Magnitude Of Translocation Research Articles

Plant‐facilitated mobilization and translocation of weathered 2,2‐bis(p‐chlorophenyl)‐1,1‐dichloroethylene(p,p′‐DDE) from an agricultural soil

AbstractField experiments were conducted to determine the uptake and translocation of highly weathered 2,2‐bis(p‐chlorophenyl)1,1‐dichloroethylene (p,p′‐DDE) from an agricultural soil. In soil containing known amounts of p,p′‐DDE, experimental plots containing zucchini, pumpkin, or spinach were constructed. At destructive harvest, three soil fractions were collected that differed in the degree of influence exerted by the plant roots. The bulk soil was vegetation‐free, the near‐root zone was within the area encompassed by the roots, and the rhizosphere remained physically attached to the roots at harvest. For each crop, statistically significant decreases were found in the concentration of p,p′‐DDE in either the near‐root zone or the rhizosphere relative to the bulk soil, suggesting plant‐facilitated mobilization and/or degradation of the residue. Plant tissues were analyzed to determine the extent of contaminant removal from the soil and the magnitude of translocation through the shoot system. The concentration of p,p′‐DDE in the roots of both zucchini and pumpkin was more than an order of magnitude larger than the bulk soil concentration, followed by significant translocation through the plant tissues to the fruit. The data indicate that certain plants may effectively accumulate residues of persistent organic pollutants in their tissues, suggesting phytoremediation as a possible treatment strategy.

Movement and Deposition of Two Organophosphorus Pesticides within a Residence after Interior and Exterior Applications

ABSTRACT Post-application temporal and spatial distributions of two organophosphorus pesticides, diazinon (O,O-diethyl O-[6-methyl-2-(1-methylethyl)-4-pyrimidinyl] phosphorothioate, CAS No. 333-41-5) and chlorpyrifos [O,O-diethyl-O-(2-isopropyl-6-methyl-4-pyrimidinyl) phosphorothioate, CAS No. 2921-88-2], were monitored after homeowner applications for indoor and outdoor insect control. Samples of indoor air, vacuumable carpet dust, carpet dislodgeable residues, deposits on bare floors, table tops and dinnerware, surrogate food, and residues on children's hands and toys were taken before and up to 12 days after treatments in the family room, kitchen, and child's bedroom. Results from the study demonstrate the nature and magnitude of translocation of pesticides from the areas of application to surfaces accessible for human contact and permit comparisons of potential exposures via respiration and dermal contact/oral ingestion. Potential indoor inhalation exposures were estimated to be as high as 0.5 ^g/kg/day for diazinon applied indoors and 0.05 |ag/kg/day for chlorpyrifos applied to the outside perimeter of the house. While ingestion of carpet dust at the rate of 100 ^g/day would have added a maximum of only ~0.01 ^g/kg/day to the daily dose, residues found on the children's hands suggest that repeated mouthing could have contributed as much as 1-1.5 ^g/kg/day. These estimates are below the U.S. Environmental Protection Agency (EPA) reference dose for chlorpyrifos, but exceed those for diazinon.

Plant-facilitated mobilization and translocation of weathered 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE) from an agricultural soil.

Field experiments were conducted to determine the uptake and translocation of highly weathered 2,2-bis(p-chlorophenyl)1,1-dichloroethylene (p,p'-DDE) from an agricultural soil. In soil containing known amounts of p,p'-DDE, experimental plots containing zucchini, pumpkin, or spinach were constructed. At destructive harvest, three soil fractions were collected that differed in the degree of influence exerted by the plant roots. The bulk soil was vegetation-free, the near-root zone was within the area encompassed by the roots, and the rhizosphere remained physically attached to the roots at harvest. For each crop, statistically significant decreases were found in the concentration of p,p'-DDE in either the near-root zone or the rhizosphere relative to the bulk soil, suggesting plant-facilitated mobilization and/or degradation of the residue. Plant tissues were analyzed to determine the extent of contaminant removal from the soil and the magnitude of translocation through the shoot system. The concentration of p,p'-DDE in the roots of both zucchini and pumpkin was more than an order of magnitude larger than the bulk soil concentration, followed by significant translocation through the plant tissues to the fruit. The data indicate that certain plants may effectively accumulate residues of persistent organic pollutants in their tissues, suggesting phytoremediation as a possible treatment strategy.

Demonstration of insulin-responsive trafficking of GLUT4 and vpTR in fibroblasts.

