Radioisotopes studies

Kharkar DP, Thomson J, Turekian KK, Forster WO (1976) Uranium and thorium series nuclides in plankton from the Caribbean. Limnol Oceanogr 21 294-299 Krishnaswami S, Lai D, Somayajulu BLK, Weiss R, Craig H (1976) Large-volume in situ filtration of deep Pacific waters mineralogical and radioisotope studies. Earth Planet Sci Lett 32 420-429 Livingston HD, Cochran JK (1987) Determination of transuranic and thorium isotopes in ocean water in solution and in filterable particles. J Radioanal Nucl Chem 115 299-308 Masque P, Sanchez-Cabeza JA, Braach JM, Palacios E, Canals M (2002) Balance and residence times of °Pb and 4 o in surface waters of the northwestern Mediterranean Sea. Cont Shelf Res 22 2127-2146 Matsumoto E (1975) Th-234-U-238 radioactive disequilibrium in the surface layer of the oceans. Geochim Cosmochim Acta 39 205-212... 

Krishnaswami S, Lai D, Somayajulu BLK (1976) Large-volume in-situ filtration of deep Pacific waters Mineralogical and radioisotope studies. Earth Planet Sci Lett 32 420-429 Krishnaswami S, Mangini A, Thomas JH, Sharma P, Cochran JK, Turekian KK, Parker PD (1982) °Be and Th isotopes in manganese nodules and adjacent sediments nodule growth histories and nuclide behavior. Earth Planet Sci Lett 59 217-234... 

Ultrastructural and radioisotope studies on the phagocytosis of particles by gills [84] or lungs [85] demonstrate the endocytosis of particles by mobile macrophages, and their subsequent lysosomal attack. 

Schrader, M.E. (1970). Radioisotopic studies of bonding at the interface. J. Adhesion 2, 202-212. Schrader, M.E, and Block, A. (1971). Tracer study of kinetics and mechanism of hydrolytically induced interfacial failure. J. Polym. Sci.. Part C, Polym. Symposia. 34, 281-291. 

There is a good deal of support for such an origin of the carbonate ion. Certainly, in invertebrates there are conclusive kinetic data based on radioisotope studies to show that, although the blood supplies Ca2+ for egg shell formation, the plasma bicarbonate plays no direct role602). 

Buchsbaum Pearse, V. Radioisotopic study of calcification in the articulated coralline alga Bossiella orbigniana. J. Phycol. 8, 88-97 (1972). 

Santschi, P.H., Adler, D.M. and Amdurer, M., 1983. The fate of particles and particle-reactive trace metals in coastal waters Radioisotope studies in microcosmsln Wong, Boyle, Bruland, Burton and Goldberg (eds), Trace Metals in Sea Water. Plenum Publishing Corporation, pp. 331-349. 

Krishnaswami, S., Lai, D., Somayajulu, B.L.K., Weiss, R. F., and Craig, H. Large-volume situ filtration of deep Pacific waters mineralogical and radioisotope studies. 

Will G. The absorption, distribution and utilization of intramuscularly administered iron-dextran a radioisotope study. Br J Haematol 65. 1968 14 395-406. 

For a certain drug, the total residue is determined from a radioisotope study, and the marker concentration is determined by the approved regulatory method. Once the Rm value is known, a marker residue tolerance is established. This value is then used in field monitoring programs to ensure that no edible tissues containing drug residue above the safe concentration will reach the consumer. For albendazole, the Rm value for the 2-aminosulfone metabolite in 0.20 or 20% of the total residue. Since the safe concentration for albendazole residues in liver is 1.2 ppm (0.6 ppm in meat x 2 (food factor)), the marker tolerance has been established at 240 ppb. 

Born in Budapest in 1885, he began his first radioisotope studies in plants in 1923. In 1934, he left Berlin for pohtical reasons to go to Copenhagen to work with Niels Bohr. In 1935, Ernest Lawrence sent phosphorus-32 by regular mail from California. Hevesy published more than 400 scientific articles, and won the Nobel prize in 1944. In 1959, he received the Atoms For Peace award by the US Atomic Energy Commission. He died on July 5,1966 in Freiburg, Germany. 

Isotope Labeling. Heavy isotope labels, alone, would very likely not produce better results than radioisotope labels. Problems of isolation and purification would be more difficult than radioisotope studies due to the nature of the detection system which would be needed, mass spectrometry. However, the combined use of heavy isotope and radioisotope labeling can provide very definitive information on confirming the identification of suspected metabolites in the same manner as using dual radioisotopes, such as and H, or and How-... 

Also, the isotope retention curves and estimates of the rate constants appear to be very sensitive to the dose. It is usually assumed, particularly in radioisotope studies, that the amount of tracer is much smaller than the pool size. Johansson et al. (1966a Johansson and Tiselius, 1973) used doses of 5 to 200 /xg of pyridoxine, which they acknowledged would constitute a significant fraction of the pool (Johansson et al, 1966a). This may partially explain why the rate constant(Ac3) for excretion from the small pool averages 0.60 when calculated from their data for the 20-jug dose compared with 2.3-4.1 based on the 200-/ug dose (Johansson and Tiselius, 1973). 

Early radiotracer work showed that most injected phosphate penetrates to the liver, where it participates in numerous biochemical reactions and rapidly passes to other parts of the body. Some appears in the kidneys and is excreted in the urine, but the remainder becomes generally distributed in the body tissues within a day or two. Subsequently, however, the levels in most body tissues falls to zero, while the concentration in bones rises to a high level. The latter falls only gradually, due to normal molecular turnover (Chapter 11.1). Radioisotope studies have indicated that a continuous interchange of Ca and P between bones and soft tissues takes place, and this amounts to 1% per day. 

During these radioisotope studies, the total protein content of liver remains unchanged therefore, the stock of newly synthesized protein must be balanced by the catabolism or excretion of an equivalent amount of protein. Remarkable experiments of Shoenheimer and his associates [59] using N-labeled amino acid as precursor of the total protein contained in the organism have clearly established that proteins are continuously broken down, and that the endogenous amino acid pool is freely mixed with the exogenous amino acid pool. 

Impairment of remethylation is strongly implicated as the cause of hyper-homocysteinemia in patients with CKD, which has been demonstrated in a radioisotope study in patients with CKD (Van Guldener et al. 1999), although reduced clearance of homocysteine has been suggested as the possible cause in some reports. We reported that supplementation with folic add and methyl-cobalamin normalized the remethylation pathway (Koyama et al. 2002). Compared with the decreases in homocysteine of 17.3 8.4% after supplementation with folic add alone and 18.7 7.5% after that with methylcoba-lamin alone, a combination of foUc acid and methyleobalamin decreased homocysteine by approximately 60% and normalized the findings of the methionine loading test Table 47.1. This result suggest that both coenzymes, folic acid and methyleobalamin, were insufficient due to reduced availability of these coenzymes in patients with CKD. There is also a report that increased MMA in dialysis patients was reduced by the administration of methylcoba-lamin (Nakamura et al. 2002). 

Glucose and ammonia are the natural precursors of glucosamine 299, 300). Radioisotopic studies using indicate that glucosone may be on the path of biosynthesis 300). (See also Chapter XIV.)... 

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