Live cells

Campagnola P J, Wei M D, Lewis A and Loew L M 1999 High-resolution nonlinear optical imaging of live cells by second harmonic generation Biophys. J. 77 3341-9... 

Lemasters J J 1996 Confocal microscopy of single living cells Chem. Anal., NY 137 157-77... 

The reactions of biopolymers at interfaces fonn tire basis of some extremely important industrial processes. The primary process in all cases is tire adsorjDtion of biomolecules, usually proteins. If ultimately living cells are adsorbed, tliis always takes place onto a preadsorbed protein layer (which may be secreted by tire cells themselves [130]). These processes can be classified into tliree categories ... 

Although the idea on which NSOM is based goes back more than 50 years (32), D. W. Pohl first beheved it could be achieved with visible light and brought the concept to do it to fmition in 1984 (33). There is considerable interest in NSOM, and two commercial instmments have already been aimounced. A recent appHcation involves using NSOM for localized absorption spectroscopy and fluorescence imaging of living cells (33). 

Proteias are metabolized coatiauously by all living organisms, and are ia dyaamic equilibrium ia living cells (6,12). The role of amino acids ia proteia biosyathesis has beea described (2). Most of the amino acids absorbed through the digestioa of proteias are used to replace body proteias. The remaining portioa is metabolized iato various bioactive substances such as hormones and purine and pyrimidine nucleotides, (the precursors of DNA and RNA) or is consumed as an energy source (6,13). 

In many cases only the racemic mixtures of a-amino acids can be obtained through chemical synthesis. Therefore, optical resolution (42) is indispensable to get the optically active L- or D-forms in the production of expensive or uncommon amino acids. The optical resolution of amino acids can be done in two general ways physical or chemical methods which apply the stereospecific properties of amino acids, and biological or enzymatic methods which are based on the characteristic behavior of amino acids in living cells in the presence of enzymes. 

Biosynthesis of Protein. The dynamic equilibrium of body protein was confirmed by animal experiments using A/-labeled amino acids in 1939 (104). The human body is maintained by a continuous equilibrium between the biosynthesis of proteins and their degradative metabolism where the nitrogen lost as urea (about 85% of total excreted nitrogen) and other nitrogen compounds is about 12 g/d under ordinary conditions. The details of protein biosynthesis in living cells have been described (2,6) (see also Proteins). 

Research based on Wolff s law of bone transformation has resulted in some other important observations. Fluctuating loads, such as those that occur in walking, are better for bone than consistentiy appUed loads, such as weight gain. However, if the effective appUed load becomes extreme, pressure necrosis, ie, bone death, occurs. Pressure necrosis is a significant concern in hip arthroplasty. Necrosis means the localized death of living tissue. Undue pressure on living cells causes death. Some total hip replacement failures are the direct result of pressure necrosis. 

Proteins, ubiquitous to all living systems, are biopolymers (qv) built up of various combinations of 20 different naturally occurring amino acids (qv). The number of proteins in an organism may be as small as half a do2en, as in the case of the simple bacterial vims M13, or as large as 50,000, as in the human system. Proteins are encoded by the deoxyribonucleic acid (DNA) that is present in all living cells. 

Just under the bark of a tree is a thin layer of cells, not visible to the naked eye, called the cambium. Here, cells divide and eventually differentiate to form bark tissue outside of the cambium and wood or xylem tissue iaside of the cambium. This newly formed wood on the iaside contains many living cells and conducts sap upward ia the tree, and hence, is called sapwood. Eventually, the inner sapwood cells become iaactive and are transformed iato heartwood. This transformation is often accompanied by the formation of extractives that darken the wood, make it less porous, and sometimes provide more resistance to decay. 

The Ionic Basis of Membrane Activity. Almost all living cells maintain specific internal chemical environments that ate different from their external environments. In cardiac cells the principal ions involved in maintaining membrane activity are sodium, Na" potassium, K" chloride, CU and calcium, Ca ". The internal (i) and external (o) concentrations of these ions are Na" = 140 mM, Na" = 30 mM = 4 mM, = 140 mM Cl ... 

Probably the most surprising aspect of the putative oxidation of alkynes to oxirenes is the fact that evidence has recently been obtained that oxirenes may be formed, enzymatically, in living cells. The oxidation of labelled 4-biphenylylacetylene (94) to the carboxylic acid (95 Scheme 92) may involve an oxirene, since the alkyne gave acid with complete deuterium retention (path a) path (b) should have given unlabelled acid (80JA7373). 

MUTAGEN A chemical or physical agent that can cause a change (mutation) in the genetic material of a living cell. 

Viable count Measurement of the concentration of live cells in a microbial population. 

Virus Any of a large group of submicroscopic infective agents that typically contain a protein coat sunounding a nucleic acid core and are capable of growth only in a living cell. 

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