Whole tissue studies

Schmidt A., Naujoks-Manteuffel C. and Roth G. (1988). Olfactory and vomeronasal projections and the pathway of the Nervus terminalis in ten species of salamanders — a whole mount study employing the horseradish-peroxidase technique. Cell Tissue Res 251, 45-50. 

The enthusiasm for using Caco-2 cells and other epithelial cell cultures in studies of drug transport processes has been explained by the ease with which new information can be derived from these fairly simple in vitro models [7]. For instance, drug transport studies in Caco-2 cells grown on permeable supports are easy to perform under controlled conditions. This makes it possible to extract information about specific transport processes that would be difficult to obtain in more complex models such as those based on whole tissues from experimental animals. Much of our knowledge about active and passive transport mechanisms in epithelia has therefore been obtained from Caco-2 cells and other epithelial cell cultures [10-15]. This has been possible since Caco-2 cells are unusually well differentiated. In many respects they are therefore functionally similar to the human small intestinal enterocyte, despite the fact that they originate from a human colorectal carcinoma [16, 17]. 

The tissue surrogates described here clearly represent a simplification of real FFPE tissues. However, they represent a useful and efficient construct for the evaluation and optimization of tissue extraction conditions for proteomic studies. More informative studies will likely be realized by using more complex tissue surrogates, which can be created by incorporating additional proteins into lysozyme solutions. Tissue surrogates comprised of up to five proteins have been successfully analyzed by MS (Fowler, unpublished data). Additionally, RNA, DNA, lipids, or carbohydrates can be added at nanomolar to millimolar concentrations to increase the complexity of the model system to better mimic whole tissue. The use of these more complex tissue surrogates should facilitate the development of protein recovery protocols optimal for proteomic investigation. 

The developmental regulation and tissue-specific expression of PAL has been analysed in a whole plant study in bean and has shown that differential expression of PAL genes can be detected in different tissues (Liang etal., 1989b). However, this study has not been complemented by a detailed analysis of PAL biochemistry at the cellular or tissue level. 

Kemp, R.B. (1987). Heat dissipation and metabolism in isolated animal cells and whole tissues/organs. In Thermal and Energetic Studies of Cellular Biological Systems (James, A.M., ed.), pp. 147-166, Wright, Bristol. 

In contrast to nucleic acids where polymerase chain reaction (PCR) allows the investigation of single cells, no amplification technology is available at the protein level. As such, proteomic studies require relatively large sample volume. Because of this limitation, it is not a surprising that most proteomic studies have been performed on whole tissue samples. This approach in cancer research is, however, unfortunate because cellular heterogeneity within a biopsy or tissue sample will likely impair the quality and reproducibility of information generated. 

Traditional endoscopic and surgical procedures provide whole tumor samples well suited for microscopic examination and analysis in the pathology laboratory. The use of whole tissue tumor biopsies for proteomic studies has, however, raised several important issues that have been well demonstrated in CRC [9]. These include cellular heterogeneity in the different bowel parietal layers (mucosa, submucosa, muscularis mucosa, serosa) that may or may not be infiltrated, epithelial cell diversity in the mucosa itself, tissue infiltration by inflammatory cells such as lymphocytes, contamination with other body fluids, and protein degradation following tumor necrosis. In fact, epithelial cell content was found to vary between 9 and 67% in whole biopsies of normal mucosa and between 7 and 95% in tumor biopsies [10]. This study clearly demonstrates the likelihood of large cellular variation between tissue samples. 

Electrophysiology — Electrophysiology is the study of the electrochemical phenomena associated with biological cells and tissues in animals, plants, bacteria, and insects. It involves measurements of electrical -> potentials or - current on a wide variety of scales from single ion channel, to whole tissues like the heart, muscles, phloem,... 

CELLULAR STUDIES IN INTACT TISSUE 8.2.1 Whole-Animal Studies... 

Whole-animal studies assess the percent of the applied dose absorbed into the body using classic techniques of bioavailability, where absorbed chemical is measured in the blood, urine, feces, and tissues with mass balance techniques. Recently, methods have been developed to assess absorption by measuring the amount of chemical in the stratum comeum because it is the driving force for diffusion. Cellophane tape strips are collected 30 minutes after chemical exposure and the amount of drug assayed in these tape strips correlates to the amount systemically absorbed. If the focus of the research is to determine the amount of chemical that has penetrated into skin, core biopsies may be collected and serially sectioned, and a profile of the chemical as a function of skin depth may be obtained. 

The preceding description of the use of chromatographic methods in the purification of prostatic acid phosphatase (B24, 04) has already indicated that this enzyme exists in more than one molecular form, or isoenzyme. There is, in addition, immunological (S19) and starch gel electrophoretic evidence (L14, L15, S24, S31) of the existence of several forms. In order to ensure that no isoenzymes are lost during any purification, it is preferable to perform such studies on a homogenate of the whole tissue. It should be recognized that the isoenzymatic composition may not be characteristic of the prostatic cell per se, but may also represent components from blood cells, secretory ducts, connective tissue, and other sources. 

---