Home About us Contact
|
Home About us Contact | ||
|
|
||
Storage Pools (storage + pool)
Selected AbstractsDynamics of metal subcellular distribution and its relationship with metal uptake in marine musselsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2005Tania Y-T. Abstract We examined the dynamics of subcellular distribution of metals (Cd, Ag, and Zn) in the marine green mussel Perna viridis by partitioning the metals into the insoluble fraction (IF), heat-sensitive proteins (HSP), and metallothionein-like proteins (MTLP) during metal uptake and elimination. Variations in metal uptake and elimination then were correlated with the subcellular distributions of these metals. The IF and HSP were the first ligands to bind with the metals during the dissolved exposure, and more metals were found in the HSP when the metal influx rate was higher. However, to minimize toxicity, metals were redistributed from HSP to MTLP afterwards. The subcellular distribution of metals was dependent of the exposure route in the mussels. During dietary metal exposure, the metals attained equilibrium before they were assimilated and the metal assimilation efficiency was independent of the metal partitioning in different subcellular fractions. During the efflux, metals in the soluble fraction mediated depuration, whereas metals in the insoluble fraction acted as a final storage pool. Redistribution also may occur between the metal-sensitive and inactive pools without significant depuration as a secondary protective mechanism. We further demonstrated that the higher efflux rate of Ag and Cd was related to a higher partitioning in the MTLP and a lower partitioning in the IF. Our study shows that subcellular pools other than MTLP were involved in immediate metal handling in the bivalves. The wide dynamics of subcellular metal distribution suggests that the relevance of individual subcellular fractions is dependent on the exposure pathway. [source] Cryopreserved iliac artery is indispensable interposition graft material for middle hepatic vein reconstruction of right liver graftsLIVER TRANSPLANTATION, Issue 6 2005Shin Hwang Cryopreserved iliac vein grafts (IVGs) have often been used for reconstruction of middle hepatic vein (MHV) branches in right liver grafts, but their storage pool has often been exhausted in our institution due to the low incidence of deceased donor organ procurement. To overcome this shortage of IVG, we started to use cryopreserved iliac artery graft (IAG). During September and October 2004, we carried out 41 cases of adult living donor liver transplantation, including 29 right lobe grafts with MHV reconstruction. Interposition vessel grafts were autologous vein (n = 6), IVG (n = 13), and IAG (n = 10). IAG was used in 3 (21%) of 13 cases during the first month. For the next month, it was more frequently used (7 [44%] of 16) because handling of cryopreserved IAG was not difficult and its outcome was favorable. On follow-up with computed tomography for 3 months, outflow disturbance occurred in 1 (17%) of 6 autologous vein cases, in 2 (15%) of 13 IVG cases, and in 1 (10%) of 10 IAG cases. Two-month patency rate of IAG was not lower than that of IVG. In conclusion, we feel that cryopreserved IAG can be used as an interposition vessel graft for MHV reconstruction of right liver graft when cryopreserved IVG is not available. (Liver Transpl 2005;11:644,649.) [source] From ancient genes to modern communities: the cellular stress response and the evolution of plant strategiesFUNCTIONAL ECOLOGY, Issue 5 2005S. PIERCE Summary 1Two major plant strategy theories attempt to explain how phenotype determines community structure. Crucially, CSR plant strategy theory suggests that stress and sporadic resource availability favour conservative phenotypes, whereas the resource-ratio hypothesis views the spatial heterogeneity of resources as selecting for optimal foraging in chronically unproductive habitats. Which view is most realistic? 2The ecophysiology literature demonstrates that stress is comprised of two processes: (1) limitation of resource supply to metabolism; and (2) damage to biomembranes, proteins and genetic material (chronic stress). Thus stress is defined mechanistically as the suboptimal performance of metabolism. 3Adaptations to limitation buffer metabolism against variability in external resource supply; internal storage pools are more consistent. Chronic stress elicits the same ancient cellular stress response in all cellular life: investment in stress metabolites that preserve the integrity and compartmentalization of metabolic components in concert with molecular damage-repair mechanisms. 