Chemical and Biological Factors

Oliver and Schafer (443) discovered vasopressin in 1894, when they observed the increase of blood pressure due to aqueous extracts of the posterior lobe of bovine pituitary. A great deal of research has been done on the substance responsible for this physiological activity and has resulted in the isolation of vasopressin which, like ocytocin, is an octa-peptide. The same remarks which were made with respect to ocytocin, concerning the state of the peptide in the cell and its relationships with a high molecular weight protein molecule are applicable to vasopressin (see p. 101). 

---

The condition of any soil represents a stage in the changing process of soil evolution. Soils develop, mature and change with the passage of time. Whereas the time required for a true soil to develop from the parent rock of the earth may be thousands of years, rapid changes can result in a few years when soils are cultivated, irrigated, or otherwise subjected to man s manipulation. The type of soil that develops from the parent material will depend upon the various physical, chemical and biological factors of the environment. 

The following physical, chemical, and biological factors related to the metabolism of inhaled and ingested radiocerium are recommended for establishing radiation protection guidelines ... 

The influence of chemical and biological factors on brain uptake of drugs has been reviewed by Audus et al. (1992). 

In the preceding two chapters, the disposition and metabolism of foreign compounds, as determinants of their toxic responses, were discussed. In this chapter, the influence of various chemical and biological factors on these determinants will be considered. 

The factors affecting the disposition and toxicity of a foreign compound may be divided into chemical and biological factors. 

Aly and Faust (3) investigated the physical, chemical, and biological factors which influence the persistence of 2,4-D compounds in natural surface waters. They found that esters of 2,4-D in aerobically incubated lake waters were hydrolyzed biologically to the free acid and corresponding alcohol within 9 days and that 2,4-D was decomposed 81-85% within 24 hours by lake muds after microbial adaptation. 

Harrison, P., and Turpin, D. (1982). The manipulation of physical, chemical, and biological factors to select species from natural phytoplankton populations. In Marine Mesocosms Biological and Chemical Research in Experimental Ecosystems (Grice, G., and Reeve, M., eds.). Springer, New York. pp. 275-287. 

Conradi RA, Burton PS, Borchardt RT. Physico-chemical and biological factors that influence a drug s cellular permeability by passive diffusion methods and principles in medicinal chemistry. Lipophil. Drug Action Toxicol. 1996 4 233-252. 

Conradi, R.A. Burton, P.S. Borchard, R.T. Physico-Chemical and Biological Factors That Influence a Drug s Cellular Permeability by Passive Diffusion. In Lipophilicity in Drug Action and Toxicology, PUska, V., Testa, B., van de Waterbeemd, H., Eds. VCH Weinheim, 1996 233-252. 

Nelwm.S 0. Chemical and biological factors influencing drug biotransfor mulion. In Wrdff. M. E. (ed.). Burger s Medicinal Chemistry. Part I. 4ih cd. New York. Wiley-InteiNcience. 1980. p. 227. 

In addition, laboratory-prepared water used for diluting the effluent is relatively free of suspended solids, humic matter, and other varying components (e.g., hardness level) that may serve as nutrients, provide sorption sites, and have direct effects on the functional expression of toxicity. Thus, toxicity as expressed by the LC50 should not be viewed as a biological constant but as a value that varies with age and physical, chemical, and biological factors. 

Although variability is inherent in all environmental measurements, a variety of physical, chemical, and biological factors should be noted in compliance biomonitoring to enhance the consistency and de-fensibility of toxicity test results. These various parameters may affect the effluent toxicity to aquatic biota, and it is important that the investigator take them into account. Test conditions should mimic receiving water conditions, whenever feasible, to allow accurate assessment of the in-stream effect of an effluent. However, the use of upstream water for dilution should be avoided due to the potential variability in quality, or toxicity, over the testing period. 

Brain uptake of drugs The influence of chemical and biological factors, 23, 1 Bromocriptine, 12, 247... 

Numerous physical, chemical and biological factors influence vims persistence and activity. Some of the primary physical factors involved in the persistence of vimses outside living hosts include temperature, ultraviolet light, moisture (or relative humidity) and pH. These factors may interact with each other, and their effect can be additionally altered by vimcidal chemicals, formulation additives, and a variety of substrates, including soil, fabrics and plant foliage. 

Objectives. It is the objective of this presentation to review some of the chemical and biological factors that regulate the composition of natural waters, to illustrate the variables and modes by which stability is imparted to natural systems, to interpret pollution in terms of disturbance of ecological balances and mitigation of ecosystem stability, and to discuss some means of water pollution control beyond those of waste treatment. 

The complex interplay of this multiplicity of physical, chemical and biological factors which affect aldicarb residue concentrations in the groundwater at any place and time makes... 

Fisk, A.T., Hobson, K.A. and Norstrom, RJ. (2001) Influence of chemical and biological factors on trophic transfer of persistent organic pollutants in die northwater polynya marine food web. Environmental Science and Technology, 35, 732—738. 

Conversion from the [PS7+] to the [psi ] state is known as curing. While this phenomenon occurs spontaneously at a low frequency (Cox, 1965), both chemical and biological factors that increase curing rates have been identified. New information is emerging on the molecular mechanisms by which these treatments act, and these studies provide new insights into the prion replication process in vivo. 

Bush IE. Chemical and biological factors in the activity of adrenocortical steroids. Pharmacol Rev 1962 14 317-336. 

The average persistence in the environment is greatest with DDT and dieldrin with lesser times for the other chlorinated hydrocarbons (I). Chemical and biological factors are involved in the environmental degradation of pesticides. It is difficult to evaluate the contribution of each factor to the degradation of the chlorinated hydrocarbons. 

---