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1.
Equilibrium dialysis is often used to study the binding of steroids to proteins. With this technique it is customary to determine the percent bound and unbound steroid in the sample, the affinity constant for the steroid-protein binding reaction, and the concentration of binding sites on the protein. Investigators have used many different ratios of dialysis buffer to sample volumes in their experiments assuming that the equilibrium in the post-dialysis sample was the same as existed before dialysis. Chemical equilibrium expressions for the system before and after dialysis indicate that during dialysis the concentration of steroid in the sample decreases resulting in a new equilibrium in which the percent bound and unbound are different from the original sample. The magnitude of the difference between the pre- and post-dialysis systems is proportional to the ratio of dialysis buffer to sample volumes. Accurate values for the affinity constant and binding site can be obtained only if this change in the equilibrium is considered.Experimental verification of the application of these principles was made in an equilibrium dialysis study of testosterone-albumin binding.  相似文献   

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Shet T  Rege J 《Acta cytologica》2000,44(2):163-168
OBJECTIVE: To examine problems encountered in the cytologic interpretation of phyllodes tumor (PT) with cystic degeneration and solutions thereof. STUDY DESIGN: Cystic degeneration was found in seven PTs (five benign, one low grade and one high grade). Aspirates from these yielded fluid and were usually labelled fibrocystic change on the original cytology. Smears were retrospectively analyzed, with special attention to the background, presence and nature of the epithelial and stromal fragments, foam cells and naked nuclei in the background. RESULTS: PTs with cystic degeneration on cytology showed thick fluid in the background, foamy macrophages (100%), apocrine cells (28%) and epithelial fragments, which showed nuclear atypia in two cases. On reviewing the smears, five of seven PTs had stromal fragments, albeit in small numbers. Most important, even in the absence of stromal fragments, all cases showed 5-50% naked nuclei of the fibroblastic type dispersed within the fluid background. CONCLUSION: In cases of fluid aspirates from well-defined lumps, one must search for fibroblastlike naked nuclei or stromal fragments within the fluid to clinch the diagnosis of phyllodes tumor.  相似文献   

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A continuous recording viscometer using oscillating capillary tubes has been developed. The basic principles, general design, and construction details of the viscosity sensing device are given. Two such devices, mechanically coupled, comprise a bridge viscometer with which two fluids can be compared directly. A bridge viscometer complete with the electronic amplifier circuits is described. The general design is readily adaptable to automatic systems.The instrument has a wide dynamic range. The fluid under test may be allowed to flow through the system. The capacity of each arm of the viscometer bridge is less than 100 μl.  相似文献   

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It is possible to measure pH values in immobilized pH gradients (IPG) when the polyacrylamide matrix is made to contain an additional, carrier ampholyte-generated pH gradient. After an IPG run, 5 mm gel segments, along the separation axis, are cut and eluted in 300 microliter of 10 mM KCl and the pH read with a standard pH meter. When using ultranarrow pH gradients, larger gel segments (ca. 265 microliter) are eluted in 900 microliter of 100 mM KCl and the pH assessed with a differential pH meter. In the latter case, either internal or external standards are used as a reference, or starting point, to convert delta pH values into an actual pH curve. The reproducibility of the system is better than +/- 0.05 pH units, with a ca. 15% error over a 0.3 pH unit span. In ultranarrow pH gradients, it is imperative to use mixtures of all commercially available carrier ampholytes, so as to smoothen conductivity and buffering capacity gaps. By the present method, it is also possible to convert a wide (2-3 pH unit) carrier ampholyte interval into a narrow (0.2-0.3 pH unit) one.  相似文献   

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The radioautographs and statistical data presented herein indicate that the uptake of glucose [14C] into rat diaphragm sections does not depend solely on the insulin concentration of the incubation medium. It is shown that by taking into account the tissue weight of the diaphragm section, a linear relationship for uptake vs log (insulin concentration) may be obtained. This serves to emphasize how careful one must be when modifying a biological assay so that previously unimportant conditions do not become significant enough to invalidate the results.  相似文献   

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This article quantifies the errors inherent in the measurement of myocardial strain in the canine left ventricle when the motion of four radiopaque marker beads is used to determine this strain. These errors are introduced because the strain is strongly inhomogeneous and only an averaged value of this strain can be determined by measuring the displacements of four points with finite separation. In this work, the error in the principal strains has been estimated by modeling the primary deformation components of the left ventricle and comparing the true strains obtained from these models with the strains computed according to the protocol typically used in experimental studies to determine strain from the motion of marker beads. Both a cylindrical and a spherical model of the left ventricle are used. For the cylindrical model, it is found that the traditional tetrahedra used may give errors as high as 20% in the maximum principal strain. A six-marker prism is found to give more consistent results, underestimating the maximum principal strain, which is in the radial direction, by no more than 8% in almost all cases. The spherical model, having double curvature, gives larger errors. In both models, the error in the other two principal strains was usually less than 5%. Furthermore, the principal strain directions were correct to within 6 degrees.  相似文献   

