A simple method for measurement of angiotensin II in plasma

A simple radioimmunological (RIA) method for the determination of angiotensin II in 0.5-1.0 ml samples of plasma is described and carefully evaluated. Before RIA was performed, the interfering plasma proteins were eliminated by ion exchange chromatography, and recovery from every column was checked with a small amount of [125I]angiotensin II. The sensitivity of the method was 4.0 ng/l; the coefficient of intra-assay variation was 10.0% and that of inter-assay variation 12.1%. Accuracy was studied both by adding various amounts of angiotensin II to plasma samples and by diluting plasma containing angiotensin II with the RIA buffer. Both studies gave very good correlations between found and expected values (r=0.998 and r=0.987). In a normal material (n=36), the mean angiotensin II concentration at 8 a.m. after 2 h ambulation 42.4 +/- 12.8 (S.D.) ng/l. Because the present method is accurate, precise, and practical, and allows measurement of angiotensin II in small samples, it seems useful for routine as well as for research work.     

A simple and robust HPLC method for the determination of paroxetine in human plasma

The objective of this investigation was to establish and validate an HPLC method with UV detection for the determination of paroxetine in human plasma. The method was validated in the concentration range from 6 to 100 ng ml-1. The lower limit of reliable quantification (LLQ) was 6 ng ml-1. The extraction efficiency varied from 67.1 to 85.5% over this range. Accuracies calculated at three concentrations in each of three separate runs were between 99.4 and 109.6%, and precision data were between 1.86 and 9.1%. The means of the between-day precision at all concentrations were between 2.77 and 7.32%. The corresponding means of the accuracy data were in the region of 102.4 to 106.3%.     

A simple radioimmunoassay for plasma cortisol: comparison with the fluorimetric method of determination

A quick and simple method for the radioimmunoassay of plasma cortisol is described. The mean morning plasma cortisol concentration in 43 normal subjects was 9.8 +/- 3.1 (S.D.) microgram/100 ml with a range of 5.0-19.5 microgram/100 ml. Mean midnight concentration in 24 normal subjects was 4.3 +/- 2.3 (S.D.) microgram/100 ml with a range of 1.4-9.6 microgram/100 ml. When compared with the fluorimetric method the mean results by radioimmunoassay of 154 routine specimens were 23% lower. In samples from unstimulated patients, regression analysis of results obtained by the two methods gave a correlation coefficient (r) of 0.93, regression line slope of 1.1, and intercept of 1.4 microgram. Mean radioimmunoassay results were 15% lower. When plasma cortisol concentration was above the normal range (greater than 30 microgram/100 ml) the regression line slope was 0.87, the intercept 17.9 microgram, r = 0.87 and mean radio immunoassay results were 37% lower. Plasma cortisol concentration in patients after insulin or Synacthen stimulation exhibited similar responses when measured by either method. Plasma cortisol concentration in normal subjects given metyrapone was lower when measured by radioimmunoassay (mean +/- S.D. = 8.7 +/- 2.7 microgram/100 ml) than when measured by fluorimetry (18.5 +/- 10.8 microgram/100 ml). The diagnostic usefulness of the two methods, ease of assay, and costs are compared.     

A simple rapid radiometric assay for pyrimidine-5'-nucleotidase

Pyrimidine-5'-nucleotidase deficiency appears to be an important cause of hemolytic anemia associated with basophilic stippling of the red cells. A new radiometric method for the assay of this enzyme has been developed. In this technique, 14C-CMP serves as substrate. The CMP which is not dephosphorylated to cytidine is bound to the barium sulfate precipitate which forms in the deproteinization process. The cytidine remains in solution and is counted. The method is simple and reproducible and can be carried out on large numbers of samples. Two patients with pyrimidine-5'-nucleotidase deficiency have been detected by means of this technique.     

A simple method for quantifying tremor in rodents

A simple and accurate device to evaluate frequency and intensity of involuntary tremor is described. Discrete and quantifiable measures of tremor could be obtained in terms of vertical (i.e., absolute effects at a given time) and horizontal (i.e. temporal) changes. The technique was evaluated employing dosages of physostigmine 0.1-0.7 mg/kg. Applications to other behavioral indices, such as locomotor activity and wet-dog shakes, are discussed.     

A simple method for evaluating cemented carbides

A simple method is proposed whereby meaningful comparisons can be made between the mechanical properties of cermet cutting tool materials. The method is based upon a test originally described by Palmqvist, but includes a procedure for analyzing the data which makes the test much more useful. Thus, it is shown experimentally and analytically that the parameters measured by the Palmqvist test, the crack resistance parameter,W, (which is shown to be linearly related to the critical strain energy release rateG _IC) and the hardness,H, are related by the following expression 1/W=AH-B whereA andB are constants. The significance of this result is that it can be employed to quickly classify experimental carbide/binder combinations according to their potential as cutting tool materials havingboth high hardness and good resistance to impact. Thus, a few simple measurements to establish the constantsA andB appropriate to the carbide/binder combination under investigation allow a ready comparison to be made with another system for which the constants have previously been established.     

