Effects on 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. 

Gamer AL, Yu J, Struss AK, Lowery CA, Zhu J, Kim SK, Park J, Mayorov AV, Kaufmann GF, Kravchenko VV, Janda KD (2011) Synthesis of clickable acylhomoserine lactone quorum sensing probes unanticipated effects on mammalian cell activation. Bioorg Med Chem Lett 21 2702... 

Penicillin interferes with the synthesis of the bacterial cell wall. A nucleophilic OH group of the glycopeptide transpeptidase enzyme cleaves the P-lactam ring of penicillin by a nucleophilic acyl substitution reaction. The opened ring of the penicillin molecule remains covalently bonded to the enzyme, thus deactivating the enzyme, halting cell wall construction, and killing the bacterium. Penicillin has no effect on mammalian cells because they are surrounded by a flexible membrane composed of a lipid bilayer (Chapter 3) and not a cell wall. 

The plant extracts with IC50 <10)j,g/ml offer the potential for the isolation of lead antimalarial compounds, or for the characterization of some active compounds that could be used as markers for standardization of the extracts for use as traditional antimalarials. We suggest that some Samburu plants used in traditional medicine possess potent antiplasmodial activity with minor effects on mammalian cells and hence we propose that those plants should be further investigated to contribute to the development of potential antimalarial medicines. The results of the preliminary studies carried out with the above-mentioned plants are encouraging. 

The compound bergapten was found to induce lethal and mutagenic photosensitization of bacteria, "dark"-induced frameshift mutagenesis in bacteria, and lethal and clastogenic effects on mammalian cells in tissue cultures (Ashwood-Smith et al. 1980). 

Have no adverse effects on mammalian cell membranes. 

When testing for effects on mammalian cells, it is necessary first to remove free formaldehyde because of its cytotoxicity. Thus, experiments were carried out with formaldehyde-treated RNA from which unbound formaldehyde was removed by dialysis [12]. The RNA was treated with formaldehyde under conditions where the formation of methylene-bridged dimers of A A, A G and G G had been shown to involve 15 to 19% of the purine bases in RNA [5]. A proportion of the remaining purine bases may be either unmodified or hydroxymethylated, even after dialysis. 

Middleton Jr, E. 1988, Plant flavonoid effects on mammalian cell systems , in L. E. Cracker and J. E. Simon (eds), Herbs, Spices Medicinal Plants, Vol. 3, Oryx Press, Arizona. 

Acylation inactivates the enzyme, and actively growing bacteria die because they are unable to synthesize functional cell walls. PenidUin has no effect on mammalian cells because they are not enclosed by cell walls. PeniciUins are stored at cold tempa-atures to minimize hydrolysis of the /3-lactam. 

Shear effects on mammalian cells due to hydrodynamic forces or bubble aeration in bioreactor systems are still one of the most important aspects in the design of these systems. A number of reviews have summarized the main... 

Methoxypsoralen (5-MOP) appears in blood serum following topical application of bergamot essential oil to human skin and has shown mutagenic effects on mammalian cells... 

There seems to be little more evidence in the literature to allow a more coherent discussion of the effects of surfactants on herbicide activity and explanation of their intrinsic phytotoxicity. It may be that with such a diversity of plant structures the task of rationalizing the activity of surfactants (with the complex pattern of wetting effects, evaporation retardation, solubilization, particle size alteration of precipitated active ingredient, membrane permeability effects and intrinsic biological effects on enzyme systems) will be more daunting than with the relatively simple problem that must be faced with surfactant effects on the human organism. It is likely, however, that study of surfactant effects on plant cells will give useful information to help in the elimination of effects on mammalian cells. 

---