Biological agents replicating

Key aspects are the potential of the biological agent to cause harm and the nature and degree of worker exposure to it. Risk assessments should reflect the ability they have to infect and replicate, and the possibility that there may be a significant risk to health at low exposures. 

Exposure to a biological agent should be either prevented, or where this is not reasonably practicable, adequate control measures applied. Schedule 3 of COSHH is concerned with the special control provisions for biological agents. The selection of control measures should take into account the fact that biological agents do not have any air quality exposure limits and that they are able to infect and replicate at very small doses. An appropriate blend of controls is needed based on perceived levels of risk. 

Cancer occurs when the body s own (somatic) cells undergo uncontrolled replication and growth. As with mutations, cancer often results from alterations in cellular DNA. Many cancers occur as apparently random events. Study of the human genome has shown genetic characteristics indicative of a propensity to certain kinds of cancers. For experimental purposes, animals have been bred that have inherited tendencies toward certain kinds of cancers. Some biological agents including hepad-naviruses or retroviruses are known to cause cancer. 

Bacteria are vulnerable to the selective attack of chemotherapeutic agents because of the many metabolic and molecular differences between them and animal cells. The biology of vims replication, with its considerable dependence on host-cell energy-producing, protein-synthesizing and biosynthetic enzyme systems, severely limits the opportunities for selective attack. Another problem is that many vims diseases only become apparent after extensive viral multiplication and tissue damage has been done. 

Dannomycin was the first antibiotic to be used in the treatment of leukemia in human(39-40). Dannomycin (Fig. 11) and the closely related adriamycin (14-hydro dannomycin) are both widely used in the treatment of human tumors. Even though these substances are closely related to each other, they have q.uite distinct biological activities. Daunomycin is used in the treatment of leukemias, whereas adriamycin is used in the treatment of solid tumors. These agents are believed to act by inhibiting both IMA replication and transcription. 

Physiological sites proposed for nitric oxide action include the immune system, where nitric oxide acts as a cytostatic agent, is tumoricidal, and can inhibit viral replication. In the cardiovascular system, nitric oxide is the biological mediator of vasodilator responses to agents such as acetylcholine and bradykinin, which act as receptors on endothelial cells to activate NOS and stimulate nitric oxide production. Diffusible nitric oxide then activates guanylate cyclase in vascular smooth muscle cells, leading to the production of cyclic guano-sine monophosphate (GMP) and vasodilation. In the brain, stimulation of A-methyl-o-aspartate receptors on... 

This nitrogen mustard is a biological alkylating agent that inhibits replication and transcription of DNA by forming cross-links between two molecules of nucleoprotein. DNA miscoding and breakage may also occur.2... 

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