Metabolism explants

It was shown that microsomal epoxide hydrolase-catalyzed trans-addition of water to BaP 9,10-epoxide occurs stereospecifically at the C-9 position (15). Since BaP is metabolized essentially to an optically pure 9R,10R-dihydrodiol (13 and L5 Table I), the 9,10-epoxide formed in BaP metabolism must have 9S,10R absolute stereochemistry (Figure 1). Similarly, the 7,8-epoxide formed in BaP metabolism is hydrated specifically at the C-8 position to form the 7R,8R-dihydrodiol (14.21). Hence the enzymatically formed 7,8-epoxide intermediate has 7R,8S absolute stereochemistry (Figure 1). Although the 7R,8R-dihydrodiol is formed almost exclusively from BaP metabolism in rat liver microsomes (Table I) and in bovine bronchial explants (25). the 7S,8S-dihydrodiol is also formed from BaP metabolism in mouse skin epidermis in vivo (5). 

B[/ ]P metabolites have been shown to bind to DNA in culmred human hepatocytes and in human bladder and tracheobronchial explants. The metabolites identified were identical to those produced in other species and differed only in the relative percentages of formation. Human tissues were most active in metabolizing P>[a P and exhibited at least a threefold higher covalent binding of metabolites to DNA than hamsters, dogs, monkeys, or rats. In addition, P>[a P has been tested extensively in several bacterial and mammalian cell systems and has been chosen as a positive control for the validation of some of these systems. ... 

A combined in vivolin vitro system for chemical metabolites has been developed that demonstrates the role of metabolism in activating compounds. In this system, rats are treated with a chemical and serum is removed 1 h later and cultured with explanted embryos. This system has been used to demonstrate that metabolites of procarbazine are toxic to explanted embryos, but that procarbazine and a microsomal preparation are not toxic to explanted embryos grown in culture medium (Schmid et al., 1982). 

Steinmeyer J, Ackermann B, Raiss RX. Intermittent cyclic loading of cartilage explants modulates fibronectin metabolism. Osteoarth Cart. 1997 5 331-341. 

Callus cultures derived from Jerusalem artichoke tubers are initially quiescent and have to be induced to divide. The induction of division is accompanied by a transformation in cell structure, which reflects changes in metabolism (e.g., Gamburg et al., 1999). Within an hour of the excision of Jerusalem artichoke tuber explants, ribosomes increase in abundance. They take the form of helices when scattered in the cytoplasm, and spirals when associated with the endoplasmic reticulum, and increase in frequency over time in line with the rate of protein synthesis (Yeoman and Street, 1973). Electron-dense bodies appear soon after in cell vacuoles, and to a lesser extent in the cytoplasm (Bagshaw et al., 1969), while crystal-containing bodies form in cells, which may contain hydrolytic enzymes (Bagshaw et al., 1969 Gerola and Bassi, 1964). Dormant Jerusalem artichoke tuber explants contain a variety of mitochondrial profiles, including distinctive cup-shaped... 

Wolf A, Raiss RX, Steinmeyer J (2003) Fibronectin metabolism of cartilage explants in response to the frequency of intermittent loading. J Orthopaedic Res 21 1081-1089... 

Todhunter R J, Fubini S L, Wootton J A M et al 1996 Effect of methylprednisolone acetate on proteoglycan and collagen metabolism of articular cartilage explants. Journal of Rheumatology 23 1207-1213... 

It is known that all the organs and tissues display drug metabolism, which vary vastly qualitatively, quantitatively, and regionally [26, 27]. This complexity makes it even more important to characterize isolated cells or cell lines of the organs under study with respect to metabolic enzyme profile and activity. A series of questions should be posed, such as the following What should be known about a cell line before its use for experiments How to link the purpose of the study with appropriate cells or tools Is a single cell line appropriate or should tissue explant be used ... 

Recent advances in cell and tissue culture techniques provide the potential for evaluation of drug transport or metabolism processes at the placenta. Techniques are available for culturing trophoblasts of both animal and human origin.106 However, our focus here is primarily on human systems. Primary explant and isolated cell cultures of human cytotrophoblasts have been well described 106-109 however, these systems do not form confluent monolayer systems adequate for transcellular transport studies.105... 

Chin, B.H., L.J. Sullivan and J.E. Eldridge. In vitro metabolism of carbaryl by fiver explants of bluegill, catfish, perch, goldfish, and kissing gourami. J. Agricul. Food Chem. 27 1395-1398, 1979. 

Unlike other disease entities, excejit for canine cystinuria, no other nonhuman inherited amino acid disorders have been uncovered. In place of animal studies, increasing emphasis is being placed on the use of cultured explants of tissues removed from patients with hereditary metabolic disease. Cultured explants of skin, leukocytes, and erythrocytes have been used to study the metabolism of such disorders as citrullinemia, branch-chain ketoaciduria, cystinosis, homocystinuria, and isovalericacidemia (S18). 

Metabolism of Castasterone and Brassinolide in Rice Seedlings and Etiolated Leaf Explants... 

Thus castasterone is not converted to brassinolide in either rice seedlings or etiolated leaf explants, but it is metabolized to seemingly non-glycosidic compounds. Therefore it might be postulated that castasterone seems to be biologically active by itself in rice. 

For decades, brown fat metabolism has been studied with tissue explants. While WAT is important for the storage of energy in the form of triacylglycerol, BAT functions to dissipate energy in the form of heat through the action of a specific mitochondrial proton transporter, UCPl. While the 3T3-L1 or 3T3-F442A cells lines provided a convenient... 

Metabolism of castasterone, brassinolide, 24-epibrassinolide, 22,23,24-triepibrassinolide in plants or explants... 

Chin, B, H Eldridge. J. M., Anderson, J. H., and Sullivan. L J. (1979c). Carbaryl metabolism in the rat. A comparison of in vivo, in vitro (tissue explant) and liver perfusion techniques. J. Agric. Food Chent. 27,716-720. 

Stoner GD. 1988. Metabolism of 4,4 -methylene-bis(2-chloroaniline) in explant cultures of human and dog bladder and dog liver cell cultures. In Proceeding of the Fourth NCI/EPA/NIOSH Collaborative Workshop Progress on Joint Environmental and Occupational Cancer Studies, April 22-23, 1986. Rockville, MD National Institutes of Health. Publication No. 88-2960, 343-350. 

In cell suspension cultures producing alkaloids, it is possible to choose and grow high-yielding cell lines. Cells and their metabolic capacity may differ as a result of genetic variability, the explants determination, and cell culture acting Therefore, clones and hybrids... 

Studies on the metabolism of cyclic nitrosamines in organ culture systems have been carried out on NPYR, NPIP, NNN, and A, 7V -dinitrosopiperazine (DNP). In cultured human bronchi, NPYR, NPIP, and, to a lesser extent, DNP, were metabolized to CO2 178). All three nitrosamines were bound to protein and DNA of the bronchial explants. In cultured human colon, NPYR and DNP were metabolized to CO2 and were bound to DNA and protein (75). Low levels of binding were observed for NNN and NPIP. 

Steinmeyer, J., and Knue, S. (1997), The proteoglycan metabolism of mature bovine articular cartilage explants superimposed to continuously applied cyclic mechanical loading, Biocfrcm. Biophys. Res. Common. 2 1) 216-221. 

---