By isolated cells

The major tissues that use glutamine are kidney, small intestine, colon, immune cells and bone marrow cells. Rates of utilisation by these last four tissues cannot be measured in vivo. Rates of utilisation by isolated cells have been measured in vitro (Chapters 17 and 21). 

The interactions between immune and inflammatory cells are mediated in large part by certain proteins, called lym-phokines, or interleukins (IL), that are able to promote cell growth, differentiation, and functional activation. Interleukins resemble hormones, which also function as intercellular messengers. In contrast to hormones, however, they are secreted by isolated cells rather than discrete glands. Several interleukins have been described each has unique biological activities as well as some that overlap with the oth-... 

The production of flavour substances by cell or tissue cultures is still a dream for the future in most cases. Today the extraction of product from intact living plants is still less expensive than the production by isolated cells and tissues. On the other hand, it is very attractive to make use of the secondary metabolism of plant cells for the synthesis of natural flavours in a controlled way to avoid contaminating by-products and thus considerably simplify downstream processing. Further advantages of such cell culture systems would be the independence from agriculture combined with the risk for possible shortage and variances in product quality, the ability to scale-up the process to create an inexhaustible source of well-defined product. 

Elstner, E.F. and A. Heupel (1976). Formation of hydrogen peroxide by isolated cell walls from horseradish (axmoracla lapathifolla Glllb.). Plante, 130, 175-180. 

Gross G G, Janse C, Elstner E F 1977 Involvement of malate, monophenols, and the superoxide radical in hydrogen peroxide formation by isolated cell walls from horseradish Armoracia lapathifolia Gilib.). Planta 136 271-276... 

A variety of agents has been reported to stimulate or inhibit acid secretion by a direct action on the parietal cell. Many of these (e.g., cAMP derivatives, forskolin) do not act through cellular receptors, whereas others are suggested to reflect the presence of parietal cell receptors. Although no direct evidence for a parietal cell location exists, the ability of some substances to inhibit histamine stimulation of acid secretion argues for the presence of a parietal cell receptor, because the action of histamine is direct. Even in these cases, caution is necessary to interpret the inhibition as being direct rather than due to the release of another inhibitor. With this caveat in mind, the parietal cell appears to contain inhibitory receptors for somatostatin, prostaglandins (PG, EP3), and EGF. Each of these has been shown to inhibit histamine stimulation of acid formation by isolated cell preparations. 

Cooper, C., Jones, H. G., Weller, R. O., Walker, V., 1984 Production of prostaglandins and thromboxane by isolated cells from intracranial tumours. J. Neurol. Neurosurg. Psychiat. 47, 579-584. 

Biotransformations are carried out by either whole cells (microbial, plant, or animal) or by isolated enzymes. Both methods have advantages and disadvantages. In general, multistep transformations, such as hydroxylations of steroids, or the synthesis of amino acids, riboflavin, vitamins, and alkaloids that require the presence of several enzymes and cofactors are carried out by whole cells. Simple one- or two-step transformations, on the other hand, are usually carried out by isolated enzymes. Compared to fermentations, enzymatic reactions have a number of advantages including simple instmmentation reduced side reactions, easy control, and product isolation. 

In designing a process we have the choice of using the whole organism or specific enzymes isolated from it. As always both options have pro s and cons. Broadly speaking we could say that biosynthetic processes mostly rely on whole cells, whereas biotransformations can be catalysed by whole cells and by enzyme preparations. 

Hydrogen peroxide (H202) exhibits insulin-like activity in isolated cells. Like that of vanadate, this effect is thought to be mediated by inhibition of protein-tyrosine phosphatases. 

Nevertheless, the isolation of these metabolites was interesting in two respects. First, the structure of the thiazole glycol stimulated the research of functionalized carbohydrate chains as precursors of thiazole. Second, the thiazolecar-boxylic acid 40 can be secreted by derepressed cells in relatively high amounts, 0.24 nmol per mg of dried cells, which is nearly half the amount of synthesized thiamine. The presence of this free thiazolic derivative in the cells contrasts with... 

