[Determination of lecithin: cholesterol acyltransferase activity by a radioisotopic assay (author's transl)]

A method for determining Lecithin: Cholesterol Acyltransferase (LCAT) activity is presented. Trace amounts of labelled cholesterol are added to innactivated homologous substrate from a pool of normal serum. LCAT activity is determined measuring the cholesterol esterification, and is expressed as micrograms of cholesterol esters formed per milliliter plasma per hour. LCAT time-course, reproducibility, activity after serum storage at 4 degrees C, and normal values from 20 healthy subjects are studied.

An analysis of lamellar x-ray diffraction from disordered membrane multilayers with application to data from retinal rod outer segments

Oriented multilayers containing a membrane pair within the unit cell potentially possess both lattice disorder and substitution disorder. Lattice disorder occurs when there is a lack of long-range order in the lattice spacings produced by a variation in the nearest neighbor distances between unit cells. A simple form of substitution disorder can arise from a variation in the separation of the two membranes within the unit cells in the multilayer. Lattice disorder produces a monotonically increasing width for higher order lamellar "reflections" while simple substitution disorder produces an incoherent intensity underlying the coherent intensity. A generalized Patterson function analysis has been developed for treating lamellar diffraction from lattice disordered multilayers. This analysis allows the identification of the autocorrelation function of the unit cell electron density profile and its subsequent deconvolution to provide the unit cell electron density profile. A recursive procedure has been developed for separating the incoherent intensity from the coherent intensity via a Gaussian probability model of the membrane intra-pair separation. In cases studied so far both disorders can be quantitatively accounted for and eliminated from interfering with the phasing of the coherent intensity or distorting the derived electron density profile. Lamellar X-ray diffraction data from intact retinal rods, using either film or position sensitive detectors, shows severe effects of both forms of disorder which have not been taken into account in past analysis of such data. We have applied our analysis to the data on dark adapted rod outer segments in electrophysiologically intact retinas of Chabre and Cavaggioni (unpublished). An electron density profile is derived at 25 A resolution. The lattice nearest neighbor spacing has a variation of +/- 19 A out of a 295 A repeat. The intra-unit cell membrane pair center to center distance of 88 A varies +/-8 A.

Starling curves as a guide to fluid management in the critically ill

Information derived from Starling curves is useful in following the course of critically ill patients. With this knowledge, the physician can better assess the efficiency of the myocardium and determine the optimal filling pressure. Thus, he is enabled to prescribe the necessary fluid and/or drug therapy to maintain the patient at his most efficient cardiac performance. The nurse who monitors cardiac output and wedge at frequent intervals can regulate fluid replacement on this basis.

Use of leuco-dyes in the quantitative colorimetric microdetermination of hemoglobin and other heme compounds

Sensitivity, stability, and specificity of the color-producing reaction of hydrogen peroxide with bezidine, leuco-malachite green, or o-dianisidine were tested in numerous systems containing hemoglobin and other hemoproteins. Use of urea or low temperature (to minus 12 degrees C), or both, was highly beneficial, especially with leuco-malachite green, for which the color reaction was stable, after about 15 min, for longer than 24 h, with a colorless bank. Absorbance was 0.3 at a final hemoglobin concentration of 0.27 mg/liter. Nonspecific color produced by substances such as FeCl-3 and ascorbic acid was completely eliminated. Of the three leuco-dyes studied, only benzidine yielded a completely linear calibration curve, but its relative instability and reported carcinogenicity are serious disadvantages. No system tested eliminated completely the known inhibition by plasma of the peroxidase activity of these leuco dyes.