Human metabolism studies

These in vivo and in vitro human metabolism studies indicate that pyrethroids undergo rapid metabolism and elimination as observed in rats, and qualitative metabolic profiles (e.g., kinds of metabolites) of pyrethroids are assumed to be almost the same between humans and rats, suggesting that a large database of animal metabolism of pyrethroids could provide useful information for the evaluation of behavior of pyrethroids in humans. Nowadays, human pesticide dosing studies for regulatory propose are severely restricted in the US, and thus detailed comparison of in vitro metabolism (e.g., metabolic rate constants of pathways on a step-by-step basis) using human and animal tissues could be an appropriate method to confirm the similarity or differences in metabolism between humans and animals. 

We have conducted two human metabolic studies (5,6) to compare the effects of increasing phosphorus intake on calcium utilization in healthy young adults maintained at low (ca. 400 mg/day) and high (ca. 1200 mg/day) levels of calcium intake. Increasing dietary phosphorus, as orthophosphate, caused a slight reduction in fecal calcium and a substantial reduction in urinary calcium losses (Table III). 

Another therapeutic class to be briefly discussed is that of the lipid-lowering agents known as fibrates, e.g., clofibrate and fenofibrate (8.5). Here also, the acidic metabolite is the active form clofibrate (an ethyl ester) is rapidly hydrolyzed to clofibric acid by liver carboxylesterases and blood esterases [11], Human metabolic studies of fenofibrate (8.5), the isopropyl ester of fenofibric acid, showed incomplete absorption after oral administration, while hydrolysis of the absorbed fraction was quantitative [12], This was followed by other reactions of biotransformation, mainly glucuronidation of the carboxylic acid group. 

Disposition Human metabolism studies of Humalog have not been conducted. Studies in animals indicate that the metabolism of insuUn Uspro is identical to that of regular human insuUn. 

MDOH, that is the factor intrinsic to the intoxication that is produced. Human metabolic studies are needed, and they have not yet been done. 

If human metabolism studies with radiolabeled drug have not been performed prior to the conduct of reaction phenotyping studies, the initial experiments should use as complete an in vitro test system as possible, depending on the drug (e.g., tissue homogenates, liver slices, hepatocytes, etc.). 

Besides their utilization in the production of many compounds with therapeutic, diagnostic, and immunizing applications, animal cell cultures have undoubted utility in the performance of in vitro cytotoxicity tests. They can be used for the evaluation of potential anti-neoplastic agents and assessment of the safety of various products, such as pharmaceuticals, cosmetics, alimentary additives, pesticides, and industrial chemical products. Cell culture systems are frequently employed in the cancer chemotherapy field, in which their potential value for viability and cytotoxicity tests is largely accepted. Animal models play an important role in toxicity testing, but the pressure to adopt in vitro tests is growing since they present considerable economical advantages over in vivo tests. The use of animal models is limited to human metabolism studies, and there are... 

Three human metabolic studies have examined the effect of dietary zinc Intake on apparent copper absorption. Greger et al. (37) studied 11 adolescent girls, ranging in age from 12.5 to... 

A number of studies have investigated the bioconversion, fate, and elimination of CR in various animal species (French et al, 1983 Fumival et al, 1983 Balfour, 1978 Harrison et al, 1978). Human metabolic studies on CR have not been performed due to the high degree of sensitivity of human tissues to CR. The maximum tolerated dosage is far too low to allow for detection in metabohc studies (Olajos,... 

The data available from the study described here do not permit a conclusive statement as to which of the above reasons offers the best explanation of the results. However, in future planning of human metabolic studies, the factors mentioned above should be taken into consideration. 

Hussein, L. and El-Tohamy, M. 1990. Vitamin A potency of carrot and spinach carotenes in human metabolic studies. Ini. J. Vit. Nutr. Res. 60 229-235. 

Ting. B.T.G. and Janghorbani, M. (1987). Application of ICP-MS to accurate isotopic anaiysis for human metabolic studies. Spectrochim. Acta. 42B, 21. 

While such advantages may be cited, it would not be suggested that microbial models will replace all animal metabolism studies, anymore than the animal models have "replaced" human metabolism studies. But such systems should be particularly useful in predicting routes of metabolism resulting in bioactivation, detoxification, or generation of toxic metabolites. 

I would put my money on the likelihood of MDA going to MDOH if it should turn out that the two drugs interconvert in the body. And in that case, it would be MDOH, or another metabolite on down the line that is common to both MDA and MDOH, that is the factor intrinsic to the intoxication that is produced. Human metabolic studies are needed, and they have not yet been done. 

Rapid Gas Chromatographic-Mass Spectrometric Analysis of Urea Application in Human Metabolic Studies... 

Vandael, P. (2004) Stable isotope-enriched selenite and selenate tracers for human metabolic studies a fast and accurate method for their preparation from elemental selenium and their identification and quantification using hydride generation atomic absorption spectrometry. 

The use of stable isotopes as tracers in clinical studies is becoming more commonplace. Human metabolism studies have been reported with enriched Mg and Mg measuring plasma, faecal and urine samples. In another study using Mg, the absorption of magnesium was seen to increase when certain fatty acids were also administered. Enriched boron stable isotopes have also been determined in rat urine and faeces to establish excretion pathways and found that... 

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