Chemical balance studies

With the purified yeast enzyme, a chemical-balance study of GSH synthesis has been made. The data shown in Table I demonstrate that the condensation of glutamylcysteine and glycine is accompanied by the splitting of ATP to yield ADP and P in amounts equivalent to the GSH formed in accordance with the equation... 

Early attempts to study element absorption in humans were based on chemical balance studies. They are often referred to as cold balance studies as they do not involve the use of isotopic tracers. In such studies, volunteers are fed a highly controlled diet and absorption of the element is assessed by subtracting the amount recovered in feces from the amount present in the food consumed. Element retention can be assessed in a similar maimer by subtracting the amount of element recovered in urine over the observational period. 

Some of the technical difficulties associated with chemical balance studies can be overcome by measuring the increase in element concentration in plasma over several hours after test meal intake instead of analyzing the feces. In such tests, the area under the curve describing changes in element concentration is... 

The crudest approach to study element absorption is by taking the human body as a black box. As for chemical balance studies, element absorption can then be assessed as the difference between dietary intake of an isotopic label and its fecal recovery. This approach, however, does not deliver the fraction of element that has truly been absorbed, that is, the fraction of element in the digested food moiety that has passed the intestinal mucosa. Digestion can only occur by action of... 

The synthesis of virus protein has not been worked out in any such detail as has that of nucleic acid. The only information comes from 3 sources (1) chemical balance studies already reviewed, (2) tracer studies of the origin of the N of T6 and T7 phages (160,163,262), and (3) a single investigation of the metabolism of lysine in cells infected with T6 (287). From the origin experiments it was found that a very small fraction of the protein N of T6 was derived from the host cell. This indicates that most of the virus protein is formed from extracellular ammonia by a... 

The dispersant used in these studies is Chevron Chemicals OLOA 1200, a polybutene of about 70 carbon atoms attached to a succinic acid group which is reacted with diethylene triamine to provide the basic anchoring group. Film balance studies showed that the adsorbed films have a film thickness of 50 X. This dispersant is supplied as a 50 w% solution in a mineral oil. It can be deoiled by adsorption from toluene onto silica with elution by acetone. In this paper the w% of dispersant refers to the deoiled material. 

Fig. 46. An overhead view of the electrodynamic balance and Raman spectrometer developed by Buehler (1991) for gas/microparticle chemical reaction studies.

For analytical studies involving the interplay of flow processes and chemical reactions, we require a set of chemically balanced equations that lead from the known reactants to the measured reaction products. For the complete oxidation of CH4, this last statement implies that we need a reaction scheme producing only H20 and C02. This requirement is incompatible with Equations 1-1 to 1-10. To achieve consistency, we first replace Equation I—1 by the balanced process... 

Note the equation of an extremely stimulated imagination with a dreamlike state. From the facts that he found the daylight to be unpleasantly glaring and the corresponding release of an uninterrupted stream of fantastic pictures, we can safely conclude that Hofmann s LSD visions were produced by a dreamlike shift in the chemical balance of his visual brain. And, indeed, Hofmann himself offered the hypothesis that the stimulating effects on his visual brain were caused by LSD s interference with serotonin, the brain modulator that later physiological studies showed to be radically reduced in REM sleep. 

Standard operating procedures (SOPs) are required for all routine activities that are critical to the successful outcome of the study including quality assurance procedures and inspections. Most of the SOPs for the field activities are written by the field scientists with guidance from the Quality Assurance Section. For the field activities, it is required that at each site there be SOPs for such things as how field plots are established and the plot boundaries marked, the maintenance of sample freezers, how to calibrate and maintain chemical balances and chemical application equipment, and how to obtain test chemicals. If an SOP for a critical item of equipment is not available, the study would be considered to be not in compliance with the principles of the GLP guidelines. The distribution of SOPs is carefully controlled so that when an SOP is changed, all outdated copies can be exchanged for the new version. 

Balance studies involve the measurement of both the intake of a substance and the excretion (urine and feces). The interpretation of some published studies is therefore difficult since the intake has been calculated merely from tables. A reliable balance study should include a chemical analysis of a comparable aliquot of the intake. The vomiting which is a feature of idiopathic hypercalcemia of infancy may also make accurate balance studies very difficult technically. 

The chemical balance technique is inadequate for the accurate assessment of dietary zinc availability and it does not permit, in any case, an evaluation of zinc availability from the separate components of a composite meal. Furthermore, although measurement of changes in the concentration of plasma zinc (3) following ingestion of pharmacological doses of the metal, has been used in studies of dietary zinc availability, this approach has not been validated with regard to its reliability and it cannot provide absolute data on the absorption of zinc. Indeed the only viable approach that can be followed is one Involving use of a suitable isotopic zinc tracer. 

Modern psychopharmacology has built its strongest base on the power of mind-altering drugs to influence the neuromodulatory system of the subcortical brain. One general rule that emerges from our studies of neuromodulators in health and disease is that of chemical balance. In many parts of the brain, acetylcholine tends to have a reciprocal relationship... 

Yuretich R. F. and Batchelder G. L. (1988) Hydrogeochemical cycling and chemical denudation in the Fort River watershed, central Massachussets an appraisal of mass-balance studies. Water Resour. Res. 24, 105-114. 

The true detoxification products as a rule appear in the urine, while the reactive intermediate toxic products remain in the body, tightly bound to tissue components, and thus chemically sequestered in the tissues. From the toxicological point of view therefore, it is not the percentage of the pharmacon and its metabolites recovered from urine, feces, and from the carcass by extraction that is most important in balance studies it is in fact the fraction of the... 

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