Physiological factors

Elevation of temperature increases tyrosinase activity, shortens the induction period and stimulates melanin formation within physiological limits. The enzyme activity is optimal in the pH range 6.1-1.2 during in vitro reactions 183). The temperature responses of melanin-stimulating hormones have also been studied (226). 

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Human perception creates difficulty ia the characterization of flavor people often, if not always, perceive flavors differently due to both psychological and physiological factors. For example, certain aryl thiocarbamates, eg, phenylthiocarbamide, taste exceedingly bitter to some people and are almost tasteless to others (5). This difference is genetically determined, and the frequency of its occurrence differs from one population to another 40% of U.S. Caucasians are nontasters, whereas only 3% of the Korean population caimot perceive the strong bitter taste of the aryl thiocarbamates (6). Similar differences were found ia the sense of smell for compounds such as menthol, carvone, and ethyl butyrate (7). 

The high permeability of carboxyl CP in combination with their considerable selectivity of bonding protein macromolecules have made it possible to use them as carriers for the immobilization of proteins and enzymes with the aim of protection against some physiological factors (e.g., the pH of the medium). 

Physiological Factors that Influence Drug Delivery for HCV Drugs. 43... 

Sato A, Endoh K, Kaneko T, et al. 1991. A simulation study of physiological factors affecting pharmacokinetic behavior of organic solvent vapours. Br J Ind Med 48 342-347. 

Lewis TA, RL Crawford (1993) Physiological factors affecting carbon tetrachloride dehalogenation by the denitrifying bacterium Pseudomonas sp. strain KC. Appl Environ Microbiol 59 1635-1641. 

Fitzgerald JW, HW Maca, FA Rose (1979) Physiological factors regulating tyrosine-sulphate sulphohydrolase activity in Comamonas terrigena occurrence of constitutive and inducible enzymes. J Gen Microbiol 111 407-415. 

W. H. Barr and S. Riegelman, Intestinal drug absorp- 28. tion and metabolism. I. Comparison of methods and models to study physiological factors in vitro and in... 

M. Rowland, Effect of some physiologic factors on bioavailability of oral dosage forms, in Dosage Form Design and Bioavailability (J. Swarbrick, Ed.), Lea Febiger, Philadelphia, 1973, pp. 181-222. 

Factors determining resistance to airflow are also analogous to those determining the resistance to blood flow and include viscosity, length of the airway, and airway radius. Under normal conditions, the viscosity of the air is fairly constant and the length of the airway is fixed. Therefore, airway radius is the critically important physiological factor determining airway resistance ... 

It appears that, in beetles, pheromone production is regulated by JH III, despite the variations in biosynthetic pathways. JH apparently regulates pheromone production in beetles that utilize both fatty acid and isoprenoid biosynthetic pathways [8,98]. Environmental and physiological factors will in turn regulate production of JH. The endocrine regulation of pheromone production in the beetles has been best studied with regard to the bark beetles. 

Orally administered dosage forms are absorbed into the systemic circulation following dissolution in the GI tract. Because substances must be in solution for the absorption from the GI lumen, the absorption rate of poorly water-soluble drugs is limited by their rate of dissolution. The dissolution rate is affected by the unique physicochemical properties of the drug and by physiological factors the pH, composition, and hydrodynamics of the GI medium. 

A summary of how physiological factors affect the dissolution rate is given in Table 21.2. The effective surface area will be affected by the wetting properties of the bile acids and other surface-active agents in the gastrointestinal tract. The dif-fusivity of a drug molecule in the intestinal juice will be altered by changes in viscosity that are induced, for instance, by meal components. An increased dissolution rate could be obtained at more intense intestinal motility patterns or increased... 

Leonard, T.L., G.E. Taylor, Jr., M.S. Gustin, and C.J. Fernandez. 1998b. Mercury and plants in contaminated soils 2. Environmental and physiological factors governing mercury flux to the atmosphere. Environ. Toxicol. Chem. 17 2072-2079... 

The etiology of obesity is usually unknown, but it is likely multifactorial and related to varying contributions from genetic, environmental, and physiologic factors. 

Dl. Dalderup, L. M, Atherosclerosis and toxemia of pregnancy in relation to nutrition and other physiological factors. Vitamins and Hormones 17, 223-306 (1959). 

Koski K, Luukinen H, Laippala P et al. (1996) Physiological factors and medications as predictors of injurious falls by elderly people a prospective population-based study. Age Ageing 25(1) 29-38... 

When the estimates of bioavailability were compared ( ), in vivo absorption was higher than in vitro solubility for two of the foods We had expected absorption to be less than solubility due to physiological factors (lt9). Thus, this surprising result led to the reexamination of in vitro digestion conditions which is reported in this paper. 

Table I. Comparison of Various Dietary and Physiological Factors on Apparent Calcium Absorption by Rats and Humans...

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