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1. Some properties of the open-tipped, uninsulated, pH-sensitive glass microelectrode were examined in several electrical experiments. 2. Based on these observations, technical and theoretical problems were considered for application to the pH measurement in small cells. 3. The intracellular pH, (pH)i, of the epithelial cell in rat duodenum measured was approximately 7.0. A reduction in (pH)i was apparent (about 0.3) with the addition of 20 mM-glucose to the bathing fluid. 4. It was concluded that with certain limitations such uninsulated, open-tipped microelectrodes may be successfully utilized for intracellular pH measurements.  相似文献   

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The often employed practice of reporting continuous variation experiments with polynucleotides in terms of relative ultraviolet absorbance, to better portray the hypochromicity of the complex whose stoichiometry is under investigation, is shown to be incorrect. Ways in which this type of plot can lead to erroneous conclusions are discussed. It is concluded that plotting the observed absorbance measurements is the appropriate method for data analysis and presentation.  相似文献   

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BACKGROUND: Lipogranulomatosis refers to the presence, in lymph nodes and spleen, of lipid material arising from endogenous sources, such as tumors, hematomas, cholesterol deposits, fat embolism and fat necrosis. The histologic image is similar to that seen in lymph nodes after lymphography, with vacuolized histiocytes; round, empty spaces; and numerous multinucleated giant cells (MGC). CASE: A 27-year-old woman was referred to our department for fine needle aspiration of bilateral inguinal lymph nodes. One year before, a giant cell tumor of the sacrum was surgically excised at another medical center. The aspirated material showed a normal lymphoid cell background in addition to several MGC and ill-defined cellular groups of mononuclear, histiocytelike cells admixed with mature lymphocytes. After the cytologic report was issued both nodes were surgically excised. The most remarkable histologic finding was the presence of sinus histiocytosis and multifocal subcapsular and sinusoidal lipogranulomas with numerous MGC. CONCLUSION: Lipogranulomatous lymphadenopathy is a rare pathologic condition and may be responsible for smears with numerous MGC. This entity should be considered when evaluating lymph node aspirates from patients with neoplasia, particularly that with a giant cell component.  相似文献   

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A simple experiment was conducted to test the hypothesis that variation in humidity causes expansion of bone and, thereby, affects measurements of dried, preserved skulls. The experiment consisted of subjecting ten macaque skulls to increased humidity for 24 hours. Measurements of nine skull dimensions taken immediately before and after humidification revealed a statistically significant treatment effect of increased skull size with increased humidity. The length of the molar tooth row increased by about 0.1 mm (0.50%) while the greatest length of the skull increased by about 0.9 mm (0.57%). The specimens returned to their original dimensions within 1-2 days after being removed from the humidity chamber. These results confirm the impression gained by the practical experience of measuring museum specimens in different locations and environments. It appears that bony changes associated with humidity differences represent a real, though minor, source of measurement error in osteometrics.  相似文献   

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Almost half the sphygmomanometers in a teaching hospital group had defects in the control valve which interfered with accurate blood-pressure reading. Ward staff should be taught to check sphygmomanometers regularly and replace control valves; time consumption and cost are low. The cuffs in general use in these hospitals, and of the standard size sold in Britain, had rubber bags which did not encircle the arm of more than half the patients on whom they were used. This deficiency causes over-reading of blood pressure in obese people. The size of error is uncertain but it should be avoided by adopting a cuff with a longer bag.  相似文献   

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A means of measuring pH spectrophotometrically with two pH-sensitive indicators, neutral red (NR) and bromcresol purple (BCP), is presented. Theoretical calculations and experimental measurements of pH in solution correspond in a satisfactory manner for both dyes. Spectrophotometric determinations of pH were made of dye-equilibrated frog sartorius muscles. A more accurate indication of shifting intracellular pH (pHi) was obtained with NR than with BCP, since only the spectra of NR-equilibrated muscles were insensitive to changes in external pH over the range 7.0–6.0. Muscles were stimulated in oxygenated Ringer's and the latent phase of acidification correlated with lactic acid production by analysis of tissue frozen after spectral determination of ΔpHi. Buffering capacities were calculated to be 0.041 to 0.048 g equiv per liter of strong acid or base per resultant ΔpH for a pHi range covering 0.25 unit.  相似文献   

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