In recent years ionic liquids have also been employed as media for reactions catalyzed both by isolated enzymes and by whole cells, and excellent reviews on this topic are already available [47]. Biocatalysis has been mainly conducted in those room-temperature ionic liquids that are composed of a 1,3-dialkylimidazolium or N-alkylpyridinium cation and a noncoordinating anion [47aj. 

The yield and the composition of the fractions from soy bean meal obtmned with isolating WUS is shown in Table 1. The removal of cold water solubles, proteins and starch from soy meal was successful. The larger part of the material appeared in CWS, 59.1%. UFF contained mainly oligosaccharides and some water soluble proteins and UFR contained mainly water soluble proteins. The solution of SDSS and DTT extracted the residual proteins from the soy meal and the extract consisted for over 80% of proteins. Since the yield of the HWS fraction is only 0.4%, the composition is not discussed here. The remaining WUS contained 90% of NSP and the yield was 15.7%, which indicates that from the polysaccharides present in soy meal 92% was recovered in the WUS. By isolating WUS a fraction is obtained in which almost all cell wall polysaccharides are recovered and which contained only little other components. 

In terms of the average fi om 20 mature fiiiits, floss silk, seeds and fruit coat were isolated, the ratio being 14 %, 15 % and 71 % respectively. The filaments of floss silk on submission to microscopy, showed mainly unicellular trichomas, some of them being formed by two cells. The presence of lignin in the filaments was suggested by the characteristic reaction with phloroglucinol hydrochloride. 

Pectins were extracted from isolated cell walls of 5-week-old wheat plants using different methods. Enzymic digestions of the cell walls involved pectinases such as a commercial pectolayse or recombinant endopolygalacturonase [Maness Mort, 1989]. Chemical extractions involved the chelating agent imidazole [Mort et al., 1991] or solvolysis with anhydrous HF at 0 °C in a closed teflon line [Mort et al., 1989] followed by imidazole extraction. 

Feedback inhibition of amino acid transporters by amino acids synthesized by the cells might be responsible for the well known fact that blocking protein synthesis by cycloheximide in Saccharomyces cerevisiae inhibits the uptake of most amino acids [56]. Indeed, under these conditions, endogenous amino acids continue to accumulate. This situation, which precludes studying amino acid transport in yeast in the presence of inhibitors of protein synthesis, is very different from that observed in bacteria, where amino acid uptake is commonly measured in the presence of chloramphenicol in order to isolate the uptake process from further metabolism of accumulated substances. In yeast, when nitrogen starvation rather than cycloheximide is used to block protein synthesis, this leads to very high uptake activity. This fact supports the feedback inhibition interpretation of the observed cycloheximide effect. 

Thor, H., Smith, M.T., Hartzell, P., Bellomo, G., Jewell, S.A. and Orrenius, S. (1982). The metabolism of menadione (2-methyl-1,4-naphthoquinone) by isolated hepatocytes. A study of the impact of oxidative stress in the intact cell. J. Biol. Chem. 257, 12419-12425. 

The in-line configuration consists of deposition chambers that are separated by isolation chambers [153]. The layer sequence of a solar cell structure prescribes the actual sequence of deposition chambers. The flexibility is much less than with a cluster configuration, and costs are generally much higher, but the throughput can also be much larger. In an in-line system the substrates can move while deposition takes place, which leads to very uniformly deposited layers, as uniformity of deposition is required only in one dimension (perpendicular to the moving direction). 

Choe H, Farzan M, Sun Y, et al. The beta-chemokine receptors CCR3 and CCR5 facilitate infection by primary HIV-1 isolates. Cell 1996 85 1135-1148. 

Although several allelochemicals (primarily phenolic acids and flavonoids) have been shown to inhibit mineral absorption, only the phenolic acids have been studied at the physiological and biochemical levels to attempt to determine if mineral transport across cellular membranes can be affected directly rather than indirectly. Similar and even more definitive experiments need to be conducted with other allelochemicals that are suspected of inhibiting mineral absorption. Membrane vesicles isolated from plant cells are now being used to elucidate the mechanism of mineral transport across the plasma membrane and tonoplast (67, 68). Such vesicle systems actively transport mineral ions and thus can serve as simplified systems to directly test the ability of allelochemicals to inhibit mineral absorption by plant cells. 

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