4The cellular stress response was augmented by morphological innovations during the Silurian,Devonian terrestrial radiation, during which nutrient limitation appears to have been a principal selection pressure (sensu CSR theory). 5The modern stress,tolerator syndrome is conservative and supports metabolism in limiting or fluctuating environmental conditions: standing resource pools with high investment/maintenance costs impose high internal diffusion resistances and limit inherent growth rate (sensu CSR theory). 6The resource-ratio hypothesis cannot account for the cellular stress response or the crucial role of ombrotrophy in primary succession. CSR theory agrees with current understanding of the cellular stress response, terrestrial radiation and modern adaptations recorded in chronically unproductive habitats, and is applicable as CSR classification. [source] Partitioning sources of soil respiration in boreal black spruce forest using radiocarbonGLOBAL CHANGE BIOLOGY, Issue 2 2006Edward A.G. Schuur Abstract Separating ecosystem and soil respiration into autotrophic and heterotrophic component sources is necessary for understanding how the net ecosystem exchange of carbon (C) will respond to current and future changes in climate and vegetation. Here, we use an isotope mass balance method based on radiocarbon to partition respiration sources in three mature black spruce forest stands in Alaska. Radiocarbon (,14C) signatures of respired C reflect the age of substrate C and can be used to differentiate source pools within ecosystems. Recently-fixed C that fuels plant or microbial metabolism has ,14C values close to that of current atmospheric CO2, while C respired from litter and soil organic matter decomposition will reflect the longer residence time of C in plant and soil C pools. Contrary to our expectations, the ,14C of C respired by recently excised black spruce roots averaged 14, greater than expected for recently fixed photosynthetic products, indicating that some portion of the C fueling root metabolism was derived from C storage pools with turnover times of at least several years. The ,14C values of C respired by heterotrophs in laboratory incubations of soil organic matter averaged 60, higher than the contemporary atmosphere ,14CO2, indicating that the major contributors to decomposition are derived from a combination of sources consistent with a mean residence time of up to a decade. Comparing autotrophic and heterotrophic ,14C end members with measurements of the ,14C of total soil respiration, we calculated that 47,63% of soil CO2 emissions were derived from heterotrophic respiration across all three sites. Our limited temporal sampling also observed no significant differences in the partitioning of soil respiration in the early season compared with the late season. Future work is needed to address the reasons for high ,14C values in root respiration and issues of whether this method fully captures the contribution of rhizosphere respiration. [source] The regulation and function of phosphate in the human bodyBIOFACTORS, Issue 1-4 2004Eiji Takeda Abstract Inorganic phosphate (Pi) is required for cellular function and skeletal mineralization. Serum Pi level is maintained within a narrow range through a complex interplay between intestinal absorption, exchange with intracellular and bone storage pools, and renal tubular reabsorption. Pi is abundant in the diet, and intestinal absorption of Pi is efficient and minimally regulated. The kidney is a major regulator of Pi homeostasis and can increase or decrease its Pi reabsorptive capacity to accommodate Pi need. The crucial regulated step in Pi homeostasis is the transport of Pi across the renal proximal tubule. Type II sodium-dependent phosphate (Na/Pi) cotransporter (NPT2) is the major molecule in the renal proximal tubule and is regulated by hormones and nonhormonal factors. Recent studies of inherited and acquired hypophosphatemia which exhibit similar biochemical and clinical features, have led to the identification of novel genes, phosphate regulating gene with homologies to endopeptidases on the X chromosome (PHEX) and fibroblast growth factor-23 (FGF-23), that play a role in the regulation of Pi homeostasis. The PHEX gene encodes an endopeptidase, predominantly expressed in bone and teeth but not in kidney. FGF-23 may be a substrate of this endopeptidase and inhibit renal Pi reabsorption. In a survey in the United States and in Japan, the amount of phosphorus from food is gradually increasing. It is thought that excess amounts of phosphorus intake for long periods are a strong factor in bone impairment and ageing. The restriction of phosphorus intake seems to be important under low calcium intake to keep QOL on high level. [source] | ||||||||||