Vitros analyzer

The Vitros analyzer (Ortho-Cfinical Diagnostics, Raritan, N.J.) uses an assay in which lactic acid is oxidized to pyruvate by lactate oxidase. The H2O2 generated oxidizes a chromogen system, and the absorbance of the resulting dye complex, measured by a spectrophotometer at 540nm, is directly proportional to the lactate concentration in the specimen. Each mole oflactate oxidized produces O.Smol of dye complex. 

Clinical Applications Perhaps the area in which ion-selective electrodes receive the widest use is in clinical analysis, where their selectivity for the analyte in a complex matrix provides a significant advantage over many other analytical methods. The most common analytes are electrolytes, such as Na+, K+, Ca +, H+, and Ch, and dissolved gases, such as CO2. For extracellular fluids, such as blood and urine, the analysis can be made in vitro with conventional electrodes, provided that sufficient sample is available. Some clinical analyzers place a series of ion-selective electrodes in a flow... 

Nonvolatile Nitrosamines In Saliva. In vitro experiments had indicated that the tobacco-specific nitrosamines are formed also during snuff dipping (26). Therefore, we analyzed the saliva of snuff dippers and tobacco chewers. A comparison of the results demonstrated the presence of TSNA in saliva at a wide range of concentrations (Table Vl), which could be ascribed to differences in the product, but also to differences in the manner of chewing, and, lastly, to individual factors in each person s saliva. 

High Performance Liquid Chromatographic (HPLC) Analysis. A Waters HPLC system (two Waters 501 pumps, automated gradient controller, 712 WISP, and 745 Data module) with a Shimadzu RF-535 fluorescence detector or a Waters 484 UV detector, and a 0.5 pm filter and a Rainin 30 x 4.6 mm Spheri-5 RP-18 guard column followed by a Waters 30 x 3.9 cm (10 pm particle size) p-Bondapak C18 column was used. The mobile phase consisted of a 45% aqueous solution (composed of 0.25% triethylamine, 0.9% phosphoric acid, and 0.01% sodium octyl sulfate) and 55% methanol for prazosin analysis or 40% aqueous solution and 60% methanol for naltrexone. The flow rate was 1.0 mL/min. Prazosin was measured by a fluorescence detector at 384 nm after excitation at 340 nm (8) and in vitro release samples of naltrexone were analyzed by UV detection at 254 nm. 

Since the widely accepted in vitro permeability model in the pharmaceutical industry is based on the use of cultured cells, such as Caco-2 or MDCK, it was appropriate to analyze the regression correlation coefficients based on the comparisons of Caco-2 log Pe and the log Pe values based on the human jejunal measurements [56]. 

Alternative tests can be divided into two categories in vitro and in silico. In vitro methods refer to the fact that experiments are done in a tube, generally. In silico methods refer to the use of the computer to model a certain property of interest. Below, we will analyze these two categories, and which criteria can be used to choose a suitable methodology. 

Analyzing the use of models, it is possible to underline that in vitro systems are mainly used for research and for testing/screening of compounds. In the first case, these tools are employed to test hypothesis and the experimental model is chosen taking into account the nature of the hypothesis to be tested. 

These incubations are often carried out at 37 °C for 1-2 h. At different time points, 20-200 /aL of incubation mixture is withdrawn from each incubation and mixed with equal volume of ice-cold acetonitrile by vortexing. For preparation of acyl glucuronide, ice-cold acetonitrile containing 1% of formic acid is used to minimize acyl-migration [3,14]. After centrifugation at 13 000 rpm for 5-15 min, the supernatant (10-30 /aU) is analyzed by high-performance liquid chromatography (HPUC)-UV-MS. The metabolite of interest is identified based on HPLC retention time, UV spectrum and MS/MS data. Conversion yield is estimated based on UV absorption peak areas. A suitable in vitro enzyme system for scale-up is then... 

