Tube assays

Tube assays use liquid medium, and growth inhibiting and growth promoting systems differ. 

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EIAs are more desirable for the measurement of agrochemicals than enzyme-linked immunosorbent assays (ELISAs) for several reasons. EIAs are easier to run, require minimal liquid transfers, and are completed in brief time frames, approximately 40 min for tube assays to 2.5 h for microtiter plate assays. In contrast, ELISAs are more complex, have many steps involving transfer of reagents, and require 6-8 h to complete. Most commercially available immunoassays utilize the EIA format. 

Maintaining a moderate, consistent pipetting rhythm is the best way to ensure that all samples and standards are treated equally. This is easy to accomplish with tube assays, because relatively few samples can be analyzed per set. Microtiter plates present more of a challenge, because up to 96 wells may be utilized at the same time. One solution developed in this laboratory involves the use of a microtiter plate not coated with reagent - the reservoir plate." An excess of all samples and standards is loaded into the reservoir plate. If 0.10 mL is needed for the inhibition step, for example, 0.15 or 0.20 mL of each solution is added to a pre-determined position in the reservoir plate the excess amount simplifies the next pipetting step. The location of each sample and standard is identified on a plate layout sheet, a map of the reservoir plate previously completed by the analyst (Figure 3). When the reservoir... 

PCB in soil (tube assay) EnviroLogix http //www.envirologix.com/... 

B20. Banhidi, Z. G., Some aspects of the nutrition of Lactobacillus fermenti 36 on the tube assay of thiamine. Acta Chem. Scand. 12, 517-527 (1958). 

Figure 4. Oxidative titration of activated aconitase with potassium fenicyanide. Aliquots of activated aconitase and a measured amount of K3Fe(CN)6 were added to individual EPR tubes, assayed for enzymatic activity ( ), and frozen. After deteimination of the number of spins by EPR at g = 2.01 (x), the samples were thawed and assayed again (o). (Reproduced with permission from Ref. 47. Copyright 1983 American Society Biological Chemists.)...

The CHARM inhibition assay (CIA), Charm farm test (CFT), and Valio TlOl test are all simple multiresidue screening tests based on microbial inhibition (34, 35). The CIA test is actually a disc assay using Bacillus stearothermophilus and specially formulated agar media to increase the sensitivity to sulfonamides. The CFT is a tube assay using the same test organism in a specific formulation, which, along with the nutrients, is in a tablet form. To roughly identify penicillins and sulfonamides with the CIA and CFT tests, positive samples should be reanalyzed after the addition of penicillinase and p-aminobenzoic acid. 

Serum or plasma samples are collected from the test animals (if plasma is used, blood should be collected in heparinized tubes). Assay methods vary, and are outlined below. 

Halliwell (1978) proposed aromatic hydroxylation as an assay for OH radical production. Hydroxylated products are quantitated using a colorimetric method that measures o-dihyric phenols. The assay has since been improved by Richmond et al. (1981) and has often been used as a simple test tube assay of OH formation (Halliwell et al., 1988) in activated phagoctic cells, isolated hepatocytes, soluble en-... 

If the tube assay is to be employed, 0.25 ml amounts of serially diluted antigen, made in the same diluent, and 0.25 ml amounts of the selected antiserum dilution are mixed and incubated for 30 min at room temperature. The test cells (0.05 ml of 2.5% suspension) are added, the tubes are shaken virogously, and the agglutination patterns are read after 1.5-2 hr... 

Potency of cephalothin is routinely determined by agar-diffusion (plate) assay using Staphylococcus aureus or Bacillus subtilis. and by turbidimetric (tube) assay using S j aureus.35 Of the two plate methods, the subtilis assay produces better defined zones of inhibition. 

Some important conclusions can be drawn for solid-phase EIA (i) the higher the diffusion constant of the substrate, the lower the increase in of the reaction, resulting in an increased reaction rate and, (ii) the accumulation or depletion of ionic species (e.g., protons) influences the reaction rate. Therefore, extreme care should be taken to agitate equally each reaction vessel. This is often more difficult with coated tube assays than with microtitre plates. Shaking of plates during the enzyme reaction may be advantageous. 

