Development of the NIST bone ash standard reference material for environmental radioactivity measurement.

The bone ash standard reference material (SRM), a blend of 4% contaminated human bone and 96% diluent bovine bone, has been developed for radiochemical method validation and quality control for radio-bone analysis. The massic activities of 90Sr, 226Ra, 230Th, 232Th, 234U, 235U, 238U, 238Pu, (239 + 240)Pu and (243 + 244)Cm were certified using a variety of radiochemical procedures and detection methods. Measurements confirmed undetectable radionuclide heterogeneity down to a sample size of 5 g. thereby implying adequate blending of particulate materials with dilution factors of up to 17,900. The results among most of the intercomparison laboratories and their methods were consistent. Disequilibrium was observed for decay chains: 234U(0.67 mBq/g)-230Th(0.47 mBq/g)-226Ra(15.1 mBq/g)-210Pb(23 mBq/g)-210Po(13 mBq/g) and 232Th(0.99 mBq/g)-228 Ra(6.1 mBq/g)-228Th(7.1 mBq/g). The disequilibria were the results of mixing occupationally contaminated human bone with natural bovine bone and the fractionation during internal biological processes. The massic activity of 210Pb, 228Th and 241Am were not certified because of insufficient 228Ra and 241Pu data and lack of knowledge in how 222Rn and its daughters will be fractionated in the SRM bottle over time.

[Rapid simultaneous assay of the principalamide-type local anesthetics by gas-liquid chromatography]. / Dosage rapide et simultané des principaux anesthésiques locaux de type amidé par chromatographie gaz-liquide.

This method can assay simultaneously, using 300 microliters of plasma, of the three principle local anesthetic agents used by peridural injection for post-operative anesthesia and analgesia: xylocaïne, etidocaïne, bupivacaïne. The assay method consists of three steps: (a) the addition of an internal calibrating agent (mepivacaïne). (b) defecation using trichlorocetic acid. (c) alcalinization of the supernatent (pH 11), extraction with dichloromethane and concentration at room temperature of the organic phase. (d) chromotography using an SE 30 or OV 17 impregnated column. The method is sensitive between 0.37 mumoles per l-1 (0.1 microgram . ml-1) and the coefficient for the mean deviation is 10.9% for concentration between 0.37 mumoles 1-1 and 75 mumole1-1 (0.1 microgram . ml-1 and 20 micrograms . ml-1). The correspondence of the figures recorded in this large concentration range without any change in the technique means that the kinetics of the plasma concentrations before and after peridural injection can be followed. The results obtained by gas liquid chromatography for the assay of lidocaïne were compared in 115 different plasma samples with concentrations obtained by an immuno enzymatic method ("EMIT") fitted to a centrifuge analyser. The correlation coefficient between the two methods was: (r = 0.95 with y = 0.09 x +0.25 microgram . ml-1 implying the absence of any interference and the specificity of the two methods. The columns also separate in 20 minutes the two main metabolites of lidocaïne: monoethylglycinexylidide (M.E.G.X.) and glycinexylidide (G.X.). These results demonstrate that continuous peridural injection of lidocaïne produces a high plasma concentration without any clinical toxic phenomena.

[Use of Autobac system in the study of the bacteriostatic effect of combinations of antibiotics (author's transl)]. / Application du système Autobac à l'étude de l'activité bactériostatique des associations d'antibiotiques.

After determining the LSI80 (light scattering index 80) concentration X and Y of two antibiotics for a given bacteria by an automated light scatter photometric method, we use the same process to test the bacteriostatic effect of all the combinations between the values 2X, X, X/2, X/4, X/8 and 2Y, Y, Y/2, Y/4, Y/8. The results read on the light scatter photometer are interpreted: --approximatealy by means of a simplified schematic diagram; --more precisely by drawing three curves: we begin with two inhibiton curves in order to determine the LSI50 concentrations (CLSI50) of each antibiotic, isolted and in the presence of defined concentrations of the complementary antibiotic; then from these CLSI50 we draw the bacteriostatic effect curve of the combination. When the LSI50 effect of the combination occurs with less than 50% of the CLSI50 of each isolated antibiotic, the combination is synergistic. It is antagonist if the bacteriostase is obtained with more than 100% of the CLSI50 of each isolated antibiotic. The intermediate percentages determine the indifferent effects. The additive effects come to an equilateral hyperbola passing through the points 50%-50%, 25%-75%. The Autobac system allows inoculum standardization, very simplified handlihg and automatic reading. It takes only 9 h to handle the complete process, including the determinations of the CLSI80 and the study of the combination. There is a high correlation between the results obtained and those given by the Patte and Chabbert "carre method".

Evaluation of exogenous insulin homoeostasis by the artificial pancreas in insulin-dependent diabetes.

With the artificial pancreas used by the authors, insulin was delivered through a venous infusion and the rate of delivery was adjusted according to data provided by a continuous blood glucose monitor. After different trials we selected control algorithms integrating two parameters: instantaneous blood glucose concentration and increasing or decreasing patterns of blood glucose. A constant basal insulin infusion rate was added and improved the control of glycaemic excursions. Different parameters concerning exogenous insulin homoeostasis were determined. The delay to reach an insulin effect was 18+/-2 min and was shortened by a priming-dose at the beginning of the infusion. The insulin effect remained for 28+/-2 min after the infusion had been stopped, but differences were noted in the morning (21+/-2 min), in the afternoon (32+/-2 min) and during the night (25+/-3 min). Insulin needs were evaluated during meals. Related to the amount of carbohydrates, the doses fell from 0.53 units/hr/g of carbohydrate for breakfast to 0.15 for dinner. From these data, it appears that the efficiency of exogenous insulin exhibits a circadian rhythm.