A simple spectrophotometric method for the determination of carbofuran residues

A method has been developed for carbofuran residues, based on coupling carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methyl carbamate) with diazotized aniline to form a yellow compound with an absorption maximum at 460 nm. The relationship between absorbance and concentration is linear for 1-10 mug carbofuran/5 ml. The method is sensitive and can be applied to the determination of levels as low as 0.025 ppm carbofuran in a 40 g crop or soil sample.     

Right ventricular volumes revisited: a simple model and simple formula for echocardiographic determination

Our objective was to establish a crescentic model of the right ventricle as the basis of a reported 2/3 (Area)(Length) empirical formula for volume. This formula has been investigated by others without cognizance of its connection to a clear geometric model. The particular model, an ellipsoidal shell or difference of ellipsoids, has been investigated by several groups by using different volume formulas. Accordingly, we obtained echocardiographic images in 2 orthogonal planes from 7 patients and 4 volunteers. Specified area and length measurements from these images were used to calculate right ventricular volumes. These volumes were compared with values determined through multislice, magnetic resonance imaging with summation of lumen areas, a widely accepted standard. Obtained high correlations compared favorably with those of previous investigators who used equivalent but less well understood methods. We conclude that the ellipsoidal shell model of the right ventricle provides a simple area-length formula for the determination of lumen volume with echocardiography.     

A simple method for matching electron beams in radiotherapy

Many solutions have been proposed to solve the problem of 'hot' and 'cold' spots in the junction between abutting electron fields. Although some of these methods have proved satisfactory, the designs of the modifications to the applicators are generally applicator dependent and involve measuring data for individual fields. An idea which was originally proposed as a solution to a different problem is resurrected here because it happens to solve the beam-matching problem and because it is very simple to apply. The idea is to cover the end of the electron applicator completely with a slab of plastic, called a 'spoiler'. Formulae are proposed and tested for estimating the penumbra broadening and the extent of over- or underdosing at field junctions. The technique is applicator independent, and no extra beam-data measurements need be made for computer treatment planning of matching fields. The price paid for such simplicity is that consideration needs to be given to leading-off the other borders of the treatment fields because of the increased penumbra widths.     

A colorimetric assay method for the evaluation of neurotrophic activity in vitro

A colorimetric assay was established to detect neurotrophic activity by measuring the lysosomal enzyme, acid phosphatase (AP) activity of cultured neuronal cells. Neurons from the cerebral cortex of 14- or 15-day mouse embryo were cultured in serum-free medium for 3 days in 96-well culture plates. A linear relationship was obtained between the AP activity and the number of viable neurons counted under a microscope. The AP assay was used to evaluate the neurotrophic activity of basic fibroblast growth factor. This assay is shown to be simple, sensitive and convenient to detect neurotrophic activity.     

A simple method for automatically locating the nipple on mammograms

This paper outlines a simple, fast, and accurate method for automatically locating the nipple on digitized mammograms that have been segmented to reveal the skin-air interface. If the average gradient of the intensity is computed in the direction normal to the interface and directed inside the breast, it is found that there is a sudden and distinct change in this parameter close to the nipple. A nipple in profile is located between two successive maxima of this parameter; otherwise, it is near the global maximum. Specifically, the nipple is located midway between a successive maximum and minimum of the derivative of the average intensity gradient; these being local turning points for a nipple in profile and global otherwise. The method has been tested on 24 images, including both oblique and cranio-caudal views, from two digital mammogram databases. For 23 of the images (96%), the rms error was less than 1 mm at image resolutions of 400 microns and 420 microns per pixel. Because of its simplicity, and because it is based both on the observed behavior of mammographic tissue intensities and on geometry, this method has the potential to become a generic method for locating the nipple on mammograms.     

Methods for determination of vitamins A and E our simple HPLC assay

Biological effects of reactive oxygen species and other radicals which are controlled by antioxidant mechanism are exerted on the basis of enzymes and substrates. Antioxidant substrates are divided into lipophilic and hydrophilic groups. Main representants of lipophilic antioxidants are retinol and tocopherol which are closely related to ascorbate in the hydrophilic compartment. Described methods for detection of retinol and alpha-tocopherol are simple, sensitive, specific and precise. They are reliable, economic and fast. Only small amounts of serum are used for one analysis which is convenient for patients, too. Our methods can be recommended for routine use in laboratories of clinical biochemistry. Haemodialyzed patients, retinol serum level was higher than that in blood donors while alpha-tocopherol serum level did not differ. Both vitamin A and E serum levels were similar in alcoholics compared to controls.