PubMed · 9136981
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L K Nielsen. 1997. Limiting dilution assay: single or multiple dilution protocol?. https://pubmed.ncbi.nlm.nih.gov/9136981/
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OBJECT: Evaluation of accuracy of three common dilution methods for drugs. EXPERIMENTAL PLAN: Perspective double blind investigation from March to June 1995. PLACE: Anaesthesia and Resuscitation Service of Children's Hospital of Iglesias (CA). METHODS: Forty dopamine at 2/1000 samples, obtained by dilution of dopamine at 40/1000 on sale with three different methods by five different operators, were analysed with a chromatography system in liquid phase at high pressure. RESULTS: Mean concentration with difference not exceeding 5% from the goal, are considered acceptable. Only one group of samples was found to be into these limits, but it was also the most dangerous for the high percentage of great mistakes in dilution. Although there are significant differences in the accuracy and safety of the three dilution methods, the highest and lowest final concentrations obtained differ very much from those estimated. CONCLUSIONS: It is suggested that drugs confections with proper dilution for different clinical uses might be on sale.
Mass isotopomer distribution analysis (MIDA) is a technique for measuring biosynthesis and turnover of polymers in vivo. A stable isotopically enriched precursor is administered, and the relative abundances of different mass isotopomers in the polymer of interest are measured by mass spectrometry (MS). By comparison of statistical distributions predicted from the binomial or multinomial expansion to the pattern of excess isotopomer frequencies observed in the polymer, the enrichment of the biosynthetic precursor subunits (p) for newly synthesized polymers is calculated. MIDA thereby provides a solution to the problem of determining the isotope content in the actual precursor molecules that entered a particular polymeric product (the "true" precursor). The fraction of polymer molecules in a mixture that were newly synthesized during an isotopic experiment (fractional synthesis) can then be calculated. We describe some mathematical characteristics of MIDA and point out certain advantageous features. For example, mathematical estimates of p remain valid even if there does not exist a single anatomic or functional precursor pool. The interpretation of decay curves of endogenously labeled polymers may be improved by the use of higher mass isotopomers, which better fulfill the assumption of flash labeling. By combining fractional synthesis values with rate constants of decay, absolute endogenous synthesis rates can be calculated. Thus, by using probability logic combined with MS analysis, MIDA allows dynamic measurements to be made through analyses on a polymer alone during both isotopic incorporation and decay phases. The method has been applied to fatty acids, cholesterol, and glucose and is potentially applicable to nucleic acids, porphyrins, perhaps proteins, and many other classes of polymers.
We present a computer program that is based on Karber's approximation of endpoint titers, written in GW-BASIC and provides an easy means for analyzing the results of dilution endpoint assays. The program provides estimates of standard error that are not possible from other statistical procedures for this type of data.