Tissue accumulation

The carotenoid pathway may also be regulated by feedback inhibition from the end products. Inhibition of lycopene cyclisation in leaves of tomato causes increase in the expression of Pds and Psy-1 (Giuliano et al, 1993 Corona et al, 1996). This hypothesis is supported by other studies using carotenoid biosynthesis inhibitors where treated photosynthetic tissues accumulated higher concentrations of carotenoids than untreated tissues (reviewed by Bramley, 1993). The mechanism of this regulation is unknown. A contrary view, however, comes from studies on the phytoene-accumulating immutans mutant of Arabidopsis, where there is no feedback inhibition of phytoene desaturase gene expression (Wetzel and Rodermel, 1998). 

Omata S, Kasama H, Hasegawa H, Hasegawa K, Ozaki K, Sugano H. 1986. Species difference between rat and hamster in tissue accumulation of mercury after administration of methyhnercury. Arch Toxicol 59 249-254. 

When pharmaceuticals are administered to feed animals there is a special concern about the possible accumulation of drug residues in the animals tissues. Thus, in these bioequivalency studies it may be appropriate to carefully monitor parameters that define possible tissue accumulation [45]. 

It has also been demonstrated in animals that lead blocks the intestinal responses to vitamin D and its metabolites (Smith et al. 1981). Dietary concentrations of lead in combination with a low phosphorus or a low calcium diet administered to rats suppressed plasma levels of the vitamin D metabolite, 1,25-dihydroxycholecaliferol, while dietary intakes rich in calcium and phosphorus protected against this effect (Smith et al. 1981). Thus, animals fed a diet high in calcium or phosphorus appear to be less susceptible to the effects of lead, because of hindered tissue accumulation of lead. 

Tissue accumulation of exogenously added tritiated PGs was shown for the spider crab Libinia emarginata [107]. The earliest report of possible oxylipin production in marine arthropods was from gill and stomach tissues of the lobster Homarus sp. [15]. These were tested for their ability to produce prostaglandins in incubations with all-cis-[8,9,ll,12,14,15-3H6]eicosatrienoic acid. Carrier PGEj was added and the PGErtype compounds from the extract were purified by TLC. Quantitation was done by UV absorption at 278 nm after... 

Protein Regulatory elements Additional elements to the construct Species/Tissue Accumulation level Literature... 

Most, and possibly all of these changes result from the tissue accumulation of phytanic acid. Phytanic is of dietary origin exclusively, and dietary restriction of phytanic and plasmapheresis are of clinical benefit. The defective gene and pathogenic mutations have been identified. The clinical manifestations can also be mimicked by defects of PEX7. 

Schumann, K., P. Friebel, G. Schmolke, and B. Elsenhans. 1996. State of iron repletion and cadmium tissue accumulation as a function of growth in young rats after oral exposure. Arch. Environ. Contam. Toxicol. 31 483-487. 

Buhler, D.R., R.M. Stokes, and R.S. Caldwell. 1977. Tissue accumulation and enzymatic effects of hexavalent chromium in rainbow trout (Salmo gairdneri). Jour. Fish. Res. Board Canada 34 9-18. 

Pilgaard, L., H. Malte, and F.B. Jensen. 1994. Physiological effects and tissue accumulation of copper in freshwater rainbow trout (Oncorhynchus mykiss) under normoxic and hypoxic conditions. Aquat. Toxicol. 29 197-212. 

Lead adversely affected the survival of sensitive mammals tested at different concentrations (Table 4.8) 5 to 108 mg Pb/kg BW in rats (acute oral), 0.32 mg Pb/kg BW daily in dogs (chronic oral), and 1.7 mg Pb/kg diet in horses (chronic dietary). Adverse sublethal effects (Table 4.8) were noted in monkeys given 0.1 mg Pb/kg BW daily (impaired learning 2 years postadministration) or fed diets containing 0.5 mg Pb/kg (abnormal social behavior) in rabbits given 0.005 mg Pb/kg BW (reduced blood ALAD activity) or 0.03 mg Pb/kg BW (elevated blood lead levels) in mice at 0.05 mg Pb/kg BW (reduced ALAD activity) or in sheep at 0.05 mg Pb/kg BW (tissue accumulations). 

Nickel retention in the body of mammals is low. The half-time residence of soluble forms of nickel is several days, with little evidence for tissue accumulation except in the lung (USEPA 1980, 1986). Radionickel-63 (63Ni) injected into rats and rabbits cleared rapidly most (75%) of the injected dose was excreted within 24 to 72 h (USEPA 1980). Nickel clears at different rates from various tissues. In mammals, clearance was fastest from serum, followed by kidney, muscle, stomach, and uterus relatively slow clearance was evident in skin, brain, and especially lung (Kasprzak 1987). The half-time persistence in human lung for insoluble forms of nickel is 330 days (Sevin 1980). 

Equilibrium dialysis of homogenates of kidneys of rats given mercuric chloride, revealed that over 99% of the mercury was not diffusible [40]. Diffusible compounds of mercury have the opportunity to cross the capillary membrane and enter the tissue spaces however, due to chemical affinities for cellular binding sites and the diffusible complex, and the ability to penetrate the cell membrane, not all diffusible complexes of mercury present in plasma lead to tissue accumulation. 

Linder RE, Scotti TM, McElroy WK, et al. 1983. Spermotoxicity and tissue accumulation of chlordecone (Kepone) in male rats. J Toxicol Environ Health 12 183-192. 

The mechanism of DEA toxicity is unknown but may be related to its high tissue accumulation and effects on phospholipid metabolism, resulting in alterations in membrane structure and function. ... 

Pharmacokinetics Phytonadione is only absorbed from the Gl tract via intestinal lymphatics in the presence of bile salts. Although initially concentrated in the liver, vitamin K is rapidly metabolized, and very little tissue accumulation occurs. Parenteral phytonadione is generally detectable within 1 to 2 hours. Phytonadione usually controls hemorrhage within 3 to 6 hours. A normal prothrombin level may be obtained in 12 to 14 hours. Oral phytonadione exerts its effect in 6 to 10 hours. 

Seizures There have been rare reports of seizures following sumatriptan use. Binding to melanin-containing tissues Accumulation in melanin-rich tissues (such as the eye) could occur over time, raising the possibility that toxicity in these tissues could occur after extended use. 

Absorption of Salicylic Acid. Excised oat roots absorbed salicylic acid in two distinct phases (Figure 1). Upon exposure to salicylic acid the root segments rapidly absorbed the eompound to attain a concentration of about 0.5 pmole/g of tissue. On the assumption that 1 g of tissue equals 1 mL of tissue, this translates to 0.5 mM salicylic acid inside the tissue, the same concentration as the external solution. This coneentration of salicylic acid was present in the tissue after 1 h and was maintained for over 3 h. By 4 h a second phase of absorption was evident (Figure 1). During the second phase, salicylic acid was absorbed at a greater rate that lasted for at least 24 h. At that time, enough salicylic acid had been absorbed that the eoncentration in the tissue was 8.0 mM. Thus, the tissue accumulated salicylic acid to concentrations greater than that in the external solution. An additional experiment (not shown) showed that the tissue would continue to absorb salicylic acid until the compound was depleted from the external solution. 

The detection of tumors with [ F] FDG is based on the increase of glucose metabolism in tumor cells the transport of [ F] FDG in tumor cells is enhanced compared to healthy tissue. Accumulation of [ F] FDG is measured and visuahzed by... 

---