As mentioned earlier, biological systems have developed optimized strategies to design materials with elaborate nanostructures [6]. A straightforward approach to obtaining nanoparticles with controlled size and organization should therefore rely on so-called biomimetic syntheses where one aims to reproduce in vitro the natural processes of biomineralization. In this context, a first possibility is to extract and analyze the biological (macro)-molecules that are involved in these processes and to use them as templates for the formation of the same materials. Such an approach has been widely developed for calcium carbonate biomimetic synthesis [13]. In the case of oxide nanomaterials, the most studied system so far is the silica shell formed by diatoms [14]. 

Some investigators described artifactual DNA sequence alterations after formalin fixation, when testing DNA samples extracted from FFPE tissues. Williams et al.46 reported that up to one mutation artifact per 500 bases was found in FFPE tissue. They also found that the chance of artificial mutations in FFPE tissue sample was inversely correlated with the number of cells used for DNA extraction that is, the fewer cells, the more the artifacts. However, they mentioned that these artifacts can be distinguished from true mutations by confirmational sequencing of independent amplification products, in essence comparing the product of different batches. Quach et al.47 documented that damaged bases can be found in DNA extracted from FFPE tissues, but are still readable after in vitro translesion synthesis by Taq DNA polymerase. They pointed out that appropriate caution should be exercised when analyzing small numbers of templates or cloned PCR products derived from FFPE tissue samples. 

Fig. 8.6 In vitro bioassay ofT] generation chloroplast transgenic line against P. aeruginosa. Bacterial cells from an overnight culture were diluted to A6oo 0.1 -0.3 and incubated for 2 hours at 25 °C with 100 xg of total protein extract. One ml of LB was added to each sample and incubated overnight at 26 °C. Absorbance was recorded at 600 nm. Data was analyzed using a GraphPad Prism.

The use of complementary, multimodal imaging techniques to analyze probes both in vivo and in vitro may be helpful in speeding up this process this should ensure that laboratory-based experiments mimic and are able to predict more closely the expected behavior of the probe in vivo. 

Lipid peroxidation is probably the most studied oxidative process in biological systems. At present, Medline cites about 30,000 publications on lipid peroxidation, but the total number of studies must be much more because Medline does not include publications before 1970. Most of the earlier studies are in vitro studies, in which lipid peroxidation is carried out in lipid suspensions, cellular organelles (mitochondria and microsomes), or cells and initiated by simple chemical free radical-produced systems (the Fenton reaction, ferrous ions + ascorbate, carbon tetrachloride, etc). In these in vitro experiments reaction products (mainly, malon-dialdehyde (MDA), lipid hydroperoxides, and diene conjugates) were analyzed by physicochemical methods (optical spectroscopy and later on, HPLC and EPR spectroscopies). These studies gave the important information concerning the mechanism of lipid peroxidation, the structures of reaction products, etc. 

For that purpose, interesting strains, which have been identified in the first stage of the screening system should be further analyzed not only by an in vitro test, but also by techniques which enable an exact determination of the respective in vivo activity. This... 

MUELLER-URI, F., PARTHIER, B., NOVER, L., Jasmonate-induced alteration of gene expression in barley leaf segments analyzed by in vivo and in vitro protein synthesis, Planta, 1988,176,241-247. 

GEA-3175 is more stable than GEA-3162 in vitro but still retains its biological activity [95]. The release of NO and NO2 by GEA 3175 was increased 140-fold in the presence of human plasma, as analyzed by ozone chemiluminescence [94]. GEA 3175 inhibited agonist-induced platelet aggregation and induced a more than 4-fold increase in platelet cGMP without affecting cAMP levels [94]. Thrombin-stimulated rises in the cytosolic free Ca2+ concentration and secretion were dose-dependently inhibited by GEA 3175. GEA 3175 showed a reduced capacity to inhibit platelet aggregation of uremic platelets compared to controls [96]. 

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