Extracellular constituents

One problem unique to these slides is the closed system in place in the cell culture well. As these cells grow, their metabolites are shed into the surrounding medium. If a particular analyte is in high enough concentrations to be contained in the spent medium, it could also be left behind attached to some cells because of inadequate washing. It is very important to wash the spent medium away with many PBS washes before fixation. This way, no extracellular constituent will cause aberrant reactions because it remained on the cell inappropriately. 

They are cell-wall constituents, non-cell-wall constituents, and storage materials in algae. In microorganisms, they may be cellular or extracellular constituents. The polysaccharide chitin is a structural component in the exoskeletons of crustaceans and insects. The greatest amount of polysaccharides is found in plant cell walls (higher plants, algae, and fungi). 

Two separate processes are involved in the maintenance of the dynamic equilibrium of the body constituents namely (1) the destruction and replacement of whole cells and (2) the destruction and replacement of intracellular and extracellular constituents. 

The sodium content of the body is 1.4g/kg. Sodium is present mostly as an extracellular constituent and maintains the osmotic pressure of the extracellular fluid. In addition, it activates some enzymes, such as amylase. Sodium absorption is rapid it starts 3-6 min after intake and is corr tleted within 3 h. Daily intake of sodium averages 2.5 g (females) to 3.3 g (males) the adult s average requirement ranges from... 

The presence and biological importance of oligosaccharide structures, usually as components of glycolipids and glycoproteins, in bacterial capsular and cell-wall polysaccharides, in mammalian cell membranes, in cytoplasm, and in extracellular fluids, are now well documented. They are important constituents in... 

Several glyculosonic acids have been identified as components of bacterial polysaccharides. D-/yxo-Hexulosonic acid, as Q -D-pyranosyl residues (23), is a component of the extracellular polysaccharide from a Rhodococcus species. The LPS from Acinetobacter calcoaceticus NCTC 10305 contains - D-g/ycero-D-/a/o-octulosonic acid (24). It is isosteric with 3-deoxy-D-mnnno-octulosonic acid (25), which is a constituent of bacterial LPS and links the polysaccharide part to the lipid A region. It seems possible that D-g/ycero-D-tfl/o-octulosonic acid replaces 3-deoxy-D-/wan o-octulosonic acid in the A. calcoaceticus LPS. 

At harvest, the benzylpenicilhn is in solution extracellularly, together with a range of other metabolites and medium constituents. The first step in downstream processing is to remove the cells by filtration or centrifugation. This stage is carried out under conditions that avoid contamination with (3-lactamase-producing microorganisms which could lead to serious or total loss of product. 

The matrix metalloendoproteinases (MMPs or matrixins) are a family of zinc and calcium dependent extracellular proteases that collectively degrade most of the protein constituents of the extracellular matrix [9]. There are at least 23 members of this family and are divided primarily on the basis of sequence homology and substrate specificity into the following grouping collagenases (MMP-1, -8, -13, -18) gelatinases... 

The process of tubular reabsorption is essential for the conservation of plasma constituents important to the body, in particular electrolytes and nutrient molecules. This process is highly selective in that waste products and substances with no physiological value are not reabsorbed, but instead excreted in the urine. Furthermore, reabsorption of many substances, such as Na+, H+, and Ca++ ions, and water is physiologically controlled. Consequently, volume, osmolarity, composition, and pH of the extracellular fluid are precisely regulated. 

Since in mammalian species metals first need to be assimilated from dietary sources in the intestinal tract and subsequently transported to the cells of the different organs of the body through the bloodstream, we will restrict ourselves in this section to the transport of metal ions across the enterocytes of the upper part of the small intestine (essentially the duodenum), where essentially all of the uptake of dietary constituents, whether they be metal ions, carbohydrates, fats, amino acids, vitamins, etc., takes place. We will then briefly review the mechanisms by which metal ions are transported across the plasma membrane of mammalian cells and enter the cytoplasm, as we did for bacteria, fungi and plants. The specific molecules involved in extracellular metal ion transport in the circulation will be dealt with in Chapter 8. 

An extracellular lactase enzyme, isolated from the fungus Rhizoctonia prati-cola, was shown to mediate cross-coupling between phenolic constituents of HS and 2,4-dichlorophenol formed during the decomposition of 2,4-D, thus leading to the incorporation of this xenobiotic into SP0M. 

Collectively, the MMP are capable of degrading all of the major protein constituents of the extracellular matrix. The interstitial collagenases that are the focus of this review dissolve collagen fibrils by making a single scission across all three a. chains at a specific, sensitive locus of exposed type I, II... 

---