Enzyme activity changes

The field of electrochemical effects in biology is broad, although up to the end of the twentieth century, the study of their mechanisms had been little pursued. Among the electrochemical effects that have attained the early experimental stage (Findl, 1995) are an increase in enzyme activity, change in shape of DNA with potential when adsorbed on an Hg electrode, acceleration of wound healing, and prevention of bacterial infection. 

Role of Drugs. The role of drugs as a factor in the enzyme activity changes brought about by the organic phosphates and carbamates has been the subject of several recent papers. Gaines (57) has shown that phenothiazine derivatives potentiate the toxicity of organophosphate... 

While RBC-ChE inhibition in the blood is considered an operationally acceptable surrogate for CNS inhibition, plasma ChE is more labile and is a less rehable reflection of enzyme activity change at neuro-effector sites (USEPA, 2000 Young et al, 1999). 

Fig. 30. Comparison of ESR and enzyme activity changes with hydration. Effect of hydration on lysozyme dynamic properties. (Curve f) Log rate of peptide hydrogen exchange. (Curve g) , Enzyme activity (log uo) O, rotational relaxation time (log t ) of the ESR probe TEMPONE. From Rupley et al. (1983).

The iso-osmolar non-ionic dimer iotrolan and the low-osmolar ionic monomer iopromide (osmolarity about twice that of the blood) have been compared in 40 patients who underwent ERCP (159). They were randomized to receive either iopromide (iodine 300 mg/ml, 770 mosmol/kg, mean dose 15 ml) or iotrolan (iodine 300 mg/ ml, 320 mosmol/kg, mean dose 12 ml). Pancreatitis after ERCP occurred in two patients given iopromide and in five given iotrolan. There were no significant differences between the groups in the time-course of changes in serum pancreatic enzyme activities, changes in acute-phase proteins, or the incidence of abdominal pain. 

If an assay procedure fails to detect any enzyme activity, changing the procedure to make it more sensitive, or changing to an inherently more sensitive one may demonstrate that some enzyme activity is indeed present. The particular silent serum may contain an enzyme variant which has a very large Michaelis constant for the substrate employed in the assay, in which case a higher substrate concentration may be able to demonstrate the existence of enzyme activity. On the other hand, the silent serum may contain an enzyme variant which truly has no hydrolytic activity toward the substrate employed in the assay, but which may have readily detectable hydrolytic activity toward another choline-containing substrate. Several examples will be discussed below. 

Enzyme Activity Changes from Normal in Scorbutic Guinea Pigs... 

Although sample processing is similar, temperature is a far more critical factor, since enzyme activity changes at a rate of about 7% per °C. Therefore, temperature equilibrium and constancy in the reaction cuvette are critical. Temperature control to within 0.1°C is commonly specified. 

In addition to various treatments that alter enzyme activities, changes in Ratios A, B and B may also occur by changes in the size of the dose of the toxicant. At low... 

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