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Freezing cell models

Compound (Miles Laboratories, Elkhart, IN), snap-frozen, and cut into sections for comparison with paraffin-embedded cell sections (3) FFPE Cell Blocks Six cell pellets were fixed in 10% neutral buffered formalin immediately after harvest, at room temperature for 6,12,24h, 3,7, and 30 days, respectively. For further comparison with the cell model system, recently collected sample of human breast cancer tissues were processed by OCT-embedding and snap-freezing the corresponding routine FFPE block that was obtained from the Norris Cancer Hospital and Research Institute at the University of Southern California Keck School of Medicine (USC). This tissue block was processed routinely (formalin-fixed 24h and processed by automatic equipment). [Pg.60]

Figure 4.26 shows a cell model of the three phases. Gas in the upper region has a very low density and the molecules are free to fly around. When the vapor condenses into a liquid (shown lower right), the density is greatly increased so that there is very little free volume space the molecules have limited ability to move around, and they have random orientation that is, they can rotate and point in random directions. When the liquid freezes into a solid (shown lower left), the density is slightly increased to eliminate the void space, the molecules have assigned positions and are not free to move around, and there is now an orientation order that is, they cannot rotate freely and they all point at the same direction. [Pg.124]

A change in composition or a commercial food product s formulation is most likely to affect its cellular stmcture, especially if formed by extrusion or puffing. Thus, studying the effect of stmcture or composition in isolation may not be an easy task. However, there are ways to investigate their effects. For example, freezing at different rates usually produces ice crystals of different sizes, which upon dehydration can produce foams with almost identical composition but different cellular stmcture. Freeze-dried model foams, based on food gums with and without additives can be used to study the effect of the cell wall material in foams that have a similar stmcture (see, e.g., Nussinovitch et al. 2000, 2001). Whether this kind of study will generate wide interest, however, is uncertain. [Pg.199]

Why should contact between shrunken cells be damaging One possibility is that the contacts induce damaging membrane-membrane fusion, for close contact between shnmken cells has been found to induce membrane fusion above 0 °C. Moreover, freezing has been shown to induce fusion in model membranes (Anchor-doguy et al., 1987) and to produce changes in fungal hyphae that are symptomatic of fusion (Fujikawa and Miura, 1986). [Pg.374]

From these results it is possible to make another estimate of a property of the solution system. It is known that the freezing point of a solvent is lowered by approximately 1.86°C for every mole of the solute present. From the estimates of the temperature of the solvent and the solution modeled above, the decrease in the temperature can be estimated. From this value, the number of cells comprising a mole of solute may be reckoned. Thus, a value may be stated for an imaginary molecular weight of the cells used in the study. [Pg.70]

The freeze-resistant 2005 FCX models can operate at -20°C. Other companies, including DaimlerChrysler and GM have also had success with cold-starting cells. The technique used is to keep all water present as a vapor and not allow water droplets to occur. [Pg.179]

For the quantitative description of the metabolic state of a cell, and likewise which is of particular interest within this review as input for metabolic models, experimental information about the level of metabolites is pivotal. Over the last decades, a variety of experimental methods for metabolite quantification have been developed, each with specific scopes and limits. While some methods aim at an exact quantification of single metabolites, other methods aim to capture relative levels of as many metabolites as possible. However, before providing an overview about the different methods for metabolite measurements, it is essential to recall that the time scales of metabolism are very fast Accordingly, for invasive methods samples have to be taken quickly and metabolism has to be stopped, usually by quick-freezing, for example, in liquid nitrogen. Subsequently, all further processing has to be performed in a way that prevents enzymatic reactions to proceed, either by separating enzymes and metabolites or by suspension in a nonpolar solvent. [Pg.146]

In conclusion, we have demonstrated that high resolution TEM is a valuable complement to x-ray fiber diffraction analysis and chemical structural elucidation. Its application provided information about the organization of pectin in cell walls and in calcium-free gels. Using freeze-dried samples that were Pt/C replicated, we demonstrated tobacco pectin filaments in a gel to be of the same diameter as the filaments on the noncutinized lower epidermal surface of senescing Coker 319 tobacco leaves. These filaments were 7.1 3A and 4.6 4.8A, respectively, and roughly the same diameter, 7A, as fiber-diffraction modeled citrus pectin (32). Replicated... [Pg.307]


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