Proteins to be tested were diluted in buffer E (10 mM HEPES-KOH, pH 7.4,100 mM KC1), at five times their final concentration in the assay. Assay volume was 25 qL and assays were performed in 0.5 mL microcentrifuge tubes. Assays used Buffer L (125 mMKCl, 0.5 mMMgCl2, 3.0 mM succinic acid, 3.0 mM glutamic acid, 10 mM HEPES-KOH, pH 7.4, containing 25 qg/mL leupeptin, 25 qg/mL pepstatin, 3 qg/mL aprotinin, 100 mMPMSL, and 10 qM of the caspase inhibitor Boc-Asp-LMK). Protease inhibitors were added immediately to Buffer L prior to its use. 

Biochemical Induct Assay (BIA) (.5,6) The semi-quantitative spot test version (not the one-tube assay for the quantitative measurement of induction) was used for most of the work. The bacteria are poured in agar with or without rat liver S9 activation mix, onto large (24 cm x 24 cm) bioassay plates. Largomycin fermentation broth or test solutions are spotted onto the plates, allowed to incubate for three hours at 37°C, and overlaid with a second agar layer containing substrate. Within five or ten minutes, areas of induction are seen as red spots of insoluble dye formed by cleavage of the colorless substrate. Rapid sampling with the wide end of pasteur pipettes allows an operator to spot 100 samples on two plates in 20 minutes. 

The deoxyribose assay is a simple test tube assay to determine the antioxidant or pro-oxidant properties of test compounds against carbohydrates [151-152]. In the deoxyribose assay, OH are produced from the reaction of H2O2 with Fe2+ (Fenton reaction), where the latter is formed by the ability of ascorbic acid to reduce ferric iron (Fe3+) to ferrous iron (Fe2+) (Eq. 27). 

Hardenbol P, et al. (2005). Highly multiplexed molecular inversion probe genotyping Over 10,000 targeted SNPs genotyped in a single tube assay. Genome Res. 15(2) 269-275. 

Too much P-amyloid is the result of the action of other enzymes with other roles, so that blocking them may cause side effects. Using cultured human and mouse cells, as well as test tube assays. University of Texas Southwestern researchers singled out how just one portion of the enzyme, a protein called nicastrin, is involved in the pathway that produces P-amyloid, thereby leading to AD. They hope next to work on ways to specifically block nicastrin (August 12 issue of Cell). 

The EIA system examined here is available on mlcrotlter plates or small polystyrene tubes. The latter was used here. The tube assay has short incubation periods and is suitable for field work and a small number of samples. 

A lot of preliminary work is necessary for microbiological assays, and if only a small number of samples are expected irregularly, the method is inefficient. Two assay methods are normally used, agar diffusion and tube assays. They have several common features ... 

Antibiotic assays can be carried out in the form of agar diffusion assays, or as tube assays in liquid media. ... 

Tube assays of disinfectants are considered in Chapter 10 under the heading of MIC values. The principles for antibiotic assay using these methods is the same. 

Bisphenol A (BPA), which is a commonly used name for 2,2-(4,4-dihydroxydiphenyl)-propane (CAS number 80-05-7), exhibits extremely weak hormonal activity in test tube assays and in vivo mammalian assays (Krishnan et al, 1993 Ashby and Tinwell, 1998 ... 

The measurement of discrete droplet volumes is now pla5dng a more and more important role in various applications such as pipettes, drug dispensing systems, inkjet printer heads, and microarray biochip spotters. The purpose of dispensing is to deliver a certain amount of a liquid sample, buffer solution, or frequently used library compound from a storage vial or mother plate to a cultivation container, test tube, assay plate, or microarray chip for subsequent handling. Applications in this field today are showing a trend toward a decrease in the volume of liquid to be handled, a trend that is promoted by the common... 

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