Representative and valid cytoplasmic concentrations are essential for ensuring the significance of results in the field of metabolome analysis. One of the most crucial points in this respect is the sampling itself. A rapid and sudden stopping of the metabolism on a timescale that is much faster than the conversion rates of investigated metabolites is worthwhile. This can be achieved by applying of cold methanol quenching combined with reproducible, fast, and automated sampling. Unfortunately, quenching the metabolism by a sharp temperature shift leads to what is known as cold shock or the cell-leakage effect. In the present work, we applied a microstructure heat exchanger to analyze the cold shock effect using Corynebacterium glutamicum as a model microorganism. Using this apparatus together with a silicon pipe, it was possible to assay the leakage effect on a timescale starting at 1 s after cooling cell suspension. The high turnover rates not only require a rapid quenching technique, but also the correct application. Moreover, we succeeded in showing that even when the required appropriate setup of methanol quenching is not used, the metabolism is not stopped within the required timescale. By applying robust techniques like rapid sampling in combination with reproducible sample processing, we ensured fast and reliable metabolic inactivation during all steps.
The first part of this paper deals with the regulations in the DAB 8/78 stating that eye-drops are to be preserved. A questionnaire prepared by the German Association of Ophthalmologists is analyzed. The four questions put to 353 ophthalmologists and answered by 350 of these concern the need for unpreserved eye-drops because of the danger of allergization; the expiry date once the bottle has been opened; infections due to eye-drops without preservatives; and the need for eye-drops made up by pharmacists. The second part deals with studies on the pH-values of lacrimal fluid in cases of normal and decreased lacrimation, as well as with the bactericidal action of the normal tear fluid containing lysozyme and lactotransferrine and various eye-drops containing preservatives. The authors conclude that the general addition of preservatives to eye-drops, especially to those containing antiphlogistic and astringent substances, is unnecessary. Concerning the expiry date on the bottle, it is suggested that the period of use be extended to three months, thus helping to cut costs.
Bei Verwendung einer Celluloseacetatfolie kann man aus einer 10 mg-Leberportion, etwa einer ßlindbiopsieprobe von l cm Länge, eine klare elektrophoretische Darstellung von Leberproteincn erhalten. Wesentlich ist, Blut-und Serumreste zunächst gründlich zu entfernen. Dann konnten 17 Fraktionen dargestellt werden. Die Ergebnisse waren leicht und sicher reproduzierbar.
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