Disruption treatments

Pheromone Purity. An intriguing challenge concerns chemical purity of disruptant formulations. For disruption purposes, is it necessary to treat with the precise blend of pheromone iscmers and secondary components or is only the major pheromone chemical necessary The answer to this question could be different for different pests, but in most cases it could influence treatment costs. Our experience with the western spruce budworm, Choristoneura occidentalis. Freeman, suggests that only the major component of that pheromone is necessary for disruption. Conversely, some recent work on an orchard pest (9) indicates that a complete pheromone-blend disruption treatment is more effective. 

For perspective, however, we must also consider the successful disruption treatments that have resulted from placement of relatively few releasers at wide spacings. Farkas et al. (10) reported disruption of cabbage looper, Trichoplusia ni (Hubner), with releasers spaced at up to 400 m. Hand applied releasers placed at intervals of 5-10 m and emitting ca. 3.5-14.0 g pheromone/ha/season have been successful in reducing damage caused by western pine shoot borer (5). 

In a 1981 study on western pine shoot borer, three sets of traps baited with synthetic pheromone in controlled release PVC (polyvinyl chloride) pellets (12) were placed in ponderosa pine plantations (16 or more ha in size), treated with (a) Health Chemicals Hereon laminated flakes at some 20,000 flakes/ha with a pheromone release capacity of 10 g/ha/season (b) strips of Hereon laminated plastic (30 x 2 cm) at 25 strips/ha stapled on trees at 20 m intervals with a pheromone release capacity of 5 g/ha/season and, (c) an untreated check plot. The Pherocon II adhesive traps were baited with PVC pellets at five different bait strengths of 0.001%, 0.01%, 0.1%, 1.0%, and 10% pheromone by weight. Each of these baits was replicated seven times in each disruption treatment for a total of 35 traps per plantation and 105 overall. The traps were placed in lines of five with each bait concentration represented once in each line. The positions of the traps were randomized by bait concentration within each line, and traps were spaced at least 20 m apart. All traps were left in place through 4-weeks of the shoot borer s seasonal flight. 

Table 3.3. Advantages and disadvantages of cell disruption treatments.

There is some evidence for chemically mediated endocrine disruption in amphibians. The egg yolk protein, vitellogenin, is inducible in amphibians by exposure to DDT. " Males of the short clawed toad Xenopus laevis given 250 fig/g or 1 fig/g o,p -DDT for seven days have been shown to produce vitellogenin, although the induction was less than that achieved by treatment with 1 fig/g of either 17/1-oestradiol or diethylstilboestrol. Research has also shown that endocrine disrupting chemicals can alter sex ratios in wild populations of certain species PCB congeners and organochlorine compounds have been linked with male domination of sex ratios in polluted compared to unpolluted sites. ... 

Lipoteichoic acids (from gram-positive bacteria) [56411-57-5J. Extracted by hot phenol/water from disrupted cells. Nucleic acids that were also extracted were removed by treatment with nucleases. Nucleic resistant acids, proteins, polysaccharides and teichoic acids were separated from lipoteichoic acids by anion-exchange chromatography on DEAE-Sephacel or by hydrophobic interaction on octyl-Sepharose [Fischer et al. Ear J Biochem 133 523 1983]. 

If the protein of interest is a heteromultimer (composed of more than one type of polypeptide chain), then the protein must be dissociated and its component polypeptide subunits must be separated from one another and sequenced individually. Subunit associations in multimeric proteins are typically maintained solely by noncovalent forces, and therefore most multimeric proteins can usually be dissociated by exposure to pEI extremes, 8 M urea, 6 M guanidinium hydrochloride, or high salt concentrations. (All of these treatments disrupt polar interactions such as hydrogen bonds both within the protein molecule and between the protein and the aqueous solvent.) Once dissociated, the individual polypeptides can be isolated from one another on the basis of differences in size and/or charge. Occasionally, heteromultimers are linked together by interchain S—S bridges. In such instances, these cross-links must be cleaved prior to dissociation and isolation of the individual chains. The methods described under step 2 are applicable for this purpose. 

A widely used technique for cell disruption is high-pressure homogenisation. Shear forces generated in this treatment are sufficient to completely disrupt many types of cell. A common... 

The mode of action of metronidazole (Flagyl) is not well understood, but it is thought to disrupt DNA and protein syndiesis in susceptible organisms. This drug may be used in the treatment of serious infections, such as intraabdominal, bone, soft tissue, lower respiratory, gynecologic, and CNS infections caused by susceptible anaerobic (able to live without oxygen) microorganisms. 

The antimetabolites interfere with various metabolic functions of cells, thereby disrupting normal cell functions. They inactivate enzymes or alter the structure of DNA, changing the DNA s ability to replicate These drag are most effective in the treatment of rapidly dividing neoplastic cells. Examples of the antimetabolites include methotrexate and fluorouracil (Adrucil). 

Clofibrate causes a necrotizing myopathy, particularly in patients with renal failure, nephrotic syndrome or hypothyroidism. The myopathy is painful and myokymia of unknown origin is sometimes present. The mechanism of damage is not known, but p-chlorophenol is a major metabolite of clofibrate and p-chlorophe-nol is a particularly potent uncoupler of cellular oxidative phosphorylation and disrupts the fluidity of lipid membranes. Muscle damage is repaired rapidly on the cessation of treatment. 

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