Penetration and translocation

If the formulation performs satisfactorily in spray equipment, one is concerned with the way in which the spray interacts with the pest to be controlled, particularly with (a) percent retention on foliage, animals, and insects, including bouncing and wetting, (b) residual nature of sprays, (c) penetration and translocation, (d) crystal size of deposit, (e) control of the pest, and (f) site and mode of action. 

A number of simplistic applications could result from assays to a group of candidate pesticides early in development. Such assays would be very cost effective in monitoring penetration and translocation. If a molecule is large, there is hope that immunochemical techniques could even be used to localize the compound in the target species and possibly to purify the target. 

Use of the cucumber cotyledon bioassay is limited because of probable differences in herbicide penetration and translocation. If all DPE herbicides affect the same site(s), then discrepancies in activity could also be related to the differential ability of cucumber cotyledons to detoxify these compounds. Further structure-activity studies must utilize in vitro assays to measure intrinsic activity. 

The low partition coefficient of 1 indicates that it has no potential to accumulate in biological tissues and, therefore, also not in the food chain. The rapid uptake and translaminar transport of 1 is excellent, as observed in cabbage leaves [23] and in rice and cucumber [24]. Additionally, 1 has a considerable acropetal mobility in xylem of plants. In contrast, its penetration and translocation in cotton leaves was less pronounced, as shown by phosphor-imager autoradiography [25]. This xylem mobility makes 1 especially useful for seed treatment and soil application, but it is equally active for foliar application. Owing to its lack of any acidic hydrogen, the pK of 1 is >14 and, therefore, its transport within the... 

The penetration and translocation behavior of [ " C]-9 [59] in cabbage is comparable that those reported for imidacloprid (1). Translaminar and acropetal aphicidal efficacy clearly confirmed that 9 can be systemically translocated. The... 

Biochemistry and Physiology. The principle clmllenge here is the multiplicity of crop plants and pests of interest. Two broadly applicable research areas are penetration and translocation of xenobiotics in plants, and their metabolism in crops and pests. The... 

Inhibitors must possess chemical and physical properties that will ensure absorption by root tips or penetration by foliar surfaces, and translocation to the active site. Once there they must assume the precise spatial configuration required to complement the molecular architecture of the active center if they are to block the key reaction. A comprehension of comparative biochemistry and information on how plants differ in the architecture of the reactive sites should assist in developing truly selective herbicides. 

Thoren, P, D. Persson, E. Esbjomer, M. Goksor, B. Lincoln, and B. Norden (2004) Membrane binding and translocation of cell-penetrating peptides. Biochemistry 43, 3471-3489. 

Steroid hormone receptors (for gonadal steroids and adrenocortical steroids) are complex proteins inside the target cell. The steroid penetrates, is bound and translocates into the cell nucleus, which is the principal site of action and where RNA/protein synthesis occurs. Compounds that occupy the receptor without causing translocation into the nucleus or the replenishment of receptors act as antagonists, e.g. spironolactone to aldosterone, cyproterone to androgens, clomiphene to oestrogens. 

Engineered reed-bed and constructed wetland systems for removal of heavy metals from wastewater using phytoremediation are in use in some developed Asian countries. The root system of the hyper-accumulator plant penetrates a permeable rock bed. The wastewater is introduced into one end of the bed and flows through the permeable rock layer. The rock layer should be inert to heavy metals binding so that it does not unwittingly serve as a sink for heavy metals. These metals are sequestered by the root system and translocated to the shoots. Periodically, the metal-containing shoots are harvested. The biomass can be burned off or composted to yield a low volume of metal-rich ash. 

The use of plant cell cultures in pesticide metabolism studies has a history of only about 20 years, but pioneers of the technique have laid the groundwork for an increasing number of researchers interested in the advantages the cell culture systems offer. Host have chosen to use suspension cultures, because of the ease with which they can be manipulated, and the increased possibility for standardization of conditions from laboratory to laboratory. As an adjunct to whole plant studies cell cultures provide information as to the changes that structural modifications of a basic molecule may have on phytotoxicity, especially in detecting the inherent toxicity of a molecule that fails to penetrate or translocate in a whole plant. 

A multicompartmental model of the kinetics of dust retention in the pulmonary region and in the tracheobronchial lymph nodes has been developed by Katnelson et al. (1992). Penetration into the in-terstitium and translocation to the lymph nodes are possible for nonphagocytosed particles only. 

Fig. 13 Amino acid sequences of some cell-penetrating peptides (CPP) and translocation of CPP-conjugated carriers across the plasma membrane...

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