Small-animal tissue samples

Figure 12.1. Scheme outlining individual steps for profiling and IMS of small-animal tissue samples. 

Lithium is a fairly common element its abundance in the earth s crust is greater than those of copper and zinc. It too may be determined in many samples by flame atomic absorption. However, flame emission in the NOA flame was shown to be valuable for determining lithium in very small animal tissues at normal physiological levels. The 10 ngl detection limit permitted analysis for lithium in individual rat pituitaries at 30 pg Li per g dry weight, and eventually enabled establishing the essentiality of lithium in the rat. 

Matsumoto et al. developed an immunoassay for the determination of clenbuterol in bovine and equine tissues and in bovine milk. The LOD of clenbuterol in milk, muscle, liver, kidney, small intestine, and adipose tissues was 0.1 qgkg Bovine tissue samples fortified wifh 1 qg kg of clenbuterol had recoveries that varied from 75 to 96%, but recoveries from milk samples were 99%. The authors utilized this method to estimate the clenbuterol withdrawal periods for cattle and horses. Cattle were treated with a bolus dose of either 0.3 or 0.6 qg kg body weight, by intravenous injection, and three animals were slaughtered at days 1, 6, and 9. Tissue clenbuterol levels were detectable only on day 1. Clenbuterol in milk was not detectable after a 2.5-day withdrawal period. Liver contained the highest clenbuterol concentration of the tissues measured, but this group did not measure eye tissues. 

In residue surveys, tissue samples are also collected at random to be submitted to routine testing. If a violative residue is found, the producer is notified and the animals are held in the farm, and tested until they are proven to be residue-free. To provide this proof, producers are allowed to submit a small number of animals for residue evaluation. The marketing status of the producer is reevaluated based on the tissue test results. The carcasses are retained usually for 14-30 days until the test results are available and will be condemned if the results indicate the presence of violative residues. In many cases, producers incur additional expenses for the packer to debone, freeze, and store the retained carcasses. 

A chemical analysis is most often performed on only a small fraction of the material whose composition is of interest. Clearly, the composition of this fraction must reflect as closely as possible the average composition of the bulk of the material if the results are to have value. The process by which a representative fraction is acquired is termed sampling. Often, sampling is the most difficult step in the entire analytical process and the step that limits the accuracy of the procedure. This statement is particularly true when the material to be analyzed is a large and inhomogeneous liquid, such as a lake, or an inhomogeneous solid, such as an ore, a soil, or a piece of animal tissue. 

Only trace amounts of copper are present in biological material, in the general range 0.1-10 /ig/g (0.1-10 ppm). These trace amounts are in complex mixture with innumerable other metals and elements, some of which are present in much larger quantities. In addition the sample size is often limited, as in blood samples from infants and small animals or needle biopsy specimens from tissues. Methods for copper therefore must be highly sensitive as well as highly specific, since the analyst faces the problem of trace analysis on a micro- or ultramicroscale. 

Several types of tests have been employed to demonstrate the insuhn-potentiating activity of Cr(III) in vitro. In the early studies of Mertz and coworkers (489, 490), glucose uptake or CO2 production by isolated epididymal fat tissue (from Cr-deficient rats) in the presence or absence of Cr(III) complexes were compared. This method required a large number of animals per small number of samples and did not allow for data comparison among different laboratories (491). To overcome this limitation, Anderson et al. (491) proposed the use of isolated adipocytes from rats raised on low-Cr diets. Significantly enhanced CO2 production due to glucose oxidation by adipocytes... 

The types of samples which may be analyzed by 2D6EL are varied. Including virtually all animal tissues, fluids, and cells, and many microbial and plant specimens. The resulting patterns for most of these specimens are complex, and often contain more information than the researcher can immediately utilize, especially since 2D6EL is most often done to study a small subset of the total protein set present. This type of local" analysis may be done visually, or with the aid of a small densitometer (IQ). However, much more complex analyses are possible ("global" analyses) with the aid of a computerized Image analysis system (ID- This is discussed in more detail below. 

The recent discovery of high-level thallium pollution in the environment has focused attention on the teratogenicity (fetus malformation). For detailed investigations in this field a method is required which enables the quantitative detection of thallium in extremely small tissue samples (embryos, placenta tissues etc.) thus permitting to establish a correlation between measured values and teratological findings. Regarding the pharmacokinetics of thallium in a test animal (mouse) the first results obtained by FDMS have been reported . 

Another study described simple photometric determination of the iodine concentration in the thyroid tissue of small animals. Again, the method was based on the well-known catalytic Sandell-Kolthoff reaction. Prior to the analysis, the tissue was digested in a mixture of sodium chlorate and perchloric acid at 100 degrees C. Using this manner of digestion between 94 and 110% of iodine in the sample was recovered. Comparison with the neutron activation analysis showed excellent agreement of the obtained values (Tiran et al., 1991). 

In the closed segment procedure, referred to above, the extent of absorption is calculated on the basis of disappearance of the test substance from both the lumen and the intestinal tissue. With the closed segment method, at the end of the absorption period, the entire segment, both intestinal wall and contents, is assayed quantitatively for the amount of the test substance remaining. A disadvantage to this technique when compared with perfusion methods is that sequential samples cannot be taken from a single animal. However, this method is readily used in small animals and can therefore be relatively economical. 

In order to clarify the possibilities for creation of hyperthermai zones, the nonresonance (thermal) influence of electromagnetic radiation (A = 3 cm) was investigated on the model animal muscular tissues in vitro injected by nanodisperse magnetite (Figure 10.5). The mass of the tissue samples was 5 g. Samples 2 and 3 differed by the content of a small quantity of grease layer. The area of radiation was 2 cm. ... 

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