Vectorial markers

To identify bacteria which have taken up the vector, a common ploy is to utilize a characteristic of the vector, i.e. a vectorial marker. Plasmids possessing an antibiotic-resistance marker will enable a microorganism to grow in culture medium containing that antibiotic. Bacteria lacking the plasmid fail to develop colonies. For example, the plasmid pBR 322 contains antibiotic-resistance markers for tetracycline and ampicillin. Therefore, bacteria transformed by this plasmid are capable of colony formation in tetracycline- and/or ampi-cillin-containing medium and are easily selected. 

Proximal tubule cells in culture should have retained functional attributes such as (1) polar architecture and junctional assembly of epithelia and correct membrane distribution of enzymes and transport systems (2) vectorial transport of solutes and water, manifested by the formation of domes when cultured on solid supports [81] and the generation of transepithelial electrophysiological properties [82, 83] due to the expression of proximal tubule specific claudins 2- and 10 [84, 85] (3) cellular uptake of xenobiotics from either the apical or basolateral side, as observed in vivo and (4) expression of nephron segment-specific characteristics, i.e., distinct expression of differentiation markers, metabolic and transport properties, and hormone responsiveness. Such markers include the expression of the brush border enzymes alkaline phosphatase, leucine aminopeptidase, and y-glutamyl transferase [4, 86], In addition, proximal tubule cells should possess Na+,K+-ATPase activities, Na+-dependent glucose, and p-aminohippurate transport. Proximal tubule cells increase cAMP levels in response to parathyroid... 

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