Insulin-responsive trafficking of the GLUT4 glucose transporter and the insulin-regulated aminopeptidase (IRAP) in adipose and muscle cells is well established. Insulin regulation of GLUT4 trafficking in these cells underlies the role that adipose tissue and muscle play in the maintenance of whole body glucose homeostasis. GLUT4 is expressed in a very limited number of tissues, most highly in adipose and muscle, while IRAP is expressed in many tissues. IRAP's physiological role in any of the tissues in which it is expressed, however, is unknown. The fact that IRAP, which traffics by the same insulin-regulated pathway as GLUT4, is expressed in 'non-insulin responsive' tissues raises the question of whether these other cell types also have a specialized insulin-regulated trafficking pathway. The existence of an insulin-responsive pathway in other cell types would allow regulation of IRAP activity at the plasma membrane as a potentially important physiological function of insulin. To address this question we use reporter molecules for both GLUT4 and IRAP trafficking to measure insulin-stimulated translocation in undifferentiated cells by quantitative fluorescence microscopy. One reporter (vpTR), a chimera between the intracellular domain of IRAP and the extracellular and transmembrane domains of the transferrin receptor, has been previously characterized. The other is a GLUT4 construct with an exofacial HA epitope and a C-terminal GFP. By comparing these reporters to the transferrin receptor, a marker for general endocytic trafficking, we demonstrate the existence of a specialized, insulin-regulated trafficking pathway in two undifferentiated cell types, neither of which normally express GLUT4. The magnitude of translocation in these undifferentiated cells (approximately threefold) is similar to that reported for the translocation of GLUT4 in muscle cells. Thus, undifferentiated cells have the necessary retention and translocation machinery for an insulin response that is large enough to be physiologically important.

Bacterial Translocation

Infections from enteric bacteria are a major cause of morbidity and mortality during acute pancreatitis (AP), but the pathways by which these organisms reach distant organs remains speculative. Experiments were conducted to determine if bacterial translocation could be a mechanism for infection during this disease. AP was induced in Lewis rats by i.v. infusion of caerulein (experiment I) or ligation of the head of the pancreas (experiment II). In a third experiment, rats were gavaged with 1 x 10(8) 14C-radiolabeled Escherichia coli and pancreatitis was induced with caerulein. Results in all three experiments showed that AP increased the number of viable bacteria recovered in peritoneal fluid, mesenteric lymph nodes (MLN), liver, lungs, and pancreas. Radionuclide counting indicated that AP enhanced the gut permeability to 14C E. coli. To estimate the impact of AP on the magnitude of translocation and on the ability of the host to clear bacteria, the nuclide and colony-forming units (CFU) ratios were calculated between animals with and without AP. Blood, peritoneal fluid, and MLN had the highest nuclide ratio. During AP, these tissues may be the principal routes for bacterial spreading from the gut lumen. Peritoneal fluid, pancreas, and lung were the tissues with the highest CFU ratio. Bacterial killing ability of these tissues is likely impaired during AP.

Influence of leaf traits on the spatial distribution of insect herbivores associated with an overstorey rainforest tree.

The spatial distribution of insect herbivores associated with the Australian rainforest treeArgyrodendron actinophyllum (Sterculiaceae) was investigated by restricted canopy fogging. The foliage of this species was low in nitrogen and water content, and high in fibre content. Herbivore abundance was positively correlated with the amount of young foliage present within the samples and in adjacent samples, and with the nitrogen content of young leaves. In particular, the occurrence of phloem-feeders was correlated with the magnitude of translocation within the samples. The influence of leaf water content upon herbivore distribution was marginal, presumably because this factor is not limiting in rain-forest environments during the wet season, which usually coincides with the season of leaf-flush. Specific leaf weight, leaf size and foliage compactness had little or no apparent effect on herbivore distribution. Since the magnitude of leaf turnover affected both the quantity and the quality, as exemplified by translocation effects, of young foliage available, this factor may be critical to herbivores associated with evergreen rainforest trees which are particularly low in foliar nutrients, such asA. actinophyllum.

The effect of water stress on the translocation of recent photosynthate to the roots of young plants of Pinus strobus

White pine plants in their third year of growth were maintained for a 4-month period on soil having a moisture content of either 7% or 14%. In September, at the end of this period and at a time when translocation to the root is known to be high, the plants were permitted to photoassimilate 14CO2, and 8 hours later the distribution of 14C among the root, the old shoot, and the new shoot was determined.The plants maintained for the 4-month period on the 7% soil moisture environment had values for new needle length and root and new shoot fresh weights which were approximately 55–60% of the values from those plants grown on the higher soil moisture environment. However, despite such retarded growth, the magnitude of translocation to the root during the 8 hours after 14CO2 assimilation was only slightly lower in those plants grown on the lower soil moisture environment.From the results it is suggested that the decreased amount of translocation to the roots previously observed in pine plants in June and July cannot be attributed to reduced root metabolic activity and growth caused at that time by lowered soil water content.