Biological consequences mammalian cells

In general, penicillins exert thek biological effect, as do the other -lactams, by inhibiting the synthesis of essential structural components of the bacterial cell wall. These components are absent in mammalian cells so that inhibition of the synthesis of the bacterial cell wall stmcture occurs with Htde or no effect on mammalian cell metaboHsm. Additionally, penicillins tend to be kreversible inhibitors of bacterial cell-wall synthesis and are generally bactericidal at concentrations close to thek bacteriostatic levels. Consequently penicillins have become widely used for the treatment of bacterial infections and are regarded as one of the safest and most efficacious classes of antibiotics. 

While the amino acid, which has been replaced by its fluorinated analogue, is essential for the functionality of the protein, some biological consequences can occur. Thus, incorporation of 2-F-His into mammalian proteins (4-F-His cannot be incorporated), in cell culture or invivo, is accompanied by inhibition of the induction of several enzymes (e.g., inhibition of acetyltransferase activity of the pineal gland). This probably stems from the formation of defective or inactive enzymes. Indeed, histidine plays an important role in the nucleophilic and acid-base processes connected to the catalytic activity of numerous enzymes. 

Most target proteins of therapeutic interest are human or mammalian in origin, but some require post-translational modification during expression for optimum biological and pharmacokinetic properties. Bacterial expression systems do not allow most post-translational modifications. In those cases, eukaryotic expression systems are chosen. These systems, however, are more complex and require more time and resources to engineer, especially in mammalian cells. Consequently, the final products produced in mammalian cells are more expensive than those produced by bacterial expression systems. 

The production of oxygen free radicals was not considered to be of biological consequence until 1969, when McCord and Fridovich discovered that superoxide dis-mutase exists in essentially every mammalian cell, suggesting ubiquitous superoxide formation in vivo (Figure 18.3). 

Biological Consequences of Platinum—DNA Crosslinks in Mammalian Cells... 

L. A. Zwelling Biological Consequences of Platinum-DNA Cross-links in Mammalian Cells (Platinum, Gold, and Other Metal Chemotherapeutic Agents, Ed. S. J. Lippard), pp. 27—50. ACS Symposium Series 209, Washington (1983). 

Instructions for the behaviour of every cell in the bodies of worms, flies and humans will soon reside in public databases for all to read. A complete set of these instructions, packaged as chromosomes, is inherited by most cells in our body. Because of this, many if not most somatic nuclei in mammals are totipotent that is, they are capable of programming all of mammalian development when injected into enucleated eggs (Wilmut et al 1997). Dolly s creation had dramatic practical consequences but its feasibility was never improbable on theoretical grounds. How cells inherit two complete packages of the genome at each cell division is one of the most fundamental questions in biology (Fig. la). 

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