Storage tissue-/cell specific

Hardwoods contain several cell types, specialized for different functions (Fig. 1-9). The supporting tissue consists mainly of libriform cells, the conducting tissue of vessels with large cavities, and the storage tissue of ray parenchyma cells. In addition, hardwood contains hybrids of the above-mentioned cells which are classified as fiber tracheids. Although the term fiber is frequently used for any kind of wood cells, it more specifically denotes the supporting tissue, including both libriform cells and fiber tracheids. In birch these cells constitute 65 to 70% of the stem volume. 

When the chylomicrons reach tissue cells the triacylglycerols are again hydrolyzed by lipoprotein lipase to fatty acids which can be taken up by the peripheral tissue cells. In adipose cells the fatty acids are then converted into fatty acyl CoA s and combined into triacylglycerols for storage. Alternatively tlie fatty acids can be broken down for energy using the various oxidative pathway in specific tissues. 

By far the most work on the control of enzymes responsible for the mobilization of stored reserves has been carried out on cereal grains and some of the possible reasons for the preferential use of this material should become clear in this chapter. Discussion of this topic inevitably involves a consideration of the effects of plant hormones on cell metabolism and, more specifically, of their actions in non-growing storage tissue. The reason for this is that in the best-understood system—the cereal grain—mobilization of food reserves is quite clearly under hormonal control. The major part of this chapter is therefore devoted to regulation in these grains, especially barley and wheat, but we conclude with an account of control processes in other seeds. 

Insulin is the only hormone known to reduce the blood sugar level. It is secreted by the -cells of the islets of Langerhans in the pancreas in response to an elevated level of blood glucose. The overall action of insulin is to promote storage pathways. More specifically it stimulates the transport of glucose across the plasma membrane of certain cells, especially of muscle and adipose tissue, but not of liver. In this way it promotes the synthesis of glycogen in the liver and fatty acids in both liver and adipose tissue. Insulin also stimulates protein synthesis. 

Uptake of LCFAs across the lipid-bilayer of most mammalian cells occurs through both a passive diffusion of LCFAs and a protein-mediated LCFA uptake mechanism. At physiological LCFA concentrations (7.5 nM) the protein-mediated, saturable, substrate-specific, and hormonally regulated mechanism of fatty acids accounts for the majority (>90%) of fatty acid uptake by tissues with high LCFA metabolism and storage such as skeletal muscle, adipose tissue, liver,... 

There are important methodologic considerations which apply to the use of cultured amniotic fluid cells for the detection of biochemical disorders. The first is that the enzymes which can be sampled are those which are usually present in fibroblasts or fibroblast-like cells. Therefore, conditions such as phenylketonuria and glycogen storage disease type I, which are associated with deficiencies of enzymes present only in liver and kidney, are not amenable to this approach. The same also pertains to enzyme deficiencies affecting other specific tissues. 

Improved characterization of the morphological/microstructural properties of porous solids, and the associated transport properties of fluids imbibed into these materials, is crucial to the development of new porous materials, such as ceramics. Of particular interest is the fabrication of so-called functionalized ceramics, which contain a pore structure tailored to a specific biomedical or industrial application (e.g., molecular filters, catalysts, gas storage cells, drug delivery devices, tissue scaffolds) [1-3]. Functionalization of ceramics can involve the use of graded or layered pore microstructure, morphology or chemical composition. 

Compartmentation means both spatial separation of potentially harmful but essential compounds (e.g., storage of iron in ferritin) and cell- and tissue-specific distribution of antioxidative compounds, and it serves to prevent uncontrolled oxidation. 

Mast Cells and Basophils. The chief sites of histamine storage are mast cells in the tissues and basophils in blood. These cells synthesize histamine and store it in secretory granules along with a heparin-protein complex. In response to specific antigens, mast cells or basophils are sensitized. Histamine is then secreted from the storage granules. Besides the histamine stores in mast cells and basophils, there is evidence of non-mast cell histamine in some tissues, particularly gastric and intestinal mucosa (60). 

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