500 and 48,200, respectively, in SDS and that of oligomers in octaethyleneglycol dodeclyl ether was 149,000.

Chromatography, Gel↗